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  • richardmitnick 9:51 pm on July 9, 2021 Permalink | Reply
    Tags: "ATLAS measurement supports lepton universality", , , , , , , Physics Today   

    From Physics Today : “ATLAS measurement supports lepton universality” 

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    From Physics Today

    9 Jul 2021
    Christine Middleton

    The collaboration’s result is consistent with the standard-model prediction that W bosons are equally likely to decay into muons and tauons.

    Particle-physics collaborations are always on the lookout for discrepancies between their measurements and the standard model’s predictions.

    Deviations can help point the researchers in the right direction (see, for example, Physics Today, June 2021, page 14). Researchers were therefore excited when a working group combed through data from four earlier experiments performed at European Organization for Nuclear Research [Organisation européenne pour la recherche nucléaire] [Europäische Organisation für Kernforschung](CH) [CERN]’s now-dismantled Large Electron–Positron Collider (LEP) and found that the results were inconsistent with the standard model’s assertion of lepton universality, albeit with a probability of less than 1%.

    All three leptonic generations—electronic, muonic, and tauonic—supposedly have the same coupling to weak force–mediating W bosons. So when a W boson decays, it should be equally likely to produce any one of the leptons, along with its associated antineutrino. Several experiments at DOE’s Fermi National Accelerator Laboratory (US) and CERN have confirmed that W bosons generate electrons and muons at the same rate. But the LEP data showed that tauons were produced slightly more often than muons; the ratio of their production rates was R(τ/μ) = 1.070 ± 0.026. Other experiments studying particles that contain bottom quarks have seen hints of the same problem.

    Now the ATLAS collaboration has collected and analyzed data at the Large Hadron Collider (LHC) that resolves the apparent disagreement. The precision of the collaboration’s measurement is twice that of the LEP result, and the value, R(τ/μ) = 0.992 ± 0.013, agrees with the standard-model prediction of unity.

    The experiment exploited the fact that the LHC’s proton–proton collisions produce a large number of top–antitop quark pairs. A top quark nearly always decays into a W boson and a bottom quark, so the researchers had easy access to many W bosons whose decays they could observe. Some of the W bosons directly produced muons, whereas others produced intermediate tauons that later decayed into muons. Because of their different origins, the muons formed two populations whose signals in the detector could be differentiated by the particles’ impact parameters and transverse momenta. The ATLAS researchers analyzed tens of thousands of W-boson decays for each type of lepton, compared with only a couple thousand each in the LEP data, and counted how many took each path.

    On the whole, data now support the standard model’s prediction of lepton universality in W-boson decays. But the search continues: Hints of lepton universality violations have also been seen in beauty-meson decays at significance levels that are starting to draw attention from high-energy physicists.

    See the full article here .

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    Please help promote STEM in your local schools.

    Stem Education Coalition

    “Our mission

    The mission of Physics Today is to be a unifying influence for the diverse areas of physics and the physics-related sciences.

    It does that in three ways:

    • by providing authoritative, engaging coverage of physical science research and its applications without regard to disciplinary boundaries;
    • by providing authoritative, engaging coverage of the often complex interactions of the physical sciences with each other and with other spheres of human endeavor; and
    • by providing a forum for the exchange of ideas within the scientific community.”

     
  • richardmitnick 3:13 pm on February 25, 2021 Permalink | Reply
    Tags: "A tabletop waveguide delivers focused x rays", , Bright X-ray beams that are emitted in a single direction onto the target of interest are difficult to come by in a laboratory setting., Physics Today, , University of Göttingen [Georg-August-Universität Göttingen](DE) has now developed and demonstrated an approach for generating the radiation directly within a waveguide structure.,   

    From Physics Today: “A tabletop waveguide delivers focused x rays” 

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    From Physics Today(US)

    25 Feb 2021
    Rachel Berkowitz

    By simultaneously generating and guiding beams, the layered anode emits x rays in one direction without the need for mirrors or large-scale accelerators.

    1
    Credit: University of Göttingen [Georg-August-Universität Göttingen](DE)/Julius Hilbig.

    Despite the widespread use of x rays as a fundamental tool for visualizing interior features of solid objects, bright X-ray beams that are emitted in a single direction onto the target of interest are difficult to come by in a laboratory setting. Unlike large-scale accelerators, which emit highly collimated beams, conventional small-scale sources generate x-ray radiation in all directions. Once they’re emitted, x rays cannot easily be manipulated with mirrors or lenses.

    To obtain bright x rays in a clearly defined path, Malte Vassholz and Tim Salditt of the University of Göttingen [Georg-August-Universität Göttingen](DE) have now developed and demonstrated an approach for generating the radiation directly within a waveguide structure. The layered material that makes up the waveguide emits x rays within a nanometers-wide channel, and the resulting beam’s brilliance exceeds that of a conventional µ-focus x-ray tube by two orders of magnitude. The method could lead to a tool for soft-matter imaging and coherent scattering experiments in laboratories.

    Laboratory-scale sources produce x rays by hitting a metal anode with electrons accelerated by a high voltage. Radiation is emitted at all angles when the atoms in the metal deflect and slow those electrons as well as when the electrons excite the metal atoms. To better control the angles at which a metal emits x rays, Vassholz and Salditt built a sandwich-like structure, illustrated in the figure, that was made up of a fluorescent metal layer embedded between guiding and cladding layers. Using a high-energy electron beam that was generated by an instrument adapted from an x-ray tube, the researchers excited the central metal layer, which caused it to emit x rays that were funneled into the guiding layers. Those beams traveled through the guiding layers and were emitted through the waveguide exit. A detector placed across from the exit showed sharp emission peaks corresponding to the waveguide modes, indicating that the device had effectively channeled x rays of up to 35 keV onto a target.

    Additional experiments and calculations suggested that the brightness of the emitted x rays could be further enhanced by using different metals or by varying the thickness of the layers. The researchers propose that the design could enable benchtop measurements of microscale structures that until now have only been accessible using synchrotron radiation. (M. Vassholz, T. Salditt, Sci. Adv. 7, eabd5677, 2021.)

    Science paper:
    Observation of electron-induced characteristic x-ray and bremsstrahlung radiation from a waveguide cavity
    Science Advances

    See the full article here .

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    Please help promote STEM in your local schools.

    Stem Education Coalition

    “Our mission

    The mission of Physics Today(US) is to be a unifying influence for the diverse areas of physics and the physics-related sciences.

    It does that in three ways:

    • by providing authoritative, engaging coverage of physical science research and its applications without regard to disciplinary boundaries;
    • by providing authoritative, engaging coverage of the often complex interactions of the physical sciences with each other and with other spheres of human endeavor; and
    • by providing a forum for the exchange of ideas within the scientific community.”

     
  • richardmitnick 10:37 am on February 21, 2021 Permalink | Reply
    Tags: , , Einsteinium [Es] chemistry captured, LBNLheavy element chemistry program, , Physics Today, To date researchers have created more than two dozen synthetic chemical elements that don’t exist naturally on Earth.   

    From Physics Today: “Einsteinium chemistry captured” 

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    From Physics Today

    18 Feb 2021
    Johanna L. Miller

    The creation of a rare molecule offers a glimpse of how atoms behave at the Periodic Table’s outer reaches.

    To date, researchers have created more than two dozen synthetic chemical elements that don’t exist naturally on Earth. Neptunium (atomic number Z = 93) and plutonium (Z = 94), the first two artificial elements after naturally occurring uranium, are produced in nuclear reactors by the thousands of kilograms. But the accessibility of transuranic elements drops quickly with Z: Einsteinium (Z = 99) can be made only in microgram quantities in specialized laboratories, fermium (Z = 100) is produced by the picogram and has never been purified, and all elements after that are made just one atom at a time.

    There are ways to probe the atomic properties of elements produced atom by atom (see, for example, Physics Today, June 2015, page 14). But when it comes to the traditional way of investigating how atoms behave—mixing them with other substances in solution to form chemical compounds—Es is effectively the end of the periodic table.

    Now Rebecca Abergel (head of Lawrence Berkeley National Laboratory’s heavy element chemistry program) and her colleagues have performed the most complicated and informative Es chemistry experiment to date. They chose to react Einsteinium [Es] with a so-called octadentate ligand—a single organic molecule, held together by the backbone shown in blue, that wraps around a central metal atom and binds to it from all sides—to create the molecular structure shown in the figure. In their previous work, Abergel and colleagues used the same ligand to study transition metals, lanthanides, and lighter actinides. When they were fortunate enough to acquire a few hundred nanograms of Es from Oak Ridge National Laboratory, they used it on that as well.

    1
    Credit: Adapted from K. P. Carter et al., Nature 590, 85 (2021)

    Among other useful properties, the ligand acts as an antenna: It absorbs light in the UV and efficiently channels the energy to the central metal atom, which emits light at a range of longer wavelengths. That luminescence spectrum, which can be measured with just a tiny quantity of material, carries information about the central atom’s electronic energy levels.

    Between the luminescence spectroscopy and complementary x-ray absorption measurements, the researchers discovered that Es differs significantly in its behavior from both its upstairs neighbor holmium and the lighter actinides. The difference is almost certainly due to relativistic effects. The more highly charged an atomic nucleus, the faster the electrons whiz around it. When the electron speed is a significant fraction of the speed of light, it affects the atom’s quantum states in a way that’s extraordinarily difficult to model.

    All actinides exhibit relativistic effects, but the heavier ones especially so. Although Es is so scarce that its chemistry is unlikely to be of any technological importance, it could provide a benchmark for better theoretical understanding of the more abundant lighter actinides’ chemical behavior. Abergel and colleagues are especially interested in how those radioactive elements behave inside the human body—with an eye toward both harnessing their radiation as a cancer treatment and designing new drugs to treat radiation poisoning. (K. P. Carter et al., Nature 590, 85, 2021 [above]).

    See the full article here .

    five-ways-keep-your-child-safe-school-shootings

    Please help promote STEM in your local schools.

    Stem Education Coalition

    “Our mission

    The mission of Physics Today is to be a unifying influence for the diverse areas of physics and the physics-related sciences.

    It does that in three ways:

    • by providing authoritative, engaging coverage of physical science research and its applications without regard to disciplinary boundaries;
    • by providing authoritative, engaging coverage of the often complex interactions of the physical sciences with each other and with other spheres of human endeavor; and
    • by providing a forum for the exchange of ideas within the scientific community.”

     
  • richardmitnick 2:36 pm on February 12, 2021 Permalink | Reply
    Tags: , , , , Physics Today, The red supergiant Betelgeuse, The researchers determined that VY CMa underwent significant localized mass-loss events about 250; 200; 120; and 70 years ago., VY Canis Majoris   

    From Physics Today: “Outbursts from a Milky Way hypergiant” 

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    From Physics Today

    12 Feb 2021
    Andrew Grant

    The star VY Canis Majoris’s recent episodes of mass loss may provide clues about what’s behind the fading of fellow giant Betelgeuse.

    A luminous, sprawling red star in the Milky Way, surrounded by gas and dust and prone to violent mass ejections, abruptly fades in brightness when viewed from Earth. That could well describe Betelgeuse, the famous red supergiant whose fluctuations in apparent magnitude since 2019 have captured the attention of sky watchers and stellar astronomers.

    But that description also fits the profile of VY Canis Majoris, a red hypergiant—and one of the largest known stars in the galaxy by radius—that has fluctuated in brightness and shed mass frequently for at least a century and a half. After obtaining the highest precision measurements of VY CMa and its surroundings to date, Roberta Humphreys of the University of Minnesota Twin Cities and her colleagues now report a correlation in the timing of major episodes of mass loss with that of reported dimming of the star. The findings could help astronomers understand the interplay between surface activity, magnetic fields, and mass loss in the extreme red stars, including Betelgeuse, that sit atop the Hertzsprung–Russell diagram.

    1
    This Hubble image of VY Canis Majoris reveals the asymmetric distribution of material surrounding the star. Credit: R. Humphreys/ NASA/ESA.

    Betelgeuse in the infrared from the Herschel Space Observatory is a superluminous red giant star 650 light-years away. Stars much more massive- like Betelgeuse- end their lives as supernova. Credit: ESA/Herschel/PACS/L. Decin et al).

    When Humphreys, who specializes in very massive stars in the Milky Way and its neighbors, started studying VY CMa, it was thought to be shrouded in a relatively uniform shell of previously expelled gas and dust. In 1999 Humphreys and her team found evidence that the red hypergiant is surrounded instead by knots, filaments, and other discrete clumps of material—presumably the remnants of multiple recent outbursts. The clumps’ movements in different directions suggest that localized instabilities on the stellar surface are responsible.

    In their new study [The Astronomical Journal], Humphreys and colleagues examined several of the clumps nearest to the star by using observations taken in 2018 by the Hubble Space Telescope. An order-of-magnitude improvement in spatial resolution over previous measurements, combined with the strong potassium emission lines from the ejecta, allowed the researchers to pinpoint the positions and velocities of the clumps. Extrapolating from those measurements, the researchers determined that VY CMa underwent significant, localized mass-loss events about 250, 200, 120, and 70 years ago. A small knot of material closer to the star may have been expelled as recently as 1995, which indicates that the star remains highly active.

    In a final step, Humphreys and colleagues compared the timing of VY CMa’s outbursts with measurements of the star’s apparent magnitude dating back to the early 19th century, when the star clocked in at about +6.5 magnitude. The events matched up with periods of variable and fading brightness, which have culminated in the star’s apparent magnitude dipping to around +8.5 today. The researchers attribute the star’s prolonged dimming to a dust-filled expulsion whose direction toward Earth has led to sustained obscuration. Other outbursts in different directions obscured our line of sight only temporarily.

    Does VY CMa yield lessons for those examining Betelgeuse’s mysterious and precipitous drop in brightness? Humphreys and colleagues highlight evidence that Betelgeuse has recently ejected material of its own. Studying the outbursts and brightness changes of a remarkable star like VY CMa, the researchers say, may expose the slightly smaller-scale processes that are influencing the merely extraordinary Betelgeuse.

    See the full article here .

    five-ways-keep-your-child-safe-school-shootings

    Please help promote STEM in your local schools.

    Stem Education Coalition

    “Our mission

    The mission of Physics Today is to be a unifying influence for the diverse areas of physics and the physics-related sciences.

    It does that in three ways:

    • by providing authoritative, engaging coverage of physical science research and its applications without regard to disciplinary boundaries;
    • by providing authoritative, engaging coverage of the often complex interactions of the physical sciences with each other and with other spheres of human endeavor; and
    • by providing a forum for the exchange of ideas within the scientific community.”

     
  • richardmitnick 2:18 pm on February 6, 2021 Permalink | Reply
    Tags: "South Africa develops a transient-tracking 'intelligent observatory'", Astronomers in the country are adapting algorithms and upgrading equipment to enable a network of optical telescopes to autonomously choose and observe targets., , , Automating SAAO’s older instruments is a difficult undertaking. The observatory’s 1.9 m telescope for example is about 80 years old., , , Having designed and built South Africa’s 64-dish MeerKAT radio telescope the radio astronomy engineers are waiting for construction of the Square Kilometre Array to start within the next two years., Las Cumbres pioneered open-source software that allows its network to receive alerts from researchers or large survey projects and automatically schedule observations on one or more of the telescopes., LCO tracks transient events with a global network of telescopes including some at the Sutherland site that are equipped with uniform instruments., On the software side SAAO is building on the expertise of a collaborator- Las Cumbres Observatory., Physics Today, , The formidable feat of retrofitting optical telescopes is being supported by the country’s radio telescope engineers., The intelligent observatory will use an adapted version of LCO’s Target and Observation Manager software., The project’s engineers have begun modifying three of the locally owned telescopes to allow remote automatic observing., The SAAO Sutherland site is home to more than two dozen optical telescopes of different sizes., The SKA will be the largest radio observatory in the world with hundreds of dishes on the African continent and more than a million antennas in Australia., The team has already adapted the SALT telescope which is the largest optical telescope in the Southern Hemisphere., What sets SAAO’s intelligent observatory apart from LCO and other projects is its automated access to telescopes of different sizes and a wide variety of component instruments at a single site.   

    From Physics Today: “South Africa develops a transient-tracking ‘intelligent observatory'” 

    Physics Today bloc

    From Physics Today

    Astronomers in the country are adapting algorithms and upgrading equipment to enable a network of optical telescopes to autonomously choose and observe targets.

    1
    The 1 m Lesedi telescope near Sutherland, South Africa, will be part of an “intelligent observatory” focused on observing transient astronomical objects. Credit: South African Astronomical Observatory.

    On 18 August 2017, astronomer Petri Vaisanen was in the right place at the right time—near a giant telescope. The previous day the LIGO and Virgo observatories had detected gravitational waves, and astronomers around the world were desperately seeking access to telescopes so they could observe the remnants of the neutron-star collision that had sent the ripples through time and space (see Physics Today, December 2017, page 19).

    That night, Vaisanen happened to be the observer on the Southern African Large Telescope (SALT), an 11 m optical telescope near Sutherland, South Africa.


    South African Large Telescope, close to the town of Sutherland in the semi-desert region of the Karoo, South Africa, Altitude 1,798 m (5,899 ft)

    Using the coordinates forwarded to him by South African Astronomical Observatory (SAAO) colleagues in the LIGO and Virgo collaboration, he was able to produce one of the first optical spectra clearly showing the residual fireball that resulted from the violent collision.

    Vaisanen’s presence in the observing room that night was pure chance, he said at a conference celebrating SAAO’s 200-year anniversary in October. A new initiative at the SAAO aims to take some of the luck out of observing future brief but momentous events. Astronomers and engineers there are developing an “intelligent observatory,” in which networked telescopes will receive and filter discovery alerts from facilities around the world and then automatically point to astronomical objects of interest. To achieve that capability, SAAO is retrofitting its stable of reliable, but also relatively old, optical telescopes.

    Transients, such as the neutron-star collision, are a growing area of astrophysics study. Other targets include fast radio bursts (see Physics Today, January 2021, page 15), supernovae, and gamma-ray bursts. Although astronomers are working on ways to more rapidly disseminate the details of new transient discoveries, the current process often involves time-consuming chains of phone calls and emails. An automated process offers the advantages of identifying targets and commencing observations with minimal delay.

    The SAAO Sutherland site is home to more than two dozen optical telescopes of different sizes. Some of them are fully owned by South Africa; others are hosted in exchange for observing time and data. The goal is to have all the telescopes incorporated into a single network that is controlled by a centralized algorithm. Upon receiving alerts from partner institutions, the intelligent observatory would prioritize particular astronomical targets, determine the best telescopes and instruments for the observation, and then automatically insert the required observation duration and location into the telescopes’ observing queues. “Having that capability to access a suite of instruments at the same time, that’s powerful,” says SALT observatory scientist Lisa Crause.

    The project’s engineers have begun modifying three of the locally owned telescopes to allow remote automatic observing. The team has already adapted the SALT telescope, which is the largest optical telescope in the Southern Hemisphere, so that astronomers can both observe and choose instruments remotely.

    Automating SAAO’s older instruments is a difficult undertaking. The observatory’s 1.9 m telescope, for example, is about 80 years old. For now, its three observing instruments—for imaging, acquiring spectra, and measuring polarization—have to be swapped in and out manually by technicians.

    SAAO 1.9 meter telescope, located in Sutherland, which is 370 kilometres (230 mi) from Observatory, Cape Town, where the headquarters is located, altitude 1,450 metres (4,760 ft) above sea level.

    Las Cumbres Observatory site at the SAAO observing station at Sutherland, South Africa, altitude 1,450 metres (4,760 ft) above sea level.

    .

    South African Astronomical Observatory, a photograph of some of the existing telescopes at the site near Sutherland, Northern Cape, SA, altitude 1,450 metres (4,760 ft) above sea level.

    The formidable feat of retrofitting optical telescopes is being supported by the country’s radio telescope engineers. Having designed and built South Africa’s 64-dish MeerKAT radio telescope, they are waiting for construction of the Square Kilometre Array to start within the next two years.

    SKA Meerkat SARAO radio telescopes, South Africa, 90 km outside the small Northern Cape town of Carnarvon, SA.

    SKA- South Africa.

    The SKA will be the largest radio observatory in the world, with hundreds of dishes on the African continent and more than a million antennas in Australia.

    SKA -low frequency at Murchison Widefield Array, Boolardy station in outback Western Australia, at the Murchison Radio-astronomy Observatory (MRO).

    SKA Murchison Widefield Array, Boolardy station in outback Western Australia, at the Murchison Radio-astronomy Observatory (MRO).

    Australian Square Kilometre Array Pathfinder (ASKAP) is a radio telescope array located at Murchison Radio-astronomy Observatory (MRO) in the Australian Mid West. ASKAP consists of 36 identical parabolic antennas, each 12 metres in diameter, working together as a single instrument with a total collecting area of approximately 4,000 square metres.

    “We are providing resources and direct funding primarily to ensure gainful employment for all our engineers . . . and to assist the optical astronomy discipline,” says Willem Esterhuyse, head of engineering at the South African Radio Astronomy Observatory.

    On the software side, SAAO is building on the expertise of a collaborator, Las Cumbres Observatory.

    LCO tracks transient events with a global network of telescopes, including some at the Sutherland site, that are equipped with uniform instruments.

    Las Cumbres pioneered open-source software that allows its network to receive alerts from researchers or large survey projects and automatically schedule observations on one or more of the telescopes. The software takes into consideration what needs to be observed and when, and if needed it can bump scheduled observations out of the queue.

    LCOGT Las Cumbres Observatory Global Telescope Network, Haleakala Hawaii, USA, Elevation 10,023 ft (3,055 m).

    Las Cumbres Observatory Global Telescope Network 1-meter telescope node at Cerro Tololo, Chile, Altitude 2,207 m (7,241 ft).

    What sets SAAO’s intelligent observatory apart from LCO and other projects is its automated access to telescopes of different sizes and a wide variety of component instruments at a single site. “Covering this large scale, from a 1.9-meter up to 11-meter telescope, this is definitely new,” says Mirko Krumpe, an astronomer at the Leibniz Institute for Astrophysics [Leibniz-Institut für Astrophysik] Potsdam (DE) who works on data from the space-based eROSITA telescope and collaborates with SAAO.

    eRosita DLR MPG, on Russian German space telescope The Russian-German space probe Spektrum-Roentgen-Gamma (SRG) .


    After about ten years of development and integration the eROSITA X-ray telescope is complete: with 7 mirror modules and 54 mirror shells each combined with 7 specially built X-ray cameras. You see the telescope here after final integration at MPE, shortly before transport to further testing. Credit: MPG Institute for Extraterrestrial Physics [MPG Institut für extraterrestrische Physik] ( DE)

    “What they are attempting to do is tremendous,” LCO project scientist Rachel Street says of SAAO’s aspirations. The intelligent observatory will use an adapted version of LCO’s Target and Observation Manager software, which, among other things, allows astronomers to easily interact with and display their observation data. “SAAO wants to say, ‘Tell us what we need to observe [for you] and we will send you reduced data,’” says Street. “They will deliver that observation across multiple instruments and wavelengths. It cuts down the path to science.”

    Unlike purely robotic observatories, SAAO’s telescopes, such as SALT, also have time allocated for observing astronomers. When one telescope is in use, the intelligent observatory will divert incoming observation alerts to other available telescopes on the Sutherland site. Which alerts get preference is still up for discussion, says Vaisanen, who is now the observatory’s director. “That’s why it is important to write down the rules or flowcharts beforehand; otherwise you’ll get into almighty fights.”

    The team plans to have half a dozen telescopes upgraded and ready for intelligent observing by late next year, when the NSF Vera C. Rubin Observatory in Chile begins its Legacy Survey of Space and Time (LSST).

    NOIRLab Vera C. Rubin Observatory Telescope currently under construction on the El Peñón peak at Cerro Pachón Chile, a 2,682-meter-high mountain in Coquimbo Region, in northern Chile, alongside the existing Gemini South and Southern Astrophysical Research Telescopes, altitude 2,715 m (8,907 ft).

    The observatory’s 8.4 m telescope will scan large tracts of the sky, acting as a discovery engine for transients and other phenomena. The survey will generate some 10 million alerts a night, and it will be the role of other observatories, such as SAAO, to follow up on them as quickly as possible.

    Federica Bianco, the project’s science collaborations coordinator, says algorithms and intelligent telescopes, such as those SAAO is planning, are necessary to keep up with the deluge of data coming out of large surveys such as the LSST. “You can’t take a month to decide what is worth following,” she says. “You need automation in the selection of what to observe, and automation in pointing to it, collecting the data optimally. You don’t have enough time for individual human decisions.”

    See the full article here .

    five-ways-keep-your-child-safe-school-shootings

    Please help promote STEM in your local schools.

    Stem Education Coalition

    “Our mission

    The mission of Physics Today is to be a unifying influence for the diverse areas of physics and the physics-related sciences.

    It does that in three ways:

    • by providing authoritative, engaging coverage of physical science research and its applications without regard to disciplinary boundaries;
    • by providing authoritative, engaging coverage of the often complex interactions of the physical sciences with each other and with other spheres of human endeavor; and
    • by providing a forum for the exchange of ideas within the scientific community.”

     
  • richardmitnick 4:05 pm on December 15, 2020 Permalink | Reply
    Tags: "Open letter on the Arecibo Observatory", , Physics Today, , The 85 signatories (as of 14 December) come from around the world and are mostly users of Arecibo.   

    From Physics Today: “Open letter on the Arecibo Observatory” 

    Physics Today bloc

    From Physics Today

    Several dozen aeronomists, astronomers, and planetary scientists urge NSF to recover and preserve equipment that wasn’t irreparably damaged in the 1 December platform collapse.

    1
    The instrument platform at the Arecibo Observatory in Puerto Rico, in an undated photo taken before the 1 December collapse of the platform onto the telescope dish. Credit: University of Central Florida, via NSF.

    The following is an open letter, dated 4 December 2020, on the Arecibo Observatory in Puerto Rico. The letter has been lightly edited for style. The video below is courtesy of Carlos Pérez.

    Positional statement on the recovery of Arecibo scientific assets.

    The terrible events regarding the Arecibo platform collapse have deeply impacted the national and international scientific community. In particular, there has been widespread and understandably intense shock and grief at the catastrophic loss of all the equipment located on the Arecibo platform for radio astronomy, planetary radar, and atmospheric science.

    However, preliminary assessments have indicated that significant observatory resources located on the ground near the Arecibo reflector are not completely destroyed. These items have great potential for future scientific observations and should not be immediately consigned to materials recycling without an assessment of salvage potential and a subsequent plan for careful extraction and preservation of material that still has productivity. For instance, some of the HF heating facility antennas on the bottom of the dish are still standing. The HF facility’s transmission lines are intact below the damaged reflector panels. Aside from the area of main platform impact, the reflector ground screen is untouched. Reflector use at lower frequencies may be possible at reduced effective gain with relatively modest repairs using existing panel material already on site. Most of the supporting reflector cables and panels are still in place. HF and UHF transmitters, modulators, control hardware, data servers, generators, and other ground equipment remain intact in buildings 1 and 2, the optics facility, the 12 m very long baseline interferometry telescope area, the main warehouse, and other areas away from the main reflector.

    For these reasons, we strongly advise that during post-collapse site cleanup, a carefully considered and deliberate course of action should be taken that protects remaining Arecibo equipment and assets that were not severely or irreparably damaged by the platform’s collapse. Preservation of these assets is a key step to allowing portions of the Arecibo radio science portfolio to be restored in innovative ways through future community proposals and other efforts. This approach will truly make the best out of the current situation, with direct benefit to human science explorations of our planet’s atmosphere and the universe.


    Arecibo Observatory, The Last Dawn 32X speed..

    The 85 signatories (as of 14 December) come from around the world and are mostly users of Arecibo.

    Eliana Nossa
    Jorge L. Herrera
    Dale C. Ferguson
    Ashton S. Reimer
    Richard L. Ferranti
    Asti Bhatt
    Gerald Lehmacher
    Cesar Valladares
    Sean Marshall
    Khushboo Jain
    Erhan Kudeki
    Alireza Mahmoudian
    Meers Oppenheim
    Lewis Duncan
    Min-Chang Lee
    Luisa Fernanda Zambrano-Marin
    Jeff Dumps
    Pablo Reyes
    Bill Amatucci
    Anne Virkki
    Nipuni Palliyaguru
    James P. Conroy
    Danny Scipión
    Trond S. Trondsen
    Robert Minchin
    Michael Rietveld
    Ashanthi Maxworth
    Marcus Leech
    Carlos Pérez
    Andreas Kvammen
    Cissi Ying-tsen Lin
    Mariangelly Díaz-Rodríguez
    Evgeny Sergeev
    Alessondra Springmann
    Gonzalo Cucho-Padin
    Tapasi Ghosh
    Christopher Salter
    Binghui Wang
    Rob Pfaff
    Michael W. Busch
    Glenn Hussey
    Rob Miceli
    Kevin Ortiz Ceballos
    Bárbara Rojas-Ayala
    Tim Dolch
    Philip J. Erickson
    Lindsay Goodwin
    Thomas Leyser
    Angeline G. Burrell
    Tima Sergienko
    Theresa Rexer
    Lisa Baddeley
    Nicole Lloyd-Ronning
    Brian Gilchrist
    Aram Vartanyan
    Katie Herlingshaw
    Lindis Bjoland
    Andy López-Oquendo
    Juha Vierinen
    Stan Briczinski
    David Hysell
    Erkka Heino
    Abniel Machín
    Wilbert Ruperto Hernández
    Denton Ebel
    Anthea Coster
    Christiano Garnett Marques Brum
    Patrick Taylor
    Susan Nossal
    Scott Rohan
    Abel Méndez
    Carl Friedberg
    Laird Whitehill
    Poorya Hosseini
    Mary Putman
    Natasha Cooke-Nieves
    Amanda Dawn Christie
    Alexander Chernyshov
    Jim Breakall
    Marcel Agüeros
    Julia Deneva
    Frank Djuth
    Jonathan Krall
    Joel Weisberg
    Andrei Demekhov

    See the full article here .

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    Please help promote STEM in your local schools.

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    “Our mission

    The mission of Physics Today is to be a unifying influence for the diverse areas of physics and the physics-related sciences.

    It does that in three ways:

    • by providing authoritative, engaging coverage of physical science research and its applications without regard to disciplinary boundaries;
    • by providing authoritative, engaging coverage of the often complex interactions of the physical sciences with each other and with other spheres of human endeavor; and
    • by providing a forum for the exchange of ideas within the scientific community.”

     
  • richardmitnick 4:47 pm on December 14, 2020 Permalink | Reply
    Tags: "Silicon scaffolds support complex microlenses", A new laser-writing technique produces refractive-index gradients in microscale photonic elements., Physics Today, ,   

    From University of Illinois and Stanford University via Physics Today: “Silicon scaffolds support complex microlenses” 

    U Illinois bloc

    From University of Illinois

    and

    Stanford University Name
    From Stanford University

    via

    Physics Today bloc

    Physics Today

    14 Dec 2020
    Christine Middleton

    A new laser-writing technique produces refractive-index gradients in microscale photonic elements.

    The human eye’s lens has a refractive index that varies radially from about 1.386 at the outer edge to 1.406 at the center. The gradient reduces aberration, thereby enabling the eye to form clearer images than it would with a uniform lens. Now for the first time, three-dimensional gradient-index optics are available for fabricated microscopic devices thanks to a technique developed by Christian Ocier, Corey Richards, and coworkers at the University of Illinois at Urbana-Champaign, in collaboration with researchers at Stanford University.

    The new technique relies on multiphoton direct laser writing (DLW), a lithographic process in which a focused laser beam prints 3D optical components in a volume of light-sensitive polymer photoresist. The beam chemically alters the illuminated polymer as it traces out the desired object’s shape. The untreated polymer is removed, leaving behind a lens, waveguide, or other component. Conventional DLW produces a single refractive index—that of the processed photoresist.

    Instead of starting with a uniform layer of photoresist, Ocier, Richards, and colleagues infused it into scaffolds of either porous silicon or porous silica. The average pore size was about 60 nm—small enough that the material was effectively uniform to visible and IR light—and the scaffolds were transparent at the wavelength used for writing. Each scaffold gave the researchers access to a range of refractive indices: Increasing the power of the laser left increasing amounts of polymer in the pores after the untreated material was washed away. With the silicon scaffold, achievable indices ranged from 1.28, corresponding to the empty scaffold, to 1.85 at maximal filling; those values were lower for the silica scaffolds. The technique, dubbed SCRIBE (subsurface controllable refractive index via beam exposure), has a resolution of a few hundred nanometers, which is determined by the extent of the focused laser’s point-spread function.

    1
    Credit: Adapted from C. R. Ocier et al., Light Sci. Appl. 9, 196 (2020)

    Using SCRIBE, the researchers fabricated a range of optical components, including cylinders, prisms, waveguides, and various lenses. In particular, they made the smallest-ever Luneburg lens, shown in the figure. The first two panels are a schematic of the lens’s refractive-index gradient and a fluorescent image in which the signal corresponds to the amount of photoresist polymer. Because of its spherical symmetry and radially varying refractive index, a Luneburg lens can focus a plane wave to a single point, shown in the third panel, regardless of the wave’s incident angle. Although larger versions are often used with microwaves and radio waves, the SCRIBE-made lens is the first with features small enough to focus visible light.

    Science paper:
    “Direct laser writing of volumetric gradient index lenses and waveguides”
    Light: Science & Applications

    See the full article here .

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    Stanford University campus. No image credit

    Stanford University

    Leland and Jane Stanford founded the University to “promote the public welfare by exercising an influence on behalf of humanity and civilization.” Stanford opened its doors in 1891, and more than a century later, it remains dedicated to finding solutions to the great challenges of the day and to preparing our students for leadership in today’s complex world. Stanford, is an American private research university located in Stanford, California on an 8,180-acre (3,310 ha) campus near Palo Alto. Since 1952, more than 54 Stanford faculty, staff, and alumni have won the Nobel Prize, including 19 current faculty members

    Stanford University Seal

    U Illinois campus

    The University of Illinois at Urbana-Champaign community of students, scholars, and alumni is changing the world.

    With our land-grant heritage as a foundation, we pioneer innovative research that tackles global problems and expands the human experience. Our transformative learning experiences, in and out of the classroom, are designed to produce alumni who desire to make a significant, societal impact.

    The University of Illinois at Chicago (UIC) is a public research university in Chicago, Illinois. Its campus is in the Near West Side community area, adjacent to the Chicago Loop. The second campus established under the University of Illinois system, UIC is also the largest university in the Chicago area, having approximately 30,000 students enrolled in 15 colleges.

    UIC operates the largest medical school in the United States with research expenditures exceeding $412 million and consistently ranks in the top 50 U.S. institutions for research expenditures. In the 2019 U.S. News & World Report’s ranking of colleges and universities, UIC ranked as the 129th best in the “national universities” category. The 2015 Times Higher Education World University Rankings ranked UIC as the 18th best in the world among universities less than 50 years old.

    UIC competes in NCAA Division I Horizon League as the UIC Flames in sports. The Credit Union 1 Arena (formerly UIC Pavilion) is the Flames’ venue for home games.

     
  • richardmitnick 12:47 pm on December 2, 2020 Permalink | Reply
    Tags: "Dust storms starve Mars of water", , , Physics Today   

    From Physics Today and U Arizona: “Dust storms starve Mars of water” 

    Physics Today bloc

    From Physics Today

    and

    University of Arizona

    2 Dec 2020
    Alex Lopatka

    New observations demonstrate that water is transported directly to the Martian upper atmosphere, where it escapes to space after dissociating into atomic hydrogen.

    1
    This true-color image of Mars was captured by the Rosetta spacecraft in 2007. Credit: ESA & MPS for OSIRIS Team, MPS/UPD/LAM/IAA/RSSD/INTA/UPM/DASP/IDA, CC BY-SA 3.0 IGO.

    ESA/Rosetta spacecraft, European Space Agency’s legendary comet explorer Rosetta annotated.

    The geologic record of Mars suggests that the planet once experienced wet weather that may have helped sustain extraterrestrial life. But much of its water presently exists as ice, either at the poles or beneath the surface. Relative to the past, today’s thinner, cooler, drier Martian atmosphere cannot support liquid water.

    Isotopic evidence shows a high ratio of deuterium to hydrogen in the planet’s atmosphere, which has led scientists to conclude that water vapor undergoes photodissociation reactions in the lower atmosphere below the water vapor minimum, called the hygropause. Most of the molecular hydrogen product—containing either hydrogen or deuterium—then diffuses across that barrier to the upper atmosphere and eventually escapes to space; the hydrogen leaves more readily than the heavier deuterium.

    Now Shane Stone and Roger Yelle of the University of Arizona in Tucson and their colleagues have compiled observations and conducted simulations that suggest water may have left Mars’s atmosphere more quickly than previously thought. Recent data from NASA’s MAVEN spacecraft show seasonal variations in the abundance of water in the upper atmosphere that are punctuated by surges of water during dust storms.

    NASA/Mars MAVEN.

    The figure below shows an increase in the abundance of water in the upper atmosphere during one global dust storm in 2018; the amount of molecular hydrogen, however, remains constant (not shown). The high abundance of water vapor in the upper atmosphere indicates a weakening of the hygropause.

    2
    Credit: Shane Stone and Dan Gallagher.

    To better understand how the water vapor moves through the atmosphere and eventually escapes, Yelle and his graduate student Daniel Lo used the MAVEN data as inputs in a one-dimensional photochemical model they constructed. Previous simulations reported that neutral photolysis reactions dissociate water in the lower atmosphere to yield molecular hydrogen. The H2 diffuses to the upper atmosphere, where ions break it up into atomic hydrogen that then escapes to space. But with the help of the MAVEN data, the new model shows that water is transported directly to the upper atmosphere, where it rapidly reacts with ionized chemical species to form atomic hydrogen.

    The calculations of the various reaction rates indicate that before water is destroyed, it has a lifetime of only four hours or so in the upper atmosphere, which is about an order of magnitude shorter than the photolysis of water in the middle atmosphere. The finding means that water vapor may escape the atmosphere in the form of atomic hydrogen faster than previously thought. By Stone and his colleagues’ estimates, a single dust storm could have instigated more hydrogen loss than would happen in an entire average Martian year. [Science]

    See the full article here .

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    The University of Arizona (UA) is a place without limits-where teaching, research, service and innovation merge to improve lives in Arizona and beyond. We aren’t afraid to ask big questions, and find even better answers.

    In 1885, establishing Arizona’s first university in the middle of the Sonoran Desert was a bold move. But our founders were fearless, and we have never lost that spirit. To this day, we’re revolutionizing the fields of space sciences, optics, biosciences, medicine, arts and humanities, business, technology transfer and many others. Since it was founded, the UA has grown to cover more than 380 acres in central Tucson, a rich breeding ground for discovery.

    U Arizona mirror lab-Where else in the world can you find an astronomical observatory mirror lab under a football stadium?

    University of Arizona’s Biosphere 2, located in the Sonoran desert. An entire ecosystem under a glass dome? Visit our campus, just once, and you’ll quickly understand why the UA is a university unlike any other.

    “Our mission

    The mission of Physics Today is to be a unifying influence for the diverse areas of physics and the physics-related sciences.

    It does that in three ways:

    • by providing authoritative, engaging coverage of physical science research and its applications without regard to disciplinary boundaries;
    • by providing authoritative, engaging coverage of the often complex interactions of the physical sciences with each other and with other spheres of human endeavor; and
    • by providing a forum for the exchange of ideas within the scientific community.”

     
  • richardmitnick 9:36 pm on September 25, 2020 Permalink | Reply
    Tags: "Synchrotrons face a data deluge", , , , , EBS-Extremely Brilliant Source, European Synchrotron Research Facility, , National Synchrotron Light Source II, Physics Today   

    From Physics Today: “Synchrotrons face a data deluge” 

    Physics Today bloc

    From Physics Today

    25 Sep 2020
    Rahul Rao

    The latest upgrades at light sources around the world are only accelerating the growth in data rates, and automation is struggling to keep pace.

    1
    The storage ring of the European Synchrotron Research Facility sits at the confluence of the Drac and Isère rivers in Grenoble, France. Credit: ESRF/Jocelyn Chavy.

    In August the European Synchrotron Research Facility (ESRF) in Grenoble, France, opened the Extremely Brilliant Source (EBS), a newly upgraded light source that is 100 times as brilliant as its predecessor and some 100 billion times as powerful as the average hospital x-ray source.

    ESRF Grenoble, France re-opened as
    Extremely Brilliant Source (EBS).

    There’s something else EBS can do better than its predecessor: produce data.

    The light source has a theoretical capacity to produce 1 petabyte of data per day, says Harald Reichert, ESRF’s director of research in physical sciences. “We don’t have the capacity to analyze this data, or even store it, if that machine fires continuously, day after day.”

    Since the 1980s, both beamline photon fluxes and detector data rates have far outpaced the rate of increase in Moore’s law. Even as scientists turn to automation, the unique nature of synchrotrons, with their myriad applications, makes automating their outputs uniquely complicated.

    In the early 2000s, three months’ worth of data from a detector could fit into a 100-megabyte archive, says Stefan Vogt, an x-ray scientist at Argonne National Laboratory’s Advanced Photon Source (APS).


    ANL Advanced Photon Source.

    “These days, for these specific types of experiments, it’s several terabytes.” APS will soon be capable of producing around 200 petabytes per year. A single beamline can produce as much as 12 gigabytes per second.

    The data transfer and storage infrastructure can and does fail to keep up, resulting in lags that can stretch up to days, according to James Holton, a biophysicist at Lawrence Berkeley National Laboratory’s Advanced Light Source.

    LBNL ALS .

    The rapid inflation of data also makes it difficult to future-proof new beamlines. “You have to be making choices now against what the computing infrastructure is going to look like in about five years’ time,” says Graeme Winter, an x-ray crystallographer at the Diamond Light Source in the UK.

    Diamond Light Source, located at the Harwell Science and Innovation Campus in Oxfordshire U.K.

    Upgrading the storage infrastructure only shifts the bottleneck further downstream. There, automation can pick up the reins. Not only can AI, machine learning, and neural networks help in analysis, but they can make data much more manageable by throwing away poor-quality data. They can also reduce excess by stopping data collection in mid-experiment when certain conditions have been reached.

    Indeed, the Large Hadron Collider (LHC), which CERN claims can produce around 25 gigabytes per second recording the aftermath of particle collisions, relies on a worldwide computing grid to handle its data deluge.

    CERN LHC Maximilien Brice and Julien Marius Ordan.


    MonALISA LHC Computing GridMap monalisa.caltech.edu/ml/_client.beta

    But Reichert says that the LHC’s detectors capture each collision in essentially the same way, producing predictable data sets that lend themselves well to automation. In contrast, a synchrotron facility can host multiple beamlines with a far more diverse array of applications, such as determining protein crystal structures, charting the brain’s neural connections, and watching chemical catalysis and additive manufacturing in real time. “They have nothing in common,” says Reichert. “They use different detectors. The data is completely different.”

    Consequently, it’s often left to the users of each beamline and application to develop their own specialized firmware and algorithms. When large synchrotrons like APS host dozens of beamlines, some of which are deeply customizable, the volume of specialized use cases renders a streamlined system like CERN’s impractical.

    2
    The sample chamber within a beamline at the National Synchrotron Light Source II in Upton, New York. State-of-the-art synchrotron beamlines can produce up to 12 gigabytes of data per second. Credit: Brookhaven National Laboratory, CC BY-NC-ND 2.0

    BNL NSLS II.

    When users do take up the challenge of building tools, the programmers who make them often approach the problem differently from the scientists who need them. Earlier this year, crystallographers used Diamond to aid drug discovery efforts by scanning a protease in the virus responsible for COVID-19. Collecting the data took mere days, but it took longer to convert the observational data into structures detailed enough for chemists to use. The researchers’ tools also provided output that was difficult for chemists to interpret. Without an effective means of communicating and checking their results with chemists, the project was delayed by weeks.

    Frank von Delft, a macromolecular crystallographer at Diamond, says that programmers should focus on making their tools easier to use. “When that’s achieved,” he says, “your whole platform suddenly becomes powerful.” In particular, he cites Phenix, a crystallography tool that can help determine molecular structures. Phenix is one of the most popular tools of its kind, in large part thanks to a graphical user interface designed by a biologist rather than a career programmer.

    Fortunately, the future seems to be pointing toward greater streamlining, including at the synchrotron end. Traditionally, facilities left the data-handling part of their science to the users, but the enormous data volumes, as well as other factors such as more computation shifting to the cloud, are changing that.

    Reichert believes each synchrotron facility should help provide scientists the tools they need and assist with the computation. “When we give [a scientist] beam time,” he says, “we’d better ask the question: What do you do with the data, and what kind of help do you need to actually get an answer to your scientific problem and put the answer out in the open?”

    See the full article here .

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    Please help promote STEM in your local schools.

    Stem Education Coalition

    “Our mission

    The mission of Physics Today is to be a unifying influence for the diverse areas of physics and the physics-related sciences.

    It does that in three ways:

    • by providing authoritative, engaging coverage of physical science research and its applications without regard to disciplinary boundaries;
    • by providing authoritative, engaging coverage of the often complex interactions of the physical sciences with each other and with other spheres of human endeavor; and
    • by providing a forum for the exchange of ideas within the scientific community.”

     
  • richardmitnick 5:19 pm on September 15, 2020 Permalink | Reply
    Tags: "Quantum computer models a chemical reaction", , , Google’s superconducting processor simulates molecules with the help of a classical computer and a method to deal with errors., Physics Today, The Hartree–Fock method   

    From Physics Today: “Quantum computer models a chemical reaction” 

    Physics Today bloc

    From Physics Today

    8 Sep 2020
    Heather Hill

    Google’s superconducting processor simulates molecules with the help of a classical computer and a method to deal with errors.

    Google 54-qubit Sycamore superconducting processor quantum computer.

    The Google AI Quantum team made a big media splash a year ago when it announced quantum supremacy [Nature], the point at which a quantum device can solve a problem that a classical computer can’t in a reasonable time frame. But quantum computing still faces many challenges before it becomes practical. As academic and industrial researchers work to increase the number of qubits, reduce error rates, and find more effective error-mitigation strategies, they’ve also become interested in near-term quantum devices, which work with current capabilities.

    In that spirit, the Google team has now applied its 54-qubit Sycamore superconducting processor, shown in the above photo, to chemistry simulations. The researchers are the first to include a quantum computer in the modeling of a chemical reaction, and their Hartree–Fock calculations are a performance yardstick for a combined quantum and classical computation.

    The Hartree–Fock method assumes that the wavefunction for a system of electrons can be written in terms of single-electron functions, without electron–electron interactions, and that each electron feels the average electric field from other electrons. The wavefunction is then adjusted to minimize its energy.

    In the Google team’s calculations, each qubit represents a single-electron wavefunction, or orbital. The researchers apply a series of rotation logic gates to effectively rewrite the system’s wavefunction as a sum of those orbitals. The qubits’ degrees of excitation—between 0 and 1—indicate the probability that each orbital is filled. The wavefunction’s energy is measured and fed into a classical computer, which sets new rotation parameters for the gates. The parameters are repeatedly tweaked to find the minimum energy.

    The researchers used that method for two common electronic-structure benchmarks: distinguishing the pathways for a diazene molecule, HNNH, to transform between cis and trans isomers and finding the binding energy of stretched linear hydrogen chains for lengths of 6, 8, 10, and 12 atoms. Previous electronic-structure calculations by quantum computers required only up to 6 qubits, but here the researchers used as many as 12 qubits interacting through 72 two-qubit logic gates.

    With all those qubits and gates, error mitigation was essential. The team kept only measurements in which the number of particles stayed the same; a change in that number is a clear sign of an error. The researchers also looked at the one-particle densities, and if the wavefunction didn’t yield the expected 0 and 1 eigenvalues, they projected it onto the closest state that did. They were able to get an accuracy that was high enough to make chemical predictions with 99% fidelity for the logic gates and 97% fidelity for readout.

    Science paper:
    Hartree-Fock on a superconducting qubit quantum computer
    Science

    See the full article here .

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    Please help promote STEM in your local schools.

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    “Our mission

    The mission of Physics Today is to be a unifying influence for the diverse areas of physics and the physics-related sciences.

    It does that in three ways:

    • by providing authoritative, engaging coverage of physical science research and its applications without regard to disciplinary boundaries;
    • by providing authoritative, engaging coverage of the often complex interactions of the physical sciences with each other and with other spheres of human endeavor; and
    • by providing a forum for the exchange of ideas within the scientific community.”

     
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