Roughness and Finite Size Effect in the NYSE Stock-Price Fluctuations

We consider the roughness properties of NYSE (New York Stock Exchange) stock-price fluctuations. The statistical properties of the data are relatively homogeneous within the same day but the large jumps between different days prevent the extension of the analysis to large times. This leads to intrinsic finite size effects which alter the apparent Hurst (H) exponent. We show, by analytical methods, that finite size effects always lead to an enhancement of H. We then consider the effect of fat tails on the analysis of the roughness and show that the finite size effects are strongly enhanced by the fat tails. The non stationarity of the stock price dynamics also enhances the finite size effects which, in principle, can become important even in the asymptotic regime. We then compute the Hurst exponent for a set of stocks of the NYSE and argue that the interpretation of the value of H is highly ambiguous in view of the above results. Finally we propose an alternative determination of the roughness in terms of the fluctuations from moving averages with variable characteristic times. This permits to eliminate most of the previous problems and to characterize the roughness in useful way. In particular this approach corresponds to the automatic elimination of trends at any scale.Comment: 13 pages, 11 fugure

The role of Ru clusters in Fe carbide suppression for the reverse water gas shift reaction over electropromoted Ru/FeOx catalysts

Abstract The formation of an iron carbide phase has been shown to inhibit the efficiency of Fe-based catalysts in the initial step of adsorbing carbon dioxide (CO2). In this study, we evaluate the effect of adding Ru clusters (20% at.) to FeOx nanowires deposited on yttria-stabilized zirconia (YSZ) for the reverse water gas shift (RWGS) reaction carried out at 300–400 °C under atmospheric conditions. STEM shows that Ru-FeOx formed a bi-phase structure with Ru clusters (1.5–2 nm) supported on FeOx nanowires (5 nm) that remain as mixed oxides after the reaction. Open-circuit catalytic measurements demonstrated that addition of Ru increased the catalytic activity and stabilized high selectivity (>99%) towards CO. The synergetic effect of Ru and FeOx was further emphasized through electrochemical polarization, which led to a reversible catalytic activity increase of up to 2.4 times. The addition of Ru inhibits the formation of inactive Fe carbide by acting as the reducing component and stabilizing the FeOx active state. This results in an improved and lasting catalytic performance and makes Ru/FeOx catalysts attractive for industrial applications

Mapping local optical densities of states in silicon photonic structures with nanoscale electron spectroscopy

Relativistic electrons in a structured medium generate radiative losses such as Cherenkov and transition radiation that act as a virtual light source, coupling to the photonic densities of states. The effect is most pronounced when the imaginary part of the dielectric function is zero, a regime where in a non-retarded treatment no loss or coupling can occur. Maps of the resultant energy losses as a sub-5nm electron probe scans across finite waveguide structures reveal spatial distributions of optical modes in a spectral domain ranging from near-infrared to far ultraviolet.Comment: 18 pages, 4 figure

Mesenchymal Stem Cells Promote Oligodendroglial Differentiation in Hippocampal Slice Cultures

We have previously shown that soluble factors derived from mesenchymal stem cells (MSCs) induce oligodendrogenic fate and differentiation in adult rat neural progenitors (NPCs) in vitro. Here, we investigated if this pro-oligodendrogenic effect is maintained after cells have been transplanted onto rat hippocampal slice cultures, a CNS-organotypic environment. We first tested whether NPCs, that were pre-differentiated in vitro by MSC-derived conditioned medium, would generate oligodendrocytes after transplantation. This approach resulted in the loss of grafted NPCs, suggesting that oligodendroglial pre-differentiated cells could not integrate in the tissue and therefore did not survive grafting. However, when NPCs together with MSCs were transplanted in situ into hippocampal slice cultures, the grafted NPCs survived and the majority of them differentiated into oligodendrocytes. In contrast to the prevalent oligodendroglial differentiation in case of the NPC/MSC co-transplantation, naive NPCs transplanted in the absence of MSCs differentiated predominantly into astrocytes. In summary, the pro-oligodendrogenic activity of MSCs was maintained only after co-transplantation into hippocampal slice cultures. Therefore, in the otherwise astrogenic milieu, MSCs established an oligodendrogenic niche for transplanted NPCs, and thus, co-transplantation of MSCs with NPCs might provide an attractive approach to re-myelinate the various regions of the diseased CNS. Copyright (C) 2009 S. Karger AG, Base

Enacting The Spirit Of The United Nations Convention On The Rights Of Persons With Disabilities: The Role Of Postsecondary Faculty In Ensuring Access

Nations throughout the world have signed the United Nations (UN) Convention on the Rights of Persons With Disabilities.  Many postsecondary educators support the ideals of access and equity for students with disabilities, but have received no training in how to ensure that these goals are achieved.  This paper introduces the concepts of universal design and universal instructional design and provides specific guidelines for general communication and for creating accessible classrooms, lectures or presentations, documents, media, websites, and distance education courses

Optimal Fleet Composition via Dynamic Programming and Golden Section Search

In this paper, we consider an optimization problem arising in vehicle fleet management. The problem is to construct a heterogeneous vehicle fleet in such a way that cost is minimized subject to a constraint on the overall fleet size. The cost function incorporates fixed and variable costs associated with the fleet, as well as hiring costs that are incurred when vehicle requirements exceed fleet capacity. We first consider the simple case when there is only one type of vehicle. We show that in this case the cost function is convex, and thus the problem can be solved efficiently using the well-known golden section method. We then devise an algorithm, based on dynamic programming and the golden section method, for solving the general problem in which there are multiple vehicle types. We conclude the paper with some simulation results

Reply to Lipworth et al.

We thank Dr. Lipworth and colleagues for their interest in our work published recently in the Journal (1). They rightly point out that the biology of asthma attacks is more complex than blood eosinophils alone and that corticosteroids have a wide range of other potentially relevant antiinflammatory effects. However, local treatment with inhaled corticosteroids (ICS) is usually the mainstay of patients with frequent eosinophilic exacerbations, and therefore in the great majority of patients, the key question is what oral corticosteroids (OCS) add to ICS in an acute attack (2) and whether this effect is seen with benralizumab. We suggest that depletion of circulating eosinophils is the only effect OCS are likely to have that are not shared with ICS (3)

A cross scale investigation of galena oxidation and controls on mobilization of lead in mine waste rock.

Abstract Galena and Pb-bearing secondary phases are the main sources of Pb in the terrestrial environment. Oxidative dissolution of galena releases aqueous Pb and SO4 to the surficial environment and commonly causes the formation of anglesite (in acidic environments) or cerussite (in alkaline environments). However, conditions prevalent in weathering environments are diverse and different reaction mechanisms reflect this variability at various scales. Here we applied complementary techniques across a range of scales, from nanometers to 10 s of meters, to study the oxidation of galena and accumulation of secondary phases that influence the release and mobilization of Pb within a sulfide-bearing waste-rock pile. Within the neutral-pH pore-water environment, the oxidation of galena releases Pb ions resulting in the formation of secondary Pb-bearing carbonate precipitates. Cerussite is the dominant phase and shannonite is a possible minor phase. Dissolved Cu from the pore water reacts at the surface of galena, forming covellite at the interface. Nanometer scale characterization suggests that secondary covellite is intergrown with secondary Pb-bearing carbonates at the interface. A small amount of the S derived from galena is sequestered with the secondary covellite, but the majority of the S is oxidized to sulfate and released to the pore water

Raphe-mediated signals control the hippocampal response to SRI antidepressants via miR-16

Serotonin reuptake inhibitor (SRI) antidepressants such as fluoxetine (Prozac), promote hippocampal neurogenesis. They also increase the levels of the bcl-2 protein, whose overexpression in transgenic mice enhances adult hippocampal neurogenesis. However, the mechanisms underlying SRI-mediated neurogenesis are unclear. Recently, we identified the microRNA miR-16 as an important effector of SRI antidepressant action in serotonergic raphe and noradrenergic locus coeruleus (LC). We show here that miR-16 mediates adult neurogenesis in the mouse hippocampus. Fluoxetine, acting on serotonergic raphe neurons, decreases the amount of miR-16 in the hippocampus, which in turn increases the levels of the serotonin transporter (SERT), the target of SRI, and that of bcl-2 and the number of cells positive for Doublecortin, a marker of neuronal maturation. Neutralization of miR-16 in the hippocampus further exerts an antidepressant-like effect in behavioral tests. The fluoxetine-induced hippocampal response is relayed, in part, by the neurotrophic factor S100β, secreted by raphe and acting via the LC. Fluoxetine-exposed serotonergic neurons also secrete brain-derived neurotrophic factor, Wnt2 and 15-Deoxy-delta12,14-prostaglandin J2. These molecules are unable to mimic on their own the action of fluoxetine and we show that they act synergistically to regulate miR-16 at the hippocampus. Of note, these signaling molecules are increased in the cerebrospinal fluid of depressed patients upon fluoxetine treatment. Thus, our results demonstrate that miR-16 mediates the action of fluoxetine by acting as a micromanager of hippocampal neurogenesis. They further clarify the signals and the pathways involved in the hippocampal response to fluoxetine, which may help refine therapeutic strategies to alleviate depressive disorders