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861.
Fabrication of chitosan/poly(ε-caprolactone) composite hydrogels for tissue engineering applications
Zhong X Ji C Chan AK Kazarian SG Ruys A Dehghani F 《Journal of materials science. Materials in medicine》2011,22(2):279-288
The aim of this study was to fabricate three-dimensional (3D) porous chitosan/poly(ε-caprolactone) (PCL) hydrogels with improved
mechanical properties for tissue engineering applications. A modified emulsion lyophilisation technique was developed to produce
3D chitosan/PCL hydrogels. The addition of 25 and 50 wt% of PCL into chitosan substantially enhanced the compressive strength
of composite hydrogel 160 and 290%, respectively, compared to pure chitosan hydrogel. The result of ATR–FTIR imaging corroborated
that PCL and chitosan were well mixed and physically co-existed in the composite structures. The composite hydrogels were
constructed of homogenous structure with average pore size of 59.7 ± 14 μm and finer pores with average size of 4.4 ± 2 μm
on the wall of these larger pores. The SEM and confocal laser scanning microscopy images confirmed that fibroblast cells were
attached and proliferated on the 3D structure of these composite hydrogels. The composite hydrogels acquired in this study
possessed homogeneous porous structure with improved mechanical strength and integrity. They may have a high potential for
the production of 3D hydrogels for tissue engineering applications. 相似文献
862.
Boyang Ding Maria Bardosova Martyn E. Pemble Alexander V. Korovin Ulf Peschel Sergei G. Romanov 《Advanced functional materials》2011,21(21):4182-4192
Broadband, omnidirectional, and polarization‐independent diversion has been achieved of more than 90% of the light flow intensity off its incidence direction using hybrid metal–dielectric plasmonic‐photonic heterocrystals. These architectures were prepared by depositing metal film on the interface between two photonic crystals of different parameters. The magnitude of light losses was extracted from angle‐resolved measurements of transmission and reflectance spectra. Comparing these data for different stages of constructing the complex architecture, the diffraction in colloidal crystals, the excitation and radiative decay of short‐living surface plasmon polaritons in a corrugated metal film and the eigenmode mismatch at the interface between two different photonic crystals were identified as corroborating physical mechanisms behind the light diversion. 相似文献
863.
Ron Aroshas Idan Rosenthal Adin Stern Zvia Shmul Sergei Kalabukhov Nachum Frage 《Materials and Manufacturing Processes》2015,30(1):122-126
This work reports results of silicon carbide plates, disks, pipes, and pipe–disk couples bonded by a spark plasma sintering apparatus. The joining was conducted at 1900 °C for 30 min with a 35 MPa uniaxial pressure. The samples were analyzed by Scanning acoustic microscopy, which in turn revealed a low amount of small defects at the samples’ periphery. Scanning acoustic microscopy results were verified through scanning electron microscopy and nanoindentation. It was concluded that Spark Plasma Sintering technique may serve as a valid and effective tool for diffusion bonding of high-temperature-resistant silicon carbide with different geometries. 相似文献
864.
Changes in ionic concentration and electrochemical processes in solids are invariably associated with changes in molar volume. Correspondingly, materials with mobile ions develop strain in response to applied electric bias. This electromechanical coupling mediated by mobile ions lays the foundation for the electrochemical strain microscopy (ESM) of energy storage and conversion materials. Here, we analyze the imaging and spectroscopic mechanism in ESM in the diffusion limit and discuss the similarities between ESM and macroscopic current-based electrochemical measurements. The theoretical challenges in ESM are formulated. 相似文献
865.
Yulia Plekhanova Sergei Tarasov Aleksandr Bykov Anatoly Reshetilov 《IET nanobiotechnology / IET》2019,13(3):332
This work considers the effects of various carbon nanomaterials and fibres on bioelectrocatalytic and respiratory activity of bacterial cells during the oxidation of ethanol in the presence of an electron transport mediator. Gluconobacter oxydans sbsp. industrius VKM B‐1280 cells were immobilised on the surfaces of graphite electrodes and had an adsorption contact with a nanomaterial (multi‐walled carbon nanotubes, thermally expanded graphite, highly oriented pyrolytic graphite, graphene oxide, reduced graphene oxide). The electrochemical parameters of the electrodes (the polarisation curves, the value of generated current at the introduction of substrate, the impedance characteristics) were measured in two‐electrode configuration. Modification by multi‐walled carbon nanotubes led to the increase of microbial fuel cell (MFC) electric power by 26%. The charge transfer resistance of modified electrodes was 47% lower than unmodified ones. Thermally expanded and pyrolytic graphites had a slight negative effect on the electrochemical properties of modified electrodes. The respiratory activity of bacterial cells did not change in the presence of nanomaterials. The data can be used in the development of microbial biosensors and MFC electrodes based on Gluconobacter cells.Inspec keywords: nanofabrication, catalysis, microorganisms, adsorption, charge exchange, microbial fuel cells, electrochemical electrodes, graphite, graphene, oxidation, multi‐wall carbon nanotubes, cellular biophysicsOther keywords: reduced graphene oxide, electrochemical parameters, two‐electrode configuration, multiwalled carbon nanotubes, microbial fuel cell, respiratory activity, bacterial cells, microbial biosensors, MFC electrodes, microbial living cells, electron transport mediator, graphite electrodes, adsorption contact, highly oriented pyrolytic graphite, Gluconobacter oxydans sbsp. industrius VKM B‐1280 cells, polarisation curves, bioelectrocatalytic activity, ethanol, thermally expanded graphite, charge transfer resistance, C 相似文献
866.
Michael J. Spriggs J. Mark Keil Sergei Bespamyatnikh Michael Segal Jack Snoeyink 《Algorithmica》2004,38(4):577-589
Given a set P of points in the plane,
a geometric minimum-diameter spanning tree (GMDST) of P is a
spanning tree of P such that the longest path through the
tree is minimized.
For several years, the best upper bound on the time to
compute a GMDST was cubic with respect to the
number of points in the input set.
Recently, Timothy Chan introduced a subcubic time
algorithm.
In this paper we present an algorithm
that generates a tree whose diameter is no more than (1 + )
times that of a GMDST, for any > 0.
Our algorithm reduces the problem to several grid-aligned versions of the
problem and runs within time $O(-3+ n)
and space O(n). 相似文献
867.
Sergei A. Decterov Youn-Bae Kang In-Ho Jung 《Journal of Phase Equilibria and Diffusion》2009,30(5):443-461
Computerized thermodynamic databases for solid and liquid metals, slag, and solid oxide phases in the Al2O3-CaO-CoO-CrO-Cr2O3-FeO-Fe2O3-MgO-MnO-NiO-SiO2 system (with dissolved S and P) have been developed by critical evaluation/optimization of various available phase equilibrium
and thermodynamic data. The databases contain parameters of models specifically developed for molten slags, liquid steel,
and solid oxide solutions such as spinel, pyroxenes, olivine, monoxide (wustite, periclase, lime), corundum, etc. By means
of the optimization process, model parameters are found which reproduce various thermodynamic and phase equilibrium data within
experimental error limits. Furthermore, the models permit extrapolation into regions of temperature and composition where
data are not available. The databases are automatically accessed by user-friendly software that calculates complex equilibria
involving slag, metals, refractories, and gases simultaneously, for systems with many components, over wide ranges of temperature,
oxygen potential, and pressure. A short review of the available databases is presented. The critical evaluation/optimization
procedure is outlined using the Al2O3-CaO-FeO-Fe2O3-MgO-SiO2 and Al2O3-CaO-MnO-SiO2 systems as examples. Several applications of the databases to deoxidation, dehydrogenation, and dephosphorization of iron
and to inclusion control in steel are discussed. 相似文献
868.
Benny Applebaum Sergei Artemenko Ronen Shaltiel Guang Yang 《Computational Complexity》2016,25(2):349-418
A circuit C compresses a function \({f : \{0,1\}^n\rightarrow \{0,1\}^m}\) if given an input \({x\in \{0,1\}^n}\), the circuit C can shrink x to a shorter ?-bit string x′ such that later, a computationally unbounded solver D will be able to compute f(x) based on x′. In this paper we study the existence of functions which are incompressible by circuits of some fixed polynomial size \({s=n^c}\). Motivated by cryptographic applications, we focus on average-case \({(\ell,\epsilon)}\) incompressibility, which guarantees that on a random input \({x\in \{0,1\}^n}\), for every size s circuit \({C:\{0,1\}^n\rightarrow \{0,1\}^{\ell}}\) and any unbounded solver D, the success probability \({\Pr_x[D(C(x))=f(x)]}\) is upper-bounded by \({2^{-m}+\epsilon}\). While this notion of incompressibility appeared in several works (e.g., Dubrov and Ishai, STOC 06), so far no explicit constructions of efficiently computable incompressible functions were known. In this work, we present the following results:
相似文献
- (1)Assuming that E is hard for exponential size nondeterministic circuits, we construct a polynomial time computable boolean function \({f:\{0,1\}^n\rightarrow \{0,1\}}\) which is incompressible by size n c circuits with communication \({\ell=(1-o(1)) \cdot n}\) and error \({\epsilon=n^{-c}}\). Our technique generalizes to the case of PRGs against nonboolean circuits, improving and simplifying the previous construction of Shaltiel and Artemenko (STOC 14).
- (2)We show that it is possible to achieve negligible error parameter \({\epsilon=n^{-\omega(1)}}\) for nonboolean functions. Specifically, assuming that E is hard for exponential size \({\Sigma_3}\)-circuits, we construct a nonboolean function \({f:\{0,1\}^n\rightarrow \{0,1\}^m}\) which is incompressible by size n c circuits with \({\ell=\Omega(n)}\) and extremely small \({\epsilon=n^{-c} \cdot 2^{-m}}\). Our construction combines the techniques of Trevisan and Vadhan (FOCS 00) with a new notion of relative error deterministic extractor which may be of independent interest.
- (3)We show that the task of constructing an incompressible boolean function \({f:\{0,1\}^n\rightarrow \{0,1\}}\) with negligible error parameter \({\epsilon}\) cannot be achieved by “existing proof techniques”. Namely, nondeterministic reductions (or even \({\Sigma_i}\) reductions) cannot get \({\epsilon=n^{-\omega(1)}}\) for boolean incompressible functions. Our results also apply to constructions of standard Nisan-Wigderson type PRGs and (standard) boolean functions that are hard on average, explaining, in retrospect, the limitations of existing constructions. Our impossibility result builds on an approach of Shaltiel and Viola (STOC 08).
869.
Yuan Zhou Kasun Fernando Juanyong Wan Fangze Liu Shreetu Shrestha Jeremy Tisdale Chris J. Sheehan Andrew C. Jones Sergei Tretiak Hsinhan Tsai Huihui Huang Wanyi Nie 《Advanced functional materials》2021,31(23):2101058
The chemical vapor deposition (CVD) method is a dry approach that can produce high quality crystals and thin films at large scale which can be easily adapted by industry. In this work, CVD technology is employed to grow high quality, large size all-inorganic cesium lead bromide perovskite crystalline film for the first time. The obtained films have millimeter size crystalline domains with high phase purity. The growth kinetics are examined in detail by optical microscopy and X-ray diffraction. The deposition rate and growth temperature are found to be the key parameters allowing to achieve large scale crystal growth. The large crystalline grains exhibit exceptional optical properties including negligible Stokes shift and uniform photoluminescence over a large scale. This suggests a high degree of crystallinity free from internal strain or defects. A lateral diode within one large crystalline grain is further fabricated and significant photo-generated voltage and short circuit current are observed, suggesting highly efficient carrier transport and collections without scattering within the grain. This demonstration suggests that the CVD grown all-inorganic perovskite thin films enable a promising fabrication route suitable for photovoltaic or photo-detector applications. 相似文献
870.
Mikhail Popov Boris Kulnitskiy Igor Perezhogin Vladimir Mordkovich Danila Ovsyannikov Sergei Perfilov 《Fullerenes, Nanotubes and Carbon Nanostructures》2018,26(8):465-470
The present study addresses the problems of catalytic synthesis of C60-based 3D polymers in the presence of carbon disulfide CS2. It is shown that CS2 lowers the pressure of fullerite 3D polymerization at room temperature. In particular, the pressure at which the 3D ultrahard fullerite C60 phase is formed decreases from 18 GPa to 7 GPa. The catalyst plays no significant role at room temperature and low pressures up to 6 GPa. When the C60 + CS2 is heated to 1200 K, the pressure of the 3D C60 polymerization is further reduced to 2–4 GPa. Based on the TEM data, we propose a 3D polymer structure based on C60 obtained by the catalytic synthesis. 相似文献