105 research outputs found

    H3K4 demethylase KDM5B regulates global dynamics of transcription elongation and alternative splicing in embryonic stem cells

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    Epigenetic regulation of chromatin plays a critical role in controlling embryonic stem (ES) cell selfrenewal and pluripotency. However, the roles of histone demethylases and activating histone modifications such as trimethylated histone 3 lysine 4 (H3K4me3) in transcriptional events such as RNA polymerase II (RNAPII) elongation and alternative splicing are largely unknown. In this study, we show that KDM5B, which demethylates H3K4me3, plays an integral role in regulating RNAPII occupancy, transcriptional initiation and elongation, and alternative splicing events in ES cells. Depletion of KDM5B leads to altered RNAPII promoter occupancy, and decreased RNAPII initiation and elongation rates at active genes and at genes marked with broad H3K4me3 domains. Moreover, our results demonstrate that spreading of H3K4me3 from promoter to gene body regions, which is mediated by depletion of KDM5B, modulates RNAPII elongation rates and RNA splicing in ES cells. We further show that KDM5B is enriched nearby alternatively spliced exons, and depletion of KDM5B leads to altered levels of H3K4 methylation in alternatively spliced exon regions, which is accompanied by differential expression of these alternatively splice exons. Altogether, our data indicate an epigenetic role for KDM5B in regulating RNAPII elongation and alternative splicing, which may support the diverse mRNA repertoire in ES cells

    Pembuatan Alat Peraga Lemari Pendingin Sebagai Media Pembelajaran Mata Kuliah Teknik Pendingin Di Universitas Negeri Semarang

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    — Media pembelajaran merupakan segala fisik yang menyajikan pesan serta perangsang peserta didik untuk belajar, sehingga keberadaan media pembelajaran penting untuk membantu dalam proses belajar mengajar. Alat peraga adalah salah satu media pembelajaran, dengan memanfaatkan alat peraga proses pembelajaran akan dapat mempermudah dalam memahami materi yang dipelajari oleh mahasiswa, karena ditampilkan dalam bentuk nyata. Teknik Pendingin adalah salah satu mata kuliah yang ada pada Prodi Pendidikan Teknik Elektro. Permasalahannya apakah alat peraga lemari pendingin layak sebagai media pembelajaran pada mata kuliah Teknik Pendingin jurusan Teknik Elektro Universitas Negeri Semarang. Untuk itu perlu diadakan penelitian untuk mengetahui apakah alat peraga lemari pendingin ini layak untuk dignakan sebagai media pembelajaran. Data dikumpulkan dengan metode angket tertutup maupun terbuka. Alat peraga lemari pendingin ini diujicoba oleh dosen ahli materi teknik pendingin. Metode analisis yang digunakan adalah metode analisis statistik deskriptif. Menurut hasil penelitian dari responden secara keseluruhan, alat peraga lemari pendingin pada mata kuliah Teknik Pendingin ini layak digunakan sebagai media pembelajaran. Dosen ahli materi mengemukakan alat peraga ini layak dijadikan alat peraga setelah adanya revisi alat. Berdasarkan dari hasil penelitian dan pembahasan, dapat disimpulkan bahwa menurut mahasiswa media pembelajaran yang berupa alat peraga lemari pendingin pada mata kuliah Teknik Pendingin diwujudkan dengan menyusun prosedur kerja dengan langkah-langkah sebagai berikut: perencanaan alat peraga, penyediaan alat dan bahan, pembuatan alat peraga, validasi alat peraga, uji coba alat peraga, dan evaluasi. Dari hasil penelitian yang telah dilakukan kepada mahasiswa dengan beberapa aspek, alat peraga lemari pendingin ini termasuk dalam kategori layak, sehingga alat peraga ini dapat digunakan sebagai media pembelajaran. Namun masih terdapat kekurangan pada bahan penutup yang dugunakan seharusnya tidak menggunakan kaca agar tidah mudah pecah, dan jika menggunakan kaca suhu yang ada di dalam lemari pendingin masih dapat terpengaruh oleh suhu udara luar. Kata kunci— Media Pembelajaran, teknik pendingin, universitas negeri semarang, alat peraga, lemari pendingi

    Wolf 1130: A Nearby Triple System Containing a Cool, Ultramassive White Dwarf

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    Following the discovery of the T8 subdwarf WISEJ200520.38+542433.9 (Wolf 1130C), with common proper motion to a binary (Wolf 1130AB) consisting of an M subdwarf and a white dwarf, we set out to learn more about the old binary in the system. We find that the A and B components of Wolf 1130 are tidally locked, which is revealed by the coherence of more than a year of V band photometry phase folded to the derived orbital period of 0.4967 days. Forty new high-resolution, near-infrared spectra obtained with the Immersion Grating Infrared Spectrometer (IGRINS) provide radial velocities and a projected rotational velocity (v sin i) of 14.7 +/- 0.7 km/s for the M subdwarf. In tandem with a Gaia parallax-derived radius and verified tidal-locking, we calculate an inclination of i=29 +/- 2 degrees. From the single-lined orbital solution and the inclination we derive an absolute mass for the unseen primary (1.24+0.19-0.15 Msun). Its non-detection between 0.2 and 2.5 microns implies that it is an old (>3.7 Gyr) and cool (Teff<7000K) ONe white dwarf. This is the first ultramassive white dwarf within 25pc. The evolution of Wolf 1130AB into a cataclysmic variable is inevitable, making it a potential Type Ia supernova progenitor. The formation of a triple system with a primary mass >100 times the tertiary mass and the survival of the system through the common-envelope phase, where ~80% of the system mass was lost, is remarkable. Our analysis of Wolf 1130 allows us to infer its formation and evolutionary history, which has unique implications for understanding low-mass star and brown dwarf formation around intermediate mass stars.Comment: 37 pages, 9 Figures, 5 Table

    Non-precessional spin-orbit effects on gravitational waves from inspiraling compact binaries to second post-Newtonian order

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    We derive all second post-Newtonian (2PN), non-precessional effects of spin- orbit coupling on the gravitational wave forms emitted by an inspiraling binary composed of spinning, compact bodies in a quasicircular orbit. Previous post- Newtonian calculations of spin-orbit effects (at 1.5PN order) relied on a fluid description of the spinning bodies. We simplify the calculations by introducing into post-Newtonian theory a delta-function description of the influence of the spins on the bodies' energy-momentum tensor. This description was recently used by Mino, Shibata, and Tanaka (MST) in Teukolsky-formalism analyses of particles orbiting massive black holes, and is based on prior work by Dixon. We compute the 2PN contributions to the wave forms by combining the MST energy-momentum tensor with the formalism of Blanchet, Damour, and Iyer for evaluating the binary's radiative multipoles, and with the well-known 1.5PN order equations of motion for the binary. Our results contribute at 2PN order only to the amplitudes of the wave forms. The secular evolution of the wave forms' phase, the quantity most accurately measurable by LIGO, is not affected by our results until 2.5PN order, at which point other spin-orbit effects also come into play. We plan to evaluate the entire 2.5PN spin-orbit contribution to the secular phase evolution in a future paper, using the techniques of this paper.Comment: 11 pages, submitted to Phys. Rev.

    Effective Temperatures of Low-Mass Stars from High-Resolution H-band Spectroscopy

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    High-resolution, near-infrared spectra will be the primary tool for finding and characterizing Earth-like planets around low-mass stars. Yet, the properties of exoplanets can not be precisely determined without accurate and precise measurements of the host star. Spectra obtained with the Immersion GRating INfrared Spectrometer (IGRINS) simultaneously provide diagnostics for most stellar parameters, but the first step in any analysis is the determination of the effective temperature. Here we report the calibration of high-resolution H-band spectra to accurately determine effective temperature for stars between 4000-3000 K (∼\simK8--M5) using absorption line depths of Fe I, OH, and Al I. The field star sample used here contains 254 K and M stars with temperatures derived using BT-Settl synthetic spectra. We use 106 stars with precise temperatures in the literature to calibrate our method with typical errors of about 140 K, and systematic uncertainties less than ∼\sim120 K. For the broadest applicability, we present Teff_{\rm eff}--line-depth-ratio relationships, which we test on 12 members of the TW Hydrae Association and at spectral resolving powers between ∼\sim10,000--120,000. These ratios offer a simple but accurate measure of effective temperature in cool stars that is distance and reddening independent.Comment: 19 pages, 11 figures and 3 tables. Accepted in Ap

    Systematic effects from black hole-neutron star waveform model uncertainties on the neutron star equation of state

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    We identify various contributors of systematic effects in the measurement of the neutron star (NS) tidal deformability and quantify their magnitude for several types of neutron star - black hole (NSBH) binaries. Gravitational waves from NSBH mergers contain information about the components' masses and spins as well as the NS equation of state. Extracting this information requires comparison of the signal in noisy detector data with theoretical templates derived from some combination of post-Newtonian (PN) approximants, effective one-body (EOB) models and %analytic fits to numerical relativity (NR) simulations. The accuracy of these templates is limited by errors in the NR simulations, by the approximate nature of the PN/EOB waveforms, and by the hybridization procedure used to combine them. In this paper, we estimate the impact of these errors by constructing and comparing a set of PN-NR hybrid waveforms, for the first time with NR waveforms from two different codes, namely, SpEC and SACRA, for such systems. We then attempt to recover the parameters of the binary using two non-precessing template approximants. We find that systematic errors are too large for tidal effects to be accurately characterized for any realistic NS equation of state model. We conclude that NSBH waveform models must be significantly improved if they are to be useful for the extraction of NS equation of state information or even for distinguishing NSBH systems from binary black holes
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