Effect of Al Doping on Structural, Electrical, Optical and Photoluminescence Properties of Nano-Structural ZnO Thin Films

The nano-structural Al-doped ZnO thin films of different morphologies deposited on glass substrate were successfully fabricated at substrate temperature of 350 C by an inexpensive spray pyrolysis method. The structural, electrical, optical and photoluminescence properties were investigated. X-ray diffraction study revealed the crystalline wurtzite (hexagonal) structure of the films with nano-grains. Scanning electron mi- croscopy (SEM) micrographs indicated the formation of a large variety of nano-structures during film growth. The spectral absorption of the films occurred at the absorption edge of ～410 nm. In the present study, the optical band gap energy 3.28 eV of ZnO decreased gradually to 3.05 eV for 4 mol% of Al doping. The deep level activation energy decreased and carrier concentrations increased substantially with increasing doping. Exciting with the energy 3.543 eV (λ=350 nm), a narrow and a broad characteristic photoluminescence peaks that correspond to the near band edge (NBE) and deep level emissions (DLE), respectively emerged.     

Effect of Cerium Doping on Microstructure and Dielectric Properties of BaTiO3 Ceramics

A solid state reaction method was used to synthesize barium titanate (BT) and barium cerium titanate (BCT) ceramics at sintering temperature of 1473 K for 4 h. The effect of cerium (Ce) on the structure, microstructure and dielectric properties of BCT was investigated. The scanning electron microscopy (SEM) investigations revealed that the grain size increases with increasing Ce content. The X-ray diffraction (XRD) patterns showed mostly the BT phase, where the lattice parameter decreased with the addition of Ce. The temperature dependence of dielectric constant showed decrease in the phase transition temperature with higher Ce content. The dielectric constant decreased slightly with increasing frequency. The direct current (dc) density-voltage characteristics of the ceramics showed ohmic behavior for both the BT and BCT. As the temperature increased, the dc resistivity of the ceramics decreased. The activation energy increased with increasing Ce content.     

Histone Deacetylases Function in the Control of Early Hematopoiesis and Erythropoiesis

Numerous studies have highlighted the role of post-translational modifications in the regulation of cell proliferation, differentiation and death. Among these modifications, acetylation modifies the physicochemical properties of proteins and modulates their activity, stability, localization and affinity for partner proteins. Through the deacetylation of a wide variety of functional and structural, nuclear and cytoplasmic proteins, histone deacetylases (HDACs) modulate important cellular processes, including hematopoiesis, during which different HDACs, by controlling gene expression or by regulating non-histone protein functions, act sequentially to provide a fine regulation of the differentiation process both in early hematopoietic stem cells and in more mature progenitors. Considering that HDAC inhibitors represent promising targets in cancer treatment, it is necessary to decipher the role of HDACs during hematopoiesis which could be impacted by these therapies. This review will highlight the main mechanisms by which HDACs control the hematopoietic stem cell fate, particularly in the erythroid lineage.     

Molecular mechanisms involved in the inhibition of neutrophil locomotion by tumor cells

A chronic myelogenous leukemia cell line (K562) releases a factor of about 8 kD which we have named K562-inhibitory factor (K562-IF) because it inhibits neutrophil locomotion. This factor has potent anti-inflammatory activity in mice, associated with an inhibition of neutrophil function including not only random locomotion and fMetLeuPhe- or serum-induced locomotion but also adherence and zymosan-induced chemiluminescence and degranulation. In contrast, K562-IF does not affect the oxidative burst induced by soluble compounds such as fMetLeuPhe and phorbol esters. Analysis of the mechanism of action of K562-IF on neutrophils showed that it involves an adherence protein, mainly CR3 (the receptor of complement fraction iC3b). Neither, CR3 expression nor its up-regulation were altered, whereas the function of CR3 was depressed, i.e., it failed to cap upon neutrophil stimulation and did not bind iC3b. One unexplained finding is that K562-IF inhibits actin polymerization induced by fMetLeuPhe but not by activation of the Fc-gamma receptor III. Studies are underway to establish whether K562 cells are representative of other malignant cells with regard to the production of neutrophil inhibitors.     

Regional activation of L-type voltage-sensitive calcium channels in experimental thiamine deficiency

At present (putative) human carcinogens are identified via epidemiological studies and testing using the chronic 2-yr rodent bioassay. Both methods have severe limitations in that they are slow, insensitive, expensive, and are also hampered by many uncertainties. The development of methods to modify specific genes in the mammalian genome has provided promising new tools for use in identifying carcinogens and characterizing their (qualitative) risk. Several transgenic mouse lines are currently under study to test their possible use in short-term carcinogenicity testing. One such candidate alternative transgenic model is the XPA knock-out mouse. These mice have an almost complete deficiency in DNA nucleotide excision repair (NER). Nevertheless, XPA-deficient mice are viable and have a background of a low incidence of spontaneous development of cancers. Approximately 15% of the mice develop hepatocellular adenomas (only after 1.5 yr). After treatment with ultraviolet-B radiation or 7,12-dimethylbenz(a)anthracene, the XPA-deficient mice developed squamous cell carcinomas and papillomas, respectively, on their skin. Oral treatment of XPA-deficient mice with benzo[a]pyrene (B[a]P), 2-acetylaminofluorene (2-AAF), and 2-amino-1-methyl-6-phenylimidazo [4,5-b]-pyridine (PhIP) resulted in lymphomas (B[a]P), liver and bladder tumors (2-AAF), and intestinal adenomas plus lymphomas (PhIP). These results look encouraging, but it should be noted that the compounds and agents tested thus far have all been substrate for nucleotide excision repair. Animal studies with different genotoxic or nongenotoxic compounds, as organized for instance within the framework of the International Life Sciences Institute/Health and Environmental Sciences Institute program, are needed to further evaluate the suitability of the XPA model for short-term carcinogenicity testing.     

Temperature-dependent studies on the electrical properties of pyrolytic ZnO thin film prepared from Zn(C2H3O2)2

Pyrolytically deposited transparent conducting zinc oxide thin films on glass substrates were successively subjected to a post-deposition heat treatment in air and in vacuum. The effects of heat treatment on the electrical transport properties were studied in detail. The films were polycrystalline in structure and the oxygen chemisorption-desorption process was found to play an important role in controlling the electronic properties. Various grain-boundary and energy-band parameters were calculated by taking conventional extrinsic semiconductor theory and grain-boundary trapping models into account. The samples were non-degenerative at room temperature and Hall mobility was found to be modulated by the grain-boundary potential barrier height via sample temperature.     

Staurosporine stimulates phospholipase D activation in human polymorphonuclear leukocytes

Oropharyngeal pressure during swallowing was studied in a total of 40 healthy adult males and females in two age groups (21-27 yr and 62-75 yr). Effects of bolus volume, bolus viscosity, age, and gender were analyzed, and dry and bolus swallows were compared. The duration of the intrabolus pressure, reflecting the pressure exerted by the tongue on the bolus and preceding the generation of the pharyngeal pressure, was significantly affected by bolus volume. The duration of oropharyngeal pressure was affected by age, gender, and bolus type (bolus vs. dry swallow). Peak oropharyngeal pressure was not affected by any of the test factors, although there was a tendency for older subjects to have higher pressures than young subjects.