Studies on the reduction of hematite by carbon

Single pellet experiments have been carried out in a nitrogen atmosphere to study the reduction of hematite by graphite in the temperature range 925 to 1060°C. The effect of variables such as c/Fe2O3 molar ratio, pellet size, and so forth, has been investigated. Gas analysis data show a continuous decrease in CO2/CO ratio during reduction, the values being far away from Fe/FeO equilibrium for wustite reduction by CO. The activation energies associated with different degrees of reduction appear to be widely different suggesting a possible changeover in reaction mechanism during the progress of reduction. X-ray diffraction studies confirm the stepwise nature of hematite reduction.

High pressure clamp for electrical measurements up to 8 GPa and temperature down to 77 K

A compact clamp-type high pressure cell for carrying out electrical conductivity measurements on small solid samples of size 1 mm or less at pressures upto 8 GPa (i.e., 80 kbar) and for use down to 77 K has been designed and fabricated. The pressure generated in the sample region has been calibrated at room temperature against the polymorphic phase transitions of Bismuth and Ytterbium. The pressure relaxation of the clamp at low temperatures has been estimated by monitoring the electrical conductivity behavior of lead. Review of Scientific Instruments is copyrighted by The American Institute of Physics.

Involvement of Synthesis and Phosphorylation of Nuclear Protein Factors That Bind to the Positivecis-Acting Element in the Transcriptional Activation of the CYP2B1/B2 Gene by Phenobarbitonein Vivo

The synthesis and phosphorylation of protein factor(s) that bind to the positivecis-acting element (−69 to −98 nt) of the CYP2B1/B2 gene have been examinedin vivoin the rat. Treatment of rats with cycloheximide, a protein synthetic inhibitor, suppresses basal as well as phenobarbitone-induced levels of CYP2B1/B2 mRNA and its run-on transcription. Under these conditions, complex formation of the nuclear extract with the positive element is also inhibited, as judged by gel shift assays. Treatment of rats with 2-aminopurine, a general protein kinase inhibitor, blocks the phenobarbitone-mediated increase in CYP2B1/B2 mRNA, cell-free transcription of a minigene construct containing the positive element, pP450e179DNA, and binding of nuclear proteins to the positive element. Treatment of rats with okadaic acid, a protein phosphatase inhibitor, mimics the effects of phenobarbitone, but only partially. Thus, both phenobarbitone and okadaic acid individually enhance binding of the nuclear protein(s) to the positive element, cell-free transcription of the minigene construct, and phosphorylation of the not, vert, similar26- and 94-kDa proteins binding to the positive element. But unlike phenobarbitone, okadaic acid is not an inducer of CYP2B1/B2 mRNA or its run-on transcription. Thus, phenobarbitone-responsive positive element interactions constitute only a minimal requirement, and okadaic acid is perhaps not able to bring about the total requirement for activation of CYP2B1/B2 gene transcription that should include interaction between the minimal promoter and further upstream elements. An intriguing feature is the antagonistic effect of okadaic acid on phenobarbitone-mediated effects on CYP2B1/B2 mRNA levels, cell-free and run-on transcription, and nuclear protein binding to the positive element. The reason for this antagonism is not clear. It is concluded that phenobarbitone treatment enhancesin vivothe synthesis and phosphorylation of protein factors binding to the positive element and these constitute a minimal requirement for the transcriptional activation of the CYP2B1/B2 gene.

Microbial activities in boreal soils: Biodegradation of organic contaminants at low temperature and ammonia oxidation

This thesis deals with the response of biodegradation of selected anthropogenic organic contaminants and natural autochthonous organic matter to low temperature in boreal surface soils. Furthermore, the thesis describes activity, diversity and population size of autotrophic ammonia-oxidizing bacteria (AOB) in a boreal soil used for landfarming of oil-refinery wastes, and presents a new approach, in which the particular AOB were enriched and cultivated in situ from the landfarming soil onto cation exchange membranes. This thesis demonstrates that rhizosphere fraction of natural forest humus soil and agricultural clay loam soil from Helsinki Metropolitan area were capable of degrading of low to moderate concentrations (0.2 50 µg cm-3) of PCP, phenanthrene and 2,4,5-TCP at temperatures realistic to boreal climate (-2.5 to +15 °C). At the low temperatures, the biodegradation of PCP, phenanthrene and 2,4,5-TCP was more effective (Q10-values from 1.6 to 7.6) in the rhizosphere fraction of the forest soil than in the agricultural soil. Q10-values of endogenous soil respiration (carbon dioxide evolution) and selected hydrolytic enzyme activities (acetate-esterase, butyrate-esterase and β-glucosidase) in acid coniferous forest soil were 1.6 to 2.8 at temperatures from -3 to +30 °C. The results indicated that the temperature dependence of decomposition of natural autochthonous soil organic matter in the studied coniferous forest was only moderate. The numbers of AOB in the landfarming (sandy clay loam) soil were determined with quantitative polymerase chain reaction (real-time PCR) and with Most Probable Number (MPN) methods, and potential ammonium oxidation activity was measured with the chlorate inhibition technique. The results indicated presence of large and active AOB populations in the heavily oil-contaminated and urea-fertilised landfarming soil. Assessment of the populations of AOB with denaturing gradient gel electrophoresis (DGGE) profiling and sequence analysis of PCR-amplified 16S rRNA genes showed that Nitrosospira-like AOB in clusters 2 and 3 were predominant in the oily landfarming soil. This observation was supported by fluorescence in situ hybridization (FISH) analysis of the AOB grown on the soil-incubated cation-exchange membranes. The results of this thesis expand the suggested importance of Nitrosospira-like AOB in terrestrial environments to include chronically oil-contaminated soils.

Bustle behind the scenes of action : nemosis as a model for fibroblast inflammatory activation

Wound healing is a complex process that requires an interplay between several cell types. Classically, fibroblasts have been viewed as producers of extracellular matrix, but more recently they have been recognized as orchestrators of the healing response, promoting and directing, inflammation and neovascularization processes. Compared to those from healthy tissue, inflammation-associated fibroblasts display a dramatically altered phenotype and have been described as sentinel cells, able to switch to an immunoregulatory profile on cue. However, the activation mechanism still remains largely uncharacterized. Nemosis is a model for stromal fibroblast activation. When normal human primary fibroblasts are deprived of growth support they cluster, forming multicellular spheroids. Clustering results in upregulation of proinflammatory markers such as cyclooxygenase-2 and secretion of prostaglandins, proteinases, cytokines, and growth factors. Fibroblasts in nemosis induce wound healing and tumorigenic responses in many cell types found in inflammatory and tumor microenvironments. This study investigated the effect of nemotic fibroblasts on two components of the vascular system, leukocytes and endothelium, and characterized the inflammation-promoting responses that arose in these cell types. Fibroblasts in nemosis were found to secrete an array of chemotactic cytokines and attract leukocytes, as well as promote their adhesion to the endothelium. Nuclear factor-kB, the master regulator of many inflammatory responses, is activated in nemotic fibroblasts. Nemotic fibroblasts are known to produce large amounts of hepatocyte growth factor, a motogenic and angiogenic factor. Also, as shown in this study, they produce vascular endothelial growth factor. These two factors induced migratory and sprouting responses in endothelial cells, both required for neovascularization. Nemotic fibroblasts also caused a decrease in the expression of adherens and tight junction components on the surface of endothelial cells. The results allow the conclusion that fibroblasts in nemosis share many similarities with inflammation-associated fibroblasts. Both inflammation and stromal fibroblasts are known to be involved in tumorigenesis and tumor progression. Nemosis may be viewed as a model for stromal fibroblast activation, or it may correlate with cell-cell interactions between adjacent fibroblasts in vivo. Nevertheless, due to nemosis-derived production of proinflammatory cytokines and growth factors, fibroblast nemosis may have therapeutic potential as an inducer of controlled tissue repair. Knowledge of stromal fibroblast activation gained through studies of nemosis, could provide new strategies to control unwanted inflammation and tumor progression.

Microbe-induced activation of inflammatory cytokine response in human cells

Human body is in continuous contact with microbes. Although many microbes are harmless or beneficial for humans, pathogenic microbes possess a threat to wellbeing. Antimicrobial protection is provided by the immune system, which can be functionally divided into two parts, namely innate and adaptive immunity. The key players of the innate immunity are phagocytic white blood cells such as neutrophils, monocytes, macrophages and dendritic cells (DCs), which constantly monitor the blood and peripheral tissues. These cells are armed for rapid activation upon microbial contact since they express a variety of microbe-recognizing receptors. Macrophages and DCs also act as antigen presenting cells (APCs) and play an important role in the development of adaptive immunity. The development of adaptive immunity requires intimate cooperation between APCs and T lymphocytes and results in microbe-specific immune responses. Moreover, adaptive immunity generates immunological memory, which rapidly and efficiently protects the host from reinfection. Properly functioning immune system requires efficient communication between cells. Cytokines are proteins, which mediate intercellular communication together with direct cell-cell contacts. Immune cells produce inflammatory cytokines rapidly following microbial contact. Inflammatory cytokines modulate the development of local immune response by binding to cell surface receptors, which results in the activation of intracellular signalling and modulates target cell gene expression. One class of inflammatory cytokines chemokines has a major role in regulating cellular traffic. Locally produced inflammatory chemokines guide the recruitment of effector cells to the site of inflammation during microbial infection. In this study two key questions were addressed. First, the ability of pathogenic and non-pathogenic Gram-positive bacteria to activate inflammatory cytokine and chemokine production in different human APCs was compared. In these studies macrophages and DCs were stimulated with pathogenic Steptococcus pyogenes or non-pathogenic Lactobacillus rhamnosus. The second aim of this thesis work was to analyze the role of pro-inflammatory cytokines in the regulation of microbe-induced chemokine production. In these studies bacteria-stimulated macrophages and influenza A virus-infected lung epithelial cells were used as model systems. The results of this study show that although macrophages and DCs share several common antimicrobial functions, these cells have significantly distinct responses against pathogenic and non-pathogenic Gram-positive bacteria. Macrophages were activated in a nearly similar fashion by pathogenic S. pyogenes and non-pathogenic L. rhamnosus. Both bacteria induced the production of similar core set of inflammatory chemokines consisting of several CC-class chemokines and CXCL8. These chemokines attract monocytes, neutrophils, dendritic cells and T cells. Thus, the results suggest that bacteria-activated macrophages efficiently recruit other effector cells to the site of inflammation. Moreover, macrophages seem to be activated by all bacteria irrespective of their pathogenicity. DCs, in contrast, were efficiently activated only by pathogenic S. pyogenes, which induced DC maturation and production of several inflammatory cytokines and chemokines. In contrast, L. rhamnosus-stimulated DCs matured only partially and, most importantly, these cells did not produce inflammatory cytokines or chemokines. L. rhamnosus-stimulated DCs had a phenotype of "semi-mature" DCs and this type of DCs have been suggested to enhance tolerogenic adaptive immune responses. Since DCs have an essential role in the development of adaptive immune response the results suggest that, in contrast to macrophages, DCs may be able to discriminate between pathogenic and non-pathogenic bacteria and thus mount appropriate inflammatory or tolerogenic adaptive immune response depending on the microbe in question. The results of this study also show that pro-inflammatory cytokines can contribute to microbe-induced chemokine production at multiple levels. S. pyogenes-induced type I interferon (IFN) was found to enhance the production of certain inflammatory chemokines in macrophages during bacterial stimulation. Thus, bacteria-induced chemokine production is regulated by direct (microbe-induced) and indirect (pro-inflammatory cytokine-induced) mechanisms during inflammation. In epithelial cells IFN- and tumor necrosis factor- (TNF-) were found to enhance the expression of PRRs and components of cellular signal transduction machinery. Pre-treatment of epithelial cells with these cytokines prior to virus infection resulted in markedly enhanced chemokine response compared to untreated cells. In conclusion, the results obtained from this study show that pro-inflammatory cytokines can enhance microbe-induced chemokine production during microbial infection by providing a positive feedback loop. In addition, pro-inflammatory cytokines can render normally low-responding cells to high chemokine producers via enhancement of microbial detection and signal transduction.

A green protocol for room temperature synthesis of silver nanoparticles in seconds

We describe here a rapid, energy-efficient, green and economically scalable room temperature protocol for the synthesis of silver nanoparticles. Tannic acid, a polyphenolic compound derived from plant extracts is used as the reducing agent. Silver nanoparticles of mean size ranging from 3.3 to 22.1 nm were synthesized at room temperature by the addition of silver nitrate to tannic acid solution maintained at an alkaline pH. The mean size was tuned by varying the molar ratio of tannic acid to silver nitrate. We also present proof of concept results demonstrating its suitability for room temperature continuous flow processing.

Synthesis of ZnO Nanoneedles on Flexible Polymer Substrates at Room Temperature by Activated Reactive Evaporation

ZnO nanoneedles were successfully deposited on flexible polymer substrates at room temperature by activated reactive evaporation. Neither a catalyst nor a template was employed in this synthesis. These synthesized needles measured 500 - 600 nm in length and its diameter varied from 30 - 15 nm from the base to the tip. The single-crystalline nature of the nanoneedle was observed by high-resolution transmission electron microscopy studies. The Raman studies on these nanoneedles had shown that they are oxygen deficient in nature. A possible growth mechanism has been proposed here, in which the nanoneedles nucleate and grow in the gas phase by vapor-solid mechanism.

Fabrication and mechanisms of densification of ZrB2-based ultra high temperature ceramics by reactive hot pressing

Dense ZrB2-SiC (25-30 vol%) composites have been produced by reactive hot pressing using stoichiometric Zr, B4C, C and Si powder mixtures with and without Ni addition at 40 MPa, 1600 degrees C for 60 min. Nickel, a common additive to promote densification, is shown not to be essential; the presence of an ultra-fine microstructure containing a transient plastic ZrC phase is suggested to play a key role at low temperatures, while a transient liquid phase may be responsible at temperatures above 1350 degrees C. Hot Pressing of non-stoichiometric mixture of Zr, B4C and Si at 40 MPa, 1600 degrees C for 30 min resulted in ZrB2-ZrCx-SiC (15 vol%) composites of similar to 98% RD.

Farnesyltransferase Inhibitors Reduce Ras Activation and Ameliorate Acetaminophen-Induced Liver Injury in Mice

Hepatotoxicity due to overdose of the analgesic and antipyretic acetaminophen (A-PAIP) is a major cause of liver failure in adults. To better understand the contributions of different signaling pathways, the expression and role of Ras activation was evaluated after oral dosing of mice with APAP (400-500 mg/kg). Ras-guanosine triphosphate (GTP) is induced early and in an oxidative stress-dependent manner. The functional role of Ras activation was studied by a single intraperitoneal injection of the neutral sphingomyelinase and farnesyltransferase inhibitor (FTI) manumycin A (I mg/kg), which lowers induction of Ras-GTP and serum amounts of alanine aminotransferase (ALT). APAP dosing decreases hepatic glutathione amounts, which are not affected by manumycin A treatment. However, APAP-induced activation of c-Jun N-terminal kinase, which plays an important role, is reduced by manumycin A. Also, APAP-induced mitochondrial reactive oxygen species are reduced by manumycin A at a later time point during liver injury. Importantly, the induction of genes involved in the inflammatory response (including iNos, gp91phox, and Fasl) and serum amounts of proinflammatory cytokines interferon-gamma (IFN gamma) and tumor necrosis factor alpha, which increase greatly with APAP challenge, are suppressed with manumycin A. The FTI ctivity of manumycin A is most likely involved in reducing APAP-induced liver injury, because a specific neutral sphingomyelinase inhibitor, GW4869 (I mg/kg), did not show any hepatoprotective effect. Notably, a structurally distinct FTI, gliotoxin (I mg/kg), also inhibits Ras activation and reduces serum amounts of ALT and IFN-gamma after APAP dosing. Finally, histological analysis confirmed the hepatoprotective effect f manumycin A and gliotoxin during APAP-induced liver damage. Conclusion: This study identifies a key role for Ras activation and demonstrates the therapeutic efficacy of FTIs during APAP-induced liver injury.

Magnesium ion conducting, room temperature molten electrolytes

Room temperature, magnesium ion conducting binary molten electrolyte consisting of acetamide and magnesium perchlorate has been prepared and characterized. The molten liquid is very stable and shows high ionic conductivity, of the order of several mS cm(-1) at 25 degrees C with other favourable physicochemical properties. Vibrational spectroscopic studies reveal that the free ion concentration is higher than that of ion pairs and aggregates in the melt. The electrochemical reversibility of magnesium deposition and dissolution is demonstrated using voltammetry and impedance studies. Preliminary studies on rechargeable batteries assembled using gamma-MnO2 and Mg metal as the electrodes together with the molten electrolyte show high discharge capacity.

Influence of Temperature and High Electric Field on Power Consumption by Piezoelectric Actuated Integrated Structure

The influence of electric field and temperature on power consumption of piezoelectric actuated integrated structure is studied by using a single degree of freedom mass-spring-damper system model coupled with a piezoactuator. The material lead zirconate titanate, is considered as it is capable of producing relatively high strains (e.g., 3000 mu epsilon). Actuators are often subject to high electric fields to increase the induced strain produced, resulting in field dependant piezoelectric coefficient d(31), dielectric coefficient epsilon(33) and dissipation factor delta. Piezostructures are also likely to be used across a wide range of temperatures in aerospace and undersea operations. Again, the piezoelectric properties can vary with temperature. Recent experimental studies by physics researchers have looked at the effect of high electric field and temperature on piezoelectric properties. These properties are used together with an impedance based power consumption model. Results show that including the nonlinear variation of dielectric permittivity and dissipation factor with electric field is important. Temperature dependence of the dielectric constant also should be considered.

A Novel Invertase from a Thermophilic FungusThermomyces lanuginosus:Its Requirement of Thiol and Protein for Activation

Unlike the invertases from the mesophilic fungi and yeasts, invertase from a thermophilic fungus,Thermomyces lanuginosus,was unusually unstable bothin vivoandin vitro.The following observations suggested that the unstable nature of the enzyme activity in the cell-free extracts was due to the oxidation of the cysteine residue(s) in the enzyme molecule: (a) the addition of dithiothreitol or reduced glutathione stabilized invertase activity during storage of the extracts and also revived enzyme activity in the extracts which had become inactive with time; (b)N-ethylmaleimide, iodoacetamide, oxidized glutathione, cystine, or oxidized coenzyme A-inactivated invertase; (c) invertase activity was low when the ratio reduced/oxidized glutathione was lower and high when this ratio was higher, suggesting regulation of the enzyme by thiol/disulfide exchange reaction. In contrast to the activation of invertase by the thiol compounds and its inactivation by the disulfides in the cell-free extracts, the purified enzyme did not respond to these compounds. Following its inactivation, the purified enzyme required a helper protein in addition to dithiothreitol for maximal activation. A cellular protein was identified that promoted activation of invertase by dithiothreitol and it was called “PRIA” for theprotein which helps inrestoringinvertaseactivity. The revival of enzyme activity was due to the conversion of the inactive invertase molecules into an active form. A model is presented to explain the modulation of invertase activity by the thiol compounds and the disulfides, both in the crude cell-free extracts and in the purified preparations. The requirement of free sulfhydryl group(s) for the enzyme activity and, furthermore, the reciprocal effects of the thiols and the disulfides on invertase activity have not been reported for invertase from any other source. The finding of a novel invertase which shows a distinct mode of regulation demonstrates the diversity in an enzyme that has figured prominently in the development of biochemistry.

Preparation temperature effect on the synthesis of various carbon nanostructures

Various carbon nanostructures (CNs) have been prepared by a simple deposition technique based on the pyrolysis of a new carbon source material tetrahydrofuran (THF) mixed with ferrocene using quartz tube reactor in the temperature range 700-1100 degrees C. A detailed study of how the synthesis parameter such as growth temperature affects the morphology of the carbon nanostructures is presented. The obtained CNs are investigated by scanning electron microscope (SEM), X-ray diffraction (XRD), electron dispersive scattering (EDS)thermogravimetry analysis (TGA), Raman and transmission electron microscope (TEM). It is observed that at 700 degrees C. normal CNTs are formed. Iron filled multi-walled carbon nanotubes (MWCNTs) and carbon nanoribbons (CNRs) are formed at 950 degrees C. Magnetic characterization of iron filled MWCNTs and CNRs studied at 300 K by superconducting quantum interference device (SQUID) reveals that these nanostructures have an enhanced coercivity (Hc = 1049 Oe) higher than that of bulk Fe. The large shape anisotropy of MWCNTs, which act on the encapsulated material (Fe), is attributed for the contribution of the higher coercivity. Coiled carbon nanotubes (CCNTs) were obtained as main products in large quantities at temperature 1100 degrees C.