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Hollow Space (hollow + space)
Selected AbstractsSynthesis of hollow crosslinked miktoarm polymer using miniemulsion as templatesJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 6 2009De'an Xiong Abstract Hollow crosslinked polymers (HCPs) were synthesized using arm first method via atom transfer radical polymerization. The polymerization process was performed in miniemulsion system, in which the macroinitiator, PEG-Br, was in the water phase, whereas the vinyl-monomer, 4-vinylpyridine (4VP), and the crosslinker, DVB, were in the butanone phase. TEM images and light scattering characterization showed that the resultant polymer contained a hollow space, and the volume of the hollow space could be adjusted by changing the ratio of water to butanone. Also, hollow crosslinked Miktoarm polymers (HCMPs) were synthesized through this method when two different macroinitiators, PEG-Br and PNIPAM-Br, were used to coinitiate the polymerization of the vinyl-monomer, 4VP and DVB. The 1H NMR spectra showed that the hollow polymers contained both PEG arms and PNIPAM arms. The hollow morphologies of the resultant Miktoarm polymers were the same as the HCPs. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 1651,1660, 2009 [source] Nanometer-Scaled Hollow Spherical Micelles with Hydrophilic Channels and the Controlled Release of IbuprofenMACROMOLECULAR RAPID COMMUNICATIONS, Issue 23 2008De'an Xiong Abstract PS- b -PAA spherical micelles with a liquid core and a PAA shell are prepared with the assistance of 1,2-dichloroethane. During the process of adding a mixture of PNIPAM- b -P4VP and PEG- b -P4VP, multi-layered micelles with a mixed corona that consists of both PNIPAM and PEG chains are constructed through the electrostatic interaction and hydrogen bonding between the PAA block and the P4VP block. When heating above the LCST, the PNIPAM chains collapse onto the PAA/P4VP complex layer while the PEG chains still stretch into the solution through the collapsed PNIPAM layer, which leads to the formation of hydrophilic channels around the PEG chains. The ibuprofen encapsulated in the hollow space can diffuse through the channels and its release rate can be controlled by changing the ratio of PEG chains to PNIPAM chains in the corona. [source] Bonding environment and electronic structure of Gd metallofullerene and Gd nanowire filled single-wall carbon nanotubesPHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 10 2008T. Pichler Abstract Being single-walled carbon nanotubes, archetypical 1D systems with peculiar anisotropic electronic properties, it is possible to infer modifications in a controlled manner by filling their inner hollow space. One successful approach was proposed for Gd, which regards filling with metallofullerenes and a successful transformation into different novelmetal nanowires by a versatile nanochemical reaction. In this contribution we report on a combined high resolution photoemission and X-ray absorption study on Gd@C82 peapods and Gd nanowires. From a detailed analysis of the Gd 4d response and the valence band in photoemission we are able to elucidate the changes in the bonding environment and charge transfer in these 1D systems. We observe a clear modification of the low energy electronic properties of the SWCNT by the filling with Gd nanowires. Our findings provide important input to understand the interplay between charge transfer and hyridisation in the nanochemical processes in these hybrid systems and to elucidate their electronic transport properties regarding their application potential in nanoelectronic devices. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Freeze-dried bone for maxillary sinus augmentation in sheepCLINICAL ORAL IMPLANTS RESEARCH, Issue 6 2002Part II: Biomechanical findings Abstract: This study examines the biomechanical loading capacity of dental implants placed in the posterior maxilla in conjunction with subantral augmentation with either homogeneous demineralized freeze-dried bone from sheep (s-DFDB) or heterogeneous demineralized freeze-dried human bone (h-DFDB) as grafting material in sheep. In 36 adult female mountain sheep, the Schneiderian membrane was elevated extraorally in both maxillary sinuses, and two titanium plasma-flame-sprayed cylindrical implants were inserted in each lateral antral wall. Three groups of 18 maxillary sinuses each were augmented with s-DFDB, h-DFDB and autogenous bone from the illiac crest, respectively. In the remaining 18 sinuses, the subantral hollow space was left empty. Pull-out tests were carried out after intervals of 12, 16 and 26 weeks. The mean pull-out force needed, irrespective of time, was 259.3 N in the empty control group, 356.7 N in the group augmented with autogenous bone, 278.1 N in the test group augmented with h-DFDB and 365.2 N in the group augmented with s-DFDB, revealing no significant difference between the individual groups (P > 0.05). The implants of the group augmented with autogenous bone showed an increase in the mean pull-out force from 223.8 N after 12 weeks to 523.7 N after 26 weeks. The nonaugmented control group yielded values of 248 N after 12 weeks, which rose to 269.8 N at the last test, while the values of the h-DFDB group increased from 275.4 N to 325.4 N. The highest initial pull-out values were obtained in the s-DFDB group. They amounted to 310.5 N after 12 weeks and rose to 481.4 N after 26 weeks. Time thus proved to have a significant influence on the pull-out forces (P = 0.014) with a statistically proven linear trend (P = 0.007). The findings of this experimental study indicate that the use of homogeneous DFDB in one-stage sinus lift procedures results in a mechanical loading capacity of implants comparable to that achieved by autogenous cancellous bone from the iliac crest. In contrast, the use of heterogenous-DFDB resulted in only slightly higher pull-out forces than those observed in the nonaugmented control group after 26 weeks. [source] | ||||||||||