bluuebunny/crossref_metadata_2025 huggingface dataset:
Specifying a role‐based guide for learning to work with an enterprise framework
Authors: Hasselbring Wilhelm , van den Houdt Ralph
Published: October 2002

Learning to work with enterprise frameworks requires considerable effort, because of the inherent complexity of all the knowledge that is needed. However, different roles in project teams need to learn different knowledge components according to the different tasks to be performed. A role‐based guide that has been developed for new developers in the California projects at the software house International Business Systems, Inc. (IBS) Consist is presented. The California projects develop financial applications based on the IBM SanFrancisco enterprise framework. The requirement for this guide originates in the need to guide (new) project members in learning the required skills for being able to work productively after focused training for the California projects.

The starting point for this guide is the IBS development process. The individual tasks during the different phases in the process are specified by means of the Unified Modeling Language (UML) use case diagrams. An important property is that the guide is role‐based to allow new project members to focus on their roles in the project, while learning to work with the framework. For each role, a UML activity diagram guides one to find the right paths for learning the required skills (which we call knowledge components) for the particular project role. The knowledge components are related to the tasks in the development process and to the roles. For all roles, at least some basic knowledge of the UML is required. Therefore, it is reasonable to specify this learning guide by means of the UML. This paper illustrates the use of the UML for specifying such a guide in a specific setting, namely the California projects of IBS Consist. Copyright © 2002 John Wiley & Sons, Ltd.
Dose‐dependent effects of Δ9‐tetrahydrocannabinol on rates of local cerebral glucose utilization in rat
Authors: Freedland Cory S. , Whitlow Christopher T. , Miller Mack D. , Porrino Linda J.
Published: October 2002

Recent reports have demonstrated that Δ9‐tetrahydrocannabinol (Δ9‐THC) stimulates locomotor activity at low doses (<2.5 mg/kg), while higher doses (>2.5 mg/kg) produce decreases in spontaneous activity. Using quantitative 2‐[14C]deoxyglucose (2‐DG) autoradiography, we systematically studied the effects of acute Δ9‐THC on rates of local cerebral glucose utilization. The first series of experiments was designed to determine if Δ9‐THC‐mediated changes in cerebral metabolism followed a clear dose–response relationship. Adult male Sprague‐Dawley rats were treated with either vehicle or Δ9‐THC (0.25–2.5 mg/kg) and the 2‐DG procedure was initiated 15 min following exposure. Administration of 2.5 mg/kg Δ9‐THC produced significant decreases in cerebral metabolism in most brain regions studied. In contrast, administration of 0.25 mg/kg Δ9‐THC produced no significant alterations in any brain region studied, while 1.0 mg/kg of Δ9‐THC produced a restricted pattern of metabolic decreases. Significant decreases in metabolism following 1.0 mg/kg were concentrated in structures subserving limbic and sensory functions. In a second series of experiments, the effects of pretreatment with the cannabinoid receptor antagonist SR141716A (1.0 mg/kg) on Δ9‐THC‐induced changes in functional activity were measured. Pretreatment with SR141716A attenuated the majority of functional changes produced by Δ9‐THC, suggesting that these effects are primarily mediated by central cannabinoid receptors. Moreover, these findings indicate that the effects of Δ9‐THC on cerebral metabolism are dose‐dependent and that there are regional differences in the metabolic response to acute cannabinoid exposure. Synapse 45:134–142, 2002. © 2002 Wiley‐Liss, Inc.
Catalyzing “Hot” Reactions: Enzymes from Hyperthermophilic Archaea
Authors: Imanaka Tadayuki , Atomi Haruyuki
Published: October 2002

We reflect on some of our studies on the hyperthermophilic archaeon, Thermococcus kodakaraensis KOD1 and its enzymes. The strain can grow at temperatures up to the boiling point and also represents one of the simplest forms of life. As expected, all enzymes displayed remarkable thermostability, and we have determined some of the basic principles that govern this feature. To our delight, many of the enzymes exhibited unique biochemical properties and novel structures not found in mesophilic proteins. Here, we focus on a few enzymes that are useful in application, and whose three‐dimensional structures are characteristic of thermostable enzymes. © 2002 The Japan Chemical Journal Forum and Wiley Periodicals, Inc. Chem Rec 2: 149–163, 2002: Published online in Wiley InterScience (www.interscience.wiley.com) DOI 10.1002/tcr.10023
Fostering students' knowledge and argumentation skills through dilemmas in human genetics
Authors: Zohar Anat , Nemet Flora
Published: October 2002

This study examined the outcomes of a unit that integrates explicit teaching of general reasoning patterns into the teaching of a specific science content. Specifically, this article examined the teaching of argumentation skills in the context of dilemmas in human genetics. Before instruction only a minority (16.2%) of the students referred to correct, specific biological knowledge in constructing arguments in the context of dilemmas in genetics. Approximately 90% of the students were successful in formulating simple arguments. An assessment that took place following instruction supported the conclusion that integrating explicit teaching of argumentation into the teaching of dilemmas in human genetics enhances performance in both biological knowledge and argumentation. An increase was found in the frequency of students who referred to correct, specific biological knowledge in constructing arguments. Students in the experimental group scored significantly higher than students in the comparison group in a test of genetics knowledge. An increase was also found in the quality of students' argumentation. Students were able to transfer the reasoning abilities taught in the context of genetics to the context of dilemmas taken from everyday life. The effects of metacognitive thinking and of changing students' thinking dispositions by modifying what is considered valuable in the class culture are discussed. © 2002 John Wiley & Sons, Inc. J Res Sci Teach 39: 35–62, 2002
Talipes equinovarus and maternal smoking: A population‐based case‐control study in Washington state
Authors: Skelly Andrea C. , Holt Victoria L. , Mosca Vincent S. , Alderman Beth W.
Published: October 2002

Background

Talipes equinovarus (TEV), also called congenital idiopathic clubfoot, true clubfoot and common clubfoot, is one of the most common major birth defects. Its correction is often difficult and expensive. Its etiology is poorly understood and few analytic epidemiological studies have been devoted to exploring specific risk factors for TEV.

Methods

Our population‐based study consists of 239 documented cases of idiopathic TEV obtained from hospital and outpatient sources and 365 controls identified via random digit dialing from five Western Washington counties. Structured maternal interviews were conducted by trained interviewers and multiple logistic regression used to evaluate associations between maternal smoking and birth of a child with TEV.

Results

Our study shows strong associations between maternal smoking and idiopathic TEV. Case mothers were more likely to have smoked during pregnancy (OR = 2.2; 95% CI = 1.5, 3.3). Increased TEV risk was seen with increased smoking and estimates ranged from 1.5 for the lightest smokers to 3.9 for the heaviest smokers. Gender specific differences in risk were also noted with risk estimates of 1.8 (95% CI = 1.2, 3.0) for boys whose mothers smoked during pregnancy and 2.8 (95% CI = 1.4, 5.4) for girls. Trends for increased risk with higher numbers of cigarettes were noted for both genders. For isolated TEV, the overall odds ratio (OR) for smoking was 2.4 (95% CI = 1.6, 3.6) with a range from 1.4–4.6. No confounders were noted.

Conclusions

As postulated, maternal smoking during pregnancy appears to increase the risk of having a child with idiopathic clubfoot and the number of cigarettes smoked influence that risk. Further delineation of dose‐response is warranted as are continued efforts to decrease maternal smoking during pregnancy. Teratology 66:91–100, 2002. © 2002 Wiley‐Liss, Inc.
Applications of MALDI‐TOF MS analysis in cyanotoxin research
Authors: Welker Martin , Fastner Jutta , Erhard Marcel , von Döhren Hans
Published: October 2002

Recent advances in analytical chemistry have provided an array of techniques to analyze cyanotoxins in a variety of samples. Mass spectral analysis by matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry (MALDI‐TOF MS) has proven to be a reliable and rapid tool to detect and identify microcystin variants in very small samples such as single Microcystis colonies. Mass signals presumptive of microcystin variants can be characterized further and identified by postsource‐decay fragmentation and comparison of observed fragment spectra with theoretical ones or with those of pure reference compounds. By analyzing Microcystis colonies from water blooms, the high metabolic diversity among individual colonies in the communities could be established. For monitoring microcystins in environmental samples, MALDI‐TOF MS can provide considerable support to HPLC by identifying microcystin variants not available as purified standards, especially in Planktothrix‐dominated blooms in which demethylated variants are predominant. A short description of the principles of MALDI‐TOF MS is provided, followed by examples of its application and a discussion of its potential use in cyanotoxin research. © 2002 Wiley Periodicals, Inc. Environ Toxicol 17: 367–374, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/tox.10073
Scale‐invariant segmentation of dynamic contrast‐enhanced perfusion MR images with inherent scale selection
Authors: Janssen J. P. , Egmont‐Petersen M. , Hendriks E. A. , Reinders M. J. T. , van der Geest R. J. , Hogendoorn P. C. W. , Reiber J. H. C.
Published: October 2002

Selection of the best set of scales is problematic when developing signal‐driven approaches for pixel‐based image segmentation. Often, different possibly conflicting criteria need to be fulfilled in order to obtain the best trade‐off between uncertainty (variance) and location accuracy. The optimal set of scales depends on several factors: the noise level present in the image material, the prior distribution of the different types of segments, the class‐conditional distributions associated with each type of segment as well as the actual size of the (connected) segments. We analyse, theoretically and through experiments, the possibility of using the overall and class‐conditional error rates as criteria for selecting the optimal sampling of the linear and morphological scale spaces. It is shown that the overall error rate is optimized by taking the prior class distribution in the image material into account. However, a uniform (ignorant) prior distribution ensures constant class‐conditional error rates. Consequently, we advocate for a uniform prior class distribution when an uncommitted, scale‐invariant segmentation approach is desired. Experiments with a neural net classifier developed for segmentation of dynamic magnetic resonance (MR) images, acquired with a paramagnetic tracer, support the theoretical results. Furthermore, the experiments show that the addition of spatial features to the classifier, extracted from the linear or morphological scale spaces, improves the segmentation result compared to a signal‐driven approach based solely on the dynamic MR signal. The segmentation results obtained from the two types of features are compared using two novel quality measures that characterize spatial properties of labelled images. Copyright © 2002 John Wiley & Sons, Ltd.
Multi‐carrier platform for wireless communications. Part 1: High‐performance, high‐throughput TDMA and DS‐CDMA via multi‐carrier implementations
Authors: Nassar Carl R. , Natarajan Bala , Wu Zhiqiang
Published: October 2002

Multi‐carrier technologies in general, and OFDM and MC‐CDMA in particular, are quickly becoming an integral part of the wireless landscape. In this first of a two‐part survey, the authors present the innovative transmit/receive multi‐carrier implementation of TDMA and DS‐CDMA systems. Specifically, at the transmit side, the pulse shape (in TDMA) and the chip shape (in DS‐CDMA) corresponds to a linear combining of in‐phase harmonics (called a CI signal). At the receiver side, traditional time‐domain processing (equalization in TDMA and RAKE reception in DS‐CDMA) is replaced by innovative frequency based processing. Here, receivers decompose pulse (or chip) shapes into carrier subcomponents and recombine these in a manner achieving both high frequency diversity gain and low MAI. The resulting system outperforms traditional TDMA and DS‐CDMA systems by 10–14 dB at typical BERs, and, by application of pseudo‐orthogonal pulse shapes (chip shapes), is able to double system throughput while maintaining performance gains of up to 8 dB. Copyright © 2002 John Wiley & Sons, Ltd.
Positive youth development initiatives in Chicago
Authors: Ogletree Renae , Bell Tony , Smith Natasha K.
Published: October 2002

Chicago has put in place a number of interwoven structures supporting young people during out‐of‐school hours, emphasizing alignment between community‐based organizations and public entities.
San Diego's 6 to 6: A community's commitment to out‐of‐school time
Authors: Ferrin Deborah , Amick Steven
Published: October 2002

San Diego is the first major city in the nation to provide free before‐ and after‐school services to every public elementary and middle school within its borders.
The various roles of municipal leaders
Authors: Ouellette Mark , Kyle John E.
Published: October 2002

Municipal officials can take an important role in developing a community‐wide after‐school system. This chapter examines how mayors and city council members can serve as catalysts for far‐reaching efforts that address key challenges.
Distribution of acetylated tubulin in cultured cells and tissues from the Atlantic cod (Gadus morhua). Role of acetylation in cold adaptation and drug stability
Authors: Rutberg M. , Billger M. , Modig C. , Wallin M.
Published: October 2002

The Atlantic cod (Gadus morhua) is a poikilothermic animal living at temperatures between 2‐15°C. Isolated cod brain tubulin is, in contrast to mammalian brain tubulin, posttranslationally modified by acetylation to a high extent. To investigate the role of acetylation in cold adaptation, microtubules were isolated by a taxol‐dependent procedure from different organs of the cod, and cells from different tissues were cultured. All cells from skin and brain were able to grow between 4°C and room temperature. Microtubules in the cultured cells were sometimes severed near the periphery of the cells. Microtubules in brain cells were in general more stable to vinblastine and colchicine, when compared to skin cells. Acetylated microtubules were found only in brain cells, in peripheral nerves on scales and in nerves of the intestinal tract and in microtubules isolated from neuronal tissue. Our results show that acetylated microtubules are found both in the central and peripheral nervous system, but that there is no correlation between acetylation and cold‐adaptation.
STRUCTURAL BIOLOGY OF THE FIBRES OF THE COLLAGENOUS AND ELASTIC SYSTEMS
Authors: MONTES GREGORIO S.
Published: October 2002

The different types of fibres of the collagenous and elastic systems can be demonstrated specifically in tissue sections by comparing the typical ultrastructural picture of each of the fibre types with studies using selective staining techniques for light microscopy. A practicalmodus operandi, which includes the recommended staining procedures and interpretation of the results, is presented. Micrographs and tables are provided to summarize the differential procedures. Reticulin fibres display a distinct argyrophilia when studied by means of silver impregnation techniques, and show up as a thin meshwork of weakly birefringent, greenish fibres when examined with the aid of the Picrosirius‐polarization method. In addition, electron‐microscopic studies showed that reticulin fibres are composed of a small number of thin collagen fibrils, contrasting with the very many thicker fibrils that could be localized ultrastructurally to the sites where non‐argyrophilic, coarse collagen fibres had been characterized by the histochemical methods used. The three different fibre types of the elastic system belong to a continuous series: oxytalan—elaunin—elastic (all of the fibre types comprising collections of microfibrils with, in the given sequence, increasing amounts of elastin). The three distinct types of elastic system fibres have different staining characteristics and ultrastructural patterns. Ultrastructurally, a characteristic elastic fibre consists of two morphologically different components: a centrally located solid cylinder of amorphous and homogeneous elastin surrounded by tubular microfibrils. An oxytalan fibre is composed of a bundle of microfibrils, identical to the elastic fibre microfibrils, without amorphous material. In elaunin fibres, dispersed amorphous material (elastin) is intermingled among the microfibrils.
α‐KETOGLUTARATE UPTAKE IN HUMAN FIBROBLASTS
Authors: AUSSEL C. , COUDRAY‐LUCAS C. , LASNIER E. , CYNOBER L. , EKINDJIAN O. G.
Published: October 2002

Glutamine requirements are increased during injury, in particular to sustain the needs of rapidly growing cells. This includes fibroblasts involved in wound healing. α‐Ketoglutarate (α‐KG) has been proved to be a potent precursor of glutamine. However, little is known about the process of its cell uptake. Since this first step could be crucial in α‐KG metabolism, we have characterized α‐ketoglutarate uptake in fibroblasts. Total uptake of α‐ketoglutarate was linear up to 1mmol and temperature independent. Rate of uptake was independent of the presence of Na+in the medium. Competition studies with another ketoacid demonstrated the non‐specificity of α‐ketoglutarate uptake. In addition, 4‐hydroxy‐α‐cyanocinnamate, a known inhibitor of anion transport, was ineffective on α‐ketoglutarate uptake. Taken as a whole, these data provide evidence that α‐ketoglutarate uptake in fibroblast occurs by an unmediated diffusion process. This suggests that α‐ketoglutarate uptake is not the controlling step in fibroblasts, i.e. only the availability of extracellular α‐ketoglutarate. This could be an advantage since during injury, cell membrane depolarization and dissipation of Na+gradient may limit cellular glutamine uptake.
CONNEXIN43 GAP JUNCTION LEVELS DURING DEVELOPMENT OF THE THORACIC AORTA ARE TEMPORALLY CORRELATED WITH ELASTIC LAMINAE DEPOSITION AND INCREASED BLOOD PRESSURE
Authors: BLACKBURN J.P , CONNAT J.‐L , SEVERS N.J , GREEN C.R
Published: October 2002

A characteristic property of the vascular smooth muscle cell is its ability to modulate between a contractile phenotype, responsible for control of vascular tone and tension, through to a synthetic phenotype, capable of migration and synthesis of extracellular matrix molecules. Smooth muscle cells are coupled by gap junctions, the membrane structures which permit direct intercellular passage of ions and small molecules, and which play a role both in electrical coupling and intercellular communication during patterning and development. We have previously found that connexin43 type gap junction expression is upregulated in the synthetic phenotype smooth muscle cellin vitroand during atherosclerotic plaque formation in human coronary arteries. On the basis of immunohistochemical labelling, confocal laser scanning microscopy and digital image analysis, we now report that relatively high levels of connexin43 are expressed during development of the rat thoracic aorta, temporally correlating with reported periods of smooth muscle cell proliferation and secretion of elastic laminae. A major peak in expression occurs at seven days post‐natal, with a second less pronounced peak at 72 days post‐natal. The principal peak in gap junction levels appears to coincide with increased post‐natal blood pressure and aorta media thickening. The amount of gap junction labelling falls off to normal adult levels as the smooth muscle cells modulate towards the contractile phenotype and growth is completed. The results indicate an association between direct cell‐to‐cell communication and synthetic phenotype smooth muscle cell activity during aortic growth and patterning.
ADHESION‐DEPENDENT F‐ACTIN PATTERN INAMOEBA PROTEUSAS A COMMON FEATURE OF AMOEBAE AND THE METAZOAN MOTILE CELLS
Authors: GREBECKA LUCYNA , POMORSKI PAWEŁ , GRE ANDRZEJ , ŁOPATOWSKA ANNA
Published: October 2002

Adhesion and movement ofAmoeba proteusare both dependent on the appropriate arrangement of the F‐actin cytoskeleton and on the presence of the cell nucleus. In this study the F‐actin organization was examined by routine FITC‐phalloidin staining and confocal laser microscopy in intact amoebae and in their nucleated and anucleated fragments, at different levels of cell adherence to the substratum. In the adhering and migrating intact cells and nucleated cell fragments dot‐like aggregates of F‐actin are scattered over the ventral side at sites close to the substratum. In the case of de‐adhesion of nucleated specimens this pattern disappears and F‐actin is accumulated in the cell centre and/or dispersed in the cytoplasm. The same actin distribution, without ventral dots, is found in the anucleated fragments which usually fail to attach to the substratum. Re‐adhesion of anucleated fragments, induced by a modified substratum or spontaneous, is accompanied by restoration of actin dots at the lower cell side. It is concluded that: (1) adhering specimens ofA. proteusdisplay the same dot‐like actin pattern on the ventral cell side, as many metazoan motile cells; (2) organization or disorganization of this pattern may occur independently of the presence of the cell nucleus, under the control of cell adhesion to the substratum.
DNA PLASMID TRANSMISSION IN YEAST IS ASSOCIATED WITH SPECIFIC SUB‐NUCLEAR LOCALISATION DURING CELL DIVISION
Authors: Scott‐Drew Suzanna , Wong C. Michael V. L. , Murray James A. H.
Published: October 2002

Circular plasmids in yeast carrying only an origin of DNA replication (ARS) exhibit maternal inheritance bias (MIB) and are poorly transmitted from mother to daughter cell during division. A variety of different sequences that overcome MIB have been described, including centromeric sequences (CEN), telomere‐associated repeats, silencer sequences and a specific system encoded by the endogenous 2μ circle plasmid requiring the cis‐acting locus STB and the proteins Rep1 and Rep2. In each case, DNA segregation between mother and daughter cells is dependent on DNA‐protein interactions. Using plasmids carrying multiple copies of a lac repressor binding sequence, we have localised DNA molecules in the yeast nucleus using a green fluorescent protein (GFP)‐lac repressor fusion protein. We compared GFP localised plasmids carrying a centromere sequence with plasmids based on 2μ circle carrying or lacking the STB sequences required for their segregation. We show that GFP localised plasmid carrying the complete STB locus co‐localises with the plasmid proteins Rep1 and Rep2 to discrete chromatin sites. These sites are distinct from both the telomeres and from sites of cohesin binding. Deletion of the region of STB essential for the stability of the plasmid, leads to a loss of plasmid association with chromatin, relocalisation of plasmids towards the nuclear periphery, and a decrease in the Rep1 protein associated with the plasmid. We conclude that specific plasmid localisation is likely to be important in the overcoming of MIB in yeast.
Glacial-Lake Outburst Erosion of the Grand Valley, Michigan, and Impacts on Glacial Lakes in the Lake Michigan Basin
Authors: Kehew Alan E.
Published: October 2002

Geomorphic and sedimentologic evidence in the Grand Valley, which drained the retreating Saginaw Lobe of the Laurentide Ice Sheet and later acted as a spillway between lakes in the Huron and Erie basins and in the Michigan basin, suggests that at least one drainage event from glacial Lake Saginaw to glacial Lake Chicago was a catastrophic outburst that deeply incised the valley. Analysis of shoreline and outlet geomorphology at the Chicago outlet supports J H Bretz's hypothesis of episodic incision and lake-level change. Shoreline features of each lake level converge to separate outlet sills that decrease in elevation from the oldest to youngest lake phases. This evidence, coupled with the presence of boulder lags and other features consistent with outburst origin, suggests that the outlets were deepened by catastrophic outbursts at least twice. The first incision event is correlated with a linked series of floods that progressed from Huron and Erie basin lakes to glacial Lake Saginaw to glacial Lake Chicago and then to the Mississippi. The second downcutting event occurred after the Two Rivers Advance of the Lake Michigan Lobe. Outbursts from the eastern outlets of glacial Lake Agassiz to glacial Lake Algonquin are a possible cause for this period of downcutting at the Chicago outlets.
Late Quaternary Lacustrine Pollen Records from Southwestern Beringia
Authors: Lozhkin Anatoly V. , Anderson Patricia M. , Eisner Wendy R. , Ravako Lilia G. , Hopkins David M. , Brubaker Linda B. , Colinvaux Paul A. , Miller Michael C.
Published: October 2002

Sediment cores from three lakes in the Upper Kolyma region, northeast Russia, provide the first well-dated continuous record of late Quaternary vegetation change from far southwestern Beringia. The oldest pollen zone, tentatively assigned to the Karginsk (mid-Wisconsinan) Interstade, indicates anArtemisiashrub tundra withPinus pumila,Betula, andAlnusat mid- to low elevations. With the onset of the Sartan (late Wisconsinan) Stade,Pinusdisappeared, probably indicating severely cold, dry winters and cool summers. As conditions deteriorated further, anArtemisia-Gramineae tundra developed.Selaginella rupestrisand minor herb taxa indicate the presence of poor soils and disturbed ground. This herb tundra was replaced by a short-lived (< 1000 yr)Betula-Alnusshrub tundra followed by the rapid establishment of aLarix dahuricaforest with aBetula exilis-ericales-lichen understory.Populus suaveolensandChoseniamay have formed limited hardwood gallery forests at this time. Modern vegetation associations probably developed during the early Holocene with the arrival ofPinus pumilaca. 9000 yr B.P. This shrub became important in the forest understory and, withB. exilis, formed a belt of shrub tundra beyond altitudinal treeline. Comparison of the Upper Kolyma and Alaskan pollen records indicates that important differences in vegetation types and timing of vegetation change occurred across Beringia during the late Quaternary.
Late Pleistocene Climate Record in the Eustis Loess Section, Nebraska, Based on Land Snail Assemblages and Magnetic Susceptibility
Authors: Rousseau Denis-Didier , Kukla George
Published: October 2002

Based on multivariate analysis of mollusk assemblages and magnetic susceptibility of the Eustis section in western Nebraska, the climate of the Peoria loess steppe was relatively mild and, in terms of annual precipitation, relatively moist during the advance stages of Woodfordian ice. It was cold and dry during ice retreat. The diversity and composition of mollusk species indicates that the extreme cold and dry climate was reached during the late phase of Peoria time, in mollusk zone MZ3. Although soil moisture during the growing season at that time was high, the growing season was short and annual precipitation totals were low. Low values of magnetic susceptibility imply relatively rapid dust deposition during this interval, Judging from the current ecological tolerance of the species, no closed forest existed in the area. Only scattered shrubs or isolated tree stands may have been present. The late Peoria MZ3 assemblage compares favorably with theColumellafauna of Europe. In contrast, the early Peoria mollusk assemblages MZ1 and MZ2 compare well with the European pleniglacialPupillaassociations. Based on available14C dates from the studied region and on assumed relation of magnetic susceptibility to sedimentation rates, the estimated age of the MZ1 and MZ2 zones is 24,000 to 16,000 yr, whereas that of MZ3 is 16,000 to 12,000 yr.
Mid-Pleistocene Change in Large Mammal Faunas of East Africa
Authors: Potts Richard , Deino Alan
Published: October 2002

Single-crystal40Ar/39Ar age estimates of 392,000 ± 4000 to 330,000 ± 6000 yr from Lainyamok, a middle Pleistocene fossil locality in the southern Kenya rift, document the oldest evidence from sub-Saharan Africa of a diverse, large mammal fauna consisting entirely of extant species. The inferred age of this fauna implies an upper limit for extinction of species that characterize well-calibrated, mid-Pleistocene fossil assemblages in East Africa. For its age and species richness, the Lainyamok fauna is surprising for its lack of extinct forms (e.g., the bovinePelorovis) well documented in later faunal assemblages of East and South Africa. Definitive presence of the South African blesbok(Damaliscus dorcas)is also unexpected, especially as this alcelaphine bovid is the dominant large mammal in the Lainyamok fauna. These age estimates and the faunal composition at Lainyamok indicate that geographic ranges and taxonomic associations of extant largebodied mammals were susceptible to wide fluctuations in sub-Saharan Africa over the past 330,000 yr. This inference is consistent with the hypothesis of nonanalogue, or ephemeral, biotas believed to characterize late Quaternary ecosystems of northern continents.
Glacial Meltwater in Lake Huron during Early Postglacial Time as Inferred from Single-Valve Analysis of Oxygen Isotopes in Ostracodes
Authors: Dettman David L. , Smith Alison J. , Rea David K. , Moore Theodore C. , Lohmann Kyger C.
Published: October 2002

δ18O measurements of benthic ostracodes are used to reconstruct the δ18O history of Lake Huron and Georgian Bay water between 10,600 and 760014C yr B.P. This δ18O record was calibrated using a comparison of the δ18O values of modern ostracodes and Lake Huron water, where a fractionation of 1.0358 was measured between the oxygen isotope ratios of the most isotopically positive ostracodeCandona subtriangulataand lake water. The most positive shell δ18O value was used because it is precipitated in the cold (0° to 2°C) water common to both deep and shallow environments. The δ18O of Lake Huron water reflects a large glacial meltwater component for much of its history before 760014C yr B.P. Times of low lake level correlate with the highest ratio of glacial meltwater to local precipitation in the basin (most negative δ18O values). Georgian Bay water was more negative in δ18O than Lake Huron water of the same age; this reflects a higher proportion of glacial meltwater in Georgian Bay and its separation from Lake Huron during times of low lake level.
Uranium-Series Dating of Carbonate (Tufa) Deposits Associated with Quaternary Fluctuations of Pyramid Lake, Nevada
Authors: Szabo Barney J. , Bush Charles A. , Benson Larry V.
Published: October 2002

Uranium-series dating of dense tufa deposited in a small cave, at former lake margins, and in large tufa mounds clarifies the timing of lake-level variation during the past 400,000 yr in the Pyramid Lake basin. A moderate-sized lake occasionally overflowed the Emerson Pass sill at elevation of ∼1207 m between ca. 400,000 and 170,000 and from ca. 60,000 to 20,000 yr B.P., as shown by 230Th/234U ages of the cave samples, 230Th-excess ages of tubular tufas, and average isochron-plot ages of shoreline-deposited tufas. (By comparison, modern Pyramid Lake is ∼50 m below this sill). There is a lack of tufa record during the intervening period from ca. 170,000 to 60,000 yr B.P. After ca. 20,000 yr, Pyramid Lake underwent abrupt changes in level and, based on previous 14C ages, reached its highest elevation (ca 1335 m) at ca. 14,000 yr B.P. The youngest uranium-series ages are comparable with previously reported 14C ages.
Calibration, Review, and Geomorphic Implications of Postglacial Radiocarbon Ages in Southeastern Alberta, Canada
Authors: Campbell Celina , Campbell Ian A.
Published: October 2002

Calibration of radiocarbon dates of postglacial geomorphic events in southeastern Alberta, Canada, reveals a strong association between type of geomorphic event and seasonality of insolation. The late glacial and postglacial periods can be divided into four major episodes: glaciation, ca. >20,000 cal yr B.P.; deglaciation, ca. 20,000–12,000 cal yr B.P.; landscape stability, ca. 12,000–10,000 cal yr B.P.; and landscape instability, ca. 10,000–0 cal yr B.P. This indicates that there was significantly more time than previously thought (12,000–13,000 yr) for postglacial processes. Glaciation, deglaciation, maximum landscape stability (indicating maximum aridity), and landscape instability did not lag behind minimum, increasing, maximum, and decreasing seasonality of insolation, respectively.
Improving Methodology for High-Resolution Reconstruction of Sea-Level Rise and Neotectonics by Paleoecological Analysis and AMS 14C Dating of Basal Peats
Authors: Törnqvist Torbjörn E. , van Ree Mark H.M. , van 't Veer Ron , van Geel Bas
Published: October 2002

Sea-level research in several submerging coastal regions has traditionally been based on 14C dating of basal peats that overlie a compaction-free substratum and can be related to paleo-(ground)water levels. Provided that an unequivocal relationship between (ground)water level and sea level can be assumed, this approach contains two sources of uncertainty: (1) the paleoenvironmental interpretation of samples is usually based on inherently inaccurate macroscopic descriptions in the field, and (2) 14C ages of bulk peat samples may be erroneous as a result of contamination. Due to the uncertainties in both the altitude and the age—the two crucial sources of evidence necessary to arrive at accurate sea-level curves—sea-level index points are therefore represented by considerable, but typically not quantified, error boxes. Accelerator mass spectrometry (AMS) opens new perspectives for this type of sea-level research, as illustrated by a paleoecological and AMS 14C study of basal peats from a small study area in the Rhine–Meuse Delta (The Netherlands), where previous (conventional) work revealed highly problematic results. A detailed macrofossil analysis has two purposes: (1) an inferred paleoecological succession indicates a relatively accurate level of paludification of the site, and hence rise of the (ground)water level; (2) suitable macrofossils from that specific level are then selected for AMS 14C dating. In spite of very small sample sizes, our results are consistent and indicate that this approach can constitute a step forward in high-resolution reconstruction of sea-level rise. The new results further enable a revision of Holocene (ground)water gradient lines for the Rhine–Meuse Delta. A knickpoint in these gradient lines can be related to the effect of faulting. This approach therefore also has considerable potential to unravel and quantify neotectonic activity in submerging coastal settings.
Comparison of Late Pleistocene and Modern Glacier Extents in Central Nepal Based on Digital Elevation Data and Satellite Imagery
Authors: Duncan Christopher C. , Klein Andrew J. , Masek Jeffrey G. , Isacks Bryan L.
Published: October 2002

Late Pleistocene and modern ice extents in central Nepal are compared to estimate equilibrium line altitude (ELA) depressions. New techniques are used for determining the former extent of glaciers based on quantitative, objective geomorphic analyses of a ∼90-m resolution digital elevation model (DEM). For every link of the drainage network, valley form is classified as glacial or fluvial based on cross-valley shape and slope statistics. Down-valley transitions from glacial to fluvial form indicate the former limits of glaciation in each valley. Landsat Multispectral Scanner imagery for the same region is used to map current glacier extents. For both full-glacial and modern cases, ELAs are computed from the glacier limits using the DEM and a toe-to-headwall altitude ratio of 0.5. Computed ELA depressions range from 100–900 m with a modal value of ∼650 m and a mean of ∼500 m, values consistent with previously published estimates for the central Himalaya but markedly smaller than estimates for many other regions. We suggest that this reflects reduced precipitation, rather than a small temperature depression, consistent with other evidence for a weaker monsoon under full-glacial conditions.
Evidence from Lake Baikal for Siberian Glaciation during Oxygen-Isotope Substage 5d
Authors: Karabanov Eugene B. , Prokopenko Alexander A. , Williams Douglas F. , Colman Steven M.
Published: October 2002

The paleoclimatic record from bottom sediments of Lake Baikal (eastern Siberia) reveals new evidence for an abrupt and intense glaciation during the initial part of the last interglacial period (isotope substage 5d). This glaciation lasted about 12,000 yr from 117,000 to 105,000 yr B.P. according to correlation with the SPECMAP isotope chronology. Lithological and biogeochemical evidence of glaciation from Lake Baikal agrees with evidence for the advance of ice sheet in northwestern Siberia during this time period and also with cryogenic features within the strata of Kazantzevo soils in Southern Siberia. The severe 5d glaciation in Siberia was caused by dramatic cooling due to the decrease in solar insolation (as predicted by the model of insolation changes for northern Asia according to Milankovich theory) coupled with western atmospheric transport of moisture from the open areas of Northern Atlantic and Arctic seas (which became ice-free due to the intense warming during preceeding isotope substage 5e). Other marine and continental records show evidence for cooling during 5d, but not for intense glaciation. Late Pleistocene glaciations in the Northern Hemisphere may have begun in northwestern Siberia.
Changes in Sand Content of Loess Deposits along a North–South Transect of the Chinese Loess Plateau and the Implications for Desert Variations
Authors: Ding Zhongli , Sun Jimin , Rutter Nat W. , Rokosh Dean , Liu Tungsheng
Published: October 2002

Geological records have shown that the deserts east of the Helan Mountains in northern China were covered by grass during the Holocene Optimum, whereas during marine oxygen isotope stages 2 and 4 distribution of the deserts was almost the same as at present. The wide advance–retreat cycles of the deserts may have exerted an important control on grain-size changes in the loess of the Loess Plateau by altering the distance between the source and the accumulation zone of the loess. This challenges the widely accepted model that winter monsoon winds were the sole factor responsible for spatial and temporal changes in loess texture. To observe spatial changes in sedimentological characteristics of loess during the last glacial–interglacial cycle, the texture of loess was measured along a north–south transect of the Loess Plateau. This transect consists of nine loess sections, starting at Yulin in the transitional region between the Loess Plateau and the Mu Us Desert and ending at Weinan in the southernmost part of the Loess Plateau. Southward changes in sand (>63 μm) content along the transect suggest that variations in desert extent have indeed played a significant role in loess grain-size distributions, particularly in the northern part of the Loess Plateau. It is proposed that sand content (>63 μm%) of loess in the loess–desert transitional zone may be used as a proxy indicator for proximity to the desert margin.
Development of a Late Quaternary Marine Terraced Landscape during On-Going Tectonic Contraction, Crescent City Coastal Plain, California
Authors: Polenz Michael , Kelsey Harvey M.
Published: October 2002

The Crescent City coastal plain is a low-lying surface of negligible relief that lies on the upper plate of the Cascadia subduction zone in northernmost California. Whereas coastal reaches to the north in southern Oregon and to the south near Cape Mendocino contain flights of deformed marine terraces from which a neotectonic history can be deduced, equivalent terraces on the Crescent City coastal plain are not as pronounced. Reexamination of the coastal plain revealed three late Pleistocene marine terraces, identified on the basis of subtle geomorphic boundaries and further delineated by differentiable degrees of soil development. The youngest marine terrace is preserved in the axial valley of a broad syncline, and the two older marine terraces face each other across the axial region. An active thrust fault, previously recognized offshore, underlies the coastal plain, and folding in the hanging wall of this thrust fault has dictated, through differential uplift, the depositional limits of each successive marine terrace unit. This study demonstrates the importance of local structures in coastal landscape evolution along tectonically active coastlines and exemplifies the utility of soil relative-age determinations to identify actively growing folds in landscapes of low relief.
Lake Manly(?) Shorelines in the Eastern Mojave Desert, California
Authors: Hooke Roger LeB.
Published: October 2002

Near Mesquite Spring on the southern edge of the Soda Lake basin in the Mojave Desert, there is a shoreline of an ancient lake at an elevation of 340 m above sea level. At present, Soda Lake would overflow at 280 m; a lake surface at 340 m would extend ∼240 km northward, to the northern end of Death Valley. Shorelines and lacustrine deposits near the Salt Spring and Saddle Peak Hills, 75 km north of Mesquite Spring, are at ∼180 m; a lake surface at this elevation today would also extend to the northern end of Death Valley. The most prominent shoreline of the pluvial lake that occupied Death Valley during the Pleistocene, Lake Manly, is that of the Blackwelder stand which ended ∼120,000 yr ago. This shoreline is ∼90 m above sea level. The Mesquite Spring and Salt Spring Hills shorelines were probably formed by the Blackwelder stand and subsequently displaced with respect to one another, tectonically, due to transpression in the northeastern Mojave Desert and NW–SE extension across Death Valley. This tectonic regime would result in subsidence of Death Valley and the Salt Spring Hills relative to Mesquite Spring. A reconstruction suggests that the topography at the time of the Blackwelder stand would have had a sill near the level of the highest lake, and also one ∼20 m lower, corresponding to the next most prominent shoreline in Death Valley. Expansion of the lake over these sills would have increased evaporation, thus possibly stabilizing the lake level.
Paleoclimatic Reconstruction Using Mutual Climatic Range on Terrestrial Mollusks
Authors: Moine Olivier , Rousseau Denis-Didier , Jolly Dominique , Vianey-Liaud Marc
Published: October 2002

Terrestrial mollusks, easily identified in Quaternary sediments, represent a reliable tool for quantitative estimates of environmental parameters. Our study, comparing the species distribution with meteorological parameters in Europe, shows that mean temperature of the coldest month and annual thermal magnitude are the most important forcing parameters. This survey allows us to adapt the mutual climatic range (MCR) method to terrestrial mollusk assemblages following two main steps. A set of assemblages from different European regions (northern Norway to southern France) is used to apply the method to present-day mollusks. The reconstructed values describe the latitudinal temperature gradient prevailing over Europe. However, the comparison between the reconstructed and the measured values indicates a shift, similar to that observed, with the same method applied to beetle assemblages. Thus, estimates must be calculated after the reconstruction is tuned with the observations. The results from the modern mollusk assemblages indicate that the MCR method can be safely applied to reconstructing temperatures from terrestrial mollusk assemblages in any worldwide Quaternary sequence. A trial application is made on Late Pleistocene assemblages from Achenheim (Alsace, France).
Sediment-Color Record from the Northeast Atlantic Reveals Patterns of Millennial-Scale Climate Variability during the Past 500,000 Years
Authors: Helmke Jan P. , Schulz Michael , Bauch Henning A.
Published: October 2002

A 500,000-yr-long deep-sea sediment-color record from the Northeast Atlantic was investigated to reconstruct the evolution of late Pleistocene climate variability on millennial time scales. Variations of the red–green color intensity are probably caused by climatically induced changes in the ice-rafted input of red-colored iron-bearing terrigenous material to the core site. The resolution of the age model impedes the detection of distinct spectral features at sub-Milankovitch periodicities. Hence, millennial-scale climate variability is quantified as time-dependent variance of the high-pass filtered color time series. The course of the estimated variance shows distinct patterns, which can be linked to continental ice mass. During the past 500,000 yr, large-amplitude millennial-scale climate variability occurs only if continental ice mass exceeds a threshold level, equivalent to sea level at approximately 40% of the lowering during the last glacial maximum.
Generalised Stream X-Machines and Cooperating Distributed Grammar Systems
Authors: Gheorghe Marian
Published: October 2002

Stream X-machines are a general and powerful computational model. By coupling the control structure of a stream X-machine with a set of formal grammars a new machine called a
generalised stream X-machine with underlying distributed grammars
, acting as a translator, is obtained. By introducing this new mechanism a hierarchy of computational models is provided. If the grammars are of a particular class, say regular or context-free, then finite sets are translated into finite sets, when ?
k
, =
k
derivation strategies are used, and regular or context-free sets, respectively, are obtained for ?
k
, * and
terminal
derivation strategies. In both cases, regular or context-free grammars, the regular sets are translated into non-context-free languages. Moreover, any language accepted by a Turing machine may be written as a translation of a regular set performed by a generalised stream X-machine with underlying distributed grammars based on context-free rules, under =
k
derivation strategy. On the other hand the languages generated by some classes of cooperating distributed grammar systems may be obtained as images of regular sets through some X-machines with underlying distributed grammars. Other relations of the families of languages computed by generalised stream X-machines with the families of languages generated by cooperating distributed grammar systems are established. At the end, an example dealing with the specification of a scanner system illustrates the use of the introduced mechanism as a formal specification model.