The LHCb upgrade I

The LHCb upgrade represents a major change of the experiment. The detectors have been almost completely renewed to allow running at an instantaneous luminosity five times larger than that of the previous running periods. Readout of all detectors into an all-software trigger is central to the new design, facilitating the reconstruction of events at the maximum LHC interaction rate, and their selection in real time. The experiment's tracking system has been completely upgraded with a new pixel vertex detector, a silicon tracker upstream of the dipole magnet and three scintillating fibre tracking stations downstream of the magnet. The whole photon detection system of the RICH detectors has been renewed and the readout electronics of the calorimeter and muon systems have been fully overhauled. The first stage of the all-software trigger is implemented on a GPU farm. The output of the trigger provides a combination of totally reconstructed physics objects, such as tracks and vertices, ready for final analysis, and of entire events which need further offline reprocessing. This scheme required a complete revision of the computing model and rewriting of the experiment's software

Gold-loaded organic/inorganic nanocomposite honeycomb membranes

RAFT polymerization was used to prepare polystyrene ? poly(4-vinyl pyridine) block copolymers, PSn-b-P(4VP)m. Well-defined block copolymers were obtained despite some indications of hydrolysis of the RAFT endgroup during synthesis. The block copolymer PS70-b-P(4VP) 55 was self-assembled into micellar structures in dichloromethane, leading to nanoparticles with hydrodynamic diameters of 70 nm. The micelles were loaded with HAuCl4 and, upon reduction, micellar gold-containing nanoparticles with hydrodynamic diameters of 240 nm were obtained. These nanoparticles were employed in the preparation of honeycomb-structured porous films by means of the breath figures technique to yield gold nanocomposites with a hexagonal porous array. © CSIRO 2006

Honeycomb structured porous films from amphiphilic block copolymers prepared via RAFT polymerization

The synthesis of polystyrene-block-poly(N,N-dimethylacrylamide) (PS-b-PDMA) via RAFT polymerization was investigated in detail. Two different RAFT agents - benzyl dithiobenzoate and 3-(benzylsulfanylthiocarbonylsufanyl) propionic acid, were employed to prepare polystyrene macroRAFT agents with molecular weights varying between 3000 g mol-1 and 62,000 g mol-1 and polydispersities between 1.1 and 1.4. Chain extensions with N,N-dimethylacrylamide (DMA) were carried out using a constant monomer to RAFT agent concentration ([DMA]/[RAFT] = 500), to compare the rate of polymerization in dependency of the polystyrene chain length. A decreasing rate of polymerization with increasing block length was observed. Depending on the sizes of the first block and type of RAFT agents used, chain extension polymerization with DMA was found to be incomplete, leading to significant low molecular weight tailing in the GPC analyses. Block copolymers prepared using 3-(benzylsulfanylthiocarbonylsufanyl) propionic acid, followed the expected molecular weight evolutions with polydispersity indices of 1.2-1.4. In contrast, block copolymers using benzyl dithiobenzoate clearly showed bimodal molecular weight distributions, especially when the longest PS macroRAFT agent with a molecular weight of 38,000 g mol-1 was employed. These amphiphilic block copolymers were used to fabricate honeycomb structured porous films using the breath figure technique. The regularity of the film was considerably influenced by the humidity of the environment, which could be controlled by the rate of the airflow or the humidity in the casting chamber. The interaction between the hydrophilic block copolymer and the humidity was found responsible for the delicate equilibrium during the casting process, which prevented high pores regularity at very low (below 50%) and at elevated (above 80%) humidity. The interactions of the hydrophilic block with the humidity were observed to superimpose an additional nano-scaled order onto the hexagonal micron-sized porous array. Pores, which are created by encapsulation of water droplets, were found to be more hydrophilic than the surface. Confocal microscopy studies were employed to locate hydrophilic blocks within the film using a fluorescence labeled PDMA polymer. Crown Copyright © 2007

Honeycomb structured porous film from amphiphilic block copolymers for biomedical applications

In recent times, it was divulged that highly ordered honeycomb structured porous films from a variety of polymers could be fabricated by breath figures (water droplets) templating technique. In contrast to existing macroporous fabrication techniques, this technique is simple, more versatile and very cost effective.Amphiphilic block copolymers composed of a hydrophobic and a hydrophilic block were employed in this research to examine the process of porous film formation and the outcome of films generated using breath figure technique. A customized film casting system, established according to the casting parameters affecting the outcome of films was used to generate honeycomb structured porous films for the studies. The casting method best suited to generate highly ordered honeycomb structured porous films and the procedures to manipulate the size of the pores in films generated from amphiphilic block copolymers were also investigated and identified.Analyses into the formation process of the honeycomb structured porous films revealed that the airflow casting method where the cast of polymer solution was supplied with a flow of moist air was the most suitable method to generate highly ordered honeycomb structured porous films from amphiphilic block copolymers. Variations to the casting conditions of the airflow casting method such as the rate of moist airflow could only provide limited alterations to the size of pores on films generated. However, changes to the chemical system of the casting solution such as the concentration and the molecular weight of polymers in the polymer solvent was more prominent in manipulating the size of pores in the generated films. On the other hand, any extreme variations to either the physical conditions or the chemical system could devastate the hexagonal arrangement of pores in these films.In the synthesis of amphiphilic block copolymers in this research, RAFT polymerization technique was used to generate the hydrophobic polymer block followed by the subsequent chain extension polymerization of the hydrophilic polymer block. The polymerization 'process, especially the hydrophilic chain extension polymerization, was investigated in details. It was established that there were significant dependence on the composition of the initial polymer block used, particularly the molecular weight and the type of chain transfer (RAFT) end group in the hydrophobic polymer chain. Incompatible RAFT end group and high polymer molecular weights of the initial block usually lead to slower rate of subsequent chain extension coupled with increased terminations. These copolymers generated were usually bimodal in molecular weightdistributions and broad in polydispersity indexes. Honeycomb structured porous films generated from one of these amphiphilic block copolymers were assessed as scaffoldings for cell culture to regenerate cells. In particular, the effects of cellular attachments and proliferations on the honeycomb porous structures were investigated. The assessment of these honeycomb structured porous films indicated that not only were these films not cytotoxic but they also enhanced the quantity of cellular proliferation (2.7x) when used as cell culture substrate compared to standard non-porous polystyrene cell culture surfaces.Finally, this research had shown a simple way to generate a new class of highly ordered porous material that could be customized individually for a wide range of applications. The synthesis of amphiphilic block copolymers to generate these films could be achieved by RAFT polymerization with a board selection of polymers choices according to applications. A porous cell substrate such as honeycomb structured porous films could enhance cellular growth when used as a cell culture substrate

Water-assisted formation of honeycomb structured porous films

Honeycomb structured porous materials were formed using four different casting variations of the water droplet templating method. The film quality of the materials generated from these casting techniques (airflow, cold stage, casting on water, and emulsion methods) was investigated by altering the polymer architecture and composition. Linear, star, and comb polystyrene as well as an amphiphilic diblock copolymer comprised of polystyrene-block- poly(dimethylacrylamide) (PS-b-PDMA) were previously synthesized and cast into films via these techniques. While irregular pore distributions were observed for linear polystyrene films generated by every technique screened, increasing the architectural complexity of the polymer yielded more regular films for a broad range of casting conditions for each of the techniques. With the exception of linear polystyrene, the airflow casting technique was shown to be the only technique capable of generating regular porous films for all of the polymeric materials. © Springer Science + Business Media, LLC 2006

Honeycomb-Structured Porous Films from Polypyrrole-Containing Block Copolymers Prepared via RAFT Polymerization as a Scaffold for Cell Growth

Honeycomb-structured porous films were prepared using customized amphiphilic block copolymers, synthesized by RAFT polymerization. Pyrrole was templated along an amphiphilic block copolymer, composed of polystyrene and poly(acrylic acid). Subsequent oxidation of pyrrol to polypyrrole, resulted in the formation of a soluble polypyrrole-containing polymer. Gel permeation chromatography and dynamic light scattering studies confirmed the solubility of the resulting customized amphiphilic block copolymer, in both water and organic solvent, forming either micelles or inverse aggregates. Porous films with a hexagonal array of micron-sized pores were generated with the polymer, using the breath figures templating technique. The resulting films were found to be non-cytotoxic and hence suitable as scaffolds for tissue engineering. Initial fibroblast cell culture studies on these scaffolds demonstrated a dependency of cell attachment on the pore size of scaffolds. © 2006 American Chemical Society

Diffusion and viscosity in arabinoxylan solutions: Implications for nutrition

Non-starch polysaccharides such as arabinoxylans have important roles in the human diet, resulting in potential benefits such as increased microbial fermentation, promotion of beneficial microflora, prevention of re-absorption of bile acids leading to lower plasma cholesterol, and retardation of starch digestion. The latter two beneficial effects may arise from viscosity and/or diffusion phenomena in the gastrointestinal tract. To study this, measurements of the viscosity and diffusion coefficients of a polymer probe similar in size to both bile salt micelles and alpha-amylase were carried out for water solutions of three arabinoxylans with differing viscosities. Diffusion coefficients were obtained using fluorescence recovery after photobleaching (FRAP). The concentration dependence of both viscosity and diffusion coefficients followed the usual behaviour of polymers for each of three arabinoxylan samples. However, at a given concentration, the sample with the highest viscosity also had the highest probe diffusion coefficient: the reverse of what would be expected for homogeneous solutions. This apparent anomaly is ascribed to differences in polymer structure between the three samples giving rise to varying levels of local polymer aggregation and consequent microvoids. These differences are verified using characterisation with multiple-detection size-exclusion chromatography. Deviations from simple Stokes–Einstein behaviour are ascribed to the existence of aggregates in solution. The results show that studies of the role of arabinoxylans in human nutrition cannot assume that the diffusion coefficients of species with sizes in the range important for digestive processes in a series of samples will increase with decreasing viscosity at a given concentration: diffusion coefficient and viscosity must be measured independently. © 2010 Elsevier Ltd. All rights reserved