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排序方式: 共有163条查询结果,搜索用时 906 毫秒
61.
Lee JW Park JA Lee JJ Bae SJ Lee SH Jung JC Kim MN Lee J Woo S Chang Y 《Magnetic resonance imaging》2007,25(5):652-656
Recent studies have demonstrated the use of manganese ion (Mn2+)) as an in vivo neuronal tract tracer. In contrast to histological approaches, manganese tracing can be performed repeatedly on the same living animal. In this study, we describe the neuroaxonal tracing of the auditory pathway in the living guinea pig, relying on the fact that Mn2+ ion enters excitable cells through voltage-gated calcium channels and is an excellent MRI paramagnetic tract-tracing agent. Small focal injections of Mn2+ ion into the cochlea produced significant contrast enhancement along the known neuronal circuitry. This in vivo approach, allowing repeated measures, is expected to open new vistas to study auditory physiology and to provide new insights on in vivo axonal transport and neuronal activity in the central auditory system. 相似文献
62.
Substituted 3-hydroxy-delta-lactones (3HLs) are valuable intermediates in the synthesis of pharmaceuticals and other biologically active natural products. Herein we report the first example of the catalytic carbonylation of substituted homoglycidols to 3HLs using HCo(CO)4. Upon optimization of the catalyst and reaction conditions, a functionally diverse set of 3HLs was prepared. Mechanistic insight was gained by observation of the carbonylation reaction using in situ IR spectroscopy, and we propose a mechanism that is consistent with previously studied epoxide carbonylation systems. 相似文献
63.
Rezaei F Joh LD Kashima H Reddy AP VanderGheynst JS 《Applied biochemistry and biotechnology》2011,164(6):793-803
Solid-state fermentation has been widely used for enzyme production. However, secreted enzymes often bind to the solid substrate
preventing their detection and recovery. A series of screening studies was performed to examine the role of extraction buffer
composition including NaCl, ethylene glycol, sodium acetate buffer, and Tween 80, on xylanase and cellulase recovery from
switchgrass. Our results indicated that the selection of an extraction buffer is highly dependent on the nature and source
of the enzyme being extracted. While a buffer containing 50 mM sodium acetate at pH 5 was found to have a positive effect
on the recovery of commercial fungal-derived cellulase and xylanase amended to switchgrass, the same buffer had a significant
negative effect on enzyme extraction from solid fermentation samples colonized by the bacterium Acidothermus cellulolyticus. Xylanase activity was more affected by components in the extraction buffers compared to cellulase. This study demonstrated
that extraction followed by diafiltration is important for assessing enzyme recovery from solid fermentation samples. Reduction
in activity due to compounds present in the switchgrass extracts is reversible when the compounds are removed via diafiltration. 相似文献
64.
In scale-up, the potential of ethanol production by dilute sulfuric acid pretreatment using corncob was investigated. Pretreatments were performed at 170 °C with various acid concentrations ranging from 0% to 1.656% based on oven dry weight. Following pretreatment, pretreated biomass yield ranged from 59% to 67%. More than 90% of xylan was removed at 0.828% of sulfuric acid. At same pretreatment condition, the highest glucose yield obtained from pretreated biomass by enzymatic hydrolysis was about 76%, based on a glucan content of 37/100 g. In hydrolysate obtained by pretreatment, glucose concentration was low, while xylose concentration was significantly increased above 0.368% of sulfuric acid. At 1.656% of sulfuric acid, xylose and glucose concentration was highest. In subsequent, fermentation with hydrolysate, maximal ethanol yield was attained after 24 h with 0.368% of sulfuric acid. The fermentation efficiency of hydrolysate obtained by enzymatic hydrolysis reached a maximum of 75% at an acid charge of 0.368%. 相似文献
65.
Minsoo Koo Jong-Seong Bae Seong Eun Shim Dongmin Kim Dae-Geun Nam Jae-Won Lee Gang-Woo Lee Jeong Hyun Yeum Weontae Oh 《Colloid and polymer science》2011,289(13):1503-1509
Polyimide–graphene composites (PIG) were prepared with variable amounts of graphene, and their thermal properties were analyzed
in films on substrates or sheet states. The thermal conductivities of PIG composite sheets gradually moved upwards with increase
of graphene loading. Coefficient of thermal expansion of composite sheet was higher in out-of-plane mode than in-plane mode.
The residual stress of a composite film was monotonously changed in accordance with the variation of temperature and lowered
with increase of graphene. In addition, the residual stress of a composite film reached to the initial stress value during
cooling process after heating. The stress profiles on further heating and cooling runs closely followed the stress profile
during the first cooing run. 相似文献
66.
Yasuhi Joh Heimei Yuki Shunsuke Murahashi 《Journal of polymer science. Part A, Polymer chemistry》1970,8(11):3311-3328
The effect of polymerization conditions such as aging time of the catalyst, polymerization temperature, polymerization time, monomer concentration, and catalyst concentration on the polymerization of isobutyl vinyl ether was intensively studied by using the VCI3·LiCl–Al(i-Bu)3 system at an Al(i-Bu)/VCl3·LiCl ratio of 6 at which the cationic polymerization by VCl3·LiCl is sufficiently depressed. About 10 min aging of the catalyst in the presence of monomer yields a fairly stable catalytie system. The optimum polymerization temperature is around 30°C. The conversion increased with increasing monomer concentration, whereas the stereospecificity of polymerization decreased. Unexpectedly, the conversion decreased as total catalyst concentration increased. This phenomenon is explained by considering the deactivation of catalytic sites by the excess of Al(i-Bu)3. A reasonable mechanism from kinetic considerations is that two molecules of Al(i-Bu)3 deactivate the catalytic site in an equilibrium reaction. This deactivation is understandable by considering that the coordination of two molecules of Al(i-Bu)3 will occupy all the coordination positions of vanadium, so that there is no room for coordination of monomer coming to the catalytic site. 相似文献
67.
Chen X Jeon YM Jang JW Qin L Huo F Wei W Mirkin CA 《Journal of the American Chemical Society》2008,130(26):8166-8168
On-wire lithography (OWL) fabricated nanogaps are used as a new testbed to construct molecular transport junctions (MTJs) through the assembly of thiolated molecular wires across a nanogap formed between two Au electrodes. In addition, we show that one can use OWL to rapidly characterize a MTJ and optimize gap size for two molecular wires of different dimensions. Finally, we have used this new testbed to identify unusual temperature-dependent transport mechanisms for alpha,omega-dithiol terminated oligo(phenylene ethynylene). 相似文献
68.
Summary Multiple protein expression forms (MPEFs) presenting splicing forms or co- and posttranslation modifications, account for
the vast diversity, the myriad of gene products and clearly indicate problems which proteomics research is facing. In the
present study, we generated a rat brain map representing MPEFs by the use of an analytical method based on two-dimensional
electrophoresis combined with mass spectrometry. Forty-nine individual proteins were selected that showed more than two spots,
resulting altogether into a total number of 357 expression forms. Some proteins showed large MPEFs numbers as e.g. tubulin
alpha-1 chain (24 spots), ATP synthase alpha-chain (28), beta chain (17) or septin 7 (13).
The molecular diversity observed in this map clearly shows that immunochemical or even protein chemical results from expressional
studies have to be interpreted with caution, in particular if one dimensional electrophoretic or western blot techniques are
applied and MPEFs are poorly resolved. 相似文献
69.
Rudolf Ochs W. Fresenius P. Saccardi Weber J. M. Kolthoff H. Hamer H. Röttger E. Schowalter E. Spaeth A. Gompf J. Gerum G. Metge A. Röhrig L. Fresenius G. de Astis A. Bornträger H. Astruc Radet M. Martini A. Nourrisson L. Roos A. Kling A. Lassieur M. François Ch. Lormand J. Dubaquié P. Chauvet J. L. Chelle G. Filaudeau Bonis H. Boßelmannn F. Mach M. Fischler C. von der Heide Joh Pinnow D. Fonzes-Diakon L. Semichon K. Kroemer R. Meissner A. Widmer O. Kalberer L. Minder Th. v. Fellenberg G. Chancel P. Balavoine X. Roques C. Lagneau von der Heide 《Analytical and bioanalytical chemistry》1926,68(12):469-480
70.
Yasushi Joh Seiki Kurihara Toshio Sakurai Tatsunori Tomita 《Journal of polymer science. Part A, Polymer chemistry》1970,8(9):2383-2392
The stereospecific polymerizations of methacrylonitrile with diethylmagnesium were carefully studied by using various ethers as complexing agents. The complexed ethers exhibit a beneficial effect on the stereoregularity of the resulting polymer, namely, the crystallinity increased by using ethers as a complexing agent. The polymerization rate and the molecular weight of the polymer also increased by using ether-complexed catalysts. The polymerization behavior was studied with the dioxane–diethylmagnesium complex as a typical complexed catalyst. The behavior was mostly similar to that of the diethymagnesium alone, that is, the rate of the polymerization increased in proportion to monomer concentration, and the solubility index increased with increasing monomer concentration. Interestingly, the viscosity of the acetone-insoluble fraction increased with increasing monomer concentration, while that of the acetone-soluble fraction was independent of monomer concentration. This is explained by considering that the catalyst has at least two kinds of catalytic species, one being the species that produces the crystalline polymer by a coordinated anionic polymerization, another being the one from which an amorphous polymer is obtained by a conventional anionic mechanism. The fact that the viscosity of the polymer decreased with increasing the initiator concentration is explained in terms of chain trasfer to the initiator. In case of diethylmagnesium alone, the viscosity of the polymer is independent of the initiator concentration. 相似文献