31 research outputs found
Changes in sensory profile and microbiological quality during chill storage of cured and uncured cooked sliced emulsion-type sausages
Nine batches of cooked sliced emulsion type sausages, produced from organic meat with or without the use of nitrite, were packed under N2/CO2 (7:3) and vacuum, respectively, and stored at 8°C. During two weeks of storage, the microbiological quality was determined, as well as the sensory quality by using profile analysis. The spoilage flora consisted of lactic acid bacteria and Brochothrix thermosphacta, without clear evidence of an inhibitory effect of nitrite on the growth of these organisms. The sensory profile showed an increase of the sour and rancid aroma and flavour, in parallel to the growth of these microorganisms. These changes were more pronounced in the batches prepared without nitrite. Spots of red discolourations were occasionally observed during storage of uncured sausage slices. These may have been caused by reduction of traces of nitrate from spices by psychrotrophic Enterobacteriaceae
Syntheses and Properties of Cycloamidines Based on 4H-Imidazoles*
Employing three different syntheses a broad spectrum of 4H-imidazoles 3a -3s has been synthesized. In the course of the two-fold aminolysis reaction leading to derivatives 3q -3s, deeply colored byproducts could be isolated and structural characterized.These novel donor-acceptor derivatives of type 7 consist of an 1H-and 4H-imidazole which are connected by a nitrogen bridge and rearrange via rapid 1,3-/1,5-hydride shifts. Using 1 H NMR experiments the aminolysis product 3p shows prototropic isomers which could be detected in equilibrium for the first time. Cyclovoltammetric measurements of a series of substituted 2-aryl derivatives 3d -3i displayed two reversible single electron transfer steps with relatively small semiquinone formation constants between 10 2 and 4 × 10 3 . The 4H-imidazole 3d was successfully converted into boratetraaza-pentalene 8a, which showed two well separated reduction potentials. The value of semiquinone formation constant of 8a (1.8 × 10 15 ) is even higher than those reported for similar derivatives. 4H-imidazoles can also be employed for the efficient complexation of catalytically important metals as exemplified by copper complexes 11 and 12. Derivative 3m, which possesses an additional chelating pyridine substructure, formed a stable complex of structural composition Zn(3m) 2 with diethyl zinc
A multi-center study of their physicochemical characteristics, cell culture and in vivo experiments
PVP-capped silver nanoparticles with a diameter of the metallic core of 70 nm,
a hydrodynamic diameter of 120 nm and a zeta potential of −20 mV were prepared
and investigated with regard to their biological activity. This review
summarizes the physicochemical properties (dissolution, protein adsorption,
dispersability) of these nanoparticles and the cellular consequences of the
exposure of a broad range of biological test systems to this defined type of
silver nanoparticles. Silver nanoparticles dissolve in water in the presence
of oxygen. In addition, in biological media (i.e., in the presence of
proteins) the surface of silver nanoparticles is rapidly coated by a protein
corona that influences their physicochemical and biological properties
including cellular uptake. Silver nanoparticles are taken up by cell-type
specific endocytosis pathways as demonstrated for hMSC, primary T-cells,
primary monocytes, and astrocytes. A visualization of particles inside cells
is possible by X-ray microscopy, fluorescence microscopy, and combined FIB/SEM
analysis. By staining organelles, their localization inside the cell can be
additionally determined. While primary brain astrocytes are shown to be fairly
tolerant toward silver nanoparticles, silver nanoparticles induce the
formation of DNA double-strand-breaks (DSB) and lead to chromosomal
aberrations and sister-chromatid exchanges in Chinese hamster fibroblast cell
lines (CHO9, K1, V79B). An exposure of rats to silver nanoparticles in vivo
induced a moderate pulmonary toxicity, however, only at rather high
concentrations. The same was found in precision-cut lung slices of rats in
which silver nanoparticles remained mainly at the tissue surface. In a human
3D triple-cell culture model consisting of three cell types (alveolar
epithelial cells, macrophages, and dendritic cells), adverse effects were also
only found at high silver concentrations. The silver ions that are released
from silver nanoparticles may be harmful to skin with disrupted barrier (e.g.,
wounds) and induce oxidative stress in skin cells (HaCaT). In conclusion, the
data obtained on the effects of this well-defined type of silver nanoparticles
on various biological systems clearly demonstrate that cell-type specific
properties as well as experimental conditions determine the biocompatibility
of and the cellular responses to an exposure with silver nanoparticles
Correlating Atom Probe Tomography with Atomic-Resolved Scanning Transmission Electron Microscopy: Example of Segregation at Silicon Grain Boundaries
In the course of a thorough investigation of the performance-structure-chemistry interdependency at silicon grain boundaries, we successfully developed a method to systematically correlate aberration-corrected scanning transmission electron microscopy and atom probe tomography. The correlative approach is conducted on individual APT and TEM specimens, with the option to perform both investigations on the same specimen in the future. In the present case of a Σ9 grain boundary, joint mapping of the atomistic details of the grain boundary topology, in conjunction with chemical decoration, enables a deeper understanding of the segregation of impurities observed at such grain boundaries
Role of Nanostructuring and Microstructuring in Silver Antimony Telluride Compounds for Thermoelectric Applications
Thermoelectric
(TE) materials are of utmost significance for conversion
of heat flux into electrical power in the low-power regime. Their
conversion efficiency depends strongly on the microstructure. AgSbTe<sub>2</sub>-based compounds are high-efficiency TE materials suitable
for the mid-temperature range. Herein, we explore an Ag<sub>16.7</sub>Sb<sub>30</sub>Te<sub>53.3</sub> alloy (at %) subjected to heat treatments
at 380 °C for different durations aimed at nucleation and coarsening
of Sb<sub>2</sub>Te<sub>3</sub>-precipitates. To characterize the
Sb<sub>2</sub>Te<sub>3</sub>-precipitation, we use a set of methods
combining thermal and electrical measurements in concert with transmission
electron microscopy and atom probe tomography. We find correlations
between the measured TE transport coefficients and the applied heat
treatments. Specifically, the lowest electrical and thermal conductivity
values are obtained for the as-quenched state, whereas the highest
values are observed for alloys aged for 8 h. In turn, long-term heat
treatments result in intermediate values of transport coefficients.
We explain these findings in terms of interplay between precipitate
formation and variations in the matrix composition, highlighting the
importance of thermal stability of the material under service conditions
A Pregnant Adolescent with COVID-19 and Multisystem Inflammatory Syndrome in Children
Multisystem inflammatory syndrome in children (MIS-C), a new condition related to coronavirus disease 2019 (COVID-19) in the pediatric population, was recognized by physicians in the United Kingdom in April 2020. Given those up to the age of 21 years can be affected, pregnant adolescents and young adults are susceptible. However, there is scant information on how MIS-C may affect pregnancy and whether the presentation differs in the pregnant population. We report a case of a pregnant adolescent with COVID-19 and MIS-C with a favorable outcome. This case highlights the considerations in managing a critically ill pregnant patient with a novel illness and the importance of a multidisciplinary team in coordinating care