A comparison of category and letter fluency in Alzheimer's disease and Huntington's disease.

44 patients with dementia of the Alzheimer type (DAT), 44 elderly normal control (ENC) Ss demographically matched to the DAT group, 42 patients with Huntington's disease (HD), and 42 middle-aged normal control (MNC) Ss demographically matched to the HD group were administered letter and category fluency tasks. DAT patients showed an overproportional impairment on category than on letter fluency tasks, whereas HD patients were equally impaired. Analyses based on receiver operating characteristic curves revealed that category fluency correctly classified significantly more DAT and ENC Ss than did letter fluency, whereas the 2 fluency tasks did not differ in this respect for HD and MNC Ss. Results suggest that HD patients' failures on fluency tasks are caused by impaired initiation/retrieval capacities. In contrast, DAT patients' greater category than letter fluency deficits are primarily due to a breakdown in the structure of semantic knowledge. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Subsynchronous resonance phenomena considering skin effects insolid iron rotor turbo-generators

The question of how the skin effects of the eddy current in the rotor of a synchronous generator influence the induction generation modes and the torsional interaction modes of the subsynchronous resonance (SSR) phenomena is addressed. The 3-D magnetic diffusion equation is solved in a round solid iron rotor to provide data for comparison and discussion purposes. The problem of representing skin depth, which is frequency dependent, in the time-domain stability analysis based on dx/dt=[A]x is examined     

Halo World: Tools for Parallel Cluster Finding in Astrophysical N-body Simulations

Cosmological N-body simulations on parallel computers produce large datasets--gigabytes at each instant of simulated cosmological time, and hundreds of gigabytes over the course of a simulation. These large datasets require further analysis before they can be compared to astronomical observations. The “Halo World” tools include two methods for performing halo finding: identifying all of the gravitationally stable clusters in a point-sampled density field. One of these methods is a parallel implementation of the friends of friends (FOF) algorithm, widely used in the field of N-body cosmology. The new IsoDen method based on isodensity surfaces has been developed to overcome some of the shortcomings of FOF. Parallel processing is the only viable way of obtaining the necessary performance and storage capacity to carry out these analysis tasks. Ultimately, we must also plan to use disk storage as the only economically viable alternative for storing and manipulating such large data sets. Both IsoDen and friends of friends have been implemented on a variety of computer systems, with parallelism up to 512 processors, and successfully used to extract halos from simulations with up to 16.8 million particles.     

Fibroblasts prevent apoptosis of IL-2-deprived T cells without inducing proliferation: a selective effect on Bcl-XL expression

Tumour hypoxia is well recognised as a major factor contributing to radioresistance. This article examines the role of hypoxia in influencing the treatment outcome following radiotherapy (RT), and reviews the rationale and results of clinical trials that utilise hypoxic sensitizers or cytotoxins in the treatment of head and neck carcinoma. Histologic evidence for tumour hypoxia in human neoplasms was first reported in 1955. Since then, direct measurement by microelectrodes has revealed heterogeneity in intratumoural oxygen concentrations, and low oxygen concentrations are associated with poor local-regional control by RT. These findings coupled with the result of nuclear imaging studies employing radiolabelled imidazoles, provide strong evidence for the existence of tumour hypoxia which influences RT treatment outcome. Hyperbaric oxygen (HBO) trials for head and neck cancer, conducted in the early 1970s, demonstrated that HBO improved local control and survival rates in patients with head and neck cancer receiving radiotherapy (RT). Since the mid-1970s, clinical research in overcoming tumour hypoxia was mainly centred on the use of nitro-imidazoles as hypoxic cell sensitizers. However, the results from several major clinical trials remain inconclusive. Specifically, the Radiation Therapy Oncology Group (RTOG) misonidazole head and neck trial (298 patients) showed no benefit. The Danish misonidazole trial (626 patients) showed no overall benefit, however positive results were observed in a subgroup (304 pharyngeal cancer patients). Although the European Organisation for Research and Teaching of Cancer (EORTC) misonidazole trial with hyperfractionated RT showed no benefit, the Danish nimorazole trial demonstrated an overall benefit in survival as well as local control. The European etanidazole (ETA) trial (374 patients) showed no advantage of adding the drug to RT. The RTOG ETA trial (504 patients) showed no global benefit. However, positive results were observed in a subset of patients with early nodal disease (197 patients). In addition, a recent meta-analysis by Overgaard, utilising pooled results in the literature demonstrated that modification of tumour hypoxia significantly improved local-regional control in head and neck cancers with an odds ratio of 1.23 (95% confidence limits 1.09 to 1.37). Hypoxic cytotoxins, such as tirapazamine, represent a novel approach in overcoming radioresistant hypoxic cells. Tirapazamine is a bioreductive agent which, by undergoing one electron reduction in hypoxic conditions, forms cytotoxic free radicals that produce DNA strand breaks causing cell death. In vitro and in vivo laboratory studies demonstrate that tirapazamine is 40 to 150 times more toxic to cells under hypoxic conditions as compared to oxygenated conditions and that tirapazamine is superior to ETA in enhancing fractionated irradiation in mouse SCCVII and other tumour types with an enhancement ratio of 1.5 to 3.0. Phase I studies demonstrated that therapeutic doses of tirapazamine can be given safely. A multi-institutional phase II trial using tirapazamine with concurrent RT for head and neck cancer is now in progress.     

Use of superoxide as an electron shuttle for iron acquisition by the marine cyanobacterium Lyngbya majuscula

Reduction of iron from the ferric state to the ferrous state is one strategy employed by microorganisms in nearneutral environments to increase its biological availability. In recent years, the existence of mobile reducing agents produced bymicroorganismsto promote iron reduction, known as electron shuttles, has been demonstrated. Production of electron shuttles has been shown for several organisms, employing a variety of mostly organic molecules as the electron carrier. Here we show that the coastal cyanobacterium Lyngbya majuscula produces iron-reducing superoxide radicals (02*-) and that this facilitates increased iron uptake. We suggest that superoxide is a useful electron shuttle because it reacts rapidly and almost indiscriminately with Fe(lll)-organic complexes and its precursor, dissolved oxygen, is ubiquitous in the photic zone. We further suggest that, for these reasons, the generation of superoxide by marine oxygenic photosynthetic microorganisms and its use in facilitating iron uptake may be a reasonably widespread process.