Selective formation of 2-imidazolines and 2-substituted oxazoles by using a three-component reaction

Selective formation of 2H‐2‐imidazolines and 2‐substituted oxazoles by using a multicomponent reaction of amines, either aldehydes or ketones, and α‐acidic isocyano amides or esters is described. By selecting the appropriate solvent, Ag^I or Cu^I catalyst, or by employing a weak Brønsted acid, the product formation can be fully controlled and directed quantitatively to the desired heterocyclic scaffold. The described experimental procedures not only significantly increase the scope of compatible inputs for this complexity‐generating three‐component reaction, but also allow for considerable chemical diversity: At least four diversity points in two distinct scaffolds can be exploited in this way.     

Fatty acid profiling of raw human plasma and whole blood using direct thermal desorption combined with gas chromatography-mass spectrometry

Gas chromatography (GC) has in recent times become an important tool for the fatty acid profiling of human blood and plasma. An at-line procedure used in the fatty acid profiling of whole/intact aquatic micro-organisms without any sample preparation was adapted for this work. A direct thermal desorption (DTD) interface was used to profile the fatty acid composition of human plasma and whole human blood of eight volunteers in a procedure omitting the usual lipid extraction steps that precede sample methylation in the traditional (off-line) protocols. Trimethylsulfonium hydroxide (TMSH) was used as reagent for thermally assisted methylation. In a fully automated manner, the liner of the GC injector is used as a sample-and-reaction container with the aid of the DTD interface. The fatty acid methyl ester (FAME) profiles obtained using this novel approach, were very identical to those obtained when the traditional off-line protocol was applied. FAME yields obtained in the at-line DTD method were found to be very similar for saturated fatty acids, but significantly higher for polyunsaturated fatty acids compared to off-line yields. As a result of the contribution of circulating cell membranes in blood, substantial differences were observed when the amount of FAMEs obtained in whole human blood and human plasma samples were compared after their analysis. Thanks to the fully automated operation of this novel procedure, large series of analyses can easily be performed.     

Perpendicular ultrasound velocity measurement by 2D cross correlation of RF data. Part A: validation in a straight tube

An ultrasound velocity assessment technique was validated, which allows the estimation of velocity components perpendicular to the ultrasound beam, using a commercially available ultrasound scanner equipped with a linear array probe. This enables the simultaneous measurement of axial blood velocity and vessel wall position, rendering a viable and accurate flow assessment. The validation was performed by comparing axial velocity profiles as measured in an experimental setup to analytical and computational fluid dynamics calculations. Physiologically relevant pulsating flows were considered, employing a blood analog fluid, which mimics both the acoustic and rheological properties of blood. In the core region (|r|/a < 0.9), an accuracy of 3 cm s⁻¹ was reached. For an accurate estimation of flow, no averaging in time was required, making a beat to beat analysis of pulsating flows possible.     

Resolvents in Semi-linear Harmonic Spaces

We will show that the semi-linear potential kernels defined in [4] have a resolvent associated with them. Furthermore, the bounded excessive functions of this resolvent correspond to the bounded hyperharmonic functions as they do in linear potential theory.     

Crystal structure of 2-{(R)-1-hydroxy-1-[(2S)-1-tritylaziridin-2-yl] methyl}acrylate and spectroscopic properties of the (R,S) and (S,S) stereoisomers

The crystal and molecular structure of 2-{(R)-1-Hydroxy-1-[(2S)-1-tritylaziridin-2-y1] methy1}acrylate is described. Crystal data: C₂₆H₂₅NO₃, orthorhombic, space group P2₁2₁2₁, a = 9.6954(5), b = 13.1458(5), c = 16.7885(7) Å, V = 2139.8(2) ų, Z = 4. The (R,S) diastereomer shows an intramolecular hydrogen bonding N···H—O under formation of a five-membered ring with N···O distance of 2.664 Å. IR, ¹H NMR and ¹³C NMR data are discussed. The ¹H NMR of the (R,S) diastereomer shows a singlet- whereas the (S,S) diastereomer exhibits a doublet-pattern for the hydroxyl proton.     

When tethered chains meet free ones; the stability of polymer wetting films on polymer brushes

We present a combined experimental and theoretical self-consistent field (SCF) investigation of the wetting behavior of a polystyrene melt (composed of chains with degree of polymerization P) on top of a polystyrene brush (composed of chains with length N) grafted onto a silica surface. The control variables are the grafting density σ of the brush chains and the length of mobile chains P. Experiments show in agreement with the theory that there is a window of complete wetting. Both at very low and at high grafting densities the system remains partial wet. At large degree of polymerization P, there is a difference between the experimental and theoretical results. Theory predicts partial wetting only, whereas the window of complete wetting persists in the experiments even when P >> N. This difference is attributed to the double-well structure of the disjoining pressure as revealed by the SCF theory. With this type of disjoining pressure it is conceivable that a metastable zero contact angle remains present for very long times.