Review and Harmonization of the Life-Cycle Global Warming Impact of PV-Powered Hydrogen Production by Electrolysis

This work presents a review of life-cycle assessment (LCA) studies of hydrogen electrolysis using power from photovoltaic (PV) systems. The paper discusses the assumptions, strengths and weaknesses of 13 LCA studies and identifies the causes of the environmental impact. Differences in assumptions of system boundaries, system sizes, evaluation methods, and functional units make it challenging to directly compare the Global Warming Potential (GWP) resulting from different studies. To simplify this process, 13 selected LCA studies on PV-powered hydrogen production have been harmonized following a consistent framework described by this paper. The harmonized GWP values vary from 0.7 to 6.6 kg CO2-eq/kg H2 which can be considered a wide range. The maximum absolute difference between the original and harmonized GWP results of a study is 1.5 kg CO2-eq/kg H2. Yet even the highest GWP of this study is over four times lower than the GWP of grid-powered electrolysis in Germany. Due to the lack of transparency of most LCAs included in this review, full identification of the sources of discrepancies (methods applied, assumed production conditions) is not possible. Overall it can be concluded that the environmental impact of the electrolytic hydrogen production process is mainly caused by the GWP of the electricity supply. For future environmental impact studies on hydrogen production systems, it is highly recommended to 1) divide the whole system into well-defined subsystems using compression as the final stage of the LCA and 2) to provide energy inputs/GWP results for the different subsystems.

Evaluation of a novel metric for personalized opioid prescribing after hospitalization

Background The duration of an opioid prescribed at hospital discharge does not intrinsically account for opioid needs during a hospitalization. This discrepancy may lead to patients receiving much larger supplies of opioids on discharge than they truly require. Objective Assess a novel discharge opioid supply metric that adjusts for opioid use during hospitalization, compared to the conventional discharge prescription signature. Design, setting, & participants Retrospective study using electronic health record data from June 2012 to November 2018 of adults who received opioids while hospitalized and after discharge from a single academic medical center. Measures & analysis We ascertained inpatient opioids received and milligrams of opioids supplied after discharge, then determined days of opioids supplied after discharge by the conventional prescription signature opioid-days (“conventional days”) and novel hospital-adjusted opioid-days (“adjusted days”) metrics. We calculated descriptive statistics, within-subject difference between measurements, and fold difference between measures. We used multiple linear regression to determine patient-level predictors associated with high difference in days prescribed between measures. Results The adjusted days metric demonstrates a 2.4 day median increase in prescription duration as compared to the conventional days metric (9.4 vs. 7.0 days; P<0.001). 95% of all adjusted days measurements fall within a 0.19 to 6.90-fold difference as compared to conventional days measurements, with a maximum absolute difference of 640 days. Receiving a liquid opioid prescription accounted for an increased prescription duration of 135.6% by the adjusted days metric (95% CI 39.1–299.0%; P = 0.001). Of patients who were not on opioids prior to admission and required opioids during hospitalization but not in the last 24 hours, 325 (8.6%) were discharged with an opioid prescription. Conclusions The adjusted days metric, based on inpatient opioid use, demonstrates that patients are often prescribed a supply lasting longer than the prescription signature suggests, though with marked variability for some patients that suggests potential under-prescribing as well. Adjusted days is more patient-centered, reflecting the reality of how patients will take their prescription rather than providers’ intended prescription duration.

Validation of the Absorbing Aerosol Height Product from GOME-2 using CALIOP Aerosol Layer Information

Within the framework of aviation safety, knowledge on the location and height of volcanic ash layers is of extreme importance. Several ground based instruments (such as lidars) can provide detailed information on the height and vertical extent of these ash layers, however with a limited spatial coverage. The biggest advantage of satellite instruments is their ability to have near daily global coverage which makes them the perfect candidate for locating and tracking aerosol layers around the globe. Since the Global Ozone Monitoring Experiment 2 (GOME-2) instrument is carried on the MetOp series of operational satellites, it is designed to cover a long time period from 2007 until 2022 (and beyond) and global coverage is achieved within one day. The GOME-2 Absorbing Aerosol Height (AAH) is a new product for aerosol detection, developed by the Royal Netherlands Meteorological Institute (KNMI) which uses the Absorbing Aerosol Index (AAI) to detect the presence of absorbing aerosol and derives the actual height of the absorbing aerosol layer in the O2-A band using the Fast Retrieval Scheme for Clouds from the Oxygen A band (FRESCO) algorithm. The first results of a quantitative validation of the AAH product focusing on case studies of volcanic eruptions will be presented here. For a total of 15 different volcanic eruptions, GOME-2 AAH data are compared to the minimum and maximum aerosol layer height provided by Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) for pixels within 100 km distance from each other. For GOME-2A and -2B, about 50 to 60 % of the AAH pixels are within the EUMETSAT threshold requirements (for layers which are located lower than 10 km, the maximum absolute difference should be within 3 km; for layers which are located higher than 10 km, the maximum absolute difference should be within 4 km), while for GOME-2C this is about 70 %. The optimal requirement threshold (for layers which are located lower than 10 km, the maximum absolute difference should be within 1 km; for layers which are located higher than 10 km, the maximum absolute difference should be within 2 km) is reached for GOME-2A, GOME-2B and GOME-2C in 17 %, 28 % and 41.5 % of the cases. If only tropospheric aerosol species are studied, the results improve. This can also be seen when looking at the mean error of GOME-2. GOME-2A, GOME-2B and GOME-2C are able to represent the minimum CALIOP layer height with a mean error of −2.5 ± 5 km, −1.2 ± 5.9 km and −2 ± 5.8 km respectively. If the stratospheric aerosol layers are removed from the data, the errors obtained are −0.2 ± 3.6 km, −0.1 ± 5.4 km and −0.8 ± 3.8 km for GOME-2A, GOME-2B and GOME-2C respectively (for the minimum CALIOP layer height). The results from two specific case studies (i.e. the Calbuco eruption in 2015 and the Sarychev Peak eruption in 2009) are highlighted and show that GOME-2 underestimates the height of volcanic ash layers. Especially if the layers are located at altitudes above 15 km, since GOME-2 is not able to detect these layers due to the loss of sensitivity of the FRESCO algorithm at these algorithms.

The clinical applicability of an automated plethysmographic determination of the ankle-brachial index after vascular surgery

An automated ankle-brachial index device could lead to potential time savings and more accuracy in ankle-brachial index-determination after vascular surgery. This prospective cross-sectional study compared postprocedural ankle-brachial indices measured by a manual method with ankle-brachial indices of an automated plethysmographic method. Forty-two patients were included. No significant difference in time performing a measurement was observed (1.1 min, 95% CI: −0.2 to +2.4; P = 0.095). Mean ankle-brachial index with the automated method was 0.105 higher (95% CI: 0.017 to 0.193; P = 0.020) than with the manual method, with limits of agreement of −0.376 and +0.587. Total variance amounted to 0.0759 and the correlation between both methods was 0.60. Reliability expressed as maximum absolute difference (95% level) between duplicate ankle-brachial index-measurements under identical conditions was 0.350 (manual) and 0.152 (automated), although not significant ( p = 0.053). Finally, the automated method had 34% points higher failure rate than the manual method. In conclusion based on this study, the automated ankle-brachial index-method seems not to be clinically applicable for measuring ankle-brachial index postoperatively in patients with vascular disease.

A MODIFIED CORRELATION METHOD FOR T-WAVE ALTERNANS DETECTION

Identification of individuals who are at risk for sudden cardiac death (SCD) remains a formidable challenge. T-wave alternans (TWA) evaluation is emerging as an important tool for risk stratification in patients with heart diseases. Several methods have been developed in recent years to detect and quantify TWA. One such method is known as the correlation method (CM). This method performs well for different levels of TWA and phase shifts in the time domain, but it is sensitive to noise and requires higher quality of electrocardiogram (ECG) signal for test. In this paper, we propose a modified correlation method (MCM) to ensure a robust and accuracy detection of TWA. Compared with CM, MCM add a stage of T-wave curve fitting before media T-wave template, and the TWA magnitude is obtained by meaning the maximum absolute difference between even and odd T-wave. Our assessment study demonstrates the improved performance of the proposed algorithm.

Schnur's Site-Index Curves Formulated for Computer Applications

Two systems of interpolation equations are offered for the graphic site-index curves of Schnur for even-aged upland oak stands. One is Wiant's equation system, adjusted to pass through site index at index age. The second is similar but some-what more precise. For both, the average absolute difference between equation system and table values is about 0.73 foot and the maximum absolute difference is about 1.9 feet.

Cumulative Interarrival Time Distributions of Freeway Entrance Ramp Traffic for Traffic Simulations

Cumulative interarrival time (IAT) distributions for signalized and non-signalized freeway entrance ramps were developed to be used in digital computer traffic simulation models. The data from four different non-signalized entrance ramps (three ramps with a single lane, one ramp with two lanes) and two different signalized entrance ramps (both with a single lane) were used for developing the cumulative IAT distributions. The cumulative IAT distributions for the signalized and non-signalized entrance ramps were compared with each other and with the cumulative IAT distributions of the lanes for freeways. The comparative results showed that the cumulative IAT distributions for non-signalized entrance ramps are very close to the leftmost lane of a 3-lane freeway where the maximum absolute difference between the cumulative IAT distribution of the leftmost lane of a 3-lane freeway and the entrance ramps cumulative IAT distribution was 3%. The cumulative IAT distribution for the signalized entrance ramps was found to be different from the non-signalized entrance ramp cumulative IAT distribution. The approximated cumulative IAT distributions for signalized and non-signalized entrance ramp traffic for any hourly traffic volume from a few vehicles/hour up to 2,500 vehicles/hour can be obtained at http://www.ohio.edu/orite/research/uitds.cfm.

Site-index Curve Shape in Spruce

Sets of site-index curves were prepared from stem analyses of white spruce (Picea glauca (Moench) Voss) and black spruce (P. mariana (Mill.) BSP.) from various regions in the boreal forest of Canada. Ordinates of the site-index curves, computed for 5-year breast-height age intervals up to 75 years, and for 10-foot site-index intervals up to 70 feet, were compared within the species for the same values of site index and age. For breast-height ages below 55 years and for site index below 70 feet, the maximum absolute difference among the ordinates did not exceed 2.0 feet in white spruce, and 1.6 feet in black spruce; the corresponding average deviations were 0.75 and 0.80 feet. For breast-height ages above 55 years, these differences increased with age and, at 75 years, reached 8.8 feet in white spruce, and 3.8 feet in black spruce; the corresponding average deviations were 4.40 and 1.53 feet.