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Trivalent Al3+-doped samples of magnetite (Alx ${\mathrm {Fe}}_{3-x}\text{O}$ 4, $0.01\le x \le1.0$) were produced by wet chemical method. The X-ray diffraction studies confirmed the formation of a single-phase inverse spinel-type structure. Particles having spherical morphology and size range lying between 4 and 25 nm were observed during transmission electron microscopic investigation. Magnetic measurement displayed increase in saturation magnetization with a maximum value of ~62 $\text{A}\cdot \text{m}$ 2/kg for $x =0.1$ , and thereafter, it started decreasing with increased concentration of Al. The temperature during magnetic hyperthermia got stabilized near therapeutic range (~315 K) for the samples such as $x =0.01$ , 0.5, 0.7, and 1.0 at various external alternating current magnetic fields. [ABSTRACT FROM AUTHOR]

Selective detection and quantification of biomarkers related to human diseases are essential for preventive healthcare. Surface-enhanced Raman scattering (SERS) spectroscopy is a powerful analytical tool offering high sensitivity. However, the success of this promising analytical tool relies on the ability to effectively fabricate SERS substrate. Herein we have demonstrated a plasmonic paper-based flexible substrate (PPFS) for SERS sensing. In situ growth of silver nanostructures (AgNS) on the paper-based substrate was achieved by using a simple one-step silver mirror reaction (SMR). FESEM and TEM results depicts that the increasing silver ion content influences the morphology (growth of multifacets), as well as size of AgNS. Further, the PPFS substrate was tested with Rhodamine-6G (Rh-6G) dye and an attomole sensitivity with a LOD of 4.54 $\times \,\,10^{-{18}}$ M was achieved. Further, two biomarkers, lactic acid (LA) and uric acid (UA) were detected on the PPFS substrate, with ${\mu }\text{M}$ and pM sensitivity, having LOD values of 0.6 $\times \,\,10^{-{6}}$ and 0.3 $\times \,\,10^{-{12}}$ M respectively. Above detection levels for UA on PPFS is two orders better than reported values, whereas for LA it is comparable with reported substrates. Finally, UA, LA and their mixtures were tested on PPFS and results compared with commercial substrate. The performance of PPFS were found better in all cases, thus, multifaceted AgNS paper based PPFS offers the potential to be used as a biosensor for detection of various biomarkers from body fluids, responsible for the detection of the critical disease for preventive health care. [ABSTRACT FROM AUTHOR]

Back electromotive force (EMF)-based sensorless vector control of permanent magnet synchronous motor (PMSM) drives provides a simple, robust, and low-cost solution for applications requiring only medium- and high-speed control. However, during the low-speed operation, back EMF is nearly zero, and hence, for starting and speed ramp-up, open-loop I−ƒ control is used. Once the motor attains a sufficient speed, the control is transferred to sensorless vector control. However, an arbitrary choice of the slope of frequency ramp leads to pole slipping. Pole slipping is usually prevented by fixing the frequency ramp slope to a minimum value, which deteriorates the dynamic performance during starting. In this article, a torque controller is proposed to dynamically vary the frequency slope depending on the moment of inertia and load torque present in the system, achieving fast and reliable starting. A reference frequency modulation algorithm for overcoming the inherent mid-frequency instability of the open-loop control is also included. An additional slope attenuator is proposed to minimize the torque oscillations caused by the reference frequency modulation during the transition from a ramp-up interval to a constant-speed interval with I−ƒ control. The proposed methods are experimentally verified on a 25-kW PMSM drive, which is started using open-loop I−ƒ control. [ABSTRACT FROM AUTHOR]