196,579 research outputs found
Spectroscopy and scattering for chemistry:new possibilities and challenges with large scale facilities
No full textKirsten M. o. Jensen, Dorota Koziej and Serena DeBeer introduce theNanoscalethemed issue on spectroscopy and scattering for chemistry: new possibilities and challenges with large scale facilities
Relation between the structure of an aerobic biofilm and transport phenomena
No full textAn aerobic biofilm was characterized using confocal scanning laser microscopy (CSLM), O2 micro-electrodes, particle tracking and microinjection of fluorescent dyes. The biofilms were found to consist of microbial clusters of cells and Extra-cellular Polymeric Substance (EPS) separated by interstitial voids. The cell clusters were ca 300 m and the voids were ca 100 m wide. The voids were open channels connected with the bulk fluid. Fluorescein micro-injection showed that liquid could flow through the voids, but was always stagnant in the cell clusters. Consequently, in voids both diffusion and convection may contribute to mass transfer, while in cell clusters transport is determined by diffusion only. Particle tracking with CSLM showed that flow velocity inside the biofilm was proportional to the bulk flow velocity. The importance of convective mass transport in biofilms was demonstrated by oxygen distribution measurements. At high flow velocities of the bulk liquid, the mass boundary layer followed the irregular biofilm surface. At lower velocities the mass boundary layer was parallel to the substratum. Mass transfer from voids to cell clusters increased with flow velocity, as result from convective mass transport from the bulk to the voids. Convective transport was insignificant at low flow velocities, but at high flow velocities it increased the total mass transport by 200-250%. The local diffusion coefficients in biofilms were measured using microinjection of fluorescent dyes and quantitative analysis of the subsequent plume formation using CSLM. The diffusion coefficient of small, non-binding molecules in cell clusters is close to that in water. Very large molecules were impeded in their diffusion through the biofilm matrix. It was calculated that the cell cluster matrix had the characteristics of a gel network with pore diameters of 80 nm
Powered brushing and fluoride in a streptococcus mutans typodont biofilm
No full textObjectives: to develop a typodont biofilm model to measure the effect of powered brushing on biofilm removal and the delivery of fluoride into biofilm remaining in accessible areas in an anatomically relevant geometry.Methods: streptococcus mutans biofilms were grown on sections of a typodont (A-PZ Frasaco) for three or six days. The typodont sections contained either incisors and cuspids or premolars and molars. The biofilm was observed on various surfaces before and after brushing facial surfaces for 10 seconds with a powered toothbrush (Philips Sonicare FlexCare), according to manufacturer instructions. A pH microelectrode was used to measure profiles in the biofilm. To measure profiles of free fluoride ion in the biofilm we constructed a fluoride microelectrode. The electrode was calibrated and profiles measured in an agar gel.Results: biofilm grew on the hard plastic tooth and soft gum materials of the typodont on all surfaces. The pH microelectrode showed that acid was produced in the presence of sucrose due to acid respiration. The pH dropped from approximately 7 to as low as 5.5. After hand brushing the typodont was reexamined. The facial surfaces were almost devoid of biofilm, however, there was still biofilm remaining in the interproximal spaces and molar occlusal surfaces. The fluoride microelectrode had a tip diameter of 5 µm and had a measurement range from approximately 1 to 1000 ppm F-, in a log-linear relationship.Conclusion: the typodont model is a good system for quantifying biofilm removal and measuring remaining biofilm in “hard to reach locations” in an anatomically relevant model. Microelectrodes can be used to measure local activity and zones of acid production. The fluoride microelectrode has potential for measuring the local delivery of fluoride to biofilm on various typodont surface
Dr. Duane M. Jackson, Morehouse College, July 2011
No full textThis video is a conversation with Dr. Duane M. Jackson. Dr. Jackson talks about his paper, "Recall and the Serial Position Effect: The Role of Primacy and Recency on Accounting Students' Performance." Jackie Daniel, AUC Woodruff Library, is the interviewer
"Reflections on the subject of Emigration from Europe with a view to Settlement in the United States" By M. Carey.
No full text"Reflections on the subject of Emigration from Europe with a view to Settlement in the United States: containing bried sketches of the moral and political character of those states.
By M. Carey, member of the American philosophical, and of the American Antiquarian Society, and author of The Olive Branch, Cindiciae Hibernicae, essays on banking, on political economy, and on internal improvement.
To which are now added the English editor's comments on the subject; together with Important Advice to Emigrants, and Cautions Against Impositions Practiced in the Outports
Intermediate sulfur oxidation state compounds in the euxinic surface sediments of the Dvurechenskii mud volcano (Black Sea)
No full textThe deep Black Sea is known to be depleted in electron-acceptors for sulfide oxidation. This study on depth distributions of sulfur species (S(II), S(0), View the MathML sourceSn2-, View the MathML sourceS2O32-, View the MathML sourceSO32-, View the MathML sourceSO42-) in the Dvurechenskii mud volcano, a cold seep situated in the permanently anoxic eastern Black Sea basin (Sorokin Trough, 2060 m water depth), showed remarkable concentrations of sulfide oxidation products. Sulfite concentrations of up to 11 μmol L−1, thiosulfate concentrations of up to 22 μmol L−1, zero-valent sulfur concentrations of up to 150 μmol L−1 and up to five polysulfide species were measured in the upper 20 cm of the sediment. Electron-acceptors found to be available in the Dvurechenskii mud volcano (DMV) for the oxidation of hydrogen sulfide to sulfide oxidation intermediates are iron-minerals, and probably also reactive manganese phases. Up to 60 μmol g−1 of reactive iron-minerals and up to 170 μmol L−1 dissolved iron was present in the central summit with the highest fluid upflow and fresh mud outflow. Thus, the source for the oxidative power in the DMV are reactive iron phases extruded with the mud from an ancient source in the deeply buried sediments, leading to the formation of various sulfur intermediates in comparably high concentrations. Another possible source of sulfide oxidation intermediates in DMV sediments could be the formation of zero-valent sulfur by sulfate dependent anaerobic microbial oxidation of methane followed by disproportionation of zero-valent sulfur. Sulfide oxidation intermediates, which are produced by these processes, do not reach thermodynamic equilibrium with rhombic sulfur, especially close to the active center of the DMV due to a short equilibration time. Thus, mud volcano sediments, such as in the DMV, can provide oxidizing niches even in a highly reduced environment like the abyssal part of the Black Sea
sj-pdf-1-hpi-10.1177_11207000221111101 – Supplemental material for Causes and predictors of failed same-day home discharge following primary hip and knee total joint arthroplasty: a Canadian perspective
No full textSupplemental material, sj-pdf-1-hpi-10.1177_11207000221111101 for Causes and predictors of failed same-day home discharge following primary hip and knee total joint arthroplasty: a Canadian perspective by Aaron M Gazendam, Daniel Tushinski, Mansi Patel, Kamal Bali, Danielle Petruccelli, Mitchell Winemaker, Justin DeBeer, Leslie Gillies, Katie Best, Jennifer Fife and Thomas J Wood in HIP International</p
Dispelling the Myths Behind First-author Citation Counts
No full textWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
Dr. Glendon Swarthout
No full textHosted by Roger M. Busfield, MSU Assistant Professor of Speech and Theater, Meet the Author is designed to introduce a general audience to a contemporary author and their work through in-depth interviews. This episode features a conversation between Dr. Glendon Swarthout, prolific author and English professor at MSU, and assistant professors Sam S. Baskett and Theodore B. Strandness
sj-pdf-2-hpi-10.1177_11207000221111101 – Supplemental material for Causes and predictors of failed same-day home discharge following primary hip and knee total joint arthroplasty: a Canadian perspective
No full textSupplemental material, sj-pdf-2-hpi-10.1177_11207000221111101 for Causes and predictors of failed same-day home discharge following primary hip and knee total joint arthroplasty: a Canadian perspective by Aaron M Gazendam, Daniel Tushinski, Mansi Patel, Kamal Bali, Danielle Petruccelli, Mitchell Winemaker, Justin DeBeer, Leslie Gillies, Katie Best, Jennifer Fife and Thomas J Wood in HIP International</p
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