bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of welding parameters on nugget zone microstructure and properties in high strength aluminium alloy friction stir welds
Authors: Hassan Kh. A. A. , Prangnell P. B. , Norman A. F. , Price D. A. , Williams S. W.
Published: September 2003

Theeffects ofthemainwelding variables,apart form tool design,on themicrostructureandproperties ofthenugget zone in friction stir welds have been investigated for a typical high strength Al alloy (AA7010). It has been found that there is an optimum rotational speed, for a given travel speed, that gives the highest strength and ductility for the nugget zone. As the travel speed is increased, it is necessary to increase the spindle speed to maintain this condition, although the optimum condition does notdirectlyrelatetoa constantratioof rotationalto travel speed. This condition coincides with a heat input, for a given travel speed, that gives the maximum level of solute in solution in the nugget and the lowest density of coarse second phase particles. For low travel speeds, this is limited at excessive heat inputs by reprecipitation occurringduringtheweldcoolingcycles,whereas for high travel speeds incipient melting within the nugget appears to be an important factor.
Weldability of 1.6 mm thick aluminium alloy 5182 sheet by single and dual beam Nd: YAG laser welding
Authors: Deutsch M. G. , Punkari A. , Weckman D. C. , Kerr H. W.
Published: September 2003

The weldability of 1.6 mm thick 5182 Al–Mg alloy sheet by the single- and dual-beam Nd:YAG laser welding processes has been examined. Bead-on-plate welds were made using total laser powers from 2.5 to 6 kW, dual-beam lead/lag laser beam power ratios ranging from 3:2 to 2:3 and travel speeds from 4 to 15 m min-1. The effects of focal position and shielding gas conditions on weld quality were also investigated. Whereas full penetration laser welds could be made using the 3 kW single-beam laser welder at speeds up to 15 m min-1, the underbead surface was always very rough with undercutting and numerous projections or spikes of solidified ejected metal. This ‘spikey’ underbead surface geometry was attributed to the effects of the high vapour pressure Mg in the alloy on the keyhole dynamics. The undesirable ‘spikey’ underbead geometry was unaffected by changes in focal position, shielding gas parameters or other single-beam welding process parameters. Most full penetration dual-beam laser welds exhibited either blow-through porosity at low welding speeds (4–6 m min-1) or unacceptable ‘spikey’ underbead surface quality at increased welding speeds up to 13.5 m min-1. Radiography revealed significant occluded porosity within borderline or partial penetration welds. This was thought to be caused by significant keyhole instability that exists under these welding conditions. A limited range of dual-beam laser process conditions was found that produced sound, pore-free laser welds with good top and underbead surface quality. Acceptable welds were produced at welding speeds of 6 to 7.5 m min-1 using total laser powers of 4.5–5 kW, but only when the lead laser beam power was greater than or equal to the lagging beam power. The improved underbead quality was attributed to the effect of the second lagging laser beam on keyhole stability, venting of the high vapour pressure Mg from the keyhole and solidification of the underbead weld metal during full penetration dual-beam laser welding.
Effects of magnesium content on dual beam Nd : YAG laser welding of Al – Mg alloys
Authors: Punkari A. , Weckman D. C. , Kerr H. W.
Published: September 2003

The effects of Mg content on the weldability of aluminium alloy sheet using the dual-beam Nd:YAG laser welding process have been studied by making bead-on-plate welds on 1.6 mm thick AA 1100, AA 5754 (3.2 wt-%Mg) and AA 5182 (4.6 wt-%Mg) alloy sheets. Whereas all full-penetration laser welds made in 1100 aluminium were of excellent quality,many of the welds produced in the aluminium–magnesium alloys exhibited rough, spiky underbead surfaces with drop-through and undercut. A limited range of process variables was found, however, that allowed welds with acceptable weld bead quality to be produced in the 5754 and the 5182 alloy sheet. Goodwelds were only produced in these alloys if the lead/lag laser beam power ratio was ≥1. Weld penetration and the maximum welding speed allowing full penetration keyhole-mode welding were observed to increase with Mg content. This was attributed to the effect of Mg on the vapour pressure within the keyhole and the surface tension of the Al–Mg alloys. Significant occluded vapour porosity was seen in the 5754 and 5182 alloy welds with borderline penetration; however, there was no evidence of porosity in the acceptable full-penetration welds with smooth underbead surfaces. Hardness profiles in the 5754 and 5182 welds showed a gradual increase in hardness from the base metal values through the heat affected zone (HAZ) to a peak in hardness in the weld metal adjacent the fusion boundary. It is possible that this increase in hardness may be the result of the presence of Mg2Al3 or metastable Mg2Al3′ precipitates in this region of the weld and HAZ.
Fatigue life prediction for AISI 304L butt welded joints having different bead geometry using local stress approach
Authors: Singh P. Johan , Guha B. , Achar D. R. G.
Published: September 2003

It is indicated in the literature that the toe geometry affects the fatigue properties of butt welded joints in structural steels. In an attempt to study the above effect with respect to stainless steel sheet metal welded joints, butt welded joints having two bead geometries were fabricated using AISI 304L stainless steel using gas tungsten arc welding and gas metal arc welding processes. The objective of the present work was to predict the fatigue life of AISI 304L butt joints failing at the weld toe, using a local stress approach (a two stage model). The notch root stress method was applied to calculate the fatigue crack initiation life, whereas the fatigue crack propagation life was estimated using fracture mechanics concepts. Constant amplitude fatigue tests with a stress ratio R=0 were carried out using a 100 kN servohydraulic Dartec universal testing machine at a frequency of 30 Hz. The crack initiation points were determined using strain gauges, and crack propagation gauges were used to obtain the crack propagation data during the fatigue process. The predicted lives were compared with the experimental values.
Development of new high strength Al – Sc filler wires for fusion welding 7000 series aluminium aerospace alloys
Authors: Norman A. F. , Birley S. S. , Prangnell P. B.
Published: September 2003

It has been reported that the transition metal scandium (Sc) can improve the weldability and mechanical properties of aluminium aerospace alloys that are normally considered to be ‘unweldable’. However, little is currently known about the mechanisms by which Sc leads to such improvements. Here, the effect of the Sc concentration in the fusion zone of metal inert gas (MIG) welds in a typical 7000 series Al aerospace alloy has been investigated in detail. It was found that at a critical Sc level (∼ 0.4 wt-%) a dramatic level of grain refinement occurs, leading to a highly uniform, ultrafine (∼ 10 μ m) grain structure across the entire the fusion zone. Grain refinement was accompanied by an increase in the concentration of solute that was retained in solid solution after solidification, which led to a reduction in the volume fraction of eutectic per unit grain boundary area, and a significant age hardening response in the fusion zone. The tensile properties of single pass MIG welds, produced with an Al–Sc filler wire, were compared to welds made using commercial Al filler wires recommended for welding 7000 series alloys (5087, 5180, and 5039). The Sc containing filler wire greatly outperformed all the commercial filler wires, both in terms of weld strength and ductility. Further improvements in the tensile properties of the welds were achieved by exploiting the enhanced aging response of the Al–Sc filler wires, through welding in a solution heat treated condition and using a post-weld aging treatment. The underlying metallurgical processes by which Sc brings about these improvements are discussed.
In situ thermal studies and post-weld mechanical properties of friction stir welds in age hardenable aluminium alloys
Authors: Nelson T. W. , Steel R. J. , Arbegast W. J.
Published: September 2003

The ‘quench sensitivity’ of various friction stir welded (FSW) aluminium alloys were investigated. Cooling rates of FSW were altered by utilising various active (weld side) and passive (anvil side) cooling/heating conditions. Media used included a chilled water mist (active cooling) and hot air (active heating) immediately behind the tool, and water chilled (passive cooling) or heated (passive heating) anvil. Microhardness and transverse tensile properties were used to assess the natural aging response of friction stir welds (FSWs) in 2195-T8 and 7075-T7351 subject to these conditions. Test results indicated that the quench sensitive alloy 7075 exhibits a more rapid natural aging response and improved mechanical properties while the less quench sensitive 2195 exhibits little or no change in mechanical properties. In the present investigation FSWs in alloy 7075 under active and passive cooling conditions exhibited an increase of approximately 10% in tensile properties over conventional FSWs.
Bcl-xL antagonism of BCR-coupled mitochondrial phospholipase A2 signaling correlates with protection from apoptosis in WEHI-231 B cells
Authors: Katz Elad , Lord Caroline , Ford Catriona A. , Gauld Stephen B. , Carter Natalie A. , Harnett Margaret M.
Published: September 2003

Crosslinking of the antigen receptors on the immature B-cell lymphoma, WEHI-231, leads to growth arrest and apoptosis. Commitment to such B-cell receptor (BCR)–mediated apoptosis correlates with mitochondrial phospholipase A2 activation, disruption of mitochondrial function, and cathepsin B activation. CD40 signaling has been reported to rescue WEHI-231 B cells from BCR-driven apoptosis primarily via up-regulation of the antiapoptotic protein Bcl-xL. Coupling of the BCR to the mitochondrial phospholipase A2–dependent apoptotic pathway can be prevented by rescue signals via CD40. We now show that overexpression of Bcl-xL can prevent mitochondrial phospholipase A2 activation, disruption of mitochondrial potential, and postmitochondrial execution of BCR-mediated apoptosis via cathepsin B activation. Moreover, overexpression of Bcl-xL protects WEHI-231 B cells from mitochondrial disruption and apoptosis resulting from culture with exogenous arachidonic acid, the product of phospholipase A2 action, suggesting that Bcl-xL may act to antagonize arachidonic acid–mediated disruption of mitochondrial integrity. However, although Bcl-xL expression can mimic CD40-mediated rescue of BCR-driven apoptosis, it cannot substitute for CD40 signaling in the reversal of BCR-mediated growth arrest of WEHI-231 B cells. Rather, CD40 signaling additionally induces conversion of arachidonic acid to prostaglandin E2 (PGE2), which promotes WEHI-231 B-cell proliferation by restoring the sustained, cycling extracellular signal–regulated/mitogen-activated protein kinase (ErkMAPkinase) signaling required for cell cycle progression.
Improvement of Commercial Active Carbon for Use in an Adsorption Cooling System
Authors: Buczek B. , Czepirski L. , Komorowska-Czepirska E.
Published: September 2003

Of the various gas/solid adsorption processes, the adsorption of methanol on active carbon seems to be most interesting for use in thermodynamic systems such as heat pumps and transformers, as well as in cooling systems. The porous structures of two series of active carbons modified by the successive removal of the external layers from the particle surface, one by abrasion in a spouted bed and the other by subsequent demineralization of the abraded particles, were evaluated on the basis of nitrogen and methanol adsorption data. The porous structure parameters for these two sorbate series agreed reasonably well and allowed the D–R approach to be usefully applied for the characterization of these systems. The methods for calculating the heat effects associated with methanol adsorption over wide ranges of temperature and pressure are discussed.
Kinetics of Mixed Adsorbent Systems in Gas–Solid Adsorption
Authors: Webley Paul A. , Todd Richard S.
Published: September 2003

Mixtures of solid adsorbents often occur in the process industries through either accident or design. To model such systems, a common approach is to define a pseudo-adsorbent with equilibrium properties equal to the mass fraction weighted average of the components in the mixture. The selection of an appropriate mass-transfer rate constant for the mixture is, however, more complicated.

In this study, we have derived simple relationships between the linear driving force rate constants for a pseudo-mixture in terms of the rate constants, equilibrium parameters and mass fractions of the components of the mixture. The reciprocal rate constant for a mixture of adsorbents was shown to be related to the mass fraction weighted average reciprocal rates of the components of the mixture for the case of equal equilibrium isotherms. Expressions of greater complexity resulted for non-linear and non-equal isotherms.

Experimental testing was undertaken of the breakthrough behaviour in adsorbent mixtures using the air system with mixtures of CaX and NaX in an adiabatic packed column. The mass-transfer behaviour of the solid mixtures was in good agreement with that predicted by the simple models.
A Method for the Determination of Composition Profiles in Industrial Air Separation, Pressure Swing Adsorption Systems
Authors: Beh C.C.K. , Webley P.A.
Published: September 2003

A simplified energy-balance equation has been proposed as an aid to online measurement of the adsorbed-phase nitrogen loading in industrial-scale pressure and vacuum swing adsorption systems consisting of one preferentially adsorbed component. Implementation of this technique to current and future plants requires the addition of thermocouples (which are relatively inexpensive) located axially through the bed and pressure transmitters at the bottom and top of the bed. This methodology has the advantage that the composition front may be inferred accurately from direct measurements of the local pressure and temperature, and used as the basis for process monitoring and diagnostics of plant purity, recovery and production rate.
Chemisorption of Hydrogen Ions on Aminosilica Surfaces at Different Temperatures
Authors: Kholin Yuriy V. , Myerniy Sergiy A. , Shabaeva Yutta V. , Khristenko Inna V. , Samoteikin Anton A. , Sumskaya Nina R.
Published: September 2003

The chemisorption of hydrogen ions by silicas chemically modified with aliphatic amines was discussed. The sorption kinetics followed the model of sorption from a semi-infinite solution, with sorption being of a two-stage nature. The first stage, involving the overwhelming majority of sorption centres, was very fast. In contrast, the second stage was rather slow and diffusion-controlled.

A proper description of the protolytic equilibria on the aminosilica surface required account to be taken not only of the protonization of the grafted amino groups but also of their homoconjugation. The latter reaction resulted from interactions between neighbouring groups and led to the non-random (islandlike) coverage of the surface by amino groups. Both the nature of the background electrolyte in the solution and its concentration had no effect on the model structure.

The thermodynamic equilibrium constants for the heterogeneous protonization reaction were determined from the dependencies of the mixed equilibrium constants on the concentration of the background electrolyte in solution. Chemisorption of H+ ions, accompanied by penetration of the counterions into the subsurface layer, was of an endothermic nature and associated with increasing entropy.
Adsorption Behaviour of Hg(II) from Acetate Medium onto PAR-Imbedded Polyurethane Foam
Authors: Saeed Muhammad Mufazzal , Ahmed Munir , Ghaffar Abdul
Published: September 2003

The sorption behaviour of a 2.46 • 10−5 M solution of Hg(II) on 4-(2-pyridylazo)resorcinol (PAR)-loaded polyurethane foam (PUF) was investigated. Optimum sorption was observed from acetate medium at pH 6 with the maximum equilibration time being 30 min. The kinetic data indicated an intraparticle diffusion process with sorption being first order. The rate constant k was 0.053 min−1. The classical Freundlich and Langmuir adsorption isotherms were tested. The Freundlich constants 1/n and Kf were determined as 0.40 and 1.07 • 10−3 mol/g, respectively, and the Langmuir constants ‘M’ and ‘b’ were 3.84 • 10−5 mol/g and 3.5 • 104 dm3/mol, respectively. A sorption free energy (E) of 12.9 kJ/mol indicated chemisorption. The numerical values of the thermodynamic parameters ΔH, ΔS and ΔG indicated that sorption was spontaneous and exothermic in nature. The Scatchard equation was tested as a means of evaluating the binding sites of PUF with Hg(II). The stability constants for sorption were determined and the sorption mechanism was discussed.
Adsorption Kinetic Behaviour of Pure CO2, N2 and CH4 in Natural Clinoptilolite at Different Temperatures
Authors: Aguilar-Armenta Gelacio , Patiño-Iglesias María E. , Leyva-Ramos Roberto
Published: September 2003

The adsorption kinetics of pure CO2, N2 and CH4 on a natural clinoptilolite (ZSL) sample from Villa de Reyes (San Luis Potosí, México) were measured at different temperatures using a glass, high-vacuum volumetric system. The ability of the natural zeolite to adsorb these gases depended on the gas–adsorbent contact time, t. For short values of t, the gas adsorption uptakes decreased in the order CO2 >> N2 > CH4. However, for long t values, the adsorption uptakes decreased in the sequence CO2 > CH4 > N2. It was established that the activation energies (kJ/mol) for the adsorption process increased in the following order CO2 (15) < N2 (18) < CH4 (40), correlating fairly well with the increasing order of kinetic diameter (Å) of the molecules: CO2 (3.3) < N2 (3.64) < CH4 (3.8). In comparison to the ZSL sample, the rate of adsorption of N2 and CH4 on H-ZSL increased and the total adsorption capacity decreased. The ZSL sample may be recommended as an effective adsorbent for the separation of CO2/CH4 and N2/CH4 mixtures.
Adsorption of Biologically Active Compounds from Aqueous Solutions on to Commercial Unmodified Activated Carbons. Part IV. Do the Properties of Amphoteric Carbon Surface Layers Influence the Adsorption of Paracetamol at Acidic pH Levels?
Authors: Terzyk Artur P.
Published: September 2003

Three previously characterised, unmodified commercial activated carbons (D43/1, WD and AHD), differing in porosity and surface layer composition, were further examined using some additional methods of surface chemical description (electrochemical studies, acid–base site distribution, pHPZC and resistance measurements). Paracetamol adsorption isotherms (as well as kinetic curves) were measured on these carbons at acidic pH (1.5) and three temperatures, i.e. 300, 310 and 320 K. Measurements of the enthalpies of immersion in HCl and paracetamol solutions were also performed at 310 K, and diffusion coefficients and energies calculated.

The results of measurements at acidic pH were compared with those obtained under neutral pH conditions. Some new correlations between the properties of the carbon surface and the constants characterising the process of paracetamol adsorption suggested recently were extended from data measured initially for six carbons. The mechanism of adsorption at both pH values was elaborated with the importance of surface carbonyls and basic groups being emphasised. The adsorption of the polymerisation product of paracetamol at acidic pH was determined using FT-IR and UV–vis spectroscopic measurements.
Smart Panel Technology for Broadband Noise Reduction
Authors: Kim Jaehw an
Published: September 2003

The possibility of a broadband noise reduction by piezoelectric smart panels is demonstrated. A smart panel is basically a plate structure on which piezoelectric patches with electrical shunt circuits are mounted and sound absorbing material is bonded on the surface of the structure. Sound absorbing material can absorb the sound transmitted at the mid frequency region effectively while the use of piezoelectric shunt damping can reduce the transmission at resonance frequencies of the panel structure. To be able to reduce the sound transmission at low panel resonance frequencies, piezoelectric damping is adopted. A resonant shunt circuit for piezoelectric shunt damping is composed of resistor and inductor in series, and they are determined by maximizing the dissipated energy through the circuit.

The transmitted noise reduction performance of smart panels was tested in an acoustic tunnel. Sound absorbing material and air gap reduces the sound transmitted at the mid-frequency region effectively while the use of piezoelectric shunt damping works at the low frequency region. As a result, a remarkable noise reduction of 9-15dB was achieved in broadband frequency. Double panel exhibits better noise reduction than other panels. This approach was also applied to the structural acoustic problem of turbulent boundary layer (TBL) induced sound radiated from a panel, and the possibility of TBL noise reduction was demonstrated. The hybrid approach of smart panels is a promising technology for noise reduction over broad frequency band.
Synthesis, characterization, and electroluminescent properties of a novel perylene‐containing copolyimide
Authors: Yang Mujie , Xu Shengang , Wang Jianpu , Ye Hui , Liu Xu
Published: September 2003

A novel diphenylfluorene‐based Cardo copolyimide containing perylene (PFB5) was designed and synthesized by polycondensation of a diamine 4,4′‐(9H‐fluoren‐9‐ylidene)bisphenylamine with perylene dianhydride and another dianhydride in m‐cresol with isoquinoline as a catalyst at 200°C. PFB5 was characterized by FTIR, EA, GPC, TGA, DSC, UV‐vis, and PL. Because of the existence of the bulky diphenylfluorene units in the backbone, PFB5 showed high thermal stability and good solubility in common solvents such as chloroform. Solubility of PFB5 in low boiling point solvents allows direct spin coating of the polymer films, which exhibit intense photo‐ and electroluminescence (EL) in the visible range. This nonconjugated polymer could be used as emitting and electron‐hole transporting layers in polymer electroluminescent devices (PELDs). EL properties of the unilayer ELDs based on PFB5 are discussed. The device emitted a greenish yellow light. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 786–791, 2003
Transport and solubility of fluids into polyphenylene sulfide (PPS)
Authors: Wolf Clarence J.
Published: September 2003

The solubility and transport of toluene and carbon disulfide into amorphous and crystalline polyphenylene sulfide (PPS) was investigated. The rates of sorption, desorption, and resorption of both fluids were measured as a function of temperature. The sorption of these fluids into amorphous PPS produces a semi‐crystalline material by solvent induced crystallinity (SIC). Although the rate of diffusion of carbon disulfide (CS2) into crystalline PPS, (produced either thermally or by SIC), is several orders of magnitude slower than that observed in amorphous PPS, the solubility is only slightly reduced, by approximately 10%. The PPS films exhibit highly stressed surface regions that rapidly sorb the penetrant. Thermal annealing at temperatures as high as 100°C (note Tg of PPS is 85°C) has little or no effect on the surface stress, the diffusion process or the solubility of toluene into PPS. In addition to SIC, PPS undergoes cold crystallization at 130°–140°C; however, the degree of crystallinity induced by cold crystallization is approximately 60% of that formed by cooling from the melt. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 615–625, 2003
Effect of interfacial crosslinking on miscibility behavior between isocyanate‐functionalized poly(n‐butyl methacrylate) particles and carboxylic alkali‐soluble resin
Authors: Yoon Chul‐Hyun , Shin Jin‐Sup , Cheong In‐Woo , Lee Doug‐Youn , Park Young‐Jun , Kim Jung‐Hyun
Published: September 2003

The effect of interfacial crosslinking on miscibility behavior in blend systems of isocyanate‐functionalized poly(n‐butyl methacrylate) (PBMA) and a carboxylic alkali‐soluble resin, poly(styrene/alpha‐methylstyrene/acrylic acid) (SAA), was studied with different dimethyl meta‐isopropenyl benzyl isocyanate (TMI) concentrations. For the blend films of pure PBMA and SAA, both theoretical analysis and direct observation showed immiscibility between PBMA and SAA. For the blend systems of isocyanated PBMA and SAA, Fourier transform infrared spectra and gel permeation chromatography analyses qualitatively showed the crosslinking between the isocyanate group in isocyanated PBMA and the carboxylic group in SAA. Two tan δ peaks were shown in the blend system of SAA and isocyanated PBMA containing low concentrations of TMI (from 0 to 5 wt %), and the span of the two peaks became shorter as the TMI concentration increased. For a high TMI concentration (7 wt %), only one tan δ peaks was observed. This result means the interfacial crosslinking between isocyanated PBMA and SAA occurred fully, and thus the miscibility between two polymers was significantly improved. As these results showed, the tensile strength of the blend film of isocyanated PBMA and SAA was higher than that of pure PBMA and SAA. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 792–798, 2003
Synthesis and properties of hydrophilic polymers. IX. Synthesis, biodegradability, and metal complexation of copolymers of ethylenediaminetetraacetic acid dianhydride and lactose
Authors: Choi S. J. , Geckeler K. E.
Published: September 2003

The synthesis and characterization of poly(ethylenediaminetetraacetic acid‐co‐lactose) with pendant carboxylic groups of high molar mass (132 kg mol−1) is described. The polycondensate was hydrolytically and microbiologically degradable with conventional microbiological methods. The metal‐complexing properties of the polyester were studied for Cr(III), Fe(III), Co(II), Ni(II), Cu(II), Zn(II), Sr(II), Cd(II), Pb(II), and Al(III) ions in aqueous solution with the liquid‐phase polymer‐based retention (LPR) method. In addition, the complexing capacity of the Cu(II)‐saturated copolymer was determined by thermogravimetric analysis to be 182 mg g−1 of polymer. According to the retention profiles determined as a function of the filtration factor with LPR in conjunction with inductively coupled plasma spectrometry, Cr(III) and Fe(III) showed a strong interaction with this polymer under these conditions, as indicated by retention values of about 100% at pH 5. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 650–657, 2003
Role of a chelating agent in the formation of polyaniline films on aluminum
Authors: Huerta‐Vilca D. , Moraes Sandra R. , Motheo Artur J.
Published: September 2003

A chelating agent, alizarin, was used to pretreat an aluminum surface before the electrochemical synthesis of polyaniline. Alizarin had two main effects on the process: (1) it suppressed the hydrogen evolution reaction and increased the current efficiency and (2) it stabilized the open‐circuit potential in a corroding environment, such as in 0.1M NaCl. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 819–823, 2003
Styrene‐assisted free‐radical graft copolymerization of maleic anhydride onto polypropylene in supercritical carbon dioxide
Authors: Dong Qingzhi , Liu Ying
Published: September 2003

The free‐radical graft copolymerization of maleic anhydride (MAH) onto polypropylene (PP) with the assistance of styrene (St) in supercritical carbon dioxide (CO2) was studied. The effects of the St concentration and initiator concentration on the functionality degree of the grafted PP in supercritical CO2 were investigated. The addition of St drastically increased the MAH functionality degree, which reached a maximum when the molar ratio of MAH and St was 1:1. St, an electron‐donating monomer, could interact with MAH through charge‐transfer complexes to form the St–MAH copolymer (SMA), which could then react with PP macroradicals to produce branches by termination between radicals. There was SMA in the grafting reaction system characterized by Fourier transform infrared and differential scanning calorimetry. Furthermore, the highest MAH functionality degree was obtained when the concentration of 2,2′‐azobisisobutyronitrile (AIBN) was 0.6 wt % based on PP. The effects of the temperature and pressure of supercritical CO2 on the functionality degree of the grafted PP were analyzed. An increase in the temperature accelerated the decomposition rate constant of AIBN, thereby promoting the grafting reaction. In addition, an increase in the temperature increased the diffusion of monomers and radicals in the disperse reaction system of supercritical CO2. The highest degree of functionality was found at 80°C. Also, the functionality degree of grafted PP decreased with an increase in the pressure of supercritical CO2 within the experimental range. The morphologies of pure PP and grafted PP were significantly different under polarizing optical microscopy. The PP spherulites were about 38 μm in size, and the grafted PP spherulites were significantly reduced because of heterogeneous nucleation. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 853–860, 2003
Thermal memory of polyethylenes analyzed by temperature modulated differential scanning calorimetry
Authors: Amarasinghe G. , Chen F. , Genovese A. , Shanks R. A.
Published: September 2003

Temperature modulated differential scanning calorimetry (TMDSC) was employed to study the melting and crystallization behavior of various polyethylenes (PEs). Samples of high density PE (HDPE), low density PE (LDPE), linear low density PE (LLDPE), and very low density PE (VLDPE) with different crystal structures and morphologies were prepared by various thermal treatments (isothermal crystallization and slow, fast, and dynamic cooling). The reversing and nonreversing contributions, measured on the experimental time scale, were varied, depending on the crystal stability. A relatively large reversing melt contribution occurs for unstable crystals formed by fast cooling compared to those from slow cooling treatments. All samples of highly branched LDPE, LLDPE, and VLDPE showed a broad exotherm before the main melting peak in the nonreversing curve, suggesting crystallization and annealing of crystals to more stable forms. Other samples of HDPE, except when cooled quickly, did not show any significant crystallization and annealing before melting. The crystallinity indicated that dynamically cooled polymers were much more crystalline, which can be attributed to crystal perfection at the lamellar surface. A reversible melting component was also detected during the quasiisothermal TMDSC measurements. Melting is often accompanied by large irreversible effects, such as crystallization and annealing, where the crystals are not at equilibrium. Such phenomena during a TMDSC scan provide information on the polymer thermal history. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 681–692, 2003
Molecular transport of n‐alkanes into PU/PBMA interpenetrating polymer network systems
Authors: Begum Muneera , Siddaramaiah  , Kumar H. , Aminabhavi Tejraj M.
Published: September 2003

The methylene diisocyanate (MDI) and toluene diisocyanate (TDI) based polyurethane/polybutyl methacrylate (PU/PBMA‐50/50) interpenetrating polymer network (IPN) membranes have been prepared. The molecular migration of n‐alkane penetrants such as hexane, heptane, octane, nonane, and decane through PU/PBMA (50/50) membranes has been studied at 25, 40, and 60°C using a weight gain method. From the sorption results, diffusion (D) and permeation (P) coefficients of n‐alkane penetrants have been calculated. Molecular migration depends on membrane‐solvent interactions, size of the penetrants, temperature, and availability of free volume within the membrane matrix. Attempts have been made to estimate the parameters of an empirical equation and these data suggest that molecular transport follows Fickian mode. From a study of temperature dependence of transport parameters, activation energy for diffusion (ED) and permeation (EP) have been estimated from the Arrhenius relation. Furthermore, sorption results have been interpreted in terms of enthalpy (ΔH) and entropy (ΔS) of sorption. The liquid concentration profiles have been computed using Fick's equation with appropriate initial and boundary conditions. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 739–746, 2003
Solution properties of a hyamine based on N,N‐dimethyl diallyl ammonium chloride–acrylamide copolymer
Authors: Tian Li‐Ying , Tang Xiao‐Zhen , Fa‐Xiang Ji
Published: September 2003

A hyamine based on N,N‐dimethyl diallyl ammonium chloride–acrylamide copolymer was successfully synthesized in this study. Solution properties of this hyamine including electrical conductivity and viscosity behavior were studied in detail, and effects of temperature and counter ion concentration on electrical conductivity of the solution were also discussed. It was found that a solution of hyamine in water showed a typical viscosity behavior of polyelectrolytes, which followed the Fuoss equation. With the increase of ion radius (cationic ion or anionic ion), or with the increase of salt concentration, the shrinkage degree of the polymer chain increased, with a concomitant decrease in reduced viscosity and intrinsic viscosity and an increase of Huggins constant. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 765–771, 2003
Fractal analysis of worn surfaces of ZnO whisker/natural rubber‐styrene butadiene rubber‐butyl rubber composites
Authors: Zhou Zuowan , Liu Shikai , Chu Longsheng , Gu Lixia
Published: September 2003

The wear resistance of zinc oxide whisker (ZnOw)/natural rubber‐styrene butadiene rubber‐butyl rubber (NR‐SBR‐BR) composites showed that a tetra‐needle like ZnOw, which is treated by a coupling agent, improved the wear resistance of the rubber composites. The topography of the worn surfaces of the ZnOw/NR‐SBR‐BR composites was fractal, and the fractal dimension and abrasion loss decreased synchronously as the ZnOw content increased in the composites. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 667–670, 2003
Optomechanical variations in cold‐drawn thermally treated polypropylene fibers
Authors: Fouda I. M. , El‐Sharkawy F. M.
Published: September 2003

A two‐beam polarizing interference microscope with a microstrain device was used for measuring some optical and mechanical parameters for polypropylene (PP) fibers at room temperature (28 ± 1°C). The changes in the molecular orientation were evaluated to obtain orientation factorsf2(θ),f4(θ),f6(θ), 〈P2(cos θ)〉, 〈P4(cos θ)〉, and crystalline and amorphous orientation functionsFcandFa, respectively. The shrinkage factor, uniaxial tension, true stress, molar refractivityR, surface reflectivityR′, the crosslink densityNs, the chain entanglement densityNc, the segment anisotropyγs, and the number of chainsN′ were calculated. In addition, the shrinkage stress was found to increase with the increase of draw ratio. The dielectric constant ε, the dielectric susceptibility η, the average work per chainw′, and the constants of the stress–birefringence equation were obtained. Comparison between Hermans's optical orientation functions and the corrected formulas by de Vries are given. The values of fully oriented refractive indicesn1andn2were found. The generalized Lorentz–Lorenz equation given by de Vries was used to determine the structural parameters of PP fibers. An empirical formula was suggested to correlate the changes in the evaluated parameters with different draw ratios, and its constants were determined. The study demonstrated changes on the molecular orientation factors and evaluated microstructural parameters as a result of an applied cold‐drawing process. Relationships between the calculated parameters and the draw ratios, together with microinterferograms were presented for illustration. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 729–738, 2003
Association of mortality with disease severity in rheumatoid arthritis, independent of comorbidity
Authors: Navarro‐Cano Gregorio , del Rincón Inmaculada , Pogosian Samvel , Roldán José F. , Escalante Agustín
Published: September 2003

Objective

To measure the extent to which mortality in rheumatoid arthritis (RA) is associated with disease severity, independent of the presence of coexistent diseases (comorbidity).

Methods

We measured disease severity and comorbidity among RA patients attending scheduled appointments at a rheumatology clinic. We used the Duke Severity of Illness Checklist (DUSOI), a clinical judgment‐based measure of the severity of disease. We disaggregated the DUSOI into an RA component (RADUSOI), which we used to measure RA disease severity, together with a physician‐rated 10‐point global RA severity assessment. We measured comorbidity using the non‐RA component of the DUSOI (COMDUSOI) and using the Charlson Comorbidity Index. Patients were contacted periodically for up to 6 years, during which we recorded deaths. We estimated the effect of disease severity and comorbidity on mortality using Kaplan‐Meier survival curves, Cox proportional hazards models, and logistic regression with receiver operating characteristics (ROC) curve analysis.

Results

The sample comprised 779 patients. Followup ranged from 0.1 year to 6.3 years (mean 2.52 years), for an observation period of 2,315 patient‐years. Seventy‐five patients died (9.6%), for a total mortality of 3.2 per 100 patient‐years (95% confidence interval 2.6–4.1). Both disease severity and comorbidity displayed significant bivariate associations with mortality. In multivariate Cox models adjusted for age, sex, and disease duration, the RADUSOI and global RA severity scores were associated with mortality independent of either the COMDUSOI or Charlson Comorbidity scores. The area under the ROC curve for a logistic model on mortality increased from 0.79 with age, sex, and disease duration included, to 0.84 after adding RA severity and comorbidity (P ≤ 0.005 for the increase in ROC area).

Conclusion

RA disease severity is significantly associated with mortality regardless of the presence of comorbid disease. Combined with each patient's age, sex, and disease duration, information on RA severity and comorbidity allows an accurate prediction of mortality among patients with RA.
Systemic sclerosis Th2 cells inhibit collagen production by dermal fibroblasts via membrane‐associated tumor necrosis factor α
Authors: Chizzolini Carlo , Parel Yann , De Luca Carmelina , Tyndall Alan , Åkesson, Anita , Scheja Agneta , Dayer Jean‐Michel
Published: September 2003

Objective

In systemic sclerosis (SSc; scleroderma), T cells infiltrate organs undergoing fibrotic changes and may participate in dysregulated production of collagen by fibroblasts. The objective of this study was to functionally characterize T cells infiltrating skin lesions in early SSc and investigate their capacity to affect production of type I collagen and interstitial collagenase (matrix metalloproteinase 1 [MMP‐1]) by dermal fibroblasts.

Methods

Four‐color cytometric analysis was used to characterize subset distribution and production of interferon‐γ (IFNγ) and interleukin‐4 (IL‐4) in T cell lines generated from the skin of patients with SSc. T cell clones were generated, and their capacity to modulate collagen and MMP‐1 production by fibroblasts derived from patients with SSc and from normal individuals was assessed. Neutralizing reagents were used to identify T cell mediators involved in fibroblast modulation.

Results

The skin of individuals with early‐stage SSc contained T cells preferentially producing high levels of IL‐4. Cloned CD4+ Th2‐like cells inhibited collagen production by normal fibroblasts. Th2 cell‐dependent inhibition was, at least in part, contact‐dependent, was essentially mediated by tumor necrosis factor α (TNFα), and was dominant over the enhancement induced by profibrotic IL‐4 and transforming growth factor β cytokines. The simultaneous induction of MMP‐1 production confirmed the specificity of these observations. To be inhibitory, Th2 cells required activation by CD3 ligation. Th2 cells were less potent than were Th1 cells in inhibiting collagen production by normal fibroblasts via cell‐to‐cell interaction, and SSc fibroblasts were resistant to inhibition.

Conclusion

These findings indicate that, despite their production of IL‐4, Th2 cells reduce type I collagen synthesis by dermal fibroblasts because of the dominant effect of TNFα, and suggest that strategies based on TNFα blockade aimed at controlling fibrosis in SSc may be unwise.
Favorable preliminary experience with etanercept in two patients with the hyperimmunoglobulinemia D and periodic fever syndrome
Authors: Takada Kazuki , Aksentijevich Ivona , Mahadevan Vijayabhanu , Dean Jane A. , Kelley Richard I. , Kastner Daniel L.
Published: September 2003

Objective

The hyperimmunoglobulinemia D and periodic fever syndrome (HIDS; MIM 260920) is caused by recessive mutations in the mevalonate kinase gene (MVK), which encodes an enzyme involved in cholesterol and nonsterol isoprenoid biosynthesis. HIDS is characterized by persistently elevated polyclonal IgD and recurrent febrile episodes. Although abnormalities in tumor necrosis factor α (TNFα) are not the primary cause of HIDS, plasma TNFα levels are elevated in HIDS patients during attacks and thus may be a therapeutic target. This study assessed the effects of etanercept, a soluble p75 TNFα receptor‐Fc fusion protein, in 2 patients with HIDS.

Methods

We performed biochemical and molecular genetic analyses on 2 girls with periodic episodes of fever, skin rash, abdominal pain, and arthralgia, of whom 1 had elevated levels of serum IgD. After the diagnosis of HIDS was made, treatment with etanercept was initiated in both patients. Clinical response was recorded in a standardized diary, and serum levels of cytokines and their decoy receptors were serially measured in 1 of the 2 patients.

Results

Urinary mevalonate levels were elevated in both girls. Patient 1 was heterozygous for a known MVK missense mutation (V377I) and a novel mutation that led to skipping of exon 3. Patient 2 was found to have V377I and a new missense mutation, S329R. Neither patient had mutations in TNFRSF1A or MEFV, the genes for the TNF receptor–associated periodic syndrome and familial Mediterranean fever, respectively. Etanercept reduced the frequency and severity of symptoms in both patients, whereas the levels of serum IgD and urine mevalonate remained unchanged.

Conclusion

Our favorable experience with etanercept for the treatment of HIDS suggests that further investigation of this therapy is warranted.
Rheumatoid fibroblast‐like synoviocytes overexpress the chemokine stromal cell–derived factor 1 (CXCL12), which supports distinct patterns and rates of CD4+ and CD8+ T cell migration within synovial tissue
Authors: Bradfield Paul F. , Amft Nicole , Vernon‐Wilson Elizabeth , Exley Andrew E. , Parsonage Greg , Rainger G. Ed , Nash Gerard B. , Thomas Andrew M. C. , Simmons David L. , Salmon Mike , Buckley Christopher D.
Published: September 2003

Objective

A characteristic feature of the inflammatory infiltrate in rheumatoid arthritis is the segregation of CD4 and CD8 T lymphocyte subsets into distinct microdomains within the inflamed synovium. The aim of this study was to test the hypothesis that chemokines in general and stromal cell–derived factor 1 (SDF‐1; CXCL12) in particular are responsible for generating this distinctive microcompartmentalization.

Methods

We examined how synovial CD4/CD8 T cell subsets interacted in coculture assays with fibroblasts derived from chronic inflammatory synovial lesions and normal synovial tissue as well as from fetal lung and adult skin. We used the ability of T cells to migrate beneath fibroblasts (a process called pseudoemperipolesis) as an in vitro marker of T cell accumulation within synovial tissue.

Results

Rheumatoid fibroblast‐like synoviocytes (FLS) displayed a unique ability to support high levels of CD4 and CD8 T cell pseudoemperipolesis. Nonrheumatoid FLS as well as fetal lung fibroblasts supported low levels of pseudoemperipolesis, while skin‐derived fibroblasts were unable to do so. CD8 T cells migrated under fibroblasts more efficiently and at a higher velocity than CD4 T cells, a feature that was intrinsic to CD8 T cells. Rheumatoid fibroblasts constitutively produced high levels of SDF‐1 (CXCL12), which was functionally important, since blocking studies showed reductions in T cell pseudoemperipolesis to levels seen in nonrheumatoid FLS. Rheumatoid fibroblasts also constitutively produced high levels of vascular cell adhesion molecule 1 (VCAM‐1; CD106), but this did not contribute to T cell pseudoemperipolesis, unlike the case for B cells, which require SDF‐1 (CXCL12)–CXCR4 and CD49d–VCAM‐1 (CD106) interactions. Importantly, only combinations of rheumatoid FLS and rheumatoid‐derived synovial fluid T cells supported pseudoemperipolesis when examined ex vivo, confirming the in vivo relevance of these findings.

Conclusion

These studies demonstrate that features intrinsic to both fibroblasts (the production of SDF‐1) and CD8/CD4 T cells (the expression of CXCR4) are responsible for the characteristic pattern of T lymphocyte accumulation seen in the rheumatoid synovium. These findings suggest that the SDF‐1/CXCR4 ligand/receptor pair is likely to play an important functional role in T lymphocyte accumulation and positioning within the rheumatoid synovium.
Predicting the onset of widespread body pain among children
Authors: Jones Gareth T. , Silman Alan J. , Macfarlane Gary J.
Published: September 2003

Objective

To determine factors associated with, and the predictors of, widespread body pain in children.

Methods

A population‐based prospective study was conducted among school children in Northwest England. At baseline, subjects completed a self‐report questionnaire on widespread body pain. Information was collected on behavioral and emotional factors, other somatic symptoms, and measures of physical activity/inactivity. Children who were free of widespread pain were contacted again 12 months later to determine any new onset of widespread pain. Regression analyses were used to identify the factors that were associated with the reporting of widespread pain at baseline, and to determine the factors that predicted the new onset of symptoms at followup among those children free of widespread pain at baseline. Results were expressed as relative risks (RR) with 95% confidence intervals (95% CI).

Results

A total of 1,440 children (96%) agreed to participate in the survey at baseline, and of those eligible, 1,081 (88%) participated at followup. The reporting of widespread pain (prevalence 14.6%) and its new onset at the 12‐month followup (prevalence 7.7%) was common. At baseline, symptoms were associated with adverse behavioral and emotional factors (RR 2.5, 95% CI 1.8–3.6), with the report of other common childhood somatic symptoms (e.g., frequent headache; RR 3.5, 95% CI 2.2–5.5), and with high levels of sports activity (RR 1.9, 95% CI 1.3–2.9). Furthermore, all of these factors (in the absence of widespread pain at baseline) increased the likelihood of symptom onset at followup.

Conclusion

Children who report behavioral problems or other somatic symptoms are at increased risk, at least in the short term, of developing chronic widespread pain. It remains to be determined whether these are long‐term risk factors for the onset of such symptoms, and whether they could be predictors of the development of other functional syndromes.