•A complete ammonia-only ship propulsion system is conceptually designed.•Along with the engine, ammonia decomposition and SCR reactors are designed.•The energy and exergy efficiency of the system is ...42.4% and 48.1%, respectively.•The global investment is 784 €/kW with an operating cost of about 225 €/MWh.•The cost of ammonia highly influenced the profitability of the propulsion system.
To reach the decarbonisation goals, a zero CO2 emissions large ship propulsion system is proposed in this work. The ship selected is a large ferry propelled by an internal combustion engine fuelled by an ammonia-hydrogen blend. The only fuel loaded in the vessel will be ammonia. The hydrogen required for the combustion in the engine will be produced onboard employing ammonia decomposition. The heat required for this decomposition section will be supplied by using the hot flue gases of the combustion engine. To address the issues regarding NOx emissions, a selective catalytic reduction (SCR) reactor was designed. The main operating variables for all the equipment were computed for engine load values of 25%, 50%, 75%, and 100%. Considering the lowest SCR removal rate (91% at an engine load of 100%), the NOx emissions of the vessel were less than 0.5 g/kWh, lower than the IMO requirements. An energy analysis of the system proposed to transform ammonia into energy for shipping was conducted. The global energy and exergy efficiencies were 42.4% and 48.1%. In addition, an economic analysis of the system was performed. The total capital cost (CAPEX) for the system can be estimated at 8.66 M€ (784 €/kW) while the operating cost (OPEX) ranges between 210 €/MWh (engine load 100%) and 243 €/MWh (engine load of 25%). Finally, a sensitivity analysis for the price of ammonia was performed resulting in the feasibility of reducing the operating cost to below 150 €/MWh in the near horizon.
Aims.
We study the effect of disequilibrium processes (photochemistry and vertical transport) on mixing ratio profiles of neutral species and on the simulated spectra of a hot Jupiter exoplanet that ...orbits stars of various spectral types. We additionally address the impact of stellar activity that should be present, to various degrees, in all stars with convective envelopes.
Methods.
We used the VULCAN chemical kinetic code to compute number densities of species in irradiated planetary atmospheres. The temperature-pressure profile of the atmosphere was computed with the HELIOS code. We also utilized the
τ
-REx forward model to predict the spectra of planets in primary and secondary eclipses. In order to account for the stellar activity, we made use of the observed solar extreme ultraviolet (XUV) spectrum taken from Virtual Planetary Laboratory as a proxy for an active sun-like star.
Results.
We find large changes in the mixing ratios of most chemical species in planets orbiting A-type stars, which radiate strong XUV flux thereby inducing a very effective photodissociation. For some species, these changes can propagate very deep into the planetary atmosphere to pressures of around 1 bar. To observe disequilibrium chemistry we favor hot Jupiters with temperatures
T
eq
= 1000 K and ultra-hot Jupiters, with
T
eq
≈ 3000 K,which also have temperature inversion in their atmospheres. On the other hand, disequilibrium calculations predict no noticeable changes in spectra of planets with intermediate temperatures. We also show that stellar activity similar to that of the modern Sun drives important changes in mixing ratio profiles of atmospheric species. However, these changes take place at very high atmospheric altitudes and thus do not affect predicted spectra. Finally, we estimate that the effect of disequilibrium chemistry in planets orbiting nearby bright stars could be robustly detected and studied with future missions with spectroscopic capabilities in infrared such as
James Webb
Space Telescope and ARIEL.
Background
Treatment of schizophrenia requires long-term medication to prevent relapse. Treatment nonadherence may increase the risk of relapse, leading to increased hospitalizations and emergency ...room (ER) visits. Long-acting injectables (LAIs) such as paliperidone palmitate have improved treatment adherence and therefore symptoms. However, real-world studies comparing 3-monthly LAI formulations with other LAIs and oral antipsychotics (OAs) are scarce.
Objective
The objective of this study was to investigate and evaluate the clinical effectiveness of paliperidone palmitate LAI monthly (PP1M; Xeplion
®
) and 3-monthly (PP3M; Trevicta
®
) formulations compared with the monthly LAI aripiprazole (AM; Abilify Maintena
®
) and OAs in Spain.
Methods
This was a retrospective, observational study including 2275 adult patients with schizophrenia in a Spanish population. Data from hospital, primary care, and pharmacy dispensation electronic medical records were obtained between January 2017 and February 2018. The main outcomes included psychiatric hospitalizations and ER visit rates, days on treatment, and treatment persistence.
Results
Patients receiving PP3M had a significantly lower mean hospitalization rate (0.00046 ± standard deviation SD 0.00181;
p
< 0.0001) than other treatment groups. Kaplan–Meier curves revealed that 92.0 and 88.4% of patients receiving PP3M remained hospitalization free by 12 and 18 months, respectively. All treatment groups had at least a twofold significantly higher risk of psychiatric hospitalizations compared with those receiving PP3M or OAs, and the hospitalization risk among the PP3M group was significantly lower (hazard ratio HR 0.46; 95% confidence interval CI 0.31–0.67). The risk of ER visits was significantly lower with both PP3M and PP1M than with OAs, and lowest with PP3M (HR 0.462 95% CI 0.29–0.62 and HR 0.833 95% CI 0.59–0.97, respectively). Time until treatment switch with PP3M was high, with more than 86.5% of patients remaining on treatment at 18 months.
Conclusions
PP3M was more effective than OAs and monthly LAIs in improving clinical outcomes for patients with schizophrenia in a real-world setting in Spain.
Context. Thanks to the advances in modern instrumentation we have learned about many exoplanets that span a wide range of masses and composition. Studying their atmospheres provides insight into ...planetary origin, evolution, dynamics, and habitability. Present and future observing facilities will address these important topics in great detail by using more precise observations, high-resolution spectroscopy, and improved analysis methods. Aims. We investigate the feasibility of retrieving the vertical temperature distribution and molecular number densities from expected exoplanet spectra in the near-infrared. We use the test case of the CRIRES+ instrument at the Very Large Telescope which will operate in the near-infrared between 1 and 5 μm and resolving powers of R = 100 000 and R = 50 000. We also determine the optimal wavelength coverage and observational strategies for increasing accuracy in the retrievals. Methods. We used the optimal estimation approach to retrieve the atmospheric parameters from the simulated emission observations of the hot Jupiter HD 189733b. The radiative transfer forward model is calculated using a public version of the τ-REx software package. Results. Our simulations show that we can retrieve accurate temperature distribution in a very wide range of atmospheric pressures between 1 bar and 10−6 bar depending on the chosen spectral region. Retrieving molecular mixing ratios is very challenging, but a simultaneous observations in two separate infrared regions around 1.6 and 2.3 μm helps to obtain accurate estimates; the exoplanetary spectra must be of relatively high signal-to-noise ratio S∕N ≥ 10, while the temperature can already be derived accurately with the lowest value that we considered in this study (S∕N = 5). Conclusions. The results of our study suggest that high-resolution near-infrared spectroscopy is a powerful tool for studying exoplanet atmospheres because numerous lines of different molecules can be analyzed simultaneously. Instruments similar to CRIRES+ will provide data for detailed retrieval and will provide new important constraints on the atmospheric chemistry and physics.
Aims.
The aim of this study is to measure the vertical distribution of HCN on Titan’s stratosphere using ground-based submillimetre observations acquired quasi-simultaneously with the
Herschel
ones. ...This allows us to perform a consistency check between space and ground-based observations and to build a reference mean HCN vertical profile in Titan’s stratosphere.
Methods.
Using APEX and IRAM 30-m, we obtained the spectral emission of HCN (4-3) and (3-2) lines. Observations were reduced with GILDAS-CLASS. We applied a line-by-line radiative transfer code to calculate the synthetic spectra of HCN, and a retrieval algorithm based on optimal estimation to retrieve the temperature and HCN vertical distributions. We used the standard deviation-based metric to quantify the dispersion between the ground-based and
Herschel
HCN profiles and the mean one.
Results.
Our derived HCN abundance profiles are consistent with an increase from 40 ppb at ~100 km to 4 ppm at ~200 km, which is an altitude region where the HCN signatures are sensitive. We also demonstrate that the retrieved HCN distribution is sensitive to the data information and is restricted to Titan’s stratosphere. The HCN obtained from APEX data is less accurate than the one from IRAM data because of the poorer data quality, and covers a narrower altitude range. Comparisons between our results and the values from
Herschel
show similar abundance distributions, with maximum differences of 2.5 ppm ranging between 100 and 300 km in the vertical range. These comparisons also allow us to inter-validate both data sets and indicate reliable and consistent measurements. The inferred abundances are also consistent with the vertical distribution in previous observational studies, with the profiles from ALMA, Cassini/CIRS, and SMA (the latest ones below ~230 km). Our HCN profile is also comparable to photochemical models by Krasnopolsky (2014) and Vuitton et al. (2019) below 230 km and consistent with that of Loison et al. (2015) above 250 km. However, it appears to show large differences with respect to the estimates by Loison et al. (2015), Dobrijevic & Loison (2018), and Lora et al. (2018) below 170 km, and by Dobrijevic & Loison (2018) and Lora et al. (2018) above 400 km, although they are similar in shape. We conclude that these particular photochemical models need improvement.
Context.
Observationally constraining the atmospheric temperature-pressure (TP) profile of exoplanets is an important step forward for improving planetary atmosphere models, thus further enabling one ...to place the detection of spectral features and the measurement of atomic and molecular abundances through transmission and emission spectroscopy on solid ground.
Aims.
The aim is to constrain the TP profile of the ultra-hot Jupiter KELT-9b by fitting synthetic spectra to the observed H
α
and H
β
lines and identify why self-consistent planetary TP models are unable to fit the observations.
Methods.
We constructed 126 one-dimensional TP profiles varying the lower and upper atmospheric temperatures, as well as the location and gradient of the temperature rise. For each TP profile, we computed the transmission spectra of the H
α
and H
β
lines employing the Cloudy radiative transfer code, which self-consistently accounts for non-local thermodynamic equilibrium (NLTE) effects.
Results.
The TP profiles, leading to best fit the observations, are characterised by an upper atmospheric temperature of 10 000–11 000 K and by an inverted temperature profile at pressures higher than 10
−4
bar. We find that the assumption of local thermodynamic equilibrium (LTE) leads one to overestimate the level population of excited hydrogen by several orders of magnitude and hence to significantly overestimate the strength of the Balmer lines. The chemical composition of the best fitting models indicate that the high upper atmospheric temperature is most likely driven by metal photoionisation and that Fe
II
and Fe
III
have comparable abundances at pressures lower than 10
−6
bar, possibly making the latter detectable.
Conclusions.
Modelling the atmospheres of ultra-hot Jupiters requires one to account for metal photoionisation. The high atmospheric mass-loss rate (>10
11
g s
−1
), caused by the high temperature, may have consequences on the planetary atmospheric evolution. Other ultra-hot Jupiters orbiting early-type stars may be characterised by similarly high upper atmospheric temperatures and hence high mass-loss rates. This may have consequences on the basic properties of the observed planets orbiting hot stars.
The study of planetary atmospheres is crucial for understanding the origin, evolution, and processes that shape celestial bodies like planets, moons and comets. The interpretation of planetary ...spectra requires a detailed understanding of radiative transfer (RT) and its application through computational codes. With the advancement of observations, atmospheric modelling, and inference techniques, diverse RT and retrieval codes in planetary science have been proliferated. However, the selection of the most suitable code for a given problem can be challenging. To address this issue, we present a comprehensive mini-overview of the different RT and retrieval codes currently developed or available in the field of planetary atmospheres. This study serves as a valuable resource for the planetary science community by providing a clear and accessible list of codes, and offers a useful reference for researchers and practitioners in their selection and application of RT and retrieval codes for planetary atmospheric studies.
Context . On October 31, 2009, the Photodetector Array Camera and Spectrometer (PACS) on board the Herschel Space Observatory observed far-infrared spectra of Jupiter in the wavelength range between ...50 and 220 µm as part of the program “Water and Related Chemistry in the Solar System”. The spectra have an effective spectral resolution between 900 and 3500, depending on the wavelength and grating order. Aims . We investigate the disk-averaged chemical composition of Jupiter’s atmosphere as a function of height using these observations. Methods . We used the Planetary Spectrum Generator and the least-squares fitting technique to infer the abundances of trace constituents. Results . The PACS data include numerous spectral lines attributable to ammonia (NH 3 ), methane (CH 4 ), phosphine (PH 3 ), water (H 2 O), and deuterated hydrogen (HD) in the Jovian atmosphere and probe the chemical composition from p ~ 275 mbar to p ~ 900 mbar. From the observations, we infer an ammonia abundance profile that decreases from a mole fraction of (1.7 ± 0.8) × 10 −4 at p ~ 900 mbar to (1.7 ± 0.9) × 10 −8 at p ~ 275 mbar, following a fractional scale height of about 0.114. For phosphine, we find a mole fraction of (7.2 ± 1.2) × 10 −7 at pressures higher than (550 ± 100) mbar and a decrease of its abundance at lower pressures following a fractional scale height of (0.09 ± 0.02). Our analysis delivers a methane mole fraction of (1.49 ± 0.09) × 10 −3 . Analyzing the HD R (0) line at 112.1 µm yields a new measurement of Jupiter’s D/H ratio, D/H = (1.5 ± 0.6) × 10 −5 . Finally, the PACS data allow us to put the most stringent 3 σ upper limits yet on the mole fractions of hydrogen halides in the Jovian troposphere. These new upper limits are <1.1 × 10 −11 for hydrogen fluoride (HF), <6.0 × 10 −11 for hydrogen chloride (HCl), <2.3 × 10 −10 for hydrogen bromide (HBr) and <1.2 × 10 −9 for hydrogen iodide (HI) and support the proposed condensation of hydrogen halides into ammonium halide salts in the Jovian troposphere.
Recent stellar occultations have allowed accurate instantaneous size and apparent shape determinations of the large Kuiper belt object (50000) Quaoar and the detection of two rings with spatially ...variable optical depths. In this paper we present new visible range light curve data of Quaoar from the
Kepler
/K2 mission, and thermal light curves at 100 and 160 µm obtained with
Herschel
/PACS. The K2 data provide a single-peaked period of 8.88 h, very close to the previously determined 8.84 h, and it favours an asymmetric double-peaked light curve with a 17.76 h period. We clearly detected a thermal light curve with relative amplitudes of ~ 10% at 100 and at 160 µm. A detailed thermophysical modelling of the system shows that the measurements can be best fit with a triaxial ellipsoid shape, a volume-equivalent diameter of 1090 km, and axis ratios of a/b = 1.19 and b/c = 1.16. This shape matches the published occultation shape, as well as visual and thermal light curve data. The radiometric size uncertainty remains relatively large (±40 km) as the ring and satellite contributions to the system-integrated flux densities are unknown. In the less likely case of negligible ring or satellite contributions, Quaoar would have a size above 1100 km and a thermal inertia ≤ 10 J m
−2
K
−1
s
−1/2
. A large and dark Weywot in combination with a possible ring contribution would lead to a size below 1080 km in combination with a thermal inertia ≳10 J m
−2
K
−1
s
−1/2
, notably higher than that of smaller Kuiper belt objects with similar albedo and colours. We find that Quaoar’s density is in the range 1.67–1.77 g cm
−3
, significantly lower than previous estimates. This density value closely matches the relationship observed between the size and density of the largest Kuiper belt objects.
The method reported in the literature to calculate the stress–strain curve of nuclear fuel cladding from ring tensile test is revisited in this paper and a new alternative is presented. In the former ...method, two universal curves are introduced under the assumption of small strain. In this paper it is shown that these curves are not universal, but material-dependent if geometric nonlinearity is taken into account. The new method is valid beyond small strains, takes geometric nonlinearity into consideration and does not need universal curves. The stress–strain curves in the hoop direction are determined by combining numerical calculations with experimental results in a convergent loop. To this end, ring tensile tests were performed in unirradiated hydrogen-charged samples. The agreement among the simulations and the experimental results is excellent for the range of concentrations tested (up to 2000wppm hydrogen). The calculated stress–strain curves show that the mechanical properties do not depend strongly on the hydrogen concentration, and that no noticeable strain hardening occurs. However, ductility decreases with the hydrogen concentration, especially beyond 500wppm hydrogen. The fractographic results indicate that as-received samples fail in a ductile fashion, whereas quasicleavage is observed in the hydrogen-charged samples.
PDF
