Periodic water waves generate Stokes drift as manifest from the orbits of Lagrangian particles not fully closing. Stokes drift can contribute to the transport of floating marine litter, including plastic. Previously, marine litter objects have been considered to be perfect Lagrangian tracers, travelling with the Stokes drift of the waves. However, floating marine litter objects have large ranges of sizes and densities, which potentially result in different rates of transport by waves due to the non-Lagrangian behaviour of the objects. Through a combination of theory and experiments for idealised spherical objects in deep-water waves, we show that different objects are transported at different rates depending on their size and density, and that larger buoyant objects can have increased drift compared with Lagrangian tracers. We show that the mechanism for the increased drift observed in our experiments comprises the variable submergence and the corresponding dynamic buoyancy force components in a direction perpendicular to the local water surface. This leads to an amplification of the drift of these objects compared to the Stokes drift when averaged over the wave cycle. Using an expansion in wave steepness, we derive a closed-form approximation for this increased drift, which can be included in ocean-scale models of marine litter transport.

Owing to the interplay between the forward Stokes drift and the backward wave-induced Eulerian return flow, Lagrangian particles underneath surface gravity wave groups can follow different trajectories depending on their initial depth below the surface. The motion of particles near the free surface is dominated by the waves and their Stokes drift, whereas particles at large depths follow horseshoe-shaped trajectories dominated by the Eulerian return flow. For unidirectional wave groups, a small net displacement in the direction of travel of the group results near the surface, and is accompanied by a net particle displacement in the opposite direction at depth. For deep-water waves, we study these trajectories experimentally by means of particle tracking velocimetry in a two-dimensional flume. In doing so, we provide visual illustration of Lagrangian trajectories under groups, including the contributions of both the Stokes drift and the Eulerian return flow to both the horizontal and the vertical Lagrangian displacements. We compare our experimental results to leading-order solutions of the irrotational water wave equations, finding good agreement.

A simple geometry that exhibits near motion trapping is tested experimentally, along with perturbed versions of the structure. The motion of the freely floating structure and the surrounding wave field is tracked and the near-motion-trapped mode is found, characterised by a slowly decaying heave motion with very small linear radiation of energy. It is found that the latter property is a better discriminator of the perturbed geometries as viscous damping masks fine differences in radiation damping as far as the motion of the structure is concerned. The magnitude of this viscous damping is reasonably well predicted by a simple Stokes oscillatory boundary layer analysis.

Beveled retouch on stone projectile points has often been considered as a device to spin and stabilize a projectile. A recent paper showed that a beveled point will spin a small shaft under tightly controlled laboratory conditions. However, this experiment has little relevance for real projectiles such as atlatl darts, which flex dramatically and spin unevenly inflight, quite independent of point form. The spinning is related to the flexibility of the dart, which is necessary for spearthrower functión. A beveled point cannot spin a dart in the air, but is likely to cause some rotation when encountering a solid target like flesh. Beveled points are probably not related to spinning either darts or arrows inflight and present a good example of why we need to have both theoretical understanding and experimental observations of details of projectile behavior before interpreting artifacts. Spinning in a carcass could make beveled points more lethal, but the suggestion that beveling mostly results from sharpening and other modification of stone points remains the best explanation.

The British Museum's Aztec atlatl is one of their most famous Mesoamerican objects, yet it has not been studied as a weapon in light of current knowledge of spear-throwers, and the details necessary to do so have not been published. Close examination and experimental replication shows that although it is ornately decorated, it is a serviceable spear-thrower. While evidence of actual use of this specimen is ambiguous, we can at least accept the form as an example of working weapons of Contact period Mesoamerica. The actual effects and circumstances of atlatl use against the Spanish and others are difficult to judge from surviving accounts. The iconography of the decoration, as in other instances, associated this atlatl with elite warfare and deities of war and sacrifice.

Metal borides (AlB2, MgB2, Mg0.5Al0.5B2, AlB12, SiB6 and MgAlB14) and boron carbide (B4C) reacted with Al were compared to B, Mg, Al, Mg-Al and Si as potential energetic fuel additives. Stoichiometric physical mixtures of powders corresponding to unreacted boride compounds (Al+2B, Mg+2B, Mg-Al+2B, Al+12B, Si+6B, Mg-Al+14B, and B4C+2Al) were also investigated in comparison to the compounds. Submicron boron was used, which resulted in very fine particle sizes for all materials studied. It was demonstrated that boride compounds were less sensitive to low-temperature oxidation in flowing air than physical mixtures or metallic fuels. Compounds with high mole fractions of boron were generally less sensitive, but their high temperature oxidation behavior showed no improvement over boron. Cylinder expansion testing of MgAlB14 exposed its poor performance in an energetic mixture. However, aluminum and magnesium diborides (AlB2, MgB2 and Mg0.5Al0.5B2) also had relatively low sensitivity and exhibited mechanisms to increase the rate of boron oxidation at high temperatures, showing promise as insensitive high-energy-density fuel additives. Detonation calorimetry of mixtures with AlB2 or Al+2B suggested that the AlB2 mixture released approximately 50% more heat per gram than Al +2B and underwent complete reaction. These results warrant further testing of the diboride compounds in energetic formulations. Due to the high cost of boron and acceptable performance of B4C-Al mixtures, B4C should also be investigated as a lower-cost alternative to boron.

A method of using information on the location of markers to improve the efficiency of markerassisted selection (MAS) in a population produced by a cross between two inbred lines is developed. The method is closer to mapping QTL than the selection index approaches to MAS described by previous authors. We use computer simulations to compare our method with phenotypic selection and two selection index approaches, simulations being performed on three genetic maps. The simulations show that whilst MAS can be considerably more efficient than phenotypic selection differences between the three MAS methods are slight. Which of the MAS methods is best depends on a number of factors: in particular the genetic map, the time scale under consideration and the population size are of importance.

Cahal Tok (Place of Flint) is a limestone rise with some structural evidence, associated with the previously designated LDF Chert Site, close to the ceremonial center of El Pilar. Excavations uncovered evidence that during the Late Classic period, specialized flintknappers produced bifaces, primarily chert axes, at the Cahol Tok locus, first on a cleared limestone shelf then on a prepared cobble platform. Small flakes remained in situ whereas much of the larger debris was deposited to the east off the edge of the platform and into the LDF debitage dump. The identification of a specialized manufacturing locale near the ceremonial precinct of a major center is unusual in Maya archaeology. Central control of an important industry may be implied, although knapping could equally well be organized more independently. We expect that small industrial areas are actually present at most large sites, but may often be difficult to recognize.

A national outbreak of verotoxin-producing Escherichia coli O157 infection affected five English regions and Wales. Twelve cases were associated with lemon-and-coriander chicken wrap from a single supermarket chain consumed over a 5-day period. An outbreak investigation aimed to identify the source of infection. Descriptive epidemiology and phenotypic and genotypic tests on human isolates indicated a point-source outbreak; a case-control study showed a very strong association between consumption of lemon-and-coriander chicken wrap from the single supermarket chain and being a case (OR 46·40, 95% CI 5·39–∞, P=0·0002). Testing of raw ingredients, products and faecal samples from staff in the food production unit did not yield any positive results. The outbreak was probably caused by one contaminated batch of an ingredient in the chicken wrap. Even when current best practice is in place, ready-to-eat foods can still be a risk for widespread infection.

Ten years of Oregon Seed Certification Service (OSCS) preharvest field inspections converted from a nonspatial database to a geographic information system (GIS) were analyzed for patterns in spatial distribution of occurrence and severity of the 36 most common weeds of grass seed crops. This was done under the assumptions that those patterns would be primarily consequences of interactions among farming practices, soil properties, and biological traits of the weeds, and that improved understanding of the interactions would benefit the grass seed industry. Kriging, Ripley's K-function, and both Moran's I spatial autocorrelation and Getis-Ord General G high/low clustering using the multiple fixed distance band option all produced roughly similar classifications of weeds possessing strongest and weakest spatial clustering patterns. When Moran's I and General G analyses of maximum weed severity observed within individual fields over the life of stands were conducted using the inverse distance weighting option, however, results were highly sensitive to the presence of a small number of overlapping fields in the 10-yr record. Addition of any offset in the range from 6 to 6,437 m to measured distances between field centroids in inverse distance weighting matrices removed this sensitivity, and produced results closely matching those for the multiple fixed distance band method. Clustering was significant for maximum severity within fields over the 10-yr period for all 43 weeds and in 78% of single-year analyses. The remaining 22% of single-year cases showed random rather than dispersed distribution patterns. In decreasing order, weeds with strongest inverse-distance spatial autocorrelation were German velvetgrass, field bindweed, roughstalk bluegrass, annual bluegrass, orchardgrass, common velvetgrass, Italian ryegrass, Agrostis spp., and perennial ryegrass. Of these nine weeds, distance for peak spatial autocorrelation ranged from 2 km for Agrostis spp. to 34 km for common velvetgrass. Weeds with stronger spatial autocorrelation had greater range between distance of peak spatial autocorrelation and maximum range of significance. Z-scores for General G high/low clustering were substantially lower than corresponding values for Moran's I spatial autocorrelation, although the same two weeds (German velvetgrass and field bindweed) showed strongest clustering using both measures. Simultaneous patterns in Moran's I and General G implied that management practices relatively ineffective in controlling weeds usually played a greater role in causing weeds to cluster than highly effective practices, although both types of practices impacted Italian ryegrass distribution. Distance of peak high/low clustering among perennial weeds was smallest (1 to 3 km) for Canada thistle, field bindweed, Agrostis spp., and western wildcucumber, likely indicating that these weeds occurred in patchy infestations extending across neighboring fields. Although both wild carrot and field bindweed doubled in average severity over the period from 1994 to 2003, wild carrot was the only weed clearly undergoing an increase in spatial autocorrelation. Soil chemical and physical properties and dummy variables for soil type and crop explained small but significant portions of total variance in redundancy and canonical correspondence analysis of weed occurrence and severity. Fitch-Morgoliash tree diagrams and Redundancy Analysis (RDA) and Canonical Correspondence Analysis (CCA) ordinations revealed substantial differences among soil types in weed occurrence and severity. Gi∗ local hot-spot clustering combined with feature class to raster conversion protected grower expectations of confidentiality while describing dominant spatial features of weed distribution patterns in maps released to the public.

The introduction of a fifth amphibole group, the Na-Ca-Mg-Fe-Mn-Li group, defined by 0.50 < B(Mg,Fe2+,Mn2+,Li) < 1.50 and 0.50 ≤ B(Ca,Na) ≤ 1.50 a.f.p.u. (atoms per formula unit), with members whittakerite and ottoliniite, has been required by recent discoveries of B(LiNa) amphiboles. This, and other new discoveries, such as sodicpedrizite (which, here, is changed slightly, but significantly, from the original idealized formula), necessitate amendments to the IMA 1997 definitions of the Mg-Fe-Mn-Li, calcic, sodic-calcic and sodic groups. The discovery of obertiite and the finding of an incompatibility in the IMA 1997 subdivision of the sodic group, requires further amendments within the sodic group. All these changes, which have IMA approval, are summarized.

The CAA has recognised the need to develop civil standards for unmanned aerial vehicles (UAVs). Accordingly the CAA Directorate of Airspace Policy has published the document ‘CAP 722 – Unmanned Air Vehicle Operation in UK Airspace – Guidance’, (which can be accessed via the CAA website — http://www.caa.co.uk/docs/33/CAP722.pdf). The document itemises the top-level military and civil regulations which impact upon the operation of UAVs in the UK. One of the items listed within the document is ‘Civil Certification’ of UAVs. This particular aspect is the responsibility of the Design and Production Standards Division, (D&PSD), of the CAA Safety Regulation Group. The purpose of this paper is to present and explain the current position of D&PSD regarding the appropriate design standards to be applied for the civil certification of the airworthiness of UAVs.

This paper presents the CAA position that UAVs should be granted permission to fly by qualifying for certificates of airworthiness, by demonstration of compliance with defined airworthiness standards comparable to, and derived from, those applied to manned aircraft. The paper also presents a method for determining, to a first approximation, the level of airworthiness standards which should be applied to any particular design of UAV by reference to the existing codes of airworthiness requirements for manned aircraft.

The CAA has recognised the need to develop civil standards for unmanned aerial vehicles (UAVs). Accordingly the CAA Directorate of Airspace Policy has published the document ‘CAP 722 –Unmanned Air Vehicle Operation in UK Airspace – Guidance’, (which can be accessed via the CAA website — http://www.caa.co.uk/docs/33/CAP722.pdf). The document itemises the top-level military and civil regulations which impact upon the operation of UAVs in the UK. One of the items listed within the document is ‘Civil Certification’ of UAVs. This particular aspect is the responsibility of the Design and Production Standards Division, (D&PSD), of the CAA Safety Regulation Group. The purpose of this paper is to present and explain the current position of D&PSD regarding the appropriate design standards to be applied for the civil certification of the airworthiness of UAVs.

This paper presents the CAA position that UAVs should be granted permission to fly by qualifying for certificates of airworthiness, by demonstration of compliance with defined airworthiness standards comparable to, and derived from, those applied to manned aircraft. The paper also presents a method for determining, to a first approximation, the level of airworthiness standards which should be applied to any particular design of UAV by reference to the existing codes of airworthiness requirements for manned aircraft.

The large literature on family-based tests of association and/or linkage is reviewed, concentrating on the underlying principles and on recent methodological developments. We explain the distinction between testing for association and testing for linkage, and give our views on the circumstances in which each is the appropriate null hypothesis.

A set of gunflints and other artefacts produced by Fred Snare at Brandon is an example of ways in which craftsmen in a declining trade attempted to create new markets by introducing new techniques and forms, and finding new ways to sell traditional skills. Sample sets and artefacts made for collectors reflect how some gunflint knappers, drawing on romantic conceptions of their craft as ‘heritage’, assigned new meanings to the flint industry as part of a survival strategy for an obsolescent trade.

UK legislation dictates that all pigs shall have access to straw or other material or object suitable to satisfy their behavioural needs (Welfare of Livestock Regulations, 1994). However, it is unknown how much straw must be provided to be behaviourally rewarding, and whether pigs’ prior experience of straw can impact upon their subsequent behavioural needs. Therefore, the aim of the current experiment was to investigate these issues by exposing pigs which did, or did not, have prior experience of straw to four levels of straw bed depth.