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•Oil palm trunk and oil palm frond cogasification yielded high H2 and CO.•Syngas was influenced more by temperature, then particle size and blending ratio.•Optimum parameters; ...Temperature 900 °C, blending ratio OPT20:OPF80, and PS 2.59 mm.•Gas cooling and cleaning unit cost accounted for 89% of the total capital cost.•The cost of syngas at optimized conditions was $0.35/Nm3.•Electricity cost influenced the final syngas cost.
Biomass co-gasification is among the most encouraging bio-conversion technologies used in the production of clean and sustainable fuel. This research work was performed on the co-gasification of oil palm trunk and frond to explore the mutual relation of input variables on syngas and optimize them for maximum syngas generation. Air was utilised as the agent of gasification, while a downdraft gratifier was used as the reactor. The operating variables are temperature (700–900 °C), blending ratio (20–80 wt%) and particle size (1.18–4 mm). Optimization was achieved through Response Surface Methodology, Box-Behnken design. The results showed that the operating variables influenced the results in increasing order of temperature, particle size, and blending ratio. Optimum syngas composition was obtained as 20.22 vol% H2, 24.86 vol% CO, and 13.78 vol% CH4 at a temperature of 900 °C, particle size of 2.59 mm and a blending ratio of 20OPT:80OPF.The optimized values resulted in a high syngas yield and co-gasification performance. Cost analysis of the optimum blend was carried out, and it was found that the operating cost played a significant role in the final syngas cost. It occupied about 49% of the production cost, while the capital and other cost occupied occupy 44% and 7% respectively.
Collisionless shocks vary drastically from terrestrial to astrophysical regimes resulting in radically different characteristics. This poses two complexities. First, separating the influences of ...these parameters on physical mechanisms such as energy dissipation. Second, correlating observations of shock waves over a wide range of each parameter, enough to span across different regimes. Investigating the latter has been restricted since the majority of studies on shocks at exotic regimes (such as supernova remnants) have been achieved either remotely or via simulations, but rarely by means of in situ observations. Here we present the parameter space of MA bow shock crossings from 2004 to 2014 as observed by the Cassini spacecraft. We find that Saturn's bow shock exhibits characteristics akin to both terrestrial and astrophysical regimes (MA of order 100), which is principally controlled by the upstream magnetic field strength. Moreover, we determined the θBn of each crossing to show that Saturn's (dayside) bow shock is predominantly quasi‐perpendicular by virtue of the Parker spiral at 10 AU. Our results suggest a strong dependence on MA in controlling the onset of physical mechanisms in collisionless shocks, particularly nontime stationarity and variability. We anticipate that our comprehensive assessment will yield deeper insight into high MA collisionless shocks and provide a broader scope for understanding the structures and mechanisms of collisionless shocks.
Key Points
Alfvén Mach number parameter space of Saturn is presented
Saturn's bow shock is physically variable with terrestrial and astrophysical characteristics
New technique to determine Alfvén Mach numbers with potential applications to other planetary systems
Literature emerging from Western countries has reported increased levels of serum oxidative stress markers among polycystic ovarian syndrome (PCOS) women. In the Arab region, there is limited ...research about the association between oxidative stress and PCOS. This study aimed to compare sociodemographic and clinical characteristics, sex hormones, and oxidative stress indices between PCOS women and non-PCOS women and to investigate the correlation between oxidative stress biomarkers and sex hormones.
This hospital-based case-control study was conducted among reproductive-aged women. The study included 51 women diagnosed with PCOS (as per Rotterdam 2003 criteria) and 45 control women who were not diagnosed with PCOS. Serum samples were collected to measure the mean levels of the following sex hormones: total testosterone, dehydroepiandrosterone sulfate, estradiol and progesterone, as well as to measure biomarkers of oxidative stress including glutathione peroxidase (GPx), glutathione reductase (GR), glutathione (GSH), and total antioxidant capacity (TAC).
PCOS women exhibited clinical characteristics including irregular menses, hirsutism, and acne compared to the control group (
≤0.05). Significant differences were observed in the waist-hip ratio of PCOS women compared to controls (
=0.004). GPx and GR activity levels appeared to be higher among PCOS women compared to controls; however, no statistically significant differences were observed between the two groups (
>0.05). PCOS women had lower GSH and TAC levels compared to controls with a statistically significant difference observed for GSH levels (
=0.006). Correlation analysis showed a significant negative correlation between estradiol and TAC in the total sample (
=-0.284,
=0.005).
This study provides supportive evidence that oxidative stress might play a role in the pathogenesis of PCOS and, hence, oxidative stress parameters could be suggested as diagnostic markers for early diagnosis of high-risk groups. Also, the study provides supportive evidence that obesity and sex hormones, particularly estradiol, in PCOS may contribute to enhanced oxidative stress.
Electric field antennas are capable of detecting dust impacts in different space environment. We analyze the dust impact signals detected by the Cassini Radio and Plasma Wave Science instrument at ...different locations around Saturn and compare them with dust impact signals simulated in laboratory conditions and numerically. The spacecraft potential, the size, and capacitance of the impacted element and ambient plasma have a strong effect on the amplitude and the shape of impact signals, providing important clues to understanding the signal generation mechanism. The voltage signal on the antenna is due to the separation of the impact generated charges, which occurs as electrons and ions can either escape (at different speeds) or be collected by the impacted element depending on the spacecraft potential.
Key Points
Dust impact signals detected by Cassini can be understood as spacecraft potential perturbation due to the impact‐generated charges
The shape of impact signal is consistent with the separate movements ofthe electrons and ions of the impact plasma
Better‐controlled laboratory simulations of Cassini observations improved the understanding of impact signal generation
Abstract Objectives To investigate listening habits and hearing risks associated with the use of personal listening devices among urban high school students in Malaysia. Study design Cross-sectional, ...descriptive study. Methods In total, 177 personal listening device users (13–16 years old) were interviewed to elicit their listening habits (e.g. listening duration, volume setting) and symptoms of hearing loss. Their listening levels were also determined by asking them to set their usual listening volume on an Apple iPod TM playing a pre-selected song. The iPod's sound output was measured with an artificial ear connected to a sound level meter. Subjects also underwent pure tone audiometry to ascertain their hearing thresholds at standard frequencies (0.5–8 kHz) and extended high frequencies (9–16 kHz). Results The mean measured listening level and listening duration for all subjects were 72.2 dBA and 1.2 h/day, respectively. Their self-reported listening levels were highly correlated with the measured levels ( P < 0.001). Subjects who listened at higher volumes also tend to listen for longer durations ( P = 0.012). Male subjects listened at a significantly higher volume than female subjects ( P = 0.008). When sound exposure levels were compared with the recommended occupational noise exposure limit, 4.5% of subjects were found to be listening at levels which require mandatory hearing protection in the occupational setting. Hearing loss (≥25 dB hearing level at one or more standard test frequencies) was detected in 7.3% of subjects. Subjects' sound exposure levels from the devices were positively correlated with their hearing thresholds at two of the extended high frequencies (11.2 and 14 kHz), which could indicate an early stage of noise-induced hearing loss. Conclusions Although the average high school student listened at safe levels, a small percentage of listeners were exposed to harmful sound levels. Preventive measures are needed to avoid permanent hearing damage in high-risk listeners.
Integrating simultaneous in situ measurements of magnetic field fluctuations, precipitating electrons, and ultraviolet auroral emissions, we find that Alfvénic acceleration mechanisms are responsible ...for Ganymede's auroral footprint tail. Magnetic field perturbations exhibit enhanced Alfvénic activity with Poynting fluxes of ~100 mW/m2. These perturbations are capable of accelerating the observed broadband electrons with precipitating fluxes of ~11 mW/m2, such that Alfvénic power is transferred to electron acceleration with ~10% efficiency. The ultraviolet emissions are consistent with in situ electron measurements, indicating 13 ± 3 mW/m2 of precipitating electron flux. Juno crosses flux tubes with both upward and downward currents connected to the auroral tail exhibiting small‐scale structure. We identify an upward electron conic in the downward current region, possibly due to acceleration by inertial Alfvén waves near the Jovian ionosphere. In concert with in situ observations at Io's footprint tail, these results suggest that Alfvénic acceleration processes are broadly applicable to magnetosphere‐satellite interactions.
Plain Language Summary
Jupiter's moon Ganymede interacts with the planet's rapidly rotating magnetic field, which generates an aurora in the Jovian upper atmosphere. The Juno spacecraft crossed magnetic field lines connected to this aurora. We found that a specific type of wave, similar to a wave produced when a string is plucked, is responsible for accelerating the electrons sustaining this aurora. This type of interaction between a moon and the planet it orbits is likely a common process occurring at other exoplanetary systems.
Key Points
First in situ particles and fields measurements connected to Ganymede's auroral tail are reported
Alfvén wave activity is observed with Poynting fluxes of ~100 mW/m2 capable of accelerating electrons into the atmosphere
Ganymede's footprint tail contains electron populations consistent with Alfvénic acceleration and precipitating energy fluxes of ~11 mW/m2
The interaction of Io with the corotating magnetosphere of Jupiter is known to produce Alfvén wings that couple the moon to Jupiter's ionosphere. We present first results from a new numerical model ...to describe the propagation of these Alfvén waves in this system. The model is cast in magnetic dipole coordinates and includes a dense plasma torus that is centered around the centrifugal equator. Results are presented for two density models, showing the dependence of the interaction on the magnetospheric density. Model results are presented for the case when Io is near the centrifugal and magnetic equators as well as when Io is at its northernmost magnetic latitude. The effect of the conductance of Jupiter's ionosphere is considered, showing that a long auroral footprint tail is favored by high Pedersen conductance in the ionosphere. The current patterns in these cases show a U‐shaped footprint due to the generation of field‐aligned current on the Jupiter‐facing and Jupiter‐opposed sides of Io, which may be related to the structure in the auroral footprint seen in the infrared by Juno. A model for the development of parallel electric fields is introduced, indicating that the main auroral footprints of Io can generate parallel potentials of up to 100 kV.
Plain Language Summary
Jupiter's moon Io generates electrical currents when it passes through Jupiter's magnetic field. These currents take the form of fluctuations in the magnetic field lines, much like the waves on a stringed musical instrument. Due to the motion of Io, these waves follow behind Io and bounce back and forth between Jupiter and the dense ionized gas emitted by Io. This process creates auroral emissions that can be observed, e.g., with the Hubble Space Telescope.
Key Points
The spacing of the main auroral spots in Io's footprint tail depends on the density profile assumed as well as the magnetic latitude of Io
Partial reflections at the boundary of the Io plasma torus lead to secondary reflections and weaker auroral spots between the main spots
The length of the auroral tail depends on the ionospheric conductance at Jupiter, with higher conductances leading to longer tails
Between 26 April and 15 September 2017, Cassini executed 23 highly inclined Grand Finale orbits through a new frontier for space exploration, the narrow region between Saturn and the D Ring, ...providing the first opportunity for obtaining in situ ionospheric measurements. During the Grand Finale orbits, the Radio and Plasma Wave Science instrument observed broadband whistler mode emissions and narrowband upper hybrid frequency emissions. Using known wave propagation characteristics of these two plasma wave modes, the electron density is derived over a broad range of ionospheric latitudes and altitudes. A two‐part exponential scale height model is fitted to the electron density measurements. The model yields a double‐layered ionosphere with plasma scale heights of 545/575 km for the northern/southern hemispheres below 4,500 km and plasma scale heights of 4,780/2,360 km for the northern/southern hemispheres above 4,500 km. The interpretation of these layers involves the interaction between the rings and the ionosphere.
Plain Language Summary
For the final 5 months of the Cassini mission in 2017, the spacecraft executed 23 orbits through a new frontier for space exploration, the narrow region between Saturn and the innermost of Saturn's main rings, the D Ring. For the first time in the history of space exploration, the Cassini instruments were able to take measurements inside Saturn's ionosphere. This paper provides the density distribution of Saturn's ionospheric electrons, derived from plasma waves detected by the Radio and Plasma Wave Science instrument. The electron density distributions with altitude and latitude show that the ionospheric electron densities peak at 10,000 particles per cubic centimeter at low altitudes in the equatorial region and drop below 100 particles per cubic centimeter at higher altitudes and latitudes. Two simple ionospheric scale height density models for the northern and southern hemispheres are presented.
Key Points
We present the first in situ measurements of the electron density in the low to middle latitudes of Saturn's ionosphere
The distribution of electron density measurements with altitude shows evidence of a two‐layered ionospheric electron density distribution up to an altitude of 15,000 km
We present a scale height electron density model for a double‐layered ionosphere for both the northern and southern hemispheres
We analyze precipitating electron fluxes connected to 18 crossings of Io's footprint tail aurora, over altitudes of 0.15 to 1.1 Jovian radii (RJ). The strength of precipitating electron fluxes is ...dominantly organized by “Io‐Alfvén tail distance,” the angle along Io's orbit between Io and an Alfvén wave trajectory connected to the tail aurora. These fluxes best fit an exponential as a function of down‐tail extent with an e‐folding distance of 21°. The acceleration region altitude likely increases down‐tail, and the majority of parallel electron acceleration sustaining the tail aurora occurs above 1 RJ in altitude. We do not find a correlation between the tail fluxes and the power of the initial Alfvén wave launched from Io. Finally, Juno has likely transited Io's Main Alfvén Wing fluxtube, observing a characteristically distinct signature with precipitating electron fluxes ~600 mW/m2 and an acceleration region extending as low as 0.4 RJ in altitude.
Plain Language Summary
The Juno spacecraft crossed magnetic field lines connected to Io's auroral signature in Jupiter's atmosphere. By measuring the electrons sustaining this auroral feature, we find that the region these electrons are accelerated is typically more than one Jovian radius away from Jupiter's atmosphere. For one of the 18 transits, we find Juno has most likely directly transited above the main auroral spot in Io's auroral signature.
Key Points
Electron fluxes are best organized by the “Io‐Alfvén tail distance,” following an exponential with e‐folding distance of 21°
Juno has likely directly crossed the Main Alfvén Wing spot, observing precipitating electron fluxes ~600 mW/m2
The majority of parallel electron acceleration sustaining the Io footprint tail occurs above 1 RJ altitude
We report the first in situ observations of electron measurements at a Europa footprint tail (FPT) crossing in the auroral region. During its 12th science perijove pass, Juno crossed magnetic field ...lines connected to Europa's FPT. We find that electrons in the range ~0.4 to ~25 keV, with a characteristic energy of 3.6 ± 0.5 keV, precipitate into Jupiter's atmosphere to create the footprint aurora. The energy flux peaks at ~36 mW/m2, while the peak ultraviolet (UV) brightness is estimated at 37 kR. We estimate the peak electron density and temperature to be 17.3 cm−3 and 1.8 ± 0.1 keV, respectively. Using magnetic flux shell mapping, we estimate that the radial width of the interaction at Europa's orbit spans roughly 3.6 ± 1.0 Europa radii. In contrast to typical Io FPT crossings, the instrument background caused by penetrating energetic radiation (> ~5–10 MeV electrons) increased during the Europa FPT crossing.
Plain Language Summary
Jupiter's moons interact with Jupiter's space environment, or magnetosphere, and create auroral spots and tails in Jupiter's ionosphere. Io's aurora footprint on Jupiter is the strongest and most persistent of all moons, but Ganymede, Callisto, and Europa's auroral footprints are also routinely observed by remote platforms. NASA's Juno mission and its instrument suite occasionally fly through regions that are connected to the moon‐magnetosphere interactions. During these crossings, Juno samples the electrons and ions that create the aurora. This paper is the first report of electron measurements taken during a Juno crossing of Europa's tail. These measurements confirm previous results based on remote observations. Most importantly, they provide a sample of the conditions in the regions associated with Europa's footprint aurora in Jupiter's magnetosphere.
Key Points
This is the first report of in situ electron measurements of a Europa footprint tail crossing
Precipitating electron energies range from ~0.4 to ~25 keV with a characteristic energy of 3.6 keV, consistent with a low color ratio of the auroral emissions
The instrument background caused by > ~5–10 MeV penetrating electrons increased during the crossing, opposite to what is observed at Io
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