bluuebunny/crossref_metadata_2025 huggingface dataset:
Patterns of gene expression in rat bone marrow stromal cells cultured on titanium alloy discs of different roughness
Authors: Leven Robert M. , Virdi Amarjit S. , Sumner Dale R.
Published: June 2004

Rat bone marrow stromal cells were cultured on either Ra (0.14 μm) or Ra (5.8 μm) Ti6Al4V discs for 24 or 48 h. Cells on the Ra (0.14 μm) surface showed typical fibroblastic morphology, whereas cells on the Ra (5.8 μm) surface were in clusters with a more epithelial appearance. RNA was extracted from the cells at both time points, and gene expression was analyzed by using a rat gene microarray. At 24 and 48 h, a similar number of genes were both up‐ and down‐regulated at least twofold on the Ra (5.8 μm) surface compared to the Ra (0.14 μm) surface. We analyzed the relative level of specific groups of genes related to bone and cartilage development, cell adhesion and extracellular matrix proteins, transcription factors, bone morphogenetic proteins, phospholipases, and protein kinases. Roughness did not appear to be a specific stimulator of osteogenesis because genes of both the bone and cartilage lineage were up‐regulated on the Ra (5.8 μm) surface. The most prominent change among transcription factors was up‐regulation of Hox 1.4 on the Ra (5.8 μm) surface. Up‐regulation of phospholipase A2 and SMAD 4 indicate these genes are also involved in the response of cells to an Ra (5.8 μm) surface. Our data show surface roughness alters the expression of a large number of genes in marrow stromal cells, which are related to multiple pathways of mesenchymal cell differentiation. © 2004 Wiley Periodicals, Inc. J Biomed Mater Res 70A: 391–401, 2004
Solvent effects on the microstructure and properties of 75/25 poly(D,L‐lactide‐co‐glycolide) tissue scaffolds
Authors: Sander Edward A. , Alb Alina M. , Nauman Eric A. , Reed Wayne F. , Dee Kay C
Published: June 2004

Poly(lactide‐co‐glycolide) (PLGA) is used in many biomedical applications because it is biodegradable, biocompatible, and FDA approved. PLGA can also be processed into porous tissue scaffolds, often through the use of organic solvents. A static light scattering experiment showed that 75/25 PLGA is well solvated in acetone and methylene chloride, but forms aggregates in chloroform. This led to an investigation of whether the mechanical properties of the scaffolds were affected by solvent choice. Porous 75/25 PLGA scaffolds were created with the use of the solvent casting/particulate leaching technique with three different solvents: acetone, chloroform, and methylene chloride. Compression testing resulted in stiffness values of 21.7 ± 4.8 N/mm for acetone, 18.9 ± 4.2 N/mm for chloroform, and 30.2 ± 9.6 N/mm for methylene chloride. Permeability testing found values of 3.9 ± 1.9 × 10−12 m2 for acetone, 3.6 ± 1.3 × 10−12 m2 for chloroform, and 2.4 ± 1.0 × 10−12 m2 for methylene chloride. Additional work was conducted to uncouple polymer/solvent interactions from evaporation dynamics, both of which may affect the scaffold properties. The results suggest that solvent choice creates small but significant differences in scaffold properties, and that the rate of evaporation is more important in affecting scaffold microstructure than polymer/solvent interactions. © 2004 Wiley Periodicals, Inc. J Biomed Mater Res 70A: 506–513, 2004
Increased apoptosis of periprostatic adipose tissue in VDR null mice
Authors: Guzey Meral , Jukic Drazen , Arlotti Julie , Acquafondata Marie , Dhir Rajiv , Getzenberg Robert H.
Published: June 2004

The vitamin D receptor (VDR) is a member of the steroid/retinoid receptor superfamily of nuclear receptors that controls mineral ion homeostatis and has potential tumor‐suppressive functions for various cancer types, specifically prostate cancer. A VDR ablated transgenic animal model (VDDRII, vitamin D‐dependent rickets type II) has been developed and the animals typically have various diseases including, hypocalcemia, hyperparathyroidism, rickets, osteomalacia, and alopecia. This transgenic mouse system provides us with a model to decipher the influences of the VDR on prostatic growth and function. VDRs are abundant both in prostatic epithelial and stromal cells, and vitamin D signaling can be studied in this model. Although, there were no gross differences between the prostate tissue of the experimental and control groups, VDR null mice showed fat necrosis and individual cell apoptosis in the periprostatic adipose tissue. This indicates a possible role of VDR in the signaling pathways resulting the prostate. This may be particularly attractive for VDR targets for the inhibition of cancer progression using VD3 and its analogs as potential chemo‐preventive agents. © 2004 Wiley‐Liss, Inc.
Role of N‐methyl‐D‐aspartate receptors in gastric mucosal blood flow induced by histamine
Authors: Tsai Li Hsueh , Lee Yih‐Jing , Wu Jang‐Yen
Published: June 2004

Ionotropic N‐methyl‐D‐aspartate (NMDA) receptor agonists, L‐aspartic acid (L‐Asp) and NMDA, have been shown to inhibit histamine‐stimulated acid secretion, but their effect on gastric mucosal blood flow (GMBF) is largely unknown. The aim of this study was to investigate whether L‐Asp and NMDA inhibit histamine‐stimulated GMBF and to examine the expression patterns of NMDA receptor subunits NR1, NR2A, and NR2B in rat stomach. Laser Doppler flowmetry was used to measure gastric blood flow in anesthetized rats. The GMBF was assessed during an intravenous infusion of histamine in the presence of tripelennamine. The effects of L‐Asp and NMDA on histamine‐induced gastric blood flow were examined. In addition, the distribution patterns of NR1‐, NR2A‐, and NR2B‐contaning NMDA receptors in rat stomach were determined immunohistochemically by using specific antibodies against NR1, NR2A, and NR2B. Histamine‐induced enhancement of GMBF depended on acid secretion and the activation of H2‐receptors. Neither L‐Asp nor NMDA had an effect on the spontaneous GMBF. However, L‐Asp and NMDA reduced the histamine‐induced increase in GMBF. DL‐2‐amino‐5‐phosphonopentanoic acid (AP‐5), an NMDA receptor antagonist; and prazosin, an α1‐receptor antagonist; but not propanolol, a β2‐receptor antagonist; or yohimbine, a α2‐receptor antagonist; reversed the inhibitory effect of L‐Asp and NMDA on the histamine‐induced increase in GMBF. Therefore, L‐Asp and NMDA inhibit histamine‐induced GMBF via a mechanism involving the activation of NMDA receptors and α1‐ adrenoceptors. The fact that NMDA receptor subunits NR1, NR2A, and NR2B were found to be localized in the rat stomach as visualized immunohistochemically with specific antibodies against NR1, NR2A, and NR2B is consistent with this hypothesis. © 2004 Wiley‐Liss, Inc.
Antinociceptive effects of galanin in the rat tuberomammillary nucleus and the plasticity of galanin receptor 1 during hyperalgesia
Authors: Sun Yan‐Gang , Li Ji , Yang Bo‐Ning , Yu Long‐Chuan
Published: June 2004

Although the tuberomammillary nucleus (TM) is well defined in terms of anatomy and neurochemistry, little is known about its function in nociceptive modulation. There was an abundance of galanin‐immunoreactive fibers in the TM, and galanin has been implicated in pain processing. The present study assessed the role of galanin in the modulation of nociception in the TM of rats. Intra‐TM injection of galanin dose‐dependently increased the hindpaw withdrawal latency of rats to a noxious thermal stimulus, indicating an antinociceptive role of galanin in the TM. The antinociceptive effect of galanin was blocked by a subsequent intra‐TM injection of galantide, a putative galanin receptor antagonist, suggesting that the antinociceptive effect of galanin is mediated by galanin receptors. Moreover, there was abundant galanin receptor 1 (GalR1) in the TM, and the number of GalR1‐positive neurons in the ipsilateral TM increased significantly after unilateral loose ligation of the sciatic nerve compared with the contralateral TM or the TM of intact rats. However, the number of GalR1‐positive neurons was not significantly altered by carrageenan‐induced inflammation, in either the ipsilateral or the contralateral TM. The results suggest that galanin and GalR1 in the TM may play important roles in pain regulation. © 2004 Wiley‐Liss, Inc.
On‐site Raman analysis of Iznik pottery glazes and pigments
Authors: Colomban Philippe , Milande Véronique , Le Bihan Lionel
Published: June 2004

On‐site Raman analyses were performed at the Musée National de Céramique, Sèvres, France, on rare Iznik (former Nicaea) pottery produced from ∼1480 to ∼1620. A comparison was made with a series of shards. The town of production of these potteries was highly disputed in the 1980s and many questions still remain. The potential of glaze on‐site analyses as a classification/dating tool was evaluated. The structure of the silicate glaze does not change with the sample (index of polymerization ∼0.5–0.8, indicating a lead silicate composition); characteristic SiO stretching mode doublet at ∼985 and 1030–1050 cm−1. By contrast, the corresponding signature of most of the ‘Kütahya’ wares peaks at ∼1070–1090 cm−1. The lowest index is measured for a brilliant overglazed red bole, according to a lower temperature of (post)firing. The different crystalline phases identified in the glaze are α‐quartz, haematite, spinel, cassiterite, uvarovite garnet and zircon. White colour arises from α‐quartz slip in most samples studied. Cassiterite (SnO2) opacifier is only present in some early blue‐and‐white ceramics (Master of the Knots and Baba Nakkas style, ∼1510–1530) and we do not have other evidence of its intentional use as an opacifier. Intentional addition of tin oxide is likely for colour lightening in some red, blue and in clear green boles. At least two types of red glazes and two types of Cr‐containing green pigments are evidenced. Copyright © 2004 John Wiley & Sons, Ltd.
Raman scattering probe of anharmonic effects in NiSi
Authors: Donthu S. K. , Tripathy S. , Chi D. Z. , Chua S. J.
Published: June 2004

We report a systematic temperature‐dependent Raman scattering study of NiSi thin films. In agreement with the basic anharmonic theory, the strong Raman peak from NiSi at about 214 cm−1 shows phonon softening and broadening with an increase in the sample temperature. Comparative study of the temperature dependence of this first‐order Raman peak from NiSi powder and the film show that NiSi layers of thickness 15–90 nm are under tensile thermal stress. The results also show that the total phonon shift observed in the temperature range 80–500 K is independent of the silicide film thickness. We have also shown that Raman spectroscopy is a faster and more sensitive technique than x‐ray diffraction for phase identification in NiSi nanolayers, hence Raman scattering can be used as a valuable tool for in situ growth and process monitoring of nickel silicides. Copyright © 2004 John Wiley & Sons, Ltd.
Use of a fibre‐optic probe for the identification of asbestos fibres in bulk materials by Raman spectroscopy
Authors: Bard Delphine , Tylee Barry , Williams Ken , Yarwood Jack
Published: June 2004

Within the UK, a large number of surveys are being carried out for the identification of asbestos in building materials. Pre‐demolition or major refurbishment and building sampling surveys require that representative samples be analysed for asbestos. The primary technique for the analysis of asbestos fibres in bulk materials is polarized light microscopy (PLM). Since this method is based on visual estimation, it depends on the competence and experience of the analyst. Furthermore, PLM, in common with the other analytical methods used for the identification of asbestos in bulk materials, is a laboratory‐based technique requiring samples to be collected and then sent to a laboratory for analysis. Raman spectroscopy is a powerful tool for mineral characterization and provides a molecular fingerprint for material. In recent years, new developments in optics and electronics have permitted the development of compact Raman spectrometers allowing in situ measurements. We report the performance of a robust, laboratory‐based fibre‐optic probe for the identification of asbestos in bulk materials by Raman spectroscopy. Thirty‐eight samples were analysed, and the results showed that 95% of the samples were successfully identified as either asbestos free or containing one or more asbestos components. A success rate of 100% was found for asbestos insulating board and asbestos cement materials. The results indicated that a Raman probe device for detecting asbestos does have potential, but a number of issues need to be addressed before an on‐site system can be developed. Copyright © 2004 John Wiley & Sons, Ltd.
Raman spectroscopic study of the epicuticular wax layer of mature mango (Mangifera indica) fruit
Authors: Prinsloo Linda C , du Plooy Wilma , van der Merwe Chris
Published: June 2004

Little is known about the chemical composition of the natural wax layer covering mango (Mangifera indica) fruit. We report here on the role of Raman spectroscopy in a study that was undertaken to characterize the epicuticular wax of mature mango fruit. Scanning electron microscope measurements showed two morphologically distinct parts in the wax layer and Raman microscopy determined that they are chemically distinct. Crystalline aliphatic compounds protrude from an amorphous layer in which long‐chain aliphatic, aromatic and unsaturated compounds are present. Raman spectra recorded on the perimeter of lenticels indicate an absence of the crystalline aliphatic compounds in this region and this information could assist in the solution of the problem faced by the mango industry of the discoloration around lenticels, which makes the fruit unacceptable as an export product. The results are supported by Fourier transform IR spectroscopy and both techniques are now employed as probes in a long‐term project to study dynamic changes of the wax during fruit development and eventual processing, which includes the monitoring of possible changes in carotenoid content and the role of dust particles embedded in the wax. Copyright © 2004 John Wiley & Sons, Ltd.
Preparation of SERS‐active gold film electrodes via electrocrystallization: their characterization and application with NIR excitation
Authors: Sauer G. , Brehm G. , Schneider S.
Published: June 2004

The electrodeposition of a sufficiently large amount of gold on vapor‐deposited film electrodes at high overpotentials leads to excellent substrates for surface‐enhanced Raman scattering (SERS) spectroscopy. The SERS enhancement factor is estimated to be >107 with near‐infrared excitation, a value which is superior to that for gold surfaces roughened by conventional oxidation–reduction cycles. Its wavelength dependence was studied over a wide range of excitation wavelengths and compared with that of silver electrodes prepared in an analogous manner. Furthermore, the broad applicability of the SERS‐active gold film electrodes was demonstrated using numerous environmentally relevant s‐triazine derivatives containing amino and/or thioether groups as probe molecules. Finally, it is shown that the high stability of the roughened gold surfaces allows even strongly adsorbed molecules to be removed by plasma cleaning without distinctly altering the SERS enhancement factor. First results allow the conclusion that this type of SERS‐active surfaces is well suited for their repeated use. Copyright © 2004 John Wiley & Sons, Ltd.
Raman investigation of the structural changes in anatase LixTiO2 upon electrochemical lithium insertion
Authors: Baddour‐Hadjean Rita , Bach Stéphane , Smirnov Mikhail , Pereira‐Ramos Jean‐Pierre
Published: June 2004

Micro‐Raman spectrometry and x‐ray diffraction (XRD) experiments were performed on the anatase LixTiO2 system (0 ≤ x ≤ 0.6) produced from the electrochemical discharge of a TiO2 composite cathode in propylene carbonate LiClO4 solution at room temperature. Raman spectrum modifications indicate local structural and chemical changes as lithium enters the anatase host lattice. The existence of a tetragonal to orthorhombic phase transition is clearly demonstrated by the Raman and XRD measurements. Moreover, lithium extraction is only partially quantitative for Li uptake ≤0.5, as shown both from structural and electrochemical data in the 3–1.5 V potential range. For the first time, the Raman fingerprint of the lithium titanate (LT) Li0.5TiO2 orthorhombic phase is clearly evidenced. A theoretical analysis of the lattice dynamics suggested a complete interpretation of the experimental Raman spectra in the LixTiO2 system, which provided valuable information on the Li atom positions and coordination in LT. Taking into account the possibility of rather short LiO distances, the complex band structure in the high‐wavenumber region is assigned to the LiO vibrations. Furthermore, spectra simulation offers an explanation for the new shape of the TiO2 lattice modes observed in the low‐wavenumber region. Copyright © 2004 John Wiley & Sons, Ltd.
Conformational analysis of tetrapeptides by exploiting the excitonic coupling between amide I modes
Authors: Huang Qing , Schweitzer‐Stenner Reinhard
Published: June 2004

The amide I band of the IR and to a lesser extent also of the corresponding visible Raman spectra of peptides and proteins are frequently used to determine their secondary structure composition. Thus far, however, this analytical approach is generally a low‐resolution technique, particularly because it mostly discriminates only between α‐helical, β‐sheet (parallel and antiparallel) and so‐called random coil conformations. This study shows that for tetrapeptides the combined use of the IR and Raman amide I band profiles allows one to discriminate currently known secondary structure motifs. To exploit the spectral information to its fullest extent, we developed an algorithm which calculates the amide I intensity profiles of IR, isotropic and anisotropic Raman scattering and also the depolarization ratios of the Raman bands as a function of the dihedral angles of the two central amino acid resides. The approach is based on a quantum mechanical treatment of the vibrational coupling between the amide I modes of the three peptide groups in the framework of a coupled oscillator model. We calculated the band profiles of a representative set of secondary structures, i.e. a right‐handed α‐helix, a 310‐helix, β‐sheets and a polyproline II (PPII)‐type 31‐helix and β‐turns. Our results unambiguously show that all these secondary structure motifs can be identified by comparing experimentally observed IR and Raman amide I bands with their respective calculated intensity distributions. Copyright © 2004 John Wiley & Sons, Ltd.
Application of Raman spectroscopy and quantum chemistry for featuring the structure of positively charged species in macrocyclic π‐conjugated diacetylene‐bridged oligothiophenes
Authors: Casado J. , Hernández V. , Ponce Ortiz R. , Ruiz Delgado M. C. , López Navarrete J. T. , Fuhrmann G. , Bäuerle P.
Published: June 2004

Different types of stable positively charged defects compatible with the electronic and molecular structure of a series of macrocyclic molecular materials containing symmetrically butylated terthienyl or quinquethienyl segments connected through diacetylenic bridges were studied by means of Raman spectroscopy. In all cases iodine was used as the oxidant, whereas for the largest macrocycle in situ spectroelectrochemistry was also employed. Comparison of the Raman spectra obtained either electrochemically or on treatment with iodine indicates that iodine behaves as a moderate oxidant giving rise to fairly stable positive charged defects. The comparison of the Raman spectra obtained upon iodine doping for two series of homologous molecules, namely open‐chain diacetylene‐bridged and non‐bridged oligothiophenes, with those of the macrocyclic compounds suggests that each terthienyl or quinquethienyl building block is able to accommodate one positive charge in the form of a polaron. Density functional theory quantum chemical calculations were performed, at the DFT//B3LYP/3–21G* level, for two model systems to assess useful information about the evolution of the molecular structure and charge distribution upon oxidative doping of the compounds. Copyright © 2004 John Wiley & Sons, Ltd.
Identification by Raman microscopy of pigments on early postage stamps: distinction between original 1847 and 1858–1862, forged and reproduction postage stamps of Mauritius
Authors: Chaplin Tracey D. , Jurado‐López Alicia , Clark Robin J. H. , Beech David R.
Published: June 2004

An extremely rare used 1847 1d orange–red Mauritian stamp, a rare 1847 2d deep blue unused stamp, a 1913 reproduction 2d stamp, early forgeries and 1858–1862 Britannia‐type Mauritian stamps were analysed using Raman microscopy in order to determine the identities of the pigments on the stamps. That in the printing ink of the 1d stamp was identified to be lead(II,IV) oxide (‘red lead’), with a cancel mark composed of carbon‐based black. Prussian blue was identified as having been used in the genuine and reproduction 2d issues, these being distinguished only by the presence of crystals of ultramarine blue dispersed between the paper fibres of the genuine issues. The 4d green Britannia‐type stamp is pigmented with ‘chrome green’, a mixture of Prussian blue and chrome yellow, and the 6d ‘vermilion’ Britannia‐type stamp is pigmented with vermilion. Raman microscopy was shown to be a rapid, highly specific and non‐destructive technique for the expertising of stamps whose authenticity is in question via the precise identification of the pigments used on the surface of each stamp and dispersed between the paper fibres. Copyright © 2004 John Wiley & Sons, Ltd.
Raman spectrum of fully reduced flavin
Authors: Zheng Yuangang , Carey Paul R. , Palfey Bruce A.
Published: June 2004

Protein–flavin interactions modify the chemistry of the flavin, ‘tuning’ it to its biological function. In order to understand protein interactions with reduced flavins, the Raman spectrum of reduced FAD was recorded at pH values where the reduced isoalloxazine is neutral and anionic. Reduced isoalloxazine is a weaker Raman scatterer than oxidized isoalloxazine by at least an order of magnitude in both ionization states. Substitution of exchangeable protons for deuterium, the effect of ionization and DFT calculations allowed the assignment of the observed Raman bands to normal modes of vibration. Copyright © 2004 John Wiley & Sons, Ltd.
Synthesis and Characterization of Polymeric Linseed Oil Grafted Methyl Methacrylate or Styrene
Authors: Cakmakli Birten , Hazer Baki , Tekin Ishak Ozel , Kizgut Sait , Koksal Murat , Menceloglu Yusuf
Published: June 2004

Summary: Syntheses of wholly natural polymeric linseed oil (PLO) containing peroxide groups have been reported. Peroxidation, epoxidation and/or perepoxidation reactions of linseed oil, either under air or under oxygen flow at room temperature, resulted in polymeric peroxides, PLO‐air and PLO‐ofl, containing 1.3 and 3.5 wt.‐% of peroxide, with molecular weights of 2 100 and 3 780 Da, respectively. PLO‐air contained cross‐linked film up to 46.1 wt.‐% after a reaction time of 60 d, associated with a waxy, soluble part (PLO‐air‐s) that was isolated with chloroform extraction. PLO‐ofl was obtained as a waxy, viscous liquid without any cross‐linked part at the end of 24 d under visible irradiation and oxygen flow. Polymeric peroxides, PLO‐air‐s and PLO‐ofl initiated the free radical polymerization of both methyl methacrylate (MMA) and styrene (S) to give PMMA‐graft‐PLO and PS‐graft‐PLO graft copolymers in high yields with $\overline M _{\rm w}$ varying from 37 to 470 kDa. The polymers obtained were characterized by FT‐IR, 1H NMR, TGA, DSC and GPC techniques. Cross‐linked polymers were also studied by means of swelling measurements. PMMA‐graft‐PLO graft copolymer film samples were also used in cell‐culture studies. Fibroblast cells were well adhered and proliferated on the copolymer film surfaces, which is important in tissue engineering.

Proliferation of the fibroplast cells on the PS‐graft‐PLO film.

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Proliferation of the fibroplast cells on the PS‐graft‐PLO film.
Novel Photopolymerizable Biodegradable Triblock Polymers for Tissue Engineering Scaffolds: Synthesis and Characterization
Authors: Chan‐Park Mary B. , Zhu Ai P. , Shen Jin Y. , Fan Ai L.
Published: June 2004

Summary: For use in micro‐patterned scaffolds in tissue engineering, novel diacrylated triblock macromers (PLA‐b‐PCL‐b‐PLA, PGA‐b‐PCL‐b‐PGA and PCL‐b‐PEO‐b‐PCL) were synthesized and characterized by Fourier transform infrared spectroscopy (FTIR), nuclear magnetic resonance spectroscopy (NMR) and gel permeation chromatography (GPC). All diacrylated polymers were designed as triblock copolymers and involved biodegradable blocks of relatively non‐polar ε‐caprolactone (CL) and polar monomers such as glycolide (GA), lactide (LA) or ethylene oxide (EO). All triblock polymers were prepared in molecular weights of a few kilo daltons via the anionic ring‐opening polymerization (ROP) of the corresponding lactide, glycolide or caprolactone using stannous octoate [Sn(Oct)2] as catalyst. The polymers had low polydispersity indices, ranging from 1.23 to 1.56. Biodegradable polymeric networks were prepared with conversions of 72–84% via photopolymerization of the triblock diacrylated polymers with 2,2‐dimethoxy‐2‐phenylacetophenone (DMPA) as photoinitiator. PLA‐b‐PCL‐b‐PLA copolymers crumbled easily and were not suitable for micro‐patterning. PGA‐b‐PCL‐b‐PGA copolymers had higher water contact angles than PCL‐b‐PEO‐b‐PCL and were also cytocompatible with Fibroblasts 3T3.

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Concanavalin A Immobilized Affinity Adsorbents for Reversible Use in Yeast Invertase Adsorption
Authors: Yavuz Handan , Akgöl Sinan , Arica Yakup , Denizli Adil
Published: June 2004

Summary: Concanavalin A (Con A) immobilized poly(2‐hydroxyethyl methacrylate) (PHEMA) beads were investigated for specific adsorption of yeast invertase from aqueous solutions. PHEMA beads were prepared by a suspension polymerization technique with an average size of 150–200 μm, and activated by epichlorohydrin. Con A was then immobilized by covalent binding onto these beads. The maximum Con A immobilization was found to be 10 mg/g. The invertase‐loading capability of the PHEMA/Con A beads was 107 mg/g. The maximum invertase adsorption capacity on the PHEMA/Con A adsorbents was observed at pH 5.0. The values of the Michaelis constant Km of invertase were significantly larger upon adsorption, indicating decreased affinity by the enzyme for its substrate, whereas Vmax was smaller for the adsorbed invertase. Adsorption improved the pH stability of the enzyme as well as its temperature stability. Thermal stability was found to increase with adsorption. The adsorbed enzyme activity was found to be quite stable in repeated experiments.

Storage stability of adsorbed invertase.

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Storage stability of adsorbed invertase.
Design of Temperature Sensitive Imprinted Polymer Hydrogels Based on Multiple‐Point Hydrogen Bonding
Authors: Liu Xue‐Yong , Guan Ying , Ding Xiao‐Bin , Peng Yu‐Xing , Long Xin‐Ping , Wang Xiao‐Chuan , Chang Kun
Published: June 2004

Summary: Weakly cross‐linked temperature sensitive imprinted polymer hydrogels that recognize L‐pyroglutamic acid (Pga) molecules via multiple‐point hydrogen bonding were designed and synthesized. The amount of adsorption for Pga in imprinted hydrogels is 3–4 times higher than that in non‐imprinted hydrogels. The selectivity test of imprinted polymer gels was carried out by using a series of structurally related compounds Pga, pyrrolidine, 2‐pyrrolidone, L‐proline as substrates. The results show that imprinted polymer gels exhibit high selectivity for Pga as compared to all the other tested substrates. The imprinted polymer hydrogels show good temperature sensitivity, special selectivity and reusability, suggesting that the polymer hydrogels would have an enormous potential for application in controlled drug release and separation field.

Schematic representation of the adsorption and release process of Pga by the imprinted polymeric gels.

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Schematic representation of the adsorption and release process of Pga by the imprinted polymeric gels.
Modulation of Proteins Adsorption onto the Surface of Chitosan Complexed with Anionic Copolymers. Real Time Analysis by Surface Plasmon Resonance
Authors: Aguilar María R. , Gallardo Alberto , Lechuga Laura M. , Calle Ana , San Román Julio
Published: June 2004

Summary: The interpolyelectrolyte complex formation between chitosan and anionic polyacrylic derivatives, bearing sulfonic moieties, as well as the protein adsorption onto the chitosan/polyacrylic complexes were studied by surface plasmon resonance (SPR) optical biosensor. This unique technique allows a real time monitoring of different surface molecular interactions with very high sensitivity. The acrylic macromolecules are two families of copolymers of 2‐acrylamido‐2‐methylpropane sulfonic acid (AMPS) and, respectively, 2‐hydroxyethylmethacrylate (HEMA) and N,N′‐dimethylacrylamide (DMAA). The complexation process was evaluated through the SPR measurements resulting from the flowing of polyacrylic aqueous solution over the sensor previously coated with chitosan. The SPR was able to differentiate strong ionic bonds from other weak and reversible interactions. By means of the coated sensors (uncomplexed and the whole series of complexed chitosan), SPR cold be used for a simple “in vitro” protein adsorption analysis, by flowing aqueous solutions of albumin and fibrinogen. While both proteins were adsorbed on the uncomplexed chitosan, the complexed coatings exhibited different and very promising behaviors. In particular, they showed no adsorption or only selective adsorption of albumin.

A SPR experimental set‐up in the Kretschmann configuration.

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A SPR experimental set‐up in the Kretschmann configuration.
Korrosionsverhalten ausgewählter Werkstoffe in Lithiumbromid‐Lösung für den Anwendungsfall Absorptionskältemaschinen
Authors: Brandt B.
Published: June 2004

Absorptionskältemaschinen auf der Basis von Lithiumbromid‐Wasser stellen eine interessante Möglichkeit zur effizienten und energiesparenden Versorgung mit Kälte dar. Die zum Antrieb erforderliche Wärmeenergie kann idealerweise aus regenerativen Energien, wie z.B. Solarwärme, oder Abwärme aus der Industrie bereitgestellt werden. Um die Energieeffizienz zu steigern, können die Prozesse mehrstufig betrieben werden. Bei den dreistufigen, sogenannten Triple‐Effekt‐Anlagen, sind im Generator Temperaturen bis zu etwa 200–220°C erforderlich. Die Faktoren hohe Temperatur, hohe Halogenidkonzentration (Lithiumbromid) und die Anwesenheit von Wasserdampf führen zu einer besonders starken korrosiven Beanspruchung der Werkstoffe.

Aufgabe des vorliegenden Beitrages war deshalb die Betrachtung handelsüblicher Werkstoffe und Inhibitoren auf ihre Eignung für Triple‐Effekt‐Absorptionskältemaschinen. Die Messungen wurden unter analogen Bedingungen in ruhender Lösung unter nahezu vollständigem Ausschluss von Luft durchgeführt.

Die Untersuchungen haben ergeben, dass nichtrostender Stahl hinsichtlich seiner Materialstabilität besonders aussichtsreich ist. Weiterhin hat sich gezeigt, dass die Art des Inhibitors und das Zusammenwirken unterschiedlicher Phasen die Korrosion erheblich beeinflussen können.
Influence of drying temperature on the corrosion performance of chromate coatings on galvanized steel
Authors: Zhang X. , Böhm S. , Bosch A. J. , van Westing E. P. M. , de Wit J. H. W.
Published: June 2004

The influence of drying temperature on the corrosion performance of chromate coatings on electro‐galvanized (EG) steel has been investigated using electrochemical impedance spectroscopy (EIS) and potentiodynamic measurements in 3.5% NaCl solutions. The chromate coatings were applied to the EG steel in a solution (pH 1.2) containing sodium dichromate and sulfuric acid at room temperature. The coatings were dried in an oven at three different temperatures: 60, 110 and 210°C. The surface of the chromate coatings was analyzed using atomic force microscopy (AFM) and scanning electron microscopy (SEM) combined with energy‐dispersive spectrometry (EDS). The results show that the drying temperature significantly affects the morphology of the chromate coatings and consequently affects their corrosion behavior. The chromate coatings dried at 110°C had few cracks and the lowest corrosion current. The chromate coatings dried at 60°C showed passivity. The EIS results show that the chromate coatings dried at 60°C has the largest impedance in a neutral 3.5% NaCl solution. Drying at higher temperature (210°C) degrades the chromate coatings by widening the cracks and reducing soluble Cr(VI) in the chromate layer. The favorable drying temperature for the chromate coatings on the EG steel is between 60 and 110°C.
The effect of fluoride on the electrochemical behavior of Ti and some of its alloys for dental applications
Authors: Al‐Mayouf A. M. , Al‐Swayih A. A. , Al‐Mobarak N. A. , Al‐Jabab A. S.
Published: June 2004

Titanium is the best metal for making dental implants and restorations. In the last decade, new titanium alloys have been developed in different areas of dentistry. Concurrently, treatments using fluoride supplementation, such as odontology fluoride containing gels, have also been widely used in odontology.

The aim of this study is to investigate the electrochemical behaviour of a new titanium alloy containing Cu and Ag, in fluoride‐containing media, and compare it with the behavior of Ti and Ti6Al4V, which are used frequently as biomaterials. Open circuit potential, polarization resistance and electrochemical impedance spectroscopy measurements revealed that the corrosion resistance of titanium and its alloys is controlled by the fluoride ion concentration and the pH of the solution. The presence of F− ions in neutral solution does not hinder the formation of a protective layer of Ti and its alloys. Thus, the corrosion resistance of Ti is maintained in this medium. However, the corrosion of Ti and its alloys are enhanced in an acidic environment, because F− ions in the solution combines with H+ ion to form HF, even in low fluoride concentration.
Potential of biocorrosion in Danish district heatings sytems
Authors: Kjellerup B. V. , Olesen B. H. , Frølund B. , Nielsen P. H.
Published: June 2004

Danish district heating (DH) systems utilise water with unique characteristics that include low conductivity, high pH, nutrient poor and anaerobic (oxygen free) conditions in order to reduce corrosion rates. This survey was carried out in order to investigate the potential for biofilm formation and biocorrosion in these systems. Determination of total bacterial numbers in water samples were performed in 29 DH systems and showed a range of 102–105 cells · ml−1. The potential for biofilm growth was further examined in corrosion monitoring units located at 6 DH locations. Total bacterial numbers in biofilm on mild steel were found in the range of 104–106 cells · cm−2. The mild steel coupons were examined for general corrosion rates based on weight loss together with an investigation of pitting corrosion. The general corrosion rates were up to 12 μm · year−1, while the pitting analysis showed pit depths up to 90 μm for half a year of exposure. Presence of sulphate reducing bacteria (SRB) was found in all systems tested with corrosion monitoring units, whereas sulphide was found to different extents in the biofilms on all mild steel coupons.

It was shown that DH systems with the highest number of bacteria in the biofilm generally had the most pronounced corrosion. The results show that despite the nutrient poor environment in the DH systems the potential for biofilm formation and biocorrosion was present.
Metallic dental materials in patient's oral cavity acting as electrodes of electrochemical cells
Authors: Opydo W. , Opydo‐Szymaczek J.
Published: June 2004

The work was aimed at studying of standard potentials of commonly used metallic dental materials and determining of the effect of saliva conductivity and reaction on value of the potentials. The following materials have been examined: gold alloy (a material used for crowns and bridgeworks), chromium‐cobalt alloy (for frameworks in removable partial dentures), and silver amalgams (used for fillings) manufactured by three different companies.

Taking into account that mucosa makes one of the electrodes existing in oral cavity the rest potentials of mucosa have been in vivo measured in several patients. Their values, converted with respect to NHE, oscillated within the range from + 0.31 V to + 0.47 V.

Among metallic dental materials examined in the experiment maximal standard potential was found for the gold alloy, further materials having lower potentials, in decreasing order, were chromium‐cobalt alloy, and the amalgams Amalcap Plus, ANA 2000 and Septalloy.

Significant differences between standard potentials of examined materials and mucosa indicate spontaneous formation of galvanic cells of electromotive force reaching even about 0.6 V.
Ronald Koningsveld
Authors: Hess Michael
Published: June 2004

This section contains news of the macromolecular community all over the world. Articles about, for example, people, projects, and market trends are welcome. Suggestions should be sent to the editorial office of the Macromolecular journals, preferably by E‐mail to macromol@wiley‐vch.de. The editorial office decides which articles will be published.
Investigation of the Peak Width of Polystyrene Prepared by Rotating‐Sector Polymerization in Microemulsion
Authors: Schnöll‐Bitai Irene , Pfeisinger Christian
Published: June 2004

Styrene was polymerized by intermittent photoinitiation (at a constant sector speed and a light to dark ratio of 1:5) in microemulsion. The molecular weight distribution was measured by size‐exclusion chromatography and turned out to be extremely well structured. When the points of inflection were used for the calculation of the rate constant of propagation in analogy to pulsed‐laser polymerization/size‐exclusion chromatography (PLP‐SEC), values were obtained which were lower than those accepted for bulk polymerization but good agreement was achieved with a slightly modified equation. The absolute peak width (introduced as the difference between two successive points of inflection) turned out to be an invariant quantity no matter which type of distribution curve (number, molar mass, or hyper distribution) was analyzed, thus demonstrating the Poissonian character of the peaks. Furthermore, the relative peak widths (defined as the ratio of two successive points of inflection) for the first peak scattered between 1.35–1.45, those for the second peak between 1.26–1.30. After subtracting the respective value for the theoretical peak width, the same value for the first and second peaks was obtained for all experiments over a broad range of experimental parameters. As the appearing peaks are well resolved and narrow, the influence of axial dispersion on the results is, therefore, conclusively demonstrated. A simple procedure for the direct determination of axial dispersion is presented based on the relative peak widths and the additivity of the peak variances. The invariance of the peak widths is an easily verifiable theoretical and experimental prerequisite for this procedure.

Comparison of GPC traces of a microemulsion polymerization of styrene (t0 = 1.4 s, [M] = 4.326 mol · l−1; light‐to‐dark ratio 1:5; full line) and of a standard mixture (styrene, peak masses: 1 950, 89 400, 993 000; dashed line).

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Comparison of GPC traces of a microemulsion polymerization of styrene (t0 = 1.4 s, [M] = 4.326 mol · l−1; light‐to‐dark ratio 1:5; full line) and of a standard mixture (styrene, peak masses: 1 950, 89 400, 993 000; dashed line).
Stereospecific Nature of Active Sites on TiCl4/MgCl2 Ziegler–Natta Catalyst in the Presence of an Internal Electron Donor
Authors: Liu Boping , Nitta Takashi , Nakatani Hisayuki , Terano Minoru
Published: June 2004

Based on our previous study on the donor‐free TiCl4/MgCl2 catalyst, the stereospecific nature of active sites on this catalyst after the addition of an internal donor, ethylbenzoate (EB), was investigated by stopped‐flow propylene polymerization combined with temperature rising elution fractionation (TREF) and gel permeation chromatography (GPC) methods. The addition of donor EB was observed to significantly restrain the formation of aspecific sites (AS sites), to drastically promote formation of sites with the second highest isospecificity (IS2 sites) and to construct some new active sites with the highest isospecificity (IS3 sites). It was first observed that the formation of IS3 sites still strongly depends on the interaction between the catalyst and cocatalyst (up to 10 s of pretreatment) even in the presence of internal donor. Based on Busico and co‐workers' three sites model and our previous report, a plausible mechanism for the transformation of stereospecific active sites through some secondary bimetallic complexation reactions was proposed. The extraction of EB from the catalyst by the cocatalyst was found to initiate after 10 s of pretreatment resulting in partial transformation of IS3 sites into AS sites and IS1 sites.

Plausible mechanism for the transformation of active sites with lower isospecificity (AS sites) into the highest isospecific active site (IS3 sites) on the TiCl4/MgCl2 catalyst in the presence of internal donor EB during the pretreatment, X: Cl or Et; M: Mg or Ti. M and Mg are bound to the catalyst substrate through chlorine bridges; □: coordination vacancy.

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Plausible mechanism for the transformation of active sites with lower isospecificity (AS sites) into the highest isospecific active site (IS3 sites) on the TiCl4/MgCl2 catalyst in the presence of internal donor EB during the pretreatment, X: Cl or Et; M: Mg or Ti. M and Mg are bound to the catalyst substrate through chlorine bridges; □: coordination vacancy.
Improved Electro‐Optic Effect by Hyperbranched Chromophore Structures in Side‐Chain Polyimide
Authors: Do Jung Y. , Park Seung K. , Ju Jung‐Jin , Park Suntak , Lee Myung‐Hyun
Published: June 2004

Hyperbranched structures of chromophores were developed to improve the nonlinearity of optical polymers. Macromolecules with 3‐[p‐(2′‐hydroxyethylmethylamino)styryl]‐1‐dicyanomethylene‐5,5‐dimethylcyclohex‐2‐ene (AIDC) were prepared using 3,5‐dihydroxyphenyl groups as building blocks. When the molecule was incorporated into a polyimide backbone (PI‐DAIDC101), a high electro‐optic coefficient was obtained, giving 32 pm · V−1 at 1.55 μm. The nonlinearity is at least doubly enhanced in comparison with that of conventional side chain‐optical polyimides. This is mainly attributable to an increased polarizing efficiency derived from the chromophore structures.

The structure of the linear polyimide backbone (PI‐OH) and the chromophore‐attached optical polyimide (PI‐DAIDC101).

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The structure of the linear polyimide backbone (PI‐OH) and the chromophore‐attached optical polyimide (PI‐DAIDC101).
Shear‐Induced Crystallization and Shear‐Induced Dissolution of Poly(ethylene oxide) in Mixtures with Tetrahydronaphthalene and Oligo(dimethyl siloxane‐b‐ethylene oxide)
Authors: Madbouly Samy A. , Wolf Bernhard A.
Published: June 2004

Cloud point temperatures (Tcp) and crystallization temperatures (Tl/s) were measured at different constant shear rates for the ternary system tetrahydronaphthalene/poly(ethylene oxide)/oligo(dimethyl siloxane‐b‐ethylene oxide) using a rheo‐optical device and in the case of Tl/s additionally a viscometer. This system enables for the first time a joint investigation of both transitions with a given mixture. Shear favors the homogeneous liquid state and the formation of crystals. Tcp (liquid/liquid demixing, UCST) shifts to lower and Tl/s (liquid/solid, segregation of PEO) to higher temperatures by several degrees as the shear rate,$\dot \gamma$, is increased up to 500 s−1. The normalized shift in Tcp fits well into previous results for high molecular weight blends, oligomer mixtures, polymer solutions in single solvents and low molecular weight mixtures. A phase separated near critical blend was examined 1 K below its Tcp by means of a shear cell (Linkam) in the quiescent state and under shear with respect to its morphology. Upon an increase in $\dot \gamma$one observes a transition from the co‐continuous structures existing in the quiescent state via deformed and oriented particles to string like morphologies. Finally, at sufficiently high shear rates the mixture becomes homogeneous and structures can no longer be seen under the microscope. The morphologies developing after the secession of shear are pointing to pronounced influences of the flow history of the system on the final structure of two phase blends.

Equilibrium phase diagram of the system THN/COP/PEO at the indicated temperatures as obtained from turbidimetric titration. The curve for 42 °C indicates the compositions under which the mixtures segregate the first solid PEO particles upon cooling. The curves for the higher temperatures denote the demixing of the homogeneous system into two liquid phases.

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Equilibrium phase diagram of the system THN/COP/PEO at the indicated temperatures as obtained from turbidimetric titration. The curve for 42 °C indicates the compositions under which the mixtures segregate the first solid PEO particles upon cooling. The curves for the higher temperatures denote the demixing of the homogeneous system into two liquid phases.
Free Radical Polymerization of Styrene with a New Tetrafunctional Peroxide Initiator
Authors: Fityani‐Trimm Sabile , Dhib Ramdhane , Penlidis Alexander
Published: June 2004

Bulk, free‐radical polymerization of styrene was carried out in the presence of a new tetrafunctional initiator (JWEB50, ATOFINA Chemicals, Inc.). The objective was to investigate the effect of initiator functionality on the free radical polymerization process. Size exclusion chromatography (SEC) with an on‐line multi‐angle laser light scattering (MALLS) detector was used to measure molecular weight (MW), molecular weight distribution (MWD), and radius of gyration (Rg) of polystyrene. These results were compared to those with a monofunctional initiator, LupTBEC, also from ATOFINA. At equivalent molar concentrations, initiation with JWEB50 and LupTBEC produced polystyrene with similar MWs and MWDs. However, the rate of polymerization was faster with JWEB50. When LupTBEC was four times the molar concentration of JWEB50, equal rates of polymerization were achieved for both initiators. The MWDs were again similar, but the MWs were higher for the tetrafunctional initiation. Degree of branching and gelation were also investigated. A mixture of branched and linear polymer was produced by JWEB50, while no insoluble gel was formed.

Decomposition of JWEB50, a tetrafunctional initiator.

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Decomposition of JWEB50, a tetrafunctional initiator.
Preparation and Electrorheological Characterization of Suspensions of Monodisperse Micron‐Sized Styrene–Acrylonitrile Copolymer Particles
Authors: Jun Jung‐Bae , Uhm Seong‐Yong , Suh Kyung‐Do
Published: June 2004

Monodisperse micron‐sized styrene–acrylonitrile copolymer (SAN) particles were prepared by a seeded swelling and polymerization method. Polystyrene particles prepared by dispersion polymerization were used as the seed latex. Characteristics of the particles were examined by scanning electron microscopy, FT‐IR spectroscopy, 1H NMR spectroscopy, thermogravimetric analysis and dielectric analysis, then the electrorheological (ER) behavior of the particle suspensions in silicone oil was investigated. The polarization ability of particles represented by the particle dipole coefficient increased greatly with the degree of hydrolysis of the nitrile component of SAN particles. As the acrylonitrile content of the copolymer particles was increased, the hydrolyzed particles exhibited higher dipole coefficients and, consequently, increased ER properties. Also, the effect of particle size on ER properties was studied by varying the size of these monodisperse copolymer particles.

SEM photographs of nonhydrolyzed SAN50 microspheres (a) and the corresponding hydrolyzed SAN50 microspheres (b).

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SEM photographs of nonhydrolyzed SAN50 microspheres (a) and the corresponding hydrolyzed SAN50 microspheres (b).