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71.
AbstractFirst, we give a partial solution to the isomorphism problem for uniserial modules of finite length with the help of the morphisms between these modules. Later, under suitable assumptions on the lattice of the submodules, we give a method to partially solve the isomorphism problem for uniserial modules over an arbitrary ring. Particular attention is given to the natural class of uniserial modules defined over algebras given by quivers. 相似文献
72.
Song J Kahveci D Chen M Guo Z Xie E Xu X Besenbacher F Dong M 《Langmuir : the ACS journal of surfaces and colloids》2012,28(14):6157-6162
Use of biocatalysis for industrial synthetic chemistry is on the verge of significant growth. Enzyme immobilization as an effective strategy for improving the enzyme activity has emerged from developments especially in nanoscience and nanotechnology. Here, lipase from Burkholderia cepacia (LBC), as an example of the luxuriant enzymes, was successfully encapsulated in polycaprolactone (PCL) nanofibers, proven by X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM). Evaluated in both organic and aqueous medium, the activation factor of the encapsulated enzymes in the hydrolysis reaction was generally higher than that in the transesterification reaction. Enhanced catalytic activities were found when 5-20 w/w % of LBC was loaded. The effect of different solvents pretreatment on the activity of immobilized LBC was also investigated. The highest activation factor was found up to 14 for the sample containing acetone-treated LBC/PCL (10 w/w %). The encapsulated lipase reserved 50% of its original activity after the 10th run in the transesterification reaction in hexane medium. The mechanism of activation of lipase catalytic ability based on active PCL nanofiberous matrix is proposed. 相似文献
73.
Stochastic reaction systems with discrete particle numbers are usually described by a continuous-time Markov process. Realizations
of this process can be generated with the stochastic simulation algorithm, but simulating highly reactive systems is computationally
costly because the computational work scales with the number of reaction events. We present a new approach which avoids this
drawback and increases the efficiency considerably at the cost of a small approximation error. The approach is based on the
fact that the time-dependent probability distribution associated to the Markov process is explicitly known for monomolecular,
autocatalytic and certain catalytic reaction channels. More complicated reaction systems can often be decomposed into several
parts some of which can be treated analytically. These subsystems are propagated in an alternating fashion similar to a splitting
method for ordinary differential equations. We illustrate this approach by numerical examples and prove an error bound for
the splitting error. 相似文献
74.
We describe the characterization of a new optical CO2 sensor based on the change in the fluorescence signal intensity of 8-hydroxypyrene-1,3,6-trisulfonic acid trisodium salt
(HPTS) in green chemistry reagents—room-temperature ionic liquids (RTILs). As far as we are aware, this is the first time
RTILs, 1-methyl-3-butylimidazolium tetrafluoroborate (RTIL-I) and 1-methyl-3-butylimidazolium bromide (RTIL-II), have been
used as matrix materials with HPTS in an optical CO2 sensor. It should be noted that the solubility of CO2 in water-miscible ionic liquids is approximately 10 to 20 times that in conventional solvents, polymer matrices, or water.
The response of the sensor to gaseous and dissolved CO2 has been evaluated. The luminescence intensity of HPTS at 519 and 521 nm decreased with the increasing concentrations of
CO2 by 90 and 75% in RTIL-I and RTIL-II, respectively. The response times of the sensing reagents were in the range 1–2 min for
switching from nitrogen to CO2, and 7–10 min for switching from CO2 to nitrogen. The signal changes were fully reversible and no significant hysteresis was observed during the measurements.
The stability of HPTS in RTILs was excellent and when stored in the ambient air of the laboratory there was no significant
drift in signal intensity after 7 months. Our stability tests are still in progress.
相似文献
75.
76.
Ibrahim Erol Derya Nimet Devrim Hakan Ciftci Bahri Ersoy I. Hakkı Cigerci 《高分子科学杂志,A辑:纯化学与应用化学》2017,54(7):434-445
A new methacrylate monomer 2-(4-nitrophenyl)-2-oxoethyl-2-methacrylate (NFM) was synthesized and its radical copolymerization with glycidyl methacrylate (GMA) was studied in 1,4-dioxane solution at 65°C using 2,2′-azobisisobutyronitrile as an initiator. The synthesized monomer and copolymers were characterized by FTIR, 1H and 13C-NMR spectroscopy. The analysis of reactivity ratios revealed that NFM is less reactive than GMA, and copolymers formed are statistically in nature. Thermogravimetric analysis of the polymers reveals that the thermal stability of the copolymers increases with an increasing in the mole fraction of NFM in the copolymers. Glass transition temperatures of the copolymers decreased with an increasing of NFM molar fraction in copolymers. In addition, according to the results obtained from the contact angle and zeta potential measurements the hydrophobic character of the polymer decreases (it means surface free energy increases) and its zeta potential becomes more negative with increase of NFM ratio in the copolymer. Polymers with carbonyl functional groups have been particularly interesting because of their use as photoresists. 相似文献
77.
Catalytically active and low-cost electrocatalysts for the production of hydrogen from water are extremely important for future renewable energy systems. Here, we report the fabrication of a facile pencil graphite electrode modified with polypyrrole-chitosan/Au nanoparticles and tested its performance for electrocatalytic hydrogen evolution reaction (HER) as a model process. The porous surface of the pencil graphite electrode (PGE) was modified potentiostically by polypyrrole (PPy) at various film thicknesses in the presence of chitosan (Chi), which is a natural biopolymer, in the electrolyte medium. After the optimum film thickness had been obtained, the Au particles electrodeposited on to the PPy/Chi composite film at the nano-scale to benefit both from its well-known high catalytic activity and to reduce the amount of precious metal Au to prepare a low-cost eletrocatalyst. The performance of this composite catalyst on the H+ reduction (Had formation) and thereby on the hydrogen evolution was investigated. Data from cyclic voltammetry (CV), Tafel polarization curves, and electrochemical impedance spectroscopy (EIS) demonstrated that the current densities related to the electron transfer rate changed with the thickness of the composite film, and the catalytic activity was enhanced more with deposition small amount of Au on to the catalyst surface. 相似文献
78.
Af?in Y. ?etinkaya Emre O?uz K?ro?lu Neslihan Manav Demir Derya Y?lmaz Baysoy Bestamin ?zkaya Mehmet ?akmak?? 《催化学报》2015,(7):1068-1076
Electricity production from brewery wastewater using dual-chamber microbial fuel cells (MFCs) with a tin-coated copper mesh in the anode was investigated by changing the hydraulic retention time (HRT). The MFCs were fed with wastewater samples from the inlet (inflow, MFC-1) and outlet (outflow, MFC-2) of an anaerobic digester of a brewery wastewater treatment plant. Both chemical oxygen demand removal and current density were improved by decreasing HRT. The best MFC performance was with an HRT of 0.5 d. The maximum power densities of 8.001 and 1.843 μW/cm2 were obtained from reactors MFC-1 and MFC-2, respectively. Microbial diversity at different condi-tions was studied using PCR-DGGE profiling of 16S rRNA fragments of the microorganisms from the biofilm on the anode electrode. The MFC reactor had mainlyGeobacter,Shewanella, andClostridium species, and some bacteria were easily washed out at lower HRTs. The fouling characteristics of the MFC Nafion membrane and the resulting degradation of MFC performance were examined. The ion exchange capacity, conductivity, and diffusivity of the membrane decreased significantly after foul-ing. The morphology of the Nafion membrane and MFC degradation were studied using scanning electron microscopy and attenuated total reflection-Fourier transform infrared spectroscopy. 相似文献
79.
Derya İlem-Özdemir Makbule Aşıkoğlu Hayal Özkılıç 《Journal of Radioanalytical and Nuclear Chemistry》2013,298(3):1635-1642
Since radiolabeled antibiotics specifically bind to the bacterial components they are promising radiopharmaceuticals for the precise diagnosis and detection of infectious lesions. Doxycycline hyclate (DOX) was chosen to investigate as a new radiolabeled antibacterial agent since its bacteriostatic activity against a wide variety of microorganisms. The aim of the present study is to develop simple and easy formulation of DOX with 99mTc ready to use kit. 99mTc-DOX was developed and standardized under varying conditions of reducing and antioxidant agent concentration, pH, radioactivity dose and reducing agent type. Labeling studies were performed by changing the selected parameters one by one and optimum labeling conditions were determined. After observing the conditions for maximum labeling efficiency and stability, lyophilized freeze dry kits were prepared accordingly. Radiochemical purity was determined with RTLC and RHPLC which was found more than >95 %. Two different freeze dry kits were formulated with optimum labeling conditions. The improved kits were found stable up to 6 months. 相似文献
80.
Öktem G Balan A Baran D Toppare L 《Chemical communications (Cambridge, England)》2011,47(13):3933-3935
Copolymerization towards obtaining full visible light absorption is highlighted. Randomly distributed segments of different oligomers resulted in neutral state black copolymers. Solution processability and highly transmissive gray oxidized states make copolymers great candidates to be used in low cost flexible organic electronics. 相似文献