bluuebunny/crossref_metadata_2025 huggingface dataset:
Characterisation of the surface of wool and hair using microscopical and fluorescence probe techniques
Authors: Jurdana Lucia E. , Leaver Ian H.
Published: April 2007

Fluorescence probing methods, in combination with light microscopy, were used to image and characterise the hydrophobic surfaces of wool and human hair fibres. When applied from an aqueous dispersion, uncharged lipophilic fluorescent probes displayed a selective affinity for the boundaries of the cuticle cells on the fibre surface. Adsorption generally occurred on the surface of the lower scale emerging from each cell junction. An indication of the fibre surface polarity was given by the fluorescence fine structure of adsorbed pyrene molecules.

Treatment of hair with the lipid stain Nile Red produced an unusual diamondshaped pattern (each segment approximately 40 μm in length and 10 μm in width) in areas where the cuticle had been damaged. Cuticle cells isolated from hair fibres showed distinct geometrical features on their surfaces when examined using differential interference contrast microscopy. The results are interpreted to indicate the presence of a residue of lipid‐staining material adhering to the cuticle cells of hair, the residue possibly being derived from adhesive material produced at the areas of contact between presumptive cuticle cells during the early stages of cuticle shape differentiation.
Synthesis and Characterization of Poly (Acrylic Acid‐co‐Divinylbenzene) Microgels by Ultrasonic Degradation
Authors: Kim Young‐June , Kim Kong‐Soo , Park Myung‐Hwan
Published: April 2007

The preparation of pure microgels in high yield was investigated by a new method which restricts the intermolecular crosslinking reaction between second‐stage crosslinked products by steric hindrance of the first‐stage crosslinked products. This is followed by ultrasonic degradation of the first‐stage crosslinked products. The first‐stage crosslinked products were prepared by copolymerization of styrene and divinylbenzene monomer in dioxane. with α,α′‐azobisisobutyronitrile as initiator. The second‐stage crosslinked products were prepared by copolymerization of acrylic acid and divinylbenzene monomer in first‐stage crosslinked products highly swollen in dioxane, using α,α′‐azobisisobutyronitrile as initiator. Degradation of first‐ and second‐stage crosslinked products was carried out using an ultrasonic vibrator.

The characteristics of the crosslinked products synthesized were investigated by gel permeation chromatography, dynamic laser light scattering and electron microscopy. It was found that the styrene‐divinylbenzene gel of high molecular weight was scissioned preferentially with increasing ultrasonic degradation time and that ultrasonic degradation of compact and small size crosslinked products was very difficult. The crosslinked poly(acrylic acid)s are small compact microgels having a very narrow size distribution of 20‐30 nm diameter.

A pure microgel at nearly 100% conversion was obtained by the new preparation method suggested in this study.
Effect of Space Charge on Polarization Reversal Currents in a Vinylidene Fluoride/Trifluoroethylene Copolymer
Authors: Guy Ian L. , Das‐Gupta Dilip K.
Published: April 2007

Polyvinylidene fluoride and its copolymers with trifluoroethylene and tetrafluoroethylene are ferroelectric. Reversal of polarization in these polymers is known to occur by a rotation of the polar molecular chains, in response to an externally applied electric field. Recent evidence suggests that the dynamics of polarization reversal can be affected by movement of space charges in the amorphous phase of the polymers. If a 75/25 mol.% vinylidene fluoride/trifluoro‐ethylene (VF2/VF3) copolymer is poled at elevated temperature, the subsequent polarization reversal currents show large asymmetry and significant shifts in successive reversals. The field required to reverse the polarization in such high‐temperature poled material is significantly larger than the normal coercive field. The asymmetry in the reversal currents is consistent with the presence of local fields within the polymer, generated by space charge which accumulates during the poling process. The subsequent movement of this space charge causes the shift in successive reversal currents. The variation of reversal current with temperature indicates that the movement of space charge within the copolymer is a thermally activated process.
Interaction between Poly(2‐ hydroxyethyl methacrylate) and High Energy Excimer Laser Radiation
Authors: Vernon Chris F. , Klauber Craig , van Saarloos Paul P. , Chirila Traian V.
Published: April 2007

Poly(2‐hydroxyethyl methacrylate) was prepared by bulk polymerization and then exposed to ablation by 193‐nm pulsed radiation provided by an ArF excimer laser. The etch curve, i.e. ablation rate versus radiation fluence, presents two changes in the slope, which are consistent with a presumably characteristic behaviour of addition polymers with a strong tendency towards thermal depolymerization. Samples exposed to two fluences, each in the vicinity of one of the inflection points, were analysed by X‐ray photoelectron spectra (XPS) at two different take‐off angles. The results suggest that the ablation mechanism may vary when the fluence changes. At the higher fluence (280mJ/cm2), depolymerization is the dominant process and the material left after etching displays almost no change in the O/C atomic ratio. At the lower fluence (80mJ/cm2), cleavage of the pendant group is dominant and the O/C ratio decreases significantly, especially on the polymer surface.
Electroplasticity memory devices using conducting polymers and solid polymer electrolytes
Authors: Takashima Wataru , Sasano Kiyotaka , Asano Tanemasa , Kaneto Keiichi
Published: April 2007

Erasable memory devices are fabricated by the combination of a conducting polymer and solid polymer electrolyte. The former is used as a memory channel and the latter as an electrolyte medium. The channel conductivity can be controlled over 3‐4 orders of magnitude by electrochemical doping through a writing electrode. The response time, depending on the writing voltage, is several seconds. The characteristics of the memory device are discussed.
Factors influencing the rate of the electrochemical oxidation of heterocyclic monomers
Authors: John R. , Wallace G. G.
Published: April 2007

The influence of several variables on the rate of oxidation of heterocycles to form conductive, electroactive polymers has been considered. It has been shown that the extent to which variables such as electrode size, monomer/counterion concentrations and applied potential influence the rate depends on the monomer and counterion being employed.
Synthesis and characterization of novel liquid‐crystalline copolymers containing thermally stable photochromic groups
Authors: Liu Jui‐Hsiang , Yang Po‐Chih , Chiu Yi‐Hong , Suda Yasuo
Published: April 2007

To overcome the defects of the thermal instability of azobenzene, a series of novel photochromic, chiral, liquid‐crystalline monomers and polymers were synthesized from (+)‐camphor. The copolymerization of the photochromic monomers with comonomers was carried out. The synthesized monomers and polymers were identified with nuclear magnetic resonance, Fourier transform infrared, and elemental analysis. The composition of the copolymers was estimated with elemental analysis. The specific rotation of the chiral compounds and polymers was evaluated. The thermal stability and phases of the polymers during heating and cooling cycles were studied with differential scanning calorimetry and thermogravimetric analysis. The phases of the polymers were identified with polarized optical microscopy textures and X‐ray diffraction analysis. The distance between the layers of smectic liquid crystals was estimated from the diffraction angles. Photoisomerization of the configurational E/Z structures was investigated with an ultraviolet–visible spectrophotometer with 300‐nm ultraviolet irradiation. The thermal stability of the Z‐structural segment in the polymers was confirmed through the heating of the polymer at 70 °C for over 10 h. The photoisomerization and thermal stability of the CC bond in the polymeric materials were demonstrated through a series of novel chiral polymers synthesized in this investigation. Both the polarity of the center part and the molecular length at the ends of the molecules were found to be necessary factors for the formation of liquid‐crystalline molecules. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 2026–2037, 2007
Synthesis and optical properties of light‐emitting π‐conjugated polymers containing biphenyl and dithienosilole
Authors: Liao Liang , Cirpan Ali , Chu Qinghui , Karasz Frank E. , Pang Yi
Published: April 2007

Copolymers containing oligo(phenylene vinylene) (2.5), fluorene, and 4,4‐dihexyldithienosilole (DTS) units were synthesized and characterized. The π‐conjugated monomers were joined with the palladium(0)‐catalyzed Suzuki–Miyaura coupling reaction, thus forming either biphenyl– or phenyl–thiophene linkages. These polymers were photoluminescent, with the fluorescent quantum efficiency between 54 and 63% and with λmaxfor fluorescence at ∼448 nm in tetrahydrofuran. The presence of 5% DTS in the copolymers had little influence on the optical absorption and emission wavelengths. Double‐layer light‐emitting‐diode devices using these polymers as emissive layers had low turn‐on voltages (3.5–4 V) and moderate external quantum efficiencies (0.14–0.30%). The results show that DTS plays a positive role in improving the charge‐injection characteristics of poly(phenylene vinylene) materials. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 2048–2058
Recent advances in the synthesis of well‐defined glycopolymers
Authors: Spain Sebastian G. , Gibson Matthew I. , Cameron Neil R.
Published: April 2007

Glycopolymers are receiving increasing interest due to their application in areas, such as glycomics, medicine, biotechnology, sensors, and separation science. Consequently, new methods for their synthesis are constantly being developed, with an increasing emphasis on the preparation of well‐defined polymers and on the production of complex macromolecular architectures such as stars. This review covers recent developments in the synthesis of glycopolymers, with a particular emphasis on (i) the use of controlled radical polymerization to prepare well‐defined glycopolymers from unprotected monomers and (ii) postpolymerization modification strategies using reactive polymer precursors (including “click” reactions). Recent work on the production of glycosylated polypeptides, which are under investigation as mimics of naturally occurring glycoproteins, is also included. The authors offer some suggestions as to future developments and remaining challenges in this topical area of polymer chemistry. © 2007 Wiley Periodicals, Inc. J Polym Sci PartA: Polym Chem45: 2059–2072, 2007
Elevation of the glass transition temperature in flexible‐chain semicrystalline polymers
Authors: Yee‐Chan Christopher K. , Scogna Robert C. , Register Richard A.
Published: April 2007

In the idealized two‐phase model of a semicrystalline polymer, the amorphous intercrystalline layers are considered to have the same properties as the fully‐amorphous polymer. In reality, these thin intercrystalline layers can be substantially influenced by the presence of the crystals, as individual polymer molecules traverse both crystalline and amorphous phases. In polymers with rigid backbone units, such as poly(etheretherketone), PEEK, previous work has shown this coupling to be particularly severe; the glass transition temperature (Tg) can be elevated by tens of degrees celsius, with the magnitude of the elevation correlating directly with the thinness of the amorphous layer. However, this connection has not been explored for flexible‐chain polymers, such as those formed from vinyl‐type monomers. Here, we examine Tg in both isotactic polystyrene (iPS) and syndiotactic polystyrene (sPS), crystallized under conditions that produce a range of amorphous layer thicknesses. Tg is indeed shown to be elevated relative to fully‐amorphous iPS and sPS, by an amount that correlates with the thinness of the amorphous layer; the magnitude of the effect is severalfold less than that in PEEK, consistent with the minimum lengths of polymer chain required to make a fold in the different cases. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 1198–1204, 2007
Mechanism for effect of ultrasound on polymer melt in extrusion
Authors: Chen Yingzi , Li Huilin
Published: April 2007

This paper explores the rheological characteristic and molecular mechanism of the polymer melts during extrusion when ultrasound is applied to them at the entrance of the die. Applying of ultrasound disturbs the convergent flow of polymer melt in the entry zone and changes the stream patterns, which leads to lesser elastic tensile strains happen. It also activates the molecular chains, so that the elastic tensile strains can be recovered very quickly. That is why the ΔP measured is reduced. These conclusions are made based not only on rheological calculations but also on looking‐inside characterizations of the molecular conformations. Ultrasound irradiation increases the free volume of PS, reduces the molecular entanglements of polymer melt. All these effects of ultrasound contribute to the productivity raising and product quality improvement of extrusion processing. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 1226–1233, 2007
Expansion properties of random Cayley graphs and vertex transitive graphs via matrix martingales
Authors: Christofides Demetres , Markström Klas
Published: April 2007

The Alon–Roichman theorem states that for every ε> 0 there is a constant c(ε), such that the Cayley graph of a finite group G with respect to c(ε)log ∣G∣ elements of G, chosen independently and uniformly at random, has expected second largest eigenvalue less than ε. In particular, such a graph is an expander with high probability.

Landau and Russell, and independently Loh and Schulman, improved the bounds of the theorem. Following Landau and Russell we give a new proof of the result, improving the bounds even further. When considered for a general group G, our bounds are in a sense best possible. We also give a generalization of the Alon–Roichman theorem to random coset graphs.

Our proof uses a Hoeffding‐type result for operator valued random variables, which we believe can be of independent interest. © 2007 Wiley Periodicals, Inc. Random Struct. Alg., 2008
Trends in worldwide intellectual property protection: The case of the pharmaceutical patent
Authors: Tancer Robert S.
Published: April 2007

The protection of intellectual property is of growing concern as an issue in international trade. Both the NAFTA and the TRIPS provide chapters on intellectual property, a subject matter included in multilateral trade agreements for the first time. These provisions were designed to reassure owners of such property that their rights would be protected in participating countries. Few industries are as dependent on adequate protection than the patent protected segment of the pharmaceutical industry. It is only through enforceable patent policies that drug companies can generate sufficient revenues to undertake the costly research and development that make the introduction of new products possible. This article examines recent trends in intellectual property protection on a global basis, focusing on differences and similarities within the pharmaceutical industry both in the European Community and the United States. Despite the focus on the pharmaceutical industry, the trends discussed should be of interest to any firm that utilizes intellectual property in its overseas activities. © 1995 John Wiley & Sons, Inc.
Changing barriers to the internationalization of franchising operations: Perceptions of domestic and international franchisors
Authors: Kedia Ben L. , Ackerman David J. , Justis Robert T.
Published: April 2007

This study examines factors that inhibit the internationalization of franchising operations. The factors are classified along the dimensions of importance and difficulty. The perceptions of domestic franchisors and international franchisors are compared. The results indicate that different factors inhibit internationalization of franchising efforts depending upon the stage of the franchising process. Comparisons of the results with previous studies indicate that significant changes have occurred in the perceived importance, changes which are understandable in light of changes in franchising practices as well as changes in the international environment. © 1995 John Wiley & Sons, Inc.
Industrial buyers' expectations of supplier‐attributes across developing countries: Implications for marketing strategies
Authors: Rao C. P. , Seshadri Srivatsa
Published: April 2007

This paper presents a cross‐country comparative study of industrial buyers' expectations of supplier attributes which manifest in the process of supplier selection. The results indicate a variance in these expectations across the countries, implying a multinational rather than a global approach in marketing industrial goods beyond domestic borders. The possible role of cultural factors in the formation of these divergent expectations is suggested. The implications of the findings for developing appropriate marketing strategies, and for future research, are discussed.
Investment banking in the gulf: A case study of investcorp in bahrain
Authors: Khan Golam M. , Amine Lyn S. , Ali Ebrahim
Published: April 2007

Investcorp is a low‐profile investment banking company that was originally founded on the tiny island of Bahrain in the Arabian Gulf. Although little known to the general public, the company is a major player in North American and European investment markets. This case study presents a profile of the company, its founder, Nemir Kirdar, and his three “founding friends.” It relates details of the company's successes and explores how these were achieved. As most of the original Management Committee members are preparing to retire, efforts are being made to ensure the continuing prosperity of the company. This requires the risky step of appointing an almost completely new management team. Readers are invited to reflect on the likely success of this strategy and whether Investcorp's focus on North America and Europe remains appropriate in a global marketplace.
In praise of ethnocentricity: Expatriate policies in European multinationals
Authors: Mayrhofer Wolfgang , Brewster Chris
Published: April 2007

The international HRM literature identifies different stages of internationalisation (ethnocentric, polycentric, regiocentric, geocentric); with a progression towards the later, most “advanced” stage. This paper uses information from European international companies to argue that most organizations still organize international HRM along ethnocentric lines and that, for a number of reasons, they are right to do so. We argue that a model where nearly all cases fall into one category may have reached the limits of its usefulness.
Judgmental heuristics in overseas vendor search and evaluation: A proposed model of importer buying behavior
Authors: Liang Neng , Stump Rodney L.
Published: April 2007

This article identifies theimplicitimporter buying behavior model that is suggested by import decision studies and reviews contextual factors that distinguish international sourcing from its domestic counterpart. We then discuss the major shortcomings of the implicit model, namely, the failure to take into account the cognitive processes that influence vendor search and evaluation patterns. Drawing on the cognitive psychology and artificial intelligence literatures, this paper proposes an alternative model of importer buying behavior that explicitly accounts for the use of cognitive heuristics and presents a series of testable research propositions. Theoretical and managerial implications are also discussed.
Trends in international business thought and literature: A review of international market entry mode research: Integration and synthesis
Authors: Sarkar Mitrabarun , Cavusgil S. Tamer
Published: April 2007

Although entry mode strategy has traditionally been a central topic of research in international business, it is only recently that integrated research frameworks have developed. Largely in response to the dynamic reconfiguration of global business, these new insights from channel management, global strategy, alliances, and political economy have infused new perspectives into entry mode research. This article reviews and synthesizes this literature. Within an over‐arching classificatory framework, central themes and sub‐themes within this body of literature are identified and their inter‐linkages investigated. The evolutionary process of entry mode research is examined. The article concludes with directions for future research and the need to integrate entry mode research with partnering strategies.
Trends in international business thought and literature (supplement): The transatlantic business dialogue: Business at the negotiating table
Authors: Cowles Maria Green
Published: April 2007

The Transatlantic Business Dialogue (TABD) is a novel coalition of American and European business leaders who seek to influence their respective governments on transatlantic trade and investment matters. In the past year, the TABD has emerged as a powerful voice in setting the agenda for the “transatlantic marketplace.” This article examines the TABD's origins and development, and suggests that the TABD may serve as a future model for trade and investment negotiations.
The compleat executive: The state of international business education and some future directions
Authors: Contractor Farok J.
Published: April 2007

This essay examines the current state of International Business education worldwide and comments on evolving trends. The degree of internationalization of curricula at the undergraduate, postgraduate and doctoral levels is examined. In a world facing the contrary pulls of global consumerism versus the search for a local identity, what exactly should the manager learn about International Business in order to complete his or her education? The essay also examines alternative methods for organizing International Business studies at universities, as well as in the growing number of off‐site and certificate programs. It also ventures opinions on the value of an International Business major in the job market for graduating students, on whether the International Business label confers an advantage on faculty, or whether it confers a stigma, and on academic orthodoxies which have slowed the internationalization of business curricula.
New rules for multinational investment
Authors: Rugman Alan M. , Gestrin Michael
Published: April 2007

Currently, new rules are being negotiated governing the foreign direct investment undertaken by multinational enterprises in order to generate a Multilateral Agreement on Investment (MAI). Here an analytical framework for the MAI is developed, building upon conventional international business theory, in particular the concepts of globalization and sovereignty.
From multinational to transnational?
Authors: Robinson Richard D. , Dickson John P. , Knutsen John A.
Published: April 2007

A little‐researched area of international business is the extent to which U.S.‐based firms have stripped decision‐making of national bias, that is, have become true transnationals. Whether they should or not, from a nationalistic point of view, is of course a matter of opinion and the topic of this article.
The development of international business in Africa (1947–1997)
Authors: Ibru Olorogun Michael C. O.
Published: April 2007

The genesis of international business in Africa from 1947 to 1996 is traced to colonial times. The article analyzes the dynamics and observes that international business in Africa witnessed growth but has not meaningfully influenced Africa's general economic development because of constraints: poor infrastructure, lack of maintenance culture, inadequate funding, debt burden and overemphasis on export of raw materials instead of manufactured goods. The article suggests placing a greater emphasis on the development of intermediate and capital goods industries and granting debt relief to all African countries as a means of further promoting international business entente in Africa.
The globalization of business in Latin America
Authors: Gómez Henry
Published: April 2007

New trade and exchange strategies, economic integration, political reforms, and privatization are driving Latin American firms to expand operations both within and outside the area. Additionally, multinational firms have stepped up operations, entered sectors previously dominated by state‐owned enterprises, and restructured their management. Vast projects are upgrading transport, seaports, and airports. Communications and emerging patterns in consumer life styles are redefining markets. Sweeping change, plus the challenge of becoming internationally competitive, has burgeoned management training needs for both the business and public sectors. Yet in some countries the prospects for continued reform could be reversed by hardening social tensions and voter skepticism that free market policies will effectively reduce poverty and persistent unemployment.
Case study: TV globo– the Brazilian media giant
Authors: Neto Raul De Gouvea
Published: April 2007

Brazilian multinational corporations are operating in several markets around the globe. The export of technology is an important development toward diversification of exports and gains in global competitiveness. This article shows that a Brazilian multinational, TV Globo, has engaged in the exportation of indigenous technology in an area where the level of sophistication is relatively high and traditionally controlled by multinationals from developed countries.
A retrospective of international business education in the United States over the past fifty years
Authors: Voris William
Published: April 2007

International business relationships are almost as old as mankind, but the idea that people needed to be educated to manage global business enterprises is less than 50 years old. The American Graduate School of International Management (Thunderbird), established in 1946 was the first school to provide languages, international studies, and business management as a basic education in international management. Business schools in America have been slow to realize and to promulgate courses and curriculums in the field. It has only been in the last ten years that the American Assembly of Collegiate Schools of Business, composed of over 700 colleges and universities in the country, has become an advocate through a revision in its standards. After the words “and worldwide” were inserted in the AACSB standards of accreditation, international business education began to permeate the offerings of American business schools.
Action, regulation, and response: The tobacco industry in the United States and Canada
Authors: Tancer Shoshana B.
Published: April 2007

One of the discoveries of the New World was tobacco. It was brought to Spain by Columbus and other explorers and used for a multitude of medicinal purposes, but not until Sir Walter Raleigh brought tobacco to the English throne, explaining that the native peoples smoked this leaf, and started using a clay pipe in 1586, did smoking tobacco become known and accepted in Europe. From these beginnings in what would become Virginia, the United States tobacco industry of today grew. Today, tobacco generates some $45 billion profits for the publicly held companies in the United States, while in Canada in 1983, the sale of cigarettes alone generated Canadian $62.7 billion.
Strategic network development—the European perspective
Authors: Hinterhuber Hans H. , Levin Boris M.
Published: April 2007

A strategic network is a system of small or mid‐size firms or, strategic business units, functional and regional units, suppliers, controlled firms, and partners to satisfy key stakeholders by optimizing specific core competencies and improving critical business processes.
Perceptual differences in appropriateness and likelihood of use of negotiation behaviors: A cross‐cultural analysis
Authors: Volkema Roger
Published: April 2007

This paper examines the influence of culture and economic climate on perceptions of ethicality of negotiation behaviors between two emerging trading partners in the Western Hemisphere. Three hundred and forty future business leaders from Brazil and the United States rated their perceptions of the appropriateness and likelihood of use of eighteen negotiation behaviors. The results indicate significant differences in perceptions of the appropriateness of most tactics, but similarities in terms of respondents' likelihood of employing tactics that involve third parties. For respondents from both countries, traditional competitive bargaining behaviors (e.g., pretending you are in no hurry, hiding your bottom line, exaggerating an opening demand) were among the most accepted tactics. The implications of these findings for cross‐cultural negotiations are discussed, along with opportunities for future research.
An environmental agenda for APEC: Lessons from NAFTA
Authors: Rugman Alan M. , Soloway Julie A.
Published: April 2007

The Asia Pacific Economic Cooperation (APEC) forum has been slow to deal with trade and the environment issues. In contrast, the North American Free Trade Agreement (NAFTA) and its environmental side agreement incorporate extensive environmental provisions and institutions in its framework. APEC could usefully build upon the NAFTA experience.
Integrating ethics into international marketing strategy: An extension of Robin and Reidenbach's framework
Authors: Griffith David A. , Mayo Michael A.
Published: April 2007

This study proposes and tests an extension of Robin and Reidenbach's (1987) model of integrating ethics into the strategic marketing development process. The model extension may help marketing managers to identify the publics that might be negatively impacted by a given strategic option and the duties marketers may assume to safeguard public welfare in these instances. A sample of 155 marketing practitioners was used to examine how marketers apply ethical values upon entering new markets. This study suggests that, contrary to public sentiment, marketers are sensitive to potential consumer harm and act to minimize this risk.
Small‐Bowel Obstruction Secondary to Bezoar Impaction: A Diagnostic Dilemma
Authors: Ho Thomas W. , Koh Dean C.
Published: April 2007

Background

Gastrointestinal bezoar (GIB) is uncommon and is reported to occur in 4% of all admissions for small‐bowel obstruction (SBO). Because of a lack of diagnostic features, it is often associated with a delay in treatment, with increased morbidity. In this article, we report our experience with managing bezoar‐induced SBO and the role of early computed tomography (CT) imaging in establishing the diagnosis.

Methods

We retrospectively reviewed all cases of bezoar‐induced SBO treated in our unit between 1999 and 2005.

Results

There were 43 patients, of whom 2 had a recurrence, giving a total of 45 episodes. The frequency of bezoar in our patients presenting with SBO was 4.3%. All patients were of Asian origin: 41 Chinese, 1 Indian, and 1 Malay. Twenty‐eight (65%) patients had previous abdominal surgery of which 26 were gastric surgery. Thirty‐eight (88%) patients were edentulous. Forty‐one (91%) underwent serial abdominal radiography, whereas only 4 patients (9%) had either CT imaging or contrast study alone. Only 11 (24%) cases had a correct diagnosis of bezoar impaction made preoperatively by CT imaging. The diagnostic accuracy of CT imaging in our series was 65%, with six cases of misdiagnosis. Overall, CT led to a change in management of 76% (13 in 17). The median time to surgery from admission was 2 (0–0) days. There were 2 cases of ischemic bowel that necessitated bowel resection. The median length of hospital stay was 11 (5–100) days. Ten patients (22%) had postoperative complications, and there was one death.

Conclusion

Bezoar‐induced SBO is uncommon and remains a diagnostic and management challenge. It should be suspected in patients with an increased risk of formation of GIB, such as previous gastric surgery, poor dentition, and a suggestive history of increased fibre intake. We advocate that CT imaging be performed early in these at‐risk patients and in patients presenting with SBO with or without a history of abdominal surgery in order to reduce unnecessary delays before appropriate surgical intervention.
Survival after Parathyroidectomy in Patients with End‐stage Renal Disease and Severe Hyperparathyroidism
Authors: Trombetti Andrea , Stoermann Catherine , Robert John H. , Herrmann François R. , Pennisi Pietra , Martin Pierre‐Yves , Rizzoli René
Published: April 2007

Background

Patients with end‐stage renal disease (ESRD) and secondary hyperparathyroidism (SHPT) are at high risk of mortality. Whether an increased risk of death persists after a parathyroidectomy (PTX) is not clearly established.

Subjects and methods

The survival of 40 patients with ESRD and SHPT who underwent PTX was compared with that of 664 ESRD patients.

Results

From first dialysis, a lower mortality rate was found in the group of patients who underwent PTX than in the nonoperated ESRD group (hazard ratio: 0.23; 95% CI: 0.14–0.37). The patients who underwent PTX were younger, had a longer time on dialysis, and had a higher prevalence of kidney transplantation. The mean number of comorbidities was lower (Charlson score 4.2 ± 2.1 versus 6.4 ± 2.9, p < 0.001). Then, we randomly selected two matched controls for each PTX case (80 controls, 40 PTX) who had at least an equivalent mean duration of dialysis between the first dialysis and PTX of the PTX group. In a univariate model, there was a trend for PTX being associated with prolonged survival. The mortality was higher both among those at an advanced age and those with a high Charlson score. Adjustments for these covariates made the effect of PTX no more significant.

Conclusions

The risk of death of patients with severe SHPT leading to PTX differed from that of nonoperated subjects. The apparent differences in survival may be related to the number and severity of associated comorbidities. ESRD patients who undergo PTX may represent a subset of healthier subjects.
A new root‐based direction‐finding algorithm
Authors: Wasylkiwskyj Wasyl , Kopriva Ivica , Doroslovački Miloš , Zaghloul Amir I.
Published: April 2007

Polynomial rooting direction‐finding (DF) algorithms are a computationally efficient alternative to search‐based DF algorithms and are particularly suitable for uniform linear arrays of physically identical elements provided that mutual interaction among the array elements can be either neglected or compensated for. A popular algorithm in such situations is Root Multiple Signal Classification (Root MUSIC (RM)), wherein the estimation of the directions of arrivals (DOA) requires the computation of the roots of a (2N − 2) ‐order polynomial, where N represents number of array elements. The DOA are estimated from the L pairs of roots closest to the unit circle, where L represents number of sources. In this paper we derive a modified root polynomial (MRP) algorithm requiring the calculation of only L roots in order to estimate the L DOA. We evaluate the performance of the MRP algorithm numerically and show that it is as accurate as the RM algorithm but with a significantly simpler algebraic structure. In order to demonstrate that the theoretically predicted performance can be achieved in an experimental setting, a decoupled array is emulated in hardware using phase shifters. The results are in excellent agreement with theory.
Equatorial spread F modeling: Multiple bifurcated structures, secondary instabilities, large density ‘bite‐outs,’ and supersonic flows
Authors: Huba J. D. , Joyce G.
Published: April 2007

The Naval Research Laboratory has recently developed a new two‐dimensional code to study equatorial spread F (ESF): NRLESF2. The code uses an 8th order spatial interpolation scheme and the partial donor cell method. This allows the model to capture very sharp gradients over ∼ 4 grid cells and to assess the impact of numerical diffusion on the dynamics of ‘bubble’ evolution. Simulation results are presented that show new and complex ESF bubble dynamics: multiple bifurcations, secondary instabilities, density ‘bite‐outs’ of over three orders of magnitude, and supersonic flows within low density channels (V ≃ few km/s). These results are consistent with radar and satellite observations, as well as optical images. It is also shown that numerical diffusion can inhibit bubble bifurcation and the development of small‐scale structure.
Earthquake swarms driven by aseismic creep in the Salton Trough, California
Authors: Lohman R. B. , McGuire J. J.
Published: April 2007

In late August 2005, a swarm of more than a thousand earthquakes between magnitudes 1 and 5.1 occurred at the Obsidian Buttes, near the southern San Andreas Fault. This swarm provides the best opportunity to date to assess the mechanisms driving seismic swarms along transform plate boundaries. The recorded seismicity can only explain 20% of the geodetically observed deformation, implying that shallow, aseismic fault slip was the primary process driving the Obsidian Buttes swarm. Models of earthquake triggering by aseismic creep can explain both the time history of seismic activity associated with the 2005 swarm and the ∼1 km/h migration velocity exhibited by this and several other Salton Trough earthquake swarms. A combination of earthquake triggering models and denser geodetic data should enable significant improvements in time‐dependent forecasts of seismic hazard in the key days to hours before significant earthquakes in the Salton Trough.
Frequency‐dependent phase coherence for noise suppression in seismic array data
Authors: Schimmel M. , Gallart J.
Published: April 2007

We introduce a coherence measure for seismic signal enhancement through incoherent noise attenuation. Our processing tool is designed for densely spaced arrays and identifies signals by their coherent appearance. The approach is based on the determination of the lateral phase coherence as function of distance, time, frequency, and slowness. The coherence is derived from the local phases of neighboring stations which we obtain from analytic signals through the S‐transform. The coherence is used to attenuate incoherent components in the time‐frequency representations of the seismic records. No waveforms are averaged in our approach to maintain local amplitude information. This way we construct a data‐adaptive filter which enhances coherent signals using the frequency‐dependent and slowness‐dependent phase coherence. We explain the method and show its abilities and limitations with theoretical test data. Furthermore, we have selected an ocean bottom seismometer (OBS) record section from NW‐Spain and a teleseismic event registered at Spanish broadband stations to show the filter performance on real array data. Incoherent noise has been attenuated in all cases to enable a less ambiguous signal detection. In our last example, the filter also reveals weak conversions/reflections at the 410‐km and 660‐km discontinuities which are hardly visible in the unfiltered input data.
Comparison of Arctic sea ice thickness variability in IPCC Climate of the 20th Century experiments and in ocean–sea ice hindcasts
Authors: Gerdes Rüdiger , Köberle Cornelia
Published: April 2007

Arctic sea ice is an important climate component and often regarded as an early indicator of anthropogenic global change. For an assessment of coupled climate models, their performance with respect to the development of Arctic sea ice thickness during the 20th century is examined. Their behavior is compared with results from an ocean–sea ice model using the Arctic Ocean Model Intercomparison Project (AOMIP) atmospheric forcing for the period 1948–2000. In lieu of actually observed sea ice thickness, this model result under realistic atmospheric forcing serves as a benchmark for the coupled climate models. The hindcast exhibits virtually no trend in Arctic ice volume over its integration period 1948–2000. Most of the coupled climate models show a negative trend over the 20th century that accelerates towards the end of that century.
Flow of abyssal water into Wake Island Passage: Properties and transports from hydrographic surveys
Authors: Uchida Hiroshi , Yamamoto Hirofumi , Ichikawa Kaoru , Kaneko Ikuo , Fukasawa Masao , Kawano Takeshi , Kumamoto Yuichiro
Published: April 2007

Water mass characteristics and volume transports of abyssal water flowing northward into Wake Island Passage in the North Pacific Ocean were examined by carrying out high‐quality hydrographic surveys in May 2003, October 2004, and December 2005 along with mooring observations from May 2003 to December 2005. Close linear relationships between potential temperature (θ) and salinity, dissolved oxygen, and silicate were seen below θ ≈ 1.1°C (≈4000 m). The relationships above θ ≈ 1.1°C were scattered and were separated into relatively salty, oxygen‐rich, silicate‐poor water to the south, and water with the opposite properties to the north. The results suggested that there was a boundary between water masses at θ ≈ 1.1°C in the deep passage. In addition to the three hydrographic sections, two hydrographic sections previously surveyed in the deep passage in 1975 and 1999 were reexamined for transport estimates. Geostrophic calculations relative to the θ = 1.1°C surface indicated northward transports of the abyssal water from 0.5 to 2.2 Sv (1 Sv = 106 m3 s−1) below this surface. When 1‐year mean estimated velocities at θ = 1.1°C surface were used for reference, mean transport from the five estimates increased from 1.4 to about 4 Sv. The temperature of abyssal water colder than 1.1°C was found to have increased by an average of 0.012°C between 1975 and 2005. This warming is greater than double the standard deviation from the temporal mean temperature profile obtained from mooring observations.
Scanning multichannel microwave radiometer snow water equivalent assimilation
Authors: Dong Jiarui , Walker Jeffrey P. , Houser Paul R. , Sun Chaojiao
Published: April 2007

Accurate prediction of snowpack status is important for a range of environmental applications, yet model estimates are typically poor and in situ measurement coverage is inadequate. Moreover, remote sensing estimates are spatially and temporally limited due to complicating effects, including distance to open water, presence of wet snow, and presence of thick snow. However, through assimilation of remote sensing estimates into a land surface model, it is possible to capitalize on the strengths of both approaches. In order to achieve this, reliable estimates of the uncertainty in both remotely sensed and model simulated snow water equivalent (SWE) estimates are critical. For practical application, the remotely sensed SWE retrieval error is prescribed with a spatially constant but monthly varying value, with data omitted for (1) locations closer than 200 km to significant open water, (2) times and locations with model‐predicted presence of liquid water in the snowpack, and (3) model SWE estimates greater than 100 mm. The model error is estimated using standard error propagation with a calibrated spatially and temporally constant model error contribution. A series of tests have been performed to assess the assimilation algorithm performance. Multiyear model simulations with and without remotely sensed SWE assimilation are presented and evaluated with in situ SWE observations. The SWE estimates from assimilation were found to be superior to both the model simulation and remotely sensed estimates alone, except when model SWE estimates rapidly and erroneously crossed the 100‐mm SWE cutoff early in the snow season.
Dissipative particle dynamics simulation of pore‐scale multiphase fluid flow
Authors: Liu Moubin , Meakin Paul , Huang Hai
Published: April 2007

Multiphase fluid flow through porous media involves complex fluid dynamics, and it is difficult to model such complex behavior, on the pore scale, using grid‐based continuum models. In this paper, the application of dissipative particle dynamics (DPD), a relatively new mesoscale method, to the simulation of pore‐scale multiphase fluid flows under a variety of flow conditions is described. We demonstrate that the conventional DPD method using purely repulsive conservative (nondissipative) particle‐particle interactions is capable of modeling single‐phase flow fields in saturated porous media. In order to simulate unsaturated multiphase flow through porous media, we applied a modified model for the conservative particle‐particle interactions that combines short‐range repulsive and long‐range attractive interactions. This form for the conservative particle‐particle interactions allows the behavior of multiphase systems consisting of gases, liquids, and solids to be simulated. We also demonstrated that the flow of both wetting and nonwetting fluids through porous media can be simulated by controlling the ratios between the fluid‐fluid and fluid‐solid (fluid‐wall) interparticle interaction strengths.
Modeling a nonlinear water transfer between two reservoirs in a midterm hydroelectric scheduling tool
Authors: Moraga Rocío , García‐González Javier , Parrilla Ernesto , Nogales Sergio
Published: April 2007

In a competitive environment, operation and planning decisions of generating units are decentralized. Therefore the management of hydroelectric generation resources requires the development of advanced planning and scheduling tools adapted to the particular needs of each company. This paper presents a method for considering natural water transfers through a pipeline in the context of a midterm hydro scheduling model. The main complexity of gravitational transfer modeling resides in considering the nonlinear relation between the water levels in the connected reservoirs and the transfer flow. The methodology proposed consists first in simplifying the problem by means of a change of variables, subsequently using a piecewise linear approximation of the transfer flow equation in order to consider it within a mixed integer linear programming tool, and ultimately adjusting the final solution. The proposed methodology is currently being used to manage the Sil River hydro basin in the northwest of Spain, with satisfactory results, as shown in the case study.
Improved finite‐sample Hurst exponent estimates using rescaled range analysis
Authors: Hamed Khaled H.
Published: April 2007

Rescaled range analysis is one of the classical methods used for detecting and quantifying long‐term dependence in time series. However, rescaled range analysis has been shown in several studies to give biased estimates of the Hurst exponent in finite samples. A new estimator based on a modified expression of the expected value of the rescaled range is proposed. A comparison of the modified estimator with other alternatives shows that the modified estimator offers a great improvement over the classical rescaled range estimator in terms of bias and root mean square error, which makes it comparable to some of the leading estimators. The application of the proposed modified rescaled range estimator to a group of temperature, rainfall, river flow, and tree‐ring time series in the Midwest USA demonstrates the extent to which classical rescaled range analysis can give misleading results. Based on a statistical test of significance, the number of time series exhibiting the Hurst effect is reduced from 36 to only 11 out of 56 temperature series, and from 23 to 7 out of 60 rainfall series. On the other hand, the number of time series exhibiting the Hurst effect marginally increased from 8 to 9 out of 49 river flow series, and from 49 to 54 out of 88 tree‐ring series.