bluuebunny/crossref_metadata_2025 huggingface dataset:
CHAPTER 7 Methods for detection of HPV infection and its clinical utility
Authors: Villa Luisa Lina , Denny Lynette
Published: February 2007

HPVs cannot be cultured and the detection of virus relies on a variety of techniques used in immunology, serology, and molecular biology. Currently the only FDA‐approved commercially available method for the detection of HPV DNA is the Hybrid Capture assay, version hc2 (Digene, Gaithersburg, MD, USA) which is able to detect 13 high‐risk types of HPV. The advantage of PCR‐based methods of HPV DNA detection is that they allow for the identification of different types of HPV. This article discusses the advantages and disadvantages of the different methods of HPV DNA detection. HPV DNA testing can be used in a variety of clinical scenarios that include a primary screening test, particularly in women older than 30 years;as an adjunctive test to cytology;to triage women who have an equivocal cytologic finding, e.g., ASC‐US, or for follow up post‐treatment. In addition, HPV DNA testing can be performed on samples obtained by women themselves (so‐called self‐sampling), which may be useful in women who are resistant to undergoing gynecologic examinations.
CHAPTER 10 A public health approach to cervical cancer control: Considerations of screening and vaccination strategies
Authors: Goldie Sue
Published: February 2007

Cervical cancer remains a leading cause of cancer death among women living in low‐resource settings. In the last 3 decades, cytologic screening has —in theory —been available and yet more than 6 million women have died of this preventable disease. The necessary resources, infrastructure, and technological expertise, together with the need for repeated screenings at regular intervals, make cytologic screening difficult to implement in poor countries. As noncytologic approaches for the detection of HPV, simple visual screening methods for anogenital lesions caused by HPV, and the availability of an HPV‐16/18 vaccine will enhance the linkage between screening and treatment, multiple factors will need to be considered when designing new, or modifying existing prevention strategies. Countryspecific decisions regarding the best strategy for cervical cancer control will need to rely on data from many sources and take into account complex epidemiologic, economic, social, political, and cultural factors, and be made despite uncertainty and incomplete information. A rigorous decision analytic approach using computerbased modeling methods enables linkage of the knowledge gained from empirical studies to real‐world situations. This chapter provides an introduction to these methods, reviews lessons learned from cost‐effectiveness analyses of cervical cancer screening in developed and developing countries, and emphasizes important qualitative themes to consider in designing cervical cancer prevention policies.
Vaccination against ectoparasites
Authors: WILLADSEN P.
Published: February 2007

Ectoparasites of livestock are of great economic and social importance but their effective control remains difficult. The feasibility of vaccination as a novel control measure was established over a decade ago with the commercial release of a recombinant vaccine against the cattle tickBoophilus microplus. Since then, research has continued on ticks and other ectoparasites. While some ectoparasite species will undoubtedly be refractory to immunological control, for others there has been a steady accumulation of knowledge of partially protective antigens, now accelerating through the application of genomic technologies. Nevertheless, progress towards usable, commercially available vaccines has been limited by a number of factors. The number of highly effective antigens is still very small. Although some classes of antigen have been investigated in more detail than others, we have no systematic knowledge of what distinguishes an effective antigen. Much hope has been placed on the potential of multi-antigen mixtures to deliver the efficacy required of a successful vaccine but with little experimental evidence. The application of current knowledge across parasite and host species needs to be explored but little has been done. In most cases, the path to commercial delivery is uncertain. Although many constraints and challenges remain, the need for vaccines and our capacity to develop them can only increase.
Cestode vaccines: origins, current status and future prospects
Authors: LIGHTOWLERS M. W.
Published: February 2007

Recombinant vaccines have been developed which are highly effective in preventing infection with Taenia ovis in sheep, Taenia saginata in cattle, Taenia solium in pigs and Echinococcus granulosus in livestock animals. T. ovis and T. saginata are economically significant parasites and the commercial success or otherwise of vaccines against them will rely on their economic value. E. granulosus and T. solium are zoonotic parasites that cause cystic hydatid disease and neurocysticercosis, respectively, in humans. Vaccines against these parasites have been developed to assist with the control of transmission of the human diseases rather than for prevention of infections in livestock per se. Regions of high prevalence for cystic hydatid disease and neurocysticercosis occur primarily in the developing world. As a consequence, vaccines against them are of little or no commercially interest – they are Orphan Vaccines. Lack of commercial interest in these vaccines has made public sector support for their development necessary well beyond the research phase trough into completion of commercial scale-up and other more commercially-related assessments. Practical use of the vaccines will require commercial-scale production according to international manufacturing standards. Identifying partners and support in this endeavour is now of prime importance in efforts to achieve the potential of these vaccines as new tools for the control of cystic hydatid disease and neurocysticercosis.
High road, low road? Choices and challenges on the pathway to a malaria vaccine
Authors: RICHIE T.
Published: February 2007

Malaria causes much physical and economic hardship in endemic countries with billions of people at risk. A vaccine would clearly benefit these countries, reducing the requirement for hospital care and the economic impact of infection. Successful immunization with irradiated sporozoites and the fact that repeated exposure to malaria induces partial immunity to infection and high levels of protection against the clinical manifestations, suggest that a vaccine is feasible. Numerous candidate antigens have been identified but the vaccine, which has been promised to be ‘just round the corner’ for many years, remains elusive. The factors contributing to this frustratingly slow progress are discussed including gaps in the knowledge of host/parasite biology, methods to induce potent cell-mediated immune responses, the difficulties associated with defining immune correlates of protection and antigen production and delivery. Finally, the use of attenuated organism vaccines is discussed.
Vaccination as a control strategy against the coccidial parasitesEimeria,ToxoplasmaandNeospora
Authors: INNES E. A. , VERMEULEN A. N.
Published: February 2007

The protozoan parasitesEimeriaspp.Toxoplasma gondiiandNeospora caninumare significant causes of disease in livestock worldwide andT. gondiiis also an important human pathogen. Drugs have been used with varying success to help control aspects of these diseases and commercial vaccines are available for all three groups of parasites. However, there are issues with increasing development of resistance to many of the anti-coccidial drugs used to help control avian eimeriosis and public concerns about the use of drugs in food animals. In addition there are no drugs available that can act against the tissue cyst stage of eitherT. gondiiorN. caninumand thus cure animals or people of infection. All three groups of parasites multiply within the cells of their host species and therefore cell mediated immune mechanisms are thought to be an important component of host protective immunity. Successful vaccination strategies for bothEimeriaandToxoplasmahave relied on using a live vaccination approach using attenuated parasites which allows correct processing and presentation of antigen to the host immune system to stimulate appropriate cell mediated immune responses. However, live vaccines can have problems with safety, short shelf-life and large-scale production; therefore there is continued interest in devising new vaccines using defined recombinant antigens. The major challenges in devising novel vaccines are to select relevant antigens and then present them to the immune system in an appropriate manner to enable the induction of protective immune responses. With all three groups of parasites, vaccine preparations comprising antigens from the different life cycle stages may also be advantageous. In the case ofEimeriaparasites there are also problems with strain-specific immunity therefore a cocktail of antigens from different parasite strains may be required. Improving our knowledge of the different parasite transmission routes, host-parasite relationships, disease pathogenesis and determining the various roles of the host immune response being at times host-protective, parasite protective and in causing immunopathology will help to tailor a vaccination strategy against a particular disease target. This paper discusses current vaccination strategies to help combat infections withEimeria,ToxoplasmaandNeosporaand recent research looking towards developing new vaccine targets and approaches.
Ozonolysis of α‐pinene at atmospherically relevant concentrations: Temperature dependence of aerosol mass fractions (yields)
Authors: Pathak Ravi K. , Stanier Charles O. , Donahue Neil M. , Pandis Spyros N.
Published: February 2007

Despite a number of smog chamber studies of the α‐pinene/O3 system, the effect of temperature on α‐pinene secondary organic aerosol (SOA) mass fractions (or yields) remains poorly understood. In this study, the temperature dependence of secondary organic aerosol mass fractions (AMF) during ozonolysis of α‐pinene is investigated in a temperature controlled smog chamber. Experiments were performed with and without ammonium sulfate aerosol seeds at RH < 10% and at 0°C, 15°C, 20°C, 30°C and 40°C. The initial α‐pinene concentration varied from 3.5 to 50 ppb, and an excess of ozone was used. High time resolution secondary organic AMFs were obtained combining continuous gas‐phase concentration measurements (using proton transfer reaction mass spectrometry, PTR‐MS) with continuous aerosol concentration measurements (using a scanning mobility particle sizer, SMPS). The presence of inert aerosol seeds is often necessary to minimize experimental errors due to loss of semivolatile vapors to the walls of the chamber. The α‐pinene secondary organic AMFs show a weak dependence on temperature in the 15° to 40°C range and stronger temperature dependence in the 0° and 15°C range.
Effects of lymphotoxin-α gene and galectin-2 gene polymorphisms on inflammatory biomarkers, cellular adhesion molecules and risk of coronary heart disease
Authors: Asselbergs Folkert W. , Pai Jennifer K. , Rexrode Kathryn M. , Hunter David J. , Rimm Eric B.
Published: February 2007

The pro-inflammatory cytokine LTA (lymphotoxin-α) has multiple functions in regulating the immune system and may contribute to inflammatory processes leading to CHD (coronary heart disease). The aim of the present study was to investigate whether the common C804A (resulting in a Thr26→Asp amino acid substitution) and A252G polymorphisms of the LTA gene and the C3279T polymorphism of the galectin-2 (LGALS2) gene, which affects LTA secretion, are associated with inflammatory parameters and cell adhesion molecules, and whether these polymorphisms are related to CHD in American women and men. We conducted a prospective nested case-control study within the Nurses' Health Study and Health Professionals Follow-Up Study. Among participants free of cardiovascular disease at baseline, 249 women and 266 men developed CHD during 8 and 6 years of follow-up respectively, and we matched controls 2:1 based on age and smoking. The LGALS2 gene variant was significantly associated with a decreased risk of CHD in women [odds ratio (95% confidence interval), 0.70 (0.50–0.97); P=0.03]. In addition, the LGALS2 polymorphism was directly associated with CRP (C-reactive protein) levels in cases from both studies (P<0.05). The LTA gene polymorphisms were directly associated with levels of sTNFRs (soluble tumour necrosis factor receptors) and VCAM-1 (vascular cell adhesion molecule-1) in both women and men with CHD (P<0.05). However, no overall effect was demonstrated between LTA gene polymorphisms and risk of CHD.
Data Protection in the Pharmaceutical Industry
Authors: Ranson Paul
Published: February 2007

In relation to the development of medicinal products within Europe, the European Commission seeks to strike a balance between the encouragement of innovation and the avoidance of unnecessary research. This balance is supposedly represented by the rules that afford research-based companies a degree of protection against the use by the authorities assessing subsequent applications, of data submitted in support of the application made by the innovator. This paper reviews these rules as they presently stand, how the European Court of Justice (ECJ) and the national courts have interpreted the many ‘grey areas’ in such rules and the proposals for change for the current regime within the overall review of pharmaceutical regulatory rules to be implemented in time for the enlargement of the Community in early 2004
Protection and Challenge of Pharmaceutical Patents
Authors: Mándi Attila
Published: February 2007

Recent trends of patent enforcement in the pharmaceutical industry are discussed with particular reference to chemical process patents, formulation patents, patented salts and derivatives, polymorph patents, second indication inventions, metabolite patents and dosage regimen patents.

The basic principles of patent rights are summarised and practical recommendations are disclosed on the patentability, enforceability and invalidation of the patent types discussed above.

Some tactical advice is presented for generics companies on how to endeavour to avoid patent conflicts and what to do in case of an infringement suit. The importance of patenting the R&D results of generic companies, in terms of the creation of chemical and biological generic products, is emphasised.
Utilisation of Generic Medicines in the Australian Healthcare System
Authors: Hassali Mohamed Azmi , Kong David C. M. , Stewart Kay
Published: February 2007

Generic medicines have a key role to play in the efficient allocation of financial resources for pharmaceutical medicines. In Australia, the current utilisation of generic medicines is comparatively low compared with other Organization for Economic Co-operation and Development countries. This paper discusses the current issues and problems relating to the use of generic medicines in Australia and the role they play in the Pharmaceutical Benefits Scheme, which is a comprehensive system for subsidy of prescription drugs covering the whole population.
Scientific Issues for Biogenerics/Biosimilars
Authors: Roth Robert I. , Fleischer Nicholas M.
Published: February 2007

Recent changes in perspective at the US Food and Drug Administration and in the EU have clearly indicated a commitment to an abbreviated development and regulatory pathway for follow-on biological drugs (or biogenerics). This process has been discussed only in fairly abstract terms, however, and definitions and concrete requirements that could guide manufacturers of these products with regard to data requirements for an abbreviated submission are still needed. The aim of this paper is to summarise some of the critical scientific issues that will have an impact on the development of programmes for biogenerics. This paper discusses in some detail the likely necessity for developers of biogenerics to chemically and structurally characterise both their own follow-on product as well as the innovator's product in order to demonstrate a sufficient level of biosimilarity. Issues related to the characterisation of a biogeneric's biological activity are discussed, as are issues related to toxicity risks. It is the authors' belief that the term ‘biosimilar’, as opposed to the high level of required structural identity between a generic chemical drug and its innovative product, best describes the nature of follow-on biologics that would qualify for expedited development. Interpreting the clinical importance of demonstrated dissimilarities between innovator and biosimilar products is likely to be the greatest challenge for manufacturers of biogenerics, with requirements for human clinical testing being decided by regulatory agencies on a case by case basis.
Assessing the Economics of Biogenerics
Authors: Greuel Joachim M.
Published: February 2007

Investment in the development of biogenerics is frequently seen as a means to escape the intense price competition that characterises the generics market. As the costs of goods sold are much higher for biopharmaceuticals than for synthetic, small molecule drugs, however, and successful market penetration may be more difficult to achieve, economic profitability is not guaranteed. One way to avoid unpleasant surprises is to invest early in the development of economic models that allow decision makers to understand the risks, rewards and sensitivities of the biogenerics business before significant investments are committed. As pricing will be decisive for commercial success or failure, careful pricing studies, such as conjoint analyses, are suggested.
Agony in the Antipodes: The Generic Drug Provisions of the Australia-USA Free Trade Agreement
Authors: Outterson Kevin
Published: February 2007

The Australia–USA Free Trade Agreement (AUSFTA), which entered into force on 1st January, 2005, contains many remarkable provisions of interest to generic drug companies. The AUSFTA selectively exports US generic drug laws of great import to generic drug manufacturers, and is uniquely intrusive into domestic pharmaceutical and political spheres. The AUSFTA is important both in its own right, and as a model for future US free trade agreement negotiations.
Comprehensive Characterisation of the Innovator Product: Targeting Bioequivalent Generics
Authors: Koradia Vishal S. , Chawla Garima , Bansal Arvind K.
Published: February 2007

Generic products are cost effective and speedy surrogates for high-priced innovator/branded products. The prerequisite for the development of a generic product is therapeutic equivalence (comprising pharmaceutical equivalence and bioequivalence) to the innovator product, thus ensuring comparable efficacy and safety profile. The probability of successfully developing a bioequivalent product can be improved by developing a formulation equivalent to the reference listed drug (RLD), in terms of the quantitative, solid-state characteristics of the active pharmaceutical ingredient (API) and the manufacturing process. This can be achieved by a systematic and thorough characterisation of the RLD. The present study was aimed at developing a methodology for characterisation of ranitidine hydrochloride tablets, with special emphasis on the solid-state characterisation of the API in the tablet.

A differential solubility method was employed for the separation and quantification of excipients present in the tablet. Solid-state properties were characterised using a range of microscopic, thermal, spectroscopic and crystallographic techniques. In addition, results were confirmed by preparing inhouse tablets of the polymorphic forms I and II, using the decoded quantitative formula.
New Incentives for SMEs: Life Made Easier for Small Manufacturers in Europe
Authors: Rossignol Nicolas
Published: February 2007

Small and medium-sized enterprises (SMEs) are at the core of the European Commission competitiveness policy. With the entering into force of the latest revision of the European pharmaceutical legislation, new regulatory provisions have been laid down to help these small but dynamic players when dealing with the so-called centralised marketing authorisation procedure and the European Medicines Agency (EMEA). The new incentives address both financial and administrative aspects, such as fee reductions and deferrals for a number of EMEA services, handling of translations, and the establishment of a dedicated SME Office within the Agency. In this paper we explore the newly established regulation and the various provisions to analyse its implications for SMEs in general and generic manufacturers in particular. We also review the underlying assumptions, especially the Community SME definition, and discuss the policy objectives that led to the establishment of this new piece of legislation.
Is Europe Ahead of the USA in Biosimilars?
Authors: DiCicco Richard L.
Published: February 2007

This article is about a race between the USA and Europe in biosimilars. The race can be defined in several ways: the first launch of a biosimilar; the first cross-border use of a biosimilar in the USA or Europe which was approved in a neighbouring country; the greatest value or profits of biosimilars in 2004; the first legal provision for an abbreviated regulatory pathway applied in a consistent and continued manner; and the race for interchangeability or substitution of biosimilars for reimbursement, a race that is just beginning. The USA has won three of the five races, first-launch, first cross-border use and greatest value of biosimilars according to 2004 sales, but Europe is ahead in the most important race: the application of a consistent and continued regulatory pathway. This paper provides the race results and looks at the race for biosimilar regulatory pathways. Once the regulatory pathway is applied by governments in a consistent and continued manner and many biosimilars are launched, the race begins for interchangeability that affects physician prescribing and generic substitution. Biosimilar interchangeability and subsequent biopharmaceutical affordability, is the ultimate prize for the real winners of the race: the patients.
First-principles calculation of interaction between interstitial O and As dopant in heavily As-doped Si
Authors: Lu Guang-Hong , Wang Q. , Liu Feng
Published: February 2007

We investigate the interaction between interstitial oxygen (Oi) and As dopant in heavily As-doped Si using first-principles total-energy calculations. The interaction between Oi and As (substitutional) is found to be short ranged. The most stable configuration is with As and Oi as second nearest neighbors, forming –Si–O–Si–As– type complexes, with a binding energy of 0.14–0.21eV. These complexes can trap Oi in their vicinity and thus reduce the Oi mobility. But the magnitude of trapping energy by such complexes is about fives times smaller than the value estimated from the experimentally observed retardation of Oi diffusion in heavily As-doped Si. We suggest that structural complexes involving other defects may resolve this discrepancy.
Double elliptic equation method and new exact solutions of the (n+1)-dimensional sinh-Gordon equation
Authors: Chen Huaitang , Yin Huicheng
Published: February 2007

The double elliptic equation method is presented for constructing exact traveling wave solutions of nonlinear partial differential equations. With the aid of Maple, more new exact solutions are obtained for the (n+1)-dimensional sinh-Gordon equation. These solutions contain logarithmic functions, Jacobi elliptic functions, hyperbolic functions, trigonometric functions, and their combinations.
The influence of annihilation processes on the threshold current density of organic laser diodes
Authors: Gärtner Christian , Karnutsch Christian , Lemmer Uli , Pflumm Christof
Published: February 2007

We examine the impact of various annihilation processes on the laser threshold current density of a multilayer organic laser diode by numerical simulation. Our self-consistent numerical model treats the dynamics of electrons, holes, and singlet as well as triplet excitons in the framework of a drift-diffusion model. The resulting particle distributions enter into an optical model. In our approach, a three layer waveguide structure is taken into account and the resulting laser rate equations are solved. Various annihilation processes are included as reactions between the different particle species in the device employing typical annihilation rates and material properties of organic semiconductors. By systematically varying the device dimensions and the annihilation rate coefficients, the dominating quenching processes are identified. The threshold current density is found to depend sensitively on the thickness of the emission layer. The influence of annihilation processes on the threshold current density is quantified as a function of the emission layer thickness and various annihilation rate coefficients. Using typical annihilation rate coefficients singlet-polaron annihilation is found to be the dominating quenching process. Maximum annihilation rate coefficients are calculated allowing a threshold current density below 1kA∕cm2. Singlet-triplet annihilation is recognized as another main loss process for singlet excitons. In our model the singlet exciton density is increased by triplet-triplet annihilation whereas it is diminished by singlet-triplet annihilation. The ratio of the rate coefficients for singlet-triplet and triplet-triplet annihilations is identified to be critical for the total number of singlet excitons being quenched by triplet excitons.
Temperature-dependent electrical characteristics of bulk GaN Schottky rectifier
Authors: Zhou Yi , Wang Dake , Ahyi Claude , Tin Chin-Che , Williams John , Park Minseo , Williams N. Mark , Hanser Andrew , Preble Edward A.
Published: February 2007

The temperature-dependent electrical characteristics of Schottky rectifiers fabricated with a SiO2 field plate on a freestanding n− gallium nitride (GaN) substrate were reported in the temperature range of 298–473K. The Schottky barrier heights evaluated from forward current-voltage measurement revealed an increase of Schottky barrier height and series resistance but a decrease of ideality factor (n) with increasing temperature. However, the Schottky barrier heights evaluated from capacitance-voltage measurement remained almost the same throughout the temperature range measured. The Richardson constant extrapolated from ln(J0∕T2) vs 1∕T plot was found to be 0.029Acm−2K−2. A modified Richardson plot with ln(J0∕T2) vs 1∕nT showed better linearity, and the corresponding effective Richardson constant was 35Acm−2K−2. The device showed a high reverse breakdown voltage of 560V at room temperature. The negative temperature coefficients were found for reverse breakdown voltage, which is indicative of a defect-assisted breakdown.
Mechanical behavior of ultralong multiwalled carbon nanotube mats
Authors: Deck Christian P. , Flowers Jason , McKee Gregg S. B. , Vecchio Kenneth
Published: February 2007

Carbon nanotubes (CNTs) have been a subject of great interest partially due to their potential for exceptional material properties. Improvements in synthesis methods have facilitated the production of ultralong CNT mats, with lengths in the millimeter range. The increased length of these ultralong mats has, in return, opened the way to greater flexibility to probe their mechanical response. In this work, mats of dense, well-aligned, multiwalled carbon nanotubes were grown with a vapor-phase chemical vapor deposition technique using ferrocene and benzene as reactants, and subsequently tested in both tension and compression using two methods, in a thermomechanical analyzer and in situ inside a scanning electron microscope. In compression, measured stiffness was very low, due to buckling of the nanotubes. In tension, the nanotube mats behaved considerably stiffer; however, they were still more compliant than expected for nanotubes (∼1TPa). Analysis of both the growth method used and the nanotube mat fracture surface suggests that the mats grown in this method are not composed of continuous nanotubes and their strengths actually closely match those of woven nanotube yarns and ropes.
Amide I two-dimensional infrared spectroscopy of β-hairpin peptides
Authors: Smith Adam W. , Tokmakoff Andrei
Published: February 2007

In this report, spectral simulations and isotope labeling are used to describe the two-dimensional IR spectroscopy of β-hairpin peptides in the amide I spectral region. 2D IR spectra of Gramicidin S, PG12, Trpzip2 (TZ2), and TZ2-T3*T10*, a dual C′13 isotope label, are qualitatively described by a model based on the widely used local mode amide I Hamiltonian. The authors' model includes methods for calculating site energies for individual amide oscillators on the basis of hydrogen bonding, nearest neighbor and long-range coupling between sites, and disorder in the site energy. The dependence of the spectral features on the peptide backbone structure is described using disorder-averaged eigenstates, which are visualized by mapping back onto the local amide I sites. β-hairpin IR spectra are dominated by delocalized vibrations that vary by the phase of adjacent oscillators parallel and perpendicular to the strands. The dominant ν⊥ band is sensitive to the length of the hairpin and the amount of twisting in the backbone structure, while the ν‖ band is composed of several low symmetry modes that delocalize along the strands. The spectra of TZ2-T3*T10* are used to compare coupling models, from which we conclude that transition charge coupling is superior to transition dipole coupling for amide groups directly hydrogen bound across the β strands. The 2D IR spectra of TZ2-T3*T10* are used to resolve the redshifted amide I band and extract the site energy of the labeled groups. This allows the authors to compare several methods for calculating the site energies used in excitonic treatments of the amide I band. Gramicidin S is studied in dimethyl sulfoxide to test the role of solvent on the spectral simulations.
Effect of the geometric phase on the dynamics of the hydrogen-exchange reaction
Authors: Juanes-Marcos Juan Carlos , Althorpe Stuart C. , Wrede Eckart
Published: February 2007

A recent puzzle in nonadiabatic quantum dynamics is that geometric phase (GP) effects are present in the state-to-state opacity functions of the hydrogen-exchange reaction, but cancel out in the state-to-state integral cross sections (ICSs). Here the authors explain this result by using topology to separate the scattering amplitudes into contributions from Feynman paths that loop in opposite senses around the conical intersection. The clockwise-looping paths pass over one transition state (1-TS) and scatter into positive deflection angles; the counterclockwise-looping paths pass over two transition states (2-TS) and scatter into negative deflection angles. The interference between the 1-TS and 2-TS paths thus integrates to a very small value, which cancels the GP effects in the ICS. Quasiclassical trajectory (QCT) calculations reproduce the scattering of the 1-TS and 2-TS paths into positive and negative deflection angles and show that the 2-TS paths describe a direct insertion mechanism. The inserting atom follows a highly constrained “S-bend” path, which allows it to avoid both the other atoms and the conical intersection and forces the product diatom to scatter into high rotational states. By contrast, the quantum 2-TS paths scatter into a mainly statistical distribution of rotational states, so that the quantum 2-TS total ICS is roughly twice the QCT ICS at 2.3eV total energy. This suggests that the S-bend constraint is relaxed by tunneling in the quantum system. These findings on H+H2 suggest that similar cancellations or reductions in GP effects are likely in many other reactions.
Effective potentials for 1:1 electrolyte solutions incorporating dielectric saturation and repulsive hydration
Authors: Lenart Philip J. , Jusufi Arben , Panagiotopoulos Athanassios Z.
Published: February 2007

Implicit water potentials are developed for the study of thermodynamic and structural properties of solutions of NaCl, LiCl, and KCl. The interaction potential between cations and anions is parametrized from the ionic crystal potential. Two short-range corrections were added to the system to account for the water solvent. The first is due to dielectric saturation which reduces the dielectric permittivity in the vicinity of an ion. The second is a repulsive Gaussian potential which represents the first hydration shell around the ions. Grand canonical Monte Carlo simulations were performed to calculate the mean ionic activity coefficients. Molecular dynamics simulations were performed to calculate the radial distribution functions of 1.0 molal solutions at 298 K which were used to compare the structure of the explicit and implicit water simulations. The implementation of dielectric saturation and a repulsive hydration potential results in an excellent description of the mean activity coefficient and is able to capture structural features of contact ion pairs and solvent separated ions.
Phase separation in H2O:N2 mixture: Molecular dynamics simulations using atomistic force fields
Authors: Maiti Amitesh , Gee Richard H. , Bastea Sorin , Fried Laurence E.
Published: February 2007

A class II atomistic force field with Lennard-Jones 6–9 nonbond interactions is used to investigate equations of state (EOS) for important high explosive detonation products N2 and H2O in the temperature range of 700–2500K and pressure range of 0.1–10GPa. A standard sixth order parameter-mixing scheme is then employed to study a 2:1 (molar) H2O:N2 mixture, to investigate, in particular, the possibility of phase separation under detonation conditions. The simulations demonstrate several important results, including (i) the accuracy of computed EOS for both N2 and H2O over the entire range of temperature and pressure considered, (ii) accurate mixing-demixing phase boundary as compared to experimental data, and (iii) the departure of mixing free energy from that predicted by ideal mixing law. The results provide comparison and guidance to state-of-the-art chemical kinetic models.
Numerical study of the gel transition in reversible associating polymers
Authors: Baljon Arlette R. C. , Flynn Danny , Krawzsenek David
Published: February 2007

Four temperatures to characterize the gel transition in reversible associating polymers have been calculated in a novel mixed molecular dynamics/Monte Carlo model. (1) The temperature below which relaxation times no longer show Arrhenius dependence on temperature; (2) the Vogel-Fulcher temperature at which the structural relaxation time extrapolates to infinity; (3) the micelle formation temperature at which the number of reversible bonds sharply increases; and (4) a crossover temperature at which the viscosity exhibits a power law divergence as predicted by mode coupling theory. These specific temperatures are obtained from measurements of diffusivity, specific heat, and network topology.
Doubly resonant three-wave-mixing spectroscopy of a chiral coupled-chromophore system in solution: Coherent two-dimensional optical activity spectroscopy
Authors: Cheon Sangheon , Lee Hochan , Choi Jun-Ho , Cho Minhaeng
Published: February 2007

Theoretical descriptions of doubly resonant two-dimensional (2D) sum-frequency-generation (SFG) and difference-frequency-generation (DFG) spectroscopies of coupled-chromophore systems are presented. Despite that each electronic or vibrational chromophore is achiral, the interaction-induced chirality of a coupled multichromophore system in solution can be measured by using the doubly resonant 2D three-wave-mixing (3WM) spectroscopic method. An electronically coupled dimer, where each monomer is modeled as a simple two-level system, can have nonvanishing SFG (or DFG) properties, e.g., susceptibility in frequency domain or nonlinear response function in time domain, if the induced dipole vector of the dimer is not orthogonal to the vector product of the two monomer electronic transition dipole vectors. In order to demonstrate that these 2D 3WM spectroscopic methods can be used to determine the solution structure of a polypeptide, the authors carried out quantum chemistry calculations for an alanine dipeptide and obtained first- and second-order dipole derivatives associated with the amide I vibrational transitions of the dipeptide. It is shown that the numerically simulated 2D IR-IR SFG spectrum is highly sensitive to the dipeptide secondary structure and provides rich information on the one- and two-exciton states. It is believed that the theoretically proposed doubly resonant 2D 3WM spectroscopy, which can be considered to be an optical activity spectroscopy, will be of use in studying both structural and dynamical aspects of coupled multichromophore systems, such as proteins, nucleic acids, nanoparticle aggregates etc.
The irrotational motion generated by two planar stirrers in inviscid fluid
Authors: Crowdy D. G. , Surana A. , Yick K-Y.
Published: February 2007

The irrotational motion of an inviscid incompressible fluid driven by two objects, of arbitrary shape, moving at specified velocities in a two-dimensional fluid region is determined. The problem is shown to be equivalent to a standard mathematical problem in potential theory known as the modified Schwarz problem. The solution is given, up to conformal mapping, by the classical Villat formula.
Electron paramagnetic resonance of magnetoelectric Pb(Fe1∕2Nb1∕2)O3
Authors: Blinc R. , Cevc P. , Zorko A. , Holc J. , Kosec M. , Trontelj Z. , Pirnat J. , Dalal N. , Ramachandran V. , Krzystek J.
Published: February 2007

To check on the nature of the weak magnetic order in polycrystalline magnetoelectric Pb(Fe1∕2Nb1∕2)O3 the X-band, Q-band, and far infrared electron paramagnetic resonance (EPR) spectra have been measured between 4 and 600K and compared with magnetic susceptibility and magnetization data. The asymmetric line shapes can be simulated at higher temperature by thermally fluctuating superparamagnetic nanoclusters. The pronounced temperature dependence of the position of the spectra demonstrates the presence of an internal magnetic field which is small but nonzero even at room temperature, i.e., far above the antiferromagnetic transition. The electronic spin-spin exchange has been found to be in the terahertz range. The magnetization data reveal a weak ferromagnetism even above 300K and a break in the temperature dependence of susceptibility at the paramagnetic to ferromagnetic transition.
Anomalous, non-Gaussian transport of charged particles in anisotropic magnetic turbulence
Authors: Pommois P. , Zimbardo G. , Veltri P.
Published: February 2007

The transport of energetic particles in a mean magnetic field and in the presence of anisotropic magnetic turbulence is studied numerically, for parameter values relevant to astrophysical plasmas. A numerical realization of magnetic turbulence is set up, in which the degree of anisotropy is varied by changing the correlation lengths lx, ly, and lz. The ratio ρ∕λ of the particle Larmor radius ρ over the turbulence correlation length λ is also varied. It is found that for lx,ly⪢lz, and for ρ∕λ≲10−2 transport can be non-Gaussian, with superdiffusion along the average magnetic field and subdiffusion perpendicular to it. In addition, the spatial distribution of particles is clearly non-Gaussian. Such regimes are characterized by a Levy statistics, with diverging second-order moments. Decreasing the ratio lx∕lz, nearly Gaussian (normal) diffusion is obtained, showing that the transport regime depends on the turbulence anisotropy. Changing the particle Larmor radius, normal diffusion is found for 10−2≲ρ∕λ≲1 because of increased pitch angle diffusion. New anomalous superdiffusive regimes appear when ρ∕λ≳1 showing that the interaction between particles and turbulence decreases in these cases. A new regime, called generalized double diffusion, is proposed for the cases when particles are able to trace back field lines. A summary of the physical conditions which lead to non-Gaussian transport is given.
On the particle fluxes and density profiles in helical systems
Authors: Yamagishi Osamu , Yokoyama Masayuki , Nakajima Noriyoshi , Tanaka Kenji
Published: February 2007

Quasilinear and neoclassical particle fluxes and their relation to the density profiles in helical plasmas are discussed, by taking the Large Helical Device (LHD) [O. Motojima et al., Nucl. Fusion 43, 1674 (2003)] as a representative example. Various magnetic configurations can be realized in the LHD experiments by changing the coil currents. The neoclassical particle flux shows strong configuration dependence through the significant change of effective helical ripple, while it is insensitive to the change of density profiles. On the other hand, the quasilinear flux shows weak dependence on the magnetic configurations while it strongly depends on the density profiles. As a result of the particle balance in the steady state in the no-source region, a qualitative explanation for the hollow density profiles, which are often observed experimentally in LHD, is proposed. In the appendixes, properties of quasilinear particle flux in a simple model tokamak are discussed, and expressions for neoclassical fluxes in the 1∕ν regime in a coordinate system are given.
Heteroepitaxial growth of Nb-doped SrTiO3 films on Si substrates by pulsed laser deposition for resistance memory applications
Authors: Xiang Wenfeng , Dong Rui , Lee Dongsoo , Oh Seokjoon , Seong Dongjun , Hwang Hyunsang
Published: February 2007

Epitaxial Nb-doped SrTiO3 films grown on Si substrates for nonvolatile resistance memory applications were investigated. With a TiN buffer layer, a high-quality epitaxial Nb-doped SrTiO3 film was grown on the Si substrate, which was confirmed through x-ray diffraction and transmission electron microscopy. Compared with a control sample grown on a silicon substrate without a TiN buffer layer, the epitaxial Nb-doped SrTiO3 samples with the TiN buffer layer show the good resistance memory characteristics of a high resistance ratio, good retention characteristics, and uniformity. In terms of process compatibility with the standard silicon process, epitaxial Nb-doped SrTiO3 samples with a TiN buffer layer have the potential for use in future nonvolatile resistance memory applications.
Heat capacity in magnetic and electric fields near the ferroelectric transition in triglycine sulfate
Authors: Lashley J. C. , Hundley M. F. , Mihaila B. , Smith J. L. , Opeil C. P. , Finlayson T. R. , Fisher R. A. , Hur N.
Published: February 2007

Specific-heat measurements are reported near the Curie temperature (TC=320K) on triglycine sulfate. Measurements were made on crystals whose surfaces were either nongrounded or short circuited, and were carried out in magnetic fields up to 9T and electric fields up to 220V∕cm. In nongrounded crystals the authors find that the shape of the specific-heat anomaly near TC is thermally broadened. However, the anomaly changes to the characteristic sharp λ shape expected for a continuous transition with the application of either a magnetic field or an electric field. In crystals whose surfaces were short circuited with gold, the characteristic λ shape appeared in the absence of an external field. This effect enabled a determination of the critical exponents above and below TC, and may be understood on the basis that the surface charge originating from the pyroelectric coefficient, dP∕dT, behaves as if shorted by external magnetic or electric fields.
Small scale windmill
Authors: Myers Robert , Vickers Mike , Kim Hyeoungwoo , Priya Shashank
Published: February 2007

In this letter the authors report experimental results on an optimized small scale piezoelectric windmill, which can solve the problems associated with autonomous sensor networks in outdoor, remote or inaccessible locations. The whole structure of the windmill is made of plastic, and it utilizes 18 piezoelectric bimorphs which makes this design extremely cost effective. The windmill was tested at average wind speed of 10miles∕h and it provided 5mW continuous power. The threshold wind speed for the windmill was found to be of the order of 5.4miles∕h. Further, the authors present analysis on two other windmill structures which illustrate the design parameters required for small scale windmill.
Electrohydrodynamic force and scaling laws in surface dielectric barrier discharges
Authors: Lagmich Y. , Callegari Th. , Unfer Th. , Pitchford L. C. , Boeuf J. P.
Published: February 2007

The electrohydrodynamic force generated by surface dielectric barrier discharges is analyzed with a fluid mode under conditions where the electrode above the dielectric surface is the anode.. The calculated current is composed of successive large pulses associated with filamentary discharges spreading along the dielectric surface, separated by low current periods where the discharge is in a transient “coronalike” regime. The contribution of the corona discharges to the overall force is by far dominant. An important result is that the extension of the region above the surface where the electrohydrodynamic force is significant depends on the product of the dielectric layer capacitance and the rate of voltage increase (spatial extension is larger when this parameter is smaller), but that the total, integrated force is not very sensitive to these parameters.
Self-organization of hydrophobic soil and granular surfaces
Authors: McHale Glen , Shirtcliffe Neil J. , Newton Michael I. , Pyatt F. Brian , Doerr Stefan H.
Published: February 2007

Soil can become extremely water repellent following forest fires or oil spillages, thus preventing penetration of water and increasing runoff and soil erosion. Here the authors show that evaporation of a droplet from the surface of a hydrophobic granular material can be an active process, lifting, self-coating, and selectively concentrating small solid grains. Droplet evaporation leads to the formation of temporary liquid marbles and, as droplet volume reduces, particles of different wettabilities compete for water-air interfacial surface area. This can result in a sorting effect with self-organization of a mixed hydrophobic-hydrophilic aggregate into a hydrophobic shell surrounding a hydrophilic core.
Degenerate discrete energy spectra and associated coherent states
Authors: Dello Sbarba L. , Hussin V.
Published: February 2007

Generalized and Gaussian coherent states constructed for quantum system with degeneracies in the energy spectrum are compared with respect to some minimal definitions and fundamental properties they have to satisfy. The generalized coherent states must be eigenstates of a certain annihilation operator that has to be properly defined in the presence of degeneracies. The Gaussian coherent states are, in the particular harmonic oscillator case, an approximation of the generalized coherent states and so the localizability in phase space of the particle in those states is very good. For other quantum systems, this last property serves as a definition of those Gaussian coherent states. The example of a particle in a two-dimensional square box is thus revisited having in mind the preceding definitions of generalized and Gaussian coherent states and also the preservation of the important property known as the resolution of the identity operator.
Metal-enhanced fluorescence: Surface plasmons can radiate a fluorophore’s structured emission
Authors: Zhang Yongxia , Aslan Kadir , Previte Michael J. R. , Geddes Chris D.
Published: February 2007

In this letter, the authors report the observation of metal-enhanced structured fluorescence emission. Perylene in close proximity to silver island films (SiFs) enhances the structured fluorescence emission intensity. In this regard, an approximately two-fold higher perylene fluorescence intensity was observed from SiFs as compared to a glass control sample, containing no silver nanoparticles. The findings strongly suggest that surface plasmons can radiate a fluorophore’s vibrational structure. This observation is helpful in the authors’ understanding, not only for studying the interactions between plasmons and lumophores but also for their laboratories’ continued efforts to develop a unified plasmon-lumophore theory.