Vertical migration during tidal transport of megalopae of Necora puber in coastal shallow waters during daytime

For meroplanktonic larvae that must settle in coastal areas, their successful return to the shore is determined largely by physical transport processes; however, many organisms perform vertical movements to aid successful recruitment. In this study, daytime tidal vertical migration of megalopae of the velvet swimming crab Necora puber was investigated across two different exposures in the shallow waters of Plymouth Sound. Crabs were collected using a plankton net at the surface and near the bottom during flood and ebb tides. Distribution of the pelagic postlarvae was patchy and the abundance varied spatially in tens and thousands of metres. In temporal scales, the annual pattern was dominated by low occurrence of megalopae, punctuated by episodic peaks of high abundance. Most megalopae were collected at the surface irrespective of the tidal phase. The effect of wave exposure on the vertical migration of megalopae was not clear, although there was a general higher abundance of megalopae on exposed shores. Daytime abundance in the water column appears to be regulated by the tidal cycle, as megalopae were more abundant during flood than ebb tides. Although the megalopae do not appear to make large vertical migrations, this behaviour should produce a net shoreward transport. © 2005 Elsevier Ltd. All rights reserved.

On the nucleation of GaP/GaAs and the effect of buried stress fields

We have recently shown that spatial ordering for epitaxially grown InP dots can be obtained using the periodic stress field of compositional modulation on the InGaP buffer layer. The aim of this present work is to study the growth of films of GaP by Chemical Beam Epitaxy (CBE), with in-situ monitoring by Reflection High Energy Electron Diffraction (RHEED), on layers of unstressed and stressed GaAs. Complementary, we have studied the role of a buried InP dot array on GaP nucleation in order to obtain three-dimensional structures. In both cases, the topographical characteristics of the samples were investigated by Atomic Force Microscopy (AFM) in non-contact mode. Thus vertically-coupled quantum dots of different materials have been obtained keeping the in-place spatial ordering originated from the composition modulation. © 2006 Materials Research Society.

Optimal Boussinesq model for shallow-water waves interacting with a microstructure

In this paper, we consider the propagation of water waves in a long-wave asymptotic regime, when the bottom topography is periodic on a short length scale. We perform a multiscale asymptotic analysis of the full potential theory model and of a family of reduced Boussinesq systems parametrized by a free parameter that is the depth at which the velocity is evaluated. We obtain explicit expressions for the coefficients of the resulting effective Korteweg-de Vries (KdV) equations. We show that it is possible to choose the free parameter of the reduced model so as to match the KdV limits of the full and reduced models. Hence the reduced model is optimal regarding the embedded linear weakly dispersive and weakly nonlinear characteristics of the underlying physical problem, which has a microstructure. We also discuss the impact of the rough bottom on the effective wave propagation. In particular, nonlinearity is enhanced and we can distinguish two regimes depending on the period of the bottom where the dispersion is either enhanced or reduced compared to the flat bottom case. © 2007 The American Physical Society.

A logical approach to the management of object identifiers in non-conventional database management systems

Non-conventional database management systems are used to achieve a better performance when dealing with complex data. One fundamental concept of these systems is object identity (OID), because each object in the database has a unique identifier that is used to access and reference it in relationships to other objects. Two approaches can be used for the implementation of OIDs: physical or logical OIDs. In order to manage complex data, was proposed the Multimedia Data Manager Kernel (NuGeM) that uses a logical technique, named Indirect Mapping. This paper proposes an improvement to the technique used by NuGeM, whose original contribution is management of OIDs with a fewer number of disc accesses and less processing, thus reducing management time from the pages and eliminating the problem with exhaustion of OIDs. Also, the technique presented here can be applied to others OODBMSs. © 2011 IEEE.

Computational tool to support design of DAC Converter model AD7528 with the object code in XML

Based on literature review, electronic systems design employ largely top-down methodology. The top-down methodology is vital for success in the synthesis and implementation of electronic systems. In this context, this paper presents a new computational tool, named BD2XML, to support electronic systems design. From a block diagram system of mixed-signal is generated object code in XML markup language. XML language is interesting because it has great flexibility and readability. The BD2XML was developed with object-oriented paradigm. It was used the AD7528 converter modeled in MATLAB / Simulink as a case study. The MATLAB / Simulink was chosen as a target due to its wide dissemination in academia and industry. From this case study it is possible to demonstrate the functionality of the BD2XML and make it a reflection on the design challenges. Therefore, an automatic tool for electronic systems design reduces the time and costs of the design.

Managing object identity with less I/O operations

Non-conventional database management systems are used to achieve a better performance when dealing with complex data. One fundamental concept of these systems is object identity (OID). Two techniques can be used for the implementation of OIDs: physical or logical. A logical implementation of OIDs, based on an Indirection Table, is used by NuGeM, a multimedia data manager kernel which is described in this paper. NuGeM Indirection Table allows the relocation of all pages in a database. The proposed strategy modifies the workings of this table so that it is possible to reduce considerably the number of I/O operations during the request and release of pages containing objects and their OIDs. Tests show a reduction of 84% in reading operations and a 67% reduction in writing operations when pages are requested. Although no changes were observed in writing operations during the release of pages, a 100% of reduction in reading operations was obtained. © 2012 IEEE.

Detection of buried pipes using a shear wave ground surface vibration technique

A major UK initiative, entitled 'Mapping the Underworld', is seeking to address the serious social, environmental and economic consequences arising from an inability to locate the buried utility service infrastructure without resorting to extensive excavations. Mapping the Underworld aims to develop and prove the efficacy of a multi-sensor device for accurate remote buried utility service detection, location and, where possible, identification. One of the technologies to be incorporated in the device is low-frequency vibro-acoustics, and the application of this technology for detecting buried infrastructure is currently being investigated. Here, a shear wave ground vibration technique for detecting buried pipes is described. For this technique, shear waves are generated at the ground surface, and the resulting ground surface vibrations measured, using geophones, along a line traversing the anticipated run of the pipe. Measurements were made at a test site with a single pressurized polyethylene mains water pipe. Time-extended signals were employed to generate the illuminating wave. Cross-correlation functions between the measured ground velocities and a reference measurement adjacent to the excitation were then calculated and summed using a stacking method to generate a cross-sectional image of the ground. The wide cross-correlation peaks caused by high ground attenuation were partially compensated for by using a generalized cross-correlation function called the smoothed coherence transform. To mitigate the effects of other potential sources of vibration in the vicinity, the excitation signal was used as an additional reference when calculating the generalized cross-correlation functions. For two out of three tests, the pipe was detected, indicating that this technique will be a valuable addition to the Mapping the Underworld armoury.

How domestic violence came to be viewed as a public issue and policy object

Includes bibliography

Lower Permian stems as fluvial paleocurrent indicators of the Parnaíba Basin, northern Brazil

A comprehensive biostratinomic study was carried out with abundant stems from the Lower Permian Motuca Formation of the intracratonic Parnaíba Basin, central-north Brazil. The fossils represent a rare tropical to subtropical paleofloristic record in north Gondwana. Tree ferns dominate the assemblages (mainly Tietea, secondarily Psaronius), followed by gymnosperms, sphenophytes, other ferns and rare lycophytes. They are silica-permineralized, commonly reach 4 m length (exceptionally more than 10 m), lie loosely on the ground or are embedded in the original sandstone or siltstone matrix, and attract particular attention because of their frequent parallel attitudes. Many tree fern stems present the original straight cylindrical to slightly conical forms, other are somewhat flattened, and the gymnosperm stems are usually more irregular. Measurements of stem orientations and dimensions were made in three sites approximately aligned in a W-E direction in a distance of 27.3 km at the conservation unit Tocantins Fossil Trees Natural Monument In the eastern site, rose diagrams for 54 stems indicate a relatively narrow azimuthal range to SE. These stems commonly present attached basal bulbous root mantles and thin cylindrical sandstone envelopes, which sometimes hold, almost adjacent to the lateral stem surface, permineralized fern pinnae and other small plant fragments. In the more central site, 82 measured stems are preferentially oriented in the SW-NE direction, the proportion of gymnosperms is higher and cross-stratification sets of sandstones indicate paleocurrents mainly to NE and secondarily to SE. In the western site, most of the 42 measured stems lie in E-W positions. The predominantly sandy succession, where the fossil stems are best represented, evidences a braided fluvial system under semiarid conditions. The low plant diversity, some xeromorphic features and the supposedly almost syndepositional silica impregnation of the plants are coherent with marked dry seasons. Thick mudstones and some coquinites below and above the sandy interval may represent lacustrine facies formed in probably more humid conditions. The taphonomic history of the preserved plants began with exceptional storms that caused fast-flowing high water in channels and far into the floodplains. In the eastern site region, many tree ferns only fell, thus sometimes covering and protecting plant litter and leaves from further fragmentation. Assemblages of the central and western sites suggest that the trees were uprooted and transported in suspension (floating) parallel to the flow. Heavier ends of stems (according to their form or because of attached basal bulbous root mantle or large apical fronds) were oriented to upstream because of inertial forces. During falling water stage, the stems were stranded on riverbanks, usually maintaining the previous transport orientation, and were slightly buried. The perpendicular or oblique positions of some stems may have been caused by interference with other stems or shallow bars. Rare observed stems were apparently waterlogged before the final depositional process and transported as bedload. The differences of interpreted channel orientations between the three sites are expected in a braided fluvial system, considering the very low gradients of the basin and the work scale in the order of tens of kilometers. The mean direction of the drainage probably was to east and the flows apparently became weaker downstream. This study seems to provide reliable data for paleocurrent interpretations, especially considering areas with scarce preserved sedimentary structures. © 2013 Elsevier Ltd.

The dynamic behaviour of a buried water pipe and its effect on leak location using acoustic methods

Leakage in buried pipes is one of the main concerns for water companies due to the scarcity of potable water sources. Older metallic pipelines have been replaced by plastic pipes in such systems, which makes it more difficult to locate leaks using acoustics and vibration. This is mainly because of the high attenuation of leak signals caused by the damping in the pipe wall. To investigate acoustic methods in leak location in controlled conditions, a bespoke test rig was constructed in the UK. In this paper, data from this test-rig is used to discuss some issues that arise when using two contemporary correlators. Of particular interest, is the way in which a resonance in the system can have a profound effect on the estimate of the position of the leak depending on the way in which the leak noise signals are processed. © (2013) Trans Tech Publications.

Wavespeed measurement in buried water distribution pipes and its significance in leak location

To determine the location of leaks in buried water pipes, acoustic methods are often used. These have proven to be very effective in metallic pipes but have been problematic in modern plastic pipes. In this paper the reason why this is so is discussed together with some measurements that were made on a bespoke test rig built by South Staffs Water plc. A particular problem is the estimate of the wavespeed. Tables are frequently used for this purpose, but these are often inaccurate and this means that a leak cannot be located accurately. An in-situ measure of the wavespeed is thus preferable. In this paper it is shown that there are significant issues in obtaining an accurate estimate of the wavespeed when a leak is present in the system. A method is proposed that overcomes some of these problems, which is discussed and is demonstrated using some data from the bespoke test-rig. © (2013) Trans Tech Publications.

Measurement of Wave Attenuation in Buried Plastic Water Distribution Pipes

Leaks in pipes are a common issue encountered in the water industry. Acoustic methods are generally successful in finding and locating leaks in metallic pipes, however, they are less effective when applied to plastic pipes. This is because leak-noise signals are heavily attenuated due to high damping in the pipe-wall and sound radiation into the soil. As result, high frequency leak noise does not travel long distances. To determine how far leak noise may travel in a pipe at any frequency, the attenuation of the wave responsible for leak noise propagation should be known. In this paper a new method to estimate this is described. The method is then applied to some measurements made on a bespoke pipe-test rig in the UK, and the results are compared with theoretical predictions.

Cleaning interactions between shrimps (Palaemonidae) and freshwater stingrays (Potamotrygonidae) in the Parana River, Southeastern Brazil

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

On the Acoustic Filtering of the Pipe and Sensor in a Buried Plastic Water Pipe and its Effect on Leak Detection: An Experimental Investigation

Acoustic techniques have been used for many years to find and locate leaks in buried water distribution systems. Hydrophones and accelerometers are typically used as sensors. Although geophones could be used as well, they are not generally used for leak detection. A simple acoustic model of the pipe and the sensors has been proposed previously by some of the authors of this paper, and their model was used to explain some of the features observed in measurements. However, simultaneous measurements of a leak using all three sensor-types in controlled conditions for plastic pipes has not been reported to-date and hence they have not yet been compared directly. This paper fills that gap in knowledge. A set of measurements was made on a bespoke buried plastic water distribution pipe test rig to validate the previously reported analytical model. There is qualitative agreement between the experimental results and the model predictions in terms of the differing filtering properties of the pipe-sensor systems. A quality measure for the data is also presented, which is the ratio of the bandwidth over which the analysis is carried out divided by the centre frequency of this bandwidth. Based on this metric, the accelerometer was found to be the best sensor to use for the test rig described in this paper. However, for a system in which the distance between the sensors is large or the attenuation factor of the system is high, then it would be advantageous to use hydrophones, even though they are invasive sensors.

Combining ALOS/PALSAR derived vegetation structure and inundation patterns to characterize major vegetation types in the Mamiraua Sustainable Development Reserve, Central Amazon floodplain, Brazil

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)