Current strategies of regenerative medicine are focused on the restoration of pathologically altered tissue architectures by transplantation of cells in combination with supportive scaffolds and biomolecules. In recent years, considerable interest has been given to biologically active scaffolds which are based on similar analogs of the extracellular matrix that have induced synthesis of tissues and organs. To restore function or regenerate tissue, a scaffold is necessary that will act as a temporary matrix for cell proliferation and extracellular matrix deposition, with subsequent ingrowth until the tissues are totally restored or regenerated. Scaffolds have been used for tissue engineering such as bone, cartilage, ligament, skin, vascular tissues, neural tissues, and skeletal muscle and as vehicle for the controlled delivery of drugs, proteins, and DNA. Various technologies come together to construct porous scaffolds to regenerate the tissues/organs and also for controlled and targeted release of bioactive agents in tissue engineering applications. In this paper, an overview of the different types of scaffolds with their material properties is discussed. The fabrication technologies for tissue engineering scaffolds, including the basic and conventional techniques to the more recent ones, are tabulated.

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Polymeric scaffolds in tissue engineering application: a review

ALICE (A Large Ion Collider Experiment) is a general-purpose, heavy-ion detector at the CERN LHC which focuses on QCD, the strong-interaction sector of the Standard Model. It is designed to address the physics of strongly interacting matter and the quark-gluon plasma at extreme values of energy density and temperature in nucleus-nucleus collisions. Besides running with Pb ions, the physics programme includes collisions with lighter ions, lower energy running and dedicated proton-nucleus runs. ALICE will also take data with proton beams at the top LHC energy to collect reference data for the heavy-ion programme and to address several QCD topics for which ALICE is complementary to the other LHC detectors. The ALICE detector has been built by a collaboration including currently over 1000 physicists and engineers from 105 Institutes in 30 countries. Its overall dimensions are 161626 m3 with a total weight of approximately 10 000 t. The experiment consists of 18 different detector systems each with its own specific technology choice and design constraints, driven both by the physics requirements and the experimental conditions expected at LHC. The most stringent design constraint is to cope with the extreme particle multiplicity anticipated in central Pb-Pb collisions. The different subsystems were optimized to provide high-momentum resolution as well as excellent Particle Identification (PID) over a broad range in momentum, up to the highest multiplicities predicted for LHC. This will allow for comprehensive studies of hadrons, electrons, muons, and photons produced in the collision of heavy nuclei. Most detector systems are scheduled to be installed and ready for data taking by mid-2008 when the LHC is scheduled to start operation, with the exception of parts of the Photon Spectrometer (PHOS), Transition Radiation Detector (TRD) and Electro Magnetic Calorimeter (EMCal). These detectors will be completed for the high-luminosity ion run expected in 2010. This paper describes in detail the detector components as installed for the first data taking in the summer of 2008.

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The ALICE experiment at the CERN LHC

A review of stimuli-responsive shape memory polymer composites

The market sales of ready-to-use fresh vegetables have grown rapidly in recent decades as a result of changes in consumer attitudes, especially consumption of fresh-cut lettuce and carrot due to their use in prepared salads. Chlorine solutions have been widely used to sanitise fruit and vegetables in the fresh-cut industry. However, the association of chlorine with the possible formation of carcinogenic chlorinated compounds in water has called into question the use of chlorine in food processing. There is a real need to find alternatives for preservation of fresh-cut fruit and vegetables in order to improve the efficacy of washing treatments. Alternatives or modified methods have been proposed, as antioxidants, irradiation, ozone, organics acids, modified atmosphere packaging, whey permeate, etc.; however, none have yet gained widespread acceptance by the industry. For this reason the development of alternatives and markers in order to measure the efficacy of these alternatives are needed.

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Extending and Measuring the Quality of Fresh-cut Fruit and Vegetables: a Review

The thermally-induced shape-memory effect (SME) is the capability of a material to change its shape in a predefined way in response to heat. In shape-memory polymers (SMP) this shape change is the entropy-driven recovery of a mechanical deformation, which was obtained before by application of external stress and was temporarily fixed by formation of physical crosslinks. The high technological significance of SMP becomes apparent in many established products (e.g., packaging materials, assembling devices, textiles, and membranes) and the broad SMP development activities in the field of biomedical as well as aerospace applications (e.g., medical devices or morphing structures for aerospace vehicles). Inspired by the complex and diverse requirements of these applications fundamental research is aiming at multifunctional SMP, in which SME is combined with additional functions and is proceeding rapidly. In this review different concepts for the creation of multifunctionality are derived from the various polymer network architectures of thermally-induced SMP. Multimaterial systems, such as nanocomposites, are described as well as one-component polymer systems, in which independent functions are integrated. Future challenges will be to transfer the concept of multifunctionality to other emerging shape-memory technologies like light-sensitive SMP, reversible shape changing effects or triple-shape polymers.

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Multifunctional Shape-Memory Polymers

Crosslinking of recycled polyethylene by gamma and electron beam irradiation

Crosslinking of recycled polyethylene by gamma irradiation in the presence of sensitizers

Meta-alca-1,3-diynylbenzoic acids with different chain lengths were synthesized and the formation of Langmuir-Blodgett (LB) membranes was studied. Benzoic acids with alkyl chain length greater than 8 formed stable monolayers while those with 4 and 6 did not form good condensed phases. Multilayer films were irradiated with UV light and the diacetylenic groups polymerized to give polydiacetylene LB films having absorption maxima at around 640 nm.

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Langmuir-Blodgett Membranes of m-Alca-1,3-Diynylbenzoic Acids

To study the formation and properties of Langmuir-Blodgett membranes of aromatic diacetylenes, 4 novel diacetylenics amphiphiles were synthesized, and their multilayer membranes were prepared and photopolymerization was carried out. 13-Phenyl-10,12-tridecynoic acid did not give a stable isotherm, and the structure appeared not proper for topochemical polymerization of the diacetylenic group, but substitution on the para-position of the acids stabilized the isotherm giving multilayer Y type membranes whose diacetylene groups readily polymerized on irradiation of UV light. There was a clear relationship between electronic density of aromatic groups, absorption maxima of polydiacetylene films and resistance to radiation.

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Langmuir-Blodgett Membranes of 13-Aryltrideca-10, 12-diynoic Acids

A theoretical thermodynamical study was carried out on the formation of Langmuir-Blodgett films of phenyl diacetylene carboxylic acid derivatives containing a lateral chain. Two cases were computed: one for the isolated molecule and another one for the same structure immersed in water with an acid pH. The result of this process shows that the formation of the film under the latter conditions is favoured by the moiety of the carboxylic group. An analysis of the frontier orbitals and the dipole moment in both situations is also presented.

María del Pilar Carreón

Papers

Crosslinking of recycled polyethylene by gamma and electron beam irradiation

Crosslinking of recycled polyethylene by gamma irradiation in the presence of sensitizers

Langmuir-Blodgett Membranes of m-Alca-1,3-Diynylbenzoic Acids

Langmuir-Blodgett Membranes of 13-Aryltrideca-10, 12-diynoic Acids

Theoretical study of the interaction between phenyl diacetylenes and the solvent for the formation of Langmuir-Blodgett films