Chemoenzymatic Asymmetric Synthesis of Pyridine-Based α-Fluorinated Secondary Alcohols

Fluoro-substituted and heteroaromatic compounds are valuable intermediates for a variety of applications in pharma- and agrochemistry and synthetic chemistry. This study investigates the chemoenzymatic preparation of chiral alcohols bearing a heteroaromatic ring with an increasing degree of fluorination in α-position. Starting from readily available picoline derivatives prochiral α-halogenated acyl moieties were introduced with excellent selectivity and 64–95 % yield. The formed carbonyl group was subsequently reduced to the corresponding alcohols using the alcohol dehydrogenase from Lactobacillus kefir, yielding an enantiomeric excess of 95–>99 % and up to 98 % yield.     

The Determinants of Debt and (Private) Equity Financing: The Case of Young, Innovative SMEs from Germany

Financial theory creates a puzzle. Some authors argue that high-risk entrepreneurs choose debt contracts instead of equity contracts since risky but high returns are of relatively more value for a loan-financed firm. Conversely, authors who focus explicitly on start-up finance predict that entrepreneurs are the more likely to seek equity-like venture capital contracts, the more risky their projects are. Our paper is an initial step towards resolving this puzzle empirically. We present microeconometric evidence on the determinants of debt and equity financing in young and innovative SMEs. We pay special attention to the role of risk for the choice of the method of financing. Since risk is not directly observable we use different indicators for financial and project risk. It turns out that our data generally confirms the hypothesis that the probability that a young high-tech firm receives equity financing is an increasing function of the financial risk. With regard to the intrinsic project risk, our results are less conclusive, as some of our indicators of a risky project are found to have a negative effect on the likelihood to be financed by private equity.     

Somatic symptoms and panic attacks: a retrospective study of learning experiences

To determine the clinical significance of ST-segment depression observed in paroxysmal supraventricular tachycardia (PSVT), we evaluated the 12-lead electrocardiogram (ECG) during spontaneous PSVT in 54 patients (27 men and 27 women: mean age +/- SD; 47 +/- 18 years), who came to our clinic for the treatment of PSVT. Coronary angiography was performed in 16 patients (16 to 74 years; mean = 50 +/- 18) and treadmill exercise testing was performed in 21 patients. A cardiac electrophysiological study was carried out in 24 patients. During PSVT, ST-segment score was calculated as the sum of the ST-segment depression in 12 leads. The correlations between the ST-segment score, PSVT rate and age of the patient were analyzed as follows: The most significant positive correlation was observed between the ST-segment score and the PSVT rate (r = 0.615, p < 0.000001). The next most significant correlation was found between the PSVT rate and the age of the patient (r = -0.500, p = 0.00011). A negative correlation was also observed between the ST-segment score and the age of the patient (r = -0.429, p = 0.0012). In 13 of 16 patients, coronary angiography did not reveal any significant (> or = 75% in area) stenosis. Exercise testing induced significant ST-segment depression in 3 patients, of whom two had significant coronary artery lesions. PSVT was due to atrioventricular reentry via an overt (n = 3) or concealed accessory pathway (n = 15), atrioventricular nodal reentry (n = 5) and sinus node reentry (n = 1). In conclusion, patients with a faster PSVT rate revealed more pronounced ST-segment depression than did those with a slower PSVT rate, possibly reflecting the modified repolarization process instead of coronary artery involvement.     

Enhanced oxidation of the 9%Cr steel P91 in water vapour containing environments

The short term (∼100 h) oxidation behaviour of the 9%Cr steel P91 was studied at 650 °C in N₂-O₂-H₂O gas mixtures containing a relatively low oxygen level of 1%. The oxidation kinetics were measured thermogravimetrically and the oxide scale growth mechanisms were studied using H₂¹⁸O-tracer with subsequent analyses of oxide scale composition and tracer distribution by MCs⁺-SIMS depth profiling. The corrosion products were additionally characterised by light optical microscopy, SEM-EDX and XRD. It was found that the transition from protective, Cr-rich oxide formation into non-protective mixed oxide scales is governed by the ratio H₂O^(g)/O₂ ratio rather than the absolute level of H₂O^(g). The results of the tracer studies in combination with the data obtained from experiments involving in situ gas changes clearly illustrated that under the prevailing conditions the penetration of water vapour molecules triggers the enhanced oxidation and sustains the high growth rates of the poorly protective Fe-rich oxide scale formed in atmospheres with high H₂O^(g)/O₂ ratios. The experimental observations can be explained if one assumes the scale growth to be governed by a competitive adsorption of oxygen and water vapour molecules on external and internal surfaces of the oxide scales in combination with the formation of a volatile Fe-hydroxide during transient oxidation. The formation of the non-protective Fe-rich oxide scales is suppressed in atmospheres with low H₂O^(g)/O₂ -ratios, and the healing of any such scale is promoted.     

Bestimmung von Pentan als Indikator für die oxidative Ranzigkeit von Ölen

Determination of Pentane as an Indicator of Oil Rancidity Pentane, determined by a headspace gas chromatographic method, is an excellent indicator of oil rancidity. The methodology applied is very simple and could be performed in an oil laboratory without purchasing additional equipment. The amount of pentane correlated well with the iodometrically determined peroxide value (R²-value of 0.976). Heating the oil sample in air followed by an estimation of pentane is an alternative means to assess oil stability against oxidative deterioration.     

Properties of a single-chain antibody containing different linker peptides

Single-chain antibodies were constructed using six differentlinker peptides to join the V_H and V_L domains of an anti-2-phenyloxazolone(Ox) antibody. Four of the linker peptides originated from theinterdomain linker region of the fungal cellulase CBHI and consistedof 28, 11, six and two amino acid residues. The two other linkerpeptides used were the (GGGGS)₃ linker with 15 amino acid residuesand a modified IgG2b hinge peptide with 22 residues. Proteolyticstability and Ox binding properties of the six different scFvderivatives produced in Escherichia coli were investigated andcompared with those of the corresponding Fv fragment containingno joining peptide between the V domains. The hapten bindingproperties of different antibody fragments were studied by ELISAand BIAcore^TM. The interdomain linker peptide improved the haptenbinding properties of the antibody fragment when compared withFv fragment, but slightly increased its susceptibility to proteases.Single-chain antibodies with short CBHI linkers of 11, six andtwo residues had a tendency to form multimers which led to ahigher apparent affinity. The fragments with linkers longerthan 11 residues remained monomeric.     

On finite dynamic equations for fluid-saturated porous media

Summary The paper concerns the relations between two principally different approaches to the formulation of momentum balance equations in porous media theories, namely, the dynamic approach similar to Biot's theory and the modern approach as a result of mixture theories extended by the concept of volume fractions. In particular, it is shown that both approaches necessarily lead to the same type of momentum balance equations and furthermore contain, in a certain sense, within the geometrically linear case, the well-known classical equations of Biot's theory.     

Spray-Coating of Superhydrophobic Coatings for Advanced Applications

Superhydrophobic coatings are widely applicable, e.g., as self-cleaning surfaces or water–oil separation membranes, yet their wider usage is impeded due to costs of fabrication, size, or substrate limitation. Spray-coating is a versatile coating procedures and might offer a good solution for the fabrication of these superhydrophobic coatings, due to the fact that coatings can be fabricated on various materials in a simple, fast, and inexpensive manner. Most procedures rely on hybrid coatings of hydrophobized nanoparticles and a polymeric matrix, which have several drawbacks including the easy loss of nanoparticles and difficult waste handling. Here, the fabrication of the superhydrophobic material, called Fluoropor, for the first time, by spray-coating on various substrates including metals, tissues, concrete, and glass is presented. It is fabricated by spray-coating a mixture of a highly fluorinated monomer blended with porogens followed by photopolymerization. The superhydrophobicity of the material relies on the porous structure on the micro-/nanoscale across the bulk material and does not require any nanoparticles. Excellent self-cleaning ability of these coatings, resistance against thermal and abrasive impact, and their application as oil–water separation membranes are shown. This versatile applicability is highly promising for real-world application as self-cleaning coatings or oil–water separating membranes.     

Rapid Aging as a Key to Understand Deactivation of Ni/Al2O3 Catalysts Applied for the CO2 Methanation

Catalysis Letters - We developed a rapid aging method for Ni/Al2O3 methanation catalysts mimicking the real aging in the actual application. The method is based on hydrothermal deactivation of the...