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1
Faizal Agung Riyadi, Tedy Agung Cahyadi, Nurkhamim, and Supandi. "Desain Saluran Terbuka Berbasis Microsoft Excel Perhitungan dan Pemodelan yang Praktis dan Effisien." KURVATEK 4, no. 2 (December 21, 2019): 61–78. http://dx.doi.org/10.33579/krvtk.v4i2.1563.
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Saluran dibangun sebagai media yang berfungsi untuk mengalirkan air. Di dalam kegiatan perencanaan, desain, dan konstruksi saluran memerlukan banyak waktu, upaya , dan biaya. Desain dan konstruksi saluran harus sesuai dengan kebutuhan dan karakteristik lokasi yang digunakan. Seringkali terjadi perubahan parameter dalam menentukan desain saluran akibat pertimbangan teknis maupun ekonomis. Hal tersebut menuntut perubahan desain saluran yang sesuai dengan parameter yang baru. Oleh sebab itu, diperlukan alat untuk mempermudah perhitungan desain saluran. Parameter yang diperlukan untuk menghitung desain saluran adalah debit (Q), faktor tahanan Chezy (C), Koefisien Darcy-Weisbach (f), atau faktor kekasaran Manning (n), dan parameter gradien alas saluran (i). Penelitian bertujuan untuk menghitung dan memodelkan desain saluran, serta menyediakan alat atau media praktis dan mudah digunakan. Metode yang dilakukan adalah dengan menerapkan formula perhitungan Chezy, Darchy-Weisbach, dan Manning untuk berbagai bentuk saluran menggunakan perangkat lunak Microsoft Excel. Penentuan nilai faktor tahanan Chezy (C), Koefisien Darcy-Weisbach (f), dapat dihubungkan dari faktor kekasaran Manning (n). Koefisien kekasaran Manning (n) dapat diperkirakan dari ukuran partikel material penyusun alas saluran (d) menggunakan formula, maupun mengacu kepada tabel faktor kekasaran Manning. Penelitian ini menghasilkan alat untuk menghitung dan memodelkan desain saluran terbuka “Kalkulator Desain Saluran – FAR”. Penulis mengusulkan formula baru untuk memperkirakan nilai faktor kekasaran Manning (n) dari ukuran partikel material penyusun alas saluran (d). Selain itu, penulis mengusulkan formula untuk menghitung langsung tinggi air dalam penampang geometri saluran (y). Formula tersebut diperoleh dengan memasukkan koefisien α yang berdasar dari hubungan antar parameter geometri saluran kedalam formula Chezy, Darchy-Weisbach, dan Manning.
Kata Kunci: alat, desain, geometri, praktis, saluran.
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Kitaytseva, Elena. "A new approach to hydraulic calculations of free-flow drainage systems." MATEC Web of Conferences 144 (2018): 01018. http://dx.doi.org/10.1051/matecconf/201814401018.
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The accuracy of hydraulic calculations is determined by the accuracy of the mathematical models inherent in their foundation. The results of calculations, obtained by different models, and differing from each other by 5-10% is considered identical. The present study examines classical ways of finding the Chezy formula that are used for calculations of free-flow pipelines. These formulas differ from each other not only in parameters but also in the form of the functional dependence. The equation, underlying the hydraulic calculations, is nonlinear. Its solution is possible only in the number of well-established methods. It offers numerical computing to find pipelines diameters and their filling, as well as the algorithm to realize it. It conducts numerical experiment to compare pipelines diameters and filling and flow velocities. It presents frequency characteristics to distribute the parameters under analysis. For a specific example, the difference of cost of pipes, the diameters of which was found using the various formulas for coefficient Chezy, was calculated.
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Guhaniyogi, Jayita, Ti Wu, Smita S. Patel, and Ann M. Stock. "Interaction of CheY with the C-Terminal Peptide of CheZ." Journal of Bacteriology 190, no. 4 (December 14, 2007): 1419–28. http://dx.doi.org/10.1128/jb.01414-07.
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ABSTRACT Chemotaxis, a means for motile bacteria to sense the environment and achieve directed swimming, is controlled by flagellar rotation. The primary output of the chemotaxis machinery is the phosphorylated form of the response regulator CheY (P∼CheY). The steady-state level of P∼CheY dictates the direction of rotation of the flagellar motor. The chemotaxis signal in the form of P∼CheY is terminated by the phosphatase CheZ. Efficient dephosphorylation of CheY by CheZ requires two distinct protein-protein interfaces: one involving the strongly conserved C-terminal helix of CheZ (CheZC) tethering the two proteins together and the other constituting an active site for catalytic dephosphorylation. In a previous work (J. Guhaniyogi, V. L. Robinson, and A. M. Stock, J. Mol. Biol. 359:624-645, 2006), we presented high-resolution crystal structures of CheY in complex with the CheZC peptide that revealed alternate binding modes subject to the conformational state of CheY. In this study, we report biochemical and structural data that support the alternate-binding-mode hypothesis and identify key recognition elements in the CheY-CheZC interaction. In addition, we present kinetic studies of the CheZC-associated effect on CheY phosphorylation with its physiologically relevant phosphodonor, the histidine kinase CheA. Our results indicate mechanistic differences in phosphotransfer from the kinase CheA versus that from small-molecule phosphodonors, explaining a modest twofold increase of CheY phosphorylation with the former, observed in this study, relative to a 10-fold increase previously documented with the latter.
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Elgamal, Mohamed. "A Moment-Based Chezy Formula for Bed Shear Stress in Varied Flow." Water 13, no. 9 (April 30, 2021): 1254. http://dx.doi.org/10.3390/w13091254.
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Despite its limitations, the Chezy bed shear stress formula is commonly used in depth-averaged flow numerical models as closure for estimating mutual tractive stresses with underneath boundaries. This paper proposes a novel moment-based formula that could be considered a revised version of the Chezy formula and can be used to estimate local variations of the bed shear stress under more complex and varied flow conditions with accelerating–decelerating flow fields. The formula depends on two velocity scales: the depth-averaged velocity, Uo, and a new moment-based velocity scale, u1. The new formula is calibrated using 10 experiments for flow over fixed bedforms, and the calibration coefficient is found to linearly correlate with h/Δ and h/zo ratios. The formula is also applied for the case of air flow across a negative step, jet water flow downstream a gate, and 2D water flow downstream an oblique negative step, and reasonably satisfactory agreement with the measured data is found. The new formula could be used in vertically averaged and moment models to disclose part of the information already lost by the vertical integration procedure.
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Yakhtenfel'd, I. P. "Accuracy criterion of equations for determination of the Chezy coefficient." Hydrotechnical Construction 26, no. 4 (April 1992): 203–4. http://dx.doi.org/10.1007/bf01545322.
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Antuono, Matteo, Luciano Soldini, and Maurizio Brocchini. "On the role of the Chezy frictional term near the shoreline." Theoretical and Computational Fluid Dynamics 26, no. 1-4 (January 29, 2011): 105–16. http://dx.doi.org/10.1007/s00162-010-0220-8.
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Ho, Choo Tai, Yoon Hyeon Cheol, Yun Gwan Seon, Noh Hyun Suk, and Bae Chang Yeon. "The Estimation of Discharge in an Experimental Open Channel." Advanced Materials Research 905 (April 2014): 369–73. http://dx.doi.org/10.4028/www.scientific.net/amr.905.369.
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The estimation of a river discharge by using a mean velocity equation is very convenient and rational. Nevertheless, a research on an equation calculating a mean velocity in a river was not entirely satisfactory after the development of Chezy and Mannings formulas which are uniform equations. In this paper, accordingly, the mean velocity in unsteady flow conditions which are shown loop form properties was estimated by using a new mean velocity formula derived from Chius 2-D velocity formula. The results showed that the proposed method was more accurate in estimating discharge, when compared with the conventional formulas.
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Boesch, Kristin C., Ruth E. Silversmith, and Robert B. Bourret. "Isolation and Characterization of Nonchemotactic CheZ Mutants of Escherichia coli." Journal of Bacteriology 182, no. 12 (June 15, 2000): 3544–52. http://dx.doi.org/10.1128/jb.182.12.3544-3552.2000.
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ABSTRACT The Escherichia coli CheZ protein stimulates dephosphorylation of CheY, a response regulator in the chemotaxis signal transduction pathway, by an unknown mechanism. Genetic analysis of CheZ has lagged behind biochemical and biophysical characterization. To identify putative regions of functional importance in CheZ, we subjected cheZ to random mutagenesis and isolated 107 nonchemotactic CheZ mutants. Missense mutations clustered in six regions of cheZ, whereas nonsense and frameshift mutations were scattered reasonably uniformly across the gene. Intragenic complementation experiments showed restoration of swarming activity when compatible plasmids containing genes for the truncated CheZ1–189 peptide and either CheZA65V, CheZL90S, or CheZD143G were both present, implying the existence of at least two independent functional domains in each chain of the CheZ dimer. Six mutant CheZ proteins, one from each cluster of loss-of-function missense mutations, were purified and characterized biochemically. All of the tested mutant proteins were defective in their ability to dephosphorylate CheY-P, with activities ranging from 0.45 to 16% of that of wild-type CheZ. There was good correlation between the phosphatase activity of CheZ and the ability to form large chemically cross-linked complexes with CheY in the presence of the CheY phosphodonor acetyl phosphate. In consideration of both the genetic and biochemical data, the most severe functional impairments in this set of CheZ mutants seemed to be concentrated in regions which are located in a proposed large N-terminal domain of the CheZ protein.
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Zhou, Junwei, Weimin Bao, Yu Li, Li Cheng, and Muxi Bao. "The Modified One-Dimensional Hydrodynamic Model Based on the Extended Chezy Formula." Water 10, no. 12 (November 27, 2018): 1743. http://dx.doi.org/10.3390/w10121743.
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Although steady uniform friction formulas have been introduced to the framework of a one-dimensional (1D) hydrodynamic model for centuries, the error of friction calculation inevitably undermines the performance of flood routing. Based on successful results of unsteady channel friction research studies, a newly proposed unsteady friction model is introduced to establish a modified 1D hydrodynamic model (namely, the modified SVN model). With the help of a carefully designed parameter calibration method, the performance of the modified SVN model was compared with that of the original SVN model in a simulation test for a hydraulic experiment. This study’s results revealed that compared with the original SVN model, the modified SVN model could achieve a better simulation in both the flow depth and the sectional averaged velocity simulations. Furthermore, it could reduce the peak value error and the time-at-peak error as well, indicating that the use of an unsteady friction model can efficiently improve the performance of a 1D hydrodynamic model.
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Karim, Lahmar, and Jean-Pierre Larue. "Évaluation du Coefficient De Frottement Dans Le Cas D’un Écoulement À Surface Libre." European Scientific Journal, ESJ 12, no. 15 (May 30, 2016): 418. http://dx.doi.org/10.19044/esj.2016.v12n15p418.
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A large number of empirical formulas such as Bazin and Manning’s formulas are used to estimate stream flows for design purpose. Discharge is calculated by standard equations that are all based on an empirical coefficient found to be a characteristic of the wall and not of its relative roughness features. This, in turn, would yield different results displayed during the calculation of Chezy coefficient while using standard materials. In open channel flows, features on the wall may have an important effect in assessing flow properties such as friction, velocity, and discharge. In this context, we have led an experimental study on a rectangular channel using the boundary layer and turbulence theory. The rectangular channel understudy is characterized by Plexiglas walls having three different roughness conditions. The study is carried out using abrasive papers with different dimensions. The results of the experiment reveals that for the three wall conditions (i.e. Plexiglas P220 and P80) and in the case of hydraulically smooth and torrential flow, the friction is estimated by Pranldt Von Karman’s formula. The same conclusion can be drawn for the different experimental tests performed on a bi-dimensional channel with a bottom made of PVC in a hydraulically smooth and fluvial flow. However, considerable discrepancy between results obtained has been inferred. Actually, there is a difference between values calculated by Chezy coefficient formula and those calculated by Manning’s formula. The latter is widely used in recent investigation especially when it comes to the transition from open channel flow to pipe flow (i.e. closed-conduit flow). In the present study, in the case of transition between a hydraulically smooth flow and a rough one (detected only in the case of P80), the friction factor is represented by a form similar to that of Colebrook White.
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Constain Aragón, Alfredo José, and Gina Alexandra Peña-Olarte. "Determination of the factors of variation of mean velocity in natural channels at steady state." DYNA 86, no. 210 (July 1, 2019): 240–46. http://dx.doi.org/10.15446/dyna.v86n210.78860.
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From the Chezy-Manning equation, considered valid for the "steady state" of a natural channel, as an extension of the condition of "uniform flow," it is interesting to determine the degree of variation of the average flow velocity, depending on the variations of the factors involved. That is why this article presents a theoretical analysis which yields a first approximation of the sensitivity of the variation of the magnitude of the average speed to changes in the geometry or geomorphology of a section of the channel. It is found that the concept of "stable state" for the thermodynamic state of a natural channel can be assimilated to that of "dynamic equilibrium," in which the values of the state parameters vary slowly, in a "regional" sense.
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Goldfarb, Maurício C., Tarciso C. da Silva, Carlos A. V. de Azevedo, and Vera L. A. de Lima. "Escoamento uniforme em canais circulares lisos. Parte II: comparação entre o método de Kazemipour e a equação de Manning." Revista Brasileira de Engenharia Agrícola e Ambiental 8, no. 2-3 (December 2004): 180–83. http://dx.doi.org/10.1590/s1415-43662004000200003.
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A equação de Chezy-Manning e diversas outras utilizadas no cálculo do escoamento uniforme em canais, não representam satisfatoriamente o efeito da forma da seção transversal do escoamento, o que geralmente conduz a resultados de pouca precisão. Uma metodologia desenvolvida por Kazemipour & Apelt (1980) a partir da equação de von Karman Prandtl para tubos pressurizados, denominada método de Kazemipour, tem-se mostrado bastante eficiente no cálculo do escoamento em canais circulares lisos. Neste trabalho, o método de Kazemipour, ajustado numericamente, foi confrontado com a equação de Manning. Utilizaram-se, na análise, valores de vazão calculados pelas duas metodologias e dados experimentais de confiabilidade. De acordo com os parâmetros avaliados, o método de Kazemipour mostrou-se superior à equação de Manning para cálculo do escoamento em canais circulares lisos.
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MOHAPATRA, P. K., and A. B. PALANIAPPAN. "Analysis of paradoxes arising from the Chezy formula with constant roughness. I. Depthdischarge curve." Hydrological Sciences Journal 42, no. 5 (October 1997): 781. http://dx.doi.org/10.1080/02626669709492072.
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Razak, Mohd Shahrizal Ab, and Nur Arriffah Zaimah Mohd Nor. "XBeach Process-Based Modelling of Coastal Morphological Features Near Breakwater." MATEC Web of Conferences 203 (2018): 01007. http://dx.doi.org/10.1051/matecconf/201820301007.
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An effective role of a detached breakwater as a coastal protection structure leads to morphological evolutions of tombolo. This paper presents the application of process based model of XBeach to investigate the morphological tombolo evolution using the model domain from the previous case study. Sensitivity analysis with optimum model parameters such as facua 0.1, Chezy coefficient 60, directional energy distribution, dtheta 10 and morfac 100 is conducted and the model results are compared to the empirical models. At 50 and 75 days simulation time, XBeach model results for breakwater at distance 120 m, 150 m, 200 m and 300 m offshore forms tombolo and salient at a distance of 500 m from the shoreline. Numerical investigation of tombolo through XBeach model has given us an understanding on the morphological effects of breakwater offshore distance towards evolution of coastal features like tombolo and salient.
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STRUPCZEWSKI, WITOLD G., and ROMUALD SZYMKIEWICZ. "Analysis of paradoxes arising from the Chezy formula with constant roughness: I. Depth-discharge curve." Hydrological Sciences Journal 41, no. 5 (October 1996): 659–73. http://dx.doi.org/10.1080/02626669609491537.
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Papikyan, M. R., and S. R. Papikyan. "Response to I. P. Yakhternfel'd's article ?accuracy criterion of formulas for determining the Chezy coefficient?" Hydrotechnical Construction 27, no. 5 (May 1993): 313–14. http://dx.doi.org/10.1007/bf01545674.
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Terskii, Pavel, Elizaveta Rakcheeva, Maksim Kharlamov, Andrey Pavlovskiy, and Igor Zemlyanov. "Maximum water level calculation based on 2-dimensional DELFT-3D model, the case study of the Oka river." E3S Web of Conferences 163 (2020): 01012. http://dx.doi.org/10.1051/e3sconf/202016301012.
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This research represents methodical approach and main results of water level hydrodynamic modeling for real summer low-water season and extreme spring flood of 1% probability. The object of modeling is 105 km length section of the Oka River in Moscow region between Kashira and Kolomna urban districts. Modeling object includes also the Moscow River section downstream the Severka River mouth. Two-dimensional hydrodynamic model constructed using DELFT-3D. To build the model we used the detailed elevation model and hydrological conditions based on in-situ measurements in 2019, special estimated discharge and water level time-series of 1% exceedance probability based on reference year observations and distributed Chezy coefficient calibration. The model implementation resulted in the actual detailed distribution of the water discharge, velocity and level along the Oka River section (including the downstream Moscow River) for low-water and extremely high water periods. These results are used for the flood zone delineation in the Kashira and Kolomna urban districts.
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Scharf, Birgit E., Karen A. Fahrner, and Howard C. Berg. "CheZ Has No Effect on Flagellar Motors Activated by CheY13DK106YW." Journal of Bacteriology 180, no. 19 (October 1, 1998): 5123–28. http://dx.doi.org/10.1128/jb.180.19.5123-5128.1998.
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ABSTRACT The behaviors of both cheZ-deleted and wild-type cells of Escherichia coli were found to be very sensitive to the level of expression of CheZ, a protein known to accelerate the dephosphorylation of the response regulator CheY-phosphate (CheY-P). However, cells induced to run and tumble by the unphosphorylated mutant protein CheY13DK106YW (CheY**) failed to respond to CheZ, even when CheZ was expressed at high levels. Therefore, CheZ neither affects the flagellar motors directly nor sequesters CheY**. In in vitro cross-linking studies, CheY** promoted trimerization of CheZ to the same extent as wild-type CheY but failed to induce the formation of complexes of higher molecular weight observed with CheY-P. Also, CheY** could be cross-linked to FliM, the motor receptor protein, nearly as well as CheY-P. Thus, to CheZ, CheY** looks like CheY, but to FliM, it looks like CheY-P.
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STRUPCZEWSKI, WITOLD G., and ROMUALD SZYMKIEWICZ. "Analysis of paradoxes arising from the Chezy formula with constant roughness: II. Flow area-discharge curve." Hydrological Sciences Journal 41, no. 5 (October 1996): 675–82. http://dx.doi.org/10.1080/02626669609491538.
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Torabizadeh, Abbas, Ahmad Tahershamsi, and Mohammad Reza Majdzadeh Tabatabai. "Measurement of dimensionless Chezy coefficient in step-pool reach (Case Study of Dizin River in Iran)." Flow Measurement and Instrumentation 61 (June 2018): 15–25. http://dx.doi.org/10.1016/j.flowmeasinst.2018.03.012.
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Silversmith, Ruth E., Gerald P. Guanga, Laurie Betts, Carolyn Chu, Rui Zhao, and Robert B. Bourret. "CheZ-Mediated Dephosphorylation of the Escherichia coli Chemotaxis Response Regulator CheY: Role for CheY Glutamate 89." Journal of Bacteriology 185, no. 5 (March 1, 2003): 1495–502. http://dx.doi.org/10.1128/jb.185.5.1495-1502.2003.
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ABSTRACT The swimming behavior of Escherichia coli at any moment is dictated by the intracellular concentration of the phosphorylated form of the chemotaxis response regulator CheY, which binds to the base of the flagellar motor. CheY is phosphorylated on Asp57 by the sensor kinase CheA and dephosphorylated by CheZ. Previous work (Silversmith et al., J. Biol. Chem. 276:18478, 2001) demonstrated that replacement of CheY Asn59 with arginine resulted in extreme resistance to dephosphorylation by CheZ despite proficient binding to CheZ. Here we present the X-ray crystal structure of CheYN59R in a complex with Mn2+ and the stable phosphoryl analogue BeF3 −. The overall folding and active site architecture are nearly identical to those of the analogous complex containing wild-type CheY. The notable exception is the introduction of a salt bridge between Arg59 (on the β3α3 loop) and Glu89 (on the β4α4 loop). Modeling this structure into the (CheY-BeF3 −-Mg2+)2CheZ2 structure demonstrated that the conformation of Arg59 should not obstruct entry of the CheZ catalytic residue Gln147 into the active site of CheY, eliminating steric interference as a mechanism for CheZ resistance. However, both CheYE89A and CheYE89Q, like CheYN59R, conferred clockwise flagellar rotation phenotypes in strains which lacked wild-type CheY and displayed considerable (≈40-fold) resistance to dephosphorylation by CheZ. CheYE89A and CheYE89Q had autophosphorylation and autodephosphorylation properties similar to those of wild-type CheY and could bind to CheZ with wild-type affinity. Therefore, removal of Glu89 resulted specifically in CheZ resistance, suggesting that CheY Glu89 plays a role in CheZ-mediated dephosphorylation. The CheZ resistance of CheYN59R can thus be largely explained by the formation of the salt bridge between Arg59 and Glu89, which prevents Glu89 from executing its role in catalysis.
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Nearing, Mark A., Viktor O. Polyakov, Mary H. Nichols, Mariano Hernandez, Li Li, Ying Zhao, and Gerardo Armendariz. "Slope–velocity equilibrium and evolution of surface roughness on a stony hillslope." Hydrology and Earth System Sciences 21, no. 6 (June 30, 2017): 3221–29. http://dx.doi.org/10.5194/hess-21-3221-2017.
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Abstract. Slope–velocity equilibrium is hypothesized as a state that evolves naturally over time due to the interaction between overland flow and surface morphology, wherein steeper areas develop a relative increase in physical and hydraulic roughness such that flow velocity is a unique function of overland flow rate independent of slope gradient. This study tests this hypothesis under controlled conditions. Artificial rainfall was applied to 2 m by 6 m plots at 5, 12, and 20 % slope gradients. A series of simulations were made with two replications for each treatment with measurements of runoff rate, velocity, rock cover, and surface roughness. Velocities measured at the end of each experiment were a unique function of discharge rates, independent of slope gradient or rainfall intensity. Physical surface roughness was greater at steeper slopes. The data clearly showed that there was no unique hydraulic coefficient for a given slope, surface condition, or rainfall rate, with hydraulic roughness greater at steeper slopes and lower intensities. This study supports the hypothesis of slope–velocity equilibrium, implying that use of hydraulic equations, such as Chezy and Manning, in hillslope-scale runoff models is problematic because the coefficients vary with both slope and rainfall intensity.
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Achour, Bachir. "Chezy’s Resistance Coefficient in a Circular Conduit." Open Civil Engineering Journal 9, no. 1 (April 24, 2015): 187–95. http://dx.doi.org/10.2174/1874149501509010187.
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In the literature, there is no explicit method for calculating the resistance coefficient of Chezy, especially for a circular conduit. Existing relationships are either implicit or do not take into account all parameters influencing the flow such as kinematic viscosity or the slope of the conduit. In many practical cases, one affects arbitrarily a constant value for Chezy’s coefficient. It is a physically unjustified approach, because Chezy’s coefficient varies with flow parameters, especially the filling rate of the conduit and the absolute roughness. In this paper, simple and explicit relationships are presented for the calculation of Chezy’s resistance coefficient in a circular conduit. These relationships have been established based on the rough model method. The Chezy’s resistance coefficient is expressed in terms of known hydraulic parameters of the flow in a referential rough model. For fast calculation of Chezy’s coefficient, the simplified method is the most appropriate since it requires only four parameters which are the discharge, the absolute roughness, the slope and the kinematic viscosity. The study also shows that the Chezy’s resistance coefficient reaches a maximum whose expression is well defined. Some examples are presented showing how to calculate Chezy's coefficient in a circular conduit with a minimum practical data.
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EL, G. A., R. H. J. GRIMSHAW, and A. M. KAMCHATNOV. "Evolution of solitary waves and undular bores in shallow-water flows over a gradual slope with bottom friction." Journal of Fluid Mechanics 585 (August 7, 2007): 213–44. http://dx.doi.org/10.1017/s0022112007006817.
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This paper considers the propagation of shallow-water solitary and nonlinear periodic waves over a gradual slope with bottom friction in the framework of a variable-coefficient Korteweg–de Vries equation. We use the Whitham averaging method, using a recent development of this theory for perturbed integrable equations. This general approach enables us not only to improve known results on the adiabatic evolution of isolated solitary waves and periodic wave trains in the presence of variable topography and bottom friction, modelled by the Chezy law, but also, importantly, to study the effects of these factors on the propagation of undular bores, which are essentially unsteady in the system under consideration. In particular, it is shown that the combined action of variable topography and bottom friction generally imposes certain global restrictions on the undular bore propagation so that the evolution of the leading solitary wave can be substantially different from that of an isolated solitary wave with the same initial amplitude. This non-local effect is due to nonlinear wave interactions within the undular bore and can lead to an additional solitary wave amplitude growth, which cannot be predicted in the framework of the traditional adiabatic approach to the propagation of solitary waves in slowly varying media.
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Chung, S. W., and J. K. Oh. "Calibration of CE-QUAL-W2 for a monomictic reservoir in a monsoon climate area." Water Science and Technology 54, no. 11-12 (December 1, 2006): 29–37. http://dx.doi.org/10.2166/wst.2006.841.
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The impact of inflow mixing on reservoir stratification is significant for reservoirs situated in a monsoon climate area. It cause difficulty in the calibration of a two-dimensional hydrodynamic and water quality model, CE-QUAL-W2 that was recently adopted for a real-time turbidity monitoring and modelling system (RTMMS) for a reservoir in Korea. This paper presents a systematic calibration and verification processe of the model for the reservoir. A sensitivity analysis showed that wind sheltering, Chezy, and sediment heat exchange coefficients are most sensitive to stratification structure. Inflow temperature was very sensitive during a year of normal precipitation, but it is not significant during a year of drought. Residual analysis revealed that the model has shortcomings in the simulation of water temperature near the metalimnetic zone without calibration. After calibration, however, the absolute mean errors between observed and simulated values were placed within 0.116–1.190 °C. Its performance was maintained under heavy flood events during the verification stage, which implies that the model is ready to use for the simulation of turbidity plume in the RTMMS under various hydrologic conditions. The suggested model calibration strategy and relevant results may be adopted for other reservoirs located in a monsoon climate area.
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Zakariah, Ridzwan Bin, Norzila Binti Othman, Mohd Azlan bin Mohd Yusoff, and Wahid Ali Hamood Altowayti. "Determination of Stage Discharge Rating Curve at Sungai Batang Melaka." Journal of Southwest Jiaotong University 56, no. 3 (June 30, 2021): 248–61. http://dx.doi.org/10.35741/issn.0258-2724.56.3.21.
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The river is a natural source of water with distinctive hydraulic features. The hydraulic characteristic is a factor in morphology changes. The article describes a determination of a stage discharge rating curve at Sungai Batang Melaka that has been developed for the first time. The stage discharge rating curve is used to determine whether the rivers of this area are the cause of floods that have occurred in Malacca. Based on data collection for width and depth at four locations, enabling to evaluate and analysis the data of each cross-section for Sungai Batang Melaka. By observing the river velocity, the condition of the river flow in the area will be obtained. The two-point method and mid-section method is used to measure the flow rates in the rivers. Following the calculation using Chezy-Manning’s equation, the authors research shows that this river produces a good stage discharge rating curve. Overall, a stage discharge rating curve for each location shows it is associated with gradation and degradation rates. From the findings, the outflow, storage capacity, and discharge rating curve in Sungai Batang Melaka were successfully obtained. It will benefit future studies, especially in facilitating measures to be taken to avoid flash floods that keep occurring in Malacca.
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Sanayei, Hamed Reza Zarif, and Fatemeh Nasiri. "Simple Semi-analytical Solutions Using the Perturbation Method for Gradually Varied Flow Profile in Triangular Channels." Mathematical Modelling of Engineering Problems 7, no. 4 (December 18, 2020): 642–48. http://dx.doi.org/10.18280/mmep.070417.
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In hydraulic engineering, the steady non-uniform flow in a channel with the gradual changes at the water surface level is introduced as the Gradually Varied Flow (GVF). For the design of open channels, it is necessary to calculate the GVF profile along the channel flow. The GVF profile is described by a nonlinear Ordinary Differential Equation (ODE). Because this equation is strongly nonlinear, providing new analytical and/or semi-analytical solutions for this equation without any simplifications and/or linearizations would be necessary and helpful. In this research, the Perturbation Method (PM) is proposed to present a semi-analytical solution for solving the GVF equation in the prismatic triangular channel. A total of two cases are studied in this paper. In case 1, the Manning equation and in case 2, the Chezy equation are applied as the resistance equations. The GVF profiles in the two cases are compared with the Finite Difference Method (FDM) profiles. Also, the effect of the summation truncation in the PM is studied for these cases. The results show that by increasing the terms approximation in the PM, the GVF profile converges to the FDM profile. A reference solution for efficiency assessment of numerical techniques can be provided by presented semi-analytical solutions in this paper. Furthermore, the proposed method in this paper can be used as a new idea in providing semi-analytical solutions to other open channel works.
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Ferro, Vito. "Comments on “Measurement of dimensionless Chezy coefficient in step-pool reach (Case study of Dizin River in Iran)” by Torabizadeh A., Tahershamsi A., Tabatabai M.R.M." Flow Measurement and Instrumentation 64 (December 2018): 190–93. http://dx.doi.org/10.1016/j.flowmeasinst.2018.10.023.
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Appleby, Jeryl L., and Robert B. Bourret. "Proposed Signal Transduction Role for Conserved CheY Residue Thr87, a Member of the Response Regulator Active-Site Quintet." Journal of Bacteriology 180, no. 14 (July 15, 1998): 3563–69. http://dx.doi.org/10.1128/jb.180.14.3563-3569.1998.
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ABSTRACT CheY serves as a structural prototype for the response regulator proteins of two-component regulatory systems. Functional roles have previously been defined for four of the five highly conserved residues that form the response regulator active site, the exception being the hydroxy amino acid which corresponds to Thr87 in CheY. To investigate the contribution of Thr87 to signaling, we characterized, genetically and biochemically, several cheY mutants with amino acid substitutions at this position. The hydroxyl group appears to be necessary for effective chemotaxis, as a Thr→Ser substitution was the only one of six tested which retained a Che+ swarm phenotype. Although nonchemotactic, cheY mutants with amino acid substitutions T87A and T87C could generate clockwise flagellar rotation either in the absence of CheZ, a protein that stimulates dephosphorylation of CheY, or when paired with a second site-activating mutation, Asp13→Lys, demonstrating that a hydroxy amino acid at position 87 is not essential for activation of the flagellar switch. All purified mutant proteins examined phosphorylated efficiently from the CheA kinase in vitro but were impaired in autodephosphorylation. Thus, the mutant CheY proteins are phosphorylated to a greater degree than wild-type CheY yet support less clockwise flagellar rotation. The data imply that Thr87 is important for generating and/or stabilizing the phosphorylation-induced conformational change in CheY. Furthermore, the various position 87 substitutions differentially affected several properties of the mutant proteins. The chemotaxis and autodephosphorylation defects were tightly linked, suggesting common structural elements, whereas the effects on self-catalyzed and CheZ-mediated dephosphorylation of CheY were uncorrelated, suggesting different structural requirements for the two dephosphorylation reactions.
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Muff, Travis J., Richard M. Foster, Peter J. Y. Liu, and George W. Ordal. "CheX in the Three-Phosphatase System of Bacterial Chemotaxis." Journal of Bacteriology 189, no. 19 (August 3, 2007): 7007–13. http://dx.doi.org/10.1128/jb.00896-07.
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ABSTRACT Bacterial chemotaxis involves the regulation of motility by a modified two-component signal transduction system. In Escherichia coli, CheZ is the phosphatase of the response regulator CheY but many other bacteria, including Bacillus subtilis, use members of the CheC-FliY-CheX family for this purpose. While Bacillus subtilis has only CheC and FliY, many systems also have CheX. The effect of this three-phosphatase system on chemotaxis has not been studied previously. CheX was shown to be a stronger CheY-P phosphatase than either CheC or FliY. In Bacillus subtilis, a cheC mutant strain was nearly complemented by heterologous cheX expression. CheX was shown to overcome the ΔcheC adaptational defect but also generally lowered the counterclockwise flagellar rotational bias. The effect on rotational bias suggests that CheX reduced the overall levels of CheY-P in the cell and did not truly replicate the adaptational effects of CheC. Thus, CheX is not functionally redundant to CheC and, as outlined in the discussion, may be more analogous to CheZ.
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Che, Yong-Suk, Takashi Sagawa, Yuichi Inoue, Hiroto Takahashi, Tatsuki Hamamoto, Akihiko Ishijima, and Hajime Fukuoka. "Fluctuations in Intracellular CheY-P Concentration Coordinate Reversals of Flagellar Motors in E. coli." Biomolecules 10, no. 11 (November 12, 2020): 1544. http://dx.doi.org/10.3390/biom10111544.
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Signal transduction utilizing membrane-spanning receptors and cytoplasmic regulator proteins is a fundamental process for all living organisms, but quantitative studies of the behavior of signaling proteins, such as their diffusion within a cell, are limited. In this study, we show that fluctuations in the concentration of the signaling molecule, phosphorylated CheY, constitute the basis of chemotaxis signaling. To analyze the propagation of the CheY-P signal quantitatively, we measured the coordination of directional switching between flagellar motors on the same cell. We analyzed the time lags of the switching of two motors in both CCW-to-CW and CW-to-CCW switching (∆τCCW-CW and ∆τCW-CCW). In wild-type cells, both time lags increased as a function of the relative distance of two motors from the polar receptor array. The apparent diffusion coefficient estimated for ∆τ values was ~9 µm2/s. The distance-dependency of ∆τCW-CCW disappeared upon loss of polar localization of the CheY-P phosphatase, CheZ. The distance-dependency of the response time for an instantaneously applied serine attractant signal also disappeared with the loss of polar localization of CheZ. These results were modeled by calculating the diffusion of CheY and CheY-P in cells in which phosphorylation and dephosphorylation occur in different subcellular regions. We conclude that diffusion of signaling molecules and their production and destruction through spontaneous activity of the receptor array generates fluctuations in CheY-P concentration over timescales of several hundred milliseconds. Signal fluctuation coordinates rotation among flagella and regulates steady-state run-and-tumble swimming of cells to facilitate efficient responses to environmental chemical signals.
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Antúnez-Lamas, María, Ezequiel Cabrera-Ordóñez, Emilia López-Solanilla, Rosa Raposo, Oswaldo Trelles-Salazar, Andrés Rodríguez-Moreno, and Pablo Rodríguez-Palenzuela. "Role of motility and chemotaxis in the pathogenesis of Dickeya dadantii 3937 (ex Erwinia chrysanthemi 3937)." Microbiology 155, no. 2 (February 1, 2009): 434–42. http://dx.doi.org/10.1099/mic.0.022244-0.
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Dickeya dadantii 3937 (ex Erwinia chrysanthemi), a member of the Enterobacteriaceae, causes soft rot in many economically important crops. A successful pathogen has to reach the interior of the plant in order to cause disease. To study the role of motility and chemotaxis in the pathogenicity of D. dadantii 3937, genes involved in the chemotactic signal transduction system (cheW, cheB, cheY and cheZ) and in the structure of the flagellar motor (motA) were mutagenized. All the mutant strains grew like the wild-type in culture media, and the production and secretion of pectolytic enzymes was not affected. As expected, the swimming ability of the mutant strains was reduced with respect to the wild-type: motA (94 %), cheY (80 %), cheW (74 %), cheB (54 %) and cheZ (48 %). The virulence of the mutant strains was analysed in chicory, Saintpaulia and potato. The mutant strains were also tested for their capability to enter into Arabidopsis leaves. All the mutants showed a significant decrease of virulence in certain hosts; however, the degree of virulence reduction varied depending on the virulence assay. The ability to penetrate Arabidopsis leaves was impaired in all the mutants, whereas the capacity to colonize potato tubers after artificial inoculation was affected in only two mutant strains. In general, the virulence of the mutants could be ranked as motA<cheY<cheB=cheW<cheZ, which correlated with the degree to which swimming was affected. These results clearly indicate that motility plays an important role in the pathogenicity of this bacterium.
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Ding, J. Y. "A measure of watershed nonlinearity: interpreting a variable instantaneous unit hydrograph model on two vastly different sized – watersheds." Hydrology and Earth System Sciences Discussions 2, no. 5 (September 27, 2005): 2111–51. http://dx.doi.org/10.5194/hessd-2-2111-2005.
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Abstract. This paper reviews the use of an input-dependent kernel in a linear convolution integral as a quasi-nonlinear approach to unify nonlinear overland flow, channel routing and catchment runoff processes. The conceptual model of a variable kernel or instantaneous unit hydrograph (IUH) is characterized by a nonlinear storage-discharge relation, q=cNsN where the storage exponent N is an index or degree of watershed nonlinearity. When the causative rainfall excess intensity of a unit hydrograph is known, parameters N and c can be determined directly from its shape factor, the product of the unit peak ordinate and the time to peak. The model is calibrated by the shape factor and verified by convolution integral on two watersheds of vastly different sizes, each having a family of four or five unit hydrographs, data of which were published by Childs in 1958 for the Naugatuck River and by Minshall in 1960 for the Edwardsville catchment. For an 11-hectare catchment near Edwardsville in southern Illinois, the US, four moderate storms show an average N value of 1.79, which is 7% higher than the theoretical value of 1.67 by Manning friction law, while the heaviest storm, which is three to six times larger than the next two events in terms of the peak discharge and runoff volume, follows the Chezy law of 1.5. At the other end of scale, for the Naugatuck River at Thomaston in Connecticut, the US, having a drainage area of 186.2 km2, the average N value of 2.28 varies from 1.92 for a minor flood to 2.68 for a hurricane-induced flood, all of which lie between the theoretical value of 1.67 for turbulent overland flow and that of 3.0 for laminar overland flow. Short examples and a spreadsheet template are given to illustrate key steps in generating the direct runoff hydrograph by convolution integral with the 2-parameter variable IUH model.
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Hyakutake, Akihiro, Michio Homma, Melissa J. Austin, Markus A. Boin, Claudia C. Häse, and Ikuro Kawagishi. "Only One of the Five CheY Homologs in Vibrio cholerae Directly Switches Flagellar Rotation." Journal of Bacteriology 187, no. 24 (December 15, 2005): 8403–10. http://dx.doi.org/10.1128/jb.187.24.8403-8410.2005.
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ABSTRACT Vibrio cholerae has three sets of chemotaxis (Che) proteins, including three histidine kinases (CheA) and four response regulators (CheY) that are encoded by three che gene clusters. We deleted the cheY genes individually or in combination and found that only the cheY3 deletion impaired chemotaxis, reinforcing the previous conclusion that che cluster II is involved in chemotaxis. However, this does not exclude the involvement of the other clusters in chemotaxis. In other bacteria, phospho-CheY binds directly to the flagellar motor to modulate its rotation, and CheY overexpression, even without CheA, causes extremely biased swimming behavior. We reasoned that a V. cholerae CheY homolog, if it directly controls flagellar rotation, should also induce extreme swimming behavior when overproduced. This was the case for CheY3 (che cluster II). However, no other CheY homolog, including the putative CheY (CheY0) protein encoded outside the che clusters, affected swimming, demonstrating that these CheY homologs cannot act directly on the flagellar motor. CheY4 very slightly enhanced the spreading of an Escherichia coli cheZ mutant in semisolid agar, raising the possibility that it can affect chemotaxis by removing a phosphoryl group from CheY3. We also found that V. cholerae CheY3 and E. coli CheY are only partially exchangeable. Mutagenic analyses suggested that this may come from coevolution of the interacting pair of proteins, CheY and the motor protein FliM. Taken together, it is likely that the principal roles of che clusters I and III as well as cheY0 are to control functions other than chemotaxis.
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Montrone, Marco, Michael Eisenbach, Dieter Oesterhelt, and Wolfgang Marwan. "Regulation of Switching Frequency and Bias of the Bacterial Flagellar Motor by CheY and Fumarate." Journal of Bacteriology 180, no. 13 (July 1, 1998): 3375–80. http://dx.doi.org/10.1128/jb.180.13.3375-3380.1998.
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ABSTRACT The effect of CheY and fumarate on switching frequency and rotational bias of the bacterial flagellar motor was analyzed by computer-aided tracking of tethered Escherichia coli. Plots of cells overexpressing CheY in a gutted background showed a bell-shaped correlation curve of switching frequency and bias centering at about 50% clockwise rotation. Gutted cells (i.e., withcheA to cheZ deleted) with a low CheY level but a high cytoplasmic fumarate concentration displayed the same correlation of switching frequency and bias as cells overexpressing CheY at the wild-type fumarate level. Hence, a high fumarate level can phenotypically mimic CheY overexpression by simultaneously changing the switching frequency and the bias. A linear correlation of cytoplasmic fumarate concentration and clockwise rotation bias was found and predicts exclusively counterclockwise rotation without switching when fumarate is absent. This suggests that (i) fumarate is essential for clockwise rotation in vivo and (ii) any metabolically induced fluctuation of its cytoplasmic concentration will result in a transient change in bias and switching probability. A high fumarate level resulted in a dose-response curve linking bias and cytoplasmic CheY concentration that was offset but with a slope similar to that for a low fumarate level. It is concluded that fumarate and CheY act additively presumably at different reaction steps in the conformational transition of the switch complex from counterclockwise to clockwise motor rotation.
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Li, Mingshan, and Gerald L. Hazelbauer. "Cellular Stoichiometry of the Components of the Chemotaxis Signaling Complex." Journal of Bacteriology 186, no. 12 (June 15, 2004): 3687–94. http://dx.doi.org/10.1128/jb.186.12.3687-3694.2004.
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ABSTRACT The chemotactic sensory system of Escherichia coli comprises membrane-embedded chemoreceptors and six soluble chemotaxis (Che) proteins. These components form signaling complexes that mediate sensory excitation and adaptation. Previous determinations of cellular content of individual components provided differing and apparently conflicting values. We used quantitative immunoblotting to perform comprehensive determinations of cellular amounts of all components in two E. coli strains considered wild type for chemotaxis, grown in rich and minimal media. Cellular amounts varied up to 10-fold, but ratios between proteins varied no more than 30%. Thus, cellular stoichiometries were almost constant as amounts varied substantially. Calculations using those cellular stoichiometries and values for in vivo proportions of core components in complexes yielded an in vivo stoichiometry for core complexes of 3.4 receptor dimers and 1.6 CheW monomers for each CheA dimer and 2.4 CheY, 0.5 CheZ dimers, 0.08 CheB, and 0.05 CheR per complex. The values suggest a core unit of a trimer of chemoreceptor dimers, a dimer (or two monomers) of kinase CheA, and two CheW. These components may interact in extended arrays and, thus, stoichiometries could be nonintegral. In any case, cellular stoichiometries indicate that CheY could be bound to all signaling complexes and this binding would recruit essentially the entire cellular complement of unphosphorylated CheY, and also that phosphatase CheZ, methylesterase CheB, and methyltransferase CheR would be present at 1 per 2, per 14, and per 20 core complexes, respectively. These characteristic ratios will be important in quantitative treatments of chemotaxis, both experimental and theoretical.
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Motaleb, M. A., Michael R. Miller, Chunhao Li, Richard G. Bakker, Stuart F. Goldstein, Ruth E. Silversmith, Robert B. Bourret, and Nyles W. Charon. "CheX Is a Phosphorylated CheY Phosphatase Essential for Borrelia burgdorferi Chemotaxis." Journal of Bacteriology 187, no. 23 (December 1, 2005): 7963–69. http://dx.doi.org/10.1128/jb.187.23.7963-7969.2005.
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ABSTRACT Motility and chemotaxis are believed to be important in the pathogenesis of Lyme disease caused by the spirochete Borrelia burgdorferi. Controlling the phosphorylation state of CheY, a response regulator protein, is essential for regulating bacterial chemotaxis and motility. Rapid dephosphorylation of phosphorylated CheY (CheY-P) is crucial for cells to respond to environmental changes. CheY-P dephosphorylation is accomplished by one or more phosphatases in different species, including CheZ, CheC, CheX, FliY, and/or FliY/N. Only a cheX phosphatase homolog has been identified in the B. burgdorferi genome. However, a role for cheX in chemotaxis has not been established in any bacterial species. Inactivating B. burgdorferi cheX by inserting a flgB-kan cassette resulted in cells (cheX mutant cells) with a distinct motility phenotype. While wild-type cells ran, paused (stopped or flexed), and reversed, the cheX mutant cells continuously flexed and were not able to run or reverse. Furthermore, swarm plate and capillary tube chemotaxis assays demonstrated that cheX mutant cells were deficient in chemotaxis. Wild-type chemotaxis and motility were restored when cheX mutant cells were complemented with a shuttle vector expressing CheX. Furthermore, CheX dephosphorylated CheY3-P in vitro and eluted as a homodimer in gel filtration chromatography. These findings demonstrated that B. burgdorferi CheX is a CheY-P phosphatase that is essential for chemotaxis and motility, which is consistent with CheX being the only CheY-P phosphatase in the B. burgdorferi chemotaxis signal transduction pathway.
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Alibekov, A. K., and G. A. Аlibekov. "MODELS FOR DETERMINING MAXIMUM DEGREE FILLING CHANNELS OF CIRCULAR SECTION SHAPE." Herald of Dagestan State Technical University. Technical Sciences 46, no. 2 (August 28, 2019): 28–36. http://dx.doi.org/10.21822/2073-6185-2019-46-2-28-36.
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Objectives The task was to obtain a model for determining the maximum possible degree of filling the circular section channels in the earthen channel based on the condition of ensuring the stability of slopes and the minimum volume of excavation during their construction, as well as finding the optimum degree of filling fortified channels of a closed profile corresponding to maximum throughput.Method In work analytical methods of differential calculus and the solution of implicit equations are used.Result The experience of domestic and foreign researchers was taken into account to solve the set tasks, select research methods and criteria for optimizing channel parameters. Two cases of circular-shaped channels are considered: 1) in the earth channel, 2) reinforced with a closed transverse profile. For the case of a hydraulically most advantageous circular channel in the earthchannel channel, equating the first derivative of the equation of a circle with the reciprocal of the allowable embedding coefficient of the slopes obtained an analytical solution for determining the maximum degree of filling from the slope stability condition, which was not dependent on hydraulic flow elements. In the case of non-cohesive soils that form the channel, the circular channel can be filled to a depth not exceeding 20 percent of the channel radius. At the same time, the average flow rate should remain in the range from non-venting to non-blurring. In order to be able to determine the flow rate, analytical expressions are given for finding hydraulic flow elements in a circular channel. When determining the volume of excavation for the construction of the channel, the excess of the channel edge above the maximum water level in the channel was taken into account. For the case of a fortified channel of a closed transverse profile, by taking the derivatives from the Chezy formula, we obtained the optimal values of flow rate and average velocity.Conclusion A fortified closed circular profile channel has a maximum capacity with a relative degree of filling of 0.938, and the maximum average velocity of a fluid in a pressureless channel is achieved with a degree of filling of 0.815. To determine the maximum permissible relative degree of filling in the case of a circular section channel in the earthen channel, analytical dependences were obtained, before using which, according to the reference literature, it is necessary to take the value of the slope coefficient for this type of channel bed soil.
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Abouhamad, Walid N., Dennis Bray, Martin Schuster, Kristin C. Boesch, Ruth E. Silversmith, and Robert B. Bourret. "Computer-Aided Resolution of an Experimental Paradox in Bacterial Chemotaxis." Journal of Bacteriology 180, no. 15 (August 1, 1998): 3757–64. http://dx.doi.org/10.1128/jb.180.15.3757-3764.1998.
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ABSTRACT Escherichia coli responds to its environment by means of a network of intracellular reactions which process signals from membrane-bound receptors and relay them to the flagellar motors. Although characterization of the reactions in the chemotaxis signaling pathway is sufficiently complete to construct computer simulations that predict the phenotypes of mutant strains with a high degree of accuracy, two previous experimental investigations of the activity remaining upon genetic deletion of multiple signaling components yielded several contradictory results (M. P. Conley, A. J. Wolfe, D. F. Blair, and H. C. Berg, J. Bacteriol. 171:5190–5193, 1989; J. D. Liu and J. S. Parkinson, Proc. Natl. Acad. Sci. USA 86:8703–8707, 1989). For example, “building up” the pathway by adding back CheA and CheY to a gutted strain lacking chemotaxis genes resulted in counterclockwise flagellar rotation whereas “breaking down” the pathway by deleting chemotaxis genes except cheA and cheY resulted in alternating episodes of clockwise and counterclockwise flagellar rotation. Our computer simulation predicts that trace amounts of CheZ expressed in the gutted strain could account for this difference. We tested this explanation experimentally by constructing a mutant containing a new deletion of the che genes that cannot express CheZ and verified that the behavior of strains built up from the new deletion does in fact conform to both the phenotypes observed for breakdown strains and computer-generated predictions. Our findings consolidate the present view of the chemotaxis signaling pathway and highlight the utility of molecularly based computer models in the analysis of complex biochemical networks.
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Lux, Renate, V. Ranjit N. Munasinghe, Fred Castellano, Joseph W. Lengeler, John E. T. Corrie, and Shahid Khan. "Elucidation of a PTS–Carbohydrate Chemotactic Signal Pathway inEscherichia coliUsing a Time-resolved Behavioral Assay." Molecular Biology of the Cell 10, no. 4 (April 1999): 1133–46. http://dx.doi.org/10.1091/mbc.10.4.1133.
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Chemotaxis of Escherichia coli toward phosphotransferase systems (PTSs)–carbohydrates requires phosphoenolpyruvate-dependent PTSs as well as the chemotaxis response regulator CheY and its kinase, CheA. Responses initiated by flash photorelease of a PTS substrates d-glucose and its nonmetabolizable analog methyl α-d-glucopyranoside were measured with 33-ms time resolution using computer-assisted motion analysis. This, together with chemotactic mutants, has allowed us to map out and characterize the PTS chemotactic signal pathway. The responses were absent in mutants lacking the general PTS enzymes EI or HPr, elevated in PTS transport mutants, retarded in mutants lacking CheZ, a catalyst of CheY autodephosphorylation, and severely reduced in mutants with impaired methyl-accepting chemotaxis protein (MCP) signaling activity. Response kinetics were comparable to those triggered by MCP attractant ligands over most of the response range, the most rapid being 11.7 ± 3.1 s−1. The response threshold was <10 nM for glucose. Responses to methyl α-d-glucopyranoside had a higher threshold, commensurate with a lower PTS affinity, but were otherwise kinetically indistinguishable. These facts provide evidence for a single pathway in which the PTS chemotactic signal is relayed rapidly to MCP–CheW–CheA signaling complexes that effect subsequent amplification and slower CheY dephosphorylation. The high sensitivity indicates that this signal is generated by transport-induced dephosphorylation of the PTS rather than phosphoenolpyruvate consumption.
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Pazy, Y., M. A. Motaleb, M. T. Guarnieri, N. W. Charon, R. Zhao, and R. E. Silversmith. "Identical phosphatase mechanisms achieved through distinct modes of binding phosphoprotein substrate." Proceedings of the National Academy of Sciences 107, no. 5 (January 14, 2010): 1924–29. http://dx.doi.org/10.1073/pnas.0911185107.
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Two-component signal transduction systems are widespread in prokaryotes and control numerous cellular processes. Extensive investigation of sensor kinase and response regulator proteins from many two-component systems has established conserved sequence, structural, and mechanistic features within each family. In contrast, the phosphatases which catalyze hydrolysis of the response regulator phosphoryl group to terminate signal transduction are poorly understood. Here we present structural and functional characterization of a representative of the CheC/CheX/FliY phosphatase family. The X-ray crystal structure of Borrelia burgdorferi CheX complexed with its CheY3 substrate and the phosphoryl analogue reveals a binding orientation between a response regulator and an auxiliary protein different from that shared by every previously characterized example. The surface of CheY3 containing the phosphoryl group interacts directly with a long helix of CheX which bears the conserved (E - X2 - N) motif. Conserved CheX residues Glu96 and Asn99, separated by a single helical turn, insert into the CheY3 active site. Structural and functional data indicate that CheX Asn99 and CheY3 Thr81 orient a water molecule for hydrolytic attack. The catalytic residues of the CheX·CheY3 complex are virtually superimposable on those of the Escherichia coli CheZ phosphatase complexed with CheY, even though the active site helices of CheX and CheZ are oriented nearly perpendicular to one other. Thus, evolution has found two structural solutions to achieve the same catalytic mechanism through different helical spacing and side chain lengths of the conserved acid/amide residues in CheX and CheZ.
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Jiménez-Pearson, María-Antonieta, Isabel Delany, Vincenzo Scarlato, and Dagmar Beier. "Phosphate flow in the chemotactic response system of Helicobacter pylori." Microbiology 151, no. 10 (October 1, 2005): 3299–311. http://dx.doi.org/10.1099/mic.0.28217-0.
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It is well established that motility is an essential virulence trait of the human gastric pathogen Helicobacter pylori. Accordingly, chemotaxis contributes to the ability of H. pylori to colonize animal infection models. Chemotactic signal transduction in H. pylori differs from the enterobacterial paradigm in several respects. In addition to a separate CheY response regulator protein (CheY1), H. pylori contains a CheY-like receiver domain (CheY2) which is C-terminally fused to the histidine kinase CheA. Furthermore, the genome of H. pylori encodes three CheV proteins consisting of an N-terminal CheW-like domain and a C-terminal receiver domain, while there are no orthologues of the chemotaxis genes cheB, cheR and cheZ. To obtain insight into the mechanisms controlling the chemotactic response of H. pylori, we investigated the phosphotransfer reactions between the purified two-component signalling modules in vitro. We demonstrate that both CheY1 and CheY2 are phosphorylated by CheA∼P and that the three CheV proteins mediate the dephosphorylation of CheA∼P, but with a clearly reduced efficiency as compared to CheY1 and CheY2. Furthermore, our data indicate retrophosphorylation of CheAY2 by CheY1∼P, suggesting a role of CheY2 as a phosphate sink to modulate the half-life of CheY1∼P.
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Ding, J. Y. "A measure of watershed nonlinearity: interpreting a variable instantaneous unit hydrograph model on two vastly different sized watersheds." Hydrology and Earth System Sciences 15, no. 1 (January 31, 2011): 405–23. http://dx.doi.org/10.5194/hess-15-405-2011.
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Abstract. The linear unit hydrograph used in hydrologic design analysis and flood forecasting is known as the transfer function and the kernel function in time series analysis and systems theory, respectively. This paper reviews the use of an input-dependent or variable kernel in a linear convolution integral as a quasi-nonlinear approach to unify nonlinear overland flow, channel routing and catchment runoff processes. The conceptual model of a variable instantaneous unit hydrograph (IUH) is characterized by a nonlinear storage-discharge relation, q = cNsN, where the storage exponent N is an index or degree of watershed nonlinearity, and the scale parameter c is a discharge coefficient. When the causative rainfall excess intensity of a unit hydrograph is known, parameters N and c can be determined directly from its shape factor, which is the product of the unit peak ordinate and the time to peak, an application of the statistical method of moments in its simplest form. The 2-parameter variable IUH model is calibrated by the shape factor method and verified by convolution integral using both the direct and inverse Bakhmeteff varied-flow functions on two watersheds of vastly different sizes, each having a family of four or five unit hydrographs as reported by the well-known Minshall (1960) paper and the seldom-quoted Childs (1958) one, both located in the US. For an 11-hectare catchment near Edwardsville in southern Illinois, calibration for four moderate storms shows an average N value of 1.79, which is 7% higher than the theoretical value of 1.67 by Manning friction law, while the heaviest storm, which is three to six times larger than the next two events in terms of the peak discharge and runoff volume, follows the Chezy law of 1.5. At the other end of scale, for the Naugatuck River at Thomaston in Connecticut having a drainage area of 186.2 km2, the average calibrated N value of 2.28 varies from 1.92 for a minor flood to 2.68 for a hurricane-induced flood, all of which lie between the theoretical value of 1.67 for turbulent overland flow and that of 3.0 for laminar overland flow. Based on analytical results from the small Edwardsville catchment, the 2-parameter variable IUH model is found to be defined by a quadruplet of parameters N, c, the storm duration or computational time step Δt, and the rainfall excess intensity i(0), and that it may be reduced to an 1-parameter one by defaulting the degree of nonlinearity N to 1.67 by Manning friction. For short, intense storms, the essence of the Childs – Minshall nonlinear unit hydrograph phenomenon is encapsulated in a peak flow equation having a single (scale) parameter c, and in which the impact of the rainfall excess intensity increases from the linear assumption by a power of 0.4. To illustrate key steps in generating the direct runoff hydrograph by convolution integral, short examples are given.
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Chen, Bryan G., Linda Turner, and Howard C. Berg. "The Wetting Agent Required for Swarming in Salmonella enterica Serovar Typhimurium Is Not a Surfactant." Journal of Bacteriology 189, no. 23 (September 28, 2007): 8750–53. http://dx.doi.org/10.1128/jb.01109-07.
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ABSTRACT We compared the abilities of media from agar plates surrounding swarming and nonswarming cells of Salmonella enterica serovar Typhimurium to wet a nonpolar surface by measuring the contact angles of small drops. The swarming cells were wild type for chemotaxis, and the nonswarming cells were nonchemotactic mutants with motor biases that were counterclockwise (cheY) or clockwise (cheZ). The latter strains have been shown to be defective for swarming because the agar remains dry (Q. Wang, A. Suzuki, S. Mariconda, S. Porwollik, and R. M. Harshey, EMBO J. 24:2034-2042, 2005). We found no differences in the abilities of the media surrounding these cells, either wild type or mutant, to wet a low-energy surface (freshly prepared polydimethylsiloxane); although, their contact angles were smaller than that of the medium harvested from the underlying agar. So the agent that promotes wetness produced by wild-type cells is not a surfactant; it is an osmotic agent.
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Blat, Yuval, and Michael Eisenbach. "Phosphorylation-dependent binding of the chemotaxis signal molecule CheY to its phosphatase, CheZ." Biochemistry 33, no. 4 (February 1994): 902–6. http://dx.doi.org/10.1021/bi00170a008.
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Blat, Yuval, and Michael Eisenbach. "Oligomerization of the Phosphatase CheZ Upon Interaction with the Phosphorylated Form of CheY." Journal of Biological Chemistry 271, no. 2 (January 12, 1996): 1226–31. http://dx.doi.org/10.1074/jbc.271.2.1226.
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Zhu, Xiangyang, Karl Volz, and Philip Matsumura. "The CheZ-binding Surface of CheY Overlaps the CheA- and FliM-binding Surfaces." Journal of Biological Chemistry 272, no. 38 (September 19, 1997): 23758–64. http://dx.doi.org/10.1074/jbc.272.38.23758.
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Luo, Biao, Chengyuan Wang, and Liang Liang. "Chery Automobile." Asian Case Research Journal 21, no. 01 (June 2017): 37–80. http://dx.doi.org/10.1142/s021892751750002x.
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Chery, which used to be the leader of Chinese indigenous automobile manufacturers as well as the entry-level market, has been losing its leader position since 2010. Chery, founded in 1997, has experienced a radical expansion along with industrial liberalization and economic growth in China since 2000. In 2007, Chery started the internationalization strategy by launching two middle and high-end brands and developing a series of joint ventures consecutively. However, Chery has confronted various challenges since 2010 with the growing maturity of Chinese automobile industry, including declining domestic sales and market share, and thus was in a weak position under attack. Finally, Chery announced its tactical adjustments in April 2013. This case describes the co-evolution between the environmental transitions of Chinese automotive industry and the business strategies of Chery. Students are asked to analyze the development of Chery and provide specific suggestions of future directions on competitive strategy for Chery.
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Tjandradipura, Carina. "KAJIAN IKLAN MOBIL CHERY QQ DENGAN PENDEKATAN SEMIOTIKA." Idealog: Ide dan Dialog Desain Indonesia 2, no. 3 (April 5, 2018): 263. http://dx.doi.org/10.25124/idealog.v2i3.1233.
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Iklan merupakan salah satu bentuk komunikasi berupa pesan dari suatu produk tertentu yang ingin disampaikan kepada masyarakat melalui media. Mobil Chery QQ dengan kategori city tampil dalam sebuah iklan yang dihadirkan melalui tampilan desain poster yang menarik. Iklan mobil Chery QQ berupa poster bertujuan untuk menyampaikan suatu pesan kepada masyarakat car sebagai salah satu mobil dengan konsumsi bahan bakar hemat. Metode penelitian yang digunakan pada poster iklan Chery QQ adalah teori semiotika yang dikemukakan Pierce berupa ikon, indeks, dan simbol. Tujuan penelitian untuk mengetahui makna-makna yang ingin disampaikan oleh perusahaan automotif tersebut dalam poster iklan mobil Chery QQ. Iklan tersebut ingin mengkomunikasikan bahwa mobil Chery QQ merupakan kendaraan bermotor beroda empat yang hemat konsumsi bahan bakar ditampilkan melalui penggambaran ilustrasi kartun dan slogan berbahasa Spanyol “Menos visitas al surtidor†pada sebuah poster iklan mobil Chery QQ dengan segmen pasar di Meksiko yang terletak di Amerika Utara dan mayoritas penduduknya menggunakan bahasa Spanyol. Poster iklan tersebut menceritakan bahwa Chery QQ diasumsikan memiliki gender wanita, sedangkan mesin pengisi bahan bakar yang digambarkan melalui ilustrasi kartun berwarna merah memiliki gender pria, keduanya memiliki sebuah hubungan khusus, layaknya sebuah pasangan kekasih. Mobil Chery QQ merupakan kendaraan yang memerlukan bahan bakar agar dapat beroperasi, sedangkan mesin pengisi bahan bakar menyediakan bahan bakar yang diperlukan oleh mobil Chery QQ. Dengan demikian, poster iklan Chery QQ dapat mengkomunikasikan keunggulannya dengan baik kepada masyarakat melalui makna-maknanya berupa pesan dalam bahasa tanda yang ditampilkan Mobil Chery QQ merupakan kendaraan beroda empat yang hemat konsumsi bahan bakar serta ramah lingkungan.
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Huang, Chongxi, and Richard C. Stewart. "CheZ mutants with enhanced ability to dephosphorylate CheY, the response regulator in bacterial chemotaxis." Biochimica et Biophysica Acta (BBA) - Protein Structure and Molecular Enzymology 1202, no. 2 (October 1993): 297–304. http://dx.doi.org/10.1016/0167-4838(93)90019-n.
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