Toxicity to neuroblastoma cells and spheroids of benzylguanidine conjugated to radionuclides with short-range emissions

Radiolabelled meta-iodobenzylguanidine (MIBG) is selectively taken up by tumours of neuroendocrine origin, where its cellular localization is believed to be cytoplasmic. The radiopharmaceutical [131I]MIBG is now widely used in the treatment of neuroblastoma, but other radioconjugates of benzylguanidine have been little studied. We have investigated the cytotoxic efficacy of beta, alpha and Auger electron-emitting radioconjugates in treating neuroblastoma cells grown in monolayer or spheroid culture. Using a no-carrier-added synthesis route, we produced 123I-, 125I-, 131I- and 211At-labelled benzylguanidines and compared their in vitro toxicity to the neuroblastoma cell line SK-N-BE(2c) grown in monolayer and spheroid culture. The Auger electron-emitting conjugates ([123I]MIBG and [125I]MIBG) and the alpha-emitting conjugate ([211At]MABG) were highly toxic to monolayers and small spheroids, whereas the beta-emitting conjugate [131I]MIBG was relatively ineffective. The Auger emitters were more effective than expected if the cellular localization of MIBG is cytoplasmic. As dosimetrically predicted however, [211At]MABG was found to be extremely potent in terms of both concentration of radioactivity and number of atoms ml(-1) administered. In contrast, the Auger electron emitters were ineffective in the treatment of larger spheroids, while the beta emitter showed greater efficacy. These findings suggest that short-range emitters would be well suited to the treatment of circulating tumour cells or small clumps, whereas beta emitters would be superior in the treatment of subclinical metastases or macroscopic tumours. These experimental results provide support for a clinical strategy of combinations ('cocktails') of radioconjugates in targeted radiotherapy.     

Nano- and microscale mechanical characterization using instrumented indentation

This overview presents instrumented indentation as a powerful tool for qualitative and quantitative mechanical characterization of nano-andmicroscale volumes and structures. A brief review of existing methodologies for estimating elasto-plasticpropertiesfromrepresentative load-depth data is presented and the principle behind such approaches is emphasized. Selected examples are also presented to illustrate the applicability of nanoindentation to a variety of material classes and geometries.     

The Bus-Connected Ringed Tree: A Versatile Interconnection Network

We consider the use of multiple-bus networks (MBNs) in a synchronous parallel processing environment. We propose a class of MBNs called bus-connected ringed trees (BRTs). A 1-dimensional BRT is shown to have an optimal processor fan-out of 2 and to be capable of optimally simulating a complete binary tree and a ring. The results for the 1-dimensional BRT extend to higher dimensional BRTs. In particular, the 2-dimensional BRT is shown to have a constant processor fan-out of 4 and to be capable of efficiently simulating a complete binary tree, ring, and fixed-degree 2-dimensional structures that include the torus, mesh, and mesh of trees. The 2-dimensional BRT serves as a uniform platform on which all algorithms for the above topologies can be run efficiently.     

Practical OEICs based on the monolithic integration of GaAs-InGaPLEDs with commercial GaAs VLSI electronics

Recent advances in the epitaxy-on-electronics (EoE) integration process, which combines commercial GaAs VLSI electronics with conventional epitaxial growth and fabrication to produce complex, monolithic optoelectronic integrated circuits (OEICs), have resulted in improved integrated light-emitting diodes (LEDs), eliminated any impact on the preexisting electronics, and increased the robustness of the integration process. An EoE-integrated OEIC combining a photodetector, electronics, and LED is presented which demonstrates the capability of this technology to now satisfy practical optoelectronic systems requirements     

Large leak sodium-water reaction analysis of an LMFBR steam generator using a variable temperature spherical bubble model

A simplified 1-D numerical model has been developed to study the pressure transients due to a large leak sodium-water reaction. In the initial stage the hydrogen generated in the reaction is taken to be of spherical shape and once the diameter of the bubble equals the shell diameter its growth is modelled in a columnar form. The model has been used to predict the pressure evolution in the reaction site for a typical experiment and has performed well. Also presented is a comparison with the predictions of a numerical 3-D model for the same experiment.     

Scaling simulation of the fusing-restricted reconfigurable mesh

This paper deals with the ability of a model to adapt algorithm instances of different sizes to run on a given model size without significant loss of efficiency. The overhead in simulating a step of a large instance of the model on a smaller instance can quantify this ability. A reconfigurable mesh (R-Mesh) can use its bus structure as a computational resource, presenting an obstacle to efficiently scaling down algorithms to run on a smaller R-Mesh. We construct a scaling simulation of a Fusing-Restricted Reconfigurable Mesh (FR-Mesh), a version of the R-Mesh. The overhead of this simulation depends only on the simulating machine size and not on the simulated machine size. Previously, the R-Mesh was not known to admit such a simulation overhead without significantly reducing its computational power. The small overhead holds importance for flexibility in algorithm design and for running algorithms with various input sizes on an available model of given size. The results of this paper extend to a variety of concurrent write rules and also translate to an improved scaling simulation of an unrestricted R-Mesh     

Theory and design of optimum FIR compaction filters

The problem of optimum FIR energy compaction filter design for a given number of channels M and a filter order N is considered. The special cases where N相似文献   

On optimal analysis/synthesis filters for coding gain maximization

We consider the use of pre and postfilters in conjunction with M-channel, uniform-band paraunitary (orthonormal) filter banks. We show that given any orthonormal filter bank, the pre and postfilters that maximize the coding gain are determined entirely by the power spectrum of the input process regardless of the details of the orthonormal filter blank (which could be FIR, IIR, or even the ideal brickwall filter bank). The optimized coding gain, however, depends on the prefilter as well as the sandwiched orthonormal filter bank. The coding gain improvement due to pre and postfiltering is often significant as we demonstrate with numerical examples and comparisons. The validity of our results depends strongly on the orthonormality property of the filter bank in between the pre and postfilters. In the nonorthonormal case, most of these results are not true, as is demonstrated     

Some results in the theory of crosstalk-free transmultiplexers

The crosstalk-free transmultiplexer (CF-TMUX) focuses on crosstalk cancellation (CC) rather than on suppressing it. The authors present an analysis of the CF-TMUX based on the polyphase component matrices of the filter banks used in TDM→FDM and FDM→TDM conversions, respectively. Thus a necessary and sufficient condition for complete CC is obtained. It is shown that the filters for a CF-TMUX are the same as the filters for a 1-skewed alias free QMF bank. In addition, if the QMF bank satisfies the perfect reconstruction (PR) property, then the TMUX also satisfies PR. The relation between CF-TMUX filters and alias-free QMF banks is used to obtain a direct design procedure for CF-TMUX filters (both FIR and IIR). It is also shown that approximately crosstalk-free TMUX filters can be obtained from any approximately alias-free QMC bank. Design examples and comparison tables are included