Human occupation of the northern Arabian interior during early Marine Isotope Stage 3          下载免费PDF全文

Richard P. Jennings  Ash Parton  Laine Clark‐Balzan  Tom S. White  Huw S. Groucutt  Paul S. Breeze  Adrian G. Parker  Nick A. Drake  Michael D. Petraglia 《第四纪科学杂志》2016,31(8):953-966

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Drained cavity expansions in soils of finite radial extent subjected to two boundary conditions     

Mohammad Pournaghiazar  Adrian R. Russell  Nasser Khalili 《国际地质力学数值与分析法杂志》2013,37(4):331-352

The problem of drained cavity expansion in soils of finite radial extent is investigated. Cylindrical and spherical cavities expanded from zero radius subjected to either constant stress or zero displacement at the finite boundary are considered. The generalised analytical solution procedure presented enables more advanced constitutive models to be implemented than have been possible in previous studies. Results generated for Sydney quartz sand highlight substantial differences between cavity limit pressures for the two boundary conditions and for boundaries of finite and infinite radial extent. This is of significance in accounting for boundary effects when interpreting cone penetration tests conducted in calibration chambers. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献   

Extreme events as drivers of early human behaviour in Africa? The case for variability,not catastrophic drought     

David S. G. Thomas  Sallie L. Burrough  Adrian G. Parker 《第四纪科学杂志》2012,27(1):7-12

Extreme Late Quaternary climatic events, sometimes of considerable continental extent, are being proposed as major contributors to ancestral human behaviour, particularly migration, in Africa. Most recently, a catastrophic drought in the Afro‐Asian monsoon region has been proposed for 16 000–17 000 years ago, driven by global impacts of the Heinrich event 1 (H1), with potentially significant consequences for Palaeolithic cultures. We provide a new analysis of the assertion and find, on examination of a wide set of palaeoenvironmental records, that the scale and extent of the proposed drought is not supported. While some parts of the African tropics, close to the equator, do appear dry at this time, data for the tropics as a whole suggest markedly variable terrestrial conditions, with some environmental systems experiencing very positive hydrological excursions during H1. We contend that in the quest for evidence of climate drivers of ancestral human behaviour, the variability associated with spatially and temporally complex climatic conditions is a significant factor in itself. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献   

Geophysical surveys of the sediments of Loch Ness,Scotland: implications for the deglaciation of the Moray Firth Ice Stream,British–Irish Ice Sheet     

Andrew J. Turner  John Woodward  Stuart A. Dunning  Adrian J. Shine  Chris R. Stokes  Colm Ó Cofaigh 《第四纪科学杂志》2012,27(2):221-232

We present results from three geophysical campaigns using high‐resolution sub‐bottom profiling to image sediments deposited in Loch Ness, Scotland. Sonar profiles show distinct packages of sediment, providing insight into the loch's deglacial history. A recessional moraine complex in the north of the loch indicates initial punctuated retreat. Subsequent retreat was rapid before stabilisation at Foyers Rise formed a large stillstand moraine. Here, the calving margin produced significant volumes of laminated sediments in a proglacial fjord‐like environment. Subsequent to this, ice retreated rapidly to the southern end of the loch, where it again deposited a sequence of proglacial laminated sediments. Sediment sequences were then disturbed by the deposition of a thick gravel layer and a large turbidite deposit as a result of a jökulhlaup from the Spean/Roy ice‐dammed lake. These sediments are overlain by a Holocene sheet drape. Data indicate: (i) a former tributary of the Moray Firth Ice Stream migrated back into Loch Ness as a major outlet glacier with a calving margin in a fjord‐like setting; (ii) there was significant sediment supply to the terminus of this outlet glacier in Loch Ness; and (iii) that jökulhlaups are important for sediment supply into proglacial fjord/lake environments and may compose >20% of proglacial sedimentary sequences. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献   

The connection of geodynamics with seismicity patterns     

Adrian E. Scheidegger 《Natural Hazards》1988,1(1):5-13

When a study is to be made of seismic risks, the present-day geodynamic conditions are of fundamental importance: Earthquakes do not happen by themselves, they do have a cause. The cause of earthquakes is that the tectonic stresses exceed a critical limit. The build-up of these stresses is conditioned by the geodynamic processes occurring in the region in question. A knowledge of the geodynamics characteristic of a region is therefore fundamental for seismic risk studies. The general methodology for making such a geodynamic study is based on the entire set of manifestations of the plate-tectonic conditions of that region: these include the mechanism of earthquakes, the stresses observed in mines, the orientation of surface joints and even the direction of river valleys. Examples of geodynamic studies and their bearing on seismic risks are shown from various areas of the world, notably from China, India, and Colombia.  相似文献   

Vibrational spectra,lattice dynamics and chemical constitution of oxides     

Adrian N. Lazarev 《Physics and Chemistry of Minerals》1988,16(1):61-72

The relationships among lattice dynamics of oxides and their chemical constitution are discussed in terms of the concept of dynamic crystal chemistry. A new approach to the design of a dynamic model of an ionic-covalent crystal combining molecular force constants with explicit treatment of long-range electrostatic forces in a lattice is outlined and its applications exemplified. The conditions of introduction of scaled quantum chemical force constants of a suitable molecular system into the secular equation for lattice vibrations are determined rigorously. The importance of unified treatment of stability conditions and various dynamic properties of crystals including phonon spectra, macroscopic elastic and piezoelectric constants etc., is emphasized. Several results of ab initio quantum chemical SCF computations by the gradient method for molecular species containing silicon-oxygen bonds are presented and are used to explain some empirical regularities in silicate structures.  相似文献   

Going Home: The Migration of Puerto Rican-Born Women from the United States to Puerto Rico*     

Adrian J. Bailey  Mark Ellis 《The Professional geographer》1993,45(2):148-158

This paper analyzes the migration of Puerto Rican-born women from the United States to Puerto Rico using longitudinal data. We hypothesize that sojourn length in the United States is a function of both structural (macro-level economic and cultural factors) and behavioral (micro-level life-cycle experiences and personal attributes) variables. We test these hypotheses by estimating a proportional hazards model. The parameter estimates of this model indicate that sojourn length in the United States, and thus the decision to return to Puerto Rico, is a function of wage trends and community characteristics on the mainland plus a number of individual attributes that include education, marriage, and childbirth.  相似文献   

The Faunal Remains from Evron Quarry in Relation to Other Lower Paleolithic Hominid Sites in the Southern Levant     

Eitan Tchernov  Liora Kolska Horwitz  Avraham Ronen  Adrian Lister 《Quaternary Research》1994,42(3)

The mammalian assemblage and archaeological finds from the Lower Palaeolithic hominid site of Evron Quarry, situated on the northern coastal plain of Israel, are described and discussed. In their lithic and faunal composition, the sites of Latamne (QfIII) (Latamne Formation, Orontes, Syria) and Sitt Markho (Nahr elKebir, Syria) resemble Evron and are probably contemporaneous. It is suggested here, based on their lithic and faunal composition, that these sites may be chronologically closer to the site of Ubeidiya ('Ubeidiya Formation, Jordan Valley, Israel; 1.4 myr) than to the sites of Gesher Benot Ya'akov (dated as <800,000 yr B.P.), which differs in both aspects from Evron. The mammalian faunule from Evron comprises a biogeographical mixture, a result of biotic exchanges with Africa, the Oriental region, and the Palaearctic. This exchange may have been associated with a post-'Ubeidiya hominid dispersal, either from Africa or south Asia via the Levantine "corridor."  相似文献   

Telecommunications and the Large City-Small City Divide: Evidence from Indiana Cities*     

Patrick Alles  Adrian Esparza  Susan Lucas 《The Professional geographer》1994,46(3):307-316

Urban systems are increasingly dominated by large cities that house a disproportionate share of telecommunications infrastructure. This paper investigates whether telecommunications is defining a technological divide between large and smaller cities. The paper provides a conceptual basis for large-city dominance and presents the results of surveys that investigate the use of telecommunications in medium and small Indiana cities. The survey data indicate that telecommunications is used by the set of Indiana cities, but is less prevalent among the set of smallest cities. Chi-square tests, however, suggest that city size does not adequately explain these variations in use.  相似文献   

The significance of surface joints     

Adrian E. Scheidegger 《Surveys in Geophysics》1985,7(3):259-271

This brief review demonstrates the significance, on a global scale, of joints as shearing surfaces in the neotectonic stress field. Thus, the principal directions of the neotectonic stress field can be determined by a statistical treatment of joint orientation data. These principal stress directions agree with those postulated from plate tectonic theory in every case, on five continents.  相似文献