In 1927, at the Solvay conference, Einstein posed a thought experiment with the primary intention of showing the incompleteness of quantum mechanics; to prove it, he employed the instantaneous ...nonlocal effects caused by the collapse of the wavefunction of a single particle-the spooky action at a distance-, when a measurement is done. This historical event preceded the well-know Einstein-Podolsk-Rosen criticism over the incompleteness of quantum mechanics. Here, by using the Stern-Gerlach experiment, we demonstrate how the instantaneous nonlocal feature of the collapse of the wavefunction together with the single-particle entanglement can be used to produce the nonlocal effect of steering, i.e. the single-particle steering. In the steering process Bob gets a quantum state depending on which observable Alice decides to measure. To accomplish this, we fully exploit the spreading (over large distances) of the entangled wavefunction of the single-particle. In particular, we demonstrate that the nonlocality of the single-particle entangled state allows the particle to "know" about the kind of detector Alice is using to steer Bob's state. Therefore, notwithstanding strong counterarguments, we prove that the single-particle entanglement gives rise to truly nonlocal effects at two faraway places. This opens the possibility of using the single-particle entanglement for implementing truly nonlocal task.
Macroscopic fibers of carbon nanotubes (CNT) have emerged as an ideal architecture to exploit the exceptional properties of CNT building blocks in applications ranging from energy storage to ...reinforcement in structural composites. Controlled synthesis and scalability are amongst the most pressing challenges to further materialize the potential of CNT fibers. This work shows that under floating catalyst chemical vapor conditions in the direct spinning method, used both in research and industry, the ceramic reactor tube plays an unsuspected active role in CNT growth, leading for example to doubling of reaction yield when mullite (Al
Si
O
(x ≈ 0:4)) is used instead of alumina (Al
O
), but without affecting CNT morphology in terms of number of layers, purity or degree of graphitization. This behaviour is confirmed for different carbon sources and when growing either predominantly single-walled or multi-walled CNTs by adjusting promotor concentration. Analysis of large Si-based impurities occasionally found in CNT fiber fabric samples, attributed to reactor tube fragments that end up trapped in the porous fibers, indicate that the role of the reactor tube is in catalyzing the thermal decomposition of hydrocarbons, which subsequently react with floating Fe catalyst nanoparticles and produce extrusion of the CNTs and formation of an aerogel. Reactor gas analysis confirms that extensive thermal decomposition of the carbon source occurs in the absence of Fe catalyst particles, and that the concentration of different carbon species (e.g. carbon dioxide and ethylene) is sensitive to the reactor tube type. These finding open new avenues for controlled synthesis of CNT fibers by decoupling precursor decomposition from CNT extrusion at the catalyst particle.
Hydroxylamine (NH2OH), a short‐lived intermediate in the nitrogen cycle, is a potential precursor of nitrous oxide (N2O) in the ocean. However, measurements of NH2OH in the ocean are sparse. Here we ...present a data set of depth profiles of NH2OH from the equatorial Atlantic Ocean and the eastern tropical South Pacific and compare it to N2O, nitrate, and nitrite profiles under varying oxygen conditions. The presence of NH2OH in surface waters points toward surface nitrification in the upper 100 m. Overall, we found a ratio of 1:3 between NH2OH and N2O in open ocean areas when oxygen concentrations were >50 μmol/L. In the equatorial Atlantic Ocean and the open ocean eastern tropical South Pacific, where nitrification is the dominant N2O production pathway, stepwise multiple regressions demonstrated that N2O, NH2OH, and nitrate concentrations were highly correlated, suggesting that NH2OH is a potential indicator for nitrification.
Plain Language Summary
Hydroxylamine (NH2OH) is a short‐lived intermediate in the nitrogen cycle. It could be a precursor of nitrous oxide (N2O) in the ocean. Nitrous oxide (N2O) is an important greenhouse gas and leads to the production of other nitrogen species that can deplete the ozone layer. In the ocean, N2O can be produced by two processes—nitrification and denitrification, while only during nitrification, the oxidation of ammonia to nitrate, is NH2OH involved. The key aim of this study is to decipher the role of NH2OH as a potential indicator for N2O production. We found out that NH2OH is strongly correlated with N2O in open ocean areas, where nitrification is the main N2O pathway and can therefore be used as an indicator for active nitrification and in situ N2O production.
Key Points
Hydroxylamine concentrations are significantly correlated with nitrous oxide concentrations in oxygenated waters
In waters that likely were influenced by denitrification the correlation between hydroxylamine and nitrous oxide breaks down
Hydroxylamine may be useful as an indicator for active in situ production of nitrous oxide by nitrification in the open ocean
Summary Objective To determine the magnitude of medial femoral cartilage deformation using ultrasonography (US) following walking and running in healthy individuals. Design Twenty-five healthy ...participants with no history of osteoarthritis or knee injury volunteered for this study. Medial femoral cartilage thickness was assessed using US before and after three separate 30-minute loading conditions: 1) walking at a self-selected speed, 2) running at a self-selected speed, and 3) sitting on a treatment table (i.e. control). Cartilage deformation was calculated as the percent change score from pre to post loading in each loading condition. The magnitude of cartilage deformation was compared between the three loading conditions. Results There was no difference in baseline cartilage thickness between the three sessions (F1,24 =0.18, p=0.68). Cartilage deformation was different between the loading conditions (F1,24 =47.54, p<0.001). The walking (%Δ=-6.7, t24 =6.90, p<0.001, d =-1.92) and running (%Δ=-8.9, t24 =8.14, p<0.001, d =-1.85) conditions resulted in greater cartilage deformation when compared to the control condition (%Δ=+3.4). There was no difference in cartilage deformation between the running and walking conditions (t24 =1.10, p=0.28, d =0.33). US measured medial femoral cartilage thickness demonstrated reliability and precision within a single session (ICC2,k =0.966, SEM=0.07mm) and between additional sessions separated by seven (ICC2,k =0.964, SEM=0.08mm) and sixteen days (ICC2,k =0.919, SEM=0.11mm). Conclusions US demonstrated to be a reliable and sensitive imaging modality at quantifying medial femoral cartilage deformation in healthy individuals. Both walking and running conditions created greater cartilage deformation when compared to the control conditions, but no difference was observed between the walking and running conditions.
Carbon monoxide (CO) influences the radiative budget and oxidative capacity of the atmosphere over the Arctic Ocean, which is a source of atmospheric CO. Yet, oceanic CO cycling is understudied in ...this area, particularly in light of the ongoing rapid environmental changes. We present results from incubation experiments conducted in the Fram Strait in August–September 2019 under different environmental conditions: while lower pH did not affect CO production (GPCO) or consumption (kCO) rates, enhanced GPCO and kCO were positively correlated with coloured dissolved organic matter (CDOM) and dissolved nitrate concentrations, respectively, suggesting microbial CO uptake under oligotrophic conditions to be a driving factor for variability in CO surface concentrations. Both production and consumption of CO will likely increase in the future, but it is unknown which process will dominate. Our results will help to improve models predicting future CO concentrations and emissions and their effects on the radiative budget and the oxidative capacity of the Arctic atmosphere.
Oxygen-deficient zones (ODZs) are major sites of net natural
nitrous oxide (N2O) production and emissions. In order to understand
changes in the magnitude of N2O production in response to global
...change, knowledge on the individual contributions of the major microbial
pathways (nitrification and denitrification) to N2O production and
their regulation is needed. In the ODZ in the coastal area off Peru, the
sensitivity of N2O production to oxygen and organic matter was
investigated using 15N tracer experiments in combination with quantitative PCR (qPCR) and
microarray analysis of total and active functional genes targeting archaeal amoA
and nirS as marker genes for nitrification and denitrification, respectively.
Denitrification was responsible for the highest N2O production with a
mean of 8.7 nmol L−1 d−1 but up to 118±27.8 nmol L−1 d−1 just below the oxic–anoxic interface. The highest N2O production
from ammonium oxidation (AO) of 0.16±0.003 nmol L−1 d−1
occurred in the upper oxycline at O2 concentrations of 10–30 µmol L−1 which coincided with the highest archaeal amoA transcripts/genes.
Hybrid N2O formation (i.e., N2O with one N atom from NH4+
and the other from other substrates such as NO2-) was the dominant
species, comprising 70 %–85 % of total produced N2O from
NH4+, regardless of the ammonium oxidation rate or O2
concentrations. Oxygen responses of N2O production varied with
substrate, but production and yields were generally highest below 10 µmol L−1 O2. Particulate organic matter additions increased
N2O production by denitrification up to 5-fold, suggesting increased
N2O production during times of high particulate organic matter export.
High N2O yields of 2.1 % from AO were measured, but the overall
contribution by AO to N2O production was still an order of magnitude
lower than that of denitrification. Hence, these findings show that
denitrification is the most important N2O production process in low-oxygen conditions fueled by organic carbon supply, which implies a positive
feedback of the total oceanic N2O sources in response to increasing
oceanic deoxygenation.
The Heisenberg uncertainty principle, which underlies many quantum key features, is under close scrutiny regarding its applicability to new scenarios. Using both the Bell-Kochen-Specker theorem ...establishing that observables do not have predetermined values before measurements and the measurement postulate of quantum mechanics, we propose that in order to describe the disturbance produced by the measurement process, it is convenient to define disturbance by the changes produced on quantum states. Hence, we propose to quantify disturbance in terms of the square root of the Jensen-Shannon entropy distance between the probability distributions before and after the measurement process. Additionally, disturbance and statistical distinguishability of states are fundamental concepts of quantum mechanics that have thus far been unrelated; however, we show that they are intermingled thereupon we enquire into whether the statistical distinguishability of states, caused by statistical fluctuations in the measurement outcomes, is responsible for the disturbance's magnitude.
The open ocean is a major source of nitrous oxide
(N2O), an atmospheric trace gas attributable to global warming and
ozone depletion. Intense sea-to-air N2O fluxes occur in major oceanic
upwelling ...regions such as the eastern tropical South Pacific (ETSP). The
ETSP is influenced by the El Niño–Southern Oscillation that leads to
inter-annual variations in physical, chemical, and biological properties in
the water column. In October 2015, a strong El Niño event was developing
in the ETSP; we conduct field observations to investigate (1) the N2O
production pathways and associated biogeochemical properties and (2) the
effects of El Niño on water column N2O distributions and fluxes
using data from previous non-El Niño years. Analysis of N2O natural
abundance isotopomers suggested that nitrification and partial
denitrification (nitrate and nitrite reduction to N2O) were occurring
in the near-surface waters; indicating that both pathways contributed to
N2O effluxes. Higher-than-normal sea surface temperatures were
associated with a deepening of the oxycline and the oxygen minimum layer.
Within the shelf region, surface N2O supersaturation was nearly an
order of magnitude lower than that of non-El Niño years. Therefore, a
significant reduction of N2O efflux (75 %–95 %) in the ETSP
occurred during the 2015 El Niño. At both offshore and coastal stations,
the N2O concentration profiles during El Niño showed moderate
N2O concentration gradients, and the peak N2O concentrations
occurred at deeper depths during El Niño years; this was likely the
result of suppressed upwelling retaining N2O in subsurface waters. At
multiple stations, water-column inventories of N2O within the top 1000 m were up to 160 % higher than those measured in non-El Niño years,
indicating that subsurface N2O during El Niño could be a reservoir
for intense N2O effluxes when normal upwelling is resumed after El
Niño.
Ground-based atmospheric observations of CO2, δ(O2∕N2), N2O, and CH4
were used to make estimates of the air–sea fluxes of these species from the Lüderitz and Walvis Bay upwelling cells in the ...northern Benguela region, during upwelling events. Average flux densities (±1σ) were 0.65±0.4 µmol m−2 s−1 for CO2, -5.1±2.5 µmol m−2 s−1 for O2 (as APO), 0.61±0.5 nmol m−2 s−1 for N2O, and 4.8±6.3 nmol m−2 s−1 for CH4. A comparison of our top-down (i.e., inferred from atmospheric anomalies) flux estimates with shipboard-based measurements showed that the two approaches agreed within ±55 % on average, though the degree of agreement varied by species and was best for CO2. Since the top-down method overestimated the flux density relative to the shipboard-based approach for all species, we also present flux density estimates that have been tuned to best match the shipboard fluxes. During the study, upwelling events were sources of CO2, N2O, and CH4 to the atmosphere. N2O fluxes were fairly low, in accordance with previous work suggesting that the evasion of this gas from the Benguela is smaller than for other eastern boundary upwelling systems (EBUS). Conversely, CH4 release was quite high for the marine environment, a result that supports studies that indicated a large sedimentary source of CH4 in the Walvis Bay area. These results demonstrate the suitability of atmospheric time series for characterizing the temporal variability of upwelling events and their influence on the overall marine greenhouse gas (GHG) emissions from the northern Benguela region.
Agroforestry systems can play an important role in mitigating the effects of climate change given their capacity to increase tree diversity and to store more carbon than conventional farming. This ...study aims at assessing carbon stocks and the use of shade trees in different coffee growing systems in the Northeast Peruvian Amazon. Carbon stocks in trees were estimated by field-based measurements and allometric equations. Carbon stocks in dead wood, litter and soil (upper 60 cm) were determined using field sampling and laboratory analysis. The diversity analysis drew on the Shannon–Weiner diversity index, and focus groups were used to obtain information about the local use of shade trees. The total carbon stock in the polyculture-shaded coffee system was 189 t C/ha, while the Inga-shaded and unshaded systems totalled 146 and 113 t C/ha, respectively. The soil compartment contributed the largest carbon stock in the coffee growing systems and contained 67, 82 and 96% of the total carbon stock in the polyculture-shaded, Inga-shaded and unshaded coffee systems, respectively. The Shannon–Weiner index and tree species richness values were highest for the polyculture-shaded coffee system, with a total of 18 tree species identified as important sources of fodder, food, wood, firewood and medicine. Therefore, coffee agroforestry systems play a significant role in carbon storage, while promoting conservation of useful trees in agricultural landscapes in the Peruvian Amazon.
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