bluuebunny/crossref_metadata_2025 huggingface dataset:
Visual Exploration and Analysis of Historic Hotel Visits
Authors: Weaver Chris , Fyfe David , Robinson Anthony , Holdsworth Deryck , Peuquet Donna , MacEachren Alan M.
Published: February 2007

Understanding the spatial and temporal characteristics of individual and group behavior in social networks is a critical component of visual tools for intelligence analysis, emergency management, consumer analysis, and human geography. Identification and analysis of patterns of recurring events is an essential feature of such tools. In this paper, we describe an interactive visual tool for exploring the visitation patterns of guests at two hotels in central Pennsylvania from 1894 to 1900. The centerpiece of the tool is a wrapping spreadsheet technique, called reruns, that reveals regular and irregular periodic patterns of events in multiple overlapping artificial and natural calendars. Implemented as a coordinated multiple view visualization in Improvise, the tool is in ongoing development through an iterative process of data collection, transcription, hypothesis, design, discovery, analysis, and evaluation in close collaboration with historical geographers. Numerous discoveries have driven additional data collection from archival newspaper and census sources, as well as plans to enhance analysis of spatial patterns using historic weather records and railroad schedules. Distributed online evaluations of usability and usefulness have resulted in feature and design recommendations that are being incorporated into the tool.
Presages to the Coming War over Generic Biologics
Authors: Karst Kurt
Published: February 2007

There are sufficient legal and scientific precedents to support positions ranging from arguments against the approval of any ‘generic’ biologic to arguments that support the position that existing Food and Drug Administration (FDA) precedents permit the approval of a generic biologic. While it seems highly likely that at some point there will be a legally and scientifically acceptable construct for the approval of generic biologics, given the diverse opinions and varied interests of the US Congress, the FDA, the pharmaceutical and biotechnology industries, health service providers, insurers, consumers and the scientific community with regard to generic biologics, it is difficult to determine what such a construct will entail, or when it might be implemented. The only certainty is that there are presently no absolutes regarding this issue, either legally or scientifically. This paper seeks to trace past and current events that are quickly culminating to set the stage for a war over generic biologics, and which may offer some insight into the agency's thinking on their uncertain future.
Pharmaceutical Pricing: Overview of the Impact of Genericisation
Authors: Barak Adam
Published: February 2007

Patent expiry signals a fundamental shift in the way in which drugs are marketed and purchased. The entry of generic competitors requires a variety of different healthcare stakeholders to implement an alternative set of objectives and approaches in order to take advantage of the new opportunities which genericisation brings about. This paper concentrates on two perspectives, that of the original brand manufacturer and that of the payer. It examines, through the use of international examples, how approaches to pricing change pre- and postpatent expiry in view of the altered objectives and regulatory framework. It is demonstrated that manufacturer and payer alike have a number of alternative pricing approaches which could be implemented, each having a different set of aims and consequences.
Extending the Monopoly – How ‘Secondary Patents’ Can Be Used to Delay or Prevent Generic Competition upon Expiry of the Basic Product Patent
Authors: Hutchins Mike
Published: February 2007

Over the past few decades, increasingly sophisticated patent strategies have been employed by many companies in the research-based pharmaceutical industry to protect drug products beyond expiry of the basic patents to the active ingredients per se using so-called ‘secondary patents’. A company wishing to enter the market with a generic product should now be prepared to navigate its way through a maze of additional patents surrounding the drug product before it can get to the market. Even then, the generics company may find itself at a competitive disadvantage in that it may be blocked from using the compound produced by the most economical route or using the most stable or efficacious forms of the drug. This paper discusses and illustrates the ways in which patents can be obtained for developments at various stages in the life cycle of a drug, thereby helping to extend the effective patent life for the drug beyond the expiry date of the basic patents.
US Generic Drug Litigation Update
Authors: Fastiff Eric B.
Published: February 2007

The Hatch–Waxman Act produced the unintended consequence of allowing brand name and generic drug companies to agree, in exchange for substantial payments, for the generic drug companies to drop their patent challenges and not to bring their generic versions to market. This paper summarises three recent court decisions. In each case, the plaintiffs were the purchasers of the generic drugs — both consumers and insurance companies. They challenged the drug companies' agreements not to compete, claiming antitrust violations. The drug companies defended the agreements as legal uses of their patent monopolies. Each court analysed the agreement differently, demonstrating the novel and complex issues that these cases raise.
Orange Book Patent Listing: The Rationale and Economic Impact of the New Rule
Authors: Pohl Mark
Published: February 2007

Listing a patent in the US Food and Drug Administration's (FDA) ‘Orange Book’ of approved pharmaceuticals brings some significant advantages to the patent owner. The FDA has recently changed its requirements for listing patents in the Orange Book. The rule's significant economic impact creates a unique opportunity to build valuable new pharmaceutical product lines. In this paper, the rationale for the new rule will be reviewed and its significant economic impact — expected, over the next decade, to add $19bn in revenues to generic drug manufacturers and to take away $52bn in innovator manufacturer revenues — measured. Moreover, the legal advantages of listing patents in the Orange Book, potential obstacles to listing a patent and the way in which the rule applies to patents on polymorphic forms of approved therapeutic products will be examined.
Innovation – Patents, Generics and Payers: The Political Dynamics of Interaction
Authors: Redwood Heinz
Published: February 2007

This paper sets out to explore the relationship between pharmaceutical innovation, its industrial dependence on patent protection, the advent of cheaper generics after patent expiry and the cumulative impact of these issues and events on healthcare payers. Three observations will help to set the scene.

These relationships are not static, but dynamic. They change over time as the pendulum tends to swing. The issues under observation are heavily politicised because the conduct, financing and outcome of healthcare are all politically controversial and influential in general elections. Pharmaceuticals are both an industry and a component of healthcare. The political balance, at government level, between healthcare policy and industrial policy for pharmaceuticals will profoundly affect the prospects of both the research-based and the generics sector of the industry. Historically, the two sectors became clearly distinguishable in the 1930s.
Are Biopharmaceuticals Immune to the Generics Threat?
Authors: Polastro Enrico T. , Tulcinsky Sonia
Published: February 2007

Although patents on several key biopharmaceuticals expired some years ago, biogenerics have not yet reached the market in the Triad (Japan, North America and Western Europe)1— a situation contrasting with other markets such as China, South-East Asia and Latin America, where biogenerics are a reality. This paper provides a broad overview of the ongoing developments in the biogenerics scene and discusses the issues and hurdles faced by prospective biogenerics developers in the Triad.
‘Better Medicines for Children’ — Which is the Right Way Forward for Europe?
Authors: McClay Nadene
Published: February 2007

It is widely recognised that information relating to the use of medicines in children is sorely lacking, causing substantial ‘off-label use’ of adult medicines in paediatric populations. Attempts have been made to address this shortfall in the USA through the introduction of specific legislation. The EU also intends to put forward legislation, but whether, or how much, EU law should reflect that of the USA is a matter of some considerable analysis and debate.
Generics Companies: Aspiring to Innovate
Authors: Kermani Faiz
Published: February 2007

Many generics companies have low-cost structure margins and have produced simple copies of brand-name drugs. A number of them, however, have become involved in innovative R&D to produce new chemical entities and products incorporating novel drug delivery systems. The market for innovative pharmaceuticals continues to grow as new improved therapies become available, thus offering ambitious generics companies an incentive to develop novel products alongside their more traditional ones. The strategies needed to succeed in innovative R&D are very different to that for generic drugs, however, and so far only a few generics companies have succeeded in taking such steps.
The Manufacture of Generic Pharmaceuticals in Malta: A First Step
Authors: McKenna Anne , Galea Mario
Published: February 2007

Malta, with a population of circa 400,000 and no natural resources, has had to exploit every niche business opportunity to enhance its economic prosperity since gaining independence in 1964. In this respect, current endeavours are focused on the generic pharmaceuticals industry. This sector should form the foundation upon which to build a Mediterranean healthcare centre of excellence. This paper explains why generic pharmaceuticals manufacturers locating in Malta within the next few years will have a distinct competitive advantage. Timing holds the key to success in this fiercely competitive industry. Malta offers a unique blend: the Bolar exemption incorporated into patent legislation; the negligible number of patents registered; and its location between Southern European and North African markets. Together, these bestow the desired timing and attractive marketing opportunities for generics manufacturers.
The EU Regulatory Environment for ‘Biosimilars’: Today's Picture and Future Prospects
Authors: Rossignol Nicolas
Published: February 2007

Times are changing in biotechnology. With the expiration of patent protection for some of the most profitable biologics in the next few years, a new, fast-growing field has started to emerge: ‘biogenerics’. Known as ‘similar biological medicinal products’ or ‘biosimilars’ in Europe, these products are about to enter the now-enlarged Community market.

A number of uncertainties and challenges still lie ahead, though. To regulate biosimilars means dealing with complex molecules, which are tricky to characterise and highly sensitive to manufacturing changes, to which a ‘classical’ generics approach is not directly applicable. Specific legislation needs to be put in place.

While hearings regarding the need for special regulation on ‘biogenerics’ are now being held in the USA, European regulatory authorities have taken the lead by establishing a tailor-made legal framework for biosimilars with the publication of the so-called ‘Annex I’, in 2003. Further developments are expected with the revision of the EU pharmaceutical legislation (the Pharma Review), which was adopted by European institutions in 2004.

The purpose of this article is to provide an overview of this framework, the main consequences of the Pharma Review and a discussion on key points to be considered when entering this emerging market.
Generic Biopharmaceuticals: Towards a Science-Based Abbreviated Process
Authors: Johnston Gordon
Published: February 2007

This paper provides an overview of key regulatory and technical issues related to the approval of biotechnology products in the USA by an abbreviated pathway. Technological advances now permit accurate analytical comparisons of innovative and generic biotechnology products. These sophisticated analytical techniques, along with pharmacodynamic, pharmacokinetic and limited clinical testing, provide an array of comparative tools to demonstrate the equivalence of innovative and generic products. Using a case by case evaluation, there are currently biotechnology products that could be approved based on abbreviated data packages.
Constructing an Immunogenicity Risk Assessment for Follow-On Biologics
Authors: Chamberlain Paul , Mire-Sluis Anthony
Published: February 2007

The registration of follow-on biologics will depend on the availability of data demonstrating comparability with a reference product. It is recognised that measurement of relative immunogenicity will be an important component of the product comparability assessment. The way in which this is done will depend on a multidimensional risk-based approach that considers the probability of generating an immune response relative to the consequences of such a response. This paper presents principles and practical guidance for constructing a risk assessment, building on the experience gained for a variety of biopharmaceutical products. This includes the use of preclinical models and validated bioanalytical methods. Ultimately, post-marketing monitoring will be required to evaluate more fully the risk in representative settings, given the multifactorial nature of the potential immunogenicity of different therapeutic proteins.
A Study of Patient Responses to a Perceived Change in Salbutamol Metered Dose Inhalers
Authors: Levine Mitchell , Gaebel Kathryn , Spino Michael
Published: February 2007

Experience in the clinic reveals that some patients have attributed negative changes in their respiratory health status to generic substitution of inhaled medications, even though — from a pharmacological perspective — therapeutic equivalence would be expected. The objective of this study was to evaluate patient-reported changes in efficacy or toxicity following a perceived switch of an inhaled drug product. Forty-eight patients with air flow limitation had their usual brand of salbutamol metered-dose inhaler (MDI) replaced for one week with a new MDI. Patients were not informed that the replacement MDI was exactly the same brand as their usual MDI, and the product identity was disguised by a label. Forced expiratory volume in one second, respiratory symptoms and MDI use were compared between the week when the patients knew they were using their usual brand of MDI and the week they were using the perceived new MDI. Patient MDI preference was assessed at the end of the study. Even though there was no change in the brand of salbutamol MDI, 46 per cent of patients thought that the new MDI was better at managing their symptoms, 27 per cent thought that the new MDI was worse and 27 per cent perceived no difference (p<0.05 for rejecting the null hypothesis that all responses would be for no difference). Seventy per cent of patients stated that they had a preference for one MDI over the other, even though there had been no change in inhaler. Factors other than product differences are likely to be responsible for patient claims of changes in respiratory health status subsequent to generics substitution with inhaled medications when equivalent products are used. If such changes are reported following the introduction of a new generic product, the changes may be incorrectly attributed to the new product, confounding the ability to assess the quality of the new product in post-marketing evaluation.
Current Situation for Generic Drugs in Japan
Authors: Riku Juichi
Published: February 2007

Although the Japanese pharmaceutical market is the second largest market in the world, the share of generics is extremely low when compared with those in the USA, the UK and Germany. The reason for this is that there are several obstacles to quick access to, and market penetration of, generics that would be incomprehensible to foreign companies. In Japan, systems such as substitution of generics for brands, reference pricing, etc have not yet been implemented. Similarly, the complete separation of prescribing and dispensing medicines has not occurred in Japan, where 48 per cent of medical institutions both prescribe and dispense pharmaceutical products. This is in stark contrast to both the USA and the EU, where complete separation exists. Medical institutions that gain profits from the gap between the purchasing and reimbursement price still tend to use brands with higher profit margins than generics; however, the push to promote the use of generics has just started. Therefore, generics companies and their associations must implement appropriate strategies in response to the changing circumstances.
Whither Generics? Why Major Restructuring Lies Ahead
Authors: Class Selena
Published: February 2007

Generics manufacturers have undergone some of the fastest growth in the pharmaceutical sector in recent years, but can their impressive growth rate be maintained post-2006–2007, when a number of blockbusters are due to lose exclusivity? Some of their major long-term challenges include the dearth of new blockbusters as branded pharma's pipeline dwindles; aggressive defence tactics — such as the development of combination products and over-the-counter switching; authorised generics deals; the lack of an established approval path for biogenerics; and increasing competition from manufacturers in developing countries. For many, maintaining market share will require a transformation of their business practices. The successful organisations will be those that recognise the need for change early and start to plan their campaign of response accordingly. This paper outlines the issues they face and discusses some of the potential ramifications.
Impact of Court Cases on Summary of Product Characteristics Harmonisation
Authors: Milchior Richard
Published: February 2007

This paper deals with the evolution of European Court of Justice (ECJ) case law. The ECJ had to decide in the Artedogan case whether the national authorities or the Commission should be able to modify marketing authorisation granted at the national level. The ECJ decided that in the situation where the marketing authorisation was of national origin, a modification could not be decided on by the European Commission on the basis of the then article 15a of directive 75/189 (today article 36 of directive 2001/83). The debate has now shifted, and the new issue is to decide who is authorised to force harmonisation of summaries of product characteristics (SmPC) and when this can be contested in front of the Court of First Instance. The three decisions pending in the Zocor, Lopid and Renitil cases, which concern SmPC harmonisation, will pave the way to finding out if the development of generic products can be impeded through the development or lack of SmPC harmonisation at the EU level.
Meeting the Challenge of Growth and Profitability
Authors: Tempest Brian
Published: February 2007

The global increase in the cost of health has become an enormous issue, and one that is set to continue as a consequence of the ageing population. Pressure mounts within the big pharmaceutical companies, where there is an increasingly sharp focus on the productivity and efficiency of R&D operations. By contrast, we are seeing an almost global expansion of the generics pharmaceutical sector, a trend that is forecast to continue. Without generics, the pharmaceutical component of healthcare budgets would increase substantially, and this, in turn, would bring about further increments in the overall cost of healthcare. Whereas many people regard the generics and branded patented medicines industries as competitors, in fact they sit synergistically together. Against this background, a pharmaceutical company based in India has real potential to meet the challenge of growth and profitability on a global scale. India not only has a long and successful history in generics but also possesses many inherent competitive advantages, a key one being the low cost of innovation, for succeeding in the area of drug discovery. If the current productivity seen in India can continue with a conscience, and be expanded through optimal and cohesive communication with key customers in the Western world, this will lead to significant shareholder wealth and benefit to patients.
International Intellectual Property and Development: A Roadmap to Balance?
Authors: Gervais Daniel
Published: February 2007

This paper examines the emergence of the World Trade Organization Trade-Related Aspects of Intellectual Property Agreement and the changing face of international intellectual property agenda, evidenced by the Doha Ministerial Declaration of November 2001. Follow-up work on access to medicines and the recent adoption of a ‘development agenda’ by the World Intellectual Property Organization will be discussed. The paper then looks at the current quest for a ‘balanced’ approach and suggests ways in which such a balance may be achieved.
Generics Growth in the USA and the EU: The Role of India
Authors: Hoffman Jean
Published: February 2007

This paper examines issues impacting the global generics sector and the role of Indian generics companies. The USA, which has been the primary regulated market focus for Indian companies, and the EU, are covered. Key success factors for generics companies are described. Various approaches by Indian companies to selling in the regulated markets are discussed, including partnership and direct selling models, and Indian competitive advantages and weaknesses compared to global and regional generics companies described.
Battle for the Market: Branded Drug Companies' Secret Weapons Generic Drug Makers Must Know
Authors: Hess Jon , Litalien Shannon
Published: February 2007

Generic drugs now account for more than $40bn in prescription sales worldwide. More than $80bn worth of global blockbuster drugs face US patent expiration by 2008. The battle for market share between the booming generics drug industry and the at-risk branded drug industry is raging.

As patent expiry looms, branded drugs can no longer only focus on extending product lives. They need defensive strategies to combat their generics competitors actively and retain market share. To maintain rapid growth, generic drugs makers not only need to understand the nature of these defensive strategies, but they must also be prepared to deal with them as they bring their products to market. The most important and commonly-implemented strategies are discussed in this paper and the authors suggest that branded and generic drugs companies can successfully apply or manoeuvre against these strategies to distinguish themselves within an industry where lines are blurring and competition is increasing.
Similarity of Medicinal Products and Free Movement of Goods: Is Parallel Distribution the Beginning of the end for Mutual Recognition?
Authors: Faus Jordi
Published: February 2007

Marketing authorisation procedures should facilitate global access to the European Union market. Restrictions to free movement of goods are only compatible with the EC Treaty in very limited situations, and national authorities must not oppose the placing on the market of a medicinal product approved in another member state unless the protection of public health so requires. Generic medicines are products whose efficacy and safety are well known. Once approved in one member state it seems rather difficult to justify a restriction to free movement based on the need to protect public health. The jurisprudence on parallel trade of medicinal products may help to revisit the current mutual recognition system.
Safeguarding Access to Medicines in Developing Countries: Strategies and Principles
Authors: Timmermans Karin
Published: February 2007

The Agreement on Trade-related Aspects of Intellectual Property Rights (TRIPS) has harmonised standards for intellectual property rights, including patents. For developing countries, these new standards are usually higher than their previous standards. As a result, it will take longer for generic versions of new drugs to enter their markets. This risks compromising access to medicines.

This paper points out that developing countries can mitigate the negative impact on access by ensuring that domestic laws contain workable provisions for compulsory licensing and other TRIPS-compliant safeguard mechanisms and by gaining experience in using them. But countries should also avoid issuing trivial patents, for instance by applying strict criteria for patentability. This will, however, require a change in attitude towards and administration of intellectual property rights. Generics companies should nurture and actively support a more critical attitude to pharmaceutical patents.
Ongoing Monitoring of Antiretroviral Products as Part of WHO's Prequalification Project
Authors: Dekker Theo G. , van Zyl Adriaan J. , Gross Olivier , Taševská Ivana , Stahl Matthias M. S. , Rabouhans Marie L. , Rägo Lembit
Published: February 2007

The supply of quality medicines used in the treatment of HIV/AIDS has become a major concern at both international and country level. The Prequalification Project, set up in 2001, is a service provided by the World Health Organization (WHO) to facilitate access to medicines that meet unified standards of quality, safety and efficacy for HIV/AIDS, malaria and tuberculosis.

The main purpose of the project with respect to HIV/AIDS is to assess the quality, safety and efficacy of medicines (both antiretrovirals [ARVs] and medicines for HIV/AIDS care) in accordance with international standards and to ensure that good manufacturing practice is applied at the manufacturing sites. The assessment further includes reviewing bioequivalence data and inspecting respective contract research organisations where the clinical trials were conducted for compliance with good clinical practice. Only products meeting all the requirements are listed on the prequalified products list.

As part of the quality assurance element of the Prequalification Project, samples of 33 HIV/AIDS products, of which 24 were ARVs and 9 were for HIV/AIDS care, submitted for prequalification were subjected to quality control (QC) testing in 2002. This was followed by a second round of QC testing during 2004 on 11 ARV products, including comparison of dissolution profiles of generic products against the relevant innovator products. Some of the products tested appear on the current Prequalification list. All samples but one met the shelf-life specifications for content and, where tested, for identification of the active pharmaceutical ingredient, dissolution, average mass and uniformity of mass. One product sample did not meet the content specifications; however, the number of tablets required for assay testing and consequently also for confirmative retesting was insufficient, and therefore the result cannot be considered conclusive. Another product did not meet the requirements for similarity of dissolution profile against the innovator product, though it proved to be rapidly dissolving.
Creating eCTD Applications
Authors: Nordfjeld Kim , Strasberger Vito
Published: February 2007

The electronic Common Technical Document (eCTD) is defined as an interface for industry to agency transfer of regulatory information, while at the same time taking into consideration the facilitation of the creation, review, lifecycle management and archival of the electronic submission. eCTD is just an ‘envelope’ that will enable industry to communicate and exchange information easily and should be considered only as the final step in the process of generating an electronic submission. The authors firmly believe that optimal eCTD is based on a solid integrated document management system.

Submission management in the generics industry is a process and the document management system should therefore be adapted to support this process of dossier creation and post-application management of hundreds, or even thousands, of dossiers. In order to effectively implement this process, it is highly recommended that a document management system is configured in such away that every individual document is stored in the system only once. The most effective integration of a document management system and publishing system will enable production of a CTD or eCTD from the same initial documents. This will enable companies to support the submission process in cases where only paper submission is needed, only electronic, or both.
Will India become the Global Centre for Pharmaceutical Research & Development?
Authors: Singh Malvinder Mohan
Published: February 2007

This paper is an edited version of a presentation given at the IGPA Conference in June 2005 in Malta. The global pharmaceutical industry is undergoing enormous change characterised by pressures on the big pharmaceutical sector, the advent of biotech and the global expansion of the generics industry. Big pharma continues to face difficulties with respect to productivity and the returns generated by its R&D. However, growth of the generic industry is forecast to remain strong, as a result of burgeoning healthcare costs facing governments around the world and the global ageing population, leading to increased need for more affordable medicines. Against this background, India is emerging as one of the major centres for global pharma, whether it be in drug discovery and its related aspects or in the development of generic medicines. Until recently India was scarcely in the forefront, but today it is increasingly being considered as providing unique competitive advantages in R&D and manufacturing. If India utilises these advantages optimally the result will be significant benefits to patients both in terms of innovative and newer medicines and more affordable alternatives around the world.
Generic Medicines: Perceptions of General Practitioners in Melbourne, Australia
Authors: Hassali Mohamed Azmi , Kong David C. M. , Stewart Kay
Published: February 2007

The aims of this study were to investigate factors affecting generic medicine prescribing among general practitioners (GPs) in Melbourne, Australia. A qualitative approach was used. A convenience sample of GPs practising in Melbourne was interviewed using a semi-structured interview guide. Thematic content analysis of the interviews identified seven major themes: medicine prescribing patterns, knowledge and confidence with generic medicines, patient acceptance of generic medicines, issues related to ‘pseudo-generics’ and medicine labelling, drug advertising and marketing, brand substitution by community pharmacists and, finally, strategies to increase generics prescribing. Informants suggested some methods that could be used to increase the current rate of generics prescribing, including financial reward for GPs, patient education on generic medicines, convincing GPs of the safety and efficacy of generic medicines and educating senior medical students on issues involving generic medicines and generics prescribing. This study suggested that GPs in Melbourne have mixed attitudes to generics prescribing. The findings also show that misconceptions about safety and efficacy of generic medicines still persist among some GPs. Unless they are sufficiently educated by interested parties, such as the government and the generic medicines industry, this will have a negative impact on utilisation of generic medicines in future.
Saddle-node bifurcation and modulational instability associated with the pulse propagation of dust ion-acoustic waves in a viscous dusty plasma: A complex nonlinear Schrödinger equation
Authors: Misra Amar P. , Roy Chowdhury K. , Roy Chowdhury A.
Published: February 2007

Using the standard reductive perturbation technique, a nonlinear Schrödinger equation (NLSE) with complex coefficients is derived in a dusty plasma consisting of positive ions, nonthermal electrons, and charged dust grains. The effect of ion kinematic viscosity is taken into consideration, which makes the coefficients of NLSE complex. By means of a matching approach, the appearance mechanism of static pulses through a saddle-node bifurcation in the complex nonlinear Schrödinger equation is studied analytically. The analytical results are in good agreement with the direct numerical simulation. The modulational instability analysis is carried out for the dust ion-acoustic envelope solitary waves. The important role of the real part of the complex group velocity in the propagation of the one-dimensional wave packets in homogeneous active medium is predicted.
Experimental test on the applicability of the standard retardation condition to bound magnetic fields
Authors: Kholmetskii A. L. , Missevitch O. V. , Smirnov-Rueda R. , Ivanov R. , Chubykalo A. E.
Published: February 2007

We start with the fact that the actual consensus on the empirical verification of the standard retardation condition does not take into account the complex structure of the whole electromagnetic field in the near zone. The most rigorous and methodologically consistent way to the empirical test of the causal behavior of the whole EM field should be based on testing causal properties for each component—velocity dependent (bound) and acceleration dependent (radiation)—taken separately. Preliminary discussions on the relative contribution of bound and radiation terms for an idealized magnetic dipole provided us with a methodological approach to causal characteristics of bound fields. In view of practical implementation of this method, we made an analysis of the finite size loop antennas. The use of multisection loop antennas was fully justified by a substantial rise of the ratio of bound-to-radiation field strength. Finally, we effected numerical calculations, taking into account particular experimental settings. Comparison with the experimentally obtained data showed considerable discrepancy with the predictions of the standard electromagnetic theory. A possible interpretation in terms of nonlocal properties of bound fields in near zone is proposed.
Cathodoluminescence, photoluminescence, and reflectance of an aluminum nitride layer grown on silicon carbide substrate
Authors: Prinz G.i M. , Ladenburger A. , Schirra M. , Feneberg M. , Thonke K. , Sauer R. , Taniyasu Y. , Kasu M. , Makimoto T.
Published: February 2007

Aluminum nitride (AlN) has an ultrawide direct band gap of approximately 6.1 eV at low temperature and is fully miscible with gallium nitride. This makes AlN a promising material for ultraviolet optoelectronic applications. Here, we apply cathodoluminescence, photoluminescence, and reflectance spectroscopies to the same AlN layer grown by metalorganic vapor phase epitaxy on silicon carbide. In cathodoluminescence and photoluminescence, we observe strong near band edge emission at ≈6 eV. The contribution appearing at an energetic position of 5.983 eV could be identified as A free exciton recombination, strongly redshifted due to strain effects. The spectra obtained by reflectance measurements show features at 5.985 eV and ≈6.2 eV which we assign to the A exciton—in accordance to our luminescence measurements—and a combination of the B and C free excitons, respectively.
Dufour and Soret effects in a magnetized and nonmagnetized plasma
Authors: García-Colín L. S. , García-Perciante A. L. , Sandoval-Villalbazo A.
Published: February 2007

It is well known that magnetic fields affect heat conduction in a different way in the direction parallel and perpendicular to the field. In this paper, a formal derivation of this phenomenon and analytical expressions for the transport coefficients based in the Boltzmann equation are presented. Moreover, the Dufour effect or diffusion thermo-effect is usually ignored in plasma transport theory. This effect is shown here to be not only relevant but also the most important source of heat conduction for weak magnetic fields. In this work, analytic expressions for the parallel and perpendicular thermal conductivities as well as the coefficients for both the thermal diffusion, or Soret, effect and the Dufour effect are formally derived. It is also shown how the heat conduction in the perpendicular direction decreases with increasing magnetic field and how in both directions the diffusion thermo-effect is far more important than thermal conduction, leading to a new effective thermal conductivity coefficient. Other aspects of this work are also emphasized.
Temporal chaos in Boussinesq magnetoconvection
Authors: Bekki Naoaki , Moriguchi Hirofumi
Published: February 2007

Two-dimensional Boussinesq magnetoconvection with idealized stress-free boundary conditions is numerically investigated in order to make clear the difference between chaos and turbulence. It is shown that the long-term behavior of magnetoconvection exhibits spatially coherent and temporally chaotic rolls in marked contrast to highly turbulent fluids. It is also shown that heat transport becomes larger anomalously when the polarity reversal of the magnetic field occurs intermittently in the case of temporally chaotic magnetoconvection. It is found that the Poincaré return map of the relative maximum temperature fluctuation of partial differential equations as a function of the preceding maximum resembles the famous Lorenz plot in narrow rolls of magnetoconvection. The chaotic behavior of narrow rolls for individual parameter values robustly persists up to rolls about one fifth as wide as they are high near the codimension-two bifurcation point.
Short-time dynamics of polypeptides
Authors: Arashiro Everaldo , Drugowich de Felício J. R. , Hansmann Ulrich H. E.
Published: February 2007

The authors study the short-time dynamics of helix-forming polypeptide chains using an all-atom representation of the molecules and an implicit solvation model to approximate the interaction with the surrounding solvent. The results confirm earlier observations that the helix-coil transition in proteins can be described by a set of critical exponents. The high statistics of the simulations allows the authors to determine the exponent values with increased precision and support universality of the helix-coil transition in homopolymers and (helical) proteins.
Intra-miniband gain in a super-superlattice structure with alternating electric-field domains
Authors: Schrottke L. , Giehler M. , Grahn H. T.
Published: February 2007

A super-superlattice structure containing a conventional superlattice, a graded-gap superlattice, and a wide quantum well in its unit cell is analyzed. It is designed in such a way that alternating high- and low-electric-field domains appear due to the presence of positive and negative space charges. The positive space charge is formed by ionized donors, while electrons, which are trapped in the wide quantum well, provide the negative space charge. Since the low-field domain spans the conventional superlattice and the high-field domain is located in the graded-gap superlattice, the flatband condition can be simultaneously achieved for the two superlattices. The self-consistent solution of the Poisson and Schrödinger equations using a simplified scattering-rate approach demonstrates that the conventional superlattice exhibits an inversion of the intra-miniband population. Such structures may be useful for terahertz lasers, since the large dipole matrix element of the intra-miniband transitions allow for a rather low doping density and hence a reduction of scattering processes. Furthermore, they permit the study of superlattices under flatband conditions with a nonequilibrium population, which is achieved without optical excitation.
Free energy landscapes of electron transfer system in dipolar environment below and above the rotational freezing temperature
Authors: Suzuki Yohichi , Tanimura Yoshitaka
Published: February 2007

Electron transfer reaction in a polar solvent is modeled by a solute dipole surrounded by dipolar molecules with simple rotational dynamics posted on the three-dimensional distorted lattice sites. The interaction energy between the solute and solvent dipoles as a reaction coordinate is adopted and free energy landscapes are calculated by generating all possible states for a 26 dipolar system and by employing Wang-Landau sampling algorithm for a 92 dipolar system. For temperatures higher than the energy scale of dipole-dipole interactions, the free energy landscapes for the small reaction coordinate region have quadratic shape as predicted by Marcus [Rev. Mod. Phys. 65, 599 (1993)] whereas for the large reaction coordinate region, the landscapes exhibit a nonquadratic shape. When the temperature drops, small notched structures appear on the free energy profiles because of the frustrated interactions among dipoles. The formation of notched structure is analyzed with statistical approach and it is shown that the amplitude of notched structure depend upon the segment size of the reaction coordinate and is characterized by the interaction energy among the dipoles. Using simulated free energy landscapes, the authors calculate the reaction rates as a function of the energy gap for various temperatures. At high temperature, the reactions rates follow a bell shaped (inverted parabolic) energy gap law in the small energy gap regions, while it becomes steeper than the parabolic shape in a large energy gap regions due to the nonquadratic shape of the free energy landscape. The peak position of parabola also changes as the function of temperature. At low temperature, the profile of the reaction rates is no longer smooth because of the many local minima of the free energy landscape.
On the development of a confocal Rayleigh-Brillouin microscope
Authors: Liptak David C. , Reber Jason C. , Maguire John F. , Amer Maher S.
Published: February 2007

This Note illustrates how a confocal microscope may be modified to conduct Rayleigh-Brillouin mapping experiments that yield very useful information on the mechanical properties of interfacial materials in small volume elements. While the modifications to the microscope are quite straightforward, they do entail significant changes in the optical design. The instrument described herein consists of an argon ion laser equipped with an actively stabilized intercavity étalon that serves as the excitation source for a modified Zeiss LSM 310 confocal laser scan microscope. The optics of the microscope were reconfigured to enable interfacing of the microscope with a tandem triple-pass Fabry-Pérot interferometer. This instrument enables three-dimensional Rayleigh-Brillouin spectral mapping of samples at micron spatial resolution. The performance of the instrument and its ability to perform both lateral and depth scans of the acoustic phonon velocity and, hence, the longitudinal modulus across bonded polymer/polymer and polymer/ceramic interfaces are illustrated and discussed.
Wavelength switching dynamics in injected fiber ring lasers
Authors: Dragic Peter D.
Published: February 2007

We experimentally and theoretically investigate the wavelength switching dynamics of an injection-seeded Er doped fiber ring laser. The fiber ring laser is seeded by an external cavity laser diode that is amplitude modulated with a long period 50% duty cycle wave form so that the return to steady state can be investigated. It is found that the laser suffers from severe large-amplitude relaxation oscillations and slow decay times that limit the available wavelength switching speed.
Surface treatment effect on temperature-dependent properties of InGaP∕GaAs heterobipolar transistors
Authors: Chen Tzu-Pin , Fu Ssu-I , Liu Wen-Chau , Cheng Shiou-Ying , Tsai Jung-Hui , Guo Der-Feng , Lour Wen-Shiung
Published: February 2007

Specific treatments of the base surface of InGaP∕GaAs heterojunction bipolar transistors are studied experimentally. The dual treatment method, based on the combination of ledge and sulfur passivation, shows better temperature-dependent characteristics including higher dc gain, lower saturation voltage, lower base-emitter junction turn on voltage, lower leakage current, lower collector and base current ideality factors nC and nB, and wider collector current operating regimes over the measured temperature range (300–400K). Therefore, the dual surface treatment method provides promise for high-performance electronic applications.
Direct simulation of film boiling including electrohydrodynamic forces
Authors: Welch Samuel W. J. , Biswas Gautam
Published: February 2007

This paper presents simulations of film boiling including electrohydrodynamic forces. The coupled level-set and volume-of-fluid interface tracking method is augmented with a mass transfer model, a model for surface tension, and electrohydrodynamic force terms. The bulk fluids are perfect dielectrics—viscous, heat conducting, and incompressible. We explore film boiling on a horizontal surface and we consider the effect of an applied electric potential. The electrodynamic equation for the evolving electric field is solved in both phases during saturated horizontal film boiling, and the effects are described.
Sublimation phenomena of Lennard-Jones fluids in slit nanopores
Authors: Kanda Hideki , Miyahara Minoru
Published: February 2007

Using molecular dynamics simulations, The authors studied the solid-vapor coexistence states of Lennard-Jones methane confined in slit-shaped graphite nanopores. Both the intrapore solid and extrapore vapor were simulated using a unit cell which they previously developed. Frozen critical condensates in the pores were cooled stepwise, and the equilibrium vapor pressure was determined at each temperature. The obtained solid-vapor coexistence curves were remarkably lower than that of the bulk phase. Their thermodynamic model successfully predicts the simulation results without the need to introduce any adjustable parameter, and thus proves its reliability.
On the determination of the structure and tension of the interface between a fluid and a curved hard wall
Authors: Blokhuis Edgar M. , Kuipers Joris
Published: February 2007

The structure and tension of the interface between a fluid and a spherically shaped hard wall are studied theoretically. The authors show the equivalence of different expressions for the surface tension and Tolman length using the squared-gradient model and density functional theory with a nonlocal, integral expression for the interaction between molecules. Even though both these models yield equilibrium density profiles that do not satisfy the wall theorem, they still obey the basic requirement of mechanical equilibrium. The authors trace back the origin of the difference between these two observations to the (lack of) continuity of the cavity function at the hard wall.
Self-organization of Pb islands on Si(111) caused by quantum size effects
Authors: Hong Hawoong , Basile L. , Czoschke P. , Gray A. , Chiang T.-C.
Published: February 2007

Growth of metallic Pb islands on Si(111) by vacuum deposition was studied in real time using synchrotron x-ray diffraction. The islands coarsen and order, maintaining a nearly uniform interisland distance but without angular correlation. The resulting interisland structure is akin to a two-dimensional liquid. Over a wide temperature range, the interisland ordering is well correlated with the development of “magic” island heights caused by energy minimization of the Pb electrons. The results demonstrate quantum confinement effects as a driving force for self-organization, as opposed to strain effects that generally govern the formation of semiconductor quantum dot arrays.
Spin transport through a single self-assembled InAs quantum dot with ferromagnetic leads
Authors: Hamaya K. , Masubuchi S. , Kawamura M. , Machida T. , Jung M. , Shibata K. , Hirakawa K. , Taniyama T. , Ishida S. , Arakawa Y.
Published: February 2007

The authors have fabricated a lateral double barrier magnetic tunnel junction (MTJ) which consists of a single self-assembled InAs quantum dot (QD) with ferromagnetic Co leads. The MTJ shows clear hysteretic tunnel magnetoresistance (TMR) effect, which is evidence for spin transport through a single semiconductor QD. The TMR ratio and the curve shapes are varied by changing the gate voltage.