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Src tyrosine kinases and spleen tyrosine kinase (Syk) have recently been shown to contribute to sustained platelet aggregation on collagen under arterial shear. In the present study, we have investigated whether Src and Syk are required for aggregation under minimal shear following activation of glycoprotein VI (GPVI) and have extended this to C-type lectin-like receptor-2 (CLEC-2) which signals through the same pathway. Aggregation was induced by the GPVI ligand collagen-related peptide (CRP) and the CLEC-2 ligand rhodocytin and monitored by light transmission aggregometry (LTA). Aggregation and tyrosine phosphorylation by both receptors were sustained for up to 50 min. The addition of inhibitors of Src, Syk or Bruton's tyrosine kinase (Btk) at 150 sec, by which time aggregation was maximal, induced rapid loss of tyrosine phosphorylation of their downstream proteins, but only Src kinase inhibition caused a weak (~10%) reversal in light transmission. A similar effect was observed when the inhibitors were combined with apyrase and indomethacin or glycoprotein IIb-IIIa (GPIIb-IIIa) antagonist, eptifibatide. On the other hand, activation of GPIIb-IIIa by GPVI in a diluted platelet suspension, as measured by binding of fluorescein isothiocyanate-labeled antibody specific for the activated GPIIb-IIIa (FITC-PAC1), was reversed on the addition of Src and Syk inhibitors showing that integrin activation is rapidly reversible in the absence of outside-in signals. The results demonstrate that Src but not Syk and Btk contribute to sustained aggregation as monitored by LTA, possibly as a result of inhibition of outside-in signaling from GPIIb-IIIa to the cytoskeleton through a Syk-independent pathway. This is in contrast to the role of Syk in supporting sustained aggregation on collagen under arterial shear. [ABSTRACT FROM AUTHOR]

GPVI and CLEC-2 have emerged as promising targets for long-term prevention of both arterial thrombosis and thrombo-inflammation with a decreased bleeding risk relative to current drugs. However, while there are potent blocking antibodies of both receptors, their protein nature comes with decreased bioavailability, making formulation for oral medication challenging. Small molecules are able to overcome these limitations, but there are many challenges in developing antagonists of nanomolar potency, which is necessary when considering the structural features that underlie the interaction of CLEC-2 and GPVI with their protein ligands. In this review, we describe current small-molecule inhibitors for both receptors and strategies to overcome such limitations, including considerations when it comes to in silico drug design and the importance of complex compound library selection. [ABSTRACT FROM AUTHOR]

This paper analyzes and proposes technical considerations for the selection and design of passive filter schemes rated at several mega VARs to compensate reactive power and current harmonics in mining power distribution systems. The paper includes technical information and analysis required to select the most adequate passive filter topology, to select the tuning frequency for each unit, to calculate filter parameters, and to distribute reactive power between passive filters. Passive filter schemes analyzed in this paper are used to compensate mining power distribution systems, especially when high-power grinding mill drives energized from 12-pulse cycloconverters are used in conjunction with several other nonlinear loads. This paper also analyzes technical limitations that passive filters present in the attenuation of low-frequency current harmonics. Finally, two power distribution systems with different passive filters schemes are evaluated, and the limitations in the attenuation of low-frequency current harmonics generated by cycloconverters are demonstrated with measured results. [ABSTRACT FROM AUTHOR]

A single-objective predictive control method that deals with four main control objectives applied to a multivariable single-phase three-level neutral-point-clamped converter operating as an active power filter is proposed in this paper. The four control objectives are to self-support the dc-bus voltage under load variations, to compensate the reactive power and the current harmonics, and to balance the dc capacitor voltages by using a predefined combination of the redundant switching states of the converter. The main contribution of the proposed method is that these objectives are accomplished without using weighting factors in the cost function, which eliminates problems such as multiobjective optimization or additional empirical procedures for determination of these factors. As a result, the method is easy to implement and rapidly selects the optimal voltage to improve the dynamic-state performance. Experimental results from a 2-kVA prototype are presented to prove that the method is valid for single-phase compensation. The well-known effect of model parameter errors' issue, which is inherent in predictive control methods, is also tested to confirm that the harmonic distortion in the grid current is below 5% even when the predictive model has a 25% error between actual and theoretically estimated grid impedance values. [ABSTRACT FROM PUBLISHER]

This paper presents practical aspects related with the operation, compensation, and protection of high-power cycloconverters used in the mining industry. Practical recommendations related with startup, compensation requirements, operational characteristics, and unexpected shutdown process are described. Fuseless characteristics of modern cycloconverters are also discussed. Relevant current waveforms associated with the operation of a 20-MW synchronous motor semiautogenous grinding mill drive are presented, as well as current and voltage waveforms under fault operating conditions. [ABSTRACT FROM AUTHOR]

An active power filter implemented with a four-leg voltage-source inverter using a predictive control scheme is presented. The use of a four-leg voltage-source inverter allows the compensation of current harmonic components, as well as unbalanced current generated by single-phase nonlinear loads. A detailed yet simple mathematical model of the active power filter, including the effect of the equivalent power system impedance, is derived and used to design the predictive control algorithm. The compensation performance of the proposed active power filter and the associated control scheme under steady state and transient operating conditions is demonstrated through simulations and experimental results. [ABSTRACT FROM AUTHOR]

Presents the modeling and analysis of a medium voltage current-source inverter drive. Description of the drive; Voltages in the drive system; Simulation of the drive.

This paper presents the performance analysis of a hybrid filter composed of passive and active filters connected in series. The analysis is done by evaluating the influence of passive filter parameters variations and the effects that different active power filter's gain have in the compensation performance of the hybrid scheme. The compensation performance is quantified by evaluating the attenuation factor in a power distribution system energizing high-power nonlinear loads compensated with passive filters and then improved with the connection of a series active power filter. Finally, compensation characteristics of the hybrid topology are tested on a 10-kVA experimental setup. [ABSTRACT FROM AUTHOR]

Presents a switching strategy for multilevel cascade inverters based on the space-vector theory. Description of the inverter; Vector control scheme; Generation of the gating pulses.

Presents information on a study which analyzed a protection scheme for series active power filters. Principles of operation; Specification criteria; Experimental results; Conclusions.

Presents the proposed control strategy in terms of principles of operation, circuit design and implementation for active power filters. How is this control strategy connected; Reference to an experiment done on strategy; Description of controlled strategy.

Introduction: The 135 km² Cerrón Grande reservoir is the largest wetland in El Salvador, recognized as “Wetland of International Importance” by the Ramsar Convention. It is also one of the most polluted ecosystems nationwide, facing serious problems, among them, a proliferation of cyanobacteria. Objective: To assess the relationships among environmental factors and the spatial and temporary distribution of cyanobacteria in the reservoir throughout a hydrological year. Methods: We extracted water with cyanobacteria from six fixed sites, from October 2018 through September 2019. Results: We identified 16 genera, the most abundant Microcystis sp. And Dolichospermum sp.; Microcystis sp. reached 1.5 x 106 cells/ml in June 2019, mainly in the north-west sector, which is shallow and close to the confluence zones where highly polluted tributaries reach the reservoir. The deeper south-east sector had low concentrations of these organisms. The environmental factors mostly related to this behavior were: phosphorus, electrical conductivity and Secchi value, as expected from a eutrophic body. Conclusions: Variation in the cellular concentration of cyanobacteria in this reservoir is highly influenced by rain, water mixing and nutrient content. [ABSTRACT FROM AUTHOR]

Nowadays, energy and water are some of the most important issues facing the mining industry. Many mines are located in desert areas, and they need to pump water from isolated wells or from the ocean. Therefore, in order to satisfy the water demand, many high-power water pump stations are required. The operation of these systems is expensive due to the high energy cost. This paper presents a case of study of a solar photovoltaic (PV) system to assist the operation of a water pump station of a mineral processing operation in Chile. An economical analysis is carried out with respect to different design variables and the percentage of the total power required for operating the system in the less favorable conditions (degree of assistance). It is demonstrated that the maximum net present value is obtained for the maximum assistance, i.e., supplying the full energy in the less favorable conditions. However, the internal rate of return will be maximized at the point where the system only supplies the energy to satisfy the full demand at the most favorable conditions. Finally, the study shows that from an economical point of view, PV technology is an attractive alternative to support the mining operation at present time. [ABSTRACT FROM PUBLISHER]

In the field of water management, desalination industry has faced various economic and environmental challenges. Renewable energies and the incorporation of operational strategies such as demand-side management have been able to contribute with the aim of facing them. Nonetheless, it is necessary to continue studying demand-side management for water supply systems emphasising it as a strategic tool to make operational decisions. This article presents a methodology based on a novel Mixed-Integer Linear Programming model in order to program the operation of a seawater reverse osmosis desalination plant with one pumping station for a desertic remote agricultural zone, in accordance with the principles of demand-side management. A photovoltaic solar plant connected to the grid is considered as a renewable energy source. The mathematical model aims to establish the optimal hourly operating load of the system that minimises the daily margin of purchased electricity costs minus sales income of generated electricity. The case study where the methodology is tested is an agricultural area in Northern Chile. The proposed methodology in this paper establishes the basis for future research and industrial applications, considering that it can be generalised to other geographical situations, as well as being modifiable to be adapted for more complex water supply systems and/or other renewable energy sources. • A novel optimisation model was developed to manage a water supply system operation. • The developed optimisation model is based on demand-side management principles. • Demand-side management enables more efficient use of renewable energy. [ABSTRACT FROM AUTHOR]

This paper presents a method for predicting the flicker level that is generated by the high-power load in a distribution system. Through the development of the Flickermeter that met the International Electrotechnical Commission requirements, a reference curve is obtained based on the variation of voltage and the amount of changes per minute of the load. The purpose of this prediction is to determine if the load operation will produce flicker before being connected to the electrical system. This analysis cannot be developed by power system software due to the Flickermeter complexity and the amount of data that is required for processing. [ABSTRACT FROM PUBLISHER]

A design procedure to select the components in a modular unified power-quality conditioner configuration based on single-phase cells is presented. The procedure is based on the fact that the load and distributor operating conditions range are known and it is required to impose stiff operating conditions in both the load side (regulation) and the point of common coupling side (power factor). Due to the arbitrary number of cells to be used in a modular approach, the proposed design procedure allows to select the power semiconductors and capacitors based on an economical evaluation, so an optimal number of cells can be chosen to minimize the overall power cell cost. This design procedure is well suited for modular configurations, where several degrees of freedom are not covered if just technical criteria are followed. Thus, an economic approach can be used to select the appropriate components. The rest of the devices, i.e., the transformers turn ratio and passive filters, are chosen using classical design methods based on technical issues such that the power cells operate within its permissible ratings. A practical case evaluation is presented for a medium voltage system application. [ABSTRACT FROM AUTHOR]

In this paper, a phase-locked loop algorithm appropriated for digital-signal-processor-based control implementations, where the operation of a static-power converter needs to be synchronized with an ac network, is presented. The proposed algorithm includes a multiplier, a filter, a feedback closed loop, and a numerically controlled oscillator stage. As a result, a discrete sine (and cosine) signal is generated in synchronism with the fundamental component of an external-reference (ER) signal. Moreover, the sampling period of the algorithm is adjusted at each sampling instant such that an integer number of sampling periods per period of the ER signal is ensured. This is the main feature, and it is achieved by using a discrete rectangular window filter and a discrete controller. The proposed algorithm code is simple, stable, and presents high noise rejection. A comprehensive theoretical justification and various rigorous experimental tests are included. [ABSTRACT FROM AUTHOR]

Presents an analysis of a voltage sag compensator for critical loads in electrical power distribution systems. Conceptual design of the proposed approach; Topology of the pulsewidth modulation ac-ac converter; Details of the simulation and experimental results.

Given that most of the mines in Chile are situated in regions with high solar resources, solar power could play a significant role as an alternative solution to satisfy the electricity demand in the mining industry. This paper aims to investigate the feasibility of integrating solar power technology into copper concentrate plants (CCPs). Three commercial technologies (PV, CSP, and hybrid PV-CSP) are considered for integration into four existing CCPs of different sizes and located in different regions. To provide comprehensive analysis, the design, performance and economic assessment of 12 cases are carried and the investment costs are estimated taking into account characteristics of the Chilean market as well as the effect of scale. The performance analysis reveals a strong influence of the degradation rate on the electricity production of solar power plants. The first-year capacity factor of the CSP units is around 68% while it is around 32% for the case of PV units. Due to the degradation in the performance of the components, the lifetime-averaged capacity factor is about 9% lower than that of the first year. The economic assessment indicates that PV is the most suitable technology for integration into the CCPs. The Levelized Cost of Electricity (LCOE) of PV-CCPs ranges from 35.53 to 44.40 USD/MWhe, depending on the size and the location of the plant. The LCOE for the cases of CSP-CCPs and PV-CSP-CCPs ranges from 127.08 to 168.88 USD/MWhe and from 91.89 to 118.91 USD/MWhe, respectively. The modified internal rate of return (MIRR) of the PV-CCPs ranges from 8 to 9%, it discounted pack-back period (DPP) ranges from 5 to 6 years. The DPP PV-CSP-CCPs ranges from and from 15 to 23 years respectively. Overall, the CSP-CCPs are not atractive investments due to high LCOE, longer DPP, and MIRR. However, the sensitivity analysis revealed that its LCOE could be lowered by reducing the investment costs. For instance, a reduction of about 10% in the LCOE is possible if the specific investment costs of the TES is cut to about 10UDS/kW th. Image 1 • We focus on the integration of solar power technologies (SPTs) into the copper mining plants (CCPs). • 12 cases of solarized-CCPs is evaluated technically and economically. • The costs of solar power technologies in Chile (PV, CSP, and PV-CSP) are established. • The LCOE of PV-CCPs is about 4 times lower than that of CSP-CCPs and 50% that of PV-CSP-CCPs. • PV-CCPs and CSP-PV-CCPs are viable options but CSP-CCPs is viable only in sites of high solar radiation. [ABSTRACT FROM AUTHOR]

A modular and decoupled approach to achieve harmonic cancellation in a multilevel Static Compensator (STATCOM) is presented in this paper. This work shows that it is possible to split the compensation tasks depending on the frequency components present on the line current that is intended to be compensated by using the superposition principle and the modular features of an H-bridge based multilevel STATCOM. This approach allows the implementation of the topology with dedicated modules in order to decouple and simplify the control algorithms. The H-bridge modules can be implemented with two different kinds of semiconductors: (i) slow switches for fundamental frequency compensation modules and (ii) fast switches for harmonic frequency compensation modules. As the modules meant for harmonic cancellation can self-regulate its dc voltage, they can follow the load requirements and thus operate with minimum power. The theoretical analysis is validated in a laboratory prototype. [ABSTRACT FROM AUTHOR]

An asymmetric inverter features different dc-link voltages for each power cell and depending on the dc voltage ratios, there are binary, trinary, etc., asymmetric topologies. In particular, the trinary one can provide a waveform with 3^n levels, where n is the number of cells connected in cascade. Hence, for $n = 3$, an output voltage with 27 levels can be obtained, ensuring a low total harmonic distortion (THD) and reduced $dv/dt$. However, when the load consumes active power, some power cells of the inverter can operate in regeneration mode, complicating the topology and control. To overcome this problem, a new modulation method for asymmetric inverters is presented. It features an ac output voltage of 13 levels for $n = 3$, and ensures unidirectional power flow in every power cell. This new modulation method also provides a voltage waveform with low $dv/dt$ and reduced THD (5.7%). To confirm the approach, power flow and sensitivity analysis to changes in the dc voltage ratios are performed. Finally, simulation and experimental results are provided. [ABSTRACT FROM PUBLISHER]

A discrete-time linear control strategy for a multilevel three-phase unified power quality conditioner (UPQC) based on single-phase power cells is presented. The multi-variable, nonlinear, and coupled features of these topologies make the control strategy design a difficult task. Controlling this kind of system with single-variable linear controllers—as proposed in this work—presents significant advantages compared with other approaches as simplicity in the design steps due to the large amount of tools developed for this kind of schemes. Particularly, a classic design method based on the root locus approach is used to choose the controllers parameters in order to achieve a given dynamical behavior. Compensation of reactive power and fundamental frequency disturbances is presented in this paper as part of a general control strategy for multilevel active power filters. The proposed control strategy is implemented on the TMS320C6713 DSP-based system for a low-power laboratory prototype, and thus the controllers design is carried out on the discrete-time and -frequency domain. Also, due to the inherent asymmetries among the power cells in a modular topology, a dedicated local control strategy is proposed to ensure a symmetrical distribution of the power among the power cells. This feature allows the semiconductor devices of each module to operate under the same voltage and current ratings. Simulated and experimental results showing stationary and transient conditions demonstrate the feasibility of the control scheme. [ABSTRACT FROM PUBLISHER]

Grinding mill drives play an important role in the mining industry. Almost 60% of the electrical energy consumed by modem concentrator plants goes to grinding mill drives. Different technologies are used in grinding systems presenting special characteristics from the electrical and process points of view. This paper presents a technical evaluation and practical experience of two different technologies used in high-power grinding mill drives. The analysis is focused on the static power converter and associated control scheme required to drive the motor. Cycloconverters and load-commutated inverters are analyzed in terms of power grid interaction, motor interaction, and the required control scheme. The evaluation is supported with practical results obtained in different concentrator plant facilities. [ABSTRACT FROM AUTHOR]

Two hundred and twenty Argentinian primary school children (122 boys, 98 girls, aged 6-13 years) were studied to establish reference values of 24-h urinary calcium excretion (UCa) and calcium/creatinine ratio (Ca/Cr) in 24-h urine collections and in first-morning urine samples. Mean UCa excretion was 2.05±1.40 mg/kg per day and the 95th percentile was 4.74 mg/kg per day. UCa excretion was higher in boys than girls (2.33±1.47 and 1.70±1.24 mg/kg per day respectively, P < 0.001). Statistically significant differences were found between the 6to 9-year and the 10- to 13-year age groups (2.37 ± 1.49 vs. 1.73 ± 1.25 mg/kg per day, P < 0.001). Mean Ca/Cr ratios in 24-h collections and in first-morning urine samples were 0.129±0.086 and 0.105±0.079 for the group overall (P < 0.001). The Ca/Cr ratio in the first-morning urine sample correlated poorly with the 24-h calcium excretion, suggesting that the Ca/Cr ratio in first-morning urine samples cannot replace the 24-h measurement. [ABSTRACT FROM AUTHOR]