Synthesis and characterization of microencapsulated dicyclopentadiene with melamine–formaldehyde resins

Microcapsules containing healing agents have been used to develop the self-healing polymeric composites. These microcapsules must possess special properties such as appropriate strength and stability in surrounding medium. A new series of microcapsules containing dicyclopentadiene (DCPD) with melamine–formaldehyde (MF) resin as shell material were synthesized by in situ polymerization technology. These microcapsules may satisfy the requirements for self-healing polymeric composites. The chemical structure of microcapsule was identified by using Fourier transform infrared (FTIR) spectrometer. The morphology of microcapsule was observed by using optical microscope (OM) and scanning electron microscope. Size distribution and mean diameter of microcapsules were determined with OM. The thermal properties of microcapsules were investigated by using thermogravimetric analysis and differential scanning calorimetry. Additionally, the self-healing efficiency was evaluated. The results indicate that the poly(melamine–formaldehyde) (PMF) microcapsules containing DCPD have been synthesized successfully, and their mean diameters fall in the range of 65.2∼202.0 μm when the adjusting agitation rate varies from 150 to 500 rpm. Increasing the surfactant concentration can decrease the diameters of microcapsules. The prepared microcapsules are thermally stable up to 69 °C. The PMF microcapsules containing DCPD can be applied to polymeric composites to fabricate the self-healing composites.     

Preparation of Small Particle Sized ZnAl-Hydrotalcite-Like Compounds by Ultrasonic Crystallization

Ultrasonic technology has been intensively studied recently due to its special features. In this paper, an ultrasonic crystallization method was introduced for the preparation of ZnAl-Hydrotalcite-Like compounds (ZnAl-HTLcs). Samples with high crystallinity, small particle size and narrow particle size distribution were obtained and fully characterized using conventional techniques of XRD, FT-IR and TGDTA. The results prove that both ultrasonic frequency and ultrasonic power have effects on the sizes of the product particles. By varying the ultrasonic power from 250 W to 88 W, with the ultrasonic frequency fixed at 59 kHz, the median particle size of the samples increased from 0.37 μm to 0.82 μm. By altering the hydrothermal treatment time from 1 h to 5 h at 110℃, the median particle size of ZnAl-HTLcs synthesized via ultrasonic crystallization increased from 0.88 μm to 1.11 μm.     

Exciton interactions in CdS nanocrystal aggregates in reverse micelle

Here we report the formation and spectroscopic properties of cadmium sulfide (CdS) nanocrystal systems: individual nanocrystal and CdS aggregates. The optical absorption and luminescence spectra of the aggregated CdS nanocrystals and individual nanocrystal show exciton aggregate and individual exciton characteristics. Although it is not Bose-Einstein condensation, such aggregated quantum dots (QDs) seem to supply us opportunity to study the interactions and condensation of excitons in multi-QDs system, not in the separated QDs system.     

Effect of drug-loading methods on drug load, encapsulation efficiency and release properties of alginate/poly-L-arginine/chitosan ternary complex microcapsules

The drug-loaded alginate/poly-L-arginine/chitosan ternary complex microcapsules were prepared by mixing method, absorption method and the combined method of mixing and absorption, respectively. The effect of drug-loading methods on drug load, the encapsulation efficiency and the release properties of the complex microcapsules were investigated. The results showed that the absorption process is a dominating factor to greatly increase the drug load of Hb into microcapsules. Upon loading Hb into microcapsules by combined method of mixing and absorption, the drug load (19.9%) is up to the maximum value, and the encapsulation efficiency is 93.8%. Moreover, the drug release is a zero-order kinetics process for the ternary complex microcapsules made by mixing. For the complex microcapsules made by absorption, the drug release is a first-order kinetics. However, for the complex microcapsules made by combining the mixing and the absorption, the drug release obeys a first-order kinetics during the first eighteen hours, changing afterwards to a zero-order kinetics process. Effect of drug-loading methods on drug load and encapsulation efficiency of alginate/poly-L-arginine/chitosan ternary complex microcapsules.     

CURING KINETICS AND PROPERTIES OF ACRYLIC RESIN CURED WITH AZIRIDINE CROSSLINKER

A kind of aziridine crosslinkers was synthesized and used to crosslink acrylate copolymers. The crosslinkingproperties and curing kinetics of the resin were studied. It was found that with the increase of the content of crosslinker in theemulsion, the mechanical properties and solvent resistance of the resin will be apparently improved, but its glass transitiontemperature (T_g) is very low. The lowest amount of crosslinker used in the acrylic resin emulsion is 0.25%. Curing kineticsstudied by DSC show that this curing reaction occurs readily because the apparent activation energy of the reaction is low(65.1 kJ/mol). These results demonstrate that the aziridine crosslinker is indeed a low temperature crosslinking agent and canbe used at room temperature.     

A new method for the quantitation of aflatoxin M1 in urine by high performance liquid chromatography and its application to the etiologic study of hepatoma

A high performance liquid chromatographic (HPLC) method for the analysis of aflatoxin M1 (AFM1) in urine is described. Urine samples were treated with saturated lead acetate and AFM1 was extracted with chloroform. After washing with water to remove impurities the compound was derivatized with trifluoroacetic acid and the AFM1 derivative was analyzed quantitatively by HPLC. The sample pretreatment is simple and more selective. A good line correlation between AFM1 peak height and its concentration was obtained when AFM1 content was in the range of 50-400 pg. The ratio of recovery was 87.42%. Sensitivity is 0.01 ppb. The method is applicable to trace analysis. Results in urine of residents who live in the high/low liver cancer incidence area in Fushui county were the same as that of previous epidemiological investigation.     

Unexpected differences in the alpha-halogenation and related reactivity of sulfones with perhaloalkanes in KOH-t-BuOH

Most alkyl phenyl sulfones are readily alpha-chlorinated with CCl(4) and alpha-brominated with CBrCl3 in KOH-t-BuOH via radical-anion radical pair (RARP) reactions. While isopropyl mesityl sulfone (4) is easily alpha-chlorinated with CCl(4), it was completely recovered when treated with the more reactive CBrCl3. Subsequent investigations showed the latter result to be due to the poor acidity of 4 together with the rapid depletion of CBrCl3 and KOH by their reaction with each other, and led to a variety of other important results. 4-Hydroxyphenyl isopropyl sulfone (6) is unreactive with either CCl4 or CBrCl3 in KOH-t-BuOH, its phenoxide anion strongly reducing the electronegativity of the sulfonyl group, thereby inhibiting alpha-anion formation. This effect is reversed by the electron-withdrawing influence of two alpha-phenyls, so that benzhydryl 4-hydroxyphenyl sulfone (8) is readily alpha-halogenated in KOH-t-BuOH with CCl4 or CBrCl3. On further contact with KOH-t-BuOH the alpha-halogenated sulfones from 8 are decomposed into benzophenone and phenol. While the alpha-halogenated derivatives of 4-methoxyphenyl benzhydryl sulfone (9) are stable to base, they are decomposed even under mildly acidic conditions into 4-methoxyphenyl 4-methoxybenzenethiolsulfonate (9c), phenol, and benzophenone. Mono-alpha-halogenation of benzyl phenyl sulfone (10) enhances the rate of the subsequent halogenation, so that alpha,alpha-dihalogenation is attained while much substrate is still present and the mono-alpha-halogenated product is not detected. The ease of reductive debromination of alpha-bromo sulfones with Cl3C- was correlated with the stability of the formed alpha-anions, explaining the success with alpha-bromobenzylic sulfones but failure with alpha-bromoalkyl sulfones. In the presence of air and the absence of competing halogenation, formation of the alpha-anions of alkyl aryl sulfones is quickly accompanied by oxidative cleavage by atmospheric O2, leading to the formation of arenesulfonyl alcohols, arenesulfonyl halides, and haloarenes.     

Surface-enhanced Raman scattering (SERS) from different azobenzene self-assembled monolayers and sandwiches

Self-assembled monolayers (SAMs) of functionalized azobenzene thiols (RAzoCnSH, n=3-6 for R=H, abbreviated as AzoCnSH; and n=4 for R=CH(3)CONH, abbreviated as aaAzoC4SH) on different substrates RAzoCnSz.sbnd;z.sfnc;S (S represents substrates of vacuum-deposited gold (Au), silver foil (Ag), HNO(3) etched silver foil (EAg), and silver mirror (mAg)) have been studied by SERS in the near-infrared region. SERS of the SAMs on EAg and/or mAg exhibit SERS effects that vary with etching time and/or deposition time. The most appropriate time is 5 s for etching in 1:1 HNO(3) and 40 s for deposition in 0.1 M Ag(NH(3))(2)NO(3). Further, a layer of Ag mirror was conveniently deposited on the top of the SAMs on different substrates, yielding a more efficient SERS-active system possessing a "sandwiched" structure of mAgz.sfnc;RAzoCnS-z.sfnc;S. An appropriate surface roughness is required for the strongest SERS effect. Scanning electron microscopy (SEM) indicates that there exist a large number of projects around 100 nm on the surface showing the strongest SERS effect. When the surface roughness is decreased or increased, the SERS effect decreases sharply. The relationship between the SERS effect and the structural nature was investigated and showed that the enhancement factor decays exponentially with increasing in distances of the azobenzene group from the underlying substrate or the overlying silver mirror. This result reveals that the SERS effect may be the result of the electromagnetic coupling effect between two metal layers.     

Dexmedetomidine promotes the progression of hepatocellular carcinoma through hepatic stellate cell activation

Dexmedetomidine (DEX) is an anesthetic that is widely used in the clinic, and it has been reported to exhibit paradoxical effects in the progression of multiple solid tumors. In this study, we sought to explore the mechanism by which DEX regulates hepatocellular carcinoma (HCC) progression underlying liver fibrosis. We determined the effects of DEX on tumor progression in an orthotopic HCC mouse model of fibrotic liver. A coculture system and a subcutaneous xenograft model involving coimplantation of mouse hepatoma cells (H22) and primary activated hepatic stellate cells (aHSCs) were used to study the effects of DEX on HCC progression. We found that in the preclinical mouse model of liver fibrosis, DEX treatment significantly shortened median survival time and promoted tumor growth, intrahepatic metastasis and pulmonary metastasis. The DEX receptor (ADRA2A) was mainly expressed in aHSCs but was barely detected in HCC cells. DEX dramatically reinforced HCC malignant behaviors in the presence of aHSCs in both the coculture system and the coimplantation mouse model, but DEX alone exerted no significant effects on the malignancy of HCC. Mechanistically, DEX induced IL-6 secretion from aHSCs and promoted HCC progression via STAT3 activation. Our findings provide evidence that the clinical application of DEX may cause undesirable side effects in HCC patients with liver fibrosis.Subject terms: Cancer microenvironment, Cell growth