Transversal interface dynamics of a front connecting a stripe pattern to a uniform state

Interfaces in two-dimensional systems exhibit unexpected complex dynamical behaviors, the dynamics of a border connecting a stripe pattern and a uniform state is studied. Numerical simulations of a prototype isotropic model, the subcritical Swift-Hohenberg equation, show that this interface has transversal spatial periodic structures, zigzag dynamics and complex coarsening process. Close to a spatial bifurcation, an amended amplitude equation and a one-dimensional interface model allow us to characterize the dynamics exhibited by this interface.Comment: 4 pages. To be published in Europhysics Letter

On the monotonicity of the correction term in Ramanujan's factorial approximation

We present two new proofs of the monotonicity of the correction term $\theta_n$ in Ramanujan's refinement of Stirling's formula.Comment: Latex, 5 page

Novel nanomaterials for lab on a chip devices development: application to environmental stressors in food system and their effect on the oxidative stress in select cell

This thesis project is focused on the development of a high-tech platform capable to assess the level of oxidative stress (OS) in selected cell cultures and the effect of supplementation of functional food in the levels of OS. To do so, we will study and exploit different analytical techniques combined in a microfluidic system using a bottom-up strategy. Firstly, we will design and develop the sensing systems able to detect oxidative stress biomarkers and functional food components. Further, all the developed technology will be couple in a new integrated microfluidic platform able to quantify OS status and response to functional food supplementation of selected cell cultures. Doing so, we expect to pave the way to the study of oxidative stress depended diseases and it treatment using functional food. To date, a new nanomaterial based on carbon black (CB) and Prussian Blue (PB) was synthetized and optimized for the electrochemical sensing of hydrogen peroxide (H2O2) in a range from 200 nM to 1 mM with a limt of detection (LOD) of 20 nM. This sensor was successfully applied to the determination of H2O2 in SHSY5Y differentiated in neurons cell cultures challenged with hydroxydopamine (6-OHDA) as model of Parkinson’s disease (Provided by Prof. Cimini group). The levels of H2O2 were followed by 24 h and it changes from 15.2±0.8 µM at 30 min to 51.9±0.3 µM at 24h. These results could pave the way for future studies of the role of H2O2 in Parkinson’s diseas

Study on Mechanical Relaxations of 7075 (Al–Zn–Mg) and 2024 (Al–Cu–Mg) Alloys by Application of the Time-Temperature Superposition Principle

The viscoelastic response of commercial Al–Zn–Mg and Al–Cu–Mg alloys was measured with a dynamic-mechanical analyzer (DMA) as a function of the temperature (from 30 to 425ºC) and the loading frequency (from 0.01 to 150 Hz). The time-temperature superposition (TTS) principle has proven to be useful in studying mechanical relaxations and obtaining master curves for amorphous materials. In this work, the TTS principle is applied to the measured viscoelastic data (i.e., the storage and loss moduli) to obtain the corresponding master curves, and to analyze the mechanical relaxations responsible for the viscoelastic behavior of the studied alloys. For the storage modulus it was possible to identify a master curve for a low-temperature region (from room temperature to 150ºC) and, for the storage and loss moduli, another master curve for a high-temperature region (from 320 to 375ºC). These temperature regions are coincidental with the stable intervals where no phase transformations occur. The different temperature dependencies of the shift factors for the identified master curves, manifested by different values of the activation energy in the Arrhenius expressions for the shift factor, are due to the occurrence of microstructural changes and variations in the relaxation mechanisms between the mentioned temperature regions.Peer ReviewedPostprint (published version

Persuasive behavior as a moderator of the relationship between strategic behavior and leadership effectiveness

Based on the notion that leader behaviors are mutually facilitative on their effects on leader effectiveness, this study tested the hypothesis that Persuasive behaviors enhance the predictive relationship between Strategic behaviors and Leadership Effectiveness. Persuasive was hypothesized to act as an enhancer based on the notion that the leader\u27s ability to influence others and develop followership can enhance the impact of a leader\u27s ability to set strategy, provide direction, make decisions and plan on perceived effectiveness

Molecular and metabolic mechanisms underlying diabetic neuropathy

Diabetes is a metabolic disease with increasing incidence worldwide and with important economic effects. The disease is characterized by hyperglycaemia, which may be caused by an alteration of insulin production secondary to degeneration of pancreatic beta cells (type-1 diabetes), or by an insulin resistance and insufficient secretion from the pancreas (type-2 diabetes). Diabetic neuropathy is the most frequent complication of diabetes mellitus and is characterised by demyelination of neurons accompanied by sensory loss. In addition, hyperglycaemia and local hypoxia can cause glucose oxidation, formation and accumulation of glycation end-products, which lead to oxidative stress. In this work, we investigated the sequence of event occurring in alteration of metabolic pathways in relation to nerve damage and sensory loss in C57BL6/j mice in the model of type 1 diabetes. We employed a mass spectrometry-based screen to study alterations in levels of metabolites in peripheral sciatic nerve and amino acids in serum over several months. Our results indicated that the impaired metabolites in peripheral nerve are the primary cause of shunting metabolic substrate to compensatory pathways, which leads to sensory nerve fibre loss in skin and contribute to onset and progression of peripheral neuropathy. Furthermore, hyperglycaemia-induced mitochondrial dysfunction and the generation of reactive oxygen species (ROS) have gained attention as possible mechanisms of organ damage in diabetes. We analysed the regulation of transcription factor HIF1α in response to prolonged hyperglycaemia in mutant mice, lacking HIF1α in peripheral sensory neurons. Our results indicated that HIF1α is an upstream modulator of ROS in peripheral sensory neurons and possess a protective function in suppressing hyperglycaemia-induced nerved damage by limiting ROS levels, therefore, HIF1α stabilization may be thus a new strategy target for limiting sensory loss, a debilitating late complication of diabetes. In peripheral nervous system, Schwann cells wrap and myelinate spirally around axons, which is indispensable for the efficient propagation of nerve impulses along axons by saltatory conduction. Periaxin protein is expressed in the membrane of myelinating Schwann cells and it is a scaffold protein for coupling peripheral proteins to elements of the Schwann cell cytoskeleton. Post-translational modification via sumoylation has emerged as a central regulatory mechanism of protein function in health and disease. We studied the role of sumoylation on Periaxin by generating conditional PLP-CreERT2+/+Ubc9fl/fl mice lacking sumo conjugating enzyme (Ubc9), which is expected to delete sumoylation in Schwann cells and oligodendrocytes. The conditional deletion of Ubc9 in Schwann cells considerably reduced the walking and running behaviour of PLP-CreERT2+/+Ubc9fl/fl mice, which can be considered as early symptoms of onset of peripheral neuropathy. Although our results cannot be generalised to other mouse genotypes, our conditional Ubc9-knock-out mice may be useful for assessing the cell-specific role of sumoylation in myelination and peripheral neuropathies