The onset of coulomb explosions in polyatomic molecules

With the development of high intensity femtosecond lasers, the ionisation and dissociation dynamics of molecules has become an area of considerable interest. Using the technique of femtosecond laser mass spectrometry (FLMS), the molecules carbon disulphide, pyrimidine, toluene, cyclohexanone and benzaldehyde are studied with pulse widths of 50 fs in the near infrared (IR) wavelength region (790 nm). Results are presented and contrasted for laser beam intensities around 10(15) and 10(16) W cm(-2). For the lower intensities, the mass spectra yield dominant singly charged parent ions. Additionally, the appearance of doubly charged parent ions is evident for carbon disulphide, toluene and benzaldehyde with envelopes of doubly charged satellite species existing in these local regions. Carbon disulphide also reveals a small triply charged component. Such atomic-like features are thought to be a strong fingerprint of FLMS at these intensities. However, upon increasing the laser intensity to approximately 10(16) W cm(-2), parent ion dominance decreases and the appearance of multiply charged atomic species occurs, particularly carbon. This phenomenon has been attributed to Coulomb explosions in which the fast absorption of many photons may produce transient highly ionised parent species which can subsequently blow apart. Copyright 1999 John Wiley & Sons, Ltd.     

A reformulation for the stochastic lot sizing problem with service-level constraints

We study the stochastic lot-sizing problem with service level constraints and propose an efficient mixed integer reformulation thereof. We use the formulation of the problem present in the literature as a benchmark, and prove that the reformulation has a stronger linear relaxation. Also, we numerically illustrate that it yields a superior computational performance. The results of our numerical study reveals that the reformulation can optimally solve problem instances with planning horizons over 200 periods in less than a minute.     

Imination of sulfoxides using 3-acetoxyaminoquinazolinone as nitrogen source in the presence of hexamethyldisilazane

The reaction of 3-acetoxyaminoquinazolinone (QNHOAc) with various sulfoxides in the presence of HMDS as an acetic acid scavenger, afforded the corresponding sulfoximides in good yields. Sulfoximidation of phenyl methyl sulfoxide using a Q*NHOAc having a stereogenic centre on its 2-position gave the products in 1.3:1 ratio of diastereomers.     

Synthesis and spectral characterization of macrocyclic Ni<Superscript>II</Superscript> complexes derived from various diamines,Ni<Superscript>II</Superscript> perchlorate and 1,4-bis(2-carboxyaldehydephenoxy)butane

Six new macrocyclic complexes were synthesized by reaction of 1,4-bis(2-carboxyaldehyde phenoxy)butane with various diamines. Then, their nickel(II) perchlorate complexes were synthesized by the template effect by reaction of 1,4-bis(2-carboxyaldehyde phenoxy)butane, Ni(ClO₄)₂ · 6H₂O and various diamines. The metal-to-ligand ratio of Ni^II metal complexes was found to be 1:1. The compounds are coordinated to the central metal as tetradentate O₂N₂ ligands The Ni^II complexes are proposed to exhibit tetrahedral geometry. Ni^II metal complexes are 1:2 electrolytes as shown by their molar conductivities (Λ_M) in DMF (dimethyl formamide) at 10⁻³ m. The structure of Ni^II metal complexes is proposed from elemental analysis, f.t.-i.r., u.v.-vis., magnetic susceptibility measurements, molar conductivity measurements and mass spectra.     

Determining optimal treatment rate after a disaster

From the standpoint of medical services, a disaster is a calamitous event resulting in an unexpected number of casualties that exceeds the therapeutic capacities of medical services. In these situations, effective medical response plays a crucial role in saving life. To model medical rescue activities, a two-priority non-preemptive S-server, and a finite capacity queueing system is considered. After constructing Chapman–Kolmogorov differential equations, Pontryagin's minimum principle is used to calculate optimal treatment rates for each priority class. The performance criterion is to minimize both the expected value of the square of the difference between the number of servers and the number of patients in the system, and also the cost of serving these patients over a determined time period. The performance criterion also includes a final time cost related to deviations from the determined value of the desired queue length. The two point boundary value problem is numerically solved for different arrival rate patterns and selected parameters.     

A value-adding approach to reliability under preventive maintenance costs and its applications

No equipment (system) can be perfectly reliable in spite of the utmost care and best efforts on the part of the designer, decision-maker and manufacturer. The two sides of maintenance are corrective and preventive maintenance. It is generally assumed that a preventive maintenance action is less costly than a repair maintenance action. We examine this proposition in detail on the basis of a failure-time model that relates conformance quality to reliability. Illustratively, we present reliability in the context of contracts with asymmetric information. The model shows how to overcome information rents through price distortions and quantity rationing. The paper ends with a conclusion and an outlook to future studies.     

An adaptive dynamic relaxation method for quasi-static simulations using the peridynamic theory

The peridynamic theory is advantageous for problems involving damage since the peridynamic equation of motion is valid everywhere, regardless of existing discontinuities, and an external criterion is not necessary for predicting damage initiation and propagation. However, the current solution methods for the equations of peridynamics utilize explicit time integration, which poses difficulties in simulations of most experiments under quasi-static conditions. Thus, there is a need to obtain steady-state solutions in order to validate peridynamic predictions against experimental measurements. This study presents an extension of dynamic relaxation methods for obtaining steady-state solutions of nonlinear peridynamic equations.