Rough Fraction Research Articles

Physicochemical characteristics of highly concentrated suspensions with some types of Ukrainian coal

ABSTRACT The investigation results of granulometric composition, zeta potential, sedimentation stability, and viscosity of some water-coal suspensions made of Ukrainian coal from the “Stepova” mine, Lviv-Volyn region, are reported. The most effective granulometric composition of the water-coal suspension consisting of the rough and fine fractions is found from the analysis of the abovementioned physicochemical characteristics of the suspensions. Based on the complex investigation of the zeta potential of the dispersed phase particles, viscosity, and sedimentation stability of the suspensions, it was established that the best technological effectiveness can be expected for the suspensions containing 60% of the rough fraction (sized between 100 and 250 µm) and fine particles sized between 20 and 40 µm. In such systems, the particles form a quasi-stable structure, where the lower-charged small particles are located in the interparticle space between the highly charged bigger particles. All particles bear the same charge, increasing the system’s sedimentation stability and avoiding decomposition for at least 5 days. This time seems reasonable for the preparation, storage, and pumping of the suspensions while their viscosity and stability meet the relevant technological requirements.

Quantitative Microtubule Fractionation Technique to Separate Stable Microtubules, Labile Microtubules, and Free Tubulin in Mouse Tissues.

Microtubules, composed of α/β-tubulin dimers, are a crucial component of the cytoskeleton in eukaryotic cells. These tube-like polymers exhibit dynamic instability as tubulin heterodimer subunits undergo repetitive polymerization and depolymerization. Precise control of microtubule stability and dynamics, achieved through tubulin post-translational modifications and microtubule-associated proteins, is essential for various cellular functions. Dysfunctions in microtubules are strongly implicated in pathogenesis, including neurodegenerative disorders. Ongoing research focuses on microtubule-targeting therapeutic agents that modulate stability, offering potential treatment options for these diseases and cancers. Consequently, understanding the dynamic state of microtubules is crucial for assessing disease progression and therapeutic effects. Traditionally, microtubule dynamics have been assessed in vitro or in cultured cells through rough fractionation or immunoassay, using antibodies targeting post-translational modifications of tubulin. However, accurately analyzing tubulin status in tissues using such procedures poses challenges. In this study, we developed a simple and innovative microtubule fractionation method to separate stable microtubules, labile microtubules, and free tubulin in mouse tissues. The procedure involved homogenizing dissected mouse tissues in a microtubule-stabilizing buffer at a 19:1 volume ratio. The homogenates were then fractionated through a two-step ultracentrifugation process following initial slow centrifugation (2,400 × g) to remove debris. The first ultracentrifugation step (100,000 × g) precipitated stable microtubules, while the resulting supernatant was subjected to a second ultracentrifugation step (500,000 × g) to fractionate labile microtubules and soluble tubulin dimers. This method determined the proportions of tubulin constituting stable or labile microtubules in the mouse brain. Additionally, distinct tissue variations in microtubule stability were observed that correlated with the proliferative capacity of constituent cells. These findings highlight the significant potential of this novel method for analyzing microtubule stability in physiological and pathological conditions.

1Progress, applications, challenges and prospects of protein purification technology.

Protein is one of the most important biological macromolecules in life, which plays a vital role in cell growth, development, movement, heredity, reproduction and other life activities. High quality isolation and purification is an essential step in the study of the structure and function of target proteins. Therefore, the development of protein purification technologies has great theoretical and practical significance in exploring the laws of life activities and guiding production practice. Up to now, there is no forthcoming method to extract any proteins from a complex system, and the field of protein purification still faces significant opportunities and challenges. Conventional protein purification generally includes three steps: pretreatment, rough fractionation, and fine fractionation. Each of the steps will significantly affect the purity, yield and the activity of target proteins. The present review focuses on the principle and process of protein purification, recent advances, and the applications of these technologies in the life and health industry as well as their far-reaching impact, so as to promote the research of protein structure and function, drug development and precision medicine, and bring new insights to researchers in related fields.

Thermophysical Modeling of 20 Themis Family Asteroids with WISE/NEOWISE Observations

Abstract Themis family is one of the largest and oldest asteroid populations in the main belt. Water ice may widely exist on the parent body (24) Themis. In this work, we employ the Advanced Thermophysical Model as well as midinfrared measurements from NASA’s Wide-field Infrared Survey Explorer to explore thermal parameters of 20 Themis family members. Here we show that the average thermal inertia and geometric albedo are 39.5 ± 26.0 J m−2 s−1/2 K−1 and 0.067 ± 0.018, respectively. The family members have a relatively moderate roughness fraction on their surfaces. We find that the relatively low albedos of Themis members are consistent with the typical values of B-type and C-type asteroids. As mentioned, the Themis family bears a very low thermal inertia, which indicates a fine and mature regolith on their surfaces. The resemblance of thermal inertia and geometric albedo of Themis members may reveal their close connection in origin and evolution. In addition, we present the compared results of thermal parameters for several prominent families.

Thermophysical Model for Realistic Surface Layers on Airless Small Bodies: Applied to Study the Spin Orientation and Surface Dust Properties of (24) Themis from WISE/NEOWISE Multiepoch Thermal Light Curves

Abstract This work proposes a thermophysical model for realistic surface layers on airless small bodies (RSTPM) for the use of interpreting their multiepoch thermal light curves (e.g., WISE/NEOWISE). RSTPM considers the real orbital cycle, rotation cycle, rough surface, temperature-dependent thermal parameters, as well as contributions of sunlight reflection to observations. It is thus able to produce a precise temperature distribution and thermal emission of airless small bodies regarding the variations on orbital timescales. Details of the physics, mathematics, and numerical algorithms of RSTPM are presented. When used to interpret multiepoch thermal light curves by WISE/NEOWISE, RSTPM can give constraints on the spin orientation and surface physical properties, such as the mean thermal inertia or the mean size of dust grains, the roughness fraction, and the albedo via a radiometric procedure. As an application example, we apply this model to the main-belt object (24) Themis, the largest object of the Themis family, which is believed to be the source region of many main-belt comets. We find multiepoch (2010, 2014–2018) observations of Themis by WISE/NEOWISE, yielding 18 thermal light curves. By fitting these data with RSTPM, the best-fit spin orientation of Themis is derived to be (λ = 137°, β = 59°) in ecliptic coordinates, and the mean radius of dust grains on the surface is estimated to be b ˜ = 140 − 114 + 500 ( 6 ∼ 640 ) μm, indicating that the surface thermal inertia varies from ∼3 Jm−2 s−0.5 K−1 to ∼60 Jm−2 s −0.5 K−1 due to seasonal temperature variation. A more detailed analysis found that the thermal light curves of Themis show a weak feature that depends on the rotation phase, which is indicative of heterogeneous thermal properties or imperfections of the light-curve inversion shape model.

Colloid Interaction Energies for Surfaces with Steric Effects and Incompressible and/or Compressible Roughness

Colloid aggregation and retention in the presence of macromolecular coatings (e.g., adsorbed polymers, surfactants, proteins, biological exudates, and humic materials) have previously been correlated with electric double layer interactions or repulsive steric interactions, but the underlying causes are not fully resolved. An interaction energy model that accounts for double layer, van der Waals, Born, and steric interactions as well as nanoscale roughness and charge heterogeneity on both surfaces was extended, and theoretical calculations were conducted to address this gap in knowledge. Macromolecular coatings may produce steric interactions in the model, but non-uniform or incomplete surface coverage may also create compressible nanoscale roughness with a charge that is different from the underlying surface. Model results reveal that compressible nanoscale roughness reduces the energy barrier height and the magnitude of the primary minimum at separation distances exterior to the adsorbed organic layer. The depth of the primary minimum initially alters (e.g., increases or decreases) at separation distances smaller than the adsorbed organic coating because of a decrease in the compressible roughness height and an increase in the roughness fraction. However, further decreases in the separation distance create strong steric repulsion that dominates the interaction energy profile and limits the colloid approach distance. Consequently, adsorbed organic coatings on colloids can create shallow primary minimum interactions adjacent to organic coatings that can explain enhanced stability and limited amounts of aggregation and retention that have commonly been observed. The approach outlined in this manuscript provides an improved tool that can be used to design adsorbed organic coatings for specific colloid applications or interpret experimental observations.

Determination of Size, Albedo, and Thermal Inertia of 10 Vesta Family Asteroids with WISE/NEOWISE Observations

Abstract In this work, we investigate the size, thermal inertia, surface roughness, and geometric albedo of 10 Vesta family asteroids using the Advanced Thermophysical Model, based on the thermal-infrared data acquired by mainly NASA’s Wide-field Infrared Survey Explorer. Here, we show that the average thermal inertia and geometric albedo of the investigated Vesta family members are 42 J m−2 s−1/2 K−1 and 0.314, respectively, where the derived effective diameters are less than 10 km. Moreover, the family members have a relatively low roughness fraction on their surfaces. The similarity in thermal inertia and geometric albedo among the V-type Vesta family members may reveal their close connection in origin and evolution. As the fragments of the cratering event of Vesta, the family members may have undergone a similar evolutionary process, thereby leading to very close thermal properties. Finally, we estimate their regolith grain sizes with different volume filling factors.

Evidence for the critical role of nanoscale surface roughness on the retention and release of silver nanoparticles in porous media

Although nanoscale surface roughness has been theoretically demonstrated to be a crucial factor in the interaction of colloids and surfaces, little experimental research has investigated the influence of roughness on colloid or silver nanoparticle (AgNP) retention and release in porous media. This study experimentally examined AgNP retention and release using two sands with very different surface roughness properties over a range of solution pH and/or ionic strength (IS). AgNP transport was greatly enhanced on the relatively smooth sand in comparison to the rougher sand, at higher pH, and lower IS and fitted model parameters showed systematic changes with these physicochemical factors. Complete release of the retained AgNPs was observed from the relatively smooth sand when the solution IS was decreased from 40 mM NaCl to deionized (DI) water and then the solution pH was increased from 6.5 to 10. Conversely, less than 40% of the retained AgNPs was released in similar processes from the rougher sand. These observations were explained by differences in the surface roughness of the two sands which altered the energy barrier height and the depth of the primary minimum with solution chemistry. Limited numbers of AgNPs apparently interacted in reversible, shallow primary minima on the smoother sand, which is consistent with the predicted influence of a small roughness fraction (e.g., pillar) on interaction energies. Conversely, larger numbers of AgNPs interacted in deeper primary minima on the rougher sand, which is consistent with the predicted influence at concave locations. These findings highlight the importance of surface roughness and indicate that variations in sand surface roughness can greatly change the sensitivity of nanoparticle transport to physicochemical factors such as IS and pH due to the alteration of interaction energy and thus can strongly influence nanoparticle mobility in the environment.

Revisiting the Advanced Thermal Physical Model: New Perspectives on Thermophysical Characteristics of (341843) 2008 EV5 from Four-bandWISEData with the Sunlight-reflection Model

In this paper, we investigate thermophysical characteristics of near-Earth asteroid (341843) 2008 EV5, based on our improved Advanced Thermal Physical Model (ATPM) by considering the contribution of sunlight-reflection for rough surface, along with four wavebands observations from Wide-field Infrared Survey Explorer (WISE) and the radar-derived shape model. Here we derive that 2008 EV5 has a relatively low thermal inertia of $\Gamma=110 _{-12}^{+40}\rm~J m^{-2} s^{-1/2} K^{-1}$ but a high roughness fraction. The geometric albedo and effective diameter are then constrained to be $p_v=0.095_{-0.003}^{+0.016}$ and $D_{\rm eff}=431_{-33}^{+6}\rm~m$, respectively. The low thermal inertia indicates that 2008 EV5 may have undergone sufficient space weathering over secular evolution. The high roughness may have resemblances to the appearances of Bennu and Ryugu recently observed by spacecrafts, where a great number of boulders are widely distributed on the asteroid's surface. Moreover, we numerically perform 1000 backward simulations of 2008 EV5's cloned orbits within 1 Myr to explore its origin, and present a probability of $\sim6.1\%$ that the asteroid originates from the main belt. Finally, we estimate that the mean grain size of the surface ranges from 0.58 to 1.3 mm, and infer that it is unlikely to find water ice on most area of 2008 EV5, but there may exist water ice on high-latitudes near polar region.

Tribological characterization of Nb ion implanted WC-5wt%Ni cold sprayed coatings in dry sliding contact

Niobium ions were implanted into WC-5wt%Ni cold sprayed coatings at an acceleration voltage of 60 keV. The ion dosages were varied as 2 × 1016, 5 × 1016, and 8 × 1016 ions cm−2, and the resulting influence on surface, friction, wear, and stress properties of the Nb-implanted layers, in comparison to the non-ion implanted coating, was investigated. Dry sliding wear behaviour was assessed using a ball-on-disk tribometer, with 100Cr6 stainless steel balls as the counterface, at a sliding velocity of 0.05 ms−1 and an applied load of 1 N. The Nb ion dosage of 8 × 1016 ions cm−2 produced the best coating surface properties, achieving a high hardness (14.58 GPa), low plasticity index (53.83), low wear rate (35.7 × 10−12 m2 N−1), low wear coefficient (0.52), high shear strength (891 MPa) and a high local maximum von Mises yield strength (1546 MPa). This coating also produced a low Rq roughness value (10.22 nm), great mean radius of asperities (35.88 × 10−2 nm), and a high reciprocal value of the comprehensive roughness fraction (4.77 × 10−3). The wear mechanisms of all the coatings were found to be similar, showing oxidation, scratching, ploughing, smearing, material transfer, and tribo-layer formation.

Physical model of near-Earth asteroid (1917) Cuyo from ground-based optical and thermal-IR observations

Context.The near-Earth asteroid (1917) Cuyo was subject to radar and light curve observations during a close approach in 1989, and observed up until 2008. It was selected as one of our ESO Large Programme targets, aimed at observational detections of the Yarkovsky-O’Keefe-Radzievskii-Paddack (YORP) effect through long-term light curve monitoring and physical modelling of near-Earth asteroids.Aims.We aim to constrain the physical properties of Cuyo: shape, spin-state, and spectroscopic and thermo-physical properties of the surface.Methods.We acquired photometric light curves of Cuyo spanning the period between 2010 and 2013, which we combined with published light curves from 1989 to 2008. Our thermal-infrared observations were obtained in 2011. Rotationally resolved optical spectroscopy data were acquired in 2011 and combined with all available published spectra to investigate any surface material variegation.Results.We developed a convex light curve-inversion shape of Cuyo that suggests the presence of an equatorial ridge, typical for an evolved system close to shedding mass due to fast rotation. We determine limits of YORP strength through light curve-based spin-state modelling, including both negative and positive acceleration values, between − 0.7 × 10−8and 1.7 × 10−8rad day−2. Thermo-physical modelling with the ATPM provides constraints on the geometric albedo,pV= 0.24 ± 0.07, the effective diameter,Deff= 3.15 ± 0.08km, the thermal inertia, Γ = 44 ± 9 J m−2s−1∕2K−1, and a roughness fraction of 0.52 ± 0.26. This enabled a YORP strength prediction ofν= (−6.39 ± 0.96) × 10−10rad day−2. We also see evidence of surface compositional variation.Conclusions.The low value of YORP predicted by means of thermo-physical analysis, consistent with the results of the light curve study, might be due to the self-limiting properties of rotational YORP, possibly involving movement of sub-surface and surface material. This may also be consistent with the surface compositional variation that we see. The physical model of Cuyo can be used to investigate cohesive forces as a way to explain why some targets survive rotation rates faster than the fission limit.

Sensing of Escherichia coli and LPS by mammary epithelial cells is modulated by O-antigen chain and CD14.

Escherichia coli is one of the major pathogens causing mastitis in dairy cattle. Yet, the factors which mediate the ability for E. coli to develop in the bovine mammary gland remain poorly elucidated. In a mouse model, infections induced by the reference mastitis E. coli P4 showed a strong colonisation of the mammary gland, while this strain had a low stimulating power on cells of the PS bovine mammary epithelial cell line. In order to understand if such a reduced response contributes to the severity of infection, a library of random mutants of P4 strain was screened to identify mutants inducing stronger response of PS cells. Among hyper-stimulating mutants, six were altered in genes involved in biosynthesis of lipopolysaccharide (LPS) and had lost their O-polysaccharide region, suggesting that the presence of O-antigen impairs the response of PS cells to LPS. Using purified smooth (S) and rough (R) fractions of LPS, we showed that the R-LPS fraction induced a stronger response from PS cells than the smooth LPS fraction. Biological activity of the S-LPS fraction could be restored by the addition of recombinant bovine CD14 (rbCD14), indicating a crucial role of CD14 in the recognition of S-LPS by Mammary Epithelial Cells (MEC). When S-LPS and R-LPS were injected in udder quarters of healthy lactating cows, an inflammation developed in all infused quarters, but the S-LPS induced a more intense pro-inflammatory response, possibly in relation to sizeable concentrations of CD14 in milk. Altogether, our results demonstrate that the O-antigen modulates the pro-inflammatory response of MEC to LPS, that S-LPS and R-LPS trigger different responses of MEC and that these responses depend on the presence of CD14.

Contributions of Nanoscale Roughness to Anomalous Colloid Retention and Stability Behavior.

All natural surfaces exhibit nanoscale roughness (NR) and chemical heterogeneity (CH) to some extent. Expressions were developed to determine the mean interaction energy between a colloid and a solid-water interface, as well as for colloid-colloid interactions, when both surfaces contain binary NR and CH. The influence of heterogeneity type, roughness parameters, solution ionic strength (IS), mean zeta potential, and colloid size on predicted interaction energy profiles was then investigated. The role of CH was enhanced on smooth surfaces with larger amounts of CH, especially for smaller colloids and higher IS. However, predicted interaction energy profiles were mainly dominated by NR, which tended to lower the energy barrier height and the magnitudes of both the secondary and primary minima, especially when the roughness fraction was small. This dramatically increased the relative importance of primary to secondary minima interactions on net electrostatically unfavorable surfaces, especially when roughness occurred on both surfaces and for conditions that produced small energy barriers (e.g., higher IS, lower pH, lower magnitudes in the zeta potential, and for smaller colloid sizes) on smooth surfaces. The combined influence of roughness and Born repulsion frequently produced a shallow primary minimum that was susceptible to diffusive removal by random variations in kinetic energy, even under electrostatically favorable conditions. Calculations using measured zeta potentials and hypothetical roughness properties demonstrated that roughness provided a viable alternative explanation for many experimental deviations that have previously been attributed to electrosteric repulsion (e.g., a decrease in colloid retention with an increase in solution IS; reversible colloid retention under favorable conditions; and diminished colloid retention and enhanced colloid stability due to adsorbed surfactants, polymers, and/or humic materials).

Surface thermophysical properties on the potentially hazardous asteroid (99942) Apophis

We investigate the surface thermophysical properties (thermal emissivity, thermal inertia, roughness fraction and geometric albedo) of asteroid (99942) Apophis, using the currently available mid-infrared observations from CanariCam on Gran Telescopio CANARIAS and far-infrared data from PACS on Herschel, based on the Advanced Thermophysical Model. We show that the thermal emissivity of Apophis should be wavelength dependent from 8.70 μm to 160 μm, and the maximum emissivity may appear around 20 μm, similar to that of Vesta. Moreover, we further derive the thermal inertia, roughness fraction, geometric albedo and effective diameter of Apophis within a possible 1 scale of , , and , and 3 scale of , , and . The derived low thermal inertia but high roughness fraction may imply that Apophis could have regolith on its surface, where stronger space weathering but weaker regolith migration has happened in comparison with asteroid Itokawa. Our results show that small-size asteroids could also have fine regolith on the surface, and further infer that Apophis may have been delivered from the Main Belt by the Yarkovsky effect.

Temperature dependency of virus and nanoparticle transport and retention in saturated porous media

The influence of temperature on virus (PRD1 and ΦX174) and carboxyl-modified latex nanoparticle (50 and 100nm) attachment was examined in sand-packed columns under various physiochemical conditions. When the solution ionic strength (IS) equaled 10 and 30mM, the attachment rate coefficient (katt) increased up to 109% (p<0.0002) and the percentage of the sand surface area that contributed to attachment (Sf) increased up to 160% (p<0.002) when the temperature was increased from 4 to 20°C. Temperature effects at IS=10 and 30mM were also dependent on the system hydrodynamics; i.e., enhanced retention at a lower pore water velocity (0.1m/day). Conversely, this same temperature increase had a negligible influence on katt and Sf values when IS was 1mM or >50mM. An explanation for these observations was obtained from extended interaction energy calculations that considered nanoscale roughness and chemical heterogeneity on the sand surface. Interaction energy calculations demonstrated that the energy barrier to attachment in the primary minimum (∆Φa) decreased with increasing IS, chemical heterogeneity, and temperature, especially in the presence of small amounts of nanoscale roughness (e.g., roughness fraction of 0.05 and height of 20nm in the zone of influence). Temperature had a negligible effect on katt and Sf when the IS=1mM because of the large energy barrier, and at IS=50mM because of the absence of an energy barrier. Conversely, temperature had a large influence on katt and Sf when the IS was 10 and 30mM because of the presence of a small ∆Φa on sand with nanoscale roughness and a chemical (positive zeta potential) heterogeneity. This has large implications for setting parameters for the accurate modeling and transport prediction of virus and nanoparticle contaminants in ground water systems.

Nanocrystalline diamond films prepared by pulsed electron beam ablation on different substrates

Abstract

Thermophysical Characteristics of OSIRIS-REx Target Asteroid (101955) Bennu

AbstractIn this work, we investigate the thermophysical properties, including thermal inertia, roughness fraction and surface grain size of OSIRIS-REx target asteroid (101955) Bennu by using a thermophysical model with the recently updated 3D radar-derived shape model (Nolan et al., 2013) and mid-infrared observations (Müller et al. 2012, Emery et al., 2014). We find that the asteroid bears an effective diameter of 510+6−40 m, a geometric albedo of 0.047+0.0083−0.0011, a roughness fraction of 0.04+0.26−0.04, and thermal inertia of 240+440−60 Jm−2s−0.5K−1 for our best-fit solution. The best-estimate thermal inertia suggests that fine-grained regolith may cover a large portion of Bennu's surface, where a grain size may vary from 1.3 to 31 mm. Our outcome suggests that Bennu is suitable for the OSIRIS-REx mission to return samples to Earth.

Surface thermophysical properties determination ofOSIRIS-RExtarget asteroid (101955) Bennu

In this work, we investigate the thermophysical properties of OSIRIS-REx target asteroid (101955) Bennu (hereafter, Bennu), where thermal inertia plays an important role in understanding the nature of the asteroid's surface, and will definitely provide substantial information for the sampling return mission. Using a thermophysical model incorporating the recently updated 3D radar-derived shape model \citep{Nolan2013} and mid-infrared observations of Spitzer-PUI, Spitzer-IRAC, Herschel/PACS and ESO VLT/VISIR \citep{Muller2012,Emery2014}, we derive the surface thermophysical properties of Bennu. The asteroid has an effective diameter of $510^{+6}_{-40}$ m, a geometry albedo of $0.047^{+0.0083}_{-0.0011}$, a roughness fraction of $0.04^{+0.26}_{-0.04}$, and thermal inertia of $240^{+440}_{-60}\rm~Jm^{-2}s^{-0.5}K^{-1}$ for a best-fit solution at 1$\sigma$ level. The best-estimate thermal inertia indicates that fine-grained regolith may cover a large area of Bennu's surface, with a grain size that may range from $1.3$ to $31$~mm, and our outcome further supports that Bennu would be a suitable target for the OSIRIS-REx mission to return samples from the asteroid to Earth.

Physical characterisation of near-Earth asteroid (1620) Geographos

The Yarkovsky (orbital drift) and YORP (spin state change) effects play important roles in the dynamical and physical evolution of asteroids. Thermophysical modelling of these observed effects, and of thermal-infrared observations, allows a detailed physical characterisation of an individual asteroid to be performed. We perform a detailed physical characterisation of near-Earth asteroid (1620) Geographos, a potential meteor stream source and former spacecraft target, using the same techniques as previously used in Rozitis et al. (2013) for (1862) Apollo. We use the advanced thermophysical model (ATPM) on published light-curve, radar, and thermal-infrared observations to constrain the thermophysical properties of Geographos. The derived properties are used to make detailed predictions of the Yarkovsky orbital drift and YORP rotational acceleration, which are then compared against published measurements to determine Geographos's bulk density. We find that Geographos has a thermal inertia of 340 +140/-100 J m-2 K-1 s-1/2, a roughness fraction of >50%, and a bulk density of 2100 +550/-450 kg m-3 when using the light-curve-derived shape model with the radar-derived maximum equatorial diameter of 5.04 +/- 0.07 km. It is also found that the radar observations had overestimated the z-axis in Geographos's shape model because of their near-equatorial view. This results in a poor fit to the thermal-infrared observations if its effective diameter is kept fixed in the model fitting. The thermal inertia derived for Geographos is slightly higher than the typical values for a near-Earth asteroid of its size, and its derived bulk density suggests a rubble-pile interior structure. Large uncertainties in shape model z-axes are likely to explain why radar and thermal-infrared observations sometimes give inconsistent diameter determinations for other asteroids.

Shape, thermal and surface properties determination of a candidate spacecraft target asteroid (175706) 1996 FG3

In this paper, a 3D convex shape model of (175706) 1996 FG3, which consists of 2040 triangle facets and 1022 vertices, is derived from the known lightcurves. The best-fit orientation of the asteroid's spin axis is determined to be $\lambda =237.7^\circ$ and $\beta=-83.8^{\circ}$ considering the observation uncertainties, and its rotation period is $\sim$ 3.5935 h . Using the derived shape model, we adopt the so-called advanced thermophysical model (ATPM) to fit three published sets of mid-infrared observations of 1996 FG3 \citep{Wolters2011,Walsh2012}, so as to evaluate its surface properties. Assuming the primary and the secondary bear identical shape, albedo, thermal inertia and surface roughness, the best-fit parameters are obtained from the observations. The geometric albedo and effective diameter of the asteroid are reckoned to be $p_{\rm v}=0.045\pm0.002$, $D_{\rm eff}=1.69^{+0.05}_{-0.02}$ km. The diameters of the primary and secondary are determined to be $D_{1}=1.63^{+0.04}_{-0.03}$ km and $D_{2}=0.45^{+0.04}_{-0.03}$ km, respectively. The surface thermal inertia $\Gamma$ is derived to be a low value of $80\pm40\rm Jm^{-2}s^{-0.5}K^{-1}$ with a roughness fraction $f_{\rm R}$ of $0.8^{+0.2}_{-0.4}$. This indicates that the primary possibly has a regolith layer on its surface, which is likely to be covered by a mixture of dust, fragmentary rocky debris and sand. The minimum regolith depth is estimated to be $5\sim20\rm mm$ from the simulations of subsurface temperature distribution, indicating that 1996 FG3 could be a very suitable target for a sample return mission.