Stability Study and Nonlinear Analysis of DC-DC Power Converters with Constant Power Loads at the Fast Timescale

Rapidly growing distributed renewable networks make an increasing demand on various types of power converters to feed different loads. Power converters with constant power load are one typical configuration that can degrade the stability of the power conversion system due to the negative impedance characteristic. This paper presents a nonlinear analysis method using the developed complete-cycle solution matrix method by transforming the original linear time-variant system into a summation of segmented linear time-invariant systems. Thus, the stability of the nonlinear system can be studied using a series of the corresponding state transition matrix and saltation matrix. As this derived matrix contains all the comprehensive information relating to the system’s stability, the influence of the constant power load to system’s fast-timescale stability in both continuous conduction mode and the discontinuous conduction mode can be fully investigated and analyzed. The phenomena of fast-timescale instability around switching frequency for power converters with a constant power load are observed and investigated numerically. Finally, experimental results have proven the analysis and verified the effectiveness of the developed method

a meta-analysis of the 5-year efficacy and safety

Background The objective of this study was to compare the efficacy and safety of taxane (docetaxel or paclitaxel), cisplatin, and fluorouracil (Tax-PF) with cisplatin plus fluorouracil (PF) regimen by a meta-analysis of data retrieved from the literature. Methods Seven randomized clinical trials were identified, which included patients with advanced head and neck cancer who underwent induction chemotherapy with either a Tax-PF or PF protocol. The outcomes included the 3-year and 5-year overall survival (OS) and progression-free survival (PFS), overall response rate (ORR) and different types of adverse events. Results The 3-year OS rate (HR: 1.14; 95% CI: 1.03 to 1.25; P = 0.008), 3-year PFS rate (HR: 1.24; 95% CI: 1.08 to 1.43; P = 0.002), 5-year OS rate (HR: 1.30; 95% CI, 1.09 to 1.55;P = 0.003), 5-year PFS rate (HR: 1.39; 95% CI, 1.14 to 1.70; P = 0.001) and ORR to chemotherapy (OR 1.66; 95% CI, 1.35 to 2.05; P < 0.001) of the patients in the Tax-PF group were statistically superior to those in the PF group. In terms of toxicities, the incidence of febrile neutropenia (OR 2.36; 95% CI, 1.62 to 3.46; P < 0.001), alopecia (OR 8.22; 95% CI, 3.99 to 16.92; P < 0.001), diarrhea (OR 1.57; 95% CI, 1.05 to 2.36; P = 0.03) and leukopenia (OR 2.79; 95% CI, 1.86 to 4.21; P < 0.001) was higher in the Tax-PF group. Conclusion The Tax-PF induction chemotherapy improved PFS and OS, and the ORR was better as compared to PF- based therapy regimens at the cost of a higher incidence of adverse events

Enhance Connectivity of Promising Regions for Sampling-based Path Planning

Sampling-based path planning algorithms usually implement uniform sampling methods to search the state space. However, uniform sampling may lead to unnecessary exploration in many scenarios, such as the environment with a few dead ends. Our previous work proposes to use the promising region to guide the sampling process to address the issue. However, the predicted promising regions are often disconnected, which means they cannot connect the start and goal state, resulting in a lack of probabilistic completeness. This work focuses on enhancing the connectivity of predicted promising regions. Our proposed method regresses the connectivity probability of the edges in the x and y directions. In addition, it calculates the weight of the promising edges in loss to guide the neural network to pay more attention to the connectivity of the promising regions. We conduct a series of simulation experiments, and the results show that the connectivity of promising regions improves significantly. Furthermore, we analyze the effect of connectivity on sampling-based path planning algorithms and conclude that connectivity plays an essential role in maintaining algorithm performance.Comment: Accepted in Transactions on Automation Science and Engineering, 202

Method of Optimal Scheduling of Cascade Reservoirs based on Improved Chaotic Ant Colony Algorithm

Abstract: On the basis of the analysis of the basic information of the river basin reservoirs and application of chaotic ant swarm algorithm, the medium-and long-term optimization operation model is established, which regards the maximum annual generation capacity of the cascade hydropower stations as the main purpose. The simulation result shows the algorithm improves the total annual power generation of the cascade reservoirs, and is better than the basic chaotic ant colony solving method of reservoir operation model, finally provides an effective solution to solve the cascade reservoirs optimization operation problem

Method of Optimal Scheduling of Cascade Reservoirs based on Improved Chaotic Ant Colony Algorithm

On the basis of the analysis of the basic information of the river basin reservoirs and application of chaotic ant swarm algorithm, the medium-and long-term optimization operation model is established, which regards the maximum annual generation capacity of the cascade hydropower stations as the main purpose. The simulation result shows the algorithm improves the total annual power generation of the cascade reservoirs, and is better than the basic chaotic ant colony solving method of reservoir operation model, finally provides an effective solution to solve the cascade reservoirs optimization operation problem

Funktionsanalyse des Gens WDR66

Esophageal cancer has long been considered one of the deadliest malignancies and considerable controversy has surrounded its management. Esophageal cancer patients have a dismal prognosis, because of the late presentation of patients with this disease and the technical difficulty of an adequate surgical resection in the presence of advanced local and regional involvement. The most common histological type is esophageal squamous cell carcinoma (ESCC), which is distributed throughout the length of the esophagus. In order to achieve a more tailored therapy and, consequently, improved prognosis, we studied gene expression profiles of ESCC in comparison to that of normal esophageal squamous epithelium with the aim of characterizing the changes in gene expression that underlie ESCC progression. Laser capture microdissection of frozen specimens in collaboration with an experienced pathologist was applied to collect the cells from well-defined tumor areas. Whole human gene expression profiling of ESCC specimens (n=10) and normal esophageal squamous tissue (n=18) was performed using microarray technology. Microarray results were validated by quantitative real-time polymerase chain reaction (qRT-PCR) in a second and independent cohort (n=71) consisting of ESCC (n=25), normal esophagus (n=11), esophageal adenocarcinoma (n=13), gastric adenocarcinoma (n=15) and colorectal cancers (n=7). In order to understand the functional relevance of a newly identified marker gene, siRNA-mediated knockdown was performed in a human esophageal squamous cell carcinoma cell line, KYSE520, and the effects of this treatment were checked by another microarray analysis. A gene encoding WDR66, WD repeat-containing protein 66, was found whose expression was significantly high in ESCC specimens (P < 0.0001). High WDR66 expression was significantly associated with poor overall survival (P = 0.031) of patients suffering from ESCC. Multivariate Cox regression analysis revealed that WDR66 expression remained an independent prognostic factor (P = 0.042). WDR66 knockdown by RNA interference resulted particularly in changes of the expression of membrane components. This was validated by qRT-PCR and western blotting experiments in the human squamous cell carcinoma cell line KYSE520, providing independent evidence of the changes of Vimentin (VIM) and occluding (OCLN) expression associated with the WDR66 knockdown. Gene expression level of VIM was significantly down-regulated whereas OCLN expression was significantly higher in cells treated with WDR66 siRNA by qRT-PCR (VIM, P = 0.0286; OCLN, P = 0.0186). Detection of VIM and OLCN protein by immunoblotting showed that VIM expression was significantly down-regulated while the expression of OCLN was significantly higher in KYSE520 cells treated with WDR66 siRNA. Interestingly, VIM was highly expressed (P = 0.0008) while OCLN was less expressed (P < 0.0001) in ESCC specimens in comparison to normal esophagus. This may underline a central role of WDR66 for ESCC development. Furthermore, siRNA-mediated knockdown of WDR66 resulted in suppression of cell growth, reduced cancer cell motility and enhanced cancer cell apoptosis after addition of Staurosporine and 5-Fluorouracil. According to these studies, WDR66 might be a useful biomarker for risk stratification of ESCC. As a positive modulator of epithelial-mesenchymal transition, WDR66 expression is likely to play an important role in ESCC growth and invasion. Moreover, our functional studies point toward an important role of WDR66 for squamous carcinoma cell growth and motility. In the future, WDR66 might become a novel drug target for the treatment of esophageal squamous cell carcinoma.Karzinome der Speiseröhre werden schon lange als besonders gefährlich für den Patienten und ihre Behandlung wird weiterhin kontrovers diskutiert. Aufgrund der späten Vorstellung von Patienten mit dieser Krankheit und der technischen Schwierigkeit einer adäquaten chirurgischen Resektion bei Vorliegen von erweiterten lokalen und regionalen Rezidiven haben Patienten mit Karzinomen der Speiseröhre eine schlechte Prognose. Das häufigste Karzinom der Speiseröhre ist das Plattenepithelkarzinom des Ösophagus, dessen Verteilung sich über die gesamte Länge der Speiseröhre erstreckt. Um eine maßgeschneiderte Therapie und damit verbesserte Prognose zu erreichen, suchten wir hier nach Genen mit erhöhter Expression in Plattenepithelkarzinomen des Ösophagus. Dazu untersuchten wir die Genexpressionsprofile von Plattenepithelkarzinomen des Ösophagus im Vergleich zu normalem Ösophagus Plattenepithel. Die Laser-Mikrodissektion von gefrorenem Probenmaterial wurde angewandt, um in Zusammenarbeit mit einem erfahrenen Pathologen (Prof. Michael Vieth, Universität Bayreuth) nur Zellen aus wohldefinierten Tumorbereichen für die Untersuchung zu selektieren. Unter Verwendung der Mikroarray-Technologie wurde ein sogenanntes „Whole human Genome Expression Profiling“ von Ösophagus- Plattenepithelkarzinomproben (n = 10) und gesundem Ösophagus Gewebe (n = 18) durchgeführt. Die Ergebnisse der Microarrayanalyse wurden mittels quantitativer real-time Polymerase-Kettenreaktion (qRT-PCR) in einer zweiten und unabhängigen Kohorte (n = 71), bestehend aus Plattenepithelkarzinomen des Ösophagus (n = 25), gesundem Ösophagus (n = 11), Adenokarzinomen des Ösophagus (n = 13), Adenokarzinomen des Magens (n = 15) und des Kolons (n = 7) validiert. Um die funktionelle Relevanz eines neu identifizierten Markergens zu verstehen, wurde dessen Expression mittels siRNA-vermittelten Knockdown in einer humanen Plattenepithelkarzinom-Zelllinie unterdrückt und die Wirkung dieser Behandlung mit Hilfe einer weiteren Mikroarray-Analyse überprüft. Ein Gen, das WD repeat Protein enthaltende Gen 66 (WDR66), erwies sich als hochsignifikant überexprimiert in Plattenepithelkarzinomproben (P < 0,0001). Eine hohe WDR66 Expression von solchen Karzinomen korrelierte signifikant mit schlechtem Überleben (P = 0,031) der Patienten mit Ösophagus- Plattenepithelkarzinomen. Multivariate Cox Regressionsanalyse zeigte, dass die WDR66 Expression ein unabhängiger prognostischer Faktor (P = 0,042) blieb. WDR66 Knockdown durch RNA-Interferenz hatte insbesondere Einfluss auf Veränderungen der Expression von Membran-Komponenten. In Plattenepithelkarzinomen des Ösophagus im Vergleich zu gesundem Epithel wurde Vimentin stark exprimiert (P = 0,0008), während die Occludin Expression reduziert war (P < 0,0001). Die Microarray-Daten wurden mittels qRT-PCR und Western Blot Experimenten validiert. Der siRNA-vermittelte Knockdown von WDR66 führte außerdem zu einer Unterdrückung des Zellwachstums, zu reduzierter Zellmotilität und einer verstärkten Apoptose der Zellen nach Zugabe von Staurosporin und 5-Fluorouracil. Die Ergebnisse dieser Studie zeigen, dass WDR66 ein nützlicher Biomarker für die Risikostratifizierung von Patienten mit Ösophagus-Plattenepithelkarzinomen ist. Als positiver Modulator der Epithelial-mesenchymalen Transition (EMT) spielt WDR66 vermutlich eine wichtige Rolle für Wachstum und Invasion von Ösophagus- Plattenepithelkarzinomen. Dafür sprechen auch die Ergebnisse unserer funktionellen Studien im in-vitro System. Darüber hinaus ist WDR66 möglicherweise ein neues Drug-Target für die Behandlung von Plattenepithelkarzinomen des Ösophagus

Stroke-Related Changes in the Complexity of Muscle Activation during Obstacle Crossing Using Fuzzy Approximate Entropy Analysis

This study investigated the complexity of the electromyography (EMG) of lower limb muscles when performing obstacle crossing tasks at different heights in poststroke subjects versus healthy controls. Five poststroke subjects and eight healthy controls were recruited to perform different obstacle crossing tasks at various heights (randomly set at 10, 20, and 30% of the leg’s length). EMG signals were recorded from bilateral biceps femoris (BF), rectus femoris (RF), medial gastrocnemius, and tibialis anterior during obstacle crossing task. The fuzzy approximate entropy (fApEn) approach was used to analyze the complexity of the EMG signals. The fApEn values were significantly smaller in the RF of the trailing limb during the swing phase in poststroke subjects than healthy controls (p &lt; 0.05), which may be an indication of smaller number and less frequent firing rates of the motor units. However, during the swing phase, there were non-significant increases in the fApEn values of BF and RF in the trailing limb of the stroke group compared with those of healthy controls, resulting in a coping strategy when facing challenging tasks. The fApEn values that increased with height were found in the BF of the leading limb during the stance phase and in the RF of the trailing limb during the swing phase (p &lt; 0.05). The reason for this may have been a larger muscle activation associated with the increase in obstacle height. This study demonstrated a suitable and non-invasive method to evaluate muscle function after a stroke

Possible Causes of the Occurrence of a Rare Antarctic Sudden Stratospheric Warming in 2019

A minor Antarctic sudden stratospheric warming (SSW) with the strongest circulation changes since the first major SSW over the Antarctic was recorded in 2002 occurred in early September 2019. The diagnosis demonstrates two possible causes of this SSW. First, the tropical central Pacific warming is identified, which enhanced the amplitude of tropospheric planetary wavenumber 1 (W1) in the extratropics on the seasonal time scale. Second, the impact of intraseasonal convection anomalies similar to previous studies is also suggested here. The enhanced deep convection over the South Pacific Convergence Zone (SPCZ) in late August–early September excited a Rossby wave train to deepen an anomalous ridge, which significantly and persistently strengthened the tropospheric W1. The central Pacific warming and intraseasonal convection anomalies jointly provided the conditions for the occurrence of the Antarctic SSW in 2019 on different time scales. On the other hand, the difference of the stratospheric state between the Antarctic SSWs in 2019 and 2002 may be an important reason why the 2019 event did not meet the major SSW criteria. The stratospheric state before the 2019 SSW event is somewhat not as ideal as that of the 2002 event. Vertical planetary waves are, hence, more difficult to enter into the polar stratosphere, making it more difficult to trigger major events