Self-Organized Criticality model for Brain Plasticity

Networks of living neurons exhibit an avalanche mode of activity, experimentally found in organotypic cultures. Here we present a model based on self-organized criticality and taking into account brain plasticity, which is able to reproduce the spectrum of electroencephalograms (EEG). The model consists in an electrical network with threshold firing and activity-dependent synapse strenghts. The system exhibits an avalanche activity power law distributed. The analysis of the power spectra of the electrical signal reproduces very robustly the power law behaviour with the exponent 0.8, experimentally measured in EEG spectra. The same value of the exponent is found on small-world lattices and for leaky neurons, indicating that universality holds for a wide class of brain models.Comment: 4 pages, 3 figure

Undamped electrostatic plasma waves

Electrostatic waves in a collision-free unmagnetized plasma of electrons with fixed ions are investigated for electron equilibrium velocity distribution functions that deviate slightly from Maxwellian. Of interest are undamped waves that are the small amplitude limit of nonlinear excitations, such as electron acoustic waves (EAWs). A deviation consisting of a small plateau, a region with zero velocity derivative over a width that is a very small fraction of the electron thermal speed, is shown to give rise to new undamped modes, which here are named {\it corner modes}. The presence of the plateau turns off Landau damping and allows oscillations with phase speeds within the plateau. These undamped waves are obtained in a wide region of the $(k,\omega_{_R})$ plane ($\omega_{_R}$ being the real part of the wave frequency and $k$ the wavenumber), away from the well-known `thumb curve' for Langmuir waves and EAWs based on the Maxwellian. Results of nonlinear Vlasov-Poisson simulations that corroborate the existence of these modes are described. It is also shown that deviations caused by fattening the tail of the distribution shift roots off of the thumb curve toward lower $k$-values and chopping the tail shifts them toward higher $k$-values. In addition, a rule of thumb is obtained for assessing how the existence of a plateau shifts roots off of the thumb curve. Suggestions are made for interpreting experimental observations of electrostatic waves, such as recent ones in nonneutral plasmas.Comment: 11 pages, 10 figure

The Role of Multiple Sclerosis as a Risk Factor for the Development of Osteoporosis

Background: Osteoporosis is the most common bone disease in the United States, and it is particularly common among women with multiple sclerosis (MS). However, despite this association, the temporal relationship between these two conditions has not been previously studied. Data from the Women’s Health Initiative provides a unique opportunity to examine the risk of developing osteoporosis over time in individuals diagnosed with MS. Objective: The purpose of this study is to refine the relationship between MS and osteoporosis, clarifying the impact of environmental and pharmacologic factors on each condition, as well as addressing treatment and preventative efforts for a patient population at a greater potential risk for osteoporosis. Methods: The study sample, derived from the Women’s Health Initiative, included 449 women who reported an MS diagnosis at baseline and 161,359 women without MS who comprised a control group. Baseline measures of self-reported osteoporosis, age, smoking status, steroid and anti-inflammatory use, and supplementary as well as dietary calcium and vitamin D were compared. MS patients reporting osteoporosis at baseline were removed, resulting in 355 women with MS to monitor for time to incident osteoporosis. Survival analyses were performed on follow-up data gathered annually between 1993 and 2005 to factor out significant associations of additional factors. Proportions of participants on osteoporosis-related medications as well as latency to use were compared between the multiple sclerosis and control cohorts. Results: At baseline, women with MS are nearly three times as likely to report osteoporosis (p Conclusions: A higher prevalence of osteoporosis at baseline suggests MS may significantly increase the risk of osteoporosis in premenopausal women. In contrast, environmental and pharmacologic variables appear to have a more significant role in the post-menopausal population. While osteoporosis was treated similarly between both groups, the point for intervention or prevention of osteoporosis in MS patients may be earlier in the disease course

In situ generation of silver nanoparticles in PVDF for the development of resistive switching devices

It is widely accepted that resistive switching devices (RSDs) are extremely appealing as active components in computer memories and logic gates in electronics, directly enabling neuromorphic functionalities. The aim of this study is to investigate the chemical and electrical properties of a nanocomposite polymer, the active component of the device, in order to characterise its composition and behaviour under electric field. This paper presents the morphological and chemical characterization of an in-situ generated silver – Polyvinylidene fluoride-hexafluoropropylene PVDF-HFP nanocomposite (NC) material. A silver salt is added as precursor to the polymer solution and then, after a film casting step, the nanoparticles generation and growth processes are carried out by way of UV irradiation; the growth and the distribution of in-situ generated silver nanoparticles (NPs) in the polymer matrix are described. The devices, built on a planar electrode structure, undergo an I/V test to explore their resistance states at different switching voltages. Furthermore, after electrical analysis a remarkable R off /R on ratio and a relatively low switching voltage (3 V) are achieved, demonstrating the suitability of the developed material for the next generation of soft, wearable, RSDs

Conserved presence of G-quadruplex forming sequences in the Long Terminal Repeat Promoter of Lentiviruses

G-quadruplexes (G4s) are secondary structures of nucleic acids that epigenetically regulate cellular processes. In the human immunodeficiency lentivirus 1 (HIV-1), dynamic G4s are located in the unique viral LTR promoter. Folding of HIV-1 LTR G4s inhibits viral transcription; stabilization by G4 ligands intensifies this effect. Cellular proteins modulate viral transcription by inducing/unfolding LTR G4s. We here expanded our investigation on the presence of LTR G4s to all lentiviruses. G4s in the 5'-LTR U3 region were completely conserved in primate lentiviruses. A G4 was also present in a cattle-infecting lentivirus. All other non-primate lentiviruses displayed hints of less stable G4s. In primate lentiviruses, the possibility to fold into G4s was highly conserved among strains. LTR G4 sequences were very similar among phylogenetically related primate viruses, while they increasingly differed in viruses that diverged early from a common ancestor. A strong correlation between primate lentivirus LTR G4s and Sp1/NF\u3baB binding sites was found. All LTR G4s folded: their complexity was assessed by polymerase stop assay. Our data support a role of the lentiviruses 5'-LTR G4 region as control centre of viral transcription, where folding/unfolding of G4s and multiple recruitment of factors based on both sequence and structure may take place

Using the properties of Primate Motion Sensitive Neurons to extract camera motion and depth from brief 2-D Monocular Image Sequences

Humans and most animals can run/fly and navigate efficiently through cluttered environments while avoiding obstacles in their way. Replicating this advanced skill in autonomous robotic vehicles currently requires a vast array of sensors coupled with computers that are bulky, heavy and power hungry. The human eye and brain have had millions of years to develop an efficient solution to the problem of visual navigation and we believe that it is the best system to reverse engineer. Our brain and visual system appear to use a very different solution to the visual odometry problem compared to most computer vision approaches. We show how a neural-based architecture is able to extract self-motion information and depth from monocular 2-D video sequences and highlight how this approach differs from standard CV techniques. We previously demonstrated how our system works during pure translation of a camera. Here, we extend this approach to the case of combined translation and rotation

The Air Microwave Yield (AMY) experiment - A laboratory measurement of the microwave emission from extensive air showers

The AMY experiment aims to measure the microwave bremsstrahlung radiation (MBR) emitted by air-showers secondary electrons accelerating in collisions with neutral molecules of the atmosphere. The measurements are performed using a beam of 510 MeV electrons at the Beam Test Facility (BTF) of Frascati INFN National Laboratories. The goal of the AMY experiment is to measure in laboratory conditions the yield and the spectrum of the GHz emission in the frequency range between 1 and 20 GHz. The final purpose is to characterise the process to be used in a next generation detectors of ultra-high energy cosmic rays. A description of the experimental setup and the first results are presented.Comment: 3 pages -- EPS-HEP'13 European Physical Society Conference on High Energy Physics (July, 18-24, 2013) at Stockholm, Swede

<em>Aspergillus luchuensis</em>, an industrially important black <em>Aspergillus</em> in East Asia

Aspergilli known as black- and white-koji molds which are used for awamori, shochu, makgeolli and other food and beverage fermentations, are reported in the literature as A. luchuensis, A. awamori, A. kawachii, or A. acidus. In order to elucidate the taxonomic position of these species, available ex-type cultures were compared based on morphology and molecular characters. A. luchuensis, A. kawachii and A. acidus showed the same banding patterns in RAPD, and the three species had the same rDNA-ITS, β-tubulin and calmodulin sequences and these differed from those of the closely related A. niger and A. tubingensis. Morphologically, the three species are not significantly different from each other or from A. niger and A. tubingensis. It is concluded that A. luchuensis, A. kawachii and A. acidus are the same species, and A. luchuensis is selected as the correct name based on priority. Strains of A. awamori which are stored in National Research Institute of Brewing in Japan, represent A. niger (n = 14) and A. luchuensis (n = 6). The neotype of A. awamori (CBS 557.65 = NRRL 4948) does not originate from awamori fermentation and it is shown to be identical with the unknown taxon Aspergillus welwitschiae. Extrolite analysis of strains of A. luchuensis showed that they do not produce mycotoxins and therefore can be considered safe for food and beverage fermentations. A. luchuensis is also frequently isolated from meju and nuruk in Korea and Puerh tea in China and the species is probably common in the fermentation environment of East Asia. A re-description of A. luchuensis is provided because the incomplete data in the original literature. © 2013 Hong et al