Cytotoxic effects,microbiological analysis and inhibitory properties on carbonic anhydrase isozyme activities of 2-hydroxy-5-methoxyacetophenone thiosemicarbazone and its Cu(II), Co(II), Zn(II) and Mn(II) complexes

Research on Chemical Intermediates - Metal complexes of thiosemicarbazones have been receiving considerable attention in biological applications such as antimicrobial and anticancer therapies. In...     

Copolymers of 4-thieno[3,2-b]thiophen-3-ylbenzonitrile with anthracene and biphenyl; synthesis,characterization, electronic,optical, and thermal properties

Two novel copolymers of 4-thieno[3,2-b]thiophen-3-ylbenzonitrile (TT-CN), possessing electron withdrawing cyano moiety, with anthracene (P1) and biphenyl (P2) were prepared via Suzuki coupling. Optic, electronic, and thermal properties of the copolymers were investigated through UV–Vis spectroscopy, cyclic voltammetry, gel permeation chromatography, and thermal gravimetric analysis. The polymers with anthracene and biphenyl had electronic band gaps of 2.01 and 1.90 eV, respectively. Both polymers demonstrated excellent large Stokes shifts of 101 (anthracene) and 105 nm (biphenyl) as well as very good thermal properties. As they had good optical, electronic, and thermal properties, they are promising candidates for electronic applications.     

The self-consistent calculation of Si δ-doped GaAs structures

In this study, we report results of a self-consistent calculation obtained for the sub-band structure of Si δ-doped GaAs material by using a new alternative method. We will discuss the influence of the δ-doping concentration and the δ-layerthickness on the sub-band structure for a non-uniform distribution, which is taken as different from the known Gaussian distribution. The confining potential, the sub-band energies, the sub-band occupations, and the Fermi energy have been calculated by solving the Schr?dinger and Poisson equations by using the Airy functions self-consistently. Received: 4 December 2000 / Accepted: 31 January 2001 / Published online: 26 April 2001     

Selective syntheses of vinylenedithiathiophenes (VDTTs) and dithieno[2,3-b;2′,3′-d]thiophenes (DTTs); building blocks for π-conjugated systems

Selective syntheses of 3,4-vinylenedithiathiophenes (VDTTs) and dithieno[2,3-b;2′,3′-d]thiophenes (DTTs), having Ph, 4-CH₃OC₆H₄, 4-BrC₆H₄, 4-NO₂C₆H₄ and 4-(CH₃)₂NC₆H₄ groups, were achieved through the reaction of 1,8-diketone with phosphorus decasulfide (P₄S₁₀). The reaction could be shifted between VDTT and DTT by adding base (sodium bicarbonate) or acid (para-toluenesulfonic acid), respectively, to the reaction mixture. While the VDTTs were obtained in moderate yields, an important achievement has been made with the syntheses of the DTTs, obtaining them in higher yields compared with the previous report. Polymers of the VDTTs, which are the analogues of ethylenedioxythiophene, EDOT, were prepared using FeCl₃. Unfortunately, all attempts for their electropolymerization failed. Spin density calculations revealed that none of the VDTTs had a significant positive spin density at the ‘α’ carbon atoms of the thiophene ring. Considering their solubility and functional groups, which could be further derivatized, they are useful building blocks for the preparation of new organic materials.     

MOCVD growth and optical properties of non-polar (1 1–2 0) a-plane GaN on (1 0–1 2) r-plane sapphire substrate

Non-polar a-plane GaN film with crystalline quality and anisotropy improvement is grown by use of high temperature AlN/AlGaN buffer, which is directly deposited on r-plane sapphire by pulse flows. Compared to the a-plane GaN grown on AlN buffer, X-ray rocking curve analysis reveals a remarkable reduction in the full width at half maximum, both on-axis and off-axis. Atomic force microscopy image exhibits a fully coalesced pit-free surface morphology with low root-mean-square roughness (∼1.5 nm). Photoluminescence is carried out on the a-plane GaN grown on r-plane sapphire. It is found that, at low temperature, the dominant emission at ∼3.42 eV is composed of two separate peaks with different characteristics, which provide explanations for the controversial attributions of this peak in previous studies.     

Facile syntheses of 3-hydroxyflavones

Modification of the present synthetic methods led to the syntheses of 3-hydroxyflavones in a shorter reaction time, with simple purification and higher yields. Application of the method provided the syntheses of 3HFs having a hydroxyl group on the phenyl ring (ring B) in one step, which is an improvement compared to the four steps, long reaction time, and low yield using the current method available in the literature.     

Defining order picking policy: A storage assignment model and a simulated annealing solution in AS/RS systems

Improving technology, variable customer demands, variety of products and increasing improvement of production systems has brought storage facilities, which has an important role on business operations, to a critical point. This circumstance has revealed the necessity on activating of storage systems and operations. In this study, mathematical model, which minimizes simultaneously storage allocation, storage retrieval and storage keeping costs, is generated for an AS/RS system of an enterprise. The mathematical model has run for small solution space and optimal solution is obtained. The problem in this study is an NP hard problem that is why optimal solution cannot be obtained for large solution spaces. So the problem in existing system is solved by using simulated annealing and an optimal order policy is proposed.