Showing papers by "San Diego State University published in 1989"

Revised optical air mass tables and approximation formula

Abstract: We correct an error in a widely used air mass table by recalculating the values on the basis of the ISO Standard Atmosphere (1972) and revise its approximation formula.

Approximate Bayesian Inference in Conditionally Independent Hierarchical Models (Parametric Empirical Bayes Models)

Abstract: We consider two-stage models of the kind used in parametric empirical Bayes (PEB) methodology, calling them conditionally independent hierarchical models. We suppose that there are k “units,” which may be experimental subjects, cities, study centers, etcetera. At the first stage, the observation vectors Yi for units i = 1, …, k are independently distributed with densities p(yi | θi ), or more generally, p(yi | θi, λ). At the second stage, the unit-specific parameter vectors θi are iid with densities p(θi | λ). The PEB approach proceeds by regarding the second-stage distribution as a prior and noting that, if λ were known, inference about θ could be based on its posterior. Since λ is not known, the simplest PEB methods estimate the parameter λ by maximum likelihood or some variant, and then treat λ as if it were known to be equal to this estimate. Although this procedure is sometimes satisfactory, a well-known defect is that it neglects the uncertainty due to the estimation of λ. In this article w...

Grafting fibroblasts genetically modified to produce L-dopa in a rat model of Parkinson disease.

Abstract: Rat fibroblasts were infected with a retroviral vector containing the cDNA for rat tyrosine hydroxylase [TH; tyrosine 3-monooxygenase; L-tyrosine, tetrahydropteridine:oxygen oxidoreductase (3-hydroxylating), EC 1.14.16.2]. A TH-positive clone was identified by biochemical assay and immunohistochemical staining. When supplemented in vitro with pterin cofactors required for TH activity, these cells produced L-dopa and released it into the cell culture medium. Uninfected control cells and fibroblasts infected with the TH vector were grafted separately to the caudate of rats with unilateral 6-hydroxydopamine lesions of the nigrostriatal pathway. Only grafts containing TH-expressing fibroblasts were found to reduce rotational asymmetry. These results have general implications for the application of gene therapy to human neurological disease and specific implications for Parkinson disease.

Reactive and proactive aggression in childhood: relations to peer status and social context dimensions.

Abstract: Although there has been an accumulation of evidence to suggest a link between peer-directed aggression and social rejection, little attention has been given to the relations between specific subtypes of aggressive behavior and social rejection. The purpose of this investigation was to examine the relations between two subtypes of aggressive behavior (reactive and proactive aggression) and children's classroom peer status. The reciprocity of each of these subtypes of aggressive behavior and the social contexts in which these behaviors occur were also examined. Assessments of each of these forms of aggression among 70 boys (ages 5 and 6) were conducted using direct observations and teacher ratings. In general, directing reactive aggressive behavior toward peers was associated with social rejection, while utilization of instrumental aggression was positively related to peer status. The findings also indicated that directing proactive forms of aggression toward peers was related to being the target of proactive aggression. Finally, among older boys, both subtypes of aggression were more likely to occur during rough play than during any other type of play activity.

A Family Approach to Cardiovascular Risk Reduction: Results from The San Diego Family Health Project:

Abstract: The effectiveness of a family-based cardiovascular disease risk reduction intervention was evaluated in two ethnic groups. Participants were 206 healthy, volunteer low-to-middle-income Mexican-American and non-Hispanic white (Anglo-American) families (623 individuals), each with a fifth or a sixth-grade child. Families were recruited through elementary schools. Half of the families were randomized to a year-long educational intervention designed to decrease the whole family's intake of high salt, high fat foods, and to increase their regular physical activity. Eighty-nine percent of the enrolled families were measured at the 24-month follow-up. Both Mexican- and Anglo-American families in the experimental groups gained significantly more knowledge of the skills required to change dietary and exercise habits than did those in the control groups. Experimental families in both ethnic groups reported improved eating habits on a food frequency index. Anglo families reported lower total fat and sodium intake. There were no significant group differences in reported physical activity or in tested cardiovascular fitness levels. Significant differences for Anglo-American experimental vs. control adult subjects were found for LDL cholesterol. Significant intervention-control differences ranging from 2.2 to 3.4 mmHg systolic and/or diastolic blood pressure were found in all subgroups. Direct observation of diet and physical activity behaviors in a structured environment suggested generalization of behavior changes. There was evidence that behavior change persisted one year beyond the completion of the intervention program. It is concluded that involvement of families utilizing school based resources is feasible and effective. Future studies should focus on the most cost-effective methods of family involvement, and the potential for additive effects when family strategies are combined with other school health education programs.

Evaporation Minus Precipitation and Density Fluxes for the North Atlantic

Abstract: Estimates of evaporation (E) over the North Atlantic Ocean by Bunker have been combined with estimates of precipitation (P) by Dorman and Bourke to produce new annual and seasonal maps of E–P and surface density flux. Although uncertainties about precipitation algorithms and exchange coefficients still presist, it is felt that the high spatial resolution of these data set permits an estimate of E–P that is a significant improvement over previous work. The maps of E–P show considerably more detail than earlier maps, including a previously uncharted minimum with a northeast to southwest trend across the subtropical gyre. The two regions of maximal E–P display a close connection with continental air flows off Africal and North America, suggesting that the relative narrowness of the North Atlantic contributes to its status as a net evaporation basin. The zonally integrated E–P values are combined with river runoff estimates to obtain the meridional flux of freshwater, which can be compared with fluxe...

Responses of the non7hyphen;mycotrophic plant Salsola kali to invasion by vesicular–arbuscular mycorrhizal fungi

Abstract: SUMMARY Vesicular–arbuscular mycorrhizal fungi reduced the growth and survival of the non-mycotrophic weed, Salsola kali (Chenopodiaceae) in field and greenhouse experiments. To determine the mechanisms by which mycorrhizal fungi can affect a non-mycotrophic plant, we mapped the root responses of S. kali and the mycotrophic grass Agropyron dasystachyum to invasion by a mixture of Glomus spp. and by Gigaspora margarita. The fungi invaded the roots of both species within 10 days following seed germination. In A. dasystachyum normal mycorrhizal development occurred and no root browning or autofluorescence was observed, indicating a compatible reaction. In S. kali, the fungi initially invaded the roots and formed arbuscules and peletons. The roots reacted to invasion by autofluorescing bright yellow, suggesting lignification. With 1 or 2 days following root penetration by the fungus, the invaded root segment turned brown and, with the exception of some vesicles, the fungus disappeared from the root. The fungus sometimes then reinvaded new root segments farther down the root. These observations suggest that there is an incompatible reaction beween this non-mycotrophic annual and VA mycorrhizal fungi whereby the plant actively rejects infection. This response could form the basis for initiating studies on the genetics of mutualistic versus parasitic symbioses.

The dynamics of interstructural connection to prevent pounding

Abstract: Etude du comportement sismique de deux bâtiments relies par un systeme de transmission de forces entre etages, en modelisant le systeme comme un probleme de matrices combinees de masse et de rigidite; influence de la liaison sur la reduction du deplacement relatif et sur l'augmentation du cisaillement a la base de la structure plus rigide, pour frequences inferieures a la fondamentale

Irradiance and temperature effects on photosynthesis of tussock tundra Sphagnum mosses from the foothills of the Philip Smith Mountains, Alaska.

Abstract: Photosynthetic characteristics of three species of Sphagnum common in the foothills of the Brooks Range on the North Slope of Alaska were investigated. Generally, light-saturated rates of net photosynthesis decreased in the order S. squarrosum, S. angustifolium, and S. warnstorfii when plants were grown under common growth chamber conditions. For field-grown S. angustifolium, average light compensation point at 10°C was 37 μmol m-2s-1 photosynthetic photon flux density (PPFD), and light saturation occurred between 250 and 500 μmol m-2 s-1. At 20°C, compensation point increased to 127 μmol m-2s-1 and the PPFD required for light saturation increased to approximately 500 μmol m-2s-1, while maximum rates of CO2 uptake increased only slightly. Light response curves of chamber-grown plants exhibited substantially lower compensation points and higher light-saturated rates of CO2 assimilation than field-grown material, due perhaps to a higher percentage of green, photosynthetically competent tissue. All three species exhibited broad responses to temperature, with optima near 20°C, and maintained at least 75% of maximum assimilation between approx. 13° and 30°C. Rates at 5°C were approx. 50% of maximum. Studies of the microclimate of Sphagnum at the field research site suggest that CO2 uptake should occur at near light-saturated rates during the day in open tussock tundra but that PPFD may often be limiting under Salix and Betula canopies in a water track drainage. Simulations using a simple model provided a seasonal estimate of 0.78 g dry weight (DW) of S. angustifolium produced from each initial g of photosynthetic tissue under willow canopies, assuming no water limitations. Although the simulation model suggests that production would be 66% higher in open tussock tundra, S. angustifolium is rarely found in this potentially more stressful habitat. To explain the relative abundance of Sphagnum in shaded water track areas as compared to open tussock tundra, we postulate that the vascular plant canopies provide protection from adverse effects of high temperatures, excess irradiance and reduced water availability. Under conditions of normal water availability, removal of the vascular plant cover did not affect the tissue water content of S. squarrosum, but resulted in a strong decrease in photosynthetic capacity, accompanied by chlorophyll bleaching. These results suggest that photoinhibition may limit production under certain conditions.

Prevalence of the use of unconventional remedies for arthritis in a metropolitan community.

Abstract: Of 1,811 individuals sampled in a metropolitan community, 382 reported having a musculoskeletal complaint. Eighty-four percent of them had used an unconventional remedy within the previous 6 months. Most individuals used inexpensive, unharmful remedies such as exercise, prayer, and relaxation. This study indicates that people with musculoskeletal disorders often use unconventional remedies, but raises questions regarding the seriousness of this problem.

CASE productivity perceptions of software engineering professionals

Abstract: Computer-aided software engineering (CASE) is moving into the problem-solving domain of the systems analyst. The authors undertook a study to investigate the various functional and behavioral aspects of CASE and determine the impact it has over manual methods of software engineering productivity.

The Development of Concepts and Strategies Used in Computational Estimation

Abstract: Twelve students at each of Grades 3, 5, 7, and 9 were individually given tasks that presented problems with solutions from hypothetical students, accompanied by questions requiring students to contrast and compare the solutions. These tasks were followed by open-response estimation problems. The older children understood better than the younger children what was asked but were uncomfortable with estimation processes and outcomes. Acceptance of multiple estimates and rounding-then-computing rather than computing-then-rounding were both slow to develop. Recognition of the need to compensate for rounding errors increased with grade level. Schooling factors such as emphasis on unique answers and instruction on rounding and computional procedures seemed to influence results. Careful development of foundational concepts is recommended to prevent learning computational estimation as a set of algorithmic rules.

Student attitudes toward science and sciencerelated careers: A program designed to promote a stimulating gender-free learning environment

Abstract: A project designed to foster the full and fair participation of girls in high-school science classes addressed obstacles, both perceived and actual, to equal participation In order to modify existing classroom techniques and environments, a Teacher Intervention Program was designed By means of a workshop and periodic personal communications, teachers were sensitized to the importance of a stimulating, gender-free learning environment In addition, they were presented with a variety of methods and materials which had been shown to encourage girls in science Twelve teachers, who were selected randomly, taught in diverse communities throughout one Midwestern state The subjects tested were students in 24 general biology classes taught by the 12 teachers Although both qualitative and quantitative measures were used during the research, only the quantitative results are discussed in this paper Using ANOVA's, treatment group by student sex, a comparison of the mean scores was made for all students, as well as for all females and for all males The results indicated that the experimental group, compared to the control group, had significantly higher mean scores on tests of attitudes toward science, perceptions of science, extracurricular science activities, and interest in a science-related career

Plant-Feeding Nematodes in Deep-Rooting Desert Ecosystems

Abstract: In the Chihuahuan Desert of southern New Mexico, mesquite (Prosopis glandulosa) occurs in a variety of landscape positions where water may accumulate to varying depths. The structure of Chihuahuan Desert landscapes has changed dramatically in the past 100 yr with mesquite expanding from its original distribution (playa, arroyo) into grassland and dune ecosystems. Our objective was to examine spatial and seasonal distribution of plant—feeding nematodes and the potential importance of herbivory in four mesquite communities (playa, arroyo, dunes, grassland) hypothesized to differ in rooting depth and distribution. These sites were compared to a more shallow—rooted creosote bush (Larrea tridentata) community. Intact soil cores were recovered to depths of 13 m beneath the canopies of mesquite or creosote bush using a continuous sampling tube drilling system in the winter, spring, and fall on the Jornada LTER site, Las Cruces, New Mexico. Nematode density and root mass decreased with depth. Nematodes were found to the maximum depth of recovered roots only at the playa (11—12 m) and occurred as deep as 5—6 m at the arroyo, 2—3 m at the dunes, and 1—2 m at the grassland and creosote bush sites. At the playa, 75% of the nematodes and 90% of the roots were below 0.5 m, whereas, in the creosote bush system 79% of the roots and 99.7% of the nematodes were recovered in the upper 0.5 m of soil. Nematode diversity (seven genera) and endoparasite densities were greatest at the playa. Only ectoparasites (three genera) were found at the creosote bush system. Total nematodes across all sites were highly correlated with total soil N, NH4+, and PO4—3, but not NO3—. Nematodes were not positively correlated with soil moisture. Potential herbivory was best described by nematode numbers per gram root or an herbivory index (based on nematode density weighted by an impact factor for each genus), rather than the ratio of endoparasite:ectoparasite numbers. The herbivory index decreased in the order playa > creosote bush > dune > grassland > arroyo. The movement of mesquite into new habitats (grassland, dunes) is associated with shallow rooting, and relative to the playa, a greater allocation of roots to the upper 0.5 m soil layer, a decrease in nematode herbivory and diversity, and, a failure of the nematodes to be distributed throughout the entire rooting zone. The densities of ecto— and endoparasites varied with site, thus, plant—feeding nematodes should not be treated as a single guild since they have different effects on roots. Our study shows that in some ecosystems the majority of herbivory may occur at soil depths rarely studied. Although technically difficult to examine in ecosystems where deep—rooted plants occur, the potential importance of deep soil biota and their effects on plant growth and nutrient cycling should be considered.

Magnetic properties of Gd2CuO4 crystals.

Abstract: Magnetic-susceptibility and magnetization measurements on single crystals of the CuO2-planar compound Gd2CuO4 indicate copper moment ordering near 260 K, producing an internal field at the gadolinium site that induces substantial anisotropy in the magnetic response. Dilute substitutions for gadolinium and copper leave the essential physics unaffected. We suggest that copper ordering also occurs in Eu2CuO4 on the basis of substitutional studies but is not detected in other rare-earth-based compounds in this series. Rare-earth size appears to play an important role. © 1989 The American Physical Society.

Quality-specific effects of aging on the human taste system.

Abstract: Elderly persons are known to have elevated taste thresholds, with those for bitter more affected by age, for example, than those for sweet. Do analogous quality-specific effects occur at suprathreshold levels? Young (mean age = 20.3 years,SD = 2.99) and elderly (mean age = 72.5 years,SD = 4.58) subjects made magnitude estimates of sweetness, bitterness, sourness, and saltiness for the unmixed components sucrose, caffeine, citric acid, and NaCI at three concentration levels for each. They also made magnitude estimates of the separate taste qualities in two-component mixtures of sucrose with each of the other three qualities, at various levels of the two components in each mixture. Magnitude estimates of taste intensity were interweaved with magnitude estimates of the heaviness of six weights, which subjects were to judge on the same subjective intensity scale: This is the calibration feature of the method of magnitude matching, and permits the comparison of elderly and young subjects on the absolute intensity of tastes. When unmixed components were judged, elderly subjects found the characteristic tastes of caffeine and citric acid less intense than, but those of sucrose and NaCI as intense as, younger subjects did. In judging mixtures, the elderly found bitterness, but not the other three qualities, less intense than did the young subjects.

Recruiting survey respondents to mailed surveys: controlled trials of incentives and prompts

Abstract: Three controlled experiments tested the efficacy of 1) a postcard or telephone prompt, 2) a lottery, 3) monetary incentives, and 4) questionnaire length to recruit adult survey respondents to a random sample of residences in San Diego, California, during 1986-1988. In experiment 1, the group randomly assigned to receive a telephone call prenotification plus the lottery incentive responded 26-66% more frequently than did controls (p = 0.02) after a single mailing. The postcard plus lottery was 17-54% more effective than no intervention with controls (p = 0.05). A second mailing of the survey weakened these effects. In experiment 2, the group randomly assigned to receive a two-page survey with the lottery announcement responded 69% more frequently after one mailing (p = 0.03) and 53% more frequently after a second mailing (p = 0.04) than the group that received an eight-page survey without the lottery incentive. The shorter form alone or the lottery alone did not increase response rates significantly relative to the long form without a lottery. In experiment 3, a monetary incentive of $5.00 contingent on response to the second mailing of the survey increased the rate of response from initial "nonresponders" by 100% relative to control who received no incentive (p = 0.03) and 75% over those who received $1.00 not contingent on response (p = 0.04). Little sampling bias and no reactivity was attributable to the recruitment procedures.

The diageotropica mutant of tomato lacks high specific activity auxin binding sites.

Abstract: Tomato plants homozygous for the diageotropica (dgt) mutation exhibit morphological and physiological abnormalities which suggest that they are unable to respond to the plant growth hormone auxin (indole-3-acetic acid). The photoaffinity auxin analog [3H]5N3-IAA specifically labels a polypeptide doublet of 40 and 42 kilodaltons in membrane preparations from stems of the parental variety, VFN8, but not from stems of plants containing the dgt mutation. In roots of the mutant plants, however, labeling is indistinguishable from that in VFN8. These data suggest that the two polypeptides are part of a physiologically important auxin receptor system, which is altered in a tissue-specific manner in the mutant.

Skeleton of the Oldest Known Pinniped, Enaliarctos mealsi

Abstract: A nearly complete skeleton of the archaic pinniped Enaliarctos, found in late Oligocene or early Miocene rocks (approximately 23 million years old) of California, provides new evidence on the origin of pinnipeds. Enaliarctos retains many primitive features expected in the hypothesized common ancestor of pinnipeds. Skeletal modifications seen in Enaliarctos document swimming adaptations and indicate that pinnipeds primitively used the axial skeleton and both fore and hindflippers as sources of propulsion. Elongate hindlimbs with prominent bony processes (reflecting powerful musculature) suggest that Enaliarctos was more active on land than modern pinnipeds.

The Social Functioning of Depressed Patients: A Longitudinal Assessment

Abstract: The present study was designed to examine the social functioning of depressed patients. Depressed and nondepressed psychiatric outpatients and nondepressed nonpsychiatric community control subjects completed measures of social functioning at two points in time: the first while the depressed patients met criteria for a diagnosis of major affective disorder, and the second 7 to 10 months later. The results of this study indicated that depressed patients reported more impaired social functioning than did either the nondepressed patients or the community controls. This pattern of results suggests that social dysfunction is specific to depression, rather than characteristic of general psychiatric disorder. Furthermore, despite a significant reduction in depressive symptomatology in the second session, the social functioning of the depressed patients did not improve over the course of the follow-up period. The possible role of social dysfunction as a risk factor for depression is discussed, and directions for f...

Inhibition of interleukin-1 production by 1,25-dihydroxyvitamin D3.

Abstract: The hormonal form of vitamin D, 1,25-dihydroxyvitamin D3 [1,25-(OH)2D3], inhibits the proliferation of T lymphocytes and production of growth-promoting factors [including interleukin-2) (IL2) in CTLL2 murine cells. In this study, we investigated the role of monocytes in this hormone-mediated inhibitory effect, by testing the effects of 1,25-(OH)2D3 on the ability of the mitogenic lectin phytohemagglutinin (PHA) to induce T cell activation in either a monocyte-dependent or phorbol myristate acetate (PMA)-driven (monocyte-independent) system. The results indicate that proliferation of T cells and production of growth-promoting factors are inhibited by 1,25-(OH)2D3 only in the monocyte-dependent system. Preincubation of monocytes with 1,25-(OH)2D3 for various periods of time and subsequent removal of the hormone resulted in inhibition of the PHA-driven proliferation of T cells. Preincubation for 2 h resulted in 20% inhibition, while preincubation for 36 h reduced proliferation to 50% of the control ...