The SDSS-GALEX viewpoint of the truncated red sequence in field environments at z~0

We combine GALEX near-UV photometry with a volume-limited sample of local (0.005<z<0.037) SDSS DR4 galaxies to examine the composition and the environmental dependencies of the optical and UV-optical colour-magnitude (C-M) diagrams. We find that ~30% of red sequence galaxies in the optical C-M diagram show signs of ongoing star-formation from their spectra having EW(Halpha)>2A. This contamination is greatest at faint magnitudes (Mr>-19) and in field regions where as many as three-quarters of red sequence galaxies are star-forming, and as such has important consequences for following the build-up of the red sequence. We find that the NUV-r colour instead allows a much more robust separation of passively-evolving and star-forming galaxies, which allows the build-up of the UV-selected red sequence with redshift and environment to be directly interpreted in terms of the assembly of stellar mass in passively-evolving galaxies. We find that in isolated field regions the number density of UV-optical red sequence galaxies declines rapidly at magnitudes fainter than Mr~-19 and appears completely truncated at Mr~-18. This confirms the findings of Haines et al. (2007) that no passively-evolving dwarf galaxies are found more than two virial radii from a massive halo, whether that be a group, cluster or massive galaxy. These results support the downsizing paradigm whereby the red sequence is assembled from the top down, being already largely in place at the bright end by z~1, and the faint end filled in at later epochs in clusters and groups through environment-related processes such as ram-pressure stripping or galaxy harassment.Comment: 12 pages, 7 figures, MNRAS submitte

Electronic transport within a quasi two-dimensional model for rubrene single-crystal field effect transistors

Spectral and transport properties of the quasi two-dimensional adiabatic Su-Schrieffer-Heeger model are studied adjusting the parameters in order to model rubrene single-crystal field effect transistors with small but finite density of injected charge carriers. We show that, with increasing temperature $T$, the chemical potential moves into the tail of the density of states corresponding to localized states, but this is not enough to drive the system into an insulating state. The mobility along different crystallographic directions is calculated including vertex corrections which give rise to a transport lifetime one order of magnitude smaller than spectral lifetime of the states involved in the transport mechanism. With increasing temperature, the transport properties reach the Ioffe-Regel limit which is ascribed to less and less appreciable contribution of itinerant states to the conduction process. The model provides features of the mobility in close agreement with experiments: right order of magnitude, scaling as a power law $T^{-\gamma}$, with $\gamma$ close or larger than two, and correct anisotropy ratio between different in-plane directions. Due to a realistic high dimensional model, the results are not biased by uncontrolled approximations.Comment: 10 pages, 9 figures, Submitte

Chemo-Archaeological Downsizing in a Hierarchical Universe: Impact of a Top Heavy IGIMF

We make use of a semi-analytical model of galaxy formation to investigate the origin of the observed correlation between [a/Fe] abundance ratios and stellar mass in elliptical galaxies. We implement a new galaxy-wide stellar initial mass function (Top Heavy Integrated Galaxy Initial Mass Function, TH-IGIMF) in the semi-analytic model SAG and evaluate its impact on the chemical evolution of galaxies. The SFR-dependence of the slope of the TH-IGIMF is found to be key to reproducing the correct [a/Fe]-stellar mass relation. Massive galaxies reach higher [a/Fe] abundance ratios because they are characterized by more top-heavy IMFs as a result of their higher SFR. As a consequence of our analysis, the value of the minimum embedded star cluster mass and of the slope of the embedded cluster mass function, which are free parameters involved in the TH-IGIMF theory, are found to be as low as 5 solar masses and 2, respectively. A mild downsizing trend is present for galaxies generated assuming either a universal IMF or a variable TH-IGIMF. We find that, regardless of galaxy mass, older galaxies (with formation redshifts > 2) are formed in shorter time-scales (< 2 Gyr), thus achieving larger [a/Fe] values. Hence, the time-scale of galaxy formation alone cannot explain the slope of the [a/Fe]-galaxy mass relation, but is responsible for the big dispersion of [a/Fe] abundance ratios at fixed stellar mass.We further test the hyphothesis of a TH-IGIMF in elliptical galaxies by looking into mass-to-light ratios, and luminosity functions. Models with a TH-IGIMF are also favoured by these constraints. In particular, mass-to-light ratios agree with observed values for massive galaxies while being overpredicted for less massive ones; this overprediction is present regardless of the IMF considered.Comment: 24 pages, 15 figures, 2 tables. (Comments most welcome). Summited to MNRA

Development of interconnected silicon micro-evaporators for the on-detector electronics cooling of the future ITS detector in the ALICE experiment at LHC

This paper was presented at the 4th Micro and Nano Flows Conference (MNF2014), which was held at University College, London, UK. The conference was organised by Brunel University and supported by the Italian Union of Thermofluiddynamics, IPEM, the Process Intensification Network, the Institution of Mechanical Engineers, the Heat Transfer Society, HEXAG - the Heat Exchange Action Group, and the Energy Institute, ASME Press, LCN London Centre for Nanotechnology, UCL University College London, UCL Engineering, the International NanoScience Community, www.nanopaprika.eu.The design of the future High Energy Physics (HEP) particle detectors for the upgrade of the LHC (Large Hadron Collider) experiments at CERN (European Organization for Nuclear Research) is pushing technological frontiers to the limit trying to reach unprecedented accuracy in particles identification and particle production dynamics in ultra-relativistic hadron collisions. The thermal management of the on-detector electronics and the development of low mass integrated cooling systems have become a crucial task in the design of silicon tracking detectors for HEP applications. In this paper, we present a novel concept of low mass interconnected silicon microchannel devices for the future Inner Tracking System of the ALICE (A Large Ion Collider Experiment) detector at LHC. This innovative design achieves the requirements of the detector while minimizing the total material budget

Laparoscopic Treatment of Inguinal Ovarian Hernia in Female Infants and Children: Standardizing the Technique

Sliding indirect inguinal hernias containing ovary are not uncommon in girls. We reported our experience with laparoscopic treatment of inguinal ovarian hernias in female infants and children with the aim to standardize the surgical technique. METHODS: The medical records of all girls who underwent laparoscopic inguinal hernia repair in our unit over the past 5 years were retrospectively reviewed. Only patients with an ovary found intraoperatively in the hernia sac were included in the study. All patients younger than 1 year received preoperatively a bowel preparation with simethicone and enemas. RESULTS: A total of 289 girls (median age 3.2 ± 0.5 years) underwent laparoscopic inguinal hernia repair during the study period. Thirty-seven patients (12.8%) had an ovarian hernia and were included in the study. Of these 37 girls, 9 (28.1%) were younger than 1 month, 20 (62.5%) ranged in age from 2 months to 1 year, and 3 (9.4%) were from 1 to 7 years. The average operative time was 23.7 minutes (range 18-43 minutes). No necrotic ovary was found intraoperatively, and all the procedures were accomplished laparoscopically. Neither intraoperative nor postoperative complications were reported. A patency of the contralateral canal of Nuck was found in 16 of the 37 patients (43.2%) and repaired during the same procedure. The average length of hospitalization was 21.8 hours (range 18-36 hours). No hernia recurrence or ovarian atrophy was recorded at a mean follow-up of 36 months (range 1-60 months). CONCLUSIONS: On the basis of our experience, laparoscopy should be considered the gold standard for the treatment of inguinal ovarian hernias in girls. Key points for standardization of the technique are as follows: bowel preparation in children younger than 1 year, use of 5-mm umbilical balloon trocar, correct positioning of 3-mm working screw trocars, section of the abnormal attachment of ovarian suspensory ligament, section of the periorificial peritoneum, and use of nonresorbable sutures

Pediatric Endoscopic Pilonidal Sinus Treatment: An Effective Procedure for Children with Recurrent Pilonidal Sinus Disease after Failed Open Surgery

Background: The traditional open excision of pilonidal sinus disease (PSD) is associated with a painful postoperative course and high recurrence rates. We recently published our technique of pediatric endoscopic pilonidal sinus treatment (PEPSiT). We aimed to report our long-term outcome including using PEPSiT for recurrent PSD after failed open repair. Methods: All patients with recurrent PSD after open excision who underwent PEPSiT in our unit over the past 2 years were included in the study. During surgery a fistuloscope was introduced through the fistula's orifice. All identifiable hairs were removed using endoscopic forceps. Thereafter, the cavity was debrided with endobrush and ablated with monopolar electrode. External openings were not closed. Results: In the past 2 years, 40 patients with PSD underwent PEPSiT. Ten of 40 patients (6 boys and 4 girls with an average age of 16.8 years [range = 14-18]) had recurrent PSD after open surgery and were included in the study. The average operative time was 27.7 minutes (range = 24-43). No perioperative complications occurred. The average analgesic requirement was 20 hours (range = 16-26) and the average hospitalization was 22.4 hours (range = 18-36). The average time to return to full daily activities was 2.3 days (range = 1-5) and all patients were highly satisfied of postoperative course. At 1 month postoperatively, the external openings were completely healed. No recurrence was recorded at a mean follow-up of 18 months (range = 6-24). Conclusions: Our results demonstrated that PEPSiT is an excellent technique for surgical treatment of PSD in children and teenagers. In fact, it is technically easy and fast to perform, with a short and painless hospital stay and it allows to the operated patients an early return to full daily activities without any physical limitations compared with open repair. In addition, it is also effective for treatment of recurrent PSD after failed open repair

Indocyanine Green Fluorescence Lymphography: A New Technique to Perform Lymphatic Sparing Laparoscopic Palomo Varicocelectomy in Children

Laparoscopic Palomo varicocelectomy is one the most common approaches adopted to treat pediatric varicocele, but postoperative hydrocele still remains a potential problem with this procedure. This study aimed to evaluate the outcome of a new technique of lymphography using indocyanine green (ICG)-enhanced fluorescence to perform lymphatic sparing laparoscopic Palomo varicocelectomy

Calibration of semi-analytic models of galaxy formation using Particle Swarm Optimization

We present a fast and accurate method to select an optimal set of parameters in semi-analytic models of galaxy formation and evolution (SAMs). Our approach compares the results of a model against a set of observables applying a stochastic technique called Particle Swarm Optimization (PSO), a self-learning algorithm for localizing regions of maximum likelihood in multidimensional spaces that outperforms traditional sampling methods in terms of computational cost. We apply the PSO technique to the SAG semi-analytic model combined with merger trees extracted from a standard $\Lambda$CDM N-body simulation. The calibration is performed using a combination of observed galaxy properties as constraints, including the local stellar mass function and the black hole to bulge mass relation. We test the ability of the PSO algorithm to find the best set of free parameters of the model by comparing the results with those obtained using a MCMC exploration. Both methods find the same maximum likelihood region, however the PSO method requires one order of magnitude less evaluations. This new approach allows a fast estimation of the best-fitting parameter set in multidimensional spaces, providing a practical tool to test the consequences of including other astrophysical processes in SAMs.Comment: 11 pages, 4 figures, 1 table. Accepted for publication in ApJ. Comments are welcom