Flexible torque control for wind turbines considering frequency response under wind speed crossing region

The operational range of a wind turbine is typically divided into two regions based on wind speed: below and above the rated wind speed. The turbine switches between these two regions depending on the prevailing wind speed; however, during the transition, the generator may undergo transient shocks in torque, which can negatively impact both the mechanical load of the turbine and the reliability of the power system. This article presents a flexible torque control method for wind turbines, specifically designed to handle the transition between wind speed regions when the turbine is participating in frequency regulation. First, the anomalies in generator torque caused by traditional torque control methods during frequency response scenarios are analyzed. Next, two methods—dynamic deloading and flexible torque control—are developed to address these issues. The developed methods set transition regions based on generator speed, which helps to reduce the impact of transient changes in generator torque. Importantly, the addition of transition regions does not require additional feedback, making the controller easy to implement. The response characteristics of the proposed methods are then analyzed under different deloading factors and wind speeds using model linearization. Simulation studies are presented to verify the effectiveness of the proposed methods. Overall, this study demonstrates the potential value of flexible torque control methods for wind turbines, which can help to mitigate the negative impact of torque shocks and improve the reliability and efficiency of wind power systems

Three Pairs of New Spirocyclic Alkaloid Enantiomers From the Marine-Derived Fungus Eurotium sp. SCSIO F452

Three pairs of new spirocyclic alkaloid enantiomers eurotinoids A–C (1–3), as well as a known biogenetically related racemate dihydrocryptoechinulin D (4) were isolated from a marine-derived fungus Eurotium sp. SCSIO F452. Their structures were determined by spectroscopic analyses and electronic circular dichroism (ECD) calculations. Compounds 1 and 2 represent the first two “meta” products from a non-stereoselective [4 + 2] Diels-Alder cycloaddition presumably between an enone group of a diketopiperazine alkaloid and a diene group of a benzaldehyde derivative via a new head-to-tail coupling mode biosynthetically, while 3 and 4 were “ortho” products. Their enantiomers exhibited different antioxidative and cytotoxic activities. The modes of action were investigated by a preliminary molecular docking study

Analysis of Frequency Regulation Capability and Fatigue Loads of Wind Turbine Based on Over-Speed Control

This study primarily analyzes the frequency regulation capability and fatigue loads of wind turbines based on over-speed control. Initially, a small-signal model of the wind turbine is established, which describes the output characteristics of the wind turbine under different control modes and wind speeds. Next, the model is used to analyze the wind turbine’s frequency regulation capability and to calculate the optimal frequency regulation parameter range based on the phase margin. Finally, a combination of frequency domain and time domain analysis is used to examine the influence of over-speed control on the fatigue loads of low-speed shafts, towers, and blades, which determines the wind speed range suitable for frequency regulation. The Fast (Fatigue, Aerodynamics, Structures, and Turbulence) Code V8 is used to simulate the dynamic characteristics of the wind turbine

Engineering the biosynthesis of fungal nonribosomal peptides

Covering: 2011 up to the end of 2021. Fungal nonribosomal peptides (NRPs) and the related polyketide-nonribosomal peptide hybrid products (PK-NRPs) are a prolific source of bioactive compounds, some of which have been developed into essential drugs. The synthesis of these complex natural products (NPs) utilizes nonribosomal peptide synthetases (NRPSs), multidomain megaenzymes that assemble specific peptide products by sequential condensation of amino acids and amino acid-like substances, independent of the ribosome. NRPSs, collaborating polyketide synthase modules, and their associated tailoring enzymes involved in product maturation represent promising targets for NP structure diversification and the generation of small molecule unnatural products (uNPs) with improved or novel bioactivities. Indeed, reprogramming of NRPSs and recruiting of novel tailoring enzymes is the strategy by which nature evolves NRP products. The recent years have witnessed a rapid development in the discovery and identification of novel NRPs and PK-NRPs, and significant advances have also been made towards the engineering of fungal NRP assembly lines to generate uNP peptides. However, the intrinsic complexities of fungal NRP and PK-NRP biosynthesis, and the large size of the NRPSs still present formidable conceptual and technical challenges for the rational and efficient reprogramming of these pathways. This review examines key examples for the successful (and for some less-successful) re-engineering of fungal NRPS assembly lines to inform future efforts towards generating novel, biologically active peptides and PK-NRPs.</p

Diverse Secondary Metabolites from the Coral-Derived Fungus Aspergillus hiratsukae SCSIO 5Bn1003

Three new metabolites, including a cyclic tetrapeptide asperhiratide (1), an ecdysteroid derivative asperhiratine (2), and a sesquiterpene lactone asperhiratone (3), were isolated and identified from the soft coral-derived fungus Aspergillus hiratsukae SCSIO 5Bn1003, together with 10 known compounds. Their structures were elucidated via spectroscopic analysis, X-ray diffraction analysis, and electronic circular dichroism calculations. In addition, the absolute configuration of 1 was determined by Marfey&rsquo;s technique and an analysis of the acid hydrolysates using a chiral phase HPLC column. Among all the compounds, 6 and 8 showed medium cytotoxic activities against four tumor cell lines (SF-268, HepG-2, MCF-7, and A549), with IC50 values ranging from 31.03 &plusmn; 3.04 to 50.25 &plusmn; 0.54 &micro;M. Meanwhile, they strongly inhibited &alpha;-glucosidase activities, with IC50 values of 35.73 &plusmn; 3.94 and 22.00 &plusmn; 2.45 &micro;M, which were close to and even stronger than the positive control acarbose (IC50 = 32.92 &plusmn; 1.03 &micro;M). Compounds 6&ndash;8 showed significant antibacterial activities against Bacillus subtilis, with MIC values of 10.26 &plusmn; 0.76 &micro;M, 17.00 &plusmn; 1.25 &micro;M, and 5.30 &plusmn; 0.29 &micro;M, respectively. Compounds 9 and 12 exhibited potent radical scavenging activities against DPPH, with IC50 values of 12.23 &plusmn; 0.78 &micro;M and 7.38 &plusmn; 1.16 &micro;M. In addition, asperhiratide (1) was evaluated for anti-angiogenic activities in the in vivo zebrafish model, which showed a weak inhibitory effect on intersegmental vessel (ISV) formation

Noninvasive diagnosis of significant liver inflammation in patients with chronic hepatitis B in the indeterminate phase

ABSTRACTThe presence of significant liver inflammation is an important indication for antiviral treatment in patients with chronic hepatitis B (CHB) in the indeterminate phase. We aimed to establish a non-invasive nomogram to predict significant liver inflammation in these patients. A total of 195 CHB patients in the indeterminate phase were randomly split into training and validation sets. The least absolute shrinkage and selection operator and logistic regression were applied to identify risk factors and establish a predictive model. A calibration curve, decision curve analysis (DCA), and receiver operating characteristic (ROC) curve were applied to assess the performance of the nomogram. The median age was 42.0 y and 59.5% of the patients were male. Alkaline phosphatase, γ-glutamyl transpeptidase, and prothrombin time were independent predictors for significant liver inflammation and selected to establish the AGP-nomogram. The calibration plot demonstrated that the predicted results matched the actual values. The DCA showed a high net benefit when the threshold probability was 25-83% in the training set and 31-100% in the validation set. The areas under ROC curves of AGP-nomogram in predicting significant inflammation were significantly higher than ALT in the training set (0.744 vs. 0.642, P = 0.049) and validation set (0.766 vs. 0.660, P = 0.047). The ability of AGP-nomogram in predicting advanced inflammation was also superior to ALT. The AGP-nomogram can accurately identify significant inflammation in CHB patients in the indeterminate phase, and its application may reduce the need for liver biopsy and help identify candidates for antiviral treatment.Abbreviations: AASLD: American Association for the Study of Liver Diseases; ALB: albumin; ALP: alkaline phosphatase; ALT: alanine aminotransferase; APRI: aspartate aminotransferase-to-platelet ratio index; AST: aspartate aminotransferase; AUROC: area under the receiver operating characteristic curve; CHB: chronic hepatitis B; CI: confidence interval; DCA: decision curve analysis; FIB-4: fibrosis index based on the four factors; GLB: globulin; GGT: γ-glutamyl transpeptidase; HBcAb: hepatitis B core antibody; HBeAg: hepatitis B e antigen; HBsAg: hepatitis B surface antigen; HBV: hepatitis B virus; HCC: hepatocellular carcinoma; HIV: human immunodeficiency virus; INR: international-normalized ratio; IQR: interquartile range; LASSO: least absolute shrinkage and selection operator; LB: liver biopsy; LR: Likelihood ratio; NAFLD: non-alcoholic fatty liver disease; NPV: negative predictive value; PLT: platelets; PPV: positive predictive value; PT: prothrombin time; ROC: receiver operating characteristic; TB: total bilirubin; TE: transient elastography; ULN: upper limit of normal

Variecolortins A–C, Three Pairs of Spirocyclic Diketopiperazine Enantiomers from the Marine-Derived Fungus <i>Eurotium</i> sp. SCSIO F452

Three pairs of spirocyclic diketopiperazine enantiomers, variecolortins A–C (<b>1</b>–<b>3</b>), were isolated from marine-derived fungus <i>Eurotium</i> sp. SCSIO F452. Compound <b>1</b> possesses an unprecedented highly functionalized <i>seco</i>-anthronopyranoid carbon skeleton featuring a 2-oxa-7-azabicyclo[3.2.1]­octane core. Compounds <b>2</b> and <b>3</b> represent rare examples of a 6/6/6/6 tetracyclic cyclohexene–anthrone carbon scaffold. Their structures were determined by spectroscopic analyses, X-ray diffraction, and ECD calculations. Their enantiomers exhibited different antioxidative and cytotoxic activities, and their modes of action were investigated