ABSTRACT
We obtained high-resolution infrared spectroscopy and short-cadence photometry of the 600–800 Myr Praesepe star K2-100 during transits of its 1.67-d planet. This Neptune-size object, ...discovered by the NASA K2 mission, is an interloper in the ‘desert’ of planets with similar radii on short-period orbits. Our observations can be used to understand its origin and evolution by constraining the orbital eccentricity by transit fitting, measuring the spin-orbit obliquity by the Rossiter–McLaughlin effect, and detecting any extended, escaping the hydrogen–helium envelope with the 10 830 -Å line of neutral helium in the 2s3S triplet state. Transit photometry with 1-min cadence was obtained by the K2 satellite during Campaign 18 and transit spectra were obtained with the IRD spectrograph on the Subaru telescope. While the elevated activity of K2-100 prevented us from detecting the Rossiter–McLaughlin effect, the new photometry combined with revised stellar parameters allowed us to constrain the eccentricity to e < 0.15/0.28 with 90/99 per cent confidence. We modelled atmospheric escape as an isothermal, spherically symmetric Parker wind, with photochemistry driven by ultraviolet radiation, which we estimate by combining the observed spectrum of the active Sun with calibrations from observations of K2-100 and similar young stars in the nearby Hyades cluster. Our non-detection (<5.7 m Å) of a transit-associated He i line limits mass-loss of a solar-composition atmosphere through a T ≤ 10000 K wind to <0.3 M⊕ Gyr−1. Either K2-100b is an exceptional desert-dwelling planet, or its mass-loss is occurring at a lower rate over a longer interval, consistent with a core accretion-powered scenario for escape.
This work investigated the effective mass of electrons in silicon nanosheets confined in the 001 and 1̄10 directions and having thicknesses of several nanometers with uniaxial tensile stress in the ...110 direction, using density functional theory. The results show that the confinement along 1̄10 substantially reduces the effective mass in the 110 direction even in the absence of stress—a phenomenon not observed under 100 confinement. Our theoretical analysis reveals that confinement in the 110 direction acts as an effective shear strain. Furthermore, our study identifies an optimal stress that minimizes the effective mass in the transport direction, m110, thereby improving the nanosheet’s transport properties.
We study the full-counting statistics of charges transmitted through a single-level quantum dot weakly coupled to a local Einstein phonon which causes fluctuations in the dot energy. An analytic ...expression for the cumulant generating function, accurate up to second order in the electron-phonon coupling and valid for finite voltages and temperatures, is obtained in the extended wide-band limit. The result accounts for nonequilibrium phonon distributions induced by the source-drain bias voltage, and concomitantly satisfies the fluctuation theorem. Extending the counting field to the complex plane, we investigate the locations of possible singularities of the cumulant generating function, and exploit them to identify regimes in which the electron transfer is affected differently by the coupling to the phonons. Within a large-deviation analysis, we find a kink in the probability distribution, analogous to a first-order phase transition in thermodynamics, which would be a unique hallmark of the electron-phonon correlations. This kink reflects the fact that although inelastic scattering by the phonons once the voltage exceeds their frequency can scatter electrons opposite to the bias, this will never generate current flowing against the bias at zero temperature, in accordance with the fluctuation theorem.
ABSTRACT
M dwarf stars are high-priority targets for searches for Earth-size and potentially Earth-like planets, but their planetary systems may form and evolve in very different circumstellar ...environments than those of solar-type stars. To explore the evolution of these systems, we obtained transit spectroscopy and photometry of the Neptune-size planet orbiting the ≈650-Myr-old Hyades M dwarf K2-25. An analysis of the variation in spectral line shape induced by the Doppler ‘shadow’ of the planet indicates that the planet’s orbit is closely aligned with the stellar equator ($\lambda =-1.7_{-3.7}^{+5.8}$ deg), and that an eccentric orbit found by previous work could arise from perturbations by another planet on a coplanar orbit. We detect no significant variation in the depth of the He i line at 1083 nm during transit. A model of atmospheric escape as an isothermal Parker wind with a solar composition shows that this non-detection is not constraining compared to escape rate predictions of ∼0.1 M⊕ Gyr−1; at such rates, at least several Gyr are required for a Neptune-like planet to evolve into a rocky super-Earth.
Charge ordering (CO) is a phenomenon in which electrons in solids crystallize into a periodic pattern of charge-rich and charge-poor sites owing to strong electron correlations. This usually results ...in long-range order. In geometrically frustrated systems, however, a glassy electronic state without long-range CO has been observed. We found that a charge-ordered organic material with an isosceles triangular lattice shows charge dynamics associated with crystallization and vitrification of electrons, which can be understood in the context of an energy landscape arising from the degeneracy of various CO patterns. The dynamics suggest that the same nucleation and growth processes that characterize conventional glass-forming liquids guide the crystallization of electrons. These similarities may provide insight into our understanding of the liquid-glass transition.
This study was designed to investigate differences in patterns of physiological responses to salinity stress among five japonica rice cultivars in comparison with FL478 as a salinity tolerance check. ...Five japonica cultivars were screened for salinity tolerance at seedling stage based on visual symptoms of salt injury index and physiological parameters including dry matter production, electrolyte leakage ratio and ion concentration. The results indicated that cultivars Ouukan383 and FL478 were relatively more salinity tolerant than other cultivars and that Kanniho was the most salinity‐sensitive cultivar. Ouukan383 showed higher leaf water content and lower electrolyte leakage ratio under salinity stress. Notably, under salinity stress, Na+ concentration in the leaf blades was much lower in Ouukan383 than in FL478, but was much higher in Kanniho. To understand the basis for these differences, we studied transcript levels of the genes encoding Na+ transport proteins in different tissues. In response to salinity stress, Ouukan383 had highly induced expression of the OsHKT1;4 gene in the leaf sheaths, corresponding to higher Na+ accumulation in the leaf sheaths and lower Na+ accumulation in the leaf blades. On the other hand, the sensitive cultivar, Kanniho, had highly induced expression of the OsSOS1 and OsNHX1 genes in the leaf blades, whose gene products are responsible for Na+ efflux outside cells and Na+ compartmentalization into vacuoles. Thus, the salinity‐tolerant and salinity‐sensitive cultivars differed in their responses to Na+ fluxes in plant cells using different transport systems in each tissue type. The salinity‐tolerant japonica cultivar, Ouukan383, has an effective Na+ exclusion mechanism at the leaf sheaths to prevent Na+ accumulation in the leaf blades. Such a mechanism, in combination with other genetic traits (e.g. Na+ exclusion at the roots mediated by OsHKT1;5), offers the potential to improve salinity tolerance in rice.
Strongly enhanced quantum fluctuations often lead to a rich variety of quantum-disordered states. Developing approaches to enhance quantum fluctuations may open paths to realize even more fascinating ...quantum states. Here, we demonstrate that a coupling of localized spins with the zero-point motion of hydrogen atoms, that is, proton fluctuations in a hydrogen-bonded organic Mott insulator provides a different class of quantum spin liquids (QSLs). We find that divergent dielectric behavior associated with the approach to hydrogen-bond order is suppressed by the quantum proton fluctuations, resulting in a quantum paraelectric (QPE) state. Furthermore, our thermal-transport measurements reveal that a QSL state with gapless spin excitations rapidly emerges upon entering the QPE state. These findings indicate that the quantum proton fluctuations give rise to a QSL-a quantum-disordered state of magnetic and electric dipoles-through the coupling between the electron and proton degrees of freedom.
The objective of this study was to determine quarters requiring antimicrobial treatment using either a benchtop somatic cell counter (S-SDCT) or culture with gram-positive selective media (C-SDCT) ...and compare outcomes in these cows to those receiving blanket dry cow therapy (BDCT) in a randomized, controlled trial. Two novel methods of identifying cows with intramammary infections followed by selective antimicrobial treatment were evaluated at a commercial dairy farm to determine their usefulness in decreasing antibiotic usage during the dry period without significant detrimental effects on milk quality and production. Cows (n = 840) were randomly allocated to one of 3 groups (BDCT, C-SDCT, S-SDCT) the day before dry-off and quarter-level milk samples (QLMS) were collected. The QLMS from cows in the S-SDCT group were evaluated using the cell counter and quarters were treated if somatic cell count (SCC) was ≥200,000 cells/mL, while QLMS from cows in the C-SDCT group were cultured and quarters were treated if the culture showed growth. All cows in the BDCT received antimicrobial therapy and all cows received an internal teat sealant regardless of treatment group. Outcomes measured were first and second DHIA test somatic cell count, milk production through 60 d in milk, cows leaving the farm, clinical mastitis, and bacteriologic new infections in a subset of quarters. Cows in both SDCT groups had fewer antimicrobial treatments than cows in the BDCT group as was expected, and cows in the C-SDCT group had fewer treatments than those in the S-SDCT group. Cows in both SDCT groups had higher linear score at the first DHIA test (BDCT: 1.8, S-SDCT: 2.2, C-SDCT: 2.2), however there were no other differences between groups regarding any other outcomes measured. While antimicrobial use was significantly reduced, farms should use caution in adopting the benchtop analyzer and the selective media described in this study as ways to identify infected cows for dry cow therapy as they may result in increased linear score early in lactation.
We describe a black-tailed prairie dog (Cynomys ludovicianus) with a benign biphasic nodular tumour that recurred as a malignant biphasic tumour at the same site 2 years after resection. Both tumours ...were biphasic with regard to the glandular epithelium and basal cells and contained little of the mucus, cartilage or fibrous tissue that characterize pleomorphic adenoma and carcinoma ex-pleomorphic adenoma. Both the first and second tumours exhibited histopathological features similar to those exhibited by human basal cell adenoma and adenocarcinoma, respectively. Both were resected and the animal was alive with no recurrence or metastasis at the time of writing, 9 months after the second surgery.
Uterine atony is one of the leading causes of maternal death, and the use of intrauterine balloon tamponade is recommended for the treatment of atonic postpartum hemorrhage. The success rate of ...balloon tamponade for uterine atony is high, but some cases with atonic postpartum hemorrhage require arterial embolization or hysterectomy. Therefore, it is important to understand the underlying causes of refractory atonic postpartum hemorrhage and the limitations of balloon tamponade to choose an appropriate treatment for atonic postpartum hemorrhage. In clinical settings, few obstetricians that use balloons have an understanding of the site of bleeding and where the balloon is lodged in the uterus. Given the recent advances in our understanding of the pathogenesis of refractory atonic postpartum hemorrhage and the shape of the postpartum uterine cavity, we outline our thoughts on the use of intrauterine balloon tamponade for the treatment of atonic postpartum hemorrhage. (145/150 words).
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