Characteristics of proton velocity distribution functions in the near-lunar wake from Chandrayaan-1/SWIM observations

Due to the high absorption of solar wind plasma on the lunar dayside, a large scale wake structure is formed downstream of the Moon. However, recent in-situ observations have revealed the presence of protons in the near-lunar wake (100 km to 200 km from the surface). The solar wind, either directly or after interaction with the lunar surface (including magnetic anomalies), is the source of these protons in the near-wake region. Using the entire data from the SWIM sensor of the SARA experiment onboard Chandrayaan-1, we analysed the velocity distribution of the protons observed in the near-lunar wake. The average velocity distribution functions, computed in the solar wind rest frame, were further separated based on the angle between the upstream solar wind velocity and the IMF. Several proton populations were identified from the velocity distribution and their possible entry mechanism were inferred based on the characteristics of the velocity distribution. These entry mechanisms include (i) diffusion of solar wind protons into the wake along IMF, (ii) the solar wind protons with finite gyro-radii that are aided by the wake boundary electric field, (iii) solar wind protons with gyro-radii larger than lunar radii from the tail of the solar wind velocity distribution, and (iv) scattering of solar wind protons from the dayside lunar surface or from magnetic anomalies. In order to gain more insight into the entry mechanisms associated with different populations, backtracing is carried out for each of these populations. For most of the populations, the source of the protons obtained from backtracing is found to be in agreement with that inferred from the velocity distribution. There are few populations that could not be explained by the known mechanisms and remain unknown.Comment: 8 figures, paper accepted in Icarus (2016), http://dx.doi.org/10.1016/j.icarus.2016.01.03

PDE-Foam - a probability-density estimation method using self-adapting phase-space binning

Probability Density Estimation (PDE) is a multivariate discrimination technique based on sampling signal and background densities defined by event samples from data or Monte-Carlo (MC) simulations in a multi-dimensional phase space. In this paper, we present a modification of the PDE method that uses a self-adapting binning method to divide the multi-dimensional phase space in a finite number of hyper-rectangles (cells). The binning algorithm adjusts the size and position of a predefined number of cells inside the multi-dimensional phase space, minimising the variance of the signal and background densities inside the cells. The implementation of the binning algorithm PDE-Foam is based on the MC event-generation package Foam. We present performance results for representative examples (toy models) and discuss the dependence of the obtained results on the choice of parameters. The new PDE-Foam shows improved classification capability for small training samples and reduced classification time compared to the original PDE method based on range searching.Comment: 19 pages, 11 figures; replaced with revised version accepted for publication in NIM A and corrected typos in description of Fig. 7 and

Extremely high reflection of solar wind protons as neutral hydrogen atoms from regolith in space

We report on measurements of extremely high reflection rates of solar wind particles from regolith-covered lunar surfaces. Measurements by the Sub-keV Atom Reflecting Analyzer (SARA) instrument on the Indian Chandrayaan-1 spacecraft in orbit around the Moon show that up to 20% of the impinging solar wind protons are reflected from the lunar surface back to space as neutral hydrogen atoms. This finding, generally applicable to regolith-covered atmosphereless bodies, invalidates the widely accepted assumption that regolith almost completely absorbs the impinging solar wind.Comment: 2 figure

Three-Dimensional Modeling of Callisto's Surface Sputtered Exosphere Environment

We study the release of various elements from Callisto's surface into its exosphere by plasma sputtering. The cold Jovian plasma is simulated with a 3D plasma-planetary interaction hybrid model, which produces 2D surface precipitation maps for magnetospheric H+ , O+ , O++ , and S++ . For the hot Jovian plasma, we assume isotropic precipitation onto the complete spherical surface. Two scenarios are investigated: One where no ionospheric shielding takes place and accordingly full plasma penetration is implemented ('no ionosphere' scenario), and one where an ionosphere lets virtually none of the cold plasma but all of the hot plasma reach Callisto's surface ('ionosphere' scenario). In the 3D exosphere model, neutral particles are sputtered from the surface and followed on their individual trajectories. The 3D density profiles show that whereas in the 'no ionosphere' scenario the ram direction is favored, the 'ionosphere' scenario produces almost uniform density profiles. In addition, the density profiles in the 'ionosphere' scenario are reduced by a factor of ~2.5 with respect to the 'no ionosphere' scenario. We find that the Neutral gas and Ion Mass spectrometer, which is part of the Particle Environment Package on board the JUICE mission, will be able to detect the different sputter populations from Callisto's icy surface and the major sputter populations from Callisto's non-icy surface. The chemical composition of Callisto's exosphere can be directly linked to the chemical composition of its surface, and will offer us information not only on Callisto's formation scenario but also on the building blocks of the Jupiter system.Comment: Published in JGR: Space Physic

First observation of a mini-magnetosphere above a lunar magnetic anomaly using energetic neutral atoms

The Sub-keV Atom Reflecting Analyzer (SARA) instrument on the Indian Chandrayaan-1 spacecraft has produced for the first time an image of a lunar magnetic anomaly in backscattered hydrogen atoms. The image shows that a partial void of the solar wind, a mini-magnetosphere, is formed above the strong magnetic anomaly near the Crisium antipode. The mini-magnetosphere is 360 km across at the surface and is surrounded by a 300-km-thick region of enhanced plasma flux that results from the solar wind flowing around the mini-magnetosphere. The mini-magnetosphere is visible only in hydrogen atoms with energy exceeding 150 eV. Fluxes with energies below 100 eV do not show corresponding spatial variations. While the high-energy atoms result from the backscattering process, the origin of the low-energy component is puzzling. These observations reveal a new class of objects, mini-magnetospheres, and demonstrate a new observational technique to study airless bodies, imaging in backscattered neutral atoms.Comment: 17 pages, 3 figure

A giant comet-like cloud of hydrogen escaping the warm Neptune-mass exoplanet GJ 436b

Exoplanets orbiting close to their parent stars could lose some fraction of their atmospheres because of the extreme irradiation. Atmospheric mass loss primarily affects low-mass exoplanets, leading to suggest that hot rocky planets might have begun as Neptune-like, but subsequently lost all of their atmospheres; however, no confident measurements have hitherto been available. The signature of this loss could be observed in the ultraviolet spectrum, when the planet and its escaping atmosphere transit the star, giving rise to deeper and longer transit signatures than in the optical spectrum. Here we report that in the ultraviolet the Neptune-mass exoplanet GJ 436b (also known as Gliese 436b) has transit depths of 56.3 +/- 3.5% (1 sigma), far beyond the 0.69% optical transit depth. The ultraviolet transits repeatedly start ~2 h before, and end >3 h after the ~1 h optical transit, which is substantially different from one previous claim (based on an inaccurate ephemeris). We infer from this that the planet is surrounded and trailed by a large exospheric cloud composed mainly of hydrogen atoms. We estimate a mass-loss rate in the range of ~10^8-10^9 g/s, which today is far too small to deplete the atmosphere of a Neptune-like planet in the lifetime of the parent star, but would have been much greater in the past.Comment: Published in Nature on 25 June 2015. Preprint is 28 pages, 12 figures, 2 table

Production and Characterization of Peptide Antibodies to the C-Terminal of Frameshifted Calreticulin Associated with Myeloproliferative Diseases

Myeloproliferative Neoplasms (MPNs) constitute a group of rare blood cancers that are characterized by mutations in bone marrow stem cells leading to the overproduction of erythrocytes, leukocytes, and thrombocytes. Mutations in calreticulin (CRT) genes may initiate MPNs, causing a novel variable polybasic stretch terminating in a common C-terminal sequence in the frameshifted CRT (CRTfs) proteins. Peptide antibodies to the mutated C-terminal are important reagents for research in the molecular mechanisms of MPNs and for the development of new diagnostic assays and therapies. In this study, eight peptide antibodies targeting the C-terminal of CRTfs were produced and characterised by modified enzyme-linked immunosorbent assays using resin-bound peptides. The antibodies reacted to two epitopes: CREACLQGWTE for SSI-HYB 385-01, 385-02, 385-03, 385-04, 385-07, 385-08, and 385-09 and CLQGWT for SSI-HYB 385-06. For the majority of antibodies, the residues Cys1, Trp9, and Glu11 were essential for reactivity. SSI-HYB 385-06, with the highest affinity, recognised recombinant CRTfs produced in yeast and the MARIMO cell line expressing CRTfs when examined in Western immunoblotting. Moreover, SSI-HYB 385-06 occasionally reacted to CRTfs from MPN patients when analysed by flow cytometry. The characterized antibodies may be used to understand the role of CRTfs in the pathogenesis of MPNs and to design and develop new diagnostic assays and therapeutic targets. Keywords: calreticulin; epitope mapping; frameshift mutations; myeloproliferative neoplasms; peptide antibodies

First Observation of Transport of Solar Wind Protons Scattered From Magnetic Anomalies Into the Near Lunar Wake: Observations by SARA/Chandrayaan-1

We report the first observational evidence for the transport of the solar wind protons scattered from the lunar magnetic anomaly (LMA) into the near wake region from SWIM/Sub‐keV Atom Reflecting Analyzer (SARA) aboard Chandrayaan‐1. These protons with high angular spread are observed in the near wake region for specific orientations of interplanetary magnetic field. The typical energy range is 600–1,000 eV, which is either smaller or comparable to that of solar wind. Using our backtracing model, the source region of these protons is found to be the large LMA at South Pole‐Aitken basin on the dayside, suggesting that these are solar wind protons forward scattered from LMA at the South Pole‐Aitken. The flux of these protons is ~5 × 10⁻⁴ of the solar wind proton flux, which is comparable to the proton population in near wake due to other known processes. Such protons can significantly affect the electromagnetic environment in near wake region

Levofloxacin prophylaxis in patients with newly diagnosed myeloma (TEAMM): a multicentre, double-blind, placebo-controlled, randomised, phase 3 trial.

BACKGROUND: Myeloma causes profound immunodeficiency and recurrent, serious infections. Around 5500 new cases of myeloma are diagnosed per year in the UK, and a quarter of patients will have a serious infection within 3 months of diagnosis. We aimed to assess whether patients newly diagnosed with myeloma benefit from antibiotic prophylaxis to prevent infection, and to investigate the effect on antibiotic-resistant organism carriage and health care-associated infections in patients with newly diagnosed myeloma. METHODS: TEAMM was a prospective, multicentre, double-blind, placebo-controlled randomised trial in patients aged 21 years and older with newly diagnosed myeloma in 93 UK hospitals. All enrolled patients were within 14 days of starting active myeloma treatment. We randomly assigned patients (1:1) to levofloxacin or placebo with a computerised minimisation algorithm. Allocation was stratified by centre, estimated glomerular filtration rate, and intention to proceed to high-dose chemotherapy with autologous stem cell transplantation. All investigators, patients, laboratory, and trial co-ordination staff were masked to the treatment allocation. Patients were given 500 mg of levofloxacin (two 250 mg tablets), orally once daily for 12 weeks, or placebo tablets (two tablets, orally once daily for 12 weeks), with dose reduction according to estimated glomerular filtration rate every 4 weeks. Follow-up visits occurred every 4 weeks up to week 16, and at 1 year. The primary outcome was time to first febrile episode or death from all causes within the first 12 weeks of trial treatment. All randomised patients were included in an intention-to-treat analysis of the primary endpoint. This study is registered with the ISRCTN registry, number ISRCTN51731976, and the EU Clinical Trials Register, number 2011-000366-35. FINDINGS: Between Aug 15, 2012, and April 29, 2016, we enrolled and randomly assigned 977 patients to receive levofloxacin prophylaxis (489 patients) or placebo (488 patients). Median follow-up was 12 months (IQR 8-13). 95 (19%) first febrile episodes or deaths occurred in 489 patients in the levofloxacin group versus 134 (27%) in 488 patients in the placebo group (hazard ratio 0·66, 95% CI 0·51-0·86; p=0·0018. 597 serious adverse events were reported up to 16 weeks from the start of trial treatment (308 [52%] of which were in the levofloxacin group and 289 [48%] of which were in the placebo group). Serious adverse events were similar between the two groups except for five episodes (1%) of mostly reversible tendonitis in the levofloxacin group. INTERPRETATION: Addition of prophylactic levofloxacin to active myeloma treatment during the first 12 weeks of therapy significantly reduced febrile episodes and deaths compared with placebo without increasing health care-associated infections. These results suggest that prophylactic levofloxacin could be used for patients with newly diagnosed myeloma undergoing anti-myeloma therapy. FUNDING: UK National Institute for Health Research