This work assesses the vertical accuracy of eight Digital Surface Models (DSMs) currently available for Mexico (LiDAR, ALOS AW3D30 V2 and V3, ASTER GDEM V2 and V3, SRTM, NASADEM and Mexico's ...Continuous Elevation Model (CEM)). The AW3D30, ASTER GDEM, SRTM and NASADEM DSMs cover nearly the entire globe and can be downloaded at no cost, while the LiDAR and CEM DSMs are distributed by Mexico's Institute of Geography and Statistics (INEGI). The accuracy of these DSMs is assessed by considering: 1) benchmarks as reference data at the national level, and 2) LiDAR DSM as reference data on six different zones with variability in slope, vegetation cover and elevation. Using geodetic benchmarks as reference elevation on those areas covered by LiDAR (ALiDAR=370,200 km2, nbench=24,175), it was found that LiDAR has the best vertical accuracy of all DSMs considered (MAELiDAR = 1.96), which is why it was used as reference elevation to develop seven DEMs of Difference (DoDs) with the remainder DSMs. Using ncells = 350 × 106 for the aforementioned comparisons, it was found that the vertical accuracy of AW3D30 V2 and V3 is similar (MAE=2.5 m), followed by NASADEM, SRTM, CEM, ASTER GDEM3 and ASTER GDEM 2, with MAE values of 3.1, 3.8, 4.6, 6.0 and 7.2 m respectively. The previously mentioned values vary according to slope and slope orientation (i.e. aspect): for flat areas (slope≤5∘), the NASADEM exhibits the lowest MAE (with MAE values of 1.6 for slope≤1∘ and MAE = 2.0 m when 1∘<slope≤5∘), whereas MAEAW3D30V3=1.9 and 2.2 m for the previously mentioned slopes. With the use of radial boxplots developed on slope groups of 5∘, it was found that both MAE and bias are increasingly affected by aspect as slope increases on all the DSMs. In the case of both AW3D30 DSMs, on flat terrain a difference of only 0.1 m in bias (i.e. median of differences with respect to LiDAR) is found between SE and NW slopes; however, this difference increases according to slope: 0.6 m for 5∘<slope≤10∘, 1.2 m for 10∘<slope≤15∘, and 1.9 m for 15∘<slope≤20∘. Through the analyses undertaken, it is shown that slope—and not vegetation cover—is the factor that has the largest impact on the error of DSMs, and that the effect of aspect on error increases as terrain steepens. This work shows that all DSMs present errors and that an adequate accuracy assessment of DSMs needs to consider the spatial distribution of GCPs, Difference of DSMs (DoDs) and derivatives of DSMs (i.e., slope and aspect) as the use of DoDs provide information on DSM errors (i.e. interpolation artefacts) that can not be assessed through the use of geodetic benchmarks and because DSM errors depend on both slope and aspect.
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The creation of high-resolution Digital Elevation Models (DEMs) through the acquisition of images with a consumer-grade camera mounted on a light Unmanned Aerial Vehicle (UAV) and their processing ...with Structure from Motion (SfM) software has been widely adopted in different fields. Despite this wide adoption, its use has been limited to research projects - as in our experience most practising surveyors, think that the topography obtained through this technology is subpar to that obtained with surveys undertaken with traditional methods. To address this concern, we compare these two approaches in a heterogeneous built-up area of nearly 33 ha with an elevation between 1899 and 1944 m a.s.l. This comparison shows that the UAV-SfM methodology provides better results than the traditional method, is less prone to human error and also requires significantly less time: 4 h of fieldwork instead of 1 week. Furthermore, the spatial resolution of a Total Station (TS) survey is only limited to those points surveyed, whereas the UAV-SfM derived topography is a subproduct of the resultant three dimensional point cloud, which can also be used to generate a high-resolution orthophoto.
Fluorescence in situ hybridization (FISH) has become a powerful technique for prognostic assessment in multiple myeloma (MM). However, the existence of associations between cytogenetic abnormalities ...compels us to re-assess the value of each abnormality. A total of 260 patients with MM at the time of diagnosis, enrolled in the GEM-2000 Spanish transplant protocol, have been analyzed by FISH in order to ascertain the independent influence on myeloma prognosis of IGH translocations, as well as RB and P53 deletions. Survival analyses showed that patients with t(4;14), RB or P53 deletions had a significantly shorter survival than patients without these abnormalities. However, patients with RB deletions without other abnormalities in FISH analysis, displayed a similar outcome to those patients without genetic changes by FISH (46 vs 54 months, P=0.3). In the multivariate analysis the presence of t(4;14), RB deletion associated with other abnormalities, age >60 years, high proportion of S-phase cells and advanced stage of the disease according to the International Staging System retained their independent prognostic influence. In summary, RB deletion as a sole abnormality does not lead to a shortening in the survival of MM patients, whereas t(4;14) confers the worst prognosis in MM patients treated with high-dose chemotherapy.
The spatial distribution of climatological variables such as rainfall and temperature is needed whenever hydrological modelling is undertaken at the watershed scale. These models can be used to ...simulate hydrological processes at a daily or hourly time step and the interpolation of climatological variables (in particular precipitation) at this time scale poses a particular problem due to its large spatial variation. This work analyzes the temporal variation of both minimum and maximum temperature and rainfall, its correlation with elevation and whether or not this relationship should be used when daily data are interpolated. In order to achieve this, the monthly distribution of these variables is derived from daily interpolations, which is compared to their monthly accumulated value for each climatological station. The interpolation methods used to undertake the analysis were Ordinary Kriging (OK), Kriging with External Drift (KED), Block Kriging with External Drift (BKED), Ordinary Kriging in a local neighborhood (OK
l) and Kriging with External Drift in a local neighborhood (KED
l). This analysis used daily climatological data from approximately 200 stations located in the Basin of Mexico for June 1978 and June 1985, from which accumulated monthly data were derived. The results of this analysis show that the interpolation of daily events is improved by the use of elevation as a secondary variable even when these variables show a low correlation.
Objectives
To propose national diagnostic reference levels (DRLs) for interventional radiology and to evaluate the impact of the procedural complexity on patient doses.
Methods
Eight interventional ...radiology units from Spanish hospitals were involved in this project. The participants agreed to undergo common quality control procedures for X-ray systems. Kerma area product (KAP) was collected from a sample of 1,649 procedures. A consensus document established the criteria to evaluate the complexity of seven types of procedures. DRLs were set as the 3rd quartile of KAP values.
Results
The KAP (3rd quartile) in Gy cm
2
for the procedures included in the survey were: lower extremity arteriography (n = 784) 78; renal arteriography (n = 37) 107; transjugular hepatic biopsies (THB) (n = 30) 45; biliary drainage (BD) (n = 314) 30; uterine fibroid embolization (UFE) (n = 56) 214; colon endoprostheses (CE) (n = 31) 169; hepatic chemoembolization (HC) (n = 269) 303; femoropopliteal revascularization (FR) (n = 62) 119; and iliac stent (n = 66) 170. The complexity involved the increases in the following KAP factors from simple to complex procedures: THB x4; BD x13; UFE x3; CE x3; HC x5; FR x5 and IS x4.
Conclusions
The evaluation of the procedure complexity in patient doses will allow the proper use of DRLs for the optimization of interventional radiology.
Key Points
•
National DRLs for interventional procedures have been proposed given level of complexity
•
For clinical audits, the level of complexity should be taken into account.
•
An evaluation of the complexity levels of the procedure should be made.
In this work, we quantify the differential subsidence that occurred between 2015 and 2016 in a maar-lake that has been desiccating due to the large groundwater extraction rates of the aquifer that ...used to feed it. The relatively small size of the bottom of the crater (1.2 km in diameter) and the scale of its structures (e.g. mud-injection domes that range in height from a few decimetres to 12 m and individual fault scarp heights that vary from a few cm to 15 m), along with the high albedo of the maar's sediments provide a difficult setting to develop a series of high-resolution Digital Elevation Models (DEMs) required to quantify its subsidence. Through the use of a small quadcopter that carried a consumer-grade compact camera along a portable Global Positioning System (GPS) - which was used to georeference the acquired images - we were finally able to develop two high resolution (4.7 cm) DEMs for years 2015 and 2016. These DEMs allowed us to identify the geologic structures (faults, domes, and fault scarps) developed on the dry bottom of the crater. Through a Difference of Digital Elevation Models (DoDs = (DEM
2015
)-(DEM
2016
)), we were able to prove that subsidence is not uniform in the crater, as subsidence is mainly occurring on its western side. We also found that the largest subsidence occurs on the crater's southwestern region (with some areas subsiding more than 1 m) followed by the northwestern area - where the crater's highest normal fault is found. From these results, we can conclude that: (1) movement of the sediments inside the crater can not be interpreted as a simple piston-like downward displacement occurring near the centre of the basin and (2) Unmanned Aerial Vehicles (UAVs) are an efficient tool to quantify terrain changes as periodic flights can be repeated over the same area.
The Trans‐Mexican Volcanic Belt is an active continental volcanic arc related to subduction along the Middle America trench. It is characterized by intra‐arc extension resulting into several major ...arc‐parallel active fault systems and tectonic basins. The Acambay graben, one of the largest of these basins, is located near Mexico City, in the central part of this province. In 1912, a M 6.9 earthquake ruptured the surface along the northern border of the graben together with at least two other faults. In this paper, we analyze the paleoseismic history of the southern border of the Acambay Graben, with new observations made in one natural outcrop and four paleoseismological trenches excavated across branches of the Venta de Bravo Fault at the site where it overlaps with the Pastores Fault. We present evidence of at least two paleo‐earthquakes that occurred between 12,190 ± 175 and 5,822 ± 87 cal year BP and between 647 ± 77 and 250 cal year BP. On one of these branches, we estimate a minimum slip‐rate value between 0.1 and 0.23 mm/year for the last 12 ka and a mean recurrence interval of 8.5 ± 3 ka. By considering several likely rupture lengths along the Venta de Bravo and Pastores faults, we calculated a maximum possible magnitude of Mw 7.01 ± 0.27. Finally, by correlating events recorded along different faults within the Acambay Graben, we discuss several possible rupture coalescent scenarios and related consequences for Mexico City.
Plain Language Summary
The Trans‐Mexican Volcanic arc is affected by several fault systems. Activity on these faults results in an extension of the crust and the formation of elongated topographic depressions. The study region, called the Acambay Graben, is one of these depressions and is bounded by normal E‐W active faults. In 1912 an M 6.9 earthquake caused nearly 300 fatalities and generated a surface rupture along three faults which are the boundaries of this depression. The epicenter of this event is in a region where close to 24 million inhabitants are living; therefore, the history of past earthquakes is crucial in evaluating the seismic hazard of central Mexico. We conducted paleoseismological excavations on one of these faults, the Venta de Bravo Fault, to infer the record of past earthquakes. The results show that at least two earthquakes occurred in the past: one between 12,365 and 5,735 cal year BP and the other between 724 and 250 cal year BP. With this new data and the previously published, we compiled the paleoseismic catalog for this region and discussed the different possibilities of earthquake surface ruptures implying multiple faults. This new data will help to better understand central Mexico's seismic hazard assessment, especially relevant for Mexico City.
Key Points
Paleoseismological characterization of the longest crustal seismic fault system near Mexico City
New stratigraphic evidence of two paleoearthquakes along the Venta de Bravo Fault in the Acambay Graben
New evidence of possible seismic rupture coalescence associated with an M > 7 earthquake in the densely populated Central Mexico
We find two chemically distinct populations separated relatively cleanly in the Fe/H-Mg/Fe plane, but also distinguished in other chemical planes, among metal-poor stars (primarily with metallicities ...) observed by the Apache Point Observatory Galactic Evolution Experiment (APOGEE) and analyzed for Data Release 13 (DR13) of the Sloan Digital Sky Survey. These two stellar populations show the most significant differences in their X/Fe ratios for the -elements, C+N, Al, and Ni. In addition to these populations having differing chemistry, the low metallicity high-Mg population (which we denote "the HMg population") exhibits a significant net Galactic rotation, whereas the low-Mg population (or "the LMg population") has halo-like kinematics with little to no net rotation. Based on its properties, the origin of the LMg population is likely an accreted population of stars. The HMg population shows chemistry (and to an extent kinematics) similar to the thick disk, and is likely associated with in situ formation. The distinction between the LMg and HMg populations mimics the differences between the populations of low- and high- halo stars found in previous studies, suggesting that these are samples of the same two populations.
Data from the SDSS-IV/Apache Point Observatory Galactic Evolution Experiment (APOGEE-2) have been released as part of SDSS Data Releases 13 (DR13) and 14 (DR14). These include high-resolution H-band ...spectra, radial velocities, and derived stellar parameters and abundances. DR13, released in 2016 August, contained APOGEE data for roughly 150,000 stars, and DR14, released in 2017 August, added about 110,000 more. Stellar parameters and abundances have been derived with an automated pipeline, the APOGEE Stellar Parameter and Chemical Abundance Pipeline (ASPCAP). We evaluate the performance of this pipeline by comparing the derived stellar parameters and abundances to those inferred from optical spectra and analysis for several hundred stars. For most elements-C, Na, Mg, Al, Si, S, Ca, Cr, Mn, Ni-the DR14 ASPCAP analyses have systematic differences with the comparisons samples of less than 0.05 dex (median), and random differences of less than 0.15 dex (standard deviation). These differences are a combination of the uncertainties in both the comparison samples as well as the ASPCAP analysis. Compared to the references, magnesium is the most accurate alpha-element derived by ASPCAP, and shows a very clear thin/thick disk separation, while nickel is the most accurate iron-peak element (besides iron itself).
•The energy performance of liquid chiller is compared using R1234yf and R134a.•The Buckingham π-theorem was applied to modeling drop-in.•The predicted and experimental data are correlated in order to ...study the accuracy of the model.•R1234yf shows that COP reduces about 2%–11.3% taking R134a as baseline.•Indirect emissions are similar for R1234yf and R134a using several energy sources.
This paper presents a model for a variable-speed liquid chiller integrating a compressor model based on Buckingham π-theorem to accurately predict the system performance when R134a is replaced with R1234yf, using a wide range of data obtained from an experimental setup. Relevant variables such as temperature, pressure, mass and volumetric flow rates, compressor power consumption and rotation speed were measured at several positions along the refrigeration and secondary circuits and were used to validate the developed model. Model results show that cooling capacity and power consumption predicted values are in good agreement with experimental data, within ±5%, being slightly higher for the deviation obtained for R134a than for R1234yf. Moreover, model results indicate that R1234yf has a reduction of coefficient of performance (COP) compared with R134a (between 2 and 11.3%), and that R1234yf COP reduction is diminished at intermediate volumetric flow rate and higher inlet temperature for the evaporator secondary fluid, respectively. On the other hand, an environmental analysis based on TEWI (total equivalent warming impact) method showed that direct emissions are almost negligible for R1234yf. However, there are no environmental benefits in terms of indirect greenhouse gas emissions using R1234yf without system modifications (as for instance the addition of internal heat exchanger or R1234yf new design components), which are required to reduce the liquid chiller climate change contribution using it as low GWP alternative in comparison with the typically used R134a refrigerant.
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