bluuebunny/crossref_metadata_2025 huggingface dataset:
Protein hydrolysis under anaerobic, saline conditions in presence of acetic acid
Authors: González G , Urrutia H , Roeckel M , Aspé E
Published: December 2004

The hydrolysis of soluble proteins in an anaerobic, saline (24 g dm−3 NaCl) and mesophilic (37 °C) environment was studied. The inhibitory effect of a volatile fatty acid, acetic acid (HAc), on the hydrolysis rate and hydrolytic biomass activity for a model saline wastewater with a high protein load (total organic carbon, 1153 mg dm−3 and 1572 mg dm−3 proteins) was studied. Initial inhibitor concentrations were tested in the range of 0–2000 mg dm−3 HAc. The microbiological characterization was performed using a total microorganism count by epifluorescence, and hydrolytic bacterial activity was determined by plate count. The protein hydrolysis was modeled according to first order kinetics. The effect of biomass on hydrolysis was analyzed by varying its concentration in the range of 42–210 mg dm−3 volatile suspended solids. The following apparent hydrolysis kinetic constants (Kh) for proteins at 37 °C were obtained: 1.3, 0.8, 0.6, 0.2 and 0.1 d−1 for initial concentrations of 250, 500, 750, 880, and 1000 mg dm−3 HAc, respectively. At concentrations of HAc greater than 1000 mg dm−3, total inhibition of hydrolysis was observed. The intrinsic hydrolysis constant ($K_{{\rm h}}^{0}$) at 37 °C, without inhibition, was 2.3 d−1. The hydrolysis kinetic constant was not affected by the biomass concentration. The hydrolysis kinetics constant was filted to three models: Luong, Levenspiel and non‐competitive inhibition. The model that best represented the experimental data was Luong, obtaining an inhibition constant (KI) of 1087 mg dm−3 of HAc and the exponent γ = 0.54. The hydrolysis was inhibited by the presence of HAc, which corresponds to an intermediate compound of the anaerobic process. Copyright © 2004 Society of Chemical Industry
On the computation of material forces in continuum‐atomistic modelling
Authors: Abdi Tadesse , Denzer Ralf , Steinmann Paul
Published: December 2004

Material forces govern the behavior and evolution of defects in solids. In elastic materials these forces which are associated with the Eshelby stress tensor are used to describe fracture sensitivities and can be employed to compute the J‐integral [2]. Since crack propagation begins with a variety of fundamental processes which occur within highly localized ultra–fine volume of material that constitute the fracture process zone surrounding a crack tip [3], the question of appropriate growth criteria, i.e. how far and in which direction a crack will glide under a certain loading condition is implied by the material force. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Energetic aspects regarding the VIPAS1 industrial robot working. Second Part: Graphical Interpretation
Authors: Ispas Viorel , Arghir Mariana , Ispas Virgil
Published: December 2004

The paper studies the motion laws influence over the VIPAS1 industrial robot working. The motion differential equations, that govern the motion robot were established. Using them we can study the direct problem for the robot dynamics. There are the given motion laws for the accelerated and decreasing motion having triangular, trapezoidal and parabolic forms. The graphics of the forces and moments give us the possibility to make some recommandations under energetic aspects, for the optimal solutions about the VIPAS1 industrial robot. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Adaptive Finite Element Simulation of the Human Mandible Using a New Physiological Model of the Masticatory Muscles
Authors: Kober Cornelia , Erdmann Bodo , Lang Jens , Sader Robert , Zeilhofer Hans‐Florian
Published: December 2004

Structural mechanics simulation of bony organs is of general medical and biomechanical interest, because of the interdependence of the inner architecture of bone and its functional loading already stated by Wolff in 1892.

This work is part of a detailed research project concerning the human mandible. By adaptive finite element techniques, stress/strain profiles occurring in the bony structure under biting were simulated. Estimates of the discretization errors, local grid refinement, and multilevel techniques guarantee the reliability and efficiency of the method.

In general, our simulation requires a representation of the organ's geometry, an appropriate material description, and the load case due to teeth, muscle, or joint forces. In this paper, we want to focus on the influence of the masticatory system. Our goal is to capture the physiological situation as far as possible. By means of visualization techniques developed by the group, we are able to extract individual muscle fibres from computed tomography data. By a special algorithm, the fibres are expanded to fanlike (esp. for the musc. temporalis) coherent vector fields similar to the anatomical reality. The activity of the fibres can be adapted according to compartmentalisation of the muscles as measured by electromyological experiments. A refined sensitivity analysis proved remarkable impact of the presented approach on the simulation results. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Numerical aspects of X‐SIMP‐based topology optimization
Authors: Kotucha Gregor , Hackl Klaus
Published: December 2004

The discretization of topology design problems on the basis of the finite‐element‐method results in general in large‐scale combinatorial optimization problems, which are usually relaxed by the introduction of a continuous material density function as design variable. To avoid optimal designs containing unfavourable microstructures such as the well‐known “checkerboard” patterns, the relaxed problem can be regularized by the X‐SIMP‐approach, which penalizes intermediate density values as well as high density gradients within the design domain. In this context we discuss numerical aspects of the X‐SIMP‐based regularization such as the discretization of the regularized problem, the formulation of the corresponding stiffness matrix and the numerical solution of the discretized problem. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A finite element method for cohesive crack modelling
Authors: Mergheim Julia , Kuhl Ellen , Steinmann Paul
Published: December 2004

The present contribution is concerned with the computational modelling of cohesive cracks, whereby the discontinuity is not limited to interelement boundaries, but is allowed to propagate freely through the elements. Inelastic material behaviour is described by a discrete constitutive law, formulated in terms of tractions and displacements at the surface. Details on the implementation and numerical examples are given. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A Hybrid Variational Model for the Analysis of Free‐Corner Effects in Layered Plates
Authors: Mittelstedt Christian , Becker Wilfried
Published: December 2004

A variational model for the assessment of free‐edge and free‐corner effects [1‐3] in thermally loaded rectangular cross‐ply laminate plates is presented. The physical layers of the plate are discretized by an arbitrary number of mathematical layers through the laminate thickness. A layerwise displacement field with unknown interface functions which depend on the inplane coordinates is formulated wherein an a priori assumed layerwise linear thickness interpolation scheme is employed. The application of the principle of minimum elastic potential yields a set of governing Euler‐Lagrange differential equations for the unknown inplane functions which for the special free‐corner problem in rectangular cross‐ply plates can be solved in a closed‐form analytical manner. Boundary conditions of traction free laminate edges are fulfilled in an average sense. Since the approach utilizes a discretization through the plate thickness yet allows for closed‐form solutions within the layer planes for all state variables it is appropriate to speak of a hybrid analysis approach. The presented method allows easy application, can be run on every standard personal computer and is in favourable agreement with comparative finite element calculations. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Frictional contact of elastomer materials on rough rigid surfaces
Authors: Nettingsmeier Jana , Wriggers Peter
Published: December 2004

The frictional behavior of elastomer materials is still unexplored, but very important for many industrial applications. Special attention is turned to rubber friction on rough road tracks. Due to the non‐rigid material characteristics of the rubber it is not sufficient to use a constant friction coefficient like Coulombs law. The frictional qualities depend on many different influences like sliding velocity, applied normal stress, surface roughness, material properties and the temperature in the contact zone. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Simulation of crack–propagation using embedded discontinuities
Authors: Peters M. , Hoppe U. , Hackl K.
Published: December 2004

The transition from microscale damage phenomena to crack initiation and growth at the macroscale is an important mechanism which constrains the lifetime of concrete structures. Analysing crack growth using the finite element method without enhancement of the shape functions is possible only by continuously updating the corresponding meshes, which constitutes a significant computational effort. But even then the results can be substantially mesh–dependent and hard to interpret. The extended Finite Element Method (XFEM) uses additional discontinuous shape–functions and is one possibility to overcome these problems. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Polymer–montmorillonite clay nanocomposites. Part 1: Complexation of montmorillonite clay with a vinyl monomer
Authors: Khalil Hanaa , Mahajan Devinder , Rafailovich Mariam
Published: December 2004

An organo‐clay complex was formed by the exchange reaction of a quaternary ammonium salt of a derivatized styrene monomer with Na+‐montmorillonite clay. The binding of the derivatized styrene monomer with the montmorillonite clay was confirmed by FTIR and the diffused reflectance analysis. The increase of the d‐spacing of the derivatized styrene‐N+–montmorillonite clay complex to 1.47 nm, measured by X‐ray diffraction, indicates that a monolayer of the monomer is adsorbed between adjacent montmorillonite layers. A molecular modeling of the monomer suggested a benzene ring tilted to the c‐axis of the montmorillonite clay. The carbon content of the styrene‐N+–montmorillonite clay of 11.02 % suggested a complete surface coverage of the clay by the monomer and a surface coverage of 0.74 nm2 per exchange site of the montmorillonite. Copyright © 2004 Society of Chemical Industry
Synthesis and photophysical characterization of the free‐radical copolymerization of metaloquinolate‐pendant monomers with methyl methacrylate
Authors: Du Naiying , Tian Renyu , Peng Junbiao , Lu Mangeng
Published: December 2004

A series of novel metaloquinolate [aluminum quinolate (Alq3), zinc quinolate (Znq2), and lithium quinolate (Liq)]‐containing copolymers were prepared. This is the first report of the synthesis of metaloquinolate‐containing polymers by free‐radical copolymerization. The structures of the metaloquinolate monomers and copolymers were characterized by 1H NMR and Fourier transform infrared techniques. The differential scanning calorimetry and thermogravimetric analysis results showed that the copolymers were more thermally stable than the methyl methacrylate homopolymer. The copolymers (<25 wt % Alq3, <20 wt % Znq2, or <15 wt % Liq) could be dissolved in common solvents without crosslinking. The ultraviolet–visible absorption and photoluminescence (PL) emission properties of the copolymers were consistent with the literature data of metaloquinolate complexes. The PL efficiencies of the metaloquinolate‐containing copolymers with 25 wt % Alq3, 20 wt % Znq2, or 15 wt % Liq were 19.89, 13.24, and 11.82%, respectively. The experimental results indicated that these kinds of materials could be used for practical applications in organic light‐emitting diodes. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 397–406, 2005
All‐optical poling behavior in side‐chain azobenzene homopolymer
Authors: Guo Bin , Su Wei , Jia Yajie , Li Zengchang , Zhang Qijin , Wang Gongming
Published: December 2004

All‐optical poling of side‐chain azobenzene homopolymers PCN2 and PCN6, i.e. poly (6‐[4‐(4‐cyanophenylazo) phenoxy] x‐methylene methacrylate) for x = 2 and 6, with different spacer lengths was experimentally investigated. Due to the low absorption of the samples at 532 nm, it was found that there is a nearly quadratic increase in second‐harmonic generation (SHG) when the film thickness of the sample films increases from 4 μm to 100 μm. The time constant τA of the fitted photoinduced SHG decay process shows that PCN2 and PCN6 have higher temporal stability than the typical guest–host DR1‐PMMA system, and different methylene conjugation lengths give slightly different time constants for disorientation. The possible reason from the molecule structure is discussed in detail. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Thirty‐year durability of a 20‐mil PVC geomembrane
Authors: Newman E. J. , Stark T. D. , Rohe F. P. , Diebel P.
Published: December 2004

In 1971, twenty circular aquaculture ponds were constructed for the W. K. Kellogg Biological Research Station in Hickory Corners, Michigan. The 30.5‐m‐diameter research ponds were lined using a 0.51‐mm‐thick fish‐grade PVC geomembrane. Over the years the ponds became congested with dense, persistent stands of cattails, trees, and other vegetation, which required the ponds to be cleared and relined in September 2000 in order to allow the initiation of new experiments. The lack of holes in the exhumed geomembrane suggests that it resisted biological attack from microorganisms and also root penetration. Laboratory testing shows that the tensile behavior of the nearly 30‐year‐old PVC geomembrane is within current specifications for new 0.51‐mm‐thick PVC geomembranes. Test results also indicate that performing laboratory tests at in‐situ moisture conditions provides a better estimate of the field properties of PVC geomembranes than desiccating the material prior to testing, as is required by ASTM Standard Test Methods. J. Vinyl Addit. Technol. 10:168–173, 2004. © 2004 Society of Plastics Engineers.
Mold susceptibility of rigid PVC/wood‐flour composites
Authors: Dawson‐Andoh Benjamin , Matuana Laurent M. , Harrison Joel
Published: December 2004

Rigid PVC/wood‐flour composite lumber containing either hardwood (maple) or a softwood (southern pine) wood flour at different levels of wood‐flour content was evaluated for susceptibility to fungal colonization and discoloration by using standard tests that mimicked exterior (ASTM G21) and interior (ASTM D3273) environments, respectively. In the exterior test protocol, although both types of PVC/wood‐flour composite lumber exhibited fungal colonization and discoloration, the composites containing maple exhibited greater discoloration than those containing pine. Irrespective of wood species, fungal colonization and discoloration in the composite lumber were greater at the bottom faces where they were in constant contact with moisture. The wood content range (50–100 phr) used in this study showed no effect on extent of fungal colonization and discoloration. All composites showed no discoloration in the interior test protocol. Both optical microscopy and environmental scanning electron microscopy clearly demonstrated that wood flour particulates are not completely encapsulated by the PVC matrix, so that exposed wood flour in the surface crevices of the composite lumber may serve as points of moisture sorption and staging points for fungal colonization and discoloration. J. Vinyl Addit. Technol. 10:179–186, 2004. © 2004 Society of Plastics Engineers.
Three independent mutations in the same exon of thePCCB gene: Differences between Caucasian and Japanese propionic acidaemia
Authors: Tahara T. , Kraus J. P. , Ohura T. , Rosenberg L. E. , Fenton W. A.
Published: December 2004

Propionic acidaemia is an inborn error of organic acid metabolism caused by deficiency of propionyl‐CoA carboxylase (PCC). Enzyme deficiency can result from mutations in either of the non‐identical α‐ and β‐subunits. We have screened genomic DNA from patients with defects in the β‐subunit from two ethnic groups (Caucasians and Japanese) and detected three types of mutations in the same exon of the coding sequence of the β‐subunit: an insertion/deletion that replaces 14 nucleotides with 12 nucleotides of unrelated sequence and eliminates anMsp I site; a 3‐bp deletion of a single isoleucine codon immediately proximal to thatMsp I site; and a C → T transition in the sameMsp I site. The insertion/deletion was detected only in Caucasian patients in 11 of 34 mutant alleles; the C → T transition was found only in Japanese patients in 4 of 12 mutant alleles. Following digestion of genomic DNA byMsp I, both of these mutations were detected on Southern blots by the presence of a 2.7‐kbp band; they can be distinguished from one another by allele‐specific oligonucleotide hybridization following PCR amplification. These results underscore the independent origin of the mutations in the two populations and suggest a key role of this exon in the β‐subunit of PCC.
Acylcarnitines in amniotic fluid: Application to the prenatal diagnosis of propionic acidaemia
Authors: Van Hove J. L. K. , Chace D. H. , Kahler S. G. , Millington D. S.
Published: December 2004

Acylcarnitines were assayed in amniotic fluid by isotope dilution tandem mass spectrometry. Control values for propionylcarnitine, C4 and C5 acylcarnitines were established. Propionylcarnitine was elevated by a factor of 5 relative to controls in the amniotic fluid of three pregnancies affected with propionic acidaemia. This may provide a convenient new method for prenatal diagnosis of propionic acidaemia. One pregnancy at risk for propionic acidaemia but unaffected according to methylcitrate analysis had an intermediate level of propionylcarnitine, indicating the need for further studies to determine the range of concentration in probable heterozygotes.
Urinary sugar phosphates and related organic acids in fructose‐1,6‐diphosphatase deficiency
Authors: Nakai A. , Shigematsu Y. , Liu Y. Y. , Kikawa Y. , Sudo M.
Published: December 2004

Two sisters with fructose‐1,6‐diphosphatase deficiency are reported. They presented with ketonuria, elevated plasma transaminase activity and severe metabolic acidosis during hypoglycaemic crises, which resembled Reye syndrome. Intravenous fructose tolerance tests provoked severe hypoglycaemia and metabolic acidosis. Fructose‐1,6‐diphosphatase activities in both peripheral leukocytes and cultured lymphocytes were below the limit of detection. Urinary organic acid analysis during crises revealed markedly increased excretion of lactate, ketone bodies, glycerol and glycerol‐3‐phosphate. We newly identified other glycolytic intermediates, glyceraldehyde, 3‐phosphoglycerate and fructose‐1,6‐diphosphate, in the urine during hypoglycaemic attacks or after fructose tolerance tests. Identification of such compounds may be useful in the early diagnosis of this disease.
Functional studies in fibroblasts of adenylosuccinase‐deficient children
Authors: Van den Bergh F. , Vincent M. F. , Jaeken J. , Van den Berghe G.
Published: December 2004

In fibroblasts of severely retarded (type I) adenylosuccinase (ASase)‐deficient children, activities with the two substrates of the enzyme, succinylaminoimidazole carboxamide ribotide (succinyl‐AICAR) and adenylosuccinate are decreased in parallel, to about 30% of normal. In a markedly less retarded (type II) patient, ASase activity with adenylosuccinate reaches only 3% of normal, whereas activity with succinyl‐AICAR is also about 30% of normal. To assess the functional significance of a partial versus a profound deficiency of ASase, precursor incorporation studies were performed in intact fibroblasts. In cells from controls and from type I patients, incorporation of 0.2 mmol/L [14C]formate into adenine and guanine nucleotides was not accompanied by accumulation of either [14C]succinyl‐AICAR or [14C]adenylosuccinate. Similarly, incorporation of 20 µmol/L [14C]hypoxanthine was not accompanied by accumulation of [14C]adenylosuccinate. In contrast, in fibroblasts of the type II patient, in accordance with the profound deficiency of ASase with adenylosuccinate, and with the inhibitory effect of Cl− and nucleotides on the activity with succinyl‐AICAR, incorporation of [14C]formate resulted in accumulation of [14C]succinyl‐AICAR and [14C]adenylosuccinate, and incorporation of [14C]hypoxanthine in a marked build‐up of [14C]adenylosuccinate. That both precursors were still incorporated into the adenine nucleotides of the fibroblasts of the type II patient indicates that adenylate synthesis remains possible even with 3% residual ASase activity, as also shown by their grossly normal ATP concentrations. The results suggest that the pathophysiology of ASase deficiency may be mediated at least in part by accumulation of succinyladenosine and succinyl‐AICAriboside.
A fluorimetric enzyme assay for the diagnosis of Sanfilippo disease C (MPS III C)
Authors: Voznyi Ya. V. , Karpova E. A. , Dudukina T. V. , Tsvetkova I. V. , Boer A. M. , Janse H. C. , van Diggelen O. P.
Published: December 2004

Both the α‐ and β‐anomers of 4‐methylumbelliferyl‐D‐glucosaminide were synthesized and shown to be substrates for the lysosomal acetyl‐CoA: glucosaminideN‐acetyltransferase. Using the β‐anomer, fibroblasts and leukocytes from 11 different Sanfilippo C patients showed <1% of mean normalN‐acetyltransferase activity. Heterozygotes showed intermediate activities. The enzymatic liberation of the fluorochrome from 4‐methylumbelliferyl‐β‐d‐glucosaminide requires the sequential action of theN‐acetyltransferase and β‐hexosaminidase. Normal β‐hexosaminidase activity caused complete hydrolysis of the reaction intermediate 4‐methylumbelliferyl‐β‐d‐N‐acetylglucosaminide formed by theN‐acetyltransferase. In cell extracts with a β‐hexosaminidase deficiency, however, a second incubation in the presence of excess β‐hexosaminidase is needed to avoid underestimation of theN‐acetyltransferase activity.
Nutritional value of essential amino acids in the treatment of adults with phenylketonuria
Authors: Dotremont H. , François B. , Diels M. , Gillis P.
Published: December 2004

Conclusion

The present short‐term N‐balance study in adult PKU patients receiving a mixture of LNAA establishes a limited retention of nitrogen. Whether lysine could be the limiting amino acid remains to be determined by new short‐term N‐balance studies, with lysine added to the LNAA mixture. Therefore, special caution should be taken in the long‐term use in PKU patients of LNAA without any added lysine.
Acylcarnitine profile in tissues and body fluids of biotin‐deficient rats with and withoutl‐carnitine supplementation
Authors: Shigematsu Y. , Bykov I. L. , Liu Y. Y. , Nakai A. , Kikawa Y. , Sudo M. , Fujioka M.
Published: December 2004

Since biotin‐deficient (BD) rats are a good animal model for human multiple carboxylase deficiency and have low plasma free carnitine levels, short‐chain acylcarnitine profiles in biotin‐deficient rats withl‐carnitine supplementation (BDC rats) and BD rats were investigated by fast‐atom bombardment and tandem mass spectrometry and gas chromatography/mass spectrometry. By the latter method, 3‐hydroxyisovalerylcarnitine was identified in BD rats, and showed the greatest accumulation among short‐chain acylcarnitines in tissues of BD rats, while the tissue levels of propionic acid were more markedly elevated than those of 3‐hydroxyisovaleric acid. The tissue levels of 3‐hydroxyisovaleryl‐carnitine were significantly lower and those of propionyl‐carnitine were somewhat higher in BDC rats than in BD rats, while the tissue levels of propionic acid and 3‐hydroxyisovaleric acid in BDC rats were lower than those in BD rats. These changes were more apparent in kidney than in other tissues. The amounts of urinary excretion of acylcarnitines were markedly larger, and those of 3‐hydroxyisovaleric acid were somewhat smaller in BDC rats than in BD rats, while those of propionic acid were very low in BD and BDC rats as compared with those of 3‐hydroxyisovaleric acid. It seems that the relationship between the concentrations of 3‐hydroxyisovalerylcarnitine and those of propionylcarnitine reflects the unique metabolism of the related metabolites in tissues, especially in kidney, which may be influenced by their urinary excretion and the availability of free carnitine. These data in biotin deficiency suggest that carnitine supplementation is possibly beneficial for patients with holocarboxylase synthetase deficiency who respond incompletely to biotin therapy.
A Thermodynamic Study of Arctic Paleoclimatology
Authors: Shaw David M. , Donn William L.
Published: December 2004

The thermodynamic model of J. Adem has been applied to the determination of Arctic and hemispheric surface temperatures with both ice-covered and ice-free states of the Arctic Ocean. The effect of glaciated and nonglaciated continents is included in the investigation. With an ice cover over the Arctic, as at present, computed temperatures for the polar sea and the Northern Hemisphere correspond closely with present observations. Over a broad range of the critical parameters, removal of the ice cover yields computed temperatures that remain well above freezing level throughout the year. With glaciated continents computed Arctic temperatures are depressed.
Possible Causes of the Variability of Postglacial Uplift in North America
Authors: Fillon Richard H.
Published: December 2004

Postglacial uplift data from 33 sites in northeastern North America reveal that during the period from 11,000 years B.P. to 7000 years B.P., glacio-isostatic uplift rates varied in a consistent manner with distance from the former margin of the Laurentide Ice Sheet. The consistent trends of these uplift rate variations with distance from the former ice sheet margin suggest that they were not the result of changes in the rate of ice sheet retreat or local tectonic activity. They instead may have resulted from rebound affected significantly by the earth's viscosity at a depth approximately equal to the wavelength of isostatic deformation [McConnell, R.K., Jr., Journal of Geophysical Research70, 5171 (1965)]. Extremely high viscosities below 600 km, however, probably provide the lower limit for this relationship.
Retreat of the Laurentide Ice Sheet from 14,000 to 9000 Years Ago
Authors: Wright H. E.
Published: December 2004

The intricate pattern of moraines of the Laurentide ice sheet in the Great Lakes region reflects the marked lobation of the ice margin in late Wisconsin time, and this in turn reflects the distribution of steam-cut lowlands etched in preglacial times in the weak-rock belts of gentle Paleozoic fold structures. It is difficult to trace and correlate moraines from lobe to lobe and to evaluate the magnitude of recession before readvance, but three breaks stand out in the sequence, with readvances at about 14,500, 13,000, and 11,500 years ago. The first, corresponding to the Cary advance of the Lake Michigan lobe, is represented to the west by distant advance of the Des Moines lobe in Iowa, and to the east by the overriding of lake beds by the Erie lobe. The 13,000-year advance is best represented by the Port Huron moraine of the Lake Michigan and Huron lobes, but by relatively little action to west and east. The 11,500-year advance is based on the Valders till of the Lake Michigan lobe, but presumed correlations to east and west prove to be generally older, and the question is raised that these and some other ice advances in the Great Lakes region may represent surges of the ice rather than regional climatic change. Surging may involve the buildup of subglacial meltwater, which can provide the basal sliding necessary for rapid forward movement. It would be most favored by the conditions in the western Lake Superior basin, where the Superior lobe had a suitable form and thermal regime, as estimated from geomorphic and paleoclimatic criteria. The Valders advance of the Lake Michigan and Green Bay lobes may also have resulted from a surge: the eastern part of the Lake Superior basin, whence the ice advanced, has a pattern of deep gorges that resemble subglacial tunnel valleys, which imply great quantities of subglacial water that may have produced glacial surges before the water became channeled.
Past Sea Levels, Eustasy and Deformation of the Earth
Authors: Walcott R. I.
Published: December 2004

Vertical movements of the earth's surface related to postglacial rebound, the eustatic rise in sea level and the elastic deformation of the globe due to melting of late glacial ice sheets are calculated for simplified models of the earth. The movements of the ground are large and require a reevaluation of what is meant by eustatic sea level change. This is defined here as an ocean-wide average change in mean sea level and its measurement requires widely distributed observations weighted according to the areas of oceans they represent. Evidence of a postglacial (6000-0 years BP) relative rise in sea level comes largely from regions affected by ground subsidence related to adjacent upward postglacial rebound movements in deglaciated areas: evidence for a relative fall of sea level comes from coastlines well removed from areas of rebound and which have been affected by a rise of the continental areas through compensation for the eustatic load. It is concluded: (1) no substantial eustatic change of sea level in the past 6,000 years is required to explain postglacial sea levels: (2) in late glacial time the eustatic curve is probably more like the sea level curve of Texas and Mexico than that of the Atlantic seaboard of the United States: (3) that the information of past sea levels, when sufficiently widespread, can provide an important method of studying the deep mechanical structure of the earth.
Late- and Postglacial Climatic Change in the Northern Midwest, USA: Quantitative Estimates Derived from Fossil Pollen Spectra by Multivariate Statistical Analysis
Authors: Webb Thompson , Bryson Reid A.
Published: December 2004

Canonical correlation analysis provides a means of reconstructing quantitative time series of past climatic variables during the last 15,000 years from fossil pollen spectra collected at three sites in the northern Midwest. This multivariate statistical technique was applied to a spatial array of modern pollen and climatic data in order to derive a set of mathematical transfer functions. These transform the fossil pollen spectra directly into quantitative estimates of past climatic values. The basic sequence of climatic events that is reconstructed is in general agreement with previous studies of postglacial climates in the Midwest, but quantitative estimates for certain of the variables, e.g., temperature and precipitation, are given for the first time.

Fossil pollen from three cores collected from lakes in Wisconsin and Minnesota allow a preliminary reconstruction of past east-west and north-south gradients of the climatic variables. Because changes in the circulation patterns in midlatitudes are the principal mechanism causing fluctuations in temperature and precipitation, past records of the atmospheric circulation are reconstructed along with records of temperature and rainfall. The time series derived show that the most pronounced climatic change indicated in Wisconsin and Minnesota occurred at the end of the Pleistocene (the beginning of the Holocene). This change is particularly evident in the climatic variables related to temperature, which rose ca. 3.3°C. A decrease in snowfall also occurred.

During the Holocene, the most marked change appears in the results from Kirchner Marsh, where the amount of dry western air began to increase and the precipitation to decrease about 9500 B.P. A reversal of these changes occurred about 5000 B.P. In contrast, relatively little change occurred among the reconstructed values from Wisconsin; a marked east-west precipitation gradient, therefore, developed in this region of the Midwest from 9500 to 5000 B.P.
Absolute Pollen Diagram of Redrock Lake, Boulder County, Colorado
Authors: Maher Louis J.
Published: December 2004

Redrock Lake is situated at 3,095 m in the subalpine zone on the east flank of the Front Range, Boulder County, Colorado. The lake lies on Pinedale moraine, and it contains 170 cm of organic sediments that overlie 10 cm of silty clay. The oldest of seven 14C dates from the organic sediment is 9,490 ± 150 yr B.P., a minimum estimate of the time since Middle Pinedale ice receded from the lake basin.

A percentage pollen diagram and an absolute pollen diagram providing pollen deposition rates in grains/cm2/14C yr are compared and contrasted. Possible measurement errors are considered in detail, and for the first time confidence limits are assigned to all pollen data. A means of converting 14C years to calendar years is presented, and its effect on the diagram's deposition rates is discussed.

The silty clay contains a peculiar Artemisia-dominated pollen assemblage with very low pollen influx rates, which suggests the lake was receiving large volumes of glacial meltwater during its early history. The overlying organic sediments are characterized by pollen deposition rates of 4,000–6,000 grains/cm2/yr. With fluctuations, deposition rates of Pinus and total anemophilous pollen increase upward in the core; this evidence for a general upward shift in the region's vegetation zones during Postglacial time is supported by pollen trends from modern surface samples.
Late Quaternary Glacial and Climatic History of Northern Cumberland Peninsula, Baffin Island, N.W.T., Canada
Authors: Miller Gifford H.
Published: December 2004

Radiocarbon dates on molluses in marine facies associated with glacial deposits in northern Cumberland Peninsula indicate both main fiord (Laurentide) ice and local glaciers remained at their late Wisconsin maxima until ca. 8000 BP. Essentially continuous deglaciation followed; local corrie glaciers melted out by 7100 BP and by 5500 BP fiord glaciers had receded behind the present margin of the Penny Ice Cap. The Hypsithermal warm interval probably lasted from ca. 8000 to 5000 BP. Lichenometry and radiocarbon dates on peat and buried organic horizons delimit a detailed Neoglacial chronology. Of 46 outlet and corrie glaciers investigated, the oldest Neoglacial moraines are dated lichenometrically at 3200 ± 600 BP. Subsequent advances terminated immediately prior to ca. 1650, 780, 350, and 65 yr BP, the most recent of which marked the most extensive ice coverage during the Neoglacial. The highest occurrence of lateral moraines from late Wisconsin advances of local and Laurentide ice suggest that at the late Wisconsin glacial maximum, depression of snowline varied from 450 m below present at the coast to 350 m below present level in the vicinity of the Penny Ice Cap. Moraines, surrounded by glacial ice and lying above the present steady-state ELA, suggest that during the Hypsithermal snowline was up to ca. 200 m above its present elevation. A radiometrically controlled reconstruction of relative summer paleotemperatures for the postglacial derived independently of lichenometry agrees well with the lichenometric age dating of moraines. The data suggest that between ca. 1650 and 900 BP climatic conditions were unfavorable for glacier growth, whereas the period ca. 800-65 yr BP was one of general glacial activity. During the last decade permanent snow cover has been increasing in the area. Previously reported data on climatic trends in the Canadian Arctic based on palynological analyses are similar to the chronology reported here.
Chronology of Cirque Glaciation, Colorado Front Range
Authors: Benedict James B.
Published: December 2004

Moraines and rock glaciers in Front Range cirques record at least four, and possibly five, intervals of Holocene glacier expansion. The earliest and most extensive was the Satanta Peak advance, which deposited multiple terminal moraines near present timberline shortly before 9915 ± 165 BP. By 9200 ± 135 BP, timberline had risen to at least its modern elevation; by 8460 ± 140 BP, patterned ground on Satanta Peak moraines had become inactive. Although a minor ice advance may have occurred just prior to 7900 ± 130 BP, there is no evidence that glaciers or perennial snowbanks survived in the Front Range during the “Altithermal” maximum (ca. 7500–6000 BP), or during a subsequent interval of alpine soil formation (ca. 6000–5000 BP).

Glaciers were larger during the Triple Lakes advance (5000–3000 BP) than at any other time during Neoglaciation. Minimum ages of 4485 ± 100 BP, 3865 ± 100 BP, and ca. 3150 BP apply to a threefold sequence of Triple Lakes deposits in Arapaho Cirque. After an important interval of soil formation and cavernous weathering, glaciers and rock glaciers of the Audubon advance (1850–950 BP) reoccupied many cirques, and perennial snowbanks blanketed much of the area above present timberline; although the general Audubon snow cover had begun to melt from valley floors by 1505 ± 95 BP, expanded snowbanks lingered on tundra ridge crests until 1050–1150 BP, and glaciers persisted is sheltered cirques until at least 955 ± 95 BP. Following a minor interval of ice retreat, glaciers of the Arapaho Peak advance (300–100 BP) deposited multiple moraines in favorably oriented cirques.

Interpretation of Holocene glacial deposits in the Southern and Central Rocky Mountains has been hampered by (1) a heavy reliance upon relative-dating criteria, many of which are influenced by factors other than age; (2) the assumption that glacial advances in high-altitude cirques can be correlated directly with alluvial deposition in far-distant lowlands; and (3) the assumption that glacial advances have necessarily been synchronous throughout the Rocky Mountain region and the world. Although Holocene glacier fluctuations in the Front Range are believed to reflect changes in regional climate, the Front Range chronology does not have particularly close analogs in other parts of North America. Better-dated local sequences are needed before the hypothesis of global synchroneity can be adequately evaluated; until synchroneity has been proven, long-distance correlations and worldwide cycles of recurring glaciation will remain unconvincing.
Correlation of Marine and Continental Quaternary Pollen Records from the Northeast Pacific and Western Washington
Authors: Heusser Calvin J. , Florer Linda E.
Published: December 2004

Late-glacial and postglacial pollen stratigraphy and radiocarbon chronology of a marine core from the continental slope and a core from the western Olympic Peninsula, ca. 110 km apart, are compared. Divisible into four pollen assemblage zones (L, P-1, P-2, and P-3), the cores exhibit a succession of correlative zonal prominences: grass-sedge (L), pine (P-1), alder (P-1-P-2 boundary), and hemlock (P-3). Volcanic ash of Mt. Mazama provenance is also correlative in zone P-2. Quantitative relationships of the pollen in the cores (relative and absolute numbers and pollen influx) are dissimilar, however, and are attributed to the influence of the Columbia River pollen load reaching the locale of the continental slope core compared with the local pollen rain influencing the Olympic Peninsula core site.
Paleoenvironments and Cultural Diversity in Late Pleistocene South America
Authors: Bryan Alan L.
Published: December 2004

After a summary assessment of certain selected early man sites in various parts of America, the environment of the Venezuelan coastal plain is discussed in order to evaluate the stratigraphy and radiometric dating of the Taima-Taima site, near Coro, Venezuela, where mammals, many now extinct, were killed by people making El Jobo points about 13,000 years ago.

Potentially important areas in Peru, Chile and Brazil are mentioned. Certain problems in the models and interpretation of South American paleoclimates are pointed out.

The presence of at least four different bifacially flaked stone projectile point traditions in widely separated and environmentally diverse parts of America between 11,000 and 13,000 yr ago suggests that the immediate cultural antecedents of these traditions were essentially independent of one another. From this it is argued that several early American flaked-stone point traditions developed indigenously in America from technological bases which were present in the Old World Middle Paleolithic.
Analysis of a Core Through the Meighen Ice Cap, Arctic Canada, and its Paleoclimatic Implications
Authors: Koerner R.M. , Paterson W.S.B.
Published: December 2004

Analyses of crystal size, bubble content, oxygen isotope ratio, specific electrolytic conductivity, and the distribution of firn and dirt layers in a core, 121.2 m long, from surface to bedrock near the highest point of the Meighen Ice Cap, leads to the following outline of the ice cap's history. The ice cap, which has always been stagnant, originated in the cold period that followed the postglacial Climatic Optimum. After initial growth came a period of negative mass balance in which the area and thickness of the ice cap diminished and the surface slope at the core site steepened. The end of this period, at least 600 y.a., is marked by a discontinuity at 54 m depth in the core; above this level, the values of most parameters differ significantly from their values below. There followed a period of growth by the end of which, some 80 y.a., the ice cap had attained its maximum thickness; this period included the coldest interval in the ice cap's history. Ablation has predominated since then and up to 13 m of ice have been lost at the core site. This history resembles that of the Ward Hunt Ice Shelf.
Sediment Analysis of a Prehistoric Rockshelter: The Abri Pataud
Authors: Farrand William R.
Published: December 2004

Rockshelter and cave-mouth deposits accumulate in specialized niches through the breakdown of the enclosing bedrock, the addition of windblown and fluvial sediment and, in the case of prehistoric sites, human habitation debris. Certain modifications of routine sediment analysis are necessary in order to realize the full potential of paleoenvironmental interpretation. These sediments are coarse, necessitating the collection of large samples, commonly 10–20 kg. The size and shape of the coarse fraction yields information on rockfalls, freeze-thaw activity, and weathering effects. Travertine and soil-carbonate coatings on the rock fragments indicate variations in ambient humidity and soil formation, respectively. Studies of the granulometry, mineralogy, and geochemistry of the fine fraction lead to conclusions concerning primarily the postdepositional modification of the sediments. Heavy minerals can be important in determining the provenience of the fine sediment. These methods of analysis are discussed in detail with the Abri Pataud as a specific example, and caution is urged in making regional generalizations from the study of a single site.
Note on Pollen Extraction from Coarse Sediments
Authors: Juvigné E.
Published: December 2004

The following note on a new method for extracting pollen from fossil pollen grains summarizes two articles in French, published in Annales de la Société Géologique de Belgique (Juvigné, 1973a; 1973b).

The new method proposed has three important parts: (1) Elutriation of the sediment in water; (2) the specific gravity of the heavy liquid must be between 2.25 and 2.5; and (3) the dispersion of the sediment in the heavy liquid is made with a high-speed mixer.
Growth rate of the Laurentide Ice Sheet and sea Level Lowering (with Emphasis on the 115,000 BP Sea Level Low)
Authors: Andrews J.T. , Mahaffy M.A.W.
Published: December 2004

A physically plausible three-dimensional numerical ice flow model is used to examine the rate at which the Laurentide Ice Sheet could spread and thicken using as input likely values for the rate of fall of snowline and the amount of net mass balance over the growing ice sheet. This provides then both a test of the hypothesis of “instantaneous glacierization” and of the suggested rapid fall of world sea level to between −20 and −70 m below present at 115,000 BP. Two experiments are described: The first terminated after 10,050 years of model run with ice sheets centered over Labrador-Ungava and Baffin Island with a total volume of 3.0 × 106 km3 of ice, whereas the second was completed after 10,000 years and resulted in a significantly larger ice sheet (still with two main centers) with a volume of 7.78 × 106 km3 of ice. This latter figure is equivalent to the mass required to lower world sea level by 19.4 m. Our results indicate that large ice sheets can develop in about 10,000 years under optimum conditions.
Pleistocene Climates in Central Europe: At least 17 Interglacials after the Olduvai Event
Authors: Fink Julius , Kukla George J.
Published: December 2004

At least 17 times during the past 1.7 million years, the deposition of loess containing characteristic cold-resistant gastropods was interrupted by the development of temperate interglacial forests. This conclusion was reached in a study of paleomagnetically dated fossiliferous loess sequences in Krems, Austria and Brno, Czechoslovakia. Sequences of windblown loess interlayered with hillwash loams and steppe and forest soils exposed in brickyards around Brno and Praha, Czechoslovakia, revealed eight major depositional cycles within the Brunhes paleomagnetic epoch. We now report nine additional cycles of late and middle Matuyama age bringing the total number of glacial-interglacial cycles to 17, which occurred after the end of the Olduvai. The cycles are separated bymarklines, levels of abrupt environmental change correlative with the terminations in deep-sea sediments. They are the boundaries between the windblown loess containing cold-resistant snail assemblages and between the clayey originally decalcified soils, accompanied by warmth lovingHelixandBanaticasnail faunas of hardwood forests. Because the presence of temperate forests in northwestern and central Europe is instrumental in the definition of an interglacial, each markline represents a glacial-interglacial boundary and each cycle is a glacial-interglacial cycle.
Paleomagnetic Study at a Nuclear Power Plant Site near Bakersfield, California
Authors: Davis P. , Smith J. , Kukla G.J. , Opdyke N.D.
Published: December 2004

At the San Joaquin plant site near Bakersfield, California, the Brunhes/Matuyama reversal was identified 4 m below an ash probably correlative with the Bishop Tuff. Deposition of coarse detritus in a high-energy environment preceded the reversal, whereas a low-energy lake and back-swamp type sedimentation persisted through most of the interval, separating the reversal and the ash. Sediments below the reversal are strongly remagnetized in a normal field. Identification of the original polarity is possible only with some of the specimens, so that accurate positioning of the reversal plane required dense and multiple sampling. Similar precaution at all sites where reversals are used for time-stratigraphic correlations is recommended. Paleomagnetic investigation was particularly useful in proving the presence of unfaulted strata at least 0.5 my old, as required by safety regulations of the U.S. Nuclear Regulatory Commission (NRC). This is due to the fact that any thick layer of reversely magnetized sediment is with high probability older than 0.7 my.