The catalytic performances of silica supported aluminum,gallium and indium for the <Emphasis Type="Italic">tert</Emphasis>-butylation of aromatics

RHA-Al, RHA-Ga and RHA-In catalysts were synthesized by the direct incorporation of aluminum, gallium and indium ions, respectively, into rice husk ash (RHA) silica at room temperature using the sol–gel method. The prepared catalysts were characterized by physicochemical methods, viz. N₂-adsorption, XRD, FT-IR, SEM-EDX, ICP-MS and Solid-state NMR. These catalysts were used to study the tert-butylation of benzene (Bz) and some substituted benzenes with tert-butyl chloride (TBC). The reaction was proposed to proceed initially through the radical mechanism and subsequently the tert-butyl cation was formed, which in turn attacks the benzene ring for the formation of tert-butyl benzene (TBB) and di-tert-butyl benzene (DTBB) via the S_N1 mechanism (main reaction). However, a proton elimination reaction (side reaction) also occurred, resulting in the formation of isobutene dimers (IBD) and isobutene trimers (IBT). The extent of these side products were found to decrease significantly with time, indicating the reversibility of the oligomerization reactions. The catalysts were stable against leaching and were reusable several times but with observable drop in catalytic activity. RHA-Ga lost almost 20% of its activity after each run, whereas, RHA-In was stable until the 3rd run and then lost ~13% of its activity at the 5th run. The deactivation was suggested to be induced by the poisoning effect of the bulky side products.     

New approaches to due date assignment in job shops

In this study, two new approaches for due date assignment in job shops are evaluated. Proposed approaches use statistical prediction techniques for dynamic prediction of job flowtimes in a job shop environment as the job arrives to the shop floor. Primary objective of this research is to compare the performance of the proposed due date assignment model (PDDAM) with several conventional due date assignment models (CDDAM). For this purpose, simulation models are developed and comparisons of the PDDAM and CDDAM are made in terms of the mean absolute percent error (MAPE), mean percent error (MPE) and mean tardiness (MT). Simulation experiments showed that for many test conditions, PDDAM dominates CDDAM. Therefore, case by case findings are summarized in the paper.     

Reduction of chromium(VI) by phosphonic acid

The kinetics of electron transfer between chromium(VI) and H3PO3, yielding chromium(III), have been investigated in HClO4 and H2SO4 media by visible spectrophotometry. The rate of reaction increased with increasing [H2SO4] and [HClO4]. A rate law based on ester formation preceding the electron transfer has been established and a possible mechanism has been proposed. The mechanism and the derived rate law are consistent with the observed kinetics. This revised version was published online in June 2006 with corrections to the Cover Date.     

Preparation of multicomponent oxides via non-hydrolytic sol-gel routes from novel bimetallic alkoxides

New series of double alkoxides of erbium and its oxides have been prepared by non-hydrolytic sol-gel reactions for the first time. These compounds were characterized with the help of FT-IR, NMR, Mass, DTA-TGA and SEM. The mass spectra show similar types of fragmentation pattern in all compounds. The XRD diffraction pattern shows an enhanced homogeneity at high temperature. TGA/DTA measurements show that thermal decomposition occurs in steps and entirely depends on the chemical compositions and the synthesis routes. The SEM observation reveals a high dense and smooth microstructural uniformity of polycrystalline nature. The physico-chemical properties show that crystallization behaviors can be controlled with the help of fine-tuning the chemical properties of chelating agents in order to increase the solubility of metal alkoxides.     

Stage-specific alterations of cyclin expression during UVB-induced murine skin tumor development

We have evaluated the in vivo correlation between the expression of cell cycle markers and skin tumor development in SKH-1 hairless mice in a complete photocarcinogenesis protocol. Irradiated mice developed an average of 16 tumors per animal by week 23 with the average number of carcinomas per mouse being 2.1. The expression of p53 and cyclins A and D1 was confined initially to sporadic single cells and gradually developed into foci of patchy intense staining in the basal and granular layers of UVB-exposed epidermis. p53 was expressed in all the papilloma sections examined, whereas cyclins D1 and A were expressed in 68 and 71% of these lesions, respectively. In UVB-induced squamous cell carcinomas (SCC), p53 was expressed in >90% of the tumors, whereas cyclin D1 was detected in 55% of the lesions, and cyclin A staining was limited to 27%. These immunohistochemical observations were confirmed by Western blotting and protein kinase assays. We observed an early wave of cyclin A overexpression and cyclin A protein kinase activity preceding the appearance of detectable tumors. Cyclin D1 and p53 overexpression were coupled with the development of tumors, and these changes are likely to be relevant to the pathogenesis of these lesions.     

Ni(II) ion-imprinted solid-phase extraction and preconcentration in aqueous solutions by packed-bed columns

Solid-phase extraction (SPE) columns packed with materials based on molecularly imprinted polymers (MIPs) were used to develop selective separation and preconcentration for Ni(II) ion from aqueous solutions. SPE is more rapid, simple and economical method than the traditional liquid-liquid extraction. MIPs were used as column sorbent to increase the grade of selectivity in SPE columns. In this study, we have developed a polymer obtained by imprinting with Ni(II) ion as a ion-imprinted SPE sorbent. For this purpose, NI(II)-methacryloylhistidinedihydrate (MAH/Ni(II)) complex monomer was synthesized and polymerized with cross-linking ethyleneglycoldimethacrylate to obtain [poly(EGDMA-MAH/Ni(II))]. Then, Ni(II) ions were removed from the polymer getting Ni(II) ion-imprinted sorbent. The MIP-SPE preconcentration procedure showed a linear calibration curve within concentration range from 0.3 to 25 ng/ml and the detection limit was 0.3 ng/ml (3 s) for flame atomic absorption spectrometry (FAAS). Ni(II) ion-imprinted microbeads can be used several times without considerable loss of adsorption capacity. When the adsorption capacity of nickel imprinted microbeads were compared with non-imprinted microbeads, nickel imprinted microbeads have higher adsorption capacity. The K_d (distribution coefficient) values for the Ni(II)-imprinted microbeads show increase in K_d for Ni(II) with respect to both K_d values of Zn(II), Cu(II) and Co(II) ions and non-imprinted polymer. During that time K_d decreases for Zn(II), Cu(II) and Co(II) ions and the k′ (relative selectivity coefficient) values which are greater than 1 for imprinted microbeads of Ni(II)/Cu(II), Ni(II)/Zn(II) and Ni(II)/Co(II) are 57.3, 53.9, and 17.3, respectively. Determination of Ni(II) ion in sea water showed that the interfering matrix had been almost removed during preconcentration. The column was good enough for Ni determination in matrixes containing similar ionic radii ions such as Cu(II), Zn(II) and Co(II).     

Clouding behavior of nonionic–cationic and nonionic–anionic mixed surfactant systems in presence of carboxylic acids and their sodium salts

The study is focused on evaluation of clouding phenomena of the aqueous single nonionic surfactant system Triton X-100 (TX-100) and its mixed systems with anionic aerosol-OT (AOT) and cationic dodecylpyridinium chloride (DPC) in presence of hydrophobic ions furnished by sodium salts of carboxylic acids, viz., sodium ethanoate, sodium propanoate, sodium butanoate, and sodium hexanoate and the respective carboxylic acids [ethanoic acid, propanoic acid, butanoic acid, and hexanoic acid]. The influence of salts on the cloud point (CP) has been explained on the basis of salt effect as well as the solubilization of higher alkyl chain hydrophobic ions furnished by these salts. Moreover, the co- and counterion effect has been taken into account to explain the variation of the CP in the mixed systems. However, the effect of acids on CP has been explained in the light of their aqueous solubility and their partitioning ability between octanol and water as reflected by their K _OW values.     

Reactions of α,β-unsaturated ketones with cyanoacetamide

3-Aryl-1-phenyl-2-propen-1-ones Ia-f and aroylphenylacetylenes Va-d reacted under reflux for 3 hours with cyanoacetamide in the presence of sodium ethoxide to give the corresponding 4-aryl-3-cyano-6-phenyl-2-(1H)pyridones VI. However, when ketones Ia-e were refluxed with cyanoacetamide for one hour in the presence of sodium ethoxide or piperidine, they gave the corresponding 4-aryl-3-cyano-3,4-dihydro-6-phenyl-2-(1H)pyridones IIIa-e, which upon heating with selenium gave the corresponding 2-pyridones VI. The structures of the products are based on chemical and spectroscopic evidence.     

PHOTODYNAMIC THERAPY OF CHEMICALLY- AND ULTRAVIOLET B RADIATION-INDUCED MURINE SKIN PAPILLOMAS BY CHLOROALUMINUM PHTHALOCYANINE TETRASULFONATE

Photodynamic therapy (PDT) of cancer combines irradiation of tumors with visible light following selective uptake of the photosensitizer by the tumor cells. PhotofrinR-II (Pf-II) is the only photosensitizer which is in clinical use in PDT, whereas chloroaluminum phthalocyanine tetrasulfonate (AlPcTS) has also shown promise in preclinical studies. In most such studies, the effectiveness of the photosensitizers has been assessed in implanted tumor model systems rather than in model systems where tumors are allowed to grow in their own connective tissue matrix. In this study the pharmacokinetics, tumor ablation capability and cutaneous photosensitization response of AlPcTS have been assessed in mice bearing chemically- and ultraviolet B radiation (UVB)-induced benign skin papillomas. When tumor-bearing animals were injected intraperitoneally with AlPcTS (5 mg/kg body wt), maximum tumor:normal skin ratio of 2.4 was observed at 48 h, at which time the mice were irradiated within the absorption spectrum of the photosensitizer. In tumor ablation studies with SENCAR mice bearing chemically-induced skin tumors, AlPcTS resulted in greater than 80% ablation in tumor volume at 20 days post-irradiation. In cutaneous photosensitization response, AlPcTS produced only transient effects (no effect after 24 h) in SENCAR mice. Pharmacokinetics data, tumor ablation effects and cutaneous photosensitization response of AlPcTS were comparable in SKH-1 hairless mice bearing UVB-induced skin tumors. Our data indicate that AlPcTS produces significant photodynamic effects towards the ablation of murine skin tumors, and that it does not produce prolonged cutaneous photosensitivity.     

Synthesis,spectral and biological studies of organotin(IV) complexes of heteroscorpionate

A heteroscorpionate ligand, potassium hydrobis(benzoato)(salicylaldehyde)borate (KL), has been synthesized. This was converted into organotin complexes R₂SnL₂ and R₃SnL complexes by mixing and stirring with a methanolic solution/suspension of organotin chloride. The ligand and its complexes were characterized by elemental analyses and spectral studies (IR, ¹H NMR, ¹³C NMR, ESI mass spectra and Thermo gravimetric analysis (TGA)). Antibacterial and antifungal studies of these compounds were evaluated by the disc diffusion method at variable concentration against three species of bacteria (Staphylococcus aureus, Klebsiella pneumonia and Bacillius subtillis) and two species of fungi (Asperjillius fiavus and Candida albicans). It was found that triorganotin derivatives (R₃SnL) of the ligand were more effective as compared with diorganotin derivatives (R₂SnL₂). The organotin complexes of borates were tested for their algicidal activity on the cyanobacterial strains Aulosira fertilissma, Anabaena species, Anabaena variabilis and Nostoc muscorum and showed high to moderate toxicity towards the above species. The ligand and its complexes were also tested for its pH effect on soil in vitro for a duration of more than one month and it was found that they are able to kill pests without damaging the soil quality. Copyright © 2006 John Wiley & Sons, Ltd.