679 research outputs found
Effect of dimethyl sulfoxide on dentin collagen
Objectives. Infiltration of adhesive on dentin matrix depends on interaction of surface and adhesive. Interaction depends on dentin wettability, which can be enhanced either by increasing dentin surface energy or lowering the surface energy of adhesive. The objective was to examine the effect of dimethyl sulfoxide (DMSO) on demineralized dentin wettability and dentin organic matrix expansion. Methods. Acid-etched human dentin was used for sessile drop contact angle measurement to test surface wetting on 1-5% DMSO-treated demineralized dentin surface, and linear variable differential transformer (LVDT) to measure expansion/shrinkage of dentinal matrix. DMSO-water binary liquids were examined for surface tension changes through concentrations from 0 to 100% DMSO. Kruskal-Wallis and Mann-Whitney tests were used to test the differences in dentin wettability, expansion and shrinkage, and Spearman test to test the correlation between DMSO concentration and water surface tension. The level of significance was p 80%) DMSO concentrations which expanded demineralized dentin more than water. Drying times of LVDT samples increased significantly with the use of DMSO. Significance. Increased dentin wettability may explain the previously demonstrated increase in adhesive penetration with DMSO-treated dentin, and together with the expansion of collagen matrix after drying may also explain previously observed increase in dentin adhesive bonding. (C) 2017 The Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.Peer reviewe
Characterization of the “in vitro pulp chamber” using the cytotoxicity of phenol
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/71980/1/j.1600-0714.1989.tb00744.x.pd
A new type of reconstruction on the InSb() surface determined by grazing incidence X-ray diffraction
The (3Ă—3) reconstruction of the InSb( ) surface has been investigated by grazing incidence X-ray diffraction and scanning tunneling microscopy. The structure is characterized by 6-atom rings on top of a slightly buckled InSb top double layer. Two types of rings have been found, an elliptic ring consisting of 4 In and 2 Sb atoms and a trigonal ring with 3 In and 3 Sb atoms. The bond angles and lengths are consistent with the concept of rehybridization and depolarization which explains the reconstructions of the (111) and (110) surfaces
Substantivity of Carbodiimide Inhibition on Dentinal Enzyme Activity over Time
The use of 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide HCl (EDC) has recently been investigated for its effectiveness in the prevention of collagen degradation over time and the improvement of resin-dentin bond durability. The objective of the present study was to evaluate the effects of a 0.3 M EDC-containing conditioner on endogenous enzymatic activities within the hybrid layer (HL) created by a self-etch or an etch-and-rinse adhesive after 1 y. The activity within the HL was examined using in situ zymography and confocal laser scanning microscopy after 24 h or 1-y storage in artificial saliva. Dentin specimens were bonded with Clearfil SE Bond (CSE) or XP Bond (XPB). For CSE, the self-etching primer was applied and treated with 0.3 M EDC for 1 min, and then the bonding agent was applied. For XPB, dentin was etched and treated with 0.3 M EDC for 1 min and then bonded with the primer-bonding agent. Control specimens were prepared without EDC treatment. Slices containing the adhesive-dentin interface were covered with fluorescein-conjugated gelatin and observed with a multiphoton confocal microscope. Fluorescence intensity emitted by hydrolyzed fluorescein-conjugated gelatin was quantified, and the amount of gelatinolytic activity was represented by the percentage of green fluorescence emitted within the HL. After 24 h of storage, enzymatic activity was detected by in situ zymography within the HLs of both tested adhesives, with XPB higher than CSE (P <0.05). Almost no fluorescence signal was detected when specimens were pretreated with EDC compared to controls (P <0.05). After 1 y of storage, enzymatic activities significantly increased for all groups (excluding XPB control) compared to 24-h storage (P <0.05), with EDC pretreated specimens exhibiting significantly lower activity than controls (P <0.05). The present study showed, for the first time, that the use of EDC for both the self-etch and the etch-and-rinse approaches results in the reduction but not complete inhibition of matrix-bound collagenolytic enzyme activities over time in the HL.Peer reviewe
A lattice gas model of II-VI(001) semiconductor surfaces
We introduce an anisotropic two-dimensional lattice gas model of metal
terminated II-IV(001) seminconductor surfaces. Important properties of this
class of materials are represented by effective NN and NNN interactions, which
result in the competition of two vacancy structures on the surface. We
demonstrate that the experimentally observed c(2x2)-(2x1) transition of the
CdTe(001) surface can be understood as a phase transition in thermal
equilbrium. The model is studied by means of transfer matrix and Monte Carlo
techniques. The analysis shows that the small energy difference of the
competing reconstructions determines to a large extent the nature of the
different phases. Possible implications for further experimental research are
discussed.Comment: 7 pages, 2 figure
Hydration interactions: aqueous solvent effects in electric double layers
A model for ionic solutions with an attractive short-range pair interaction
between the ions is presented. The short-range interaction is accounted for by
adding a quadratic non-local term to the Poisson-Boltzmann free energy. The
model is used to study solvent effects in a planar electric double layer. The
counter-ion density is found to increase near the charged surface, as compared
with the Poisson-Boltzmann theory, and to decrease at larger distances. The ion
density profile is studied analytically in the case where the ion distribution
near the plate is dominated only by counter-ions. Further away from the plate
the density distribution can be described using a Poisson-Boltzmann theory with
an effective surface charge that is smaller than the actual one.Comment: 11 Figures in 13 files + LaTex file. 20 pages. Accepted to Phys. Rev.
E. Corrected typos and reference
Unintentional high density p-type modulation doping of a GaAs/AlAs core-multi-shell nanowire
Achieving significant doping in GaAs/AlAs core/shell nanowires (NWs) is of
considerable technological importance but remains a challenge due to the
amphoteric behavior of the dopant atoms. Here we show that placing a narrow
GaAs quantum well in the AlAs shell effectively getters residual carbon
acceptors leading to an \emph{unintentional} p-type doping. Magneto-optical
studies of such a GaAs/AlAs core multi-shell NW reveal quantum confined
emission. Theoretical calculations of NW electronic structure confirm quantum
confinement of carriers at the core/shell interface due to the presence of
ionized carbon acceptors in the 1~nm GaAs layer in the shell.
Micro-photoluminescence in high magnetic field shows a clear signature of
avoided crossings of the Landau level emission line with the Landau
level TO phonon replica. The coupling is caused by the resonant hole-phonon
interaction, which points to a large 2D hole density in the structure.Comment: just published in Nano Letters
(http://pubs.acs.org/doi/full/10.1021/nl500818k
Quaternary Ammonium Silane-Functionalized, Methacrylate Resin Composition With Antimicrobial Activities and Self-Repair Potential
The design of antimicrobial polymers to address healthcare issues and minimize environmental problems is an important endeavor with both fundamental and practical implications. Quaternary ammonium silane-functionalized methacrylate (QAMS) represents an example of antimicrobial macromonomers synthesized by a sol–gel chemical route; these compounds possess flexible Si–O–Si bonds. In present work, a partially hydrolyzed QAMS co-polymerized with 2,2-[4(2-hydroxy 3-methacryloxypropoxy)-phenyl]propane is introduced. This methacrylate resin was shown to possess desirable mechanical properties with both a high degree of conversion and minimal polymerization shrinkage. The kill-on-contact microbiocidal activities of this resin were demonstrated using single-species biofilms of Streptococcus mutans (ATCC 36558), Actinomyces naeslundii (ATCC 12104) and Candida albicans (ATCC 90028). Improved mechanical properties after hydration provided the proof-of-concept that QAMS-incorporated resin exhibits self-repair potential via water-induced condensation of organic modified silicate (ormosil) phases within the polymerized resin matrix
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