A review of the changes in carotenes during ensiling of forages

The dietary availability of carotenes to the animal depends in part on the relative proportions of different isomers and these may alter during ensiling. The proportions of the more available β-carotenes are higher in well preserved silages than in clostridial silages. Under anaerobic conditions only small losses of carotenes occur with acidtreated silages but the provitamins are degraded rapidly in some fodder plants in the presence of both acids and oxygen. The presence of nitrites in silages is considered to increase destruction of carotenes.     

Radioisotopic method for the determination of low and very low proteolytic activities in foodstuffs

Zusammenfassung Das Verfahren zum Nachweis der proteolytischen Aktivitat unter Verwendung von mit¹²⁵I-markiertem menschlichen Serumalbumin als Substrat wurde auf die Bestimmung der proteolytischen Aktivität in Lebensmitteln angewendet. Die Methode ist sehr empfindlich and ermöglicht auch die Bestimmung sehr niedriger proteolytischer Aktivitäten in allen Lebensmittel. Es wird die Optimierung der Methode zur Bestimmung der proteolytischen Aktivitäten in Fleisch und Fleischprodukten beschrieben, Bowie die Bestimmung der proteolytischen Aktivitat in Milchprodukten und Getreideprodukten.

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Radioisotopic method for the determination of low and very low proteolytic activities in foodstuffs

Summary A proteolytic activity assay using denatured¹²⁵I-labelled human serum albumin as substrate was applied to the determination of proteolytic activity of foodstuffs. The method is very sensitive and enables the determination of very low activities in all kinds of foodstuffs. The optimization of the method for the determination of proteolytic activities in meat and meat products is described. The determination of activities in milk products and cereals is also presented.

     

Hydriding properties of the nanocomposite 85 wt.% Mg–15 wt.% Mg2Ni0.8Co0.2 obtained by ball milling

The hydrogen sorption properties of the nanocomposite 85 wt.% Mg–15 wt.% Mg₂Ni_0.8Co_0.2 obtained by mechanical alloying in inert atmosphere were investigated. Absorption measurements were performed under a hydrogen pressure P = 1 MPa at temperartures ranging from 373 to 573 K, while desorption studies proceeded at P = 0.15 MPa and temperatures of 573 and 553 K. The addition of the intermetallic compound Mg₂Ni_0.8Co0_0.2 was shown to improve the hydriding kinetics of magnesium. The composite exhibited a high hydrogen capacity which did not decrease even after a large number of absorption–desorption cycles. Comparison of the hydriding kinetics of the intermetallic compounds Mg₂Ni and Mg₂Ni_0.8Co_0.2 indicated facilitation of the process by the presence of cobalt in the alloy. Magnetic measurement data on Mg₂Ni_0.8Co_0.2 showed formation of superparamagnetic precipitations of nickel and cobalt playing the role of active centres for dissociative chemisorption of hydrogen. The behaviour of the composite was explained by the catalytic effect of the intermetallic Mg₂Ni_0.8Co0_0.2, the existence of Ni and Co clusters on the surface and the process of mechanical alloying.     

Retrovirus-mediated in vitro gene transfer into chicken male germ line cells

Chicken testicular cells, including spermatogonia, transplanted into the testes of recipient cockerels sterilized by repeated gamma-irradiation repopulate the seminiferous epithelium and resume the exogenous spermatogenesis. This procedure could be used to introduce genetic modifications into the male germ line and generate transgenic chickens. In this study, we present a successful retroviral infection of chicken testicular cells and consequent transduction of the retroviral vector into the sperm of recipient cockerels. A vesicular stomatitis virus glycoprotein G-pseudotyped recombinant retroviral vector, carrying the enhanced green fluorescent protein reporter gene was applied to the short-term culture of dispersed testicular cells. The efficiency of infection and the viability of infected cells were analyzed by flow cytometry. No significant CpG methylation was detected in the infected testicular cells, suggesting that epigenetic silencing events do not play a role at this stage of germ line development. After transplantation into sterilized recipient cockerels, these retrovirus-infected testicular cells restored exogenous spermatogenesis within 9 weeks with approximately the same efficiency as non-infected cells. Transduction of the reporter gene encoding the green fluorescent protein was detected in the sperms of recipient cockerels with restored spermatogenesis. Our data demonstrate that, similarly as in mouse and rat, the transplantation of retrovirus-infected spermatogonia provides an efficient system to introduce genes into the chicken male germ line.     

Temperature-induced inversion of the elution order of enantiomers in gas chromatography: N-ethoxycarbonyl propylamides and N-trifluoroacetyl ethyl esters of alpha-amino acids on Chirasil-Val-C11 and Chirasil-Dex stationary phases

Inversion of the elution order of enantiomers caused by enthalpy-entropy compensation at the isoenantioselective temperature (Tiso) was experimentally observed by gas chromatography on the diamide-type chiral stationary phase (CSP), Chirasil-L-Val-C11, with N-ethoxycarbonyl propylamide (ECPA) derivatives of a number of alpha-amino acids. For the first time, a clear visual representation of the increase of the apparent enantioseparation factor alpha app from 1.00 to 1.08 as the temperature is raised from 120 to 170 degrees C is presented. The increase of alpha app is accompanied by a concomitant reduction of the retention factors of the enantiomers. The Tiso values were in the range from 110 to 130 degrees C depending on the nature of the alpha-amino acid. On the contrary, the Tiso values of the N(O)-trifluoroacetyl ethyl ester derivatives (TFA-Et) of the same alpha-amino acids were approximately 80 degrees higher than that of ECPA derivatives. The comprehensive thermodynamic investigation of the enantioseparation of ECPA and TFA-Et derivatives of valine and alanine using the retention increment method showed that the Delta L,D(DeltaH) difference between the diastereomeric selector-selectand associates was almost the same for ECPA and TFA-Et derivatives despite a much stronger bonded selector-selectand association taking place for the ECPA derivatives. On the other hand, the Delta L,D(DeltaS) values were found to be more negative in the case of ECPA derivatives, resulting in the unusually low values of Tiso. A temperature-dependent inversion of the elution order of enantiomers was also observed on the cyclodextrin-type CSP, Chirasil-Dex, with TFA-Et derivatives of several alpha-amino acids. The Tiso values were in the range from 20 to 170 degrees C depending on the nature of the alpha-amino acid. The results obtained demonstrate the necessity to conduct temperature-dependent studies in order to optimize the enantiomeric separation of single racemates isothermally or of mixtures of racemates in temperature-programmed runs using enantioselective GC. It is also shown that consideration of the elution order of enantiomers and the value of the apparent enantioseparation factor alpha app alone, without performing temperature-dependent measurements, can easily lead to wrong conclusions regarding the enantiorecognition mechanism.     

Increasing the quantum efficiency of InAs/GaAs QD arrays for solar cells grown by MOVPE without using strain‐balance technology

Research into the formation of InAs quantum dots (QDs) in GaAs using the metalorganic vapor phase epitaxy technique is presented. This technique is deemed to be cheaper than the more often used and studied molecular beam epitaxy. The best conditions for obtaining a high photoluminescence response, indicating a good material quality, have been found among a wide range of possibilities. Solar cells with an excellent quantum efficiency have been obtained, with a sub‐bandgap photo‐response of 0.07 mA/cm² per QD layer, the highest achieved so far with the InAs/GaAs system, proving the potential of this technology to be able to increase the efficiency of lattice‐matched multi‐junction solar cells and contributing to a better understanding of QD technology toward the achievement of practical intermediate‐band solar cells. Copyright © 2016 John Wiley & Sons, Ltd.     

Recyclable Enantioselective Catalysts Based on Copper(II) Complexes of 2‐(Pyridine‐2‐yl)imidazolidine‐4‐thione: Their Application in Asymmetric Henry Reactions

This paper describes the preparation of enantioselective catalysts based on derivatives of imidazolidine‐4‐thione and their subsequent anchoring by means of a sulfur atom on a polymeric carrier. First, we verified the catalytic activity and enantioselectivity in the Henry reaction of the homogeneous variants of the catalysts, i.e., the copper(II) complexes of 2‐(pyridine‐2‐yl)imidazolidine‐4‐thiones and 4‐benzylsufanyl‐2‐(pyridine‐2‐yl)imidazolines themselves. It was found that these catalysts exhibit high enantioselectivity (up to 98% ee). Subsequently, the imidazolidine‐4‐thione catalysts were immobilized by anchoring to polymeric carriers based on a copolymer of styrene and 4‐vinylbenzyl chloride. These heterogeneous catalysts were analogously tested with regard to their catalytic activity and enantioselectivity in the Henry reaction, and moreover, the possibility of their separation and reuse was studied. It was found that all the prepared immobilized catalysts are highly enantioselective (up to 97% ee). Their recycling ability was tested in Henry reaction of 2‐methoxybenzaldehyde with nitromethane. It was found that they can be recycled more than ten times without any decrease of their enantioselectivity. Therefore, they present a better means of catalysis than the original copper(II) complexes of imidazolidine‐4‐ones from both economic as well as ecological points of view. Thus, such immobilized catalysts exhibit high application potential for the asymmetric Henry reaction.

     

南极冰钻钻井液应用性试验研究

钻井液的性质及性能参数对于南极科学钻探有着重要的影响。钻井液除了必须要具备合适的粘度和密度,以满足冷却钻头、平衡孔壁压力、携带冰屑、清洁孔底的要求外,钻井液的性质如导电性、导热性及其腐蚀性对于保证钻具的正常工作、输送孔内信息也有着重要的影响。根据目前已经在南极使用的钻井液类型,分别对6种介质(国产硅油-3cst、KF96硅油-2cst、丁酸乙酯、丁酸丁酯、丁酸戊酯、丙酸丙酯)在不同温度下的电导率、导热系数和对密封件的腐蚀性进行了试验测试,选出了适合南极应用的钻井液类型及在钻具中使用的密封件材质,可供极地钻探选择钻井液类型及钻具设计提供重要的参考。