Power Flow Control in Multi-Terminal HVDC Grids Using a Serial-Parallel DC Power Flow Controller

© 2013 IEEE. Multi-terminal HVDC (MT-HVDC) grids have no capability of power flow control in a self-sufficient manner. To address this important issue, utilization of dc-dc high power and high-voltage converters is motivated. However, proposing suitable partial-rated dc-dc converters as well as their suitable modeling and control in both primary and secondary control layers as well as the stability analysis are the existing challenges that should be alleviated beforehand. This paper addresses the control of power flow problem through the application of a power converter with a different connection configuration, namely, serial parallel dc power flow controller (SPDC-PFC). The SPDC-PFC input is the transmission line voltage, and its output is transmission line current. Therefore, employing a full-power dc-dc converter is avoided as a merit. Additionally, in this paper, the common two-layer MT-HVDC grid control framework comprised of primary and secondary layers is efficiently modified in order to integrate the SPDC-PFC. A differential direct voltage versus active power droop control scheme is applied to the SPDC-PFC at the local control layer, guaranteeing dynamic stability, while an extended dc power-flow routine - integrating the SPDC-PFC - is developed at the secondary control layer to ensure the static stability of the entire MT-HVDC grid. The proposed control framework enables the SPDC-PFC to regulate the flow of current/power in the envisioned HVDC transmission line. From the static and dynamic simulation results conducted on the test CIGRE B4 MT-HVDC grid, successful operation of the proposed SPDC-PFC and control solutions are demonstrated by considering power flow control action. In more detail, the SPDC-PFC successfully regulates the compensated lines' power to the desired reference both in static and dynamic simulations by introducing suitable compensation voltages. In addition, good dynamic performance under both SPDC-PFC power reference and wind power-infeed change is observed

Therapeutic effect of adjunctive N-acetyl cysteine (NAC) on symptoms of chronic schizophrenia: A double-blind, randomized clinical trial

Abstract Background Schizophrenia is one of the most disabling psychiatric syndromes with the prevalence of 1% in the general population. Despite availability of various antipsychotics, negative symptoms and cognitive impairment are difficult to treat. In addition antipsychotic monotherapy is not effective in most of these patients. Current evidence indicates the roles of glutamatergic system in this disorder. N-acetyl cysteine (NAC) also increases extracellular glutamate. This study was conducted to evaluate the clinical effects of oral NAC as an add-on to maintenance medication for the treatment of chronic schizophrenia. Materials and methods This 12-week, double-blind, randomized, placebo-controlled, clinical trial was performed to determine the effectiveness of 1200 mg N-acetyl cysteine as an adjunctive treatment with conventional antipsychotic medications in 84 patients with chronic schizophrenia. The subjects were evaluated with the Positive and Negative Syndrome Scale (PANSS), Mini-Mental State Examination (MMSE), and a standard neuropsychological screening test. Data were analyzed with SPSS-16 software. Results NAC-treated patients showed significantly improvement in the positive (F = 5.47, P = 0.02) and negative (F = 0.20, df = 1) PANSS subscale. Also the general and total PANSS score of NAC group declined over times whilst it was increased for placebo group. Regarding cognitive functions, improvement was observed in some explored areas, such as attention, short-term and working memory, executive functioning and speed of processing. There was no significant difference between the 2 groups in the frequency of adverse effects. Conclusion The present study detected improvement in positive, negative, general and total psychopathology symptoms as well as cognitive performance with NAC treatment. It is also well-tolerated, safe and easy-to-use agent as an effective therapeutic strategy to improve outcome in schizophrenia treatment. Keywords N-acetyl cysteine Schizophrenia Cognitive impairment Positive and negative symptoms scale (PANSS) Glutamatergic syste

Supervised and non-supervised AE data classification of nanomodified CFRP during DCB tests

Aim of the paper is to use acoustic emissions to study the effect of electrospun nylon 6,6 Nanofibrous mat on carbon-epoxy composites during Double Cantilever beam (DCB) tests. In order to recognize the effect of the nanofibres and to detect different damage mechanisms, k-means clustering of acoustic emission signals applied to rise time, count, energy, duration and amplitude of the events is used. Supervised neural network (NN) is then applied to verify clustered signals. Results showed that clustered acoustic emission signals are a reliable tool to detect different damage mechanisms; neural network showed the method has a 99% of accuracy

How native state topology affects the folding of Dihydrofolate Reductase and Interleukin-1beta

The overall structure of the transition state and intermediate ensembles experimentally observed for Dihydrofolate Reductase and Interleukin-1beta can be obtained utilizing simplified models which have almost no energetic frustration. The predictive power of these models suggest that, even for these very large proteins with completely different folding mechanisms and functions, real protein sequences are sufficiently well designed and much of the structural heterogeneity observed in the intermediates and the transition state ensembles is determined by topological effects.Comment: Proc. Natl. Acad. Sci. USA, in press (11 pages, 4 color PS figures) Higher resolution PS files can be found at http://www-physics.ucsd.edu/~cecilia/pub_list.htm

Microgrids interconnection to upstream AC grid using a dual-function fault current limiter and power flow controller: Principle and test results

This study presents a novel magnetic-based solid-state dual-function fault current limiter and power flow controller (FLPFC) that offers a promising application for safe and controllable interconnection of microgrids to upstream AC grids. The proposed structure includes series reactors and power electronic switches that protects microgrid from upstream AC grid short-circuit fault and it controls the power flow between microgrid and upstream grid. Performance of the proposed FLPFC is analysed and simulated using Matlab/Simulink and results are confirmed by experimental tests

Altered Backbone and Side-Chain Interactions Result in Route Heterogeneity during the Folding of Interleukin-1b (IL-1b)

Deletion of the b-bulge trigger-loop results in both a switch in the preferred folding route, from the functional loop packing folding route to barrel closure, as well as conversion of the agonist activity of IL-1b into antagonist activity. Conversely, circular permutations of IL-1b conserve the functional folding route as well as the agonist activity. These two extremes in the folding-functional interplay beg the question of whether mutations in IL-1b would result in changes in the populations of heterogeneous folding routes and the signaling activity. A series of topologically equivalent water-mediated b-strand bridging interactions within the pseudosymmetric b-trefoil fold of IL-1b highlight the backbone water interactions that stabilize the secondary and tertiary structure of the protein. Additionally, conserved aromatic residues lining the central cavity appear to be essential for both stability and folding. Here, we probe these protein backbone-water molecule and side chain-side chain interactions and the role they play in the folding mechanism of this geometrically stressed molecule. We used folding simulations with structure-based models, as well as a series of folding kinetic experiments to examine the effects of the F42W core mutation on the folding landscape of IL-1b. This mutation alters water-mediated backbone interactions essential for maintaining the trefoil fold. Our results clearly indicate that this perturbation in the primary structure alters a structural water interaction and consequently modulates the population of folding routes accessed during folding and signaling activity

Distribution system protection by coordinated fault current limiters

The protection of distribution networks is one of the most substantial issues, which needs special attention. Using appropriate protective equipment enhances the safety of the power distribution network during the fault conditions. Fault current limiter (FCL) is a kind of modern preserving system being used for protecting power networks and equipment. One of the main concerns of power networks is the voltage restoration of buses during faulty conditions. In this study, a group of coordinated DC reactor type faults current limiters are designed and tested to protect the network and restore its buses voltage within the fault period. To coordinate FCLs and measurement devices during the fault sequences, a wireless communication system and decision-making computer are used. The proposed FCLs coordination strategy is modelled and simulated in MATLAB platform and the results are validated by the developed laboratory test setu

Application of autologous platelet-rich plasma (PRP) on wound healing after caesarean section in high-risk patients

Background: Platelet-rich plasma (PRP) is ahumanplasma product enriched by platelets, growth factors, and fibrinogen with high hemostatic and healing properties. Objectives: The aim of this study was to evaluate the effect of autologous PRP on wound healing in high-risk women undergoing cesarean sections. Patients and Methods: In this balanced, randomized, and controlled trial, 140 patients were admitted to Arash women�s hospital, Tehran, Iran from May of 2013 to November of 2014 for elective cesarean surgery. The patients were randomly assigned into two groups. The intervention group received PRP after surgery, whereas the control group received the usual care. All patients were evaluated at baseline, five days, and eight weeks after the cesarean section. The primary endpoint used the REEDA scale for assessing the changes in wound healing. The secondary outcome measures used were the Vancouver scar scale (VSS) and the visual analog scale (VAS). All scale scores were analyzed using a repeated measures test for variance. Results: At the end of study, the PRP group showed a greater reduction in the edema ecchymosed discharge approximation (REEDA) score compared to the control group (85.5 reduction in the PRP group; 72 in the control group) (P < 0.001). Compared with the control group, the PRP group had a significantly greater reduction in the VANscore, beginning on the fifth day after the cesarean section (-0.7, 38 reduction in PRP group;-0.8, 33 in control group) (P < 0.001), and this trend was stable at the end of the eighth week (-0.6, 54 reduction in PRP group;-0.3, 18 in control group). Furthermore, patients treated with PRP experienced a 93 reduction in the VAS score at the end of follow-up, but the control group only observed a 79 reduction (P < 0.001). Conclusions: It seems that applying PRP is an effective therapeutic approach for wound healing, and faster wound healing is expected due to the presence of more platelets and growth factors. © 2016, Iranian Red Crescent Medical Journal

Folding Circular Permutants of IL-1β: Route Selection Driven by Functional Frustration

Interleukin-1β (IL-1β) is the cytokine crucial to inflammatory and immune response. Two dominant routes are populated in the folding to native structure. These distinct routes are a result of the competition between early packing of the functional loops versus closure of the β-barrel to achieve efficient folding and have been observed both experimentally and computationally. Kinetic experiments on the WT protein established that the dominant route is characterized by early packing of geometrically frustrated functional loops. However, deletion of one of the functional loops, the β-bulge, switches the dominant route to an alternative, yet, as accessible, route, where the termini necessary for barrel closure form first. Here, we explore the effect of circular permutation of the WT sequence on the observed folding landscape with a combination of kinetic and thermodynamic experiments. Our experiments show that while the rate of formation of permutant protein is always slower than that observed for the WT sequence, the region of initial nucleation for all permutants is similar to that observed for the WT protein and occurs within a similar timescale. That is, even permutants with significant sequence rearrangement in which the functional-nucleus is placed at opposing ends of the polypeptide chain, fold by the dominant WT “functional loop-packing route”, despite the entropic cost of having to fold the N- and C- termini early. Taken together, our results indicate that the early packing of the functional loops dominates the folding landscape in active proteins, and, despite the entropic penalty of coalescing the termini early, these proteins will populate an entropically unfavorable route in order to conserve function. More generally, circular permutation can elucidate the influence of local energetic stabilization of functional regions within a protein, where topological complexity creates a mismatch between energetics and topology in active proteins

Prevalence and antimicrobial resistance of shigella species isolated from diarrheal patients in Ahvaz, Southwest Iran

Introduction: Shigellosis is a significant global human health problem, and Shigella is in charge of almost 165 million cases of this disease annually, of whom 163 million cases are in developing countries and 1.5 million cases are in developed countries. The main aims of the current survey were to identify Shigella spp. isolated from diarrheal patients by conventional biochemical tests, determine the antimicrobial susceptibility profiles by disk diffusion method, and detect the ipaH gene using the PCR assay. Methods: The bacterial isolates were identified as Shigella spp. by microbiological tests and were serogrouped by the slide agglutination test. Antimicrobial susceptibility testing was performed using the disk diffusion method. PCR was performed to detect the ipaH gene. Results: The Shigella strains were isolated from 522 patients with various diarrhea, including bloody diarrhea (3), mucoid plus bloody diarrhea (1.9), mucoid diarrhea (3.2), and watery diarrhea (3.2). Overall, 69 (13.2) isolates were positive for Shigella spp., of which 34 (49.3) serotypes were identified as Shigella flexneri, 22 (31.9) serotypes were identified as Shigella sonnei, 9 (13) serotypes were identified as Shigella boydii, and 4 (5.8) serotypes were identified as Shigella dysenteriae. Antibiotic susceptibility tests revealed that the highest resistance percentage was related to ampicillin (82) and trimethoprim-sulfamethoxazole (77), and ciprofloxacin and ceftriaxone were the best antibiotics against Shigella isolates. Conclusion: We concluded that Shigella spp. can be considered as an etiological agent of diarrhea in southwest Iran. Since the drug resistance pattern of Shigella differs geographically and over time within a country, continuous and regular surveillance program is necessary. © 2019 Sheikh et al