1,395 research outputs found
Electron transfer in two and three dimensions
No full textA number of osmium bipyndyl complexes have been synthesised and characterised using spectroscopic, chromatographic and electrochemical techniques. The complexes formed are [Os(bpy)2 4-tet C1]C104, [Os(bpy)2 4-bpt C1]PF6 and [Os(bpy)2 Cl 4-bpt Os(bpy) 2 C1](PF6)2, where bpy is 2 ,2 ’-bipyridyl, 4-tet is 3,6-bis(4-pyndyl)-l,2,455-tetrazine and 4- bpt is 3,5-bis(pyridin-4-yl)-l,2,4-tnazole Monolayers of [Os(bpy) 2 4-tet C1]C1 0 4 have been formed by spontaneous adsorption onto clean gold microelectrodes. The tetrazine bridge between the [Os(bpy)2Cl]+ head group and the metal electrode surface undergoes a reversible protonation/deprotonation reaction depending on the pH of the contacting electrolyte solution High speed cyclic voltammetry reveals that the redox switching mechanism is best described as a non-adiabatic, through-bond tunnelling mechanism Significantly, while protonating the bridging ligand does not influence the free energy of activation, 10 3±1 1 kJ mol *, k° decreases by 1 order of magnitude from 1 1 x 104 s 1 to 1 2 x 103 s 1 upon going from a deprotonated to a protonated bridge. These observations are interpreted in terms of a through-bond tunnelling mechanism m which protonation decreases the electron density on the bridge and reduces the strength of electronic coupling between the redox centre and the electrode.
Solid deposits of the dimeric complex [Os(bpy) 2 Cl 4-bpt Os(bpy)2 C1](PF6)2 have been deposited on platinum microelectrodes by mechanical attachment. The electrochemical response exhibited by these deposits is unusually ideal over a wide range of electrolyte compositions and pH values Dct, the charge transport diffusion coefficient, is independent of the electrolyte concentration, indicating that electron self-exchange between adjacent redox centres limits the overall rate of charge transport through the solid In 1 0 M L1CIO4 and 1 0 M HCIO4, Dct values are 2 0±0 lxlO10 and 1 7±0 4x10 10 cm2 s corresponding to second order electron transfer rate constants of 18 x l07 and 3xl07 M 1 s 1. The standard rate of heterogeneous electron transfer across the electrode/deposit interface is 1 08+0 05x10 cm s. This value is approximately one order of magnitude lower than that found for a similar monomeric complex in which the bridging ligand is attached directly to the electrode surface, indicating that the 4-bpt ligand does not promote strong electronic communication between the [Os(bpy)2CI]+ head group and the electrode surface.
Monolayers of [Os(bpy)2 4-bptCl]PF6 have been formed by spontaneous adsorption onto platinum microelectrodes. These monolayers are extremely stable under a wide range of electrolyte compositions and pH values Significantly, the 4-bpt ligand is capable of undergoing a protonation/deprotonation reaction depending on the pH of the contacting electrolyte solution. High speed chronoamperometry reveals that protonation of the 4-bpt bridging ligand causes the standard rate of heterogeneous electron transfer to decrease by at least an order of magnitude from 2 67 x 106 to 4 5 x 104 s' 1 for the oxidation process and from 1 60 x 106 to 1 9 x 105 for the reduction process Consistent with a superexchange mechanism, these observation are interpreted in terms of a hole superexchange process, the rate of which decreases with increasing energy gap between the osmium metal dn orbitals and the highest occupied molecular orbital of the bridge
Characterization and applications of microfluidic devices based on immobilized biomaterials
No full textMicrofluidic biosensors and bioreactors based on
immobilized biomaterials are described in this dissertation.
Photocrosslinkable hydrogel or polymeric microbeads
were used as a supporting matrix for immobilizing E.coli or
enzymes in a microfluidic device. This dissertation covers
a microfluidic bioreactor based on hydrogel-entrapped
E.coli, a microfluidic biosensor based on an array of
hydrogel-entrapped enzymes, and a microfluidic bioreactor
based on microbead-immobilized enzymes.
Hydrogel micropatches containing E.coli were
fabricated within a microfluidic channel by in-situ
photopolymerization. The cells were viable in the hydrogel
micropatch and their membranes could be porated by lysating
agents. Entrapment of viable cells within hydrogels,
followed by lysis, could provide a convenient means for preparing biocatalysts without the need for enzyme
extraction and purification. Our results suggested that
hydrogel-entrapped cells, immobilized within microfluidic
channels, can act as sensors for small molecules and as
bioreactors for carrying out reactions.
A microfluidic biosensor based on an array of
hydrogel-entrapped enzymes could be used to simultaneously
detect different concentrations of the same analyte or
multiple analyte in real time. The concentration of an
enzyme inhibitor could be quantified using the same basic
approach. Isolations of the microchannels within different
microfluidic channels could eliminate the possibility of
cross talk between enzymes.
Finally, we characterized microfluidic bioreactors
packed with microbead-immobilized enzymes that can carry
out sequential, two-step enzyme-catalyzed reactions under
flow conditions. The overall efficiency of the reactors
depended on the spatial relationship of the two enzymes
immobilized on the beads. Digital simulations confirmed the
experimental results
A lag of 25 years: Evidence from an old capture of Fistularia commersonii Rüppell, 1838 from Lebanon (Mediterranean Sea)
No full text[No abstract available]Azzurro E, 2012, BIOL INVASIONS, V15, P977; Azzurro Ernesto, 2013, Management of Biological Invasions, V4, P167, DOI 10.3391-mbi.2013.4.2.10; Azzurro E, 2011, PLOS ONE, V6, DOI 10.1371-journal.pone.0024885; Bariche M, 2009, J APPL ICHTHYOL, V25, P460, DOI 10.1111-j.1439-0426.2008.01202.x; Bariche M, 2012, J BIOL RES-THESSALON, V17, P74; Bariche M, 2013, MAR BIOL RES, V9, P169, DOI 10.1080-17451000.2012.707322; Crooks J. A., 2011, ENCY BIOL INVASIONS, P404; Crooks J. A., 2005, ECOSCIENCE, V12, P3116; DAISIE, 2008, EUR INV AL SPEC GAT; FRITZSCHE RA, 1976, B MAR SCI, V26, P196; Golani Daniel, 2010, P145; Golani D, 2000, J FISH BIOL, V56, P1545, DOI 10.1006-jfbi.2000.1263; Golani D, 2007, BIOLOGY LETT, V3, P541, DOI 10.1098-rsbl.2007.0308; Kalogirou S, 2007, BIOL INVASIONS, V9, P887, DOI 10.1007-s10530-006-9088-3; Sanna D, 2011, J MAR BIOL ASSOC UK, V91, P1289, DOI 10.1017-S0025315410001451; Streftaris N, 2006, MEDITERR MAR SCI, V7, P87; Whitehead P. J. P., 1963, Bulletin of the British Museum (Natural History) Zoology, V10, P3050
Integration of functional components into microfluidic chemical systems: bioimmobilization and electrochemiluminescent detection on-chip
No full textWe have investigated and implemented several general strategies in the development of microfluidics-based chemical/biochemical sensing systems. The research in this dissertation covers the immobilization of biological reagents inside microfluidic channels using polystyrene (PS) microbeads and photopolymerizable hydrogel, electrochemical sensing via electrochemiluminescence (ECL) reporting with bipolar and two-electrode configurations, and integration of these general functions to realize multiplexing and networking on-chip. Photopolymerizable hydrogel based on Poly(ethylene glycol) (PEG) and streptavidin-coated polystyrene (PS) microbeads were employed as building blocks as well as functional components in microfluidic system. PEG hydrogels can be used to define local microenvironments at different locations in the same microchannel, which enables the introduction of multiple sensing events on the same device. Monitoring of DNA hybridization and enzyme/substrate interaction were realized thereafter by using either fluorescence or electrochemistry as the detection method. Electrogenerated chemiluminescence based on Ru(bpy)32+ (bpy = 2,2??-bipyridine) and tripropylamine (TPA) was used to photonically report various redox events in microfluidic systems. By using microfluidic electrochemical cells based on either two-electrode or bipolar electrode (one-electrode), electroactive species that undergo reduction can be electrically linked to this anodic ECL process and thus be reported by the latter. This ECL sensing scheme essentially broadens the spectrum of redox compounds that can be detected by ECL since the analytes are not required to directly participate into the light-generating processes. Microfluidics offers some unique technical advantages of performing electrochemistry over conventional methods. In particular, laminar flow allows multiple analyte streams to be brought together in parallel with little mixing. Moreover, electrochemical signals can be generally utilized as a convenient means to link individual microchannels together hence to realize microfluidic networking and cross-communication. Electrochemical microfluidic devices can be used to mimic general functions of microelectronic devices such as diodes, transistors, and logic gates. These novel functions rendered by electrochemistry are believed to bring us closer to the final goals of micro total analysis systems and lab-on-a-chip
Dendrimer-Encapsulated Nanoparticles: New Synthetic and Characterization Methods and Catalytic Applications
No full textIn this article we describe the synthesis, characterization, and applications of dendrimer-encapsulated nanoparticles (DENs). These materials are synthesized using a template approach in which metal ions are extracted into the interior of dendrimers and then subsequently reduced chemically to yield nearly size-monodisperse particles having diameters in the 1-2 nm range. Monometallic, bimetallic (alloy and core@shell), and semiconductor nanoparticles have been prepared by this route. The dendrimer component of these composites serves not only as a template for preparing the nanoparticle replica, but also as a stabilizer for the nanoparticle. In this perspective, we report on progress in the synthesis, characterization, and applications of these materials since our last review in 2005. Significant advances in the synthesis of core@shell DENs, characterization, and applications to homogeneous and heterogeneous catalysis (including electrocatalysis) are emphasized.U.S. Department of Energy, Office of Basic Energy Sciences DE-FG02-09ER16090U.S. National Science Foundation 0847957Robert A. Welch Foundation F-0032Chemistr
Lettre de M. C. Cameron à Alexander Morris sur la faveur dont jouit Morris parmi ses commettants
No full text4 pages, originalLettre de M. C. Cameron à [Alexander] Morris sur : la faveur dont jouit Morris parmi ses commettants; une suggestion à Morris de rester à Perth aussi longtemps que possible; des renseignements que D. G. Hewitt pourrait donner à Morris concernant ses terres; la popularité de Cameron; une rumeur selon laquelle la Chambre d'Assemblée serait bientôt dissoute
Thou charming bird = La perle du Bresil / Felicien David, words by Gabriel Etienne and S. Etienne, translated by Percy M. Crooks
No full textFor high voice (in G). ; Cover subtitle : Charmant oiseau. ; Pl. no. : 2048 S& Co
Textural analysis demonstrates heterogeneous [18F]-fluorodeoxyglucose uptake in radiologically normal lung in patients with idiopathic pulmonary fibrosis
No full textPositron Emission Tomography (PET) scanning in idiopathic pulmonary fibrosis (IPF) has revealed increased [18F]-fluorodeoxyglucose ([18F]-FDG) uptake in areas of the lungs that appear normal on high resolution computed tomography (HRCT). We hypothesised that “microscopic” disease identified using PET would be heterogeneous because IPF is characterised histologically by patchy fibrosis. We applied textural analysis to PET scans to evaluate heterogeneity of [18F]-FDG uptake in lung regions that appeared normal on HRCT. We identified six textural features that demonstrated significantly more heterogeneous [18F]-FDG uptake in radiologically normal lung in IPF patients compared with controls. Textural analysis of lung PET-CT imaging is a novel approach to study early changes in IPF before HRCT abnormalities are apparent
Radiotherapy: Impact of quality of life and need for psychological care: Results of a longitudinal study
No full textBackground: In the framework of a prospective longitudinal study, the quality of life (QoL) and support requirements of patients from a university hospital department of radiotherapy were evaluated for the first time by means of established psychodiagnostic questionnaires. Patients and Methods: At first, 732 patients were screened, of whom 446 (60.9%) fulfilled the criteria for inclusion; 39.1% did not (refusals 21.0%, low Karnofsky performance status 6.6%, management problems 3.4%, language barriers 3.0%, cognitive restrictions 2.6%, death 2.5%). Disease-specific aspects of QoL (Functional Assessment of Cancer Treatment - General, FACT-G) and moderating variables {[}Social Support Scale (SSS), Disease Coping (FKV), Self-Assessment Depression Scale (SDS), and Self-Defined Care Requirements (BB)] were self-rated by patients with different tumor types before radiotherapy (T1), after radiotherapy (T2), and 6 weeks after the end of radiotherapy (T3). We studied 265 patients (157 male, 108 female; median age 58.6 years) with complete data of three time points. Results: In general, QoL of patients decreased significantly over all time points in all subscales. Social support was rated high and remained constant throughout the treatment. Apparent coping mechanisms were active problem-oriented coping, leisure activities, and self-support. The patients' depression proved to be an important and constant factor without significant changes. The support requirement is characterized by the need for more medical information and dialogue with a physician. Conclusions: Early specific support from personnel with radiotherapeutic skills, during the disease-coping process as well as during rehabilitation, should be a permanent component of an integrated radiooncological treatment schedule
Public Health Rep
No full textPublic policy is an area of increasing study. Of concern in this presentation is the consensus-building feature of policymaking in the U.S.. The role of government in following the procedures established to achieve consensus and the importance of citizen participation in this open process cannot be under-estimated. The five central features of American consensus building are separation of powers, multiple levels of government, citizen participation, policymaker accountability, and individual freedoms. These features frame the efforts of those who shape the public policies that determine the ways laws are made and enforced and public funds are spent
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