A Spectrometer to Study Elastic and Diffractive Physics at LHC

The possibility to study elastic and diffractive physics in pp collisions at LHC is investigated. For this purpose we have considered detectors close to the beam in conjunction with the magnetic elements of the accelerator to provide a high precision spectrometer for very forward final state protons. The geometrical acceptance is given and momentum resolution is calculated for different spatial resolution detectors.Comment: 26 pages, 13 figures, Latex, submitted in International Journal of Modern Physics

Interpreting the Transmission Windows of Distant Quasars

We propose the Apparent Shrinking Criterion (ASC) to interpret the spatial extent, R_w, of transmitted flux windows in the absorption spectra of high-z quasars. The ASC can discriminate between the two regimes in which R_w corresponds either to the physical size, R_HII, of the quasar HII region, or to the distance, R^{max}_w, at which the transmitted flux drops to =0.1 and a Gunn-Peterson (GP) trough appears. In the first case (HR regime), one can determine the IGM mean HI fraction, x_HI; in the second (PR regime), the value of R_w allows to measure the local photoionization rate and the local enhancement of the photoionization rate, Gamma_G, due to nearby/intervening galaxies. The ASC has been tested against radiative transfer+SPH numerical simulations, and applied to 15 high-z (z>5.8) quasars sample from Fan et al. (2006). All sample quasars are found to be in the PR regime; hence, their observed spectral properties (inner flux profile, extent of transmission window) cannot reliably constrain the value of x_HI. Four sample quasars show evidence for a local enhancement (up to 50%) in the local photoionization rate possibly produced by a galaxy overdensity. We discuss the possible interpretations and uncertainties of this result.Comment: 10 pages, 2 figures, accepted for publication in MNRA

Reflectivity measurements in uniaxial superconductors: a methodological discussion applied to the case of La(2-x)Sr(x)CuO(4)

Most of the novel superconductors are uniaxial crystals, with metallic planes ($ab$) orthogonal to an insulating axis ($c$). Far-infrared measurements of the reflectivity $R_{ab} (\omega)$ provide valuable information on their low-energy electrodynamics, but involve delicate experimental issues. Two of them are a possible contamination of $R_{ab} (\omega)$ from the c axis and the extrapolation of the $R_{ab}$ data to $\omega$ =0, both above and below $T_c$. Here we discuss quantitatively these issues with particular regard to La$_{2-x}$Sr$_x$CuO$_{4+y}$, one of the most studied high-$T_c$ materials.Comment: 13 pages with 3 Fig

Can We Detect the Anisotropic Shapes of Quasar HII Regions During Reionization Through The Small-Scale Redshifted 21cm Power Spectrum?

Light travel time delays distort the apparent shapes of HII regions surrounding bright quasars during early stages of cosmic reionization. Individual HII regions may remain undetectable in forthcoming redshifted 21 cm experiments. However, the systematic deformation along the line of sight may be detectable statistically, either by stacking tomographic 21cm images of quasars identified, for example, by JWST, or as small-scale anisotropy in the three-dimensional 21cm power spectrum. Here we consider the detectability of this effect. The anisotropy is largest when HII regions are large and expand rapidly, and we find that if bright quasars contributed to the early stages of reionization, then they can produce significant anisotropy, on scales comparable to the typical sizes of HII regions of the bright quasars (approx. 30 Mpc and below). The effect therefore cannot be ignored when analyzing future 21cm power spectra on small scales. If 10 percent of the volume of the IGM at redshift z=10 is ionized by quasars with typical ionizing luminosity of S= 5 x 10^{56} photons/second, the distortions can enhance by more than 10 percent the 21cm power spectrum in the radial (redshift) direction, relative to the transverse directions. The level of this anisotropy exceeds that due to redshift-space distortion, and has the opposite sign. We show that on-going experiments such as MWA should be able to detect this effect. A detection would reveal the presence of bright quasars, and shed light on the ionizing yield and age of the ionizing sources, and the distribution and small-scale clumping of neutral intergalactic gas in their vicinity.Comment: Version accepted by ApJ, with new fiducial model and improved discussio

Galaxy formation with radiative and chemical feedback

Here we introduce GAMESH, a novel pipeline which implements self-consistent radiative and chemical feedback in a computational model of galaxy formation. By combining the cosmological chemical-evolution model GAMETE with the radiative transfer code CRASH, GAMESH can post process realistic outputs of a N-body simulation describing the redshift evolution of the forming galaxy. After introducing the GAMESH implementation and its features, we apply the code to a low-resolution N-body simulation of the Milky Way formation and we investigate the combined effects of self-consistent radiative and chemical feedback. Many physical properties, which can be directly compared with observations in the Galaxy and its surrounding satellites, are predicted by the code along the merger-tree assembly. The resulting redshift evolution of the Local Group star formation rates, reionisation and metal enrichment along with the predicted Metallicity Distribution Function of halo stars are critically compared with observations. We discuss the merits and limitations of the first release of GAMESH, also opening new directions to a full implementation of feedback processes in galaxy formation models by combining semi-analytic and numerical methods.Comment: This version has coloured figures not present in the printed version. Submitted to MNRAS, minor revision

Fixation of genetic variation and optimization of gene expression: The speed of evolution in isolated lizard populations undergoing Reverse Island Syndrome

The ecological theory of island biogeography suggests that mainland populations should be more genetically divergent from those on large and distant islands rather than from those on small and close islets. Some island populations do not evolve in a linear way, but the process of divergence occurs more rapidly because they undergo a series of phenotypic changes, jointly known as the Island Syndrome. A special case is Reversed Island Syndrome (RIS), in which populations show drastic phenotypic changes both in body shape, skin colouration, age of sexual maturity, aggressiveness, and food intake rates. The populations showing the RIS were observed on islets nearby mainland and recently raised, and for this they are useful models to study the occurrence of rapid evolutionary change. We investigated the timing and mode of evolution of lizard populations adapted through selection on small islets. For our analyses, we used an ad hoc model system of three populations: wild-type lizards from the mainland and insular lizards from a big island (Capri, Italy), both Podarcis siculus siculus not affected by the syndrome, and a lizard population from islet (Scopolo) undergoing the RIS (called P. s. coerulea because of their melanism). The split time of the big (Capri) and small (Scopolo) islands was determined using geological events, like sea-level rises. To infer molecular evolution, we compared five complete mitochondrial genomes for each population to reconstruct the phylogeography and estimate the divergence time between island and mainland lizards. We found a lower mitochondrial mutation rate in Scopolo lizards despite the phenotypic changes achieved in approximately 8,000 years. Furthermore, transcriptome analyses showed significant differential gene expression between islet and mainland lizard populations, suggesting the key role of plasticity in these unpredictable environments

Distinguishing double neutron star from neutron star-black hole binary populations with gravitational wave observations

Gravitational waves from the merger of two neutron stars cannot be easily distinguished from those produced by a comparable-mass mixed binary in which one of the companions is a black hole. Low-mass black holes are interesting because they could form in the aftermath of the coalescence of two neutron stars, from the collapse of massive stars, from matter overdensities in the primordial Universe, or as the outcome of the interaction between neutron stars and dark matter. Gravitational waves carry the imprint of the internal composition of neutron stars via the so-called tidal deformability parameter, which depends on the stellar equation of state and is equal to zero for black holes. We present a new data analysis strategy powered by Bayesian inference and machine learning to identify mixed binaries, hence low-mass black holes, using the distribution of the tidal deformability parameter inferred from gravitational-wave observations.Comment: 13 pages, 6 figures - v2: matches the published version in Phys. Rev. D 102, 02302

Effective optical identification of type "0-IIb" early gastric cancer with narrow band imaging magnification endoscopy, successfully treated by endoscopic submucosal dissection

Background Endoscopic submucosal dissection (ESD) is currently considered the minimal invasive endoscopic treatment for early gastric cancer. Most superficial gastric neoplastic lesions are depressed type ”0-IIc” (70-80%), while totally flat, classified as type ”0-IIb” early gastric cancer, is rarely reported (0.4%). The aim of the present study was to assess the efficacy of narrow band imaging (NBI) magnification endoscopy in identifying type “0-IIb” early gastric cancer and ESD treatment with curative intention.Methods Twelve of 615 (2%) patients (10 males, median 72 years), treated by ESD at our center, were diagnosed as type “0-IIb” gastric cancer. Ten had exclusively type “0-IIb”, while two had combined types “0-IIb+IIc” and “0-IIa+IIb” gastric cancer. Initial diagnosis was made during screening gastroscopy, while NBI magnification endoscopy combined with indigo-carmine chromoendoscopy were also used.Results White light endoscopy showed only superficial redness. One patient with signet-ring carcinoma showed whitish appearance. Indigo-carmine chromoendoscopy showed better visualization, while NBI magnification endoscopy revealed abnormal mucosal microsurface and microvascular findings which enabled border marking. ESD with curative intention was completed without complications. Histological examination showed complete (R0) resection, in 10 patients (83%). One patient with positive margins received additional surgery (8%). Mean procedure time was 149 (range 60-190) min. One to six years post-ESD all patients remain alive.Conclusions ESD is considered a safe and effective curative treatment for type “0-IIb” gastric cancer, resulting in long-term disease-free survival. NBI magnification endoscopy is effective for accurate optical identification and border marking of type “0-IIb” early gastric cancer

S5 1803+78 Revisited

We report on our optical monitoring of the BL Lac object S5 1803+78 from 1996 to 2011. The source showed no clear periodicity, but a time scale of about 1 300 days between major flares is possibly present. No systematic trend of the color index with flux variations is evident, at variance with other BL Lacs. In one flare, however, the source was bluer in the rising phase and redder in the falling one. Two ?-ray flares were detected by Fermi-GST during our monitoring: on the occasion of only one of them we found simultaneous optical brightening. A one-zone Synchrotron Self Compton (SSC) model appears too simple to explain the source behavior