Stephen Sekula

Dallas, TX, USA

Husband; Associate Professor of Physics; I teach at SMU in Dallas, TX; I study the Higgs Particle with the ATLAS Experiment at the Large Hadron Collider at CERN; writer and blogger; drummer; programmer; teacher; scientist; traveler; runner; gardener; open-source aficionado.

  • JanKusanagi at 2019-01-17T19:03:10Z

    I feel relaxed already! 😌

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  • Astronomy Picture of the Day for 2019-01-14 12:30:02.260530

    Astronomy Picture of the Day (Unofficial) at 2019-01-14T18:30:03Z

    Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.

    2019 January 14
    See Explanation.  Clicking on the picture will download
the highest resolution version available.

    Meteor and Milky Way over the Alps
    Image Credit & Copyright: Nicholas Roemmelt (Venture Photography)

    Explanation: Now this was a view with a thrill. From Mount Tschirgant in the Alps, you can see not only nearby towns and distant Tyrolean peaks, but also, weather permitting, stars, nebulas, and the band of the Milky Way Galaxy. What made the arduous climb worthwhile this night, though, was another peak -- the peak of the 2018 Perseids Meteor Shower. As hoped, dispersing clouds allowed a picturesque sky-gazing session that included many faint meteors, all while a carefully positioned camera took a series of exposures. Suddenly, a thrilling meteor -- bright and colorful -- slashed down right next the nearly vertical band of the Milky Way. As luck would have it, the camera caught it too. Therefore, a new image in the series was quickly taken with one of the sky-gazers posing on the nearby peak. Later, all of the images were digitally combined.

    Tomorrow's picture: heart & soul

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  • Jason Self at 2019-01-14T02:05:49Z

    I removed 15 of the 16 RAM modules and the computer boots into the Trisquel installer just fine. It would appear the problems can be explained away with bad memory. Time to break out Memtest86+...

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    at 2019-01-15T00:05:23Z

    What? You don't know what a TARDIS is?

    Don't you have a plain old dictionary? 😆

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  • This weekend we have a Debian Bugsquashing Party in Venlo #Debian #BSP #Party

    Debian Project at 2019-01-11T22:15:05Z

    This weekend we have a Debian Bugsquashing Party in Venlo #Debian #BSP #Party

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  • JanKusanagi at 2019-01-11T19:18:58Z

    Some giant took a bite out of the Sun!!!!! 😱

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  • JanKusanagi at 2019-01-08T04:48:14Z

    Gifted. But the thing about the Navier-Stokes problem was just a background thing. It was just funny to see it mentioned 😆

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  • JanKusanagi at 2019-01-08T02:10:51Z

    Weird, I was under the impression that it was day 7... 🤔

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  • New blog post: "Debian is back in the Mastodon/GNU Social fediverse, follow"

    Laura Arjona Reina at 2018-12-21T12:36:07Z

    New blog post: "Debian is back in the Mastodon/GNU Social fediverse, follow"

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    dw shared this.

    Cool, but I already follow @Debian Project right here 😎

    JanKusanagi at 2018-12-21T13:28:48Z

  • Stephen Michael Kellat at 2019-01-06T18:07:41Z

    I had to move off to

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  • JanKusanagi at 2019-01-06T17:54:40Z

    I think at least the first one is. IIRC @Laura Arjona Reina was on it and had to move.

    She might have commented on it on her feed 😄

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  • Astronomy Picture of the Day for 2019-01-04 12:30:02.139948

    Astronomy Picture of the Day (Unofficial) at 2019-01-04T18:30:02Z

    Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.

    2019 January 4
    See Explanation.  Clicking on the picture will download
the highest resolution version available.

    Ultima Thule Rotation Gif
    Image Credit: NASA, Johns Hopkins University APL, Southwest Research Institute

    Explanation: Ultima Thule is the most distant world explored by a spacecraft from Earth. In the dim light 6.5 billion kilometers from the Sun, the New Horizons spacecraft captured these two frames 38 minutes apart as it sped toward the Kuiper belt world on January 1 at 51,000 kilometers per hour. A contact binary, the two lobes of Ultima Thule rotate together once every 15 hours or so. Shown as a blinking gif, the rotation between the frames produces a tantalizing 3D perspective of the most primitive world ever seen. Dubbed separately by the science team Ultima and Thule, the larger lobe Ultima, is about 19 kilometers in diameter. Smaller Thule is 14 kilometers across.

    Tomorrow's picture: on the Far Side

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  • I have three words for you...

    JanKusanagi at 2019-01-04T19:46:36Z



    Suck 😠

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  • Startup Time for Ion Collisions Exploring the Phases of Nuclear Matter

    ParticleNews at 2019-01-04T16:27:37Z

    "Startup Time for Ion Collisions Exploring the Phases of Nuclear Matter"

    Startup Time for Ion Collisions Exploring the Phases of Nuclear MatterPress Releasexeno Fri, 01/04/2019 - 09:01119

    19th year of operations at the Relativistic Heavy Ion Collider will continue search for critical point in transition from protons and neutrons to quark-gluon plasma.


    The Relativistic Heavy Ion Collider (RHIC) is actually two accelerators in one. Beams of ions travel around its 2.4-mile-circumference rings in opposite directions at nearly the speed of light, coming into collision at points where the rings cross.

    UPTON, NY—January 2 marked the startup of the 19th year of physics operations at the Relativistic Heavy Ion Collider (RHIC), a U.S. Department of Energy Office of Science user facility for nuclear physics research at Brookhaven National Laboratory. Physicists will conduct a series of experiments to explore innovative beam-cooling technologies and further map out the conditions created by collisions at various energies. The ultimate goal of nuclear physics is to fully understand the behavior of nuclear matter—the protons and neutrons that make up atomic nuclei and those particles’ constituent building blocks, known as quarks and gluons.

    Many earlier experiments colliding gold ions at different energies at RHIC have provided evidence that energetic collisions create extreme temperatures (trillions of degrees Celsius). These collisions liberate quarks and gluons from their confinement with individual protons and neutrons, creating a hot soup of quarks and gluons that mimics what the early universe looked like before protons, neutrons, or atoms ever formed.

    “The main goal of this run is to turn the collision energy down to explore the low-energy part of the nuclear phase diagram to help pin down the conditions needed to create this quark-gluon plasma,” said Daniel Cebra, a collaborator on the STAR experiment at RHIC. Cebra is taking a sabbatical leave from his position as a professor at the University of California, Davis, to be at Brookhaven to help coordinate the experiments this year.

    STAR is essentially a house-sized digital camera with many different detector systems for tracking the particles created in collisions. Nuclear physicists analyze the mix of particles and characteristics such as their energies and trajectories to learn about the conditions created when ions collide.

    STAR Phase diagram

    The STAR collaboration's exploration of the "nuclear phase diagram" so far shows signs of a sharp border—a first-order phase transition—between the hadrons that make up ordinary atomic nuclei and the quark-gluon plasma (QGP) of the early universe when the QGP is produced at relatively low energies/temperatures. The data may also suggest a possible critical point, where the type of transition changes from the abrupt, first-order kind to a continuous crossover at higher energies. New data collected during this year's run will add details to this map of nuclear matter's phases.

    By colliding gold ions at various low energies, including collisions where one beam of gold ions smashes into a fixed target instead of a counter-circulating beam, RHIC physicists will be looking for signs of a so-called “critical point.” This point marks a spot on the nuclear phase diagram—a map of the phases of quarks and gluons under different conditions—where the transition from ordinary matter to free quarks and gluons switches from a smooth one to a sudden phase shift, where both states of matter can coexist.

    STAR gets a wider view

    STAR will have new components in place that will increase its ability to capture the action in these collisions. These include new inner sectors of the Time Projection Chamber (TPC)—the gas-filled chamber particles traverse from their point of origin in the quark-gluon plasma to the sensitive electronics that line the inner and outer walls of a large cylindrical magnet. There will also be a “time of flight” (ToF) wall placed on one of the STAR endcaps, behind the new sectors.

    “The main purpose of these is to enhance STAR's sensitivity to signatures of the critical point by increasing the acceptance of STAR—essentially the field of view captured in the pictures of the collisions—by about 50 percent,” said James Dunlop, Associate Chair for Nuclear Physics in Brookhaven Lab’s Physics Department.

    STAR Detector

    RHIC's STAR detector tracks the thousands of particles produced by each ion collision. It weighs 1,200 tons and is as large as a house.

    “Both of these components have large international contributions,” Dunlop noted. “A large part of the construction of the iTPC sectors was done by STAR’s collaborating institutions in China. The endcap ToF is a prototype of a detector being built for an experiment called Compressed Baryonic Matter (CBM) at the Facility for Antiproton and Ion Research (FAIR) in Germany. The early tests at RHIC will allow CBM to see how well the detector components behave in realistic conditions before it is installed at FAIR while providing both collaborations with necessary equipment for a mutual-benefit physics program,” he said.

    Tests of electron cooling

    Before the collision experiments begin in mid-February, RHIC physicists will be testing a new component of the accelerator designed to maximize collision rates at low energies.

    “RHIC operation at low energies faces multiple challenges, as we know from past experience,” said Chuyu Liu, the RHIC Run Coordinator for Run 19. “The most difficult one is that the tightly bunched ions tend to heat up and spread out as they circulate in the accelerator rings.”

    That makes it less likely that an ion in one beam will strike an ion in the other.

    e cooling layout

    A schematic of low-energy electron cooling at RHIC, from right: 1) a section of the existing accelerator that houses the beam pipe carrying heavy ion beams in opposite directions; 2) the direct current (DC) electron gun and other components that will produce and accelerate the bright beams of electrons; 3) the line that will transport and inject cool electrons into the ion beams; and 4) the cooling sections where ions will mix and scatter with electrons, giving up some of their heat, thus leaving the ion beam cooler and more tightly packed.

    To counteract this heating/spreading, accelerator physicists at RHIC have added a beamline that brings accelerated “cool” electrons into a section of each RHIC ring to extract heat from the circulating ions. This is very similar to the way the liquid running through your home refrigerator extracts heat to keep your food cool. But instead of chilled ice cream or cold cuts, the result is more tightly packed ion bunches that should result in more collisions when the counter-circulating beams cross.

    Last year, a team led by Alexei Fedotov demonstrated that the electron beam has the basic properties needed for cooling. After a number of upgrades to increase the beam quality and stability further, this year’s goal is to demonstrate that the electron beam can actually cool the gold-ion beam. The aim is to finish fine-tuning the technique so it can be used for the physics program next year.

    Berndt Mueller, Brookhaven’s Associate Laboratory Director for Nuclear and Particle Physics, noted, “This 19th year of operations demonstrates once again how the RHIC team — both accelerator physicists and experimentalists — is continuing to explore innovative technologies and ways to stretch the physics capabilities of the most versatile particle accelerator in the world.”

    Research at RHIC is funded primarily by the DOE Office of Science (NP) and by these agencies and organizations.

    Brookhaven National Laboratory is supported by the Office of Science of the U.S. Department of Energy. The Office of Science is the single largest supporter of basic research in the physical sciences in the United States, and is working to address some of the most pressing challenges of our time. For more information, please visit

    Follow @BrookhavenLab on Twitter or find us on Facebook.

    Brookhaven National Laboratory

    Brookhaven National Laboratory

    We advance fundamental research in nuclear and particle physics to gain a deeper understanding of matter, energy, space, and time; apply photon sciences and nanomaterials research to energy challenges of critical importance to the nation; and perform cross-disciplinary research on climate change, sustainable energy, and Earth’s ecosystems.  


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  • JanKusanagi at 2019-01-03T15:08:27Z

    Shitty is a weak word 😆

    They're also super spammy, towards people that have nothing to do with them.

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  • JanKusanagi at 2019-01-03T12:55:03Z

    What? 😕

    As usual, depends greatly on who you follow, and the Meanwhile feed is a thing.

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  • Happy GNU year!!

    at 2018-12-31T23:16:11Z

    🥳 🎉

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  • Alexandre Oliva at 2018-12-30T02:37:59Z

    #GNU #Linux-libre 4.19.13-gnu, 4.14.91-gnu, and 4.9.148-gnu source tarballs and patches are now available

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  • Astronomy Picture of the Day for 2018-12-29 12:30:01.589759

    Astronomy Picture of the Day (Unofficial) at 2018-12-29T18:30:02Z

    Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.

    2018 December 29
    See Explanation.  Clicking on the picture will download
the highest resolution version available.

    New Horizons at Ultima Thule
    Illustration Credit: Carlos Hernandez for NASA, Johns Hopkins Univ./APL, Southwest Research Institute

    Explanation: When we celebrate the start of 2019, on January 1 the New Horizons spacecraft will flyby Ultima Thule. A world of the Kuiper belt 6.5 billion kilometers from the Sun, the nickname Ultima Thule (catalog designation 2014 MU69) fittingly means "beyond the known world". Following its 2015 flyby of Pluto, New Horizons was targeted for this journey, attempting the most distant flyby for a spacecraft from Earth by approaching Ultima Thule to within about 3500 kilometers. The tiny world itself is about 30 kilometers in size. This year, an observing campaign with Earth-based telescopes determined the shape of the object to be a contact binary or a close binary sytem as in this artist's illustration. New Horizons will image close up its unexplored surface in the dim light of the distant Sun.

    Tomorrow's picture: galaxy tree

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