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排序方式: 共有1022条查询结果,搜索用时 31 毫秒
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42.
Guusje van Schaick Nadi el Hajjouti Simone Nicolardi Joost den Hartog Romana Jansen Rob van der Hoeven Wim Bijleveld Nicolas Abello Manfred Wuhrer Maurien M. A. Olsthoorn Elena Domínguez-Vega 《International journal of molecular sciences》2022,23(3)
Xylanases are of great value in various industries, including paper, food, and biorefinery. Due to their biotechnological production, these enzymes can contain a variety of post-translational modifications, which may have a profound effect on protein function. Understanding the structure–function relationship can guide the development of products with optimal performance. We have developed a workflow for the structural and functional characterization of an endo-1,4-β-xylanase (ENDO-I) produced by Aspergillus niger with and without applying thermal stress. This workflow relies on orthogonal native separation techniques to resolve proteoforms. Mass spectrometry and activity assays of separated proteoforms permitted the establishment of structure–function relationships. The separation conditions were focus on balancing efficient separation and protein functionality. We employed size exclusion chromatography (SEC) to separate ENDO-I from other co-expressed proteins. Charge variants were investigated with ion exchange chromatography (IEX) and revealed the presence of low abundant glycated variants in the temperature-stressed material. To obtain better insights into the effect on glycation on function, we enriched for these species using boronate affinity chromatography (BAC). The activity measurements showed lower activity of glycated species compared to the non-modified enzyme. Altogether, this workflow allowed in-depth structural and functional characterization of ENDO-I proteoforms. 相似文献
43.
Eric Newman Rob Reeder 《今日电子》2006,(5):32-36
高采样速率模数转换器(ADC)通常用在现代无线接收器设计中,以中频(IF)采样速率采集复数调制的信号.这类设计通常都选用基于CMOS开关电容的ADC,因为它们的低成本和低功耗特点很吸引人。但这类ADC采用一种直接连接到采样网络的无缓冲器的前端,这样就会出现驱动ADC的放大器的输入跟踪和保持阻抗随时间变化的问题.为了有效地驱动ADC,使噪声最低和有用信号失真最小,必须设计一种无源网络接口帮助抑制宽带噪声,并对跟踪阻抗和保持阻抗进行变换以便为驱动放大器提供更好的负载阻抗。针对几种常见的IF频率,本文中提出了一种谐振匹配方法,用于将跟踪和保持阻抗转换为比较容易计算的负载,从而实现抗锯齿滤波器的精密设计。 相似文献
44.
Steffen A Schroeder W Macdonald R Poissant L Konoplev A 《The Science of the total environment》2005,342(1-3):185-198
Eight years of gaseous elemental mercury (GEM) concentration measurements from Alert, Nunavut, Canada (between 1995 and 2002) is presented. The annual time series shows a distinct repeating seasonal pattern with an overall annual median concentration for this time period of 1.58 (S.D.=0.04 ng m(-3)). Strong seasonal variation was observed throughout the years with springtime displaying strong variability in the GEM and overall lower median concentrations due to the so-called mercury depletion events (MDEs). Summer concentrations are higher than the annual average and show a decrease in variability. Fall and winter concentrations are distributed around the annual median concentrations and show little variability. The relationship between the springtime depression and the summer increase shows a change in the behaviour of mercury between 1995 and 2002. Preliminary results suggest that during this period an increasing amount of the mercury lost from the atmosphere in the spring is not returned to atmosphere in summer. A comparison of GEM concentration data from three sites--Alert (Canada), Amderma (Russia) and Kuujjuarapik (Canada)--demonstrated similar monthly distribution of GEM between Alert and Amderma, with the latter not showing as high summer concentrations. Monthly distribution of GEM at Kuujjuarapik varied considerably from the other two sites. MDEs were found to occur at each site in the spring yet displayed different characteristics. MDEs appear to start at Alert shortly after polar sunrise but in Amderma their initiation is delayed approximately 2 months following polar sunrise. MDEs occur in Kuujjuarapik in the springtime despite an incomplete development of the polar day-night cycle. In spring, as soon as air temperature attained temperatures consistently above 0 degrees C, MDEs ended immediately at all three sites. Continued studies into MDEs are warranted, but clearly an important component of future studies must focus on the origins of the variation of GEM behaviour at different sites. 相似文献
45.
Adsorption, desorption and isotopic exchange of cadmium on illite: evidence for complete reversibility 总被引:2,自引:0,他引:2
Rob N.J. Comans 《Water research》1987,21(12):1573-1576
Adsorption, desorption and isotopic exchange of Cd on illite clay have been studied at low Cd concentrations and low ionic strength. The results indicate that under the conditions of the experiments Cd sorption on illite is completely reversible. Long equilibration times (7–8 weeks) were shown to be essential because of slow desorption kinetics. 相似文献
46.
Mapping of background air pollution at a fine spatial scale across the European Union 总被引:5,自引:0,他引:5
Rob Beelen Gerard Hoek Danielle Vienneau David J. Briggs 《The Science of the total environment》2009,407(6):1852-1867
Background
There is a need to understand much more about the geographic variation of air pollutants. This requires the ability to extrapolate from monitoring stations to unsampled locations. The aim was to assess methods to develop accurate and high resolution maps of background air pollution across the EU.Methods
We compared the validity of ordinary kriging, universal kriging and regression mapping in developing EU-wide maps of air pollution on a 1 × 1 km resolution. Predictions were made for the year 2001 for nitrogen dioxide (NO2), fine particles < 10 µm (PM10), ozone (O3), sulphur dioxide (SO2) and carbon monoxide (CO) using routine monitoring data in Airbase. Predictor variables from EU-wide databases were land use, road traffic, population density, meteorology, altitude, topography and distance to sea. Models were developed for the global, rural and urban scale separately. The best method to model concentrations was selected on the basis of predefined performance measures (R2, Root Mean Square Error (RMSE)).Results
For NO2, PM10 and O3 universal kriging performed better than regression mapping and ordinary kriging. Validation of the final universal kriging estimates with results from all validation sites gave R2-values and RMSE-values of 0.61 and 6.73 µg/m3 for NO2; 0.45 and 5.19 µg/m3 for PM10; and 0.70 and 7.69 µg/m3 for O3. For SO2 and CO none of the three methods was able to provide a satisfactory prediction.Conclusion
Reasonable prediction models were developed for NO2, PM10 and O3 on an EU-wide scale. Our study illustrates that it is possible to develop detailed maps of background air pollution using EU-wide databases. 相似文献47.
v. Schröder Karl Boresch K. Dirr R. Ammon Diemair Griebel Schwaibold G. Mall Felicitas Rolleri Kanitz O. Windhausen K. Felix von Querner W. Ludorff E. Fischbach W. Sutthoff Frey-Wyssling Schormüller A. Pirson J. Großfeld E. Chytrek Koelitz Hans Hawelka W. Schreiber Brüning Estler Pawletta W. Wodsak Jesser H. J. Steinbeck Seuss Schmitz Lars Erlandsen W. Hämmerle Masch A. Bäurle W. Leithe Rudolj Abderhalden Haevecker Fr. Bartschat Garber G. Stamm Gertraude Körner-Hennig G. Steinhoff Johannes Wolf Rob Jungkunz Schönfeld Ed. Rentz Klinc K. Höll 《European Food Research and Technology》1940,79(6):568-608
48.
Schormüller J. Großfeld H. Mohler Carls Kanitz Griebel Rudolf Abderhalden W. Schreiber W. Hämmerle Brüning W. Ludorff Pawletta W. Bartels Fr. Bartschat M. Gordienko L. W. Jirak O. Windhausen H. -A. Oelkers I. Stahn J. Ph. Bruno Roßmann Lars Erlandsen Lintzel Flößner Bäurle Reschke Haevecker W. Sutthoff H. Schanderl Masling H. Süllmann v. Noël Reichard E. Dinslage G. Steinhoff Jesser Rob Jungkunz C. Pyriki W. Preiβ K. Müller L. Klinc Zacher Beckel K. Höll 《European Food Research and Technology》1939,78(6):480-496
49.
A practical evaluation of spectrum-based fault localization 总被引:1,自引:0,他引:1
Spectrum-based fault localization (SFL) shortens the test–diagnose–repair cycle by reducing the debugging effort. As a light-weight automated diagnosis technique it can easily be integrated with existing testing schemes. Since SFL is based on discovering statistical coincidences between system failures and the activity of the different parts of a system, its diagnostic accuracy is inherently limited. Using a common benchmark consisting of the Siemens set and the space program, we investigate this diagnostic accuracy as a function of several parameters (such as quality and quantity of the program spectra collected during the execution of the system), some of which directly relate to test design. Our results indicate that the superior performance of a particular similarity coefficient, used to analyze the program spectra, is largely independent of test design. Furthermore, near-optimal diagnostic accuracy (exonerating over 80% of the blocks of code on average) is already obtained for low-quality error observations and limited numbers of test cases. In addition to establishing these results in the controlled environment of our benchmark set, we show that SFL can effectively be applied in the context of embedded software development in an industrial environment. 相似文献
50.
Guoliang Zhu Yongbing Dai Da Shu Yanping Xiao Yongxiang Yang Jun Wang Baode Sun Rob Boom 《Intermetallics》2011,19(7):1036-1040
First-principles calculations were employed to study the migration of vacancy in clean and Si-doped Al3Ti. The effect of Si doping on the formation of vacancy and the diffusion of doped-Si atom in the Al3Ti were also investigated. It is found that, under Al-rich condition, the formation energies of Al vacancies in Al3Ti with Si doping are decreased compared with those in clean Al3Ti. The preferred migration paths of vacancies are not changed when Si occupies Al site, but the migration energy barriers for the majority of paths are decreased after Si doping. The doped-Si atom on Al site prefers to diffuse via the nearest Al vacancy. 相似文献