bluuebunny/crossref_metadata_2025 huggingface dataset:
Computer enumeration of walks on directed graphs
Authors: Balasubramanian K.
Published: January 2005

A vectorized computer code is developed for the enumeration of walks through the matrix power method for directed graphs. Application of this code to several graphs is considered. It is shown that the coefficients in the generating functions for signed graphs are much smaller in magnitude. It is shown that self‐avoiding walks on some graphs can be enumerated as a linear combination of walk GFs of directed paths and rooted‐directed paths.
Ab initio study of ascorbic acid conformations
Authors: Al‐Laham Mohammad A. , Petersson G. A. , Haake Paul
Published: January 2005

The STO‐3G optimized structures of nine different staggered conformers of ascorbic acid are presented. The largest energy difference between the nine local minima is 5.1 kcal/mol. Comparison of the relative energies of the fully optimized structures of ascorbic acid conformers with those of nonoptimized conformers shows that full optimization is essential to obtain meaningful results. However, optimization of the ring structure is almost independent of optimization of the side‐chain structure. One of the STO‐3G optimized gas phase conformers is very close to the X‐ray structure of the crystal.
Ab initio characterization of several states of nitroxylium (NO). Comparison of fragmentation energies of nitroxylium, nitroxyl (NO3), and nitrate
Authors: Boehm Randall C. , Lohr Lawrence L.
Published: January 2005

Ab initio calculations have been performed at the self‐consistent field (HF) level, and its perturbative extensions up to fourth‐order (MPn), for several electronic states of nitroxylium (NO) as well as for a large number of reference species. Geometries are optimized at the HF/DZ and HF/DZP levels (double zeta and double zeta plus polarization bases). The ground state is found to be the D3h 1A1′ state, with the C2v 1A1 (closed Y) state higher by 0.94 eV. The relationship between adding electrons or oxygen atoms to NO+ and NO is explored, especially in relation to fragmentation energies of NO (q = 0 or 1). A comparison is drawn between NO and two isoelectronic species, CO3 and C(CH2)3, where no surprises are found.
Dependence of axon initial segment formation on Na+ channel expression
Authors: Xu Xiaorong , Shrager Peter
Published: January 2005

Spinal motor neurons were isolated from embryonic rats, and grown in culture. By 2 days in vitro, the axon initial segment was characterized by colocalization and clustering of Na+ channels and ankyrinG. By 5 days, NrCAM, and neurofascin could also be detected at most initial segments. We sought to determine, as one important aim, whether Na+ channels themselves played an essential role in establishing this specialized axonal region. Small hairpin RNAs (shRNAs) were used to target multiple subtypes of Na+ channels for reduced expression by RNA interference. Transfection resulted in substantial knockdown of these channels within the cell body and also as clusters at initial segments. Furthermore, Na+ currents originating at the initial segment, and recorded under patch clamp, were strongly reduced by shRNA. Control shRNA against a nonmammalian protein was without effect. Most interestingly, targeting Na+ channels also blocked clustering of ankyrinG, NrCAM, and neurofascin at the initial segment, although these proteins were seen in the soma. Thus, both Na+ channels and ankyrinG are required for formation of this essential axonal domain. Knockdown of Na+ channels was somewhat less effective when introduced after the initial segments had formed. Disruption of actin polymerization by cytochalasin D resulted in multiple initial segments, each with clusters of both Na+ channels and ankyrinG. The results indicate that initial segment formation occurs as Na+ channels are transported into the nascent axon membrane, diffuse distally, and link to the cytoskeleton by ankyrinG. Subsequently, other components are added, and stability is increased. A computational model closely reproduced the experimental results. © 2005 Wiley‐Liss, Inc.
Shoreline tufa and tufaglomerate from Pleistocene Lake Bonneville, Utah, USA: stable isotopic and mineralogical records of lake conditions, processes, and climate
Authors: Nelson Stephen T. , Wood M. Jay , Mayo Alan L. , Tingey David G. , Eggett Dennis
Published: January 2005

Shoreline carbonate deposits of Pleistocene Lake Bonneville record the conditions and processes within the lake, including the evaporative balance as well as vertical and lateral chemical and isotopic gradients. Tufas (swash‐zone) and tufaglomerates (cemented, subaqueous colluvium or beachrock) on multiple, well‐developed shorelines near the Silver Island Range, Utah, also present an opportunity to examine physicochemical lake processes through time. Three shorelines are represented by carbonate deposits, including the 23–20 ka Stansbury stage, 15–14.5 ka Bonneville stage, and 14.5–14 ka Provo stage.

Mean δ18OVSMOWvalues of all three shorelines are statistically indistinguishable ( ∼ 27 ± 1‰), when a few Bonneville samples of unusual composition are neglected. However, differences in primary carbonate mineralogy indicate that the correspondence is an artefact of the different fractionation factors between calcite or aragonite and water. Second, in order to sustain a much smaller, shallower lake during the colder Stansbury stage, the climate must have also been relatively dry. Third, δ18O values in tufa are higher than tufaglomerate by  ∼ 0.5‰, consistent with greater evaporative enrichment of lake water in the swash zone. Fourth, mean δ13C values for the Provo, Stansbury and Bonneville shorelines (4.4, 5.0 and 5.2‰, respectively) show that carbon species were dominated by atmospheric exchange, with the variations produced by differences in the oxidation of organic matter.

Comparisons of shoreline carbonates with deep‐lake marls of the same approximate age indicate that shoreline carbonate was much higher in δ13C and δ18O values (both ∼ 2.5‰) during Bonneville time, whereas isotopic differences were minor (both ∼ 1‰) in Stansbury time. In particular, the Bonneville stage may have sustained large vertical or lateral isotopic gradients due to evaporative enrichment effects on δ18O values. In contrast, the lake during the much shallower Stansbury stage may have been well mixed.

Differences in the primary mineralogy (Stansbury and Bonneville, aragonite > calcite; Provo, calcite > aragonite) reflect profound differences in lake chemistry in terms of open versus closed‐basin lakes. The establishment of a continuous outlet during Provo time probably reduced the Mg2+/Ca2+ratio of lake water. Curiously, regardless of primary mineralogy, tufaglomerate cements are enriched in Na+and Cl−and depleted in Mg2+relative to capping tufa of the same age. This probably reflects vital or kinetic effects in the swash zone (tufa). We suspect that ‘abiotic’ effects may have been important in the dark pore space of developing tufaglomerate, where the absence of light suppressed photosynthesis. Copyright © 2005 John Wiley & Sons, Ltd.
Palaeomagnetic correlation and dating of Plio/Pleistocene sediments at the southern margins of the North Sea Basin
Authors: Maher B. A. , Hallam D. F.
Published: January 2005

A series of discontinuous sediment sequences, of Plio/Pleistocene age, occur onshore around the southern North Sea margins, notably in the East Anglian region of Britain. Intensive lithological and palaeontological analyses of these sediments have shown that they record both major and minor oscillations in climate, sea level and environmental conditions. However, significant uncertainties exist regarding the absolute and relative chronostratigraphies of many of these sequences, hindering understanding of the relative impacts of climatic, eustatic and tectonic changes on the palaeogeographic development of the southern North Sea basin. Here, a number of key East Anglian Plio/Pleistocene sites are subjected to robust palaeomagnetic and mineralogical examination, in order to determine those sediments which display reliable, syn‐depositional magnetic polarities, which are thus of use in ascribing a palaeomagnetically determined age from comparison with the Geomagnetic Polarity Timescale (GPTS). Based on a range of palaeomagnetic and complementary mineralogical methods, reliable palaeomagnetic directions were obtained from eight sites, with reversed polarities displayed by sediments from three sites. These polarity determinations can be used to infer absolute ages and test published, between‐site correlations. Copyright © 2005 John Wiley & Sons, Ltd.
Holocene sedimentation in the Skagerrak interpreted from chirp sonar and core data
Authors: Gyllencreutz Richard , Jakobsson Martin , Backman Jan
Published: January 2005

High‐resolution chirp sonar profiling in the northeastern Skagerrak shows acoustically stratified sediments draping a rough‐surfaced substratum. A 32 metre long sediment core retrieved from the survey area encompasses the entire Holocene and latest Pleistocene. The uppermost seismo‐acoustic units in the chirp profiles represent Holocene marine sediments. The lowermost unit is interpreted as ice‐proximal glacial‐marine sediments rapidly deposited during the last deglaciation. The end of ice‐proximal sedimentation is marked by a strong reflector, interpreted to have been formed during latest Pleistocene time as a consequence of rapid ice retreat and drastically lowered sedimentation rate. The subsequent distal glacial‐marine sediments were deposited with initially high sedimentation rates caused by an isostatic rebound‐associated sea‐level fall. Based on correlation between the core and the chirp sonar profiles using measured sediment physical properties and AMS 14C dating, we propose a revised position for the Pleistocene/Holocene boundary in the seismo‐acoustic stratigraphy of the investigated area. Copyright © 2005 John Wiley & Sons, Ltd.
Magnetic carriers and remanence mechanisms in magnetite‐poor sediments of Pleistocene age, southern North Sea margin
Authors: Maher B. A. , Hallam D. F.
Published: January 2005

Pleistocene sedimentary sequences in the East Anglian region of Britain record both major and minor climatic oscillations, and the impact of isostatic and eustatic variations. Intensively studied in terms of their lithology and biostratigraphy, the sequences have been difficult to place in an absolute timeframe. Dating and correlation by magnetostratigraphy has been attempted over a number of years. However, these sediments are difficult to date by palaeomagnetic means because they are poor in detrital magnetite, are subject to post‐depositional deformation and diagenesis, and have unknown rates of sedimentation. Determining whether their natural remanence magnetisation (NRM) directions are reliable thus requires information on the mode and timing of remanence acquisition. Here, we apply palaeomagnetic, rock magnetic and mineralogical analyses to identify the NRM carriers in these sediments and hence their palaeomagnetic reliability. Within oxidised fluvial sediments (the Kesgrave Formation), the magnetic carriers appear to be relict magnetic minerals (ferrian ilmenites, chromites, haematite and goethite), which sometimes carry a reliable primary depositional remanence (DRM) but often an overprinting viscous (time‐varying) remanence (VRM). Within some reduced marine and intertidal sediments (within the Crag basin), the iron sulphide, greigite, has been found to carry a reliable, ‘syn’‐depositional chemical remanence (CRM). In all the sediments, magnetic inclusions within silicates are abundant, are significant for the mineral magnetic signal but contribute little to any recoverable palaeomagnetic information. Copyright © 2005 John Wiley & Sons, Ltd.
Reconstruction of Late Glacial summer temperatures from chironomid assemblages in Lac Lautrey (Jura, France)
Authors: Heiri Oliver , Millet Laurent
Published: January 2005

A chironomid–July air temperature inference model based on chironomid assemblages in the surface sediments of 81 Swiss lakes was used to reconstruct Late Glacial July air temperatures at Lac Lautrey (Jura, Eastern France). The transfer‐function was based on weighted averaging–partial least squares (WA‐PLS) regression and featured a leave‐one‐out cross‐validated coefficient of determination (r2) of 0.80, a root mean square error of prediction (RMSEP) of 1.53 ° C, and was applied to a chironomid record consisting of 154 samples covering the Late Glacial period back to the Oldest Dryas. The model reconstructed July air temperatures of 11–12 ° C during the Oldest Dryas, increasing temperatures between 14 and 16.5 ° C during the Bølling, temperatures around 16.5–17.0 ° C for most of the Allerød, temperatures of 14–15 ° C during the Younger Dryas and temperatures of ca. 16.5 ° C during the Preboreal. The Lac Lautrey record features a two‐step July air temperature increase after the Oldest Dryas, with an abrupt temperature increase of ca. 3–3.5 ° C at the Oldest Dryas/Bølling transition followed by a more gradual warming between ca. 14 200 and 13 700 BP. The transfer‐function reconstructs a less rapid cooling at the Allerød/Younger Dryas transition than other published records, possibly an artefact caused by the poor analogue situation during the earliest Younger Dryas, and an abrupt warming at the Younger Dryas/Holocene transition. During the Allerød, two centennial‐scale 1.5–2.0 ° C coolings are apparent in the record. Although chronologically not well constrained, the first of these cold events may be synchronous with the beginning of the Gerzensee Oscillation. The second is inferred just before deposition of the Laachersee tephra at Lac Lautrey and is therefore coeval with the end of the Gerzensee Oscillation. In contrast to the Greenland oxygen isotope records, the Lac Lautrey palaeotemperature reconstruction lacks a clearly defined Greenland Interstadial (GI) event 1d and the decreasing temperature trend during the Bølling/Allerød Interstadial. Copyright © 2005 John Wiley & Sons, Ltd.
Towards a comprehensive distal andesitic tephrostratigraphic framework for New Zealand based on eruptions from Egmont volcano
Authors: Shane Phil
Published: January 2005

The chronology and glass composition of 43 andesitic tephra layers in palaeolake sediments in northern New Zealand provide the basis for a fine‐resolution tephrostratigraphy of the interval 10–70 cal. ka. Their ages are constrained by 14 interbedded, (mostly) well‐dated rhyolitic tephra layers. The andesitic tephra have the potential to subdivide time intervals (1–5 kyr) bracketed by well known rhyolitic layers, including periods of rapid climate change such as the last glacial–interglacial transition and the Younger Dryas. The source of the distal andesitic tephra is identified as Egmont volcano (some 270 km S‐SW) on the basis of glass shard composition. The tephra contain high‐K2O (3–6 wt%) andesitic‐dacitic (SiO2 = 60–73 wt%) glass, with commonly heterogeneous shard populations (2–10 wt% SiO2). Within stratigraphic intervals of < 10 kyr, individual tephra layers can be distinguished on the basis of their SiO2 and K2O contents, and variability in these contents can also be a distinguishing characteristic. The tephra record greatly extends the dated pyroclastic and geochemical record of Egmont volcano, and demonstrates that the volcano has frequently produced widely dispersed tephra over the last 70 kyr at a generally constant rate. Copyright © 2005 John Wiley & Sons, Ltd.
U‐series dating of the Late Pleistocene mammalian fauna from Wood Quarry (Steetley), Nottinghamshire, UK
Authors: Pike A. W. G. , Eggins S. , Grün R. , Hedges R. E. M. , Jacobi R. M.
Published: January 2005

We present the U‐series dating of bones from Wood Quarry (‘Steetley Quarry Cave’) using the diffusion–adsorption model to account for uranium uptake. The results give a weighted mean date of 66.8 ± 3.0 kyr, placing this assemblage within or just before Marine Oxygen Isotope Stage 4. The fauna is thought to correlate with the Banwell Bone Cave mammal assemblage‐zone of the Early Devensian in Britain. Our results support the idea that this assemblage‐zone immediately precedes the assemblage represented nearby at Pin Hole in Creswell Crags which is contemporary with the Mid‐Devensian and correlates with MIS 3. Our dates, and dates for the Banwell Bone Cave mammal assemblage‐zone from Stump Cross Cavern and evidence from other sites may indicate a longevity for this fauna. Copyright © 2005 John Wiley & Sons, Ltd.
Investigation of Fungal Deterioration of Synthetic Paint Binders Using Vibrational Spectroscopic Techniques
Authors: Cappitelli Francesca , Vicini Silvia , Piaggio Paolo , Abbruscato Pamela , Princi Elisabetta , Casadevall Arturo , Nosanchuk Joshua D. , Zanardini Elisabetta
Published: January 2005

Summary: The deterioration of synthetic polymers caused by biological process is usually evaluated by visual inspection and measuring physical effects. In contrast to this approach, we have applied vibrational spectroscopies to study the biodegradation of the synthetic resins. 29 synthetic resins used as paint binding media, including acrylic, alkyd and poly(vinyl acetate) polymers, were examined for potential susceptibility to fungal degradation using the standard method ASTM G21‐96(2002). In addition, the degraded resins were analysed by Raman spectroscopy, FT‐IR and FT‐IR photoacoustic spectroscopy. Almost all the acrylic resins studied proved to be resistant to microbial attack, while all alkyd resins and some poly(vinyl acetates) turned out to be biodegradable. Within a few days of inoculation Aspergillus niger was the most copious fungus on the biodegraded resins. A comparison of the IR and Raman spectra of control and biodegraded resins did not show any differences, but photoacoustic spectroscopy revealed additional bands for the fungal‐degraded resins, consistent with the presence of fungal‐derived substances. The additional bands in the photoacoustic spectra were due to the presence of Aspergillus niger and melanin, a fungal pigment. Since IR photoacoustic spectroscopy can be also a suitable technique for the chemical characterisation of binding media, the same spectroscopic analysis can be employed to both characterise the material and obtain evidence for fungal colonization.

Microbial growth on Sobral 1241ML (alkyd resin) after 28 d (growth rating 4) compared with the non‐inoculated resin.

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Microbial growth on Sobral 1241ML (alkyd resin) after 28 d (growth rating 4) compared with the non‐inoculated resin.
Characterization of Methyl Methacrylate Grafting onto Preirradiated Biodegradable Lignocellulose Fiber by γ‐Radiation
Authors: Khan Ferdous
Published: January 2005

Summary: Gamma‐radiation‐induced graft copolymerization of methyl methacrylate onto natural lignocellulose (jute) fiber was carried out by the preirradiation method in an aqueous medium by using octylphenoxy‐polyethoxyethanol as an emulsifier. The different factors that influenced the graft copolymer reaction process were investigated. In the case of radiation‐dose‐dependent grafting, samples irradiated in the presence of air produced up to 73% graft weight compared to 53% obtained in the case of irradiation in a nitrogen environment. By assuming Arrhenius reaction kinetics, the activation energy (Ea) of the grafting reaction process was evaluated for different reaction temperatures. Moreover, the graft copolymer reaction was controlled by incorporating a homopolymer‐inhibiting agent and three different chain‐transfer agents in the reaction medium. The mechanical and thermal properties of jute fiber ‘as received’ and jute‐graft‐poly(methyl methacrylate) were also investigated. The results showed that the percentage of grafting with jute fiber has a significant effect on the properties. The kinetic parameters were evaluated from TGA thermograms by using Broido's method in the temperature range 240–350 °C. Scanning electron micrographs show that the structural changes on the surface of jute fibers were induced by graft copolymerization of methyl methacrylate monomer. Fiber‐fiber surface friction was measured in terms of the average maximum load and the kinetic friction.

SEM of jute‐graft‐poly(methyl methacrylate).

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SEM of jute‐graft‐poly(methyl methacrylate).
Cover Picture: Macromol. Biosci. 12/2004
Authors: Yang Jing , Jia Lin , Yin Lingzhi , Yu Jianyong , Shi Zhen , Fang Qiang , Cao Amin
Published: January 2005

Cover: The Figure schematically shows the synthesis of novel aluminum metal complexes bearing chiral Salen ligand and mono‐/difunctional water‐soluble poly(ethylene glycol) MPEG/PEG. The complexes are used as synthetic templates for the preparation of amphiphilic MPEG‐b‐PCL/PVL, PCL/PVL‐b‐PEG‐b‐PCL/PVL di‐/triblock copolymers with well‐defined macromolecular architectures. The amphiphilic biodegradable copolymers provide new possibilities for preparing uniform biodegradable micelles and/or external‐stimulus sensitive biodegradable gel networks for applications as biomimetic and functional biomaterials.

Further details can be found in the Full Paper by J. Yang, L. Jia, L. Yin, J. Yu, Z. Shi, Q. Fang, and A. Cao* on page 1092.
A Mathematical Model for Photopolymerization From a Stationary Laser Light Source
Authors: Perry Michael F. , Young Gerald W.
Published: January 2005

Summary: A mathematical model of photopolymerization is presented for a stationary laser. Termination by radical combination and radical trapping is considered. Using simplifying assumptions, we derive analytical equations for the concentration of photoinitiator and monomer in the system. With these equations, we show that the light intensity and the initial amount of photoinitiator highly influence the polymerization process and determine the shape of the polymer that is formed. We also provide an analytic expression to determine the amount of polymer formed during dark reactions.

Percent conversion of monomer as a function of time at z = 0 and r = 0 (Data from Table 1).

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Percent conversion of monomer as a function of time at z = 0 and r = 0 (Data from Table 1).
Selective effect of repetitive hand movements on intracortical excitability
Authors: Renner Caroline I. E. , Schubert Margot , Hummelsheim Horst
Published: January 2005

Repetitive training of isolated movements induces local reorganization of the motor cortex. To investigate the effect of repetitive movements on intracortical inhibition and facilitation shortly after the movements, we performed paired‐pulse transcranial magnetic stimulation in 12 healthy subjects by using interstimulus intervals of 2 and 8 ms, respectively. Motor evoked potentials (MEPs) were recorded simultaneously from the extensor carpi radialis (ECR) and the flexor carpi ulnaris muscle (FCU) following paired stimuli at rest or 1 s after repetitive (every 6 s) active or passive wrist extensions and compared with MEPs produced by single stimuli at rest. The active movements produced significantly larger MEPs in the ECR but not the FCU muscle. Passive movements had no effect. Intracortical facilitation increased significantly after movements in the ECR only. Intracortical inhibition, however, did not change significantly after repetitive movements in either muscle. These findings support the notion that intracortical inhibition and facilitation may be controlled independently. Further, these data suggest that shortly after repetitive movements the excitability of the primary motor cortex representing the agonist muscle is increased by interaction with intracortical facilitatory circuits rather than by inactivating inhibitory circuits. Muscle Nerve, 2005
Radiation‐induced conduction block: Resolution following anticoagulant therapy
Authors: Soto Oscar
Published: January 2005

Neurophysiologic studies documented proximal conduction blocks in a patient harboring a delayed radiation‐induced brachial plexopathy. Since anticoagulants have been reported to be beneficial in radiation‐induced neuropathies, the patient was started on acenocumarol. After 3 months of treatment there was significant improvement of clinical deficits, which correlated with resolution of conduction blocks. This observation suggests that ischemic nerve injury leading to disruption of the conduction properties of motor axons contributes to the pathogenesis of delayed radiation‐induced peripheral nerve injuries. Muscle Nerve, 2005
Thermo‐solvatochromism of zwitterionic probes in aqueous aliphatic alcohols and in aqueous 2‐alkoxyethanols: relevance to the enthalpies of activation of chemical reactions
Authors: Tada Erika B. , Silva Priscilla L. , Tavares Clarissa , El Seoud Omar A.
Published: January 2005

The thermo‐solvatochromic behavior of 2,6‐dichloro‐4‐(2,4,6‐triphenylpyridinium‐1‐yl)phenolate (WB), 1‐methylquinolinium‐8‐olate (QB) and 4‐[2‐(1‐methylpyridinium‐4‐yl)ethenyl]phenolate (MC) was investigated in binary mixtures of water (W) and 2‐alkoxyethanols (ROEtOH) in the temperature ranges from 10 to 60°C (2‐ethoxyethanol and 2‐n‐propoxyethanol) and 10 to 40°C (2‐n‐butoxyethanol). Thermo‐solvatochromic data were treated according to a model that is based on the presence in bulk solution of three solvents, W, ROEtOH and a 1:1 H‐bonded species, ROEtOH–W. Solvation by ROEtOH–W is favored over solvation by either of the two precursor solvents. The present data, and those recently published on thermo‐solvatochromism of the same probes in five alcohols (methanol, ethanol, 1‐propanol, 2‐propanol and 2‐methyl‐2‐propanol) and one ROEtOH (2‐methoxyethanol), were submitted to regression analysis. The results indicate that solvation is more sensitive to solute–solvent hydrophobic interactions than H‐bonding between the probe phenoxy oxygen and the hydroxyl group of the H‐bond donating solvent (HBD). Temperature increase results in gradual desolvation of the probes, due to the concomitant decrease of the structure of all components of the binary solvent mixture. For pure solvents, the temperature‐induced desolvation depends on the structure of the probe (order: WB>MC>QB) and the HBD solvent (order: 2‐ethoxyethanols>aliphatic alcohols, for the same alkyl group; organic solvent>water). The probe solvatochromic response is due to the electronic transition zwitterion→di‐radical; it serves as a model for reactions that are associated with a large polarity difference between the reagents and activated complexes. For WB, for ΔT = 50°C, the desolvation energies range from 2.1 to 3.7 kcal mol−1. The contribution of temperature‐induced desolvation to the activation enthalpies of these reactions is, therefore, important. Copyright © 2005 John Wiley & Sons, Ltd.
Development of an improved synthetic route to an AB phenylquinoxaline monomer
Authors: Baek Jong‐Beom , Harris Frank W.
Published: January 2005

The primary objective of this research was the development of an efficient synthetic route for a previously prepared self‐polymerizable PPQ monomer mixture, 2‐(4‐hydroxyphenyl)‐3‐phenyl‐6‐fluoroquinoxaline and 3‐(4‐hydroxyphenyl)‐2‐phenyl‐6‐fluoroquinoxaline. Thus, the intermediate, 4‐hydroxybenzil, was synthesized in good yield, starting from phenol with phenylacetyl chloride, followed by oxidation. The other intermediate, 4‐fluoro‐1,2‐phenylenediamine, was also less costly synthesized, starting from 2,4‐difluoronitrobenzene with ammonium hydroxide, followed by reduction, giving excellent yield. The overall monomer yield was superior to previous reports. Another research objective involved preparation of various monomer mixtures that could be synthesized even less costly, and attempts on polymerization could generate the same structure of PPQ from an original monomer mixture. Thus, the monomer mixture that had switched functional groups from the original one, 2‐(4‐fluorophenyl)‐3‐phenyl‐6‐hydroxyquinoxaline and 3‐(4‐fluorophenyl)‐2‐phenyl‐6‐hydroxyquinoxaline, was prepared. Various monomers with different functional groups attached on the 6‐position of the quinoxaline ring, such as chloro‐ and nitro‐substituted monomers instead of fluoro‐substituted ones, were also prepared. Several attempts to build up high molecular weights were not successful. In the case of the switched monomer mixture, weaker nucleophility and less activation on the fluorine atom were to be the reason in the switched monomer. In the cases of chloro‐ and nitro‐substituted monomers, poorer leaving power and side reactions were to be the reasons. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 801–814, 2005
Single electron transfer–degenerative chain transfer mediated living radical polymerization (SET–DTLRP) of vinyl chloride initiated with methylene iodide and catalyzed by sodium dithionite
Authors: Percec Virgil , Popov Anatoliy V. , Ramirez‐Castillo Ernesto , Coelho Jorge F. J.
Published: January 2005

Single electron transfer–degenerative chain transfer mediated living radical polymerization (SET–DTLRP) of vinyl chloride (VC) initiated with methylene iodide (CH2I2) and catalyzed by sodium dithionite (Na2S2O4) in water at 35 °C produces a telechelic poly(vinyl chloride) (LRP–PVC) with two different active chain ends:ICH2(CH2CHCl)n‐1CH2CHClI, and 2.0 functionality. The reactivity and initiator efficiency of CH2I2in SET–DTLRP of VC was lower than those of iodoform. A possible mechanism for the CH2I2‐initiated SET–DTLRP of VC was suggested. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 773–778, 2005
Phase transfer catalyzed single electron transfer–degenerative chain transfer mediated living radical polymerization (PTC‐SET–DTLRP) of vinyl chloride catalyzed by sodium dithionite and initiated with iodoform in water at 43 °C
Authors: Percec Virgil , Popov Anatoliy V. , Ramirez‐Castillo Ernesto , Coelho Jorge F. J. , Hinojosa‐Falcon Luis A.
Published: January 2005

To accelerate the living radical polymerization (LRP) of vinyl chloride (VC) in water the phase transfer catalyzed single electron transfer–degenerative chain transfer mediated living radical polymerization (SET–DTLRP) of VC mediated by sodium dithionite (Na2S2O4) was investigated. The fastest polymerization reaction that still produces thermally stable poly(vinyl chloride) (PVC) takes place at 43 °C with the ratio [PTC]0/[Na2S2O4]0= 0.0075/1. Cetyltrimethylammonium bromide (nC16H33(CH3)3N+Br−, CetMe3NBr) was the phase‐transfer catalyst (PTC) of choice. Under these conditions the first, fast stage of SET–DTLRP of VC was accomplished within 7–8 h when the initial ratio monomer/initiator [VC]0/[CHI3]0was 800. The number‐average molecular weight (Mn) of the resulting PVC was in good agreement with the theoretical molecular weight (Mth). When the [VC]0/[CHI3]0ratio was 4800, the fast step of the reaction was accomplished within 17 h, to produce 72% monomer conversion. A deviation of theMnfrom theMthwas observed in this case. Possible mechanistic explanations for this deviation as well as for the phase transfer catalyzed SET–DTLRP of VC were suggested. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 779–788, 2005
Synthesis, isolation, and characterization of polytitanasiloxanes and zirconasiloxanes by the hydrolytic cocondensation of tetraethoxysilane and titanium or zirconium tetraisopropoxide
Authors: Gunji Takahiro , Yokogawa Masanari , Hongo Masahiro , Abe Yoshimoto
Published: January 2005

Polytitanasiloxanes and polyzirconasiloxanes were synthesized through the hydrolytic cocondensation of tetraethoxysilane (TEOS) and tetraisopropoxytitanium (TPT) or tetraisopropoxyzirconium (TPZ) 2‐propanol adduct (process A) and through the reaction of partially hydrolyzed TEOS with TPT or TPZ (process B) and were isolated as acetylacetonato derivatives stable against self‐condensation. In both processes, acetylacetone was added to provide acetylacetonato derivatives of polytitanasiloxanes and polyzirconasiloxanes. In process A, titanium‐ or zirconium‐rich polymetallasiloxanes were formed during the initial stage of the process, whereas the molar ratio of silicon to titanium or zirconium was gradually increased up to almost unity with an increasing reaction time. In process B, the molar ratio gradually increased below and above unity as the molar ratio of water to TEOS increased. When the acetylacetonato derivatives of polymetallasiloxanes were subjected to heat treatment, the titania or zirconia component was crystallized. The crystallization temperature increased as the silica content and the molar ratio of water to TEOS increased, and this demonstrated that the crystallization was dependent on the sequence in the main chain of the polymetallasiloxanes. The 29Si NMR spectra of the polymetallasiloxanes led to the idea that the backbone metallasiloxane linkages consisted of random and block sequences for processes A and B, respectively. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 763–772, 2005
Synthesis and characterization of single‐wall‐carbon‐nanotube‐doped emeraldine salt and base polyaniline nanocomposites
Authors: Do Nascimento Gustavo M. , Corio Paola , Novickis Richard W. , Temperini Marcia L. A. , Dresselhaus Mildred S.
Published: January 2005

Nanocomposites of polyaniline (PANI) and single‐wall carbon nanotubes (SWNTs) were prepared and characterized via resonance Raman and electronic absorption spectroscopy (ultraviolet–visible/near‐infrared). The chemical synthesis of PANI was performed in the presence of SWNTs in concentrations ranging from 10 to 50 wt % (SWNT/PANI). The obtained materials were hydrophilic, homogeneous composite compounds. The chemical interaction between PANI (in the conducting emeraldine salt form and in the insulating emeraldine base form) and metallic and semiconducting nanotubes was investigated. The emeraldine salt form of the polymer was significantly stabilized in the composite in comparison with plain PANI. A selective electronic interaction process between PANI and metallic SWNTs was found. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 815–822, 2005
FTIR spectroscopic investigation of thermal effects in semi‐syndiotactic polypropylene
Authors: Sevegney Michael S. , Kannan Rangaramanujam M. , Siedle Allen R. , Percha Pamela A.
Published: January 2005

The temperature‐dependent behavior of individual components within metallocene‐catalyzed semisyndiotactic polypropylenes (semi‐sPP) with a wide range of stereoregular content (26 to 96% rr) is studied using Fourier transform infrared (FTIR) spectroscopy and temperature‐modulated differential scanning calorimetry (DSC). Changes in sensitive, high‐resolution absorbance spectra are observed as melt‐slow‐cooled thin films are subjected to stepwise temperature increases. In general, spectral bands previously identified as being sensitive to ordered structures (e.g., conformed chains, crystal morphs) appear to follow overall trends of shifting to lower wavenumbers (energies), broadening, and decreasing in peak area intensity as temperature increases. Peaks that appear due to “splitting” (observed in more stereoregular materials) show a trend toward coalescence as temperature increases; this corresponds to a gradual loss of chain conformational order. Gauche‐gauche‐trans‐trans (ggtt)n helical and all‐trans (tttt)n planar zigzag‐conformed chains that participate in the crystalline‐amorphous interfacial region (“mesophase”) appear to be more stable (i.e., they do not lose their conformational order as easily) with increasing temperature in materials with a greater degree of syndiotacticity. Moreover, IR data correspond well with modulated DSC endotherms located near 50 °C and 70 °C. At each transition temperature—thought to represent, respectively, a thermally driven chain conformation from planar zigzags to helices, and a dynamic disorder of helices marked by rapid gauche ↔ trans isomerization—the IR absorbance ratio, A978/A963, which represents the relative population of helical chains, undergoes an accelerated decrease. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 439–461, 2005
Morphology and mechanical properties of binary triblock copolymer blends
Authors: Lach Ralf , Weidisch Roland , Knoll Konrad
Published: January 2005

The influence of the morphology on the mechanical properties of binary styrene–butadiene (SB) triblock copolymer blends of a thermoplastic block copolymer and a thermoplastic elastomer (TPE) with different molecular architectures was studied with bulk samples prepared from toluene. Both block copolymers contained SB random copolymer middle blocks, that is, the block sequence S–SB–S. The two miscible triblock copolymers were combined to create a TPE with increased tensile strength without a change in their elasticity. The changes in the equilibrium morphology of the miscible triblock copolymer blends as a function of the TPE content (lamellae, bicontinuous morphology, hexagonal cylinders, and worms) resulted in a novel morphology–property correlation: (1) the strain at break and Young's modulus of blends with about 20 wt % TPE were larger than those of the pure thermoplastic triblock copolymer; (2) at the transition from bicontinuous structures to hexagonal structures (∼35 wt % TPE), a change in the mechanical properties from thermoplastic to elastomeric was observed; and (3) in the full range of wormlike and hexagonal morphology (60–100 wt % TPE), elastomeric properties were observed, the strength greatly increasing and high‐strength elastomers resulting. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 429–438, 2005
Studies on electron beam evaporated ZrO2/AlGaN/GaN metal–oxide–semiconductor high‐electron‐mobility transistors
Authors: Balachander Krishnan , Arulkumaran Subramaniam , Ishikawa Hiroyasu , Baskar Krishnan , Egawa Takashi
Published: January 2005

Metal–oxide–semiconductor high‐electron‐mobility transistors were demonstrated on AlGaN/GaN with electron beam (EB) evaporated ZrO2. The composition of the EB deposited ZrO2 thin films was confirmed using X‐ray photoelectron spectroscopy (XPS). The fabricated ZrO2‐based MOSHEMTs exhibited high positive gate voltage of operation up to +7 V with low gate leakage current. For a comparison, conventional high‐electron‐mobility transistors (HEMTs) were also fabricated with identical device dimensions. The maximum drain current densities of 1168 and 538 mA/mm were observed on MOSHEMTs and HEMTs, respectively. Low gate leakage current density of four orders of magnitude was observed on ZrO2‐based MOSHEMTs when compared with the conventional HEMTs. The observation of high forward on‐voltage with low gate leakage current density and high positive operational voltage reveals the importance of ZrO2 dielectric films for MOSHEMT devices. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Aktive und wandelbare Ingenieurbauten
Authors: Schlaich Mike
Published: January 2005

Brücken, Türme und weitgespannte Dächer werden geplant und gebaut, um eine bestimmte Funktion zu übernehmen. Sie bleiben dann während ihrer Lebensdauer allen Umwelteinflüssen und Belastungen hilflos ausgesetzt, ohne auf diese irgendwie reagieren zu können. Das heißt, die heute üblichen Ingenieurbauten sind fast ausnahmslos passiv. Sie sind also nicht aktiv in dem Sinne, daß sie sich verändernden Einflüssen anpassen können. Sie haben meist nicht die Intelligenz, ihr Tragverhalten situationsabhängig zu ändern, z. B. um sich wechselnden Lasten anzupassen.

Sie sind zugleich nicht wandelbar und können sich deshalb den veränderten Nutzungsbedingungen nicht anpassen. Dächer und Brücken, die sich wegfalten können, wenn sie nicht gebraucht werden, sind Ausnahmen.

Mit dem Konstruieren solcher aktiven und veränderbaren Tragwerke können wir Bauingenieure uns neue Geschäftsfelder erschließen. Die Natur kann uns mit ihren Lösungen für solche Probleme inspirieren. Jahrmillionen der Optimierung haben eine erstaunliche Vielfalt an Konstruktionen, vor allem Leichtbauten, hervorgebracht, die sich “ganz natürlich” allen wechselnden Randbedingungen anpassen.

Dazu kommen die Fortschritte auf dem Gebiet der Elektronik, die schon jetzt bisher passive Ingenieursysteme wie Automobile, Flugzeuge und sogar Haushaltsgeräte revolutioniert haben. Vor allem durch den Einsatz billiger massengefertigter Mikrosysteme erreichen solche Systeme heute schon einen gewissen Grad von Autonomie.

Dieser Artikel soll dazu anregen, in diesem Sinne über Ingenieurbauten nachzudenken, um sie aktiv oder wandelbar, intelligent, smart, adaptiv und autonom, auf jeden Fall also zeitgemäß werden zu lassen. Die gleichzeitige Anwendung von Erkenntnissen des Leichtbaus, der Bionik und der Mikrosystemtechnik auf künftige Tragwerke steht im Mittelpunkt. Nach einem Blick in die Zukunft werden vorhandene wandelbare Ingenieurbauten gezeigt, die einen ersten Schritt in die zuvor beschriebene Richtung bedeuten.
Gespannte Seilnetzfassaden
Authors: Schober Hans
Published: January 2005

Die Erfindung der gespannten Seilnetzfassade durch Prof. Jörg Schlaich im Jahre 1989/1990 für das Hotel Kempinski in München stellte einen Meilenstein auf dem Weg zu optimaler Transparenz von Glasfassaden dar. Diese Innovation prägte die Glasarchitektur danach ganz wesentlich und führte zur weltweiten Anwendung und infolge versäumten Patentschutzes auch zur weltweiten Kopie.

Die tragende Konstruktion besteht aus einem ebenen einlagigen gespannten Seilnetz, an dessen Knoten die quadratischen oder rechteckigen Glasscheiben punktförmig befestigt sind, ohne das Glas zu durchbohren.

Dadurch verlaufen die Seile genau hinter den vertikalen und horizontalen Glasfugen und werden als Konstruktion fast nicht mehr wahrgenommen.

Die Konstruktion benötigt einem Tennisschläger gleich tragfähige Ränder, welche die Vorspannkräfte aufnehmen, besser noch, kurzschließen.
Sociological explanations for faculty and student classroom incivilities
Authors: Bray Nathaniel J. , Del Favero Marietta
Published: January 2005

To understand the current apparent upsurge in classroom incivility, the authors turn to the literature for possible causes and solutions.
Dynamics of gender, ethnicity, and race in understanding classroom incivility
Authors: Alexander‐Snow Mia
Published: January 2005

Classroom incivility is influenced by many factors. This chapter identifies three that are commonly thought of as influencing the degree to which students will engage in inappropriate behaviors in the classroom.
Incidence and student response to faculty teaching norm violations
Authors: Braxton John M. , Rogers Mann Melinda
Published: January 2005

This chapter reports the results of research into how frequently students perceive faculty to engage in classroom improprieties and what they tend to do
about it.
Effects of student classroom incivilities on students
Authors: Hirschy Amy S. , Braxton John M.
Published: January 2005

Student violations of behavior norms affect the learning of others, the teaching of the instructor, and the atmosphere of the classroom.
Promulgating statements of student rights and responsibilities
Authors: Bayer Alan E.
Published: January 2005

Students must learn to balance what they can expect from faculty with what they need to do themselves to make the classroom a safe and welcoming climate for everyone.
Conclusions and recommendations: Avenues for addressing teaching and learning improprieties
Authors: Bayer Alan E. , Braxton John M.
Published: January 2005

Based on the research reported in this volume, the authors offer recommendations for all affected parties.
Über salzartige Derivate von Säureradikalen. 2. Mitteilung. Die Acylderivate der Antimon(V)‐chlorwasserstoffsäure. I
Authors: Seel F.
Published: January 2005

1. Die in einer vorangehenden Arbeit beschriebene Darstellung des Acetylfluoborats und seine Charakterisierung als Elektrolyt [CH3CO]+[BF4]−gab Veranlassung zu Untersuchungen, inwieweit andere, bisher meist als Molekülverbindungen formulierte Additionsverbindungen von Carbonsäurehalogeniden an Halogenosäurebildner als salzartige Komplexe mit Acylionen als Kationen aufzufassen sind.

Die Existenzmöglichkeiten solcher Acylsalze werden zunächst in einer energetischen Betrachtung behandelt, wodurch sich Voraussagen über die Stabilität und die Abstufungen in der Beständigkeit machen lassen.

Durch experimentelle Untersuchungen ergibt sich, daß die bereits bekannten Produkte CH3COCl·SbCl5und C6H5COCl·SbCl5tatsächlich Acylsalze der Antimonchlorwasserstoffsäure im Sinne der Formulierung CH3CO[SbCl6], C6H5CO[SbCl6] darstellen: In flüssigem Schwefeldioxyd sind ihre 1/50‐molaren Lösungen größenordnungsmäßig ebenso gute Stromleiter wie die Lösungen des Kaliumsalzes K[SbCl6] oder anderer bekannter Salze, während die Komponenten Säurechlorid und Antimon(V)‐chlorid nur äußerst schwache Stromleiter sind. Hiermit ist ein neuer Typ starker Elektrolyte in flüssigem Schwefeldioxyd gefunden worden.
Zur Kenntnis der sogenannten „Alkalicarbonyle”︁. II. Die Kristallstrukturen des Rubidium‐ und Caesium‐acetylendiolats, RbOCCORb und CsOCCOCs
Authors: Weiss E. , Büchner W.
Published: January 2005

Die durch Umsetzung von Kohlenmonoxid mit in flüssigem Ammoniak gelöstem Rubidium oder Caesium erhältlichen Präparate erweisen sich nach röntgenographischen Untersuchungen als Rubidium‐ bzw. Caesiumacetylendiolat, RbOCCORb bzw. CsOCCOCs. Sie sind mit der früher beschriebenen kaliumverbindung isotyp und kristallisieren im tetragonalen System (Raumgruppe I 4/mmm) mit Z = 2 und folgenden Gitterkonstanten:

equation image

Unter Verwendung der an der Kaliumverbindung abgeleiteten CC‐ und CO‐Abstände des linearen OCCO2−‐Ions ergeben sich folgende Ionen‐ bzw. Atomabstände:

equation image

Der CO‐Abstand erscheint etwas kürzer, als der für eine Einfachbindung berechnete, was auf einen Konjugationseffekt schließen läßt.
Farbe und Konstitution bei anorganischen Feststoffen. VI. Über die Lichtabsorption des dreiwertigen Chroms in indiumhaltigen Wirtsgittern mit Granatstruktur
Authors: Schmitz‐Dumont O. , Moulin N.
Published: January 2005

In der Granatphase Y3Ga4CrO12 konnte 1 Ga3+ durch In3+ isomorph ersetzt werden. Hierbei besetzt In3+ ausschließlich Oktaederlücken. Durch die beim Einbau von In3+ bewirkte Gitteraufweitung erfolgt eine IR‐Verschiebung der Hauptabsorptionsbanden des Cr3+. In der Granatphase mit maximalem In‐Gehalt Y3Ga3In2O12 kann alles In3+ sukzessive durch Cr3+ ausgetauscht werden, wobei die erwartete UV‐Verschiebung der Absorptions‐banden des Cr3+ beobachtet wird. Versuche, Al3+ und Cr3+ in Y3Al5‐XCrXO12 durch In3+ zu ersetzen, blieben erfolglos.
Über wasserfreie und wasserhaltige Silbergermanate
Authors: Krüger G.
Published: January 2005

Es wird über die Darstellung von Silbermono‐ und ‐polygermanat Ag4GeO4 und (Ag2GeO3)n berichtet.

Ferner wird festgestellt, daß aus Silbernitratlösungen mit Alkaligermanatlösungen schwerlösliche gefärbte Silberhydrogengermanate der allgemeinen Zusammensetzung Agn+2[HnGenO3n+1] ausfallen. Die (Ag:Ge)‐Verhältnisse und damit auch der Farbton dieser Verbindungen sind abhängig vom (Na:Ge)‐Verhältnis und der Konzentration des Germanates in den Ausgangslösungen. Die Verbindungen enthalten unabhängig vom (Ag:Ge)‐Verhältnis stets ½ Mol H2O pro Mol Ge. Diese Fakten führen zu Rückschlüssen auf die konzentrationsabhängige Kondensation der Germanationen in den Ausgangslösungen.

Es werden vergleichende Betrachtungen über das Verhalten von Germanat‐ und Silicationen in Lösungen angestellt.
Zur Kenntnis der Thioselensäure H2SSeO3 und einiger ihrer Halbester
Authors: Schmidt Max , Wilhelm Irmgard
Published: January 2005

Schwefelwasserstoff wird in Äther auch unter schonenden Bedingungen von Selentrioxid oxydiert. Dagegen erhält man aus Mercaptanen und SeO3 S‐Alkyl‐ bzw. Arylhalbester der Thioselensäure, die bei Zimmertemperatur nicht beständig sind. Diäthylsulfid bildet ein Addukt (C2H5)2S · SeO3, das auf Pyridin selenonierend wirkt. Chloroselensäure liefert bei der Thiolyse freie Thioselensäure, allerdings nicht in reiner Form. Mit Mercaptanen entstehen daraus wieder S‐Halbester. Durch Thiolyse von Trimethylsilylchloroselenat ist der O‐Trimethysilylester der Thioselensäure darstellbar.
Beiträge zur Kenntnis der Alkalitellurate. I. Über ein neues Kaliumtellurat und seinen Strukturtyp
Authors: Lammers P. , Zemann J.
Published: January 2005

Durch hydrothermale Behandlung (125–145 °C) von wäßrigen Lösungen von K2CO3 und Te(OH)6 im Molverhältnis 2 : 1 oder größer erhält man morphologisch tetragonale Kriställchen der Zusammensetzung KTeO2(OH)3, die jedoch optisch anomal sind. Nach der röntgenographischen Untersuchung ist die Kristallstruktur durch [Te[6] (O, OH)5]1−‐Ketten charakterisiert, die durch K+‐Ionen zusammengehalten werden.