Search results for "Photo"
showing 10 items of 11789 documents
Radiance-based NIRv as a proxy for GPP of corn and soybean
2020
Abstract Substantial uncertainty exists in daily and sub-daily gross primary production (GPP) estimation, which dampens accurate monitoring of the global carbon cycle. Here we find that near-infrared radiance of vegetation (NIRv,Rad), defined as the product of observed NIR radiance and normalized difference vegetation index, can accurately estimate corn and soybean GPP at daily and half-hourly time scales, benchmarked with multi-year tower-based GPP at three sites with different environmental and irrigation conditions. Overall, NIRv,Rad explains 84% and 78% variations of half-hourly GPP for corn and soybean, respectively, outperforming NIR reflectance of vegetation (NIRv,Ref), enhanced vege…
Photoreduction of gaseous oxidized mercury changes global atmospheric mercury speciation, transport and deposition
2018
9 pags, 8 figs. -- Correction autor: https://doi.org/10.1038/s41467-022-28455-w http://hdl.handle.net/10261/268181
Observation of classically 'forbidden' electromagnetic wave propagation and implications for neutrino detection.
2018
Ongoing experimental efforts in Antarctica seek to detect ultra-high energy neutrinos by measurement of radio-frequency (RF) Askaryan radiation generated by the collision of a neutrino with an ice molecule. An array of RF antennas, deployed either in-ice or in-air, is used to infer the properties of the neutrino. To evaluate their experimental sensitivity, such experiments require a refractive index model for ray tracing radio-wave trajectories from a putative in-ice neutrino interaction point to the receiving antennas; this gives the degree of signal absorption or ray bending from source to receiver. The gradient in the density profile over the upper 200 meters of Antarctic ice, coupled wi…
Results from DROXO IV. EXTraS discovery of an X-ray flare from the Class I protostar candidate ISO-Oph 85
2016
X-ray emission from Young Stellar Objects (YSOs) is crucial to understand star formation. A very limited amount of X-ray results is available for the protostellar (ClassI) phase. A systematic search of transient X-ray phenomena combined with a careful evaluation of the evolutionary stage offer a widely unexplored window to our understanding of YSOs X-ray properties. Within the EXTraS project, a search for transients and variability in the whole XMM-Newton archive, we discover transient X-ray emission consistent with ISO-Oph 85, a strongly embedded YSO in the rho Ophiuchi region, not detected in previous time-averaged X-ray studies. We extract an X-ray light curve for the flare and determine…
GRB 050904 at redshift 6.3: observations of the oldest cosmic explosion after the Big Bang
2005
We present optical and near-infrared observations of the afterglow of the gamma-ray burst GRB 050904. We derive a photometric redshift z = 6.3, estimated from the presence of the Lyman break falling between the I and J filters. This is by far the most distant GRB known to date. Its isotropic-equivalent energy is 3.4x10^53 erg in the rest-frame 110-1100 keV energy band. Despite the high redshift, both the prompt and the afterglow emission are not peculiar with respect to other GRBs. We find a break in the J-band light curve at t_b = 2.6 +- 1.0 d (observer frame). If we assume this is the jet break, we derive a beaming-corrected energy E_gamma = (4-12)x10^51 erg. This limit shows that GRB 050…
First M87 Event Horizon Telescope Results. I. the Shadow of the Supermassive Black Hole
2019
When surrounded by a transparent emission region, black holes are expected to reveal a dark shadow caused by gravitational light bending and photon capture at the event horizon. To image and study this phenomenon, we have assembled the Event Horizon Telescope, a global very long baseline interferometry array observing at a wavelength of 1.3 mm. This allows us to reconstruct event-horizon-scale images of the supermassive black hole candidate in the center of the giant elliptical galaxy M87. We have resolved the central compact radio source as an asymmetric bright emission ring with a diameter of 42 ± 3 μas, which is circular and encompasses a central depression in brightness with a flux rati…
Social Lives of Monumental Walls: Hunting along the Upper Tigris
2021
On the left bank of the Tigris in northern Iraq, in an area today partially flooded by the Mosul Dam reservoir, lies an enigmatic monumental enclosure known in the literature as the “Tigris Wall.” Before its partial submersion under the waters of the modern lake, the large L-shaped embankment, about 4 × 4 km long, enclosed an area of ca. 1600 ha, overlooking the Tigris and its alluvial plain. By means of a holistic strategy that includes different levels of analysis (remote sensing, pedestrian and UAV photogrammetric surveys, excavation, and settlement pattern analysis), this paper addresses the structure, its context, and its environment. Relying on the results of this multi-disciplinary a…
Unmanned Aerial Vehicle (UAV) Survey with Commercial-Grade Instruments: A Case Study from the Eastern Ḫabur Archaeological Survey, Iraq
2018
Low-altitude photography in archaeology is now common practice at the scale of excavations; however, landscape-scale applications are a relatively new endeavor with promising analytical potential. From 2014–2016, an unmanned aerial vehicle (UAV) with a mounted camera was used to document sites recorded as part of the Eastern Ḫabur Archaeological Survey (EḪAS), an archaeological reconnaissance project in western Dohuk Province, Iraqi Kurdistan. The EḪAS team documented over 70 archaeological sites with the UAV, from single-phase artifact scatters, to archaeological remains with standing architecture, to tells that cover more than 30 hectares. Representative examples from this survey are pres…
Unknown Deformations on the Facades of the Pyramid of Khafre at Giza Pyramid Complex in Egypt
2016
Abstract The pyramids of Giza in Egypt are the architectural heritage of ancient civilizations and for many thousand years served as great examples of ancient design, planning and construction solutions. Their scale is grandiose and the attempts of ancient architects to find perfect forms to ensure the structure stands for eternity are admirable. The initial geometry of the structures, their form, proportions and symmetry, was adapted to construction material and technologies available at that time. However, during more than 4500 years these monuments were damaged and partly destroyed; some pyramids were razed to the ground due to construction faults and seismic activity. The second largest…
Early Diagnosis of Vegetation Health From High-Resolution Hyperspectral and Thermal Imagery: Lessons Learned From Empirical Relationships and Radiati…
2019
[Purpose of Review] We provide a comprehensive review of the empirical and modelling approaches used to quantify the radiation–vegetation interactions related to vegetation temperature, leaf optical properties linked to pigment absorption and chlorophyll fluorescence emission, and of their capability to monitor vegetation health. Part 1 provides an overview of the main physiological indicators (PIs) applied in remote sensing to detect alterations in plant functioning linked to vegetation diseases and decline processes. Part 2 reviews the recent advances in the development of quantitative methods to assess PI through hyperspectral and thermal images.