Main Shell Research Articles

A JWST Survey of the Supernova Remnant Cassiopeia A

We present initial results from a James Webb Space Telescope (JWST) survey of the youngest Galactic core-collapse supernova remnant, Cassiopeia A (Cas A), made up of NIRCam and MIRI imaging mosaics that map emission from the main shell, interior, and surrounding circumstellar/interstellar material (CSM/ISM). We also present four exploratory positions of MIRI Medium Resolution Spectrograph integral field unit spectroscopy that sample ejecta, CSM, and associated dust from representative shocked and unshocked regions. Surprising discoveries include (1) a weblike network of unshocked ejecta filaments resolved to ∼0.01 pc scales exhibiting an overall morphology consistent with turbulent mixing of cool, low-entropy matter from the progenitor’s oxygen layer with hot, high-entropy matter heated by neutrino interactions and radioactivity; (2) a thick sheet of dust-dominated emission from shocked CSM seen in projection toward the remnant’s interior pockmarked with small (∼1″) round holes formed by ≲0.″1 knots of high-velocity ejecta that have pierced through the CSM and driven expanding tangential shocks; and (3) dozens of light echoes with angular sizes between ∼0.″1 and 1′ reflecting previously unseen fine-scale structure in the ISM. NIRCam observations place new upper limits on infrared emission (≲20 nJy at 3 μm) from the neutron star in Cas A’s center and tightly constrain scenarios involving a possible fallback disk. These JWST survey data and initial findings help address unresolved questions about massive star explosions that have broad implications for the formation and evolution of stellar populations, the metal and dust enrichment of galaxies, and the origin of compact remnant objects.

Study on the oxidation mechanism of micron- and nano-sized aluminum powders influenced by alumina shell

Thermal behaviors for aluminum particles at oxidative atmosphere gradually heating system were discussed. Heating micron- and nano-sized aluminum powders from room temperature to 1400℃ using thermal analysis method. The results showed that the reaction process for micron-sized aluminum particles can be divided into four stages which include the phase change of oxidized shell, increasing thickness of alumina shell, main broken shell oxidizing process and the phase change of alumina shell in high temperature. Thermal analysis for micro aluminum particles was carried out with shell thickness adjustments via ambient manual means. It turned out that the oxide layer thickness would have full limitation effects on the slow oxidation for micro aluminum particles with shell structure when it was increased above twice of the original thickness. The limitation effects of oxide shell thickness on the heating processes in gradually heating system were proposed. Humidity environment can make the thickness of alumina increase in a certain range when the particles are in nano-scale. Complete oxidation processes were observed but an increase of the oxidation temperature was identified.

Nuclear collectivity growth rate in the main shell (Z=56-80, N=84-122) area and its correlation to the valance nucleon product.

Nuclear collectivity growth rate in the main shell (Z=56-80, N=84-122) area and its correlation to the valance nucleon product.

Encapsulation of Carbon Dots in a Core-Shell Mesh through Coaxial Direct Ink Writing for Improved Crop Growth.

Through coaxial direct ink writing, we fabricated a core-shell mesh system for the controlled release of carbon dots (C-dots). In the core ink, we developed an ink formulation with tuned viscosity using hydroxypropyl cellulose and polyethylene glycol to host C-dots. Polycaprolactone was employed as the main shell material, in combination with sodium alginate, to control the degradation rate of the shell. We investigated the degradation profile of the 3D-printed meshes and tracked the weekly release of C-dots in an aqueous medium by spectrofluorometry. We tested the efficacy of the C-dot release on plants by placing the meshes in transparent soil with Triticum aestivum L. seeds. We observed the in vivo translocation of the C-dots in the plant using confocal microscopy. We measured the root elongation and shoot length to assess the effect of C-dots on plant growth. Our study revealed that the plants exposed to C-dots grew 2.5-fold faster than the control group, indicating that C-dots are promising nanofertilizers for aggrotech and non-toxic fluorescent biolabels for in vivo applications.

Design of heat exchanger for producing nickel ferrite (NiFe2O4) nanoparticles using coprecipitation method

This study examines the design of a heat exchanger (HE) in the production process of nickel ferrite (NiFe2O4) nanoparticles using the coprecipitation method by determining the shell and tube heat exchanger. The Microsoft Excel application is used as a manual calculating machine to facilitate the analysis of heat exchanger (HE) data calculations. The research flowchart starts with a literature study, preparation of tools and materials for design, calculation of the main shell and tube components, and then fabrication. Based on the calculation results, the design specification data for a shell and tube heat exchanger has a shell diameter of 0.032 m, a shell length of 4.267 mm, a thickness of 0.002 m with an initial heat transfer rate (Q) of 460130 W resulting in a heat transfer efficiency of 95.706% and an NTU of 6.165. The high effectiveness value makes the design of the one shell and tube type turbulent flow heat exchanger (HE) considered to have met the standards of high effectiveness and good performance. The design and design process is complete if the device functions properly. This study can be used as a reference for researchers in designing heat exchangers during production to make them more effective, reliable, and economical.

Effect of grain boundary reconstruction and regenerated main phase shell on magnetic properties in high-abundance (NdLaCeY)-Fe-B magnets

The (NdLaCeY)-Fe-B magnets with 45–50 wt% high-abundance rare earth substitution were systematically investigated by co-mixing high boron content matrix phase and Pr–Fe alloy powders (0, 1, 3, 5, 7, and 9 wt%) during the preparation process. The coercivity of magnets increased successively with the addition of Pr70Fe30 (wt.%) and reached 9.32 kOe at the addition amount of 9 wt% from the initial 7.33 kOe without addition, while the remanence had a very small decrease of only 0.13 kGs. The analyses showed that the B-rich phase in the high-boron powders reacted with Pr70Fe30 to form the main phase shell, forming a core-shell structure with a Pr-rich shell and a Y-rich core. Meanwhile, the grain boundary was significantly widened with the introduction of Pr70Fe30. Then, just the improved anisotropy of the main phase grain surface, accompanied with the enhanced magnetic de-coupling effect between the main phase grains, resulted in a great coercivity increment. Notably, on the remanence, the beneficial effect of increased main-phase proportion by regenerated grain shell had a competitive relationship with the deteriorating effect of the magnetic dilution by the non-magnetic material introduction, thus under the combined effects, the remanence firstly increased and then decreased with the addition of Pr–Fe.

Rapid Expansion of the Young Type Ia Supernova Remnant 0519–69.0: More Evidence for a Circumstellar Shell

The nature of Type Ia supernovae remains controversial. The youngest remnants of Ia supernovae hold clues to the explosion and to the immediate surroundings. We present a third epoch of Chandra observations of the ∼600 yr old Type Ia remnant 0519–69.0 in the Large Magellanic Cloud, extending the time baseline to 21 yr from the initial 2000 observations. We find rapid expansion of X-ray emitting material, with an average velocity of 4760 km s−1. At the distance of the LMC, this corresponds to an undecelerated age of 750 yr, with the true age somewhat lower. We also find that the bright ring of emission has expanded by 1.3%, corresponding to a velocity of 1900 km s−1 and an undecelerated age of 1600 yr. The high velocity of the peripheral X-rays, contrasted with the modest expansion of the main X-ray shell, provides further evidence for a massive shell of circumstellar material.

The [S ii] Spectral Images of the Planetary Nebula NGC 7009. II. Major Axis

We derived position–velocity density distribution diagrams along the major (PA = 77°) axis of the elliptical planetary nebula NGC 7009 with the Keck HIRES [S ii] 6716/6731 Å doublet spectral images. The average densities of the main shell and knots of NGC 7009 derived from the [S ii] 6716/6731 Å fluxes integrated over the line of sight indicate a density range of N e = 103.4 to 103.9 cm−3, while the local densities from the volume fraction resolved in radial velocities along the line of sight show a considerably large range of about 102.8–104.7 cm−3. The derived projection angle of the major axis of the main shell is ψ ∼ 18.3° (±2°). Assuming that the main shell is an ellipsoidal shell with a ≃ 16″ and b ≃ 6″, we found the range of the expansion velocity, radius, and latitude of four knots and a hot bubble. The four knots at points in symmetrical positions are roughly aligned with the same axis of expansion of latitudes ϕ ∼ ±34.5° (±0.6°): one pair expands at about 35 km s−1 close to the main ellipsoidal shell, and the other expands rapidly at about 60 km s−1 at a distance of r ∼ 16″. In the latitude range ϕ = 65°–75°, the hot bubble of a relatively large structure expands rapidly with a velocity of 130–150 km s−1. The four knots and hot bubble points, which expand faster than the main shell, appear to have been formed by two to three eruptions at a different epoch from the primary structure formation.

Silicon-Containing Additives in Encapsulation of Phase Change Materials for Thermal Energy Storage

Microencapsulated phase change materials (MEPCMs) are effective solutions for addressing the issue of leakage that phase change materials (PCMs) face in thermal energy storage devices. Their applications are ubiquitous as PCMs are utilized in industries such as logistics, construction, electronics, etc., thus, an efficient method to prevent problems such as leakage and poor thermal conductivity is to encapsulate the PCM which not only renders it leakage-proof but also impart mechanical strength and enhanced thermal properties. The application of silicon-based additives is one of the most studied methods to impart such desired properties. We discuss the silicon-containing compounds which are commonly employed in core-shell matrix of encapsulated PCMs, namely, siloxanes and silicone, silicon nitride, silicon carbide, silica/SiO2, and other silicon-containing additives as they are able to provide synergistic improvements and exhibit enhanced physical properties. In this review, the different silicon compounds used as additives or main shell matrix are discussed, the general fabrication of the MEPCM and its thermophysical properties will be briefly highlighted. Lastly, we also examine its application and performance in thermal storage and thermal management. We hope to provide a broader perspective of silicon-containing MEPCM for those who are working in the similar field of research.

NGC 6153: Reality is Complicated* *Based on observations collected at the European Southern Observatory under ESO program(s) 69.D-0174(A).

We study the kinematics of emission lines that arise from many physical processes in NGC 6153 based upon deep, spatially resolved, high-resolution spectra acquired with the UVES spectrograph at the European Southern Observatory Very Large Telescope. Our most basic finding is that the plasma in NGC 6153 is complex, especially its temperature structure. The kinematics of most emission lines defines a classic expansion law, with the outer part expanding fastest (normal nebular plasma). However, the permitted lines of O i, C ii, N ii, O ii, and Ne ii present a constant expansion velocity that defines a second kinematic component (additional plasma component). The physical conditions imply two plasma components, with the additional plasma component having lower temperature and higher density. The [O ii] density and the [N ii] temperature are anomalous, but may be understood considering the contribution of recombination to these forbidden lines. The two plasma components have very different temperatures. The normal nebular plasma appears to have temperature fluctuations in part of its volume (main shell), but only small fluctuations elsewhere. The additional plasma component contains about half of the mass of the N2+ and O2+ ions, but only 3%–5% of the mass of H+ ions, so the two plasma components have very different chemical abundances. We estimate abundances of dex and He/H ∼ 0.13. Although they are all complications, multiple plasma components, temperature fluctuations, and the contributions of multiple physical processes to a given emission line are all part of the reality in NGC 6153, and should generally be taken into account.

3D spatio-kinematic modelling of Abell 48, a planetary nebula around a Wolf–Rayet [WN] star

ABSTRACT The planetary nebula (PN) Abell 48 (PN G029.0+00.4) is around a rare Wolf–Rayet [WN5] star whose stellar history is as yet unknown. Using the integral field observations of the H αλ6563 and [N ii] λ6584 line emissions, we conducted a comprehensive spatio-kinematic analysis of this PN. A three-dimensional spatio-kinematic ionization model was developed with the kinematic modelling tool shape to replicate the observed spatially resolved velocity channels and position–velocity diagrams. According to our kinematic analysis of the H α emission, this object possesses a deformed elliptic toroidal shell with an outer radius of 23 arcsec and a thickness of 15 arcsec associated with an integrated H α emission-line expansion of ∼35 ± 5 km s−1, a maximum poloidal expansion of around 70 ± 20 km s−1 at an inclination angle of ∼30° with respect to the line of sight, and a position angle of ∼130° measured from east towards north in the equatorial coordinate system. Furthermore, [N ii] kinematic modelling reveals the presence of narrow (∼3 arcsec) exterior low-ionization structures surrounding the main elliptical shell, which could have formed as a result of shock collisions with the interstellar medium. The torus-shaped morphology of this PN could be related to its unusual hydrogen-deficient [WN] nucleus that needs to be inspected further.

DSPC or DPPC As Main Shell Component Influences Ligand Distribution and Binding Area of Lipid‐Coated Targeted Microbubbles

Eur. J. Lipid Sci. Technol. 2014, 116, 1217 https://doi.org/10.1002/ejlt.201300434 The authors regret that there was a mistake in calculating the mol% of the microbubble coating composition used. For all experiments the unit in mg mL−1 was utilized and the conversion mistake only came when converting to mol% in order to define the ratio between the coating formulation components. The correct molecular weight of PEG-40 stearate is 2046.54 g mol−1,[1, 2] not 328.53 g mol−1. On page 1219, Section 2.2.1, it should read: “Biotinylated lipid-coated microbubbles (composition in mol %: DSPC or DPPC 84.8; PEG-40 stearate 8.2; DSPE-PEG2000 5.9, DSPE-PEG2000-biotin 1.1) with a C4F10 gas core were made by sonication for 10 s using the method described by Klibanov et al.[30]” This correction does not change the conclusions published in this work. The authors apologize for any inconvenience caused.

Shaping “Ears” in Planetary Nebulae by Early Jets

Abstract We conduct three-dimensional hydrodynamical numerical simulations of planetary nebula (PN) shaping and show that jets that precede the ejection of the main PN shell can form the morphological feature of ears. Ears are two opposite protrusions from the main nebula that are smaller than the main nebula and with a cross section that decreases monotonically from the base of an ear at the shell to its far end. Only a very small fraction of PNe have ears. The short-lived jets, about a year in the present simulations, interact with the regular asymptotic giant branch wind to form the ears, while the later blown dense wind forms the main PN dense shell. Namely, the jets are older than the main PN shell. We also find that for the jets to inflate ears they cannot be too energetic, cannot be too wide, and cannot be too slow. A flow structure where short-lived jets precede the main phase of nebula ejection by a few years or less can result from a system that enters a common envelope evolution. The low mass companion accretes mass through an accretion disk and launches jets just before it enters the envelope of the giant progenitor star of the PN. Shortly after that the companion enters the envelope and spirals-in to eject the envelope that forms the main PN shell.

Design and test of a flat capillary pump with ceramic wick

<p indent=0mm>A novel flat capillary pump was designed to solve the problem of heat leakage from the evaporator to the accumulator in flat capillary pumps. The materials used to obtain the porous wick and main shell were silicon nitride and low-thermal conductivity titanium alloy, respectively. The size of the resulting capillary pump was <sc>82.0 mm</sc> × <sc>53.0 mm</sc> × <sc>16.0 mm,</sc> and eight cylindrical silicon nitride porous wicks were arranged inside the pump. The pore size, porosity, and heat conductivity of the porous wick were <sc>0.5 µm,</sc> 70%, and 2.7 W/(m K), respectively. Experimental results showed that the flat evaporator loop heat pipe can be started quickly and that no obvious overheating occurs in the evaporator under a heat load in the range of <sc>5.0–20.0 W</sc> when the angle of the capillary pump is 0°. The time required to start the flat evaporator loop heat pipe remarkably increased and the temperature increment evidently increased under a <sc>5 W</sc> start load when the angle of the capillary pump was increased. However, when the start load was increased to <sc>20 W,</sc> the starting characteristics of the pipe improved. The heat-transfer ability of the flat evaporator loop heat pipe, equilibrium temperature of the accumulator, and thermal resistance of the pipe were subsequently tested, and results revealed that the heat transfer and heat flux limits are <sc>400.0 W</sc> and <sc>26.3 W/cm²,</sc> respectively. The equilibrium temperature of the accumulator changed with the heat sink and load, and this is consistent with the typical running characteristic of the loop heat pipe. The minimum thermal resistance tested was 0.018°C/W. Finally, the back heat leakage from the evaporator to the compensation chamber was estimated from the energy balance of the compensation chamber.

The concentration of intellectual and material wealth: Development of the military and barrack infrastructure of the St. Petersburg Military District in 1864-1917

The article is devoted to the Russian military construction on the example of the St. Petersburg Military District in the period from 1864 to 1917. Without taking into account the military factor, it is impossible to reconstruct the socio-economic development of our country’s regions. The scale and priority of military construction affect the long-term goals of the state. “Strategic” motives could both give an impetus to the economic growth of some regions, and on the contrary significantly restrain the development of others. St. Petersburg contains the results of many years of headquarters work such as all plans for mobilization and the sequence of replenishment, loss and restoration of the armed forces, stocks of maps. The main gunpowder, cannon and shell factories were located near St. Petersburg, while pipe, cartridge and mine factories are located in St. Petersburg itself. In St. Petersburg are stored the vast reserves of the State Bank, the Mint, the treasures of the Hermitage, the incalculable capitals of private financial enterprises, the money reserves of the State Treasury.The conditions of quartering significantly determine the combat training of troops in peacetime and, accordingly, their combat qualities in military conditions.

The road and Fortification Preparation of Border Areas in the Recommendations of the Russian military theorist A.A. Svechin (the late 1920s)

The article is devoted to the Russian military construction on the example of the St. Petersburg Military District in the period from 1864 to 1917. Without taking into account the military factor, it is impossible to reconstruct the socio-economic development of our country’s regions. The scale and priority of military construction affect the long-term goals of the state. “Strategic” motives could both give an impetus to the economic growth of some regions, and on the contrary significantly restrain the development of others. St. Petersburg contains the results of many years of headquarters work such as all plans for mobilization and the sequence of replenishment, loss and restoration of the armed forces, stocks of maps. The main gunpowder, cannon and shell factories were located near St. Petersburg, while pipe, cartridge and mine factories are located in St. Petersburg itself. In St. Petersburg are stored the vast reserves of the State Bank, the Mint, the treasures of the Hermitage, the incalculable capitals of private financial enterprises, the money reserves of the State Treasury.The conditions of quartering significantly determine the combat training of troops in peacetime and, accordingly, their combat qualities in military conditions.

The fully developed remnant of a neutrino-driven supernova

Context. The remnants of core-collapse supernovae (SNe) are probes of the physical processes associated with their parent SNe. Aims. Here we aim to explore to which extent the remnant keeps memory of the asymmetries that develop stochastically in the neutrino-heating layer due to hydrodynamic instabilities (e.g., convective overturn and the standing accretion shock instability; SASI) during the first second after core bounce. Methods. We coupled a three-dimensional (3D) hydrodynamic model of a neutrino-driven SN explosion, which has the potential to reproduce the observed morphology of the Cassiopeia A (Cas A) remnant, with 3D (magneto)-hydrodynamic simulations of the remnant formation. The simulations cover ≈2000 yr of expansion and include all physical processes relevant to describe the complexities in the SN evolution and the subsequent interaction of the stellar debris with the wind of the progenitor star. Results. The interaction of large-scale asymmetries left from the earliest phases of the explosion with the reverse shock produces, at the age of ≈350 yr, an ejecta structure and a remnant morphology which are remarkably similar to those observed in Cas A. Small-scale structures in the large-scale Fe-rich plumes that were created during the initial stages of the SN, combined with hydrodynamic instabilities that develop after the passage of the reverse shock, naturally produce a pattern of ring- and crown-like structures of shocked ejecta. The consequence is a spatial inversion of the ejecta layers with Si-rich ejecta being physically interior to Fe-rich ejecta. The full-fledged remnant shows voids and cavities in the innermost unshocked ejecta, which are physically connected with ring-like features of shocked ejecta in the main shell in most cases, resulting from the expansion of Fe-rich plumes and their inflation due to the decay of radioactive species. The asymmetric distributions of 44Ti and 56Fe, which are mostly concentrated in the northern hemisphere, and pointing opposite to the kick velocity of the neutron star, as well as their abundance ratio are both compatible with those inferred from high-energy observations of Chandra and NuSTAR. Finally, the simulations show that the fingerprints of the SN can still be visible ≈2000 yr after the explosion. Conclusions. The main asymmetries and features observed in the ejecta distribution of Cas A can be explained by the interaction of the reverse shock with the initial large-scale asymmetries that developed from stochastic processes (e.g., convective overturn and SASI activity) that originate during the first seconds of the SN blast.

Optimisation of crack groove depth of QT450 rear axles' main reducer shell bearing seats based on numerical analysis

This paper studies the fracture splitting of shell bearing seat, and determines the optimised range for prefabricated crack groove depth. Firstly, crack initiation during the fracture splitting process of shell bearing seat is numerically simulated. Secondly, the fracture-split force of different crack groove depths is determined. Finally, plastic deformation and out-of-roundness of the shell bearing seat at different crack groove depths are investigated. The results show that the crack initiation point of the reducer shell bearing seat is located near the middle of the crack tip and the position is slightly closer to the flat end face side. Plastic areas with different crack groove depths produced at the root of the crack tip are butterfly-shaped distribution and the out-of-roundness of bearing hole is small. This shows that fracture-splitting technology is suitable for shell bearing seat. The result provides rationality for the design of reducer shell bearing seat cracking equipment and prefabricated crack groove parameters. [Submitted 7 November 2018; Accepted 27 July 2019]

Optimisation of crack groove depth of QT450 rear axles' main reducer shell bearing seats based on numerical analysis

This paper studies the fracture splitting of shell bearing seat, and determines the optimised range for prefabricated crack groove depth. Firstly, crack initiation during the fracture splitting process of shell bearing seat is numerically simulated. Secondly, the fracture-split force of different crack groove depths is determined. Finally, plastic deformation and out-of-roundness of the shell bearing seat at different crack groove depths are investigated. The results show that the crack initiation point of the reducer shell bearing seat is located near the middle of the crack tip and the position is slightly closer to the flat end face side. Plastic areas with different crack groove depths produced at the root of the crack tip are butterfly-shaped distribution and the out-of-roundness of bearing hole is small. This shows that fracture-splitting technology is suitable for shell bearing seat. The result provides rationality for the design of reducer shell bearing seat cracking equipment and prefabricated crack groove parameters. [Submitted 7 November 2018; Accepted 27 July 2019]

Large-scale spatial biostratinomic patterns along the Eastern Indian coasts: Identification of a generalized siliciclastic beach taphofacies applicable in analogues (paleo)environments

Studies on biostratinomy of modern molluscs are biogeographically (mostly from the Americas and Europe) and environmentally (mostly from subtropical and temperate carbonate settings) restricted, documenting local variation, while large-scale spatio-environmental patterns from the siliciclastic settings are less understood. Here, 8670 dead bivalve specimens were collected from several sandy, sandy-rock mixed, and sandy-clay mixed beach, and beaches associated with tidal flat and sea-grass habitat. Sampling stations were located along a stretch of about 2500 km covering several ecoregions along the eastern Indian coast, a large-scale, biogeographic pattern in biostratinomy is studied. Each shell was assigned seven grades based on shell damages intensities in reference to seven biostratinomic attributes (shell completeness, surface bioerosion, secondary rounding, abrasion, ligament loss, and external and internal wear); the summation of these values indicate the Total Taphonomic Grade (TTG) of individual specimens. Our results suggest, TTG values do not vary systematically with ecological factors (e.g., body size and shape, shell microstructure, etc.), although environmental (e.g., substrate and energy conditions) factors could play some role (e.g., high energy sandy beaches have higher TTG values); no large-scale biogeographic gradient is observed. Based on the characteristics of damage profiles, a siliciclastic beach taphofacies, common in all locations, is proposed: abrasion is the main damage type, whereas, shell fragmentation or biotic damages are negligible. Based on these, a biostratinomic pathway of shells is inferred: after death, shells are immediately locally transported to the beach, reducing exposure time for biotic damages; on beaches, constant swash and backwash cause external and internal abrasion. These taphofacies and biostratinomic pathway models can be used to identify the biostratinomic conditions of analogous modern and fossil assemblages.