Two-shell structured PMAA@CeO2 nanocontainers loaded with 2-mercaptobenzothiazole for corrosion protection of damaged epoxy coated AA 2024-T3.

In this work, novel two-shell structured inhibitor-loaded poly(methacrylic acid)@cerium oxide (PMAA@CeO2) nanocontainers were synthesised and characterized. The purpose of the nanocontainers is to increase the corrosion protection provided by an epoxy coating applied to an aerospace alloy (AA 2024-T3). The (PMAA@CeO2) nanocontainers with diameters of 550 nm were synthesised by a four-step process with the method of distillation precipitation polymerization for the synthesis of the inner PMAA layer, and the sol-gel method for the development of the outer CeO2 layer. The loaded nanocontainers were characterized by scanning and transmission electron microscopies. The corrosion protection properties of the epoxy coated AA 2024-T3 with 2-mercaptobenzothiazole (2-MBT) loaded PMAA@CeO2 nanocontainers were evaluated with and without artificial scribes by electrochemical impedance spectroscopy (EIS). The results indicated that the epoxy coating containing the 2-MBT-loaded nanocontainers provided enhanced protection of the AA 2024-T3 substrate.

Broad ion beam serial section tomography.

Here we examine the potential of serial Broad Ion Beam (BIB) Ar+ ion polishing as an advanced serial section tomography (SST) technique for destructive 3D material characterisation for collecting data from volumes with lateral dimensions significantly greater than 100µm and potentially over millimetre sized areas. Further, the associated low level of damage introduced makes BIB milling very well suited to 3D EBSD acquisition with very high indexing rates. Block face serial sectioning data registration schemes usually assume that the data comprises a series of parallel, planar slices. We quantify the variations in slice thickness and parallelity which can arise when using BIB systems comparing Gatan PECS and Ilion BIB systems for large volume serial sectioning and 3D-EBSD data acquisition. As a test case we obtain 3D morphologies and grain orientations for both phases of a WC-11%wt. Co hardmetal. In our case we have carried out the data acquisition through the manual transfer of the sample between SEM and BIB which is a very slow process (1-2 slice per day), however forthcoming automated procedures will markedly speed up the process. We show that irrespective of the sectioning method raw large area 2D-EBSD maps are affected by distortions and artefacts which affect 3D-EBSD such that quantitative analyses and visualisation can give misleading and erroneous results. Addressing and correcting these issues will offer real benefits when large area (millimetre sized) automated serial section BIBS is developed.

Antibacterial and non-cytotoxic effect of nanocomposites based in polyethylene and copper nanoparticles.

In this study, an antibacterial, but not cytotoxic nanomaterial based on polyethylene and copper nanoparticles was prepared by in situ polymerization. PE-CuNps nanocomposites against Escherichia coli, completely suppressed the number of live bacteria after 12 h incubation compared to neat PE. TEM images showed that nanocomposites damage the plasma membrane of the bacteria, revealing a bacteriolytic effect. Toxic effects of copper nanoparticles on viability of neuroblastoma line cell also was evaluated, revealing a non cytotoxic effect for the doses used, showing that this nanocomposite is a ideal material for medical devices.

Revelation of intertwining organic and inorganic fractal structures in polymer coatings.

X-ray microtomography and serial block face scanning electron microscopy are used to reveal independent clusters of inorganic particles embedded within a polymer. These clusters are interpenetrating, of varying size, and have fractal dimensions that strongly influence transport and structure-property relations. This interpretation forms a baseline for designing hybrid materials for applications in self-healing, drug delivery, and membranes.

Release of silver and copper nanoparticles from polyethylene nanocomposites and their penetration into Listeria monocytogenes.

Since infection is a major cause of death in a patient whose immune responses have been compromised (immunocompromised patient), considerable attention has been focused on developing materials for the prevention of infections. This has been directed primarily at suppressing or eliminating the host's endogenous microbial burden and decreasing the acquisition of new organisms. In this study, the antibacterial properties of two nanocomposites, polyethylene modified with silver nanoparticles (PE-AgNps) or copper nanoparticles (PE-CuNps), against Listeria monocytogenes have been investigated. In order to elucidate the antibacterial mechanism, specifically whether this mechanism corresponds to bactericidal or bacteriolytic activities, we have determined the extent of release of metal ions (Ag(+) and Cu(2+)) and, also, the morphology of the bacteria. The metal ion release from nanocomposites was followed by inductively coupled plasma spectrometry and the morphology of the bacteria was revealed through examination of ultramicrotomed sections of bacteria in a transmission electron microscope. The study of metal ion release from the nanocomposites shows that for both nanocomposites the amount of ions released varies with time, which initially displays a linear behavior until an asymptotic behavior is reached. Further, TEM images show that silver nanoparticles (AgNps) and copper nanoparticles (CuNps), which are released from the nanocomposites, can penetrate to the cell wall and the plasma membrane of bacteria. Resulting morphological changes involve separation of the cytoplasmic membrane from the cell wall, which is known to be an effect of plasmolysis. It was revealed that the antibacterial abilities of the two nanocomposites against L. monocytogenes are associated with both bactericidal and bacteriolytic effects.

Correlative tomography.

Increasingly researchers are looking to bring together perspectives across multiple scales, or to combine insights from different techniques, for the same region of interest. To this end, correlative microscopy has already yielded substantial new insights in two dimensions (2D). Here we develop correlative tomography where the correlative task is somewhat more challenging because the volume of interest is typically hidden beneath the sample surface. We have threaded together x-ray computed tomography, serial section FIB-SEM tomography, electron backscatter diffraction and finally TEM elemental analysis all for the same 3D region. This has allowed observation of the competition between pitting corrosion and intergranular corrosion at multiple scales revealing the structural hierarchy, crystallography and chemistry of veiled corrosion pits in stainless steel. With automated correlative workflows and co-visualization of the multi-scale or multi-modal datasets the technique promises to provide insights across biological, geological and materials science that are impossible using either individual or multiple uncorrelated techniques.

Calcium and titanium release in simulated body fluid from plasma electrolytically oxidized titanium.

The release of titanium and calcium species to a simulated body fluid (SBF) at 37 degrees C has been investigated for titanium treated by dc plasma electrolytic oxidation (PEO) in three different electrolytes, namely phosphate, silicate and calcium- and phosphorus-containing. The average rate of release of titanium over a 30 day period in immersion tests, determined by solution analysis, was in the range approximately 1.5-2.0 pg cm(-2) s(-1). Calcium was released at an average rate of approximately 11 pg cm(-2) s(-1). The passive current densities, determined from potentiodynamic polarization measurements, suggested titanium losses of a similar order to those determined from immersion tests. However, the possibility of film formation does not allow for discrimination between the metal releases due to electrochemical oxidation of titanium and chemical dissolution of the coating.

Dye-sensitization of self-assembled titania nanotubes prepared by galvanostatic anodization of Ti sputtered on conductive glass.

Self-organized porous TiO(2) nanotubes (NTs) were prepared on conductive glass by galvanostatic anodizing of sputtered titanium in an NH(4)F /glycerol electrolyte. DC magnetron sputtering at an elevated substrate temperature (500 degrees C) was used to deposit 650 nm thick titanium films. After anodizing, NTs, 830 nm long, with an average external diameter of 92 nm, were grown; this gave a high conversion rate of oxide from titanium (1.9), with a 220 nm thick layer of titanium, which was not oxidized, located at the base of the tubes. The NTs revealed a mainly amorphous structure, which transformed mostly to anatase upon thermal treatment in air at 450 degrees C. The tubes were sensitized by the N719 complex and the resultant photoelectrodes were incorporated into liquid dye solar cells (DSCs) and further tested under back-side illumination. High values of V(oc) (714 mV) were obtained under 1 sun (AM 1.5), assigned to low dark current magnitude and large recombination resistance and electron lifetime. In addition, typical values of fill factors (of the order of 0.62) were attained, in agreement with the estimated ohmic resistance of the cells in combination with low electron transfer resistance at the platinum/electrolyte interface. The overall moderate power conversion efficiency (of the order of 0.3%) was mainly due to the low short-circuit photocurrents (J(sc) = 0.68 mA cm(-2)), which was confirmed further by the corresponding IPCE values (5.2% at 510 nm). The magnitude of J(sc) was attributed to absorbed light losses due to back-side illumination of the cells, the low dye loading (due to the limited thickness of anodic titania) and the high charge transfer resistance at the TiO(2)/conductive substrate due to the presence of barrier layer(s) underneath the tubes. These preliminary results encourage the DSC community to explore further the galvanostatic anodizing of titanium in order to produce highly efficient porous TiO(2) NTs directly on conductive glass. Current work is focusing on achieving complete anodizing of the metal substrate and full transparency for the photoelectrode in order to increase and optimize the resultant cell efficiencies.

Conical tungsten stamps for the replication of pore arrays in anodic aluminium oxide films.

A tungsten master stamp has been generated by applying a novel procedure that includes two-step anodizing, followed by sequential anodizing and pore widening to develop nominally funnelled pores. These conical-shaped pores were filled with tungsten by sputter coating to manufacture a master stamp. Under a pressure of 65 MPa, the master stamp successfully embossed the surface of annealed and electropolished aluminium. The embossed surface was then used to control the position of pores created by anodizing under the conditions used to produce the original pore array.

Transmission electron microscopy of coatings formed by plasma electrolytic oxidation of titanium.

Transmission electron microscopy and supporting film analyses are used to investigate the changes in composition, morphology and structure of coatings formed on titanium during DC plasma electrolytic oxidation in a calcium- and phosphorus-containing electrolyte. The coatings are of potential interest as bioactive surfaces. The initial barrier film, of mixed amorphous and nanocrystalline structure, formed below the sparking voltage of 180 V, incorporates small amounts of phosphorus and calcium species, with phosphorus confined to the outer approximately 63% of the coating thickness. On commencement of sparking, calcium- and phosphorus-rich amorphous material forms at the coating surface, with local heating promoting crystallization in underlying and adjacent anodic titania. The amorphous material thickens with increased treatment time, comprising almost the whole of the approximately 5.7-microm-thick coating formed at 340 V. At this stage, the coating is approximately 4.4 times thicker than the oxidized titanium, with a near-surface composition of about 12 at.% Ti, 58 at.% O, 19 at.% P and 11 at.% Ca. Further, the amount of titanium consumed in forming the coating is similar to that calculated from the anodizing charge, although there may be non-Faradaic contributions to the coating growth.

Synthesis of malachite nanoparticles and their evolution during transmission electron microscopy.

Malachite nanoparticles have been synthesized utilising the polyol-mediated synthesis. Reaction of copper sulphate with sodium carbonate in ethylene glycol medium results in the formation of malachite nanoparticles of sub-10 nm dimensions. The structure of malachite in the synthesized product was confirmed by X-ray diffraction and FTIR spectroscopy. Examination by high-resolution transmission electron microscopy revealed that nanoparticles are thermally decomposed to Cu(2)O and copper during exposure to the electron beam.

The efficiency of nanotube formation on titanium anodized under voltage and current control in fluoride/glycerol electrolyte.

The formation of nanotubes on titanium is compared for anodizing under controlled voltage and controlled current in a fluoride/glycerol electrolyte. Rutherford backscattering spectroscopy and nuclear reaction analysis are employed to determine the film compositions. Film morphologies are examined by electron microscopy. The findings reveal films of approximate composition TiO(2).0.15TiF(4) that probably also contain derivatives of glycerol. Controlled voltage conditions resulted in more uniform final nanotube dimensions, for a particular charge density, and the highest efficiency of film growth, with the charge of the titanium in the film representing ∼48% of the charge passed during anodizing. Under current control, the efficiency decreased from ∼40% to ∼23% with increase of the current density from 0.1 to 0.5 mA cm(-2). Further, the thickness of the barrier layer was sometimes enhanced under current control, possibly due to a non-uniform current distribution and consequently elevated local temperature.

Mineralogical study of salt crusts formed on historic building stones.

A historic building stone, Baumberger sandstone, was exposed to gaseous SO(2) under dry and wet surface conditions in an atmospheric test chamber. The extent of salt formation resulting from the exposure to pollutant gases as well as the variations in mineralogical composition were studied based on petrological thin sections. Results reveal that the salts are formed only over the surface of the sample. The thickness of the formed salt crusts is determined. Calcite dissolution as well as porosity decreases are due to gypsum formation.

A comparison of epidural levobupivacaine 0.75% with racemic bupivacaine for lower abdominal surgery.

UNLABELLED: Levobupivacaine, the S(-) isomer of bupivacaine, is less cardiotoxic than racemic bupivacaine. In this prospective, randomized, double-blinded study of epidural anesthesia, the onset, extent, and duration of sensory and motor block produced by 0.75% levobupivacaine (20 mL, 150 mg) was compared with that of 0.75% racemic bupivacaine in 56 patients undergoing elective lower abdominal surgery. The time to onset of adequate sensory block (T10 dermatome) was similar in both treatment groups (13.6 +/- 5.6 min for levobupivacaine and 14.0 +/- 9.9 min for bupivacaine), with an average peak block height of T5 reached at 24.3 +/- 9.4 and 26.5 +/- 13.2 min, respectively. Time to complete regression of sensory block was significantly longer with levobupivacaine (550.6 +/- 87.6 min) than bupivacaine (505.9 +/- 71.1 min) (P = 0.016). Abdominal muscle relaxation was adequate for the scheduled procedure in all patients, and there were no significant differences between the groups in rectus abdominis muscle scores (P = 0.386) and quality of muscle relaxation as determined by the surgeon and anesthesiologist (P = 0. 505 and 0.074, respectively). In conclusion, both 0.75% levobupivacaine and 0.75% bupivacaine produced effective epidural anesthesia and their effects were clinically indistinguishable. IMPLICATIONS: The results of this study indicate that the sensory and motor block produced by 0.75% levobupivacaine is equivalent to that of 0.75% racemic bupivacaine. Both local anesthetics are well tolerated and effective in producing epidural anesthesia for patients undergoing lower abdominal surgery.

Commentary: neurotoxicity of local anesthetics--an issue or a scapegoat?

BACKGROUND AND OBJECTIVES: To evaluate the etiologies of cauda equina syndrome (CES) and transient radicular irritation (TRI) or transient neurologic symptoms (TNSs) following hyperbaric spinal anesthesia. METHODS: A review of recent (since 1991) and prior (since 1941) investigations regarding CES and TRI (TNSs) was conducted. RESULTS: Recent publications fail to recognize significant prior information regarding CES and TRI (TNSs). CONCLUSIONS: Cauda equina syndrome is, in all probability, explainable. Further investigation to pinpoint the etiology of TRI (TNSs) is needed.

Microsatellite deletion mapping on chromosome 10q and mutation analysis of MMAC1, FAS, and MXI1 in human glioblastoma multiforme.

Glioblastoma multiforme (GBM) is an end-stage brain tumor of glial origin. Allelic deletions encompassing all or part of chromosome 10q occur frequently in GBMs, indicating that loss of one or more tumor suppressor genes on 10q plays a role in GBM formation. One of these genes is MMAC1 (PTEN), a gene on 10q23 which encodes a dual-specificity protein phosphatase. We carried out a loss of heterozygosity (LOH) analysis of 66 GBM patients using microsatellite markers for 27 loci on 10q. Overall, LOH was detected in 70% of cases, most showing LOH with every informative marker. Eleven patients showed partial 10q deletions, the smallest spanning a 35 cM region distal to D10S187. Sequence analysis of the MMAC1 gene in 45 of these tumors revealed mutations in eleven cases (24%), all with LOH on 10q. None of these mutations was present in normal DNA from the same patients. In addition, we utilized SSCP analysis to test two other candidate genes on 10q: FAS, a cell surface receptor which transduces an apoptotic, cell death signal and MXI1, a transcriptional repressor. The absence of mutations in these genes suggested that FAS and MXI1 are not likely to be tumor suppressor genes physiologically relevant to GBM. These data do support a significant role for MMAC1 in GBM.