bluuebunny/crossref_metadata_2025_split huggingface dataset:
Seismic isolation of civil buildings in the People's Republic of China
Authors: Zhou Fu Lin 
Published: August 2002

AbstractBuildings designed with traditional anti‐seismic systems are susceptible to damage by certain levels of earthquake activity, and may be seriously damaged or collapsed by unpredicted earthquakes. More and more un‐expectedly strong earthquakes represent a severe threat to human life and safety. The people urgently demand buildings that are guaranteed safe in strong earthquakes. Seismic isolation provides a new way to satisfy this human need. About 450 buildings with seismic isolation had been built in China up to the end of 2000. The safety level of buildings with seismic isolation is increased by a factor of 2–8, but building cost are 3–15% lower for general civil buildings. Wide application of seismic isolation of civil buildings has become a strong tendency in China and other countries. This paper briefly introduces recent research, applications and developments in seismic isolation of civil buildings in China, including, different isolation systems and different design levels, a series of tests and research projects, design codes and analysis programs, a summary of application status and examples, with discussion of some problems in the future development of seismic isolation of buildings.
Design criteria for unified strut and tie models
Authors: Su R K L , Chandler A M 
Published: August 2002

AbstractIn the past two decades, the concept of strut and tie models (STM) has been used as one of the most popular and rational approaches for the design of non‐flexural members of reinforced concrete structures. Design guidelines based mainly on technology from past decades are given in many national codes. The review of recent advancement in strut and tie modelling given in this paper enables a new set of design criteria and design tables for the strength of strut, node and bearing to be derived and presented. The design formulae proposed for strut and node in this paper are in the form of the product of two partial safety factors which take into account: (i) the orientation of the strut–tie; (ii) the brittle effects as the strength of concrete increases; (iii) the strain state of both concrete and steel; and (iv) the stress state of the node boundary. The design values proposed for plain concrete with a bearing plate ensure that the node does not crack under service conditions and that it possesses sufficient strength under ultimate load conditions. To enhance the worldwide use of such design tables, both the concrete cylinder strength and the concrete cube strength have been used to define the strength of the concrete.
Chemoprotective effect of Ixora coccinea L. flowers on cisplatin induced toxicity in mice
Authors: Latha P. G. , Panikkar K. R. 
Published: August 2002

AbstractThe active fraction from Ixora coccinea flowers prevented a decrease in body weight, haemoglobin levels and leucocyte counts of mice treated with cisplatin. It also significantly prolonged the life span of cisplatin treated mice and maintained their blood urea nitrogen levels in the near normal range, indicating its chemoprotective effects. Copyright © 2001 John Wiley & Sons, Ltd.
Antibacterial activity of Harungana madagascariensis leaf extracts
Authors: Okoli A. S. , Okeke M. I. , Iroegbu C. U. , Ebo P. U. 
Published: August 2002

AbstractAqueous extracts of the leaf of Harungana madagascariensis were analysed phytochemically and evaluated for antimicrobial activity against strains of Bacillus subtilis, Staphylococcus aureus, Escherichia coli, Salmonella typhi and Pseudomonas aeruginosa. Glycosides, tannins, saponins, flavonoids and alkaloids were detected in the plant material. B. subtilis, E. coli and S. typhi, but not Ps. aeruginosa, showed susceptibility at MICs of 2.0 and 15.6 mg/mL; and MBCs of 2.0–3.9 mg/mL and 15.6–31.3 mg/mL, respectively, for the cold and hot extracts. Staph. aureus showed susceptibility only to the hot extract. Concentrations of 2.5–10.0 mg/mL of the cold extract killed over 7 log10 of the test bacterial population within 30–60 min of exposure. The hot extract needed higher concentrations and longer treatment to achieve similar levels of bacterial cell killing. The results provide a rationalization for the traditional use of H. madagascariensis leaf extracts for the treatment of gastrointestinal disorders. Copyright © 2002 John Wiley & Sons, Ltd.
Minimum cross‐entropy estimation of internally folded densities from Compton profiles
Authors: Antolín J. , Cuchí J. C. , Angulo J. C. 
Published: August 2002

AbstractThe internally folded density or reciprocal form factor B(r) of many‐electron systems is tightly estimated from the knowledge of a small discrete set of values of the Compton profile J(q). In doing so, the minimum cross‐entropy technique is employed. A numerical analysis of the approximations is carried out for the Helium atom. © 2002 John Wiley & Sons, Inc. Int J Quantum Chem, 2002
A new version of the multireference averaged coupled‐pair functional (MR‐ACPF‐2)
Authors: Gdanitz Robert J. 
Published: August 2002

AbstractThe averaged coupled‐pair functional (ACPF), as found in R. J. Gdanitz and R. Ahlrichs, Chem. Phys. Lett. 143 (1988), is probably the most successful method to approximate full configuration interaction (CI) on the multireference (MR) level of theory. However, ACPF has a tendency to slightly overestimate the effect of higher than double substitutions, which, when the zeroth‐order wavefunction is of poor quality, may deteriorate the accuracy or even create instabilities. Since the properties of the ACPF and similar methods have apparently not always been correctly described in the literature, we repeat the derivation of this method in some detail. We analyze the connection between the (original) ACPF and the similar averaged quadratic coupled cluster (AQCC) method (which may be regarded as a damped ACPF), on one hand, and the different versions (0–3) of the coupled electron‐pair approximation (CEPA), on the other hand. We find that ACPF and AQCC may be regarded as CEPA‐1, respectively, CEPA‐3, where the shifts of the Hamiltonian are substituted by a single averaged shift. As CEPA‐3 considerably underestimates correlation effects, AQCC shows the same behavior. However, when the zeroth‐order wavefunction is of poor quality, AQCC may be more stable and thus more accurate than ACPF. By analyzing the role of the single substitutions, we find that ACPF may especially overestimate their contribution to unlinked clusters like \documentclass{article}\pagestyle{empty}\begin{document}$\textstyle\frac{1}{2}\hat{T}^{2}_{1}$\end{document}. We therefore propose a new version, called ACPF‐2, where (in contrast to AQCC) only the renormalization factor, g, that corresponds to the singles, is damped; i.e., we have (4/N)[1−1/(2N−2)]. In the limit of a large number of electrons, N, this factor becomes two times as large as in the (original) ACPF, where 2/N is used. In order to test the new ACPF‐2 method, we perform numerous comparisons with full CI, as well as calculations including terms that are linear in the interelectronic distances, rij. We find that in difficult cases, ACPF‐2 is of similar stability as is AQCC and is thus considerably more accurate than the original ACPF. In contrast to AQCC, however, ACPF‐2 achieves this stability without sacrificing the high accuracy which is obtained by ACPF in well‐behaved cases. © 2001 John Wiley & Sons, Inc. Int J Quantum Chem, 2001
Computer modeling of C2 cluster addition to fullerene C60
Authors: Budyka Mikhayl F. , Zyubina Tatyana S. , Ryabenko Alexander G. 
Published: August 2002

AbstractThe reaction between C2 cluster and C60 fullerene resulting in C2 insertion to C60 with formation of closed C62 cage (reaction of C2 ingestion by C60) was investigated by the semiempirical MNDO‐PM3 method. The geometries and energies of extremal points on the C62 potential energy surface were calculated. Several reaction pathways leading to the formation of three different closed C62 fullerenes were investigated. All insertion reactions proceed stepwise through intermediate adducts of different structures. The main reaction pathways were found to be addition of C2 by its one side to the 6,6‐ or 5,6‐bond of C60 with formation of primary unclosed C62 adducts of “ball‐with‐fork” structures, lying in deep potential wells. Back reaction of C2 detachment from primary adducts can compete with that of their transformation to the closed C62 cages inasmuch as calculated activation barriers of the both reactions are comparable. Model calculations at the B3LYP/6‐31G* level, using C32H12 semisphere instead of C60, confirmed the conclusion about two competitive pathways of the primary adducts transformation, C2 detachment, and C2 ingestion. The concerted insertion of C2 to C60 was realized only in the case of severe restrictions on starting geometry of the C2 + C60 system. The results of calculations explain recent experimental data on the formation of metastable adducts upon addition of C2 to C60, obtained using the time‐of‐flight mass spectrometer with laser desorption. © 2002 Wiley Periodicals, Inc. Int J Quantum Chem, 2002
Configuration interaction calculation of electronicgtensors in transition metal complexes*
Authors: Neese Frank 
Published: August 2002

AbstractAn algorithm for the calculation of electronicgtensors from configuration interaction (CI) wave functions and its implementation for any ground‐state spinSis described. The algorithm can be used together with either single‐ or multireference CI wave functions but assumes a spatially nondegenerate ground state. A one‐electron approximation to the spin–orbit coupling (SOC) operator is used. Presently the implementation uses the INDO/S model of Zerner and coworkers. Results are presented for a representative collection of Cu(II) complexes with N‐, O‐, and S‐containing ligands. The calculations reproduce the trends in the experimental data well and show no systematic errors. For the test set thegvalues are reproduced with a standard deviation of 0.021. The method has therefore a good cost–performance ratio and is expected to be helpful in chemical and biochemical applications. Further improvements are feasible and necessary and are briefly discussed. © 2001 John Wiley & Sons, Inc. Int J Quant Chem 83: 104–114, 2001
Long‐range effects in optimizing the geometry of stereoregular polymers—IV: Explicit determination of the helical angle
Authors: Jacquemin Denis , Champagne Benoît 
Published: August 2002

AbstractWe study the converging behavior of the analytical gradient of the energy per unit cell with respect to the helical angle in stereoregular polymers. Similarly to the other forces (with respect to nuclei coordinates or unit cell length), this gradient presents unique particularities. A technique based on multiple Taylor expansions is developed in order to evaluate accurately and directly the long‐range contributions to this gradient. These LR contributions have analytical characteristics similar to the one of the stress‐tensor, although the latter presents diverging sums. The method is tested on model system and is shown to be extremely efficient, allowing great improvement in accuracy at a negligible cost. © 2001 John Wiley & Sons, Inc. Int J Quantum Chem, 2001
Substituent effects on the physical properties and pKa of phenol
Authors: Gross Kevin C. , Seybold Paul G. 
Published: August 2002

AbstractSubstituent effects on the physical properties and pKa of phenol were studied using density functional theory [B3LYP/6‐311G(d,p)] calculations. Substituents alter the physical properties of phenol such as the hydroxyl‐group CO and OH bond lengths, the C OH bond angle, and the energy barrier to rotation about the C O bond, and also influence the hydroxyl‐group pKa. Except for the rotational barrier, Hammett σ constants showed strong correlation with these property changes. Several quantum chemical parameters, including the natural charge on the phenolic hydrogen Qn(H) and the natural charge on the phenoxide oxygen Qn(O−), the HF/6‐311G(d,p) HOMO energy Ehomo, and the proton‐transfer energy ΔEprot, outperformed the empirical Hammett constants in modeling changes in the pKa. All of these latter parameters yielded correlation coefficients ∣r∣>0.94 for the pKa. © 2001 John Wiley & Sons, Inc. Int J Quantum Chem, 2001
Computer simulation of cluster assembling
Authors: Duque F. , Mañanes A. , Molina L. M. , López M. J. , Alonso J. A. 
Published: August 2002

AbstractDensity functional theory is used to investigate the assembling of metallic clusters to yield stable or metastable cluster solids. Motivated by the observed high stability of the Al13H cluster, which has a substantial highest occupied and lowest unoccupied molecular orbitals (HOMO–LUMO) gap, we have modeled the assembling of those clusters. For a favorable relative orientation of each cluster with respect to all its neighbors, a cluster solid is predicted and its structure appears to be stable at least up to 150 K, which is the highest temperature in our simulations. We have also studied the chemical bonding in the stoichiometric solid alloys PbA, where A is one of the alkali elements Na, K, Rb, or Cs. Those crystals exist in an ordered phase formed by tetrahedral Pb4 clusters surrounded by the alkali atoms. The study of this family of natural cluster compounds reveals the coating role played by the cations, providing further insight into the favorable conditions required for the formation of cluster solids. © 2001 John Wiley & Sons, Inc. Int J Quantum Chem, 2001
On the influence of nuclear fluctuations on calculated NMR shieldings of benzene and ethylene: a Feynman path integral–ab initio investigation*
Authors: Böhm Michael C. , Schulte Joachim , Ramírez Rafael 
Published: August 2002

AbstractThe absolute magnetic shieldings of benzene and ethylene have been theoretically studied under the conditions of thermal equilibrium, i.e., under explicit consideration of the nuclear degrees of freedom. For this purpose we have combined the Feynman path integral quantum Monte Carlo (PIMC) formalism with the gauge‐including atomic orbital (GIAO) approach in the Hartree–Fock (HF) approximation. The HF operator has been employed to derive the NMR parameters of the two hydrocarbons via an ensemble averaging over large sets of molecular configurations that are populated in thermal equilibrium. The nuclear fluctuations are responsible for a deshielding of the nuclei relative to the shieldings at the vibrationless minimum of the potential energy surface (PES). The influence of the nuclear degrees of freedom is largest for the isotropic part of the13C shielding tensor. The theoretical results can be explained on the basis of simple geometrical considerations. The bond lengths in thermal equilibrium are larger than the bond lengths at the minimum of the PES. This length enhancement is the prerequisite for a deshielding of the nuclei in thermal equilibrium. The vibrational corrections of the nuclear magnetic resonance (NMR) parameters of benzene and ethylene are quantum driven; classical thermal degrees of freedom of the nuclei are of minor importance. Conceptual problems of theoretical studies of NMR parameters on the basis of a single molecular geometry are emphasized. The influence of the spatial uncertainty of the nuclei becomes decisive in molecules with light atoms. It is pointed out that the combination of the PIMC formalism with electronic Hamiltonians of state‐of‐the‐art quality renders possible accurate determinations of NMR parameters. © 2002 John Wiley & Sons, Inc. Int J Quantum Chem 86: 280–296, 2002
Ultra‐fast gradient vs. fast isocratic chromatography in bioanalytical quantification by liquid chromatography/tandem mass spectrometry
Authors: Romanyshyn Leslie , Tiller Philip R. , Alvaro Raul , Pereira Antonio , Hop Cornelis E. C. A. 
Published: August 2002

AbstractLiquid chromatography/tandem mass spectrometry (LC/MS/MS) methods developed for quantification using rapid (‘ballistic’) gradients on narrow bore, short HPLC columns have been previously described by this laboratory. This paper compares the fast gradient approach with the more traditional high‐organic isocratic LC/MS/MS methods. The comparison is based on an analysis of the effectiveness of the chromatographic separations when using the two approaches (i.e. k′, N, and W). The data presented herein are derived from actual biological samples analyzed as part of the drug discovery process. Copyright © 2001 John Wiley & Sons, Ltd.
A new technique for unbiased external ion accumulation in a quadrupole two‐dimensional ion trap for electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry
Authors: Belov Mikhail E. , Nikolaev Evgenii N. , Alving Kim , Smith Richard D. 
Published: August 2002

AbstractExternal ion accumulation in a two‐dimensional (2D) multipole trap has been shown to increase the sensitivity, dynamic range and duty cycle of a Fourier transform ion cyclotron resonance (FTICR) mass spectrometer. However, it is important that trapped ions be detected without significant bias at longer accumulation times in the external 2D multipole trap. With increasing ion accumulation time pronounced m/z discrimination was observed when trapping ions in an accumulation quadrupole. In this work we show that superimposing lower rf‐amplitude dipolar excitation over the main rf‐field in the accumulation quadrupole results in disruption of the m/z discrimination and can potentially be used to achieve unbiased external ion accumulation with FTICR. Copyright © 2001 John Wiley & Sons, Ltd.
Improved low‐energy electron injection systems for high rate electron capture dissociation in Fourier transform ion cyclotron resonance mass spectrometry
Authors: Tsybin Youri O. , Håkansson Per , Budnik Bogdan A. , Haselmann Kim F. , Kjeldsen Frank , Gorshkov Michael , Zubarev Roman A. 
Published: August 2002

AbstractNew low‐energy electron injection systems based on indirectly heated dispenser cathodes facilitate electron capture dissociation (ECD) in Fourier transform ion cyclotron resonance (FTICR) mass spectrometry. In this joint report, details are presented of the design and performance of these systems on two commercial FTICR instruments, 9.4 T Bruker BioAPEX in Uppsala and 4.7 T IonSpec Ultima in Odense. New results include obtaining meaningful one‐scan MS/MS data for isolated precursor ions with millisecond irradiation times. The ECD rate improvement is not only due to the larger total electron current, but the larger emitting area as well. Copyright © 2001 John Wiley & Sons, Ltd.
Description and validation of a staggered parallel high performance liquid chromatography system for good laboratory practice level quantitative analysis by liquid chromatography/tandem mass spectrometry
Authors: King Richard C. , Miller‐Stein Cynthia , Magiera Daniel J. , Brann John 
Published: August 2002

AbstractThe Aria LX4 staggered parallel high performance liquid chromatography (HPLC) system is evaluated for application to good laboratory practice (GLP) level quantitative analysis by liquid chromatography/tandem mass spectrometry (LC/MS/MS). This system consists of four fully independent binary HPLC pumps, a modified autosampler, and a series of switching and selector valves all controlled by a single computer program. The system improves sample throughput without sacrificing chromatographic separation or data quality. Validation results for four different compounds, each analyzed on a separate channel of the Aria system, show precision and accuracy equivalent to that required of a single‐channel system. The results show that sample throughput can be increased nearly four‐fold without requiring significant changes in current analytical procedures. The flexibility and ease of use of the Aria system suggest that it should be possible to quickly implement it in any analytical LC/MS/MS environment. Copyright © 2001 John Wiley & Sons, Ltd.
Comparison of the positive and negative ion electrospray mass spectra of some small peptides containing pyroglutamate
Authors: Boontheung Pinmanee , Brinkworth Craig S. , Bowie John H. , Baudinette Russell V. 
Published: August 2002

AbstractThe positive ion electrospray mass spectra of [M + H]+ and the negative ion electrospray mass spectra of [M − H]− ions of selected pyroglutamate containing peptides both provide sequencing data. The negative ion spectra show the normal α and β backbone cleavages in addition to δ and γ backbone cleavages initiated by the side chains of Glu and Phe residues. For example, the [M − H]− ion of pGlu Pro Gln Val Phe Val‐NH2 shows δ and γ peaks at m/z 224 (δ, Gln3), 244 (γ, Phe4), 451 (δ, Phe4), 471 (γ, Gln3). Some of the negative ion spectra show unusual grandaughter peaks that originate by α and β, or δ and γ backbone cleavages of a β1 cleavage ion. Copyright © 2002 John Wiley & Sons, Ltd.
Self‐esterification of fulvic acid model compounds in methanolic solvents as observed by electrospray ionization mass spectrometry
Authors: McIntyre Cameron , McRae Christopher , Jardine Daniel , Batts Barry D. 
Published: August 2002

AbstractThe self‐esterification of two fulvic acid model compounds in methanolic solvents was studied by electrospray ionization mass spectrometry (ESI‐MS). The strongly acidic tetrahydrofurantetracarboxylic acid rapidly self‐esterified to form mono‐ and dimethyl esters when stored in methanol, even at reduced temperatures. The weakly acidic analogue, cyclopentanetetracarboxylic acid, reacted minimally under the same conditions. The use of 50:50 methanol/water as a solvent reduced self‐esterification of the strong acid. However, the presence of water promoted the formation of multiply charged ions in the ESI mass spectra. The use of water and 50:50 acetonitrile/water as solvents eliminated self‐esterification but the mass spectra still contained multiply charged ions. This study implies that the use of methanolic solvents with humic substances may compromise analytical data through the formation of methyl esters. Copyright © 2002 John Wiley & Sons, Ltd.
Some aspects of matrix‐assisted laser desorption/ionization analysis of hemoglobin from whole human blood
Authors: Bajuk Anna , Michalak Leszek 
Published: August 2002

AbstractSome aspects of the matrix‐assisted laser desorption/ionization (MALDI) method in the analysis of hemoglobin from whole human blood are described. These aspects are: sensitivity of this method, fragmentation of hemoglobin ions, and influence of some impurities (sodium chloride NaCl, sodium sulfate Na2SO4, and potassium ferrocyanide K4Fe(CN)6) on the detection process. As a matrix, α‐cyano‐4‐hydroxycinnamic acid (CCA) was used. The estimated maximum concentrations of tested salts for which no hemoglobin signal was observed were determined. Copyright © 2002 John Wiley & Sons, Ltd.
Non‐nucleoside inhibitors of herpesviruses
Authors: Wathen Michael W. 
Published: August 2002

AbstractWhile the treatment of herpes simplex virus with acyclovir and similar nucleoside analogues was one of the first success stories in antiviral chemotherapy, substantial unmet medical needs remain for herpesvirus diseases. In particular, the increasing numbers of immunosuppressed people due to AIDS, transplantation, cancer and aging has driven the need for improved antivirals to treat diseases caused by human cytomegalovirus (HCMV). Currently available drugs for the treatment of HCMV diseases are less than ideal agents due to issues of toxicity, modest efficacy and poor oral bioavailability. High throughput screening of large compound collections for inhibitors of specific viral enzymes or inhibition of viral growth in cell culture have identified a number of new HCMV inhibitors at several pharmaceutical companies. These compounds act by inhibition of novel molecular targets such as the viral protein kinase, viral protease and viral proteins involved in DNA cleavage/packaging. In addition, novel non‐nucleoside inhibitors of the herpesvirus DNA polymerase have recently been described. This review will summarise some of these research efforts and will focus on non‐nucleoside compounds that directly inhibit a viral process. Copyright © 2002 John Wiley & Sons, Ltd.