Multiplicity dependence of the average transverse momentum in pp, p-Pb, and Pb-Pb collisions at the LHC

Cyanobacteria, a group of photosynthetic prokaryotes, oscillate between day and night time metabolisms with concomitant oscillations in gene expression in response to light/dark cycles (LD). The oscillations in gene expression have been shown to sustain in constant light (LL) with a free running period of 24 h in a model cyanobacterium Synechococcus elongatus PCC 7942. However, equivalent oscillations in metabolism are not reported under LL in this non-nitrogen fixing cyanobacterium. Here we focus on Cyanothece sp. ATCC 51142, a unicellular, nitrogen-fixing cyanobacterium known to temporally separate the processes of oxygenic photosynthesis and oxygen-sensitive nitrogen fixation. In a recent report, metabolism of Cyanothece 51142 has been shown to oscillate between photosynthetic and respiratory phases under LL with free running periods that are temperature dependent but significantly shorter than the circadian period. Further, the oscillations shift to circadian pattern at moderate cell densities that are concomitant with slower growth rates. Here we take this understanding forward and demonstrate that the utradian rhythm under LL sustains at much higher cell densities when grown under turbulent regimes that simulate flashing light effect. Our results suggest that the ultradian rhythm in metabolism may be needed to support higher carbon and nitrogen requirements of rapidly growing cells under LL. With a comprehensive Real time PCR based gene expression analysis we account for key regulatory interactions and demonstrate the interplay between clock genes and the genes of key metabolic pathways. Further, we observe that several genes that peak at dusk in Synechococcus peak at dawn in Cyanothece and vice versa. The circadian rhythm of this organism appears to be more robust with peaking of genes in anticipation of the ensuing photosynthetic and respiratory metabolic phases

Acoustic imaging of the Dvurechenskii mud volcano in the Black Sea

In the CRIMEA project submarine gas emitting sites in the Black Sea are investigated in order to quantify methane transfer through the water column into the atmosphere. One target area is the Dvurechenskii mud volcano (DMV) in the Sorokin Trough south-east of the Crimea peninsula. The occurrence of gas hydrates and high methane concentrations in the sediment of this mud volcano are known. A seismic wide-angle experiment was performed at the DMV with twelve Ocean Bottom Hydrophones and Seismometers and a GI gun source with frequencies around 100 Hz. By using Kirchhoff depth migration the seismogram sections are transformed to images, which extent to 4 km laterally and 600 metres in depth. The images show the conduit of the DMVand the nearby sediment layers. The DMV has a diameter of 800-1000 m at the sea floor and its conduit has the same form and diameter up to 600 m depth. Several plane sediment layers are disrupted by the conduit, and strong reflectors are identified in 100 m and 400 m depth in the conduit. The lower bowl shaped reflectors are interpreted as collapsed parts of the disrupted sediment layers, which sunk in the lighter material of the conduit. This is also a possible explanation for the upper reflections. Compressional wave velocities are obtained from Kirchhoff migration, and the model is refined by using seismic ray tracing. Bulk density and shear wave velocity can also be obtained by analyzing the data. With the help of these elastic parameters and by using the Frenkel-Gassmann theory, the free gas saturation of the sediment pore space and the gas hydrate saturation can be quantified

Enhanced production of multi-strange hadrons in high-multiplicity proton-proton collisions

At sufficiently high temperature and energy density, nuclear matter undergoes a transition to a phase in which quarks and gluons are not confined: the quark-gluon plasma (QGP)(1). Such an exotic state of strongly interacting quantum chromodynamics matter is produced in the laboratory in heavy nuclei high-energy collisions, where an enhanced production of strange hadrons is observed(2-6). Strangeness enhancement, originally proposed as a signature of QGP formation in nuclear collisions(7), is more pronounced for multi-strange baryons. Several effects typical of heavy-ion phenomenology have been observed in high-multiplicity proton-proton (pp) collisions(8,9), but the enhanced production of multi-strange particles has not been reported so far. Here we present the first observation of strangeness enhancement in high-multiplicity proton-proton collisions. We find that the integrated yields of strange and multi-strange particles, relative to pions, increases significantly with the event charged-particle multiplicity. The measurements are in remarkable agreement with the p-Pb collision results(10,11), indicating that the phenomenon is related to the final system created in the collision. In high-multiplicity events strangeness production reaches values similar to those observed in Pb-Pb collisions, where a QGP is formed.Peer reviewe

Charged-particle multiplicities in proton-proton collisions at root s=0.9 to 8 TeV

A detailed study of pseudorapidity densities and multiplicity distributions of primary charged particles produced in proton-proton collisions, atv root s = 0.9, 2.36, 2.76, 7 and 8 TeV, in the pseudorapidity range vertical bar n vertical bar<2, was carried out using the ALICE detector. Measurements were obtained for three event classes: inelastic, non-single diffractive and events with at least one charged particle in the pseudorapidity interval vertical bar n vertical barPeer reviewe

Measurement of D-s(+) product ion and nuclear modification factor in Pb-Pb collisions at root S-NN=2.76 TeV

Peer reviewe