Impact of material properties in determining quaternary ammonium compound adsorption and wipe product efficacy against biofilms.

BACKGROUND: Disinfectant wipes containing quaternary ammonium compounds (QACs) are widely used within health care. Viscose remains a popular material for these products, although limited information is available concerning its impact on performance against biofilms when compared with alternatives. AIM: To identify disinfectant wipe materials and surface properties which optimize product performance against biofilms. METHODS: Biofilm eradication performance of two commercial viscose-QAC wipes was determined against Staphylococcus aureus and Acinetobacter baumannii dry surface biofilms (DSBs) using an ASTM E2967-based procedure. Additionally, five materials were impregnated with a commercial liquid formulation containing didecyldimethylammonium chloride (DDAC). Following 24 h of storage, eradication performance and DDAC content of extracted liquid were determined and compared with material properties, including zeta potential, hydrophobicity and surface area. FINDINGS: Under stringent test conditions, eradication of DSBs by commercial products was no greater than equivalent materials impregnated with water. Extract from one viscose-based product contained 89% less DDAC than the impregnation solution, indicating extensive adsorption. Of the other tested materials, viscose performed worst; nearly 70% of DDAC had depleted from material extracts within 24 h. In contrast, DDAC depletion from polypropylene extracts was only 25%, and DSB eradication was >100 times greater than viscose. Biofilm eradication performance against both species correlated with the DDAC content of extracts, which, in turn, correlated with zeta potential and hydrophobicity. CONCLUSION: Biofilm eradication performance of QAC-based wipes was significantly greater when selecting thermoplastic substrates over viscose. However, these materials are non-sustainably sourced and non-biodegradable. This study highlights a need to develop new wipe products that are more effective against biofilms.

Observation of a superconducting glass state in granular superconducting diamond.

The magnetic field dependence of the superconductivity in nanocrystalline boron doped diamond thin films is reported. Evidence of a superconducting glass state is presented, as demonstrated by the observation of a quasi de Almeida-Thouless line in the phase diagram and a logarithmic time dependence of the magnetism. The position of the phase boundary in the H-T plane is determined from electrical transport data by detailed fitting to quasi-zero-dimensional fluctuation conductivity theory. This allows determination of the boundary between resistive and non-resistive behaviour to be made with greater precision than the standard ad hoc onset/midpoint/offset criterion. We attribute the glassy superconductivity to the morphological granularity of the diamond films.

A pilot study of performance among hospitalised elderly patients on a novel test of visuospatial cognition: the letter and shape drawing (LSD) test.

OBJECTIVES: Conventional bedside tests of visuospatial function such as the clock drawing (CDT) and intersecting pentagons tests (IPT) are subject to considerable inconsistency in their delivery and interpretation. We compared performance on a novel test - the letter and shape drawing (LSD) test - with these conventional tests in hospitalised elderly patients. METHODS: The LSD, IPT, CDT and the Montreal Cognitive Assessment (MoCA) were performed in 40 acute elderly medical inpatients at University Hospital Limerick The correlation between these tests was examined as well as the accuracy of the visuospatial tests to identify significant cognitive impairment on the MoCA. RESULTS: The patients (mean age 81.0±7.71; 21 female) had a median MoCA score of 15.5 (range=1-29). There was a strong, positive correlation between the LSD and both the CDT (r=0.56) and IPT (r=0.71). The correlation between the LSD and MoCA (r=0.91) was greater than for the CDT and IPT (both 0.67). The LSD correlated highly with all MoCA domains (ranging from 0.54 to 0.86) and especially for the domains of orientation (r=0.86), attention (0.81) and visuospatial function (r=0.73). Two or more errors on the LSD identified 90% (26/29) of those patients with MoCA scores of ⩽20, which was substantially higher than for the CDT (59%) and IPT (55%). CONCLUSION: The LSD is a novel test of visuospatial function that is brief, readily administered and easily interpreted. Performance correlates strongly with other tests of visuospatial ability, with favourable ability to identify patients with significant impairment of general cognition.

Thin conductive diamond films as beam intensity monitors for soft x-ray beamlines.

Quantitative analysis of X-ray absorption and dichroism data requires knowledge of the beamline photon flux during the measurements. We show that thin conductive (B-doped) diamond thin films can be an alternative to the widely used gold meshes for monitoring the beam intensity of soft X-ray beamlines in situ. Limited by the carbon extended x-ray absorption fine structure oscillations, the diamond films become applicable beginning from about 600 eV photon energy, where the important transition metal edges and the rare-earth edges are found. The 100 nm and 250 nm thick free-standing diamond films were grown and tested against standard gold meshes in real-life dichroism experiments performed at beamline ID08 of the European Synchrotron Radiation Facility, Grenoble, France. Quantitative agreement was found between the two experimental data sets. The films feature an extremely high transmission of about 90% and, at the same time, yield a sufficiently strong and clean reference signal. Furthermore, the thin films do not affect the shape of the transmitted beam. X-rays passing mesh-type monitors are subject to diffraction effects, which widen the beam and become particularly disturbing for small beamsizes in the micrometer range.

Piezoelectric actuated micro-resonators based on the growth of diamond on aluminum nitride thin films.

Unimorph heterostructures based on piezoelectric aluminum nitride (AlN) and diamond thin films are highly desirable for applications in micro- and nanoelectromechanical systems. In this paper, we present a new approach to combine thin conductive boron-doped as well as insulating nanocrystalline diamond (NCD) with sputtered AlN films without the need for any buffer layers between AlN and NCD or polishing steps. The zeta potentials of differently treated nanodiamond (ND) particles in aqueous colloids are adjusted to the zeta potential of AlN in water. Thereby, the nucleation density for the initial growth of diamond on AlN can be varied from very low (10(8) cm(-2)), in the case of hydrogen-treated ND seeding particles, to very high values of 10(11) cm(-2) for oxidized ND particles. Our approach yielding high nucleation densities allows the growth of very thin NCD films on AlN with thicknesses as low as 40 nm for applications such as microelectromechanical beam resonators. Fabricated piezo-actuated micro-resonators exhibit enhanced mechanical properties due to the incorporation of boron-doped NCD films. Highly boron-doped NCD thin films which replace the metal top electrode offer Young's moduli of more than 1000 GPa.

Characterisation of capacitive field-effect sensors with a nanocrystalline-diamond film as transducer material for multi-parameter sensing.

The feasibility of a capacitive field-effect EDIS (electrolyte-diamond-insulator-semiconductor) platform for multi-parameter sensing is demonstrated by realising EDIS sensors with an O-terminated nanocrystalline-diamond (NCD) film as transducer material for the detection of pH and penicillin concentration as well as for the label-free electrical monitoring of adsorption and binding of charged macromolecules, like polyelectrolytes. The NCD films were grown on p-Si-SiO(2) substrates by microwave plasma-enhanced chemical vapour deposition. To obtain O-terminated surfaces, the NCD films were treated in an oxidising medium. The NCD-based field-effect sensors have been characterised by means of constant-capacitance method. The average pH sensitivity of the O-terminated NCD film was 40 mV/pH. A low detection limit of 5 microM and a high penicillin G sensitivity of 65-70 mV/decade has been obtained for an EDIS penicillin biosensor with the adsorptively immobilised enzyme penicillinase. Alternating potential changes, having tendency to decrease with increasing the number of adsorbed polyelectrolyte layers, have been observed after the layer-by-layer deposition of polyelectrolyte multilayers, using positively charged PAH (poly (allylamine hydrochloride)) and a negatively charged PSS (poly (sodium 4-styrene sulfonate)) as a model system. The response mechanism of the developed EDIS sensors is discussed.

Topographical and functional characterization of the ssDNA probe layer generated through EDC-mediated covalent attachment to nanocrystalline diamond using fluorescence microscopy.

The covalent attachment method for DNA on nanocrystalline diamond (NCD), involving the introduction of COOH functionalities on the surface by photoattachment of 10-undecenoic acid (10-UDA), followed by the 1-ethyl-3-(3-dimethylaminopropyl)-carbodiimide (EDC)-mediated coupling to NH 2-labeled ssDNA, is evaluated in terms of stability, density, and functionality of the resulting biological interface. This is of crucial importance in DNA biosensor development. The covalent nature of DNA attachment will infer the necessary stability and favorable orientation to the ssDNA probe molecules. Using confocal fluorescence microscopy, the influence of buffer type for the removal of excess 10-UDA and ssDNA, the probe ssDNA length, the probe ssDNA concentration, and the presence of the COOH-linker on the density and functionality of the ssDNA probe layer were investigated. It was determined that the most homogeneously dense and functional DNA layer was obtained when 300 pmol of short ssDNA was applied to COOH-modified NCD samples, while H-terminated NCD was resistant for DNA attachment. Exploiting this surface functionality dependence of the DNA attachment efficiency, a shadow mask was applied during the photochemical introduction of the COOH-functionalities, leaving certain regions on the NCD H-terminated. The subsequent DNA attachment resulted in a fluorescence pattern corresponding to the negative of the shadow mask. Finally, NCD surfaces covered with mixtures of the 10-UDA linker molecule and a similar molecule lacking the COOH functionality, functioning as a lateral spacer, were examined for their suitability in preventing nonspecific adsorption to the surface and in decreasing steric hindrance. However, purely COOH-modified NCD samples, patterned with H-terminated regions and treated with a controlled amount of probe DNA, proved the most efficient in fulfilling these tasks.

Towards a real-time, label-free, diamond-based DNA sensor.

Most challenging in the development of DNA sensors is the ability to distinguish between fully complementary target ssDNA (single-strand DNA) and 1-mismatch ssDNA. To deal with this problem, we performed impedance spectroscopy on DNA-functionalized nanocrystalline diamond (NCD) layers during hybridization and denaturation. In both reactions, a difference in behavior was observed for 1-mismatch target DNA and complementary target DNA in real-time. During real-time hybridization, a decrease of the impedance was observed at lower frequencies when the complementary target DNA was added, while the addition of 1-mismatch target ssDNA caused no significant change. Fitting these results to an electrical circuit demonstrates that this is correlated with a decrease of the depletion zone in the space charge region of the diamond. During real-time denaturation, differentiation between 1-mismatch and complementary target DNA was possible at higher frequencies. Denaturation of complementary DNA showed the longest exponential decay time of the impedance, while the decay time during 1-mismatch denaturation was the shortest. The real-time hybridization and denaturation experiments were carried out on different NCD samples in various buffer solutions at temperatures between 20 and 80 degrees C. It was revealed that the best results were obtained using a Microhyb hybridization buffer at 80 degrees C and 10x PCR buffer at 30 degrees C for hybridization and 0.1 M NaOH at temperatures above 40 degrees C for denaturation. We demonstrate that the combination of real-time hybridization spectra and real-time denaturation spectra yield important information on the type of target. This approach may allow a reliable identification of the mismatch sequence, which is the most biologically relevant.

Germination Stimulation of Striga gesnerioides Seeds by Hosts and Nonhosts.

Cowpea (Vigna unguiculata) is an important source of protein in Africa, but production is hindered by the parasitic plant Striga gesnerioides. Crop rotation with nonhost cultivars, selected to stimulate parasite seed germination, is being used successfully to control other Striga spp. and may have potential to control S. gesnerioides. Little information has been available on nonhosts of S. gesnerioides that are capable of stimulating germination of parasite seeds. A laboratory procedure was used to evaluate species and cultivars for their ability to stimulate S. gesnerioides seed germination. Genotypes of all Vigna spp. tested stimulated parasite seed germination. Some genotypes of the nonhost species Cajanus cajan, Lablab purpureus, stenocarpa, and Sorghum bicolor also stimulated parasite seed germination. One cultivar of Sorghum bicolor stimulated significantly more germination than any other cultivar or species. Control of S. gesnerioides through rotation with selected nonhost cultivars has potential if selection is done with the parasite isolate(s) from the locality of intended use. When seeds of single-plant isolates of S. gesnerioides were tested against roots of seedlings from Sorghum bicolor landraces and from a susceptible cowpea cultivar, only specific isolate and plant combinations resulted in parasite seed germination. These specific interactions have broader implications for parasite survival.

Gastric emptying is delayed at 8-12 weeks' gestation.

Gastric emptying was studied indirectly by paracetamol absorption in 20 patients at 8-12 weeks' gestation and also in 20 non-pregnant controls. Subjects received paracetamol 1.5 g in a tablet with 50 ml of water and remained semi-recumbent for 2 h while venous blood samples were obtained at 15-min intervals. The maximum concentration of paracetamol was significantly lower and the time to maximum concentration significantly greater in pregnant patients. In addition, the areas under the time-concentration curves at 60 and 120 min were significantly smaller in the pregnant group. These changes are indicative of a delay in gastric emptying at 8-12 weeks' gestation.

Addition of droperidol to patient-controlled analgesia: effect on nausea and vomiting.

A double-blind trial of the effect of droperidol on the incidence of nausea and vomiting in patients using patient-controlled analgesia was carried out in 60 healthy women undergoing abdominal hysterectomy. After a standard anaesthetic including droperidol 2.5 mg as a prophylactic antiemetic, patients were randomly allocated to receive postoperative patient-controlled analgesia with either morphine alone (2 mg.ml-1) or morphine (2 mg.ml-1) with droperidol (0.2 mg.ml-1) added to the syringe. Verbal scores and visual analogue scores for nausea, vomiting, pain and sedation were made at 4, 12 and 24 h postoperatively, and any requirement for intramuscular prochlorperazine noted. There was no difference between the groups at any time in the amount of morphine consumed or in pain scores. At 12 h, patients receiving droperidol experienced significantly less nausea, and over the first 24 h, 31% required prochlorperazine compared with 59.3% of patients not receiving droperidol. The number of patients with sedation at 24 h was significantly greater in the droperidol group. We conclude that the addition of droperidol to morphine both reduces nausea and the need for further antiemetic treatment.

Patient knowledge of operative care.

To investigate knowledge of perioperative events, a questionnaire was administered to 111 elective surgical patients. Six topics were covered: the operation, the anaesthetic, time spent in the operating theatre, amount of post-operative pain, duration of hospital admission and time required to return to normal fitness. Apart from evaluating information-sources for each topic, the questionnaire assessed degree of knowledge and satisfaction with this information, and the relationship of these to anxiety. More than 30% of the patients responded that they had received no information about anaesthesia, time in theatre, return to fitness or pain. For each topic more than 40% desired further information. Nursing staff provided most information, although for the anaesthetic, time in theatre, return to fitness and pain, more than 60% of patients responded that nobody had provided explanation. There was no correlation between knowledge relating to the topics per se and anxiety, but there was a significant correlation between satisfaction with information and anxiety. This survey shows a considerable need for improved information provision, especially for patients in whom anxiety is associated with a desire for further explanation of operative care.

Lignocaine spray applicators are a potential source of cross-infection in the anaesthetic room.

Ten percent lignocaine spray is in widespread clinical use as a means of suppressing responses to tracheal intubation. It is sprayed from a multidose container into the glottis and on to the vocal cords through an applicator nozzle, which may be used on successive patients. We have investigated the likelihood of the contamination of these nozzles, with patients' mouth flora. Spray applicators from four of the 20 cases investigated showed contamination with potential bacterial pathogens. We therefore recommend that lignocaine spray should not be applied to successive patients using the same applicator nozzle.

Pulmonary collapse during anaesthesia in children with respiratory tract symptoms.

A frequent dilemma facing the anaesthetist is the child with respiratory tract symptoms. The risks of anaesthesia and surgery in these patients have not been clearly established. We present three cases which illustrate a potentially serious complication which may arise. Our patients each had symptoms of cough, but were systemically healthy. Two of the children had absent clinical signs, whilst the third had a normal chest X ray. However, during surgery and anaesthesia each child developed significant pulmonary collapse, associated with desaturation on oximetry.