Seasonal changes in populations of Caulerpa taxifolia var. distichophylla in the Maltese Islands

Caulerpa taxifolia var. distichophylla, an alien alga in the Mediterranean Sea, was first recorded from the Maltese Islands in 2013. Initial observations suggested that it underwent complete frond regression in winter, possibly due to the colder temperatures. Since then it has spread rapidly and has become abundant in the infralittoral in some localities. The present two-year study on the Maltese populations indicates that the alga is able to resist low seawater temperatures during the winter and is not regressing completely, potentially increasing its ecological impact.peer-reviewe

Algal substratum preferences of the alien foraminiferan Amphistegina lobifera in shallow water

The Lessepsian foraminiferan Amphistegina lobifera is particularly numerous on algae in shallow water. We sampled foraminiferans from three algae (Cystoseira spp., Padina pavonica and Halopteris sp.) within the 0.75 - 2.0 m depth zone from five different sites around the island of Malta. There was a significant difference in the population density of live Amphistegina between the algae studied with Halopteris being preferred to Padina and with very sparse populations on Cystoseira.peer-reviewe

Habitat Characterisation of Infralittoral Pebble Beds in the Maltese Islands

The Mediterranean biocoenosis of infralittoral pebbles has been poorly studied and very little information is available on the physical characteristics of pebble beds, on the diversity of the associated assemblages, on the spatial and temporal variation in assemblage structure, or on interactions between the physical and biotic components. The present study was therefore carried out to characterise pebble-bed assemblages as a first step towards understanding the ecological dynamics of these habitats. Preliminary surveys were made along the low-lying coasts of the Maltese Islands to map the occurrence of pebble-bed habitats. Fifteen locations with pebble coverage >25 m² were chosen for study and benthic sampling was undertaken between July–September 2011; water samples were also collected on a monthly basis. Five shallow sites were sampled for biota again at six-month intervals until April 2013. The pebble beds were characterised in terms of environmental parameters and biotic composition. A total of 62,742 individuals belonging to 360 macrofaunal taxa were recorded (total sampling area: 16 m²). Polychaetes, crustaceans and molluscs were the most common faunal groups. The recorded species included the endemic gastropod Gibbula nivosa, and the first central Mediterranean records of three gobiid species. Three distinct pebble-bed types were characterised based on physical and biological features: shallow beds occurring in rocky coves, beds found within creeks or seagrass meadows, and beds located in harbour environments; amendments to internationally used benthic habitat classification schemes have been proposed, since only a single category of pebble-bed habitats is currently recognised in these. A significant seasonal reduction in species richness and abundance was recorded from shallow sites, related to the higher level of disturbance occurring during winter storms. Analysis of diversity patterns in harbour sites indicated that a high richness per site and between-site variation in species composition led to the observed high diversity. Site richness was associated with fine-scale structural complexity, while environmental characteristics were correlated with variation in assemblage structure over a broad range of spatial scales. These findings suggest that pebble beds have a higher conservation value than generally thought. The biologically derived habitat classification scheme and knowledge on assemblage-environment relationships derived from the present work will be useful to inform and guide management decisions concerning these pebble-bed habitats.STEPS Malt

Computer Generation of Metal Components by Simultaneous Deposition of Mould, Cores and Part

A new solid freeforming method based on co-delivery of mould powder materials and part powder materials using vibration-controlled, dry powder valves is presented in this paper. Thin layers of stainless steel powder are delivered to the forming area according to the cross-section of the CAD file to produce the component. Mould powder which has low sinterability is delivered to the non-forming areas of the same layer. All powders are delivered by computer-controlled, acoustic powder valves. The flow rate and switching of the valves provides the composition and shape control during fabrication. The stacked layers of loose powder are then sintered in a conventional furnace. The mould materials are removed after sintering. This method avoids the high thermal stress problem in selective laser sintering, avoids high capitalisation, makes use of conventional furnaces and allows for the incorporation of three dimensional function gradients. Test pieces including step wedge and Spierpinski’s cube were fabricated. Advantages, limitations and problems are discussed.Mechanical Engineerin

Dry Powder Microfeeding System for Solid Freeform Fabrication

Second generation SFF techniques allow both composition and shape to be downloaded directly from a computer file so that 3D functionally graded materials (FGM) can be assembled. Methods for multi-material deposition are also needed in combinatorial research, colour management and pharmaceutical dosing. In this work, computer-controlled microfeeding systems using ultrasonic vibration of a capillary were built. A wide range of stable flow rate control and switching control were achieved in the acoustic vibration system, and uniform powder doses were obtained in the ultrasonic system. The experimental results show that the nozzle diameter, transmission fluid depth, waveforms, voltage amplitude, frequency and oscillation duration all influence the dose mass. Among these factors, the nozzle diameter, voltage amplitude and oscillation duration can be used to control the dose mass. Raster printing of patterns with various resolution and dot size are demonstrated.Mechanical Engineerin

Direct Extrusion Freeforming of Ceramic Pastes

Microextrusion freeforming of ceramic lattices from high solids ceramic pastes provides multi-scale hierarchical void structures with the advantages of low shrinkage stress and high sintered density. Alumina lattices were directly fabricated using 80-500 Pm diameter filaments. We report here on the implementation of design and fabrication of these scaffolds for band gap materials and micro fluidic devices.Mechanical Engineerin

Kinetic Monte Carlo simulations of oscillatory shape evolution for electromigration-driven islands

The shape evolution of two-dimensional islands under electromigration-driven periphery diffusion is studied by kinetic Monte Carlo (KMC) simulations and continuum theory. The energetics of the KMC model is adapted to the Cu(100) surface, and the continuum model is matched to the KMC model by a suitably parametrized choice of the orientation-dependent step stiffness and step atom mobility. At 700 K shape oscillations predicted by continuum theory are quantitatively verified by the KMC simulations, while at 500 K qualitative differences between the two modeling approaches are found.Comment: 7 pages, 6 figure

Newcomer species from Maltese waters: additions and amendments

The inventory of newcomers in Maltese waters is updated with the addition of 7 alien and 1 range-expanding species, while one previous entry in the inventory is omitted. Thus, a total of 72 alien and 8 range-expanding species have been recorded by February 2016. Half of these species have established populations in Maltese waters while a further 10% are considered to be invasive. The main modes of introduction for alien species in Maltese waters are ‘Shipping’ and ‘Secondary dispersal’ from elsewhere in the Mediterranean. More than half of these newcomer species were recorded since the year 2000.peer-reviewe