bluuebunny/crossref_metadata_2025 huggingface dataset:
Science of Analytical Reasoning
Authors: Ribarsky William , Fisher Brian , Pottenger William M.
Published: September 2009

There has been progress in the science of analytical reasoning and in meeting the recommendations for future research that were laid out when the field of visual analytics was established. Researchers have also developed a group of visual analytics tools and methods that embody visual analytics principles and attack important and challenging real-world problems. However, these efforts are only the beginning and much study remains to be done. This article examines the state of the art in visual analytics methods and reasoning and gives examples of current tools and capabilities. It shows that the science of visual analytics needs interdisciplinary efforts, indicates some of the disciplines that should be involved and presents an approach to how they might work together. Finally, the article describes some gaps, opportunities and future directions in developing new theories and models that can be enacted in methods and design principles and applied to significant and complex practical problems and data.
Developing a Legislative Pathway for Biosimilars in the United States
Authors: Waxman Henry A.
Published: September 2009

Biologies are one of the fastest growing, most important, and most expensive segments of the pharmaceutical industry. The high price of biologies in the United States is making these life-saving drugs unaffordable for many Americans and creating unsustainable burdens on purchasers. While the EU has created an abbreviated approval process for biosimilars, there is no explicit legislative pathway in the United States that would enable generic competition for biologics. The Promoting Innovation and Access to Life-Saving Medicine Act would provide such a generic pathway for biologics, using competition to lower drug prices. The bill provides an appropriate balance between access to affordable medicine and retaining incentives for innovation.
Mergers & Acquisitions Update: Changing the Strategic Paradigm in the Global Generics Market
Authors: Karwal Vijay P.
Published: September 2009

The generic pharmaceutical sector has witnessed an unprecedented level of mergers & acquisitions (M&A) activity in recent years. Companies are engaging in merger activity to strengthen their strategic positioning in response to the changing competitive landscape in the industry. In a growing global generic market, having adequate scale and financial strength will be key attributes to manage pressure on pricing and margins, capture growth opportunities globally, establish a competitive cost base, and be able to pursue high value but high investment opportunities in niche generics and biologics. The emergence of a tier of large leading generic companies as well as the renewed interest by big pharma in the generic market are forcing industry participants to determine their strategy and role towards the consolidation trend. In an industry that remains highly fragmented, the changing market environment is expected to lead to continued M&A activity which will change the shape of the industry in the future.
A Review of Recent Developments at the Multilateral Level with Respect to Intellectual Property and the Pharmaceutical Industry
Authors: Cruz Maximiliano Santa , Roffe Pedro
Published: September 2009

The adoption in 1994 of the World Trade Organization's Agreement on Trade Related aspects of Intellectual Property Rights (TRIPS) meant the incorporation of intellectual property as an important component of the international trading system. It meant also an end to the exclusive treatment of intellectual property issues in the World Intellectual Property Organization (WIPO). TRIPS meant also, the end of the accepted practice of excluding pharmaceutical products and or processes from patent protection, a practice that was particularly important for developing countries. This note reviews recent developments at the multilateral level after the adoption of TRIPS, namely the adoption of the Declaration on the TRIPS Agreement and Public Health in 2001 and the subsequent decision to amend the TRIPS for the effective use of the compulsory licensing system; the adoption of the Development Agenda by the WIPO General Assembly in 2007 and related recent developments in WIPO; and finally the adoption of the Global strategy and plan of action on public health, innovation and intellectual property by the 61st World Health Assembly in 2008. One common feature of these developments is the attempt to bring some balance to the international intellectual property system that has been characterised by an upward tendency to strengthen private rights and their enforcement to the detriment of public interest considerations.
Opportunities and Challenges in an Ever Generic World
Authors: Sheppard Alan
Published: September 2009

The global generics industry is about to embark on a decade of seismic change, and the impact to both patients and health-care systems cannot be overstated. This paper provides an overview of the global pharmaceutical market in the context of today's economic crisis, and a corresponding outline of key trends shaping the global generics market. It then focuses-in on an examination of the trend toward centralized contracting and how it will benefit those generics manufacturers with a broad portfolio and low-cost manufacturing base.
An Exploratory Study Identifying Soft Skill Competencies in Entry-Level Managers
Authors: Weber Melvin R. , Finley Dori A. , Crawford Alleah , Rivera David
Published: September 2009

The identification of competencies needed by hospitality managers has been investigated since the 1980s. In all of the competency research related to hospitality management, essential competencies include skills that can be classified as soft skills, yet a comprehensive list of these soft skills has not been identified. The purpose of this project is to have industry professionals rate the importance of soft skill competencies found in literature, and then reduce this list of competencies by completing a factor analysis. This study serves as the beginning for a comprehensive study of soft skills needed in entry-level hospitality management positions.
Formation mechanisms of oxygen atoms in the O(PJ3) state from the 157nm photoirradiation of amorphous water ice at 90K
Authors: Hama Tetsuya , Yabushita Akihiro , Yokoyama Masaaki , Kawasaki Masahiro , Watanabe Naoki
Published: September 2009

Desorption of ground state O(PJ=2,1,03) atoms following the vacuum ultraviolet photolysis of water ice in the first absorption band was directly measured with resonance-enhanced multiphoton ionization (REMPI) method. Based on their translational energy distributions and evolution behavior, two different formation mechanisms are proposed: One is exothermic recombination reaction of OH radicals, OH+OH→H2O+O(PJ3) and the other is the photodissociation of OH radicals on the surface of amorphous solid water. The translational and internal energy distributions of OH radicals as well as the evolution behavior were also measured by REMPI to elucidate the roles of H2O2 and OH in the O(PJ3) formation mechanisms.
Formation mechanisms of oxygen atoms in the O(D21) state from the 157nm photoirradiation of amorphous water ice at 90K
Authors: Hama Tetsuya , Yabushita Akihiro , Yokoyama Masaaki , Kawasaki Masahiro , Watanabe Naoki
Published: September 2009

Vacuum ultraviolet photolysis of water ice in the first absorption band was studied at 157nm. Translational and internal energy distributions of the desorbed species, O(D1) and OH(v=0,1), were directly measured with resonance-enhanced multiphoton ionization method. Two different mechanisms are discussed for desorption of electronically excited O(D1) atoms from the ice surface. One is unimolecular dissociation of H2O to H2+O(D1) as a primary photoprocess. The other is the surface recombination reaction of hot OH radicals that are produced from photodissociation of hydrogen peroxide as a secondary photoprocess. H2O2 is one of the major photoproducts in the vacuum ultraviolet photolysis of water ice.
Theoretical study of phase transitions in Kr and Ar clathrate hydrates from structure II to structure I under pressure
Authors: Subbotin Oleg S. , Adamova Tatiana P. , Belosludov Rodion V. , Mizuseki Hiroshi , Kawazoe Yoshiyuki , Kudoh Jun-ichi , Rodger P. M. , Belosludov Vladimir R.
Published: September 2009

The theory developed in our earlier papers is extended to predict dynamical and thermodynamic properties of clathrate structures by accounting for the possibility of multiple filling of cavities by guest molecules. The method is applied to the thermodynamic properties of argon and krypton hydrates, considering both structures I (sI) and II (sII), in which the small cages can be singly occupied and large cages of sII can be singly or doubly occupied. It was confirmed that the structure of the clathrate hydrate is determined by two main factors: intermolecular interaction between guest and host molecules and the configurational entropy. It is shown that for guests weakly interacting with water molecules, such as argon or krypton, the free energy of host lattices without the contribution of entropy is the main structure-determining factor for clathrate hydrates, and it is a cause of hydrate sII formation at low pressure with these guests. Explicit account of the entropy contribution in the Gibbs free energy allows one to determine the stability of hydrate phases and to estimate the line of structural transition from sII to sI in P-T plane. The structural transition between sII and sI in argon and krypton hydrates at high pressure is shown to be the consequence of increasing intermolecular interaction and the degree of occupancy of the large cavities.
Crystalline-to-plastic phase transitions in molecularly thin n-dotriacontane films adsorbed on solid surfaces
Authors: Cisternas Edgardo A. , Corrales Tomás P. , del Campo Valeria , Soza Pamela A. , Volkmann Ulrich G. , Bai Mengjun , Taub Haskell , Hansen Flemming Y.
Published: September 2009

Crystalline-to-rotator phase transitions have been widely studied in bulk hydrocarbons, in particular in normal alkanes. But few studies of these transitions deal with molecularly thin films of pure n-alkanes on solid substrates. In this work, we were able to grow dotriacontane (n-C32H66) films without coexisting bulk particles, which allows us to isolate the contribution to the ellipsometric signal from a monolayer of molecules oriented with their long axis perpendicular to the SiO2 surface. For these submonolayer films, we found a step in the ellipsometer signal at ∼331 K, which we identify with a solid-solid phase transition. At higher coverages, we observed additional steps in the ellipsometric signal that we identify with a solid-solid phase transition in multilayer islands (∼333 K) and with the transition to the rotator phase in bulk crystallites (∼337 K), respectively. After considering three alternative explanations, we propose that the step upward in the ellipsometric signal observed at ∼331 K on heating the submonolayer film is the signature of a transition from a perpendicular monolayer phase to a denser phase in which the alkane chains contain on average one to two gauche defects per molecule.
Application of the entropy theory of glass formation to poly(α-olefins)
Authors: Stukalin Evgeny B. , Douglas Jack F. , Freed Karl F.
Published: September 2009

The entropy theory of glass formation, which has previously been developed to describe general classes of polymeric glass-forming liquids, is extended here to model the thermodynamic and dynamic properties of poly(α-olefins). By combining this thermodynamic theory with the Adam–Gibbs model (which relates the configurational entropy to the rate of structural relaxation), we provide systematic computations for all four characteristic temperatures (TA, Tc, Tg, T0), governing the position and breadth of the glass transition, and the fragility parameters (D,m) describing the strength of the temperature dependence of the structural relaxation time, where TA is the temperature below which the relaxation is non-Arrhenius, Tc is the crossover or empirical mode-coupling temperature, Tg is the glass transition temperature, and T0 is the temperature at which the extrapolated relaxation time diverges. These temperatures and fragility parameters are evaluated as a function of molar mass, pressure, and the length n of the α-olefin side chains. The nearest neighbor interaction energy and local chain rigidities are found to strongly influence the four characteristic temperatures and the low temperature fragility. We also observe an “internal plasticization” of the poly(α-olefins) wherein the fragility decreases as the number n of “flexible” side group units increases. Our computations provide solid support for a pressure counterpart of the Vogel–Fulcher–Tammann relation. The entropy theory of glass formation predicts systematic changes in fragility with chain stiffness, cohesive energy, polymerization index, and side chain length, and qualitative trends in these parameters are discussed.
Local correlation calculations using standard and renormalized coupled-cluster approaches
Authors: Li Wei , Piecuch Piotr , Gour Jeffrey R. , Li Shuhua
Published: September 2009

The linear scaling local correlation approach, termed “cluster-in-molecule” (CIM), is extended to the coupled-cluster (CC) theory with singles and doubles (CCSD) and CC methods with singles, doubles, and noniterative triples, including CCSD(T) and the completely renormalized CR-CC(2,3) approach. The resulting CIM-CCSD, CIM-CCSD(T), and CIM-CR-CC(2,3) methods are characterized by (i) the linear scaling of the CPU time with the system size, (ii) the use of orthonormal orbitals in the CC subsystem calculations, (iii) the natural parallelism, (iv) the high computational efficiency, enabling calculations for much larger systems and at higher levels of CC theory than previously possible, and (v) the purely noniterative character of local triples corrections. By comparing the results of the canonical and CIM-CC calculations for normal alkanes and water clusters, it is shown that the CIM-CCSD, CIM-CCSD(T), and CIM-CR-CC(2,3) approaches accurately reproduce the corresponding canonical CC correlation and relative energies, while offering savings in the computer effort by orders of magnitude.
Auto-oligomerization and hydration of pyrrole revealed by x-ray absorption spectroscopy
Authors: Schwartz Craig P. , Uejio Janel S. , Duffin Andrew M. , England Alice H. , Prendergast David , Saykally Richard J.
Published: September 2009

Near edge x-ray absorption fine structure spectra have been measured at the carbon and nitrogen K-edges of the prototypical aromatic molecule, pyrrole, both in the gas phase and when solvated in water, and compared with spectra simulated using a combination of classical molecular dynamics and first principles density functional theory in the excited state core hole approximation. The excellent agreement enabled detailed assignments. Pyrrole is highly reactive, particularly in water, and reaction products formed by the auto-oligomerization of pyrrole are identified. The solvated spectra have been measured at two different temperatures, indicating that the final states remain largely unaffected by both hydration and temperature. This is somewhat unexpected, since the nitrogen in pyrrole can donate a hydrogen bond to water.
Induced fit for mRNA/TIS11d complex
Authors: Qin Fang , Chen Yue , Li Yi-Xue , Chen Hai-Feng
Published: September 2009

TIS11d tandem zinc finger (TZF) domain can bind the class II AU-rich element of target mRNA and regulate mRNA turnover by promoting or inhibiting degradation. NMR spectra show that TIS11dTZF undergoes a transition from disordered to well folded upon binding to Zn and mRNA. To gain an insight into the mechanism, we have performed explicit-solvent molecular dynamics simulations (MD) for both bound and apo-TIS11dTZF to study the interdependence of binding and folding in the mRNA-TIS11dTZF complex. These results are in qualitative agreement with NMR experiment. Furthermore, this method could be used to other study about protein folding upon ligand binding.
Non-Markovian theory for the waiting time distributions of single electron transfers
Authors: Welack Sven , Yan YiJing
Published: September 2009

We derive a non-Markovian theory for waiting time distributions of consecutive single electron transfer events. The presented microscopic Pauli rate equation formalism couples the open electrodes to the many-body system, allowing to take finite bias and temperature into consideration. Numerical results reveal transient oscillations of distinct system frequencies due to memory in the waiting time distributions. Memory effects can be approximated by an expansion in non-Markovian corrections. This method is employed to calculate memory landscapes displaying preservation of memory over multiple consecutive electron transfers.
Slow kinetics of phase transformation in a dipole-functionalized discotic liquid crystal
Authors: Elmahdy Mahdy M. , Mondeshki Mihail , Dou Xi , Butt Hans-Jürgen , Spiess Hans W. , Müllen Klaus , Floudas George
Published: September 2009

The kinetics of phase transformation from the liquid crystalline mesophase to the crystalline phase has been studied in a model dipole-functionalized hexabenzocoronene derivative by x-ray diffraction, solid state NMR recoupling techniques, and dielectric spectroscopy. These probes revealed long-lived metastability and an intermediate state involving a change in the unit cell prior to crystallization. The barrier properties were dominant and amount to 1 and 2.5 eV, respectively, for the unit cell transformation and crystallization processes. These effects should be considered in the design of discotic liquid crystals for electronic applications.
Glass formation and structure in the MgSiO3–Mg2SiO4 pseudobinary system: From degraded networks to ioniclike glasses
Authors: Kalampounias A. G. , Nasikas N. K. , Papatheodorou G. N.
Published: September 2009

A series of glasses xMgO–(1−x)SiO2 with compositions from enstatite MgSiO3 (x=0.5) to forsterite Mg2SiO4 (x=0.667) in mole fraction intervals of x≈0.02 have been prepared by containerless levitation techniques and CO2 laser heating. Polarized and depolarized Raman spectra measured at ambient conditions for all these glasses show systematic and smooth band intensity changes with composition. Analysis of the Raman band contours in terms of vibrations due to different oxygen bridged SiO4 tetrahedra (Qi, species analysis) undoubtedly shows that bridging oxygens are present in all glasses studied even in the limit of the forsterite composition where bridged Si2O76− ionic dimers are formed. Furthermore the relative amounts of the Qi species change smoothly with composition while at high MgO content “free” oxygens are present presumably forming Mg–O–Mg bridges, which contribute to the glass stability at these compositions. Raman spectra measurements at different temperature below Tg show small alterations in the Qi species in the MgSiO3 region while no changes were observed in the Mg2SiO4 region. The Boson peak frequency is practically invariant on both composition and temperature and this is in contrast to the systematics followed by most silicate glasses. It is suggested that at compositions near the forsterite ioniclike glasses are formed arising from a very fragile liquid.
Photophysics and rotational relaxation dynamics of cationic phenazinium dyes in anionic reverse micelles: Effect of methyl substitution
Authors: Bose Debosreeta , Sarkar Deboleena , Girigoswami Agnishwar , Mahata Atanu , Ghosh Debanjana , Chattopadhyay Nitin
Published: September 2009

We present here, a detailed photophysical and rotational relaxation dynamical study of three structurally analogous cationic dyes, namely, phenosafranin (PSF), safranin-T (ST), and safranin-O (SO), carried out in well characterized, monodispersed biomimicking anionic reverse micellar nanocavities composed of sodium bis(2-ethylhexyl)sulfosuccinate (AOT)/heptane with increasing water contents. The dyes belong to the phenazinium family and they differ in terms of methyl substitution on the planar phenazinium skeleton. The objective of the present study is to investigate the modification in the photophysical and dynamical behavior of the dyes with the change in the size of the water pool of the reverse micelle and thereby to explore the role of methyl substitution. Steady state and time resolved emission and anisotropy studies have been exploited for the purpose. The dyes are found to exhibit a marked decrease in the fluorescence anisotropy with increasing water/surfactant mole ratio (w), i.e., the water pool size in the reverse micellar core, implying that overall motional restriction experienced by the molecules are decreased with increasing hydration. Some of the depth dependent fluorescence parameters such as fluorescence maximum, fluorescence anisotropy (r) have been monitored for exploring the microenvironment around the probes in the reverse micelles. Fluorescence studies suggest that at low w values, the probes do not penetrate into the reverse micellar core; rather it binds at the interfacial region. Estimates of the micropolarity at the binding sites of the probe molecule have been determined as a function of w. Finally, dynamic studies reveal that both the lifetime and rotational relaxation time decrease with an increase in w for all the three probes, the extent of the decrease being more for PSF than ST and SO. This indicates a stronger binding of the reverse micelle with ST and SO compared to that with PSF which is rationalized in terms of an increase in the hydrophobicity of the former two dyes because of the methyl substitution on the phenazinium moiety.
Primitive chain network simulations for entangled DNA solutions
Authors: Masubuchi Yuichi , Furuichi Kenji , Horio Kazushi , Uneyama Takashi , Watanabe Hiroshi , Ianniruberto Giovanni , Greco Francesco , Marrucci Giuseppe
Published: September 2009

Molecular theories for polymer rheology are based on conformational dynamics of the polymeric chain. Hence, measurements directly related to molecular conformations appear more appealing than indirect ones obtained from rheology. In this study, primitive chain network simulations are compared to experimental data of entangled DNA solutions [Teixeira et al., Macromolecules 40, 2461 (2007)]. In addition to rheological comparisons of both linear and nonlinear viscoelasticities, a molecular extension measure obtained by Teixeira et al. through fluorescent microscopy is compared to simulations, in terms of both averages and distributions. The influence of flow on conformational distributions has never been simulated for the case of entangled polymers, and how DNA molecular individualism extends to the entangled regime is not known. The linear viscoelastic response and the viscosity growth curve in the nonlinear regime are found in good agreement with data for various DNA concentrations. Conversely, the molecular extension measure shows significant departures, even under equilibrium conditions. The reason for such discrepancies remains unknown.
Defect-induced chemisorption of nitrogen oxides on (10,0) single-walled carbon nanotubes: Insights from density functional calculations
Authors: Tang Shaobin , Cao Zexing
Published: September 2009

The interactions of NOx (x=1,2,3) with the defective semiconducting (10,0) carbon nanotubes were studied by the density functional theory. Optimized geometries, binding energies, and electronic structures of the NOx-adsorbed nanotubes were determined on the basis of calculations. Effects of the defect density and the electric field on the binding energy and charge transfer have been investigated. In sharp contrast with the case of perfect nanotube, the adsorption of NOx at the defect site of (10,0) tube is generally chemical, and after the chemisorption of one NO2 or one NO3 the carbon nanotubes with various defects behave as conductors, while the consecutive adsorption of the second NO2 or the second NO3 makes these tubes become semiconductors again. Calculations show that the NO2 adsorption at a topological defect is a barrier-free process, while the NO3 adsorption experiences a barrier due to transition of the π↔s electronic configuration of the NO3 moiety.
The permanent electric dipole moments of cobalt monofluoride, CoF, and monohydride, CoH
Authors: Wang Hailing , Zhuang Xiujuan , Steimle Timothy C.
Published: September 2009

The optical Stark spectra of the R(4) and Q(4) lines of the [18.8]Φ34−X Φ34(0,0) band systems of cobalt monofluoride, CoF, and the A′ Φ34−X Φ34(0,0) band systems of cobalt monohydride, CoH, have been recorded using laser induced fluorescence technique. The shifts and splittings caused by the static electric field have been analyzed to give the permanent electric dipole moments, μe, of 4.51(5) and 2.82(5) D for the [18.8]Φ34 and X Φ34 states of CoF, and 0.01(8) and 1.88(8) D for the A′ Φ34 and X Φ34 states of CoH. The experimental dipole moments are compared with theoretical predictions. A molecular orbital correlation description is used to explain the relative ground state μe values for CoH and CoF.
Static and alternating electric field and distance-dependent effects on carbon nanotube-assisted water self-diffusion across lipid membranes
Authors: Garate José-Antonio , English Niall J. , MacElroy J. M. D
Published: September 2009

Water-self-diffusion through single-walled carbon nanotubes (SWCNTs) inserted normal to a phospholipid membrane has been studied using equilibrium and nonequilibrium molecular dynamics simulations in the presence of static and alternating electrical fields. Four different SWCNTs were investigated: (5,5), (6,6), (8,8), and (11,11) and also three arrays of four (6,6) SWCNTs separated by 15, 20, and 25 Å, respectively. The (5,5) system shows interesting behavior, where an increase in the applied field frequency in the z direction decreases the water permeation rates, reaching values at higher frequencies similar to zero-field conditions. The (6,6) arrays simulations demonstrated that there is a friction effect, when the nanotubes are closely packed, which retards the movement of the individual water files.
Phase transitions of a single polymer chain: A Wang–Landau simulation study
Authors: Taylor Mark P. , Paul Wolfgang , Binder Kurt
Published: September 2009

A single flexible homopolymer chain can assume a variety of conformations which can be broadly classified as expanded coil, collapsed globule, and compact crystallite. Here we study transitions between these conformational states for an interaction-site polymer chain comprised of N=128 square-well-sphere monomers with hard-sphere diameter σ and square-well diameter λσ. Wang–Landau sampling with bond-rebridging Monte Carlo moves is used to compute the density of states for this chain and both canonical and microcanonical analyses are used to identify and characterize phase transitions in this finite size system. The temperature-interaction range (i.e., T-λ) phase diagram is constructed for λ≤1.30. Chains assume an expanded coil conformation at high temperatures and a crystallite structure at low temperatures. For λ>1.06 these two states are separated by an intervening collapsed globule phase and thus, with decreasing temperature a chain undergoes a continuous coil-globule (collapse) transition followed by a discontinuous globule-crystal (freezing) transition. For well diameters λ<1.06 the collapse transition is pre-empted by the freezing transition and thus there is a direct first-order coil-crystal phase transition. These results confirm the recent prediction, based on a lattice polymer model, that a collapsed globule state is unstable with respect to a solid phase for flexible polymers with sufficiently short-range monomer-monomer interactions.
Strong double excitation and open-shell features in the near-edge x-ray absorption fine structure spectroscopy of ferrocene and ferrocenium compounds
Authors: Otero Edwige , Kosugi Nobuhiro , Urquhart Stephen G.
Published: September 2009

We have recorded the iron 2p and carbon 1s near-edge x-ray absorption fine structure (NEXAFS) spectra of decamethyl ferrocene (Fe 3d6) and ferrocenium hexafluorophosphate (Fe 3d5), two low spin compounds with closed- and open-shell electron configurations, respectively. These species have a similar covalent bonding environment but a different electron configuration, allowing us to examine the role of ligand-metal interactions and electron correlation responsible for their NEXAFS spectra. We have interpreted these spectra with the aid of ab initio configuration interaction (CI) calculations. The CI calculations indicate that double excitation is essential to interpret the Fe 2p NEXAFS spectra of not only the open-shell ferrocenium ion but also the closed-shell ferrocene species, even though the ground states of both species are well described within the Hartree–Fock single-configuration approximation.
Fragmentation patterns of doubly charged acrylonitrile molecule following carbon core ionization
Authors: Itälä E. , Kukk E. , Ha D. T. , Granroth S. , Caló A. , Partanen L. , Aksela H. , Aksela S.
Published: September 2009

Dissociation of acrylonitrile into pairs of cations and neutral fragments following molecular core ionization was investigated using the photoelectron-photoion-photoion coincidence (PEPIPICO) technique. The fragment ion mass spectra were recorded in coincidence with the carbon 1s photoelectrons. Deuterated and C13-substituted samples were used for resolving fragment mass ambiguities. Slope analysis of the PEPIPICO patterns was used in determining the fragment separation sequences in case of multiparticle processes. The results show that there are several fragmentation channels producing a wide range of charged coincident fragments. The dynamics of the dominant fragmentation processes is investigated in detail.
Heavy atom nitroxyl radicals. I: An ab initio study of the ground and lower electronic excited states of the H2As=O free radical
Authors: Tarroni Riccardo , Clouthier Dennis J.
Published: September 2009

A series of ab initio calculations have been undertaken to predict the spectroscopic properties of the ground and first two excited states of the recently discovered arsenyl (H2AsO) free radical. This 13 valence electron species can be viewed as similar to the formaldehyde radical anion with a ground state electron configuration of ⋯(π)2(n)2(π∗)1. The arsenyl radical is nonplanar (pyramidal) in the ground state with a 59° out-of-plane angle and a 1.67 Å AsO bond length. It has a low-lying n-π∗(Ã A2″) excited state (Te∼5000 cm−1) which has a much larger out-of-plane angle (86°) and longer AsO bond length (1.81 Å). The π-π∗(B̃ A2′) excited state at ∼20 500 cm−1 is less pyramidal (out-of-plane angle=70°) and has a somewhat shorter AsO bond (1.77 Å). Similar trends are found for the H2PO and H2NO free radicals, although the latter has a planar ground state, due to sp2 hybridization of the N atom, and a very long B̃ state AsO bond length. The geometric variations of the ground and excited states of the H2EO (E=N, P, As) radicals, as well as the ground states of the corresponding anions and cations, can be readily rationalized from the Walsh diagram of the anion. The variations in the E-O bond length are a result of changes in both the orbital occupancy and pyramidalization of the molecule. The results of the present work have been employed in the analysis of the B̃ A2′-X̃ A2′ electronic band system of the H2AsO free radical as reported in the companion paper.
Perturbative triples correction for the equation-of-motion coupled-cluster wave functions with single and double substitutions for ionized states: Theory, implementation, and examples
Authors: Manohar Prashant U. , Stanton John F. , Krylov Anna I.
Published: September 2009

A noniterative N6 triples energy correction is presented for the equation-of-motion coupled-cluster method with single and double substitutions for ionized states (EOM-IP-CCSD). The correction, which is size intensive, is derived using a second-order Rayleigh–Schrödinger perturbative treatment and is similar to the approach of Stanton and Gauss [Theor. Chim. Acta 93, 303 (1996)]. In the present implementation, only the target EOM-IP states are corrected, and the reference state is described by CCSD; the method is therefore more useful for the study of the target states themselves than ionization potentials. The performance of the correction, which demonstrates the caveat above, is demonstrated by applications to singlet methylene, BNB−, nitrogen, carbon monoxide, acetylene, benzene, thymine, and adenine.
Vibration-induced inelastic effects in the electron transport through multisite molecular bridges
Authors: Zimbovskaya Natalya A. , Kuklja Maija M.
Published: September 2009

We theoretically analyzed inelastic effects in the electron transport through molecular junctions originating from electron-vibron interactions. The molecular bridge was simulated by a periodical chain of identical hydrogenlike atoms with the nearest neighbors interaction thus providing a set of energy states for the electron tunneling. To avoid difficulties inevitably arising when advanced computational techniques are employed to study inelastic electron transport through multilevel bridges, we propose and develop a semiphenomenological approach. The latter is based on Buttiker’s dephasing model within the scattering matrix formalism. We apply the proposed approach to describe features associated with electron energy transfer to vibrational phonons that appear in the second derivative of the current in the junction with respect to the bias voltage. In the particular case of a single level bridge our results agree with those obtained by proper calculations carried out within the nonequilibrium Green’s functions method indicating the usefulness of the suggested approach.
Full-electron calculation of effective electronic couplings and excitation energies of charge transfer states: Application to hole transfer in DNA π-stacks
Authors: Migliore Agostino
Published: September 2009

In this work I develop and apply a theoretical method for calculating effective electronic couplings (or transfer integrals) between redox sites involved in hole or electron transfer reactions. The resulting methodology is a refinement and a generalization of a recently developed approach for transfer integral evaluation. In fact, it holds for any overlap between the charge-localized states used to represent charge transfer (CT) processes in the two-state model. The presented theoretical and computational analyses show that the prototype approach is recovered for sufficiently small overlaps. The method does not involve any empirical parameter. It allows a complete multielectron description, therefore including electronic relaxation effects. Furthermore, its theoretical formulation holds at any value of the given reaction coordinate and yields a formula for the evaluation of the vertical excitation energy (i.e., the energy difference between the adiabatic ground and first-excited electronic states) that rests on the same physical quantities used in transfer integral calculation. In this paper the theoretical approach is applied to CT in B-DNA base dimers within the framework of Density Functional Theory (DFT), although it can be implemented in other computational schemes. The results of this work, as compared with previous Hartree–Fock (HF) and post-HF evaluations, support the applicability of the current implementation of the method to larger π-stacked arrays, where post-HF approaches are computationally unfeasible.
Density-functional study of structural, electronic, and magnetic properties of the EuSin (n=1–13) clusters
Authors: Zhao Gao-feng , Sun Jian-min , Gu Yu-zong , Wang Yuan-xu
Published: September 2009

The geometries, stabilities, and electronic and magnetic properties of europium encapsulated EuSin (n=1–13) clusters have been investigated systematically by using relativistic density functional theory with generalized gradient approximation. Starting from n=12, the Eu atom completely falls into the center of the Si frame, i.e., EuSi12 is the smallest fully endohedral Eu silicon cluster. The interesting finding is in good agreement with the recent experimental results on the photoelectron spectroscopy of the europium silicon clusters [A. Grubisic, H. P. Wang, Y. J. Ko, and K. H. Bowen, J. Chem. Phys. 129, 054302 (2008)]. The magnetic moments of the EuSin (n=1–13) clusters are also studied, and the results show that the total magnetic moments of the EuSin clusters and the magnetic moments on Eu do not quench when the Eu is encapsulated in the Si outer frame cage. It is concluded that most of the 4f electrons of the Eu atom in the EuSi12 cluster do not interact with the silicon cage and the total magnetic moments are overwhelming majority contributed by the 4f electrons of the Eu atom. According to the binding energy per atom, the second difference in energy (Δ2E), and vertical ionization potential, the EuSin (n=4,9,12) clusters are very stable.
The shapes of H-comb polymers
Authors: Zweier Steven , Bishop Marvin
Published: September 2009

The Monte Carlo pivot algorithm is employed to investigate the shapes of continuum, tangent hard sphere H-comb polymers in both the ideal and excluded volume regimes. Polymers with a number of units ranging from 241 to 931 have been simulated. It is found that the extrapolated asphericity values are in excellent agreement with theory in the ideal regime and that, somewhat, higher values occur in the excluded volume regime.
Artificial neural network approach for modeling the impact of population density and weather parameters on forest fire risk
Authors: Li Li-Ming , Song Wei-Guo , Ma Jian , Satoh Kohyu
Published: September 2009

The risk of forest fire occurrence is affected by the interactions among forest fuels, weather, human activities, etc. In the present paper, we try to build a method to model and forecast forest fire risk based on artificial neural networks. The data considered include population density and several weather parameters, i.e. average relative humidity, wind velocity and daily sunshine hours. With an interpolation method, these data have been expanded into 1 by 1 km meshes that are calculated according to the standard mesh code system in Japan, where the Japanese territory is divided into a lattice by latitude and longitude. Different parameter combinations and corresponding fire probabilities are computed. The correlations between forest fire probability and population density, and sequentially that between forest fire probability and combinations of population density together with one or several weather parameters are analyzed with three back-propagation neural networks in comparison with polynomial regression investigations. The results indicate that non-linear relationships exist among the influential factors and forest fire probability; artificial neural networks could better capture the non-linearity and give closer results to the test set compared with polynomial regression. The proposed method may be used to investigate and forecast forest fire risk providing there are enough data.
Ground-based LIDAR: a novel approach to quantify fine-scale fuelbed characteristics
Authors: Loudermilk E. Louise , Hiers J. Kevin , O'Brien Joseph J. , Mitchell Robert J. , Singhania Abhinav , Fernandez Juan C. , Cropper Wendell P. , Slatton K. Clint
Published: September 2009

Ground-based LIDAR (also known as laser ranging) is a novel technique that may precisely quantify fuelbed characteristics important in determining fire behavior. We measured fuel properties within a south-eastern US longleaf pine woodland at the individual plant and fuelbed scale. Data were collected using a mobile terrestrial LIDAR unit at sub-cm scale for individual fuel types (shrubs) and heterogeneous fuelbed plots. Spatially explicit point-intercept fuel sampling also measured fuelbed heights and volume, while leaf area and biomass measurements of whole and sectioned shrubs were determined from destructive sampling. Volumes obtained by LIDAR and traditional methods showed significant discrepancies. We found that traditional means overestimated volume for shrub fuel types because of variation in leaf area distribution within shrub canopies. LIDAR volume estimates were correlated with biomass and leaf area for individual shrubs when factored by species, size, and plant section. Fuelbed heights were found to be highly variable among the fuel plots, and ground LIDAR was more sensitive to capturing the height variation than traditional point intercept sampling. Ground LIDAR is a promising technology capable of measuring complex surface fuels and fuel characteristics, such as fuel volume.
The fire history of an arid grassland: the influence of antecedent rainfall and ENSO
Authors: Greenville Aaron C. , Dickman Chris R. , Wardle Glenda M. , Letnic Mike
Published: September 2009

Implementing appropriate fire regimes has become an increasingly important objective for biodiversity conservation programs. Here, we used Landsat imagery from 1972 to 2003 to describe the recent fire history and current wildfire regime of the north-eastern Simpson Desert, Australia, within each of the region’s seven main vegetation classes. We then explored the relationship between antecedent rainfall and El Niño–Southern Oscillation with wildfire area. Wildfires were recorded in 11 years between 1972 and 2003, each differing in size. In 1975, the largest wildfire was recorded, burning 55% (4561 km2) of the study region. Smaller fires in the intervening years burnt areas that had mostly escaped the 1975 fire, until 2002, when 31% (2544 km2) of the study region burnt again. Wildfires burnt disproportionally more spinifex (Triodia basedowii) than any other vegetation class. A total of 49% of the study area has burnt once since 1972 and 20% has burnt twice. Less than 1% has burnt three times and 36% has remained unaffected by wildfire since 1972. The mean minimum fire return interval was 26 years. Two years of cumulative rainfall before a fire event, rainfall during the year of a fire event, and the mean Southern Oscillation Index from June to November in the year before a fire event could together be used to successfully predict wildfire area. We use these findings to describe the current fire regime.
A model for calculating the temperature of aluminium particles ejected from overhead low-voltage lines owing to a short-circuit
Authors: Psarros E. G. , Polykrati A. D. , Karagiannopoulos C. G. , Bourkas P. D.
Published: September 2009

Wildfires, which are uncontrolled fires spreading readily over vast areas, are usually the result of human negligence, arson or lightning. There are cases of fires close to electrical distribution lines for which the network has been blamed. In the present paper, the risk of a wildfire breaking out owing to the temperature of molten metal particles that are possibly created on bare conductors of low-voltage networks in short-circuit faults (unless they are interrupted by the protection systems) is examined. Thus, a mathematical model is proposed for the estimated temperature rise of those molten metal particles ejected from bare conductors of low-voltage overhead lines. Moreover, this model can be applied to medium- or high-voltage networks. The model takes into account the weather conditions and particles’ height above the ground. Further, an arithmetic example for an incandescent particle ejected from aluminium conductors of a low-voltage network is given. According to this example, there is no risk of dead leaves or wood catching fire owing to this particle.
Disengagement of the deeply engaged fetal head during cesarean section in advanced labor: Conventional method versus reverse breech extraction
Authors: CHOPRA SEEMA , BAGGA RASHMI , KEEPANASSERIL ANISH , JAIN VANITA , KALRA JASVINDER , SURI VANITA
Published: September 2009

Maternal and fetal morbidity of two different methods of delivering the baby during cesarean section performed in advanced labor when the fetal head is deeply engaged was assessed retrospectively, i.e. delivering as ‘cephalic’ with or without assistance to push up the fetal head from the vagina (head first or push method) and ‘reverse breech extraction’ (feet first or pull method). Records of 182 women with a single fetus in cephalic presentation, who had undergone cesarean section at cervical dilatation at ≥7 cm, with the vertex at or below zero station, were reviewed. Extension of the uterine incision occurred in significantly more women during ‘cephalic’ delivery as compared to ‘reverse breech extraction’ (22.8% versus 2.2%; p = 0.001). Use of ‘reverse breech extraction’ is an attractive and safe alternative to the standard methods for intra‐operative disengagement of a deeply impacted fetal head in order to reduce maternal and fetal morbidity.
Adolescent idiopathic scoliosis may not be associated with brain abnormalities
Authors: Lee Jung Sub , Kim Seong-Jang , Suh Kuen Tak , Kim In Joo , Kim Yong-Ki
Published: September 2009

Background: The etiology of adolescent idiopathic scoliosis (AIS) is uncertain and multifactorial. Recently, regional brain volume differences have been reported in the pathogenesis of AIS.

Purpose: To examine cerebral glucose metabolism using 18F-fluorodeoxyglucose (FDG) brain positron emission tomography (PET) in patients with AIS and in gender-matched healthy control subjects.

Material and Methods: Twenty-six right-handed AIS patients (six male, 20 female; mean age 14.6±2.22 years, range 11–18 years) were prospectively recruited for this study. Fourteen young adults (three male, 11 female; mean age 27±1.54 years, range 25–29 years) were included as a control group. Statistical parametric mapping (SPM) was used to determine cerebral glucose metabolism. Statistical probabilistic anatomical mapping (SPAM) was used to investigate the metabolic differences between AIS and normal control subjects with respect to previously reported brain areas.

Results: SPM analysis showed no voxels with differing cerebral glucose metabolism in AIS patients. SPAM analysis revealed no significant differences between AIS and normal control subjects.

Conclusion: SPM and SPAM analyses showed no statistically significant differences in cerebral glucose metabolism between AIS and normal control subjects. These results may suggest that there is no relationship between AIS and brain abnormalities.
Book Reviews
Authors: Smith Hans-Jørgen
Published: September 2009

Cardiac Imaging - A Multimodality Approach. Edited by M. Thelen, R. Erbel, K.-F. Kreitner, & J. Barkhausen. Stuttgart/New York: Thieme, 2009. ISBN 978-3-13-147781-1. 289 pages/608 illustrations. Price (hardback): EUR 149.95
Magnetic resonance imaging findings of ovarian stromal hyperthecosis
Authors: Fujii S. , Kiyokawa T. , Tsukihara S. , Senda T. , Tahara T. , Kaminou T. , Ogawa T.
Published: September 2009

Ovarian stromal hyperthecosis is characterized by diffuse distribution of luteinized stromal cells accompanied by varying degrees of stromal hyperplasia. We report a case of ovarian stromal hyperthecosis with particular regard to magnetic resonance (MR)–pathologic correlation. At initial MR imaging, the central areas of the bilateral ovarian masses showed hypointensity on T1-weighted images and hyperintensity on T2-weighted images, while the peripheries of the bilateral masses showed isointensity to myometrium on T1-weighted images and heterogeneous signal intensities on T2-weighted images. At 15 days after the initial MR imaging examination, a second MR imaging demonstrated shrinkage of the bilateral ovarian masses. Change in the peripheries to predominantly isointensity to myometrium on the T2-weighted images was also observed. The patient underwent bilateral oophorectomy. Microscopic examination revealed scattered nests of lutein cells on a background of densely proliferated ovarian stroma with minimal collagen production in both ovaries. Edema was occasionally seen in the outer portion but was marked in the central zone of the ovaries, particularly on the left. The final pathologic diagnosis was stromal hyperthecosis. With regard to MR–pathologic correlation, the MR findings in the peripheries of the bilateral masses (isointensity relative to myometrium on both T1- and T2-weighted imaging) showed the characteristics of stromal hyperthecosis.