836 research outputs found
When your eyes betray you: is virtual reality too close for comfort?
With the dawn of immersive virtual reality (VR) technologies, data-collection is taking another leap toward recording our subtlest physical reactions and even our emotional states, writes Finn Lützow-Holm Myrstad, Head of section, digital services and electricity at the Norwegian Consumer Council and EU Co-chair of the Infosoc Committee of the Transatlantic Consumer Dialogue (TACD)
Reachability Analysis of ARMAX Models
Reachability analysis is a powerful tool for computing the set of states or
outputs reachable for a system. While previous work has focused on systems
described by state-space models, we present the first methods to compute
reachable sets of ARMAX models - one of the most common input-output models
originating from data-driven system identification. The first approach we
propose can only be used with dependency-preserving set representations such as
symbolic zonotopes, while the second one is valid for arbitrary set
representations but relies on a reformulation of the ARMAX model. By analyzing
the computational complexities, we show that both approaches scale
quadratically with respect to the time horizon of the reachability problem when
using symbolic zonotopes. To reduce the computational complexity, we propose a
third approach that scales linearly with respect to the time horizon when using
set representations that are closed under Minkowski addition and linear
transformation and that satisfy that the computational complexity of the
Minkowski sum is independent of the representation size of the operands. Our
numerical experiments demonstrate that the reachable sets of ARMAX models are
tighter than the reachable sets of equivalent state space models in case of
unknown initial states. Therefore, this methodology has the potential to
significantly reduce the conservatism of various verification techniques.Comment: \copyright 2023 IEEE. Personal use of this material is permitted.
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Effect of in-situ aged and fresh biochar on soil hydraulic conditions and microbial C use under drought conditions
Biochar (BC) amendments may be suitable to increase the ecosystems resistance to drought due to their positive effects on soil water retention and availability. We investigated the effect of BC in situ ageing on water availability and microbial parameters of a grassland soil. We used soil containing 13C labeled BC and determined its water holding capacity, microbial biomass and activity during a 3 months incubation under optimum and drought conditions. Our incubation experiment comprised three treatments: soil without BC (Control), soil containing aged BC (BCaged) and soil containing fresh BC (BCfresh), under optimum soil water (pF 1.8) and drought conditions (pF 3.5). Under optimum water as well as drought conditions, soils containing BC showed higher soil organic carbon (SOC) mineralization as compared to control soil. Moreover, BC effects on the soil water regime increase upon in situ aging. Native SOC mineralization increased most for soils containing BCaged. The BCaged led to improved C use under drought as compared to the other treatments. We conclude that BC addition to soils can ameliorate their water regime, especially under drought conditions. This beneficial effect of BC increases upon its aging, which also improved native substrate availability
A global database of historic glacier lake outburst floods
Ongoing atmospheric warming has accelerated glacier mass loss in
many mountain regions worldwide. Glacier lakes trap part of the glacial
meltwater and have increased by about 50 % in number and area since the 1990s.
Some of these glacier lakes may empty catastrophically and pose hazards to
mountain communities, infrastructure, and habitats. Such glacier lake
outburst floods (GLOFs) have caused millions of dollars of damages and
fatalities and are one of many concerns about future changes in the
magnitude, frequency, and impacts of processes of a shrinking mountain
cryosphere. Consistently compiled inventories are thus vital to assess
regional and local trends in GLOF occurrence, hazard, and risk. To this end,
we studied 769 literature and internet sources and developed a standardized
database with 57 attributes that describe and quantify the location, dam
type, size, timing, and impacts of GLOFs in nine glaciated mountain regions.
Our GLOF inventory also includes details about the lake area before and
after the outburst for 391 cases that we manually mapped from optical
satellite images since 1984. In total, we compiled 3151 reported GLOFs that
occurred in 27 countries between 850 and 2022 CE. Most GLOFs have been
reported in NW North America (26 %) and Iceland (19 %). However, the
reporting density in our inventory varies. During the 20th century
alone, the number of yearly documented GLOFs increased 6-fold. Less than
one-quarter of all reported cases feature hydrodynamic characteristics such
as flood peak discharge or volume or estimates of loss and damage. Our
inventory more than doubles the number of reported GLOFs in a previous
global inventory, though gaps in attributes remain. Our data collection
process emphasizes the support of local experts in contributing previously
undocumented cases, and we recommend applying protocols when reporting new
cases. The global database on historic GLOFs is archived at https://doi.org/10.5281/zenodo.7330344 (Lützow and Veh,
2023a) and regularly updated at http://glofs.geoecology.uni-potsdam.de/ (last access: 9 May 2023).</p
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Less extreme and earlier outbursts of ice-dammed lakes since 1900
Episodic failures of ice-dammed lakes have produced some of the largest floods in history, with disastrous consequences for communities in high mountains1–7. Yet, estimating changes in the activity of ice-dam failures through time remains controversial because of inconsistent regional flood databases. Here, by collating 1,569 ice-dam failures in six major mountain regions, we systematically assess trends in peak discharge, volume, annual timing and source elevation between 1900 and 2021. We show that extreme peak flows and volumes (10 per cent highest) have declined by about an order of magnitude over this period in five of the six regions, whereas median flood discharges have fallen less or have remained unchanged. Ice-dam floods worldwide today originate at higher elevations and happen about six weeks earlier in the year than in 1900. Individual ice-dammed lakes with repeated outbursts show similar negative trends in magnitude and earlier occurrence, although with only moderate correlation to glacier thinning8. We anticipate that ice dams will continue to fail in the near future, even as glaciers thin and recede. Yet widespread deglaciation, projected for nearly all regions by the end of the twenty-first century9, may bring most outburst activity to a halt
Short-Term Supplementation of Sodium Nitrate vs. Sodium Chloride Increases Homoarginine Synthesis in Young Men Independent of Exercise
The aim of the study was to investigate the effects of short-term oral administration of inorganic nitrate (NaNO3; n = 8) or placebo (NaCl; n = 9) (each 0.1 mmol/kg body weight/d for 9 days) on plasma amino acids, creatinine, and oxidative stress in healthy young men. At baseline, the plasma concentrations of amino acids did not differ between the groups. At the end of the study, the plasma concentrations of homoarginine (hArg; by 24%, p = 0.0001), citrulline and ornithine (Cit/Orn; by 16%, p = 0.015), and glutamine/glutamate (Gln/Glu; by 6%, p = 0.0003) were higher in the NaNO3 group compared to the NaCl group. The plasma concentrations of sarcosine (Sarc; by 28%, p hArg + Orn, with equilibrium constant Kharg; (2) the formation of guanidinoacetate (GAA) and Orn from Arg and glycine (Gly): Arg + Gly GAA + Orn, with equilibrium constant Kgaa. The plasma Kgaa/KhArg ratio was lower in the NaNO3 group compared to the NaCl group (1.57 vs. 2.02, p = 0.0034). Our study suggests that supplementation of inorganic nitrate increases the AGAT-catalyzed synthesis of hArg and decreases the N-methyltransferase-catalyzed synthesis of GAA, the precursor of creatine. To our knowledge, this is the first study to demonstrate elevation of hArg synthesis by inorganic nitrate supplementation. Remarkably, an increase of 24% corresponds to the synthesis capacity of one kidney in healthy humans. Differences in the association between plasma concentrations of amino acids in the NaNO3 and NaCl groups suggest changes in amino-acid homeostasis. Plasma concentrations of the oxidative stress marker malondialdehyde (MDA) did not change after supplementation of NaNO3 or NaCl over the whole exercise time range. Plasma nitrite concentration turned out to be a more discriminant marker of NaNO3 ingestion than plasma nitrate (area under the receiver operating characteristic curve: 0.951 vs. 0.866, p < 0.0001 each)
Multivalent grafting of hyperbranched oligo- and polyglycerols shielding rough membranes to mediate hemocompatibility
Hemocompatible materials are needed for internal and extracorporeal biomedical
applications, which should be realizable by reducing protein and thrombocyte
adhesion to such materials. Polyethers have been demonstrated to be highly
efficient in this respect on smooth surfaces. Here, we investigate the
grafting of oligo- and polyglycerols to rough poly(ether imide) membranes as a
polymer relevant to biomedical applications and show the reduction of protein
and thrombocyte adhesion as well as thrombocyte activation. It could be
demonstrated that, by performing surface grafting with oligo- and
polyglycerols of relatively high polydispersity (>1.5) and several reactive
groups for surface anchoring, full surface shielding can be reached, which
leads to reduced protein adsorption of albumin and fibrinogen. In addition,
adherent thrombocytes were not activated. This could be clearly shown by
immunostaining adherent proteins and analyzing the thrombocyte covered area.
The presented work provides an important strategy for the development of
application relevant hemocompatible 3D structured materials
A Microring Resonator Sensor for Sensitive Detection of 1,3,5-Trinitrotoluene (TNT)
A microring resonator sensor device for sensitive detection of the explosive 1,3,5-trinitrotoluene (TNT) is presented. It is based on the combination of a silicon microring resonator and tailored receptor molecules
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