bluuebunny/crossref_metadata_2025 huggingface dataset:
Who goes? Who stays back? Seasonal migration and staying put among rural manual workers in Eastern India
Authors: Rogaly Ben
Published: March 2004

In Barddhaman District, West Bengal, India, large numbers of rice transplanters and harvesters are seasonal migrant workers, who are unable to make a living in their home areas. They often come from households where other members have stayed put. This paper illustrates the interdependence between those who move and those who stay. It also shows that structural factors, such as age, gender, class and ethnicity, though important, do not determine who migrates or who stays put in a particular season. Indeed, the paper raises questions about the very categories ‘migrant’ and ‘person who stays put’ in relation to seasonal migration. This is because such migration inevitably involves doing both; and because for some of those who move and stay for longer, lifeworlds are ‘stretched’ between places. Moreover, whether a person stays put or migrates varies over the life course. Ironically, perhaps, migration for arduous manual work away from home can be part of a struggle to be able to afford to stay put. © 2003 John Wiley & Sons, Ltd.
Sending money home: are remittances always beneficial to those who stay behind?
Authors: Bracking Sarah
Published: March 2004

This paper examines the importance of remittances from international migrants to those who stay behind. The paper looks in particular at the Zimbabwean case, and argues that while money sent from the ‘other side’ has a beneficial effect on close kin, remittances can also undermine the purchasing power of those households without migrating members. This is in part a result of asset price inflation, and in part due to the inflationary effects of parallel currency markets. The situation for those excluded from benefiting from foreign currency inputs is aggravated by chronic scarcity in the availability of consumables. The paper argues that further research is required to understand the costs, as well as the benefits, of money sent home by migrants, in terms of assessing the class and social agency of different groups of remittance senders and receivers. The paper suggests that one non‐economic, but significant effect, of remittance‐underwritten parallel markets might be an undermining of inclusive governance and democratic state accountability in the long‐run. © 2003 John Wiley & Sons, Ltd.
Staying put and staying poor?
Authors: Kothari Uma
Published: March 2004

This paper provides an overview of conceptual understandings of the relationship between migration, staying put and poverty. While livelihood strategies are diverse and multiple, for many poor people, migration represents a central component of these. However, moving from one place to another has economic and social costs and requires a certain level of human, physical, social and economic capital, thus the option of moving is not available to all amongst the poor. This paper examines the characteristics of those who stay put or are left behind in an environment characterised by out‐migration, the processes by which they are excluded from adopting migration as a livelihood strategy and the circumstances under which not migrating sustains poverty or presents an opportunity to move out of poverty. These issues are examined through an analysis of social relations and processes of exclusion, and the ways in which these are structured around poverty‐related capitals. © 2003 John Wiley & Sons, Ltd.
Dynamic responses of a three‐dimensional framework due to a moving carriage hoisting a swinging object
Authors: Wu Jia‐Jang
Published: March 2004

The literature regarding the three‐dimensional responses of a structure due to moving loads(s) is rare and that due to the moving swinging object has not been found yet. The purpose of this paper is to provide some information in this area, where the axial (x̄), vertical (ȳ) and horizontal (z̄) dynamic responses of the three‐dimensional framework of a tyred overhead crane under the action of a moving trolley (mT) hoisting a swinging object (msw) were calculated using the finite element method and the direct integration method. Instead of the conventional moving force problem where only the vertical (ȳ) inertia effect of the moving trolley was considered, the three‐dimensional inertial effects due to the masses of both the moving trolley and the swinging object have been considered in this paper. To this end, an equivalent moving mass matrix has been presented and which is dependent on both the instantaneous swinging angle of the hoisted object (msw) and the instantaneous position of the moving trolley so that the contribution of the moving mass on the overall mass matrix of the entire structure itself is easily tackled. Finally, the title problem was solved by calculating the forced vibration responses of the three‐dimensional framework with time‐dependent overall mass and damping matrices and subjected to an equivalent moving force. Some factors pertinent to the title problem, such as the magnitude, velocity and acceleration of the moving trolley and the swinging angles of the hoisted object, were studied. Numerical results reveal that, in addition to the conventional dynamic responses in the vertical (ȳ) direction, the other two components in the axial (x̄) and horizontal (z̄) directions for a three‐dimensional structure are also significant. Copyright © 2004 John Wiley & Sons, Ltd.
Automated refinement of conformal quadrilateral and hexahedral meshes
Authors: Tchon Ko‐Foa , Dompierre Julien , sCamarero Ricardo
Published: March 2004

Conformal refinement using a shrink and connect strategy, known as pillowing or buffer insertion, contracts and reconnects contiguous elements of an all‐quadrilateral or an all‐hexahedral mesh in order to locally increase vertex density without introducing hanging nodes or non‐cubical elements. Using layers as shrink sets, the present method automates the anisotropic refinement of such meshes according to a prescribed size map expressed as a Riemannian metric field. An anisotropic smoother further enhances vertex clustering to capture the features of the metric. Both two‐ and three‐dimensional test cases with analytic control metrics confirm the feasibility of the present approach and explore strategies to minimize the trade‐off between element shape quality and size conformity. Additional examples using discrete metric maps illustrate possible practical applications. Although local vertex removal and reconnection capabilities have yet to be developed, the present refinement method is a step towards an automated tool for conformal adaptation of all‐quadrilateral and all‐hexahedral meshes. Copyright © 2004 John Wiley & Sons, Ltd.
A fast collocation method for an inverse boundary value problem
Authors: Fang Weifu , Lu Mingying
Published: March 2004

In this paper, we present an implementation of a fast multiscale collocation method for boundary integral equations of the second kind, and its application to solving an inverse boundary value problem of recovering a coefficient function from a boundary measurement. We illustrate by numerical examples the insensitive nature of the map from the coefficient to measurement, and design and test a Gauss–Newton iteration algorithm for obtaining the best estimate of the unknown coefficient from the given measurement based on a least‐squares formulation. Copyright © 2004 John Wiley & Sons, Ltd.
Modelling error estimation and adaptive modelling of perforated materials
Authors: Vemaganti Kumar
Published: March 2004

Traditional computational analyses of perforated materials, much like traditional computational analyses of heterogeneous materials, involve the use of homogenization, using either the assumption of periodicity or the assumption of statistical homogeneity. Recently, Oden and Vemaganti (Journal of Computational Physics 2000; 164:22–47) have proposed a goal‐oriented approach to the modelling of heterogeneous multi‐phase linearly elastic materials that does not rely on such idealized situations. In this approach, the mathematical model is adaptively selected based on estimates of the modelling error: the error resulting from the smearing out of rapidly varying material moduli. The approach is said to be goal‐oriented because the adaptive process is driven by local estimates of modelling error in quantities of interest to the analyst, instead of global estimates. We extend this goal‐oriented adaptive approach to the case of perforated domains composed of linearly elastic materials. Toward this end, new global and local bounds on modelling errors resulting from homogenization of perforated materials are developed. A representative numerical experiment is presented. Copyright © 2004 John Wiley & Sons, Ltd.
On a method for vibration analysis of viscous compressible fluid–structure systems
Authors: Mokeyev Vladimir V.
Published: March 2004

A fluid–structure interaction formulation for viscous compressible fluid is under consideration. The formulation involves finite element approximation of linearized Navier–Stokes equations and response determination made by means of modal superposition analysis. Standard and simplified schemes of the viscous compressible fluid–structure interaction problem solution are developed. The schemes are based on the frequency condensation method of a complex eigenvalue problem solving. Free and forced oscillations of several fluid–structure systems are studied by the standard and simplified schemes. The analysis of the results obtained shows that the simplified scheme provides a saving of 90% of the computational time required to define oscillation of the structure with viscous compressible fluid in the lowest frequency range. A certain influence of the fluid viscosity on the transient response of the fluid–structure system is also demonstrated. Copyright © 2004 John Wiley & Sons, Ltd.
Non‐linear analysis of the thermo‐electro‐mechanical behaviour of shear deformable FGM plates with piezoelectric actuators
Authors: Yang J. , Kitipornchai S. , Liew K. M.
Published: March 2004

This paper investigates the non‐linear bending behaviour of functionally graded plates that are bonded with piezoelectric actuator layers and subjected to transverse loads and a temperature gradient based on Reddy's higher‐order shear deformation plate theory.The von Karman‐type geometric non‐linearity, piezoelectric and thermal effects are included in mathematical formulations. The temperature change is due to a steady‐state heat conduction through the plate thickness. The material properties are assumed to be graded in the thickness direction according to a power‐law distribution in terms of the volume fractions of the constituents. The plate is clamped at opposite edges, while the remaining edges can be free, simply supported or clamped. Differential quadrature approximation in the X‐axis is employed to convert the partial differential governing equations and the associated boundary conditions into a set of ordinary differential equations. By choosing the appropriate functions as the displacement and stress functions on each nodal line and then applying the Galerkin procedure, a system of non‐linear algebraic equations is obtained, from which the non‐linear bending response of the plate is determined through a Picard iteration scheme. Numerical results for zirconia/aluminium rectangular plates are given in dimensionless graphical form. The effects of the applied actuator voltage, the volume fraction exponent, the temperature gradient, as well as the characteristics of the boundary conditions are also studied in detail. Copyright © 2004 John Wiley & Sons, Ltd.
A numerical methodology to assess the quality of the design velocity field computation methods in shape sensitivity analysis
Authors: Ródenas J. J. , Fuenmayor F. J. , Tarancón J.E.
Published: March 2004

The velocity field in shape sensitivity analysis is not uniquely defined although it must meet numerous theoretical and practical criteria. These practical criteria can be used to compare the existing velocity field computation methods which meet the theoretical criteria, but only in qualitative terms.

When the FEM is used in design sensitivity analysis (DSA), due to the FE discretization error, the DSA errors will depend on the design velocity field considered. This paper presents a numerical methodology for quality evaluation of design velocity field computation methods in quantitative terms based on the analysis of the DSA discretization error.

The sensitivity of the squared energy norm (χm = ∂∥u∥2/∂am, am being a design variable) has been taken as the magnitude to measure the error of the DSA. For h‐refinements, the squared error in energy norm (∥e(u) ∥2) and the error in χm(e(χm)) are theoretically related by a constant which is independent of the refinement degree of the FE model. The quality of the design velocity field computation methods can therefore be assessed in terms of the stability of e(χm) /∥e(u) ∥2 in sequences of meshes. An example of the use of this methodology, where six design velocity field computation methods are compared, is presented. Copyright © 2004 John Wiley & Sons, Ltd.
Numerical modelling of impulse wave generated by fast landslides
Authors: Quecedo M. , Pastor M. , Herreros M. I.
Published: March 2004

The damage caused by impulse waves generated in water bodies by fast landslides can be very high in terms of human lives and economic losses. The complex phenomena taking place in this highly unsteady process are difficult to model because three interacting phases: air, water and soil are involved. Solutions currently available are based on either closed form equations supported experimentally or the depth integrated Navier–Stokes equations. The latter, although of more general applicability, requires knowledge of the evolution of the bathimetry and slide drag forces and their applicability may be restricted by the steep slopes existing in most real cases.

To avoid these limitations, the authors propose the solution of the full Navier–Stokes equations, using indicator functions to assign the material properties to each spatial point in the domain. The method performance is illustrated by comparison against the experimental results obtained in a physical model of an actual case. Copyright © 2004 John Wiley & Sons, Ltd.
Which are the important modes of a subsystem?
Authors: Givoli Dan , Barbone Paul E. , Patlashenko Igor
Published: March 2004

A linearly behaving vibrational substructure (or more generally a linear dynamic subsystem) attached to a main structure (or a main dynamic system) is considered. After discretization, the substructure is represented by a finite, typically large, number of degrees of freedom,Nsand hence also byNSeigenmodes. In order to reduce the computational effort, it is common to apply ‘modal reduction’ to the subsystem such that onlyNrmodes out of the total number ofNSmodes are retained, whereNr≪Ns. The following question then arises: ‘WhichNrmodes should be retained?’ In structural dynamics, it is traditional to retain those modes associated with the lowest frequencies. In this paper, the question is answered by solving an appropriate optimization problem. The most important modes of the subsystem are shown to be those whose coupling matrices, which are defined in a particular way, have the highest norm. This leads to a simple and effective algorithm for optimal modal reduction. The new criterion for ‘modal importance’ is explained both mathematically and physically, and is demonstrated by numerical examples. Copyright © 2004 John Wiley & Sons, Ltd.
Shear loaded interface crack under the influence of friction: a finite difference solution
Authors: Dorogoy Avraham , Banks‐Sills Leslie
Published: March 2004

Formulation of the elastic two‐dimensional problem of contact with friction is presented. Two‐dimensional equilibrium equations and boundary conditions in an orthogonal curvilinear co‐ordinate system are written explicitly. The above formulation is solved with the aid of the finite difference technique. An iterative algorithm which does not require load increments is employed for solving interface fracture problems with contact and friction subjected to a monotonically increasing load. The J‐integral is extended for problems in which there is friction along the crack faces. Stress intensity factors are calculated by means of the J‐integral, as well as an asymptotic expansion of the tangential shift. Two problems are analysed: (1) a crack in homogeneous material in the presence of friction involving stationary contact; and (2) an interface crack in the presence of friction involving receding contact. Results are compared to those found by analytical and semi‐analytical methods which are presented in the literature, as well as to those obtained by means of the finite element method. The accuracy of the results establishes the reliability of the finite difference analysis, as well as the post‐processors. In addition, a problem involving stick conditions is considered. It is observed that with increasing friction, the normal gaps and tangential shifts decrease. The size of the contact zone increases and values of the stress intensity factor decrease. Copyright © 2004 John Wiley & Sons, Ltd.
Finite element response sensitivity analysis using force‐based frame models
Authors: Conte J. P. , Barbato M. , Spacone E.
Published: March 2004

This paper presents a method to compute consistent response sensitivities of force‐based finite element models of structural frame systems to both material constitutive and discrete loading parameters. It has been shown that force‐based frame elements are superior to classical displacement‐based elements in the sense that they enable, at no significant additional costs, a drastic reduction in the number of elements required for a given level of accuracy in the computed response of the finite element model. This advantage of force‐based elements is of even more interest in structural reliability analysis, which requires accurate and efficient computation of structural response and structural response sensitivities. This paper focuses on material non‐linearities in the context of both static and dynamic response analysis. The formulation presented herein assumes the use of a general‐purpose non‐linear finite element analysis program based on the direct stiffness method. It is based on the general so‐called direct differentiation method (DDM) for computing response sensitivities. The complete analytical formulation is presented at the element level and details are provided about its implementation in a general‐purpose finite element analysis program. The new formulation and its implementation are validated through some application examples, in which analytical response sensitivities are compared with their counterparts obtained using forward finite difference (FFD) analysis. The force‐based finite element methodology augmented with the developed procedure for analytical response sensitivity computation offers a powerful general tool for structural response sensitivity analysis. Copyright © 2004 John Wiley & Sons, Ltd.
Synthesis, UV photo‐polymerization and degradation study of PEG containing polyester polyol acrylates
Authors: Nivasu Venkata M. , Yarapathi Reddy V. , Tammishetti Shekharam
Published: March 2004

Succinic acid‐co‐polyethylene glycol polyester polyol acrylates, capable of in situ polymerization with UV radiation, were synthesized and characterized. Effect of structural changes such as internal branching, external crosslinking on their polymerization and degradation properties were investigated. Use of external crosslinkers reduced the polymerizability of the polymer. Lipases of different origins expedited the degradation to different extents and lipase isolated from porcine pancreas appeared to be more efficient than lipases from other sources. Copyright © 2004 John Wiley & Sons, Ltd.
Cellulose acetate and polyethersulfone blend ultrafiltration membranes. Part I: Preparation and characterizations
Authors: Mahendran Rajagopalan , Malaisamy Ramamoorthy , Mohan Doraiswamy Raju
Published: March 2004

The overall objective of this investigation is to achieve high‐performance membranes with respect to flux and rejection characteristics, with an interplay of blending polymers having desired qualities. Thus, cellulose diacetate and polyethersulfone as candidate materials, in the presence of polyethylene glycol 600 as a pore forming agent, were blended in 100/0, 95/5, 90/10, 85/15, 80,20 and 75/25% compositions using N,N′‐dimethylformamide as solvent and membranes were prepared by the phase inversion technique. Polymer blend composition, additive concentration, and casting and gelation conditions were standardized for the preparation of asymmetric membranes with various pore statistics and morphology. These blend membranes were characterized for compaction in ultrafiltration experiments at 414 kPa pressure in order to attain steady state flux and is reached within 4–5 hr. The pure water flux was measured at 345 kPa pressure and is determined largely by the composition of polyethersulfone and additive concentration. The flux was found to reach the highest values of 66.5 and 275 1/(cm2 hr) at 0 and 10 wt% additive concentrations respectively, at 25% SPS content of the blend. Membrane hydraulic resistance derived by measuring water flux at various transmembrane pressure and by using an algorithm was found to be inversely proportional to pure water flux. Water content is estimated by simple drying and weighing procedures and found proportional to pure water flux for all the membranes. The molecular weight cut‐offs (MWCOs) of different membranes were determined with proteins of different molecular weights and found to vary from 20–69 kDa (globular proteins) depending on the PEG and SPS content in the casting dope. Skin surface porosity of the membranes were analyzed by scanning the frozen membrane samples using scanning electron microscopy (SEM) at different magnifications. The surface porosity is in direct correlation to the MWCO derived from solute retention experiments. Copyright © 2004 John Wiley & Sons, Ltd.
Controlled/‘living’ radical polymerization of methyl methacrylate with p‐TsCl/CuBr/BPY initiating system under microwave irradiation
Authors: Chen Gaojian , Zhu Xiulin , Cheng Zhenping , Lu Jianmei , Chen Jianying
Published: March 2004

Atom‐transfer radical polymerization of methyl methacrylate under microwave irradiation (MI) using p‐TsCl/CuBr/BPY as the initiating system was successfully carried out. The polymerization of methyl methacrylate under MI shows linear first‐order rate plots, a linear increase in the number‐average molecular weight with conversion and low polydispersities, 1.1 < Mw/Mn < 1.3. The influence of polymerization time, temperature and monomer/initiator ratio on the conversion, molecular weight and polymer distribution were studied using the MI process, and compared with that obtained by the corresponding conventional heating (CH) process. The MI process not only increases the rate of polymerization, but also narrows the polydispersity index of polymers. The apparent rate constant, $k_{\rm p}^{\rm app}$, under MI is 6–8 times higher than that under CH with an identical initiating system and polymerization temperature. The effect of MI on the stereoregularity and Tg of PMMA were investigated by 13C NMR spectroscopy and DSC, respectively. Copyright © 2004 Society of Chemical Industry
Synthesis and polymerization of a novel oxirane bearing a cyclic acetal of salicylaldehyde chain moiety
Authors: Maślińska‐Solich Jolanta , Sowa Mirosław , Neugebauer Dorota
Published: March 2004

The novel compound 2(1,3‐dioxolan‐2‐yl)phenoxymethyloxirane was synthesized and anionically polymerized with potassium hydroxide, potassium hydride and potassium tert‐butoxide. Polymers were characterized by 1H and 13C NMR spectroscopy, size exclusion chromatography and electrospray mass spectrometry. Copyright © 2004 Society of Chemical Industry
Physical properties and β‐phase increment of AgNO3‐filled poly(vinylidene fluoride) films
Authors: Tawansi A , Oraby AH , Badr SI , Elashmawi IS
Published: March 2004

X‐ray diffraction (XRD), infrared (IR) transmition and optical absorption (OA) spectra, differential thermal analysis (DTA), dc electrical resistivity (ρ), magnetic susceptibility (χ) and electron spin resonance (ESR) of AgNO3‐filled poly(vinylidene fluoride) (PVDF) films, were measured over the filler mass fraction range 0.001 ≤ W ≤ 15%. XRD and IR analysis evidenced the increase of α‐ and β‐PVDF crystalline phases due to the AgNO3 filler. The maximum crystallinity increment was found at W = 0.5%. Three endothermic peaks were detected by DTA, and were attributed subsequently to: the first order para–para‐electric phase transition, the first‐order ferro‐para‐electric phase transition and the melting. The melting peak was used to calculate the order of reaction and the activation energy of melting. The observed OA peaks and/or plateau were attributed to the charge‐transfer complex formed mainly by the AgNO3 filler. This assumption was supported by the diamagnetic susceptibility detected for the present system. The temperature dependence of ρ was explored according to a previously proposed one‐dimensional interpolaron‐hopping model. The hopping distance was formulated numerically as a function of temperature and filling level. The ESR findings were attributed to the roles of AgNO3 and dimethylformamide solvent in complex formation. Copyright © 2004 Society of Chemical Industry
Synthesis and physico‐chemical characterization of networks based on methacryloxypropyl‐grafted nano‐silica and methyl methacrylate
Authors: Mauger M , Dubault A , Halary JL
Published: March 2004

Model hybrid materials were prepared by using a well‐known four‐step procedure, including (a) preparation of spherical silica particles of nanometre size and narrow size‐distribution, (b) grafting of 3‐methacryloxypropyl units (MOPGS) at the surface of the particles, (c) formation of stable dispersions of the grafted particles in methyl methacrylate (MMA), and (d) copolymerization of MMA and MOPGS, initiated by UV irradiation, and then completed by thermal reaction. Progressive changes in network architecture were obtained by changing the particle diameter, d, the volume fraction of filler, ϕ, the number of MOP units grafted per surface unit of silica particle, n, and the nature of the grafting agent bearing the MOP unit. Materials of good transparency were obtained, even at high volume fractions of filler. This feature is the result of an excellent dispersion of the particles within the polymer matrix, as confirmed by transmission electron microscopy and atomic force microscopy. Swelling experiments were carried out to define the conditions, and function of d, ϕ, and n for preparing networks, in which the sol phase is almost lacking. The results were rationalized by defining a new parameter: ξD = 6ϕn/(1–ϕ)d. DSC plots were used as a first characterization of the materials. The presence of filler was accompanied by a slight increase in the glass transition onset temperature, T, and a marked broadening of the transition range, ΔTg. Both T and ΔTg were shown to increase linearly as a function of ξD. Copyright © 2004 Society of Chemical Industry
In situ formed processable polypyrrole nanoparticle/amphiphilic elastomer composites and their properties
Authors: Lee Eun Seong , Park Jae Hyung , Wallace Gordon G , Bae You Han
Published: March 2004

A lack of processability is one of the major problems associated with practical applications of conductive and electroactive polypyrrole. Polypyrrole nanoparticles that were sterically stabilized in a solution and supported by an amphiphilic elastomer of poly(ethylene glycol) (Mn 2000 g mol−1)/poly(tetramethylene ether glycol) (Mn 2000 g mol−1) multiblock copolymer, were investigated in terms of conductivity, processability and mechanical properties. The hydrogel, amphiphilic elastomer was soluble in various organic solvents such as methanol, acetone and ethanol, but only swellable in water. The synthetic conditions of polypyrrole nanoparticles in the presence of the multiblock copolymer were optimized. The conductivity of polypyrrole film formed from the nanoparticle suspension was measured with the van der Pauw four‐probe method and reached as high as 3.0 ± 0.2 S cm−1. The film also showed elastomeric properties, which were influenced by the amount of multiblock copolymer added during nanoparticle synthesis. Copyright © 2004 Society of Chemical Industry
Curing and barrier properties of NBR/organo‐clay nanocomposite
Authors: Kim Jin‐tae , Oh Taeg‐su , Lee Dong‐ho
Published: March 2004

Organo‐montmorillonite/NBR nanocomposites were prepared by a melt intercalation process. The characteristics of NBR nanocomposites were characterized by oscillating‐disk rheometer, water‐vapour transmission and transmission electron microscopy (TEM). Changes in cure characteristics resulting from changes in clay content and the addition of silane coupling agent were investigated. The study confirmed that organo‐montmorillonite/NBR nanocomposites cure characteristics, viz minimum torque, maximum torque, scorch time and curing time, change according to the change in clay content and the addition of silane coupling agent. Of the water‐vapour transport properties, the clay content and silane content are the dominating factors in determining the individual water‐vapour permeability of these NBR nanocomposites. TEM analysis provided clear evidence for the homogeneous dispersion of clay in the NBR matrix without regard to increases in clay content. Copyright © 2004 Society of Chemical Industry
Synthesis of poly(styrene‐block‐methylphenylsilane‐block‐styrene) via TEMPO‐mediated controlled free radical polymerisation
Authors: Rossi Nicholas A A , Anderson Robert M , Jones Richard G , Holder Simon J
Published: March 2004

ABA block copolymers of styrene and methylphenylsilane were synthesized using a methodology based on 2,2,6,6‐tetramethyl‐1‐piperidinyloxy (TEMPO)‐mediated controlled free radical polymerisation. Samples of α,ω‐dihalo(polymethylphenysilane) were reacted with a hydroxyl derivative of TEMPO to give suitable macroinitiators for the controlled (‘living’) free radical polymerisation of styrene. The polymerisation of styrene was carried out in bulk at 130 °C. Block copolymers were characterised using size exclusion chromatography and 1H and 13C NMR spectroscopy. Copyright © 2004 Society of Chemical Industry
Structural evolution of cylindrical‐phase diblock copolymer thin films
Authors: Black C. T. , Guarini K. W.
Published: March 2004

We have measured the time evolution of the self‐assembly process in perpendicular‐oriented cylindrical‐phase diblock copolymer thin films using statistical analysis of high‐resolution scanning electron microscope (SEM) images. Within minutes of annealing above the polymer glass‐transition temperature, microphase separation between polymer blocks results in formation of uniform nanometer‐scale domains whose relative position is initially largely uncorrelated. On further annealing, the cylindrical polymer domains organize into a two‐dimensional hexagonal lattice whose characteristic grain size increases slowly with time (∼t1/4). © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 1970–1975, 2004
Calcium‐containing poly(urethane‐urea)s: Synthesis, spectral, and thermal studies
Authors: Jayakumar R. , Nanjundan S.
Published: March 2004

A calcium salt of mono(hydroxypentyl)phthalate [Ca(HPP)2] was synthesized by the reaction of 1,5‐pentanediol, phthalic anhydride, and calcium acetate. Four different bisureas such as hexamethylene bis(ω,N‐hydroxyethylurea), tolylene 2,4‐bis(ω,N‐hydroxyethylurea), hexamethylene bis(ω,N‐hydroxypropylurea), and tolylene 2,4‐bis(ω,N‐hydroxypropylurea) were prepared by reacting ethanolamine or propanolamine with hexamethylene diisocyanate (HMDI) or tolylene 2,4‐diisocyanate (TDI). Calcium‐containing poly(urethane‐urea)s (PUUs) were synthesized by reacting HMDI or TDI with 1:1 mixtures of Ca(HPP)2 and each of the bisureas with di‐n‐butyltin dilaurate as a catalyst. The PUUs were well characterized by Fourier transform infrared spectroscopy, 1H and 13C NMR, solid‐state 13C–cross‐polarization/magic‐angle spinning NMR, viscosity, solubility, elemental analysis, and X‐ray diffraction studies. Thermal properties of the polymers were also examined with thermogravimetric analyses and differential scanning calorimetry. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 1809–1819, 2004
Polycarbonate particles and dye‐labeled particles by miniemulsion polymerization
Authors: Tronc Frédéric , Winnik Mitchell A. , Kaul Bansi Lal , Graciet Jean‐Christophe
Published: March 2004

We describe the synthesis of several different polycarbonate particles by miniemulsion polymerization. The monomers were allylmethyl carbonate (AlMeC), di(ethylene glycol) bisallylcarbonate (DBAC), and 4‐vinyl‐1,3‐dioxan‐2‐one [vinyl ethylene carbonate (VEC)]. For these polymerizations, higher monomer conversions were obtained with oil‐soluble initiators (azobisisobutyronitrile and benzoyl peroxide) than with a water‐soluble initiator (potassium persulfate). Benzoyl peroxide was particularly effective in yielding particles with a narrow size distribution. Although increasing amounts of a surfactant (sodium dodecyl sulfate) led to smaller particles, the choice of the monomer was the major determinant. For example, in polymerization reactions carried out at 85 °C with benzoyl peroxide as the initiator and with otherwise identical recipes, we obtained particle sizes of 181 nm with AlMeC, 296 nm with VEC, and 203 nm with DBAC. Fluorescent particles were synthesized with comonomers based on the benzothioxanthene nucleus. Because the dyes had poor solubility in the monomers, it was necessary to include typically 20 wt % bromobenzene or dichlorobenzene based on the monomer in the miniemulsion reaction mixture. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 1999–2009, 2004
Microparticles of poly(methacrylic acid)–gadolinium ion complex and their magnetic force microscopic images
Authors: Michinobu Tsuyoshi , Sasao Norikatsu , Nishide Hiroyuki
Published: March 2004

Modified poly(methacrylic acid) microparticles complexed with gadolinium(III) (Gd3+) ions were prepared in 100 nm. The emulsion terpolymerization of methacrylic acid, ethyl acrylate, and allyl methacrylate and the following complexation with Gd3+ ions yielded the polymer particles with different Gd3+ ion contents. Potentiometric titration of the complexation of the particle with Gd3+ ions indicated the formation of a very stable tris‐carboxylate coordinate complex with the Gd3+ ion. Electron spin resonance and IR spectra of the complexed particles were dependent on the Gd3+ ion content and the coordination environment in each particle. The microparticles dispersed on a mica substrate were subjected to atomic force microscopy (AFM), followed by magnetic force microscopy (MFM). AFM showed 100‐nm‐sized and monodispersed spherical images. The following MFM clearly provided strong magnetic responses exactly on the same particle positions, of which the images were also dependent on the Gd3+ ion content in the particle. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 1912–1918, 2004
Preparation and properties of epoxy/amine hybrid resins from in situ polymerization
Authors: Wu Chuan‐Shao , Liu Ying‐Ling
Published: March 2004

Homogeneous and transparent epoxy/amine hybrid resins were successfully obtained through the in situ curing of bisphenol A epoxy and hexakis(methoxymethyl)melamine with 2 wt % (3‐glycidoxypropyl)trimethoxysilane as a facial coupling agent. The hybrid resins showed good miscibility, high glass‐transition temperatures, good thermooxidative stability, and good flame retardance. The outstanding properties of the hybrid resins may lead to their use in high‐performance green electronic products. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 1868–1875, 2004
Ring‐opening polymerization of ε‐caprolactone and L‐lactide from silica nanoparticles surface
Authors: Joubert Mathieu , Delaite Christelle , Bourgeat‐Lami Elodie , Dumas Philippe
Published: March 2004

Coating of silica nanoparticles by biocompatible and biodegradable polymers of ε‐caprolactone and L‐lactide was performed in situ by ring‐opening polymerization of the cyclic monomers with aluminum, yttrium, and tin alkoxides as catalysts. Hydroxyl groups were introduced on the silica surface by grafting of a prehydrolyzed 3‐glycidoxypropyl trimethoxysilane to initiate a catalytic polymerization in the presence of metal alkoxides. In this manner, free polymer chains were formed to grafted ones, and the graft density was controlled by the nature of the metal and the alcohol‐to‐metal ratio. The grafting reaction was extensively characterized by spectroscopic techniques and quantified. Nanocomposites containing up to 96% of polymer were obtained by this technique. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 1976–1984, 2004
Synthesis of 1‐methoxypoly(oxyethylene)benzocyclobutene and its diels–alder reactions
Authors: Herati Reza Sedaghat , Herati Ramin Sedaghat
Published: March 2004

A new poly(ethylene glycol) derivative, 1‐methoxypoly(oxyethylene)benzocyclobutene (1) was prepared from the reaction of 1‐benzocyclobutenyl 1‐hydroxyethyl ether with mesylate of methoxypoly(oxyethylene) in tetrahydrofuran. The degree of end‐group conversion, as determined by NMR, was 100%. The Diels–Alder reactions of 1 with maleic anhydride and N‐phenylmaleimide were carried out in refluxing toluene to obtain the corresponding adducts (2 and 3, respectively) in excellent yields. NMR analyses of 2 and 3 indicated complete conversion of 1 to the corresponding products. The reaction of 2 with o‐toluidine resulted in complete conversion of the anhydride adduct to the corresponding products. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 1934–1938, 2004
Preparation and characterization of graft terpolymers with controlled molecular structure
Authors: Lutz Jean‐François , Jahed Nazeem , Matyjaszewski Krzysztof
Published: March 2004

Segmented terpolymers, poly(alkyl methacrylate)‐g‐poly(D‐lactide)/poly(dimethylsiloxane) (PLA/PDMS), were prepared with a combination of the “grafting through” technique (macromonomer method) and controlled/living radical polymerization (atom transfer radical polymerization or reversible addition–fragmentation transfer polymerization). Two synthetic pathways were used. The first was a single‐step approach in which a low‐molecular‐weight methacrylate monomer (methyl methacrylate or butyl methacrylate) was copolymerized with a PLA macromonomer and a PDMS macromonomer. The second strategy was a two‐step approach in which a graft copolymer containing one macromonomer was chain‐extended by a copolymerization of the second macromonomer and the low‐molecular‐weight methacrylate. The kinetics of both synthetic approaches were investigated, showing that the polymerizations exhibited a controlled/living behavior. Furthermore, the molecular structure of the terpolymers (composition, molecular weight distribution, and microstructure) was investigated by two‐dimensional liquid chromatography. Well‐defined terpolymers with controlled branch distribution, composition (Fw,PMMA/Fw,PLA/Fw,PDMS ∼ 50/30/20) molecular weight (Mn ∼ 50,000 g · mol−1), and a narrow molecular weight distribution (Mw/Mn ∼ 1.3) were prepared via both pathways. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 1939–1952, 2004
Fourier transform infrared spectroscopy study of the effect of pH on anion and cation adsorption onto poly(acrylo‐amidino diethylenediamine)
Authors: Ko Young Gun , Choi Ung Su , Park Yong Sung , Woo Je Wan
Published: March 2004

The role of hydrogen bonding in the chemistry of transition‐metal complexes remains a topic of intense scientific and technological interest. Poly(acrylo‐amidino diethylenediamine) was synthesized to study the effects of hydrogen bonding on complexes at different pHs. The polymer was synthesized through the coupling of diethylene triamine with polyacrylonitrile fiber in the presence of AlCl3 · 6H2O addition. The adsorption capacity of this polymer was 11.4 mequiv/g. The ions used for the adsorption test were CrO, PO, Cu2+, Ni2+, Fe2+, and Ag+. All experiments were confirmed with Fourier transform infrared. In the study of anion adsorption, at low pHs, only ionic bonds existed, whereas at high pHs, no bonds existed. However, in the middle pH region, both ionic bonds and hydrogen bonds formed between poly(acrylo‐amidino diethylenediamine) and the chromate ion or phosphate ion. When poly(acrylo‐amidino diethylenediamine) and metal ions (Cu2+, Ni2+, Fe2+, and Ag+) formed complexes, a hydrogen‐bonding effect was not observed with Fourier transform infrared. The quantity of metal ions adsorbed onto poly(acrylo‐amidino diethylenediamine) followed the order Ag+ > Cu2+ > Fe2+ > Ni2+. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 2010–2018, 2004
Fumigant combinations for Cyperus esculentum L control
Authors: Hutchinson Chad M , McGiffen Milton E , Sims James J , Ole Becker J
Published: March 2004

The phase‐out of methyl bromide as a soil fumigant has stimulated research into the use of other soil fumigants for weed control. Methyl bromide, methyl iodide, propargyl bromide, 1,3‐dichloropropene (1,3‐D) and metam‐sodium were tested alone and in combination with chloropicrin in laboratory experiments to determine their efficacy against Cyperus esculentus L (yellow nutsedge) tubers. Propargyl bromide and metam‐sodium were the most efficacious fumigants tested, with EC50 values of 3.7 and 6.5 µM, respectively. The relative potencies of methyl iodide and chloropicrin were not significantly different but were 2.6 and 2.9 times more potent than methyl bromide, respectively. The EC50 values for all fumigants other than 1,3‐D were significantly lower than that of methyl bromide. Combining each fumigant with 17% chloropicrin resulted in a synergistic interaction. The greatest increase in potency between the expected result and the actual result was a relative potency of 3.8 with the methyl bromide/chloropicrin combination. The smallest increase in efficacy was with propargyl bromide and chloropicrin, with a relative potency of 1.5. There was no significant difference between the EC50 values of methyl bromide/chloropicrin and methyl iodide/chloropicrin combinations. Combining 1,3‐D with 17% chloropicrin resulted in an EC50 value for C esculentus control similar to that of methyl iodide applied alone. Copyright © 2003 Society of Chemical Industry
Pyrethroid tolerance in Culex pipiens pipiens var molestus from Marin County, California
Authors: McAbee Rory D , Kang Kyung‐Don , Stanich Matthew A , Christiansen Julie A , Wheelock Craig E , Inman Allan D , Hammock Bruce D , Cornel Anthony J
Published: March 2004

In May 2001 a sample of Culex pipiens pipiens variety molestus Forskål from Marin County, California, collected as larvae and reared to adults, was found to show reduced resmethrin and permethrin knock‐down responses in bottle bioassays relative to a standard susceptible Cx pipiens quinquefasciatus Say colony (CQ1). Larval susceptibility tests, using CQ1 as standard susceptible, indicated that the Marin mosquitoes had LC50 resistance ratios of 18.3 for permethrin, 12 for deltamethrin and 3.3 for pyrethrum. A colony of Marin was established and rapidly developed higher levels of resistance in a few generations after exposure to permethrin as larvae. These selected larvae were shown to cross‐resist to lambda‐cyhalothrin as well as to DDT. However, adult knock‐down time in the presence of permethrin, resmethrin and pyrethrum was not increased after increase in tolerance to pyrethroids as larvae. Partial and almost complete reversion to susceptibility as larvae was achieved with S, S, S‐tributylphosphorotrithioate and piperonyl butoxide (PBO), respectively, suggesting the presence of carboxylesterase and P450 monooxygenase mediated resistance. Insensitive target site resistance (kdr) was also detected in some Marin mosquitoes by use of an existing PCR‐based diagnostic assay designed for Cx p pipiens L mosquitoes. Carboxylesterase mediated resistance was supported by use of newly synthesized novel pyrethroid‐selective substrates in activity assays. Bottle bioassays gave underestimates of the levels of tolerance to pyrethroids of Marin mosquitoes when compared with mortality rates in field trials using registered pyrethroid adulticides with and without PBO. This study represents the first report of resistance to pyrethroids in a feral population of a mosquito species in the USA. Copyright © 2003 Society of Chemical Industry
Esterase‐mediated tolerance to a formulation of the organophosphate insecticide monocrotophos in the entomopathogenic fungus, Beauveria bassiana (Balsamo) Vuill: a promising biopesticide
Authors: Uma Devi K , Nageswara Rao Reddy N , Sridevi D , Sridevi V , Murali Mohan C
Published: March 2004

The use of biopesticides compatible with chemical pesticides is recommended in pest management as an effective and ecologically sound strategy. The entomopathogenic fungus Beauveria bassiana (Balsamo) Vuill, which is used as a biopesticide, was found to exhibit and lose tolerance to two organophosphorus insecticides widely used in Indian fields. The pattern of response is similar to the esterase‐mediated organophosphate tolerance in aphids achieved through esterase gene duplication. Therefore the role of esterase in the tolerance exhibited by isolates of B bassiana to the organophosphate, monocrotophos, was studied. Both the total soluble protein content and esterase activity were found to increase significantly in B bassiana cultures that were able to grow in the presence of monocrotophos. With the hitherto established linkage between esterase overproduction and organophosphate tolerance in insects and the observed similarity in response of the insects and B bassiana to the chemical, it is concluded that tolerance to monocrotophos in B bassiana may be due to a mechanism similar to that operating in insects. Habituation of the fungus to monocrotophos to initiate expression of esterase gene may help in achieving compatibility between the two. Copyright © 2004 Society of Chemical Industry
Insecticidal activity of chemical constituents from Aristolochia pubescens against Anticarsia gemmatalis larvae
Authors: Nascimento Isabele R , Murata Afonso T , Bortoli Sergio A , Lopes Lucia MX
Published: March 2004

Acetone and ethanol extracts of the tubercula and several compounds isolated from Aristolochia pubescens (Willd) were bioassayed on velvetbean caterpillars, Anticarsia gemmatalis (Hübner), for evaluation of the insecticidal activities. Of the extracts subjected to bioassay, the acetone extract showed the highest activity. (−)‐Cubebin did not show activity against soybean caterpillars, whereas aristolochic acid and ent‐kaur‐15‐en‐17‐ol increased the larval period. These compounds, and (+)‐eudesmin and (+)‐sesamin, reduced the viability of this period, giving rise to malformed adults. These extracts and compounds are therefore potential botanical insecticide agents for the control of velvetbean caterpillars in soybean crops. Copyright © 2004 Society of Chemical Industry