Dissipative Quantum Ising model in a cold atomic spin-boson mixture

Using cold bosonic atoms with two (hyperfine) ground states, we introduce a spin-boson mixture which allows to implement the quantum Ising model in a tunable dissipative environment. The first specie lies in a deep optical lattice with tightly confining wells and forms a spin array; spin-up/down corresponds to occupation by one/no atom at each site. The second specie forms a superfluid reservoir. Different species are coupled coherently via laser transitions and collisions. Whereas the laser coupling mimics a transverse field for the spins, the coupling to the reservoir sound modes induces a ferromagnetic (Ising) coupling as well as dissipation. This gives rise to an order-disorder quantum phase transition where the effect of dissipation can be studied in a controllable manner.Comment: 4 pages, 2 figures, 1 table; Title modified and cosmetic change

Lung region segmentation based on computer tomographic images

The article is written for the benefit of hospitals in order to identify segments of the lungs and thereby help in the process of bisecting lungs according to their respective segments during surgery. Further research in this area can also help in identification of various abnormalities related to each segment and also identify abnormal walls of unhealthy lungs. Segmentation of the lungs has not been implemented in reality, as the lung, being an organ with dynamic chest volumes during respiratory cycles, makes it impossible to address changes during respiration unlike fixed structures like the brain. Further, abnormalities situated on the walls of lung segments, make it more difficult to address volume changes concerned with the lungs. The author of this paper has provided a more effective method to identify various lung segments by using various well known segmentation techniques combined together to identify moving lung image segments more effectively

Sequence Variability of P2-Like Prophage Genomes Carrying the Cytolethal Distending Toxin V Operon in Escherichia coli O157

Cytolethal distending toxins (CDT) are potent cytotoxins of several Gram-negative pathogenic bacteria, including Escherichia coli, in which five types (CDT-I to CDT-V) have been identified so far. CDT-V is frequently associated with Shiga-toxigenic E. coli (STEC), enterohemorrhagic E. coli (EHEC) O157 strains, and strains not fitting any established pathotypes. In this study, we were the first to sequence and annotate a 31.2-kb-long, noninducible P2-like prophage carrying the cdt-V operon from an stx- and eae-negative E. coli O157:H43 strain of bovine origin. The cdt-V operon is integrated in the place of the tin and old phage immunity genes (termed the TO region) of the prophage, and the prophage itself is integrated into the bacterial chromosome between the housekeeping genes cpxP and fieF. The presence of P2-like genes (n = 20) was investigated in a further five CDT-V-positive bovine E. coli O157 strains of various serotypes, three EHEC O157:NM strains, four strains expressing other variants of CDT, and eight CDT-negative strains. All but one CDT-V-positive atypical O157 strain uniformly carried all the investigated genomic regions of P2-like phages, while the EHEC O157 strains missed three regions and the CDT-V-negative strains carried only a few P2-like sequences. Our results suggest that P2-like phages play a role in the dissemination of cdt-V between E. coli O157 strains and that after integration into the bacterial chromosome, they adapted to the respective hosts and became temperate

Transition from participant to spectator fragmentation in Au+Au reaction between 60 AMeV and 150 AMeV

Using the quantum molecular dynamics approach, we analyze the results of the recent INDRA Au+Au experiments at GSI in the energy range between 60 AMeV and 150 AMeV. It turns out that in this energy region the transition toward a participant-spectator scenario takes place. The large Au+Au system displays in the simulations as in the experiment simultaneously dynamical and statistical behavior which we analyze in detail: The composition of fragments close to midrapidity follows statistical laws and the system shows bi-modality, i.e. a sudden transition between different fragmentation pattern as a function of the centrality as expected for a phase transition. The fragment spectra at small and large rapidities, on the other hand, are determined by dynamics and the system as a whole does not come to equilibrium, an observation which is confirmed by FOPI experiments for the same system.Comment: published versio

Thermal and Chemical Freeze-out in Spectator Fragmentation

Isotope temperatures from double ratios of hydrogen, helium, lithium, beryllium, and carbon isotopic yields, and excited-state temperatures from yield ratios of particle-unstable resonances in 4He, 5Li, and 8Be, were determined for spectator fragmentation, following collisions of 197Au with targets ranging from C to Au at incident energies of 600 and 1000 MeV per nucleon. A deviation of the isotopic from the excited-state temperatures is observed which coincides with the transition from residue formation to multi-fragment production, suggesting a chemical freeze-out prior to thermal freeze-out in bulk disintegrations.Comment: 14 pages, 10 figures, submitted to Phys. Rev. C, small changes as suggested by the editors and referee

Pion radii in nonlocal chiral quark model

The electromagnetic radius of the charged pion and the transition radius of the neutral pion are calculated in the framework of the nonlocal chiral quark model. It is shown in this model that the contributions of vector mesons to the pion radii are noticeably suppressed in comparison with a similar contribution in the local Nambu--Jona-Lasinio model. The form-factor for the process gamma*pi+pi- is calculated for the -1 GeV^2<q^2<1.6 GeV^2. Our results are in satisfactory agreement with experimental data.Comment: 7 pages, 7 figure