They might be giants: luminosity class, planet frequency, and planet-metallicity relation of the coolest Kepler target stars

We estimate the stellar parameters of late K and early M type Kepler target stars. We obtain medium resolution visible spectra of 382 stars with Kp-J>2 (~K5 and later spectral type). We determine luminosity class by comparing the strength of gravity-sensitive indices (CaH, K I, Ca II, and Na I) to their strength in a sample of stars of known luminosity class. We find that giants constitute 96+-% of the bright (Kp<14) Kepler target stars, and 7+-3% of dim (Kp>14) stars, significantly higher than fractions based on the stellar parameters quoted in the Kepler Input Catalog (KIC). The KIC effective temperatures are systematically (110 +15 -35} K) higher than temperatures we determine from fitting our spectra to PHOENIX stellar models. Through Monte Carlo simulations of the Kepler exoplanet candidate population, we find a planet occurrence of 0.36+-0.08 when giant stars are properly removed, somewhat higher than when a KIC log(g)>4 criterion is used (0.27+-0.05). Lastly, we show that there is no significant difference in g-r color (a probe of metallicity) between late-type Kepler stars with transiting Earth-to-Neptune sized exoplanet candidates and dwarf stars with no detected transits. We show that a previous claimed offset between these two populations is most likely an artifact of including a large number of misidentified giants.Comment: Accepted to Ap

Energy Efficient Load Latency Tolerance: Single-Thread Performance for the Multi-Core Era

Around 2003, newly activated power constraints caused single-thread performance growth to slow dramatically. The multi-core era was born with an emphasis on explicitly parallel software. Continuing to grow single-thread performance is still important in the multi-core context, but it must be done in an energy efficient way. One significant impediment to performance growth in both out-of-order and in-order processors is the long latency of last-level cache misses. Prior work introduced the idea of load latency tolerance---the ability to dynamically remove miss-dependent instructions from critical execution structures, continue execution under the miss, and re-execute miss-dependent instructions after the miss returns. However, previously proposed designs were unable to improve performance in an energy-efficient way---they introduced too many new large, complex structures and re-executed too many instructions. This dissertation describes a new load latency tolerant design that is both energy-efficient, and applicable to both in-order and out-of-order cores. Key novel features include formulation of slice re-execution as an alternative use of multi-threading support, efficient schemes for register and memory state management, and new pruning mechanisms for drastically reducing load latency tolerance\u27s dynamic execution overheads. Area analysis shows that energy-efficient load latency tolerance increases the footprint of an out-of-order core by a few percent, while cycle-level simulation shows that it significantly improves the performance of memory-bound programs. Energy-efficient load latency tolerance is more energy-efficient than---and synergistic with---existing performance technique like dynamic voltage and frequency scaling (DVFS)

Testing the Metal of Late-Type Kepler Planet Hosts with Iron-Clad Methods

It has been shown that F, G, and early K dwarf hosts of Neptune-sized planets are not preferentially metal-rich. However, it is less clear whether the same holds for late K and M dwarf planet hosts. We report metallicities of Kepler targets and candidate transiting planet hosts with effective temperatures below 4500 K. We use new metallicity calibrations to determine [Fe/H] from visible and near-infrared spectra. We find that the metallicity distribution of late K and M dwarfs monitored by Kepler is consistent with that of the solar neighborhood. Further, we show that hosts of Earth- to Neptune-sized planets have metallicities consistent with those lacking detected planets and rule out a previously claimed 0.2 dex offset between the two distributions at 6sigma confidence. We also demonstrate that the metallicities of late K and M dwarfs hosting multiple detected planets are consistent with those lacking detected planets. Our results indicate that multiple terrestrial and Neptune-sized planets can form around late K and M dwarfs with metallicities as low as 0.25 of the solar value. The presence of Neptune-sized planets orbiting such low-metallicity M dwarfs suggests that accreting planets collect most or all of the solids from the disk and that the potential cores of giant planets can readily form around M dwarfs. The paucity of giant planets around M dwarfs compared to solar-type stars must be due to relatively rapid disk evaporation or a slower rate of core accretion, rather than insufficient solids to form a core.Comment: 9 pages, 5 figures. Accepted to Ap

Totem and Taboo: Fluids in sepsis

The need for early, rapid, and substantial fluid resuscitation in septic patients has long been an article of faith in the intensive care community, a tribal totem that is taboo to question. The results of a recent multicenter trial in septic children in Africa, published in The New England Journal of Medicine, powerfully challenge the fluid paradigm. The salient aspects of the trial need to be understood and reflected upon. In this commentary, we discuss the background to and findings of the trial and explain why they will likely trigger a re-evaluation of our thinking about fluids in sepsis, a re-evaluation that is already happening in the treatment of acute respiratory distress syndrome and acute kidney injury and in postoperative care

Behavioural counselling to increase consumption of fruit and vegetables in low income adults : randomised trial

Objective To measure the effect of brief behavioural counselling in general practice on patients’ consumption of fruit and vegetables in adults from a low income population. Design Parallel group randomised controlled trial. Setting Primary health centre in a deprived, ethnically mixed inner city area. Participants 271 patients aged 18-70 years without serious illness. Intervention Brief individual behavioural counselling based on the stage of change model; time matched nutrition education counselling. Main outcome measures Self reported number of portions of fruit and vegetables eaten per day, plasma β carotene, α tocopherol, and ascorbic acid concentrations, and 24 hour urinary potassium excretion. Assessment at baseline, eight weeks, and 12 months. Results Consumption of fruit and vegetables increased from baseline to 12 months by 1.5 and 0.9 portions per day in the behavioural and nutrition groups (mean difference 0.6 portions, 95% confidence interval 0.1 to 1.1). The proportion of participants eating five or more portions a day increased by 42% and 27% in the two groups (mean difference 15%, 3% to 28%). Plasma β carotene and α tocopherol concentrations increased in both groups, but the rise in β carotene was greater in the behavioural group (mean difference 0.16 μmol/l, 0.001 μmol/l to 1.34 μmol/l). There were no changes in plasma ascorbic acid concentrations or urinary potassium excretion. Differences were maintained when analysis was restricted to the 177 participants with incomes ≤ £400 (€596, $640) a week. Conclusions Brief individual counselling in primary care can elicit sustained increases in consumption of fruit and vegetables in low income adults in the general population

A Charcoalified Ovule Adapted for Wind Dispersal and Deterring Herbivory from the Late Viséan (Carboniferous) of Scotland

International audiencePremise of research : Mississippian (Lower Carboniferous) anatomically preserved ovules are pivotal to our present understanding of the Paleozoic primary seed plant radiation, but few are known from the late Viséan stratigraphic interval approximately 330 million years ago. Here, we document an exceptionally well-preserved mesoscopic charcoalified ovule from late Viséan limestones that is adapted for wind dispersal and for deterring herbivory.Methodology : We use synchrotron radiation X-ray tomographic microscopy (SRXTM) and low-vacuum scanning electron microscopy (LVSEM) to analyze histological features not identifiable through traditional methods.Pivotal results:The ovule is small, 2 mm long and 1.25 mm in maximum diameter, and has a dense covering of spirally arranged, long, slender, hollow hairs with glandular apexes and a distal papilla. The nucellus is fused to the integument up to the nucellar apex, and above this, the integument comprises eight apical lobes, each with a single vascular bundle. The nucellar apex has a domed pollen chamber and large central column characteristic of hydrasperman-type (lagenostomalean) pteridosperms, but it lacks the distal salpinx seen in most hydrasperman ovules, leaving an exposed distal opening to the pollen chamber for pollination. Differences with existing taxa lead to the erection of Hirsutisperma rothwellii gen. et sp. nov.Conclusions : The apical glands presumably functioned as granivory deterrents; coprolites (fossilized feces) from herbivorous arthropods are abundant in the fossiliferous horizon and at this stratigraphic interval. The small ovule size and its dense covering of hairs indicate Hirsutisperma was adapted for wind dispersal and was an r-selected species, producing large numbers of small offspring in unstable or changing environments. Taphonomic implications are discussed, including preservational biases for charcoalification. Hirsutisperma provides the first clear evidence for ecological niche partitioning in Mississippian hydrasperman-type ovules