Low-mass dark matter search with the DarkSide-50 experiment

We present the results of a search for dark matter weakly interacting massive particles (WIMPs) in the mass range below 20 GeV=c2using a target of low-radioactivity argon with a 6786.0 kg d exposure. The data were obtained using the DarkSide-50 apparatus at Laboratori Nazionali del Gran Sasso. The analysis is based on the ionization signal, for which the DarkSide-50 time projection chamber is fully efficient at 0.1 keVee. The observed rate in the detector at 0.5 keVee is about 1.5 event=keVee=kg=d and is almost entirely accounted for by known background sources. We obtain a 90% C.L. exclusion limit above 1.8 GeV=c2for the spin-independent cross section of dark matter WIMPs on nucleons, extending the exclusion region for dark matter below previous limits in the range 1.8-6 GeV=c2

Analysis and Assembling of Network Structure in Mutualistic Systems

It has been observed that mutualistic bipartite networks have a nested structure of interactions. In addition, the degree distributions associated with the two guilds involved in such networks (e.g. plants & pollinators or plants & seed dispersers) approximately follow a truncated power law. We show that nestedness and truncated power law distributions are intimately linked, and that any biological reasons for such truncation are superimposed to finite size effects . We further explore the internal organization of bipartite networks by developing a self-organizing network model (SNM) that reproduces empirical observations of pollination systems of widely different sizes. Since the only inputs to the SNM are numbers of plant and animal species, and their interactions (i.e., no data on local abundance of the interacting species are needed), we suggest that the well-known association between species frequency of interaction and species degree is a consequence rather than a cause, of the observed network structure.Comment: J. of. Theor. Biology, in pres

Colorectal cancer surgery in the very elderly patient: a systematic review of laparoscopic versus open colorectal resection.

INTRODUCTION: Colorectal cancer is the second most common cause of death from neoplastic disease in men and third in women of all ages. Globally, life expectancy is increasing, and consequently, an increasing number of operations are being performed on more elderly patients with the trend set to continue. Elderly patients are more likely to have cardiovascular and pulmonary comorbidities that are associated with increased peri-operative risk. They further tend to present with more locally advanced disease, more likely to obstruct or have disseminated disease. The aim of this review was to investigate the feasibility of laparoscopic colorectal resection in very elderly patients, and whether there are benefits over open surgery for colorectal cancer. METHODS: A systematic literature search was performed on Medline, Pubmed, Embase and Google Scholar. All comparative studies evaluating patients undergoing laparoscopic versus open surgery for colorectal cancer in the patients population over 85 were included. The primary outcomes were 30-day mortality and 30-day overall morbidity. Secondary outcomes were operating time, time to oral diet, number of retrieved lymph nodes, blood loss and 5-year survival. RESULTS: The search provided 1507 citations. Sixty-nine articles were retrieved for full text analysis, and only six retrospective studies met the inclusion criteria. Overall mortality for elective laparoscopic resection was 2.92% and morbidity 23%. No single study showed a significant difference between laparoscopic and open surgery for morbidity or mortality, but pooled data analysis demonstrated reduced morbidity in the laparoscopic group (p = 0.032). Patients undergoing laparoscopic surgery are more likely to have a shorter hospital stay and a shorter time to oral diet. CONCLUSION: Elective laparoscopic resection for colorectal cancer in the over 85 age group is feasible and safe and offers similar advantages over open surgery to those demonstrated in patients of younger ages

Integrated Geomechanical and Digital Photogrammetric Survey in the Study of Slope Instability Processes of a Flysch Sea Cliff (Debeli Rtic Promontory, Slovenia)

This work presents an integrated study approach that combines the results of a geomechanical survey with data obtained using digital photogrammetry (DP), to assess slope instability processes affecting a sea cliff at the Debeli Rtic promontory (Slovenia). The investigated cliff is 4-18 m-high and is made up of an alternation of sandstones and marlstones belonging to the Flysch Formation of Trieste, which is Eocene in age. The studied cliff was subjected to localized slope failures that occurred in the past and is currently subject to frequent rock collapses, thus resulting in its partial and episodic retreat. Field evidence acquired through a traditional survey was integrated with outputs of the DP technique based on 1399 images that were collected using both a commercial unmanned aerial vehicle (UAV) and a mobile phone (MP). UAV-derived images were useful for performing rock mass structure analysis in the upper part of the investigated cliff, where the traditional survey was not possible due to hazardous operating conditions. In addition, the use of a MP was observed to be a useful tool for the rapid collection of images at the toe of unsafe marine cliff environments. This study highlights that UAV-DP and MP-DP techniques can only be effective if the outcomes obtained from the 3D model reconstruction are validated by direct measurements acquired by means of the traditional field survey, thus avoiding improper or even erroneous results while enlarging the amount of data and the area of investigation. The study approach presented herein allowed for the assessment of slope instabilities affecting the Flysch Sea cliff, whose retreat is caused by the combined action of marine erosion and slope gravitational processes

Integrated Geomechanical and Digital Photogrammetric Survey in the Study of Slope Instability Processes of a Flysch Sea Cliff (Debeli Rtič Promontory, Slovenia)

This work presents an integrated study approach that combines the results of a geomechanical survey with data obtained using digital photogrammetry (DP), to assess slope instability processes affecting a sea cliff at the Debeli Rtič promontory (Slovenia). The investigated cliff is 4–18 m-high and is made up of an alternation of sandstones and marlstones belonging to the Flysch Formation of Trieste, which is Eocene in age. The studied cliff was subjected to localized slope failures that occurred in the past and is currently subject to frequent rock collapses, thus resulting in its partial and episodic retreat. Field evidence acquired through a traditional survey was integrated with outputs of the DP technique based on 1399 images that were collected using both a commercial unmanned aerial vehicle (UAV) and a mobile phone (MP). UAV-derived images were useful for performing rock mass structure analysis in the upper part of the investigated cliff, where the traditional survey was not possible due to hazardous operating conditions. In addition, the use of a MP was observed to be a useful tool for the rapid collection of images at the toe of unsafe marine cliff environments. This study highlights that UAV-DP and MP-DP techniques can only be effective if the outcomes obtained from the 3D model reconstruction are validated by direct measurements acquired by means of the traditional field survey, thus avoiding improper or even erroneous results while enlarging the amount of data and the area of investigation. The study approach presented herein allowed for the assessment of slope instabilities affecting the Flysch Sea cliff, whose retreat is caused by the combined action of marine erosion and slope gravitational processes

High energy photon-neutrino elastic scattering

The one-loop helicity amplitudes for the elastic scattering process $\gamma\nu\to\gamma\nu$ in the Standard Model are computed at high center of mass energies. A general decomposition of the amplitudes is utilized to investigate the validity of some of the key features of our results. In the center of mass, where $\sqrt{s} = 2\omega$, the cross section grows roughly as $\omega^6$ to near the threshold for $W$-boson production, $\sqrt{s} = m_W$. Although suppressed at low energies, we find that the elastic cross section exceeds the cross section for $\gamma\nu\to\gamma\gamma\nu$ when $\sqrt{s}>13$ GeV. We demonstrate that the scattered photons are circularly polarized and the net value of the polarization is non-zero. Astrophysical implications of high energy photon-neutrino scattering are discussed.Comment: 9 pages, 7 figures, RevTeX