92,594 research outputs found

    Pola Variasi Reguler Medan Magnet Bumi Di Tondano

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    Data variasi medan magnet bumi komponen horisontal diambil dari komputer akuisisi yang merekam data secara real time. Dibuat grafik data magnet bumi komponen horisontal versus waktu per hari. Dipilih grafik quite days dan dibandingkan dengan quiet days di Lerwick (Inggris). Dihitung nilai rata-rata dari Quiet days yang sama perbulan untuk dijadikan pola variasi reguler bulanan, sehingga dalam satu tahun dapat dibuat dua belas pola variasi reguler medan magnet bumi. Hasilnya menunjukkan bahwa variasi reguler medan magnet bumi polanya teratur, nilai variasi tertinggi berkisar 39308,3– 39409,5 nT pada kisaran waktu 02:39–03:38 Universal Time. Pola variasi reguler medan magnet bumi digunakan sebagai acuan untuk menganalisis variasi harian medan magnet bumi. Pada tahun 2011 tercatat badai besar geomagnet sebanyak 11 kali yang nilai variasinya berkisar 71–20 nT dengan nilai K indeks sama dengan lima.Data variation of the horizontal component of the earth\u27s magnetic field was taken from the acquisition computer which records data in real time. Graphs describing the horizontal component data versus time were created daily. Graphs of quiet days were selected and compared with quiet days in Lerwick (England). Average value the same of quiet days were calculated in order to create monthly regular variation pattern, so that in one year there were twelve regular variation patterns of the earth \u27s magnetic field created. The results showed that the regular variations of the earth \u27s magnetic field is on a regular pattern, the value of the highest variation ranged 39308.3-39409.5 nT at around 2:39 to 3:38 Universal Time. Regular variation patterns of the earth \u27s magnetic field were used as references for analyzing the daily variation of the earth \u27s magnetic field. In 2011, the large geomagnetic storms were recorded 11 times, the value of the variation range 71–20 nT with the K index value equal to five

    Attosecond sampling of arbitrary optical waveforms

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    Advances in the generation of ultrashort laser pulses, and the emergence of new research areas such as attosecond science, nanoplasmonics, coherent control, and multidimensional spectroscopy, have led to the need for a new class of ultrafast metrology that can measure the electric field of complex optical waveforms spanning the ultraviolet to the infrared. Important examples of such waveforms are those produced by spectral control of ultrabroad bandwidth pulses, or by Fourier synthesis. These are typically tailored for specific purposes, such as to increase the photon energy and flux of high-harmonic radiation, or to control dynamical processes by steering electron dynamics on subcycle time scales. These applications demand a knowledge of the full temporal evolution of the field. Conventional pulse measurement techniques that provide estimates of the relative temporal or spectral phase are unsuited to measure such waveforms. Here we experimentally demonstrate a new, all-optical method for directly measuring the electric field of arbitrary ultrafast optical waveforms. Our method is based on high-harmonic generation (HHG) driven by a field that is the collinear superposition of the waveform to be measured with a stronger probe laser pulse. As the delay between the pulses is varied, we show that the field of the unknown waveform is mapped to energy shifts in the high-harmonic spectrum, allowing a direct, accurate, and rapid retrieval of the electric field with subcycle temporal resolution at the location of the HHG

    Functional imaging of plants: A nuclear magnetic resonance study of a cucumber plant

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    Functional magnetic resonance imaging was used to study transients of biophysical parameters in a cucumber plant in response to environmental changes. Detailed flow imaging experiments showed the location of xylem and phloem in the stem and the response of the following flow characteristics to the imposed environmental changes: the total amount of water, the amount of stationary and flowing water, the linear velocity of the flowing water, and the volume flow. The total measured volume flow through the plant stem was in good agreement with the independently measured water uptake by the roots. A separate analysis of the flow characteristics for two vascular bundles revealed that changes in volume flow of the xylem sap were accounted for by a change in linear-flow velocities in the xylem vessels. Multiple-spin echo experiments revealed two water fractions for different tissues in the plant stem; the spin-spin relaxation time of the larger fraction of parenchyma tissue in the center of the stem and the vascular tissue was down by 17% in the period after cooling the roots of the plant. This could point to an increased water permeability of the tonoplast membrane of the observed cells in this period of quick recovery from severe water los

    Differences between Doppler velocities of ions and neutral atoms in a solar prominence

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    This is the author accepted manuscript. The final version is available from EDP Sciences via the DOI in this record.Context. In astrophysical systems with partially ionized plasma the motion of ions is governed by the magnetic field while the neutral particles can only feel the magnetic field’s Lorentz force indirectly through collisions with ions. The drift in the velocity between ionized and neutral species plays a key role in modifying important physical processes like magnetic reconnection, damping of magnetohydrodynamic waves, transport of angular momentum in plasma through the magnetic field, and heating. Aims. This paper investigates the differences between Doppler velocities of calcium ions and neutral hydrogen in a solar prominence to look for velocity differences between the neutral and ionized species. Methods. We simultaneously observed spectra of a prominence over an active region in H I 397 nm, H I 434 nm, Ca II 397 nm, and Ca II 854 nm using a high dispersion spectrograph of the Domeless Solar Telescope at Hida observatory, and compared the Doppler velocities, derived from the shift of the peak of the spectral lines presumably emitted from optically-thin plasma. Results. There are instances when the difference in velocities between neutral atoms and ions is significant, e.g. 1433 events (∼ 3 % of sets of compared profiles) with a difference in velocity between neutral hydrogen atoms and calcium ions greater than 3σ of the measurement error. However, we also found significant differences between the Doppler velocities of two spectral lines emitted from the same species, and the probability density functions of velocity difference between the same species is not significantly different from those between neutral atoms and ions. Conclusions. We interpreted the difference of Doppler velocities as a result of motions of different components in the prominence along the line of sight, rather than the decoupling of neutral atoms from plasma.This work was supported by a Grant-in-Aid for Scientific Research (No. 22244013, P.I. K. Ichimoto; No. 15K17609, P.I. T. Anan; No. 16H01177, P.I. T. Anan) from the Ministry of Education, Culture, Sports, Science and Technology of Japan. A.H. is supported by his STFC Emest Rutherford Fellowship grant number ST/L00397X/2

    Compatible actions and non-abelian tensor products

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    For a pair of groups G,HG, H we study pairs of actions GG on HH and HH on GG such that these pairs are compatible and non-abelian tensor products GHG \otimes H are defined.Comment: 9 page

    Current status of laboratory and imaging diagnosis of neonatal necrotizing enterocolitis

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    Necrotizing enterocolitis continues to be a devastating disease process for very low birth weight infants in Neonatal Intensive Care Units. The aetiology and pathogenesis of necrotizing enterocolitis are not definitively understood. It is known that necrotizing enterocolitis is secondary to a complex interaction of multiple factors that results in mucosal damage, which leads to intestinal ischemia and necrosis. Advances in neonatal care, including resuscitation and ventilation support technology, have seen increased survival rates among premature neonates and a concomitant detection in the incidence of this intestinal disease.Diagnosis can be difficult, and identifying infants at the onset of disease remains a challenge. Early diagnosis, which relies on imaging findings, and initiation of prompt therapy are essential to limit morbidity and mortality. Moreover, early management is critical and life-saving.This review summarizes what is known on the laboratory and instrumental diagnostic strategies needed to improve neonatal outcomes and, possibily, to prevent the onset of an overt necrotizing enterocolitis
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