Geometry of α-Cr2O3(0001) as a Function of H2O Partial Pressure.

Surface X-ray diffraction has been employed to elucidate the surface structure of α-Cr2O3(0001) as a function of water partial pressure at room temperature. In ultra high vacuum, following exposure to ∼2000 Langmuir of H2O, the surface is found to be terminated by a partially occupied double layer of chromium atoms. No evidence of adsorbed OH/H2O is found, which is likely due to either adsorption at minority sites, or X-ray induced desorption. At a water partial pressure of ∼30 mbar, a single OH/H2O species is found to be bound atop each surface Cr atom. This adsorption geometry does not agree with that predicted by ab initio calculations, which may be a result of some differences between the experimental conditions and those modeled.

Safe extubation of a parturient using an airway exchange technique.

The difficult obstetric airway is a well-recognised anaesthetic challenge but little emphasis is placed on the difficulty of performing a safe tracheal extubation. We report the use of an airway exchange technique to extubate a difficult obstetric airway and discuss the role of these techniques in the obstetric population.

A pilot study to examine the effect of the Tulip oropharyngeal airway on ventilation immediately after mask ventilation following the induction of anaesthesia.

The Tulip airway is an adult, disposable, single-sized oropharyngeal airway, that is connectable to an anaesthetic circuit. After a standardised induction of anaesthesia in 75 patients, the ease of insertion, intracuff pressure and intracuff volume were measured, as were the end-tidal carbon dioxide levels, airway pressures and tidal volumes over three breaths. Successful first-time insertion was achieved in 72 patients (96%, CI 88.8-99.2%) and after two attempts in 74 patients (99%, CI 92.8-100%). There was outright failure only in one patient. In 60 patients (80%, CI 72.2-90.4%), the Tulip airway provided a patent airway without additional manoeuvres, but in 14 patients, jaw thrust or head extension was necessary for airway patency. The main need for these adjuncts appeared to be an initial under-inflation of the cuff. These promising results are consistent with recent manikin studies using this device.

Controlled cobalt doping in biogenic magnetite nanoparticles.

Cobalt-doped magnetite (CoxFe3 -xO4) nanoparticles have been produced through the microbial reduction of cobalt-iron oxyhydroxide by the bacterium Geobacter sulfurreducens. The materials produced, as measured by superconducting quantum interference device magnetometry, X-ray magnetic circular dichroism, Mössbauer spectroscopy, etc., show dramatic increases in coercivity with increasing cobalt content without a major decrease in overall saturation magnetization. Structural and magnetization analyses reveal a reduction in particle size to less than 4 nm at the highest Co content, combined with an increase in the effective anisotropy of the magnetic nanoparticles. The potential use of these biogenic nanoparticles in aqueous suspensions for magnetic hyperthermia applications is demonstrated. Further analysis of the distribution of cations within the ferrite spinel indicates that the cobalt is predominantly incorporated in octahedral coordination, achieved by the substitution of Fe(2+) site with Co(2+), with up to 17 per cent Co substituted into tetrahedral sites.

Arsenic release and attenuation in low organic carbon aquifer sediments from West Bengal.

High arsenic concentrations in groundwater are causing a humanitarian disaster in Southeast Asia. It is generally accepted that microbial activities play a critical role in the mobilization of arsenic from the sediments, with metal-reducing bacteria stimulated by organic carbon implicated. However, the detailed mechanisms underpinning these processes remain poorly understood. Of particular importance is the nature of the organic carbon driving the reduction of sorbed As(V) to the more mobile As(III), and the interplay between iron and sulphide minerals that can potentially immobilize both oxidation states of arsenic. Using a multidisciplinary approach, we identified the critical factors leading to arsenic release from West Bengal sediments. The results show that a cascade of redox processes was supported in the absence of high loadings of labile organic matter. Arsenic release was associated with As(V) and Fe(III) reduction, while the removal of arsenic was concomitant with sulphate reduction. The microbial populations potentially catalysing arsenic and sulphate reduction were identified by targeting the genes arrA and dsrB, and the total bacterial and archaeal communities by 16S rRNA gene analysis. Results suggest that very low concentrations of organic matter are able to support microbial arsenic mobilization via metal reduction, and subsequent arsenic mitigation through sulphate reduction. It may therefore be possible to enhance sulphate reduction through subtle manipulations to the carbon loading in such aquifers, to minimize the concentrations of arsenic in groundwaters.

Model system studies of the influence of bacterial biofilm formation on mineral surface reactivity.

Biofilm development on mineral surfaces and related changes in surface reactivity were studied using batch and flow through experiments. An artificial groundwater was used as the primary nutrient medium, Pseudomonas aeruginosa (PAO1) was the model microbial organism and 'mineral' surfaces were kept as simple as possible by using glass or a polished quartz tile. Experiments were also completed with very low concentrations (100 mg l(-1)) of iron, Fe(2+ ), in the solution. In situ confocal laser scanning microscopy of developing colonies during the live growth phase, and of thick, mature biofilms, revealed only sporadic coverage of biofilm cells and associated polymers at the 'mineral-microbe interface'. Imaging and analysis of biofilm-conditioned surfaces doped with Fe(2+ )-rich solutions allowed the locus and form of Fe-rich mineral precipitation to be determined and show that biological surface components can cause mineral precipitation from dilute dissolved species which might otherwise remain in solution.

Biomineralization: linking the fossil record to the production of high value functional materials.

The microbial cell offers a highly efficient template for the formation of nanoparticles with interesting properties including high catalytic, magnetic and light-emitting activities. Thus biomineralization products are not only important in global biogeochemical cycles, but they also have considerable commercial potential, offering new methods for material synthesis that eliminate toxic organic solvents and minimize expensive high-temperature and pressure processing steps. In this review we describe a range of bacterial processes that can be harnessed to make precious metal catalysts from waste streams, ferrite spinels for biomedicine and catalysis, metal phosphates for environmental remediation and biomedical applications, and biogenic selenides for a range of optical devices. Recent molecular-scale studies have shown that the structure and properties of bionanominerals can be fine-tuned by subtle manipulations to the starting materials and to the genetic makeup of the cell. This review is dedicated to the late Terry Beveridge who contributed much to the field of biomineralization, and provided early models to rationalize the mechanisms of biomineral synthesis, including those of geological and commercial potential.

Changes in arsenic speciation through a contaminated soil profile: a XAS based study.

An impacted soil located near an industrial waste site in the Massif Central near Auzon, France, where arsenical pesticides were manufactured, has been studied in order to determine the speciation (chemical forms) of arsenic as a function of soil depth. Bulk As concentrations range from 8780 mg kg(-1) in the topsoil horizon to 150 mg kg(-1) at 60 cm depth. As ores (orpiment As2S3, realgar AsS, arsenopyrite FeAsS) and former Pb- and Al-arsenate pesticides have been identified by XRD at the site and are suspected to be the sources of As contamination for this soil. As speciation was found to vary with depth, based on XRD, SEM-EDS, EPMA measurements and selective chemical extractions. Based on oxalate extraction, As is mainly associated with amorphous Fe oxides through the soil profile, except in the topsoil horizons where As is hosted by another phase. SEM-EDS and EPMA analyses led to the identification of arseniosiderite (Ca2Fe3+3(AsVO4)3O2.3H2O), a secondary mineral that forms upon oxidation of primary As-bearing minerals like arsenopyrite, in these topsoil horizons. These mineralogical and chemical results were confirmed by synchrotron-based X-ray absorption spectroscopy. XANES spectra of soil samples indicate that As occurs exclusively as As(V), and EXAFS results yield direct evidence of changes in As speciation with depth. Linear combination fits of EXAFS spectra of soil samples with those of various model compounds indicate that As occurs mainly As-bearing Fe(III)-(hydr)oxides (65%) and arseniosiderite (35%) in the topsoil horizon (0-5 cm depth). Similar analyses also revealed that there is very little arseniosiderite below 15 cm depth and that As(V) is associated primarily with amorphous Fe oxides below this depth. This vertical change of As speciation likely reflects a series of chemical reactions downward in the soil profile. Arseniosiderite, formed most likely by oxidation of arsenopyrite, is progressively dissolved and replaced by less soluble As-bearing poorly ordered Fe oxides, which are the main hosts for As in well aerated soils.

Oxygen therapy for cystic fibrosis.

BACKGROUND: The most serious complications of cystic fibrosis (CF) relate to respiratory insufficiency. Oxygen supplementation therapy has been a standard of care for individuals with chronic lung diseases associated with hypoxemia for decades. It is common for physicians to prescribe oxygen therapy for people with CF when hypoxemia occurs. However, it is unclear if empiric evidence is available to provide indications for this therapy with its financial costs and often profound impact on lifestyle. OBJECTIVES: To assess whether oxygen therapy improves the longevity or quality of life of individuals with CF. SEARCH STRATEGY: We searched the Cochrane Cystic Fibrosis and Genetic Disorders Group Trials Register, comprising references identified from comprehensive electronic database searches and handsearches of relevant journals and abstract books of conference proceedings. Most recent search of Group's Trials Register: April 2005. SELECTION CRITERIA: Randomized or quasi-randomized controlled trials comparing oxygen, administered at any concentration, by any route, in people with documented CF for any time period. DATA COLLECTION AND ANALYSIS: Two authors independently assessed study quality and extracted data. MAIN RESULTS: Nine published studies (149 participants) are included in this review, of which only one examined long-term oxygen therapy (28 participants). There was no statistically significant improvement in survival, lung, or cardiac health. Four studies examined the effect of oxygen supplementation during sleep by polysomnography. Although oxygenation improved, there were no demonstrable improvements in qualitative sleep parameters and modest hypoventilation was noted. In three studies, oxygen supplementation was evaluated during exercise. Hypoxemia was prevented, but mild hypercapnia resulted. Work performance was not improved, as measured in one study, but was improved in a second study. Furthermore, in two studies, exercise duration was enhanced by oxygen supplementation. In the study examining the impact of oxygen supplementation after exercise, recovery time was enhanced. AUTHORS' CONCLUSIONS: There are no published data to guide the prescription of chronic oxygen supplementation to people with advanced lung disease due to CF. Short-term oxygen therapy during sleep and exercise improves oxygenation but is associated with modest and probably clinically inconsequential hypercapnia. During exercise, there are improvements in exercise duration and peak performance. There is a need for larger, well-designed clinical trials to assess the benefits of long-term oxygen therapy in people with CF administered continuously or during exercise or sleep or both.

The effect of remifentanil on the middle latency auditory evoked response and haemodynamic measurements with and without the stimulus of orotracheal intubation.

BACKGROUND AND OBJECTIVE: Changes in the middle latency auditory evoked response following the administration of opioids have been shown. However, it remains unclear as to whether these changes are due to a direct depressant effect of opioids on the middle latency auditory evoked response itself, or an indirect effect on account of their action in attenuating central nervous system arousal associated with noxious stimuli. By comparing changes in the middle latency auditory evoked response in intubated and non-intubated patients, receiving saline or remifentanil in different doses, this study attempts to answer this question. METHODS: Fifty-four patients were anaesthetized with isoflurane and nitrous oxide (0.9 MAC) and randomized to 1-6 groups. Groups 1-3 received a bolus injection of either saline 0.9%, low-dose remifentanil (1 microg kg(-1)) or high-dose remifentanil (3 microg kg(-1)) prior to intubation of the trachea. Groups 4-6 were not intubated following the bolus injection. RESULTS: Pa and Nb amplitudes of the middle latency auditory evoked response increased by 82% and 79% with intubation in the saline group (P < 0.005) and these changes were not seen in the patients given remifentanil. There was a significant linear trend for the reduction in Pa and Nb amplitude with increasing remifentanil dose (P < 0.05). In the absence of endotracheal intubation remifentanil had no effect on either the amplitudes or latencies of the waves Pa and Nb and there was no effect of dose. For the haemodynamic measurements remifentanil attenuated the pressor response to intubation (P < 0.001) and had a significant dose-related effect (P < 0.001) in the absence of intubation. CONCLUSIONS: We demonstrated an effect of remifentanil on both the middle latency auditory evoked response and haemodynamic changes to endotracheal intubation. For the non-intubated patients there was only an effect of remifentanil on the haemodynamic measurements. This suggests that remifentanil has an effect on the middle latency auditory evoked response in attenuating the arousal associated with intubation of the trachea but has no effect in the absence of a stimulus.

Retained wooden foreign body in a child's thigh complicated by severe necrotizing fasciitis: a case report and discussion of imaging modalities for early diagnosis.

Soft tissue foreign bodies (FB) represent a common cause for emergency department visits. Diagnosis may be difficult especially with non-radiopaque FB. The clinical course may be complicated by superficial or deep tissue infection. Use of imaging modalities such as ultrasound may be important for early diagnosis. We report a case of retained foreign body with a complicated clinical course and discuss imaging modalities that may have aided in the early diagnosis.

Choice of opioid for initiation of combined spinal epidural analgesia in labour--fentanyl or diamorphine.

Sixty-two women requesting regional analgesia in labour were allocated to receive a 1.5 ml intrathecal injection as part of a combined spinal-epidural (CSE) analgesic technique. This contained either bupivacaine 2.5 mg plus fentanyl 25 microg (group F) or bupivacaine 2.5 mg plus diamorphine 250 microg (group D). Times of analgesic onset and offset were recorded, motor and proprioceptive assessments made and side-effects noted. Analgesic onset was not significantly different between the groups (group F, 8.0 min; group D, 9.5 min; P = 0.3) but time to first top-up request was significantly longer in the diamorphine group (group F, 73 min; group D, 101 min; P = 0.003). Motor loss, assessed by the modified Bromage score, was statistically but not clinically greater in the fentanyl group (P = 0.01). Maternal hypotension, pruritus, proprioceptive loss, nausea and fetal bradycardia were rare and not severe, and their incidences did not differ between groups. No respiratory depression was observed after CSE. This use of diamorphine was not associated with increased side-effects compared with fentanyl/bupivacaine, and it has a longer duration of action.

Effect of tramadol on electroencephalographic and auditory-evoked response variables during light anaesthesia.

Tramadol is a centrally acting opioid-like analgesic commonly used for analgesia during surgery. It has been stated that the use of tramadol increases the risk of awareness during anaesthesia. We studied 29 patients under steady state anaesthesia, ventilated via a laryngeal mask airway with 0.6 MAC isoflurane in 50% nitrous oxide, and with no surgical stimulus. The electroencephalogram (EEG) and auditory-evoked response (AER) were recorded throughout the study period, as were pulse and arterial pressure. Patients were given randomly a bolus of either saline (S), tramadol 100 mg (T1), or tramadol 200 mg (T2). Significant increases in systolic arterial pressure and decreases in heart rate were seen in the tramadol groups compared to the saline group. Significant, dose-related activation in all EEG variables (median power frequency, spectral edge, Delta Power and Alpha/Delta ratio) but no significant change in Pa or Nb amplitudes or latencies were noted. The EEG changes were not at levels thought to be associated with awareness. This study indicates that tramadol, whilst causing EEG activation, has no effect on depth of anaesthesia as measured by the AER.

Cranial subdural haematoma associated with dural puncture in labour.

A 23-yr-old primagravida sustained a dural puncture during epidural catheter insertion and developed a headache that settled with oral diclofenac and codydramol. On the third day after delivery, she convulsed twice without warning. As plasma urate was increased, the putative diagnosis of an eclamptic fit was made, and magnesium therapy was started. A contrast CT scan revealed that the cause of the patient's symptoms was a subdural haematoma with raised intracranial pressure. A coincidental arteriovenous malformation was noted. This case emphasises the need to consider the differential diagnoses of post-partum headache. The management of acute intracranial haematoma is described.