共查询到20条相似文献,搜索用时 15 毫秒
1.
Weifeng Dai Yan Zhang Zhengzhen Du Minliang Ru Meidong Lang 《Journal of materials science. Materials in medicine》2010,21(6):1881-1890
The macromonomer of 2-hydroxyethyl methyacrylate-caprolactone (HPCL) was synthesized by the ring-opening polymerization (ROP) of ε-caprolactone, which was initiated by 2-hydroxyethyl methyacrylate (HEMA). Then, the graft terpolymers of NIPAAm-co-AAc-co-HEMA-g-PCL (PHNA-CL) with varying mole ratios were subsequently synthesized by free radical polymerization of HEMA-PCL, N-isopropylacrylamide (NIPAAm) and acrylic acid (AAc). PHNA-CL was further self-assembled in different types of solvent. All the as-prepared copolymers were characterized by 1H NMR, FT-IR and GPC. Micellization behaviors of micelles were studied by TEM and DLS. The micelles exhibited a phase transition temperature which can be readily adjusted by changing pH value of the micellization system. Micelle loaded with doxorubicin (DOX) was used to evaluate the drug release behavior. The release of DOX from micelles could be controlled by changing pH value and temperature in buffer solutions. The micelles are potentially to be used as a new anticancer drug carrier for intracellular delivery. 相似文献
2.
In recent times, polymer-layered silicate nanocomposites have drawn a great deal of attention because they often exhibit tremendous
improvements in material properties compared with virgin polymers or conventional micro- or macro-composites. In the present
study, nanocomposites were developed from organically modified clay and poly(ethylene-co-vinyl acetate-co-carbon monoxide) by melt mixing. FTIR spectroscopy reveals that the interaction between the organoclay and EVACO is thermodynamically
favored. High resolution wide angle X-ray diffraction and transmission electron microscopy were used to study the morphology
of the nanocomposites. Elemental mapping by scanning electron microscopy indicates good dispersion and distribution of the
nanoclay in EVACO matrix. The mechanical properties of the nanocomposites are optimum at a clay loading of 3%. 相似文献
3.
Poly (d,l-lactide-co-glycolide) (PLGA) copolymers are among the few synthetic polymers approved for human use, but the biocompatibility of PLGA-derived
oligomers and particles remains questionable. Here, high molecular weight PLGA (Mw = 32,000) was radiolabeled with 125I in chloroform solution, and the body distribution of PLGA copolymer degradation products was examined following subcutaneous
implantation of round 125I-PLGA films on the back of Sprague Dawley rats. Autoradiographic images of the PLGA implant taken at 2, 4, 6, 8, 10, and
12 weeks revealed that the central portion of the film degraded much more rapidly than the marginal portions. Examination
of the body compartment distribution at these time points revealed that over one-half of the radioactivity was recovered from
skin. The remaining radioactivity was concentrated in the blood, liver, and kidneys. Radioactivity steadily appeared in the
blood and remained elevated up to 12 weeks after implantation, while the liver to kidney distribution began to decrease after
6 weeks. Cumulatively, these results indicate that the clearance of degraded particles and fragments from the implantation
site is extremely delayed. Moreover, the degraded particles and fragments were selectively concentrated in the liver and kidneys,
following release of degraded products into the bloodstream from the implantation site. 相似文献
4.
JINGLONG LI QIN PENG ANRONG ZENG JUNLIN LI XIAOLE WU XIAOFEI LIU 《Bulletin of Materials Science》2016,39(1):109-117
Jute fibres-reinforced sandwich regenerated composite panels were fabricated using industrial waste thermosetting styrene-co-acrylonitrile (SAN) foam scraps via compression moulding for the purpose of recycling waste SAN foam and obtaining high physical performance. The jute fibres were, respectively, treated by heat, sodium hydroxide (NaOH) solution (5.0 wt%), and N,N-dimethylacetamide (DMAc) in order to improve the mechanical properties of the composites. The structures and mechanical properties of the composites were studied. The SAN matrix got compact and some crystalline region formed in SAN matrix via compression moulding. The composite reinforced by DMAc-treated jute fibres performed optimum mechanical properties among the regenerated panels whose impact strength, flexural strength, and compressive strength were 19.9 kJ m?2, 41.7 MPa, and 61.0 MPa, respectively. Good interfacial bonding between DMAc-treated fibres and SAN matrix was verified by peel test and exhibited in SEM photographs. Besides, the water absorption of DMAc-treated fibres composite was lower than other SAN/jute fibre-reinforced sandwich composite panels. 相似文献
5.
Petra J. Kluger Ralf Wyrwa Jürgen Weisser Julia Maierle Miriam Votteler Claudia Rode Matthias Schnabelrauch Heike Walles Katja Schenke-Layland 《Journal of materials science. Materials in medicine》2010,21(9):2665-2671
Electrospinning is a long-known polymer processing technique that has received more interest and attention in recent years
due to its versatility and potential use in the field of biomedical research. The fabrication of three-dimensional (3D) electrospun
matrices for drug delivery and tissue engineering is of particular interest. In the present study, we identified optimal conditions
to generate novel electrospun polymeric scaffolds composed of poly-d/l-lactide and poly-l-lactide in the ratio 50:50. Scanning electron microscopic analyses revealed that the generated poly(d/l-lactide-co-l-lactide) electrospun hybrid microfibers possessed a unique porous high surface area mimicking native extracellular matrix
(ECM). To assess cytocompatibility, we isolated dermal fibroblasts from human skin biopsies. After 5 days of in vitro culture,
the fibroblasts adhered, migrated and proliferated on the newly created 3D scaffolds. Our data demonstrate the applicability
of electrospun poly(d/l-lactide-co-l-lactide) scaffolds to serve as substrates for regenerative medicine applications with special focus on skin tissue engineering. 相似文献
6.
Mukherjee S Gualandi C Focarete ML Ravichandran R Venugopal JR Raghunath M Ramakrishna S 《Journal of materials science. Materials in medicine》2011,22(7):1689-1699
In myocardial tissue engineering the use of synthetically bioengineered flexible patches implanted in the infarcted area is
considered one of the promising strategy for cardiac repair. In this work the potentialities of a biomimetic electrospun scaffold
made of a commercial copolymer of (l)-lactic acid with trimethylene carbonate (P(l)LA-co-TMC) are investigated in comparison to electrospun poly(l)lactic acid. The P(l)LA-co-TMC scaffold used in this work is a glassy rigid material at room temperature while it is a rubbery soft material at 37°C.
Mechanical characterization results (tensile stress–strain and creep-recovery measurements) show that at 37°C electrospun
P(l)LA-co-TMC displays an elastic modulus of around 20 MPa and the ability to completely recover up to 10% of deformation. Cell culture
experiments show that P(l)LA-co-TMC scaffold promotes cardiomyocyte proliferation and efficiently preserve cell morphology, without hampering expression
of sarcomeric alpha actinin marker, thus demonstrating its potentialities as synthetic biomaterial for myocardial tissue engineering. 相似文献
7.
S. L. Liu 《Journal of Superconductivity and Novel Magnetism》2008,21(3):199-203
Based on the Arrhenius equation, a method to calculate the activation energy from the resistance transition is proposed for
high temperature superconductors. This method is applied to the Y-based superconductors. The activation energy is found to
be U(T,H)∼(1−T/T
c
)4.8(H/H
0)−3.8 of YBCO crystal, and U(T,H)∼(1−T/T
c
)3.3(H/H
0)−2.2 of Er doped MTG YBCO crystal, respectively. With the obtained activation energy U(T,H), the lower part of the experimental curve ρ(T,H) and its derivative can be reproduced.
相似文献
8.
A. P. Astakhova B. E. Zhurtanov A. N. Imenkov M. P. Mikhailova M. A. Sipovskaya N. D. Stoyanov Yu. P. Yakovlev 《Technical Physics Letters》2007,33(1):11-13
Photodiodes sensitive in the wavelength ranges 1–2.5 μm and 1–4.8 μm at room temperature have been created on the basis of n-GaSb/n-GaInAsSb/p-AlGaAsSb double-junction heterostructures of two types. The broadband photosensitivity of the diode structures of both types is indicative of the complete separation of photogenerated electron-hole pairs in the staggered n-p heterojunction (n-GaInAsSb/p-AlGaAsSb). The noise characteristics of photodetectors based on the proposed diode structures have been studied. Prospects of the use of these devices in thermophotovoltaic cells for low-temperature radiation sources are considered. 相似文献
9.
N. L. Bazhenov B. E. Zhurtanov K. D. Mynbaev A. P. Astakhova A. N. Imenkov M. P. Mikhaĭlova V. A. Smirnov N. D. Stoyanov Yu. P. Yakovlev 《Technical Physics Letters》2007,33(12):987-989
We have studied electroluminescence in n-GaSb/n-AlGaAsSb/n-GaInAsSb heterostructures with isotype heterojunctions, in which the quantum efficiency of emission is increased due to the additional production of electron-hole pairs as a result of the impact ionization that takes place near the heterointerface. The impact ionization in such heterostructures is possible due to the presence of deep wells in the energy band structure. 相似文献
10.
11.
T. S. Khasanshin V. S. Samuilov A. P. Shchemelev 《Journal of Engineering Physics and Thermophysics》2008,81(4):760-765
This paper describes an improved experimental facility for measuring the speed of sound in liquids with an accuracy of up
to 0.1%. Measurements of the speed of sound in liquid n-hexane, n-octane, n-decane, and n-hexadecane at temperatures of 298–433
K and pressures of 0.1–100 MPa have been made. It has been shown that in the possible comparison range the obtained values
of the speed of sound are in good agreement with the literature data.
Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 81, No. 4, pp. 732–736, July–August, 2008. 相似文献
12.
Biopharmaceuticals, including proteins, DNAs, and RNAs, hold vast promise for the treatment of many disorders, such as cancer, diabetes, autoimmune diseases, infectious diseases, and rare diseases. The application of biopharmaceuticals, however, is limited by their poor stability, immunogenicity, suboptimal pharmacokinetic performance, undesired tissue distribution, and low penetration through biological barriers. In situ polymerization provides an appealing and promising platform to improve the pharmacological characteristics of biopharmaceuticals. Instead of the traditional “grafting to” polymer–biomolecule conjugation, in situ polymerization grows polymers on the surfaces of the biomacromolecules, resulting in easier purification procedures, high conjugation yields, and unique structures. Herein, this review surveys recent advances in the polymerization methodologies. Additionally, we further review improved therapeutic performance of the resultant nanomedicines. Finally, the opportunities, as well as the challenges, of these nanocomposites in the biomedical fields are discussed. 相似文献
13.
A system with n independent components which works if and only if a least k of its n components work is called a k-out-of-n system. For exponentially distributed component lifetimes, we obtain point and interval estimators for the scale parameter of the component lifetime distribution of a k-out-of-n system when the system failure time is observed only. In particular, we prove that the maximum likelihood estimator (MLE) of the scale parameter based on progressively Type-II censored system lifetimes is unique. Further, we propose a fixed-point iteration procedure to compute the MLE for k-out-of-n systems data. In addition, we illustrate that the Newton–Raphson method does not converge for any initial value. Finally, exact confidence intervals for the scale parameter are constructed based on progressively Type-II censored system lifetimes. 相似文献
14.
V VASUDEVAN R RAMESH BABU A REICHER NELCY G BHAGAVANNARAYANA K RAMAMURTHI 《Bulletin of Materials Science》2011,34(3):469-475
Semi-organic nonlinear optical material, L-lysine L-lysinium dichloride nitrate (2C6H15N2O2+_{2}^{+} · H + · NO3-_{3}^{-} · 2Cl − ) was synthesized at room temperature. Single crystals of L-LLDN were grown by slow cooling solution growth technique. The grown crystal was confirmed by powder X-ray diffraction analysis.
The crystalline perfection of the grown single crystal was characterized by high-resolution X-ray diffraction (HRXRD) studies.
The cut-off wavelength was determined by UV-vis transmission spectral analysis. The frequency doubling of the grown crystal
was confirmed by powder second harmonic generation (SHG) measurement. The refractive index and birefringence of the crystal
were determined using He–Ne laser source. Mechanical property of the crystal was determined by Vickers hardness tester. The
frequency and temperature dependence of dielectric constant (ε
r), dielectric loss (tan δ) and a.c. conductivity (σ
ac) were also measured. 相似文献
15.
G. A. Il’chuk S. E. Nikitin Yu. A. Nikolaev V. Yu. Rud’ Yu. V. Rud’ E. I. Terukov 《Technical Physics Letters》2004,30(11):967-969
Photosensitive structures of the n-ZnO:Al/CoPc/p-Si type were synthesized for the first time using vacuum sublimation of cobalt phthalocyanine (CoPc) and magnetron sputtering of a ZnO:Al target. The maximum photoresponse is observed when the structure is illuminated from the side of the ZnO layer and amounts to ?400 V/W at T = 300 K. Mechanisms of current transfer and peculiarities of the photosensitivity spectrum are considered. It is suggested that the new photosensitive structures can be used in multiband photoconverters of natural radiation with a broad working spectral range. 相似文献
16.
I. V. Rogozin A. N. Georgobiani M. B. Kotlyarevsky V. I. Demin A. V. Marakhovskii 《Inorganic Materials》2010,46(9):948-952
n-Type ZnO〈Ga〉 films were implanted with 150-keV N+ (As+) ions to a dose of 7 × 1015 cm−2 and then annealed in atomic oxygen at different temperatures. p-Type conductivity was obtained at annealing temperatures in the range 770–870 K. The parameters of the p-type layers were determined by photoluminescence spectroscopy, secondary ion mass spectrometry, and Hall effect measurements.
According to the Hall data, the p-type layers had a resistivity of ∼30 Ω cm, carrier mobility of ∼2 cm2/(V s), and carrier concentration of ∼1018 cm−3. The electroluminescence spectra of the p-n junctions produced by ion implantation showed a band at 440 nm, due to recombination via donor-acceptor pairs. 相似文献
17.
Naiyan Zhang Mingzhu Liu Yueguo Shen Jun Chen Liangliang Dai Chunmei Gao 《Journal of Materials Science》2011,46(5):1523-1534
In this paper, a series of semi-interpenetrating polymer network (semi-IPN) hydrogels based on poly((2-dimethylamino)ethyl
methacrylate)/poly (N,N-diethylacrylamide) (PDMAEMA/PDEA) were synthesized by changing the initial PDMAEMA/DEA molar ratio at room temperature. The
influence of this additive on the property of resulting PDEA hydrogels was investigated and characterized. The interior morphology
by scanning electron microscopy (SEM) revealed that the semi-IPN hydrogels have interconnected porous network structures.
The glass transition temperature (T
g) of the semi-IPN hydrogels was observed by differential scanning calorimetry (DSC). Equilibrium swelling ratio (ESR), swelling
and deswelling dynamics of the hydrogels responding to temperature and pH were investigated in detail. Compared to PDEA, the
semi-IPN hydrogels exhibited excellent mutative values in response to an alternation of the temperature and pH, and showed
fast swelling and deswelling rates in response to temperature and pH change. The release behaviors of the model drug, aminophylline,
were found dependent on hydrogel compositions and environmental temperature. These results suggest that the stimuli semi-IPN
hydrogel have potential application as intelligent drug carriers. 相似文献
18.
V. R. Shayapov M. L. Kosinova A. P. Smirnov E. A. Maksimovskii B. M. Ayupov Yu. M. Rumyantsev 《Inorganic Materials》2011,47(3):262-266
Boron carbonitride (BC
x
N
y
) films of different compositions have been grown by low-pressure chemical vapor deposition using triethylamine borane as
a single-source precursor and ammonia as an additional nitrogen source. Experiments were performed at various initial vapor
compositions. The resultant films have been characterized by ellipsometry, IR spectroscopy, energy dispersive X-ray spectroscopy,
scanning electron microscopy, nanoindentation, and surface acoustic wave spectroscopy. The mechanical properties of the films
are shown to correlate with their density and chemical composition. With increasing initial ammonia partial pressure in the
vapor phase, the elemental composition of the films moves away from boron carbide, approaching boron nitride, which is accompanied
by a reduction in the Young’s modulus, hardness, and density of the films. 相似文献
19.
A. L. Ivanovskii 《Journal of Superhard Materials》2011,33(2):73-87
The state of the art in the search for novel superhard and (or) incompressible materials on the basis of higher borides of
s, p, d metals has been briefly reviewed. The information has been considered about experimental and theoretical studies of the following
groups of borides: diborides of 4d, 5d heavy metals (Tc, Ru, Rh, Re, Os, and Ir), hexagonal tetraborides with the WB4-type structure, and AMB14 borides (where A, M are s, p metals) as well as of a number of related systems. 相似文献
20.
The time-dependent Ginzburg–Landau equation with thermal noise is used to calculate the Nernst signal e
N
, describing the Nernst effect, in type-II superconductor in the vortex-liquid regime. The Gaussian method used is an elaboration
of the Hartree–Fock method. An additional assumption often made in analytical calculations that only the lowest Landau level
significantly contributes to physical quantities of interest in the high-field limit is lifted by including all the Landau
levels. The values of e
N
are in good quantitative agreement with experimental data for temperature close to T
c
on Bi2Sr2CaCu2O8+δ
and Bi2Sr2Ca2Cu3O10+δ
. 相似文献