Intermittency in the Slow Particle Emission During Hadron–Nucleus Interactions

The study of the angular distribution of slow particles during high energy hadron-nucleus interaction indicates that emission of slow particles takes place from a thermally non-equilibrated system. This evidence has come out from the presence of intermittency - a phenomenon that reveals a fractal structure and represents a self-similarity in the particle production process. Hence, this study highlights inadequacy of cascade-evaporation model and advocates the need of its refinement.     

Energy crisis or a new soliton in the noncommutative CP(1) model?

The non-commutative (NC) CP(1) model is studied from field theory perspective. Our formalism and definition of the NC CP(1) model differs crucially from the existing one [Phys. Lett. B 498 (2001) 277, hep-th/0203125, hep-th/0303090].

Due to the U(1) gauge invariance, the Seiberg–Witten map is used to convert the NC action to an action in terms of ordinary spacetime degrees of freedom and the subsequent theory is studied. The NC effects appear as (NC parameter) θ-dependent interaction terms. The expressions for static energy, obtained from both the symmetric and canonical forms of the energy momentum tensor, are identical, when only spatial noncommutativity is present. Bogomolny analysis reveals a lower bound in the energy in an unambiguous way, suggesting the presence of a new soliton. However, the BPS equations saturating the bound are not compatible to the full variational equation of motion. This indicates that the definitions of the energy momentum tensor for this particular NC theory (the NC theory is otherwise consistent and well defined), are inadequate, thus leading to the “energy crisis”.

A collective coordinate analysis corroborates the above observations. It also shows that the above mentioned mismatch between the BPS equations and the variational equation of motion is small.     

The first examples of anthracene capped chiral carbohydrate derived dendrimers: synthesis, fluorescence and chiroptical properties

The first examples of anthracene capped chiral dendrimers derived from a 1,3,5-trisubstituted aromatic core and carbohydrate units in the interior and periphery are described. Excimer formation was evident from the fluorescence spectrum, and both fluorescence and chiroptical properties indicated that the dendrimer does not undergo aggregation in the ground state.     

Synthesis of heliannuol D, an allelochemical from Helianthus annus

A synthesis of heliannuol D 1 is described involving regioselective oxidation of the benzoxabicyclo[3.2.1]octanone 20 followed by hydrogenolysis to generate the benzoxepane ring system of 1.     

Transient streaming potential in a finite length microchannel

Pressure-driven flow of an electrolyte solution in a microchannel with charged solid surfaces induces a streaming potential across the microchannel. Such a flow also causes rejection of ions by the microchannel, leading to different concentrations in the feed and permeate reservoirs connecting the capillary, which forms the basis of membrane based separation of electrolytes. Modeling approaches traditionally employed to assess the streaming potential development and ion rejection by capillaries often present a confusing picture of the governing electrochemical transport processes. In this paper, a transient numerical simulation of electrochemical transport process leading to the development of a streaming potential across a finite length circular cylindrical microchannel connecting two infinite reservoirs is presented. The solution based on finite element analysis shows the transient development of ionic concentrations, electric fields, and the streaming potential over the length of the microchannel. The transient analysis presented here resolves several contradictions between the two types of modeling approaches employed in assessing streaming potential development and ion rejection. The simulation results show that the streaming potential across the channel is predominantly set up at the timescale of the developing convective transport, while the equilibrium ion concentrations are developed over a considerably longer duration.     

Intramolecular 1,3-dipolar nitrone and nitrile oxide cycloaddition of 2- and 4-O-allyl and propargyl glucose derivatives: a versatile approach to chiral cyclic ether fused isoxazolidines, isoxazolines and isoxazoles

2-O- and 4-O-Allyl and -propargyl glucose and the corresponding oxime derivatives were prepared from readily available glucose dithioacetals. Intramolecular 1,3-dipolar cycloaddition of the N-benzyl and N-methyl nitrones of the above acyclic 2-O-allyl glucose derivatives led to the diastereoselective formation of chiral isoxazolidines incorporating the tetrahydrofuran ring. The EI mass spectra revealed a characteristic cleavage of the C-alkyl group adjacent to the furan oxygen atom. An enantiopure trisubstituted tetrahydrofuran was obtained by the reductive cleavage of the isoxazolidine ring of one of the cycloadducts. In contrast, the nitrile oxide cycloaddition of the 2-O-allyl derivatives afforded diastereomeric mixtures of the corresponding dihydroisoxazolines, the stereochemistry of which was tentatively assigned on the basis of the principle of optical superposition. The exclusive formation of a tetrahydrofuran ring from pentaallyl nitrone or nitrile oxide demonstrated the preferred formation of a five-membered ring to that of six or seven-membered rings. The nitrile oxide generated from a 3,4,5,6,7-pentaallyloxy-1-nitroheptane derivative obtained from pentaallylglucose underwent diastereoselective cycloaddition to give an isoxazoline fused to a pyran ring. Enantiopure isoxazoles containing tetrahydrofuran and oxepane rings were also prepared in good yields by the nitrile oxide cycloaddition of the 2-O- and 4-O-propargyl derivatives.     

Efficiency of connected binary block designs when a single observation is unavailable

In this paper the problem of finding the design efficiency is considered when a single observation is unavailable in a connected binary block design. The explicit expression of efficiency is found for the resulting design when the original design is a balanced incomplete block design or a group divisible, singular or semiregular or regular with ₁>0, design. The efficiency does not depend on the position of the unavailable observation. For a regular group divisible design with ₁>0, the efficiency depends on the position of the unavailable observation. The bounds, both lower and upper, on the efficiency are given in this situation. The efficiencies of designs resulting from a balanced incomplete block design and a group divisible design are in fact high when a single observation is unavailable.The work of the first author is sponsored by the Air Force Office of Scientific Research under Grant AFOSR-90-0092.On leave from Indian Statistical Institute, Calcutta, India. The work of the third author was supported by a grant from the CMDS, Indian Institute of Management, Calcutta.     

Novel Synthesis of Agaritine,a 4-Hydrazinobenzyl-Alcohol Derivative Occurring in Agaricaceae

The 4-hydrazinobenzyl alcohol ( 3 was prepared (58%)) by diiobutylaluminiumhydride reduction of methyl 4-hydrazinobenzoate ( 4 ), whereas LiA1H₄ or LiBh₄ reduction of 4 proceeded further to yield (via intermediate 3 ) (4-tolyl)hydrazine ( 5 ). The alcohol 3 was stable under O₂-free conditions and exhibited no tendency to eliminate H₂O, neither thermally nor with H⁺ catalysis. Oxidation of 3 with SeO₂ yielded 4-(hydroxymethyl)benzine-diazonium ion ( 8 ), identified by its azo coupling product 9 with 2-naphthol. Condensation of 3 with 1-benzyl 5-Hydrogen N-(benzyloxycarbonyl)-L-glutamate ( 10 ) in presence of dicyclohexylcarbodiimide afforded 81% of N²-(benzyloxycarbonyl)-L- glutamic acid 1-(benzyl-ester) 5-{2-[4-(hydroxymethyl)phenyl]hydrazide} ( 11 ) which upon controlled hydrogenolysis (quinoline-sulfur-poisoned Pd/C catalyst) gave 82% of L-Glutamic acid 5-{2-[4-(hydroxymethyl)phenyl] hydrazide} ( 1 ), i. e. agaritine, a metabolite of Agaricus bisporus. Without poisoning of the catalyst, hydrogenolysis of ( 11 ) yielded L-glutamic acid 5-[2-(4-tolyl)hydrazide] ( 12 ).     

Recursive dynamics simulator (ReDySim): A multibody dynamics solver

Recursive formulations have significantly helped in achieving real-time computations and model-based control laws. The recursive dynamics simulator (ReDySim) is a MATLAB-based recursive solver for dynamic analysis of multibody systems. ReDySim delves upon the decoupled natural orthogonal complement approach originally developed for serial-chain manipulators. In comparison to the commercially available software, dynamic analyses in ReDySim can be performed without creating solid model. The input parameters are specified in MATLAB environment. ReDySim has the capability to incorporate any control algorithm with utmost ease. In this work, the capabilities of ReDySim for solving open-loop and closed-loop systems are shown by examples of robotic gripper, KUKA KR5 industrial manipulator and four-bar mechanism. ReDySim can be downloaded for free from http://www.redysim.co.nr and can be used almost instantly.