On the Definition of Gauge Field Operators in Lattice Gauge-Fixed Theories

We address the problem of defining the gauge four-potential on the lattice, in terms of the natural link variables. Different regularized definitions are shown, through non perturbative numerical computation, to converge towards the same continuum renormalized limit.Comment: 8 pages, LaTeX2e/LaTeX209, 3 eps figure

Functionalized platinum nanoparticles with surface charge trigged by pH: synthesis, characterization and stability studies

In this work, the synthesis and characterization of functionalized platinum nanoparticles (PtNPs) have been investigated. PtNPs were obtained by a wet redox procedure using 2-diethylaminoethanethiol hydrochloride (DEA) as capping agent. By varying the Pt/thiol molar ratio, monodispersed and stable particles with diameters in the range of 3-40 nm were isolated. The amino functionality allows neutral particles to be obtained in basic water solution and positive charged nanoparticles in neutral or acidic water solution (pH 7-2), as confirmed by DLS and ζ-potential measurements. FTIR spectroscopy, FE-SEM, DLS and ζ-potential measurements confirmed the size and showed long term water stability (up to three months) of the colloidal system

X-ray Spectroscopy of the Contact Binary VW Cephei

Short-period binaries represent extreme cases in the generation of stellar coronae via a rotational dynamo. Such stars are important for probing the origin and nature of coronae in the regimes of rapid rotation and activity saturation. VW Cep (P=0.28 d) is a relatively bright, partially eclipsing, and very active object. Light curves made from Chandra/HETGS data show flaring and rotational modulation, but no eclipses. Velocity modulation of emission lines indicates that one component dominates the X-ray emission. The emission measure is highly structured, having three peaks. Helium-like triplet lines give electron densities of about 3.0E+10 - 18.0E+10 /cm^3. We conclude that the corona is predominantly on the polar regions of the primary star and compact.Comment: Accepted for publication in the Astropysical Journal, 23 June 2006; 22 pages, 15 figure

Observations of Subarcsecond Bright Dots in the Transition Region above Sunspots with the Interface Region Imaging Spectrograph

Observations with the Interface Region Imaging Spectrograph (IRIS) have revealed numerous sub-arcsecond bright dots in the transition region above sunspots. These bright dots are seen in the 1400\AA{} and 1330\AA{} slit-jaw images. They are clearly present in all sunspots we investigated, mostly in the penumbrae, but also occasionally in some umbrae and light bridges. The bright dots in the penumbrae typically appear slightly elongated, with the two dimensions being 300--600 km and 250--450 km, respectively. The long sides of these dots are often nearly parallel to the bright filamentary structures in the penumbrae but sometimes clearly deviate from the radial direction. Their lifetimes are mostly less than one minute, although some dots last for a few minutes or even longer. Their intensities are often a few times stronger than the intensities of the surrounding environment in the slit-jaw images. About half of the bright dots show apparent movement with speeds of $\sim$10--40~km~s$^{-1}$ in the radial direction. Spectra of a few bright dots were obtained and the Si~{\sc{iv}}~1402.77\AA{} line profiles in these dots are significantly broadened. The line intensity can be enhanced by one to two orders of magnitude. Some relatively bright and long-lasting dots are also observed in several passbands of the Atmospheric Imaging Assembly onboard the Solar Dynamics Observatory, and they appear to be located at the bases of loop-like structures. Many of these bright dots are likely associated with small-scale energy release events at the transition region footpoints of magnetic loops.Comment: 5 figures, will appear in ApJ

On lattice chiral gauge theories

The Smit-Swift-Aoki formulation of a lattice chiral gauge theory is presented. In this formulation the Wilson and other non invariant terms in the action are made gauge invariant by the coupling with a nonlinear auxilary scalar field, omega. It is shown that omega decouples from the physical states only if appropriate parameters are tuned so as to satisfy a set of BRST identities. In addition, explicit ghost fields are necessary to ensure decoupling. These theories can give rise to the correct continuum limit. Similar considerations apply to schemes with mirror fermions. Simpler cases with a global chiral symmetry are discussed and it is shown that the theory becomes free at decoupling. Recent numerical simulations agree with those considerations

Potato R1 resistance gene confers resistance against Phytophthora infestans in transgenic tomato plants

Tomato is challenged by several pathogens which cause loss of production. One such pathogen is the oomycete Phytophthora infestans which is able to attack all the aerial parts of the plant. Although a wide range of resistance sources are available, genetic control of this disease is not yet successful. Pyramiding R-genes through genetic transformation could be a straightforward way to produce tomato and potato lines carrying durable resistance to P. infestans. In this work the R1 potato gene was transferred into tomato lines. The tomato transgenic lines were analyzed by using q-RT-PCR and progeny segregation to determine the gene copy number. To test the hypothesis that R1 represents a specifically regulated R-gene, transgenic tomato plants were inoculated with P. infestans isolate 88133 and IPO. All the plants containing the R1 gene were resistant to the late blight isolate IPO-0 and susceptible to isolate 88133. These results provide evidence for specific activation of the R1 gene during pathogen challenge. Furthermore, evidence for enhancement of PR-1 gene expression during P. infestans resistance response was obtained

On the color structure of Yang-Mills theory with static sources in a periodic box

We present an exploratory numerical study on the lattice of the color structure of the wave functionals of the SU(3) Yang-Mills theory in the presence of a $q\bar q$ static pair. In a spatial box with periodic boundary conditions we discuss the fact that all states contributing to the Feynman propagation kernel are global color singlets. We confirm this numerically by computing the correlations of gauge-fixed Polyakov lines with color-twisted boundary conditions in the time direction. The values of the lowest energies in the color singlet and octet external source sectors agree within statistical errors, confirming that both channels contribute to the lowest (global singlet) state of the Feynman kernel. We then study the case of homogeneous boundary conditions in the time direction for which the gauge-fixing is not needed. In this case the lowest energies extracted in the singlet external source sector agree with those determined with periodic boundary conditions, while in the octet sector the correlator is compatible with being null within our statistical errors. Therefore consistently only the singlet external source contribution has a non-vanishing overlap with the null-field wave functional.Comment: 9 pages, 3 figure

qqˉq\bar{q}-potential: a numerical study

We report the results of recent lattice simulations aimed at computing the $q$ and $\bar q$ potential energies in the singlet and the octet (adjoint) representation.Comment: 7 pages, 4 figures, poster presented at the 31st International Symposium on Lattice Field Theory (Lattice 2013), 29 July - 3 August 2013, Mainz, German

Rate-Control or Rhythm-Contol: Where do we stand?

Atrial fibrillation is the most common sustained rhythm disturbance and its prevalence is increasing worldwide due to the progressive aging of the population. Current guidelines clearly depict the gold standard management of acute symptomatic atrial fibrillation but the best-long term approach for first or recurrent atrial fibrillation is still debated with regard to quality of life, risk of new hospitalizations, and possible disabling complications, such as thromboembolic stroke, major bleeds and death. Some authors propose that regaining sinus rhythm in all cases, thus re-establishing a physiologic cardiac function not requiring a prolonged antithrombotic therapy, avoids the threat of intracranial or extracranial haemorrhages due to Vitamin K antagonists or aspirin. On the contrary, advocates of a rate control approach with an accurate antithrombotic prophylaxis propose that such a strategy may avoid the risk of cardiovascular and non cardiovascular side effects related to antiarrhythmic drugs. This review aims to explore the state of our knowledge in order to summarize evidences and issues that need to be furthermore clarified