Distribution of glycan motifs at the surface of midgut cells in the cotton leafworm (Spodoptera littoralis) demonstrated by lectin binding

Glycans are involved in many biological phenomena, including signal transduction, cell adhesion, immune response or differentiation. Although a few papers have reported on the role of glycans in the development and proper functioning of the insect midgut, no data are available regarding the localization of the glycan structures on the surface of the cells in the gut of insects. In this paper, we analyzed the spatial distribution of glycans present on the surface of the midgut cells in larvae of the cotton leafworm Spodoptera littoralis, an important agricultural pest insect worldwide. For this purpose, we established primary midgut cell cultures, probed these individual cells that are freely suspended in liquid medium with a selection of seven fluorescently labeled lectins covering a range of different carbohydrate binding specificities [mannose oligomers (GNA and HHA), GalNAc/Gal (RSA and SSA), GlcNAc (WGA and Nictaba) and Neu5Ac(alpha-2,6)Gal/GalNAc (SNA-I)], and visualized the interaction of these lectins with the different zones of the midgut cells using confocal microscopy. Our analysis focused on the typical differentiated columnar cells with a microvillar brush border at their apical side, which are dominantly present in the Lepidopteran midgut and function in food digestion and absorption, and as well as on the undifferentiated stem cells that are important for midgut development and repair. Confocal microscopy analyses showed that the GalNAc/Gal-binding lectins SSA and RSA and the terminal GlcNAc-recognizing WGA bound preferentially to the apical microvillar zone of the differentiated columnar cells as compared to the basolateral pole. The reverse result was observed for the mannose-binding lectins GNA and HHA, as well as Nictaba that binds preferentially to GlcNAc oligomers. Furthermore, differences in lectin binding to the basal and lateral zones of the cell membranes of the columnar cells were apparent. In the midgut stem cells. GNA and Nictaba bound more strongly to the membrane of these undifferentiated cells compared to the microvillar pole of the columnar cells, while SSA, HHA, WGA, and SNA-I showed stronger binding to the microvilli. Our results indicated that polarization of the midgut cells is also reflected by a specific distribution of glycans, especially between the basal and microvillar pole. The data are discussed in relation to the functioning and development of the insect midgut

Some explicit formulations of Colebrook-White friction factor considering accuracy vs. computational speed

The Colebrook–White formulation of the friction factor is implicit and requires some iterations to be solved given a correct initial search value and a target accuracy. Some new explicit formulations to efficiently calculate the Colebrook–White friction factor are presented herein. The aim of this investigation is twofold: (i) to preserve the accuracy of estimates while (ii) reducing the computational burden (i.e. speed). On the one hand, the computational effectiveness is important when the intensive calculation of the friction factor (e.g. large-size water distribution networks (WDN) in optimization problems, flooding software, etc.) is required together with its derivative. On the other hand, the accuracy of the developing formula should be realistically chosen considering the remaining uncertainties surrounding the model where the friction factor is used. In the following, three strategies for friction factor mapping are proposed which were achieved by using the Evolutionary Polynomial Regression (EPR). The result is the encapsulation of some pieces of the friction factor implicit formulae within pseudo-polynomial structures

Technical Report EL-88-18: Reliability of the Federally Owned Water Main System

The reliability of the Federally Owned Water Main (FOWM) system was examined, and recommendations to improve system reliability are made. The existing FOWM system is very dependent upon three different pipe links. The first and most important link is the Francis Scott Key Bridge river crossing. This link carries the entire FOWM supply, and if taken out of service, an alternate means of supply must be used. At present, the only alternate source of supply is through interconnections with the adjacent Arlington County, Virginia, system. The second vital link is the 30-in. steel main which extends from the Key Bridge river crossing to the Pentagon. This line carries approximately 83 percent of the total delivery to the FOWM system. If taken out of service, all flow in the FOWM system would have to be routed through the 16-in. main along George Washington Parkway and Eisenhower Drive. During periods of high water use, flow in this 16-in. line would cause excessive friction losses. As a result, adequate system pressures cannot be maintained, and system demands cannot be fully met. The final critical pipe link is the feed to National Airport. This link consists of a 24-in. pipe and a 16-in. pipe connected in series. At present, this is the only source of water for National Airport. If this line were taken out of service, an alternate source of supply must be found. Furthermore, the available fire flow to the airport through this line during maximum daily demands falls below Insurance Services Office requirements. Several system improvements were evaluated to determine their contribution to the overall reliability of the FOWM system. System improvements consisted of operating existing and new interconnections, constructing new river crossings, installing a new storage tank, new line construction, and combinations of the above. System improvements were evaluated and ranked based on hydraulic performance, engineering impact, and total cost

Pressure-driven Demand and Leakage Simulation for Water Distribution Networks

Copyright © 2008 American Society of Civil EngineersIncreasingly, water loss via leakage is acknowledged as one of the main challenges facing water distribution system operations. The consideration of water loss over time, as systems age, physical networks grow, and consumption patterns mature, should form an integral part of effective asset management, rendering any simulation model capable of quantifying pressure-driven leakage indispensable. To this end, a novel steady-state network simulation model that fully integrates into a classical hydraulic representation, pressure-driven demand and leakage at the pipe level is developed and presented here. After presenting a brief literature review about leakage modeling, the importance of a more realistic simulation model allowing for leakage analysis is demonstrated. The algorithm is then tested from a numerical standpoint and subjected to a convergence analysis. These analyses are performed on a case study involving two networks derived from real systems. Experimentally observed convergence/error statistics demonstrate the high robustness of the proposed pressure-driven demand and leakage simulation model

Water Distribution Modeling

To effectively use water distribution models, the engineer must be able to link knowledge of basic hydraulic theory and the mechanics of the program with that of the operation of real-world systems. Water Distribution Modeling does just that. Written by industry experts, it provides a practical resource for engineers and modelers that goes well beyond being a how-to guide for typing data into a computer program. It contains straightforward answers to common questions related both to modeling and to distribution systems in general. This textbook walks the practicing engineer or student through the modeling process from start to finish — from data collection and field-testing to using a model for system design and complex operational tasks

Techniques for Improving Energy Efficiency at Water Supply Pumping Stations

This report describes the application of methods presented in Engineer Technical Letter (ETL) Energy Efficiency at Water Supply Pumping Stations\u27\u27 to the Washington, DC, and vicinity water system. Both the ETL and this report were prepared under the Water System Operation, Maintenance and Rehabilitation Work Unit (CWIS 31794) of the Water Supply and Conservation Research Program. The technical monitors for this program in the Office, Chief of Engineers, were Mr. James Ballif (DAEN-ECE-B) and Mr. Robert Daniel (DAEN-CWP-D). The work was conducted at the US Army Engineer (USAE) Waterways Experiment Station (WES), Vicksburg, Miss., and the University of Kentucky (UK) Civil Engineering Department. The report was written by Dr. Lindell E. Ormsbee, assistant professor of civil engineering at UK, working with WES under an Intergovernmental Personnel Act agreement; Dr. Thomas M. Walski, a research civil engineer with the Water Resources Engineering Group (WREG) of the Environmental Engineering Division (EED), Environmental Laboratory (EL), WES; and Messrs. Donald V. Chase and Wayne W. Sharp, UK students employed by WES under the contract student program. Mr. Anthony C. Gibson of the WREG assisted in field data collection. Work done with the Washington Aqueduct Division (WAD) of the USAE District, Baltimore, was performed under the purview of Mr. Harry C. Ways, Chief, WAD; Mr. Perry Costas, Assistant Chief, WAD; and Mr. Douglas B. Pickering, Chief, Plant Operations Branch, WAD. The report was reviewed by Mr. M. John Cullinane of the Water Supply and Waste Treatment Group, EED, and Dr. Keith W. Little of the Research Triangle Institute, Research Triangle Park, N.C. The report was edited by Ms. Jessica S. Ruff of the WES Information Technology Laboratory. The study was conducted under the supervision of Mr. F. Douglas Shields, Jr., Acting Chief, WREG; Dr. Raymond L. Montgomery, Chief, EED; and Dr. John Harrison, Chief, EL. Commander and Director of WES was Col. Dwayne G. Lee, CE. Technical Director was Dr. Robert W. Whalin

Advanced Water Distribution Modeling and Management

Advanced Water Distribution Modeling and Management builds on Haestad Press’ Water Distribution Modeling book. Addressing the modeling process from data collection to application, Advanced Water Distribution Modeling and Management adds extensive material from an international team of experts from both academia and consulting firms and includes topics such as: In-depth coverage of optimization techniques for model calibration, system design, and pump operations. Advanced water quality modeling topics including tank mixing, water quality solution algorithms, sampling techniques, tracer studies, tank design, and maintenance of adequate disinfectant residuals. Integration of SCADA systems with water distribution modeling for estimating model demands, initial conditions, and control settings; forecasting system operations; calibrating extended-period simulation models; streamlining water quality analysis; and estimating water loss during a main break. The essentials of transient analysis including the causes and sources of transients, as well as the potential effects of transients on water distribution systems. Application of GIS technology for skeletonization, demand allocation, and pipe break analysis; discussion of the technological issues that arise when integrating GIS and water distribution modeling; and the current state of the technology. Use of models to assess water system vulnerability and security, respond to emergencies in real-time, simulate contamination events, prioritize physical security improvements, and unravel past contamination events

Evaluating the approximation of the affinity laws and improving the efficiency estimate for variable speed pumps

Affinity laws relate to the characteristics of pumps operating at different speeds, and in a water distribution context, are usually used to predict the pump curve of variable speed pumps (VSPs). VSPs can adjust the pump curve to meet the network requirements more efficiently with resultant savings of energy. The estimation of the effectiveness of a VSP is based on hydraulic simulations, in which the behavior of VSPs is described using the affinity laws. The affinity laws, however, contain approximations because they do not take into account factors that do not scale with velocity. In particular, the approximation inherent in the affinity law that computes power and efficiency can produce a misleading result, especially for small-size pumps. The research reported in this paper estimates the error in efficiency for a wide range of pump sizes and tests the use of a previously proposed formula as an alternative to the affinity law. Results show that a better estimation can be achieved for the efficiency of small- and medium-size pumps. Moreover the formula can be easily implemented in hydraulic solvers. © 2013 American Society of Civil Engineers.Angus R. Simpson and Angela March

Pressure-dependent EPANET extension

In water distribution systems (WDSs), the available flow at a demand node is dependent on the pressure at that node. When a network is lacking in pressure, not all consumer demands will be met in full. In this context, the assumption that all demands are fully satisfied regardless of the pressure in the system becomes unreasonable and represents the main limitation of the conventional demand driven analysis (DDA) approach to WDS modelling. A realistic depiction of the network performance can only be attained by considering demands to be pressure dependent. This paper presents an extension of the renowned DDA based hydraulic simulator EPANET 2 to incorporate pressure-dependent demands. This extension is termed “EPANET-PDX” (pressure-dependent extension) herein. The utilization of a continuous nodal pressure-flow function coupled with a line search and backtracking procedure greatly enhance the algorithm’s convergence rate and robustness. Simulations of real life networks consisting of multiple sources, pipes, valves and pumps were successfully executed and results are presented herein. Excellent modelling performance was achieved for analysing both normal and pressure deficient conditions of the WDSs. Detailed computational efficiency results of EPANET-PDX with reference to EPANET 2 are included as well