1,721,182 research outputs found
Spatial GNSS Spoofing against Drone Swarms with Multiple Antennas and Wiener Filter
No full textSpoofing of global-navigation satellite system (GNSS) signals to induce a target position estimate is a relevant security threat to the navigation of drones. However, spoofing multiple drones simultaneously as they move in a swarm, without disrupting their formation, is a complex task. In this paper, we propose to transmit spoofing signals from the ground, such that the fake position can be estimated in any point of an area of the plane where the swarm is moving. To this end we filter the satellite-generated GNSS signals with a multidimensional linear filter, and transmit the filtered signal with multiple ground antennas. The multidimensional filter is designed according to a generalized Wiener-filter criterion, such that the fake signal is accurately reproduced (in terms of mean squared error (MSE)) in the whole spoofed area. We investigate the impact of various design parameters (among others, the size of the spoofed area, the number of ground antennas, and the number of spoofed satellites) on both the MSE, and the probability of acquisition of the spoofed signal by the drones
Authentication of satellite navigation signals by wiretap coding and artificial noise
Full text linkAbstract In order to combat the spoofing of global navigation satellite system (GNSS) signals, we propose a novel signal authentication method based on information-theoretic security. In particular, the satellite superimposes to the navigation signal an authentication signal containing a secret authentication message corrupted by artificial noise (AN). We impose the following properties: a)Authentication and navigation signals are synchronous,b)Authentication and navigation signals are orthogonal andc)The secret message is undecodable by the attacker due to the AN. The legitimate receiver synchronizes with the navigation signal and stores the samples of the authentication signal with the same synchronization. After the transmission of the authentication signal, through a separate public asynchronous ground channel (e.g., a secure Internet connection) additional information is made public allowing the receiver to a)Decode the authentication message, thus overcoming the effects of AN, andb)Verify the authentication message. We assess the performance of the proposed scheme by the analysis of both the secrecy capacity of the authentication message and the attack success probability under various attack scenarios
Generalized Likelihood Ratio Test for GNSS Spoofing Detection in Devices with IMU
No full textSpoofing attacks in global navigation satellite systems (GNSSs) aim at inducing the estimation of a fake position at the victim receiver. Many devices, including smartphones, are nowadays equipped with both a GNSS receiver and an inertial measurement unit (IMU), which also provides location/movement information, while being immune from GNSS attacks. We propose a spoofing detection technique based on the comparison between GNSS and IMU measurements. The detection is performed through a generalized likelihood ratio test (GLRT), which is efficiently implemented by a matrix multiplication approach. In particular, the device a) estimates its orientation from magnetometer and gyroscope measurements, b) estimates its position, acceleration, and velocity by a maximum likelihood approach, and c) performs the GLRT for spoofing detection. The performance of the proposed GLRT is compared with the Kalman filter innovation test and with the direct comparison method (DCM), both in terms of false alarm/missed detection probabilities and computational complexity
Peptide-Based Biopesticides
No full textIn this presentation we describe the great potential of peptides as biopesticides. Currently Europe is greatly encouraging research in sustainable pest-management. Finding eco-friendly, effective alternatives to synthetic pesticides is of paramount importance, especially against the so-called priority pests of fruits and vegetables. For some of these pests, such as botrytis cinerea and peronospora viticola, no effective bio-alternatives to small organic molecules are available so far. Fungi belonging to the genus Trichoderma are distributed worldwide and have been used successfully in field trials against many crop pathogens. They produce peptaibols, a peculiar family of peptides, as part of their defense system against other microorganisms. Such secondary metabolites are known for their plantprotection properties: they (i) possess antimicrobial activity, (ii) act as stimulants of plant defences and growth (iii) elicit plant production of volatiles to attract natural enemies of herbivorous insects. By means of a versatile SPPS strategy, we produced several analogs of such naturally occurring peptides. With such compounds, we can circumvent both the health hazards and the unreliable effectiveness in open field connected with the use of antagonistic microorganisms as biological control agents, while keeping the biomolecules responsible for their beneficial effects. Our peptides have been tested (alone or in combination) both in vitro and in vivo against a variety of priority pests, such as the fungi Botrytis cinerea and Penicillum italicum, and the bacterium Pectobacterium carotovorum. We identified several peptaibol analogs with a broad-spectrum activity as biopesticides, able to completely inhibit the growth of B. cinerea and many other pathogens for over a week at low micromolar concentrations
On trading the spreading gain with the coding rate and its application to GNSS data component design
No full textThe ubiquity of global navigation satellite system (GNSS)-based positioning and timing services is often frustrated by the necessity to operate in harsh environments, where the carrier-to-noise ratio is low, and hence, decoding of navigation data and even tracking of an acquired symbol are difficult. We consider the possibility of improving the decoding performance of the GNSS data component by trading the spreading gain against the coding rate. The rationale is that spreading codes can be seen as a form of repetition coding that can be (at least partially) replaced by more robust coding forms to improve robustness to (any form of) noise. This is true both for the classical additive white Gaussian noise channel case and for more realistic GNSS channel formats severely degraded by multiple access interference and near-far effects. By bringing results on finite-block-length channel capacity and coding rates from information/communication theory to the GNSS domain, we are able to establish and discuss the expected performance gap, as well as the limits of such tradeoff
beta-Pseudopeptide foldamers. The homo-oligomers of (4R)-(2-oxo-1,3-oxazolidin-4-yl)-acetic acid (D-Oxac)
No full textDynamic expression of homeostatic ion channels in differentiated cortical astrocytes in vitro
Full text linkThe capacity of astrocytes to adapt their biochemical and functional features upon physiological and pathological stimuli is a
fundamental property at the basis of their ability to regulate the homeostasis of the central nervous system (CNS). It is well
known that in primary cultured astrocytes, the expression of plasma membrane ion channels and transporters involved in
homeostatic tasks does not closely reflect the pattern observed in vivo. The individuation of culture conditions that promote
the expression of the ion channel array found in vivo is crucial when aiming at investigating the mechanisms underlying their
dynamics upon various physiological and pathological stimuli. A chemically defined medium containing growth factors and
hormones (G5) was previously shown to induce the growth, differentiation, and maturation of primary cultured astrocytes.
Here we report that under these culture conditions, rat cortical astrocytes undergo robust morphological changes acquir-
ing a multi-branched phenotype, which develops gradually during the 2-week period of culturing. The shape changes were
paralleled by variations in passive membrane properties and background conductance owing to the differential temporal
development of inwardly rectifying chloride (Cl−) and potassium (K+) currents. Confocal and immunoblot analyses showed
that morphologically differentiated astrocytes displayed a large increase in the expression of the inward rectifier Cl− and K+
channels ClC-2 and Kir4.1, respectively, which are relevant ion channels in vivo. Finally, they exhibited a large diminution
of the intermediate filaments glial fibrillary acidic protein (GFAP) and vimentin which are upregulated in reactive astrocytes
in vivo. Taken together the data indicate that long-term culturing of cortical astrocytes in this chemical-defined medium
promotes a quiescent functional phenotype. This culture model could aid to address the regulation of ion channel expression
involved in CNS homeostasis in response to physiological and pathological challenge
Isolated α-turns in peptides: a selected literature survey
No full textThe results of classifying into various types the 68 examples of isolated α-turns in the X-ray diffraction crystal structures of peptides documented in the literature are presented and discussed in this review article. α-Turns characterized by the trans disposition of all ω torsion angles are common for the backbone linear peptides investigated. In contrast, the cis arrangement of the N-terminal (ωi + 1) torsion angle, among those generated by the three residues internal to the α-turn, is a peculiar feature of 65% of the cyclic peptides. Among linear and cyclic peptides featuring the all-trans disposition of the ω torsion angles, only one third of the α-turns display φ,ψ values not too far from those characterizing regular α-helices. In general, our findings, taken together, suggest that a significant conformational diversity is compatible with the formation of an intramolecularly H-bonded C13-member pseudocycle (α-turn) in linear and cyclic peptides
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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