A system for priority routing and capacity assignment in packet switched networks

A model and its associated solution procedure for the problem of concurrent flow and capacity assignment in a packet switched network are presented. The distinguishing feature of the model lies in the fact that a user defined priority level is associated with each message in the network. Different service requirements and message characteristics are associated with each message class. An algorithm that generates good feasible solutions to the model, together with tight lower bounds on the value of the objective function, is developed. Results of numerical experiments using several network topologies are reported.     

Kinetics of the gas phase reaction of hydroxyl radicals with ethane,benzene, and a series of halogenated benzenes over the temperature range 234–438 K

Absolute rate constants for the gas phase reactions of OH radicals with ethane (k₁), benzene (k₂), fluorobenzene (k₃), chlorobenzene (k₄), bromobenzene (k₅), iodobenzene (k₆), and hexafluorobenzene (k₇) have been measured over the temperature range 234–438 K using the flash photolysis resonance fluorescence technique. The rate constants measured at room temperature (296 K), at total pressures of argon diluent between 25 and 50 Torr, were (in units of 10^?13 cm³ molecule^?1 s^?1): k₁ = (2.30 ± 0.26), k₂ = (12.9 ± 1.4), k₃ = (6.31 ± 0.81), k₄ = (7.41 ± 0.94), k₅ = (9.15 ± 0.97), k₆ = (13.2 ± 1.6), and k₇ = (1.61 ± 0.24), respectively. The indicated errors are our estimate of 95% confidence limits and include two standard deviations from the least-squares analysis together with an allowance for any possible systematic errors in the measurements. At elevated temperatures and under pseudo-first-order reaction conditions, non-exponential hydroxyl radical decays were observed for benzene and the monosubstituted halo-aromatics. For ethane and hexafluorobenzene, exponential decays were observed over the complete temperature range and the data were fit by the Arrhenius expressions: k₁ = (8.4 ± 3.1) × 10^?12 exp[(?1050 ± 100)/T] and k₇ = (1.3 ± 0.3) × 10^?12 exp[(?610 ± 80)/T], respectively. The results are compared with previous literature data and the mechanistic implications are discussed.     

On the linear two-point boundary-value problem

In this note, a noniterative scheme for solving two-point boundary-value problems for single and multi-input, linear constant systems is developed. The scheme requires the solution of 2n differential equations.     

Limit behavior of solutions of ordinary linear differential equations

A classification of classes of equivalent linear differential equations with respect to -limit sets of their canonical representations is introduced. Some consequences of this classification with respect to the oscillatory behavior of solution spaces are presented.     

Host-guest interactions at self-assembled monolayers of cyclodextrins on gold

We have developed synthesis routes for the introduction of short and long dialkylsulfides onto the primary side of alpha-, beta-, and gamma-cyclodextrins. Monolayers of these cyclodextrin adsorbates were characterized by electrochemistry, wettability studies, X-ray photoelectron spectroscopy (XPS), time-of-flight secondary ion mass spectrometry (TOF-SIMS), and atomic force microscopy (AFM). The differences in thickness and polarity of the outerface of the monolayers were measured by electro-chemistry and wettability studies. On average about 70% of the sulfide moieties were used for binding to the gold, as measured by XPS. Tof-SIMS measurements showed that the cyclodextrin adsorbates adsorb without any bond breakage. AFM measurements revealed for beta-cyclodextrin monolayers a quasi-hexagonal lattice with a lattice constant of 20.6 A, which matches the geometrical size of the adsorbate. The alpha-cyclodextrin and gamma-cyclodextrin monolayers are less ordered. Interactions of the anionic guests 1-anilinonaphthalene-8-sulfonic acid (1,8-ANS) and 2-(p-toluidinyl)naphthalene-6-sulfonic acid (2,6-TNS) and the highly ordered monolayers of heptapodant beta-cyclodextrin adsorbates were studied by surface plasmon resonance (SPR) and electrochemical impedance spectroscopy. The SPR measurements clearly showed interactions between a beta-cyclodextrin monolayer and 1,8-ANS. Electrochemical impedance spectroscopy measurements gave high responses even at low guest concentrations (< or = 5 microM). The association constant for the binding of 1,8-ANS (K = 289,000 +/- 13,000M-1) is considerably higher than the corresponding value in solution. (Partial) methylation of the secondary side of the beta-cyclodextrin strongly decreases the binding.     

Analytical performance characteristics of thin and thick film amperometric microcells

The analytical performance of amperometric microcells with different electrode geometries is compared for enzyme activity measurements. The microcells were fabricated with thin film photolithography or thick film screen-printing in four different designs. The cells made with the thin film process used flexible substrate with microelectrode array or a circular, disk-shaped working electrode. The screen-printed working electrodes had semicircle or disk shape on ceramic chips. Putrescine oxidase (PUO) activity measurement was used as a model. The determination of PUO activity is important in the clinical diagnosis of premature rupture of the amniotic membrane. An electropolymerized m-phenylenediamine size-exclusion layer was used to eliminate common interferences. The size exclusion layer revealed also to be advantageous in protecting the electrodes from fouling by putrescine (enzyme substrate). The electrode fouling of bare electrodes was insignificant for screen-printed electrodes, but very severe for electroplated platinum working electrodes. The microelectrode array electrodes demonstrated smaller RSD and higher normalized sensitivities for hydrogen peroxide and PUO activity. All the other electrodes were demonstrating comparable analytical performances.     

Rapid determination of molybdenum in botanical material by electrothermal atomic absorption spectrometry

Low levels of molybdenum in plant samples are determined by simple digestion in nitric acid followed by electrothermal spectrometry. Sensitivity is enhanced by nitric acid whereas chloride, sulfuric acid, and perchloric acid have inhibiting effects. Recovery of molybdate added to plant samples averaged 94.3%, with a relative standard deviation of 10% for 0.50 μg Mo g^-1 of plant material. Large numbers of samples can be screened for molybdenum content without tedious organic extractions or long dry ashing processes.     

Convex interpolating splines of arbitrary degree II

For given data {(x _i ,y _i )} _i=0 ⁿ , (x ₀<x ₁<...<x _n ) we consider the possibility of finding a spline functions of arbitrary degreek+1 (k 1) with preassigned smoothnessl, where 1 l [(k+1)/2]. The splines should be such thats(x _i )=y _i ,i=0, 1,...,n ands is increasing and convex on [x ₀,x _n ]. Sufficient conditions which guarantee the existence ofs and an explicit formula for this function are derived.     

Structural and functional characteristics of rhenium clusters derived from redox chemistry of the triangular [ReIII3(mu-Cl)3] core unit

The present study investigates structural and functional aspects of the redox chemistry of rhenium(III) chloride [Re3Cl9] (1) in aqueous and organic solvents, with emphasis on the dioxygen-activating capabilities of reduced rhenium clusters bearing the Re3(8+) core. Dissolution of 1 in HCl (6 M) generates [Re3(mu-Cl)3Cl9]3- (2a), which can be isolated as the tetraphenylphosphonium salt (2b). Anaerobic one-electron reduction of 1 by Hg in HCl (6-12 M) produces [(C6H5)4P]2[Re3(mu-Cl)3Cl7(H2O)2].H2O (3), the structure of which features a planar [Re3(mu-Cl)3Cl3] framework (Re3(8+) core), involving two water ligands that occupy out-of-plane positions in a trans arrangement. Compound 3 dissociates in the presence of CO, yielding [(C6H5)4P]2[ReIII2Cl8] (4) and an unidentified red carbonyl species. In situ oxidation (O2) of the reduced Re3(8+)-containing cluster in HCl (6 M) produces quantitatively 2a, whereas oxidation of 3 in organic media results in the formation of [(C6H5)4P]4[(Re3(mu-Cl)3Cl7(mu-OH))2].2CH2Cl2 (5). The structure of 5 reveals that two oxygen ligands (hydroxo units) bridge asymmetrically two Re3(9+) triangular clusters. The origin of these hydroxo units derives from the aquo ligands, rather than O2, as shown by 18O2 labeling studies. The hydroxo bridges of 5 can be replaced by chlorides upon treatment with Me3SiCl to afford the analogous [(C6H5)4P]4[(Re3(mu-Cl)3Cl7(mu-Cl))2].10CH2Cl2 (6). The reaction of 5 with Hg in HCl (6 M)/tetrahydrofuran regenerates compound 3. Complexes 1-3 exhibit nitrile hydratase type activity, inducing hydrolysis of CH3CN to acetamide. The reaction of 3 with CH3CN yields [(C6H5)4P]2[Re3(mu-Cl)3Cl6.5(CH3CN)1.5(CH3C(O)NH)0.5] (7), the structure of which is composed of [Re3(mu-Cl)3Cl7(CH3CN)2]2- (7a) and [Re3(mu-Cl)3Cl6(CH3CN)(CH3C(O)NH)]2- (7b) (Re3(8+) cores) as a disordered mixture (1:1). Oxidation of 7 with O2 in CH3CN affords [(C6H5)4P]2[Re3(mu-Cl)3Cl7(CH3C(O)NH)].CH3CN (8) and small amounts of [(C6H5)4P][ReO4] (9). Compound 8 is also independently isolated from the reaction of 2b with wet CH3CN, or by dissolving 5 in CH3CN. In MeOH, 5 dissociates to afford [(C6H5)4P]2[Re3(mu-Cl)3Cl8(MeOH)].MeOH (10).