A Novel PWM Scheme with Two Switching Frequencies and Wider Carrier to Improve the THD in Voltage Source Converters

The integration of renewable energy resources presents a significant set of technical and infrastructure challenges to power grid operation and control. Besides, it has been proven that it is less harmful to the environment. Power electronics technology has the capability to mitigate the effects of the issues imposed on the power system by the rapid expansion of renewable energy development and increased penetration level at the utility scale. Although power electronics technology is considered a promising potential solution, power conversion efficiency in the rectifiers and inverters must be improved to optimize system performance. A novel pulse width modulation technique is presented to improve the conversion efficiency. This method has two major concepts. First, widening the on-state of the converter's operation will increase the output fundamental component. Inverse sinusoidal pulse width modulation is one of the methods that can achieve this concept. Second, the rate of change in the information at the peak of the sinusoidal reference is relatively small. The modulation of this period has less significance in comparison to the rest of the reference cycle. Hence, a frequency modulation technique is applied to fulfill this task. The novel development and utilization of these two techniques in combination will prove that; in comparison to the sinusoidal pulse width modulation, the fundamental output will increase substantially. Also, this new technique extensively suppresses the harmonic distortion of the converter operation. Furthermore, these results are attained by using lower switching frequency to produce lower switching losses and improves converter operation efficiency

A Modulation Scheme for Floating Source Multilevel Inverter Topology with Increased Number of Output Levels

This paper presented and studied a new switching scheme for floating source multilevel inverters to produce more levels with the same number of switching devices. In the proposed scheme, the function of the dc sources, except the inner one, is to build up square wave or blocks that is close in the shape to the desired sinusoidal wave. The job of the inner switching devices is to increase the number of the levels to produce smother sinusoidal wave in the inverter output. This job can be done by adding or subtracting the value of the inner dc source to/from the blocks. The topology used in this paper is based on the conventional floating source multi-level inverter using two legs. This topology and modulation technique show substantial reduction in the total harmonics distortion when the modulation technique is the hybrid method. The performance of the proposed switching scheme in generating more levels has been evaluated by PSCAD/EMTDC simulation

Impact of phase locked loop with different types and control dynamics on resonance of DFIG system

In recent years, the doubly fed induction generator (DFIG) operates in a weak grid, rather than a strong grid due to the high proportion of wind energy into the power grid. The impedance interaction between the DFIG system and series and parallel compensated weak grid might cause the subsynchronous resonance (SSR) and high frequency resonance (HFR) in the DFIG system, respectively. Phase locked loop (PLL) is a popular grid synchronization technique, and the high bandwidth PLL can cause resonance at middle frequencies in the DFIG system. However, the impact of PLL types and their controller dynamics on the resonance in the DFIG system are not adequately researched. The impact of the PLL controller with different types, such as synchronous reference frame (SRF) and Lead/Lag PLL, is studied in this paper to fill this gap. Additionally, an improved PLL is proposed, which can guarantee the high phase margin and decrease the likelihood of the resonance at middle frequencies in the DFIG system under a weak grid. Moreover, the phase margin of the DFIG system impedance with an improved PLL is less sensitive to its controller parameters. Simulation and experimental results verify the effectiveness of the proposed method

Hardware Approach To Mitigate The Effects Of Module Mismatch In A Grid-Connected Photovoltaic System: A Review

This study reviews the hardware approach to mitigate the effects of module mismatch in a grid-connected photovoltaic (PV) system. Unlike software solutions, i.e. the maximum power tracking algorithm, hardware techniques are well suited to enhance energy yield because of their inherent ability to extract energy from the mismatched module. Despite the extra cost of the additional circuitry, hardware techniques have recently gained popularity because of their long-term financial benefits. Notwithstanding the growing interest in this topic, review papers that provide updates on the technological developments of the three main hardware solutions, namely micro inverter,DC power optimizer, and energy recovery circuits, are lacking. This is in contrast to software solutions, which have had a considerable number of reputable reviews. Thus, a comprehensive review paper is appropriate at this juncture to provide up-to-date information on the latest topologies, highlight their merits/drawbacks, and evaluate their comparative performance

Long-term results of a phase II study of synchronous chemoradiotherapy in advanced muscle invasive bladder cancer.

We conducted a phase I/II study investigating synchronous chemoradiotherapy with mitomycin C and infusional 5-fluorouracil (5-FU) in muscle invasive bladder cancer. Early dose escalation results were previously published. We report the long-term toxicity and efficacy results with the optimised regimen. Patients with muscle invasive bladder cancer with glomerular filtration rate >25 ml min(-1) were eligible. Mitomycin (12 mg m(-2) on day 1 only) and infusional 5-FU (500 mg m(-2) day(-1)) for 5 days were administered during weeks 1 and 4 of radiotherapy of 55 Gy in 20 fractions. A total of 41 patients were enrolled, median age was 68 years, 33 were male and eight female patients. Out of the 41 patients, 20 (49%) had hydronephrosis at presentation and 25 (62%) had T3b or T4 disease. Four patients experienced Grade III thrombocytopenia and three patients had Grade III neutropenia. There were no episodes of febrile neutropenia. Four patients experienced Grade III diarrhoea and 1 Grade III urgency and dysuria. Six patients did not undergo cystoscopic evaluation due to early metastatic spread although there was no clinical suggestion of bladder failure. In all, out of 35 evaluable patients, 25 (71%) had macroscopic complete response at 3-month cystoscopy, and biopsy confirmed in 24 out of 25. A total of 16 (39%) patients remain alive with a median follow-up of 50.7 (range 23.5-68.8) months, 14 with a functioning bladder with no reported long-term treatment-related bladder or bowel toxicity. Five out of 41 patients have undergone salvage cystectomy: two for persistent CIS, two T1 and one muscle invasive recurrence. Four patients have received intravesical chemotherapy, of whom two remain alive with a functioning bladder. Overall 12-, 24- and 60-month (m) survival rates were 68, 49 and 36%. Local and distant progression free rates were 82 and 86% at 12-m and 79 and 75% at 24-m. Organ preservation using multimodality therapy is feasible and safe, even in patients with poor renal reserve, and does not compromise salvage therapies. A national phase III trial BC2001 (www.bc2001.org.uk) exploring the effects of synchronous chemoradiotherapy with this regimen is currently recruiting

Epigenetic therapy in urologic cancers: an update on clinical trials

Epigenetic dysregulation is one of many factors that contribute to cancer development and progression. Numerous epigenetic alterations have been identified in urologic cancers including histone modifications, DNA methylation changes, and microRNA expression. Since these changes are reversible, efforts are being made to develop epigenetic drugs that restore the normal epigenetic patterns of cells, and many clinical trials are already underway to test their clinical potential. In this review we analyze multiple clinical trials (n=51) that test the efficacy of these drugs in patients with urologic cancers. The most frequently used epigenetic drugs were histone deacetylase inhibitors followed by antisense oligonucleotides, DNA methyltransferase inhibitors and histone demethylase inhibitors, the last of which are only being tested in prostate cancer. In more than 50% of the clinical trials considered, epigenetic drugs were used as part of combination therapy, which achieved the best results. The epigenetic regulation of some cancers is still matter of research but will undoubtedly open a window to new therapeutic approaches in the era of personalized medicine. The future of therapy for urological malignancies is likely to include multidrug regimens in which epigenetic modifying drugs will play an important role

Erratum to: 36th International Symposium on Intensive Care and Emergency Medicine

[This corrects the article DOI: 10.1186/s13054-016-1208-6.]

Intraperitoneal drain placement and outcomes after elective colorectal surgery: international matched, prospective, cohort study

Despite current guidelines, intraperitoneal drain placement after elective colorectal surgery remains widespread. Drains were not associated with earlier detection of intraperitoneal collections, but were associated with prolonged hospital stay and increased risk of surgical-site infections.Background Many surgeons routinely place intraperitoneal drains after elective colorectal surgery. However, enhanced recovery after surgery guidelines recommend against their routine use owing to a lack of clear clinical benefit. This study aimed to describe international variation in intraperitoneal drain placement and the safety of this practice. Methods COMPASS (COMPlicAted intra-abdominal collectionS after colorectal Surgery) was a prospective, international, cohort study which enrolled consecutive adults undergoing elective colorectal surgery (February to March 2020). The primary outcome was the rate of intraperitoneal drain placement. Secondary outcomes included: rate and time to diagnosis of postoperative intraperitoneal collections; rate of surgical site infections (SSIs); time to discharge; and 30-day major postoperative complications (Clavien-Dindo grade at least III). After propensity score matching, multivariable logistic regression and Cox proportional hazards regression were used to estimate the independent association of the secondary outcomes with drain placement. Results Overall, 1805 patients from 22 countries were included (798 women, 44.2 per cent; median age 67.0 years). The drain insertion rate was 51.9 per cent (937 patients). After matching, drains were not associated with reduced rates (odds ratio (OR) 1.33, 95 per cent c.i. 0.79 to 2.23; P = 0.287) or earlier detection (hazard ratio (HR) 0.87, 0.33 to 2.31; P = 0.780) of collections. Although not associated with worse major postoperative complications (OR 1.09, 0.68 to 1.75; P = 0.709), drains were associated with delayed hospital discharge (HR 0.58, 0.52 to 0.66; P < 0.001) and an increased risk of SSIs (OR 2.47, 1.50 to 4.05; P < 0.001). Conclusion Intraperitoneal drain placement after elective colorectal surgery is not associated with earlier detection of postoperative collections, but prolongs hospital stay and increases SSI risk

Guidelines for the use and interpretation of assays for monitoring autophagy (3rd edition)

In 2008 we published the first set of guidelines for standardizing research in autophagy. Since then, research on this topic has continued to accelerate, and many new scientists have entered the field. Our knowledge base and relevant new technologies have also been expanding. Accordingly, it is important to update these guidelines for monitoring autophagy in different organisms. Various reviews have described the range of assays that have been used for this purpose. Nevertheless, there continues to be confusion regarding acceptable methods to measure autophagy, especially in multicellular eukaryotes. For example, a key point that needs to be emphasized is that there is a difference between measurements that monitor the numbers or volume of autophagic elements (e.g., autophagosomes or autolysosomes) at any stage of the autophagic process versus those that measure fl ux through the autophagy pathway (i.e., the complete process including the amount and rate of cargo sequestered and degraded). In particular, a block in macroautophagy that results in autophagosome accumulation must be differentiated from stimuli that increase autophagic activity, defi ned as increased autophagy induction coupled with increased delivery to, and degradation within, lysosomes (inmost higher eukaryotes and some protists such as Dictyostelium ) or the vacuole (in plants and fungi). In other words, it is especially important that investigators new to the fi eld understand that the appearance of more autophagosomes does not necessarily equate with more autophagy. In fact, in many cases, autophagosomes accumulate because of a block in trafficking to lysosomes without a concomitant change in autophagosome biogenesis, whereas an increase in autolysosomes may reflect a reduction in degradative activity. It is worth emphasizing here that lysosomal digestion is a stage of autophagy and evaluating its competence is a crucial part of the evaluation of autophagic flux, or complete autophagy. Here, we present a set of guidelines for the selection and interpretation of methods for use by investigators who aim to examine macroautophagy and related processes, as well as for reviewers who need to provide realistic and reasonable critiques of papers that are focused on these processes. These guidelines are not meant to be a formulaic set of rules, because the appropriate assays depend in part on the question being asked and the system being used. In addition, we emphasize that no individual assay is guaranteed to be the most appropriate one in every situation, and we strongly recommend the use of multiple assays to monitor autophagy. Along these lines, because of the potential for pleiotropic effects due to blocking autophagy through genetic manipulation it is imperative to delete or knock down more than one autophagy-related gene. In addition, some individual Atg proteins, or groups of proteins, are involved in other cellular pathways so not all Atg proteins can be used as a specific marker for an autophagic process. In these guidelines, we consider these various methods of assessing autophagy and what information can, or cannot, be obtained from them. Finally, by discussing the merits and limits of particular autophagy assays, we hope to encourage technical innovation in the field

Elective cancer surgery in COVID-19-free surgical pathways during the SARS-CoV-2 pandemic: An international, multicenter, comparative cohort study

PURPOSE As cancer surgery restarts after the first COVID-19 wave, health care providers urgently require data to determine where elective surgery is best performed. This study aimed to determine whether COVID-19–free surgical pathways were associated with lower postoperative pulmonary complication rates compared with hospitals with no defined pathway. PATIENTS AND METHODS This international, multicenter cohort study included patients who underwent elective surgery for 10 solid cancer types without preoperative suspicion of SARS-CoV-2. Participating hospitals included patients from local emergence of SARS-CoV-2 until April 19, 2020. At the time of surgery, hospitals were defined as having a COVID-19–free surgical pathway (complete segregation of the operating theater, critical care, and inpatient ward areas) or no defined pathway (incomplete or no segregation, areas shared with patients with COVID-19). The primary outcome was 30-day postoperative pulmonary complications (pneumonia, acute respiratory distress syndrome, unexpected ventilation). RESULTS Of 9,171 patients from 447 hospitals in 55 countries, 2,481 were operated on in COVID-19–free surgical pathways. Patients who underwent surgery within COVID-19–free surgical pathways were younger with fewer comorbidities than those in hospitals with no defined pathway but with similar proportions of major surgery. After adjustment, pulmonary complication rates were lower with COVID-19–free surgical pathways (2.2% v 4.9%; adjusted odds ratio [aOR], 0.62; 95% CI, 0.44 to 0.86). This was consistent in sensitivity analyses for low-risk patients (American Society of Anesthesiologists grade 1/2), propensity score–matched models, and patients with negative SARS-CoV-2 preoperative tests. The postoperative SARS-CoV-2 infection rate was also lower in COVID-19–free surgical pathways (2.1% v 3.6%; aOR, 0.53; 95% CI, 0.36 to 0.76). CONCLUSION Within available resources, dedicated COVID-19–free surgical pathways should be established to provide safe elective cancer surgery during current and before future SARS-CoV-2 outbreaks