Metropolitan Optical Networks: When to Change to DWDM

In this article we propose a new methodology to estimate the change in the bandwidth demand in time, mainly in residential areas. The bandwidth demand forecast is a basic aspect to decide the evolution of metropolitan optical networks. The word evolution refers to the necessity of making changes in networks, either by upgrading or replacing different elements that are part of the network. This analysis, along with a technological alternatives analysis, provides the operator the needed information to achieve the appropriate network planning and to make investment decisions.     

Equivalence of Lyapunov stability criteria in a class of Markov decision processes

We are concerned with Markov decision processes with countable state space and discrete-time parameter. The main structural restriction on the model is the following: under the action of any stationary policy the state space is acommunicating class. In this context, we prove the equivalence of ten stability/ergodicity conditions on the transition law of the model, which imply the existence of average optimal stationary policies for an arbitrary continuous and bounded reward function; these conditions include the Lyapunov function condition (LFC) introduced by A. Hordijk. As a consequence of our results, the LFC is proved to be equivalent to the following: under the action of any stationary policy the corresponding Markov chain has a unique invariant distribution which depends continuously on the stationary policy being used. A weak form of the latter condition was used by one of the authors to establish the existence of optimal stationary policies using an approach based on renewal theory.This research was supported in part by the Third World Academy of Sciences (TWAS) under Grant TWAS RG MP 898-152.     

Self-consistent Overhauser model for the pair distribution function of an electron gas at finite temperature

We present calculations of the spin-averaged pair distribution function g(r) in a homogeneous gas of electrons moving in dimensionality D=3 or D=2 at finite temperature. The model involves the solution of a two-electron scattering problem via an effective potential, which embodies many-body effects through a self-consistent Hartree approximation, leading to two-body wave functions to be averaged over a temperature-dependent distribution of relative momentum for electron pairs. We report illustrative numerical results for g(r) in an intermediate-coupling regime and interpret them in terms of changes of short-range order with increasing temperature.     

Contractive Approximations in Risk-Sensitive Average Semi-Markov Decision Chains on a Finite State Space

Journal of Optimization Theory and Applications - This work concerns with semi-Markov decision chains evolving on a finite state space. The controller has a positive and constant risk sensitivity...     

The Photobiological Differences of Gilvocarcins V and M Are not Related to their Transient Intermediates and Triplet Yields

Abstract— The transient absorption spectra of the intermediates produced by the 355 nm laser excitation of gilvocarcin derivatives have been investigated in various solvents. The spectra consist of a triplet-triplet absorption in the visible region and a residual absorption observed between 340 and 700 nm due to a long-lived species, assigned to the radical cation. A broad-fast decaying band with a maximum at around 700 nm attributed to the solvated electron is also seen in solutions containing a low DMSO/water volume ratio and at 266 nm irradiation of a 50% methanol/water solvent mixture. The molar absorption coefficient of the triplet state of gilvocarcin V (GV) and gilvocarcin M (GM), determined by the energy transfer method, is independent of the solvent properties and has a value of 3.0 × 10⁴/ M cm. The triplet decay rate constants for both drugs are between 1 and 5 × 10⁴/s. A similar initial yield and triplet decay rate constant of GV were observed in the presence of 3.4 m M thymine. Thus, a quenching rate constant of the GV's triplet state by thymine is estimated to be lower than 10⁶/Ms. The triplet quantum yields of both antibiotics determined by using the comparative method are higher in dimethylsulfoxide (DMSO) (0.18) than are those corresponding to 25% DMSO/water (0.06). The decrease in φ_T in the presence of water could be attributed to an enhanced internal conversion rate constant from the S₁ state or to an increase in the photoionization yield. The similarity of the transient intermediates and their yields for GV and GM suggest that their photobiological differences are due to other factors such as DNA binding constants, preferential localization of the drugs in the cell or the enhanced reactivity of the vinyl group toward cellular components.     

The CuII−CuI−Cu0(Hg) system in the presence of benzotriazole: Part I. A polarographic investigation

A polarographic investigation of Cu^II electroreduction from solutions of benzotriazole (BTA) of pH from 1 to 3 at a dropping mercury electrode shows the presence of two successive adsorption waves of equal height (waves Ic and IIIc) due, respectively, to the formation and to the subsequent dissolution of an adsorbed film of a Cu^I compound. The dependence of the half-wave potential of wave IIIc, which is polarographically reversible, upon pH and BTA concentration indicates that the adsorbed film has the composition [Cu^I(BTA^?)], where BTA^? denotes the deprotonated anionic form of benzotriazole. Moreover, the maximum height of wave IIIc indicates that this film is one monolayer thick. A third cathodic wave (wave IIc), lying between waves Ic and IIIc, stems from the reduction to the metal state of the Cu^II ions diffusing from the bulk solution. Copper(0) oxidation at dropping amalgam electrodes in BTA solutions yields two successive adsorption waves (waves Ia and IIa). Wave Ia is due to the same electrode process, Cu⁰ (Hg)+BTA?Cu^I(BTA^?)+H⁺+e, responsible for the cathodic wave IIIc. On the other hand, wave IIa is due to the formation of roughly two adsorbed monolayers of [Cu^I(BTA^?)] upon that formed along wave Ia.     

Symmetrisation of β-alkoxyalkylmercury(II) acetates

β-Alkoxyalkylmercury(II) acetates have been symmetrised in situ with alkaline sodium stannite to afford good yields of bis(β-alkoxyalkyl)mercurials, [R¹R²C(OR)CHR³]₂ Hg.     

Regiospecific synthesis of symmetrical (1E,3E) 2,3-difluoro-1,4-diphenyl-buta-1,3-dienes via palladium-catalyzed cross-coupling of (Z) 2-bromo-2-fluoroethenylbenzenes in presence of bis(pinacolato)diboron

The cross-coupling reaction of (Z) 1-bromo-1-fluoroalkenes catalyzed by PdCl₂(PPh₃)₂-2PPh₃ (3%) and CsF in Tetrahydrofuran (THF) in presence of bis(pinacolato)diboron led to (1E,3E) 2,3-difluoro-1,4-disubstituted-buta-1,3-dienes in high yields.     

Infrared study of the stability and folding kinetics of a 15-residue beta-hairpin

The thermal stability and folding kinetics of a 15-residue beta-hairpin (SESYINPDGTWTVTE) have been studied by using infrared (IR) spectroscopy coupled with laser-induced temperature-jump (T-jump) technique for rapid folding-unfolding initiation. An alternative method based on analyzing IR difference spectra was also introduced to obtain thermodynamic properties of beta-sheets, which complements the commonly used circular dichroism (CD) and fluorescence techniques. Equilibrium IR measurements indicate that the thermal unfolding of this beta-hairpin is fairly broad. However, it can be described by a two-state transition with a thermal melting temperature of approximately 29 degrees C. Time-resolved IR measurements following a T-jump, probed at 1634 cm(-1), indicate that the folding of this beta-hairpin follows first-order kinetics and is amazingly fast. At 300 K, the folding time is approximately 0.8 micros, which is only 2-3 times slower than that of alpha-helix formation. Additionally, the energetic barrier for folding is small (approximately 2 kcal mol(-1)). These results, in conjunction with results from other studies, support a view that the details of native contacts play a dominant role in the kinetics of beta-hairpin folding.     

Access to the spiro hydrindandione ring system of Fredericamycin A through spiroalkylation and oxidation.

Indene could be spiro alkylated with bis-1,2-bromomethyl benzene derivatives. Further functionalization of the benzylic positions led to the dihydroxy dibenzospiro 4,4 nonane dione ring system of Fredericamycin A.