The stopping of slow75As recoil atoms in He,Ne and H2

Recent measurements of the 2p—1s X-ray line in theK ^? p atom indicate that the 1s level shift is very different from the theoretical prediction based on the extrapolation from theK ^? p scattering data. Deloff and Law have suggested that an anomalously large Coulomb effect could be responsible for this discrepancy. We examine this possibility by carrying out an explicit model calculation, using the method by which Sauer demonstrated the possible existence of an anomalously large Coulomb effect in the proton-proton system. Our conclusion is that if there exists an anomalous Coulomb effect which explains theK ^? p atomic level shift result, then the same effect would cause a serious conflict with theK ^? p scattering data above threshold.     

F?llungstitrimetrische Bestimmung von Esterchelatanionen mit Tensidkationen. Amperometrische und voltametrische Endpunktsanzeige

Zusammenfassung Die fällungstitrimetrische Bestimmung von Brenzcatechinatochelatanionen des MoO ₄ ^2– , WO ₄ ^2– und VO ₃ ^2–/s- mit R₄N⁺¹ wird untersucht. Zur Aufklärung des Indikationsmechanismus werden auch vergleichende Untersuchungen mit substituiertem Brenzcatechin und mit Zusatz aprotischer Lösungsmittel beschrieben.Die Indikation erfolgt durch Oxidation von adsorbiertem Komplex vor dem Endpunkt bzw. von überschüssigem Ligand nach dem Endpunkt. Der Endpunkt selbst wird durch ein Maximum bzw. durch einen Sprung angezeigt. Dieser einfache Mechanismus wird durch verschiedene Adsorptionsgleichgewichte beeinflußt. Alle drei untersuchten Übergangsmetalle lassen sich nach der beschriebenen Methode nachweisempfindlich und genau bestimmen. Eediglich VO ₃ ^– macht eine Ausnahme, indem es als einfach geladenes Esterchelatanion zur Dimerisierung neigt und die Anodenoberfläche blockiert: Die Eichfunktion verläuft hier schon bei kleinen Konzentrationen in Form einer Sättigungskurve. Die Standardabweichung für die fällungstitrimetrische Bestimmung der zweiwertigen Esterchelatanionen beträgt dagegen bei 0,1 mmol erst etwa 1% rel.

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Precipitation titration of esterchelate-anions using tenside cations. Amperometric and voltametric indication

Summary The precipitation-titrimetric determination of catechol-chelate anions of MoO ₄ ^2– , WO ₄ ^2– and VO ₃ ^2–/s- by R₄N^{+ 1} is examined. The mechanism of the amperometric resp. voltametric indication is elucidated by comparative examinations using substituted catechols and adding aprotic solvents to the test solutions.Indication is achieved by oxidation of the adsorbed complex prior to reaching the endpoint and by oxidation of ligand excess after having passed the endpoint. Thus, the indication signal is a maximum (catechol) resp. a break (4-nitrocatechol). This simple mechanism is superimposed by several adsorption equilibria. All transition metals under examination may be determined very sensitively and accurately by the method presented with the exception of VO ₃ ^– which because of the monovalency of its complex tends towards dimerisation and blockage of the electrodes' surfaces. In this case, the calibration plot shows saturation already at a low concentration. In contrast, the divalent esterchelate anions have a linear calibration curve and can be determined down to a level of 5×10^–3 mmols. The standard deviation is about 1% rel. at 0.1 mmol.

     

Coulomb correction to Delbrück scattering investigated atZ=94

Differential cross sections for the elastic scattering of 2.754 MeV photons by Pu were measured for angles ranging from 45 to 120° and interpreted in terms of Delbrück, nuclear Thomson, Rayleigh and nuclear resonance scattering. It is shown that the largest part of the discrepancy between experiment and the lowest-order Delbrück theory can be removed by introducing a (Zα)⁴-dependent Coulomb correction term. Evidence is obtained for additional Coulomb correction terms of higher order in (Z α).     

Die sterischen Bedingungen der Fragmentierungsreaktion I. Teil. Stereoisomere 3-Chlortropane. Fragmentierungsreaktionen, 14. Mitteilung

The steric requirements for the synchronous fragmentation of γ-aminohalides as previously postulated have been confirmed by a study of the solvolysis of stereoisomeric 3β- and 3β-chloro-tropanes and -nortropanes. 3β-chloro-tropanes ( 7 a ) and 3β-chloro-nortropane ( 7 b ), which fulfil the stereoelectronic requirements, undergo quantitative fragmentation in 80 vol.% ethanol. They react 1.35 × 10⁴ and 1.35 × 10³ times, respectively, as fast as the ‘homomorphous’ exo-3-chloro-bicyclo[3.2.1]octane ( 12 a ). Fragmentation therefore takes place by the synchronous mechanism.     

Photofragmentation of Dibenzyl Ketone in the Presence of Tetramethylpiperidine Derivatives. Studies on light stabilizer mechanisms [1]

The interaction of selected tetramethylpiperidine derivatives with radicals arising from the Norrish-type I cleavage of dibenzyl ketone under oxygen was studied. Product analyses and kinetic studies showed that the investigated sterically hindered piperidine derivatives have a pronounced effect on both the nature and distribution of the products of photolysis of dibenzyl ketone in the presence of oxygen. Observations indicated that the phenylperacetoxyl radical is formed as an intermediate during irradiation and that it interacts with the additives used. Possible mechanisms of the reactions studied are discussed. The observation that oxidation of an isolated double bond by the radicals formed in dibenzyl ketone photolysis under oxygen is strongly inhibited in the presence of the studied sterically hindered amines is discussed in the light of the results presented. The findings are considered in relation to the problem of polymer stabilization.     

Successive substitution titration of cadmium and zinc with EGTA using carbon paste electrode for indication

Summary Cadmium and zinc can be determined in a single titration in the following manner: To the sample solution an ammonia/ammoniumchloride buffer is added to make the ammonia concentration 1,0–1,2 M (pH ca. 10). The titration is performed with amperometric indication using a carbon paste electrode and EGTA [ethyleneglycol-bis-(2-aminoethylether)-tetra acetic acid] as the titrant. After the end point for cadmium, excess amount of calcium-EDTA complex is added, and zinc is successively titrated with EGTA. The influences of iron(III), copper(II), lead(II) and manganese(II) have been examined. The conditions for carbon paste electrode indication have also been studied.

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Sukzessive Substitutions-Titration von Cadmium und Zink mit ÄGTA, indiziert mit der Kohlepaste-Elektrode

Zusammenfassung Cadmium und Zink können in einer einzigen Titration folgendermaßen bestimmt werden: Zu der Probelösung wird Ammoniak-Ammoniumchlorid-Puffer zugesetzt. Die Ammoniakkonzentration in der Endlösung sollte 1,0–1,2 M (pH ca. 10) betragen. Die Titration erfolgt mit ÄGTA [Äthylenglycolbis-(2-Aminoäthyläther)-tetraessigsäure] und wird amperometrisch mit der Kohlepasteelektrode indiziert. Nach dem Endpunkt für Cadmium wird ein Überschuß an CaÄDTA zugesetzt. Danach wird auch Zink mit ÄGTA titriert. Die Störungen durch Fe(III), Cu(II), Pb(II) und Mn(II) werden untersucht. Ebenso werden die Bedingungen für die Indikation mit der Kohlepasteelektrode untersucht.

     

Extending the solvent palette for cw jet stream dye lasers

The use of viscosity-raising additives (VRAs) for jet stream dye lasers is proposed and examples for all common organic solvents given. The use of water-based dye solutions with polyvinyl alcohol as a VRA offers substantial advantages for high stability and high power applications.     

Remarks on semilinear partial functional-differential equations with infinite delay

In this paper we will be concerned with the abstract semilinear equation x(Φ)(t) = Ax(Φ)(t) + F(t, x_t(Φ)), t ? τ, x_τ(Φ) = Φ, where A represents the infinitesimal generator of a linear C₀-semigroup in a Banach space and x_～(Φ) denotes the segment of the solution x due to the initial function Φ taken from ?∞ up to t. Conditions for existence, continuous dependence, and regularity of solutions are given which are independent of the topology of the phase space, as well as conditions which guarantee the compactness of bounded orbits, even if exp(At) is not compact for t > 0.     

Ethynylphosphonamidates for the Rapid and Cysteine‐Selective Generation of Efficacious Antibody–Drug Conjugates

Requirements for novel bioconjugation reactions for the synthesis of antibody–drug conjugates (ADCs) are exceptionally high, since conjugation selectivity as well as the stability and hydrophobicity of linkers and payloads drastically influence the performance and safety profile of the final product. We report Cys‐selective ethynylphosphonamidates as new reagents for the rapid generation of efficacious ADCs from native non‐engineered monoclonal antibodies through a simple one‐pot reduction and alkylation. Ethynylphosphonamidates can be easily substituted with hydrophilic residues, giving rise to electrophilic labeling reagents with tunable solubility properties. We demonstrate that ethynylphosphonamidate‐linked ADCs have excellent properties for next‐generation antibody therapeutics in terms of serum stability and in vivo antitumor activity.