ALBERT

Description: The sequence of dyke intrusions between 2005 and 2010 in the Manda Hararo rift segment, Ethiopia, provided an opportunity to test conceptual models of continental rifting. Based on trends up to dyke 13 in the sequence, it was anticipated that, should magma supply continue, dykes would shorten in length and eruptions would increase in size and decrease in distance from the segment centre as extensional stress was progressively released. In this paper we revisit these predictions by presenting a comprehensive overview of the May 2010 dyke and fissure eruption, the 14th and last in the sequence, from InSAR, seismicity, satellite thermal data, ultraviolet SO 2 retrievals and multiple LiDAR surveys. We find the dyke is longer than other eruptive dykes in the sequence, propagating in two directions from the segment centre, but otherwise fairly typical in terms of opening, propagation speed and geodetic and seismic moment. However, though the eruption is located closer to the segment centre, it is much smaller than previous events. We interpret this as indicating that either the Manda Hararo rifting event was magma limited, or that extensional stress varies north and south of the segment centre.

Description: We report the results of a systematic atomic-scale analysis of the reactions of small mobile helium clusters (He n , 4 ≤ n ≤ 7) near low-Miller-index tungsten (W) surfaces, aiming at a fundamental understanding of the near-surface dynamics of helium-carrying species in plasma-exposed tungsten. These small mobile helium clusters are attracted to the surface and migrate to the surface by Fickian diffusion and drift due to the thermodynamic driving force for surface segregation. As the clusters migrate toward the surface, trap mutation (TM) and cluster dissociation reactions are activated at rates higher than in the bulk. TM produces W adatoms and immobile complexes of helium clusters surrounding W vacancies located within the lattice planes at a short distance from the surface. These reactions are identified and characterized in detail based on the analysis of a large number of molecular-dynamics trajectories for each such mobile cluster near W(100), W(110), and W(111) surfaces. TM is found to be the dominant cluster reaction for all cluster and surface combinations, except for the He 4 and He 5 clusters near W(100) where cluster partial dissociation following TM dominates. We find that there exists a critical cluster size, n = 4 near W(100) and W(111) and n = 5 near W(110), beyond which the formation of multiple W adatoms and vacancies in the TM reactions is observed. The identified cluster reactions are responsible for important structural, morphological, and compositional features in the plasma-exposed tungsten, including surface adatom populations, near-surface immobile helium-vacancy complexes, and retained helium content, which are expected to influence the amount of hydrogen re-cycling and tritium retention in fusion tokamaks.

Description: We present atomistic simulations that show the effect of surface orientation on helium depth distributions and surface feature formation as a result of low-energy helium plasma exposure. We find a pronounced effect of surface orientation on the initial depth of implanted helium ions, as well as a difference in reflection and helium retention across different surface orientations. Our results indicate that single helium interstitials are sufficient to induce the formation of adatom/substitutional helium pairs under certain highly corrugated tungsten surfaces, such as {1 1 1}-orientations, leading to the formation of a relatively concentrated layer of immobile helium immediately below the surface. The energies involved for helium-induced adatom formation on {1 1 1} and {2 1 1} surfaces are exoergic for even a single adatom very close to the surface, while {0 0 1} and {0 1 1} surfaces require two or even three helium atoms in a cluster before a substitutional helium cluster and adatom will form with reasonable probability. This phenomenon results in much higher initial helium retention during helium plasma exposure to {1 1 1} and {2 1 1} tungsten surfaces than is observed for {0 0 1} or {0 1 1} surfaces and is much higher than can be attributed to differences in the initial depth distributions alone. The layer thus formed may serve as nucleation sites for further bubble formation and growth or as a source of material embrittlement or fatigue, which may have implications for the formation of tungsten “fuzz” in plasma-facing divertors for magnetic-confinement nuclear fusion reactors and/or the lifetime of such divertors.

Description: Environmental Science & Technology DOI: 10.1021/es2017158

Description: A stochastic background of gravitational waves is expected to arise from a superposition of a large number of unresolved gravitational-wave sources of astrophysical and cosmological origin. It should carry unique signatures from the earliest epochs in the evolution of the Universe, inaccessible to standard astrophysical observations. Direct measurements of the amplitude of this background are therefore of fundamental importance for understanding the evolution of the Universe when it was younger than one minute. Here we report limits on the amplitude of the stochastic gravitational-wave background using the data from a two-year science run of the Laser Interferometer Gravitational-wave Observatory (LIGO). Our result constrains the energy density of the stochastic gravitational-wave background normalized by the critical energy density of the Universe, in the frequency band around 100 Hz, to be 〈6.9 x 10(-6) at 95% confidence. The data rule out models of early Universe evolution with relatively large equation-of-state parameter, as well as cosmic (super)string models with relatively small string tension that are favoured in some string theory models. This search for the stochastic background improves on the indirect limits from Big Bang nucleosynthesis and cosmic microwave background at 100 Hz.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉LIGO Scientific Collaboration & Virgo Collaboration -- Abbott, B P -- Abbott, R -- Acernese, F -- Adhikari, R -- Ajith, P -- Allen, B -- Allen, G -- Alshourbagy, M -- Amin, R S -- Anderson, S B -- Anderson, W G -- Antonucci, F -- Aoudia, S -- Arain, M A -- Araya, M -- Armandula, H -- Armor, P -- Arun, K G -- Aso, Y -- Aston, S -- Astone, P -- Aufmuth, P -- Aulbert, C -- Babak, S -- Baker, P -- Ballardin, G -- Ballmer, S -- Barker, C -- Barker, D -- Barone, F -- Barr, B -- Barriga, P -- Barsotti, L -- Barsuglia, M -- Barton, M A -- Bartos, I -- Bassiri, R -- Bastarrika, M -- Bauer, Th S -- Behnke, B -- Beker, M -- Benacquista, M -- Betzwieser, J -- Beyersdorf, P T -- Bigotta, S -- Bilenko, I A -- Billingsley, G -- Birindelli, S -- Biswas, R -- Bizouard, M A -- Black, E -- Blackburn, J K -- Blackburn, L -- Blair, D -- Bland, B -- Boccara, C -- Bodiya, T P -- Bogue, L -- Bondu, F -- Bonelli, L -- Bork, R -- Boschi, V -- Bose, S -- Bosi, L -- Braccini, S -- Bradaschia, C -- Brady, P R -- Braginsky, V B -- Brand, J F J van den -- Brau, J E -- Bridges, D O -- Brillet, A -- Brinkmann, M -- Brisson, V -- Van Den Broeck, C -- Brooks, A F -- Brown, D A -- Brummit, A -- Brunet, G -- Bullington, A -- Bulten, H J -- Buonanno, A -- Burmeister, O -- Buskulic, D -- Byer, R L -- Cadonati, L -- Cagnoli, G -- Calloni, E -- Camp, J B -- Campagna, E -- Cannizzo, J -- Cannon, K C -- Canuel, B -- Cao, J -- Carbognani, F -- Cardenas, L -- Caride, S -- Castaldi, G -- Caudill, S -- Cavaglia, M -- Cavalier, F -- Cavalieri, R -- Cella, G -- Cepeda, C -- Cesarini, E -- Chalermsongsak, T -- Chalkley, E -- Charlton, P -- Chassande-Mottin, E -- Chatterji, S -- Chelkowski, S -- Chen, Y -- Christensen, N -- Chung, C T Y -- Clark, D -- Clark, J -- Clayton, J H -- Cleva, F -- Coccia, E -- Cokelaer, T -- Colacino, C N -- Colas, J -- Colla, A -- Colombini, M -- Conte, R -- Cook, D -- Corbitt, T R C -- Corda, C -- Cornish, N -- Corsi, A -- Coulon, J-P -- Coward, D -- Coyne, D C -- Creighton, J D E -- Creighton, T D -- Cruise, A M -- Culter, R M -- Cumming, A -- Cunningham, L -- Cuoco, E -- Danilishin, S L -- D'Antonio, S -- Danzmann, K -- Dari, A -- Dattilo, V -- Daudert, B -- Davier, M -- Davies, G -- Daw, E J -- Day, R -- De Rosa, R -- Debra, D -- Degallaix, J -- Del Prete, M -- Dergachev, V -- Desai, S -- Desalvo, R -- Dhurandhar, S -- Di Fiore, L -- Di Lieto, A -- Di Paolo Emilio, M -- Di Virgilio, A -- Diaz, M -- Dietz, A -- Donovan, F -- Dooley, K L -- Doomes, E E -- Drago, M -- Drever, R W P -- Dueck, J -- Duke, I -- Dumas, J-C -- Dwyer, J G -- Echols, C -- Edgar, M -- Effler, A -- Ehrens, P -- Ely, G -- Espinoza, E -- Etzel, T -- Evans, M -- Evans, T -- Fafone, V -- Fairhurst, S -- Faltas, Y -- Fan, Y -- Fazi, D -- Fehrmann, H -- Ferrante, I -- Fidecaro, F -- Finn, L S -- Fiori, I -- Flaminio, R -- Flasch, K -- Foley, S -- Forrest, C -- Fotopoulos, N -- Fournier, J-D -- Franc, J -- Franzen, A -- Frasca, S -- Frasconi, F -- Frede, M -- Frei, M -- Frei, Z -- Freise, A -- Frey, R -- Fricke, T -- Fritschel, P -- Frolov, V V -- Fyffe, M -- Galdi, V -- Gammaitoni, L -- Garofoli, J A -- Garufi, F -- Genin, E -- Gennai, A -- Gholami, I -- Giaime, J A -- Giampanis, S -- Giardina, K D -- Giazotto, A -- Goda, K -- Goetz, E -- Goggin, L M -- Gonzalez, G -- Gorodetsky, M L -- Gobler, S -- Gouaty, R -- Granata, M -- Granata, V -- Grant, A -- Gras, S -- Gray, C -- Gray, M -- Greenhalgh, R J S -- Gretarsson, A M -- Greverie, C -- Grimaldi, F -- Grosso, R -- Grote, H -- Grunewald, S -- Guenther, M -- Guidi, G -- Gustafson, E K -- Gustafson, R -- Hage, B -- Hallam, J M -- Hammer, D -- Hammond, G D -- Hanna, C -- Hanson, J -- Harms, J -- Harry, G M -- Harry, I W -- Harstad, E D -- Haughian, K -- Hayama, K -- Heefner, J -- Heitmann, H -- Hello, P -- Heng, I S -- Heptonstall, A -- Hewitson, M -- Hild, S -- Hirose, E -- Hoak, D -- Hodge, K A -- Holt, K -- Hosken, D J -- Hough, J -- Hoyland, D -- Huet, D -- Hughey, B -- Huttner, S H -- Ingram, D R -- Isogai, T -- Ito, M -- Ivanov, A -- Johnson, B -- Johnson, W W -- Jones, D I -- Jones, G -- Jones, R -- Sancho de la Jordana, L -- Ju, L -- Kalmus, P -- Kalogera, V -- Kandhasamy, S -- Kanner, J -- Kasprzyk, D -- Katsavounidis, E -- Kawabe, K -- Kawamura, S -- Kawazoe, F -- Kells, W -- Keppel, D G -- Khalaidovski, A -- Khalili, F Y -- Khan, R -- Khazanov, E -- King, P -- Kissel, J S -- Klimenko, S -- Kokeyama, K -- Kondrashov, V -- Kopparapu, R -- Koranda, S -- Kozak, D -- Krishnan, B -- Kumar, R -- Kwee, P -- La Penna, P -- Lam, P K -- Landry, M -- Lantz, B -- Laval, M -- Lazzarini, A -- Lei, H -- Lei, M -- Leindecker, N -- Leonor, I -- Leroy, N -- Letendre, N -- Li, C -- Lin, H -- Lindquist, P E -- Littenberg, T B -- Lockerbie, N A -- Lodhia, D -- Longo, M -- Lorenzini, M -- Loriette, V -- Lormand, M -- Losurdo, G -- Lu, P -- Lubinski, M -- Lucianetti, A -- Luck, H -- Machenschalk, B -- Macinnis, M -- Mackowski, J-M -- Mageswaran, M -- Mailand, K -- Majorana, E -- Man, N -- Mandel, I -- Mandic, V -- Mantovani, M -- Marchesoni, F -- Marion, F -- Marka, S -- Marka, Z -- Markosyan, A -- Markowitz, J -- Maros, E -- Marque, J -- Martelli, F -- Martin, I W -- Martin, R M -- Marx, J N -- Mason, K -- Masserot, A -- Matichard, F -- Matone, L -- Matzner, R A -- Mavalvala, N -- McCarthy, R -- McClelland, D E -- McGuire, S C -- McHugh, M -- McIntyre, G -- McKechan, D J A -- McKenzie, K -- Mehmet, M -- Melatos, A -- Melissinos, A C -- Mendell, G -- Menendez, D F -- Menzinger, F -- Mercer, R A -- Meshkov, S -- Messenger, C -- Meyer, M S -- Michel, C -- Milano, L -- Miller, J -- Minelli, J -- Minenkov, Y -- Mino, Y -- Mitrofanov, V P -- Mitselmakher, G -- Mittleman, R -- Miyakawa, O -- Moe, B -- Mohan, M -- Mohanty, S D -- Mohapatra, S R P -- Moreau, J -- Moreno, G -- Morgado, N -- Morgia, A -- Morioka, T -- Mors, K -- Mosca, S -- Mossavi, K -- Mours, B -- Mowlowry, C -- Mueller, G -- Muhammad, D -- Muhlen, H Zur -- Mukherjee, S -- Mukhopadhyay, H -- Mullavey, A -- Muller-Ebhardt, H -- Munch, J -- Murray, P G -- Myers, E -- Myers, J -- Nash, T -- Nelson, J -- Neri, I -- Newton, G -- Nishizawa, A -- Nocera, F -- Numata, K -- Ochsner, E -- O'Dell, J -- Ogin, G H -- O'Reilly, B -- O'Shaughnessy, R -- Ottaway, D J -- Ottens, R S -- Overmier, H -- Owen, B J -- Pagliaroli, G -- Palomba, C -- Pan, Y -- Pankow, C -- Paoletti, F -- Papa, M A -- Parameshwaraiah, V -- Pardi, S -- Pasqualetti, A -- Passaquieti, R -- Passuello, D -- Patel, P -- Pedraza, M -- Penn, S -- Perreca, A -- Persichetti, G -- Pichot, M -- Piergiovanni, F -- Pierro, V -- Pinard, L -- Pinto, I M -- Pitkin, M -- Pletsch, H J -- Plissi, M V -- Poggiani, R -- Postiglione, F -- Principe, M -- Prix, R -- Prodi, G A -- Prokhorov, L -- Punken, O -- Punturo, M -- Puppo, P -- Putten, S van der -- Quetschke, V -- Raab, F J -- Rabaste, O -- Rabeling, D S -- Radkins, H -- Raffai, P -- Raics, Z -- Rainer, N -- Rakhmanov, M -- Rapagnani, P -- Raymond, V -- Re, V -- Reed, C M -- Reed, T -- Regimbau, T -- Rehbein, H -- Reid, S -- Reitze, D H -- Ricci, F -- Riesen, R -- Riles, K -- Rivera, B -- Roberts, P -- Robertson, N A -- Robinet, F -- Robinson, C -- Robinson, E L -- Rocchi, A -- Roddy, S -- Rolland, L -- Rollins, J -- Romano, J D -- Romano, R -- Romie, J H -- Rover, C -- Rowan, S -- Rudiger, A -- Ruggi, P -- Russell, P -- Ryan, K -- Sakata, S -- Salemi, F -- Sandberg, V -- Sannibale, V -- Santamaria, L -- Saraf, S -- Sarin, P -- Sassolas, B -- Sathyaprakash, B S -- Sato, S -- Satterthwaite, M -- Saulson, P R -- Savage, R -- Savov, P -- Scanlan, M -- Schilling, R -- Schnabel, R -- Schofield, R -- Schulz, B -- Schutz, B F -- Schwinberg, P -- Scott, J -- Scott, S M -- Searle, A C -- Sears, B -- Seifert, F -- Sellers, D -- Sengupta, A S -- Sentenac, D -- Sergeev, A -- Shapiro, B -- Shawhan, P -- Shoemaker, D H -- Sibley, A -- Siemens, X -- Sigg, D -- Sinha, S -- Sintes, A M -- Slagmolen, B J J -- Slutsky, J -- van der Sluys, M V -- Smith, J R -- Smith, M R -- Smith, N D -- Somiya, K -- Sorazu, B -- Stein, A -- Stein, L C -- Steplewski, S -- Stochino, A -- Stone, R -- Strain, K A -- Strigin, S -- Stroeer, A -- Sturani, R -- Stuver, A L -- Summerscales, T Z -- Sun, K-X -- Sung, M -- Sutton, P J -- Swinkels, B L -- Szokoly, G P -- Talukder, D -- Tang, L -- Tanner, D B -- Tarabrin, S P -- Taylor, J R -- Taylor, R -- Terenzi, R -- Thacker, J -- Thorne, K A -- Thorne, K S -- Thuring, A -- Tokmakov, K V -- Toncelli, A -- Tonelli, M -- Torres, C -- Torrie, C -- Tournefier, E -- Travasso, F -- Traylor, G -- Trias, M -- Trummer, J -- Ugolini, D -- Ulmen, J -- Urbanek, K -- Vahlbruch, H -- Vajente, G -- Vallisneri, M -- Vass, S -- Vaulin, R -- Vavoulidis, M -- Vecchio, A -- Vedovato, G -- van Veggel, A A -- Veitch, J -- Veitch, P -- Veltkamp, C -- Verkindt, D -- Vetrano, F -- Vicere, A -- Villar, A -- Vinet, J-Y -- Vocca, H -- Vorvick, C -- Vyachanin, S P -- Waldman, S J -- Wallace, L -- Ward, H -- Ward, R L -- Was, M -- Weidner, A -- Weinert, M -- Weinstein, A J -- Weiss, R -- Wen, L -- Wen, S -- Wette, K -- Whelan, J T -- Whitcomb, S E -- Whiting, B F -- Wilkinson, C -- Willems, P A -- Williams, H R -- Williams, L -- Willke, B -- Wilmut, I -- Winkelmann, L -- Winkler, W -- Wipf, C C -- Wiseman, A G -- Woan, G -- Wooley, R -- Worden, J -- Wu, W -- Yakushin, I -- Yamamoto, H -- Yan, Z -- Yoshida, S -- Yvert, M -- Zanolin, M -- Zhang, J -- Zhang, L -- Zhao, C -- Zotov, N -- Zucker, M E -- Zweizig, J -- England -- Nature. 2009 Aug 20;460(7258):990-4. doi: 10.1038/nature08278.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Lists of participants and their affiliations appear at the end of the paper.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/19693079" target="_blank"〉PubMed〈/a〉

Description: Measurement of the Earth tides with a MEMS gravimeter Nature 531, 7596 (2016). doi:10.1038/nature17397 Authors: R. P. Middlemiss, A. Samarelli, D. J. Paul, J. Hough, S. Rowan & G. D. Hammond The ability to measure tiny variations in the local gravitational acceleration allows, besides other applications, the detection of hidden hydrocarbon reserves, magma build-up before volcanic eruptions, and subterranean tunnels. Several technologies are available that achieve the sensitivities required for such applications (tens of microgal per hertz1/2): free-fall gravimeters, spring-based gravimeters, superconducting gravimeters, and atom interferometers. All of these devices can observe the Earth tides: the elastic deformation of the Earth’s crust as a result of tidal forces. This is a universally predictable gravitational signal that requires both high sensitivity and high stability over timescales of several days to measure. All present gravimeters, however, have limitations of high cost (more than 100,000 US dollars) and high mass (more than 8 kilograms). Here we present a microelectromechanical system (MEMS) device with a sensitivity of 40 microgal per hertz1/2 only a few cubic centimetres in size. We use it to measure the Earth tides, revealing the long-term stability of our instrument compared to any other MEMS device. MEMS accelerometers—found in most smart phones—can be mass-produced remarkably cheaply, but none are stable enough to be called a gravimeter. Our device has thus made the transition from accelerometer to gravimeter. The small size and low cost of this MEMS gravimeter suggests many applications in gravity mapping. For example, it could be mounted on a drone instead of low-flying aircraft for distributed land surveying and exploration, deployed to monitor volcanoes, or built into multi-pixel density-contrast imaging arrays.