Radiative corrections for associatedZH production at futuree + e − colliders

The \(ZHf\bar f\) four-point function is calculated in the one-loop approximation of the Standard Model and full analytic results are presented. The loop contributions due to both light and new heavy fermions are inspected in detail. The dominant mechanisms of Higgs-boson production from fermions are compared. The effect of radiative corrections on the cross section of \(f\bar f \to ZH\) including bremsstrahlung is studied. The spectrum of hard bremsstrahlung is integrated analytically. The implications for Higgs-boson searches at futuree ⁺ e ^? colliders in the energy range 200 \(200GeV \le \sqrt s \le 1.5TeV\) , which includes both LEP 2 and the Next Linear Collider, are analyzed. ForM _H <2m _t weak corrections in the modified on-mass-shell scheme are generally negative and feebly vary withM _H , while forM _H >2m _t , they strongly increase withM _H and may take large positive values. Electromagnetic corrections dramatically reduce the cross section close to theZH-production threshold, while they may considerably enhance it far above this threshold.     

Beitrag zur direkten Sauerstoffbestimmung in organischen Verbindungen

Zusammenfassung Es wird über zehnjährige Erfahrungen mit der maßanalytischen Mikrobestimmung des Sauerstoffes nachUnterzaucher berichtet. Silikon-schlauchverbindungen dürfen nicht verwendet werden, da sie gasdurchlässig sind. Die Gesamtanalysenzeit kann durch Verwendung eines Klappbrenners auf 15 Minuten verkürzt werden. Die Möglichkeit, das vonEmich im Prinzip vorgeschlagene CO₂-Multiplikationsverfahren anzuwenden, wurde überprüft. Zur Endbestimmung wird für Routine-analysen dem jodometrischen Verfahren wegen seiner Schnelligkeit und Empfindlichkeit der Vorzug gegeben.

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Summary A report is given of 10 years of experiences with the volumetric micro determination of oxygen by theUnterzaucher procedure. Silicone tube connections must not be used since they are permeable to gases. The total analysis time can be shortened to 15 minutes by using a shutter burner. A study was made of the possibility of using the multiplication procedure that in principle was recommended byEmich. For routine analyses, it was found preferable to employ the iodometric method for the final measurement because of its rapidity and sensitivity.

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Résumé On donne un compte rendu sur des expériences effectuées depuis une dizaine d'années sur le microdosage volumétrique de l'oxygène d'aprèsUnterzaucher. Il ne faut pas employer pour ces expériences de tubes siliconés car ils sont perméables aux gaz. La durée totale d'une analyse peut être ramenée à 15 minutes en employant un brûleur à charnière. On a examiné la possibilité d'appliquer le procédé de multiplication de CO₂ préconisé dans le principe parEmich. Pour la détermination du point équivalent dans les analyses en série, on donne la préférence au procédé iodométrique en raison de sa rapidité et de sa sensibilité.

     

N‐Silylaminotitanium Chlorides — Synthesis,Structures, Multinuclear Magnetic Resonance,and some Applications

N‐Silylaminotitanium trichlorides, Me₃S(R)N‐TiCl₃ ( 18 ) [R = ^tBu ( a ), SiMe₃ ( b ), 9‐borabicyclo[3.3.1]nonyl (9‐BBN)( c )], and (CH₂SiMe₂)₂N‐TiCl₃ ( 18d ) were obtained in high yield and high purity from the reaction of the respective bis(silylamino)plumbylene with an excess of titanium tetrachloride. The crystal structure of 18a was determined by X‐ray analysis. The reactions of the analogous stannylenes with an excess of TiCl₄ did not lead to 18 . N‐Lithio‐trimethylsilyl[9‐(9‐borabicyclo[3.3.1]nonyl)]amine ( 8 ) was prepared, structurally characterized and used for the synthesis of a new bis(amino)stannylene 10 and a plumbylene 11 . The compounds 18a—d served as ideal starting materials for the synthesis of bis(silylamino)titanium dichlorides, where the silylamino groups can be identical ( 19 ) or different ( 20 ). This was achieved either by the reaction of 18 again with bis(amino)plumbylenes or with lithium N‐silylamides. In contrast to the direct synthesis starting from titanium tetrachloride and two equivalents of the respective lithium amide, which in general affords 19 with identical amino groups only in low yield, the procedure starting from 18 is much more versatile and gave the pure compounds 19 or 20 in almost quantitative yield. Further treatment of the dichlorides 19 or 20 with lithium amides led to tris(amino)titanium chlorides 21 . The dichlorides 19 or 20 reacted with two equivalents of alkynyllithium reagents to give the first well characterized examples of di(alkyn‐1‐yl)bis(N‐silylamino)titanium compounds 22 — 27 . These compounds reacted with trialkylboranes (triethyl or tripropylborane) by 1, 1‐organoboration. In some cases, the extremely reactive reaction products could be identified as novel 1, 1‐bis(silylamino)titana‐2, 4‐cyclopentadienes 28 — 31 bearing a dialkylboryl group in 3‐position. In solution, the proposed structures of all products were deduced from a consistent set of data derived from multinuclear magnetic resonance spectroscopy (¹H, ¹¹B, ¹³C, ¹⁴N, ¹⁵N, ²⁹Si, ³⁵Cl NMR).     

An Efficient Strategy to Orthogonally Protected (R)- and (S)-alpha-Methyl(alkyl)serine-Containing Peptides via a Novel Azlactone/Oxazoline Interconversion Reaction

A novel strategy for the synthesis of (R)- and (S)-alpha-methyl(alkyl)serine-containing peptides is presented. Using (S)-phenylalanine cyclohexylamide 6 as chiral auxiliary, the optically pure azlactones (R)- and (S)-2 were synthesized via a novel azlactone/oxazoline interconversion reaction (Figures 3 and 6). These azlactones constitute fully protected and activated synthetic equivalents of (R)- and (S)-alpha-methylserine and can be directly incorporated into peptides without further protective group manipulations. Like other alpha,alpha-dialkylated glycines, optically pure alpha-alkylserines can be used to stabilize beta-turn and alpha-helical conformations in short peptides.     

A multi-angle magnetic spectrograph for nuclear reaction studies

A multi-angle magnetic spectrograph for recording spectra of charged particles emitted in nuclear reactions has been built. The apparatus and the beam transport system are described and their parameters are discussed.     

Weak itinerant magnetism as inhibited superconductivity

Thep-state pairing idea proposed recently to explain the ferromagnetism of ZrZn₂ is described in more detail, and the underlying soft-mode hypothesis is examined in relation with experiments, in particular the discovery of antiferromagnetism in TiBe₂. The key result, namely an electron-phonon contribution to the Stoner factor given essentially by the mass enhancement factor, is used to explain the behaviour of the Curie pointT _m and to predict an isotope effect.p-state superconductivity with a transition temperature determined by is predicted in TiBe₂ and, above the critical pressure whereT _m =0, also in ZrZn₂.Work in La Jolla supported by NSF/DMR 77-08469.