Search

An efficient computational scheme has been developed that includes many-body hydrodynamics for viscosity in a suspension of spheres following the approach of Jones and Muthukumar [J. Chem. Phys. 89, 6406 (1988)] for friction coefficients. The method combines the hydrodynamic scattering formalism of Freed and Muthukumar [J. Chem. Phys. 76, 6186 (1982)] with angular momentum diagrammatic techniques from quantum mechanics. The concentration dependence of the viscosity is expressed as a series of finite integrals labeled by the equivalent of angular momentum quantum numbers. This series is smoothly convergent in contrast to the case of the alternate formalism of a series of terms of inverse powers of the sphere separation. A comparison between different methods and the slowness of convergence of the series are addressed in detail. At the two-body level, the virial expansion for the shear viscosity η of a suspension of hard spheres of volume fraction [uppercase_phi_synonym] is determined to be η/η0=1+2.5[uppercase_phi_synonym]+4.8292[uppercase_phi_synonym]2+O([uppercase_phi_synonym]3), where η0 is the viscosity of the fluid and the correction for the Brownian motion [G. K. Batchelor, J. Fluid Mech. 83, 97 (1977)] has been ignored. Our value for the two-body coefficient differs in 3.4% from the extrapolated value 5.0019 obtained by Cichocki and Felderhof [J. Chem. Phys. 89, 1049 (1988)]. [ABSTRACT FROM AUTHOR]

The article reports that Opioid use and misuse is a serious public health problem in Texas. Topics include physicians in Texas wrote opioid prescriptions per 100 population; Naloxone is an opioid antagonist that can rapidly reverse the effects of an opioid overdose; and intentional abuse and suspected suicide attempts and lowest for unintentional (accidental) exposures and adverse reactions.

Abstract: The space weathering process and its implications for the relationships between S- and Q-type asteroids and ordinary chondrite meteorites is an often debated topic in asteroid science. Q-type asteroids have been shown to display the best spectral match to ordinary chondrites (McFadden, L.A., Gaffey, M.J., McCord, T.B. [1985]. Science 229, 160–163). While the Q-types and ordinary chondrites share some spectral features with S-type asteroids, the S-types have significantly redder spectral slopes than the Q-types in visible and near-infrared wavelengths. This reddening of spectral slope is attributed to the effects of space weathering on the observed surface composition. The analysis by Binzel et al. (Binzel, R.P., Rivkin, A.S., Stuart, J.S., Harris, A.W., Bus, S.J., Burbine, T.H. [2004]. Icarus 170, 259–294) provided a missing link between the Q- and S-type bodies in near-Earth space by showing a reddening of spectral slope in objects from 0.1 to 5km that corresponded to a transition from Q-type to S-type asteroid spectra, implying that size, and therefore surface age, is related to the relationship between S- and Q-types. The existence of Q-type asteroids in the main-belt was not confirmed until Mothé-Diniz and Nesvorny (Mothé-Diniz, T., Nesvorny, D. [2008]. Astron. Astrophys. 486, L9–L12) found them in young S-type clusters. The young age of these families suggest that the unweathered surface could date to the formation of the family. This leads to the question of whether older S-type main-belt families can contain Q-type objects and display evidence of a transition from Q- to S-type. To answer this question we have carried out a photometric survey of the Koronis family using the Kitt Peak 2.1m telescope. This provides a unique opportunity to compare the effects of the space weathering process on potentially ordinary chondrite-like bodies within a population of identical initial conditions. We find a trend in spectral slope for objects 1–5km that shows the transition from Q- to S-type in the main-belt. This data set will prove crucial to our understanding of the space weathering process and its relevant timescales. [Copyright &y& Elsevier]

The article focuses on trends in laundry detergent packs or pods consisting has concentrated laundry detergent has enclosed in a water-soluble membrane has introduced in the U.S. Topics include the majority of exposures has occurred by ingestion, a portion involved ocular exposures, the number of ocular exposures and exposures with ocular clinical effects increased from 2012 to 2016 and then declined to 2018, and reporting ocular injuries were consistent with those described in the literature.

Nanosystems represent new opportunities, new research and development efforts and new possibilities for advanced materials. Many industrial scientists are focusing on nanotechnology and many chemical industries are indeed funding ambitious but valuable efforts. These efforts are based on the belief and realization that nanosystems are basic and important blocks for building new businesses. Industrial computational experts find themselves at the right intersect: an intersect where their technology is uniquely capable to access understanding, to stimulate thoughts and possibilities, to run "what-if" scenarios, and to "truly" discover new nanosystems capable of providing the advanced material capability that future businesses foresee. This paper will focus on describing computational methodologies that we are currently using. The paper will also extend to cover the application of these methods to aromatics, in particular, pentacenes and benzene derivatives. [ABSTRACT FROM AUTHOR]

The article talks about the statistics of turpentine ingestion cases in Texas from 2000-2017 as reported to the Texas Poison Center Network (TPCN). It notes that 5 to 12-year-old children and adults aged 20 and older had the most cases of ingestions. It also reports on the clinical effects of the liquid on patients and their treatment.

The article focuses on the Adenium obesum being a member of the dogbane family. Topics include the Sahel and eastern and southern regions of Africa and the Arabian Peninsula it may be grown as a houseplant or bonsai, the cardiac glycosides are organic compounds that may block the conduction, and the electrical impulse that causes contraction of the heart and may produce abnormal cardiac rhythm.

Abstract Impacts due to near-Earth objects (NEOs) are responsible for causing some of the great mass extinctions on Earth. While nearly all NEOs of diameter > 1 km, capable of causing a global climatic disaster, have been discovered and have negligible chance of impacting in the near future, we are far from completion in our effort to detect and characterize smaller objects. In an effort to test our preparedness to respond to a potential NEO impact threat, we conducted a community-led global planetary defense exercise with support from the NASA Planetary Defense Coordination Office. The target of our exercise was 2012 TC4, the ~10 m diameter asteroid that made a close pass by the Earth on 2017 October 12 at a distance of about 50,000 km. The goal of the TC4 observing campaign was to recover, track, and characterize 2012 TC4 as a hypothetical impactor in order to exercise the global planetary defense system involving observations, modeling, prediction, and communication. We made three attempts with the Very Large Telescope (VLT) on 2017 July 27, 31 and on 2017 August 5 and recovered 2012 TC4 within its ephemeris uncertainty at 2.2 arcmin from the nominal prediction. At visual magnitude V = 27, the recovery of 2012 TC4 is the faintest NEA detection thus far. If an impact during the 2017 close approach had been possible based on the 2012 astrometric data, these recovery observations would have been sufficient to confirm or rule out the impact. The first automatic detection by a survey (Pan-STARRS1) was on September 25, which is the earliest that 2012 TC4 would have been discovered in survey mode, if it had not been discovered in 2012. We characterized 2012 TC4 using photometry, spectroscopy and radar techniques. Based on photometric observations, we determined a rotation period of 12.2 min with an amplitude of 0.9 magnitudes. An additional lower amplitude period was detected, indicating that 2012 TC4 was in a state of non-principal axis rotation. The combined visible and near-infrared spectrum puts it in the taxonomic X-class. Radar images at 1.875 m resolution placed only a few range pixels on the asteroid, reveal an angular, asymmetric, and elongated shape, and establish that 2012 TC4 is less than 20 m on its long axis. We estimate a circular polarization ratio of 0.57 + -0.08 that is relatively high among NEAs observed to date by radar. We also performed a probabilistic impact risk assessment exercise for hypothetical impactors based on the 2012 TC4 observing campaign. This exercise was performed as part of ongoing efforts to advance effective impact risk models and assessment processes for planetary defense. The 2012 TC4 close approach provided a valuable opportunity to test the application of these methods using realistically evolving observational data to define the modeling inputs. To this end, risk assessments were calculated at several epochs before and during the close approach, incorporating new information about 2012 TC4 as it became available. Two size ranges were assessed—one smaller size range (H = 26.7) similar to the actual 2012 TC4, and one larger size range (H = 21.9) to produce a greater-damage scenario for risk assessment. Across the epochs, we found that only irons caused significant damage for smaller size. For the larger size case, however, hydrous stones caused the greatest damage, anhydrous stones caused the least damage, and irons caused moderate damage. We note that the extent of damage depends on composition in different size regimes and, after astrometry, size is the most important physical property to determine for an incoming object. Highlights • We conducted a community-led global planetary defense exercise • The goal was to recover, track, and characterize 2012 TC4 as a hypothetical impactor • We found that after astrometric observations, size of the asteroid is the most important property for an impactor [ABSTRACT FROM AUTHOR]

The Asteroid Impact & Deflection Assessment (AIDA) mission is an international cooperation between NASA and ESA. NASA plans to provide the Double Asteroid Redirection Test (DART) mission which will perform a kinetic impactor experiment to demonstrate asteroid impact hazard mitigation. ESA proposes to provide the Hera mission which will rendezvous with the target to monitor the deflection, perform detailed characterizations, and measure the DART impact outcomes and momentum transfer efficiency. The primary goals of AIDA are (i) to demonstrate the kinetic impact technique on a potentially hazardous near-Earth asteroid and (ii) to measure and characterize the deflection caused by the impact. The AIDA target will be the binary asteroid (65803) Didymos, which is of spectral type Sq, with the deflection experiment to occur in October, 2022. The DART impact on the secondary member of the binary at ∼6 km/s changes the orbital speed and the binary orbit period, which can be measured by Earth-based observatories with telescope apertures as small as 1 m. The DART impact will in addition alter the orbital and rotational states of the Didymos binary, leading to excitation of eccentricity and libration that, if measured by Hera, can constrain internal structure of the target asteroid. Measurements of the DART crater diameter and morphology can constrain target properties like cohesion and porosity based on numerical simulations of the DART impact. [ABSTRACT FROM AUTHOR]

Evidence is seen for young, fresh surfaces among Near-Earth and Main-Belt asteroids even though space-weathering timescales are shorter than the age of the surfaces. A number of mechanisms have been proposed to refresh asteroid surfaces on short timescales, such as planetary encounters, YORP spinup, thermal degradation, and collisions. Additionally, other factors such as grain size effects have been proposed to explain the existence of these "fresh-looking" spectra. To investigate the role each of these mechanisms may play, we collected a sample of visible and near-infrared spectra of 477 near-Earth and Mars Crosser asteroids with similar sizes and compositions — all with absolute magnitude H > 16 and within the S-complex and having olivine to pyroxene (ol/(ol+opx)) ratios > 0.65. We taxonomically classify these objects in the Q (fresh) and S (weathered) classes. We find four trends in the Q/S ratio: (1) previous work demonstrated the Q/S ratio increases at smaller sizes down to H ≲ 16, but we find a sharp increase near H ∼ 19 after which the ratio decreases monotonically. (2) in agreement with many previous studies, the Q/S ratio increases with decreasing perihelion distance, and we find it is non-zero for larger perihelia > 1.2AU, (3) as a new finding our work reveals the Q/S ratio has a sharp, significant peak near ∼ 5° orbital inclination, and (4) we confirm previous findings that the Q/S ratio is higher for objects that have the possibility of encounter with Earth and Venus versus those that do not, however this finding cannot be distinguished from the perihelion trend. No single resurfacing mechanism can explain all of these trends, so multiple mechanisms are required. YORP spin-up scales with size, thermal degradation is dependent on perihelion, planetary encounters trend with inclination, perihelion and MOID, noting that asteroid–asteroid collisions are also dependent on inclination. It is likely that a combination of all four resurfacing mechanisms are needed to account for all observational trends. • We analyze visible and near-ir spectra of 477 S-complex NEOs and Mars Crossers. • We calculate the fresh-to-space-weathered (Q/S) ratio to understand physical processes. • The Q/S ratio depends on size, perihelion, inclination, and MOID. • No single resurfacing mechanism can explain all of these trends. • Four mechanisms are likely: YORP, thermal degradation, planetary encounters, and collisions. [ABSTRACT FROM AUTHOR]

Ordinary chondrites comprise a significant fraction (~75%) of meteorites that fall on the Earth. A key goal in small body science is to link meteorites to their parent bodies in order to understand their formation conditions early in our Solar System history. Dunn et al. (2010a) provided a robust set of equations for deriving olivine/pyroxene chemistry and abundance ratio from visible and near-infrared (0.35–2.5 μm) spectra of silicate-rich asteroids. These equations were calibrated to X-ray diffraction (XRD) and electron microprobe measurements as ground truth for the spectrally derived values. The small body community employs a range of methods to extract spectral band parameters from telescopic spectra of S-/Q-type asteroids and use the Dunn et al. (2010a) equations to constrain mineral chemistry and abundance. The goal of this work is to understand how the changing of polynomial order and method of extracting spectral band parameters from spectra of ordinary chondrite meteorites affects the precision of derived olivine and pyroxene chemistry and abundance compared with laboratory XRD and microprobe values. Based on our analysis, we find that 2nd order polynomials provide good agreement with the linear relationship found by Dunn et al. (2010a), but with a systematic offset. We also find that Band I center values derived from differing polynomial orders cannot be used for extracting mineral chemistry with Dunn et al. (2010a) equations. We find that the Band Area Ratio (BAR) values are independent of polynomial order and the olivine to pyroxene abundance ratio extracted from BAR is immune to changing polynomial order. Of the four published methods for extracting spectral band parameters (Sanchez et al. 2015, Dunn et al. 2010a, Spectral Analysis Routine for Asteroids, or SARA, Modeling for Asteroids, or M4AST), Dunn et al. (2010a)'s method most successfully reproduces both olivine and pyroxene chemistry, followed by Sanchez et al. (2015). SARA most successfully reproduces the olivine to pyroxene abundance ratio, very closely followed by the other three methods. We find systematic underestimation of ordinary chondrite Band I centers compared to Dunn et al. (2010a) and the resulting chemistry derived from them. To account for this underestimation, we have developed a correction factor for band parameters extracted using other methods that must be added to Band I centers for asteroids that fall in H, L, LL chondrite zones when using Dunn et al. (2010a) equations. • Ordinary chondrites are the dominant meteorite group that fall on Earth. • Existing lab calibrations fall short when interpreting telescopic asteroid spectra. • We present improved method to identify ordinary chondrite parent asteroids. [ABSTRACT FROM AUTHOR]

Some active asteroids have been proposed to be formed as a result of impact events 1 . Because active asteroids are generally discovered by chance only after their tails have fully formed, the process of how impact ejecta evolve into a tail has, to our knowledge, not been directly observed. The Double Asteroid Redirection Test (DART) mission of NASA 2 , in addition to having successfully changed the orbital period of Dimorphos 3 , demonstrated the activation process of an asteroid resulting from an impact under precisely known conditions. Here we report the observations of the DART impact ejecta with the Hubble Space Telescope from impact time T + 15 min to T + 18.5 days at spatial resolutions of around 2.1 km per pixel. Our observations reveal the complex evolution of the ejecta, which are first dominated by the gravitational interaction between the Didymos binary system and the ejected dust and subsequently by solar radiation pressure. The lowest-speed ejecta dispersed through a sustained tail that had a consistent morphology with previously observed asteroid tails thought to be produced by an impact 4,5 . The evolution of the ejecta after the controlled impact experiment of DART thus provides a framework for understanding the fundamental mechanisms that act on asteroids disrupted by a natural impact 1,6 ., (© 2023. The Author(s).)

Although no known asteroid poses a threat to Earth for at least the next century, the catalogue of near-Earth asteroids is incomplete for objects whose impacts would produce regional devastation 1,2 . Several approaches have been proposed to potentially prevent an asteroid impact with Earth by deflecting or disrupting an asteroid 1-3 . A test of kinetic impact technology was identified as the highest-priority space mission related to asteroid mitigation 1 . NASA's Double Asteroid Redirection Test (DART) mission is a full-scale test of kinetic impact technology. The mission's target asteroid was Dimorphos, the secondary member of the S-type binary near-Earth asteroid (65803) Didymos. This binary asteroid system was chosen to enable ground-based telescopes to quantify the asteroid deflection caused by the impact of the DART spacecraft 4 . Although past missions have utilized impactors to investigate the properties of small bodies 5,6 , those earlier missions were not intended to deflect their targets and did not achieve measurable deflections. Here we report the DART spacecraft's autonomous kinetic impact into Dimorphos and reconstruct the impact event, including the timeline leading to impact, the location and nature of the DART impact site, and the size and shape of Dimorphos. The successful impact of the DART spacecraft with Dimorphos and the resulting change in the orbit of Dimorphos 7 demonstrates that kinetic impactor technology is a viable technique to potentially defend Earth if necessary., (© 2023. The Author(s).)

The Double Asteroid Redirection Test (DART) spacecraft successfully performed the first test of a kinetic impactor for asteroid deflection by impacting Dimorphos, the secondary of near-Earth binary asteroid (65803) Didymos, and changing the orbital period of Dimorphos. A change in orbital period of approximately 7 min was expected if the incident momentum from the DART spacecraft was directly transferred to the asteroid target in a perfectly inelastic collision 1 , but studies of the probable impact conditions and asteroid properties indicated that a considerable momentum enhancement (β) was possible 2,3 . In the years before impact, we used lightcurve observations to accurately determine the pre-impact orbit parameters of Dimorphos with respect to Didymos 4-6 . Here we report the change in the orbital period of Dimorphos as a result of the DART kinetic impact to be -33.0 ± 1.0 (3σ) min. Using new Earth-based lightcurve and radar observations, two independent approaches determined identical values for the change in the orbital period. This large orbit period change suggests that ejecta contributed a substantial amount of momentum to the asteroid beyond what the DART spacecraft carried., (© 2023. The Author(s).)