Interplay of Boltzmann equation and continuity equation for accelerated electrons in solar flares

During solar flares a large amount of electrons are accelerated within the plasma present in the solar atmosphere. Accurate measurements of the motion of these electrons start becoming available from the analysis of hard X-ray imaging-spectroscopy observations. In this paper, we discuss the linearized perturbations of the Boltzmann kinetic equation describing an ensemble of electrons accelerated by the energy release occurring during solar flares. Either in the limit of high energy or at vanishing background temperature such an equation reduces to a continuity equation equipped with an extra force of stochastic nature. This stochastic force is actually described by the well known energy loss rate due to Coulomb collision with ambient particles, but, in order to match the collision kernel in the linearized Boltzmann equation it needs to be treated in a very specific manner. In the second part of the paper the derived continuity equation is solved with some hyperbolic techniques, and the obtained solution is written in a form suitable to be compared with data gathered by hard X-ray imaging-spectroscopy telescopes. Finally, a first validation of the model with NASA Reuven Ramaty High Energy Solar Spectroscopic Imager spectrometer measurements is provided.Comment: submitted to SIAM/ASA Journal on Uncertainty Quantificatio

An Easy-to-Construct Automated Winkler Titration System

The instrument described in this report is an updated version of the high precision, automated Winkler titration system described by Friederich et al.(1984). The original instrument was based on the work of Bryan et al. (1976) who developed a colorimetric endpoint detector and on the work of Williams and Jenkinson (1982) who produced an automated system that used this detector. The goals of our updated version of the device described by Friederich et al. (1984) were as follows: 1) Move control of the system to the MS-DOS environment because HP-85 computers are no longer in production and because more user-friendly programs could be written using the IBM XT or AT computers that control the new device. 2) Use more "off the shelf" components and reduce the parts count in the new system so that it could be easily constructed and maintained. This report describes how to construct and use the new automated Winkler titration device. It also includes information on the chemistry of the Winkler titration, and detailed instructions on how to prepare reagents, collect samples, standardize and perform the titrations (Appendix I: Codispoti, L.A. 1991 On the determination of dissolved oxygen in sea water, 15pp.). A disk containing the program needed to operate the new device is also included. (pdf contains 33 pages

Measurement of inclusive W and Z cross sections in pp collisions at √s = 7 TeV

Journal of High Energy Physics 2011.1 (2011): 080 reproduced by permission of Scuola Internazionale Superiore di Studi Avanzati (SISSA)Measurements of inclusive W and Z boson production cross sections in pp collisions at √s = 7 TeV are presented, based on 2.9 pb-1 of data recorded by the CMS detector at the LHC. The measurements, performed in the electron and muon decay channels, are combined to give σ(pp → WX) × B(W → lʋ) = 9.95 ± 0.07 (stat.) ± 0.28 (syst.) ± 1.09 (lumi.) nb and σ(pp → ZX) × B(Z → l +l-) = 0.931 ± 0.026 (stat.) ± 0.023 (syst.) ± 0.102 (lumi.) nb, where ℓ stands for either e or μ. Theoretical predictions, calculated at the next-to-next-to-leading order in QCD using recent parton distribution functions, are in agreement with the measured cross sections. Ratios of cross sections, which incur an experimental systematic uncertainty of less than 4%, are also reporte

CMS search for Standard Model Higgs: H→\toW+^+W−^- and H→\toZZ

A search for the Standard Model Higgs decaying to W$^+$W$^-$ and ZZ in pp collisions from LHC at $\sqrt{s}$ = 7 TeV using up to 1.7 fb$^{-1}$ of data recorded by the CMS detector is presented. This search covers a mass range from 110 GeV/c$^2$ to 600 GeV/c$^2$. No significant excess above Standard Model background expectations is observed. Upper limits on the production cross section are derived.Comment: "Presented at the 2011 Hadron Collider Physics symposium (HCP-2011), Paris, France, November 14-18 2011, 4 pages, 10 figure.

Potential use of human periapical cyst-mesenchymal stem cells (hPCy-MSCs) as a novel stem cell source for regenerative medicine applications

Mesenchymal stem cells (MSCs) are attracting growing interest by the scientific community due to their huge regenerative potential. Thus, the plasticity of MSCs strongly suggests the utilization of these cells for regenerative medicine applications. The main issue about the clinical use of MSCs is related to the complex way to obtain them from healthy tissues; this topic has encouraged scientists to search for novel and more advantageous sources of these cells in easily accessible tissues. The oral cavity hosts several cell populations expressing mesenchymal stem cell like-features, furthermore, the access to oral and dental tissues is simple and isolation of cells is very efficient. Thus, oral-derived stem cells are highly attractive for clinical purposes. In this context, human periapical cyst mesenchymal stem cells (hPCy-MSCs) exhibit characteristics similar to other dental-derived MSCs, including their extensive proliferative potential, cell surface marker profile and the ability to differentiate into various cell types such as osteoblasts, adipocytes and neurons. Importantly, hPCy-MSCs are easily collected from the surgically removed periapical cysts; this reusing of biological waste guarantees a smart source of stem cells without any impact on the surrounding healthy tissues. In this review, we report the most interesting research topics related to hPCy-MSCs with a newsworthy discussion about the future insights. This newly discovered cell population exhibits interesting and valuable potentialities that could be of high impact in the future regenerative medicine applications

Eye tracking applied to tobacco smoking: current directions and future perspectives

Over the years the general awareness of the health costs associated with tobacco smoking has motivated scientists to apply the measurement of eye movements to this form of addiction. On one hand they have investigated whether smokers attend and look preferentially at smoking related scenes and objects. In parallel, on the other hand eye tracking has been used to test how smokers and nonsmokers interact with the different types of health warning that policymakers have mandated in tobacco advertisements and packages. Here we provide an overview of the main findings from the different lines of research, such as the evidence related to the attentional bias for smoking cues in smokers and the evidence that graphic warning labels and plain packages measurably increase the salience of the warning labels. We point to some open questions, such as the conditions that determine whether heavy smokers exhibit a tendency to actively avoid looking at graphic warning labels. Finally we argue that the research applied to gaze exploration of warning labels would benefit from a more widespread use of the more naturalistic testing conditions (e.g. mobile eye tracking or virtual reality) that have been introduced to study the smokers’ attentional bias for tobacco-related objects when freely exploring the surrounding environment.  

Micronutrient Distributions in the East Siberian and Laptev Seas during summer 1963

Discusses phosphate, silicate, nitrate, temperature and salinity (T/S) data collected at 140 oceanographic stations occupied by the USCGC Northwind in these seas 7 Aug - 10 Sept 1963, cf No. 92559. These shallow seas deepen gradually toward the shelf edge, the East Siberian toward the E. Precipitation in the excess of evaporation should add ~50 km³/yr of fresh-water to the area; runoff from the seven rivers is ~250 km³/yr for the E Siberian and ~700 km³/yr for the Laptev Sea. Ice ~2 m thick forms in winter, summer melt is ~1 m, the difference compensated by net ice drift out of the area. Surface currents reduce the ice cover near shore in summer, but there is close-pack ice adjacent to Taymyr Peninsula. Annual and seasonal variations in air temperature, wind regime and river runoff obviate steady-state currents and T/S in the region. Silicate concentrations in the surface layer were almost always 5ug-at/liter, those of phosphate or nitrate or both were often so low as to suggest nutrient limitation of phytoplankton production. The nutrients in both seas are compared and discussed in relation to the intense stratification and turbidity of the waters, ice cover, and river discharge. The micronutrient distributions appear to be influenced mainly by summer phytoplankton bloom, respiratory processes, outflow of the Lena, and the different origins of the high-salinity waters found in the two seas.Distribution des microéléments nutritifs dans la mer de Sibérie orientale et dans la mer de Laptev au cours de l'été 1963. L'éclosion estivale du plancton, les processus respiratoires, la décharge du fleuve Léna et les origines diverses des eaux de haute salinité semblent être les facteurs dominants qui influencent la distribution des microéléments nutritifs observée dans la mer de Sibérie orientale et dans la mer de Laptev

On some factors influencing dissolved silicon distribution over the northwest African shelf

Nitrate concentrations in the upwelling source waters observed near Cabo Corbeiro during the JOINT-I experiment were more than twice as high as dissolved silicon concentrations, but dissolved silicon concentrations in the surface layers fell below 0.5 µg-atoms..

Denitrification rates in the eastern tropical South Pacific

Measurements of microbial metabolism suggest that the denitrification rate in the oxygen deficient waters of the eastern tropical South Pacific was approximately 2.5 × 1013g N yr-1 during September 1976-May 1977. This rate may be considerably higher than the rate that existed before ~ 1972...