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This work presents a comprehensive method for precisely determining the equivalent circuit characteristics of single-phase induction motors (SPIM), including both direct and indirect steps. First, a DC test, a no-load test and a locked-rotor test are performed to ascertain the primary electrical characteristics of both the main and auxiliary windings. Next, the indirect phase consists of iteratively modifying the mechanical characteristics, such as the inertial moment and friction factor, in a motor simulation model in Simulink until they match the previously determined electrical parameters. In addition, the motor parameter estimate process can be improved by applying the Nelder–Mead optimisation approach, which eliminates the need to calculate partial derivatives of a cost function. The study also applies the scalar control to the SPIM. Ultimately, the efficacy of the suggested methodology is confirmed through a comparison of simulated and actual outcomes.

The Escherichia coli AcrAB-TolC efflux pump is the archetype of the resistance nodulation cell division (RND) exporters from Gram-negative bacteria. Overexpression of RND-type efflux pumps is a major factor in multidrug resistance (MDR), which makes these pumps important antibacterial drug discovery targets. We have recently developed novel pyranopyridine-based inhibitors of AcrB, which are orders of magnitude more powerful than the previously known inhibitors. However, further development of such inhibitors has been hindered by the lack of structural information for rational drug design. Although only the soluble, periplasmic part of AcrB binds and exports the ligands, the presence of the membrane-embedded domain in AcrB and its polyspecific binding behavior have made cocrystallization with drugs challenging. To overcome this obstacle, we have engineered and produced a soluble version of AcrB [AcrB periplasmic domain (AcrBper)], which is highly congruent in structure with the periplasmic part of the full-length protein, and is capable of binding substrates and potent inhibitors. Here, we describe the molecular basis for pyranopyridine-based inhibition of AcrB using a combination of cellular, X-ray crystallographic, and molecular dynamics (MD) simulations studies. The pyranopyridines bind within a phenylalanine-rich cage that branches from the deep binding pocket of AcrB, where they form extensive hydrophobic interactions. Moreover, the increasing potency of improved inhibitors correlates with the formation of a delicate protein- and water-mediated hydrogen bond network. These detailed insights provide a molecular platform for the development of novel combinational therapies using efflux pump inhibitors for combating multidrug resistant Gram-negative pathogens.

Recently we described a novel pyranopyridine inhibitor (MBX2319) of RND-type efflux pumps of the Enterobacteriaceae. MBX2319 (3,3-dimethyl-5-cyano-8-morpholino-6-(phenethylthio)-3,4-dihydro-1H-pyrano[3,4-c]pyridine) is structurally distinct from other known Gram-negative efflux pump inhibitors (EPIs), such as 1-(1-naphthylmethyl)-piperazine (NMP), phenylalanylarginine-β-naphthylamide (PAβN), D13-9001, and the pyridopyrimidine derivatives. Here, we report the synthesis and biological evaluation of 60 new analogs of MBX2319 that were designed to probe the structure activity relationships (SARs) of the pyranopyridine scaffold. The results of these studies produced a molecular activity map of the scaffold, which identifies regions that are critical to efflux inhibitory activities and those that can be modified to improve potency, metabolic stability and solubility. Several compounds, such as 22d-f, 22i and 22k, are significantly more effective than MBX2319 at potentiating the antibacterial activity of levofloxacin and piperacillin against Escherichia coli.

Efflux pumps of the resistance nodulation division (RND) superfamily, such as AcrB, make a major contribution to multidrug resistance in Gram-negative bacteria. The development of inhibitors of the RND pumps would improve the efficacy of current and next-generation antibiotics. To date, however, only one inhibitor has been cocrystallized with AcrB. Thus, in silico structure-based analysis is essential for elucidating the interaction between other inhibitors and the efflux pumps. In this work, we used computer docking and molecular dynamics simulations to study the interaction between AcrB and the compound MBX2319, a novel pyranopyridine efflux pump inhibitor with potent activity against RND efflux pumps of Enterobacteriaceae species, as well as other known inhibitors (D13-9001, 1-[1-naphthylmethyl]-piperazine, and phenylalanylarginine-β-naphthylamide) and the binding of doxorubicin to the efflux-defective F610A variant of AcrB. We also analyzed the binding of a substrate, minocycline, for comparison. Our results show that MBX2319 binds very tightly to the lower part of the distal pocket in the B protomer of AcrB, strongly interacting with the phenylalanines lining the hydrophobic trap, where the hydrophobic portion of D13-9001 was found to bind by X-ray crystallography. Additionally, MBX2319 binds to AcrB in a manner that is similar to the way in which doxorubicin binds to the F610A variant of AcrB. In contrast, 1-(1-naphthylmethyl)-piperazine and phenylalanylarginine-β-naphthylamide appear to bind to somewhat different areas of the distal pocket in the B protomer of AcrB than does MBX2319. However, all inhibitors (except D13-9001) appear to distort the structure of the distal pocket, impairing the proper binding of substrates.

This paper aims to study the intensity of trade between Vietnam and its trading partners. Vietnam's revealed trade preference with a country was found to be negatively correlated with distance, but positively correlated with contiguity, colonial linkages and having a free trade agreement between the pair. At the disaggregate level, contiguity leads to higher revealed export preferences in labour-intensive goods for Vietnam, but this effect on revealed import preferences is less significant. The revealed trade preference indices show that among major trading partners, China's role is important for Vietnam's trade, but this role is less dominant than what traditional trade share analysis shows. [ABSTRACT FROM AUTHOR]

Two-dimensional (2D) metallic TaSe2 and semiconducting WSe2 materials have been successfully fabricated in experiments and are considered as promising contact and channel materials, respectively, for the design of next-generation electronic devices. Herein, we design a metal–semiconductor (M–S) heterostructure combining metallic TaSe2 and semiconducting WSe2 materials and investigate the atomic structure, electronic properties and controllable contact types of the combined TaSe2/WSe2 M–S heterostructure using first-principles calculations. Our results reveal that the TaSe2/WSe2 M–S heterostructure can adopt four different stable stacking configurations, all of which exhibit enhanced elastic constants compared to the constituent monolayers. Furthermore, the TaSe2/WSe2 M–S heterostructure exhibits p-type Schottky contact (SC) with Schottky barriers ranging from 0.36 to 0.49 eV, depending on the stacking configurations. The TaSe2/WSe2 M–S heterostructure can be considered as a promising M–S contact for next-generation electronic Schottky devices owing to its small tunneling resistivity of about 2.14 × 10−9 Ω cm2. More interestingly, the TaSe2/WSe2 M–S heterostructure exhibits tunable contact types and contact barriers under the application of an electric field. A negative electric field induces a transition from Schottky contact type to ohmic contact (OC) type. On the other hand, a positive electric field leads to a transformation from p-type SC to n-type SC. Our findings provide valuable insights into the practical applications of the TaSe2/WSe2 M–S heterostructure towards next-generation electronic devices. [ABSTRACT FROM AUTHOR]

The paper examines the forestland conversion in the period 2001-2005 and its socioeconomic determinants affecting such a change in Kien Luong district of southern Vietnam using Geographic Information Systems (GIS), Remote Sensing (RS), and multiple regression techniques. The land use/ land cover (LULC) classes of the years 2001 and 2005 were in turn classified from Landsat ETM Plus 2001 and digitized from the district land-use map 2005. Corresponding socioeconomic data to the derived LULC classes were aggregated for the multiple regression analysis of determinants of the forestland conversion. The findings indicated that the loss of forestlands was driven by the quick growth of the rural economy in which the two largest contributors were the prompt expansion of agricultural and aquaculture lands. Such a land-use change initially hampered the agricultural development and ecological services. Addressing land-use suitability for production systems and socio-environmental costs of the changes was therefore an urgent need for the aim of more effective policies of utilization and management of land resources.

This article describes the development of a low-cost, real-time simulator of several control strategies for brushed DC motor drives. An educational brushed DC motor drive test bench and an Arduino Mega 2560 microcontroller board were used to build the simulation system. The system can serve as a platform for laboratory studies in which various control strategies helpful for instruction and research purposes. The interaction between MATLAB Simulink and the Arduino board can be managed through the exploration of the MATLAB Support Package for Arduino. Different speed control algorithms for brushed DC motors can be easily deployed, monitored, and analysed using the Simulink multiform library. Three different types of controllers have been used in this study: a standard PI controller, a fuzzy logic controller, and a fuzzy PI controller. Finally, the system is particularly helpful in comparing various control approaches for many other controlled objects in addition to drives for brushed DC motors. [ABSTRACT FROM AUTHOR]