Initial Mass Research Articles

Drying Kinetics of Microwave-Assisted Drying of Leaching Residues from Hydrometallurgy of Zinc.

In the hydrometallurgical process of zinc production, the residue from the leaching stage is an important intermediate product and is treated in a Waelz kiln to recover valuable metals. To ensure optimal results during the Waelz kiln process, it is necessary to pre-treat the residues by drying them first due to their higher water content. This work studies the residue's drying process using microwave technology. The study results indicate that microwave technology better removes the residue's oxygen functional groups and moisture. The dehydration process's effective diffusion coefficient increases as the microwave's heating power, the initial moisture content, and the initial mass increase. The Page model is appropriate for imitating the drying process, and the activation energy of the drying process for the residues is -13.11217 g/W. These results indicate that microwave technology efficiently dries the residues from the leaching stage. Furthermore, this study provides a theoretical basis and experimental data for the industrial application of microwave drying.

Degradation of 2-Chlorophenol in Aqueous Solutions Using Persulfate Activated by Biochar Supported Sulfide-Modified Nanoscale Zero-Valent Iron: Performance and Mechanisms

In this work, soybean biochar-supported sulfide-modified nanoscale zero-valent iron (BC@S-nZVI) was synthesized and used to activate persulfate (PS) to degrade 2-chlorophenol (2-CP) in aqueous solutions. Batch experiments were carried out to investigate the degradation effects under different conditions, including initial mass ratios among 2-CP, PS, and BC@S-nZVI, initial pH values, temperature, and anions. The results showed that the mass ratio of PS to 2-CP equal to 70 and the mass ratio of BC@S-nZVI to PS equal to 0.4 were the optimum mass ratios in the degradation system. The degradation efficiency of 2-CP was higher under acidic and alkaline conditions than the neutral condition, and the effect was best at a pH of 3; meanwhile, it increased with the increase in temperature. Moreover, the degradation rate was restrained with the addition of Cl−, promoted with the addition of NO3− and CO32−. Both free radical and material functions played leading roles in the degradation of 2-CP, and the stability of BC@S-nZVI was better than nZVI and S-nZVI. The experimental results showed that it was promising to remove 2-CP and other organic pollutants from groundwater by PS activated with BC@S-nZVI.

Forming rocky exoplanets around K-dwarf stars

Context. New space telescopes, such as the upcoming PLATO mission, aim to detect and study thousands of exoplanets, especially terrestrial planets around main-sequence stars. This motivates us to study how these planets formed. How multiple close-in super-Earths form around stars with masses lower than that of the Sun is still an open issue. Several recent modeling studies have focused on planet formation around M-dwarf stars, but so far no studies have focused specifically on K dwarfs, which are of particular interest in the search for extraterrestrial life. Aims. We aim to reproduce the currently known population of close-in super-Earths observed around K-dwarf stars and their system characteristics. Additionally, we investigate whether the planetary systems that we form allow us to decide which initial conditions are the most favorable. Methods. We performed 48 high-resolution N-body simulations of planet formation via planetesimal accretion using the existing GENGA software running on GPUs. In the simulations we varied the initial protoplanetary disk mass and the solid and gas surface density profiles. Each simulation began with 12 000 bodies with radii of between 200 and 2000 km around two different stars, with masses of 0.6 and 0.8 M⊙. Most simulations ran for 20 Myr, with several simulations extended to 40 or 100 Myr. Results. The mass distributions for the planets with masses between 2 and 12 M⊕ show a strong preference for planets with masses Mp < 6 M⊕ and a lesser preference for planets with larger masses, whereas the mass distribution for the observed sample increases almost linearly. However, we managed to reproduce the main characteristics and architectures of the known planetary systems and produce mostly long-term angular-momentum-deficit-stable, nonresonant systems, but we require an initial disk mass of 15 M⊕ or higher and a gas surface density value at 1 AU of 1500 g cm−2 or higher. Our simulations also produce many low-mass planets with M < 2 M⊕, which are not yet found in the observed population, probably due to the observational biases. Earth-mass planets form quickly (usually within a few million years), mostly before the gas disk dispersal. The final systems contain only a small number of planets with masses Mp > 10 M⊕, which could possibly accrete substantial amounts of gas, and these formed after the gas had mostly dissipated. Conclusions. We mostly manage to reproduce observed K-dwarf exoplanetary systems from our GPU simulations.

A Becker–Döring Type Model for Cell Polarization

We propose a model for cell polarization based on the Becker–Döring equations with the first coagulation coefficient equal to zero. We show convergence to equilibrium for power-law coagulation and fragmentation rates and obtain a loss of mass in the limit t rightarrow infty depending on the initial mass and the relative strengths of the coagulation and fragmentation processes. In the case of linear rates, we further show that large clusters evolve in a self-similar manner at large times by comparing limits of appropriately rescaled solutions in different spaces.

Atmospheric Circulation Anomalies and Key Physical Processes behind Two Categories of Anomalous Eurasian Spring Snowmelt

Abstract Eurasian spring snowmelt plays an important role in the subsequent climate and hydrological cycle, however, the understanding of snowmelt itself and its causes remains insufficient. This study explored the basic characteristics of spring snowmelt in the eastern Europe–western Siberia (EEWS) region by classifying snowmelt anomalies into two categories based on the different factors that dominate spring snowmelt, and then investigated the associated atmospheric circulation anomalies and local physical processes. The first category of anomalous snowmelt (category 1) is controlled by both the initial snow mass and the later snowmelt process, while the second category of anomalous snowmelt (category 2) is mainly linked to the later snowmelt process. Specifically, category 1 is characterized by an anomalous trough in EEWS in winter, where water vapor transported and converged, accompanied by anomalous upward motion, which promotes snowfall and snow accumulation, providing initial conditions conducive to snowmelt. In April, this region is controlled by an anomalous ridge, with significant warm advection anomalies and subsidence promoting surface warming, thereby accelerating snow melting. In contrast, the winter circulation anomalies are insignificant in category 2, while the anomalous ridge in April is stronger than in category 1, accompanied by more intense snowmelt processes. In addition, from the surface energy balance perspective, atmospheric downward sensible heat transport is an important factor influencing the anomalous snowmelt in category 1, while shortwave radiation plays a secondary role. Conversely, the snowmelt in category 2 is dominated by shortwave radiation forcing, but the sensible heat effect is slightly weaker. Significance Statement Eurasian spring snowmelt significantly impacts the subsequent climate and hydrological cycle, but the understanding of snowmelt itself and its causes is still inadequate. The purpose of this study is to explore the monthly evolution of atmospheric circulation associated with anomalous snowmelt and its local physical processes associated by categorizing them based on snowmelt characteristics. Category 1 is jointly affected by winter snow accumulation and later warming, while category 2 is dominated by strong snowmelt process in late spring. These two categories are accompanied by different winter and spring circulation configurations. Our results provide a basis for further investigation of snowmelt precursor signals.

The origin of the planetary nebula M 1–16

We investigated the origin of the Planetary Nebula (PN) M 1–16 using narrow-band optical imaging, and high- and low-resolution optical spectra to perform a detailed morpho-kinematic and chemical studies. M 1–16 is revealed to be a multipolar PN that predominantly emits in [O III] in the inner part of the nebula and [N II] in the lobes. A novel spectral unsharp masking technique was applied to the position-velocity (PV) maps to reveal a set of multiple structures at the centre of M 1–16 spanning radial velocities from −40 km s−1 to 20 km s−1, with respect to the systemic velocity. The morpho-kinematic model indicates that the deprojected velocity of the lobe outflows are ≥100 km s−1, and particularly the larger lobes and knots have a deprojected velocity of ≃350 km s−1; the inner ellipsoidal component has a deprojected velocity of ≃29 km s−1. A kinematical age of ~8700 yr has been obtained from the model assuming a homologous velocity expansion law and a distance of 6.2 ± 1.9 kpc. The chemical analysis indicates that M 1–16 is a Type I PN with a central star of PN (CSPN) mass in the range of ≃0.618 – 0.713 M⊙ and an initial mass for the progenitor star between 2.0 and 3.0 M⊙ (depending on metallicity). An Teff ≃ 140 000 K and log(L/L⊙) = 2.3 was estimated using the 3MdB photoionisation models to reproduce the ionisation. stage of the PN. All of these results have led us to suggest that M 1–16 is an evolved PN, contrary to the scenario of proto-PN suggested in previous studies. We propose that the mechanism responsible for the morphology of M 1–16 is related to the binary (or multiple star) evolution scenario.

Evolved massive stars at low-metallicity

The mass-loss rate (MLR) is one of the most important parameters in astrophysics, because it impacts many areas of astronomy, such as ionizing radiation, wind feedback, star-formation rates, initial mass functions, stellar remnants, supernovae, and so on. However, the most important modes of mass loss are also the most uncertain, as the dominant physical mechanisms that lead to this phenomenon are stull largely unknown. Here we assemble the most complete and clean red supergiant (RSG) sample (2121 targets) so far in the Small Magellanic Cloud (SMC) with 53 different bands of data to study the MLR of RSGs. In order to match the observed spectral energy distributions (SEDs), we created a theoretical grid of 17 820 oxygen-rich models (“normal” and “dusty” grids are half-and-half) using the radiatively driven wind model of the DUSTY code, covering a wide range of dust parameters. We select the best model for each target by calculating the minimal modified chi-square and visual inspection. The resulting MLRs from DUSTY are converted to real MLRs based on the scaling relation, for which a total MLR of 6.16 × 10−3 M⊙ yr−1 is measured (corresponding to a dust-production rate of ∼6 × 10−6 M⊙ yr−1), with a typical MLR of ∼10−6 M⊙ yr−1 for the general population of the RSGs. The complexity of mass-loss estimations based on the SED is fully discussed for the first time, and our results indicate large uncertainties based on the photometric data (potentially up to one order of magnitude or more). The Hertzsprung-Russell (HR) and luminosity versus median-absolute-deviation (MAD) diagrams of the sample indicate the positive relation between luminosity and MLR. Meanwhile, the luminosity versus MLR diagrams show a “knee-like” shape with enhanced mass loss occurring above log10(L/L⊙)≈4.6, which may be due to the degeneracy of luminosity, pulsation, low surface gravity, convection, and other factors. We derive our MLR relation using a third-order polynomial to fit the sample and compare our results with previous empirical MLR prescriptions. Given that our MLR prescription is based on a much larger sample than previous determinations, it provides a more accurate relation at the cool and luminous region of the HR diagram at low metallicity compared to previous studies. Finally, nine targets in our sample were detected in the UV, which could be an indicator of OB-type companions of binary RSGs.

Possible Detection of the Progenitor of the Type II Supernova SN 2023ixf

Stellar evolution theory predicts multiple pathways to the explosive deaths of stars as supernovae. Locating and characterizing the progenitors of well-studied supernovae is important to constrain the theory and to justify and design future surveys to improve on progenitor detections. Here we report the serendipitous preexplosion imaging, by the Hubble Space Telescope, of SN 2023ixf, one of the nearest extragalactic supernovae ever discovered, in the galaxy M101. The extremely red color and absolute magnitude mag suggest that the progenitor was a red supergiant. Comparison with stellar evolutionary isochrones suggests it is within the relatively low initial mass range of ∼8–10 M ⊙ and that there is likely a lot of dust present at the supernova site.

Diffuse Neutrino Flux Based on the Rates of Core-collapse Supernovae and Black Hole Formation Deduced from a Novel Galactic Chemical Evolution Model

Fluxes of the diffuse supernova neutrino background (DSNB) are calculated based on a new modeling of galactic chemical evolution, where a variable stellar initial mass function (IMF), depending on the galaxy type, is introduced and black hole (BH) formation from the failed supernova is considered for progenitors heavier than 18M ⊙. The flux calculations are performed for different combinations of the star formation rate, nuclear equation of state, and neutrino mass hierarchy, to examine the systematic effects from these factors. In any case, our new model predicts the enhanced DSNB flux at E ν ≳ 30 MeV and E ν ≲ 10 MeV, due to more frequent BH formation and a larger core-collapse rate at high redshifts in early-type galaxies, respectively. Event rate spectra of the DSNB at a detector from the new model are shown, and the detectability at water-based Cherenkov detectors, Super-Kamiokande with a gadolinium dissolution and Hyper-Kamiokande, is discussed. In order to investigate the impacts of the assumptions in the new model, we prepare alternative models, based on different IMF forms and treatments of BH formation, and estimate the discrimination capabilities between the new and alternative models at these detectors.

Failed supernovae as a natural explanation for the binary black hole mass distribution

Context. As the number of detected gravitational wave sources increases, the better we can understand the mass distribution of binary black holes (BBHs). This “stellar graveyard” shows several features, including an apparent mass gap that makes the distribution bimodal. In turn, the observed chirp mass distribution appears to be trimodal. Aims. We aim to investigate the extent to which we can explain the observed mass distribution based on stellar evolution, specifically with the hypothesis that the mass gap is caused by the difference between successful and failed supernovae (SNe). Methods. We posed a hypothetical remnant function, based on the literature of stellar evolution simulations, which relates initial mass to remnant mass, while including a “black hole island” and producing a bimodal remnant distribution. Moreover, we looked at observed type II SN rates in an attempt to detect the effect of failed SNe. Finally, using a simplified estimation of binary evolution, we determined the remnant distribution resulting from our remnant function and compared it with observations. Results. We find that failed SNe lower type II SN rates by approximately 25%, but the inferred rate from SN surveys is not accurate enough to confirm this. Furthermore, our estimation based on the remnant function produces a mass distribution that matches the general shape of the observed distributions of individual as well as chirp masses. Conclusions. Based on our research, we conclude that the failed SN mechanism and the presence of the black hole island are a natural hypothesis for explaining the individual BBH mass distribution and chirp mass distribution. However, to obtain a firmer conclusion, more detailed simulations are needed.

A Luminous Red Supergiant and Dusty Long-period Variable Progenitor for SN 2023ixf

We analyze pre-explosion near- and mid-infrared (IR) imaging of the site of SN 2023ixf in the nearby spiral galaxy M101 and characterize the candidate progenitor star. The star displays compelling evidence of variability with a possible period of ≈1000 days and an amplitude of Δm ≈ 0.6 mag in extensive monitoring with the Spitzer Space Telescope since 2004, likely indicative of radial pulsations. Variability consistent with this period is also seen in the near-IR J and K s bands between 2010 and 2023, up to just 10 days before the explosion. Beyond the periodic variability, we do not find evidence for any IR-bright pre-supernova outbursts in this time period. The IR brightness ( mag) and color (J − K s = 1.6 mag) of the star suggest a luminous and dusty red supergiant. Modeling of the phase-averaged spectral energy distribution (SED) yields constraints on the stellar temperature ( K) and luminosity (). This places the candidate among the most luminous Type II supernova progenitors with direct imaging constraints, with the caveat that many of these rely only on optical measurements. Comparison with stellar evolution models gives an initial mass of M init = 17 ± 4 M ⊙. We estimate the pre-supernova mass-loss rate of the star between 3 and 19 yr before explosion from the SED modeling at to 3 × 10−4 M ⊙ yr−1 for an assumed wind velocity of v w = 10 km s−1, perhaps pointing to enhanced mass loss in a pulsation-driven wind.

Thermally Reduced Graphene Oxide Membranes Revealed Selective Adsorption of Gold Ions from Mixed Ionic Solutions.

The recovery of gold from water is an important research area. Recent reports have highlighted the ultrahigh capacity and selective extraction of gold from electronic waste using reduced graphene oxide (rGO). Here, we made a further attempt with the thermal rGO membranes and found that the thermal rGO membranes also had a similarly high adsorption efficiency (1.79 g gold per gram of rGO membranes at 1000 ppm). Furthermore, we paid special attention to the detailed selectivity between Au3+ and other ions by rGO membranes. The maximum adsorption capacity for Au3+ ions was about 16 times that of Cu2+ ions and 10 times that of Fe3+ ions in a mixture solution with equal proportions of Au3+/Cu2+ and Au3+/Fe3+. In a mixed-ion solution containing Au3+:Cu2+:Na+:Fe3+:Mg2+ of printed circuit board (PCB), the mass of Au3+:Cu2+:Na+:Fe3+:Mg2+ in rGO membranes is four orders of magnitude higher than the initial mass ratio. A theoretical analysis indicates that this selectivity may be attributed to the difference in the adsorption energy between the metal ions and the rGO membrane. The results are conducive to the usage of rGO membranes as adsorbents for Au capture from secondary metal resources in the industrial sector.

Unboundedness phenomenon in a model of urban crime

We show that spatial patterns (“hotspots”) may form in the crime model [Formula: see text] which we consider in [Formula: see text], [Formula: see text], [Formula: see text] with [Formula: see text], [Formula: see text] and initial data [Formula: see text], [Formula: see text] with sufficiently large initial mass [Formula: see text]. More precisely, for each [Formula: see text] and fixed [Formula: see text], [Formula: see text] and (large) [Formula: see text], we construct initial data [Formula: see text] exhibiting the following unboundedness phenomenon: Given any [Formula: see text], we can find [Formula: see text] such that the first component of the associated maximal solution becomes larger than [Formula: see text] at some point in [Formula: see text] before the time [Formula: see text]. Since the [Formula: see text] norm of [Formula: see text] is decreasing, this implies that some heterogeneous structure must form. We do this by first constructing classical solutions to the nonlocal scalar problem [Formula: see text] from the solutions to the crime model by taking the limit [Formula: see text] under the assumption that the unboundedness phenomenon explicitly does not occur on some interval [Formula: see text]. We then construct initial data for this scalar problem leading to blow-up before time [Formula: see text]. As solutions to the scalar problem are unique, this proves our central result by contradiction.

A model for GN-z11: top-heavy stellar initial mass functions in forming galactic nuclei and ultra-compact dwarfs

ABSTRACT Recent JWST observations of the z = 10.6 galaxy GN-z11 have revealed a very high gas-phase nitrogen abundance (higher than four times the solar value), a very small half-light radius (≈60 pc), and a large stellar mass (Ms ≈ 109 M⊙) for its size. We consider that this object is a forming galactic nucleus or ultra-compact dwarf galaxy rather than a proto globular cluster, and thereby investigate the chemical abundance pattern using one-zone chemical evolution models. The principal results of the models are as follows. The observed log (N/O) > −0.24, log (C/O) > −0.78, and 12 + log (O/H) ≈ 7.8 can be self-consistently reproduced by the models both with very short star formation time-scales (<107 yr) and with top-heavy stellar initial mass functions. The adopted assumption of no chemical enrichment by massive (m > 25 M⊙) core collapse supernovae (CCSNe) is also important for the reproduction of high gas-phase log (N/O), because such CCSNe can decrease high log (N/O) of gas polluted by OB and Wolf–Rayet stars. GN-z11 can have a significant fraction (>0.5) of nitrogen-rich ([N/Fe] > 0.5) stars, which implies a possible link between nitrogen-rich stellar populations of the inner Galaxy and giant elliptical galaxies and high-z objects with high gas-phase log (N/O) like GN-z11.

A micro-sized high-temperature thorium reactor with Duplex TRISO fuel with enhanced thorium utilization compared to the SBU configuration

This study offers a neutronisc core calculation to assess the potential of the compact microheterogeneous thorium-uranium TRistructural ISOtropic (TRISO) fuel design for the micro-modular high temperature reactor. The Duplex-fueled core and the Seed-and-Blanket-Unit (SBU)-fueled core were modelled and compared using the MCNPX 2.7 Monte Carlo code. The Th:U ratio and initial fissile mass of both cores were set to be the same. The dispersion of thorium and uranium in the Duplex-fueled core is more uniform compared to that in the SBU-fueled core. The study demonstrates that Duplex TRISO fuel offers both improved core power distribution uniformity and superior neutronic performance compared to SBU fuel in a core. The utilisation of a Duplex-fueled core leads to a 5 % higher core conversion ratio and resonance capture rate, which ultimately results in an extra long-term production of 233U. Additionally, its FTC value is lower. The required material and thickness of the neutron reflector, are also discussed, though only as a preliminary analysis. Nevertheless, the findings clearly demonstrate that the Duplex TRISO fuel design concept offers valuable flexibility and optimization in the distribution of fertile and fissile material mass. These characteristics are of utmost importance for the advancement of thorium reactors, as they significantly enhance neutronic performance.

Tidal Angular Momentum in Close Binary Systems in presence of Wind Driven Non-conservative Mass Transfer with Uniform Mass Accretion Rate

A very well-known property of close binary stars is that they usually rotate slowly than a similar type single star. Massive stars in close binary systems are supposed to experience an exchange of mass and angular momentum via mass transfer and tidal interaction, and thus the evolution of binary stars becomes more complex than that of individual stars. In recent times, it has become clear that a large number of massive stars interact with binary companions before they die. The observation also reveals that in close pairs the rotation tends to be synchronized with the orbital motion and the companions are naturally tempted to invoke tidal friction. We here introduce the effect of tidal angular momentum in the model of wind driven non-conservative mass transfer taking mass accretion rate as uniform with respect to time. To model the angular momentum evolution of a low mass main sequence companion star can be a challenging task. So, to make the present study more interesting, we have considered initial masses of the donor and gainer stars at the proximity of bottom-line main sequence stars and they are taken with lower angular momentum. We have produced a graphical profile of the rate of change of tidal angular momentum and the variation of tidal angular momentum with respect to time under the present consideration.

The energy distribution of the first supernovae

ABSTRACT The nature of the first Pop III stars is still a mystery and the energy distribution of the first supernovae is completely unexplored. For the first time we account simultaneously for the unknown initial mass function (IMF), stellar mixing, and energy distribution function (EDF) of Pop III stars in the context of a cosmological model for the formation of a MW-analogue. Our data-calibrated semi-analytic model is based on a N-body simulation and follows the formation and evolution of both Pop III and Pop II/I stars in their proper time-scales. We discover degeneracies between the adopted Pop III unknowns, in the predicted metallicity and carbonicity distribution functions and the fraction of C-enhanced stars. None the less, we are able to provide the first available constraints on the EDF, $dN/dE_\star \propto E_{\star }^{-\alpha _e}$ with 1 ≤ αe ≤ 2.5. In addition, the characteristic mass of the Pop III IMF should be mch < 100 M⊙, assuming a mass range consistent with hydrodynamical simulations (0.1–1000 M⊙). Independent of the assumed Pop III properties, we find that all $\rm [C/Fe]\gt +0.7$ stars (with $\rm [Fe/H]\lt -2.8$) have been enriched by Pop III supernovae at a $\gt 20~{{\ \rm per\ cent}}$ level, and all $\rm [C/Fe]\gt +2$ stars at a $\gt 95~{{\ \rm per\ cent}}$ level. All very metal-poor stars with $\rm [C/Fe]\lt 0$ are predicted to be predominantly enriched by Pop III hypernovae and/or pair instability supernovae. To better constrain the primordial EDF, it is absolutely crucial to have a complete and accurate determination of the metallicity distribution function, and the properties of C-enhanced metal-poor stars (frequency and [C/Fe]) in the Galactic halo.

Performance analysis on the structure of the bracket mounting for hybrid converter kit: Finite-element approach

Abstract An electric motor mounting bracket is used in electric vehicles, especially hybrid ones using a parallel hybrid configuration. This study aims to analyze the strength and performance of the initial design and topology optimized design. This study uses the finite-element method (FEM) in the bracket design modeling by applying topology optimization. The topology optimization results show a mass reduction of 50% from the initial design mass. In the case of static loading, the results of optimized design 2 have a stress of 142.19 MPa and a safety factor of 3.09. While optimized design 1 has a stress of 313.8 MPa and a safety factor of 1.4. In terms of dynamic loading, the initial design, optimized design 1, and optimized design 2 have the first natural frequency, which is higher than the operating frequency of the electric motor, respectively, 100.49, 69.043, and 74.864 Hz. Optimized design 1 has the lowest natural frequency and the highest amplitude compared to the initial design, and optimized design 2 has lower damping characteristics. The study results conclude that optimized design 2 is superior in static and dynamic loading.

Long-duration Gamma-Ray Burst Progenitors and Magnetar Formation

Millisecond magnetars produced in the center of dying massive stars are one prominent model to power gamma-ray bursts (GRBs). However, their detailed nature remains a mystery. To explore the effects of the initial mass, rotation rate, wind mass loss, and metallicity on the GRB progenitors and the newborn magnetar properties, we evolve 227 of 10–30 M ⊙ single star models from the pre-main sequence to core collapse by using the stellar evolution code MESA. The presupernova properties, the compactness parameter, and the magnetar characteristics of models with different initial parameters are presented. The compactness parameter remains a nonmonotonic function of the initial mass and initial rotation rate when the effects of varying metallicity and the “Dutch” wind scale factor are taken into account. We find that the initial rotation rate and mass play the dominant roles in whether a star can evolve into a GRB progenitor. The minimum rotation rate necessary to generate a magnetar gradually reduces as the initial mass increases. The greater the initial metallicity and “Dutch” wind scale factor, the larger the minimum rotation rate required to produce a magnetar. In other words, massive stars with low metallicity are more likely to harbor magnetars. Furthermore, we present the estimated period, magnetic field strength, and masses of magnetars in all cases. The typical rotational energy of these millisecond magnetars is sufficient to power long-duration GRBs.

Effects of sample mass and suspension salinity on particle size distribution in predominantly medium to heavy textured soils using the hydrometer method

AbstractBackgroundParticle size distribution (PSD) is a fundamental soil measurement that is crucial for agriculture, engineering, hydrological, and environmental applications as well as in basic research such as in developing water release curves in flow and transport modeling. The accurate determination of PSD, particularly clay content, is especially critical in ascertaining the magnitude and rates of many physical, chemical, and hydrological processes in soils. The accuracy of the hydrometer method for PSD, which relies on the settling velocity of soil particles in a soil suspension, could be affected by the density of the suspension, which in turn, depends on the initial sample mass, texture, and mineralogy of the soil.AimsWe hypothesized that (1) initial mass determines the concentration and the physical interaction of particles in a soil suspension and affects particle settlement, recovery, and the accuracy of the hydrometer method, and (2) the widely used initial air‐dry mass of 50 g underestimates the clay percentage of medium to heavy textured tropical soils. The objective of this study was to investigate the effect of mass and KCl on clay recovery in tropical soils with varying texture and mineralogy using the hydrometer method.MethodsThe experiment comprised seven soils, four soil masses (10, 20, 30, 50 g), and two KCl treatments in a 7 × 4 × 2 factorial design replicated three times.ResultsResults showed a general trend of increasing estimates of clay % as the soil mass decreased from 50 to 10 g and the KCl concentration increased from 0 to 0.0025 M. This implies that using an initial sample mass of 50 g in sedimentation methods, underestimates, and 10 g overestimates the clay % in predominantly medium to heavy textured tropical soils. Interestingly, there was a drastic change in texture for most of the soils as the sample mass decreased to 10 g.ConclusionsWe conclude that the initial air‐dry mass affects the clay recovery of medium to heavy textured humid tropical soils. Results suggest that the ideal initial mass for these soils lies between 20 and 30 g. Furthermore, the mechanistic pathway that drives the observed decrease in clay recovery as soil sample mass increase could be due to the flocculating tendency of KCl.