The electron-positron collider DA Phi NE, the Italian Phi factory, has been recently upgraded in order to implement an innovative collision scheme based on large crossing angle, small beam sizes at ...the crossing point, and compensation of beam-beam interaction by means of sextupole pairs creating a "crab-waist" configuration in the interaction region. Experimental tests of the novel scheme exhibited an increase by a factor of 3 in the peak luminosity of the collider with respect to the performances reached before the upgrade. In this Letter we present the new collision scheme, discuss its advantages, describe the hardware modifications realized for the upgrade, and report the results of the experimental tests carried out during commissioning of the machine in the new configuration and standard operation for the users.
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CMK, CTK, FMFMET, IJS, NUK, PNG, UM
The formation and the properties of luminescent complexes of europium and terbium with a variety of organic ligands have been investigated in aqueous solutions. The ligands used include model ...compounds such as thenoyltrifluoroacetone and pyridine-2,6-dicarboxylic acid and organic analytes of biological or pharmaceutical interest. It is shown that the formation and the luminescent properties of these complexes depend at first on several parameters including the pH and the buffer, the synergic agent and the surfactant. In neutral solutions, trioctylphosphine oxide in the presence of Triton X-100 may act as a co-ligand to promote complex formation and protect the complex from radiationless deactivation processes. Working in slightly alkaline solutions in the presence of EDTA and hexadecyltrimethylammonium chloride may induce the deprotonation of a second coordinating group and favour the formation of a new complex with stronger luminescent properties. In both cases, the luminescence lifetimes are then ultimately related to the energy gap between the ligand triplet and the resonance level of the ion and to the number of water molecules coordinated to the lanthanide ion.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
The formation and the properties of luminescent complexes of europium and terbium with a variety of organic ligands have been investigated in aqueous solutions. The ligands used include model ...compounds such as thenoyltrifluoroacetone and pyridine-2,6-dicarboxylic acid and organic analytes of biological or pharmaceutical interest. It is shown that the formation and the luminescent properties of these complexes depend at first on several parameters including the pH and the buffer, the synergic agent and the surfactant. In neutral solutions, trioctylphosphine oxide in the presence of Triton X-100 may act as a co-ligand to promote complex formation and protect the complex from radiationless deactivation processes. Working in slightly alkaline solutions in the presence of EDTA and hexadecyltrimethylammonium chloride may induce the deprotonation of a second coordinating group and favour the formation of a new complex with stronger luminescent properties. In both cases, the luminescence lifetimes are then ultimately related to the energy gap between the ligand triplet and the resonance level of the ion and to the number of water molecules coordinated to the lanthanide ion.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
The timing of E–W extension of the Tibetan plateau provides a test of mechanical models of the geodynamic evolution of the India–Asia convergence zone. In this work we focus on the Kung Co half ...graben (Southern Tibet, China), bounded by an active N–S normal fault with a minimum vertical offset of 1600 m. To estimate the onset of normal faulting we combined high and medium temperature (U–Pb, Ar/Ar) and low temperature ((U–Th)/He) thermochronometry of the Kung Co pluton, a two-mica granite of the northern Himalayan granitic belt that outcrop in the footwall of the fault. Biotite and muscovite Ar/Ar ages , are close from each other ∼
16 Ma
±
0.2 (Ms) and ∼
15
±
0.4 Ma (Bt), which is typical of fast cooling. The zircon and apatite (U–Th)/He ages range from 11.3 to 9.6 Ma and 9.9 to 3.7 Ma respectively. These He ages are indicative of (1) fast initial cooling, from 11.3 to ∼
9 Ma, gradually decreasing with time and (2) a high geothermal gradient (∼
400 °C/km), close to the surface at ∼
10 Ma.
The Kung Co pluton was emplaced at about 22 Ma (U–Pb on zircon) at less than 10 km depth and 520–545 °C. Subsequent to its shallow emplacement, the pluton underwent fast thermal re-equilibration ending around 7.5 Ma, followed by a period of slow cooling caused either by the end of the thermal re-equilibration or by very slow exhumation (0.02–0.03 mm/yr) from ∼
7.5 Ma to at least 4 Ma. In either case the data suggest that the exhumation rate increased after 4 Ma. We infer this increase to be related to the initiation of the Kung Co normal fault. A critical examination of previously published data show that most ∼
N–S Tibetan normal faults may have formed less than 5 Ma ago rather than in the Miocene as assumed by several authors. Such a young age implies that E–W extension is not related to the Neogene South Tibetan magmatism (25 to 8 Ma). Consequently, models relating E–W extension to magmatism, such as convective removal of the lower lithosphere, may be inappropriate. We rather think that this extension is related with local accommodation of boundary forces and displacements.
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15.
Design and performance of the focusing DIRC detector Dey, B.; Borsato, M.; Arnaud, N. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
03/2015, Volume:
775, Issue:
C
Journal Article
Peer reviewed
Open access
We present the final results from a novel Cherenkov imaging detector called the Focusing DIRC (FDIRC). This detector was designed as a full-scale prototype of the particle identification system for ...the SuperB experiment 1, and comprises 1/12 of the SuperB barrel azimuthal coverage, with partial photodetector and electronics implementation. The prototype was tested in the SLAC Cosmic Ray Telescope which provided 3D tracking of cosmic muons with an angular resolution of ~1.5mrad, a position resolution of 4–5mm, a start time resolution of 70ps, and muon tracks above ~2GeV tagged using an iron range stack. The fused silica focusing photon camera was coupled to a full-size BaBar DIRC bar box and was read out, over part of the full coverage, by 12 Hamamatsu H8500 multi-anode photomultipliers (MaPMTs) providing 768 pixels. We used waveform digitizing electronics to read out the MaPMTs. We give a detailed description of our data analysis methods and point out limitations on the present performance. We present results that demonstrate some basic performance characteristics of this design, including (a) single photon Cherenkov angle resolutions with and without chromatic corrections, (b) signal-to-noise (S/N) ratio between the Cherenkov peak and background, which primarily consists of ambiguities of the possible photon paths from emission along the track to a given pixel, (c) dTOP=TOPmeasured – TOPexpected resolutions (with TOP being the photon Time-of-Propagation in fused silica), and (d) performance of the detector in the presence of high-rate backgrounds.
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The alpine structural evolution of the Mont Blanc, highest point of the Alps (4810 m), and of the surrounding area has been reexamined. The Mont Blanc and the Aiguilles Rouges external crystalline ...massifs are windows of Variscan basement within the Penninic and Helvetic nappes. New structural, 40Ar/39Ar, and fission track data combined with a compilation of earlier P‐T estimates and geochronological data give constraints on the amount and timing of the Mont Blanc and Aiguilles Rouges massifs exhumation. Alpine exhumation of the Aiguilles Rouges was limited to the thickness of the overlying nappes (∼10 km), while rocks now outcropping in the Mont Blanc have been exhumed from 15 to 20 km depth. Uplift of the two massifs started ∼22 Myr ago, probably above an incipient thrust: the Alpine sole thrust. At ∼12 Ma, the NE‐SW trending Mont Blanc shear zone (MBsz) initiated. It is a major steep reverse fault with a dextral component, whose existence has been overlooked by most authors, that brings the Mont Blanc above the Aiguilles Rouges. Total vertical throw on the MBsz is estimated to be between 4 and 8 km. Fission track data suggest that relative motion between the Aiguilles Rouges and the Mont Blanc stopped ∼4 Myr ago. Since that time, uplift of the Mont Blanc has mostly taken place along the Mont Blanc back thrust, a steep north dipping fault bounding the southern flank of the range. The “European roof” is located where the back thrust intersects the MBsz. Uplift of the Mont Blanc and Aiguilles Rouges occurred toward the end of motion on the Helvetic basal décollement (HBD) at the base of the Helvetic nappes but is coeval with the Jura thin‐skinned belt. Northwestward thrusting and uplift of the external crystalline massifs above the Alpine sole thrust deformed the overlying Helvetic nappes and formed a backstop, inducing the formation of the Jura arc. In that part of the external Alps, ∼NW‐SE shortening with minor dextral NE‐SW motions appears to have been continuous from ∼22 Ma until at least ∼4 Ma but may be still active today. A sequential history of the alpine structural evolution of the units now outcropping NW of the Pennine thrust is proposed.
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FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
The geology of the Jingyu basin (north Tibet) provides constraints on the relationship between localized E‐W extension in the Qiangtang block and strike‐slip motion along the Kunlun fault. Eocene to ...Oligocene SW‐NE compression formed topographic relief in the present western Kunlun Shan. Pull‐apart basins started forming in the western Kunlun ranges around 15 Ma, possibly coincident with the initiation of subduction of the Tarim‐Qaidam lithosphere under the Kunlun Shan. Extensional tectonism is still active, and the Jingyu basin is extending, as a normal fault connected with the Kunlun fault was recently active. Localized extension allows Tertiary and Quaternary shoshonitic magmas to reach the surface from crustal depths of 50 to 60 km. Miocene strike‐slip faulting indicates that the initiation of the Kunlun strike‐slip fault is early Neogene in age and that the total amount of horizontal movement that occurred along the fault has to be reconsidered.
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New structural observations coupled with 15 U/Pb and 24 Ar/Ar new ages from the Karakorum shear zone (KSZ) constrain the timing and slip rate of the right‐lateral Karakorum fault zone (KFZ), one of ...the great continental Asian strike‐slip faults. In the Tangtse‐Darbuk area, the Tangtse (SW) and Muglib (NE) mylonitic strands of the KSZ frame the less deformed Pangong Range. Inherited U/Pb ages show that granitic protoliths are mostly from the Karakorum and Ladakh batoliths, with a major Miocene melting event lasting from ≥21.5 to 13.5 Ma. Some of the Miocene granitic bodies show structural evidence for intrusion synkinematic to the KSZ. The oldest of these granitoids is 18.8 ± 0.4 Ma old, implying that deformation started prior to ∼19 Ma. Microstructural data show that right‐lateral deformation pursued during cooling. Ar/Ar data show that ductile deformation stopped earlier in the Tangtse (∼11 Ma) than in the Muglib strand (∼7 Ma). Deformation ended at ∼11 Ma in the Tangtse strand while it is still active in the Muglib strand, suggesting a progressive localization of deformation. When merged with published observations along the KFZ, these data suggest that the KFZ nucleated in the North Ayilari range at least ∼22 Ma ago. The long‐term fault rate is 0.84 to 1.3 cm/yr, considering a total offset of 200 to 240 km. The KSZ collected magma produced within the shear zone and/or deeper in crust for which the producing mechanism stays unclear but was not the lower crustal channel flow.
Key Points
New U/Pb and Ar/Ar ages on the Karakroum shear zone in the Tangtse region India
Syn‐kinematic magmatism and cooling between at least 19 Ma and 11 Ma
Diachronic cooling across strike with deformation migration and localization
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Potassic volcanism has been widespread and semi-continuous on the Tibetan plateau since ∼13 Ma, post-dating the orogenic thickening of the India-Asia collision. Volcanism may have commenced slightly ...earlier (∼16–20 Ma) in the southern portion of the plateau and then ceased around 10 Ma. The dominant lavas are pyroxené- and plagioclase-phyric shoshonites with subordinate occurrences of dacites and rhyolites. Their mineralogy reflects crystallization from high-temperature (≦1100°C) magmas which had elevated oxygen and water fugacities. Geochemically, they are characterized by relatively low TiO2, Al2O3 and Fe2O3, and high Na2O, coupled with variable abundances of compatible trace elements and very high contents of incompatible trace elements. Normalized incompatible element patterns have marked negative Nb, Ta and Ti anomalies whereas K2O appears to be buffered at ∼4% over a wide range of SiO2. Isotope data show a relatively broad and enriched range of 87Sr/86 Sr (0.7076–0.7106) at more restricted ENd (−5.2 to −8.1). Pb isotopes are characterized by a range of 207Pb/204 Pb (15.51–15.72) and 208 Pb/204Pb (38.67–39. 30) at very uniform 206Pb/204 Pb (18.39–18.83), leading to vertical arrays. Volcanics from the southern parts of the plateau have more primitive isotopic compositions: 87Sr/86 Sr 0.7048–0.7080, εNd 1.4 to −3.3, 206Pb/204 Pb 18.48–18.67, 207Pb/204 Pb 15.59–15.68 and 208Pb/204 Pb 38. 73–38.98. In general, the geochemical and isotopic data most closely approximate partial melting arrays, although fractionation processes have clearly operated. The isotopic ratios and the enrichment of incompatible elements and LREE/HREE cannot be derived from a depleted mantle source via a single-stage melting process. Instead, a metasomatized, garnet peridotite source containing ∼6% phlogopite is required and this is inferred to lie within the lithospheric mantle. The enrichment in incompatible elements in this source must have been sufficiently ancient to generate the observed isotopic ratios, and Nd depleted mantle model ages suggest this was Proterozoic in age (∼1.2 Ga), whereas Pb model ages record an Archaean event, suggesting the source had a multi-stage enrichment history. The negative Ta, Nb and Ti anomalies and low Rb/Ba suggest that metasomatism may have occurred during an ancient subduction episode. The high 208Pb/204Pb, 207Pb/204 Pb and low Nb/U, Ce/Pb of the Tibetan shoshonites are distinct from ocean island basalts. Thus, if convectively removed lithospheric mantle provides a source for ocean island basalts, it must differ significantly from the source of the Tibetan shoshonites. A lithospheric mantle source for the volcanism places important constraints on geodynamic models for the evolution of the Tibetan plateau and the India-Asia collision. For likely thermal structures beneath the plateau, the temperatures required to trigger melting within the lithospheric mantle can only be plausibly obtained if the lower parts of the lithospheric mantle were removed by convective thinning. This is consistent with recent models which invoke the same process to explain the current elevation and extensional deformation of the plateau. The age data suggest this occurred at ∼13 Ma and the duration of volcanism may be explained by continued conductive heating since that time. Poorly sampled but slightly older volcanics from the southern portions of the plateau may indicate that convective thinning began in the south and migrated northwards. Rapid uplift of the plateau may have resulted in increased rates of chemical weathering, which led to global cooling, as indicated by oxygen isotope data from Atlantic sediments.
In the work of Manuel Vázquez Montalbán, the city (particularly Barcelona) represents the main subject of writing. The writer goes through this sometimes labyrinthine geometry as an explorer to ...highlight the most significant strata where the history of a people is found, a history of drives, aspirations, frustrations and violence. Our work, therefore, will demonstrate the always dynamic and innovative attitude of the author in permanent rupture with current conventions and generic codes. Our approach is a type of stroll, to gradually discover this space, which is still little known, through a reading of the narrative and poetic works that have a declared or implicit relationship with the city of Barcelona.
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