105 research outputs found
Synthesis of Thermal Polymerizable Alginate-GMA Hydrogel for Cell Encapsulation
No full textAlginate is a negative ionic polysaccharide that is found abundantly in nature. Calciumis usually used as a cross-linker for alginate. However, calcium cross-linked alginate is used only for in vitro culture. In the present work, alginate was modified with glycidyl methacrylate (GMA) to produce a thermal polymerizable alginate-GMA (AA-GMA) macromonomer. The molecular structure and methacrylation (%DM) of the macromonomer were determined by H-1 NMR. After mixing with the correct amount of initiator, the AA-GMA aqueous solution can be polymerized at physiological temperature. The AA-GMA hydrogels exhibited a three-dimensional porous structure with an average pore size ranging from 50 to 200 mu m, directly depending on the macromonomer concentration. Biocompatibility of the AA-GMA hydrogel was determined by in vivo muscle injection and cell encapsulation. Muscle injection in vivo showed that the AA-GMA solution mixed with initiator could form a hydrogel in situ and had a mild inflammatory effect. Human umbilical vein endothelial cells (HUVECs) were encapsulated in the AA-GMA hydrogels in situ at 37 degrees C. Cell viability and proliferation were unaffected by macromonomer concentrations, which suggests that AA-GMA has a potential application in the field of tissue engineering, especially for myocardial repair.National Basic Research Program of China [2012CB933903]SCI(E)[email protected]
Development of new diacrylate monomers as substitutes for Bis-GMA and UDMA
No full textObjective. Bisphenol A-glycidyl methacrylate (Bis-GMA) and urethane dimethacrylate (UDMA) are widely used as the primary components of (meth)acrylic monomers. However, the use of Bis-GMA, which is a bisphenol A derivative, in dentistry is being questioned after bisphenol A was found to exhibit estrogenic activity. Although UDMA is being considered as a substitute for bis-GMA, the mechanical properties of cured resin composites containing UDMA are less than desirable. Therefore, in this study, we developed new alternative (meth)acrylic monomers to enhance the mechanical strength of cured composite resins. Methods. Five urethane acrylic monomers were synthesized in this study as (meth)acrylic monomer substituents to replace Bis-GMA and UDMA. The elastic modulus, strength, and breaking energy values of cured resins consisting of mixtures of the urethane acrylates and diluting monomers were determined using the three-point flexural test. The data obtained were analyzed using one-way ANOVA and the post-hoc Tukey HSD tests (p < 0.05). Viscosities of the urethane acrylic monomers were measured with a cone-plate viscometer. Refractive indices of the urethane acrylic monomers were determined with an Abbe refractometer. Results. The results of the three-point flexural tests revealed that the cured urethane acrylic monomer-based resin exhibited higher elastic modulus (up to 40%) and strength (up to 21%) compared to the cured UDMA-based resin. Viscosity and refractive index of the urethane acrylic monomers were between those of UDMA and Bis-GMA. Significance. The developed urethane diacrylates prepared from diisocyanates which have an aromatic or aliphatic ring, 1,3-bis(1-isocyanato-1-methylethyl)benzene (TMXDI), 1,3-bis(isocyanatomethyl)benzene (XDI), or norbornane diisocyanate (NBDI) are worth considering as alternative options of Bis-GMA and UDMA for restorative resin composites. (c) 2021 The Academy of Dental Materials. Published by Elsevier Inc. All rights reserved
GMA-PSMH: A semantic metadata publish-harvest protocol for dynamic metadata management under grid environment
No full textThe imperative demand on the description of semantic metadata and the processing of real-time data presents unique challenge to Grid Metadata Service. Grid Monitoring Architecture (GMA), which is a framework for dynamic data management, is limited by its conventional interface of relational database and therefore fails to address the problem of interoperability. Faced with the problem of metadata publishing in GMA, we present a new publish-harvest protocol for semantic metadata called GMA-PSMH (Grid Monitoring Architecture-Protocol for Semantic Metadata Harvesting) by modifying the OAI-PMH metadata, harvest framework. As part of the Semantic Metadata Service Project in Peking University, the associated dynamic metadata. management framework is then implemented according to the above protocol. At the end, we make the conclusion and overview the future work,Computer Science, Information SystemsComputer Science, Theory & MethodsSCI(E)CPCI-S(ISTP)
Achieving aerospace standard porosity levels when welding thin and thick-section aluminium using fibre-delivered lasers : executive summary
No full textEnvironmental and commercial pressures have forced the aerospace industry to look at
alternatives to riveting for the manufacture of aluminium aircraft structures. This resulted, at
the end of last century, in an extensive study by Airbus into the possiblities of using CO2
lasers, which led to the process being implemented for a (small) number of stringer-to-skin
fuselage panels in the newer Airbus models. Since this initial commercial success, new laser
sources have become available that are more suitable for the welding of aluminium than CO2
lasers, in the form of Nd: YAG and Yb-fibre lasers. Both produce a wavelength that is
absorbed more efficiently by aluminium alloys than the CO2 laser wavelength, resulting in an
improved keyhole stability, as demonstrated in the late nineties for Nd: YAG lasers. In addition,
Yb-fibre lasers have become available at output powers higher than available for Nd: YAG
lasers, allowing thicker sections of aluminium to be welded in a single pass. However, despite
their claimed advantages, no efforts were made to demonstrate the potential of these lasers
for (aluminium) aircraft manufacture. For this reason, the author initiated a series of studies in
2001, with the overall aim to develop procedures to laser weld both thin (3.2mm) and thicksection
(12.7mm) aerospace aluminium alloys using these fibre-delivered lasers to a weld
quality, in particular related to weld metal porosity, suitable for aerospace service. The focus
in this research was on weld metal porosity, because this is a particular problem when laser
welding aluminium, either in the form of fine (hydrogen) porosity or larger porosity associated
with an unstable keyhole behaviour. The benchmark weld metal porosity for this study was
obtained from the stringent weld quality classes defined in BS EN 13919-2 and AWS D17.1.
The approach to this research was in three parts, with work in the first aimed at demonstrating
that a 3kW Nd: YAG laser was capable of producing low-porosity welds in 3.2mm thickness
2024 aluminium alloy, and thus can be considered for replacing the CO2 laser currently used
for the stringer-to-skin fuselage application. Prior to the final part of the research, in which a
7kW Yb-fibre laser was used to demonstrate that these benchmark porosity levels could also
be achieved in thicker section (aerospace-grade) aluminium, a comparison study was carried
out to quantify the difference in welding performance between the Nd: YAG and the Yb-fibre
laser. At an output power of 4kW focused in a 0.4mm diameter spot, the Yb-fibre laser was
capable of a 30% higher welding speeds in 4mm (5083) aluminium alloy, or a 20% increase in
depth of penetration for welding speeds between 1 and 15m/min, compared with the Nd: YAG
laser. This improvement in welding performance, together with an output power of 7W,
produced full penetration in 12.7mm thickness (aerospace-grade) AI-Zn-Mg-Cu aluminium
alloy using the Yb-fibre laser autogenously, or in a hybrid configuration with a MIG arc. Both
the autogenous laser and hybrid laser-MIG process were capable of producing welds with a
weld metal porosity in line with the BS EN 13919-2 and AWS D17.1 benchmark conditions, at
welding speeds of 0.55 and 0.75m/min, respectively. At these production rates, the 248
metres of stringer incorporated in a typical aluminium wing structure can be welded in 7.5 and
5.5 hours, in case of autogenous laser and hybrid laser-MIG, respectively, compared with
37.6 hours currently needed for the riveting process
Improved performance of Bis-GMA/TEGDMA dental composites by net-like structures formed from SiO2 nanofiber fillers
No full textThe major objective of this study was to explore the effects of silicon dioxide (SiO2) nanofibers on the performance of 2, 2-bis-[4-(methacryloxypropoxy)-phenyl]-propane (Bis-GMA)/tri-(ethyleneglycol) dimethacrylate (TEGDMA) dental composites. At first, the mechanical properties of Bis-GMA/TEGDMA (50/50, w/w) resins containing different contents of SiO2 nanofibers were evaluated to identify the appropriate composition to achieve the significant reinforcing effect. Secondly, optimized contents (5 or 10 wt.%) of SiO2 nanofibers were mixed into resins together with SiO2 microparticles, which was 60 wt.% of the resin. Controls for comparison were Bis-GMA/TEGDMA resins containing only SiO2 microparticles (60 wt.%) or with additional SiO2 nanoparticles (5 or 10 wt.%). Properties including abrasion, polymerization shrinkage and mechanical properties were evaluated to determine the contribution of SiO2 nanofibers. In comparison with SiO2 nanoparticles, SiO2 nanofibers improved the overall performance of Bis-GMA/TEGDMA composite resins, especially in improving abrasion resistance and decreasing polymerization shrinkage. The explanations were that one-dimensional SiO2 nanofibers were able to shield particular fillers from being abraded off, and able to form a kind of overlapped fibrous network to resist polymerization shrinkage. With these approaches, SiO2 nanofiber-containing Bis-GMA composite resins were envisioned a promising choice to achieve long-term durable restorations in clinical therapies. (C) 2 015 Elsevier B.V. All rights reserved.National Natural Science Foundation of China [51373016, 81425007]; Beijing Municipal Science & Technology Commission [Z121100005212007]; Beijing Municipal Commission of Education [ZDZH20141001001]SCI(E)[email protected]; [email protected]
Novel multifunctional chitosan-GMA-IDA-Cu(II) nanospheres for high dynamic range characterization of the human plasma proteome
No full textIn this study, we describe characterization of the human plasma proteome based on analysis with multifunctional chitosan-GMA-IDA-Cu(II) nanospheres. Chitosan-GMA-IDA-Cu(II) nanospheres with diameters of 20 to 100 nm have unique properties due to multifunctional chemical moieties, high surface area, high capacity, good dispersibility in buffer solution as well as good biocompatibility and chemical stability which improves their specific interaction with peptides and proteins of the human plasma using different binding buffers. Combining these chitosan-GMA-IDA-Cu(II) nanospheres with MS spectrometry results in a novel strategy which should make it possible to characterize the plasma proteome in a single test. Peptides and proteins adsorbed on the nanosphere can be directly detected by MALDI-TOF-MS. The eluted lower molecular weight peptides and proteins are identified by nano-LC-ESI-MS/MS. A total of 842 unique LMW peptides and 1,682 human unredundant proteins IDs were identified in two different binding buffers, which included relatively low-level proteins (e.g., pg/mL of IL3 Interleukin-3) co-distributed with high-abundance proteins (e.g., 35-55 mg/mL level serum albumin). As such, this nanosphere technique selectively enabled the identification of proteins over a dynamic range of greater than 8 orders of magnitude. Considering this capacity for selective enrichment of peptides and proteins in human plasma, and the large number of LMW peptides and proteins which can be identified, this method promises to accelerate discovery of biomarkers for clinical application.http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=WOS:000289297000018&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=8e1609b174ce4e31116a60747a720701Biochemical Research MethodsChemistry, AnalyticalSCI(E)EIPubMed7ARTICLE3747-75640
Impact of interpass temperature on the microstructure and mechanical properties of super duplex stainless steel in CW-GMA additive manufacturing
No full textThis study investigates the influence of interpass temperature (IPT) on microstructure evolution and mechanical properties of super duplex stainless steel (SDSS) manufactured by cold wire gas metal arc (CW-GMA) additive manufacturing. Thermal cycle analysis showed that cooling rates were not significantly affected by IPT under constant process parameters. However, higher IPTs resulted in higher thermal accumulation and extended exposure to elevated temperatures. Microstructural characterisation revealed the transformation of δ-ferrite grains into various austenitic phases and secondary chromium nitrides during cooling. Fine, needle-like secondary austenite formation was more pronounced at higher IPTs, driven by chromium nitride precipitation near layer transitions. Mechanical testing demonstrated consistent ultimate tensile strength around 810 MPa across IPTs, with ductility variations attributed to porosity. Hardness profiles were uniform, averaging approximately 300 Hv. These findings suggest that while IPT influences thermal accumulation and microstructural details, its effect on ferrite-to-austenite ratio and mechanical properties is minimal. Optimising IPT remains essential for increasing the productivity of SDSS in CW-GMA additive manufacturing.The author expresses gratitude to Christof Group SBN for initiating the project and providing financial support.Journal of Manufacturing Processe
NOBODY LIED / (When they said that I cried over you.) / Words by / KARYL NORMAN / & HYATT BERRY. / Music by / EDWIN J. WEBER:
No full textBox no. 1This item has been bound together with items gma-doc-00524 and gma-doc-00034.Edwin J. Weber: Nobody Lied; music printItem type: book | Content type: music and text | Writing material: pencil | Counting of pages: page numbersvocal-instrumental score | staff notation; tonic sol-fa | voice; piano"I have wander'd my whole life through [...]
PINKIE. / "The Flapper Song." / Fox-Trot Song. / Words by / HERBERT W. WEISE . / Music by / WILLIAM F. CAESAR.
No full textBox no. 1After page 2 an unknow number of pages is missing.This item has been bound together with items gma-doc-00525 and gma-doc-00524.William F. Cesar: Pinkie. "The Flapper Song."; music printItem type: book | Content type: music and text | Counting of pages: page numbersVocal-instrumental score | staff notation; tonic sol-fa | voice; piano"Pinkie Perkins is the cutest flapper in our town [...]
- …
