Bottom Sensors Research Articles

On-chip magnetic bead-based DNA melting curve analysis using a magnetoresistive sensor

We present real-time measurements of DNA melting curves in a chip-based system that detects the amount of surface-bound magnetic beads using magnetoresistive magnetic field sensors. The sensors detect the difference between the amount of beads bound to the top and bottom sensor branches of the differential sensor geometry. The sensor surfaces are functionalized with wild type (WT) and mutant type (MT) capture probes, differing by a single base insertion (a single nucleotide polymorphism, SNP). Complementary biotinylated targets in suspension couple streptavidin magnetic beads to the sensor surface. The beads are magnetized by the field arising from the bias current passed through the sensors. We demonstrate the first on-chip measurements of the melting of DNA hybrids upon a ramping of the temperature. This overcomes the limitation of using a single washing condition at constant temperature. Moreover, we demonstrate that a single sensor bridge can be used to genotype a SNP.

Design of Fire Alarm System in Laboratory

Fire warning is a matter of concern in laboratory, this paper presents the design of distributed sensors fire warning system. The core idea is that a number of the bottom sensor collection terminals that consists of temperature and smoking sensors are evenly distributed in the laboratory; when there is a fire to happen, the bottom sensor collection terminals will send an alarming signal by the way of wireless communication to the middle layer alarming signal collection terminal, which starts a GPRS module to capture the scene and send the image to the senior monitoring management center. The senior manager receives an alarming image information, analysis and process, start the appropriate fire alarm system. After a year of testing and running, the system achieves the originally designed aim, and is reliable and stable.

Data processing techniques for a wireless data transmission application via mud

The data measured by well bottom sensors can be transmitted to the surface through the drilling mud during oil drilling operations. This article introduces a data processing scheme for a wireless data transmission application via mud. The detailed signal processing procedure is given, and several data processing techniques used are discussed, mainly including data encoding and signal integrating method, signal filtering, data storage and manage method, peak detection, signal recognition, and data decoding method. The article uses M pulses in N slots to encode the values of actual parameters. A two step filtering method and a dynamic data storing and managing method are proposed. A mix peak detection method is utilized to find the position of a pulse by combining threshold method and neighbor comparison method. These techniques have been successfully used in an oil well drilling operation.

An automated method to monitor lake ice phenology

A simple method to automatically measure the date of ice‐on, the date of ice‐off, and the duration of lake ice cover is described. The presence of ice cover is detected by recording water temperature just below the ice/water interface and just above the lake bottom using moored temperature sensors. The occurrence of ice‐on rapidly leads to detectible levels of inverse stratification, defined as existing when the upper sensor records a temperature at least 0.1°C below that of the bottom sensor, whereas the occurrence of ice‐off leads to the return of isothermal mixing. Based on data from 10 lakes over a total of 43 winter seasons, we found that the timing and duration of inverse stratification monitored by recording temperature sensors compares well with ice cover statistics based on human observation. The root mean square difference between the observer‐based and temperature‐based estimates was 7.1 d for ice‐on, 6.4 d for ice‐off, and 10.0 d for the duration of ice cover. The coefficient of determination between the two types of estimates was 0.93, 0.86, and 0.91, respectively. The availability of inexpensive self‐contained temperature loggers should allow expanded monitoring of ice cover in a large and diverse array of lakes. Such monitoring is needed to improve our ability to monitor the progression of global climate change, and to improve our understanding of the relationship between climate and ice cover over a wide range of temporal and spatial scales.

3D technology for intelligent trackers

At Super-LHC luminosity it is expected that the standard suite of level 1 triggers for CMS will saturate. Information from the tracker will be needed to reduce trigger rates to satisfy the level 1 bandwidth. Tracking trigger modules which correlate information from closely-spaced sensor layers to form an on-detector momentum filter are being developed by several groups. We report on a trigger module design which utilizes three dimensional integrated circuit technology incorporating chips which are connected both to the top and bottom sensor, providing the ability to filter information locally. A demonstration chip, the VICTR, has been submitted to the Chartered/Tezzaron two-tier 3D run coordinated by Fermilab. We report on the 3D design concept, the status of the VICTR chip and associated sensor integration utilizing oxide bonding.

The GITEWS ocean bottom sensor packages

Abstract. The German-Indonesian Tsunami Early Warning System (GITEWS) aims at reducing the risks posed by events such as the 26 December 2004 Indian Ocean tsunami. To minimize the lead time for tsunami alerts, to avoid false alarms, and to accurately predict tsunami wave heights, real-time observations of ocean bottom pressure from the deep ocean are required. As part of the GITEWS infrastructure, the parallel development of two ocean bottom sensor packages, PACT (Pressure based Acoustically Coupled Tsunameter) and OBU (Ocean Bottom Unit), was initiated. The sensor package requirements included bidirectional acoustic links between the bottom sensor packages and the hosting surface buoys, which are moored nearby. Furthermore, compatibility between these sensor systems and the overall GITEWS data-flow structure and command hierarchy was mandatory. While PACT aims at providing highly reliable, long term bottom pressure data only, OBU is based on ocean bottom seismometers to concurrently record sea-floor motion, necessitating highest data rates. This paper presents the technical design of PACT, OBU and the HydroAcoustic Modem (HAM.node) which is used by both systems, along with first results from instrument deployments off Indonesia.

An Experimental Multi-disciplinary observatory (VENUS) at the Ryukyu Trench using the Guam-Okinawa Geophysical Submarine Cable

A MultiDisciplinary Ocean Bottom Observatory (MDOBO) was installed on VENUS (Versatile Eco-monitor- ing Network by Undersea-cable System) at a depth of 2170 m on the slope of the Ryukyu Trench. In this con- text, «Eco-»refers to both economic (e.g., earthquake hazard mitigation) and ecological motivation. The first step in this instillation was to insert a telemetry/power system into the submarine coaxial cable; this system could then service the MDOBO, which consists of seven major bottom sensor packages. During August-Sep- tember 1999, using a deep-towed unit and both manned and unmanned submersibles coupled with precise ship navigation, the MDOBO system and its attendant cables were deployed over a range of distances from 80 m to 1 km from the telemetry system, with several meters allowance for navigational uncertainty in positioning. The unmanned submersible then extended the multi-conductor extension cables from the instrument units toward the telemetry system and connected them to undersea mateable connectors on a junction box installed on the submarine cable. The MDOBO collected one and half months of continuous records. Several kinds of useful data were collected after installation, including an aftershock (Ms= 6.1) of the 1999 Chi-Chi earthquake (Ms= 7.7) in Taiwan.

Uma implementação do método da refletividade para modelagem eficiente de dados sísmicos marítimos e de OBC

Neste trabalho é demonstrado como o método da refletividade pode ser eficientemente implementado para simular aquisições sísmicas marítimas. Isto inclui o registro de pressão no caso da fonte e dos receptores (hidrofones) estarem localizados na camada de água, o deslocamento (ou velocidade de vibração) vertical e horizontal no caso dos receptores estarem plantados no leito do oceano, simulando aquisições multicomponentes tipo OBC (Ocean Bottom Cable) ou OBS (Ocean Bottom Sensor). Uma das vantagens do presente método é a facilidade de seleção dos eventos que farão parte da resposta, tais como múltiplas internas, múltiplas associadas à superfície livre e ondas convertidas no caso P-Sv. Os fenômenos da atenuação e da dispersão podem ser levados em conta facilmente considerando as velocidades complexas, já que o método é desenvolvido no domínio ω-p. O algoritmo proposto possui custo computacional bem menor quando comparado com métodos puramente numéricos como diferenças finitas ou elementos finitos. Sendo assim, no caso onde um modelo de camadas planas horizontais seja suficiente para descrever a subsuperfície, este torna-se uma ferramenta prática para tarefas como prever com bastante precisão e rigor a sensibilidade sísmica de um determinado reservatório com relação à substituição de fluidos ou prever como uma determinada mudança de propriedade petrofísica pode influenciar a resposta de AVO multicomponente.

Hybrid and module designs for ATLAS silicon tracker upgrade for super LHC

Based on the ATLAS SCT experience, hybrid and module designs of a short strip silicon detector for an upgraded ATLAS inner tracker for the super LHC have been pursued. At the super LHC, which provides 10 times more intense beam collisions than the LHC, the detectors envisage a very high rate operation in a much harsher radiation environment. Immediate concern is an increase of leakage current due to a radiation damage, which may induce a catastrophic break down of a thermal runaway. We have deduced a simple model for the thermal runaway, which can be conveniently utilized for the module designs. The thermal runaway model was verified by comparing with the corresponding FEM thermal analyses. The upgraded module is structurally similar to the present SCT barrel module. Two rectangular sensors, each of 12.5 × 6.4 cm 2 , are sandwiched along with a thermo-mechanical baseboard to provide two-dimensional space points. A one-piece wrap-around hybrid bridged over the sensors serves both the top and bottom sensors. Mounting and cooling schemes also follow the present barrel SCT designs with necessary modifications and improvements.

Why bury ocean bottom seismometers?

Theory, testing, and use of ocean bottom seismic sensors show that the fidelity of data, particularly measurements of horizontal motion, can be severely distorted and noisy because of mechanical interactions between the sensor package, the ocean bottom, and the ocean water. This lack of fidelity is common, particularly for instruments with large cross sections in the water. These problems should be minimized by burial of the seismic package below the ocean‐sediment interface. To test this hypothesis, two identical seismic packages were operated on the shallow ocean floor within meters of each other with a real‐time connection to land. The packages were configured in a variety of ways, with both packages buried in the sediment, one buried and one on the bottom, and one on a circular 1‐m‐diameter plate and the other buried or on the ocean floor. The resulting data are compared with data from both packages resting on a stable cement slab in the frequency range from 0.2 Hz to above 20 Hz. Data show convincingly that burial of seismic sensors in soft sediment greatly increases data fidelity over sensors placed on the bottom or on a plate on the bottom. While vertical sensors provide reasonable fidelity in most situations, the horizontal data are consistently reliable only when the sensor packages are buried.

Influence of the steady background turbulence level on second sound dynamics in He II – II

We report complementary results to our previous publication [Dalban-Canassy M, Hilton DK, Van Sciver SW. Influence of the steady background turbulence level on second sound dynamics in He II. Adv Cryo Eng 2006;51:371–8], both of which are aimed at determining the influence of background turbulence on the breakpoint energy of second sound pulses in He II. The apparatus consists of a channel 175 mm long and 242 mm 2 in cross section immersed in a saturated bath of He II at 1.7 K. A heater at the bottom end generates both background turbulence, through a low level steady heat flux (up to q s = 2.6 kW/m 2), and high intensity square second sound pulses ( q p = 100 or 200 kW/m 2) of variable duration Δ t 0 (up to 1 ms). Two superconducting filament sensors, located 25.4 mm and 127 mm above the heater, measure the temperature profiles of the traveling pulses. We present here an analysis of the measurements gathered on the top sensor, and compare them to similar results for the bottom sensor [1]. The strong dependence of the breakpoint energy on the background heat flux previously illustrated is also observed on the top sensor. The present work shows that the ratio of energy received at the top sensor to that at the bottom sensor diminishes with increasing background heat flux.

Measurements of distance fished during the trawl retrieval period

Observations of sampling trawl performance made during a multi-vessel groundfish survey raised concerns that the trawls continue to fish during the retrieval period, after the end of the pre-specified sampling period but before coming off bottom. A trigonometric analysis was undertaken to estimate the distance traversed along the bottom, and the trawl speed along the seabed during the retrieval period. The distances traversed were substantial and systematically increased with the depth of the tow. The effective trawl speed approached or even exceeded the towing speed specified by the sampling protocols, and varied systematically among the participating vessels. Subsequently, this analysis was compared to trawl positions and times recorded during the same period by an ultra-short baseline (split-beam) acoustic positioning system and a bottom contact sensor. No marked difference was found between the two methodological approaches. Neglect of the observed effects increases the impact of depth-related bias and inter-vessel variability on survey results while knowledge of these effects may help explain the “vessel effect” commonly observed when comparing the fishing performance of two or more vessels.

The effect of net spread on the capture efficiency of a demersal survey trawl used in the eastern Bering Sea

Abstract Relative abundance estimates generated from the National Marine Fisheries Service's annual groundfish trawl surveys in the eastern Bering Sea shelf are based on mean catch per area swept. In the calculation of these estimates, the capture efficiency is assumed to be independent of net spread, which, in turn, increases with depth throughout the depth range of the survey area, and also varies substantially with bottom type and currents. The validity of this assumption was tested using a linear model of catch-per-unit-towed distance versus net spread and depth that was fit to 14 years of survey data for seven species. Catch rates decreased significantly with increasing net spreads for six of the seven species despite the larger area swept at greater net spreads. The magnitude of the downward trends varied considerably by species. Purple sea star (Asterias amurensis) and northern rock sole (Lepidopsetta polyxystra) exhibited the strongest negative relationships between catch rate and net spread, while Alaska plaice (Pleuronectes quadrituberculatus) exhibited the weakest relationship. We attribute this decrease in catch rate to a decrease in capture efficiency. For the benthic species we consider, the decrease in capture efficiency is likely due to increased escapement under the footrope, because calibrated bottom contact sensors indicate that footrope clearance with the bottom increases with net spread. The current assumption of constant capture efficiency at all net spreads may result in biased size distributions and sex ratios for species displaying size and sex segregation by depth. This assumption may also have negative implications for the assessment of highly patchily distributed species as well as those whose depth distribution changes with environmental conditions. Controlling trawl geometry by means of restrictor cables on the warps is a feasible method to address this problem.

Multiparameter studies of surf infrasound

Infrasound stations on islands or near coastlines routinely detect signals associated with breaking ocean waves. Although the source mechanisms of these infrasonic surf signals are not well understood, they might provide useful insight into coastal processes and permit an assessment of wave energy distribution in the littoral zone. Near-shore infrasonic arrays, ocean bottom sensors, an infrared imager, and a video camera were deployed on rocky and sandy coastlines in Hawaii during the 2004–2005 Winter swell season, with the aim of establishing a relationship between the directional ocean swell height and the infrasonic source distribution, intensity, and spectral content. The cameras targeted acoustically active regions for selected time periods to associate the timing of the infrasonic signal arrivals with the breaking and dissipation of ocean wave sets. A wide range of sea states and weather conditions were captured during two separate deployments. The results of our multiparameter analyses and preliminary comparisons of our observations with mesoscale ocean wave model predictions will be presented. [Work supported by the Defense Advanced Research Projects Agency. Support of the State of Hawaii is acknowledged.]

The effect of improved footrope contact measurements on trawl area swept estimates

Abstract Various net monitoring instruments have been used during the evolution of the Gulf of Alaska demersal trawl survey conducted by the Alaska Fisheries Science Center in an attempt to reduce haul-to-haul variability in estimates of relative density due to variation in trawl efficiency and swept area. The introduction of a bottom contact sensor greatly enhanced our ability to identify important haul events and has resulted in altered definitions of the start and end of a tow. An unintended consequence of these changed definitions is that the tow distances are longer which, in turn, has affected the time series because no corrections have been made to tow distances of hauls conducted prior to the introduction of the bottom contact sensor. The mean additional distance fished since the introduction of the bottom contact sensor was 223 m, or 8.0% of the total length of a standard 30 min haul. The challenges of correcting the time series, including differences in capture efficiencies during various stages of a tow and the need for further standardization of operating procedures are discussed.

Challenges for efficient communication in underwater acoustic sensor networks

Ocean bottom sensor nodes can be used for oceanographic data collection, pollution monitoring, offshore exploration and tactical surveillance applications. Moreover, Unmanned or Autonomous Underwater Vehicles (UUVs, AUVs), equipped with sensors, will find application in exploration of natural undersea resources and gathering of scientific data in collaborative monitoring missions. Underwater acoustic networking is the enabling technology for these applications. Underwater Networks consist of a variable number of sensors and vehicles that are deployed to perform collaborative monitoring tasks over a given area.In this paper, several fundamental key aspects of underwater acoustic communications are investigated. Different architectures for two-dimensional and three-dimensional underwater sensor networks are discussed, and the underwater channel is characterized. The main challenges for the development of efficient networking solutions posed by the underwater environment are detailed at all layers of the protocol stack. Furthermore, open research issues are discussed and possible solution approaches are outlined.

Influence of stress and unidirectional field annealing on structural and magnetic performance of PtMn bottom spin-filter spin valves

The influence of unidirectional field annealing (UDA) and subsequent stress annealing (SA) on the structure and magnetic response of PtMn bottom spin-filter spin-valve sensors with a NiFeCr/NiFe seed layer was investigated. A time constant of 1.17h for the FCC–FCT phase transition of the PtMn layer was obtained upon UDA at 265°C in an external magnet field of 13 kOe, which is consistent with 1.1h observed for the GMR. A lower time constant of 0.7h was determined for the exchange interaction field. The SA with similar conditions as in the manufacturing environment leads to a UDA time-dependent alteration of sensor performance. A SA up to 38h causes a GMR value reduction, which becomes more pronounced with increasing UDA duration prior to SA. Furthermore, SA causes a progressive oxidation of the Ta cap layer; in contrast, the exchange field remains nearly unaffected, particularly for the sensors with 5 or 6h UDA. From the point view of application, an UDA treatment of (5–6)h yields the optimal sensor performance for the finished read-write head.

A high‐resolution magnetic mosaic at the Kyme archaeological site (Turkey)

AbstractAn extended high‐resolution magnetic investigation was undertaken at the archaeological site in Kyme (Turkey). In order to obtain highly resolved digital raster images, the gradient data sets were processed by using digital image processing techniques. In addition to these sets of data, the magnetic field measurements acquired by the bottom sensor alone were also processed. A careful comparison between the gradient data magnetograms and the bottom sensor magnetograms revealed how the entire mosaic, elaborated by processing the bottom sensor data, could fruitfully integrate and improve the information inferred by the vertical gradient magnetograms. Finally, the main archaeological features outlined from this magnetic investigation, as well as the results of a first guided excavation, are presented. Copyright © 2003 John Wiley & Sons, Ltd.

Bridle efficiency of a survey trawl for flatfish: measuring the length of the bridles in contact with the bottom

A bottom trawl catch of flatfish is composed of fish that were initially in the path of the net and fish that were initially in the path of the bridles and were subsequently herded into the net path. Bridle efficiency (i.e. the proportion of fish in the bridle path herded into the net path) can be estimated by fitting a model to catch and trawl measurement data collected in a field experiment in which the bridle path is varied in width by varying bridle length. Since flatfish are herded by the direct contact or close approach of the bridles with the bottom, part of the necessary field work is estimating the length of the bridles in contact with the bottom. Previously, bottom contact of the bridles has been determined using video cameras, but this is not possible when the bridles are entirely obscured by the mud clouds generated by the trawl doors. As an alternative approach, a bridle-mounted bottom contact sensor (BCS) was developed to allow measurement of the off-bottom distance of a bridle and the percentage of time it is in contact with the bottom. For the survey trawl studied, approximately 43% of the lower bridle was sufficiently close to the bottom to presumably elicit a herding response; however, the middle of the three bridles sagged to such an extent that it touched the bottom ahead of the lower bridle and extended the length to 51%.

Real-time geophysical measurements on the deep seafloor using submarine cable in the southern Kurile subduction zone

A permanent real-time geophysical observatory using a submarine cable was developed and deployed to monitor seismicity, tsunamis, and other geophysical phenomena in the southern Kurile subduction zone. The geophysical observatory comprises six bottom sensor units, two branching units, a main electro-optical cable with a length of 240 km and two land stations. The bottom sensor units are: 1) three ocean bottom broadband seismometers with hydrophone; 2) two pressure gauges (PGs); 3) a cable end station with environmental measurement sensors. Real-time data from all the undersea sensors are transmitted through the main electro-optical cable to the land station. The geophysical observatory was installed on the continental slope of the southern Kurile trench, southeast Hokkaido, Japan in July 1999. Examples of observed data are presented. Sensor noises and resolution are mentioned for the ocean bottom broadband seismometers and the PGs, respectively. An adaptable observation system including very broadband seismometers is scheduled to be connected to the branching unit in late 2001. The real-time geophysical observatory is expected to greatly advance the understanding of geophysical phenomena in the southern Kurile subduction zone.