Exact solutions of solid-liquid phase-change heat transfer when subjected to convective boundary conditions

A closed-form expression is presented to find the location of solid-liquid interface motion in convection-dominated solidification and melting problems. In this regard, the solutions are expressed in terms of the generalized representations of error functions,E (u, v) andF (u, v), which are useful to heat-conduction problems with convective-type boundary conditions. It is demonstrated that for constant surface temperature, the interface solution reduces to the classical Neumann solution.     

Thermal studies of some aryloxides of titanium(IV)

Thermal behaviour of aryloxides of titanium(IV) of composition TiCl_n(OAr)_4?n (wheren=0→3 and OAr=OC₆Bu^t-4, OC₆H₄OMe-4 and OC₆H₂-Bu ₂ ^t -2,6?Me-4) has been studied by DTA and TG analysis. Multiple decomposition steps have been indicated by thermal weight losses which are both exothermic and endothermic as shown by DTA curves. Based upon the total % loss in weight; during entire decomposition titanium dioxide has been found to be the final residue in each case.     

4-t-Butylphenoxo complexes of oxovanadium(V)

Summary Complexes of composition [VOCl₂(OC₆H₄Bu-t-4)] (1) and [VOCl(OC₆H₄Bu-t-4)₂] (2) have been synthesized by the reaction of VOCl₃ with equimolar and bimolar amounts, respectively, of 4-t-BuC₆H₄OSiMe₃ in CCl₄ and characterized by physio-chemical techniques. The complexes react with -hydroxyaldehydes and ketones such as 2-hydroxybenzaldehyde (salicylaldehyde, salH), and 2-hydroxy-2-phenylacetophenone (benzoin, benzH), 2-hydroxyacetophenone (hapH) and also with the potassium salt of p-chlorobenzohydroxamic acid (KBHACl) in 11 and 12 molar ratios, to yield five- and six-coordinate complexes.     

Acceptor properties of titanium(IV) phenoxides

Summary Compounds of composition TiCl_4–n(OPh)_n · 2L (L = monodentate ligand, n = 1–4) have been prepared by the reaction of the parent titanium phenoxides (1 mol) with the ligand (2 mols) and characterized by elemental analysis, molar conductance, molecular weight and i.r. spectral studies.     

Effect of niobium doping on physical, thermal, and spectral parameters of infrared transmitting BGO70 glasses

Heavy metal oxide glasses doped with 2d transition metal niobium were casted through normal melt-quench technique in the formula composition (100?x) [3Bi₂O₃–7GeO₂ (BGO70)]?xNb₂O₅ where 5 ≤ x ≤ 25. Experimentally measured values of density d _exp were 6.737–7.149 g/cc ± 0.06 %. Corresponding molar volume V _m exp had values 29.677–31.550 cc ± 0.04 %, V _pyc varied 32.28–34.71 cc ± 0.03 % and oxygen molar volume $ V_{{{\text{mO}}^{2-} }} $ increased linearly from 17.761 to 20.467 cc ± 0.06 %. Thermal coefficient of linear expansion was between 5.316 ± 0.001 × 10^?6 and 8.033 ± 0.001 × 10^?6 K^?1. Glass transition temperature T _g, onset of crystallization temperature T _x, and the stability factor ΔT were noted from DTA curves. Direct allowed energy gap E _g was between 1.809–2.988 eV and Urbach energy had value 0.32–1.49 eV. Maximum transmission efficiency was 74 % for glass BGO70-Nb10. FTIR spectra revealed that lattice vibration modes were active in 400–1,300 cm^?1 range. A modifying behavior was assigned to Nb⁵⁺ ion in the system.     

Beiträge zur Chemie der Halogensilan-Addukte. XVII. Darstellung,Kristall- und Molekülstruktur von (2, 2′ -Bipyridin)- trichloro (trichlorosiloxy)- silicium,Cl3SiOSiCl3. bipy

Contributions to the Chemistry of Halosilane Adducts. XVII. Preparation, Crystal and Molecular Structure of (2, 2′ -Bipyridine) - trichloro - (trichlorosiloxy) -silicon, Cl₃SiOSiCl₃. bipy 1 is obtained by the reaction of Cl₃SiOSiCl₃ and bipy. It crystallizes orthorhombic in the space group Pca2₁ (Z = 4). 1 contains a tetracoordinated and a hexacoordinated Si atom. The plain defined by coordinated bipy also contains the SiOSi group. The SiOSi bonding angle (152.8°) is larger than that of Cl₃SiOSiCl₃ (146°). The SiCl bonds are about 8% longer than the tetrahedral SiCl bonds. The two SiO bond lengths are different (1.684; 1.554 Å). The SiN distances (average 1.967 Å) as well as the other bond distances correspond to values found for related compounds. Configuration, SiOSi bond angle and other structural features are due to steric requirements. 1 represents the structure of least steric hindrance. The same structure is found in solution (¹H-NMR). The results confirm that sterically more demanding ligands preferentially occupy the positions vertical to the plain of bipy (phen) in octahedral bip(phen) complexes of Si, hereby minimizing steric repulsions among each other(trans positions) and by CH groups of bipy(phen) exerted on ligands in he plain of bipy(phen).     

Numerical analysis for bulk-arrival queueing systems: Root-finding and steady-state probabilities inGI r /M/1 queues

Queueing theorists have presented, as solutions to many queueing models, probability generating functions in which state probabilities are expressed as functions of the roots of characteristic equations, evaluation of the roots in particular cases being left to the reader. Many users have complained that such solutions are inadequate. Some queueing theorists, in particular Neuts [6], rather than use Rouché's theorem to count roots and an equation-solver to find them, have developed new algorithms to solve queueing problems numerically, without explicit calculation of roots. Powell [7] has shown that in many bulk service queues arising in transportation models, characteristic equations can be solved and state probabilities can be found without serious difficulty, even when the number of roots to be found is large. We have slightly modified Powell's method, and have extended his work to cover a number of bulk-service queues discussed by Chaudhry et al. [1] and a number of bulk-arrival queues discussed in the present paper.     

Facile,eco-friendly,one-pot protocol for the synthesis of indole-imidazole derivatives catalyzed by amino acids

An efficient, convenient green approach for the synthesis of indole-based 2,4,5-trisubstituted and 1,2,4,5-tetrasubstituted imidazoles by multicomponent reaction of substituted 2-arylindole-3-carbaldehydes, benzil, substituted anilines, and ammonium acetate using catalytic amino acid (glycine) in ethanol is described. Several amino acids have also been evaluated as organic catalysts for these reactions. The structures of the compounds have been established on the basis of infrared, mass, and ¹H NMR spectral data. The mild reaction conditions, inexpensive/economical reagents, and good yield show the usefulness of this approach.     

Global QSAR models of skin sensitisers for regulatory purposes

Background

The new European Regulation on chemical safety, REACH, (Registration, Evaluation, Authorisation and Restriction of CHemical substances), is in the process of being implemented. Many chemicals used in industry require additional testing to comply with the REACH regulations. At the same time EU member states are attempting to reduce the number of animals used in experiments under the 3 Rs policy, (refining, reducing, and replacing the use of animals in laboratory procedures). Computational techniques such as QSAR have the potential to offer an alternative for generating REACH data. The FP6 project CAESAR was aimed at developing QSAR models for 5 key toxicological endpoints of which skin sensitisation was one.

Results

This paper reports the development of two global QSAR models using two different computational approaches, which contribute to the hybrid model freely available online.

Conclusions

The QSAR models for assessing skin sensitisation have been developed and tested under stringent quality criteria to fulfil the principles laid down by the OECD. The final models, accessible from CAESAR website, offer a robust and reliable method of assessing skin sensitisation for regulatory use.