bluuebunny/crossref_metadata_2025_split huggingface dataset:
Studying protein‐carbohydrate interactions by amide hydrogen/deuterium exchange mass spectrometry
Authors: King Daniel , Lumpkin Michelle , Bergmann Carl , Orlando Ron 
Published: October 2002

AbstractProtein‐carbohydrate interactions play a significant role in biological processes. Presented here is the novel application of amide hydrogen/deuterium exchange mass spectrometry (amide exchange‐MS) to the study of the interaction between a protein and its carbohydrate substrate. The degree of deuterium incorporation into hen egg lysozyme was monitored with and without substrate to verify that a carbohydrate can provide sufficiently stable protection of the amide hydrogen atoms in a protein's backbone from exchange with deuterated solvent. The substrate protected a number of amide hydrogens from exchange, implying that protein‐carbohydrate binding systems will be compatible with amide exchange‐MS. Endopolygalacturonase‐II (EPG‐II) from Aspergillus niger, a pectin‐degrading enzyme, was chosen as the first carbohydrate‐binding system to be extensively studied using quenched amide exchange‐MS. Monitoring the changes in deuterium incorporation of EPG‐II in the presence and absence of an oligomer of galacturonic acid implied the location of substrate binding. This study demonstrates the ability of amide exchange‐MS to investigate protein‐carbohydrate interactions. Copyright © 2002 John Wiley & Sons, Ltd.
Study of structural characteristic features of phenanthriondolizidine alkaloids by fast atom bombardment with tandem mass spectrometry
Authors: Xiang Yun , Abliz Zeper , Li Li‐jun , Huang Xue‐shi , Yu Shi‐shan 
Published: October 2002

AbstractThe mass spectrometric behavior of phenanthroindolizidine alkaloids has been investigated in detail by positive ion fast atom bombardment tandem mass spectrometry (FAB‐MS/MS) combined with collision‐induced dissociation (CID). The fragmentation has been correlated with the skeleton structure and positions of substituents. The product ions arising from retro‐Diels‐Alder cleavages differ clearly for compounds with different skeletons. The substituents at C‐14 were observed to markedly influence the fragmentation pathway of [M + H]+ ions. A diversity of dissociation behavior initiated by the variation of substituents on the aromatic ring was also observed in the CID spectra. Product ions resulting from loss of CH4 were obtained for compounds in which both C‐6 and C‐7 are occupied by methoxy groups. FAB‐MS/MS spectra can reflect the connection between the fragmentation behavior and structural features of these phenanthroindolizidine alkaloids rapidly and effectively, and should prove to be a powerful method to determine the structures of related compounds. Copyright © 2002 John Wiley & Sons, Ltd.
Temporal changes in macroinvertebrate assemblages following experimental flooding in permanent and temporary wetlands in an Australian floodplain forest
Authors: Hillman T.J. , Quinn G.P. 
Published: October 2002

AbstractThe River Murray, Australia, is a highly regulated river from which almost 80% of mean annual flow is removed for human use, primarily irrigated agriculture. Consequent changes to the pattern and volume of river flow are reflected in floodplain hydrology and, therefore, the wetting/drying patterns of floodplain wetlands. To explore the significance of these changes, macroinvertebrate samples were compared between permanent and temporary wetlands following experimental flooding in a forested floodplain of the River Murray. Weekly samples from two permanent wetlands and four associated temporary sites were used to track changes in macroinvertebrate assemblage composition. Non‐metric multidimensional scaling was used to ordinate the macroinvertebrate data, indicating consistent differences between the biota of permanent and temporary wetlands and between the initial and later assemblages in the temporary sites. There were marked changes over time, but little sign that the permanent and temporary assemblages were becoming more alike over the 25‐week observation period. The apparent heterogeneity of these systems is of particular importance in developing river management plans which are likely to change flooding patterns. Such plans need to maintain a mosaic of wetland habitats if floodplain biodiversity is to be supported. Copyright © 2002 John Wiley & Sons, Ltd.
Performance of a fishway system in a major South American dam on the Parana River (Argentina–Paraguay)
Authors: Oldani Norberto O. , Baigún Claudio R. M. 
Published: October 2002

AbstractSuccessful design and operation of fish passage systems are important to protect fish communities from impacts of hydroelectric dams in the Río de la Plata River basin. We evaluated the performance of an elevator lift system to pass adult fish through Yacyretá dam on the Paraná River between 1995 and 1998, both for mechanical reliability and performance. The elevator lift system was mechanically inoperative 30–38% of the time during the October–December period of greatest fish migration. Target species represented 30% of total fish number in gillnet samples in the tailwater, but constituted only 10% of the total number of fish transferred. Fish collected within the system were dominated by Pimelodus clarias (>69%), although this species represented less than 10% of captures in experimental gillnets set in the tailwater. Prochilodus lineatus, a key species, represented less than 5% of transferred fish, but constituted 22.1% of tailwater samples. Estimated number of fish transferred per year ranged between 1 210 000 (1995) and 3 610 000 (1996) with biomass ranging from 631 to 1989 tons, respectively. We estimated a fish passage efficiency of 1.88% for all species and 0.62% for target species. At this efficiency, transferred species would increase the total fish yield in the reservoir by as much as 4.9 kg/ha/year, but only 0.5 kg/ha/year for target species. We conclude that fish transfer efficiency is inadequate to maintain populations of target species in the Paraná River system. We identify critical research needs to improve the passage of fish at dams. Copyright © 2002 John Wiley & Sons, Ltd.
A systems approach to river restoration: a case study in the lower Seine valley, France
Authors: Poudevigne I. , Alard D. , Leuven R. S. E. W. , Nienhuis P. H. 
Published: October 2002

AbstractRestoration of regulated rivers presents fundamental challenges because of the complexity and adaptive nature of riverine ecosystems. It is now agreed that restoration strategies need to restore the system as a whole (structure, function and dynamics). Most studies are faced with the same difficulties concerning the right scale for restoration actions, the representative attributes of the riverine system and the measures capable of surveying restoration action impacts.This work proposes an approach to river restoration borrowed from the conceptual and theoretical background of landscape ecology. Leaning on experience on biodiversity restoration along the Lower Seine river, we propose a systemic approach based on the hierarchical nature of riverine systems. This approach suggests that like any system, riverine ecosystems can be simplified into basic units which are complementary and integrated in a hierarchical structure. Simplification leads to focusing on one component of the ecosystem at a relevant scale of space and time (organization level). Here, we focus on two attributes of this ecosystem at different scales: community organization and landscape organization. These organization measures, realized at different observation scales, provide insight to the ecological response of the system in time. They are measures of the stability of the system and can provide effective tools for predicting or following the impact of restoration actions on riverine landscapes. Copyright © 2002 John Wiley & Sons, Ltd.
Effect of flow‐related substrate alteration on physical habitat: a case study of the endemic river loach Sinogastromyzon puliensis (Cypriniformes, Homalopteridae) downstream of Chi‐Chi Diversion Weir, Chou‐Shui Creek, Taiwan
Authors: Wu Fu‐Chun , Wang Chi‐Fang 
Published: October 2002

AbstractThis paper addresses the variation of substrate status with flow in the framework of habitat simulation. The Physical Habitat Simulation System (PHABSIM) was developed as a tool for water management and has become one of the most popular methods worldwide. Despite its many advantages, the variation of channel properties with flow is not addressed in PHABSIM. We modified PHABSIM by incorporating a sub‐program that can perform substrate analyses under five different schemes for evaluating the substrate suitability. These schemes include the conventional methods to specify the substrate attribute (scheme 1) and to use the mean grain size of the original bed material for determining the substrate suitability (scheme 2), or employ the threshold conditions for sediment entrainment to evaluate the nominal grain size of the stable substrate (schemes 3–5). As a case study, Sinogastromyzon puliensis in Chou‐Shui Creek (Taiwan) is selected as the target species for the habitat simulation. For schemes 1 and 2, the substrate attribute specified for each cell of a cross‐section does not change with flow. The nominal grain size of the stable armour material (scheme 5) is generally greater than the nominal grain sizes of the above‐critical bed material (scheme 3) and the static armour layer (scheme 4). The simulation results indicate that the suitability values specified in scheme 1 and the resulting habitat area are on the optimistic side, whereas scheme 2 tends to undervalue the suitability of the hydraulically worked substrate. The overall variation trends of the weighted usable area (or percentage usable area) curves for different substrate schemes are similar, especially in the in‐phase regions of the water velocity and depth. The results of this study appear to imply that the flow‐related habitat analyses are not usually sensitive to substrate. Copyright © 2002 John Wiley & Sons, Ltd.
The development of preservice chemistry teachers' pedagogical content knowledge
Authors: Van Driel Jan H. , Jong Onno De , Verloop Nico 
Published: October 2002

AbstractThis study investigated the development of pedagogical content knowledge (PCK) within a group of 12 preservice chemistry teachers (all M.Sc.) during the first semester of their one‐year post‐graduate teacher education program. The study focused on PCK with respect to a central issue in science teaching, that is, the relation between observable phenomena, like chemical reactions, and macroscopic properties (e.g., boiling point, solubility) on the one hand, and their interpretation in terms of corpuscular characteristics on the other hand (macro–micro). For secondary school students, shifting mentally between the macro and micro levels is usually problematic, whereas their teachers are often unaware of students' learning difficulties in this domain. The collection of data involved two written questionnaires, interviews with each preservice teacher and their respective mentors, and an audio recording of a specific workshop session in the teacher education program. Results indicated a growing awareness among the preservice teachers concerning the need, in teaching situations, to explicitly relate the macro and micro levels to each other. Moreover, the importance of the careful and consistent use of language was noticed by many preservice teachers. The growth of PCK was influenced mostly by the preservice teachers' teaching experiences. Also, the workshop contributed substantially. Finally, for some preservice teachers, their mentors had influenced the growth of PCK. Implications for science teacher education are discussed. © 2002 Wiley Periodicals, Inc. Sci Ed 86:572–590, 2002; Published online in Wiley Interscience (www.interscience.wiley.com). DOI 10.1002/sce.10010
Disease prevalence estimations based on contact registrations in general practice
Authors: Hoogenveen Rudolf , Westert Gert , Dijkgraaf Marcel , Schellevis François , de Bakker Dinny 
Published: October 2002

AbstractThis paper describes how to estimate the prevalence of chronic diseases in a population using data from contact registrations in general practice with a limited time length. Instead of using only total numbers of observed patients adjusted for the length of the observation period, we propose the use of (i) the time of the first contact of patients, (ii) the joint total numbers of patients and contacts, and (iii) the sets of patients in distinct time intervals, to generate prevalence rate estimates. The three new prevalence rate estimators have been developed assuming either a homogeneous or a parameterized heterogeneous patient population. Systematic and stochastic components of the estimators have been analysed by cross‐validation for five chronic diseases using data from the Dutch ‘Study on Chronic Conditions’. The results show that the first two estimators work well for diseases with a relatively structured visiting behaviour, such as hypertension and diabetes mellitus, assuming a time‐constant contact rate and homogeneous patient population. For diseases such as ischaemic heart disease, chronic non‐specific respiratory diseases and osteoarthritis, that do not satisfy these assumptions, the methods generally result in underestimations. Copyright © 2002 John Wiley & Sons, Ltd.
When are technologies disruptive? a demand‐based view of the emergence of competition
Authors: Adner Ron 
Published: October 2002

AbstractBy identifying the possibility that technologies with inferior performance can displace established incumbents, the notion of disruptive technologies, pioneered by Christensen (1997), has had a profound effect on the way in which scholars and managers approach technology competition. While the phenomenon of disruptive technologies has been well documented, the underlying theoretical drivers of technology disruption are less well understood. This article identifies the demand conditions that enable disruptive dynamics. By examining how consumers evaluate technology and how this evaluation changes as performance improves, it offers new theoretical insight into the impact of the structure of the demand environment on competitive dynamics. Two new constructs—preference overlap and preference symmetry—are introduced to characterize the relationships among the preferences of different market segments. The article presents a formal model that examines how these relationships lead to the emergence of different competitive regimes. The model is analyzed using computer simulation. The theory and model results hold implications for understanding the dynamics of disruptive technologies and suggest new indicators for assessing disruptive threats. Copyright © 2002 John Wiley & Sons, Ltd.
Second step algorithms in the Burrows–Wheeler compression algorithm
Authors: Deorowicz Sebastian 
Published: October 2002

AbstractIn this paper we focus our attention on the second step algorithms of the Burrows–Wheeler compression algorithm, which in the original version is the Move To Front transform. We discuss many of its replacements presented so far, and compare compression results obtained using these replacements. Then we propose a new algorithm that yields a better compression ratio than the previous algorithms. Copyright © 2001 John Wiley & Sons, Ltd.
Chiral Proton Donor Reagents: Tin Tetrachloride—Coordinated Optically Active Binaphthol Derivatives
Authors: Ishibashi Hideaki , Ishihara Kazuaki , Yamamoto Hisashi 
Published: October 2002

AbstractThe Lewis acid–assisted chiral Brønsted acids (chiral LBAs), which are prepared from tin tetrachloride and optically active binaphthol derivatives, are highly effective chiral proton donor reagents for enantioselective protonation and biomimetic polyene cyclization. These chiral LBAs can directly protonate various silyl enol ethers and ketene disilyl acetals to give the corresponding α‐aryl or α‐halo ketones and α‐arylcarboxylic acids, respectively, with high enantiomeric excess (up to 98% ee). A catalytic version of enantioselective protonation was also achieved using stoichiometric amounts of 2,6‐dimethylphenol and catalytic amounts of monomethyl ether of optically active binaphthol in the presence of tin tetrachloride. The biomimetic cyclization of simple isoprenoids to polycyclic isoprenoids using chiral LBA is also described. This is the first example of a chiral Brønsted acid–induced enantioselective ene cyclization in synthetic chemistry. Geranyl phenyl ethers, o‐geranylphenols, and homogeranylphenol derivatives were directly cyclized in the presence of (R)‐binaphthol derivatives and tin tetrachloride (up to 90% ee). Compounds bearing a farnesyl group could also be cyclized under the same conditions to give the natural products (−)‐ambrox® and (−)‐chromazonarol, and (−)‐tetracyclic polyprenoids of sedimentary origin. These chiral LBAs recognize the prochiral face of a trisubstituted terminal olefin and site selectively generate carbocations on the substrates. © 2002 The Japan Chemical Journal Forum and Wiley Periodicals, Inc. Chem Rec 2: 177–188,2002: Published online in Wiley InterScience (www.interscience.wiley.com) DOI 10.1002/tcr.10020
The Art of Acetylenic Scaffolding: Rings, Rods, and Switches
Authors: Brøndsted Nielsen Mogens , Diederich François 
Published: October 2002

AbstractAcetylenic scaffolding with derivatives of tetraethynylethene (TEE, 3,4‐diethynylhex‐3‐ene‐1,5‐diyne) and (E)‐1,2‐diethynylethene (DEE, (E)‐hex‐3‐ene‐1,5‐diyne) provides carbon‐rich compounds with interesting physicochemical properties. Thus, these modules are building blocks for monodisperse, linearly π‐conjugated oligomers [polytri(acetylene)s, PTAs] extending in length beyond 10nm, and for large, macrocyclic, all‐carbon cores (dehydroannulenes and expanded radialenes) exhibiting strong chromophoric properties. The advanced materials' properties were strongly influenced by the presence of electron‐donating substituents at the lateral positions, decreasing the decreasing the (HOMO–LUMO) gap in both PTAs and expanded radialenes. Arylated TEEs were found to undergo photochemically induced cis–trans isomerization, paving the way for applications as light‐driven molecular switches in optoelectronic devices. Derivatives of 1,3‐diethynylallene are new modules that offer the prospect of scaffolding in an orthogonal manner; that is, they represent precursors for helical oligomers. © 2002 The Japan Chemical Journal Forum and Wiley Periodicals, Inc. Chem Rec 2: 189–198,2002: Published online in Wiley InterScience (www.interscience.wiley.com) DOI 10.1002/tcr.10022
Properties of Some Alkyl Substituted Phthalocyanines and Related Macrocycles
Authors: Cook Michael J. 
Published: October 2002

AbstractThis report provides an account of research undertaken at the University of East Anglia, United Kingdom, into phthalocyanine derivatives substituted at six or more of the nonperipheral sites by alkyl groups. When first prepared they were only the second series of substituted phthalocyanines known to exhibit columnar liquid crystal behaviour. The compounds also form structured films by the spin‐coating technique, a formulation with potential for FET devices. The zinc metallated derivatives are photosensitisers of singlet oxygen and show good potential for applications in photodynamic therapy. A mixed cyclotetramerisation of a 3,6‐dialkylphthalonitrile with a second aromatic dinitrile forms so‐called 3 : 1 phthalocyanines in which three of the benzenoid rings are substituted with two alkyl groups and the fourth is substituted differently. Appropriate substituents provide amphiphilic compounds that form well‐ordered films by the Langmuir‐Blodgett method and self‐assembly techniques. Characterisation of the films using a variety of methods is discussed and applications described. Examples of 3 : 1 phthalocyanine‐like macrocycles in which one of the benzenoid rings is replaced by a heterocycle extend the range of properties exhibited. These include broadband absorption in the near infrared and, in particular cases, edge‐to‐face dimerisation through coordination of a pyridine nitrogen to a zinc centre in a second macrocycle. The potential for using suitably functionalised 3 : 1 phthalocyanines as building blocks for more complex structures such as liquid crystalline main‐chain polymeric phthalocyanines and phthalocyanino‐dehydroannulenes is described. © 2002 The Japan Chemical Journal Forum and Wiley Periodicals, Inc., Chem Rec 2: 225–236, 2002: Published online in Wiley InterScience (www.interscience.wiley.com) DOI 10.1002/tcr.10028
Using a cross section to train veterinary students to visualize anatomical structures in three dimensions*
Authors: Provo Judy , Lamar Carlton , Newby Timothy 
Published: October 2002

AbstractA cross section was used to enhance three‐dimensional knowledge of anatomy of the canine head. All veterinary students in two successive classes (n = 124) dissected the head; experimental groups also identified structures on a cross section of the head. A test assessing spatial knowledge of the head generated 10 dependent variables from two administrations. The test had content validity and statistically significant interrater and test–retest reliability. A live‐dog examination generated one additional dependent variable. Analysis of covariance controlling for performance on course examinations and quizzes revealed no treatment effect. Including spatial skill as a third covariate revealed a statistically significant effect of spatial skill on three dependent variables. Men initially had greater spatial skill than women, but spatial skills were equal after 8 months. A qualitative analysis showed the positive impact of this experience on participants. Suggestions for improvement and future research are discussed. © 2002 John Wiley & Sons, Inc. J Res Sci Teach 39: 10–34, 2002
Biomarker study of a municipal effluent dispersion plume in two species of freshwater mussels
Authors: Gagné F. , Blaise C. , Aoyama I. , Luo R. , Gagnon C. , Couillard Y. , Campbell P. , Salazar M. 
Published: October 2002

AbstractThe toxicological effects of a primary‐treated municipal effluent plume were investigated in two species of freshwater mussels, Elliptio complanata and Dreissena polymorpha, exposed for 62 days at sites upstream and downstream of an effluent outfall in the St. Lawrence River (Quebec, Canada). Levels of metallothioneins (MT), cytochrome P4501A1 activity, DNA damage, total lipids, relative levels of vitellins, and phagocytic activity (in E. complanata hemocytes) were determined after the exposure period. A parallel analysis measured heavy metals and coprostanol in mussel tissues. The results show that significant levels of coprostanol and some metals (specifically, Cu, Hg, Sb, Se, and Zn) had accumulated in mussels caged 5 km downstream of the effluent plume. Mixed‐function oxidase activity, MT in gills, total lipids, DNA damage (in D. polymorpha only), and total hemolymph bacteria (in E. complanata only) had increased in these mussels, while levels of total cadmium (Cd), MT in digestive glands or whole soft tissues, phagocytic activity, and DNA damage in the digestive gland (in E. complanata only) were diminished. The exposure of mussels to surface waters contaminated by a municipal effluent led to many stress responses, depending on both the tissues and the species being examined. © 2002 Wiley Periodicals, Inc. Environ Toxicol 17: 149–159, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/tox.10046