248 research outputs found
Assessing Potential Shale Gas Impacts on Groundwater Resources: Recommendations for Groundwater Monitoring and Definition of Baseline Conditions
Exploitation of shale gas by hydraulic fracturing (fracking) is highly controversial and concerns have been raised regarding induced risks from this extraction technique. The SHEER project, an EU Horizon 2020-funded project, is developing best practice to understand, prevent and mitigate the potential short- and long-term environmental impacts and risks of shale gas exploration and exploitation. Three major potential impacts were identified: groundwater contamination, air pollution and induced seismicity. This presentation will deal with the hydrogeological aspect. As part of the SHEER project, baseline and operational groundwater monitoring was carried out at an extraction site in Wysin, Northern Poland. Baseline monitoring was carried out from December 2015 to June 2016 in four monitoring wells intercepting the main drinking water aquifer located in Quaternary sediments. Fracking operations occurred in two deviated horizontal wells in June and July 2016. Monitoring continued for 1.5 years post-fracking although no significant gas production occurred during this period. Collected data include measurements of groundwater level, electrical conductivity and temperature at 15-min intervals, field measurements of groundwater physico-chemical parameters and frequent sampling for laboratory analyses. Groundwater samples were analysed for a range of constituents including dissolved gases and stable isotopes. This presentation will provide an overview of the monitoring results and the ensuing recommendations for groundwater monitoring in the context of shale gas exploitation. These recommendations relate to: (1) site characterisation prior to any activity, (2) baseline and on-going groundwater monitoring, and (3) relationships between regulators, operators and general public. During the presentation, we will particularly focus on the monitoring methodology and establishing accurate background values for key parameters for baseline monitoring, including suggestions on how to clearly communicate the information to the general public. We will conclude on techniques to identify deviations from baseline values
On the use of the Gram matrix for multivariate functional principal components analysis
Dimension reduction is crucial in functional data analysis (FDA). The key
tool to reduce the dimension of the data is functional principal component
analysis. Existing approaches for functional principal component analysis
usually involve the diagonalization of the covariance operator. With the
increasing size and complexity of functional datasets, estimating the
covariance operator has become more challenging. Therefore, there is a growing
need for efficient methodologies to estimate the eigencomponents. Using the
duality of the space of observations and the space of functional features, we
propose to use the inner-product between the curves to estimate the
eigenelements of multivariate and multidimensional functional datasets. The
relationship between the eigenelements of the covariance operator and those of
the inner-product matrix is established. We explore the application of these
methodologies in several FDA settings and provide general guidance on their
usability.Comment: 23 pages, 12 figure
PMD tolerance of 288 Gbit/s Coherent WDM and transmission over unrepeatered 124 km of field-installed single mode optical fiber
Low-cost, high-capacity optical transmission systems are required for metropolitan area networks. Direct-detected multi-carrier systems are attractive candidates, but polarization mode dispersion (PMD) is one of the major impairments that limits their performance. In this paper, we report the first experimental analysis of the PMD tolerance of a 288Gbit/s NRZ-OOK Coherent Wavelength Division Multiplexing system. The results show that this impairment is determined primarily by the subcarrier baud rate. We confirm the robustness of the system to PMD by demonstrating error-free performance over an unrepeatered 124km field-installed single-mode fiber with a negligible penalty of 0.3dB compared to the back-to-back measurements. (C) 2010 Optical Society of Americ
Satellite Navigation for the Age of Autonomy
Global Navigation Satellite Systems (GNSS) brought navigation to the masses.
Coupled with smartphones, the blue dot in the palm of our hands has forever
changed the way we interact with the world. Looking forward, cyber-physical
systems such as self-driving cars and aerial mobility are pushing the limits of
what localization technologies including GNSS can provide. This autonomous
revolution requires a solution that supports safety-critical operation,
centimeter positioning, and cyber-security for millions of users. To meet these
demands, we propose a navigation service from Low Earth Orbiting (LEO)
satellites which deliver precision in-part through faster motion, higher power
signals for added robustness to interference, constellation autonomous
integrity monitoring for integrity, and encryption / authentication for
resistance to spoofing attacks. This paradigm is enabled by the 'New Space'
movement, where highly capable satellites and components are now built on
assembly lines and launch costs have decreased by more than tenfold. Such a
ubiquitous positioning service enables a consistent and secure standard where
trustworthy information can be validated and shared, extending the electronic
horizon from sensor line of sight to an entire city. This enables the
situational awareness needed for true safe operation to support autonomy at
scale.Comment: 11 pages, 8 figures, 2020 IEEE/ION Position, Location and Navigation
Symposium (PLANS
Nanostructural changes in cell wall pectins during strawberry fruit ripening assessed by atomic force microscopy
Rapid loss of firmness occurs during strawberry (Fragaria × ananassa Duch) ripening, resulting in a short shelf life and high economic losses. The disassembly of cell walls is considered the main responsible for fruit softening, being pectins extensively modified during strawberry ripening (Paniagua et al. 2014). Atomic force microscopy allows the analysis of individual polymer chains at nanostructural level with a minimal sample preparation (Morris et al., 2001). The main objective of this research was to compare pectins of green and red ripe strawberry fruits at the nanostructural level to shed light on structural changes that could be related to softening.
Cell walls from strawberry fruits were extracted and fractionated with different solvents to obtain fractions enriched in a specific component. The yield of cell wall material, as well as the amount of the different fractions, decreased in ripe fruits. CDTA and Na2CO3 fractions underwent the largest decrements, being these fractions enriched in pectins supposedly located in the middle lamella and primary cell wall, respectively. Uronic acid content also decreased significantly during ripening in both pectin fractions, but the amount of soluble pectins, those extracted with phenol:acetic acid:water (PAW) and water increased in ripe fruits. Monosaccharide composition in CDTA and Na2CO3 fractions was determined by gas chromatography. In both pectin fractions, the amount of Ara and Gal, the two most abundant carbohydrates, decreased in ripe fruits. The nanostructural characteristics of CDTA and Na2CO3 pectins were analyzed by AFM. Isolated pectic chains present in the CDTA fraction were significantly longer and more branched in samples from green fruits than those present in samples obtained from red fruit. In spite of slight differences in length distributions, Na2CO3 samples from unripe fruits displayed some longer chains at low frequency that were not detected in ripe fruits. Pectin aggregates were more frequently observed in green fruit samples from both fractions. These results support that pectic chain length and the nanostructural complexity of the pectins present in CDTA and Na2CO3 fractions diminish during strawberry fruit development, and these changes, jointly with the loss of neutral sugars, could contribute to the solubilization of pectins and fruit softening.
Paniagua et al. (2014). Ann Bot, 114: 1375-1383
Morris et al. (2001). Food Sci Tech 34: 3-10
This research was supported by FEDER EU Funds and the Ministerio de Educación y Ciencia of Spain (grant reference AGL2011-24814)Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech
Multi-wavelength regeneration of phase encoded signals based on phase sensitive amplifiers
Future high capacity optical links will have to make use of frequent signal regeneration to enable long distance transmission. In this respect, the role of all-optical signal processing becomes increasingly important because of its potential to mitigate signal impairments at low cost and power consumption. More substantial benefits are expected if regeneration is achieved simultaneously on a multiple signal band. Until recently, this had been achieved only for on-off keying modulation formats. However, as in future transmission links the information will be encoded also in the phase for enhancing the spectral efficiency, novel subsystem concepts will be needed for multichannel processing of such advanced signal formats. In this paper we show that phase sensitive amplifiers can be an ideal technology platform for developing such regenerators and we discuss our recent demonstration of the first multi-channel regenerator for phase encoded signals
DNA probe detection within 3D hydrogel matrix in a hollow core photonic crystal fibre
In this paper, we report for the first time the detection of a Cy5-labelled DNA probe immobilised within a 3D hydrogel matrix formed, inside a hollow core Photonic Crystal Fibre (HC-PCF). We show both the sensitivity of fluorescence detection inside the HC-PCF using a supercontinuum light source and of the variation of the luminescence intensity with the concentration DNA probe within the hydrogel. The 3D hydrogel matrix is a network of polymer chains, which is expected to provide highly sensitive detection and selection of bio-molecules, in comparison with 2D coverage. The biocompatibility of hydrogel in the HC-PCF suggests numerous applications associated with immobilised DNA probe detection for point-of-care or remote systems
Chromatic dispersion compensation using full-field maximum-likelihood sequence estimation
We investigate full-field detection-based maximum-likelihood sequence estimation (MLSE) for chromatic dispersion compensation in 10 Gbit/s OOK optical communication systems. Important design criteria are identified to optimize the system performance. It is confirmed that approximately 50% improvement in transmission reach can be achieved compared to conventional direct-detection MLSE at both 4 and 16 states. It is also shown that full-field MLSE is more robust to the noise and the associated noise amplifications in full-field reconstruction, and consequently exhibits better tolerance to nonoptimized system parameters than full-field feedforward equalizer. Experiments over 124 km spans of field-installed single-mode fiber without optical dispersion compensation using full-field MLSE verify the theoretically predicted performance benefits
Shale Gas Impacts on Groundwater Resources: Understanding the Behavior of a Shallow Aquifer Around a Fracking Site in Poland
Exploitation of shale gas by hydraulic fracturing (fracking) is highly controversial and concerns have been raised regarding induced risks from this technique. As part of the EU-funded SHEER Project, a shallow aquifer used for drinking water, overlying a zone of active shale-gas fracking, has been monitored for more than a year. Early results reveal the functioning of the shallow aquifer and hydrochemistry, focusing on the identification of potential impacts from the shale gas operation. This stage is an essential precursor to modeling impact scenarios of contamination and to predict changes in the aquifer
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