JOURNAL OF FOOD PROCESS ENGINEERING, Issue 1 2009
BIN YANG
ABSTRACT To study resin adsorptions and investigate the differences between processes in crude extracts and microfiltrates, the adsorption characteristics of crocin in the extract of Gardenia jasminoides Ellis on 10 macroporous styrene-divinylbenzene (SDVB) resins were investigated. Ground gardenia fruit was extracted with water and the crude extract was partially purified by microfiltration. The crude extract and microfiltrate were mixed with the 10 resins until the adsorption of crocin reached equilibrium on resins. The adsorption followed the pseudo-second-order kinetics closely, but the data also fitted the first-order and intraparticle diffusion models. Furthermore, the Freundlich isotherm was found suitable for describing the equilibrate adsorption data. XAD-1180, HP20, HPD-100A and AB-8 stood out as the best performing resins in terms of their adsorptive capacities and selectivities for crocin. The thermodynamics of the adsorption process was shown to be spontaneous and exothermal in nature, and controlled by physical rather than chemical mechanisms. Adsorption with SDVB resins in conjunction with microfiltration was found to be an efficient process for the purification of crocin in gardenia extract. PRACTICAL APPLICATIONS Macroporous resins have been industrially applied in the recovery and purification of some products from plant extracts. However, there is a lack of understanding of the adsorption process and many of the applications are based on empirical data rather than on predicable models. Therefore, the development of reliable mathematical models that can accurately describe and predicate experimental data of adsorption would be extremely helpful in understanding the adsorption process as well as optimizing the design of adsorption systems. [source]

Nitrate-Selective Solid Contact Electrodes with Poly(3-octylthiophene) and Poly(aniline) as Ion-to-Electron Transducers Buffered with Electron-Ion-Exchanging Resin

ELECTROANALYSIS, Issue 13-14 2006
Galina
Abstract The study of nitrate selective solid contact electrodes containing poly(3-octyl)thiophene and poly(aniline) demonstrated the advantage of buffering the transducing layer with electron-ion-exchanging resin. The buffering, in particular in the case of poly(aniline) doped with nitrate anions ensured significant improvement of the long-term stability and piece-to-piece reproducibility of the electrode potentials. It is shown that the redox species causes potential drift after a long time delay, probably because of slow diffusion in the membrane bulk. [source]

Ten-years degradation of resin,dentin bonds

EUROPEAN JOURNAL OF ORAL SCIENCES, Issue 4 2010
Masanori Hashimoto
Hashimoto M, Fujita S, Nagano F, Ohno H, Endo K. Ten-years degradation of resin,dentin bonds. Eur J Oral Sci 2010; 118: 404,410. © 2010 The Authors. Journal compilation © 2010 Eur J Oral Sci The purpose of this study was to evaluate the durability of resin,dentin bonds in 10-yr water-storage testing. Resin,dentin bonded bulk specimens were prepared using six commercially available resin adhesives. The resin,dentin bonded specimens were stored in water for 24 h (control group) or for 10 yr (experimental groups). After each storage period, the specimens were sectioned to make specimen beams and then subjected to a microtensile bond test. After the bond test, fractured surfaces were examined by scanning electron microscopy (SEM). In addition, interfacial observation of silver nanoleakage was performed using the backscatter electron mode of SEM. The bond strengths of four of the six adhesive systems tested decreased significantly after 10 yr. However, no significant bond-strength reduction was recorded for the other two systems. The interfacial observations showed water tree propagation in the bonding resin layer as a typical morphological change after aging for five of the six adhesives tested. Water tree propagation may be a symptom of degradation in the resin bonding layer of resin,dentin bonds. [source]

A Highly Rearranged Pentaprenylxanthonoid from the Resin of Garcinia hanburyi

HELVETICA CHIMICA ACTA, Issue 7 2010
Si-Jia Tao
Abstract Gamboketanol (1), a highly rearranged pentaprenylated xanthonoid, two new caged pentaprenylated xanthonoids, gambogefic acid A (2) and gambogellic acid A (3), together with two known compounds, were isolated from the acetone extract of the resin of Garcinia hanburyi. Their structures were established on the basis of extensive spectroscopic and mass-spectrometric analyses. The cytotoxicity of compounds 1,3 against HeLa tumor cell line was evaluated, with all of them being modestly active. [source]

Hyperbranched Polymers for Photolithographic Applications , Towards Understanding the Relationship between Chemical Structure of Polymer Resin and Lithographic Performances

ADVANCED MATERIALS, Issue 10-11 2009
Christos L. Chochos
A chemically amplified resist based on a hyperbranched polymer resin is demonstrated for the first time. The hyperbranched polymer is synthesized using the atom-transfer radical polymerization (ATRP) technique, and resists prepared from this hyperbranched polymer present good pattern profiles and line-edge roughness (3,) values comparable to those of the reference (commercial) resist. [source]

Fracture resistance of root filled molar teeth restored with glass fibre bundles

INTERNATIONAL ENDODONTIC JOURNAL, Issue 5 2010
F. B. Rodrigues
Rodrigues FB, Paranhos MPG, Spohr AM, Oshima HMS, Carlini B, Burnett LH Jr. Fracture resistance of root filled molar teeth restored with glass fibre bundles. International Endodontic Journal, 43, 356,362, 2010. Abstract Aim, To evaluate the effect of unidirectional or woven glass fibre tapes inserted into MOD cavity preparations on the fracture resistance of root filled molar teeth. Methodology, Extracted human molar teeth were randomly divided into six groups (n = 15) : G1 , sound teeth, control; G2 , MOD cavity preparation; G3 , MOD + root canal treatment (Endo); G4 , MOD + Endo + composite resin restoration (Resin); G5 , MOD + Endo + unidirectional fibre (UF) + Resin; G6 , MOD + ;Endo + woven fibre (WF) + Resin. The teeth were subjected to a compressive fracture test in a universal testing machine. After testing, two failure modes were classified: pulp chamber floor or cusp. Results, The highest and the lowest mean fracture strengths were found in sound teeth (G1) (4960N) and MOD + root canal treatment (G3) (612.84N), respectively, with significant differences from the other groups (P < 0.05). The remaining groups had statistically similar means. In G5 and G6, there was a tendency for fracture to occur in the pulp chamber floor compromising tooth integrity. Conclusions, The insertion of glass fibres into MOD cavity preparations and restoring them with composite resin was not different than molar teeth filled with composite resin only in terms of fracture resistance. Fibres placed into MOD cavities do not reinforce teeth. [source]

Microstructure and Mechanical Properties of Lu2O3 -Doped Porous Silicon Nitride Ceramics Using Phenolic Resin as Pore-Forming Agent

INTERNATIONAL JOURNAL OF APPLIED CERAMIC TECHNOLOGY, Issue 3 2010
Xiaowei Yin
The joint process consisting of pressureless sintering and chemical vapor infiltration (CVI) was developed to prepare porous Si3N4 ceramics with controlled microstructure. Lu2O3 and phenolic resin acted as sintering aid and pore-forming agent, respectively. The 5 wt% Lu2O3 -doped ceramics using 12,57 vol% phenolic resin attained a porosity ranging from 46% to 53%. With increasing the resin content, the average pore size increased from 1 to 2 ,m. The porous ceramic infiltrated with CVI Si3N4 had an improved microstructure. The decreased pore size and porosity led to an increase in flexural strength, and the densified surface led to an improved surface hardness. [source]

Effect of oxygen inhibition on composite repair strength over time

JOURNAL OF BIOMEDICAL MATERIALS RESEARCH, Issue 2 2007
Susanna Dall'Oca
Abstract The study was aimed at examining whether an oxygen inhibition layer is required for bonding a repairing to a pre-existing composite, and to determine the time required for free radicals within a composite substrate to decay to the extent that the composite repair strength drops significantly. Ten slabs of Gradia Direct Anterior (GC Corp.) were divided into (1) control group: an interfacial oxygen inhibition layer was created by applying and light-curing two layers of bonding resin (D/E Resin, Bisco) to the slabs surface in atmospheric air; (2) experimental group: the absence of an interfacial oxygen inhibition layer was obtained by light-curing the second bonding resin layer in a nitrogen atmosphere. After 1 and 2 h, 1, 14, and 30 days of air storage, a composite repair was layered over the bonding resin. Microtensile bond strengths were measured and statistically analyzed. The curing atmosphere was not a significant factor for bond strength (p = 0.82), and time and curing atmosphere-time interaction were significant (p < 0.001). The 30 day-strengths were the lowest (p < 0.05). An oxygen-inhibited layer is not initially required for bonding to resin composite, and it takes more than 14 days before the bond strength between a pre-existing and a fresh composite drops. © 2006 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2006 [source]

OXYGEN-INHIBITED LAYER IN ADHESION DENTISTRY

JOURNAL OF ESTHETIC AND RESTORATIVE DENTISTRY, Issue 5 2004
Byoung I. Suh MS
ABSTRACT Purpose:: Characteristics of the oxygen-inhibited layer, including bond strength, photoinitiator decomposition, and post-curing degree of conversion, were investigated. Materials and Methods: To investigate shear bond strength, BisCover (Bisco, Inc., Schaumburg, IL, USA) and D/E Resin (Bisco, Inc.) were placed on disks of Renew composite (Bisco, Inc.) and cured both with and without an oxygen-inhibited layer. Light-Bond composite (Reliance Orthodontic, Itasca, IL, USA) was placed in a gelatin capsule and light cured over the cured resin. After soaking in water for 2 hours at 37°C, specimens were sheared to failure using a universal testing machine (Model 4466, Instron Inc., Canton, MA, USA). To investigate microtensile bond strength, composite substrates prepared using Renew A2 composite were light cured either in air or under nitrogen. Light-Core (Bisco, Inc.) was placed on each substrate and light cured. The resulting specimens were sectioned into composite beams and stressed to failure using a microtensile tester (built by Bisco, Inc.). To determine camphorquinone (CQ) decomposition, an experimental CQ resin was placed between two glass plates and irradiated for different time intervals. The absorption spectrum was obtained using a Cary 50 Bio UV-Visible Spectrometer (Varian, Mulgrave, Australia). To explore the degree of conversion, polyester film strips (Mylar, DuPont, Wilmington, DE, USA) coated with the CQ resin were pre-cured in air for different time periods, and then post-cured at low intensity for 5 minutes under nitrogen. A Spectrum 1000FTIR Spectrometer (Perkin Elmer, Norwalk, CT, USA) was used to measure the degree of conversion. Results: Bond strength tests resulted in no significant difference between samples with or without an oxygen-inhibited layer. The oxygen-inhibited layer contained reduced amounts of photoinitiator. The degree of conversion of post-cured oxygen-inhibited layers was lower than that for the control. Conclusion: An oxygen-inhibited layer is not necessary for bonding with composite resin. [source]

Posterior Resin-Based Composite Restorations: Clinical Recommendations for Optimal Success

JOURNAL OF ESTHETIC AND RESTORATIVE DENTISTRY, Issue 2 2001
ANDRE V. RITTER DDS
ABSTRACT Resin-based composites are increasingly used for the restoration of defects in posterior teeth. This review describes, illustrates and discusses important clinical aspects of the posterior composite technique. A relatively new stratification concept oriented to the development of functional and anatomic restorations is proposed. [source]

Influence of Tithonia diversifolia and triple superphosphate on dissolution and effectiveness of phosphate rock in acidic soil

JOURNAL OF PLANT NUTRITION AND SOIL SCIENCE, Issue 5 2006
Isaac Savini
Abstract An incubation and a pot experiment were conducted to evaluate the dissolution and agronomic effectiveness of a less reactive phosphate rock, Busumbu soft ore (BPR), in an Oxisol in Kenya. Resin (anion and anion + cation)-extractable P and sequentially extracted P with 0.5 M NaHCO3, 0.1 M NaOH, and 1 M HCl were analyzed. Dissolution was determined from the increase in anion resin (AER),, NaHCO3 -, and NaOH-extractable P in soil amended with PR compared with the control soil. Where P was applied, resin P significantly increased above the no-P treatment. Busumbu-PR solubility was low and did not increase significantly in 16 weeks. Anion + cation (ACER)-extractable P was generally greater than AER-P. The difference was greater for PR than for triple superphosphate (TSP). The ACER extraction may be a better estimate of plant P availability, particularly when poorly soluble P sources are used. Addition of P fertilizers alone or in combination with Tithonia diversifolia (TSP, BPR, TSP + Tithonia, and BPR + Tithonia) increased the concentration of labile inorganic P pools (NaHCO3 - and NaOH-Pi). Cumulative evolved CO2 was significantly correlated with cumulative N mineralized from Tithonia (r, 0.51, p < 0.05). Decrease in pH caused NH -N accumulation while NO -N remained low where Tithonia was incorporated at all sampling times. However, when pH was increased, NH -N declined with a corresponding rise in NO -N. Tithonia significantly depressed soil exchangeable acidity relative to control with time. A significant increase (p < 0.05) was observed for P uptake but not dry-mass production in maize where BPR was applied. The variations in yield and P uptake due to source and rates of application were statistically significant. At any given P rate, highest yields were obtained with Tithonia alone. Combination of Busumbu PR with TSP or Tithonia did not enhance the effectiveness of the PR. The poor dissolution and plant P uptake of BPR may be related to the high Fe content in the PR material. [source]

Effect of Aluminum Oxide Addition on the Flexural Strength and Thermal Diffusivity of Heat-Polymerized Acrylic Resin

JOURNAL OF PROSTHODONTICS, Issue 6 2008
Ayman E. Ellakwa BDS
Abstract Purpose: This work was undertaken to investigate the effect of adding from 5% to 20% by weight aluminum oxide powder on the flexural strength and thermal diffusivity of heat-polymerized acrylic resin. Materials and Methods: Seventy-five specimens of heat-polymerized acrylic resin were fabricated. The specimens were divided into five groups (n = 15) coded A to E. Group A was the control group (i.e., unmodified acrylic resin specimens). The specimens of the remaining four groups were reinforced with aluminum oxide (Al2O3) powder to achieve loadings of 5%, 10%, 15%, and 20% by weight. Specimens were stored in distilled water at 37°C for 1 week before flexural strength testing to failure (5 mm/min crosshead speed) in a universal testing machine. Results were analyzed by one-way analysis of variance and post hoc Tukey paired group comparison tests (p < 0.05). Weibull analysis was used to calculate the Weibull modulus, characteristic strength, and the required stress for 1% and 5% probabilities of failure. Cylindrical test specimens (5 specimens/group) containing an embedded thermocouple were used to determine thermal diffusivity over a physiologic temperature range (0 to 70°C). Results: The mean flexural strength values of the heat-polymerized acrylic resin were (in MPa) 99.45, 119.92, 121.19, 130.08, and 127.60 for groups A, B, C, D, and E, respectively. The flexural strength increased significantly after incorporation of 10% Al2O3. The mean thermal diffusivity values of the heat-polymerized acrylic resin (in m2/sec) were 6.8, 7.2, 8.0, 8.5, and 9.3 for groups A, B, C, D, and E, respectively. Thermal diffusivities of the composites were found to be significantly higher than the unmodified acrylic resin. Thermal diffusivity was found to increase in proportion to the weight percentage of alumina filler, which suggested that the proper distribution of alumina powders through the insulating polymer matrix might form a pathway for heat conduction. Conclusion: Al2O3 fillers have potential as added components in denture bases to provide increased flexural strength and thermal diffusivity. Increasing the flexural strength and heat transfer characteristics of the acrylic resin base material could lead to more patient satisfaction. [source]

Periimplant Strain Comparison Generated by Resin and Bone Models Using Strain Gages

JOURNAL OF PROSTHODONTICS, Issue 3 2000
Carlos H. Barrero BDS
[source]

Novel Microcellular Ceramics from a Silicone Resin

JOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 1 2004
Paolo Colombo
Microcellular silicon oxycarbide open cell ceramic foams were fabricated from a silicone resin. Microcellular foams, with a cell size ranging from ,1,80 ,m, were fabricated using poly(methyl methacrylate) microbeads as sacrificial templates. The compression strength of the foams decreased with increasing cell size. [source]

Novel Phosphorus-Containing Poly(ether sulfone)s and Their Blends with an Epoxy Resin: Thermal Decomposition and Fire Retardancy

MACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 16 2006
Ulrike Braun
Abstract Summary: The decomposition of novel phosphorus-containing poly(oxyphenylene-sulfonyl-phenylene-oxy-diphenyl phenylene phosphine oxide) (PSU_I), 2,5-dihydroxy-1-biphenylene-phosphine oxide based polysulfone (PSU_II), poly(sulfonyl-diphenylphenylene phosphonate) (PSU_P) and bisphenol A-based polysulfone (PSU) is studied. The influence of the chemical structure, charring and phosphorus release is discussed based on the mass loss, kinetics and products. The pyrolysis and fire behaviour of blends with epoxy resin (EP) are studied. For EP-PSU_II, phosphorus initiates water elimination and changes the decomposition pathway of EP. The fire behaviour of EP-PSU shows some improvements, whereas the heat release rate is crucially reduced for EP-PSU_II due to simultaneous char formation and flame inhibition. Decomposition model of PSU_II. [source]

Toughening of Epoxy Resin by Methyl Methacrylate/2-Ethylhexyl Acrylate Copolymers: The Effect of Copolymer Composition

MACROMOLECULAR MATERIALS & ENGINEERING, Issue 12 2007
Soraia Zaioncz
Abstract MMA-EHA copolymers with different compositions and with a low amount of AA were synthesized and used as impact modifier for epoxy networks. The effect of the copolymers on the tensile and dynamic mechanical properties as well as impact resistance of the epoxy network was evaluated. The addition of 10 phr of low-molar-mass MMA-EHA copolymer with defined composition resulted in a significant increase in impact resistance without any significant changes in the tensile strength, modulus, and glass transition temperature. The morphology of the modified epoxy network depends upon the copolymer composition. [source]

Curing Behavior of Epoxy Resin Using Controllable Curing Agents Based on Nickel Complexes

MACROMOLECULAR MATERIALS & ENGINEERING, Issue 2 2006
Abdollah Omrani
Abstract Summary: The curing reaction kinetics and mechanism of the diglycidyl ether of bisphenol A (DGEBA) with three complexes of Ni(II) with diethylentriamine (Dien), Pyrazole (Pz) and Pyridine (Py) as ligands have been studied using differential scanning calorimetry (DSC). The curing reaction was characterized by high cure onset and peak maximum temperatures. The kinetics of the curing reaction were evaluated using the Ozawa method. The average values of activation energy for the three nickel complexes increased in the order: Dien-based curing agent,>,Pz-based curing agent,>,Py-based curing agent. Three main curing mechanisms (catalytic, complex cation and free ligand polymerization path) have been proposed depending on the cure temperature. It was also shown that the cure kinetics of DGEBA with Dien- and Py-based complexes could be described by the Sestak-Berggren equation. The water absorption, chemical resistance and thermal stability of the thermosets were also studied. The results showed that the thermoset obtained with the Py-based complex was more thermally stable than those obtained with the other two curing agents. Activation energy versus conversion plots for the epoxy systems studied. [source]

Polyhedral Oligomeric Silsesquioxane (POSS) Nanoscale Reinforcement of Thermosetting Resin from Benzoxazine and Bisoxazoline

MACROMOLECULAR RAPID COMMUNICATIONS, Issue 23 2005
Qiao Chen
Abstract Summary: The reaction between octaaminophenyl polyhedral oligomeric silsesquioxane (OAPS) and 2,2,-(1,3-phenylene)-bis(4,5-dihydro-oxazoles) (PBO) over different temperature ranges was confirmed by FT-IR spectroscopy. The OAPS was used to modify benzoxazine (BZ) in the presence of PBO. The novel polybenzoxazine (PBZ)-PBO/OAPS hybrid nanocomposite was prepared by solvent methods. Dynamic mechanical analyses indicated that the nanocomposites exhibited much higher Tg values than the pristine PBZ and PBZ-PBO resin, and the storage modulus of the nanocomposites was maintained at higher temperatures, although only a small amount of OAPS was incorporated into the systems. Dynamic thermogravimetric analysis showed that the thermal stability of the hybrid was also improved by the inclusion of OAPS. DMA of PBZ (a), PBZ-PBO (b), and PBZ-PBO/OAPS nanocomposites (c,e). [source]

Glass Transition Temperature Depression at the Percolation Threshold in Carbon Nanotube,Epoxy Resin and Polypyrrole,Epoxy Resin Composites

MACROMOLECULAR RAPID COMMUNICATIONS, Issue 5 2005
Sophie Barrau
Abstract Summary: The glass transition temperatures of conducting composites, obtained by blending carbon nanotubes (CNTs) or polypyrrole (PPy) particles with epoxy resin, were investigated by using both differential scanning calorimetry (DSC) and dynamical mechanical thermal analysis (DMTA). For both composites, dc and ac conductivity measurements revealed an electrical percolation threshold at which the glass transition temperature and mechanical modulus of the composites pass through a minimum. DC conductivity, ,dc, as a function of the conducting filler concentration of the CNT, (,) and PPy, (,) epoxy resin composites. [source]

Synthesis of High Solid-Content Latex using Alkali-Soluble Resin as Sole Surfactant

MACROMOLECULAR RAPID COMMUNICATIONS, Issue 22 2004
Marcelo do Amaral
Abstract Summary: A novel polymerization procedure to synthesize latex stabilized by alkali-soluble resin (ASR) is detailed. According to this process, latexes with a high solid content and low viscosity are obtained using a substantially lower amount of ASR when compared with existing techniques. Similar rewet properties were found for the latexes obtained by a standard process and for the one obtained by the process described in this work. Comparison of the particle size distributions obtained by conventional emulsion polymerization (,) and by miniemulsion polymerization (,). [source]

Modelling and Simulation of Curing Processes of Epoxy Resin

PROCEEDINGS IN APPLIED MATHEMATICS & MECHANICS, Issue 1 2009
Bülent Yagimli
During the curing reaction, the adhesive changes its thermomechanical material behaviour from a viscous fluid to a viscoelastic solid. This phase transition is an exothermal chemical reaction which is accompanied by thermal expansion, chemical shrinkage and changes in temperature. In this work the numerical simulation of the curing process will be presented. The material model for the implementation is presented in [1]. For the implementation of the material model the consistent tangent operator has been derived. In the presentation, experimental data and simulation are shown. (© 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Fractured Teeth Bonded With Dentine Adhesives With And Without Unfilled Resin

AUSTRALIAN ENDODONTIC JOURNAL, Issue 2 2002
Article first published online: 11 FEB 2010
No abstract is available for this article. [source]

Development of a high throughput protein a well-plate purification method for monoclonal antibodies

BIOTECHNOLOGY PROGRESS, Issue 5 2009
Jennifer Hopp
Abstract We have developed a new high throughput method for the purification of monoclonal antibodies from harvested cell culture fluid for analytical characterization. This method uses Protein A resin in a 96 well-plate format with protein loading sufficient to perform multiple analyses per well. Resin and buffer conditions were optimized to obtain aggregate and charge variant comparability with three preparative Protein A purified monoclonal antibodies. We are able to successfully demonstrate comparability for aggregate within 0.25% based upon size-exclusion chromatography. Acidic species were found to be within 2% from the preparative purified control based upon cation-exchange chromatography, 5% based upon capillary zone electrophoresis, and 3% based upon imaged capillary isoelectric focusing. Glycan distribution was analyzed and was within 1% of the preparative purified controls. A tryptic digest was performed and all peaks in the preparative purified control were found in the first elution from the well-plate format. © 2009 American Institute of Chemical Engineers Biotechnol. Prog., 2009 [source]

Colesevelam: Potential Uses for the Newest Bile Resin

CARDIOVASCULAR THERAPEUTICS, Issue 1 2005
Karen L. Steinmetz
ABSTRACT Colesevelam is the newest bile resin with a unique chemical structure. It binds to bile acids with higher affinity than traditional bile acid sequestrants and has fewer gastrointestinal side effects and drug interactions. Colesevelam is safe and efficacious alone or in combination with HMG-CoA reductase inhibitors (statins) in reducing low-density lipoprotein cholesterol (LDL-C) levels. Despite this, the role of colesevelam in the treatment of hyperlipidemia remains limited, particularly in the face of new lipid lowering agents. As guidelines for cholesterol control become more stringent, the need to maximize therapeutic benefit through combination therapy will become increasingly more important. Colesevelam has a dose-sparing effect on statin therapy, potentially decreasing the risk of unwanted side effects or drug-drug interactions associated with statin use. This makes colesevelam a viable option for addition to a statin regimen when goal LDL-C levels cannot be achieved with a statin alone. Additionally, anecdotal reports indicate that colesevelam may have potential benefits in certain patient populations that cannot tolerate other lipid lowering therapies, including organ transplant recipients, cholestatic liver disesase, and end-stage renal disease. By recognizing the potential utility of colesevelam, clinicians can better manage those patients who are not able to tolerate first-line therapies. [source]

Synthesis of peptide sequences related to thrombospondin: factors affecting aspartimide by-product formation

CHEMICAL BIOLOGY & DRUG DESIGN, Issue 6 2003
J. Cebrián
Abstract:, Aspartimide formation is one of the most common secondary reactions on solid phase peptide synthesis. In the present work, we describe the optimization of the synthesis of two thrombospondin fragments containing an Asp-Gly sequence that show a strong tendency to form cyclic aspartimide derivatives in an unusual high percentage. Several different strategies were applied changing type of resin, Fmoc-deprotection reagents, coupling additives, resin cleavage cocktails and the use of Hmb-Gly derivative to minimize the extension of this byproduct. Best results were obtained with cross-linked ethoxylate acrylate (CLEAR® -cross-linked ethoxylate Acrylate Resin)-type resin and pip/dimethylformamide deprotection. Besides, as in biological assays the aspartimide containing sequence resulted to be more active than the linear one, the optimization of its synthesis was also carried out. [source]

Production of Highly Loaded Nanocomposites by Dispersing Nanoparticles in Epoxy Resin

CHEMICAL ENGINEERING & TECHNOLOGY (CET), Issue 9 2010
H. Nolte
Abstract The objective of this study was the investigation of techniques for dispersing alumina nanoparticles with different surface modifications in epoxy resin. In order to prepare the matrix suspension, high contents of fillers (up to 50,wt,%) were dispersed by conducting shear mixing techniques in a high performance laboratory kneader. The intention was to attain solutions that were stable against re-agglomeration, while the mass fraction and the product fineness were maintained as high as possible. Therefore, both the formulations and the dispersion parameters were varied systematically. An epoxy resin was used as a carrier fluid and a corresponding amine hardener system was chosen. Tests were performed using alumina particles and surface modified alumina particles at different particle concentrations. Furthermore, the effect of diluting the colloidal suspensions and the resulting long term stability were also examined. The matrix suspension was examined with respect to viscosity, stability and particle size distribution. [source]

ChemInform Abstract: A Convenient Synthesis of Pyrroles Catalyzed by Acidic Resin under Solvent-Free Condition.

CHEMINFORM, Issue 43 2010
Shi Zhen Yuan
Abstract The catalyst corresponds to Amberlite 200 and Lewatit SP-210 and can be recycled on treatment with hydrochloric acid. [source]

ChemInform Abstract: N-Substituted Pyrrole Synthesis by Paal,Knorr Condensation Using Recyclable Cationic Exchange Resin in Water.

CHEMINFORM, Issue 35 2010
Yan-Hong He
Abstract A simple and effective Paal-Knorr condensation catalyzed by a reusable cationic exchange resin is reported. [source]

ChemInform Abstract: Palladium Supported on a Polyionic Resin as an Efficient, Ligand-Free, and Recyclable Catalyst for Heck, Suzuki,Miyaura, and Sonogashira Reactions.

CHEMINFORM, Issue 34 2009
Basudeb Basu
Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source]