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Sample records for magnetic cycles influence

  1. Stellar magnetic cycles

    NASA Astrophysics Data System (ADS)

    Baliunas, S. L.

    2004-05-01

    Is hope for understanding the solar magnetic cycle to be found in stars? Observations of stars with significant sub-surface convective zones -- masses smaller than about 1.5 solar masses on the lower main sequence and many types of cool, post-main-sequence stars -- indicate the presence of surface and atmospheric inhomogeneities analogous to solar magnetic features, making stellar magnetic activity a cosmically widespread phenomenon. Observations have been made primarily in visible wavelengths, and important information has also been derived from the ultraviolet and x-ray spectrum regions. Interannual to interdecadal variability of spectrum indicators of stellar magnetic features is common, and in some cases similar in appearance to the 11-year sunspot cycle. Successful models of the physical processes responsible for stellar magnetic cycles, typically cast as a magnetohydrodynamic dynamo, require advances in understanding not only convection but also the magnetic field's interaction with it. The observed facts that underpin the hope for models will be summarized. Properties of stellar magnetic cycles will be compared and contrasted with those of the sun, including inferences from paleo-environmental reservoirs that contain information on solar century- to millennial-scale magnetic variability. Partial support of this research came from NASA NAG5-7635, NRC COBASE, CRDF 322, MIT-MSG 5710001241, JPL 1236821, AF 49620-02-1-0194, Richard Lounsberry Foundation, Langley-Abbot, Rollins, Scholarly Studies and James Arthur Funds (Smithsonian Institution) and several generous individuals.

  2. Rapid cycling superconducting magnets

    NASA Astrophysics Data System (ADS)

    Fabbricatore, P.; Farinon, S.; Gambardella, U.; Greco, M.; Volpini, G.

    2006-04-01

    The paper deals with the general problematic related to the development of fast cycled superconducting magnets for application in particle accelerator machines. Starting from the requirements of SIS300 synchrotron under design at GSI and an envisaged future Super-SPS injector at CERN, it is shown which developments are mandatory in the superconducting wire technology and in the magnet design field.

  3. Influence of the cardiac cycle on time-intensity curves using multislice dynamic magnetic resonance perfusion.

    PubMed

    Nchimi, Alain; Mancini, Isabelle; Broussaud, Thomas K Y

    2014-10-01

    Flow and pressure variations cause potential changes in magnetic resonance imaging (MRI) signal intensity across the cardiac cycle. Nevertheless, cardiac dynamic contrast-enhanced (perfusion) MRI is performed and analyzed regardless of the cardiac phase. We investigate whether the cardiac phase impacts myocardial and left ventricle (LV) cavity time intensity curves (TICs) at rest and during vasodilatation. Fifteen healthy volunteers (seven females, eight males; mean age: 32.5 ± 9.3 years; age range: 19-49 years) were included in this prospective study. They underwent four separate short-axis multislice (apical, mid and basal) LV perfusion MRI, with different electrocardiogram-triggering during normal vasotone and adenosine-stress. TIC parameters were extracted from the myocardium and the LV cavity. General linear mixed model analyses were used to evaluate their variability according to vasotone, cardiac phase and slice-position. Maximal enhancement and normalized Steepest slopes were higher at stress than at rest (p values <0.001). A similar trend towards higher inflow was shown on systole versus diastole in the LV cavity and diastole versus systole in the myocardium (p < 0.05).These TIC parameters were slice-position dependent, as the inflow decreased from the base to the apex in the LV, and peaked on the mid-slice for the myocardium. There are significant variability of both the LV and the myocardial TICs, with respect to the cardiac cycle phase and the slice position where imaging actually takes place. These appeal to measurement standardization for a better intra- and inter-study reproducibility.

  4. Influence of aging and thermomechanical cycling on the magnetostriction and magnetic shape memory effect in martensitic alloy

    NASA Astrophysics Data System (ADS)

    L'vov, Victor A.; Kosogor, Anna; Barandiaran, Jose M.; Chernenko, Volodymyr A.

    2015-10-01

    An influence of internal stress created by the crystal defects on the magnetically induced reorientation (MIR) of martensite variants in the ferromagnetic shape memory alloy (FSMA) has been analyzed. Using the internal stress conception, a noticeable influence of the spatial reconfiguration of crystal defects on the ordinary magnetostriction of FSMA and magnetic shape memory (MSM) effect has been predicted. It has been shown that the defect reconfiguration, which stabilizes the martensitic phase during martensite aging, increases the shear elastic modulus. The increase of shear modulus reduces the magnetostriction value and in this way suppresses the MSM effect. The magneto-thermo-mechanical training of aged alloys destabilizes the martensitic phase, restores the initial magnetostriction value, and promotes the MSM effect.

  5. MAGNETIC WREATHS AND CYCLES IN CONVECTIVE DYNAMOS

    SciTech Connect

    Nelson, Nicholas J.; Toomre, Juri; Brown, Benjamin P.; Brun, Allan Sacha

    2013-01-10

    Solar-type stars exhibit a rich variety of magnetic activity. Seeking to explore the convective origins of this activity, we have carried out a series of global three-dimensional magnetohydrodynamic simulations with the anelastic spherical harmonic code. Here we report on the dynamo mechanisms achieved as the effects of artificial diffusion are systematically decreased. The simulations are carried out at a nominal rotation rate of three times the solar value (3 {Omega}{sub Sun }), but similar dynamics may also apply to the Sun. Our previous simulations demonstrated that convective dynamos can build persistent toroidal flux structures (magnetic wreaths) in the midst of a turbulent convection zone and that high rotation rates promote the cyclic reversal of these wreaths. Here we demonstrate that magnetic cycles can also be achieved by reducing the diffusion, thus increasing the Reynolds and magnetic Reynolds numbers. In these more turbulent models, diffusive processes no longer play a significant role in the key dynamical balances that establish and maintain the differential rotation and magnetic wreaths. Magnetic reversals are attributed to an imbalance in the poloidal magnetic induction by convective motions that is stabilized at higher diffusion levels. Additionally, the enhanced levels of turbulence lead to greater intermittency in the toroidal magnetic wreaths, promoting the generation of buoyant magnetic loops that rise from the deep interior to the upper regions of our simulated domain. The implications of such turbulence-induced magnetic buoyancy for solar and stellar flux emergence are also discussed.

  6. Magnetic cycles at different ages of stars

    NASA Astrophysics Data System (ADS)

    Oláh, K.; Kővári, Zs.; Petrovay, K.; Soon, W.; Baliunas, S.; Kolláth, Z.; Vida, K.

    2016-06-01

    Aims: We study the different patterns of interannual magnetic variability in stars on or near the lower main sequence, approximately solar-type (G-K dwarf) stars in time series of 36 yr from the Mount Wilson Observatory Ca ii H&K survey. Our main aim is to search for correlations between cycles, activity measures, and ages. Methods: Time-frequency analysis has been used to discern and reveal patterns and morphology of stellar activity cycles, including multiple and changing cycles, in the datasets. Both the results from short-term Fourier transform and its refinement using the Choi-Williams distribution, with better frequency resolution, are presented in this study. Rotational periods of the stars were derived using multifrequency Fourier analysis. Results: We found at least one activity cycle on 28 of the 29 stars we studied. Twelve stars, with longer rotational periods (39.7 ± 6.0 days), have simple smooth cycles, and the remaining stars, with much faster rotation (18.1 ± 12.2 days) on average, show complex and sometimes vigorously changing multiple cycles. The cycles are longer and quite uniform in the first group (9.7 ± 1.9 yr), while they are generally shorter and vary more strongly in the second group (7.6 ± 4.9). The clear age division between stars with smooth and complex cycles follows the known separation between the older and younger stars at around 2 to 3 Gyr of age.

  7. Quadrupole magnet for a rapid cycling synchrotron

    SciTech Connect

    Witte, H.; Berg, J. S.

    2015-05-03

    Rapid Cycling Synchrotrons (RCS) feature interleaved warm and cold dipole magnets; the field of the warm magnets is used to modulate the average bending field depending on the particle energy. It has been shown that RCS can be an attractive option for fast acceleration of particles, for example, muons, which decay quickly. In previous studies it was demonstrated that in principle warm dipole magnets can be designed which can provide the required ramp rates, which are equivalent to frequencies of about 1 kHz. To reduce the losses it is beneficial to employ two separate materials for the yoke; it was also shown that by employing an optimized excitation coil geometry the eddy current losses are acceptable. In this paper we show that the same principles can be applied to quadrupole magnets targeting 30 T/m with a repetition rate of 1kHz and good field quality.

  8. Magnetic Stirling cycles - A new application for magnetic materials

    NASA Technical Reports Server (NTRS)

    Brown, G. V.

    1977-01-01

    There is the prospect of a fundamental new application for magnetic materials as the working substance in thermodynamic cycles. Recuperative cycles which use a rare-earth ferromagnetic material near its Curie point in the field of a superconducting magnet appear feasible for applications from below 20 K to above room temperature. The elements of the cycle, advanced in an earlier paper, are summarized. The basic advantages include high entropy density in the magnetic material, completely reversible processes, convenient control of the entropy by the applied field, the feature that heat transfer is possible during all processes, and the ability of the ideal cycle to attain Carnot efficiency. The mean field theory is used to predict the entropy of a ferromagnet in an applied field and also the isothermal entropy change and isentropic temperature change caused by applying a field. Results are presented for J = 7/2 and g = 2. The results for isentropic temperature change are compared with experimental data on Gd. Coarse mixtures of ferromagnetic materials with different Curie points are proposed to modify the path of the cycle in the T-S diagram in order to improve the efficiency or to increase the specific power.

  9. Magnetic stirling cycles: A new application for magnetic materials

    NASA Technical Reports Server (NTRS)

    Brown, G. V.

    1977-01-01

    The elements of the cycle are summarized. The basic advantages include high entropy density in the magnetic material, completely reversible processes, convenient control of the entropy by the applied field, the feature that heat transfer is possible during all processes, and the ability of the ideal cycle to attain Carnot efficiency. The mean field theory is used to predict the entropy of a ferromagnet in an applied field and also the isothermal entropy change and isentropic temperature change caused by applying a field. The results for isentropic temperature change are compared with experimental data on Gd. Coarse mixtures of ferromagnetic materials with different Curie points are proposed to modify the path of the cycle in the T-S diagram in order to improve the efficiency or to increase the specific power.

  10. Influence of moderate cycling on scrotal temperature.

    PubMed

    Jung, A; Strauss, P; Lindner, H J; Schuppe, H C

    2008-08-01

    Testicular temperature highly correlates with scrotal temperature. It has been postulated that cycling is associated with increased scrotal temperatures with time and consecutively with impaired semen quality. The aim of this study was to evaluate the influence of moderate cycling on scrotal temperature during highly standardized conditions in an experimental lab. A total of 25 volunteers without a history of infertility and normal andrological examination were included for scrotal temperature evaluation. Scrotal temperatures were measured every minute with a portable data recorder connected with two thermistor temperature sensors, which were attached on either side of the scrotum. A further thermistor sensor was attached on the central surface of the bicycle saddle. Ambient temperature in the study room was adjusted to 22 degrees C throughout the whole experiment. All volunteers started the experiment at the same daytime. Clothing of the volunteers consisted of standardized cotton wool trousers and shirts fitting to body size. After acclimatization to the study room in a sitting posture, each volunteer cycled on an exercise cycle for 60 min with a power of 25 Watt representing a speed of 25.45 km/h respectively. The saddle surface temperature reached in the median 35.59 degrees C after 60 min cycling. Median values of scrotal temperatures increased from 35.75 degrees C at the beginning to 35.82 degrees C after 60 min for the left side and from 35.50 to 35.59 degrees C for the right side. No correlation between cycling duration and scrotal temperatures could be found using multivariate anova for repeated measurements. However, scrotal temperatures during cycling were significantly lower (p < 0.001) compared with the last 10 min in sitting posture before starting cycling with a difference of 1.31 degrees C for the left and 1.46 degrees C for the right side. The present study suggests that moderate cycling under standardized conditions with a power of 25 Watt is not

  11. Desktop fast-field cycling nuclear magnetic resonance relaxometer.

    PubMed

    Sousa, Duarte Mesquita; Marques, Gil Domingos; Cascais, José Manuel; Sebastião, Pedro José

    2010-07-01

    In this paper a new type of Fast Field Cycling (FFC) Nuclear Magnetic Resonance (NMR) relaxometer with low power consumption (200W) and cycle to cycle field stability better than 10(-4) is described. The new high-permeability magnet was designed to allow for good magnetic field homogeneity and allows for the sample rotation around an axis perpendicular to magnetic field, operating with magnetic fields between 0 and 0.21T. The power supply of the new relaxometer was specially developed in order to have steady state accurate currents and allow for magnetic field switching times less than 3ms. Additional control circuits were developed and included to compensate the Earth magnetic field component parallel to the field axis and to compensate for parasitic currents. The main aspects of the developed circuits together with some calibrating experimental results using the liquid crystal compounds 5CB and 8CB are presented and discussed.

  12. Atmospheric influence of Earth's earliest sulfur cycle

    PubMed

    Farquhar; Bao; Thiemens

    2000-08-01

    Mass-independent isotopic signatures for delta(33)S, delta(34)S, and delta(36)S from sulfide and sulfate in Precambrian rocks indicate that a change occurred in the sulfur cycle between 2090 and 2450 million years ago (Ma). Before 2450 Ma, the cycle was influenced by gas-phase atmospheric reactions. These atmospheric reactions also played a role in determining the oxidation state of sulfur, implying that atmospheric oxygen partial pressures were low and that the roles of oxidative weathering and of microbial oxidation and reduction of sulfur were minimal. Atmospheric fractionation processes should be considered in the use of sulfur isotopes to study the onset and consequences of microbial fractionation processes in Earth's early history.

  13. The connection between stellar activity cycles and magnetic field topology

    NASA Astrophysics Data System (ADS)

    See, V.; Jardine, M.; Vidotto, A. A.; Donati, J.-F.; Boro Saikia, S.; Bouvier, J.; Fares, R.; Folsom, C. P.; Gregory, S. G.; Hussain, G.; Jeffers, S. V.; Marsden, S. C.; Morin, J.; Moutou, C.; do Nascimento, J. D.; Petit, P.; Waite, I. A.

    2016-08-01

    Zeeman Doppler imaging has successfully mapped the large-scale magnetic fields of stars over a large range of spectral types, rotation periods and ages. When observed over multiple epochs, some stars show polarity reversals in their global magnetic fields. On the Sun, polarity reversals are a feature of its activity cycle. In this paper, we examine the magnetic properties of stars with existing chromospherically determined cycle periods. Previous authors have suggested that cycle periods lie on multiple branches, either in the cycle period-Rossby number plane or the cycle period-rotation period plane. We find some evidence that stars along the active branch show significant average toroidal fields that exhibit large temporal variations while stars exclusively on the inactive branch remain dominantly poloidal throughout their entire cycle. This lends credence to the idea that different shear layers are in operation along each branch. There is also evidence that the short magnetic polarity switches observed on some stars are characteristic of the inactive branch while the longer chromospherically determined periods are characteristic of the active branch. This may explain the discrepancy between the magnetic and chromospheric cycle periods found on some stars. These results represent a first attempt at linking global magnetic field properties obtained form ZDI and activity cycles.

  14. The connection between stellar activity cycles and magnetic field topology

    NASA Astrophysics Data System (ADS)

    See, V.; Jardine, M.; Vidotto, A. A.; Donati, J.-F.; Boro Saikia, S.; Bouvier, J.; Fares, R.; Folsom, C. P.; Gregory, S. G.; Hussain, G.; Jeffers, S. V.; Marsden, S. C.; Morin, J.; Moutou, C.; do Nascimento, J. D.; Petit, P.; Waite, I. A.

    2016-11-01

    Zeeman-Doppler imaging (ZDI) has successfully mapped the large-scale magnetic fields of stars over a large range of spectral types, rotation periods and ages. When observed over multiple epochs, some stars show polarity reversals in their global magnetic fields. On the Sun, polarity reversals are a feature of its activity cycle. In this paper, we examine the magnetic properties of stars with existing chromospherically determined cycle periods. Previous authors have suggested that cycle periods lie on multiple branches, either in the cycle period-Rossby number plane or the cycle period-rotation period plane. We find some evidence that stars along the active branch show significant average toroidal fields that exhibit large temporal variations while stars exclusively on the inactive branch remain dominantly poloidal throughout their entire cycle. This lends credence to the idea that different shear layers are in operation along each branch. There is also evidence that the short magnetic polarity switches observed on some stars are characteristic of the inactive branch while the longer chromospherically determined periods are characteristic of the active branch. This may explain the discrepancy between the magnetic and chromospheric cycle periods found on some stars. These results represent a first attempt at linking global magnetic field properties obtained from ZDI and activity cycles.

  15. Lunar Cycle Influences Spontaneous Delivery in Cows.

    PubMed

    Yonezawa, Tomohiro; Uchida, Mona; Tomioka, Michiko; Matsuki, Naoaki

    2016-01-01

    There is a popular belief that the lunar cycle influences spontaneous delivery in both humans and cattle. To assess this relationship, we investigated the synodic distribution of spontaneous deliveries in domestic Holstein cows. We used retrospective data from 428 spontaneous, full-term deliveries within a three-year period derived from the calving records of a private farm in Hokkaido, Japan. Spontaneous birth frequency increased uniformly from the new moon to the full moon phase and decreased until the waning crescent phase. There was a statistically significant peak between the waxing gibbous and full moon phases compared with those between the last quarter and the waning crescent. These changes were clearly observed in deliveries among multiparous cows, whereas they were not evident in deliveries among nulliparous cows. These data suggest the utility of dairy cows as models for bio-meteorological studies, and indicate that monitoring lunar phases may facilitate comprehensive understanding of parturition. PMID:27580019

  16. Lunar Cycle Influences Spontaneous Delivery in Cows

    PubMed Central

    Yonezawa, Tomohiro; Uchida, Mona; Tomioka, Michiko; Matsuki, Naoaki

    2016-01-01

    There is a popular belief that the lunar cycle influences spontaneous delivery in both humans and cattle. To assess this relationship, we investigated the synodic distribution of spontaneous deliveries in domestic Holstein cows. We used retrospective data from 428 spontaneous, full-term deliveries within a three-year period derived from the calving records of a private farm in Hokkaido, Japan. Spontaneous birth frequency increased uniformly from the new moon to the full moon phase and decreased until the waning crescent phase. There was a statistically significant peak between the waxing gibbous and full moon phases compared with those between the last quarter and the waning crescent. These changes were clearly observed in deliveries among multiparous cows, whereas they were not evident in deliveries among nulliparous cows. These data suggest the utility of dairy cows as models for bio-meteorological studies, and indicate that monitoring lunar phases may facilitate comprehensive understanding of parturition. PMID:27580019

  17. Lanthanide Al-Ni base Ericsson cycle magnetic refrigerants

    DOEpatents

    Gschneidner, K.A. Jr.; Takeya, Hiroyuki

    1995-10-31

    A magnetic refrigerant for a magnetic refrigerator using the Ericsson thermodynamic cycle comprises DyAlNi and (Gd{sub 0.54}Er{sub 0.46})AlNi alloys having a relatively constant {Delta}Tmc over a wide temperature range. 16 figs.

  18. Lanthanide Al-Ni base Ericsson cycle magnetic refrigerants

    DOEpatents

    Gschneidner, Jr., Karl A.; Takeya, Hiroyuki

    1995-10-31

    A magnetic refrigerant for a magnetic refrigerator using the Ericsson thermodynamic cycle comprises DyAlNi and (Gd.sub.0.54 Er.sub.0.46)AlNi alloys having a relatively constant .DELTA.Tmc over a wide temperature range.

  19. Solar Cycle: Magnetized March to Equator

    NASA Video Gallery

    Bands of magnetized solar material – with alternating south and north polarity – march toward the sun's equator. Comparing the evolution of the bands with the sunspot number in each hemisphere over...

  20. Influence of Solar Cycles on Earthquakes

    NASA Astrophysics Data System (ADS)

    Tavares, M.

    2011-12-01

    This research inspects possible influence of solar cycles on earthquakes through of statistical analyses. We also discussed the mechanism that would drive the occurrence of increasing of earthquakes during solar maxima. The study was based on worldwide earthquakes events during approximately four hundred years (1600-2010). The increase of earthquakes events followed the Maxima of Solar cycle, and also depends on the tectonic plate location. From 1600 until 1645 events increased during the Maxima in some of the tectonic plates as Pacific, Arabian and South America. The earthquakes analyzed during two grand solar minima, the Maunder (1645-1720) and the Dalton (1790-1820) showed a decrease in the number of earthquakes and the solar activity. It was observed during these minima a significant number of events at specific geological features. After the last minima (Dalton) the earthquakes pattern increased with solar maxima. The calculations showed that events increasing during solar maxima most in the Pacific, South America or Arabian until 1900. Since there were few records during these three centuries we needed additional analysis on modern data. We took the last four solar cycles events (1950-2010) and made similar calculations. The results agreed with the former calculations. It might be that the mechanism for the Sun-Earth connection relies on the solar wind speed. In both records (1600-1900) and (1950-2010) the results showed a significant increase in earthquakes events in some of the tectonic plates linked to solar maxima. The Solar wind energy striking the Earth's magnetosphere affects the entire environment because the pressure on the region increases and the magnetosphere shrinks sometimes four Earth's radii. This sudden compression causes earthquakes in specific plates. During the times of solar minima the pressure from the solar wind on the earth decreases, then the magnetosphere expands and earthquakes happen in a different pattern according to the

  1. Investigation of a theoretical magnetic refrigeration cycle

    NASA Astrophysics Data System (ADS)

    Snead, Joshua D.

    This research paper studies the concept of developing a different type of freezer rather than vapor-compression for Dippin' Dots, a company who sells frozen goods. The freezer in question is a magnetic freezer that works by removing the compressor and bringing in magnetocaloric materials, which provide cooling by being subjected to a magnetic field. Many possibilities for improvements are available from this technology including a safer more environmentally benign fluid, a higher efficiency, and a possible cost savings. A theoretical model was designed and efficiency calculations and a cost analysis were both performed to determine if there were any improvements and if constructing a prototype freezer was feasible. The coefficient of performance of the designed freezer had the theoretical capability of being up to 5 times that of the vapor-compression freezer, but with the pumps found to complete the design this high number fell significantly short. The price to build a prototype was calculated to be around $7,050. After considering the data building a magnetic freezer prototype does not seem feasible. Although this freezer does not seem reasonable, the magnetic refrigerator technology seems applicable for other uses and is capable of developing in the future.

  2. Experimental simulation of a magnetic refrigeration cycle in high magnetic fields

    NASA Astrophysics Data System (ADS)

    Dilmieva, E. T.; Kamantsev, A. P.; Koledov, V. V.; Mashirov, A. V.; Shavrov, V. G.; Cwik, J.; Tereshina, I. S.

    2016-01-01

    The complete magnetic refrigeration cycle has been simulated on a sample of gadolinium in magnetic fields of a Bitter coil magnet up to 12 T. The total change of temperature of the sample during the cycle is a consequence of magnetic refrigeration, and the dependence of the magnetization of the sample on the magnetic field exhibits a hysteretic behavior. This makes it possible to determine the work done by the magnetic field on the sample during the magnetic refrigeration cycle and to calculate the coefficient of performance of the process. In a magnetic field of 2 T near the Curie temperature of gadolinium, the coefficient of performance of the magnetic refrigeration is found to be 92. With an increase in the magnetic field, the coefficient of performance of the process decreases sharply down to 15 in a magnetic field of 12 T. The reasons, for which the coefficient of performance of the magnetic refrigeration is significantly below the fundamental limitations imposed by the reversed Carnot theorem, have been discussed.

  3. Lithium-Ion Battery Cycling for Magnetism Control.

    PubMed

    Zhang, Qingyun; Luo, Xi; Wang, Luning; Zhang, Lifang; Khalid, Bilal; Gong, Jianghong; Wu, Hui

    2016-01-13

    Magnetization and electric-field coupling is fundamentally interesting and important. Specifically, current- or voltage-driven magnetization switching at room temperature is highly desirable from scientific and technological viewpoints. Herein, we demonstrate that magnetization can be controlled via the discharge-charge cycling of a lithium-ion battery (LIB) with rationally designed electrode nanomaterials. Reversible manipulation of magnetism over 3 orders of magnitude was achieved by controlling the lithiation/delithiation of a nanoscale α-Fe2O3-based electrode. The process was completed rapidly under room-temperature conditions. Our results indicate that in addition to energy storage LIBs, which have been under continuous development for several decades, provide exciting opportunities for the multireversible magnetization of magnetic fields.

  4. Effects of thermal cycling on magnetic properties of lunar analogs

    NASA Technical Reports Server (NTRS)

    Barron, A. M.; Shive, P. N.

    1984-01-01

    An experimental study has been performed to determine whether stresses associated with thermal cycling cracks can affect the coercivity of remanence carried by iron in lunar samples. Initially, samples were cycled up to 100 times in a refrigerator over a period of about 30 min per cycle. In a second set of experiments, samples were dipped directly into liquid nitrogen up to 100 times at about 1 min per cycle. Comparison of AF demagnetization curves of weak field anhysteretic remanent magnetization before and after cycling revealed no systematic differences. Calculations based on a model of spherical iron grains within olivine or troilite indicate that it is unlikely that the iron will crack under thermal stress. Thus, thermal cycling does not appear to provide an explanation for increasing the stability of remanence in samples from the lunar surface.

  5. Response of Solar Oscillations to Magnetic Activity in Cycle 24

    NASA Astrophysics Data System (ADS)

    Jain, K.; Tripathy, S. C.; Hill, F.

    2015-12-01

    Acoustic mode parameters are generally used to study the variability of the solar interior in response to changing magnetic activity. While oscillation frequencies do vary in phase with the solar activity, the mode amplitudes are anti-correlated. Now, continuous measurements from ground and space allow us study the origin of such variability in detail. Here we use intermediate-dgree mode frequencies computed from a ground-based 6-site network ( GONG), covering almost two solar cycles from the minimum of cycle 23 to the declining phase of cycle 24, to investigate the effect of remarkably low solar activity on the solar oscillations in current cycle and the preceding minimum; is the response of acoustic oscillations to magnetic activity in cycle 24 similar to cycle 23 or there are differences between cycles 23 and 24? In this paper, we analyze results for both solar cycles, and try to understand the origin of similarities/differences between them. We will also compare our findings with the contemporaneous observations from space (SOHO/MDI and SDO/HMI).

  6. Three Solar Cycles of Non-Increasing Magnetic Field

    NASA Astrophysics Data System (ADS)

    Hildner, E.; Arge, N.; Pizzo, V. J.; Harvey, J. W.

    2001-05-01

    Since measurements started in the late 19th century, there has been a secular increase (with superposed ripples due to solar cycles) of the aa geomagnetic index. Starting from this observation, Lockwood, Stamper, and Wild (hereafter, LSW) conclude (Nature, 399, 1999; see also Lockwood et al., Astronomy and Geophysics, 40, 1999) that the total source's magnetic flux in the Sun's atmosphere has risen by 41% since 1964\\" and by 130% in the 20th century. However, solar data over nearly three solar cycles - near-daily magnetograms from Mt Wilson, and Wilcox Solar Observatories and newly reanalyzed data from the National Solar Observatory - show no secular trend in overall photospheric flux. More importantly, the magnetic field open to interplanetary space (as calculated from photospheric measurements and assuming potential fields to a height of 2.5 Rsun) fails to show a secular increase over the last three solar cycles. Like LSW, we do not explicitly take account of transient events. Thus, both data and calculations imply that the Sun's average coronal magnetic flux has not increased over the last three solar cycles. Analysis of simulations with the potential field source surface model shows that the interplanetary magnetic flux is not simply related to the overall, photospheric, solar magnetic flux. Both results are in agreement with the findings of Wang, Lean, and Sheeley (GRL, 27, 2000). The topology, not just the strength, of the emergent solar magnetic field is a major determinant of the interplanetary magnetic field experienced at Earth. In principle, secular change in non-potentiality of the coronal field could lead to secular increase in interplanetary magnetic flux, but this seems unlikely.

  7. Towards better constrained models of the solar magnetic cycle

    NASA Astrophysics Data System (ADS)

    Munoz-Jaramillo, Andres

    2010-12-01

    The best tools we have for understanding the origin of solar magnetic variability are kinematic dynamo models. During the last decade, this type of models has seen a continuous evolution and has become increasingly successful at reproducing solar cycle characteristics. The basic ingredients of these models are: the solar differential rotation -- which acts as the main source of energy for the system by shearing the magnetic field; the meridional circulation -- which plays a crucial role in magnetic field transport; the turbulent diffusivity -- which attempts to capture the effect of convective turbulence on the large scale magnetic field; and the poloidal field source -- which closes the cycle by regenerating the poloidal magnetic field. However, most of these ingredients remain poorly constrained which allows one to obtain solar-like solutions by "tuning" the input parameters, leading to controversy regarding which parameter set is more appropriate. In this thesis we revisit each of those ingredients in an attempt to constrain them better by using observational data and theoretical considerations, reducing the amount of free parameters in the model. For the meridional flow and differential rotation we use helioseismic data to constrain free parameters and find that the differential rotation is well determined, but the available data can only constrain the latitudinal dependence of the meridional flow. For the turbulent magnetic diffusivity we show that combining mixing-length theory estimates with magnetic quenching allows us to obtain viable magnetic cycles and that the commonly used diffusivity profiles can be understood as a spatiotemporal average of this process. For the poloidal source we introduce a more realistic way of modeling active region emergence and decay and find that this resolves existing discrepancies between kinematic dynamo models and surface flux transport simulations. We also study the physical mechanisms behind the unusually long minimum of

  8. MAGNETIC FLUX CONSERVATION IN THE HELIOSHEATH INCLUDING SOLAR CYCLE VARIATIONS OF MAGNETIC FIELD INTENSITY

    SciTech Connect

    Michael, A. T.; Opher, M.; Provornikova, E.; Richardson, J. D.; Tóth, G. E-mail: mopher@bu.edu E-mail: jdr@space.mit.edu

    2015-04-10

    In the heliosheath (HS), Voyager 2 has observed a flow with constant radial velocity and magnetic flux conservation. Voyager 1, however, has observed a decrease in the flow’s radial velocity and an order of magnitude decrease in magnetic flux. We investigate the role of the 11 yr solar cycle variation of the magnetic field strength on the magnetic flux within the HS using a global 3D magnetohydrodynamic model of the heliosphere. We use time and latitude-dependent solar wind velocity and density inferred from Solar and Heliospheric Observatory/SWAN and interplanetary scintillations data and implemented solar cycle variations of the magnetic field derived from 27 day averages of the field magnitude average of the magnetic field at 1 AU from the OMNI database. With the inclusion of the solar cycle time-dependent magnetic field intensity, the model matches the observed intensity of the magnetic field in the HS along both Voyager 1 and 2. This is a significant improvement from the same model without magnetic field solar cycle variations, which was over a factor of two larger. The model accurately predicts the radial velocity observed by Voyager 2; however, the model predicts a flow speed ∼100 km s{sup −1} larger than that derived from LECP measurements at Voyager 1. In the model, magnetic flux is conserved along both Voyager trajectories, contrary to observations. This implies that the solar cycle variations in solar wind magnetic field observed at 1 AU does not cause the order of magnitude decrease in magnetic flux observed in the Voyager 1 data.

  9. Influence of magnetic domain walls and magnetic field on the thermal conductivity of magnetic nanowires.

    PubMed

    Huang, Hao-Ting; Lai, Mei-Feng; Hou, Yun-Fang; Wei, Zung-Hang

    2015-05-13

    We investigated the influence of magnetic domain walls and magnetic fields on the thermal conductivity of suspended magnetic nanowires. The thermal conductivity of the nanowires was obtained using steady-state Joule heating to measure the change in resistance caused by spontaneous heating. The results showed that the thermal conductivity coefficients of straight and wavy magnetic nanowires decreased with an increase in the magnetic domain wall number, implying that the scattering between magnons and domain walls hindered the heat transport process. In addition, we proved that the magnetic field considerably reduced the thermal conductivity of a magnetic nanowire. The influence of magnetic domain walls and magnetic fields on the thermal conductivity of polycrystalline magnetic nanowires can be attributed to the scattering of long-wavelength spin waves mediated by intergrain exchange coupling.

  10. DYNAMO ACTION AND MAGNETIC CYCLES IN F-TYPE STARS

    SciTech Connect

    Augustson, Kyle C.; Toomre, Juri; Brun, Allan Sacha

    2013-11-10

    Magnetic activity and differential rotation are commonly observed features on main-sequence F-type stars. We seek to make contact with such observations and to provide a self-consistent picture of how differential rotation and magnetic fields arise in the interiors of these stars. The three-dimensional magnetohydrodynamic anelastic spherical harmonic code is employed to simulate global-scale convection and dynamo processes in a 1.2 M{sub ☉} F-type star at two rotation rates. The simulations are carried out in spherical shells that encompass most of the convection zone and a portion of the stably stratified radiative zone below it, allowing us to explore the effects a stable zone has upon the morphology of the global-scale magnetic fields. We find that dynamo action with a high degree of time variation occurs in the star rotating more rapidly at 20 Ω{sub ☉}, with the polarity of the mean field reversing on a timescale of about 1600 days. Between reversals, the magnetic energy rises and falls with a fairly regular period, with three magnetic energy cycles required to complete a reversal. The magnetic energy cycles and polarity reversals arise due to a linking of the polar-slip instability in the stable region and dynamo action present in the convection zone. For the more slowly rotating case (10 Ω{sub ☉}), persistent wreaths of magnetism are established and maintained by dynamo action. Compared to their hydrodynamic progenitors, the dynamo states here involve a marked reduction in the exhibited latitudinal differential rotation, which also vary during the course of a cycle.

  11. On the Influence of the Solar Bi-Cycle on Comic Ray Modulatio

    NASA Astrophysics Data System (ADS)

    Lifter, N. Part Xxvii: A. Defect Of The Solar Dynamo. B.; Scissors, K.; Sprucener, H.

    In this presentation we propose a new paradigm that explains the different lengths of individual solar Hale cycles. It proves beneficial to distinguish between a so-called inHale and ex-Hale cycle, which together form the solar bi-cycle. We carefully analyzed the influence of so-called complex mode excitations (CMEs) on comic ray modulation, in particular on the drifts of the comic isotope O+3 , which we found to induce characteristic anisotropies. This comic isotope anisotropy (CIA) is caused by the wellknown north-south asymmetry (NSA) and can be observed as a rare Forbush increase (FBI). The latter is linked to the solar magnetic field which appears to have a chaotic behaviour (for details see part I-XXVI). Especially during an ex-Hale cycle magnetic flux is pseudo-pneumatically escaping through a coronal hole. Consequently, the solar dynamo can no longer operate efficiently, i.e. is defect.

  12. The influence of magnetic aftereffects on the magnetic anisotropy

    NASA Astrophysics Data System (ADS)

    Mashukov, A.; Mashukova, A.

    2012-04-01

    There were investigated the time dependences of the magnetic anisotropy characteristics of artificial depositions received in the geomagnetic field. The content of magnetite in the nonmagnetic matrix of kaolin did not exceed 1%. The Co content in the grains of magnetite Fe3 O4 was 0.0018%. The viscous magnetization was created in the depositions with grain sizes of Fe3O4 in micrometers (0 ÷ 8), (9 ÷ 16), (17 ÷ 32), (33 ÷ 64), (65 ÷ 100), (101 ÷ 150). The X-ray method of direct pole figures indicates that the intensity of the ordering of the ferromagnetic grains in the depositions depends strongly on the grain size in the above-mentioned ranges, getting reduced from 1.9 to 1.1. Compared with the characteristics received immediately after drying the samples and after holding them for two years in the earth's magnetic field in the direction of In, one could observe increase in all the characteristics of the magnetic anisotropy. The magnitude Hd of the magnetic field having the periodicity change of Hd 2π to π increases. This indicates the stabilization of the new domain structure. The increase in the uniaxial anisotropy constant (K) is associated with the emergence of the large induced anisotropy due to the diffusion of Co ions. It was found out that the constant K decreases markedly with increasing particle size in the range from 8 mm to 40 microns. Based on the results of the X-ray analysis by using the method direct pole figures, it may be explained by the creation of the axial texture in the depositions with grains having the size less than 40 microns. The intensity of more than 40 microns decreases insignificantly - from 1.3 to 1.1. After creating the viscous magnetization in two years, the constant K has increased by 1.5 - 2 times. The influence of the magnetic after-effects on K in strong magnetic fields denotes the diffusion nature of the viscous magnetization. The losses of the rotational magnetic hysteresis (W) also rise in the presence of the

  13. SOLAR CYCLE VARIATION OF THE INTER-NETWORK MAGNETIC FIELD

    SciTech Connect

    Jin, Chunlan; Wang, Jingxiu

    2015-06-20

    The solar inter-network magnetic field is the weakest component of solar magnetism, but it contributes most of the solar surface magnetic flux. The study of its origin has been constrained by the inadequate tempospatial resolution and sensitivity of polarization observations. With dramatic advances in spatial resolution and detecting sensitivity, the solar spectropolarimetry provided by the Solar Optical Telescope on board Hinode in an interval from the solar minimum to maximum of cycle 24 opens an unprecedented opportunity to study the cyclic behavior of the solar inter-network magnetic field. More than 1000 Hinode magnetograms observed from 2007 January to 2014 August are selected in the study. It has been found that there is a very slight correlation between sunspot number and magnetic field at the inter-network flux spectrum. From solar minimum to maximum of cycle 24, the flux density of the solar inter-network field is invariant, at 10 ± 1 G. The observations suggest that the inter-network magnetic field does not arise from flux diffusion or flux recycling of solar active regions, thereby indicating the existence of a local small-scale dynamo. Combining the full-disk magnetograms observed by the Solar and Heliospheric Observatory/Michelson Doppler Imager and the Solar Dynamics Observatory/Helioseismic and Magnetic Imager in the same period, we find that the area ratio of the inter-network region to the full disk of the Sun apparently decreases from solar minimum to maximum but always exceeds 60%, even in the phase of solar maximum.

  14. Numerical Analysis of an Active Magnetic Regenerator (AMR) Refrigeration Cycle

    NASA Astrophysics Data System (ADS)

    Dikeos, J.; Rowe, A.; Tura, A.

    2006-04-01

    An alternative cycle proposed for refrigeration and gas liquefaction is active magnetic regenerator (AMR) refrigeration. This technology relies on solid materials exhibiting the magnetocaloric effect (MCE), a nearly reversible temperature change induced by a magnetic field change. This work focuses on numerical simulations of the AMR refrigeration cycle. A transient one-dimensional finite element model developed in FEMLAB™ incorporates energy equations for the refrigerant and the heat transfer fluid. The results of the model are validated by comparison to room temperature experiments with Gd. Predictions are then made for the performance of DyAl2 AMR beds near 70 K. Numerical results for simulations significantly above the Curie temperature are found to be dependent upon the initial conditions.

  15. [Influence of chosen metals on the citric acid cycle].

    PubMed

    Rojczyk-Gołebiewska, Ewa; Kucharzewski, Marek

    2013-03-01

    Industrial activity growth influenced not only technological progress, but also had negative effects on human natural environment. It results among others in increased human exposition to heavy metals. In case of detoxication mechanisms disturbance in organism, heavy metals cumulate in tissues causing mutations and disrupting metabolism, including Krebs cycle. Recent studies have revealed that iron, zinc and manganese have especially strong influence on Krebs cycle. These elements act as cofactors or inhibitors regulating activity of particular enzymes of this cycle, which has a reflection in cellular energy production disturbances.

  16. Thermonuclear inverse magnetic pumping power cycle for stellarator reactors

    NASA Astrophysics Data System (ADS)

    Ho, D. D. M.; Kulsrud, R. M.

    1985-09-01

    A novel power cycle for direct conversion of alpha-particle energy into electricity is proposed for an ignited plasma in a stellerator reactor. The plasma column is alternately compressed and expanded in minor radius by periodic variation of the toroidal magnetic field strength. As a result of the way a stellarator is expected to work, the plasma pressure during expansion is greater than the corresponding pressure during compression. Therefore, negative work is done on the plasma during a complete cycle. This work manifests itself as a back-voltage in the toroidal field coils, and direct electrical energy is obtained from this voltage. For a typical reactor, the average power obtained from this cycle (with a minor radius compression factor on the order of 50%) can be as much as 50% of the electrical power obtained from the thermonuclear neutrons without compressing the plasma. Thus, if it is feasible to vary the toroidal field strength, the power cycle provides an alternative scheme of energy conversion for a deuterium-tritium fueled reactor. The cycle may become an important method of energy conversion for advanced neutron-lean fueled reactors. By operating two or more reactors in tandem, the cycle can be made self-sustaining.

  17. Solar-Cycle Evolution of Subsurface Flows and Magnetic Field

    NASA Astrophysics Data System (ADS)

    Kosovichev, Alexander G.; Zhao, Junwei

    2016-05-01

    Local helioseismology and magnetic field measurements from the HMI instrument on SDO provide unique high-resolution data that allow us to investigate detailed dynamics of the upper convection zone and its relation to the magnetic field evolution during the first five years of the current solar cycle. This study is focused on the understanding the role of the near-surface shear layer (NSSL) in the dynamo process, generation, emergence and transport of the solar magnetic flux. The helioseismology data represent 3D flow maps in the depth range of 0-20 Mm, obtained uninterruptedly every 8 hours for almost the whole solar disk with the spatial sampling of two arcsec. We calculate the flow characteristics (such as divergence, vorticity and kinetic helicity) on different spatio-temporal scales from supergranulation to global-scale zonal and meridional flows. We investigate the multi-scale organization of the subsurface flows, including the inflows into active regions, the hemispheric `flip-flop’ asymmetry of variations of the meridional flows, the structure and dynamics of torsional oscillations, and compare the flow behavior with the evolution of the observed magnetic activity of the current cycle.

  18. MAGNETIC ACTIVITY CYCLES IN THE EXOPLANET HOST STAR {epsilon} ERIDANI

    SciTech Connect

    Metcalfe, T. S.; Mathur, S.; Buccino, A. P.; Mauas, P. J. D.; Petrucci, R.; Brown, B. P.; Soderblom, D. R.; Henry, T. J.; Hall, J. C.; Basu, S.

    2013-02-01

    The active K2 dwarf {epsilon} Eri has been extensively characterized both as a young solar analog and more recently as an exoplanet host star. As one of the nearest and brightest stars in the sky, it provides an unparalleled opportunity to constrain stellar dynamo theory beyond the Sun. We confirm and document the 3-year magnetic activity cycle in {epsilon} Eri originally reported by Hatzes and coworkers, and we examine the archival data from previous observations spanning 45 years. The data show coexisting 3-year and 13-year periods leading into a broad activity minimum that resembles a Maunder minimum-like state, followed by the resurgence of a coherent 3-year cycle. The nearly continuous activity record suggests the simultaneous operation of two stellar dynamos with cycle periods of 2.95 {+-} 0.03 years and 12.7 {+-} 0.3 years, which, by analogy with the solar case, suggests a revised identification of the dynamo mechanisms that are responsible for the so-called 'active' and 'inactive' sequences as proposed by Boehm-Vitense. Finally, based on the observed properties of {epsilon} Eri, we argue that the rotational history of the Sun is what makes it an outlier in the context of magnetic cycles observed in other stars (as also suggested by its Li depletion), and that a Jovian-mass companion cannot be the universal explanation for the solar peculiarities.

  19. Properties of Magnetic Tongues over a Solar Cycle

    NASA Astrophysics Data System (ADS)

    Poisson, Mariano; Démoulin, Pascal; López Fuentes, Marcelo; Mandrini, Cristina H.

    2016-08-01

    The photospheric spatial distribution of the main magnetic polarities of bipolar active regions (ARs) present during their emergence deformations are known as magnetic tongues. They are attributed to the presence of twist in the toroidal magnetic-flux tubes that form the ARs. The aim of this article is to study the twist of newly emerged ARs from the evolution of magnetic tongues observed in photospheric line-of-sight magnetograms. We apply the procedure described by Poisson et al. ( Solar Phys. 290, 727, 2015a) to ARs observed over the full Solar Cycle 23 and the beginning of Cycle 24. Our results show that the hemispherical rule obtained using the tongues as a proxy of the twist has a weak sign dominance (53 % in the southern hemisphere and 58 % in the northern hemisphere). By defining the variation of the tongue angle, we characterize the strength of the magnetic tongues during different phases of the AR emergence. We find that there is a tendency of the tongues to be stronger during the beginning of the emergence and to become weaker as the AR reaches its maximum magnetic flux. We compare this evolution with the emergence of a toroidal flux-rope model with non-uniform twist. The variety of evolution of the tongues in the analyzed ARs can only be reproduced when using a broad range of twist profiles, in particular having a large variety of twist gradients in the direction vertical to the photosphere. Although the analytical model used is a special case, selected to minimize the complexity of the problem, the results obtained set new observational constraints to theoretical models of flux-rope emergence that form bipolar ARs.

  20. Solar-cycle variations of the internetwork magnetic field

    NASA Astrophysics Data System (ADS)

    Faurobert, M.; Ricort, G.

    2015-10-01

    Context. The quiet Sun exhibits a rich and complex magnetic structuring that is still not fully resolved or understood. Aims: We intend to contribute to the debate about the origin of the internetwork magnetic fields and whether or not they are related to the global solar dynamo. Methods: We analyzed center-to-limb polarization measurements obtained with the SOT/SP spectropolarimeter onboard the Hinode satellite outside active regions in 2007 and 2013, that is, at a minimum and a maximum of the solar cycle, respectively. We examined 10'' × 10'' maps of the unsigned circular and linear polarization in the FeI 630.25 nm line in regions located away from network elements. The maps were corrected for bias and focus variations between the two data sets. Then we applied a Fourier spectral analysis to examine wether the spatial structuring of the internetwork magnetic fields shows significant differences between the minimum and maximum of the cycle. Results: Neither the mean values of the unsigned circular and linear polarizations in the selected 10'' × 10'' maps nor their spatial fluctuation power spectra show significant center-to-limb variations. For the unsigned circular polarization the power of the spatial fluctuations is lower in 2013 than in 2007, but the spectral slope is unchanged. The linear polarization spectra show no significant differences in 2013 and 2007, but the spectrum of 2013 is more strongly affected by noise. Conclusions: The small-scale magnetic structuring in the internetwork is different in our 2013 and 2007 data. Surprisingly, we find a lower spatial fluctuation power at the solar maximum in the internetwork magnetic structuring. This indicates some complex interactions between the small-scale magnetic structures in the quiet Sun and the global dynamo, as predicted by recent numerical simulations. This result has to be confirmed by further statistical studies with larger data sets.

  1. Magnetic field influence on paramecium motility

    SciTech Connect

    Rosen, M.F.; Rosen, A.D. )

    1990-01-01

    The influence of a moderately intense static magnetic field on movement patterns of free swimming Paramecium was studied. When exposed to fields of 0.126 T, these ciliated protozoa exhibited significant reduction in velocity as well as a disorganization of movement pattern. It is suggested that these findings may be explained on the basis of alteration in function of ion specific channels within the cell membrane.

  2. Dynamic simulation of FES-cycling: influence of individual parameters.

    PubMed

    Gföhler, Margit; Lugner, Peter

    2004-12-01

    Cycling by means of functional electrical simulation (FES) is an attractive training method for spinal cord injured (SCI) subjects. FES-cycling performance is influenced by a number of parameters like seating position, physiological parameters, conditions of surface stimulation, and pedaling rate. The objective of this paper was the determination of the influence of the most important parameters on optimal muscle stimulation patterns and power output of FES-cycling on a noncircular pedal path. The rider-cycle system was modeled as a planar articulated rigid body linkage on which the muscle forces are applied via joint moments and implemented into a forward dynamic simulation of FES-cycling. For model validation, the generated drive torques that are predicted by the simulation were compared to measurements with an individual paraplegic subject. Then, a sensitivity analysis was carried out to determine the influences of the most important parameters for surface stimulation of gluteus maximus, quadriceps, hamstrings, and peroneus reflex. The results show how optimal stimulation patterns and the expected mean active power output can be estimated based on measured individual parameters and adjusted geometry and stimulation parameters for a particular SCI-subject. This can considerably improve FES-cycling performance and relieve the patients by shortening the time that is necessary for experimental adaptation of the stimulation patterns.

  3. Developing a Solar Magnetic Catalog Spanning Four Cycles

    NASA Astrophysics Data System (ADS)

    Werginz, Zachary; Munoz-Jaramillo, Andres; DeLuca, Michael D.; Vargas Acosta, Juan Pablo; Vargas Dominguez, Santiago; Zhang, Jie; Longcope, Dana; Martens, Petrus C.

    2016-05-01

    Bipolar magnetic regions (BMRs) are the cornerstone of solar cycle propagation, the building blocks that give structure to the solar atmosphere, and the origin of the majority of space weather events. However, in spite of their importance, there is no homogeneous BMR catalog spanning the era of systematic solar magnetic field measurements. Here we present the results of an ongoing project to address this deficiency applying the Bipolar Active Region Detection (BARD) code to magnetograms from the 512 Channel of the Kitt Peak Vaccum Telescope, SOHO/MDI, and SDO/HMI.The BARD code automatically identifies BMRs and tracks them as they are rotated by differential rotation. The output of the automatic detection is supervised by a human observer to correct possible mistakes made by the automatic algorithm (like incorrect pairings and tracking mislabels). Extra passes are made to integrate fragmented regions as well as to balance the flux between BMR polarities. At the moment, our BMR database includes 6,885 unique objects (detected and tracked) belonging to four separate solar cycles (21-24).

  4. Magnetic resonance imaging without field cycling at less than earth's magnetic field

    NASA Astrophysics Data System (ADS)

    Lee, Seong-Joo; Shim, Jeong Hyun; Kim, Kiwoong; Yu, Kwon Kyu; Hwang, Seong-min

    2015-03-01

    A strong pre-polarization field, usually tenths of a milli-tesla in magnitude, is used to increase the signal-to-noise ratio in ordinary superconducting quantum interference device-based nuclear magnetic resonance/magnetic resonance imaging experiments. Here, we introduce an experimental approach using two techniques to remove the need for the pre-polarization field. A dynamic nuclear polarization (DNP) technique enables us to measure an enhanced resonance signal. In combination with a π / 2 pulse to avoid the Bloch-Siegert effect in a micro-tesla field, we obtained an enhanced magnetic resonance image by using DNP technique with a 34.5 μT static external magnetic field without field cycling. In this approach, the problems of eddy current and flux trapping in the superconducting pickup coil, both due to the strong pre-polarization field, become negligible.

  5. Magnetic resonance imaging without field cycling at less than earth's magnetic field

    SciTech Connect

    Lee, Seong-Joo Shim, Jeong Hyun; Kim, Kiwoong; Yu, Kwon Kyu; Hwang, Seong-min

    2015-03-09

    A strong pre-polarization field, usually tenths of a milli-tesla in magnitude, is used to increase the signal-to-noise ratio in ordinary superconducting quantum interference device-based nuclear magnetic resonance/magnetic resonance imaging experiments. Here, we introduce an experimental approach using two techniques to remove the need for the pre-polarization field. A dynamic nuclear polarization (DNP) technique enables us to measure an enhanced resonance signal. In combination with a π/2 pulse to avoid the Bloch-Siegert effect in a micro-tesla field, we obtained an enhanced magnetic resonance image by using DNP technique with a 34.5 μT static external magnetic field without field cycling. In this approach, the problems of eddy current and flux trapping in the superconducting pickup coil, both due to the strong pre-polarization field, become negligible.

  6. Magnetic Influences on the Solar Wind

    NASA Astrophysics Data System (ADS)

    Woolsey, Lauren N.

    2016-01-01

    The Sun is our closest star, and even with the ability to resolve fine structure, there are several large mysteries that remain unsolved. One of these unanswered questions is how the supersonic outflow from the Sun, the solar wind, is generated and accelerated. In this dissertation, I have investigated the role of Alfvén waves in heating the corona and accelerating the wind. I focus on modeling of flux tubes that are open to the heliosphere, i.e. bundles of magnetic field that stretch beyond a few solar radii into the heliosphere. In these flux tubes, Alfvén waves are launched by the shaking of the footpoints from the convective motions of granulation on the solar photosphere. I present results of modeling efforts in one dimension that investigate how this process changes for a variety of different magnetic field structures over a solar cycle and three-dimensional modeling of time-dependent processes that unlock a connection between pico- and nanoflare-scale events and the turbulent heating generated by counter-propagating Alfvén waves. In addition to computational modeling, I also present efforts to find magnetic thresholds in observations of small-scale network jets seen with the Interface Region Imaging Spectrograph (IRIS). These jets were first discovered by IRIS due to their short lifetimes (10s of seconds) and small size (widths of 100s of kilometers). The findings for this project suggest that the modeled Alfvén-wave-driven turbulence is consistent with these network jets.

  7. The Influence of Eccentricity Cycles on Exoplanet Habitability

    NASA Astrophysics Data System (ADS)

    Baskin, N. J. K.; Fabrycky, D. C.; Abbot, D. S.

    2015-12-01

    In our search for habitable exoplanets, it is important to understand how planetary habitability is influenced by orbital configurations that differ from those of the terrestrial planets in our Solar system. In particular, observational surveys have revealed the prevalence of planetary systems around binary stars. Within these systems, the gravitational influence of a companion star can induce libration in the eccentricity of the planet's orbit (referred to as Kozai Cycles) on timescales as short as thousands of years. The resulting fluctuations in stellar flux at the top of the atmosphere can potentially induce dramatic variations in surface temperatures, with direct implications for the planet's habitability prospects. We investigate this research problem using two steps. First, we utilize the MERCURY N-body integrator in order to calculate the eccentricity of a hypothetical Earth-analogue under the gravitational influence of a stellar companion. Second, we run a coupled Global Climate Model (GCM) at various stages of a cycle provided by the MERCURY runs in order to examine if the increase in insolation renders the planet uninhabitable. This work will allow us to better understand how Kozai cycles influence the boundaries of a planet's habitable zone.

  8. Solar magnetic activity cycles, coronal potential field models and eruption rates

    NASA Astrophysics Data System (ADS)

    Petrie, Gordon

    2013-07-01

    We study the evolution of the observed photospheric magnetic field and the modeled global coronal magnetic field during the past 3 1/2 solar activity cycles observed since the mid-1970s. We use synoptic magnetograms and extrapolated potential-field models based on longitudinal full-disk photospheric magnetograms from the NSO's three magnetographs at Kitt Peak, the Synoptic Optical Long-term Investigations of the Sun (SOLIS) vector spectro-magnetograph (VSM), the spectro-magnetograph and the 512-channel magnetograph instruments, and from the U. Stanford's Wilcox Solar Observatory. The associated multipole field components are used to study the dominant length scales and symmetries of the coronal field. Of the axisymmetric multipoles, only the dipole and octupole follow the poles whereas the higher orders follow the activity cycle. All non-axisymmetric multipole strengths are well correlated with the activity cycle. The axial dipole and octupole are the largest contributors to the global field except while the polar fields are reversing. This influence of the polar fields extends to modulating eruption rates. According to the Computer Aided CME Tracking (CACTus), Solar Eruptive Event Detection System (SEEDS), and Nobeyama radioheliograph prominence eruption catalogs, the rate of solar eruptions is found to be systematically higher for active years between 2003-2012 than for those between 1997-2002. This behavior appears to be connected with the weakness of the late-cycle 23 polar fields as suggested by Luhmann. We see evidence that the process of cycle 24 field reversal is well advanced at both poles.

  9. Solar Magnetic Activity Cycles, Coronal Potential Field Models and Eruption Rates

    NASA Astrophysics Data System (ADS)

    Petrie, G. J. D.

    2013-05-01

    We study the evolution of the observed photospheric magnetic field and the modeled global coronal magnetic field during the past 3 1/2 solar activity cycles observed since the mid-1970s. We use synoptic magnetograms and extrapolated potential-field models based on longitudinal full-disk photospheric magnetograms from the National Solar Observatory's three magnetographs at Kitt Peak, the Synoptic Optical Long-term Investigations of the Sun vector spectro-magnetograph, the spectro-magnetograph and the 512-channel magnetograph instruments, and from Stanford University's Wilcox Solar Observatory. The associated multipole field components are used to study the dominant length scales and symmetries of the coronal field. Polar field changes are found to be well correlated with active fields over most of the period studied, except between 2003 and 2006 when the active fields did not produce significant polar field changes. Of the axisymmetric multipoles, only the dipole and octupole follow the poles whereas the higher orders follow the activity cycle. All non-axisymmetric multipole strengths are well correlated with the activity cycle. The tilt of the solar dipole is therefore almost entirely due to active-region fields. The axial dipole and octupole are the largest contributors to the global field except while the polar fields are reversing. This influence of the polar fields extends to modulating eruption rates. According to the Computer Aided CME Tracking, Solar Eruptive Event Detection System, and Nobeyama radioheliograph prominence eruption catalogs, the rate of solar eruptions is found to be systematically higher for active years between 2003 and 2012 than for those between 1997 and 2002. This behavior appears to be connected with the weakness of the late-cycle 23 polar fields as suggested by Luhmann. We see evidence that the process of cycle 24 field reversal is well advanced at both poles.

  10. SOLAR MAGNETIC ACTIVITY CYCLES, CORONAL POTENTIAL FIELD MODELS AND ERUPTION RATES

    SciTech Connect

    Petrie, G. J. D.

    2013-05-10

    We study the evolution of the observed photospheric magnetic field and the modeled global coronal magnetic field during the past 3 1/2 solar activity cycles observed since the mid-1970s. We use synoptic magnetograms and extrapolated potential-field models based on longitudinal full-disk photospheric magnetograms from the National Solar Observatory's three magnetographs at Kitt Peak, the Synoptic Optical Long-term Investigations of the Sun vector spectro-magnetograph, the spectro-magnetograph and the 512-channel magnetograph instruments, and from Stanford University's Wilcox Solar Observatory. The associated multipole field components are used to study the dominant length scales and symmetries of the coronal field. Polar field changes are found to be well correlated with active fields over most of the period studied, except between 2003 and 2006 when the active fields did not produce significant polar field changes. Of the axisymmetric multipoles, only the dipole and octupole follow the poles whereas the higher orders follow the activity cycle. All non-axisymmetric multipole strengths are well correlated with the activity cycle. The tilt of the solar dipole is therefore almost entirely due to active-region fields. The axial dipole and octupole are the largest contributors to the global field except while the polar fields are reversing. This influence of the polar fields extends to modulating eruption rates. According to the Computer Aided CME Tracking, Solar Eruptive Event Detection System, and Nobeyama radioheliograph prominence eruption catalogs, the rate of solar eruptions is found to be systematically higher for active years between 2003 and 2012 than for those between 1997 and 2002. This behavior appears to be connected with the weakness of the late-cycle 23 polar fields as suggested by Luhmann. We see evidence that the process of cycle 24 field reversal is well advanced at both poles.

  11. Influence of Phosphorus Cycle Coupling on Carbon-Climate Feedbacks

    NASA Astrophysics Data System (ADS)

    Yang, X.; Thornton, P. E.; Ricciuto, D. M.; Hoffman, F. M.

    2014-12-01

    It is being increasingly recognized that carbon-nutrient interactions play important roles in regulating terrestrial carbon cycle responses to increasing CO2 in the atmosphere and climate change. Nitrogen-enabled models in CMIP5 indicated that the inclusion of nitrogen cycle reduces CO2 fertilization effect and warming-induced carbon loss from land ecosystems. None of the CMIP5 models has considered phosphorus (P) as a limiting nutrient. Phosphorus has been commonly considered to be the most limiting nutrient in lowland tropical forests. Only recently a few land models have considered P dynamics and C-N-P interactions (CASA-CNP, JSBACH-CNP and CLM-CNP) and these models show strong P limitation in tropical forest responses to increasing atmospheric CO2. In this study, we have performed a set of offline global-scale simulations using CLM-CNP constrained by realistic maps of phosphorus distribution. We examine the influence of including phosphorus cycle dynamics and C-N-P interactions on C-climate feedbacks. We illustrate the spatial patterns of dominant nutrient limitation (N-limited vs. P-limited) on the global scale. We show that P-limitation dominates over most of the tropics and sub-tropics, while N limitation dominates over most of the temperate and high-latitude regions. We also show that phosphorus cycle coupling reduces the sensitivity of net carbon exchange to variations in both temperature and precipitation.

  12. Oscillating dynamo in the presence of a fossil magnetic field - The solar cycle

    NASA Technical Reports Server (NTRS)

    Levy, E. H.; Boyer, D.

    1982-01-01

    Hydromagnetic dynamo generation of oscillating magnetic fields in the presence of an external, ambient magnetic field introduces a marked polarity asymmetry between the two halves of the magnetic cycle. The principle of oscillating dynamo interaction with external fields is developed, and a tentative application to the sun is described. In the sun a dipole moment associated with the stable fluid beneath the convection zone would produce an asymmetrical solar cycle.

  13. Factors Influencing Phosphorous Cycling in Biogeochemical 'Hot Spots'

    NASA Astrophysics Data System (ADS)

    Saia, S. M.; Walter, M. T.; Buda, A. R.; Carrick, H. J.; Regan, J. M.

    2015-12-01

    Anthropogenic alteration of the phosphorus (P) cycle has led to subsequent soil and water quality issues. For example, P build up in soils due to historic fertilizer application may become biologically available and exacerbate eutrophication and anoxia in nearby water bodies. In the humid Northeastern United States, storm runoff transports P and also stimulates biogeochemical processes, these locations are termed biogeochemical 'hot spots'. Many studies have looked at nitrogen and carbon cycling in biogeochemical hot spots but few have focused on P. We hypothesize the periodic wetting and drying of biogeochemical hot spots promotes a combination of abiotic and biotic processes that influence the mobility of P. To test this hypothesis, we took monthly soil samples (5 cm deep) from May to October in forest, pasture, and cropped land near Ithaca, NY. In-situ measurements taken with each sample included volumetric soil moisture and soil temperature. We also analyzed samples for 'runoff generated' phosphate, nitrate, and sulfate (from 0.01 M CaCl2 extraction), Fe(II), percent organic matter, pH, as well as oxalate extractable and total P, Al, and Fe. We used linear mixed effects models to test how runoff generated phosphate concentrations vary with soil moisture and whether other environmental factors strengthen/weaken this relationship. The knowledge gained from this study will improve our understanding of P cycling in biogeochemical hot spots and can be used to improve the effectiveness of agricultural management practices in the Northeastern United States.

  14. Elevated CO2 influences microbial carbon and nitrogen cycling

    PubMed Central

    2013-01-01

    Background Elevated atmospheric CO2 (eCO2) has been shown to have significant effects on terrestrial ecosystems. However, little is known about its influence on the structure, composition, and functional potential of soil microbial communities, especially carbon (C) and nitrogen (N) cycling. A high-throughput functional gene array (GeoChip 3.0) was used to examine the composition, structure, and metabolic potential of soil microbial communities from a grassland field experiment after ten-year field exposure to ambient and elevated CO2 concentrations. Results Distinct microbial communities were established under eCO2. The abundance of three key C fixation genes encoding ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco), carbon monoxide dehydrogenase (CODH) and propionyl-CoA/acetyl-CoA carboxylase (PCC/ACC), significantly increased under eCO2, and so did some C degrading genes involved in starch, cellulose, and hemicellulose. Also, nifH and nirS involved in N cycling were significantly stimulated. In addition, based on variation partitioning analysis (VPA), the soil microbial community structure was largely shaped by direct and indirect eCO2-driven factors. Conclusions These findings suggest that the soil microbial community structure and their ecosystem functioning for C and N cycling were altered dramatically at eCO2. This study provides new insights into our understanding of the feedback response of soil microbial communities to elevated CO2 and global change. PMID:23718284

  15. Exotic Earthworm Influence on Nitrogen Cycling in FACE Forest Soils

    NASA Astrophysics Data System (ADS)

    Top, S. M.; Filley, T. R.

    2010-12-01

    Exotic earthworm invasion in northern North American forests has the potential to significantly alter nitrogen and carbon cycling in forest soils, through litter layer losses, loss of organic horizon, and changes in fine root density. Earthworm influence on nitrogen cycling is currently being investigated in the free-air CO2 enrichment (FACE) sites at Rhinelander, WI. Because of the 13C depleted CO2 used in the FACE experiment and a 15N addition to the soil, this system affords an ideal opportunity to determine the impact of earthworm activity on soil organic matter dynamics by tracking the relative abundance and stable isotope compositions of biopolymers (amino acids, etc.) isolated in earthworms fecal pellets and soils. The 15N and 13C isotope composition of earthworm fecal matter from epigeic (litter and organic matter horizon dwelling) and endogeic (predominantly mineral soil dwelling) species highlighted their distinct role in litter, surface soil, and deeper soil movement through the soil. Specifically, endogeic fecal matter exhibited a lower uptake of FACE-derived C and a more enriched 15N signal. Nitrogen content of soil between the control and elevated CO2 treatments is not significantly different; however, elevated CO2 treatments exhibited relative depletion in both the soil and root 15N with respect to controls. The loss of 15N in the roots and the top 5 cm of the soil under elevated CO2, suggests that there is greater cycling power with increased below ground productivity and earthworm activity under elevated CO2, as higher abundances of earthworms exist in the elevated CO2 treatments. Amino acid extractions from the soil and fecal matter are ongoing and will help clarify the details regarding molecular nitrogen cycling.

  16. Influences of Vegetation Phenological Shifts on Water and Energy Cycle

    NASA Astrophysics Data System (ADS)

    Xu, X.; Riley, W. J.; Koven, C. D.

    2015-12-01

    Remote sensed vegetation indices and field measurements have demonstrated that climate change has influenced vegetation phenology. The phenological changes are expressed in shifts in the timing of spring vegetation activity and the length of the active growing season. According to NDVI data from NOAA and GIMMS, the length of the active growing season north of 45°N has extended by 12 days due to 8 days advancement in spring and 4 days prolongation in autumn between July 1981 and June 1991. The same NDVI dataset from July 1981 to December 1999 has shown the growing season increased by 18 days in Eurasia and 12 days in North America. Phenology regulates vegetation interactions with climate by influencing the energy, water and carbon cycles. Here, we use observations and the Community Land Model 4.5 (CLM4.5) in offline mode and coupled with CESM to evaluate influences of shifts in phenology on energy and water budget and partitioning and on interactions with the atmosphere. Satellite retrieved leaf area index (LAI) is used to prescribe shifts in vegetation phenology in CLM4.5. We find that phenological advancement of 12 days over the past few decades can result in monthly mean changes of (-5-7 Wm-2) in latent heat and (-5-9Wm-2) in sensible heat balance over wide regions. We will discuss (1) the capability of current climate models to predict the impacts of phenological shifts on climate change, (2) seasonal to annual changes in energy and water cycles in response to phenological shifts, (3) the spatial heterogeneity in phenological-induced energy and water partitioning in different plant functional types across regions and continents, and (4) phenology and plant-climate interactions in changing climate.

  17. ISOTHERMAL PHASE TRANSFORMATION CYCLING IN STEEL BY APPLICATION OF A HIGH MAGNETIC FIELD

    SciTech Connect

    Ludtka, Gerard Michael; Jaramillo, Roger A; Ludtka, Gail Mackiewicz-; Kisner, Roger A; Wilgen, John B

    2007-01-01

    A phase transformation reversal via the application and removal of a large magnetic field was investigated. Because a large magnetic field can alter the phase equilibrium between paramagnetic austenite and ferromagnetic ferrite, volume fractions for each phase constituent can be modified at constant temperature by changing the magnetic field strength. In this research elevated temperature isothermal hold experiments were performed for 5160 steel. During the isothermal hold, the magnetic field was cycled between 0 and 30 Tesla. As companion experiments, temperature cycling and isothermal holds were performed without magnetic fields. The resulting microstructures were examined using optical and SEM metallography. These microstructures indicate that a portion of the microstructure experiences isothermal transformation cycling between austenite and ferrite due to the application and removal of the 30T (Tesla) magnetic field.

  18. Influence of Plants on Chlorine Cycling in Terrestrial Environments

    NASA Astrophysics Data System (ADS)

    Montelius, Malin; Thiry, Yves; Marang, Laura; Ranger, Jacques; Cornelis, Jean-Thomas; Svensson, Teresia; Bastviken, David

    2016-04-01

    Chlorine (Cl), one of the 20 most abundant elements on Earth, is crucial for life as a regulator of cellular ionic strength and an essential co-factor in photosynthesis. Chlorinated organic compounds (Clorg) molecules are surprisingly abundant in soils, in fact many studies during the last decades show that Clorg typically account for more than 60% of the total soil Cl pool in boreal and temperate forest soils and frequently exceed chloride (Cl-) levels. The natural and primarily biotic formation of this Clorg pool has been confirmed experimentally but the detailed content of the Clorg pool and the reasons for its high abundance remains puzzling and there is a lack of Cl budgets for different ecosystems. Recently, the radioisotope 36Cl has caused concerns because of presence in radioactive waste, a long half-life (301 000 years), potential high mobility, and limited knowledge about Cl residence times, speciation and uptake by organisms in terrestrial environments. The chlorination of organic molecules may influence the pool of available Cl- to organisms and thereby the Cl cycling dynamics. This will prolong residence times of total Cl in the soil-vegetation system, which affects exposure times in radioactive 36Cl isotope risk assessments. We tested to what extent the dominating tree species influences the overall terrestrial Cl cycling and the balance between Cl- and Clorg. Total Cl and Clorg were measured in different tree compartments and soil horizons in the Breuil experimental forest, Bourgogne, established in 1976 and located at Breuil-Chenue in Eastern France. The results from this field experiment show how the dominating tree species affected Cl cycling and accumulation over a time period of 30 years. Cl uptake by trees as well as content of both total Cl and Clorg in soil humus was much higher in experimental plots with coniferous forests compared to deciduous forests. The amounts of Clorg found in plant tissue indicate significant Clorg production inside

  19. Menstrual cycle influence on cognitive function and emotion processing—from a reproductive perspective

    PubMed Central

    Sundström Poromaa, Inger; Gingnell, Malin

    2014-01-01

    The menstrual cycle has attracted research interest ever since the 1930s. For many researchers the menstrual cycle is an excellent model of ovarian steroid influence on emotion, behavior, and cognition. Over the past years methodological improvements in menstrual cycle studies have been noted, and this review summarizes the findings of methodologically sound menstrual cycle studies in healthy women. Whereas the predominant hypotheses of the cognitive field state that sexually dimorphic cognitive skills that favor men are improved during menstrual cycle phases with low estrogen and that cognitive skills that favor women are improved during cycle phases with increased estrogen and/or progesterone, this review has not found sufficient evidence to support any of these hypotheses. Mental rotation has gained specific interest in this aspect, but a meta-analysis yielded a standardized mean difference in error rate of 1.61 (95% CI −0.35 to 3.57), suggesting, at present, no favor of an early follicular phase improvement in mental rotation performance. Besides the sexually dimorphic cognitive skills, studies exploring menstrual cycle effects on tasks that probe prefrontal cortex function, for instance verbal or spatial working memory, have also been reviewed. While studies thus far are few, results at hand suggest improved performance at times of high estradiol levels. Menstrual cycle studies on emotional processing, on the other hand, tap into the emotional disorders of the luteal phase, and may be of relevance for women with premenstrual disorders. Although evidence at present is limited, it is suggested that emotion recognition, consolidation of emotional memories, and fear extinction is modulated by the menstrual cycle in women. With the use of functional magnetic resonance imaging, several studies report changes in brain reactivity across the menstrual cycle, most notably increased amygdala reactivity in the luteal phase. Thus, to the extent that behavioral changes

  20. Magnetic stability under magnetic cycling of MgO-based magnetic tunneling junctions with an exchange-biased synthetic antiferromagnetic pinned layer

    NASA Astrophysics Data System (ADS)

    Hao, Qiang; Reid, Cameron; Xiao, Gang; Chan, Hon Ming

    2016-02-01

    We investigate the magnetic stability and endurance of MgO-based magnetic tunnel junctions (MTJs) with an exchange-biased synthetic antiferromagnetic (SAF) pinned layer. When a uniaxially cycling switching field is applied along the easy axis of the free magnetic layer, the magnetoresistance varies only by 1.7% logarithmically with the number of cycles, while no such change appears in the case of a rotating field. This observation is consistent with the effect of the formation and motion of domain walls in the free layer, which create significant stray fields within the pinned hard layer. Unlike in previous studies, the decay we observed only occurs during the first few starting cycles (<20), at which point there is no further variance in all performance parameters up to 107 cycles. Exchange-biased SAF structure is ideally suited for solid-state magnetic sensors and magnetic memory devices.

  1. The influence of stray magnetic fields on ion beam neutralization

    NASA Technical Reports Server (NTRS)

    Feng, Y.-C.; Wilbur, P. J.

    1982-01-01

    An experimental investigation is described of a comparison between the ion beam neutralization characteristics of a local neutralizer (within approximately 5 cm of the beam edge) and those associated with a distant one (approximately 1 meter away from the thruster). The influence of magnetic fields in the vicinity of the neutralizer cathode orifice which are either parallel or normal to the neutralizer axis is assessed. The plasma property profiles which reflect the influence of the magnetic fields are measured. The results suggest that magnetic fields at the region of a neutralizer cathode orifice influence its ability to couple to the ion beam. They reveal that there is a potential jump from the neutralizer cathode orifice to the plasma which exists close to the orifice. This potential drop is found to increase as the axial component of magnetic flux density increases. A magnetic field perpendicular to the neutralizer axis induces a potential rise a few centimeters downstream from the neutralizer cathode.

  2. Differential leaflet mortality may influence biogeochemical cycling following tropical cyclones.

    PubMed

    Marler, Thomas E; Ferreras, Ulysses

    2014-01-01

    Intensity of tropical cyclones is expected to increase in the coming century, and an improved understanding of their influence on biogeochemical cycles would benefit ecologists and conservationists. We studied the November 2013 Typhoon Haiyan damage to observe that numerous examples of partial leaf necrosis on intact leaves of trees in the Cycadaceae and Arecaceae families resulted, leaving behind a copious amount of arboreal dead leaf material attached to live leaves. The decay process of this form of arboreal litter has not been previously studied. When compared with decay of ground litter or detached litter suspended in the canopy, we predict the decay process of this form of arboreal litter will include increased photooxidation, leaching, and comminution by detritivorous insects and mites; but decreased catabolism of organic molecules by saprophytic organisms.

  3. Characterization of biological types of cattle (Cycle VII): influence of postpartum interval and estrous cycle length on fertility.

    PubMed

    Cushman, R A; Allan, M F; Thallman, R M; Cundiff, L V

    2007-09-01

    Genetic improvement in reproductive efficiency through selection is difficult because many reproductive traits are binomial and have low heritabilities. Before genetic markers can be generated for fertility in cows, greater characterization of reproductive phenotypes is needed to understand the components of the trait. The current study tested the hypotheses that: 1) breeds vary in postpartum interval to estrus (PPIE) and estrous cycle length, 2) a longer estrous cycle immediately before breeding increased pregnancy rates, and 3) a greater number of cycles before breeding increased conception rates. The postpartum interval to estrus, estrous cycle length, and number of cycles before breeding were examined in F1 cows (n = 519) obtained from mating Hereford, Angus, and MARC III cows to Hereford, Angus, Simmental, Limousin, Charolais, Gelbvieh, and Red Angus sires. Cows were classified as having 0, 1, 2, or 3 observed estrous cycles before breeding. All traits analyzed were adjusted to constant BCS. Sire breed of the cow influenced length of the PPIE and number of cycles before the start of breeding (P <0.001). Simmental-sired cows had the shortest PPIE and greatest number of cycles before breeding, whereas Limousin-sired cows had the longest PPIE and least number of cycles before breeding. Cows with a greater number of cycles before breeding did not have greater conception rates than cows that had not exhibited standing estrus before breeding (P = 0.87). In cows that cycled before breeding, the length of the estrous cycle immediately before breeding was influenced by dam breed and BCS (P <0.01). Cows out of Hereford dams had shorter estrous cycles than cows out of MARC III or Angus dams, and estrous cycle length increased as BCS increased. Conception rate decreased as length of the estrous cycle immediately before breeding increased (P = 0.05, -2.2% per d of cycle length). Therefore, previously anestrous cows were just as likely to conceive as cows that had cycled

  4. Characterization of biological types of cattle (Cycle VII): influence of postpartum interval and estrous cycle length on fertility.

    PubMed

    Cushman, R A; Allan, M F; Thallman, R M; Cundiff, L V

    2007-09-01

    Genetic improvement in reproductive efficiency through selection is difficult because many reproductive traits are binomial and have low heritabilities. Before genetic markers can be generated for fertility in cows, greater characterization of reproductive phenotypes is needed to understand the components of the trait. The current study tested the hypotheses that: 1) breeds vary in postpartum interval to estrus (PPIE) and estrous cycle length, 2) a longer estrous cycle immediately before breeding increased pregnancy rates, and 3) a greater number of cycles before breeding increased conception rates. The postpartum interval to estrus, estrous cycle length, and number of cycles before breeding were examined in F1 cows (n = 519) obtained from mating Hereford, Angus, and MARC III cows to Hereford, Angus, Simmental, Limousin, Charolais, Gelbvieh, and Red Angus sires. Cows were classified as having 0, 1, 2, or 3 observed estrous cycles before breeding. All traits analyzed were adjusted to constant BCS. Sire breed of the cow influenced length of the PPIE and number of cycles before the start of breeding (P <0.001). Simmental-sired cows had the shortest PPIE and greatest number of cycles before breeding, whereas Limousin-sired cows had the longest PPIE and least number of cycles before breeding. Cows with a greater number of cycles before breeding did not have greater conception rates than cows that had not exhibited standing estrus before breeding (P = 0.87). In cows that cycled before breeding, the length of the estrous cycle immediately before breeding was influenced by dam breed and BCS (P <0.01). Cows out of Hereford dams had shorter estrous cycles than cows out of MARC III or Angus dams, and estrous cycle length increased as BCS increased. Conception rate decreased as length of the estrous cycle immediately before breeding increased (P = 0.05, -2.2% per d of cycle length). Therefore, previously anestrous cows were just as likely to conceive as cows that had cycled

  5. Prediction of Solar Activity from Solar Background Magnetic Field Variations in Cycles 21-23

    NASA Astrophysics Data System (ADS)

    Shepherd, Simon J.; Zharkov, Sergei I.; Zharkova, Valentina V.

    2014-11-01

    A comprehensive spectral analysis of both the solar background magnetic field (SBMF) in cycles 21-23 and the sunspot magnetic field in cycle 23 reported in our recent paper showed the presence of two principal components (PCs) of SBMF having opposite polarity, e.g., originating in the northern and southern hemispheres, respectively. Over a duration of one solar cycle, both waves are found to travel with an increasing phase shift toward the northern hemisphere in odd cycles 21 and 23 and to the southern hemisphere in even cycle 22. These waves were linked to solar dynamo waves assumed to form in different layers of the solar interior. In this paper, for the first time, the PCs of SBMF in cycles 21-23 are analyzed with the symbolic regression technique using Hamiltonian principles, allowing us to uncover the underlying mathematical laws governing these complex waves in the SBMF presented by PCs and to extrapolate these PCs to cycles 24-26. The PCs predicted for cycle 24 very closely fit (with an accuracy better than 98%) the PCs derived from the SBMF observations in this cycle. This approach also predicts a strong reduction of the SBMF in cycles 25 and 26 and, thus, a reduction of the resulting solar activity. This decrease is accompanied by an increasing phase shift between the two predicted PCs (magnetic waves) in cycle 25 leading to their full separation into the opposite hemispheres in cycle 26. The variations of the modulus summary of the two PCs in SBMF reveals a remarkable resemblance to the average number of sunspots in cycles 21-24 and to predictions of reduced sunspot numbers compared to cycle 24: 80% in cycle 25 and 40% in cycle 26.

  6. Prediction of solar activity from solar background magnetic field variations in cycles 21-23

    SciTech Connect

    Shepherd, Simon J.; Zharkov, Sergei I.; Zharkova, Valentina V. E-mail: s.zharkov@hull.ac.uk

    2014-11-01

    A comprehensive spectral analysis of both the solar background magnetic field (SBMF) in cycles 21-23 and the sunspot magnetic field in cycle 23 reported in our recent paper showed the presence of two principal components (PCs) of SBMF having opposite polarity, e.g., originating in the northern and southern hemispheres, respectively. Over a duration of one solar cycle, both waves are found to travel with an increasing phase shift toward the northern hemisphere in odd cycles 21 and 23 and to the southern hemisphere in even cycle 22. These waves were linked to solar dynamo waves assumed to form in different layers of the solar interior. In this paper, for the first time, the PCs of SBMF in cycles 21-23 are analyzed with the symbolic regression technique using Hamiltonian principles, allowing us to uncover the underlying mathematical laws governing these complex waves in the SBMF presented by PCs and to extrapolate these PCs to cycles 24-26. The PCs predicted for cycle 24 very closely fit (with an accuracy better than 98%) the PCs derived from the SBMF observations in this cycle. This approach also predicts a strong reduction of the SBMF in cycles 25 and 26 and, thus, a reduction of the resulting solar activity. This decrease is accompanied by an increasing phase shift between the two predicted PCs (magnetic waves) in cycle 25 leading to their full separation into the opposite hemispheres in cycle 26. The variations of the modulus summary of the two PCs in SBMF reveals a remarkable resemblance to the average number of sunspots in cycles 21-24 and to predictions of reduced sunspot numbers compared to cycle 24: 80% in cycle 25 and 40% in cycle 26.

  7. Environmental magnetic fields: Influences on early embryogenesis

    SciTech Connect

    Cameron, I.L.; Hardman, W.E.; Winters, W.D.; Zimmerman, S.; Zimmerman, A.M. )

    1993-04-01

    A 10-mG, 50 to 60-Hz magnetic field is in the intensity and frequency range that people worldwide are often exposed to in homes and in the workplace. Studies about the effects of 50- to 100-Hz electromagnetic fields on various species of animal embryos (fish, chick, fly, sea urchin, rat, and mouse) indicate that early stages of embryonic development are responsive to fluctuating magnetic fields. Chick, sea urchin, and mouse embryos are responsive to magnetic field intensities of 10-100 mG. Results from studies on sea urchin embryos indicate that exposure to conditions of rotating 60-Hz magnetic fields, e.g., similar to those in our environment, interferes with cell proliferation at the morula stage in a manner dependent on field intensity. The cleavage stages, prior to the 64-cell stage, were not delayed by this rotating 60-Hz magnetic field suggesting that the ionic surges, DNA replication, and translational events essential for early cleavage stages were not significantly altered. Studies of histone synthesis in early sea urchin embryos indicated that the rotating 60-Hz magnetic field decreased zygotic expression of early histone genes at the morula stage and suggests that this decrease in early histone production was limiting to cell proliferation. Whether these comparative observations from animal development studies will be paralleled by results from studies of human embryogenesis, as suggested by some epidemiology studies, has yet to be established. 38 refs.

  8. Influence of soil moisture-carbon cycle interactions on the terrestrial carbon cycle over Europe

    NASA Astrophysics Data System (ADS)

    Mystakidis, Stefanos; Davin, Edouard L.; Gruber, Nicolas; Seneviratne, Sonia I.

    2016-04-01

    Water availability is a crucial limiting factor for terrestrial ecosystems, but relatively few studies have quantitatively assessed the influence of soil moisture variability on the terrestrial carbon cycle. Here, we investigate the role of soil moisture variability and state in the contemporary terrestrial carbon cycle over Europe. For this we use a Regional Earth System Model (RESM) based on the COSMO-CLM Regional Climate Model, coupled to the Community Land Model version 4.0 (CLM4.0) and its carbon-nitrogen module. The simulation setup consists of a control simulation over the period 1979-2010 in which soil moisture is interactive and three sensitivity simulations in which soil moisture is prescribed to a mean, a very dry or a very wet seasonal cycle without inter-annual variability. The cumulative net biome productivity varies markedly between the different experiments ranging from a strong sink of up to 6PgC in the wet experiment to a source of up to 1.2PgC in the dry experiment. Changes in the land carbon uptake are driven by a combination of two factors: the direct impact of soil moisture on plant's carbon uptake (essentially in southern Europe) and an indirect effect through changes in temperature affecting ecosystem respiration (mainly in central and northern Europe). We find that removing temporal variations in soil moisture dampens interannual variations in terrestrial carbon fluxes (Gross Primary Productivity, respiration, Net Biome Productivity) by more than 50% over most of Europe. Moreover, the analysis reveals that on annual scale about two-thirds of central Europe and about 70% of southern Europe display statistically significant effect of drying and/or wetting on the terrestrial carbon budget and its components. Our findings confirm the crucial role of soil moisture in determining the magnitude and the inter-annual variability in land CO2 uptake which is a key contributor to the year-to-year variations in atmospheric CO2 concentration.

  9. Training effects induced by cycling of magnetic field in ferromagnetic rich phase-separated nanocomposite manganites

    NASA Astrophysics Data System (ADS)

    Das, Kalipada; Das, I.

    2015-12-01

    We have carried out an experimental investigation of magneto-transport and magnetic properties of charge-ordered Pr0.67Ca0.33MnO3 (PCMO) and ferromagnetic La0.67Sr0.33MnO3 (LSMO) nanoparticles along with a nanocomposite consisting of those two types of nanoparticles. From the magneto-transport measurements, clear irreversibility is observed in the field dependence of resistance due to magnetic field cycling in the case of PCMO nanoparticles. The value of resistance increases during such a field cycling. However such an irreversibility is absent in the case of LSMO nanoparticles as well as nanocomposites. On the other hand, the magnetic measurements indicate the gradual growth of antiferromagnetic phases in all samples leading to a decrease in magnetization. These inconsistencies between magneto-transport and magnetic behaviors are attributed to the magnetic training effects.

  10. Magnetic flux density in the heliosphere through several solar cycles

    SciTech Connect

    Erdős, G.; Balogh, A.

    2014-01-20

    We studied the magnetic flux density carried by solar wind to various locations in the heliosphere, covering a heliospheric distance range of 0.3-5.4 AU and a heliolatitudinal range from 80° south to 80° north. Distributions of the radial component of the magnetic field, B{sub R} , were determined over long intervals from the Helios, ACE, STEREO, and Ulysses missions, as well as from using the 1 AU OMNI data set. We show that at larger distances from the Sun, the fluctuations of the magnetic field around the average Parker field line distort the distribution of B{sub R} to such an extent that the determination of the unsigned, open solar magnetic flux density from the average (|B{sub R} |) is no longer justified. We analyze in detail two methods for reducing the effect of fluctuations. The two methods are tested using magnetic field and plasma velocity measurements in the OMNI database and in the Ulysses observations, normalized to 1 AU. It is shown that without such corrections for the fluctuations, the magnetic flux density measured by Ulysses around the aphelion phase of the orbit is significantly overestimated. However, the matching between the in-ecliptic magnetic flux density at 1 AU (OMNI data) and the off-ecliptic, more distant, normalized flux density by Ulysses is remarkably good if corrections are made for the fluctuations using either method. The main finding of the analysis is that the magnetic flux density in the heliosphere is fairly uniform, with no significant variations having been observed either in heliocentric distance or heliographic latitude.

  11. Deciphering solar magnetic activity. I. On the relationship between the sunspot cycle and the evolution of small magnetic features

    SciTech Connect

    McIntosh, Scott W.; Wang, Xin; Markel, Robert S.; Thompson, Michael J.; Leamon, Robert J.; Malanushenko, Anna V.; Davey, Alisdair R.; Howe, Rachel; Krista, Larisza D.; Cirtain, Jonathan W.; Gurman, Joseph B.; Pesnell, William D.

    2014-09-01

    Sunspots are a canonical marker of the Sun's internal magnetic field which flips polarity every ∼22 yr. The principal variation of sunspots, an ∼11 yr variation, modulates the amount of the magnetic field that pierces the solar surface and drives significant variations in our star's radiative, particulate, and eruptive output over that period. This paper presents observations from the Solar and Heliospheric Observatory and Solar Dynamics Observatory indicating that the 11 yr sunspot variation is intrinsically tied to the spatio-temporal overlap of the activity bands belonging to the 22 yr magnetic activity cycle. Using a systematic analysis of ubiquitous coronal brightpoints and the magnetic scale on which they appear to form, we show that the landmarks of sunspot cycle 23 can be explained by considering the evolution and interaction of the overlapping activity bands of the longer-scale variability.

  12. SOLAR CYCLE PROPAGATION, MEMORY, AND PREDICTION: INSIGHTS FROM A CENTURY OF MAGNETIC PROXIES

    SciTech Connect

    Munoz-Jaramillo, Andres; DeLuca, Edward E.; Dasi-Espuig, Maria; Balmaceda, Laura A. E-mail: edeluca@cfa.harvard.edu E-mail: lbalmaceda@icate-conicet.gob.ar

    2013-04-20

    The solar cycle and its associated magnetic activity are the main drivers behind changes in the interplanetary environment and Earth's upper atmosphere (commonly referred to as space weather). These changes have a direct impact on the lifetime of space-based assets and can create hazards to astronauts in space. In recent years there has been an effort to develop accurate solar cycle predictions (with aims at predicting the long-term evolution of space weather), leading to nearly a hundred widely spread predictions for the amplitude of solar cycle 24. A major contributor to the disagreement is the lack of direct long-term databases covering different components of the solar magnetic field (toroidal versus poloidal). Here, we use sunspot area and polar faculae measurements spanning a full century (as our toroidal and poloidal field proxies) to study solar cycle propagation, memory, and prediction. Our results substantiate predictions based on the polar magnetic fields, whereas we find sunspot area to be uncorrelated with cycle amplitude unless multiplied by area-weighted average tilt. This suggests that the joint assimilation of tilt and sunspot area is a better choice (with aims to cycle prediction) than sunspot area alone, and adds to the evidence in favor of active region emergence and decay as the main mechanism of poloidal field generation (i.e., the Babcock-Leighton mechanism). Finally, by looking at the correlation between our poloidal and toroidal proxies across multiple cycles, we find solar cycle memory to be limited to only one cycle.

  13. Magnetic Tilts and Polarity Separations in Sunspot Groups and Active Regions the Cycle 23

    NASA Astrophysics Data System (ADS)

    Zharkov, S. I.; Zharkova, V. V.

    2006-08-01

    We present the analysis of magnetic tilts in active regions and sunspot groups for 1996-2005 that are automatically extracted from the Solar Feature Catalogues (http://solar.inf.brad.ac.uk ). We investigate the statistical variations of magnetic field tilt in sunspot groups and whole active regions, their longitudinal and latitudinal distributions, drifts and daily polarity separation during different phases of the solar cycle 23. The classification results are compared with the similar research for the previous cycles and the specifics on the cycle 23 is discussed in conjunction to the solar dynamo theory.

  14. Design Considerations of Fast-cycling Synchrotrons Based on Superconducting Transmission Line Magnets

    SciTech Connect

    Piekarz, H.; Hays, S.; Huang, Y.; Shiltsev, V.; /Fermilab

    2008-06-01

    Fast-cycling synchrotrons are key instruments for accelerator based nuclear and high-energy physics programs. We explore a possibility to construct fast-cycling synchrotrons by using super-ferric, {approx}2 Tesla B-field dipole magnets powered with a superconducting transmission line. We outline both the low temperature (LTS) and the high temperature (HTS) superconductor design options and consider dynamic power losses for an accelerator with operation cycle of 0.5 Hz. We also briefly outline possible power supply system for such accelerator, and discuss the quench protection system for the magnet string powered by a transmission line conductor.

  15. Magnetic Influences on the Solar Wind

    NASA Astrophysics Data System (ADS)

    Woolsey, Lauren

    2016-05-01

    The steady, supersonic outflow from the Sun we call the solar wind was first posited in the 1950s and initial theories rightly linked the acceleration of the wind to the existence of the million-degree solar corona. Still today, the wind acceleration mechanisms and the coronal heating processes remain unsolved challenges in solar physics. In this work, I seek to answer a portion of the mystery by focusing on a particular acceleration process: Alfven waves launched by the motion of magnetic field footpoints in the photosphere. The entire corona is threaded with magnetic loops and flux tubes that open up into the heliosphere. I have sought a better understanding of the role these magnetic fields play in determining solar wind properties in open flux tubes. After an introduction of relevant material, I discuss my parameter study of magnetic field profiles and the statistical understanding we can draw from the resulting steady-state wind. In the chapter following, I describe how I extended this work to consider time dependence in the turbulent heating by Alfven waves in three dimensional simulations. The bursty nature of this heating led to a natural next step that expands my work to include not only the theoretical, but also a project to analyze observations of small network jets in the chromosphere and transition region, and the underlying photospheric magnetic field that forms thresholds in jet production. In summary, this work takes a broad look at the extent to which Alfven-wave-driven turbulent heating can explain measured solar wind properties and other observed phenomena.

  16. Low field magnetic resonance imaging to visualize chronic and cycling hypoxia in tumor-bearing mice

    PubMed Central

    Yasui, Hironobu; Matsumoto, Shingo; Devasahayam, Nallathamby; Munasinghe, Jeeva P.; Choudhuri, Rajani; Saito, Keita; Subramanian, Sankaran; Mitchell, James B.; Krishna, Murali C.

    2010-01-01

    Tumors exhibit fluctuations in blood flow that influence oxygen concentrations and therapeutic resistance. To assist therapeutic planning and improve prognosis, non-invasive dynamic imaging of spatial and temporal variations in oxygen partial pressure (pO2) would be useful. Here we illustrate the use of pulsed electron paramagnetic resonance imaging (EPRI) as a novel imaging method to directly monitor fluctuations in oxygen concentrations in mouse models. A common resonator platform for both EPRI and magnetic resonance imaging (MRI) provided pO2 maps with anatomical guidance and microvessel density. Oxygen images acquired every 3 min for a total of 30 min in two different tumor types revealed that fluctuations patterns in pO2 are dependent on tumor size and tumor type. The magnitude of fluctuations in pO2 in SCCVII tumors ranged between 2-18 fold, whereas the fluctuations in HT29 xenografts were of lower magnitude. Alternating breathing cycles with air or carbogen (95 % O2 plus 5 % CO2) distinguished higher and lower sensitivity regions which responded to carbogen, corresponding to cycling hypoxia and chronic hypoxia, respectively. Immunohistochemical analysis suggests that the fluctuation in pO2 correlated with pericyte density rather than vascular density in the tumor. This EPRI technique, combined with MRI, may offer a powerful clinical tool to noninvasively detect variable oxygenation in tumors. PMID:20647318

  17. Influence of High Harmonics of Magnetic Fields on Trapped Magnetic Fluxes in HTS Bulk

    NASA Astrophysics Data System (ADS)

    Yamagishi, K.; Miyagi, D.; Tsukamoto, O.

    Various kinds of HTS bulk motors are proposed and have been developed. Generally, those motors are driven by semiconductor inverters and currents fed to the armature windings contain high harmonics. Therefore, the bulks are exposed to high harmonics magnetic fields and AC losses are produced in the bulks. The AC losses deteriorate the efficiency of the motors and cause temperature rise of the bulks which decrease the trapped magnetic fluxes of the bulks. Usually, electro-magnetic shielding devices are inserted between the bulks and armature windings. However, the shielding devices degrade compactness of the motors. Therefore, it is important to have knowledge of the influence of the high harmonics magnetic fields on the AC losses and trapped magnetic fluxes of the bulk for optimum design of the shielding devices. In this work, the authors experimentally study the influence of high harmonics magnetic fields.

  18. Mushroom host influence on Lycoriella mali (Diptera: Sciaridae) life cycle.

    PubMed

    O'Connor, L; Keil, C B

    2005-04-01

    Lycoriella mali Fitch (Diptera: Sciaridae) infests mushroom crops early in the crop cycle. Recent observations in mushroom houses indicated a difference in emergence time and size of adult L. mali developing on various strains of commercial mushrooms. Samples of adult flies from isolated mushroom houses growing Portabella mushrooms were significantly heavier then those from oyster mushroom houses, whereas flies from shiitake mushroom houses were lightest in weight. Flies collected from isolated Portabella mushroom houses were reared on four strains and species of Agaricus and Pleurotus mushrooms. After the adults emerged, females were weighed, mated, and allowed to oviposit. The number of eggs laid increased as the weight of the female increased. Flies collected from isolated Portabella mushroom houses were reared on eight strains and species of mushrooms. Flies were reared for four generations on each host mushroom mycelium then switched to different host mushrooms. Overall, the hybrid strain of Agaricus bisporus (Lange) Imbach (Agaricales: Agaricomycetideae) was the most favorable host for L. mali, whereas the wild strain of A. bisporus was the least favorable host. Mushroom hosts influence developmental time, survivorship, weight, and reproduction of L. mali. PMID:15889722

  19. Influence of magnetic shear on impurity transport

    SciTech Connect

    Nordman, H.; Fueloep, T.; Candy, J.; Strand, P.; Weiland, J.

    2007-05-15

    The magnetic shear dependence of impurity transport in tokamaks is studied using a quasilinear fluid model for ion temperature gradient (ITG) and trapped electron (TE) mode driven turbulence in the collisionless limit and the results are compared with nonlinear gyrokinetic results using GYRO [J. Candy and R. E. Waltz, J. Comput. Phys 186, 545 (2003)]. It is shown that the impurity transport is sensitive to the magnetic shear, in particular for weak, negative, and large positive shear where a strong reduction of the effective impurity diffusivity is obtained. The fluid and gyrokinetic results are in qualitative agreement, with the gyrokinetic diffusivities typically a factor 2 larger than the fluid diffusivities. The steady state impurity profiles in source-free plasmas are found to be considerably less peaked than the electron density profiles for moderate shear. Comparisons between anomalous and neoclassical transport predictions are performed for ITER-like profiles [R. Aymar, P. Barabaschi, and Y. Shimomura, Plasma Phys. Controlled Fusion 44, 519 (2002)].

  20. Influence of menstrual cycle, parity and oral contraceptive use on steroid hormone receptors in normal breast.

    PubMed Central

    Battersby, S.; Robertson, B. J.; Anderson, T. J.; King, R. J.; McPherson, K.

    1992-01-01

    Steroid receptor was assessed immunohistochemically in 158 samples of normal breast for variation through the menstrual cycle. Patterns and intensity of reaction were used in a semi-quantitative scoring system to examine the influence of cycle phase, cycle type, parity and age. The changes in oestrogen receptor for natural cycle and oral contraceptive (OC) cycles indicated down-regulation by progestins. Progesterone receptor did not vary significantly in natural cycles, but increased steadily through OC cycles. This study provides strong evidence that both oestrogen and progesterone influence breast epithelium, but dissimilarities from the endometrium are apparent. The interval since pregnancy had a significant negative effect on frequency and score of oestrogen receptor and score of progesterone receptor. Multivariate analysis established the phase of cycle and OC use as independent significant influences on oestrogen receptor. The interval since pregnancy was an independent significant factor for both oestrogen and progesterone receptor presence. Images Figure 1 Figure 2 PMID:1562470

  1. Influence of ferroelectric polarization on magnetic anisotropy

    NASA Astrophysics Data System (ADS)

    Mardana, A.; Ducharme, S.; Adenwalla, S.

    2010-03-01

    Thin film heterostructures of transition metal ferromagnets (FM) and polymer ferroelectrics (FE) are investigated to look for changes in the magnetic anisotropy of the FM layer that occur on switching the FE polarization (with an ensuing change in the electric field direction).[1] Samples of [Glass/ Pd (50 nm)/Co wedge (0.9-2.6nm)/ferroelectric P(VDF-TrFE) (53 nm)/Al (30nm)] are deposited via sputtering or evaporation for the metallic layers and via Langmuir-Schaefer deposition for the polymer ferroelectric. [2] Magnetic and FE properties have been characterized using the Magneto-Optical Kerr Effect (MOKE) and the pyroelectric effect. Polar and longitudinal MOKE loops are measured across the Co wedge for both positive and negative FE polarization and the difference in the two MOKE loops is ascribed to the changes in the magnetic anisotropy of the FM layer. [3] These changes are most apparent in the region where the Co undergoes a transition from in-plane to out-of-plane anisotropy. This research is supported by the NSF MRSEC through Grant No. DMR- 0820521 1. Chun-Gang Duan et al, Appl. Phys. Lett. 92, 122905 (2008) 2. A. V. Bune, et al, Nature (London) 391, 874 (1998) 3. P. F. Carcia, J.Appl. Phys. 63, 5066 (1988)

  2. HIGH-LATITUDE SOLAR TORSIONAL OSCILLATIONS DURING PHASES OF CHANGING MAGNETIC CYCLE AMPLITUDE

    SciTech Connect

    Rempel, M.

    2012-05-01

    Torsional oscillations are variations of the solar differential rotation that are strongly linked to the magnetic cycle of the Sun. Helioseismic inversions have revealed significant differences in the high-latitude branch of torsional oscillations between cycle 23 and cycle 24. Here we employ a non-kinematic flux-transport dynamo model that has been used previously to study torsional oscillations and simulate the response of the high-latitude branch to a change in the amplitude of the magnetic cycle. It is found that a reduction of the cycle amplitude leads to an increase in the amplitude of differential rotation that is mostly visible as a drop in the high-latitude rotation rate. Depending on the amplitude of this adjustment the high-latitude torsional oscillation signal can become temporarily hidden due to the unknown changing mean rotation rate that is required to properly define the torsional oscillation signal.

  3. The Life Cycle of Active Region Magnetic Fields

    NASA Astrophysics Data System (ADS)

    Cheung, M. C. M.; van Driel-Gesztelyi, L.; Martínez Pillet, V.; Thompson, M. J.

    2016-08-01

    We present a contemporary view of how solar active region magnetic fields are understood to be generated, transported and dispersed. Empirical trends of active region properties that guide model development are discussed. Physical principles considered important for active region evolution are introduced and advances in modeling are reviewed.

  4. Static magnetic fields aggravate the effects of ionizing radiation on cell cycle progression in bone marrow stem cells.

    PubMed

    Sarvestani, Amir Sabet; Abdolmaleki, Parviz; Mowla, Seyed Javad; Ghanati, Faezeh; Heshmati, Emran; Tavasoli, Zeinab; Jahromi, Azadeh Manoochehri

    2010-02-01

    In order to evaluate the influence of static magnetic fields (SMF) on the progression of cell cycle as a monitor of presumptive genotoxicity of these fields, the effects of a 15 mT SMF on cell cycle progression in rat bone marrow stem cells (BMSC) were examined. The cells were divided into two groups. One group encountered SMF alone for 5h continuously but the other group exposed with X ray before treatment with SMF. The population of cells did not show any significant difference in the first group but the second group that was exposed with acute radiation before encountering SMF showed a significant increase in the number of cells in G(2)/M phase. So SMF has intensified the effects of X ray, where SMF alone, did not had any detectable influence on cell cycle. These findings suggest that magnetic fields (MF) play their role by increasing the effects of genotoxic agents and because of the greater concentration of free radicals in the presence of radical pair producers, this effect is better detectable. PMID:19926297

  5. Influence of magnetic reluctances of magnetic elements on servo valve torque motors

    NASA Astrophysics Data System (ADS)

    Liu, Changhai; Jiang, Hongzhou

    2016-01-01

    The current research of electro-hydraulic servo valves mainly focuses on the vibration, pressure oscillating and source of noise. Unfortunately, literatures relating to the study of the influence of the magnetic reluctances of the magnetic elements are rarely available. This paper aims to analyze the influence of the magnetic reluctances of the magnetic elements on torque motor. Considering these magnetic reluctances ignored in previous literatures, a new mathematical model of servo valve torque motor is developed and proposed based on the fundamental laws of electromagnetism. By using this new mathematical model and the previous models, electromagnetic torque constant and magnetic spring stiffness are evaluated for a given set of torque motor parameters. A computer simulation by using AMESim software is also performed for the same set of torque motor parameters to verify the proposed model. The theoretical results of electromagnetic torque constant and magnetic spring stiffness evaluated by the proposed model render closer agreement with the simulation results than those evaluated by the previous models. In addition, an experimental measurement of the magnetic flux densities in the air-gaps is carried out by using SFL218 servo valve torque motor. Compared with the theoretical results of the magnetic flux densities in the air-gaps evaluated by the previous models, the theoretical results evaluated by the proposed model also show better agreement with the experimental data. The proposed model shows the influence of the magnetic reluctances of the magnetic elements on the servo valve torque motor, and offers modified and analytical expressions to electromagnetic torque constant and magnetic spring stiffness. These modified and analytical expressions could provide guidance more accurately for a linear control design approach and sensitivity analysis on electro-hydraulic servo valves than the previous expressions.

  6. A Comparison Between Global Proxies of the Sun's Magnetic Activity Cycle: Inferences from Helioseismology

    NASA Astrophysics Data System (ADS)

    Broomhall, A.-M.; Nakariakov, V. M.

    2015-11-01

    The last solar minimum was, by recent standards, unusually deep and long. We are now close to the maximum of the subsequent solar cycle, which is relatively weak. In this article we make comparisons between different global (unresolved) measures of the Sun's magnetic activity to investigate how they are responding to this weak-activity epoch. We focus on helioseismic data, which are sensitive to conditions, including the characteristics of the magnetic field, in the solar interior. Also considered are measures of the magnetic field in the photosphere (sunspot number and sunspot area), the chromosphere and corona (10.7 cm radio flux and 530.3 nm green coronal index), and two measures of the Sun's magnetic activity closer to Earth (the interplanetary magnetic field and the galactic cosmic-ray intensity). Scaled versions of the activity proxies diverge from the helioseismic data around 2000, indicating a change in relationship between the proxies. The degree of divergence varies from proxy to proxy, with sunspot area and 10.7 cm flux showing only small deviations, while sunspot number, coronal index, and the two interplanetary proxies show much larger departures. In Cycle 24 the deviations in the solar proxies and the helioseismic data decrease, raising the possibility that the deviations observed in Cycle 23 are just symptomatic of a 22-year Hale cycle. However, the deviations in the helioseismic data and the interplanetary proxies increase in Cycle 24. Interestingly, the divergence in the solar proxies and the helioseismic data are not reflected in the shorter-term variations (often referred to as quasi-biennial oscillations) observed on top of the dominant 11-year solar cycle. However, despite being highly correlated in Cycle 22, the short-term variations in the interplanetary proxies show very little correlation with the helioseismic data during Cycles 23 and 24.

  7. Influence of driving cycles on unit emissions from passenger cars

    NASA Astrophysics Data System (ADS)

    Joumard, R.; André, M.; Vidon, R.; Tassel, P.; Pruvost, C.

    Small samples of petrol engine or diesel cars, equipped with or without catalysts, were tested over 36 driving cycles divided into four categories - standard cycles and three sets of cycles more representative of real-world driving conditions. The tests addressed standard gaseous pollutants and fuel consumption and also less frequently measured pollutant such as CH 4. In the first part of this paper we examine cold emissions in order to assess the duration of the cold start impact and the representativity of the cold ECE15 cycle. Then unit emissions are compared over the four driving cycle families. As compared to representative cycles, the standardised cycles underestimate hot emissions by almost 50% for petrol engine cars and 30% for diesel vehicles. Conversely, the results obtained for the three representative cycle families are in relatively close agreement with each other - within approximately 10%. However, the cinematic properties of the three families differ. Finally, we demonstrate that weighting all emission data equally, not taking into account the weight of each cycle in overall traffic, introduces significant biases, particularly when plotting emission vs. average speed curves.

  8. Thermonuclear inverse magnetic pumping power cycle for stellarator reactor

    DOEpatents

    Ho, Darwin D.; Kulsrud, Russell M.

    1991-01-01

    The plasma column in a stellarator is compressed and expanded alternatively in minor radius. First a plasma in thermal balance is compressed adiabatically. The volume of the compressed plasma is maintained until the plasma reaches a new thermal equilibrium. The plasma is then expanded to its original volume. As a result of the way a stellarator works, the plasma pressure during compression is less than the corresponding pressure during expansion. Therefore, negative work is done on the plasma over a complete cycle. This work manifests itself as a back-voltage in the toroidal field coils. Direct electrical energy is obtained from this voltage. Alternatively, after the compression step, the plasma can be expanded at constant pressure. The cycle can be made self-sustaining by operating a system of two stellarator reactors in tandem. Part of the energy derived from the expansion phase of a first stellarator reactor is used to compress the plasma in a second stellarator reactor.

  9. Solar grand and super-grand cycles derived with PCA from the solar background magnetic field

    NASA Astrophysics Data System (ADS)

    Zharkova, Valentina; Shepherd, Simon; Zharkov, Sergei; Popova, Elena

    2016-04-01

    We present principal components analysis (PCA) of temporal magnetic field variations over the solar cycles 21-24. These PCs reveal two main magnetic waves with close frequencies (covering 40% of data variance) travelling from the opposite hemispheres with an increasing phase shift. Extrapolation of these PCs through their summary curve backward for 2000 years reveals a number of ~350-year grand cycles and about 2000 super-grand cycles superimposed on 22 year-cycles with the features showing a remarkable resemblance to sunspot activity reported in the past. The summary curve calculated forward for the next millennium predicts further three grand cycles with the closest grand minimum occurring in the forthcoming cycles 25-27 when the two magnetic field waves have a phase shift of 11 years. We explore a role of other independent components derived with PCA and their expected effects on the resulting summary curve, or solar activity curve. We suggest that these grand and super-grand cycles can be produced by two dynamo waves generated in different layers with close frequencies whose interaction leads to beating effects that is discussed in the work by Popova et al (2016) presented here. This approach opens a new era in investigation and prediction of solar activity on long-term timescales.

  10. Variation in the statistical properties of IMF direction fluctuations during the 22-year solar magnetic cycle

    NASA Astrophysics Data System (ADS)

    Erofeev, D. V.

    2014-12-01

    The variation in the IMF direction distribution during the 22-year solar magnetic cycle has been studied. Data obtained in near-Earth orbits and measurements in the heliospheric regions located far from the Earth, performed with the Helios and Ulysses spacecraft devices, have been analyzed. It has been found that the correlation between the azimuth and magnetic field fluctuations is statistically significant in the low-latitude heliospheric region at heliocentric distances of 0.3-5.4 AU, and the sign of this correlation reverses at a change in the polar solar magnetic field orientation. In the polar zones of the heliosphere outside the latitudinal extension of the heliospheric current sheet, the angle correlation coefficient rapidly decreases with increasing heliographic latitude. The angle correlation sign reversal during the 22-year cycle is accompanied by a change of the asymmetry sign of the magnetic field inclination distribution.

  11. Solar-cycle variation of oscillation frequencies and surface magnetic field

    NASA Astrophysics Data System (ADS)

    Tan, S.; Thompson, M. J.; Centeno, R.

    2011-12-01

    We investigate the relationship between solar oscillation frequencies and surface magnetic fields over the course of the last solar cycle. Using MDI and GONG data, we study the variation in the even frequency-splitting coefficients ak (describing solar asphericity and effects of the magnetic field), and the variation in the coefficients Bk of the latitudinal Lengendre decomposition of the surface magnetic field, during the period 1996 - 2010. We find a strong linear correlation between the a and B coefficients, during both the rising and declining phases of the solar cycle, consistent with results published in 2001 (Antia et al.). We also investigated different ways to handle the magnetic field decomposition at the poles, and find that the linear correlation persists, though with varying intercepts. The variation of slope with coefficient index that we find is non-monotonic, which disagrees with the previous study by Antia et al. (2001).

  12. CoRoT Reveals a Magnetic Activity Cycle in a Sun-Like Star

    NASA Astrophysics Data System (ADS)

    García, Rafael A.; Mathur, Savita; Salabert, David; Ballot, Jérôme; Régulo, Clara; Metcalfe, Travis S.; Baglin, Annie

    2010-08-01

    The 11-year activity cycle of the Sun is a consequence of a dynamo process occurring beneath its surface. We analyzed photometric data obtained by the CoRoT space mission, showing solarlike oscillations in the star HD49933, for signatures of stellar magnetic activity. Asteroseismic measurements of global changes in the oscillation frequencies and mode amplitudes reveal a modulation of at least 120 days, with the minimum frequency shift corresponding to maximum amplitude as in the Sun. These observations are evidence of a stellar magnetic activity cycle taking place beneath the surface of HD49933 and provide constraints for stellar dynamo models under conditions different from those of the Sun.

  13. ON POLAR MAGNETIC FIELD REVERSAL AND SURFACE FLUX TRANSPORT DURING SOLAR CYCLE 24

    SciTech Connect

    Sun, Xudong; Todd Hoeksema, J.; Liu, Yang; Zhao, Junwei

    2015-01-10

    As each solar cycle progresses, remnant magnetic flux from active regions (ARs) migrates poleward to cancel the old-cycle polar field. We describe this polarity reversal process during Cycle 24 using four years (2010.33-2014.33) of line-of-sight magnetic field measurements from the Helioseismic and Magnetic Imager. The total flux associated with ARs reached maximum in the north in 2011, more than two years earlier than the south; the maximum is significantly weaker than Cycle 23. The process of polar field reversal is relatively slow, north-south asymmetric, and episodic. We estimate that the global axial dipole changed sign in 2013 October; the northern and southern polar fields (mean above 60° latitude) reversed in 2012 November and 2014 March, respectively, about 16 months apart. Notably, the poleward surges of flux in each hemisphere alternated in polarity, giving rise to multiple reversals in the north. We show that the surges of the trailing sunspot polarity tend to correspond to normal mean AR tilt, higher total AR flux, or slower mid-latitude near-surface meridional flow, while exceptions occur during low magnetic activity. In particular, the AR flux and the mid-latitude poleward flow speed exhibit a clear anti-correlation. We discuss how these features can be explained in a surface flux transport process that includes a field-dependent converging flow toward the ARs, a characteristic that may contribute to solar cycle variability.

  14. Fertility cycle influence on surgical breast cancer cure.

    PubMed

    Bove, Kathleen; Lincoln, David W; Wood, Patricia A; Hrushesky, William J M

    2002-09-01

    Cancer growth and spread is an intricate process dependent upon both tumor and host. This laboratory is interested in the role of the fertility cycle, specifically cyclic changes in steroid hormone levels, in tumor growth and metastases. Our previous studies, using a murine model, have documented that breast cancer growth rate and post-resection metastatic behavior each change reproducibly during the estrous cycle, and that post-resection cancer spread depends upon the time within the estrous cycle that an advanced transplanted cancer is resected. Twelve to thiry-two percent cure rates were seen in these studies. That early work described estrous cycle stages just prior and near to putative ovulation to be superior while those stages farther from ovulation were disadvantageous times for surgery. Data presented here confirm the role of the estrous cycle in post-resection metastatic spread. This current work validates vaginal smear determined estrous cycle stage with uterine weight. A primary, transplantable, mammary carcinoma, which metastasizes to the lungs, was resected for surgical cure in cycling C3HeB/FeJ female mice at each fertility cycle stage. A group of oophorectomized (ovx) animals was also used. In two large, independent studies resecting much earlier stage cancers than in prior studies, a 96% surgical cure frequency was documented when the tumor is resected during estrus. The second best surgical cure rate is achieved when tumors are resected during metestrus (79% overall cure rate). Cure frequency in ovx animals is intermediate. These results further support a probable role for circulating E2 and P4 levels in modulating the metastatic process. We conclude that the timing of surgical resection within the estrous cycle affects the cancer's metastatic potential and that the optimal timing of resection may also depend to some extent upon the size (stage) of the resected cancer.

  15. Do the quiet sun magnetic fields vary with the solar cycle?

    NASA Astrophysics Data System (ADS)

    Faurobert, Marianne; Ricort, Gilbert; Lites, Bruce

    2015-10-01

    The quiet Sun observed in polarized light exhibits a rich and complex magnetic structuring which is still not fully resolved nor understood. The present work is intended to contribute to the debate about the origin of the quiet sun magnetic fields, in relation or not to the global solar dynamo. We present analysis of center-to-limb polarization measurements obtained with the SOT/SP spectropolarimeter onboard the Hinode satellite outside active regions, in 2007 and 2013, i.e. at a minimum and a maximum of the solar cycle, respectively. We compare the spatial fluctuation Fourier spectra of unsigned circular and linear polarization images after corrections for polarization bias and focus variations between the two data sets. The decay of active regions is clearly a source of magnetic fields in the quiet Sun. It leads to a global increase of the polarization fluctuation power spectrum in 2013 in the network. In the internetwork, we observe no variation of the polarization fluctuation power at mesogranular and granular scales, whereas it increases at sub-granular scales. We interpret these results in the following way. At the mesogranular and granular scales very efficient mechanisms of magnetic field removal are operating in the internetwork, that leads to a dissipation or a concentration of magnetic fields on smaller scales. So the cycle-invariant magnetic signal that we detect at mesogranular and granular scales must be continuously created by a dynamo mechanism which is independent of the solar cycle.

  16. Lack of Influence of the Menstrual Cycle on Blood Lactate.

    ERIC Educational Resources Information Center

    Lamont, Linda S.

    1986-01-01

    Nine healthy women were tested before, during, and after exercise during the follicular and luteal phases of their menstrual cycles to determine the effect of menstruation on blood lactate levels. Findings are discussed. (Author/MT)

  17. Influence of static magnetic field strength on the temperature resolution of a magnetic nanoparticle thermometer

    NASA Astrophysics Data System (ADS)

    Zhong, Jing; Dieckhoff, Jan; Schilling, Meinhard; Ludwig, Frank

    2016-10-01

    This paper investigates the influence of dc magnetic field strength on the resolution of a magnetic nanoparticle (MNP) thermometer, which employs the fundamental f0 and 2f0 harmonics of the MNP magnetization induced by ac and superimposed dc magnetic fields. In ac and parallel dc magnetic fields, the strength of dc magnetic field modulates the harmonics of the MNP magnetization, which affects their temperature sensitivities and measurement signal-to-noise ratios (SNRs). A temperature-adjustable fluxgate-based magnetic particle spectrometer was used to measure the spectra of the MNP magnetization at different temperatures. To determine the temperature, the amplitudes of the measured f0 and 2f0 harmonics were modeled based on the static Langevin function. AC susceptibility measurements on a MNP sample demonstrate the applicability of the static Langevin function for the description of the MNP magnetization spectra at a low frequency ac magnetic field without taking into account the MNP dynamics. Our simulations and experiments show that with increasing dc magnetic field from 0.2 mT to 2.0 mT, both the amplitude of the 2f0 harmonic and the temperature sensitivity of the amplitude ratio of the 2f0 to f0 harmonics increase by a factor of about 10 in an ac magnetic field with a frequency of 70 Hz and an amplitude of 1 mT. Concomitantly, the SNR of the 2f0 harmonic significantly increases by about 20 dB. Consequently, the temperature resolution of the MNP thermometer is improved from 1.97 K to 0.26 K.

  18. Magnetic Field Influence on Atmospheric Escape and Planetary Evolution

    NASA Astrophysics Data System (ADS)

    Driscoll, P. E.; Bercovici, D.

    2012-12-01

    Planetary magnetic fields are maintained by a convective dynamo within the deep interior but their influence extends all the way up to the magnetopause, where the solar wind is deflect around the planet. The presence of a magnetic field is thought to influence the atmosphere-solar wind interaction in a variety of ways, but there is no clear consensus as to whether it impedes or facilitates volatile loss to space. Escape of planetary atmospheres to space is of central importance to studying the evolution of planetary climates, volatile exchange with the interior, and interaction with the space environment. Out of the terrestrial planets Earth has by far the largest surface hydrogen inventory (mainly in the form of liquid water) and furthest magnetopause at ~10 Earth radii. Evidence from volatile concentrations and isotopic ratios imply that Mars and Venus have both lost a significant amount of H over their history, and have maintained little to no magnetic barrier, respectively, to hold off the erosive solar wind. Venus is a particularly interesting case because it is most similar to Earth in mass and density, yet has no detectable magnetic field and an isotopic D/H ratio that implies the loss of a significant amount of water in the past. Is the decline of Venus' dynamo related to the loss of hydrogen from its atmosphere? Is the stability of Earth's unusually large volatile reservoir over billions of years related to the presence of a strong magnetic field over that period of time? We explore conditions under which the presence of a magnetic barrier at the top of the atmosphere may operate as an additional limit to escape. We derive a model for magnetic field limited escape that depends on the terrestrial number density, area, scale height, and loss time scale at the magnetopause. This model predicts rapid escape when magnetic field is weak and magnetopause altitude is low, and a decrease in escape as magnetic field strength increases. This coupling between field

  19. THE SUN'S SMALL-SCALE MAGNETIC ELEMENTS IN SOLAR CYCLE 23

    SciTech Connect

    Jin, C. L.; Wang, J. X.; Song, Q.; Zhao, H. E-mail: wangjx@nao.cas.cn

    2011-04-10

    With the unique database from the Michelson Doppler Imager on board the Solar and Heliospheric Observatory in an interval embodying solar cycle 23, the cyclic behavior of solar small-scale magnetic elements is studied. More than 13 million small-scale magnetic elements are selected, and the following results are found. (1) The quiet regions dominated the Sun's magnetic flux for about 8 years in the 12.25 year duration of cycle 23. They contributed (0.94-1.44) x10{sup 23} Mx flux to the Sun from the solar minimum to maximum. The monthly average magnetic flux of the quiet regions is 1.12 times that of the active regions in the cycle. (2) The ratio of quiet region flux to that of the total Sun equally characterizes the course of a solar cycle. The 6 month running average flux ratio of the quiet regions was larger than 90.0% for 28 continuous months from July 2007 to October 2009, which very well characterizes the grand solar minima of cycles 23-24. (3) From the small to the large end of the flux spectrum, the variations of numbers and total flux of the network elements show no correlation, anti-correlation, and correlation with sunspots, respectively. The anti-correlated elements, covering the flux of (2.9-32.0)x10{sup 18} Mx, occupy 77.2% of the total element number and 37.4% of the quiet-Sun flux. These results provide insight into the reason for anti-correlations of small-scale magnetic activity during the solar cycle.

  20. CORRELATION BETWEEN THE 22-YEAR SOLAR MAGNETIC CYCLE AND THE 22-YEAR QUASICYCLE IN THE EARTH'S ATMOSPHERIC TEMPERATURE

    SciTech Connect

    Qu Weizheng; Zhao Jinping; Huang Fei; Deng Shenggui

    2012-07-15

    According to the variation pattern of the solar magnetic field polarity and its relation to the relative sunspot number, we established the time series of the sunspot magnetic field polarity index and analyzed the strength and polarity cycle characteristics of the solar magnetic field. The analysis showed the existence of a cycle with about a 22-year periodicity in the strength and polarity of the solar magnetic field, which proved the Hale proposition that the 11-year sunspot cycle is one-half of the 22-year solar magnetic cycle. By analyzing the atmospheric temperature field, we found that the troposphere and the stratosphere in the middle latitude of both the northern and southern hemispheres exhibited a common 22-year quasicycle in the atmospheric temperature, which is believed to be attributable to the 22-year solar magnetic cycle.

  1. Performance predictions for a room temperature, Ericsson cycle, magnetic heat pump

    NASA Astrophysics Data System (ADS)

    Purnell, J. G.

    1982-05-01

    The performance potential of a room temperature magnetic heat pump utilizing Gadolinium and operating on an Ericsson Cycle was investigated at magnetic flux densities of 2 and 7-Tesla which represent the upper limits of conventional and superconducting electromagnetics, respectively. At a coefficient of performance of 5, a 7-Tesla system would provide a cooling capacity of at best 1200 BTU per hour per pound of Gadolinium while a 2-Tesla system would operate at approximately 130 BTU per hour per pound of Gadolinium. Magnetic circuit efficiency was not determined but must be high (95-percent or better) in order for the magnetic heat pump performance to compete with conventional cooling systems. It is unlikely the magnetic heat pump investigated could approach the performance and compactness of the conventional cooling systems unless field strengths much greater than 7-Tesla are possible.

  2. DISTRIBUTION OF MAGNETIC BIPOLES ON THE SUN OVER THREE SOLAR CYCLES

    SciTech Connect

    Tlatov, Andrey G.; Vasil'eva, Valerya V.; Pevtsov, Alexei A. E-mail: apevtsov@nso.ed

    2010-07-01

    We employ synoptic full disk longitudinal magnetograms to study latitudinal distribution and orientation (tilt) of magnetic bipoles in the course of sunspot activity during cycles 21, 22, and 23. The data set includes daily observations from the National Solar Observatory at Kitt Peak (1975-2002) and Michelson Doppler Imager on board the Solar and Heliospheric Observatory (MDI/SOHO, 1996-2009). Bipole pairs were selected on the basis of proximity and flux balance of two neighboring flux elements of opposite polarity. Using the area of the bipoles, we have separated them into small quiet-Sun bipoles (QSBs), ephemeral regions (ERs), and active regions (ARs). We find that in their orientation, ERs and ARs follow Hale-Nicholson polarity rule. As expected, AR tilts follow Joy's law. ERs, however, show significantly larger tilts of opposite sign for a given hemisphere. QSBs are randomly oriented. Unlike ARs, ERs also show a preference in their orientation depending on the polarity of the large-scale magnetic field. These orientation properties may indicate that some ERs may form at or near the photosphere via the random encounter of opposite polarity elements, while others may originate in the convection zone at about the same location as ARs. The combined latitudinal distribution of ERs and ARs exhibits a clear presence of Spoerer's butterfly diagram (equatorward drift in the course of a solar cycle). ERs extend the ARs' 'wing' of the butterfly diagram to higher latitudes. This high latitude extension of ERs suggests an extended solar cycle with the first magnetic elements of the next cycle developing shortly after the maximum of the previous cycle. The polarity orientation and tilt of ERs may suggest the presence of poloidal fields of two configurations (new cycle and old cycle) in the convection zone at the declining phase of the sunspot cycle.

  3. Study and Development of an Air Conditioning System Operating on a Magnetic Heat Pump Cycle

    NASA Technical Reports Server (NTRS)

    Wang, Pao-Lien

    1991-01-01

    This report describes the design of a laboratory scale demonstration prototype of an air conditioning system operating on a magnetic heat pump cycle. Design parameters were selected through studies performed by a Kennedy Space Center (KSC) System Simulation Computer Model. The heat pump consists of a rotor turning through four magnetic fields that are created by permanent magnets. Gadolinium was selected as the working material for this demonstration prototype. The rotor was designed to be constructed of flat parallel disks of gadolinium with very little space in between. The rotor rotates in an aluminum housing. The laboratory scale demonstration prototype is designed to provide a theoretical Carnot Cycle efficiency of 62 percent and a Coefficient of Performance of 16.55.

  4. The solar magnetic cycle and the presence of an inclined relic field in the sun

    NASA Astrophysics Data System (ADS)

    Bravo, S.; Stewart, G. A.

    The evolution of the solar magnetic field through its 22 year cycle shows a varying inclination of the magnetic equator at 2.5 Rs from about 0 deg during solar minimum up to 90 deg during solar maximum, as measured with respect to the solar equator. We show that this behavoir could be explained by the presence of a small dipole relic field which has a high inclination with respect to the solar rotation axis and points southward. This fossil field would lead to a larger polar field during the negative polarity phase of the cycle, in accordance with observations. It may also help to explain the asymmetry observed in the solar activity of the northern and southern hemispheres, the appearance of some particularly active longitudes on the Sun, as well as other asymmetrical characteristics of the solar activity cycles.

  5. Influence of the Earth's magnetic field on large area photomultipliers

    SciTech Connect

    Leonora, E.; Aiello, S.; Leotta, G.

    2011-07-01

    The influence of the Earth's magnetic field on large area photomultipliers proposed for a future deep sea neutrino telescope was studied under the EU-funded KM3NeT design study. The aims were to evaluate variations in PMT performance in the Earth's magnetic field and to decide whether the use of magnetic shielding is necessary. Measurements were performed on three Hamamatsu PMTs: two 8-inch R5912 types, one of these with super-bi-alkali photocathode, and a 10-inch R7081 type with a standard bi-alkali photocathode. The various characteristics of the PMTs were measured while varying the PMT orientations with respect to the Earth's magnetic field, both with and without a mu-metal cage as magnetic shield. In the 8-inch PMTs the impact of the magnetic field was found to be smaller than that on the 10-inch PMT. The increased quantum efficiency in the 8 super-bi-alkali PMT almost compensated its smaller detection surface compared to the 10' PMT. No significant effects were measured upon transit time and the fraction of spurious pulses. (authors)

  6. INFLUENCE OF RESIDENTIAL HVAC DUTY CYCLE ON INDOOR AIR QUALITY

    EPA Science Inventory

    Measurements of duty cycle, the fraction of time the heating and cooling (HVAC) system was operating, were made in homes during the spring season of the RTP Particulate Matter Panel Study and the Tampa Asthmatic Children's Study. A temperature sensor/logger placed on an outlet...

  7. Rotation of solar magnetic fields for the current solar cycle 24

    SciTech Connect

    Shi, X. J.; Xie, J. L.

    2014-11-01

    The rotation of solar magnetic fields for the current solar cycle 24 is investigated through a cross-correlation analysis of the Carrington synoptic maps of solar photospheric magnetic fields during Carrington rotation numbers 2076-2146 (2008 October to 2014 January). The sidereal rotation rates of positive and negative magnetic fields at some latitudes are shown, and it can be found that the positive (negative) fields generally rotate faster than the negative (positive) fields in the southern (northern) hemisphere at low latitudes. The mean rotation profiles of total, positive, and negative magnetic fields between ±60° latitudes in the time interval are also obtained. It should be noted that both of the mean rotation profiles of the positive and negative magnetic fields, as well as the mean rotation profile of the total magnetic field, exhibit a quasi-rigid rotation at latitudes above about 55°. The mean rotation rates of the positive (negative) polarity reach their maximum values at about 9°(6)° latitude in the southern (northern) hemisphere. The mean rotation profile of the total magnetic field displays an obvious north-south asymmetry, where the rotation seems to be more differential in the northern hemisphere. The latitude variation in the rotation rate differences between positive and negative magnetic fields is further studied, and it is found that magnetic fields with the same polarity as the leading sunspots at a given hemisphere rotate faster than those with the opposite polarity, except for the zones around 52° latitude of the southern hemisphere and around 35° latitude of the northern hemisphere. The implication of these results is discussed. It is clear that the obtained results can provide some observational constraints on the theoretical research of the mechanisms of differential rotation and solar cycle.

  8. Evolution of sunspot activity and inversion of the Sun's polar magnetic field in the current cycle

    NASA Astrophysics Data System (ADS)

    Mordvinov, A. V.; Grigoryev, V. M.; Erofeev, D. V.

    2015-06-01

    A spatiotemporal analysis of the Sun's magnetic field was carried out to study the polar-field inversion in the current cycle in relation to sunspot activity. The causal relationship between these phenomena was demonstrated in a time-latitude aspect. After decay of long-lived activity complexes their magnetic fields were redistributed into the surrounding photosphere and formed unipolar magnetic regions which were transported to high latitudes. Zones of intense sunspot activity during 2011/2012 produced unipolar magnetic regions of the following polarities, whose poleward drift led to the inversion of the Sun's polar fields at the North and South Poles. At the North Pole the polar field reversal was completed by May 2013. It was demonstrated that mixed magnetic polarities near the North Pole resulted from violations of Joy's law at lower latitudes. Later sunspot activity in the southern hemisphere has led to a delay in magnetic polarity reversal at the South Pole. Thus, the north-south asymmetry of sunspot activity resulted in asynchronous polar field reversal in the current cycle.

  9. Air core notch-coil magnet with variable geometry for fast-field-cycling NMR.

    PubMed

    Kruber, S; Farrher, G D; Anoardo, E

    2015-10-01

    In this manuscript we present details on the optimization, construction and performance of a wide-bore (71 mm) α-helical-cut notch-coil magnet with variable geometry for fast-field-cycling NMR. In addition to the usual requirements for this kind of magnets (high field-to-power ratio, good magnetic field homogeneity, low inductance and resistance values) a tunable homogeneity and a more uniform heat dissipation along the magnet body are considered. The presented magnet consists of only one machined metallic cylinder combined with two external movable pieces. The optimal configuration is calculated through an evaluation of the magnetic flux density within the entire volume of interest. The magnet has a field-to-current constant of 0.728 mT/A, allowing to switch from zero to 0.125 T in less than 3 ms without energy storage assistance. For a cylindrical sample volume of 35 cm(3) the effective magnet homogeneity is lower than 130 ppm. PMID:26367321

  10. Air core notch-coil magnet with variable geometry for fast-field-cycling NMR

    NASA Astrophysics Data System (ADS)

    Kruber, S.; Farrher, G. D.; Anoardo, E.

    2015-10-01

    In this manuscript we present details on the optimization, construction and performance of a wide-bore (71 mm) α -helical-cut notch-coil magnet with variable geometry for fast-field-cycling NMR. In addition to the usual requirements for this kind of magnets (high field-to-power ratio, good magnetic field homogeneity, low inductance and resistance values) a tunable homogeneity and a more uniform heat dissipation along the magnet body are considered. The presented magnet consists of only one machined metallic cylinder combined with two external movable pieces. The optimal configuration is calculated through an evaluation of the magnetic flux density within the entire volume of interest. The magnet has a field-to-current constant of 0.728 mT/A, allowing to switch from zero to 0.125 T in less than 3 ms without energy storage assistance. For a cylindrical sample volume of 35 cm3 the effective magnet homogeneity is lower than 130 ppm.

  11. Air core notch-coil magnet with variable geometry for fast-field-cycling NMR.

    PubMed

    Kruber, S; Farrher, G D; Anoardo, E

    2015-10-01

    In this manuscript we present details on the optimization, construction and performance of a wide-bore (71 mm) α-helical-cut notch-coil magnet with variable geometry for fast-field-cycling NMR. In addition to the usual requirements for this kind of magnets (high field-to-power ratio, good magnetic field homogeneity, low inductance and resistance values) a tunable homogeneity and a more uniform heat dissipation along the magnet body are considered. The presented magnet consists of only one machined metallic cylinder combined with two external movable pieces. The optimal configuration is calculated through an evaluation of the magnetic flux density within the entire volume of interest. The magnet has a field-to-current constant of 0.728 mT/A, allowing to switch from zero to 0.125 T in less than 3 ms without energy storage assistance. For a cylindrical sample volume of 35 cm(3) the effective magnet homogeneity is lower than 130 ppm.

  12. Influence of the submersed plant, Potamogeton perfoliatus, on nitrogen cycling in estuarine sediments

    USGS Publications Warehouse

    Caffrey, J.M.; Kemp, W.M.

    1993-01-01

    Using 15N isotope techniques P. perfoliatus is shown to have a significant influence on sediment N cycling by direct uptake of NH4+ and NO3- and by indirect mechanisms leading to enhanced nitrification and denitrification. -from Authors

  13. Magnetic activity in the young solar analog LQ Hydrae. I. Active longitudes and cycles

    NASA Astrophysics Data System (ADS)

    Berdyugina, S. V.; Pelt, J.; Tuominen, I.

    2002-11-01

    We present the first evidence that a single active dwarf of solar type can show a long-lived, nonaxisymmetric spot distribution - active longitudes on opposite hemispheres, similar to evolved, rapidly rotating RS CVn-type binary stars. We analyse new as well as published photometric observations of the young active dwarf LQ Hya, spanning almost 20 years. We find that activity of the star has three activity cycles: a 5.2-yr ``flip-flop'' cycle, a 7.7-yr period in the amplitude modulation of the brightness and an approximately 15-yr period in variations of the mean brightness. The two shorter cycles are related to the alternating active longitudes and are similar to cycles observed in RS CVn-type stars. The 15-yr cycle reflects periodic changes of the mean spottedness of the star and resembles the solar 11-year cycle. The spot rotation period (about 1.6 days) changes during the 15-yr cycle, indicating the presence of small differential rotation. The lengths of the three cycles are related as 3:2:1, with the repetition of the spot configuration after 15 years. We discuss the possibility that the observed spot cycles represent two different magnetic dynamo modes operating in LQ Hya: an axisymmetric mode, as in the Sun, and a nonaxisymmetric higher order mode with two cycles in spot patterns. Our results suggest that young stars exhibit their cycles in spot distribution, as seen in LQ Hya. This is in contrast to the conclusion based on the analysis of Ca Ii H&K emission from plages. The results suggest also that the Vaughan-Preston gap represents a transition from a multiple-mode dynamo to a single-mode dynamo. Table 2 is only available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/394/505

  14. Influence of Cycle Temperature on the Wear Resistance of Vermicular Iron Derivatized with Bionic Surfaces

    NASA Astrophysics Data System (ADS)

    Sui, Qi; Zhang, Peng; Zhou, Hong; Liu, Yan; Ren, Luquan

    2016-11-01

    Depending on their applications, such as in brake discs, camshafts, etc., the wear behavior of vermicular iron is influenced by the thermal cycling regime. The failure of a working part during its service life is a consequence of both thermal fatigue and wear. Previously, the wear and thermal fatigue resistance properties of vermicular iron were separately investigated by researchers, rather than a study combining these two factors. In the present work, the effect of cycle temperature on the wear resistance of specimens with bionic units processed by laser has been investigated experimentally. The wear behavior pre- and post-thermal cycling has also been investigated, and the influence of different cycle temperatures on the wear resistance is discussed. The results indicate that the thermal cycling regime brought about negative influences with varying degrees, on the material properties, such as the microstructures, micro-hardness, cracks, and oxidation resistance properties. All these factors synergistically reduced the wear resistance of vermicular iron. In particular, the negative influence apparently increased with an increase in cycle temperature. Nevertheless, the post-thermal-cycle wear resistance of the specimens with bionic units was superior to those without bionic units. Hence, the laser bionic process is an effective way to improve the performance of vermicular iron in combined thermal cycling and wear service conditions.

  15. Influence of Cycle Temperature on the Wear Resistance of Vermicular Iron Derivatized with Bionic Surfaces

    NASA Astrophysics Data System (ADS)

    Sui, Qi; Zhang, Peng; Zhou, Hong; Liu, Yan; Ren, Luquan

    2016-08-01

    Depending on their applications, such as in brake discs, camshafts, etc., the wear behavior of vermicular iron is influenced by the thermal cycling regime. The failure of a working part during its service life is a consequence of both thermal fatigue and wear. Previously, the wear and thermal fatigue resistance properties of vermicular iron were separately investigated by researchers, rather than a study combining these two factors. In the present work, the effect of cycle temperature on the wear resistance of specimens with bionic units processed by laser has been investigated experimentally. The wear behavior pre- and post-thermal cycling has also been investigated, and the influence of different cycle temperatures on the wear resistance is discussed. The results indicate that the thermal cycling regime brought about negative influences with varying degrees, on the material properties, such as the microstructures, micro-hardness, cracks, and oxidation resistance properties. All these factors synergistically reduced the wear resistance of vermicular iron. In particular, the negative influence apparently increased with an increase in cycle temperature. Nevertheless, the post-thermal-cycle wear resistance of the specimens with bionic units was superior to those without bionic units. Hence, the laser bionic process is an effective way to improve the performance of vermicular iron in combined thermal cycling and wear service conditions.

  16. Magnetic Interactions Influence the Properties of Helium Defects in Iron.

    SciTech Connect

    Seletskaia, Tatiana; Osetskiy, Yury N; Stoller, Roger E; Stocks, George Malcolm

    2005-01-01

    Density functional theory calculations of He defect properties in iron have shown an unexpected influence of magnetism arising from the defect's electronic structure. In contrast with previous work that neglected such effects, the results indicate that the tetrahedral position is energetically more favorable for the He interstitial than the octahedral site. This may have significant implications for He clustering and bubble nucleation, which will impact material performance in future fusion reactors. These results provide the basis for development of improved atomistic models.

  17. In vivo detection of brain Krebs cycle intermediate by hyperpolarized magnetic resonance.

    PubMed

    Mishkovsky, Mor; Comment, Arnaud; Gruetter, Rolf

    2012-12-01

    The Krebs (or tricarboxylic acid (TCA)) cycle has a central role in the regulation of brain energy regulation and metabolism, yet brain TCA cycle intermediates have never been directly detected in vivo. This study reports the first direct in vivo observation of a TCA cycle intermediate in intact brain, namely, 2-oxoglutarate, a key biomolecule connecting metabolism to neuronal activity. Our observation reveals important information about in vivo biochemical processes hitherto considered undetectable. In particular, it provides direct evidence that transport across the inner mitochondria membrane is rate limiting in the brain. The hyperpolarized magnetic resonance protocol designed for this study opens the way to direct and real-time studies of TCA cycle kinetics.

  18. Real-time assessment of Krebs cycle metabolism using hyperpolarized 13C magnetic resonance spectroscopy.

    PubMed

    Schroeder, Marie A; Atherton, Helen J; Ball, Daniel R; Cole, Mark A; Heather, Lisa C; Griffin, Julian L; Clarke, Kieran; Radda, George K; Tyler, Damian J

    2009-08-01

    The Krebs cycle plays a fundamental role in cardiac energy production and is often implicated in the energetic imbalance characteristic of heart disease. In this study, we measured Krebs cycle flux in real time in perfused rat hearts using hyperpolarized magnetic resonance spectroscopy (MRS). [2-(13)C]Pyruvate was hyperpolarized and infused into isolated perfused hearts in both healthy and postischemic metabolic states. We followed the enzymatic conversion of pyruvate to lactate, acetylcarnitine, citrate, and glutamate with 1 s temporal resolution. The appearance of (13)C-labeled glutamate was delayed compared with that of other metabolites, indicating that Krebs cycle flux can be measured directly. The production of (13)C-labeled citrate and glutamate was decreased postischemia, as opposed to lactate, which was significantly elevated. These results showed that the control and fluxes of the Krebs cycle in heart disease can be studied using hyperpolarized [2-(13)C]pyruvate.

  19. Influence of magnetic electrodes thicknesses on the transport properties of magnetic tunnel junctions with perpendicular anisotropy

    SciTech Connect

    Cuchet, Léa; Rodmacq, Bernard; Auffret, Stéphane; Sousa, Ricardo C.; Dieny, Bernard

    2014-08-04

    The influence of the bottom and top magnetic electrodes thicknesses on both perpendicular anisotropy and transport properties is studied in (Co/Pt)/Ta/CoFeB/MgO/FeCoB/Ta magnetic tunnel junctions. By carefully investigating the relative magnetic moment of the two electrodes as a function of their thicknesses, we identify and quantify the presence of magnetically dead layers, likely localized at the interfaces with Ta, that is, 0.33 nm for the bottom electrode and 0.60 nm for the top one. Critical thicknesses (spin-reorientation transitions) are determined as 1.60 and 1.65 nm for bottom and top electrodes, respectively. The tunnel magnetoresistance ratio reaches its maximum value, as soon as both effective (corrected from dead layer) electrode thicknesses exceed 0.6 nm.

  20. Solar Sources and Geospace Consequences of Interplanetary Magnetic Clouds Observed During Solar Cycle 23

    NASA Technical Reports Server (NTRS)

    Gopalswamy, N.; Akiyama, S.; Yashiro, S.; Michalek, G.; Lepping, R. P.

    2007-01-01

    We present results of a statistical investigation of 99 magnetic clouds (MCs) observed during 1995-2005. The MC-associated coronal mass ejections (CMEs) are faster and wider on the average and originate within +/-30deg from the solar disk center. The solar sources of MCs also followed the butterfly diagram. The correlation between the magnetic field strength and speed of MCs was found to be valid over a much wider range of speeds. The number of south-north (SN) MCs was dominant and decreased with solar cycle, while the number of north-south (NS) MCs increased confirming the odd-cycle behavior. Two-thirds of MCs were geoeffective; the Dst index was highly correlated with speed and magnetic field in MCs as well as their product. Many (55%) fully northward (FN) MCs were geoeffective solely due to their sheaths. The non-geoeffective MCs were slower (average speed approx. 382 km/s), had a weaker southward magnetic field (average approx. -5.2nT), and occurred mostly during the rise phase of the solar activity cycle.

  1. Polarity Reversal of the Solar Photospheric Magnetic Field During Activity Cycle 24

    NASA Astrophysics Data System (ADS)

    Sun, Xudong; Hoeksema, Jon Todd; Liu, Yang; Zhao, Junwei

    2014-06-01

    The large-scale solar magnetic field reverses its polarity during the maximum phase of each activity cycle. As observed on the photosphere, active region (AR) magnetic flux migrates poleward in narrow, sheared streams resulted from large-scale flows and diffusion. A small net flux of the trailing sunspot polarity eventually aggregates at high latitudes, manifesting the poloidal field of the next cycle. We characterize this process for the ongoing cycle 24 based on four years' line-of-sight magnetograms from the Helioseismic and Magnetic Imager (HMI). The axial dipole component reversed sign in early 2012, but the poleward flux migration was grossly out of phase in the two hemispheres. As a proxy, the northern polar field (taken as mean above 70 degrees latitude) switched from negative to positive in late 2012, whereas the southern remained positive as of March 2014. Three factors that are in line with the surface flux transport model may have contributed. First, AR emergence started and peaked earlier in the north. Second, several ARs with small or inverse tilt angles (w.r.t. the Joy's law) emerged in the south in late 2010. Third, meridional flow speed inferred from helioseismology varied greatly prior to 2013; slower streams (compared to a three-year mean at the same latitude) appeared earlier in the north. We correlate HMI with the long-running Wilcox Solar Observatory (WSO) dataset, and compare the current cycle with the previous three.

  2. SUN-LIKE MAGNETIC CYCLES IN THE RAPIDLY ROTATING YOUNG SOLAR ANALOG HD 30495

    SciTech Connect

    Egeland, Ricky; Metcalfe, Travis S.; Hall, Jeffrey C.; Henry, Gregory W.

    2015-10-10

    A growing body of evidence suggests that multiple dynamo mechanisms can drive magnetic variability on different timescales, not only in the Sun but also in other stars. Many solar activity proxies exhibit a quasi-biennial (∼2 year) variation, which is superimposed upon the dominant 11 year cycle. A well-characterized stellar sample suggests at least two different relationships between rotation period and cycle period, with some stars exhibiting long and short cycles simultaneously. Within this sample, the solar cycle periods are typical of a more rapidly rotating star, implying that the Sun might be in a transitional state or that it has an unusual evolutionary history. In this work, we present new and archival observations of dual magnetic cycles in the young solar analog HD 30495, a ∼1 Gyr old G1.5 V star with a rotation period near 11 days. This star falls squarely on the relationships established by the broader stellar sample, with short-period variations at ∼1.7 years and a long cycle of ∼12 years. We measure three individual long-period cycles and find durations ranging from 9.6 to 15.5 years. We find the short-term variability to be intermittent, but present throughout the majority of the time series, though its occurrence and amplitude are uncorrelated with the longer cycle. These essentially solar-like variations occur in a Sun-like star with more rapid rotation, though surface differential rotation measurements leave open the possibility of a solar equivalence.

  3. Stellar Magnetic Cycles in the Solar-like Stars Kepler-17 and Kepler-63

    NASA Astrophysics Data System (ADS)

    Estrela, Raissa; Valio, Adriana

    2016-11-01

    The stellar magnetic field plays a crucial role in the star internal mechanisms, as in the interactions with its environment. The study of starspots provides information about the stellar magnetic field and can characterize the cycle. Moreover, the analysis of solar-type stars is also useful to shed light onto the origin of the solar magnetic field. The objective of this work is to characterize the magnetic activity of stars. Here, we studied two solar-type stars, Kepler-17 and Kepler-63, using two methods to estimate the magnetic cycle length. The first one characterizes the spots (radius, intensity, and location) by fitting the small variations in the light curve of a star caused by the occultation of a spot during a planetary transit. This approach yields the number of spots present in the stellar surface and the flux deficit subtracted from the star by their presence during each transit. The second method estimates the activity from the excess in the residuals of the transit light curves. This excess is obtained by subtracting a spotless model transit from the light curve and then integrating all the residuals during the transit. The presence of long-term periodicity is estimated in both time series. With the first method, we obtained P cycle = 1.12 ± 0.16 year (Kepler-17) and P cycle = 1.27 ± 0.16 year (Kepler-63), and for the second approach the values are 1.35 ± 0.27 year and 1.27 ± 0.12 year, respectively. The results of both methods agree with each other and confirm their robustness.

  4. Colaba-Alibag magnetic observatory and Nanabhoy Moos: the influence of one over the other

    NASA Astrophysics Data System (ADS)

    Gawali, P. B.; Doiphode, M. G.; Nimje, R. N.

    2015-09-01

    The first permanent magnetic observatories in colonial India were established by the East India Company and under the Göttingen Magnetic Union. One of the world's longest running observatories was set up at Colaba (Bombay) in 1841, which was shifted to Alibag in 1904 to avoid electric traction effects on magnetic recordings. The observatory is located at the northwestern tip of Maharashtra, India, on the Arabian Sea. The magnetic data at Colaba were collected through eye-observation instruments from 1841 to 1872 and by photographic (magnetograph) instruments from 1872 to 1905, which reveal seasonal and other periodic effects on geomagnetic elements. Seasonal influence can be deciphered on the H minimum, but not on the maximum; the disturbances in March and April were opposite to those in December and January. D was maximum in 1880 (57' E) and minimum in 1904 (10' E). The data from 1882 to 1905 revealed that H annual inequality was influenced by 5.5-year periodicity, D by 13.5 days from 1888 to 1905, and I and Z by 11-year periodicity from 1894 to 1905 and 1873 to 1905, respectively. Secular variation of Z was parallel to that of I. Z exhibited an increasing trend from 1868 (12 874 nT) to 1905 (15 083 nT). The plan and location of Colaba-Alibag as well as the instruments used are discussed. The initial Colaba magnetic data containing "magnetic disturbances" was harnessed to identify the "disturbing point" on Earth. Nanabhoy Moos, the first Indian director, presciently hinted at a solar origin for magnetic disturbances, revealed the dependence of magnetic elements on the sunspot cycle, unraveled disturbance daily variation, and tried to understand the association, if any, between geomagnetic, seismological and meteorological phenomena. The two giant volumes published in 1910 attest to Moos' seminal work and his inventiveness in organizing and analyzing long series data. He also had a major role in moving Colaba magnetic observatory to Alibag. Thus, the observatory

  5. Effect of mixing water magnetic activation cycle on cement stone structure

    NASA Astrophysics Data System (ADS)

    Kugaevskaya, S. A.; Abzaev, Yu A.; Safronov, V. N.; Sarkisov, Yu S.; Gorlenko, N. P.; Ermilova, T. A.

    2015-01-01

    The paper presents results of investigations of hydration processes and structure formation of the cement paste matrix mixed with water activated by magneto static field using water treatment cycle technology. It is shown that crystallization of phases occurs in the cement-water system at different rates, and phase redistribution in the structure of the cement paste matrix is described before and after magnetic activation of mixing water. Also, modeling of the cement-water system and calculations of amorphous and crystalline phases using the Rietveld refinement method before and after magnetic activation show that strength properties of the cement paste matrix depend not only on quantitative but also qualitative relationship between phases.

  6. CoRoT reveals a magnetic activity cycle in a Sun-like star.

    PubMed

    García, Rafael A; Mathur, Savita; Salabert, David; Ballot, Jérôme; Régulo, Clara; Metcalfe, Travis S; Baglin, Annie

    2010-08-27

    The 11-year activity cycle of the Sun is a consequence of a dynamo process occurring beneath its surface. We analyzed photometric data obtained by the CoRoT space mission, showing solarlike oscillations in the star HD49933, for signatures of stellar magnetic activity. Asteroseismic measurements of global changes in the oscillation frequencies and mode amplitudes reveal a modulation of at least 120 days, with the minimum frequency shift corresponding to maximum amplitude as in the Sun. These observations are evidence of a stellar magnetic activity cycle taking place beneath the surface of HD49933 and provide constraints for stellar dynamo models under conditions different from those of the Sun. PMID:20798310

  7. Influence of magnetic fields on magneto-aerotaxis.

    PubMed

    Bennet, Mathieu; McCarthy, Aongus; Fix, Dmitri; Edwards, Matthew R; Repp, Felix; Vach, Peter; Dunlop, John W C; Sitti, Metin; Buller, Gerald S; Klumpp, Stefan; Faivre, Damien

    2014-01-01

    The response of cells to changes in their physico-chemical micro-environment is essential to their survival. For example, bacterial magnetotaxis uses the Earth's magnetic field together with chemical sensing to help microorganisms move towards favoured habitats. The studies of such complex responses are lacking a method that permits the simultaneous mapping of the chemical environment and the response of the organisms, and the ability to generate a controlled physiological magnetic field. We have thus developed a multi-modal microscopy platform that fulfils these requirements. Using simultaneous fluorescence and high-speed imaging in conjunction with diffusion and aerotactic models, we characterized the magneto-aerotaxis of Magnetospirillum gryphiswaldense. We assessed the influence of the magnetic field (orientation; strength) on the formation and the dynamic of a micro-aerotactic band (size, dynamic, position). As previously described by models of magnetotaxis, the application of a magnetic field pointing towards the anoxic zone of an oxygen gradient results in an enhanced aerotaxis even down to Earth's magnetic field strength. We found that neither a ten-fold increase of the field strength nor a tilt of 45° resulted in a significant change of the aerotactic efficiency. However, when the field strength is zeroed or when the field angle is tilted to 90°, the magneto-aerotaxis efficiency is drastically reduced. The classical model of magneto-aerotaxis assumes a response proportional to the cosine of the angle difference between the directions of the oxygen gradient and that of the magnetic field. Our experimental evidence however shows that this behaviour is more complex than assumed in this model, thus opening up new avenues for research. PMID:24983865

  8. Influence of Magnetic Fields on Magneto-Aerotaxis

    PubMed Central

    Bennet, Mathieu; McCarthy, Aongus; Fix, Dmitri; Edwards, Matthew R.; Repp, Felix; Vach, Peter; Dunlop, John W. C.; Sitti, Metin; Buller, Gerald S.; Klumpp, Stefan; Faivre, Damien

    2014-01-01

    The response of cells to changes in their physico-chemical micro-environment is essential to their survival. For example, bacterial magnetotaxis uses the Earth's magnetic field together with chemical sensing to help microorganisms move towards favoured habitats. The studies of such complex responses are lacking a method that permits the simultaneous mapping of the chemical environment and the response of the organisms, and the ability to generate a controlled physiological magnetic field. We have thus developed a multi-modal microscopy platform that fulfils these requirements. Using simultaneous fluorescence and high-speed imaging in conjunction with diffusion and aerotactic models, we characterized the magneto- aerotaxis of Magnetospirillum gryphiswaldense. We assessed the influence of the magnetic field (orientation; strength) on the formation and the dynamic of a micro-aerotactic band (size, dynamic, position). As previously described by models of magnetotaxis, the application of a magnetic field pointing towards the anoxic zone of an oxygen gradient results in an enhanced aerotaxis even down to Earth's magnetic field strength. We found that neither a ten-fold increase of the field strength nor a tilt of 45° resulted in a significant change of the aerotactic efficiency. However, when the field strength is zeroed or when the field angle is tilted to 90°, the magneto-aerotaxis efficiency is drastically reduced. The classical model of magneto-aerotaxis assumes a response proportional to the cosine of the angle difference between the directions of the oxygen gradient and that of the magnetic field. Our experimental evidence however shows that this behaviour is more complex than assumed in this model, thus opening up new avenues for research. PMID:24983865

  9. Variable spatial magnetic field influences peripheral nerves regeneration in rats.

    PubMed

    Suszyński, Krzysztof; Marcol, Wiesław; Szajkowski, Sebastian; Pietrucha-Dutczak, Marita; Cieślar, Grzegorz; Sieroń, Aleksander; Lewin-Kowalik, Joanna

    2014-09-01

    Generator of spatial magnetic field is one of most recent achievements among the magnetostimulators. This apparatus allows to obtain the rotating magnetic field. This new method may be more effective than other widely used techniques of magnetostimulation and magnetotherapy. We investigated the influence of alternating, spatial magnetic field on the regeneration of the crushed rat sciatic nerves. Functional and morphological evaluations were used. After crush injury of the right sciatic nerve, Wistar C rats (n = 80) were randomly divided into four groups (control and three experimental). The experimental groups (A, B, C) were exposed (20 min/day, 5 d/week, 4 weeks) to alternating spatial magnetic field of three different intensities. Sciatic Functional Index (SFI) and tensometric assessments were performed every week after nerve crush. Forty-eight hours before the sacrificing of animals, DiI (1,1'-di-octadecyl-3,3,3',3'-tetramethyloindocarbocyanine perchlorate) was applied 5 mm distally to the crush site. Collected nerves and dorsal root ganglia (DRG) were subjected to histological and immunohistochemical staining. The survival rate of DRG neurons was estimated. Regrowth and myelination of the nerves was examined. The results of SFI and tensometric assessment showed improvement in all experimental groups as compared to control, with best outcome observed in group C, exposed to the strongest magnetic field. In addition, DRG survival rate and nerve regeneration intensity were significantly higher in the C group. Above results indicate that strong spatial alternating magnetic field exerts positive effect on peripheral nerve regeneration and its application could be taken under consideration in the therapy of injured peripheral nerves. PMID:23781984

  10. Influence of magnetic fields on magneto-aerotaxis.

    PubMed

    Bennet, Mathieu; McCarthy, Aongus; Fix, Dmitri; Edwards, Matthew R; Repp, Felix; Vach, Peter; Dunlop, John W C; Sitti, Metin; Buller, Gerald S; Klumpp, Stefan; Faivre, Damien

    2014-01-01

    The response of cells to changes in their physico-chemical micro-environment is essential to their survival. For example, bacterial magnetotaxis uses the Earth's magnetic field together with chemical sensing to help microorganisms move towards favoured habitats. The studies of such complex responses are lacking a method that permits the simultaneous mapping of the chemical environment and the response of the organisms, and the ability to generate a controlled physiological magnetic field. We have thus developed a multi-modal microscopy platform that fulfils these requirements. Using simultaneous fluorescence and high-speed imaging in conjunction with diffusion and aerotactic models, we characterized the magneto-aerotaxis of Magnetospirillum gryphiswaldense. We assessed the influence of the magnetic field (orientation; strength) on the formation and the dynamic of a micro-aerotactic band (size, dynamic, position). As previously described by models of magnetotaxis, the application of a magnetic field pointing towards the anoxic zone of an oxygen gradient results in an enhanced aerotaxis even down to Earth's magnetic field strength. We found that neither a ten-fold increase of the field strength nor a tilt of 45° resulted in a significant change of the aerotactic efficiency. However, when the field strength is zeroed or when the field angle is tilted to 90°, the magneto-aerotaxis efficiency is drastically reduced. The classical model of magneto-aerotaxis assumes a response proportional to the cosine of the angle difference between the directions of the oxygen gradient and that of the magnetic field. Our experimental evidence however shows that this behaviour is more complex than assumed in this model, thus opening up new avenues for research.

  11. How the cell cycle impacts chromatin architecture and influences cell fate

    PubMed Central

    Ma, Yiqin; Kanakousaki, Kiriaki; Buttitta, Laura

    2015-01-01

    Since the earliest observations of cells undergoing mitosis, it has been clear that there is an intimate relationship between the cell cycle and nuclear chromatin architecture. The nuclear envelope and chromatin undergo robust assembly and disassembly during the cell cycle, and transcriptional and post-transcriptional regulation of histone biogenesis and chromatin modification is controlled in a cell cycle-dependent manner. Chromatin binding proteins and chromatin modifications in turn influence the expression of critical cell cycle regulators, the accessibility of origins for DNA replication, DNA repair, and cell fate. In this review we aim to provide an integrated discussion of how the cell cycle machinery impacts nuclear architecture and vice-versa. We highlight recent advances in understanding cell cycle-dependent histone biogenesis and histone modification deposition, how cell cycle regulators control histone modifier activities, the contribution of chromatin modifications to origin firing for DNA replication, and newly identified roles for nucleoporins in regulating cell cycle gene expression, gene expression memory and differentiation. We close with a discussion of how cell cycle status may impact chromatin to influence cell fate decisions, under normal contexts of differentiation as well as in instances of cell fate reprogramming. PMID:25691891

  12. The spiral interplanetary magnetic field - A polarity and sunspot cycle variation

    NASA Technical Reports Server (NTRS)

    Svalgaard, L.; Wilcox, J. M.

    1974-01-01

    Spacecraft observations near the earth of the average direction of the interplanetary magnetic field during the sunspot maximum year 1968 showed a deviation from the spiral field of Parker's classical description. The included angle between the average field direction when the field polarity was away from the sun and the average direction when the field polarity was toward the sun was 168 deg, rather than 180 deg as predicted by Parker. This effect appears to have a sunspot cycle variation.

  13. The spiral interplanetary magnetic field: A polarity and sunspot cycle variation

    NASA Technical Reports Server (NTRS)

    Svalgaard, L.; Wilcox, J. M.

    1974-01-01

    Spacecraft observations near the earth of the yearly average direction of the interplanetary magnetic field during the sunspot maximum year 1968 showed a deviation from the spiral field. The angle between the average field direction when the field polarity was away from the sun and the average direction for toward polarity was 168 deg, rather than 180 deg. This effect appears to have a sunspot cycle variation.

  14. Magnetic stability in exchange-spring and exchange bias systems after multiple switching cycles.

    SciTech Connect

    Jiang, J. S.; Inomata, A.; You, C.-Y.; Pearson, J. E.; Bader, S. D.

    2001-06-01

    We have studied the magnetic stability in exchange bias and exchange spring systems prepared via epitaxial sputter deposition. The two interfacial exchange coupled systems, Fe/Cr(211) double superlattices consisting of a ferromagnetic and an antiferromagnetic Fe/Cr superlattice that are exchange coupled through a Cr spacer, and Sin-Co/Fe exchange-spring bilayer structures with ferromagnetically coupled hard Sin-Co layer and soft Fe layer, were epitaxially grown on suitably prepared Cr buffer layers to give rise to different microstructure and magnetic anisotropy. The magnetic stability was investigated using the magneto-optic Kerr effect during repeated reversal of the soft layer magnetization by field cycling up to 10{sup 7} times. For uniaxial Fe/Cr exchange biased double superlattices and exchange spring bilayers with uniaxial Sin-Co, small but rapid initial decay in the exchange bias field HE and in the remanent magnetization is observed. However, the exchange spring bilayers with biaxial and random in-plane anisotropy in the Sin-Co layer shows gradual decay in H{sub E} and without large reduction of the magnetization. The different decay behaviors are attributed to the different microstructure and spin configuration of the pinning layers.

  15. Magnetic-field cycling instrumentation for dynamic nuclear polarization-nuclear magnetic resonance using photoexcited triplets.

    PubMed

    Kagawa, Akinori; Negoro, Makoto; Takeda, Kazuyuki; Kitagawa, Masahiro

    2009-04-01

    To advance static solid-state NMR with hyperpolarized nuclear spins, a system has been developed enabling dynamic nuclear polarization (DNP) using electron spins in the photoexcited triplet state with X-band microwave apparatus, followed by static solid-state nuclear magnetic resonance (NMR) experiments using the polarized nuclear-spin system with a goniometer. In order to perform the DNP and NMR procedures in different magnetic fields, the DNP system and the NMR system are spatially separated, between which the sample can be shuttled while its orientation is controlled in a reproducible fashion. We demonstrate that the system developed in this work is operational for solid-state NMR with hyperpolarized nuclear-spin systems in static organic materials, and also discuss the application of our system.

  16. MAGNETIC CYCLES IN A CONVECTIVE DYNAMO SIMULATION OF A YOUNG SOLAR-TYPE STAR

    SciTech Connect

    Brown, Benjamin P.; Miesch, Mark S.; Browning, Matthew K.; Brun, Allan Sacha

    2011-04-10

    Young solar-type stars rotate rapidly and many are magnetically active. Some appear to undergo magnetic cycles similar to the 22 yr solar activity cycle. We conduct simulations of dynamo action in rapidly rotating suns with the three-dimensional magnetohydrodynamic anelastic spherical harmonic (ASH) code to explore dynamo action achieved in the convective envelope of a solar-type star rotating at five times the current solar rotation rate. We find that dynamo action builds substantial organized global-scale magnetic fields in the midst of the convection zone. Striking magnetic wreaths span the convection zone and coexist with the turbulent convection. A surprising feature of this wreath-building dynamo is its rich time dependence. The dynamo exhibits cyclic activity and undergoes quasi-periodic polarity reversals where both the global-scale poloidal and toroidal fields change in sense on a roughly 1500 day timescale. These magnetic activity patterns emerge spontaneously from the turbulent flow and are more organized temporally and spatially than those realized in our previous simulations of the solar dynamo. We assess in detail the competing processes of magnetic field creation and destruction within our simulations that contribute to the global-scale reversals. We find that the mean toroidal fields are built primarily through an {Omega}-effect, while the mean poloidal fields are built by turbulent correlations which are not well represented by a simple {alpha}-effect. During a reversal the magnetic wreaths propagate toward the polar regions, and this appears to arise from a poleward propagating dynamo wave. As the magnetic fields wax and wane in strength and flip in polarity, the primary response in the convective flows involves the axisymmetric differential rotation which varies on similar timescales. Bands of relatively fast and slow fluid propagate toward the poles on timescales of roughly 500 days and are associated with the magnetic structures that propagate

  17. Magnetic Tilts in Sunspot Groups and Active regions in the Cycle 23 obtained from the Solar Feature Catalogues

    NASA Astrophysics Data System (ADS)

    Zharkov, S. I.; Zharkova, V. V.; Bianda, M.; Cartesi, S.

    We compare a few methods for calculation of magnetic tilts in active regions using using the automated sunspot group classification from the Solar Feature Catalogues http solar inf brad ac uk for 1996-2005 The best performing methods were applied to investigate the statistical variations of magnetic field tilt in sunspot groups and their relation to the total magnetic field contained in sunspots during different phases of the solar cycle 23 The classification results are compared with the similar research for the cycle 22 and the specifics on the cycle 23 is discussed The results are also tested against the existing solar dynamo models and their applicability for the solar activity forecast

  18. Magnetic cycles and rotation periods of late-type stars from photometric time series

    NASA Astrophysics Data System (ADS)

    Suárez Mascareño, A.; Rebolo, R.; González Hernández, J. I.

    2016-10-01

    Aims: We investigate the photometric modulation induced by magnetic activity cycles and study the relationship between rotation period and activity cycle(s) in late-type (FGKM) stars. Methods: We analysed light curves, spanning up to nine years, of 125 nearby stars provided by the All Sky Automated Survey (ASAS). The sample is mainly composed of low-activity, main-sequence late-A to mid-M-type stars. We performed a search for short (days) and long-term (years) periodic variations in the photometry. We modelled the light curves with combinations of sinusoids to measure the properties of these periodic signals. To provide a better statistical interpretation of our results, we complement our new results with results from previous similar works. Results: We have been able to measure long-term photometric cycles of 47 stars, out of which 39 have been derived with false alarm probabilities (FAP) of less than 0.1 per cent. Rotational modulation was also detected and rotational periods were measured in 36 stars. For 28 stars we have simultaneous measurements of activity cycles and rotational periods, 17 of which are M-type stars. We measured both photometric amplitudes and periods from sinusoidal fits. The measured cycle periods range from 2 to 14 yr with photometric amplitudes in the range of 5-20 mmag. We found that the distribution of cycle lengths for the different spectral types is similar, as the mean cycle is 9.5 yr for F-type stars, 6.7 yr for G-type stars, 8.5 yr for K-type stars, 6.0 yr for early M-type stars, and 7.1 yr for mid-M-type stars. On the other hand, the distribution of rotation periods is completely different, trending to longer periods for later type stars, from a mean rotation of 8.6 days for F-type stars to 85.4 days in mid-M-type stars. The amplitudes induced by magnetic cycles and rotation show a clear correlation. A trend of photometric amplitudes with rotation period is also outlined in the data. The amplitudes of the photometric variability

  19. Flow downstream of the heliospheric terminal shock: Magnetic field line topology and solar cycle imprint

    NASA Technical Reports Server (NTRS)

    Nerney, Steven; Suess, S. T.; Schmahl, E. J.

    1995-01-01

    The topology of the magnetic field in the heliosheath is illustrated using plots of the field lines. It is shown that the Archimedean spiral inside the terminal shock is rotated back in the heliosheath into nested spirals that are advected in the direction of the interstellar wind. The 22-year solar magnetic cycle is imprinted onto these field lines in the form of unipolar magnetic envelopes surrounded by volumes of strongly mixed polarity. Each envelope is defined by the changing tilt of the heliospheric current sheet, which is in turn defined by the boundary of unipolar high-latitude regions on the Sun that shrink to the pole at solar maximum and expand to the equator at solar minimum. The detailed shape of the envelopes is regulated by the solar wind velocity structure in the heliosheath.

  20. Magnetization, anomalous Barkhausen effect, and core loss of Supermendur under high temperature cycling.

    NASA Technical Reports Server (NTRS)

    Niedra, J. M.; Schwarze, G. E.

    1971-01-01

    The magnetization and core loss of Supermendur were measured up to 900 C under conditions of slow temperature cycling in vacuum. As a consequence of this heating, the coercivity at 25 C increased from 21 A/m to about 110 A/m. This increase is less than previously reported. A prominent anomalous Barkhausen effect, pinched-in hysteresis loops, and a magnetic viscosity field in excess of 20 A/m were observed in the range of 600 to 700 C. At 850 C, Supermendur had a coercivity of 23 A/m, a saturation induction exceeding 1.5 T, a core loss of 26 W/kg at 400 Hz, and a maximum induction of 1.5 T. Supermendur may be useful for high temperature soft magnetic material applications where some history dependence of properties and instability of minor loops at lower temperatures is acceptable.

  1. Direct observations of the full Dungey convection cycle in the polar ionosphere for southward interplanetary magnetic field conditions

    NASA Astrophysics Data System (ADS)

    Zhang, Q.-H.; Lockwood, M.; Foster, J. C.; Zhang, S.-R.; Zhang, B.-C.; McCrea, I. W.; Moen, J.; Lester, M.; Ruohoniemi, J. M.

    2015-06-01

    Tracking the formation and full evolution of polar cap ionization patches in the polar ionosphere, we directly observe the full Dungey convection cycle for southward interplanetary magnetic field (IMF) conditions. This enables us to study how the Dungey cycle influences the patches' evolution. The patches were initially segmented from the dayside storm enhanced density plume at the equatorward edge of the cusp, by the expansion and contraction of the polar cap boundary due to pulsed dayside magnetopause reconnection, as indicated by in situ Time History of Events and Macroscale Interactions during Substorms (THEMIS) observations. Convection led to the patches entering the polar cap and being transported antisunward, while being continuously monitored by the globally distributed arrays of GPS receivers and Super Dual Auroral Radar Network radars. Changes in convection over time resulted in the patches following a range of trajectories, each of which differed somewhat from the classical twin-cell convection streamlines. Pulsed nightside reconnection, occurring as part of the magnetospheric substorm cycle, modulated the exit of the patches from the polar cap, as confirmed by coordinated observations of the magnetometer at Tromsø and European Incoherent Scatter Tromsø UHF radar. After exiting the polar cap, the patches broke up into a number of plasma blobs and returned sunward in the auroral return flow of the dawn and/or dusk convection cell. The full circulation time was about 3 h.

  2. Theoretical studies to elucidate the influence of magnetic dipolar interactions occurring in the magnetic nanoparticle systems, for biomedical applications

    NASA Astrophysics Data System (ADS)

    Osaci, M.; Cacciola, M.

    2016-02-01

    In recent years, the study of magnetic nanoparticles has been intensively developed not only for their fundamental theoretical interest, but also for their many technological applications, especially biomedical applications, ranging from contrast agents for magnetic resonance imaging to the deterioration of cancer cells via hyperthermia treatment. The theoretical and experimental research has shown until now that the magnetic dipolar interactions between nanoparticles can have a significant influence on the magnetic behaviour of the system. But, this influence is not well understood. It is clear that the magnetic dipolar interaction intensity is correlated with the nanoparticle concentration, volume fraction and magnetic moment orientations. In this paper, we try to understand the influence of magnetic dipolar interactions on the behaviour of magnetic nanoparticle systems, for biomedical applications. For the model, we considered spherical nanoparticles with uniaxial anisotropy and lognormal distribution of the sizes. The model involves a simulation stage of the spatial distribution and orientation of the nanoparticles and their easy axes of magnetic anisotropy, and an evaluation stage of the Néel relaxation time. To assess the Néel relaxation time, we are going to discretise and adapt, to the local magnetic field, the Coffey analytical solution for the equation Fokker-Planck describing the dynamics of magnetic moments of nanoparticles in oblique external magnetic field. There are three fundamental aspects of interest in our studies on the magnetic nanoparticles: their spatial & orientational distributions, concentrations and sizes.

  3. Influence of magnetic field on the orientation of anisotropic magnetic particles at liquid interfaces.

    PubMed

    Newton, Bethany J; Brakke, Kenneth A; Buzza, D Martin A

    2014-12-21

    We study theoretically the influence of an external magnetic field on the orientation of an ellipsoidal magnetic particle adsorbed at a liquid interface. Using the finite element program Surface Evolver, we calculate the equilibrium meniscus shape around the ellipsoidal particle and its equilibrium tilt angle with respect to the undeformed interface θt when a magnetic field B is applied perpendicular to the interface. We find that as we increase field strength, θt increases and at a critical magnetic field Bc1 and tilt angle θc1, the particle undergoes a discontinuous transition to the 'perpendicular' orientation (θt = 90°). Our results agree qualitatively with the simplified theory of Bresme and Faraudo [F. Bresme and J. Faraudo, J. Phys.: Condens. Matter, 2007, 19, 375110] which assumes that the liquid interface is flat, while they agree quantitatively with recent lattice-Boltzmann simulations of Davies et al. [G. Davies et al., Soft Matter, 2014, 10, 6742] which account for the deformation of the liquid meniscus. We also show for the first time that upon reducing the external magnetic field, at a critical magnetic field Bc2 < Bc1, the particle undergoes a second discontinuous transition from the perpendicular orientation to a finite tilt angle θc2 < θc1. In other words, for micron-sized particles where the thermal energy kBT is negligible compared to the interfacial energy, the tilt angle vs. magnetic field curve exhibits hysteresis behaviour. Due to the higher degree of accuracy of the Surface Evolver method, we are able to analyse the behaviour of the particles near these orientational transitions accurately and study how the critical quantities Bc1, Bc2, θc1 and θc2 vary with particle aspect ratio and contact angle.

  4. Magnetic Properties of Bermuda Rise Sediments Controlled by Glacial Cycles During the Late Pleistocene

    NASA Astrophysics Data System (ADS)

    Roud, S.

    2015-12-01

    Sediments from ODP site 1063 (Bermuda Rise, North Atlantic) contain a high-resolution record of geomagnetic field behavior during the Brunhes Chron. We present rock magnetic data of the upper 160 mcd (<900 ka) from hole 1063D that show magnetic properties vary in concert with glacial cycles. Magnetite appears to be the main magnetic carrier in the carbonate-dominated interglacial horizons, yet exhibits contrasting grain size distributions depending on the redox state of the horizons. Higher contributions of single domain magnetite exist above the present day sulfate reduction zone (ca. 44 mcd) with relatively higher multidomain magnetite components below that likely arise from the partial dissolution of SD magnetite in the deeper, anoxic horizons. Glacial horizons on the other hand, characterized by enhanced terrigenous deposition, show no evidence for diagenetic dissolution but do indicate the presence of authigenic greigite close to glacial maxima (acquisition of gyro-remanence, strong magnetostatic interactions and SD properties). Glacial horizons contain hematite (maxima in HIRM and S-Ratio consistent with a reddish hue) and exhibit higher ARM anisotropy and pronounced sedimentary fabrics. We infer that post depositional processes affected the magnetic grain size and mineralogy of Bermuda rise sediments deposited during the late Pleistocene. Hematite concentration is interpreted to reflect primary terrigenous input that is likely derived from the Canadian Maritime Provinces. A close correlation between HIRM and magnetic foliation suggests that changes in sediment composition (terrigenous vs. marine biogenic) were accompanied by changes in the depositional processes at the site.

  5. Sex and menstrual cycle phase at encoding influence emotional memory for gist and detail.

    PubMed

    Nielsen, Shawn E; Ahmed, Imran; Cahill, Larry

    2013-11-01

    Sex influences on emotional memory have received increasing interest over the past decade. However, only a subset of this previous work explored the influence of sex on memory for central information (gist) and peripheral detail in emotional versus neutral contexts. Here we examined the influence of sex and menstrual cycle phase at encoding on memory for either an emotional or neutral story, specifically with respect to the retention of gist and peripheral detail. Healthy naturally cycling women and men viewed a brief, narrated, three-phase story containing neutral or emotionally arousing elements. One week later, participants received a surprise free recall test for story elements. The results indicate that naturally cycling women in the luteal (high hormone) phase of the menstrual cycle at encoding show enhanced memory for peripheral details, but not gist, when in the emotional compared with neutral stories (p<.05). In contrast, naturally cycling women in the follicular (low hormone) phase of the menstrual cycle at encoding did not show enhanced memory for gist or peripheral details in the emotional compared with neutral stories. Men show enhanced memory for gist, but not peripheral details, in the emotional versus neutral stories (p<.05). In addition, these sex influences on memory cannot be attributed to differences in attention or arousal; luteal women, follicular women, and men performed similarly on measures of attention (fixation time percentage) and arousal (pupil diameter changes) during the most arousing phase of the emotional story. These findings suggest that sex and menstrual cycle phase at encoding influence long term memory for different types of emotional information.

  6. Buffer influence on magnetic dead layer, critical current, and thermal stability in magnetic tunnel junctions with perpendicular magnetic anisotropy

    NASA Astrophysics Data System (ADS)

    Frankowski, Marek; Żywczak, Antoni; Czapkiewicz, Maciej; Zietek, Sławomir; Kanak, Jarosław; Banasik, Monika; Powroźnik, Wiesław; Skowroński, Witold; Checiński, Jakub; Wrona, Jerzy; Głowiński, Hubert; Dubowik, Janusz; Ansermet, Jean-Philippe; Stobiecki, Tomasz

    2015-06-01

    We present a detailed study of Ta/Ru-based buffers and their influence on features crucial from the point of view of applications of Magnetic Tunnel Junctions (MTJs) such as critical switching current and thermal stability. We study buffer/FeCoB/MgO/Ta/Ru and buffer/MgO/FeCoB/Ta/Ru layers, investigating the crystallographic texture, the roughness of the buffers, the magnetic domain pattern, the magnetic dead layer thickness, and the perpendicular magnetic anisotropy fields for each sample. Additionally, we examine the effect of the current induced magnetization switching for complete nanopillar MTJs with lateral dimensions of 270 × 180 nm. Buffer Ta 5/Ru 10/Ta 3 (thicknesses in nm), which has the thickest dead layer, exhibits a much larger thermal stability factor (63 compared to 32.5) while featuring a slightly lower critical current density value (1.25 MA/cm2 compared to 1.5 MA/cm2) than the buffer with the thinnest dead layer Ta 5/Ru 20/Ta 5. We can account for these results by considering the difference in damping which compensates for the difference in the switching barrier heights.

  7. Nonlinear analysis of brain activity in magnetic influenced Parkinson patients.

    PubMed

    Anninos, P A; Adamopoulos, A V; Kotini, A; Tsagas, N

    2000-01-01

    Magnetoencephalogram (MEG) recordings were obtained from the brain of patients suffering from Parkinson's disease (PD) using the Superconductive Quantum Interference Device (SQUID). For each patient the magnetic activity was recorded from a total of 64 points of the skull (32 points from each temporal lobe) as defined by a recording reference system, which is based on the 10-20 Electrode Placement System. Some of the recorded points were observed to exhibit abnormal rhythmic activity, characterized by high amplitudes and low frequencies. External magnetic stimulation (EMS) with intensity 1-7.5pT, and frequency the alpha-rhythm of the patient (8-13 Hz) was applied in the left-right temporal, frontal-occipital and vertex (2 minutes over each of the above regions) and the brain magnetic activity was recorded again. The application of the EMS resulted in rapid attenuation of the MEG activity of PD patients. Furthermore, chaotic dynamic methods were used, in order to estimate the correlation dimension D of the reconstructed phase spaces. The estimated values of D, in conjunction with the results derived from the other data analysis methods, strongly support the existence of low dimension chaotic structures in the dynamics of cortical activity of PD patients. In addition, the increased values of D of the MEG after the application of EMS when compared with the corresponding ones obtained from the MEGs prior to the EMS, suggest that the neural dynamics are strongly influenced by the application of EMS. PMID:11154103

  8. Influence of crop management on take-all development and disease cycles on winter wheat.

    PubMed

    Colbach, N; Lucas, P; Meynard, J M

    1997-01-01

    ABSTRACT Wheat was assessed at four crop growth stages for take-all (Gaeumannomyces graminis var. tritici) in a series of field trials that studied the effects of five wheat management practices: sowing date, plant density, nitrogen fertilizer dose and form, and removal/burial of cereal straw. An equation expressing disease level as a function of degree days was fitted to the observed disease levels. This equation was based on take-all epidemiology and depended on two parameters reflecting the importance of the primary and secondary infection cycles, respectively. Early sowing always increased disease frequency via primary infection cycle; its influence on the secondary cycle was variable. Primary infection and earliness of disease onset were increased by high density; however, at mid-season take-all was positively correlated to the root number per plant, which was itself negatively correlated to plant density. At late stages of development, neither plant density nor root number per plant had any influence on disease. A high nitrogen dose increased both take-all on seminal roots and severity of primary infection cycle but decreased take-all on nodal roots and secondary infection cycle. Ammonium (versus ammonium nitrate) fertilizer always decreased disease levels and infection cycles, whereas straw treatment (burial versus removal of straw from the previous cereal crop) had no influence.

  9. Influence of the Schwabe/Hale solar cycles on climate change during the Maunder Minimum

    NASA Astrophysics Data System (ADS)

    Miyahara, Hiroko; Yokoyama, Yusuke; Yamaguchi, Yasuhiko T.

    2010-02-01

    We have examined the variation of carbon-14 content in annual tree rings, and investigated the transitions of the characteristics of the Schwabe/Hale (11-year/22-year) solar and cosmic-ray cycles during the last 1200 years, focusing mainly on the Maunder and Spoerer minima and the early Medieval Maximum Period. It has been revealed that the mean length of the Schwabe/Hale cycles changes associated with the centennial-scale variation of solar activity level. The mean length of Schwabe cycle had been ~14 years during the Maunder Minimum, while it was ~9 years during the early Medieval Maximum Period. We have also found that climate proxy record shows cyclic variations similar to stretching/shortening Schwabe/Hale solar cycles in time, suggesting that both Schwabe and Hale solar cycles are playing important role in climate change. In this paper, we review the nature of Schwabe and Hale cycles of solar activity and cosmic-ray flux during the Maunder Minimum and their possible influence on climate change. We suggest that the Hale cycle of cosmic rays are amplified during the grand solar minima and thus the influence of cosmic rays on climate change is prominently recognizable during such periods.

  10. SOLAR MAGNETIC HELICITY INJECTED INTO THE HELIOSPHERE: MAGNITUDE, BALANCE, AND PERIODICITIES OVER SOLAR CYCLE 23

    SciTech Connect

    Georgoulis, M. K.; Rust, D. M.; Bernasconi, P. N.; Pevtsov, A. A.; Kuzanyan, K. M.

    2009-11-01

    Relying purely on solar photospheric magnetic field measurements that cover most of solar cycle 23 (1996-2005), we calculate the total relative magnetic helicity injected into the solar atmosphere, and eventually shed into the heliosphere, over the latest cycle. Large active regions dominate the helicity injection process with approx5.7 x 10{sup 45} Mx{sup 2} of total injected helicity. The net helicity injected is approx<1% of the above output. Peculiar active-region plasma flows account for approx80% of this helicity; the remaining approx20% is due to solar differential rotation. The typical helicity per active-region CME ranges between (1.8-7) x 10{sup 42} Mx{sup 2} depending on the CME velocity. Accounting for various minor underestimation factors, we estimate a maximum helicity injection of approx6.6 x 10{sup 45} Mx{sup 2} for solar cycle 23. Although no significant net helicity exists over both solar hemispheres, we recover the well-known hemispheric helicity preference, which is significantly enhanced by the solar differential rotation. We also find that helicity injection in the solar atmosphere is an inherently disorganized, impulsive, and aperiodic process.

  11. Synchronized Northern Hemisphere climate change and solar magnetic cycles during the Maunder Minimum.

    PubMed

    Yamaguchi, Yasuhiko T; Yokoyama, Yusuke; Miyahara, Hiroko; Sho, Kenjiro; Nakatsuka, Takeshi

    2010-11-30

    The Maunder Minimum (A.D. 1645-1715) is a useful period to investigate possible sun-climate linkages as sunspots became exceedingly rare and the characteristics of solar cycles were different from those of today. Here, we report annual variations in the oxygen isotopic composition (δ(18)O) of tree-ring cellulose in central Japan during the Maunder Minimum. We were able to explore possible sun-climate connections through high-temporal resolution solar activity (radiocarbon contents; Δ(14)C) and climate (δ(18)O) isotope records derived from annual tree rings. The tree-ring δ(18)O record in Japan shows distinct negative δ(18)O spikes (wetter rainy seasons) coinciding with rapid cooling in Greenland and with decreases in Northern Hemisphere mean temperature at around minima of decadal solar cycles. We have determined that the climate signals in all three records strongly correlate with changes in the polarity of solar dipole magnetic field, suggesting a causal link to galactic cosmic rays (GCRs). These findings are further supported by a comparison between the interannual patterns of tree-ring δ(18)O record and the GCR flux reconstructed by an ice-core (10)Be record. Therefore, the variation of GCR flux associated with the multidecadal cycles of solar magnetic field seem to be causally related to the significant and widespread climate changes at least during the Maunder Minimum.

  12. Supersubstorms (SML < -2500 nT): Magnetic storm and solar cycle dependences

    NASA Astrophysics Data System (ADS)

    Hajra, Rajkumar; Tsurutani, Bruce T.; Echer, Ezequiel; Gonzalez, Walter D.; Gjerloev, Jesper W.

    2016-08-01

    We study extremely intense substorms with SuperMAG AL (SML) peak intensities < -2500 nT ("supersubstorms"/SSSs) for the period from 1981 to 2012. The SSS events were often found to be isolated SML peaks and not statistical fluctuations of the indices. The SSSs occur during all phases of the solar cycle with the highest occurrence (3.8 year-1) in the descending phase. The SSSs exhibited an annual variation with equinoctial maximum altering between spring in solar cycle 22 and fall in solar cycle 23. The occurrence rate and strength of the SSSs did not show any strong relationship with the intensity of the associated geomagnetic storms. All SSS events were associated with strong southward interplanetary magnetic field Bs component. The Bs fields were part of interplanetary magnetic clouds in 46% and of interplanetary sheath fields in 54% of the cases. About 77% of the SSSs were associated with small regions of very high density solar wind plasma parcels or pressure pulses impinging upon the magnetosphere. Comments on how SSS events may cause power outages at Earth are discussed at the end of the paper.

  13. Influence on cell death of high frequency motion of magnetic nanoparticles during magnetic hyperthermia experiments

    NASA Astrophysics Data System (ADS)

    Hallali, N.; Clerc, P.; Fourmy, D.; Gigoux, V.; Carrey, J.

    2016-07-01

    Studies with transplanted tumors in animals and clinical trials have provided the proof-of-concept of magnetic hyperthermia (MH) therapy of cancers using iron oxide nanoparticles. Interestingly, in several studies, the application of an alternating magnetic field (AMF) to tumor cells having internalized and accumulated magnetic nanoparticles (MNPs) into their lysosomes can induce cell death without detectable temperature increase. To explain these results, among other hypotheses, it was proposed that cell death could be due to the high-frequency translational motion of MNPs under the influence of the AMF gradient generated involuntarily by most inductors. Such mechanical actions of MNPs might cause cellular damages and participate in the induction of cell death under MH conditions. To test this hypothesis, we developed a setup maximizing this effect. It is composed of an anti-Helmholtz coil and two permanent magnets, which produce an AMF gradient and a superimposed static MF. We have measured the MNP heating power and treated tumor cells by a standard AMF and by an AMF gradient, on which was added or not a static magnetic field. We showed that the presence of a static magnetic field prevents MNP heating and cell death in standard MH conditions. The heating power of MNPs in an AMF gradient is weak, position-dependent, and related to the presence of a non-zero AMF. Under an AMF gradient and a static field, no MNP heating and cell death were measured. Consequently, the hypothesis that translational motions could be involved in cell death during MH experiments is ruled out by our experiments.

  14. Influence of external magnetic field and magnetic-site dilution on the magnetic dynamics of a one-dimensional Tb(III)-radical complex.

    PubMed

    Li, Leilei; Liu, Shuang; Li, Han; Shi, Wei; Cheng, Peng

    2015-07-11

    A new Tb(III)-radical chain complex was synthesized and characterized, which exhibited two separate relaxation processes. The influence of external magnetic field and magnetic-site dilution on the magnetic dynamics of a one-dimensional Tb(III)-radical complex was studied.

  15. Influence of nuclear spin on chemical reactions: Magnetic isotope and magnetic field effects (A Review)

    PubMed Central

    Turro, Nicholas J.

    1983-01-01

    The course of chemical reactions involving radical pairs may depend on occurrence and orientation of nuclear spins in the pairs. The influence of nuclear spins is maximized when the radical pairs are confined to a space that serves as a cage that allows a certain degree of independent diffusional and rotational motion of the partners of the pair but that also encourages reencounters of the partners within a period which allows the nuclear spins to operate on the odd electron spins of the pair. Under the proper conditions, the nuclear spins can induce intersystem crossing between triplet and singlet states of radical pairs. It is shown that this dependence of intersystem crossing on nuclear spin leads to a magnetic isotope effect on the chemistry of radical pairs which provides a means of separating isotopes on the basis of nuclear spins rather than nuclear masses and also leads to a magnetic field effect on the chemistry of radical pairs which provides a means of influencing the course of polymerization by the application of weak magnetic fields. PMID:16593273

  16. MAGNETIC CYCLES IN GLOBAL LARGE-EDDY SIMULATIONS OF SOLAR CONVECTION

    SciTech Connect

    Ghizaru, Mihai; Charbonneau, Paul; Smolarkiewicz, Piotr K.

    2010-06-01

    We report on a global magnetohydrodynamical simulation of the solar convection zone, which succeeds in generating a large-scale axisymmetric magnetic component, antisymmetric about the equatorial plane and undergoing regular polarity reversals on decadal timescales. We focus on a specific simulation run covering 255 years, during which 8 polarity reversals are observed, with a mean period of 30 years. Time-latitude slices of the zonally averaged toroidal magnetic component at the base of the convecting envelope show a well-organized toroidal flux system building up in each solar hemisphere, peaking at mid-latitudes and migrating toward the equator in the course of each cycle, in remarkable agreement with inferences based on the sunspot butterfly diagram. The simulation also produces a large-scale dipole moment, varying in phase with the internal toroidal component, suggesting that the simulation may be operating as what is known in mean-field theory as an {alpha}{Omega} dynamo.

  17. Tuning of magnetic parameters in cobalt-polystyrene nanocomposites by reduction cycling

    SciTech Connect

    Nair, Swapna S.; Sunny, Vijutha; Anantharaman, M.R.

    2011-10-15

    Graphical abstract: Cobalt nanoparticles were prepared by a reduction process inside polymer pores. A porous polymer network (polystyrene) was chosen as the template for the synthesis of elementary cobalt as high surface area cobalt nanoparticles are prone to oxidation. The preliminary studies reveal that the cobalt is first formed with an oxide protective layer outside and upon repeating the reduction cycles, inner pores of the polymers are opened which enhanced the yield of metallic cobalt. These high surface area cobalt nanoparticles embedded in a polymer are ideal for the synthesis of carbon nanotubes as cobalt can act as a catalyst for the nanotube synthesis. The concentration of cobalt can be tuned in this technique by repeating the cycling process. Highlights: {yields} Elementary cobalt nanoparticles were synthesized inside polystyrene by a novel process. {yields} The self protection is achieved by the auto-shelling with the metal oxide. {yields} The magnetisation and coercivity could be tuned by repeating the cycles. {yields} Tuning of magnetic properties (both coercivity and magnetisation) could be achieved by the repetition of reduction cycles. {yields} Synthesized nanocomposite can act as a catalyst for carbon nanotube synthesis. -- Abstract: Cobalt nanoparticles were prepared by a reduction process inside polymer pores using CoSO{sub 4}.7H{sub 2}O and NaBH{sub 4}. A porous polymer network (sulphonated polystyrene) was chosen, as the template for the synthesis of elementary cobalt as high surface area cobalt nanoparticles are prone to oxidation. The preliminary studies reveal that the cobalt is first formed with an oxide protective layer outside and upon repeating the reduction cycles, inner pores of the polymers are opened which enhanced the yield of metallic cobalt. These high surface area cobalt nanoparticles embedded in a polymer are ideal for the synthesis of carbon nanotubes as cobalt can act as a catalyst for the nanotube synthesis. The

  18. Controlling Influence of Magnetic Field on Solar Wind Outflow: An Investigation using Current Sheet Source Surface Model

    NASA Astrophysics Data System (ADS)

    Poduval, B.

    2016-08-01

    This Letter presents the results of an investigation into the controlling influence of large-scale magnetic field of the Sun in determining the solar wind outflow using two magnetostatic coronal models: current sheet source surface (CSSS) and potential field source surface. For this, we made use of the Wang and Sheeley inverse correlation between magnetic flux expansion rate (FTE) and observed solar wind speed (SWS) at 1 au. During the period of study, extended over solar cycle 23 and beginning of solar cycle 24, we found that the coefficients of the fitted quadratic equation representing the FTE-SWS inverse relation exhibited significant temporal variation, implying the changing pattern of the influence of FTE on SWS over time. A particularly noteworthy feature is an anomaly in the behavior of the fitted coefficients during the extended minimum, 2008-2010 (CRs 2073-2092), which is considered due to the particularly complex nature of the solar magnetic field during this period. However, this variation was significant only for the CSSS model, though not a systematic dependence on the phase of the solar cycle. Further, we noticed that the CSSS model demonstrated better solar wind prediction during the period of study, which we attribute to the treatment of volume and sheet currents throughout the corona and the more accurate tracing of footpoint locations resulting from the geometry of the model.

  19. Controlling Influence of Magnetic Field on Solar Wind Outflow: An Investigation using Current Sheet Source Surface Model

    NASA Astrophysics Data System (ADS)

    Poduval, B.

    2016-08-01

    This Letter presents the results of an investigation into the controlling influence of large-scale magnetic field of the Sun in determining the solar wind outflow using two magnetostatic coronal models: current sheet source surface (CSSS) and potential field source surface. For this, we made use of the Wang and Sheeley inverse correlation between magnetic flux expansion rate (FTE) and observed solar wind speed (SWS) at 1 au. During the period of study, extended over solar cycle 23 and beginning of solar cycle 24, we found that the coefficients of the fitted quadratic equation representing the FTE–SWS inverse relation exhibited significant temporal variation, implying the changing pattern of the influence of FTE on SWS over time. A particularly noteworthy feature is an anomaly in the behavior of the fitted coefficients during the extended minimum, 2008–2010 (CRs 2073–2092), which is considered due to the particularly complex nature of the solar magnetic field during this period. However, this variation was significant only for the CSSS model, though not a systematic dependence on the phase of the solar cycle. Further, we noticed that the CSSS model demonstrated better solar wind prediction during the period of study, which we attribute to the treatment of volume and sheet currents throughout the corona and the more accurate tracing of footpoint locations resulting from the geometry of the model.

  20. Quasiperiodicity in cataclysmic variable stars caused by solar-type magnetic cycles

    NASA Technical Reports Server (NTRS)

    Warner, Brian

    1988-01-01

    Cyclical variations of orbital periods, quiescent magnitudes and outburst intervals in the activity of cataclysmic variable binary stars are inter-related and are ascribed to variations in radii of the secondaries, caused by solar-type (sunspot) magnetic cycles. In the nova remnant DQ Herculis the observed variations in orbital period and quiescent magnitude are consistent with this mechanism. But accretion onto the white dwarf, from an accretion disk acquired from its companion, cannot explain the observed variation of the 71-second oscillations.

  1. Influence of hydrogen on the magnetic properties of Terfenol-D

    NASA Astrophysics Data System (ADS)

    Angulo, L. Ruiz De; Abell, J. S.; Harris, I. R.

    1994-11-01

    The reactions with hydrogen of the C15-type Laves phase Tb0.27Dy0.73Fe2 have been studied by differential thermal analysis and the influence of this hydrogenation upon the magnetic properties was observed with Curie-Faraday balance and a vibrating sample magnetometer. It has been found that a slightly rare earth rich composition allows the hydrogenation to take place at room temperature. Two endothermic peaks observed on heating under 1.2 bar of hydrogen are attributed to hydrogen desorption, due possibly to the form of the pressure isotherms. At a pressure of 1.2 bar, the amorphization and disproportionation peaks are combined as a single peak, but a higher pressures these two phenomena separate into two peaks. After the first absorptio/desorption cycle, the hydrogenation occurs at temperatures as low as -75 C, and is highly exothermic and very rapid in nature. The magnetic susceptibility of the compound suffers a dramatic drop when it is hydrided, and the magnetization at 1100 kA/m falls from 77.5 J/T/kg to 9.2J/T/kg. When heated in hydrogen, a peak in susceptibility was observed at about the same temperatures as those of the amorphization/disproportionation reactions. The Curie point of the amorphous hydrided material was found to be around 68 C, with a magnetization at room temperature and 1100 kA/m of 46 J/T/kg. The fully disproportionated material had a magnetization of 82 J/T/kg at 1100 kA/m, which was related to the proportion of alpha-Fe formed during the disproportionation reaction.

  2. Influence of hydrogen on the magnetic properties of Terfenol-D

    NASA Astrophysics Data System (ADS)

    Ruiz de Angulo, L.; Abell, J. S.; Harris, I. R.

    1994-11-01

    The reactions with hydrogen of the C15-type Laves phase Tb0.27Dy0.73Fe2 have been studied by differential thermal analysis and the influence of this hydrogenation upon the magnetic properties was observed with a Curie-Faraday balance and a vibrating sample magnetometer. It has been found that a slightly rare earth rich composition allows the hydrogenation to take place at room temperature. Two endothermic peaks observed on heating under 1.2 bar of hydrogen are attributed to hydrogen desorption, due possibly to the form of the pressure isotherms. At a pressure of 1.2 bar, the amorphization and disproportionation peaks are combined as a single peak, but a higher pressures these two phenomena separate into two peaks. After the first absorption/desorption cycle, the hydrogenation occurs at temperatures as low as -75 °C, and is highly exothermic and very rapid in nature. The magnetic susceptibility of the compound suffers a dramatic drop when it is hydrided, and the magnetization at 1100 kA m-1 falls from 77.5 J T-1 kg-1 to 9.2 J T-1 kg-1. When heated in hydrogen, a peak in susceptibility was observed at about the same temperatures as those of the amorphization/disproportionation reactions. The Curie point of the amorphous hydrided material was found to be around 68 °C, with a magnetization at room temperature and 1100 kA m-1 of 46 J T-1 kg-1. The fully disproportionated material had a magnetization of 82 J T- kg-1 at 1100 kA m-1, which was related to the proportion of α-Fe formed during the disproportionation reaction.

  3. Influence of coupling of sorption and photosynthetic processes on trace element cycles in natural waters

    USGS Publications Warehouse

    Fuller, C.C.; Davis, J.A.

    1989-01-01

    Chemical and biological processes have important roles in the transport and cycling of trace elements in natural waters, but their complex interactions are often not well understood. Trace-element concentrations may, for example, be controlled by adsorption-desorption reactions at mineral surfaces, with the equilibrium strongly influenced by pH. Variations in pH due to photosynthetic activity should result in concentration fluctuations as the adsorption-desorption equilibrium shifts with pH. To investigate these interactions, we have studied the effect of diurnal cycling of pH on dissolved arsenate in a perennial stream contaminated with arsenic. As expected, a diurnal cycle in arsenate concentration was observed, but surprisingly, the arsenate cycle lags several hours behind the pH cycle. Laboratory experiments show that the lag results from a slow approach to sorption equilibrium. Our observations demonstrate that the coupling of photosynthesis and sorption processes may have an important influence on the cycling of many trace elements and emphasize the importance of understanding sorption kinetics in modelling these processes.

  4. Influences of surface coating, UV irradiation and magnetic field on the algae removal using magnetite nanoparticles.

    PubMed

    Ge, Shijian; Agbakpe, Michael; Wu, Zhiyi; Kuang, Liyuan; Zhang, Wen; Wang, Xianqin

    2015-01-20

    Magnetophoretic separation is a promising and sustainable technology for rapid algal separation or removal from water. This work demonstrated the application of magnetic magnetite nanoparticles (MNPs) coated with a cationic polymer, polyethylenimine (PEI), toward the separation of Scenedesmus dimorphus from the medium broth. The influences of surface coating, UV irradiation, and magnetic field on the magnetophoretic separation were systematically examined. After PEI coating, zeta potential of MNPs shifted from −7.9 ± 2.0 to +39.0 ± 3.1 mV at a pH of 7.0, which improved MNPs-algae interaction and helped reduce the dose demand of MNPs (e.g., from 0.2 to 0.1 g·g(–1) while the harvesting efficiency (HE) of over 80% remained unchanged). The extended Derjaguin–Landau–Verwey–Overbeek theory predicted a strong attractive force between PEI-coated MNPs and algae, which supported the improved algal harvesting. Moreover, the HE was greater under the UV365 irradiation than that under the UV254, and increased with the irradiation intensity. Continuous application of the external magnetic field at high strength remarkably improved the algal harvesting. Finally, the reuse of MNPs for multiple cycles of algal harvesting was studied, which aimed at increasing the sustainability and lowering the cost. PMID:25486124

  5. Influences of surface coating, UV irradiation and magnetic field on the algae removal using magnetite nanoparticles.

    PubMed

    Ge, Shijian; Agbakpe, Michael; Wu, Zhiyi; Kuang, Liyuan; Zhang, Wen; Wang, Xianqin

    2015-01-20

    Magnetophoretic separation is a promising and sustainable technology for rapid algal separation or removal from water. This work demonstrated the application of magnetic magnetite nanoparticles (MNPs) coated with a cationic polymer, polyethylenimine (PEI), toward the separation of Scenedesmus dimorphus from the medium broth. The influences of surface coating, UV irradiation, and magnetic field on the magnetophoretic separation were systematically examined. After PEI coating, zeta potential of MNPs shifted from −7.9 ± 2.0 to +39.0 ± 3.1 mV at a pH of 7.0, which improved MNPs-algae interaction and helped reduce the dose demand of MNPs (e.g., from 0.2 to 0.1 g·g(–1) while the harvesting efficiency (HE) of over 80% remained unchanged). The extended Derjaguin–Landau–Verwey–Overbeek theory predicted a strong attractive force between PEI-coated MNPs and algae, which supported the improved algal harvesting. Moreover, the HE was greater under the UV365 irradiation than that under the UV254, and increased with the irradiation intensity. Continuous application of the external magnetic field at high strength remarkably improved the algal harvesting. Finally, the reuse of MNPs for multiple cycles of algal harvesting was studied, which aimed at increasing the sustainability and lowering the cost.

  6. Influence of spherical assembly of copper ferrite nanoparticles on magnetic properties: orientation of magnetic easy axis.

    PubMed

    Chatterjee, Biplab K; Bhattacharjee, Kaustav; Dey, Abhishek; Ghosh, Chandan K; Chattopadhyay, Kalyan K

    2014-06-01

    The magnetic properties of copper ferrite (CuFe2O4) nanoparticles prepared via sol-gel auto combustion and facile solvothermal method are studied focusing on the effect of nanoparticle arrangement. Randomly oriented CuFe2O4 nanoparticles (NP) are obtained from the sol-gel auto combustion method, while the solvothermal method allows us to prepare iso-oriented uniform spherical ensembles of CuFe2O4 nanoparticles (NS). X-ray diffractometry (XRD), atomic absorption spectroscopy (AAS), infra-red (IR) spectroscopy, Raman spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), (57)Fe Mössbauer spectroscopy and vibrating sample magnetometer (VSM) are used to investigate the composition, microstructure and magnetic properties of as-prepared ferrite nanoparticles. The field-dependent magnetization measurement for the NS sample at low temperature exhibits a step-like rectangular hysteresis loop (M(R)/M(S) ~ 1), suggesting cubic anisotropy in the system, whereas for the NP sample, typical features of uniaxial anisotropy (M(R)/M(S) ~ 0.5) are observed. The coercive field (HC) for the NS sample shows anomalous temperature dependence, which is correlated with the variation of effective anisotropy (K(E)) of the system. A high-temperature enhancement of H(C) and K(E) for the NS sample coincides with a strong spin-orbit coupling in the sample as evidenced by significant modification of Cu/Fe-O bond distances. The spherical arrangement of nanocrystals at mesoscopic scale provokes a high degree of alignment of the magnetic easy axis along the applied field leading to a step-like rectangular hysteresis loop. A detailed study on the temperature dependence of magnetic anisotropy of the system is carried out, emphasizing the influence of the formation of spherical iso-oriented assemblies. PMID:24714977

  7. Peripheral nerve magnetic stimulation: influence of tissue non-homogeneity

    PubMed Central

    Krasteva, Vessela TZ; Papazov, Sava P; Daskalov, Ivan K

    2003-01-01

    Background Peripheral nerves are situated in a highly non-homogeneous environment, including muscles, bones, blood vessels, etc. Time-varying magnetic field stimulation of the median and ulnar nerves in the carpal region is studied, with special consideration of the influence of non-homogeneities. Methods A detailed three-dimensional finite element model (FEM) of the anatomy of the wrist region was built to assess the induced currents distribution by external magnetic stimulation. The electromagnetic field distribution in the non-homogeneous domain was defined as an internal Dirichlet problem using the finite element method. The boundary conditions were obtained by analysis of the vector potential field excited by external current-driven coils. Results The results include evaluation and graphical representation of the induced current field distribution at various stimulation coil positions. Comparative study for the real non-homogeneous structure with anisotropic conductivities of the tissues and a mock homogeneous media is also presented. The possibility of achieving selective stimulation of either of the two nerves is assessed. Conclusion The model developed could be useful in theoretical prediction of the current distribution in the nerves during diagnostic stimulation and therapeutic procedures involving electromagnetic excitation. The errors in applying homogeneous domain modeling rather than real non-homogeneous biological structures are demonstrated. The practical implications of the applied approach are valid for any arbitrary weakly conductive medium. PMID:14693034

  8. Influence of driving cycles on exhaust emissions and fuel consumption of gasoline passenger car in Bangkok.

    PubMed

    Nutramon, Tamsanya; Supachart, Chungpaibulpatana

    2009-01-01

    The influence of different driving cycles on their exhaust emissions and fuel consumption rate of gasoline passenger car was investigated in Bangkok based on the actual measurements obtained from a test vehicle driving on a standard chassis dynamometer. A newly established Bangkok driving cycle (BDC) and the European driving cycle (EDC) which is presently adopted as the legislative cycle for testing automobiles registered in Thailand were used. The newly developed BDC is constructed using the driving characteristic data obtained from the real on-road driving tests along selected traffic routes. A method for selecting appropriate road routes for real driving tests is also introduced. Variations of keyed driving parameters of BDC with different driving cycles were discussed. The results showed that the HC and CO emission factors of BDC are almost two and four times greater than those of EDC, respectively. Although the difference in the NOx emission factor is small, the value from BDC is still greater than that of EDC by 10%. Under BDC, the test vehicle consumes fuel about 25% more than it does under EDC. All these differences are mainly attributed to the greater proportion of idle periods and higher fluctuations of vehicle speed in the BDC cycle. This result indicated that the exhausted emissions and fuel consumption of vehicles obtained from tests under the legislative modal-type driving cycle (EDC) are significantly different from those actually produced under real traffic conditions especially during peak periods. PMID:20108661

  9. Rieger-type Periodicity during Solar Cycles 14–24: Estimation of Dynamo Magnetic Field Strength in the Solar Interior

    NASA Astrophysics Data System (ADS)

    Gurgenashvili, Eka; Zaqarashvili, Teimuraz V.; Kukhianidze, Vasil; Oliver, Ramon; Ballester, Jose Luis; Ramishvili, Giorgi; Shergelashvili, Bidzina; Hanslmeier, Arnold; Poedts, Stefaan

    2016-07-01

    Solar activity undergoes a variation over timescales of several months known as Rieger-type periodicity, which usually occurs near maxima of sunspot cycles. An early analysis showed that the periodicity appears only in some cycles and is absent in other cycles. But the appearance/absence during different cycles has not been explained. We performed a wavelet analysis of sunspot data from the Greenwich Royal Observatory and the Royal Observatory of Belgium during cycles 14–24. We found that the Rieger-type periods occur in all cycles, but they are cycle dependent: shorter periods occur during stronger cycles. Our analysis revealed a periodicity of 185–195 days during the weak cycles 14–15 and 24 and a periodicity of 155–165 days during the stronger cycles 16–23. We derived the dispersion relation of the spherical harmonics of the magnetic Rossby waves in the presence of differential rotation and a toroidal magnetic field in the dynamo layer near the base of the convection zone. This showed that the harmonics of fast Rossby waves with m = 1 and n = 4, where m (n) indicates the toroidal (poloidal) wavenumbers, perfectly fit with the observed periodicity. The variation of the toroidal field strength from weaker to stronger cycles may lead to the different periods found in those cycles, which explains the observed enigmatic feature of the Rieger-type periodicity. Finally, we used the observed periodicity to estimate the dynamo field strength during cycles 14–24. Our estimations suggest a field strength of ˜40 kG for the stronger cycles and ˜20 kG for the weaker cycles.

  10. The influence of the hydrologic cycle on the extent of sea ice with climatic implications

    NASA Technical Reports Server (NTRS)

    Dean, Ken; Gosink, Joan

    1991-01-01

    The role was analyzed of the hydrologic cycle on the distribution of sea ice, and its influence on forcings and fluxes between the marine environment and the atmosphere. River discharge plays a significant role in degrading the sea ice before any melting occurs elsewhere along the coast. The influence is considered of river discharge on the albedo, thermal balance, and distribution of sea ice. Quantitative atmospheric-hydrologic models are being developed to describe these processes in the coastal zone. Input for the models will come from satellite images, hydrologic data, and field observations. The resulting analysis provides a basis for the study of the significance of the hydrologic cycle throughout the Arctic Basin and its influence on the regional climate as a result of possible climatic scenarios. The area offshore from the Mackenzie River delta was selected as the study area.

  11. Hale cycle effects in cosmic ray east-west anisotropy and interplanetary magnetic field

    NASA Technical Reports Server (NTRS)

    Ahluwalia, H. S.

    1993-01-01

    We have reanalyzed diurnal anisotropy data obtained with the shielded ion chamber (IC) at Cheltenham/Fredericksburg and the neutron monitor (NM) at Swarthmore/Newark. IC data are for the 1936-1977 period and NM data are for the 1965-1988 period. We have corrected IC data for the diurnal temperature effect. Application of this correction results in a better agreement between IC and other data sets, thereby making it possible to study the long-term changes in the diurnal anisotropy using IC data. The behavior of the annual mean east-west anisotropy is studied for 53 years of observations. The period encompasses more than two solar magnetic (Hale) cycles. Its amplitude undergoes the expected 11 and 22 year variations, with the largest changes occurring near solar activity minima. Moreover, the data indicate the presence of the subsidiary maxima for the entire 53-year period, following the solar polar field reversals, during the declining phases of activity cycles when high-speed solar wind streams are present in the heliosphere. The data suggest that the amplitude of the subsidiary maximum is large when the solar polar magnetic field points toward the sun in the Northern Hemisphere, and radial anisotropy is absent.

  12. Environmental and organizational influences on magnet hospital recognition.

    PubMed

    Powers, Thomas L; Sanders, Tom J

    2013-01-01

    This article reports on research studying the influence of environmental and organizational factors on the adoption of the magnet hospital concept. Although research has been reported on the adoption of innovations by healthcare organizations, research on factors influencing the adoption of administrative advances remains an important area to investigate. Logistic regression was used to determine both the significance and direction of the association of environmental and organizational factors with innovation adoption. In addition, the size and type of the hospitals in the sample was used as a control variable. It was found for environmental factors that environmental complexity and community resources were associated with innovation adoption and that competition and network externalities were not. For the organizational factors examined, it was found that organizational complexity and control of domain were associated with innovation adoption. Slack resources and external communications were not associated with adoption. The findings from this study contribute to healthcare management research by enhancing the understanding of the innovation adoption process. The results have important implications for both healthcare providers and policy makers. PMID:24195343

  13. THE LATITUDE DISTRIBUTION OF SMALL-SCALE MAGNETIC ELEMENTS IN SOLAR CYCLE 23

    SciTech Connect

    Jin, C. L.; Wang, J. X. E-mail: wangjx@nao.cas.cn

    2012-01-20

    With the unique data set from full-disk observations provided by Michelson Doppler Imager on board the Solar and Heliospheric Observatory in the interval embodying solar cycle 23, we have found that the cyclic variations of numbers and total flux of these small-scale magnetic elements covering fluxes of (2.9-32.0) Multiplication-Sign 10{sup 18} Mx and (4.27-38.01) Multiplication-Sign 10{sup 19} Mx show anticorrelation and correlation with sunspots, respectively. In this study, the time-latitude distributions of these anticorrelated and correlated elements are analyzed. The following results are disclosed: (1) for the correlated elements, the cyclic variations of the total flux in low-latitude and middle-latitude regions show a longer duration of cyclic maximum phase than that of an active region (AR) in the corresponding latitude region; the total flux of these elements shows the accordant south-north asymmetry with that of AR; the time-latitude distribution of their number displays a similar butterfly diagram but with a latitude distribution that is twice as wide as that of sunspots. (2) For the anticorrelated elements, the time-latitude distribution of number shows a solar cycle variation different from the sunspot butterfly diagram; in each latitude, the distribution of anticorrelated elements always shows the anticorrelated variation with that of sunspots; during solar cycle 23, the average speed of the peak latitudinal migration for anticorrelated elements reaches 7.5 deg year{sup -1}, almost three times that for sunspots. These results seem to imply that the correlated elements are the debris of decayed sunspots, and the anticorrelated elements have a different source but are affected or modulated by sunspot magnetic field.

  14. Abnormal fb Es enhancements in equatorial Es layers during magnetic storms of solar cycle 23

    NASA Astrophysics Data System (ADS)

    Resende, L. C. A.; Denardini, C. M.; Batista, I. S.

    2013-09-01

    We have analyzed the behavior of blanketing frequency of the Es layer (fb Es) occurring at an equatorial station covering the days before, during and subsequent to 24 intense and very intense magnetic storms (Dst≤-100 nT) that occurred during the solar cycle 23. The fb Es was measured by digital ionosonde over São Luís, Brazil (2.33° S, 44.2° W, dip: -4.5°). Our analysis shows that there are significant changes in the fb Es, mainly during the recovery phase of magnetic storms, characterized by occurrence of peaks that exceed the ambient background values. Also, these peaks are associated to other types of sporadic E layer than the Esq (a non-blanketing layer detected due the plasma irregularities in the equatorial electrojet), which in turn means competing mechanisms. The results are discussed in terms of the statistics of the abnormal enhancement taking into account the phase of the magnetic storm.

  15. Rapid and Efficient Protein Digestion using Trypsin Coated Magnetic Nanoparticles under Pressure Cycles

    SciTech Connect

    Lee, Byoungsoo; Lopez-Ferrer, Daniel; Kim, Byoung Chan; Na, Hyon Bin; Park, Yong Il; Weitz, Karl K.; Warner, Marvin G.; Hyeon, Taeghwan; Lee, Sang-Won; Smith, Richard D.; Kim, Jungbae

    2011-01-01

    Trypsin-coated magnetic nanoparticles (EC-TR/NPs), prepared via a simple crosslinking of the enzyme to magnetic nanoparticles, were highly stable and could be easily captured using a magnet after the digestion was complete. EC-TR/NPs showed a negligible loss of trypsin activity after multiple uses and continuous shaking, while a control sample of covalently-attached trypsin on NPs resulted in a rapid inactivation under the same conditions due to the denaturation and autolysis of trypsin. Digestions were carried out on a single model protein, a five protein mixture, and a whole mouse brain proteome, and also compared for digestion at atmospheric pressure and 37 ºC for 12 h, and in combination with pressure cycling technology (PCT) at room temperature for 1 min. In all cases, the EC-TR/NPs performed equally as well or better than free trypsin in terms of the number of peptide/protein identifications and reproducibility across technical replicates. However, the concomitant use of EC-TR/NPs and PCT resulted in very fast (~1 min) and more reproducible digestions.

  16. Rapid and Efficient Protein Digestion using Trypsin Coated Magnetic Nanoparticles under Pressure Cycles

    PubMed Central

    Lee, Byoungsoo; Lopez-Ferrer, Daniel; Kim, Byoung Chan; Na, Hyon Bin; Park, Yong Il; Weitz, Karl K.; Warner, Marvin G.; Hyeon, Taeghwan; Lee, Sang-Won; Smith, Richard D.; Kim, Jungbae

    2011-01-01

    Trypsin-coated magnetic nanoparticles (EC-TR/NPs), prepared via a simple multilayer random crosslinking of the trypsin molecules onto magnetic nanoparticles, were highly stable and could be easily captured using a magnet after the digestion was complete. EC-TR/NPs showed a negligible loss of trypsin activity after multiple uses and continuous shaking, while the conventional immobilization of covalently-attached trypsin on NPs resulted in a rapid inactivation under the same conditions due to the denaturation and autolysis of trypsin. A single model protein, a five protein mixture, and a whole mouse brain proteome were digested at atmospheric pressure and 37 °C for 12 h or in combination with pressure cycling technology (PCT) at room temperature for 1 min. In all cases, EC-TR/NPs performed equally to or better than free trypsin in terms of both identified peptide/protein number and the digestion reproducibility. In addition, the concomitant use of EC-TR/NPs and PCT resulted in very rapid (~1 min) and efficient digestions with more reproducible digestion results. PMID:21204257

  17. Influence of estrous and circadian cycles on calcium intake of the rat.

    PubMed

    Voznesenskaya, Anna; Tordoff, Michael G

    2013-03-15

    The food, water and sodium intake of laboratory rats fluctuates over the circadian and estrous cycles. Blood calcium and calcium-regulating hormones also wax and wane in response to these cycles, raising the possibility that the same might be true of calcium intake. To investigate this, we monitored the fluid intakes of female Long-Evans rats given a choice between water and 10mM CaCl2 solution for two consecutive estrous cycles. We found that calcium solution intake changed over the circadian cycle in a similar manner to water intake; the preference scores for CaCl2 solution remained stable. We did not detect any changes in calcium solution intake or preference scores during the estrous cycle despite a decrease in fluid intake at estrus. Thus, fluctuations in intake of calcium solution during the circadian cycle appear to be nonspecific and probably the result of changes in fluid balance. Estrous changes either do not influence calcium intake or their effects are masked by other factors, resulting in stable levels of calcium intake.

  18. Solar and interplanetary signatures of declining of solar magnetic fields: Implications to the next solar cycle 25

    NASA Astrophysics Data System (ADS)

    Bisoi, Susanta Kumar; Janardhan, P.; Ananthakrishnan, S.; Tokumaru, M.; Fujiki, K.

    2015-08-01

    Our detailed study of solar surface magnetic fields at high-latitudes, using magnetic synoptic magnetograms of NSO/Kitt Peak observatory from 1975-2014, has shown a steady decline of the field strength since mid-1990's until mid-2014, i.e. the solar maximum of cycle 24. We also found that magnetic field strength at high-latitudes declines after each solar cycle maximum, and since cycle 24 is already past its peak implies that solar surface magnetic fields will be continuing to decline until solar minimum of cycle 24. In addition, interplanetary scintillation (IPS) measurements of solar wind micro-turbulence levels, from Solar and Terrestrial Environment Laboratory (STEL), Japan, have also shown a steady decline in sync with the declining surface fields. Even the heliospheric magnetic fields (HMF) at 1 AU have been declined much below the previously proposed floor level of HMF of ~4.6 nT. From study of a correlation between the high-latitude surface fields and the HMF at the last four solar minima we found a floor value of HMF of ~3.2 nT. Using the above correlation and the fact that the high-latitude surface fields is expected to decline until the minimum of cycle 24, we estimate the value of the HMF at the minimum of cycle 24 will be 3.8 ± 0.2 nT and the peak sunspot number for solar cycle 25 will be 56±12 suggesting a weak sunspot activity to be continued in cycle 25 too.

  19. Influence of duty cycle on the power-duration relationship: observations and potential mechanisms.

    PubMed

    Broxterman, R M; Ade, C J; Wilcox, S L; Schlup, S J; Craig, J C; Barstow, T J

    2014-02-01

    The highest sustainable rate of aerobic metabolism [critical power (CP)] and the finite amount of work that can be performed above CP (W' [curvature constant]) were determined under two muscle contraction duty cycles. Eight men completed at least three constant-power handgrip tests to exhaustion to determine CP and W' for 50% and 20% duty cycles, while brachial artery blood flow (Q̇BA) and deoxygenated-[hemoglobin + myoglobin] (deoxy-[Hb+Mb]) were measured. CP was lower for the 50% duty cycle (3.9 ± 0.9 W) than the 20% duty cycle (5.1 ± 0.8 W; p < 0.001), while W' was not significantly different (50% duty cycle: 452 ± 141 J vs. 20% duty cycle: 432 ± 130 J; p > 0.05). At the same power output, Q̇BA and deoxy-[Hb + Mb] achieved higher end-exercise values for the 20% duty cycle (9.87 ± 1.73 ml·s(-1); 51.7 ± 4.7 μM) than the 50% duty cycle (7.37 ± 1.76 ml·s(-1), p < 0.001; 44.3 ± 2.4 μM, p < 0.03). These findings indicate that blood flow influences CP, but not W'.

  20. Influence of Th2 cells on hair cycle/growth after repeated cutaneous application of hapten.

    PubMed

    Sugita, K; Nomura, T; Ikenouchi-Sugita, A; Ito, T; Nakamura, M; Miyachi, Y; Tokura, Y; Kabashima, K

    2014-03-01

    Exposure to contact allergens in order to produce allergic contact dermatitis (ACD) seems to induce hair cycle/growth, but the mechanism of this remains unclear. In the current study, we investigated this mechanism and found that repeated application of hapten induced production of interleukin (IL)-4 in lymph-node immune cells. In addition, hair growth was induced in mice after the adoptive transfer of T-helper (Th)2 cells that had been purified from mice exposed to repeated cutaneous application of hapten. These findings lead us to speculate that Th2 cells that are repeatedly hapten-sensitized are recruited to hapten-challenged skin areas, and thus stimulate the production of IL-4 in the vicinity of the hair follicles, which influences hair cycle/growth. Our results may provide fundamental insights into the mechanism of contact hypersensitivity-induced hair cycle/growth.

  1. Influence of age, reproductive cycling status, and menstruation on the vaginal microbiome in baboons (Papio anubis).

    PubMed

    Uchihashi, M; Bergin, I L; Bassis, C M; Hashway, S A; Chai, D; Bell, J D

    2015-05-01

    The vaginal microbiome is believed to influence host health by providing protection from pathogens and influencing reproductive outcomes such as fertility and gestational length. In humans, age-associated declines in diversity of the vaginal microbiome occur in puberty and persist into adulthood. Additionally, menstruation has been associated with decreased microbial community stability. Adult female baboons, like other non-human primates (NHPs), have a different and highly diverse vaginal microbiome compared to that of humans, which is most commonly dominated by Lactobacillus spp. We evaluated the influence of age, reproductive cycling status (cycling vs. non-cycling) and menstruation on the vaginal microbiome of 38 wild-caught, captive female olive baboons (Papio anubis) by culture-independent sequencing of the V3-V5 region of the bacterial 16S rRNA gene. All baboons had highly diverse vaginal microbial communities. Adult baboons had significantly lower microbial diversity in comparison to subadult baboons, which was attributable to decreased relative abundance of minor taxa. No significant differences were detected based on cycling state or menstruation. Predictive metagenomic analysis showed uniformity in relative abundance of metabolic pathways regardless of age, cycle stage, or menstruation, indicating conservation of microbial community functions. This study suggests that selection of an optimal vaginal microbial community occurs at puberty. Since decreased diversity occurs in both baboons and humans at puberty, this may reflect a general strategy for selection of adult vaginal microbial communities. Comparative evaluation of vaginal microbial community development and composition may elucidate mechanisms of community formation and function that are conserved across host species or across microbial community types. These findings have implications for host health, evolutionary biology, and microbe-host ecosystems.

  2. Influence of magnetic clouds on cosmic ray intensity variations

    NASA Technical Reports Server (NTRS)

    BADRUDDIN; Yadav, R. S.; Yadav, N. R.; Agrawal, S. P.

    1985-01-01

    Neutron monitor data has been analyzed to study the nature of galactic cosmic ray transient modulation associated with three types of interplanetary magnetic clouds - clouds associated with shocks, stream interfaces and cold magnetic enhancements.

  3. THE ACOUSTIC CUTOFF FREQUENCY OF THE SUN AND THE SOLAR MAGNETIC ACTIVITY CYCLE

    SciTech Connect

    Jimenez, A.; Palle, P. L.; Garcia, R. A.

    2011-12-20

    The acoustic cutoff frequency-the highest frequency for acoustic solar eigenmodes-is an important parameter of the solar atmosphere as it determines the upper boundary of the p-mode resonant cavities. At frequencies beyond this value, acoustic disturbances are no longer trapped but are traveling waves. Interference among them gives rise to higher-frequency peaks-the pseudomodes-in the solar acoustic spectrum. The pseudomodes are shifted slightly in frequency with respect to p-modes, making possible the use of pseudomodes to determine the acoustic cutoff frequency. Using data from the GOLF and VIRGO instruments on board the Solar and Heliospheric Observatory spacecraft, we calculate the acoustic cutoff frequency using the coherence function between both the velocity and intensity sets of data. By using data gathered by these instruments during the entire lifetime of the mission (1996 until the present), a variation in the acoustic cutoff frequency with the solar magnetic activity cycle is found.

  4. The influence of gouge and pressure cycling on permeability of macro-fracture in basalt

    NASA Astrophysics Data System (ADS)

    Wang, Guangzeng; Mitchell, Tom; Meredith, Philip; Wu, Zhiping

    2016-04-01

    Fractures are ubiquitous and allow crystalline rocks to store and transport fluids. But they are commonly filled with gouge-like materials and normally suffer from polyphasic evolution and multi-cycles of loading and unloading. Therefore, it's essential to investigate the influence of gouge and pressure cycling on transport properties (permeability here) of fracture. Here, we did several steady-state flow permeability measurements on a sample with 38mm diameter and length of Seljadur basalt, an intrusive basalt from SW Iceland with no visible cracks and exceptionally low initial permeability. First, using the Brazil disk technique, a macro-fracture was introduced in the sample, and baseline measurements on above unfilled macro-fractured sample under step-wise effective pressures from 5 up to 60 MPa and pressure cycling were done. Second, similar measurements were conducted on the same macro-fractured sample filled with 0.6mm thick artificial fault gouge (milled basalt) layer with the upper limit grain size of 63, 108, 125, 250, 500μm, respectively, to explore the influence of gouge grain size. Third, to investigate the influence of gouge thickness, measurements on the same sample with various thickness of gouge layers of 63 and 250μm were implemented, respectively. Forth, pressure cycling tests were done on 0.6mm thick 63, 125 and 250μm, respectively, to study the influence of pressure cycling. And at last, to understand compaction mechanism of the gouge, after tests, the thickness and grain size changes before and after tests were also measured. Results showed the adding of fine-grained (63μm here) gouge in fracture decreased its permeability significantly and barely changed with the increasing effective pressure and pressure cycles, while that filled with coarse-grained gouges (108-500μm, respectively) had very similar permeability, and gouge layers decreased its permeability under lower effective pressure, while increased its permeability instead by

  5. Features of influence of dc magnetic field pulses on a nuclear spin echo in magnets

    NASA Astrophysics Data System (ADS)

    Mamniashvili, G. I.; Gegechkori, T. O.; Akhalkatsi, A. M.; Gavasheli, C. A.

    2012-06-01

    Signal intensities of a two-pulse nuclear spin echo as a function of parameters of dc magnetic field pulses are measured in the series of materials: Li0.5Fe2.5-xZnxO4 (x < 0.25) (enriched in 57Fe isotope to 96.8%), NiMnSb, Co2MnSi, La1-хСахMnO3 (x = 0.2; 0.25) and polycrystalline Co. Two types of dependences of these signals on a supplying time of such pulses with respect to the times of the exciting RF pulses are found. The mechanisms of influence of a domain structure and a dynamic frequency shift on the observed features of the investigated signals are discussed.

  6. TWO NOVEL PARAMETERS TO EVALUATE THE GLOBAL COMPLEXITY OF THE SUN'S MAGNETIC FIELD AND TRACK THE SOLAR CYCLE

    SciTech Connect

    Zhao, L.; Landi, E.; Gibson, S. E.

    2013-08-20

    Since the unusually prolonged and weak solar minimum between solar cycles 23 and 24 (2008-2010), the sunspot number is smaller and the overall morphology of the Sun's magnetic field is more complicated (i.e., less of a dipole component and more of a tilted current sheet) compared with the same minimum and ascending phases of the previous cycle. Nearly 13 yr after the last solar maximum ({approx}2000), the monthly sunspot number is currently only at half the highest value of the past cycle's maximum, whereas the polar magnetic field of the Sun is reversing (north pole first). These circumstances make it timely to consider alternatives to the sunspot number for tracking the Sun's magnetic cycle and measuring its complexity. In this study, we introduce two novel parameters, the standard deviation (SD) of the latitude of the heliospheric current sheet (HCS) and the integrated slope (SL) of the HCS, to evaluate the complexity of the Sun's magnetic field and track the solar cycle. SD and SL are obtained from the magnetic synoptic maps calculated by a potential field source surface model. We find that SD and SL are sensitive to the complexity of the HCS: (1) they have low values when the HCS is flat at solar minimum, and high values when the HCS is highly tilted at solar maximum; (2) they respond to the topology of the HCS differently, as a higher SD value indicates that a larger part of the HCS extends to higher latitude, while a higher SL value implies that the HCS is wavier; (3) they are good indicators of magnetically anomalous cycles. Based on the comparison between SD and SL with the normalized sunspot number in the most recent four solar cycles, we find that in 2011 the solar magnetic field had attained a similar complexity as compared to the previous maxima. In addition, in the ascending phase of cycle 24, SD and SL in the northern hemisphere were on the average much greater than in the southern hemisphere, indicating a more tilted and wavier HCS in the north than

  7. Duty Cycling Influences Current Generation in Multi-Anode Environmental Microbial Fuel Cells

    SciTech Connect

    Gardel, EJ; Nielsen, ME; Grisdela, PT; Girguis, PR

    2012-05-01

    Improving microbial fuel cell (MFC) performance continues to be the subject of research, yet the role of operating conditions, specifically duty cycling, on MFC performance has been modestly addressed. We present a series of studies in which we use a 15-anode environmental MFC to explore how duty cycling (variations in the time an anode is connected) influences cumulative charge, current, and microbial composition. The data reveal particular switching intervals that result in the greatest time-normalized current. When disconnection times are sufficiently short, there is a striking decrease in current due to an increase in the overall electrode reaction resistance. This was observed over a number of whole cell potentials. Based on these results, we posit that replenishment of depleted electron donors within the biofilm and surrounding diffusion layer is necessary for maximum charge transfer, and that proton flux may be not limiting in the highly buffered aqueous phases that are common among environmental MFCs. Surprisingly, microbial diversity analyses found no discernible difference in gross community composition among duty cycling treatments, suggesting that duty cycling itself has little or no effect. Such duty cycling experiments are valuable in determining which factors govern performance of bioelectrochemical systems and might also be used to optimize field-deployed systems.

  8. Influence of creep damage on the low cycle thermal-mechanical fatigue behavior of two tantalum base alloys

    NASA Technical Reports Server (NTRS)

    Sheffler, K. D.; Doble, G. S.

    1972-01-01

    Low cycle fatigue tests have been performed on the tantalum base alloys T-111 and ASTAR 811C with synchronized, independently programmed temperature and strain cycling. The thermal-mechanical cycles applied fell into three basic categories: these were isothermal cycling, in-phase thermal cycling, and out-of-phase thermal cycling. In-phase cycling was defined as tensile deformation associated with high temperature and compressive deformation with low temperature, while out-of-phase thermal cycling was defined as the reverse case. The in-phase thermal cycling had a pronounced detrimental influence on the fatigue life of both alloys, with the life reduction being greater in the solid solution strengthened T-111 alloy than in the carbide strengthened ASTAR 811C alloy. The out-of-phase tests also showed pronounced effects on the fatigue life of both alloys, although not as dramatic.

  9. The influence of a magnetic field on the heat transfer of a magnetic nanofluid in a sinusoidal channel

    NASA Astrophysics Data System (ADS)

    Valiallah Mousavi, S.; Barzegar Gerdroodbary, M.; Sheikholeslami, Mohsen; Ganji, D. D.

    2016-09-01

    In this study, two dimensional numerical simulations are performed to investigate the influence of the magnetic field on the nanofluid flow inside a sinusoidal channel. This work reveals the influence of variable magnetic field in the heat transfer of heat exchanger while the mixture is in a single phase. In this heat exchanger, the inner tube is sinusoidal and the outer tube is considered smooth. The magnetic field is applied orthogonal to the axis of the sinusoidal tube. In our study, the ferrofluid (water with 4 vol% nanoparticles (Fe3O4)) flows in a channel with sinusoidal bottom. The finite volume method with the SIMPLEC algorithm is used for handling the pressure-velocity coupling. The numerical results present validated data with experimentally measured data and show good agreement with measurement. The influence of different parameters, like the intensity of magnetic field and Reynolds number, on the heat transfer is investigated. According to the obtained results, the sinusoidal formation of the internal tube significantly increases the Nusselt number inside the channel. Our findings show that the magnetic field increases the probability of eddy formation inside the cavities and consequently enhances the heat transfer (more than 200%) in the vicinity of the magnetic field at low Reynolds number ( Re=50). In addition, the variation of the skin friction shows that the magnetic field increases the skin friction (more than 600%) inside the sinusoidal channel.

  10. Influence of Segmentation of Ring-Shaped NdFeB Magnets with Parallel Magnetization on Cylindrical Actuators

    PubMed Central

    Eckert, Paulo Roberto; Goltz, Evandro Claiton; Filho, Aly Ferreira Flores

    2014-01-01

    This work analyses the effects of segmentation followed by parallel magnetization of ring-shaped NdFeB permanent magnets used in slotless cylindrical linear actuators. The main purpose of the work is to evaluate the effects of that segmentation on the performance of the actuator and to present a general overview of the influence of parallel magnetization by varying the number of segments and comparing the results with ideal radially magnetized rings. The analysis is first performed by modelling mathematically the radial and circumferential components of magnetization for both radial and parallel magnetizations, followed by an analysis carried out by means of the 3D finite element method. Results obtained from the models are validated by measuring radial and tangential components of magnetic flux distribution in the air gap on a prototype which employs magnet rings with eight segments each with parallel magnetization. The axial force produced by the actuator was also measured and compared with the results obtained from numerical models. Although this analysis focused on a specific topology of cylindrical actuator, the observed effects on the topology could be extended to others in which surface-mounted permanent magnets are employed, including rotating electrical machines. PMID:25051032

  11. Influence of segmentation of ring-shaped NdFeB magnets with parallel magnetization on cylindrical actuators.

    PubMed

    Eckert, Paulo Roberto; Goltz, Evandro Claiton; Flores Filho, Aly Ferreira

    2014-07-21

    This work analyses the effects of segmentation followed by parallel magnetization of ring-shaped NdFeB permanent magnets used in slotless cylindrical linear actuators. The main purpose of the work is to evaluate the effects of that segmentation on the performance of the actuator and to present a general overview of the influence of parallel magnetization by varying the number of segments and comparing the results with ideal radially magnetized rings. The analysis is first performed by modelling mathematically the radial and circumferential components of magnetization for both radial and parallel magnetizations, followed by an analysis carried out by means of the 3D finite element method. Results obtained from the models are validated by measuring radial and tangential components of magnetic flux distribution in the air gap on a prototype which employs magnet rings with eight segments each with parallel magnetization. The axial force produced by the actuator was also measured and compared with the results obtained from numerical models. Although this analysis focused on a specific topology of cylindrical actuator, the observed effects on the topology could be extended to others in which surface-mounted permanent magnets are employed, including rotating electrical machines.

  12. Magnetic properties of uncultivated magnetotactic bacteria and their contribution to a stratified estuary iron cycle.

    PubMed

    Chen, A P; Berounsky, V M; Chan, M K; Blackford, M G; Cady, C; Moskowitz, B M; Kraal, P; Lima, E A; Kopp, R E; Lumpkin, G R; Weiss, B P; Hesse, P; Vella, N G F

    2014-09-01

    Of the two nanocrystal (magnetosome) compositions biosynthesized by magnetotactic bacteria (MTB), the magnetic properties of magnetite magnetosomes have been extensively studied using widely available cultures, while those of greigite magnetosomes remain poorly known. Here we have collected uncultivated magnetite- and greigite-producing MTB to determine their magnetic coercivity distribution and ferromagnetic resonance (FMR) spectra and to assess the MTB-associated iron flux. We find that compared with magnetite-producing MTB cultures, FMR spectra of uncultivated MTB are characterized by a wider empirical parameter range, thus complicating the use of FMR for fossilized magnetosome (magnetofossil) detection. Furthermore, in stark contrast to putative Neogene greigite magnetofossil records, the coercivity distributions for greigite-producing MTB are fundamentally left-skewed with a lower median. Lastly, a comparison between the MTB-associated iron flux in the investigated estuary and the pyritic-Fe flux in the Black Sea suggests MTB play an important, but heretofore overlooked role in euxinic marine system iron cycle.

  13. Changes in voluntary activation assessed by transcranial magnetic stimulation during prolonged cycling exercise.

    PubMed

    Jubeau, Marc; Rupp, Thomas; Perrey, Stephane; Temesi, John; Wuyam, Bernard; Levy, Patrick; Verges, Samuel; Millet, Guillaume Y

    2014-01-01

    Maximal central motor drive is known to decrease during prolonged exercise although it remains to be determined whether a supraspinal deficit exists, and if so, when it appears. The purpose of this study was to evaluate corticospinal excitability and muscle voluntary activation before, during and after a 4-h cycling exercise. Ten healthy subjects performed three 80-min bouts on an ergocycle at 45% of their maximal aerobic power. Before exercise and immediately after each bout, neuromuscular function was evaluated in the quadriceps femoris muscles under isometric conditions. Transcranial magnetic stimulation was used to assess voluntary activation at the cortical level (VATMS), corticospinal excitability via motor-evoked potential (MEP) and intracortical inhibition by cortical silent period (CSP). Electrical stimulation of the femoral nerve was used to measure voluntary activation at the peripheral level (VAFNES) and muscle contractile properties. Maximal voluntary force was significantly reduced after the first bout (13 ± 9%, P<0.01) and was further decreased (25 ± 11%, P<0.001) at the end of exercise. CSP remained unchanged throughout the protocol. Rectus femoris and vastus lateralis but not vastus medialis MEP normalized to maximal M-wave amplitude significantly increased during cycling. Finally, significant decreases in both VATMS and VAFNES (∼ 8%, P<0.05 and ∼ 14%, P<0.001 post-exercise, respectively) were observed. In conclusion, reductions in VAFNES after a prolonged cycling exercise are partly explained by a deficit at the cortical level accompanied by increased corticospinal excitability and unchanged intracortical inhibition. When comparing the present results with the literature, this study highlights that changes at the cortical and/or motoneuronal levels depend not only on the type of exercise (single-joint vs. whole-body) but also on exercise intensity and/or duration. PMID:24586559

  14. The influence of cycling temperature and cycling rate on the phase specific degradation of a positive electrode in lithium ion batteries: A post mortem analysis

    NASA Astrophysics Data System (ADS)

    Darma, Mariyam Susana Dewi; Lang, Michael; Kleiner, Karin; Mereacre, Liuda; Liebau, Verena; Fauth, Francois; Bergfeldt, Thomas; Ehrenberg, Helmut

    2016-09-01

    The influence of cycling temperatures and cycling rates on the cycling stability of the positive electrode (cathode) of commercial batteries are investigated. The cathode is a mixture of LiMn2O4 (LMO), LiNi0.5Co0.2Mn0.3O2 (NCM) and LiNi0.8Co0.15Al0.05O2 (NCA). It is found that increasing the cycling temperature from 25 °C to 40 °C is detrimental to the long term cycling stability of the cathode. Contrastingly, the improved cycling stability is observed for the cathodes cycled at higher charge/discharge rate (2C/3C instead of 1C/2C). The microstructure analysis by X-ray powder diffraction reveals that a significant capacity fading and an increased overvoltage is observed for NCM and NCA in all the fatigued cathodes. After high number of cycling (above 1500 cycles), NCM becomes partially inactive. In contrast to NCM and NCA, LMO shows a good cycling stability at 25 °C. A pronounced degradation of LMO is only observed for the fatigued cathodes cycled at 40 °C. The huge capacity losses of NCM and NCA are most likely because the blended cathodes were cycled up to 4.12 V vs. the graphite anode during the cycle-life test (corresponds to 4.16 V vs. Li+/Li); which is beyond the stability limit of the layered oxides below 4.05 V vs. Li+/Li.

  15. A solar-like magnetic cycle on the mature K-dwarf 61 Cygni A (HD 201091)

    NASA Astrophysics Data System (ADS)

    Boro Saikia, S.; Jeffers, S. V.; Morin, J.; Petit, P.; Folsom, C. P.; Marsden, S. C.; Donati, J.-F.; Cameron, R.; Hall, J. C.; Perdelwitz, V.; Reiners, A.; Vidotto, A. A.

    2016-10-01

    Context. The long-term monitoring of magnetic cycles in cool stars is a key diagnostic in understanding how dynamo generation and amplification of magnetic fields occur in stars similar in structure to the Sun. Aims: We investigated the temporal evolution of a possible magnetic cycle of 61 Cyg A. The magnetic cycle is determined from 61 Cyg A's large-scale field over its activity cycle using spectropolarimetric observations and compared to the solar large-scale magnetic field. Methods: We used the tomographic technique of Zeeman Doppler imaging (ZDI) to reconstruct the large-scale magnetic geometry of 61 Cyg A over multiple observational epochs spread over a time span of nine years. We investigated the time evolution of the different components of the large-scale field and compared it with the evolution of the star's chromospheric activity by measuring the flux in three different chromospheric indicators: Ca II H&K, Hα and Ca II infrared triplet lines. We also compared our results with the star's coronal activity using XMM-Newton observations. Results: The large-scale magnetic geometry of 61 Cyg A exhibits polarity reversals in both poloidal and toroidal field components, in phase with its chromospheric activity cycle. We also detect weak solar-like differential rotation with a shear level similar to that of the Sun. During our observational time span of nine years, 61 Cyg A exhibits solar- like variations in its large-scale field geometry as it evolves from minimum activity to maximum activity and vice versa. During its activity minimum in epoch 2007.59, ZDI reconstructs a simple dipolar geometry which becomes more complex when it approaches activity maximum in epoch 2010.55. The radial field flips polarity and reverts back to a simple geometry in epoch 2013.61. The field is strongly dipolar and the evolution of the dipole component of the field is reminiscent of solar behaviour. The polarity reversal of the large-scale field indicates a magnetic cycle that is in

  16. Long periods (1 -10 mHz) geomagnetic pulsations variation with solar cycle in South Atlantic Magnetic Anomaly

    NASA Astrophysics Data System (ADS)

    Rigon Silva, Willian; Schuch, Nelson Jorge; Guimarães Dutra, Severino Luiz; Babulal Trivedi, Nalin; Claudir da Silva, Andirlei; Souza Savian, Fernando; Ronan Coelho Stekel, Tardelli; de Siqueira, Josemar; Espindola Antunes, Cassio

    The occurrence and intensity of the geomagnetic pulsations Pc-5 (2-7 mHz) and its relationship with the solar cycle in the South Atlantic Magnetic Anomaly -SAMA is presented. The study of geomagnetic pulsations is important to help the understanding of the physical processes that occurs in the magnetosphere region and help to predict geomagnetic storms. The fluxgate mag-netometers H, D and Z, three axis geomagnetic field data from the Southern Space Observatory -SSO/CRS/INPE -MCT, São Martinho da Serra (29.42° S, 53.87° W, 480m a.s.l.), RS, Brasil, a were analyzed and correlated with the solar wind parameters (speed, density and temperature) from the ACE and SOHO satellites. A digital filtering to enhance the 2-7 mHz geomagnetic pulsations was used. Five quiet days and five perturbed days in the solar minimum and in the solar maximum were selected for this analysis. The days were chosen based on the IAGA definition and on the Bartels Musical Diagrams (Kp index) for 2001 (solar maximum) and 2008 (solar minimum). The biggest Pc-5 amplitude averages differences between the H-component is 78,35 nT for the perturbed days and 1,60nT for the quiet days during the solar maximum. For perturbed days the average amplitude during the solar minimum is 8,32 nT, confirming a direct solar cycle influence in the geomagnetic pulsations intensity for long periods.

  17. The Influence of Free Space Environment in the Mission Life Cycle: Material Selection

    NASA Technical Reports Server (NTRS)

    Edwards, David L.; Burns, Howard D.; de Groh, Kim K.

    2014-01-01

    The natural space environment has a great influence on the ability of space systems to perform according to mission design specification. Understanding the natural space environment and its influence on space system performance is critical to the concept formulation, design, development, and operation of space systems. Compatibility with the natural space environment is a primary factor in determining the functional lifetime of the space system. Space systems being designed and developed today are growing in complexity. In many instances, the increased complexity also increases its sensitivity to space environmental effects. Sensitivities to the natural space environment can be tempered through appropriate design measures, material selection, ground processing, mitigation strategies, and/or the acceptance of known risks. The design engineer must understand the effects of the natural space environment on the space system and its components. This paper will discuss the influence of the natural space environment in the mission life cycle with a specific focus on the role of material selection.

  18. Evolution of a metastable phase with a magnetic phase coexistence phenomenon and its unusual sensitivity to magnetic field cycling in the alloys Tb(5 - x)Lu(x)Si3 (x ≤ 0.7).

    PubMed

    Mukherjee, K; Iyer, Kartik K; Sampathkumaran, E V

    2011-05-25

    Recently, we reported an anomalous enhancement of the positive magnetoresistance beyond a critical magnetic field in Tb(5)Si(3) in the magnetically ordered state, attributable to 'inverse metamagnetism'. This results in unusual magnetic hysteresis loops for the pressurized specimens, which are relevant to the topic of 'electronic phase separation'. In this paper, we report the influence of small substitutions of Lu for Tb, to show the evolution of these magnetic anomalies. We find that, at low temperatures, the high-field high-resistivity phase could be partially stabilized on returning the magnetic field to zero in many of these Lu substituted alloys, as measured through the electrical resistivity (ρ). Also, the relative fractions of this phase and the virgin phase appear to be controlled by a small tuning of the composition and temperature. Interestingly, at 1.8 K a sudden 'switch-over' of the value of ρ for this mixed phase to that for the virgin phase for some compositions is observed at low fields after a few field cycles, indicating metastability of this mixed phase.

  19. Influence of oblique magnetic field on electron cross-field transport in a Hall effect thruster

    SciTech Connect

    Miedzik, Jan; Daniłko, Dariusz; Barral, Serge

    2015-04-15

    The effects of the inclination of the magnetic field with respect to the channel walls in a Hall effect thruster are numerically studied with the use of a one-dimensional quasi-neutral Particle-In-Cell model with guiding center approximation of electron motion along magnetic lines. Parametric studies suggest that the incidence angle strongly influences electron transport across the magnetic field. In ion-focusing magnetic topologies, electrons collide predominantly on the side of the magnetic flux tube closer to the anode, thus increasing the electron cross-field drift. The opposite effect is observed in ion-defocussing topology.

  20. Influence of magnetic field on activity of given anaerobic sludge.

    PubMed

    Xu, Y B; Duan, X J; Yan, J N; Du, Y Y; Sun, S Y

    2009-11-01

    Two modes of magnetic fields were applied in the Cr(6+) removal sludge reactors containing two predominated strains--Bacillus sp. and Brevibacillus sp., respectively. The magnetic field mode I* of 0-4.5 or 0-14 mT between pieces was obtained by setting the magnetic pieces with the surface magnetic density of 0-6 or 0-20 mT into the reactor, and the magnetic field mode II* of 6, 20, or 40 mT on the return line was obtained by controlling the working distance of the permanent magnet outside the sludge return line. The effects of different magnetic fields on the activity of the given anaerobic sludge were studied by comparing with the control (absent of magnetic field). The results showed that the magnetic field of 0-4 mT improved the activity of given sludge most effectively, U(max) CH(4) (the peak methane-producing rate) and the methane producing volume per gCOD(Cr) reached 64.3 mlCH(4)/gVSS.d and 124 mlCH(4)/gCOD(Cr), which increased by 20.6 and 70.7%, respectively, compared with the control. And the magnetic field of 20 mT took second place. It could be concluded that the input of some magnetic field could improve the activity of anaerobic sludge by increasing the transformation efficiency of COD(Cr) matters to methane, and the total organic wastage did not increase.

  1. Environmental cycling of cellulosic thermal insulation and its influence on fire performance

    SciTech Connect

    Lawson, J.R.

    1984-08-01

    A study was conducted on climatological data for eleven cities located throughout the United States. Findings from this environmental study were used to develop conditioning cycles for a research project on the influence of environments on the fire performance of loose-fill cellulosic thermal insulation. Six cellulosic insulation materials with different compositions of fire retardant chemicals at an add-on level of 25% by weight were specially manufactured for this study. These materials were tested for fire performance using the smoldering combustion test and the attic flooring radiant panel test to establish a baseline. After the materials were exposed to the various environmental cycles, they were tested for fire performance. Results from these tests show that environmental exposure can have a significant effect on the fire performance of cellulosic insulation materials and indicates that long term fire protection provided by fire retardant compounds may be limited.

  2. Influence parameters of martensitic transformation during low cycle fatigue for steel AISI 321

    NASA Astrophysics Data System (ADS)

    Grosse, M.; Kalkhof, D.; Keller, L.; Schell, N.

    2004-07-01

    The volume fraction of martensite continuously increases with the fatigue cycle number. Consequently, the martensite amount can be used for indication of the low cycle fatigue state. Following an exponential decay function, the martensite volume fraction decreases with increasing temperature. No influence of the load frequency was found. The initial material state plays an important role for the martensite formation rate. The amount of martensite formed is much higher after cold-rolling than after solution annealing as final manufacturing process. The martensite shows a fibre texture in the annealed material. The (1 1 0) planes are preferentially oriented parallel and perpendicular to the loading direction. In the cold-rolled material no significant preferred orientation of this phase was found. The martensite is concentrated in the centre of the specimens. The shape of the distribution seems to be independent on the martensite amount.

  3. Correlation of the Global Photospheric Magnetic Field Structure with the Latitudinal Sunspot Distribution in the solar cycles 23

    NASA Astrophysics Data System (ADS)

    Gavryuseva, E.; Zharkov, S.; Zharkova, V.

    begin table htbp begin center begin tabular p 442pt hline begin itemize item We compare a basic topology of large scale solar magnetic field with newline the distribution of the sunspot activity in latitude and newline in time in the past 2 solar cycles newline The large scale magnetic fields were composed from the data of WSO observatory the sunspot characteristics we extracted for the cycle 23 from the Solar Feature Catalogues underline http solar inf brad ac uk newline newline The magnetic field variations reveal a 4-zonal structure with 22-year periodicity and running waves through the solar latitudes with the two years periods The results are compared with the sunspot latitudinal variations in time and cumulitative variations in the butterfly diagrams The comparison results are used to explain the double peaks and variable character of the solar activity that can be used for its modelling and prediction end itemize hline end tabular label tab6 end center end table

  4. The influence of magnetic field on electron beam generated plasmas

    NASA Astrophysics Data System (ADS)

    Petrov, G. M.; Boris, D. R.; Lock, E. H.; Petrova, Tz B.; Fernsler, R. F.; Walton, S. G.

    2015-06-01

    Magnetically confined argon plasma in a long cylindrical tube driven by an electron beam is studied experimentally and theoretically. Langmuir probes are used to measure the electron energy distribution function, electron density and temperature in plasmas generated by 2 keV, 10 mA electron beams in a 25 mTorr argon background for magnetic field strengths of up to 200 Gauss. The experimental results agree with simulations done using a spatially averaged Boltzmann model adapted to treat an electron beam generated plasma immersed in a constant magnetic field. The confining effect of the magnetic field is studied theoretically using fluid and kinetic approaches. The fluid approach leads to two regimes of operation: weakly and strongly magnetized. The former is similar to the magnetic field-free case, while in the latter the ambipolar diffusion coefficient and electron density depend quadratically on the magnetic field strength. Finally, a more rigorous kinetic treatment, which accounts for the impact of the magnetic field over the whole distribution of electrons, is used for accurate description of the plasma.

  5. Detection of Polonium-210 on Spirit Dust Magnets and Implications for the Global Martian Dust Cycle

    NASA Astrophysics Data System (ADS)

    Wong, R.; Meslin, P.; Sabroux, J.; Madsen, M. B.; Pineau, J.; Richon, P.

    2013-12-01

    The radioactivity of airborne aerosols, which originates from the attachment of radionuclides produced by radon disintegration, Galactic Cosmic Rays (GCR) or anthropogenic activities, especially fallouts from nuclear weapons testing, can be used to measure the residence time of these aerosols in the atmosphere and their deposition rate. It is also used to characterize soils erosion rates (Matissof et al., 2002) or to investigate the origin of desert rock varnish (Hodge et al., 2005), to name only a few terrestrial applications. A translation of these nuclear methods to the Martian atmosphere, which is characterized by a very active dust cycle, is tempting, and has the potential to offer a unique insight into the present-day recycling of the Martian surface. This approach is made possible by two facts: 1) the presence of radon in the Martian atmosphere, which produces long-lived radioactive decay products, in particular polonium-210, and whose abundance can be indirectly inferred by gamma ray spectrometry from orbit using Mars Odyssey Gamma Ray Spectrometer (GRS) (Meslin et al., 2012); 2) the presence at the surface of Mars of two Alpha Particle X-Ray Spectrometers (APXS), onboard Opportunity and Spirit Mars Exploration Rovers, whose energy range (in the alpha mode) very fortuitously happens to include the energy of alpha particles emitted by the decay of polonium-210. The long half-life of this radionuclide is such that it is almost entirely attached to the particles that have been in suspension in the atmosphere, especially those characterized by a large specific surface area or by a long atmospheric residence time. It can therefore be used as a tracer of the dust cycle. An analysis of the alpha spectra acquired on the dust Capture and Filter magnets of the Spirit rover confirms results obtained by Meslin et al. (2006) that the Martian dust is radioactive w/r to polonium-210, thereby extending Opportunity's result to a global scale. This result enables us to

  6. Characterizing and modeling magnetic flux transport in the sun's photosphere and determining its impact on the sunspot cycle

    NASA Astrophysics Data System (ADS)

    Upton, Lisa A.

    The characterization and modeling of magnetic flux transport within the surface layers of the Sun are vital to explaining the sunspot cycle. The Sun's polar fields at solar cycle minimum are the seeds of the next solar cycle: weak polar fields produce weak cycles. Magnetic flux transport is key to the buildup of the polar fields and the subsequent magnetic reversals that are essential to modulating the sunspot cycle. The primary goals of this dissertation are threefold: 1. Make precise measurements of the Sun's axisymmetric flows (i.e., differential rotation and meridional flow). 2. Create a realistic surface flux transport model that reproduces the magnetic field evolution at the surface by incorporating the observed flows. 3. Investigate the role of flux transport in modulating the polar fields, and thereby the solar activity cycle. This work has been done in collaboration with Dr. David H. Hathaway of NASA Marshall Space Flight Center. In Chapter 1, I provide an introduction to the Sun as a star. I begin with a discussion on stellar structure and evolution. I then discuss the techniques and instruments that have been used to study the Sun. I conclude Chapter 1 with a section on magnetic activity cycles on the Sun and in other stars. Magnetic flux on the Sun is transported by supergranular flows and the axisymmetric flows of differential rotation (DR) and meridional flow (MF). In Chapter 2, I introduce these flows. I then show a derivation of the Surface Flux Transport equation starting from Maxwell's equations and Ohm's Law. I conclude this chapter with an introduction to prior Surface Flux Transport models. In Chapter 3, I discuss a cross-correlation technique that we have used on magnetograms (maps of the magnetic field strengths over the surface of the Sun) to characterize the DR and MF and their variations from 1996 to present. Results show that while variability in DR is negligible, the MF varies in two fundamental ways: over the course of a solar cycle and

  7. Vagus Nerve Stimulation Applied with a Rapid Cycle Has More Profound Influence on Hippocampal Electrophysiology Than a Standard Cycle.

    PubMed

    Larsen, Lars E; Wadman, Wytse J; Marinazzo, Daniele; van Mierlo, Pieter; Delbeke, Jean; Daelemans, Sofie; Sprengers, Mathieu; Thyrion, Lisa; Van Lysebettens, Wouter; Carrette, Evelien; Boon, Paul; Vonck, Kristl; Raedt, Robrecht

    2016-07-01

    Although vagus nerve stimulation (VNS) is widely used, therapeutic mechanisms and optimal stimulation parameters remain elusive. In the present study, we investigated the effect of VNS on hippocampal field activity and compared the efficiency of different VNS paradigms. Hippocampal electroencephalography (EEG) and perforant path dentate field-evoked potentials were acquired before and during VNS in freely moving rats, using 2 VNS duty cycles: a rapid cycle (7 s on, 18 s off) and standard cycle (30 s on, 300 s off) and various output currents. VNS modulated the evoked potentials, reduced total power of the hippocampal EEG, and slowed the theta rhythm. In the hippocampal EEG, theta (4-8 Hz) and high gamma (75-150 Hz) activity displayed strong phase amplitude coupling that was reduced by VNS. Rapid-cycle VNS had a greater effect than standard-cycle VNS on all outcome measures. Using rapid cycle VNS, a maximal effect on EEG parameters was found at 300 μA, beyond which effects saturated. The findings suggest that rapid-cycle VNS produces a more robust outcome than standard cycle VNS and support already existing preclinical evidence that relatively low output currents are sufficient to produce changes in brain physiology and thus likely also therapeutic efficacy. PMID:27102987

  8. Vagus Nerve Stimulation Applied with a Rapid Cycle Has More Profound Influence on Hippocampal Electrophysiology Than a Standard Cycle.

    PubMed

    Larsen, Lars E; Wadman, Wytse J; Marinazzo, Daniele; van Mierlo, Pieter; Delbeke, Jean; Daelemans, Sofie; Sprengers, Mathieu; Thyrion, Lisa; Van Lysebettens, Wouter; Carrette, Evelien; Boon, Paul; Vonck, Kristl; Raedt, Robrecht

    2016-07-01

    Although vagus nerve stimulation (VNS) is widely used, therapeutic mechanisms and optimal stimulation parameters remain elusive. In the present study, we investigated the effect of VNS on hippocampal field activity and compared the efficiency of different VNS paradigms. Hippocampal electroencephalography (EEG) and perforant path dentate field-evoked potentials were acquired before and during VNS in freely moving rats, using 2 VNS duty cycles: a rapid cycle (7 s on, 18 s off) and standard cycle (30 s on, 300 s off) and various output currents. VNS modulated the evoked potentials, reduced total power of the hippocampal EEG, and slowed the theta rhythm. In the hippocampal EEG, theta (4-8 Hz) and high gamma (75-150 Hz) activity displayed strong phase amplitude coupling that was reduced by VNS. Rapid-cycle VNS had a greater effect than standard-cycle VNS on all outcome measures. Using rapid cycle VNS, a maximal effect on EEG parameters was found at 300 μA, beyond which effects saturated. The findings suggest that rapid-cycle VNS produces a more robust outcome than standard cycle VNS and support already existing preclinical evidence that relatively low output currents are sufficient to produce changes in brain physiology and thus likely also therapeutic efficacy.

  9. Influence of the female sexual cycle on BALB/c mouse calling behaviour during mating

    NASA Astrophysics Data System (ADS)

    Barthelemy, Mathieu; Gourbal, Benjamin E. F.; Gabrion, Claude; Petit, Gilles

    Real-time recording technology was used in this study to analyse calling activity during heterosexual encounters in BALB/c mice. The spectrographic analyses revealed distinct types of calls that could be linked to a precise pre-ejaculatory behavioural sequence. In addition, the oestrous cycle of the female was observed to influence the vocalization emission pattern. The recording technology used in this study provides numerous improvements in the characterization description of mice calling behaviour during mating and is expected to be useful in studies of vocal communication in many rodent species.

  10. Diode magnetic-field influence on radiographic spot size

    SciTech Connect

    Ekdahl, Carl A. Jr.

    2012-09-04

    Flash radiography of hydrodynamic experiments driven by high explosives is a well-known diagnostic technique in use at many laboratories. The Dual-Axis Radiography for Hydrodynamic Testing (DARHT) facility at Los Alamos was developed for flash radiography of large hydrodynamic experiments. Two linear induction accelerators (LIAs) produce the bremsstrahlung radiographic source spots for orthogonal views of each experiment ('hydrotest'). The 2-kA, 20-MeV Axis-I LIA creates a single 60-ns radiography pulse. For time resolution of the hydrotest dynamics, the 1.7-kA, 16.5-MeV Axis-II LIA creates up to four radiography pulses by slicing them out of a longer pulse that has a 1.6-{micro}s flattop. Both axes now routinely produce radiographic source spot sizes having full-width at half-maximum (FWHM) less than 1 mm. To further improve on the radiographic resolution, one must consider the major factors influencing the spot size: (1) Beam convergence at the final focus; (2) Beam emittance; (3) Beam canonical angular momentum; (4) Beam-motion blur; and (5) Beam-target interactions. Beam emittance growth and motion in the accelerators have been addressed by careful tuning. Defocusing by beam-target interactions has been minimized through tuning of the final focus solenoid for optimum convergence and other means. Finally, the beam canonical angular momentum is minimized by using a 'shielded source' of electrons. An ideal shielded source creates the beam in a region where the axial magnetic field is zero, thus the canonical momentum zero, since the beam is born with no mechanical angular momentum. It then follows from Busch's conservation theorem that the canonical angular momentum is minimized at the target, at least in principal. In the DARHT accelerators, the axial magnetic field at the cathode is minmized by using a 'bucking coil' solenoid with reverse polarity to cancel out whatever solenoidal beam transport field exists there. This is imperfect in practice, because of

  11. Influence of external magnetic field on dynamics of open quantum systems

    SciTech Connect

    Kalandarov, Sh. A.; Kanokov, Z.; Adamian, G. G.; Antonenko, N. V.

    2007-03-15

    The influence of an external magnetic field on the non-Markovian dynamics of an open two-dimensional quantum system is investigated. The fluctuations of collective coordinate and momentum and transport coefficients are studied for a charged harmonic oscillator linearly coupled to a neutral bosonic heat bath. It is shown that the dissipation of collective energy slows down with increasing strength of the external magnetic field. The role of magnetic field in the diffusion processes is illustrated by several examples.

  12. Influence of Y substitutions on the magnetism of Gd5Ge4

    SciTech Connect

    Paudyal, Durga; Mudryk, Y.; Pecharsky, V.K.; Misra, S.; Miller, G.J.; and Gschneidner, Jr., K.A.

    2010-04-21

    The interrelation between the specific crystallographic positions and their influence on the magnetism of neighboring atoms is examined from first principles electronic structure calculations using the Gd{sub 5}Ge{sub 4} compound as a model system. The predicted preferences of the specific occupations by nonmagnetic yttrium atoms and the resulting magnetism of substituted Gd{sub 5}Ge{sub 4} have been confirmed, respectively, by single crystal x-ray diffraction and magnetization experiments.

  13. The solar wind structure and heliospheric magnetic field in the solar Cycle 23-24 minimum and in the increasing phase of Cycle 24

    NASA Astrophysics Data System (ADS)

    Gibson, S. E.; Zhao, L.; Fisk, L. A.

    2011-12-01

    The solar wind structure and the heliospheric magnetic field were substantially different in the latest solar minimum between solar Cycle 23 and 24 from the previous minimum. Compared with the previous minimum, in the latest solar minimum, the heliospheric magnetic field strength was substantially reduced; the streamer-associated-low-temperature solar wind (streamer-stalk wind) was distributed in a narrower region relative to the heliospheric current sheet (HCS); the slow-proton-speed solar wind was scattered in a wider latitudinal region; and there are more large and steady coronal holes at low latitude. We offer an explanation for the decreased magnetic-field strength and the narrowed streamer-stalk wind based on an analysis of the Ulysses and ACE in-situ observations. Solar-wind composition data are used to demonstrate that there are two distinct structures of solar wind: solar wind likely to originate from the stalk of the streamer belt (the highly elongated loops that underlie the HCS), and solar wind from outside this region. The region outside the streamer-stalk region is noticeably larger in the Cycle 23-24 minimum; however, the increased area can account for the reduction in the heliospheric magnetic-field strength in that minimum. Thus, the total magnetic flux contained in this region is the same in the two minima. To have a further understanding of the solar wind structure and its solar source, we ballistically map the ACE in-situ observation back along a radial trajectory from 1 AU to the solar source surface (r = 2.5Rsun) using the observed proton speeds. Then we track the field line from the source surface to the solar surface using a potential-field-source-surface (PFSS) extrapolation model. So the ACE observations, including the heliospheric magnetic field, the solar wind compositional and dynamic properties at 1AU, can be connected to their coronal sources on the solar surface. Synoptic maps showing this connection will be provided, and based on

  14. Influence of magnetic fields on structural martensitic transitions

    SciTech Connect

    Lashley, J C; Cooley, J C; Smith, J L; Fisher, R A; Modic, K A; Yang, X- D; Riseborough, P S; Opeil, C P; Finlayson, T R; Goddard, P A; Silhanek, A V

    2009-01-01

    We show evidence that a structural martensitic transition is related to significant changes in the electronic structure, as revealed in thermodynamic measurements made in high-magnetic fields. The magnetic field dependence is considered unusual as many influential investigations of martensitic transitions have emphasized that the structural transitions are primarily lattice dynamical and are driven by the entropy due to the phonons. We provide a theoretical framework which can be used to describe the effect of magnetic field on the lattice dynamics in which the field dependence originates from the dielectric constant.

  15. THE INFLUENCE OF MAGNETIC FIELDS ON INHIBITION OF MCF-7 CELL GROWTH BY TAMOXIFEN

    EPA Science Inventory

    THE INFLUENCE OF MAGNETIC FIELDS ON INHIBITION OF MCF-7 CELL GROWTH BY TAMOXIFEN.
    Harland and Liburdy (1) reported that 1.2-uT, 60-Hz magnetic fields could significantly block the inhibitory action of pharmacological levels of tamoxifen (10-7 M) on the growth of MCF-7 human br...

  16. Influence Of Nanoparticles Diameter On Structural Properties Of Magnetic Fluid In Magnetic Field

    NASA Astrophysics Data System (ADS)

    Kúdelčík, Jozef; Bury, Peter; Hardoň, Štefan; Kopčanský, Peter; Timko, Milan

    2015-07-01

    The properties of magnetic fluids depend on the nanoparticle diameter, their concentration and the carrier liquid. The structural changes in magnetic fluids with different nanoparticle diameter based on transformer oils TECHNOL and MOGUL under the effect of a magnetic field and temperature were studied by acoustic spectroscopy. At a linear and jump changes of the magnetic field at various temperatures a continuous change was observed of acoustic attenuation caused by aggregation of the magnetic nanoparticles to structures. From the anisotropy of acoustic attenuation and using the Taketomi theory the basic parameters of the structures are calculated and the impact of nanoparticle diameters on the size of structures is confirmed.

  17. Influence of 60-Hz magnetic fields on sea urchin development

    SciTech Connect

    Zimmerman, S.; Zimmerman, A.M.; Winters, W.D.; Cameron, I.L. )

    1990-01-01

    Continuous exposure of sea urchin (Strongylocentrotus purpuratus) embryos at 18 degrees C to a cyclic 60-Hz magnetic field at 0.1 mT rms beginning 4 min after insemination caused a significant developmental delay during the subsequent 23 hours. No delay in development was recorded for periods up to 18 hours after fertilization. At 18 h, most embryos were in the mesenchyme blastula stage. At 23 h, most control embryos were in mid-gastrula whereas most magnetic-field-exposed embryos were in the early gastrula stage. Thus an estimated 1-h delay occurred between these developmental stages. The results are discussed in terms of possible magnetic-field modification of transcription as well as interference with cell migration during gastrulation. The present study extends and supports the growing body of information about potential effects of exposures to extremely-low-frequency (ELF) magnetic fields on developing organisms.

  18. Coronal Rain in Magnetic Arcades: Rebound Shocks, Limit Cycles, and Shear Flows

    NASA Astrophysics Data System (ADS)

    Fang, X.; Xia, C.; Keppens, R.; Van Doorsselaere, T.

    2015-07-01

    We extend our earlier multidimensional, magnetohydrodynamic simulations of coronal rain occurring in magnetic arcades with higher resolution, grid-adaptive computations covering a much longer (>6 hr) time span. We quantify how blob-like condensations forming in situ grow along and across field lines and show that rain showers can occur in limit cycles, here demonstrated for the first time in 2.5D setups. We discuss dynamical, multi-dimensional aspects of the rebound shocks generated by the siphon inflows and quantify the thermodynamics of a prominence-corona transition-region-like structure surrounding the blobs. We point out the correlation between condensation rates and the cross-sectional size of loop systems where catastrophic cooling takes place. We also study the variations of the typical number density, kinetic energy, and temperature while blobs descend, impact, and sink into the transition region. In addition, we explain the mechanisms leading to concurrent upflows while the blobs descend. As a result, there are plenty of shear flows generated with relative velocity difference around 80 km s-1 in our simulations. These shear flows are siphon flows set up by multiple blob dynamics and they in turn affect the deformation of the falling blobs. In particular, we show how shear flows can break apart blobs into smaller fragments, within minutes.

  19. Determining diffusion coefficients of ionic liquids by means of field cycling nuclear magnetic resonance relaxometry

    NASA Astrophysics Data System (ADS)

    Kruk, D.; Meier, R.; Rachocki, A.; Korpała, A.; Singh, R. K.; Rössler, E. A.

    2014-06-01

    Field Cycling Nuclear Magnetic Resonance (FC NMR) relaxation studies are reported for three ionic liquids: 1-ethyl-3- methylimidazolium thiocyanate (EMIM-SCN, 220-258 K), 1-butyl-3-methylimidazolium tetrafluoroborate (BMIM-BF4, 243-318 K), and 1-butyl-3-methylimidazolium hexafluorophosphate (BMIM-PF6, 258-323 K). The dispersion of 1H spin-lattice relaxation rate R1(ω) is measured in the frequency range of 10 kHz-20 MHz, and the studies are complemented by 19F spin-lattice relaxation measurements on BMIM-PF6 in the corresponding frequency range. From the 1H relaxation results self-diffusion coefficients for the cation in EMIM-SCN, BMIM-BF4, and BMIM-PF6 are determined. This is done by performing an analysis considering all relevant intra- and intermolecular relaxation contributions to the 1H spin-lattice relaxation as well as by benefiting from the universal low-frequency dispersion law characteristic of Fickian diffusion which yields, at low frequencies, a linear dependence of R1 on square root of frequency. From the 19F relaxation both anion and cation diffusion coefficients are determined for BMIM-PF6. The diffusion coefficients obtained from FC NMR relaxometry are in good agreement with results reported from pulsed- field-gradient NMR. This shows that NMR relaxometry can be considered as an alternative route of determining diffusion coefficients of both cations and anions in ionic liquids.

  20. CORONAL RAIN IN MAGNETIC ARCADES: REBOUND SHOCKS, LIMIT CYCLES, AND SHEAR FLOWS

    SciTech Connect

    Fang, X.; Xia, C.; Keppens, R.; Doorsselaere, T. Van

    2015-07-10

    We extend our earlier multidimensional, magnetohydrodynamic simulations of coronal rain occurring in magnetic arcades with higher resolution, grid-adaptive computations covering a much longer (>6 hr) time span. We quantify how blob-like condensations forming in situ grow along and across field lines and show that rain showers can occur in limit cycles, here demonstrated for the first time in 2.5D setups. We discuss dynamical, multi-dimensional aspects of the rebound shocks generated by the siphon inflows and quantify the thermodynamics of a prominence–corona transition-region-like structure surrounding the blobs. We point out the correlation between condensation rates and the cross-sectional size of loop systems where catastrophic cooling takes place. We also study the variations of the typical number density, kinetic energy, and temperature while blobs descend, impact, and sink into the transition region. In addition, we explain the mechanisms leading to concurrent upflows while the blobs descend. As a result, there are plenty of shear flows generated with relative velocity difference around 80 km s{sup −1} in our simulations. These shear flows are siphon flows set up by multiple blob dynamics and they in turn affect the deformation of the falling blobs. In particular, we show how shear flows can break apart blobs into smaller fragments, within minutes.

  1. Determining diffusion coefficients of ionic liquids by means of field cycling nuclear magnetic resonance relaxometry.

    PubMed

    Kruk, D; Meier, R; Rachocki, A; Korpała, A; Singh, R K; Rössler, E A

    2014-06-28

    Field Cycling Nuclear Magnetic Resonance (FC NMR) relaxation studies are reported for three ionic liquids: 1-ethyl-3- methylimidazolium thiocyanate (EMIM-SCN, 220-258 K), 1-butyl-3-methylimidazolium tetrafluoroborate (BMIM-BF4, 243-318 K), and 1-butyl-3-methylimidazolium hexafluorophosphate (BMIM-PF6, 258-323 K). The dispersion of (1)H spin-lattice relaxation rate R1(ω) is measured in the frequency range of 10 kHz-20 MHz, and the studies are complemented by (19)F spin-lattice relaxation measurements on BMIM-PF6 in the corresponding frequency range. From the (1)H relaxation results self-diffusion coefficients for the cation in EMIM-SCN, BMIM-BF4, and BMIM-PF6 are determined. This is done by performing an analysis considering all relevant intra- and intermolecular relaxation contributions to the (1)H spin-lattice relaxation as well as by benefiting from the universal low-frequency dispersion law characteristic of Fickian diffusion which yields, at low frequencies, a linear dependence of R1 on square root of frequency. From the (19)F relaxation both anion and cation diffusion coefficients are determined for BMIM-PF6. The diffusion coefficients obtained from FC NMR relaxometry are in good agreement with results reported from pulsed- field-gradient NMR. This shows that NMR relaxometry can be considered as an alternative route of determining diffusion coefficients of both cations and anions in ionic liquids.

  2. Construction and calibration of a 12 T pulsed magnet integrated with a 4 K closed-cycle refrigerator.

    PubMed

    Murthy, O V S N; Venkataraman, V

    2007-11-01

    A low cost 12 T pulsed magnet system has been integrated with a closed-cycle helium refrigerator for performing magnetotransport measurements. Minimal delay between pulses and ac current excitation with software lock-in to reduce noise enables quick but accurate measurements to be performed at temperatures of 4-300 K up to 12 T. An additional pulsed magnet operating with a liquid nitrogen cryostat extends the range up to 19 T. The instrument has been calibrated against a commercial superconducting magnet by comparing quantum Hall effect data in a p-channel SiGe/Si heterostructure, and common issues arising out of pulsed magnet usage have been addressed. The versatility of the system is demonstrated through magnetotransport measurements in a variety of samples such as heterostructures, narrow gap semiconductors, and those exhibiting giant magnetoresistance.

  3. Influence of temperature difference calculation method on the evaluation of Rankine cycle performance

    NASA Astrophysics Data System (ADS)

    Morisaki, Takafumi.; Ikegami, Yasuyuki.

    2014-02-01

    In the new century, energy and environmental problems are becoming more critical, and the development of natural energy is desired. Low-grade Thermal Energy Conversion (LTEC) is refocused as one of the renewable energy methods. The usefulness of LTEC is expected using hot springs and waste heat. In the case of the Rankine cycle using ammonia as the working fluid, the thermal properties of the working fluid changes in the evaporator. The traditional evaluation method of heat exchanger performance is the LMTD (Logarithmic Mean Temperature Difference) method. On the other hand, the GMTD (Generalized Mean Temperature Difference) method allows the variation of thermal properties in the heat exchanger. The aim of this study is to compare the two methods for the calculation of temperature differences and the corresponding influence on the total performance of the Rankine cycle that is operated using ammonia as a working fluid. As a result, the thermal efficiency of the Rankine cycle is greater than that of the LMTD method. Moreover, the computable range of the GMTD calculation method is less than that of the LMTD calculation method.

  4. The influence of gender and the estrous cycle on learned helplessness in the rat.

    PubMed

    Jenkins, J A; Williams, P; Kramer, G L; Davis, L L; Petty, F

    2001-11-01

    Although the etiology of clinical depression is unknown, women are more likely to suffer from major depressive disorder than men. In addition, in some women, there is a clear association between depression and specific phases of the menstrual cycle. Surprisingly little research has examined gender differences and the influences of the estrous cycle in this and other animal behavioral models of clinical depression. Learned helplessness is a valid animal model of stress-induced behavioral depression in which prior exposure to inescapable stress produces deficits in escape testing. Learned helplessness was studied in rats using an inescapable tail shock stress followed by a shuttle box test to determine escape latencies. Animals with mean escape latencies of >or=20 s after shuttle-box testing are defined as learned helpless. Males and normal cycling female rats in the estrus and diestrus II phases were studied. Female rats in the diestrus II phase had significantly higher escape latencies and exhibited a more helpless behavior than female rats in the estrus phase. Male rat escape latencies were intermediate between the two female phases. These results suggest a role for gonadal hormones in the development of stress-induced behavioral depression or 'learned helplessness.'

  5. The female menstrual cycle does not influence testosterone concentrations in male partners

    PubMed Central

    2012-01-01

    Background The time of ovulation has since long been believed to be concealed to male heterosexual partners. Recent studies have, however, called for revision of this notion. For example, male testosterone concentrations have been shown to increase in response to olfactory ovulation cues, which could be biologically relevant by increasing sexual drive and aggressiveness. However, this phenomenon has not previously been investigated in real-life human settings. We therefore thought it of interest to test the hypothesis that males' salivary testosterone concentrations are influenced by phases of their female partners' menstrual cycle; expecting a testosterone peak at ovulation. Methods Thirty young, healthy, heterosexual couples were recruited. During the course of 30-40 days, the women registered menses and ovulation, while the men registered sexual activity, physical exercise, alcohol intake and illness (confounders), and obtained daily saliva samples for testosterone measurements. All data, including the registered confounders, were subjected to multiple regression analysis. Results In contrast to the hypothesis, the ovulation did not affect the testosterone levels, and the resulting testosterone profile during the menstrual cycle was on the average flat. The specific main hypothesis, that male testosterone levels on the day of ovulation would be higher than day 4 of the cycle, was clearly contradicted by a type II error(β)-analysis (< 14.3% difference in normalized testosterone concentration; β = 0.05). Conclusions Even though an ovulation-related salivary testosterone peak was observed in individual cases, no significant effect was found on a group level. PMID:22214343

  6. Temperature and Cyanobacterial Bloom Biomass Influence Phosphorous Cycling in Eutrophic Lake Sediments

    PubMed Central

    Chen, Mo; Ye, Tian-Ran; Krumholz, Lee R.; Jiang, He-Long

    2014-01-01

    Cyanobacterial blooms frequently occur in freshwater lakes, subsequently, substantial amounts of decaying cyanobacterial bloom biomass (CBB) settles onto the lake sediments where anaerobic mineralization reactions prevail. Coupled Fe/S cycling processes can influence the mobilization of phosphorus (P) in sediments, with high releases often resulting in eutrophication. To better understand eutrophication in Lake Taihu (PRC), we investigated the effects of CBB and temperature on phosphorus cycling in lake sediments. Results indicated that added CBB not only enhanced sedimentary iron reduction, but also resulted in a change from net sulfur oxidation to sulfate reduction, which jointly resulted in a spike of soluble Fe(II) and the formation of FeS/FeS2. Phosphate release was also enhanced with CBB amendment along with increases in reduced sulfur. Further release of phosphate was associated with increases in incubation temperature. In addition, CBB amendment resulted in a shift in P from the Fe-adsorbed P and the relatively unreactive Residual-P pools to the more reactive Al-adsorbed P, Ca-bound P and organic-P pools. Phosphorus cycling rates increased on addition of CBB and were higher at elevated temperatures, resulting in increased phosphorus release from sediments. These findings suggest that settling of CBB into sediments will likely increase the extent of eutrophication in aquatic environments and these processes will be magnified at higher temperatures. PMID:24682039

  7. Influence of suction cycles on the soil fabric of compacted swelling soil

    NASA Astrophysics Data System (ADS)

    Nowamooz, Hossein; Masrouri, Farimah

    2010-12-01

    The soil fabric plays an important role in complex hydromechanical behaviour of the expansive soils. This article addresses the influence of the wetting and drying paths on the soil fabric of compacted bentonite and silt mixtures at two different initial dry densities corresponding to loose and dense states. To obtain the hydric response of the soil, two suction imposition techniques were used: osmotic technique for the suction range less than 8.5 MPa and the vapour equilibrium or the salt solution technique for the suction range between 8.5 and 287.9 MPa. Additionally, the soil fabric analysis was performed using mercury intrusion porosimetry (MIP) and nitrogen gas adsorption (BET) techniques. The dense samples produced cumulative swelling strains during the suction cycles, while shrinkage was observed for the loose samples. The suction cycles induced an equilibrium state indicative of the elastic behaviour of the samples. The soil fabric analysis showed that regardless of the soil's initial state (loose or dense), the samples obtained the same soil fabric at the equilibrium state. The experimental results illustrated also the existence of an elastic void ratio ( e0el) where the compacted soils at this state present an elastic hydric behaviour during the successive suction cycles.

  8. Temperature and cyanobacterial bloom biomass influence phosphorous cycling in eutrophic lake sediments.

    PubMed

    Chen, Mo; Ye, Tian-Ran; Krumholz, Lee R; Jiang, He-Long

    2014-01-01

    Cyanobacterial blooms frequently occur in freshwater lakes, subsequently, substantial amounts of decaying cyanobacterial bloom biomass (CBB) settles onto the lake sediments where anaerobic mineralization reactions prevail. Coupled Fe/S cycling processes can influence the mobilization of phosphorus (P) in sediments, with high releases often resulting in eutrophication. To better understand eutrophication in Lake Taihu (PRC), we investigated the effects of CBB and temperature on phosphorus cycling in lake sediments. Results indicated that added CBB not only enhanced sedimentary iron reduction, but also resulted in a change from net sulfur oxidation to sulfate reduction, which jointly resulted in a spike of soluble Fe(II) and the formation of FeS/FeS2. Phosphate release was also enhanced with CBB amendment along with increases in reduced sulfur. Further release of phosphate was associated with increases in incubation temperature. In addition, CBB amendment resulted in a shift in P from the Fe-adsorbed P and the relatively unreactive Residual-P pools to the more reactive Al-adsorbed P, Ca-bound P and organic-P pools. Phosphorus cycling rates increased on addition of CBB and were higher at elevated temperatures, resulting in increased phosphorus release from sediments. These findings suggest that settling of CBB into sediments will likely increase the extent of eutrophication in aquatic environments and these processes will be magnified at higher temperatures.

  9. Light/dark cycle manipulation influences mice behaviour in the elevated plus maze.

    PubMed

    Clénet, Florence; Bouyon, Eric; Hascoët, Martine; Bourin, Michel

    2006-01-01

    The sensitization of animal models of anxiety is of great importance to detect potential anxiolytic drugs. Our goal was to evaluate the influence of manipulations of the light/dark cycle on the basal anxious behaviour of mice and the efficacy of two anxiolytic treatments in the mouse elevated plus maze (EPM). Male Swiss mice were exposed to different conditions of illumination for one week prior to testing. In the first experiment of the study, we evaluated the anxiolytic effects of diazepam, at the dose of 1 mg/kg, intraperitoneally (i.p.) administered 30 min before the test. In the second experiment, we examined the effects of WAY 100635, a 5-HT(1A) receptor antagonist, at the doses of 0.03 and 2 mg/kg, i.p. administered 30 min before the test. The locomotor activity of control mice and the anxiolytic efficacy of diazepam in the EPM were not affected by manipulation of the light/dark cycle. Conversely, the effects of WAY 100635, which were qualitatively different from those of diazepam, seemed to be influenced by the illumination conditions imposed before the test. We can conclude that diazepam's effect, which is characterized by a strong "disinhibition", was more robust than the 5-HT(1A) antagonist's effect, which was more anxioselective. Moreover, the light conditions imposed on mice before the test may be an important factor in the variability of the response to serotonergic but not to benzodiazepine treatments.

  10. Influence of cycle variability and coital frequency on the risk of pregnancy.

    PubMed

    Steiner, M J; Hertz-Picciotto, I; Raymond, E; Trussell, J; Wheeless, A; Schoenbach, V

    1999-09-01

    Researchers have cautioned against generalizing results from contraceptive trials because these studies rely on self-selected participants meeting strict selection criteria who may differ from typical users. Using information collected on daily diaries, we reanalyzed data from the recently completed Reality female condom clinical trial to evaluate factors that influence the probability of pregnancy. Noncompliant women, women with less variable menstrual cycles (17-43 days), and women engaging in intercourse frequently (> or = 11 acts per month) were more likely to conceive during this 6-month trial. The adjusted hazard ratios and 95% confidence intervals for these three covariates were 6.1 (2.0-18.7), 7.2 (1.0-54.3), and 2.0 (0.7-5.3), respectively. The strict selection criteria used in this study failed to recruit a homogeneous cohort with respect to factors that influence the risk of pregnancy. The overall pregnancy rate does not pertain to individual study participants, but rather represent average effects for a population with the particular mix of characteristics found in this study. In particular, we not only confirm the well known importance of compliance and the obvious role of frequency of intercourse, but also demonstrate that women with cycles outside the range of 17-43 days appear to be at a much lower risk of pregnancy.

  11. Three-dimensional Features of the Outer Heliosphere due to Coupling between the Interstellar and Interplanetary Magnetic Fields. IV. Solar Cycle Model Based on Ulysses Observations

    NASA Astrophysics Data System (ADS)

    Pogorelov, N. V.; Suess, S. T.; Borovikov, S. N.; Ebert, R. W.; McComas, D. J.; Zank, G. P.

    2013-07-01

    The solar cycle has a profound influence on the solar wind (SW) interaction with the local interstellar medium (LISM) on more than one timescales. Also, there are substantial differences in individual solar cycle lengths and SW behavior within them. The presence of a slow SW belt, with a variable latitudinal extent changing within each solar cycle from rather small angles to 90°, separated from the fast wind that originates at coronal holes substantially affects plasma in the inner heliosheath (IHS)—the SW region between the termination shock (TS) and the heliopause (HP). The solar cycle may be the reason why the complicated flow structure is observed in the IHS by Voyager 1. In this paper, we show that a substantial decrease in the SW ram pressure observed by Ulysses between the TS crossings by Voyager 1 and 2 contributes significantly to the difference in the heliocentric distances at which these crossings occurred. The Ulysses spacecraft is the source of valuable information about the three-dimensional and time-dependent properties of the SW. Its unique fast latitudinal scans of the SW regions make it possible to create a solar cycle model based on the spacecraft in situ measurements. On the basis of our analysis of the Ulysses data over the entire life of the mission, we generated time-dependent boundary conditions at 10 AU from the Sun and applied our MHD-neutral model to perform a numerical simulation of the SW-LISM interaction. We analyzed the global variations in the interaction pattern, the excursions of the TS and the HP, and the details of the plasma and magnetic field distributions in the IHS. Numerical results are compared with Voyager data as functions of time in the spacecraft frame. We discuss solar cycle effects which may be reasons for the recent decrease in the TS particles (ions accelerated to anomalous cosmic-ray energies) flux observed by Voyager 1.

  12. THREE-DIMENSIONAL FEATURES OF THE OUTER HELIOSPHERE DUE TO COUPLING BETWEEN THE INTERSTELLAR AND INTERPLANETARY MAGNETIC FIELDS. IV. SOLAR CYCLE MODEL BASED ON ULYSSES OBSERVATIONS

    SciTech Connect

    Pogorelov, N. V.; Zank, G. P.; Suess, S. T.; Borovikov, S. N.; Ebert, R. W.; McComas, D. J.

    2013-07-20

    The solar cycle has a profound influence on the solar wind (SW) interaction with the local interstellar medium (LISM) on more than one timescales. Also, there are substantial differences in individual solar cycle lengths and SW behavior within them. The presence of a slow SW belt, with a variable latitudinal extent changing within each solar cycle from rather small angles to 90 Degree-Sign , separated from the fast wind that originates at coronal holes substantially affects plasma in the inner heliosheath (IHS)-the SW region between the termination shock (TS) and the heliopause (HP). The solar cycle may be the reason why the complicated flow structure is observed in the IHS by Voyager 1. In this paper, we show that a substantial decrease in the SW ram pressure observed by Ulysses between the TS crossings by Voyager 1 and 2 contributes significantly to the difference in the heliocentric distances at which these crossings occurred. The Ulysses spacecraft is the source of valuable information about the three-dimensional and time-dependent properties of the SW. Its unique fast latitudinal scans of the SW regions make it possible to create a solar cycle model based on the spacecraft in situ measurements. On the basis of our analysis of the Ulysses data over the entire life of the mission, we generated time-dependent boundary conditions at 10 AU from the Sun and applied our MHD-neutral model to perform a numerical simulation of the SW-LISM interaction. We analyzed the global variations in the interaction pattern, the excursions of the TS and the HP, and the details of the plasma and magnetic field distributions in the IHS. Numerical results are compared with Voyager data as functions of time in the spacecraft frame. We discuss solar cycle effects which may be reasons for the recent decrease in the TS particles (ions accelerated to anomalous cosmic-ray energies) flux observed by Voyager 1.

  13. Influence of strong static magnetic field on human cancer HT 1080 cells

    NASA Astrophysics Data System (ADS)

    Rodins, Juris; Korhovs, Vadims; Freivalds, Talivaldis; Buikis, Indulis; Ivanova, Tatjana

    2001-10-01

    The aim of this study was to investigate strong uniform magnetic field influence on the human cancer cells HT 1080. The cells were treated with magnetic field of intensity 1,16 Tesla and with anticancer agent - cis-platinum 0.025 mg/ml or vincristinum 2-3 ng/ml. The intact and the treated cell samples were incubated in a medium with acridine orange (AO). The magnetic field after 15 minutes of influence significantly increased cytoplasmic red fluorescence. Increased AO accumulation in lysosomes suggested to cancer cell metabolic activity stimulation.

  14. On the dynamics of the large-scale magnetic fields of the sun and the sunspot cycle

    NASA Astrophysics Data System (ADS)

    Mouradian, Z.; Soru-Escaut, I.

    1991-11-01

    The purpose of the present article is to analyze the solar activity cycle from the point of view of large-scale magnetic fields (LSMFs), i.e., the 'polarity background' (unipolar magnetic regions) and the 'polar islands' (bipolar magnetic regions) with or without active regions. Using synoptic charts of the magnetic field (Stanford, McIntosh) and daily KPNO and Mount Wilson observations, a scenario has been developed that is based on the dynamics of the LSMFs. The activity cycle appears to be asymmetrical, with the north polar background predominating at the minimum and the south polar background at the maximum. The polarity islands in the background cover a large area and as they develop, they 'push' the magnetic field background toward the poles and thereby establish an equator-to-pole circulation at the solar surface. This circulation is also affected by the differential rotation of the sun. A fractal dimension analysis shows that the polarity islands become 'turbulent' as sunspot activity.

  15. Muskie Lunacy: does the lunar cycle influence angler catch of muskellunge (Esox masquinongy)?

    PubMed

    Vinson, Mark R; Angradi, Ted R

    2014-01-01

    We analyzed angling catch records for 341,959 muskellunge (Esox masquinongy) from North America to test for a cyclic lunar influence on the catch. Using periodic regression, we showed that the number caught was strongly related to the 29-day lunar cycle, and the effect was consistent across most fisheries. More muskellunge were caught around the full and new moon than at other times. At night, more muskellunge were caught around the full moon than the new moon. The predicted maximum relative effect was ≈5% overall. Anglers fishing exclusively on the peak lunar day would, on average, catch 5% more muskellunge than anglers fishing on random days. On some lakes and at night, the maximum relative effect was higher. We obtained angler effort data for Wisconsin, Mille Lacs (MN), and Lake Vermilion (MN). For Lake Vermilion there was a significant effect of the lunar cycle on angler effort. We could therefore not conclude that the lunar effect on catch was due to an effect on fish behavior alone. Several factors affected the amount of variation explained by the lunar cycle. The lunar effect was stronger for larger muskellunge (>102 cm) than for smaller fish, stronger in midsummer than in June or October, and stronger for fish caught at high latitudes (>48°N) than for fish caught further south. There was no difference in the lunar effect between expert and novice muskellunge anglers. We argue that this variation is evidence that the effect of the lunar cycle on catch is mediated by biological factors and is not due solely to angler effort and reflects lunar synchronization in feeding. This effect has been attributed to variation among moon phases in lunar illumination, but our results do not support that hypothesis for angler-caught muskellunge.

  16. Muskie Lunacy: Does the Lunar Cycle Influence Angler Catch of Muskellunge (Esox masquinongy)?

    PubMed Central

    Vinson, Mark R.; Angradi, Ted R.

    2014-01-01

    We analyzed angling catch records for 341,959 muskellunge (Esox masquinongy) from North America to test for a cyclic lunar influence on the catch. Using periodic regression, we showed that the number caught was strongly related to the 29-day lunar cycle, and the effect was consistent across most fisheries. More muskellunge were caught around the full and new moon than at other times. At night, more muskellunge were caught around the full moon than the new moon. The predicted maximum relative effect was ≈5% overall. Anglers fishing exclusively on the peak lunar day would, on average, catch 5% more muskellunge than anglers fishing on random days. On some lakes and at night, the maximum relative effect was higher. We obtained angler effort data for Wisconsin, Mille Lacs (MN), and Lake Vermilion (MN). For Lake Vermilion there was a significant effect of the lunar cycle on angler effort. We could therefore not conclude that the lunar effect on catch was due to an effect on fish behavior alone. Several factors affected the amount of variation explained by the lunar cycle. The lunar effect was stronger for larger muskellunge (>102 cm) than for smaller fish, stronger in midsummer than in June or October, and stronger for fish caught at high latitudes (>48°N) than for fish caught further south. There was no difference in the lunar effect between expert and novice muskellunge anglers. We argue that this variation is evidence that the effect of the lunar cycle on catch is mediated by biological factors and is not due solely to angler effort and reflects lunar synchronization in feeding. This effect has been attributed to variation among moon phases in lunar illumination, but our results do not support that hypothesis for angler-caught muskellunge. PMID:24871329

  17. Muskie lunacy: does the lunar cycle influence angler catch of muskellunge (Esox masquinongy)?

    USGS Publications Warehouse

    Vinson, Mark R.; Angradi, Ted R.

    2014-01-01

    We analyzed angling catch records for 341,959 muskellunge (Esox masquinongy) from North America to test for a cyclic lunar influence on the catch. Using periodic regression, we showed that the number caught was strongly related to the 29-day lunar cycle, and the effect was consistent across most fisheries. More muskellunge were caught around the full and new moon than at other times. At night, more muskellunge were caught around the full moon than the new moon. The predicted maximum relative effect was ≈5% overall. Anglers fishing exclusively on the peak lunar day would, on average, catch 5% more muskellunge than anglers fishing on random days. On some lakes and at night, the maximum relative effect was higher. We obtained angler effort data for Wisconsin, Mille Lacs (MN), and Lake Vermilion (MN). For Lake Vermilion there was a significant effect of the lunar cycle on angler effort. We could therefore not conclude that the lunar effect on catch was due to an effect on fish behavior alone. Several factors affected the amount of variation explained by the lunar cycle. The lunar effect was stronger for larger muskellunge (>102 cm) than for smaller fish, stronger in midsummer than in June or October, and stronger for fish caught at high latitudes (>48°N) than for fish caught further south. There was no difference in the lunar effect between expert and novice muskellunge anglers. We argue that this variation is evidence that the effect of the lunar cycle on catch is mediated by biological factors and is not due solely to angler effort and reflects lunar synchronization in feeding. This effect has been attributed to variation among moon phases in lunar illumination, but our results do not support that hypothesis for angler-caught muskellunge.

  18. Influence of thermal debinding on the final properties of Fe-Si soft magnetic alloys for metal injection molding (MIM)

    NASA Astrophysics Data System (ADS)

    Páez-Pavón, A.; Jiménez-Morales, A.; Santos, T. G.; Quintino, L.; Torralba, J. M.

    2016-10-01

    Metal injection molding (MIM) may be used to produce soft magnetic materials with optimal mechanical and magnetic properties. Unlike other techniques, MIM enables the production of complex and small Fe-Si alloy parts with silicon contents greater than 3% by weight. In MIM process development, it is critical to design a proper debinding cycle not only to ensure complete removal of the binder system but also to obtain improved properties in the final part. This work is a preliminary study on the production of Fe-3.8Si soft magnetic parts by MIM using pre-alloyed powders and a non-industrialized binder. Two different heating rates during thermal debinding were used to study their effect on the final properties of the part. The final properties of the sintered parts are related to thermal debinding. It has been demonstrated that the heating rate during thermal debinding has a strong influence on the final properties of Fe-Si soft magnetic alloys.

  19. BLOOD PRESSURE, HEART RATE AND MELATONIN CYCLES SYNCHRONIZATION WITH THE SEASON, EARTH MAGNETISM AND SOLAR FLARES.

    PubMed

    Cornélissen, G; Halberg, F; Sothern, R B; Hillman, D C; Siegelová, J

    2010-01-01

    other aspect of RBS' physical environment, namely the seasons (at ~1.0 year), earth magnetism (at ~0.5 year) and/or solar flares (at ~0.42 year). Cosmic-biotic transfer of information, albeit hardly of energy (the biospheric amplitudes are very small) may be mediated in this set of frequency windows. As found earlier, RBS' circulation is also frequency-trapped environmentally in multidecadal windows, HR being locked into the transtridecadal Brückner, or rather Brückner-Egeson-Lockyer, BEL sunspot and terrestrial weather cycle, while his BP follows Hale's didecadal cycle in the changing polarity of sunspots.The ~0.41-year HR cycle may be associated with changes in solar flares, the cis-half-year amplitude of HR showing a cross-correlation coefficient of 0.79 with the total solar flare index (from both solar hemispheres) at a lag of ~3.2 years. The superposed time courses of these two variables indicate the presence of a shared Horrebow-Arago-Schwabe sunspot cycle of ~11 years, the cis-half-year in HR being more prominent after the total solar flare index reaches its ~11-year peak. Differences in the time-varying behavior of BP vs. HR are also described.

  20. Influence of seasonal cycles in Martian atmosphere on entry, descent and landing sequence

    NASA Astrophysics Data System (ADS)

    Marčeta, Dušan; Šegan, Stevo; Rašuo, Boško

    2014-05-01

    The phenomena like high eccentricity of Martian orbit, obliquity of the orbital plane and close alignment of the winter solstice and the orbital perihelion, separately or together can significantly alter not only the level of some Martian atmospheric parameters but also the characteristics of its diurnal and seasonal cycle. Considering that entry, descent and landing (EDL) sequence is mainly driven by the density profile of the atmosphere and aerodynamic characteristic of the entry vehicle. We have performed the analysis of the influence of the seasonal cycles of the atmospheric parameters on EDL profiles by using Mars Global Reference Atmospheric Model (Mars-GRAM). Since the height of the deployment of the parachute and the time passed from the deployment to propulsion firing (descent time) are of crucial importance for safe landing and the achievable landing site elevation we paid special attention to the influence of the areocentric longitude of the Sun (Ls) on these variables. We have found that these variables have periodic variability with respect to Ls and can be very well approximated with a sine wave function whose mean value depends only on the landing site elevation while the amplitudes and phases depend only on the landing site latitude. The amplitudes exhibit behavior which is symmetric with respect to the latitude but the symmetry is shifted from the equator to the northern mid-tropics. We have also noticed that the strong temperature inversions which are usual for middle and higher northern latitudes while Mars is around its orbital perihelion significantly alter the descent time without influencing the height of the parachute deployment. At last, we applied our model to determine the dependence of the accessible landing region on Ls and found that this region reaches maximum when Mars is around the orbital perihelion and can vary 50° in latitude throughout the Martian year.

  1. Influence of the curing cycles on the fatigue performance of unidirectional glass fiber reinforced epoxy composites

    NASA Astrophysics Data System (ADS)

    Hüther, Jonas; Brøndsted, Povl

    2016-07-01

    During the manufacturing process of fiber reinforced polymers the curing reaction of the resin results in shrinkage of the resin and introduces internal stresses in the composites. When curing at higher temperatures in order to shorten up the processing time, higher curing stresses and thermal stresses are built up and frozen, as residual stresses occur. In the present work, a glass fiber reinforced epoxy composite laminate with an unidirectional architecture based on non-crimp fabrics with backing fibers is investigated. Three different curing cycles (time-temperature cycles) are used, leading to different levels of internal stresses. The mechanical properties, static strength and fatigue life time, are measured in three different directions of the material, i.e. the fiber direction, 0°, the 30° off axis direction, and the 90° direction transverse to the fiber direction. It is experimentally demonstrated that the resulting residual stresses barely influences the quasi-static mechanical properties of reinforced glass-fiber composites. It is found that the fatigue performance in the 0° direction is significantly influenced by the internal stresses, whereas the fatigue performance in the off axes directions so is not significantly influenced of these stresses. This is related to the observations that the damage mechanisms in the off axes directions are mainly related to shear failure in the matrix and in the interface between fiber and matrix and different from the damage mechanisms in the fiber direction, where the damage initiates in the transverse backing fibers and is directly related to fiber fractures in the load-carrying axial fiber bundles.

  2. Magnetic influence on the unidentified luminous phenomena in Hessdalen, Norway

    NASA Astrophysics Data System (ADS)

    Gitle Hauge, Bjørn; Kjøniksen, Anna-Lena; Petter Strand, Erling; Zlotnicki, Jaques; Vargemezis, George

    2016-04-01

    Unidentified luminous phenomena have been observed in the low atmosphere over the Hessdalen valley for decades. First scientific investigation was done by E.Strand in 1984, where spiral movements of lights was recorded. The Science Camp program has conducted yearly field investigations since 2002 and has confirmed the existence of this spiral-behavior. (http://sciencecamp.no) Such behavior has also been documented in Alabama, USA. In September 2015 spiral like movement of lights was observed together with the more common spherical lights. This spiral movement indicates the presence of low atmospheric charged matter, moving in a magnetic field. A geological survey in 2014 reviled the presence of strong magnetic anomalies. The valley contains several abandoned copper mines containing Chalcopyrite and Magnetite. The Magnetite was not useful in the copper production, and left in heaps around the valley unused. This may contribute to the magnetic anomalies in the valley.

  3. ELECTRON TRANSPORT IN CORONAL LOOPS: THE INFLUENCE OF THE EXPONENTIAL SEPARATION OF MAGNETIC FIELD LINES

    SciTech Connect

    Bitane, R.; Zimbardo, G.; Veltri, P.

    2010-08-20

    Observations by the TRACE spacecraft have shown that coronal emission in the extreme ultraviolet is characterized by filamentary structures within coronal loops, with transverse sizes close to the instrumental resolution. Starting from the observed filament widths and using the concepts of braided magnetic fields, an estimate of the turbulence level in the coronal loops can be obtained. Magnetic turbulence in the presence of a background magnetic field can be strongly anisotropic, and such anisotropy influences the separation of magnetic field lines, as well as the magnetic field line diffusion coefficient. Careful computations of the magnetic field line diffusion coefficient D{sub m} and of the rate of exponential separation of magnetic field lines h, also allowing for the possibility of anisotropic magnetic turbulence, enable computation of the effective perpendicular diffusion coefficient for electrons. When compared with observations this yields magnetic turbulence levels on the order of {delta}B/B {sub 0} = 0.05-0.7, which are larger than previous estimates. These values of the magnetic fluctuation level support the idea that magnetic turbulence can contribute to coronal heating by means of MHD turbulence dissipation. It is also found that field line transport is not governed by the quasilinear regime, but by a nonlinear regime which includes an intermediate and the percolation regimes.

  4. Constant magnetic field influence on a heart beat in rats

    SciTech Connect

    Lazetic, B.; Pekaric-Nadj, N.; Kasas-Lazetic, K.

    1991-03-11

    The authors used uretan narcose to implant constant magnets of 50 mT under the skin of rats in head region. The ECG was registrated in the next 6 hours. From it they found much slower heart beat which culminated in the first 105 minutes. After 6 weeks of continual exposure the heart beat of the exposed rats was still slower then in the controls. It is concluded that a chronical exposition to the constant magnetic field affected rats organisms and no regulatory mechanism could prevent it.

  5. The influence of electron discharge and magnetic field on calcium carbonate (CaCO3) precipitation

    NASA Astrophysics Data System (ADS)

    Putro, Triswantoro; Endarko

    2016-04-01

    The influences of electron discharge and magnetic field on calcium carbonate (CaCO3) precipitation in water have been successfully investigated. The study used three pairs of magnetic field 0.1 T whilst the electron discharge was generated from television flyback transformer type BW00607 and stainless steel SUS 304 as an electrode. The water sample with an initial condition of 230 mg/L placed in the reactor with flow rate 375 mL/minutes, result showed that the electron discharge can be reduced contain of calcium carbonate the water sample around 17.39% within 2 hours. Meanwhile for the same long period of treatment and flow rate, around 56.69% from initial condition of 520 mg/L of calcium carbonate in the water sample can be achieved by three pairs of magnetic field 0.1 T. When the combination of three pairs of magnetic field 0.1 T and the electron discharge used for treatment, the result showed that the combination of electron discharge and magnetic field methods can be used to precipitate calcium carbonate in the water sample 300 mg/L around 76.66% for 2 hours of treatment. The study then investigated the influence of the polar position of the magnetic field on calcium carbonate precipitation. Two positions of magnetic field were tested namely the system with alternated polar magnetics and the system without inversion of the polar magnetics. The influence of the polar position showed that the percentage reduction in levels of calcium carbonate in the water sample (360 mg/L) is significant different. Result showed that the system without inversion of the polar magnetics is generally lower than the system with alternated polar magnetics, with reduction level at 30.55 and 57.69%, respectively.

  6. The influence of ecosystem nitrogen status on carbon cycling in forests

    NASA Astrophysics Data System (ADS)

    Ollinger, S. V.; Smith, M.; Richardson, A.; Hollinger, D. Y.; Martin, M.; Jenkins, J.

    2006-12-01

    The carbon and nitrogen cycles in terrestrial ecosystems are tightly coupled through a shared set of biological processes. The N status of plant canopies exerts a direct influence on carbon assimilation through its well-known effect on net photosynthesis. In soils, both the accumulation of N and the decay of organic matter are often related to the initial C/N ratio of litterfall. Similarly, respiration rates in both roots and foliage have been shown to be positively correlated with tissue N concentrations. These linkages suggest that the N status of ecosystems may provide a useful indicator of their overall C metabolism. Further, evidence from both CO2 and N enrichment experiments indicates that alteration of one cycle can have important implications for the other. This is significant in that global cycles of both C and N have been greatly perturbed by humans. Despite the well-known influence of nitrogen availability on fluxes of carbon, few studies have explicitly examined the role of nitrogen as it pertains to spatial and temporal variation in carbon cycling. This is due, in part, to limited crossover between different scientific communities, but also stems from some very real methodological limitations that make regional-scale assessment of N status difficult. Here, we report on an NACP investigation that examines the degree to which rates of carbon assimilation and growth in forests can be related to both local and regional variation in ecosystem N status. Field measurements from a series of forested research sites within the AmeriFlux network have been combined with hyperspectral remote sensing data from the AVIRIS and Hyperion instruments. Results from a cross-site synthesis indicate a positive relationship between canopy N and the maximum rate of carbon assimilation, as measured by flux towers. Because existing methods of canopy N detection are restricted to small landscapes, a parallel investigation involves developing generalizeable canopy N detection

  7. Studies of solar magnetic fields during the rise of Solar Cycle 22. Final report, 1 Oct 86-30 Sep 89

    SciTech Connect

    Martin, S.F.

    1991-01-15

    New information about the solar cycle and the changing magnetic fields includes: (1) Every solar cycle has a duration of 18-22 years even though the peak between successive cycles is approximately 11 years. This means that there are two solar cycles on the sun nearly all of the time; the exception is the few years preceeding solar maximum. (2) a large-scale velocity field was discovered around the perimeter of one of the major active regions that developed during the rise of the current solar cycle. If averaged over a several month interval, the velocity would be of the same order of magnitude as the velocity pattern of the torsional oscillation signal that varies systematically over the solar cycle. The newly discovered velocity pattern can be interpreted as either a severe contamination to the torsional oscillation signal or another way of observing the torsional oscillation velocity field. (3) Our analyses of small-scale magnetic fields on the quiet sun has shown that network magnetic fields are continuously being replaced by intranetwork magnetic fields. The replacement occurs when intranetwork magnetic fields collide with network magnetic fields; both polarities are observed to cancel each other at a mean rates of 10 to the 18th power Maxwells/hour. The non-cancelling components of the intranetwork magnetic field replace the cancelled components of the network. No net long-term increases or decreases in magnetic flux occur as a consequence of these processes.

  8. Influence of noise on a magnetically sensitive atom interferometer

    NASA Astrophysics Data System (ADS)

    Desavage, Sara A.; Srinivasan, Arvind; Davis, Jon P.; Zimmermann, Matthias; Efremov, Maxim; Rasel, Ernst; Schleich, Wolfgang; Welch, George R.; Mimih, Jihane; Narducci, Frank A.

    2016-05-01

    The inherent sensitivity of atom interferometer sensors has been well established and much progress has been made in the development of atom interferometer gravimeters, gravity gradiometers and gyroscopes e.g.. These interferometers use the ``clock'' transition which is magnetically insensitive. When considering interferometers with magnetically sensitive transitions operating in unshielded environments additional noise sources must be considered. The frequency content of the noise from these sources can vary dramatically, depending on the environment. In this talk, we will discuss these various noise sources and their impact on the performance of magnetically sensitive interferometers. Specifically, we identify three ways by which noise can be introduced into the system and their effect: fluctuating detuning, leading to a randomness of the interference pattern; fluctuating Rabi frequency, leading to pulse errors; non-uniformity of the magnetic field across the atom cloud, which can, under certain circumstances lead to a complete washing out of the interference pattern. Implications for our current experiments will be discussed. Sponsored by the Office of Naval Research.

  9. The influence of quarantine on reproductive cycling in wild-caught Baboons (Papio anubis).

    PubMed

    Liechty, Emma R; Wang, Diane Y; Chen, Emily; Chai, Daniel; Bell, Jason D; Bergin, Ingrid L

    2015-12-01

    Stress impacts nonhuman primate menstrual cycle length but the impact of quarantine is unknown. A retrospective analysis was performed on cycle data from 31 wild-caught baboons during and following quarantine. Cycling initiated in 94 days (19-181) and length normalized within 4-6 cycles. Quarantine significantly impacts menstrual cycle length.

  10. Determining diffusion coefficients of ionic liquids by means of field cycling nuclear magnetic resonance relaxometry

    SciTech Connect

    Kruk, D.; Meier, R.; Rössler, E. A.; Rachocki, A.; Korpała, A.; Singh, R. K.

    2014-06-28

    Field Cycling Nuclear Magnetic Resonance (FC NMR) relaxation studies are reported for three ionic liquids: 1-ethyl-3- methylimidazolium thiocyanate (EMIM-SCN, 220–258 K), 1-butyl-3-methylimidazolium tetrafluoroborate (BMIM-BF{sub 4}, 243–318 K), and 1-butyl-3-methylimidazolium hexafluorophosphate (BMIM-PF{sub 6}, 258–323 K). The dispersion of {sup 1}H spin-lattice relaxation rate R{sub 1}(ω) is measured in the frequency range of 10 kHz–20 MHz, and the studies are complemented by {sup 19}F spin-lattice relaxation measurements on BMIM-PF{sub 6} in the corresponding frequency range. From the {sup 1}H relaxation results self-diffusion coefficients for the cation in EMIM-SCN, BMIM-BF{sub 4}, and BMIM-PF{sub 6} are determined. This is done by performing an analysis considering all relevant intra- and intermolecular relaxation contributions to the {sup 1}H spin-lattice relaxation as well as by benefiting from the universal low-frequency dispersion law characteristic of Fickian diffusion which yields, at low frequencies, a linear dependence of R{sub 1} on square root of frequency. From the {sup 19}F relaxation both anion and cation diffusion coefficients are determined for BMIM-PF{sub 6}. The diffusion coefficients obtained from FC NMR relaxometry are in good agreement with results reported from pulsed- field-gradient NMR. This shows that NMR relaxometry can be considered as an alternative route of determining diffusion coefficients of both cations and anions in ionic liquids.

  11. Influence of magnetic field on the compressive behavior of carbon nanotube with magnetic nanoparticles

    NASA Astrophysics Data System (ADS)

    Reddy, S. K.; Suri, A.; Misra, A.

    2013-06-01

    Carbon nanotubes (CNT) in their cellular like micro-structure have presented an excellent mechanical energy absorption capacity. Although, several efforts have been progressed to modify the CNT structure for further enhancing their energy absorption capacity but yet no report has revealed the effect of magnetic field on the mechanical behavior of as-grown CNT mat that contains magnetic iron nanoparticles in the form of decorated nanoparticles on the surface or filled inside core of the CNT. We report a significant impact of the presence of magnetic content that modifies the mechanical behavior of the entangled CNT mat in the presence of an external magnetic field. The energy absorption capacity doubles when magnetic field was applied in the radial direction of the CNT mat under uniaxial compression.

  12. Amplification of the Steady Toroidal Magnetic Field in Solar Interior and Asymmetry of Sunspot Activity in Neighbouring Cycles

    NASA Astrophysics Data System (ADS)

    Kryvodubskyj, V. N.

    2006-08-01

    This investigation deals with the problem of the asymmetry of sunspot activity maximums in neighbouring solar cycles. The Gnevyshev-Ohl rule (Gnevyshev and Ohl 1948, Astron. Zhurn. 25, 18) is a likely evidence for the radiative interior pervaded by a strong steady magnetic field. Therefore, some effects are required to ensure existence this deep-laid field for long-duration times. The way for search of excitation mechanism of strong magnetic field gives us the helioseismological experiments. We take the physical parameters of the interiors from standard solar model by Allen (1973, Astrophysical Quantities, London) for calculations. It was found that main limiting factor on the magnetic field value is the magnetic flux loss due to buoyancy in the radiative (non-turbulent) zone (RZ) which overcomes the rate of the field decay caused by ohmic dissipation. The helioseismology inversions indicate that the radial, but not latitudinal, shear in the internal rotation of the Sun penetrates rather deep, almost to the solar core (Duval et al.1984, Nature 310, 22; Brown 1985, Nature 317, 591; Libbrecht 1986, Nature 319, 753). This radial differential rotation, acting on a weak relict poloidal magnetic field, about 1 G, in the stable RZ, can excite the rather strong steady toroidal fields (10 KG - 10 MG). Obtained estimations agree with the helioseismically determined magnetic intensities in the solar interiors (Dziembowski and Goode 1989, ApJ 347, 540; Antia, Chitre and Thompson 2003, A&A 399, 329). We assume that due to magnetic buoyancy and meridional circulation at the upper boundary of the RZ the power toroidal field may penetrate, partly, into the convective zone (CZ). Here stationary steady directed field will be add to oscillating toroidal field excited by αΩ-dynamo. Since the oscillating dynamo-field changes their own direction with 11-years cycle-period, then the amplitude of total, oscillating plus steady, toroidal field in the CZ has to be a few differing in

  13. Influence of the magnetic field on microorganisms in the oral cavity

    PubMed Central

    BRKOVIC, Snezana; POSTIC, Srdjan; ILIC, Dragan

    2015-01-01

    Since the beginning of their lives, all living organisms are exposed to the influence of geomagnetic fields. Objectives : With respect to the positive effects that magnetic fields have on human tissues, especially the bactericidal effect, this investigation aimed to assess their influence on the reduction of oral microorganisms. Material and Methods : In order to obtain adequate specimens of dental plaque deposit, microbes such as Streptococcus parasanguinis, Staphylococcus epidermidis, Rhodococcus equi and Candida albicans were isolated from the human mouth. To establish the intensity of microbial growth on the basis of the modified optical density (OD) of agar turbidimetry assay, microbial count and spectrophotometry were applied. The study was carried out with two microbial concentrations (1 and 10 CFU/ml) after periods of incubation of 24 and 48 h and using micromagnets. Results : A positive effect of the magnetic field, resulting in the reduction of dental plaque microbes in vitro, was found. In the first 24 hours of exposure to the magnetic field, the number of all isolated microbes was significantly reduced. The most potent influence of magnets and the most intensified reduction after 24 hours were evident in Candida albicans colonies. The decrease in the influence of magnets on microbes in vitro was also detected. Conclusions : Magnets reduce the number of microbes and might be recommended as a supplement in therapy for reduced periodontal tissues. This is important because periodontal tissues that are in good conditions provide prolonged support to the oral tissues under partial and supradental denture. PMID:26018310

  14. Imaging of magnetic colloids under the influence of magnetic field by cryogenic transmission electron microscopy

    NASA Astrophysics Data System (ADS)

    Wu, Jinsong; Aslam, M.; Dravid, Vinayak P.

    2008-08-01

    The application of superparamagnetic nanoparticles for in vivo magnetic resonance imaging (MRI) under external ac magnetic field has attracted considerable research efforts in recent years. However, it is unclear how superparamagnetic nanostructures arrange themselves in fluidic environment under external magnetic field. Here, we report direct visualization of the effect of applied magnetic field to the ferrofluids (about 6 nm superparamagnetic magnetite (Fe3O4) nanoparticle "colloidal" suspension) using the cryogenic transmission electron microscopy (cryo-TEM). While long dipole chains (up to millimeter range) of the magnetite along the magnetic lines are found in samples dried inside the magnetic field, only short dipole chains (within tens of nanometer scale) with random orientations are observed in the wet sample observed by cryo-TEM. In the wet sample, aggregations of medium-length dipole chains (up to hundreds of nanometer) can be observed at the areas where the nanoparticles are "solidified" when phase separation occurs. In situ formation of flux-closure rings is observed at the edge where vitreous ice sublimes due to high-energy electron radiation that leaves magnetite nanoparticles isolated in the vacuum. Such observations may help elucidate the nature of magnetic field-induced assembly in fluidic environment as in the physiological aqueous conditions in MRI and related applications.

  15. Mutagenicity of diesel exhaust particle extracts: influence of driving cycle and environmental temperature.

    PubMed

    Clark, C R; Dutcher, J S; Brooks, A L; McClellan, R O; Marshall, W F; Naman, T M

    1982-01-01

    General Motors and Volkswagen diesel passenger cars (1980 and 1981 model year) were operated on a climate controlled chassis dynomometer and the particulate portion of the exhaust was collected on high volume filters. Dichloromethane extracts of the exhaust particles (soot) collected while the cars were operated under simulated highway, urban and congested urban driving cycles were assayed for mutagenicity in Salmonella strains TA-98 and TA-100. Driving pattern did not significantly influence the mutagenic potency of the exhaust particle extracts or estimates of the amount of mutagenicity emitted from the exhaust despite large differences in particle emission rates and extractable fraction of the particles. Mutagenicity of extracts of exhaust particles collected while the vehicles were operated at test chamber temperatures of 25, 50, 75 and 100 degrees F were also very similar. The results suggest that driving pattern and environmental temperature do not significantly alter the emission of genotoxic combustion products from the exhaust. PMID:6193022

  16. Mutagenicity of diesel exhaust particle extracts: influence of driving cycle and environmental temperature.

    PubMed

    Clark, C R; Dutcher, J S; Brooks, A L; McClellan, R O; Marshall, W F; Naman, T M

    1982-01-01

    General Motors and Volkswagen diesel passenger cars (1980 and 1981 model year) were operated on a climate controlled chassis dynomometer and the particulate portion of the exhaust was collected on high volume filters. Dichloromethane extracts of the exhaust particles (soot) collected while the cars were operated under simulated highway, urban and congested urban driving cycles were assayed for mutagenicity in Salmonella strains TA-98 and TA-100. Driving pattern did not significantly influence the mutagenic potency of the exhaust particle extracts or estimates of the amount of mutagenicity emitted from the exhaust despite large differences in particle emission rates and extractable fraction of the particles. Mutagenicity of extracts of exhaust particles collected while the vehicles were operated at test chamber temperatures of 25, 50, 75 and 100 degrees F were also very similar. The results suggest that driving pattern and environmental temperature do not significantly alter the emission of genotoxic combustion products from the exhaust.

  17. A model of the ocean iron cycle and its influence on biological production

    NASA Astrophysics Data System (ADS)

    Dutkiewicz, S.; Parekh, P.; Follows, M.

    2003-04-01

    Biological productivity in large regions of the ocean, specifically high nutrient, low chlorophyll regions, is limited by the deficit in iron relative to other nutrients. We have developed a parameterization of the iron cycle of the world's oceans which attempts to explicitly represent the processes by which this deficit in iron occurs. We have implemented this parameterization in the context of the MIT three dimensional global ocean model and examined the consequences for nutrient distributions, new production and primary production. The iron model parameterizes the mechanisms of scavenging of iron onto sinking particles and complexation with an organic ligand and is driven by specified aeolian flux patterns. First, using an idealized representation of export production, limited by light, phosphate and iron, the model reproduces the broad features of the observed ocean phosphate and iron distributions. We replace the simplified export parameterization with an explicit, but highly idealized, ecosystem model. The model represents a simplified food web with two phytoplankton size classes and a single grazer. The base currency for this model is phosphorus, but the larger phytoplankton class (i.e. diatoms) is also limited by silica. Both classes are limited by the availability of iron. The results of this model are also generally consistent with the observed patterns of phosphate and iron. In addition, the model captures the broad features of the distributions and cycles of silica, chlorophyll and primary production. We will also explore the sensitivities of this model to the forcing fields (e.g. aeolian iron flux) and parameter choices of the ecosystem model. This model represents a step towards the explicit representation of the ocean iron cycle, and its biogeochemical influences, in global biogeochemical models.

  18. Influence of Hormonal Changes on Audiologic Examination in Normal Ovarian Cycle Females: An Analytic Study

    PubMed Central

    Adriztina, Indri; Adnan, Adlin; Adenin, Ichwanul; Haryuna, Siti Hajar; Sarumpaet, Sorimuda

    2015-01-01

    Introduction There is only limited information from previous studies that suggest that auditory function may be influenced by hormones. Recent advances in the field have exposed the potential role of hormones in modulating the auditory system. Objective This study aims to investigate the relationship between menstrual cycle and outer hair cell function with audiological examination. Methods This is an analytic study with a cross-sectional design. The sampling was a systematic random sampling. We found 49 women with normal menstrual cycle and collected their data through interviews, physical examination, and examination of the ear, with otoscopic and other routine otorhinolaryngology examinations. We evaluated Tympanometry, distortion-product otoacoustic emissions (DPOAE), and pure tone audiometry. Results We found the audiometric threshold worse in the follicular phase than other phases at 4000 Hz of the right ear, and in the ovulation was found best than any other phases at 1000 Hz of the left ear with significant difference. We found significant difference of DPOAE between ovulation time and follicular phase at 3000 Hz and 1000 Hz in the left ear and between ovulation and luteal phased at 2000 Hz, 3000 Hz and 5000 Hz in the right ear and at 1000 Hz in the left ear with p < 0.05. Conclusion The result of this study showed that only a small part of audiometry threshold had a significant difference between each menstrual phase. In other words, we found no correlation between menstrual and audiometry threshold. Nonetheless, there is a correlation between menstrual cycle phase and DPOAE amplitude.

  19. The influence of woody encroachment on the nitrogen cycle: fixation, storage and gas loss

    NASA Astrophysics Data System (ADS)

    Soper, F.; Sparks, J. P.

    2015-12-01

    Woody encroachment is a pervasive land cover change throughout the tropics and subtropics. Encroachment is frequently catalyzed by nitrogen (N)-fixing trees and the resulting N inputs potentially alter whole-ecosystem N cycling, accumulation and loss. In the southern US, widespread encroachment by legume Prosopis glandulosa is associated with increased soil total N storage, inorganic N concentrations, and net mineralization and nitrification rates. To better understand the effects of this process on ecosystem N cycling, we investigated patterns of symbiotic N fixation, N accrual and soil N trace gas and N2 emissions during Prosopis encroachment into the southern Rio Grande Plains. Analyses of d15N in foliage, xylem sap and plant-available soil N suggested that N fixation rates increase with tree age and are influenced by abiotic conditions. A model of soil N accrual around individual trees, accounting for atmospheric inputs and gas losses, generates lifetimes N fixation estimates of up to 9 kg for a 100-year-old tree and current rates of 7 kg N ha-1 yr-1. However, these N inputs and increased soil cycling rates do not translate into increased N gas losses. Two years of field measurements of a complete suite of N trace gases (ammonia, nitrous oxide, nitric oxide and other oxidized N compounds) found no difference in flux between upland Prosopis groves and adjacent unencroached grasslands. Total emissions for both land cover types average 0.56-0.65 kg N ha-1 yr-1, comparable to other southern US grasslands. Additional lab experiments suggested that N2 losses are low and that field oxygen conditions are not usually conducive to denitrification. Taken together, results suggest that this ecosystem is currently experiencing a period of net N accrual under ongoing encroachment.

  20. Using Polar Coronal Hole Area Measurements to Determine the Solar Polar Magnetic Field Reversal in Solar Cycle 24

    NASA Technical Reports Server (NTRS)

    Karna, N.; Webber, S.A. Hess; Pesnell, W.D.

    2014-01-01

    An analysis of solar polar coronal hole (PCH) areas since the launch of the Solar Dynamics Observatory (SDO) shows how the polar regions have evolved during Solar Cycle 24. We present PCH areas from mid-2010 through 2013 using data from the Atmospheric Imager Assembly (AIA) and Helioseismic and Magnetic Imager (HMI) instruments onboard SDO. Our analysis shows that both the northern and southern PCH areas have decreased significantly in size since 2010. Linear fits to the areas derived from the magnetic-field properties indicate that, although the northern hemisphere went through polar-field reversal and reached solar-maximum conditions in mid-2012, the southern hemisphere had not reached solar-maximum conditions in the polar regions by the end of 2013. Our results show that solar-maximum conditions in each hemisphere, as measured by the area of the polar coronal holes and polar magnetic field, will be offset in time.

  1. Magnetic structure and frequency scaling of limit-cycle oscillations close to L- to H-mode transitions

    NASA Astrophysics Data System (ADS)

    Birkenmeier, G.; Cavedon, M.; Conway, G. D.; Manz, P.; Stroth, U.; Fischer, R.; Fuchert, G.; Happel, T.; Laggner, F. M.; Maraschek, M.; Medvedeva, A.; Nikolaeva, V.; Prisiazhniuk, D.; Pütterich, T.; Ryter, F.; Shao, L. M.; Willensdorfer, M.; Wolfrum, E.; Zohm, H.; the ASDEX Upgrade Team

    2016-08-01

    Limit-cycle oscillations (LCOs) close to the power threshold of L- to H-mode transitions are investigated in plasmas of ASDEX Upgrade. During this phase, referred to as I-phase, a strong magnetic activity in the poloidal magnetic field {{\\overset{\\centerdot}{{B}} }θ} with an up–down asymmetry is found. In some cases, the regular LCOs during I-phase transition smoothly into a phase with intermittent bursts which have similar properties to type-III edge localised modes (ELMs). Indications of precursors during the intermittent phase as well as in the regular LCO phase point to a common nature of the I-phase and type-III ELMs. The LCO frequency measured in a set of discharges with different plasma currents and magnetic fields scales as f∼ ≤ft(B\\text{t}1/2I\\text{p}3/2\\right)/(nT) .

  2. Weekly cycle of magnetic characteristics of PM2.5 and PM2.5-10 in Beijing, China

    NASA Astrophysics Data System (ADS)

    SHI, M.; Wu, H.; Zhang, S.; Li, H.; Yang, T.

    2013-12-01

    In urban areas,fine particle matter with aerodynamic diameter between 2.5 um and 10 um (PM2.5-10), and 2.5 um (PM2.5), as an important source of urban particulate matter (PM) pollutants, have significant negative effects on health, atmospheric visibility and climate. PM has increasingly become a significant index of indicating the atmospheric pollution of city. In recent years, Beijing, China has been listed as one of the most serious air pollution city in the world. In order to investigate the sources of air pollutants, a total of 283 pairs of PM2.5 and PM2.5-10 samples were collected daily from July, 2010 to June, 2011 in Beijing. Mineral magnetic properties and Scanning electron microscope (SEM) observations and energy dispersive X-ray spectroscopy (EDS) analyses of PM2.5 and PM2.5-10 were measured to verify the magnetic materials. Magnetic measures for PM indicated that the major magnetic phase was coarse-grained magnetite-like material. The χlf, χarm, SIRM and χarm/SIRM series of the PM2.5 and PM2.5-10 show seasonal dependences: high values in winter and low values in summer. In additional the parameters analyzed by Time-series methods show a strong cycle about 7 days above 95% confidence level. Weekly cycle of magnetic characteristics of PM2.5 and PM2.5-10 show different pattern: the concentration of magnetic particles in PM2.5-10 show high values in mid-week, and particle sizes is steady, while the concentration of magnetic particles in PM2.5 show reverse a weekly cycle pattern, and particle sizes is smaller in the mid-week.Microscopy analyses reveal basically three morphologies of magnetic grains: aggregate, spherules and angular particles. The ultrafine carbonaceous particles which tend to form complex clusters and chain-like structures, most likely come from coal burning and motor vehicle exhaust. Spherical particles in PM2.5 are dominantly composed of Fe, O and C, grain-diameters of particles range from 0.3 to 2 um. Angular particles of Fe

  3. In vivo nuclear magnetic resonance spectroscopy studies of the relationship between the glutamate-glutamine neurotransmitter cycle and functional neuroenergetics.

    PubMed Central

    Rothman, D L; Sibson, N R; Hyder, F; Shen, J; Behar, K L; Shulman, R G

    1999-01-01

    In this article we review recent studies, primarily from our laboratory, using 13C NMR (nuclear magnetic resonance) to non-invasively measure the rate of the glutamate-glutamine neurotransmitter cycle in the cortex of rats and humans. In the glutamate-glutamine cycle, glutamate released from nerve terminals is taken up by surrounding glial cells and returned to the nerve terminals as glutamine. 13C NMR studies have shown that the rate of the glutamate-glutamine cycle is extremely high in both the rat and human cortex, and that it increases with brain activity in an approximately 1:1 molar ratio with oxidative glucose metabolism. The measured ratio, in combination with proposals based on isolated cell studies by P. J. Magistretti and co-workers, has led to the development of a model in which the majority of brain glucose oxidation is mechanistically coupled to the glutamate-glutamine cycle. This model provides the first testable mechanistic relationship between cortical glucose metabolism and a specific neuronal activity. We review here the experimental evidence for this model as well as implications for blood oxygenation level dependent magnetic resonance imaging and positron emission tomography functional imaging studies of brain function. PMID:10466144

  4. The QBO as Potential Amplifier and Conduit to Lower Altitudes of Solar Cycle Influence?

    NASA Technical Reports Server (NTRS)

    Mayr, Hans G.; Mengel, John G.; Porter, Hayden S.

    2005-01-01

    The solar cycle (SC) effect in the lower atmosphere has been linked observationally to the Quasi-biennial Oscillation (QBO), which is generated primarily by small-scale gravity waves (GW). Following up on a 2D study with our Numerical Spectral Model (NSM), we discuss here a 3D study in which we simulated the QBO under the influence of the SC. For a SC period of 10 years, the relative amplitude of radiative forcing is taken to vary exponentially with height, i.e., 0.2% at the surface, 2% at 50 km, 20% at 100 km and above. Applying spectral analysis to filter out and identify the SC signature, this model produces a relatively large modulation in the QBO of the lower stratospheric circulation, which is in qualitative agreement with the results obtained by Salby and Callaghan (2000) who analyzed zonal wind observations covering more than 40 years. The modeled SC modulation of the QBO extends to high latitudes where it produces temperature variations of about 1 K in the troposphere below 10 km. We report that the SC also generates in the model a hemispherically symmetric Equatorial Annual Oscillation (EAO, with 12-month period) that is largely confined to low latitudes. Under the influence of the GWs, the SC modulated EA0 propagates down into the lower stratosphere like the QBO. As is the case for the QBO, the energy of this EA0 is partially redistributed by the meridional circulation and planetary waves, presumably, to generate measurable SC signatures in the tropospheric temperature of the polar regions, which may be related to the so called Arctic Oscillation (Thompson and Wallace, 1998). The larger SC influence at higher altitudes is apparently transferred to the lower and denser regions of the atmosphere by tapping the momentum from the upward propagating GWs that drive the oscillations. The SC modulation of the QBO period could prove to be very effective in this process, as our earlier 2D study indicated. Further studies are needed, (1) to make sure that the SC

  5. Factors influencing the life cycle burdens of the recovery of energy from residual municipal waste.

    PubMed

    Burnley, Stephen; Coleman, Terry; Peirce, Adam

    2015-05-01

    A life cycle assessment was carried out to assess a selection of the factors influencing the environmental impacts and benefits of incinerating the fraction of municipal waste remaining after source-separation for reuse, recycling, composting or anaerobic digestion. The factors investigated were the extent of any metal and aggregate recovery from the bottom ash, the thermal efficiency of the process, and the conventional fuel for electricity generation displaced by the power generated. The results demonstrate that incineration has significant advantages over landfill with lower impacts from climate change, resource depletion, acidification, eutrophication human toxicity and aquatic ecotoxicity. To maximise the benefits of energy recovery, metals, particularly aluminium, should be reclaimed from the residual bottom ash and the energy recovery stage of the process should be as efficient as possible. The overall environmental benefits/burdens of energy from waste also strongly depend on the source of the power displaced by the energy from waste, with coal giving the greatest benefits and combined cycle turbines fuelled by natural gas the lowest of those considered. Regardless of the conventional power displaced incineration presents a lower environmental burden than landfill. PMID:25758908

  6. Factors influencing the life cycle burdens of the recovery of energy from residual municipal waste.

    PubMed

    Burnley, Stephen; Coleman, Terry; Peirce, Adam

    2015-05-01

    A life cycle assessment was carried out to assess a selection of the factors influencing the environmental impacts and benefits of incinerating the fraction of municipal waste remaining after source-separation for reuse, recycling, composting or anaerobic digestion. The factors investigated were the extent of any metal and aggregate recovery from the bottom ash, the thermal efficiency of the process, and the conventional fuel for electricity generation displaced by the power generated. The results demonstrate that incineration has significant advantages over landfill with lower impacts from climate change, resource depletion, acidification, eutrophication human toxicity and aquatic ecotoxicity. To maximise the benefits of energy recovery, metals, particularly aluminium, should be reclaimed from the residual bottom ash and the energy recovery stage of the process should be as efficient as possible. The overall environmental benefits/burdens of energy from waste also strongly depend on the source of the power displaced by the energy from waste, with coal giving the greatest benefits and combined cycle turbines fuelled by natural gas the lowest of those considered. Regardless of the conventional power displaced incineration presents a lower environmental burden than landfill.

  7. Lunar cycles at mating do not influence sex ratio at birth in horses.

    PubMed

    Aguilar, J J; Cuervo-Arango, J; Santa Juliana, L

    2015-02-01

    It is scientifically demonstrated that lunar cycles have important effects on several biological events. Controversy exists about the lunar influence on human and animal parturition. In addition, in the horse industry, especially in Polo Horse breeders of Argentina and around the world there is a higher demand for female offspring than for males. The objective of this study was to determine whether there is a significant association between the lunar phase at the time of mating and the sex ratio at birth in horses. The Argentinean Stud Book provided information related to all matings registered for Thoroughbred and Arab horses between 2003 and 2011. Statistical associations were tested between dates of matings at different lunar phases or days and sex ratio at birth. A total of 65.535 gestations were studied. Overall, sex ratio at birth resulted in 33.396 fillies (50.96%) and 32.139 colts (49.04%). The percentages of males and females at birth were not statistically different amongst the different lunar phases or days. We can strongly conclude that managing the breeding dates in relation to lunar cycles in order to manipulate the sex ratio of the offspring is not a viable option in horses.

  8. The factors influencing car use in a cycle-friendly city: the case of Cambridge.

    PubMed

    Carse, Andrew; Goodman, Anna; Mackett, Roger L; Panter, Jenna; Ogilvie, David

    2013-04-01

    Encouraging people out of their cars and into other modes of transport, which has major advantages for health, the environment and urban development, has proved difficult. Greater understanding of the influences that lead people to use the car, particularly for shorter journeys, may help to achieve this. This paper examines the predictors of car use compared with the bicycle to explore how it may be possible to persuade more people to use the bicycle instead of the car. Multivariable logistic regression was used to examine the socio-demographic, transport and health-related correlates of mode choice for work, shopping and leisure trips in Cambridge, a city with high levels of cycling by UK standards. The key findings are that commuting distance and free workplace parking were strongly associated with use of the car for work trips, and car availability and lower levels of education were associated with car use for leisure, shopping and short-distanced commuting trips. The case of Cambridge shows that more policies could be adopted, particularly a reduction in free car parking, to increase cycling and reduce the use of the car, especially over short distances.

  9. Selection of organic process and source indicator substances for the anthropogenically influenced water cycle.

    PubMed

    Jekel, Martin; Dott, Wolfgang; Bergmann, Axel; Dünnbier, Uwe; Gnirß, Regina; Haist-Gulde, Brigitte; Hamscher, Gerd; Letzel, Marion; Licha, Tobias; Lyko, Sven; Miehe, Ulf; Sacher, Frank; Scheurer, Marco; Schmidt, Carsten K; Reemtsma, Thorsten; Ruhl, Aki Sebastian

    2015-04-01

    An increasing number of organic micropollutants (OMP) is detected in anthropogenically influenced water cycles. Source control and effective natural and technical barriers are essential to maintain a high quality of drinking water resources under these circumstances. Based on the literature and our own research this study proposes a limited number of OMP that can serve as indicator substances for the major sources of OMP, such as wastewater treatment plants, agriculture and surface runoff. Furthermore functional indicators are proposed that allow assessment of the proper function of natural and technical barriers in the aquatic environment, namely conventional municipal wastewater treatment, advanced treatment (ozonation, activated carbon), bank filtration and soil aquifer treatment as well as self-purification in surface water. These indicator substances include the artificial sweetener acesulfame, the anti-inflammatory drug ibuprofen, the anticonvulsant carbamazepine, the corrosion inhibitor benzotriazole and the herbicide mecoprop among others. The chemical indicator substances are intended to support comparisons between watersheds and technical and natural processes independent of specific water cycles and to reduce efforts and costs of chemical analyses without losing essential information.

  10. The factors influencing car use in a cycle-friendly city: the case of Cambridge

    PubMed Central

    Carse, Andrew; Goodman, Anna; Mackett, Roger L.; Panter, Jenna; Ogilvie, David

    2013-01-01

    Encouraging people out of their cars and into other modes of transport, which has major advantages for health, the environment and urban development, has proved difficult. Greater understanding of the influences that lead people to use the car, particularly for shorter journeys, may help to achieve this. This paper examines the predictors of car use compared with the bicycle to explore how it may be possible to persuade more people to use the bicycle instead of the car. Multivariable logistic regression was used to examine the socio-demographic, transport and health-related correlates of mode choice for work, shopping and leisure trips in Cambridge, a city with high levels of cycling by UK standards. The key findings are that commuting distance and free workplace parking were strongly associated with use of the car for work trips, and car availability and lower levels of education were associated with car use for leisure, shopping and short-distanced commuting trips. The case of Cambridge shows that more policies could be adopted, particularly a reduction in free car parking, to increase cycling and reduce the use of the car, especially over short distances. PMID:24954981

  11. High-power UV-LED degradation: Continuous and cycled working condition influence

    NASA Astrophysics Data System (ADS)

    Arques-Orobon, F. J.; Nuñez, N.; Vazquez, M.; Segura-Antunez, C.; González-Posadas, V.

    2015-09-01

    High-power (HP) UV-LEDs can replace UV lamps for real-time fluoro-sensing applications by allowing portable and autonomous systems. However, HP UV-LEDs are not a mature technology, and there are still open issues regarding their performance evolution over time. This paper presents a reliability study of 3 W UV-LEDs, with special focus on LED degradation for two working conditions: continuous and cycled (30 s ON and 30 s OFF). Accelerated life tests are developed to evaluate the influence of temperature and electrical working conditions in high-power LEDs degradation, being the predominant failure mechanism the degradation of the package. An analysis that includes dynamic thermal and optical HP UV-LED measurements has been performed. Static thermal and stress simulation analysis with the finite element method (FEM) identifies the causes of package degradation. Accelerated life test results prove that HP UV-LEDs working in cycled condition have a better performance than those working in continuous condition.

  12. Selection of organic process and source indicator substances for the anthropogenically influenced water cycle.

    PubMed

    Jekel, Martin; Dott, Wolfgang; Bergmann, Axel; Dünnbier, Uwe; Gnirß, Regina; Haist-Gulde, Brigitte; Hamscher, Gerd; Letzel, Marion; Licha, Tobias; Lyko, Sven; Miehe, Ulf; Sacher, Frank; Scheurer, Marco; Schmidt, Carsten K; Reemtsma, Thorsten; Ruhl, Aki Sebastian

    2015-04-01

    An increasing number of organic micropollutants (OMP) is detected in anthropogenically influenced water cycles. Source control and effective natural and technical barriers are essential to maintain a high quality of drinking water resources under these circumstances. Based on the literature and our own research this study proposes a limited number of OMP that can serve as indicator substances for the major sources of OMP, such as wastewater treatment plants, agriculture and surface runoff. Furthermore functional indicators are proposed that allow assessment of the proper function of natural and technical barriers in the aquatic environment, namely conventional municipal wastewater treatment, advanced treatment (ozonation, activated carbon), bank filtration and soil aquifer treatment as well as self-purification in surface water. These indicator substances include the artificial sweetener acesulfame, the anti-inflammatory drug ibuprofen, the anticonvulsant carbamazepine, the corrosion inhibitor benzotriazole and the herbicide mecoprop among others. The chemical indicator substances are intended to support comparisons between watersheds and technical and natural processes independent of specific water cycles and to reduce efforts and costs of chemical analyses without losing essential information. PMID:25563167

  13. Lunar cycles at mating do not influence sex ratio at birth in horses.

    PubMed

    Aguilar, J J; Cuervo-Arango, J; Santa Juliana, L

    2015-02-01

    It is scientifically demonstrated that lunar cycles have important effects on several biological events. Controversy exists about the lunar influence on human and animal parturition. In addition, in the horse industry, especially in Polo Horse breeders of Argentina and around the world there is a higher demand for female offspring than for males. The objective of this study was to determine whether there is a significant association between the lunar phase at the time of mating and the sex ratio at birth in horses. The Argentinean Stud Book provided information related to all matings registered for Thoroughbred and Arab horses between 2003 and 2011. Statistical associations were tested between dates of matings at different lunar phases or days and sex ratio at birth. A total of 65.535 gestations were studied. Overall, sex ratio at birth resulted in 33.396 fillies (50.96%) and 32.139 colts (49.04%). The percentages of males and females at birth were not statistically different amongst the different lunar phases or days. We can strongly conclude that managing the breeding dates in relation to lunar cycles in order to manipulate the sex ratio of the offspring is not a viable option in horses. PMID:25153135

  14. Intertidal Concentrations of Microplastics and Their Influence on Ammonium Cycling as Related to the Shellfish Industry.

    PubMed

    Cluzard, Melanie; Kazmiruk, Tamara N; Kazmiruk, Vasily D; Bendell, L I

    2015-10-01

    Microplastics are ubiquitous within the marine environment. The last 10 years have seen research directed at understanding the fate and effect of microplastics within the marine environment; however, no studies have yet addressed how concentrations of these particles could affect sedimentary processes such as nutrient cycling. Herein we first determine the concentration and spatial distribution of microplastics within Baynes Sound, a key shellfish-growing area within coastal British Columbia (BC). We also determined sediment grain size and % organic matter (OM) such that we could relate spatial patterns in sediment microplastic concentrations to sedimentary processes that determine zones of accretion and erosion. Using field-determined concentrations of microplastics, we applied laboratory microcosms studies, which manipulated sediment concentrations of microplastics, OM, and bivalves to determine the influence of sediment microplastics on ammonium cycling within intertidal sediments. Concentrations of microplastics determined within the intertidal sediment varied spatially and were similar to those found in other coastal regions of high urban use. Concentrations were independent of grain size and OM suggesting that physical processes other than those that govern natural sediment components determine the fate of microplastics within sediments. Under laboratory conditions, concentrations of ammonium were significantly greater in the overlying water of treatments with microplastics, clams, and OM compared with treatments without microplastics. These preliminary studies suggest that high concentrations of microplastics have the potential to alter key sedimentary processes such as ammonium flux. This could have serious implications, for example, contributing to eutrophication events in regions of the coast that are highly urbanized.

  15. The effect of restraint stress on paradoxical sleep is influenced by the circadian cycle.

    PubMed

    Koehl, M; Bouyer, J J; Darnaudéry, M; Le Moal, M; Mayo, W

    2002-05-24

    It is well known that the physiological impact imposed by events or behaviors displayed during the waking period determines the way organisms sleep. Among the situations known to affect sleep both in its duration and quality, stress has been widely studied and it is now admitted that its effects on sleep architecture depend on several factors specific to the stressor or the individual itself. Although numerous reports have highlighted the prominent role of the circadian cycle in the physiological, endocrine and behavioral consequences of restraint stress, a possible circadian influence in the effects of stress on the sleep-wake cycle has never been studied. Thus the present study was designed to compare the effects on sleep of a 1 h-lasting restraint stress applied at light onset to those observed after the same stressor was applied at light offset. We report that in both conditions stress induced a marked paradoxical sleep increase, whereas wakefulness displayed a moderate decrease and slow wave sleep a moderate augmentation. Although the effects of stress at lights on were of similar magnitude than those of stress at lights off, important differences in the sleep rebound latencies were observed: whatever the time of day the stress was applied, its effects on sleep always occurred during the dark period. This result thus shows that restraint stress could be efficiently used to study the interaction between the circadian and homeostatic components of sleep regulation. PMID:12020861

  16. [Modeling the Influencing Factors of Karstification and Karst Carbon Cycle in Laboratory].

    PubMed

    Zhao, Rui-yi; Lü, Xian-fu; Duan, Yi-fan

    2015-08-01

    To analyze the influencing factors of karstification and karst carbon cycle, a simulation experiment was carried out and 6 soil columns were designed. The results showed that the content of H2O4, hydrodynamic condition and thickness of the soil had important influence on karstification and karst carbon cycle. For the soil columns which were covered by the same thickness of soil, the concentrations of Ca2+ + Mg2+ and SO4(2-) followed the order of B20-2 > B20-1 > B20-3, B50-2 > B50-1 > B50-3. This meant that input of H2SO4 enhanced the karstification and increasing infiltration water had significant dilution effect on the chemical properties. For the soil columns with different thickness of soil but with the same slag pile and hydrodynamic conditions, the concentrations of Ca2+ + Mg2+ and SO4(2-) followed the order of B50-1 > B20-1, B50-2 > B20-2, B50-3 > B20-3. It was demonstrated that more carbonate rock was dissolved under the thick soil columns. In addition, the net consumption of CO2 mainly depended on the content of H2SO4 in this experiment due to slight contribution of H2CO3 to carbonate rock dissolution. More content of H2SO4 brought about less net consumption of C02, but B50-2 was an exception. Organic matter and other nutrients might be input into deep soil with the slag pile, and they promoted the production of soil C)2. Therefore, more CO2 was consumed due to the increased contribution of H2CO to karstification. PMID:26592011

  17. [Modeling the Influencing Factors of Karstification and Karst Carbon Cycle in Laboratory].

    PubMed

    Zhao, Rui-yi; Lü, Xian-fu; Duan, Yi-fan

    2015-08-01

    To analyze the influencing factors of karstification and karst carbon cycle, a simulation experiment was carried out and 6 soil columns were designed. The results showed that the content of H2O4, hydrodynamic condition and thickness of the soil had important influence on karstification and karst carbon cycle. For the soil columns which were covered by the same thickness of soil, the concentrations of Ca2+ + Mg2+ and SO4(2-) followed the order of B20-2 > B20-1 > B20-3, B50-2 > B50-1 > B50-3. This meant that input of H2SO4 enhanced the karstification and increasing infiltration water had significant dilution effect on the chemical properties. For the soil columns with different thickness of soil but with the same slag pile and hydrodynamic conditions, the concentrations of Ca2+ + Mg2+ and SO4(2-) followed the order of B50-1 > B20-1, B50-2 > B20-2, B50-3 > B20-3. It was demonstrated that more carbonate rock was dissolved under the thick soil columns. In addition, the net consumption of CO2 mainly depended on the content of H2SO4 in this experiment due to slight contribution of H2CO3 to carbonate rock dissolution. More content of H2SO4 brought about less net consumption of C02, but B50-2 was an exception. Organic matter and other nutrients might be input into deep soil with the slag pile, and they promoted the production of soil C)2. Therefore, more CO2 was consumed due to the increased contribution of H2CO to karstification.

  18. Paleomagnetism in speleothems: Influence of calcite growth dip on the natural remanent magnetization

    NASA Astrophysics Data System (ADS)

    Ponte, Jorge; Font, Eric; Veiga-Pires, Cristina; Hillaire Marcel, Claude

    2016-04-01

    Recent studies recognized speleothems as excellent recorders of the Earth's magnetic field. However, some questions remain about the origin of the natural remanent magnetization and about the influence of the speleothem shape on the recorded magnetic directions. Preliminary paleomagnetic data acquired in a Portuguese speleothem (cubic samples with 8 cm3), dated in the Holocene period (5000-6500 yrs BP), showed that the values of the remanent magnetic inclination vary in function of the orientation (dip) of the calcite growth and of the orientation of the K3 axis measured by Anisotropy of Magnetic Susceptibility (AMS) techniques. In counterpart, declination does not exhibit significant variations. On this basis, we suggested that the recorded remanent magnetic directions are affected by the shape of the stalagmite. Here, we duplicated the paleomagnetic analysis by using smaller cylindrical samples with 2 cm3 in volume in order to check for possible artifact due to sampling technique and to improve our temporal resolution. Our new results confirmed a good correlation between the inclination values of the natural remanent magnetization and the dip of the calcite growth. Once compared with paleosecular variation models, our data fit the expected declination and inclination values at 5000-6500 yrs BP. These new findings highlight the importance of the influence of the stalagmite shape on the recorded remanent magnetization and provides us new clues to improve the quality of the high-resolution geomagnetic records in speleothems. Funded by IDL (FCT UID/GEO/50019/2013)

  19. Influence of technology on magnetic tape storage device characteristics

    NASA Technical Reports Server (NTRS)

    Gniewek, John J.; Vogel, Stephen M.

    1994-01-01

    There are available today many data storage devices that serve the diverse application requirements of the consumer, professional entertainment, and computer data processing industries. Storage technologies include semiconductors, several varieties of optical disk, optical tape, magnetic disk, and many varieties of magnetic tape. In some cases, devices are developed with specific characteristics to meet specification requirements. In other cases, an existing storage device is modified and adapted to a different application. For magnetic tape storage devices, examples of the former case are 3480/3490 and QIC device types developed for the high end and low end segments of the data processing industry respectively, VHS, Beta, and 8 mm formats developed for consumer video applications, and D-1, D-2, D-3 formats developed for professional video applications. Examples of modified and adapted devices include 4 mm, 8 mm, 12.7 mm and 19 mm computer data storage devices derived from consumer and professional audio and video applications. With the conversion of the consumer and professional entertainment industries from analog to digital storage and signal processing, there have been increasing references to the 'convergence' of the computer data processing and entertainment industry technologies. There has yet to be seen, however, any evidence of convergence of data storage device types. There are several reasons for this. The diversity of application requirements results in varying degrees of importance for each of the tape storage characteristics.

  20. Influence of the dipolar interactions in the magnetization reversal asymmetry of hard-soft magnetic ribbons

    SciTech Connect

    Rivas, M.; Garcia, J.A.; Tejedor, M.; Bertran, E.; Cespedes, J.G.

    2005-01-15

    Partial crystallization of the metallic glass Co{sub 66}Si{sub 16}B{sub 12}Fe{sub 4}Mo{sub 2} was performed by annealing at temperatures between 500 and 540 deg. C for 10-20 min, resulting in crystallite volume fractions of (0.7-5)x10{sup -3} and sizes of 50-100 nm. This two-phase alloy presents a remarkable feature: a hysteresis loop shift that can be tailored by simply premagnetizing the sample in the adequate magnetic field. Shifts as large as five times the coercive field have been obtained which make them interesting for application as magnetic cores in dc pulse transformers. The asymetrical magnetic reversal is explained in terms of the magnetic dipolar field interaction and the observed hysteresis loops have been satisfactorily simulated by a modification of Stoner-Wohlfarth's model of coherent rotations.

  1. Influence of Observed Diurnal Cycles of Aerosol Optical Depth on Aerosol Direct Radiative Effect

    NASA Technical Reports Server (NTRS)

    Arola, A.; Eck, T. F.; Huttunen, J.; Lehtinen, K. E. J.; Lindfors, A. V.; Myhre, G.; Smirinov, A.; Tripathi, S. N.; Yu, H.

    2013-01-01

    The diurnal variability of aerosol optical depth (AOD) can be significant, depending on location and dominant aerosol type. However, these diurnal cycles have rarely been taken into account in measurement-based estimates of aerosol direct radiative forcing (ADRF) or aerosol direct radiative effect (ADRE). The objective of our study was to estimate the influence of diurnal aerosol variability at the top of the atmosphere ADRE estimates. By including all the possible AERONET sites, we wanted to assess the influence on global ADRE estimates. While focusing also in more detail on some selected sites of strongest impact, our goal was to also see the possible impact regionally.We calculated ADRE with different assumptions about the daily AOD variability: taking the observed daily AOD cycle into account and assuming diurnally constant AOD. Moreover, we estimated the corresponding differences in ADREs, if the single AOD value for the daily mean was taken from the the Moderate Resolution Imaging Spectroradiometer (MODIS) Terra or Aqua overpass times, instead of accounting for the true observed daily variability. The mean impact of diurnal AOD variability on 24 h ADRE estimates, averaged over all AERONET sites, was rather small and it was relatively small even for the cases when AOD was chosen to correspond to the Terra or Aqua overpass time. This was true on average over all AERONET sites, while clearly there can be much stronger impact in individual sites. Examples of some selected sites demonstrated that the strongest observed AOD variability (the strongest morning afternoon contrast) does not typically result in a significant impact on 24 h ADRE. In those cases, the morning and afternoon AOD patterns are opposite and thus the impact on 24 h ADRE, when integrated over all solar zenith angles, is reduced. The most significant effect on daily ADRE was induced by AOD cycles with either maximum or minimum AOD close to local noon. In these cases, the impact on 24 h ADRE was

  2. The Influence of Serial Carbohydrate Mouth Rinsing on Power Output during a Cycle Sprint

    PubMed Central

    Phillips, Shaun M.; Findlay, Scott; Kavaliauskas, Mykolas; Grant, Marie Clare

    2014-01-01

    The objective of the study was to investigate the influence of serial administration of a carbohydrate (CHO) mouth rinse on performance, metabolic and perceptual responses during a cycle sprint. Twelve physically active males (mean (± SD) age: 23.1 (3.0) years, height: 1.83 (0.07) m, body mass (BM): 86.3 (13.5) kg) completed the following mouth rinse trials in a randomized, counterbalanced, double-blind fashion; 1. 8 x 5 second rinses with a 25 ml CHO (6% w/v maltodextrin) solution, 2. 8 x 5 second rinses with a 25 ml placebo (PLA) solution. Following mouth rinse administration, participants completed a 30 second sprint on a cycle ergometer against a 0.075 g·kg-1 BM resistance. Eight participants achieved a greater peak power output (PPO) in the CHO trial, resulting in a significantly greater PPO compared with PLA (13.51 ± 2.19 vs. 13.20 ± 2.14 W·kg-1, p < 0.05). Magnitude inference analysis reported a likely benefit (81% likelihood) of the CHO mouth rinse on PPO. In the CHO trial, mean power output (MPO) showed a trend for being greater in the first 5 seconds of the sprint and lower for the remainder of the sprint compared with the PLA trial (p > 0.05). No significant between-trials difference was reported for fatigue index, perceived exertion, arousal and nausea levels, or blood lactate and glucose concentrations. Serial administration of a CHO mouth rinse may significantly improve PPO during a cycle sprint. This improvement appears confined to the first 5 seconds of the sprint, and may come at a greater relative cost for the remainder of the sprint. Key points The paper demonstrates that repeated administration of a carbohydrate mouth rinse can significantly improve peak power output during a single 30 second cycle sprint. The ergogenic effect of the carbohydrate mouth rinse may relate to the duration of exposure of the oral cavity to the mouth rinse, and associated greater stimulation of oral carbohydrate receptors. The significant increase in peak power

  3. The Influence of Serial Carbohydrate Mouth Rinsing on Power Output during a Cycle Sprint.

    PubMed

    Phillips, Shaun M; Findlay, Scott; Kavaliauskas, Mykolas; Grant, Marie Clare

    2014-05-01

    The objective of the study was to investigate the influence of serial administration of a carbohydrate (CHO) mouth rinse on performance, metabolic and perceptual responses during a cycle sprint. Twelve physically active males (mean (± SD) age: 23.1 (3.0) years, height: 1.83 (0.07) m, body mass (BM): 86.3 (13.5) kg) completed the following mouth rinse trials in a randomized, counterbalanced, double-blind fashion; 1. 8 x 5 second rinses with a 25 ml CHO (6% w/v maltodextrin) solution, 2. 8 x 5 second rinses with a 25 ml placebo (PLA) solution. Following mouth rinse administration, participants completed a 30 second sprint on a cycle ergometer against a 0.075 g·kg(-1) BM resistance. Eight participants achieved a greater peak power output (PPO) in the CHO trial, resulting in a significantly greater PPO compared with PLA (13.51 ± 2.19 vs. 13.20 ± 2.14 W·kg(-1), p < 0.05). Magnitude inference analysis reported a likely benefit (81% likelihood) of the CHO mouth rinse on PPO. In the CHO trial, mean power output (MPO) showed a trend for being greater in the first 5 seconds of the sprint and lower for the remainder of the sprint compared with the PLA trial (p > 0.05). No significant between-trials difference was reported for fatigue index, perceived exertion, arousal and nausea levels, or blood lactate and glucose concentrations. Serial administration of a CHO mouth rinse may significantly improve PPO during a cycle sprint. This improvement appears confined to the first 5 seconds of the sprint, and may come at a greater relative cost for the remainder of the sprint. Key pointsThe paper demonstrates that repeated administration of a carbohydrate mouth rinse can significantly improve peak power output during a single 30 second cycle sprint.The ergogenic effect of the carbohydrate mouth rinse may relate to the duration of exposure of the oral cavity to the mouth rinse, and associated greater stimulation of oral carbohydrate receptors.The significant increase in peak power

  4. Influence of temperature, current and number of cycles on the efficiency of the closed oxygen cycle in VRLA batteries

    NASA Astrophysics Data System (ADS)

    Pavlov, D.; Ruevski, S.; Naidenov, V.; Sheytanov, G.

    An experimental method was created for assessment of the efficiency of the closed oxygen cycle in VRLA cells. It was experimentally established that at 25% compression of the AGM separator the battery life is the longest one. On the other hand, the efficiency of the closed oxygen cycle (COC) is the highest at 20% compression of the AGM. With an increase of the compression the efficiency of the COC decreases because of the decreasing of the number of the channels (pores) along which the oxygen flows can move through the AGM separator. It was established that the polarization of the VRLA cell is mainly determined by the resistance arising at transportation of the oxygen through the AGM. There is an upper limit of the rate of recombination of oxygen that depends on the structure and properties of the AGM. With increase of the temperature the efficiency of the COC and polarization of the VRLA cell decrease. During cycling, the properties and structure of the AGM change that affects the parameters of VRLAB.

  5. A Pinger Magnet System For Tune Measurements in the IPNS Rapid Cycling Synchrotron (RCS)

    SciTech Connect

    Dooling, J. C.; Donley, L.; Brumwell, F. R.; McMichael, G. E.; Wang, S.

    2006-11-20

    Pinger magnets for measuring horizontal and vertical tunes in the IPNS RCS have been constructed and installed. Reference horizontal tune data was collected using the extraction kicker magnets in December 2005. More recent data collected at the end of February 2006 with the dedicated pinger magnets confirms December measurements and provided simultaneous vertical tune information. Chromaticity variation with sextupole field strength is examined in an effort to optimize tune profiles.

  6. A pinger magnet system for tune measurements in the IPNS Rapid Cycling Synchrotron (RCS).

    SciTech Connect

    Dooling, J. C.; Donley, L. I.; Brumwell, F. R.; McMichael, G. E.; Wang, S.; Intense Pulsed Neutron Source

    2006-01-01

    Pinger magnets for measuring horizontal and vertical tunes in the IPNS RCS have been constructed and installed. Reference horizontal tune data was collected using the extraction kicker magnets in December 2005. More recent data collected at the end of February 2006 with the dedicated pinger magnets confirms December measurements and provided simultaneous vertical tune information. Chromaticity variation with sextupole field strength is examined in an effort to optimize tune profiles.

  7. A Pinger Magnet System For Tune Measurements in the IPNS Rapid Cycling Synchrotron (RCS)

    NASA Astrophysics Data System (ADS)

    Dooling, J. C.; Donley, L.; Brumwell, F. R.; McMichael, G. E.; Wang, S.

    2006-11-01

    Pinger magnets for measuring horizontal and vertical tunes in the IPNS RCS have been constructed and installed. Reference horizontal tune data was collected using the extraction kicker magnets in December 2005. More recent data collected at the end of February 2006 with the dedicated pinger magnets confirms December measurements and provided simultaneous vertical tune information. Chromaticity variation with sextupole field strength is examined in an effort to optimize tune profiles.

  8. Deconfinement to quark matter in neutron stars - The influence of strong magnetic fields

    SciTech Connect

    Dexheimer, V.; Negreiros, R.; Schramm, S.; Hempel, M.

    2013-03-25

    We use an extended version of the hadronic SU(3) non-linear realization of the sigma model that also includes quarks to study hybrid stars. Within this approach, the degrees of freedom change naturally as the temperature/density increases. Different prescriptions of charge neutrality, local and global, are tested and the influence of strong magnetic fields and the anomalous magnetic moment on the particle population is discussed.

  9. The influence of combined magnetic field on the fusion of plant protoplasts.

    PubMed

    Nedukha, O; Kordyum, E; Bogatina, N; Sobol, M; Vorobyeva, T; Ovcharenko, Yu

    2007-07-01

    The study of the influence of weak, alternating magnetic field, which was adjusted to the cyclotron frequency of Ca2+ and K+ ions, on the fusion of tobacco and soya protoplasts was carried out using the extra apparatus with ferromagnetic shield. An increase in the frequency of protoplasts fusion in 2-3 times and participation of calcium ions in the induction of protoplast fusion in weak alternating magnetic field have been established.

  10. Influence of carbon doping on the reversible magnetization of MgB 2 single crystals

    NASA Astrophysics Data System (ADS)

    Eisterer, M.; Krutzler, C.; Zehetmayer, M.; Weber, H. W.; Kazakov, S. M.; Karpinski, J.

    2007-09-01

    The reversible magnetization of Mg(B1-xCx)2 single crystals with varying carbon content (x = 0-0.095) was measured by SQUID magnetometry. It was found to be strongly influenced by the two-band character of this material. At low magnetic fields charge carriers of both bands contribute to superconductivity and to diamagnetism. At high fields the π-band is suppressed and the σ-band mainly determines the magnetization. This allows us to extract information on both bands by analyzing the reversible magnetization in terms of two band Ginzburg-Landau (GL) theory. The "intrinsic" magnetic penetration increases in both bands with increasing carbon content, but the σ-band remains crucial for the upper critical field. Changes in the field dependence of the resulting "effective" penetration depth by carbon doping are discussed.

  11. The influence of eddy currents on magnetic actuator performance

    NASA Technical Reports Server (NTRS)

    Zmood, R. B.; Anand, D. K.; Kirk, J. A.

    1987-01-01

    The present investigation of the effects of eddy currents on EM actuators' transient performance notes that a transfer function representation encompassing a first-order model of the eddy current influence can be useful in control system analysis. The method can be extended to represent the higher-order effects of eddy currents for actuators that cannot be represented by semiinfinite planes.

  12. Dynamics assembly of magnetic microparticles suspended in moving droplets under the influence of magnetic fields

    NASA Astrophysics Data System (ADS)

    Strey, Helmut; Brouzes, Eric; Kruse, Travis

    2013-03-01

    Droplet microfluidics has experienced tremendous growth, particularly since it is well suited for single-cell manipulation and analysis. As mature methods for high throughput droplet manipulation have been developed a technological bottleneck of current droplet microfluidics is that because droplets are separated, sequential chemical reactions are more difficult to achieve. For example, it is very difficult to concentrate target molecules, especially since every reaction step adds volume to the droplets. Our solution to this problem is to employ functionalized magnetic beads inside droplets. The basic idea is that an external magnetic field could be used to concentrate the magnetic beads in one part of the droplet and those could then be extracted by splitting the droplet. Here we present an experimental study of the self-assembly of superparamagnetic microparticles that are suspended in moving droplets and experience a combination of forces due to the internal fluid flow fields and external magnetic fields. We observed that this interplay of flow fields coupled to the formation of particle assemblies leads to the formations of stable patterns depending on the flow speed and magnetic field strength. An understanding of this dynamic assembly is critical in employing external forces for applications in separation and sorting. Funding through NYSTAR, Center for Advanced Technology and a grant from NIH-NHGRI (1 R21 HG006206-01).

  13. An influence of cobalt impurities distribution on electronic and magnetic properties of Cr3Si

    NASA Astrophysics Data System (ADS)

    Matwiejczyk, Anna; Pylak, Maciej; Dobrzyński, Ludwik

    2015-12-01

    Electronic and magnetic structure of Cr3Si doped with Co atoms is theoretically studied. Co-Co distance as well as an influence of nearest neighbors are discussed. Two concentrations of Co impurity were taken into account: x=0.0625 and x=0.125. In case of the former, unambiguous determination of ground-state magnetic structure is not possible. At higher concentration, the total energy decreases with decreasing distance between cobalt atoms which could indicate a tendency to clustering. Negative magnetic polarization has been observed in the interstitial region.

  14. Influence of a Static Magnetic Field on Laser Induced Tungsten Plasma in Air

    NASA Astrophysics Data System (ADS)

    Wu, Ding; Liu, Ping; Sun, Liying; Hai, Ran; Ding, Hongbin

    2016-04-01

    In this work, laser induced tungsten plasma has been investigated in the absence and presence of 0.6 T static transverse magnetic field at atmospheric pressure in air. The spectroscopic characterization of laser induced tungsten plasma was experimentally studied using space-resolved emission spectroscopy. The atomic emission lines of tungsten showed a significant enhancement in the presence of a magnetic field, while the ionic emission lines of tungsten presented little change. Temporal variation of the optical emission lines of tungsten indicated that the atomic emission time in the presence of a magnetic field was longer than that in the absence of a magnetic field, while no significant changes occurred for the ionic emission time. The spatial resolution of optical emission lines of tungsten demonstrated that the spatial distribution of atoms and ions were separated. The influence of a magnetic field on the spatial distribution of atoms was remarkable, whereas the spatial distribution of ions was little influenced by the magnetic field. The different behaviors between ions and atoms with and without magnetic field in air were related to the various atomic processes especially the electrons and ions recombination process during the plasma expansion and cooling process.

  15. Radial and Solar Cycle Variations of the Magnetic Fields in the Heliosheath: Voyager 1 Observations from 2005 to 2008

    NASA Technical Reports Server (NTRS)

    Burlaga, Leonard; Ness, N.

    2009-01-01

    We discuss the magnetic field strength B(t) and polarity observed by Voyager 1 (V1) in the heliosheath at the heliographic latitude approximately equal 34 deg as it moved away from the sun from 2005 through 2008.82. The pattern of the polarity of the magnetic field changed from alternating positive and negative polarities to predominantly negative polarities (magnetic fields pointing along the Archimedean spiral field angle toward the sun) at approximately equal 2006.23). This transition indicates that the latitudinal extent of the heliospheric current sheet (HCS) was decreasing in the supersonic solar wind, as expected for the declining phase of the solar cycle, and as predicted by extrapolation of the magnetic neutral line near the photosphere to the position of V1. However, the polarity was not uniformly negative in during 2008, in contrast to the predicted polarity. This difference suggests that the maximum latitudinal extent of the HCS was tending to increase in the northern hemisphere in the heliosheath, while it was decreasing in the supersonic solar wind. The large-scale magnetic field strength B(t) HCS was observed by V1 from 2005 through 2008.820. During this interval of decreasing solar activity toward solar minimum, B(t) at 1 AU was decreasing and the solar wind speed V at the latitude of V1 was increasing. Adjusting the temporal profile of B(t) observed by V1 for the solar cycle variations of B and V in the supersonic solar wind, we find that the radial gradient of B(R) in heliosheath from the radial distance R = 94.2 AU to 107.9 AU between 2005.0 and 2008.82 was 0.0017 nT/AU <= grad B <= 0.0055 nT/AU or grad B = (0.0036 +/- 0.0019) nT/AU

  16. The influence of dimensionality on the behavior of magnetic dipolar soft spheres: calculation of the pressure.

    PubMed

    Minina, E; Kantorovich, S

    2013-04-17

    We investigate the influence of dimensionality of a sample on the properties of magnetic dipolar soft spheres. Molecular dynamics simulations and diagram expansion are employed to analyze the pressure and microscopic structure of model monodisperse magnetic fluids in a bulk and in a monolayer. We found that, for a broad range of densities and dipolar interaction strengths, strong geometrical confinement weakens the influence of the dipole-dipole interaction on the pressure and, as a result, steric repulsion of dipolar particles provides the main contribution to the thermodynamic properties of ferrofluids in strong confinement. PMID:23515201

  17. TURBULENT PUMPING OF MAGNETIC FLUX REDUCES SOLAR CYCLE MEMORY AND THUS IMPACTS PREDICTABILITY OF THE SUN'S ACTIVITY

    SciTech Connect

    Karak, Bidya Binay; Nandy, Dibyendu E-mail: dnandi@iiserkol.ac.in

    2012-12-10

    Prediction of the Sun's magnetic activity is important because of its effect on space environment and climate. However, recent efforts to predict the amplitude of the solar cycle have resulted in diverging forecasts with no consensus. Yeates et al. have shown that the dynamical memory of the solar dynamo mechanism governs predictability, and this memory is different for advection- and diffusion-dominated solar convection zones. By utilizing stochastically forced, kinematic dynamo simulations, we demonstrate that the inclusion of downward turbulent pumping of magnetic flux reduces the memory of both advection- and diffusion-dominated solar dynamos to only one cycle; stronger pumping degrades this memory further. Thus, our results reconcile the diverging dynamo-model-based forecasts for the amplitude of solar cycle 24. We conclude that reliable predictions for the maximum of solar activity can be made only at the preceding minimum-allowing about five years of advance planning for space weather. For more accurate predictions, sequential data assimilation would be necessary in forecasting models to account for the Sun's short memory.

  18. Influence of cycle ergometer type and sex on assessment of 30-second anaerobic capacity and power.

    PubMed

    Leicht, A S; Sealey, R M; Sinclair, W H

    2011-09-01

    This study examined the influence of cycle ergometer type and sex on assessment of 30-s anaerobic capacity and power. 41 healthy adults performed a 30-s anaerobic cycle test using a mechanically- (ME) and air-braked (AE) ergometer in a randomised order, approximately 7 days apart. Peak heart rate (HR) and rating of perceived exertion were similar between tests with peak HR greater for females compared to males (187.0 ± 9.1 vs. 180.8 ± 9.9 bpm, p<0.05). Peak power (1 100 ± 330 vs. 802 ± 225 W), mean power (793 ± 223 vs. 587 ± 156 W) and total work (23.8 ± 6.7 vs. 17.6 ± 4.7 kJ) were greater for AE compared to ME (p<0.001) and greater for males compared to females (p<0.001). The mean difference for anaerobic capacity and power between AE and ME were similar for males and females (37-41% vs. 33-35%, p>0.05). Peak lactate was greater for AE compared to ME (16.1 ± 3.4 vs. 14.8 ± 2.9 mmol·L (-1); p<0.05) and greater for males compared to females (16.2 ± 3.5 vs. 14.6 ± 2.7 mmol·L (-1); p<0.05). The current study demonstrated that anaerobic power and capacity were substantially greater when assessed using AE compared to the traditional ME with the difference between ergometer types unaffected by sex. Ergometer type should be considered when comparing anaerobic results across populations and/or studies.

  19. Mosses influence phosphorus cycling in rich fens by driving redox conditions in shallow soils.

    PubMed

    Crowley, Katherine F; Bedford, Barbara L

    2011-09-01

    Mosses play an integral role in the hydrologic regimes of ecosystems where they cover the soil surface, and thus affect biogeochemical cycling of elements influenced by soil oxidation-reduction (redox) reactions, including the plant growth-limiting nutrients, nitrogen and phosphorus (P). In rich fens where P often limits plant growth, we hypothesized that feedbacks between mosses and redox conditions would determine P availability to shallow-rooted forb species that constitute much of these wetlands' unusually high plant species diversity. In a moss removal experiment in three fens, forb tissue P and microbial P were greater while anion exchange membrane (AEM) resin P was lower where mosses occurred than where they were removed, suggesting both higher availability and greater demand for P in moss-covered soils. Coupled physicochemical and biological mechanisms drove moss effects on P cycling, ultimately through effects on soil oxygenation or reduction: higher redox potential underlying mosses corresponded to greater microbial activity, phosphatase enzyme activity, and colonization by arbuscular mycorrhizal fungi (AMF), all of which can promote greater P availability to plants. These more oxidized soils stimulated: (1) greater microbial activity and root vigor; (2) correspondingly greater P demand via microbial uptake, forb uptake, and iron (Fe)-P reactions; and (3) greater P supply through soil and root phosphatase activity and AMF colonization. This work demonstrates that mosses improve vascular plant P acquisition by alleviating stresses caused by reducing conditions that would otherwise prevail in shallow underlying soils, thus providing a mechanism by which mosses facilitate plant species diversity in rich fens.

  20. The Influence of Solar Proton Events in Solar Cycle 23 on the Neutral Middle Atmosphere

    NASA Technical Reports Server (NTRS)

    Jackman, Charles H.; vonKonig, Miriam; Anderson, John; Roble, Raymond G.; McPeters, Richard D.; Fleming, Eric L.; Russell, James M.

    2004-01-01

    Solar proton events (SPEs) can cause changes in constituents in the Earth's middle atmosphere. The highly energetic protons cause ionizations, excitations, dissociations, and dissociative ionizations of the background constituents, which lead to the production of HO(x) (H, OH, HO2) and NO(y) (N, NO, NO2, NO3, N2O5, HNO3, HO2NO2, ClONO2, BrONO2). The HO(x) increases lead to short-lived ozone decreases in the mesosphere and upper stratosphere due to the short lifetimes of the HO, constituents. The NO(x) increases lead to long-lived stratospheric ozone changes because of the long lifetime of NO(y) constituents in this region. Solar cycle 23 was quite active with SPEs and very large fluxes of high energy protons occurred in July and November 2000, November 200 1, and April 2002. Smaller, but still substantial, proton fluxes impacted the Earth during other months in the 1997-2003 time period. The impact of the very large SPEs on the neutral middle atmosphere during solar cycle 23 will be discussed, including the HO(x), NO(y), ozone variations and induced atmospheric transport changes. Two multi-dimensional models, the Goddard Space Flight Center (GSFC) Two-dimensional (2D) Model and the Thermosphere Ionosphere Mesosphere Electrodynamic General Circulation Model (TIME-GCM), were used in computing the influence of the SPEs. The results of the GSFC 2D Model and the TIME-GCM will be shown along with comparisons to the Upper Atmosphere Research Satellite (UARS) Halogen Occultation Experiment (HALOE) and Solar Backscatter Ultraviolet 2 (SBUV/2) instruments.

  1. Influence of electrically assisted cycling on physiological parameters in untrained subjects.

    PubMed

    de Geus, Bas; Kempenaers, Farid; Lataire, Philippe; Meeusen, Romain

    2013-01-01

    Electrically assisted bicycles (EAB) as a form of transport not only offer the potential to reduce energy use and environmental impact but could also be an effective way of encouraging active living. The purpose of this study is to assess the influence of physical active commuting to work using an EAB, on physiological parameters in 20 untrained men and women. Tests were performed at three different time points over a 10-week period, including four weeks of passive (control period) and six weeks of active commuting (intervention period). ANOVA for repeated measures was used to test differences between the testing series for the most important physiological parameters: Pmax·kg(-1), V˙O2peak·kg(-1), fixed blood lactate concentration (2, 4 mmol·l(-1)). The subjects performed over a 6-week period a mean total cycling distance of 405.1±156.0 km with a weekly frequency of 4.1±1.7 days·week(-1) for men and 246.0±116.3 km with a frequency of 2.9±1.0 days·week(-1) for women. Pmax·kg(-1) significantly increased in men and women after 6 weeks of active commuting. Power output at 2 mmol·l(-1) significantly increased in women (P=0.001) but not in men (P=0.0604). Power output at 4 mmol·l(-1) significantly increased for men and women. V˙O2peak·kg(-1) did not differ. With respect to the study limitations, it is concluded that cycling to work on an EAB was effective in increasing the maximal power output and power output at 4 mmol·l(-1) in these untrained subjects. Cycling on an EAB seems to be a promising tool as a health enhancing physical activity, for those who will benefit the most in terms of health related fitness, namely the physically inactive, unfit and older people.

  2. Influence of electrically assisted cycling on physiological parameters in untrained subjects.

    PubMed

    de Geus, Bas; Kempenaers, Farid; Lataire, Philippe; Meeusen, Romain

    2013-01-01

    Electrically assisted bicycles (EAB) as a form of transport not only offer the potential to reduce energy use and environmental impact but could also be an effective way of encouraging active living. The purpose of this study is to assess the influence of physical active commuting to work using an EAB, on physiological parameters in 20 untrained men and women. Tests were performed at three different time points over a 10-week period, including four weeks of passive (control period) and six weeks of active commuting (intervention period). ANOVA for repeated measures was used to test differences between the testing series for the most important physiological parameters: Pmax·kg(-1), V˙O2peak·kg(-1), fixed blood lactate concentration (2, 4 mmol·l(-1)). The subjects performed over a 6-week period a mean total cycling distance of 405.1±156.0 km with a weekly frequency of 4.1±1.7 days·week(-1) for men and 246.0±116.3 km with a frequency of 2.9±1.0 days·week(-1) for women. Pmax·kg(-1) significantly increased in men and women after 6 weeks of active commuting. Power output at 2 mmol·l(-1) significantly increased in women (P=0.001) but not in men (P=0.0604). Power output at 4 mmol·l(-1) significantly increased for men and women. V˙O2peak·kg(-1) did not differ. With respect to the study limitations, it is concluded that cycling to work on an EAB was effective in increasing the maximal power output and power output at 4 mmol·l(-1) in these untrained subjects. Cycling on an EAB seems to be a promising tool as a health enhancing physical activity, for those who will benefit the most in terms of health related fitness, namely the physically inactive, unfit and older people. PMID:23679145

  3. Technical Note: Glacial influence in tropical mountain hydrosystems evidenced by the diurnal cycle in water levels

    NASA Astrophysics Data System (ADS)

    Cauvy-Fraunié, S.; Condom, T.; Rabatel, A.; Villacis, M.; Jacobsen, D.; Dangles, O.

    2013-12-01

    Worldwide, the rapid shrinking of glaciers in response to ongoing climate change is modifying the glacial meltwater contribution to hydrosystems in glacierized catchments. Determining the influence of glacial runoff to streams is therefore of critical importance to evaluate potential impact of glacier retreat on water quality and aquatic biota. This task has challenged both glacier hydrologists and ecologists over the last 20 yr due to both structural and functional complexity of the glacier-stream system interface. Here we propose quantifying the diurnal cycle amplitude of the streamflow to determine the glacial influence in glacierized catchments. We performed water-level measurements using water pressure loggers over 10 months at 30 min time steps in 15 stream sites in 2 glacier-fed catchments in the Ecuadorian Andes (> 4000 m a.s.l.) where no perennial snow cover is observed outside the glaciers. For each stream site, we performed wavelet analyses on water-level time series, determined the scale-averaged wavelet power spectrum at 24 h scale and defined three metrics, namely the power, frequency and temporal clustering of the diurnal flow variation. The three metrics were then compared to the percentage of the glacier cover in the catchments, a metric of glacial influence widely used in the literature. As expected, we found that the diurnal variation power of glacier-fed streams decreased downstream with the addition of non-glacial tributaries. We also found that the diurnal variation power and the percentage of the glacier cover in the catchment were significantly positively correlated. Furthermore, we found that our method permits the detection of glacial signal in supposedly non-glacial sites, thereby revealing glacial meltwater resurgence. While we specifically focused on the tropical Andes in this paper, our approach to determine glacial influence may have potential applications in temperate and arctic glacierized catchments. The measure of diurnal water

  4. The rock magnetic characteristics of last glacial cycle loess from the island of Susak (Adriatic Sea, Croatia)

    NASA Astrophysics Data System (ADS)

    Hambach, Ulrich; Duchoslav, Maguerita; Rolf, Christian; Wacha, Lara; Frechen, Manfred; Galovic, Lidija

    2010-05-01

    palaeosols occur at 3 and 5.5 metre depth and two macroscopically visible volcanic tephra layers are intercalated in the upper part of the section. At present, we assume that the sequence represents the entire last glacial cycle (11-130 kyr). The concentration dependent magnetic parameters (e.g. magnetic low field susceptibility, SIRM) do not at all resemble the lithology. Volume susceptibility in unaltered loess exceeds even 1*10-3 SI which is at least 3 times higher compared to loess from the middle Danube basin only a few hundreds of kilometres to the East (Markovic et al. 2009). Grain size dependent magnetic parameters (e.g. frequency dependent magnetic susceptibility, S-ratio, etc.) reveal the relative enhancement of superparamagnetic particles and the formation of high-coercivity minerals in the pedogenetically altered horizons. However, in general the magnetic signal seems to be controlled by the primarily detrital minerals and climatically governed relatively weak alterations occur only in the macroscopically visible pedohorizons. During the last glacial cycle, the sea level of the Adriatic Sea was lowered by several decametres at least. As a consequence, the alluvial plain of the Po River extended far to the Southeast and provided the sand and silt which were blown to the shallow mountain ranges forming today the islands of the Dalmatian archipelago (Cremaschi 1990). Pleistocene and recent floodplain deposits of the Po River in North Italy contain large amounts of heavy minerals from the metamorphic series of the Central Alps. This detritus may control the magnetic properties of the aeolian deposits on the island of Susak. Further petrographical and mineral magnetic studies are necessary to prove our hypothesis.

  5. How do changes in dissolved oxygen concentration influence microbially-controlled phosphorus cycling in stream biofilms?

    NASA Astrophysics Data System (ADS)

    Saia, S. M.; Locke, N. A.; Regan, J. M.; Carrick, H. J.; Buda, A. R.; Walter, M. T.

    2014-12-01

    Advances in molecular microbiology techniques (e.g. epi-fluorescent microscopy and PCR) are making it easier to study the influence of specific microorganisms on nutrient transport. Polyphosphate accumulating organisms (PAOs) are commonly used in wastewater treatment plants to remove excess phosphorus (P) from effluent water. PAOs have also been identified in natural settings but their ecological function is not well known. In this study, we tested the hypothesis that PAOs in natural environments would release and accumulate P during anaerobic and aerobic conditions, respectively. We placed stream biofilms in sealed, covered tubs and subjected them to alternating air (aerobic conditions) and N2 gas (anaerobic condition) bubbling for 12 hours each. Four treatments investigated the influence of changing dissolved oxygen on micribially-controlled P cycling: (1) biofilms bubbled continuously with air, (2) biofilms bubbled alternatively with air and N2, (3) biocide treated biofilms bubbled continuously with air, and (4) biocide treated biofilms bubbled alternatively with air and N2. Treatments 3 and 4 serve as abiotic controls to treatments 1 and 2. We analyzed samples every 12 hours for soluble reactive P (SRP), temperature, dissolved oxygen, and pH. We also used fluorescent microscopy (i.e. DAPI staining) and PCR to verify the presence of PAOs in the stream biofilms. SRP results over the course of the experiment support our hypothesis that anaerobic and aerobic stream conditions may impact PAO mediated P release and uptake, respectively in natural environments. The results of these experiments draw attention to the importance of microbiological controls on P mobility in freshwater ecosystems.

  6. Histological evaluation of the influence of magnetic field application in autogenous bone grafts in rats

    PubMed Central

    Puricelli, Edela; Dutra, Nardier B; Ponzoni, Deise

    2009-01-01

    Background Bone grafts are widely used in oral and maxillofacial reconstruction. The influence of electromagnetic fields and magnets on the endogenous stimulation of target tissues has been investigated. This work aimed to assess the quality of bone healing in surgical cavities filled with autogenous bone grafts, under the influence of a permanent magnetic field produced by in vivo buried devices. Methods Metal devices consisting of commercially pure martensitic stainless steel washers and titanium screws were employed. Thirty male Wistar rats were divided into 3 experimental and 3 control groups. A surgical bone cavity was produced on the right femur, and a bone graft was collected and placed in each hole. Two metallic washers, magnetized in the experimental group but not in the control group, were attached on the borders of the cavity. Results The animals were sacrificed on postoperative days 15, 45 and 60. The histological analysis of control and experimental samples showed adequate integration of the bone grafts, with intense bone neoformation. On days 45 and 60, a continued influence of the magnetic field on the surgical cavity and on the bone graft was observed in samples from the experimental group. Conclusion The results showed intense bone neoformation in the experimental group as compared to control animals. The intense extra-cortical bone neoformation observed suggests that the osteoconductor condition of the graft may be more susceptible to stimulation, when submitted to a magnetic field. PMID:19134221

  7. Sedimentary iron cycling and the origin and preservation of magnetization in platform carbonate muds, Andros Island, Bahamas

    NASA Astrophysics Data System (ADS)

    Maloof, Adam C.; Kopp, Robert E.; Grotzinger, John P.; Fike, David A.; Bosak, Tanja; Vali, Hojotollah; Poussart, Pascale M.; Weiss, Benjamin P.; Kirschvink, Joseph L.

    2007-07-01

    Carbonate muds deposited on continental shelves are abundant and well-preserved throughout the geologic record because shelf strata are difficult to subduct and peritidal carbonate units often form thick, rheologically strong units that resist penetrative deformation. Much of what we know about pre-Mesozoic ocean chemistry, carbon cycling, and global change is derived from isotope and trace element geochemistry of platform carbonates. Paleomagnetic data from the same sediments would be invaluable, placing records of paleolatitude, paleogeography, and perturbations to the geomagnetic field in the context and relative chronology of chemostratigraphy. To investigate the depositional and early diagenetic processes that contribute to magneitzation in carbonates, we surveyed over 500 core and surface samples of peritidal, often microbially bound carbonate muds spanning the last ˜ 1000 yr and deposited on top of Pleistocene aeolianites in the Triple Goose Creek region of northwest Andros Island, Bahamas. Sedimentological, geochemical, magnetic and ferromagnetic resonance properties divide the sediment columns into three biogeochemical zones. In the upper sediments, the dominant magnetic mineral is magnetite, produced by magnetotactic bacteria and dissimiliatory microbial iron metabolism. At lower depths, above or near mean tide level, microbial iron reduction dissolves most of the magnetic particles in the sediment. In some cores, magnetic iron sulfides precipitate in a bottom zone of sulfate reduction, likely coupled to the oxidation of decaying mangrove roots. The remanent magnetization preserved in all oriented samples appears indistinguishable from the modern local geomagnetic field, which reflects the post-depositional origin of magnetic particles in the lower zone of the parasequence. While we cannot comment on the effects of late-stage diagenesis or metamorphism on remanence in carbonates, we postulate that early-cemented, thin-laminated parasequence tops in

  8. Reproducing the Photospheric Magnetic Field Evolution during the Rise of Cycle 24 with Flux Transport by Supergranules

    NASA Technical Reports Server (NTRS)

    Hathaway, David; Upton, Lisa

    2012-01-01

    We simulate the transport of magnetic flux in the Sun s photosphere by an evolving pattern of cellular horizontal flows (supergranules). Characteristics of the simulated flow pattern can match observed characteristics including the velocity power spectrum, cell lifetimes, and cell motions in longitude and latitude. Simulations using an average, and north-south symmetric, meridional motion of the cellular pattern produce polar magnetic fields that are too weak in the North and too strong in the South. Simulations using cellular patterns with meridional motions that evolve with the observed changes in strength and north-south asymmetry will be analyzed to see if they reproduce the polar field evolution observed during the rise of Cycle 24.

  9. Reproducing the Photospheric Magnetic Field Evolution During the Rise of Cycle 24 with Flux Transport by Supergranules

    NASA Technical Reports Server (NTRS)

    Hathaway, David H.; Upton, Lisa

    2012-01-01

    We simulate the transport of magnetic flux in the Sun s photosphere by an evolving pattern of cellular horizontal flows (supergranules). Characteristics of the simulated flow pattern match observed characteristics including the velocity power spectrum, cell lifetimes, and cell pattern motion in longitude and latitude. Simulations using an average, and north-south symmetric, meridional motion of the cellular pattern produce polar magnetic fields that are too weak in the North and too strong in the South. Simulations using cellular patterns with meridional motions that evolve with the observed changes in strength and north-south asymmetry will be analyzed to see if they reproduce the polar field evolution observed during the rise of Cycle 24.

  10. Influence of axial self-magnetic field component on arcing behavior of spiral-shaped contacts

    SciTech Connect

    Feng, Dingyu; Xiu, Shixin Wang, Yi; Liu, Gang; Zhang, Yali; Bi, Dongli

    2015-10-15

    The transverse magnetic field (TMF) contact design is commonly used in vacuum interrupters. When arcing occurs between the TMF contacts, the contact structure can create a self-induced magnetic field that drives the arc to move and rotate on the contact, and thus local overheating and severe erosion can be avoided. However, TMF contacts could also create an axial self-magnetic component, and the influence of this component on the arc behavior has not been considered to date. In this paper, five different types of Cu-Cr spiral-shaped TMF contacts with three different structures are investigated in a demountable vacuum chamber that contains a high-speed charge-coupled device video camera. It was found that the contact structure greatly influenced the arc behavior, especially in terms of arc rotation and the effective contact area, while contacts with the same slot structure but different diameters showed similar arc behavior and arc motion. The magnetic field distribution and the Lorentz force of each of the three different contact structures are simulated, and the axial self-magnetic field was first taken into consideration for investigation of the TMF contact design. It was found that contact designs that have higher axial self-magnetic field components tend to have arc columns with larger diameters and show poorer arc motion and rotation performance in the experiments.

  11. Magnetic activity cycles in solar-like stars: The cross-correlation technique of p-mode frequency shifts

    NASA Astrophysics Data System (ADS)

    Régulo, C.; García, R. A.; Ballot, J.

    2016-05-01

    Aims: We set out to study the use of cross-correlation techniques to infer the frequency shifts that are induced by changing magnetic fields in p-mode frequencies and to provide a precise estimation of error bars. Methods: This technique and the calculation of the associated errors is first tested and validated on the Sun where p-mode magnetic behaviour is very well known. These validation tests are performed on 6000-day time series of Sun-as-a-star observations delivered by the SoHO spacecraft. Errors of the frequency shifts are quantified through Monte Carlo simulations. The same methodology is then applied to three solar-like oscillating stars: HD 49933, observed by CoRoT, as well as KIC 3733735 and KIC 7940546, observed by Kepler. Results: We first demonstrate the reliability of the error bars computed with the Monte Carlo simulations using the Sun. From the three stars analyzed, we confirm the presence of a magnetic activity cycle in HD 49933 with this methodology and we unveil the seismic signature of ongoing magnetic variations in KIC 3733735. Finally, the third star, KIC 7940546, seems to be in a quiet regime.

  12. How does complex terrain influence responses of carbon and water cycle processes to climate variability and climate change?

    EPA Science Inventory

    We are pursuing the ambitious goal of understanding how complex terrain influences the responses of carbon and water cycle processes to climate variability and climate change. Our studies take place in H.J. Andrews Experimental Forest, an LTER (Long Term Ecological Research) site...

  13. Comparison of the pedalling performance induced by magnetic and electrical stimulation cycle ergometry in able-bodied subjects.

    PubMed

    Szecsi, J; Straube, A; Fornusek, C

    2014-04-01

    The purpose of the study was to compare the mechanical power and work generated by able-bodied subjects during functional magnetic stimulation (FMS) vs. functional electrical stimulation (FES) induced ergometer training conditions. Both stimulation methods were applied at a 30 Hz frequency to the quadriceps muscles of 22 healthy able-bodied subjects to induce cycling for 4× four minutes or until exhaustion. FMS was performed via large surface, cooled coils, while FES was applied with a typical stimulation setup used for cycling. Significantly more (p<10(-3)) muscular power was generated by FMS (23.8 ± 9.1W [mean ± SD]) than by FES (11.3 ± 11.3 W). Additionally, significantly more (p<10(-6)) work was produced by FMS than by FES (4.413 ± 2.209 kJ vs. 0.974 ± 1.269 kJ). The increase in the work was paralleled by a significant prolongation of time to cycling failure (181.8 ± 33.4s vs. 87.0 ± 54.0 s, respectively, p<10(-5)). Compared to FES, FMS can produce more intense and longer cycling exercise in able-bodied subjects. The differing dynamic behaviour of FMS and FES in the presented measurement setup might be related to stimulation induced pain and fatigue mechanisms of the neuromuscular system.

  14. Comparison of the pedalling performance induced by magnetic and electrical stimulation cycle ergometry in able-bodied subjects.

    PubMed

    Szecsi, J; Straube, A; Fornusek, C

    2014-04-01

    The purpose of the study was to compare the mechanical power and work generated by able-bodied subjects during functional magnetic stimulation (FMS) vs. functional electrical stimulation (FES) induced ergometer training conditions. Both stimulation methods were applied at a 30 Hz frequency to the quadriceps muscles of 22 healthy able-bodied subjects to induce cycling for 4× four minutes or until exhaustion. FMS was performed via large surface, cooled coils, while FES was applied with a typical stimulation setup used for cycling. Significantly more (p<10(-3)) muscular power was generated by FMS (23.8 ± 9.1W [mean ± SD]) than by FES (11.3 ± 11.3 W). Additionally, significantly more (p<10(-6)) work was produced by FMS than by FES (4.413 ± 2.209 kJ vs. 0.974 ± 1.269 kJ). The increase in the work was paralleled by a significant prolongation of time to cycling failure (181.8 ± 33.4s vs. 87.0 ± 54.0 s, respectively, p<10(-5)). Compared to FES, FMS can produce more intense and longer cycling exercise in able-bodied subjects. The differing dynamic behaviour of FMS and FES in the presented measurement setup might be related to stimulation induced pain and fatigue mechanisms of the neuromuscular system. PMID:24209389

  15. Induction of mammary tumors in rat by intraperitoneal injection of NMU: histopathology and estral cycle influence.

    PubMed

    Rivera, E S; Andrade, N; Martin, G; Melito, G; Cricco, G; Mohamad, N; Davio, C; Caro, R; Bergoc, R M

    1994-11-11

    In order to obtain an experimental model we induced mammary tumors in female Sprague-Dawley rats. The carcinogen N-nitroso-N-methylurea (NMU) was injected intraperitoneally (i.p.) at doses of 50 mg/kg body weight when animals were 50, 80 and 110 days old. Tumor sizes were measured with a caliper and their growth parameters and histopathological properties were tested. For 100 rats, 88.4% of developed lesions were ductal carcinomas, histologically classified as 52.8% cribiform variety, 30.6% solid carcinoma. Metastases in liver, spleen and lung were present. Other primary tumors were detected with low incidence. The influence of the rat estrous cycle during the first exposure to intraperitoneal NMU injection was studied. The latency period in estrus, proestrus and diestrus was 82 +/- 15, 77 +/- 18 and 79 +/- 18 days, respectively. Tumor incidence was significantly higher in estrus (95.2%) than proestrus (71.4%) or diestrus (77.4), (P < 0.01). Mean number or tumors per animal was similar among the three groups (4.4 +/- 3.2, 3.8 +/- 3.6, 3.2 +/- 1.8). The procedure described appears to be the simplest method for inducing experimental mammary tumors in rats.

  16. Evidence for Solar Cycle Influence on the Infrared Energy Budget and Radiative Cooling of the Thermosphere

    NASA Technical Reports Server (NTRS)

    Mlynczak, Martin G.; Martin-Torres, F. Javier; Marshall, B. Thomas; Thompson, R. Earl; Williams, Joshua; Turpin, TImothy; Kratz, D. P.; Russell, James M.; Woods, Tom; Gordley, Larry L.

    2007-01-01

    We present direct observational evidence for solar cycle influence on the infrared energy budget and radiative cooling of the thermosphere. By analyzing nearly five years of data from the Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) instrument, we show that the annual mean infrared power radiated by the nitric oxide (NO) molecule at 5.3 m has decreased by a factor of 2.9. This decrease is correlated (r = 0.96) with the decrease in the annual mean F10.7 solar index. Despite the sharp decrease in radiated power (which is equivalent to a decrease in the vertical integrated radiative cooling rate), the variability of the power as given in the standard deviation of the annual means remains approximately constant. A simple relationship is shown to exist between the infrared power radiated by NO and the F10.7 index, thus providing a fundamental relationship between solar activity and the thermospheric cooling rate for use in thermospheric models. The change in NO radiated power is also consistent with changes in absorbed ultraviolet radiation over the same time period.

  17. Influence of the pulsating electric field on the ECR heating in a nonuniform magnetic field

    SciTech Connect

    Balmashnov, A. A. Umnov, A. M.

    2011-12-15

    According to a computer simulation, the randomized pulsating electric field can strongly influence the ECR plasma heating in a nonuniform magnetic field. It has been found out that the electron energy spectrum is shifted to the high energy region. The obtained effect is intended to be used in the ECR sources for effective X-ray generation.

  18. Influence of thermal agitation on the electric field induced precessional magnetization reversal with perpendicular easy axis

    SciTech Connect

    Cheng, Hongguang Deng, Ning

    2013-12-15

    We investigated the influence of thermal agitation on the electric field induced precessional magnetization switching probability with perpendicular easy axis by solving the Fokker-Planck equation numerically with finite difference method. The calculated results show that the thermal agitation during the reversal process crucially influences the switching probability. The switching probability can be achieved is only determined by the thermal stability factor Δ of the free layer, it is independent on the device dimension, which is important for the high density device application. Ultra-low error rate down to the order of 10{sup −9} can be achieved for the device of thermal stability factor Δ of 40. Low damping factor α material should be used for the free layer for high reliability device applications. These results exhibit potential of electric field induced precessional magnetization switching with perpendicular easy axis for ultra-low power, high speed and high density magnetic random access memory (MRAM) applications.

  19. SOLAR CYCLE VARIATIONS OF CORONAL NULL POINTS: IMPLICATIONS FOR THE MAGNETIC BREAKOUT MODEL OF CORONAL MASS EJECTIONS

    SciTech Connect

    Cook, G. R.; Mackay, D. H.; Nandy, Dibyendu E-mail: duncan@mcs.st-and.ac.u

    2009-10-20

    In this paper, we investigate the solar cycle variation of coronal null points and magnetic breakout configurations in spherical geometry, using a combination of magnetic flux transport and potential field source surface models. Within the simulations, a total of 2843 coronal null points and breakout configurations are found over two solar cycles. It is found that the number of coronal nulls present at any time varies cyclically throughout the solar cycle, in phase with the flux emergence rate. At cycle maximum, peak values of 15-17 coronal nulls per day are found. No significant variation in the number of nulls is found from the rising to the declining phase. This indicates that the magnetic breakout model is applicable throughout both phases of the solar cycle. In addition, it is shown that when the simulations are used to construct synoptic data sets, such as those produced by Kitt Peak, the number of coronal nulls drops by a factor of 1/6. The vast majority of the coronal nulls are found to lie above the active latitudes and are the result of the complex nature of the underlying active region fields. Only 8% of the coronal nulls are found to be connected to the global dipole. Another interesting feature is that 18% of coronal nulls are found to lie above the equator due to cross-equatorial interactions between bipoles lying in the northern and southern hemispheres. As the majority of coronal nulls form above active latitudes, their average radial extent is found to be in the low corona below 1.25 R {sub sun} (175, 000 km above the photosphere). Through considering the underlying photospheric flux, it is found that 71% of coronal nulls are produced though quadrupolar flux distributions resulting from bipoles in the same hemisphere interacting. When the number of coronal nulls present in each rotation is compared to the number of bipoles emerging, a wide scatter is found. The ratio of coronal nulls to emerging bipoles is found to be approximately 1/3. Overall

  20. Latitudinal variations of sunspots and active regions in the cycle 23 and the periodicity of a global magnetic field of the Sun

    NASA Astrophysics Data System (ADS)

    Zharkov, S. I.; Gavryuseva, E.; Zharkova, V. V.

    We investigate latitudinal activity of sunspots and plages in the cycle 23 extracted from the Solar Feature Catalogues underline http solar inf brad ac uk and compare them with large scale magnetic field variations extracted from the MDI and WSO magnetograms The area and magnetic field variations in time and cumulitative variations in the butterfly diagrams for sunspots and plages are compared with the zone structure and periodicity of the global magnetic field detected by different instruments for the cycles 23 MDI and WSO and 22 WSO The results are discussed in applications to the theoretical dynamo models

  1. Influence of steering magnetic field on the time-resolved plasma chemistry in cathodic arc discharges

    NASA Astrophysics Data System (ADS)

    Ehiasarian, A. P.; Hovsepian, P. Eh; New, R.; Valter, J.

    2004-08-01

    External magnetic fields are used extensively to steer the cathode spot of arc discharges in order to improve target utilization and minimize droplet generation. Optical emission spectroscopy (OES) and electrostatic probe measurements in a Cr arc discharge were used to characterize the effect of the external magnetic field on the ion flux to the substrates and on the composition and time evolution of the plasma. A combination of a permanent magnet array and an electromagnetic coil was used to vary the shape and strength of the magnetic field on the cathode surface. Finite element modelling of the magnetic field distribution identified two types of geometry—through-field, with lines normal to the cathode surface, and arched-field, with lines forming a magnetic 'tunnel'. The magnetic flux densities measured with a Hall probe were in the range from -15 to +15 mT. The particular shape and strength of the magnetic field determined the specific confinement regions and diffusion pathways for the plasma. The total ion saturation current density at the substrate position was in the range between 2 and 11.5 mA cm-2 depending on the magnetic field shape. The magnetic field strongly influenced the relative optical emission from Cr0, Cr1+ and Cr2+ metal species, and the resulting charge state distribution. Time-resolved OES and probe measurements of a particular position on the arc cathode revealed that an Ar plasma is trapped near the cathode and is sustained even when the cathode spot is a significant distance from the observation volume. The importance of this 'residual' Ar plasma for the charge state distribution of metal ions is discussed.

  2. Graphene under the influence of Aharonov-Bohm flux and constant magnetic field

    NASA Astrophysics Data System (ADS)

    Stepanov, E. A.; Zhukovsky, V. Ch.

    2016-09-01

    Investigation of real two-dimensional systems with Dirac-like electronic behavior under the influence of magnetic field is challenging and leads to many interesting physical results. In this paper we study a 2D graphene model with a particular form of magnetic field as a superposition of a homogeneous field and an Aharonov-Bohm vortex. For this configuration, electronic wave functions and the energy spectrum are obtained and it is shown that the magnetic Aharonov-Bohm vortex plays the role of a charge impurity. As a demonstration of vacuum properties of the system, vacuum current, as well as an electric current, is calculated and their representation for particular limiting cases of a magnetic field is obtained.

  3. Influence of various surfactants on magnetic property of cobalt ferrite prepared by Co-precipitation technique

    NASA Astrophysics Data System (ADS)

    Solanki, Neha; Khatri, Hemal; Jotania, R. B.

    2016-05-01

    Cobalt Ferrite (CoFe2O4) particles were synthesised using a Co-precipitation method. Influence of three different surfactants i.e. (1) Cationic - CTAB (Cetyl Tri-Methyl Ammonium Bromide), (2) Anionic - SDBS (Sodium Dodecyl Benzene Sulphonate) and (3) Nonionic - Triton X-100, on magnetic property of Cobalt Ferrite were investigated. Magnetic property of Cobalt ferrite powder was studied at room temperature using Vibrating Sample Measurements (VSM) technique under an applied magnetic field of 15kOe. The results show maximum value of saturation magnetization - Ms (81.87 emu/g) for the sample synthesised without surfactant and Coercivity value found maximum (2086 kOe) for the sample synthesized in presence of surfactant SDBS.

  4. Influences of different parameters on the microstructure of magnetic-field-induced self-assembled film

    NASA Astrophysics Data System (ADS)

    Dan, X.; Yang, J. J.

    2016-07-01

    Self-assembled films with needle-like microarrays were fabricated using a mixture of cobalt and fluorocarbon resin under a magnetic field. The various influences of magnetic powder content, viscosity and size distribution on the structure of the self-assembled films were investigated. The self-assembled film morphologies were characterized by stereomicroscope and scanning electron microscopy. Experimental results indicate that an increase in magnetic powder content results in greater unit height and diameter, and that a reduction in viscosity results in increasing array density and decreasing unit width. Additionally, particles with narrow size distribution were able to attain more regular microarray structures. The structural alterations were closely related to numerous effects such as van der Waals forces, dipole-dipole interactions, and external-dipole interactions. The self-assembled film demonstrated magnetic anisotropy, as identified by vibrating sample magnetometry (VSM).

  5. Influence of structure of iron nanoparticles in aggregates on their magnetic properties

    NASA Astrophysics Data System (ADS)

    Rosická, Dana; Šembera, Jan

    2011-09-01

    Zero-valent iron nanoparticles rapidly aggregate. One of the reasons is magnetic forces among the nanoparticles. Magnetic field around particles is caused by composition of the particles. Their core is formed from zero-valent iron, and shell is a layer of magnetite. The magnetic forces contribute to attractive forces among the nanoparticles and that leads to increasing of aggregation of the nanoparticles. This effect is undesirable for decreasing of remediation properties of iron particles and limited transport possibilities. The aggregation of iron nanoparticles was established for consequent processes: Brownian motion, sedimentation, velocity gradient of fluid around particles and electrostatic forces. In our previous work, an introduction of influence of magnetic forces among particles on the aggregation was presented. These forces have significant impact on the rate of aggregation. In this article, a numerical computation of magnetic forces between an aggregate and a nanoparticle and between two aggregates is shown. It is done for random position of nanoparticles in an aggregate and random or arranged directions of magnetic polarizations and for structured aggregates with arranged vectors of polarizations. Statistical computation by Monte Carlo is done, and range of dominant area of magnetic forces around particles is assessed.

  6. Probing latitudinal variations of the solar magnetic field in cycles 21-23 by Parker's Two-Layer Dynamo Model with meridional circulation

    NASA Astrophysics Data System (ADS)

    Popova, E.; Zharkova, V.; Zharkov, S.

    2013-11-01

    Principle component analysis (PCA) of the solar background magnetic field (SBMF) measured from Wilcox Solar Observatory (WSO) magnetograms revealed the following principal components (PCs) in latitudes: two main symmetric components, which are the same for all cycles 21-23, and three pairs of asymmetric components, which are unique for each cycle. These SBMF variations are assumed to be those of poloidal magnetic field travelling slightly off-phase from pole to pole while crossing the equator. They are assumed to be caused by a joint action of dipole and quadruple magnetic sources in the Sun. In the current paper, we make the first attempt to interpret these latitudinal variations in the surface magnetic field with Parker's two-layer dynamo model. The latitudinal distributions of such waves are simulated for cycles 21-23 by the modified Parker's dynamo model taking into account both α and ω effects operating simultaneously in the two (upper and lower) layers of the solar convective zone (SCZ) and having opposite directions of meridional circulation. The simulations are carried out for both dipole and quadruple magnetic sources with the dynamo parameters specifically selected to provide the curves fitting closely the PCs derived from SBMF variations in cycles 21-23. The simulations are optimised for matching the positions of maximums in latitude, the number of equator crossings and the phase difference between the two dynamo waves operating in the two layers. The dominant pair of PCs present in each cycle is found to be fully asymmetric with respect to the magnetic poles and produced by a magnetic dipole. This pair is found to account for the two main dynamo waves operating between the two magnetic poles. There are also three further pairs of waves unique to each cycle and associated with multiple magnetic sources in the Sun. For the odd cycle 21 the simulated poloidal field fits the observed PCs, only if they are produced by magnetic sources with a quadruple

  7. THE MORPHOLOGIC PROPERTIES OF MAGNETIC NETWORKS OVER THE SOLAR CYCLE 23

    SciTech Connect

    Huang Chong; Yan Yihua; Zhang Yin; Tan Baolin; Li Gang E-mail: yyh@nao.cas.cn

    2012-11-10

    The morphologic properties of the magnetic networks during Carrington Rotations (CRs) 1955-2091 (from 1999 to 2010) have been analyzed by applying the watershed algorithm to magnetograms observed by the Michelson Doppler Interferometer on board the Solar and Heliospheric Observatory spacecraft. We find that the average area of magnetic cells on the solar surface at lower latitudes (within {+-}50 Degree-Sign ) is smaller than that at higher latitudes (beyond {+-}50 Degree-Sign ). Statistical analysis of these data indicates that the magnetic networks are fractal in nature and the average fractal dimension is D{sub f} = 1.253 {+-} 0.011. We also find that both the fractal dimension and the size of the magnetic networks are anti-correlated with the sunspot area. This is perhaps because a strong magnetic field can suppress spatially modulated oscillation and compress the boundaries of network cells, leading to smoother cell boundaries. The fractal dimension of the cell deviates from that predicted from an isobar of Kolmogorov k {sup -5/3} homogeneous turbulence.

  8. Meridional Flow in Solar Cycle 24: The Impact on the Polar Magnetic Fields

    NASA Technical Reports Server (NTRS)

    Upton, Lisa; Hathaway, David; Kosak, Katie

    2012-01-01

    Axisymmetric flows, Differential Rotation and Meridional Flow (MF), were measured by tracking the motion of magnetic elements on the surface of the Sun using data obtained by the Helioseismic and Magnetic Imager (HMI) on the NASA Solar Dynamics Observatory (SDO) Mission. HMI provides the highest resolution full ]disk magnetograms available to date. This dramatically reduces the noise in axisymmetric flows, particularly at high latitudes (i.e. near the poles). The MF was found to vary greatly from one Carrington Rotation to the next. Furthermore, a distinct north ]south difference was found in the MF at high latitudes: Flow in the South was persistently weaker than flow in the North. Conclusions will be drawn concerning the MF variability, north ]south differences, and the impact on the polar magnetic field strengths and the timing of their reversals.

  9. Interplanetary magnetic field and solar cycle dependence of Northern Hemisphere F region joule heating

    NASA Astrophysics Data System (ADS)

    Bjoland, L. M.; Chen, X.; Jin, Y.; Reimer, A. S.; Skjæveland, Å.; Wessel, M. R.; Burchill, J. K.; Clausen, L. B. N.; Haaland, S. E.; McWilliams, K. A.

    2015-02-01

    Joule heating in the ionosphere takes place through collisions between ions and neutrals. Statistical maps of F region Joule heating in the Northern Hemisphere polar ionosphere are derived from satellite measurements of thermospheric wind and radar measurements of ionospheric ion convection. Persistent mesoscale heating is observed near postnoon and postmidnight magnetic local time and centered around 70° magnetic latitude in regions of strong relative ion and neutral drift. The magnitude of the Joule heating is found to be largest during solar maximum and for a southeast oriented interplanetary magnetic field. These conditions are consistent with stronger ion convection producing a larger relative flow between ions and neutrals. The global-scale Joule heating maps quantify persistent (in location) regions of heating that may be used to provide a broader context compared to small-scale studies of the coupling between the thermosphere and ionosphere.

  10. Magnetic activity of red secondaries: clues from the outburst cycle variations of dwarf novae

    NASA Astrophysics Data System (ADS)

    Chinarova, L. L.

    Photometric variations of 6 dwarf novae stars are studied based on the photographic observations from the Odessa, Moscow and Sonneberg plate collections and published visual monitoring data from the AFOEV database (Schweitzer E.: 1993, Bull. AFOEV, 64, 14). The moments of maxima are determined by using the "running parabola" fit (Andronov I.L., 1990, Kinematika Fizika Nebesn. Tel., v.6,,N 6, 87) with automatically determined filter half-width (Andronov I.L., 1997, As.Ap. Suppl., in press). All investigated stars exhibit significant changes not only from cycle-to-cycle, but from season-to-season as well. Secondary decade-scale cycles of smooth variations (Bianchini A., 1990, AJ 99, 1941) and abrupt switchings (Andronov I.L., Shakun L.I., 1990, ASS 169, 237) were interpreted by a solar-type activity of the red dwarf secondary in a binary system and may argue for existence of two different subgroups of the dwarf novae.

  11. Earth's Magnetic Field Dynamics: Space Weather and Solar Cycle Effect Exhibiting

    NASA Astrophysics Data System (ADS)

    Sukharev, A. L.; Sobitnyak, L. I.; Ryabov, M. I.; Orlyuk, M. I.; Orliuk, I. M.; Romenets, A. A.

    According to the 'Odessa' and 'Kiev' observatories total vector magnetic field variations data for 2008-2010 period, dynamics of the space weather manifestations were considered. Wavelet analysis application made the determination of structure changing in circadian period possible. The features of displaying 12, 8 and 6 hour periods are shown. The nature of their correlation and modulation in solar and geomagnetic activity changing is seen. Two stations changes differences that can result from the latitudinal dependence are examined. The existence of 'Odessa' magnetic anomaly located on land and at sea is reviewed.

  12. Influence of number of dental autoclave treatment cycles on rotational performance of commercially available air-turbine handpieces.

    PubMed

    Nagai, Masahiro; Takakuda, Kazuo

    2006-06-01

    The influence of number of autoclave treatment cycles (N) on rotational speed and total indicated run-out of commercially available air-turbine handpieces from five manufacturers was investigated at N=0, 50, 100, 150, 200, 250 and 300 cycles, and the significance in the test results was assessed by Dunnett's multiple comparison test. Some air-turbine handpieces showed the significant differences in rotational speed at N=300 cycles, however, the decreases of the rotational speeds were only 1 to 3.5 percent. Some air-turbine handpieces showed the significant differences in total indicated run-out, however, the respective values were smaller than that at N=0 cycle. Accordingly, it can be considered that the ball bearing in the air-turbine handpieces is not affected significantly by autoclave. To further evaluate rotational performance, this study focused on the rotational vibration of the ball bearing components of the air-turbine, as measured by Fast Fourier Transform (FFT) analysis; the power spectra of frequency of the ball's revolution, frequency of the cage's rotation and frequency of the ball's rotation were comparatively investigated at N=0, 150 and 300 cycles, and the influence of autoclave was evaluated qualitatively. No abnormalities in the ball bearings were recognized. PMID:16913570

  13. Social contact influences on the menstrual cycle of the female Chacma baboon (Papio ursinus).

    PubMed

    Howard-Tripp, M E; Bielert, C

    1978-09-01

    The menstrual cycle characteristics of 2 groups of adult female Chacma baboons were compared. Out of a group of 27 female baboons, 41% (11/27) failed to cycle during the 6 month study period but were all under the stresses of fairly severe experimental manipulation. Data on the menstrual cycles of the remaining 16 unmanipulated females was collected and carefully analysed. These 16 females were individually caged and denied social contact with other baboons. Their menstrual cycles were then contrasted to those of a group of 8 individually caged females which received 24 minute mating tests with vasectomized males on alternate days during their cycles. The females denied the social contact of the mating tests showed significantly longer cycles as a result of significantly lengthened periods up to the time of perineal detumescence.

  14. Influence of induced axial magnetic field on plasma dynamics and radiative characteristics of Z pinches

    SciTech Connect

    Kantsyrev, V. L.; Esaulov, A. A.; Safronova, A. S.; Osborne, G. C.; Shrestha, I.; Weller, M. E.; Stafford, A.; Shlyaptseva, V. V.; Velikovich, A. L.; Rudakov, L. I.; Williamson, K. M.

    2011-10-15

    The influence of an induced axial magnetic field on plasma dynamics and radiative characteristics of Z pinches is investigated. An axial magnetic field was induced in a novel Z-pinch load: a double planar wire array with skewed wires (DPWAsk), which represents a planar wire array in an open magnetic configuration. The induced axial magnetic field suppressed magneto-Rayleigh-Taylor (MRT) instabilities (with m = 0 and m = 1 instability modes) in the Z-pinch plasma. The influence of the initial axial magnetic field on the structure of the plasma column at stagnation was manifested through the formation of a more uniform plasma column compared to a standard double planar wire array (DPWA) load [V. L. Kantsyrev et al., Phys. Plasmas 15, 030704 (2008)]. The DPWAsk load is characterized by suppression of MRT instabilities and by the formation of the sub-keV radiation pulse that occurs before the main x-ray peak. Gradients in plasma parameters along the cathode-anode gap were observed and analyzed for DPWAsk loads made from low atomic number Z (Al) and mid-Z (brass) wires.

  15. Influence of science and technology magnet middle schools on students' motivation and achievement in science

    NASA Astrophysics Data System (ADS)

    Allen, David

    Some informal discussions among educators regarding motivation of students and academic performance have included the topic of magnet schools. The premise is that a focused theme, such as an aspect of science, positively affects student motivation and academic achievement. However, there is limited research involving magnet schools and their influence on student motivation and academic performance. This study provides empirical data for the discussion about magnet schools influence on motivation and academic ability. This study utilized path analysis in a structural equation modeling framework to simultaneously investigate the relationships between demographic exogenous independent variables, the independent variable of attending a science or technology magnet middle school, and the dependent variables of motivation to learn science and academic achievement in science. Due to the categorical nature of the variables, Bayesian statistical analysis was used to calculate the path coefficients and the standardized effects for each relationship in the model. The coefficients of determination were calculated to determine the amount of variance each path explained. Only five of 21 paths had statistical significance. Only one of the five statistically significant paths (Attended Magnet School to Motivation to Learn Science) explained a noteworthy amount (45.8%) of the variance.

  16. Influence of a magnetic field during directional solidification of MAR-M 246 + Hf superalloy

    NASA Technical Reports Server (NTRS)

    Andrews, J. Barry; Alter, Wendy; Schmidt, Dianne

    1991-01-01

    An area that has been almost totally overlooked in the optimization of properties in directionally solidified superalloys is the control of microstructural features through the application of a magnetic field during solidification. The influence of a magnetic field on the microstructural features of a nickel-base superalloys is investigated. Studies were performed on the dendritic MAR-M 246+Hf alloy, which was solidified under both a 5 K gauss magnetic field and under no-applied-field conditions. The possible influences of the magnetic field on the solidification process were observed by studying variations in microstructural features including volume fraction, surface area, number, and shape of the carbide particles. Stereological factors analyzed also included primary and secondary dendrite arm spacing and the volume fraction of the interdendritic eutectic constituent. Microprobe analysis was performed to determine the chemistry of the carbides, dendrites, and interdendritic constituents, and how it varied between field and no-field solidification samples. Experiments involving periodic application and removal of the magnetic field were also performed in order to permit a comparison with structural variations observed in a MAR-M 246+Hf alloy solidified during KC-135 high-g, low-g maneuvers.

  17. The influence of fixation delay on mitotic activity and flow cytometric cell cycle variables.

    PubMed

    Bergers, E; Jannink, I; van Diest, P I; Cuesta, M A; Meyer, S; van Mourik, J C; Baak, J P

    1997-01-01

    Proliferation variables such as mitotic activity and the percentage of S-phase cells have been shown to be of prognostic value in many tumors, especially in breast cancer. However, some studies reported a decrease in mitotic activity caused by delay in fixation of the tissue. In contrast, other studies showed that the identifiability of mitotic figures decreases after fixation delay, but the total number of mitotic figures and also the percentage of S-phase cells remain unchanged. Most studies have been done on small numbers of experimental tumors, thus introducing the risk of selection bias. The aim of this study was to reinvestigate the influence of fixation delay on mitotic activity and cell cycle variables assessed by flow cytometry in an adequate number of resected human tissues to reach firmer conclusions. Resection specimens of 19 and 21 cases, respectively, for the mitotic activity estimate and the flow cytometric percentage of S-phase calculation were collected directly from the operating theater using lung, breast, and intestinal cancers and normal intestinal mucosa. The tissues were cut in pieces, and from each specimen, pieces were fixed in 4% buffered formaldehyde (for mitosis counting) as well as snap frozen (for flow cytometry) immediately after excision, as well as after a fixation delay of 1, 2, 4, 6, 8, 18, and 24 hours. Moreover, during the fixation delay, one series from each specimen was kept in the refrigerator and the second at room temperature. Thus, a total of 304 (19 X 16) and 336 (21 X 16) specimens were investigated for the mitotic activity estimate and the percentage of S-phase cells calculation, respectively. With regard to the estimation of the mitotic activity, both clear and doubtful mitotic figures were registered separately, obtaining an "uncorrected" and "corrected" (for doubtful mitotic figures) mitotic activity estimate. The percentage of S-phase cells was obtained by cell cycle analysis of flow cytometric DNA-histograms. The

  18. Sex and estrous cycle influence diazepam effects on anxiety and memory: Possible role of progesterone.

    PubMed

    Silva, Anatildes Feitosa; Sousa, Diego Silveira; Medeiros, André Macêdo; Macêdo, Priscila Tavares; Leão, Anderson Henrique; Ribeiro, Alessandra Mussi; Izídio, Geison Souza; Silva, Regina Helena

    2016-10-01

    Studies with rodents and humans show the relationship between female sex hormones and cognitive/emotional tasks. However, despite the greater incidence of anxiety disorders in women, the data are still inconclusive regarding the mechanisms related to this phenomenon. We evaluated the effects of a classical anxiolytic/amnestic drug (diazepam; DZP) on female (at different estrous cycle phases) and male rats tested in the plus-maze discriminative avoidance task (PMDAT), that allows the concomitant evaluation of memory and anxiety-like behavior. Further, in order to investigate the role of progesterone and its metabolites in the effects of DZP in the PMDAT, female rats were pre-treated with the progesterone receptor antagonist mifepristone or the 5-alpha-reductase inhibitor finasteride. The main findings were: (1) DZP caused memory impairment and anxiolysis in both sexes, but only the highest dose induced the anxiolytic effect in females; (2) females in proestrus did not present the amnestic and anxiolytic effects of DZP (at 2.0 and 4.0mg/kg, respectively) and (3) the co-administration of mifepristone reestablished both amnestic and anxiolytic effects of DZP, while finasteride reinstated the amnestic effect in proestrus female rats. These results suggest that changes in the endogenous levels of progesterone and its metabolites are important in the modulation of emotional/cognitive behavior in female rats. Based on the influence on different aspects of DZP action, the mechanisms related to this modulation are probably linked to GABAergic transmission, but this point remains to be investigated. Further, the variation in therapeutic and adverse effects of DZP depending on sex and hormonal state is of great relevance considering the higher prevalence of anxiety disorders in women. PMID:27208614

  19. Sex and estrous cycle influence diazepam effects on anxiety and memory: Possible role of progesterone.

    PubMed

    Silva, Anatildes Feitosa; Sousa, Diego Silveira; Medeiros, André Macêdo; Macêdo, Priscila Tavares; Leão, Anderson Henrique; Ribeiro, Alessandra Mussi; Izídio, Geison Souza; Silva, Regina Helena

    2016-10-01

    Studies with rodents and humans show the relationship between female sex hormones and cognitive/emotional tasks. However, despite the greater incidence of anxiety disorders in women, the data are still inconclusive regarding the mechanisms related to this phenomenon. We evaluated the effects of a classical anxiolytic/amnestic drug (diazepam; DZP) on female (at different estrous cycle phases) and male rats tested in the plus-maze discriminative avoidance task (PMDAT), that allows the concomitant evaluation of memory and anxiety-like behavior. Further, in order to investigate the role of progesterone and its metabolites in the effects of DZP in the PMDAT, female rats were pre-treated with the progesterone receptor antagonist mifepristone or the 5-alpha-reductase inhibitor finasteride. The main findings were: (1) DZP caused memory impairment and anxiolysis in both sexes, but only the highest dose induced the anxiolytic effect in females; (2) females in proestrus did not present the amnestic and anxiolytic effects of DZP (at 2.0 and 4.0mg/kg, respectively) and (3) the co-administration of mifepristone reestablished both amnestic and anxiolytic effects of DZP, while finasteride reinstated the amnestic effect in proestrus female rats. These results suggest that changes in the endogenous levels of progesterone and its metabolites are important in the modulation of emotional/cognitive behavior in female rats. Based on the influence on different aspects of DZP action, the mechanisms related to this modulation are probably linked to GABAergic transmission, but this point remains to be investigated. Further, the variation in therapeutic and adverse effects of DZP depending on sex and hormonal state is of great relevance considering the higher prevalence of anxiety disorders in women.

  20. Nitrification and its influence on biogeochemical cycles from the equatorial Pacific to the Arctic Ocean

    PubMed Central

    Shiozaki, Takuhei; Ijichi, Minoru; Isobe, Kazuo; Hashihama, Fuminori; Nakamura, Ken-ichi; Ehama, Makoto; Hayashizaki, Ken-ichi; Takahashi, Kazutaka; Hamasaki, Koji; Furuya, Ken

    2016-01-01

    We examined nitrification in the euphotic zone, its impact on the nitrogen cycles, and the controlling factors along a 7500 km transect from the equatorial Pacific Ocean to the Arctic Ocean. Ammonia oxidation occurred in the euphotic zone at most of the stations. The gene and transcript abundances for ammonia oxidation indicated that the shallow clade archaea were the major ammonia oxidizers throughout the study regions. Ammonia oxidation accounted for up to 87.4% (average 55.6%) of the rate of nitrate assimilation in the subtropical oligotrophic region. However, in the shallow Bering and Chukchi sea shelves (bottom ⩽67 m), the percentage was small (0–4.74%) because ammonia oxidation and the abundance of ammonia oxidizers were low, the light environment being one possible explanation for the low activity. With the exception of the shallow bottom stations, depth-integrated ammonia oxidation was positively correlated with depth-integrated primary production. Ammonia oxidation was low in the high-nutrient low-chlorophyll subarctic region and high in the Bering Sea Green Belt, and primary production in both was influenced by micronutrient supply. An ammonium kinetics experiment demonstrated that ammonia oxidation did not increase significantly with the addition of 31–1560 nm ammonium at most stations except in the Bering Sea Green Belt. Thus, the relationship between ammonia oxidation and primary production does not simply indicate that ammonia oxidation increased with ammonium supply through decomposition of organic matter produced by primary production but that ammonia oxidation might also be controlled by micronutrient availability as with primary production. PMID:26918664

  1. Microbial Influences on Trace Metal Cycling in a Meromictic Lake, Fayetteville Green Lake, NY

    NASA Astrophysics Data System (ADS)

    Zerkle, A. L.; House, C.; Kump, L.

    2002-12-01

    dominant microorganisms to influence trace metal cycling and bioavailability in the FGL water column.

  2. Nitrification and its influence on biogeochemical cycles from the equatorial Pacific to the Arctic Ocean.

    PubMed

    Shiozaki, Takuhei; Ijichi, Minoru; Isobe, Kazuo; Hashihama, Fuminori; Nakamura, Ken-Ichi; Ehama, Makoto; Hayashizaki, Ken-Ichi; Takahashi, Kazutaka; Hamasaki, Koji; Furuya, Ken

    2016-09-01

    We examined nitrification in the euphotic zone, its impact on the nitrogen cycles, and the controlling factors along a 7500 km transect from the equatorial Pacific Ocean to the Arctic Ocean. Ammonia oxidation occurred in the euphotic zone at most of the stations. The gene and transcript abundances for ammonia oxidation indicated that the shallow clade archaea were the major ammonia oxidizers throughout the study regions. Ammonia oxidation accounted for up to 87.4% (average 55.6%) of the rate of nitrate assimilation in the subtropical oligotrophic region. However, in the shallow Bering and Chukchi sea shelves (bottom ⩽67 m), the percentage was small (0-4.74%) because ammonia oxidation and the abundance of ammonia oxidizers were low, the light environment being one possible explanation for the low activity. With the exception of the shallow bottom stations, depth-integrated ammonia oxidation was positively correlated with depth-integrated primary production. Ammonia oxidation was low in the high-nutrient low-chlorophyll subarctic region and high in the Bering Sea Green Belt, and primary production in both was influenced by micronutrient supply. An ammonium kinetics experiment demonstrated that ammonia oxidation did not increase significantly with the addition of 31-1560 nm ammonium at most stations except in the Bering Sea Green Belt. Thus, the relationship between ammonia oxidation and primary production does not simply indicate that ammonia oxidation increased with ammonium supply through decomposition of organic matter produced by primary production but that ammonia oxidation might also be controlled by micronutrient availability as with primary production. PMID:26918664

  3. Do solar cycles influence giant cell arteritis and rheumatoid arthritis incidence?

    SciTech Connect

    Wing, Simon; Rider, Lisa G.; Johnson, Jay R.; Miller, Federick W.; Matteson, Eric L.; Crowson, C. S.; Gabriel, S. E.

    2015-05-15

    Our objective was to examine the influence of solar cycle and geomagnetic effects on the incidence of giant cell arteritis (GCA) and rheumatoid arthritis (RA). Methods: We used data from patients with GCA (1950-2004) and RA (1955-2007) obtained from population-based cohorts. Yearly trends in age-adjusted and sex-adjusted incidence were correlated with the F10.7 index (solar radiation at 10.7 cm wavelength, a proxy for the solar extreme ultraviolet radiation) and AL index (a proxy for the westward auroral electrojet and a measure of geomagnetic activity). Fourier analysis was performed on AL, F10.7, and GCA and RA incidence rates. Results: The correlation of GCA incidence with AL is highly significant: GCA incidence peaks 0-1 year after the AL reaches its minimum (ie, auroral electrojet reaches a maximum). The correlation of RA incidence with AL is also highly significant. RA incidence rates are lowest 5-7 years after AL reaches maximum. AL, GCA and RA incidence power spectra are similar: they have a main peak (periodicity) at about 10 years and a minor peak at 4-5 years. However, the RA incidence power spectrum main peak is broader (8-11 years), which partly explains the lower correlation between RA onset and AL. The auroral electrojets may be linked to the decline of RA incidence more strongly than the onset of RA. The incidences of RA and GCA are aligned in geomagnetic latitude. Conclusions: AL and the incidences of GCA and RA all have a major periodicity of about 10 years and a secondary periodicity at 4-5 years. Geomagnetic activity may explain the temporal and spatial variations, including east-west skewness in geographic coordinates, in GCA and RA incidence, although the mechanism is unknown. Lastly, the link with solar, geospace and atmospheric parameters need to be investigated. These novel findings warrant examination in other populations and with other autoimmune diseases.

  4. Nitrification and its influence on biogeochemical cycles from the equatorial Pacific to the Arctic Ocean.

    PubMed

    Shiozaki, Takuhei; Ijichi, Minoru; Isobe, Kazuo; Hashihama, Fuminori; Nakamura, Ken-Ichi; Ehama, Makoto; Hayashizaki, Ken-Ichi; Takahashi, Kazutaka; Hamasaki, Koji; Furuya, Ken

    2016-09-01

    We examined nitrification in the euphotic zone, its impact on the nitrogen cycles, and the controlling factors along a 7500 km transect from the equatorial Pacific Ocean to the Arctic Ocean. Ammonia oxidation occurred in the euphotic zone at most of the stations. The gene and transcript abundances for ammonia oxidation indicated that the shallow clade archaea were the major ammonia oxidizers throughout the study regions. Ammonia oxidation accounted for up to 87.4% (average 55.6%) of the rate of nitrate assimilation in the subtropical oligotrophic region. However, in the shallow Bering and Chukchi sea shelves (bottom ⩽67 m), the percentage was small (0-4.74%) because ammonia oxidation and the abundance of ammonia oxidizers were low, the light environment being one possible explanation for the low activity. With the exception of the shallow bottom stations, depth-integrated ammonia oxidation was positively correlated with depth-integrated primary production. Ammonia oxidation was low in the high-nutrient low-chlorophyll subarctic region and high in the Bering Sea Green Belt, and primary production in both was influenced by micronutrient supply. An ammonium kinetics experiment demonstrated that ammonia oxidation did not increase significantly with the addition of 31-1560 nm ammonium at most stations except in the Bering Sea Green Belt. Thus, the relationship between ammonia oxidation and primary production does not simply indicate that ammonia oxidation increased with ammonium supply through decomposition of organic matter produced by primary production but that ammonia oxidation might also be controlled by micronutrient availability as with primary production.

  5. Strong evidence for the influence of solar cycles on a Late Miocene lake system revealed by biotic and abiotic proxies

    PubMed Central

    Kern, A.K.; Harzhauser, M.; Piller, W.E.; Mandic, O.; Soliman, A.

    2012-01-01

    The Late Miocene paleogeography of central Europe and its climatic history are well studied with a resolution of c. 106 years. Small-scale climatic variations are yet unresolved. Observing past climatic change of short periods, however, would encourage the understanding of the modern climatic system. Therefore, past climate archives require a resolution on a decadal to millennial scale. To detect such a short-term evolution, a continuous 6-m-core of the Paleo-Lake Pannon was analyzed in 1-cm-sample distance to provide information as precise and regular as possible. Measurements of the natural gamma radiation and magnetic susceptibility combined with the total abundance of ostracod shells were used as proxies to estimate millennial- to centennial scale environmental changes during the mid-Tortonian warm period. Patterns emerged, but no indisputable age model can be provided for the core, due to the lack of paleomagnetic reversals and the lack of minerals suitable for absolute dating. Therefore, herein we propose another method to determine a hypothetic time frame for these deposits. Based on statistical processes, including Lomb–Scargle and REDFIT periodograms along with Wavelet spectra, several distinct cyclicities could be detected. Calculations considering established off-shore sedimentation rates of the Tortonian Vienna Basin revealed patterns resembling Holocene solar-cycle-records well. The comparison of filtered data of Miocene and Holocene records displays highly similar patterns and comparable modulations. A best-fit adjustment of sedimentation rate results in signals which fit to the lower and upper Gleissberg cycle, the de Vries cycle, the unnamed 500-year- and 1000-year-cycles, as well as the Hallstatt cycle. Each of these cycles has a distinct and unique expression in the investigated environmental proxies, reflecting a complex forcing-system. Hence, a single-proxy-analysis, as often performed on Holocene records, should be considered cautiously as

  6. Strong evidence for the influence of solar cycles on a Late Miocene lake system revealed by biotic and abiotic proxies.

    PubMed

    Kern, A K; Harzhauser, M; Piller, W E; Mandic, O; Soliman, A

    2012-04-15

    The Late Miocene paleogeography of central Europe and its climatic history are well studied with a resolution of c. 10(6) years. Small-scale climatic variations are yet unresolved. Observing past climatic change of short periods, however, would encourage the understanding of the modern climatic system. Therefore, past climate archives require a resolution on a decadal to millennial scale. To detect such a short-term evolution, a continuous 6-m-core of the Paleo-Lake Pannon was analyzed in 1-cm-sample distance to provide information as precise and regular as possible. Measurements of the natural gamma radiation and magnetic susceptibility combined with the total abundance of ostracod shells were used as proxies to estimate millennial- to centennial scale environmental changes during the mid-Tortonian warm period. Patterns emerged, but no indisputable age model can be provided for the core, due to the lack of paleomagnetic reversals and the lack of minerals suitable for absolute dating. Therefore, herein we propose another method to determine a hypothetic time frame for these deposits. Based on statistical processes, including Lomb-Scargle and REDFIT periodograms along with Wavelet spectra, several distinct cyclicities could be detected. Calculations considering established off-shore sedimentation rates of the Tortonian Vienna Basin revealed patterns resembling Holocene solar-cycle-records well. The comparison of filtered data of Miocene and Holocene records displays highly similar patterns and comparable modulations. A best-fit adjustment of sedimentation rate results in signals which fit to the lower and upper Gleissberg cycle, the de Vries cycle, the unnamed 500-year- and 1000-year-cycles, as well as the Hallstatt cycle. Each of these cycles has a distinct and unique expression in the investigated environmental proxies, reflecting a complex forcing-system. Hence, a single-proxy-analysis, as often performed on Holocene records, should be considered cautiously as

  7. Destabilization of the plasma membrane of isolated plant protoplasts during a freeze-thaw cycle: the influence of cold acclimation

    SciTech Connect

    Steponkus, P.L.; Dowgert, M.F.; Gordon-Kamm, W.J.

    1983-01-01

    The functional characteristics of the plasma membrane in response to a free-thaw cycle are studied in isolated protoplasts with the plasma membrane still intact. Three different forms of injury have been characterized: intracellular ice formation, hypertonic-induced loss of osmotic responsiveness, and expansion-induced lysis. In this report, the influence of cold acclimation on the incidence of these forms of injury is emphasized. Isolated protoplasts are an excellent arena in which destabilization of the plasma membrane can be directly observed during a freeze-thaw cycle by cryomicroscopy. 65 references, 8 figures.

  8. Influence of dipolar interaction on magnetic properties of ultrafine ferromagnetic particles

    PubMed

    Garcia-Otero; Porto; Rivas; Bunde

    2000-01-01

    We use Monte Carlo simulations to study the influence of dipolar interaction and polydispersity on the magnetic properties of single-domain ultrafine ferromagnetic particles. From the zero field cooling (ZFC)/field cooling (FC) simulations we observe that the blocking temperature T(B) clearly increases with increasing strength of interaction, but it is almost not effected by a broadening of the distribution of particle sizes. While the dependence of the ZFC/FC curves on interaction and cooling rate are reminiscent of a spin glass transition at T(B), the relaxational behavior of the magnetic moments below T(B) is not in accordance with the picture of cooperative freezing.

  9. Influence of Josephson current second harmonic on stability of magnetic flux in long junctions

    NASA Astrophysics Data System (ADS)

    Atanasova, P. K. H.; Boyadjiev, T. L.; Shukrinov, Y. U. M.; Zemlyanaya, E. V.; Seidel, P.

    2010-11-01

    We study the long Josephson junction (LJJ) model which takes into account the second harmonic of the Fourier expansion of Josephson current. The dependence of the static magnetic flux distributions on parameters of the model are investigated numerically. Stability of the static solutions is checked by the sign of the smallest eigenvalue of the associated Sturm-Liouville problem. New solutions which do not exist in the traditional model, have been found. Investigation of the influence of second harmonic on the stability of magnetic flux distributions for main solutions is performed.

  10. Influence of hydrogen patterning gas on electric and magnetic properties of perpendicular magnetic tunnel junctions

    SciTech Connect

    Jeong, J. H.; Endoh, T.; Kim, Y.; Kim, W. K.; Park, S. O.

    2014-05-07

    To identify the degradation mechanism in magnetic tunnel junctions (MTJs) using hydrogen, the properties of the MTJs were measured by applying an additional hydrogen etch process and a hydrogen plasma process to the patterned MTJs. In these studies, an additional 50 s hydrogen etch process caused the magnetoresistance (MR) to decrease from 103% to 14.7% and the resistance (R) to increase from 6.5 kΩ to 39 kΩ. Moreover, an additional 500 s hydrogen plasma process decreased the MR from 103% to 74% and increased R from 6.5 kΩ to 13.9 kΩ. These results show that MTJs can be damaged by the hydrogen plasma process as well as by the hydrogen etch process, as the atomic bonds in MgO may break and react with the exposed hydrogen gas. Compounds such as MgO hydrate very easily. We also calculated the damaged layer width (DLW) of the patterned MTJs after the hydrogen etching and plasma processes, to evaluate the downscaling limitations of spin-transfer-torque magnetic random-access memory (STT-MRAM) devices. With these calculations, the maximum DLWs at each side of the MTJ, generated by the etching and plasma processes, were 23.8 nm and 12.8 nm, respectively. This result validates that the hydrogen-based MTJ patterning processes cannot be used exclusively in STT-MRAMs beyond 20 nm.

  11. Spectropolarimetry of Giant stars: Probing the influence of magnetic field on evolved stars Spectropolarimetry of Giant stars: Probing the influence of magnetic field on evolved stars

    NASA Astrophysics Data System (ADS)

    da Costa, Jefferson; Castro, Matthieu; Petit, Pascal; do Nascimento, José-Dias, Jr.

    2015-08-01

    It is know that lithium is element easily destroyed in stellar interior, the existence of lithium rich stars means a great challenge in stellar evolution. In this context our observations ravels the serendipitous discovery of an unusually high lithium abundance star. This is a K0III HD 150050, which has strong deepening on lithium line (6707.8 Å) this means lithium abundance of 2.81 0.2 dex, therefore this star belong a rare group called super Li-Rich stars. A possible source of the non-standard episodes required to produce Li-rich stars were identified in magneto-thermohaline mixing accounted by models of extra-mixing induced by magnetic buoyancy. However to better understand this is necessary more observational data. In last three decades several studies has showed that late type red giant stars presents a remarkable modifications in these outer atmosphere layers when they become late type star in HR diagram. These changes are founded through X-ray, Ultraviolet, and Chromospheric activity analyses, and then we can establish the called “Dividing lines”. We made spectropalarimetric observations with ESPaDOnS@CFHT to achieve two main objectives: analyze the influence of magnetic field in the Li-rich giant stars, and understand how works the magnetic field in late type giants and supergiants across the “dividing line”.

  12. A PILOT STUDY OF THE INFLUENCE OF RESIDENTIAL HAC DUTY CYCLE ON INDOOR AIR QUALITY (AE)

    EPA Science Inventory

    A simple methodology was developed to collect measurements of duty cycle, the fraction of time the heating and air conditioning (HAC) system was operating, inside residences. The primary purpose of the measurements was to assess whether the HAC duty cycle was related to reductio...

  13. A PILOT STUDY OF THE INFLUENCE OF RESIDENTIAL HAC DUTY CYCLE ON INDOOR AIR QUALITY

    EPA Science Inventory

    A simple methodology was developed to collect measurements of duty cycle, the fraction of time the heating and air conditioning (HAC) system was operating inside residences. The primary purpose of the measurements was to assess whether the HAC duty cycle was related to reducti...

  14. Influence of applied magnetic field strength and frequency response of pick-up coil on the magnetic barkhausen noise profile

    NASA Astrophysics Data System (ADS)

    Vashista, M.; Moorthy, V.

    2013-11-01

    The influence of applied magnetic field strength and frequency response of the pick-up coil on the shape of Magnetic Barkhausen Noise (MBN) profile have been studied. The low frequency MBN measurements have been carried out using 5 different MBN pick-up coils at two different ranges of applied magnetic field strengths on quenched and tempered (QT) and case-carburised and tempered (CT) 18CrNiMo7 steel bar samples. The MBN pick-up coils have been designed to obtain different frequency response such that the peak frequency response varies from ˜4 kHz to ˜32 kHz and the amplitude of low frequency signals decreases gradually. At lower applied magnetic field strength of ±14,000 A/m, all the pick-up coils produced a single peak MBN profile for both QT and CT sample. However, at higher applied magnetic field strength of ±22,000 A/m, the MBN profile showed two peaks for both QT and CT samples for pick-up coils with peak frequency response up to ˜17 kHz. Also, there is systematic reduction in peak 2 for QT sample and asymmetric reduction in the heights of peak 1 and peak 2 for CT sample with increase in peak frequency response of the pick-up coils. The decreasing sensitivity of pick-up coils with increasing peak frequency response to MBN signal generation is indicated by the gradual reduction in width of MBN profile and height of peak 2 in the QT sample. The drastic reduction in peak 1 as compared to peak 2 in the CT sample shows the effect of decreasing low frequency response of the pick-up coils on lowering skin-depth of MBN signal detection. This study clearly suggests that it is essential to optimise both maximum applied magnetic field strength and frequency response of the MBN pick-up coil for maximising the shape of the MBN profile for appropriate correlation with the magnetisation process and hence the material properties.

  15. Simulations of the mean solar magnetic field during sunspot cycle 21

    NASA Technical Reports Server (NTRS)

    Sheeley, N. R., Jr.; Devore, C. R.; Boris, J. P.

    1985-01-01

    Regarding new bipolar magnetic regions as sources of flux, the evolution of the photospheric magnetic field during 1976-1984 was computed and the corresponding evolution of the mean line-of-sight field as seen from earth was derived. A good, but imperfect, agreement was obtained between the observed mean field and the field computed for a nominal choice of flux transport parameters. The response of the computed mean field to variations in the transport parameters and the source properties was determined. The results suggest that the mean-field evolution is a random-walk process with dissipation. New eruptions of flux produce the random walk, and together differential rotation, meridional flow, and diffusion provide the dissipation. The net effect of each new source depends on its strength and orientation and on the time elapsed before the next eruption.

  16. The influence of a magnetic field on the microhardness of K, Rb, Cs, NH{sub 4}, and Tl acid phthalate crystals

    SciTech Connect

    Koldaeva, M. V. Turskaya, T. N.; Zakalyukin, R. M.; Darinskaya, E. V.

    2009-11-15

    The influence of a magnetic field on the microhardness of potassium acid phthalate has been studied for different magnetic inductions, exposure times, sample orientations in a magnetic field, and impurity compositions of the crystals. It was shown that the magnetic field effect is multiply repeated on the (010) face after relaxation. The influence of magnetic treatment on ammonium, rubidium, thallium, and cesium acid phthalate crystals is analyzed. The reasons for the observed changes in the crystal microhardness in the magnetic field are discussed.

  17. Influence of controlled surface oxidation on the magnetic anisotropy of Co ultrathin films

    SciTech Connect

    Di, N.; Maroun, F. Allongue, P.; Kubal, J.; Zeng, Z.; Greeley, J.

    2015-03-23

    We studied the influence of controlled surface-limited oxidation of electrodeposited epitaxial Co(0001)/Au(111) films on their magnetic anisotropy energy using real time in situ magneto optical Kerr effect and density functional theory (DFT) calculations. We investigated the Co first electrochemical oxidation step which we demonstrate to be completely reversible and determined the structure of this oxide layer. We show that the interface magnetic anisotropy of the Co film increases by 0.36 erg/cm{sup 2} upon Co surface oxidation. We performed DFT calculations to determine the different surface structures in a wide potential range as well as the charge transfer at the Co surface. Our results suggest that the magnetic anisotropy change is correlated with a positive charge increase of 0.54 e{sup −} for the Co surface atom upon oxidation.

  18. Influence of deforestation on the future of the Amazonian climate and water cycle

    NASA Astrophysics Data System (ADS)

    Lejeune, Quentin; Davin, Edouard; Guillod, Benoit; Seneviratne, Sonia

    2014-05-01

    , submitted to Climate Dynamics, Influence of deforestation on the future of the Amazonian climate and water cycle

  19. Do solar cycles influence giant cell arteritis and rheumatoid arthritis incidence?

    PubMed Central

    Wing, Simon; Rider, Lisa G; Johnson, Jay R; Miller, Federick W; Matteson, Eric L; Gabriel, Sherine E

    2015-01-01

    Objective To examine the influence of solar cycle and geomagnetic effects on the incidence of giant cell arteritis (GCA) and rheumatoid arthritis (RA). Methods We used data from patients with GCA (1950–2004) and RA (1955–2007) obtained from population-based cohorts. Yearly trends in age-adjusted and sex-adjusted incidence were correlated with the F10.7 index (solar radiation at 10.7 cm wavelength, a proxy for the solar extreme ultraviolet radiation) and AL index (a proxy for the westward auroral electrojet and a measure of geomagnetic activity). Fourier analysis was performed on AL, F10.7, and GCA and RA incidence rates. Results The correlation of GCA incidence with AL is highly significant: GCA incidence peaks 0–1 year after the AL reaches its minimum (ie, auroral electrojet reaches a maximum). The correlation of RA incidence with AL is also highly significant. RA incidence rates are lowest 5–7 years after AL reaches maximum. AL, GCA and RA incidence power spectra are similar: they have a main peak (periodicity) at about 10 years and a minor peak at 4–5 years. However, the RA incidence power spectrum main peak is broader (8–11 years), which partly explains the lower correlation between RA onset and AL. The auroral electrojets may be linked to the decline of RA incidence more strongly than the onset of RA. The incidences of RA and GCA are aligned in geomagnetic latitude. Conclusions AL and the incidences of GCA and RA all have a major periodicity of about 10 years and a secondary periodicity at 4–5 years. Geomagnetic activity may explain the temporal and spatial variations, including east-west skewness in geographic coordinates, in GCA and RA incidence, although the mechanism is unknown. The link with solar, geospace and atmospheric parameters need to be investigated. These novel findings warrant examination in other populations and with other autoimmune diseases. PMID:25979866

  20. Do solar cycles influence giant cell arteritis and rheumatoid arthritis incidence?

    DOE PAGESBeta

    Wing, Simon; Rider, Lisa G.; Johnson, Jay R.; Miller, Federick W.; Matteson, Eric L.; Crowson, C. S.; Gabriel, S. E.

    2015-05-15

    Our objective was to examine the influence of solar cycle and geomagnetic effects on the incidence of giant cell arteritis (GCA) and rheumatoid arthritis (RA). Methods: We used data from patients with GCA (1950-2004) and RA (1955-2007) obtained from population-based cohorts. Yearly trends in age-adjusted and sex-adjusted incidence were correlated with the F10.7 index (solar radiation at 10.7 cm wavelength, a proxy for the solar extreme ultraviolet radiation) and AL index (a proxy for the westward auroral electrojet and a measure of geomagnetic activity). Fourier analysis was performed on AL, F10.7, and GCA and RA incidence rates. Results: The correlationmore » of GCA incidence with AL is highly significant: GCA incidence peaks 0-1 year after the AL reaches its minimum (ie, auroral electrojet reaches a maximum). The correlation of RA incidence with AL is also highly significant. RA incidence rates are lowest 5-7 years after AL reaches maximum. AL, GCA and RA incidence power spectra are similar: they have a main peak (periodicity) at about 10 years and a minor peak at 4-5 years. However, the RA incidence power spectrum main peak is broader (8-11 years), which partly explains the lower correlation between RA onset and AL. The auroral electrojets may be linked to the decline of RA incidence more strongly than the onset of RA. The incidences of RA and GCA are aligned in geomagnetic latitude. Conclusions: AL and the incidences of GCA and RA all have a major periodicity of about 10 years and a secondary periodicity at 4-5 years. Geomagnetic activity may explain the temporal and spatial variations, including east-west skewness in geographic coordinates, in GCA and RA incidence, although the mechanism is unknown. Lastly, the link with solar, geospace and atmospheric parameters need to be investigated. These novel findings warrant examination in other populations and with other autoimmune diseases.« less

  1. Polarized magnetic field fluctuations at the Apollo 15 site - Possible regional influence on lunar induction

    NASA Technical Reports Server (NTRS)

    Schubert, G.; Smith, B. F.; Colburn, D. S.; Sonett, C. P.; Schwartz, K.

    1974-01-01

    High-frequency (5 to 40 millihertz) induced lunar magnetic fields, observed at the Apollo 15 site near the southeastern boundary of Mare Imbrium and the southwestern boundary of Mare Serenitatis, show a strong tendency toward linear polarization in a direction radial to the Imbrium basin and circumferential to the Serenitatis basin, a property that could be indicative of a possible regional influence on the induction.

  2. Influence of PVP in magnetic properties of NiSn nanoparticles prepared by polyol method

    NASA Astrophysics Data System (ADS)

    Bobadilla, L. F.; García, C.; Delgado, J. J.; Sanz, O.; Romero-Sarria, F.; Centeno, M. A.; Odriozola, J. A.

    2012-11-01

    The influence of PVP on the magnetic properties of NiSn nanoparticles prepared by polyol method has been studied. NiSn nanoparticles exhibit superparamagnetic behavior although there is a ferromagnetic contribution due to particles agglomerated below the blocking temperature. The particle size is controlled by the addiction of PVP in varying amounts. The addition of PVP also favours the particles isolation, narrow the particle size distribution and decrease the interparticle interaction strength increasing the superparamagnetic contribution.

  3. Optical detection of nanoparticle agglomeration in a living system under the influence of a magnetic field

    NASA Astrophysics Data System (ADS)

    Müller, Robert; Stranik, Ondrej; Schlenk, Florian; Werner, Sebastian; Malsch, Daniéll; Fischer, Dagmar; Fritzsche, Wolfgang

    2015-04-01

    Nanoparticles are important in diagnosis and therapy. In order to apply their potential, an understanding of the behavior of particles in the body is crucial. However, in vitro experiments usually do not mimic the dynamic conditions of the in vivo situation. The aim of our work was an in vivo observation of particle transport in chicken egg vessels in the presence of a magnetic field by particle tracking. For that we demonstrate the spatial resolution of our observations in a vein and a temporal resolution by observation of the cardiac cycle in an artery. Microscopic images were recorded in dark field reflection and fluorescence mode.

  4. Climate and landscape influence on indicators of lake carbon cycling through spatial patterns in dissolved organic carbon.

    PubMed

    Lapierre, Jean-Francois; Seekell, David A; Del Giorgio, Paul A

    2015-12-01

    Freshwater ecosystems are strongly influenced by both climate and the surrounding landscape, yet the specific pathways connecting climatic and landscape drivers to the functioning of lake ecosystems are poorly understood. Here, we hypothesize that the links that exist between spatial patterns in climate and landscape properties and the spatial variation in lake carbon (C) cycling at regional scales are at least partly mediated by the movement of terrestrial dissolved organic carbon (DOC) in the aquatic component of the landscape. We assembled a set of indicators of lake C cycling (bacterial respiration and production, chlorophyll a, production to respiration ratio, and partial pressure of CO2 ), DOC concentration and composition, and landscape and climate characteristics for 239 temperate and boreal lakes spanning large environmental and geographic gradients across seven regions. There were various degrees of spatial structure in climate and landscape features that were coherent with the regionally structured patterns observed in lake DOC and indicators of C cycling. These different regions aligned well, albeit nonlinearly along a mean annual temperature gradient; whereas there was a considerable statistical effect of climate and landscape properties on lake C cycling, the direct effect was small and the overall effect was almost entirely overlapping with that of DOC concentration and composition. Our results suggest that key climatic and landscape signals are conveyed to lakes in part via the movement of terrestrial DOC to lakes and that DOC acts both as a driver of lake C cycling and as a proxy for other external signals.

  5. Climate and landscape influence on indicators of lake carbon cycling through spatial patterns in dissolved organic carbon.

    PubMed

    Lapierre, Jean-Francois; Seekell, David A; Del Giorgio, Paul A

    2015-12-01

    Freshwater ecosystems are strongly influenced by both climate and the surrounding landscape, yet the specific pathways connecting climatic and landscape drivers to the functioning of lake ecosystems are poorly understood. Here, we hypothesize that the links that exist between spatial patterns in climate and landscape properties and the spatial variation in lake carbon (C) cycling at regional scales are at least partly mediated by the movement of terrestrial dissolved organic carbon (DOC) in the aquatic component of the landscape. We assembled a set of indicators of lake C cycling (bacterial respiration and production, chlorophyll a, production to respiration ratio, and partial pressure of CO2 ), DOC concentration and composition, and landscape and climate characteristics for 239 temperate and boreal lakes spanning large environmental and geographic gradients across seven regions. There were various degrees of spatial structure in climate and landscape features that were coherent with the regionally structured patterns observed in lake DOC and indicators of C cycling. These different regions aligned well, albeit nonlinearly along a mean annual temperature gradient; whereas there was a considerable statistical effect of climate and landscape properties on lake C cycling, the direct effect was small and the overall effect was almost entirely overlapping with that of DOC concentration and composition. Our results suggest that key climatic and landscape signals are conveyed to lakes in part via the movement of terrestrial DOC to lakes and that DOC acts both as a driver of lake C cycling and as a proxy for other external signals. PMID:26150108

  6. Mass community cycling events: Who participates and is their behaviour influenced by participation?

    PubMed Central

    Bowles, Heather R; Rissel, Chris; Bauman, Adrian

    2006-01-01

    Background Participation in mass physical activity events may be a novel approach for encouraging inactive or low active adults to trial an active behaviour. The public health applicability of this strategy has not been investigated thoroughly. The purpose of this study to was describe participants in a mass cycling event and examine the subsequent effect on cycling behaviour. Methods A sample of men and women aged 16 years and older (n = 918) who registered online for a mass cycling event reported cycling ability and number of times they rode a bicycle during the month before the event. One month after the event participants completed an online follow-up questionnaire and reported cycling ability, lifestyle physical activity, and number of times they rode a bicycle during the month after the event. McNemar's test was used to examine changes in self-rated cycling ability, and repeated measures mixed linear modeling was used to determine whether average number of monthly bicycle rides changed between pre-event and post-event assessment. Results Participants in the cycling event were predominantly male (72%), 83% rated themselves as competent or regular cyclists, and 68% rated themselves as more active than others of the same sex and age. Half of the survey respondents that rated their cycling ability as low before the event subsequently rated themselves as high one month after the event. Respondents with low pre-event self-rated cycling ability reported an average 4 sessions of bicycle riding the month before the event and an average 6.8 sessions of bicycle riding a month after the event. This increase in average sessions of bicycle riding was significant (p < .0001). Similarly, first-time participants in this particular cycling event significantly increased average sessions of cycling from 7.2 pre-event to 8.9 sessions one month after the event. Conclusion Participants who were novice riders or first time participants significantly increased their number of bicycle

  7. The magnetic and electronic properties of oxyselenides-influence of transition metal ions and lanthanides.

    PubMed

    Stock, C; McCabe, E E

    2016-11-16

    Magnetic oxyselenides have been a topic of research for several decades, firstly in the context of photoconductivity and thermoelectricity owing to their intrinsic semiconducting properties and ability to tune the energy gap through metal ion substitution. More recently, interest in the oxyselenides has experienced a resurgence owing to the possible relation to strongly correlated phenomena given the fact that many oxyselenides share a similar structure to unconventional superconducting pnictides and chalcogenides. The two dimensional nature of many oxyselenide systems also draws an analogy to cuprate physics where a strong interplay between unconventional electronic phases and localised magnetism has been studied for several decades. It is therefore timely to review the physics of the oxyselenides in the context of the broader field of strongly correlated magnetism and electronic phenomena. Here we review the current status and progress in this area of research with the focus on the influence of lanthanides and transition metal ions on the intertwined magnetic and electronic properties of oxyselenides. The emphasis of the review is on the magnetic properties and comparisons are made with iron based pnictide and chalcogenide systems. PMID:27608752

  8. Influence of magnetic domain landscape on the flux dynamics in superconductor/ferromagnet bilayers

    NASA Astrophysics Data System (ADS)

    Adamus, Z.; Cieplak, Marta Z.; Kończykowski, M.; Zhu, L. Y.; Chien, C. L.

    2016-02-01

    We use a line of miniature Hall sensors to study the influence of the magnetic domain distribution on the flux dynamics in superconductor/ferromagnet bilayers. Two bilayers are built of a ferromagnetic Co/Pt multilayer with perpendicular magnetic anisotropy and a superconducting Nb layer, with the insulating layer in-between to avoid proximity effect. The magnetic domain patterns of various geometries are reversibly predefined in the Co/Pt multilayers using the appropriate magnetization procedure. The Pt thickness is different in the two bilayers, resulting in different width and length of the domains, which profoundly affects vortex dynamics. We show that narrow short domains lead to strong confinement of vortices at the sample edge, while narrow elongated domains of uniform width induce smaller confinement and easy vortex entry. Large enhancement of flux pinning and critical current density, by a factor of more than 7, is observed in the last case, while the former results in smaller enhancement. When domains are wide, the disorder in the domain widths becomes beneficial for larger enhancement of pinning, while more uniform distribution of domain widths results in a precipitous drop of the enhancement. The analysis of these results suggests that with increasing domain width, a transition occurs from vortex chains pinned by narrow domains to disordered triangular vortex lattice pinned by a maze of multiply interconnected magnetic domains.

  9. Thermal and magnetic properties of iron oxide colloids: influence of surfactants.

    PubMed

    Soares, Paula I P; Lochte, Frederik; Echeverria, Coro; Pereira, Laura C J; Coutinho, Joana T; Ferreira, Isabel M M; Novo, Carlos M M; Borges, João P M R

    2015-10-23

    Iron oxide nanoparticles (NPs) have been extensively studied in the last few decades for several biomedical applications such as magnetic resonance imaging, magnetic drug delivery and hyperthermia. Hyperthermia is a technique used for cancer treatment which consists in inducing a temperature of about 41-45 °C in cancerous cells through magnetic NPs and an external magnetic field. Chemical precipitation was used to produce iron oxide NPs 9 nm in size coated with oleic acid and trisodium citrate. The influence of both stabilizers on the heating ability and in vitro cytotoxicity of the produced iron oxide NPs was assessed. Physicochemical characterization of the samples confirmed that the used surfactants do not change the particles' average size and that the presence of the surfactants has a strong effect on both the magnetic properties and the heating ability. The heating ability of Fe3O4 NPs shows a proportional increase with the increase of iron concentration, although when coated with trisodium citrate or oleic acid the heating ability decreases. Cytotoxicity assays demonstrated that both pristine and trisodium citrate Fe3O4 samples do not reduce cell viability. However, oleic acid Fe3O4 strongly reduces cell viability, more drastically in the SaOs-2 cell line. The produced iron oxide NPs are suitable for cancer hyperthermia treatment and the use of a surfactant brings great advantages concerning the dispersion of NPs, also allowing better control of the hyperthermia temperature. PMID:26421876

  10. Cryogenics - Its influence on the selection of the ASTROMAG superconducting magnet coils

    NASA Technical Reports Server (NTRS)

    Green, M. A.

    1990-01-01

    ASTROMAG, a particle astrophysics experimental facility proposed for running alongside a Space Station, has a large superconducting magnet to analyze particles coming from deep space. Several types of magnets were investigated for use in the ASTROMAG central facility. The factors which influence the selection of the magnet coil design include: (1) the upper limit of particle momentum resolved (proportional to the integrated field) as a function of solid angle; (2)cryogenic design and its effect on cryogen lifetime for a given central facility mass; and (3) the overall cost of the magnet coils and cryostat. Four magnet types are analyzed in this paper. These include a simple two-coil solenoid (the baseline design),two disk coils at the ends of the helium tank, a two-coil toroid and a thin solenoid plus bucking coil. A balance must be struck between cryostat lifetime, total mass and the integrated field through the detectors. This balance tends to favor coils which are in the same vacuum vessel as the cryogen.

  11. Thermal and magnetic properties of iron oxide colloids: influence of surfactants.

    PubMed

    Soares, Paula I P; Lochte, Frederik; Echeverria, Coro; Pereira, Laura C J; Coutinho, Joana T; Ferreira, Isabel M M; Novo, Carlos M M; Borges, João P M R

    2015-10-23

    Iron oxide nanoparticles (NPs) have been extensively studied in the last few decades for several biomedical applications such as magnetic resonance imaging, magnetic drug delivery and hyperthermia. Hyperthermia is a technique used for cancer treatment which consists in inducing a temperature of about 41-45 °C in cancerous cells through magnetic NPs and an external magnetic field. Chemical precipitation was used to produce iron oxide NPs 9 nm in size coated with oleic acid and trisodium citrate. The influence of both stabilizers on the heating ability and in vitro cytotoxicity of the produced iron oxide NPs was assessed. Physicochemical characterization of the samples confirmed that the used surfactants do not change the particles' average size and that the presence of the surfactants has a strong effect on both the magnetic properties and the heating ability. The heating ability of Fe3O4 NPs shows a proportional increase with the increase of iron concentration, although when coated with trisodium citrate or oleic acid the heating ability decreases. Cytotoxicity assays demonstrated that both pristine and trisodium citrate Fe3O4 samples do not reduce cell viability. However, oleic acid Fe3O4 strongly reduces cell viability, more drastically in the SaOs-2 cell line. The produced iron oxide NPs are suitable for cancer hyperthermia treatment and the use of a surfactant brings great advantages concerning the dispersion of NPs, also allowing better control of the hyperthermia temperature.

  12. The magnetic and electronic properties of oxyselenides—influence of transition metal ions and lanthanides

    NASA Astrophysics Data System (ADS)

    Stock, C.; McCabe, E. E.

    2016-11-01

    Magnetic oxyselenides have been a topic of research for several decades, firstly in the context of photoconductivity and thermoelectricity owing to their intrinsic semiconducting properties and ability to tune the energy gap through metal ion substitution. More recently, interest in the oxyselenides has experienced a resurgence owing to the possible relation to strongly correlated phenomena given the fact that many oxyselenides share a similar structure to unconventional superconducting pnictides and chalcogenides. The two dimensional nature of many oxyselenide systems also draws an analogy to cuprate physics where a strong interplay between unconventional electronic phases and localised magnetism has been studied for several decades. It is therefore timely to review the physics of the oxyselenides in the context of the broader field of strongly correlated magnetism and electronic phenomena. Here we review the current status and progress in this area of research with the focus on the influence of lanthanides and transition metal ions on the intertwined magnetic and electronic properties of oxyselenides. The emphasis of the review is on the magnetic properties and comparisons are made with iron based pnictide and chalcogenide systems.

  13. Influence of structural and magnetic properties in the heating performance of multicore bioferrofluids

    NASA Astrophysics Data System (ADS)

    Bustamante, R.; Millán, A.; Piñol, R.; Palacio, F.; Carrey, J.; Respaud, M.; Fernandez-Pacheco, R.; Silva, N. J. O.

    2013-11-01

    Biomedical applications of superparamagnetic iron oxide particles have been of interest for quite a number of years. Recent developments show that multifunctionality can be efficiently achieved using polymers to coat the particles and to provide anchoring elements to their surface. This leads to the formation of nanobeads with a reduced number of particles trapped by the polymeric structure. While the magnetothermic behavior of isolated nanoparticles has been a subject of interest over the past several years, multicore magnetic nanobeads have thus far not received the same attention. The influence of structural and magnetic properties in the hyperthermia performance of a series of magnetic fluids designed for biomedical purposes is studied here. The fluids are made of maghemite multicore polymeric beads, with variable nanoparticle size and hydrodynamic size, dispersed in a buffer solution. The specific loss power (SLP) was measured from 5 to 100 kHz with a field intensity of 21.8 kA/m. SLP increases with increasing magnetic core size, reaching 32 W/g Fe2O3 at 100 kHz for 16.2 nm. Within the framework of the linear response theory, a graphical construction is proposed to describe the interplay of both size distributions and magnetic properties in the heating performance of such fluids in a given frequency range. Furthermore, a numerical model is developed to calculate the spare contribution of Néel and Brown relaxation mechanisms to SLP, which gives a fair reproduction of the experimental data.

  14. Influence of number and depth of magnetic mirror on Alfvénic gap eigenmode

    NASA Astrophysics Data System (ADS)

    Chang, Lei; Hu, Ning; Yao, Jianyao

    2016-10-01

    Alfvénic gap eigenmode (AGE) can eject energetic particles from confinement and thereby threaten the success of magnetically controlled fusion. A low-temperature plasma cylinder is a promising candidate to study this eigenmode, due to easy diagnostic access and simple geometry, and the idea is to arrange a periodic array of magnetic mirrors along the plasma cylinder and introduce a local defect to break the field periodicity. The present work validates this idea by reproducing a clear AGE inside a spectral gap, and more importantly details the influence of the number and depth (or modulation factor) of magnetic mirror on the characteristics of AGE. Results show that AGE is suppressed by other modes inside the spectral gap when the number of magnetic mirrors is below a certain value, which leads to a weakened Bragg’s effect. The structure and frequency of AGE remain unchanged for a decreased number of magnetic mirrors, as long as this number is enough for the AGE formation. The width of spectral gap and decay constant (inverse of decay length) of AGE are linearly proportional to the depth of magnetic mirror, implying easier observation of AGE through a bigger mirror depth. The frequency of AGE shifts to a lower range with the depth increased, possibly due to the unfrozen plasma with field line and the invalidity of small-perturbation analysis. Nevertheless, it is exciting to find that the depth of field modulation can be increased to form AGE for a very limited number of magnetic mirrors. This is of particular interest for the experimental implementation of AGE on a low-temperature plasma cylinder with limited length. Project supported by the National Natural Science Foundation of China (Grant Nos. 11405271, 11372104, 75121543, 11332013, 11372363, and 11502037).

  15. Coronal holes, large-scale magnetic field, and activity complexes in solar cycle 23

    NASA Astrophysics Data System (ADS)

    Tavastsherna, K. S.; Polyakow, E. V.

    2014-12-01

    A correlation among coronal holes (CH), a large-scale magnetic field (LMF), and activity complexes (AC) is studied in this work for 1997-2007 with the use of a coronal hole series obtained from observations at the Kitt Peak Observatory in the HeI 10830 Å line in 1975-2003 and SOHO/EIT-195 Å in 1996-2012 (Tlatov et al., 2014), synoptic Hα charts from Kislovodsk Mountain Astonomical Station, and the catalog of AC cores (Yazev, 2012). From the imposition of CH boundaries on Hα charts, which characterize the positions of neutral lines of the radial components of a large-scale solar magnetic field, it turns out that 70% of CH are located in unipolar regions of their sign during the above period, 10% are in the region of an opposite sign, and 20% are mainly very large CH, which are often crossed by the neutral lines of several unipolar regions. Data on mutual arrangement of CH and AC cores were obtained. It was shown that only some activity comples cores have genetic relationships with CH.

  16. Applied AC and DC magnetic fields cause alterations in the mitotic cycle of early sea urchin embryos

    SciTech Connect

    Levin, M.; Ernst, S.G.

    1995-09-01

    This study demonstrates that exposure to 60 Hz magnetic fields (3.4--8.8 mt) and magnetic fields over the range DC-600 kHz (2.5--6.5 mT) can alter the early embryonic development of sea urchin embryos by inducing alterations in the timing of the cell cycle. Batches of fertilized eggs were exposed to the fields produced by a coil system. Samples of the continuous cultures were taken and scored for cell division. The times of both the first and second cell divisions were advanced by ELF AC fields and by static fields. The magnitude of the 60 Hz effect appears proportional to the field strength over the range tested. the relationship to field frequency was nonlinear and complex. For certain frequencies above the ELF range, the exposure resulted in a delay of the onset of mitosis. The advance of mitosis was also dependent on the duration of exposure and on the timing of exposure relative to fertilization.

  17. A Statistical Study of the Average Iron Charge State Distributions inside Magnetic Clouds for Solar Cycle 23

    NASA Astrophysics Data System (ADS)

    Song, H. Q.; Zhong, Z.; Chen, Y.; Zhang, J.; Cheng, X.; Zhao, L.; Hu, Q.; Li, G.

    2016-06-01

    Magnetic clouds (MCs) are the interplanetary counterparts of coronal magnetic flux ropes. They can provide valuable information regarding flux rope characteristics at their eruption stage in the corona, which is unable to be explored in situ at present. In this paper, we make a comprehensive survey of the average iron charge-state (< Q> {Fe}) distributions inside 96 MCs for solar cycle 23 using Advanced Composition Explorer (ACE) data. Since the < Q> {Fe} in the solar wind are typically around 9+ to 11+, the Fe charge state is defined as being high when the < Q> {Fe} is larger than 12+, which implies the existence of a considerable amount of Fe ions with high charge states (e.g., ≥16+). The statistical results show that the < Q> {Fe} distributions of 92 (˜96%) MCs can be classified into four groups with different characteristics. In group A (11 MCs), the < Q> {Fe} shows a bi-modal distribution with both peaks being higher than 12+. Group B (4 MCs) presents a unimodal distribution of < Q> {Fe}, with its peak being higher than 12+. In groups C (29 MCs) and D (48 MCs), the < Q> {Fe} remains higher and lower than 12+ throughout ACE’s passage through the MC, respectively. Possible explanations of these distributions are discussed.

  18. The seasonal and solar cycle variations of electron density gradient scale length during magnetically disturbed days: implications for Spread F

    NASA Astrophysics Data System (ADS)

    Manju, G.; Devasia, C. V.; Ravindran, S.

    2009-07-01

    The behaviour of electron density gradient scale length, L, around post-sunset hours during the magnetically disturbed days of the summer, winter and equinox seasons of solar maximum (2002) and minimum years (1995) has been studied, using ionosonde data of Trivandrum (8.5°N, 76.5°E, dip = 0.5°N) in the Indian longitude sector. The results indicate a clear seasonal and solar cycle variation in L. Seasonal variations of the maximum vertical drift of the F layer were also examined on these days. In particular, the seasonal variation of the Equatorial Spread F (ESF) during this period is examined in terms of the relative roles of L and the vertical drift of the F layer in the triggering of the collisional Rayleigh-Taylor instability. Our results on the clear-cut seasonal and solar cycle variation in L for disturbed days and its control of ESF occurrence are presented and discussed.

  19. Seasonal and solar-cycle variations of DP-type polar magnetic fields resolved via EOF analysis

    NASA Astrophysics Data System (ADS)

    Shore, Robert; Freeman, Mervyn; Wild, James; Dorrian, Gareth; Gjerloev, Jesper

    2016-04-01

    We describe our application of the Empirical Orthogonal Function (EOF) method to characterise and separate contributions to the variability of the Earth's external magnetic field (EMF) in the northern polar region, using ground magnetometer measurements. The EOF method analyses the spatio-temporal co-variance of the data to decompose it into dynamically distinct modes (each mode is a pair of spatial and temporal basis vectors). Briefly, the benefits of this analysis method are firstly that a small number of the modes can cumulatively represent most of the variance of the original data, and secondly that the basis vectors are defined by the data. Hence, the structure of the EMF is resolved compactly without a priori assumptions, in contrast to other decomposition methods such as Fourier and spherical harmonic expansions. We present the modes from 11 years (1997 - 2008) of magnetic vector data at 5 minutes resolution, recently collated by the SuperMAG archive of observatory and variometer data. Despite the sparse and irregular station distribution, a complete spatial morphology of the EMF is achieved using a self-consistent iterative infill method. Using a comparison of the temporal behaviour of the modes alongside independent measures of solar-terrestrial coupling, we demonstrate that the leading three modes describe the well-known Disturbance-Polar currents types 2 and 1 (DP2, DP1) and the system of cusp currents (DPY). These three modes account for the majority of the variance of the data - other modes describe the spatial motions of these current systems. The variation in the DP2, DP1 and DPY currents throughout the last solar cycle is presented, and the utility of this database of magnetic perturbations (to which further analysis methods can be applied) is highlighted.

  20. Strong Solar Wind Dynamic Pressure Pulses during Solar Cycle 23 and Their Impacts on Geosynchronous Magnetic Fields

    NASA Astrophysics Data System (ADS)

    Zuo, P.

    2015-12-01

    Solar wind dynamic pressure pulse (DPP) structures, across which the dynamic pressure abruptly changes over timescales from a few seconds to several minutes, are often observed in the near-Earth space environment. In this investigation, we first present a statistical study on the properties of strong dynamic pressure pulses in the solar wind during solar cycle 23. It is found that overwhelming majority of DPPs are associated with the solar wind disturbances including the CME-related flows, the corotating interaction regions, as well as the complex ejecta. The annual variations of the averaged occurrence rate of DPPs are roughly in phase with the solar activities. Although the variabilities of geosynchronous magnetic fields (GMFs) due to the impact of positive DPPs have been well established, there appears no systematic investigations on the response of GMFs to negative DPPs. Here we also study the decompression/compression effects of very strong negative/positive DPPs on GMFs under northward IMFs. In response to the decompression of strong negative DPPs, GMFs on dayside, near the dawn and dusk on nightside are generally depressed. But near the midnight region, the responses of GMF are very diverse, being either positive or negative. For part of events when GOES is located at the midnight sector, GMF is found to abnormally increase as the result of magnetospheric decompression caused by negative DPPs. It is known that on certain conditions magnetic depression of nightside GMFs can be caused by the impact of positive DPPs. Here we found that, a stronger pressure enhancement may have a higher probability of producing the exceptional depression of GMF at midnight region. Statistically, both the decompression effect of strong negative DPPs and the compression effect of strong positive DPPs depend on the magnetic local time, being stronger at the noon sector.

  1. Spatial distribution of cosmic rays in magnetic cycles of the Sun

    NASA Technical Reports Server (NTRS)

    Alania, M. V.; Gushchina, R. T.; Dorman, L. I.

    1985-01-01

    The space-time distribution of cosmic ray (CR) density is determined from the solution of the anisotropic diffusion equation. The boundary problem is solved in a quasistationary axisymmetric case, taking into account the delay of cosmic rays relative to the cyclic variations of solar activity. The specificty of the modulation model is the use of the empirical dependence of the free path of particles for scattering on the observed latitudinal distribution of solar activity. Another specific feature of the model is an account of an additional effect due to the drift of charged particles towards the helio-equator plane or backward, depending on the direction of the total magnetic field of the Sun.

  2. A 3D computer simulation of negative ion extraction influenced by electron diffusion and weak magnetic field

    SciTech Connect

    Turek, M.; Sielanko, J.

    2008-03-19

    The numerical model of negative ion beam extraction from the RF ion source by different kinds of large extraction grid systems is considered. The model takes into account the influence of the transversal magnetic field and the electron diffusion. The magnetic filter field increases H{sup -} yields significantly. The random-walk electron diffusion model enables electrons to travel through magnetic field. The H{sup -} currents obtained from simulations with or without the diffusion are compared.

  3. Influence of menstrual cycle phase on pulmonary function in asthmatic athletes.

    PubMed

    Stanford, Kristin I; Mickleborough, Timothy D; Ray, Shahla; Lindley, Martin R; Koceja, David M; Stager, Joel M

    2006-04-01

    The main aim of this study was to investigate whether there is a relationship between menstrual cycle phase and exercise-induced bronchoconstriction (EIB) in female athletes with mild atopic asthma. Seven eumenorrheic subjects with regular 28-day menstrual cycles were exercised to volitional exhaustion on day 5 [mid-follicular (FOL)] and day 21 [mid-luteal (LUT)] of their menstrual cycle. Pulmonary function tests were conducted pre- and post-exercise. The maximal percentage decline in post-exercise forced expiratory volume in 1 s (FEV(1)) and forced expiratory flow from 25 to 75% of forced vital capacity (FEF(25-75%)) was significantly greater (P<0.05) on day 21 (mid-LUT phase) (-17.35+/-2.32 and -26.28+/-6.04%, respectively), when salivary progesterone concentration was highest, compared to day 5 (mid-FOL phase) (-12.81+/-3.35 and -17.23+/-8.20%, respectively), when salivary progesterone concentration was lowest. The deterioration in the severity of EIB during the mid-LUT phase was accompanied by worsening asthma symptoms and increased bronchodilator use. There was a negative correlation between the percent change in pre- to post-exercise FEV(1) and salivary progesterone concentration. However, no such correlation was found between salivary estradiol and the percentage change in pre- to post-exercise FEV(1). This study has shown for the first time that menstrual cycle phase is an important determinant of the severity of EIB in female athletes with mild atopic asthma. Female asthmatic athletes may need to adjust their training and competition schedules to their menstrual cycle and to consider the potential negative effects of the LUT phase of the menstrual cycle on exercise performance.

  4. Unravelling Orbital Climatic Cycles from Devonian Magnetic Susceptibility Signal - The Quest for a Better Age Model for the Lochkovian and Pragian Stages (Czech Republic)

    NASA Astrophysics Data System (ADS)

    da Silva, A. C.; Chadimova, L.; Hladil, J.; Slavik, L.; Hilgen, F. J.; Dekkers, M. J.

    2015-12-01

    The uncertainties on the Devonian stage boundaries are currently in the order of several millions of years. When shown to reflect a detrital signal, which is influenced by climatic variations, Magnetic Susceptibility (MS) has been proven as a useful tool for identifying climatic cycles; which can subsequently be used to improve the time scale. Here, we focus on two sections from the Prague Synform (Czech Republic) cutting through the Lochkovian, Pragian and the lower part of the Emsian. Sedimentation is rhythmic, dominated by slightly clayey offshore limestones, being mostly calciturbidites and hemipelagites. We provide hysteresis analysis in order to get insight into the nature and the origin of the magnetic minerals driving the variation in the MS signal. The results point to a MS signal mostly carried by clay minerals. Subsequently, to improve estimation of the duration of the stages, we apply different spectral analysis techniques on this MS signal. From the Continuous Wavelet Transform (CWT), Evolutive Harmonic Analysis (EHA) and field observations, we subdivide the section into portions with a steady sedimentation rate (a first estimate of this rate is also delivered by these analyzes). Then, we apply Multitaper Method (MTM) and Multitaper harmonic Analysis (F-test) and extract the frequencies reaching 95% Confidence Level. These frequencies are then implemented into the Average Spectral Misfit procedures (ASM) which enables comparison with orbital targets. By combining these different techniques, 405 kyr cyclicty is identifed, a powerful duration paleochronometer. These new results indicate a duration of 7.7 ± 2 Myr for the Lochkovian stage and of 1.7 Myr ± 1.4 for the Pragian stage (compared to respectively 8.4 ± 6 Myr and 3.2 ± 5.4 Myr in the 2012 Geological Time Scale).

  5. The influence of anthropogenic pure iron on magnetic properties of indoor dust.

    NASA Astrophysics Data System (ADS)

    Górka-Kostrubiec, Beata; Teisseyre-Jeleńska, Maria

    2015-04-01

    observed for the samples containing high contribution of pure iron. After heating, the loops were wide and their parameters are characteristic for SD+MD grains of the magnetite. The results show that the small amount of soft-magnetic pure iron significantly affects the values of hysteresis parameters , i.e. shifts the ratios Bcr/Bc towards larger value and Mrs/Ms towards smaller values on the Day-Dunlop's diagram. The recognition of morphology and chemical composition of the magnetic fraction was confirmed by the scanning electron microscope observation and the energy dispersive X-ray spectrometer measurement. Microscopic observations of dust samples revealed the presence of the elongated particles composed of pure iron. We found that magnetic susceptibility correlates with the concentration of following anthropogenic elements: Co, Cr, Fe, Ni but only Fe concentration influences high values of susceptibility observed in 2nd set of samples. Reference: B. Górka-Kostrubiec, M. Jeleńska and E. Król. (2014) Magnetic signature of indoor air pollution: household dust study. Acta Geophysica vol. 62, 1478-1503, DOI: 10.2478/s11600-014-0238-1.

  6. Influence of magnetic fields on calcium salts crystal formation: an explanation of the 'pulsed electromagnetic field' technique for bone healing.

    PubMed

    Madroñero, A

    1990-09-01

    In the search for a mechanism by means of which a magnetic field deparalyses non-unions and enhances bone tissue formation, the influence of continuous magnetic fields on the formation of calcium phosphate crystal seeds has been investigated. From this perspective, an explanation is given of a working mode in conventional equipment for pulsed electromagnetic field treatment; this is compared with multifunction equipment.

  7. About the Influence of the Magnetic Field Configuration on the Levitation Characteristics of the System Superconductor - Array of Magnets

    NASA Astrophysics Data System (ADS)

    Ermolaev, Yu. S.; Rudnev, I. A.

    2014-07-01

    Interaction of a superconductor with an array of magnets having different orientations of the magnetization vector is theoretically investigated. Based on a critical state model, the interaction force arising in the system superconductor - array of magnets is calculated by the method of finite elements. Optimal configurations of the magnetic system are established in which maximum values of both attractive and repulsive forces are created.

  8. Does Pulsed Magnetic Field Therapy Influence Nerve Regeneration in the Median Nerve Model of the Rat?

    PubMed Central

    Beck-Broichsitter, Benedicta E.; Lamia, Androniki; Fregnan, Federica; Smeets, Ralf; Becker, Stephan T.; Sinis, Nektarios

    2014-01-01

    The aim of this study was to evaluate the impact of pulsed magnetic field therapy on peripheral nerve regeneration after median nerve injury and primary coaptation in the rat. Both median nerves were surgically exposed and denervated in 24 female Wistar rats. A microsurgical coaptation was performed on the right side, whereas on the left side a spontaneous healing was prevented. The study group underwent a daily pulsed magnetic field therapy; the other group served as a control group. The grasping force was recorded 2 weeks after the surgical intervention for a period of 12 weeks. The right median nerve was excised and histologically examined. The histomorphometric data and the functional assessments were analyzed by t-test statistics and one-way ANOVA. One-way ANOVA indicated a statistically significant influence of group affiliation and grasping force (P = 0.0078). Grasping strength was higher on a significant level in the experimental group compared to the control group permanently from the 9th week to the end of the study. T-test statistics revealed a significantly higher weight of the flexor digitorum sublimis muscle (P = 0.0385) in the experimental group. The histological evaluation did not reveal any statistically significant differences concerning the histomorphometric parameters. Our results suggest that the pulsed magnetic field therapy has a positive influence on the functional aspects of neural regeneration. More studies are needed to precisely evaluate and optimize the intensity and duration of the application. PMID:25143937

  9. Analysis of the Magnetic Field Influence on the Rheological Properties of Healthy Persons Blood

    PubMed Central

    Nawrocka-Bogusz, Honorata

    2013-01-01

    The influence of magnetic field on whole blood rheological properties remains a weakly known phenomenon. An in vitro analysis of the magnetic field influence on the rheological properties of healthy persons blood is presented in this work. The study was performed on blood samples taken from 25 healthy nonsmoking persons and included comparative analysis of the results of both the standard rotary method (flow curve measurement) and the oscillatory method known also as the mechanical dynamic analysis, performed before and after exposition of blood samples to magnetic field. The principle of the oscillatory technique lies in determining the amplitude and phase of the oscillations of the studied sample subjected to action of a harmonic force of controlled amplitude and frequency. The flow curve measurement involved determining the shear rate dependence of blood viscosity. The viscoelastic properties of the blood samples were analyzed in terms of complex blood viscosity. All the measurements have been performed by means of the Contraves LS40 rheometer. The data obtained from the flow curve measurements complemented by hematocrit and plasma viscosity measurements have been analyzed using the rheological model of Quemada. No significant changes of the studied rheological parameters have been found. PMID:24078918

  10. Influence of geomagnetic activity and atmospheric pressure on human arterial pressure during the solar cycle 24

    NASA Astrophysics Data System (ADS)

    Azcárate, T.; Mendoza, B.; Levi, J. R.

    2016-11-01

    We performed a study of the systolic (SBP) and diastolic (DBP) arterial blood pressure behavior under natural variables such as the atmospheric pressure (AtmP) and the horizontal geomagnetic field component (H). We worked with a sample of 304 healthy normotense volunteers, 152 men and 152 women, with ages between 18 and 84 years in Mexico City during the period 2008-2014, corresponding to the minimum, ascending and maximum phases of the solar cycle 24. The data was divided by gender, age and day/night cycle. We studied the time series using three methods: Correlations, bivariate and superposed epochs (within a window of three days around the day of occurrence of a geomagnetic storm) analysis, between the SBP and DBP and the natural variables (AtmP and H). The correlation analysis indicated correlation between the SBP and DBP and AtmP and H, being the largest during the night. Furthermore, the correlation and bivariate analysis showed that the largest correlations are between the SBP and DBP and the AtmP. The superposed epoch analysis found that the largest number of significant SBP and DBP changes occurred for women. Finally, the blood pressure changes are larger during the solar minimum and ascending solar cycle phases than during the solar maximum; the storms of the minimum were more intense than those of the maximum and this could be the reason of behavior of the blood pressure changes along the solar cycle.

  11. Stride-Cycle Influences on Goal-Directed Head Movements Made During Walking

    NASA Technical Reports Server (NTRS)

    Peters, Brian T.; vanEmmerik, Richard E. A.; Bloomberg, Jacob J.

    2006-01-01

    Horizontal head movements were studied in six subjects as they made rapid horizontal gaze adjustments while walking. The aim of the present research was to determine if gait-cycle events alter the head movement response to a visual target acquisition task. Gaze shifts of approximately 40deg were elicited by a step change in the position of a visual target from a central location to a second location in the left or right horizontal periphery. The timing of the target position change was constrained to occur at 25,50,75 and 100% of the stride cycle. The trials were randomly presented as the subjects walked on a treadmill at their preferred speed (range: 1.25 to 1.48 m/s, mean: 1.39 +/- 0.09 m/s ) . Analyses focused on the movement onset latencies of the head and eyes and on the peak velocity and saccade amplitude of the head movement response. A comparison of the group means indicated that the head movement onset lagged the eye onset (262 ms versus 252 ms). The head and eye movement onset latencies were not affected by either the direction of the target change nor the point in the gait cycle during which the target relocation occurred. However, the presence of an interaction between the gait cycle events and the direction of the visual target shift indicates that the peak head saccade velocity and head saccade amplitude are affected by the natural head oscillations that occur while walking.

  12. The influence of photoperiod and temperature on the Neosho Madtom (norturus placidus) reproductive cycle

    USGS Publications Warehouse

    Albers, J.L.; Wildhaber, M.L.; Noltie, Douglas B.

    2001-01-01

    The key to successful fish culture is to understand the environmental cues that trigger spawning. In temperate fishes, photoperiod and temperature are important in many species including the family Ictaluridae. The object of this study was to examine whether natural photo-thermal conditions in the laboratory could stimulate the reproductive cycle of Neosho madtoms (Noturus placidus). For three years a small population of Neosho madtoms were maintained under natural conditions and continually sampled using ultrasound to examine interior gonad state and exterior body measurements. The purpose was to examine the secondary sexual characteristics that normally occur during the spawning period. Every year the fish cycled in and out of spawning condition, including production and reabsorbtion of eggs. The best external measurement found to distinguish between sexes was the ratio of head length to total length. Internal measurements found the average number of eggs per female increased as the fish length increased and over time but the average sizes of the eggs were constant. After years in the simulated environment 13 different fish were involved in ten spawns. The use of ultrasound to examine gonad in madtoms is promising, especially the lack of injury associated with the procedure. Overall laboratory conditions that simulated the natural photo-thermal environment, especially daily temperature fluctuations, were successful at stimulating the reproductive cycle of Neosho madtoms including egg cycling and spawning. These results show promise towards culture of madtoms especially for those species that are rare and endangered.

  13. The influence of the menstrual cycle on the metabolism and clearance of methaqualone.

    PubMed

    Wilson, K; Oram, M; Horth, C E; Burnett, D

    1982-09-01

    1 The rate of methaqualone metabolism in women was shown to be significantly increased at the time of ovulation. 2 The apparent first order rate constants for the formation of five C-monohydroxy metabolites of methaqualone on day 15 of the menstrual cycle were approximately double that on day 1. 3 The N-oxidation of methaqualone showed considerable inter-individual variation in its sensitivity to the menstrual cycle, and in a group of ten women the difference in N-oxide excretion between days 1 and 15 was not statistically significant. 4 The serum clearance of methaqualone on day 15 was higher (mean value 94.6 ml min-1 on day 1, 176.0 ml min-1 on day 15), serum half-life shorter (mean t1/2 beta 16.3 h on day 1, 11.6 h on day 15) and the AUC alpha smaller (mean value 44.0 micrograms ml-1 h on day 1, 24.4 micrograms ml-1 h on day 15) than on day 1. 5 The relative importance of the five hydroxy metabolites was unchanged during the menstrual cycle but the C/N oxidation ratio was greater on day 15 than on day 1. 6 The data for methaqualone metabolism in a control group of men was similar to than in women on day 1 of a menstrual cycle.

  14. THE INFLUENCE OF IRON AND SULFUR CYCLING ON ARSENIC PARTITIONING IN SOILS AND SEDIMENTS

    EPA Science Inventory

    Field evidence suggests that arsenic solid-solution partitioning in natural systems is often tied to iron and sulfur cycling. This is likely due to the coprecipitation of arsenic as a trace component in poorly crystalline iron oxides and monosulfides. However, there is limited ...

  15. Experimental investigation on butane diffusion flames under the influence of magnetic field by using digital speckle pattern interferometry.

    PubMed

    Kumar, Manoj; Agarwal, Shilpi; Kumar, Varun; Khan, Gufran S; Shakher, Chandra

    2015-03-20

    In this paper, the effect of magnetic fields on the temperature and temperature profile of a diffusion flame obtained from a butane torch burner are investigated experimentally by using digital speckle pattern interferometry (DSPI). Experiments were conducted on a diffusion flame generated by a butane torch burner in the absence of a magnetic field and in the presence of uniform and nonuniform magnetic fields. A single DSPI fringe pattern was used to extract phase by using a Riesz transform and monogenic signal. Temperature inside the flame was determined experimentally both in the absence and in the presence of magnetic fields. Experimental results reveal that the maximum temperature of the flame is increased under the influence of an upward-decreasing magnetic gradient and decreased under an upward-increasing magnetic gradient while a negligible effect on temperature in a uniform magnetic field was observed. PMID:25968534

  16. Stray magnetic field influence on the CPT resonance in a coated Rb vacuum cell

    NASA Astrophysics Data System (ADS)

    Taskova, E.; Alipieva, E.; Todorov, G.

    2016-03-01

    Interaction of a resonant laser beam with an atomic absorption medium creates population redistribution and interference between atomic levels. This anisotropy of the medium is experimentally observed as coherent population trapping (CPT) or electromagnetically induced transparency (EIT). Due to the small sub-natural width of the CPT and EIT resonances, they find wide applications in metrology, quantum optics, atom cooling. A non-compensated stray magnetic field (SMF) can change the shape and sign of the resonance or destroy it completely. In this work, we present an experimental and theoretical investigation of the influence of a stray magnetic field on the CPT resonances obtained on Zeeman sublevels of the D1 line of 87Rb in a paraffin-coated vacuum cell. The role is clarified of the polarization moments with different rank in creating the integral registered fluorescent signal in the presence of a stray magnetic field. It is shown that a transverse magnetic field plays an important role in changing the shape of the signal.

  17. Influence of magnetic fields on spin-mixing in transition metals

    NASA Astrophysics Data System (ADS)

    Haag, Michael; Illg, Christian; Fähnle, Manfred

    2014-10-01

    In a relativistic description of a real solid the crystal wave functions are never pure but spin-mixed functions. As a direct result of the spin-mixing, scattering mechanisms, which are in principal diagonal in spin-space, as for example the deformation potential part of the electron-phonon scattering potential, may lead to spin flips. Spin-mixing thereby affects damping and lifetimes in the fast and ultrafast regime of magnetization dynamics. The average spin-mixing appears as an important parameter in many models, the most prominent being the Elliott-Yafet model of spin relaxation. The application of an external magnetic field, a laser-field, or a Faraday-field induced by a laser may be considered as a source of magnetic field in a sample. Therefore we will discuss the influence of a homogeneous applied magnetic field on the average spin-mixing calculated in the framework of spin-density-functional theory. It is shown that even high fields do not significantly change the spin-mixing in 3d transition metals. Therefore the related dynamics are unaffected, which is in accordance with the experimental data on ultrafast demagnetization's dependence on light polarization.

  18. Change of deformation characteristics and dislocation substructure of nonferrous metals under influence of magnetic field

    NASA Astrophysics Data System (ADS)

    Zagulyaev, D. V.; Konovalov, S. V.; Shlyarov, V. V.; Anuchina, E. A.; Komissarova, I. A.; Gromov, V. E.

    2016-09-01

    The objects of the study were polycrystalline copper of M00b grade and commercially pure titanium BT1-0. Microindentation was carried out on the samples of titanium BT1-0 in the initial state, immediately after magnetic field exposure of 0.4 T and after certain time intervals. The defect substructure of cooper samples M00b, subjected to loading to failure in the creep mode under the influence of magnetic field of 0.35 T and without it, was investigated by the methods of electron diffraction microscopy. It was revealed that the effect of magnetic field exposure on commercially pure titanium BT1-0 leads to the decrease in microhardness with the subsequent stabilization during the time that depends on the processing parameters. And the effect of the magnetic field exposure on copper during the process of creeping results in the redistribution of dislocation substructure types. Also, there are changes in quantitative characteristics of dislocation substructures.

  19. The influence of water on the cycling behavior of the polypyrrole electrode in lithium cells

    SciTech Connect

    Novak, P.; Vielstich, W. . Inst. fuer Physikalische und Theoretische Chemie)

    1990-04-01

    Two different types of polypyrrole (PPy) have been synthesized: the dry form from 0.2{ital M} pyrrole (Py) + 0.5{ital M} LiClO{sub 4} propylene carbonate (PC) and the wet one from 0.2{ital M} Py + 0.56{ital M} H{sub 2}O + 0.5{ital M} LiClO{sub 4} in PC. The polymerization of pyrrole in both electrolytes starts at + 3.46 V ({ital vs}. Li/Li{sup +}) and follows nearly the same {ital E-I} curve. During the first discharge clear differences in electrochemical behavior can already be seen. During the first 1,000 cycles performed on 1-{mu}m thin PPy layers in the dry 0.5{ital M} LiClO{sub 4} (PC) electrolyte, the coulombic capacity of the dry form of PPy dropped to about 80% of its initial value. The cycling behavior of the wet form is even better---the doping level is slightly higher and the capacity drops to 80% of its initial value after more than 20,000 cycles, when cycled in the optimum potential interval from 2.0 to 4.0 V ({ital vs}. Li/Li{sup +}). Cyclic voltammograms and {ital in situ} FTIR measurements revealed that there is a gradual, slight loss of the most negative redox sites with increasing cycle number, accompanied by an increase in the amount of the irreversibly (over)oxidized PPy found in the neutral form of the polymer. The self-discharge loss on {approx} 50-{mu}m-thick PPy foils was found to be about 1% per day.

  20. The influence of defects on magnetic properties of fcc-Pu

    SciTech Connect

    Shorikov, A. O.; Anisimov, V. I.; Korotin, M. A.; Dremov, V. V. Sapozhnikov, Ph. A.

    2013-10-15

    The influence of vacancies and interstitial atoms on magnetism in Pu is considered in the framework of the density functional theory. The crystal structure relaxation arising due to various types of defects is calculated using the molecular dynamics method with a modified embedded atom model. The local density approximation with explicit inclusion of Coulomb and spin-orbit interactions is applied in matrix invariant form to describe correlation effects in Pu with these types of defects. The calculations show that both vacancies and interstitials give rise to local moments in the f-shell of Pu in good agreement with experimental data for aged Pu. Magnetism appears due to the destruction of a delicate balance between spin-orbit and exchange interactions.

  1. The influence of magnetic fields exposure on neurite outgrowth in PC12 rat pheochromocytoma cells

    NASA Astrophysics Data System (ADS)

    Fan, W.; Ding, J.; Duan, W.; Zhu, Y. M.

    2004-11-01

    The aim of present work was to investigate the influence of magnetic fields exposure on neurite outgrowth in PC12 cells. The neurite number per cell, length of neurites and directions of neurite growth with respect to the direction of the magnetic field were analyzed after exposure to 50 Hz electromagnetic field for 96 h. A promotion was observed under a weak field (0.23 mT), as the average number of neurites per cell increased to 2.38±0.06 compared to 1.91±0.07 neurites/cell of the control dishes, while inhibition and directional outgrowth was evident under a relatively stronger field (1.32 mT). Our work shows that biological systems can be very sensitive to the strength of electromagnetic field.

  2. Influence of resonant charge exchange on the viscosity of partially ionized plasma in a magnetic field

    SciTech Connect

    Zhdanov, V. M. Stepanenko, A. A.

    2013-12-15

    The influence of resonant charge exchange for ion-atom interaction on the viscosity of partially ionized plasma embedded in the magnetic field is investigated. The general system of equations used to derive the viscosity coefficients for an arbitrary plasma component in the 21-moment approximation of Grad’s method is presented. The expressions for the coefficients of total and partial viscosities of a multicomponent partially ionized plasma in the magnetic field are obtained. As an example, the coefficients of the parallel and transverse viscosities for the ionic and neutral components of the partially ionized hydrogen plasma are calculated. It is shown that the account for resonant charge exchange can lead to a substantial change of the parallel and transverse viscosity of the plasma components in the region of low degrees of ionization on the order of 0.1.

  3. Heating influence on magnetic structure in Co and Fe rich amorphous microwires

    NASA Astrophysics Data System (ADS)

    Chizhik, A.; Stupakiewicz, A.; Maziewski, A.; Zhukov, A.; Gonzalez, J.

    2016-02-01

    The influence of temperature on surface magnetic structure has been studied in Co- and Fe-rich magnetic glass covered microwires. The investigations have been performed using magneto-optical Kerr effect technique with a thermo-controlled system. It was found different types of domain structures depending on the temperature and the microwire composition. These types are characterised by the different domain period and the angle of the inclination of domain walls. It was established the direct correlation between surface domain structures and hysteresis loops. The coexistence of domain walls with different value of mobility has been found. It was observed original mechanism of the domain structure transformation: sharp change in the domain structure without movement of the domain walls.

  4. Influence of ionization on reflection of solitary waves in a magnetized plasma

    SciTech Connect

    Jyoti,; Malik, Hitendra K.; Kumar, Ravinder; Dahiya, Raj P.

    2013-09-15

    The reflection of nonlinear solitary waves is studied in a nonuniform, magnetized plasma diffusing from an ionization source along the magnetic field lines. Contribution of the ionization term is included in the continuity equation. The behavior of solitary waves is governed by modified form of Korteweg–de Vries equation (called mKdV equation). In order to investigate the reflection of solitary waves, the mKdV equations for the right and left going waves are derived, and solved by finding new transformations coupled at the point of reflection, for obtaining the expression of reflection coefficient. Contrary to the case of usual inhomogeneous plasma, the present analysis shows that a combination of usual sech{sup 2} structure and tanh structure (called the tail of soliton) arises due to the influence of ionization term. Interestingly, this tailing structure disappears after the reflection of the soliton and hence, the soliton is downshifted prominently.

  5. Magnetic field strength influence on the reactive magnetron sputter deposition of Ta2O5

    NASA Astrophysics Data System (ADS)

    Hollerweger, R.; Holec, D.; Paulitsch, J.; Rachbauer, R.; Polcik, P.; Mayrhofer, P. H.

    2013-08-01

    Reactive magnetron sputtering enables the deposition of various thin films to be used for protective as well as optical and electronic applications. However, progressing target erosion during sputtering results in increased magnetic field strengths at the target surface. Consequently, the glow discharge, the target poisoning, and hence the morphology, crystal structure and stoichiometry of the prepared thin films are influenced. Therefore, these effects were investigated by varying the cathode current Im between 0.50 and 1.00 A, the magnetic field strength B between 45 and 90 mT, and the O2/(Ar + O2) flow rate ratio Γ between 0% and 100%. With increasing oxygen flow ratio a substoichiometric TaOx oxide forms at the metallic Ta target surface which further transfers to a non-conductive tantalum pentoxide Ta2O5, impeding a stable dc glow discharge. These two transition zones (from Ta to TaOx and from TaOx to Ta2O5) shift to higher oxygen flow rates for increasing target currents. In contrast, increasing the magnetic field strength (e.g., due to sputter erosion) mainly shifts the TaOx to Ta2O5 transition to lower oxygen flow rates while marginally influencing the Ta to TaOx transition. To allow for a stable dc glow discharge (and to suppress the formation of non-conductive Ta2O5 at the target) even at Γ = 100% either a high target current (Im ⩾ 1 A) or a low magnetic field strength (B ⩽ 60 mT) is necessary. These conditions are required to prepare stoichiometric and fully crystalline Ta2O5 films.

  6. Influence of a constant and variable magnetic field on the coagulation of human blood in vitro and in vivo

    NASA Technical Reports Server (NTRS)

    Degen, I. L.; Plaksenko, V. Y.

    1974-01-01

    The influence of constant and varying magnetic fields on the coagulation of the blood was studied in experiments performed in vitro and vivo. In the in vitro tests it was found that a constant magnetic field with a strength of 100 or 200 oersteds influences the coagulation of the blood, retarding it in some cases and speeding up the coagulation time in others. In the in vivo studies, both retarding and accelerating effects were likewise observed with respect to the coagulation of the blood, but the nature of the change was a function of the background. A normalizing effect of the magnetic field on the coagulation of the blood was observed.

  7. Enhanced magnetic hysteresis in Ni-Mn-Ga single crystal and its influence on magnetic shape memory effect

    SciTech Connect

    Heczko, O. Drahokoupil, J.; Straka, L.

    2015-05-07

    Enhanced magnetic hysteresis due to boron doping in combination with magnetic shape memory effect in Ni-Mn-Ga single crystal results in new interesting functionality of magnetic shape memory (MSM) alloys such as mechanical demagnetization. In Ni{sub 50.0}Mn{sub 28.5}Ga{sub 21.5} single crystal, the boron doping increased magnetic coercivity from few Oe to 270 Oe while not affecting the transformation behavior and 10 M martensite structure. However, the magnetic field needed for MSM effect also increased in doped sample. The magnetic behavior is compared to undoped single crystal of similar composition. The evidence from the X-ray diffraction, magnetic domain structure, magnetization loops, and temperature evolution of the magnetic coercivity points out that the enhanced hysteresis is caused by stress-induced anisotropy.

  8. Influence of menstrual cycle phase on muscle metaboreflex control of cardiac baroreflex sensitivity, heart rate and blood pressure in humans.

    PubMed

    Hartwich, Doreen; Aldred, Sarah; Fisher, James P

    2013-01-01

    We sought to determine whether menstrual cycle phase influences muscle metaboreflex control of spontaneous cardiac baroreflex sensitivity (cBRS), blood pressure (BP) and heart rate (HR). Twenty-three young women not taking oral contraceptives were studied during the early (EF; low oestrogen, low progesterone) and late follicular menstrual phases (LF; high oestrogen, low progesterone). Protocol 1 consisted of leg cycling at low (21 ± 2 W) and moderate workloads (71 ± 3 W) in free-flow conditions and with partial flow restriction (bilateral thigh-cuff inflation at 100 mmHg) to activate the muscle metaboreflex. Protocol 2 consisted of rhythmic hand-grip exercise with incremental upper arm-cuff inflation (0, 80, 100 and 120 mmHg) to elicit graded metaboreflex activation. Both protocols were followed by post-exercise ischaemia. Leg cycling decreased cBRS (EF, 20 ± 5, 6 ± 1 and 1 ± 0.1 ms mmHg(-1); and LF, 19 ± 3, 6 ± 0.4, 1 ± 0.1 ms mmHg(-1) during rest, low- and moderate-intensity leg cycling, respectively) and increased HR in an intensity-dependent manner, while BP remained unchanged. Partial flow restriction during leg cycling decreased cBRS, and increased HR and BP. During post-exercise ischaemia, HR and BP remained elevated, while cBRS remained suppressed (EF, 4.2 ± 0.6 ms mmHg(-1); and LF, 4.7 ± 0.5 ms mmHg(-1); P < 0.05 versus rest). Cardiac baroreflex sensitivity was unchanged during hand-grip with and without partial flow restriction and post-exercise ischaemia. No differences in cBRS, HR or BP responses were observed between EF and LF at any time during either protocol. These data indicate that endogenous fluctuations in oestrogen between the EF and LF phases of the menstrual cycle do not influence muscle metaboreflex control of cBRS, BP or HR in young women.

  9. The influence of sexual cycle on the MFO activity: A practical problem in biomonitoring

    SciTech Connect

    Fossi, C.; Leonzio, C.; Focardi, S. )

    1988-09-01

    During the last several years the induction of the mixed function oxidases system has been commonly used as a biochemical markers of xenobiotics contamination in aquatic, marine and terrestrial animals. The use of this index of stress in wild animals like birds has directly contributed to their ability to detect and understand the significance of the exposure to liphosoluble contaminants in the environment. Nevertheless, several intrinsic factors, such as for example the hormonal modulation during the sexual cycle, seems to significantly modify the activity of some monooxygenases. The aim of this paper is to underline, using three different examples of studies in wild birds exposed to PCBs, the role of the sexual cycles in the modification of MFO activity and consequently the importance of considering this aspect in planning biomonitoring.

  10. Influence of autotrophic assimilation on diel cycling of major and trace elements in streams

    NASA Astrophysics Data System (ADS)

    Kurz, M. J.; Martin, J. B.; Cohen, M. J.; Douglass, R. L.; Foster, C.

    2011-12-01

    Ecosystem respiration and photosynthesis by submerged aquatic plants result in diel (24-hr) cycles in dissolved oxygen (DO) concentrations, pH, redox conditions and metal saturation states in streams, which in turn create diel variations in trace metal concentrations. Direct assimilatory uptake of metals may also be a significant driver of in-stream diel metal cycles, particularly in systems with high primary productivity. The objective of this study is to quantify the importance of biotic assimilation relative to abiotic mechanisms for controlling elemental cycling at the ecosystem scale. Meeting this objective required better understanding of primary producer tissue stoichiometry, its relationship with environmental element availability, and the magnitude and phase of diel variation. We combined high-frequency, automatic sensor deployment with ICP-MS analysis of metal concentrations in the water and dominant aquatic algae and vascular plant species in the Ichetucknee River and its five main source springs in north-central Florida. The Ichetucknee River is an entirely spring-fed system characterized by stable discharge (6-9 m3/s), constant but distinct spring chemistry through time, and high primary productivity making it a model system for distinguishing between the multiple drivers of diel chemical cycles. At a station 5 km downstream of the main input springs, diel cycles were observed in DO (3-9 mg/L), pH (7.1-7.9), NO3 (6.1-7.9 μM) and PO4 (1.45-1.65 μM), reflecting aquatic primary production. As previously observed, diel variation in NO3 was out of phase with DO while the PO4 minima lagged the DO maxima by 7 hours. Eleven major and trace elements also exhibited diel cycling. Concentrations of Mg, Fe, V, As, Cu, Cr, and U peaked in the afternoon, in phase with DO and pH, while Ca, Mn and Ba concentrations peaked in the morning. Ni, Co, Zn, and Pb showed no clear diel variability. Elemental concentrations in both plant species decrease with atomic weight and

  11. Influence of generalized focusing of few-cycle Gaussian pulses in attosecond pulse generation.

    PubMed

    Karimi, Ebrahim; Altucci, Carlo; Tosa, Valer; Velotta, Raffaele; Marrucci, Lorenzo

    2013-10-21

    In contrast to the case of quasi-monochromatic waves, a focused optical pulse in the few-cycle limit may exhibit two independent curved wavefronts, associated with phase and group retardations, respectively. Focusing optical elements will generally affect these two wavefronts differently, thus leading to very different behavior of the pulse near focus. As limiting cases, we consider an ideal diffractive lens introducing only phase retardations and a perfect non-dispersive refractive lens (or a curved mirror) introducing equal phase and group retardations. We study the resulting diffraction effects on the pulse, finding both strong deformations of the pulse shape and shifts in the spectrum. We then show how important these effects can be in highly nonlinear optics, by studying their role in attosecond pulse generation. In particular, the focusing effects are found to affect substantially the generation of isolated attosecond pulses in gases from few-cycle fundamental optical fields. PMID:24150342

  12. Influence of High Cycle Thermal Loads on Thermal Fatigue Behavior of Thick Thermal Barrier Coatings

    NASA Technical Reports Server (NTRS)

    Zhu, Dongming; Miller, Robert A.

    1997-01-01

    Thick thermal barrier coating systems in a diesel engine experience severe thermal Low Cycle Fatigue (LCF) and High Cycle Fatigue (HCF) during engine operation. In the present study, the mechanisms of fatigue crack initiation and propagation, as well as of coating failure, under thermal loads which simulate engine conditions, are investigated using a high power CO2 laser. In general, surface vertical cracks initiate early and grow continuously under LCF and HCF cyclic stresses. It is found that in the absence of interfacial oxidation, the failure associated with LCF is closely related to coating sintering and creep at high temperatures, which induce tensile stresses in the coating after cooling. Experiments show that the HCF cycles are very damaging to the coating systems. The combined LCF and HCF tests produced more severe coating surface cracking, microspallation and accelerated crack growth, as compared to the pure LCF test. It is suggested that the HCF component cannot only accelerate the surface crack initiation, but also interact with the LCF by contributing to the crack growth at high temperatures. The increased LCF stress intensity at the crack tip due to the HCF component enhances the subsequent LCF crack growth. Conversely, since a faster HCF crack growth rate will be expected with lower effective compressive stresses in the coating, the LCF cycles also facilitate the HCF crack growth at high temperatures by stress relaxation process. A surface wedging model has been proposed to account for the HCF crack growth in the coating system. This mechanism predicts that HCF damage effect increases with increasing temperature swing, the thermal expansion coefficient and the elastic modulus of the ceramic coating, as well as the HCF interacting depth. A good agreement has been found between the analysis and experimental evidence.

  13. How to assess performance in cycling: the multivariate nature of influencing factors and related indicators

    PubMed Central

    Castronovo, A. Margherita; Conforto, Silvia; Schmid, Maurizio; Bibbo, Daniele; D'Alessio, Tommaso

    2013-01-01

    Finding an optimum for the cycling performance is not a trivial matter, since the literature shows the presence of many controversial aspects. In order to quantify different levels of performance, several indexes have been defined and used in many studies, reflecting variations in physiological and biomechanical factors. In particular, indexes such as Gross Efficiency (GE), Net Efficiency (NE) and Delta Efficiency (DE) have been referred to changes in metabolic efficiency (EffMet), while the Indexes of Effectiveness (IE), defined over the complete crank revolution or over part of it, have been referred to variations in mechanical effectiveness (EffMech). All these indicators quantify the variations of different factors [i.e., muscle fibers type distribution, pedaling cadence, setup of the bicycle frame, muscular fatigue (MFat), environmental variables, ergogenic aids, psychological traits (PsychTr)], which, moreover, show high mutual correlation. In the attempt of assessing cycling performance, most studies in the literature keep all these factors separated. This may bring to misleading results, leaving unanswered the question of how to improve cycling performance. This work provides an overview on the studies involving indexes and factors usually related to performance monitoring and assessment in cycling. In particular, in order to clarify all those aspects, the mutual interactions among these factors are highlighted, in view of a global performance assessment. Moreover, a proposal is presented advocating for a model-based approach that considers all factors mentioned in the survey, including the mutual interaction effects, for the definition of an objective function E representing the overall effectiveness of a training program in terms of both EffMet and EffMech. PMID:23734130

  14. Nitrogen cycle and ecosystem services in the Brazilian La Plata Basin: anthropogenic influence and climate change.

    PubMed

    Watanabe, M; Ortega, E; Bergier, I; Silva, J S V

    2012-08-01

    The increasing human demand for food, raw material and energy has radically modified both the landscape and biogeochemical cycles in many river basins in the world. The interference of human activities on the Biosphere is so significant that it has doubled the amount of reactive nitrogen due to industrial fertiliser production (Haber-Bosch), fossil fuel burning and land-use change over the last century. In this context, the Brazilian La Plata Basin contributes to the alteration of the nitrogen cycle in South America because of its huge agricultural and grazing area that meets the demands of its large urban centres - Sao Paulo, for instance - and also external markets abroad. In this paper, we estimate the current inputs and outputs of anthropogenic nitrogen (in kg N.km(-2).yr(-1)) in the basin. In the results, we observe that soybean plays a very important role in the Brazilian La Plata, since it contributes with an annual entrance of about 1.8 TgN due to biological nitrogen fixation. Moreover, our estimate indicates that the export of soybean products accounts for roughly 1.0 TgN which is greater than the annual nitrogen riverine exports from Brazilian Parana, Paraguay and Uruguay rivers together. Complimentarily, we built future scenarios representing changes in the nitrogen cycle profile considering two scenarios of climate change for 2070-2100 (based on IPCC's A2 and B2) that will affect land-use, nitrogen inputs, and loss of such nutrients in the basin. Finally, we discuss how both scenarios will affect human well-being since there is a connection between nitrogen cycle and ecosystem services that affect local and global populations, such as food and fibre production and climate regulation.

  15. The influence of recovery duration after heavy resistance exercise on sprint cycling performance.

    PubMed

    Thatcher, Rhys; Gifford, Rhys; Howatson, Glyn

    2012-11-01

    The aim of this study was to determine the optimal recovery duration after prior heavy resistance exercise (PHRE) when performing sprint cycling. On 5 occasions, separated by a minimum of 48 hours, 10 healthy male subjects (mean ± SD), age 25.5 ± 7.7 years, body mass 82.1 ± 9.0 kg, stature 182.6 ± 87 cm, deadlift 1-repetition maximum (1RM) 142 ± 19 kg performed a 30-second sprint cycling test. Each trial had either a 5-, 10-, 20-, or 30-minute recovery after a heavy resistance activity (5 deadlift repetitions at 85% 1RM) or a control trial with no PHRE in random order. Sprint cycling performance was assessed by peak power (PP), fatigue index, and mean power output over the first 5 seconds (MPO5), 10 seconds (MPO10), and 30 seconds (MPO30). One-way analysis of variance with repeated measures followed by paired t-tests with a Bonferroni adjustment was used to analyze data. Peak power, MPO5, and MPO10 were all significantly different during the 10-minute recovery trial to that of the control condition with values of 109, 112, and 109% of control, respectively; no difference was found for the MPO30 between trials. This study supports the use of PHRE as a strategy to improve short duration, up to, or around 10-second, sprint activity but not longer duration sprints, and a 10-minute recovery appears to be optimal to maximize performance. PMID:22190162

  16. The influence of recovery duration after heavy resistance exercise on sprint cycling performance.

    PubMed

    Thatcher, Rhys; Gifford, Rhys; Howatson, Glyn

    2012-11-01

    The aim of this study was to determine the optimal recovery duration after prior heavy resistance exercise (PHRE) when performing sprint cycling. On 5 occasions, separated by a minimum of 48 hours, 10 healthy male subjects (mean ± SD), age 25.5 ± 7.7 years, body mass 82.1 ± 9.0 kg, stature 182.6 ± 87 cm, deadlift 1-repetition maximum (1RM) 142 ± 19 kg performed a 30-second sprint cycling test. Each trial had either a 5-, 10-, 20-, or 30-minute recovery after a heavy resistance activity (5 deadlift repetitions at 85% 1RM) or a control trial with no PHRE in random order. Sprint cycling performance was assessed by peak power (PP), fatigue index, and mean power output over the first 5 seconds (MPO5), 10 seconds (MPO10), and 30 seconds (MPO30). One-way analysis of variance with repeated measures followed by paired t-tests with a Bonferroni adjustment was used to analyze data. Peak power, MPO5, and MPO10 were all significantly different during the 10-minute recovery trial to that of the control condition with values of 109, 112, and 109% of control, respectively; no difference was found for the MPO30 between trials. This study supports the use of PHRE as a strategy to improve short duration, up to, or around 10-second, sprint activity but not longer duration sprints, and a 10-minute recovery appears to be optimal to maximize performance.

  17. Deception by manipulating the clock calibration influences cycle ergometer endurance time in males.

    PubMed

    Morton, R Hugh

    2009-03-01

    It is common for athletes striving to achieve maximal effort to exercise in the presence of a visible clock. It is implicitly assumed that calibration of the clock is normal (i.e. accurate). This study was designed to test the effect of secretly manipulating the clock calibration on maximal effort as measured by endurance times in cycle ergometry. Twelve subjects (6 male and 6 female) each undertook three identical rides to exhaustion on a cycle ergometer. In one the clock was normally calibrated, in another it was calibrated 10% faster, and in the third 10% slower. Tests were conducted double blind and in fully counterbalanced orders within gender. Clocked endurance times were recorded, and later converted to real times. Analysis of clocked times revealed no significant effects. Over all subjects, real endurance times showed a significant calibration effect, being on average 18.3% (73.4s) longer when the clock ran slow, compared to normal, and 20.5% (80.8s) longer when compared to fast. Because males exercised significantly longer than females, separate analyses reveal that the calibration effect was only significant in males, 27.7% (143.2s) and 29.7% (151.2s), respectively, and present but not significant in females, 1.3% (3.6s) and 3.8% (10.5s), respectively. These results suggest that, when deceived by a visible clock running slower than normal, times to exhaustion on the cycle ergometer were significantly longer in male subjects.

  18. The influence of space weather on ionospheric total electron content during the 23rd solar cycle

    NASA Astrophysics Data System (ADS)

    Bergeot, Nicolas; Tsagouri, Ioanna; Bruyninx, Carine; Legrand, Juliette; Chevalier, Jean-Marie; Defraigne, Pascale; Baire, Quentin; Pottiaux, Eric

    2013-07-01

    This paper presents a new empirical model for predicting the daily mean ionospheric Total Electron Content (TEC) at a given latitude from only one solar index as input. For the development of the model we take advantage of the availability of 15 years of global GNSS-based TEC information and solar indices (Sunspot Number, F10.7 and derived F10.7P) including the 23rd solar cycle. Among all the tests, our preferred ionospheric climatological model to predict daily mean TEC presents yearly median differences with observed values of 1.4 ± 0.9 TECu (11.5 ± 2.9% for the relative differences) with no significant degradation during the different phases of the solar cycle. To realize this empirical model we used a least-square adjustment with (1) a combination of linear, annual and semi-annual terms between the TEC and F10.7P; (2) a discretization with respect to the phases of the solar cycle. The main differences between the modelled and the observed TEC occur during identified geomagnetic storms: the maximum differences (-3.2 ± 1.5 TECu) and relative differences (-19.6 ± 15.0%) occur one day after the storm onset. The typical time to retrieve the pre-storm conditions is 3-4 days after the onset. These results show a global picture of the effect of extreme Space Weather events on the Earth’s upper atmosphere.

  19. Meridional Flow Variations in Cycles 23 and 24: Active Latitude Control of Sunspot Cycle Amplitudes

    NASA Technical Reports Server (NTRS)

    Hathaway, David H.; Upton, Lisa

    2013-01-01

    We have measured the meridional motions of magnetic elements observed in the photosphere over sunspot cycles 23 and 24 using magnetograms from SOHO/MDI and SDO/HMI. Our measurements confirm the finding of Komm, Howard, and Harvey (1993) that the poleward meridional flow weakens at cycle maxima. Our high spatial and temporal resolution analyses show that this variation is in the form of a superimposed inflow toward the active latitudes. This inflow is weaker in cycle 24 when compared to the inflow in 23, the stronger cycle. This systematic modulation of the meridional flow can modulate the amplitude of the following sunspot cycle through its influence on the Sun's polar fields.

  20. THE INFLUENCE OF THERMAL EVOLUTION IN THE MAGNETIC PROTECTION OF TERRESTRIAL PLANETS

    SciTech Connect

    Zuluaga, Jorge I.; Bustamante, Sebastian; Cuartas, Pablo A.; Hoyos, Jaime H. E-mail: sbustama@pegasus.udea.edu.co E-mail: jhhoyos@udem.edu.co

    2013-06-10

    Magnetic protection of potentially habitable planets plays a central role in determining their actual habitability and/or the chances of detecting atmospheric biosignatures. Here we develop a thermal evolution model of potentially habitable Earth-like planets and super-Earths (SEs). Using up-to-date dynamo-scaling laws, we predict the properties of core dynamo magnetic fields and study the influence of thermal evolution on their properties. The level of magnetic protection of tidally locked and unlocked planets is estimated by combining simplified models of the planetary magnetosphere and a phenomenological description of the stellar wind. Thermal evolution introduces a strong dependence of magnetic protection on planetary mass and rotation rate. Tidally locked terrestrial planets with an Earth-like composition would have early dayside magnetopause distances between 1.5 and 4.0 R{sub p} , larger than previously estimated. Unlocked planets with periods of rotation {approx}1 day are protected by magnetospheres extending between 3 and 8 R{sub p} . Our results are robust in comparison with variations in planetary bulk composition and uncertainties in other critical model parameters. For illustration purposes, the thermal evolution and magnetic protection of the potentially habitable SEs GL 581d, GJ 667Cc, and HD 40307g were also studied. Assuming an Earth-like composition, we found that the dynamos of these planets are already extinct or close to being shut down. While GL 581d is the best protected, the protection of HD 40307g cannot be reliably estimated. GJ 667Cc, even under optimistic conditions, seems to be severely exposed to the stellar wind, and, under the conditions of our model, has probably suffered massive atmospheric losses.

  1. Metachronal beating of cilia under the influence of Casson fluid and magnetic field

    NASA Astrophysics Data System (ADS)

    Akbar, Noreen Sher; Khan, Zafar Hayat

    2015-03-01

    Metachronal beating of cilia under the influence of Casson fluid and magnetic field is considered. The model for cilia literature is modelled for the first time. The governing coupled equations are constructed under long wavelength and low Reynold's number approximation. Exact solutions are evaluated for stream function and pressure gradient. The important results in this study are the variation of the Hartmann number M, Casson fluid parameter ζ. The velocity field increases due to the increase in Hartmann number M near the channel walls while velocity field decreases at the center of the channel. Comparative study is also made for Casson fluid with Newtonian fluid.

  2. Influence of surface spins on the magnetization of fine maghemite nanoparticles

    SciTech Connect

    Nadeem, K.; Krenn, H.; Szabó, D. V.

    2013-12-16

    Influence of surface spins on magnetization of maghemite nanoparticles have been studied by using SQUID measurements and also comparison done with theoretical simulations. Surface spin disorder arises in these nanoparticles due to the randomness of surface spins. A model of AC-susceptibility has been used to investigate the experimental results. The comparison between experiment and theory signifies the presence of large effective anisotropy and freezing effects on the surface of maghemite nanoparticles. The enhanced effective anisotropy constant of these nanoparticles as compared to bulk maghemite is due to presence of disordered surface spins.

  3. Influence of magnetic and acoustic treatment of superplasticizer solutions on the properties of portland cement concretes

    NASA Astrophysics Data System (ADS)

    Belous, N. Kh.; Azharonok, V. V.; Rodtsevich, S. P.; Koshevar, V. D.; Goncharik, S. V.; Chubrik, N. I.; Orlovich, A. I.; Rubannik, V. V.

    2012-05-01

    We have investigated the influence of the regimes of high-frequency magnetic-impulse and acoustic action on the physicochemical properties of water solutions of polycarboxylate superplasticizers and technological indices of fine concretes plasticized by them. The dependences of technological properties of concretes on the concentration of water solutions of the superplasticizers, the content of impurity ions in the water used for dilution, and the conditions of acousto-radiowave treatment have been determined. The regimes of activation of superplasticizer solutions, which permit increasing the mobility and keeping quality of concrete and solution mixes tempered with water and the density and strength of fine concretes formed from them, have been established.

  4. Influence of magnetic field on 1/f noise in GaAs resistors without surface effects

    SciTech Connect

    Song, M.H.; Birbas, A.N.; van der Ziel, A.; van Rheenen, A.D.

    1988-07-15

    The influence on magnetic field on 1/f noise in a planar GaAs resistor grown by molecular-beam epitaxy and without surface effects was investigated experimentally. The experimental results can be explained by the number fluctuation model but not by the mobility fluctuation model. Previously, experimental results indicating number fluctuation type of 1/f noise were mostly attributed to the surface effects associated with the particular structures used for the experiments. In our device the surface effects were diminished so that the fluctuations of the bulk current could be considered to produce the 1/f noise.

  5. Magnetics and control in power electronics: I. Modeling of coupled inductors. II. One-cycle control of switching converters

    SciTech Connect

    Santi, E.

    1994-12-31

    Part I. For coupled-inductor and integrated-magnetics design it is of paramount importance to accurately model leakages. Air gap position has a dramatic effect on coupled-inductor characteristics. Improved reluctance models that capture this effect are proposed. For the most common coupled-inductor structures, i.e., UU and UI cores with windings on different legs, a simple model valid for any gap arrangement is proposed. The model has a single leakage reluctance that is constant for a given core geometry and can be determined from a single set of measurements. A method to estimate this reluctance from core geometry is also suggested. A new coupled-inductor structure that achieves quasi-zero current riple without need for turns ratio adjustment is introduced. Part 2. The concept of One-Cycle control has recently been proposed. The generality of this control technique is demonstrated through description of its implementation for different DC-DC switching converters. It is a nonlinear control technique with significant advantages in terms of rejection of line perturbation, speed of response and insensitivity to circuit parameters. Until now, no stability analysis was available and, under certain conditions, instability was observed. In this paper a stability analysis of a One-Cycle controlled Cuk converter (a fourth order system) is performed, which shows that stability depends on the value of parasitic elements. A modification of the control to eliminate steady-state output voltage error is proposed. Finally, a modification of the control that ensures stability independently of the value of parasitic elements is suggested. All theoretical results are experimentally verified.

  6. 13C and 1H Nuclear Magnetic Resonance Study of Glycogen Futile Cycling in Strains of the Genus Fibrobacter

    PubMed Central

    Matheron, Christelle; Delort, Anne-Marie; Gaudet, Geneviève; Forano, Evelyne; Liptaj, Tibor

    1998-01-01

    We investigated the carbon metabolism of three strains of Fibrobacter succinogenes and one strain of Fibrobacter intestinalis. The four strains produced the same amounts of the metabolites succinate, acetate, and formate in approximately the same ratio (3.7/1/0.3). The four strains similarly stored glycogen during all growth phases, and the glycogen-to-protein ratio was close to 0.6 during the exponential growth phase. 13C nuclear magnetic resonance (NMR) analysis of [1-13C]glucose utilization by resting cells of the four strains revealed a reversal of glycolysis at the triose phosphate level and the same metabolic pathways. Glycogen futile cycling was demonstrated by 13C NMR by following the simultaneous metabolism of labeled [13C]glycogen and exogenous unlabeled glucose. The isotopic dilutions of the CH2 of succinate and the CH3 of acetate when the resting cells were metabolizing [1-13C]glucose and unlabeled glycogen were precisely quantified by using 13C-filtered spin-echo difference 1H NMR spectroscopy. The measured isotopic dilutions were not the same for succinate and acetate; in the case of succinate, the dilutions reflected only the contribution of glycogen futile cycling, while in the case of acetate, another mechanism was also involved. Results obtained in complementary experiments are consistent with reversal of the succinate synthesis pathway. Our results indicated that for all of the strains, from 12 to 16% of the glucose entering the metabolic pathway originated from prestored glycogen. Although genetically diverse, the four Fibrobacter strains studied had very similar carbon metabolism characteristics. PMID:12033219

  7. Influences of the Landscape on Life Cycle Carbon Intensity of Biofuels

    NASA Astrophysics Data System (ADS)

    Adler, P. R.; Del Grosso, S.; Parton, W. J.; Spatari, S.

    2011-12-01

    Biofuels derived from first (sugar and starch based) and second (lignocellulosic) generation agricultural feedstocks will continue to expand into the market between now and 2022 as incentivized through the federal Energy Independence and Security Act (EISA). Nitrogen use is one of the key environmental concerns within the life cycle since it is both the dominant source of life cycle greenhouse gas (GHG) emissions (energy from N fertilizer production and N2O emissions) and poses risks of reactive N movement throughout agricultural landscapes and watersheds. The other dominant components of the feedstock production on life cycle GHG emissions are tillage and land use change impacts on soil organic carbon (SOC). Opportunities to reduce reactive N through winter double crops may satisfy the dual goal of mitigating N2O emissions and reducing NO3 loses while meeting the objectives of EISA. However, changes in N2O, NO3, and SOC are variable within the agricultural landscape due to soil texture, climate, and crop rotation history thereby increasing the complexity of developing mitigation recommendations. Moreover, the inherent variability in N2O emissions makes it difficult to develop single life cycle carbon intensity profiles for specific fuel pathways that apply across the US, since those pathways will have geographic dependencies. Estimating the expected changes in N2O and SOC is an integral part of quantifying the life cycle GHG profile of biofuels derived from winter double crop feedstocks, while NO3 losses affect both indirect N2O emissions and water quality. The biogeochemical model DayCent was used to simulate the impact of growing winter barley as a double crop following corn before soybean establishment during the winter fallow period for six states in the Mid Atlantic region of the Eastern US on SOC and direct and indirect N2O. EPA is currently reviewing the addition of an advanced fuel pathway for winter barley in the Mid Atlantic region as part of the RFS2

  8. Weekly cycles of global fires—Associations with religion, wealth and culture, and insights into anthropogenic influences on global climate

    NASA Astrophysics Data System (ADS)

    Earl, Nick; Simmonds, Ian; Tapper, Nigel

    2015-11-01

    One approach to quantifying anthropogenic influences on the environment and the consequences of those is to examine weekly cycles (WCs). No long-term natural process occurs on a WC so any such signal can be considered anthropogenic. There is much ongoing scientific debate as to whether regional-scale WCs exist above the statistical noise level, with most significant studies claiming that anthropogenic aerosols and their interaction with solar radiation and clouds (direct/indirect effect) is the controlling factor. A major source of anthropogenic aerosol, underrepresented in the literature, is active fire (AF) from anthropogenic burning for land clearance/management. WCs in AF have not been analyzed heretofore, and these can provide a mechanism for observed regional-scale WCs in several meteorological variables. We show that WCs in AFs are highly pronounced for many parts of the world, strongly influenced by the working week and particularly the day(s) of rest, associated with religious practices.

  9. Rock Magnetic Cyclostratigraphy of the Mid-Cretaceous Greenhorn Limestone, South-Central Colorado---Influence of Orbitally Induced Climate Variability for Chornostratigraphy

    NASA Astrophysics Data System (ADS)

    Sellers, T.; Geissman, J. W.; Jackson, J.

    2015-12-01

    We are testing the hypothesis that depositional processes of the mid-Cretaceous Greenhorn Limestone were influenced by orbitally-driven climate variations using rock magnetic data. Correlation of the data, including anhysteretic remanent magnetization (ARM), magnetic susceptibility, isothermal remanent magnetization in different DC fields to saturation, and hysteresis properties, from three continuously exposed sections of the full Greenhorn Limestone provides detailed spatial distribution for the depositional processes and magnetic mineral climate encoding. The Greenhorn Limestone includes the Lincoln Limestone, Hartland Shale, and the Bridge Creek Limestone members and consists of calcareous shales and limestones representing near maximum depths in the Cretaceous interior seaway. The sections, each about 30 m thick, extend from the upper Graneros Shale, through the Greenhorn Formation, to the lower Carlisle Shale, with samples collected at a two to five cm interval and are located at Badito, CO; north of Redwing, CO; and at the Global boundary Stratotype Section and Point (GSSP) at Lake Pueblo, CO. Our over 1000 samples were hand crushed to granule size pieces and packed into 7cc IODP boxes. Bulk magnetic susceptibility, anhysteretic remanent magnetization (ARM) intensity at different peak AF levels, and isothermal remanent magnetization (IRM) intensity record variations in magnetic mineral concentration and are proxies to determine orbital scale cycles and precise stratigraphic correlation between sections. ARM intensities in a peak field of 100 mT at both sites range between 1.2 x 10-3 and 1.3 x 10-4 A/m and better define periodic variation within the Greenhorn Limestone displaying differences in ferromagnetic mineral content of detrital origin. Magnetic susceptibility, which ranges from 3.5 x 10-2 to 2.86 x 10-3, also shows periodic variation with a strong correlation among the three sections. Saturation IRM at 100 mT ranges from 3.2 x 10-1 to 1.1x 10-2 A

  10. The Influence of Menstrual Cycle and Androstadienone on Female Stress Reactions: An fMRI Study

    PubMed Central

    Chung, Ka Chun; Peisen, Felix; Kogler, Lydia; Radke, Sina; Turetsky, Bruce; Freiherr, Jessica; Derntl, Birgit

    2016-01-01

    Communicating threats and stress via biological signaling is common in animals. In humans, androstadienone (ANDR), a synthetic male steroid, is a socially relevant chemosignal exhibited to increase positive mood and cortisol levels specifically in (periovulatory) females in positively arousing contexts. In a negative context, we expected that such effects of ANDR could amplify social evaluative threat depending on the stress sensitivity, which differs between menstrual cycle phases. Therefore, this fMRI study aimed to examine psychosocial stress reactions on behavioral, hormonal and neural levels in 31 naturally cycling females, between 15 early follicular (EF) and 16 mid-luteal (ML) females tested with ANDR and placebo treatment in a repeated-measures design. Regardless of odor stimulation, psychosocial stress (i.e., mental arithmetic task with social evaluative threat) led to elevated negative mood and anxiety in all females. A negative association of social threat related amygdala activation and competence ratings appeared in ML-females, indicating enhanced threat processing by ANDR, particularly in ML-females who felt less competent early in the stress experience. Further, ML-females showed reduced performance and stronger stress-related hippocampus activation compared to EF-females under ANDR. Hippocampal activation in ML-females also correlated positively with post-stress subjective stress. Contrarily, such patterns were not observed in EF-females or under placebo in either group. Strikingly, unlike passive emotional processing, ANDR in a stressful context decreased cortisol concentration in all females. This points to a more complex interaction of ovarian/gonadal hormones in social threat processing and stress reactivity. Our findings suggest that ANDR enhanced initial evaluation of self-related social threat in ML-females. Female stress reactions are related to stress sensitivity through enhanced awareness and processing of social cues in a stressful

  11. Subalpine Forest Carbon Cycling Short- and Long-Term Influence ofClimate and Species

    SciTech Connect

    Kueppers, L.; Harte, J.

    2005-08-23

    Ecosystem carbon cycle feedbacks to climate change comprise one of the largest remaining sources of uncertainty in global model predictions of future climate. Both direct climate effects on carbon cycling and indirect effects via climate-induced shifts in species composition may alter ecosystem carbon balance over the long term. In the short term, climate effects on carbon cycling may be mediated by ecosystem species composition. We used an elevational climate and tree species composition gradient in Rocky Mountain subalpine forest to quantify the sensitivity of all major ecosystem carbon stocks and fluxes to these factors. The climate sensitivities of carbon fluxes were species-specific in the cases of relative above ground productivity and litter decomposition, whereas the climate sensitivity of dead wood decay did not differ between species, and total annual soil CO2 flux showed no strong climate trend. Lodge pole pine relative productivity increased with warmer temperatures and earlier snowmelt, while Engelmann spruce relative productivity was insensitive to climate variables. Engelmann spruce needle decomposition decreased linearly with increasing temperature(decreasing litter moisture), while lodgepole pine and subalpine fir needle decay showed a hump-shaped temperature response. We also found that total ecosystem carbon declined by 50 percent with a 2.88C increase in mean annual temperature and a concurrent 63 percent decrease ingrowing season soil moisture, primarily due to large declines in mineral soil and dead wood carbon. We detected no independent effect of species composition on ecosystem C stocks. Overall, our carbon flux results suggest that, in the short term, any change in subalpine forest net carbon balance will depend on the specific climate scenario and spatial distribution of tree species. Over the long term, our carbon stock results suggest that with regional warming and drying, Rocky Mountain subalpine forest will be a net source of carbon

  12. Increased impulsive choice for saccharin during PCP withdrawal in female monkeys: influence of menstrual cycle phase

    PubMed Central

    Carroll, Marilyn E.; Kohl, Emily A.; Johnson, Krista M.; LaNasa, Rachel M.

    2013-01-01

    Background In previous studies with male and female rhesus monkeys withdrawal of access to oral phencyclidine (PCP) self administration reduced responding for food under a high fixed-ratio (FR) schedule more in males than females and with a delay discounting (DD) task with saccharin (SACC) as the reinforcer. Impulsive choice for SACC increased during PCP withdrawal more than females. Objectives The goal of the present study was to examine the effect of PCP (0.25 or 0.5 mg/ml) withdrawal on impulsive choice for SACC in females during the follicular and luteal phases of the menstrual cycle. Materials and methods In Component 1 PCP and water were available from 2 drinking spouts for 1.5 h sessions under concurrent FR 16 schedules. In Component 2 a SACC solution was available for 45 min under a DD schedule. Monkeys had a choice of one immediate SACC delivery (0.6 ml) or 6 delayed SACC deliveries, and the delay was increased by 1 sec after a response on the delayed lever and decreased by 1 sec after a response on the immediate lever. There was then a 10-day water substitution phase, or PCP-withdrawal, that occurred during the mid-folllicular phase (Days 7–11) or the late-luteal (Days 24–28) phase of the menstrual cycle. Access to PCP and concurrent water was then restored, and the PCP withdrawal procedure was repeated over several follicular and luteal menstrual phases. Results PCP deliveries were higher during the luteal vs the follicular phase. Impulsive choice was greater during the luteal (vs follicular) phase during withdrawal of the higher PCP concentration. Conclusions PCP withdrawal was associated with elevated impulsive choice for SACC, especially in the luteal (vs follicular) phase of the menstrual cycle in female monkeys. PMID:23344553

  13. Influence of accurate and inaccurate 'split-time' feedback upon 10-mile time trial cycling performance.

    PubMed

    Wilson, Mathew G; Lane, Andy M; Beedie, Chris J; Farooq, Abdulaziz

    2012-01-01

    The objective of the study is to examine the impact of accurate and inaccurate 'split-time' feedback upon a 10-mile time trial (TT) performance and to quantify power output into a practically meaningful unit of variation. Seven well-trained cyclists completed four randomised bouts of a 10-mile TT on a SRM™ cycle ergometer. TTs were performed with (1) accurate performance feedback, (2) without performance feedback, (3) and (4) false negative and false positive 'split-time' feedback showing performance 5% slower or 5% faster than actual performance. There were no significant differences in completion time, average power output, heart rate or blood lactate between the four feedback conditions. There were significantly lower (p < 0.001) average [Formula: see text] (ml min(-1)) and [Formula: see text] (l min(-1)) scores in the false positive (3,485 ± 596; 119 ± 33) and accurate (3,471 ± 513; 117 ± 22) feedback conditions compared to the false negative (3,753 ± 410; 127 ± 27) and blind (3,772 ± 378; 124 ± 21) feedback conditions. Cyclists spent a greater amount of time in a '20 watt zone' 10 W either side of average power in the negative feedback condition (fastest) than the accurate feedback (slowest) condition (39.3 vs. 32.2%, p < 0.05). There were no significant differences in the 10-mile TT performance time between accurate and inaccurate feedback conditions, despite significantly lower average [Formula: see text] and [Formula: see text] scores in the false positive and accurate feedback conditions. Additionally, cycling with a small variation in power output (10 W either side of average power) produced the fastest TT. Further psycho-physiological research should examine the mechanism(s) why lower [Formula: see text] and [Formula: see text] scores are observed when cycling in a false positive or accurate feedback condition compared to a false negative or blind feedback condition.

  14. Research on Chinese Life Cycle-Based Wind Power Plant Environmental Influence Prevention Measures

    PubMed Central

    Wang, Hanxi; Xu, Jianling; Liu, Yuanyuan; Zhang, Tian

    2014-01-01

    The environmental impact of wind power plants over their life cycle is divided into three stages: construction period, operation period and retired period. The impact is mainly reflected in ecological destruction, noise pollution, water pollution and the effect on bird migration. In response to these environmental effects, suggesting reasonable locations, reducing plant footprint, optimizing construction programs, shielding noise, preventing pollution of terrestrial ecosystems, implementing combined optical and acoustical early warning signals, making synthesized use of power generation equipment in the post-retired period and using other specific measures, including methods involving governance and protection efforts to reduce environmental pollution, can be performed to achieve sustainable development. PMID:25153474

  15. The influence of {sup 18}F induced reactions in the hot CNO cycle

    SciTech Connect

    Rehm, K.E.; Roberts, A.D.; Jiang, C.L.

    1996-08-01

    The contribution of the {sup 18}F(p,{gamma}) reaction to the production of {sup 19}Ne, which is an important isotope in connection with the breakout from the hot CNO cycle, has been investigated in experiments with {sup 18}F beams. Measurements of the cross sections for the {sup 18}F(p,{alpha}){sup 15}O and {sup 18}F(p,{gamma}){sup 19 }Ne reactions indicate that the contribution of the {sup 18}F(p, {gamma}) route to the formation or {sup 19}Ne is small.

  16. Analysis of factors influencing morphokinetic characteristics of embryos in ART cycles.

    PubMed

    Gryshchenko, Mykola Grygorievich; Pravdyuk, Alexey Igorovich; Parashchyuk, Valentin Yurievich

    2014-10-01

    In this article, some factors were evaluated for their impact on embryo morphokinetics during assisted reproductive technology (ART) cycles. We detected significant differences in the fourth cell division time (t5) of embryos obtained after controlled ovarian stimulation in long GnRH agonists and GnRH antagonist protocols. We also found that higher gonadotropin dose may slow down the development of embryos. However, both male and female age, the number of oocytes and number of normal forms of sperm in the ejaculate did not affect the kinetic parameters of embryo development. Further research is needed to identify all the spectrum of factors, which can affect the rate of embryo development.

  17. Research on Chinese life cycle-based wind power plant environmental influence prevention measures.

    PubMed

    Wang, Hanxi; Xu, Jianling; Liu, Yuanyuan; Zhang, Tian

    2014-08-19

    The environmental impact of wind power plants over their life cycle is divided into three stages: construction period, operation period and retired period. The impact is mainly reflected in ecological destruction, noise pollution, water pollution and the effect on bird migration. In response to these environmental effects, suggesting reasonable locations, reducing plant footprint, optimizing construction programs, shielding noise, preventing pollution of terrestrial ecosystems, implementing combined optical and acoustical early warning signals, making synthesized use of power generation equipment in the post-retired period and using other specific measures, including methods involving governance and protection efforts to reduce environmental pollution, can be performed to achieve sustainable development.

  18. Influence of Different Thermo-mechanical Cycling Routes on Recovery Stresses of Annealed NiTi Wires

    NASA Astrophysics Data System (ADS)

    Yan, X. J.; Ge, Y. L.; Van Humbeeck, J.

    2016-01-01

    In this study, the influence of different thermo-mechanical cycling routes on recovery stresses of annealed NiTi wires has been investigated by using a dynamic mechanical analyzer. The as-received wire was annealed in Argon atmosphere in the temperature range of 350 to 900 °C. Differential scanning calorimeter was used to study the martensite transformation. In route I, the sample is deformed to 2% pre-strain and recovery stress is measured after unloading. In route II, the sample undergoes 3% deformation followed by a free shape recovery and then is reloaded to 2% pre-strain and recovery stress is measured after unloading. In route III, the sample undergoes a constrained thermal cycling at 3% pre-strain followed by a free shape recovery and then recovery stress is measured at 2% pre-strain. The results show that both route II and III can improve the recovery stresses. Route III has higher recovery stresses than route II for samples annealed at 550-700 °C. The improvements of recovery stresses under route II and III are partly attributed to the decrease of A s temperatures after thermo-mechanical cycling. Such information is essential for the proper use of NiTi alloys in smart structures, intelligent controllers, and memory devices.

  19. Influence of corn oil recovery on life-cycle greenhouse gas emissions of corn ethanol and corn oil biodiesel

    DOE PAGESBeta

    Wang, Zhichao; Dunn, Jennifer B.; Han, Jeongwoo; Wang, Michael

    2015-11-04

    Corn oil recovery and conversion to biodiesel has been widely adopted at corn ethanol plants recently. The US EPA has projected 2.6 billion liters of biodiesel will be produced from corn oil in 2022. Corn oil biodiesel may qualify for federal renewable identification number (RIN) credits under the Renewable Fuel Standard, as well as for low greenhouse gas (GHG) emission intensity credits under California’s Low Carbon Fuel Standard. Because multiple products [ethanol, biodiesel, and distiller’s grain with solubles (DGS)] are produced from one feedstock (corn), however, a careful co-product treatment approach is required to accurately estimate GHG intensities of bothmore » ethanol and corn oil biodiesel and to avoid double counting of benefits associated with corn oil biodiesel production. This study develops four co-product treatment methods: (1) displacement, (2) marginal, (3) hybrid allocation, and (4) process-level energy allocation. Life-cycle GHG emissions for corn oil biodiesel were more sensitive to the choice of co-product allocation method because significantly less corn oil biodiesel is produced than corn ethanol at a dry mill. Corn ethanol life-cycle GHG emissions with the displacement, marginal, and hybrid allocation approaches are similar (61, 62, and 59 g CO2e/MJ, respectively). Although corn ethanol and DGS share upstream farming and conversion burdens in both the hybrid and process-level energy allocation methods, DGS bears a higher burden in the latter because it has lower energy content per selling price as compared to corn ethanol. As a result, with the process-level allocation approach, ethanol’s life-cycle GHG emissions are lower at 46 g CO2e/MJ. Corn oil biodiesel life-cycle GHG emissions from the marginal, hybrid allocation, and process-level energy allocation methods were 14, 59, and 45 g CO2e/MJ, respectively. Sensitivity analyses were conducted to investigate the influence corn oil yield, soy biodiesel, and defatted DGS displacement

  20. Influence of corn oil recovery on life-cycle greenhouse gas emissions of corn ethanol and corn oil biodiesel

    SciTech Connect

    Wang, Zhichao; Dunn, Jennifer B.; Han, Jeongwoo; Wang, Michael

    2015-11-04

    Corn oil recovery and conversion to biodiesel has been widely adopted at corn ethanol plants recently. The US EPA has projected 2.6 billion liters of biodiesel will be produced from corn oil in 2022. Corn oil biodiesel may qualify for federal renewable identification number (RIN) credits under the Renewable Fuel Standard, as well as for low greenhouse gas (GHG) emission intensity credits under California’s Low Carbon Fuel Standard. Because multiple products [ethanol, biodiesel, and distiller’s grain with solubles (DGS)] are produced from one feedstock (corn), however, a careful co-product treatment approach is required to accurately estimate GHG intensities of both ethanol and corn oil biodiesel and to avoid double counting of benefits associated with corn oil biodiesel production. This study develops four co-product treatment methods: (1) displacement, (2) marginal, (3) hybrid allocation, and (4) process-level energy allocation. Life-cycle GHG emissions for corn oil biodiesel were more sensitive to the choice of co-product allocation method because significantly less corn oil biodiesel is produced than corn ethanol at a dry mill. Corn ethanol life-cycle GHG emissions with the displacement, marginal, and hybrid allocation approaches are similar (61, 62, and 59 g CO2e/MJ, respectively). Although corn ethanol and DGS share upstream farming and conversion burdens in both the hybrid and process-level energy allocation methods, DGS bears a higher burden in the latter because it has lower energy content per selling price as compared to corn ethanol. As a result, with the process-level allocation approach, ethanol’s life-cycle GHG emissions are lower at 46 g CO2e/MJ. Corn oil biodiesel life-cycle GHG emissions from the marginal, hybrid allocation, and process-level energy allocation methods were 14, 59, and 45 g CO2e/MJ, respectively. Sensitivity analyses were conducted to investigate the influence corn oil yield, soy biodiesel, and

  1. The potential influence of perception of achievement on performance in volitional time-to-exhaustion cycle ergometer trials.

    PubMed

    Lorimer, Ross; Babraj, John

    2013-06-01

    The purpose of this short communication was to report the findings of an investigation of the potential influence of spontaneous goal setting on subjects undertaking maximal fitness testing. Subjects were asked to complete a single incremental volitional time-to-exhaustion cycle ergometer trial. The final minute of the trial, after the last increase in increment in resistance, was broken down into six 10-second intervals and a frequency count made of how many subjects stopped within each interval. A chi-square test was used to determine that there was a significant difference between the expected and the observed frequencies (p < 0.05), with 45% of subjects stopping in the first interval (0-10 seconds) and 0% within the last interval (51-60 seconds). Reflections of the subjects revealed that those who were close to exhaustion but near to reaching the next increment of resistance were more likely to "push on." However, despite having been told to keep going as long as they could, subjects upon reaching that increment stopped almost immediately as they believed they could not manage to reach the next increment. This suggests a potential psychological element related to goal achievement that influences performance in incremental volitional time-to-exhaustion cycle ergometer trials. Practically, this means that the information participants have available on which to base goals (level of increment, time, etc.) needs to be minimized to prevent spontaneous goal setting.

  2. Stud arc welding in a magnetic field - Investigation of the influences on the arc motion

    NASA Astrophysics Data System (ADS)

    Hartz-Behrend, K.; Marqués, J. L.; Forster, G.; Jenicek, A.; Müller, M.; Cramer, H.; Jilg, A.; Soyer, H.; Schein, J.

    2014-11-01

    Stud arc welding is widely used in the construction industry. For welding of studs with a diameter larger than 14 mm a ceramic ferrule is usually necessary in order to protect the weld pool. Disadvantages of using such a ferrule are that more metal is molten than necessary for a high quality welded joint and that the ferrule is a consumable generally thrown away after the welding operation. Investigations show that the ferrule can be omitted when the welding is carried out in a radially symmetric magnetic field within a shielding gas atmosphere. Due to the Lorentz force the arc is laterally shifted so that a very uniform and controlled melting of the stud contact surface as well as of the work piece can be achieved. In this paper a simplified physical model is presented describing how the parameters welding current, flux density of the magnetic field, radius of the arc and mass density of the shielding gas influence the velocity of the arc motion. The resulting equation is subsequently verified by comparing it to optical measurements of the arc motion. The proposed model can be used to optimize the required field distribution for the magnetic field stud welding process.

  3. Influence of the terrestrial magnetic field geometry on the cutoff rigidity of cosmic ray particles

    NASA Astrophysics Data System (ADS)

    Herbst, K.; Kopp, A.; Heber, B.

    2013-10-01

    Studies of the propagation of charged energetic particles in the Earth's magnetic field go back to Carl Størmer. In the end, his investigations finally lead to the definition of the so-called cutoff rigidity RC; that is, the minimum momentum per charge a particle must have in order to reach a certain geographical location. Employing Monte Carlo simulations with the PLANETOCOSMICS code we investigate the correlation between the geomagnetic field structure and the cutoff rigidity. We show that the geometry of the magnetic field has a considerable influence on the resulting cutoff rigidity distribution. Furthermore, we will present a simple geometry-based parameter, δB, which is able to reflect the location-dependent cutoff rigidity. We show that this correlation is also visible in the temporal evolution of the Earth's magnetic field, at least over the last 100 yr. Using latitude scans with neutron monitors, changes of the relative counting rates at different positions are calculated, showing small variations for, e.g., Kiel and Moscow, while large ones occur at Mexico City as well as on the British Virgin Islands.

  4. Energetic particle transport in the presence of magnetic turbulence: influence of spectral extension and intermittency

    NASA Astrophysics Data System (ADS)

    Pucci, F.; Malara, F.; Perri, S.; Zimbardo, G.; Sorriso-Valvo, L.; Valentini, F.

    2016-07-01

    The transport of energetic particles in the presence of magnetic turbulence is an important but unsolved problem of space physics and astrophysics. Here, we aim at advancing the understanding of energetic particle transport by means of a new numerical model of synthetic magnetic turbulence. The model builds up a turbulent magnetic field as a superposition of space-localized fluctuations at different spatial scales. The resulting spectrum is isotropic with an adjustable spectral index. The model allows us to reproduce a spectrum broader than four decades, and to regulate the level of intermittency through a technique based on the p-model. Adjusting the simulation parameters close to solar wind conditions at 1 au, we inject ˜1 MeV protons in the turbulence realization and compute the parallel and perpendicular diffusion coefficients as a function of spectral extension, turbulence level, and intermittency. While a number of previous results are recovered in the appropriate limits, including anomalous transport regimes for low turbulence levels, we find that long spectral extensions tend to reduce the diffusion coefficients. Furthermore, we find for the first time that intermittency has an influence on parallel transport but not on perpendicular transport, with the parallel diffusion coefficient increasing with the level of intermittency. We also obtain the distribution of particle inversion times for parallel velocity, a power law for more than one decade, and compare it with the pitch angle scattering times observed in the solar wind. This parametric study can be useful to interpret particle propagation properties in astrophysical systems.

  5. The influence of preceding dive cycles on the foraging decisions of Antarctic fur seals

    PubMed Central

    Iwata, T.; Sakamoto, K. Q.; Edwards, E. W. J.; Staniland, I. J.; Trathan, P. N.; Goto, Y.; Sato, K.; Naito, Y.; Takahashi, A.

    2015-01-01

    The foraging strategy of many animals is thought to be determined by their past experiences. However, few empirical studies have investigated whether this is true in diving animals. We recorded three-dimensional movements and mouth-opening events from three Antarctic fur seals during their foraging trips to examine how they adapt their behaviour based on past experience—continuing to search for prey in the same area or moving to search in a different place. Each dive cycle was divided into a transit phase and a feeding phase. The linear horizontal distance travelled after feeding phases in each dive was affected by the mouth-opening rate during the previous 244 s, which typically covered two to three dive cycles. The linear distance travelled tended to be shorter when the mouth-opening rate in the previous 244 s was higher, i.e. seals tended to stay in the same areas with high prey-encounter rates. These results indicate that Antarctic fur seals follow decision-making strategies based on the past foraging experience over time periods longer than the immediately preceding dive. PMID:26156132

  6. Structures of dolomite at ultrahigh pressure and their influence on the deep carbon cycle.

    PubMed

    Merlini, Marco; Crichton, Wilson A; Hanfland, Michael; Gemmi, Mauro; Müller, Harald; Kupenko, Ilya; Dubrovinsky, Leonid

    2012-08-21

    Carbon-bearing solids, fluids, and melts in the Earth's deep interior may play an important role in the long-term carbon cycle. Here we apply synchrotron X-ray single crystal micro-diffraction techniques to identify and characterize the high-pressure polymorphs of dolomite. Dolomite-II, observed above 17 GPa, is triclinic, and its structure is topologically related to CaCO(3)-II. It transforms above 35 GPa to dolomite-III, also triclinic, which features carbon in [3 + 1] coordination at the highest pressures investigated (60 GPa). The structure is therefore representative of an intermediate between the low-pressure carbonates and the predicted ultra-high pressure carbonates, with carbon in tetrahedral coordination. Dolomite-III does not decompose up to the melting point (2,600 K at 43 GPa) and its thermodynamic stability demonstrates that this complex phase can transport carbon to depths of at least up to 1,700 km. Dolomite-III, therefore, is a likely occurring phase in areas containing recycled crustal slabs, which are more oxidized and Ca-enriched than the primitive lower mantle. Indeed, these phases may play an important role as carbon carriers in the whole mantle carbon cycling. As such, they are expected to participate in the fundamental petrological processes which, through carbon-bearing fluids and carbonate melts, will return carbon back to the Earth's surface. PMID:22869705

  7. The influence of preceding dive cycles on the foraging decisions of Antarctic fur seals.

    PubMed

    Iwata, T; Sakamoto, K Q; Edwards, E W J; Staniland, I J; Trathan, P N; Goto, Y; Sato, K; Naito, Y; Takahashi, A

    2015-07-01

    The foraging strategy of many animals is thought to be determined by their past experiences. However, few empirical studies have investigated whether this is true in diving animals. We recorded three-dimensional movements and mouth-opening events from three Antarctic fur seals during their foraging trips to examine how they adapt their behaviour based on past experience--continuing to search for prey in the same area or moving to search in a different place. Each dive cycle was divided into a transit phase and a feeding phase. The linear horizontal distance travelled after feeding phases in each dive was affected by the mouth-opening rate during the previous 244 s, which typically covered two to three dive cycles. The linear distance travelled tended to be shorter when the mouth-opening rate in the previous 244 s was higher, i.e. seals tended to stay in the same areas with high prey-encounter rates. These results indicate that Antarctic fur seals follow decision-making strategies based on the past foraging experience over time periods longer than the immediately preceding dive.

  8. Daily Rhythms of Serum Lipids in Dogs: Influences of Lighting and Fasting Cycles

    PubMed Central

    Bertolucci, Cristiano; Fazio, Francesco; Piccione, Giuseppe

    2008-01-01

    Circadian clocks organize a wide array of metabolic functions in a coherent daily schedule and ensure synchrony of this schedule with environmental rhythms. Daily rhythmicity of lipid metabolism occurs in rodents and ruminants. We examined daily level variations of serum lipids (nonesterified fatty acids [NEFA], triglycerides, phospholipids, total cholesterol and total lipids) in healthy dogs, particularly focusing on their temporal relationship to lighting and fasting cycles. Whereas serum NEFA levels did not change across the day, levels of total lipids, total cholesterol, phospholipids, and triglycerides occurred in dogs maintained under 12:12-h light:dark cycles and fed a single meal daily. Only the rhythmic pattern of triglycerides responded to a 6 h delay in light onset, suggesting a cardinal role of a light-entrained circadian oscillator in its generation. To investigate whether temporal variations in serum lipids depend to physiological postprandial changes, we measured lipid levels in fasted dogs. Rhythms of total lipids, total cholesterol, phospholipids, and triglycerides vanished when dogs were food-deprived, indicating that these rhythms are driven by the digestive process. Levels of serum NEFA patterns were significantly higher during fasting than after food intake. The increase of NEFA concentrations during fasting may reflect the mobilization of adipose tissue NEFA mediated by the decrease in insulin with its lypolitic effects. Elucidating the daily rhythmicity of lipid levels is fundamental to understanding the metabolism of the dog, an animal model frequently used for research in metabolic pathophysiology. PMID:19004375

  9. Hybrid Simulation of Duty Cycle Influences on Pulse Modulated RF SiH4/Ar Discharge

    NASA Astrophysics Data System (ADS)

    Wang, Xifeng; Song, Yuanhong; Zhao, Shuxia; Dai, Zhongling; Wang, Younian

    2016-04-01

    A one-dimensional fluid/Monte-Carlo (MC) hybrid model is developed to describe capacitively coupled SiH4/Ar discharge, in which the lower electrode is applied by a RF source and pulse modulated by a square-wave, to investigate the modulation effects of the pulse duty cycle on the discharge mechanism. An electron Monte Carlo simulation is used to calculate the electron energy distribution as a function of position and time phase. Rate coefficients in chemical reactions can then be obtained and transferred to the fluid model for the calculation of electron temperature and densities of different species, such as electrons, ions, and radicals. The simulation results show that, the electron energy distribution f(ɛ) is modulated evidently within a pulse cycle, with its tail extending to higher energies during the power-on period, while shrinking back promptly in the afterglow period. Thus, the rate coefficients could be controlled during the discharge, resulting in modulation of the species composition on the substrate compared with continuous excitation. Meanwhile, more negative ions, like SiH‑3 and SiH‑2, may escape to the electrodes owing to the collapse of ambipolar electric fields, which is beneficial to films deposition. Pulse modulation is thus expected to provide additional methods to customize the plasma densities and components. supported by National Natural Science Foundation of China (No. 11275038)

  10. Influence of the hair cycle on the thickness of mouse skin

    SciTech Connect

    Hansen, L.S.; Coggle, J.E.; Wells, J.; Charles, M.W.

    1984-12-01

    The data on mouse skin thickness reported here was prompted by the need to know the true position of basal cells of the epidermis and hair follicles as these are important cells at risk for a variety of skin reactions including carcinogenesis following exposure to radiation. There is little reliable data in the literature and most previous reports have ignored the shrinkage of skin that occurs because of its natural elasticity. The values determined for mouse flank skin in telogen--the resting phase of the hair cycle for the different skin layers--are epidermis 10 micron, corium 250 micron, adipose layer 150 micron, and hair follicle depth 150 micron. Three days after chemical depilation which triggers the hair follicles into active cycle (anagen) the epidermis doubles in thickness, remains at this value for 7 days, and then gradually returns to telogen values by day 18. The corium and adipose layers also increase significantly to reach approximately 390 micron and approximately 260 micron, respectively, by day 10 and then return to control values from day 15 onward. The change in hair follicles depths are more dramatic with active follicle basal cells reaching approximately 450-550 micron into the adipose layer between days 7 and 15. One important finding is that chemical depilation does not affect the telogen thickness of skin-the teleogen values for the epidermis and dermis immediately prior to and immediately after depilation were similar to those 23 days later at the beginning of the next telogen phase.

  11. Structures of dolomite at ultrahigh pressure and their influence on the deep carbon cycle.

    PubMed

    Merlini, Marco; Crichton, Wilson A; Hanfland, Michael; Gemmi, Mauro; Müller, Harald; Kupenko, Ilya; Dubrovinsky, Leonid

    2012-08-21

    Carbon-bearing solids, fluids, and melts in the Earth's deep interior may play an important role in the long-term carbon cycle. Here we apply synchrotron X-ray single crystal micro-diffraction techniques to identify and characterize the high-pressure polymorphs of dolomite. Dolomite-II, observed above 17 GPa, is triclinic, and its structure is topologically related to CaCO(3)-II. It transforms above 35 GPa to dolomite-III, also triclinic, which features carbon in [3 + 1] coordination at the highest pressures investigated (60 GPa). The structure is therefore representative of an intermediate between the low-pressure carbonates and the predicted ultra-high pressure carbonates, with carbon in tetrahedral coordination. Dolomite-III does not decompose up to the melting point (2,600 K at 43 GPa) and its thermodynamic stability demonstrates that this complex phase can transport carbon to depths of at least up to 1,700 km. Dolomite-III, therefore, is a likely occurring phase in areas containing recycled crustal slabs, which are more oxidized and Ca-enriched than the primitive lower mantle. Indeed, these phases may play an important role as carbon carriers in the whole mantle carbon cycling. As such, they are expected to participate in the fundamental petrological processes which, through carbon-bearing fluids and carbonate melts, will return carbon back to the Earth's surface.

  12. Hybrid Simulation of Duty Cycle Influences on Pulse Modulated RF SiH4/Ar Discharge

    NASA Astrophysics Data System (ADS)

    Wang, Xifeng; Song, Yuanhong; Zhao, Shuxia; Dai, Zhongling; Wang, Younian

    2016-04-01

    A one-dimensional fluid/Monte-Carlo (MC) hybrid model is developed to describe capacitively coupled SiH4/Ar discharge, in which the lower electrode is applied by a RF source and pulse modulated by a square-wave, to investigate the modulation effects of the pulse duty cycle on the discharge mechanism. An electron Monte Carlo simulation is used to calculate the electron energy distribution as a function of position and time phase. Rate coefficients in chemical reactions can then be obtained and transferred to the fluid model for the calculation of electron temperature and densities of different species, such as electrons, ions, and radicals. The simulation results show that, the electron energy distribution f(ɛ) is modulated evidently within a pulse cycle, with its tail extending to higher energies during the power-on period, while shrinking back promptly in the afterglow period. Thus, the rate coefficients could be controlled during the discharge, resulting in modulation of the species composition on the substrate compared with continuous excitation. Meanwhile, more negative ions, like SiH-3 and SiH-2, may escape to the electrodes owing to the collapse of ambipolar electric fields, which is beneficial to films deposition. Pulse modulation is thus expected to provide additional methods to customize the plasma densities and components. supported by National Natural Science Foundation of China (No. 11275038)

  13. Influence of Electric, Magnetic, and Electromagnetic Fields on the Circadian System: Current Stage of Knowledge

    PubMed Central

    Żak, Arkadiusz

    2014-01-01

    One of the side effects of each electrical device work is the electromagnetic field generated near its workplace. All organisms, including humans, are exposed daily to the influence of different types of this field, characterized by various physical parameters. Therefore, it is important to accurately determine the effects of an electromagnetic field on the physiological and pathological processes occurring in cells, tissues, and organs. Numerous epidemiological and experimental data suggest that the extremely low frequency magnetic field generated by electrical transmission lines and electrically powered devices and the high frequencies electromagnetic radiation emitted by electronic devices have a potentially negative impact on the circadian system. On the other hand, several studies have found no influence of these fields on chronobiological parameters. According to the current state of knowledge, some previously proposed hypotheses, including one concerning the key role of melatonin secretion disruption in pathogenesis of electromagnetic field induced diseases, need to be revised. This paper reviews the data on the effect of electric, magnetic, and electromagnetic fields on melatonin and cortisol rhythms—two major markers of the circadian system as well as on sleep. It also provides the basic information about the nature, classification, parameters, and sources of these fields. PMID:25136557

  14. Influence of electric, magnetic, and electromagnetic fields on the circadian system: current stage of knowledge.

    PubMed

    Lewczuk, Bogdan; Redlarski, Grzegorz; Zak, Arkadiusz; Ziółkowska, Natalia; Przybylska-Gornowicz, Barbara; Krawczuk, Marek

    2014-01-01

    One of the side effects of each electrical device work is the electromagnetic field generated near its workplace. All organisms, including humans, are exposed daily to the influence of different types of this field, characterized by various physical parameters. Therefore, it is important to accurately determine the effects of an electromagnetic field on the physiological and pathological processes occurring in cells, tissues, and organs. Numerous epidemiological and experimental data suggest that the extremely low frequency magnetic field generated by electrical transmission lines and electrically powered devices and the high frequencies electromagnetic radiation emitted by electronic devices have a potentially negative impact on the circadian system. On the other hand, several studies have found no influence of these fields on chronobiological parameters. According to the current state of knowledge, some previously proposed hypotheses, including one concerning the key role of melatonin secretion disruption in pathogenesis of electromagnetic field induced diseases, need to be revised. This paper reviews the data on the effect of electric, magnetic, and electromagnetic fields on melatonin and cortisol rhythms-two major markers of the circadian system as well as on sleep. It also provides the basic information about the nature, classification, parameters, and sources of these fields.

  15. The influence of magnetic fields on the wake field and stopping power of an ion-beam pulse in plasmas

    SciTech Connect

    Zhao, Xiao-ying; Zhang, Ya-ling; Duan, Wen-shan; Qi, Xin E-mail: lyang@impcas.ac.cn; Shi, Jian; Zhang, Ling-yu; Yang, Lei E-mail: lyang@impcas.ac.cn

    2015-09-15

    We performed two-dimensional particle-in-cell simulations to investigate how a magnetic field affects the wake field and stopping power of an ion-beam pulse moving in plasmas. The corresponding density of plasma electrons is investigated. At a weak magnetic field, the wakes exhibit typical V-shaped cone structures. As the magnetic field strengthens, the wakes spread and lose their typical V-shaped structures. At a sufficiently strong magnetic field, the wakes exhibit conversed V-shaped structures. Additionally, strengthening the magnetic field reduces the stopping power in regions of low and high beam density. However, the influence of the magnetic field becomes complicated in regions of moderate beam density. The stopping power increases in a weak magnetic field, but it decreases in a strong magnetic field. At high beam density and moderate magnetic field, two low-density channels of plasma electrons appear on both sides of the incident beam pulse trajectory. This is because electrons near the beam pulses will be attracted and move along with the beam pulses, while other electrons nearby are restricted by the magnetic field and cannot fill the gap.

  16. Topoisomerase IIα Binding Domains of Adenomatous Polyposis Coli Influence Cell Cycle Progression and Aneuploidy

    PubMed Central

    Wang, Yang; Coffey, Robert J.; Osheroff, Neil; Neufeld, Kristi L.

    2010-01-01

    Background Truncating mutations in the tumor suppressor gene APC (Adenomatous Polyposis Coli) are thought to initiate the majority of colorectal cancers. The 15- and 20-amino acid repeat regions of APC bind β-catenin and have been widely studied for their role in the negative regulation of canonical Wnt signaling. However, functions of APC in other important cellular processes, such as cell cycle control or aneuploidy, are only beginning to be studied. Our previous investigation implicated the 15-amino acid repeat region of APC (M2-APC) in the regulation of the G2/M cell cycle transition through interaction with topoisomerase IIα (topo IIα). Methodology/Principal Findings We now demonstrate that the 20-amino acid repeat region of APC (M3-APC) also interacts with topo IIα in colonic epithelial cells. Expression of M3-APC in cells with full-length endogenous APC causes cell accumulation in G2. However, cells with a mutated topo IIα isoform and lacking topo IIβ did not arrest, suggesting that the cellular consequence of M2- or M3-APC expression depends on functional topoisomerase II. Both purified recombinant M2- and M3-APC significantly enhanced the activity of topo IIα. Of note, although M3-APC can bind β-catenin, the G2 arrest did not correlate with β-catenin expression or activity, similar to what was seen with M2-APC. More importantly, expression of either M2- or M3-APC also led to increased aneuploidy in cells with full-length endogenous APC but not in cells with truncated endogenous APC that includes the M2-APC region. Conclusions/Significance Together, our data establish that the 20-amino acid repeat region of APC interacts with topo IIα to enhance its activity in vitro, and leads to G2 cell cycle accumulation and aneuploidy when expressed in cells containing full-length APC. These findings provide an additional explanation for the aneuploidy associated with many colon cancers that possess truncated APC. PMID:20368985

  17. Characterization of uniaxial stiffness of extracellular matrix embedded with magnetic beads via bio-conjugation and under the influence of an external magnetic field.

    PubMed

    Herath, Sahan C B; Du, Yue; Wang, Dong-an; Liao, Kin; Wang, Qingguo; Asada, Harry; Chen, Peter C Y

    2014-02-01

    In this paper, we study the deformation, and experimentally quantify the change in stiffness, of an extracellular matrix (ECM) embedded with magnetic beads that are bio-conjugated with the collagen fibers and under the influence of an external magnetic field. We develop an analytical model of the viscoelastic behavior of this modified ECM, and design and implement a stretch test to quantify (based on statistically meaningful experiment data) the resulting changes in its stiffness induced by the external magnetic field. The analytical results are in close agreement with that obtained from the experiments. We discuss the implication of these results that point to the possibility of creating desired stiffness gradients in an ECM in vitro to influence cell behavior.

  18. The environmental magnetic record of palaeoenvironmental variations during the past 3100 years: A possible solar influence?

    NASA Astrophysics Data System (ADS)

    Sandeep, K.; Shankar, R.; Warrier, Anish K.; Weijian, Z.; Xuefeng, Lu

    2015-07-01

    Sediments from Pookot Lake (PK) in southern India have provided a record of local environmental changes and catchment processes during the past 3100 cal. years B.P. Variations in the rock magnetic parameters (χlf, χfd, χARM and IRM's at different field strengths) of sediments from two AMS 14C-dated cores reflect climate-induced changes in the catchment of Pookot Lake. Assuming that rainfall is most likely the dominant driving mechanism behind the rock magnetic variations of PK sediments, the environmental history of the site has been reconstructed. Rock magnetic parameters exhibit significant variations during the past 3100 years. The palaeoenvironmental history of the Pookot Lake region may be divided into three phases. During the first phase (~ 3100 to 2500 cal. years B.P.), catchment erosion and detrital influx were high, indicating a strong monsoon. The second phase, which lasted from 2500 to 1000 cal. years B.P., was characterised by low and steady rainfall, resulting in a low and uniform catchment erosion and detrital influx. Phase 2 was interspersed with brief intervals of strong monsoon and characterised by frequent drying up of the lake. During Phase 3 (~ 1000 cal. years B.P. to the present), catchment erosion was high, indicating a shift to strong monsoonal conditions. It appears that monsoonal rainfall in the region is influenced by solar activity, with periods of high total solar irradiance being characterised by high rainfall and vice versa; it was relatively low during the Little Ice Age and high during the Medieval Warm Period. The magnetic susceptibility (χlf) data exhibit a number of periodicities which might have a solar origin. The χlf record exhibits similarities with other continental and marine palaeoclimatic records from the region, indicating that regional trends in the monsoon during the Late Holocene are broadly similar.

  19. Influence of near null magnetic field on in vitro growth of potato and wild Solanum species.

    PubMed

    Rakosy-Tican, Lenuta; Aurori, C M; Morariu, V V

    2005-10-01

    The influence of near null magnetic field on in vitro growth of different cultures of potato and related Solanum species was investigated for various exposure times and dates. Potato (Solanum tuberosum L. cv. Désirée) in vitro cultures of shoot tips or nodal segments were used. Three different exposure periods revealed either stimulation or inhibition of root, stem, or leaf in vitro growth after 14 or 28 days of exposure. In one experiment the significant stimulation of leaf growth was also demonstrated at biochemical level, the quantity of chlorophyll a and b and carotenoids increasing more than two-fold. For the wild species Solanum chacoense, S. microdontum, and S. verrucosum, standardized in vitro cultures of nodal stem segments were used. Root and stem growth was either stimulated or slightly inhibited after 9 days exposure to near null magnetic field. Callus cultures obtained from potato dihaploid line 120/19 were maintained in near null magnetic field in 2 different months. For these experiments as well as for Solanum verrucosum, callus cultures recorded either slight inhibition or no effect on fresh weight. For all experiments significant growth variation was brought about only when geomagnetic activity (AP index) showed variations at the beginning of in vitro growth and when the explant had at least one meristematic tissue. Moreover longer maintenance in near null magnetic field, 28 days as compared to 14 days or the controls, can also make a difference in plant growth in response to geomagnetic field variations when static component was reduced to zero value. These results of in vitro plant growth stimulation by variable component of geomagnetic field also sustain the so-called seasonal "window" effect.

  20. Beyond Vmax and Km: How details of enzyme function influence geochemical cycles

    NASA Astrophysics Data System (ADS)

    Steen, A. D.

    2015-12-01

    Enzymes catalyze the vast majority of chemical reactions relevant to geomicrobiology. Studies of the activities of enzymes in environmental systems often report Vmax (the maximum possible rate of reaction; often proportional to the concentration of enzymes in the system) and sometimes Km (a measure of the affinity between enzymes and their substrates). However, enzyme studies - particularly those related to enzymes involved in organic carbon oxidation - are often limited to only those parameters, and a relatively limited and mixed set of enzymes. Here I will discuss some novel methods to assay and characterize the specific sets of enzymes that may be important to the carbon cycle in aquatic environments. First, kinetic experiments revealed the collective properties of the complex mixtures of extracellular peptidases that occur where microbial communities are diverse. Crystal structures combined with biochemical characterization of specific enzymes can yield more detailed information about key steps in organic carbon transformations. These new techniques have the potential to provide mechanistic grounding to geomicrobiological models.

  1. Mouth rinsing with a carbohydrate solution does not influence cycle time trial performance in the heat.

    PubMed

    Watson, Phillip; Nichols, David; Cordery, Philip

    2014-09-01

    Ten endurance-trained males were recruited to examine the possible role of carbohydrate (CHO) receptors in the mouth influencing exercise performance in the heat. Volunteers completed an incremental test to exhaustion to determine peak oxygen uptake, a familiarisation trial, followed by 2 experimental trials. Trials consisted of a 1-h time trial undertaken in a climatic chamber maintained at 30 °C, 60% relative humidity. Immediately before, and at regular intervals throughout exercise, subjects ingested a bolus of water and then were provided with either a placebo (PLA) or a 6.4% glucose (CHO) solution to rinse in the mouth for 10 s before being expectorated. There was no difference in total work done between the PLA and CHO trials (758.8 ± 149.0 kJ; 762.6 ± 141.1 kJ; P = 0.951). Pacing was also similar, with no differences in power output apparent during the experimental trials (P = 0.546). Core temperature (P = 0.615), heart rate (P = 0.505), ratings of perceived exertion (P = 0.181), and perceived thermal stress (P = 0.416) were not influenced by the nature of the intervention. Blood glucose concentrations were similar during the CHO and PLA trials (P = 0.117). In contrast to the findings of several studies undertaken in temperate conditions, the present investigation failed to support role of oral sensing of CHO in influencing performance during prolonged exercise in warm conditions. PMID:25154896

  2. Mouth rinsing with a carbohydrate solution does not influence cycle time trial performance in the heat.

    PubMed

    Watson, Phillip; Nichols, David; Cordery, Philip

    2014-09-01

    Ten endurance-trained males were recruited to examine the possible role of carbohydrate (CHO) receptors in the mouth influencing exercise performance in the heat. Volunteers completed an incremental test to exhaustion to determine peak oxygen uptake, a familiarisation trial, followed by 2 experimental trials. Trials consisted of a 1-h time trial undertaken in a climatic chamber maintained at 30 °C, 60% relative humidity. Immediately before, and at regular intervals throughout exercise, subjects ingested a bolus of water and then were provided with either a placebo (PLA) or a 6.4% glucose (CHO) solution to rinse in the mouth for 10 s before being expectorated. There was no difference in total work done between the PLA and CHO trials (758.8 ± 149.0 kJ; 762.6 ± 141.1 kJ; P = 0.951). Pacing was also similar, with no differences in power output apparent during the experimental trials (P = 0.546). Core temperature (P = 0.615), heart rate (P = 0.505), ratings of perceived exertion (P = 0.181), and perceived thermal stress (P = 0.416) were not influenced by the nature of the intervention. Blood glucose concentrations were similar during the CHO and PLA trials (P = 0.117). In contrast to the findings of several studies undertaken in temperate conditions, the present investigation failed to support role of oral sensing of CHO in influencing performance during prolonged exercise in warm conditions.

  3. The Simulated Influence of Anthropogenic Climate Warming on the Oceanic Carbon Cycle

    NASA Astrophysics Data System (ADS)

    Jain, A. K.; Cao, L.; Caldeira, K.; Kheshgi, H.

    2001-12-01

    Prediction of the redistribution of anthropogenic CO2 in the atmosphere-ocean-land biosphere system is complicated by our limited understanding of the mechanisms driving carbon sequestration by the ocean and the terrestrial biosphere. Furthermore, the rates of carbon sequestration are sensitive to climate change projected to result from increases in CO2 and other greenhouse gas and changes in aerosol concentrations. This sensitivity creates feedback loops; an understanding of these feedbacks is prerequisite to forecasting future atmospheric CO2 concentrations and climate change. For instance, climate affects the oceanic carbon reservoir through the temperature-dependent relationship between total dissolved carbon and the partial pressure of CO2, and through potential climate-induced changes in ocean transport and ocean biological activity. A two-dimensional (latitude-depth) coupled atmosphere-ocean climate-carbon cycle model is developed and used to examine possible feedbacks between global climate change and the ocean carbon cycle system. The model has surface-air, land-sea, and latitudinal resolution, and is forced with diurnally averaged but seasonally varying insolation. The ocean component consists of the zonal mean balance equations of horizontal momentum, mass, temperature and salinity. The momentum balance is diagnostic, and time dependence enters through the advection-diffusion equations for temperature and salinity. The density field is calculated using a nonlinear, pressure-dependent equation of state. In this study the model is used to project future atmospheric CO2 concentrations and temperature change due to greenhouse gas and aerosol scenarios recently developed by IPCC (Nakicenovic et al., 2000), and evaluated the climate change feedback contribution to spatial and temporal changes in ocean carbon uptake. Globally, projected warming over the next century can decrease the strength of oceanic uptake of CO2 resulting in a positive feedback on CO2

  4. Influence of aerosols on the life cycle of a radiation fog event. A numerical and observational study

    NASA Astrophysics Data System (ADS)

    Stolaki, S.; Haeffelin, M.; Lac, C.; Dupont, J.-C.; Elias, T.; Masson, V.

    2015-01-01

    Despite the knowledge gained on the physical processes dominating the formation, development and dissipation of radiation fog events, uncertainties still exist about the role of the microphysical processes related to aerosol characteristics. The objective of this work is to analyze the sensitivity of fog to aerosols through their impacts on the fog droplets. A radiation fog event that formed on 15/11/2011 at the SIRTA Observatory near Paris in the context of the 2011-2012 ParisFog field campaign is the basis of this study. The selected case is one that initially forms a few hundred meters above the surface and within half an hour lowers down to the surface. A combination of SIRTA's sophisticated observations and 1D numerical simulations is employed with the aim of better understanding the influence of thermodynamics and microphysics on the life-cycle of the fog event and the degree to which aerosol characteristics such as concentration of potentially activated aerosols, size and solubility affect its characteristics. It results that the model simulates fairly well the fog life cycle, with only one half hour advance in the onset and one hour in the dissipation at the surface. The quality of the reference simulation is evaluated against several in-situ and remote sensing measurements. A numerical sensitivity analysis shows that the fog characteristics are strongly influenced by the aerosols. Doubling (halving) the cloud condensation nuclei (CCN) number translates into a 160% increase (65% decrease) in the production of fog droplets, and a 60% increase (40% decrease) of the liquid water path (LWP). The aerosols influence up to 10% the fog geometrical thickness. The necessity for more detailed local forcings that will produce better thermohygrometric conditions in the upper levels above the formed fog layer is underlined, as well as the addition of microphysical measurements in the vertical that will allow to improve two-moment microphysics schemes.

  5. Influence of thickness of Fe-3% Si single crystals on ratio of magnetic losses in rotating and linearly polarized magnetic fields

    NASA Astrophysics Data System (ADS)

    Tiunov, V. F.

    2013-06-01

    The influence of the thickness of Fe-3% Si single crystals on the ratio of magnetic losses in rotating magnetic fields to losses measured in linearly polarized magnetic fields is investigated. A nonmonotonic character of the behavior of this ratio depending on the thickness of the samples in the range of its variation of 0.09-040 mm is revealed. It is established that the thickness of samples, which corresponds to minimal losses upon rotating remagnetization, exceeds their thickness measured for the samples in linearly polarized fields by a factor of almost two. The revealed features in the behavior of magnetic losses of the samples studied are discussed based on the dynamics of their domain structure.

  6. Measurement of changes in high-energy phosphates in the cardiac cycle by using gated /sup 31/P nuclear magnetic resonance. [Rats

    SciTech Connect

    Fossel, E.T.; Morgan, H.E.; Ingwall, J.S.

    1980-06-01

    Levels of the high-energy phosphate-containing compounds, ATP and creatine phosphate, and of inorganic phosphate (P/sub i/ were measured as a function of position in the cardiac cycle. Measurements were made on isolated, perfused, working rat hearts through the use of gated /sup 31/P nuclear magnetic resonance spectroscopy. Levels of ATP and creatine phosphate were found to vary during the cardiac cycle and were maximal at minimal aortic pressure and minimal at maximal aortic pressure. P/sub i/ varied inversely with the high-energy phosphates.

  7. Evolution of Tidal Influence During the ETS Seismic Cycle Reveals Competition Between Tectonic Loading and Fault Healing

    NASA Astrophysics Data System (ADS)

    Houston, H.

    2015-12-01

    Following the discovery of the evolution of tremor response to tidal stress over the duration of ETS slip at a spot (Houston 2015; Royer et al 2015;Yabe et al 2015), we investigate whether and how it may evolve between major large ETSs, which occur quasi-periodically in several subduction zones. Preliminary results show that tidal response does evolve over the average interETS period in northern Cascadia - decaying over the first quarter of the cycle to lowest values then climbing back up in the second half of the cycle part of the way toward the strong response seen late during major ETSs. Thus far, we have ignored the possible role of transient stresses during interETS tremor because tremor bursts are mostly small. We explore a strength-threshold model where tidal influence is stronger when stress is close to strength and weaker when they are farther apart. Shortly after a major ETS, both stress and strength are presumed to have fallen over the large region where slow slip occurred. Then, however, stress rebuilds quasi-linearly by plate tectonic loading, whereas strength rebuilds as the logarithm of time (e.g., Vidale et al 1994). Thus, model stress and strength diverge the most midway through the interETS cycle, the period of weakest tidal sensitivity. Tidal stresses become more effective in triggering tremor later in the cycle as the linearly-growing stress approaches the logarithmically-growing strength. This model broadly fits our observed evolution of tidal response. However, the tendency of ETSs to initiate downdip may require an additional process that varies along dip. This approach illuminates the competition between healing on the plate interface and reloading with tectonic stress, and can help constrain and perhaps even monitor physical conditions on the deep subduction interface. The figure shows the evolution of two measures of tidal influence on tremor, consistency and sensitivity (right), and the data on which they are based - probability

  8. The potential influence of thaw slumps and sea-level rise on the Arctic carbon cycle (Invited)

    NASA Astrophysics Data System (ADS)

    Rowland, J. C.; Crosby, B. T.; Travis, B. J.

    2010-12-01

    Potential soil carbon stores in the Arctic are estimated to be second only in size to that of the oceans. The majority of this carbon lies within permafrost dominated regions and is presently stored in frozen soils in the shallow subsurface (the upper 3 meters). Considerable attention and research is presently focused on how climate warming-induced thawing of permafrost and deepening of the seasonally thawed upper layer of the permafrost may alter the carbon cycle across the Arctic and globally. Less studied, however, many natural hazards have the potential to influence the Arctic carbon cycle due to their alteration of the landsurface. The temperature dependence and the influence of hydrology on Arctic landsurface processes make the occurrence of many natural hazards in the Arctic critically dependent on interactions between the landsurface, atmosphere, and oceans. Here we explore the potential role of two natural hazards in the Arctic carbon cycle: deep, retrogressive thaw slumps; and sea-level rise. Retrogressive thaw slumps are deep landslide features hypothesized to be initially triggered by the melting of bodies of ice contained within frozen sediments. Once triggered continued thawing of frozen soils and melting of buried ice along the failure face of the slide drives retreat of the slump headwall. Along the Selawik River in northwest Alaska a thaw slump triggered in 2004 has retreated approximately 300 m into a high river bluff and liberated more than a half million cubic meters of ice and sediment. The slump failure has mobilized both shallow soil carbon and much older carbon previously buried within the glacial deposits but now exposed in the actively retreating slump face. An unknown fraction of the carbon contained within slump sediments may be released directly to the atmosphere by oxidation or microbially mediated transformations. The remaining carbon is physically transported first onto the slump floor and then into the Selawik River. Once in the

  9. The Influence of Landscape Drainage on Biogeochemical Cycling of Carbon in Agricultural Ecosystems

    NASA Astrophysics Data System (ADS)

    Dalzell, B. J.; King, J. Y.; Mulla, D. J.; Finlay, J. C.; Sands, G. R.

    2008-12-01

    The movement of water through agricultural ecosystems is often modified by the presence of open ditches and subsurface tile drainage systems. Despite the common occurrence of these practices, particularly in the corn- and soybean-producing regions of the midwestern United States, much remains unknown about how altered drainage patterns may influence carbon export from agricultural landscapes. In this study, we examined the role of subsurface drainage systems on the quantity and quality of dissolved carbon export from experimental agricultural fields located in south-central Minnesota. Results from two years of observations show that fields with more intense drainage designs (e.g., greater density of subsurface drain lines) have dissolved organic carbon (DOC) concentrations that are similar to conventionally drained fields. However, fields with more intense drainage exhibit greater annual DOC loads due to higher water yields resulting from more intense drainage. In contrast, dissolved inorganic carbon (DIC) concentrations were consistently greater in fields with more intense drainage practices across all flow conditions. Our ongoing work is focused on determining if these differences in DIC concentrations are the result of either increased weathering or increased soil/plant root respiration resulting in increased soil CO2 concentrations. Molecular weight characterization of samples from our experimental fields shows that DOC from subsurface tile drainage is generally comprised of low molecular weight compounds. This low molecular weight signal is less apparent in samples from downstream ditch and river sites which are dominated by higher molecular weight compounds; suggesting that differences in organic matter source and/or processing are apparent over spatial scales transitioning from the field to small watershed. Overall, these results show that subsurface drainage practices fundamentally alter annual DOC and DIC carbon export from agricultural ecosystems as well

  10. [Influence of different combination of mental activity and respiratory cycle on heart rate variability].

    PubMed

    Sun, F L; Li, D M; Li, G Y

    1996-03-01

    By means of spectral analysis of P-R interval, different characteristics of heart rate variability in different form of respiratory exercise was observed. The results of observation on 32 volunteers showed that mental activity that affected respiration can influence the function of autonomic nerve system in a different way. When the mind was concentrated at the inspiration, the function of autonomic nerve system was kept in balance, and both the sympathetic and the vagal activities enhanced significantly and while mind concentrated at the expiration could induce a reduction of vagal activity so as to produce marked change in the sympathovagal balance.

  11. Modeling the influence of atmospheric leading modes on the variability of the Arctic freshwater cycle

    NASA Astrophysics Data System (ADS)

    Niederdrenk, L.; Sein, D.; Mikolajewicz, U.

    2013-12-01

    Global general circulation models show remarkable differences in modeling the Arctic freshwater cycle. While they agree on the general sinks and sources of the freshwater budget, they differ largely in the magnitude of the mean values as well as in the variability of the freshwater terms. Regional models can better resolve the complex topography and small scale processes, but they are often uncoupled, thus missing the air-sea interaction. Additionally, regional models mostly use some kind of salinity restoring or flux correction, thus disturbing the freshwater budget. Our approach to investigate the Arctic hydrologic cycle and its variability is a regional atmosphere-ocean model setup, consisting of the global ocean model MPIOM with high resolution in the Arctic coupled to the regional atmosphere model REMO. The domain of the atmosphere model covers all catchment areas of the rivers draining into the Arctic. To account for all sinks and sources of freshwater in the Arctic, we include a discharge model providing terrestrial lateral waterflows. We run the model without salinity restoring but with freshwater correction, which is set to zero in the Arctic. This allows for the analysis of a closed freshwater budget in the Artic region. We perform experiments for the second half of the 20th century and use data from the global model MPIOM/ECHAM5 performed with historical conditions, that was used within the 4th Assessment Report of the IPCC, as forcing for our regional model. With this setup, we investigate how the dominant modes of large-scale atmospheric variability impact the variability in the freshwater components. We focus on the two leading empirical orthogonal functions of winter mean sea level pressure, as well as on the North Atlantic Oscillation and the Siberian High. These modes have a large impact on the Arctic Ocean circulation as well as on the solid and liquid export through Fram Strait and through the Canadian archipelago. However, they cannot explain

  12. Influence of a caffeine mouth rinse on sprint cycling following glycogen depletion.

    PubMed

    Kizzi, Joseph; Sum, Alvin; Houston, Fraser E; Hayes, Lawrence D

    2016-11-01

    Attenuated performance during intense exercise with limited endogenous carbohydrate (CHO) is well documented. Therefore, this study examined whether caffeine (CAF) mouth rinsing would augment performance during repeated sprint cycling in participants with reduced endogenous CHO. Eight recreationally active males (aged 23 ± 2 yr, body mass 84 ± 4 kg, stature 178 ± 7 cm) participated in this randomized, single-blind, repeated-measures crossover investigation. Following familiarization, participants attended two separate evening glycogen depletion sessions. The following morning, participants completed five, 6 s sprints on a cycle ergometer (separated by 24 s active recovery), with mouth rinsing either (1) a placebo solution or (2) a 2% CAF solution. During a fifth visit, participants completed the sprints without prior glycogen depletion. Repeated-measures ANOVA identified significant main effect of condition (CAF, placebo, and control [P < .05; effect size (ES) = 0.850-0.897]), sprint (1-5 [P < .005; ES = 0.871-0.986]), and interaction (condition × sprint [P < .05; ES = 0.831-0.846]), for peak and mean power. The control condition exhibited the highest peak power (overall mean 760 ± 77 W) and mean power (overall mean 699 ± 83W) over the five sprints (P < .001 in both instances). CAF peak power (overall mean 643 ± 79 W) was significantly greater than placebo (mean 573 ± 79 W [P < .05; ES = 0.850]). Additionally, CAF mean power (overall mean 589 ± 80 W) was significantly greater than placebo (519 ± 82 W [P < .05; ES = 0.397]). These data indicate that mouth rinsing a caffeinated solution reduces decrements caused by CHO reduction, which may benefit athletes wishing to train in a low-CHO state. PMID:27686403

  13. Analysis of the influence of external magnetic field on transition matrix elements in quantum well and quantum cascade laser structures

    NASA Astrophysics Data System (ADS)

    Demić, Aleksandar; Radovanović, Jelena; Milanović, Vitomir

    2016-08-01

    We present a method for modeling nonparabolicity effects (NPE) in quantum nanostructures in presence of external electric and magnetic field by using second order perturbation theory. The method is applied to analysis of quantum well structure and active region of a quantum cascade laser (QCL). This model will allow us to examine the influence of magnetic field on dipole matrix element in QCL structures, which will provide a better insight to how NPE can affect the gain of QCL structures.

  14. Sleep-wake cycle of adolescents in Côte d'Ivoire: influence of age, gender, religion and occupation.

    PubMed

    Borchers, Claudia; Randler, Christoph

    2012-12-01

    The human sleep-wake cycle is characterized by significant individual differences. Those differences in the sleep-wake cycle are partially heritable but are also influenced by environmental factors like the light/dark cycle or social habits. In this study we analyse for the first time the sleep-wake rhythm of adolescent pupils and working adolescents in a less industrialised country in West Africa near the equator. The aim of this study was to explore the sleep wake cycle in this geographical region, using Côte d'Ivoire as an example. Data collection took place between 2nd of March and 10th of June 2009. 588 adolescents (338 girls, 250 boys) between 10 and 15 years (mean ± SD: 12.72 ± 1.63) participated in this study. We collected data on the religion of the participants (Christian (N = 159), Muslim (N = 352), other/no religion (N = 77)) and their occupation. Participants were either pupils attending school (N = 336) or adolescents that were already working (N = 252) and not attending school. The interviewer filled in the questionnaire. We found significant effects of age (p < 0.001), gender (p < 0.001), occupation (p = 0.002), religion (p < 0.001) and region (p < 0.001). The midpoint of sleep was on average 1:26 (SD: 00:30) on weekdays and 1:37 (SD: 00:42) on weekend days. There are significant differences between weekdays and weekend days, but these were only small. Sleep duration suggests that adolescents in Côte d'Ivoire may gain sufficient sleep during week and weekend days, and thus, may live more in accordance with their own biological clock than adolescents in the northern hemisphere. In contrast, the data can be interpreted that adolescents live in a permanent 'jetlag'. Factors may be the more continuous light/dark cycle in the tropics, low amount of ambient light and less electricity.

  15. Evaluation of the Analysis Influence on Transport in Reanalysis Regional Water Cycles

    NASA Technical Reports Server (NTRS)

    Bosilovich, M. G.; Chen, J.; Robertson, F. R.

    2011-01-01

    Regional water cycles of reanalyses do not follow theoretical assumptions applicable to pure simulated budgets. The data analysis changes the wind, temperature and moisture, perturbing the theoretical balance. Of course, the analysis is correcting the model forecast error, so that the state fields should be more aligned with observations. Recently, it has been reported that the moisture convergence over continental regions, even those with significant quantities of radiosonde profiles present, can produce long term values not consistent with theoretical bounds. Specifically, long averages over continents produce some regions of moisture divergence. This implies that the observational analysis leads to a source of water in the region. One such region is the Unite States Great Plains, which many radiosonde and lidar wind observations are assimilated. We will utilize a new ancillary data set from the MERRA reanalysis called the Gridded Innovations and Observations (GIO) which provides the assimilated observations on MERRA's native grid allowing more thorough consideration of their impact on regional and global climatology. Included with the GIO data are the observation minus forecast (OmF) and observation minus analysis (OmA). Using OmF and OmA, we can identify the bias of the analysis against each observing system and gain a better understanding of the observations that are controlling the regional analysis. In this study we will focus on the wind and moisture assimilation.

  16. Influence of cycle ergometer characteristics on the adolescents' anaerobic abilities testing.

    PubMed

    Delgado, A; Peres, G; Allemandou, A; Monod, H

    1993-01-01

    The present study examined whether the reported lower values of anaerobic abilities in children and adolescents, both in absolute and related to bodyweight values, as compared to adults can be explained, partially at least, by a non-optimal testing apparatus. So, they cannot express their anaerobic abilities. Specifically, we examined the force-velocity (F-V) relationship on a mechanical cycle ergometer, in 23 adolescents and 11 adults, with two wheels of very different weights: 6.3 kg (Wh6) and 18 kg (Wh18). A higher wheel inertia might explain a late reach or no reach of the true peak velocity and the maximal anaerobic power (PmaxAn). The adolescent group showed higher Vo (V for zero braking force) values with Wh6 (238 +/- 14 vs 223 +/- 16 rpm) (P < 0.001) than with Wh18. The absolute or relative PmaxAn values for this group were slightly higher, but not significantly, with Wh6 (10.6 +/- 2.2 vs 10.2 +/- 1.9 W/kg). The delay to reach peak velocity was higher with Wh18 than with Wh6 (P < 0.001) in the two groups. In addition, the delay was always higher (P < 0.001) in the adolescent group compared to the adult group for both wheels. This suggests that the fatigue related to the observed late reach and the rapid decrease of power over time could lead to an underestimation of the PmaxAn peak in children.

  17. Influence of AC external magnetic field on guidance force relaxation between HTS bulk and NdFeB guideway

    NASA Astrophysics Data System (ADS)

    Zhang, Longcai; Wang, Suyu; Wang, Jiasu; Zheng, Jun

    2007-12-01

    Superconducting maglev vehicle is one of the most promising applications of HTS bulks. In such a system, the HTS bulks are always exposed to time-varying external magnetic field, which is generated by the inhomogeneous surface magnetic field of the NdFeB guideway. So it is required to study whether the guidance force of the bulks is influenced by the inhomogeneity. In this paper, we studied the characteristics of the guidance force relaxation between the HTS bulk and the NdFeB guideway by an experiment in which AC external magnetic field generated by an electromagnet was used to simulate the time-varying external magnetic field caused by the inhomogeneity of the guideway. From the experiment results, it was found that the guidance force was decreased with the application of the AC external magnetic field, and the decay increased with the amplitude and was almost independent of the frequency.

  18. Respective influence of in-plane and out-of-plane spin-transfer torques in magnetization switching of perpendicular magnetic tunnel junctions

    NASA Astrophysics Data System (ADS)

    Timopheev, A. A.; Sousa, R.; Chshiev, M.; Buda-Prejbeanu, L. D.; Dieny, B.

    2015-09-01

    The relative contributions of in-plane (damping-like) and out-of-plane (field-like) spin-transfer torques (STT) in the magnetization switching of out-of-plane magnetized magnetic tunnel junctions (pMTJ) has been theoretically analyzed using the transformed Landau-Lifshitz-Gilbert (LLG) equation with the STT terms. It is demonstrated that in a pMTJ structure obeying macrospin dynamics, the out-of-plane torque influences the precession frequency, but it does not contribute significantly to the STT switching process (in particular to the switching time and switching current density), which is mostly determined by the in-plane STT contribution. This conclusion is confirmed by finite temperature and finite writing pulse macrospin simulations of the current field switching diagrams. It contrasts with the case of STT switching in in-plane magnetized magnetic tunnel junction (MTJ) in which the field-like term also influences the switching critical current. This theoretical analysis was successfully applied to the interpretation of voltage field STT switching diagrams experimentally measured on pMTJ pillars 36 nm in diameter, which exhibit macrospin behavior. The physical nonequivalence of Landau and Gilbert dissipation terms in the presence of STT-induced dynamics is also discussed.

  19. The influence of particle size and static magnetic fields on the uptake of magnetic nanoparticles into three dimensional cell-seeded collagen gel cultures.

    PubMed

    Lewis, Emily E L; Child, Hannah W; Hursthouse, Andrew; Stirling, David; McCully, Mark; Paterson, David; Mullin, Margaret; Berry, Catherine C

    2015-08-01

    Over recent decades there has been and continues to be major advances in the imaging, diagnosis and potential treatment of medical conditions, by the use of magnetic nanoparticles. However, to date the majority of cell delivery studies employ a traditional 2D monolayer culture. This article aims to determine the ability of various sized magnetic nanoparticles to penetrate and travel through a cell seeded collagen gel model, in the presence or absence of a magnetic field. Three different sized (100, 200, and 500 nm) nanoparticles were employed in the study. The results showed cell viability was unaffected by the presence of nanoparticles over a 24-h test period. The initial uptake of the 100 nm nanoparticle into the collagen gel structure was superior compared to the larger sized nanoparticles under the influence of a magnetic field and incubated for 24 h. Interestingly, it was the 200 nm nanoparticles, which proved to penetrate the gel furthest, under the influence of a magnetic field, during the initial culture stage after 1-h incubation. PMID:25358626

  20. White Synchortron Radiation Topography of (1????10) Nickel Single Crystal. The Influence of a (1????10) Magnetic Field

    NASA Astrophysics Data System (ADS)

    Stephenson, J. D.

    1982-05-01

    Changes in 70.53° magnetic domain structure on the surface of a perfect (11¯0) nickel crystal have been observed using white synchrotron X-radiation topography. The crystal was influenced by a variable [11¯0] magnetic field. At field strengths ≿ 100 A/m [111¯]-spike domains, thought to be traces of [011], 70.53° (oblique) magnetic domain walls, appeared within [111]-bands (0.4 mm wide) in the topographs. Reversal of the field produced similar spikes at equivalent field values but in different regions of the crystal.

  1. Influence of Interface Structure on Magnetic Proximity Effect in Pt/Y3Fe5O12 Heterostructures.

    PubMed

    Liang, Xiao; Zhu, Yupeng; Peng, Bo; Deng, Longjiang; Xie, Jianliang; Lu, Haipeng; Wu, Mingzhong; Bi, Lei

    2016-03-01

    The influence of interface structure on the magnetic proximity effect (MPE) in Pt/Y3Fe5O12 (YIG) bilayered heterostructures is studied by first-principles calculations based on the density functional theory (DFT). When Pt atoms are in close proximity with Y or Fe ions at the interface, Pt-Y and Pt-Fe bonds are observed. The crystalline orientations and interface termination layers of the YIG strongly modify both the strength and the length of the Pt-Fe bonding and thereby influence the magnetic properties of the Pt. Point defects including tetrahedral Fe, octahedral Fe, and Y vacancies are introduced at the Pt/YIG interface to quantitatively evaluate the influence on the MPE from individual atoms. For the Pt(100)/YIG(100) structure, the interface tetrahedral Fe vacancies can significantly reduce or even completely diminish the magnetic moments in the Pt. In a stark contrast, the octahedral Fe vacancies slightly enhance the Pt magnetism, and the nonmagnetic Y vacancies cause little influences to the Pt magnetism. These results indicate that the strength of the MPE at the Pt/YIG interface strongly depends on the interface structure. This dependence originated from the direct exchange interaction between the Fe 3d and Pt 5d electrons via electronic state hybridization as well as the electron exchange coupling between the Pt atoms. PMID:26967756

  2. Salmon cycles: Influences of a science field study immersion experience with Native American young women

    NASA Astrophysics Data System (ADS)

    Ault, Phyllis Campbell

    Native Americans, and particularly Native women, are not proportionally represented in higher education, or in science, mathematics, technology, and engineering fields. This study examined an out-of-school science education program which combined traditional Native American cultural and ecological knowledge with Western science in conducting authentic field studies. A qualitative, embedded case study approach was used to explore how young Native American women were influenced by an out-of-school program integrating a culturally responsive approach and experiential research projects. Within this context of combined cultures, three significant domains emerged: field study in science, sense of place, and networks of supportive relationships. These domains interacted with the aspirations of the eight Native women in the study. Using interview transcripts, reflective writings, and participant data, the study explored the blending of Indigenous and Western science in "communities of practice" (e.g., fisheries biology, restoration ecology, and forestry). The eight Native women in this study participated as young adolescents and later returned as counselors. Interviews focused on their postsecondary aspirations and choices. Findings validated previous research on the value of infusing Traditional Ecological Knowledge and Western science for Native students. The study found the combination of culturally responsive pedagogy and authentic experiences in "communities-of-practice" held a beneficial influence on postsecondary pathways. The importance of respect and friendships fostered through the program was associated with resilience and perseverance in educational aspirations. Immersion in field study with Native peers as well as Native and non-Native researchers was a catalyst for all the women, in a number of different ways, such as: deeper involvement with the Native community, strengthening cultural and academic identity, inspiration to learn more about their cultural

  3. The Anthropogenic Influence on Atmospheric Carbonyl Sulfide: Implications for Inverse Analysis of Process-Level Carbon Cycle Fluxes

    NASA Astrophysics Data System (ADS)

    Zumkehr, A. L.; Hilton, T. W.; Whelan, M.; Smith, S. J.; Campbell, J. E.

    2014-12-01

    Carbonyl sulfide (COS) is the most abundant sulfur containing gas in the troposphere and a significant precursor to stratospheric aerosol. Recent insights on the plant uptake of atmospheric COS suggest that plant uptake is the largest component of the global COS budget and that COS may provide a powerful new tool for partitioning sources and sinks of atmospheric CO2 at regional to global scales. However, alternative sources and sinks of COS must also be accounted for to minimize the uncertainty of this carbon cycle tracer approach. Here we focus on direct and indirect sources of atmospheric COS from anthropogenic activities. We construct bottom-up gridded inventories of anthropogenic COS sources and compare these to previous estimates that were based on relatively sparse emissions data. Furthermore, we simulate COS concentrations with an regional atmospheric chemistry model to show the influence of these alternative source estimates in relation to plant uptake at a range of surface and airborne monitoring sites.

  4. The Influence of Dissolved Organic Matter on the Photochemical Cycling of Mercury

    NASA Astrophysics Data System (ADS)

    Latch, D. E.; Aiken, G. R.

    2006-12-01

    The aquatic cycling of Hg has been shown to be strongly light dependent. Photochemical processes have been demonstrated to oxidize Hg(0), reduce Hg(II), and degrade methylmercury. The apparent magnitude of the rates of these processes show considerable variability in published reports. In an effort to reconcile the results of these studies, we have undertaken work to elucidate the mechanistic underpinnings of these processes. To measure photoreduction kinetics, we used a solar simulator to irradiate a series of solutions containing Hg(II), and the samples are continuously sparged so that any Hg(0) produced during the course of the photolysis experiment is removed from the tubes. To quantify Hg(II) photoreduction rates, we measured the loss of Hg(II) from the tubes. We have found that the photoreduction kinetics observed for Hg(II) in natural organic matter solutions are similar to that of Hg-thiolate species. This finding is consistent with recent reports which indicate that at environmentally relevant Hg concentrations, thiolate sites dominate Hg(II) binding. Our results also indicate that a direct photoreduction process is operative. Photostationary state experiments, in which the sample tubes are sealed and both reduction and oxidation reactions are allowed to occur, indicate that photooxidation of Hg(0) is faster than photoreduction of Hg(II). From these results, we conclude that the photoredox mechanisms will be similar for all natural water systems where Hg(II) is bound primarily by thiolate sites, with the microscopic rate constants being dependent on irradiation levels and independent of organic matter concentrations.

  5. Topographic variability and the influence of soil erosion on the carbon cycle

    NASA Astrophysics Data System (ADS)

    Dialynas, Yannis G.; Bastola, Satish; Bras, Rafael L.; Billings, Sharon A.; Markewitz, Daniel; Richter, Daniel deB.

    2016-05-01

    Soil erosion, particularly that caused by agriculture, is closely linked to the global carbon (C) cycle. There is a wide range of contrasting global estimates of how erosion alters soil-atmosphere C exchange. This can be partly attributed to limited understanding of how geomorphology, topography, and management practices affect erosion and oxidation of soil organic C (SOC). This work presents a physically based approach that stresses the heterogeneity at fine spatial scales of SOC erosion, SOC burial, and associated soil-atmosphere C fluxes. The Holcombe's Branch watershed, part of the Calhoun Critical Zone Observatory in South Carolina, USA, is the case study used. The site has experienced some of the most serious agricultural soil erosion in North America. We use SOC content measurements from contrasting soil profiles and estimates of SOC oxidation rates at multiple soil depths. The methodology was implemented in the tRIBS-ECO (Triangulated Irregular Network-based Real-time Integrated Basin Simulator-Erosion and Carbon Oxidation), a spatially and depth-explicit model of SOC dynamics built within an existing coupled physically based hydro-geomorphic model. According to observations from multiple soil profiles, about 32% of the original SOC content has been eroded in the study area. The results indicate that C erosion and its replacement exhibit significant topographic variation at relatively small scales (tens of meters). The episodic representation of SOC erosion reproduces the history of SOC erosio