KELT-7b: A hot Jupiter transiting a bright V=8.54 rapidly rotating F-star

We report the discovery of KELT-7b, a transiting hot Jupiter with a mass of $1.28 \pm 0.18$ MJ, radius of $1.53_{-0.047}^{+0.046}$ RJ, and an orbital period of $2.7347749 \pm 0.0000039$ days. The bright host star (HD33643; KELT-7) is an F-star with $V=8.54$, Teff $=6789_{-49}^{+50}$ K, [Fe/H] $=0.139_{-0.081}^{+0.075}$, and $\log{g}=4.149 \pm 0.019$. It has a mass of $1.535_{-0.054}^{+0.066}$ Msun, a radius of $1.732_{-0.045}^{+0.043}$ Rsun, and is the fifth most massive, fifth hottest, and the ninth brightest star known to host a transiting planet. It is also the brightest star around which KELT has discovered a transiting planet. Thus, KELT-7b is an ideal target for detailed characterization given its relatively low surface gravity, high equilibrium temperature, and bright host star. The rapid rotation of the star ($73 \pm 0.5$ km/s) results in a Rossiter-McLaughlin effect with an unusually large amplitude of several hundred m/s. We find that the orbit normal of the planet is likely to be well-aligned with the stellar spin axis, with a projected spin-orbit alignment of $\lambda=9.7 \pm 5.2$ degrees. This is currently the second most rapidly rotating star to have a reflex signal (and thus mass determination) due to a planetary companion measured.Comment: Accepted to The Astronomical Journa

Results from the Mars Phoenix Lander Robotic Arm experiment

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/95618/1/jgre2693.pd

hEGR1 is induced by EGF, inhibited by gefitinib in bladder cell lines and related to EGF receptor levels in bladder tumours

The effect of EGF and gefitinib on two EGFR-positive human bladder cancer cell lines has been investigated using array-based gene expression profiling. The most prominent transcript, increased up to 6.7-fold by EGF compared with controls in RT112 cells, was human early growth response protein 1 (hEGR1). This induction was prevented by gefitinib. The hEGR1 mRNA in EGF-treated samples was reduced in the presence of gefitinib, as was hEGR1 protein in cell lysates. In the RT4 cells, hEGR1 expression was halved in the presence of EGF and gefitinib in combination. In bladder tumour samples, there was a significant correlation between hEGR1 mRNA detected by RT-PCR and EGFR detected by ligand binding, (P=0.042). The induction by EGF of the hEGR1 gene, mRNA and protein in RT112 cells, and its inhibition by gefitinib, together with the detection of hEGR1 mRNA in bladder tumours, suggests that hEGR1 may be important in the EGFR growth-signalling pathway in bladder cancer and should be further investigated for its prognostic significance and as a potential therapeutic target

MutLα heterodimers modify the molecular phenotype of Friedreich ataxia

This article has been made available through the Brunel Open Access Publishing Fund.Background: Friedreich ataxia (FRDA), the most common autosomal recessive ataxia disorder, is caused by a dynamic GAA repeat expansion mutation within intron 1 of FXN gene, resulting in down-regulation of frataxin expression. Studies of cell and mouse models have revealed a role for the mismatch repair (MMR) MutS-heterodimer complexes and the PMS2 component of the MutLα complex in the dynamics of intergenerational and somatic GAA repeat expansions: MSH2, MSH3 and MSH6 promote GAA repeat expansions, while PMS2 inhibits GAA repeat expansions. Methodology/Principal Findings: To determine the potential role of the other component of the MutLα complex, MLH1, in GAA repeat instability in FRDA, we have analyzed intergenerational and somatic GAA repeat expansions from FXN transgenic mice that have been crossed with Mlh1 deficient mice. We find that loss of Mlh1 activity reduces both intergenerational and somatic GAA repeat expansions. However, we also find that loss of either Mlh1 or Pms2 reduces FXN transcription, suggesting different mechanisms of action for Mlh1 and Pms2 on GAA repeat expansion dynamics and regulation of FXN transcription. Conclusions/Significance: Both MutLα components, PMS2 and MLH1, have now been shown to modify the molecular phenotype of FRDA. We propose that upregulation of MLH1 or PMS2 could be potential FRDA therapeutic approaches to increase FXN transcription. © 2014 Ezzatizadeh et al.This article has been made available through the Brunel Open Access Publishing Fund

Rock size‐frequency distributions on Mars and implications for Mars Exploration Rover landing safety and operations

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/95449/1/jgre1686.pd

Distinct Properties of Hexameric but Functionally Conserved Mycobacterium tuberculosis Transcription-Repair Coupling Factor

Transcription coupled nucleotide excision repair (TC-NER) is involved in correcting UV-induced damage and other road-blocks encountered in the transcribed strand. Mutation frequency decline (Mfd) is a transcription repair coupling factor, involved in repair of template strand during transcription. Mfd from M. tuberculosis (MtbMfd) is 1234 amino-acids long harboring characteristic modules for different activities. Mtbmfd complemented Escherichia coli mfd (Ecomfd) deficient strain, enhanced survival of UV irradiated cells and increased the road-block repression in vivo. The protein exhibited ATPase activity, which was stimulated ∼1.5-fold in the presence of DNA. While the C-terminal domain (CTD) comprising amino acids 630 to 1234 showed ∼2-fold elevated ATPase activity than MtbMfd, the N-terminal domain (NTD) containing the first 433 amino acid residues was able to bind ATP but deficient in hydrolysis. Overexpression of NTD of MtbMfd led to growth defect and hypersensitivity to UV light. Deletion of 184 amino acids from the C-terminal end of MtbMfd (MfdΔC) increased the ATPase activity by ∼10-fold and correspondingly exhibited efficient translocation along DNA as compared to the MtbMfd and CTD. Surprisingly, MtbMfd was found to be distributed in monomer and hexamer forms both in vivo and in vitro and the monomer showed increased susceptibility to proteases compared to the hexamer. MfdΔC, on the other hand, was predominantly monomeric in solution implicating the extreme C-terminal region in oligomerization of the protein. Thus, although the MtbMfd resembles EcoMfd in many of its reaction characteristics, some of its hitherto unknown distinct properties hint at its species specific role in mycobacteria during transcription-coupled repair

KELT-6b: A P~7.9 d Hot Saturn Transiting a Metal-Poor Star with a Long-Period Companion

We report the discovery of KELT-6b, a mildly-inflated Saturn-mass planet transiting a metal-poor host. The initial transit signal was identified in KELT-North survey data, and the planetary nature of the occulter was established using a combination of follow-up photometry, high-resolution imaging, high-resolution spectroscopy, and precise radial velocity measurements. The fiducial model from a global analysis including constraints from isochrones indicates that the V=10.38 host star (BD+31 2447) is a mildly evolved, late-F star with T_eff=6102 \pm 43 K, log(g_*)=4.07_{-0.07}^{+0.04} and [Fe/H]=-0.28 \pm 0.04, with an inferred mass M_*=1.09 \pm 0.04 M_sun and radius R_star=1.58_{-0.09}^{+0.16} R_sun. The planetary companion has mass M_P=0.43 \pm 0.05 M_J, radius R_P=1.19_{-0.08}^{+0.13} R_J, surface gravity log(g_P)=2.86_{-0.08}^{+0.06}, and density rho_P=0.31_{-0.08}^{+0.07} g~cm^{-3}. The planet is on an orbit with semimajor axis a=0.079 \pm 0.001 AU and eccentricity e=0.22_{-0.10}^{+0.12}, which is roughly consistent with circular, and has ephemeris of T_c(BJD_TDB)=2456347.79679 \pm 0.00036 and P=7.845631 \pm 0.000046 d. Equally plausible fits that employ empirical constraints on the host star parameters rather than isochrones yield a larger planet mass and radius by ~4-7%. KELT-6b has surface gravity and incident flux similar to HD209458b, but orbits a host that is more metal poor than HD209458 by ~0.3 dex. Thus, the KELT-6 system offers an opportunity to perform a comparative measurement of two similar planets in similar environments around stars of very different metallicities. The precise radial velocity data also reveal an acceleration indicative of a longer-period third body in the system, although the companion is not detected in Keck adaptive optics images.Comment: Published in AJ, 17 pages, 15 figures, 6 table

Block of NMDA receptor channels by endogenous neurosteroids: implications for the agonist induced conformational states of the channel vestibule

N-methyl-D-aspartate receptors (NMDARs) mediate synaptic plasticity, and their dysfunction is implicated in multiple brain disorders. NMDARs can be allosterically modulated by numerous compounds, including endogenous neurosteroid pregnanolone sulfate. Here, we identify the molecular basis of the use-dependent and voltage-independent inhibitory effect of neurosteroids on NMDAR responses. The site of action is located at the extracellular vestibule of the receptor's ion channel pore and is accessible after receptor activation. Mutations in the extracellular vestibule in the SYTANLAAF motif disrupt the inhibitory effect of negatively charged steroids. In contrast, positively charged steroids inhibit mutated NMDAR responses in a voltage-dependent manner. These results, in combination with molecular modeling, characterize structure details of the open configuration of the NMDAR channel. Our results provide a unique opportunity for the development of new therapeutic neurosteroid-based ligands to treat diseases associated with dysfunction of the glutamate system

Water induced sediment levitation enhances downslope transport on Mars

On Mars, locally warm surface temperatures (~293 K) occur, leading to the possibility of (transient) liquid water on the surface. However, water exposed to the martian atmosphere will boil, and the sediment transport capacity of such unstable water is not well understood. Here, we present laboratory studies of a newly recognized transport mechanism: “levitation” of saturated sediment bodies on a cushion of vapor released by boiling. Sediment transport where this mechanism is active is about nine times greater than without this effect, reducing the amount of water required to transport comparable sediment volumes by nearly an order of magnitude. Our calculations show that the effect of levitation could persist up to ~48 times longer under reduced martian gravity. Sediment levitation must therefore be considered when evaluating the formation of recent and present-day martian mass wasting features, as much less water may be required to form such features than previously thought