New transit observations for HAT-P-30 b, HAT-P-37 b, TrES-5 b, WASP-28 b, WASP-36 b, and WASP-39 b

We present new transit light curves for planets in six extrasolar planetary systems. They were acquired with 0.4-2.2 m telescopes located in west Asia, Europe, and South America. When combined with literature data, they allowed us to redetermine system parameters in a homogeneous way. Our results for individual systems are in agreement with values reported in previous studies. We refined transit ephemerides and reduced uncertainties of orbital periods by a factor between 2 and 7. No sign of any variations in transit times was detected for the planets studied.Comment: Submitted to Acta Astronomic

Complete X-ray census of Mdwarfs in the solar Neighborhood I. GJ 745 AB: Coronal-hole Stars in the 10 pc Sample

We have embarked in a systematic study of the X-ray emission in a volume-limited sample of M dwarf stars, in order to explore the full range of activity levels present in their coronae and, thus, to understand the conditions in their outer atmospheres and their possible impact on the circumstellar environment. We identify in a recent catalog of the Gaia objects within 10 pc from the Sun all the stars with spectral type between M0 and M4, and search systematically for X-ray measurements of this sample. To this end, we use both archival data (from ROSAT, XMM-Newton, and from the ROentgen Survey with an Imaging Telescope Array (eROSITA) onboard the Russian Spektrum-Roentgen-Gamma mission) and our own dedicated XMM-Newton observations. To make inferences on the properties of the M dwarf corona we compare the range of their observed X-ray emission levels to the flux radiated by the Sun from different types of magnetic structures: coronal holes, background corona, active regions and cores of active regions. At the current state of our project, with more than 90\% of the 10pc M dwarf sample observed in X-rays, only GJ 745 A has no detection. With an upper limit luminosity of log Lx [erg/s] < 25.4 and an X-ray surface flux of log FX,SURF [erg/cm^2/s] < 3.6 GJ 745 A defines the lower boundary of the X-ray emission level of M dwarfs. Together with its companion GJ 745 B, GJ 745 A it is the only star in this volume-complete sample located in the range of FX,SURF that corresponds to the faintest solar coronal structures, the coronal holes. The ultra-low X-ray emission level of GJ 745 B (log Lx [erg/s] = 25.6 and log FX,SURF [erg/cm^2/s] = 3.8) is entirely attributed to flaring activity, indicating that, while its corona is dominated by coronal holes, at least one magnetically active structure is present and determines the total X-ray brightness and the coronal temperature of the star.Comment: accepted for publication in Astronomy & Astrophysics (A&A

Constraints on a second planet in the WASP-3 system

There have been previous hints that the transiting planet WASP-3 b is accompanied by a second planet in a nearby orbit, based on small deviations from strict periodicity of the observed transits. Here we present 17 precise radial velocity measurements and 32 transit light curves that were acquired between 2009 and 2011. These data were used to refine the parameters of the host star and transiting planet. This has resulted in reduced uncertainties for the radii and masses of the star and planet. The radial-velocity data and the transit times show no evidence for an additional planet in the system. Therefore, we have determined the upper limit on the mass of any hypothetical second planet, as a function of its orbital period.Comment: Accepted for publication in The Astronomical Journa

Diagnosing the Clumpy Protoplanetary Disk of the UXor Type Young Star GM Cephei

UX Orionis stars (UXors) are Herbig Ae/Be or T Tauri stars exhibiting sporadic occultation of stellar light by circumstellar dust. GM\,Cephei is such a UXor in the young ($\sim4$~Myr) open cluster Trumpler\,37, showing prominent infrared excess, emission-line spectra, and flare activity. Our photometric monitoring (2008--2018) detects (1)~an $\sim$3.43~day period, likely arising from rotational modulation by surface starspots, (2)~sporadic brightening on time scales of days due to accretion, (3)~irregular minor flux drops due to circumstellar dust extinction, and (4)~major flux drops, each lasting for a couple of months with a recurrence time, though not exactly periodic, of about two years. The star experiences normal reddening by large grains, i.e., redder when dimmer, but exhibits an unusual "blueing" phenomenon in that the star turns blue near brightness minima. The maximum extinction during relatively short (lasting $\leq 50$~days) events, is proportional to the duration, a consequence of varying clump sizes. For longer events, the extinction is independent of duration, suggestive of a transverse string distribution of clumps. Polarization monitoring indicates an optical polarization varying $\sim3\%$--8$\%$, with the level anticorrelated with the slow brightness change. Temporal variation of the unpolarized and polarized light sets constraints on the size and orbital distance of the circumstellar clumps in the interplay with the young star and scattering envelope. These transiting clumps are edge-on manifestations of the ring- or spiral-like structures found recently in young stars with imaging in infrared of scattered light, or in submillimeter of thermalized dust emission.Comment: 20 pages, 9 figure

Resistance to the Antimicrobial Peptide Polymyxin Requires Myristoylation of Escherichia Coli and Salmonella Typhimurium Lipid A

Attachment of positively charged, amine-containing residues such as 4-amino-4-deoxy-L-arabinose (L-Ara4N) and phosphoethanolamine (pEtN) to Escherichia coli and Salmonella typhimurium lipid A is required for resistance to the cationic antimicrobial peptide, polymyxin. In an attempt to discover additional lipid A modifications important for polymyxin resistance, we generated polymyxin-sensitive mutants of an E. coli pmrAC strain, WD101. A subset of polymyxin-sensitive mutants produced a lipid A that lacked both the 3′-acyloxyacyl-linked myristate (C14) and L-Ara4N, even though the necessary enzymatic machinery required to synthesize L-Ara4N-modified lipid A was present. Inactivation of lpxM in both E. coli and S. typhimurium resulted in the loss of L-Ara4N addition, as well as, increased sensitivity to polymyxin. However, decoration of the lipid A phosphate groups with pEtN residues was not effected in lpxM mutants. In summary, we demonstrate that attachment of L-Ara4N to the phosphate groups of lipid A and the subsequent resistance to polymyxin is dependent upon the presence of the secondary linked myristoyl group

Export of functional Streptomyces coelicolor alditol oxidase to the periplasm or cell surface of Escherichia coli and its application in whole-cell biocatalysis

Streptomyces coelicolor A3(2) alditol oxidase (AldO) is a soluble monomeric flavoprotein in which the flavin cofactor is covalently linked to the polypeptide chain. AldO displays high reactivity towards different polyols such as xylitol and sorbitol. These characteristics make AldO industrially relevant, but full biotechnological exploitation of this enzyme is at present restricted by laborious and costly purification steps. To eliminate the need for enzyme purification, this study describes a whole-cell AldO biocatalyst system. To this end, we have directed AldO to the periplasm or cell surface of Escherichia coli. For periplasmic export, AldO was fused to endogenous E. coli signal sequences known to direct their passenger proteins into the SecB, signal recognition particle (SRP), or Twin-arginine translocation (Tat) pathway. In addition, AldO was fused to an ice nucleation protein (INP)-based anchoring motif for surface display. The results show that Tat-exported AldO and INP-surface-displayed AldO are active. The Tat-based system was successfully employed in converting xylitol by whole cells, whereas the use of the INP-based system was most likely restricted by lipopolysaccharide LPS in wild-type cells. It is anticipated that these whole-cell systems will be a valuable tool for further biological and industrial exploitation of AldO and other cofactor-containing enzymes.

Non-thermal transport of energy driven by photoexcited carriers in switchable solid states of GeTe

Phase change alloys have seen widespread use from rewritable optical discs to the present day interest in their use in emerging neuromorphic computing architectures. In spite of this enormous commercial interest, the physics of carriers in these materials is still not fully understood. Here, we describe the time and space dependence of the coupling between photoexcited carriers and the lattice in both the amorphous and crystalline states of one phase change material, GeTe. We study this using a time-resolved optical technique called picosecond acoustic method to investigate the \textit{in situ} thermally assisted amorphous to crystalline phase transformation in GeTe. Our work reveals a clear evolution of the electron-phonon coupling during the phase transformation as the spectra of photoexcited acoustic phonons in the amorphous ($a$-GeTe) and crystalline ($\alpha$-GeTe) phases are different. In particular and surprisingly, our analysis of the photoinduced acoustic pulse duration in crystalline GeTe suggests that a part of the energy deposited during the photoexcitation process takes place over a distance that clearly exceeds that defined by the pump light skin depth. In the opposite, the lattice photoexcitation process remains localized within that skin depth in the amorphous state. We then demonstrate that this is due to supersonic diffusion of photoexcited electron-hole plasma in the crystalline state. Consequently these findings prove the existence of a non-thermal transport of energy which is much faster than lattice heat diffusion

New Transit Observations for HAT-P-30 b, HAT-P-37 b, TrES-5 b, WASP-28 b, WASP-36 b and WASP-39 b

We present new transit light curves for planets in six extrasolar planetary systems. They were acquired with 0.4–2.2 m telescopes located in west Asia, Europe, and South America. When combined with literature data, they allowed us to redetermine system parameters in a homogeneous way. Our results for individual systems are in agreement with values reported in previous studies. We refined transit ephemerides and reduced uncertainties of orbital periods by a factor between 2 and 7. No sign of any variations in transit times was detected for the planets studied.Fil: Maciejewski, G.. Nicolaus Copernicus University; PoloniaFil: Dimitrov, D.. Bulgarian Academy Of Sciences; BulgariaFil: Mancini, L.. Max Planck Institute for Astronomy; Alemania. Osservatorio Astrofisico Di Torino; Italia. Istituto Nazionale di Astrofisica; ItaliaFil: Southworth, J.. Keele University; Reino UnidoFil: Ciceri, S.. Max Planck Institute For Astronomy; AlemaniaFil: D'Ago, G.. Istituto Internazionale per gli Alti Studi ; ItaliaFil: Bruni, I.. Osservatorio Astrofisico di Bologna; Italia. Istituto Nazionale di Astrofisica; ItaliaFil: Raetz, St.. Universitat Erlangen-nurmberg. Astronomisches Institut-dr. Karl Remeis-sternwarte & Ecap; Alemania. European Space Agency; Países BajosFil: Nowak, G.. Instituto de Astrofísica de Canarias; España. Nicolaus Copernicus University; Polonia. Universidad de La Laguna; EspañaFil: Ohlert, J.. University of Applied Sciences; Alemania. Michael Adrian Observatorium; AlemaniaFil: Puchalski, D.. Nicolaus Copernicus University; PoloniaFil: Saral, G.. Istanbul University; Turquía. University Of Geneva (ug);Fil: Derman, E.. Ankara University; TurquíaFil: Petrucci, Romina Paola. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Astronomía Teórica y Experimental. Universidad Nacional de Córdoba. Observatorio Astronómico de Córdoba. Instituto de Astronomía Teórica y Experimental; ArgentinaFil: Jofré, E.. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Astronomía Teórica y Experimental. Universidad Nacional de Córdoba. Observatorio Astronómico de Córdoba. Instituto de Astronomía Teórica y Experimental; ArgentinaFil: Seeliger, M.. Universitat Erlangen-nurmberg. Astronomisches Institut-dr. Karl Remeis-sternwarte & Ecap; AlemaniaFil: Henning, T.. Max Planck Institute for Astronomy; Alemani

A Possible Detection of Occultation by a Proto-planetary Clump in GM Cephei

GM Cep in the young (~4 Myr) open cluster Trumpler 37 has been known to be an abrupt variable and to have a circumstellar disk with very active accretion. Our monitoring observations in 2009-2011 revealed the star to show sporadic flare events, each with brightening of < 0.5 mag lasting for days. These brightening events, associated with a color change toward the blue, should originate from an increased accretion activity. Moreover, the star also underwent a brightness drop of ~1 mag lasting for about a month, during which the star became bluer when fainter. Such brightness drops seem to have a recurrence time scale of a year, as evidenced in our data and the photometric behavior of GM Cep over a century. Between consecutive drops, the star brightened gradually by about 1 mag and became blue at peak luminosity. We propose that the drop is caused by obscuration of the central star by an orbiting dust concentration. The UX Orionis type of activity in GM Cep therefore exemplifies the disk inhomogeneity process in transition between grain coagulation and planetesimal formation in a young circumstellar disk.Comment: In submission to the Astrophysical Journal, 4 figure

Inherited coding variants at the CDKN2A locus influence susceptibility to acute lymphoblastic leukaemia in children

There is increasing evidence from genome-wide association studies for a strong inherited genetic basis of susceptibility to acute lymphoblastic leukaemia (ALL) in children, yet the effects of protein-coding variants on ALL risk have not been systematically evaluated. Here we show a missense variant in CDKN2A associated with the development of ALL at genome-wide significance (rs3731249, P=9.4 × 10(-23), odds ratio=2.23). Functional studies indicate that this hypomorphic variant results in reduced tumour suppressor function of p16(INK4A), increases the susceptibility to leukaemic transformation of haematopoietic progenitor cells, and is preferentially retained in ALL tumour cells. Resequencing the CDKN2A-CDKN2B locus in 2,407 childhood ALL cases reveals 19 additional putative functional germline variants. These results provide direct functional evidence for the influence of inherited genetic variation on ALL risk, highlighting the important and complex roles of CDKN2A-CDKN2B tumour suppressors in leukaemogenesis.Heng Xu, Hui Zhang, Wenjian Yang, Rachita Yadav, Alanna C. Morrison, Maoxiang Qian, Meenakshi Devidas, Yu Liu, Virginia Perez-Andreu, Xujie Zhao, Julie M. Gastier-Foster, Philip J. Lupo, Geoff Neale, Elizabeth Raetz, Eric Larsen, W. Paul Bowman, William L. Carroll, Naomi Winick, Richard Williams, Torben Hansen, Jens-Christian Holm, Elaine Mardis, Robert Fulton, Ching-Hon Pui, Jinghui Zhang, Charles G. Mullighan, William E. Evans, Stephen P. Hunger, Ramneek Gupta, Kjeld Schmiegelow, Mignon L. Loh, Mary V. Relling, Jun J. Yan