Angular Diameters of the G Subdwarf μ\mu Cassiopeiae A and the K Dwarfs σ\sigma Draconis and HR 511 from Interferometric Measurements with the CHARA Array

Using the longest baselines of the CHARA Array, we have measured the angular diameter of the G5 V subdwarf $\mu$ Cas A, the first such determination for a halo population star. We compare this result to new diameters for the higher metallicity K0 V stars, $\sigma$ Dra and HR 511, and find that the metal-poor star, $\mu$ Cas A, has an effective temperature ($T_{\rm eff}=5297\pm32$ K), radius ($R=0.791\pm0.008 R_{\rm \odot}$), and absolute luminosity ($L=0.442\pm0.014 L_{\rm \odot}$) comparable to the other two stars with later spectral types. We show that stellar models show a discrepancy in the predicted temperature and radius for $\mu$ Cas A, and we discuss these results and how they provide a key to understanding the fundamental relationships for stars with low metallicity.Comment: Accepted for publication in The Astrophysical Journa

Shape model and spin-state analysis of PHA contact binary (85990) 1999 JV6 from combined radar and optical observations

Context. The potentially hazardous asteroid (85990)1999 JV6 has been a target of previously published thermal-infrared observations and optical photometry. It has been identified as a promising candidate for possible Yarkovsky-O’Keefe-Radzievskii-Paddack (YORP) effect detection. Aims. The YORP effect is a small thermal-radiation torque considered to be a key factor in spin-state evolution of small Solar System bodies. In order to detect YORP on 1999 JV6 we developed a detailed shape model and analysed the spin-state using both optical and radar observations. Methods. For 1999 JV6, we collected optical photometry between 2007 and 2016. Additionally, we obtained radar echo-power spectra and imaging observations with Arecibo and Goldstone planetary radar facilities in 2015, 2016, and 2017. We combined our data with published optical photometry to develop a robust physical model. Results. We determine that the rotation pole resides at negative latitudes in an area with a 5◦ radius close to the south ecliptic pole. The refined sidereal rotation period is 6.536787±0.000007 h. The radar images are best reproduced with a bilobed shape model. Both lobes of 1999 JV6 can be represented as oblate ellipsoids with a smaller, more spherical component resting at the end of a larger, more elongated component. While contact binaries appear to be abundant in the near-Earth population, there are only a few published shape models for asteroids in this particular configuration. By combining the radar-derived shape model with optical light curves we determine a constant-period solution that fits all available data well. Using light-curve data alone we determine an upper limit for YORP of 8.5×10−8 rad day−2. Conclusions. The bifurcated shape of 1999 JV6 might be a result of two ellipsoidal components gently merging with each other, or a deformation of a rubble pile with a weak-tensile-strength core due to spin-up. The physical model of 1999 JV6 presented here will enable future studies of contact binary asteroid formation and evolution

A low-memory algorithm for finding short product representations in finite groups

We describe a space-efficient algorithm for solving a generalization of the subset sum problem in a finite group G, using a Pollard-rho approach. Given an element z and a sequence of elements S, our algorithm attempts to find a subsequence of S whose product in G is equal to z. For a random sequence S of length d log_2 n, where n=#G and d >= 2 is a constant, we find that its expected running time is O(sqrt(n) log n) group operations (we give a rigorous proof for d > 4), and it only needs to store O(1) group elements. We consider applications to class groups of imaginary quadratic fields, and to finding isogenies between elliptic curves over a finite field.Comment: 12 page

K^0 pi^0 Sigma^+ and K^*0 Sigma^+ photoproduction off the proton

The exclusive reactions $\gamma p \to K^{*0} \Sigma^+(1189)$ and $\gamma p \to K^{0} \pi^{0}\Sigma^+(1189)$, leading to the p 4$\pi^{0}$ final state, have been measured with a tagged photon beam for incident energies from threshold up to 2.5 GeV. The experiment has been performed at the tagged photon facility of the ELSA accelerator (Bonn). The Crystal Barrel and TAPS detectors were combined to a photon detector system of almost 4$\pi$ geometrical acceptance. Differential and total cross sections are reported. At energies close to the threshold, a flat angular distribution has been observed for the reaction $\gamma p\to K^{0} \pi^{0}\Sigma^+$ suggesting dominant s-channel production. $\Sigma^*(1385)$ and higher lying hyperon states have been observed. An enhancement in the forward direction in the angular distributions of the reaction $\gamma p \to K^{*0}\Sigma^+$ indicates a $t$-channel exchange contribution to the reaction mechanism. The experimental data are in reasonable agreement with recent theoretical predictions.Comment: 11 pages, 13 figures, submitted to EPJ

Isogeny-Based Quantum-Resistant Undeniable Signatures

Abstract. We propose an undeniable signature scheme based on el-liptic curve isogenies, and prove its security under certain reasonable number-theoretic computational assumptions for which no efficient quan-tum algorithms are known. Our proposal represents only the second known quantum-resistant undeniable signature scheme, and the first such scheme secure under a number-theoretic complexity assumption

Attitudes of US medical trainees towards neurology education: "Neurophobia" - a global issue

<p>Abstract</p> <p>Background</p> <p>Several studies in the United Kingdom and Asia have suggested that medical students and residents have particular difficulty in diagnosing and managing patients with neurological problems. Little recent information is available for US trainees. We examined whether students and residents at a US university have difficulty in dealing with patients with neurological problems, identified the perceived sources of these difficulties and provide suggestions for the development of an effective educational experience in neurology.</p> <p>Methods</p> <p>A questionnaire was administered to third and fourth year medical students at a US school of medicine and to residents of an internal medicine residency program affiliated with that school. Perceived difficulties with eight medical specialties, including neurology, were examined. Methods considered to be most useful for learning medicine were documented. Reasons why neurology is perceived as difficult and ways to improve neurological teaching were assessed.</p> <p>Results</p> <p>152 surveys were completed. Participation rates varied, with medical students having higher response rates (> 50%) than medical residents (27%-48%). Respondents felt that neurology was the medical specialty they had least knowledge in (p < 0.001) and was most difficult (p < 0.001). Trainees also felt they had the least confidence when dealing with patients with neurological complaints (p < 0.001). Residents felt more competent in neurology than students (p < 0.001). The paramount reasons for perceived difficulties with neurology were the complexity of neuroanatomy, limited patient exposure and insufficient teaching. Transition from pre-clinical to clinical medicine led to a doubling of "poor" ratings for neurological teaching. Over 80% of the respondents felt that neurology teaching could be improved through greater exposure to patients and more bedside tutorials.</p> <p>Conclusions</p> <p>Medical students and residents at this US medical university found neurology difficult. Although this is consistent with prior reports from Europe and Asia, studies in other universities are needed to confirm generalizability of these findings. The optimal opportunity for improvement is during the transition from preclinical to clinical years. Enhanced integration of basic neurosciences and clinical neurology with emphasis on increased bedside tutorials and patient exposure should improve teaching. Studies are needed to quantify the effect of these interventions on confidence of trainees when dealing with patients presenting with neurological complaints.</p

Threshold Schemes from Isogeny Assumptions

We initiate the study of threshold schemes based on the Hard Homogeneous Spaces (HHS) framework of Couveignes. Quantum-resistant HHS based on supersingular isogeny graphs have recently become usable thanks to the record class group precomputation performed for the signature scheme CSI-FiSh. Using the HHS equivalent of the technique of Shamir\u27s secret sharing in the exponents, we adapt isogeny based schemes to the threshold setting. In particular we present threshold versions of the CSIDH public key encryption, and the CSI-FiSh signature schemes. The main highlight is a threshold version of CSI-FiSh which runs almost as fast as the original scheme, for message sizes as low as 1880 B, public key sizes as low as 128 B, and thresholds up to 56; other speed-size-threshold compromises are possible

The First Habitable-Zone Earth-Sized Planet From TESS. I. Validation Of The TOI-700 System

We present the discovery and validation of a three-planet system orbiting the nearby (31.1 pc) M2 dwarf star TOI-700 (TIC 150428135). TOI-700 lies in the TESS continuous viewing zone in the Southern Ecliptic Hemisphere; observations spanning 11 sectors reveal three planets with radii ranging from 1 R⊕ to 2.6 R⊕ and orbital periods ranging from 9.98 to 37.43 days. Ground-based follow-up combined with diagnostic vetting and validation tests enables us to rule out common astrophysical false-positive scenarios and validate the system of planets. The outermost planet, TOI-700 d, has a radius of 1.19 ± 0.11 R⊕ and resides within a conservative estimate of the host star\u27s habitable zone, where it receives a flux from its star that is approximately 86% of Earth\u27s insolation. In contrast to some other low-mass stars that host Earth-sized planets in their habitable zones, TOI-700 exhibits low levels of stellar activity, presenting a valuable opportunity to study potentially rocky planets over a wide range of conditions affecting atmospheric escape. While atmospheric characterization of TOI-700 d with the James Webb Space Telescope (JWST) will be challenging, the larger sub-Neptune, TOI-700 c (R = 2.63 R⊕), will be an excellent target for JWST and future space-based observatories. TESS is scheduled to once again observe the Southern Hemisphere, and it will monitor TOI-700 for an additional 11 sectors in its extended mission. These observations should allow further constraints on the known planet parameters and searches for additional planets and transit timing variations in the system

TESS Spots A Hot Jupiter With An Inner Transiting Neptune

Hot Jupiters are rarely accompanied by other planets within a factor of a few in orbital distance. Previously, only two such systems have been found. Here, we report the discovery of a third system using data from the Transiting Exoplanet Survey Satellite (TESS). The host star, TOI-1130, is an eleventh magnitude K-dwarf in Gaia G-band. It has two transiting planets: a Neptune-sized planet (3.65 ± 0.10 ${R}_{\oplus }$) with a 4.1 days period, and a hot Jupiter (${1.50}_{-0.22}^{+0.27}$ ${R}_{{\rm{J}}}$) with an 8.4 days period. Precise radial-velocity observations show that the mass of the hot Jupiter is ${0.974}_{-0.044}^{+0.043}$ ${M}_{{\rm{J}}}$. For the inner Neptune, the data provide only an upper limit on the mass of 0.17 ${M}_{{\rm{J}}}$ (3σ). Nevertheless, we are confident that the inner planet is real, based on follow-up ground-based photometry and adaptive-optics imaging that rule out other plausible sources of the TESS transit signal. The unusual planetary architecture of and the brightness of the host star make TOI-1130 a good test case for planet formation theories, and an attractive target for future spectroscopic observations