Measurement of the laser-pulse group velocity in plasma waveguides

Electrically discharged plasma channels can guide laser pulses, extending the laser-plasma interaction length to many Rayleigh ranges. In applications such as the laser-plasma accelerator, the laser group velocity in the channel plays a critical role. The laser travel time (and thus the averaged group velocity) was measured through two-pulse frequency-domain interferometry and was found to depend on the on-axis plasma density and laser spot size. The data is in agreement with theory.

Effects of aqueous suspensions of titanium dioxide nanoparticles on Artemia salina: assessment of nanoparticle aggregation, accumulation, and toxicity

Aquatic stability and impact of titanium dioxide nanoparticles (TiO2 NPs, 10-30 nm) were investigated using Artemia salina. Acute exposure was conducted on nauplii (larvae) and adults in seawater in a concentration range from 10 to 100 mg/L TiO2 NPs for 24 and 96 h. Rapid aggregation occurred in all suspensions of TiO2 NPs to form micrometer size particles. Yet, both nauplii and adults accumulated the aggregates significantly. Average TiO2 content in nauplii ranged from 0.47 to 3.19 and from 1.29 to 4.43 mg/g in 24 and 96 h, respectively. Accumulation in adults was higher ranging from 2.30 to 4.19 and from 4.38 to 6.20 mg/g in 24 and 96 h, respectively. Phase contrast microscopy images revealed that Artemia were unable to excrete the particles. Thus, the TiO2 aggregates filled inside the guts. No significant mortality or toxicity occurred within 24 h at any dose. Lipid peroxidation levels characterized with malondialdehyde concentrations were not statistically different from those of the controls (p > 0.05). These results suggested that suspensions of the TiO2 NPs were nontoxic to Artemia, most likely due to the formation of benign TiO2 aggregates in water. In contrast, both mortality and lipid peroxidation increased in extended exposure to 96 h. Highest mortality occurred in 100 mg/L TiO2 NP suspensions; 18 % for nauplii and 14 % for adults (LC50 > 100 mg/L). These effects were attributed to the particle loading inside the guts leading to oxidative stress as a result of impaired food uptake for a long period of time.

Comparative evaluation of impact of Zn and ZnO nanoparticles on brine shrimp (Artemia salina) larvae: effects of particle size and solubility on toxicity

Brine shrimp (Artemia salina) larvae were exposed to different sizes of zinc (Zn) and zinc oxide (ZnO) nanoparticles (NPs) to evaluate their toxicity in marine aquatic ecosystems. Acute exposure was conducted in seawater with 10, 50 and 100 mg L(-1) concentrations of the NPs for 24 h and 96 h. Phase contrast microscope images confirmed the accumulation of the NPs inside the guts. Artemia were unable to eliminate the ingested particles, which was thought to be due to the formation of massive particles in the guts. Although the suspensions of the NPs did not exhibit any significant acute toxicity within 24 h, mortalities increased remarkably in 96 h and escalated with increasing concentration of NP suspension to 42% for Zn NPs (40-60 nm) (LC50∼ 100 mg L(-1)) and to about 34% for ZnO NPs (10-30 nm) (LC50 > 100 mg L(-1)). The suspensions of Zn NPs were more toxic to Artemia than those of ZnO NPs under comparable regimes. This effect was attributed to higher Zn(2+) levels (ca. up to 8.9 mg L(-1)) released to the medium from Zn NPs in comparison to that measured in the suspensions of ZnO NPs (ca. 5.5 mg L(-1)). In addition, the size of the nanopowders appeared to contribute to the observed toxicities. Although the suspensions possessed aggregates of comparable sizes, smaller Zn NPs (40-60 nm) were relatively more toxic than larger Zn NPs (80-100 nm). Likewise, the suspensions of 10-30 nm ZnO NPs caused higher toxicity than those of 200 nm ZnO NPs. Lipid peroxidation levels were substantially higher in 96 h (p < 0.05), indicating that the toxic effects were due to the oxidative stress.

Time to listen: a review of methods to solicit patient reports of adverse events

BACKGROUND

Patients have been shown to report accurate observations of medical errors and adverse events. Various methods of introducing patient reporting into patient safety systems have been published with little consensus among researchers on the most effective method. Terminology for use in patient safety reporting has yet to be standardised.

METHODS

Two databases, PubMed and MEDLINE, were searched for literature on patient reporting of medical errors and adverse events. Comparisons were performed to identify the optimal method for eliciting patient initiated events.

RESULTS

Seventeen journal publications were reviewed by patient population, type of healthcare setting, contact method, reporting method, duration, terminology and reported response rate.

CONCLUSION

Few patient reporting studies have been published, and those identified in this review covered a wide range of methods in diverse settings. Definitive comparisons and conclusions are not possible. Patient reporting has been shown to be reliable. Higher incident rates were observed when open-ended questions were used and when respondents were asked about personal experiences in hospital and primary care. Future patient reporting systems will need a balance of closed-ended questions for cause analysis and classification, and open-ended narratives to allow for patient's limited understanding of terminology. Establishing the method of reporting that is most efficient in collecting reliable reports and standardising terminology for patient use should be the focus of future research.

Spironolactone therapy is associated with reduced ventricular tachycardia rate in patients with cardiomyopathy

INTRODUCTION

Multiple pharmacological therapies currently in prevalent clinical use for cardiac diseases have antifibrotic properties. Spironolactone, a potent antifibrotic agent, is currently used for advanced heart failure. Therapies such as HMG-CoA reductase inhibitors (statins) and angiotensin-converting enzyme inhibitors (ACEi) also have antifibrotic properties. However, the effect of these medications on the ventricular arrhythmia phenotype is currently unknown. Therefore, we set out to define the ventricular arrhythmia rates in patients actively treated with such therapies.

METHODS AND RESULTS

We retrospectively evaluated the ventricular tachycardia (VT) rates in patients with structural heart disease actively treated with therapies with antifibrotic properties. VT rates were significantly diminished in patients treated with spironolactone (158 ± 26 beats per minute [bpm], n = 21) compared to patients on no medications (205 ± 22 bpm, n = 13) or those who were on similar heart-failure therapies but not on spironolactone (186 ± 32 bpm, n = 82). In addition, we observed that VT rates showed a significant trend toward lower rates in patients receiving either statins or ACEi, compared to patients on no medical therapy. In multivariate analysis, spironolactone therapy was identified as the single most significant variable for reduced VT rate.

CONCLUSION

Use of spironolactone in patients with heart failure is associated with reduced VT rate. Similar but less-significant reductions in VT rates were observed with use of other pharmacological agents with antifibrotic properties, such as statins and ACEi. Our findings, at least in part, could account for reduction in sudden cardiac death rates documented with use of these therapies.

Rapid testing for group B streptococcus during labour: a test accuracy study with evaluation of acceptability and cost-effectiveness

OBJECTIVE

To determine the accuracy, acceptability and cost-effectiveness of polymerase chain reaction (PCR) and optical immunoassay (OIA) rapid tests for maternal group B streptococcal (GBS) colonisation at labour.

DESIGN

A test accuracy study was used to determine the accuracy of rapid tests for GBS colonisation of women in labour. Acceptability of testing to participants was evaluated through a questionnaire administered after delivery, and acceptability to staff through focus groups. A decision-analytic model was constructed to assess the cost-effectiveness of various screening strategies.

SETTING

Two large obstetric units in the UK.

PARTICIPANTS

Women booked for delivery at the participating units other than those electing for a Caesarean delivery.

INTERVENTIONS

Vaginal and rectal swabs were obtained at the onset of labour and the results of vaginal and rectal PCR and OIA (index) tests were compared with the reference standard of enriched culture of combined vaginal and rectal swabs.

MAIN OUTCOME MEASURES

The accuracy of the index tests, the relative accuracies of tests on vaginal and rectal swabs and whether test accuracy varied according to the presence or absence of maternal risk factors.

RESULTS

PCR was significantly more accurate than OIA for the detection of maternal GBS colonisation. Combined vaginal or rectal swab index tests were more sensitive than either test considered individually [combined swab sensitivity for PCR 84% (95% CI 79-88%); vaginal swab 58% (52-64%); rectal swab 71% (66-76%)]. The highest sensitivity for PCR came at the cost of lower specificity [combined specificity 87% (95% CI 85-89%); vaginal swab 92% (90-94%); rectal swab 92% (90-93%)]. The sensitivity and specificity of rapid tests varied according to the presence or absence of maternal risk factors, but not consistently. PCR results were determinants of neonatal GBS colonisation, but maternal risk factors were not. Overall levels of acceptability for rapid testing amongst participants were high. Vaginal swabs were more acceptable than rectal swabs. South Asian women were least likely to have participated in the study and were less happy with the sampling procedure and with the prospect of rapid testing as part of routine care. Midwives were generally positive towards rapid testing but had concerns that it might lead to overtreatment and unnecessary interference in births. Modelling analysis revealed that the most cost-effective strategy was to provide routine intravenous antibiotic prophylaxis (IAP) to all women without screening. Removing this strategy, which is unlikely to be acceptable to most women and midwives, resulted in screening, based on a culture test at 35-37 weeks' gestation, with the provision of antibiotics to all women who screened positive being most cost-effective, assuming that all women in premature labour would receive IAP. The results were sensitive to very small increases in costs and changes in other assumptions. Screening using a rapid test was not cost-effective based on its current sensitivity, specificity and cost.

CONCLUSIONS

Neither rapid test was sufficiently accurate to recommend it for routine use in clinical practice. IAP directed by screening with enriched culture at 35-37 weeks' gestation is likely to be the most acceptable cost-effective strategy, although it is premature to suggest the implementation of this strategy at present.

Clinical evaluation of algorithms for context-sensitive physiological monitoring in children

BACKGROUND

Subtle changes in monitored physiological signals might be used to guide clinical actions and give early warning of potential adverse events. Automated early warning systems could enhance the clinician's interpretation of data by instantaneously processing new information and presenting it within the context of previous observations. In this study, we tested algorithms for tracking the behaviour of dynamic physiological systems and automatically detecting key events over time.

METHODS

Algorithms were activated in real-time during anaesthesia to run context-sensitive monitoring of six variables (end-tidal PCO(2), heart rate, exhaled minute ventilation, non-invasive arterial pressure, respiratory rate, and oxygen saturation), alongside standard physiological monitors. The clinical evaluation included real-time feedback on each change point (change in the physiological trend) detected by the algorithms and the completion of a usability questionnaire.

RESULTS

Fifteen anaesthetists completed the evaluation during paediatric surgical cases. A total of 38 cases were evaluated, with a mean duration of 103 (102) min. The mean number of change points per case was 22.8 (23.4). Sixty-one per cent of all rated change points were considered clinically significant, and <7% were due to artifacts.

CONCLUSIONS

The algorithms were able to detect a range of clinically significant physiological changes during paediatric anaesthesia, and were considered useful by participating anaesthetists. These findings indicate that automated detection of context-sensitive changes is possible and could be used by early warning systems during physiological monitoring. Further investigations are required to assess how this information can best be communicated to the anaesthetist.

Barnacle reattachment: a tool for studying barnacle adhesion

Standard approaches for measuring adhesion strength of fouling organisms use barnacles, tubeworms or oysters settled and grown in the field or laboratory, to a measurable size. These approaches suffer from the vagaries of larval supply, settlement behavior, predation, disturbance and environmental stress. Procedures for reattaching barnacles to experimental surfaces are reported. When procedures are followed, adhesion strength measurements on silicone substrata after 2 weeks are comparable to those obtained using standard methods. Hydrophilic surfaces require reattachment for 2-4 weeks. The adhesion strength of barnacles in reattachment assays was positively correlated to results obtained from field testing a series of experimental polysiloxane fouling-release coatings (r = 0.89). The reattachment method allows for precise barnacle orientation, enabling the use of small surfaces and the potential for automation. The method enables down-selection of coatings from combinatorial approaches to manageable levels for definitive field testing. Reattachment can be used with coatings that combine antifouling and fouling-release technologies.