High Thermopower in Molybdenum Disulfide MoS2 Layers

by Tommy on 27/05/2015

http://arxiv.org/abs/1505.06779

Record High Thermoelectric Powerfactor in Single and Few-Layer MoS2, Kedar Hippalgaonkar, Ying Wang, Yu Ye, Hanyu Zhu, Yuan Wang, Joel Moore and Xiang Zhang

The quest for high-efficiency heat-to-electricity conversion has been one of the major driving forces towards renewable energy production for the future. Efficient thermoelectric devices require careful material engineering such as high voltage generation from a temperature gradient, and high electrical conductivity while maintaining a low thermal conductivity. Significant progress in the thermoelectric performance of materials has been made by exploring the ultralow thermal conductivity at high temperature, reducing the thermal conductivity by nanostructuring, resonant doping and energy-dependent scattering. For a given thermal conductivity and temperature, thermoelectric powerfactor is determined by the electronic structure of the material. Low dimensionality (1D and 2D) opens new routes to high powerfactor due to their unique density of states of confined electrons and holes. Emerging 2D transition metal dichalcogenide (TMDC) semiconductors represent a new class of thermoelectric materials not only from their discretized density of states, but especially due to their large effective masses and high carrier mobilities, different from gapless semi-metallic graphene. Here we report a measured powerfactor of MoS2 as large as 8.5 mWm−1K−2 at room temperature, the highest among all thermoelectric materials and twice that of commercial thermoelectric material Bi2Te3. For the first time, the measurement of the thermoelectric properties of monolayer MoS2 allows us to determine the quantum confined 2D density of states near the conduction band edge, which cannot be measured by electrical conductivity alone. The demonstrated record high powerfactor in 2D TMDCs holds promise for efficient thermoelectric energy conversion.

No Comments

NASA Is Too Stupid To Figure Out How To Live On Mars

by Tommy on 22/05/2015

NASA Journey To Mars Challenge

NASA Announces Journey to Mars Challenge, Seeks Public Input on Establishing Sustained Human Presence on Red Planet

NASA is embarking on an ambitious journey to Mars and Tuesday announced a challenge inviting the public to write down their ideas, in detail, for developing the elements of space pioneering necessary to establish a continuous human presence on the Red Planet. This could include shelter, food, water, breathable air, communication, exercise, social interactions and medicine, but participants are encouraged to consider innovative and creative elements beyond these examples.

Participants are asked to describe one or more Mars surface systems or capabilities and operations that are needed to achieve this goal and, to the greatest extent possible, are technically achievable, economically sustainable, and minimize reliance on support from Earth. NASA expects to make up to three awards at a minimum of $5,000 each from a total award pool of $15,000.

And then they send you to some Innocentive scam site.

https://www.innocentive.com/ar/challenge/9933746

I have already solved this problem. Trivially.

http://lifeform.net/archimedes/GroX.pdf

Two words young man.

Stackable Plastics

There is more.

But quite honestly you would have to be a complete idiot to want to tackle the problems of living sustainably on the surface of Mars when there are much easier and more accessible near term destinations like free space, the moon, the moon of Mars and the planet Ceres. Mars is right off the bat going to need long, rolled up, inflatable, pressurized cylinders, with 1/4 circumference transparency for light, and a massive amount of solar panels, batteries and infrastructure. And just moving around in the heavy gravity of Mars in a bulky spacesuit is going to be a real hassle.

On the other hand, the massive amount of stackable polyethylene and polypropylene plant growing equipment you will need just to survive – will make excellent radiation protection.

Clandestine California growing operations are decades and light years ahead of NASA. This is an entire industry that I personally invented and developed way back in the seventies. Old news.

My Biography, if you are interested. It all ended in tears, of course.

Silo View Farm

Silo View Farm

No Comments

Warming Oceans Have Initiated Massive Antarctic Ice Losses

by Tommy on 22/05/2015

http://www.sciencemag.org/content/348/6237/899

Dynamic thinning of glaciers on the Southern Antarctic Peninsula

B. Wouters, A. Martin-Español, V. Helm, T. Flament, J. M. van Wessem, S. R. M. Ligtenberg, M. R. van den Broeke and J. L. Bamber, Science, 348, 6237 pp. 899-903 (22 May 2015), DOI: 10.1126/science.aaa5727

Growing evidence has demonstrated the importance of ice shelf buttressing on the inland grounded ice, especially if it is resting on bedrock below sea level. Much of the Southern Antarctic Peninsula satisfies this condition and also possesses a bed slope that deepens inland. Such ice sheet geometry is potentially unstable. We use satellite altimetry and gravity observations to show that a major portion of the region has, since 2009, destabilized. Ice mass loss of the marine-terminating glaciers has rapidly accelerated from close to balance in the 2000s to a sustained rate of –56 ± 8 gigatons per year, constituting a major fraction of Antarctica’s contribution to rising sea level. The widespread, simultaneous nature of the acceleration, in the absence of a persistent atmospheric forcing, points to an oceanic driving mechanism.

No Comments

Optically Pumped Superconductivity for Semiconductors

by Tommy on 21/05/2015

http://arxiv.org/abs/1406.7299

Photo-induced superconductivity in semiconductors, Garry Goldstein, Camille Aron and Claudio Chamon, Physical Review B, PRB 91, 054517 (24 February 2015)

We show that optically pumped semiconductors can exhibit superconductivity. We illustrate this phenomenon in the case of a two-band semiconductor tunnel-coupled to broad-band reservoirs and driven by a continuous wave laser. More realistically, we also show that superconductivity can be induced in a two-band semiconductor interacting with a broad-spectrum light source. We furthermore discuss the case of a three-band model in which the middle band replaces the broad-band reservoirs as the source of dissipation. In all three cases, we derive the simple conditions on the band structure, electron-electron interaction, and hybridization to the reservoirs that enable superconductivity. We compute the finite superconducting gap and argue that the mechanism can be induced through both attractive and repulsive interactions and is robust to high temperatures.

http://journals.aps.org/prb/abstract/10.1103/PhysRevB.91.054517

No Comments

Preformed Real Space Negative-U Electron Pairs Observed

by Tommy on 18/05/2015

http://www.nature.com/nature/journal/v521/n7551/full/nature14398.html

Electron pairing without superconductivity, Guanglei Cheng, Michelle Tomczyk, Shicheng Lu, Joshua P. Veazey, Mengchen Huang, Patrick Irvin, Sangwoo Ryu, Hyungwoo Lee, Chang-Beom Eom, C. Stephen Hellberg and Jeremy Levy, Nature, 521, 196–199 (14 May 2015), doi:10.1038/nature14398

Strontium titanate (SrTiO3) is the first and best known superconducting semiconductor. It exhibits an extremely low carrier density threshold for superconductivity, and possesses a phase diagram similar to that of high-temperature superconductors — two factors that suggest an unconventional pairing mechanism. Despite sustained interest for 50 years, direct experimental insight into the nature of electron pairing in SrTiO3 has remained elusive. Here we perform transport experiments with nanowire-based single-electron transistors at the interface between SrTiO3 and a thin layer of lanthanum aluminate, LaAlO3. Electrostatic gating reveals a series of two-electron conductance resonances—paired electron states—that bifurcate above a critical pairing field Bp of about 1–4 tesla, an order of magnitude larger than the superconducting critical magnetic field. For magnetic fields below Bp, these resonances are insensitive to the applied magnetic field; for fields in excess of Bp, the resonances exhibit a linear Zeeman-like energy splitting. Electron pairing is stable at temperatures as high as 900 millikelvin, well above the superconducting transition temperature (about 300 millikelvin). These experiments demonstrate the existence of a robust electronic phase in which electrons pair without forming a superconducting state. Key experimental signatures are captured by a model involving an attractive Hubbard interaction that describes real-space electron pairing as a precursor to superconductivity.

I see David Eagles got some press out of this too. Good for him.

Now if it only sticks together.

No Comments

Glacial Lake Agassiz Moorhead Phase Drawdown Reassessed

by Tommy on 16/05/2015

http://www.sciencedirect.com/science/article/pii/S0277379115001511

The Tintah-Campbell gap and implications for glacial Lake Agassiz drainage during the Younger Dryas cold interval, Andy Breckenridge, Quaternary Science Reviews, Volume 117, Pages 124–134 (1 June 2015) doi:10.1016/j.quascirev.2015.04.009

Reconstructions of glacial Lake Agassiz paleogeography and drainage have been an important contribution to formulating a hypothesis in which glacial Lake Agassiz drainage to the Atlantic Ocean initiated the Younger Dryas cold interval. This study evaluates the lake level and outlet history of Lake Agassiz as recorded by strandlines visible on lidar digital elevation models from North Dakota and Minnesota. The former lake levels are warped due to glacial isostatic adjustment. Older levels have experienced more uplift and therefore have more curvature. The strandline data establish that the Moorhead lowstand of Lake Agassiz was bracketed by the strongly diverging Campbell and Tintah lake levels, which creates a vertical gap between the former lake levels. This gap exists due to a lake level drop of ∼90 m when the Laurentide Ice Sheet retreat opened a lower outlet, which must have been a northwest outlet to the Arctic Ocean. By applying an exponential decay rebound model, this event dates to 12,180 ± 480 cal yr BP, post-dating the beginning of the Younger Dryas at 12,900 cal yr BP. Eastern drainage outlets to the Atlantic Ocean through the Laurentian Great Lakes that were contemporaneous with the onset of the Younger Dryas cannot be ruled out, but if these outlets existed, their duration of occupation was short-lived and not characterized by significant drawdown events within glacial Lake Agassiz.

This might explain why the Younger Dryas lasted so long, but it does not describe initiation.

No Comments

Milankovitch Cycle Effect on Pleistocene Glaciation Reassessed

by Tommy on 16/05/2015

http://arxiv.org/abs/1505.02183

Obliquity and precession as pacemakers of Pleistocene deglaciations, Fabo Feng and C. A. L. Bailer-Jones, Accepted for Publication in Quaternary Science Reviews

The Milankovitch theory states that the orbital eccentricity, precession, and obliquity of the Earth influence our climate by modulating the summer insolation at high latitudes in the northern hemisphere. Despite considerable success of this theory in explaining climate change over the Pleistocene epoch (2.6 to 0.01 Myr ago), it is inconclusive with regard to which combination of orbital elements paced the 100 kyr glacial-interglacial cycles over the late Pleistocene. Here we explore the role of the orbital elements in pacing the Pleistocene deglaciations by modeling ice-volume variations in a Bayesian approach. When comparing models, this approach takes into account the uncertainties in the data as well as the different degrees of model complexity. We find that the Earth’s obliquity (axial tilt) plays a dominant role in pacing the glacial cycles over the whole Pleistocene, while precession only becomes important in pacing major deglaciations after the transition of the dominant period from 41 kyr to 100 kyr (the mid-Pleistocene transition). We also find that geomagnetic field and orbital inclination variations are unlikely to have paced the Pleistocene deglaciations. We estimate that the mid-Pleistocene transition took place over a 220 kyr interval centered on a time 715 kyr ago, although the data permit a range of 600–1000 kyr. This transition, occurring within just two 100\,kyr cycles, indicates a relatively rapid change in the climate response to insolation.

No Comments

Geosynchronous Upper Stage Solar Array Above Ceres’ Spot

by Tommy on 14/05/2015
Ceres Bright Spots

Ceres Bright Spots

That’s basically less than 500 miles above the surface with periodic planetary occultations.

In equatorial orbit that would have the spacecraft moving up and down in elevation (or a lazy 8) and fixed in azimuth (or a lazy 8). Then one could easily set down an ISRU unit (Dragon science platform) with a large solar array and a couple of rechargable rovers. This is perfect for SpaceX.

Equatorial Ceres crustal breakthroughs are like some manna from heaven. Or hell, lol. Salt!

Mars, Schmars. Cars, bars, guitars and stars can’t be far behind now.

No Comments

Sea Level Rise and Acceleration Since 1994 Further Refined

by Tommy on 11/05/2015

http://www.nature.com/nclimate/journal/vaop/ncurrent/full/nclimate2635.html

Unabated global mean sea-level rise over the satellite altimeter era, Christopher S. Watson, Neil J. White, John A. Church, Matt A. King, Reed J. Burgette and Benoit Legresy, Nature Climate Change (11 May 2015), doi:10.1038/nclimate2635

The rate of global mean sea-level (GMSL) rise has been suggested to be lower for the past decade compared with the preceding decade as a result of natural variability, with an average rate of rise since 1993 of +3.2 ± 0.4 mm yr−1. However, satellite-based GMSL estimates do not include an allowance for potential instrumental drifts (bias drifts). Here, we report improved bias drift estimates for individual altimeter missions from a refined estimation approach that incorporates new Global Positioning System (GPS) estimates of vertical land movement (VLM). In contrast to previous results, we identify significant non-zero systematic drifts that are satellite-specific, most notably affecting the first 6 years of the GMSL record. Applying the bias drift corrections has two implications. First, the GMSL rate (1993 to mid-2014) is systematically reduced to between +2.6 ± 0.4 mm yr−1 and +2.9 ± 0.4 mm yr−1, depending on the choice of VLM applied. These rates are in closer agreement with the rate derived from the sum of the observed contributions, GMSL estimated from a comprehensive network of tide gauges with GPS-based VLM applied (updated from ref. 8) and reprocessed ERS-2/Envisat altimetry. Second, in contrast to the previously reported slowing in the rate during the past two decades, our corrected GMSL data set indicates an acceleration in sea-level rise (independent of the VLM used), which is of opposite sign to previous estimates and comparable to the accelerated loss of ice from Greenland and to recent projections, and larger than the twentieth-century acceleration.

No Comments

Electronic Polymer Physics Proposed for Underdoped Cuprates

by Tommy on 11/05/2015

http://arxiv.org/abs/1505.01847

Electronic polymers and soft-matter-like broken symmetries in underdoped cuprates
M. Capati, S. Caprara, C. Di Castro, M. Grilli, G. Seibold and J. Lorenzana

Empirical evidence in heavy fermion, pnictide, and other systems suggests that unconventional superconductivity appears associated to some form of real-space electronic order. For the cuprates, despite several proposals, the emergence of order in the phase diagram between the commensurate antiferromagnetic state and the superconducting state is not well understood. Here we show that in this regime doped holes assemble in “electronic polymers.” Within a Monte Carlo study we find, that in clean systems by lowering the temperature the polymer melt condenses first in a smectic state and then in a Wigner crystal both with the addition of inversion symmetry breaking. Disorder blurs the positional order leaving a robust inversion symmetry breaking and a nematic order, accompanied by vector chiral spin order and with the persistence of a thermodynamic transition. Such electronic phases, whose properties are reminiscent of soft-matter physics, produce charge and spin responses in good accord with experiments.

No Comments

UV – Optical – IR Space Telescope Proposed for Earth Analogs

by Tommy on 11/05/2015

http://arxiv.org/abs/1505.01840

Characterizing the Habitable Zones of Exoplanetary Systems with a Large Ultraviolet/Visible/Near-IR Space Observatory, Kevin France, Evgenya Shkolnik, Jeffrey Linsky, Aki Roberge, Thomas Ayres, Travis Barman, Alexander Brown, James Davenport, Jean-Michel Desert, Shawn Domagal-Goldman, Brian Fleming, Juan Fontenla, Luca Fossati, Cynthia Froning, Gregg Hallinan, Suzanne Hawley, Renyu Hu, Lisa Kaltenegger, James Kasting, Adam Kowlaski, Parke Loyd, Pablo Mauas, Yamila Miguel, Rachel Osten, Seth Redfield, Sarah Rugheimer, Christian Schneider, Antigona Segura, John Stocke, Feng Tian, Jason Tumlinson, Mariela Vieytes, Lucianne Walkowicz, Brian Wood and Allison Youngblood, Submitted in response to NASA call for white papers: “Large Astrophysics Missions to Be Studied by NASA Prior to the 2020 Decadal Survey’

Understanding the surface and atmospheric conditions of Earth-size, rocky planets in the habitable zones (HZs) of low-mass stars is currently one of the greatest astronomical endeavors. Knowledge of the planetary effective surface temperature alone is insufficient to accurately interpret biosignature gases when they are observed in the coming decades. The UV stellar spectrum drives and regulates the upper atmospheric heating and chemistry on Earth-like planets, is critical to the definition and interpretation of biosignature gases, and may even produce false-positives in our search for biologic activity. This white paper briefly describes the scientific motivation for panchromatic observations of exoplanetary systems as a whole (star and planet), argues that a future NASA UV/Vis/near-IR space observatory is well-suited to carry out this work, and describes technology development goals that can be achieved in the next decade to support the development of a UV/Vis/near-IR flagship mission in the 2020s.

No Comments

Quantum Spin Hall States of a Bismuth Surface Investigated

by Tommy on 10/05/2015

http://journals.aps.org/prb/abstract/10.1103/PhysRevB.91.165307

One-dimensional spin texture of Bi(441): Quantum spin Hall properties without a topological insulator, M. Bianchi, F. Song, S. Cooil, Å. F. Monsen, E. Wahlström, J. A. Miwa, E. D. L. Rienks, D. A. Evans, A. Strozecka, J. I. Pascual, M. Leandersson, T. Balasubramanian, Ph. Hofmann, and J. W. Wells. Phys. Rev. B 91, 165307 (21 April 2015), DOI: 10.1103/PhysRevB.91.165307

The high index (441) surface of bismuth has been studied using scanning tunneling microscopy (STM), angle resolved photoemission spectroscopy (APRES), and spin-resolved ARPES. The surface is strongly corrugated, exposing a regular array of (110)-like terraces. Two surface localized states are observed, both of which are linearly dispersing in one in-plane direction (kx), and dispersionless in the orthogonal in-plane direction (ky), and both of which have a Dirac-like crossing at kx = 0. Spin ARPES reveals a strong in-plane polarization, consistent with Rashba-like spin-orbit coupling. One state has a strong out-of-plane spin component, which matches with the miscut angle, suggesting its possible origin as an edge state. The electronic structure of Bi(441) has significant similarities with topological insulator surface states and is expected to support one-dimensional quantum spin Hall-like coupled spin-charge transport properties with inhibited backscattering, without requiring a topological insulator bulk.

No Comments

Low Earth Orbit Zero Gravity Espresso Coffee Finally Brewed

by Tommy on 9/05/2015

International Space Station ISS Cupola Coffee

It took them long enough. They should name that thing the Gemini 7.

No Comments

Jeff Bezos Blue Origin Flies Crashes BE-3 Hydrogen Booster

by Tommy on 1/05/2015
Jeff Bezos - Blue Origin - BE-3 - First Flight

Jeff Bezos – Blue Origin – BE-3 – First Flight

That was quick. And a wildly successful mission as well.

One month after announcing flight readiness.

No Comments

Alkaline White Smokers Contain Catalytic Biological Surfaces

by Tommy on 1/05/2015
Alkaline White Smokers

Alkaline White Smokers

http://pubs.rsc.org/en/Content/ArticleLanding/2015/CC/C5CC02078F#!divAbstract

A. Roldan, N. Hollingsworth, A. Roffey, H.-U. Islam, J. B. M. Goodall, C. R. A. Catlow, J. A. Darr, W. Bras, G. Sankar, K. B. Holt, G. Hogarth and N. H. de Leeuw. Bio-inspired CO2 conversion by iron sulfide catalysts under sustainable conditions. Chem. Commun., 2015; 51 (35): 7501 DOI: 10.1039/C5CC02078F

The mineral greigite presents similar surface structures to the active sites found in many modern-day enzymes. We show that particles of greigite can reduce CO2 under ambient conditions into chemicals such as methanol, formic, acetic and pyruvic acid. Our results also lend support to the Origin of Life theory on alkaline hydrothermal vents.

I’ll drink to that!

No Comments

Ice Core Yields Evidence of Robust Oceanic Bipolar Seesaw

by Tommy on 30/04/2015

http://www.nature.com/nature/journal/v520/n7549/full/nature14401.html

Precise interpolar phasing of abrupt climate change during the last ice age, WAIS Divide Project Members, Nature, 520, 661–665 (30 April 2015), doi:10.1038/nature14401

The last glacial period exhibited abrupt Dansgaard–Oeschger climatic oscillations, evidence of which is preserved in a variety of Northern Hemisphere palaeoclimate archives. Ice cores show that Antarctica cooled during the warm phases of the Greenland Dansgaard–Oeschger cycle and vice versa, suggesting an interhemispheric redistribution of heat through a mechanism called the bipolar seesaw. Variations in the Atlantic meridional overturning circulation (AMOC) strength are thought to have been important, but much uncertainty remains regarding the dynamics and trigger of these abrupt events. Key information is contained in the relative phasing of hemispheric climate variations, yet the large, poorly constrained difference between gas age and ice age and the relatively low resolution of methane records from Antarctic ice cores have so far precluded methane-based synchronization at the required sub-centennial precision. Here we use a recently drilled high-accumulation Antarctic ice core to show that, on average, abrupt Greenland warming leads the corresponding Antarctic cooling onset by 218 ± 92 years (2σ) for Dansgaard–Oeschger events, including the Bølling event; Greenland cooling leads the corresponding onset of Antarctic warming by 208 ± 96 years. Our results demonstrate a north-to-south directionality of the abrupt climatic signal, which is propagated to the Southern Hemisphere high latitudes by oceanic rather than atmospheric processes. The similar interpolar phasing of warming and cooling transitions suggests that the transfer time of the climatic signal is independent of the AMOC background state. Our findings confirm a central role for ocean circulation in the bipolar seesaw and provide clear criteria for assessing hypotheses and model simulations of Dansgaard–Oeschger dynamics.

No Comments

Glacial Lake Agassiz Meltwater Discharge into the St. Lawrence at the Younger Dryas

by Tommy on 29/04/2015

http://www.sciencedirect.com/science/article/pii/S0921818115000764

Evidence for meltwater drainage via the St. Lawrence River in marine cores from the Laurentian Channel at the time of the Younger Dryas, Elisabeth Levac, Michael Lewis, Vanessa Stretch, Katie Duchesne, and Thomas Neulieb, Global and Planetary Change (23 April 2015), doi:10.1016/j.gloplacha.2015.04.002

Debate is ongoing about the source(s) and paths of meltwater that drained into the North Atlantic Ocean at the time of the Younger Dryas (YD), especially the eastern route from glacial Lake Agassiz and predecessor lakes of the Laurentian Great Lakes located along the southeastern edge of the Laurentide Ice Sheet. Here, evidence is presented for meltwater drainage via the St. Lawrence eastern route from five new sediment cores from Cabot Strait, Laurentian Channel and Scotian Shelf at the time of the YD. Palynological analyses are used to reconstruct sea surface conditions based on dinoflagellate cyst records, and pollen data are used for additional correlation. The reconstructions show distinct drops in salinity and temperature and increased sea ice cover duration within the YD period. In addition to these new records, we present a re-examination of original data and paleoceanographic interpretation of surface waters based on a new analysis of dinoflagellate cyst zonation in combination with an updated chronology supported by new radiocarbon dates and refined calibrations. The results clearly define the YD core intervals which contain strong evidence of lowered salinity, thereby re-establishing the St. Lawrence drainage system as a significant route for inflow of YD meltwater to the North Atlantic. This inflow does not exclude the possibility for another source of freshwater, as suggested by geographical differences in the duration of cold, low salinity conditions west and east of Laurentian Channel associated with the YD climatic event.

Ok, then. Game on. Again.

No Comments

Artificial Gauge Forcing of the BCS-BEC Crossover Transition

by Tommy on 24/04/2015

Fluctuation Theory of Rashba Fermi Gases

Fluctuation Theory of Rashba Fermi Gases, Jayantha P. Vyasanakere and Vijay B. Shenoy

Fermi gases with generalized Rashba spin orbit coupling induced by a synthetic gauge field have the potential of realizing many interesting states such as rashbon condensates and topological phases. Here we develop a fluctuation theory of such systems and demonstrate that beyond-Gaussian effects are essential to capture the physics of such systems. We obtain their phase diagram by constructing an approximate non-Gaussian theory. We conclusively establish that spin-orbit coupling can enhance the exponentially small transition temperature (Tc) of a weakly attracting superfluid to the order of Fermi temperature, paving a pathway towards high Tc superfluids.

So in addition to raising Tc of superfluids, we can also observe directly the weirdness in the matrix as a result of the strong coupling of non-linear state machines, the beyond Gaussian distributions of the statistical fluctuations. Something very profound is happening here.

No Comments

Stochastic Thermodynamics, Fluctuation Theorems, and Molecular Machines

by Tommy on 22/04/2015

http://iopscience.iop.org/0034-4885/75/12/126001/

http://arxiv.org/abs/1205.4176

Stochastic thermodynamics, fluctuation theorems, and molecular machines, Udo Seifert, Rep. Prog. Phys. 75 126001 (20 November 2012), doi:10.1088/0034-4885/75/12/126001

Stochastic thermodynamics as reviewed here systematically provides a framework for extending the notions of classical thermodynamics like work, heat and entropy production to the level of individual trajectories of well-defined non-equilibrium ensembles. It applies whenever a non-equilibrium process is still coupled to one (or several) heat bath(s) of constant temperature. Paradigmatic systems are single colloidal particles in time-dependent laser traps, polymers in external flow, enzymes and molecular motors in single molecule assays, small biochemical networks and thermoelectric devices involving single electron transport. For such systems, a first-law like energy balance can be identified along fluctuating trajectories. Various integral and detailed fluctuation theorems, which are derived here in a unifying approach from one master theorem, constrain the probability distributions for work, heat and entropy production depending on the nature of the system and the choice of non-equilibrium conditions. For non-equilibrium steady states, particularly strong results hold like a generalized fluctuation-dissipation theorem involving entropy production. Ramifications and applications of these concepts include optimal driving between specified states in finite time, the role of measurement-based feedback processes and the relation between dissipation and irreversibility. Efficiency and, in particular, efficiency at maximum power, can be discussed systematically beyond the linear response regime for two classes of molecular machines, isothermal ones like molecular motors, and heat engines like thermoelectric devices, using a common framework based on a cycle decomposition of entropy production.

See also Matteo Smerlak’s guest post on John Baez’s blog Azimuth.

The Mathematical Origin of Irreversibility

So to me this is the paradigm of life, the non-linear coupling of machines generating arithmetic coding based on the partitioning of sets and the factorization of integers. Very large integers.

And getting bigger all the time.

A geometric ratchet.

A Ponzi scheme.

“Help, I’m a Bug!”

Update: See also http://arxiv.org/abs/1206.3441

Self-organization without heat: the geometric ratchet effect, Matteo Smerlak and Ahmed Youssef

We point out a surprising feature of diffusion in inhomogeneous media: under suitable conditions, the rectification of the Brownian paths by a diffusivity gradient can result in initially spread tracers spontaneously concentrating. This “geometric ratchet effect” demonstrates that, in violation of the classical statements of the second law of (non-equilibrium) thermodynamics, self-organization can take place in thermodynamic systems at local equilibrium without heat being produced or exchanged with the environment. We stress the role of Bayesian priors in a suitable reformulation of the second law accommodating this geometric ratchet effect.

No Comments

Chucky Bouldin Say – All Your Planet Are Belong To US

by Tommy on 17/04/2015
Chucky Bouldin NASA Administrator

Chucky Bouldin NASA Administrator

“No commercial company without the support of NASA and government is going to get to Mars,”

Dream on Chuck – “There’s no place like home.”

“I Yam What I Yam”

No Comments

Emergent Quantum Proton Liquid and Tunneling in Water Ice

by Tommy on 17/04/2015

http://arxiv.org/abs/1504.04158

Electromagnetism on ice: classical and quantum theories of proton disorder in hexagonal water ice, Owen Benton, Olga Sikora and Nic Shannon

Water ice is simultaneously one of the most ubiquitous and most mysterious materials on Earth. The arrangement of protons in hexagonal water ice (ice Ih) is subject to strong local constraints (“the ice rules”) but remains globally disordered, leading to a large entropy even at very low temperatures. Experimental measurements have indicated that quantum tunnelling of protons persists down to the low temperature regime, possibily proceeding via loop processes which preserve the ice rules. In a related class of systems- “the spin ices” such processes are known to give rise to a quantum spin-liquid state at low temperatures, featuring fractionalized “magnetic monopole” excitations and emergent photons. In this paper, we explore the consequences of the formation of an analogous “proton liquid” state in ice Ih, via the same mechanism. We construct field theories describing both the classical and quantum regimes of proton correlations obtaining good agreement with Monte Carlo simulations in both cases. We find that the quantum liquid state possesses birefringent “photons” and additional, gapped, local fluctuations of the electric polarisation.

Shocking! Call the neighbors, wake the kids.

No Comments

The Surface of the Fifth Planet Ceres As We Now Know It

by Tommy on 14/04/2015
Ceres Surface Color

Ceres Surface Color

http://www.nature.com/news/mystery-of-ceres-bright-spots-grows-1.17313

Mystery of Ceres’ bright spots grows, Alexandra Witze, Nature (13 April 2015), doi:10.1038/nature.2015.17313

No Comments

Cosmic Weather Report – 75% Chance of Change Tomorrow

by Tommy on 13/04/2015
SpaceX Landing Barge ASDS Just Read The Instructions

SpaceX Landing Barge ASDS Just Read The Instructions

SpaceX image taken from the drone.

Update: Another SpaceX Close But No Cigar Moment.

Update 2: I think Ben Cooper took this shot.

SpaceX Booster Landing

SpaceX Booster Landing

No Comments

Coherent Fluctuation Spectroscopy To Disentangle Cuprates

by Tommy on 13/04/2015

http://arxiv.org/abs/1504.02760

Probing the electron-phonon interaction in correlated systems with coherent lattice fluctuation spectroscopy, Andreas Mann, Edoardo Baldini, Antonio Tramontana, Ekaterina Pomjakushina, Kazimierz Conder, Christopher Arrell, Frank van Mourik, José Lorenzana and Fabrizio Carbone

Tailoring the properties of correlated oxides is accomplished by chemical doping, pressure, temperature or magnetic field. Photoexcitation is a valid alternative to reach out-of-equilibrium states otherwise inaccessible. Here, we quantitatively estimate the coupling between a lattice distortion and the charge-transfer excitation in (La2CuO4+δ). We photoinduce a coherent La ion vibration and monitor the response of the optical constants in a broad energy range, providing quantitative information on the electron-phonon matrix element that can be compared to theoretical models. We propose the same methodology to probe electron-electron interactions in other materials.

No Comments

Record High Thermopower By Localization and Phonon Drag

by Tommy on 9/04/2015

http://arxiv.org/abs/1504.01901

Giant Oscillating Thermopower at Oxide Interfaces, I. Pallecchi, F. Telesio, D. Li, A. Fête, S. Gariglio, J.-M. Triscone, A. Filippetti, P. Delugas, V. Fiorentini and D. Marré

Understanding the nature of charge carriers at the LaAlO3/SrTiO3 interface is one of the major open issues in the full comprehension of the charge confinement phenomenon in oxide heterostructures. Here, we investigate thermopower to study the electronic structure in LaAlO3/SrTiO3 at low temperature as a function of gate field. In particular, under large negative gate voltage, corresponding to the strongly depleted charge density regime, thermopower displays record-high negative values of the order of 104 – 105 µV/K, oscillating at regular intervals as a function of the gate voltage. The huge thermopower magnitude can be attributed to the phonon-drag contribution, while the oscillations map the progressive depletion and the Fermi level descent across a dense array of localized states lying at the bottom of the Ti 3d conduction band. This study is the first direct evidence of a localized Anderson tail in the two-dimensional (2D) electron liquid at the LaAlO3/SrTiO3 interface.

This just keeps getting better every day.

No Comments

Gross Error Found in the Tunneling Spectra of Superconductors

by Tommy on 9/04/2015

http://arxiv.org/abs/1504.01932

Coupling to real and virtual phonons in tunneling spectroscopy of superconductors, Jasmin Jandke, Patrik Hlobil, Michael Schackert, Wulf Wulfhekel and Jörg Schmalian

Fine structures in the tunneling spectra of superconductors have been widely used to identify fingerprints of the interaction responsible for Cooper pairing. Here we show that for scanning tunneling microscopy (STM) of Pb, the inclusion of inelastic tunneling processes is crucial for the proper interpretation of these fine structures. For STM the usual McMillan inversion algorithm of tunneling spectra must therefore be modified to include inelastic tunneling events, an insight that is crucial for the identification of the pairing glue in conventional and unconventional superconductors alike.

No Comments

Cuprate Structural Instability By Electron Lattice Interaction

by Tommy on 9/04/2015

http://arxiv.org/abs/1504.01779

Oxygen Isotope Effects on Lattice Properties of La2-xBaxCuO4 (x = 1/8), Z. Guguchia, D. Sheptyakov, E. Pomjakushina, K. Conder, R. Khasanov, A. Shengelaya, A. Simon, A. Bussmann-Holder and H. Keller

A novel negative oxygen-isotope (16O/18O) effect (OIE) on the low-temperature tetragonal phase transition temperature TLTT was observed in La2-xBaxCuO4 (x = 1/8) using high-resolution neutron powder diffraction. The corresponding OIE exponent α(TLTT) = – 0.36(5) has the same sign as α(Tso) = -0.57(6) found for the spin-stripe order temperature Tso. The fact that the LTT transition is accompanied by charge ordering (CO) implies the presence of an OIE also for the CO temperature Tco. Furthermore, a temperature dependent shortening of the c-axis with the heavier isotope is observed. These results combined with model calculations demonstrate that anharmonic electron-lattice interactions are essential for all transitions observed in the stripe phase of cuprates.

No Comments

Even More Bizarre Weyl Semimetal States Proposed – SrSi2

by Tommy on 8/04/2015

http://arxiv.org/abs/1503.05868

A new type of Weyl semimetal with quadratic double Weyl fermions in SrSi2, Shin-Ming Huang, Su-Yang Xu, Ilya Belopolski, Chi-Cheng Lee, Guoqing Chang, BaoKai Wang, Nasser Alidoust, Madhab Neupane, Hao Zheng, Daniel Sanchez, Arun Bansil, Guang Bian, Hsin Lin and M. Zahid Hasan

We identify a Weyl semimetal state in an inversion breaking, stoichiometric compound strontium silicide, SrSi2, with many new and novel properties that are distinct from the TaAs family. We theoretically show that SrSi2 is a Weyl semimetal even without spin-orbit coupling and that, after the inclusion of spin-orbit coupling, two Weyl fermions stick together forming an exotic double Weyl fermion with quadratic dispersions and a higher chiral topological charge of 2. Moreover, we find that the Weyl nodes with opposite charges are located at different energies due to the absence of mirror symmetry in SrSi2, leading to a unique topological quantum response that an external magnetic field can induce a dissipationless current. Our systematic results not only identify a much-needed robust Weyl semimetal candidate but also open the door to new topological Weyl physics that is not possible in the TaAs family of materials.

I’m cracking up! I can’t take it anymore!

No Comments

Earth Moon Solar System Formation Dynamics Investigated

by Tommy on 8/04/2015

http://arxiv.org/abs/1504.01421

Highly Siderophile Elements in the Earth’s Mantle as a Clock for the Moon-forming Impact, Seth A. Jacobson, Alessandro Morbidelli, Sean N. Raymond, David P. O’Brien, Kevin J. Walsh and David C. Rubie

According to the generally accepted scenario, the last giant impact on the Earth formed the Moon and initiated the final phase of core formation by melting the Earth’s mantle. A key goal of geochemistry is to date this event, but different ages have been proposed. Some argue for an early Moon-forming event, approximately 30 million years (Myr) after the condensation of the first solids in the Solar System, whereas others claim a date later than 50 Myr (and possibly as late as around 100 My) after condensation. Here we show that a Moon-forming event at 40 Myr after condensation, or earlier, is ruled out at a 99.9 per cent confidence level. We use a large number of N-body simulations to demonstrate a relationship between the time of the last giant impact on an Earth-like planet and the amount of mass subsequently added during the era known as Late Accretion. As the last giant impact is delayed, the late-accreted mass decreases in a predictable fashion. This relationship exists within both the classical scenario and the Grand Tack scenario of terrestrial planet formation, and it holds across a wide range of disk conditions. The concentration of highly siderophile elements (HSEs) in Earth’s mantle constrains the mass of chondritic material added to Earth during Late Accretion. Using HSE abundance measurements, we determine a Moon-formation age of 95 +/- 32 Myr since condensation. The possibility exists that some late projectiles were differentiated and left an incomplete HSE record in Earth’s mantle. Even in this case, various isotopic constraints strongly suggest that the late-accreted mass did not exceed 1 per cent of Earth’s mass, and so the HSE clock still robustly limits the timing of the Moon-forming event to significantly later than 40 My after condensation.

No Comments

Blue Origin Announces Flight Ready BE-3 Hydrogen Engine

by Tommy on 7/04/2015
Blue Origin BE-3 Hydrogen Engine

Blue Origin BE-3 Hydrogen Engine

http://lifeform.net/tsiolkovsky/Delta_9_RLV.pdf

http://lifeform.net/tsiolkovsky/Delta_V.pdf

No Comments

Predicted New Class of Binary Weyl Semimetals Discovered

by Tommy on 7/04/2015

http://arxiv.org/abs/1504.01350

Discovery of Weyl semimetal NbAs, Su-Yang Xu, Nasser Alidoust, Ilya Belopolski, Chenglong Zhang, Guang Bian, Tay-Rong Chang, Hao Zheng, Vladimir Strokov, Daniel S. Sanchez, Guoqing Chang, Zhujun Yuan, Daixiang Mou, Yun Wu, Lunan Huang, Chi-Cheng Lee, Shin-Ming Huang, BaoKai Wang, Arun Bansil, Horng-Tay Jeng, Titus Neupert, Adam Kaminski, Hsin Lin, Shuang Jia and M. Zahid Hasan

We report the discovery of Weyl semimetal NbAs featuring unusual Fermi arc surface states.

Three types of Fermions play a fundamental role in our understanding of nature: Dirac, Majorana, and Weyl. While Dirac fermions are known, the latter two have not been observed as any fundamental particle in high energy physics and have emerged as a much-sought-out treasure in condensed matter physics. A Weyl semimetal is a novel crystal whose low-energy electronic excitations behave as Weyl fermions. It has received worldwide interest and is believed to open the next era of condensed matter physics after graphene and three-dimensional topological insulators.

However, experimental research has been held back because Weyl semimetals are extremely rare in nature. Here, we present the experimental discovery of the Weyl semimetal state in niobium arsenide (NbAs). Utilizing the combination of soft X-ray and ultraviolet photoemission spectroscopy,
we systematically study both the surface and bulk electronic structure of NbAs. We experimentally observe both the Weyl cones and Weyl nodes in the bulk and the Fermi arcs on the surface of this system. Our ARPES data, in agreement with our previous theoretical prediction and present band structure calculations, provide conclusive evidence for the topological Weyl semimetal state in NbAs. Our discovery not only paves the way for the many fascinating topological quantum phenomena predicted in Weyl semimetals, but also establishes a new cornerstone in the correspondence between high-energy and condensed matter physics.

Ok then, the revolution will be televised in quantum holography.

Hasan is really tearing it up.

See the original theory paper here: http://arxiv.org/abs/1501.00755

An inversion breaking Weyl semimetal state in the TaAs material class, Shin-Ming Huang, Su-Yang Xu, Ilya Belopolski, Chi-Cheng Lee, Guoqing Chang, BaoKai Wang, Nasser Alidoust, Guang Bian, Madhab Neupane, Arun Bansil, Hsin Lin and M. Zahid Hasan

The recent discoveries of Dirac fermions in graphene and on the surface of topological insulators have ignited worldwide interest in physics and materials science. A Weyl semimetal is an unusual crystal where electrons also behave as massless quasi-particles but interestingly they are not Dirac fermions. These massless particles, Weyl fermions, were originally considered in massless quantum electrodynamics but have not been observed as a fundamental particle in nature. A Weyl semimetal provides a condensed matter realization of Weyl fermions, leading to unique transport properties with novel device applications. Such a semimetal is also a topologically non-trivial metallic phase of matter extending the classification of topological phases beyond insulators. The signature of a Weyl semimetal in real materials is the existence of unusual Fermi arc surface states, which can be viewed as half of a surface Dirac cone in a topological insulator. Here, we identify the first Weyl semimetal in a class of stoichiometric materials, which break crystalline inversion symmetry, including TaAs, TaP, NbAs and NbP. Our first-principles calculations on TaAs reveal the spin-polarized Weyl cones and Fermi arc surface states in this compound. We also observe pairs of Weyl points with the same chiral charge which project onto the same point in the surface Brillouin zone, giving rise to multiple Fermi arcs connecting to a given Weyl point. Our results show that TaAs is the first topological semimetal identified which does not depend on fine-tuning of chemical composition or magnetic order, greatly facilitating an exploration of Weyl physics in real materials.

No Comments

The Congressional Mandate for Hazardous Asteroid Detection

by Tommy on 6/04/2015

http://arxiv.org/abs/1504.00712

The Need for Speed in Near-Earth Asteroid Characterization, J. L. Galache, C. L. Beeson, K. K. McLeod, M. Elvis, Accepted for Publication in Planetary & Space Science

We have used Minor Planet Center data and tools to explore the discovery circumstances and properties of the currently known population of over 10,000 NEAs, and to quantify the challenges for follow-up from ground-based telescopes. The increasing rate of discovery has grown to ~1,000/year as surveys have become more sensitive, by 1mag every ~7.5 years. However, discoveries of large (H =< 22) NEAs have remained stable at ~365/year over the past decade, at which rate the 2005 Congressional mandate to find 90% of 140m NEAs will not be met before 2030. Meanwhile, characterization is falling farther behind: Fewer than 10% of NEAs are well characterized in terms of size, rotation periods, and spectra, and at current rates of follow-up it will take about a century to determine them even for the known population. Over 60% of NEAs have an orbital uncertainty parameter, U >= 4, making reacquisition more than a year following discovery difficult; for H > 22 this fraction is over 90%. We argue that rapid follow-up will be essential to characterize newly-discovered NEAs. Most new NEAs are found within 0.5 mag of peak brightness and fade quickly, typically by 0.5/3.5/5 mag after 1/4/6 weeks. About 80% have synodic periods of < 3 years that bring them close to Earth several times a decade. However, follow-up observations on subsequent apparitions will be near impossible for the bulk of new discoveries, as these will be H > 22 NEAs that tend to return 100 times fainter. We show that for characterization to keep pace with discovery would require: Visible spectroscopy within days with a dedicated > 2m telescope; long-arc astrometry, used also for phase curves, with a > 4m telescope; and fast-cadence (= 4m telescope. For the already-known large (H =< 22) NEAs, subsequent-apparition spectroscopy, astrometry, and photometry could be done with 1-2m telescopes.

No Comments

Early Earth Was Very Warm With Only Occasional Glaciation

by Tommy on 3/04/2015

http://arxiv.org/abs/1504.00401

The Case for a Hot Archean Climate and its Implications to the History of the Biosphere, David W. Schwartzman

The case for a much warmer climate on the early Earth than now is presented. The oxygen isotope record in sedimentary chert and the compelling case for a near constant isotopic oxygen composition of seawater over geologic time support thermophilic surface temperatures prevailing in the Archean, with some support for hot conditions lasting until about 1.5 billion years ago, aside from lower temperatures including glacial episodes at 2.1-2.4 Ga and possibly an earlier one at 2.9 Ga. Other evidence includes the following: 1) Melting temperatures of proteins resurrected from sequences inferred from robust molecular phylogenies give paleotemperatures at emergence consistent with a very warm early climate. 2) High atmospheric pCO2 levels in the Archean are consistent with high climatic temperatures near the triple point of primary iron minerals in banded iron formations, the formation of Mn-bicarbonate clusters leading to oxygenic photosynthesis and generally higher weathering intensities on land. These higher weathering intensities would not have occurred if seafloor weathering dominated the carbon sink, pulling down the temperature, hence this empirical evidence supports a hot climate and high carbon dioxide levels. 3) The inferred viscosity of seawater at 2.7 Ga is consistent with a hot Archean climate. 5) A cold Archean is hard to explain taking into account the higher outgassing rates of carbon dioxide, significantly smaller land areas and weaker biotic enhancement of weathering than present in the context of the long-term carbon cycle, taking into account the fainter Archean sun in climate modeling. This evidence points to an important conclusion regarding biological evolution, namely to the critical role of a temperature constraint holding back the emergence of major organismal groups, starting with phototrophs, culminating with metazoans in the latest Precambrian.

No Comments

One Dimensional Carbyne Would Be The Strongest Material

by Tommy on 2/04/2015

http://arxiv.org/abs/1504.00347

Relation between the strength and dimensionality of defect-free carbon crystals, Sergey Kotrechko, Andrey Timoshevskii, Eugene Kolyvoshko and Yuriy Matviychuk

On the basis of ab-initio simulations, the value of strength of interatomic bonds in one-, two- and three-dimensional carbon crystals is obtained. It is shown that decreasing in dimensionality of crystal gives rise to nearly linear increase in strength of atomic bonds. It is ascertained that growth of strength of the crystal with a decrease in it dimensionality is due to both a reduction in coordination number of atom and increase in the angle between the directions of atomic bonds. Based on these data, it is substantiated that the one-dimensional crystals have maximum strength, and strength of carbyne is the absolute upper limit of strength of materials.

The Mythical Unobtanium.

No Comments

Moderate Pressure Drastically Changes Black Phosphorus

by Tommy on 2/04/2015

http://arxiv.org/abs/1504.00125

Pressure-induced Lifshitz transition in black phosphorus, Z. J. Xiang, G. J. Ye, C. Shang, B. Lei, N. Z. Wang, K. S. Yang, D. Y. Liu, F. B. Meng, X. G. Luo, L. J. Zou, Z. Sun, Y. B. Zhang and X.H. Chen,

In a semimetal, both electron and hole carriers contribute to the density of states at the Fermi level. The small band overlaps and multi-band effects give rise to many novel electronic properties, such as relativistic Dirac fermions with linear dispersion, titanic magnetoresistance and unconventional superconductivity. Black phosphorus has recently emerged as an exceptional semiconductor with high carrier mobility and a direct, tunable bandgap. Of particular importance is the search for exotic electronic states in black phosphorus, which may amplify the material’s potential beyond semiconductor devices. Here we show that a moderate hydrostatic pressure effectively suppresses the band gap and induces a Lifshitz transition from semiconductor to semimetal in black phosphorus; a colossal magnetoresistance is observed in the semimetallic phase. Quantum oscillations in high magnetic field reveal the complex Fermi surface topology of the semimetallic black phosphorus. In particular, a Dirac-like fermion emerges at around 1.2 GPa, which is continuously tuned by external pressure. The observed semi-metallic behavior greatly enriches black phosphorus’s material property, and sets the stage for the exploration of novel electronic states in this material. Moreover, these interesting behaviors make phosphorene a good candidate for the realization of a new two-dimensional relativistic electron system, other than graphene.

Phosphorus is the new bismuth!

No Comments