Computational Analysis of the Active Control of Incompressible Airfoil Flutter Vibration Using a Piezoelectric V-Stack Actuator

The flutter phenomenon is a potentially destructive aeroelastic vibration studied for the design of aircraft structures as it limits the flight envelope of the aircraft. The aim of this work is to propose a heuristic design of a piezoelectric actuator-based controller for flutter vibration suppression in order to extend the allowable speed range of the structure. Based on the numerical model of a three degrees of freedom (3DOF) airfoil and taking into account the FEM model of a V-stack piezoelectric actuator, a filtered PID controller is tuned using the population decline swarm optimizer PDSO algorithm, and gain scheduling (GS) of the controller parameters is used to make the control adaptive in velocity. Numerical simulations are discussed to study the performance of the controller in the presence of external disturbances

K-space use for MRI intra-voxel analysis: advantage in neuroimaging

Analyzing signals inside MRI K-space with the use of compressed sensing algorithms we want to separate, inside single voxel, the different kind of tissues eventually present inside it. The use of compressed sensing is well known in many other fields for image analysis (i.e. remote sensing) related to separation of random intra-voxel contributes so is specifically suitable also in MRI acquisitions having them same kind of characteristics. So using it for clustering single contributions inside a single voxel can be a big step forward in MRI imaging. Using Spin-Echo sequences we find that different materials evidence the different response in terms of TE signaling so to compose the 100% inside the examinated single voxel. Analyzing relaxation time due to spin-spin interaction of considered materials we can put in evidence the different nature of signals sources therefore also the different tissues composing the single voxel. While with the above described use of compressed sensing k-space analysis our goal is to improve the spatial resolution obtained with the actual MRI imaging techniques we can reach another target considering the intrinsic characteristics of compressed sensing k-space processing. We can insulate single contributions coming from random signal analysis in not completely defined k-spaces (under-sampled) so we can moreover use these algorithms for faster than actual time acquisition imaging. In this way we obtain an improved temporal resolution compared with same time acquisition as actual. This kind of advantage can be immediately used for such sampling as fMRI where an high temporal resolution is suitable for image analysis where an high time domain resolution shows clear advantages when is maintained an affordable spatial domain one getting affordable acquisition times. Having such possibility to separate different intra-voxel contributes, something in some way similar to what is done with MRS techniques, but with much less complications and with not so high fields involved, permits to give an important contribution to understanding and reading MRI results expanding the possibility related to their use

The cortico-pallidal projection in the human: a tracking study with DT I technique

We investigated the globus pallidus starting from basal ganglia circuits scheme based on cortico-basal ganglia-thalamo-cortical loop. Globus pallidus represents the exit module from previous cited loop and having the role of locking or unlocking the motor gesture through its inhibition state. Such activities are regulated by direct, indirect and hyperdirect ways. Some studies demonstrated an immediate globus pallidus activation after cortex stimulation; another one provided the existence of a bundle of cortico-pallidal fibers, not crossing the neostriatum, in laboratory animals. Existence of such pathways is not demonstrated in human beings. Using DTI tecnique in this study we found an ipsilateral fiber bundle starting from prefrontal cortex and clearly directed to the globus pallidus. The existence of such direct cortico-pallidal projection, not crossing the neostriatum, was suggested by Testut and Latarjet and following asserted anatomically and by neuronography. Furthermore the presence of glutamatergic and dopaminergic receptors in the animal globus pallidus, already demonstrated in other studies, reinforces the validity of the results obtained in the present one also if should be important to demonstrate the presence of such receptors in humans

Diffusion tensor imaging (DT I) and Transcranial magnetic stimulation (TMS): an integrated approach

In present study we adopted an innovative approach, integrating the “Diffusion Tensor Imaging tractography (DTI)” technique with navigated transcranial magnetic stimulation (nTMS). In this way it is possible to improve accuracy of motor fiber reconstruction by positioning the fiducial seeding from DTI reconstruction, over the motor areas localized by nTMS. This will allow a direct comparison between the density of the motor map obtained with nTMS with the related axonal density obtained with DTI. DTI uses anisotropic water diffusion like test to study in vivo white matter anatomy in order to reconstruct tri-dimensional fiber bundles improving the practical 1 mm. MRI scanning resolution. Therefore we used the appropriate acquisition and reconstruction DTI techniques in order to study local cerebral pathways. Related acquisition must be done following resonance protocol and varying the magnetic gradient, in order to have the following steps: DWI acquisition; tensor calculation; scalar maps; 3d visualization; fiducial seeding. DTI technique can exploit two different classes of fiber tracking algorithms: “deterministic” or “probabilistic” tracking higherorder integration schemes. The deterministic one, allows to calculate the directions of streamline propagation, and reveals only, presence or absence of a connection. On the other hand a probabilistic tracking approach is achieved: starting from a basic point, fibers are propagated multiple times through the tensor field while varying, in a stochastic way, the estimated fiber orientation along the traversed voxels. In addition nTMS is a newly evolving technique for in vivo investigating human motor system combining spatial information from high-resolution MRI with the functionality of non-invasive cortical stimulation. In this way it is possible to target motor areas more precisely obtaining a discrete motor maps of facial, hand and leg muscles. This innovative approach will indeed provide a new tool in neuroscience for an in vivo direct correlation between anatomical circuits and electrophysiological data

Non-Invasive Brain Stimulation for the Modulation of Aggressive Behavior—A Systematic Review of Randomized Sham-Controlled Studies

Intro: Aggressive behavior represents a significant public health issue, with relevant social, political, and security implications. Non-invasive brain stimulation (NIBS) techniques may modulate aggressive behavior through stimulation of the prefrontal cortex. Aims: To review research on the effectiveness of NIBS to alter aggression, discuss the main findings and potential limitations, consider the specifics of the techniques and protocols employed, and discuss clinical implications. Methods: A systematic review of the literature available in the PubMed database was carried out, and 17 randomized sham-controlled studies investigating the effectiveness of NIBS techniques on aggression were included. Exclusion criteria included reviews, meta-analyses, and articles not referring to the subject of interest or not addressing cognitive and emotional modulation aims. Conclusions: The reviewed data provide promising evidence for the beneficial effects of tDCS, conventional rTMS, and cTBS on aggression in healthy adults, forensic, and clinical samples. The specific stimulation target is a key factor for the success of stimulation on aggression modulation. rTMS and cTBS showed opposite effects on aggression compared with tDCS. However, due to the heterogeneity of stimulation protocols, experimental designs, and samples, we cannot exclude other factors that may play a confounding role

Limbic-motor areas interactions as revealed by Constrained Spherical Deconvolution tractography: a mechanism to shape complex motor behaviors?

Although there are several evidences in animal research on the emotional motor-limbic subcortical system including amygdala, hyppocampus, parahyppocampal cortex and nucleus accumbens, little is known about its connections to cortical motor-related areas. All these structures are in a position to influence behavior via cortical motor-related areas, which in turn have access, both directly and indirectly, to descending motor pathways. If on the one hand, many animal studies have investigated the neural connectivity of the motor-limbic system using electrophysiological and tracing techniques, on the other hand the use of these methods in the live human brain is limited and elusive due to their invasive nature [1]. By contrast, recent developments in diffusion magnetic resonance imaging and tractography have allowed for non-invasive and in vivo investigation of the human brain. Diffusion-based tractography is a method analyzing the preferential water diffusivity directionality along white matter bundles, thus calculating the highest mathematical probability that water diffuses in a given direction [2]. Using diffusion-weighted magnetic resonance imaging and Constrained Spherical Deconvolution tractography on a population of 15 healthy subjects, we provided tractographic evidence of a structural connection between the amygdala and motor-related areas in humans. These direct limbic-motor pathways may allow for the regulation and modulation of complex motor behaviors and subtle behaviors such as social interactions. The demonstration of these interactions might be fundamental for the comprehension of the pathophysiology of several limbic-sensorimotor diseases, such autism spectrum disorders and motor conversion disorders

Morphometric evaluation of the pedicles of the lumbar spine according to L5 lateral tilt classification

A classification of the lumbar spine according to the pedicle lateral tilt (PLT) of L5 pedicle was recently proposed [1]. In this work the sample was divided into three categories, the first or Wing Type (WT) includes people with a PLT >36° (41,8%), the second or V Type (VT) includes people with a PLT between 30° and 36° (48%) and the third or U Type (UT) includes people with a PL

Advances from probabilistic tractography in connections of the limbic system with the cerebellum

The limbic system is a complex set of brain structures located on both sides of the thalamus, right under the cerebrum. It is not a separate system but a collection of structures from the telencephalon, diencephalon, and mesencephalon, including the hippocampus, amygdala, anterior thalamic nuclei, fornix, columns of fornix, mammillary body, septum pellucidum, habenular commissure, cingulate gyrus, parahippocampal gyrus, limbic cortex, pars of olfactory system and limbic midbrain areas. Nevertheless, recent studies showed that the definition of anatomical structures considered part of the limbic system is a controversial subject. Although the role of the cerebellum was traditionally considered mainly associated to motion control, it has been recently suggested a cerebellar involvement in emotions control, cognitive processes and social behavior. In this regard, we have previously demonstrated that the cerebellum is interconnected with the hippocampus [1]. In this work, a wider sample of normal subjects was examined by using probabilistic Constrained Spherical Deconvolution (CSD) tractography, which represents a method able to overcome many limitations of other Diffusion Tensor Imaging (DTI) techniques, providing more accurate data [2]. We found evidences in the human brain that the cerebellum is widely linked with limbic-related structures and provided a more reliable demonstration of direct cerebello-limbic pathways. In addition, we further extendend our analysis to the other limbic connections including uncinated fasciculus, cingulate fasciculus, inferior longitudinal fasciculus, anterior thalamic connections and fornix. Although these pathways have been already described in the tractographic literature we provided reconstruction and quantitative analysis, which could be potentially useful to explore pathological conditions damaging this system. Finally, the demonstration of the existence of cerebello-limbic connections could constitute an important step in the knowledge of the anatomic substrate of non-motor cerebellar functions

Constrained Spherical Deconvolution Tractography reveals a direct cerebello-ventro tegmental pathway in humans

Introduction. In addition to its role in motor control, reflex adaption and motor learning in the past years numerous studies demonstrated the role of the cerebellum in non-motor functions. Furthermore, lesional animal and neuroimaging in vivo human studies demonstrated connections of the cerebellum with brain regions involved in cognitive, emotional, motivation linguistic processing [1, 2]. Although, studies suggest the role of the cerebellum in neuropsychiatric disorders of the mesocorticolimbic structure (i.e. schizophrenia), at the present time the existence cerebello-ventro tegmental pathway has been demonstrated in only in rodents and only hypothesized in humans. Aim. The goal of this in vivo constrained spherical deconvolution (CSD) tractography study is the investigation on the presence of a direct cerebello-ventro tegmental pathway in the human brain. Material and Methods. We recruited 15 human subjects with no previous history of neurological or psychiatric disorders. The entire study was performed using a 3T Achieva Philips scanner; a SENSE 8 channels head coil, acquiring T1 weighted 3D TFE, DTI sequence; data were analyzed by using constrained spherical deconvolution techniques (CDS). Results. We demonstrated with CSD dentate-ventral midbrain connections. In particular, we found a direct route linking between the dentate nucleus and the ventro tegmental area. Conclusions. This study provides for the first time the existence of a human dentate nucleus connections with the ventro tegmental area, moreover the existence of this cerebello-midbrain pathway suggest that the cerebellum may be involved in the modulation of the mesocorticolimbic system and in related neuropsychiatric disorders such as the schizophrenia

Does Pelvic Incidence Influence the Morphology of the Sacroiliac Joint?

Pelvic Incidence is defined as the angle between the perpendicular line to the upper plate of S1 at its midpoint and the line between this point and the center of bicoxofemoral line, it describes the position of femural heads in relation to sacrum. Recently some authors described a direct correlation between high values of PI and large AP pelvic axis (horizontal pelvis) and a wide pelvic ring [1]. Also the acetabular orientation is influenced by PI ; high values of PI means a more vertical acetabulum. Having regard to the relationship between PI and the main structures involved in the load transfer, to date no studies that correlate the morphology of the Sacroiliac Joint (SiJ) and PI were performed. The aim of this study is to evaluate the different morphology of the auricular surface of the sacrum comparing two groups of healthy young people with low (40°) PI. We retrospectively analysed 51 consecutive young (between 20 and 35 y.o.) people. After the evaluation of PI the sample was divided into two groups: 31 people belong to the group A (PI 40°). The following morphological parameters of the SiJ were analysed: length of long axis (LLA), length of short axis (LSA), length of oblique axis (LOA), ratio between long and short axis (RLSA), angle between axis (ABA) and surface; global shape of the joint was evaluated; two new parameters were introduced, SiJ Tilt (SiJT), defined as the angle between the vertical line and the long axis of the SiJ and SiJ Slope (SiJS), defined as the angle between the horizontal line and the short axis of the SiJ. We found a strong statistically significant correlations (p-value 0.05) between PI and RLSA, shape, ABA, SiJT and SiJS; a weaker correlations (p-value 0.10) between PI and LLA, LSA were observed; no statistically significant correlation between PI and LOA and surface were observed. The results underline that there is a strong correlation between pelvic morphology and SiJ anatomy. Further studies, about the different pattern of forces distribution among SiJ, will need to be performed to have a better knowledge that could help to understand the biomechanics and pathophysiology of normal and pathological SiJ