Template-free synthesis and particle size control of mesoporous calcium carbonate

Controlling particle size is important in powder technology. Here we report a scalable production process of mesoporous calcium carbonate with a controllable particle size. We focus on the effect of the aggregation rate on the obtained particles. In this study, we change the particle concentration (1.2–12 mass%) to control the aggregation rate and then obtained particles with relatively narrow range of particle size (310 ± 30–560 ± 100 nm) and nearly identical specific surface areas and particle structures by template-free method. We proposed the aggregation model to describe the formation of meso-porous calcium carbonate

Morphological and Structural Changes in Microcrystalline Cellulose from OPEFB by Mechanical Grinding

Microcrystalline cellulose derived from oil palm empty fruit bunch (OPEFB) was grinded in planetary ball mill with dry state (without solvent) and solvent-assisted (ethanol and acetone). The effect of dry state and solvent-assisted on morphological and structural changes of microcrystalline cellulose were investigated. The structure changes, including particle size, powder morphology, crystalline structure, and molecular structure during the mechanical grinding were investigated by Laser Diffraction Particle Size Analyzer, SEM, XRD and FT-IR, respectively. The original fibrous microcrystalline cellulose was changed into irregular shape with finer micronized particles by dry state and solvent-assisted. SEM results showed that solvent-assisted significantly prevented the agglomeration phenomena during the grinding process, compared to dry state. The crystallinity after 4h solvent-assisted grinding showed fairly low crystallinity, while amorphous characteristic was observed with dry state grinding. The solvent-assisted led the hydrophilic parts of microcrystalline cellulose become stiff during the grinding that might be less deformed, leading to a fairly retain in crystallinity. The finer micronized particles were obtained under acetone-assisted and its crystallinity was fairly kept. XRD results indicated that crystalline form of origin microcrystalline was not changed by mechanical grinding

Soybean oil methanolysis over scallop shell-derived CaO prepared via methanol-assisted dry nano-grinding

Calcium oxides with a specific surface area between 4.5 m2g-1 and 62.5 m2g-1 were obtained by calcination of scallop shells, following by methanol-assisted dry nano-grinding. Three distinct phases are formed on the surface of these catalysts during nano-grinding: calcium methoxide, calcium hydroxide, and calcium oxide. The effects of specific surface area and active surface phase composition on the catalytic activity of calcium oxide during methanolysis of soybean oil were investigated. The properties of the calcium oxide before, during, and after methanol assisted dry nano-grinding were studied by XRD, FTIR, and nitrogen gas adsorption based on the BET method. The ground calcium oxides were found to be effective in catalyzing the methanolysis of soybean oil, with the optimal catalyst producing a 72.3% ester yield after 20 mins of reaction. The improvements in rate of reaction were attributed to the rapid formation of calcium diglyceroxide during the initial stages of methanolysis. A combination high specific surface area and effective active phases on the surface of the calcium oxide catalysts is correlated with reductions in mass transfer limitations in the early steps of the reaction, indicated by the rapid formation of calcium diglyceroxide

New Advances in iPS Cell Research Do Not Obviate the Need for Human Embryonic Stem Cells

SummaryRecently three different studies were published demonstrating that mouse fibroblast (skin) cells can be directly reprogrammed to behave like embryonic stem cells (Okita et al., 2007; Wernig et al., 2007; Maherali et al., 2007). These studies advanced a breakthrough announced last year in which a quartet of genes (Oct-3/4, Sox2, c-Myc, and Klf4) were discovered to induce pluripotency in mouse cells, albeit incompletely (Takahashi and Yamanaka, 2006). Now a second generation of these induced pluripotent stem cells (called iPS cells) has been made to do almost everything mouse embryonic stem cells can do. When mouse iPS cells were injected into mouse blastocysts, they contributed to all tissue types in the resulting adult mice, including sperm and oocytes (Okita et al., 2007; Wernig et al., 2007; Maherali et al., 2007). And one research team produced fetal mice derived entirely from iPS cells—a key criterion for embryonic stem cells (Wernig et al., 2007)

Reduction of formaldehyde emission from plywood using composite resin composed of resorcinol–formaldehyde and urea-modified scallop shell nanoparticles

More than 200,000 tons of scallop shells are disposed annually 1 alone in Japan. Nanoparticles derived from scallop shells have the potential to adsorb gaseous formaldehyde; therefore such discarded shells have now been tested as additive filler in plywood adhesive by mixing high specific surface area, urea-modified shell nanoparticles with a resorcinol?formaldehyde resin; with this procedure it was found that the emission of formaldehyde from the resulting plywood could be substantially reduced. The urea-modified scallop shell nanoparticles were prepared by two different methods: (i) by a dry method in which the shells were treated with planetary ball-grinding under ambient conditions ? a completely dried powder was obtained after addition of the surface-modifying urea solution; (ii) by a moist method by treating dry-ground shell particles in a wet grinding process with the urea solution, followed by the use of centrifugation to obtain a paste. The specific surface area of the nanoparticles obtained by both treatments was 42 ± 3 m213 /g. Measurement of the subsequent formaldehyde emission showed that the addition of the modified scallop shell nanoparticles substantially reduced the formaldehyde emission from plywood; the reduction depends from the specific mass uptake of urea on the nanoparticles which especially was the case when resins containing nanoparticles processed by the moist method were used

Gi-Coupled GPCR Signaling Controls the Formation and Organization of Human Pluripotent Colonies

BACKGROUND:Reprogramming adult human somatic cells to create human induced pluripotent stem (hiPS) cell colonies involves a dramatic morphological and organizational transition. These colonies are morphologically indistinguishable from those of pluripotent human embryonic stem (hES) cells. G protein-coupled receptors (GPCRs) are required in diverse developmental processes, but their role in pluripotent colony morphology and organization is unknown. We tested the hypothesis that G(i)-coupled GPCR signaling contributes to the characteristic morphology and organization of human pluripotent colonies. METHODOLOGY/PRINCIPAL FINDINGS:Specific and irreversible inhibition of G(i)-coupled GPCR signaling by pertussis toxin markedly altered pluripotent colony morphology. Wild-type hES and hiPS cells formed monolayer colonies, but colonies treated with pertussis toxin retracted inward, adopting a dense, multi-layered conformation. The treated colonies were unable to reform after a scratch wound insult, whereas control colonies healed completely within 48 h. In contrast, activation of an alternative GPCR pathway, G(s)-coupled signaling, with cholera toxin did not affect colony morphology or the healing response. Pertussis toxin did not alter the proliferation, apoptosis or pluripotency of pluripotent stem cells. CONCLUSIONS/SIGNIFICANCE:Experiments with pertussis toxin suggest that G(i) signaling plays a critical role in the morphology and organization of pluripotent colonies. These results may be explained by a G(i)-mediated density-sensing mechanism that propels the cells radially outward. GPCRs are a promising target for modulating the formation and organization of hiPS and hES cell colonies and may be important for understanding somatic cell reprogramming and for engineering pluripotent stem cells for therapeutic applications

Measurement and Estimation of the Particle Size Distribution by the Buoyancy Weighing-Bar Method and the Rosin-Rammler Equation

Measuring the size distribution of fine particles (<5 µm) in a few hours is difficult when using the sedimentation method due to a decrease in sedimentation rate. Herein, we discussed the validity of using a combination of the buoyancy weighing–bar method and the Rosin–Rammler equation to estimate the particle size distribution. When the cumulative mass oversize exceeds about 0.15, the Rosin–Rammler equation can be used to estimate the particle size distributions of suspended solids