Isolation, purification and characterization of enzyme(s) responsible for conversion of sterigmatocystin to aflatoxin B1

The cell-free extract prepared from Aspergillus flavus ATCC 5517/A 228 showed activity in converting sterigmatocystin to aflatoxin B1. The extract was purified on Ultrogel AcA-54 and resulted in ten protein peaks, one of which (peak VI) showed activity in sterigmatocystin conversion. The protein in this peak gave one protein band using polyacrylamide gel (PAG)-disc electrophoresis. For further purification, protein(s) in peak VI were applied on DEAE-Sephadex A-50 and two protein peaks were detected. Only one peak showed enzyme activity which showed homogeneity as one band on PAGE and sodium dodecyl sulphate (SDS)-PAGE. The optimum temperature for the enzyme activity was 28 degrees C and the optimum pH was 8. The maximum conversion resulted from the action of 0.6 mg enzyme protein on 48 X 10(-8) mol sterigmatocystin. Zn2+, Co2+ and Mn2+ enhanced the enzyme activity, while ethylenediaminetetraacetic acid, parahydroxymercuric benzoate and phenylmethylsulphonic fluoride inhibited the enzyme activity in a dose-dependent manner. Amino-acid analysis showed the presence of 22 amino acids, three of which are unknown. The enzyme has a molecular weight of 64,000 daltons (by gel filtration) and 70,000 daltons (by SDS-PAGE).     

Model Predictive Control of Wind-Excited Building: Benchmark Study

In this paper, a “third generation” benchmark problem that focuses on the control of wind excited response of a tall building, using the Model Predictive Control (MPC) scheme, is presented. A 76 story, 306 m tall concrete office tower proposed for the city of Melbourne, Australia, is being used to demonstrate the effectiveness of MPC. The MPC scheme is based on an explicit use of a prediction model of the system response to obtain the control actions by minimizing an objective function. Optimization objectives in MPC include minimization of the difference between the predicted and desired response trajectories, and the control effort subjected to prescribed constraints. By incorporating input/output hard constraints, the MPC scheme provides an optimal control force that satisfies the prescribed constraints.     

Surge response statistics of tension leg platforms under wind and wave loads: a statistical quadratization approach

Commonly, in offshore applications, frequency domain analyses of nonlinear systems have been approximately carried out using the method of equivalent statistical linearization. This method, however, fails to capture the non-Gaussianity of the response in terms of its higher-order statistics. In addition, response energy in frequency ranges outside that of the input spectrum is not observed using this technique. Herein, a method of equivalent statistical quadratization is proposed, whereby a statistically asymmetric nonlinearity in the forcing of a tension leg platform (TLP) is cast in a quadratic form. The present quadratization method takes advantage of the Gaussianity of the first order response to simplify the recasting of the nonlinearity in its approximate polynomial form. A Volterra series approach leads to the development of transfer functions from which the response spectrum as well as statistics of the response may be obtained. Response cumulants, computed up to fourth order via direct integration or the Kac-Siegert technique, reveal the non-Gaussian character of the response which was hidden by linearization and, when used in the framework of some available non-Gaussian probability density function models, indicate acceptable agreement with time-domain simulations of the original nonlinear differential equations. In addition, the response power spectral density contains an additional peak near the resonant frequency of the TLP, where input energy at difference frequencies of the input spectrum lies, corroborating information gleaned from the time-domain simulation.     

Applications of neurocomputing in traffic management of ATMnetworks

In the near future, high speed integrated networks, employing asynchronous transfer mode (ATM) cell switching and multiplexing technique, will be used to provide new and diverse mixture of services and applications. Multimedia teleconferencing, video-on-demand, television broadcasting, and distant learning are some examples of these emerging services. The ATM technique is based on the principle of statistical multiplexing, which is flexible enough to support different types of traffic while providing efficient utilization of the network's resources. New classes of techniques such as neural networks and fuzzy logic have many adaptive, learning and computational capabilities that can be utilized to design effective traffic management algorithms. The subject of this paper is to demonstrate how such neurocomputing techniques can be used to address ATM traffic management issues such as traffic characterization, call admission control, usage parameters control and feedback congestion control     

Improved Dissolution of Indomethacin in Coprecipitates with Phospholipids-I

Indomethacin powders were blended with phospholipids to prepare physical mixtures or made into solid dispersions by the solvent method and their comparative dissolution profiles were studied. Indomethacin exhibited significantly improved dissolution rates in phospholipid coprecipitates compared to either the physical mixtures or the pure indomethacin. The coprecipitates of lecithin-indomethacin 1:16 weight ratio had a 6.5 fold greater initial dissolution rate, and the total amount dissolved after 60 minutes was 140% greater compared to indomethacin alone. Increasing the lecithin content to 1:4 resulted in only a modest additional increase in the initial dissolution rate (40%) and the limiting concentration (14%)     

Association of malignant brain tumors and cancers of other sites

PURPOSE: We conducted an exploratory study of brain tumors that occurred as a second primary malignancy to identify potential risk factors for brain tumors. METHODS: Using data from the Surveillance, Epidemiology, and End Results (SEER) Program, we calculated the sex-specific standardized incidence ratio (SIR), adjusted to age and time period, as an estimate of the relative risk (RR) of developing a second primary brain tumor following other cancers. RESULTS: We found an elevated RR of brain tumors after bladder cancer in both men (RR, 1.7; 95% confidence interval [CI], 1.2 to 2.3) and women (RR, 1.7; 95% CI, 0.8 to 3.2); this effect was present for both astrocytoma and glioblastoma multiforme. Elevated RRs of brain tumors were also found after sarcoma (RR, 4.4; 95% CI, 1.8 to 9.0) and leukemia (RR, 2.9; 95% CI, 1.6 to 4.8) in men, and after colorectal cancer (RR, 1.8; 95% CI, 1.3 to 2.4) and endometrial cancer (RR, 1.4; 95% CI, 1.0 to 1.9) in women. The highest RR observed in this study was for CNS lymphoma following any first primary malignancy in men (RR, 7.9; 95% CI, 5.5 to 11.0). CONCLUSION: The associations of brain tumors with bladder, colorectal, and endometrial cancers in women, and an increased occurrence of CNS lymphoma as a second malignancy in men, are new findings that have not been described previously.     

Application of Magnetic Susceptibility to Study Low Iron Substitution in Tricalcium Aluminate

The magnetic susceptibilities of the tricalcium aluminate prepared containing 0.5, 1, or 2 wt% FeC₂O₄ or Fe₂O₃ before firing were measured at different temperatures and different magnetic field intensities. The Curie temperature of each compound is determined from the magnetic susceptibility temperature curves. The values of the effective magnetic moments were calculated from the experimental data for the different compounds. The variations in the magnetic properties and the magnetic constants with the type and concentration of iron added to C₃A confirm that the magnetic susceptibility measurements could be considered a good tool to estimate the solubility limit of iron in different forms in C₃A. Our data confirm also the previous data of IR measurements for such samples at low iron concentrations.