Medical image computing at the Institute of Mathematics and Computer Science in Medicine,University Hospital Hamburg-Eppendorf

The author reviews the history of medical image computing at his institute, summarizes the achievements, sketches some of the difficulties encountered, and draws conclusions that might be of interest especially to people new to the field. The origin and history section provides a chronology of this work, emphasizing the milestones reached during the past three decades. In accordance with the author's group's focus on imaging, the paper is accompanied by many pictures, some of which, he thinks, are of historical value.     

ATM‐based wireless broadband access in the local loop

Broadband networks using wireless transmission techniques are a quick and flexible means of implementing subscriber access. Unoccupied frequency bands with sufficient bandwidth to allow the transmission of digital signals at very high bit rates are found only in the microwave bands. Because the path loss is fairly high at these frequencies, the diameter of radio cells is limited to a maximum of a few kilometres. This results in a microcellular system, which is best implemented in the form of a point‐to‐multipoint system, where one radio‐base station serves all subscribers registered in that radio cell. An interactive, broadband, ATM‐based radio local loop has undergone successful trials in Munich. Copyright © 2001 John Wiley & Sons, Ltd.     

Surface lipids of the social waspPolistes annularis (L.) and its nest and nest pedicel

Cuticular lipids were recovered fromPolistes annularis workers and characterized by combined gas-chromatography-mass spectrometry. These lipids were found to be straight-chain and methyl-branched hydrocarbons with the major components being 13,17-dimethylhentriacontane (18%), 3-methyl-nonacosane (13%), and 3-methylheptacosane (11%). Cuticular lipids with a very similar composition were found on the surface of the larvae, eggs, and adult males ofPolistes annularis as well as on the surface of the nest and nest pedicel of the wasp. Hexadecanoic acid and octadecenoic acid were also found on the surface of the nest pedicel and these acids and/or the hydrocarbons may play a defensive role for the wasps.     

Characterization of pedicel,paper, and larval silk from nest ofPolistes annularis (L.)

The pedicel, nest paper, and larval silk ofPolistes annularis nests were analyzed by high-resolution solid-state [¹³C]NMR. The pedicel was found to have a high nitrogen content (11%), and the NMR spectra indicated that it is a mixture of carbohydrate and protein. The pedicel protein has an amino acid composition that is very rich in glycine, alanine, serine, and proline (67% of identified residues), similar to that of some insect silks. Solid-state [¹³C]NMR indicated that the nest paper is composed predominantly of cellulose. Silk, spun by matureP. annularis larvae, was shown by [¹³C] NMR and amino acid analysis to be a protein very high in serine and alanine (53%), but the amino acid composition is distinct from that of the pedicel protein.     

Au@Hg Nanoalloy Formation Through Direct Amalgamation: Structural,Spectroscopic, and Computational Evidence for Slow Nanoscale Diffusion

Dynamic core–shell nanoparticles have received increasing attention in recent years. This paper presents a detailed study of Au–Hg nanoalloys, whose composing elements show a large difference in cohesive energy. A simple method to prepare Au@Hg particles with precise control over the composition up to 15 atom% mercury is introduced, based on reacting a citrate stabilized gold sol with elemental mercury. Transmission electron microscopy shows an increase of particle size with increasing mercury content and, together with X‐ray powder diffraction, points towards the presence of a core–shell structure with a gold core surrounded by an Au–Hg solid solution layer. The amalgamation process is described by pseudo‐zero‐order reaction kinetics, which indicates slow dissolution of mercury in water as the rate determining step, followed by fast scavenging by nanoparticles in solution. Once adsorbed at the surface, slow diffusion of Hg into the particle lattice occurs, to a depth of ca. 3 nm, independent of Hg concentration. Discrete dipole approximation calculations relate the UV–vis spectra to the microscopic details of the nanoalloy structure. Segregation energies and metal distribution in the nanoalloys were modeled by density functional theory calculations. The results indicate slow metal interdiffusion at the nanoscale, which has important implications for synthetic methods aimed at core–shell particles.     

Challenges and opportunities for next-generation intracortically based neural prostheses

Neural prosthetic systems aim to help disabled patients by translating neural signals from the brain into control signals for guiding computer cursors, prosthetic arms, and other assistive devices. Intracortical electrode arrays measure action potentials and local field potentials from individual neurons, or small populations of neurons, in the motor cortices and can provide considerable information for controlling prostheses. Despite several compelling proof-of-concept laboratory animal experiments and an initial human clinical trial, at least three key challenges remain which, if left unaddressed, may hamper the translation of these systems into widespread clinical use. We review these challenges: achieving able-bodied levels of performance across tasks and across environments, achieving robustness across multiple decades, and restoring able-bodied quality proprioception and somatosensation. We also describe some emerging opportunities for meeting these challenges. If these challenges can be largely or fully met, intracortically based neural prostheses may achieve true clinical viability and help increasing numbers of disabled patients.     

Location Estimation via Support Vector Regression

Location estimation using the global system for mobile communication (GSM) is an emerging application that infers the location of the mobile receiver from multiple signals measurements. While geometrical and signal propagation models have been deployed to tackle this estimation problem, the terrain factors and power fluctuations have confined the accuracy of such estimation. Using support vector regression, we investigate the missing value location estimation problem by providing theoretical and empirical analysis on existing and novel kernels. A novel synthetic experiment is designed to compare the performances of different location estimation approaches. The proposed support vector regression approach shows promising performances, especially in terrains with local variations in environmental factors     

Bestimmung des Endotoxin-Gehalts in Eiprodukten mit Hilfe eines miniaturisierten chromogenen Limulus-Tests

Zusammenfassung Die Eignung eines chromogenenLimulus-Tests zur Bestimmung des Endotoxin-Gehalts in Eiprodukten wurde gepruft. Dabei zeigte die Analyse verschieden stark bakteriell belasteter Volleimassen eine deutliche Korrelation zwischen Endotoxin-Konzentration und Gesamtkeimzahl (6 x 10⁴ cfu x ng^–1 Endotoxin) Bowie der Anzahl vonEnterobacteriaceen (7x10² cfu x ng^–1 Endotoxin). Vergleichbare Ergebnisse konnten auch mit Eigelb- und Eiweilßproben erzielt werden. Der Endotoxin-Nachweis wurde durch Hitzebehandlung (65 °C, 60 min) nicht beeinflußt. Endotoxinfreies steriles Volleimaterial hatte bis zu einer Konzentration im Testansatz von 10 mg x ml^–1 keinen Einfluß auf das Mcßergebnis. Im vorliegenden Bericht wird eine miniaturisierte Version des Testverfahrens vorgestellt, die im Mikro titerplatten-System durchgeführt werden kann.

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Determination of endotoxin in egg products with a miniaturized chromogenic Limulus test

Summary A chromogenicLimulus amoebocyte lysate assay was applied to monitor endotoxin concentration in egg products. Analysis of differently contaminated whole egg probes revealed a strong correlation of endotoxin concentration to total bacterial count 6 x 10⁴ cfu x ng^–1, where cfu=colony-forming unit) as well as to number ofEnterobacteriaceae (1 ng/7 x 10² cfu). Similar relations were also found for egg white and egg yolk probes. A significant influence of heat pretreatment of egg probes (65° C, 60 min) on endotoxin detection could be excluded. Up to a concentration of 10 mg x µl^–1 endotoxin-free whole egg material did not interfere with the test system. A miniaturized version of the chromogenicLimulus test, which can be carried out in microtiter plates, is described.

     

Parallel Adder Design with Reduced Circuit Complexity Using Resonant Tunneling Transistors and Threshold Logic

Quantum-effect devices utilizing resonant tunneling are promising candidates for future nano-scale integration. Originating from the technological progress of semiconductor technology, circuit architectures with reduced complexity are investigated by exploiting the negative-differential resistance of resonant tunneling devices. In this paper a resonant tunneling device threshold logic family based on the Monostable-Bistable Transition Logic Element (MOBILE) is proposed and applied to different parallel adder designs, such as ripple carry and binary carry lookahead adders. The basic device is a resonant tunneling transistor (RTT) composed of a resonant tunneling diode monolithically integrated on the drain contact layer of a heterostructure field effect transistor. On the circuit level the key components are a programmable NAND/NOR logic gate, threshold logic gates, and parallel counters. The special properties of MOBILE logic gates are considered by a bit-level pipelined circuit style. Experimental results are presented for the NAND/NOR logic gate.