Characterization of the Subsurface of 67P/Churyumov-Gerasimenko's Abydos Site

We investigate the structure of the subsurface of the Abydos site using a cometary nucleus model with parameters adapted to comet 67P/Churyumov-Gerasimenko and the Abydos landing site. We aim to compare the production rates derived from our model with those of the main molecules measured by Ptolemy. This will allow us to retrieve the depths at which the different molecules still exist in solid form

The Classical Harmonic Vibrations of the Atomic Centers of Mass with Micro Amplitudes and Low Frequencies Monitored by the Entanglement between the Two Two-level Atoms in a Single mode Cavity

We study the entanglement dynamics of the two two-level atoms coupling with a single-mode polarized cavity field after incorporating the atomic centers of mass classical harmonic vibrations with micro amplitudes and low frequencies. We propose a quantitative vibrant factor to modify the concurrence of the two atoms states. When the vibrant frequencies are very low, we obtain that: (i) the factor depends on the relative vibrant displacements and the initial phases rather than the absolute amplitudes, and reduces the concurrence to three orders of magnitude; (ii) the concurrence increases with the increase of the initial phases; (iii) the frequency of the harmonic vibration can be obtained by measuring the maximal value of the concurrence during a small time. These results indicate that even the extremely weak classical harmonic vibrations can be monitored by the entanglement of quantum states.Comment: 10 pages, 3 figure

Evolution of the subsurface of 67P/Churyumov-Gerasimenko’s Abydos Site

On November 12, 2014, Rosetta's descent module Philae landed on the Abydos site of comet 67P/Churyumov-Gerasimenko (67P). Here we investigate the structure of the subsurface of the Abydos site by making use of a cometary nucleus model [1] employing an updated set of thermodynamic parameters relevant for 67P and an appropriated parameterization of the illumination of the Abydos site. The model considers an initially homogeneous sphere composed of a predefined porous mixture of crystalline ices (H2O, CO and CO2) and dust in specified proportions, and uses parameters derived from recent 67P studies [2], [3] and [4]. The comparison of the production rates derived from our model with those of the main molecules measured by Ptolemy (the mass spectrometer performing the analysis of several samples collected from the surface and atmosphere of the comet) should allow us to place important constraints on the structure (layering and composition) of the subsurface of Philae’s landing site

From Centaurs to comets - 40 years

In 1977, while Apple II and Atari computers were being sold, a tiny dot was observed in an inconvenient orbit. The minor body 1977 UB, to be named (2060) Chiron, with an orbit between Saturn and Uranus, became the first Centaur, a new class of minor bodies orbiting roughly between Jupiter and Neptune. The observed overabundance of short-period comets lead to the downfall of the Oort Cloud as exclusive source of comets and to the rise of the need for a Trans-Neptunian comet belt. Centaurs were rapidly seen as the transition phase between Kuiper Belt Objects (KBOs), also known as Trans-Neptunian Objects (TNOs) and the Jupiter-Family Comets (JFCs). Since then, a lot more has been discovered about Centaurs: they can have cometary activity and outbursts, satellites, and even rings. Over the past four decades since the discovery of the first Centaur, rotation periods, surface colors, reflectivity spectra and albedos have been measured and analyzed. However, despite such a large number of studies and complementary techniques, the Centaur population remains a mystery as they are in so many ways different from the TNOs and even more so from the JFCs.Facultad de Ciencias Astronómicas y GeofísicasInstituto de Astrofísica de La Plat

Acute camptocormia induced by olanzapine: a case report

<p>Abstract</p> <p>Introduction</p> <p>Camptocormia refers to an abnormal posture with flexion of the thoraco-lumbar spine which increases during walking and resolves in supine position. This symptom is an increasingly recognized feature of parkinsonian and dystonic disorders, but may also be caused by neuromuscular diseases. There is recent evidence that both central and peripheral mechanisms may be involved in the pathogenesis of camptocormia. We report a case of acute onset of camptocormia, a rare side effect induced by olanzapine, a second-generation atypical anti-psychotic drug with fewer extra-pyramidal side-effects, increasingly used as first line therapy for schizophrenia, delusional disorders and bipolar disorder.</p> <p>Case presentation</p> <p>A 73-year-old Caucasian woman with no history of neuromuscular disorder, treated for chronic delusional disorder for the last ten years, received two injections of long-acting haloperidol. She was then referred for fatigue. Physical examination showed a frank parkinsonism without other abnormalities. Routine laboratory tests showed normal results, notably concerning creatine kinase level. Fatigue was attributed to haloperidol which was substituted for olanzapine. Our patient left the hospital after five days without complaint. She was admitted again three days later with acute back pain. Examination showed camptocormia and tenderness in paraspinal muscles. Creatine kinase level was elevated (2986 UI/L). Magnetic resonance imaging showed necrosis and edema in paraspinal muscles. Olanzapine was discontinued. Pain resolved quickly and muscle enzymes were normalized within ten days. Risperidone was later introduced without significant side-effect. The camptocormic posture had disappeared when the patient was seen as an out-patient one year later.</p> <p>Conclusions</p> <p>Camptocormia is a heterogeneous syndrome of various causes. We believe that our case illustrates the need to search for paraspinal muscle damage, including drug-induced rhabdomyolysis, in patients presenting with acute-onset bent spine syndrome. Although rare, the occurrence of camptocormia induced by olanzapine must be considered.</p

The Main Belt Comets and ice in the Solar System

We review the evidence for buried ice in the asteroid belt; specifically the questions around the so-called Main Belt Comets (MBCs). We summarise the evidence for water throughout the Solar System, and describe the various methods for detecting it, including remote sensing from ultraviolet to radio wavelengths. We review progress in the first decade of study of MBCs, including observations, modelling of ice survival, and discussion on their origins. We then look at which methods will likely be most effective for further progress, including the key challenge of direct detection of (escaping) water in these bodies

Entrepreneurs’ age, institutions, and social value creation goals: a multi-country study

This study explores the relationship between an entrepreneur's age and his/her social value creation goals. Building on the lifespan developmental psychology literature and institutional theory, we hypothesize a U-shaped relationship between entrepreneurs’ age and their choice to create social value through their ventures, such that younger and older entrepreneurs create more social value with their businesses while middle age entrepreneurs are relatively more economically and less socially oriented with their ventures. We further hypothesize that the quality of a country’s formal institutions in terms of economic, social, and political freedom steepen the U-shaped relationship between entrepreneurs’ age and their choice to pursue social value creation as supportive institutional environments allow entrepreneurs to follow their age-based preferences. We confirm our predictions using multilevel mixed-effects linear regressions on a sample of over 15,000 entrepreneurs (aged between 18 and 64 years) in 45 countries from Global Entrepreneurship Monitor data. The findings are robust to several alternative specifications. Based on our findings, we discuss implications for theory and practice, and we propose future research directions

Combining Logics to Transform Organizational Agency: Blending Industry and Art at Alessi

To understand how organizations combine conflicting institutional logics strategically to create and pursue new market opportunities, we conducted an in-depth longitudinal study of the multiple efforts of the Italian manufacturer of household goods Alessi to combine the logics of industrial manufacturing and cultural production. Over three decades, Alessi developed three different strategies to combine normative elements of the two logics, using each strategy to envision and pursue different market opportunities. By combining the logics of industrial manufacturing and cultural production, Alessi was able to envision new possibilities for value creation and to enact them through innovation in product design. The three strategies triggered a common set of mechanisms through which the purposeful combining of logics enabled the pursuit of opportunity, while each strategy structured the process differently. We develop a theoretical model linking the development of recombinant strategies to the dynamic restructuring of organizational agency and the related capacity to create and pursue new market opportunities. Our findings and theoretical insights advance understanding of the processes through which organizations challenge taken-for-granted beliefs and practices to create new market opportunities, use logics as resources to enable embedded agency, and design hybrid organizational arrangements

Size and Shape of Chariklo from Multi-epoch Stellar Occultation

We use data from five stellar occultations observed between 2013 and 2016 to constrain Chariklo’s size and shape, and the ring reflectivity. We consider four possible models for Chariklo (sphere, Maclaurin spheroid, triaxial ellipsoid, and Jacobi ellipsoid), and we use a Bayesian approach to estimate the corresponding parameters. The spherical model has a radius R = 129 ± 3 km. The Maclaurin model has equatorial and polar radii a=b={143}-6+3 {km} and c={96}-4+14 {km}, respectively, with density {970}-180+300 {kg} {{{m}}}-3. The ellipsoidal model has semiaxes a={148}-4+6 {km}, b={132}-5+6 {km}, and c={102}-8+10 {km}. Finally, the Jacobi model has semiaxes a = 157 ± 4 km, b = 139 ± 4 km, and c = 86 ± 1 km, and density {796}-4+2 {kg} {{{m}}}-3. Depending on the model, we obtain topographic features of 6–11 km, typical of Saturn icy satellites with similar size and density. We constrain Chariklo’s geometric albedo between 3.1% (sphere) and 4.9% (ellipsoid), while the ring I/F reflectivity is less constrained between 0.6% (Jacobi) and 8.9% (sphere). The ellipsoid model explains both the optical light curve and the long-term photometry variation of the system, giving a plausible value for the geometric albedo of the ring particles of 10%–15%. The derived mass of Chariklo of 6–8 × 1018 kg places the rings close to 3:1 resonance between the ring mean motion and Chariklo’s rotation period