Secure Anonymous Routing for MANETs Using Distributed Dynamic Random Path Selection

Most of the MANET security research has so far focused on providing routing security and confidentiality to the data packets, but less has been done to ensure privacy and anonymity of the communicating entities. In this paper, we propose a routing protocol which ensures anonymity, privacy of the user. This is achieved by randomly selecting next hop at each intermediate. This protocol also provides data security using public key ciphers. The protocol is simulated using in-house simulator written in C with OpenSSL crypto APIs. The robustness of our protocol is evaluated against known security attacks

Study and Implementation of Power Control in Ad hoc Networks

An ad hoc network facilitates communication between nodes without the existence of an established infrastructure. Random nodes are connected to one another using Ad hoc networking and routing among the nodes is done by forwarding packets from one to another which is decided dynamically. The transmission of packets among the nodes is done on a specified power level. Power control is the method used for transmission of the packets at an optimized power level so as to increase the traffic carrying capacity, reduce the usage of battery power and minimize the interference to improve the overall performance of the system with regards to the usage of power. This thesis tells us regarding COMPOW (Common Power) and CLUSTERPOW (Cluster Power) protocols, which are two existing protocols for power control in homogeneous and non-homogeneous networks respectively. We have implemented these two protocols in Java Platform and run it for different number of nodes. From the implementation we have come up with the power optimal route among the nodes and the routing table for each node for both homogeneous and non-homogeneous networks. COMPOW (Common Power) protocol is an asynchronous, distributed and adaptive algorithm for calculating the common optimized power for communication among different nodes. CLUSTERPOW (Cluster Power) protocol is a protocol designed for optimizing the transmit power and establish efficient clustering and routing in non-homogeneous networks

Neuropathological findings from COVID-19 patients with neurological symptoms argue against a direct brain invasion of SARS-CoV-2: A critical systematic review

Background and purpose: Neuropathological studies can elucidate the mechanisms of nervous system damage associated with SARS-CoV-2 infection. Despite literature on this topic is rapidly expanding, correlations between neurological symptoms and brain pathology findings in COVID-19 patients remain largely unknown. Methods: We performed a systematic literature review on neuropathological studies in COVID-19, including 438 patients from 45 articles published by April 22, 2021. We retrieved quantitative data regarding demographic, clinical, and neuropathological findings. We carried out a Wilcoxon rank sum test or χ2 test to compare patients' subgroups based on different clinical and brain pathology features. Results: Neuropathological findings in COVID-19 patients were microgliosis (52.5%), astrogliosis (45.6%), inflammatory infiltrates (44.0%), hypoxic-ischemic lesions (40.8%), edema (25.3%), and hemorrhagic lesions (20.5%). SARS-CoV-2 RNA and proteins were identified in brain specimens of 41.9% and 28.3% of subjects, respectively. Detailed clinical information was available from 245 patients (55.9%), and among them, 96 subjects (39.2%) had presented with neurological symptoms in association with typical COVID-19 manifestations. We found that: (i) the detection rate of SARS-CoV-2 RNA and proteins in brain specimens did not differ between patients with versus those without neurological symptoms; (ii) brain edema, hypoxic-ischemic lesions, and inflammatory infiltrates were more frequent in subjects with neurological impairment; (iii) neurological symptoms were more common among older individuals. Conclusions: Our systematic revision of clinical correlates in COVID-19 highlights the pathogenic relevance of brain inflammatory reaction and hypoxic-ischemic damage rather than neuronal viral load. This analysis indicates that a more focused study design is needed, especially in the perspective of potential therapeutic trials

Mode of accretion in episodic radio galaxies and the dynamics of their outer relic lobes

We present X-ray observations with the X-ray Multi-Mirror Mission Newton (XMM-Newton) telescope of three Double-Double Radio Galaxies (DDRGs). We have detected the core, lobes and the environment of our sample DDRGs in X-rays. We examine the relationships between the radio and X-ray emission and attribute the X-ray emission from the lobes to the inverse-Compton scattering of cosmic microwave background (CMB) photons against the leptons of the radio lobes. The magnetic field strength of the lobes is close to the equipartition value. The X-ray spectrum of the cores of the DDRGs consists of an unabsorbed soft power-law component and no sign of hard power law components. The soft unabsorbed component is likely to be related to the radio jets. In optical wavebands, there is no strong [O III] lines observed and the host galaxies are not detected in all four bands (namely 2.4, 4.6, 12, 22 µm) of Wide-Field Infrared Survey Explorer (WISE) survey. This shows that they are low excitation radio galaxies. These DDRGs have poor group scale ambient media. We discuss the implications of this observation for models of the episodic activity in DDRGs

Rejuvenated radio galaxies J0041+3224 and J1835+6204 : how long can the quiescent phase of nuclear activity last?

We present radio observations of two well-known doubledouble radio galaxies, J0041+3224 and J1835+6204, at frequencies ranging from 150 to 8460 MHz, using both the Giant Metrewave Radio Telescope and the Very Large Array. These observations, over a large radio frequency range, enable us to determine the spectra of the inner and outer lobes. Our detailed spectral ageing analysis of their inner and outer lobes demonstrates that the outer doubles of doubledouble radio galaxies are created by the previous cycle of activity, while the inner doubles are due to the present cycle of activity. The (core subtracted) spectra of the inner doubles of both sources are power laws over a large frequency range. We found that the duration of the quiescent phase of J0041+3224 is between 4 and 28 per cent of the active phase of the previous activity. The outer north-western lobe of J1835+6204 has a compact hotspot and the regions of both the outer hotspots have close to power-law (rather than curved) spectra, which indicates that the outer lobes are still fed by jet material ejected in the previous episode just before the central engine stopped powering the jet. We estimate that the duration of the quiescent phase of J1835+6204 is ?5 per cent of the duration of the active phase of the previous activity. Therefore, we conclude that the duration of the quiescent phase can be as short as a few per cent of the active phase in radio galaxies of this type.Peer reviewe

Optically Faint Radio Sources: Reborn AGN?

We have discovered a number of relatively strong radio sources in the field-of-view of SDSS galaxy clusters which present no optical counterparts down to the magnitude limits of the SDSS. The optically faint radio sources appear as double-lobed or core-jet objects on the FIRST radio images and have projected angular sizes ranging from 0.5 to 1.0 arcmin. We have followed-up these sources with near-infrared imaging using the wide-field imager HAWK-I on the VLT. K_s-band emitting regions, about 1.5 arcsec in size and coincident with the centers of the radio structures, were detected in all the sources, with magnitudes in the range 17-20 mag. We have used spectral modelling to characterize the sample sources. In general, the radio properties are similar to those observed in 3CRR sources but the optical-radio slopes are consistent with moderate to high redshift (z<4) gigahertz-peaked spectrum sources. Our results suggest that these unusual objects are galaxies whose black hole has been recently re-ignited but retain large-scale radio structures, signatures of previous AGN activity.Comment: Accepted for publication in A&