Approximated matrix decomposition for IMRT planning with multileaf collimators

A standard problem in intensity modulated radiation therapy is the representation of a given intensity matrix, i.e. a matrix of nonnegative integers, as a nonnegative linear combination of special 0-1-matrices, called segments. These segments can be practically realized by multileaf collimators. One important aim is the minimization of the sum of the coefficients of the linear combination, i.e. the delivery time. In this article, we study the question how much the delivery time can be reduced if some small deviation from the given intensity matrix is allowed. We characterize the optimal solutions for one-row matrices and show that the approximation can be carried out in an iterative way. The structural characterization yields a fast algorithm that minimizes the delivery time and then also the deviation. Moreover, algorithms for the general case together with numerical results are presented.     

Development of a roadmap for advanced ceramics: 2010–2025

A roadmap for advanced ceramics for the period from 2010 to 2025 has been developed to provide guidelines for future investments for policy makers, scientists and industry alike. Based on questionnaires, interviews and a final workshop with well-balanced participation of members from industry and academia three roadmaps on application fields and two roadmaps on scientific areas have been developed and contrasted. The three application fields selected are: (i) electronics, information and communication; (ii) energy and environment; (iii) mechanical engineering and the two scientific fields are: (a) structural and functional properties; (b) process technology. Within these fields the tremendous growth opportunities for ceramics as an enabling technology are highlighted and manifold suggestions for future development are provided.     

Numerical approximation of incremental infinitesimal gradient plasticity

We investigate a representative model of continuum infinitesimal gradient plasticity. The formulation is an extension of classical rate‐independent infinitesimal plasticity based on the additive decomposition of the symmetric strain tensor into elastic and plastic parts. It is assumed that dislocation processes contribute to the storage of energy in the material whereby the curl of the plastic distortion appears in the thermodynamic potential and leads to an additional nonlocal backstress tensor. The formulation is cast into a numerical framework by a saddle point approximation of the corresponding minimization problem in each incremental loading step. This allows one to reformulate the (nonlocal) dissipation inequality to a point‐wise flow rule and yields a solution scheme, which is a direct extension of the standard approach in classical plasticity. Our numerical results show the regularizing effects of the additional physically motivated terms. Copyright © 2008 John Wiley & Sons, Ltd.     

Synthesis of an Anti-CD7 Recombinant Immunotoxin Based on PE24 in CHO and E. coli Cell-Free Systems

Recombinant immunotoxins (RITs) are an effective class of agents for targeted therapy in cancer treatment. In this article, we demonstrate the straight-forward production and testing of an anti-CD7 RIT based on PE24 in a prokaryotic and a eukaryotic cell-free system. The prokaryotic cell-free system was derived from Escherichia coli BL21 Star^TM (DE3) cells transformed with a plasmid encoding the chaperones groEL/groES. The eukaryotic cell-free system was prepared from Chinese hamster ovary (CHO) cells that leave intact endoplasmic reticulum-derived microsomes in the cell-free reaction mix from which the RIT was extracted. The investigated RIT was built by fusing an anti-CD7 single-chain variable fragment (scFv) with the toxin domain PE24, a shortened variant of Pseudomonas Exotoxin A. The RIT was produced in both cell-free systems and tested for antigen binding against CD7 and cell killing on CD7-positive Jurkat, HSB-2, and ALL-SIL cells. CD7-positive cells were effectively killed by the anti-CD7 scFv-PE24 RIT with an IC₅₀ value of 15 pM to 40 pM for CHO and 42 pM to 156 pM for E. coli cell-free-produced RIT. CD7-negative Raji cells were unaffected by the RIT. Toxin and antibody domain alone did not show cytotoxic effects on either CD7-positive or CD7-negative cells. To our knowledge, this report describes the production of an active RIT in E. coli and CHO cell-free systems for the first time. We provide the proof-of-concept that cell-free protein synthesis allows for on-demand testing of antibody–toxin conjugate activity in a time-efficient workflow without cell lysis or purification required.     

Particle Distribution and Separation in Continuous Casting Tundish

The tundish as a part of a continuous casting machine combines the discontinuous ladle metallurgy with the continuous solidification of slabs in the mould. The tundish plays a major role in the challenging task of “clean steel” production. That means the smallest number of inclusions and high cleanliness in all steel grades after changing the conditions at the inlet of the tundish. Inclusions hinder the metal forming process and lead often to fatigue. The cleanliness of steels is important to fulfil the customer's requirements. In the present study inclusion removal was simulated in a 1:3 scaled water model of a single‐strand tundish for the production of stainless steels with a particle counter. The particle counter is capable of counting a large number of particles with a wide range of diameters. The separation rate for particle diameters from d_P = 1 ‐ 250 μm was determined with a counter for the water model tundish. With similarity conditions for the particles this deposition rate can be transformed to the melt flow in a steel tundish. The separation rate was measured for different flow rates in the water model tundish. A larger flow rate decreased the separation rate. Additionally, the separation rate for the tundish fitted with an impact pad was measured and showed a significant increase of separation for particles with a smaller diameter. Furthermore, the particle distribution in the tundish for different size groups of particles was investigated with and without an impact pad. Numerical simulations were carried out with the finite‐volume commercial code FLUENT using the realizable k‐ε turbulence model. A special boundary condition for the separation of particles at the surface was implemented.     

Hydroxyapatite as a filler for biosynthetic PHB homopolymer and P(HB–HV) copolymers

This paper deals with some of the fundamental problems encountered when using a semicrystalline polymer as the matrix phase for a particulate‐filled composite. As our model system we adopted poly‐(R)‐3‐hydroxybutyrate, PHB, and two copolymers of (R)‐3‐hydroxybutyrate and (R)‐3‐hydroxyvalerate, P(HB–HV), for the matrix phase, and the mineral calcium hydroxyapatite as a particulate filler. The structure and properties of compression‐moulded films of various compositions were investigated by polarized light microscopy, wide‐angle X‐ray scattering and mechanical testing. It was found that the degree of crystallinity of the matrix was lower in filled samples, and that the spherulitic crystallization of the matrix appeared to cause the filler particles to form agglomerates, which would not be as effective a reinforcement as finely dispersed primary filler particles. The tensile strength, strain‐to‐break and tensile modulus of samples of different compositions were analysed using well‐known theories for composite behaviour. Copyright © 2003 Society of Chemical Industry