Cinematic reflectometry using QIKR, the quite intense kinetics reflectometer.

The Quite Intense Kinetics Reflectometer (QIKR) will be a general-purpose, horizontal-sample-surface neutron reflectometer. Reflectometers measure the proportion of an incident probe beam reflected from a surface as a function of wavevector (momentum) transfer to infer the distribution and composition of matter near an interface. The unique scattering properties of neutrons make this technique especially useful in the study of soft matter, biomaterials, and materials used in energy storage. Exploiting the increased brilliance of the Spallation Neutron Source Second Target Station, QIKR will collect specular and off-specular reflectivity data faster than the best existing such machines. It will often be possible to collect complete specular reflectivity curves using a single instrument setting, enabling "cinematic" operation, wherein the user turns on the instrument and "films" the sample. Samples in time-dependent environments (e.g., temperature, electrochemical, or undergoing chemical alteration) will be observed in real time, in favorable cases with frame rates as fast as 1 Hz. Cinematic data acquisition promises to make time-dependent measurements routine, with time resolution specified during post-experiment data analysis. This capability will be deployed to observe such processes as in situ polymer diffusion, battery electrode charge-discharge cycles, hysteresis loops, and membrane protein insertion into lipid layers.

Revealing interfacial disorder at the growth-front of thick many-layer epitaxial graphene on SiC: a complementary neutron and X-ray scattering investigation.

Epitaxial graphene on SiC provides both an excellent source of high-quality graphene as well as an architecture to support its application. Although single-layer graphene on Si-face SiC has garnered extensive interest, many-layer graphene produced on C-face SiC could be significantly more robust for enabling applications. Little is known, however, about the structural properties related to the growth evolution at the buried interface for thick many-layer graphene. Using complementary X-ray scattering and neutron reflectivity as well as electron microscopy, we demonstrate that thick many-layer epitaxial graphene exhibits two vastly different length-scales of the buried interface roughness as a consequence of the Si sublimation that produces the graphene. Over long lateral length-scales the roughness is extremely large (hundreds of Å) and it varies proportionally to the number of graphene layers. In contrast, over much shorter lateral length-scales we observe an atomically abrupt interface with SiC terraces. Graphene near the buried interface exhibits a slightly expanded interlayer spacing (∼1%) and fluctuations of this spacing, indicating a tendency for disorder near the growth front. Nevertheless, Dirac cones are observed from the graphene while its domain size routinely reaches micron length-scales, indicating the persistence of high-quality graphene beginning just a short distance away from the buried interface. Discovering and reconciling the different length-scales of roughness by reflectivity was complicated by strong diffuse scattering and we provide a detailed discussion of how these difficulties were resolved. The insight from this analysis will be useful for other highly rough interfaces among broad classes of thin-film materials.

Ferroelectric Control of Interface Spin Filtering in Multiferroic Tunnel Junctions.

The electronic reconstruction occurring at oxide interfaces may be the source of interesting device concepts for future oxide electronics. Among oxide devices, multiferroic tunnel junctions are being actively investigated as they offer the possibility to modulate the junction current by independently controlling the switching of the magnetization of the electrodes and of the ferroelectric polarization of the barrier. In this Letter, we show that the spin reconstruction at the interfaces of a La_{0.7}Sr_{0.3}MnO_{3}/BaTiO_{3}/La_{0.7}Sr_{0.3}MnO_{3} multiferroic tunnel junction is the origin of a spin filtering functionality that can be turned on and off by reversing the ferroelectric polarization. The ferroelectrically controlled interface spin filter enables a giant electrical modulation of the tunneling magnetoresistance between values of 10% and 1000%, which could inspire device concepts in oxides-based low dissipation spintronics.

Biosynthesis of 1α-hydroxycorticosterone in the winter skate Leucoraja ocellata: evidence to suggest a novel steroidogenic route.

The present study explores the ability of intracellular bacteria within the renal-inter-renal tissue of the winter skate Leucoraja ocellata to metabolize steroids and contribute to the synthesis of the novel elasmobranch corticosteroid, 1α-hydroxycorticosterone (1α-OH-B). Despite the rarity of C1 hydroxylation noted in the original identification of 1α-OH-B, literature provides evidence for steroid C1 hydroxylation by micro-organisms. Eight ureolytic bacterial isolates were identified in the renal-inter-renal tissue of L. ocellata, the latter being the site of 1α-OH-B synthesis. From incubations of bacterial isolates with known amounts of potential 1α-OH-B precursors, one isolate UM008 of the genus Rhodococcus was seen to metabolize corticosteroids and produce novel products via HPLC analysis. Cations Zn2+ and Fe3+ altered metabolism of certain steroid precursors, suggesting inhibition of Rhodococcus steroid catabolism. Genome sequencing of UM008 identified strong sequence and structural homology to that of Rhodococcus erythropolis PR4. A complete enzymatic pathway for steroid-ring oxidation as documented within other Actinobacteria was identified within the UM008 genome. This study highlights the potential role of Rhodococcus bacteria in steroid metabolism and proposes a novel alternative pathway for 1α-OH-B synthesis, suggesting a unique form of mutualism between intracellular bacteria and their elasmobranch host.

Probing the spiral magnetic phase in 6 nm textured erbium using polarised neutron reflectometry.

We characterise the magnetic state of highly-textured, sputter deposited erbium for a film of thickness 6 nm. Using polarised neutron reflectometry it is found that the film has a high degree of magnetic disorder, and we present some evidence that the film's local magnetic state is consistent with bulk-like spiral magnetism. This, combined with complementary characterisation techniques, show that thin film erbium is a strong candidate material for incorporation into device structures.

Strain dependent selection of spin-slip phases in sputter deposited thin-film epitaxial holmium.

We report the structural and magnetic characterization of sputter deposited epitaxial Ho. We present room temperature characterization by atomic force microscopy and x-ray diffraction and temperature dependent characterization by x-ray diffraction and neutron diffraction. The data show the onset and change of the magnetic state as a function of temperature. Films of different thickness, exhibiting signs of differing epitaxially induced strain, tend towards specific spin-slip phases in the low temperature regime. The more highly strained thinnest films tend towards values with a longer magnetic wavelength.

Biotechnological uses of enzymes from psychrophiles.

The bulk of the Earth's biosphere is cold (e.g. 90% of the ocean's waters are ≤ 5°C), sustaining a broad diversity of microbial life. The permanently cold environments vary from the deep ocean to alpine reaches and to polar regions. Commensurate with the extent and diversity of the ecosystems that harbour psychrophilic life, the functional capacity of the microorganisms that inhabitat the cold biosphere are equally diverse. As a result, indigenous psychrophilic microorganisms provide an enormous natural resource of enzymes that function effectively in the cold, and these cold-adapted enzymes have been targeted for their biotechnological potential. In this review we describe the main properties of enzymes from psychrophiles and describe some of their known biotechnological applications and ways to potentially improve their value for biotechnology. The review also covers the use of metagenomics for enzyme screening, the development of psychrophilic gene expression systems and the use of enzymes for cleaning.

Biofilm removal by medical device cleaners: comparison of two bioreactor detection assays.

Currently there are no standards for testing efficacy of medical device cleaners. With fears of prion transmission, residual protein on medical devices needs to be minimised. A bioreactor model was used to grow Pseudomonas aeruginosa biofilm on polytetrafluoroethylene coupons. The biofilm was subjected to various cleaners and residual biofilm was detected either by Crystal Violet assay (CrV) or a commercially available protein assay (PA) following hydrolysis of the biofilm. Percentage reduction of biofilm was compared with untreated controls in three independent tests. There was no significant difference in percentage biofilm reduction irrespective of whether the CrV or PA was used to detect residual biofilm. Processing of coupons attached to the bioreactor rod and position of coupon within the rod had no significant effect on cleaning efficiency or detection of residual biofilm. Both within-run and between-run variation was very low for good cleaners such as 10g/L NaOH, Zen, and 3M Rapid Multi-Enzyme Cleaner (RMEC) 70500 but was higher for poor cleaners such as Tween 20 which removed less than 20% of the biofilm. Confocal microscopy and electron microscopy provided visual confirmation of the assay results. We propose that this method is suitable as a test method for evaluating the efficacy of surgical instrument cleaners in removing biofilm, as both within-run and between-run variation was low, detection of residual biofilm can be done using either CrV or PA, and the apparatus is easy to use, cheap and readily available.

Perpendicular antiferromagnetic ordering of Mn and exchange anisotropy in Fe/Mn multilayers.

Fe/Mn is a model system in which to study exchange bias, since the antiferromagnetic (AF) Mn layers are believed to have uncompensated moments with all spins aligned in the plane and parallel to those of the Fe. We have determined the microscopic AF ordering at the interfaces using single-crystal neutron diffraction. An unexpected magnetic structure is obtained, with out-of-plane Mn moments perpendicular to those of Fe. This explains the low bias field and shows that the simple AF ordering assumed in a variety of exchange-biased systems may well have to be revised.

Rotator cuff repair as an outpatient procedure.

The purpose of this study was to evaluate outpatient rotator cuff repair on the basis of patient satisfaction, pain control, early postoperative complications, and cost control. Patients were considered good candidates for an outpatient repair if they were in good health and had adequate support at home. Seventy-five rotator cuff repairs were performed on an outpatient basis. The average age of the patients was 58 years. Patients with tears smaller than 2 cm in diameter were excluded. Postoperative pain was managed effectively in 74 of 75 outpatients. There were no cases of deltoid origin compromise, deep infection, or early failure of repair, and no outpatient required readmission to the hospital. This study demonstrates that outpatient rotator cuff repair is possible in the appropriately selected patient and can be performed safely and effectively with a 43% reduction in overall cost.

A novel and sensitive method for the quantification of N-3-oxoacyl homoserine lactones using gas chromatography-mass spectrometry: application to a model bacterial biofilm.

A method is reported for the quantification of 3-oxoacyl homoserine lactones (3-oxo AHLs), a major class of quorum-sensing signals found in Gram-negative bacteria. It is based on the conversion of 3-oxo AHLs to their pentafluorobenzyloxime derivatives followed by gas chromatography-mass spectrometry (electron capture-negative ion). The method used [13C16]-N-3-oxo-dodecanoyl homoserine lactone ([13C16]-OdDHL) as the internal standard, and its validity was tested by spiking the supernatant and cell fractions with three levels of 3-oxo AHLs, i.e. 1, 10 and 100 ng per sample. These showed the method to be both sensitive (S/N ratio >10:1 for 1 ng) and accurate. The assay was applied to the biofilm and effluent of a green fluorescent protein (GFP)-expressing strain of Pseudomonas aeruginosa (6294) culture grown in flow cells. Biofilm volume was determined for three replicate flow cells by confocal scanning laser microscopy. OdDHL was detected in the biofilm at 632 +/- 381 microM and the effluent at 14 +/- 3 nM. The biofilm concentration is the highest level so far reported for an AHL in a wild-type bacterial system. The next most abundant 3-oxo AHL in the biofilm and effluent was N-3-oxo-tetradecanoyl homoserine lactone (OtDHL) at 40 +/- 15 microM and 1.5 +/- 0.7 nM respectively. OtDHL is unreported for P. aeruginosa and has an activity equivalent to OdDHL in a lasR bioassay. Two other 3-oxo AHLs were detected at lower concentrations: N3-oxo-decanoyl homoserine lactone (ODHL) in the biofilm (3 +/- 2 microM) and effluent (1 +/- 0.1 nM); and N-3-oxo-octanoyl homoserine lactone (OOHL) in the effluent (0.1 +/- 0.1 nM).

A covalent thymine-tyrosine adduct involved in DNA-protein crosslinks: synthesis, characterization, and quantification.

A thymine-tyrosine adduct, (3-[(1,3-dihydro-2,4-dioxopyrimidin-5-yl)methyl]-L-tyrosine), was synthesized using a simple, single-step condensation between 5-(hydroxymethyl)uracil and L-tyrosine. This approach provides access to useful quantities (mg-g) of analytically pure reference material, and with minor modification, to stable isotope-labeled analogues (isotopomers). With reference material and a suitable internal standard available, isotope-dilution liquid chromatography-electrospray ionization-tandem mass spectrometry (LC/MS/MS) was used to assay the adduct in a model system purged of oxygen, i.e., a gamma-irradiated N2O-saturated aqueous solution of thymine and tyrosine. The convenient synthetic route to standards and the method for quantification reported here will prove useful in assessing the significance of the adduct in biological systems. These studies also highlight the potential for artefactual adduct formation if the appropriate substrates are present under acidic conditions.

Extracellular signal molecule(s) involved in the carbon starvation response of marine Vibrio sp. strain S14.

The role of exogenous metabolites as putative signal molecules mediating and/or regulating the carbon starvation adaptation program in Vibrio sp. strain S14 was investigated. Addition of the stationary-phase supernatant extract (SSE) of Vibrio sp. strain S14 to logarithmic-phase cells resulted in a significant number of carbon starvation-induced proteins being up-regulated. Halogenated furanones, putative antagonists of acylated homoserine lactones (AHLs), inhibited the synthesis of proteins specifically induced upon carbon starvation. The effect of the furanone was the opposite of that caused by SSE with respect to the up- and down-regulation of protein expression, indicating that both the furanone and the putative signalling molecules were acting on the same regulatory pathway. Culturability was rapidly lost when Vibrio sp. strain S14 was starved in the presence of the furanone at a low concentration. The furanone also had a negative effect on the ability of carbon-starved cells to mount resistance against UV irradiation and hydrogen peroxide exposure. The SSE of Vibrio sp. strain S14 had the ability to provide cross-protection against the loss in viability caused by the furanone. We have further demonstrated that the SSE taken from low- as well as high-cell-density cultures of Vibrio sp. strain S14 induced luminescence in Vibrio harveyi. Taken together, the results in this report provide evidence that Vibrio sp. strain S14 produces extracellular signalling metabolites during carbon and energy starvation and that these molecules play an important role in the expression of proteins crucial to the development of starvation- and stress-resistant phenotypes.

Reproaching television for violence in society: passing the buck? Interim results from a naturalistic study in St Helena, South Atlantic.

This article refers to a naturalistic study of broadcast television's effects upon the social behaviour of young pupils in St Helena, South Atlantic. Interim findings showed that 2 years after the availability of television, the good behaviour noted before television arrived had been maintained. Explanations for the continuance of good behaviour focuses upon the attributes of watchfulness and care which Islanders exercise over others.

Teachers' ratings of nursery class children's behaviour before and after availability of television by satellite.

Teachers rated children's behaviour in two nursery class cohorts on St. Helena, South Atlantic Ocean. Ratings were obtained for the 1993 cohort (n = 54) prior to the availability of satellite television and the 1995 cohort (n = 57) after the introduction of television. Analysis showed some reductions in ratings of children's adaptive behaviour after the availability of television.

Rates of problem behaviour among preschoolers attending nursery classes in St. Helena, South Atlantic.

The Preschool Behaviour Checklist was used to assess rates of problem behaviour among 59 preschoolers on St. Helena. The prevalence rate (6.8%) and mean scores obtained are among the lowest found world-wide for similarly aged children.