bluuebunny/crossref_metadata_2025 huggingface dataset:
Rheology of co‐continuous phase in physical thermoplastic elastomers
Authors: Barzegari Mohammad R , Yousefi Ali A , Zeynali Mohammad E , Rabii Ahmad , Rodrigue Denis
Published: June 2004

Nowadays, chemical and physical thermoplastic elastomers have found many applications in different industries. Compatibilizer and co‐continuous composition are among the important factors which control the optimum properties of a number of physical blends. Morphology, mechanical and rheological properties of various blends of polystyrene (PS) and polybutadiene were investigated. The results show that the co‐continuous composition for these blends is located in‐between 24 and 35 wt% of PS. These blends show a negative deviation from the viscosity logarithmic additivity rule. This observation suggests an improvement in the interactions between the phases in co‐continuous composition. Rheological and mechanical properties were used in determination of the co‐continuous phase. Copyright © 2004 Society of Chemical Industry
UDP‐Glucose pyrophosphorylase is upregulated in carriers of the porcine RN− mutation in the AMP‐activated protein kinase
Authors: Hedegaard Jakob , Horn Per , Lametsch René , Søndergaard Møller Hanne , Roepstorff Peter , Bendixen Christian , Bendixen Emøke
Published: June 2004

The AMP‐activated protein kinase (AMPK) plays a key role in the regulation of energy metabolism in eukaryotic cells acting as a metabolic sensor. In its activated form AMPK inhibits ATP consuming pathways and stimulates ATP generating pathways. A dominant mutation, denoted RN−, in the porcine PRKAG3 gene, encoding the regulatory γ3 subunit of AMPK, results in hyperaccumulation of glycogen in glycolytic skeletal muscle cells. To study the effects of this mutation on protein expression patterns in skeletal muscle, comparative proteome analysis of muscle samples from 12 animals (6 rn +/rn + and 6 RN−/rn +) was performed. The major finding of the proteome analysis was that the key enzyme in the synthesis of glycogen, UDP‐glucose pyrophosphorylase, was significantly up‐regulated in RN− carriers. This observation was subsequently supported by studies of enzyme activity and Northern blot analysis. Furthermore, the expression patterns of enzymes related to glycolysis and the citric acid cycle were also affected. Our data suggests that hyperaccumulation of glycogen mediated by the RN− mutation is due to an increased synthesis of glycogen.
The identification of Dictyostelium phosphoproteins altered in response to the activation of RasG
Authors: Secko David M. , Insall Robert H. , Spiegelman George B. , Weeks Gerry
Published: June 2004

Dictyostelium RasG has been implicated in the regulation of a variety of cellular processes, including the initiation of development, cell movement, and cytokinesis, but the molecular components of the signaling pathways involved are largely unknown. We used a tetracycline‐regulated protein expression system to study the effect of activated RasG, RasG(G12T), expression on the phosphorylation state of Dictyostelium proteins. Over 70 vegetative phosphoprotein components were resolved by two‐dimensional (2‐D) immunoblot analysis and of these 16 phosphothreonine and three phosphotyrosine protein components were found to reproducibly change upon RasG(G12T) expression. Thirteen of these were recovered from 2‐D gels and identified by mass spectrometry of in‐gel tryptic digestions. The proteins identified include the signaling proteins RasGEF‐R and protein kinase B, the adhesion protein DdCAD‐1, the cytoskeletal protein actin, the mitochondrial division protein FtsZA, and proteins involved in translation and metabolism. In addition to the direct demonstration of the phosphorylation of putative downstream targets of RasG activation, these findings reveal previously undetected phosphorylation of several proteins.
Cystatin C as a potential cerebrospinal fluid marker for the diagnosis of Creutzfeldt‐Jakob disease
Authors: Sanchez Jean‐Charles , Guillaume Elisabeth , Lescuyer Pierre , Allard Laure , Carrette Odile , Scherl Alex , Burgess Jennifer , Corthals Garry L. , Burkhard Pierre R. , Hochstrasser Denis F.
Published: June 2004

The definite diagnosis of Creutzfeldt‐Jakob disease (CJD), the most common form of human prion diseases, relies upon neuropathological data usually obtained at autopsy. In living patients, the diagnosis, based on suggestive clinical features and EEG abnormalities, can be aided by the detection of altered levels of isoforms of the 14‐3‐3 protein in the cerebrospinal fluid (CSF). However, the validity of this test has been recently challenged and the search for other, more reliable biomarkers for CJD remains highly desirable. The present study describes the identification of a new potential surrogate marker in the CSF of CJD‐affected patients. A preliminary study employing surface‐enhanced laser desorption/ionization‐time of flight (SELDI‐TOF) technology highlighted a protein at 13.4 kDa in a small group (n = 8) of CJD‐affected patients. Further analysis aimed at identifying this protein using cationic exchange chromatography, sodium dodecyl sulfate‐polyacrylamide gel electrophoresis (SDS‐PAGE), and liquid chromatography‐tandem mass spectrometry (LC‐MS/MS) revealed it to be cystatin C. Additional immunoblot assays confirmed that the level of cystatin C was significantly increased (p ≤ 0.05) in all tested samples (n = 8). We conclude that the analysis of cystatin C levels in CSF could be useful as a pre‐mortem indicator of the disease.
Differential proteome analysis and mass spectrometric characterization of germ line development‐related proteins ofCaenorhabditis elegans
Authors: Bantscheff Marcus , Ringel Bruno , Madi András , Schnabel Ralf , Glocker Michael O. , Thiesen Hans‐Jürgen
Published: June 2004

Proteome maps and differences of protein patterns of the synchronized larval stage L4 of the temperature‐sensitiveCaenorhabditis elegans (C. elegans)glp‐1 mutant (e2144ts) were investigated after cultivation at 15°C (developing a normal phenotype) or 25°C (developing a mutated phenotype) by two‐dimensional gel electrophoresis (2‐DE) and matrix‐assisted laser desorption/ionization (MALDI)‐mass spectrometry. From the 183 identified protein spots six proteins were found differently expressed. The Vit‐6 vitellogenin (CE28594), the hypothetical 17.2 protein (CE25224), the hypothetical 17.4 protein (CE16999), and the heat shock protein 16 kDa (CE14249) were more abundant when growing worm cultures at 25°C. By contrast, the nucleoside diphosphate kinase (CE09650) was found increased at 15°C. Most notably, the eukariotic initiation factor 5A‐1 (CE00503), highly abundant at 15°C, was not present in cultures grown at 25°C. Its absence at 25°C can not be attributed to lack of the enzymatic machinery that is necessary for hypusinylation. Instead, a direct downstream effect of the lack of functionality of GLP‐1 may cause the expression of this protein. The yolk proteins 115 kDa and 88 kDa were attributed by mass spectrometric protein structure analysis asC‐terminal andN‐terminal fragments of the Vit‐6 vitellogin protein (CE28594), respectively. The cleavage site between both derivatives was located between R764 and A768. A conflict in the database sequences at amino acid positions 1622 and 1623 of vitellogenin‐6 was solved by mass spectrometric sequence analysis. The combination of 2‐DE with mass spectrometry enabled the identification of mutation‐associated differences on somatic gonadal cell and germ line cell development‐associated proteins.
Some physical properties of polyorganosiloxanes. II. Nonlinear and irregular polyelementorganosiloxanes
Authors: Andrianov K. A. , Slonimskiĭ G. L. , Zhdanov A. A. , Yu. Levin V. , Godovskiĭ Yu. K. , Moskalenko V. A.
Published: June 2004

Some physical properties of irregular and nonlinear polydimethylsiloxane elastomers have been studied. The effects of chemical structure, vulcanization, and filler on the glass transition, melting, and crystallization have been investigated. The crystallization kinetics has been studied in detail.
Crystallization and polymerization of 6‐aminocaproic acid as simultaneous processes
Authors: Macchi E. M.
Published: June 2004

Vapor of 6‐aminocaproic acid (ACA) at a pressure of 0.12 mm Hg was observed to polymerize when placed in the presence of different types of surfaces, crystalline and amorphous, at temperatures around 170°C. Two clearly distinct stages of the process could be detected. The first was an induction period, during which the polymer phase must be nucleated. The length of this nucleation stage depended on factors not well understood. In the second stage, polymer was produced at a constant rate which seemed to be related to the vapor pressure of ACA. The polymer produced consisted of the characteristic radiating arrays of ribbonlike crystals known as spherulites. The spherulites, in turn, were made up of primary and secondary lamellae about 90 Å thick. Electron diffraction studies showed that the polymer chains were folded within the lamellae. Further it was proved by chemical and crystallographic arguments that adsorption and polymerization should be simultaneous processes.
Effect of radical scavenger on initiation efficiency
Authors: Ito Katsukiyo
Published: June 2004

In order to analyze the effect of the scavenger on initiator efficiency f or ratio of combination between two radicals (1 − f), an equation was derived by solving the modified Smoluchowski equation under the boundary condition based on the law of conservation of mass. At time t approaching infinity in a stationary state, this equation becomes: f = {D + a(Dk[S])1/2}/{ak0 + D + a(Dk[S])1/2}, where D is the sum of the diffusion constants of two radicals, a is the diameter of the radical particle, k0 is a specific rate of recombination in the cage between two radicals, k is the rate constant of reaction between the radical and the scavenger as a pair, and [S] is the scavenger concentration. When ak0 ≪ D and k[S] is small, this equation approximates the previously derived Wijsman's equation. An equation of the same type as Noyes' equation is also derived from this equation, when [S] = 0. By using the equations derived in this paper, the effect of α,α′‐diphenyl‐β‐picrylhydrazyl on the ratio of recombination of the (CH3)‐(CN)C* radical and the effect of monomer on the initiation efficiency are satisfactorily explained.
Anionic polymerization of vinyl monomers with xanthates
Authors: Yamaguchi Koichi , Sonoda Osamu , Minoura Yuji
Published: June 2004

The polymerization of vinyl monomers with various xanthates (potassium tert‐butylxanthate, potassium benzylxanthate, zinc n‐butylxanthate, etc.) were carried out at 0°C in dimethylformamide. N‐Phenylmaleimide, acrylonitrile, methyl vinyl ketone, and methyl methacrylate were found to undergo polymerization with potassium tert‐butylxanthate; however, styrene, methyl acrylate, and acrylamide were not polymerized with this xanthate. In the anionic polymerization of methyl vinyl ketone with potassium tert‐butylxanthate, the rate of the polymerization was found to be proportional to the catalyst concentration and to the square of the monomer concentration. The activation energy of methyl vinyl ketone polymerization was 2.9 kcal/mole. In the polymerization, the order of monomer reactivity was as follows: N‐phenylmaleimide > methyl vinyl ketone > acrylonitrile > methyl methacrylate. The initiation ability of xanthates increased with increasing basicity of the alkoxide group and with decreasing electronegativity of the metal ion in the series, lithium, sodium, and potassium tert‐butylxanthate. The relative effects of the aprotic polar solvents on the reactivity of potassium tert‐butylxanthate was also determined as follows: diethylene glycol dimethyl ether > dimethylsulfoxide > hexamethylphosphoramide > dimethylformamide > tetrahydrofuran (for methyl vinyl ketone); dimethyl sulfoxide > hexamethylphosphoramide > dimethylformamide ≅ diethylene glycol dimethyl ether (for acrylonitrile).
Syntheses of vinyl polymers containing the N‐phenothiazinyl group in the side chain
Authors: Kamogawa Hiroyoshi
Published: June 2004

Four kinds of vinyl polymers containing N‐substituted phenothiazinyl groups in side chains were obtained by syntheses of the respective monomers and subsequent polymerizations. Thus, N‐acrylamidomethylphenothiazine, N‐(N‐acrylamidomethyl)carbamoylethyl phenothiazine, β‐(N‐phenothiazinyl)ethyl acrylate and methacrylate, and β‐(N‐phenothiazinyl)ethyl vinyl ether were synthesized. It was found that all monomers except the last monomer can be polymerized with typical free‐radical initiators such as α,α′‐azobisisobutyronitrile to afford stable soluble polymers with electron‐donating characteristics, presumably due to the absence of a hydrogen atom at the site of the nitrogen atom of the phenothiazinyl group. The last monomer was found to be susceptible to typical cationic initiators such as boron trifluoride etherate to afford a stable soluble polymer also with the electron‐donating characteristic.
Polymerizable siloxane precursors having in‐chain perfluoroalkyl groups
Authors: Patterson William J. , Morris Donald E.
Published: June 2004

The synthesis and polymerization of several silphenylene siloxane polymer precursors containing a perfluoroalkylsegment in the backbone was carried out. The molecular weight characteristics of polymers from 1,3‐bis[p(‐hydroxydimethylsilyl)phenyl]hexafluoropropane and 1,3‐bis[p(‐dimethylaminodimethylsilyl)phenyl]hexafluoropropane were studied as a function of polymerization conditions. Polymers containing the dodecafluorohexane chain segment were also prepared. Polymers having inherent viscosities of 0.55 to 0.9 were obtained. The polymers crosslinked at room temperature to thermoset elastomers which were characterized by improved thermal and oxidative stability over dimethylsilicones. Room temperature swelling of the experimental polymers hydrocarbon solvents was also much lower than that of dimethylsilicones. The polymers containing the (CF2)3 and (CF2)6 linkages had glass transition points of −12°C and −34°C, respectively.
Reactivities of cis‐ and trans‐3‐substituted acrylic acids on copolymerization with acrylamide
Authors: Matsuo Keizo , Machida Seishi
Published: June 2004

Several pairs of cis‐ and trans‐3‐substituted acrylic acids (3SAA) were copolymerized with acrylamide in order to determine the major factors affecting the relative reactivities of geometrical isomers of 1,2‐disubstituted ethylenes (1,2‐DE). The results were that the relative reactivity of cis isomer is larger than that of trans isomer when one substituent is electron‐withdrawing and the other is electron‐donating. The trans isomer is more reactive than the cis isomer when both substituents are electron‐withdrawing. A new method of reactivity comparison of cis‐ and trans‐1,2‐DE is proposed in regard to the inductive substituent constant.
Vinyl polymerization. 275. Polymerization of vinyl monomers photosensitized by tetramethyltetrazene
Authors: Sugiyama Kazuo , Nakaya Tadao , Imoto Minoru
Published: June 2004

A study of the photopolymerization of vinyl monomers in the presence of tetramethyltetrazene (TMT) was made. TMT was found to act as an effective sensitizer. In the photopolymerization of vinyl monomers such as methyl methacrylate or styrene the rate of polymerization was expressed by the equation: Rp = k[TMT]1/2[monomer]. The chain‐transfer constant of TMT under ultraviolet irradiation was estimated to be 3.8 × 10−2 for the above monomers. A linear correlation was found to exist between the reactivity of dimethylamino radical toward the vinyl monomers and e values for the corresponding monomers.
Kinetics of radiation‐induced grafting reactions. I. Polyethylene–styrene systems
Authors: Yasukawa T. , Takahashi T. , Murakami K. , Araki K. , Sasuga T. , Ohmichi H.
Published: June 2004

By means of bromine labeling and ESR, the grafting reactions of styrene onto preirradiated polyethylene have been investigated. Not all the radicals produced by irradiations participate in grafting reactions all together, but they are rendered active bit by bit by the swelling of crystalline parts of polyethylene. The growing rates for polystyryl graft chains at 20°C decrease from 4 monomer units/active site/sec to one‐fourth the initial value after 100 min. On the contrary, the average lifetimes increase from <103 sec to >2.6 × 103 sec. The number‐average molecular weight of graft chains also increases with reaction times and rises to 3.5 × 105 after 90 min at 20°C.
Poly(galacturonic acid)–bivalent metal complexes
Authors: Jellinek H. H. G. , Chen Pi‐Yao A.
Published: June 2004

Complexation or stability constants have been determined for complexes of poly‐(galacturonic acid) with Cu, Cd, Zn, and Ni. The stability of complexation decreases as follows: Cu > Cd > Zn > Ni.
Studies in ring‐opening polymerization. II. Cyclohexane spiro‐5‐1,3,2‐dioxathiolan‐4‐one 2‐oxide
Authors: Blackbourn G. P. , Tighe B. J.
Published: June 2004

The effect of spiro cyclohexane substitution on the polymerizability of the 1,3,2‐dioxathiolan‐4‐one‐2‐oxide ring in various solvents has been examined. The steric hindrance of the cyclohexane ring inhibits the bimolecular chain propagation reaction which involves direct attack by a terminal hydroxyl group on the ring and which has been shown to occur in simpler dioxathiolan systems. The conjoined cyclohexane ring does not, however, markedly affect the “thermal” polymerization which occurs in nonhydroxylic solvents and in which chain propagation is thought to involve a reactive α‐lactone intermediate. The rate‐determining step in the sequence of reaction leading to polymer formation is a ring‐scission process in which sulfur dioxide is evolved and the α‐lactone intermediate formed. The values of the activation energy (25–30 kcal/mole) and frequency factor (1011–1013sec−1) associated with this reaction are, therefore, those which govern the the overall polymerization, since the subsequent steps are sensibly instantaneous. In the presence of adventitious traces of water the resultant polymer, poly(1‐hydroxycyclohexanecarboxylic acid) has one carboxyl and one hydroxyl endgroup per chain. Polymers having M̄n ∼ 15,000 are readily obtained; these are amorphous materials, in contrast to the analogous poly‐β‐ester and dialkyl‐substituted poly‐α‐esters which are crystalline. At temperatures in excess of 120°C a competitive first‐order fragmentation reaction leading to the formation of cyclohexanone, carbon monoxide, and sulfur dioxide was observed. Kinetic studies demonstrated that this reaction, which is characterized by an activation energy of ∼40 kcal/mole is unimportant, in the sense that it does not interfere with polymer formation at temperatures below 100°C.
Synthesis and chemical modification of hyperbranched polyethers with terminal hydroxy groups by the anionic ring‐opening polymerization of 3‐alkyl‐3‐hydroxymethyl oxetanes
Authors: Morita Ayako , Kudo Hiroto , Nishikubo Tadatomi
Published: June 2004

The anionic ring‐opening polymerization of oxetanes containing hydroxyl groups was carried out with potassium tert‐butoxide as an initiator in the presence of 18‐crown‐6‐ether in N‐methylpyrrolidinone at 180 °C; it yielded corresponding multifunctional hyperbranched polymers: poly(3‐ethyl‐3‐hydroxymethyloxetane)s, with number‐average molecular weights of 2200–4100 in 83–95% yields, and poly(3‐methyl‐3‐hydroxymethyloxetane)s, with number‐average molecular weights of 4600–5200 in 70–95% yields. The synthesized poly(3‐ethyl‐3‐hydroxymethyloxetane)s and poly(3‐methyl‐3‐hydroxymethyloxetane)s were hyperbranched polyethers containing an oxetane moiety and many hydroxy groups at the ends. The postpolymerization of poly(3‐ethyl‐3‐hydroxymethyloxetane)s was performed in the presence of potassium tert‐butoxide and 18‐crown‐6‐ether in N‐methylpyrrolidinone at 180 °C; it yielded corresponding polymers with higher molecular weights in good yields. The cationic polymerization of poly(3‐ethyl‐3‐hydroxymethyloxetane) derivatives was carried out with boron trifluoride etherate as an initiator and was followed by alkaline hydrolysis; this yielded a new branched polymer, a poly(hyperbranched polyether), with many pendant hydroxy groups. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 3739–3750, 2004
Active‐layer spatial and temporal variability at European Russian Circumpolar‐Active‐Layer‐Monitoring (CALM) sites
Authors: Mazhitova G. , Malkova (Ananjeva) G. , Chestnykh O. , Zamolodchikov D.
Published: June 2004

Three 100 × 100 m grids were established in European Russia in the framework of the Circumpolar‐Active‐Layer‐Monitoring (CALM) project. Records range from 4 to 7 years in length. The grids are in mineral soils with mean annual permafrost temperature from −0.5 to −2.5°C. The sites are known to be sensitive to decadal‐scale climatic changes. The grids differ in mean annual air temperature, but have similar thawing indices (DDT). Two grids with deeper annual thaw, separated by 400 km, reveal remarkable similarity in thaw depths, seasonal dynamics and interannual variability. All grids respond to thermal forcing rather consistently, although thaw increments caused by similar increases in DDT are smaller at the grid with the shallowest annual thaw. Stepwise multiple regression and other statistical analyses identified organic‐layer thickness and some, but not all, topographic features as the variables having explanatory power with respect to thaw‐depth variability. These and other variables examined do not, however, explain all the variability in the thaw depth. The effects of organic‐layer thickness on thaw depth are shown to change during the warm season. Copyright © 2004 John Wiley & Sons, Ltd.
Frost‐boil ecosystems: complex interactions between landforms, soils, vegetation and climate
Authors: Walker Donald A. , Epstein Howard E. , Gould William A. , Kelley Alexia M. , Kade Anja N. , Knudson Julie A. , Krantz William B. , Michaelson Gary , Peterson Rorik A. , Ping Chien‐Lu , Raynolds Martha K. , Romanovsky Vladimir E. , Shur Yuri
Published: June 2004

Frost boils in northern Alaska vary from large, 2–3‐m diameter, barren non‐sorted circles to completely vegetated hummocks. Summer warmth increases southwards from the coast. Average thaw‐layer thickness shows the opposite trend. Frost heave shows no trend along the climate gradient but is affected by soil texture. Heave is greatest on frost boils with fine‐grained sediments. Biomass increases from 183 g m−2 at the coast to 813 g m−2 in the Arctic Foothills. An aggrading permafrost table is evident in most of the frost‐boil soil profiles, indicating that, over time, accumulation of plant biomass leads to reduced thaw‐layer thickness. A conceptual model suggests how vegetation affects the morphology of patterned ground forms. In the coldest parts of the High Arctic well‐developed frost boils do not form and there is little vegetation on frost boils or the inter‐boil areas. In the warmest parts of the Low Arctic, vegetation is usually sufficient to stabilize the frost boil soils. Frost boils play an important role in Arctic ecosystems functions, including the flux of trace gases to the atmosphere, flux of water and nutrients to streams, and the recycling of important nutrients to wildlife populations. Copyright © 2004 John Wiley & Sons, Ltd.
Meteorological control on interannual spatial and temporal variations in snow cover and ground thawing in two northeast Greenlandic Circumpolar‐Active‐Layer‐Monitoring (CALM) sites
Authors: Christiansen Hanne H.
Published: June 2004

Data on snow cover depletion and ground thawing at two sites at Zackenberg, in high arctic northeast Greenland, are presented from 1996 to 2002. Operation of the two Zackenberg Ecological Research Operations (ZERO) Circumpolar‐Active‐Layer‐Monitoring (ZEROCALM) sites is part of ZERO. Year‐round meteorological data from Zackenberg are also available from ZERO. The ZEROCALM1 site is located on flat ground, whereas ZEROCALM2 is a southward‐sloping site that includes a seasonal snowpatch, 750 m from ZEROCALM1. Average active‐layer thickness in the Zackenberg lowland is relatively consistent at 60 to 71 cm in flat parts of the landscape, but varies from 44 to 61 cm in snowpatch areas. The seasonal snow depletion and ground thaw in the two topographically different ZEROCALM sites are presented and their meteorological control discussed. Interannual variations in ground thawing are much larger at the ZEROCALM2 site compared to ZEROCALM1. Thawing at the ZEROCALM2 site was affected to a large degree by mid‐ to late‐winter wind conditions, while thaw at the ZEROCALM1 site was correlated with summer air temperature. Copyright © 2004 John Wiley & Sons, Ltd.
Stream ecosystem response to multiple experimental floods from a reservoir
Authors: Robinson Christopher T. , Uehlinger Urs , Monaghan Michael T.
Published: June 2004

The effects of multiple experimental floods in the same year on the ecology of a river (River Spöl) below a large reservoir were investigated. In the flood year (2000), three floods of different magnitude (10 m3/s on 15 June, 25 m3/s on 5 July, and 10 m3/s on 10 August) were implemented, each lasting 7–8 h. Regulated baseflow discharge was maintained at less than 2.5 m3/s. Samples of macroinvertebrates, periphyton, water chemistry, and seston were collected for one year (1999) before and then immediately before and after each flood in the Spöl and in an adjacent reference tributary (Val da l'Aqua). Samples also were collected periodically between floods to evaluate temporal response patterns. During two of the floods, suspended sediments and seston were measured at 30 min to 1 h intervals. Suspended sediment and seston reached peak concentrations within the first hour of each flood, then decreased within about 2 h. Peak seston and suspended sediment concentrations during each flood decreased by an order of magnitude from the July flood to the August flood. Two‐way ANOVA indicated significant flood effects on periphyton standing crops expressed as either chlorophyll a or ash‐free dry mass (AFDM). Recovery of periphyton following each flood appeared to be progressively slower after the later (July and August) floods. Seston chlorophyll levels also were lower following each flood, being significantly correlated to periphyton biomass. Two‐way ANOVA indicated that the floods significantly decreased macroinvertebrate taxonomic richness, density, and biomass. Taxa that decreased from the floods included the turbellarian Crenobia alpina and the gammarid Gammarus fossarum. Taxa that showed a fast recovery to the floods included the Chironomidae, Simuliidae, and Baetidae. Our data indicate a strong temporal effect of flood disturbance on benthic assemblages (periphyton and macroinvertebrates) below reservoirs that partly reflects species‐specific life histories and traits, and the cumulative effects of earlier floods. Copyright © 2004 John Wiley & Sons, Ltd.
Modelling effects of discharge on habitat quality and dispersal of juvenile humpback chub (Gila cypha) in the Colorado River, Grand Canyon
Authors: Korman Josh , Wiele Stephen M. , Torizzo Margaret
Published: June 2004

A two‐dimensional hydrodynamic model was applied to seven study reaches in the Colorado River within Grand Canyon to examine how operation of Glen Canyon Dam has affected availability of suitable shoreline habitat and dispersal of juvenile humpback chub (Gila cypha). Suitable shoreline habitat typically declined with increasing discharges above 226–425 m3/ s, although the response varied among modelled reaches and was strongly dependent on local morphology. The area of suitable shoreline habitat over cover types that are preferred by juvenile humpback chub, however, stayed constant, and in some reaches, actually increased with discharge. In general, changes in discharge caused by impoundment tended to decrease availability of suitable shoreline habitat from September to February, but increased habitat availability in spring (May–June). Hourly variation in discharge from Glen Canyon Dam substantially reduced the amount of persistent shoreline habitat at all reaches. Changes in suitable shoreline habitat with discharge were shown to potentially bias historical catch per unit effort indices of native fish abundance up to fourfold. Physical retention of randomly placed particles simulating the movement of juvenile humpback chub in the study reaches tended to decline with increasing discharge, but the pattern varied considerably due to differences in the local morphology among reaches and the type of swimming behaviour modelled. Implications of these results to current hypotheses about the effects of Glen Canyon Dam on juvenile humpback chub survival in the mainstem Colorado River are discussed. Copyright © 2004 John Wiley & Sons, Ltd.
Challenging the assumption of habitat limitation: an example from centrarchid fishes over an intermediate spatial scale
Authors: Gutreuter Steve
Published: June 2004

Habitat rehabilitation efforts are predicated on the frequently untested assumption that habitat is limiting to populations. These efforts are typically costly and will be ineffective if habitat is not limiting. Therefore it is important to assess, rather than assume, habitat limitation wherever habitat rehabilitation projects are considered. Catch‐count data from a standardized probability‐based stratified‐random monitoring programme were examined for indirect evidence of backwater habitat limitation by centrarchid fishes in the Upper Mississippi River System. The monitoring design enabled fitting statistical models of the association between mean catch at the spatial scale of tens of river kilometres and the percentage of contiguous aquatic area in backwater at least 1 m deep by maximizing a stratum‐area weighted negative binomial log‐likelihood function. Statistical models containing effects for backwater limitation failed to account for substantial variation in the data. However, 95% confidence intervals on the backwater parameter estimates excluded zero, indicating that population abundance may be limited by backwater prevalence where backwaters are extremely scarce. The combined results indicate, at most, a weak signal of backwater limitation where backwaters are extremely scarce in the lower reaches, but not elsewhere in the Upper Mississippi River System. This suggests that habitat restoration projects designed to increase the area of backwaters suitable for winter survival of centrarchids are unlikely to produce measurable benefits over intermediate spatial scales in much of the Upper Mississippi River System, and indicates the importance of correct identification of limiting processes. Published in 2004 by John Wiley & Sons, Ltd.
Foramen ovale changes in growth‐restricted fetuses
Authors: Kiserud T. , Chedid G. , Rasmussen S.
Published: June 2004

Objective

In animal experiments hypoxemia induces an increased shunting through the fetal foramen ovale (FO). Based on the hypothesis that the FO is expanded to permit more flow, the aim of this study was to determine the size of the FO in growth‐restricted human fetuses.

Methods

Thirty‐one women with singleton pregnancies complicated with growth‐restriction (< 5th percentile) were examined at 24–39 weeks of gestation. The diameter between the FO valve and the atrial septum was determined during maximum excursion in a horizontal transverse section of the fetal heart, and the transverse diameter of the right atrium (RA) was noted. The pulsatility index (PI) was determined in the umbilical artery (UA) and absent or reversed end‐diastolic flow velocity was noted. The measurements were compared with a reference population using Z‐scores.

Results

In comparison with normally grown fetuses, the growth‐restricted fetuses had a normal RA size (P = 0.08) but a smaller FO (P = 0.002), particularly when expressed as a relative size by the ratio FO/RA (P < 0.0001). This effect on the FO and FO/RA was seen mainly at < 32 weeks of gestation (P = 0.003 and P < 0.0001, respectively), and was not significant later in pregnancy. There was a tendency towards a negative relationship between relative size of the FO (FO/RA) and progressive placental compromise (overall P < 0.0001).

Conclusions

Growth‐restricted fetuses maintain a normally grown heart (expressed by the RA diameter) but a reduced FO diameter. The effect is seen before 32 weeks and tends to be more marked in fetuses with pronounced hemodynamic compromise of the placenta. This supports the theory that FO shunting is impaired in severely premature fetuses with placental compromise. Copyright © 2004 ISUOG. Published by John Wiley & Sons, Ltd.
Model of auroral electron acceleration by dissipative nonlinear inertial Alfvén wave
Authors: Wu D. J. , Chao J. K.
Published: June 2004

In a recent work [Wu, 2003a, 2003b], a dissipative nonlinear inertial Alfvén wave (DNIAW) were proposed as the physical explanation for the formation of the strong electric spikes often observed in the auroral ionosphere and the magnetosphere. DNIAW can also lead to the field_aligned electron acceleration. In the present paper, dynamical characteristics of DNIAW acceleration are discussed and its possible role in auroral electron acceleration is further investigated. The effective acceleration region for auroral electrons with energies of the order of keV produced by DNIAW acceleration is between 0.5 and 2.5 RE above the ionosphere, and the most efficient acceleration occurs around 0.8 RE where both the Alfvén velocity and the produced auroral electron energy peak, and the peak energy is around 10 keV. We suggest that this could explain the precipitous decrease of the auroral electron energy spectrum toward energies above 10 keV, which can be inferred from measurements of energy distribution of precipitating auroral electrons. Typical widths of auroral arcs caused by the DNIAW acceleration are in scales of the order of 1 km.
An experimental study of micron-scale droplet aerosols produced via ultrasonic atomization
Authors: Donnelly T. D. , Hogan J. , Mugler A. , Schommer N. , Schubmehl M. , Bernoff Andrew J. , Forrest B.
Published: June 2004

In the last 10 years, laser-driven fusion experiments performed on atomic clusters of deuterium have shown a surprisingly high neutron yield per joule of input laser energy. Results indicate that the optimal cluster size for maximizing fusion events should be in the 0.01–1 μm diameter range, but an appropriate source of droplets of this size does not exist. In an attempt to meet this need, we use ultrasonic atomization to generate micron-scale droplet aerosols of high average density, and we have developed and refined a reliable droplet sizing technique based on Mie scattering. Harmonic excitation of the fluid in the MHz range yields an aerosol of droplets with diameters of a few microns. The droplet diameter distribution is well-peaked and the relationship between average droplet size and forcing frequency follows an inviscid scaling law, predictable by dimensional analysis and consistent with the linear theory for Faraday excitation of an infinitely deep fluid.
Analysis of chaotic saddles in high-dimensional dynamical systems: The Kuramoto–Sivashinsky equation
Authors: Rempel Erico L. , Chian Abraham C.-L. , Macau Elbert E. N. , Rosa Reinaldo R.
Published: June 2004

This paper presents a methodology to study the role played by nonattracting chaotic sets called chaotic saddles in chaotic transitions of high-dimensional dynamical systems. Our methodology is applied to the Kuramoto–Sivashinsky equation, a reaction–diffusion partial differential equation. The paper describes a novel technique that uses the stable manifold of a chaotic saddle to characterize the homoclinic tangency responsible for an interior crisis, a chaotic transition that results in the enlargement of a chaotic attractor. The numerical techniques explained here are important to improve the understanding of the connection between low-dimensional chaotic systems and spatiotemporal systems which exhibit temporal chaos and spatial coherence.
Point vortices with a rational necklace: New exact stationary solutions of the two-dimensional Euler equation
Authors: Tur Anatoly , Yanovsky Vladimir
Published: June 2004

In this paper we find a new class of explicit exact stationary solutions of the two-dimensional (2D) Euler equation which describe vortex patterns of necklace type with N+1-fold symmetry in rotational shear flow. The point vortex with a strength equal to ±4πN (where N-integer number) is situated in the center of the vortex structure. The vorticity distribution outside of the center is smooth and is described by a two-parametric family of rational functions which are known in explicit form for any N. In the centers of vortex satellites the vorticity does not have any singularity and remains of finite value. When N is increasing, the solutions describe the transition layer in 2D–rotational shear flow.
Plexin-B1/RhoGEF–mediated RhoA activation involves the receptor tyrosine kinase ErbB-2
Authors: Swiercz Jakub M. , Kuner Rohini , Offermanns Stefan
Published: June 2004

Plexins are widely expressed transmembrane proteins that mediate the effects of semaphorins. The molecular mechanisms of plexin-mediated signal transduction are still rather unclear. Plexin-B1 has recently been shown to mediate activation of RhoA through a stable interaction with the Rho guanine nucleotide exchange factors PDZ-RhoGEF and LARG. However, it is unclear how the activity of plexin-B1 and its downstream effectors is regulated by its ligand Sema4D. Here, we show that plexin-B family members stably associate with the receptor tyrosine kinase ErbB-2. Binding of Sema4D to plexin-B1 stimulates the intrinsic tyrosine kinase activity of ErbB-2, resulting in the phosphorylation of both plexin-B1 and ErbB-2. A dominant-negative form of ErbB-2 blocks Sema4D-induced RhoA activation as well as axonal growth cone collapse in primary hippocampal neurons. Our data indicate that ErbB-2 is an important component of the plexin-B receptor system and that ErbB-2–mediated phosphorylation of plexin-B1 is critically involved in Sema4D-induced RhoA activation, which underlies cellular phenomena downstream of plexin-B1, including axonal growth cone collapse.
Actin dynamics coupled to clathrin-coated vesicle formation at the trans-Golgi network
Authors: Carreno Sebastien , Engqvist-Goldstein Åsa E. , Zhang Claire X. , McDonald Kent L. , Drubin David G.
Published: June 2004

In diverse species, actin assembly facilitates clathrin-coated vesicle (CCV) formation during endocytosis. This role might be an adaptation specific to the unique environment at the cell cortex, or it might be fundamental, facilitating CCV formation on different membranes. Proteins of the Sla2p/Hip1R family bind to actin and clathrin at endocytic sites in yeast and mammals. We hypothesized that Hip1R might also coordinate actin assembly with clathrin budding at the trans-Golgi network (TGN). Using deconvolution and time-lapse microscopy, we showed that Hip1R is present on CCVs emerging from the TGN. These vesicles contain the mannose 6-phosphate receptor involved in targeting proteins to the lysosome, and the actin nucleating Arp2/3 complex. Silencing of Hip1R expression by RNAi resulted in disruption of Golgi organization and accumulation of F-actin structures associated with CCVs on the TGN. Hip1R silencing and actin poisons slowed cathepsin D exit from the TGN. These studies establish roles for Hip1R and actin in CCV budding from the TGN for lysosome biogenesis.
Interferon γ Enhances Both In Vitro and In Vivo Priming of CD4+ T Cells for IL-4 Production
Authors: Bocek Petr , Foucras Gilles , Paul William E.
Published: June 2004

Classical studies have demonstrated that in vitro priming of naive CD4 T cells to become T helper (Th)2 cells is strikingly dependent on interleukin (IL)-4, whereas priming for interferon (IFN)γ production is IL-12/IFNγ-dependent. Therefore, it was quite surprising when we noted that priming of naive C57BL/6 CD4+ cells to become IL-4 producers was substantially inhibited by the addition of anti-IFNγ antibodies. This was true using immobilized anti-CD3 and anti-CD28 antibodies or soluble anti-CD3/anti-CD28 and antigen-presenting cells in the presence or absence of added IL-4. Priming of CD4 T cells from IFNγ−/− C57BL/6 mice with immobilized anti-CD3 and anti-CD28 resulted in limited production of IL-4, even with the addition of 1,000 U/ml of IL-4. Titrating IFNγ into such cultures showed a striking increase in the proportion of T cells that secreted IL-4 upon challenge; this effect was completely IL-4–dependent in that it was blocked with anti–IL-4 antibody. Thus, IFNγ plays an unanticipated but substantial role in Th2 priming, although it is an important Th1 cytokine, and under certain circumstances a Th1 inducer.
Defined αβ T Cell Receptors with Distinct Ligand Specificities Do Not Require Those Ligands to Signal Double Negative Thymocyte Differentiation
Authors: Erman Batu , Guinter Terry I. , Singer Alfred
Published: June 2004

During T cell development in the thymus, pre–T cell receptor (TCR) complexes signal CD4− CD8− (double negative [DN]) thymocytes to differentiate into CD4+ CD8+ (double positive [DP]) thymocytes, and they generate such signals without apparent ligand engagements. Although ligand-independent signaling is unusual and might be unique to the pre-TCR, it is possible that other TCR complexes such as αβ TCR or αγ TCR might also be able to signal the DN to DP transition in the absence of ligand engagement if they were expressed on DN thymocytes. Although αγ TCR complexes efficiently signal DN thymocyte differentiation, it is not yet certain if αβ TCR complexes are also capable of signaling DN thymocyte differentiation, nor is it certain if such signaling is dependent upon ligand engagement. This study has addressed these questions by expressing defined αβ TCR transgenes in recombination activating gene 2−/− pre-Tα−/− double deficient mice. In such double deficient mice, the only antigen receptors that can be expressed are those encoded by the αβ TCR transgenes. In this way, this study definitively demonstrates that αβ TCR can in fact signal the DN to DP transition. In addition, this study demonstrates that transgenic αβ TCRs signal the DN to DP transition even in the absence of their specific MHC–peptide ligands.
The Roles of Two IκB Kinase-related Kinases in Lipopolysaccharide and Double Stranded RNA Signaling and Viral Infection
Authors: Hemmi Hiroaki , Takeuchi Osamu , Sato Shintaro , Yamamoto Masahiro , Kaisho Tsuneyasu , Sanjo Hideki , Kawai Taro , Hoshino Katsuaki , Takeda Kiyoshi , Akira Shizuo
Published: June 2004

Viral infection and stimulation with lipopolysaccharide (LPS) or double stranded RNA (dsRNA) induce phosphorylation of interferon (IFN) regulatory factor (IRF)-3 and its translocation to the nucleus, thereby leading to the IFN-β gene induction. Recently, two IκB kinase (IKK)–related kinases, inducible IκB kinase (IKK-i) and TANK-binding kinase 1 (TBK1), were suggested to act as IRF-3 kinases and be involved in IFN-β production in Toll-like receptor (TLR) signaling and viral infection. In this work, we investigated the physiological roles of these kinases by gene targeting. TBK1-deficient embryonic fibroblasts (EFs) showed dramatic decrease in induction of IFN-β and IFN-inducible genes in response to LPS or dsRNA as well as after viral infection. However, dsRNA-induced expression of these genes was residually detected in TBK1-deficient cells and intact in IKK-i–deficient cells, but completely abolished in IKK-i/TBK1 doubly deficient cells. IRF-3 activation, in response not only to dsRNA but also to viral infection, was impaired in TBK1-deficient cells. Together, these results demonstrate that TBK1 as well as, albeit to a lesser extent, IKK-i play a crucial role in the induction of IFN-β and IFN-inducible genes in both TLR-stimulated and virus-infected EFs.
A CASE OF HÆMOCHROMATOSIS.—THE RELATION OF HÆMOCHROMATOSIS TO BRONZED DIABETES
Authors: Opie Eugene L.
Published: June 2004

(1) There exists a distinct morbid entity, hæmochromatosis, characterized by the widespread deposition of an iron-containing pigment in certain cells and an associated formation of iron-free pigments in a variety of localities in which pigment is found in moderate amount under physiological conditions.

(2) With the pigment accumulation there is degeneration and death of the containing cells and consequent interstitial inflammation, notably of the liver and pancreas, which become the seat of inflammatory changes accompanied by hypertrophy of the organ.

(3) When chronic interstitial pancreatitis has reached a certain grade of intensity diabetes ensues and is the terminal event in the disease.
CULTURES FROM THE BLOOD In SEPTICÆMIA, PNEUMONIA, MENINGITIS AND CHRONIC DISEASES
Authors: White Franklin Warren
Published: June 2004

Our conclusions from the literature and our own experiments may be summarized as follows:

I. Blood for bacteriological examination during life should be taken directly from the veins and in considerable quantity.

II. Resorption of toxines is the most important feature in cases of sepsis; pyogenie bacteria invade the general circulation in a rather small proportion even of severe eases, and, as a rule, late in the course of the disease.

III. A general infection by the pnenmococcus can be demonstrated occasionally in the late stages of acute lobar pneumonia.

IV. The value of blood cultures as a means of diagnosis in obscure cases of sepsis is limited by the fact that invasion of the blood by the specific organism cannot be demonstrated during life in the majority of cases. Positive cultures are very valuable; negative cultures do not exclude local septic infections.

V. The detection of specific bacteria in the blood of cases of sepsis and of pneumonia gives a very unfavorable prognosis in most cases.

VI. General terminal infections with pyogenic cocci occasionally occur as an immediate cause of death in chronic disease. Local infections processes play this part more frequently.

VII. As far as our experiments have shown, invasion of the blood by bacteria during the death agony, with subsequent distribution of the genus to the organs by the circulation, is a rather uncommon occurrence.

VIII. Owing to the relative infrequency of agonal invasion, we believe that in the majority of cases where the autopsy is performed promptly after death, the bacteria which are found in the organs succeeded in reaching these organs previously to the death agony, and are associated with the course of the disease.

IX. The presence of bacteria in the organs of late autopsies is due in many cases to post-mortem extension from one organ to another, and in some cases to the post-mortem growth of small numbers of genus which were distributed to the organs by means of the circulation.
SEROLOGICAL RELATIONSHIPS OF TYPE-SPECIFIC AND DEGRADED PNEUMOCOCCI
Authors: Reimann Hobart A.
Published: June 2004

1. Immune sera prepared with the degraded or variant forms of pneumococci (R strains) are similar in their reactions to sera prepared with the protein or cell solutions of pneumococci. They contain antibodies reactive with the protein of all types of pneumococci, but no antibodies reactive with the type-specific substances.

2. Pneumococci of the variant or R form, regardless of type derivation, are serologically identical and have the antigenic characteristics of pneumococcus protein. They evoke the species-specific and not the type-specific antibodies.

3. Antipneumococcus sera obtained by immunization with S strains may contain species-specific antibodies in addition to those which are type-specific. Each kind of antibody can be removed separately from these sera by selective absorption with the R or S strains of pneumococci.