Simultaneous protection and activation of amino acids using propargyl pentafluorophenyl carbonate

[reaction: see text] A very efficient method for the simultaneous protection of the amino group and activation of the carboxyl group of amino acids is reported using propargyl pentafluorophenyl carbonate (PocOPfp). The amino group is protected as a propargyloxycarbonyl (Poc) derivative, and the carboxyl group is activated as a pentafluorophenyl ester. The yields obtained are good to excellent ranging from 60 to 87%.     

Spin dependence of the charged-gluon contribution in deep-inelastic scattering

In the integer-charge quark model, it is found that because of the photon-gluon mixing, only the zero-helicity gluons couple to deep-inelastic probes. As a particular consequences, gluons do not contribute to the (longitudinal) polarization asymmetry σ (↑↓) ? σ (↑↑) in polarized electroproduction in the scaling limit.     

Electron-positron annihilation into three jets in the integer-charge quark model

We discuss e⁺e^? → 3 jets in the integer-charge qaurk model. In the lowest non-trivial order, ignoring coloured Higgs scalars, we find that three-gluon jets would be observable at present PETRA energies if the gluon mass m_g ? 2 GeV. As an experimental test, the angular distribution is presented.     

On Simulated Annealing and Nested Annealing

Simulated Annealing is a family of randomized algorithms used to solve many combinatorial optimization problems. In practice they have been applied to solve some presumably hard (e.g., NP-complete) problems. The level of performance obtained has been promising [2,5,6,14]. The success of this heuristic technique has motivated analysis of this algorithm from a theoretical point of view. In particular, people have looked at the convergence of this algorithm. They have shown (see e.g., [10]) that this algorithm converges in the limit to a globally optimal solution with probability 1. However few of these convergence results specify a time limit within which the algorithm is guaranteed to converge (with some high probability, say). We present, for the first time, a simple analysis of SA that will provide a time bound for convergence with overwhelming probability. The analysis will hold no matter what annealing schedule is used. Convergence of Simulated Annealing in the limit will follow as a corollary to our time convergence proof. In this paper we also look at optimization problems for which the cost function has some special properties. We prove that for these problems the convergence is much faster. In particular, we give a simpler and more general proof of convergence for Nested Annealing, a heuristic algorithm developed in [12]. Nested Annealing is based on defining a graph corresponding to the given optimization problem. If this graph is small separable, they [12] show that Nested Annealing will converge faster. For an arbitrary optimization problem, we may not have any knowledge about the separability of its graph. In this paper we give tight bounds for the separability of a random graph. We then use these bounds to analyze the expected behavior of Nested Annealing on an arbitrary optimization problem. The separability bounds we derive in this paper are of independent interest and have the potential of finding other applications.     

Effect of gluons on neutral-current interactions in deep inelastic neutrino scattering

The contribution of neutral spin-1 gluons to the deep inelastic neutral-current processesv(v)+N→v(v)+ hadrons is worked out in the parton model. Such a contribution violates Bjorken scaling strongly.     

Interpretation of the recent Kolar events

We give plausible interpretations of the unusual events seen in the proton decay detector at Kolar Gold Fields indicating the existence of a massive (≳2GeV) long lived (10⁻⁸−10⁻⁹s) particle. We show that it is possible to accommodate the particle in the standard model as a fourth generation neutrino, or inE ₆ grand unified theory as a neutral fermion occurring in27 representation or in supersymmetric theory as a scalar neutrino. However, there is a difficulty in explaining the large production rate for the particle.     

Non-renormalization of the weak vertex in gauge theories with integrally charged quarks

We give current algebra arguments to show that toO(α) the colour octet vertices do not renormalize the effective weak vertex between colour singlet hadrons in models with broken colour symmetry. The result does not depend on the details of the mixing between colour gluons and electro-weak bosons.     

Substituent effects on carbon-13 NMR chemical shifts of side chain carbonyl carbons of 4-substituted 1-naphthamides

Substituent induced¹³C NMR chemical shifts of side chain carbonyl carbons of several 4-substituted 1-naphthamides have been measured in DMSO-d ₆ solvent. Analysis of the substituent induced chemical shifts by the DSP equation gave the regression equation. Both {ie207-1} and {ie207-2} values were negative. The negative sign on {ie207-3} term indicates the operation of a reverse substituent effect and that π-polarisation is the important mechanism for the transmission of substituent effects by inductive effect. Theperi-hydrogen interaction in naphthamides forces the amide group out of the plane of the naphthalene ring.