Pseudogap and the specific heat of high TcT_c superconductors

The specific heat of a two dimensional repulsive Hubbard model with local interaction is investigated. We use the two-pole approximation which exhibits explicitly important correlations that are sources of the pseudogap anomaly. The interplay between the specific heat and the pseudogap is the main focus of the present work. Our self consistent numerical results show that above the occupation $n_T\approx 0.85$, the specific heat starts to decrease due to the presence of a pseudogap in the density of states. We have also observed a two peak structure in the specific heat. Such structure is robust with respect to the Coulomb interaction $U$ but it is significantly affected by the occupation $n_T$. A detailed study of the two peak structure is carried out in terms of the renormalized quasi-particle bands. The role of the second nearest neighbor hopping on the specific heat behavior and on the pseudogap, is extensively discussed.Comment: 6 pages, 6 figures, accepted for publication in Solid State Communication

Charting the TeV Milky Way: H.E.S.S. Galactic plane survey maps, catalog and source populations

Very-high-energy (VHE, E>100 GeV) gamma-rays provide a unique view of the non-thermal universe, tracing the most violent and energetic phenomena at work inside our Galaxy and beyond. The latest results of the H.E.S.S. Galactic Plane Survey (HGPS) undertaken by the High Energy Stereoscopic System (H.E.S.S.), an array of four imaging atmospheric Cherenkov telescopes located in Namibia, are described here. The HGPS aims at the detection of cosmic accelerators with environments suitable for the production of photons at the highest energies and has led to the discovery of an unexpectedly large and diverse population of over 60 sources of TeV gamma rays within its current range of l = 250 to 65 degrees in longitude and |b|<3.5 degrees in latitude. The data set of the HGPS comprises 2800 hours of high-quality data, taken in the years 2004 to 2013. The sensitivity for the detection of point-like sources, assuming a power-law spectrum with a spectral index of 2.3 at a statistical significance of 5 sigma, is now at the level of 2% Crab or better in the core HGPS region. The latest maps of the inner Galaxy at TeV energies are shown alongside an introduction to the first H.E.S.S. Galactic Plane Survey catalog. Finally, in addition to an overview of the H.E.S.S. Galactic source population a few remarkable, recently discovered sources will be highlighted.Comment: 8 pages, 6 figures, in Proceedings of the 48th Rencontres de Moriond (2013), La Thuile (Italy

Specific heat of a non-local attractive Hubbard model

The specific heat of an attractive (interaction $G<0$) non-local Hubbard model is investigated. We use a two-pole approximation which leads to a set of correlation functions. In particular, the correlation function $\ $plays an important role as a source of anomalies in the normal state of the model. Our results show that for a giving range of$G$and$\delta$where$\delta=1-n_T$($n_T=n_{\uparrow}+n_{\downarrow}$), the specific heat as a function of the temperature presents a two peak structure. Nevertehelesss, the presence of a pseudogap on the anti-nodal points$(0,\pm\pi)$and$(\pm\pi,0)$ eliminates the two peak structure, the low temperature peak remaining. The effects of the second nearest neighbor hopping on the specific heat are also investigated.Comment: 5 pages, 7 figure

Microbial Diversity and Safety in Fermented Beverages

For thousands of years, humans have exploited the natural process of fermentation of various foods to preserve them, and to enjoy the changes in the sensory characteristics that could be produced. Recently, the world of fermented beverages has gone through a rapid transformation linked to deep changes in consumer preferences, consumption habits, climate, new regulations and entry of emerging countries, accompanied by safety concerns and an important reduction in economic resources available to people. As with all food handling and preparation, we need to be sure the fermented food produced is safe. Fermentation is a complex biological process where microbial diversity takes place and the environment created inside of the fermented food provides the conditions to reduce the risk of pathogenic bacteria growth, thus providing safe food. In addition, food manufacturers fermenting food carefully control their processing and must comply with the National Food Standards Codes. Although these products have a generally good food safety record, sometimes inadequate manufacturing practices or the presence of acidophilic pathogens could compromise food safety. In fact, fermented beverages may adversely become contaminated with pathogens or microbial toxins and thereby transform into vehicles that can transmit diseases to the consumers. Moreover, many microorganisms can deteriorate the physical-chemical and sensory properties as well as the flavor of the final products. In this editorial, we present an overview of a review and six original research papers published in the Special Issue “Fermentation Process and Microbial Safety of Beverages” of the Beverages journal

Detection of very-high-energy gamma-ray emission from the vicinity of PSR B1706-44 with H.E.S.S

The energetic pulsar PSR B1706-44 and the adjacent supernova remnant (SNR) candidate G 343.1-2.3 were observed by H.E.S.S. during a dedicated observational campaign in 2007. A new source of very-high-energy (VHE; E > 100 GeV) gamma-ray emission, HESS J1708-443, was discovered with its centroid at RA(J2000) = 17h08m10s and Dec(J2000) = -44d21', with a statistical error of 3 arcmin on each axis. The VHE gamma-ray source is significantly more extended than the H.E.S.S. point-spread function, with an intrinsic Gaussian width of 0.29 +/- 0.04 deg. Its energy spectrum can be described by a power law with a photon index Gamma = 2.0 +/- 0.1 (stat) +/- 0.2 (sys). The integral flux measured between 1-10 TeV is ~17% of the Crab Nebula flux in the same energy range. The possible associations with PSR B1706-44 and SNR G343.1-2.3 are discussed.Comment: 4+ pages, 2 figures; v1 submitted to ICRC Proceedings on 15 May 2009; v2 has additional references and minor change

Magnetization and EPR studies of the single molecule magnet Ni4_4 with integrated sensors

Integrated magnetic sensors that allow simultaneous EPR and magnetization measurements have been developed to study single molecule magnets. A high frequency microstrip resonator has been integrated with a micro-Hall effect magnetometer. EPR spectroscopy is used to determine the energy splitting between the low lying spin-states of a Ni$_4$ single crystal, with an S=4 ground state, as a function of applied fields, both longitudinal and transverse to the easy axis at 0.4 K. Concurrent magnetization measurements show changes in spin-population associated with microwave absorption. Such studies enable determination of the energy relaxation time of the spin system.Comment: 4 pages, 4 figures, accepted for publication (Proceedings of the 10th Joint MMM/Intermag Conference, which will be published as special issues of the Journal of Applied Physics