The determination of diborane (B2H6) in gas mixtures

Summary A fast and sensitive method is described for the determination of diborane in diborane-gas mixtures. The precision of the method in the 100-ppm range is ±2%. The analysis takes about 70 min to perform. No such retention problems occur as can do in the mass spectroscopy and infrared analysis methods. It is shown that diborane stored in a pressure gas-container slowly decomposes.

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Zusammenfassung Ein rasches und empfindliches Verfahren zur Bestimmung von Diboran in Gasgemischen wurde beschrieben. Dessen Genauigkeit beträgt im 100 ppm-Bereich ±2%. Eine Analyse dauert etwa 70 min. Retentionsprobleme wie bei der Massenspektrometrie oder der IR-Analyse treten hier nicht auf. In Druckflaschen aufbewahrt, zersetzt sich Diboran langsam.

     

The correction for the counting yield in nuclear spectroscopy

Pulser and live timer are alternate tools. Dead time effects can be expressed in terms of a pulse rate dependent factor of the counting yield. The task of their correction should be shifted from the live timer of the ADC to a central timing unit. A new method is proposed, combining the advantages of the pulser and the live timer, where by each selected and accepted event is adjoined to a clock time interval and each selected but not accepted event to a dead time interval. The length of each interval is determined by the arrival of the next selected event.     

A CNDO/2 study of the OH torsion in phenol and its hydrogen bonded complex with pyridine

The CNDO/2 molecular orbital method has been applied to the study of the OH torsion, in phenol and phenol—pyridine hydrogen bonded complex. The calculated torsional barrier (13.58 kJ mol^?1) and force constant (5.4 × 10^?20 J rad^?2) of phenol agree well with the experimental quantities. The calculated force constant of the corresponding vibration in phenol—pyridine is increased sixfold, reproducing closely the rise in the torsional frequency observed when phenol is complexed to strong acceptors. It is shown that according to CNDO theory, most of the increase can be attributed to the influence of the intermolecular force field and not to a major change in the torsional force constant.     

Resolving multiple overlapping calorimetric transitions by use of a microcomputer: studies on erythrocyte membranes

Buffer changes and certain drugs cause temperature shifts, amplitude changes, and transition broadening in the differential scanning calorimetric (DSC) analysis of erythrocyte membranes. However, it has been difficult to interpret and quantitate these shifts and changes because the scans are composed of multiple overlapping transitions and because more than one transition may be simultaneously affected. An empirical approach has been developed by using Gaussian modeling to resolve these calorimetric transitions. Data analysis was carried out on a microcomputer using a nonlinear regression program (PCNONLIN) to fit the data scans. These results show that changes in the calorimetric scans of erythrocyte membranes due to alterations in the buffer environment, such as pH and osmolarity, can be resolved by fitting the data scans with the proposed mathematical model and optimizing the resolution parameters with PCNONLIN. In addition, resolution uncovered hidden characteristics that may not have been readily evident. Under certain conditions, for example, apparent transition shifts were shown to actually be amplitude changes and transition broadening. Determination of the limitations and validity of this method was accomplished with simulation studies. This technique offers a simple means for fitting overlapping DSC transitions by use of a commercially available nonlinear regression program that can be run on a microcomputer.     

Microchromatography of hemoglobins. VIII. A general qualitative and quantitative method in plastic drinking straws and the quantitative analysis of Hb-F

The microchromatographic procedure for the quantitative analysis of the hemoglobin components in a hemolysate uses columns of DEAE-cellulose in a plastic drinking straw with a glycine-KCN-NaCl developer. Not only may the method be used for the quantitative analysis of Hb-F but also for the analysis of the varied components in mixtures of hemoglobins.     

Über Veränderungen der Mikrostruktur während der Hydratation von Monocalciumaluminat bei 50°C

On the Change of Microstructure During the Hydration of Mono Calcium Aluminate at 50°C The course of hydration of mono calcium aluminate at 50°C is characterized by periods of different reaction rates. Measuring the change of specific surface area, heat evolution, degree of hydration and by chemical analysis of the liquid phase it is shown that this behaviour has to be attributed to the formation of a primary reaction layer on the surface of the CaO · Al₂O₃ in the first stage of hydration. At later times, due to conversion and crystallization processes, the reaction rate is influenced by changes of the microstructure of the shell of hydration products covering the CaO · Al₂O₃ grains.     

Aktivierungsanalytische Untersuchungen an hochreinem Silicium

Zusammenfassung Zur Aktivierungsanalyse von hochreinem Silicium wurden die vermuteten Verunreinigungen in 3 Gruppen entsprechend der Halbwertszeit ihrer zur Bestimmung herangezogenen Radionuklide zusammengefaßt und für diese Gruppen chemisch-analytische Trennungsgänge ausgearbeitet. Damit war es möglich, in relativ geringen Probemengen etwa 30 Elemente zu bestimmen. Die dargelegten Ergebnisse liegen durchweg im oder unter dem ppb-Bereich (=10^–7 %).Zur Lokalisierung einiger Verunreinigungen wird die Autoradiographie herangezogen. Einige Aufnahmen zeigen, daß dieses Verfahren auch bei Vorhegen äußerst geringer Aktivitäten noch wertvolle Aussagen zu liefern vermag.

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Summary For the activation analysis of high-purity silicon the supposed impurities are divided into 3 groups corresponding to the half-lives of the radionuclides belonging to the impurities. For these groups chemoanalytical separation schemes are developed. With this technique it was possible to determine about 30 elements in small samples. The results given are in or below the ppb-level.For localisation of the impurities autoradiography is used. Some of the pictures taken show, that also with very low activities valuable results can be obtained.

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Zum Schlu mu die freundliche Hilfe erwähnt werden, die wir an den deutschen Reaktorstationen bei der Durchuürung der Bestrahlung rehalten haben. So sind wir der Reaktorstation Garching, insbesondere den Harren Dr. Köhler und Rau zu auerordentlichem Dank für die stats gewährte Unterstüzung bei der Bestrahlung der großen Zahl der Proben verpflichtet. — Die Analyse der kurzlebigen Radionuklide verlangte das Arbeiten direkt am Reaktor. Dank dem freundlichen Entgegenkommen der Herren Prof. Dr. E. Fischer und Dr. Röbert konnten wir dieses in einem Laboratorium der Reaktorstation Geesthacht durchführen, wobei wir auch den Herren Braun und Hauser für ihre bereitwillige Unterstützung zu danken haben.Schließlich sei Herrn Dr. Brandt für die Entwicklung der erwähnten Formel auch an dieser Stelle nochmals gedankt.

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In gekürzter Form anläßlich der Tagung der Fachgruppe: Kern-, Radio- und Strahlenchemie der Gesellschaft Deutscher Chemiker in Heidelberg am 10. 9. 1963 vorgetragen.     

Tubulin rings: curved filaments with limited flexibility and two modes of association

Tubulin rings have been previously identified as composed of linear polymers of tubulin subunits, equivalent to a protofilament in the microtubule wall but in a curved rather than a straight conformation. We have examined and measured a number of different ring structures obtained under different conditions. The preferred curvature is indicated by a single ring of 380 A outside diameter. Radially double rings consist of two coplanar rings of 460 A and 350 A outside diameter, held together by a pattern of eight identical contacts between the 40 A subunits in the inner and outer rings. In some circumstances a larger ring, 570 A diameter, can be added to the outside, or a smaller ring, 240 A diameter, may be added to the inside of the radially double ring, in both cases repeating the pattern of eight radial contacts. The distortion of the filament from its relaxed 380 A diameter curvature apparently can be made without disrupting the longitudinal bond between subunits in the filament, but must be stabilized by the energy of the radial contact. All of these rings (single and radially double and triple) are observed to associate axially to form pairs or in some cases larger stacks. The radially double rings or an axially associated pair of these (quadruple ring) may also associate to form crystals. These are thin plates, up to 100 micrometers in extent and several micrometers thick which have been of limited use so far in diffraction studies because of irregularities in the packing of adjacent rings.