Short-circuiting in dc lines affects the security and reliability of dc microgrid greatly. A short-circuit current calculation method for low-voltage dc microgrid is proposed in this paper. To solve the calculation of short-circuit current, a line model of bipolar which includes π type equivalent circuits, solid-state bidirectional switches with snubber circuits and freewheeling branches is adopted. The line current under different short-circuit fault types in dc bus is discussed and the circuit working mechanisms before and after solid-state switches action are analyzed, and then the analytic expressions of the line fault current are derived. Besides, the freewheeling loop of the short-circuit current is also analyzed after the removal of fault. The correctness of the analytic expressions is verified by MATLAB/Simulink simulations.
The SARS-CoV-2 pandemic has presented new challenges to food manufacturers. During the early phase of the pandemic, several large outbreaks of coronavirus disease 2019 (COVID-19) occurred in food manufacturing plants resulting in deaths and economic loss, with approximately 15% of personnel diagnosed as asymptomatic for COVID-19. Spread by asymptomatic and presymptomatic individuals has been implicated in large outbreaks of COVID-19. In March 2020, we assisted in implementation of environmental monitoring programs for SARS-CoV-2 in zones 3 and 4 of 116 food production facilities. All participating facilities had already implemented measures to prevent symptomatic personnel from coming to work. During the study period, from 17 March to 3 September 2020, 1.23% of the 22,643 environmental samples tested positive for SARS-CoV-2, suggesting that infected individuals were actively shedding virus. Virus contamination was commonly found on frequently touched surfaces such as doorknobs, handles, table surfaces, and sanitizer dispensers. Most processing plants managed to control their environmental contamination when they became aware of the positive findings. Comparisons of positive test results for plant personnel and environmental surfaces in one plant revealed a close correlation. Our work illustrates that environmental monitoring for SARS-CoV-2 can be used as a surrogate for identifying the presence of asymptomatic and presymptomatic personnel in workplaces and may aid in controlling infection spread.
Objective To explore the establishment of The designing experiment and to evaluate the effect of it in the practicality teaching. Methods During The intensive Training before Practice, to apply The Designing Experiment to the 542 students come frome 2004 clinical medical speciality.Results More than 75% students thought that The new teaching mode can stimulate their capability to study;many teachers agreed with The new teaching mode. Conclusion Application of experiment-designing course can increase the effect of students' learing and cultivate their comprehended qualities .
LINKED CONTENT This article is linked to Ponziani et al papers. To view these articles, visit https://doi.org/10.1111/apt.15996 and https://doi.org/10.1111/apt.16052
Background: The approach to managing the footprint area and reconstructing the tendon-bone interface (TBI) is critical for optimal healing. Purpose: To evaluate the outcomes of the semi–bone tunnel (SBT) technique using a double-row suture bridge combined with platelet-rich plasma (PRP) hydrogel for rotator cuff repair in a rabbit model. Study Design: Controlled laboratory study. Methods: A total of 48 New Zealand White rabbits were divided into 4 groups. The supraspinatus tendons were severed at the footprint to create a rotator cuff tear model in the surgical groups. Rabbits were treated with the traditional onto-surface repair (control group), SBT technique (SBT group), and SBT technique combined with PRP hydrogel implantation (SBT+PRP group). The rabbits without surgery were the normal group. At 8 weeks after surgery, macroscopic observation, magnetic resonance imaging (MRI) and micro–computed tomography (μCT) examinations, histological evaluations, and biomechanical tests were performed to assess the curative effects of the given treatments. Results: The MRI results showed that the repaired supraspinatus tendon presented a uniform signal, minimal inflammatory response, and the lowest signal-to-noise quotient value in the SBT+PRP group. The μCT results suggested that the SBT technique did not reduce the local bone mineral density in the TBI area compared with the onto-surface repair technique. The histological staining results showed that the regenerated TBI in the SBT+PRP group had a 4-layer structure similar to the natural tissue. The highest values for biomechanical properties were observed in the SBT+PRP group, and there was no significant difference between the SBT+PRP group and normal group. Conclusion: The SBT technique presented a better tendon-bone healing effect for rotator cuff tear in the rabbit model compared with the traditional onto-surface repair technique. The specimens in the SBT+PRP group had a similar TBI structure and biomechanical properties to the natural tissue. Clinical Relevance: The SBT technique can be an alternative surgical approach for rotator cuff repair, especially for moderate to large tears and cases requiring scaffold implantation.
We read with great interest the study written by Fan et al.1Fan Z. et al.Clin Gastroenterol Hepatol. 2020; 18: 1561-1566Abstract Full Text Full Text PDF PubMed Scopus (551) Google Scholar The authors report the clinical features of COVID-19–related liver damage. Because liver injury in COVID-19 patients is common and occurs especially in severe cases, the results of this study therefore are important. However, we do have some concerns about it. First, Fan et al1Fan Z. et al.Clin Gastroenterol Hepatol. 2020; 18: 1561-1566Abstract Full Text Full Text PDF PubMed Scopus (551) Google Scholar defined liver injury as any one of 6 parameters more than the upper limit of normal value. We understand that guidance or consensus on classification of COVID-19–related liver injury is lacking. However, a mild abnormality of these parameters should be classified more accurately as a COVID-19–associated liver biochemistry abnormality, and be distinguished from COVID-19–related liver injury, because such exceptions can be observed in a variety of situations.2Bangash M. et al.Lancet Gastroenterol Hepatol. 2020; 5: 529-530Abstract Full Text Full Text PDF PubMed Scopus (323) Google Scholar Furthermore, according to the recommendations from the American College of Gastroenterology, only 4 parameters including alanine aminotransferase, aspartate aminotransferase, alkaline phosphatase, and bilirubin are markers of liver injury, and the increases in these parameters suggest hepatocellular injury.3Kwo P.Y. et al.Am J Gastroenterol. 2017; 112: 18-35Crossref PubMed Scopus (623) Google Scholar Second, Fan et al1Fan Z. et al.Clin Gastroenterol Hepatol. 2020; 18: 1561-1566Abstract Full Text Full Text PDF PubMed Scopus (551) Google Scholar provided valuable comparisons between 2 groups. The results showed that significant differences were found for procalcitonin and C-reactive protein, but not for CD4+ T-cell counts, CD8+ T-cell counts, and CD3+ T-cell counts. However, why these markers were selected remains unclear. As mentioned by Fan et al,1Fan Z. et al.Clin Gastroenterol Hepatol. 2020; 18: 1561-1566Abstract Full Text Full Text PDF PubMed Scopus (551) Google Scholar laboratory examination was conducted every 3 days. It is not clear whether the results were calculated using the data on the day of admission or from data collected throughout the hospitalization, which may lead to bias. In the meantime, the normal baseline levels for each parameter were not given, so the readers cannot understand the meaning of these changes between groups compared with their baseline. Third, Fan et al1Fan Z. et al.Clin Gastroenterol Hepatol. 2020; 18: 1561-1566Abstract Full Text Full Text PDF PubMed Scopus (551) Google Scholar concluded that a significantly higher proportion of patients with abnormal liver function had received lopinavir/ritonavir, recommending caution when using lopinavir/ritonavir. In a recently published randomized controlled trial,4Cao B. et al.N Engl J Med. 2020; 382: 1787-1799Crossref PubMed Scopus (3823) Google Scholar there were no significant differences in alanine aminotransferase, aspartate aminotransferase, and bilirubin between the lopinavir/ritonavir group and the standard care group, showing its safety. We believe the problem may arise from a retrospective design of this study, and the fact that more patients used lopinavir/ritonavir in the abnormal liver function group may be owing to confounding resulting from age, sex, and the severity of illness. We found that there were some studies published on the topic of COVID-19–related liver injury in recent weeks. However, current studies inevitably encounter the problem of bias owing to their retrospective design. They also have not yet addressed the causes and mechanisms of liver damage associated with COVID-19 clearly. As described in a correspondence,5Peyrin-Biroulet L. Clin Gastroenterol Hepatol 2020 Mar 30. pii: S1542-3565(20)30431-6. https://doi.org/10.1016/j.cgh.2020.03.054. Epub ahead of print.Google Scholar we hope more studies with rigorous design are conducted in the near future. Clinical Features of COVID-19-Related Liver Functional AbnormalityClinical Gastroenterology and HepatologyVol. 18Issue 7PreviewSome patients with SARS-CoV-2 infection have abnormal liver function. We aimed to clarify the features of COVID-19-related liver damage to provide references for clinical treatment. Full-Text PDF ReplyClinical Gastroenterology and HepatologyVol. 18Issue 12PreviewWe thank Chen and Zhou,1 Lv et al,2 and Ye and Song3 for the comments on our study. We did not apply the definition of drug-induced liver injury from the European Association for the Study of the Liver Clinical Practice Guidelines in our study because the exact mechanism of COVID-19-related liver damage is still unclear (eg, a drug, the virus itself, immune response, or a mixture). We defined COVID-19-related liver injury based on elevation in any 1 of the 5 (not 6) parameters including alanine aminotransferase (ALT), aspartate aminotransferase (AST), γ-glutamyltransferase (GGT), alkaline phosphatase (ALP), and total bilirubin. Full-Text PDF Liver Function Should Be Monitored When Treating COVID-19 in Chronic HBV-Infected PatientsClinical Gastroenterology and HepatologyVol. 18Issue 13PreviewWe appreciate the comment by Lv et al on our article. In our study, we aimed to describe the characteristics of liver function and its relationship with severity of disease and prognosis of patients with severe acute respiratory syndrome–associated coronavirus 2 (SARS-CoV-2) and chronic hepatitis B virus (HBV) coinfection. Therefore, only patients with SARS-CoV-2 and chronic HBV coinfection were enrolled. Although we did not compare coronavirus disease 2019 (COVID-19) patients with HBV coinfection and patients with SARS-CoV-2 infection alone in our study, Chen et al1 found no significant differences in liver function parameters, discharge rate, length of stay, severity, and mortality between COVID-19 patients with and without HBV infection. Full-Text PDF
The object of this study was to compare the outcomes of the vacuum assisted closure (VAC) therapy and conventional wound care with dressing change for treatment of complex wounds in patients with replantation of amputated upper and lower extremities. Data of 43 patients with replantation of amputated extremities from May 2004 to December 2011 were reviewed. There were 18 wounds of 18 patients with replantation, which were treated by dressing change and 26 wounds of 25 patients by VAC therapy. The outcomes were evaluated by the survival rate of replanted extremities, growth of granulation tissue, interval between wound treatment and secondary procedure and eventual secondary wound coverage methods. Vascular thromboses were found in 3 patients with wound treatment by dressing change and 5 by VAC. All replants of two groups of patients survived after salvage procedures. The wound score was 3.6 ± 0.7 in the conventional dressing change group and 5.8 ± 0.7 in the VAC group at the sixth day after treatment, respectively. The intervals between wound treatment and secondary wound coverage procedure were 12.0 ± 1.7 days in the dressing change group and 6.1 ± 0.7 days in the VAC group. Flaps were applied for wound coverage in 9 out of 18 (50.0%) wounds in the dressing change group and 5 out of 26 (19.2%) in the VAC group (P < 0.05), when the wounds of rest of patients were covered by the skin graft. The results showed that VAC could promote the growth of granulation tissue of wound, decrease the need of flap for wound coverage, and did not change the survival of replantation.
Abstract Singlet oxygen is regarded as the primary cytotoxic agent in cancer photodynamic therapy (PDT). Despite the advances in optical methods to image singlet oxygen, it remains a challenge for in vivo application due to the limited tissue penetration depth of light. Up to date, no singlet oxygen‐specific magnetic resonance imaging (MRI) probe has been reported. Herein, a T 2 ‐weighted MRI probe is reported to visually detect singlet oxygen generated in PDT in vitro and in vivo. The MRI probe Ce6/Fe 3 O 4 ‐M is constructed by co‐encapsulation of photosensitizer Ce6 and Fe 3 O 4 nanoparticles in mPEG 2000 ‐TK‐C 16 micelles. Thioketal (TK) linker in the probe is highly sensitive to singlet oxygen, but lowly sensitive to other reactive oxygen species (ROS) existing in physiological and pathological environments. Singlet oxygen, generated with light irradiation, triggers the cleavage of TK, which leads to loss of surface polyethylene glycol, increment of the hydrophobicity, and aggregation of Fe 3 O 4 nanoparticles. Subsequently, negatively enhanced T 2 ‐weighted MRI signal is obtained for visual detection of singlet oxygen in the solution, cancer cells, and in vivo. This oxidation responsive MRI probe is expected to hold great promise in evaluating the ability of photosensitizers to generate singlet oxygen and in predicting the therapeutic efficacies of PDT in vivo.
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