Mechanical properties and degradation studies of poly(D,L‐lactide‐co‐glycolide) 50:50/graphene oxide nanocomposite films

Poly(D,L‐lactide‐co‐glycolide) 50:50 (PLGA)/graphene oxide (GO) nanocomposite films were prepared with various GO weight fractions. A significant enhancement of mechanical properties of the PLGA/GO nanocomposite films was obtained with GO weight fractions. The incorporation of only 5 wt% of GO resulted in an ~2.5‐fold and ~4.7‐fold increase in the tensile strength and Young's modulus of PLGA, respectively. The thermomechanical behaviors of composite films were investigated by dynamic mechanical analysis. Results indicated that the values of T_g and storage moduli of the PLGA/GO composites were higher than those of the pristine PLGA. The improvement in oxygen barrier properties of composites was presumably attributed to the filler effect of the randomly dispersed GO throughout the PLGA matrix. In this work, we also studied in vitro biodegradation behavior. PLGA/GO composite films were hydrolyzed at 37°C for periods up to 49 days. Because of the presence of GO nanosheets, degradation of composite films took place more slowly with increasing GO amounts. Copyright © 2013 John Wiley & Sons, Ltd.     

Functional Microgels Assisted Tryptic Digestion and Quantification of Cytochrome c Through Internal Standard Mass Spectrometry

Quantitation of cytochrome c (Cyt c) in cell lysates through surface-assisted laser desorption/ionization mass spectrometry (SALDI-MS) using gold nanoparticles (Au NPs) as the matrix and GR-10 peptide as an internal standard has been demonstrated. To shorten digestion time, temperature sensitive microgels containing trypsin (TR) and Au NPs have been employed. As-prepared functional microgels (TR/Au NPs/MGs) allow digestion of Cyt c within 15 s under microwave irradiation. The internal standard SALDI-MS approach provides linearity (R² = 0.98) of MS signal ratio (I _1168.6/I _1067.6) of the tryptic digested peptide (m/z 1168.6) to GR-10 peptide (m/z 1067.6) against the concentration of Cyt c ranging from 25 to 200 nM, with a limit of detection (at a signal-to-noise ratio of 3) of 10 nM. This approach has been validated by the analysis of the lysates of HeLa cells, with an average concentration of 13.7?±?3.5 μM for cytoplasmic Cyt c. Increased concentrations of Cyt c in the HeLa cells treated with etoposide (a commercial drug) or carbon dots (potential drug) have been revealed through this simple, sensitive, and rapid SALDI-MS approach, supporting the drugs induced Cyt c-mediated apoptosis of the cells. This study has shown that this internal standard SALDI-MS approach holds great potential for cell study. Graphical Abstract

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Therapeutic effect of hepatocyte growth factor-secreting mesenchymal stem cells in a rat model of liver fibrosis

Bone marrow-derived mesenchymal stromal cells (MSCs) have been reported to be beneficial for the treatment of liver fibrosis. Here, we investigated the use of genetically engineered MSCs that overexpress hepatocyte growth factor (HGF) as a means to improve their therapeutic effect in liver fibrosis. Liver fibrosis was induced by intraperitoneal injection of dimethylnitrosamine. HGF-secreting MSCs (MSCs/HGF) were prepared by transducing MSCs with an adenovirus carrying HGF-encoding cDNA. MSCs or MSCs/HGF were injected directly into the spleen of fibrotic rats. Tissue fibrosis was assessed by histological analysis 12 days after stem cell injection. Although treatment with MSCs reduced fibrosis, treatment with MSCs/HGF produced a more significant reduction and was associated with elevated HGF levels in the portal vein. Collagen levels in the liver extract were decreased after MSC/HGF therapy, suggesting recovery from fibrosis. Furthermore, liver function was improved in animals receiving MSCs/HGF, indicating that MSC/HGF therapy resulted not only in reduction of liver fibrosis but also in improvement of hepatocyte function. Assessment of cell and biochemical parameters revealed that mRNA levels of the fibrogenic cytokines PDGF-bb and TGF-β1 were significantly decreased after MSC/HGF therapy. Subsequent to the decrease in collagen, expression of matrix metalloprotease-9 (MMP-9), MMP-13, MMP-14 and urokinase-type plasminogen activator was augmented following MSC/HGF, whereas tissue inhibitor of metalloprotease-1 (TIMP-1) expression was reduced. In conclusion, therapy with MSCs/HGF resulted in an improved therapeutic effect compared with MSCs alone, probably because of the anti-fibrotic activity of HGF. Thus, MSC/HGF represents a promising approach toward a cell therapy for liver fibrosis.     

Highly Ordered Superlattices from Self-assembly of Fe3O4 Nanocrystals

The nano materials often exhibit very interesting electrical, optical, magnetic, and chemical properties, which can not be achieved by their bulk counterparts. The development of uniform nanometer sized particles has been intensively pursued because of their technological and fundamental scientific importance. It is significant that nanostructured materials can be controllably assembled into the required geometry onto substrates, becoming the basis of the next generation of components and devices. The development of new methods and strategies for organizing the nanoparticle basic building blocks into the desired structures is required. Superlattices made from these building blocks give us the opportunity to study not only the properties of the individual building blocks, but also collective effects. The superparamagnetic iron oxide nanocrystals（NCs） have been used in the fields of bio-medicine, ferrofluids, refrigeration system, catalysis,     

身临其境 无拘无束——自由立体显示技术

 从2009 年底立体电影《阿凡达》在全球同步上映以来, 人们对立体影像的热情被迅速点燃, 《诸神之战》、《爱丽丝梦游仙境》等各类立体影视作品相继推出；美国男子职业篮球联赛（NBA）、南非世界杯以及多项体育赛事也纷纷采用立体转播以吸引眼球；中外各大显示器制造商如夏普、三星、索尼、维度（DTI）、海信、TCL 等更是大力推出各种可以播放立体影像的显示终端, 甚至各大手机厂商也纷纷开始研制立体手机。伴随着与立体相关的显示终端制造、片源设计、信号传输等一系列产业的迅速兴起, 人们不禁惊呼：属于立体显示的时代终于到来了。     

Dose verification of volumetric modulation arc therapy by using a NIPAM gel dosimeter combined with a parallel-beam optical computed tomography scanner

Volumetric modulated arc therapy (VMAT) was developed to shorten treatment time and increase target conformance. However, a true three-dimensional (3D) gel dosimeter is needed for dose verification. In this study, two clinic cases were adopted: a simple case of lung cancer and a complex case of larynx cancer. For each clinic case, two treatment plans were generated for the same planning target volume using VMAT and intensity modulated radiation therapy calculation software packages. An N-isopropylacrylamide (NIPAM) polymer gel dosimeter was used for 3D dose verification. In addition, the dose characteristics of the NIPAM gel dosimeter were investigated for the two clinic cases.

     

α-Arylation and Ring Expansion of Annulated Cyclobutanones: Stereoselective Synthesis of Functionalized Tetralones

α-Arylcyclobutanones display unique reactivity that makes them valuable synthetic intermediates and target molecules. We describe the preparation of α-aryl- and α-heteroarylcyclobutanones through a direct α-arylation reaction. Problematic fragmentations are avoided by the use of LiO^tBu, which promotes a rapid but reversible self-aldol reaction that slowly releases the enolate required for α-arylation. We also demonstrate the ring expansion of α-arylcyclobutanones, a process that is highlighted in the stereoselective synthesis of 1-methoxy coniothyrinone D.     

Further results on stabilization of neural-network-based systems using sampled-data control

Nonlinear Dynamics - This paper investigates the problem of stabilization for sampled-data neural-network-based systems under variable sampling. A novel Lyapunov–Krasovskii functional (LKF)...     

Structural rearrangement and stiffening of hydrophobically modified supramolecular hydrogels during thermal annealing

Dynamic crosslinks formed by thermoreversible associations provide an energy dissipation mechanism to toughen hydrogels. However, the details of the organization of these crosslinks impact the hydrogel properties through constraints on the network chain conformation. The physical crosslinks generated by hydrophobic association of the 2‐(N‐ethylperfluorooctane‐sulfonamido)ethyl methacrylate (FOSM) groups in a random copolymer of N,N‐dimethylacrylamide (DMA) and FOSM provide a simple system to investigate how the hydrogel structure (as determined from small angle neutron scattering impacts the mechanical properties of the hydrogel. The initial hydration of the copolymer at 25 °C leads to a kinetically trapped structure with large‐scale heterogeneities. Heating the hydrogel at 60 °C, which is above the glass transition temperature for the FOSM domains, allows the hydrogel structure to rearrange to reduce the density of network defects and the structural heterogeneities. That effectively increases the crosslink density of the network, which stiffens the hydrogel and decreases the swelling at equilibrium at 25 °C. The processing history determines how the hydrophobes aggregate to form the physically crosslinked network, whose structure defines the mechanical properties of these hydrogels. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2017 , 55, 1036–1044     

Software lens compensation applied to athermalization of infrared imaging systems

A different approach, aiming to achieve the constant blur status of point-spread function (PSF) at a certain defocused plane, is described. The correlation between the two PSF is used to control the PSF blur similarity, and simultaneously the Strehl ratio is also used to control the PSF blur minimization. By designing the PSF so that it is significantly insensitive to defocus or related defocus quantity, for example, due to temperature change, all the constantly blurred images can be accurately de-blurred by a simple inverse restoration filter for an adequate range of defocus. We refer to that as “software lens compensation” and apply a design method to solve the athermalization of middle wavelength infrared (MWIR) imaging systems. The resultant PSF is almost invariant in the temperature range from −10 to 50°C at the same focal plane. Consequently, the constant blur spot can be removed by a simple digital signal processing. Thus, clear and sharp de-blurred images at different temperatures are obtained.