Pulsar magnetospheres: numerical simulations of large amplitude electron-positron oscillations

The numerical simulation of non-linear electron-positron oscillations is reported, showing the evolution of the electric field and the plasma number density for large amplitude disturbances. Sharp density gradients and changes in the oscillation frequency are demonstrated, and a new analytical framework is presented to illustrate these phenomena, particularly in the context of pulsar plasmas

Second-order odd-harmonic repetitive control and its application to active filter control

High order repetitive control has been introduced toovercomeperformance decay of repetitive control systems undervarying frequency of the signals to be tracked/rejected orimproving the interhamonic behavior. However, most highorder repetitive internal models used to improve frequencyuncertainty are unstable, as a consequence practicalimplementations are more difficult. In this work a stable,second order odd-harmonic repetitive control system ispresented and studied.The proposed internal model has been implemented andvalidated in a shunt active filter current controller. Thishigh order controller allows dealing with the gridfrequency variations without using adaptive schemes

Neuromorphometric characterization with shape functionals

This work presents a procedure to extract morphological information from neuronal cells based on the variation of shape functionals as the cell geometry undergoes a dilation through a wide interval of spatial scales. The targeted shapes are alpha and beta cat retinal ganglion cells, which are characterized by different ranges of dendritic field diameter. Image functionals are expected to act as descriptors of the shape, gathering relevant geometric and topological features of the complex cell form. We present a comparative study of classification performance of additive shape descriptors, namely, Minkowski functionals, and the nonadditive multiscale fractal. We found that the proposed measures perform efficiently the task of identifying the two main classes alpha and beta based solely on scale invariant information, while also providing intraclass morphological assessment

Effect of salt concentrations on in vitro rumen fermentation of cellulose, starch, and protein

The aim of this study was to evaluate the effects of various concentrations of three salts (sodium chloride (NaCl), magnesium chloride (MgCl2), and calcium chloride (CaCl2)) on the in vitro rumen fermentation of cellulose, starch, and protein substrates. Six salt concentrations were tested, separately, namely 0, 100, 200, 400, 800, and 1600 mg/dL. The experiment was conducted using the completely randomized design in a 6 × 3 × 3 factorial arrangement with main effects of salt concentration and salt type (six levels of three salts (NaCl, MgCl2, or CaCl2) (0, 100, 200, 400, 800, and 1600 mg/dL) into three substrates [starch, cellulose, and glucose]) with three replicates. Cellulose- and glucose-fermenting bacteria were sensitive to NaCl concentrations greater than 400 mg/dL (17.48 decisiemens per metre (dS/m)) and 800 mg/dL (20.55 dS/m) in the media, respectively. In contrast, starch-fermenting bacteria continued to grow in NaCl concentrations up to 1600 mg/dL (29.09 dS/m). Thus, it was concluded that starch-fermenting microorganisms tolerated higher concentrations of NaCl compared with the other microbial groups. Cellulose-fermenting microorganisms are less tolerant to MgCl2 in relation to the other microbial groups. Starch, cellulose-, and glucose-fermenting bacteria from cattle tolerate CaCl2 concentrations of up to 1600 mg/dL (12.26 dS/m). These results suggest that brackish water may be used for ruminants. However, it is important perform an analysis of that water and then to adjust diets to minimize the effects of types of salt and concentrations of salt on rumen microorganisms. Keywords: brackish water, dissolved salts, rumen microbes, water qualit

Cartan's spiral staircase in physics and, in particular, in the gauge theory of dislocations

In 1922, Cartan introduced in differential geometry, besides the Riemannian curvature, the new concept of torsion. He visualized a homogeneous and isotropic distribution of torsion in three dimensions (3d) by the "helical staircase", which he constructed by starting from a 3d Euclidean space and by defining a new connection via helical motions. We describe this geometric procedure in detail and define the corresponding connection and the torsion. The interdisciplinary nature of this subject is already evident from Cartan's discussion, since he argued - but never proved - that the helical staircase should correspond to a continuum with constant pressure and constant internal torque. We discuss where in physics the helical staircase is realized: (i) In the continuum mechanics of Cosserat media, (ii) in (fairly speculative) 3d theories of gravity, namely a) in 3d Einstein-Cartan gravity - this is Cartan's case of constant pressure and constant intrinsic torque - and b) in 3d Poincare gauge theory with the Mielke-Baekler Lagrangian, and, eventually, (iii) in the gauge field theory of dislocations of Lazar et al., as we prove for the first time by arranging a suitable distribution of screw dislocations. Our main emphasis is on the discussion of dislocation field theory.Comment: 31 pages, 8 figure

Extreme Ultra-Violet Spectroscopy of the Lower Solar Atmosphere During Solar Flares

The extreme ultraviolet portion of the solar spectrum contains a wealth of diagnostic tools for probing the lower solar atmosphere in response to an injection of energy, particularly during the impulsive phase of solar flares. These include temperature and density sensitive line ratios, Doppler shifted emission lines and nonthermal broadening, abundance measurements, differential emission measure profiles, and continuum temperatures and energetics, among others. In this paper I shall review some of the advances made in recent years using these techniques, focusing primarily on studies that have utilized data from Hinode/EIS and SDO/EVE, while also providing some historical background and a summary of future spectroscopic instrumentation.Comment: 34 pages, 8 figures. Submitted to Solar Physics as part of the Topical Issue on Solar and Stellar Flare

Evaluation Of Pspl Plate Erasing Time Of A Digital Dental Radiology System

Denoptix (CEDH Gendex Dental System, Milan, Italy) dental imaging system uses photo-stimulable phosphor luminescence (PSPL) plates to store energy during X-ray exposure, being later processed by a laser reader and digitizer. Afterwards the plate is erased and re-used. The cleaning process described by the manufacturer consists of exposing the PSPL plates to negatoscope light for 5 minutes. Proper light intensity and exact erasing time must be considered in order to guarantee good quality procedures in its re-utilization. X-ray exposed plates were submitted to four negatoscopes with different measured light intensities for several periods of light exposure, until the Denoptix system was unable to process the latent image in the plates, and we considered then that the plates were cleaned. We have found the relationships between erasing time, exposed dose and negatoscope light intensity. We have also measured the relative plate image fading with negatoscope light exposure time. We have concluded that a Poisson process governs plate erasing. Considering clinical situations, we have shown that it was possible to largely reduce erasing time and increase plate re-utilization. The exponential decay of image data also suggested a still smaller erasing time, representative of a partial cleaning status assuming that residual noise presence in the erased plate is clinically acceptable.4320227235Janhom, A., Effect of noise on the compressibility and diagnostic accuracy for caries detection of digital bitewing radiographs (1999) Dentomaxillofacial Radiology, 28, pp. 6-12Huda, W., Comparison of a photo-stimulable phosphor system with film for dental radiology (1997) Oral Surgery Oral Medicine Oral Pathology, 84, pp. 725-731Brettle, D.S., The imaging performance of a storage phosphor system for dental radiography (1996) The British Journal of Radiology, 69, pp. 256-261Yoshiura, K., Physical evaluation of a system for direct digital intra-oral radiography based on a charged-coupled device (1999) Dentomaxillofacial Radiology, 28, pp. 277-283Xinhua, A novel algorithm for measuring the MTF of a digital radiographic system with a CCD array detector (2000) SPIE, 3977, pp. 580-587Hildebold, C.F., Dental photostimulable phosphor radiology (2000) Dental Clinics of North America, 44 (2), pp. 273-297(1998) Denoptix System User Manual, , CEDH Gendex Dental System, Milan, ItalyBethea, R.M., Duran, B.S., Benllion, T.L., (1995) Statistical Methods for Engineers and Scientists, , Mc Hill Reckker, New York, NYWebb, S., (1995) The Physics of Medical Imaging, , Institute of Physis Publishing, Bristol, UK(1996) Mathematics and Physics of Emerging Biomedical Imaging, , National Research Council, Institute of Medicine, National Academy Press, Washington D.CBarret, H., Harrison, H., Swindell, W., (1981) Radiological Imaging: The Theory of Image Formation, Detection and Processing, 1-2. , Academic Press, London, UKDaint, J.C., Shaw, R., (1976) Image Science - Principles, Analyses and Evaluation of Photographic-Type Imaging Process, , Academic Press, London, U

Environment Influence On Pspl-based Digital Dental Radiology Systems

Photo-stimulable phosphor luminescence technology (PSPL) has been used in Digora (Soredex, Finland) and Denoptix (CEDH Gendex, Italy) digital dental radiology imaging systems. PSPL plates store X-ray energy during exposition, being later processed by a laser reader and digitizer. Afterward they are erased and re-used. The large band of energy absorption provides PSPL systems with an extensive dynamic scale but at the same time a high sensibility to the incoming noise of environmental radiations. We have measured environment influences (electromagnetic radiation) for Digora and Denoptix plates after X-ray exposure and before digital processing. We have first compared the processing of PSPL plates "in dark" against "in light" environments. In another experiment, the exposed plates were also processed after being positioned 10 cm away from a 17 inches video monitor screen and to its laterals for 5, 10, 15, 20, 25 and 30 minutes (plates protected against light). The acquired images were used to calculate the noise power spectra (NPS) in each case. We have noticed that there was an increase in the noise spectra energy of "in light" processing compared to "in dark" processing. There was also an increment in the NPS energy when the images were processed after the exposition of the plates to the radiation emanated from video monitor.4320219226Huda, W., Comparison of a photostimulable phosphor system with film for dental radiology (1997) Oral Surgery Oral Medicine Oral Pathology, 84, pp. 725-731Brettle, D.S., The imaging performance of a storage phosphor system for dental radiography (1996) The British Journal of Radiology, 69, pp. 256-261Xinhua, A novel algorithm for measuring the MTF of a digital radiographic system with a CCD array detector (2000) SPIE, 3977, pp. 580-587Knüpfer, W., Novel X-ray detectors for medical imaging (1999) Nuclear Physics, 78, pp. 610-615Hildebold, C.F., Dental photostimulable phosphor radiology (2000) Dental Clinics of North America, 44 (2), pp. 273-297Stamatakis, Dose response of a storage phosphor system for intraoral radiography (1999) Dentomaxillofacial Radiology, 28, pp. 272-276Yoshiura, K., Physical evaluation of a system for direct digital intra-oral radiography based on a charged-coupled device (1999) Dentomaxillofacial Radiology, 28, pp. 277-283Workman, A., Brettle, D.S., Physical performance measures of radiographic imaging systems (1997) Dentomaxillofacial Radiology, 26, pp. 139-146Granfors, P.R., Performance characteristics of an amorphous silicon flat panel X-ray imaging detector (1999) SPIE, 3659, pp. 480-490Yoshiura, K., Physical evaluation of a system for direct digital intra-oral radiography based on a charged-coupled device (1999) Dentomaxillofacial Radiology, 28, pp. 277-283Kengyelics, S.M., Image quality evaluation of a direct digital radiology detector operating in a UK radiology department (1999) SPIE, 3659, pp. 24-35Granfords, P.R., Aufrichtig, P.R.R., DQE(f) of an amorphous silicon flat panel X-ray detector: Detector parameter influences and measurement methodology (2000) SPIE, 3977, pp. 2-13Dobbins III, J.T., DQE(f) of four generations of computed radiography devices (1995) Medical Physics, 22, pp. 1581-1593Cowen, A.R., Workman, A., A physical image quality evaluation of a digital spot flurography system (1992) Phys. Med. Biol., 37, pp. 325-342Daint, J.C., Shaw, R., (1976) Image Science - Principles, Analyses and Evaluation of Photographic-Type Imaging Process, , Academic Press, London, UKBethea, R.M., Duran, B.S., Benllion, T.L., (1995) Statistical Methods for Engineers and Scientists, , Mc Hill Reckker, New York, NYZanella, G., Zannoni, R., DQE of imaging detectors in terms of spatial frequency (1999) Nuclear Instruments and Methods Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 437, pp. 163-167Zanella, G., Zannoni, R., The role of the quantum efficiency on the DQE of an imaging detector (1996) Nuclear Instruments and Methods in Physics Research A, 381, pp. 157-160Costa, S., DQE measurement in a scintillating glass optical fiber detector for X-ray imaging (1996) Nuclear Instruments and Methods in Physics Research A, 380, pp. 568-571Meyer, R.R., Experimental characterization of CCD cameras for HREM at 300kV (2000) Ultramicroscopy, 85, pp. 9-13Onttonello, P., MTF and DQE measurement in imaging detectors by their single-event response (1998) Nuclear Instruments and Methods in Physics Research Section A, 419, pp. 731-735Kandarakis, I., An experimental method for the determination of spatial-frequency-dependent detective quantum efficiency (DQE) of scintillators used in X-ray imaging detectors (1997) Nuclear Instruments and Methods in Physics Research Section A, 399, pp. 335-34

Allan Sandage and the Cosmic Expansion

This is an account of Allan Sandage's work on (1) The character of the expansion field. For many years he has been the strongest defender of an expanding Universe. He later explained the CMB dipole by a local velocity of 220 +/- 50 km/s toward the Virgo cluster and by a bulk motion of the Local supercluster (extending out to ~3500 km/s) of 450-500 km/s toward an apex at l=275, b=12. Allowing for these streaming velocities he found linear expansion to hold down to local scales (~300 km/s). (2) The calibration of the Hubble constant. Probing different methods he finally adopted - from Cepheid-calibrated SNe Ia and from independent RR Lyr-calibrated TRGBs - H_0 = 62.3 +/- 1.3 +/- 5.0 km/s/Mpc.Comment: 12 pages, 11 figures, 1 table, Submitted to Astrophysics and Space Science, Special Issue on the Fundamental Cosmic Distance Scale in the Gaia Er