Adequate stewardship of geothermal resources requires accurate forecasting of long-term thermal performance. In enhanced geothermal systems and other fracture-dominated reservoirs, predictive models ...commonly assume constant-aperture fractures, although spatial variations in aperture can greatly affect reservoir permeability, fluid flow distribution, and heat transport. Whereas previous authors have investigated the effects of theoretical random aperture distributions on thermal performance, here we further explore the influence of permeability heterogeneity considering field-constrained aperture distributions from a meso-scale field site in northern New York, USA. Using numerical models of coupled fluid flow and heat transport, we conduct thermal–hydraulic simulations for a hypothetical reservoir consisting of a relatively impervious porous matrix and a single, horizontal fracture. Our results indicate that in highly channelized fields, most well design configurations and operating conditions result in extreme rates of thermal drawdown (e.g., 50% drop in production well temperatures in under 2 years). However, some other scenarios that account for the risks of short-circuiting can potentially enhance heat extraction when mass flow rate is not excessively high, and the direction of geothermal extraction is not aligned with the most permeable features in the reservoir. Through a parametric approach, we illustrate that well separation distance and relative positioning play a major role in the long-term performance of highly channelized fields, and both can be used to help mitigate premature thermal breakthrough.
Energy for Transport Figueroa, Maria; Lah, Oliver; Fulton, Lewis M ...
Annual review of environment and resources,
10/2014, Letnik:
39, Številka:
1
Journal Article
Recenzirano
Global transportation energy use is steeply rising, mainly as a result of increasing population and economic activity. Petroleum fuels remain the dominant energy source, reflecting advantages such as ...high energy density, low cost, and market availability. The movement of people and freight makes a major contribution to economic development and social well-being, but it also negatively impacts climate change, air quality, health, social cohesion, and safety. Following a review published 20 years ago in the
Annual Review of Environment and Resources
(then named the
Annual Review of Energy and the Environment
) by Lee Schipper, we examine current trends and potential futures, revising several major global transport energy reports. There are significant opportunities to slow travel growth and improve efficiency. Alternatives to petroleum exist but have different characteristics in terms of availability, cost, distribution, infrastructure, storage, and public acceptability. The transition to low-carbon equitable and sustainable transport will take time but can be fostered by numerous short- and medium-term strategies that would benefit energy security, health, productivity, and sustainability.
Abstract Fast X-ray Transients (FXTs) are extragalactic bursts of soft X-rays first identified ≳10 yr ago. Since then, nearly 40 events have been discovered, although almost all of these have been ...recovered from archival Chandra and XMM-Newton data. To date, optical sky surveys and follow-up searches have not revealed any multiwavelength counterparts. The Einstein Probe, launched in 2024 January, has started surveying the sky in the soft X-ray regime (0.5–4 keV) and will rapidly increase the sample of FXTs discovered in real time. Here we report the first discovery of both an optical and radio counterpart to a distant FXT, the fourth source publicly released by the Einstein Probe. We discovered a fast-fading optical transient within the 3′ localization radius of EP 240315a with the all-sky optical survey ATLAS, and our follow-up Gemini spectrum provides a redshift, z = 4.859 ± 0.002. Furthermore, we uncovered a radio counterpart in the S band (3.0 GHz) with the MeerKAT radio interferometer. The optical (rest-frame UV) and radio luminosities indicate that the FXT most likely originates from either a long gamma-ray burst or a relativistic tidal disruption event. This may be a fortuitous early mission detection by the Einstein Probe or may signpost a mode of discovery for high-redshift, high-energy transients through soft X-ray surveys, combined with locating multiwavelength counterparts.
On the basis of both geomechanical and thermal data, the San Andreas Fault (SAF) has been interpreted to act as a weak plane within much stronger crust, allowing it to slip at very low shear ...stresses. One explanation for this weakness is that large fluid overpressures exist locally within the fault zone. However, mechanisms for generating, maintaining, and localizing pressures within the fault are poorly quantified. Here we evaluate whether realistic sources of mantle‐derived fluids, proposed on the basis of high mantle helium signatures near the SAF, can generate localized fluid pressures within the fault zone in a manner consistent with a wide range of observations along the fault and in the San Andreas Fault Observatory at Depth borehole. We first calculate a reasonable estimate of the magnitude and location of a mantle‐derived flux of water into the crust. This fluid flux results from dehydration of a serpentinized mantle wedge following the northward migration of the Mendocino Triple Junction and the transition from subduction to strike‐slip tectonics. We then evaluate the potential effect of this water on fluid pressures within the crust using 2‐D cross‐sectional models of coupled fluid flow and heat transport. We show that in models with realistic permeability anisotropy, controlled by NE dipping faults and fractures within the country rock, large localized fluid pressures can be focused within a SAF acting as a hydrologic barrier. Our results illustrate a simple and potentially plausible means of weakening the SAF in a manner generally consistent with available hydrologic, thermal, and mechanical constraints.
Dual-modality gene reporter for in vivo imaging Patrick, P. Stephen; Hammersley, Jayne; Loizou, Louiza ...
Proceedings of the National Academy of Sciences,
01/2014, Letnik:
111, Številka:
1
Journal Article
Recenzirano
Odprti dostop
The ability to track cells and their patterns of gene expression in living organisms can increase our understanding of tissue development and disease. Gene reporters for bioluminescence, ...fluorescence, radionuclide, and magnetic resonance imaging (MRI) have been described but these suffer variously from limited depth penetration, spatial resolution, and sensitivity. We describe here a gene reporter, based on the organic anion transporting protein Oatp1a1, which mediates uptake of a clinically approved, Gd ³⁺-based, hepatotrophic contrast agent (gadolinium-ethoxybenzyl-diethylenetriamine pentaacetic acid). Cells expressing the reporter showed readily reversible, intense, and positive contrast (up to 7.8-fold signal enhancement) in T ₁-weighted magnetic resonance images acquired in vivo. The maximum signal enhancement obtained so far is more than double that produced by MRI gene reporters described previously. Exchanging the Gd ³⁺ ion for the radionuclide, ¹¹¹In, also allowed detection by single-photon emission computed tomography, thus combining the spatial resolution of MRI with the sensitivity of radionuclide imaging.
Increased anthropogenic nutrient loading has led to eutrophication of aquatic ecosystems, which is the major cause of harmful cyanobacteria blooms. Element stoichiometry of cyanobacteria bloom is ...subject to nutrient availabilities and may significantly contribute to primary production and biogeochemical cycling. Phycobilisome is the antenna of the photosynthetic pigment apparatus in cyanobacteria, which contains phycobilin pigments (PBPs) and linker proteins. This nitrogen (N)-rich protein complex has the potential to support growth as a N-storage site and may play a major role in the variability of cyanobacteria N stoichiometry. However, the regulation of PBPs during bloom formation remains unclear. We investigated the temporal variation of N allocation into PBPs and element stoichiometry for two ubiquitous cyanobacteria species,
Microcystis aeruginosa
and
Dolichospermum flos-aquae
, in a batch culture experiment with different initial N availabilities. Our results indicated that the N allocation into PBPs is species-dependent and tightly regulated by the availability of nutrients fueling population expansion. During the batch culture experiment, different nutrient uptake rates led to distinct stoichiometric imbalances of N and phosphorus (P), which substantially altered cyanobacteria C: N and C: P stoichiometry.
Microcystis
invested cellular N into PBPs and exhibited greater flexibility in C: N and C: P stoichiometry than
D. flos-aquae
. The dynamics of such N-rich macromolecules may help explain the N stoichiometry variation during a bloom and the interspecific difference between
M. aeruginosa
and
D. flos-aquae
. Our study provides a quantitative understanding of the elemental stoichiometry and the regulation of PBPs for non-diazotrophic and diazotrophic cyanobacteria blooms.
Frictional properties within the upper few kilometers of subduction zones are generally thought to inhibit rupture propagation. Understanding whether large rapid slip propagates to the surface during ...megathrust earthquakes is important for characterizing tsunami hazard. Recent vitrinite reflectance analysis by Sakaguchi et al. (2011) on cores from the NanTroSEIZE drilling transect at the Nankai Trough, Japan, has been interpreted to suggest that these faults reached temperatures ∼380°C, considerably larger than background temperature values, implying they hosted coseismic slip at shallow depths. Analysis of other temperature proxies on the megasplay by Hirono et al. (2009), however, suggests temperatures have not exceeded 300°C and is inconclusive as to whether the fault slipped at high velocity. We evaluate the effects of frictional heat generation on the spatial distribution of vitrinite reflectance, its sensitivity to slip zone thickness and slip duration, and the cumulative effects of numerous events. We build on the analysis of Sakaguchi et al. (2011) by estimating frictional heating scenarios that are consistent with both the peak and spatial extent of anomalous vitrinite reflectance data. Our results imply coseismic slip magnitudes of several 10s of meters. Peak temperature estimates from the vitrinite reflectance data can be reconciled with the other geochemical constraints only by assuming the vitrinite reflectance results from the cumulative effects of multiple earthquakes. However, this results in unrealistically large estimates of total displacement. Our results imply that current understanding of how vitrinite reflectance is affected by fault slip is incomplete.
► We investigate the sensitivity of vitrinite reflectance to frictional heating. ► Vitrinite reflectance temperature estimates are reconciled with other data. ► We estimate the characteristic amount of slip on the megasplay and frontal thrust. ► Data require very large coseismic slip or rapid afterslip.
It is well established that high cyclooxygenase-2 (COX-2) expression contributes to the aggressive behavior of breast and other malignancies. Due to concerns regarding the safety of long-term use of ...COX-2 inhibitors as well as a desire to seek more effective alternatives to prevent and treat metastatic disease, we tested the hypothesis that inhibition of downstream signaling by the COX-2 product prostaglandin E(2) (PGE(2)) would be as effective as inhibiting global prostaglandin synthesis. PGE(2) acts through four G-protein-coupled receptors designated EP1-4. Here, we summarize data from many laboratories regarding the role of individual E-series of prostaglandin (EP) receptors on cancer behavior and we discuss our own recent findings that antagonists of the PGE receptor subtype 4, EP4, inhibit experimental metastasis in a murine model of hormone-resistant, metastatic breast cancer. These initial results indicate that selective targeting of individual EP receptors should be investigated as an approach to exploit the high COX-2 activity in many epithelial malignancies.
Cyclooxygenase-2 (COX-2) expression in epithelial tumors is frequently associated with a poor prognosis. In a murine model of metastatic breast cancer, we showed that COX-2 inhibition is associated ...with decreased metastatic capacity. The COX-2 product, prostaglandin E(2) (PGE(2)), acts through a family of G protein-coupled receptors designated EP1-4 that mediate intracellular signaling by multiple pathways. We characterized EP receptor expression on three murine mammary tumor cell lines and show that all four EP isoforms were detected in each cell. Stimulation of cells with either PGE(2) or the selective EP4/EP2 agonist PGE(1)-OH resulted in increased intracellular cyclic AMP and this response was inhibited with either EP2 or EP4 antagonists. Nothing is known about the function of EP receptors in tumor metastasis. We tested the hypothesis that the prevention of EP receptor signaling would, like inhibition of PGE(2) synthesis, inhibit tumor metastasis. Our results show for the first time that antagonism of the EP4 receptor with either AH23848 or ONO-AE3-208 reduced metastasis as compared with vehicle-treated controls. The therapeutic effect was comparable to that observed with the dual COX-1/COX-2 inhibitor indomethacin. EP3 antagonism had no effect on tumor metastasis. Mammary tumor cells migrated in vitro in response to PGE(2) and this chemotactic response was blocked by EP receptor antagonists. Likewise, the proliferation of tumor cells was also directly inhibited by antagonists of either EP4 or EP1/EP2. These studies support the hypothesis that EP receptor antagonists may be an alternative approach to the use of COX inhibitors to prevent tumor metastasis.
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