Ageing of plasticized poly(lactic acid)/poly(β-hydroxybutyrate) blend films under artificial UV irradiation and under real agricultural conditions during their application as mulches

The paper is aimed on the investigation of natural ageing of plasticized poly(lactic acid)/poly(β-hydroxybutyrate) PLA/PHB blend films during their one-season application as mulches under real field conditions in the western part of Slovakia. Acetyl tributyl citrate (ATBC) was used as the plasticizer. The analysis was performed on three differently exposed parts of the foil: i) buried in soil, ii) exposed to sunlight, and iii) shadowed by plants. In parallel, UV irradiation of the blend under laboratory controlled conditions (constant temperature of 30°C and relative humidity of 55 %) was carried out. The degradation effect was followed by changes in the molar mass, chemical and crystalline structures, as well as in thermal and mechanical properties. The ternary PLA/PHB/ATBC blend lost its tensile properties faster when buried in soil than when exposed to sunlight. This result is in agreement with the data obtained for the UV-irradiated materials. Young’s modulus values showed a significant mechanical degradation under the UV irradiation as well as during natural ageing. The study was also focused on the influence of mulches on the yield and quality of sweet pepper production, characterized by carotenoids and vitamin C content.     

Protein-based fluorescent bioassay for low-dose gamma radiation exposures

Analytical and Bioanalytical Chemistry - The study suggests an application of a coelenteramide-containing fluorescent protein (CLM-CFP) as a simplest bioassay for gamma radiation exposures....     

Systematic data generation and test design for solution algorithms on the example of SALBPGen for assembly line balancing

Recently, the importance of correctly designed computational experiments for testing algorithms has been a subject of extended discussions. Whenever real-world data is lacking, generated data sets provide a substantive methodological tool for experiments. Focused research questions need to base on specialized, randomized and sufficiently large data sets, which are sampled from the population of interest. We integrate the generation of data sets into the process of scientific testing.     

Identification and determination of relatedness of lactobacilli using different DNA amplification methods

Several DNA amplification-based methods were used for identification and evaluation of the relation between lactobacilli isolated from breastfed full-term infant faeces (31 strains), dairy products (5 strains) and silage (1 strain). Twenty-seven strains isolated from infant faeces were identified as Lactobacillus rhamnosus (9), Lactobacillus gasseri (6), Lactobacillus paracasei (4), Lactobacillus fermentum (4), Lactobacillus salivarius (2), Lactobacillus plantarum (1), and Lactobacillus helveticus (1) using 10 species-specific polymerase chain reactions (PCRs), multiplex PCR for the Lactobacillus casei group, and sequencing of 16S rDNA. Four strains were not identified. Six strains isolated from dairy products and silage were identified as Lactobacillus rhamnosus. A repetitive extragenic palindromic polymerase chain reaction (rep-PCR) with primer (GTG)₅ and a randomly amplified polymorphic DNA polymerase chain reaction (RAPD-PCR) with primer M13 were used for confirmation of species identification. Fingerprints were used for evaluation of the relatedness of lactobacilli. Differences between strains from infant faeces, dairy products, and silage were not detected.     

Secondary Alkyl Halides in Transition‐Metal‐Catalyzed Cross‐Coupling Reactions

Secondary, but second to none : The use of secondary alkyl halides in transition‐metal‐catalyzed cross‐coupling reactions (see scheme) has advanced significantly over the last five years. Selected examples of these transformations are examined, including mechanistic and stereochemical aspects.

     

Detection limits of electron and electron capture negative ionization-mass spectrometry for aldehydes derivatized with o-(2,3,4,5,6-pentafluorobenzyl)-hydroxylamine hydrochloride

In contrast to common expectations, the differences in limits of detection (LODs) between electron capture negative ionization (ECNI) and electron ionization (EI) mass spectrometry (MS) were found to be insignificant for a wide range of aldehydes derivatized with o-(2,3,4,5,6-pentafluorobenzyl)-hydroxylamine hydrochloride. Comparison of the two ionization methods based on LOD confidence intervals revealed that a traditional presentation of the LOD or limit of quantitation (LOQ) as a single value may over/underestimate the significance of obtained results. LODs were between 20 and 150 pg injected for the majority of tested derivatized carbonyls using both ionization methods. ECNI-MS improved LODs by ～10- to 20-fold only for two derivatized aldehydes, 4-hydroxybenzaldehyde and 5-(hydroxymethyl)furfural. Selectivity of ECNI did not appear to be beneficial when analyzing a wood smoke particulate matter (WS-PM) extract, possibly because the majority of interferences were removed during sample preparation (i.e., liquid-liquid extraction). The impact of four different data acquisition modes of transmission quadrupole (TQ)-MS on LODs and their precisions was also investigated. As expected, LODs in the selected ion monitoring (SIM) were ～two to four times lower than those obtained using total ion current (TIC) mode. More importantly, TQ-MS in the selected ion-total ion (SITI) mode (i.e., acquiring SIM and TIC data in a single analysis) provided signal-to-noise ratios and precisions, which were comparable to SIM alone.     

Fluctuation in the ergosterol and deoxynivalenol content in barley and malt during malting process

This paper describes determination of the deoxynivalenol and ergosterol in samples from different varieties of barley and, consequently, malt produced from this barley. In total, 20 samples of barley and 20 samples of barley malt were analyzed. The alkaline hydrolysis with consequent extraction into hexane was applied to obtain the ergosterol from cereals. Extraction to acetonitrile/water and subsequent solid-phase extraction (SPE) were used for deoxynivalenol. The determination of the samples was performed on high-performance liquid chromatography using UV detection (ergosterol) and mass spectrometric detection (deoxynivalenol). The influence of the malting process on the production of two compounds of interest was assessed from obtained results. Ergosterol concentration ranged 0.88–15.87 mg/kg in barley and 2.63–34.96 mg/kg in malt, where its content increased to 95% compared to samples before malting. The malting process was observed as having a significant effect on ergosterol concentration (P = 0.07). The maximum concentration of deoxynivalenol was found to be 641 μg/kg in barley and 499 μg/kg in malt. Its concentration was lower than the legislative limit for unprocessed cereals (1,250 μg/kg). The statistic effect of the malting process on deoxynivalenol production was not found. Linear correlation between ergosterol and deoxynivalenol content was found to be very low (barley R = 0.02, malt R = 0.01). The results revealed that it is not possible to consider the ergosterol content as the indicator of deoxynivalenol contamination of naturally molded samples.     

Lebesgue measure and Hausdorff dimension of special sets of real numbers from (0,1)

We estimate the Hausdorff dimension and the Lebesgue measure of sets of continued fractions of the type a=[a ₁,a ₂,…] where a _n belongs to a set S _n ⊂ℕ for every n∈ℕ. An upper bound for the Hausdorff dimension of the set of numbers with continued fraction expansions which fulfill some properties of asymptotic densities is also included.     

Structure-based design of supercharged, highly thermoresistant antibodies

Mutation of surface residues to charged amino acids increases resistance to aggregation and can enable reversible unfolding. We have developed a protocol using the Rosetta computational design package that "supercharges" proteins while considering the energetic implications of each mutation. Using?a homology model, a single-chain variable fragment antibody was designed that has a markedly enhanced resistance to thermal inactivation and displays an unanticipated ≈30-fold improvement in affinity. Such supercharged antibodies should prove useful for assays in resource-limited settings and for developing reagents with improved shelf lives.