Regulation of cytoskeleton by myelin components: studies on shiverer oligodendrocytes carrying an Mbp transgene

Oligodendrocytes from the shiverer mutant mouse are missing most of the myelin basic protein (Mbp) gene. In axon-free cultures, they produce membrane sheets with abnormally assembled microtubule and actin-based structures. This suggests that an Mbp gene product may have an important role in regulating the organization and stability of the wild-type oligodendrocyte cytoskeleton. We now present evidence extending these observations, using cultured oligodendrocytes that carry both the shiverer mutation and the Mbp1 transgene which partially corrects their deficit. Shiverer oligodendrocytes that carry one dose of the Mbp1 transgene abnormally express MBP along major cytoskeletal vein-like structures in processes and sheets. Shiverer oligodendrocytes that carry two doses of the Mbp1 transgene contain two types of membrane sheet regions, i.e. regions filled with aberrant punctate foci of MBP, and regions with normal domains of MBP. Immunocytochemical staining data show that the distribution of cytoskeleton and associated 2',3'-cyclic nucleotide 3'-phosphohydrolase (CNPase) is dependent upon how MBP is organized. Bundling of actin filaments occurs only around MBP domains, and the colocalization of CNPase along microtubular structures also appears to be regulated by MBP domains in sheets. Multinucleated oligodendrocytes are observed, a likely result of the inability of dividing pro-oligodendrocytes to bundle actin filaments. In addition, the ability of MBP to mediate extracellular signals that modulate cytoskeleton appears to be dependent upon MBP's organization. Transduction of the galactocerebroside signaling pathway, which results in the destabilization of microtubules but not actin filaments, occurs only in sheets containing MBP domains. The distribution of MBP, however, does not affect the myelin/oligodendrocyte-specific protein signaling pathway, which results in growth of microtubular structures and extensive destabilization of the actin cytoskeleton.     

Spray casting of steel strip: Process analysis

Near-net shape manufacturing (NNSM) of thin steel sections by spray casting eliminates casting as a separate step with attendant improved microstructures and properties and significant energy savings. The process involves atomization of a stream of liquid metal and deposition of droplets in the generated spray on a moving substrate at mass flow rates of 0.25 to 2.5 kg/s. In this paper, NNSM of steel strip by the Osprey spray casting process is investigated by combining numerical simulation and experiments. Critical input parameters for the computation are quantified utilizing existing state-of-the-art mathematical models and specific experiments. Numerical computation of the consolidation of the spray at the substrate during manufacture of thin sections is conducted using bothcontinuum anddiscrete event (“splat solidification”) approaches to predict: (1) variation of strip thickness in the transverse dimension and (2) isotherms and cooling rates across the strip thickness. Predicted geometries of the strip simulated by the continuum model are in good agreement with measurements. Predicted isotherms in narrow strip by the continuum approach are in reasonable agreement with thermocouple measurements for intermediate thicknesses (2 to 5 mm), and the observed microstructure is consistent with predicted cooling rates. The discrete event model predicts significantly higher cooling rates than the continuum model in the basal portion of the strip. This is consistent with the observed grain size in thin strip (<l-mm thick) and in the basal portion of thick strip. Beyond a threshold thickness, however, the discrete event model confirms the formation and persistence of a partially liquid layer at the growing surface of the deposit with an attendant decrease in the cooling rate. The influence of critical parameters on “splat solidification” is analyzed and assessed. DIRAN APELIAN, formerly Howmet Professor of Materials Engineering at Drexel University     

制革生态学(续六)

4 Finishing The purpose of finishing leather is to improve its serviceability by protecting it from damage by water, soil and mechanical action. Finishing modifies the shade, gloss and handle of the leather, improves its physical properties such as its lightfasthess and rubfastness, and hides any defects and     

Activation in unipolar cardiac electrograms: a frequency analysis

We have developed and tested several detectors of local activations in unipolar cardiac electrograms; the detectors are based on the frequency content of the waveforms. For this study, myocardial regions with no local electrical activity were created with cryoablation in canine ventricles, so that the characteristics of electrograms reflecting local activation could be compared with those with only distant electrical activity. For each electrogram, representations of the original signal were created using the output of bandpass filters; for each representation, the value of the maximum amplitude was taken as a measurement of the frequency content of the electrogram in that frequency band. The content of each frequency band and the first derivative of the signal were tested as discriminators between local and distant electrical activity. Combinations of frequency bands were also tested using a logistic regression technique; certain combinations provided better detection than any of the individual frequencies or the first derivative. The inclusion of frequencies between 500 and 1000 Hz improved the detection performance, suggesting that sampling rates of 1000 samples per second or less may not be adequate for optimal discrimination. A detector based on multivariate analysis of different frequency components of a signal may be more effective than single-band filtering in discriminating between local and distant electrical activity in the heart, especially when those components have very different magnitudes.     

Advanced techniques for managing telecommunications networks

The advanced techniques presently used by AT&T to manage traffic flow in its Worldwide Intelligent Network are described. The role of traffic network management strategies is reviewed, and the scope and routing plan of the AT&T Worldwide Intelligent Network are characterized. Three examples of modern protective controls are considered: selective trunk reservation, hard-to-reach process, and selective dynamic overload control. Advanced network management expansive controls and AT&T's traffic network management support systems are examined. Dynamic graphical analysis of network data, interactive training of network managers, and future trends impacting traffic network management are discussed     

Cross-polarized radar reflections from wet snow and ice droplets atweather radar wavelengths

The copolar radar reflection cross sections Q_HH and Q_VV from a collection of spheroid scatterers in the melting layer formed by ice precipitation prior to becoming rain have been analyzed by the authors in a recent work (IEEE Trans. Antennas and Propagation, vol.38, p.1317-25, Sept. 1990). The model is extended to calculate the cross-polarized cross section Q_VH due to reception at an electric-field polarization orthogonal to that of transmission. The authors are specifically interested in the cross-polarized differential reflectivity L_dr=10 log₁₀(Q_VH/Q_HH)     

Predicting in silico bioprocess additive and food additive undesirable outcomes due to utilising cytochrome P450 isoform metallomimics

Up to 2700 isoforms of cytochromes P450 bioconvert components of food bioprocessing. Nutragenomics define the biotransformation abilities of particular cytochromes P450 selected from 57 human isoforms in appropriate tissues such as the liver. Safety predictions solely in silico are unreliable using metallomimics of the Fe‐containing enzymes. Copyright © 2004 Society of Chemical Industry     

Studies on a dicyanate containing four phenylene rings and polycyanurate copolymers. 3. Application of mathematical models to determine the kinetics of the thermal degradation processes

Selected copolymers of bis-4-(4-cyanatophenoxy)phenyl sulphone with a commercial dicyanate, 2,2-bis(4-cyanatophenyl)propane are analysed using thermogravimetry to examine the processes of thermal degradation. Kinetic treatment of the data from these thermal analyses yields three Arrhenius equations for each monomer individually. The kinetics are consistent with a three-stage degradation mechanism, but the total kinetics of the copolymers cannot be derived simply from the sum of the constituent parts added together in proportion to their concentration. Each copolymer reacts slightly differently and must therefore be treated individually.     

Substitution and price elasticity estimates using inter-country pooled data in a translog cost model

Pooled data across several developing countries and the U. S. were used to estimate long-run substitution and price elasticities in a translog framework for the paper, iron and steel, and aggregate manufacturing industries. While the quality of the estimates varies across the several industry-specific models, the results suggest higher values for these elasticities than appear commonly used in integrated assessment models. Estimates of own-price elasticities of energy range from − 0.80 to − 1.76 and are comparable to estimates from previous econometric studies in the context of developed countries (− 0.77 to − 0.87). Substitution elasticities show wider variation across countries and industries. For energy and capital they range from − 1.96 to 9.80, for labor and energy from 2.61 to 7.11, and for energy and material from − 0.26 to 2.07.