Gravity as a tool to improve the hydrologic mass budget in karstic areas

Monitoring the water movements in karstic areas is a fundamental but challenging task due to the complexity of the drainage system and the difficulty in deploying a network of observations. Gravimetry offers a valid complement to classical hydrologic measurements in order to characterize such systems in which the recharge process causes temporarily accumulation of large water volumes in the voids of the epi-phreatic system. We show an innovative integration of gravimetric and hydrologic observations that constrains a hydrodynamic model of the Škocjan cave system (Slovenia). We demonstrate how the inclusion of gravity observations improves water mass budget estimates for the Škocjan area based on hydrological observations only. Finally, the detectability of water storage variations in other karstic contexts is discussed with respect to the noise performances of spring and super-conducting gravimeters

Neuronal hemoglobin affects dopaminergic cells' response to stress

Hemoglobin (Hb) is the major protein in erythrocytes and carries oxygen (O2) throughout the body. Recently, Hb has been found synthesized in atypical sites, including the brain. Hb is highly expressed in A9 dopaminergic (DA) neurons of the substantia nigra (SN), whose selective degeneration leads to Parkinson's disease (PD). Here we show that Hb confers DA cells' susceptibility to 1-methyl-4-phenylpyridinium (MPP(+)) and rotenone, neurochemical cellular models of PD. The toxic property of Hb does not depend on O2 binding and is associated with insoluble aggregate formation in the nucleolus. Neurochemical stress induces epigenetic modifications, nucleolar alterations and autophagy inhibition that depend on Hb expression. When adeno-associated viruses carrying \u3b1- and \u3b2-chains of Hb are stereotaxically injected into mouse SN, Hb forms aggregates and causes motor learning impairment. These results position Hb as a potential player in DA cells' homeostasis and dysfunction in PD. Copyright The Author(s) 201

Robust control of microvibrations with experimental verification

The paper addresses the problem of actively attenuating a particular class of vibrations, known as microvibrations, which arise, for example, in panels used on satellites. A control scheme which incorporates feedback action is developed which operates at a set of dominant frequencies in a disturbance spectrum, where the control path model is estimated online. Relative to earlier published techniques, a new feature of the presented controller is the use of the inverse Hessian to improve adaptation speed. The control scheme also incorporates a frequency estimation technique to determine the relevant disturbance frequencies with higher precision than the standard fast Fourier transform (FFT). The control scheme is implemented on an experimental test-bed and the total achieved attenuation, as measured from the experiments, is 26dB. The low computational demand of the control scheme allows for single chip controller implementation, a feature which is particularly attractive for potential applications areas, such as small satellites, where there are critical overall weight restrictions to be satisfied whilst delivering high quality overall performance

A ground based gravity network for monitoring water mass movements in the Classical Karst region

The Classical Karst is a limestone plateau stretching between Italy and Slovenia over an area of about 600km2.The aquifer of Classical Karst contains a complex network of conduits, shafts and large voids that are fed by theautogenic recharge and allogenic input of the Reka River. The Reka River sinks underground in the \u160kocjan Cavesand continues its underground flow for almost 40km until it reaches the Adriatic Sea at the Timavo Springs. Theriver shows high discharge variations; with minimal discharge below 0.3 m3/s and maximal discharge reachingover 350 m3/s. As the conduit system cannot efficiently drain large discharge, huge water masses are stored inthe epiphreatic voids of the aquifer during flood events. \u160kocjan Caves present such storage, where a vast amountof water is temporary stored during intense rain. Further evidences of the impressive water movements in thissystem could be found in the geodetic time-series recorded by the Grotta Gigante horizontal pendulums, whichshow deformation transients during Reka flood events. Gravimetry could be a useful tool to obtain local mass balances of such complex system, contributing together withthe other classical hydrologic prospections in depicting the water dynamics in this karstic environment. In additionto this gravimetry represents the ideal completion to the already set up geodetic instrumentation in the ClassicalKarst region. In the last year, we installed two continuous recording gravity stations, near the \u160kocjan caves and inside the GrottaGigante cave. The \u160kocjan caves serve as a test site because the cave geometry and the hydraulic system here arewell known. The Grotta Gigante site offers a quiet place and long term geodetic time-series but on the other hand,the hydrodynamics here are less clear. In this contribution, we present the simulations in support to the placement of the instruments and the first analysisconducted on the observed gravity time-series. For the \u160kocjan caves our simulations estimate that this mass accu-mulation could generate gravity signals up to 30 microGal for extreme events with peak discharge over 250m3/slasting for 1-1.5 days, accumulating over 35 106m3of water. The recorded data in \u160kocjan supports our simula-tions: a prominent peak up to 5 microGal of amplitude was recorded during a 14 106m3flood event on October2018. We believe that the Classical Karst represents an interesting study case for both the geodetic and hydrologic com-munities; the \u160kocjan cave offers a natural laboratory to optimally assess the contribution of gravimetry as a toolfor monitoring underground fluid mass movements

Frequency selective microvibration control for a single plate

In recent years, frequency selective controllers were developed to offer an alternative to the well studied and widely used filtered reference least mean square algorithm. The motivation came from the fact, that many disturbance spectra are dominated by a finite set of frequencies (tones). Hence it was concluded that noticeable reduction could be achieved by just controlling the dominant tones. The main advantages of frequency selective controllers are that stability can be shown easily and the controller is of lower order compared to standard FIR filters. Initially, the here presented controllers were tested in sound experiments and excellent behaviour was demonstrated. Then a vibrating plate test rig was acquired and it was possible to move on to examine the control behaviour for microvibrations. A lump mass was fixed to the plate to create an unbalanced behaviour. Furthermore, 4 piezoelectric components were glued to the plate. The arrangement is, that 2 piezoelectric elements are opposite each other on either side of the plate. Different experimental trials were carried out. It was started with driving one piezoelectric element as a disturbance generator and the use of two more as actuator and accelerometer respectively. Model free and model based controllers were implemented. All controller types achieved an overall attenuation for the whole frequency band of more than 10 dB, not only for the controlled frequencies justifying the approach taken