Thermally driven acoustic oscillations,part V: Gas-liquid oscillations

Summary Thermally driven gas oscillations are considered which drive a liquid column at the cold open end. The frequency of the oscillations is lowered by the inertia of the liquid and the Stokes boundary layer is thick. Optimal conditions for thermal driving in the gas occur at correspondingly big tube radii. Experiments conducted inN ₂ confirm the theoretically calculated stability limits. With hot air driving a water column, a low critical temperature ratio for the oscillations of about 1.5 was observed.

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Zusammenfassung Thermisch getriebene akustische Schwingungen werden untersucht die eine Flüssigkeitssäule am kalten offenen Ende antreiben. Die Frequenz der Schwingungen wird durch die Trägheit der Flüssigkeit vermindert und die Stokes'sche Grenzschicht ist dick. Die optimalen Bedingungen für thermisch getriebene Schwingungen im Gas werden bei entsprechend höheren Rohr-Radien auftreten. Experimente mitN ₂ haben die theoretisch berechneten Stabilitätsgrenzen bestätigt. Bei einer Anordnung, in der heisse Luft eine Wassersäule angetrieben hat, wurde ein tiefes kritisches Temperaturverhältnis von etwa 1.5 beobachtet.

     

Eine Methode zur Bestimmung der spezifischen Radioaktivität der „freien Aminosäuren“ in Gewebeextrakten von Säugetieren

Some experiences are given with a measuring device for the determination of the specific radioactivity of ¹⁴C-labelled brain amino-acids. The apparatus consists of an automatic amino-acid analyzer combined with a flow cell filled with anthracene. The reproducibility of the method is ±5% to ±1% m.e. in the range of 1×10^?3 μCi to 5×10^?2 μCi. A quantitative determination of 3×10^?4 μCi/ml eluant is still possible.     

PopGen: population-based recruitment of patients and controls for the analysis of complex genotype-phenotype relationships

OBJECTIVE: Patient samples used for mapping complex human disease genes are unlikely to be representative of the phenotype spectrum of the respective population as a whole. On the other hand, most ongoing prospective studies are probably too small for evaluating polygenic disease markers. DESIGN: Precise estimates of population-specific genotypic risks can be obtained efficiently through the complete ascertainment of patients in a geographically confined area. The PopGen project uses the most northern part of Germany as a target region for such a pursuit. RESULTS: PopGen currently pursues recruitment, sampling and processing activities in close collaboration with a multitude of clinical partners, covering cardiovascular, neuropsychiatric and environmental diseases. CONCLUSION: PopGen has successfully established itself as a large-scale genetic epidemiological project of international recognition.     

Complete Carton-13 Assignments of the Sesquiterpene Lactone 11,13,-Dihydroparthenolide Using 2D-Inadequate

The complete ¹³C NMR resonances for the sesquiterpene lactone 11,13-dihydroparthenolide were established by the application of 2D-INADEQUATE.     

Robust spatially resolved pressure measurements using MRI with novel buoyant advection-free preparations of stable microbubbles in polysaccharide gels

MRI of fluids containing lipid coated microbubbles has been shown to be an effective tool for measuring the local fluid pressure. However, the intrinsically buoyant nature of these microbubbles precludes lengthy measurements due to their vertical migration under gravity and pressure-induced coalescence. A novel preparation is presented which is shown to minimize both these effects for at least 25 min. By using a 2% polysaccharide gel base with a small concentration of glycerol and 1,2-distearoyl-sn-glycero-3-phosphocholine coated gas microbubbles, MR measurements are made for pressures between 0.95 and 1.44 bar. The signal drifts due to migration and amalgamation are shown to be minimized for such an experiment whilst yielding very high NMR sensitivities up to 38% signal change per bar.     

Simultaneous detection of ultraviolet and infrared radiation in a single GaN/GaAlN heterojunction

Results are presented for a dual-band detector that simultaneously detects UV radiation in the 250-360 nm and IR radiation in the 5-14 microm regions with near zero spectral cross talk. In this detector having separate UV- and IR-active regions with three contacts (one common contact for both regions) allows the separation of the UV and IR generated photocurrent components, identifying the relative strength of each component. This will be an important development in UV-IR dual-band applications such as fire-flame detection, solar astronomy, and military sensing, eliminating the difficulties of employing several individual detectors with separate electronics-cooling mechanisms.     

Taking compact NMR to monitoring real reactions in large-scale chemical industries—General considerations and learnings from a lab-scale test case

The considerations for use of compact nuclear magnetic resonance in a large-scale industrial environment clearly differ from those in academic and educational settings and even from those in smaller companies. In the first part of this article, these differences will be discussed along with the additional requirements that need to be fulfilled for successful applicability in different use cases. In the second part of the article, outcomes from different research activities aiming to fulfill these requirements will be presented with a focus on an online reaction-monitoring study on a lab-scale nucleophilic chlorination reaction.     

Guayulin B

The sesquiterpene guayulin B, C₂₃H₃₀O₃, 1, crystallizes with two independent molecules in monoclinic space group P2₁ with a = 18.099 (1), b = 6.0649(6), c = 19.126(1) Å, = 100.82(1)°, V = 2062.1(5) ų, and Z = 4. The double bonds of the cyclodecadiene ring are E, both methyl groups on the 10-membered ring are -oriented. The cyclopropane ring at C6 and C7 also has the orientation, while the anisoyloxy group is oriented . The 10-membered rings of the two independent molecules have the same conformation as that of guayulin A.