bluuebunny/crossref_metadata_2025_split huggingface dataset:
Role of stabilization centers in 4 helix bundle proteins
Authors: Fuxreiter M. , Simon I. 
Published: October 2002

AbstractStabilization centers (SCs) were shown to play an important role in preventing decay of three‐dimensional protein structures. These residue clusters, stabilized by cooperative long‐range interactions, were proposed to serve as anchoring points for arranging secondary structure elements. In all‐α proteins, SC elements appear less frequently than in all‐β, α/β, and α+β proteins suggesting that tertiary structure formation of all‐α proteins is governed by different principles than in other protein classes. Here we analyzed the relation between the formation of stabilization centers and the inter‐axial angles (Ω) of α‐helices in 4 helix bundle proteins. In the distance range, where dipoles have dominant effect on the helix pair arrangement, those helix pairs, where residues from both helices participate in SC elements, appear as parallel more frequently than those helices where no SC elements are present. For SC containing helix pairs, the energetic difference between the parallel and anti‐parallel states decreases considerably from 1.1 kcal/mol to 0.4 kcal/mol. Although the observed effect is weak for more distant helices, a competition between the SC element formation and the optimal dipole–dipole interaction of α‐helices is proposed as a mechanism for tertiary structure formation in 4 helix bundle proteins. The SC‐forming potential of different arrangements as well as the pitfalls of the SC definition are also discussed. Proteins 2002;48:320–326. © 2002 Wiley‐Liss, Inc.
Quantitative structure–transformation relationships of sulfonylurea herbicides
Authors: Berger Bernhard M , Müller Martin , Eing Andreas 
Published: October 2002

AbstractModel development to predict transformation of sulfonylureas in different matrices was carried out using multiple linear regression. Descriptors for lipophilicity and molecular topology, as well as quantum chemical descriptors for energy, geometry, polarity, charges and reactivity using MOPAC with three different Hamiltonians, AM1, PM3 and MNDO, were calculated. In addition, experimental descriptors were measured and taken from the literature. End‐points were transformation rates of twelve sulfonylurea herbicides in buffers at different pH (4, 7 and 10), in sterile and native sediments, and in sterile and native soil. Inter‐correlation of reaction rates indicated four different groups of transformation types, for which sum parameters were calculated. (1) Hydrolysis at pH 4 could be estimated with pKa and charges at a specific atom of the heterocycle. (2) Hydrolysis at pH 7 and 10, as well as transformation in sterile sediments and soil, could be described with descriptors for reactivity (polarisability and superdelocalisability) at specific atoms of the molecules. (3) For transformation in native sediments different models could be found, all based on descriptors for polarisability, superdelocalisability and charges at specific atoms. (4) Modelling of biotransformation in native soil led to diverse models with a variety of descriptors reflecting electronic properties and lipophilicity. Models confirmed previous findings on reaction mechanisms and thereby prove valuable not only for quantitative prediction of reaction rates, but also for studies on transformation pathways.© 2002 Society of Chemical Industry
Cytotoxic flavonoids from the stem bark of Lonchocarpus aff. fluvialis
Authors: Blatt Cecília T. T. , Chávez Daniel , Chai Heebyung , Graham James G. , Cabieses Fernando , Farnsworth Norman R. , Cordell Geoffrey A. , Pezzuto John M. , Kinghorn A. Douglas 
Published: October 2002

AbstractActivity‐guided fractionation of a chloroform‐soluble extract of Lonchocarpus aff. fluvialis stem bark using a human epidermoid (KB) tumour cell line as a monitor afforded five rotenoids, one pterocarpan, one chalcone, three flavanones, one flavone and one triterpenoid. All of the compounds isolated proved to be of previously known structure. Among them, the rotenoids (−)‐sumatrol and (±)‐villosinol, the dibenzoylmethane derivative (+)‐3,4‐methylenedioxy‐2′‐methoxy‐[2″,3″:4′,3′]‐furanodibenzoylmethane, and the flavanones (−)‐isoglabrachromene and (−)‐candidone have been shown to exhibit significant cytotoxic activity against human cancer cells for the first time. This is the first report of the chemical constituents of this species, and the profile of compounds obtained was in accordance with the established chemosystematic patterns of species in the tribe Tephrosieae (Leguminosae, Papilionoideae). Copyright © 2002 John Wiley & Sons, Ltd.
Standard Operating Procedures for Clinical Research Personnel ‐ part 13
Authors: Bohaychuk Wendy , Ball Graham 
Published: October 2002

AbstractThis is the 13th in a series of articles containing proposals for wording and content of standard operating procedures (SOPs) for clinical research activities conducted by sponsors and Contract Research Organisations (CROs). The procedures include those required by the International Conference on Harmonisation (ICH), the Food and Drug Administration (FDA), many other guidelines and regulations, and ‘best practice’ observed by the authors. The model forms require modification for actual use. In this article, SOPs are presented for initiation activities: study site initiation visits (SOP 328); and study startup meetings for multicentre studies ( SOP 329). (The full text of all 101 SOPs is available from the authors.) Copyright © 2002 John Wiley & Sons, Ltd.
Hiding role assignment in mission‐critical collaborative systems
Authors: Fu Xinwen , Guan Yong , Bettati Riccardo , Zhao Wei 
Published: October 2002

AbstractIn a mission critical collaboration system, a group of roles are assigned to computer nodes connected by a communication network. Role assignment is mission‐critical information and needs to be protected. In this paper, we develop methods to effectively and efficiently protect the information of role assignment from traffic analysis, a passive attack. To measure the system security, we introduce a metric ofdetection probability, defined as the probability that a role assignment can be discovered. A heuristic greedy algorithm is given to minimize the resource consumption while guaranteeing a low detection‐probability level. Our performance evaluation shows that the algorithm proposed in this paper performs well in terms of execution time and resource usage compared to an exhaustive search algorithm. We also propose to use additional means (e.g. additional nodes) to further increase the security level of a system at the cost of a mild resource consumption increase. Copyright © 2002 John Wiley & Sons, Ltd.
Grid‐ and dummy‐cluster‐based learning of normal and intrusive clusters for computer intrusion detection
Authors: Li Xiangyang , Ye Nong 
Published: October 2002

AbstractAs an important part of information security, computer intrusion detection aims at capturing intrusive activities occurring in computer and network systems. Many existing signature recognition techniques for intrusion detection cannot handle huge amounts of complex data from computer and network systems to detect intrusions in a scalable, incremental manner. This paper presents an application of an innovative data‐mining algorithm—CCAS—to intrusion detection through intrusion signature recognition. CCAS provides a scalable, incremental procedure to learn clusters of different classes (i.e. normal and intrusive classes) from historic training data of normal and intrusive activities in computer and network systems. These clusters of normal and intrusive computer activities are used to classify observed data of computer activities for intrusion detection. Two different methods of learning clusters are developed, tested and compared: grid based and dummy‐cluster based. Training and testing data are computer audit data produced by the Basic Security Module of a Solaris operating system to record activities in a UNIX‐based host machine. The two methods of CCAS are tested using four different input orders of training data points to examine the robustness (sensitivity) of these methods to the input order of training data points. The detection performance and robustness of both CCAS methods are analyzed. The testing results show that different input orders of training data have a certain impact on the performance of both methods. The impact on the performance of CCAS based on dummy clusters is more significant when all normal data are presented first, before attack data in the training data set. CCAS based on dummy clusters produces a better performance than grid‐based CCAS for three of the four input orders, and in overall produces fewer clusters and thus requires less computation time in clustering and classification for intrusion detection. Copyright © 2002 John Wiley & Sons, Ltd.
Hyperspherical harmonics for polyatomic systems: Basis set for kinematic rotations
Authors: Aquilanti Vincenzo , Beddoni Andrea , Lombardi Andrea , Littlejohn Robert 
Published: October 2002

AbstractIn a symmetrical hyperspherical framework, the internal coordinates for the treatment of N‐body systems are conveniently broken up into kinematic invariants and kinematic rotations. Kinematic rotations describe motions that leave unaltered the moments of the inertia of the N‐body system and perform the permutation of particles. This article considers the corresponding expansions of the wave function in terms of hyperspherical harmonics giving explicit examples for the four‐body case, for which the space of kinematic rotations (the “kinetic cube”) is the space SO(3)/V4 and then the related eigenfunctions will provide a basis on such manifold, as well as be symmetrical with respect to the exchange of identical particles (if any). V4 is also denoted as D2. The eigenfunctions are obtained studying the action of projection operators for V4 on Wigner D‐functions. When n of the particles are identical, the exchange symmetry can be obtained using the projection operators for the Sn group. This eigenfunction expansion basis set for kinematic rotations can be also of interest for the mapping of the potential energy surfaces. © 2002 Wiley Periodicals, Inc. Int J Quantum Chem, 2002
Distributed Gaussian basis sets: Variationally optimized s‐type sets for H2, LiH, and BH
Authors: Glushkov V. N. , Wilson S. 
Published: October 2002

AbstractDistributed basis sets of s‐type Gaussian functions are determined by invoking the variation principle for the Hartree–Fock ground states of the H2, LiH, and BH molecules at their respective experimental equilibrium geometries. The calculated energy expectation values supported by these finite basis sets are compared with finite difference Hartree–Fock energies reported by Kobus et al. A distributed basis set of 54 s‐type Gaussian functions distributed along the internuclear axis is shown to support an accuracy of 0.05 μHartree for the Hartree–Fock ground‐state energy of the H2 molecule while a similar set containing 50 functions leads to an accuracy of 0.8 μHartree for the ground‐state energy of the LiH molecule. For the BH ground state, a Hartree–Fock energy in error by 1.7 μHartree is supported by a variationally optimized distributed basis set of 65 s‐type Gaussian functions distributed along the internuclear axis. The parameters, that is, the exponents and positions, defining the variationally optimized distributed basis sets are presented and discussed. © 2002 Wiley Periodicals, Inc. Int J Quantum Chem, 2002
Structural signs and carrier completeness of Liouvillian quasiparticle algebras: Dual group invariants for explicit 𝒮n‐auxiliary tensor labels via projective mappings applicable to [A]n≤20 NMR spin ensembles
Authors: Temme F. P. 
Published: October 2002

AbstractVarious structural sign aspects of (Liouvillian) dual carrier spaces are examined under (quasiparticle [QP]) dual group projective mappings and Lie‐based algebras. The completeness of these superboson mappings and the nature of the correlation between the two distinct spatial QP sets of mappings are demonstrated in a direct Lie algebraic approach as being superior to supergenerator‐based right‐derivation methods. The dual tensorial auxiliary labels of superboson dual carrier mappings are presented in terms of dual group invariants based on democratic recoupling. The 𝒮2n decompositional modeling is utilized for the cardinality of SU(2) × 𝒮2n group invariants (SIs) of (polyhedral) higher‐(2n) [A]2n: 12 ∼ 2n ≤ 20 systems and the auxiliary “v” sets. Use of (augmented Weyl) time‐reversal invariance over sets of uniform (democratic) (2n)‐apical geometric lattice points allows one to treat all the intrinsic (2i) < (2n) subproblems originating from stepwise substitution of (Î · Î) pairs by 1 unities. Use of established 𝒮2n logic provides a ∑ (χ)2(𝒮n) model for the fundamental |SI| terms. PACS: 2.10; 02.20‐a; 33.20 Vq; 33.25 + j. © 2002 Wiley Periodicals, Inc. Int J Quantum Chem, 2002
Quantum chemical study on ferromagnetic property on the N,N‐dimethylaniline dimer radical cation
Authors: Su Zhongmin , Qiu Yongqing , Zhao Hongmei , Wang Rongshun , Zhang Ruifeng , Shen Jiacong 
Published: October 2002

AbstractElectronic state of the N,N‐dimethylaniline (DMA) dimer radical cation was calculated by the quantum chemical density functional theory method and the effect of linkage and geometric conformation on its magnetic property was discussed. The results show that the m‐dimer of the DMA radical cation is in a high‐spin ground state and p‐dimer is in a low‐spin ground state; the dependence of ferromagnetic property on structure in a nonplanar conjugated system can be explained by through‐space and through‐bond interactions. In the current system, because the distance of two radicals is more than 0.8 nm through‐space interaction is less significant than through‐bond interaction, in agreement with the opinions of Hoffman et al. The conclusion provides a basis for studying ground‐state spin coupling rules of a nonplanar organic diradical system and develops a new approach of molecular design of organic magnetic materials. © 2002 Wiley Periodicals, Inc. Int J Quantum Chem, 2002
Backbone cleavages of [M − H]− anions derived from caerin 1 peptides and some synthetic modifications. Molecular recognition initiating internal cyclisation of Glu23
Authors: Brinkworth Craig S. , Bowie John H. 
Published: October 2002

AbstractThe collision induced spectra of [M − H]− anions from of caerin 1 peptides and some synthetic modifications show the usual α, β and β′ backbone cleavages together with Ser (ϵ,γ) and Glu (γ) cleavages which break the peptide backbone in the vicinity of those residues. All of these cleavages require the peptide backbone to be flexible. There is also a backbone cleavage of a type not observed before. This cleavage involves nucleophilic attack of the carboxylate anion of the Glu23 side chain at the backbone CH of Ile 21. We propose that this cleavage requires the caerin peptide to be in an alpha helical conformation (the 3D structure that this peptide adopts in solution) in order that the interacting groups are held in close proximity. Copyright © 2002 John Wiley & Sons, Ltd.
Effects of nebulizing and drying gas flow on capillary electrophoresis/mass spectrometry
Authors: Huikko Katri , Kotiaho Tapio , Kostiainen Risto 
Published: October 2002

AbstractThis study was focused on examining the influence of gas flow parameters on capillary electrophoresis/mass spectrometry (CE /MS) performance using sheath‐liquid CE /MS interfaces. The effects of nebulizing and drying gas velocity and drying gas temperature on CE separation and MS detection sensitivity were systematically determined. Nebulizing gas velocity was observed to be a critical parameter in the optimization of CE /MS method, since it affected both MS detection sensitivity, and also CE separation efficiency for one interface design tested. Better detection sensitivity was obtained when the nebulizing gas velocity was increased. However, high velocity of the nebulizing gas flow can cause a hydrodynamic bulk flow inside the CE capillary, thus clearly increasing the apparent mobility and decreasing the resolution obtained for the compounds studied. Increasing the drying gas velocity or temperature did not affect the apparent mobility or the separation efficiency and the temperature could be increased to achieve the optimal detection sensitivity in the CE /MS analysis. For comparison, the effects of nebulizing gas flow were studied using a different design of the coaxial sheath‐liquid CE /MS interface, and in this case better detection sensitivity but no effect on CE separation efficiency was observed with increased nebulizing gas velocity. These different effects of nebulizing gas flow on the CE bulk flow were concluded to result from pressure differences at the tip of the CE capillaries for the different CE /MS interface arrangements. It is therefore recommended that the cross‐sectional dimensions of the fused‐silica and steel capillaries, and the gas streamlines, should be optimized when CE /MS interfaces are built. Moreover, the effect of gas flow on CE separation should be studied when optimizing the CE /MS operation parameters. Copyright © 2002 John Wiley & Sons, Ltd.
Reactions of lead cluster ions with ethylene, propene, trans‐butene, and cis‐butene
Authors: Tian Zhixin , Xing Xiaopeng , Tang Zichao 
Published: October 2002

AbstractReactions of lead cluster cations and anions with ethylene, propene, and trans‐and cis‐butene have been studied using a home‐built reflectron time‐of‐flight mass spectrometer. Both the high‐ and low‐energy pathway reactions were observed in the lead cluster reactions. For ethylene, only association products [Pbk(C2H4)n+] were observed. For propene, both association products [Pbk(C3H6)n+], high‐energy pathway products [Pbk(CH3)+] and their further association products [Pbk(CH3)m(C3H6)n+] were observed, while for butenes, besides the three kinds of products mentioned above, Pbk(C4H8)n+,PbkCH3+ and Pbk(CH3)m(C4H8)n+, low‐energy pathway products [PbkC4H6+,PbkC3H3(5)+ , PbkC3H2(3)+ (for cis‐butene only)] and their further association products [PbkC4H6(C4H8)n+, PbkC3H3(5)(C4H8)n+,PbkC3H2(3)(C4H8)n+ (for cis‐butene only)] were also observed. Bond selectivity and effects of steric hindrance were observed in the low‐energy pathway reactions of lead cluster cations with trans‐ and cis‐butene. The same anionic products, PbkCm−, with nearly the same intensity distribution, were observed in the reactions of lead cluster anions with all four alkenes studied here. Some reaction mechanisms are proposed for these reactions. Copyright © 2002 John Wiley & Sons, Ltd.
A high‐performance liquid chromatography/tandem mass spectrometric screening method for eight synthetic corticosteroids in bovine feces and the simultaneous differentiation between dexamethasone and betamethasone
Authors: Noben J. P. , Gielen B. , Royackers E. , Missotten M. , Jacobs A. , Raus J. 
Published: October 2002

AbstractA screening method was developed to monitor the illegal use of synthetic corticosteroids in cattle. Diethyl ether extracts from spiked feces samples were cleaned‐up by solid phase extraction followed by semipreparative reversed‐phase chromatography (RPC). The fraction containing the corticosteroids was derivatized with ethoxyamine hydrochloride. The corresponding ethoximes were separated using silica‐based C18 RPC and analyzed on‐line in an ion trap mass spectrometer using atmospheric pressure positive chemical ionization. Ethoxime derivatives of dexamethasone and betamethasone were baseline resolved, allowing for the simultaneous mass spectrometric differentiation of both epimers in bovine feces by conventional non‐chiral chromatography. At the lowest level tested (1 µg/kg), corticosteroids (except triamcinolone) could be identified in compliance with the recent European criteria for residue identification. The quantitative performance of the method was best at residue levels ≥2 µg/kg. Copyright © 2002 John Wiley & Sons, Ltd.
Identification of compound classes in soil and peat fulvic acids as observed by electrospray ionization tandem mass spectrometry
Authors: Mclntyre Cameron , McRae Christopher , Jardine Daniel , Batts Barry D. 
Published: October 2002

AbstractSoil and peat fulvic acids obtained from the International Humic Substances Society were fractionated by their solubility in methanol and analyzed by electrospray ionization tandem mass spectrometry. Precursor and product ion experiments produced mass spectra that indicated the presence of benzene, phenol, dihydroxy benzene, furan and thiophene carboxylic acids. Standards were used to substantiate the fragmentation patterns observed in the product ion spectra of the fulvic acid samples. This study makes significant progress into the direct identification of individual compounds in humic substances using a non‐degradation technique. Copyright © 2002 John Wiley & Sons, Ltd.
Spatial modelling of freshwater fish in semi‐arid river systems: a tool for conservation
Authors: Filipe A. F. , Cowx I. G. , Collares‐Pereira M. J. 
Published: October 2002

AbstractThis paper examines the feasibility of using multivariate statistics to model fish species distribution and habitat requirements for intermittent streams in semi‐arid regions, many of which are coming under increasing pressure from water resource development schemes. The assessment was based on the geographical distribution of six endemic fish species in the Guadiana river, a semi‐arid river system in southern Iberia. Their presence was related to 20 environmental variables linked to climate, geomorphology, riparian vegetation and location in the drainage basin. These variables were collected in the field or from topographical maps to evaluate habitat suitability and to predict the presence of the species according to season. Multivariate logistic regression in a geographic information system (GIS) environment was performed to identify regions with high probability of occurrence for each species. The variables that best explained the occurrence of the species were the sample location in the drainage basin, the geomorphology and the riparian vegetation. The models presented have a high predictive power and can be used in monitoring and predicting temporal changes caused by human activities. This modelling approach can be used to predict the areas that need to be conserved to protect or rehabilitate the endangered species. Armed with this information, managers can formulate conservation measures to prevent further degradation of the stocks and possibly enhance the populations. Copyright © 2002 John Wiley & Sons, Ltd.
Simulation of the performance of a Ka‐band VSAT videoconferencing system with uplink power control and data rate reduction to mitigate atmospheric propagation effects
Authors: Castanet Laurent , Bousquet Michel , Mertens David 
Published: October 2002

AbstractThe purpose of this paper is to evaluate the impact of propagation effects at 20/30 GHz on the performances of the radio interface of a VSAT videoconferencing system and to demonstrate the interest to implement Fade Mitigation Techniques in order to improve the link availability. Specifications and system requirements of the VSAT network are briefly described. System performances of the physical layer are simulated using time‐series data measured with the ESA's OLYMPUS satellite. The simulations enable to implement and optimize Up‐Link Power Control and Data Rate Reduction, and to assess the related link performance improvement. Moreover, the introduction of propagation data sets allows to have a better idea of some system parameters which directly impact on the quality of service such as the switching rate or the link availability that such a system should have when deployed in operational conditions. Copyright © 2002 John Wiley & Sons, Ltd.