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排序方式: 共有411条查询结果,搜索用时 46 毫秒
81.
Yingxi Zhu Hiroko Ohtani Michael L. Greenfield Marina Ruths Steve Granick 《Tribology Letters》2003,15(2):127-134
The molecular-level function of model and commercial friction modifier additives in lubricants of the type used at the wet clutch interface in automatic transmissions has been studied using a surface forces apparatus (SFA) modified for oscillatory shear. The nanorheological properties of tetradecane with and without a model friction modifier additive (1-hexadecylamine) were examined in the boundary lubrication regime and compared to a fully-formulated automatic transmission fluid (ATF). 1-Hexadecylamine adsorbed as a single layer on the sliding surfaces, reduced the static frictional force and the limiting shear stress, and eliminated the stick–slip transition that exists in pure tetradecane. The ATF, which contains commercial-grade friction modifiers, showed nanorheological properties similar to those observed for tetradecane containing 0.1–0.2 wt% 1-hexadecylamine. 相似文献
82.
Highly Efficient 2D/3D Hybrid Perovskite Solar Cells via Low‐Pressure Vapor‐Assisted Solution Process
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Ming‐Hsien Li Hung‐Hsiang Yeh Yu‐Hsien Chiang U‐Ser Jeng Chun‐Jen Su Hung‐Wei Shiu Yao‐Jane Hsu Nobuhiro Kosugi Takuji Ohigashi Yu‐An Chen Po‐Shen Shen Peter Chen Tzung‐Fang Guo 《Advanced materials (Deerfield Beach, Fla.)》2018,30(30)
The fabrication of multidimensional organometallic halide perovskite via a low‐pressure vapor‐assisted solution process is demonstrated for the first time. Phenyl ethyl‐ammonium iodide (PEAI)‐doped lead iodide (PbI2) is first spin‐coated onto the substrate and subsequently reacts with methyl‐ammonium iodide (MAI) vapor in a low‐pressure heating oven. The doping ratio of PEAI in MAI‐vapor‐treated perovskite has significant impact on the crystalline structure, surface morphology, grain size, UV–vis absorption and photoluminescence spectra, and the resultant device performance. Multiple photoluminescence spectra are observed in the perovskite film starting with high PEAI/PbI2 ratio, which suggests the coexistence of low‐dimensional perovskite (PEA2MAn?1PbnI3n+1) with various values of n after vapor reaction. The dimensionality of the as‐fabricated perovskite film reveals an evolution from 2D, hybrid 2D/3D to 3D structure when the doping level of PEAI/PbI2 ratio varies from 2 to 0. Scanning electron microscopy images and Kelvin probe force microscopy mapping show that the PEAI‐containing perovskite grain is presumably formed around the MAPbI3 perovskite grain to benefit MAPbI3 grain growth. The device employing perovskite with PEAI/PbI2 = 0.05 achieves a champion power conversion efficiency of 19.10% with an open‐circuit voltage of 1.08 V, a current density of 21.91 mA cm?2, and a remarkable fill factor of 80.36%. 相似文献
83.
Methods for the chemical recycling of polycarbonate (PC) wastes in the forms of bisphenol A (BPA) and cyclic heterocarbonates, such as 1,3‐dithiolan‐2‐one (DTO), 1,3‐dithiane‐2‐one (DTA), and cyclic unsymmetric heterocarbonates, were investigated to prove that PC can be utilized as a phosgene equivalent for industrial purposes. Treatment of PC pellets or waste PC compact discs with 1,2‐ethanedithiol and a catalytic amount of base (e.g., 1.5 mol % NaOH) in dioxane for a short period at 40°C produced DTO and BPA, both in nearly quantitative yields. The reaction could also be carried out in DTO, which saved the use of conventional solvents. Other cyclic heterocarbonates, that is, DTA, 1,3‐oxathiolan‐2‐one, 1,3‐thiazolidine‐2‐one, and N‐methyl‐1,3‐oxazolidine‐2‐one, were prepared in high yields under analogous conditions. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 2959–2968, 2003 相似文献
84.
A procedure for the preparation of specific molecular species ofd-erythro-lactosylceramide involving deacylation and reacylation of lactosylceramide prepared from bovine brain gangliosides is described.
Lactosylceramide wasN-deacylated by alkaline hydrolysis and the resulting four lysolactosylceramides, which contained d18∶1, d20∶1, d18∶0 and d20∶0
long-chain bases, were simultaneously re-N-acylated with theN-succinimidyl ester of either 16∶0, 18∶0, 20∶0, 24∶0, 20∶1, 22∶1 or 24∶1 fatty acid. The resulting lactosylceramide contained
four molecular species of lactosylceramides, i.e., d18∶1, d20∶1, d18∶0 and d20∶0 long-chain bases coupled with the fatty acid
that was introduced. Lactosylceramides prepared in this manner were separated into four individual molecular species by high-performance
liquid chromatography (HPLC). Each of the purified molecular species of lactosylceramide was quantitated by HPLC after derivatization
with benzoylchloride and was characterized by mass spectrometry. The yields of reacylated lactosylceramide were 38–58% relative
to the starting lactosylceramide; the purity of each of the molecular species of lactosylceramide was greater than 95%.
The glycosphingolipid nomenclature is as recommended by the IUPAC-IUB Commission on Biochemical Nomenclature (1). GalCer,
galactosylceramide, Gal(β1-1)Cer; GlcCer, glucosylceramide, Glc(β1-1)Cer; LacCer, lactosylceramide, Gal(β1-4)GlcCer; GbOse3Cer, globotriaosylceramide, Gal(α1-4)Gal(β1-4)GlcCer; GbOse4Cer, globotetraosylceramide, GalNAc(β1-3)Gal(α1-4)-Gal(β1-4)GlcCer; GgOse3Cer, gangliotriaosylceramide, GalNAc-(β1-4)Gal(β1-4)GlcCer; GgOse4Cer, gangliotetraosylceramide, Gal(β1-3)GalNAc(β1-4)Gal(β1-4)GlcCer; GM3, (NeuAcα2-3)-Galβ1-4GlcCer; GM1, Galβ1-3GalNAcβ1-4(NeuAcα2-3)Galβ1-4-GlcCer.
The molecular species abbreviations suggested by Breimeret al. (2) are used. For example, in the notation d18∶1−18∶0, the d18∶1 represents the long-chain base sphingosine (d-erythro-1,3-dihydroxy-2-amino-trans-4-octadecene) and 18∶0 represents the fatty acid (octadecanoic acid). 相似文献
85.
Iain P. McTaggart Hiroko Akiyama Haruo Tsuruta Bruce C. Ball 《Nutrient Cycling in Agroecosystems》2002,63(2-3):207-217
In Japan, upland soils are an important source of nitrous oxide (N2O) and nitric oxide (NO) gas emissions. This paper reports on an investigation of the effect of soil moisture near saturation on N2O and NO emission rates from four upland soils in Japan of contrasting texture. The aim was to relate these effects to soil physical properties. Intact cores of each soil type were incubated in the laboratory at different moisture tensions after fertilisation with NH4-N, NO3-N or zero N. Emissions of N2O and NO were measured regularly over a 16–20 day period. At the end of the incubation, soil cores were analysed for physical properties. Moisture and N fertiliser significantly affected rates of emissions of both N2O and NO with large differences between the soil types. Nitrous oxide emissions were greatest in the finer-textured soils, whereas NO emissions were greater in the coarser-textured soils. Emissions of N2O increased at higher moisture contents in all soils, but the magnitude of increase was much greater in finer-textured soils. Nitric oxide emissions were only significant in soils fertilised with NH4-N and were negatively correlated with soil moisture. Analysis of soil properties showed that there was a strong relationship between the magnitude of emissions and soil physical properties. The importance of soil wetness to gas emissions was mainly through its influence on soil air-filled porosity, which itself was related to gas diffusivity. From the results of this research, we can now estimate likely effects of soil texture on emissions through the influence of soil type on soil aeration and soil drainage. This is of particular value in modelling N2O and NO emissions from soil moisture status and land use inputs. 相似文献
86.
More than 95% of polyunsaturated acid (PUFA) was converted to triacylglycerol by immobilized lipase fromCandida antarctica orRhizomucor miehei. The esterification was carried out at 50–60°C with shaking and dehydration for 24 h. The substrates consisted of glycerol
and free fatty acid or ethyl esters of the fatty acid at a 1∶3 molar ratio. The docosahexaenoic acid (DHA) or eicosapentaenoic
acid (EPA) in the substrate polymerized during the reaction, and they required 5–10% more than the stoichiometric amount to
compensate for the PUFA loss. On the contrary, ethyl esters of DHA and EPA were not polymerized. Pure tridocosahexaenoyl,
trieicosapentaenoly and triarachidonoyl glycerol were isolated after passing the product through a basic aluminum oxide column.
Industrial feasibility of this process was discussed for the ethyl ester as substrate.
Portions of this article were presented at the annual meeting of the Japan Society for Bioscience, Biotechnology, and Agrochemistry
and at the annual meeting of The Japan Oil Chemists' Society held in Kyoto, Japan, March 31, 1991, and in Hamamatsu, Japan,
October 4, 1991, respectively. 相似文献
87.
Imoto Taiji; Yamada Hidenori; Yasukochi Takanori; Yamada Eiichi; Ito Yuji; Ueda Tadashi; Nagatani Hiroko; Miki Takeyoshi; Horiuchi Tadao 《Protein engineering, design & selection : PEDS》1987,1(4):333-338
In the preceding paper in this issue, we described the overproduction of one mutant chicken lysozyme in Escherichia coil.Since this lysozyme contained two amino acid substitutions (Ala31ValandAsn106Ser)in addition to an extra methionine residue at theNH2-terminus the substituted amino acid residues were convertedback to the original ones by means of oligonucleotide-directedsite-specific mutagenesis and in vitro recombination. Thus fourkinds of chicken lysozyme [Met1 Val31Ser106-, Met1Ser106-,Met1 Val31-and Met1 (wild type)] wereexpressed in E. coli. From the results of folding experimentsof the reduced lysozymes by sulfhydryl-disulfide interchangeat pH 8.0 and 38°C, follow ed by the specific activity measurementsof the folded en zymes, the following conclusions can be drawn:(i) an extra methionine residue at the NH2-terminus reducesthe folding rate but does not affect the lysozyme activity ofthe folded enzyme; (ii) the substitution of Asn106 by Ser decreasesthe activity to 58% of that of intact native lysozyme withoutchanging the folding rate; and (iii) the substitution of Ala31Val prohibits the correct folding of lysozyme. Since the wildtype enzyme (Met1-lysozyme) was activated in vitro withoutloss of specific activity, the systems described in this study(mutagenesis, overproduction, purification and folding of inactivemutant lysozymes) may be useful in the study of folding pathways,expression of biological activity and stability of lysozyme. 相似文献
88.
89.
Kenji Kikuchi Hiroko Takeda Beatrice Rabolt Takuji Okaya Zempachi Ogumi Yasuhiro Saihara Hiroyuki Noguchi 《Journal of Applied Electrochemistry》2001,31(12):1301-1306
The supersaturated concentration of hydrogen in electrolyzed water obtained from a flow-type electrolytic cell was studied under various electrolysis conditions. The degree of supersaturation was found to decrease as the solution supply rate to the cell increased. The ratio of observed hydrogen concentration to the theoretical hydrogen concentration obtained from the electrochemical equivalent, as calculated from the transfer of charge in the cell, was found to increase with the solution supply rate. The concentration of hydrogen in solution has a maximum at a current density of approximately 0.3 A dm–2. This maximum was found to be independent of the flow rate, indicating that the hydrogen concentration is related to both the diffusion of dissolved hydrogen from the electrode surface to the bulk solution and hydrogen bubble growth. 相似文献
90.
Kamiya Noriho; Okimoto Yuko; Ding Zhen; Ohtomo Hiroko; Shimizu Masafumi; Kitayama Atsushi; Morii Hisayuki; Nagamune Teruyuki 《Protein engineering, design & selection : PEDS》2001,14(6):415-419
We have recently generated a new mutant of cytochrome b562 (cytb562)in which Met7, one of the axial heme ligands, is replaced byAla (M7A cytb562). The M7A cytb562 can bind heme and the UV-visibleabsorption spectrum is of a typical high-spin ferric heme. Toinvestigate the effect of the lack of Met7 ligation on the structuralintegrity of cytb562, thermal transition analyses of M7A cytb562were conducted. From the thermodynamic parameters obtained,it is concluded that the folding of M7A cytb562 is comparableto the apoprotein despite the presence of heme. On the otherhand, exogenous ligands such as cyanide and azide ions are readilybound to the heme iron, indicating that the axial coordinationsite is available for substrate binding. The peroxidase activityof this mutant is thus examined to evaluate new enzymatic functionat this site and M7A cytb562 was found to catalyze an oxidationreaction of aromatic substrates with hydrogen peroxide. Theseobservations demonstrate that the Met7/His102 bis-ligation tothe heme iron is crucial for the stable folding of cytb562,whereas the functional conversion of cytb562 is successfullyachieved by the loose folding together with the open coordinationsite. 相似文献