Effects of river regulation on aquatic macrophyte growth and floods in the Hadejia‐Nguru Wetlands and flow in the Yobe River,northern Nigeria; implications for future water management

The Hadejia River is a tributary of the Yobe River in semi‐arid northern Nigeria and is regulated by two major dams. The other main tributary is uncontrolled. Comparison of the discharge data for the controlled and uncontrolled rivers shows an average decrease of 33% in annual flow in the upstream part of the Hadejia River. The total annual flow and the peak flow in the Hadejia River further downstream, just above the Hadejia‐Nguru Wetlands (HNW), however, did not show a significant reduction in discharge. This is related to a relatively small river flow reduction at lower flows in the upstream part of the Hadejia River and the fact that the formal large upstream water users are not (yet) working at full capacity. The major impact of the dams on the downstream part of the river is the change in regime from ephemeral to perennial. The introduced dry season flows created favourable circumstances for the development of aquatic macrophyte blockages in the HNW. Owing to these blockages, the Hadejia River stopped contributing to the flow in the Yobe River for much of the year. Furthermore, after the completion of the dams, the timing of the floods in the HNW became less predictable. Suggestions for improvement of water management are made. These comprise engineering structures, including a flow diversion structure to regulate flows in the HNW, implementation of environmentally acceptable river flow strategies and water allocation management. Copyright © 2002 John Wiley & Sons, Ltd.     

Feature-Preserving Surface Reconstruction and Simplification from Defect-Laden Point Sets

We introduce a robust and feature-capturing surface reconstruction and simplification method that turns an input point set into a low triangle-count simplicial complex. Our approach starts with a (possibly non-manifold) simplicial complex filtered from a 3D Delaunay triangulation of the input points. This initial approximation is iteratively simplified based on an error metric that measures, through optimal transport, the distance between the input points and the current simplicial complex—both seen as mass distributions. Our approach is shown to exhibit both robustness to noise and outliers, as well as preservation of sharp features and boundaries. Our new feature-sensitive metric between point sets and triangle meshes can also be used as a post-processing tool that, from the smooth output of a reconstruction method, recovers sharp features and boundaries present in the initial point set.     

Semantic enrichment process: An approach to software component reuse in modernizing enterprise systems

In today’s dynamic business environments, organizations are under pressure to modernize their existing software systems in order to respond to changing business demands. Service oriented architectures provide a composition framework to create new business functionalities from autonomous building blocks called services, enabling organizations to quickly adapt to changing conditions and requirements. Characteristics of services offer the promise of leveraging the value of enterprise systems through source code reuse. In this respect, existing system components can be used as the foundation of newly created services. However, one problem to overcome is the lack of business semantics to support the reuse of existing source code. Without sufficient semantic knowledge about the code in the context of business functionality, it would be impossible to utilize source code components in services development. In this paper, we present an automated approach to enrich source code components with business semantics. Our approach is based on the idea that the gap between the two ends of an enterprise system—(1) services as processes and (2) source code—can be bridged via similarity of data definitions used in both ends. We evaluate our approach in the framework of a commercial enterprise systems application. Initial results indicate that the proposed approach is useful for annotating source code components with business specific knowledge.     

Behavior of mesenchymal stem cells stained with 4', 6-diamidino-2-phenylindole dihydrochloride (DAPI) in osteogenic and non osteogenic cultures

4', 6-diamidino-2-phenylindole dihydrochloride (DAPI) is a DNA dye widely used to mark and trace stem cells in therapy. We here studied the effect of DAPI staining on the behavior of mesenchymal stem cells cultured in either a control, non-osteogenic medium or in an osteogenic differentiation medium. In the control medium, the number of stem cells/field, as well as the number of fluorescent cells/field increased up to the sixth day in both control and DAPI-treated cultures. Afterwards, both the number of fluorescent cells and their fluorescence intensity decreased. Control cells were fusiform and with some long extensions that apparently linked them to neighboring cells, while DAPI-treated cells were mostly round cells with fine and short extensions. The trypan-blue exclusion method showed 99% cell viability in both groups, however, both alkaline phosphatase activity and the thiazolyl blue formazan assay (indicative of mitochondrial metabolism) gave significantly lower values in DAPI-marked cells. The mitochondrial mass, as indicated by specific staining and flow cytometry, showed no differences between groups. Mesenchymal stem cells gave origin to mineralized nodules in the osteogenic differentiation medium and there were not DAPI-marked cells on the ninth day of culture. Alkaline phosphatase activity, viability assay and number of cells/field and of mineralized nodules/field were similar in both groups. So, DAPI treatment did not change cell viability and proliferation during osteogenic differentiation of mesenchymal stem cells. However, since these cells loose DAPI marking after 9 days in osteogenic cultures suggests that DAPI may not be an effective marker for mesenchymal stem cells implanted in bone tissue for long periods.     

Analysis of a new thruway communication system with discreteminimal zones

A mobile communication system for high-speed thruways is currently under consideration in Japan. The system consists of fixed stations installed at regular intervals (2-5 km) along the thruway which are connected to a host computer. Subscribing customers can communicate with the system as they drive through each station's communication zone of minimal type (40-100 m). The authors develop and analyze a stochastic model for this new communication system. The model closely follows the sequence of operations which actually take place according to a communication protocol for handling collisions, and requires no exponential assumptions for the underlying service times. The tradeoff between the total number of stations installed and the probability of successful completion of a task within z km after the initial submission is investigated. Some numerical results are also given for illustrating the tradeoff, with validation via SIMAN simulation     

A Universal Transducer Interface for Capacitive and Resistive Sensor Elements

This paper presents a new universal transducer interface.This interface, which is read out by a microcontroller, servicesthe following sensor elements: capacitors, platinum resistors,thermistors, resistive bridges and potentiometers. The A/D conversionis based on a first-order oscillator. A combination of classicaland some new measurement techniques has been applied on a singlechip to obtain high accuracy, good long-term stability and areduction of the effects of interference and parasitic elements.The circuit has been fabricated in a 0.7 µm CMOSprocess. The main test results are: an accuracy of 10–15bits and a resolution up to 16 bits while the measurement timeis in the range 1–100ms. These results hold over the temperaturerange –20°C to 80°C. Calibrationof the electronic part is not required. The number of externalcomponents has been kept to a minimum.     

Peach-palm (Bactris gasipaes Kunth.) waste as substrate for xylanase production by Trichoderma stromaticum AM7

This work investigated the xylanase production by fungi isolates from tropical agroforestry systems using peach-palm industrial waste as a substrate. Trichoderma stromaticum AM7 was the best xylanase producer and there was a 160% increase in xylanase activity after optimizing by the Box–Behnken statistical design. The optimization process demonstrated that the maximum activity occurred at 0.95% nitrogen concentration after 6 days of cultivation at 32°C, which achieved a yield of 1440?U?g^?1 of dry initial substrate. Analysis by scanning electron microscopy showed degradation of the fibers after cultivation. The optimum pH and temperature for xylanase activity were 5.0 and 50°C, respectively. The extensive degradation of the peach-palm waste and xylanase production by T. stromaticum AM7 was due to the combination of a good physicochemical composition of the culture medium and the characteristics of the selected fungus.     

A charge-sharing analog-to-digital converter with embedded downconversion using a variable reference voltage

In the field of radio receivers, downconversion methods usually rely on one (or more) explicit mixing stage(s) before the analog-to-digital converter (ADC). These stages not only contribute to the overall power consumption but also have an impact on area and can compromise the converter's performance in terms of noise and linearity. As an alternative, we propose a receiver architecture that considers the ADC as both a quantizer and a downconverter block. This is achieved through the use of a variable reference signal (in this case, a voltage), as opposed to classic time-invariant reference signals. When embedded into a charge-sharing (CS) successive approximation register (SAR) ADC, this varying reference voltage is “saved” in the digital-to-analog converter (DAC) capacitor bank during the sampling phase, preventing any conversion errors. Furthermore, a phase-locked loop (PLL) is used in order to provide an on-chip solution for the generation of this variable reference voltage, which also removes the need for dedicated bandgap circuits and reference buffers. Post-layout simulations of an 8-bit 50 MS/s CS-SAR ADC show that the proposed “embedded mixing” technique is able to downconvert a high-frequency signal while also increasing the effective resolution by around 0.5 bits, when compared with a standard DC reference voltage.