Spectrophotometric and electrochemical behavior of a novel azocalix[4]arene derivative as a highly selective chromogenic chemosensor for Cr

In this study, a novel azocalix[4]arene derivative, 5,11,17-tris[(1-naphtyl)azo]-25,26,27,28-tetrahydroxy-calix[4]arene (NAC4) bearing napthyl groups on the upper rim was synthesized. Its complexation behavior for alkali, alkaline-earth and various heavy metal ions (Li⁺, Na⁺, K⁺, Rb⁺, Cs⁺, Mg²⁺, Ca²⁺, Sr²⁺, Ba²⁺, Pb²⁺, Hg²⁺, Ni²⁺, Cd²⁺, Cu²⁺, Zn²⁺, Co²⁺, Fe²⁺, Cr³⁺, Ag⁺) was investigated by spectroscopic and voltammetric methods. This chemosensor exhibits decreased absorbance in the presence of Hg²⁺ and a unique absorbance quenching effect only for Cr³⁺. In addition, a new absorption band centered at 565 nm with the formation of the 1:1 host–guest complex (Cr³⁺-NAC4) was observed in the case of Cr³⁺, leading to an obvious color change from light orange to dark lilac. In voltammetric experiments, Cr³⁺ ions decreased voltammetric peaks of NAC4, whereas no significant changes occurred in the presence of the other metal ions. The Benesi–Hildebrand method was used to determine a logarithmic value of 3.76 for the association constant of the complex between Cr³⁺ and NAC4.     

Modifications in the properties of gypsum construction element via addition of expanded macroporous silica granules

The present study is focused on the production of light weight silicate based macroporous filler for hardened gypsum and its effect on the product properties. Highly porous, durable foam like silica granules were produced from the relatively low cost material of silica gel desiccant. Swelling behaviour and mineralogical structure of the granules after swelling were examined. Different sample series were produced by replacing gypsum by expanded silica gel. Physical properties of the hardened gypsum were improved by the addition of expanded silica gel granules. Thermal conductivity of the gypsum decreased significantly when the expanded silica gel granules introduced into the gypsum. Expanded silica gel addition also improved the high temperature durability of gypsum. Much better integrity was observed after the testing of samples at 700 °C when compared to control series.     

An improved counting method for motile protozoan cultures

A simple counting method is described for routine cultures of highly motile organisms. It is based on dyeing the organisms with a suitable stain, filtering them through a Millipore filter and counting single organisms directly under a microscope after rendering the filter transparent.     

The Social Structure in the GAP Region and its Evolution

GAP is an integrated multisectoral development project implemented in south-east Turkey, which makes up 9.7% of the country. With its technical, economic and social dimensions, it is considered in western circles as one of the three to nine wonders of the modern world. As distinct from earlier projects implemented in Turkey (e.g. the Cukurova Plain project) and elsewhere in the world, the main objective of GAP is to improve the living conditions of the people not merely by developing the material infrastructure but by taking the people as the core factor in every component of the project. The sustainability of such projects, it is well realized, depends on the human dimension, and not on success in the achievement of the material goals alone. Within this framework, several sociological research studies were conducted in the region to determine the appropriate approach in making the people a vital component of GAP and in bringing them to participate in the project voluntarily. This article first gives a historical account of nomadic, i.e., 'tribal' (or ashiret ) aspects of Anatolian history, without which neither the past nor the present of Turkey can be adequately understood . 1 It then proceeds to summarize the findings, regarding the 'tribal' structure in the region, of the several research studies carried out in the region between 1992 and 1994 .     

Comparison of one-dimensional and multi-dimensional models in stability analysis of turning operations

Chatter is one of the main problems in machining resulting in poor surface quality and low productivity. Chatter can be avoided by applying stability diagrams which are generated using stability models. The stability analysis of turning has mostly been performed using single dimensional, so-called oriented transfer function approach whereas the actual turning processes usually involve multi-dimensional dynamics. In this paper, a comparative analysis between one dimensional (1D) and multi-dimensional stability models is given for turning operations. The multi dimensional model includes the inclination and side edge cutting angles and insert nose radius in order to demonstrate their effect on absolute stable depth of cut predictions. Chatter experiments are conducted in order to compare with both model predictions. It is demonstrated that for higher inclination angles and insert nose radii 1D models result in significant errors, and multi-dimensional solutions are required.     

Permeability properties of concretes with high reactivity metakaolin and calcined impure kaolin

This study reports the findings of an experimental study carried out on transport properties of the concretes modified with different calcined non purified kaolins (CK) and commercially available high reactivity metakaolin (MK). CK used in this study were obtained by calcining impure ground kaolins from four different quarries located on kaolin beds of different morphological and geological formations in Turkey. However, commercially available MK produced by thermal treatment of high purity kaolin from Czech Republic was used as reference material. In concrete mix design, the cement was replaced with 5, 10, 15, and 20 % by weight of CK or MK. The gas permeability, water permeability, water sorptivity, and chloride permeability tests were performed at the end of 28 and 90 days of curing periods. The results indicated that the concretes incorporated with different types of calcined kaolins had comparable performance in permeability with MK modified concrete, depending mainly on the type and amount of the mineral admixture used. Moreover, all of the concretes incorporation MK or CK had considerably better permeability than plain concrete regardless of the replacement level.     

Phenol degradation in a fixed‐bed bioreactor using micro‐cellular polymer‐immobilized Pseudomonas syringae

Highly porous (85% void volume) polymer beads with interconnecting micro‐pores were prepared for the immobilization of Pseudomonas syringae for the degradation of phenol in a fixed‐bed column bioreactor. The internal architecture of this support material (also known as PolyHIPE Polymer) could be controlled through processing before the polymerization stage. The transient and steady state phenol utilization rates were measured as a function of substrate solution flow rate and initial substrate concentration. The spatial concentration of the bacteria on the micro‐porous support particles as well as within them was studied using scanning electron microscopy at various time intervals during the continuous operation of the bioreactor. It was found that although bacterial penetration into the porous support was present after 20 days, bacterial viability however, was compromised after 120 days as a result of the formation of a biofilm on the support particles. The steady state phenol utilization at an initial phenol concentration of 200 mg cm^?3 was 100% provided that the flow rate was less than 7 cm³ min^?1. Substrate inhibition at a constant flow rate of 4.5 cm³ min^?1 was found to begin at 720 mg dm^?3. The critical dilution rate for bacteria washout was high as a result of the highly hydrophobic nature of the support and the reduction of pore interconnect size due to bacterial growth within the pores in the vicinity of the surface of the support. Copyright © 2004 Society of Chemical Industry     

Metathesis of methyl soyate with ruthenium catalysts

Three ruthenium catalysts were investigated for the metathesis reaction of methyl soyate. Dichlorotris (triphenylphosphine) ruthenium II and bis (tricyclohexyl phosphine) benzylidine ruthenium (IV) dichloride displayed no reactivity at 40 °C and atmospheric pressure. However, ruthenium [1,3-bis-(2,4,6-trimethylphenyl)-2-imidazolidinylidene] dichloro (phenylmethylene) tricyclohexylphosphine, Grubbs second generation catalyst, exhibited high activity at these mild conditions. After 2 h, 46% of the unsaturated methyl esters in a commercial methyl soyate were metathesized. This suggests a method to modify the structure of methyl soyate to improve diesel fuel performance properties.     

A lighting coordinate database for 3D art objects

Artists making three-dimensional art objects have an idea in their minds about how to illuminate their creations. For museums and galleries to illuminate these objects successfully according to the ideas of the artist, the types of light sources and their locations must be known. To fulfil this requirement, we propose a lighting coordinate database (LCD) to establish the coordinates of light sources. We describe two possible methods of obtaining data for this database: a computer software method and a hardware method. The head of Michelangelo's David is used to test the applicability of the two methods. In the software method, the scanned image of David's head is illuminated on the computer screen and data for the location of light sources are created. In the hardware method, a second set of data is created by illuminating a scale model of David using light emitting diodes (LED).