799 research outputs found
Magneto optical rib waveguide with low refractive index
The phase matching condition is an important requirement for magneto-optical waveguide devices. In this work, the design rules that must be imposed on the geometry and the index of magneto optical rib waveguides to make them behave as phase matched rib waveguides have been simulated. Using film mode matching method, the results show that operation in phase matching is possible under certain circumstances with selected index and geometries. We simulated the performance of such devices and we determined the waveguide dimensions (height, width, and etching depth) and the index that satisfy the phase matching conditions
The UK Centre for Astrobiology:A Virtual Astrobiology Centre. Accomplishments and Lessons Learned, 2011-2016
Authors thank all those individuals, UK research councils, funding agencies, nonprofit organisations, companies and corporations and UK and non-UK government agencies, who have so generously supported our aspirations and hopes over the last 5 years and supported UKCA projects. They include the STFC, the Engineering and Physical Sciences Research Council (EPSRC), the Natural Environmental Research Council (NERC), the EU, the UK Space Agency, NASA, the European Space Agency (ESA), The Crown Estate, Cleveland Potash and others. The Astrobiology Academy has been supported by the UK Space Agency (UKSA), National Space Centre, the Science and Technology Facilities Council (STFC), Dynamic Earth, The Royal Astronomical Society, The Rotary Club (Shetlands) and the NASA Astrobiology Institute.The UK Centre for Astrobiology (UKCA) was set up in 2011 as a virtual center to contribute to astrobiology research, education, and outreach. After 5 years, we describe this center and its work in each of these areas. Its research has focused on studying life in extreme environments, the limits of life on Earth, and implications for habitability elsewhere. Among its research infrastructure projects, UKCA has assembled an underground astrobiology laboratory that has hosted a deep subsurface planetary analog program, and it has developed new flow-through systems to study extraterrestrial aqueous environments. UKCA has used this research backdrop to develop education programs in astrobiology, including a massive open online course in astrobiology that has attracted over 120,000 students, a teacher training program, and an initiative to take astrobiology into prisons. In this paper, we review these activities and others with a particular focus on providing lessons to others who may consider setting up an astrobiology center, institute, or science facility. We discuss experience in integrating astrobiology research into teaching and education activities.Publisher PDFPeer reviewe
Oh Comrade, What Times those Were! History, Capital Punishment and the Urban Square.
From the perspective of traditional Western histories of the urban realm, public squares have been seen to represent a privileged site of urban containment expressive of a community's highest values of individual freedom, social inclusion and cultural refinement. But such views can be misleading. For what is omitted from the scope of these conventional historical visions and their ideal and conforming subjects of public spatial discourse, is an entire array of other and darker narratives that equally speak of personal choice, collective participation and cultural value. Capital punishment reflects such an example, a practice that once comprised an integral part of the political, social and cultural landscape of a Western city's squares and streets. Drawing from Michel Foucault's Discipline and Punish and its implications on how we might begin to re-read the history of the urban square, the following seeks to explore those practices and modes of rationality that underpinned the once public spectacle of executions and torture as a vital condition of urban life. In particular, this discussion will question the assumptions of an historical tradition that continues to reduce our understanding of the city and its open spaces of public appearance and action to an idealistic and illusory reality of the urban realm and its narrow framing of collective conduct, necessity and significance
Search for the glueball candidates f0(1500) and fJ(1710) in gamma gamma collisions
Data taken with the ALEPH detector at LEP1 have been used to search for gamma
gamma production of the glueball candidates f0(1500) and fJ(1710) via their
decay to pi+pi-. No signal is observed and upper limits to the product of gamma
gamma width and pi+pi- branching ratio of the f0(1500) and the fJ(1710) have
been measured to be Gamma_(gamma gamma -> f0(1500)). BR(f0(1500)->pi+pi-) <
0.31 keV and Gamma_(gamma gamma -> fJ(1710)). BR(fJ(1710)->pi+pi-) < 0.55 keV
at 95% confidence level.Comment: 10 pages, 3 figure
Chirality and Symmetry Breaking in a discrete internal Space
In previous papers the permutation group S_4 has been suggested as an
ordering scheme for elementary particles, and the appearance of this finite
symmetry group was taken as indication for the existence of a discrete inner
symmetry space underlying elementary particle interactions. Here it is pointed
out that a more suitable choice than the tetrahedral group S_4 is the
pyritohedral group A_4 x Z_2 because its vibrational spectrum exhibits exactly
the mass multiplet structure of the 3 fermion generations. Furthermore it is
noted that the same structure can also be obtained from a primordial symmetry
breaking S_4 --> A_4. Since A_4 is a chiral group, while S_4 is achiral, an
argument can be given why the chirality of the inner pyritohedral symmetry
leads to parity violation of the weak interactions.Comment: 42 pages, 3 table
Two-pion Bose-Einstein correlations in central Pb-Pb collisions at = 2.76 TeV
The first measurement of two-pion Bose-Einstein correlations in central Pb-Pb
collisions at TeV at the Large Hadron Collider is
presented. We observe a growing trend with energy now not only for the
longitudinal and the outward but also for the sideward pion source radius. The
pion homogeneity volume and the decoupling time are significantly larger than
those measured at RHIC.Comment: 17 pages, 5 captioned figures, 1 table, authors from page 12,
published version, figures at
http://aliceinfo.cern.ch/ArtSubmission/node/388
Search for direct production of charginos and neutralinos in events with three leptons and missing transverse momentum in √s = 7 TeV pp collisions with the ATLAS detector
A search for the direct production of charginos and neutralinos in final states with three electrons or muons and missing transverse momentum is presented. The analysis is based on 4.7 fb−1 of proton–proton collision data delivered by the Large Hadron Collider and recorded with the ATLAS detector. Observations are consistent with Standard Model expectations in three signal regions that are either depleted or enriched in Z-boson decays. Upper limits at 95% confidence level are set in R-parity conserving phenomenological minimal supersymmetric models and in simplified models, significantly extending previous results
Jet size dependence of single jet suppression in lead-lead collisions at sqrt(s(NN)) = 2.76 TeV with the ATLAS detector at the LHC
Measurements of inclusive jet suppression in heavy ion collisions at the LHC
provide direct sensitivity to the physics of jet quenching. In a sample of
lead-lead collisions at sqrt(s) = 2.76 TeV corresponding to an integrated
luminosity of approximately 7 inverse microbarns, ATLAS has measured jets with
a calorimeter over the pseudorapidity interval |eta| < 2.1 and over the
transverse momentum range 38 < pT < 210 GeV. Jets were reconstructed using the
anti-kt algorithm with values for the distance parameter that determines the
nominal jet radius of R = 0.2, 0.3, 0.4 and 0.5. The centrality dependence of
the jet yield is characterized by the jet "central-to-peripheral ratio," Rcp.
Jet production is found to be suppressed by approximately a factor of two in
the 10% most central collisions relative to peripheral collisions. Rcp varies
smoothly with centrality as characterized by the number of participating
nucleons. The observed suppression is only weakly dependent on jet radius and
transverse momentum. These results provide the first direct measurement of
inclusive jet suppression in heavy ion collisions and complement previous
measurements of dijet transverse energy imbalance at the LHC.Comment: 15 pages plus author list (30 pages total), 8 figures, 2 tables,
submitted to Physics Letters B. All figures including auxiliary figures are
available at
http://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/HION-2011-02
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