Real-time queueing theory: A tutorial presentation with an admission control application

Real-time scheduling, or scheduling with respect to a deadline, is critical in many application areas such as telecommunications, control systems, and manufacturing. This paper presents a novel approach to real-time scheduling based on a queueing theory model. Using real-time queueing theory (RTQT), one can analytically determine the distribution of the lead-time profile (i.e., the time until the deadline is reached) of customers waiting for service. Emphasis is placed on the development of the equations used to determine the lead-time profile distribution. The development of the GI/G/1 case is presented and confirmed using simulation. Simulation results confirm prior research for the M/M/1 and GI/M/1 case. As a practical application, RTQT is used to implement a packet admission control algorithm for a telecommunications network. Using this algorithm, packet lateness was reduced by up to 31%. This revised version was published online in June 2006 with corrections to the Cover Date.     

Practical routes to diacetylenic ketones and their application for the preparation of alkynyl substituted pyridines, pyrimidines and pyrazoles

Alkynyl substituted pyridines, pyrimidines and pyrazoles have been synthesised by cyclocondensations of diacetylenic ketones with enamines, amidines and hydrazines, respectively.     

Functionalisation of unactivated methyl groups through cyclopalladation reactions

The transformation of the organopalladium compound (3) into the corresponding deuteriated, chlorinated, or oxidized derivatives (7), (8), or (9), (11), and (12) respectively. is described. The palladation of compound (9) takes place regioselectively leading to the palladated system (13), which is transformed into the difunctionalised oximes (15) and (16). The palladation of $\text{E}$-2,2-dimethyl and 2,2,6,6-tetramethyl-cyclohexanone oxime leads to the corresponding organopalladium compounds (17) and (27), which through deuteriation or oxidation affords the expected products (21) and (31), or (22), (23), (24), and (32), respectively. The second palladation of the compound (22) takes place on the remaining methyl group yielding the organopalladium derivative (26). Finally, $\text{E}$-lupanone oxime is palladated selectively in the 23-position leading to the organopalladium compound (38); the transformation of this compound into its 23-deuterio and 23-acetoxy- derivatives (41) and (42), respectively is also described. The stereochemistry in the palladatlon of lupanone oxime is deduced from NOE studies at 500 MHz.     

Rearrangement of a mesylate tropane intermediate in nucleophilic substitution reactions. Synthesis of aza-bicyclo[3.2.1]octane and aza-bicyclo[3.2.2]nonane ethers,imides, and amines

Nucleophilic substitution of 2beta-mesyloxymethyl-N-methyl-3beta-p-tolyl-tropane intermediate with alkoxides, metal imides, or amines was found to lead not only to the expected bicyclo[3.2.1]octane (tropane) ether, imide, and amine derivatives but also to unexpected bicyclo[3.2.2]nonane derivatives. When alkoxides were used as nucleophile, only the rearranged bicyclo[3.2.2]nonane structure was obtained, whereas the use of amines or imides as nucleophile afforded a mixture of the two structures. The bicyclo[3.2.2]nonane structure was assigned by NMR analysis.     

Studies toward the total synthesis of the cytotoxic sponge alkaloid pyrinodemin A

[structure: see text]. The syntheses of the proposed structure of pyrinodemin A (1) and its cis double bond positional isomer (C15'-C16') in racemic form are described. The key reaction involved an intramolecular nitrone/double bond cycloaddition. Our results suggest that neither 1 nor its double positional isomer is the correct structure of pyrinodemin A     

Solution reduction synthesis of surface stabilized silicon nanoparticles

This paper describes the preparation of air and moisture stable octanol derivatized crystalline silicon nanoparticles by room temperature sodium naphthalenide reduction of silicon halides.     

Hexaamminecobalt(III) aquabis(nitrilotriacetato‐κ4N,O,O′,O′′)gadolinate(III) octahydrate

Crystals of the title compound, [Co(NH₃)₆][Gd(C₆H₆NO₆)₂(H₂O)]·8H₂O, were synthesized in and collected from aqueous solution. The hexaamminecobalt(III) cation has the expected octahedral geometry, while the Gd coordination sphere has the geometry of a tricapped trigonal prism, with the two nitrilo­tri­acetate N atoms and one water mol­ecule occupying the capping positions.     

Thermal isomerizations of cis,anti,cis-tricyclo[6.4.0.0]dodec-3-ene to trans- and cis,endo-tricyclo[6.2.2.0]dodec-9-ene: diradical conformations and stereochemical outcomes in [1,3] carbon shifts

The gas-phase thermal isomerizations at 315 °C of cis,anti,cis-tricyclo[6.4.0.0^2,7]dodec-3-ene to trans-tricyclo[6.2.2.0^2,7]dodec-9-ene and to cis,endo-tricyclo[6.2.2.0^2,7]dodec-9-ene favor the former, the more geometrically strained product, by a ratio of 2.4:1. These products correspond to suprafacial inversion (si) and suprafacial retention (sr) stereochemical outcomes. The reaction stereochemistry shown by the 11-carbon homolog, cis,anti,cis-tricyclo[6.3.0.0^2,7]undec-3-ene, is strikingly different: the [1,3] carbon shift takes place to give only the ‘forbidden’ sr product. Two related bicyclic vinylcyclobutanes, 8-deuterio- and 8-exo-methylbicyclo[4.2.0]oct-2-enes, evidence contrasting reaction stereochemical predilections in [1,3] shifts, but the 12-carbon tricyclic system and the 8-exo-methyl bicyclic analog isomerize with the same si:sr ratio! These observations prompt fresh considerations of structural influences on conformational preferences available to the alkyl, allyl diradical reactive intermediates involved.