A polymer supported Cu(I) catalyst for the 'click reaction' in aqueous media.

Polymer stabilized monovalent copper has been synthesized using an in situ chemical transformation route and was characterized by means of different microscopic, optical and surface characterization techniques, which offered information about the chemical structure of the polymer and the morphology of the complex. The supramolecular material, Cu(i)-poly(2-aminobenzoic acid), denoted Cu(i)-pABA, showed catalytic activity for the cycloaddition reaction between terminal alkynes and azides to synthesize 1,2,3-triazoles with excellent yields. The catalyst was recovered from the reaction mixture and recycled several times without an appreciable loss of catalytic activity.

Visual and digital comparative tooth colour assessment methods and atomic force microscopy surface roughness.

This study compared digital and visual colour tooth colour assessment methods in a sample of 99 teeth consisting of incisors, canines and pre-molars. The teeth were equally divided between Control, Ozicure Oxygen Activator bleach and Opalescence Quick bleach and subjected to three treatments. Colour readings were recorded at nine intervals by two assessment methods, VITA Easyshade and VITAPAN 3D MASTER TOOTH GUIDE, giving a total of 1782 colour readings.

In situ generation of a high-performance Pd-polypyrrole composite with multi-functional catalytic properties.

We report on a bottom up approach for the synthesis of a Pd-polypyrrole nanocomposite material. The composite material was characterized by means of different techniques, such as UV-vis, IR, and Raman spectroscopy, which offered information about the chemical structure of the polymer, whereas electron microscopy images provided information regarding the morphology of the composite material and the distribution of the metal particles in the polymer matrix. During the synthesis of the nanocomposite, the Pd nanoparticles act as a catalyst for a model proton-coupled electron transfer reaction.

Tooth colour change with Ozicure Oxygen Activator: a comparative in vitro tooth bleaching study.

Introduction: This in vitro study compared a new tooth bleaching product, Ozicure Oxygen Activator (O3, RSA) with Opalescence Quick (Ultradent, USA) using a randomised block design to assess tooth colour change.

Aim: Colour change, stability and relapse in canine, incisor and premolar teeth was assessed following three bleach treatments and subsequent tooth colour assessment.

Methods: Ninety nine teeth (canines, incisors and premolars), which were caries free, had no surface defects and were within the colour range 1M2 and 5M3 were selected.

WO3 nano-spheres into W18O49 one-dimensional nano-structures through thermal annealing.

We elaborate the size controlled synthesis of nano-spheres and nano-crystals of WO3 by ultrasonic spray pyrolysis. The as-deposited particles are predominantly spherical in shape and tend to exhibit less agglomeration and a decrease in diameter as the process temperature is increased. Characterization was carried out using transmission (TEM) and scanning (SEM) electron microscopy, energy dispersive X-ray spectroscopy (EDS) and X-ray diffraction (XRD).

Polymer-encapsulated metal nanoparticles: optical, structural, micro-analytical and hydrogenation studies of a composite material.

A single-step synthesis route is described for the preparation of a metal-polymer composite in which palladium acetate and meta-amino benzoic acid were used as the precursors for palladium nanoparticles and poly(meta-amino benzoic acid) (PABA). The palladium nanoparticles were found to be uniformly dispersed and highly stabilized throughout the macromolecule matrix. The resultant composite material was characterized by means of different techniques, such as IR and Raman spectroscopy, which provided information regarding the chemical structure of the polymer, whereas electron microscopy images yielded information regarding the morphology of the composite material and the distribution of the metal particles in the composite material.

Fabrication of a nanostructured gold-polymer composite material.

A facile synthesis route is described for the preparation of a poly-(o-aminophenol)-gold nanoparticle composite material by polymerization of o-aminophenol (AP) monomer using HAuCl(4) as the oxidant. The synthesis was carried out in a methanol medium so that it could serve a dual solvent role, a solvent for both the AP and the water solution of HAuCl(4). It was found that oxidative polymerization of AP leads to the formation of poly-AP with a diameter of 50+/-10nm, while the reduction of AuCl(4) (-) results in the formation of gold nanoparticles ( approximately 2nm).

Formation of palladium nanoparticles in poly (o-methoxyaniline) macromolecule fibers: an in-situ chemical synthesis method.

We report here a novel in-situ synthetic method for the preparation of poly (o-methoxyaniline) and palladium nanoparticle composite material. Ortho-Methoxyaniline and palladium acetate were used as the precursors; during the reaction o-methoxyaniline was oxidized and forms poly (o-methoxyaniline) and palladium acetate is reduced forming palladium nanoparticles. IR and Raman spectra provide information on the structure of the polymer.

Fabrication of a metal nanoparticles and polymer nanofibers composite material by an in situ chemical synthetic route.

This work demonstrated a facile route for the synthesis of poly(3,5-dimethyl aniline) nanofibers by polymerization of 3,5-dimethyl aniline using Pd-acetate as the oxidant. The reduction of Pd ion is accompanied by oxidative polymerization of 3,5-dimethyl aniline, leading to a metal-polymer composite material. Palladium nanoparticles (approximately 2 nm) are uniformly distributed throughout the polymer that makes the composite material a unique morphology.

Do junior doctors take sick leave?

Nosocomial infections place a heavy burden on overstretched health services. An audit of junior doctors' sick leave behaviour was undertaken in 1993 and again in 2001. The object was to ascertain the level of common infectious illness and to investigate whether junior doctors were remaining at work inappropriately.

Marginal seal composition in amalgam restored teeth of varying marginal leakage.

An in vitro study was performed to ascertain the marginal seal elemental composition of amalgam restored extracted teeth of known marginal leakage. Occlusal cavities were cut in 400 caries free extracted teeth and left unlined or lined with one of 5 bases. A varnish was applied to half the cavities followed by restoration with a low copper or high copper amalgam to produce 20 restoration combinations.

Method for jet polishing two-phase materials.

A two-stage jet polishing technique is described which, utilising the effects of the characteristic current-voltage behaviour of electropolishing solutions, can produce excellent TEM foils of relatively coarse two-phase materials.

Influence of amalgams, bases, and varnish on seal composition at restoration tooth interfaces.

Eighty extracted, noncarious premolars were restored with one of 20 different combinations of restorative materials: a high- or low-copper amalgam, unlined or lined with one of five bases, and varnished or unvarnished. The teeth were aged in 1% NaCl and after 3 months and 1 year the seal material deposited on the cut tooth cavity surface and the surface of the amalgam restoration was analyzed by use of energy dispersive x-ray analysis. Atomic weight percentages of marginal seal elements were statistically examined with ANOVA and Tukey's test with significance set at p < 0.

Antibiotic sensitivity of Pasteurella haemolytica isolated by means of a fibreoptic endoscope from cases of pneumonic pasteurellosis in cattle.

Bacterial isolations from tracheal and bronchial washes obtained with the aid of a fibreoptic endoscope were carried out over a 7 month period in a feedlot on calves suffering from acute pneumonic pasteurellosis. Pasteurella haemolytica and Pseudomonas aeruginosa represented the majority of isolates. Antibiotic sensitivities of the Pasteurella isolates are reported on.

The use of extraction replicas in scanning electron microscopy for the elemental analysis of marginal seals.

Elemental analysis of marginal seal material on 20 bulk samples of occlusally restored teeth have shown that, generally, more elements were detected in the seal material analyzed on the bulk restoration or fractured tooth surfaces than when such material was extracted using a nitrocellulose replica prior to analysis. No mercury was detected in any of the extracted seal material and only three of the replica specimens contained silver. This implies that the technique of using extraction replicas to remove material from the amalgam-tooth interface for subsequent x-ray microanalysis can provide an accurate elemental composition.

Antibiotic serum activities against bacterial isolations from cases of bovine pneumonic pasteurellosis in feedlot calves.

The serum bactericidal activity test was carried out in two groups of 7 calves each suspected to be suffering from pneumonic pasteurellosis. The diagnosis was based on clinical signs, endoscopic examination and bacteriological investigations. The first group of seven calves received oxytetracycline at a dosage rate of 10 mg kg-1 once a day.

Elements in marginal seals at amalgam-tooth interfaces.

X-ray micro-analysis was used to determine the elemental composition of the tooth, amalgam, and base material of ten aged, amalgam-restored, posterior teeth after they had been fractured across the amalgam-tooth interface. Subsequently, replicas were used to remove marginal seal material from each interface for examination by x-ray micro-analysis. The results show that P and Sn were present in all marginal seal material analyzed.

Successful transfer of embryos recovered from a cow with chronic cervicitis of mixed aerobic and anaerobic bacterial aetiology a case report.

An imported 13-year-old Simmentaler cow was presented with severe purulent cervicitis and endometritis from which Corynebacterium pyogenes , Fusobacterium necrophorum , Bacteroides melaninogenicus and an untyped Clostridium perfringens were isolated. The endometritis responded to treatment but the cervix did not and remained fibrous, continuously patent and purulent. Natural pregnancy was considered unlikely and the cow was prepared as an embryo transfer donor.

The suitability of various adhesives as mounting media for scanning electron microscopy. I. Epoxies, sprays and tapes.

Fifty-six relatively commonly used epoxies, sprays and tapes have been tested with respect to properties that are, or may be, important if they were to be used as scanning electron microscopy sample mounting adhesives. Recommendations are made as to the most appropriate adhesive for each type of mounting media.

Emergence of multiply resistant pneumococci.

Multiple antimicrobial resistance in pneumococci was detected in Johannesburg in July, 1977, and prompted an investigation of the prevalence of resistant strains in two hospitals. Carriers of Types 6A and 19A penicillin-resistant pneumococci, resistant to antibiotic concentrations ranging between 0.12 and 4 microgram per milliliter were found in 29 per cent of 543 pediatric patients and 2 per cent of 434 hospital staff members.

Epidemic listeriosis. Report of 14 cases detected in 9 months.

During the period August 1977 to April 1978, 14 Black patients in Johannesburg area had systemic infections caused by Listeria monocytogenes. Nine of these patients were neonates who presented with septicaemia (5 cases) or septicaemia and meningitis (4 cases) and 5 were adults, all of whom had meningitis. The mortality rate was 43% (6/14), with 4 neonatal and 2 adult deaths.