Avian lens spectrin: subunit composition compared with erythrocyte and brain spectrin

Chicken lens spectrin is composed predominantly of equimolar amounts of two polypeptides with solubility properties similar, but not identical, to erythrocyte spectrin. The larger polypeptide, Mr 240,000 (lens alpha- spectrin), co-migrates with erythrocyte and brain alpha-spectrin on one- and two-dimensional SDS polyacrylamide gels and cross-reacts with antibodies specific for chicken erythrocyte alpha-spectrin; the smaller polypeptide, Mr 235,000 (lens gamma-spectrin), co-migrates with brain gamma-spectrin and does not cross-react with either the alpha-spectrin antibodies specific for chicken erythrocyte beta-spectrin. Minor amounts of polypeptides antigenically related to erythrocyte beta- spectrin with a greater electrophoretic mobility than lens gamma- spectrin are also detected in lens. The equimolar ratio of lens alpha- and gamma-spectrin is invariantly maintained during the extraction of lens plasma membranes under different conditions, or after immunoprecipitation of whole extracts of lens with erythrocyte alpha- spectrin antibodies. Two-dimensional peptide mapping reveals that whereas alpha-spectrins from chicken erythrocytes, brain, and lens are highly homologous, the gamma-spectrins, although related, have some cell-type-specific peptides and are substantially different from erythrocyte beta-spectrin. Thus, the expression of cell-type-specific gamma- and beta-spectrins may be the basis for the assembly of a spectrin-plasma membrane complex whose molecular composition is tailored to the functional requirements of the particular cell-type

Remote sensing of the Earth with spaceborne imaging radars

Spaceborne imaging sensors in the visible, infrared and passive microwave have been used to observe and study the Earth's surface since the early stages of the space program. More recently, active microwave imaging sensors (radars) have been developed to extend our capability to study the Earth surface processes. Imaging radars, flown on Seasat (1978) and the Shuttle (1981, 1984), acquired synoptic images of a variety of geologic, biologic, and oceanographic features and provided new insight in some of the land and ocean processes. Subsurface synoptic imaging was achieved for the first time in some of the arid regions of the world. Soil moisture distribution after a rainstorm was clearly delineated, opening the possibility of its monitoring on a global basis. Polar ice distribution and dynamics over large areas in the Beaufort Sea were monitored over a three-month period, thus allowing the possibility of operational observation of ice dynamics in support of polar navigation. The successful development and flight of these spaceborne imaging radars was the result of major technological developments in the 1970s. They used some of the largest spaceborne lightweight planar array antennas (2X10 m) with printed radiating elements. The transmitters were fully solid state and generated a 1 kw peak power signal at L-band (1.2 Ghz). The processing of the received data to generate the high-resolution (25 to 40 m) imagery was done using both optical and digital processors. More advanced imaging radar systems are under development. Multispectral, multipolarization imaging radar systems are under development for flight in the late 1980s, thus extending our capability of detailed studies of the Earth surface processes and the nature of its cover. Extremely fast SAR digital processors are under development using the most advanced integrated circuits and allowing real-time processing of the data. This corresponds to a computational capability of 6 X 10^9 operations/s. This chapter consists of a review of the recent scientific and technological developments in the field of Earth observation with spaceborne imaging radars and an overview of planned activities in the 1980s

Solvable Groups, Free Divisors and Nonisolated Matrix Singularities II: Vanishing Topology

In this paper we use the results from the first part to compute the vanishing topology for matrix singularities based on certain spaces of matrices. We place the variety of singular matrices in a geometric configuration of free divisors which are the "exceptional orbit varieties" for repesentations of solvable groups. Because there are towers of representations for towers of solvable groups, the free divisors actually form a tower of free divisors $E_n$, and we give an inductive procedure for computing the vanishing topology of the matrix singularities. The inductive procedure we use is an extension of that introduced by L\^{e}-Greuel for computing the Milnor number of an ICIS. Instead of linear subspaces, we use free divisors arising from the geometric configuration and which correspond to subgroups of the solvable groups. Here the vanishing topology involves a singular version of the Milnor fiber; however, it still has the good connectivity properties and is homotopy equivalent to a bouquet of spheres, whose number is called the singular Milnor number. We give formulas for this singular Milnor number in terms of singular Milnor numbers of various free divisors on smooth subspaces, which can be computed as lengths of determinantal modules. In addition to being applied to symmetric, general and skew-symmetric matrix singularities, the results are also applied to Cohen--Macaulay singularities defined as 2 x 3 matrix singularities. We compute the Milnor number of isolated Cohen--Macaulay surface singularities of this type in $\mathbb{C}^4$ and the difference of Betti numbers of Milnor fibers for isolated Cohen--Macaulay 3--fold singularities of this type in $\mathbb{C}^5$.Comment: 53 pages. To appear in Geometry & Topology. Changes in response to helpful referee: replace the erroneous Corollary 6.2 with a new version, specify that we consider 2x3 Cohen-Macaulay singularities, calculate more entries of Table 5, improve wording, format for publicatio

Fault-Tolerant, Multiple-Zone Temperature Control

A computer program has been written as an essential part of an electronic temperature control system for a spaceborne instrument that contains several zones. The system was developed because the temperature and the rate of change of temperature in each zone are required to be maintained to within limits that amount to degrees of precision thought to be unattainable by use of simple bimetallic thermostats. The software collects temperature readings from six platinum resistance thermometers, calculates temperature errors from the readings, and implements a proportional + integral + derivative (PID) control algorithm that adjusts heater power levels. The software accepts, via a serial port, commands to change its operational parameters. The software attempts to detect and mitigate a host of potential faults. It is robust to many kinds of faults in that it can maintain PID control in the presence of those faults

Canine olfactory ensheathing cells from the olfactory mucosa can be engineered to produce active chondroitinase ABC

A multitude of factors must be overcome following spinal cord injury (SCI) in order to achieve clinical improvement in patients. It is thought that by combining promising therapies these diverse factors could be combatted with the aim of producing an overall improvement in function. Chondroitin sulphate proteoglycans (CSPGs) present in the glial scar that forms following SCI present a significant block to axon regeneration. Digestion of CSPGs by chondroitinase ABC (ChABC) leads to axon regeneration, neuronal plasticity and functional improvement in preclinical models of SCI. However, the enzyme activity decays at body temperature within 24–72 h, limiting the translational potential of ChABC as a therapy. Olfactory ensheathing cells (OECs) have shown huge promise as a cell transplant therapy in SCI. Their beneficial effects have been demonstrated in multiple small animal SCI models as well as in naturally occurring SCI in canine patients. In the present study, we have genetically modified canine OECs from the mucosa to constitutively produce enzymatically active ChABC. We have developed a lentiviral vector that can deliver a mammalian modified version of the ChABC gene to mammalian cells, including OECs. Enzyme production was quantified using the Morgan-Elson assay that detects the breakdown products of CSPG digestion in cell supernatants. We confirmed our findings by immunolabelling cell supernatant samples using Western blotting. OECs normal cell function was unaffected by genetic modification as demonstrated by normal microscopic morphology and the presence of the low affinity neurotrophin receptor (p75NGF) following viral transduction. We have developed the means to allow production of active ChABC in combination with a promising cell transplant therapy for SCI repair

Long memory and nonlinear time series

Introduction to special Annals issue of papers presented at a conference in Cardiff, UK on July 9–11th 200

Validating a large geophysical data set: Experiences with satellite-derived cloud parameters

We are validating the global cloud parameters derived from the satellite-borne HIRS2 and MSU atmospheric sounding instrument measurements, and are using the analysis of these data as one prototype for studying large geophysical data sets in general. The HIRS2/MSU data set contains a total of 40 physical parameters, filling 25 MB/day; raw HIRS2/MSU data are available for a period exceeding 10 years. Validation involves developing a quantitative sense for the physical meaning of the derived parameters over the range of environmental conditions sampled. This is accomplished by comparing the spatial and temporal distributions of the derived quantities with similar measurements made using other techniques, and with model results. The data handling needed for this work is possible only with the help of a suite of interactive graphical and numerical analysis tools. Level 3 (gridded) data is the common form in which large data sets of this type are distributed for scientific analysis. We find that Level 3 data is inadequate for the data comparisons required for validation. Level 2 data (individual measurements in geophysical units) is needed. A sampling problem arises when individual measurements, which are not uniformly distributed in space or time, are used for the comparisons. Standard 'interpolation' methods involve fitting the measurements for each data set to surfaces, which are then compared. We are experimenting with formal criteria for selecting geographical regions, based upon the spatial frequency and variability of measurements, that allow us to quantify the uncertainty due to sampling. As part of this project, we are also dealing with ways to keep track of constraints placed on the output by assumptions made in the computer code. The need to work with Level 2 data introduces a number of other data handling issues, such as accessing data files across machine types, meeting large data storage requirements, accessing other validated data sets, processing speed and throughput for interactive graphical work, and problems relating to graphical interfaces

Multilaboratory Evaluation of Real-Time PCR Tests for Hepatitis B Virus DNA Quantification

The performance characteristics of four different assays for hepatitis B virus (HBV) quantification were assessed: the Abbott RealTime HBV IUO, the Roche Cobas AmpliPrep/Cobas TaqMan HBV test, the Roche Cobas TaqMan HBV test with HighPure system, and the Qiagen artus HBV TM ASR. Limit of detection (LOD), linear range, reproducibility, and agreement were determined using a serially diluted plasma sample from a single chronically infected subject. Each assay was tested by at least three laboratories. The LOD of the RealTime and two TaqMan assays was approximately 1.0 log10 IU/ml; for artus HBV (which used the lowest volume of extracted DNA), it was approximately 1.5 log10 IU/ml. The linear range spanned 1.0 to at least 7.0 log10 IU/ml for all assays. Median values were consistently lowest for artus HBV and highest for Cobas AmpliPrep/Cobas TaqMan HBV. Assays incorporating automated nucleic acid extraction were the most reproducible; however, the overall variability was minor since the standard deviations for the means of all tested concentrations were ≤0.32 log10 IU/ml for all assays. False-positive results were observed with all assays; the highest rates occurred with tests using manual nucleic acid extraction. The performance characteristics of these assays suggest that they are useful for management and therapeutic monitoring of chronic HBV infection

Generating schemes for long memory processes: regimes, aggregation and linearity

This paper analyses a class of nonlinear time series models exhibiting long memory. These processes exhibit short memory fluctuations around a local mean (regime) which switches randomly such that the durations of the regimes follow a power law. We show that if a large number of independent copies of such a process are aggregated, the resulting processes are Gaussian, have a linear representation, and converge after normalisation to fractional Brownian motion. Alternatively, an aggregation scheme with Gaussian common components can yield the same result. However, a non-aggregated regime process is shown to converge to a Levy motion with infinite variance, suitably normalised, emphasising the fact that time aggregation alone fails to yield a FCLT. Two cases arise, a stationary case in which the partial sums of the process converge, and a nonstationary case in which the process itself converges, the Hurst coefficient falling in the ranges () and (), respectively. We comment on the relevance of our results to the interpretation of the long memory phenomenon, and also report some simulations aimed to throw light on the problem of discriminating between the models in practice