Measuring the sensitivity of microwave components to bias variations

This paper presents a method to measure the sensitivity of microwave components to memory effects caused by the dc biasing circuit. This allows us to determine the required (impedance) properties of the dc biasing circuit to reduce slow dynamics under a certain level. The proposed measurement technique is based on the nonlinear vectorial network analyzer, which allows us to measure not only the absolute magnitude but also the absolute phase relations between the waves. Superimposing a multisine excitation signal on the dc bias allows us to measure the slow dynamics caused by the dc biasing circuit as a function of frequency and input power. Furthermore, it is verified whether or not the measured phenomena depend on the type of excitation signal.     

Obtaining accurate confidence regions for the estimated zeros andpoles in system identification problems

In this note, a method is proposed to generate improved uncertainty bounds on the poles and zeros of an identified system. The uncertainty ellipsoids are replaced by dedicated uncertainty regions with a given probability level. The method can be applied to Markov estimators in the time or frequency domain     

Finding the dominant source of distortion in two-stage op-amps

Although non-linear distortion is an important specification for op-amps, it is only determined at the end of the design in classical design flows, leaving the designers without a clue about its origin. Recently, the Best Linear Approximation (BLA) has been introduced to approximate non-linear systems. It allows to describe the behaviour of a non-linear system as a linear Frequency Response Function combined with a coloured noise source to describe respectively the wanted linear response and the distortion. To determine the dominant source of non-linear distortion, we combine the BLA with a classical noise analysis in this paper. The paper explains the BLA-based noise analysis and shows the result of this simulation-based analysis when applied to various op-amp architectures. The analysis pinpoints the non-linear hot-spots in an efficient way, without the use of special simulations, manual analytical calculations or modified transistor models.     

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.     

Experimental characterization of the nonlinear behavior of RF amplifiers

Using specifically designed broadband periodic random excitation signals, the best linear approximation of RF amplifiers is measured. The proposed technique: 1) takes into account the measurement uncertainty and the nonlinear distortions and 2) detects, quantifies, and classifies the nonlinear distortions with confidence bounds. The approach is suitable for the experimental characterization of existing amplifiers.     

Broadband versus stepped sine FRF measurements

In this paper, the required measurement time to measure a transfer function with a specified accuracy is analyzed. The waiting time that is needed to balance the transient induced errors against the noise errors is calculated. This allows one to decide under what conditions broad-band measurements are faster than stepped sine measurements     

Whole Genome Analysis of 335 New Bacterial Species from Human Microbiota Reveals a Huge Reservoir of Transferable Antibiotic Resistance Determinants

Background: The emergence and diffusion of strains of pathogenic bacteria resistant to antibiotics constitutes a real public health challenge. Antibiotic resistance genes (ARGs) can be carried by both pathogenic and non-pathogenic bacteria, including commensal bacteria from the human microbiota, which require special monitoring in the fight against antimicrobial resistance. Methods: We analyzed the proteomes of 335 new bacterial species from human microbiota to estimate its whole range of ARGs using the BLAST program against ARGs reference databases. Results: We found 278 bacteria that harbor a total of 883 potential ARGs with the following distribution: 264 macrolides-lincosamides-streptogramin, 195 aminoglycosides, 156 tetracyclines, 58 β-lactamases, 58 fosfomycin, 51 glycopeptides, 36 nitroimidazoles, 33 phenicols and 32 rifamycin. Furthermore, evolutionary analyses revealed the potential horizontal transfer with pathogenic bacteria involving mobile genetic elements such as transposase and plasmid. We identified many ARGs that may represent new variants in fosfomycin and β-lactams resistance. Conclusion: These findings show that new bacterial species from human microbiota should be considered as an important reservoir of ARGs that can be transferred to pathogenic bacteria. In vitro analyses of their phenotypic potential are required to improve our understanding of the functional role of this bacterial community in the development of antibiotic resistance.     

Broadband high-frequency hybrid

Analog integrated circuit designs are often differential and require differential-to-single-ended hybrids for spectral measurements. This paper describes a broadband, high-frequency hybrid, whose output signal is proportional to the difference of two input ports, i.e., proportional to the differential signal. The main novelty of this hybrid is its high bandwidth (two to three decades). Such high bandwidth is obtained through combining broadband structures: a pair of broadband impedances are used to scale the two incoming signals; a symmetric structure of two identical broadband directional couplers and a power combiner are used afterwards to obtain the differential signal. The high bandwidths of both the impedances, the directional couplers, and the power combiner make it possible to obtain a differential coupling factor and a common-mode rejection ratio which is frequency insensitive over several decades in frequency. Measurements support the statement that bandwidths of more than three decades can be obtained using the proposed hybrid.     

Towards an ideal data acquisition channel

A method is presented for compensating in real time for a nonideal transfer function of a data acquisition channel by means of a digital IIR (infinite impulse response) filter. Real-time compensation of the amplitude and phase characteristics of an acquisition channel so that the long-term error is less than ±0.01 dB and ±0.1°, respectively, has been obtained experimentally. It is shown that stability and linearity are the main requirements for the components of the data acquisition channel. Careful selection of the components and outlining of the antialias filter and the programmable amplifier is no longer necessary