Showing papers by "San Diego State University published in 1983"

Characteristics of Adopters and Non-Adopters of Home Computers

Abstract: SUMMARY AND IMPLICATIONS This study investigated the profile of the adopter of a technological innovation, the home computer. The study used a simple trait + behavior model, whereas Rogers' diffusion model (Rogers 1962; Rogers and Shoemaker 1968) is a contingency model: trait + communication + behavior. While it is useful to examine the interaction be- tween traits and innovative characteristics, our approach only tests part of Rogers' model. To some extent, the adop- ter profile is similar to that of the adopter of many other types of innovations: middle-aged, higher income, more education, opinion leader, information seeker, and so on. On the other hand, the profile also suggests that the adopter is a "logical introvert." This finding is not unexpected, given consideration of the complex, technological nature of the innovation. We suggest that the nature of the adopter of an innovation is partially a function of the characteristics of the innovation itself-viz., the complexity of the home computer, the familiarity required to be cognizant of its relative advantage, and the need for some other type of computer-oriented experiences before it can be perceived as compatible. We have used the concept of consumer creativity in an attempt to explain the differences between the adopter pro- file we found and that found in studies of symbolic inno- vations. Hirschman (1980b) presents a model showing the hypothesized relationship of consumer creativity to adop- tive i~novativeness; using Welsh's (1975) traits of origence and intellectence, we hypothesized that home computer adopters are more likely to exhibit characteristics typical of the low origenceihigh intellectence individual (introverted, rational, quantitatively oriented, unsocial). Our results pro- vide general support that adopters of home computers have a profile similar to that individual: they are homebodies who are interested neither in the arts nor in innovations that would enhance their ability to communicate. The hypoth- esis that the low origenceihigh intellectence individual is likely to be an early adopter of a technological innovation was tested in an indirect manner, by comparing the adopter profile to that found by Welsh (1975). Future research should direct measures of the dimensions in order to relate them to early adoption of technological pr~ducts.~ More-over, there is a clear need for research investigating the role that the two creativity dimensions play in the adoption of different types of innovations. Past consumption experiences play an integral part in Hirschman's (1980a, 1980b) conceptualization of consumer

Smallest-last ordering and clustering and graph coloring algorithms

Abstract: Smallest-last vertex ordering and prlonty search are utdlzed to show for any graph G = (IT, E) that the set of all connected subgraphs maxunal with respect to their minimum degree can be determined in O(I EI + I VI) time and 21El + O(I VI) space It is further noted that the smallest-last graph coloring algonthrn can be unplemented in O(I E I + I V[) tune, and particularly effective aspects of the resulting coloring are discussed.

Thermodynamic length and dissipated availability

Abstract: New expressions for the availability dissipated in a finite-time endoreversible process are found by use of Weinhold's metric on equilibrium states of a thermodynamic system. In particular, the dissipated availability is given by the square of the length of the corresponding curve, times a mean relaxation time, divided by the total time of the process. The results extend to local thermodynamic equilibrium if instead of length one uses distance (length of the shortest curve) between initial and final states.

The role of ectomycorrhizas in drought tolerance of douglas‐fir seedlings *

Abstract: SUMMARY Experiments were conducted to test the relative ability of mycorrhizal and non-mycorrhizal Douglas-fir [Pseudotsuga menziesii (Mirb.) Franco] seedlings to tolerate and recover from drought conditions, using reduction in CO2 fixation as an overall indicator of plant moisture stress. Seedlings were watered daily or conditioned to cyclic drying and re-wetting of the soil. Net photosynthetic rates of mycorrhizal and non-mycorrhizal seedlings watered daily did not differ significantly; however, drought-stressed mycorrhizal seedlings fixed CO2 at a rate ten times that of non-mycorrhizal seedlings. Total leaf water potentials of mycorrhizal plants were lower (more negative) than those of non-mycorrhizal plants but they recovered more rapidly. Non-mycorrhizal seedlings and seedlings inoculated with four ectomycorrhizal fungus species were allowed to become desiccated, then were rewatered and compared for their ability to tolerate and recover from drought. Seedlings inoculated with Rhizopogon vinicolor were less affected by drought than any of the other mycorrhizal or non-mycorrhizal treatments. Net photosynthetic rate of Rhizopogon-inoculated seedlings 24 h following re-watering was seven times that of non-mycorrhizal seedlings. The transpiration rate of Rhizopogon-inoculated seedlings was low before desiccation, declined rapidly during the drought period and, after re-watering, quickly resumed a rate higher than that for other treatments.

Drosophila muscle myosin heavy chain encoded by a single gene in a cluster of muscle mutations.

Abstract: Drosophila muscle myosin heavy chain is encoded by a single-copy gene which is transcribed during both larval and adult development. This myosin gene maps to a chromosomal locus distant from any of the actin genes, but is within a cluster of flight muscle mutations.

Age-related effects on the threshold, psychophysical function, and pleasantness of menthol.

Abstract: Participants were 20 persons half of whom were 18 to 26 years of age (M = 21) and half of whom were over 65 years (M = 75). All were ambulatory, noninstitutionalized, and reported good to excellent health. The stimulus was menthol delivered in air to the nostrils. Threshold was measured using the up-down staircase method. Intensity and pleasantness were measured by magnitude estimation. The average threshold for the elderly participants was significantly higher than for young participants. The median slope of the intensity function was steeper by a factor of two for younger adults. The average pleasantness functions were steeper for the younger persons. Finally, although the younger adults found menthol less pleasant with repeated exposure, the elderly persons showed no effect of exposure. The results suggest that the average, healthy elderly person's odor/trigeminal world differs from that of the young adult. Further experiments are exploring the relative contributions of olfactory, trigeminal, and cognitive factors in producing this change.

Periodic response of a sliding oscillator system to harmonic excitation

Abstract: SUMMARY This paper deals with the periodic response of an oscillating system which is supported on a frictional interface. The base excitation is assumed harmonic and the frictional force is assumed to be of the Coulomb type. Though each segment of the motion of such a system is described by linear equations, its complete response is highly non-linear and varied. The most fundamental periodic solutions are derived analytically and numerically. The results indicate that such a system has several subharmonic resonant frequencies and that while the friction reduces the peak response of the system when it is excited at its ‘fixed-base’ natural frequency, w,, the sliding can induce considerably higher levels of response, when compared with those of a non-sliding, fixed-base system, for frequencies less than w,. The results obtained herein may find application in the area of vibration isolation.

Photodissociation of NH3 at 106–200 nm

Abstract: The absorption and fluorescence cross sections for NH3 are measured in the 106-200 nm region using synchrotron radiation as the light source. The threshold wavelengths for the production of the NH (b to X) and NH (c to a) emissions from NH3 dissociation are measured and compared with previous measurements. The heat of formation of NH determined from these thresholds agrees well with the value determined from thermochemical data. The process of dissociation of NH3 into NH2(2AL) and H2(S) has a significant quantum yield whose maximum at 134 nm is about twice the NH(c) production yield. All the vibronic levels of the B and C states produce the NH2(2A1) emission, contrary to previous theoretical interpretations.

Freshwater Impacts in Normally Hypersaline Marshes

Abstract: Heavy rainfall in 1978 and 1980 caused flooding of southern California salt marshes. Examination of three marshes demonstrated a broad range of freshwater effects which correlated with the degree of change in soil salinity. At Tijuana Estuary (1980), a short-term reduction in the salinity of normally hypersaline soils was followed by a 40% increase in the August biomass of Spartina foliosa. At Los Penasquitos Lagoon (1978), a longer period of brackish water influence was followed by a 160% increase in August biomass of Salicornia virginica. At the San Diego River (1980), flood flows were augmented by major reservoir discharge. Continuous freshwater flow leached most of the marsh soil salts and caused replacement of halophytes by freshwater marsh species. The first two cases probably fell within the normal range of flooding events, even though the hydrology of both watersheds has been modified. The vegetation response was functional; productivity increased but there was no major change in species composition. As expected, vegetation rapidly returned to preflood conditions. However, the long-term freshwater flow in the Dan Diego River was unnatural. Floral composition changed as soils were leached of salts. Recovery following the return of saline soils has been slow because many native halophytes are not good colonizers. The system's resilience is limited, and modification of natural stream discharge can cause permanent changes in coastal wetlands.

Simulating carbon accumulation in northern ecosystems

Abstract: A model of the carbon balance in arctic and boreal forests has been developed to estimate the effects of higher carbon diox ide levels in the atmosphere on northern ecosystems. The model predicts that northern ecosystems should accumulate 5-10% of the carbon added to the atmosphere each year. Ac cumulation rates should increase by 2-8 times by year 2020 depending on the availability of nutrients. The rates of change in several processes are only estimates. The predictions are subject to large errors because of the complexity of ecosys tems interactions and the absence of data on the long-term ef fects of higher temperature and atmospheric CO2 levels. More differentiation of plant types, more feedback interactions, and more stochastic variations could improve the model. How ever, the results show that carbon accumulation in northern ecosystems is a significant fraction of the terrestrial carbon flux. The response of these systems is therefore important in predicting global carbon balance.

Community Structure of Intertidal Sandy Beaches in New South Wales, Australia

Abstract: Sand beaches comprise approximately 60% of the intertidal shoreline of New South Wales. However, there are no published accounts of the sandy beach fauna in New South Wales, or for that matter, for any sandy beaches in Australia. The shoreline, particularly in the vicinity of Sydney, is exposed to a heavier wave regime than that of most other coasts throughout the world (Short, Wright 1981, Wright 1976, Wright et al. 1979). Hence the infauna of exposed sandy beaches inhabit an especially rigorous physical environment.

Ornitholimnology: Effects of grazing by the Andean flamingo (Phoenicoparrus andinus).

Abstract: Experimental exclusion of the Andean flamingo (Phoenicoparrus andinus) from shallow water areas of a salt lake in the Bolivian Andes caused large increases in the biomass of microorganisms inhabiting the surface sediments, especially a large diatom (Surirella wetzeli), amebas, ciliates, and nematodes. This is a conservative demonstration of the influences that water birds in general exert on the structure of aquatic ecosystems.

Advances in somatotype methodology and analysis

Abstract: During the past four decades, different approaches to somatotyping have resulted in changes in methods and analyses. The shift from a static or typological to a dynamic or phenotypical viewpoint is reviewed and different methods are summarized. Somatotype terminology and new concepts and techniques of analysis are presented as are details of two- and three-dimensional analyses. Descriptive and comparative statistical procedures are demonstrated through use of distances between somatotypes as a whole. Somatopoints, somatoplots, somatotype dispersion and attitudinal distances, t and F ratios between somatotype samples, correlation, intensity, and migratory distance are described. Suggestions are also made for approaches to somatotype analysis.

A Survey of Software Engineering Practice: Tools, Methods, and Results

Abstract: The results of a survey of software development practice are reported and analyzed. The problems encountered in various phases of the software life cycle are measured and correlated with characteristics of the responding installations. The use and acceptance of the term "software engineer" is investigated, and the functions and background of persons identified as software engineers are reported. The usage of a wide variety of software engineerilng tools and methods is measured; conclusions are drawn concerning the usefulness of these techniques.

Existence and stability of travelling wave solutions of a nonlinear integral operator

Abstract: In this paper, we establish the existence and stability property of travelling wave solutions of a nonlinear integral operator in the inferior case.

The influence of annual precipitation, topography, and vegetative cover on soil moisture and summer drought in southern California.

Abstract: The influence of annual precipitation and vegetation cover on soil moisture and on the length of the summer drought was estimated quantitatively using 9 years of soil moisture data collected at Echo Valley in southern California The measurements support the conclusions that in the semi-arid mediterranean climate a soil drought will occur regardless of vegetation cover and annual precipitation, but the length of the drought is greatly dependent on soil depth and rockiness Evergreen species which can survive this drought tend to accentuate the drought, especially in deep soil levels, by developing a canopy with a large transpiring surface

Herbivory and seedling establishment in post-fire southern California chaparral

Abstract: A caging experiment was conducted to determine the effects of herbivorous insects and small mammals on first-year establishment of Ceanothus greggii (ceanothus) and Adenostoma fasciculatum (chamise) seedlings in post-fire chaparral. Insect herbivory had no effect on either species. Observations of tagged seedlings revealed that nearly all herbivory was due to small mammals, and was preferentially greater for ceanothus. When seedlings were protected from herbivory chamise experienced higher mortality. Small-mammal herbivore pressure on ceanothus seedlings tipped the survivorship balance for unprotected seedlings in favor of chamise, allowing a relatively higher establishment of chamise seedlings during the first growing season after chaparral fire.

Demography of northern elephant seals, 1911-1982.

Abstract: Northern elephant seals (Mirounga angustirostris) were hunted to near extinction in the 19th century. Protection has allowed them to recolonize former habitat on islands off California, where the population is increasing more than 14 percent per year. Immigration of young pregnant females from Baja California initiated the California rookeries but is responsible for only a small part of recent population growth. Almost 25,000 northern elephant seal pups were born in the species' range in Mexico and the United States in 1982 in comparison with only six known births in 1911 .

Effects of nicotine on weight change and food consumption in rats.

Abstract: The present study was designed to test the effects of nicotine and nicotine withdrawal on weight change and food consumption in rats. Twelve male and 12 female three month old Sprague-Dawley rats were divided 3nto three treatment groups: 0.2, 0.4, and 0.6 mg nicotine/kg body wt. Half were given subcutaneous nicotine treatment for three weeks and then saline for three weeks; treatment sequence was reversed for the other half. Injections were administered three times daily throughout the experimental period. Prior to treatment, baseline measures were established for both food consumption and weight. Mean differences in weight change were calculated on a weekly basis throughout the experiment. Overall tests indicate that nicotine withdrawal produced significant (p<0.05) weight gains and nicotine administration produced inhibition of weight gain. A significant sex × drug × time interaction (p<0.05) demonstrated that food consumption increased when nicotine was discontinued and decreased when nicotine was administered. Specific comparison tests showed these effects on food consumption and weight were strongest at the 0.6 level and that larger effects were obtained for males than for females.

Ethnic Composition of Special Education Programs in California.

Abstract: The purpose of this study was to investigate the racial composition of mental retardation (MR), speech impairment (SPEECH), serious emotional disturbance (SED), and specific learning disability (SL...

Prehistoric Maya wetland agriculture and the alluvial soils near San Antonio Rio Hondo, Belize

Abstract: The prehistoric Lowland Maya supported an elaborate civilization, which reached peak population densities in the tropical forests of Guatemala, Belize and southern Mexico during the Classic period between AD 300 and 900. It has been proposed that the Maya turned to labour-intensive construction of raised planting platforms in wetlands for year-round cultivation. Excavations at San Antonio Rio Hondo, northern Belize1, provided the first archaeological data for this hypothesis. In our analysis of data from the San Antonio site, we conclude that the only indisputable evidence that prehistoric wetland cultivation occurred comes from a time before peak population of the Classic period, and that the technique required less labour than previously envisioned. Exploitation of swampy terrain initially involved dry-season cropping without extensive ditching and later ditching, probably for soil drainage.