bluuebunny/crossref_metadata_2025_split huggingface dataset:
Molecular orientation of ultrahigh molecular weight polyethylene induced by various sliding motions
Authors: Sambasivan Sharadha , Fischer Daniel A. , Shen Ming C. , Hsu Stephen M. 
Published: July 2004

AbstractWear and wear debris of ultrahigh molecular weight polyethylene (UHMWPE) in joint replacements have been recognized as one of the major contributors to the failure of orthopedic implants. The detailed wear mechanism of polyethylene under biomechanic motions is not well understood. In simulation wear bench tests, it was found that unidirectional sliding produces the least amount of wear, reciprocating motion increases wear significantly, and cross‐shear motion (similar to hip and knee joint motion in the human body) produces the highest amount of wear. Conventional wear theories are inadequate to explain this observation. This study utilizes resonant absorption of linearly polarized soft X‐rays at a synchrotron radiation beam line to measure the molecular orientation of a UHMWPE surface layer subjected to different wear motions. Carbon‐K‐edge partial‐electron‐yield X‐ray absorption measurements were done on the worn UHMWPE samples. X‐ray absorption measurements show conclusively that the molecular chains of UHMWPE align preferentially parallel to the direction of sliding. Examination under various wear motions showed that unidirectional shear produced the maximum chain orientation, whereas cross‐shear wear motions produced the least amount of orientation. When polymeric chains align, the surface layer tends to be more brittle and hard, thus resisting wear. When they do not align, loose chains may be subjected to both Mode I and Mode II fracture, hence increasing the wear rate. This molecular alignment observation may offer an explanation of why different wear motions have different wear characteristics. © 2004 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 70B: 278–285, 2004
Removal of cupric ions from acidic sulfate solution using reticulated vitreous carbon rotating cylinder electrodes
Authors: Reade Gavin W , Nahle Ayssar H , Bond Peter , Friedrich Jens M , Walsh Frank C 
Published: July 2004

AbstractThe potentiostatic deposition of copper from acid sulfate solutions (0.50 mol dm−3 Na2SO4 at pH 2 and 298 K) was studied at four porosity grades (10, 30, 60 and 100 pores per linear inch, ppi) of reticulated vitreous carbon (RVC) rotating cylinder electrode (RCE). The rate of removal of cupric ions from a 200 cm3 volume of electrolyte was examined as a function of the grade of RVC foam, the electrode potential and the initial cupric ion concentration. For the 100 ppi material, the product of the mass transport coefficient and the electroactive area per unit volume of electrode (kmAe) was equal to 0.28 s−1 at a potential of −500 mV vs SCE for an initial cupric ion concentration of 0.85 mmol dm−3 and a constant rotation speed of 1500 rev min−1. Under the experimental conditions, an initial dissolved copper concentration of 63.5 ppm could be reduced to <0.1 ppm in approximately 60 min using a 100 ppi RVC RCE. SEM studies showed some non‐uniform deposition of metal due to heterogeneous nucleation of copper together with the development of rough deposits. Copyright © 2004 Society of Chemical Industry
Borate–nucleotide complex formation depends on charge and phosphorylation state
Authors: Kim Danny H. , Faull Kym F. , Norris Andrew J. , Eckhert Curtis D. 
Published: July 2004

AbstractFlow injection analysis with electrospray ionization mass spectrometry was used to investigate borate–nucleotide complex formation. Solutions containing 100 µM nucleotide and 500 µM boric acid in water–acetonitrile–triethylamine (50 : 50 : 0.2, v/v/v; pH 10.3) showed that borate complexation with nicotinamide nucleotides was significantly influenced by the charge on the nicotinamide group and the number of phosphate groups on the adenine ribose. Borate binding decreased in the order of NAD+, NADH, NADP+ and NADPH. To investigate the relationship between complex formation and phosphorylation, association constants (KA) of borate–adenine (AMP, ADP, ATP), –guanine (GMP, GDP, GTP), –cytidine (CMP, CDP, CTP) and –uridine (UMP, UDP, UTP) complexes were compared. The results showed that the number of nucleotide phosphate groups was inversely proportional to the relative abundance of the borate complexes, with the KA of borate–nucleotide complex decreasing in the order mono‐, di‐ and tri‐phosphates (AMP ≈ GMP ≈ CMP ≈ UMP > ADP ≈ GDP ≈ CDP ≈ UDP > GTP > ATP ≈ CTP ≈ UTP). At pH 7.4, using ammonium bicarbonate buffer, only borate–NAD+ complex was observed. This indicates that the borate–NAD+ complex may be the most physiologically relevant of those studied. Copyright © 2004 John Wiley & Sons, Ltd.
Identification of low molecular weight proteins isolated by 2‐D liquid separations
Authors: Zhu Kan , Miller Fred R. , Barder Timothy J. , Lubman David M. 
Published: July 2004

AbstractProteins with molecular mass (Mr) <20 kDa are often poorly separated in 2‐D sodium dodecyl sulfate polyacrylamide gel electrophoresis. In addition, low‐Mr proteins may not be readily identified using peptide mass fingerprinting (PMF) owing to the small number of peptides generated in tryptic digestion. In this work, we used a 2‐D liquid separation method based on chromatofocusing and non‐porous silica reversed‐phase high‐performance liquid chromatography to purify proteins for matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometric (MALDI‐TOFMS) analysis and protein identification. Several proteins were identified using the PMF method where the result was supported using an accurate Mr value obtained from electrospray ionization TOFMS. However, many proteins were not identified owing to an insufficient number of peptides observed in the MALDI‐TOF experiments. The small number of peptides detected in MALDI‐TOFMS can result from internal fragmentation, the few arginines in its sequence and incomplete tryptic digestion. MALDI‐QTOFMS/MS can be used to identify many of these proteins. The accurate experimental Mr and pI confirm identification and aid in identifying post‐translational modifications such as truncations and acetylations. In some cases, high‐quality MS/MS data obtained from the MALDI‐QTOF spectrometer overcome preferential cleavages and result in protein identification. Copyright © 2004 John Wiley & Sons, Ltd.
Electron ionization‐induced fragmentation of N‐ and O‐alkoxymethylated carbostyril and phenanthridinone
Authors: Szmigielski Rafał , Danikiewicz Witold 
Published: July 2004

AbstractUnimolecular fragmentation patterns of N‐alkoxymethylated carbostyril and phenanthridinone and their O‐alkoxymethyl isomers were studied. The main fragmentation reaction observed for the studied compounds is the elimination of an aldehyde molecule. The main products of this reaction are the appropriate N‐methyl derivatives, but ions with other structures are also formed. This reaction is supposed to proceed via 1,3‐H shift in the alkoxymethyl group in the case of the N‐alkoxymethyl derivatives and by a multi‐step mechanism for O‐alkoxymethylated compounds. Another important fragmentation common for all studied compounds is the loss of an alkyl radical from N‐ and O‐alkoxymethyl groups, yielding the appropriate stable isomeric cations, which, according to the results of the further fragmentation, undergo fast equilibration reaction via an ion–neutral complex. This process is accompanied by the unusually high kinetic energy release value. Copyright © 2004 John Wiley & Sons, Ltd.
Fragmentation study of peptide acetals and aldehydes using in‐source collision‐induced dissociation
Authors: Buré Corinne , Falher Guy Le , Lange Catherine , Delmas Agnès 
Published: July 2004

AbstractThe fragmentation of peptide acetals and peptide diols, corresponding to the hydrated form of the peptide aldehyde, is dominated by the successive losses of two molecules of MeOH and water, respectively. Using model peptides, the fragmentation mechanism, with respect to the loss of methanol and water, was elucidated. The first loss was certainly charge‐directed whereas the second probably occurred via the nucleophilic attack of the nitrogen of an amine on the C‐terminal carbon leading to a cyclic ion. Copyright © 2004 John Wiley & Sons, Ltd.
Repeated contact with subtoxic soman leads to synaptic vulnerability in hippocampus
Authors: Munirathinam Subramani , Bahr Ben A. 
Published: July 2004

AbstractSoman, an anticholinesterase and dangerous nerve agent, produces convulsions, memory impairment, and cell loss in the brain, especially in the hippocampus. Soman‐induced accumulation of acetylcholine initiates mechanisms responsible for the development of incapacitating seizures. The prolonged epileptiform nature of these seizures causes the release of another excitatory neurotransmitter, glutamate, which has been linked to the toxic action of the nerve agent. Here, we tested whether subtoxic soman exposures influence the brain's sensitivity to glutamate‐based excitotoxicity. Over a 1‐week period, hippocampal slice cultures were exposed daily to a transient level of soman that produced no evidence of synaptic deterioration. After the subtoxic soman treatments, however, the tissue became vulnerable to a brief episode of glutamate receptor overstimulation that normally resulted in little or no excitotoxic damage. In those slice cultures treated with subtoxic soman, a decline in synaptic markers as well as an increase in spectrin breakdown occurred 24 hr after the mild excitotoxic event. Exposure to high soman concentrations alone produced similar synaptic degeneration, but without evident cell death, suggesting that synaptic decline is an early neurotoxicological response to the nerve agent. Interestingly, enhanced excitotoxic sensitivity caused the brain tissue to become susceptible to disparate insults initiated before or after the soman contact. These findings indicate that seemingly innocuous soman exposures leave the hippocampus sensitive to the types of insults implicated in traumatic brain injury and stroke. They also warn that asymptomatic contact with soman may lead to progressive synaptopathogenesis and that early indicators of soman exposure are critical to prevent potential brain injury. © 2004 Wiley‐Liss, Inc.
Fine structure of degeneration in the cochlear nucleus of the chinchilla after acoustic overstimulation
Authors: Kim J.J. , Gross J. , Potashner S.J. , Morest D.K. 
Published: July 2004

AbstractTo study plastic changes in the cochlear nucleus after acoustic stimulation, adult chinchillas were exposed once to a 4‐kHz octave‐band noise at 108 dB SPL for 3 hr. After survival times of 1, 2, 4, 8, and 16 weeks, samples were taken for electron microscopy from a part of the cochlear nucleus, where cochlear nerve fibers degenerated after the noise exposure. Progressive changes in fine structure were characterized as early, intermediate, and late stages of degeneration. Freshly occurring synaptic degeneration appeared in each period from 1–16 weeks. Endings with large round vesicles, putative excitatory synapses of the cochlear nerve, displayed progressive increases in neurofilaments and enlarged synaptic vesicles. Compared to controls, synaptic vesicles seemed fewer, often in small clusters in the interior of endings, and smaller in the synaptic zone. These early changes progressed to mitochondrial disintegration and overt “watery” degeneration. Some surviving endings, however, were shrunken and displaced partially by enlarged spaces in the synaptic complex. Dense‐cored vesicles gathered in these endings. In terminals with pleomorphic and flattened vesicles, presumed inhibitory endings, cytological changes appeared within 1 week and persisted for months. The synaptic endings darkened, some vesicles disintegrated, and many smaller flatter vesicles collapsed into heaps. Especially at the presynaptic membrane, vesicles were shriveled, but a few mitochondria were preserved. Without overt signs of synaptic degeneration, some of these cytological changes presumably reflect reduced synaptic activity in the inhibitory endings. These changes may contribute to a continuing process associated with abnormal auditory functions, including hyperacusis and tinnitus. © 2004 Wiley‐Liss, Inc.
Calendar year age estimates of Allerød–Younger Dryas sea‐level oscillations at Os, western Norway
Authors: Lohne Øystein S. , Bondevik Stein , Mangerud Jan , Schrader Hans 
Published: July 2004

AbstractA detailed shoreline displacement curve documents the Younger Dryas transgression in western Norway. The relative sea‐level rise was more than 9 m in an area which subsequently experienced an emergence of almost 60 m. The sea‐level curve is based on the stratigraphy of six isolation basins with bedrock thresholds. Effort has been made to establish an accurate chronology using a calendar year time‐scale by 14C wiggle matching and the use of time synchronic markers (the Vedde Ash Bed and the post‐glacial rise in Betula (birch) pollen). The sea‐level curve demonstrates that the Younger Dryas transgression started close to the Allerød–Younger Dryas transition and that the high stand was reached only 200 yr before the Younger Dryas–Holocene boundary. The sea level remained at the high stand for about 300 yr and 100 yr into Holocene it started to fall rapidly.The peak of the Younger Dryas transgression occurred simultaneously with the maximum extent of the ice‐sheet readvance in the area. Our results support earlier geophysical modelling concluding a causal relationship between the Younger Dryas glacier advance and Younger Dryas transgression in western Norway. We argue that the sea‐level curve indicates that the Younger Dryas glacial advance started in the late Allerød or close to the Allerød–Younger Dryas transition. Copyright © 2004 John Wiley & Sons, Ltd.
A major widespread climatic change around 5300 cal. yr BP at the time of the Alpine Iceman
Authors: Magny Michel , Haas Jean Nicolas 
Published: July 2004

AbstractPalaeoenvironmental and archaeological data from Arbon Bleiche, Lake Constance (Switzerland) give evidence of a rapid rise in lake‐level dated by tree‐ring and radiocarbon to 5320 cal. yr BP. This rise event was the latest in a series of three successive episodes of higher lake‐level between 5550 and 5300 cal. yr BP coinciding with glacier advance and tree‐limit decline in the Alps. This west‐central European climate change may have favoured the quick burial and the preservation of the Alpine Iceman recently found in the Tyrolean Alps. It has possible equivalents in many records from various regions in both hemispheres dating to 5600–5000 cal. yr BP and corresponds to global cooling and contrasting patterns of hydrological changes. This major mid‐Holocene climate event marks the Hypsithermal/Neoglaciation transition possibly resulting from a combination of different factors including orbital forcing, changes in ocean circulation and variations in solar activity. Copyright © 2004 John Wiley & Sons, Ltd.
Fluvial system response to Late Devensian (Weichselian) aridity, Baston, Lincolnshire, England
Authors: Briant Rebecca M. , Coope G. Russell , Preece Richard C. , Keen David H. , Boreham Steve , Griffiths Huw I. , Seddon Mary B. , Gibbard Philip L. 
Published: July 2004

AbstractLittle is known about the impact of Late Devensian (Weichselian) aridity on lowland British landscapes, largely because they lack the widespread coversand deposits of the adjacent continent. The concentration of large interformational ice‐wedge casts in the upper part of many Devensian fluvial sequences suggests that fluvial activity may have decreased considerably during this time. The development of optically stimulated luminescence (OSL) dating enables this period of ice‐wedge cast formation to be constrained for the first time in eastern England, where a marked horizon of ice‐wedge casts is found between two distinctive dateable facies associations. Contrasts between this horizon and adjacent sediments show clear changes in environment and fluvial system behaviour in response to changing water supply, in line with palaeontological evidence. In addition to providing chronological control on the period of ice‐wedge formation, the study shows good agreement of the radiocarbon and OSL dating techniques during the Middle and Late Devensian, with direct comparison of these techniques beyond 15 000 yr for the first time in Britain. It is suggested that aridity during the Late Devensian forced a significant decrease in fluvial activity compared with preceding and following periods, initiating a system with low peak flows and widespread permafrost development. Copyright © 2004 John Wiley & Sons, Ltd.
Reinvestigation of the classic late‐glacial Bølling Sø sequence, Denmark: chronology, macrofossils, Cladocera and chydorid ephippia
Authors: Bennike Ole , Sarmaja‐Korjonen Kaarina , SeppÄnen Anna 
Published: July 2004

AbstractThe late‐glacial Bølling period was first identified by Johs. Iversen on the basis of pollen results from Lake Bølling Sø in Denmark. Because there were no radiocarbon dates from the sequence the Bølling Chronozone (12 000–13 000 14C yr BP) was later established on the basis of dates from other sites. A new project is reinvestigating the sediments from the Bølling Sø sequence with AMS radiocarbon dating and multiproxy analyses. Here we present results of AMS radiocarbon dating, macrofossil analyses, cladoceran analyses (Cladocera concentrations and chydorid ephippia) and Pediastrum analyses (concentrations). The AMS dates on land plant remains show that the lower part of the sequence is around 12 500 14C yr BP, and thus clearly pre‐dates the Allerød chronozone. However, construction of a chronology for the sequence was problematic, partly because of reworking of macroscopic plant remains. The climate ameliorated after glacial conditions to such an extent that growth of plants could begin at ca. 12 500 14C yr BP, but the results of multiproxy analyses show little evidence for a further warming period during the pre‐Allerød part of the sequence. Lake productivity was low, and tree birch rare or maybe absent. This may reflect widespread occurrence of dead ice, unstable soils, heavy in‐wash of minerogenic matter to the lake, resulting in turbid water and rapid sedimentation. The early pioneer vegetation was characterised by Salix polaris and Dryas octopetala, and by herbs. The Allerød Chronozone, and especially its initial part, appears to have been relatively warm but reduced cladoceran concentrations and increased proportion of chydorid ephippia suggest that climate cooled in the middle Allerød and that the late Allerød was colder than the early part. The early Younger Dryas was probably colder than the late Younger Dryas. Clear warming is apparent at the beginning of the Holocene, where the first macrofossil evidence of trees (Betula pubescens, Populus tremula) is found. Copyright © 2004 John Wiley & Sons, Ltd.
Surface exposure dating of the Great Aletsch Glacier Egesen moraine system, western Swiss Alps, using the cosmogenic nuclide 10Be
Authors: Kelly Meredith A. , Kubik Peter W. , Von Blanckenburg Friedhelm , SchlÜchter Christian 
Published: July 2004

AbstractEgesen moraines throughout the Alps mark a glacial advance that has been correlated with the Younger Dryas cold period. Using the surface exposure dating method, in particular the measurement of the cosmogenic nuclide 10Be in rock surfaces, we attained four ages for boulders on a prominent Egesen moraine of Great Aletsch Glacier, in the western Swiss Alps. The 10Be dates range from 10 460±1100 to 9040±1020 yr ago. Three 10Be dates between 9630±810 and 9040±1020 yr ago are based upon samples from the surfaces of granite boulders. Two 10Be dates, 10 460±1100 and 9910±970 yr ago, are based upon a sample from a quartz vein at the surface of a schist boulder. In consideration of the numerous factors that can influence apparently young 10Be dates and the scatter within the data, we interpret the weighted mean of four boulder ages, 9640±430 yr (including the weighted mean of two 10Be dates of the quartz vein), as a minimum age of deposition of the moraine.All 10Be dates from the Great Aletsch Glacier Egesen moraine are consistent with radiocarbon dates of nearby bog‐bottom organic sediments, which provide minimum ages of deglaciation from the moraine. The 10Be dates from boulders on the Great Aletsch Glacier Egesen moraine also are similar to 10Be dates from Egesen moraines of Vadret Lagrev Glacier on Julier Pass, in the eastern Swiss Alps. Both the morphology of the Great Aletsch Glacier Egesen moraine and the comparison with 10Be dates from the inner Vadret Lagrev Egesen moraine support the hypothesis that the climatic cooling that occurred during the Younger Dryas cold episode influenced the glacial advance that deposited the Great Aletsch Glacier Egesen moraine. Because of the large size and slow response time of Great Aletsch Glacier, we suggest that the Great Aletsch Glacier Egesen moraine was formed during the last glacial advance of the multiphased Egesen cold period, the Kromer stage, during the Preboreal chron. Copyright © 2004 John Wiley & Sons, Ltd.
Enrichment of the glycoalkaloids α‐solanine and α‐chaconine from potato juice by Adsorptive Bubble Separation using a pH gradient
Authors: Backleh Marlène , Ekici Perihan , Leupold Günther , Coelhan Mehmet , Parlar Harun 
Published: July 2004

AbstractFor the first time, the solanidine alkaloids α‐solanine and α‐chaconine could be quantitatively enriched from potato juice by Adsorptive Bubble Separation (ABS) with a pH gradient. The enrichment into the foam was influenced by the pH value, bubble size, and gas flow rate. The efficiency was highest on using diluted samples with a concentration between 2 and 6 mg L–1 of the alkaloids at pH 6.0. The experiments with a standard solution of each alkaloid confirmed that these substances can be quantitatively enriched into the ‘spumat’ without surface active potato proteins. The transfer into the foam fraction under these conditions was similar to that from the aqueous potato extract.
Exponential attractors for a singularly perturbed Cahn‐Hilliard system
Authors: Efendiev Messoud , Miranville Alain , Zelik Sergey 
Published: July 2004

AbstractOur aim in this article is to give a construction of exponential attractors that are continuous under perturbations of the underlying semigroup. We note that the continuity is obtained without time shifts as it was the case in previous studies. Moreover, we obtain an explicit estimate for the symmetric distance between the perturbed and unperturbed exponential attractors in terms of the perturbation parameter. As an application, we prove the continuity of exponential attractors for a viscous Cahn‐Hilliard system to an exponential attractor for the limit Cahn‐Hilliard system. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
An iterative procedure for solving a Cauchy problem for second order elliptic equations
Authors: Johansson Tomas 
Published: July 2004

AbstractAn iterative method for reconstruction of solutions to second order elliptic equations by Cauchy data given on a part of the boundary, is presented. At each iteration step, a series of mixed well‐posed boundary value problems are solved for the elliptic operator and its adjoint. The convergence proof of this method in a weighted L2 space is included. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Remark on the Hopf Bifurcation Theorem
Authors: Krasnosel'skii A. M. , Rachinskii D. I. 
Published: July 2004

AbstractA simple generalization of the Hopf Bifurcation Theorem for scalar higher order ordinary differential equations is suggested. We study the degenerate case where several roots of the characteristic polynomial cross the imaginary axis at the same point for some value λ0 of the parameter λ. The main result is that if N1 roots cross the imaginary axis from the left to the right and N2 roots cross it from the right to the left, then λ0 is a Hopf bifurcation point whenever N1 ≠ N2. In particular, in the classical Hopf Bifurcation Theorem the numbers Nj are 0 and 1. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)