Improved control strategy of DFIG-based wind turbines using direct torque and direct power control techniques

This paper presents different control strategies for a variable-speed wind energy conversion system (WECS), based on a doubly fed induction generator. Direct Torque Control (DTC) with Space-Vector Modulation is used on the rotor side converter. This control method is known to reduce the fluctuations of the torque and flux at low speeds in contrast to the classical DTC, where the frequency of switching is uncontrollable. The reference for torque is obtained from the maximum power point tracking technique of the wind turbine. For the grid-side converter, a fuzzy direct power control is proposed for the control of the instantaneous active and reactive power. Simulation results of the WECS are presented to compare the performance of the proposed and classical control approaches.Peer reviewedFinal Accepted Versio

Effect of angiotensin-converting enzyme inhibitor and angiotensin receptor blocker initiation on organ support-free days in patients hospitalized with COVID-19

IMPORTANCE Overactivation of the renin-angiotensin system (RAS) may contribute to poor clinical outcomes in patients with COVID-19. Objective To determine whether angiotensin-converting enzyme (ACE) inhibitor or angiotensin receptor blocker (ARB) initiation improves outcomes in patients hospitalized for COVID-19. DESIGN, SETTING, AND PARTICIPANTS In an ongoing, adaptive platform randomized clinical trial, 721 critically ill and 58 non–critically ill hospitalized adults were randomized to receive an RAS inhibitor or control between March 16, 2021, and February 25, 2022, at 69 sites in 7 countries (final follow-up on June 1, 2022). INTERVENTIONS Patients were randomized to receive open-label initiation of an ACE inhibitor (n = 257), ARB (n = 248), ARB in combination with DMX-200 (a chemokine receptor-2 inhibitor; n = 10), or no RAS inhibitor (control; n = 264) for up to 10 days. MAIN OUTCOMES AND MEASURES The primary outcome was organ support–free days, a composite of hospital survival and days alive without cardiovascular or respiratory organ support through 21 days. The primary analysis was a bayesian cumulative logistic model. Odds ratios (ORs) greater than 1 represent improved outcomes. RESULTS On February 25, 2022, enrollment was discontinued due to safety concerns. Among 679 critically ill patients with available primary outcome data, the median age was 56 years and 239 participants (35.2%) were women. Median (IQR) organ support–free days among critically ill patients was 10 (–1 to 16) in the ACE inhibitor group (n = 231), 8 (–1 to 17) in the ARB group (n = 217), and 12 (0 to 17) in the control group (n = 231) (median adjusted odds ratios of 0.77 [95% bayesian credible interval, 0.58-1.06] for improvement for ACE inhibitor and 0.76 [95% credible interval, 0.56-1.05] for ARB compared with control). The posterior probabilities that ACE inhibitors and ARBs worsened organ support–free days compared with control were 94.9% and 95.4%, respectively. Hospital survival occurred in 166 of 231 critically ill participants (71.9%) in the ACE inhibitor group, 152 of 217 (70.0%) in the ARB group, and 182 of 231 (78.8%) in the control group (posterior probabilities that ACE inhibitor and ARB worsened hospital survival compared with control were 95.3% and 98.1%, respectively). CONCLUSIONS AND RELEVANCE In this trial, among critically ill adults with COVID-19, initiation of an ACE inhibitor or ARB did not improve, and likely worsened, clinical outcomes. TRIAL REGISTRATION ClinicalTrials.gov Identifier: NCT0273570

A dnaN plasmid shuffle strain for rapid in vivo analysis of mutant Escherichia coli β clamps provides insight into the role of clamp in umuDC-mediated cold sensitivity.

The E. coli umuDC gene products participate in two temporally distinct roles: UmuD2C acts in a DNA damage checkpoint control, while UmuD'2C, also known as DNA polymerase V (Pol V), catalyzes replication past DNA lesions via a process termed translesion DNA synthesis. These different roles of the umuDC gene products are managed in part by the dnaN-encoded β sliding clamp protein. Co-overexpression of the β clamp and Pol V severely blocked E. coli growth at 30°C. We previously used a genetic assay that was independent of the ability of β clamp to support E. coli viability to isolate 8 mutant clamp proteins (βQ61K, βS107L, βD150N, βG157S, βV170M, βE202K, βM204K and βP363S) that failed to block growth at 30°C when co-overexpressed with Pol V. It was unknown whether these mutant clamps were capable of supporting E. coli viability and normal umuDC functions in vivo. The goals of this study were to answer these questions. To this end, we developed a novel dnaN plasmid shuffle assay. Using this assay, βD150N and βP363S were unable to support E. coli viability. The remaining 6 mutant clamps, each of which supported viability, were indistinguishable from β+ with respect to umuDC functions in vivo. In light of these findings, we analyzed phenotypes of strains overexpressing either β clamp or Pol V alone. The strain overexpressing β+, but not those expressing mutant β clamps, displayed slowed growth irrespective of the incubation temperature. Moreover, growth of the Pol V-expressing strain was modestly slowed at 30°, but not 42°C. Taken together, these results suggest the mutant clamps were identified due to their inability to slow growth rather than an inability to interact with Pol V. They further suggest that cold sensitivity is due, at least in part, to the combination of their individual effects on growth at 30°C

Sinorhizobium meliloti YbeY is a zinc-dependent single-strand specific endoribonuclease that plays an important role in 16S ribosomal RNA processing

Single-strand specific endoribonuclease YbeY has been shown to play an important role in the processing of the 3' end of the 16S rRNA in Escherichia coli. Lack of YbeY results in the accumulation of the 17S rRNA precursor. In contrast to a previous report, we show that Sinorhizobium meliloti YbeY exhibits endoribonuclease activity on single-stranded RNA substrate but not on the double-stranded substrate. This study also identifies the previously unknown metal ion involved in YbeY function to be Zn2+ and shows that the activity of YbeY is enhanced when the occupancy of zinc is increased. We have identified a pre-16S rRNA precursor that accumulates in the S. meliloti ΔybeY strain. We also show that ΔybeY mutant of Brucella abortus, a mammalian pathogen, also accumulates a similar pre-16S rRNA. The pre-16S species is longer in alpha-proteobacteria than in gamma-proteobacteria. We demonstrate that the YbeY from E. coli and S. meliloti can reciprocally complement the rRNA processing defect in a ΔybeY mutant of the other organism. These results establish YbeY as a zinc-dependent single-strand specific endoribonuclease that functions in 16S rRNA processing in both alpha- and gamma-proteobacteria.National Institutes of Health (U.S.) (Grant GM31030

Effect of overexpression of the different <i>umuDC</i> gene products on growth of AB1157.

<p>Average colony diameters of pGB2 (control), pGY9739 (UmuD₂C) or pGY9738 (UmuD'₂C) transformants of strain AB1157 following growth at either 30°C or 42°C, as noted, are shown. No colonies were observed for the AB1157 pGY9739 transformant. Experiments were performed at least twice. Error bars represent one standard deviation. <i>P</i>-values ≤0.05 are indicated, and were calculated using the Student's <i>t</i>-test.</p

Respective abilities of mutant β clamp proteins to support DNA damage-induced mutagenesis.

<p>Frequencies of (<b>A</b>) UV- or (<b>B</b>) MMS-induced mutagenesis were measured as described in <i>Material and Methods</i> using strains RW118 (WT; <i>dnaN⁺ umuD⁺C⁺</i>), RW120 (ΔumuD; <i>dnaN⁺</i> Δ<i>umuDC595</i>::<i>cat</i>), or the <i>umuD⁺C⁺</i> plasmid shuffle strains MS202 (β⁺), MS203 (β^Q61K), MS204 (β^S107L), MS205 (β^G157S), MS206 (β^V170M), MS207 (β^E202K) and MS208 (β^M204K), as indicated. Results represent the average of 5 independent determinations. Error bars represent one standard deviation. <i>P</i>-values ≤0.05 are indicated, and were calculated using the Student's <i>t</i>-test.</p

Ability of mutant β clamp proteins to support viability of <i>E. coli</i>.

a<p>See <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0098791#pone-0098791-t001" target="_blank">Table 1</a> for a description of the plasmids.</p>b<p>Amino acid substitutions are indicated in superscript (<i>e.g</i>., Q61K represents a lysine substitution of residue Q61).</p>c<p>Amp^R CFU/Cam^R CFU is a direct measure of the fraction of Cam^R pACM clones bearing the Amp^R pAMP<i>dnaN⁺</i> plasmid. It was determined by selecting at random colonies that had been passaged for ∼100 generations on LB-Cam plates and patching them onto LB-Amp and LB-Cam plates. Ratios (Amp^R CFU/Cam^R CFU) observed for each plasmid are shown, while the % frequency is shown in parentheses. At least 1 representative clone for each Cam^R and Amp^S strain identified was further characterized to verify the presence of the chromosomal <i>dnaN^–1FS</i> allele using diagnostic PCR and <i>Xho</i>I restriction, as well as nucleotide sequence of the plasmid-encoded <i>dnaN</i> allele.</p>d<p>Viability refers to the ability of the Cam^R transforming plasmid to support growth of <i>E. coli</i> in the absence of pAMP<i>dnaN⁺</i>. Symbols are as follows: –, plasmid is unable to support viability of <i>E. coli</i>, meaning 100% of the CFUs are resistant to both Amp and Cam after ∼100 generations of growth under selection for Cam^R; +, plasmid is able to support viability of <i>E. coli</i>.</p>e<p>Plasmid pACMβ5A expresses the β^148–152 mutant, which contains alanines in place of residues H148-R152 <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0098791#pone.0098791-Sutton2" target="_blank">[10]</a>. This mutation failed to support <i>E. coli</i> viability when crossed onto the bacterial chromosome <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0098791#pone.0098791-Heltzel1" target="_blank">[6]</a>, and serves as an additional negative control for the plasmid shuffle assay.</p

Design of the <i>dnaN^–1FS</i> allele and its use in the plasmid shuffle assay.

<p>(<b>A</b>) Genomic structure of the <i>dnaA-dnaN-recF</i> operon. Genes in grey are essential for cell viability, while those in white are non-essential. Blackened triangles represent approximate positions of confirmed promoters, based on EcoGene 3.0 (<a href="http://www.ecogene.org" target="_blank">http://www.ecogene.org</a>). Gross structure of the <i>dnaA–dnaN^–1FS–tet–recF</i> cassette is depicted below. Δ<i>Xho</i>I represents the approximate location of the –1 frameshift mutation present within the <i>dnaN</i>^{–<i>1FS</i>} allele. The <i>dnaN</i>^{–<i>1FS</i>} allele is predicted to express a protein of 134 residues: the N-terminal 49 residues are identical to the wild-type β clamp protein (white), while the C-terminal 85 residues are distinct and result from the −1 frameshift mutation (light grey). The majority of the <i>dnaN^–1FS</i> allele is not translated (black), due to the premature stop codon at position 135 resulting from the altered reading frame. Relative positions of oligonucleotide primer pairs (see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0098791#pone-0098791-t001" target="_blank">Table 1</a>) used for diagnostic PCR amplification or nucleotide sequence analysis are shown. Expected sizes (in bp) for products of PCR amplified fragments using the noted primer pairs are indicated. (<b>B</b>) The MS201 strain contains <i>dnaN^–1FS</i> allele on its chromosome, and bears the Amp^R plasmid pAMP<i>dnaN⁺</i>, which expresses physiological levels of wild type β clamp that supports viability. After transforming strain MS201 to Cam^R with pACM/pACM-derivatives containing the indicated <i>dnaN</i> allele, representative pAMP<i>dnaN⁺</i> and pACM (or pACM derivative) double transformants are passaged for ∼100 generations before patching onto LB-Amp and LB-Cam plates to score for pAMP<i>dnaN⁺</i> retention (<i>i.e.</i>, Amp^R). If the mutant clamp expressed from the pACM plasmid can support viability, pAMP<i>dnaN⁺</i> is lost, and cells display an Amp^S Cam^R phenotype. If the mutant clamp expressed from pACM cannot support viability, the wild type clamp-expressing plasmid pAMP<i>dnaN⁺</i> is retained, and cells display an Amp^R Cam^R phenotype. As controls for strains that readily lost pAMP<i>dnaN⁺</i>, we verified the nucleotide sequence of the plasmid encoded <i>dnaN</i> allele, as well as the structure of the chromosomal <i>dnaN^–1FS</i> allele (see <i>Materials and Methods</i>).</p

Summary of the positions of β clamp mutations.

<p>Shown are (<b>A</b>) front and (<b>B</b>) side views of the β clamp on DNA (PDB: 3BEP). Amino acid positions bearing substitutions that failed to confer cold sensitive growth when co-overexpressed with Pol V are represented as red sticks in the green clamp protomer. The two residues mutated in the <i>dnaN159</i>(Ts) allele (β159; G66→E and G174→A) are indicated as red spacefill in the blue clamp protomer. Loops 1–3 of clamp are higlighted in orange in the blue clamp protomer; loops 1 and 2 contacted DNA in the crystal <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0098791#pone.0098791-Georgescu1" target="_blank">[5]</a>, <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0098791#pone.0098791-Heltzel1" target="_blank">[6]</a>. The grey ovals represent the approximate location of the hydrophobic cleft present in each clamp protomer that contacts the CBM located in most, if not all clamp partners. This image was generated using PyMOL v1.5.0.2.</p

<i>E. coli</i> strains, plasmid DNAs and oligonucleotides used in this study.

a<p>The complete annotated genotype for strain RW118 is: <i>rpsL31 xyl-5 mtl-1 galK2 lacY1 tsx-33 supE44 thi-1 hisG4(Oc) argE3(Oc) araD139 thr-1 Δ(gpt-proA)62 sulA211.</i></p>b<p>CGSC: <i>E. coli</i> Genetic Stock Center, Yale University, New Haven, CT 06520, USA.</p>c<p>These strains were generated by plasmid shuffle; see <i>Material and Methods</i> for a detailed description of the <i>dnaN</i> plasmid shuffle assay. For strains MS202-MS208, the sequence of each plasmid encoded <i>dnaN</i> allele was verified by automated nucleotide sequence analysis, and the –1 frameshift mutation in the <i>dnaN^–1FS</i> allele was confirmed by diagnostic PCR and <i>Xho</i>I restriction analysis.</p>d<p>The complete annotated genotype for strain AB1157 is: <i>xyl-5 mtl-1 galK2 rpsL31 kdgK51 lacY1 tsx-33 supE44 thi-1 leuB6 hisG4(Oc) mgl-51 argE3(Oc) rfbD1 proA2 ara-14 thr-1 qsr-9 qin-111.</i></p>e<p>The complete annotated genotype for strain MG1655 is: <i>ilvG rfb-50 rph-1</i>.</p>f<p>The sequence corresponding to the <i>Xho</i>I restriction endonuclease site (CTCGAG) within the <i>dnaN</i>^{–<i>1FS</i>} allele, which contains a C→T substitution and −1 dG frameshift (CTTAG), is shown in lower case italics.</p