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There was two errors in the original article [...].
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The most widely used technique for measuring capacitive impedances (or complex electrical permittivity) is to apply a frequency signal to the sensor and measure the amplitude and phase of the output signal. The technique, although efficient, involves high-speed circuits for phase measurement, especially when the medium under test has high conductivity. This paper presents a sensor to measure complex electrical permittivity based on an alternative approach to amplitude and phase measurement: The application of two distinct frequencies using a current-to-voltage converter circuit based in a transimpedance amplifier, and an 8-bit microcontroller. Since there is no need for phase measurement and the applied frequency is lower compared to the standard method, the circuit presents less complexity and cost than the traditional technique. The main advance presented in this work is the use of mathematical modeling of the frequency response of the circuit to make it possible for measuring the dielectric constant using a lower frequency than the higher cut-off frequency of the system, even when the medium under test has high conductivity (tested up to 1220 µS/cm). The proposed system caused a maximum error of 0.6% for the measurement of electrical conductivity and 2% for the relative dielectric constant, considering measurement ranges from 0 to 1220 µS/cm and from 1 to 80, respectively.
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In this article we respond to the comments made by Chavanne et al., who have questioned: (i) the name of the technique used; (ii) the ability of the system to determine both soil water content and salinity due to potential instrument biases and choice of sensor frequencies; and (iii) the procedure used to determine temperature effect on readings presented in the article "A Novel Low-Cost Instrumentation System for Measuring the Water Content and Apparent Electrical Conductivity of Soils" (Sensors 2015, 15, 25546â»25563). We have carefully analyzed the arguments in the comment, and have concluded that they only partially affect the previous conclusions, as will be discussed in this reply. We show here that the findings and conclusions previously drawn are valid and supported by the many experiments previously conducted.
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Background The surgical microscope is still essential for microsurgery, but several alternatives that show promising results are currently under development, such as endoscopes and laparoscopes with video systems; however, as yet, these have only been used for arterial anastomoses. The aim of this study was to evaluate the use of a low-cost video-assisted magnification system in replantation of the hindlimbs of rats. Methods Thirty Wistar rats were randomly divided into two matched groups according to the magnification system used: the microscope group, with hindlimb replantation performed under a microscope with an image magnification of 40× and the video group, with the procedures performed under a video system composed of a high-definition camcorder, macrolenses, a 42-in television, and a digital HDMI cable. The camera was set to 50× magnification. We analyzed weight, arterial and venous caliber, total surgery time, arterial and venous anastomosis time, patency immediately and 7 days postoperatively, the number of stitches, and survival rate. Results There were no significant differences between the groups in weight, arterial or venous caliber, or the number of stitches. Replantation under the video system took longer (p < 0.05). Patency rates were similar between groups, both immediately and 7 days postoperatively. Conclusion It is possible to perform a hindlimb replantation in rats through video system magnification, with a satisfactory success rate comparable with that for procedures performed under surgical microscopes.
