bluuebunny/crossref_metadata_2025 huggingface dataset:
Structural and molecular characterization of equine sperm‐binding fibronectin‐II module proteins
Authors: Ekhlasi‐Hundrieser Mahnaz , Schäfer Bettina , Kirchhoff Christiane , Hess Oliver , Bellair Simone , Müller Peter , Töpfer‐Petersen Edda
Published: November 2004

Phospholipid‐binding proteins in the male genital tract are characterized by differing numbers Fn‐2 modules (B‐domain) carrying N‐terminal extensions (A‐domain) of variable length. In the stallion, three different proteins were identified, SP‐1, SP‐2, and EQ‐12. SP‐1 and SP‐2 of the AA'BB'‐ and ABB'‐type, respectively, are major proteins of the seminal plasma. Here we report the cDNA sequences of SP‐1, and of a new member of the SP‐2 family (SPnew) and the partial characterization of their iso‐ and glycoforms. The phosphorylcholine (PC)‐binding ability of the long Fn‐2 protein, EQ‐12, with four tandemly arranged Fn‐2 modules was determined by PC‐affinity chromatography. Expression patterns of EQ‐12, and the SP‐proteins were studied by means of RT‐PCR, Northern blot analysis and immunological approaches indicating differential expression along the male reproductive tract. The vast majority of the short SP‐1 and SP‐2 proteins are produced by the ampulla whereas EQ‐12 originates from the epididymis. Indirect immunofluorescence microscopy of sperm isolated from different regions of the epididymis and Western blot analysis indicate that both, the long and the short Fn‐2 proteins associate to the sperm surface during post‐testicular maturation. Sperm binding of Fn‐2 proteins at the post‐acrosome and midpiece was at first detected in the corpus epididymis. Enhanced fluorescence intensity after ejaculation point to an increased number of molecules bound to the sperm surface. The function of these proteins is discussed in regard to their structure–function relationships. Mol. Reprod. Dev. 70: 45–57, 2004. © 2004 Wiley‐Liss, Inc.
Simultaneous activation of PLA2 and PLC are required to promote acrosomal reaction stimulated by progesterone via G‐proteins
Authors: Pietrobon Elisa Olivia , Soria Mariana , Domínguez Luis Ángel , Monclus María de los ángeles , Fornés Miguel Walter
Published: November 2004

The acrosome reaction (AR) is a special exocytotic process promoted by signal transduction pathways studied in many laboratories. Progesterone (P4) is one of the trigger molecules proposed. Upon the binding of P4 to its receptor, several molecules could be activated, including G‐proteins, phospholipase A2 (PLA2), and phospholipase C (PLC). The role of these molecules was analyzed in this study using the Chlortetracycline (CTC) protocol to detect and quantify the AR. Incubation of capacitated sperm cells with GTPγs (GTPγs, a mimetic of G‐protein activation), arachidonic acid (AA, product of PLA2 action), or phorbol ester (PMA, an activator of PLC) for 15 min increased the AR to a similar percentage as P4. Conversely, a decrease in the AR was detected when sperm cells were incubated with P4 after preincubation with: GDPβS (GDP, an inhibitor of G‐protein activation), ONO RS‐82 (ONO, an inhibitor of PLA2), or neomycin (Neo, an inhibitor of PLC) for 15 min. To analyze the activation sequence of G proteins, PLA2, and PLC combinations of these mimetic/inhibitors were used during successive incubation periods. Inhibition promoted by GDP, ONO, and Neo were overcome by 15‐min incubation with GTPγs, AA, or PMA, respectively. But GTPγs or P4 did not reverse the inhibition due to incubation with Neo and ONO. Interestingly, this dual inhibition was reverted by another 15‐min incubation with AA or PMA. Results presented here could indicate that the AR triggered by P4 is driven by activation of G‐proteins, that in turn activate PLA2 and PLC simultaneously, that finally promote acrosomal exocytosis. Mol. Reprod. Dev. 70: 58–63, 2004. © 2004 Wiley‐Liss, Inc.
Reflection–absorption infrared spectroscopy investigation of the crystallization kinetics of poly(ethylene terephthalate) ultrathin films
Authors: Zhang Ying , Lu Yonglai , Duan Yongxin , Zhang Jianming , Yan Shouke , Shen Deyan
Published: November 2004

Reflection–absorption infrared spectroscopy was used to study the crystallization behavior of poly(ethylene terephthalate) (PET) ultrathin films. The crystallinity of ultrathin films was estimated by the fraction of trans conformers of PET. The isothermal and nonisothermal crystallization kinetics of ultrathin films with different thicknesses were investigated. The thinner PET film showed slower kinetics during isothermal crystallization than the thicker film. Moreover, the final crystallinity of films with various thicknesses were reduced with decreasing thickness. An Avrami equation was used to fit the acquired results. The Avrami exponents decreased with the film thickness. As for the nonisothermal crystallization, the cold‐crystallization starting temperature shifted to a lower temperature as the film thickness increased. The influence of the substrate on the crystallization kinetics of the films was also studied. The half‐crystallization times and final crystallinities of ultrathin films adsorbed onto a self‐assembled‐monolayer‐treated surface and an untreated substrate were clearly different, although their thickness dependence was similar. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 4440–4447, 2004
Solvation influences flap collapse in HIV‐1 protease
Authors: Meagher Kristin L. , Carlson Heather A.
Published: November 2004

HIV‐1 protease (HIVp) is an important target for the development of therapies to treat AIDS and is one of the classic examples of structure‐based drug design. The flap region of HIVp is known to be highly flexible and undergoes a large conformational change upon binding a ligand. Accurately modeling the inherent flexibility of the HIVp system is critical for developing new methods for structure‐based drug design. We report several 3‐ns molecular dynamics simulations investigating the role of solvation in HIVp flap rearrangement. Using an unliganded crystal structure of HIVp, other groups have observed flap reorganization on the nanosecond timescale. We have also observed rapid, initial flap movement, but we propose that it may be caused by system setup. The initial solvation of the system creates vacuum regions around the protein that may encourage large conformational deformities. By reducing the vacuum space created by the solvation routine, the observed flap collapse is attenuated. Also, a more thorough equilibration procedure preserves a more stable protein conformation over the course of the simulation. Proteins 2005. © 2004 Wiley‐Liss, Inc.
Hydrostatic pressure effects on the structural and electronic properties of carbon nanotubes
Authors: Capaz Rodrigo B. , Spataru Catalin D. , Tangney Paul , Cohen Marvin L. , Louie Steven G.
Published: November 2004

This issue's Editor's Choice [1] is a theoretical study of the properties of single‐wall carbon nanotubes (SWNTs) under hydro‐static pressure. The cover picture is a snapshot of room‐temperature molecular dynamics simulations of a chiral (8,7) SWNT at a pressure of 4 GPa, where a symmetry‐breaking collapse of the tube into a flat shape is observed.

This paper is an invited presentation from the 11th Interna‐tional Conference on High Pressure Semiconductor Physics (HPSP‐11), held in Berkeley, California, USA, 2–5 August 2004. The Proceedings of this conference series have been published for the fifth time in physica status solidi (b).

The first author, Rodrigo Barbosa Capaz, is Associate Professor of Physics at Universidade Federal do Rio de Janeiro and works on electronic properties and computer modeling of materials.
Electron transport with dissipation: A quantum kinetic approach
Authors: Gebauer Ralph , Car Roberto
Published: November 2004

We present a method for calculating electronic transport properties at the nanoscale. In this approach we describe the electron kinetics in the presence of an external field and of a heat bath. While the electric field accelerates the electrons, energy is dissipated as a result of interaction with the heat bath, allowing the system to reach steady state. The method is based on a Liouville master equation that constitutes a fully quantum generalization of the Boltzmann kinetic equation. As an example we report an application to transport through a double‐barrier resonant tunneling structure. © 2004 Wiley Periodicals, Inc. Int J Quantum Chem, 2005
Fermion particle density equations in relation to relativistic density functional theory
Authors: Howard I. A. , March N. H.
Published: November 2004

Relativistic density functional theory goes back at least to the work of Vallarta and Rosen. This represents the generalization of the Thomas–Fermi method to embody the kinetic energy of an electron of momentum p and rest mass m0 as given by special relativity theory in the chemical potential Euler equation. Here we set up a relativistic density functional theory by heuristic arguments that start from well‐established exact nonrelativistic differential equations for the Fermion density n(r) in model systems. We focus first on the differential equation of Lawes and March for one‐dimensional harmonic confinement. Into their result we introduce the finiteness of the velocity of light c by replacing the Lawes–March differential equation for the Fermion density n(x) by a difference equation for the relativistic Fermion density in which the Compton wavelength h/m0c, with m0 the Fermion rest mass, plays an important role. As we take the nonrelativistic limit c → ∞, we regain the exact nonrelativistic result. Contact is then established with the Vallarta–Rosen treatment in the limit when a large number N of Fermions are harmonically confined. The remaining models investigated are two‐electron in character. Relativistic difference equations to determine the density are again presented, for two such models. © 2004 Wiley Periodicals, Inc. Int J Quantum Chem, 2005
DFT energy derivatives and their renormalization in molecular vibrations
Authors: Ordon Piotr , Komorowski Ludwik
Published: November 2004

Properties of the energy function E(N, Q) and the thermodynamic potential Ω(μ, Q) expressed in terms of the number of electrons (N) and the nuclear positions (Q) rather than conventionally, by the electrostatic potential, ν(r), have been analyzed. The whole body of derivatives up to the third order is presented for each function. Renormalization of the basic derivatives explored in conceptual density functional theory has been demonstrated (chemical potential μ, global hardness η, number of electrons N, global softness S) as a result of coupling between the oscillatory motion of nuclei and the change in N or μ, for E and Ω, respectively. Exact result of renormalization crucially depends on the level of approximation. Extending the analysis beyond the second order was possible by adopting the Liu and Parr–type approximation to the energy function. It has been determined that first derivatives (μ, N) change their values when found beyond the vibrational energy minimum only. Second derivatives (η, S) both get renormalized even at the energy minimum, and they no longer conform to the reciprocity condition (ηS ≠ 1). Possible implications for the reactivity of oscillating species have been indicated. © 2004 Wiley Periodicals, Inc. Int J Quantum Chem, 2005
Percolation in Voronoi tilings
Authors: Balister P. , Bollobás B. , Quas A.
Published: November 2004

We consider a percolation process on a random tiling of ℝd into Voronoi cells based on points of a realization of a Poisson process. We prove the existence of a phase transition as the proportion p of open cells is varied and provide estimates for the critical probability pc. Specifically, we prove that for large d, 2−d(9d log d)−1 ≤ pc(d) ≤ C2−d$\sqrt{d}$ log d. © 2004 Wiley Periodicals, Inc. Random Struct. Alg., 2005
Performance Track Places Trust in the Carrot over the Stick
Authors: Fiorino Daniel J.
Published: November 2004

A new voluntary program from the Environmental Protection Agency (EPA) rewards companies that go beyond compliance, thereby helping businesses that are top environmental performers. © 2001 John Wiley & Sons, Inc.
Case Study: Chemical Screening at Eastman Kodak Company
Authors: Ochsner Michele
Published: November 2004

This case study is the final installment in a four‐part series profiling environmental decision making at leading companies. © 2001 John Wiley & Sons, Inc.
Texas Nameplate Company: A Profile of Environmental Success
Authors: Koepsel Kirsten
Published: November 2004

An initially ignored customer request started a small Texas company on the road to environmental excellence. Ten years later, it offers an example of solid accomplishment—with more achievements sure to come. © 2001 John Wiley & Sons, Inc.
Responsible Care© Programs for Hazardous Chemicals
Authors: Weiler Ernest D. , Jayjock Michael A. , Lewis Philip G.
Published: November 2004

This article describes the development, use, and learnings of a comprehensive Responsible Care® program as applied to the management of hazardous substances at various stages during the life cycle of the product. The article offers specific examples for stewardship programs in the biocide industry, and discusses the role of the medical community. © 2001 John Wiley & Sons, Inc.
The MTBE Threat to Our Water Supply: How to Detect and Remediate It
Authors: Kahler David
Published: November 2004

Methyl tertiary butyl ether, a gasoline additive once used to reduce air pollution, is now contaminating water sources around the United States. Monitoring for this chemical—and remediating it where it is found—should be an environmental priority. © 2001 John Wiley & Sons, Inc.
Quantifying the Impact of Corporate Environmental Performance on Shareholder Value
Authors: Repetto Robert , Austin Duncan
Published: November 2004

This article demonstrates an approach for analyzing and communicating the financial implications of a company's environmental exposures. In environmentally sensitive industries, this approach can help companies to benchmark themselves against rivals, to identify major sources of environmental risk and opportunity, to assign financial values to risk‐mitigating options, and to communicate their environmental strategies to the investment community and other stake‐holders. © 2000 World Resources Institute. Used with permission.
Ergonomics: It's Here to Stay, Despite the OSHA Standard Repeal
Authors: Michael Rachel
Published: November 2004

Congress repealed OSHA's Ergonomics Program Standard. But ergonomics remains an important health and safety issue for businesses. Moreover, additional regulation in this area is likely to come in the future. © 2001 John Wiley & Sons, Inc.
Resilienz im Kindes- und Jugendalter
Authors: Holtmann Martin , Schmidt Martin H.
Published: November 2004

Zusammenfassung. Der Begriff Resilienz beschreibt einen dynamischen oder kompensatorischen Prozess positiver Anpassung angesichts bedeutender Belastungen. Beide Aspekte, die positive Entwicklung und die aversiven Lebensumstände, erfordern eine genauere Betrachtung. Um das Resilienz-Konzept für die Entwicklungspsychopathologie und die Prävention fruchtbar machen zu können, müssen einige grundlegende konzeptuelle und methodische Probleme geklärt werden. So sollten nur solche Merkmale als resilienzerhöhend bezeichnet werden, die besonders oder ausschließlich wirksam sind, wenn auch eine risikoerhöhende Gefährdung vorliegt, die einen Puffereffekt ausüben und die bereits zeitlich vor dem risikoerhöhenden Ereignis bestanden haben, um dessen Auswirkungen moderieren zu können.
Ist Bindungssicherheit entwicklungsfördernd für Kinder mit Down-Syndrom?
Authors: Rauh Hellgard , Calvet Claudine
Published: November 2004

Zusammenfassung. Die Erfassung und die Bedeutung der Bindungsqualität bei Kindern mit Down-Syndrom ist wissenschaftlich umstritten. Anhand von Längsschnittdaten bei insgesamt 16 Kindern mit Bindungsklassifikation im Entwicklungsalter von 13 bis 15 Monaten (Lebensalter um 24 Monate) wird aufgezeigt, dass die Verhaltensentwicklung dieser Kinder in Bayley-Entwicklungstestsituationen (IBR-Ratings) im ersten bis zum fünften Lebensjahr in sinnvoller Beziehung zu ihrer Bindungsentwicklung stand. Ab dem fortgeschrittenen Vorschulalter entwickelten sich Kinder mit sicherer Bindung vor allem in der sprachlichen und in der sozial-kognitiven Entwicklung günstiger als Kinder mit unsicherer Bindungsbeziehung. Bindungssicherheit scheint sich in den ersten Jahren vor allem im Verhalten der Kinder und erst nahe dem Schulalter auch in Testleistungen auszuwirken.
Bindungsrepräsentation und Coping im Jugend- und jungen Erwachsenenalter
Authors: Seiffge-Krenke Inge , Becker-Stoll Fabienne
Published: November 2004

Zusammenfassung. Zu insgesamt fünf längsschnittlichen Erhebungszeitpunkten wurde an 103 Personen der Zusammenhang zwischen deren Bindungsrepräsentation und deren Bewältigungsverhalten im Umgang mit alltäglichen Belastungen untersucht. Sowohl im Jugendalter als auch im jungen Erwachsenenalter wurden Unterschiede in der Art der Problembewältigung in Abhängigkeit von der Bindungsrepräsentation gefunden. In Übereinstimmung mit der Bindungstheorie und neueren Konzepten der Emotionsregulation setzten sich jene Personen, denen im jungen Erwachsenenalter eine sichere Bindungsrepräsentation zuerkannt wurde, sowohl in der Adoleszenz als auch im Alter von 21 Jahren aktiver mit ihren Problemen auseinander und banden ihr soziales Netzwerk in die Problembewältigung ein. Probanden mit unsicher-distanzierter Bindungsrepräsentation neigten demgegenüber eher zu passiver Verschlossenheit, die letztlich in sozialem Rückzug mündete, während Probanden mit unsicher-verwickelter Bindungsrepräsentation unklares Verhalten zeigten und zwischen der Suche nach Hilfe und sozialem Rückzug schwankten.
The Memory of Noise
Authors: Kaernbach Christian
Published: November 2004

Abstract. The memory of auditory random waveforms (i.e., noise) is a special case of auditory memory for sensory information. Five experiments are reported that evaluate the dynamics of this storage system as well as interactions with new input. Periodic waveforms can be discriminated from uncorrelated noise by naive listeners up to a cycle length of 20 s, with the major decline in performance between 5 and 10 s. Even single repetitions of a piece of the waveform can be detected up to a stimulus onset asynchrony (SOA) of 6 s. The capacity of this storage system is limited to a few items of, in total, a few hundred milliseconds length. Within this capacity, however, items do not interfere strongly. These results are compatible with the view that auditory sensory memory is a modality-specific module of short-term memory.
The Dynamics of Operations in Visual Memory:
Authors: Conci Markus , Elliott Mark A. , Müller Hermann J. , Wendt Juliane , Becker Cordula
Published: November 2004

Abstract. Evidence from neurophysiological studies indicates that the synchronization of distributed neuronal assemblies in the gamma frequency range is responsible for the integration of discrete stimulus components into coherent wholes (e.g., see Singer, 1999 for review). Psychophysical support for this hypothesis has been reported in experiments that demonstrate that the presentation of a synchronous-premask frame within a 40-Hz flickering premask matrix primes the subsequent detection of a target Kanizsa-type square by generation of a 40-Hz prime ( Elliott & Müller, 1998 ). Psychopharmacological and electrophysiological evidence suggests that this priming mechanism is related to activity in interneuronal networks and relies on the combined function of prefrontal and posterior circuits. In addition, psychophysical experiments demonstrate the existence of a prime-specific visual short-term memory that oscillates at 40 Hz and remains functional for up to 300 ms post-stimulus offset. These results are consistent with a view of the prime as a form of oscillatory mechanism, related to the persistence of visual information ( Coltheart, 1980 ) and in the capacity guided by (prefrontal) top-down influences upon visual-cortical function.
A review of applications to constrain pumping test responses to improve on geological description and uncertainty
Authors: Raghavan Rajagopal
Published: November 2004

This review examines the single‐phase flow of fluids to wells in heterogeneous porous media and explores procedures to evaluate pumping test or pressure‐response curves. This paper examines how these curves may be used to improve descriptions of reservoir properties obtained from geology, geophysics, core analysis, outcrop measurements, and rock physics. We begin our discussion with a summary of the classical attempts to handle the issue of heterogeneity in well test analysis. We then review more recent advances concerning the evaluation of conductivity or permeability in terms of statistical variables and touch on perturbation techniques. Our current view to address the issue of heterogeneity by pumping tests may be simply summarized as follows. We assume a three‐dimensional array (ordered set) of values for the properties of the porous medium as a function of the coordinates that is obtained as a result of measurements and interpretations. We presume that this array of values contains all relevant information available from prior geological and geophysical interpretations, core and outcrop measurements, and rock physics. These arrays consist of several million values of properties, and the information available is usually on a very fine scale (often <0.5 m in the vertical direction); for convenience, we refer to these as cell values. The properties are assumed to be constant over the volume of each of these cells; that is, the support volume is the cell volume, and the cell volumes define the geologic scale. In this view it is implicit that small‐scale permeability affects the movement of fluids. Although more information than porosity is available, we refer to this system as a “porosity cube.” Because it is not economically possible to carry out computations on a fine‐scale model with modern resources on a routine basis, we discuss matters relating to the aggregation and scale‐up of the fine‐scale model from the perspective of testing and show that specific details need to be addressed. The focus is on single‐phase flow. Addressing the issue of scale‐up also permits us to comment on the application of the classical or analytical solutions to heterogeneous systems. The final part of the discussion outlines the inversion process and the adjustment of cell values to match observed performance. Because the computational scale and the scale of the porosity cube are different, we recommend that the inversion process incorporate adjustments at the fine scale. In this view the scale‐up process becomes a part of the inversion algorithm.
Probability map of the next M ≥ 5.5 earthquakes in Italy
Authors: Cinti F. R. , Faenza L. , Marzocchi W. , Montone P.
Published: November 2004

The main goal of this work is to provide a probability map for the next moderate to large earthquakes (M ≥ 5.5) in Italy. For this purpose we apply a new nonparametric multivariate model to characterize the spatiotemporal distribution of earthquakes. The method is able to account for tectonics/physics parameters that can potentially influence the spatiotemporal variability and tests their relative importance; moreover, it allows straightforward testing of a variety of hypothesis, such as Seismic Gap, Cluster, and Poisson hypothesis. The method has been applied to Italian seismicity of the last four centuries for earthquakes with M ≥ 5.5. Italy has been divided into 61 irregular zones representing areas with homogeneous tectonic regime resulting from active stress data. Besides the magnitude and the time of the earthquakes, the model includes information on the tectonic stress regime, the homogeneity of its orientation, the number of active faults, the dimension of the area and the homogeneity of the topography. The time distribution of the M ≥ 5.5 earthquakes appears clustered in time for a few years after an event, and then the distribution becomes similar to a memoryless Poisson process, leading to a time‐dependent probability map. This map shows that the most likely regions where the next moderate to large earthquakes may occur are Friuli, Umbria‐Marche, and part of Southern Apennines and the Calabrian arc.
Impacts of climate change on methane emissions from wetlands
Authors: Shindell Drew T. , Walter Bernadette P. , Faluvegi Greg
Published: November 2004

We have included climate‐sensitive methane emissions from wetlands within the GISS climate model using a linear parameterization derived from a detailed process model. The geographic distribution of wetlands is also climate–dependent. Doubled CO2 simulations using this model show an increase in annual average wetland methane emissions from 156 to 277 Tg/yr, a rise of 78%. The bulk of this increase is due to enhanced emissions from existing tropical wetlands. Additionally, high northern latitude wetland areas expand and emissions nearly triple during Northern summer. The global increase represents ∼20% of present‐day inventories. These large values indicate that the potential response of natural emissions to climate change merit greater study, and should be included in projections of future global warming and tropospheric pollution.
Modeling the rupture process of the 2003 September 25 Tokachi‐Oki (Hokkaido) earthquake using 1‐Hz GPS data
Authors: Miyazaki Shin'ichi , Larson Kristine M. , Choi Kyuhong , Hikima Kazuhito , Koketsu Kazuki , Bodin Paul , Haase Jennifer , Emore Gordon , Yamagiwa Atsushi
Published: November 2004

High‐rate GPS has the potential to recover both dynamic and static displacements accurately. We analyze 1‐Hz GPS data recorded during the 2003 Tokachi‐Oki earthquake. The 1‐Hz GPS displacement waveforms show good agreement with integrated accelerometer records except for low frequency noise that are inherently present in integrated seismic records. The GPS waveforms were inverted to model the spatio‐temporal evolution of the fault slip during the rupture. The slip is found to propagate downdip in the subduction zone with largest moment release ∼50 km northwest of the hypocenter. The region of largest slip agrees in general with traditional seismic studies, indicating that 1‐Hz GPS can be used for finite fault studies. The 1‐Hz GPS slip model shows clearer contrast with afterslip distributions than those inferred from strong motion data, possibly because 1‐Hz GPS is more sensitive to cumulative slip distribution.
Heliocentric radial intensity profiles of galactic cosmic rays measured by the IMP, Voyager, and Pioneer spacecraft in solar 11‐year modulation cycles of opposite magnetic polarity
Authors: Webber W. R. , Lockwood J. A.
Published: November 2004

We examine in this paper the heliocentric radial intensity profiles at heliolatitudes <35° of five energies/species of galactic cosmic rays as measured by IMP, Pioneer 10, and Voyagers 1 and 2 over several 11‐year solar cycles of different solar magnetic polarity. At times of maximum solar modulation the radial profiles in each cycle are remarkably similar. At times of minimum solar modulation (maximum intensity) these radial profiles differ greatly in the negative and positive solar magnetic polarity cycles. At the positive polarity cycle intensity maximum in 1977 and 1997 these intensity profiles exhibit a strong radial dependence out to ∼15 AU, beyond which the intensity profile is nearly flat. Also in the positive polarity cycles the amplitude of the 11‐year solar modulation cycle from maximum to minimum intensity decreases strongly with radius. At the negative polarity cycle intensity maximum in 1987 the radial intensity profiles at all energies are all consistent with a radial gradient which is ∼r−0.50±0.03, which when extrapolated to 85–95 AU gives intensities a factor ∼2–3 times higher at that distance than those in the positive cycles. The maximum extrapolated intensities of H and He nuclei at 85–95 AU in the negative polarity cycle in 1987 are comparable to the estimated interstellar intensities at rigidities above ∼1.5 GV, but at rigidities below ∼1 GV they are considerably less. This suggests that additional modulation is occurring in the heliosphere beyond 85–95 AU at these times. This rigidity‐dependent outer heliospheric modulation would greatly affect all particles with rigidities below a few hundred megavolts. In the positive polarity cycles, because of the lower extrapolated intensities at 85–95 AU, this outer heliospheric modulation is larger by a factor of 2–3 at all rigidities. Remarkably, in the scenario described here, a cosmic ray detector fixed at ∼85 AU in the solar ecliptic plane would probably not even see a solar 11‐year variation but instead see a very asymmetrical 22‐year variation which would depend on the solar magnetic polarity. Current modulation models explain some of these features when they include a heliospheric termination shock embedded in a larger modulation region.
Ground‐truthing the boron isotope‐paleo‐pH proxy in planktonic foraminifera shells: Partial dissolution and shell size effects
Authors: Hönisch Bärbel , Hemming N. Gary
Published: November 2004

Sediment samples from the Ontong‐Java Plateau in the Pacific and the 90° east ridge in the Indian Ocean were used to investigate whether shell size and early diagenesis affect δ11B of the symbiont‐bearing planktonic foraminifer Globigerinoides sacculifer. In pristine shells from both study locations we found a systematic increase of δ11B and Mg/Ca with shell size. Shells in the sieve size class 515–865 μm revealed δ11B values +2.1 to +2.3‰ higher than shells in the 250–380 μm class. This pattern is most likely due to differences in symbiont photosynthetic activity and its integrated effect on the pH of the foraminiferal microenvironment. We therefore suggest smaller individuals must live at approximately 50–100 m water depth where ambient light levels are lower. Using the empirical calibration curve for δ11B in G. sacculifer, only shells larger than 425 μm reflect surface seawater pH. Partial dissolution of shells derived from deeper sediment cores was determined by shell weight analyses and investigation of the shell surface microstructure by scanning electron microscopy. The δ11B in partially dissolved shells is up to 2‰ lower relative to pristine shells of the same size class. In agreement with a relatively higher weight loss in smaller shells, samples from the Ontong‐Java Plateau show a more pronounced dissolution effect than larger shells. On the basis of the primary size effect and potential postdepositional dissolution effects, we recommend the use of shells that are visually pristine and, in the case of G. sacculifer, larger than 500 μm for paleoreconstructions.
Radiocarbon and stable isotope constraints on Last Glacial Maximum and Younger Dryas ventilation in the western North Atlantic
Authors: Keigwin Lloyd D.
Published: November 2004

Foraminiferal abundance, 14C ventilation ages, and stable isotope ratios in cores from high deposition rate locations in the western subtropical North Atlantic are used to infer changes in ocean and climate during the Younger Dryas (YD) and Last Glacial Maximum (LGM). The δ18O of the surface dwelling planktonic foram Globigerinoides ruber records the present‐day decrease in surface temperature (SST) of ∼4°C from Gulf Stream waters to the northeastern Bermuda Rise. If during the LGM the modern δ18O/salinity relationship was maintained, this SST contrast was reduced to 2°C. With LGM to interglacial δ18O changes of at least 2.2‰, SSTs in the western subtropical gyre may have been as much as 5°C colder. Above ∼2.3 km, glacial δ13C was higher than today, consistent with nutrient‐depleted (younger) bottom waters, as identified previously. Below that, δ13C decreased continually to −0.5‰, about equal to the lowest LGM δ13C in the North Pacific Ocean. Seven pairs of benthic and planktonic foraminiferal 14C dates from cores >2.5 km deep differ by 1100 ± 340 years, with a maximum apparent ventilation age of ∼1500 years at 4250 m and at ∼4700 m. Apparent ventilation ages are presently unavailable for the LGM < 2.5 km because of problems with reworking on the continental slope when sea level was low. Because LGM δ13C is about the same in the deep North Atlantic and the deep North Pacific, and because the oldest apparent ventilation ages in the LGM North Atlantic are the same as the North Pacific today, it is possible that the same water mass, probably of southern origin, flowed deep within each basin during the LGM. Very early in the YD, dated here at 11.25 ± 0.25 (n = 10) conventional 14C kyr BP (equal to 12.9 calendar kyr BP), apparent ventilation ages <2.3 km water depth were about the same as North Atlantic Deep Water today. Below ∼2.3 km, four YD pairs average 1030 ± 400 years. The oldest apparent ventilation age for the YD is 1600 years at 4250 m. This strong contrast in ventilation, which indicates a front between water masses of very different origin, is similar to glacial profiles of nutrient‐like proxies. This suggests that the LGM and YD modes of ocean circulation were the same.
Daytime vertical E × B drift velocities inferred from ground‐based magnetometer observations at low latitudes
Authors: Anderson David , Anghel Adela , Chau Jorge , Veliz Oscar
Published: November 2004

The daytime equatorial electrojet is a narrow band of enhanced eastward current flowing in the 100–120 km altitude region within ±2° latitude of the dip equator. A unique way of determining the daytime strength of the electrojet is to observe the difference in the magnitudes of the horizontal (H) component between a magnetometer placed directly on the magnetic equator and one displaced 6°–9° away. The difference between these measured H values provides a direct measure of the daytime electrojet current and, in turn, the magnitude of the vertical E × B drift velocity in the F region ionosphere. This paper discusses a recent study where 27 months of magnetometer H component observations and daytime, vertical E × B drift velocities were obtained in the Peruvian longitude sector between August 2001 and December 2003. In order to establish the relationships between ΔH and E × B drift velocities for the 270 days of observations, three approaches were chosen: (1) a linear regression analysis, (2) a multiple regression approach, and (3) a neural network approach. The neural network method gives slightly lower RMS error values compared with the other two methods. The relationships for all three techniques are validated using an independent set of E × B drift observations from the Jicamarca incoherent scatter radar (ISR) located at Jicamarca, Peru. The techniques presented here will be incorporated into a recently developed, real‐time Global Assimilation of Ionospheric Measurements (GAIM) model.
Pore‐scale modeling of longitudinal dispersion
Authors: Bijeljic Branko , Muggeridge Ann H. , Blunt Martin J.
Published: November 2004

We study macroscopic (centimeter scale) dispersion using pore‐scale network simulation. A Lagrangian‐based transport model incorporating flow and diffusion is applied in a diamond lattice of throats with square cross section whose radius distribution is the same as computed for Berea sandstone. We use physically consistent rules using a combination of stream‐tube routing and ideal mixing to transport particles across pore junctions. The influence of both heterogeneity and high Peclet numbers results in asymptotic behavior only being seen after movement through many throats. A comprehensive comparative study of longitudinal dispersion with experiments in consolidated and unconsolidated media indicates that the model can quantitatively predict the asymptotic macroscopic dispersion coefficient over a broad range of Peclet numbers, 0 < Pe < 105. In the low Peclet number region, molecular diffusion is more restricted for consolidated media as compared with unconsolidated media. The first effects of advection on dispersion are observed at Pe ∼ 0.1. In the advection‐dominated regions the longitudinal dispersion coefficient follows a weak nonlinear dependence on Peclet number (DL ∼ Pe1.19) followed by a linear dependence DL ∼ Pe for Pe > 400.
Embedded Coordination in a Business Network
Authors: Liere van Diederik W , Hagdorn Lorike , Hoogeweegen Martijn R , Vervest Peter HM
Published: November 2004

Information and communication technology enables a firm to maintain more links with more companies at much lower costs than before. This combined with the increasingly standardization of business processes and the application of modularity at the process level leads to embedded coordination. This case study describes how three unconnected business networks were integrated using modularity at the business process, or activity component, level and the role standardization played to implement embedded coordination. The case study was conducted at ABZ, a trusted Business Service Provisioner in the Dutch insurance industry. This study suggests that embedded coordination leads to improved performance of the business network under the condition that standardization is enforced.
Thermochemistry of disputed soot formation intermediates C4H3 and C4H5
Authors: Wheeler Steven E. , Allen Wesley D. , Schaefer Henry F.
Published: November 2004

Accurate isomeric energy differences and standard enthalpies of formation for disputed intermediates in soot formation, C4H3 and C4H5, have been determined through systematic extrapolations of ab initio energies. Electron correlation has been included through second-order Z-averaged perturbation theory (ZAPT2), and spin-restricted, open-shell coupled-cluster methods through triple excitations [ROCCSD, ROCCSD(T), and ROCCSDT] utilizing the correlation-consistent hierarchy of basis sets, cc-pVXZ (X=D, T, Q, 5, and 6), followed by extrapolations to the complete basis set limit via the focal point method of Allen and co-workers. Reference geometries were fully optimized at the ROCCSD(T) level with a TZ(2d1f,2p1d) basis set. Our analysis finds that the resonance-stabilized i-C4H3 and i-C4H5 isomers lie 11.8 and 10.7 kcal mol−1 below E-n-C4H3 and E-n-C4H5, respectively, several kcal mol−1 (more, less) than reported in recent (diffusion Monte Carlo, B3LYP density-functional) studies. Moreover, in these systems Gaussian-3 (G3) theory suffers from large spin contamination in electronic wave functions, poor reference geometries, and anomalous vibrational frequencies, but fortuitous cancellation of these sizable errors leads to isomerization energies apparently accurate to 1 kcal mol−1. Using focal-point extrapolations for isodesmic reactions, we determine the enthalpies of formation (ΔfH0∘) for i-C4H3, Z-n-C4H3, E-n-C4H3, i-C4H5, Z-n-C4H5, and E-n-C4H5 to be 119.0, 130.8, 130.8, 78.4, 89.7, and 89.1 kcal mol−1, respectively. These definitive values remove any remaining uncertainty surrounding the thermochemistry of these isomers in combustion models, allowing for better assessment of whether even-carbon pathways contribute to soot formation.
A computer simulation study of the influence of a liquid crystal medium on polymerization
Authors: Berardi Roberto , Micheletti Davide , Muccioli Luca , Ricci Matteo , Zannoni Claudio
Published: November 2004

We present a simple molecular level model based on Gay-Berne monomers linked by finitely extendable nonlinear elastic potential bonds for describing main chain polymerization in liquid crystals. We apply the model to study the influence that the order of the medium has on the characteristics of the chains obtained. We find that the chains prepared from the nematic are actually straighter than those obtained from a polymerization in the isotropic phase and that they are characterized by a small number of hairpins as experimentally observed.
Comment on “Quasielastic neutron scattering of two-dimensional water in a vermiculite clay” [J. Chem. Phys. 113, 2873 (2000)] and “A neutron spin-echo study of confined water” [J. Chem. Phys. 115, 11299 (2001)]
Authors: Mamontov E.
Published: November 2004

We suggest that in the recent papers [J. Chem. Phys. 113, 2873 (2000)] and [J. Chem. Phys. 115, 11299 (2001)] an incorrect expression was used to obtain the diffusion coefficient of water in fully hydrated vermiculite clay from the Q dependence of the quasielastic neutron scattering data. This has led to underestimating the mean square jump length and the translational diffusion coefficient by a factor of 3. We discuss the correct way to extract the diffusion parameters and their properly estimated values.
Evaluation of canonical and microcanonical nonadiabatic reaction rate constants by using the Zhu–Nakamura formulas
Authors: Zhao Yi , Mil’nikov Gennady , Nakamura Hiroki
Published: November 2004

We consider a problem of calculating both thermal and microcanonical rate constants for nonadiabatic chemical reactions. Instead of using the conventional transition state theory, we use a generalized seam surface and introduce a concept of a coordinate dependent effective nonadiabatic transition probability based on the Zhu–Nakamura theory which can treat the nonadiabatic tunneling properly. The present approach can be combined with Monte Carlo method so as to be applicable to chemical reactions in complicated systems. The method is demonstrated to work well in wide energy and temperature range. Numerical tests also show that it is very essential for accurate evaluation of the thermal rate constant to use the generalized seam surface and take into account the nonadiabatic tunneling effect.
Density-functional and electron correlated study of five linear birefringences—Kerr, Cotton–Mouton, Buckingham, Jones, and magnetoelectric—in gaseous benzene
Authors: Rizzo Antonio , Cappelli Chiara , Jansı́k Branislav , Jonsson Dan , Sałek Paweł , Coriani Sonia , Ågren Hans
Published: November 2004

We present the results of an extended study of five birefringences—Kerr, Cotton–Mouton, Buckingham, Jones, and Magnetoelectric—on benzene in the gas phase. The relevant molecular quantities—first-order properties, linear, quadratic, and cubic response functions—are computed employing the density-functional theory (DFT) response theory, with a choice of functionals. In some cases, different functionals are employed for the wave-function computational step and for the subsequent analytical response calculation to determine the combination yielding at the same time the optimal energy and energy derivative results. Augmented correlation consistent basis sets of double and triple zeta quality are used. The DFT results are compared to those obtained at the Hartree–Fock level and in some cases within a coupled cluster singles and doubles electronic structure model. The study tries to assess the ability of the DFT response theory to describe a wide range of properties in a system of rather large size and high complexity. The relative strength of the five birefringences for plausible experimental conditions is determined and, when possible, comparison is made with the results of the measurements.
Time-dependent exchange-correlation current density functionals with memory
Authors: Kurzweil Yair , Baer Roi
Published: November 2004

Most present applications of time-dependent density functional theory use adiabatic functionals, i.e., the effective potential at time t is determined solely by the density at the same time. This paper discusses a method that aims to go beyond this approximation, by incorporating “memory” effects: the derived exchange-correlation potential will depend not only on present densities but also on the past. In order to ensure the potentials are causal, we formulate the action on the Keldysh contour for electrons in electromagnetic fields, from which we derive suitable Kohn–Sham equations. The exchange-correlation action is now a functional of the electron density and velocity field. A specific action functional is constructed which is Galilean invariant and yields a causal exchange-correlation vector potential for the Kohn–Sham equations incorporating memory effects. We show explicitly that the net exchange-correlation Lorentz force is zero. The potential is consistent with known dynamical properties of the homogeneous electron gas (in the linear response limit).
Spectral diffusion in a fluctuating charge model of water
Authors: Corcelli S. A. , Lawrence C. P. , Asbury J. B. , Steinel T. , Fayer M. D. , Skinner J. L.
Published: November 2004

We apply the combined electronic structure/molecular dynamics approach of Corcelli, Lawrence, and Skinner [J. Chem. Phys. 120, 8107 (2004)] to the fluctuating charge (SPC-FQ) model of liquid water developed by Rick, Stuart, and Berne [J. Chem. Phys. 101, 6141 (1994)]. For HOD in H2O the time scale for the long-time decay of the OD stretch frequency time-correlation function, which corresponds to the time scale for hydrogen-bond rearrangement in the liquid, is about 1.5 ps. This result is significantly longer than the 0.9 ps decay previously calculated for the nonpolarizable SPC/E water model. Our results for the SPC-FQ model are in better agreement with recent vibrational echo experiments.
Translational friction coefficients for cylinders of arbitrary axial ratios estimated by Monte Carlo simulation
Authors: Hansen Steen
Published: November 2004

Translational friction coefficients for cylinders of arbitrary axial ratios (including disks) are calculated using Monte Carlo simulation and an approximate description of the hydrodynamic interaction. The calculations indicate that the approximate description is exact for ellipsoids and this result is generalized to include cylinders, which possess the same symmetry as ellipsoids. From the result an approximate formula for the translational friction coefficient of cylinders is calculated which is compared to results from other sources.
Kinetics and mechanisms of crystal growth and diffusion in a glass-forming liquid
Authors: Nascimento Marcio Luis Ferreira , Ferreira Eduardo Bellini , Zanotto Edgar Dutra
Published: November 2004

Extensive data on the viscosity, covering 15 orders of magnitude, and crystal growth rate, covering seven orders of magnitude, of liquid diopside (CaO⋅MgO⋅2SiO2) were collected in a wide range of undercoolings from 1.10Tg to 0.99Tm (Tg is the glass transition temperature and Tm the melting point). The raw growth rate data were corrected for the increased interfacial temperature produced by the heat released during crystallization. A detailed analysis confirms that growth mediated by screw dislocations reasonably explain the experimental data in these wide ranges of temperatures and growth rates. Effective diffusion coefficients were calculated from crystal growth rates and from viscosity, and were then compared with measured self-diffusion coefficients of silicon and oxygen in diopside melt. The results show that oxygen and silicon control the diffusion dynamics involved in crystal growth and viscous flow. This study not only unveils the transport mechanism in this complex liquid, but also validates the use of viscosity (through the Stokes–Einstein or the Eyring equations) to account for the kinetic term of the crystal growth expression in a wide range of temperatures.
Electronic properties of silole-based organic semiconductors
Authors: Risko C. , Kushto G. P. , Kafati Z. H. , Brédas J. L.
Published: November 2004

We report on a detailed quantum-chemical study of the geometric structure and electronic properties of 2,5-bis(6′-(2′,2″-bipyridyl))-1,1-dimethyl-3,4-diphenylsilole (PyPySPyPy) and 2,5-di- (3-biphenyl)-1,1-dimethyl-3,4-diphenylsilole (PPSPP). These molecular systems are attractive candidates for application as electron-transport materials in organic light-emitting devices. Density Functional Theory (DFT), time-dependent DFT, and correlated semiempirical (ZINDO/CIS) calculations are carried out in order to evaluate parameters determining electron-transport and optical characteristics. Experimental data show that PyPySPyPy possesses an electron-transport mobility that is significantly greater than PPSPP, while PPSPP has a significantly larger photoluminescence quantum yield; however, the theoretical results indicate that the two systems undergo similar geometric transformations upon reduction and have comparable molecular orbital structures and energies. This suggests that intermolecular interactions (solid-state packing, electronic coupling) play significant roles in the contrasting performance of these two molecular systems.