Exploiting probability density function of deep convolutional autoencoders’ latent space for reliable COVID-19 detection on CT scans

The Journal of Supercomputing - We present a probabilistic method for classifying chest computed tomography (CT) scans into COVID-19 and non-COVID-19. To this end, we design and train, in an...     

Sequence homology between 4qter and 10qter loci facilitates the instability of subtelomeric KpnI repeat units implicated in facioscapulohumeral muscular dystrophy

An analysis of 13 immunoglobulin A1 (IgA1) protease genes (iga) of strains of Streptococcus pneumoniae, Streptococcus oralis, Streptococcus mitis, and Streptococcus sanguis was carried out to obtain information on the structure, polymorphism, and phylogeny of this specific protease, which enables bacteria to evade functions of the predominant Ig isotype on mucosal surfaces. The analysis included cloning and sequencing of iga genes from S. oralis and S. mitis biovar 1, sequencing of an additional seven iga genes from S. sanguis biovars 1 through 4, and restriction fragment length polymorphism (RFLP) analyses of iga genes of another 10 strains of S. mitis biovar 1 and 6 strains of S. oralis. All 13 genes sequenced had the potential of encoding proteins with molecular masses of approximately 200 kDa containing the sequence motif HEMTH and an E residue 20 amino acids downstream, which are characteristic of Zn metalloproteinases. In addition, all had a typical gram-positive cell wall anchor motif, LPNTG, which, in contrast to such motifs in other known streptococcal and staphylococcal proteins, was located in their N-terminal parts. Repeat structures showing variation in number and sequence were present in all strains and may be of relevance to the immunogenicities of the enzymes. Protease activities in cultures of the streptococcal strains were associated with species of different molecular masses ranging from 130 to 200 kDa, suggesting posttranslational processing possibly as a result of autoproteolysis at post-proline peptide bonds in the N-terminal parts of the molecules. Comparison of deduced amino acid sequences revealed a 94% similarity between S. oralis and S. mitis IgA1 proteases and a 75 to 79% similarity between IgA1 proteases of these species and those of S. pneumoniae and S. sanguis, respectively. Combined with the results of RFLP analyses using different iga gene fragments as probes, the results of nucleotide sequence comparisons provide evidence of horizontal transfer of iga gene sequences among individual strains of S. sanguis as well as among S. mitis and the two species S. pneumoniae and S. oralis. While iga genes of S. sanguis and S. oralis were highly homogeneous, the genes of S. pneumoniae and S. mitis showed extensive polymorphism reflected in different degrees of antigenic diversity.     

Performance analysis and optimization for impulse radio and direct-sequence impulse radio in multiuser interference

The performance of two ultra wideband communication systems is investigated. The first system is the classical impulse radio (IR). The second is obtained by adding a direct-sequence (DS) code to the IR system, and is termed direct-sequence impulse radio (DS-IR). For both systems, binary pulse amplitude modulation is considered. The performance of IR and DS-IR is analyzed in a multiuser scenario, assuming an ideal channel and a correlation receiver. The performance analysis is original and general. It yields simple and exact formulas relating the performance to the system parameters. The analysis shows that IR suffers a performance degradation with respect to DS-IR unless the system parameters are chosen carefully. An optimum shape for the monocycle is identified, yielding an upper bound to the performance. The optimum system achieving this upper bound is shown to be, in principle, feasible for both DS-IR and IR. The degradation experienced by real systems with respect to the optimum system is also evaluated. Furthermore, it is shown that DS-IR has practical advantages with respect to IR. Simulations are included to validate the theoretical findings.     

Performance analysis for impulse radio and direct-sequence impulse radio in narrowband interference

The impact of narrowband interference (NBI) on two ultra wideband (UWB) systems is analyzed. The two systems are impulse radio (IR) and a variation of it, termed direct-sequence IR (DS-IR). The signal-to-noise ratio (SNR) at the decision device of a correlation receiver is computed for both systems, assuming that the NBI is wide sense stationary and that the channel is frequency-selective. The SNR is expressed by means of a simple equation involving the signal and the interference spectrum. Next, a statistical model for the interference is introduced, considering the interference as the sum of a given number of sinusoidal signals with random powers and frequencies. The bit-error rate of IR and DS-IR is derived. The results are then specialized and compared with simulations in three case studies of practical interest, where the NBI is a single jammer with deterministic power and frequency, a multitone signal with random frequencies, or a grid of interfering signals with random powers.     

Analysis of phase noise effects in OFDM modems

The effects of the phase noise (PN) on orthogonal frequency-division multiplex modems are evaluated. Three receivers are studied: a coherent receiver, a common phase error correction receiver (which is a receiver specially designed to combat PN) and a differential receiver. The impact of the PN on the decision signal-to-noise ratio (SNR) of each of these receivers is computed as a function of the PN spectrum. The resulting formulas are extremely simple. The theory is applicable to a wide range of PN models, and unifies and extends previous results on the topic. The conditions under which the decision SNR yields correct symbol error rate predictions are discussed. Simulations are reported that confirm the results.     

Fast algorithm for power and bit allocation in OFDM systems

The problem of power and bit allocation in OFDM systems is analysed. A solution algorithm with substantially lower computational complexity than existing algorithms is proposed     

Orthogonal frequency division multiplex synchronization techniquesfor frequency-selective fading channels

The effect of time-domain and frequency-domain synchronization errors is quantified in the context of various coherently and noncoherently detected 1, 2, and 4 bits/symbol OFDM constellations, in order to demonstrate the wide applicability of the techniques proposed for mitigating the bit error rate (BER) performance degradations inflicted. A reference symbol is proposed and a range of correlation techniques are suggested for coarse and fine synchronization. Their performance is studied over time-dispersive Rayleigh fading channels, with the conclusion that the proposed synchronization techniques result in virtually unimpaired BERs over the range of wideband channels investigated in comparison to a perfectly synchronized system     

A practical algorithm for power minimisation in wireless networks by means of multi-hop and load partitioning

We study the problem of minimising the power consumption of wireless networks when the traffic is specified. Initially we consider single-hop networks that model currently existing frequency division multiplex (FDM) and code division multiple access (CDMA) networks and discuss the power minimisation problem for these networks. Next we consider networks where multi-hop transmission is deployed and where a source is allowed to partition its outgoing information flow into several sub-flows each delivered through different multi-hop routes. We present a simple, versatile, suboptimum algorithm for the power minimisation in these Multi-hop, load partitioning (MLP) networks. Finally we carry out a simulation campaign in order to quantify the power savings that are attainable by means of the.proposed algorithm.     

Algorithm for SBS receivers/decoders

An efficient algorithm for symbol-by-symbol (SBS) receivers/decoders is presented. Its memory and computational requirements compare favourably with those of the existing SBS decoders. The algorithm is formulated using a simple and compact matrix notation