Evaluation of magnetic helicity density in the wave number domain using multi-point measurements in space

We develop an estimator for the magnetic helicity density, a measure of the spiral geometry of magnetic field lines, in the wave number domain as a wave diagnostic tool based on multi-point measurements in space. The estimator is numerically tested with a synthetic data set and then applied to an observation of magnetic field fluctuations in the Earth foreshock region provided by the four-point measurements of the Cluster spacecraft. The energy and the magnetic helicity density are determined in the frequency and the wave number domain, which allows us to identify the wave properties in the plasma rest frame correcting for the Doppler shift. In the analyzed time interval, dominant wave components have parallel propagation to the mean magnetic field, away from the shock at about Alfvén speed and a left-hand spatial rotation sense of helicity with respect to the propagation direction, which means a right-hand temporal rotation sense of polarization. These wave properties are well explained by the right-hand resonant beam instability as the driving mechanism in the foreshock. Cluster observations allow therefore detailed comparisons with various theories of waves and instabilities

Creation of model of the photon beam with a treatment planning system PLUNC for ELEKTA Synergy linear accelerator

In the present study, we performed a comparison and selection of the most appropriate treatment plan with an educational treatment planning system PLUNC which was provide recommended absorbed dose of ionizing radiation in tumor volume, and the minimum value of the dose in organs at risk and normal tissues surrounding the tumor. For this reason, was created model of the photon beam for ELEKTA Synergy Linear Accelerator. The treatment plan was developed for patients with rectal cancer. The simulation was performed on the basis of actual dicom - images of the tumor, which was obtained with modern medical equipment (computed tomography Aquilion Toshiba). For checking of the simulated plan quality, reference dose and dose rate measurements were performed. Present study demonstrates the relationship between the dose distributions and selected treatment plan. As result of research, was conducted comparison and analysis of algorithms for dose calculation in tissueequivalent environment with a treatment planning system PLUNC. Was developed methodological guide for work in the PLUNC software. Thereby, educational treatment planning system PLUNC was put into operation

The formation of secondary organic aerosol from the isoprene + OH reaction in the absence of NO_x

The reaction of isoprene (C₅H₈) with hydroxyl radicals has been studied in the absence of nitrogen oxides (NO_x) to determine physical and chemical characteristics of the secondary organic aerosol formed. Experiments were conducted using a smog chamber operated in a steady-state mode permitting measurements of moderately low aerosol levels. GC-MS analysis was conducted to measure methyl butenediols in the gas phase and polyols in the aerosol phase. Analyses were made to obtain several bulk aerosol parameters from the reaction including values for the organic mass to organic carbon ratio, the effective enthalpy of vaporization (ΔH_vap^eff), organic peroxide fraction, and the aerosol yield. <br><br> The gas phase analysis showed the presence of methacrolein, methyl vinyl ketone, and four isomers of the methyl butenediols. These gas-phase compounds may serve as precursors for one or more of several compounds detected in the aerosol phase including 2-methylglyceric acid, three 2-methyl alkenetriols, and two 2-methyl tetrols. In contrast to most previous studies, the 2-methyl tetrols (and the 2-methyl alkenetriols) were found to form in the absence of acidic sulfate aerosol. However, reaction conditions did not favor the production of HO₂ radicals, thus allowing RO₂+RO₂ reactions to proceed more readily than if higher HO₂ levels had been generated. <br><br> SOA/SOC (i.e. OM/OC) was found to average 1.9 in the absence of NO_x. The effective enthalpy of vaporization was measured as 38.6 kJ mol^&minus;1, consistent with values used previously in modeling studies. The yields in this work (using an independent technique than used previously) are lower than those of Kroll et al. (2006) for similar aerosol masses. SOC yields reported in this work range from 0.5–1.4% for carbon masses between 17 and 49 μgC m^&minus;3

SOA formation from the atmospheric oxidation of 2-methyl-3-buten-2-ol and its implications for PM_2.5

The formation of secondary organic aerosol (SOA) generated by irradiating 2-methyl-3-buten-2-ol (MBO) in the presence and/or absence of NO_x, H₂O₂, and/or SO₂ was examined. Experiments were conducted in smog chambers operated in either dynamic or static mode. A filter/denuder sampling system was used for simultaneously collecting gas- and particle-phase products. The structural characterization of gas and particulate products was investigated using BSTFA, BSTFA + PFBHA, and DNPH derivatization techniques followed by GC-MS and liquid chromatography analysis. This analysis showed the occurrence of more than 68 oxygenated organic compounds in the gas and particle phases, 28 of which were tentatively identified. The major components observed include 2,3-dihydroxyisopentanol (DHIP), 2-hydroxy-2-oxoisopentanol, 2,3-dihydroxy-3-methylbutanal, 2,3-dihydroxy-2-methylsuccinic acid, 2-hydroxy-2-methylpropanedioic acid, acetone, glyoxal, methylglyoxal, glycolaldehyde, and formaldehyde. Most of these oxygenated compounds were detected for the first time in this study. <br><br> While measurements of the gas-phase photooxidation products have been made, the focus of this work has been an examination of the particle phase. SOA from some experiments was analyzed for the organic mass to organic carbon ratio (OM/OC), the effective enthalpy of vaporization (&Delta;H_vap^eff), and the aerosol yield. Additionally, aerosol size, volume, and number concentrations were measured by a Scanning Mobility Particle Sizer coupled to a Condensation Particle Counter system. The OM/OC ratio was 2.1 in the MBO/H₂O₂ system. The ΔH_vap^eff was 41 kJ mol⁻¹, a value similar to that of isoprene SOA. The laboratory SOA yield measured in this study was 0.7% in MBO/H₂O₂ for an aerosol mass of 33 μg m⁻³. Secondary organic aerosol was found to be negligible under conditions with oxides of nitrogen (NO_x) present. Time profiles and proposed reaction schemes are provided for selected compounds. <br><br> The contribution of SOA products from MBO oxidation to ambient PM_2.5 was investigated by analyzing a series of ambient PM_2.5 samples collected in several places around the United States. In addition to the occurrence of several organic compounds in both field and laboratory samples, DHIP was found to originate only from the oxidation of MBO, and therefore this compound could potentially serve as a tracer for MBO SOA. Initial attempts have been made to quantify the concentrations of DHIP and other compounds based on surrogate compound calibrations. The average concentrations of DHIP in ambient PM_2.5 samples from Duke Forest in North Carolina ranged from zero during cold seasons to approximately 1 ng m⁻³ during warm seasons. This appears to be the first time that DHIP has been detected in ambient PM_2.5 samples. The occurrence of several other compounds in both laboratory and field samples suggests that SOA originating from MBO can contribute under selected ambient conditions to the ambient aerosol mainly in areas where MBO emissions are high

Organosulfate Formation in Biogenic Secondary Organic Aerosol

Organosulfates of isoprene, α-pinene, and β-pinene have recently been identified in both laboratory-generated and ambient secondary organic aerosol (SOA). In this study, the mechanism and ubiquity of organosulfate formation in biogenic SOA is investigated by a comprehensive series of laboratory photooxidation (i.e., OH-initiated oxidation) and nighttime oxidation (i.e., NO3-initiated oxidation under dark conditions) experiments using nine monoterpenes (α-pinene, β-pinene, d-limonene, l-limonene, α-terpinene, γ-terpinene, terpinolene, Δ3-carene, and β-phellandrene) and three monoterpenes (α-pinene, d-limonene, and l-limonene), respectively. Organosulfates were characterized using liquid chromatographic techniques coupled to electrospray ionization combined with both linear ion trap and high-resolution time-of-flight mass spectrometry. Organosulfates are formed only when monoterpenes are oxidized in the presence of acidified sulfate seed aerosol, a result consistent with prior work. Archived laboratory-generated isoprene SOA and ambient filter samples collected from the southeastern U.S. were reexamined for organosulfates. By comparing the tandem mass spectrometric and accurate mass measurements collected for both the laboratory-generated and ambient aerosol, previously uncharacterized ambient organic aerosol components are found to be organosulfates of isoprene, α-pinene, β-pinene, and limonene-like monoterpenes (e.g., myrcene), demonstrating the ubiquity of organosulfate formation in ambient SOA. Several of the organosulfates of isoprene and of the monoterpenes characterized in this study are ambient tracer compounds for the occurrence of biogenic SOA formation under acidic conditions. Furthermore, the nighttime oxidation experiments conducted under highly acidic conditions reveal a viable mechanism for the formation of previously identified nitrooxy organosulfates found in ambient nighttime aerosol samples. We estimate that the organosulfate contribution to the total organic mass fraction of ambient aerosol collected from K-puszta, Hungary, a field site with a similar organosulfate composition as that found in the present study for the southeastern U.S., can be as high as 30%

Titan's magnetic field signature during the Cassini T34 flyby: Comparison between hybrid simulations and MAG data

During the T34 flyby on 19 July 2007, the Cassini spacecraft passed through the magnetic pile-up region at Titan's ramside. The magnetic environment of Titan during this flyby is studied using a three-dimensional hybrid simulation model. This approach treats the electrons of the plasma as a massless, charge-neutralizing fluid, whereas the effects of finite ion gyroradii are taken into account by modeling the ions as individual particles. The simulation results are compared to data collected by the Cassini Magnetometer Instrument. The key features of the measured magnetic field signature have shown to be fully reproducible in the framework of the simulation model. Several signatures in the observed magnetic field can be ascribed to the passage of the Cassini spacecraft through the magnetic barrier upstream of Titan.Fil: Simon, S.. Technische Universitat Braunschweig; AlemaniaFil: Motschmann, U.. Technische Universitat Braunschweig; AlemaniaFil: Kleindienst, G.. Technische Universitat Braunschweig; AlemaniaFil: Glassmeier, K. H.. Technische Universitat Braunschweig; AlemaniaFil: Bertucci, Cesar. Consejo Nacional de Investigaciónes Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Astronomía y Física del Espacio. - Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Astronomía y Física del Espacio; ArgentinaFil: Dougherty, M. K.. Imperial College London; Reino Unid

Управление в области энергосбережения и повышения энергоэффективности на предприятии АО "Транснефть-Центральная Сибирь"

Рост эффективности применения энергоресурсов – это одна из самых существенных задач XXI в. от результатов разрешения данной проблемы зависит место РФ в ряду развитых в экономическом отношении государств и уровень жизни граждан. РФ не просто располагает всеми необходимыми интеллектуальным потенциалом и природными ресурсами для успешного разрешения своих энергетических проблем, но и объективно – это ресурсная база для азиатских и европейских стран, экспортируя нефтепродукты, нефть и природный газ в объемах, стратегически значимых для стран-импортеров. Однако избыточность ТЭР в России совершенно не должна предусматривать энергорасточительность, поскольку только энергоэффективное хозяйствование при открытой рыночной экономике – это важный фактор конкурентоспособности российских услуг и товаров.Growth in the efficiency of the use of energy resources is one of the most significant tasks of the 21st century. From the results of solving this problem depends on the place of the Russian Federation among a number of economically developed countries and the standard of living of citizens. Russia does not just have all the necessary intellectual potential and natural resources to successfully solve its energy problems, but also objectively is a resource base for Asian and European countries, exporting oil products, oil and natural gas in volumes strategically important for importing countries. However, the redundancy of fuel and energy resources in Russia should not at all provide for energy waste, since only energy-efficient management in an open market economy is an important factor in