• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 2096
  • 1526
  • 908
  • 860
  • 310
  • 212
  • 211
  • 153
  • 153
  • 153
  • 153
  • 153
  • 148
  • 147
  • 65
  • Tagged with
  • 7443
  • 1434
  • 1304
  • 1264
  • 1263
  • 857
  • 824
  • 678
  • 671
  • 668
  • 668
  • 623
  • 445
  • 444
  • 395
  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
161

Monumental past : interpreting the meanings of ancient monuments in later prehistoric Mecklenburg-Vorpommern (Germany)

Holtorf, Cornelius January 1998 (has links)
No description available.
162

Geology of the Ruin Basin area, Gila County, Arizona

Bejnar, Waldemere, 1920- January 1952 (has links)
No description available.
163

THE IMPLICATIONS OF ATMOSPHERIC POLLEN RAIN FOR FOSSIL POLLEN PROFILES IN THE ARID SOUTHWEST (AEROBIOLOGY, PALAEOBOTANY, TAPHONOMY, PRESERVATION).

O'ROURKE, MARY KAY. January 1986 (has links)
I compared atmospheric and soil pollen values to determine taphonomic influences on pollen in Southwestern soils. Burkard traps sampled atmospheric pollen for six years from multiple sites in Tucson, Arizona. Tauber and soil samples were collected for two years at Tumamoc Hill (Tucson). Morus, Ambrosia, Gramineae, and Chenopodiaceae-Amaranthus characterize Tucson's airborne pollen. Artemisia, Garrya and summer Pinus pollen are transported from the mountains. Annual pollen capture is similar between Burkard and Tauber samplers. Atmospheric pollen is seasonally variable; annual variability is low. Spatial variability among sites is low. Pollen concentrations vary widely among sites, but taxonomic composition remains constant. Reentrained soil pollen comprises 11% of the airborne pollen. Gramineae and Chenopodiaceae-Amaranthus pollen comprise 90% of the reentrained pollen. Pollen reentrainment varies seasonally. High maximum and minimum temperatures, low dew point and moderate wind speeds are associated with maximum atmospheric pollen concentrations. Winds preceding summer storms cause increased pollen concentrations. Deterioration characterizes pollen from soils. Chenopodiaceae-Amaranthus, Ambrosia, Other Compositae and Graminear are commonly found; Morus is rarely found. Pinus, Sphaeralcea, Boerhaavia and Kallstroemia are present in low numbers. These taxa have thick pollen walls, and they resist destruction. Seasonally collected soil samples have similar pollen spectra. Seasonal airborne pollen variability does not affect the soil pollen spectra. Inoculated soil pollen is well preserved, but pollen is lost rapidly. After one year, pollen concentrations approached background levels for seven of the eight pollen taxa tested. Solidago remained an order of magnitude higher. Pollen morphology may play a role in differential pollen loss. Pollen from the inoculated plots is lost through post-mortem transport. Pollen in soils is time-averaged and exhibits little temporal variability. The average airborne pollen spectra differs from the pollen in the soil. Soil pollen was degraded; inoculated plot pollen was well preserved. I conclude airborne pollen contributes little to the soil pollen of Tumamoc Hill. The soil pollen spectra is affected by selective- or non-deposition of airborne pollen (e.g. Morus), differential pollen destruction, and differential post mortem transport.
164

PHENOLOGICAL STUDIES OF THREE NATURAL STANDS OF JOJOBA (SIMMONDSIA CHINENSIS (LINK) SCHNEIDER) NEAR TUCSON, ARIZONA.

DE OLIVEIRA, JONAS PAES. January 1983 (has links)
Jojoba (Simmondsia chinensis (Link) Schneider) is a wild desert shrub known for the liquid wax extracted from its fruits. As the plant undergoes the first stages of domestication into a commercial crop, it is important to understand its response to environmental factors and to study its regularity of production. Phenological studies including vegetative growth, floral biology, seed production, and seed wax content were conducted from 1979 to 1982, complementing investigations in 1978 in three natural stands of jojoba, near Tucson, Arizona and air and soil precipitation, temperatures were continuously recorded at each study site. Periods of vegetative growth were identical for staminate and pistillate plants and were generally observed after the occurrence of measurable rainfall. In late winter vegetative growth occurred after monthly average minimum temperatures of 4-5°C, although local responses to small differences in temperature were observed. Anthesis was first observed in late February or early March. Fruits generally originated from flower buds produced in the previous summer. Incidence of fruit abortion was greatest in May and June. Variations from year to year in seed production from 1978 to 1982 suggested biennial bearing. Factors in addition to frost incidence were believed to be associated with the absence of seed production in 1979 and the low seed crop of 1981. Levels of foliar total nonstructural carbohydrates were not found to be appreciably different between a low production year and a high production one. Seed wax percent was found to be independent of annual variation in seed production. Plant growth and productivity was greatest on the site with the best developed soil profile, highest water holding capacity and highest exchangeable sodium percentage.
165

Geology and geochemistry of the Santa Eulalia mining district, Chihuahua, Mexico

Megaw, Peter Kenneth McNeill January 1990 (has links)
Santa Eulalia contains two separate, contrasting Pb-Zn-Ag deposits. The East Camp consists of a symmetrically zoned calc-silicate skarn with distal sulfide and tin-bearing orebodies; whereas the west Camp is composed of massive sulfide orebodies with minor proximal calc-silicate skarn and isolated intermediate calcic-iron skarns. Mineralization and alteration are zoned within each camp but do not overlap. Sulfide mineralization in both camps consists of pyrrhotite, sphalerite, galena, and pyrite with lesser amounts of arsenopyrite and chalcopyrite. The East Camp is apparently richer in zinc and copper than the West camp. Mineralization is temporally and spatially related to geochemically identical felsite intrusions which apparently have a common source. Mineralizing fluids followed these felsites through a thick section of evaporites and organic-rich shaly limestones into clean, homogeneous, relatively undeformed, limestone hosts. West Camp mineralization occurs along an interconnected network of vertically discontinuous tight fissures and sill contacts, whereas East Camp mineralization is located along vertically throughgoing faults and dike contacts. strata-bound, but not stratiform, mantos extend off discordant chimneys in both camps. Ore textures reveal that mineralization occurred primarily by limestone replacement. 21 Pressure-corrected primary fluid inclusion homogenization temperatures in fluorite range from 220 to 490 deg. C. Salinities are bimodal with high-salinity (>26.3 equivalent wt% NaCl) and low-salinity (1-12 equivalent wt% NaCl) populations. Mineralogical constraints indicate that the hydrothermal fluids were acid and reduced. Sulfur isotope analyses indicate that the ore fluids varied from -17 to +4 permil without correlation to iron-sulfide species, temperature, or salinity. Co-existing sulfides are commonly in isotopic disequilibrium. Sulfur isotopes from the West Camp are crudely zoned, but no consistent patterns exist in the East Camp. Oxygen and carbon isotope analyses of limestone wallrocks reveal a distinct isotopic alteration halo. A single analysis of gangue calcite from each camp indicates that the ore fluids contained non-carbonate-derived carbon and oxygen, possibly of magmatic origin. Metals were apparently transported as chloride complexes and deposited through coupled dissolution-precipitation replacement reactions. Most ore sulfur apparently came from diagenetic pyrite and sedimentary anhydrite, but some of the sulfur may have had a magmatic source. The metals probably came from the felsite parent magma and this magma may have also contributed fluids. Close similarities between Santa Eulalia and numerous other intrusion-related carbonate-hosted deposits in northern Mexico reinforce these interpretations.
166

The interaction of parent material and eolian debris on the formation of soils in the Silverbell Desert Biome of Arizona

Rosenthal, Randi Helaine, 1961- January 1987 (has links)
The objective of this study was to determine whether the properties of four soils of the Silverbell Desert Biome could be attributed solely to the parent material or alternately reflect the nature of contributions, if any, from eolian dust. The Anklam, Lajitas and Chimenea soils, classified as fine-loamy, mixed, thermic Lithic Haplargids and the Greyeagle (coarse-loamy, mixed, thermic, Lithic Torriorthent) soil formed an andesite, basalt, granite and basalt, respectively. They occur on gently sloping, stable terrain in Pima County, Arizona. The four soils were studied through field descriptions, particle size analysis, mineralogical analyses of light and heavy sand fractions and clay mineral identification. The light mineral fraction of all four soils is directly affected by the parent material and is influenced much less, if at all by eolian activities due to the larger particle sizes. It is concluded that the genesis of soils was influenced by both the underlying rock and the input of eolian particulates. (Abstract shortened with permission of author.)
167

The impact of urban open space on residential property values in the Tucson basin

White, Jody Lynn, 1954- January 1989 (has links)
The objective of this study was to estimate the effects of various types of urban open space on single-family residential property values in the Tucson basin in 1986. The statistical results were mixed. Urban parks which emphasize recreational facilities decreased housing prices whereas private golf courses and natural open space areas increased property values. The negative impact on housing price appears to be the result of disamenities caused by recreational consumption (noise, traffic, congestion), and recreational facilities (blocked views). The positive impact on price seems to be a function of the benefits derived from such amenities as urban wildlife and scenic mountain and city views. Public decision-makers need values of urban natural amenities to make informed policy and management decisions. The implicit prices generated here are useful in assessing whether the market prices of homes are expressing the benefits of urban open space.
168

Electrical methods surveys in southern Arizona for hydrogeological investigations

Didi, Didace, 1952- January 1990 (has links)
The central induction TEM and CSAMT strengths and weaknesses were analyzed at the San Xavier geophysical test site. TEM results indicate that the depth of investigation of the TEM sounding data is limited by the noise level. CSAMT data are contaminated by static shift effects due to shallow geological inhomogeneities or topography. CSAMT data are also contaminated by the transmitter overprint which depends on the geology beneath the transmitter dipole and the receiving stations. In the Miami Wash-Pinal Creek area of Arizona, where the groundwater contamination was to be studied by electrical methods, the complex resistivity method was first used. Results in the Miami Wash-Pinal Creek area show a trend which consists of a high-low-high trend in the resistivity/I.P. curves for soundings located in the contaminated zone and of an increase of the I.P. curve in the uncontaminated zone.
169

Economic geology and photogeology of the Tsumeb area, South West Africa

Readdy, Leigh Arthur, 1936-, Readdy, Leigh Arthur, 1936- January 1972 (has links)
No description available.
170

ASEAN a perspektivy jeho vnější integrace / ASEAN and challenges of its external integration

Svoboda, Jan January 2010 (has links)
This paper is focused on an analysis of current regionalism in Asia-Pacific region and on evaluation of creation of relatively wide and relatively deep regional integration. Possible benefits of this integration concept can be exemplified by development of Association of South East Asian Nations (ASEAN) whose member states have substantially different interests due to historic and socioeconomic reasons. However, ASEAN was able to overcome these different interests by a specific integration model which is based on mutual trust, consensual decision-making and gradual changes. As a result, natural suspicions were eliminated to some extent and member states were able to deepen their integration. Main powers in the region noticed its success and they began to strive to develop closer relations not only with ASEAN, but also with other regional powers through ASEAN structure.

Page generated in 0.0584 seconds