Step by step approach to multi-element data analysis in testing the provenance of wines

The possibility to classify the provenance of a wide variety of randomly selected wines according to multi-element analysis data was tested. Large number of parameters is used for solution of such complex problem and the role of the noise increases. Stepwise approach is tested dividing the wine origin classification into some steps to simplify the problem. Outcomes of the approach are studied on the basis of the chemical analytical data obtained for 23 elements in 103 wines from seven countries. Anova was used to select the most informative elements at each step. Three or four elements often were found sufficient to discriminate between countries at 0.9 probability level. Principal component analysis was applied for concise data presentation. The possibility of application of the multivariate normal distribution to the principal components was tested and confirmed, and thoroughly used for the classification power estimates. Problems of indication of batches and adequate representation of those by samples are emphasized.     

Risk assessment of Fusarium mycotoxins in Lithuanian small cereal grains

A total of 125 small grain samples, including 60 of winter crop and 65 of spring crop collected during 2006–2007 at harvesting in Lithuanian fields, were involved in the current study on co-occurrence of three Fusarium mycotoxins. All grain samples tested were found to be contaminated with mycotoxins. In 2006, winter cereal grain samples contaminated with one mycotoxin accounted for 16%, and those contaminated with three mycotoxins for 25%. No spring cereal grain samples containing only one toxin were found, while those contaminated with three toxins accounted for 91% of the total samples tested. In the year 2007 winter cereal grain samples contaminated with one toxin accounted for as little as 4%, and all spring cereal grain samples tested were found to be 100% contaminated with deoxynivalenol, zearalenone, and T-2 toxin. Mycotoxin concentrations in grain samples, in most cases, were within the permissible range. A trend was revealed that spring barley grain samples tested contained higher T-2 concentrations irrespective of the test year.     

Solution validation technique for optimal shakedown design problems

Modern computer technology allows conjoining shakedown theory, optimization and ever stricter standardized design requirements in a single mathematical problem formulation. However it raises a question of reliability: easily achieved solution should not be taken for granted but should be adequately assessed. This paper focuses on the physical validation technique for optimal shakedown design problem solution in the aspect of Melan theorem (statics) and residual deformation compatibility (kinematics). For that purpose Rosen gradient projection method is used. Optimization problem of bending circular, symmetric plate at shakedown, which is subjected by a variable repeated load, is considered for illustration of the validation technique.     

Kinetics of electroless copper deposition using cobalt(II)-ethylenediamine complex compounds as reducing agents

Electroless copper deposition using Co(II)-ethylenediamine (En) complexes as reducing agents was investigated in 0.4–1.2 M En solutions at 50 and 70 °C. There is a complicated dependence of the process rate on pH, En concentration and temperature. A copper deposition rate up to 6 m h^–1 (50–70 °C) in relatively stable solutions (pH 6) can be achieved. The stoichiometry of the Cu(II) reduction at pH 6–7 corresponds to the reaction:

Automatic benthic imagery recognition using a hierarchical two-stage approach

The main objective of this work is to establish an automated classification system of seabed images. A novel two-stage approach to solving the image region classification task is presented. The first stage is based on information characterizing geometry, colour and texture of the region being analysed. Random forests and support vector machines are considered as classifiers in this work. In the second stage, additional information characterizing image regions surrounding the region being analysed is used. The reliability of decisions made in the first stage regarding the surrounding regions is taken into account when constructing a feature vector for the second stage. The proposed technique was tested in an image region recognition task including five benthic classes: red algae, sponge, sand, lithothamnium and kelp. The task was solved with the average accuracy of 90.11% using a data set consisting of 4589 image regions and the tenfold cross-validation to assess the performance. The two-stage approach allowed increasing the classification accuracy for all the five classes, more than 27% for the “difficult” to recognize “kelp” class.     

Drift velocity of electrons in quantum wells in high electric fields

It is experimentally found that the maximum drift velocity of electrons in quantum wells of differently arranged AlGaAs/GaAs heterostructures and pseudoamorphous Al_0.36Ga_0.64As/In_0.15Ga_0.85 As heterostructures is higher than the maximum drift velocity of electrons in bulk materials. It is established that no negative differential conductivity is exhibited by the field dependence of the drift velocity of two-dimensional electrons in GaAs and In_0.15Ga_0.85As. The drift velocity in the GaAs quantum well is saturated in fields several times higher than the field corresponding to the Γ-L intervalley transitions of electrons in bulk GaAs.     

A graded-gap photoelectric detector for ionizing radiation

A heterostructure consisting of a graded-gap p-Al_xGa_1?xAs layer on an n-GaAs substrate is studied in relation to its role as a photoelectric-response detector of X-ray photons and α particles. It is found that the current-power sensitivity of the detector is as high as 0.13 A/W and the voltage-power sensitivity exceeds 10⁶ V/W. The effect of preliminary irradiation with 5.48-MeV α particles (²⁴¹Am) on the detector’s sensitivity is studied. It is established that the detector’s sensitivity is reduced by a factor of 1.5–2 after irradiation with α particles at a dose of 5 × 10⁹ cm^?2. A further increase in the radiation dose to 4 × 10¹⁰ cm^?2 does not affect the detector’s sensitivity.     

Effect of annealing on the resistivity of quench-condensed Cu and Cu(Fe) thin films

Pure Cu and Cu(Fe) thin films containing 0.1 and 1.0 at % Fe were prepared by low-temperature deposition onto a liquid-helium-cooled substrate. The Cu(Fe) films were annealed sequentially at approximately 17, 70, and 270 K. After each annealing stage the resistivity was measured down to 1.5K. The Cu(Fe) films exhibited a region in which the resistivity was proportional to ln T; in this region the logarithmic slope of the resistivity curve was only weakly affected by annealing. Below 10 K annealing produced a significant decrease in the impurity (Fe) contribution to the resistivity. The results are interpreted as due to increased interactions between Fe atoms produced by an increase in conduction-electron mean free path.This work was supported by the Materials Research Center, University of North Carolina, under Grant Number GH-33632 from the National Science Foundation.     

Detection and activity evaluation of radical scavenging compounds by using DPPH free radical and on-line HPLC-DPPH methods

The antiradical activity of crude extracts (80% methanol, 20% water) of S. officinalis, S. glutinosa, S. sclarea and S. aethiopis was determined using the 2,2-diphenyl-1-picrylhydrazyl (DPPH·) radical scavenging method. For validation of this method several well known antioxidants (ascorbic acid-6-palmitate, gallic, chlorogenic, ferulic, caffeic, uric, gentisic and vanillic acids, catechin, quercetin, epicatechin, phloridzin, rutin and naringin) were investigated additionally. In these experiments ascorbic acid-6-palmitate had highest antiradical activity. Within the group of phenolic acids gentisic acid had the highest antiradical activity comparing with the other tested phenolic acids. Uric acid, vanillic acid, phloridzin and naringin have a much lower antiradical activity. Different reaction kinetics behaviour was observed. The validated DPPH radical scavenging method was applied to the evaluation of the antiradical activity of plant extracts. The Salvia extracts showed very high antiradical activity towards the DPPH·. An on-line HPLC-DPPH method was developed using a methanolic solution of DPPH· for a rapid detection of radical scavenging components after HPLC separation. The HPLC-DPPH on-line method was also applied to a screening of several radical scavenging components in plant extracts as well as for quantitative analysis. The HPLC analysis revealed the presence of several radical scavenging components in the all Salvia extracts. This HPLC-DPPH on-line method can also be used for quantitative determination of radical scavenging compounds.