Ligand modified real heterogeneous catalysts for fixed-bed hydroformylation of propylene

A novel ligand modified heterogeneous catalyst has been developed for hydroformylation of propylene, which showed excellent activity, selectivity and stability and need not be separated from the product after reaction in a fixed-bed reactor. The coordination bonds between triphenyl phosphine (PPh3) and Rh/SiO2 were confirmed by means of thermogravimetric (TG), solid-state P-31 NMR, XPS and FT-IR. Two types of active species for hydroformylation were formed, which were proved by in situ FT-IR techniques. The problem of metal leaching was greatly reduced by directly fastening Rh particles on the support, and the active Rh species that was responsible for the outstanding performance of propylene hydroformylation was tightly bound by the very strong metal-metal bonds. No sign of deactivation was observed over a period of more than 1000 h on the condition that PPh3 was added at 300-350 h of time on stream. (c) 2005 Elsevier B.V. All rights reserved.

Butene catalytic cracking to propene and ethene over potassium modified ZSM-5 catalysts

Catalytic cracking of butene over potassium modified ZSM-5 catalysts was carried out in a fixed-bed microreactor. By increasing the K loading on the ZSM-5, butene conversion and ethene selectivity decreased almost linearly, while propene selectivity increased first, then passed through a maximum (about 50% selectivity) with the addition of ca. 0.7-1.0% K, and then decreased slowly with further increasing of the K loading. The reaction conditions were 620 degrees C, WHSV 3.5 h(-1), 0.1 MPa 1-butene partial pressure and 1 h of time on stream. Both by potassium modification of the ZSM-5 zeolite and by N(2) addition in the butene feed could enhance the selectivity towards propene effectively, but the catalyst stability did not show any improvement. On the other hand, addition of water to the butene feed could not only increase the butene conversion, but also improve the stability of the 0.7%K/ZSM-5 catalyst due to the effective removal of the coke formed, as demonstrated by the TPO spectra. XRD results indicated that the ZSM-5 structure of the 0.07% K/ZSM-5 catalyst was not destroyed even under this serious condition of adding water at 620 degrees C.

Age-dependence of urinary normal and modified nucleosides in childhood as determined by reversed-phase high-performance liquid chromatography

Modified nucleosides have been characterized as tumor markers for a number of malignant diseases. In order to use these markers in children, the age-dependence of the nucleoside levels in healthy children has to be established and taken into account in diagnostic decisions. In this study, the levels of 12 normal and modified nucleosides in urine of 166 healthy children and adolescents with an age between 1 day and 19 years are determined by reversed-phase HPLC, and age-dependent reference ranges are defined. The urinary nucleoside concentrations are related to the creatinine concentrations, which allows the use of randomly collected urine samples. All nucleoside levels in urine of children decrease with age, most pronounced during the first 4 years of life, and the age-dependence of the reference values of the individual nucleosides can be approximated by a mathematical function y = b(0) + b(1) (1/x) with the regression coefficients b(0) and b(1), the nucleoside levels y and the age x between 1 year and 19 years. In the very young children, the shifts in the nucleoside concentrations are more differentiated. Starting with low levels on the first day of life, the concentrations of all studied nucleosides rise up to an age of 1-2 months, when they reach their absolute maximum for all age periods, and then decrease. (C) 2004 Elsevier B.V. All rights reserved.

Deconvolution of overlapped peaks based on the exponentially modified Gaussian model in comprehensive two-dimensional gas chromatography

Comprehensive two-dimensional gas chromatography (GC x GC) has attracted much attention for the analys is of complex samples. Even with a large peak capacity in GC x GC, peak overlapping is often met. In this paper, a new method was developed to resolve overlapped peaks based on the mass conservation and the exponentially modified Gaussian (EMG) model. Linear relationships between the calculated sigma, tau of primary peaks with the corresponding retention time (t(R)) were obtained, and the correlation coefficients were over 0.99. Based on such relationships, the elution profile of each compound in overlapped peaks could be simulated, even for the peak never separated on the second-dimension. The proposed method has proven to offer more accurate peak area than the general data processing method. (c) 2005 Elsevier B.V. All rights reserved.

A modified TRIMP to quantify the in-season training load of team sport players

Thatcher, Rhys, et al., 'A modified TRIMP to quantify the in-season training load of team sport players', Journal of Sport Sciences, (2007) 25(6) pp.629-634 RAE2008

Modified cyclodextrins as novel non-viral vectors for neuronal siRNA delivery: focus on Huntington’s disease

Huntington’s Disease (HD) is a rare autosomal dominant neurodegenerative disease caused by the expression of a mutant Huntingtin (muHTT) protein. Therefore, preventing the expression of muHTT by harnessing the specificity of the RNA interference (RNAi) pathway is a key research avenue for developing novel therapies for HD. However, the biggest caveat in the RNAi approach is the delivery of short interfering RNA (siRNAs) to neurons, which are notoriously difficult to transfect. Indeed, despite the great advances in the field of nanotechnology, there remains a great need to develop more effective and less toxic carriers for siRNA delivery to the Central Nervous System (CNS). Thus, the aim of this thesis was to investigate the utility of modified amphiphilic β-cyclodextrins (CDs), oligosaccharide-based molecules, as non-viral vectors for siRNA delivery for HD. Modified CDs were able to bind and complex siRNAs forming nanoparticles capable of delivering siRNAs to ST14A-HTT120Q cells and to human HD fibroblasts, and reducing the expression of the HTT gene in these in vitro models of HD. Moreover, direct administration of CD.siRNA nanoparticles into the R6/2 mouse brain resulted in significant HTT gene expression knockdown and selective alleviation of rotarod motor deficits in this mouse model of HD. In contrast to widely used transfection reagents, CD.siRNA nanoparticles only induced limited cytotoxic and neuroinflammatory responses in multiple brain-derived cell-lines, and also in vivo after single direct injections into the mouse brain. Alternatively, we have also described a PEGylation-based formulation approach to further stabilise CD.siRNA nanoparticles and progress towards a systemic delivery nanosystem. Resulting PEGylated CD.siRNA nanoparticles showed increased stability in physiological saltconditions and, to some extent, reduced protein-induced aggregation. Taken together, the work outlined in this thesis identifies modified CDs as effective, safe and versatile siRNA delivery systems that hold great potential for the treatment of CNS disorders, such as HD.

Access to modified geiparvarins using Pd(0)-mediated C-C bond forming reactions

Geiparvarin is a natural product which contains both a 3(2H)-furanone and a coumarin moiety in its structure. The aim of this project was to investigate the use of Pd(0)-mediated C–C bondforming reactions to produce structurally modified geiparvarins. Chapter 1 consists of a review of the relevant literature, including that pertaining to the syntheses of selected naturally occurring 3(2H)-furanones. The known syntheses of geiparvarin and closely related analogues are examined, along with the documented biological activity of these compounds. The synthetic routes which allow access to 4-substituted-3(2H)-furanones are also described. Chapter 2 describes in detail the synthesis of a variety of novel structurally modified geiparvarins by two complementary routes, both approaches utilising Pd(0)-mediated crosscoupling reactions, and discusses the characterisation of these compounds. The preparation of 5-ethyl-3(2H)-furanones is described, as is their incorporation into geiparvarin and the corresponding 5″-alkylgeiparvarin analogues via formation and dehydration of intermediate alcohols. Halogenation of 5-ethyl-3(2H)-furanones and the corresponding geiparvarin derivatives is discussed, along with further reactions of the resulting halides. Preparation of 3″-arylgeiparvarins involving both Suzuki–Miyura and Stille reactions, using the appropriate intermediate iodides and bromides, is described. The application of Stille and Heck conditions to give 3″-ethenylgeiparvarin analogues and Sonogashira conditions to produce 3″-ethynylgeiparvarin analogues, using the relevant intermediate iodides, is also extensively outlined. Chapter 3 contains all of the experimental data and details of the synthetic methods employed for the compounds prepared during the course of this research. All novel compounds prepared were fully characterised using NMR spectroscopy, IR spectroscopy, mass spectrometry and elemental analysis; the details of which are included.

In vitro fluid dynamics of the Ahmed glaucoma valve modified with expanded polytetrafluoroethylene.

PURPOSE: Long-term intraocular pressure reduction by glaucoma drainage devices (GDDs) is often limited by the fibrotic capsule that forms around them. Prior work demonstrates that modifying a GDD with a porous membrane promotes a vascularized and more permeable capsule. This work examines the in vitro fluid dynamics of the Ahmed valve after enclosing the outflow tract with a porous membrane of expanded polytetrafluoroethylene (ePTFE). MATERIALS AND METHODS: The control and modified Ahmed implants (termed porous retrofitted implant with modified enclosure or PRIME-Ahmed) were submerged in saline and gelatin and perfused in a system that monitored flow (Q) and pressure (P). Flow rates of 1-50 μl/min were applied and steady state pressure recorded. Resistance was calculated by dividing pressure by flow. RESULTS: Modifying the Ahmed valve implant outflow with expanded ePTFE increased pressure and resistance. Pressure at a flow of 2 μl/min was increased in the PRIME-Ahmed (11.6 ± 1.5 mm Hg) relative to the control implant (6.5 ± 1.2 mm Hg). Resistance at a flow of 2 μl/min was increased in the PRIME-Ahmed (5.8 ± 0.8 mm Hg/μl/min) when compared to the control implant (3.2 ± 0.6 mm Hg/μl/min). CONCLUSIONS: Modifying the outflow tract of the Ahmed valve with a porous membrane adds resistance that decreases with increasing flow. The Ahmed valve implant behaves as a variable resistor. It is partially open at low pressures and provides reduced resistance at physiologic flow rates.

Solution structure of the N-terminal transactivation domain of ERM modified by SUMO-1.

ERM is a member of the PEA3 group of the Ets transcription factor family that plays important roles in development and tumorigenesis. The PEA3s share an N-terminal transactivation domain (TADn) whose activity is inhibited by small ubiquitin-like modifier (SUMO). However, the consequences of sumoylation and its underlying molecular mechanism remain unclear. The domain structure of ERM TADn alone or modified by SUMO-1 was analyzed using small-angle X-ray scattering (SAXS). Low resolution shapes determined ab initio from the scattering data indicated an elongated shape and an unstructured conformation of TADn in solution. Covalent attachment of SUMO-1 does not perturb the structure of TADn as indicated by the linear arrangement of the SUMO moiety with respect to TADn. Thus, ERM belongs to the growing family of proteins that contain intrinsically unstructured regions. The flexible nature of TADn may be instrumental for ERM recognition and binding to diverse molecular partners.

The interaction of polyacid-modified composite resins ("compomers") with aqueous fluoride solutions

OBJECTIVE: The aim of this study was to investigate how the release of fluoride from two compomers and a fluoridated composite resin was affected by exposure to KF solution. MATERIAL AND METHODS: Two compomers (Dyract AP and Compoglass F) and one fluoridated composite (Wave) were prepared as discs (6 mm diameter and 2 mm thick), curing with a standard dental lamp. They were then stored in either water or 0.5% KF for 1 week, followed by placement in water for periods of 1 week up to 5 weeks total. Fluoride was determined with and without TISAB (to allow complexed and decomplexed fluoride to be determined), and other ion release (Na, Ca, Al, Si, P) was determined by ICP-OES. RESULTS: Specimens were found not to take up fluoride from 100 ppm KF solution in 24 h, but to release additional fluoride when stored for up to five weeks. Compomers released more fluoride cumulatively following exposure to KF solution (p<0.001), all of which was decomplexed, though initial (1 week) values were not statistically significant for Dyract AP. Other ions showed no variations in release over 1 week, regardless of whether the specimens were exposed to KF. Unlike the compomers, Wave showed no change in fluoride release as a result of exposure to KF. CONCLUSIONS: Compomers are affected by KF solution, and release more fluoride (but not other ions) after exposure than if stored in water.

Using a modified shepards method for optimization of a nanoparticulate cyclosporine a formulation prepared by a static mixer technique

An innovative methodology has been used for the formulation development of Cyclosporine A (CyA) nanoparticles. In the present study the static mixer technique, which is a novel method for producing nanoparticles, was employed. The formulation optimum was calculated by the modified Shepard's method (MSM), an advanced data analysis technique not adopted so far in pharmaceutical applications. Controlled precipitation was achieved injecting the organic CyA solution rapidly into an aqueous protective solution by means of a static mixer. Furthermore the computer based MSM was implemented for data analysis, visualization, and application development. For the optimization studies, the gelatin/lipoid S75 amounts and the organic/aqueous phase were selected as independent variables while the obtained particle size as a dependent variable. The optimum predicted formulation was characterized by cryo-TEM microscopy, particle size measurements, stability, and in vitro release. The produced nanoparticles contain drug in amorphous state and decreased amounts of stabilizing agents. The dissolution rate of the lyophilized powder was significantly enhanced in the first 2 h. MSM was proved capable to interpret in detail and to predict with high accuracy the optimum formulation. The mixer technique was proved capable to develop CyA nanoparticulate formulations.

The biocompatibility of resin-modified glass-ionomer cements for dentistry

OBJECTIVES: The biological effects of resin-modified glass-ionomer cements as used in clinical dentistry are described, and the literature reviewed on this topic. METHODS: Information on resin-modified glass-ionomers and on 2-hydroxyethyl methacrylate (HEMA), the most damaging substance released by these materials, has been collected from over 50 published papers. These were mainly identified through Scopus. RESULTS: HEMA is known to be released from these materials and has a variety of damaging biological properties, ranging from pulpal inflammation to allergic contact dermatitis. These are therefore potential hazards from resin-modified glass-ionomers. However, clinical results with these materials that have been reported to date are generally positive. CONCLUSIONS/SIGNIFICANCE: Resin-modified glass-ionomers cannot be considered biocompatible to nearly the same extent as conventional glass-ionomers. Care needs to be taken with regard to their use in dentistry and, in particular, dental personnel may be at risk from adverse effects such as contact dermatitis and other immunological responses.

Water sorption/desorption in polyacid-modified composite resins for dentistry

The water sorption and desorption behaviour of three commercial polyacid-modified composite resins used in clinical dentistry have been studied in detail. Cured specimens of each material were subjected to two successive water uptake cycles in an atmosphere of 93% relative humidity, with one intervening desorption cycle in a desiccating atmosphere over concentrated sulfuric acid. Specimens were found to absorb and desorb water according Fick's law until Mt/M(infinity) values of approximately 0.5. Diffusion rates for uptake varied between cycles, ranging from 2.37-4.53 x 10(-9 )cm(2) s(-1) for 1st cycle to 0.85-2.72 x 10(-8 )cm(2 )s(-1) for 2nd cycle. Desorption rates were similar to those for 2nd cycle sorption, and ranged from 0.86 to 5.47 x 10(-8 )cm(2 )s(-1). Equilibration times for 1st cycle water uptake were greater than for 2nd cycle sorption and for desorption and overall the behaviour of polyacid-modified composites in a high humidity atmosphere was similar to that of conventional composites in water. It is concluded that the hydrophilic components of the former do not bring about an enhanced rate of water transport.

Water transport in resin-modified glass-ionomer dental cement

Water uptake and water loss have been studied in a commercial resin-modified glass-ionomer cement, Fuji II LC, under a variety of conditions. Uptake was generally non-Fickian, but affected by temperature. At room temperature, the equilibrium water uptake values varied from 2.47 to 2.78% whereas at low temperature (12 degrees C), it varied from 0.85 to 1.18%. Cure time affected uptake values significantly. Water uptake was much lower than in conventional glass-ionomer restorative cements exposed to water vapor. Loss of water under desiccating conditions was found to be Fickian for the first 5 h loss at both 22 and 12 degrees C. Diffusion coefficients were between 0.45 and 0.76 x 10( -7) cm(2)/s, with low temperature diffusion coefficients slightly greater than those at room temperature. Plotting water loss as percentage versus s(-(1/2)) allowed activation energies to be determined from the Arrhenius equation and these were found to be 65.6, 79.8, and 7.7 kJ/mol respectively for 30, 20, and 10 s cure times. The overall conclusion is that the main advantage of incorporating HEMA into resin-modified-glass-ionomers is to alter water loss behavior. Rate of water loss and total amount lost are both reduced. Hence, resin-modified glass-ionomers are less sensitive to water loss than conventional glass-ionomers.

Polyacid-modified composite resins ("compomers") and their use in clinical dentistry

OBJECTIVES: This paper describes the chemistry and properties of polyacid-modified composite resins ("compomers") designed for use in clinical dentistry, and reviews the literature in this area. METHODS: Information has been obtained from over 50 published articles appearing in the dental and biomaterials literature, with studies being principally identified through MedLine. RESULTS: Published work shows that polyacid-modified composite resins constitute a discrete class of polymeric repair material for use in dentistry. Their distinction is that they contain hydrophilic components, and these cause water to be drawn into the material following cure. This triggers an acid-base reaction, and gives the materials certain clinically-desirable properties (fluoride release, buffering capability) that are also associated with glass-ionomer cements. The water uptake leads to a decline in certain, though not all, physical properties. However, clinical studies have shown these materials to perform acceptably in a variety of applications (Class I, Class II and Class V cavities, as fissure sealants and as orthodontic band cements), especially in children's teeth. CONCLUSIONS/SIGNIFICANCE: Polyacid-modified composite resins constitute a versatile class of dental repair material, whose bioactivity confers clinical advantages, and which are particularly useful in children's dentistry.