Asterionella blooms in the northwestern Bay of Bengal during 2004

Asterionella glacialis Castracane, a diatom species of marine phytoplankton, bloomed in the coastal waters of the northwestern Bay of Bengal during 24 March to 4 April 2004. This species dominated by 99% in cell concentration on 26 March 2004. During the bloom period, phytoplankton population density increased by three orders of magnitude, while the chlorophyll a concentration increased by 70 to 80 times relative to the pre‐bloom situation. The blooming was associated with coastal upwelling and influenced water quality. Corresponding to the blooming period, satellite sensor‐derived products of sea surface temperature (SST) and chlorophyll a data were analysed to understand the coverage and dynamics of phytoplankton in the area.     

Improved field emission from multiwall carbon nanotubes with nano-size defects produced by ultra-low energy ion bombardment

Multiwalled carbon nanotubes were irradiated with ultra-low energy (few eV) nitrogen and hydrogen ions using a microwave discharge. These ultra-low energy plasma-ions remain confined to the nanotube walls, transferring their maximum energy to the carbon atoms, and produce extraordinary structural changes to the carbon nanotube pillars as well as within the carbon nanotubes. Conical shaped emitters and nanotube structures with nano-defects are produced that exhibit remarkable field emission with ultra-low turn-on electric field (∼0.16 V/μm) and a >300-fold increase in the maximum emission current density compared to non-irradiated nanotubes. Doping of nitrogen is also identified due to such irradiation processes.     

A separable method for incorporating imperfect fault-coverage intocombinatorial models

This paper presents a new method for incorporating imperfect FC (fault coverage) into a combinatorial model. Imperfect FC, the probability that a single malicious fault can thwart automatic recovery mechanisms, is important to accurate reliability assessment of fault-tolerant computer systems. Until recently, it was thought that the consideration of this probability necessitated a Markov model rather than the simpler (and usually faster) combinatorial model. SEA, the new approach, separates the modeling of FC failures into two terms that are multiplied to compute the system reliability. The first term, a simple product, represents the probability that no uncovered fault occurs. The second term comes from a combinatorial model which includes the covered faults that can lead to system failure. This second term can be computed from any common approach (e.g. fault tree, block diagram, digraph) which ignores the FC concept by slightly altering the component-failure probabilities. The result of this work is that reliability engineers can use their favorite software package (which ignores the FC concept) for computing reliability, and then adjust the input and output of that program slightly to produce a result which includes FC. This method applies to any system for which: the FC probabilities are constant and state-independent; the hazard rates are state-independent; and an FC failure leads to immediate system failure     

Hybrid inorganic-organic UV-curable abrasion-resistant coatings

Summary  By utilising the Michael addition reaction, a wide range of acrylate functional silane coupling agents have been developed. These can be used to confer functionality on the surface of nanocomposite colloidal oxides, particularly silica which can then be incorporated into acrylic UV-curable matrices. Coatings developed from these systems provide greatly enhanced abrasion resistance, and can approach the performance of thermally-cured silicone hardcoats. The wide range of coupling agents by this method allows considerable flexibility in the design of coatings suitable for different substrates and a wide range of applications. Acknowledgements: M Sollberger, T Washer, J Blizzard and J Tonge, Dow Corning Corp.     

Elastic Constants of Erbia Single Crystals

The elastic properties of single-crystalline erbia (Er₂O₃) at room temperature have been investigated using resonant ultrasound spectroscopy. The three independent stiffness constants of anisotropic Er₂O₃ cubic type-C crystals have been measured. The values of the stiffness constants were c ₁₁= 256.4 GPa, c ₁₂= 146.8 GPa, and c ₄₄= 75.2 GPa. From the stiffness constants, the estimated values for dense polycrystalline erbia for Young's modulus, the shear modulus, the bulk modulus, and Poisson's ratio at room temperature were 179 GPa, 67 GPa, 183.3 GPa, and 0.337, respectively. The value of Young's modulus is a minimum along [001] and a maximum along [111]. The value of the shear modulus is independent of the direction in the (001) and (111) planes, whereas it decreases in (11¯0) from 75 GPa along [001] to 55 GPa along [110].     

In-situ TEM study of dislocation-twin boundaries interaction in nanotwinned Cu films

Epitaxial thin films of nanotwinned face-centered cubic metals such as Cu possess an unprecedented combination of high hardness and high electrical conductivity due to the unique structure of nanometer-spaced coherent twin boundaries. Recent studies of in-situ nanoindentation in a transmission electron microscope have provided new insights on the deformation behavior of nanotwins that are reviewed here. In particular, two unit processes are highlighted: first, stress-induced migration of Σ3 {112} incoherent twin boundary that leads to de-twinning of nanotwins; second, twinning dislocation can be multiplied at Σ3 {111} coherent twin boundary.     

Thermal stresses in an infinite non-isotropic plate having a penny-shaped crack

Of concern in the paper is the distribution of thermal stresses in the vicinity of a penny-shaped crack in a thick elastic plate made of a non-isotropic material. The problem pertains to the situation where the crack is opened by a prescribed normal pressure and a prescribed heat-flux or a prescribed temperature.     

Rate-dependent serrated flow and plastic deformation in Ti45Zr16Be20Cu10Ni9 bulk amorphous alloy during nanoindentation

The plastic deformation of Ti₄₅Zr₁₆Be₂₀Cu₁₀Ni₉ bulk metallic glass has been investigated by nanoindentation performed with loads ranging from 10 to 200 mN in a wide range of loading rates. The plastic flow in the alloy exhibited conspicuous serrations at low loading rates. The serrations, however, became less prominent as the rate of indentation increased. Atomic force microscopy showed a significant pile-up of materials around the indents, indicating that a highly localized plastic deformation occurred under nanoindentation. The possible mechanism governing the plastic deformation in bulk metallic glass specimens is tentatively discussed in terms of strain-induced free volume.