bluuebunny/crossref_metadata_2025 huggingface dataset:
A performance evaluation of BGP‐based traffic engineering
Authors: Quoitin Bruno , Pelsser Cristel , Bonaventure Olivier , Uhlig Steve
Published: February 2005

Many Internet Service Providers tune the configuration of the Border Gateway Protocol on their routers to control their traffic. Content providers often need to control their outgoing traffic while access providers need to control their incoming traffic. We show, by means of measurements and simulations, that controlling the flow of the incoming interdomain traffic is a difficult problem. For this purpose, we first rely on detailed measurements to show the limitations of AS‐Path prepending. Then, we show by using large‐scale simulations that the difficulty of controlling the flow of the incoming traffic lies in the difficulty of predicting which BGP route will be selected by distant Autonomous Systems (ASs). Copyright © 2005 John Wiley & Sons, Ltd.
Synthesis and characterization of poly(L‐lactide‐co‐ε‐caprolactone) (B)‐poly(L‐lactide) (A) ABA block copolymers
Authors: Baimark Yodthong , Molloy Robert
Published: February 2005

ABA triblock copolymers of L‐lactide (LL) and ε‐caprolactone (CL), designated as PLL‐P(LL‐co‐CL)‐PLL, were synthesized via a two‐step ring‐opening polymerization in bulk using diethylene glycol and stannous octoate as the initiating system. In the first‐step reaction, an approximately 50:50 mol% P(LL‐co‐CL) random copolymer (prepolymer) was prepared as the middle (B) block. This was then chain extended in the second‐step reaction by terminal block polymerization with more L‐lactide. The percentage yields of the triblock copolymers were in excess of 95%. The prepolymers and triblock copolymers were characterized using a combination of dilute‐solution viscometry, gel permeation chromatography (GPC), 1H‐ and 13C‐NMR, and differential scanning calorimetry (DSC). It was found that the molecular weight of the prepolymer was controlled primarily by the diethylene glycol concentration. All of the triblock copolymers had molecular weights higher than their respective prepolymers. 13C‐NMR analysis confirmed that the prepolymers contained at least some random character and that the triblock copolymers consisted of additional terminal PLL end (A) blocks. From their DSC curves, the triblock copolymers were seen to be semi‐crystalline in morphology. Their glass transition, solid‐state crystallization, and melting temperature ranges, together with their heats of melting, all increased as the PLL end (A) block length increased. Copyright © 2005 John Wiley & Sons, Ltd.
Nanocomposites of poly[(butylene succinate)‐co‐(butylene adipate)] (PBSA) and twice‐functionalized organoclay
Authors: Chen Guangxin , Yoon Jin‐San
Published: February 2005

A new method is described to prepare composites of poly[(butylene succinate)‐co‐(butylene adipate)] (PBSA) with an organophilic clay having a particular functional group, namely twice‐functionalized organoclay (TFC). TFCs were produced by treating Cloisite 25A® with (glycidyloxypropyl)trimethoxy silane (GPS) or (methacryloyloxypropyl)trimethoxy silane (MPS). Reaction of the silane compound with the organoclay surface was monitored by Fourier‐transform infrared spectroscopy (FTIR). PBSA composites with the three different clays were prepared successfully via melt mixing. The d spacing and the morphology of the composites were monitored by X‐ray diffraction and by transmission electron microscopy. The linear storage modulus of the composites in the melt state increased significantly as a result of incorporation of TFC. Tensile modulus and strength at break of PBSA/TFC–GPS and those of PBSA/TFC–MPS were far superior to those of PBSA/C25A. Copyright © 2005 Society of Chemical Industry
One gene, two diseases and three conformations: Molecular dynamics simulations of mutants of human prion protein at room temperature and elevated temperatures
Authors: Shamsir Mohd S. , Dalby Andrew R.
Published: February 2005

Fatal familial insomnia (FFI) and Creutzfeldt‐Jakob disease (CJD) are associated to the same mutation at codon 178 but differentiate into clinicopathologically distinct diseases determined by this mutation and a naturally occurring methionine–valine polymorphism at codon 129 of the prion protein gene. It has been suggested that the clinical and pathological difference between FFI and CJD is caused by different conformations of the prion protein. Using molecular dynamics (MD), we investigated the effect of the mutation at codon 178 and the polymorphism at codon 129 on prion protein dynamics and conformation at normal and elevated temperatures. Four model structures were examined with a focus on their dynamics and conformational changes. The results showed differences in stability and dynamics between polymorphic variants. Methionine variants demonstrated a higher stability than valine variants. Elongation of existing β‐sheets and formation of new β‐sheets was found to occur more readily in valine polymorphic variants. We also discovered the inhibitory effect of proline residue on existing β‐sheet elongation. Proteins 2005. © 2005 Wiley‐Liss, Inc.
Statistical criteria for the identification of protein active sites using theoretical microscopic titration curves
Authors: Ko Jaeju , Murga Leonel F. , André Pierrette , Yang Huyuan , Ondrechen Mary Jo , Williams Ronald J. , Agunwamba Akochi , Budil David E.
Published: February 2005

Theoretical Microscopic Titration Curves (THEMATICS) may be used to identify chemically important residues in active sites of enzymes by characteristic deviations from the normal, sigmoidal Henderson–Hasselbalch titration behavior. Clusters of such deviant residues in physical proximity constitute reliable predictors of the location of the active site. Originally the residues with deviant predicted behavior were identified by human observation of the computed titration curves. However, it is preferable to select the unusual residues by mathematically well‐defined criteria, in order to reduce the chance of error, eliminate any possible biases, and substantially speed up the selection process. Here we present some simple statistical tests that constitute such selection criteria. The first derivatives of the predicted titration curves resemble distribution functions and are normalized. The moments of these first derivative functions are computed. It is shown that the third and fourth moments, measures of asymmetry and kurtosis, respectively, are good measures of the deviations from normal behavior. Results are presented for 44 different enzymes. Detailed results are given for 4 enzymes with 4 different types of chemistry: arginine kinase from Limulus polyphemus (horseshoe crab); β‐lactamase from Escherichia coli; glutamate racemase from Aquifex pyrophilus; and 3‐isopropylmalate dehydrogenase from Thiobacillus ferrooxidans. The relationship between the statistical measures of nonsigmoidal behavior in the predicted titration curves and the catalytic activity of the residue is discussed. Proteins 2005. © 2005 Wiley‐Liss, Inc.
Molecular characterization and biological response to respiration inhibitors of Pyricularia isolates from ctenanthe and rice plants
Authors: Paplomatas Epaminondas J , Pappas Athanasios C , Syranidou Elene
Published: February 2005

The molecular profile and the biological response of isolates of Pyricularia oryzae Cavara obtained from ctenanthe to two strobilurins (azoxystrobin, kresoxim‐methyl) and the phenylpyridinamine fungicide fluazinam were characterized, and compared with isolates from rice plants. Five different isozymes (α‐esterase, lactate, malate, isocitrate and sorbitol dehydrogenases) and five random decamer primers for RAPD‐PCR were used to generate molecular markers. Using unweighted pair‐group with arithmetic average analysis, ctenanthe isolates were found to form a separate group distinct from that of the rice isolates for both sets of markers. Amplified polymorphic sequences of mitochondrial cytochrome b that were digested with Fnu4HI or StyI revealed no differences among Pyricularia isolates at amino acid positions 143 or 129 which confer resistance to strobilurins in several fungi. In absence of the alternative respiration inhibitor salicylhydroxamic acid (SHAM) the three fungicides showed inferior and variable efficacy, with a trend toward the rice isolate being less sensitive. The addition of SHAM enhanced the effectiveness of all fungicides against isolates regardless of their origin. Appressorium formation was the most vulnerable target of action of the respiration inhibitors and azoxystrobin the most effective. This is the first report of a comparison between the molecular profiles and sensitivities to respiration inhibitors for Pyricularia oryzae isolates from a non‐gramineous host and from rice. Copyright © 2005 Society of Chemical Industry
Influence of vapor transport equilibration on spectroscopic parameters of Er3+ in LiNbO3 crystals
Authors: Zhang De‐Long , Wang Dun‐Chun , Pun E. Y. B.
Published: February 2005

A number of X‐, Y‐ and Z‐cut Er(/Yb):LiNbO3 crystals with six different doping levels of rare earth ions were annealed at 1110 °C for 120 h using the vapor transport equilibration (VTE) technique. At room temperature, α‐polarized or unpolarized absorption spectra of these VTE‐treated crystals and corresponding as‐grown crystals were recorded in the wavelength range 280–1700 nm. The absorption characteristics of the VTE‐treated crystals are summarized and compared with those of the as‐grown crystals. The (Li+ + RE3+)/Nb5+(RE3+ = Er3+ or Er3+ + Yb3+) ratios in the VTE‐treated Er(/Yb):LiNbO3 crystals were evaluated using the optical absorption edge or Raman linewidth of the 153 cm–1 E(TO) phonon. Based upon the measured spectral data, spectroscopic parameters of Er3+ ions in as‐grown and VTE‐treated crystals were calculated using the Judd–Ofelt (J–O) theory. The influences of Er3+ doping level, type of crystal cut and VTE treatment on the key spectroscopic parameters, including integrated absorption coefficient, oscillator strength, J–O parameters and radiative lifetimes of three dominant emission manifolds (4I13/2 (∼1530 nm), 4F9/2 (∼660 nm) and 4S3/2 (∼560 nm)), are discussed and summarized and compared with the results for as‐grown crystals. The results for as‐grown crystals are also compared with those reported previously. The present theoretical result concerning the VTE effect on the 1530 nm lifetime is in rough agreement with the experimental result reported previously. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
White light electroluminescence in zinc sulfide: polyflourene blends
Authors: Sundar Manoharan S. , Mohammad Qureshi
Published: February 2005

We document white light emission from ZnS:Cu–PFO blend in the device structure involving indium tin oxide (ITO)/poly(3,4‐ethylenedioxythiophene):poly(4‐styrenesulfonate) (PEDOT:PSS)/ZnS–poly(9,9‐dioctylfluorene) (PFO)/Al layers, with varying ZnS:Cu dopant concentrations in the PFO matrix. We observe that with the increase in the ZnS:Cu dopant concentration in PFO from 1 to 10 wt%, the turn‐on‐voltage shifts from 7 V to 4 V. Initial brightness of the device with 1 wt% doping is 30 cd/m2 at 7 V and 40 cd/m2 at 9 V. For a 10‐wt% ZnS:Cu–PFO blend, luminescence up to 25 cd/m2 at 4 V is achieved. The broad spectral feature in electroluminescence is attributed to the partial energy transfer from PFO to ZnS:Cu, due to π–π*, n–π*, and CT–(π–π*) transitions arising out of polyfluorene–polyfluorenone chromophores. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Appearance of copper d9 defect centres in wide‐gap CdSe nanoparticles: A high‐frequency EPR study
Authors: Poolton N. R. J. , Smith G. M. , Riedi P. C. , Allen J. W. , Firth A. V. , Cole‐Hamilton D. J. , McInnes E. J. L.
Published: February 2005

When preparing CdSe nanoparticles in polybutadiene‐based polymer matrices, quantum confinement in the smaller particles leads to the usual increase in the band‐gap energy, with associated, well defined, band‐edge luminescence emission. However, for samples whose size is smaller than 3 nm, new broad luminescence features appear, with the simultaneous appearance of a new paramagnetic defect centre that has not previously been reported in the literature. This work concentrates on analyzing the electron paramagnetic resonance of the new defect, which is found to be located at a trigonally‐distorted tetrahedral site, with a spin S = 1/2 and g‐values g|| = 2.321 ± 0.006 and g⊥ = 2.053 ± 0.006. With the attribution of very poorly resolved hyperfine interaction to a nucleus of spin I = 3/2, the identity of the defect is ascribed to copper in its d9 state, which would be expected to act as a simple acceptor centre in CdSe. Conclusions are drawn to the effect that the defect normally resides within the valence band for bulk and large particles, only becoming apparent as a defect within the band‐gap as the energy increases above 2.6 eV in the smaller particles. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Many‐body interactions of carbon monoxide cyclic oligomers: A computational study
Authors: Sahu Prabhat K. , Lee Shyi‐Long
Published: February 2005

Structural properties and energetics for the optimized carbon monoxide cyclic oligomers are analyzed at the correlated ab initio second‐order Møller–Plesset (MP2) and density functional methods (B3LYP and mPW1PW), using Dunning's cc‐pVXZ (X = D, T, Q) basis set, augmented with diffuse functions. Many‐body interactions of the stable carbon monoxide cyclic oligomers, (CO)4 and (CO)5 are computed at the MP2/aug‐cc‐pVTZ level. Contributions of two‐ to five‐body terms to each of these oligomers for their interaction energies, including corrections for basis set superposition error (BSSE) are investigated by using function counterpoise and its generalized version. It has been found that three‐body terms are attractive in nature and essential in order to describe the cooperative effects in the stable cyclic CO oligomers. © 2005 Wiley Periodicals, Inc. Int J Quantum Chem, 2005
Theoretical principles of single‐molecule electronics: A chemical and mesoscopic view
Authors: Xue Yongqiang , Ratner Mark A.
Published: February 2005

Exploring the use of individual molecules as active components in electronic devices has been at the forefront of nanoelectronics research in recent years. Compared to semiconductor microelectronics, modeling transport in single‐molecule devices is much more difficult due to the necessity of including the effects of the device electronic structure and the interface to the external contacts at the microscopic level. Theoretical formulation of the problem therefore requires integrating the knowledge base in surface science, electronic structure theory, quantum transport, and device modeling into a single unified framework starting from the first principles. In this article, we introduce the theoretical framework for modeling single‐molecule electronics and present a simple conceptual picture for interpreting the results of numerical computation. We model the device using a self‐consistent matrix Green's function method that combines nonequilibrium Green's function theory of quantum transport with atomic‐scale description of the device's electronic structure. We view the single‐molecule device as “heterostructures” composed of chemically well‐defined atomic groups, and analyze the device characteristics in terms of the charge and potential response of these atomic groups to perturbation induced by the metal–molecule coupling and the applied bias voltage. We demonstrate the power of this approach using as examples devices formed by attaching benzene‐based molecules of different size and internal structure to the gold electrodes through sulfur end atoms. © 2005 Wiley Periodicals, Inc. Int J Quantum Chem, 2005
Full quantum mechanical study of binding of HIV‐1 protease drugs
Authors: Zhang Da W. , Zhang John Z. H.
Published: February 2005

Fully quantum mechanical studies of detailed binding interactions between HIV‐1 protease and six FDA (Food and Drug Administration)‐approved drugs (saquinavir, indinavir, ritonavir, nelfinavir, amprenavir, and lopinavir) are carried out using a recently developed MFCC (molecular fractionation with conjugate caps) method. The MFCC calculation produces a quantum mechanical interaction spectrum for any protease drug binding complex. Detailed quantitative analysis on binding of lopinavir to specific residues of the protease is given from the current study. The present calculation shows that the dominant binding of lopinavir to the protease is through the formation of a strong hydrogen bond between the central hydroxyl group of the drug to the aspartate oxygen of Asp25 in one of the two chains of the protease (A chain). This is closely followed by hydrogen binding of the drug to Asp29 in the B chain and somewhat weak hydrogen bonding to Asp30, Gly27, Gly48, and Ile50 in both chains. By partitioning all six drugs into four building blocks besides the central component containing the hydroxyl group, MFCC calculation finds that block III has essentially no binding interaction with the protease and the major binding interactions of these drugs are from blocks II and IV, in addition to the dominant central hydroxyl group. This detailed quantitative information on drug binding to the protease is very useful in rational design of new and improved inhibitors of HIV‐1 protease and its mutants. © 2005 Wiley Periodicals, Inc. Int J Quantum Chem, 2005
First‐principles investigation of structure and stability of AlnNm clusters
Authors: Guo Ling , Wu Hai‐Shun , Jin Zhi‐Hao
Published: February 2005

Various structural possibilities for AlnN and AlnN2 (n = 1–7) neutral and cationic isomers are investigated, using the density functional method of Becke's three‐parameter hybrid exchange functional with the Lee–Yang–Parr nonlocal correlation. Structural optimization and frequency analyses are performed with the basis of 6‐311+G(d) for both the neutrals and cations. The calculations predicted the existence of a number of previously unknown isomers (i.e., Al5N2 and Al6N2). The resulting geometries show that the nitrogen atom prefers to be trapped and not to be on the periphery. Frequency analyses indicate that the 3‐D Al5N, which was previous proposed as the ground‐state structure, is in fact a first‐order stationary point with an imaginary frequency at 45i (a2). The optimized ground‐state structure of Al5N obtained in this work is a planar configuration with the symmetry of C2v. The calculated adiabatic ionization potentials in their ground states showed that AlN, Al2N, Al3N, and Al4N2 clusters are more stable than any others in AlnN and AlnN2 (n = 1–7) species, being consistent with the observed time‐of‐flight (TOF) signal intensities. © 2005 Wiley Periodicals, Inc. Int J Quantum Chem, 2005
Photodetachment dynamics from closed‐shell anions in the presence of a bichromatic field
Authors: Mondal Chandan Kumar
Published: February 2005

I have studied the dynamics of photodetachment from closed‐shell anions in the presence of a two‐color (bichromatic) laser field. The electronic states of halide ions are modeled by a 1‐D Hamiltonian with a potential V(x) = −V0e. The two parameters V0 and σ are fixed by requiring V(x) to reproduce the experimentally observed ground‐state ionization energy of the halide ions concerned. The potentials so generated are shown to support only one bound state in each case. The time‐dependent Fourier grid Hamiltonian method is used to follow the detachment dynamics with fairly high intensities of light. The environmental effects on the dynamics are sought to be modeled by allowing the well depth (V0) to fluctuate randomly (V0(t) = V0[1 + ΔVR(t)]; R(t) randomly fluctuates between +1 and −1 with time, when ΔV is fixed). The average detachment rate constants kav are seen to increase with increase in the intensities of used bichromatic field. An alternative model potential, V(x) = −V0e−σx, is also shown to yield similar results. © 2005 Wiley Periodicals, Inc. Int J Quantum Chem, 2005
Review of multistep methods for the numerical solution of the radial Schrödinger equation
Authors: Vigo‐Aguiar Jesús , Simos T. E.
Published: February 2005

A review of multistep methods for the numerical solution of the Schrödinger equation is presented. Since the literature reports difficulties in the production of some of the Bettis–Cowell methods, we have included a simple way that permits production of these methods for any algebraic and trigonometric order. Numerical comparisons on resonance problems and bound‐states problems are also described. © 2005 Wiley Periodicals, Inc. Int J Quantum Chem, 2005
DFT investigation of sites of protonation of antitumor of 2‐(4‐aminophenyl)benzazoles in the gas phase and in solution
Authors: Hilal Rifaat , Elroby Shabaan A. K.
Published: February 2005

The proton affinity on each of the possible sites in the antitumor 2‐(4‐aminophenyl)benzazoles has been calculated at the B3LYP/6‐311G** level of theory in the gas phase and in solution. The N3‐site of protonation is found to be strongly favored over the NH2‐site for the studied compounds both in gas phase and in solution. The stability of N3‐protonated species is explained by the resonance interaction of the NH2‐group with the heterocyclic ring. The potential energy surface (PES) for the protonation process was studied at the density functional theory (DFT)/B3LYP/6‐311++G** level of theory. Solvent effects on the PES were also examined using two models: Onsager self‐consistent field and polarizable continuum model (PCM). © 2005 Wiley Periodicals, Inc. Int J Quantum Chem, 2005
Atomic softness‐based QSAR study of testosterone
Authors: Srivastava H. K. , Pasha F. A. , Singh P. P.
Published: February 2005

Ionization potential of an atom in a molecule, electron affinity of an atom in a molecule, and quantum chemical descriptor atomic softness values En‡‐based quantitative structure–activity relationship (QSAR) study of testosterone derivatives have been done with the help of PM3 calculations on WinMOPAC 7.21 software. The 3D modeling and geometry optimization of all the compounds have been done with the help of PCMODEL software. The biological activities of testosterone derivatives have been taken from literature. The predicted values of biological activity with the help of multiple linear regression (MLR) analysis is very close to observed biological activity. The cross‐validation coefficient and correlation coefficient also indicate that the QSAR model is valuable. Regression analysis shows a very good relationship with biological activity and En‡ values. With the help of these values, prediction of the biological activity of any unknown compound is possible. © 2005 Wiley Periodicals, Inc. Int J Quantum Chem, 2005
Long‐range π‐type hydrogen bond in the dimers CH2OHF, CH2OH2O, and CH2ONH3
Authors: Li Ruiyan , Li Zhiru , Wu Di , Hao Xiyun , Li Rujiao , Sun Chiachung
Published: February 2005

Using four basis sets, 6‐311G(d,p), 6‐31+G(d,p), 6‐311++G(2d,2p), and 6‐311++G(3df,3pd), the optimized structures with all real frequencies were obtained at the MP2 level for dimers CH2OHF, CH2OH2O, CH2ONH3, and CH2OCH4. The structures of CH2OHF, CH2OH2O, and CH2ONH3 are cycle‐shaped, which result from the larger bend of σ‐type hydrogen bonds. The bend of σ‐type H‐bond O…HY (YF, O, N) is illustrated and interpreted by an attractive interaction of a chemically intuitive π‐type hydrogen bond. The π‐type hydrogen bond is the interaction between one of the acidic H atoms of CH2O and lone pair(s) on the F atom in HF, the O atom in H2O, or the N atom in NH3. By contrast with above the three dimers, for CH2OCH4, because there is not a π‐type hydrogen‐bond to bend its linear hydrogen bond, the structure of CH2OCH4 is a noncyclic shaped. The interaction energy of hydrogen bonds and the π‐type H‐bond are calculated and discussed at the CCSD(T)/6‐311++G(3df,3pd) level. © 2005 Wiley Periodicals, Inc. Int J Quantum Chem, 2005
Accurate energy eigenvalues and eigenfunctions for the two‐dimensional confined hydrogen atom
Authors: Aquino N. , Campoy G. , Flores‐Riveros A.
Published: February 2005

A study of the two‐dimensional hydrogen atom confined within a circle of impenetrable walls is presented. The potential inside the box is Coulomb type, whereas outside it is infinite. The energy eigenvalues and some radial wave function properties are computed with high accuracy for different box sizes. We derive the polarizability in the Kirkwood approximation, calculate the Fermi contact term as a function of the confinement radius, and investigate the filling order of the one‐electron states. When the electronic configuration of many electrons is constructed by means of the Aufbau principle, the model predicts the inversion 2s–3d levels in the N atom. © 2005 Wiley Periodicals, Inc. Int J Quantum Chem, 2005
Localized hybrid exchange‐correlation potentials for Kohn–Sham DFT calculations of NMR and EPR parameters
Authors: Arbuznikov Alexei V. , Kaupp Martin
Published: February 2005

In contrast to the conventional, nonlocal, and nonmultiplicative implementation of hybrid exchange‐correlation functionals in self‐consistent calculations, the exact‐exchange contribution to the functional has been implemented as a proper local and multiplicative Kohn–Sham potential, using the localized Hartree–Fock approximation to the optimized effective potential. The resulting localized hybrid potentials provide improved performance over nonlocal implementations in density functional theory (DFT) calculations of nuclear shielding constants of main‐group molecules and electronic g‐tensors of 3d transition–metal complexes. Optimum performance of the localized potentials is found at very similar amounts of exact‐exchange admixture for both properties and is almost independent of the “pure‐DFT” exchange and correlation functionals combined with exact exchange. Based on local kinetic energy density, a measure of exact‐exchange admixture is constructed that helps rationalize the relatively large optimal exact‐exchange contributions found. © 2005 Wiley Periodicals, Inc. Int J Quantum Chem, 2005
Valence and valence–core interactions in transition‐metal diatomic molecules
Authors: Boudreaux Edward A. , Baxter Eric
Published: February 2005

In this study, the correlation between open‐shell valence and closed‐shell valence‐core electrons is shown to be significant, with regard to an adequate description of the bonding in transition metal diatomic molecules. The SCMEH‐MO (self‐consistent modified extended Huckel molecular orbital) method is well suited for partitioning these two influences, in terms of their independent and collective effects on the electrons within the occupied mo‐s. Two test cases, Cr2 and Mo2 are presented to demonstrate the nature and magnitude of these valence/valence‐core interactions. © 2005 Wiley Periodicals, Inc. Int J Quantum Chem, 2005
Estimation of Hammett sigma constants of substituted benzenes through accurate density‐functional calculation of core‐electron binding energy shifts
Authors: Takahata Yuji , Chong Delano P.
Published: February 2005

For substituted benzenes such as (p‐F‐C6H4‐Z), Linderberg et al. 1 demonstrated the validity of an equation similar to: ΔCEBE ≈ κσ, where ΔCEBE is the difference in core‐electron binding energies (CEBEs) of the fluorinated carbon in p‐F‐C6H4‐Z and that in FC6H5, the parameter κ is a function of the type of reaction, and σ is the Hammett substituent (σ) constant. In this work, CEBEs of ring carbon atoms for a series of para disubstituted molecules p‐F‐C6H4‐Z were first calculated using Density Functional Theory (DFT) with the scheme ΔEKS (PW86‐PW91)/TZP+Crel//HF/6‐31G*. An average absolute deviation of 0.13 eV from experiment was obtained for the CEBEs. Then we performed a linear regression analysis in the form of Y = A+B*X for a plot of Hammett σp constants against calculated shifts ΔCEBEs (in eV) for the fluorinated carbon. The results were: A = –0.08 and B = 1.01, with correlation coefficient R = 0.973, standard deviation = 0.12, and P < 0.0001. The intercept A of the fitted line, close to zero, shows that the Hammett σp constant is proportional to the calculated ΔCEBEs. On the other hand, the slope B of the straight line gives an estimate of the parameter κ. Similar statistical correlations were obtained for the carbon atoms ortho and meta to the substituent Z. © 2005 Wiley Periodicals, Inc. Int J Quantum Chem, 2005
Theoretical investigation of hydrogen bonding in lactonitrile–water complexes
Authors: Rivelino Roberto , Canuto Sylvio
Published: February 2005

Møller‐Plesset perturbation and density functional theories were applied to study the relative strength of the H‐bonds formed in different sites (OH, CN, and CH) of lactonitrile with water. Three lactonitrile–water complexes (termed I, II, and III) were located. Then structures, binding energies, and changes in their vibrational frequencies were calculated using the MP2 method and the B3PW91 functional with the 6‐311++G(2df,2p) basis set. The binding energies were corrected for the basis set superposition errors and zero‐point vibration energies. At the MP2 level the corrected binding energy of the most strongly bonded Complex I was calculated to be 6.5 kcal/mol, whereas it is only 2.9 kcal/mol for the Complex II. The CH…O hydrogen‐bonded Complex III was found to have a very small binding energy between 1.5 and 2 kcal/mol. © 2005 Wiley Periodicals, Inc. Int J Quantum Chem, 2005
Erratum: Trial introduction of a complex potential function for perturbation that causes quantum mechanical transition in a one‐dimensional harmonic oscillator, Mitsuru Yamada, International Journal of Quantum Chemistry (2004) 99(3) 127–141
Authors: Yamada Mitsuru
Published: February 2005

The original article to which this Erratum refers was published in International Journal of Quantum Chemistry (2004) 99(3) 127–141
Development of apatite‐type oxide ion conductors
Authors: Slater P.R. , Sansom J.E.H. , Tolchard J.R.
Published: February 2005

Research into materials displaying oxide ion conductivity is attracting considerable attention due to their potential technological applications in devices such as Solid Oxide Fuel Cells. In this paper, recent work on apatite‐type oxide ion conductors is reviewed, showing that a wide range of cation substitutions are possible, due to the flexibility of the apatite structure in accommodating a range of ion sizes. The conductivity studies on these doped samples show that to achieve high oxide ion conduction, non‐stoichiometry in terms of cation vacancies and/or oxygen excess is required, with the latter resulting in the highest conductivities. In contrast to most common oxide ion conductors, e.g. perovskite and fluorite in which oxide ion conduction proceeds via oxygen vacancies, the research on these apatite systems suggests that the conductivity involves interstitial oxide ions. With further optimization of these materials, particularly in terms of the Ge‐containing systems, significant improvements in conductivity are likely, leading to the very real possibility of the application of apatite‐type electrolytes in fuel cell and other applications. © 2005 The Japan Chemical Journal Forum and Wiley Periodicals, Inc. Chem Rec 4: 373–384; 2004: Published online in Wiley InterScience (www.interscience.wiley.com) DOI 10.1002/tcr.20028
Plant responses to elevated CO2 concentration at different scales: leaf, whole plant, canopy, and population
Authors: Hikosaka Kouki , Onoda Yusuke , Kinugasa Toshihiko , Nagashima Hisae , Anten Niels PR , Hirose Tadaki
Published: February 2005

Elevated CO2 enhances photosynthesis and growth of plants, but the enhancement is strongly influenced by the availability of nitrogen. In this article, we summarise our studies on plant responses to elevated CO2. The photosynthetic capacity of leaves depends not only on leaf nitrogen content but also on nitrogen partitioning within a leaf. In Polygonum cuspidatum, nitrogen partitioning among the photosynthetic components was not influenced by elevated CO2 but changed between seasons. Since the alteration in nitrogen partitioning resulted in different CO2‐dependence of photosynthetic rates, enhancement of photosynthesis by elevated CO2 was greater in autumn than in summer. Leaf mass per unit area (LMA) increases in plants grown at elevated CO2. This increase was considered to have resulted from the accumulation of carbohydrates not used for plant growth. With a sensitive analysis of a growth model, however, we suggested that the increase in LMA is advantageous for growth at elevated CO2 by compensating for the reduction in leaf nitrogen concentration per unit mass. Enhancement of reproductive yield by elevated CO2 is often smaller than that expected from vegetative growth. In Xanthium canadense, elevated CO2 did not increase seed production, though the vegetative growth increased by 53%. As nitrogen concentration of seeds remained constant at different CO2 levels, we suggest that the availability of nitrogen limited seed production at elevated CO2 levels. We found that leaf area development of plant canopy was strongly constrained by the availability of nitrogen rather than by CO2. In a rice field cultivated at free‐air CO2 enrichment, the leaf area index (LAI) increased with an increase in nitrogen availability but did not change with CO2 elevation. We determined optimal LAI to maximise canopy photosynthesis and demonstrated that enhancement of canopy photosynthesis by elevated CO2 was larger at high than at low nitrogen availability. We also studied competitive asymmetry among individuals in an even‐aged, monospecific stand at elevated CO2. Light acquisition (acquired light per unit aboveground mass) and utilisation (photosynthesis per unit acquired light) were calculated for each individual in the stand. Elevated CO2 enhanced photosynthesis and growth of tall dominants, which reduced the light availability for shorter subordinates and consequently increased size inequality in the stand.
Estimating the risk of temporary acoustic threshold shift, caused by hydroacoustic devices, in whales in the Southern Ocean
Authors: KREMSER ULRICH , KLEMM PETER , KÖTZ WOLF-DIETRICH
Published: February 2005

There is a potential threat to marine mammals from acoustic signals emitted by hydroacoustic devices. The impact on the hearing of marine mammals depends on the technical parameters of the instruments and on the exposure of the animal to noise pulses, as well as on the properties of the biological system, that is to say, on the anatomy and the audiogram of the animal. Here, the blue whale, the sperm whale and the beaked whale are taken as examples in an investigation of the potential exposure to noise pulses from the hydroacoustic instruments Hydrosweep and Parasound. Diving depths of the whales and relative speeds of the animals with respect to the survey vessels are taken into account, as well as the area impacted by the equipment, in estimating the level of sound needed to produce “temporary threshold shift” in an animal. The results suggest that auditory damage is only likely if animals pass the transducer at close range and that the impact on marine mammals can be mitigated by implementing prior detection and shut down procedures.
The onset of deglaciation of Cumberland Bay and Stromness Bay, South Georgia
Authors: VAN DER PUTTEN N. , VERBRUGGEN C.
Published: February 2005

Carbon dating of basal peat deposits in Cumberland Bay and Stromness Bay and sediments from a lake in Stromness Bay, South Georgia indicates deglaciation at the very beginning of the Holocene before c. 9500 14C yr BP. This post-dates the deglaciation of one local lake which has been ice-free since at least 15 700 14C yr BP on account of its atypical geomorphological location. The latter indicates the likely presence of floristic refugia on South Georgia during the Last Glacial Maximum from which newly exposed terrestrial and aquatic habitats were rapidly colonized.
A 9000-year record of Adélie penguin occupation and diet in the Windmill Islands, East Antarctica
Authors: EMSLIE STEVEN D. , WOEHLER ERIC J.
Published: February 2005

We investigated 17 abandoned Adélie penguin (Pygoscelis adeliae) colonies in the Windmill Islands, East Antarctica, in summer 2002/03. Forty radiocarbon dates on penguin bones and eggshells from 13 of these sites indicate a near continuous occupation by breeding penguins in this region for over 9000 years. These dates refine the recent geological record in this region and indicate that deglaciation of the northern islands occurred much earlier than previously suggested. Dietary remains from these sites include at least 23 taxa of cephalopods and teleost fish. Quantification of these remains indicates significant fluctuations in the relative abundance of two of the more common major prey taxa. The Antarctic silverfish (Pleuragramma antarcticum Boulenger) was the most common teleost prey during all time periods represented by the ages of the sites, but preservational factors may explain a gradual decrease in the remains of this species in increasingly older sites. The most common cephalopod in the sediments was the squid, Psychroteuthis glacialis Thiele, which occurred in low numbers in most sites except one (Site 75). An unusually high number of squid beaks preserved in Site 75, dating to approximately 5700–6100 cal. yr BP, does not correlate with a decrease in fish prey at that time. The high number of abandoned penguin colonies (> 200) in the Windmill Islands may be due to population cycles in the past in association with low nest-site fidelity and movement by breeding penguins to new sites within this region.
Micropropagation of Deschampsia antarctica - a frost-resistant Antarctic plant
Authors: CUBA MARELY , GUTIÉRREZ-MORAGA ANA , BUTENDIECK BARBARA , GIDEKEL MANUEL
Published: February 2005

Deschampsia antarctica Desv. (Poaceae) is the only native Gramineae found in the Antarctic, where it is restricted to the Antarctic Peninsula and its offshore islands. Its ability to survive the harsh climate has attracted the interest of scientists searching for genes associated with freezing tolerance (Alberdi et al. 2002). For continuing research purposes it would be better if plants did not have to be collected from the field, but could be propagated effectively to provide the necessary experimental material D. antarctica normally reproduces both by seed produced by self-fertilization and also vegetatively from tillers (Holderegger et al. 2003). Vegetative propagation is slow and unable to generate enough plant material for laboratory requirements. This difficulty prompted us to develop a rapid micro-propagation method using tissue-culture methods for the production of large numbers of plants in relatively short periods.
Possible food caching and defence in the Weddell seal: observations from McMurdo Sound, Antarctica
Authors: KIM S.L. , CONLAN K. , MALONE D.P. , LEWIS C.V.
Published: February 2005

On the basis of observations of Weddell seals (Leptonychotes weddellii Lesson) made in the course of studying shallow-water benthic communities in McMurdo Sound, Antarctica, we suggest that caching and/or defence of uneaten food may be a strategy practiced by this animal. Such a phenomenon is uncommon but taxonomically widespread among vertebrates. Depending on circumstances, it is termed hoarding, caching, or storage and may be short- or long-term, include defence of the resource, or have other variable expressions, with the common threads being deferred consumption and deterrence of consumption by others (Vanderwall 1990). Many vertebrate taxa exhibit hoarding behaviour, including rodents (e.g. Sciuridae), carnivores (e.g. Canidae, Felinidae) and birds (e.g. Corvidae, Picidae). No form of food caching, to our knowledge, has ever been reported in a wild pinniped.
Permian plant macrofossils from Fossilryggen, Vestfjella, Dronning Maud Land
Authors: MCLOUGHLIN STEPHEN , LARSSON KENT , LINDSTRÖM SOFIE
Published: February 2005

A low diversity plant macrofossil assemblage described from the northern section of Fossilryggen, Vestfjella, Dronning Maud Land, Antarctica, is dominated by matted leaf impressions of Glossopteris sp. cf. G. communis Feistmantel and Glossopteris sp. cf. G. spatulata Pant & Singh, and in situ finely branched Vertebraria indica Royle rootlets. Equisetalean stems, rhizomes and leaf whorls (Phyllotheca australis Brongniart emend. Townrow), isolated seeds, scale-leaves, and fragmentary gymnosperm axes represent minor components of the assemblage. The fossils are preserved in fine-grained, floodbasin sediments and dark palaeosols. Although lacking definitive biostratigraphical indices, the flora is considered to represent a Middle Permian assemblage based principally on lithological and palynological correlation with the southern section at Fossilryggen and broad similarities to mid-Permian plant assemblages elsewhere in Gondwana.
Crustal structure beneath Discovery Bank in the Scotia Sea from group velocity tomography and seismic reflection data
Authors: VUAN A. , LODOLO E. , PANZA G.F. , SAULI C.
Published: February 2005

The Bruce, Discovery, Herdman and Jane banks, all located along the central-eastern part of the South Scotia Ridge, represent isolated topographic highs, surrounded by young oceanic crust (∼5–23 Ma), whose petrological and structural nature is still the subject of speculation due to the lack of relevant data. Surface wave tomography in and around the Scotia Sea region, performed using eight broadband seismic stations and 300 events, shows that the central-eastern part of the South Scotia Ridge is characterized by negative surface wave group velocity anomalies as large as 6% in the period range from 15 s to 50 s. The spatial resolution of our data set (∼300 km) makes it possible to study a specific area (centred at 61°S and 36°W) that includes Discovery Bank and appears to show dispersion characteristics similar to those found beneath the northern tip of the Antarctic Peninsula and southern South America. Surface wave dispersion curves are inverted to obtain 1-D isotropic shear wave velocity profiles that suggest a continental nature of Discovery Bank. Crustal thickness is in the range 23–28 km with a sub-Moho velocity of 4.1–4.2 km s−1. The boundaries of the negative group velocity anomalies are marked by a high level of seismic activity. The depth of the events and their large seismic moment suggest the presence of continental lithosphere. The continental-type crust of this topographic relief is supported by our interpretation of multichannel seismic reflection profiles acquired across this rise, where the observed seismic structures are interpreted as thinned and faulted continental plateau.
Daily cycle of the surface layer and energy balance on the high Antarctic Plateau
Authors: VAN AS DIRK , VAN DEN BROEKE MICHIEL , VAN DE WAL RODERIK
Published: February 2005

This paper focuses on the daily cycle of the surface energy balance and the atmospheric surface layer during a detailed meteorological experiment performed near Kohnen base in Dronning Maud Land, East Antarctica, in January and February 2002. Temperature, specific humidity, wind speed and the turbulent scales of these quantities, exhibit a strong daily cycle. The sensible heat flux cycle has a mean amplitude of ∼8 W m−2, while the latent heat flux has an amplitude of less than 2 W m−2, which is small compared to the amplitude of net radiation (∼ 35 W m−2) and sub-surface heat (∼ 25 W m−2). Between ∼ 9 and 16 h GMT convection occurs due to a slightly unstable atmospheric surface layer. At the end of the afternoon, the wind speed decreases abruptly and the mixed layer is no longer supported by the sensible heat input; the stratification becomes stable. At night a large near-surface wind shear is measured due to the presence of a nocturnal jet, which is likely to be katabatically driven, but can also be the result of an inertial oscillation. No strong daily cycle in wind direction is recorded, since both the katabatic forcing at night and the daytime forcing by the large-scale pressure gradient were directed approximately downslope during the period of measurement.
A comparison of parsing technologies for the biomedical domain
Authors: GROVER CLAIRE , LASCARIDES ALEX , LAPATA MIRELLA
Published: February 2005

This paper reports on a number of experiments which are designed to investigate the extent to which current NLP resources are able to syntactically and semantically analyse biomedical text. We address two tasks: (a) parsing a real corpus with a hand-built wide-coverage grammar, producing both syntactic analyses and logical forms and (b) automatically computing the interpretation of compound nouns where the head is a nominalisation (e.g. hospital arrival means an arrival at hospital, while patient arrival means an arrival of a patient). For the former task we demonstrate that flexible and yet constrained pre-processing techniques are crucial to success: these enable us to use part-of-speech tags to overcome inadequate lexical coverage, and to package up complex technical expressions prior to parsing so that they are blocked from creating misleading amounts of syntactic complexity. We argue that the XML-processing paradigm is ideally suited for automatically preparing the corpus for parsing. For the latter task, we compute interpretations of the compounds by exploiting surface cues and meaning paraphrases, which in turn are extracted from the parsed corpus. This provides an empirical setting in which we can compare the utility of a comparatively deep parser vs. a shallow one, exploring the trade-off between resolving attachment ambiguities on the one hand and generating errors in the parses on the other. We demonstrate that a model of the meaning of compound nominalisations is achievable with the aid of current broad-coverage parsers.
Comparing Self-Reports to Traces of Studying Behavior as Representations of Students' Studying and Achievement
Authors: Jamieson-Noel Dianne , Winne Philip H.
Published: February 2005

Ein Vergleich von Selbstberichtdaten mit verhaltensbasierten Indikatoren des Lernverhaltens und der Leistung von Studierenden

Zusammenfassung: In dieser Studie verglichen wir Modelle des selbstgesteuerten Lernens, die auf dem Selbstbericht versus der Aufzeichnung von “Verhaltensspuren” des Einsatzes von Lerntaktiken beim Lesen eines Textes beruhen. Die selbst berichteten Lerntaktiken unterschieden sich von den im Verhalten tatsächlich gezeigten Taktiken. In getrennten Regressionsmodellen erwiesen sich sowohl selbst berichtete als auch im Verhalten gezeigte Taktiken als Prädiktoren der Leistung, wobei jedoch unterschiedliche Arten von Taktiken in die beiden Modelle aufgenommen wurden. Getrennte Hauptkomponentenanalysen zeigten, dass verhaltensbasierte Indikatoren andere Formen selbstgesteuerten Lernens beschreiben als selbst berichtete Taktiken. Dies lässt darauf schließen, dass der Selbstbeschreibung des eigenen Lernverhaltens andere Prinzipien zugrunde liegen als der tatsächlichen Ausübung dieses Verhaltens. Wir schlagen daher vor, dass in der Forschung zum selbstgesteuerten Lernen und seiner Beziehung zu Lernleistungen sowohl Selbstberichtsdaten als auch verhaltensbasierte Indikatoren des Einsatzes von Lerntaktiken verwendet werden sollten.