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Field Intensity (field + intensity)

Distribution by Scientific Domains

Physics and Astronomy	22%
Medical Sciences	16%
Chemistry	16%
Engineering	11%

Kinds of Field Intensity

magnetic field intensity

Selected Abstracts

ARCHAEOMAGNETIC FIELD INTENSITY DURING THE ROMAN PERIOD AT SIWA AND BAHRYN OASIS, EGYPT: IMPLICATIONS FOR THE FIDELITY OF EGYPTIAN ARCHAEOMAGNETIC DATA

ARCHAEOMETRY, Issue 3 2010
R. LEONHARDT
A preliminary survey was conducted in Siwa and Bahryn Oasis to test the possible influence of various rock magnetic and experimental constraints on the fidelity of the Egyptian archaeomagnetic field record. Five potsherds from the Roman era, which lasted from 1981 bp to 1555 bp, have been investigated. Archaeologists dated the localities to ,1620 bp. Ten ceramic specimens, two of each potsherd, were subjected to archaeointensity determination, including tests for domain state effects, magnetic anisotropy and magnetic cooling rate dependency. Six successful archaeointensity determinations are obtained from three individual cooling units, revealing an average field value of 37.7 ,T for the late Roman period in Siwa and Bahryn oasis, which is comparable to the present-day field strength. The error propagation of the individual uncertainties related to all applied experimental techniques results in a maximum uncertainty estimate of 4.4 ,T. The obtained field value is significantly smaller than early results and slightly smaller than some more recent determinations of the field intensity in Egypt. The difference is attributed to a combined effect of alteration, magnetic anisotropy and magnetic cooling rate dependencies. Along with other high-quality data from the south-east Mediterranean, our data suggest a field intensity minimum during the Egyptian Roman era. [source]

Inactivation of Escherichia coli O157:H7 and Salmonella enteritidis in Liquid Egg White Using Pulsed Electric Field

JOURNAL OF FOOD SCIENCE, Issue 3 2006
Malek Amiali
ABSTRACT: The effects of temperature and pulsed electric field (PEF) intensity on inactivation of pathogens such as Escherichia coli O157:H7 and Salmonella enteritidis in egg white was investigated. Liquid egg white inoculated with 108 colony-forming units (CFU)/mL of each pathogen was treated with up to 60 pulses (each of 2 JAS width) at electric field intensities of 20 and 30 kV/cm. The processing temperatures were 10°C, 20°C, and 30°C. After treatment, uninjured and total viable cells were enumerated in selective and nonselective agars, respectively. Maximum inactivations of 3.7 and 2.9 log units were obtained for S. enteritidis and E. coli O157:H7, respectively, while injured cells accounted for 0.5 and 0.9 logs for E. coli O157:H7 and S. enteritidis, respectively. For both bacteria, increasing treatment temperature tended to increase the inactivation rate. There was synergy between electric field intensity and processing temperature. The inactivation rate constant kT values for E. coli O157:H7 on both selective and nonselective agars were 8.2 × 10 -3 and 6.6 × 10 -3/,S, whereas the values for S. enteritidis were 16.2 × 10 -3 and 12.6 × 10 -3/,S, respectively. The results suggest that E. coli O157:H7 was more resistant to heat-PEF treatment compared with S. enteritidis. [source]

Magnetotransport in AlGaN/GaN and AlGaN/AlN/GaN heterostructures

PHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 6 2007
G. A. Umana-Membreno
Abstract Two-dimensional electron gas transport in AlN/GaN and AlGaN/GaN heterostructures has been investigated employing geometrical magnetoresistance measurements and quantitative mobility-spectrum analysis. The channel magnetoresistance of ungated four-terminal test structures, with an effective width to length ratio of 10, was measured using pulsed drain-to-source voltages equivalent to longitudinal electric fields up to 750 V/cm at magnetic field intensities up to 12 T and sample temperatures from 10 to 300 K. Two distinct electron populations, with significantly different mobilities, are shown to be present in the channel of both AlGaN/AlN/GaN and AlGaN/GaN heterostructures. It is also shown that application of longitudinal electric fields up to 750 V/cm cause a reduction in the mobility of these carrier populations and change the shape of mobility spectrum of the dominant electron population. The origin of these carrier populations is discussed. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

The effects of RF absorbers on exposure levels at 100 MHz

BIOELECTROMAGNETICS, Issue 5 2007
Stewart J Allen
Abstract The study presented in this article was designed to complete a dosimetry protocol required to establish the RF exposure levels at 100 MHz for measurement of the effect on cognition in human volunteers near the resonant frequency in seated positions. The results are compared with those reported previously using the same experimental procedures, except with the vertically radiating dipole antenna and corner reflector raised by .30 m to the vertical center of the anechoic chamber. The average whole body SAR for the high and low SAR conditions used in the previous study was achieved with a 12% increase in transmitter forward power. However, the incident power density averaged over the body was increased by 42%, from 40 and 80 W/m2 in the previous study to 57 and 113 W/m2 in the current study to achieve the same whole body average SAR used in the previous study. The differences in field patterns and field intensities between the previous and current studies were introduced by interactions between the E-field and RF absorbers in the floor and ceiling, which represent resonant structures at 100 MHz. Bioelectromagnetics 28:406,408, 2007. © 2007 Wiley-Liss, Inc. [source]

ELF magnetic fields increase amino acid uptake into Vicia faba L. Roots and Alter Ion movement across the plasma membrane

BIOELECTROMAGNETICS, Issue 5 2002
B.C. Stange
Abstract Vicia faba seedlings, subjected to a 10 µT 50 Hz square wave magnetic field for 40 min together with a radioactive pulse, showed a marked increase in amino acid uptake into intact roots. A more modest increase was observed with a 100 µT 50 Hz square wave. An increase in media conductivity at low field intensities from 10 µT 50 Hz square wave, 100 µT 50 Hz sine wave, and 100 µT 60 Hz square wave fields, indicated an alteration in the movement of ions across the plasma membrane, most likely due to an increase in net outflow of ions from the root cells. Similarly, marked elevation in media pH, indicating increased alkalinity, was observed at 10 and 100µT for both square and sine waves at both 50 and 60 Hz. Our data would indicate that low magnetic field intensities of 10 and 100 µT at 50 or 60 Hz can alter membrane transport processes in root tips. Bioelectromagnetics 23:347,354, 2002. © 2002 Wiley-Liss, Inc. [source]

Palaeomagnetic records of the Brunhes/Matuyama polarity transition from ODP Leg 124 (Celebes and Sulu seas)

GEOPHYSICAL JOURNAL INTERNATIONAL, Issue 2 2000
Hirokuni Oda
Palaeomagnetic records of the Brunhes/Matuyama geomagnetic polarity transition were obtained from deep-sea sediments of ODP Leg 124 in the Celebes and Sulu seas. Advanced piston core (APC) samples with high magnetization intensities (2,200 mA m,1,) and high sedimentation rates (8.4,10 cm kyr,1,) were recovered from this cruise. Rock-magnetic measurements revealed the carrier of the remanence to be nearly pure magnetite in the pseudo-single-domain range. Pass-through measurements at intervals of 5 mm on APC cores across the Brunhes/Matuyama polarity transition for Holes 767B, 769A and 769B were deconvolved with the magnetometer sensor response using the ABIC-minimizing method. Discrete samples were also taken from the polarity transition zones and subjected to either thermal or alternating field stepwise demagnetization. The results were generally consistent with the pass-through data after the deconvolution. Results from the three holes are in good agreement, particularly those from the two holes 100 m apart at Site 769. The transitional VGP paths from these two holes show two small loops near New Zealand before the equator is crossed. The VGPs continue to swing eastwards to the North Atlantic and then move to the northeastern margin of the Pacific Ocean. The positions of the VGP loops obtained from Site 769 are different from the VGP clusters obtained from both the known volcanic records and the sediment records at the Boso Peninsula and the North Atlantic sites with high sedimentation rates. Such a difference may imply the predominance of the non-dipole field during the transition. Relatively stable mid-high northern latitude VGPs are recognized on all three cores just after the reversal, lasting about 4000 years. The plot of relative intensity versus VGP latitude for the sediment records from the North Atlantic (DSDP Hole 609B) shows a remarkable similarity with our records. Similar patterns were also obtained for the plot of the palaeointensity versus VGP latitude for the La Palma volcanic lava records. These results may suggest the existence of a metastable state of the geodynamo, producing a zonal component just after the Brunhes/Matuyama boundary, which may have played a role in the change of the field intensity. [source]

Biomagnetic fluid flow in a 3D rectangular duct

INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS, Issue 12 2004
E. E. Tzirtzilakis1
Abstract The laminar, incompressible, three-dimensional, fully developed viscous flow of a non-conducting biomagnetic fluid in a impermeable rectangular duct is numerically studied in the presence of an applied magnetic field. It is assumed that the magnetic field strength is sufficiently strong to saturate the biofluid and the magnetization is given as a function of the magnetic field intensity. The system of the partial differential equations, resulting after the introduction of appropriate non-dimensional variables, is solved applying an efficient numerical technique based on a pressure-linked pseudotransient method on a common grid. Results concerning the existence and the uniqueness of the solution, are also given. The obtained results, for different values for the parameters entering into the problem under consideration, show that the flow is appreciably influenced by the presence of the magnetic field. Copyright © 2004 John Wiley & Sons, Ltd. [source]

Inactivation of Escherichia coli O157:H7 and Salmonella enteritidis in Liquid Egg White Using Pulsed Electric Field

Pulsed radio-frequency electromagnetic fields: dose-dependent effects on sleep, the sleep EEG and cognitive performance

JOURNAL OF SLEEP RESEARCH, Issue 3 2007
SABINE J. REGEL
Summary To establish a dose,response relationship between the strength of electromagnetic fields (EMF) and previously reported effects on the brain, we investigated the influence of EMF exposure by varying the signal intensity in three experimental sessions. The head of 15 healthy male subjects was unilaterally exposed for 30 min prior to sleep to a pulse-modulated EMF (GSM handset like signal) with a 10 g-averaged peak spatial specific absorption rate of (1) 0.2 W kg,1, (2) 5 W kg,1, or (3) sham exposed in a double-blind, crossover design. During exposure, subjects performed two series of three computerized cognitive tasks, each presented in a fixed order [simple reaction time task, two-choice reaction time task (CRT), 1-, 2-, 3-back task]. Immediately after exposure, night-time sleep was polysomnographically recorded for 8 h. Sleep architecture was not affected by EMF exposure. Analysis of the sleep electroencephalogram (EEG) revealed a dose-dependent increase of power in the spindle frequency range in non-REM sleep. Reaction speed decelerated with increasing field intensity in the 1-back task, while accuracy in the CRT and N-back task were not affected in a dose-dependent manner. In summary, this study reveals first indications of a dose,response relationship between EMF field intensity and its effects on brain physiology as demonstrated by changes in the sleep EEG and in cognitive performance. [source]

Efficient low-power heteronuclear decoupling in 13C high-resolution solid-state NMR under fast magic angle spinning

MAGNETIC RESONANCE IN CHEMISTRY, Issue S1 2007
Mrignayani Kotecha
Abstract The use of a low-power two-pulse phase modulation (TPPM) sequence is proposed for efficient 1H radio frequency (rf) decoupling in high-resolution 13C solid-state NMR (SSNMR) under fast MAS conditions. Decoupling efficiency for different low-power decoupling sequences such as continuous-wave (cw), TPPM, XiX, and ,-pulse (PIPS) train decoupling has been investigated at a spinning speed of 40 kHz for 13C CPMAS spectra of uniformly 13C - and 15N -labeled L -alanine. It was found that the TPPM decoupling sequence, which was originally designed for high-power decoupling, provides the best decoupling efficiency at low power among all the low-power decoupling sequences examined here. Optimum performance of the low-power TPPM sequence was found to be obtained at a decoupling field intensity (,1) of ,,R/4 with a pulse flip angle of ,, and a phase alternation between ± ,(, = ,20° ), where ,R/2, is the spinning speed. The sensitivity obtained for 13CO2,, 13CH, and 13CH3 in L -alanine under low-power TPPM at ,1/2, of 10 kHz was only 5,15% less than that under high-power TPPM at ,1/2, of 200 kHz, despite the fact that only 0.25% of the rf power was required in low-power TPPM. Analysis of the 13CH2 signals for uniformly 13C- and 15N-labeled L -isoleucine under various low-power decoupling sequences also confirmed superior performance of the low-power TPPM sequence, although the intensity obtained by low-power TPPM was 61% of that obtained by high-power TPPM. 13C CPMAS spectra of 13C -labeled ubiquitin micro crystals obtained by low-power TPPM demonstrates that the low-power TPPM sequence is a practical option that provides excellent resolution and sensitivity in 13C SSNMR for hydrated proteins. Copyright © 2007 John Wiley & Sons, Ltd. [source]

Charged relativistic spheres with generalized potentials

MATHEMATICAL METHODS IN THE APPLIED SCIENCES, Issue 6 2009
S. Thirukkanesh
Abstract A new class of exact solutions of the Einstein,Maxwell system is found in closed form. This is achieved by choosing a generalized form for one of the gravitational potentials and a particular form for the electric field intensity. For specific values of the parameters it is possible to write the new series solutions in terms of elementary functions. We regain well-known physically reasonable models. A physical analysis indicates that the model may be used to describe a charged sphere. The influence of the electromagnetic field on the gravitational interaction is highlighted. Copyright © 2008 John Wiley & Sons, Ltd. [source]

Paleomagnetism and petrophysics of the Jänisjärvi impact structure, Russian Karelia

METEORITICS & PLANETARY SCIENCE, Issue 12 2006
J. Salminen
The impactites (tagamites, suevites, and lithic breccias) are characterized by increased porosity and magnetization, which is in agreement with observations performed at other impact structures. Thermomagnetic, hysteresis, and scanning electron microscope (SEM) analysis document the presence of primary multidomain titanomagnetite with additional secondary titanomaghemite and ilmenohematite. The characteristic impact-related remanent magnetization (ChRM) direction (D = 101.5°, I = 73.1°, ,95 = 6.2°) yields a pole (Lat. = 45.0°N, Long. = 76.9°E, dp = 9.9°, dm = 11.0°). Additionally, the same component is observed as an overprint on some rocks located in the vicinity of the structure, which provides proofs of its primary origin. An attempt was made to determine the ancient geomagnetic field intensity. Seven reliable results were obtained, yielding an ancient intensity of 68.7 ± 7.6 ,T (corresponding to VDM of 10.3 ± 1.1 times 1022 Am2). The intensity, however, appears to be biased toward high values mainly because of the concave shape of the Arai diagrams. The new paleomagnetic data and published isotopic ages for the structure are in disagreement. According to well-defined paleomagnetic data, two possible ages for magnetization of Jänisjärvi rocks exist: 1) Late Sveconorwegian age (900,850 Myr) or 2) Late Cambrian age (,500 Myr). However, published isotopic ages are 718 ± 5 Myr (K-Ar) and 698 ± 22 Myr (39Ar- 40Ar), but such isotopic dating methods are often ambiguous for the impactites. [source]

Numerical study of polarization-dependent focusing for a bilayer planar FSS reflective lens at millimeter wavelengths

MICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 5 2004
Natalia Bliznyuk
Abstract In this paper, we numerically analyze the polarization-dependent focusing properties of a planar reflective lens formed by two parallel layers of nonuniform "gangbuster" surfaces (GSs) above a ground plane. Since these GSs consist of superdense arrays of thin finite-length parallel metallic wires, the desired phase patterns on such a lens surface are achieved by adjusting the lengths of these metallic wires for appropriate polarization components. In our analysis, we use the method of moments (MoM) and the transmission-lines analogy, along with the surface-equivalence theorem, to estimate the field intensity in the focal plane. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 40: 361,365, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.11382 [source]

Therapeutic efficacy of bilateral prefrontal slow repetitive transcranial magnetic stimulation in depressed patients with Parkinson's disease: An open study

MOVEMENT DISORDERS, Issue 3 2002
a Draga, evic MD
Abstract Recent studies have suggested that both high- and low-frequency repetitive transcranial magnetic stimulation (rTMS) have antidepressant effects in patients with major depression. We conducted an open study to assess the effects of slow rTMS on mood changes in patients with depression associated with Parkinson's disease (PD). Ten depressed patients with PD (four with major depression and six with dysthymia) received daily sessions of rTMS (frequency, 0.5 Hz; pulse duration, 0.1 msec; field intensity, 10% above the motor threshold) over both prefrontal regions (a total of 100 stimuli per prefrontal region daily) over 10 consecutive days. This treatment resulted in a moderate but significant decrease in scores of the Hamilton Depression Rating Scale (33,37%) and the Beck Depression Inventory (24,34%), which persisted 20 days after finishing the stimulation. In parallel, we observed mild improvement (18,20%) of motor symptoms. No significant adverse effects were reported. These preliminary results suggest the therapeutic potential of daily prefrontal low-frequency rTMS (0.5 Hz) in depression associated with PD. © 2002 Movement Disorder Society [source]

New local hyperthermia using dextran magnetite complex (DM) for oral cavity: experimental study in normal hamster tongue

ORAL DISEASES, Issue 3 2001
S Wada
The possibility of dextran magnetite complex (DM) as a new hyperthermic material was examined in this study. DM suspension of 56 mg ml ,1 iron concentration was locally injected into the normal tongue of golden hamster. DM injected tongues were heated by 500 kHz alternating current (AC) magnetic field and its serial changes in temperature were recorded at 30-s intervals. The temperature of DM injected tongue was maintained at about 43.0,45.0°C for 30 min by changing the AC magnetic field intensity. While temperature elevations of the contralateral tongue and the rectum were only of minor degree. In experiment on the extent of heating area, there was correlation between volume of black stain area and amount of the injected DM suspension (Y =,18.1 + 1.94X, r= 0.931, P < 0.0001, n= 9). Histological examination after heating revealed brown uniform DM accumulation in the connective tissue between fibers of the tongue muscle. Except for vascular dilatations, no tissue damage was seen in the heated tongue. Thus, DM which has the possibility of selective and uniform heating in local hyperthermia might be useful for oral cancer therapy. [source]

Characterization of phase transition in new ferroelectric 2-aminopyridine phosphate crystal

PHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 3 2003
A. Hek
Abstract The dielectric properties of 2-APP, a new ferroelectric crystal, were investigated around the ferroelectric phase transition at 103.5 K. The temperature dependence of electric permittivity was measured at dc electric fields up to 1000 kV/m. The electric permittivity was also measured in the paraelectric phase at constant temperature as a function of electric field intensity up to 150 kV/m. The results are discussed in the framework of the classical dielectric state equation and expansion coefficients A, B and C were estimated. It is found that the phase transition is of second order. (© 2003 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

ARCHAEOMAGNETIC FIELD INTENSITY DURING THE ROMAN PERIOD AT SIWA AND BAHRYN OASIS, EGYPT: IMPLICATIONS FOR THE FIDELITY OF EGYPTIAN ARCHAEOMAGNETIC DATA

Does equipartition hold in HFPs?

ASTRONOMISCHE NACHRICHTEN, Issue 2-3 2009
D. Dallacasa
Abstract Equipartition of energy between relativistic particles and magnetic field is known to be consistent with observations in most of the large size (hundreds of kpc) radio galaxies. Here we discuss whether such a property holds in the smallest and youngest radio sources, the High Frequency Peakers (HFPs). A few sources have small components with a turnover frequency occurring at a few GHz and therefore a direct measure of the magnetic field intensity can be derived from the spectral peak assuming the spectral turnover is originated by synchrotron self-absorption. The field strengths computed in this way are generally in excellent agreement with the equipartition fields. However, a few exceptions have been found, in sources with an extra deficit of photons in the optically thick part of the spectrum as a consequence of free-free absorption (FFA) (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]