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排序方式: 共有259条查询结果,搜索用时 221 毫秒
51.
Galina V. Beznoussenko Sergei S. Pilyugin Willie J. C. Geerts Michael M. Kozlov Koert N. J. Burger Alberto Luini Jure Derganc Alexander A. Mironov 《International journal of molecular sciences》2015,16(3):5299-5333
Membrane organelles often have complicated shapes and differ in their volume, surface area and membrane curvature. The ratio between the surface area of the cytosolic and luminal leaflets (trans-membrane area asymmetry (TAA)) determines the membrane curvature within different sites of the organelle. Thus, the shape of the organelle could be critically dependent on TAA. Here, using mathematical modeling and stereological measurements of TAA during fast transformation of organelle shapes, we present evidence that suggests that when organelle volume and surface area are constant, TAA can regulate transformation of the shape of the Golgi apparatus, endosomal multivesicular bodies, and microvilli of brush borders of kidney epithelial cells. Extraction of membrane curvature by small spheres, such as COPI-dependent vesicles within the Golgi (extraction of positive curvature), or by intraluminal vesicles within endosomes (extraction of negative curvature) controls the shape of these organelles. For instance, Golgi tubulation is critically dependent on the fusion of COPI vesicles with Golgi cisternae, and vice versa, for the extraction of membrane curvature into 50–60 nm vesicles, to induce transformation of Golgi tubules into cisternae. Also, formation of intraluminal ultra-small vesicles after fusion of endosomes allows equilibration of their TAA, volume and surface area. Finally, when microvilli of the brush border are broken into vesicles and microvilli fragments, TAA of these membranes remains the same as TAA of the microvilli. Thus, TAA has a significant role in transformation of organelle shape when other factors remain constant. 相似文献
52.
Weir Pumps Ltd has a long history of advances in pumping technology and is at the forefront of developing novel equipment for oil production for both on and offshore installations. Willie Vance, senior project sales engineer at Weir Pumps, looks at some of the latest Downhole Fluid Handling Technologies while below Graham Kent, applications manager at Weir Pumps, provides an overview of developments in water injection technology... 相似文献
53.
Jacco C Noordam Willie HAM van den Broek Lutgarde MC Buydens 《Journal of the science of food and agriculture》2005,85(13):2249-2259
This paper describes an application of both multispectral imaging and red/green/blue (RGB) colour imaging for the discrimination between different defect and diseases on raw French fries. Four different potato cultivars generally used for French fries production are selected from which fries are cut. Both multispectral images and RGB colour images are classified with parametric and non‐parametric classifiers. The effect of applying different preprocessing techniques on the spectra was also investigated. The best classification results in terms of accuracy, yield and purity are obtained with a modified version of standard normal variate (snv_mod) preprocessing for different classifiers and potato cultivars. The classification results of the multispectral images are compared with RGB images. The results show that the support vector classifier gives the best classification performance for the snv_mod preprocessed multispectral images and k‐nearest neighbours classifier gives the best classification performance for raw RGB images. The detection of the latent greening defect in French fries with the exploration of multispectral images shows the additional value of multispectral imaging for French fries. A comparison between the multispectral images and the RGB colour images confirms this since this type of defect is not visible in the colour images. Copyright © 2005 Society of Chemical Industry 相似文献
54.
55.
Inhibition of calcium phosphate precipitation under environmentally-relevant conditions 总被引:4,自引:0,他引:4
Precipitation of Ca phosphates plays an important role in controlling P activity and availability in environmental systems. The purpose of this study was to determine inhibitory effects on Ca phosphate precipitation by Mg(2+), SO(4)(2-), CO(3)(2-), humic acid, oxalic acid, biogenic Si, and Si-rich soil clay commonly found in soils, sediments, and waste streams. Precipitation rates were determined by measuring decrease of P concentration in solutions during the first 60 min; and precipitated solid phases identified using X-ray diffraction and electron microscopy. Poorly-crystalline hydroxyapatite (HAP: Ca(5)(PO(4))(3)OH) formed in control solutions over the experiment period of 24 h, following a second-order dependence on P concentration. Humic acid and Mg(2+) significantly inhibited formation of HAP, allowing formation of a more soluble amorphous Ca phosphate phase (ACP), and thus reducing the precipitation rate constants by 94-96%. Inhibition caused by Mg(2+) results from its incorporation into Ca phosphate precipitates, preventing formation of a well-crystalline phase. Humic acid likely suppressed Ca phosphate precipitation by adsorbing onto the newly-formed nuclei. Presence of oxalic acid resulted in almost complete inhibition of HAP precipitation due to preemptive Ca-oxalate formation. Carbonate substituted for phosphate, decreasing the crystallinity of HAP and thus reducing precipitation rate constant by 44%. Sulfate and Si-rich solids had less impact on formation of HAP; while they reduced precipitation in the early stage, they did not differ from the control after 24 h. Results indicate that components (e.g., Mg(2+), humic acid) producing relatively soluble ACP are more likely to reduce P stability and precipitation rate of Ca phosphate in soils and sediments than are components (e.g., SO(4)(2-), Si) that have less effect on the crystallinity. 相似文献
56.
Merrell WC Aslam S Brown AD Chervenak JA Huang WC Quijada M Wollack EJ 《Applied optics》2012,51(15):3046-3053
The future needs of space-based, observational planetary and astronomy missions include low mass and small volume radiometric instruments that can operate in high-radiation and low-temperature environments. Here, we focus on a central spectroscopic component, the bandpass filter. We model the bandpass response of the filters to target the wavelength of the resonance peaks at 20, 40, and 60 μm and report good agreement between the modeled and measured response. We present a technique of using standard micromachining processes for semiconductor fabrication to make compact, free-standing, resonant, metal mesh filter arrays with silicon support frames. The process can be customized to include multiple detector array architectures, and the silicon frame provides lightweight mechanical support with low form factor. 相似文献
57.
The suitability of the anaerobic/aerobic process was investigated for treating phosphorus-deficient wastewaters with highly variable influent chemical oxygen demand (COD) loading patterns to produce consistently low effluent P levels. During laboratory-scale experiments, two sequencing batch reactors (SBRs), one anaerobic/aerobic (AnA) and the other completely aerobic (CA), received transient influent COD loading patterns that simulated (No. 1) daily COD loading fluctuations and (No. 2) low weekend COD loading, each for a period of approximately 6?months. The AnA SBR produced lower effluent soluble P concentrations than the CA SBR during loading pattern No. 1 (0.5 versus 1.2?mgP/L). During loading pattern No. 2, both SBRs allowed effluent acetate breakthrough, following the low weekend COD loading period, and the P removal in the AnA SBR gradually deteriorated. The AnA process has the potential to produce lower effluent P levels than the CA process during transient loading periods due to the P release and uptake characteristics associated with the polyphosphate-accumulating metabolism. Extended periods of low COD loading can however cause a loss of P removal. 相似文献
58.
John T. Feddema Rush D. Robinett Brian J. Driessen 《Journal of Intelligent and Robotic Systems》2003,36(4):349-370
This paper discusses how phase plane analysis can be used to describe the overall behavior of single and multiple autonomous robotic vehicles with finite state machine rules. The importance of this result is that we can begin to design provably stable group behaviors from a set of simple control laws and appropriate switching points with decentralized variable structure control. The ability to prove stable group behavior is especially important for applications such as locating military targets or land mines. In this paper, we demonstrate how phase plane analysis has been used to explain the behavior of a 16 cm3 autonomous line-tracking robot with four finite states. After which, the analysis is extended to include the design of a decentralized variable structure controller that guides multiple vehicles to a goal while avoiding each other. 相似文献
59.
A novel high-speed polymeric EO Modulator based on a combination of a microring resonator and an MZI
Leinse A. Diemeer M.B.J. Rousseau A. Driessen A. 《Photonics Technology Letters, IEEE》2005,17(10):2074-2076
A Mach-Zehnder interferometer with an electrooptic polymer mircroring resonator adjacent to one of its branches is realized in a polymer layer stack. The microresonator is defined by reactive ion etching in the nonlinear PMMA-DR1 polymer and waveguide definition is done without etching, by using a negative photoresist (SU8) as waveguide layer. Electrooptic coefficients of 10 pm/V and modulation frequencies of 1 GHz were measured. 相似文献
60.
Amy Gernon Ermias Woldu Michele Godlevski Willie Wilson Rodney C. Gilmore Delores J. Grant Pradeep K. Chatterjee Dan Kephart 《Journal of The Association for Laboratory Automation》2003,8(5):305
Demands for higher quantity and quality of sequence data during genome sequencing projects have led to a need for completely automated reagent systems designed to isolate, process, and analyze DNA samples. While much attention has been given to methodologies aimed at increasing the throughput of sample preparation and reaction setup, purification of the products of sequencing reactions has received less scrutiny despite the profound influence that purification has on sequence quality. Commonly used and commercially available sequencing reaction cleanup methods are not optimal for purifying sequencing reactions generated from larger templates, including bacterial artificial chromosomes (BACs) and those generated by rolling circle amplification. Theoretically, these methods would not remove the original template since they only exclude small molecules and retain large molecules in the sample. If the large template remains in the purified sample, it could understandably interfere with electrokinetic injection and capillary performance. We demonstrate that the use of MagneSil® paramagnetic particles (PMPs) to purify ABI PRISM® BigDye® sequencing reactions increases the quality and read length of sequences from large templates. The high-quality sequence data obtained by our procedure is independent of the size of template DNA used and can be completely automated on a variety of automated platforms. 相似文献