Change‐point detection in panel data

We consider N panels and each panel is based on T observations. We are interested to test if the means of the panels remain the same during the observation period against the alternative that the means change at an unknown time. We provide tests which are derived from a likelihood argument and they are based on the adaptation of the CUSUM method to panel data. Asymptotic distributions are derived under the no change null hypothesis and the consistency of the tests are proven under the alternative. The asymptotic results are shown to work in case of small and moderate sample sizes via Monte Carlo simulations.     

Phase diagram in the iron-rich corner of the Fe-Cr-Mo-V-C system below 1000 K

Relevant experimental phase equilibria were used with the THERMOCALC program to refine thermodynamic parameters for the low-temperature region, in the steels with composition 0.4 to 2.5 wt.% Cr, 0 to 1 wt.% Mo, and 0 to 0.5 wt.% V. The refined parameters were used to calculate phase relationships, which were then compared with experimental results. The main interest was focused on the temperature and concentration regions of existence of the chromium-rich carbides M₇C₃ and M₂₃C₆ and Mo-rich carbides M₆C and M₂C. Results of experiments indicate that M₇C₃ carbide replaces M₂₃C₆ carbide in the temperature region between 773 and 873 K. Similar behavior was also found for molybdenum-rich phases M₆C and M₂C. Some modifications of existing thermodynamic parameters in the low-temperature region, as well as the establishment of some new parameters, were necessary to obtain reasonable agreement between theoretical and experimental results.     

A Study of the use of Secondary Silumin in the Production of Castings for the Automobile Industry

Abstract

This presentation describes a programme designed to investigate the practicability of using worn scrap pistons made from Al Si 12Cu Mg Ni alloy as the raw material for the manufacture of new pistons. The experimental work consisted of a series of carefully-planned processes, including alloy melting, modification, refining and degassing, and subjecting the cast components to an appropriate heat-treatment regime. The aim was to produce castings of excellent quality which would meet all international standards for pistons. An original material, known as ‘Vidasil’, was used to line the feeder-head cavities. The results demonstrated the apparent economic viability of the process technology involved.     

Production of biogenic amines by lactic acid bacteria and bifidobacteria isolated from dairy products and beer

The aim was to monitor production of eight biogenic amines (BAs) (histamine, tyramine (TYR), tryptamine, putrescine, cadaverine (CAD), phenylethylamine, spermine and spermidine) by selected 81 lactic acid bacteria (LAB) strains: Lactobacillus, Lactococcus, Leuconostoc, Enterococcus, Pediococcus, Tetragenococcus and Bifidobacterium. The tested LAB and bifidobacteria were isolated from dairy products and beer. The decarboxylase activity of the micro‐organisms was studied in growth medium after cultivation. The activity was monitored by HPLC after the pre‐column derivatisation with dansylchloride. Fifty LAB showed decarboxylase activity. Thirty‐one strains produced low concentrations of CAD (≤10 mg L^?1). Almost 70% of beer isolates generated higher amounts of TYR (≤3000 mg L^?1). Most of the tested LAB demonstrated decarboxylase activity. The above micro‐organisms can contribute to the increase of content of BAs in dairy products or beer and thereby threaten food safety and health of consumers. Production of BAs even by the representatives of some probiotic strains (Bifidobacterium and Lactobacillus rhamnosus) was detected in this research. This study has also proved that contaminating LAB can act as sources of higher amounts of CAD and TYR in beer.     

Solvent retention capacity values in relation to the Czech commercial wheat quality

Technological quality in the sets of eighty commercial wheat samples was evaluated by grain milling traits (test weight, thousand kernel weight, grain hardness as Particle Size Index, one‐stream flour yield) and common analytical parameters (wet gluten and protein contents, Zeleny test value, falling number) together with the solvent retention capacity (SRC) method (AACC 56‐11). For the commercial wheat, the latter analytical procedure (originally designed for flour quality analysis) was verified also for grain wholemeal. Within the mentioned sample group, anova revealed the strongest effect of the harvest year, both for milling and for technological parameters. For the SRC profiles, the effect of the sample form used dominated the crop year influence. The grain SRCs were correlated with the milling traits foursome, while an agreement between the flour SRC profiles and technological quality data was not so tight. However, the flour lactic acid SRC was associated with the wet gluten and protein contents (r = 0.24, P < 0.05), and the protein quality as Zeleny value with the flour water SRC (r = 0.24, P < 0.05). Relationship between Zeleny's value and flour lactic acid SCR was confirmed by nonlinear Spearman correlation (R = ?0.26, P < 0.05).     

In vitro models to estimate drug penetration through the compromised stratum corneum barrier

Objectives: The phospholipid vesicle-based permeation assay (PVPA) is a recently established in vitro stratum corneum model to estimate the permeability of intact and healthy skin. The aim here was to further evolve this model to mimic the stratum corneum in a compromised skin barrier by reducing the barrier functions in a controlled manner. Methods: To mimic compromised skin barriers, PVPA barriers were prepared with explicitly defined reduced barrier function and compared with literature data from both human and animal skin with compromised barrier properties. Caffeine, diclofenac sodium, chloramphenicol and the hydrophilic marker calcein were tested to compare the PVPA models with established models. Results and discussions: The established PVPA models mimicking the stratum corneum in healthy skin showed good correlation with biological barriers by ranking drugs similar to those ranked by the pig ear skin model and were comparable to literature data on permeation through healthy human skin. The PVPA models provided reproducible and consistent results with a distinction between the barriers mimicking compromised and healthy skin. The trends in increasing drug permeation with an increasing degree of compromised barriers for the model drugs were similar to the literature data from other in vivo and in vitro models. Conclusions: The PVPA models have the potential to provide permeation predictions when investigating drugs or cosmeceuticals intended for various compromised skin conditions and can thus possibly reduce the time and cost of testing as well as the use of animal testing in the early development of drug candidates, drugs and cosmeceuticals.     

Application of Accelerated Solvent Extraction for Simultaneous Isolation and Pre-cleaning Up Procedure During Determination of Polycyclic Aromatic Hydrocarbons in Smoked Meat Products

Food Analytical Methods - A simplified method, following European Commission legislation, for the determination of four polycyclic aromatic hydrocarbons (PAH4)—benzo[a]pyrene (B[a]P),...