Analog Lock-In Amplifier Design Using Subsampling for Accuracy Enhancement in GMI Sensor Applications.

A frequency downscaling technique for enhancing the accuracy of analog lock-in amplifier (LIA) architectures in giant magneto-impedance (GMI) sensor applications is presented in this paper. As a proof of concept, the proposed method is applied to two different LIA topologies using, respectively, analog and switching-based multiplication for phase-sensitive detection. Specifically, the operation frequency of both the input and the reference signals of the phase-sensitive detector (PSD) block of the LIA is reduced through a subsampling process using sample-and-hold (SH) circuits. A frequency downscaling from 200 kHz, which is the optimal operating frequency of the employed GMI sensor, to 1 kHz has been performed. In this way, the proposed technique exploits the inherent advantages of analog signal multiplication at low frequencies, while the principle of operation of the PSD remains unaltered. The circuits were assembled using discrete components, and the frequency downscaling proposal was experimentally validated by comparing the measurement accuracy with the equivalent conventional circuits. The experimental results revealed that the error in the signal magnitude measurements was reduced by a factor of 8 in the case of the analog multipliers and by a factor of 21 when a PSD based on switched multipliers was used. The error in-phase detection using a two-phase LIA was also reduced by more than 25%.

Giant direct and inverse magnetocaloric effect linked to the same forward martensitic transformation.

Metamagnetic shape memory alloys have aroused considerable attraction as potential magnetic refrigerants due to the large inverse magnetocaloric effect associated to the magnetic-field-induction of a reverse martensitic transformation (martensite to austenite). In some of these alloys, the austenite phase can be retained on cooling under high magnetic fields, being the retained phase metastable after field removing. Here, we report a giant direct magnetocaloric effect linked to the anomalous forward martensitic transformation (austenite to martensite) that the retained austenite undergoes on heating. Under moderate fields of 10 kOe, an estimated adiabatic temperature change of 9 K has been obtained, which is (in absolute value) almost twice that obtained in the conventional transformation under higher applied fields. The observation of a different sign on the temperature change associated to the same austenite to martensite transformation depending on whether it occurs on heating (retained) or on cooling is attributed to the predominance of the magnetic or the vibrational entropy terms, respectively.

Manejo anestésico en la resección traqueal distal toracoscópica / Anaesthetic management in thoracoscopic distal tracheal resection

La resección quirúrgica de los tumores traqueales, especialmente los distales, supone un reto para los anestesiólogos implicados, principalmente por las dificultades para asegurar un adecuado control de la vía aérea y de la ventilación. Presentamos el caso de una paciente que se somete a la resección de tercio distal traqueal y anastomosis terminoterminal mediante videotoracoscopia, enfatizando sobre el manejo anestésico (AU)

Surgical resection of tracheal tumours, especially distal tracheal tumours, is a challenge for the anaesthesiologists involved, mainly due to difficulties in ensuring adequate control of the airway and ventilation. We report the case of a patient undergoing tracheal resection and anastomosis by VATS, emphasizing the anaesthetic management (AU)

Anaesthetic management in thoracoscopic distal tracheal resection. / Manejo anestésico en la resección traqueal distal toracoscópica.

Surgical resection of tracheal tumours, especially distal tracheal tumours, is a challenge for the anaesthesiologists involved, mainly due to difficulties in ensuring adequate control of the airway and ventilation. We report the case of a patient undergoing tracheal resection and anastomosis by VATS, emphasizing the anaesthetic management.