Flux Control Research Articles

Patterns and controls of carbon dioxide concentration and fluxes at the air–water interface in South American lowland streams

Patterns and controls of carbon dioxide concentration and fluxes at the air–water interface in South American lowland streams

Eccentric Exercise Causes Specific Adjustment in Pyruvate Oxidation by Mitochondria.

The impact of eccentric exercise on mitochondrial function has only been poorly investigated and remains unclear. This study aimed to identify the changes in skeletal muscle mitochondrial respiration, specifically triggered by a single bout of eccentric treadmill exercise. Male adult mice were randomly divided into eccentric (ECC; downhill running), concentric (CON; uphill running), and unexercised control groups ( n = 5/group). Running groups performed 18 bouts of 5 min at 20 cm·s -1 on an inclined treadmill (±15° to 20°). Mice were sacrificed 48 h after exercise for blood and quadriceps muscles collection. Deep proximal (red) and superficial distal (white) muscle portions were used for high-resolution respirometric measurements. Plasma creatine kinase activity was significantly higher in the ECC compared with CON group, reflecting exercise-induced muscle damage ( P < 0.01). The ECC exercise induced a significant decrease in oxidative phosphorylation capacity in both quadriceps femoris parts ( P = 0.032 in proximal portion, P = 0.010 in distal portion) in comparison with the CON group. This observation was only made for the nicotinamide adenine dinucleotide (NADH) pathway using pyruvate + malate as substrates. When expressed as a flux control ratio, indicating a change related to mitochondrial quality rather than quantity, this change seemed more prominent in distal compared with proximal portion of quadriceps muscle. No significant difference between groups was found for the NADH pathway with glutamate or glutamate + malate as substrates, for the succinate pathway or for fatty acid oxidation. Our data suggest that ECC exercise specifically affects pyruvate mitochondrial transport and/or oxidation 48 h after exercise, and this alteration mainly concerns the distal white muscle portion. This study provides new perspectives to improve our understanding of the mitochondrial adaptation associated with ECC exercise.

Development and implementation of Divertor Fast Particles Injection for EAST tokamak

The divertor is the main device in the tokamak that is subjected to heat loads, excessive high heat flux could cause damage to the divertor target. Divertor heat flux control is very important for magnetically confined fusion devices. As a method for divertor heat flux control, the Divertor Fast Particles Injection (DFPI) is successfully developed and implemented on the Experimental Advanced Superconducting Tokamak (EAST). The components of DFPI are a high-pressure gas source (0.6–1 MPa), a pulse solenoid valve, a nozzle and the pipeline etc. Compared with the Supersonic Molecular Beam Injection (SMBI) particle injection from midplane, the particles injected by DFPI are more difficult to enter the plasma core and have less impact on the performance of the core plasma; Compared with the gas puffing (GP) particle injection from the divertor, the particles injected by DFPI can enter the divertor area faster, the delay time of DFPI is about 25 ms. The successful implementation of DFPI provides an important tool for divertor heat flux control on EAST.

Investigating mitochondrial bioenergetics in peripheral blood mononuclear cells of women with childhood maltreatment from post-parturition period to one-year follow-up.

Childhood maltreatment (CM) exerts various long-lasting psychological and biological changes in affected individuals, with inflammation being an interconnecting element. Besides chronic low-grade inflammation, CM might also affect the energy production of cells by altering the function and density of mitochondria, i.e. the body's main energy suppliers. Here, we compared mitochondrial respiration and density in intact peripheral blood mononuclear cells (PBMC), from women with and without CM between two time points, i.e. at the highly inflammatory phase within 1 week after parturition (t0) and again after 1 year (t2). CM exposure was assessed with the Childhood Trauma Questionnaire. Whole blood was collected from n = 52 healthy women within the study 'My Childhood - Your Childhood' at both time points to isolate and cryopreserve PBMC. Thawed PBMC were used to measure mitochondrial respiration and density by high-resolution respirometry followed by spectrophotometric analyses of citrate-synthase activity. Over time, quantitative respiratory parameters increased, while qualitative flux control ratios decreased, independently of CM. Women with CM showed higher mitochondrial respiration and density at t0, but not at t2. We found significant CM group × time interaction effects for ATP-turnover-related respiration and mitochondrial density. This is the first study to longitudinally investigate mitochondrial bioenergetics in postpartum women with and without CM. Our results indicate that CM-related mitochondrial alterations reflect allostatic load, probably due to higher inflammatory states during parturition, which normalize later. However, later inflammatory states might moderate the vulnerability for a second-hit on the level of mitochondrial bioenergetics, at least in immune cells.

Molding 2D Exciton Flux toward Room Temperature Excitonic Devices

AbstractDevices operating with excitons have promising prospects for overcoming the dilemma of response time and integration in current generation of electron‐ or/and photon‐based elements and devices. In combination with the advantages of emerging twistronics and valleytronics, the atomically thin transition metal dichalcogenide semiconductors open up new opportunities for pursuing practical excitonic devices, where the strong exciton binding energy enables operating exciton at room temperature. The essential and foremost step toward exciton devices is the control of spatiotemporal exciton flux, which is density‐dependent and affected by the complex many‐body interactions. It can be effectively controlled by the strain, electric field, electron‐doping, and local dielectric environment. Intriguingly, exotic phenomena such as exciton condensation, electron‐hole liquid, exciton Hall effects, and exciton halo effects can be occurred in 2D exciton system, providing new possibilities for excitonic devices. Up to now, the proof‐of‐principle of room temperature exciton devices, including excitonic switching and transistor, exciton guides, and excitonic nanolaser, have been realized. Here the authors review the recent advances in molding 2D exciton flux from basic principle, manipulation, exotic phenomena to promising applications and discuss the opportunities and challenges in pushing the frontiers of room temperature excitonic devices.

RTN4/Nogo-A-S1PR2 negatively regulates angiogenesis and secondary neural repair through enhancing vascular autophagy in the thalamus after cerebral cortical infarction

ABSTRACT Cerebral infarction induces angiogenesis in the thalamus and influences functional recovery. The mechanisms underlying angiogenesis remain unclear. This study aimed to investigate the role of RTN4/Nogo-A in mediating macroautophagy/autophagy and angiogenesis in the thalamus following middle cerebral artery occlusion (MCAO). We assessed secondary neuronal damage, angiogenesis, vascular autophagy, RTN4 and S1PR2 signaling in the thalamus. The effects of RTN4-S1PR2 on vascular autophagy and angiogenesis were evaluated using lentiviral and pharmacological approaches. The results showed that RTN4 and S1PR2 signaling molecules were upregulated in parallel with angiogenesis in the ipsilateral thalamus after MCAO. Knockdown of Rtn4 by siRNA markedly reduced MAP1LC3B-II conversion and levels of BECN1 and SQSTM1 in vessels, coinciding with enhanced angiogenesis in the ipsilateral thalamus. This effect coincided with rescued neuronal loss of the thalamus and improved cognitive function. Conversely, activating S1PR2 augmented vascular autophagy, along with suppressed angiogenesis and aggravated neuronal damage of the thalamus. Further inhibition of autophagic initiation with 3-methyladenine or spautin-1 enhanced angiogenesis while blockade of lysosomal degradation by bafilomycin A1 suppressed angiogenesis in the ipsilateral thalamus. The control of autophagic flux by RTN4-S1PR2 was verified in vitro. Additionally, ROCK1-BECN1 interaction along with phosphorylation of BECN1 (Thr119) was identified in the thalamic vessels after MCAO. Knockdown of Rtn4 markedly reduced BECN1 phosphorylation whereas activating S1PR2 increased its phosphorylation in vessels. These results suggest that blockade of RTN4-S1PR2 interaction promotes angiogenesis and secondary neural repair in the thalamus by suppressing autophagic activation and alleviating dysfunction of lysosomal degradation in vessels after cerebral infarction. Abbreviations: 3-MA: 3-methyladenine; ACTA2/ɑ-SMA: actin alpha 2, smooth muscle, aorta; AIF1/Iba1: allograft inflammatory factor 1; BafA1: bafilomycin A1; BMVECs: brain microvascular endothelial cells; BrdU: 5-bromo-2’-deoxyuridine; CLDN11/OSP: claudin 11; GFAP: glial fibrillary acidic protein; HUVECs: human umbilical vein endothelial cells; LAMA1: laminin, alpha 1; MAP2: microtubule-associated protein 2; MBP2: myelin basic protein 2; MCAO: middle cerebral artery occlusion; PDGFRB/PDGFRβ: platelet derived growth factor receptor, beta polypeptide; RECA-1: rat endothelial cell antigen-1; RHOA: ras homolog family member A; RHRSP: stroke-prone renovascular hypertensive rats; ROCK1: Rho-associated coiled-coil containing protein kinase 1; RTN4/Nogo-A: reticulon 4; RTN4R/NgR1: reticulon 4 receptor; S1PR2: sphingosine-1-phosphate receptor 2; SQSTM1: sequestosome 1.

Research on a material for hydrogen purifying and flux controlling with application to space active hydrogen-masers

The Space Active Hydrogen-Maser (SAHM) can be used for the Space Very Long Baseline Interferometry Project to improve the resolution of the space astronomical telescope. The standard frequency signals provided by the SAHM have their stability dependent on the flux of effective H atoms. Therefore, a nickel (Ni) tube, one end closed, has been designed in this paper for the SAHM as a hydrogen (H2) purification and flux control device. Mechanisms of the H2 purification and flux control by a Ni tube were studied. H2 flux and ΔU, as a function of an input current, are given by experimental analyses. The diffusion activation energy of atomic H is much less than that of other atoms under the same conditions in Ni. The H atoms reversibly diffuse in Ni, and their diffusion speed has a high response to temperature. Experimental research shows that when the temperature of the tube was changed (from 27 to 700 °C), by an input heating electrical current (from 0 to 3.5 A), the H2 flux varied from 0 to 9.18 × 10−10 mol/s and no change in the phase structure of Ni. The data of flux should be useful for the frequency stability performance research of the SAHM. In addition, no phase change of the material indicates a stable performance of the tube for H-purifying and flux controlling. Finally, the above advantages make it a promising candidate for the reliability of the SAHM.

Torque ripple minimization in direct torque control at low-speed operation using alternate switching technique

Direct torque control (DTC) of induction motor is prominent to offer instant torque and flux control with a simple control structure. However, this scheme suffers from two major drawbacks namely high torque ripple and variable switching frequency of the inverter, especially during low-speed operation. During the low-speed condition, the positive torque slope is very steep and torque overshoot occurs frequently resulting in the torque ripple become of great significance. This paper proposes a new and effective technique to reduce the torque ripple by integrating the alternate switching technique to the inverter switching status to limit the torque slope surge. By varying the frequency and duty cycle of the alternate switching, the rate of surge can be controlled resulting in the chances of overshoots, and selection of reverse voltage vector can be avoided. The feasibility of the proposed technique has been validated using MATLAB/Simulink software and through experimental results. The results show the proposed alternate switching technique minimizes over 40% reduction in the torque ripple while maintaining the simple structure of DTC.

Model predictive flux control of six-phase permanent magnet synchronous motor with novel virtual voltage vectors

Model predictive flux control of six-phase permanent magnet synchronous motor with novel virtual voltage vectors

Soil Properties Interacting With Microbial Metagenome in Decreasing CH4 Emission From Seasonally Flooded Marshland Following Different Stages of Afforestation.

Wetlands are the largest natural source of terrestrial CH4 emissions. Afforestation can enhance soil CH4 oxidation and decrease methanogenesis, yet the driving mechanisms leading to these effects remain unclear. We analyzed the structures of communities of methanogenic and methanotrophic microbes, quantification of mcrA and pmoA genes, the soil microbial metagenome, soil properties and CH4 fluxes in afforested and non-afforested areas in the marshland of the Yangtze River. Compared to the non-afforested land use types, net CH4 emission decreased from bare land, natural vegetation and 5-year forest plantation and transitioned to net CH4 sinks in the 10- and 20-year forest plantations. Both abundances of mcrA and pmoA genes decreased significantly with increasing plantation age. By combining random forest analysis and structural equation modeling, our results provide evidence for an important role of the abundance of functional genes related to methane production in explaining the net CH4 flux in this ecosystem. The structures of methanogenic and methanotrophic microbial communities were of lower importance as explanatory factors than functional genes in terms of in situ CH4 flux. We also found a substantial interaction between functional genes and soil properties in the control of CH4 flux, particularly soil particle size. Our study provides empirical evidence that microbial community function has more explanatory power than taxonomic microbial community structure with respect to in situ CH4 fluxes. This suggests that focusing on gene abundances obtained, e.g., through metagenomics or quantitative/digital PCR could be more effective than community profiling in predicting CH4 fluxes, and such data should be considered for ecosystem modeling.

Circadian Control of Mitochondria in Reactive Oxygen Species Homeostasis.

Significance: Mitochondria produce most of the cellular ATP through the process of oxidative phosphorylation. Energy metabolism in the mitochondria is associated with the production of reactive oxygen species (ROS). Excessive ROS production leads to oxidative stress and compromises cellular physiology. Energy metabolism in the mitochondria depends on nutrient flux and cellular metabolic needs, which are in turn connected with the feeding/fasting cycle. In animals, the feeding/fasting cycle is controlled by the circadian clock that generates 24-h rhythms in behavior, metabolism, and signaling. Recent Advances: Here, we discuss the role of the circadian clock and rhythms in mitochondria on ROS homeostasis. The circadian clock is involved in mitochondrial ROS production and detoxification through the control of nutrient flux and oxidation, uncoupling, antioxidant defense, and mitochondrial dynamics. Critical Issues: Little is known on the molecular mechanisms of circadian control of mitochondrial functions. The circadian clock regulates the expression and activity of mitochondrial metabolic and antioxidant enzymes. The regulation involves a direct transcriptional control by Circadian Locomotor Output Cycles Kaput/brain and muscle ARNT-like 1(CLOCK/BMAL1), nuclear factor erythroid-2-related factor 2 (NRF2) transcriptional network, and sirtuin-dependent posttranslational protein modifications. Future Perspectives: We hypothesize that the circadian clock orchestrates mitochondrial physiology to synchronize it with the feeding/fasting cycle. Circadian coordination of mitochondrial function couples energy metabolism with diets and contributes to antioxidant defense to prevent metabolic diseases and delay aging. Antioxid. Redox Signal. 37, 647-663.

New simplified transient method for determining the coefficient of permeability of unsaturated soil

The instantaneous profile (IP) method is widely used for determining the coefficient of permeability of unsaturated soils. IP method requires the measurement or control (i.e., zero flux) of flux at any one end of a soil profile. Besides, there are requirements of variations in volumetric water contents (VWCs) and pore-water pressures (PWPs) at various points from the above-mentioned one end of the soil profile to a particular point in which the unsaturated coefficient of permeability is derived. The measurement or control of flux at one end of the soil profile requires high accuracy which causes difficulty while performing tests in the laboratory and field. To overcome the difficulty of the IP method, this study proposes a new simplified transient method for determining the coefficient of permeability of the unsaturated soil. Variations in volumetric water contents and corresponding pore-water pressures at three points are required in the new simplified transient method. The intellectual advantage of this method as compared to the IP method is that there is no need to measure or control the flux at one end of the soil profile. Therefore, this new method is more practical and is expected to be widely used in both laboratory tests and field tests. The validity of the new simplified transient method is verified through numerical simulations considering a one-dimensional seepage for four different types of soils including coarse-grained soil, sand, clay, and silty sand with gravel. The applicability of the new simplified transient method is demonstrated by comparing the unsaturated coefficients of permeability of soils computed by the new simplified transient method and the IP method. Good agreements in comparisons prove that the new simplified transient method is effective for determining the unsaturated coefficient of permeability of soil regardless of soil types and hydraulic functions features.

Thermal behavior of grain-oriented electrical steel wound core solid-state transformer

PurposeThis paper aims to propose a new design for high-power compact solid-state transformers (SSTs) made with grain-oriented electrical steel (GOES) wound cores that benefit from the natural reduction of iron losses at high temperatures.Design/methodology/approachAn experimental approach, coupled with numerical and analytical investigations, is widely used for proving the validity of the proposed concept.FindingsWith cores much hotter than coils, the new design of medium frequency transformers can be used for building compact SSTs that rated powers and common-mode insulation voltages much higher than existing ones with similar efficiencies.Research limitations/implicationsThe thermal design must provide a large difference between core and coil temperatures in a reasonable volume.Practical implicationsThe increasing number of intermittent renewable sources place electric grid stability at risk. Smart nodes, made of SSTs, improve the global grid stability because they are able to provide real-time control of energy fluxes at critical points. In railway applications, high-power SST cells can be distributed along the train providing a larger volume for passengers.Social implicationsThe increasing part of electricity in a flexible grid requires performant and high-power SSTs made with components that have an environmental footprint as low as possible.Originality/valueThis paper proves that the design of high-power transformers with GOES wound cores much hotter than coils is possible. It proposes also a thermal equivalent circuit that helps the design.

Advances in the long-pulse steady-state high beta H-mode scenario with active controls of divertor heat and particle fluxes in EAST

Since the last IAEA-Fusion Energy Conference, the Experimental Advanced Superconducting Tokamak (EAST) research program has been, in support of ITER and CFETR, focused on development in terms of the long-pulse steady-state (fully noninductive) high beta H-mode scenario with active controls of the stationary and transient divertor heat and particle fluxes. The operational domain of the steady-state H-mode plasma scenario has been significantly extended with ITER-like tungsten mono-block divertor, plasma control and heating schemes. EAST has achieved several important milestones in the development of high β p H-mode scenario and its key physics and technologies. A 60 s-scale long-pulse steady-state high β p H-mode discharge with the major normalized plasma parameters similar to the designed performance of the CFETR 1 GW fusion power operation scenario has been successfully established and sustained by pure RF heating and current drive. Several feedback control schemes have been developed for a sustained detachment with good core confinement. This includes control of the total radiation power, target electron temperature, and particle flux measured using divertor Langmuir probes or a combination of the control of target electron temperature and AXUV radiation near the X point. The detachment feedback control schemes have been integrated with small-ELM regimes and high β p scenario via neon seeding, enabling a core and edge compatible integrated high-beta scenario applicable to long-pulse operations. ELM suppression has been achieved using various methods, including resonant magnetic perturbations and impurity seeding. Full suppression of ELMs by using n = 4 RMPs has been demonstrated for ITER for the first time in low input torque plasmas in EAST. EAST has been operated with helium to support the ITER research requirements for the first time. For a long-pulse, high bootstrap current fraction operation, a new lower tungsten divertor with active water-cooling has been installed, along with improvements in the heating and current drive capability.

Adaptive Virtual Flux Droop Control Based on Virtual Impedance in Islanded AC Microgrids

Virtual flux droop (VFD) method is a scheme, in which, instead of frequency and voltage amplitude, the phase angle and amplitude of the virtual flux are, respectively, adjusted to active and reactive power sharing. However, mismatched line impedances lead to improper power sharing. An adaptive VFD (AVFD) control strategy is proposed in this article to solve this problem. First, the effect of the mismatched line impedances on the VFD method is analyzed. Then, the idea of virtual impedance is employed to develop the AVFD control strategy. In addition, a small-signal model is presented which is used to tune the control parameters. Furthermore, the microgrid control approach is made based on the direct flux control (DFC) method to apply the proposed strategy. The resultant control scheme is simple without needing multiple feedback loops and complex transformations. In order to validate feasibility and effectiveness of the proposed control strategy, both simulation and experimental studies are implemented. The results show that by the proposed method, accurate power sharing proportional to the ratings of the sources can be achieved in spite of mismatched line impedances.

A metabolic perspective into antimicrobial tolerance and resistance

A metabolic perspective into antimicrobial tolerance and resistance

Induction Motor DTC Performance Improvement by Reducing Flux and Torque Ripples in Low Speed

Since induction motors were invented, human civilization has changed forever. Due to their beneficial characteristics, induction motors are widely used and have become the most prevalent electrical counterparts. Many control strategies for induction motors have been developed, varying from scalar to vector control. In the class of vector control, the Direct Torque Control (DTC) was proposed as an alternative that ensures separated flux and torque control while remaining completely in a stationary reference frame. It offers direct inverter switching, reasonable simplicity than other vector control techniques, and less sensitivity to parameter variation. However, the use of hysteresis controllers in conventional DTC involves non-desired ripples in the system's flux and torque, which leads to bad system performances, primarily in low-speed operations. This paper aims to minimize the chattering and ensure the augmented system's performance in terms of robustness and stability. The proposed method is an improved version of DTC, which combines the addition of the Space Vector Machine (SVM) algorithm to the DTC and the increased number of DTC sectors that generate reference control voltages. Satisfactory results have been obtained by numerical simulation in MATLAB/Simulink. Eventually, the proposed method is proven to be a fast dynamic decoupled control that robustly responds to external disturbance and system uncertainties, especially in the low-speed range.

Flux modulation: A novel approach for ultrafiltration fouling control

Control of membrane fouling is critical for the long term production of water in a membrane system. Backwashing with or without relaxation is the most common method to control fouling in-situ with ultrafiltration (UF) hollow fiber membrane systems. The inclusion of relaxation is intended to assist with decompression of the membrane cake layers and assist with backwashing. However, it also results in a loss of membrane productivity. This study aimed to investigate the effect of flux modulation with single and dual mode cycles, as well as relaxation, on the performance of an UF membrane with respect to fouling control. Results demonstrated that modulating the flux in place of relaxation results in a substantial improvement in control of membrane fouling while still maintaining membrane productivity. By modulating the flux at different levels compared to a control of flux of 36 LMH, the fouling index values decreased by over 80% while specific water production only dropped 8% (2489 vs 2702 L/m2). Incorporating a relaxation step had minimal impact (<8%) on the performance of a given flux cycle with regards to fouling control. Therefore, high membrane performance can be achieved without the need for a relaxation step, as long as an appropriate flux modulation cycle is selected. This research demonstrates the potential for significant fouling control on an UF membrane by alternating the stress on the membrane surface through flux modulation.

Microfluidic device integrating a network of hyper-elastic valves for automated glucose stimulation and insulin secretion collection from a single pancreatic islet

Advances in microphysiological systems have prompted the need for robust and reliable cell culture devices. While microfluidic technology has made significant progress, devices often lack user-friendliness and are not designed to be industrialized on a large scale. Pancreatic islets are often being studied using microfluidic platforms in which the monitoring of fluxes is generally very limited, especially because the integration of valves to direct the flow is difficult to achieve. Considering these constraints, we present a thermoplastic manufactured microfluidic chip with an automated control of fluxes for the stimulation and secretion collection of pancreatic islet. The islet was directed toward precise locations through passive hydrodynamic trapping and both dynamic glucose stimulation and insulin harvesting were done automatically via a network of large deformation valves, directing the reagents and the pancreatic islet toward different pathways. This device we developed enables monitoring of insulin secretion from a single islet and can be adapted for the study of a wide variety of biological tissues and secretomes.

Thermodynamics of concentration vs flux control in chemical reaction networks.

We investigate the thermodynamic implications of two control mechanisms of open chemical reaction networks. The first controls the concentrations of the species that are exchanged with the surroundings, while the other controls the exchange fluxes. We show that the two mechanisms can be mapped one into the other and that the thermodynamic theories usually developed in the framework of concentration control can be applied to flux control as well. This implies that the thermodynamic potential and the fundamental forces driving chemical reaction networks out of equilibrium can be identified in the same way for both mechanisms. By analyzing the dynamics and thermodynamics of a simple enzymatic model, we also show that while the two mechanisms are equivalent at steady state, the flux control may lead to fundamentally different regimes where systems achieve stationary growth.