1,267 research outputs found
Very high-energy constraints on the infrared extragalactic background light
Context. Measurements of the Extragalactic Background Light (EBL) are a
fundamental source of information on the collective emission of cosmic sources.
Aims. At infrared wavelengths, however, these measurements are precluded by
the overwhelming dominance from Interplanetary Dust emission and the Galactic
infrared foreground. Only at m, where the foregrounds are
minimal, has the Infrared EBL (IR EBL) been inferred from analysis of the COBE
maps. The present paper aims to assess the possibility of evaluating the IR EBL
from a few m up to the peak of the emission at >100 m using an
indirect method that avoids the foreground problem.
Methods. To this purpose we exploit the effect of pair-production from
gamma-gamma interaction by considering the highest energy photons emitted by
extragalactic sources and their interaction with the IR EBL photons. We
simulate observations of a variety of low redshift emitters with the
forthcoming Imaging Atmospheric Cherenkov Telescope (IACT) arrays (CTA in
particular) and water Cherenkov observatories (LHAASO, HAWC, SWGO) to assess
their suitability to constrain the EBL at such long wavelengths.
Results. We find that, even under the most extremely favorable conditions of
huge emission flares, extremely high-energy emitting blazars are not very
useful for our purpose because they are much too distant (>100 Mpc the nearest
ones, MKN 501 and MKN 421). Observations of more local Very High Energy (VHE)
emitting AGNs, like low-redshift radio galaxies (M87, IC 310, Centaurus A), are
better suited and will potentially allow us to constrain the EBL up to m
Assessment of susceptibility to European stone fruit yellows phytoplasma of new plum variety and five rootstock/plum variety combinations
Two separate experiments were carried out to assess the plum susceptibility to infection by European stone fruit yellows phytoplasmas during a five years period. Commercial varieties/cultivars and new selections grafted on Myrabolan 29C were evaluated in at least two plots of four plants each. Visual inspection and PCR/RFLP identification of phytoplasmas detected an increasing phytoplasma presence in both symptomatic and asymptomatic plants. Eight Japanese plum selections showed ESFY symptoms or pathogen presence in the 50% of the plants and nine selections showed ESFY infection in 20% of the plants. Only nine selections showed absence of both symptoms and pathogen. Although the European selections/cultivars were not symptomatic, plants belonging to six of these cultivars were positive for phytoplasma infection. The evaluation of cultivar/rootstock combinations indicate phytoplasma presence from the first year after plantation on. Two of the rootstocks seem to induce a delay in symptoms appearance and cultivar T.C. Sun resulted to be the most susceptible to the disease independently from the rootstock employed. Keywords: Japanese plum, European plum, European stone fruit yellows phytoplasmas, resistance, disease
Effect of Mechanical Strain on the Optical Properties of Nodal-Line Semimetal ZrSiS
Optical properties of nodal-line semimetal ZrSiS are studied using first-principles calculations. Frequency-independent optical conductivity is a fingerprint of the infrared optical response in ZrSiS. It is found that this characteristic feature is robust with respect to uniaxial compressive strain of up to 10 GPa, yet with the flat region being narrowed with increasing strain. Upon uniaxial tensile stress of 2 GPa, the Fermi surface undergoes a Lifshitz transition accompanied by a weakening of the interband screening, which reduces the spectral weight of infrared excitations. It is also shown that the high-energy region is characterized by low-loss plasma excitations at ≈20 eV with essentially anisotropic dispersion. Strongly anisotropic dielectric properties suggest the existence of a hyperbolic regime for plasmons in the deep ultraviolet range. Although the frequencies of high-energy plasmons are virtually unaffected by external uniaxial deformation, their dispersion can be effectively tuned by strain. © 2019 WILEY-VCH Verlag GmbH & Co. KGaA, WeinheimNational Natural Science Foundation of China, NSFC: 117742692018FYA0305800S.Y. acknowledges financial support from the National Key R & D Program of China (Grant No. 2018FYA0305800) and National Science Foundation of China (Grant No. 11774269). A.N.R. acknowledges travel support from FLAG-ERA JTC2017 Project GRANSPORT. Numerical calculations presented in this paper were performed on a supercomputing system in the Supercomputing Center of Wuhan University
A Structured Approach to Insider Threat Monitoring for Offensive Security Teams
In many countries, government agencies resort to third parties to acquire security services of many kinds, including Red Team operations to test the effectiveness of own defenses mechanisms. Absolute trust is a key requirement, lest a potentially devastating finding be exploited by a treacherous Red Team against the same entity which commissioned the operation, or sold to its adversaries. In our endeavour as a joint private-academic initiative to address this peculiar market, we observed that a structured approach to this issue is much less common than we would have expected. In this work, we outline the process we are devising to offer customers a verified environment, but integrating it with an evidence-based proof of their correct behavior during the operation, striving to solve the “Quis custodiet ipsos custodes” struggle in an offensive setting
Towards the Creation of Interdisciplinary Consumer-Oriented Security Metrics
Information systems are evolving: IoT devices and Cyber-physical systems (CPS) impact on the security of assets and people in the real world. Old cybersecurity approaches, which focused on seeing humans 'as a problem', could be substitute by new paradigms of seeing humans 'as a solution'. Therefore, consumers awareness will be one of the building blocks, as well as initiative that aim to create a set of standardized security metrics that can evaluate the security of systems. In order to do that, researchers need to study which are the essential factors that our future metrics should focus on. In this paper we analyzed this problem over CPS while assuming the consumer perspective. We summarize the state of the art in security metrics and advocate the need for a research effort aimed at taking the field to a new level of formal soundness and practical usability by considering interdisciplinary implications on cybersecurity
Raw and extruded pea (Pisum sativum) and lupin (Lupinus albus var. Multitalia) seeds as protein sources in weaned piglets' diets: effect on growth rate and blood parameters
The 42 days trial was carried out using 140 piglets weaned at 28 days of age. The piglets were allocated according to weight and sex to the 5 dietary treatments with 7 replicates for each treatments (4 pens x 4 castrated males and 3 pens x 4 females). The piglets were fed according to the following experimental design: 1) control diet (CTR) with soybean meal (SBM) 44% c.p. as protein source; 2) CRT diets with 200 g/kg of raw pea (Pisum sativum) (RP); 3) CTR diet with 200 g/kg extruded pea (EP); 4) CRT diet with 170 g/kg raw lupin (Lupinus albusvar. Multitalia) (RL); 5) CTR diet with 170 g/kg of extruded lupin (EL). During the trial, animals were weighed at 0 - 21 and 42 days from the start of the trial. Feed intake was monitored and feed conversion ratio was calculated for the periods 0-21 d and 22-42 d. At the end of the trial, blood samples were taken for 14 animals for each dietary treatment (2 animals per replicate) and analysed for total protein, urea and liver activity (ALT, AST and ALP parameters). Average daily weight gain and feed intake did not differ according to dietary treatments whereas during the total experimental period (0-42 d), feed conversion ratio was higher for EP vsCTR diet (2.35 vs2.09, respectively; P <0.05). The growth rate for diets with extruded protein sources compared with diets containing the raw ingredients did not differ. Feed conversion ratio for the RP was numerically high- er than for the EP (2.35 vs2.16 and 2.76 vs2.32, respectively during 22-42 d and 0-42 d periods). Blood parameters did not show significant difference among dietary treatments except for higher total protein for CTR diet vsRL diet, EL and RP (67.3 vs62.2, 62.8 and 63.6 g/l, respectively; P<0.05) and urea that resulted the highest with CTR diet vsRL and RL (4.7 vs3.7 and 3.8 mmol/l respectively; P<0.05)
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