Enhanced electrochemical reduction of hydrogen peroxide on silver paste electrodes modified with surfactant and salt

The modification of silver paste electrodes with a combination of dodecylbenzenesulfonic acid and KCl has been shown to lead to significant enhancements of the electrochemical reduction of hydrogen peroxide. The catalytic enhancement was shown to be dependent on the concentration of the surfactant/salt solution, which resulted in increases of some 80-fold in amperometric response to hydrogen peroxide at −0.1 V vs Ag/AgCl, pH 6.8 over unmodified silver paste. Physical analysis showed modifications to both the surface morphology and chemical composition of the silver paste electrode surface. However, BET and electrochemical analysis revealed no significant change in surface area. It is suggested that the enhanced catalysis may result from the formation of stabilised surfactant/salt structures at the metal electrode surface. The electrode was also shown to be suitable for the amperometric detection of hydrogen peroxide with a limit of detection of 1.1 × 10⁻⁶ M (S/N = 3).     

Electronic and Ionic Trapping at Domain Walls in BaTiO3

We have coupled electron paramagnetic resonance (EPR) and polarization–voltage measurements to understand the effects of reducing ambients on the remanent polarization and density of paramagnetic centers in BaTiO₃, single crystals. Two types of reducing ambients were explored; one was done under vacuum (slightly reducing) and the second was performed in forming gas (very reducing). It is found that the vacuum anneal caused a reduction in the remanent polarization and a concomitant decrease in the isolated Fe³⁺ EPR resonance. The Fe³⁺–V_o complex EPR signal was relatively unaffected by this vacuum anneal. By injecting charge using an ultraviolet (UV) light and an applied bias combination, the polarization and the isolated Fe³⁺ signal intensity were restored, thereby suggesting that the suppression of the remanent polarization is due to trapping of electronic charge at the domain walls. For the forming gas anneal, we observe a much larger decrease in remanent polarization with an accompanying decrease in both the isolated Fe³⁺ and Fe³⁺–V_o complex EPR signals. For this anneal, charge injection by the UV light/bias combination did not restore the polarization nor the EPR densities. The remanent polarization, the isolated Fe³⁺, and the Fe³⁺–V_oV_o complex could be restored only by a reoxidizing anneal, suggesting that ionic defects {oxygen vacancies) are now responsible for pinning the domain walls. Collectively, these results suggest reducing anneals can suppress the amount of switchable polarization in BaTiO₃ by either electronic or ionic trapping mechanisms.     

Association between plasma homocysteine and extracranial carotid arterial disease in older persons

The data demonstrate that high plasma homocysteine levels and low plasma folate and vitamin B12 levels are associated with a higher prevalence of 40% to 100% extracranial carotid arterial disease (ECAD) in older men and women. Elevated plasma homocysteine levels were observed in 45% of the older men with 40% to 100% ECAD versus 20% of the older men with 0% to 39% ECAD, and in 40% of the older women with 40% to 100% ECAD versus 18% of the older women with 0% to 39% ECAD.     

The haematological management of patients with cyanotic congenital heart disease. A time for consensus?

AIMS: Recurrent venesection of patients with cyanotic congenital heart disease may be detrimental, with an increased risk of cerebrovascular events and symptomatic iron-deficiency. The aim of this study was to determine the venesection policies as practised in hospitals within a U.K. region and to determine if these policies followed current recommendations. METHODS AND RESULTS: Fifty-eight consultants (56% response rate) in cardiac specialties completed self-assessment questionnaires regarding the indications for and practice of venesection. Sixty-one percent of those responding were involved directly in the care of patients with cyanotic congenital heart disease and of these clinicians 97% used venesection. Indications for venesection varied, with 51% of those responding using an elevated haemoglobin per se (6.5-21.0 g. dl-1); 78% an elevated haematocrit (0.55-0.75) and 83% symptoms. Desired maintenance haemoglobin and haematocrit levels also varied greatly. Fifty percent of the consultants responding routinely screened their patients for iron deficiency and 23% felt there was no indication for investigating a low mean corpuscular volume. Only 18% of the policies described followed any evidence based principles. CONCLUSIONS: The practice of venesecting patients with congenital cyanotic heart disease varies greatly. Policies in many hospitals do not reflect the minimal benefits and considerable risks associated with recurrent venesection.     

Update rates and fidelity in virtual environments

Interaction is the primary characteristic of a Virtual Environment and update rate is normally taken as an index or measure of the interactivity of the system. The speed of many systems is dictated by the slowest component which is often the Computer Image Generator (CIG). It is common for the workload of the CIG to vary and hence the performance of the system. This paper shows how a variable update rate can produce undesirable results. Two solutions to this problem are presented: service degradation and worst-case. In the case of the CIG, service degradation would require the quality of the image to be reduced such that the time taken never exceeds a given deadline. The worst-case technique works by finding the longest time taken to render any view and then uses that as the deadline for completion. The support of predictive methods is one of several benefits of this approach. An implementation of the worst-case technique is described which takes finer control over the CIG than usual and may be applied to many existing systems with little modification.     

Relationship between thermal stability, degradation rate and expression yield of barnase variants in the periplasm of Escherichia coli

An advantage of exporting a recombinant protein to the periplasm of Escherichia coli is decreased proteolysis in the periplasm compared with that in the cytoplasm. However, protein degradation in the periplasm also occurs. It has been widely accepted that the thermodynamic stability of a protein is an important factor for protein degradation in the cytoplasm of E.coli. To investigate the effect of the thermodynamic stability of an exported protein on the extent of proteolysis in the periplasm, barnase (an extracellular ribonuclease from Bacillus amyloliquefaciens) fused to alkaline phosphatase leader peptide was used as a model protein. A set of singly or doubly mutated barnase variants were constructed for export to the E.coli periplasm. It was found that the half-life of the barnase variants in vivo increased with their thermodynamic stability in vitro. A dominant factor for the final yield of exported barnase was not exportability but the turnover rate of the barnase variant. The yield of a stabilized mutant was up to 50% higher than that of the wild type. This suggests that exporting a protein to the periplasm and using protein engineering to enhance the stability can be combined as a strategy to optimize the production of recombinant proteins.     

Radiological features of focal nodular hyperplasia of the liver in children

BACKGROUND: Focal nodular hyperplasia (FNH) is an unusual hepatic tumour in children and should be distinguished from other hepatic lesions. OBJECTIVE: To describe the imaging characteristics of FNH in children. MATERIALS AND METHODS: We examined five patients (three boys and two girls, mean age 9.4 years) with pathologically confirmed FNH. The diagnosis was obtained by tumour resection (n = 4) and percutaneous needle biopsy (n = 1). One patient with multiple FNHs showed recurrent lesions after tumour resection. All patients were studied with US (including colour and power Doppler US [n = 3]) and CT. Dynamic enhanced CT scans were available in three patients. MRI (n = 2) or coeliac angiography (n = 1) was performed in three patients. RESULTS: Seven of eight FNH lesions in five patients were demonstrated by imaging. The average size of the lesions was 6.5 cm. Six lesions detected on US showed variable echogenicity with a central hyperechoic scar (n = 2). On Doppler examination, central or peripheral hypervascular areas were seen (n = 3). Six lesions detected on contrast-enhanced CT showed high attenuation (n = 4) or iso-attenuation (n = 2). On early phase scans, all the lesions (n = 3) showed high attenuation. Irregular linear or ovoid central scars were detected in two patients on CT. MR demonstrated three lesions in two patients, one of which had not been detected by US or CT. A central low signal intensity scar (n = 1) was seen on T2-weighted MRI. Coeliac angiography performed in one patient showed a hypervascular mass with homogeneous staining. CONCLUSION: FNH in children shows a wide spectrum of imaging findings on various radiological examinations and the typical central scar was not always seen on imaging studies. Dynamic enhanced CT obtained in the early phase and colour Doppler studies may be helpful in the diagnosis of FNH by allowing characterisation of tumour vascularity. FNH should be included in the differential diagnosis of liver mass in children.     

Median-nerve neuropathy associated with chronic anterior dislocation of the lunate

Ten patients who had median-nerve neuropathy in association with chronic anterior dislocation of the lunate were managed operatively and were followed for an average of five years (range, three to eight years). The average time from the injury to the initial evaluation was twenty-one months (range, six to sixty-five months). All ten patients had pain as well as sensory and motor dysfunction in the distribution on the median nerve. Nerve-conduction-velocity studies revealed a delay in distal motor and sensory latencies in all patients; the distal motor latency averaged 12.5 milliseconds (range 5.6 to 18.6 milliseconds), and the distal sensory latency averaged 12.4 milliseconds (range, 4.8 to 16.8 milliseconds). Three patients had had a failed carpal tunnel release and needed excision of the lunate for decompression of the median nerve. In the other seven patients, three distinctive sites of nerve compression were identified: the volar and dorsal edges of the lunate and the proximal edge of the transverse carpal ligament. Excision of the osseous protuberance (excision of the lunate in three patients and a proximal-row carpectomy in four), combined with a release of the transverse carpal ligament, resulted in relief of the symptoms, functional improvement, and sensory and motor recovery in the distribution of the median nerve.     

Mutant rescue by BAC clone injection in zebrafish

PURPOSE: To evaluate the rate of tumor recurrence within the irradiated volume after initial low-dose irradiation of limited-stage small-cell lung cancer (SCLC), to assess the tolerance of a sequential combination of low-dose chest irradiation followed by chemotherapy, and to confirm the responsiveness of limited-stage SCLC to low-dose irradiation. METHODS AND MATERIALS: In this pilot study, 26 patients with limited-stage SCLC were treated by first-line 20-Gy thoracic irradiation followed 3 weeks later by chemotherapy (cisplatin, doxorubicin, and etoposide for six cycles). RESULTS: We present our final results with a median follow-up of surviving patients of 7 years. The response rate to this low-dose irradiation was 83%, with an overall response rate to radiochemotherapy of 96% and a median survival of 21 months. No unexpected early or late toxicity was observed. The rate of initial isolated local failure was 8%, which compares favorably with other published series using higher doses of radiochemotherapy. CONCLUSION: An initial chest irradiation of 20 Gy before chemotherapy could be sufficient to reduce the risk of local failure during the time of survival of patients with limited-stage SCLC. Potential advantages of this treatment may be the prevention of resistance mechanisms to radiotherapy induced by preliminary chemotherapy and a reduced radiation-induced toxicity.