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Background: Human adipose tissue-derived stem cells (ASCs) are widely used in regenerative medicine and tissue engineering. Magnetic-activated cell sorting (MACS) with monoclonal antibodies (mAbs) that bind surface markers of stem cells such as CD105, CD73, and CD90 is currently applied for the enrichment and isolation of ASCs. Alternatives to mAbs are the variable domains of heavy chain antibodies (VHHs), which are naturally produced in camelids. We report the application of an anti-CD105 VHH conjugated to magnetic beads in the isolation of ASCs in vitro. Results: Two identical anti-CD105 VHHs (EngVHH17) were screened by phage display from a VHH cDNA library constructed from the PBMCs of an alpaca immunized with a lysate of human bladder cancer cell line (T24 cells). EngVHH17 was cloned in pET22b(+), expressed in Escherichia coli BL21 and purified in Ni-NTA chromatography resulting in a ∼15 kDa VHH antibody. EngVHH17 binds CD105 with high affinity (Kd = 3.9 × 10−10 M). The specific binding of EngVHH17 to CD105 was visualized by fluorescence inmunolabeling of phorbol-12-myristate-13-acetate (PMA)-differentiated THP1 cells using FITC labeled anti-6 × His Tag IgG1 mouse mAb. EngVHH17-magnetic beads selectively sorted human ASCs from osteoblasts in a mixed culture in vitro. The selective recovery of ASC cells using different ASC/Osteoblast ratios was higher than 85%. Conclusions: EngVHH17 coupled to magnetic beads binds CD105 expressed on the cell surface of ASCs and isolates them from osteoblasts in mixed cultures in vitro by application of an external magnetic field. EngVHH17 can be further evaluated for the isolation of MSCs by MACS.How to cite: Gushiken E, Quintana M, Perez L, et al. Isolation of adipose derived mesenchymal stem cells by using anti-CD105 VHH-magnetic beads. Electron J Biotechnol 2023;66. https://doi.org/10.1016/j.ejbt.2023.06.004.

Solar power generation has become a solution to mitigate the severe effects on the everyday higher prices of fossil fuels. Additionally, renewable energies operation -as solar- results in a non-polluting way to supply energy, being of special interest into highly contaminated cities and/or countries. The solar energy efficiency injection system is known to be high and mainly due to the power converters effectiveness, which is over of 95% for low and medium voltage. However, this efficiency is reduced when the solar array is partially shaded because traditional maximum power point tracking (MPPT) algorithms are not able to find the maximum power point (MPP) under irregular radiation. This work presents a new algorithm to find the global MPP (GMPP) based upon two MPPTs algorithms used regularly in uniform solar condition (USC), these are the Measuring Cell (MC) and the Perturb and Observe (P&O) methods. The MC ensures to find the surroundings of every local MPP (LMPP) faster and then choose among them the surroundings of the GMPP. Once the surroundings of GMPP are found, the P&O is used to get closer to the GMPP but reducing the DC voltage oscillation to zero hence overcoming the main issue of the P&O. Thus, the proposed algorithm finds the GMPP in two main steps and eliminates the oscillations around the GMPP in steady state, despite the utilization of the P&O. The algorithm is detailed mathematically, illustrated by means of a block diagram, and validated in simulated and experimental results.

Three-phase active front end rectifiers are a widely used power topology in applications such as renewable energy interfaces and motor drives, among many others. Its control is usually performed by a cascade combination of linear controllers which must be properly tuned for correct operation, and which depend on the operating point and system parameters. These family of controllers place inherent limits on the system dynamic response. On the other hand, the predictive control approach has been proposed as an alternative technique for these converters due to its fast dynamic response, simple concept, flexibility, multiple objective capability, among other desirable properties. In the case of power converter applications, short prediction horizons are usually used due to computational limitations. However, when short horizons are considered, the non-minimum phase characteristic of the rectifier voltage response can introduce stability issues, as its direct inversion is not possible without jeopardizing it. Indeed, this may lead to voltage regulation loss, and in the worst case, overcurrents that could damage the converter. To overcome such problem, this paper proposes a new concept for a predictive horizon one voltage controller for grid-connected three-phase active front end rectifiers. The proposal is based on the minimum and non-minimum phase plant factorization concept and the use of different sampling periods, to prevent the direct inversion of the non-minimum phase voltage dynamic. Simulated and experimental results are included and show its correct operation, even with a horizon one predictive voltage controller, thus ensuring the fastest response of the system for a given sampling time.

Cell-based Surface Plasmon Resonance imaging (SPRi) with anti-endoglin VHH antibodies microarray on a gold-covered biochip was used to characterize the binding to endoglin expressed on the surface membrane of SC cells. SPRi showed the specific capture of SC cells by the immobilized anti-endoglin VHHs, but not of THP-1 cells that do not express endoglin on their plasmatic membrane. The SPRi reflectivity shifts with SC cells bound by anti-endoglin VHHs ranged from 3.59 to 5.54% (average 4.66 ± 1.18%) and with THP-1 cells from 2.23 to 3.05% (average 2.62 ± 1.32% (p

Cascaded H-bridge drives require using a significant-size capacitor on each cell to deal with the oscillatory power generated by the H-bridge inverter in the DC-link. This results in a bulky cell with reduced reliability due to the circulating second harmonic current through the DC-link capacitors. In this article, a control strategy based on a finite control set model predictive control and a proportional-resonant controller is proposed to compensate for the oscillatory power required by the H-bridge inverter through the cell’s input rectifier. With the proposed strategy, a DC-link second harmonic free operation is achieved, allowing for the possibility of reducing the capacitor size and, in consequence, the cell dimensions. The feasibility of the proposed control scheme is verified by experimental results in one cell of a cascade H-bridge inverter achieving an operation with a capacitance 141 times smaller than required by conventional control approaches for the same voltage ripple.

This article presents a novel simplified method to implement the finite set - model predictive control technique for photovoltaic generation systems connected to the ac network. This method maintains the advantages of the conventional finite set - model predictive control, such as fast response, simple implementation, and easy understanding; but it also eliminates the use of a cost function and hence the weighting factors, instead, it finds the optimal operating state directly from the model and the discrete number of valid states of the converter. Although the proposed algorithm does not compute a cost function, it is able to select the inverter state that minimizes the tracking error by using a hexagonal convergence region. The main advantage of this technique is to reduce the computational cost in 43% of the algorithm that selects the best state, presenting a simple and complete algorithm without compromising the predictive control performance. The proposed algorithm properly operates under various conditions such as changes in the network frequency and changes in the system parameters.

Multicell converters, based on power cells that use low-voltage semiconductors, implement AC motor drives for medium-and high-voltage applications. These converters feature an input multipulse transformer, which performs low-frequency harmonics cancelation generated by three-phase diode rectifiers in the power cells. Despite this advantage, the multipulse transformer is bulky, heavy, expensive, and must be designed according to the number of power cells required by a specific case, limiting the modularity of the topology. This work proposes a multicell converter based on power cells that requires a standard input transformer and uses active front-end rectifiers controlled by employing a finite control set-model predictive control algorithm. The proposed approach emulates the multipulse transformer harmonic cancelation owing to the predictive algorithm operation combined with input current references that are phase-shifted for each active front-end rectifier. Simultaneously, the DC voltages of the power cells are regulated and equalized among the cells using PI regulators. Experimental results confirm the feasibility of the proposed system as input currents in each Multicell AFE rectifier with a unitary displacement factor, and a low THD of 1.87% was obtained. It is then possible to replace the input multipulse transformer with standard ones while reducing the copper losses, reducing the K factor, and extending the modularity of the power cell to the input transformer.

The LCL filter represents the state-of-the-art passive interface type for grid tied power converters as a cost and space reducing alternative to single coil solutions for switching harmonic attenuation. However, a simple PI controller can cause instabilities when applied to control the current of this filter. Thus a general analytically closed approach is presented to determine the safe operating areas for both grid current control mode (GCM) and inverter current control mode (ICM), both with and without additional active damping feedback of the capacitor current. The proposed approach consequently applies the Nyquist criterion in the continuous frequency domain, facilitating the determination of very simple expressions of parameter stability limits. These design guidelines, which partially also confirm previous findings, are for the first time summarized all together as the results of proposed approach to aid corresponding controller design.

Renewable energy has gained significant attention of researchers in the last years, mainly due to the importance of using unlimited energy sources to supply homes, industries, cities and countries. In this context, this document focuses on the solar injection by employing a neutral point clamped (NPC) topology together with utilization of a maximum power point tracking (MPPT) and space vector modulation (SVM) techniques. Model predictive control (MPC) is employed to manage the currents and track their references. The proposed algorithms do not employ a cost function to decide which voltage to apply resulting in a spread frequency spectrum, and instead, a concentrated SVM spectrum is imposed. Notwithstanding, the DC link capacitors voltage balance is ensured and the computational burden is notably reduced as compared to traditional Finite Set Model Predictive Control (FS-MPC). Nevertheless, the consistent results are a consequence of the critical analysis that shows the feasibility of the proposal and guarantees the good performance of the entire system in simulated and experimental platforms.

This paper presents a new finite control set model predictive control strategy that, contrary to conventional approaches, achieves (i) zero steady-state error in the converter's AC current, and (ii) both fixed and lower harmonic spectrum, similar to that achieved by pulse width modulation based control schemes. These characteristics are attractive for medium and high voltage applications where high dv/dt is prohibitive and reduced switching losses are a must, or in applications that use passive filters and where a spread harmonic spectrum can cause resonances. The proposed strategy achieves dynamic results similar to those of conventional predictive control and a steady-state performance similar to that of a modulated control strategy. To do so, the strategy utilizes a modulated integral action to incorporate an input restriction into a conventional predictive control cost function. A grid-connected cascaded H-Bridge multilevel inverter is used to validate the strategy. Simulated and experimental results in both steady and transient states are presented to verify the proposed strategy's performance in the converter.

Over the last few decades, the consolidated goal of reducing greenhouse gasses has increased the relevance of renewable energy research, electromobility, energy storage, and distributed generation, micro-grids, among others. Micro-grids, systems working in islanding mode, are particular cases where some disadvantages are present due to the wide variations which may appear across their electrical quantities. Variations on the voltage amplitude and the frequency are intrinsic in the operation of weak grids, because they have low inertia and therefore the load must be able to cope with these variations, otherwise loads may trip electrical system protection. Particularly, on power electronic drives, these frequency deviations will lead to increased system nonlinearities, entailing a more critical controller design. To overcome these issues, this paper presents an implementation of a resonant controller with self-tuned gains. The strategy imposes a constant sampling time which allows these controllers to be used in variable frequency environments. In addition, the computational capacity required for the digital board is also considered. The simulated and experimental results provided demonstrate the good performance of this proposal.

Objetivo. Producir anticuerpos recombinantes de cadena única de alpaca que se unan con alta afinidad y especificidad al antígeno excretado-secretado (ES) de Fasciola hepatica para el desarrollo de tecnologías nuevas de diagnóstico de fascioliasis humana y animal. Materiales y métodos. Se ha construido una genoteca de cADNde los dominios variables de anticuerpos de cadena única pesada, conocidos como VHH, a partir de células mononucleares de sangre periférica de una alpaca inmunizada con el antígeno ES de F. hepatica. La genoteca fue tamizada con el antígeno ES por despliegue diferencial de fagos (phage display), seleccionando diez VHH que se unen específicamente a ES. El VHH anti ES fue clonado en un vector de expresión, la proteína recombinante (VHH-ES1) de 15,3 kDa fue producida por fermentación en E. coli y purificada a homogeneidad por cromatografía de afinidad. La unión del VHH-ES1 al antígeno ES fue evaluada por ELISA usando VHHES1 como anticuerpo de captura, antisuero policlonal anti-ES de conejo y conjugado anti IgG de conejo con peróxidasa de rábano. Resultados. Se ha identificado y producido un VHH-ES1 recombinante que se une al antígeno ES (VHH-ES1) que correspondía a un anticuerpo de la subclase IgG2 de bisagra larga. La unión del anticuerpo VHH-ES1 al antígeno muestra linealidad respecto a la concentración de ES en el rango de 50-5000 ng/mL y el valor límite de detección del antígeno está en el rango de 30-170 ng/mL de ES (R2=0,99). Conclusión. El VHH-ES1 se une con afinidad y especificidad al antígeno ES de F. hepatica y es un anticuerpo promisorio a evaluar para el desarrollo de nuevas tecnologías de diagnóstico de fascioliasis.

Chronic mountain sickness (CMS) is a pathological condition resulting from chronic exposure to high-altitude hypoxia. While its prevalence is high in native Andeans (>10%), little is known about the genetic architecture of this disease. Here, we performed the largest genome-wide association study (GWAS) of CMS (166 CMS patients and 146 controls living at 4,380 m in Peru) to detect genetic variants associated with CMS. We highlighted four new candidate loci, including the first CMS-associated variant reaching GWAS statistical significance (rs7304081; P = 4.58 × 10−9). By looking at differentially expressed genes between CMS patients and controls around these four loci, we suggested AEBP2, CAST, and MCTP2 as candidate CMS causal genes. None of the candidate loci were under strong natural selection, consistent with the observation that CMS affects fitness mainly after the reproductive years. Overall, our results reveal new insights on the genetic architecture of CMS and do not provide evidence that CMS-associated variants are linked to a strong ongoing adaptation to high altitude.

The main drawback of the Cascaded-H Bridge converter based on three-phase/single-phase current-source inverters is the large DC inductors needed to limit the variation of the DC current caused by the single-phase inverter oscillating power. If the oscillating power is somehow compensated, then the DC inductor can be designed just as a function of the semiconductors’ switching frequency, reducing its value. This work explores the use of three-phase/single-phase cells magnetically coupled through their DC links to compensate for the oscillating power among them and, therefore, reduce the DC inductor value. At the same time, front ends controlled by a non-linear control strategy equalize the DC currents among coupled cells to avoid saturating the magnetic core. The effectiveness of the proposal is demonstrated using mathematical analysis and corroborated by computational simulation for a 110 kVA load per phase and experimental tests in a 2 kVA laboratory prototype. The outcomes show that for the tested cases, coupling the DC links by a 1:1 ratio transformer allows reducing the DC inductor value below 20% of the original DC inductor required. The above leads to reducing by 50% the amount of magnetic energy required in the DC link compared to the original topology without oscillating power compensation, keeping the quality of the cell input currents and the load voltage.

Several control strategies have been proposed with the aim to get a desired behavior in the power converter variables. The most employed control techniques are linear control, nonlinear control based on linear and nonlinear feedback, and predictive control. The controllers associated with linear and nonlinear algorithms usually have a fixed switching frequency, featuring a defined spectrum given by the pulse width modulation (PWM) or space vector modulation (SVM) time period. On the other hand, finite set model predictive control (FS-MPC) is known to present a variable switching frequency that results too high for high power applications, increasing losses, reducing the switches lifetime and, therefore, limiting its application. This paper proposes a predictive control approach using a very low sampling frequency, allowing the use of predictive control in high power applications. The proposed method is straightforward to understand, is simple to implement, and can be computed with off-the-shelf digital systems. The main advantage of the proposed control algorithm comes from the combination of the model predictive control and the SVM technique, drawing the principal benefits of both methods. The provided experimental results are satisfactory, displaying the nature of space vector-based schemes but at the same time the fast response as expected in predictive control.