Investigation of incurred single- and multi-component model food matrices for determination of food proteins triggering allergy and coeliac disease

For detection and quantification of food proteins triggering hypersensitivity reactions, reliable, validated analytical methods are necessary. At present, the most commonly used methodology for this purpose is ELISA. The lack of incurred reference materials (RM) complicates the fulfilling of method validation. Today, a well identifiable research direction is the development of methods (immunoanalytical, PCR and MS methods) suitable for multi-component analysis. As a consequence of these R+D efforts, the development of multi-component RMs is reasonable. Our work presented here is focusing on the development and investigation of multi-component model food matrices that can be suitable for supporting the validation processes. On the basis of the relative incidence of hypersensitivity reactions, four components—wheat, milk, egg and soy—were selected for our preliminary work. The target proteins were determined in single- and multi-component matrices with different ELISA methods, and the results were compared by statistical evaluation. The main direction of our investigation was to identify the effects of the potential interactions of these proteins on the analytical results, and the influence of food processing was also investigated. The results showed that the presence of multiple allergenic components caused much less uncertainty in the analytical results than analytical and technological steps, such as sample preparation, repetition or even heat treatment. However, probably due to the relatively complex matrices, some discrepancies from the expected outcome could also be observed.     

Pore Propagation Directions in P+ Porous Silicon

A comparative study is presented on the pore propagation directions of porous silicon layers (PSL) formed on p⁺-type substrates of different orientations. PSLs were formed on plain (0 0 1) and (1 1 1) silicon wafers as well as on structured (0 0 1) wafers containing facets of various orientations. During anodization, regular pores follow the 0 0 1 direction on the (0 0 1) planes. While on the (1 1 1) planes fewer regular pores develop and seemingly propagate closely to the 1 1 1 direction. These results indicate that the pores propagate perpendicular to the surface i.e. along the field lines when the surface orientation is either (0 0 1) or (1 1 1).When the silicon surface provided (1 1 0) orientation (Chuang, Collins, and Smith, 1989), or its position is in between the (0 0 1) and (1 1 1) planes then the pores do not propagate perpendicular to the surface but along the 0 0 1 direction.All the phenomena exhibited might be explained by presuming that during formation, the pores propagate along the 1 0 0 directions, and that those 1 0 0 directions are preferred which are closely to the field lines. In PSLs formed on (0 0 1) surfaces the field lines and the 0 0 1 crystallographic direction are coincident. However, in the (1 1 1) oriented wafer where three equally probable 1 0 0 directions exist around the field lines, more irregular structure of PSLs will develop.     

From Molecular Clusters to Metal Nanoparticles

Different methods to prepare supported metal nanoparticles of uniform size are discussed. (i) Supported ruthenium particles were generated from Ru and Ru-Fe bimetallic molecular metal carbonyl cluster precursors (MCC). (ii) Gold nanoparticle formation in the supercage of Y zeolite was studied on Au/NaY, Au/HY and Au-Fe/HY system. (iii) Palladium nanoparticles were grown in liquid phase then deposited on an SiO₂ support or they were grown on the support surface in a solid-liquid interfacial layer. The particle size control was more efficient in the latter two cases than in the preparation starting from MCC.     

Determination of the nitrogen compound balance between the atmosphere and a Norway spruce forest ecosystem

Wet, throughfall and stemflow deposition measurements of nitrogen compounds (NH₄ ⁺- and NO₃ ^–-ions) were carried out in a Norway spruce forest in Hungary, together with direct dry deposition and emission estimates (NH₃, NO, NO₂, HNO₃, N₂O gases, NH₄ ⁺ and NO₃ ^– particles). The total deposition of nitrogen compounds from the atmosphere to the forest ecosystem, estimated as the sum of the wet deposition and the measured dry flux, was 1.9 g N m^–2 yr^–1 for the examined period (1996–1998). The net deposition (difference of the deposition and the emission) was 1.8 g N m^–2 yr^–1. About 61% of the deposition is due to dry deposition processes. Ammonia gas dominates in the dry deposition (48%). Soil emission of nitric oxide (NO) and nitrous oxide (N₂O) constitutes only 5% of the total (wet and dry) deposition. From the comparison of directly measured dry deposition figures and the dry deposition calculated as the difference of the throughfall plus stemflow and wet deposition, it is probable that around 60% of the dry deposited nitrogen compounds (36% of the total, dry and wet deposition) are taken up by stomata, mostly in gaseous form. The remaining part (64%) of the deposited nitrogen compounds is leached to the ground where it is partly taken up by the root system, takes part in the soil mineralisation processes, or leaves the ecosystem by ground or surface water run-off.     

On the Performance of the Fluctuation Test for Structural Change

Abstract

We discuss the performance of “closed-end” fluctuation tests, used to detect changes in the structural stability of a model, in the case where the time horizon is large and the observations do not possess high enough moments. It is demonstrated via a simulation study that, in the latter case, the choice of the boundary function should take into account the number of moments existing; otherwise the actual size of the test may exceed the nominal level. We suggest an alternative “open-end” fluctuation procedure and study its asymptotic behavior. It turns out that if an improper boundary function is chosen, then the null hypothesis may be rejected even if it is true. This means that an appropriate choice of the boundary function requires some prior information about the tail heaviness of the observations. This is different from the cumulative sum-based monitoring schemes suggested by Chu et al. (1996 Chu , C. S. J. , Stinchcombe , M. and White , H. ( 1996 ). Monitoring Structural Change , Econometrica 64 : 1045 – 1065 .[Crossref], [Web of Science ®] , [Google Scholar]) and further studied by Horváth et al. (2004 Horváth , L. , Hu?ková , M. , Kokoszka , P. , and Steinebach , J. ( 2004 ). Monitoring Changes in Linear Models , Journal of Statistical Planning and Inference 126 : 225 – 251 .[Crossref], [Web of Science ®] , [Google Scholar]).     

Preparation and characterization of hydroxyapatite from eggshell

Hydroxyapatite (HAp) was successfully produced by using recycled eggshell. The observed phases of the synthesised materials were dependent on the mechanochemical activation method (ball milling and attrition milling). The structures of the HAp were characterized by X-ray diffraction, scanning electron microscopy and infrared spectroscopy. Attrition milling proved to be more efficient than ball milling, as resulted nanosize, homogenous HAp even after milling.     

Gas Phase Reactions in Silent Electric Discharges Part III: Investigation of Chemical Reactions Involving Electron-Molecule Collisions in Various Mixtures of O2 with Ar,N2 or CO

Electron-molecule collisions play a significant role in chemical transformations in a silent electric discharge. The reaction rate coefficients of electron-molecule collisions in various gaseous mixtures of Ar, N₂ or CO with O₂ have been investigated. These coefficients can be determined experimentally and calculated theoretically. The measured values are in good agreement with those calculated by theoretical methods. The reaction rate coefficients of electron-O₂ molecule collisions increase with decrease of the amount of O₂ in Ar/O₂ mixtures, but decrease with decrease of the amount of O₂ in N₂/O₂ or CO/O₂ mixtures.