Redox activity as a powerful strategy to tune magnetic and/or conducting properties in benzoquinone-based metal-organic frameworks

Multifunctional molecular materials have attracted material scientists for several years as they are promising materials for the future generation of electronic devices. Careful selection of their molecular building blocks allows for the combination and/or even interplay of different physical properties in the same crystal lattice. Incorporation of redox activity in these networks is one of the most appealing and recent synthetic strategies used to enhance magnetic and/or conducting and/or optical properties. Quinone derivatives are excellent redox-active linkers, widely used for various applications such as electrode materials, flow batteries, pseudo-capacitors, etc. Quinones undergo a reversible two-electron redox reaction to form hydroquinone dianions via intermediate semiquinone radical formation. Moreover, the possibility to functionalize the six-membered ring of the quinone by various substituents/functional groups make them excellent molecular building blocks for the construction of multifunctional tunable metal-organic frameworks (MOFs). An overview of the recent advances on benzoquinone-based MOFs, with a particular focus on key examples where magnetic and/or conducting properties are tuned/switched, even simultaneously, by playing with redox activity, is herein envisioned

An IMU and USBL-aided buoy for underwater localization

Autonomous underwater navigation remains, as of today, a challenging task. The marine environment limits the number of sensors available for precise localization, hence Au- tonomous Underwater Vehicles (AUVs) usually rely on inertial and velocity sensors to obtain an estimate of their position either through dead reckoning or by means of more sophisticated navigation filters (such as Kalman filters and its extensions [1]). On the other hand, acoustic localization makes possible the determination of a reliable vehicles pose estimate exploiting suit- able acoustic modems [3]; such estimate can even be integrated within the navigation filter of the vehicle in order to increase its accuracy. In this paper, the authors discuss the development and the performance of an Ultra-Short BaseLine (USBL)-aided buoy to improve the localization of underwater vehicles. At first, the components and the physical realization of the buoy will be discussed; then, the procedure to compute the position of the target will be analyzed. The following part of the paper will be focused on the development of a recursive state estimation algorithm to process the measurements computed by the buoy; specifically, Extended Kalman Filter [4] has been adopted to deal with the nonlinearities of the sensors housed on the buoy. A validation of the measurement filtering through experimental tests is also proposed

An IMU and USBL-aided buoy for underwater localization

Autonomous underwater navigation remains, as of today, a challenging task. The marine environment limits the number of sensors available for precise localization, hence Au- tonomous Underwater Vehicles (AUVs) usually rely on inertial and velocity sensors to obtain an estimate of their position either through dead reckoning or by means of more sophisticated navigation filters (such as Kalman filters and its extensions [1]). On the other hand, acoustic localization makes possible the determination of a reliable vehicles pose estimate exploiting suit- able acoustic modems [3]; such estimate can even be integrated within the navigation filter of the vehicle in order to increase its accuracy. In this paper, the authors discuss the development and the performance of an Ultra-Short BaseLine (USBL)-aided buoy to improve the localization of underwater vehicles. At first, the components and the physical realization of the buoy will be discussed; then, the procedure to compute the position of the target will be analyzed. The following part of the paper will be focused on the development of a recursive state estimation algorithm to process the measurements computed by the buoy; specifically, Extended Kalman Filter [4] has been adopted to deal with the nonlinearities of the sensors housed on the buoy. A validation of the measurement filtering through experimental tests is also proposed

Influence of carbon on intraband scattering in Mg(B1-xCx)2

We report data on the Hall coefficient (RH) of the carbon substituted Mg(B1-xCx)2 single crystals with x in the range from 0 to 0.1. The temperature dependences of RH obtained for the substituted crystals differ systematically at low temperatures, but all of them converge to the value of 1.8 x 10^-10 m^3/C at room temperature. The RH(T) data together with results of the thermoelectric power and electrical resistivity measurements are interpreted within a quasi-classical transport approach, where the presence of four different conducting sheets is considered. The main influence of the carbon substitution on the transport properties in the normal state is associated with enhanced scattering rates, rather than modified concentration of charge carriers. Presumably the carbon substitution increases the electron-impurity scattering mainly in the pi band.Comment: 16 pages, 3 figure

Piecewise planar underwater mosaicing

A commonly ignored problem in planar mosaics, yet often present in practice, is the selection of a reference homography reprojection frame where to attach the successive image frames of the mosaic. A bad choice for the reference frame can lead to severe distortions in the mosaic and can degenerate in incorrect configurations after some sequential frame concatenations. This problem is accentuated in uncontrolled underwater acquisition setups as those provided by AUVs or ROVs due to both the noisy trajectory of the acquisition vehicle - with roll and pitch shakes - and to the non-flat nature of the seabed which tends to break the planarity assumption implicit in the mosaic construction. These scenarios can also introduce other undesired effects, such as light variations between successive frames, scattering and attenuation, vignetting, flickering and noise. This paper proposes a novel mosaicing pipeline, also including a strategy to select the best reference homography in planar mosaics from video sequences which minimizes the distortions induced on each image by the mosaic homography itself. Moreover, a new non-linear color correction scheme is incorporated to handle strong color and luminosity variations among the mosaic frames. Experimental evaluation of the proposed method on real, challenging underwater video sequences shows the validity of the approach, providing clear and visually appealing mosaic

Fully Band Resolved Scattering Rate in MgB2 Revealed by Nonlinear Hall Effect and Magnetoresistance Measurements

We have measured the normal state temperature dependence of the Hall effect and magnetoresistance in epitaxial MgB2 thin films with variable disorders characterized by the residual resistance ratio RRR ranging from 4.0 to 33.3. A strong nonlinearity of the Hall effect and magnetoresistance have been found in clean samples, and they decrease gradually with the increase of disorders or temperature. By fitting the data to the theoretical model based on the Boltzmann equation and ab initio calculations for a four-band system, for the first time, we derived the scattering rates of these four bands at different temperatures and magnitude of disorders. Our method provides a unique way to derive these important parameters in multiband systems.Comment: 4 pages, 4 figure

The FAOSTAT database of greenhouse gas emissions from agriculture

Peer reviewedPublisher PD