bluuebunny/crossref_metadata_2025 huggingface dataset:
Synthesis of poly(β‐pinene)‐g‐poly(meth)acrylate by the combination of living cationic polymerization and atom transfer radical polymerization
Authors: Lu Jiang , Liang Hui , Zhang Wei , Cheng Qing
Published: March 2003

New graft copolymers of β‐pinene with methyl methacrylate (MMA) or butyl acrylate (BA) were synthesized by the combination of living cationic polymerization and atom transfer radical polymerization (ATRP). β‐Pinene polymers with predetermined molecular weights and narrow molecular weight distributions (MWDs) were prepared by living cationic polymerization with the 1‐phenylethyl chloride/TiCl4/Ti(OiPr)4/nBu4NCl initiating system, and the resultant polymers were brominated quantitatively by N‐bromosuccinamide in the presence of azobisisobutyronitrile, yielding poly(β‐pinene) macroinitiators with different bromine contents (Br/β‐pinene unit molar ratio = 1.0 and 0.5 for macroinitiators a and b, respectively). The macroinitiators, in conjunction with CuBr and 2,2′‐bipyridine, were used to initiate ATRP of BA or MMA. With macroinitiator a or b, the bulk polymerization of BA induced a linear first‐order kinetic plot and gave graft copolymers with controlled molecular weights and MWDs; this indicated the living nature of these polymerizations. The bulk polymerization of MMA initiated with macroinitiator a was completed instantaneously and induced insoluble gel products. However, the controlled polymerization of MMA was achieved with macroinitiator b in toluene and resulted in the desired graft copolymers with controlled molecular weights and MWDs. The structures of the obtained graft copolymers of β‐pinene with (methyl)methacrylate were confirmed by 1H NMR spectra. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 1237–1242, 2003
Charge‐mosaic membrane prepared from microspheres
Authors: Takizawa Minoru , Sugito Yoshifumi , Oguma Naomi , Nakamura Michiei , Horiguchi Shojiro , Fukutomi Takashi
Published: March 2003

A new type of charge‐mosaic membrane was prepared from poly(4‐vinyl pyridine) microspheres 250–350 nm in diameter as an anion‐exchange element and from linear poly(sodium styrene sulfonic acid) as a cation‐exchange element. The mosaic structure on the surface of the membrane and the continuous connection of the microspheres in the membrane were confirmed by scanning electron microscopy observations and the electrical conductivity of the membrane. The microspheres were continuously connected from one side to the other side of the membrane surface when the weight fraction of the microspheres increased more than 20–25 wt % in the membrane. The flux of KCl, the permeability coefficient of KCl, the volume flux, and the selectivity dialysis separation of the electrolyte (KCl) and nonelectrolyte (glucose and saccharose) of the membrane indicated that it had the characteristic properties of a charge‐mosaic membrane. Ion‐exchange membranes composed of each raw material of the charge‐mosaic membrane did not show these properties. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 1251–1261, 2003
Main‐chain, thermotropic, liquid‐crystalline, hydrogen‐bonded polymers of 4,4′‐bipyridyl with aliphatic dicarboxylic acids
Authors: Bhowmik Pradip K. , Wang Xiaobin , Han Haesook
Published: March 2003

A series of main‐chain, thermotropic, liquid‐crystalline (LC), hydrogen‐bonded polymers or self‐assembled structures based on 4,4′‐bipyridyl as a hydrogen‐bond acceptor and aliphatic dicarboxylic acids, such as adipic and sebacic acids, as hydrogen‐bond donors were prepared by a slow evaporation technique from a pyridine solution and were characterized for their thermotropic, LC properties with a number of experimental techniques. The homopolymer of 4,4′‐bipyridyl with adipic acid exhibited high‐order and low‐order smectic phases, and that with sebacic acid exhibited only a high‐order smectic phase. Like the homopolymer with adipic acid, the two copolymers of 4,4′‐bipyridyl with adipic and sebacic acids (75/25 and 25/75) also exhibited two types of smectic phases. In contrast, the copolymer of 4,4′‐bipyridyl with adipic and sebacic acids (50/50), like the homopolymer with sebacic acid, exhibited only one high‐order smectic phase. Each of them, including the copolymers, had a broad temperature range of LC phases (36–51 °C). The effect of copolymerization for these hydrogen‐bonded polymers on the thermotropic properties was examined. Generally, copolymerization increased the temperature range of LC phases for these polymers, as expected, with a larger decrease in the crystal‐to‐LC transition than in the LC‐to‐isotropic transition. Additionally, it neither suppressed the formation of smectic phases nor promoted the formation of a nematic phase in these hydrogen‐bonded polymers, as usually observed in many thermotropic LC polymers. The thermal transitions for all of them, measured by differential scanning calorimetry, were well below their decomposition temperatures, as measured by thermogravimetric analysis, which were in the temperature range of 193–210 °C. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 1282–1295, 2003
Polyester hydrogels with swelling properties controlled by the polymer architecture, molecular weight, and crosslinking agent
Authors: Finne Anna , Albertsson Ann‐Christine
Published: March 2003

Hydrogels of poly(1,5‐dioxepan‐2‐one) and hydrogels of block copolymers of poly(1,5‐dioxepan‐2‐one) and poly(L‐lactide) were synthesized. Both star‐shaped polymers and linear polymers were polymerized with ring‐opening polymerization and crosslinked in situ with a tetrafunctional acid chloride (1,2,3,4‐cyclopentane tetracarboxylic acid chloride) or a difunctional acid chloride (succinyl chloride). Different network architectures were synthesized in this way. The initial monomer concentrations and the molecular weights of the macromonomers were also altered. The networks were characterized with 1H NMR and differential scanning calorimetry, and the swelling abilities of the different hydrogels were investigated in water and dichloromethane. The ratio of the monomer to the crosslinking agent was assessed by the quantification of the signal intensities in the 1H NMR spectra of the swelled network and agreed with the theoretical crosslinking density. Both the homopolymers of 1,5‐dioxepan‐2‐one and the copolymers of 1,5‐dioxepan‐2‐one and L‐lactide swelled to a high degree in water. The swelling properties of the materials could be varied over a broad range by changes in the architecture, molecular weight, and content of the precursor in the network. Star‐shaped poly(1,5‐dioxepan‐2‐one) crosslinked with a difunctional acid chloride had the highest degree of swelling among the different homopolymer hydrogels. This network also had the lowest glass‐transition temperature because of the flexible units in the structure. The same trends found for the homopolymer hydrogels were also seen in the hydrogels with block copolymers. The hydrogels swelled enormously in dichloromethane, and as in water, the star‐shaped copolymer crosslinked with a difunctional acid chloride had the highest degree of swelling. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 1296–1305, 2003
Modified polysulfones. VI. Preparation of polymer membrane materials containing benzimine and benzylamine groups as precursors for molecularly imprinted sensor devices
Authors: Robertson Gilles P. , Guiver Michael D. , Bilodeau François , Yoshikawa Masakazu
Published: March 2003

A modified polysulfone containing benzylamine groups was synthesized as a reactive membrane material. Polysulfone was activated at the ortho‐sulfone site by direct lithiation with n‐butyllithium, and the resulting lithiated polysulfone was then reacted with benzonitrile; this yielded a polymer with pendant benzimine groups. The structure was confirmed by NMR and IR spectroscopy and by the transformation of imine to ketone by acid hydrolysis. The polymeric benzimine was also reduced to benzylamine with sodium cyanoborohydride in an acidic medium. The structure and degree of substitution of both benzylamine derivatives were determined by NMR and IR spectroscopy. The modified polysulfone containing benzylamine groups initiated the polymerization of N‐carboxyanhydride of γ‐benzyl‐L‐glutamate [Glu(OBzl)–NCA]. The side‐chain oligopeptide of Glu(OBzl)–NCA attached to polysulfone was converted into molecular recognition sites. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 1316–1329, 2003
Synthesis, characterization, and properties of novel ladderlike phosphorus‐containing polysilsesquioxanes
Authors: Chiang Chin‐Lung , Ma Chen‐Chi M.
Published: March 2003

Novel ladderlike polysilsesquioxanes that contain phosphorus were successfully synthesized by the sol–gel method. The polysilsesquioxanes were characterized by Fourier transform infrared spectroscopy, 29Si NMR, and X‐ray diffraction. The characterizations demonstrated that the polymer possesses a typical ladderlike structure. The thermogravimetric and differential scanning calorimetric data revealed that the polysilsesquioxanes possess excellent thermal stability. A kinetic analysis of thermal degradation showed that the activation energy of thermal degradation is 187 kJ/mol, according to Kissinger's method. The activation energy of thermal degradation normally increases with conversion (from 171 to 309 kJ/mol) according to Ozawa's method. The average activation energy, calculated by Ozawa's method, was 209 kJ/mol. The scanning electron microscopic photograph and Si and P mappings of ladderlike polysilsesquioxanes showed that the particles were uniformly dispersed at the molecular level and that the sizes of the polysilsesquioxane particles were less than 100 nm. The ultraviolet–visible spectra of the ladderlike polysilsesquioxanes revealed no absorbance in the range of 400–800 nm. Ladderlike polysilsesquioxanes possess excellent optical transparency and excellent flame retardance. This transmittance may be used as a criterion for identifying the formation of a homogeneous phase. These polymers have great potential in waveguide applications. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 1371–1379, 2003
Synthesis of 1,3‐bis(2‐trimethylsilyloxyhexafluoro‐2‐propyl)‐5‐allylbenzene and its introduction into polysiloxane chains
Authors: Boutevin B. , Gaboyard M. , Guida‐Pietrasanta F. , Hairault L. , Lebret B. , Pasquinet E.
Published: March 2003

The synthesis of 1,3‐bis(2‐trimethylsilyloxyhexafluoro‐2‐propyl)‐5‐allylbenzene (IV) is described, starting from commercially available 1,3‐bis(2‐hydroxyhexafluoro‐2‐propyl)benzene. After the first step of iodination was optimized, a series of metallating agents were tested, before allylation, so that the best reagent could be selected. The allyl compound IV was then added to two different copoly(dimethyl‐methylhydro)siloxanes, PS 122.5 and PS 123 from Gelest/ABCR, via platinum‐catalyzed hydrosilylation, for the preparation of new polysiloxanes bearing specifically designed pendant aryl moieties. The different synthesized products were characterized by spectroscopic methods (IR and 1H, 13C, 19F, and 29Si NMR), and the glass‐transition temperatures of copolymers VI‐2, VI‐3, and VI‐4 were measured. It was shown that the higher the amount was of grafted fluoroaryl groups, the higher the glass‐transition temperature was. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 1400–1410, 2003
Tao Zhang, Soo‐Young Park, B. L. Farmer, Leonard V. Interrante, Synthesis of comb‐type polycarbosilanes via nucleophilic substitution reactions on the main‐chain silicon atoms, Journal of Polymer Science Part A: Polymer Chemistry (2003) 41(7) 984–997
Authors: Zhang Tao , Park Soo‐Young , Farmer B. L. , Interrante Leonard V.
Published: March 2003

The original article to which this erratum refers was published in Journal of Polymer Science Part A: Polymer Chemistry (2003) 41(7) 984–997

No abstract.
Choice of the Focal Point Position Using Lasentec FBRM
Authors: Worlitschek Jörg , Mazzotti Marco
Published: March 2003

The Focused Beam Reflectance Measurement (FBRM) technique provides on‐line and in situ information about the chord length distribution (CLD) of a population of particles in dispersion. The effect of changing the focal point position on the measured CLD is experimentally analyzed by carrying out single particle FBRM determinations in both pure water and a dispersion of fines. The results allow some general conclusions to be drawn about optimal focal point positions.
Automated Digital Image Based Measurement of Boundary Fractal Dimension for Complex Nanoparticles
Authors: Wettimuny Ramitha , Penumadu Dayakar
Published: March 2003

There is a growing realization that complex nanoparticles produced by combustion reaction, precipitation, and spray technology using supercritical fluids, are fractally structured. The boundary fractal dimension is linked to the flow, packing and consolidation dynamics of nanopowders. It also contains information on the formation dynamics of the nanoparticles produced by various methods. Extraction of the fractal dimension information embodied in the nanoparticle's fractal structure is hampered by the lack of automated characterization algorithms for processing images of particles. This paper describes an efficient algorithm for analyzing digitized images of fractally structured nanoparticles and presents a computer program that automates the procedure using digital image processing techniques. The program functionality is demonstrated and discussed using digital images of typical pigment, ceramic and pharmaceutical powders.
Selection of Descriptors for Particle Shape Characterization
Authors: Hentschel Mark L. , Page Neil W.
Published: March 2003

Conventional shape descriptors, formed from a ratio of two particle size measurements, are among the simplest of the many methods used for quantitative particle shape characterization. However, a significant limitation of using one of these shape descriptors is that its value is often not unique to a specific shape. Use of several different shape descriptors may circumvent this problem but, as particle size can be defined in a large number of ways, a similarly large number of shape descriptors can be defined. While some differ substantially, others are only subtly different, conveying similar information. Thus, it is not obvious which of the many possible descriptors should be utilized. In this paper, two‐dimensional particle shape descriptors obtained by image analysis of six different commercially sourced powders were considered. Techniques of cluster and correlation analysis were applied to assist in identifying redundant descriptors for shape characterization of these powder particles, allowing for efficient description of shape using a reduced set. It was found that at least two descriptors are required: aspect ratio and the square root of form factor. Significantly, each descriptor is most sensitive to a different attribute of shape: elongation and ruggedness, respectively.
An Experimental Study of Liquid Jets Interacting with Cross Airflows
Authors: Birouk Madjid , Stäbler Thomas , Azzopardi Barry J.
Published: March 2003

The primary break‐up of liquid jets in cross flows has been studied experimentally. An open‐circuit wind tunnel was employed in which the airflow was generated by a centrifugal fan. The test section, positioned 3 m downstream of the fan, was made of clear acrylic resin to allow optical access and visualization. The working liquid used in the present experiment was an aero‐engine lubrication oil, which was injected perpendicularly into the air flow, via a nozzle placed in the top wall of the test‐section. The study of the primary break‐up mechanisms of the jet involved three parameters, the oil viscosity, and the jet and air cross flow velocities, which were varied independently. Two different break‐up regimes were observed and identified; arcade break‐up and bag break‐up. These were separated by a transition zone. Transverse and longitudinal (or streamwise) penetrations of the jet before the liquid breakup were also measured. The correlation proposed by Wu et al. to predict the jet transverse penetration before the break‐up of the liquid, as a function of the liquid/airflow momentum‐flux ratio, was found to be applicable only to liquids with low viscosity. An empirical extension to this equation has been produced.
Viscous Interaction Between a Vortex Tube and a Rotating Spherical Particle
Authors: Niazmand Hamid , Renksizbulut Metin
Published: March 2003

The transient advection of a cylindrical vortex tube in a viscous incompressible flow field and its interaction with a rotating/spinning spherical particle has been investigated numerically at Reynolds numbers in the range of 20≤ Re≤200 for angular velocities of 0≤Ω≤0.5. The effects of vortex parameters such as size, circulation strength and initial position relative to the particle, on the temporal behavior of the lift and drag forces are studied. Vortex‐sphere interactions bring about major changes in the flow field particularly when coupled with particle rotation. It is observed that the forces acting on the particle are significantly influenced during the time that the vortex core is in the vicinity of the particle. The extent of these local changes are about ±30% in the drag coefficient and about ±200% in the lift coefficient as compared to flow over a rotating solid sphere with no vortex interaction. It is also found that a vortex with core radius between one and two particle diameters creates the strongest temporal variations in the lift and drag coefficients. Furthermore, maximum lift variations occur for the vortex‐particle head on collision, while a vortex with an offset distance of about one diameter from the principal flow axis generates the maximum drag variations.
Self Similarity of Cross‐Stream Droplet Momentum Displacement in Dispersed Multiphase Flow
Authors: Milanez Marko , Naterer Greg F. , Venn Geoff , Richardson Giles
Published: March 2003

Analytical methods are developed and applied to droplet motion, as it relates to aircraft icing. Impinging droplets largely affect the heat balance at an iced aircraft surface, as well as the final ice shape. In this study, a similarity solution of the Eulerian droplet momentum equation is developed. Droplet motion near a flat plate is investigated with a similarity solution. By using scaling, sensitivity, order of magnitude and similarity methods, a momentum displacement of droplets (or particles) due to the presence of the solid surface is predicted. Self similarity of the droplet profiles is established, such that downstream propagation can be expressed in terms of a single independent coordinate. Limiting trends of momentum/drag induced and Blasius‐diffusion profiles are found to identify the spatial range encompassing the droplet motion. The predicted results are successfully compared against the scaling requirements.
Inverse Velocity and Singularity Analysis of Low‐DOF Serial Manipulators
Authors: Fang Yuefa , Tsai Lung‐Wen
Published: March 2003

This paper presents a method for exact inverse velocity analysis of low‐DOF (degrees of freedom n<6) serial manipulators. For a low‐DOF serial manipulator, the number of independently controllable variables in the Cartesian space is equal to the number of joint variables in the joint space, and the remaining 6−n variables are linearly dependent on these independent variables. This paper employs the theory of reciprocal screws to determine a mapping between the independent velocity components in the Cartesian space and the joint rates in the joint space. It is shown that singular conditions of a low‐DOF manipulator depend on choice of independent variables. A 5‐DOF and a 4‐DOF manipulator are analyzed, and a numerical example in which the end effector of a 4‐DOF manipulator is commanded to follow a straight line is used to demonstrate the methodology. © 2003 Wiley Periodicals, Inc.
Comparing the resource‐based and market‐based views of the firm: empirical evidence from Czech privatization
Authors: Makhija Mona
Published: March 2003

The recent privatization of state‐owned enterprises in the Czech Republic forms a natural experiment to test and compare the predictive ability of the resource‐based view (RBV) against the market‐based view (MBV) under conditions of great change. It has been recognized in the literature that, under normal stable circumstances, a firm's internal resources and its external market power are fundamentally intertwined. Consequently, it is difficult to identify the relative roles of these two theories in explaining expected firm performance and firm value. However, when market conditions are in a state of flux, as in the case of the Czech Republic in 1992, we expect the firm's resources to be the primary determinants of firm value. In order to test this notion, an RBV model was developed, based on a set of firm features reflecting the rare and valuable ability to compete in the emerging capitalistic economy (as opposed to the currently prevailing bureaucratically planned economy). A contrasting MBV model was also developed, highlighting the role of market power in this regard. These models were assessed in a cross‐sectional sample of 988 Czech firms undergoing privatization. The empirical findings show that the RBV‐driven variables are remarkably better at explaining share values of Czech firms in the period of privatization than MBV‐driven variables. These results underscore the role of firm resources as a primary determinant of firm value in rapidly changing environments. Copyright © 2003 John Wiley & Sons, Ltd.
The capital structure implications of pursuing a strategy of innovation
Authors: O'Brien Jonathan P.
Published: March 2003

In this paper, we argue that consideration of firm strategy can help illuminate the choices managers make between debt and equity financing. Within an industry, the form of competition that each firm chooses will determine the strategic value to the firm of maintaining financial slack. Our empirical analysis yields strong support for the proposition that financial slack should be a particularly critical strategic imperative for firms pursuing a competitive strategy premised on innovation. We also demonstrate that firms pursuing such a strategy that fail to recognize the value of financial slack are likely to perform poorly. Copyright © 2003 John Wiley & Sons, Ltd.
Learning to time capacity expansions: an empirical analysis of the worldwide petrochemical industry, 1975–95
Authors: Henderson James , Cool Karel
Published: March 2003

This paper examines how firms may learn to better time their capacity expansion decisions through their own and their rivals' past experiences. A review of the literature shows that there may be several reasons for firms to bunch their capacity additions or ‘hop on an investment bandwagon.’ These reasons include coordinating through maintaining market shares, information effects, and decision‐making biases. Given the substantial evidence of organizational learning, firms may be expected to improve their timing skills of capacity additions through their previous capacity expansion experience. Hypotheses are developed both for proprietary learning and learning at the industry level, and for forgetting. These hypotheses are tested on a database consisting of 72 companies operating in the petrochemicals industry in the United States, Europe, and Japan from 1975 to 1995. The results indicate that learning in timing capacity expansion decisions comes primarily from within firms through an accumulation of their poor outcomes. However, this timing skill is far more apparent in greenfield than incremental expansion decisions. Copyright © 2003 John Wiley & Sons, Ltd.
Prior performance characteristics of related and unrelated acquirers
Authors: Park Choelsoon
Published: March 2003

In the diversification literature, studies, particularly those using accounting‐based performance measures, have found that related diversifiers are more profitable and that related diversifiers are in more profitable industries than unrelated diversifiers. Due to the very nature of these studies based on cross‐sectional data, however, the causal relationship between diversification strategy and performance was not clear. This paper focuses on a single event of a large acquisition, which enables us to better identify the sequential relationships between prior firm profitability, prior industry profitability, and subsequent acquisition strategies. By doing so, this paper makes clearer the causal relationships between firm profitability, industry profitability, and acquisition strategies. Copyright © 2003 John Wiley & Sons, Ltd.
Thread transparency in information flow middleware
Authors: Koster Rainer , Black Andrew P. , Huang Jie , Walpole Jonathan , Pu Calton
Published: March 2003

Applications that process continuous information flows are challenging to write because the application programmer must deal with flow‐specific concurrency and timing requirements, necessitating the explicit management of threads, synchronization, scheduling and timing. We believe that middleware can ease this burden, but many middleware platforms do not match the structure of these applications, because they focus on control‐flow centric interaction models such as remote method invocation. Indeed, they abstract away from the very things that the information‐flow centric programmer must control.

This paper describes Infopipes—a new high‐level abstraction for information flow applications—and a middleware framework that supports them. Infopipes handle the complexities associated with control flow and multi‐threading, relieving the programmer of these tasks. Starting from a high‐level description of an information flow pipeline, the framework determines which parts of a pipeline require separate threads or coroutines, and handles synchronization transparently to the application programmer. The framework also gives the programmer the freedom to write or reuse components in a passive style, even though the configuration will actually require the use of a thread or coroutine. Conversely, it is possible to write a component using a thread and know that the thread will be eliminated if it is not needed in a pipeline. This allows the most appropriate programming model to be chosen for a given task, and existing code to be reused irrespective of its activity model. Copyright © 2003 John Wiley & Sons, Ltd.
Access control and trust in the use of widely distributed services
Authors: Bacon Jean , Moody Ken , Yao Walt
Published: March 2003

OASIS is a role‐based access control (RBAC) architecture for achieving secure interoperation of independently managed services in an open, distributed environment. OASIS differs from other RBAC schemes in a number of ways: role management is decentralized, roles are parametrized, roles are activated within sessions and privileges are not delegated. OASIS depends on an active middleware platform to notify services of any relevant changes in their environment.

Services define roles and establish formally specified policy for role activation and service use (authorization); users must present the required credentials and satisfy specified constraints in order to activate a role or invoke a service. The membership rule of a role indicates which of the role activation conditions must remain true while the role is active. A role is deactivated immediately if any of the conditions of the membership rule associated with its activation become false.

OASIS introduces the notion of appointment, whereby being active in certain roles carries the privilege of issuing appointment certificates to other users. Appointment certificates capture the notion of long‐lived credentials such as academic and professional qualification or membership of an organization. The role activation conditions of a service may include appointment certificates, prerequisite roles and environmental constraints.

The role activation and authorization policies of services within an administrative domain need not embody role hierarchies nor enforce privilege delegation. But OASIS is sufficiently flexible to capture such notions, through prerequisite roles and appointments, if they are required within an application domain.

We define the model and architecture and discuss engineering details, including security issues. We illustrate how an OASIS session can span multiple domains and we propose a minimal infrastructure to enable widely distributed, independently developed services to enter into agreements to respect each other's credentials. In a multi‐domain system access control policy may come from multiple sources and must be expressed, enforced and managed. In order to respond to changing relationships between organizations it should be easy to allow role holders in one domain to obtain privileges in another. Our approach to policy and meta‐policy management is described.

We speculate on a further extension to mutually unknown, and therefore untrusted, parties. Each party will accumulate audit certificates which embody its interaction history and which may form the basis of a web of trust. Copyright © 2003 John Wiley & Sons, Ltd.
The CORBA Activity Service Framework for supporting extended transactions
Authors: Houston I. , Little M. C. , Robinson I. , Shrivastava S. K. , Wheater S. M.
Published: March 2003

Although it has long been realized that ACID (atomicity, consistency, isolation, durability) transactions by themselves are not adequate for structuring long‐lived applications and much research work has been done on developing specific extended transaction models, no middleware support for building extended transactions is currently available and the situation remains that a programmer often has to develop application specific mechanisms. The CORBA Activity Service Framework described in this paper is a way out of this situation. The design of the service is based on the insight that the various extended transaction models can be supported by providing a general purpose event signalling mechanism that can be programmed to enable activities—application specific units of computations—to coordinate each other in a manner prescribed by the model under consideration. The different extended transaction models can be mapped onto specific implementations of this framework, permitting such transactions to span a network of systems connected indirectly by some distribution infrastructure. The framework described in this paper is an overview of the OMG's (Object Management Group) Additional Structuring Mechanisms for the OTS standard. Through a number of examples the paper shows that the framework has the flexibility to support a wide variety of extended transaction models. Although the framework is presented here in CORBA specific terms, the main ideas are sufficiently general, so that it should be possible to use them in conjunction with other middleware. Copyright © 2003 John Wiley & Sons, Ltd.
Sur la classification des séries discrètes des groupes classiques p-adiques: paramètres de Langlands et exhaustivité
Authors: Moeglin Colette
Published: March 2003

In this paper, we are giving parameters for discrete series of classical p-adic groups. We first define: the analogous of the Langlands morphism of WF in the L-group, part of the analogous of the character of the centralizer of that morphism and, to supply the missing part of the full definition of that character, the cuspidal support of the representation. Then, we state an hypothesis on the reducibility points for induced of cuspidal representations. And we prove that, under this hypothesis, the 3 data characterize discrete series.
Extending the Wong-Zakai theorem to reversible Markov processes
Authors: Bass Richard F. , Hambly Ben , Lyons Terry J.
Published: March 2003

We show how to construct a canonical choice of stochastic area for paths of reversible Markov processes satisfying a weak Hölder condition, and hence demonstrate that the sample paths of such processes are rough paths in the sense of Lyons. We further prove that certain polygonal approximations to these paths and their areas converge in p-variation norm. As a corollary of this result and standard properties of rough paths, we are able to provide a significant generalization of the classical result of Wong-Zakai on the approximation of solutions to stochastic differential equations. Our results allow us to construct solutions to differential equations driven by reversible Markov processes of finite p-variation with p<4.
Plant conservation ecology for management and restoration of riparian habitats of lowland Japan
Authors: Washitani I.
Published: March 2003

Conservation ecology is a new paradigm of ecology that aims at scientific contributions to maintaining earth's biodiversity and is committed to ecosystem management indispensable to intergenerational long‐term sustainability. Population ecology plays a central role in conservation ecology. Persistence of the metapopulation rather than that of each local population should be pursued in species conservation management. Biological interactions essential to reproduction and soil seed bank components of the population should be investigated and applied to planning for the conservation of a plant population. Gravelly floodplains and moist tall grasslands are among typical riparian habitats containing many threatened plants in Japan. These riparian habitats are now subjected not only to heavy fragmentation but also to intensive invasion of highly competitive alien (nonnative) plants. Extreme habitat isolation may result in reproductive failure or fertility selection in a plant population without pollinators, as exemplified by a nature reserve population of Primula sieboldii. Biological invasions, which are facilitated by extensive changes in the river environment including decreased seasonal flooding, abandonment of traditional vegetation management, eutrophication, and extensive clearing of the land for recreational use, threaten endemic riparian species. To preserve safe sites and growing conditions for threatened plants such as Aster kantoensis, active management to suppress the dominance of alien invader plants is necessary. Population management and habitat restoration should be based on sound information on the population ecology of both threatened and alien invader plants, designed as an ecological experiment to clarify effective ways for management.
Modeling incomplete sterility in a sterile release program: interactions with other factors
Authors: Barclay H. J.
Published: March 2003

Models were constructed for control of a pest species by the release of sterile insects and these models explored the consequences of incomplete sterility. This feature was then coupled with the lack of competitive ability of released insects, the immigration of insects from outside the control area, and the mode of population regulation (density independent vs. density dependent). Using the density‐independent models, it was seen that the limits on residual fertility of treated insects become much more stringent when incomplete sterilization is combined with a lack of competitive ability and immigration of insects into the control area. Strong density dependence in the system has a marked moderating effect on the requirements for sterility, competitive ability, and immigration. However, if the density‐independent limits on these factors are exceeded, then suppression is possible, but collapse of the pest population is impossible using sterile releases alone. Even suppression might not be satisfactory if these three detrimental factors are prominent. It is suggested that one remedy is the use of the sterile release method in combination with other control methods.
Non‐ant antiherbivore defenses before plant‐ant colonization in Macaranga myrmecophytes
Authors: Nomura M. , Itioka T. , Murase K.
Published: March 2003

We examined changes in the intensity of non‐ant defenses of three myrmecophytic Macaranga species before and after the initiation of symbiosis with ants in a Bornean dipterocarp forest. The intensities of non‐ant defenses at different growth stages of each Macaranga species were estimated by measuring the survival rate of larvae of the common cutworm, Spodoptera litura, when the larvae were fed on fresh leaves from seedlings (saplings) at three growth stages of each Macaranga species. In all species, the intensity of the non‐ant defenses when seedlings had not yet received symbiont foundress queens was significantly higher than that after ant defense was well established. These results support the hypothesis that myrmecophytic Macaranga may defend themselves sufficiently via non‐ant defenses before beginning symbiosis with ants and that the intensity of non‐ant defenses may decrease as the symbiont colony size increases. We suggest that, where the status of myrmecophytism changes as plant–ant colonies grow, the decrease in the intensity of non‐ant defenses which we detected after the establishment of ant colonies might generate an optimal allocation of metabolic cost to ant and non‐ant defenses under resource limitations. We also measured leaf toughness, which is considered to be one of the most important agents of non‐ant defenses against herbivorous insects, at different plant stages to assess its contribution to the change in the intensity of non‐ant defenses after ant colonization. However, we found no evidence that changes in leaf toughness have a significant effect on the change in balance of the two antiherbivory mechanisms.
A model of dominance and resource division among a group of animals of differing quality
Authors: Broom M. , Ruxton G. D.
Published: March 2003

Individuals of many species spend a large portion of their lives within groups of conspecifics. Within such groups, there can be considerable diversity in size and other traits, with some, perhaps larger or stronger, animals laying claim to a greater than fair share of available resources. We use the word quality as a single measure of individual animal phenotypes within such a group and develop a model of resource division through contests between animals of differing quality. We investigated the effect of varying environmental factors on the level of aggressiveness used in such contests and the division of resources among the group. A numerical example shows that maximum discriminations between individuals on the basis of quality occur for medium‐sized costs of aggressive encounters, but resources are divided more equitably at either extreme, when costs are either high or low.
Genetic status of fragmented populations of the Asian black bear Ursus thibetanus in western Japan
Authors: Saitoh T. , Ishibashi Y. , Kanamori H. , Kitahara E.
Published: March 2003

The population genetic status of the Asian black bear Ursus thibetanus in the western part of Japan was examined using microsatellite DNA markers. Although three fragmented populations have been recognized in this region, i.e., the western Chugoku (WC), eastern Chugoku (EC), and northern Kinki (NK) populations, it was recently pointed out that the NK population has also been divided into two subpopulations, the western (WNK) and the eastern (ENK) populations. We examined the genetic status of these four populations based on their heterozygosities and the genetic distances (FST) between them. The mean observed heterozygosity, i.e., genetic diversity, of the six microsatellite loci examined, was significantly lower in WC (0.272; n = 52) and WNK (0.311; n = 66) than that in ENK (0.445; n = 67), respectively. Reflecting geographic distances among populations, FST was higher between WC and WNK (0.244) and between WC and ENK (0.229) than that between WNK and ENK (0.066), respectively. There was also low but significant genetic differentiation between the two nearest populations (WNK and ENK). Although the status of EC was not conclusively determined because of its small sample size (n = 24), its genetic diversity seemed to be at a level similar to that of WC and WNK. These results suggest that WC, which is isolated from the others, has been losing genetic diversity, and that WNK, which had been thought to form a relatively large population together with ENK, might be isolated genetically from other populations. WNK, as well as WC and EC, should be conserved intensively.
Regular distribution of larvae and resource monopolization in the seed beetle Bruchidius dorsalis infesting seeds of the Japanese honey locust Gleditsia japonica
Authors: Shimada M. , Kurota H. , Toquenaga Y.
Published: March 2003

Larvae of the wild multivoltine bruchid seed beetle Bruchidius dorsalis infest dry mature seeds of the Japanese honey locust Gleditsia japonica. The frequency distribution of B. dorsalis larvae per seed was examined in the laboratory. First, preliminary observation showed that the first‐instar B. dorsalis larva crawled from an eggshell and traveled in excess of 25 cm before boring into a seed. Larvae prefer boring into noninfested rather than infested seeds (indicated by a previous emergence hole). When a larva occasionally bored into a previously infested seed, it could emerge as an adult in spite of decreased body weight. Second, we conducted experiment 1 to investigate the frequency distributions of the number of boring holes per seed; results showed significantly regular distributions (a smaller variance than Poisson) in which most seeds had been bored by one larva. Third, we performed experiment 2 to examine the relationship between the initial number of larvae boring into one seed and the number of emerged adults and their body weight from a given seed. When we increased the ratio of egg density to seed abundance by experimental manipulation, multiple larvae (up to ten) could bore into one seed. However, only one adult emerged from each of about 85% seeds with multiple borings. When one adult emerged, the adult body weight was constant, independent of the initial number of larvae boring into the seed. Two adults occasionally emerged from one seed with a large difference in their body sizes. Even in this case, the larger adult was as heavy as that in a single emergence, although the other was significantly smaller (about 60%) than the normal size. These results show severe contest‐type competition among B. dorsalis larvae within one seed. The winner often monopolizes almost all the resources even though a part of the seed resource still remains.
Intraspecific competition in tadpoles of Rana arvalis: does it matter in nature? A field experiment
Authors: Loman J.
Published: March 2003

Tadpole growth and development are easily affected by intraspecific competition in tank experiments, provided treatment density is sufficiently high. Is this a phenomenon also observed in nature? A pond was divided into four tadpole‐proof sections. Each year for 8 years, all spawn laid by moorfrogs (Rana arvalis) in this pond was relocated to create relative spawn and tadpole densities of 1 : 4 : 1 : 4. No direct effect of the density manipulation on survival, tadpole size, and development and metamorph timing and size could be demonstrated. However, I also measured actual tadpole density during the time of development. Apart from the experimental density manipulation, this measure included effects of between‐year variation in amount of spawn, natural tadpole mortality, and pond drying (which concentrated the tadpoles by decreasing the area of the pond sections). Actual density had limited but significant effects on tadpole size and development. I suggest that density regulation, acting on the tadpole stage, may be present in the population but was of less short‐term importance than abiotic factors and, possibly, adult density regulation. Consequences of the findings for conservation are discussed.
Polymorphism of competition type and its genetics in Callosobruchus maculatus (Coleoptera: Bruchidae)
Authors: Takano M. , Toquenaga Y. , Fujii K.
Published: March 2003

Callosobruchus maculatus has both contest and scramble competition strategies. The currently existing theoretical models using game theory suggest that the contest strategy should be selected for. However, most geographic strains of C. maculatus show scramble competition. We experimentally crossed the representative strains of contest and scramble. We expressed the degree of contest competition by a continuous value named the C‐value, which ranges from zero (pure scramble) to unity (pure contest). The competition types expressed in the C‐value were genetically additive. Their larval developmental rates were negatively correlated with C‐values. Multiple‐generation experiments of the mixed strains confirmed that there were no overwhelming advantages of contest over scramble type. Most of the mixed strains remained in the intermediate states. We discuss the results in terms of the resource size necessary for developmental success and developmental speed.
A realistic chemical system presenting a self-organized critical behavior
Authors: Gaveau Bernard , Latrémolière Daniel , Moreau Michel
Published: March 2003

We consider a realistic example of chemical system which presents self-organized criticality. We can study the kinetic equations analytically, and show that the conditions for self-organized criticality are satisfied. We find power relaxation laws for certain variables near the critical state, confirming the self-organized critical behavior.
In
0.6
Ga
0.4
As/GaAs
quantum-dot infrared photodetector with operating temperature up to 260 K
Authors: Jiang Lin , Li Sheng S. , Yeh Nien-Tze , Chyi Jen-Inn , Ross C. E. , Jones K. S.
Published: March 2003

A high-sensitivity In0.6Ga0.4As/GaAs quantum-dot infrared photodetector (QDIP) with detection wave band in 6.7–11.5 μm and operating temperature up to 260 K under normal incident illumination has been demonstrated. The peak detection wavelength shifts from 7.6 to 8.4 μm when the temperature rises from 40 to 260 K. The background limited performance (BLIP) detectivity (DBLIP*) measured at Vb=−2.0 V, T=77 K, and λp=7.6 μm was found to be 1.1×1010 cm Hz1/2/W, with a corresponding responsivity of 0.22 A/W. The high operating temperature is attributed to the very low dark current and long carrier lifetime in the quantum dots of this device. The results show that this QDIP can operate at high temperature without using the large band gap material such as AlGaAs or InGaP as blocking barrier to reduce the device dark current.
Jahn–Teller triplet excited state structures and spectra of zinc complexes of porphyrin and phthalocyanine: A density functional theory study
Authors: Nguyen Kiet A. , Pachter Ruth
Published: March 2003

Density functional theory (DFT) electronic structure calculations were carried out to predict the triplet Jahn–Teller distorted structures and energetics for zinc complexes of porphyrin (ZnP), tetraazaporphyrin, tetrabenzoporphyrin, and phthalocyanine. The D4h square planar structures in the ground state are found to distort along the b1g mode leading to the D2h rectangle structures in the lowest triplet state. Time-dependent DFT calculations were also carried out to interpret the observed triplet–triplet spectra and to quantify the effects of meso-tetraaza substitutions and tetrabenzo annulations on ZnP. The computed triplet–triplet excitation energies and oscillator strengths are in good agreement with experiment. The effects of meso-tetraaza substitutions and tetrabenzo annulations on the triplet excited state structures and spectra are discussed in detail.