3,834 research outputs found
Spectral analysis of vertical temperature profile time-series data in Yellowstone Lake sediments
Author Posting. © American Geophysical Union, 2021. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Water Resources Research 57(4), (2021): e2020WR028430, https://doi.org/10.1029/2020WR028430.We use yearlong vertical temperature profile time-series (seven thermistors at evenly spaced depth intervals from 10 to 70 cm) from five sites in and around the Deep Hole thermal area, southeast of Stevenson Island, Yellowstone Lake, to investigate heat and mass fluxes across the lake floor. The records demonstrate that thermal gradients in surficial sediments are modulated by a rich spectrum of bottom water temperature variations generated by hydrodynamic processes, and that sites inside the thermal area also respond to hydrothermal variations. We develop and implement a new method for estimating the sediment effective thermal diffusivity and pore fluid vertical flow rate that exploits the full spectrum of observed temperature variations to generate the parameter estimates, uncertainties, and metrics to assess statistical significance. Sediments at sites outside thermal areas have gradients of ∼7.5°C/m, in situ thermal diffusivities of ∼1.6 × 10−7 m2/s consistent with highly porous (80–90%) siliceous sediments, and experience hypolentic flow in the upper ∼20 cm. Sites inside the Deep Hole thermal area exhibit considerable spatial and temporal variability, with gradients of 1–32°C/m, and higher thermal diffusivities of ∼2–12 × 10−7 m2/s, consistent with hydrothermal alteration of biogenic silica to clays, quartz, and pyrite. Upward pore fluid flow at these sites is observed across multiple depth intervals, with maximum values of ∼3 cm/day. The observed spatial and temporal variability within the thermal area is consistent with upward finger flow combined with short wavelength convection within the porous sediments above a steam reservoir.This research was supported by the National Science Foundation Grants EAR-1516361 to Robert A. Sohn and EAR-1515283 to Robert N. Harris, and by the Independent Research and Development Program at the Woods Hole Oceanographic Institution (Robert A. Sohn). All work in Yellowstone National Park was completed under an authorized Yellowstone research permit (YELL-2018-SCI-7018)
Reply to comment by T.J. Osborn and K. R. Briffa on "Mid-Latitude (30?-60?N) climatic warming inferred by combining borehole temperatures with surface air temperatures"
Journal ArticleWe thank Osborn and Briffa [2002] for their comment regarding our use of the climatic reconstruction of Overpeck et al. [1997]. We [Harris and Chapman, 2001] had taken a proxy, Arctic wide summer-weighted annual temperature reconstruction [Overpeck et al., 1997], given in dimensionless sigma units (i.e., normalized deviation from the 1901?1960 proxy mean in units of standard deviation of the new series for the period 1901?1960) and represented the reconstruction in our Figure 3 and Table 1 in terms of dimensional temperature units ?C
Geothermics and climate change: 1. Analysis of borehole temperatures with emphasis on resolving power
Journal ArticleTemperature-depth data from six boreholes in western Utah and nine boreholes in southeastern Utah are reanalyzed for evidence of ground surface temperature (GST) histories. We invert the temperature-depth data using the functional space inverse algorithm of Shen and Beck [1991, 1992] which we prefer over previous inversions of these data because of its greater sophistication and flexibility in suppressing noise. GST histories for western and southeastern Utah are generally consistent and suggest that temperatures in the mid-1800s are, on average, cooler than previous centuries, followed by about 0.6°C of warming in this century. Attention is given to the temporal resolution of our GST solutions showing the time-smearing effects of heat conduction on the solutions. GST solutions represent an average ground temperature over a time window that expands as we look farther into the past. The size of the time window is a function of measurement and geologic noise and limits the ultimate resolution of GST reconstructions
Geothermics and climate change: 2. Joint analysis of borehole temperature and meteorological data
Journal ArticleLong-period ground surface temperature variations contained in bore hole temperature-depth profiles form a complementary climate change record to high-frequency, but noisy surface air temperature (SAT) records at weather stations. We illustrate the benefits of jointly analyzing geothermal and meteorological data for two regions in Utah where both high-quality temperature-depth measurements and century long SAT records exist
Default resolution and access to fresh credit in an emerging market
We examine loan defaults by firms and identify the factors that influence both the default resolution process and firms' access to fresh credit after firms exit default. Using a dataset of all commercial loans made in Pakistan from 2006 to 2013, we find an important role for collateral. Collateral expedites both the default resolution process and access to fresh credit after exiting default. Higher interest rates increase the default duration. Relationships with multiple lenders as well as those with multiple branches of one lender are associated with obtaining fresh credit at the post default stage
Comparison of Landing Variables between Countermovement Jump Landings and Drop Vertical Jump Landings from Equal Heights
The countermovement jump (CMJ) and drop vertical jump (DVJ) are often used as a measurement of physical ability or performance potential, while analysis of landing can provide crucial information regarding injury risk. In theory, similar landing strategies should be employed when CMJ jump height and DVJ drop height are controlled, yet we know of no studies have investigated this possibility. PURPOSE: to examine and compare landing characteristics between CMJ and DVJ when flight height is controlled. METHODS: Forty (20 males; 20 females; 22.5 ± 4.3 years, 1.7 ± 0.1 m, 73.2 ± 13.3 kg) recreationally active individuals performed three CMJ and three DVJ trials, each from the same height which was controlled using a Vertec. Vertical ground reaction force (VGRF) data was obtained from a portable force platform. Landing momentum, landing time, and peak vGRF were obtained from the processed vGRF data using a custom analysis program. Variables were compared between jumps (CMJ, DVJ) using paired samples t-tests (α = 0.05). Cohen’s d is used to supplement statistical outcomes by demonstrating the magnitude of mean differences. RESULTS: Landing momentum was 4.8% greater during DVJ than during CMJ and the difference was small (DVJ = -193.6 ± 52.2, CMJ = -184.4 ± 52.5; P=0.049, d = 0.4), indicating slightly greater landing heights during DVJ. Landing time during DVJ was 52% shorter than the CMJ landing time and the difference was very large (DVJ = 0.4 ± 0.2, CMJ = 0.7 ± 0.2; P\u3c0.001, d =1.7), while DVJ peak impact force was 14.7% less than CMJ peak impact force and the difference was moderate (DVJ = 3.5 ± 1.0; CMJ = 4.1 ± 0.7; P=0.002, d = 0.6). CONCLUSION: While the significant difference in landing momentum was not random, the magnitude of mean difference was small, indicating relatively similar landing momentum between jumps. Thus, the present study shows that, even when controlling jump height between the CMJ and DVJ, the tasks do not have similar landing demands, defined by momentum, time, nor peak impact force. Due to the differences observed, the CMJ and DVJ should not be used interchangeably or as a comparison between one another when examining these specific landing variables. Finally, the DVJ might expose performers to lesser overuse injury risks related to impact forces
Automatic Detection of Seizures with Applications
There are an estimated two million people with epilepsy in the United States. Many of these people do not respond to anti-epileptic drug therapy. Two devices can be developed to assist in the treatment of epilepsy. The first is a microcomputer-based system designed to process massive amounts of electroencephalogram (EEG) data collected during long-term monitoring of patients for the purpose of diagnosing seizures, assessing the effectiveness of medical therapy, or selecting patients for epilepsy surgery. Such a device would select and display important EEG events. Currently many such events are missed. A second device could be implanted and would detect seizures and initiate therapy. Both of these devices require a reliable seizure detection algorithm. A new algorithm is described. It is believed to represent an improvement over existing seizure detection algorithms because better signal features were selected and better standardization methods were used
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Variations in air and ground temperature and the POM-SAT model: Results from the Northern Hemisphere
The POM-SAT model for comparing air and
ground temperatures is based on the supposition that surface
air temperature (SAT) records provide a good prediction
of thermal transients in the shallow subsurface of the Earth.
This model consists of two components, the forcing function
and an initial condition, termed the pre-observational mean
(POM). I explore the sensitivity of this model as a function
of forcing periods at time scales appropriate for climate
reconstructions. Synthetic models are designed to replicate
comparisons between borehole temperatures contained in the
global database of temperature profiles for climate reconstructions
and gridded SAT data. I find that the root mean
square (RMS) misfit between forcing functions and transient
temperature profiles in the subsurface are sensitive to periods
longer than about 50 years, are a maximum when the
period and the 150-year time series are equal and then decreases
for longer periods. The magnitude of the POM is
a robust parameter for periods equal to or shorter than the
length of this time series. At longer periods there is a tradeoff
between the amplitude of the forcing function and the
POM. These tests provide guidelines for assessing comparisons
between air and ground temperatures at periods appropriate
for climate reconstructions. The sensitivity of comparisons
between the average Northern Hemisphere gridded
SAT record and subsurface temperature-depth profile as a
function of forcing period is assessed. This analysis indicates
that the Northern Hemisphere extratropical average SAT and
reduced temperature-depth profile are in good agreement. By
adding modest heat to the subsurface at intermediate periods
some improvement in misfit can be made, but this extra heat
has negligible influence on the POM. The joint analysis of
borehole temperatures and SAT records indicate warming of
about 1.1°C over the last 500 years, consistent with previous
studies
Best Practice Guidelines for Regional Development Strategies
The grids project
GRIDS is an INTERREG IIIC project that is focused
on developing a series of best practice guidelines
for regional development and spatial planning. It is
especially concerned with identifying and promoting
good practice within some of the smaller countries
of the European Union. Project partners are based in Ireland, Wales, Belgium, Latvia and Lithuania and include national, regional and local public administrations as well as academic institutions. The project has also attracted
interest and involvement from government organisa-
tions in Scotland and Estonia. The project has focused on exchanging experience between partners
CMS search plans and sensitivity to new physics with dijets
CMS will use dijets to search for physics beyond the standard model during
early LHC running. The inclusive jet cross section as a function of jet
transverse momentum, with 10 inverse picobarns of integrated luminosity, is
sensitive to contact interactions beyond the reach of the Tevatron. The dijet
mass distribution will be used to search for dijet resonances coming from new
particles, for example an excited quark. Additional sensitivity to the
existence of contact interactions or dijet resonances can be obtained by
comparing dijet rates in two distinct pseudorapidity regions.Comment: 10 pages, 4 figures, accepted for publication in J. Phys. G: Nucl.
Part. Phy
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