PHOTOMINERALIZATION OF 4-CHLOROPHENOL SENSITIZED BY TITANIUM-DIOXIDE - A STUDY OF THE INITIAL KINETICS OF CARBON-DIOXIDE PHOTOGENERATION

The kinetics of photomineralization of 4-chlorophenol (4-CP) sensitized by Degussa P25 TiO2 in O2-saturated solution is studied as a function of the following different experimental parameters: pH, [TiO2], percentage O2 [O2], [4-CP], T, I, lambda and [KNO3]. At pH 2 and T=30-degrees-C the initial relative rate of CO2 photogeneration R(CO2) conforms to a Langmuir-Hinshelwood-type kinetic scheme and the relationship between R(CO2) and the various experimental parameters may be summarized as follows: R(CO2) = gammaK(O2)[O2](I(a))(theta)K(4-CP]0/(1 + K(O2])(1 + K(4-CP)[4-CP]0) where gamma is a proportionality constant, K(O2) = 0.044 +/- 0.005[O2]-1, theta = 0.74 +/- 0.05 and K(4-CP) = (29 +/- 3) x 10(3) dm3 mol-1. The overall activation energy for this photosystem was determined as 16 +/- 2 kJ mol-1. This work forms part of an overall characterization study in which it is proposed that the 4-CP-TiO2-O2 photosystem is adopted as a standard test system for incorporation into all future semiconductor-sensitized photomineralization studies in order to facilitate comparisons between the results of the different studies.

Novel UV-activated colorimetric oxygen indicator

The results of a detailed characterization study of a novel UV-activated colorimetric oxygen indicator are described. The indicator uses nanoparticles of titania to photosensitize the reduction of methylene blue by triethanolamine in a polymer encapsulation medium, using UVA light. Upon UV irradiation, the indicator bleaches and remains in this colorless state in the dark, unless and until it is exposed to oxygen, whereupon its original color is restored. The indicator is reusable and irreversible. The rate of color recovery is proportional to the level of oxygen present. A layer of PET (poly(ethylene terephthalate)), of thickness b, placed on top of the indicator film slows down its response, and the 90% recovery time is proportional to b.

A Density Functional Theory Study on the Active Center of Fe-Only Hydrogenase: Characterization and Electronic Structure of the Redox States

We have carried out extensive density functional theory (DFT) calculations for possible redox states of the active center in Fe-only hydrogenases. The active center is modeled by [(H(CH(3))S)(CO)(CN(-))Fe(p)(mu-DTN)(mu-CO)Fe(d)(CO)(CN(-))(L)](z) (z is the net charge in the complex; Fe(p)= the proximal Fe, Fe(d) = the distal Fe, DTN = (-SCH(2)NHCH(2)S-), L is the ligand that bonds with the Fed at the trans position to the bridging CO). Structures of possible redox states are optimized, and CO stretching frequencies are calculated. By a detailed comparison of all the calculated structures and the vibrational frequencies with the available experimental data, we find that (i) the fully oxidized, inactive state is an Fe(II)-Fe(II) state with a hydroxyl (OH(-)) group bonded at the Fe(d), (ii) the oxidized, active state is an Fe(II)-Fe(l) complex which is consistent with the assignment of Cao and Hall (J. Am. Chem. Soc. 2001, 123, 3734), and (iii) the fully reduced state is a mixture with the major component being a protonated Fe(l)-Fe(l) complex and the other component being its self-arranged form, Fe(II)-Fe(II) hydride, Our calculations also show that the exogenous CO can strongly bond with the Fe(II)-Fe(l) species, but cannot bond with the Fe(l)-Fe(l) complex. This result is consistent with experiments that CO tends to inhibit the oxidized, active state, but not the fully reduced state. The electronic structures of all the redox states have been analyzed. It is found that a frontier orbital which is a mixing state between the e(g) of Fe and the 2pi of the bridging CO plays a key role concerning the reactivity of Fe-only hydrogenases: (1) it is unoccupied in the fully oxidized, inactive state, half-occupied in the oxidized, active state, and fully occupied in the fully reduced state; (ii) the e(g)-2pi orbital is a bonding state, and this is the key reason for stability of the low oxidation states, such as Fe(l)-Fe(l) complexes; and (iii) in the e(g)-2pi orbital more charge accumulates between the bridging CO and the Fe(d) than between the bridging CO and the Fe(p), and the occupation increase in this orbital will enhance the bonding between the bridging CO and the Fe(d), leading to the bridging-CO shift toward the Fe(d).

LOCALIZATION, QUANTITATION, AND CHARACTERIZATION OF NEUROPEPTIDE-F-IMMUNOREACTIVE AND FMRFAMIDE-IMMUNOREACTIVE PEPTIDES IN TURBELLARIANS AND A MONOGENEAN - A COMPARATIVE-STUDY

Over the past decade it has become clear that the nervous systems of platyhelminths are both complex and highly developed, particularly in peptidergic elements. The central position of an ancestral flatworm in the evolution of the Bilateria has placed a greater importance on the study of modern flatworms. Using antisera generated to the C-terminal region of platyhelminth neuropeptide F and the molluscan neuropeptide, FMRFamide, in immunocytochemistry at both Light and ultrastructural levels, immunoreactivities have been localised within the nervous systems of three species of triclad turbellarians, Dugesia lugubris, Dendrocoelum lacteum, and Polycelis nigra, and one species of monogenean trematode, Diclidophora merlangi. Extensive immunostaining was obtained with both antisera throughout the central and peripheral nervous systems of all species studied, but intensity and abundance was significantly greater in the turbellarians. Indirect electron-immunogold labeling demonstrated that immunoreactivity to both neuropeptides was often colocalised in neurosecretory vesicles, although discrete populations of vesicles were also observed. Radioimmunoassay of extracts of all species confirmed that neuropeptide F immunoreactivity was consistently more abundant than FMRFamide immunoreactivity, and that the levels of both in the three turbellarians were several orders of magnitude greater than those found in the monogenean. Chromatographic analyses of turbellarian extracts revealed that neuropeptide F and FMRFamide immunoreactivities were attributable to different peptides. These data imply that the neuropeptidergic systems of turbellarians are considerably more extensive than those of monogeneans, and would suggest that a regression has occurred in the latter as a consequence of the adoption of a more sedentary parasitic lifestyle. (C) 1995 Wiley-Liss, Inc.

Characterization of High-Performance Organic Dyes for Dye-Sensitized Solar Cell: A DFT/TDDFT Study

Dye-sensitized solar cell (DSSC) is currently a promising technology that makes solar energy efficient and cost-effective to harness. In DSSC, metal free dyes, such indoline-containing D149 and D205, are proved to be potential alternatives for traditional metal organic dyes. In this work, a DFT/TDDFT characterization for D149 and D205 were carried out using different functionals, including B3LYP, MPW1K, CAM-B3LYP and PBE0. Three different conformers for D149 and four different conformers for D205 were identified and calculated in vacuum. The performance of different functionals on calculating the maximum absorbance of the dyes in vacuum and five common solvents (acetonitrile, chloroform, ethanol, methanol, and THF) were examined and compared to determine the suitable computational setting for predicting properties of these two dyes. Furthermore, deprotonated D149 and D205 in solvents were also considered, and the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) were calculated, which elucidates the substitution effect on the rhodanine ring of D149 and D205 dyes on their efficiency. Finally, D149 and D205 molecules were confirmed to be firmly anchored on ZnO surface by periodic DFT calculations. These results would shed light on the design of new highly efficiency metal-free dyes.

Differential Scanning Calorimetry Study and Computer Modeling of b a Phase Transformation in Ti-6Al-4V Alloy

The relationship between heat-treatment parameters and microstructure in titanium alloys has so far been mainly studied empirically, using characterization techniques such as microscopy. Calculation and modeling of the kinetics of phase transformation have not yet been widely used for these alloys. Differential scanning calorimetry (DSC) has been widely used for the study of a variety of phase transformations. There has been much work done on the calculation and modeling of the kinetics of phase transformations for different systems based on the results from DSC study. In the present work, the kinetics of the transformation in a Ti-6Al-4V titanium alloy were studied using DSC, at continuous cooling conditions with constant cooling rates of 5 °C, 10 °C, 20 °C, 30 °C, 40 °C, and 50 °C/min. The results from calorimetry were then used to trace and model the transformation kinetics in continuous cooling conditions. Based on suitably interpreted DSC results, continuous cooling–transformation (CCT) diagrams were calculated with lines of isotransformed fraction. The kinetics of transformation were modeled using the Johnson–Mehl–Avrami (JMA) theory and by applying the "concept of additivity." The JMA kinetic parameters were derived. Good agreement between the calculated and experimental transformed fractions is demonstrated. Using the derived kinetic parameters, the transformation in a Ti-6Al-4V alloy can be described for any cooling path and condition. An interpretation of the results from the point of view of activation energy for nucleation is also presented.

Characterization and optimization of experimental variables within a reproducible bladder encrustation model and in vitro evaluation of the efficacy of urease inhibitors for the prevention of medical device-related encrustation

This study presents a reproducible, cost-effective in vitro encrustation model and, furthermore, describes the effects of components of the artificial urine and the presence of agents that modify the action of urease on encrustation on commercially available ureteral stents. The encrustation model involved the use of small-volume reactors (700 mL) containing artificial urine and employing an orbital incubator (at 37 degrees C) to ensure controlled stirring. The artificial urine contained sources of calcium and magnesium (both as chlorides), albumin and urease. Alteration of the ratio (% w/w) of calcium salt to magnesium salt affected the mass of encrustation, with the greatest encrustation noted whenever magnesium was excluded from the artificial urine. Increasing the concentration of albumin, designed to mimic the presence of protein in urine, significantly decreased the mass of both calcium and magnesium encrustation until a plateau was observed. Finally, exclusion of urease from the artificial urine significantly reduced encrustation due to the indirect effects of this enzyme on pH. Inclusion of the urease inhibitor, acetohydroxamic acid, or urease substrates (methylurea or ethylurea) into the artificial medium markedly reduced encrustation on ureteral stents. In conclusion, this study has described the design of a reproducible, cost-effective in vitro encrustation model. Encrustation was markedly reduced on biomaterials by the inclusion of agents that modify the action of urease. These agents may, therefore, offer a novel clinical approach to the control of encrustation on urological medical devices. (c) 2005 Wiley Periodicals, Inc.

Cloning and characterization of the mouse homologue of the human dendritic cell maturation marker CD208/DC-LAMP

DC-LAMP, a member of the lysosomal-associated membrane protein (LAMP) family, is specifically expressed by human dendritic cells (DC) upon activation and therefore serves as marker of human DC maturation. DC-LAMP is detected first in activated human DC within MHC class II molecules-containing compartments just before the translocation of MHC class II-peptide complexes to the cell surface, suggesting a possible involvement in this process. The present study describes the cloning and characterization of mouse DC-LAMP, whose predicted protein sequence is over 50% identical to the human counterpart. The mouse DC-LAMP gene spans over 25 kb and shares syntenic chromosomal localization (16B2-B4 and 3q26) and conserved organization with the human DC-LAMP gene. Analysis of mouse DC-LAMP mRNA and protein revealed the expression in lung peripheral cells, but also its unexpected absence from mouse lymphoid organs and from mouse DC activated either in vitro or in vivo. In conclusion, mouse DC-LAMP is not a marker of mature mouse DC and this observation raises new questions regarding the role of human DC-LAMP in human DC.

Characterization of a thymidylate synthase (TS)-inducible cell line: a model system for studying sensitivity to TS- and non-TS-targeted chemotherapies

Thymidylate synthase (TS) is responsible for the de novo synthesis of thymidylate, which is required for DNA synthesis and repair and which is an important target for fluoropyrimidines such as 5-fluorouracil (5-FU), and antifolates such as Tomudex (TDX), ZD9331, and multitargeted antifolate (MTA). To study the importance of TS expression in determining resistance to these agents, we have developed an MDA435 breast cancer-derived cell line with tetracycline-regulated expression of TS termed MTS-5. We have demonstrated that inducible expression of TS increased the IC(50) dose of the TS-targeted therapeutic agents 5-FU, TDX, and ZD9331 by 2-, 9- and 24-fold respectively. An IC(50) dose for MTA was unobtainable when TS was overexpressed in these cells, which indicated that MTA toxicity is highly sensitive to increased TS expression levels. The growth inhibitory effects of the chemotherapeutic agents CPT-11, cisplatin, oxaliplatin, and Taxol were unaffected by TS up-regulation. Cell cycle analyses revealed that IC(50) doses of 5-FU, TDX and MTA caused an S-phase arrest in cells that did not overexpress TS, and this arrest was overcome when TS was up-regulated. Furthermore, the S-phase arrest was accompanied by 2- to 4-fold increased expression of the cell cycle regulatory genes cyclin E, cyclin A, and cyclin dependent kinase 2 (cdk2). These results indicate that acute increases in TS expression levels play a key role in determining cellular sensitivity to TS-directed chemotherapeutic drugs by modulating the degree of S-phase arrest caused by these agents. Moreover, CPT-11, cisplatin, oxaliplatin, and Taxol remain highly cytotoxic in cells that overexpress TS.

Development and mechanical characterization of bioadhesive semi-solid, polymeric systems containing tetracycline for the treatment of periodontal diseases

Purpose. This study examined the mechanical characteristics and release of tetracycline from bioadhesive, semi-solid systems which were designed for the treatment of periodontal diseases.

Synchrotron X-ray diffraction study of the phase transformations in titanium alloys

High-resolution synchrotron X-ray diffraction was used to study the phase transformations in titanium alloys. Three titanium alloys were investigated: Ti-6Al-4V, Ti-6Al-2Sn-4Zr-2Mo-0.08Si and beta21s. Both room and high temperature measurements were performed. The room temperature experiments were performed to study the structure of the alloys after different heat treatments, namely as received (AR), furnace cooling (FC), water quenching (WQ) and water quenching followed by ageing. The alpha, alpha', alpha'' and beta phases were observed in different combinations depending on the heat treatment conditions and the alloy studied. A multicomponent hexagonal close packed (hcp) alpha phase, with different c and the same a lattice parameters, was detected in Ti-6Al-4V after FC. High temperature synchrotron X-ray diffraction was used for 'in situ' study of the transformations on the sample surface at elevated temperatures. The results were used to trace the kinetics of surface oxidation and the concurrent phase transformations taking place under different conditions. The influence of the temperature and oxygen content on the lattice parameters of the alpha phase was derived and new data obtained on the coefficients of thermal expansion in the different directions of the hcp alpha phase, for Ti-6Al-4V and Ti-6Al-2Sn-4Zr-2Mo-0.08Si.

Characterization of the entanglement of two squeezed states

We study a continuous-variable entangled state composed of two states which are squeezed in two opposite quadratures in phase space. Various entanglement conditions are tested for the entangled squeezed state and we study decoherence models for noise, producing a mixed entangled squeezed state. We briefly describe a probabilistic protocol for entanglement swapping based on the use of this class of entangled states and the main features of a general generation scheme.

Characterization of White bream virus reveals a novel genetic cluster of nidoviruses.

The order Nidovirales comprises viruses from the families Coronaviridae (genera Coronavirus and Torovirus), Roniviridae (genus Okavirus), and Arteriviridae (genus Arterivirus). In this study, we characterized White bream virus (WBV), a bacilliform plus-strand RNA virus isolated from fish. Analysis of the nucleotide sequence, organization, and expression of the 26.6-kb genome provided conclusive evidence for a phylogenetic relationship between WBV and nidoviruses. The polycistronic genome of WBV contains five open reading frames (ORFs), called ORF1a, -1b, -2, -3, and -4. In WBV-infected cells, three subgenomic RNAs expressing the structural proteins S, M, and N were identified. The subgenomic RNAs were revealed to share a 42-nucleotide, 5' leader sequence that is identical to the 5'-terminal genome sequence. The data suggest that a conserved nonanucleotide sequence, CA(G/A)CACUAC, located downstream of the leader and upstream of the structural protein genes acts as the core transcription-regulating sequence element in WBV. Like other nidoviruses with large genomes (>26 kb), WBV encodes in its ORF1b an extensive set of enzymes, including putative polymerase, helicase, ribose methyltransferase, exoribonuclease, and endoribonuclease activities. ORF1a encodes several membrane domains, a putative ADP-ribose 1"-phosphatase, and a chymotrypsin-like serine protease whose activity was established in this study. Comparative sequence analysis revealed that WBV represents a separate cluster of nidoviruses that significantly diverged from toroviruses and, even more, from coronaviruses, roniviruses, and arteriviruses. The study adds to the amazing diversity of nidoviruses and appeals for a more extensive characterization of nonmammalian nidoviruses to better understand the evolution of these largest known RNA viruses.

Biochemical characterization of the equine arteritis virus helicase suggests a close functional relationship between arterivirus and coronavirus helicases.

The arterivirus equine arteritis virus nonstructural protein 10 (nsp10) has previously been predicted to contain a Zn finger structure linked to a superfamily 1 (SF1) helicase domain. A recombinant form of nsp10, MBP-nsp10, was produced in Escherichia coli as a fusion protein with the maltose-binding protein. The protein was partially purified by affinity chromatography and shown to have ATPase activity that was strongly stimulated by poly(dT), poly(U), and poly(dA) but not by poly(G). The protein also had both RNA and DNA duplex-unwinding activities that required the presence of 5' single-stranded regions on the partial-duplex substrates, indicating a 5'-to-3' polarity in the unwinding reaction. Results of this study suggest a close functional relationship between the arterivirus nsp10 and the coronavirus helicase, for which NTPase and duplex-unwinding activities were recently demonstrated. In a number of biochemical properties, both arterivirus and coronavirus SF1 helicases differ significantly from the previously characterized RNA virus SF1 and SF2 enzymes. Thus, the combined data strongly support the idea that nidovirus helicases may represent a separate group of RNA virus-encoded helicases with distinct properties.