A calibrated UV-LED based light source for water purification and characterisation of photocatalysis.

Photocatalysis has a potential to become a cost effective industrial process for water cleaning. One of the most studied photocatalysts is titanium dioxide which, as a wide band gap semiconductor, requires ultraviolet (UV) light for its photoactivation. This is at the wavelengths where the efficiency of present-day light emitting diodes (LEDs) decreases rapidly, which presents a challenge in the use of UV-LEDs for commercially viable photocatalysis. There is also a need for accurate photocatalysis measurement of remediation rates of water-borne contaminants for determining optimum exposure doses in industrial applications. In response to these challenges, this paper describes a UV-LED based photocatalytic test reactor that provides a calibrated adjustable light source and pre-defined test conditions to remove as many sources of uncertainty in photocatalytic analysis as possible and thereby improve data reliability. The test reactor provides a selectable intensity of up to 1.9 kW m-2 at the photocatalyst surface. The comparability of the results is achieved through the use of pre-calibration and control electronics that minimize the largest sources of uncertainty; most notably variations in the intensity and directionality of the UV light emission of LEDs and in LED device heating.

Angle dependent optical properties of polymer films with a biomimetic anti-reflecting surface replicated from cylindrical and tapered nanoporous alumina.

Anodic porous alumina nanostructures have been fabricated with tapered and cylindrical pores with a spacing of 100 and 200 nm and depth of 180-500 nm. The porous nanostructures were replicated into polymer films to create a moth-eye anti-reflecting surface by a roll-to-roll UV replication process. The angle dependent optical transmission of the resulting polymer films exhibited up to a 2% increase in transmission at a normal angle and up to a 5% increase in transmission at a 70° angle of incidence to an equivalent film with a surface replicated from polished aluminum. No significant difference was observed between the optical performance of moth-eye surfaces formed from cylindrical and tapered nano-pores.

Anodised titania nanotubes prepared in a glycerol/NaF electrolyte.

This paper discusses the preparation of titania nanotubes by anodisation of Ti in a glycerol-based electrolyte containing 0.5% wt of sodium fluoride (NaF). The influence of anodisation voltage and anodisation time on nanotube wall thickness, diameter and length has been investigated. The results indicate that nanotubes can be formed within a voltage range 10-40 V and that the tubular structure is lost when using a higher voltage. The diameter of the nanotubes is voltage dependent, with the widest tubes being obtained at the highest possible applied voltage of 40 V. An initial voltage ramp which increases at 100 mV/s to the anodisation voltage, rather than an instantaneous step, was observed to stabilise the metal-oxide interface. This enabled the growth of anodic films up to 5.5 microm in length by anodising for approximately 48 h. In the absence of a voltage ramp the films tended to collapse and become detached from the titanium electrode after 15-20 h. Electron microscopy observation suggests that the nanotubes in glycerol develop in a similar way to those produced in water-based media. The nanotubes formed using glycerol also exhibit ripples along the tube wall, although, growing at a slower rate, they are generally smoother than those formed in water.

Sources of support for older people after discharge from hospital: 10 years on.

AIMS OF THE STUDY: The aim of this research was to find out who supports older people at home after discharge from hospital and if sources of support have changed between the 1980s and the 1990s. BACKGROUND: More and more older people are being discharged from hospital earlier and this creates additional pressures on families, community health and social services and the independent care sector. The research was concerned with how sources of support may have changed in a 10-year period. METHODS: A comparison is made of two separate nonrandom samples, taken 10 years apart, of older people following discharge from hospital. Interviews were conducted in participants' homes to establish levels of dependence and the source of support given in response to the need for help with personal and domestic activities of daily living. RESULTS: Although limited by the use of relatively small, nonrandom samples, the research found that proportions needing help with domestic activities were higher than those needing help with personal activities of daily living. Although dependence for help with bathing had declined between the 1980s and 1990s, help was still needed with bathing and dressing. Unmet need for help with bathing remained a problem in the 1990s. A growing role for home helps was identified, especially in personal care (bathing and dressing), where support from district nurses had declined. By the 1990s, home helps were doing less cooking and housework, including heavy laundry. Relatives were doing more of most domestic activities except shopping, which was being carried out by home helps. CONCLUSIONS: The paper concludes by arguing that hospitals should consider if pressures to discharge older people more quickly might hinder the discharge planning process and communication between hospital and community sectors.

Analysis of biological particles using dielectrophoresis and impedance measurement.

A novel electrical technique for detecting the collection of particles by dielectrophoresis (DEP) is described. The method is based on the impedance changes resulting from this collection in a microfabricated, integrated dual-channel electrode structure. The results show good agreement with measurements of DEP collection by optical method for suspensions of bacterial species B. subtilis, E. coli and abiotic latex beads, but with substantially reduced experimental uncertainties. The technique overcomes the restriction on particle size of optical techniques and can potentially be used to investigate highly sub-micron sized particles like viruses and DNA fragments. The dual-channel electrode cells can be integrated with other structures for analysing sub-micron scale particles, for example chip-based capillary electrophoresis.

Sudden infant death syndrome (SIDS) and the toxic gas hypothesis: microbiological studies of cot mattresses.

1. Fifty infants' mattresses were studied to investigate the occurrence of viable fungal and bacterial propagules, with particular reference to Scopulariopsis brevicaulis which had been suggested to be implicated in SIDS cases. A total of 19 SIDS cases mattresses, 1 non-SIDS death, 20 used controls, and 10 new unused controls were examined. 2. Differences were found between SIDS and used controls in the variety of fungal species isolated and the numbers isolated from fillings; bacterial numbers were similar. 3. S. brevicaulis was isolated from only four mattresses, three of which were SIDS cases. It was not found in most of those on which death had occurred. 4. A number of potentially pathogenic or allergenic fungi, including Aspergillus fumigatus, were isolated more frequently from SIDS cases mattresses than new or used controls. 5. Scanning electron microscopy of mattress covers and fillings showed microbial 'biofilms' in the head areas of all SIDS cases examined. This was not seen on other samples. 6. The limited number of mattresses studied and the use of unmatched controls precludes the drawing of any general conclusions as to the significance of the biofilms or other fungi isolated. 7. Reports of the existence of a dimorphism in general growth forms of S. brevicaulis were investigated by growing and transferring authentic strains between a variety of growth media. 8. No 'slimy' state of this fungus was observed and dimorphism was not confirmed.

Beta-blockers in portal hypertension. An overview.

This paper describes a meta-analysis of data from the 5 primary and 15 secondary prevention studies in patients with portal hypertension, in which beta-blockers were compared with inactive control. These studies involved 1525 patients. Overall, the number of patients who suffered bleeding events was 38% lower in the groups treated with beta-blockers (p less than 0.001). The percentage reductions in bleeding-related deaths and in total mortality were 35% and 18%, respectively (p = 0.007 and p = 0.024). More detailed analysis supports the conclusion that propranolol, the beta-blocker predominantly used in these studies, is effective in both the primary and secondary prevention of bleeding events and mortality due to portal hypertension.

Cultured neonate rat myocytes as a model for the study of myocardial ischaemic necrosis.

The preparation of cultures of neonate rat heart muscle cells is described. These cultures, when subjected to anoxia, show enzyme release that can be directly related to the uptake of a vital dye such trypan blue. Enzyme release is a valid method of estimating cell necrosis in this model. The survival of anoxic cultures is closely associated with glycolytic activity. Glycolysis rate falls and enzyme release increases as the medium glucose concentration is reduced. If glycolysis is inhibited by either 2-deoxyglucose or L-lactate, enzyme release under anoxic conditions is enhanced. Enzyme release correlates inversely with glycolytic activity and the intracellular ATP content of the cultures. Addition of ATP to anoxic cultures partially ameliorates the effect of the anoxia on enzyme release. Elevation of the calcium content of the culture medium exacerbates the damage caused to cardiac myocytes by anoxic insult. This effect can be obtunded by calcium-antagonist drugs such as verapamil or nifedipine and can be explained in terms of reduction in utilization of intracellular ATP by the anoxic monocytes. These observations indicate that cultured myocytes may represent a useful model of hypoxic injury against which novel pharmacological agents, that may reduce hypoxic or ischaemic injury in vivo, could be evaluated.