Master integrals for massless three-loop form factors: One-loop and two-loop insertions

The three-loop form factors in massless QCD can be expressed as a linear combination of master integrals. Besides a number of master integrals which factorise into products of one-loop and two-loop integrals, one finds 16 genuine three-loop integrals. Of these, six have the form of a bubble insertion inside a one-loop or two-loop vertex integral. We compute all master integrals with these insertion topologies.     

über Katalysatoren- und Fermentmodelle (1)

Ohne Zusammenfassung Die Arbeit wurde aus Mitteln des Marshall-Planes (ERP-Mittel) und mit Spenden aus dem „Fonds Chemie“ ausgeführt. Wir sprechen den zust?ndigen Stellen für die Gew?hrung der Beihilfe unseren verbindlichsten Dank aus. Der Deutschen Forschungsgemeinschaft danken wir für die überlassung einer Ultrazentrifuge, den Behring-Werken für die uns zur Verfügung gestellten Serumalbumin- und -globulin-Pr?parate.     

Spin-dependent parton distributions from polarized structure function data

In the past year, polarized deep inelastic scattering experiments at CERN and SLAC have obtained structure function measurements off proton, neutron and deuteron targets at a level of precision never before achieved. The measurements can be used to test the Bjorken and Ellis-Jaffe sum rules, and also to obtain information on the parton distributions in polarized nucleons. We perform a global leading-order QCD fit to the proton deep inelastic data in order to extract the spin-dependent parton distributions. By using parametric forms which are consistent with theoretical expectations at large and smallx, we find that the quark distributions are now rather well constrained. We assume that there is no significant intrinsic polarization of the strange quark sea. The data are then consistent with a modest amount of the proton's spin carried by the gluon, although the shape of the gluon distribution is not well constrained, and several qualitatively different shapes are suggested. The spin-dependent distributions we obtain can be used as input to phenomenological studies for future polarized hadron-hadron and lepton-hadron colliders.     

Deep inelastic electron-pomeron scattering at HERA

The idea that the pomeron has partonic structure similar to any other hadron has been given strong support by recent measurements of the diffractive structure function at HERA. We present a detailed theoretical analysis of the diffractive structure function under the assumption that the diffractive cross section can be factorized into a pomeron emission factor and the deep inelastic scattering cross section of the pomeron. We pay particular attention to the kinematic correlations implied by this picture, and suggest the measurement of an angular correlation which should provide a first test of the whole picture. We also present two simple phenomenological models for the quark and gluon structure of the pomeron, which are consistent with various theoretical ideas and which give equally good fits to recent measurements by the H1 collaboration, when combined with the pomeron emission factor of Donnachie and Landshoff. We predict that a large fraction of diffractive deep inelastic events will contain charm, and discuss how improved data will be able to distinguish the models.     

Multiround Unconditionally Secure Authentication

Authentication codes are used to protect communication against a malicious adversary. In this paper we investigate unconditionally secure multiround authentication schemes. In a multiround scheme a message is authenticated by passing back and forth several codewords between the sender and receiver. We define a multiround authentication model and show how to calculate the probability of a successful attack for this model. We prove the security for a 3-round scheme and give a construction for the 3-round scheme based on Reed-Solomom codes. This construction has a very small key size for even extremely large messages. Furthermore, a secure scheme for an arbitrary number of rounds is given. We give a new upper bound for the keys size of an n-round scheme.     

Zirconium and hafnium (1-pyridinio)imido complexes: functionalized terminal hydrazinediido analogues

Reaction of the diamidozirconium complex [Zr(N2(TBS)Npy)(NMe2)2] (1) (N2(TBS)Npy = CH3C(C5H4N)(CH2NSiMe2tBu)2) or the diamidohafnium complex [Hf(N2(TBS)Npy)(NMe2)2] (2) with one molar equiv. of 1-aminopyridinium triflate in the presence of one equiv. of pyridine gave the corresponding (1-pyridinio)imido complexes [Zr(N2(TBS)Npy)(=N-NC5H5)(OTf)(py)] (3) and [Hf(N2(TBS)Npy)(=N-NC5H5)(OTf)(py)] (4). These were converted to the acetylide complexes [Zr(N2(TBS)Npy)(=N-NC5H5)(CCPh)(py)] (5) and [Hf(N2(TBS)Npy)(=N-NC5H5)(CCPh)(py)] (6) by reaction with lithium phenylacetylide and substitution of the triflato ligand. Upon reaction of 3 and 4 with one molar equivalent of R-NC (R = tBu, Cy, 2,6-xyl), N-N bond cleavage in the (1-pyridinio)imido unit took place and the respective carbodiimido complexes [M(N2(TBS)Npy](N=C=NR)(OTf)(py)] (7-12) were formed instantaneously. A similar type of reaction with CO gave the isocyanato complex [Zr(N2(TBS)Npy](NCO)(OTf)(py)] (13). Finally, the abstraction of the pyridine ligand in compounds 3 and 4 with B(C6F5)3 led to the formation of the triflato-bridged dinuclear complexes [Zr(N2(TBS)Npy)(=N-NC5H5)(OTf)]2 (14) and [Hf(N2(TBS)Npy)(=N-NC5H5)(OTf)]2 (15).     

Assembly of an R3N52− Chain by Cycloaddition of a Hydrazinediide and an Azide at Zirconium and its Thermal Fragmentation

Breaking the chain : Reaction of a zirconium hydrazinediide with organoazides gives 2‐pentazene‐1,4‐diyl complexes, such as [Zr(N₂^TBSN_py){N(Ad)N₃NPh₂}] (C gray, N blue, Si green, Zr turquoise), by formal [2+3] cycloaddition. Bonding within the N₅ chain is investigated using density functional calculations. These complexes thermally eject N₂ to give side‐on bonded diazenides.

     

Quality control and analytical test method for Taxus baccata tincture preparation

The homeopathic tincture of Taxus baccata L. is monographed in the current German Homeopathic Pharmacopoeia (HAB 2009). However, the described identification test is a common comparative TLC procedure that might be updated. The purpose of the current work was the quali-quantitative analysis by HPLC/DAD/MS of Taxus tincture. In this study we characterized polyphenolic compounds, in particular four hydroxycinnamic derivatives (0.85 mg/mL) and four flavonoids (quercetin and kaempferol 3-O-rutinoside and xylosyl glucosides); the total polyphenol content was 1.265 mg/mL of tincture. Starting from the official German Homeopathic Pharmacopoeia method of preparation, the aim of this work was to optimize a rapid and reproducible method for the analysis of herbal drugs and tincture, directly prepared in store or the herbalist's shop, to ensure safety and efficacy of the preparation. The procedure has to ensure validation, robustness of the results, and provide a quick response about the composition of compounds in the herbal drug preparation.