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ABSTRACT: Electrospun scaffolds are widely used in tissue engineering; however, a common problem is the poor cell infiltration because of the small pore size and tightly packed structure of these fibrous scaffolds. To address this issue, a novel technique was developed to fabricate electrospun silk fibroin (SF) scaffolds with rather macropores and high porosity using electrospraying-generated PEO microparticles as porogen. The morphology and pore size of MPES scaffolds were evaluated by scanning electron microscopy. It was revealed that MPES scaffold had a relatively loose structure with an increase of mean pore size (i.e., approx. 30 μm of MPES vs. approx. 5 μm of traditional electrospun scaffolds (TES) and porosity (i.e., 95% vs. 84% of TES). Culture of mouse 3T3 fibroblast in TES and MPES scaffold revealed that both scaffolds could support cell attachment, spread and proliferation. Yet, cell inflitration in vitro under the static culture condition only occurred in the MPES scaffold. Subcutaneous implantation of scaffolds in rats further confirmed that the tissue ingrowth was more efficient in the MPES scaffold compared to TES scaffold. Thus, the use of PEO microparticles as porogen was a feasible and effective method for creating macroporous electrospun SF scaffold, which provided an alternative to address the limitation of cell infiltration associated with electrospun fibrous scaffold. © 2013 Wiley Periodicals, Inc. J Biomed Mater Res Part A, 2013.
Journal of Biomedical Materials Research Part A 04/2013; · 2.63 Impact Factor
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ABSTRACT: By taking the Tarim Basin, Sichuan Basin and Ordos Basin as examples, the conditions for deep marine reservoir formation were
illustrated in three aspects listed below: late-stage superimposition style, burial history and structural deformation of
the marine stratigraphic system. The burial history of marine source rocks can be divided into three types, i.e., type I,
type II and type III, which are obviously different from the case with present hydrocarbon phases in terms of hydrocarbon
generation and petroleum-reservoir formation. Based on evolution history, the structural belts in the marine stratigraphic
sequence can also be divided into four types, i.e. earlier normal fault-later fault-fold type, earlier uplift-later fault-fold
type, earlier uplift-later flattened slope type, and earlier depression-later thrust type. In this paper, a successive gas
generation model was proposed, and it was particularly pointed out that coupling of geothermal field annealing evolution and
tectonic subsidence and late gas generation from dispersed liquid hydrocarbon in highly matured to over-matured source rocks
are key factors for formation of marine petroleum reservoirs. The geological conditions for formation of high-grade reservoirs
in deep marine system, covering early hydrocarbon injection, deep denudation and buried dolomitization, were summarized. It
was finally concluded that three major structural belts, i.e. paleo-uplift belt characterized by composite hydrocarbon accumulation,
paleo-fault belt and high-energy sedimentary facies belt, were involved in marine hydrocarbon accumulation.
Chinese Science Bulletin 05/2012; 52:12-27. · 1.32 Impact Factor
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ABSTRACT: Kinetic experiments of gas generation for typical samples of marine gas precursors including low-maturity kerogen, residual
kerogen and oil as well as dispersed liquid hydrocarbon (DLH) in source rocks were performed by closed system, and the evolution
trends of molecular and isotopic compositions of natural gases from different precursors against the maturity (R
0%) at laboratory conditions were analyzed. Several diagrams of gas origin were calibrated by using the experimental data.
A diagram based on the ratio of normal and isomerous butane and pentane (i/nC4 − i/nC5) was proposed and used to identify the origins of the typical marine natural gases in the Sichuan Basin and the Tarim Basin,
China. And the maturities of natural gases were estimated by using the statistical relationships between the gaseous molecular
carbon isotopic data and maturities (δ13C-R
0%) with different origins. The results indicate that the molecular and isotopic compositions of simulated gases from different
precursors are different from each other. For example, the dryness index of the oil-cracking gas is the lowest; the dryness
indices of gases from DLH and kerogen in closed system are almost the same; and the dryness index of gases from residual kerogen
is extremely high, indicating that the kerogen gases are very dry; the contents of non-hydrocarbon gases in kerogen-cracking
gases are far higher than those in oil-cracking and DLH-cracking gases. The molecular carbon isotopes of oil-cracking gases
are the lightest, those of kerogen in closed system and GLH-cracking gases are the second lightest, and those of cracking
gases from residual kerogen are the heaviest. The calibration results indicate that the diagrams of In(C1/C2)-In(C2/C3) and δ4
3C2-δ4
3C3-In(C2/C3) can discriminate primary and secondary cracking gases, but cannot be used to identify gas origin sources, while the diagram
of i/nC4 − i/nC5 can differentiate the gases from different precursors. The application results of these diagrams show that gas mixtures extensively
exist in China, which involved the gases from multiple precursors and those from different maturity stages. For example, marine
gases in the Sichuan Basin involve the mixture of oil-cracking gases and high-over-maturated kerogen gases, while those in
the Tarim Basin involve not only the mixture of gases from multiple precursors, but also those from different maturity gases
and post-reservoir alternations such as oxidized degradation and gas intrusion processes.
Science in China Series D Earth Sciences 04/2012; 51:148-164. · 1.59 Impact Factor
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ABSTRACT: The potentials of gas generation by kerogen in the late period and by crude oil cracking are closely related to the origin
of natural gas in the high-to over mature marine area and their exploration perspectives. The carbon structure of kerogens,
with different types and at different evolution stages, have been experimentally studied using the high magnetic field solid13C nuclear magnetic resonance technique in order to determine the oil and gas potential of kerogens. Results show that the
contents of gas potential carbon(GPC) of types I, II, III kerogens at the high-to over mature stage are very low, indicating
their weak gas-generating capacity and limited gas production; however, the content of oil potential carbon(OPC) of the low
mature type I kerogen is much higher, implying that a large amount of crude oil generated during the oil-generating period
will be the material for later gas generation by oil cracking. The kinetic experiment of gas generation by crude oil cracking
shows that, when the temperature is about 160°C (Ro=l.6%), the crude oil will start to produce large amounts of gas; the temperature range for major gas generation of crude
oil is higher than that of the kerogens, and the gas production is 2 to 4 times higher than that of kerogens. The natural
gas derived from oil cracking (called oil-cracked gas) is much abundant in methyl hexamethylene, which is quite different
from the natural gas produced by thermal degradation of kerogens (named kerogen degradation gas) at high-to over mature stage.
Keywordsoil-cracked gas-kerogen degradation gas-hydrocarbon-generating matrix structure-solid13C nuclear magnetic reso-nance-oil potential carbon-gas potential carbon
Chinese Science Bulletin 04/2012; 50(22):2628-2635. · 1.32 Impact Factor
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ABSTRACT: Incorporation of gene into electrospun nanofibers for localized gene transfection of target cells represents a robust platform for tissue regeneration. In this study, a new two-step approach was explored to immobilize DNA onto electrospun nanofibers for effective gene delivery, that is, nonviral gene vector of polyethylene glycol (PEG)-modified polyethylenimine (PEI) was incorporated into scaffolds by electrospinning and then target DNA was adsorbed onto the electrospun nanofibers via electrostatic interaction between DNA and PEI-PEG. PEI-PEG/DNA particles formed from the released DNA, and PEI-PEG had a uniform particle size of approximately 200 nm. This nanofiber-based gene delivery system exhibited high transfection efficiency, in which >65% of human embryonic kidney 293 cells and >40% of mesenchymal stem cells were transfected with green fluorescent protein gene. Compared with PEI, PEG modification of PEI had improved the biocompatibility and further increased the transfection efficiency. These results suggest that the combination of nonviral gene carrier with electrospun nanofibers could be used for localized gene delivery, which has multifold potential applications in tissue engineering or as an in vivo substrate for tissue regeneration.
Journal of Biomedical Materials Research Part A 01/2011; 96(1):212-20. · 2.63 Impact Factor
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ABSTRACT: Acquired or congenital abnormalities may lead to urethral damage or loss, often requiring surgical reconstruction. Urethrocutaneous fistula and strictures are common complications, due to inadequate blood supply. Thus, adequate blood supply is a key factor for successful urethral tissue reconstruction. In this study, urethral grafts were prepared by seeding rabbit bladder urothelial cells (UCs) modified with human vascular endothelial growth factor (VEGF(165)) gene in the decellularized artery matrix. A retroviral pMSCV-VEGF(165)-GFP vector was cloned by insertion of VEGF open reading frame into the vector pMSCV-GFP (murine stem cell virus [MSCV]; green fluorescent protein [GFP]). Retrovirus was generated using package cell line 293T. Rabbit UCs were expanded ex vivo and modified with either MSCV-VEGF(165)-GFP or control MSCV-GFP retrovirus. Transduction efficiency was analyzed by fluorescence-activated cell sorting. The expression of VEGF(165) was examined by immunofluorescence, reverse transcript-polymerase chain reaction, Western blot, and enzyme-linked immunosorbent assay (ELISA). Decellularized rabbit artery matrix was seeded with genetically modified UCs and was subsequently cultured for 1 week prior to subcutaneous implantation into nude mice. Four weeks after implantation, the implants were harvested and analyzed by fluorescence microscopy, and by histologic and immunohistochemical staining. Ex vivo transduction efficiency of UCs was greater than 50% when concentrated retrovirus was used. The modified cells expressed both VEGF and GFP protein. Furthermore, the VEGF-modified UCs secreted VEGF in a time-dependent manner. Scanning electron microscopy and histochemical analysis of cross sections of the cultured urethral grafts showed that the seeded cells were attached and proliferated on the luminal surface of the decellularized artery matrix. In the subcutaneously implanted vessels, VEGF-modified cells significantly enhanced neovascularization and the formation of a urethral layer compared to GFP-modified cells. These results indicate that VEGF gene therapy may be a suitable approach to increase the blood supply in tissue engineering for treatment of urethral damage or loss.
Artificial Organs 03/2008; 32(2):91-9. · 2.00 Impact Factor
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ABSTRACT: Bone marrow mesenchymal stem cells (MSCs) have demonstrated their pluripotency to differentiate into different cell lineages and may be an alternative cell source for vascular tissue engineering. The objective of this study is to create small diameter vessels by seeding and culture of genetically modified MSCs onto a synthetic polymer scaffold produced by an electrospinning technique. A tubular scaffold (2 mm in diameter) with a microstructure of nonwoven fibers was produced by electrospinning of poly (propylene carbonate) (PPC). Rat MSCs obtained from bone marrow were expanded in culture and modified with vasculoprotective gene endothelial nitric oxide synthase (eNOS) or marker gene green fluorescent protein (GFP). These MSCs were seeded onto the electrospun fibrous grafts (internal diameter = 2 mm), and cultured in 5% CO(2) at 37 degrees C. The growth of MSCs in the scaffold was analyzed with scanning electron microscopy (SEM) and hematoxylin and eosin (H&E) staining. The gene transfer and transgenic gene expression were examined with fluorescence-activated cell sorting (FACS), immunochemical staining, reverse transcriptase-polymerase chain reaction (RT-PCR), and western blot. The production of nitric oxide (NO) by the engineered vessels was measured with an NO detection kit. Our data showed that the seeded cells integrated with the microfibers of the scaffold to form a three-dimensional cellular network, indicating a favorable interaction between this synthetic PPC scaffold with MSCs. High transduction efficiency was obtained with the use of concentrated retrovirus in the gene transfection of MSCs. The eNOS gene transcripts and protein were detected in the grafts seeded with eNOS-modified MSCs by RT-PCR and immunochemical staining. The amount of NO produced by grafts seeded with eNOS-modified MSCs was comparable to that produced by native blood vessels, and it was significantly higher than that in the grafts seeded with nonmodified MSCs. In summary, the vascular graft produced by culture of eNOS gene-modified MSCs onto the electrospun tubular scaffolds shows promising results in terms of function. The use of MSCs and therapeutic genes in tissue engineering of blood vessels could be helpful in improving vessel regeneration and patency.
Artificial Organs 12/2006; 30(12):898-905. · 2.00 Impact Factor
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ABSTRACT: By breaking through the conventional ideology on the study of gas-formation mechanism of source rocks which focused on merely
the characteristics of source rocks themselves, and based on the development and distribution characteristics of marine carbonate
source rocks in the medium-to-bottom parts of the Chinese superimposed sedimentary basins as well as various processes in
the course of gas generation and reservoir forming, the complex hydrocarbon-generating model of carbonates is established.
Such a model concerns not only the “three-stage” gas formation characteristics of carbonates, but also the gas generation
process due to a thermal cracking of oil and the re-generation process of gas from heated secondary organic matters during
the gas-generation and reservoir-forming course. The high-quality hydrocarbon generating matter of marine carbonate source
rocks determined a high gas-oil ratio and tended to form paleo-oil-reservoirs, representing an enrichment process of organic
matters. The thermal cracking of oil in palaeo-oil-reservoirs is an important means for the effective formation of gas reservoirs.
The secondary organic matters in carbonate reservoirs may regenerate gas after a secondary deep burial, thus becoming an effective
gas source.
Science in China Series D Earth Sciences 01/2005; 48(4):441-453. · 1.59 Impact Factor
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ABSTRACT: A catalyst of Rh nanoparticles supported on a carbon nanofiber, 5 wt.% Rh/CNF, with an average size of 2–3 nm has been prepared by a method of incipient wetness impregnation. The catalyst presented a high activity in the ring hydrogenation of phenol in a medium of supercritical CO2 (scCO2) at a low temperature of 323 K. The presence of compressed CO2 retards hydrogenation of cyclohexanone to cyclohexanol under the reaction conditions used, and this is beneficial for the formation of cyclohexanone, increasing the selectivity to cyclohexanone. But the selectivity to cyclohexanone is very low at the completion of reaction in the absence of CO2, at low CO2 pressures, and in the presence of pressurized N2 instead of CO2. That is, high selectivity to cyclohexanone can be achieved with CO2 species at higher pressures but not with the application of an inert hydrostatic pressure on the liquid substrate phase.
Catalysis Communications.
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ABSTRACT: The thermal stability of Paleozoic oil in eastern Tarim Basin, NW China was investigated through laboratory kinetic simulation experiments. Laboratory cracking of a selected marine oil sample from Ordovician strata in well LG-1 of Tarim Basin was performed by confined, dry pyrolysis system at T = 300–650 °C, P = 50 MPa. Results indicated the oil required higher temperature for cracking. At laboratory heating rates, oil cracking started at 390–400 °C and the laboratory cracking was completed at around 650 °C. At geological heating rates, the onset temperature is about 148–162 °C for cracking start and was completed at 245–276 °C. The oil-cracking history was recovered using the acquired kinetic parameters and the geothermal history of TD-2, and the threshold temperature for oil cracking under geological conditions was calculated. The oil cracking started at 165 °C (Ro = 1.45%) and stopped in early Devonian (390 Ma), and the oil-cracking rates in the strata of -O1 reached 60–70% at the end of Silurian. The calculated oil generation and oil cracking windows overlapped to some extent and were completed rapidly. The possible geological controls for the occurrence of residual oil reservoirs in Eastern Tarim basin have been discussed, including the high stability of the Paleozoic oil in Tarim Basin, the fast heating rate and longer duration time for oil cracking, the slight biodegradation in later uplift, the good preservation of the paleo-reservoirs and the moderate structural adjustment, which were critical for the exploration of residual oil and gases in this area.
Organic Geochemistry.
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ABSTRACT: A β-cyclodextrin resin supported by partially aminated polyacrylamide was synthesized from porous polyacrylamide. The adsorption of bilirubin on the polymeric β-cyclodextrin was investigated in 0.01 M phosphate buffer (pH = 7.4) at 37°C in different conditions with various temperature, pH value, bilirubin concentration and ionic strength, etc. The results indicated that the polymeric β-cyclodextrin was a good adsorbent for unconjugated bilirubin with high capacity.
Reactive and Functional Polymers.
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ABSTRACT: The selective hydrogenation of cinnamaldehyde (CAL) was investigated using rice husk-based porous carbon (RHCs) supported platinum catalysts in supercritical carbon dioxide (scCO2). The effects of surface chemistry treatment of the support and the reaction phase behavior have been examined. The Pt/H–RHCs (HNO3-pretreated) was more active for CAL hydrogenation compared with Pt/NH3–RHCs (NH3 · H2O-pretreated). The Pt/RHCs catalyst exhibited a higher selectivity to cinnamyl alcohol (COL) compared with commercial catalyst of Pt/C, which is relative to the micro–mesoporosity structure of the RHCs. Under the reaction conditions, the product distribution changes markedly with the variation of the phase behavior. A higher selectivity to hydrocinnamyl alcohol of 90% was obtained in two-phase reaction system of CO2–riched gas phase (CO2, H2, dissolved cinnamaldehyde) and solid phase (catalyst); while, the main product changed to cinnamyl alcohol with a selectivity of 88% in three-phase reaction system of CO2–riched gas phase (CO2, H2, dissolved cinnamaldehyde), cinnamaldehyde–riched liquid phase (cinnamaldehyde, dissolved CO2 and H2) and solid phase (catalyst). It is attributed to the influence of the molecule interactions and the substrate concentration effects.
Catalysis Communications.
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ABSTRACT: An efficient enantioselective catalyst of 5 wt.% Ru/γ-Al2O3 modified with R,R-1,2-diphenylethylene-diamine ((R,R)-DPEN) for the hydrogenation of a non-activated aromatic ketone of acetophenone has been investigated, a relatively high enantiomeric excess (ee) of 60.5% was obtained at both the conversion and selectivity larger than 99%, it was about three times higher than the ee values reported up to now for acetophenone hydrogenation with the supported transition metal catalysts modified by chiral reagents. The influences of some reaction parameters such as phosphine ligand, substrate/catalyst/modifier molar ratios, base, solvent, pressure and reaction temperature have been discussed. The chiral modifier of (R,R)-DPEN was very important in controlling the enantioselectivity through adsorption competing with other substrates on the surface of active metal species. The phosphine ligand and base were also important and indispensable in the present reaction.Graphical abstractA higher ee value of 60.5% has been obtained for enantioselective hydrogenation of acetophenone with a 5 wt.% Ru/γ-Al2O3 catalyst modified by R,R-1,2-diphenylethylene-diamine and phosphine ligand.
Journal of Molecular Catalysis A Chemical 278:6-11. · 2.95 Impact Factor
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ABSTRACT: Nickel appears the most promising for the replacement of palladium among the inexpensive transition metals for that it is active for Heck reaction and about 500 times cheaper than palladium. In this article, we describe our recent results in the area of nickel-catalyzed Heck vinylations. Main focus is on the influence of ligand concentration in different organic solvents and the effects of the addition of water. The conversion is high in NMP and increases with increasing of PPh3/Ni ratio; in ethanol and toluene the conversion presents a maximum value on Ni(PPh3)2. The effect of the addition of water is sensitive to the concentration of PPh3 and the nature of solvent, it was well explained with the formation and transfer of the active species in the different solvent systems.Graphical abstractNickel appears the most promising for the replacement of palladium among the inexpensive transition metals, the effect of the addition of water is sensitive to the concentration of PPh3 and the nature of solvent in nickel-catalyzed Heck reactions.
Journal of Molecular Catalysis A Chemical 248:17-20. · 2.95 Impact Factor
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ABSTRACT: We show strong and weak convergence for Mann iteration of multivalued nonexpansive mappings T in a Banach space. Furthermore, we give a strong convergence of the modified Mann iteration which is independent of the convergence of the implicit anchor-like continuous path zt∈tu+(1−t)Tzt.
Nonlinear Analysis: Theory, Methods & Applications.
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ABSTRACT: Finger vein is a promising biometric pattern for personal identification in terms of its security and convenience. However, so residual information, such as shade produced by various thicknesses of the finger muscles, bones, and tissue networks surrounding the vein, are also captured in the infrared images of finger vein. Meanwhile, the pose variation of the finger may also cause failure to recognition. In this paper, for the first time, we address this problem by unifying manifold learning and point manifold distance concept. The experiments based on the TED-FV database demonstrate that the proposed algorithmic framework is robust and effective.
Journal of Network and Computer Applications.
