scholarly journals Novel Electrode Architecture for Subgaleal Electroencephalography: A Feasibility Study

2021 ◽  
Author(s):  
Arman Ahnood ◽  
Nhan Duy Truong ◽  
Bobbi Fleiss ◽  
Armin Nikpour ◽  
Omid Kavehei
Keyword(s):  
Community Setting ◽  
Electrode Configuration ◽  
Electrode Spacing ◽  
Lead Wire ◽  
Device Reliability ◽  
Order Of Magnitude ◽  
Source Signal ◽  
Invasive Device ◽  
Cadaver Studies

Electroencephalography (EEG) has been widely used to understand the nervous system and as a clinical diagnostic tool. In the case of neurological conditions with intermittent episodes, such as epilepsy, long-term EEG monitoring outside the clinics and in the community setting is vital. Subgaleal EEG (sgEEG) has emerged as an essential tool for long-term monitoring over several years. Current sgEEG solutions share a need for at least a 10 cm long lead wire, resulting in a bulky and invasive device. This work introduces a novel electrode architecture for subgaleal EEG recording, which forgoes the need for lead wires. A back-to-back electrode configuration with an electrode spacing of less than 1~mm is proposed. Compared to the current side-by-side approaches with an electrode spacing of several cm, our proposed approach results in at least one order of magnitude reduction in volume. The efficacy of the proposed electrode architecture is investigated through finite element modeling, phantom measurements, and cadaver studies. Our results suggest that compared to the conventional side-by-side electrode configuration, the source signal can be recorded reliably. Lead wires have posed a significant challenge from a device reliability and measurement quality perspective. Moreover, lead wires and the associated feedthrough connectors are bulky. Our proposed lead-free EEG recording solution may lead to a less invasive surgical placement through volume reduction and improve EEG recording quality.

scholarly journals Statistically rigorous calculations do not support common input and long-term synchronization of motor-unit firings

2014 ◽  
Vol 112 (11) ◽  
pp. 2729-2744 ◽  
Author(s):  
Carlo J. De Luca ◽  
Joshua C. Kline
Keyword(s):  
Motor Unit ◽  
Statistical Tests ◽  
Vastus Lateralis ◽  
Common Input ◽  
Data Set ◽  
Order Of Magnitude ◽  
Score Method ◽  
Surface Electromyographic Signal ◽  
Measure Synchronization

Over the past four decades, various methods have been implemented to measure synchronization of motor-unit firings. In this work, we provide evidence that prior reports of the existence of universal common inputs to all motoneurons and the presence of long-term synchronization are misleading, because they did not use sufficiently rigorous statistical tests to detect synchronization. We developed a statistically based method (SigMax) for computing synchronization and tested it with data from 17,736 motor-unit pairs containing 1,035,225 firing instances from the first dorsal interosseous and vastus lateralis muscles—a data set one order of magnitude greater than that reported in previous studies. Only firing data, obtained from surface electromyographic signal decomposition with >95% accuracy, were used in the study. The data were not subjectively selected in any manner. Because of the size of our data set and the statistical rigor inherent to SigMax, we have confidence that the synchronization values that we calculated provide an improved estimate of physiologically driven synchronization. Compared with three other commonly used techniques, ours revealed three types of discrepancies that result from failing to use sufficient statistical tests necessary to detect synchronization. 1) On average, the z-score method falsely detected synchronization at 16 separate latencies in each motor-unit pair. 2) The cumulative sum method missed one out of every four synchronization identifications found by SigMax. 3) The common input assumption method identified synchronization from 100% of motor-unit pairs studied. SigMax revealed that only 50% of motor-unit pairs actually manifested synchronization.

scholarly journals Mineralogical, numerical and analytical studies of the coupled oxidation of pyrite and coal

2003 ◽  
Vol 67 (2) ◽  
pp. 381-398 ◽  
Author(s):  
K. A. Evans ◽  
C. J. Gandy ◽  
S. A. Banwart
Keyword(s):  
Reactive Transport ◽  
Transport Model ◽  
Pyrite Oxidation ◽  
Spoil Heap ◽  
Reaction Fronts ◽  
Order Of Magnitude ◽  
Magnitude Variation ◽  
Discharge Chemistry ◽  
Analytical Expressions

Mineralogical, bulk and field leachate compositions are used to identify important processes governing the evolution of discharges from a coal spoil heap in County Durham. These processes are incorporated into a numerical one-dimensional advective-kinetic reactive transport model which reproduces field results, including gas compositions, to within an order of magnitude. Variation of input parameters allows the effects of incorrect initial assumptions on elemental profiles and discharge chemistry to be assessed. Analytical expressions for widths and speeds of kinetic reaction fronts are developed and used to predict long-term development of mineralogical distribution within the heap. Results are consistent with observations from the field site. Pyrite oxidation is expected to dominate O2 consumption in spoil heaps on the decadal timescale, although C oxidation may stabilize contaminants in effluents on the centennial scale.

scholarly journals Cosmogenic burial dating of in cave-deposited alluvium: unravelling long-term incision rates and complex speleogenesis in multi-level cave systems

2020 ◽  
Author(s):  
Gilles Rixhon ◽  
Didier L. Bourlès ◽  
Régis Braucher ◽  
Alexandre Peeters ◽  
Alain Demoulin
Keyword(s):  
Early Pleistocene ◽  
Middle Pleistocene ◽  
Fluvial Terrace ◽  
Base Level ◽  
Cave System ◽  
River Incision ◽  
Order Of Magnitude ◽  
History Of ◽  
Multi Level

<p>Multi-level cave systems record the history of regional river incision in abandoned alluvium-filled phreatic passages which, mimicking fluvial terrace sequences, represent former phases of fluvial base-level stability. In this respect, cosmogenic burial dating of in cave-deposited alluvium (usually via the nuclide pair <sup>26</sup>Al/<sup>10</sup>Be) represents a suitable method to quantify the pace of long-term river incision. Here, we present a dataset of fifteen <sup>26</sup>Al/<sup>10</sup>Be burial ages measured in fluvial pebbles washed into a multi-level cave system developed in Devonian limestone of the uplifted Ardenne massif (eastern Belgium). The large and well-documented Chawresse system is located along the lower Ourthe valley (i.e. the main Ardennian tributary of the Meuse river) and spans altogether an elevation difference exceeding 120 m.</p><p>The depleted <sup>26</sup>Al/<sup>10</sup>Be ratios measured in four individual caves show two main outcomes. Firstly, computed burial ages ranging from ~0.2 to 3.3 Ma allows highlighting an acceleration by almost one order of magnitude of the incision rates during the first half of the Middle Pleistocene (from ~25 to ~160 m/Ma). Secondly, according to the relative elevation above the present-day floodplain of the sampled material in the Manants cave (<35 m), the four internally-consistent Early Pleistocene burial ages highlight an “anomalous” old speleogenesis in the framework of a gradual base-level lowering. They instead point to intra-karsting reworking of the sampled material in the topographically complex Manants cave. This in turn suggests an independent, long-lasting speleogenetic evolution of this specific cave, which differs from the <em>per descensum</em> model of speleogenesis generally acknowledged for the regional multi-level cave systems and their abandoned phreatic galleries. In addition to its classical use for inferring long-term incision rates, cosmogenic burial dating can thus contribute to better understand specific and complex speleogenetic evolution.</p>

scholarly journals LARGE INFORMATION PLUS NOISE RANDOM MATRIX MODELS AND CONSISTENT SUBSPACE ESTIMATION IN LARGE SENSOR NETWORKS

2012 ◽  
Vol 01 (02) ◽  
pp. 1150006 ◽  
Author(s):  
WALID HACHEM ◽  
PHILIPPE LOUBATON ◽  
XAVIER MESTRE ◽  
JAMAL NAJIM ◽  
PASCAL VALLET
Keyword(s):  
Covariance Matrix ◽  
Estimation Method ◽  
Singular Values ◽  
Subspace Methods ◽  
Localization Function ◽  
Random Matrix Models ◽  
Order Of Magnitude ◽  
Source Signal ◽  
Subspace Estimation ◽  
Empirical Covariance

In array processing, a common problem is to estimate the angles of arrival of K deterministic sources impinging on an array of M antennas, from N observations of the source signal, corrupted by Gaussian noise. In the so-called subspace methods, the problem reduces to estimate a quadratic form (called "localization function") of a certain projection matrix related to the source signal empirical covariance matrix. The estimates of the angles of arrival are then obtained by taking the K deepest local minima of the estimated localization function. Recently, a new subspace estimation method has been proposed, in the context where the number of available samples N is of the same order of magnitude than the number of sensors M. In this context, the traditional subspace methods tend to fail because they are based on the empirical covariance matrix of the observations which is a poor estimate of the source signal covariance matrix. The new subspace method is based on a consistent estimator of the localization function in the regime where M and N tend to +∞ at the same rate. However, the consistency of the angles estimator was not addressed, and the purpose of this paper is to prove this consistency in the previous asymptotic regime. For this, we prove the property that the singular values of M × N Gaussian information plus noise matrix escape from certain intervals is an event of probability decreasing at rate [Formula: see text] for all p. A regularization trick is also introduced, which allows to confine these singular values into certain intervals and to use standard tools as Poincaré inequality to characterize any moments of the estimator. These results are believed to be of independent interest.

Inferring rock glacier genesis and dynamics from age-layer modelling and borehole age-profile

2021 ◽  
Author(s):  
Gwendolyn J.-M. C. Leysinger Vieli ◽  
Andreas Vieli ◽  
Alessandro Cicoira
Keyword(s):  
Accumulation Rate ◽  
Bottom Layer ◽  
Rock Glacier ◽  
Depth Profiles ◽  
Talus Slope ◽  
Order Of Magnitude ◽  
Rock Glaciers ◽  
Age Profile ◽  
Modelling Approach

<p>The genesis of rock glaciers differs fundamentally from ‘normal’ glaciers and results in much older landforms that are often reaching ages of several millennia. Recent datings of rock glacier material from boreholes indicate early Holocene ages for rock glaciers and allow the derivation of age-depth profiles at the borehole location. We use here a 2-dimensional numerical modelling approach that calculates age-layers (isochrones) within the rock glacier body and that considers the accretion, melt and flow-advection of rock glacier material. We apply this model to the case of Lazaun rock glacier (Southern Ötztal Alps) for which a well dated profile from a borehole exists, with ages at the bottom older than 9000 years (Krainer et al. 2015). With our modelling we are able to reproduce the observed age-depth profiles well and are able to infer a long-term accumulation rate that is around 1 cm/yr which is an order of magnitude higher than a previous estimate that does not account for deformation. The modelling is consistent with the classic rock glacier genesis of material accretion in the upstream talus slope and confirms the dominance of deformation in the shear-zone at the bottom layer of the rock glacier.<br>We conclude that combining age-layer modelling with dated depth-profiles of rock glaciers allows for important new insights into our understanding of rock glacier evolution and dynamics.</p><p>REFERENCES  <br>Krainer, K., Bressan, D., Dietre, B., Haas, J., Hajdas, I., Lang, K. & Tonidandel, D. (2015). A 10,300-year-old permafrost core from the active rock glacier Lazaun, southern Oetztal Alps (South Tyrol, Northern Italy). Quaternary Research, 83 , 324-335. </p><p> </p>

One Step Chip Attach Materials (OSCA) for Conventional Mass Reflow Processing

2014 ◽  
Vol 2014 (1) ◽  
pp. 000262-000267
Author(s):  
Daniel J. Duffy ◽  
Lin Xin ◽  
Jean Liu ◽  
Bruno Tolla
Keyword(s):  
Flip Chip ◽  
Polymeric Materials ◽  
Cure Kinetics ◽  
Filler Loading ◽  
Single Step ◽  
Seamless Integration ◽  
Device Reliability ◽  
One Step ◽  
Traditional Processing

One step chip attach (OSCA) materials are dispensable polymeric materials for flip chip assembly, which are designed to flux metallic interconnections and subsequently turn into an underfill upon curing. OSCA materials enable a drastic simplification of the assembly process by combining the reflow (fluxing/soldering), defluxing and capillary underfilling steps used in traditional processing into a single step. One key challenge for the design of OSCA materials is timing the cure kinetics with fluxing activity and solder reflow during processing. A second key challenge is to factor a process-friendly rheological design into the formulation. The OSCA material rheology must allow for high filler loading levels, seamless integration with standard dispensing equipment, flow control during and after dispense (avoid keep out zones), flow during die placement (elimination of voids), after placement (fillet formation) and during reflow. The final key requirements for a functional device are defect-free interconnections combined with optimal thermo-mechanical and water resistant properties of the final underfill to guarantee the long-term reliability of the assembly in various environmental conditions. This paper presents the properties of materials designed by Kester for use in mass reflow processing (OSCA-R). The rheological design principles behind a seamless integration into customer-friendly processes will be presented In addition results illustrating the timing of cure kinetics with fluxing and soldering events during processing will be discussed. Preliminary device reliability results will also be presented for several types of test vehicles including; Si-Si and Si-FR4.

scholarly journals NH<sub>3</sub> emissions from large point sources derived from CrIS and IASI satellite observations

2019 ◽  
Vol 19 (19) ◽  
pp. 12261-12293 ◽  
Author(s):  
Enrico Dammers ◽  
Chris A. McLinden ◽  
Debora Griffin ◽  
Mark W. Shephard ◽  
Shelley Van Der Graaf ◽  
...  
Keyword(s):  
Human Health ◽  
Reactive Nitrogen Species ◽  
Point Sources ◽  
Satellite Observations ◽  
Atmospheric Sounding ◽  
Order Of Magnitude ◽  
Short And Long Term ◽  
Current Emission ◽  
Cross Track

Abstract. Ammonia (NH3) is an essential reactive nitrogen species in the biosphere and through its use in agriculture in the form of fertilizer (important for sustaining humankind). The current emission levels, however, are up to 4 times higher than in the previous century and continue to grow with uncertain consequences to human health and the environment. While NH3 at its current levels is a hazard to environmental and human health, the atmospheric budget is still highly uncertain, which is a product of an overall lack of measurements. The capability to measure NH3 with satellites has opened up new ways to study the atmospheric NH3 budget. In this study, we present the first estimates of NH3 emissions, lifetimes and plume widths from large (>∼5 kt yr−1) agricultural and industrial point sources from Cross-track Infrared Sounder (CrIS) satellite observations across the globe with a consistent methodology. The same methodology is also applied to the Infrared Atmospheric Sounding Interferometer (IASI) (A and B) satellite observations, and we show that the satellites typically provide comparable results that are within the uncertainty of the estimates. The computed NH3 lifetime for large point sources is on average 2.35±1.16 h. For the 249 sources with emission levels detectable by the CrIS satellite, there are currently 55 locations missing (or underestimated by more than an order of magnitude) from the current Hemispheric Transport Atmospheric Pollution version 2 (HTAPv2) emission inventory and only 72 locations with emissions within a factor of 2 compared to the inventories. The CrIS emission estimates give a total of 5622 kt yr−1, for the sources analyzed in this study, which is around a factor of ∼2.5 higher than the emissions reported in HTAPv2. Furthermore, the study shows that it is possible to accurately detect short- and long-term changes in emissions, demonstrating the possibility of using satellite-observed NH3 to constrain emission inventories.

scholarly journals Long-term stability studies of a semiconductor photoelectrode in three-electrode configuration

2019 ◽  
Vol 7 (48) ◽  
pp. 27612-27619 ◽  
Author(s):  
Srinivas Vanka ◽  
Kai Sun ◽  
Guosong Zeng ◽  
Tuan Anh Pham ◽  
Francesca Maria Toma ◽  
...  
Keyword(s):  
Electrode Configuration ◽  
Stability Studies ◽  
Term Stability ◽  
Long Term Stability

GaN/Si photocathode exhibits an ultrahigh stability of 3000 h under AM 1.5G one-sun illumination.

scholarly journals Remote sensing and conservation of isolated indigenous villages in Amazonia

2014 ◽  
Vol 1 (3) ◽  
pp. 140246 ◽  
Author(s):  
Robert S. Walker ◽  
Marcus J. Hamilton ◽  
Aaron A. Groth
Keyword(s):  
Remote Sensing ◽  
Satellite Imagery ◽  
Term Survival ◽  
Surveillance Programme ◽  
Non Invasive ◽  
External Threats ◽  
Indigenous Groups ◽  
Order Of Magnitude ◽  
Population Sizes

The vast forests on the border between Brazil and Peru harbour a number of indigenous groups that have limited contact with the outside world. Accurate estimates of population sizes and village areas are essential to begin assessing the immediate conservation needs of such isolated groups. In contrast to overflights and encounters on the ground, remote sensing with satellite imagery offers a safe, inexpensive, non-invasive and systematic approach to provide demographic and land-use information for isolated peoples. Satellite imagery can also be used to understand the growth of isolated villages over time. There are five isolated villages in the headwaters of the Envira River confirmed by overflights that are visible with recent satellite imagery further confirming their locations and allowing measurement of their cleared gardens, village areas and thatch roofed houses. These isolated villages appear to have population densities that are an order of magnitude higher than averages for other Brazilian indigenous villages. Here, we report on initial results of a remote surveillance programme designed to monitor movements and assess the demographic health of isolated peoples as a means to better mitigate against external threats to their long-term survival.

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