Initial Mass Research Articles

Predicting pesticide residues in pod fruits with a modified peel-like uptake model: A green pea demonstration

Peas are among the most popular leguminous plants, consumed by both humans and animals in large quantities. Pesticides are widely used globally to increase pea yield, and as a result, pesticide residues can be taken up by pea plants and bioaccumulate in their fruits, including peas and pods. However, there is a lack of modeling approaches available to predict residue concentrations in peas. To address this issue, a pod fruit model (specifically designed for neutral organic compounds) was proposed to simulate the bioaccumulation process of pesticide residues in pea plants, which was developed by modifying a peel-like uptake model. The simulation results, based on green pea as the modeling demonstration, reveal that moderately-lipophilic pesticides (i.e., log KOW around 3) have higher simulated concentrations in peas at harvest compared to hydrophilic (i.e., log KOW less than 0) or highly-lipophilic (i.e., log KOW over 5) pesticides, which is due to the enhanced uptake process of moderately-lipophilic compounds in the pod-pea system, such as their ability to penetrate the pod cuticle and be transported via phloem sap. The sensitivity test and variability analysis conducted in this study revealed that the degradation kinetics, including metabolism, hydrolysis, and photolysis, had a significant impact on moderately-lipophilic pesticides due to their high simulated concentrations in the pea plant. This can result in substantial loss of residue mass via degradation. The validation of the model demonstrated that the simulation results, specifically residue concentrations in the fruit, were consistent with the harvested data. However, some inconsistency was observed immediately after pesticide application, which could be attributed to plant growth dynamics and initial surface mass distributions. The proposed pod fruit model provides new insights into the bioaccumulation process of pesticide residues in pea plants and enables high-throughput simulations of residue concentrations at harvest. To enhance the performance of the pod fruit model, future research should consider plant growth dynamics, plant uptake of ionizable compounds, and initial mass distribution functions.

Toxicological and hygienic assessment of modern thermo-insulating polymer materials during thermal exposure

Introduction. Polyethylene and synthetic foam caoutchouc are used for thermal insulation of communications, at temperatures not exceeding 90 °C and 105 °C, respectively. Data on how these materials will behave in the appropriate temperature conditions was not be found. 
 The purpose of the study was to conduct a toxicological and hygienic assessment of products made of polyethylene foam and synthetic foam rubber under thermal exposure.
 Materials and methods. The thermal effect on the studied samples was modelled in a climate chamber. The time interval during the mass loss of the samples was determined, a sanitary and chemical study of the gas-air mixture in the climatic chamber was carried out. To conduct a toxicological and hygienic study in animals, a swim-escape conditioned active avoidance response was developed.
 Results. Under thermal (90 °C) exposure for 72 hours to polyethylene tube, a loss of 0.77% of the initial mass of the sample occurs. Thermal exposure (105 °C) to synthetic foam caoutchouc resulted in a loss of 15.3% of the initial mass of the sample for 108 hours, while pronounced changes in the appearance of the samples were determined. When conducting a sanitary and chemical study in the climate chamber, an increase in the concentration of carbon monoxide was determined after 12, 24, and 72 hours and hydrogen chloride after 12 and 24 hours following the onset of thermal exposure compared with the values of their average daily maximum permissible concentration. Thermal exposure to the sample and synthetic foam caoutchouc led to an increase in the concentration of ammonia, carbon monoxide and hydrogen chloride 12 and 24 hours after the start of exposure compared with the average daily maximum permissible concentration. During the toxicological and hygienic study, animals exposed to thermal degradation products of the materials under study were revealed to show learning disabilities.
 Limitations. They are conditioned by the methodology of the study. A quantitative analysis of some gaseous thermal degradation products released into the climate chamber was performed, without taking into account the aerosols formed.
 Conclusion. Thermal insulation materials made of synthetic foam rubber and polyethylene foam lose their structural properties when they are operated in the maximum permissible temperature conditions (105 °C and 90 °C, respectively). When they are used in appropriate temperature conditions, the formation of toxic products occurs, the inhalation effect of which leads to a disturbances of the learning ability in laboratory animals.

Simulation of Head-on Collisions between Filamentary Molecular Clouds Threaded by a Lateral Magnetic Field and Subsequent Evolution

Filamentary molecular clouds are regarded as the place where newborn stars form. In particular, a hub region, a place where it appears as if several filaments are colliding, often indicates active star formation. To understand the star formation in filament structures, we investigate the collisions between two filaments using two-dimensional magnetohydrodynamical simulations. As a model of filaments, we assume that the filaments are in magnetohydrostatic equilibrium under a global magnetic field perpendicular to the filament axis. We set two identical filaments with an infinite length and make them collide with a zero-impact parameter (head-on). When the two filaments collide while sharing the same magnetic flux, we found two types of evolution after a merged filament is formed: runaway radial collapse and stable oscillation with a finite amplitude. The condition for the radial collapse is independent of the collision velocity and is given by the total line mass of the two filaments exceeding the magnetically critical line mass for which no magnetohydrostatic solution exists. The radial collapse proceeds in a self-similar manner, resulting in a unique distribution irrespective of the various initial line masses of the filament, as the collapse progresses. When the total line mass is less massive than the magnetically critical line mass, the merged filament oscillates, and the density distribution is well-fitted by a magnetohydrostatic equilibrium solution. The condition necessary for the radial collapse is also applicable to the collision whose direction is perpendicular to the global magnetic field.

Spectroscopic substellar initial mass function of NGC 2244

Context. The dominant formation channel of brown dwarfs (BDs) is not well constrained yet and a promising way to discriminate between scenarios is to test the environment-dependent efficiency in forming BDs. So far, the outcome of star formation, studied through the initial mass function, has been found to be very similar in all clusters that have been inspected. Aims. We aim to characterize the low-mass (sub)stellar population of the central portion (2.4 pc2) of the ∼2 Myr old cluster NGC 2244 using near-infrared spectroscopy. By studying this cluster, characterized by a low stellar density and numerous OB stars, we aim to explore the effect that OB stars may have on the production of BDs. Methods. We obtained near-infrared HK spectroscopy of 85 faint candidate members of NGC 2244. We derived the spectral type and extinction by comparison with spectral templates. We evaluated cluster membership using three gravity-sensitive spectral indices based on the shape of the H-band. Furthermore, we evaluated the infrared excess from Spitzer of all the candidate members of the cluster. Finally, we estimated the mass of all the candidate members of the cluster and derived the initial mass function, star-to-BD number ratio, and disk fraction. Results. The initial mass function is well represented by a power law (dN/dM ∝ M−α) below 0.4 M⊙, with a slope α = 0.7–1.1 depending on the fitted mass range. We calculated a star-to-BD number ratio of 2.2–2.8. We find the low-mass population of NGC 2244 to be consistent with nearby star-forming regions, although it is at the high end of BD production. We find BDs in NGC 2244 to be, on average, closer to OB stars than to low-mass stars, which could potentially be the first piece of evidence that OB stars affect the formation of BDs. We find a disk fraction of all the members with a spectral type later than K0 of 39 ± 9% which is lower than typical values found in nearby star-forming regions of similar ages.

Investigation on pyrolysis mechanism and emission characteristics of CO2, NOx and SO2 during co-pyrolysis of coal gangue and sodium alginate/sodium carboxymethylcellulose/chitosan/guar gum

Biomass materials are potential to promote coal gangue pyrolysis process. This study investigates the effects of four biomass materials derived from different sources, namely sodium alginate (SA), sodium carboxymethyl cellulose (CMC), chitosan (CS), and guar gum (GG), on the pyrolysis of coal gangue (CG) in a nitrogen atmosphere. Thermal gravimetric analysis coupled with mass spectrometry (TG-MS) was used to analyze the thermal behaviors and emission characteristics of CO2, NOx, and SO2 during the co-pyrolysis process of CG and the four different biomaterial blends, which were mixed in varying ratios. The study investigated that the interactions between the various biomaterials and CG by calculating and comparing pyrolysis parameters, such as the comprehensive pyrolysis index (CPI) of CG and the blends. Additionally, a kinetic analysis using the Kissinger-Akahira-Sunose (KAS) method was conducted to reveal the co-pyrolysis mechanism. The thermal gravity analysis results illustrated that SA, CMC, CS and GG were all conducive to enhancing CG pyrolysis. As the biomass content in the blends increases, the sample experiences greater mass loss, while the initial pyrolysis temperature and residual mass ratio decrease. This suggests the presence of biomass enables more complete pyrolysis reactions of CG. Among the four biomass materials, GG had the most positive effect on promoting CG pyrolysis, followed by CS and SA, with CMC having the least effect. The kinetic analysis showed that the primary step of each blend sample generally conformed to the first-order kinetic model. The calculated activation energies of blends groups were lower than that of CG pyrolysis, verifying the positive effects of the four biomaterials on CG pyrolysis. However, the interaction mechanism varied in different pyrolysis stages for each type of biomass material. Gas emission analysis indicated that the emission of CO2, NOx and SO2 in blends groups were significantly lower than that of CG pyrolysis. This implies that the addition of the four biomaterials could effectively control the emission of carbon dioxide and pollutants during CG pyrolysis.

On the Size of the Safety Area around the Launch Trajectory of a Rocket

The safety zone around the flight path of a rocket is determined by the fall of debris in the case of an accidental explosion or commanded termination. The trajectory of a tumbling body in a vertical plane is determined by specifying the velocity, flight path angle and angle of attack as functions of time. This involves the lift, drag and pitching moment coefficients as functions of the angle of attack over a full circle—0 to 360 degrees—to account for the tumbling motion. The problem is reduced to a third-order non-linear differential equation for the angle of attack by using the approximation of free fall coordinates. The analytical and numerical solutions show that two types of tumbling fall are possible, one with rotation and the other with oscillation. The tumbling trajectories are plotted and discussed for a variety of initial conditions, mass and aerodynamic properties of the tumbling body.

Quantitative Analysis of The High-Yield Hydrolysis of Kelp by Laminarinase and Alginate Lyase.

Kelp is an abundant, farmable biomass-containing laminarin and alginate as major polysaccharides, providing an excellent model substrate to study their deconstruction by simple enzyme mixtures. Our previous study showed strong reactivity of the glycoside hydrolase family 55 during hydrolysis of purified laminarin, raising the question of its reactivity with intact kelp. In this study, we determined that a combination of a single glycoside hydrolase family 55 β-1,3-exoglucanase with a broad-specificity alginate lyase from the polysaccharide lyase family 18 gives efficient hydrolysis of untreated kelp to a mixture of simple sugars, that is, glucose, gentiobiose, mannitol-end glucose, and mannuronic and guluronic acids and their soluble oligomers. Quantitative assignments from nanostructure initiator mass spectrometry (NIMS) and 2D HSQC NMR spectroscopy and analysis of the reaction time-course are provided. The data suggest that binary combinations of enzymes targeted to the unique polysaccharide composition of marine biomass are sufficient to deconstruct kelp into soluble sugars for microbial fermentation.

Accretion spin-up of the massive component in the neutron star stripping model for short gamma-ray bursts

ABSTRACT In this paper, we use analytical methods to study the last stages of the double neutron star (NS) system evolution. Depending on the initial masses of the components, this evolution can occur either in the framework of the merging scenario or in the NS stripping model. The main new ingredient of this work, compared with previous calculations, is accounting for accretion spin-up of the massive component. This effect leads to a significant decrease in the duration of the stable mass transfer of matter in the stripping mechanism. Within the framework of the Newtonian approximation, we determine the boundary between the merging and stripping scenarios. It is shown that this boundary weakly depends on the total mass of the system and the specific form of the NS equation of state, and is determined mainly by the initial mass ratio of the components. The stripping scenario is realized at M2/M1 ≲ 0.8, so it should make a large contribution to the population of gravitational wave events from NS–NS coalescing binaries that are close to us, and their accompanying short gamma-ray bursts. Nevertheless, the value obtained requires further clarification, taking into account relativistic effects, possible non-conservative mass transfer, etc.

The cardiovascular polypill as baseline treatment improves lipid profile and blood pressure regardless of body mass index in patients with cardiovascular disease. The Bacus study.

Pharmacological treatment with lipid-lowering and antihypertensive drugs has been proposed as a strategy to improve excess cardiovascular (CV) risk among obese individuals. The present study aimed to assess whether the CV polypill (Sincronium®) could be an effective strategy to help improve CV risk factor control in obese/overweight individuals requiring secondary prevention. This was an observational, retrospective study reviewing the hospital medical records of 479 patients with established CV disease who initiated treatment with the CV polypill between 2013 and 2019 at a general hospital in Mexico. Patients were grouped as normal weight, overweight or obese according to their initial body mass index (BMI). We collected blood pressure (BP), lipid profile, and vascular age at the last visit recorded during the period following treatment. At the end of the study, all assessed lipid parameters improved compared to baseline regardless of the initial BMI category (all p<0.001). There was an increase from baseline regarding the proportion of patients with at target low-density lipoprotein cholesterol after treatment (2.3% vs. 30.1%; p<0.001), more than 80% of patients achieved triglyceride levels <200 mg/dL (p<0.001), and more than 80% achieved target BP levels in all BMI subgroups (p<0.001). The subanalyses in the elderly population yielded similar results, with a significant overall improvement in lipid and BP control after initiating the CV polypill strategy. The use of the CV polypill as baseline therapy for secondary prevention seems to be a reasonable strategy that enhances CV risk factor control regardless of the patient's BMI.

The γ-process nucleosynthesis in core-collapse supernovae

Context. The γ-process nucleosynthesis in core-collapse supernovae is generally accepted as a feasible process for the synthesis of neutron-deficient isotopes beyond iron. However, crucial discrepancies between theory and observations still exist: the average yields of γ-process nucleosynthesis from massive stars are still insufficient to reproduce the solar distribution in galactic chemical evolution calculations, and the yields of the Mo and Ru isotopes are a factor of ten lower than the yields of the other γ-process nuclei. Aims. We investigate the γ-process in five sets of core-collapse supernova models published in the literature with initial masses of 15, 20, and 25 M⊙ at solar metallicity. Methods. We compared the γ-process overproduction factors from the different models. To highlight the possible effect of nuclear physics input, we also considered 23 ratios of two isotopes close to each other in mass relative to their solar values. Further, we investigated the contribution of C–O shell mergers in the supernova progenitors as an additional site of the γ-process. Results. Our analysis shows that a large scatter among the different models exists for both the γ-process integrated yields and the isotopic ratios. We find only ten ratios that agree with their solar values, all the others differ by at least a factor of three from the solar values in all the considered sets of models. The γ-process within C–O shell mergers mostly influences the isotopic ratios that involve intermediate and heavy proton-rich isotopes with A &gt; 100. Conclusions. We conclude that there are large discrepancies both among the different data sets and between the model predictions and the solar abundance distribution. More calculations are needed; particularly updating the nuclear network, because the majority of the models considered in this work do not use the latest reaction rates for the γ-process nucleosynthesis. Moreover, the role of C–O shell mergers requires further investigation.

Study of the behavior of cesium and strontium in co-melting basalt and silica gel containing cesium or strontium nitrates for the development of a potential material for radioactive waste immobilization

The work studied the distribution of cesium and strontium in cast stone matrices obtained by co-melting basalt and silica gel (hereinafter SiO2) containing cesium or strontium nitrates at 1623 K during 5 h. The melt cooling rate was ∼2 °C/min.Co-melting basalt and SiO2 containing CsNO3 or Sr(NO3)2 at a basalt/SiO2 initial mass ratio of 5 : 1 produced cast stone matrices, in which the main phases were Cr–Fe spinel and glass. At the same time co-melting basalt and SiO2 containing CsNO3 or Sr(NO3)2 at an initial mass ratio of 2 : 1 yielded matrices which, apart from Cr–Fe spinel and glass, included pollucite, clinopyroxene, and Ti-containing magnetite phases for Cs-containing system, magnetite and olivine phases for Sr-containing system.For Cs-containing system at a basalt/SiO2 initial mass ratio of 5 : 1 the glass phase showed almost an even distribution of cesium, whereas the spinel phase was virtually free of cesium. At a basalt/SiO2 initial mass ratio of 2 : 1 the major amount of cesium was found in the pollucite phase, where it mainly occurred in parts containing SiO2. Some amount of cesium was found in the glass phase. The other crystal phases found in the matrix were virtually free of cesium.For Sr-containing system at a basalt/SiO2 initial mass ratio of 5 : 1 the process yielded two types of glass: one rich in Ca and the other in Sr. Strontium was mainly found in the glass phases. The spinel phase was virtually free of strontium. At a basalt/SiO2 initial mass ratio of 2 : 1 strontium was mainly found in the glass phases. The magnetite, olivine, and Cr–Fe spinel phases were virtually free of strontium.

Star Formation in Self-gravitating Disks in Active Galactic Nuclei. III. Efficient Production of Iron and Infrared Spectral Energy Distributions

Strong iron lines are a common feature of the optical spectra of active galactic nuclei (AGNs) and quasars from z ∼ 6−7 to the local universe, and [Fe/Mg] ratios do not show cosmic evolution. During active episodes, accretion disks surrounding supermassive black holes (SMBHs) inevitably form stars in the self-gravitating part, and these stars accrete with high accretion rates. In this paper, we investigate the population evolution of accretion-modified stars (AMSs) to produce iron and magnesium in AGNs. The AMSs, as a new type of star, are allowed to have any metallicity but without significant loss from stellar winds, since the winds are choked by the dense medium of the disks and return to the core stars. Mass functions of the AMS population show a pile-up or cutoff pile-up shape in top-heavy or top-dominant forms if the stellar winds are strong, consistent with the narrow range of supernovae (SNe) explosions driven by the known pair-instability. This provides an efficient way to produce metals. Meanwhile, SN explosions support an inflated disk as a dusty torus. Furthermore, the evolving top-heavy initial mass functions lead to bright luminosity in infrared bands in dusty regions. This contributes a new component in infrared bands, which is independent of the emissions from the central part of accretion disks, appearing as a long-term trending of the NIR continuum compared to optical variations. Moreover, the model can be further tested through reverberation mapping of emission lines, including LIGO/LISA detections of gravitational waves and signatures from spatially resolved observations of GRAVITY+/VLTI.

A Value-added COSMOS2020 Catalog of Physical Properties: Constraining Temperature-dependent Initial Mass Function

This work presents and releases a catalog of new photometrically derived physical properties for the ∼105 most well-measured galaxies in the COSMOS field on the sky. Using a recently developed technique, spectral energy distributions are modeled assuming a stellar initial mass function (IMF) that depends on the temperature of gas in star-forming regions. The method is applied to the largest current sample of high-quality panchromatic photometry, the COSMOS2020 catalog, that allows for testing this assumption. It is found that the galaxies exhibit a continuum of IMF and gas temperatures, most of which are bottom-lighter than measured in the Milky Way. As a consequence, the stellar masses and star formation rates of most galaxies here are found to be lower than those measured by traditional techniques in the COSMOS2020 catalog by factors of ∼1.6–3.5 and 2.5–70.0, respectively, with the change being the strongest for the most active galaxies. The resulting physical properties provide new insights into variation of the IMF-derived gas temperature along the star-forming main sequence and at quiescence, produce a sharp and coherent picture of downsizing, as seen from the stellar mass functions, and hint at a possible high-temperature and high-density stage of early galactic evolution.

Bridging the gap between intermediate and massive stars II: Mmas for the most metal-rich stars and implications for Fe CCSNe rates

ABSTRACT The minimum initial mass required for a star to explode as an Fe core collapse supernova, typically denoted Mmas, is an important quantity in stellar evolution because it defines the border between intermediate mass and massive stellar evolutionary paths. The precise value of Mmas carries implications for models of galactic chemical evolution and the calculation of star formation rates. Despite the fact that stars with super-solar metallicities are commonplace within spiral and some giant elliptical galaxies, there are currently no studies of this mass threshold in super metal-rich models with Z &amp;gt; 0.05. Here, we study the minimum mass necessary for a star to undergo an Fe core collapse supernova when its initial metal content falls in the range 2.5 × 10−3 ≤ Z ≤ 0.10. Although an increase in initial Z corresponds to an increase in the Fe ignition threshold for Z ≈ 1 × 10−3 to Z ≈ 0.04, we find that there is a steady reversal in trend that occurs for Z &amp;gt; 0.05. Our super metal-rich models thus undergo Fe core collapse at lower initial masses than those required at solar metallicity. Our results indicate that metallicity-dependent curves extending to Z = 0.10 for the minimum Fe ignition mass should be utilized in galactic chemical evolution simulations to accurately model supernovae rates as a function of metallicity, particularly for simulations of metal-rich spiral and elliptical galaxies.

Zinc oxide – mesoporous silica nanocomposite: preparation, characterisation and application in water treatment for lead, cadmium and chromium removal

ABSTRACT Applications of nanomaterials in water and wastewater treatment and in environmental clean-up operations depend on the adsorption capacity of the materials for contaminants such as potentially toxic elements (PTEs). However, on their own nanoparticles can lose effectiveness as contaminant sorbents because of flocculation and aggregation. Embedding nanoparticles within a silica matrix offers one potential solution to the problem; hence, in this study, zinc oxide nanoparticles (ZnO-NP) were embedded in a mesoporous silica (MCM-41) matrix to create a composite material with potential for contaminants removal from water. The composite material (ZnO-mSiO2) and original ZnO-NP were characterised via UV-Vis, FTIR, XRD, TGA/DTA, BET, and SEM techniques, and were then evaluated for their capacities to remove cadmium (Cd), chromium (Cr) and lead (Pb) from water samples across varying conditions (pH, initial contaminant concentration, contact time and adsorbent mass: solution volume ratios). Langmuir and Freundlich adsorption isotherms were fit to the data to describe the adsorption observed. The ZnO-mSiO2 composite material proved highly effective at removing the PTEs (particularly Pb) across a wide range of conditions, with optimum removal rates achieved at pH 7 and above and 90 minutes contact time.

Adsorptive removal of tetracycline antibiotic onto magnetic graphene oxide nanocomposite modified with polyvinylpyrroilidone

Disposal of pharmaceutical compounds in wastewaters poses potential environmental risk, especially to aquatic life. Herein, magnetic CuFe2O4-graphene oxide (GO) modified with polyvinylpyrrolidone (PVP) ternary nanocomposite (PMGO) was prepared, by a simple ultrasonic method, and successfully applied to the removal of tetracycline (TC) as a model pharmaceutical species. The defect sites of graphene oxide layers served as nucleation centers that allowed the anchoring of both PVP and CuFe2O4 nanoparticles, resulting in reduced agglomeration chances of GO sheets and thus enhanced its TC removal efficiency. Furthermore, the synthesized PMGO was characterized using SEM-EDS, HRTEM, XRD, XPS, FTIR, BET, and VSM. The removal including was optimized by examining the effects of operating parameters, including, initial TC concentration, solution pH, contact time, and PMGO mass. Adsorption isotherms were examined using three-parameters (Hills and Sips) and two-parameters (Langmuir, Freundlich and Tekman) models. PMGO exhibited a maximum adsorption capacity of 193.8 mg/g according to Sips model that exhibited the best fit to experimental data. Moreover, TC removal fitted the PSO kinetics. The removal mechanism was inferred based on adsorption isotherms and kinetic investigations, as well as changes of medium pH and spectral analysis of PMGO composite after adsorption and revealed that electrostatic attraction, π-π interaction, and H-bonding were essential contributing forces, where a TC monolayer was adsorbed onto the PMGO surface and OH− and H+ exerted competitive effects. Importantly, the synthesized nanocomposite exhibited outstanding performance even in the presence of coexisting species (NaCl and SDS surfactant), as well as excellent reusability for practical applications.

Free-floating Planet Mass Function from MOA-II 9 yr Survey toward the Galactic Bulge

We present the first measurement of the mass function of free-floating planets (FFPs), or very wide orbit planets down to an Earth mass, from the MOA-II microlensing survey in 2006–2014. Six events are likely to be due to planets with Einstein radius crossing times t E < 0.5 days, and the shortest has t E = 0.057 ± 0.016 days and an angular Einstein radius of θ E = 0.90 ± 0.14 μas. We measure the detection efficiency depending on both t E and θ E with image-level simulations for the first time. These short events are well modeled by a power-law mass function, dex−1 star−1 with for M/M ⊙ < 0.02. This implies a total of FFPs or very wide orbit planets of mass 0.33 < M/M ⊕ < 6660 per star, with a total mass of star−1. The number of FFPs is times the number of planets in wide orbits (beyond the snow line), while the total masses are of the same order. This suggests that the FFPs have been ejected from bound planetary systems that may have had an initial mass function with a power-law index of α ∼ 0.9, which would imply a total mass of star−1. This model predicts that Roman Space Telescope will detect FFPs with masses down to that of Mars (including with 0.1 ≤ M/M ⊕ ≤ 1). The Sumi et al. large Jupiter-mass FFP population is excluded.

Massive binary black holes from Population II and III stars

ABSTRACT Population III stars, born from the primordial gas in the Universe, lose a negligible fraction of their mass via stellar winds and possibly follow a top-heavy mass function. Hence, they have often been regarded as the ideal progenitors of massive black holes (BHs), even above the pair instability mass gap. Here, we evolve a large set of Population III binary stars (metallicity Z = 10−11) with our population-synthesis code sevn, and compare them with Population II binary stars (Z = 10−4). In our models, the lower edge of the pair-instability mass gap corresponds to a BH mass of ≈86 (≈91) M⊙ for single Population III (II) stars. Overall, we find only mild differences between the properties of binary BHs (BBHs) born from Population III and II stars, especially if we adopt the same initial mass function and initial orbital properties. Most BBH mergers born from Population III and II stars have primary BH mass below the pair-instability gap, and the maximum secondary BH mass is &amp;lt;50 M⊙. Only up to ≈3.3 per cent (≈0.09 per cent) BBH mergers from Population III (II) progenitors have primary mass above the gap. Unlike metal-rich binary stars, the main formation channel of BBH mergers from Population III and II stars involves only stable mass transfer episodes in our fiducial model.

Optimal mass on the parabolic-elliptic-ODE minimal chemotaxis-haptotaxis in

In this paper, we study the Cauchy problem to a chemotaxis-haptotaxis model describing cancer invasion in . The main feature is to prove that 8π is the critical mass on initial data for distinguishing existence and blow-up of solutions to the model. Namely, when the initial mass is less than 8π, we prove global existence of solutions by constructing a proper free energy and using the Brezis-Merle type inequality. On the contrary, the finite time blow-up of solutions may occur if the initial mass is greater than 8π and the initial second moment is small enough. Comparing to the classical Keller-Segel model, we find that the haptotaxis has no effect on the critical mass of the model.

Confirmation and refutation of very luminous galaxies in the early Universe.

During the first 500 million years of cosmic history, the first stars and galaxies formed, seeding the Universe with heavy elements and eventually reionizing the intergalactic medium1-3. Observations withtheJames Webb Space Telescope (JWST) have uncovered a surprisingly high abundance of candidates for early star-forming galaxies, with distances (redshifts, z), estimated from multiband photometry, as large as z ≈ 16, far beyond pre-JWST limits4-9. Althoughsuch photometric redshifts are generally robust, they can suffer from degeneracies and occasionally catastrophic errors. Spectroscopic measurements are required to validate these sources and to reliably quantify physical properties that can constrain galaxy formation models and cosmology10. Here we present JWST spectroscopy that confirms redshifts for two very luminous galaxies with z > 11, and also demonstrates that another candidate with suggested z ≈ 16 instead has z = 4.9, with an unusual combination of nebular line emission and dust reddening that mimics the colours expected for much more distant objects. These results reinforce evidence for the early, rapid formation of remarkably luminous galaxies while also highlighting the necessity of spectroscopic verification. The large abundance of bright, early galaxies may indicate shortcomings in current galaxy formation models or deviations from physical properties (such as the stellar initial mass function) that are generally believed to hold at later times.