Détermination du facteur de multiplication M pour un fonctionnement optimal des photodétecteurs à avalanche

The purpose of this paper is relative to the determination of the multiplication factor Mfor an optimum behaviour of the avalanche photodetector. Two types of avalanche photodetector s are compared: a silicon structure n ⁺ πpπp ⁺ Read diode and a GaAlAs heterostructure. Calculating the Noise Equivalent Power (nep)of the whole system, the law S_i(f) =2q I_phoM_x is used, where the parameter x is determined experimentally in both avalanche photodetectors. The exponent x (between 2 and 4) dominates in the nep expression and the ideal nep for the avalanche photodetector system is obtained when x equals 2.     

Use of FRP for RC Frames in Seismic Zones: Part II. Performance of Steel-Free GFRP-Reinforced Beam-Column Joints

The use of FRP as reinforcement in concrete structures has been growing rapidly due to its advantages over conventional steel reinforcement (e.g., corrosion resistance, light weight, magnetic neutrality). A potential application of FRP reinforcement is in structural concrete frames. However, current seismic design standards and detailing criteria for beam-column joints were established for steel reinforcement and may be unsuitable for FRP reinforcement due to its different mechanical properties. During recent earthquakes, many structural collapses were initiated or caused by beam-column joint failures. Since there are no detailed specifications for the application of FRP reinforcement in seismic zones, research is needed to gain a better understanding of the behaviour of FRP-reinforced concrete under seismic loading. In this study, two full-scale beam-column joint specimens reinforced with steel and GFRP, respectively, were tested in order to investigate their performance in the event of an earthquake. The control steel-reinforced specimen is detailed according to the Canadian Code (CSA A23.3-94) recommendations. The GFRP-reinforced specimen is detailed in a similar scheme but using a GFRP grid. The behaviour of the two specimens under reversed cyclic loading, their load-storey drift envelope relationship and energy dissipation ability were compared. The GFRP-reinforced specimen showed a predominantly elastic behaviour up to failure. While its energy dissipation was low, its performance was acceptable in terms of total storey drift demand.     

New Beta-lactamases in Candidate Phyla Radiation: Owning Pleiotropic Enzymes Is a Smart Paradigm for Microorganisms with a Reduced Genome

The increased exploitation of microbial sequencing methods has shed light on the high diversity of new microorganisms named Candidate Phyla Radiation (CPR). CPR are mainly detected via 16S rRNA/metabarcoding analyses or metagenomics and are found to be abundant in all environments and present in different human microbiomes. These microbes, characterized by their symbiotic/epiparasitic lifestyle with bacteria, are directly exposed to competition with other microorganisms sharing the same ecological niche. Recently, a rich repertoire of enzymes with antibiotic resistance activity has been found in CPR genomes by using an in silico adapted screening strategy. This reservoir has shown a high prevalence of putative beta-lactamase-encoding genes. We expressed and purified five putative beta-lactamase sequences having the essential domains and functional motifs from class A and class B beta-lactamase. Their enzymatic activities were tested against various beta-lactam substrates using liquid chromatography-mass spectrometry (LC-MS) and showed some beta-lactamase activity even in the presence of a beta-lactamase inhibitor. In addition, ribonuclease activity was demonstrated against RNA that was not inhibited by sulbactam and EDTA. None of these proteins could degrade single- and double-stranded-DNA. This study is the first to express and test putative CPR beta-lactamase protein sequences in vitro. Our findings highlight that the reduced genomes of CPR members harbor sequences encoding for beta-lactamases known to be multifunction hydrolase enzymes.     

The Endothelium and COVID-19: An Increasingly Clear Link Brief Title: Endotheliopathy in COVID-19

The endothelium has a fundamental role in the cardiovascular complications of coronavirus disease 2019 (COVID-19). Infection with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) particularly affects endothelial cells. The virus binds to the angiotensin-converting enzyme 2 (ACE-2) receptor (present on type 2 alveolar cells, bronchial epithelial cells, and endothelial cells), and induces a cytokine storm. The cytokines tumor necrosis factor alpha, interleukin-1 beta, and interleukin-6 have particular effects on endothelial cells—leading to endothelial dysfunction, endothelial cell death, changes in tight junctions, and vascular hyperpermeability. Under normal conditions, apoptotic endothelial cells are removed into the bloodstream. During COVID-19, however, endothelial cells are detached more rapidly, and do not regenerate as effectively as usual. The loss of the endothelium on the luminal surface abolishes all of the vascular responses mediated by the endothelium and nitric oxide production in particular, which results in greater contractility. Moreover, circulating endothelial cells infected with SARS-CoV-2 act as vectors for viral dissemination by forming clusters that migrate into the circulation and reach distant organs. The cell clusters and the endothelial dysfunction might contribute to the various thromboembolic pathologies observed in COVID-19 by inducing the formation of intravascular microthrombi, as well as by triggering disseminated intravascular coagulation. Here, we review the contributions of endotheliopathy and endothelial-cell-derived extracellular vesicles to the pathogenesis of COVID-19, and discuss therapeutic strategies that target the endothelium in patients with COVID-19.     

Nanotechnology: Advantages and drawbacks in the field of construction and building materials

Nanotechnology seems to hold the key that allows construction and building materials to replicate the features of natural systems improved until perfection during millions of years. This paper reviews current knowledge about nanotechnology and nanomaterials used by the construction industry. It covers the nanoscale analysis of Portland cement hydration products, the use of nanoparticles to increase the strength and durability of cimentitious composites, the photocatalytic capacity of nanomaterials and also nanotoxicity risks.     

Memory Fault Modeling Trends: A Case Study

In recent years, embedded memories are the fastest growing segment of system on chip. They therefore have a major impact on the overall Defect per Million (DPM). Further, the shrinking technologies and processes introduce new defects that cause previously unknown faults; such faults have to be understood and modeled in order to design appropriate test techniques that can reduce the DPM level. This paper discusses a new memory fault class, namely dynamic faults, based on industrial test results; it defines the concept of dynamic faults based on the fault primitive concept. It further shows the importance of dynamic faults for the new memory technologies and introduces a systematic way for modeling them. It concludes that current and future SRAM products need to consider testability for dynamic faults or leave substantial DPM on the table, and sets a direction for further research.     

AODVCS,a new bio-inspired routing protocol based on cuckoo search algorithm for mobile ad hoc networks

Mobile ad hoc networks (MANETs) are becoming an emerging technology that offer several advantages to users in terms of cost and ease of use. A MANET is a collection of mobile nodes connected by wireless links that form a temporary network topology that operates without a base station and centralized administration. Routing is a method through which information is forwarded from a transmitter to a specific recipient. Routing is a strategy that guarantees, at any time, the connection between any two nodes in a network. In this work, we propose a novel routing protocol inspired by the cuckoo search method. Our routing protocol is implemented using Network simulator 2. We chose Random WayPoint model as our mobility model. To validate our work, we opted for the comparison with the routing protocol ad hoc on-demand distance vector, destination sequence distance vector and the bio-inspired routing protocol AntHocNet in terms of the quality of service parameters: packet delivery ratio and end-to-end delay (E2ED).     

Carrier transport and related phenomena in MOS devices

Silicon-based devices are currently the most attractive group because they are functioning at room temperature and can be easily integrated into conventional silicon microelectronics. There are many models and simulation programs available to compute CV curves with quantum correction [Choi C-H, Wu Y, Goo JS, Yu Z, Dutton RW. IEEE Trans on Electron Devi 2000; 47(10): 1843; Croci S, Plossu C, Burignat S. J Mater Sci Mater Electron 2003; 14: 311; Soliman L, Duval E, Benzohra M, Lheurette E, Ketata K, Ketata M. Mater Sci Semicond Process 2001; 4: 163]. This work deals with the simulation of electron transfer through SiO₂ barrier of metal–oxide–semiconductor structure (MOS). The carrier density is given by a self consistent resolution of Schrödinger and Poisson equations and then the MOS capacitance is deduced and compared with results available in literature. As it is well known, the MOS capacitance–voltage profiling provides a simple determination of structure parameters. The extracted tunnel oxide thickness and substrate doping are compared with those used in the simulation. For the purpose to investigate the electron tunnelling through the barrier, we have used the transfer matrix approach. Using I–V simulations, we have shown that the traps in SiO₂ matrix have a drastic influence on electron tunnelling through the barrier. The trap-assisted contribution to the tunnelling current is included in many models [Maserjian J, Zamani N. J Appl Phys 1982; 53(1): 559; Houssa M, Stesmans A, Heyns MM. Semicond Sci Technol 2001; 16: 427; Aziz A, Kassmi K, Kassmi Ka, Olivie F. Semicond Sci Technol 2004; 19: 877; Wu You-Lin, Lin Shi-Tin. IEEE Trans Dev Mater Reliab 2006; 6(1): 75; Larcher L. IEEE Trans Electron Dev 2003; 50(5): 1246]; this is the basis for the interpretation of stress induced leakage current (SILC) and breakdown events. Memory effect becomes typical for this structure. We have studied the I–V dependence with trap parameters.     

Performance evaluation of OFDM and single‐carrier systems using frequency domain equalization and phase modulation

In this paper, we study the performance of the continuous phase modulation (CPM)‐based orthogonal frequency division multiplexing (CPM‐OFDM) system. Also, we propose a CPM‐based single‐carrier frequency domain equalization (CPM‐SC‐FDE) structure for broadband wireless communication systems. The proposed structure combines the advantages of the low complexity of SC‐FDE, in addition to exploiting the channel frequency diversity and the power efficiency of CPM. Both the CPM‐OFDM system and the proposed system are implemented with FDE to avoid the complexity of the equalization. Two types of frequency domain equalizers are considered and compared for performance evaluation of both systems; the zero forcing (ZF) equalizer and the minimum mean square error (MMSE) equalizer. Simulation experiments are performed for a variety of multipath fading channels. Simulation results show that the performance of the CPM‐based systems with multipath fading is better than their performance with single path fading. The performance over a multipath channel is at least 5 and 12 dB better than the performance over a single path channel, for the CPM‐OFDM system and the proposed CPM‐SC‐FDE system, respectively. The results also show that, when CPM is utilized in SC‐FDE systems, they can outperform CPM‐OFDM systems by about 5 dB. Copyright © 2010 John Wiley & Sons, Ltd.