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

Student Risk Factors Identified by School Counselors and Student Achievement

The increasing emphasis in the United States on high-stakes testing for students and schools generates a great deal of quantitative data, but these data are less frequently linked to other data that are more difficult to obtain such as data on risk factors that may affect how students do on these tests. To make such comparisons, a group of counselors and counselor educators targeted a small urban school district to conduct a quantitative study of the relationship between grades, standard achievement test scores, and risk factors for K-12 students. Students in grades 4, 6, 8, and 9 were randomly selected and data were gathered from school counselors on relevant descriptive information and student risk factors. More than 50% of the students in this sample were affected by at least one risk factor. Students experiencing higher numbers of risk factors tended to have lower achievement test scores and lower grade point averages (GPAs) and were also likely to be male, Hispanic, or Black; to be receiving special education services; to have high rates of absent or tardy days; to have many suspensions or discipline reports; to have single, deceased, or stepparents; and/or to have free or reduced-price lunch status. This article discusses the research process, findings, and implications for educators, particularly in the light of other findings that the effects of some risk factors may be mitigated by the actions of school counselors.Aux États-Unis, l’importance croissante que l’on accorde aux évaluations à enjeu élevé pour les élèves et les écoles produit beaucoup de données quantitatives. Cependant, ces données ne sont pas souvent mises en rapport avec d’autres données plus difficiles à obtenir telles que celles sur les facteurs de risque pouvant affecter la performance des élèves à ces examens. Dans le but effectuer de telles comparaisons, un groupe de conseillers et d’enseignants-conseillers ont entrepris une étude quantitative dans un district scolaire urbain. Ils se sont penchés sur le rapport entre les notes, les résultats aux tests de rendement et les facteurs de risque pour les élèves de la maternelle à la 12e année. On a sélectionné au hasard des élèves des 4e, 6e, 8e et 9e années et recueilli, auprès des conseillers, des données descriptives et de l’information sur les facteurs de risque pour les élèves. Plus de 50% des élèves de l’échantillon étaient affectés par au moins un des facteurs de risque. De façon générale, les élèves qui étaient touchés par le plus grand nombre de facteurs de risque avaient des résultats aux tests de rendement et une moyenne pondérée cumulative inférieurs; étaient mâles, hispaniques ou noirs; recevaient des services d’éducation spécialisée; affichaient un taux d’absentéisme ou de retard élevé; avaient souvent été renvoyés temporairement de l’école ou fait l’objet de rapports disciplinaires; provenaient d’une famille monoparentale ou reconstituée; et recevaient le repas du dîner gratuitement ou à un prix réduit. Cet article présente le processus de recherche ainsi que les résultats et leurs conséquences vis-à-vis des enseignants, surtout par rapport à d’autres recherches indiquant que les conseillers scolaires peuvent atténuer les effets de certains facteurs de risque

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

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

Characterization of Epitaxial Film Silicon Solar Cells Grown on Seeded Display Glass: Preprint

We report characterizations of epitaxial film crystal silicon (c-Si) solar cells with open-circuit voltages (Voc) above 560 mV. The 2-um absorber cells are grown by low-temperature (<750 degrees C) hot-wire CVD (HWCVD) on Corning EAGLE XG display glass coated with a layer-transferred (LT) Si seed. The high Voc is a result of low-defect epitaxial Si (epi-Si) growth and effective hydrogen passivation of defects. The quality of HWCVD epitaxial growth on seeded glass substrates depends on the crystallographic quality of the seed and the morphology of the epitaxial growth surface. Heterojunction devices consist of glass/c-Si LT seed/ epi n+ Si:P/epi n- Si:P/intrinsic a-Si:H/p+ a-Si:H/ITO. Similar devices grown on electronically 'dead' n+ wafers have given Voc {approx}630 mV and {approx}8% efficiency with no light trapping features. Here we study the effects of the seed surface polish on epi-Si quality, how hydrogenation influences the device character, and the dominant junction transport physics

Satellite Cells Senescence in Limb Muscle of Severe Patients with COPD

Centre de recherche de l’Institut universitaire de cardiologie et de pneumologie de Québec, Québec, Canada Rationale: The maintenance of peripheral muscle mass may be compromised in chronic obstructive pulmonary disease (COPD) due to premature cellular senescence and exhaustion of the regenerative potential of the muscles. Methods: Vastus lateralis biopsies were obtained from patients with COPD (n = 16) and healthy subjects (n = 7). Satellite cell number and the proportion of central nuclei, as a marker of muscle regenerative events, were assessed on cryosections. Telomere lengths, used as a marker of cellular senescence, were determined using Southern blot analyses. Results: Central nuclei proportion was significantly higher in patients with COPD with a preserved muscle mass compared to controls and patients with COPD with muscle atrophy (p,0.001). In COPD, maximal telomere length was significantly decreased compared to controls (p,0.05). Similarly, minimal telomere length was significantly reduced in GOLD III–IV patients with muscle atrophy compared to controls (p,0.005). Minimal, mean and maximum telomere lengths correlated with mid-thigh muscle cross-sectional area (MTCSA) (R = 0.523, p = 0.005; R = 0.435, p = 0.019 and R = 0.491, p = 0.009, respectively). Conclusions: Evidence of increased regenerative events was seen in GOLD III–IV patients with preserved muscle mass. Shortening of telomeres in GOLD III–IV patients with muscle atrophy is consistent with an increased number of senescen

A Systems Biology Approach Identifies Molecular Networks Defining Skeletal Muscle Abnormalities in Chronic Obstructive Pulmonary Disease

Chronic Obstructive Pulmonary Disease (COPD) is an inflammatory process of the lung inducing persistent airflow limitation. Extensive systemic effects, such as skeletal muscle dysfunction, often characterize these patients and severely limit life expectancy. Despite considerable research efforts, the molecular basis of muscle degeneration in COPD is still a matter of intense debate. In this study, we have applied a network biology approach to model the relationship between muscle molecular and physiological response to training and systemic inflammatory mediators. Our model shows that failure to co-ordinately activate expression of several tissue remodelling and bioenergetics pathways is a specific landmark of COPD diseased muscles. Our findings also suggest that this phenomenon may be linked to an abnormal expression of a number of histone modifiers, which we discovered correlate with oxygen utilization. These observations raised the interesting possibility that cell hypoxia may be a key factor driving skeletal muscle degeneration in COPD patients

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