Identification of potential end-members and their apportionment from downstream high-frequency chemical data

High-frequency chemical measurements in streamwater give detailed information on the different hydrochemical processes occurring in the catchment. They can provide clues about the end-members (water sources) whose mixing produces the ionic stream concentrations observed. To identify and quantify the end-members and their respective contribution to streamwater chemistry, we developed a new methodology, termed “IQEA” (Identification and Quantification of End-members and their Apportionment). It consists in the resolution by a minimization process of an objective function based on downstream high-frequency chemical data and the size of the shape of a pre-defined fixed number of three end-members. We applied the IQEA method on the high-frequency concentration dataset of nitrates and calcium from the ORACLE-Orgeval Observatory in France. The results were compared with field data obtained from various potential end-members. The IQEA methodology yielded robust and very satisfactory results, apart from an exceptional flood event that occurred during the 2 years of measurements used in this study. While the IQEA model treats concentration and discharge datasets independently, its results show a strong relationship between the dominant end-member computed and the hydrological features.

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Geology and petrochemistry of lower Aphebian (2.4–2.0 Ga) alkaline plutonic and hypabyssal rocks in the East Arm of Great Slave Lake, Northwest Territories

Canadian Journal of Earth Sciences ◽

10.1139/e79-006 ◽

1979 ◽

Vol 16 (1) ◽

pp. 60-72 ◽

Cited By ~ 3

Author(s):

J. P. N. Badham

Keyword(s):

Northwest Territories ◽

Field Data ◽

Easter Island ◽

Chemical Data ◽

Lower Proterozoic ◽

Great Slave Lake ◽

Data Support ◽

Igneous Complexes ◽

Igneous Activity ◽

History Of

Two alkaline igneous complexes and three lines of diatreme breccias were emplaced in the East Arm of Great Slave Lake during the lower Proterozoic. Field relationships suggest that those rocks are broadly cogenetic and were emplaced about 2.1 Ga ago.One of the intrusions, the Easter Island dyke, was rotated subsequent to emplacement such that both top and bottom are now exposed. Field and petrographic data are indicative of progressive differentiation along (i.e., up) the dyke and are substantiated by chemical data. The differentiation history of the early gabbros of the Blachford Lake complex is similar. Late differentiates of both complexes closely resemble the igneous matrices of the breccias and petrographic and chemical data support the proposal of cogenesis and contemporaneity.The field data show that there was a period of significant faulting and concomitant alkaline igneous activity in the East Arm area in the lower Proterozoic.

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2D Laplace-Domain Waveform Inversion of Field Data Using a Power Objective Function

Pure and Applied Geophysics ◽

10.1007/s00024-013-0651-4 ◽

2013 ◽

Vol 170 (12) ◽

pp. 2075-2085 ◽

Cited By ~ 7

Author(s):

Eunjin Park ◽

Wansoo Ha ◽

Wookeen Chung ◽

Changsoo Shin ◽

Dong-Joo Min

Keyword(s):

Objective Function ◽

Field Data ◽

Waveform Inversion ◽

Laplace Domain

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Blink-Perturbed Saccades in Monkey. II. Superior Colliculus Activity

Journal of Neurophysiology ◽

10.1152/jn.2000.83.6.3430 ◽

2000 ◽

Vol 83 (6) ◽

pp. 3430-3452 ◽

Cited By ~ 63

Author(s):

H.H.L.M. Goossens ◽

A. J. Van Opstal

Keyword(s):

Superior Colliculus ◽

Firing Rate ◽

High Frequency ◽

Displacement Vector ◽

Neural Mechanism ◽

Fixed Number ◽

Deep Layers ◽

The Mean ◽

Reflex Blinks ◽

Frequency Burst

Trigeminal reflex blinks evoked near the onset of a saccade cause profound spatial-temporal perturbations of the saccade that are typically compensated in mid-flight. This paper investigates the influence of reflex blinks on the discharge properties of saccade-related burst neurons (SRBNs) in intermediate and deep layers of the monkey superior colliculus (SC). Twenty-nine SRBNs, recorded in three monkeys, were tested in the blink-perturbation paradigm. We report that the air puff stimuli, used to elicit blinks, resulted in a short-latency (∼10 ms) transient suppression of saccade-related SRBN activity. Shortly after this suppression (within 10–30 ms), all neurons resumed their activity, and their burst discharge then continued until the perturbed saccade ended near the extinguished target. This was found regardless whether the compensatory movement was into the cell's movement field or not. In the limited number of trials where no compensation occurred, the neurons typically stopped firing well before the end of the eye movement. Several aspects of the saccade-related activity could be further quantified for 25 SRBNs. It appeared that 1) the increase in duration of the high-frequency burst was well correlated with the (two- to threefold) increase in duration of the perturbed movement. 2) The number of spikes in the burst for control and perturbed saccades was quite similar. On average, the number of spikes increased only 14%, whereas the mean firing rate in the burst decreased by 52%. 3) An identical number of spikes were obtained between control and perturbed responses when burst and postsaccadic activity were both included in the spike count. 4) The decrease of the mean firing rate in the burst was well correlated with the decrease in the velocity of perturbed saccades. 5) Monotonic relations between instantaneous firing rate and dynamic motor error were obtained for control responses but not for perturbed responses. And 6) the high-frequency burst of SRBNs with short-lead and long-lead presaccadic activity (also referred to as burst and buildup neurons, respectively) showed very similar features. Our findings show that blinking interacts with the saccade premotor system already at the level of the SC. The data also indicate that a neural mechanism, rather than passive elastic restoring forces within the oculomotor plant, underlies the compensation for blink-related perturbations. We propose that these interactions occur downstream from the motor SC and that the latter may encode the desired displacement vector of the eyes by sending an approximately fixed number of spikes to the brainstem saccadic burst generator.

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Isotopic diffusion in polycrystalline ice

Journal of Glaciology ◽

10.3189/172756503781830638 ◽

2003 ◽

Vol 49 (166) ◽

pp. 397-406 ◽

Cited By ~ 13

Author(s):

Alan W. Rempel ◽

J. S. Wettlaufer

Keyword(s):

Stable Isotopes ◽

Stable Isotope ◽

Vapor Phase ◽

High Frequency ◽

Ice Core ◽

Accurate Analysis ◽

Depositional Processes ◽

Polycrystalline Ice ◽

End Members

AbstractQuantitative ice-core paleoclimatology must account for post-depositional processes, such as vapor-phase diffusion in the firn. After pore close-off, diffusion continues to smooth the stable-isotope records δ18O and δD that are eventually recovered from the ice, leading to the loss of high-frequency information. Johnsen and others (1997) found much higher rates of diffusive smoothing in the Greenland Icecore Project (GRIP) Holocene ice than would be predicted by diffusion through solid ice alone, and Nye (1998) argued that transport through liquid veins might explain this apparent excess diffusion. However, the analysis of Johnsen and others (2000) indicates that the required vein dimensions may be unrealistically large. Here, we model the diffusion of stable isotopes in polycrystalline ice and show that the predictions of Nye (1998) and those of Johnsen and others (2000) actually represent two end-members in a range of potential behavior. Our model determines which of these asymptotic regimes more closely resembles the prevailing conditions and quantifies the role of pre-melted liquid in the smoothing of isotopic signals. The procedure thereby ties together the two approaches and provides a rostrum for accurate analysis of isotope records and paleotemperature reconstructions.

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Body size and trophic divergence of two large sympatric elapid snakes (Notechis scutatus and Austrelaps superbus) (Serpentes:Elapidae) in Tasmania

Australian Journal of Zoology ◽

10.1071/zo12004 ◽

2012 ◽

Vol 60 (3) ◽

pp. 159 ◽

Cited By ~ 2

Author(s):

S. Fearn ◽

J. Dowde ◽

D. F. Trembath

Keyword(s):

Body Size ◽

High Frequency ◽

Field Data ◽

Trophic Ecology ◽

Competitive Exclusion ◽

Head Size ◽

Large Prey ◽

Potential Prey ◽

Island State ◽

Species Being

Tiger snakes (Notechis scutatus) and lowland copperheads (Austrelaps superbus) are both large viviparous elapid snakes confined to the cooler, mesic regions of southern Australia. In spite of both species being common and widespread in the island state of Tasmania, no quantified studies on the trophic ecology of these two snakes from the main island has been published. During a two-year period we collected field data from 127 adult A. superbus and 74 adult N. scutatus from throughout eastern Tasmania. For both species, males were larger than females with respect to all measured parameters, including mass and head size. Reproduction in females was strongly seasonal and clutch size was not related to maternal body size. N. scutatus has a larger head than A. superbus and consequently ingests both small and large prey. N. scutatus in our study displayed the most catholic diet of any Australian elapid studied to date and consumed mammals (possum, bandicoot, antechinus, rats, mice), birds (fairy wrens), fish (eel, trout) and frogs. A. superbus shows a more specialist diet of large volumes of predominately ectothermic prey (frogs, lizards, snakes) even at maximal sizes and was more likely to contain ingested prey than specimens of N. scutatus. Distinctive rodent bite scars were common on N. scutatus but rare on A. superbus. The high frequency of rodent bite scars on N. scutatus further supports our findings of a primarily endothermic diet for mature specimens. We suggest that significant differences in head size, and hence diet, as well as a taxonomically diverse suite of potential prey in Tasmania allow both these large snakes to coexist in sympatry and avoid interspecific competitive exclusion.

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Structurally constrained impedance inversion

Interpretation ◽

10.1190/int-2016-0049.1 ◽

2016 ◽

Vol 4 (4) ◽

pp. T577-T589 ◽

Cited By ~ 8

Author(s):

Haitham Hamid ◽

Adam Pidlisecky

Keyword(s):

Objective Function ◽

Seismic Data ◽

Field Data ◽

A Priori ◽

Structural Constraints ◽

Inversion Algorithm ◽

Data Set ◽

Impedance Inversion ◽

Single Trace ◽

Complex Geology

In complex geology, the presence of highly dipping structures can complicate impedance inversion. We have developed a structurally constrained inversion in which a computationally well-behaved objective function is minimized subject to structural constraints. This approach allows the objective function to incorporate structural orientation in the form of dips into our inversion algorithm. Our method involves a multitrace impedance inversion and a rotation of an orthogonal system of derivative operators. Local dips used to constrain the derivative operators were estimated from migrated seismic data. In addition to imposing structural constraints on the inversion model, this algorithm allows for the inclusion of a priori knowledge from boreholes. We investigated this algorithm on a complex synthetic 2D model as well as a seismic field data set. We compared the result obtained with this approach with the results from single trace-based inversion and laterally constrained inversion. The inversion carried out using dip information produces a model that has higher resolution that is more geologically realistic compared with other methods.

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Linking high-frequency DOC dynamics to the age of connected water sources

Water Resources Research ◽

10.1002/2015wr018419 ◽

2016 ◽

Vol 52 (7) ◽

pp. 5232-5247 ◽

Cited By ~ 37

Author(s):

C. Tunaley ◽

D. Tetzlaff ◽

J. Lessels ◽

C. Soulsby

Keyword(s):

High Frequency ◽

Water Sources

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Generalized radial inversion of 2D potential‐field data

Geophysics ◽

10.1190/1.1836815 ◽

2004 ◽

Vol 69 (6) ◽

pp. 1405-1413 ◽

Cited By ~ 17

Author(s):

João B. C. Silva ◽

Valéria C. F. Barbosa

Keyword(s):

Potential Field ◽

Field Data ◽

Physical Property ◽

Quantitative Information ◽

Fixed Number ◽

Polar Coordinates ◽

Inversion Method ◽

Potential Field Data ◽

Convexity Constraint ◽

Interpretation Model

We introduce a new 2D method for inverting potential‐field data with model constraints designed by the interpreter. Our method uses an interpretation model consisting of a source with polygonal cross‐section whose vertices are described by polar coordinates with an origininside the source. With this coordinate system, constraints in an inversion are easier to develop and apply. Our inversion method assumes a known physical property contrast for the source and estimates the radii associated with the polygon vertices for a fixed number of equally spaced angles from 0° to 360°. A wide variety of constraints may be used to stabilize the solutions by introducing information about the source shape. The method recovers stable solutions whose shapes range from almost circular or pear‐shaped to elongated in one or more directions. The convexity constraint applied to the source shape, despite requiring no quantitative information, is more versatile than the other constraints. The convexity constraint efficiently recovers source geometries that are either isometric or elongated in one direction.

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