oalib

Publish in OALib Journal

ISSN: 2333-9721

APC: Only $99

Submit

Any time

2018 ( 6 )

2017 ( 8 )

2016 ( 14 )

2015 ( 64 )

Custom range...

Search Results: 1 - 10 of 3122 matches for " Virginia Mabel Silbergleit "
All listed articles are free for downloading (OA Articles)
Page 1 /3122
Display every page Item
Induced Currents in Pipelines  [PDF]
Virginia Mabel Silbergleit
Engineering (ENG) , 2015, DOI: 10.4236/eng.2015.75018
Abstract: Changes in the geomagnetic field produce ground induced currents that can have impacts on artificial systems such as pipelines. According to these, geomagnetic perturbations observed during June 2005 are studied. The data measured on the Ottawa River Valley pipeline verify the appearance of induced currents greater than 700 mA and additional potential values larger than ?850 V that can produce additional corrosive effects.
Períodos perturbados: disipación de energía y corrientes geomagnéticas inducidas
Larocca,Patricia A.; Silbergleit,Virginia M.;
Geoacta , 2010,
Abstract: in a typical event (12-13 june 2005), solar wind energy rate and total energy dissipation rate in the magnetosphere (e and ut respectively) and increased induced currents in a gas pipe located in the auroral zone are studied. for the period geomagnetic indices ae and dst, and the bz component of the interplanetary geomagnetic field are analyzed as indicators of the development of the troubled period. ring current decay times are calculated using different approaches in accordance with the phases of the storm. during this period there were significant geomagnetic variations due to geomagnetic substorms and induced currents on the pipeline located in the otawa river valley, this fact could produce corrosion increases in its structure.
Períodos perturbados: disipación de energía y corrientes geomagnéticas inducidas
Patricia A. Larocca,Virginia M. Silbergleit
Geoacta , 2010,
Abstract: Se estudia, en un evento típico (12-13 de junio de 2005) las energías entrante y disipada en la magnetosfera ( y Ut respectivamente) y el aumento de corrientes inducidas en un gasoducto ubicado en altas latitudes. Se analizan para el período citado los índices geomagnéticos AE y Dst, y la componente Bz del campo geomagnético interplanetario como indicadores del desarrollo del período perturbado. Se calculan los tiempos de decaimiento del anillo de corriente utilizando distintas aproximaciones de acuerdo con las fases de la tormenta. Durante este período se observaron variaciones geomagnéticas importantes que originaron corrientes geomagnéticas inducidas significativas sobre el gasoducto de la empresa Transcanada ubicado en la zona del valle del río Ottawa; pudiendo ser afectada la vida útil del mismo. In a typical event (12-13 June 2005), solar wind energy rate and total energy dissipation rate in the magnetosphere (e and Ut respectively) and increased induced currents in a gas pipe located in the auroral zone are studied. For the period geomagnetic indices AE and Dst, and the Bz component of the interplanetary geomagnetic field are analyzed as indicators of the development of the troubled period. Ring current decay times are calculated using different approaches in accordance with the phases of the storm. During this period there were significant geomagnetic variations due to geomagnetic substorms and induced currents on the pipeline located in the Otawa River Valley, this fact could produce corrosion increases in its structure.
Transcriptomic, proteomic and metabolomic analysis of UV-B signaling in maize
Paula Casati, Mabel Campi, Darren J Morrow, John F Fernandes, Virginia Walbot
BMC Genomics , 2011, DOI: 10.1186/1471-2164-12-321
Abstract: Using transcriptome and proteomic profiling, we tracked the kinetics of transcript and protein alterations in exposed and shielded organs over 6 h. In parallel, metabolic profiling identified candidate signaling molecules based on rapid increase in irradiated leaves and increased levels in shielded organs; pathways associated with the synthesis, sequestration, or degradation of some of these potential signal molecules were UV-B-responsive. Exposure of just the top leaf substantially alters the transcriptomes of both irradiated and shielded organs, with greater changes as additional leaves are irradiated. Some phenylpropanoid pathway genes are expressed only in irradiated leaves, reflected in accumulation of pathway sunscreen molecules. Most protein changes detected occur quickly: approximately 92% of the proteins in leaves and 73% in immature ears changed after 4 h UV-B were altered by a 1 h UV-B treatment.There were significant transcriptome, proteomic, and metabolomic changes under all conditions studied in both shielded and irradiated organs. A dramatic decrease in transcript diversity in irradiated and shielded leaves occurs between 0 h and 1 h, demonstrating the susceptibility of plants to short term UV-B spikes as during ozone depletion. Immature maize ears are highly responsive to canopy leaf exposure to UV-B.Under normal solar fluence, UV-B damage to macromolecules is balanced by their subsequent repair or replacement. Sporadic ozone depletion results in local "ozone holes" and spikes in terrestrial UV-B exposure. These periodic, but unpredictable UV-B spikes increase intensity up to 10-fold in both the polar and temperate zones [1]. Furthermore, the ozone shield against UV-B is not expected to stabilize at 1950 levels until ~2050 [2]; consequently, determining the molecular bases for acclimation to normal fluence and tolerance of higher fluence UV-B are important factors in sustaining crop yield as the world's population continues to increase.Previously, we
Probable Values of Current Solar Cycle Peak
V. M. Silbergleit
Advances in Astronomy , 2012, DOI: 10.1155/2012/167375
Abstract: An analysis of multiple linear regression method applied to solar cycles 4 to 23 using lagged values of smoothed monthly mean sunspot numbers as independent variables is presented. According to that, the amplitude of current solar cycle 24 is estimated providing a quantitative prediction result. Our adjustment shows that the current cycle would have a sunspot peak less than the biggest one observed during the cycle 19 giving an additional support to the declination in solar activity which is currently happening. 1. Introduction Good predictions of the intenseness of solar activity are increasing by considering satellites information. Such satellites often provide determinative links in communications as well as defense and are also often origin of important scientific information. The enlargement of ultraviolet emission from the Sun at times of high solar activity heats the Earth’s upper atmosphere, which in turn causes the spread and enlargement of the influence on these satellites. The predictions of solar activity are important for technology, including the goodness of the operations of low-Earth orbiting satellites, electric power transmission grids, and high-frequency radio communications, among other problems. Long-term predictions of solar activity are therefore extremely important to auxiliary plan missions and to project satellites that will remain active for their available lifetime. As we know, the solar magnetism is the route to understanding the processes involved. The Sun’s differential rotation, meridional circulation, and large-scale convective motions all contribute to produce the cyclic magnetic development observed. So far we have not produced theories that combine these mechanisms in a model, then we are necessitated to predict solar activity by statistical methods that depend on determining correlations between past and future behavior. Numerous studies to predict the maximum solar activity level have been published (e.g., [1–6]). The general trend observed in recent solar activity cycles is toward larger amplitude sunspot cycles. Some articles use the analysis of the time series of historical spot numbers to obtain a power spectrum of periodicities. On the other hand, there is evidence that shows some kind of regularity in sunspot cycle modulation. The sunspot numbers present periodicities of 11 years (Schwabe cycle), 22 years (Hale cycle), and 88 years (Gleissberg cycle). As it was published by [7] the duration of each cycle could be associated with a variation in the solar energy output. Reading the above-mentioned articles, we
On cosmological evolution with the Lambda-term and any linear equation of state
A. S. Silbergleit
Physics , 2002, DOI: 10.1080/10556790215597
Abstract: Recent observational indications of an accelerating universe enhance the interest in studying models with a cosmological constant. We investigate cosmological expansion (FRW metric) with $\Lambda>0$ for a general linear equation of state $p=w\rho$, $w>-1$, so that the interplay between cosmological vacuum and quintessence is allowed, as well. Four closed-form solutions (flat universe with any $w$, and $w=1/3$, $-1/3, -2/3$) are given, in a proper compact representation. Various estimates of the expansion are presented in a general case when no closed-form solutions are available. For the open universe a simple relation between solutions with different parameters is established: it turns out that a solution with some $w$ and (properly scaled) $\Lambda$ is expressed algebraically via another solution with special different values of these parameters. The expansion becomes exponential at large times, and the amplitude at the exponent depends on the parameters. We study this dependence in detail, deriving various representations for the amplitude in terms of integrals and series. The closed-form solutions serve as benchmarks, and the solution transformation property noted above serves as a useful tool. Among the results obtained, one is that for the open universe with relatively small cosmological constant the amplitude is independent of the equation of state. Also, estimates of the cosmic age through the observable ratio $\Omega_\Lambda/\Omega_M$ and parameter $w$ are given; when inverted, they provide an estimate of $w$, i. e., the state equation, through the known $\Omega_\Lambda/\Omega_M$ and age of the universe.
On the Equation of State for Scalar Field
A. S. Silbergleit
Physics , 2002,
Abstract: We consider Friedmann cosmologies with minimally coupled scalar field. Exact solutions are found, many of them elementary, for which the scalar field energy density, rho_f, and pressure, p_f, obey the equation of state (EOS) p_f=w_f\rho_f. For any constant |w_f|<1 there exists a two-parameter family of potentials allowing for such solutions; the range includes, in particular, the quintessence (-1
Electrostatic Patch Effect in Cylindrical Geometry. I. Potential and Energy between Slightly Non-Coaxial Cylinders
Valerio Ferroni,Alexander Silbergleit
Physics , 2010, DOI: 10.1088/0264-9381/28/14/145001
Abstract: We study the effect of any uneven voltage distribution on two close cylindrical conductors with parallel axes that are slightly shifted in the radial and by any length in the axial direction. The investigation is especially motivated by certain precision measurements, such as the Satellite Test of the Equivalence Principle (STEP). By energy conservation, the force can be found as the energy gradient in the vector of the shift, which requires determining potential distribution and energy in the gap. The boundary value problem for the potential is solved, and energy is thus found to the second order in the small transverse shift, and to lowest order in the gap to cylinder radius ratio. The energy consists of three parts: the usual capacitor part due to the uniform potential difference, the one coming from the interaction between the voltage patches and the uniform voltage difference, and the energy of patch interaction, entirely independent of the uniform voltage. Patch effect forces and torques in the cylindrical configuration are derived and analyzed in the next two parts of this work.
Electrostatic Patch Effect in Cylindrical Geometry. III. Torques
Valerio Ferroni,Alexander Silbergleit
Physics , 2010, DOI: 10.1088/0264-9381/28/14/145003
Abstract: We continue to study the effect of uneven voltage distribution on two close cylindrical conductors with parallel axes started in our papers [1] and [2], now to find the electrostatic torques. We calculate the electrostatic potential and energy to lowest order in the gap to cylinder radius ratio for an arbitrary relative rotation of the cylinders about their symmetry axis. By energy conservation, the axial torque, independent of the uniform voltage difference, is found as a derivative of the energy in the rotation angle. We also derive both the axial and slanting torques by the surface integration method: the torque vector is the integral over the cylinder surface of the cross product of the electrostatic force on a surface element and its position vector. The slanting torque consists of two parts: one coming from the interaction between the patch and the uniform voltages, and the other due to the patch interaction. General properties of the torques are described. A convenient model of a localized patch suggested in [2] is used to calculate the torques explicitly in terms of elementary functions. Based on this, we analyze in detail patch interaction for one pair of patches, namely, the torque dependence on the patch parameters (width and strength) and their mutual positions. The effect of the axial torque is then studied for the experimental conditions of the STEP mission.
Electrostatic Patch Effect in Cylindrical Geometry. II. Forces
Valerio Ferroni,Alexander Silbergleit
Physics , 2010, DOI: 10.1088/0264-9381/28/14/145002
Abstract: We continue our study of patch effect (PE) for two close cylindrical conductors with parallel axes, slightly shifted against each other in the radial and by any length in the axial direction, started in [1], where the potential and energy in the gap were calculated to the second order in the small transverse shift, and to lowest order in the gap to cylinder radius ratio. Based on these results, here we derive and analyze PE force. It consists of three parts: the usual capacitor force due to the uniform potential difference, the one from the interaction between the voltage patches and the uniform voltage difference, and the force due to patch interaction, entirely independent of the uniform voltage. General formulas for these forces are found, and their general properties are described. A convenient model of a localized patch is then suggested that allows us to calculate all the forces in a closed elementary form. Using this, a detailed analysis of the patch interaction for one pair of patches is carried out, and the dependence of forces on the patch parameters (width and strength) and their mutual position is examined. We also give various estimates of the axial patch effect force important for the Satellite Test of the Equivalence Principle (STEP), and recommend intensive pre-flight simulations employing our results.
Page 1 /3122
Display every page Item


Home
Copyright © 2008-2017 Open Access Library. All rights reserved.