Simulating Film Grain using the Noise Power Spectrum

Adding grain to simulated images makes them look more exciting. While its relativly easy to add some noise, here we use the principles developed by imaging scientists to produce grain which is theoretically "correct". While the results are usefull, they also illustrate the limitations of current photographic theories of grain

The biochemistry of the developing cereal grain

Concentrations of major biochemical constituents of developing barley endosperm were measured and correlated with morphological changes during maturation.The activities of enzymes concerned with starch meta- bolism in barley endosperm were investigated. It was established that mechanisms by which sucrose can be converted to nucleotide sugars and thus incorporated into starch exist in the endosperm by 5 days after anthesis. Possible variations in these pathways during grain development are discussed.The partition of starch synthetase between soluble and amyloplast fractions of the endosperm was established at various stages of development, and changes in affinity to- wards UDPG and ADPG were demonstrated. The relevance of these results to branching enzyme activity and amylopect in content is considered.A detailed investigation of the activity and control of starch phosphorylase in barley endosperm was carried out. The existence of at least two isoenzymes was indicated by studies of pH dependence and phosphate inhibition, and was further supported by acrylamide gel electrophoresis and column chromatography using DEAE -cellulose. A change in the isoenzyme pattern during grain development was observed. Synthesis of starch by phosphorylase in an apparently primer - free system was demonstrated, and this activity integrated with starch synthetase.A pathway for the conversion of sucrose to glucan polymers via GIP in very young endosperm is proposed. It is suggested that at least one, and possibly both, isoenzymes of phosphorylase are glycoproteins. Spatial arrangements of phosphorylase, starch synthetase, and branching enzyme in relation to the amyloplast are discussed

Novel Growth Methods of Organic-Inorganic Lead Tri-Halide Perovskite Material for Photovoltaic Applications

Whilst different methodologies have been used to grow perovskite materials, still, there are demands to develop commercial approach techniques that could alleviate the problem associated with the various phases formed within the perovskite material, which may cause of its crystallographic instability. Therefore, the research study was aimed to assist in moving towards this objective by developing novel methods for the deposition of perovskite thin films (CH3NH3PbI3 = MAPbI3) that are scalable and industry-acceptable. It was also aimed to focus, along with the scalable process, on an atomic scale of processing to deposit materials with ATM (Atom to Matter), where the defect density within the films are minimised. In view of that, different CVD deposition methods to deposit MAPbI3 thin films were proposed in this study, including Radio Frequency-Plasma Enhanced Chemical Vapour Deposition (RF-PECVD) and Atmospheric-Pressure Chemical Vapour Deposition (APCVD). The first proof-of-concept was demonstrated to obtain perovskite films with a tetragonal crystal structure by a PECVD process that was not reported till date. This achievement is encouraging as the PECVD process is fully scalable and already available technology in the industries. The growth was subsequently successfully achieved by using carbon, nitrogen and hydrogen radicals that were contained a gas such as methane (CH4) and ammonia (NH3). A prior deposition of PbI2 thin films by either spin-coating or thermal evaporating was implemented previously before they were exposed to the organic molecules in the plasma state that was formed by RF power via a PECVD technique. The effect of the variation of PECVD growth parameters (such as substrate temperature, RF power density and chamber pressure) on the properties of the films deposited was critically analysed. The conditions that yielded the best quality material achieved from this study were at substrate temperature of 100 ℃ and under low power density (22 mW/cm2) and high chamber pressure (1000 mtorr). An attempt was made to understand the properties of the resultant films, in terms of the physical, optical and electrical properties, which led to develop and provide appropriate explanations of the possible growth mechanisms. Considering the cost with the use of the scalable process that any an industrial technique would prefer, a modified non-vacuum CVD system was additionally demonstrated in this work to deposit MAPbI3 films at atmospheric pressure, hence the name APCVD. The growth of the MAPbI3 films was controlled based on the concentration of the precursor and the temperature. The lower concentration of the molecules passing over the substrate enhanced the crystallographic stability, where the in-situ cubic structure was achieved. With the use of this novel design of the reactor specifically for the deposition of MAPbI3 perovskite films; excellent stability of these films at room temperature without care of storage for more than two months in an open atmosphere provided an alternative approach to obtain the stable MAPbI3 perovskite film. In addition to the low temperature and lower concentration of the precursor used for the fabrication of a novel design of the reactor to grow films with the bottom-up approach (i.e. atom by atom or molecules), this study was successful in fabricating a proof-of-concept solar cell using this method for the first time. The obtained perovskite material has significantly contributed to understanding of the crystallographic stability issues reported in the photovoltaics which are incorporated with the perovskite materials over the last recent years

Synthesis and Characterisation of Nanomaterials

Development of synthesis protocols for realising nanomaterials over a range of sizes, shapes,and chemical compositions is an important aspect of nanotechnology. The remarkable size-dependent physico-chemical properties of nanoparticles have fascinated and inspired researchactivity in this direction. This paper describes some aspects on synthesis and characterisationof nanoparticles of metals, metal alloys, and oxides, either in the form of thin films or bulk shapes.A brief discussion on processing of two-phase nanocomposite magnets is also presented.Defence Science Journal, 2008, 58(4), pp.504-516, DOI:http://dx.doi.org/10.14429/dsj.58.167

Deoxyribonucleic acid synthesis in human leukocytes

Imperial Users onl

Nanostructures and their applications

Nanostructures have been described as ‘novel materials whose size of elemental structure has been engineered at the nanometer scale’. Materials in the nanometer size range commonly exhibit fundamentally new behavior. Moreover, intervention in the properties of materials at the nanoscale enables the creation of materials and devices with enhanced or completely new characteristics and functionalities. Understanding the science of nanomaterials is important and curiosity driven not only because of the fascinating nature of the subject but also for overwhelming and novel applications of nanoscale systems in almost all branches of technology.Nanotechnology can be understood as a technology of design, fabrication and application of nanostructures and nanomaterials.The field of nanoscience and nanotechnology is interdisciplinary in nature and it is being perused by physicists, chemists, materials scientists, biologists, engineers, computer scientists etc. Nanomaterials may be classified on the basis of dimensionality and modulation. Some special nanostructures like nanotubes, nanoporous materials, aerogels, zeolites, core-shell structures have also come up with their novel characteristics. A number of methods have been used for the synthesis of nanostructure with various degrees of success and many direct and indirect techniques are employed for their characterization. The fact, which makes the nanostructures interesting, is that the properties become size dependent in nanometer range because of surface effect and quantum confinement effect. The geometric structure, chemical bonds, ionization potential, electronic properties, optical properties, mechanical strength, thermal properties, magnetic properties etc. are all affected by particle sizes in nanometer range. Nanomaterials exhibit properties often superior to those of conventional coarse-grained materials. These include increased strength/hardness, enhanced diffusivity, improved ductility/toughness, reduced density, reduced elastic modulus, higher electrical resistivity, increased specific heat, higher thermal expansion coefficient, lower thermal conductivity, increased oscillator strength, blue shifted absorption, increased luminescence and superior soft magnetic properties in comparison to conventional bulk materials. All of these properties are being extensively investigated to explore possible applications.  The fascinating field of nanotechnology has wide range of applications. Use of nanostructutred materials has produced transistors with record low speed and lasers with low threshold current. These are being used in compact disk player systems, low noise amplification in satellite receivers as sources for fiber optic communication etc. Constructive applications of nanomaterials include self-cleaning glass, UV resistant wood coating etc. Nanoscale devices are being used in medical field also for diagnosis, treatment and prevention of diseases and in drug delivery system, magnetic resonance imaging, radioactive tracers etc. Importance of nanotechnology is growing day by day. Many more applications may be possible with the novel and peculiar properties of nanostructures

Materiales y técnicas de fase vapor para la síntesis de recubrimientos cerámicos

[ES] Se hace un descripción de los avances recientes en la síntesis de recubrimientos duros de tipo cerámico, depositados mediante técnicas de deposición en fase vapor. Se dedica especial atención a los parámetros del proceso de deposición que controlan las propiedades finales de las capas (estructura cristalina, morfología, etc), tales como la energía de llegada de los átomos a las superficie en crecimiento, y la temperatura. Finalmente, se hace una revisión de los materiales más relevantes en lo que se refiere a sus aplicaciones como recubrimientos duros y protectores, o como recubrimientos decorativos, entre ellos, la familia de los nitruros, carburos y óxidos metálicos, depositados en diversos tipos de estructuras (monolíticas, multicapas y nanocomposites), y los compuestos ternarios del sistema BCN.[EN] A survey on recent advances in the synthesis of hard ceramic coatings is given, including materials processes and techniques. Emphasis is made on the parameters which control the coating properties (crystalline structure, morphology, etc), namely arrival energy of the atoms to the growing surface and substrate temperature. Some relevant coating materials are discussed in relation to their applications either as hard protective coatings or with decorative purposes, namely: the family of metal nitrides, carbides, and oxides, in different layer structures (monolithic, multilayers and nanocomposites) and ternary compounds of the BCN system.Peer reviewe

Solvothermal nanoYAG synthesis: mechanism and particle growth kinetics

NanoYAG particles with spherical morphology have been synthesised using a solvothermal method; a structure sensitive reaction, where the chemical reaction and the particle growth kinetics are interdependent. It has been observed that the primary YAG particles agglomerated into ∼30 nm clusters via a self-assembled Ostwald ripening process along (2 1 1) planes, separated by a distance of ∼0.49 nm, at 270 °C and 2.0 MPa for 2 h. These nanoclusters coalesced into single nanoparticles of ∼30 nm in size and exhibited a smaller inter planar distance of ∼0.26 nm, corresponding to the (4 2 0) planes, when synthesized at 300 °C and 8.5 MPa for 2 h. in addition, the solvent 1,4-butanediol transformed into 1,4-diacetoxybutane, this will have undergone esterification by reacting with the terminal acetate groups cleaved from the precursor, yttrium acetate. The proposed mechanism based on the analytical evidence suggests that a complete dissolution of precursors facilitated the structural re-arrangement of atoms within the planes and lead to a significantly higher degree of crystallinity. Moreover, once the particles with (4 2 0) planes had formed, they were no longer involved in facile coalescence along their preferential planes due to their lower interfacial energy compared to the (2 1 1) planes. This led to control of the particle morphology and with little agglomeration occurring in the final nanopowder