bluuebunny/crossref_metadata_2025 huggingface dataset:
Quantitative determination of the passive layer on Cu–Ni alloys
Authors: Druska Peter , Strehblow Hans‐Henning
Published: December 2004

Copper–nickel alloys are important materials for application in corrosive environments. As for many other systems, this property is a consequence of thin oxide films that are protective in weakly acidic and alkaline solutions. The passive layer formed potentiostatically in 1 M NaOH on Cu50Ni has been examined with XPS and ISS. Angular‐dependent XPS measurements provide an insight into the layered structure of depth profiles that are confirmed qualitatively and quantitatively by ISS sputter depth profiles. A method is presented to evaluate the XPS results on the basis of a multilayer structure. Thicknesses and the composition of the sublayers of the passive film, as well as the composition of the metal surface underneath, are obtained in dependence on electrochemical parameters such as potential and time of passivation. Thus, on obtains not only the chemical structure but also the changes of the passive layer during its formation. A specimen transfer in a closed system from the electrolyte into the ultrahigh vacuum of the spectrometer prevents possible changes of the passive layer. These measurements are a further example of detailed studies of passivating films on technically important alloys.
Test of elastic electron scattering corrections for quantitative XPS
Authors: Tougaard S. , Jablonski A.
Published: December 2004

Ratios of the experimental XPS peak intensities from seven metals were compared to two first‐principle theories corresponding to neglecting and including the effects of elastic electron scattering, i.e. the common formalism and the Monte Carlo model, respectively. The theoretical peak intensities were found to change by an average of 14% as a result of elastic scattering, but the standard deviation from experiment was practically the same, namely ∼15% for both theories. The deviation between experiment and theory is found to be random when elastic scattering is neglected, while a small systematic component is revealed when elastic scattering effects are included. The fact that no general reduction is observed in the deviation between experiment and theory is attributed to the error origination from parameters like the photoionization cross‐sections and the inelastic electron mean free paths. These errors apparently overshadow to a large extent the improvements of including the effects of elastic electron scattering.
EPA's viewpoint on lead and cadmium additives for PVC
Authors: Yager Kenneth A.
Published: December 2004

In addition to presenting the nature of the lead and cadmium hazard and environmental control levels, there is presented a philosophy, international in scope, for the meaningful management of EPA's legislated responsibilities to the citizens of the U.S. The profitable aspects of pollution control and waste recycling are discussed as exciting alternatives to the nonproductive character of compliance with regulations.
OSHA's position on cadmium‐ and lead‐based chemicals
Authors: Mannion Cathie M.
Published: December 2004

A discussion of the current OSHA regulations or restrictions on the manufacturing, handling, and use of inorganic or organic compounds of lead or cadmium, either in liquid or in powder form.
Lead stabilizer dispersion in PVC
Authors: Marx M. Fred
Published: December 2004

As a major consumer of lead stabilizers used in PVC wire and cable compounds, Western Electric raw material inspection personnel have seen a decline of lead stabilizer dispersion quality. For this reason, the dispersion of lead stabilizer is of major concern to us. Marginally dispersed stabilizers cause an excessive collection of lead compound on the extruder screen pack and eventual rupture of the screen. Marginal dispersion detracts from extrusion smoothness of high‐speed, thin‐wall wire insulation. Stabilizer manufacturers have acknowledged that dustless versions of their products are more difficult to disperse. Lead suppliers must meet OSHA regulations that limit employees' exposure to inorganic lead compounds. They are using different approaches that are producing a proliferation of packages as well as stabilizer surface treatments. Dispersion quality has varied from supplier to supplier and from lot to lot. Obviously, compounders find it difficult to agree on a solution to the problem. The use of bulk returnable air pallets and standard non‐treated stabilizer would satisfy dust‐level requirements, eliminate the need for additive treatment, and solve potential bag disposal restrictions.
Vinyl chloride‐ethylene copolymers: The effect of modest ethylene concentrations on the physical properties of compounds
Authors: Hanna Russell J. , Fields John W.
Published: December 2004

Vinyl chloride‐ethylene copolymers containing from 1.0 to 5.5 wt.% ethylene were synthesized and compounded with DOP plasticizer at levels of 0, 5, 10, 20, 30, and 40 parts per hundred parts of resin. Physical property tests indicated that, as an internal plasticizer, ethylene was 2 to 3 times more efficient than DOP in the range studied. An examination of room temperature modulus as well as brittleness also indicated that crystallinity was still apparent in all copolymers.
Reduction of notch sensitivity and improvement in low‐temperature impact strength of PVC
Authors: Mathur K. K. , Driscoll S. B.
Published: December 2004

PVC is a notch‐sensitive polymer. The drop weight impact strength is also lost dramatically below 0°C. This requires special formulation considerations for critical applications. The general trend is to use polymeric impact modifiers, which are rubbery, graft polymers or blends of both hard and rubbery materials. This is achieved with some sacrifice in flexural modulus and formulation economics. A recent study conducted to relate calcium carbonate particle size with notched Izod and low‐temperature drop weight impact strength has shown that the stearate‐coated Ultrafine precipitated calcium carbonate (0.07 μ), at 15 phr loading, substantially improves both properties without sacrifice in flexural modulus. The formulation cost is also favorable. It is hypothesized that improvement in the above properties is primarily due to uniform stress distribution and lack of defect structure, as observed with coarse fillers. Surprisingly, the optimum‐particle‐size, coated, precipitated calacium carbonates also improved the Ultraviolet light stability of the PVC.
Velocity profile of rigid PVC in an extrusion die
Authors: Brown Randy J.
Published: December 2004

A method to determine the velocity profile of a melt within the die for both opaque and transparent materials shows that, above the crystalline melt temperature, the velocity profile of PVC follows the power‐law relationship. Below the crystalline melt temperature, the velocity of PVC is flatter and more like plug flow than is predicted by the power‐law relationship because the high elastic modulus (due to crystallinity) leads to slippage at the wall or melt fracture. Knowledge of the expected velocity profile can be used to design dies to compensate for higher velocity in the center.
Raw material variables in flexible vinyl dry blending and extrusion
Authors: Payne Marc T. , Cannon Joseph A.
Published: December 2004

Medium‐molecular‐weight resins with medium to high porosity have the best processing characteristics of resins normally used for flexible vinyl. Plasticizers improve dryblending and fusion time by their molecular weight and solvating efficiency. Formulations should account for the effect of ingredients on processing and on expected end‐use properties. Flexible vinyl extrusions would then be produced more efficiently and have better physical properties—at lower total cost.
Development of a flame‐resistant noncontaminating PVC jacket for coaxial cable
Authors: Loadholt J. T. , Kaufman Stanley
Published: December 2004

The migration of plasticizer from a PVC jacket into the polyethylene core of a coaxial cable can significantly alter the high‐frequency transmission characteristics of the cable by effectively increasing the dissipation factor of the polyethylene. In order to determine the effect of plasticizer type on transmission loss, a series of PVC‐jacketed polyethylene core coaxial cables was manufactured, each jacket with a different plasticizer. Transmission loss was found to be directly related to plasticizer volatility. A linear trimellitate plasticizer gave stable electrical performance with a good balance of properties, including processing, cost, and fire resistance.
Plastisol copolymers of polyvinyl chloride opportunities for energy efficiencies
Authors: Hurter David R.
Published: December 2004

Simple substitution of PVC copolymer dispersion resins can offer some processing advantages over their homopolymer counterparts, in either reduced temperatures or shorter cycles. Elevated storage temperatures can affect the viscosity of the copolymer compound, but minimal reformulating (substituting a less‐solvating plasticizer in part or whole or pre‐wetting the compound with a few parts of a diluent, such as mineral spirits) can usually restore stability. The formulator must be the final judge of the compensatory steps to be taken.
Injection‐molding rigid PVC compounds
Authors: Murrey Jerry L.
Published: December 2004

Rigid PVC compounds will be specified for an ever‐increasing number of diverse applications within the next few years because of their excellent cost‐performance balance. Molders with experience and equipment to run these compounds will share in this growing business. Those grounded in the basic principles of molding rigid PVC compounds will gain the confidence and develop the capability for processing many other thermoplastics, besides reaping the profits.
Formulations for vinyl house siding: History, present, future
Authors: Summers James W.
Published: December 2004

In the early 1960s, vinyl house siding was first commercialized. The colors were pastels and included white, green, yellow, and gray. All siding tended to bleach and fade (oxidize) to an extent where medium and dark colors were unacceptable, since the fading is more noticeable in deeper colors. All the early siding was made from cubes on single‐screw extruders. Powder compounds were first introduced in the late 1960s, as was twin‐screw extrusion. At the same time higher processing temperatures were used on, both twin‐ and single‐screw extruders. That led to a well‐fused and tougher product. Formulation changes reduced bleaching and fading and permitted such medium‐depth colors as tan, gold, beige, blue, and olive.

This technology allowed rapid growth in the vinyl siding industry in the late 1970s. Surface distortion (oil canning) was recognized as a potential problem with the early gray color and recognized as a major problem with dark colors; it was resolved only by understanding the fundamental principles involved. Another major problem was the fading in dark colors and here again extensive research into the principles of weathering led to the use of a thin, highly weatherable capping as a cost‐effective solution.

For the future, many technical developments can be expected in this rapidly growing market. However, judging by the occasional withdrawal of a formulation from the market, and by an occasional homeowner complaint, present performance in several properties must be judged as just adequate. For this market to continue its rapid growth, future performance should be better than today's. This can be accomplished without hurting economics by careful understanding of all parameters involved. Formulation changes will allow better performance. Standards must be raised to control product performance, especially surface distortion and color stability in darker colors, and to insure retention of physical properties after long‐term weathering.
Heat transfer study of vinyl extrusion cooling rates
Authors: Limansky Joseph , Bochner Michael
Published: December 2004

This paper deals with a method of determining the midplane temperatures of vinyl extrusions. Knowing the surface temperature, cooling medium temperature, and flow rates, the theoretical midplane temperature can be calculated. Determining and controlling midplane temperatures of vinyl extrudates is essential for consistent part fabrication. Data are presented illustrating how flow rate of the cooling medium affects surface and midplane temperatures of the vinyl extrudate. Enthalpy and flow rate data are used to determine cooling bath requirements.
Processing and formulation effects on gel levels in flexible PVC extrusions
Authors: Pazur A. S.
Published: December 2004

Gels, or fisheyes, in flexible PVC extruded or calendered products are the ∼ 150 μm PVC grains which, for one reason or another, survive the compounding and processing steps to appear as defects on the surface of the profile, sheet, or film. In most applications they are aesthetically objectionable. In other applications, such as medical tubing or blood bags, they are functionally intolerable. Gels are a function of resin and plasticizer selection, processing temperature, residence time at temperature, and shear history. In flexible PVC extrusion, process parameters include cube or pellet versus powder processing, barrel L/D, screw compression ratio, screw RPM, and temperature profile. Choice of resin is, of course critical. Resin morphological parameters of importance include friability, porosity, and absence of glassy particles. Plasticizers vary greatly in their ability to solvate the PVC grain. Various types of dry blend and resin contamination result in large increases in gels.
Dielectric studies of poly(vinyl chloride)
Authors: Utracki L. A. , Jukes J. A.
Published: December 2004

Measurements of the dielectric constant and loss factor of polyvinyl chloride (PVC) have been made over a wide range of temperature and frequency. Maxima in dielectric loss were observed at a temperature corresponding to the α or glass transition temperature and secondary β transition temperature. The sensitivity of these maxima to both frequency and thermal pretreatment was investigated. It was found that the position of the β peak on the temperature axis changed markedly with frequency, while the glass transition or α peak showed only small variations. Neither the α nor the β peak were very sensitive to thermal pretreatment, but interesting changes in the minimum between these peaks were observed. In quenched samples a distinct shoulder peak at Tβ < Ts < Tα was observed; it was possible to eliminate it by a slow cooling of the samples. The effect of plasticizer content was also studied.
Electron microscopy and plastic processing I. Effect of lubricants in formulation
Authors: Yu A. J. , Boulier P. , Sandhu A.
Published: December 2004

Scanning electron microscopy was used to follow the fusion process of rigid PVC formulations. The results suggest that fusion involves chain entanglement across the resin grain boundary brought about by shear and heat. Heat comes from the processing machine as well as from friction when the resin particle are made to rub against each other during processing. The mechanism of lubricants, therefore, is to control the frictional heat build‐up. The level of lubricants should be just enough to prevent thermal degradation from frictional heat build‐up but not so much as to retard the chain entanglement process. Since this heat balance encompasses the total system, including the machine, the formulation and the articles being shaped, an optimum formulation has to be evolved for each case with all the system variables taken into consideration.
Chlorinated poly(vinyl chloride) (CPVC) engineering thermoplastic now a viable alternative
Authors: Dalal Girish T.
Published: December 2004

In the economic environment of today, as well as in the foreseeable future, the consumer and industry alike have to use critical value judgement on any purchase or investment made. Basically this requires stringent evaluation of cost and performance value of the selection made. In the field of engineering thermoplastics, the new generation of CPVC compounds offer a very unique and previously unattainable alternative to the plastics processor and consumer. Plastics processors can now use their expertise to develop the capability to successfully use these advanced CPVC compounds and gain the benefit of their cost/‐performance values.

This paper provides background on what CPVC is, what its rheological and thermal stability characteristics are, and describes its compounding, processing, and applications. It also describes the advances made over the past couple of years.
Co‐rotating twin screw compounding studies of PVC formulations
Authors: Karian Harutun G.
Published: December 2004

A 50 mm twin screw extruder was used to study the melting profiles of various PVC formulations. Melt temperature and degree of flux are measured axially along various mixing paddle arrangements.

The viscous work is correlated with the rheology of the PVC mass and effective shear rate of the intermeshing co‐rotating screws. The results of this investigation are used to develop a conceptual model of compounding PVC formulations.

The radial mixing patterns in paddle segments down the barrel length are analyzed by introduction of trace quantities of pigment added to the dry blend. The resulting residence time distributions coupled with localized shear rate distributions give a numerical evaluation of shear strain required to flux PVC particles into a continuous fluid mass.

By proper agitator design, compounding of PVC formulations can be accomplished with minimal thermal history.
Thermodynamics of PVC—plasticizer interaction: A review
Authors: Foss P. H. , Shaw M. T.
Published: December 2004

In this review we evaluate many of the experimental techniques for measurement of polymer solvent interaction thermodynamics, placing special emphasis on the interaction between plasticizers and semicrystalline materials. Methods are reviewed for measurement of heat and volume of mixing, Flory‐Higgins interaction parameter (chi), virial coefficients, and empirical compatibility measurements.
Solvent recycling of rigid poly(vinyl chloride) bottles
Authors: Kampouris E. M. , Diakoulaki D. C. , Papaspyrides C. D.
Published: December 2004

A solvent recycling technique is studied for treatment of waste poly(vinyl chloride) (PVC) bottles. The process proposed basically comprises dissolution of the collected material, reprecipitation, through washing of the polymer obtained, and drying. On the other hand, solvent mixtures involved are separated by distillation for further reuse. Cyclohexanone/n‐hexane proved to be the most satisfactory solvent/non‐solvent system due to the high yields attained in polymer of small grain size while recovering most of the solvents employed. Excellent molecular weight and mechanical property retention characterizes the polymer grade recycled.
Effect of precipitated silica on plate‐out of poly(vinyl chloride) compounds
Authors: Maisel J. William
Published: December 2004

Plate‐out is the undesired deposition of materials from a compound onto the surface of processing equipment. Plate‐out causes problems with quality control and down‐time. Changes in processing conditions can help alleviate plate‐out, but adjustments in the formulation are usually needed for significant improvements in plate‐out, the deposition. The addition of precipitated silica to a PVC formulation is a simple and effective method to reduce plate‐out. This study explores the relationship between plate‐out reduction and the physical properties of precipitated silica. Silica properties such as surface area, average particle size, and oil absorption can all be controlled by a patented process developed by the Chemicals Division of J. M. Huber Corporation. Plate‐out reduction is related to the properties of precipitated silica, the loading of the silica, the order of addition, and type of PVC formulation. The effect of precipitated silica on the physical properties of the PVC compound, such as, tensile strength, tear strength, elongation and stiffness, are explored. Finally, the effectiveness of plate‐out reduction by precipitated silica as compared to fumed silica will be discussed.
Coated ultrafine precipitated CaCO3 as impact modifier extender in low molecular weight PVC
Authors: Mathur K. , Rogers L. , Tapper M.
Published: December 2004

Work reported earlier had shown that the addition of 0.07 micron stearate coated ultrafine precipitated CaCO3 (CUPCC) in medium to high molecular weight PVC resulted in a significant improvement in notched Izod impact strength. The improvement was much more dramatic when the filler loading exceeded 10 phr. The addition of CUPCC to low molecular weight PVC had practically no effect on the notched Izod impact strength at equivalent loadings. More recent studies have demonstrated that when CUPCC is added to an impact modified low molecular weight PVC, it dramatically enhances the efficiency of impact modifier. This was found to be consistent with threee general classes of commercially available impact modifiers used in this study. The ability to extend the impact modifier with CUPCC in low molecular weight PVC, which has gained a wide acceptance in injection molding operations, will result in significant cost savings. The effect of CUPCC addition on other key properties and cost benefits will also be presented.
Effect of acrylic processing aids on PVC die swell
Authors: Pfennig Jean‐Louis G. , Dunkelberger David L.
Published: December 2004

The die swell behavior of PVC melts is a manifestation of melt elasticity and is of considerable commercial as well as fundamental importance. This behavior is a critical issue in extrusion blow molding application where die swell (i.e. parison thickness) needs to be controlled. Advantageously, the addition of high molecular weight acrylic processing aids to PVC provides better die swell control, thus, improving dramatically the processability of PVC. Hence, knowledge of molecular weight variables of such acrylic processing aids is important from both the commercial and rheological point of view. Various acrylic processing aids were prepared by polymerization designed to provide systematic variation of molecular parameters. Molecular weight distribution of the polymers was characterized by GPC, and their die swell behavior in a typical PVC blow molding formulation was determined at 200°C over various range of residence times using different L/D capillary dies. The results are presented showing effects of specific molecular variables.
Meaningful evaluation of plastisol gelation and fusion temperatures by dynamic mechanical analysis
Authors: Daniels Paul H. , Brofman Carl M. , Harvey Gary D.
Published: December 2004

In most PVC plastisol processing operations, gelation and fusion characteristics of the plastisol are critically important. For example, in chemically foamed plastisols, plastisol fusion temperature and blowing agent decomposition temperature must be carefully coordinated. In rotomolded parts, rates of gelation may determine the quality of the finished parts. For plastisol products made by any process, the final fusion temperature determines the processing temperatures required to give the finished product acceptable mechanical properties. For a variety of reasons, the methods commonly used to characterize plastisol gelation and fusion (hot bar test, resin in plasticizer clear point, torque rheometer measurements, etc.) provide comparisons between plastisols but do not provide temperatures that are easily related to actual industrial processes. With dynamic mechanical analysis (DMA), one can characterize, under low shear conditions, the temperatures at which gelation begins, gelation ends, and complete fusion occurs. Additionally, it is possible to record plastisol viscosities (and other dynamic mechanical properties) over the processing temperature range. We used a multiple linear regression program to analyze the DMA data for plastisols heated from 30 to 210°C and containing either 70, 80 or 90 phr of Jayflex dihexyl phthalate (DHP) or Jaylflex di‐isodecyl phthalate (DIDP). Further, we determined the plasticizer phr dependence and the reproducibility of gel and fusion temperatures given by data analyzed in this manner. Finally, for comparison, we analyzed the reproducibility of initial and final plastisol gel temperatures and fusion temperatures, which were determined by visually analyzing the DMA data for plastisols containing 70, 80, and 90 phr of Jyflex plasticizers DHP, Jayflex 77, diisononyl phthalate (DINP), and DIDP. Precise characterization of plastisol gelation and fusion behavior will, undoubtedly, facilitate substitution of plastisol ingredients as is often required by those who manufacture and process plastisols.
High heat applications for SMA modified PVC: Cost effective engineering performance
Authors: Bryner James G.
Published: December 2004

SMA polymer modifiers for PVC, of the ELIX 300 type, increase the practical heat resistance of rigid PVC blends to > 100 C, allowing cost effective competition with high heat fire retardant engineering resins. The PVC/SMA blend technology, physical property characteristics, and fire retardant properties are presented. A definition of practical heat resistance and the correlation of practical heat resistance to Vicat heat resistance measurements are given with comparisons to competitive high heat fire retardant plastics. Current commercial application experience in rigid injection molding and profile extrusion is described which has confirmed the cost/performance advantage of PVC/SMA blends. Potential market opportunities for PVC/SMA blends will be presented for discussion.
Melt filtration of recycled PVC
Authors: Boo H. Khim , Mikofalvy Bela K. , Summers James W. , Sell W. Alan , Mittendorf Don H.
Published: December 2004

The separation of PVC from contaminants is one of the most important steps in recycling PVC. Earlier works have shown that one can separate PVC from other polymers by using the X‐ray fluorescence technique. However, in many cases, even after careful separation, there is a remaining impurity level of about 0.1% due to the limitations of the separation processes. In many applications, impurities, particularly nonmeltables, cause defects in the PVC matrix and must be removed for best performance and appearance. Melt filtration appears to be the best technique to remove the nonmeltable impurities.
Effects of Se‐depletion on glutathione peroxidase and selenoprotein W gene expression in the colon
Authors: Pagmantidis Vasileios , Bermano Giovanna , Villette Stephane , Broom Iain , Arthur John , Hesketh John
Published: December 2004

Selenium (Se)‐containing proteins have important roles in protecting cells from oxidative damage. This work investigated the effects of Se‐depletion on the expression of the genes encoding selenoproteins in colonic mucosa from rats fed diets of different Se content and in human intestinal Caco‐2 cells grown in Se‐adequate or Se‐depleted culture medium. Se‐depletion produced statistically significant (P
< 0.05) falls in glutathione peroxidase (GPX) 1 mRNA (60–83%) and selenoprotein W mRNA (73%) levels, a small but significant fall in GPX4 mRNA (17–25%) but no significant change in GPX2. The data show that SelW expression in the colon is highly sensitive to Se‐depletion.
Chronic ethanol exposure induces an N‐type calcium channel splice variant with altered channel kinetics
Authors: Newton Philip M. , Tully Keith , McMahon Thomas , Connolly Jackie , Dadgar Jahan , Treistman Steven N. , Messing Robert O.
Published: December 2004

Chronic ethanol exposure increases the density of N‐type calcium channels in brain. We report that ethanol increases levels of mRNA for a splice variant of the N channel specific subunit α12.2 that lacks exon 31a. Whole cell recordings demonstrated an increase in N‐type current with a faster activation rate and a shift in activation to more negative potentials after chronic alcohol exposure, consistent with increased abundance of channels containing this variant. These results identify a novel mechanism whereby chronic ethanol exposure can increase neuronal excitability by altering levels of channel splice variants.
A unified and complete construction of all finite dimensional irreducible representations of gl(2∣2)
Authors: Zhang Yao-Zhong , Gould Mark D.
Published: December 2004

Representations of the non-semisimple superalgebra gl(2∣2) in the standard basis are investigated by means of the vector coherent state method and boson-fermion realization. All finite-dimensional irreducible typical and atypical representations and lowest weight (indecomposable) Kac modules of gl(2∣2) are constructed explicitly through the explicit construction of all gl(2)⊕gl(2) particle states (multiplets) in terms of boson and fermion creation operators in the super-Fock space. This gives a unified and complete treatment of finite-dimensional representations of gl(2∣2) in explicit form, essential for the construction of primary fields of the corresponding current superalgebra at arbitrary level.
Time- and space-fractional partial differential equations
Authors: Duan Jun-Sheng
Published: December 2004

The fundamental solution for time- and space-fractional partial differential operator Dtλ+a2(−▵)γ∕2(λ,γ>0) is given in terms of the Fox’s H-function. Here the time-fractional derivative in the sense of generalized functions (distributions) Dtλ is defined by the convolution Dtλf(t)=Φ−λ(t)*f(t), where Φλ(t)=t+λ−1∕Γ(λ) and f(t)≡0 as t<0, and the fractional n-dimensional Laplace operator (−▵)γ∕2 is defined by its Fourier transform with respect to spatial variable F[(−▵)γ∕2g(x)]=∣ω∣γF[g(x)]. The solutions for initial value problems for time- and space-fractional partial differential equation in the sense of Caputo and Riemann–Liouville time-fractional derivatives, respectively, are obtained by the fundamental solution.
Remarks on the spectrum of the Neumann problem with magnetic field in the half-space
Authors: Morame Abderemane , Truc Françoise
Published: December 2004

We consider a Schrödinger operator with a constant magnetic field in a one-half three-dimensional space, with Neumann-type boundary conditions. It is known from the works by Lu–Pan and Helffer–Morame that the lower bound of its spectrum is less than b, the intensity of the magnetic field, provided that the magnetic field is not normal to the boundary. We prove that the spectrum under b is a finite set of eigenvalues (each of infinite multiplicity). In the case when the angle between the magnetic field and the boundary is small, we give a sharp asymptotic expansion of the number of these eigenvalues.
On quasiperiodic boundary condition problem
Authors: Li Y. Charles
Published: December 2004

The paper raises the question of posing the quasiperiodic boundary condition in the Cauchy problem of partial differential equations. Using the one-dimensional cubic nonlinear Schrödinger as a simple example, we illustrated the various types of questions including global well-posedness, spectra of linear operators, and foliations.
Confinement of surface acoustic waves in AlN∕GaN∕γ-LiAlO2 acoustic wells
Authors: Takagaki Y. , Chilla E. , Ploog K. H.
Published: December 2004

We numerically investigate the characteristics of surface acoustic waves (SAWs) in AlN∕GaN∕γ-LiAlO2 heterostructures. The markedly large sound velocity in AlN in comparison to that in GaN leads to an expulsion of SAWs from the top AlN layer and their resultant relocation to the middle GaN layer in the short-wavelength regime. The SAW velocity in the limit of zero wavelength is given by a bulk sound velocity of GaN, owing to the capping by the AlN barrier layer. The extra confinement of the SAW power in the acoustic well is advantageous in manipulating the operation of GaN-based devices by SAWs. The threshold velocity for the appearance of guided Rayleigh-like modes is found to be smaller than the bulk transverse sound velocity in the substrate. The present system exhibits furthermore unusual bowing behavior in the SAW dispersion.
HIERARCHICAL GENETIC ALGORITHM FOR NEAR-OPTIMAL FEEDFORWARD NEURAL NETWORK DESIGN
Authors: YEN GARY , LU HAIMING
Published: December 2004

In this paper, we propose a genetic algorithm based design procedure for a multi-layer feed-forward neural network. A hierarchical genetic algorithm is used to evolve both the neural network's topology and weighting parameters. Compared with traditional genetic algorithm based designs for neural networks, the hierarchical approach addresses several deficiencies, including a feasibility check highlighted in literature. A multi-objective cost function is used herein to optimize the performance and topology of the evolved neural network simultaneously. In the prediction of Mackey–Glass chaotic time series, the networks designed by the proposed approach prove to be competitive, or even superior, to traditional learning algorithms for the multi-layer Perceptron networks and radial-basis function networks. Based upon the chosen cost function, a linear weight combination decision-making approach has been applied to derive an approximated Pareto-optimal solution set. Therefore, designing a set of neural networks can be considered as solving a two-objective optimization problem.
EFFECTS OF CURVATURE AND INTERACTIONS ON THE DYNAMICS OF THE DECONFINEMENT PHASE TRANSITION
Authors: CHANDRA DEEPAK , GOYAL ASHOK
Published: December 2004

We study the dynamics of first-order confinement-deconfinement phase transition through nucleation of hadronic bubbles in an expanding quark–gluon plasma in the context of heavy ion collisions for interacting quark and hadron gas and by incorporating the effects of curvature energy. We find that the interactions reduce the delay in the phase transition whereas the curvature energy has a mixed behavior. In contrast to the case of early Universe phase transition, here lower values of surface tension increase the supercooling and slow down the hadronization process. Higher values of bag pressure tend to speed up the transition. Another interesting feature is the start of the hadronization process as soon as the QGP is created.
FINITE DIFFERENCE MODELING OF THE ULTRASONIC FIELD RADIATED BY CIRCULAR TRANSDUCERS
Authors: ALIA AHLEM , DJELOUAH HAKIM , BOUAOUA NOUREDDINE
Published: December 2004

In this paper, FD formulations in cylindrical coordinates are used to model the field radiated, by a circular source, in fluid and solid media.

The stability of the used schemes is controlled by a proper choice of time and space steps. Absorbing boundary conditions are introduced to satisfy the assumption of a propagation in a half space medium. In order to minimize the CPU time, calculations are limited for regions disturbed by the propagating ultrasonic pulse then the calculus zone is incremented.

Some numerical results are presented to illustrate the effect of the medium nature, source vibration profiles and eventually the presence of targets in the acoustic field. A spatio-temporal description of the diffraction phenomena is given. The radiated field is interpreted in terms of plane and edge waves. For solid media, this interpretation allows the determination of the arrival times which are compared with those numerically predicted. Numerical results corresponding to fluid media are compared to those obtained by the Impulse Response Method. The good agreement obtained justifies the choice of the FDM for the modeling of the wave propagation problems.
SECOND ORDER NONLINEAR OPTICAL PROPERTIES OF LANGMUIR–BLODGETT FILMS CONSISTING OF NON-AMPHIPHILIC POLAR MOLECULES
Authors: KAWAMATA JUN , HIRAKAWA SHOICHIRO , TANI SEIJI , OGATA YUICHIRO , YAMAGISHI AKIHIKO
Published: December 2004

We have prepared hybrid Langmuir–Blodgett (LB) films consisting of a clay single layer and a non-amphiphilic polar molecule, 2,5-bis(p-dimethylaminocinnamylidene)-cyclopentanone. LB films deposited on solid substrates were characterized by means of UV-vis absorption spectroscopy and optical second-harmonic generation (SHG) measurements.
MONTE CARLO SIMULATIONS OF TEMPERATURE DEPENDENCE OF THE KINETICS OF DIFFRACTION GRATINGS FORMATION IN A POLYMER MATRIX CONTAINING AZOBENZENE CHROMOPHORES
Authors: PAWLIK GRZEGORZ , MITUS ANTONI C. , MINIEWICZ ANDRZEJ , KAJZAR FRANCOIS
Published: December 2004

A simple kinetic model of temperature-dependent processes accompanying the writing and decay of diffraction gratings in a polymer matrix doped with azo-dye chromophores under illumination with spatially modulated and linearly polarized light is introduced and studied using Monte Carlo simulations. The model generalizes a recently proposed athermal kinetic model based on three-channel photoizomerization cycles of trans–cis type of azobenzene molecules and orientational redistribution and diffusion. These processes are influenced by a polymer matrix in a thermal equilibrium. The Monte Carlo simulations show the important role of temperature on the kinetic processes during building and erasure of diffraction gratings. We discuss some interesting applications for photonic devices, related to all-optical processing and storage of information using holographic methods.
PUSH-PULL ELECTRO-OPTIC POLYMER MODULATORS BASED ON PHOTO-BLEACHING INDUCED WAVEGUIDES AND DUAL-DRIVING ELECTRODES
Authors: KIM SEONGKU , GEARY K. , FETTERMAN H. R. , ZHANG C. , WANG C. , STEIER W. H.
Published: December 2004

Push-pull electro-optic polymeric Mach-Zehnder modulators with photo-bleaching induced waveguides and dual-driving electrodes operating at 1.55 μm wavelength have been demonstrated. The nonlinear electro-optic polymer used in this work was based on a phenyltetraene bridged chromophore in polycarbonate, APC-CLD1. It has been shown that the predominant photo-bleaching mechanism was a photochemical decomposition of the chromophore. The half-wave voltage of the integrated polymeric modulator was 4.5 V in a push-pull configuration with a 1.5 cm interaction length. The extinction ratio was greater than 20 dB, and the fiber-to-fiber insertion loss was 8 dB for the TM polarization at 1.55 μm wavelength.
SUBSTITUENT EFFECT ON TWO-PHOTON ABSORPTION PROPERTIES OF FLUORENE DERIVATIVES
Authors: KAWAMATA JUN , AKIBA MASAHARU , INAGAKI YOSHIO , TANI TAKEHARU , HARADA AKINORI
Published: December 2004

Two novel fluorene derivatives having cationic substituents were synthesized. Two-photon absorption (TPA) properties of the derivatives were evaluated using the fluorescence-based technique with a femtosecond pulse emitted from a Ti:sapphire laser. Maximum TPA cross-sections of the compounds were estimated from the TPA spectra. Based on the results, the relationship between the TPA cross-sections and the substituent effects of the derivatives were discussed.
PHOTOINDUCED TRANSMISSION CHANGE IN BACTERIORHODOPSIN EMBEDDED PHOTONIC CRYSTAL SLAB
Authors: OKADA-SHUDO YOSHIKO
Published: December 2004

We investigate the transmission properties and its photoinduced change in a one-dimensional photonic crystal slab. This periodic waveguide consist of quartz grating substrate and a thin polymer film containing a photosensitive protein bacteriorhodopsin. We propose a scheme to achieve light-controlled optical switching using the photoinduced refractive index change of bacteriorhodopsin.
ORIENTATION REARRANGEMENT AND AGGREGATION OF OXADIAZOLE TYPE DYE
Authors: YEOM SANG GIL , SOHN DAEWON , KIM BONG GI , PARK SOO YOUNG , JUN HEESUN , KIM DOSEOK
Published: December 2004

Monolayer properties of 2-(3,4,5-tris-dodecyloxyl-phenyl)-[1,3,4] oxadiazole based "tripod" dye molecules, P2G, have been studied by Langmuir–Blodgett technique, UV and polarizing microscopic images. Pressure-area isotherm of P2G has transition at 17 mN/m and this transition is believed to be the orientation rearrangement of the molecules from perpendicular to horizontal with respect to the surface normal. The presence of water insoluble hydrophobic single alkyl chains causes restructuring edge-on orientation and aggregation by compression. The H-aggregated structure was observed by UV spectrometer, and the orientation effect was clearly observed by polarizing microscopic images and sum frequency generation.
QUASI-PHASE-MATCHED DIFFERENCE-FREQUENCY GENERATION IN NONLINEAR OPTICAL POLYMER WAVEGUIDES
Authors: LEE MYUNG-HYUN , JU JUNG JIN , KIM MIN-SU , DO JUNG YUN , PARK SEUNG KOO , PARK SUNTAK , KIM JONGBAE
Published: December 2004

Nonlinear optical (NLO) polymer is emerging as a new alternative material for a wavelength converter in optical fiber communication systems. We designed and synthesized a polyetherimide-based side-chain polymer with a 4-(dialkylamino)-4′(-(styrylsulfonyl)-stilbene chromophore as a new NLO polymer. We designed and fabricated periodically-poled NLO polymer waveguides for the wavelength converter. Difference-frequency generation (DFG) process with a quasi-phase-matching (QPM) scheme was used. For the first time, we demonstrated a wavelength converter with a DFG conversion efficiency of -47 dB in the periodically-poled NLO polymer waveguides, operating at ~ 1.55 μm.
QUASI-PHASE-MATCHED SECOND-HARMONIC GENERATION IN NONLINEAR OPTICAL POLYMER WAVEGUIDE
Authors: JU JUNG JIN , PARK SEUNG KOO , DO JUNG YUN , PARK SUNTAK , KIM MIN-SU , KIM JONGBAE , LEE MYUNG-HYUN
Published: December 2004

We address issues related to quasi-phase-matched (QPM) second-harmonic generation (SHG) in nonlinear polymer waveguide for applying at optical communication. This field of research is very challenging because the high nonlinearity of polymers leads the device to operate at low pump power levels. However, key problems to this approach include difficulty of phase matching, the high propagation losses of the guided waves, and low nonlinearity contrast in the +/0 type QPM geometry. By optimizing these points on material development, waveguide design, and device fabrication, we demonstrate a QPM SHG with the best efficiency in polymer waveguide.
FABRICATION AND OPTICAL PROPERTIES OF NANOCOMPLEXES COMPOSED OF METAL NANOPARTICLES AND ORGANIC DYES
Authors: MASUHARA AKITO , OHHASHI SATOSHI , KASAI HITOSHI , OKADA SHUJI , OIKAWA HIDETOSHI , NAKANISHI HACHIRO
Published: December 2004

We have prepared nanocomplexes composed of silver or gold nanoparticles as a core and merocyanine or phthalocyanine as a shell portion by the co-reprecipitation method. From their absorption spectra, the core metal nanoparticles seemed to interact electronically with the shell layer of organic compounds in the nanocomplexes to give different electronic states from their original states. The morphology of their nanocomplexes was observed by electron microscopies.
SYNTHESIS AND CHARACTERIZATION OF LUMINESCENT POLYHYDROXYPYRIDINE LINKED WITH AROMATIC OXADIAZOLE
Authors: KIM YOUNG-SHIN , PARK WON HO , LEE TAEK SEUNG
Published: December 2004

A new copoly(hydroxypyridine-oxadiazole) linked with 2,5-dialkoxybenzene group was prepared via simple polycondensation reaction. The polymer 4 is basically an amorphous material with thermal decomposition temperature greater than 250°C. Introduction of ethylhexyloxy groups into the rigid backbone resulted in better solubility in common organic solvents such as THF, chloroform, and DMF. UV-visible and fluorescence spectrometers were employed to investigate the optical properties both in solution and in the film state showing that the material has blue fluorescence.
COUPLING PROTEIN DYNAMICS TO REACTION CENTER ELECTRON DENSITY IN ENZYMES: AN ELECTRONIC PROTEIN PROMOTING VIBRATION IN HUMAN PURINE NUCLEOSIDE PHOSPHORYLASE
Authors: MINCER JOSHUA S. , NUÑEZ SARA , SCHWARTZ STEVEN D.
Published: December 2004

The notable three oxygen stacking that occurs upon binding of ribonucleoside substrate and phosphate nucleophile by human purine nucleoside phosphorylase (hPNP) enables the coupling of protein dynamic modes to compress this stack, squeezing the ribosyl O4' between ribosyl O5' and the nuclophilic O P . Created primarily by the motion of active site residue H257, this compression dynamically lowers the barrier height for N9–C1' ribosidic bond cleavage by as much as 20%. As such, this compression constitutes a protein promoting vibration (PPV) (S. Nuñez et al.). Presently, we demonstrate charge fluctuations in the ribose and purine components of the ribonucleoside substrate, as well as specifically across the N9–C1' ribosidic bond, that are correlated with the PPV and can explain the decrease in reaction barrier height due to their facilitating cleavage of the ribosidic bond. hPNP apparently employs protein dynamics to push electrons, a finding that suggests that this coupling may be found more generally in enzymes that catalyze substitution and elimination reactions.
Crural diaphragm inhibition during esophageal distension correlates with contraction of the esophageal longitudinal muscle in cats
Authors: Liu Jianmin , Puckett James L. , Takeda Torahiko , Jung Hwoon-Yong , Mittal Ravinder K.
Published: December 2004

Esophageal distension causes simultaneous relaxation of the lower esophageal sphincter (LES) and crural diaphragm. The mechanism of crural diaphragm relaxation during esophageal distension is not well understood. We studied the motion of crural and costal diaphragm along with the motion of the distal esophagus during esophageal distension-induced relaxation of the LES and crural diaphragm. Wire electrodes were surgically implanted into the crural and costal diaphragm in five cats. In two additional cats, radiopaque markers were also sutured into the outer wall of the distal esophagus to monitor esophageal shortening. Under light anesthesia, animals were placed on an X-ray fluoroscope to monitor the motion of the diaphragm and the distal esophagus by tracking the radiopaque markers. Crural and costal diaphragm electromyograms (EMGs) were recorded along with the esophageal, LES, and gastric pressures. A 2-cm balloon placed 5 cm above the LES was used for esophageal distension. Effects of baclofen, a GABAB agonist, were also studied. Esophageal distension induced LES relaxation and selective inhibition of the crural diaphragm EMG. The crural diaphragm moved in a craniocaudal direction with expiration and inspiration, respectively. Esophageal distension-induced inhibition of the crural EMG was associated with sustained cranial motion of the crural diaphragm and esophagus. Baclofen blocked distension-induced LES relaxation and crural diaphragm EMG inhibition along with the cranial motion of the crural diaphragm and the distal esophagus. There is a close temporal correlation between esophageal distension-mediated LES relaxation and crural diaphragm inhibition with the sustained cranial motion of the crural diaphragm. Stretch caused by the longitudinal muscle contraction of the esophagus during distension of the esophagus may be important in causing LES relaxation and crural diaphragm inhibition.
Effects of Advanced Glycation End Products on Hyaluronan Photolysis: A New Mechanism of Diabetic Vitreopathy
Authors: Katsumura Chihiro , Sugiyama Tetsuya , Nakamura Kimitoshi , Obayashi Hiroshi , Hasegawa Goji , Oku Hidehiro , Ikeda Tsunehiko
Published: December 2004

Purpose: To test the effects of advanced glycation end products (AGEs), which are increased in vitreous of diabetic patients, on photolysis of hyaluronan. Methods: Pullulan standards were used as molecular weight (MW) markers to obtain a calibration curve. 0.02% hyaluronan solutions were divided into AGE-added and AGE-free samples; each sample was irradiated using a xenon lamp or kept in the dark. Retention time (RT) was measured for each sample using high-performance liquid chromatography. Results:RTs and logarithm of MW of pullulan standards were negatively correlated. In hyaluronan samples exposed to light, RT increased significantly for both AGE-added and AGE-free samples compared with samples kept in the dark. RT in AGE-added samples was greater by 3% than that in AGE-free samples (p = 0.02). Conclusions: Exposure to light decreases MW of hyaluronan; addition of AGEs promotes this change. The photosensitizer activity of AGEs may be associated with accelerated depolymerization of hyaluronan in diabetic patients.