Acreage estimation of wheat and barley fields in the province of Adana,Turkey

In this study, the wheat (triticum) and barley (hordeurn) planted areas in the province of Adana were determined by using Landsat-5 TM data in 1991. To classify the wheat and barley fields in this region, Landsat bands 3, 4 and 5 were used. Reflectance distribution in these bands has been expected to have an ellipsoidal shape, and a method was developed to make classification for such distribution. To check the accuracy of the classification, test areas in the province were selected and the classification results were compared with ground-truth. Consequently, it was found that the error estimated wheat and barley planted areas was around 15% and the results of the acreage estimation for wheat and barley fields were 218000 ±32000 hectare in 1991.     

An experimental demonstration of tailored excitations for improved damage detection in the presence of operational variability

We have shown in previous work that the parameters governing the dynamic evolution of a system of ordinary differential equations may be modified via an evolutionary algorithm to yield excitations that improve damage detection sensitivity in a computational model of a structural health monitoring application. In this work we use the same method to develop improved excitations for an experimental system. Improvement in change detection sensitivity is shown for several generated excitations. In addition, we present an excitation that increases the robustness of the damage detection feature to the types of parameter perturbations that arise not from damage, but from environmental sources such as temperature change.     

Effects of noise on transfer entropy estimation for damage detection

Recent research has shown that transfer entropy can be effectively employed as a feature for nonlinearity detection and linear damage identification. However, computation of transfer entropy requires the estimation of non-parametric one-, two-, and three-dimensional probability density functions. Therefore, small random perturbations caused by noise could lead to large variances in transfer entropy estimates. In this paper, we evaluate the effect of input and output noise on estimation of transfer entropy, and how noise, in turn, affects the capability of transfer entropy as a damage detector in a structural health monitoring (SHM) application. A damage index from the transfer entropy is computed from the response of a simulated multi-degree-of-freedom oscillator subject to linear and nonlinear stiffness changes in the presence of various noise influences. Damage indices are also evaluated for an experimental frame structure. Based on the computational study, we find that input noise lessens the sensitivity of the damage feature by diminishing the ability of the non-parametric density estimators to produce low variance transfer entropy estimations. Despite this reduced capability, an input that has no deterministic component can still detect a 25% stiffness loss in the computational example employed. Output noise has a greater impact on the feature's ability to accurately estimate the transfer entropy, such that a signal-to-noise threshold of approximately 30 dB leads to a greatly diminished ability to detect damage. Despite these noise effects, all damage cases tested on an experimental frame structure were detectable using the transfer entropy damage index.     

Two substrate interaction sites in lignin peroxidase revealed by site-directed mutagenesis

It has been shown recently that Trp171 of lignin peroxidase (LiP) is hydroxylated at the Cbeta position [Blodig, W., Doyle, W. A., Smith, A. T., Winterhalter, K., Choinowski, T., and Piontek, K. (1998) Biochemistry 37, 8832-8838]. Comparative experiments, carried out on both wild-type fungal and recombinant LiP isoenzyme H8 (LiPH8), indicate that the process of hydroxylation is autocatalytic and that Trp171 may be implicated in catalysis. The role of this residue has therefore been examined using site-directed mutagenesis to obtain recombinant enzymes with Trp171 substituted by Phe or Ser (W171F and W171S LiPH8, respectively). The wild-type recombinant enzyme (LiPH8) was analyzed in solution using 1H NMR spectroscopy and its integrity confirmed prior to the kinetic and spectroscopic characterization of LiPH8 mutants. A charge neutralization mutation in the "classical heme edge" substrate access channel of LiP, in which Glu146 was substituted by Gly (E146G LiPH8), showed substantial activity with respect to veratryl alcohol (VA) oxidation and a marked (2.4 pH units) increase in pKa for the oxidation of a negatively charged difluoroazo dye. More surprisingly, the Trp171 LiPH8 mutants W171F and W171S LiPH8 were found to have lost all activity with VA as substrate, and compounds I and II were unable to react with VA. Both mutants, however, retained substantial activity with two dye substrates. These data provide the first direct evidence for the existence of two distinct substrate interaction sites in LiP, a heme-edge site typical of those encountered in other peroxidases and a second, novel site centered around Trp171 which is required for the oxidation of VA. Stopped-flow kinetic studies showed that all the mutants examined reacted normally with hydrogen peroxide to give a porphyrin cation radical (compound I). However, the rapid phase of spontaneous compound I reduction (2.3 s-1), typical of wild-type LiP, was absent in the Trp171 mutants, strongly suggesting that an electron-transfer pathway must exist within the protein leading from the heme to a surface site in close proximity to Trp171. The kinetic competence of such a pathway is dependent on interaction of the enzyme with VA, at or near Trp171.     

Crystal structure of RNA helicase from genotype 1b hepatitis C virus. A feasible mechanism of unwinding duplex RNA

Crystal structure of RNA helicase domain from genotype 1b hepatitis C virus has been determined at 2.3 A resolution by the multiple isomorphous replacement method. The structure consists of three domains that form a Y-shaped molecule. One is a NTPase domain containing two highly conserved NTP binding motifs. Another is an RNA binding domain containing a conserved RNA binding motif. The third is a helical domain that contains no beta-strand. The RNA binding domain of the molecule is distinctively separated from the other two domains forming an interdomain cleft into which single stranded RNA can be modeled. A channel is found between a pair of symmetry-related molecules which exhibit the most extensive crystal packing interactions. A stretch of single stranded RNA can be modeled with electrostatic complementarity into the interdomain cleft and continuously through the channel. These observations suggest that some form of this dimer is likely to be the functional form that unwinds double stranded RNA processively by passing one strand of RNA through the channel and passing the other strand outside of the dimer. A "descending molecular see-saw" model is proposed that is consistent with directionality of unwinding and other physicochemical properties of RNA helicases.     

A New Analysis of Hydrogen Diffusion in Metals with Trapping

A new model of hydrogen diffusion in metalshas been developed,it is more efficient todescribe the hydrogen diffusion with trappingin metals.In the model newly developed an impli-cit dependence on time of hydrogen diffusioncoefficient in metals with trapping was firstlybuilt and it is shown that hydrogen diffusioncoefficient will be different at different posi-tions in a dynamic process of hydrogen diffusionin a metal.Numerical solutions of the present modelwere obtained by finite difference method.Bychanging the parameters in the model the diffusionof hydrogen in a metal and the effect of trappingwere described and discussed.And the comparisonbetween the well known McNabb and Foster's modeland the present model was also made.