Search results for "recte"
showing 10 items of 463 documents
Extended causal modeling to assess Partial Directed Coherence in multiple time series with significant instantaneous interactions.
2010
The Partial Directed Coherence (PDC) and its generalized formulation (gPDC) are popular tools for investigating, in the frequency domain, the concept of Granger causality among multivariate (MV) time series. PDC and gPDC are formalized in terms of the coefficients of an MV autoregressive (MVAR) model which describes only the lagged effects among the time series and forsakes instantaneous effects. However, instantaneous effects are known to affect linear parametric modeling, and are likely to occur in experimental time series. In this study, we investigate the impact on the assessment of frequency domain causality of excluding instantaneous effects from the model underlying PDC evaluation. M…
Staphylococcus aureus alpha-toxin. Production of functionally intact, site-specifically modifiable protein by introduction of cysteine at positions 6…
1993
Staphylococcal alpha-toxin, the prototype of an oligomerizing, pore-forming cytotoxin, is sensitive to biochemical modifications and cannot be labeled with biotin or fluorescein under preservation of its biological activity. In this study, we have used site-directed mutagenesis to introduce cysteine residues at positions 69, 130, and 186. Each mutant was fully and rapidly reactive with several sulfhydryl-specific reagents, indicating superficial location. Coupling of SH-groups with fluorescein-maleimide or biotin-maleimide was tolerated without loss of hemolytic activity at position 130, and the formed hexamers were visible on target cells by fluorescence microscopy and could be detected on…
Nucleoside Analogue Mutagenesis of a Single-Stranded DNA Virus: Evolution and Resistance
2012
ABSTRACT It has been well established that chemical mutagenesis has adverse fitness effects in RNA viruses, often leading to population extinction. This is mainly a consequence of the high RNA virus spontaneous mutation rates, which situate them close to the extinction threshold. Single-stranded DNA viruses are the fastest-mutating DNA-based systems, with per-nucleotide mutation rates close to those of some RNA viruses, but chemical mutagenesis has been much less studied in this type of viruses. Here, we serially passaged bacteriophage ϕX174 in the presence of the nucleoside analogue 5-fluorouracil (5-FU). We found that 5-FU was unable to trigger population extinction for the range of conce…
Distribution of Fitness Effects Caused by Single-Nucleotide Substitutions in Bacteriophage f1
2010
Empirical knowledge of the fitness effects of mutations is important for understanding many evolutionary processes, yet this knowledge is often hampered by several sources of measurement error and bias. Most of these problems can be solved using site-directed mutagenesis to engineer single mutations, an approach particularly suited for viruses due to their small genomes. Here, we used this technique to measure the fitness effect of 100 single-nucleotide substitutions in the bacteriophage f1, a filamentous single-strand DNA virus. We found that approximately one-fifth of all mutations are lethal. Viable ones reduced fitness by 11% on average and were accurately described by a log-normal dist…
Effect of mismatch repair on the mutation rate of bacteriophage ϕX174
2015
Viral mutation rates vary widely in nature, yet the mechanistic and evolutionary determinants of this variability remain unclear. Small DNA viruses mutate orders of magnitude faster than their hosts despite using host-encoded polymerases for replication, which suggests these viruses may avoid post-replicative repair. Supporting this, the genome of bacteriophage ϕX174 is completely devoid of GATC sequence motifs, which are required for methyl-directed mismatch repair in Escherichia coli . Here, we show that restoration of the randomly expected number of GATC sites leads to an eightfold reduction in the rate of spontaneous mutation of the phage, without severely impairing its replicative capa…
Review of Infrared Nanoantennas for Energy Harvesting
2016
The Sun is the greatest source of energy providing a continuous stream of power; its exploitation has stimulated several approaches and technologies to directly or indirectly achieve renewable energy. New devices, which exploit the thermal radiation created by the Sun, that is transferred in the form of electromagnetic waves into free space, and finally absorbed by the surface of the Earth, are under study. The aim of this contribution is to critically compare advantages and disadvantages of new types of suitable antennas operating at nanometers wavelengths, called nanoantennas, for infrared energy harvesting, focusing on the state of the art and its perspectives.
Optical Nanoantennas for Energy Harvesting
2016
In the last decade, the increasing demand for renewable energy has been leading to the development of new devices, which overcome the disadvantages of the traditional photovoltaic conversion and exploit the thermal radiation created by the Sun, that is transferred in the form of electromagnetic waves into free space and finally absorbed by the surface of the Earth [1-2]. These new devices, called nanoantennas, have only recently been considered thanks to the development of electron beam lithography and similar techniques. Nanoantennas operate at nanometers wavelengths and their dimensions range from a few hundred nanometres to a few microns. They exhibit potential advantages in terms of pol…
A Novel Plasmonic Nanoantenna for High Efficiency Energy Harvesting Applications
2020
In this paper, the results of a geometric investigation of plasmonic nanoantennas for energy harvesting applications in terms of field enhancement and available power are presented. Optimum performances are obtained by a particular arrow-shaped bowtie nanoantennas geometry. The novel nanoantenna geometry is here presented. The simulations of the novel nanoantennas made of aluminium, on a three-layers substrate, composed by silicon, silicon oxide, and aluminium, carried out with CST 2018 tool, are reported and compared with the classical bowtie nanoantennas ones. This study can guide both the engineering and the fabrication of plasmonic nanoantennas.
A 3.3 V Output Voltage Optical Plasmonic Solar Energy Harvester
2021
In this paper, for the first time, the design of a solar energy-harvester (EH) based on plasmonic optical nanorectennas and without the step-up converter is presented. The novel optical harvester with a 49497∗14286 nanoarray of about 21,21 mm2 presents an output voltage value of 3.3 V and an output current of 10 mA.
A 2.6 V-10 μa Nanorectenna Harvester based on thermal radiation of the car exhaust system
2021
In this paper, for the first time, the design and simulation of a thermal nanorectenna energy harvester for harvesting the electromagnetic energy from the car exhaust system is presented. The nanorectenna system is composed of three gold arrow-bowtie nanoantennas with different resonance frequencies and a geometric nanodiode in the feed gap of each nanoantenna. The resonance frequencies at about 50 THz, 65 THz, and 83 THz correspond to the frequencies of the thermal radiation emitted from the exhaust tailpipe, catalytic converter, and manifold, respectively. The proposed $2.6 mathbf{V}-10 mumathbf{A}$ Energy Harvester with a nanoarray area of about 0,05 mm2 represents an optimum solution to…