One ring to rule them all? Another cellular responsibility for PCNA

To prevent duplication or loss of genomic regions during DNA replication, it is essential that the entire genome is copied precisely once every S phase. Cells achieve this by mutually exclusive regulation of origin firing and licensing. A crucial protein that is involved in origin licensing is chromatin licensing and DNA replication factor 1 (CDT1) and, therefore, activity of this protein must be strictly controlled. Four recent articles have demonstrated that proliferating cell nuclear antigen (PCNA), an essential sliding clamp used in replication and DNA repair, has a crucial role in this process by mediating the proteasomal degradation of CDT1

The One Ring of King Solomon

Tolkien source criticism has long been looking for the source of the One Ring in the wrong places. Neither the historical ispiration from World War II and the Atomic Bomb nor the proposed literary influences such as the Ring of the Nibelungs, Wagner\u27s Ring, or the several examples of invisibility rings found in world literature may suffice to explain the complexity of Tolkien\u27s unique creation. Nonetheless, the same cannot be said so easily with regards to another possible source once we survey the richness of the related legends: it is the fabled signet ring of King Solomon

Be stars: one ring to rule them all?

Aims. We report theoretical spectral energy distributions (SEDs), Br$\gamma$ line profiles and visibilities for two scenarios that can explain the disk dissipation of active hot stars an account for the transition from the Be to the B spectroscopic phase. Methods. We use the SIMECA code to investigate these two scenarios: the first one where the disk is formed by successive outbursts of the central star. A low-density region is developing above the star and slowly grows outward and forms a ring-like structure that will gradually excavate the disk. The second one, where a slowly decreasing mass loss, for instance due to a decrease of the radiative force through an opacity change at the base of the photosphere, may also be responsible for the vanishing of the circumstellar disk. Results. We obtain that a clear signature of the disk dissipation following the ring scenario will be the disappearance of the high velocity tails in the emission lines and a nearly constant peaks separation. Moreover, we found that following the ring-like scenario the visibilities must show an increasing second lobe, an increase of the value of the first zero and, assuming an unresolved central star, a first zero of the visibility curves that appends at shorter baselines as far as the disk is been excavate. We propose to use the AMBER instrument on the VLTI to probe if the the ring scenario is the one that rule the Be phenomenon.Comment: 10 page

Study of Inclusive Multi-Ring Events from Atmospheric Neutrinos

The current analysis of atmospheric neutrinos by the Super-Kamiokande Collaboration is based only on fully-contained one-ring events and partially contained events. We show that the up-down ratio of fully-contained, inclusive, multi-ring events gives an independent test of the atmospheric neutrino anomaly, without the need for particle identification. Moreover, this class of events is rich in neutral current events and hence gives crucial information for discriminating between oscillations of \nu_\mu into \nu_{e, \tau} and \nu_s.Comment: 12 pages, 3 figures, LaTeX2e, psfig.st

Indications of Neutrino Oscillation in a 250 km Long-baseline Experiment

The K2K experiment observes indications of neutrino oscillation: a reduction of $\nu_\mu$ flux together with a distortion of the energy spectrum. Fifty-six beam neutrino events are observed in Super-Kamiokande (SK), 250 km from the neutrino production point, with an expectation of $80.1^{+6.2}_{-5.4}$. Twenty-nine one ring $\mu$-like events are used to reconstruct the neutrino energy spectrum, which is better matched to the expected spectrum with neutrino oscillation than without. The probability that the observed flux at SK is explained by statistical fluctuation without neutrino oscillation is less than 1%.Comment: 5 pages, 3 figures embedded, LaTeX with RevTeX style, accepted for publication in PRL on December 13, 200

MIMO channel model

Multiple-input multiple-output is a system that allows the technology to meet the growing demand for high data rates in wireless communications systems. The aim of this thesis is to investigate the capacity capability of the geometric channel model by using the one-ring and two-ring channel model and attempting to explain the differences and similarities between these two models.Simulations were performed on one-ring and two-ring channel models by using mat-lab code programming. These simulations indicate the ideal capacity results of one-ring and two-ring channel models. The simulation results show that capacity increased for both one-ring and two-ring channel model. However, in one-ring model, the mean capacity is more stable than the mean capacity of two-ring model, but the two-ring model has greater mean capacity than one-ring model.There are two types of conditions that have been applied: the equal power allocation and the water-filling. Mean capacity of both equal power and water-filling increased as the signal to noise ratio (SNR) is increased. The difference between these two capacities is that the equal power method has no knowledge about the channel of the transmitter and the transmit signal power is divided equally over the transmitting antennas. Water-filling assumes perfect knowledge about the channel which allows the total power to be divided in the most efficient way over different transmitters. Therefore, the results show the equal power has less capacity than the water-filling. Another element that affects the mean capacity is mutual coupling. The results show that the mutual coupling can be increased or decreased based on the close space between antennas

Fluctuation Superconductivity in Mesoscopic Aluminum Rings

Fluctuations are important near phase transitions, where they can be difficult to describe quantitatively. Superconductivity in mesoscopic rings is particularly intriguing because the critical temperature is an oscillatory function of magnetic field. There is an exact theory for thermal fluctuations in one-dimensional superconducting rings, which are therefore expected to be an excellent model system. We measure the susceptibility of many rings, one ring at a time, using a scanning SQUID that can isolate magnetic signals from seven orders of magnitude larger background applied flux. We find that the fluctuation theory describes the results and that a single parameter characterizes the ways in which the fluctuations are especially important at magnetic fields where the critical temperature is suppressed.Comment: Reprinted with permission from AAA