Cannabis use, cognitive performance and mood in a sample of workers.

There are well documented acute and chronic effects of cannabis use on mental functioning. However, less is known about any effects on cognition within the context of work and everyday life. The aim of the study was to examine any association between cannabis use and cognitive performance, mood and human error at work. Cannabis users and controls completed a battery of laboratory based computer tasks measuring mood and cognitive function pre- and post-work at the start and end of a working week. They also completed daily diaries reporting their work performance. Cannabis use was associated with impairment in both cognitive function and mood, though cannabis users reported no more workplace errors than controls. Cannabis use was associated with lower alertness and slower response organization. In addition, users experienced working memory problems at the start, and psychomotor slowing and poorer episodic recall at the end of the working week. This pattern of results suggests two possible effects. First a 'hangover'-type effect which may increase with frequency of use. Second a subtle effect on cognitive function, perhaps more apparent under cognitive load and/or fatigue, which may increase with more prolonged use. The results also highlight the importance of the timing of testing within the context and routine of everyday life.

A community based investigation of the association between cannabis use, injuries and accidents.

There are well documented acute and chronic effects of cannabis use. However, less is known about any effects on safety within the context of work and everyday life. The aim of the study was to examine any association between cannabis use and injuries and accidents. A postal questionnaire survey was conducted among people selected at random from the electoral registers of Cardiff and Merthyr Tydfil. Cannabis use was associated with both minor injuries and accidents, particularly among those with high levels of other associated risk factors. Cannabis use was associated with a significant detrimental impact on safety. It is possible that this is linked to an amplification of other risk factors associated with accidents and injuries. This has potentially wide reaching implications particularly in the context of other work and lifestyle characteristics.

Structural properties of molten dilute aluminium-transition metal alloys.

The short-range order in liquid binary Al-rich alloys (Al-Fe, Al-Ti) was studied by x-ray diffraction. The measurements were performed using a novel containerless technique which combines aerodynamic levitation with inductive heating. The average structure factors, S(Q), have been determined for various temperatures and compositions in the stable liquid state. From S(Q), the pair correlation functions, g(r), have been calculated. The first interatomic distance is nearly temperature-independent, whereas the first-shell coordination number decreases with increasing temperature for all the alloys investigated. For the Al-Fe alloys, room-temperature scanning electron microscropy (SEM) studies show the formation of a microstructure, namely the existence of Al(13)Fe(4) inclusions in the Al matrix.

Morphological instability in InAs/GaSb superlattices due to interfacial bonds.

Synchrotron x-ray diffraction is used to compare the misfit strain and composition in a self-organized nanowire array in an InAs/GaSb superlattice with InSb interfacial bonds to a planar InAs/GaSb superlattice with GaAs interfacial bonds. It is found that the morphological instability that occurs in the nanowire array results from the large misfit strain that the InSb interfacial bonds have in the nanowire array. Based on this result, we propose that tailoring the type of interfacial bonds during the epitaxial growth of III-V semiconductor films provides a novel approach for producing the technologically important morphological instability in anomalously thin layers.

Psychotropic medication use and accidents, injuries and cognitive failures.

BACKGROUND: Psychotropic medication has the potential to impair psychomotor and cognitive function, and several medications have well documented links to increased accident and injury susceptibility. Those developed more recently have many fewer side effects. However, there is little work examining any association between psychotropic medication use and safety within the context of other demographic, health and lifestyle factors. AIMS: To examine and compare any associations between psychotropic medication use (including benzodiazepines, tricyclics and SSRIs) and accidents, injuries and cognitive failures in a community sample. METHODS: A postal questionnaire survey was conducted among people selected at random from the electoral registers of Cardiff and Merthyr Tydfil. RESULTS: Psychotropic medication use was associated with accidents, injuries and cognitive failures, particularly among those who already had higher levels of other risk factors and/or continuing mental health problems. CONCLUSIONS: The well established associations between accidents and injuries and older psychotropic medications were replicated. SSRIs, however, were relatively safer. The study also highlighted the need to consider any effect of psychotropic medication within the context of both mental health status and other factors.

Four-unit-cell superstructure in the optimally doped YBa2Cu3O6.92 superconductor.

Diffuse x-ray scattering measurements reveal that the optimally doped YBa2Cu3O6.92 superconductor is intrinsically modulated due to the formation of a kinetically limited 4-unit-cell superlattice, q(0)=(1/4, 0, 0), along the shorter Cu-Cu bonds. The superlattice consists of large anisotropic displacements of Cu, Ba, and O atoms, respectively, which are correlated over approximately 3-6 unit cells in the ab plane, and appears to be consistent with the presence of an O-ordered "ortho-IV" phase. Long-range strains emanating from these modulated regions generate an inhomogeneous lattice which may play a fundamentally important role in the electronic properties of yttrium-barium-copper-oxides.

Layer ordering and faulting in (GaAs)n/(AlAs)n ultrashort-period superlattices.

We report studies of (GaAs)(n)/(AlAs)(n) ultrashort-period superlattices using synchrotron x-ray scattering. In particular, we demonstrate that interfaces of these superlattices contain features on two different length scales: namely, random atomic mixture and ordered mesoscopic domains. Both features are asymmetric on the two interfaces (AlAs-on-GaAs and GaAs-on-AlAs) for n>2. Periodic compositional stacking faults, arising from the intrinsic nature of molecular-beam epitaxy, are found in the superlattices. In addition, the effect of growth interruption on the interfacial structure is discussed. The relevant scattering theory is developed to give excellent fits to the data.

The Bristol Stress and Health Study: accidents, minor injuries and cognitive failures at work.

BACKGROUND: Accidents and injuries at work account for several million working days lost each year. Cognitive failures (problems of memory, attention or action) can lead to accidents and injuries in certain contexts. AIM: This work describes the prevalence and associations of workplace accidents, minor injuries and cognitive failures reported by respondents to a follow-up postal questionnaire as part of the community-based Bristol Stress and Health Study. METHODS: Postal questionnaires were sent to 4673 people who participated in the first phase of the study (in which questionnaires were sent to individuals selected at random from the electoral roll). RESULTS: Four per cent of workers reported an accident at work, 8% reported quite or very frequent minor injuries and 13% reported quite or very frequent cognitive failures. Accidents at work were associated with being male, smoking and higher negative job characteristics. Respondents reported workplace accidents at a level similar to the overall UK rate. Accidents and minor injuries, and minor injuries and cognitive failures, shared common associations and all three outcomes were associated with each other. CONCLUSION: Information about cognitive failures is important in the study of accidents and injuries at work. In addition, negative job characteristics represent part of the context in which human error is translated into injury.

An experimental determination of FIDLER scanning efficiency at specific speeds.

As part of mass remediation efforts across the country some radiation detection systems are now being used in conjunction with data logging and positioning system technology. These systems can be used in the scanning mode, simultaneously recording both count rate and position. Following data analysis, hot spots can be identified and remediation efforts for that particular area can commence. This technique has been used for nearly a decade and has had success in accelerating preliminary remediation work while also reducing potential clean up costs. However, little work has been completed on how the sensitivity of these detection systems are affected when used with this technology because while the intrinsic efficiency of the detector is constant, scanning efficiency can vary depending on data sampling time and scanning speed. To better understand scanning efficiency for a detector attached to such a system, a device was developed which moved soil at a constant speed underneath a Field Instrument for Detecting Low Energy Radiation (FIDLER). Count rate was measured every 2 s as a 241Am source passed under the detector at speeds ranging from approximately 10 cm s(-1) to 100 cm s(-1). A surface source and a buried source were both examined. Experimental detection efficiency was calculated and compared to Monte Carlo generated results. For the surface source, the efficiency dropped to a value of approximately 1% at 100 cm s(-1). At the same speed, the buried source had a detection efficiency of 0.1%, primarily due to attenuation of the low energy photon in the soil. It was also noted that the response time of the meter affected the scanning efficiency. With a response time set at 1 s, higher average efficiencies were recorded but with a large standard deviation from the mean. Higher response time setting had the effect of reducing the variability of the reading but also reducing efficiency.

X-ray absorption fine-structure spectroscopy studies of Fe sites in natural human neuromelanin and synthetic analogues.

X-ray absorption fine-structure spectroscopy is used to study the local environment of the iron site in natural (human) neuromelanin extracted from substantia nigra tissue and in various synthetic neuromelanins. All the materials show Fe centered in a nearest neighbor sixfold (distorted) oxygen octahedron; the Fe-O distances, while slightly different in the natural and synthetic neuromelanin, are both approximately 2.0 A. Appreciable differences arise, however, in the second (and higher) coordination shells. In this case the synthetic melanin has the four planar oxygens bound to carbon rings with Fe-C distances of approximately 2.82 and 4.13 A; the human sample does not show the 2.82 A link but instead indicates a double shell at approximately 3.45 and 3.78 A.

X-ray characterization of melanins--I.

The intrinsic local structure characterization of natural sepia melanin and L-dopa and tyrosine synthetic melanin powder has been carried out by X-ray diffraction using synchrotron radiation. The derived structure factor, S(q), shows six significant diffuse peaks within the q-range from 0.3 A-1 to 16 A-1 in the reciprocal space (q = (4 pi sin theta)/lambda, 2 theta is the scattering angle). The Fourier transform of S(q), which yields the radial distribution function (RDF), gives us information in real space of a 1.42 A distance averaged over the C-C, C-O and C-N bond lengths as well as peaks at 2.40-2.41 A, 3.67-3.71 A and 4.67-4.70 A discrete neighbor distances. There is a great similarity in the scattering intensity profiles of the natural and synthetic melanins indicating that the synthetically prepared material may be essentially similar to "real" melanin in its local atomic arrangements. An evidence of a prepeak at q congruent to 0.45 A-1 has been confirmed which indicates a preferred length scale of approximately 13-20 A that corresponds to the initial particle size in colloidal melanin solutions.

X-ray characterization of melanins--II.

Structural modeling of amorphous eumelanin has been carried out by comparing calculated data, S(q) and RDF(r), in reciprocal and real space, respectively, for limited random network models with the experimental X-ray scattering data of tyrosine melanin (Cheng et al., 1994). A basic picture of the atomic arrangements in amorphous eumelanin, which accounts for the short and intermediate range order, has been formulated. This reveals domains of a fundamental "particle" dimension of R approximately 15 A, consisting of a paracrystalline array of disordered planar networks polymerized by 4-8 DHI monomers with a graphite-like stacking spacing of approximately 3.45 A, 4-5 layers thick.

The fundamental unit of synthetic melanin: a verification by tunneling microscopy of X-ray scattering results.

A characteristic dimension of a melanin protomolecule synthesized from tyrosine has been investigated by scanning tunneling microscopy (STM). Identification of a melanin protomolecule of approximately approximately 20 A lateral extent and approximately 10 A height has been established. This size is in good agreement with models constructed to fit wide angle X-ray diffraction experiments on melanin. These protomolecules are believed to consist of Van der Waals interacting stacks of a basic random polymer of 5.6 indolequinone units. There is extensive pi-delocalization within the individual polymeric sheets. Structure minimization and molecular orbital techniques were employed to verify the X-ray and STM results.

Age and functional abilities of people with a mental handicap: evidence from the Wessex mental handicap register.

Functional behaviours in relation to age were investigated using data from approximately 3000 people on the Wessex Mental Handicap Register. The main functional data on the register, the National Development Team's 24-item questionnaire, were cluster and factor analysed to derive a series of client-defining variables. Age-trends were analysed in relation to self and community care skills (activities of daily living and instrumental activities of daily living), problem behaviours, chronic medical conditions, mobility and sensory abilities. Generally, it was found that differential mortality leads to an older population in good health and with a high level of functional skills. As with the general population, however, people over 70 years old show increasing prevalence of age-related infirmities.

Epitaxial growth of diamond films on si(111) at room temperature by mass-selected low-energy c+ beams.

Diamond films ( approximately 0.7 micrometer thick) have been epitaxially grown on Si(111) substrates at room temperature with mass-selected 120-electronvolt C(+) ions. The diamond reflections observed in x-ray diffraction are well localized at their predicted positions, indicating that (i) the diamond(111) and (220) planes are parallel to the Si(111) and (220), respectively; (ii) the diamond rotational spread around its (111) normal is approximately 1.7 degrees ; and (iii) the mosaic block size is approximately 150 A. The film growth is discussed in terms of subplantation-a shallow subsurface implantation model. This discovery is an important step toward diamond semiconductor devices.

Nonlinear-optical energy regulation by nonlinear refraction and absorption in silicon.

We demonstrate a new silicon picosecond nonlinear-optical energy regulator for 1-microm radiation. The device has a high transmission for low input energies and a low transmission for high input energies and clamps the output at a constant value. We attribute this optical Zener action to nonlinear refraction and absorption induced in the silicon by the intense picosecond pulses.

The development and integration of fine motor sequences in 12- to 18-month-old children: a test of the modular theory of motor skill acquisition.

According to the modular model, skill development proceeds through the development of stable units of action called subroutines. The development of these programmed units frees the child to attend to those parts of the action not yet mastered. Once consolidated they can be applied to many different contexts. Thus, complex skill sequences can be produced. The theory generates several predictions, most fundamental being an association between increasing proficiency and increasing consistency. Experiment 1 was a longitudinal study in which six 12-month-old children were observed over a period of eight months. Various manipulative tasks were used, notably the placement of rods in corresponding holes. Experiment 2 was a cross-sectional study of performance consistency in rod placement (N = 30). Results showed that consistency decreases as proficiency increases. It is concluded therefore that the programmed components of complex actions are not characterized by the invariance predicted by modular theory.

Color-center laser continuously tunable from 1.67 to 2.46 microm.

Laser action is reported for a KCI crystal containing both sodium and lithium (F(2)(+))(A) centers. The laser is continuously tunable from 1.67 to 2.46 microm and is pumped with the 1.3-microm lines of a Nd:YAG laser.