Quantitative two-dimensional ultrashort echo time magnetization transfer (2D UTE-MT) imaging of cortical bone.

PubMed

Ma, Ya-Jun; Tadros, Anthony; Du, Jiang; Chang, Eric Y

2018-04-01

To investigate quantitative 2D ultrashort echo time magnetization transfer (UTE-MT) imaging in ex vivo bovine cortical bone and in vivo human tibial cortical bone. Data were acquired from five fresh bovine cortical bone samples and five healthy volunteer tibial cortical bones using a 2D UTE-MT sequence on a clinical 3T scanner. The 2D UTE-MT sequence used four or five MT powers with five frequency offsets. Results were analyzed with a two-pool quantitative MT model, providing measurements of macromolecular fraction (f), macromolecular proton transverse relaxation times (T 2m ), proton exchange rates from water/macromolecular to the macromolecular/water pool (RM 0m /RM 0w ), and spin-lattice relaxation rate of water pool (R 1w ). A sequential air-drying study for a small bovine cortical bone chip was used to investigate whether above MT modeling parameters were sensitive to the water loss. Mean fresh bovine cortical bone values for f, T 2m , R 1w , RM 0m , and RM 0w were 59.9 ± 7.3%, 14.6 ± 0.3 μs, 9.9 ± 2.4 s -1 , 17.9 ± 3.6 s -1 , and 11.8 ± 2.0 s -1 , respectively. Mean in vivo human cortical bone values for f, T 2m , R 1w , RM 0m and RM 0w were 54.5 ± 4.9%, 15.4 ± 0.6 μs, 8.9 ± 1.1 s -1 , 11.5 ± 3.5 s -1 , and 9.5 ± 1.9 s -1 , respectively. The sequential air-drying study shows that f, RM 0m , and R 1w were increased with longer drying time. UTE-MT two-pool modeling provides novel and useful quantitative information for cortical bone. Magn Reson Med 79:1941-1949, 2018. © 2017 International Society for Magnetic Resonance in Medicine. © 2017 International Society for Magnetic Resonance in Medicine.

Inter-Slice Blood Flow and Magnetization Transfer Effects as A New Simultaneous Imaging Strategy.

PubMed

Han, Paul Kyu; Barker, Jeffrey W; Kim, Ki Hwan; Choi, Seung Hong; Bae, Kyongtae Ty; Park, Sung-Hong

2015-01-01

The recent blood flow and magnetization transfer (MT) technique termed alternate ascending/descending directional navigation (ALADDIN) achieves the contrast using interslice blood flow and MT effects with no separate preparation RF pulse, thereby potentially overcoming limitations of conventional methods. In this study, we examined the signal characteristics of ALADDIN as a simultaneous blood flow and MT imaging strategy, by comparing it with pseudo-continuous ASL (pCASL) and conventional MT asymmetry (MTA) methods, all of which had the same bSSFP readout. Bloch-equation simulations and experiments showed ALADDIN perfusion signals increased with flip angle, whereas MTA signals peaked at flip angle around 45°-60°. ALADDIN provided signals comparable to those of pCASL and conventional MTA methods emulating the first, second, and third prior slices of ALADDIN under the same scan conditions, suggesting ALADDIN signals to be superposition of signals from multiple labeling planes. The quantitative cerebral blood flow signals from a modified continuous ASL model overestimated the perfusion signals compared to those measured with a pulsed ASL method. Simultaneous mapping of blood flow, MTA, and MT ratio in the whole brain is feasible with ALADDIN within a clinically reasonable time, which can potentially help diagnosis of various diseases.

Magnetization transfer studies of the fast and slow tissue water diffusion components in the human brain.

PubMed

Mulkern, Robert V; Vajapeyam, Sridhar; Haker, Steven J; Maier, Stephan E

2005-05-01

Magnetization transfer (MT) properties of the fast and slow diffusion components recently observed in the human brain were assessed experimentally. One set of experiments, performed at 1.5 T in healthy volunteers, was designed to determine whether the amplitudes of fast and slow diffusion components, differentiated on the basis of biexponential fits to signal decays over a wide range of b-factors, demonstrated a different or similar magnetization transfer ratio (MTR). Another set of experiments, performed at 3 T in healthy volunteers, was designed to determine whether MTRs differed when measured from high signal-to-noise images acquired with b-factor weightings of 350 vs 3500 s/mm2. The 3 T studies included measurements of MTR as a function of off-resonance frequency for the MT pulse at both low and high b-factors. The primary conclusion drawn from all the studies is that there appears to be no significant difference between the magnetization transfer properties of the fast and slow tissue water diffusion components. The conclusions do not lend support to a direct interpretation of the 'components' of the biexponential diffusion decay in terms of the 'compartments' associated with intra- and extracellular water. Copyright 2004 John Wiley & Sons, Ltd.

Source biases in midlatitude magnetotelluric transfer functions due to Pc3-4 geomagnetic pulsations

NASA Astrophysics Data System (ADS)

Murphy, Benjamin S.; Egbert, Gary D.

2018-01-01

The magnetotelluric (MT) method for imaging the electrical conductivity structure of the Earth is based on the assumption that source magnetic fields can be considered quasi-uniform, such that the spatial scale of the inducing source is much larger than the intrinsic length scale of the electromagnetic induction process (the skin depth). Here, we show using EarthScope MT data that short spatial scale source magnetic fields from geomagnetic pulsations (Pc's) can violate this fundamental assumption. Over resistive regions of the Earth, the skin depth can be comparable to the short meridional range of Pc3-4 disturbances that are generated by geomagnetic field-line resonances (FLRs). In such cases, Pc's can introduce narrow-band bias in MT transfer function estimates at FLR eigenperiods ( 10-100 s). Although it appears unlikely that these biases will be a significant problem for data inversions, further study is necessary to understand the conditions under which they may distort inverse solutions.[Figure not available: see fulltext.

Improved supercapacitor performance of MnO2-electrospun carbon nanofibers electrodes by mT magnetic field

NASA Astrophysics Data System (ADS)

Zeng, Zheng; Liu, Yiyang; Zhang, Wendi; Chevva, Harish; Wei, Jianjun

2017-08-01

This work reports on a finding of mT magnetic field induced energy storage enhancement of MnO2-based supercapacitance electrodes (magneto-supercapacitor). Electrodes with MnO2 electrochemically deposited at electrospun carbon nanofibers (ECNFs) film are studied by cyclic voltammetry (CV), galvanostatic charge/discharge, electrochemical impedance spectroscopy (EIS), and life cycle stability tests in the presence/absence of milli-Tesla (mT) magnetic fields derived by Helmholtz coils. In the presence of a 1.34 mT magnetic field, MnO2/ECNFs shows a magneto-enhanced capacitance of 141.7 F g-1 vs. 119.2 F g-1 (∼19% increase) with absence of magnetic field at a voltage sweeping rate of 5 mV s-1. The mechanism of the magneto-supercapacitance is discussed and found that the magnetic susceptibility of the MnO2 significantly improves the electron transfer of a pseudo-redox reaction of Mn(IV)/Mn(III) at the electrode, along with the magnetic field induced impedance effect, which may greatly enhance the interface charge density, facilitate electrolyte transportation, and improve the efficiency of cation intercalation/de-intercalation of the pseudocapacitor under mT-magnetic field exposure, resulting in enhancement of energy storage capacitance and longer charge/discharge time of the MnO2/ECNFs electrode without sacrificing its life cycle stability.

Comparison of (31)P saturation and inversion magnetization transfer in human liver and skeletal muscle using a clinical MR system and surface coils.

PubMed

Buehler, Tania; Kreis, Roland; Boesch, Chris

2015-02-01

(31)P MRS magnetization transfer ((31)P-MT) experiments allow the estimation of exchange rates of biochemical reactions, such as the creatine kinase equilibrium and adenosine triphosphate (ATP) synthesis. Although various (31)P-MT methods have been successfully used on isolated organs or animals, their application on humans in clinical scanners poses specific challenges. This study compared two major (31)P-MT methods on a clinical MR system using heteronuclear surface coils. Although saturation transfer (ST) is the most commonly used (31)P-MT method, sequences such as inversion transfer (IT) with short pulses might be better suited for the specific hardware and software limitations of a clinical scanner. In addition, small NMR-undetectable metabolite pools can transfer MT to NMR-visible pools during long saturation pulses, which is prevented with short pulses. (31)P-MT sequences were adapted for limited pulse length, for heteronuclear transmit-receive surface coils with inhomogeneous B1 , for the need for volume selection and for the inherently low signal-to-noise ratio (SNR) on a clinical 3-T MR system. The ST and IT sequences were applied to skeletal muscle and liver in 10 healthy volunteers. Monte-Carlo simulations were used to evaluate the behavior of the IT measurements with increasing imperfections. In skeletal muscle of the thigh, ATP synthesis resulted in forward reaction constants (k) of 0.074 ± 0.022 s(-1) (ST) and 0.137 ± 0.042 s(-1) (IT), whereas the creatine kinase reaction yielded 0.459 ± 0.089 s(-1) (IT). In the liver, ATP synthesis resulted in k = 0.267 ± 0.106 s(-1) (ST), whereas the IT experiment yielded no consistent results. ST results were close to literature values; however, the IT results were either much larger than the corresponding ST values and/or were widely scattered. To summarize, ST and IT experiments can both be implemented on a clinical body scanner with heteronuclear transmit-receive surface coils; however, ST results are much more robust against experimental imperfections than the current implementation of IT. Copyright © 2014 John Wiley & Sons, Ltd.

Seven-Tesla Magnetization Transfer Imaging to Detect Multiple Sclerosis White Matter Lesions.

PubMed

Chou, I-Jun; Lim, Su-Yin; Tanasescu, Radu; Al-Radaideh, Ali; Mougin, Olivier E; Tench, Christopher R; Whitehouse, William P; Gowland, Penny A; Constantinescu, Cris S

2018-03-01

Fluid-attenuated inversion recovery (FLAIR) imaging at 3 Tesla (T) field strength is the most sensitive modality for detecting white matter lesions in multiple sclerosis. While 7T FLAIR is effective in detecting cortical lesions, it has not been fully optimized for visualization of white matter lesions and thus has not been used for delineating lesions in quantitative magnetic resonance imaging (MRI) studies of the normal appearing white matter in multiple sclerosis. Therefore, we aimed to evaluate the sensitivity of 7T magnetization-transfer-weighted (MT w ) images in the detection of white matter lesions compared with 3T-FLAIR. Fifteen patients with clinically isolated syndrome, 6 with multiple sclerosis, and 10 healthy participants were scanned with 7T 3-dimensional (D) MT w and 3T-2D-FLAIR sequences on the same day. White matter lesions visible on either sequence were delineated. Of 662 lesions identified on 3T-2D-FLAIR images, 652 were detected on 7T-3D-MT w images (sensitivity, 98%; 95% confidence interval, 97% to 99%). The Spearman correlation coefficient between lesion loads estimated by the two sequences was .910. The intrarater and interrater reliability for 7T-3D-MT w images was good with an intraclass correlation coefficient (ICC) of 98.4% and 81.8%, which is similar to that for 3T-2D-FLAIR images (ICC 96.1% and 96.7%). Seven-Tesla MT w sequences detected most of the white matter lesions identified by FLAIR at 3T. This suggests that 7T-MT w imaging is a robust alternative for detecting demyelinating lesions in addition to 3T-FLAIR. Future studies need to compare the roles of optimized 7T-FLAIR and of 7T-MT w imaging. © 2017 The Authors. Journal of Neuroimaging published by Wiley Periodicals, Inc. on behalf of American Society of Neuroimaging.

The physical mechanism of "inhomogeneous" magnetization transfer MRI

NASA Astrophysics Data System (ADS)

Manning, Alan P.; Chang, Kimberley L.; MacKay, Alex L.; Michal, Carl A.

2017-01-01

Inhomogeneous MT (ihMT) is a new magnetic resonance imaging technique that shows promise for myelin selectivity. Materials with a high proportion of lipids, such as white matter tissue, show a reduced intensity in magnetic resonance images acquired with selective prepulses at positive and negative offsets simultaneously compared to images with a single positive or negative offset prepulse of the same power. This effect was initially explained on the basis of hole-burning in inhomogeneously broadened lines of the lipid proton spin system. Our results contradict this explanation. ihMT in lipids can be understood with a simple spin-1 model of a coupled methylene proton pair. More generally, Provotorov theory can be used to consider the evolution of dipolar order in the non-aqueous spins during the prepulses. We show that the flip-angle dependence of the proton spectrum of a model lipid system (Prolipid-161) following dipolar order generation is in quantitative agreement with the model. In addition, we directly observe dipolar order and ihMT signals in the non-aqueous components of Prolipid-161 and homogeneously-broadened systems (hair, wood, and tendon) following ihMT prepulses. The observation of ihMT signals in tendon suggests that the technique may not be as specific to myelin as previously thought. Our work shows that ihMT occurs because of dipolar couplings alone, not from a specific type of spectral line broadening as its name suggests.

Two-Dimensional Magnetotelluric Modelling of Ore Deposits: Improvements in Model Constraints by Inclusion of Borehole Measurements

NASA Astrophysics Data System (ADS)

Kalscheuer, Thomas; Juhojuntti, Niklas; Vaittinen, Katri

2017-12-01

A combination of magnetotelluric (MT) measurements on the surface and in boreholes (without metal casing) can be expected to enhance resolution and reduce the ambiguity in models of electrical resistivity derived from MT surface measurements alone. In order to quantify potential improvement in inversion models and to aid design of electromagnetic (EM) borehole sensors, we considered two synthetic 2D models containing ore bodies down to 3000 m depth (the first with two dipping conductors in resistive crystalline host rock and the second with three mineralisation zones in a sedimentary succession exhibiting only moderate resistivity contrasts). We computed 2D inversion models from the forward responses based on combinations of surface impedance measurements and borehole measurements such as (1) skin-effect transfer functions relating horizontal magnetic fields at depth to those on the surface, (2) vertical magnetic transfer functions relating vertical magnetic fields at depth to horizontal magnetic fields on the surface and (3) vertical electric transfer functions relating vertical electric fields at depth to horizontal magnetic fields on the surface. Whereas skin-effect transfer functions are sensitive to the resistivity of the background medium and 2D anomalies, the vertical magnetic and electric field transfer functions have the disadvantage that they are comparatively insensitive to the resistivity of the layered background medium. This insensitivity introduces convergence problems in the inversion of data from structures with strong 2D resistivity contrasts. Hence, we adjusted the inversion approach to a three-step procedure, where (1) an initial inversion model is computed from surface impedance measurements, (2) this inversion model from surface impedances is used as the initial model for a joint inversion of surface impedances and skin-effect transfer functions and (3) the joint inversion model derived from the surface impedances and skin-effect transfer functions is used as the initial model for the inversion of the surface impedances, skin-effect transfer functions and vertical magnetic and electric transfer functions. For both synthetic examples, the inversion models resulting from surface and borehole measurements have higher similarity to the true models than models computed exclusively from surface measurements. However, the most prominent improvements were obtained for the first example, in which a deep small-sized ore body is more easily distinguished from a shallow main ore body penetrated by a borehole and the extent of the shadow zone (a conductive artefact) underneath the main conductor is strongly reduced. Formal model error and resolution analysis demonstrated that predominantly the skin-effect transfer functions improve model resolution at depth below the sensors and at distance of ˜ 300-1000 m laterally off a borehole, whereas the vertical electric and magnetic transfer functions improve resolution along the borehole and in its immediate vicinity. Furthermore, we studied the signal levels at depth and provided specifications of borehole magnetic and electric field sensors to be developed in a future project. Our results suggest that three-component SQUID and fluxgate magnetometers should be developed to facilitate borehole MT measurements at signal frequencies above and below 1 Hz, respectively.

The Influence of Static and Rotating Magnetic Fields on Heat and Mass Transfer in Silicon Floating Zones

NASA Technical Reports Server (NTRS)

Croell, Arne; Dold, P.; Kaiser, Th.; Szofran, Frank; Benz, K. W.

1999-01-01

Hear and mass transfer in float-zone processing are strongly influenced by convective flows in the zone. They are caused by buoyancy convection, thermocapillary (Marangoni) convection, or artificial sources such as rotation and radio frequency heating. Flows in conducting melts can be controlled by the use of magnetic fields, either by damping fluid motion with static fields or by generating a def@ned flow with rotating fields. The possibilities of using static and rotating magnetic fields in silicon floating-zone growth have been investigated by experiments in axial static fields up to ST and in transverse rotating magnetic fields up to 7.S mT. Static fields of a few 100 MT already suppress most striations but are detrimental to the radial segregation by introducing a coring effect. A complete suppression of dopant striations caused by time-dependent thermocapillary convection and a reduction of the coring to insignificant values, combined with a shift of the axial segregation profile towards a more diffusion-limited case, is possible with static fields ? 1T. However, under certain conditions the use of high axial magnetic fields can lead to the appearance of a new type of pronounced dopant striations, caused by thermoelec:romagnetic convection. The use of a transverse rotating magnetic field influences the microscopic segregation at quite low inductions, of the order of a few mT. The field shifts time-dependent flows and the resulting striation patterns from a broad range of low frequencies at high amplitudes to a few high frequencies at low amplitudes

Ultrashort echo time magnetization transfer (UTE-MT) imaging of cortical bone.

PubMed

Chang, Eric Y; Bae, Won C; Shao, Hongda; Biswas, Reni; Li, Shihong; Chen, Jun; Patil, Shantanu; Healey, Robert; D'Lima, Darryl D; Chung, Christine B; Du, Jiang

2015-07-01

Magnetization transfer (MT) imaging is one way to indirectly assess pools of protons with fast transverse relaxation. However, conventional MT imaging sequences are not applicable to short T2 tissues such as cortical bone. Ultrashort echo time (UTE) sequences with TE values as low as 8 µs can detect signals from different water components in cortical bone. In this study we aim to evaluate two-dimensional UTE-MT imaging of cortical bone and its application in assessing cortical bone porosity as measured by micro-computed tomography (μCT) and biomechanical properties. In total, 38 human cadaveric distal femur and proximal tibia bones were sectioned to produce 122 rectangular pieces of cortical bone for quantitative UTE-MT MR imaging, μCT, and biomechanical testing. Off-resonance saturation ratios (OSRs) with a series of MT pulse frequency offsets (Δf) were calculated and compared with porosity assessed with μCT, as well as elastic (modulus, yield stress, and strain) and failure (ultimate stress, failure strain, and energy) properties, using Pearson correlation and linear regression. A moderately strong negative correlation was observed between OSR and μCT porosity (R(2)  = 0.46-0.51), while a moderate positive correlation was observed between OSR and yield stress (R(2)  = 0.25-0.30) and failure stress (R(2)  = 0.31-0.35), and a weak positive correlation (R(2)  = 0.09-0.12) between OSR and Young's modulus at all off-resonance saturation frequencies. OSR determined with the UTE-MT sequence provides quantitative information on cortical bone and is sensitive to μCT porosity and biomechanical function. Copyright © 2015 John Wiley & Sons, Ltd.

Sensitivity regularization of the Cramér-Rao lower bound to minimize B1 nonuniformity effects in quantitative magnetization transfer imaging.

PubMed

Boudreau, Mathieu; Pike, G Bruce

2018-05-07

To develop and validate a regularization approach of optimizing B 1 insensitivity of the quantitative magnetization transfer (qMT) pool-size ratio (F). An expression describing the impact of B 1 inaccuracies on qMT fitting parameters was derived using a sensitivity analysis. To simultaneously optimize for robustness against noise and B 1 inaccuracies, the optimization condition was defined as the Cramér-Rao lower bound (CRLB) regularized by the B 1 -sensitivity expression for the parameter of interest (F). The qMT protocols were iteratively optimized from an initial search space, with and without B 1 regularization. Three 10-point qMT protocols (Uniform, CRLB, CRLB+B 1 regularization) were compared using Monte Carlo simulations for a wide range of conditions (e.g., SNR, B 1 inaccuracies, tissues). The B 1 -regularized CRLB optimization protocol resulted in the best robustness of F against B 1 errors, for a wide range of SNR and for both white matter and gray matter tissues. For SNR = 100, this protocol resulted in errors of less than 1% in mean F values for B 1 errors ranging between -10 and 20%, the range of B 1 values typically observed in vivo in the human head at field strengths of 3 T and less. Both CRLB-optimized protocols resulted in the lowest σ F values for all SNRs and did not increase in the presence of B 1 inaccuracies. This work demonstrates a regularized optimization approach for improving the robustness of auxiliary measurements (e.g., B 1 ) sensitivity of qMT parameters, particularly the pool-size ratio (F). Predicting substantially less B 1 sensitivity using protocols optimized with this method, B 1 mapping could even be omitted for qMT studies primarily interested in F. © 2018 International Society for Magnetic Resonance in Medicine.

Para-hydrogen induced polarization of amino acids, peptides and deuterium-hydrogen gas.

PubMed

Glöggler, Stefan; Müller, Rafael; Colell, Johannes; Emondts, Meike; Dabrowski, Martin; Blümich, Bernhard; Appelt, Stephan

2011-08-14

Signal Amplification by Reversible-Exchange (SABRE) is a method of hyperpolarizing substrates by polarization transfer from para-hydrogen without hydrogenation. Here, we demonstrate that this method can be applied to hyperpolarize small amounts of all proteinogenic amino acids and some chosen peptides down to the nanomole regime and can be detected in a single scan in low-magnetic fields down to 0.25 mT (10 kHz proton frequency). An outstanding feature is that depending on the chemical state of the used catalyst and the investigated amino acid or peptide, hyperpolarized hydrogen-deuterium gas is formed, which was detected with (1)H and (2)H NMR spectroscopy at low magnetic fields of B(0) = 3.9 mT (166 kHz proton frequency) and 3.2 mT (20 kHz deuterium frequency).

The advantages of complementing MT profiles in 3-D environments with geomagnetic transfer function and interstation horizontal magnetic transfer function data: results from a synthetic case study

NASA Astrophysics Data System (ADS)

Campanyà, Joan; Ogaya, Xènia; Jones, Alan G.; Rath, Volker; Vozar, Jan; Meqbel, Naser

2016-12-01

As a consequence of measuring time variations of the electric and the magnetic field, which are related to current flow and charge distribution, magnetotelluric (MT) data in 2-D and 3-D environments are not only sensitive to the geoelectrical structures below the measuring points but also to any lateral anomalies surrounding the acquisition site. This behaviour complicates the characterization of the electrical resistivity distribution of the subsurface, particularly in complex areas. In this manuscript we assess the main advantages of complementing the standard MT impedance tensor (Z) data with interstation horizontal magnetic tensor (H) and geomagnetic transfer function (T) data in constraining the subsurface in a 3-D environment beneath a MT profile. Our analysis was performed using synthetic responses with added normally distributed and scattered random noise. The sensitivity of each type of data to different resistivity anomalies was evaluated, showing that the degree to which each site and each period is affected by the same anomaly depends on the type of data. A dimensionality analysis, using Z, H and T data, identified the presence of the 3-D anomalies close to the profile, suggesting a 3-D approach for recovering the electrical resistivity values of the subsurface. Finally, the capacity for recovering the geoelectrical structures of the subsurface was evaluated by performing joint inversion using different data combinations, quantifying the differences between the true synthetic model and the models from inversion process. Four main improvements were observed when performing joint inversion of Z, H and T data: (1) superior precision and accuracy at characterizing the electrical resistivity values of the anomalies below and outside the profile; (2) the potential to recover high electrical resistivity anomalies that are poorly recovered using Z data alone; (3) improvement in the characterization of the bottom and lateral boundaries of the anomalies with low electrical resistivity; and (4) superior imaging of the horizontal continuity of structures with low electrical resistivity. These advantages offer new opportunities for the MT method by making the results from a MT profile in a 3-D environment more convincing, supporting the possibility of high-resolution studies in 3-D areas without expending a large amount of economical and computational resources, and also offering better resolution of targets with high electrical resistivity.

Heat Transfer to Anode of Arc as Function of Transverse Magnetic Field and Lateral Gas Flow Velocity

NASA Astrophysics Data System (ADS)

Zama, Yoshiyuki; Shiino, Toru; Ishii, Yoko; Maeda, Yoshifumi; Yamamoto, Shinji; Iwao, Toru

2016-10-01

Gas tungsten arc welding has useful joining technology because of high-energy and high-current characteristics. It can be flexible from the transverse magnetic field and lateral gas flow velocity. In this case, the weld defect occurs. In this research, the heat transfer to the anode of the arc as a function of the transverse magnetic field and lateral gas flow velocity is elucidated. That magnetic flux density and lateral gas velocity were varied from 0 to 3 mT and 0 to 50?m?s -1, respectively. The axial plasma gas argon flow rates were 3?slm. A transverse magnetic field is applied to the arc using Helmholtz coil. The anode is used by a water-cooled copper plate, and the heat transfer is measured by temperature of cooled water. As a result, the arc is deflected by the Lorentz force and lateral gas convection. Thus, the heat transfer to the anode of the arc decreases with increasing the transverse magnetic field and lateral gas flow velocity. In addition, the heat transfer to the anode changes with different attachments modes. The lateral gas flow causes a convective heat loss from the arc to the chamber walls.

Frequency domain and full waveform time domain inversion of ground based magnetometer, electrometer and incoherent scattering radar arrays to image strongly heterogenous 3-D Earth structure, ionospheric structure, and to predict the intensity of GICs in the power grid

NASA Astrophysics Data System (ADS)

Schultz, A.; Imamura, N.; Bonner, L. R., IV; Cosgrove, R. B.

2016-12-01

Ground-based magnetometer and electrometer arrays provide the means to probe the structure of the Earth's interior, the interactions of space weather with the ionosphere, and to anticipate the intensity of geomagnetically induced currents (GICs) in power grids. We present a local-to-continental scale view of a heterogeneous 3-D crust and mantle as determined from magnetotelluric (MT) observations across arrays of ground-based electric and magnetic field sensors. MT impedance tensors describe the relationship between electric and magnetic fields at a given site, thus implicitly they contain all known information on the 3-D electrical resistivity structure beneath and surrounding that site. By using multivariate transfer functions to project real-time magnetic observatory network data to areas surrounding electric power grids, and by projecting those magnetic fields through MT impedance tensors, the projected magnetic field can be transformed into predictions of electric fields along the path of the transmission lines, an essential element of predicting the intensity of GICs in the grid. Finally, we explore GICs, i.e. Earth-ionosphere coupling directly in the time-domain. We consider the fully coupled EM system, where we allow for a non-stationary ionospheric source field of arbitrary complexity above a 3-D Earth. We solve the simultaneous inverse problem for 3-D Earth conductivity and source field structure directly in the time domain. In the present work, we apply this method to magnetotelluric data obtained from a synchronously operating array of 25 MT stations that collected continuous MT waveform data in the interior of Alaska during the autumn and winter of 2015 under the footprint of the Poker Flat (Alaska) Incoherent Scattering Radar (PFISR). PFISR data yield functionals of the ionospheric electric field and ionospheric conductivity that constrain the MT source field. We show that in this region conventional robust MT processing methods struggle to produce reliable MT response functions at periods much greater than about 2,000 s, a consequence, we believe, of the complexity of the ionospheric source fields in this high latitude setting. This provides impetus for direct waveform inversion methods that dispense with typical parametric assumptions made about the MT source fields.

Measurement of creatine kinase reaction rate in human brain using magnetization transfer image-selected in vivo spectroscopy (MT-ISIS) and a volume ³¹P/¹H radiofrequency coil in a clinical 3-T MRI system.

PubMed

Jeong, Eun-Kee; Sung, Young-Hoon; Kim, Seong-Eun; Zuo, Chun; Shi, Xianfeng; Mellon, Eric A; Renshaw, Perry F

2011-08-01

High-energy phosphate metabolism, which allows the synthesis and regeneration of adenosine triphosphate (ATP), is a vital process for neuronal survival and activity. In particular, creatine kinase (CK) serves as an energy reservoir for the rapid buffering of ATP levels. Altered CK enzyme activity, reflecting compromised high-energy phosphate metabolism or mitochondrial dysfunction in the brain, can be assessed using magnetization transfer (MT) MRS. MT (31)P MRS has been used to measure the forward CK reaction rate in animal and human brain, employing a surface radiofrequency coil. However, long acquisition times and excessive radiofrequency irradiation prevent these methods from being used routinely for clinical evaluations. In this article, a new MT (31)P MRS method is presented, which can be practically used to measure the CK forward reaction rate constant in a clinical MRI system employing a volume head (31)P coil for spatial localization, without contamination from the scalp muscle, and an acquisition time of 30 min. Other advantages associated with the method include radiofrequency homogeneity within the regions of interest of the brain using a volume coil with image-selected in vivo spectroscopy localization, and reduction of the specific absorption rate using nonadiabatic radiofrequency pulses for MT saturation. The mean value of k(f) was measured as 0.320 ± 0.075 s(-1) from 10 healthy volunteers with an age range of 18-40 years. These values are consistent with those obtained using earlier methods, and the technique may be used routinely to evaluate energetic processes in the brain on a clinical MRI system. Copyright © 2010 John Wiley & Sons, Ltd.

An optimized framework for quantitative magnetization transfer imaging of the cervical spinal cord in vivo

PubMed Central

Grussu, Francesco; Ianus, Andrada; Schneider, Torben; Prados, Ferran; Fairney, James; Ourselin, Sebastien; Alexander, Daniel C.; Cercignani, Mara; Gandini Wheeler‐Kingshott, Claudia A.M.; Samson, Rebecca S.

2017-01-01

Purpose To develop a framework to fully characterize quantitative magnetization transfer indices in the human cervical cord in vivo within a clinically feasible time. Methods A dedicated spinal cord imaging protocol for quantitative magnetization transfer was developed using a reduced field‐of‐view approach with echo planar imaging (EPI) readout. Sequence parameters were optimized based in the Cramer‐Rao‐lower bound. Quantitative model parameters (i.e., bound pool fraction, free and bound pool transverse relaxation times [ T2F, T2B], and forward exchange rate [k FB]) were estimated implementing a numerical model capable of dealing with the novelties of the sequence adopted. The framework was tested on five healthy subjects. Results Cramer‐Rao‐lower bound minimization produces optimal sampling schemes without requiring the establishment of a steady‐state MT effect. The proposed framework allows quantitative voxel‐wise estimation of model parameters at the resolution typically used for spinal cord imaging (i.e. 0.75 × 0.75 × 5 mm3), with a protocol duration of ∼35 min. Quantitative magnetization transfer parametric maps agree with literature values. Whole‐cord mean values are: bound pool fraction = 0.11(±0.01), T2F = 46.5(±1.6) ms, T2B = 11.0(±0.2) µs, and k FB = 1.95(±0.06) Hz. Protocol optimization has a beneficial effect on reproducibility, especially for T2B and k FB. Conclusion The framework developed enables robust characterization of spinal cord microstructure in vivo using qMT. Magn Reson Med 79:2576–2588, 2018. © 2017 The Authors Magnetic Resonance in Medicine published by Wiley Periodicals, Inc. on behalf of International Society for Magnetic Resonance in Medicine. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited. PMID:28921614

Perceptual learning modifies the functional specializations of visual cortical areas.

PubMed

Chen, Nihong; Cai, Peng; Zhou, Tiangang; Thompson, Benjamin; Fang, Fang

2016-05-17

Training can improve performance of perceptual tasks. This phenomenon, known as perceptual learning, is strongest for the trained task and stimulus, leading to a widely accepted assumption that the associated neuronal plasticity is restricted to brain circuits that mediate performance of the trained task. Nevertheless, learning does transfer to other tasks and stimuli, implying the presence of more widespread plasticity. Here, we trained human subjects to discriminate the direction of coherent motion stimuli. The behavioral learning effect substantially transferred to noisy motion stimuli. We used transcranial magnetic stimulation (TMS) and functional magnetic resonance imaging (fMRI) to investigate the neural mechanisms underlying the transfer of learning. The TMS experiment revealed dissociable, causal contributions of V3A (one of the visual areas in the extrastriate visual cortex) and MT+ (middle temporal/medial superior temporal cortex) to coherent and noisy motion processing. Surprisingly, the contribution of MT+ to noisy motion processing was replaced by V3A after perceptual training. The fMRI experiment complemented and corroborated the TMS finding. Multivariate pattern analysis showed that, before training, among visual cortical areas, coherent and noisy motion was decoded most accurately in V3A and MT+, respectively. After training, both kinds of motion were decoded most accurately in V3A. Our findings demonstrate that the effects of perceptual learning extend far beyond the retuning of specific neural populations for the trained stimuli. Learning could dramatically modify the inherent functional specializations of visual cortical areas and dynamically reweight their contributions to perceptual decisions based on their representational qualities. These neural changes might serve as the neural substrate for the transfer of perceptual learning.

An optimized framework for quantitative magnetization transfer imaging of the cervical spinal cord in vivo.

PubMed

Battiston, Marco; Grussu, Francesco; Ianus, Andrada; Schneider, Torben; Prados, Ferran; Fairney, James; Ourselin, Sebastien; Alexander, Daniel C; Cercignani, Mara; Gandini Wheeler-Kingshott, Claudia A M; Samson, Rebecca S

2018-05-01

To develop a framework to fully characterize quantitative magnetization transfer indices in the human cervical cord in vivo within a clinically feasible time. A dedicated spinal cord imaging protocol for quantitative magnetization transfer was developed using a reduced field-of-view approach with echo planar imaging (EPI) readout. Sequence parameters were optimized based in the Cramer-Rao-lower bound. Quantitative model parameters (i.e., bound pool fraction, free and bound pool transverse relaxation times [ T2F, T2B], and forward exchange rate [k FB ]) were estimated implementing a numerical model capable of dealing with the novelties of the sequence adopted. The framework was tested on five healthy subjects. Cramer-Rao-lower bound minimization produces optimal sampling schemes without requiring the establishment of a steady-state MT effect. The proposed framework allows quantitative voxel-wise estimation of model parameters at the resolution typically used for spinal cord imaging (i.e. 0.75 × 0.75 × 5 mm 3 ), with a protocol duration of ∼35 min. Quantitative magnetization transfer parametric maps agree with literature values. Whole-cord mean values are: bound pool fraction = 0.11(±0.01), T2F = 46.5(±1.6) ms, T2B = 11.0(±0.2) µs, and k FB  = 1.95(±0.06) Hz. Protocol optimization has a beneficial effect on reproducibility, especially for T2B and k FB . The framework developed enables robust characterization of spinal cord microstructure in vivo using qMT. Magn Reson Med 79:2576-2588, 2018. © 2017 The Authors Magnetic Resonance in Medicine published by Wiley Periodicals, Inc. on behalf of International Society for Magnetic Resonance in Medicine. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited. © 2017 The Authors Magnetic Resonance in Medicine published by Wiley Periodicals, Inc. on behalf of International Society for Magnetic Resonance in Medicine.

Structural white matter changes in adolescents and young adults with maple syrup urine disease.

PubMed

Klee, D; Thimm, E; Wittsack, H J; Schubert, D; Primke, R; Pentang, G; Schaper, J; Mödder, U; Antoch, A; Wendel, U; Cohnen, M

2013-11-01

To get insight into the nature of magnetic resonance (MR) white matter abnormalities of patients with classic maple syrup urine disease (MSUD) under diet control. Ten patients with classic MSUD and one with a severe MSUD variant (mean age 21.5 ± 5.1 years) on diet and 11 age and sex-matched healthy subjects were enrolled. Apart from standard MR sequences, diffusion weighted images (DWI), diffusion tensor images (DTI), and magnetization transfer images (MT) were obtained and comparatively analyzed for apparent diffusion coefficient (ADC), tensor fractional anisotropy (FA) and MT maps in 11 regions of interest (ROI) within the white matter. In MSUD patients DWI, DTI and FA showed distinct signal changes in the cerebral hemispheres, the dorsal limb of internal capsule, the brain stem and the central cerebellum. Signal intensity was increased in DWI with a reduced ADC and decreased values for FA. MT did not reveal differences between patients and control subjects. Signal abnormalities in the white matter of adolescents and young adults under diet control may be interpreted as consequence of structural alterations like dysmyelination. The reduced ADC and FA in the white matter with preserved MT indicate a reduction in fiber tracks.

Adiposity is associated with structural properties of the adolescent brain.

PubMed

Schwartz, Deborah H; Dickie, Erin; Pangelinan, Melissa M; Leonard, Gabriel; Perron, Michel; Pike, G Bruce; Richer, Louis; Veillette, Suzanne; Pausova, Zdenka; Paus, Tomáš

2014-12-01

Obesity, a major risk factor for cardiometabolic disease, is associated with variations in a number of structural properties in the adult brain, as assessed with magnetic resonance imaging (MRI). In this study, we investigated the cross-sectional relationship between visceral fat (VF), total body fat (TBF) and three MRI parameters in the brains of typically developing adolescents: (i) T1-weighted (T1W) signal intensity; (ii) T1W signal contrast between white matter (WM) and gray matter (GM); and (iii) magnetization transfer ratio (MTR). In a community-based sample of 970 adolescents (12-18 years old, 466 males), VF was quantified using MRI, and total body fat was measured using a multifrequency bioimpedance. T1W images of the brain were used to determine signal intensity in lobar GM and WM, as well as WM:GM signal contrast. A magnetization transfer (MT) sequence of MT(ON) and MT(OFF) was used to obtain MTR in GM and WM. We found that both larger volumes of VF and more TBF were independently associated with higher signal intensity in WM and higher WM:GM signal contrast, as well as higher MTR in both GM and WM. These relationships were independent of a number of potential confounders, including age, sex, puberty stage, household income and height. Our results suggest that both visceral fat and fat deposited elsewhere in the body are associated independently with structural properties of the adolescent brain. We speculate that these relationships suggest the presence of adiposity-related variations in phospholipid composition of brain lipids. Copyright © 2014. Published by Elsevier Inc.

A dual flip angle 3D bSSFP magnetization transfer-like method to differentiate between recent and old myocardial infarction.

PubMed

Germain, Philippe; El Ghannudi, Soraya; Labani, Aissam; Jeung, Mi Y; Gangi, Afshin; Ohlmann, Patrick; Roy, Catherine

2018-03-01

Magnetic resonance imaging (MRI) tissue signal is modulated by magnetization transfer (MT) phenomena, intrinsically induced by balanced steady-state free precession (bSSFP) imaging. To investigate the possible value of such a MT-like bSSFP approach in two clinical settings involving focal myocardial lesions highligthed by late gadolinium enhancement (LGE+): edema induced by recent myocardial infarction (MI) and fibrotic scar related to chronic infarction. Population: 48 LGE + patients were studied: 26 with recent MI, 22 with chronic MI. 20 LGE-normal subjects were considered the control group. Field strength/sequence: Navigator-based short axis 3D-bSSFP sequences with 20° and 90° excitation flip angles were acquired (1.5T). Pixel-wise normalized MT Ratio (nMTR) parametric images were calculated according to: nMTR = 100*(S 20 -S 90 *k)/S 20 , with S 20 and S 90 signal intensity in 20° and 90° flip angle images and k = Blood 20 /Blood 90 as a normalization ratio. Statistical tests: analysis of variance (ANOVA), receiver operating characteristic (ROC) analysis. Overall normal myocardial nMTR was 50.2 ± 3.6%. In recent MI, nMTR values were significantly reduced in LGE + regions (-22.3 ± 9.9%, P < 0.0001). In cases of chronic infarct, nMTR was significantly increased in LGE + regions (14.2 ± 11.4%, P < 0.0001). Comparison between observed results and theoretical values obtained with the Freeman-Hill formula showed that most variations observed in MI are related to MT effects instead of relaxation effects. In contrast to LGE imaging, which may show a similar hyperenhancement in recent and old infarctions, nMTR imaging demonstrates an opposite pattern: decreased values for recent infarction and increased values for old infarction, thus allowing to discriminate between these two clinical conditions without gadolinium injection. 3 Technical Efficacy: Stage 1 J. Magn. Reson. Imaging 2018;47:798-808. © 2017 International Society for Magnetic Resonance in Medicine.

The Influence of Static and Rotating Magnetic Fields on Heat and Mass Transfer in Silicon Floating Zones

NASA Technical Reports Server (NTRS)

Croll, A.; Dold, P.; Kaiser, Th.; Szofran, F. R.; Benz, K. W.

1999-01-01

Heat and mass transfer in float-zone processing are strongly influenced by convective flows in the zone. They are caused by buoyancy convection, thermocapillary (Marangoni) convection, or artificial sources such as rotation and radio-frequency heating. Flows in conducting melts can be controlled by the use of magnetic fields, either by damping fluid motion with static fields or by generating a defined flow with rotating fields. The possibilities of using static and rotating magnetic fields in silicon floating-zone growth have been investigated by experiments in axial static fields up to 5 T and in transverse rotating magnetic fields up to 7.5 mT. Static fields of a few 100 mT already suppress most striations but are detrimental to the radial segregation by introducing a coring effect. A complete suppression of dopant striations caused by time-dependent thermocapillary convection and a reduction of the coring to insignificant values, combined with a shift of the axial segregation profile toward a more diffusion-limited case, is possible with static fields greater than or equal to 1 T. However, under certain conditions the use of high axial magnetic fields can lead to the appearance of a new type of pronounced dopant striations, caused by thermoelectromagnetic convection. The use of a transverse rotating magnetic field influences the microscopic segregation at quite low inductions, of the order of a few millitesla. The field shifts time- dependent flows and the resulting striation patterns from a broad range of low frequencies at high amplitudes to a few high frequencies at low amplitudes.

Control over Janus micromotors by the strength of a magnetic field

NASA Astrophysics Data System (ADS)

Baraban, Larysa; Makarov, Denys; Schmidt, Oliver G.; Cuniberti, Gianaurelio; Leiderer, Paul; Erbe, Artur

2013-01-01

For transportation of molecules or biological cells using artificial motors, the control over their motion, i.e. direction and speed of transfer, is important. Here, we demonstrate that modification of the velocity and orientation of a magnetic Janus particle can be efficiently controlled by tuning the strength of an applied homogeneous magnetic field. Interestingly, by keeping the same orientation of the magnetic field but changing its magnitude not only the velocity of capped particles can be altered but even their direction of motion can be reversed. We put forth a simple qualitative model, which allows us to explain this intriguing observation.For transportation of molecules or biological cells using artificial motors, the control over their motion, i.e. direction and speed of transfer, is important. Here, we demonstrate that modification of the velocity and orientation of a magnetic Janus particle can be efficiently controlled by tuning the strength of an applied homogeneous magnetic field. Interestingly, by keeping the same orientation of the magnetic field but changing its magnitude not only the velocity of capped particles can be altered but even their direction of motion can be reversed. We put forth a simple qualitative model, which allows us to explain this intriguing observation. Electronic supplementary information (ESI) available: Videos (1-3) describe the behavior of the magnetic Janus micromotors at different magnetic fields applied. The magnetic field is always applied along the positive direction of the y-axis. All the movies are recorded at the same frame rate of 21 images per second. Experiments were performed at 30 wt% of hydrogen peroxide in aqueous solution. Video 1 shows the motion of the Janus micromotors when a small magnetic field is applied (B = 0.2 mT). The particle is propelled in the direction ``opposite to the cap'' with a velocity of about 6 μm s-1. Video 2 displays the motion of the same Janus bead when an intermediately strong magnetic field is applied (B = 1.5 mT). The particle still moves in the direction ``opposite to the cap'', but with a much smaller velocity of about 1 μm s-1. Video 3 shows the behavior of the Janus micromotor, exposed to the high magnetic field B = 2.2 mT. The particle moves in the direction ``towards the cap'' with the speed of about 4 μm s-1. See DOI: 10.1039/c2nr32662k

Effects of plasmonic field due to gold nanoparticles and magnetic field on photocurrents of zinc porphyrin-viologen linked compound-gold nanoparticle composite films

NASA Astrophysics Data System (ADS)

Yonemura, Hiroaki; Niimi, Tomoki; Yamada, Sunao

2016-03-01

Composite films of zinc-porphyrin-viologen (ZnP-V2+) linked compound containing six methylene group [ZnP(6)V]-gold nanoparticles (AuNP) were fabricated by combining electrostatic layer-by-layer adsorption and the Langmuir-Blodgett method. The anodic photocurrents of the ZnP(6)V-AuNP composite films are higher than those of the ZnP(6)V films. The large photocurrents in ZnP(6)V-AuNP composite films are most likely attributable to the combination of localized surface plasmon resonance due to AuNP and photoinduced intramolecular electron transfer from excited state of ZnP to V2+. The photocurrents of the ZnP(6)V-AuNP composite films increase in the presence of magnetic field. The photocurrents increase with low magnetic fields (B ≤ 150 mT) and are almost constant under high magnetic fields (B ≥ 150 mT). Magnetic field effects (MFEs) were clearly observed for both ZnP(6)V-AuNP composite films and ZnP(6)V films. The MFEs can be explained by a radical pair mechanism.

Magnetization transfer and adiabatic R 1ρ MRI in the brainstem of Parkinson's disease.

PubMed

Tuite, Paul J; Mangia, Silvia; Tyan, Andrew E; Lee, Michael K; Garwood, Michael; Michaeli, Shalom

2012-06-01

In addition to classic midbrain pathology, Parkinson's disease (PD) is accompanied by changes in pontine and medullary brainstem structures. These additional abnormalities may underlie non-motor features as well as play a role in motor disability. Using novel magnetic resonance imaging (MRI) methods based on rotating frame adiabatic R(1ρ) (i.e., measurements of longitudinal relaxation during adiabatic full passage pulses) and modified magnetization transfer (MT) MRI mapping, we sought to identify brainstem alterations in nine individuals with mild-moderate PD (off medication) and ten age-matched controls at 4 T. We discovered significant differences in MRI parameters between midbrain and medullary brainstem structures in control subjects as compared to PD patients. These findings support the presence of underlying functional/structural brainstem changes in mild-moderate PD. Copyright © 2012 Elsevier Ltd. All rights reserved.

On the origins of chemical exchange saturation transfer (CEST) contrast in tumors at 9.4 T.

PubMed

Xu, Junzhong; Zaiss, Moritz; Zu, Zhongliang; Li, Hua; Xie, Jingping; Gochberg, Daniel F; Bachert, Peter; Gore, John C

2014-04-01

Chemical exchange saturation transfer (CEST) provides an indirect means to detect exchangeable protons within tissues through their effects on the water signal. Previous studies have suggested that amide proton transfer (APT) imaging, a specific form of CEST, detects endogenous amide protons with a resonance frequency offset 3.5 ppm downfield from water, and thus may be sensitive to variations in mobile proteins/peptides in tumors. However, as CEST measurements are influenced by various confounding effects, such as spillover saturation, magnetization transfer (MT) and MT asymmetry, the mechanism or degree of increased APT signal in tumors is not certain. In addition to APT, nuclear Overhauser enhancement (NOE) effects upfield from water may also provide distinct information on tissue composition. In the current study, APT, NOE and several other MR parameters were measured and compared comprehensively in order to elucidate the origins of APT and NOE contrasts in tumors at 9.4 T. In addition to conventional CEST methods, a new intrinsic inverse metric was applied to correct for relaxation and other effects. After corrections for spillover, MT and T1 effects, corrected APT in tumors was found not to be significantly different from that in normal tissues, but corrected NOE effects in tumors showed significant decreases compared with those in normal tissues. Biochemical measurements verified that there was no significant enhancement of protein contents in the tumors studied, consistent with the corrected APT measurements and previous literature, whereas quantitative MT data showed decreases in the fractions of immobile macromolecules in tumors. Our results may assist in the better understanding of the contrast depicted by CEST imaging in tumors, and in the development of improved APT and NOE measurements for cancer imaging. Copyright © 2014 John Wiley & Sons, Ltd.

MR imaging of a novel NOE-mediated magnetization transfer with water in rat brain at 9.4 T.

PubMed

Zhang, Xiao-Yong; Wang, Feng; Jin, Tao; Xu, Junzhong; Xie, Jingping; Gochberg, Daniel F; Gore, John C; Zu, Zhongliang

2017-08-01

To detect, map, and quantify a novel nuclear Overhauser enhancement (NOE)-mediated magnetization transfer (MT) with water at approximately -1.6 ppm [NOE(-1.6)] in rat brain using MRI. Continuous wave MT sequences with a variety of radiofrequency irradiation powers were optimized to achieve the maximum contrast of this NOE(-1.6) effect at 9.4 T. The distribution of effect magnitudes, resonance frequency offsets, and line widths in healthy rat brains and the differences of the effect between tumors and contralateral normal brains were imaged and quantified using a multi-Lorentzian fitting method. MR measurements on reconstituted model phospholipids as well as two cell lines (HEK293 and 9L) were also performed to investigate the possible molecular origin of this NOE. Our results suggest that the NOE(-1.6) effect can be detected reliably in rat brain. Pixel-wise fittings demonstrated the regional variations of the effect. Measurements in a rodent tumor model showed that the amplitude of NOE(-1.6) in brain tumor was significantly diminished compared with that in normal brain tissue. Measurements of reconstituted phospholipids suggest that this effect may originate from choline phospholipids. NOE(-1.6) could be used as a new biomarker for the detection of brain tumor. Magn Reson Med 78:588-597, 2017. © 2016 International Society for Magnetic Resonance in Medicine. © 2016 International Society for Magnetic Resonance in Medicine.

Physical characteristics of lanthanide complexes that act as magnetization transfer (MT) contrast agents

NASA Astrophysics Data System (ADS)

Zhang, Shanrong; Sherry, A. Dean

2003-02-01

Rapid water exchange is normally considered a prerequisite for efficient Gd3+-based MRI contrast agents. Yet recent measures of exchange rates in some Gd3+ complexes have shown that water exchange can become limiting when such complexes are attached to larger macromolecular structures. A new class of lanthanide complexes that display unusually slow water exchange (bound water lifetimes (τM298) > 10 μs) has recently been reported. This apparent disadvantage may be taken advantage of by switching the metal ion from gadolinium(III) to a lanthanide that shifts the bound water resonance substantially away from bulk water. Given appropriate water exchange kinetics, one can then alter the intensity of the bulk water signal by selective presaturation of this highly shifted, Ln3+-bound water resonance. This provides the basis of a new method to alter MR image contrast in tissue. We have synthesized a variety of DOTA-tetra(amide) ligands to evaluate as potential magnetization transfer (MT) contrast agents and found that the bound water lifetimes in these complexes are sensitive to both ligand structure (a series of Eu3+ complexes have τM298 values that range from 1 to 1300 μs) and the identity of the paramagnetic Ln3+ cation (from 3 to 800 μs for a single ligand). This demonstrates that it may be possible either to fine-tune the ligand structure or to select proper lanthanide cation to create an optimal MT agent for any clinical imaging field.

3D Inversion of Natural Source Electromagnetics

NASA Astrophysics Data System (ADS)

Holtham, E. M.; Oldenburg, D. W.

2010-12-01

The superior depth of investigation of natural source electromagnetic techniques makes these methods excellent candidates for crustal studies as well as for mining and hydrocarbon exploration. The traditional natural source method, the magnetotelluric (MT) technique, has practical limitations because the surveys are costly and time consuming due to the labor intensive nature of ground based surveys. In an effort to continue to use the penetration advantage of natural sources, it has long been recognized that tipper data, the ratio of the local vertical magnetic field to the horizontal magnetic field, provide information about 3D electrical conductivity structure. It was this understanding that prompted the development of AFMAG (Audio Frequency Magnetics) and recently the new airborne Z-Axis Tipper Electromagnetic Technique (ZTEM). In ZTEM, the vertical component of the magnetic field is recorded above the entire survey area, while the horizontal fields are recorded at a ground-based reference station. MT processing techniques yield frequency domain transfer functions typically between 30-720 Hz that relate the vertical fields over the survey area to the horizontal fields at the reference station. The result is a cost effective procedure for collecting natural source EM data and for finding large scale targets at moderate depths. It is well known however that 1D layered structures produce zero vertical magnetic fields and thus ZTEM data cannot recover such background conductivities. This is in sharp contrast to the MT technique where electric fields are measured and a 1D background conductivity can be recovered from the off diagonal elements of the impedance tensor. While 1D models produce no vertical fields, two and three dimensional structures will produce anomalous currents and a ZTEM response. For such models the background conductivity structure does affect the data. In general however, the ZTEM data have weak sensitivity to the background conductivity and while we show that it is possible to obtain the background structure by inverting the ZTEM data alone, it is desirable to obtain robust background conductivity information from other sources. This information could come from a priori geologic and petrophysical information or from additional geophysical data such as MT. To counter the costly nature of large MT surveys and the limited sensitivity of the ZTEM technique to the background conductivity we show that an effective method is to collect and invert both MT and ZTEM data. A sparse MT survey grid can gather information about the background conductivity and deep structures while keeping the survey costs affordable. Higher spatial resolution at moderate depths can be obtained by flying multiple lines of ZTEM data.

Magnetotellurics with long distance remote reference to reject DC railway noise

NASA Astrophysics Data System (ADS)

Hanstein, T.; Jiang, J.; Strack, K.; Ritter, O.

2014-12-01

Some parts of railway network in Europe is electrified by DC current. The return current in the ground is varying in space, time and power when the train is moving. Since the train traffic is active 24 hours, there is no quite time. The train signal is dominating for periods longer than 1 s and is a near field source. The transfer function of the magnetotelluric sounding (MT) is influenced by this near field source, the phase is going to zero and amplitude increase with slope 1 for longer periods. Since this dominating noise is present all day robust magnetotelluric processing technique to identify and remove outliers are not applicable and sufficient. The remote reference technique has successfully been applied for magnetotelluric soundings Combining an disturbed local MT data set with the data of the remote station, which is recording simultaneously the horizontal magnetic fields, can improve the data quality. Finding a good remote station during field survey is difficult and expensive. There is a permanent MT remote reference station in Germany. The set up and maintance is done by the GFZ - Helmholtz Centre Potsdam - GFZ German Research Centre for Geosciences. The location is near Wittstock and has good signal-to-noise-ratio with low cutural noise, the ground is almost lD and recording since May 2010. The electric and magnetic field is continously recorded with 250 Hz sampling and induction coils. The magnetic field is also recorded with fluxgate magnetometers and 5 Hz sampling. The distance to the local MT site is about 600 km.

Steering microtubule shuttle transport with dynamically controlled magnetic fields

DOE PAGES

Mahajan, K. D.; Ruan, G.; Dorcéna, C. J.; ...

2016-03-23

Nanoscale control of matter is critical to the design of integrated nanosystems. Here, we describe a method to dynamically control directionality of microtubule (MT) motion using programmable magnetic fields. MTs are combined with magnetic quantum dots (i.e., MagDots) that are manipulated by external magnetic fields provided by magnetic nanowires. MT shuttles thus undergo both ATP-driven and externally-directed motion with a fluorescence component that permits simultaneous visualization of shuttle motion. This technology is used to alter the trajectory of MTs in motion and to pin MT motion. Ultimately, such an approach could be used to evaluate the MT-kinesin transport system andmore » could serve as the basis for improved lab-on-a-chip technologies based on MT transport.« less

Resolution of anisotropic and shielded highly conductive layers using 2-D electromagnetic modelling in the Rhine Graben and Black Forest

NASA Astrophysics Data System (ADS)

Tezkan, Bülent; Červ, Václav; Pek, Josef

1992-12-01

Anisotropy in magnetotelluric (MT) data has been found very often and has been explained as the result of local structures of different conductivities. In this paper, an observed anisotropy in MT data is not interpreted qualitatively in terms of local structures but is modelled quantitatively by a quasi-anisotropic layer. Besides the MT transfer functions, measurements of the vertical magnetic component are required. The second goal of this paper is to describe a method which permits the resolution of mid-crustal conductive layers in the presence of an additional high-conductivity layer at the surface. This method is possible in a two-dimensional (2-D) situation that limits the spatial extension of the surface structure. Again, vertical magnetic field recordings are necessary, but the phase of the E-polarization with respect to the 2-D structure is the most sensitive parameter. Using two field sites in Southern Germany, it has been possible to give a quantitative explanation of anisotropy and an improved depth resolution, and to derive an integrated conductivity of the highly conductive mid-crustal layers using MT and geomagnetic depth sounding data. The anisotropic highly conductive layer is located 12 km beneath the poorly conductive Black Forest crystalline rocks, whereas it is at a depth of 6 km beneath the highly conductive Rhine Graben sediments.

Cadium pathways during gestation and lactation in control vs. metallothionein 1,2-knockout mice.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Brako, E. E.; Wilson, A. K.; Jonah, M. M.

2003-01-01

Effects of metallothionein (MT) on cadmium absorption and transfer pathways during gestation and lactation in mice were investigated. Female 129/SvJ metallothionein-knockout (MT1,2KO) and metallothionein-normal (MTN) mice received drinking water containing trace amounts of {sup 109}CdCl{sub 2} (0.15 ng Cd/ml; 0.074 {mu}Ci {sup 109}Cd/ml). {sup 109}Cd and MT in maternal, fetal, and pup tissues were measured on gestation days 7, 14, and 17 and lactation day 11. In dams, MT influenced both the amount of {sup 109}Cd transferred from intestine into body (two- to three-fold higher in MT1,2KO than MTN dams) and tissue-specific {sup 109}Cd distribution (higher liver/kidney ratio in MT1,2KOmore » dams). Placental {sup 109}Cd concentrations in MT1,2KO dams were three- and seven-fold higher on gestation days 14 and 17, respectively, than in MTN dams. Fetal {sup 109}Cd levels were low in both mouse types, but at least 10-fold lower in MTN fetuses. MT had no effect on the amount of {sup 109}Cd transferred to pups via milk; furthermore, 85--90% of total pup {sup 109}Cd was recovered in gastrointestinal tracts of both types, despite high duodenal MT only in MTN pups. A relatively large percentage of milk-derived intestinal {sup 109}Cd was transferred to other pup tissues in both MT1,2KO and MTN pups (14 and 10%, respectively). These results demonstrate that specific sequestration of cadmium by both maternal and neonatal intestinal tract does not require MT. Although MT decreased oral cadmium transfer from intestine to body tissues at low cadmium exposure levels, MT did not play a major role in restricting transfer of cadmium from dam to fetus via placenta and to neonate via milk.« less

Probing the nature of superfluid helium-3 very near its critical temperature

NASA Astrophysics Data System (ADS)

Nishimori, Arito

We have measured with high resolution the static magnetization and NMR frequency shift of bulk superfluid 3He near its critical point. The static magnetization measurements at 31.4 bars and 33.7 bars in the magnetic field of 36.1 mT show that the size of the magnetization change through the A1 region is smaller than 0.1% of the total magnetization in the normal phase. NMR frequency shifts which have the similar |Delta|2 dependency(Delta:order parameter) to that of the magnetization are measured at the melting pressure in magnetic fields from 29.6 mT to 425 mT using a new feedback technique. We find that the frequency shifts agree very well with the mean field calculations based on the spin fluctuation feedback model proposed by Brinkman, Serene and Anderson(BSA) and there is no high temperature tail above T A1 nor smearing of kinks at TA 1 and TA2 originating from critical fluctuations. From the fitting parameters, the Brinkman-Anderson parameter delta averaged over the data in 92.6 mT, 154 mT and 213 mT at the melting pressure is found to be 0.57+/-0.02. We also obtained the widths of the A1 phase at low magnetic fields. Its linear dependence on magnetic field strength is consistent with the mean field calculation.

Detectability of early brain meningitis with magnetic resonance imaging

DOE Office of Scientific and Technical Information (OSTI.GOV)

Runge, V.M.; Wells, J.W.; Williams, N.M.

1995-08-01

The ability of high-field (1.5 T) magnetic resonance imaging (MRI) to detect early brain meningitis was evaluated in a canine model. Contrast dose, timing postinjection, and imaging technique (specifically the use of magnetization transfer) were assessed. Imaging of five canines was performed at 1.5 T 24 hours after injection of Cowans staphylococcus into the cisterna magna. Two control animals also were imaged using the same protocol. Contrast doses of 0.1, 0.3, and 0.8 mmol/kg gadoteridol were compared. Scans were performed at 2, 13, and 22 minutes after an initial injection of 0.1 mmol/kg. Thirty minutes after the initial injection ofmore » contrast, a supplemental dose of 0.2 mmol/kg was given. Scans were then repeated at 2, 12, and 22 minutes after this dose was administered. A second supplemental contrast injection of 0.5 mmol/kg was given at 70 minutes, and immediate postinjection scans with and without MT were acquired. Results. In the animals receiving a cisternal injection of bacteria, the degree of meningeal enhancement was greatest at 0.8 mmol/kg, intermediate at 0.3 mmol/kg, and least at 0.1 mmol/kg. Scans in control studies did not demonstrate abnormal meningeal enhancement. High-contrast dose, MT, and acquisition of immediate postcontrast scans all resulted in statistically significant improvement. On masked film review, abnormal meningeal enhancement was noted in only 2 of 5 experimental dogs at a dose of 0.1 mmol/kg (regardless of the use of MT) compared with all animals at a dose of 0.3 mmol/kg. In 18 of 37 dogs (paired scans with and without MT), when abnormal enhancement was noted, the use of MT improved the visualization of abnormal meningeal enhancement. In early brain meningitis, high-contrast dose (0.3 mmol/kg), MT, and scanning immediately after injection improve detection of abnormal meningeal enhancement, thus facilitating the diagnosis of meningitis. Of these factors, contrast dose is the most important. 14 refs., 9 figs., 2 tabs.« less

Field-cycling NMR experiments in an ultra-wide magnetic field range: relaxation and coherent polarization transfer.

PubMed

Zhukov, Ivan V; Kiryutin, Alexey S; Yurkovskaya, Alexandra V; Grishin, Yuri A; Vieth, Hans-Martin; Ivanov, Konstantin L

2018-05-09

An experimental method is described allowing fast field-cycling Nuclear Magnetic Resonance (NMR) experiments over a wide range of magnetic fields from 5 nT to 10 T. The method makes use of a hybrid technique: the high field range is covered by positioning the sample in the inhomogeneous stray field of the NMR spectrometer magnet. For fields below 2 mT a magnetic shield is mounted on top of the spectrometer; inside the shield the magnetic field is controlled by a specially designed coil system. This combination allows us to measure T1-relaxation times and nuclear Overhauser effect parameters over the full range in a routine way. For coupled proton-carbon spin systems relaxation with a common T1 is found at low fields, where the spins are "strongly coupled". In some cases, experiments at ultralow fields provide access to heteronuclear long-lived spin states. Efficient coherent polarization transfer is seen for proton-carbon spin systems at ultralow fields as follows from the observation of quantum oscillations in the polarization evolution. Applications to analysis and the manipulation of heteronuclear spin systems are discussed.

Dynamic evolution of plant mitochondrial genomes: Mobile genes and introns and highly variable mutation rates

PubMed Central

Palmer, Jeffrey D.; Adams, Keith L.; Cho, Yangrae; Parkinson, Christopher L.; Qiu, Yin-Long; Song, Keming

2000-01-01

We summarize our recent studies showing that angiosperm mitochondrial (mt) genomes have experienced remarkably high rates of gene loss and concomitant transfer to the nucleus and of intron acquisition by horizontal transfer. Moreover, we find substantial lineage-specific variation in rates of these structural mutations and also point mutations. These findings mostly arise from a Southern blot survey of gene and intron distribution in 281 diverse angiosperms. These blots reveal numerous losses of mt ribosomal protein genes but, with one exception, only rare loss of respiratory genes. Some lineages of angiosperms have kept all of their mt ribosomal protein genes whereas others have lost most of them. These many losses appear to reflect remarkably high (and variable) rates of functional transfer of mt ribosomal protein genes to the nucleus in angiosperms. The recent transfer of cox2 to the nucleus in legumes provides both an example of interorganellar gene transfer in action and a starting point for discussion of the roles of mechanistic and selective forces in determining the distribution of genetic labor between organellar and nuclear genomes. Plant mt genomes also acquire sequences by horizontal transfer. A striking example of this is a homing group I intron in the mt cox1 gene. This extraordinarily invasive mobile element has probably been acquired over 1,000 times separately during angiosperm evolution via a recent wave of cross-species horizontal transfers. Finally, whereas all previously examined angiosperm mtDNAs have low rates of synonymous substitutions, mtDNAs of two distantly related angiosperms have highly accelerated substitution rates. PMID:10860957

Relative Paleointensity of the Geomagnetic Field 12-20 kyr. From Sediment Cores, Lake Moreno (Patagonia, Argentina)

NASA Astrophysics Data System (ADS)

Gogorza, C. S.; Irurzun, M. A.; Chaparro, M. A.; Lirio, J. M.; Nunez, H.; Sinito, A. M.

2007-05-01

Four cores labeled Lmor1, Lmor2, Lmor3, Lmor98-1, Lmor98-2 from the bottom sediments of Lake Moreno (south-western Argentina) have been used to estimate regional geomagnetic paleointensity. Lake Moreno is on the east side of the Andean Cordillera Patagónica; it is located in the Llao Llao area, San Carlos de Bariloche, Argentina (41° S, 71° 30'W). The following measurements were performed: Natural Remanent Magnetization (NRM), magnetic susceptibility at low and high frequency (specific, X and volumetric, k), Isothermal Remanent Magnetization (IRM) reaching the Saturation Isothermal Remanent Magnetization (SIRM), Back Field, Anhysteric Remanent Magnetization with a direct field of 0.1mT and an alternating field between 2.5 and 100mT (ARM100mT). Associated parameters were calculated: S-ratio, Remanent Coercitive Field (BCR, anhysteric volumetric susceptibility (kanh), SIRM/k, ARM100mT/k, and SIRM/ ARM100mT. The rock magnetic studies indicate that the magnetic mineralogy of the clay-rich sediments is dominated by pseudo- single domain magnetite in a narrow range of grain size (between 1 and 4μm) and concentration (between 0.05 and 0.1%), thereby meeting established criteria for relative paleointensity studies. The remanent magnetization at 20mT (NRM20mT) has been normalized using the anhysteric remanent magnetization at 20mT (ARM20mT), the saturation of the isothermal remanent magnetization at 20mT (SIRM20mT) and k. A comparison of these results with relative paleointensity records obtained in previous works, Lake Escondido (Gogorza et al., 2004) and Lake El Trébol (Gogorza et al., 2006) allows obtaining detailed information about the disagreement observed in the period 12-20 kyr between both records. References Gogorza, C.S.G., J.M. Lirio, H. Nunez, M.A.E. Chaparro, H.R. Bertorello, A.M. Sinito. Paleointensity studies on Holocene-Pleistocene sediments from Lake Escondido, Argentina, Phys. Earth and Planet. Inter. 145: 219-238, 2004. Gogorza, C.S.G., M.A. Irurzun, M.A.E. Chaparro, J.M. Lirio, H. Nunez, P.G. Bercoff, A.M. Sinito. Relative paleointensity of the geomagnetic field over the last 21,000 years BP from sediment cores, Lake El Trébol (Patagonia, Argentina). Earth Planet Space. 58: 1323-1332, 2006.

Quantitative Study of Longitudinal Relaxation (T 1) Contrast Mechanisms in Brain MRI

NASA Astrophysics Data System (ADS)

Jiang, Xu

Longitudinal relaxation (T1) contrast in MRI is important for studying brain morphology and is widely used in clinical applications. Although MRI only detects signals from water hydrogen ( 1H) protons (WPs), T1 contrast is known to be influenced by other species of 1H protons, including those in macromolecules (MPs), such as lipids and proteins, through magnetization transfer (MT) between WPs and MPs. This complicates the use and quantification of T1 contrast for studying the underlying tissue composition and the physiology of the brain. MT contributes to T1 contrast to an extent that is generally dependent on MT kinetics, as well as the concentration and NMR spectral properties of MPs. However, the MP spectral properties and MT kinetics are both difficult to measure directly, as the signal from MPs is generally invisible to MRI. Therefore, to investigate MT kinetics and further quantify T1 contrast, we first developed a reliable way to indirectly measure the MP fraction and their exchange rate with WPs, with minimal dependence on the spectral properties of MPs. For this purpose, we used brief, highpower radiofrequency (RF) NMR excitation pulses to almost completely saturate the magnetization of MPs. Based on this, both MT kinetics and the contribution of MPs to T1 contrast through MT were studied. The thus obtained knowledge allowed us to subsequently infer the spectral properties of MPs by applying low-power, frequencyselective off-resonance RF pulses and measuring the offset-frequency dependent effect of MPs on the WP MRI signal. A two-pool exchange model was used in both cases to account for direct effects of the RF pulse on WP magnetization. Consistent with earlier works using MRI at low-field and post-mortem analysis of brain tissue, our novel measurement approach found that MPs constitute an up to 27% fraction of the total 1H protons in human brain white matter, and their spectrum follows a super-Lorentzian line with a T2 of 9.6+/-0.6 mus and a resonance frequency centered at -2.58+/-0.05 ppm, at 7 T. T1 contrast was found to be dominated by MP fraction, with iron only modestly contributing even in the iron-rich regions of brain.

Foreign Plastid Sequences in Plant Mitochondria are Frequently Acquired Via Mitochondrion-to-Mitochondrion Horizontal Transfer

PubMed Central

Gandini, C. L.; Sanchez-Puerta, M. V.

2017-01-01

Angiosperm mitochondrial genomes (mtDNA) exhibit variable quantities of alien sequences. Many of these sequences are acquired by intracellular gene transfer (IGT) from the plastid. In addition, frequent events of horizontal gene transfer (HGT) between mitochondria of different species also contribute to their expanded genomes. In contrast, alien sequences are rarely found in plastid genomes. Most of the plant-to-plant HGT events involve mitochondrion-to-mitochondrion transfers. Occasionally, foreign sequences in mtDNAs are plastid-derived (MTPT), raising questions about their origin, frequency, and mechanism of transfer. The rising number of complete mtDNAs allowed us to address these questions. We identified 15 new foreign MTPTs, increasing significantly the number of those previously reported. One out of five of the angiosperm species analyzed contained at least one foreign MTPT, suggesting a remarkable frequency of HGT among plants. By analyzing the flanking regions of the foreign MTPTs, we found strong evidence for mt-to-mt transfers in 65% of the cases. We hypothesize that plastid sequences were initially acquired by the native mtDNA via IGT and then transferred to a distantly-related plant via mitochondrial HGT, rather than directly from a foreign plastid to the mitochondrial genome. Finally, we describe three novel putative cases of mitochondrial-derived sequences among angiosperm plastomes. PMID:28262720

Glioblastoma (GBM) effects on quantitative MRI of contralateral normal appearing white matter.

PubMed

Mehrabian, Hatef; Lam, Wilfred W; Myrehaug, Sten; Sahgal, Arjun; Stanisz, Greg J

2018-03-28

The objective was to investigate (with quantitative MRI) whether the normal appearing white matter (NAWM) of glioblastoma (GBM) patients on the contralateral side (cNAWM) was different from NAWM of healthy controls. Thirteen patients with newly diagnosed GBM and nine healthy age-matched controls were MRI-scanned with quantitative magnetization transfer (qMT), chemical exchange saturation transfer (CEST), and transverse relaxation time (T 2 )-mapping. MRI scans were performed after surgery and before chemo-radiation treatment. Comprehensive qMT, CEST, T 2 data were acquired. A two-pool MT model was fit to qMT data in transient state, to calculate MT model parameters [Formula: see text]. CEST signal was isolated by removing the contributions from the MT and direct water saturation, and CEST signal was calculated for Amide (CEST Amide ), Amine (CEST Amine ) and nuclear overhauser effect, NOE (CEST NOE ). There was no difference between GBM patients and normal controls in the qMT properties of the macromolecular pool [Formula: see text]. However, their free water pool spectrum was different (1/R a T 2a , patient  = 28.1 ± 3.9, 1/R a T 2a , control  = 25.0 ± 1.1, p = 0.03). This difference could be attributed to the difference in their T 2 time ([Formula: see text] = 83 ± 4, [Formula: see text] = 88 ± 1, p = 0.004). CEST signals were statistically significantly different with the CEST Amide having the largest difference between the two cohorts (CEST Amide,patient  = 2.8 ± 0.4, CEST Amide,control  = 3.4 ± 0.5, p = 0.009). CEST in cNAWM of GBM patients was lower than healthy controls which could be caused by modified brain metabolism due to tumor cell infiltration. There was no difference in MT properties of the patients and controls, however, the differences in free water pool properties were mainly due to reduced T 2 in cNAWM of the patients (resulting from structural changes and increased cellularity).

Strychnos nux-vomica extract and its ultra-high dilution reduce voluntary ethanol intake in rats.

PubMed

Sukul, N C; Ghosh, S; Sinhababu, S P; Sukul, A

2001-04-01

To see whether Strychnos nux-vomica extract (mother tincture [MT]), its potency Nux 30c, and its principal alkaloid, strychnine, could reduce voluntary ethanol intake in rats. To analyze the solution structure of Nux MT, Nux 30c, 90% ethanol, and ethanol 30c by means of electronic (ES) and nuclear nuclear magnetic resonance (NMR) spectra. Potentially alcoholic rats were first given 20% ethanol and then kept on a two-choice bottle, one with 20% ethanol and another with tap water. These rats were given the following oral treatments for 15 days: group 1, control; group 2, strychnine at 0.36 mg/kg per day; group 3, ethanolic extract of S. nux-vomica seeds (Nux MT) at 3.6 mg/kg per day; and group 4, Nux 30c at 0.05 mL/d per rat. Nux 30c was prepared by successive dilution of Nux MT and 90% ethanol (1:100) and sonication at 20 kHz for 30 seconds in 30 steps. Both Nux MT and Nux 30c significantly reduced ethanol intake and increased water intake in rats. ES of two dilutions of Nux MT and Nux 30c showed intersections at more than one point suggesting existence of molecular complexes. ES of Nux MT in CCl4 showed a red shift when 90% ethanol was added indicating molecular complexation and charge transfer interaction between ethanol and Nux compounds. NMR spectra of Nux MT, 90% ethanol, ethanol 30c, and Nux 30c indicated a change in solution structure of the medium (90% ethanol) of Nux 30c. Nux MT and Nux 30c could reduce ethanol intake in rats. The altered solution structure of Nux 30c is thought to mimic Nux MT and produce ethanol aversion in rats.

Horizontal transfer of whole mitochondria restores tumorigenic potential in mitochondrial DNA-deficient cancer cells.

PubMed

Dong, Lan-Feng; Kovarova, Jaromira; Bajzikova, Martina; Bezawork-Geleta, Ayenachew; Svec, David; Endaya, Berwini; Sachaphibulkij, Karishma; Coelho, Ana R; Sebkova, Natasa; Ruzickova, Anna; Tan, An S; Kluckova, Katarina; Judasova, Kristyna; Zamecnikova, Katerina; Rychtarcikova, Zuzana; Gopalan, Vinod; Andera, Ladislav; Sobol, Margarita; Yan, Bing; Pattnaik, Bijay; Bhatraju, Naveen; Truksa, Jaroslav; Stopka, Pavel; Hozak, Pavel; Lam, Alfred K; Sedlacek, Radislav; Oliveira, Paulo J; Kubista, Mikael; Agrawal, Anurag; Dvorakova-Hortova, Katerina; Rohlena, Jakub; Berridge, Michael V; Neuzil, Jiri

2017-02-15

Recently, we showed that generation of tumours in syngeneic mice by cells devoid of mitochondrial (mt) DNA (ρ 0 cells) is linked to the acquisition of the host mtDNA. However, the mechanism of mtDNA movement between cells remains unresolved. To determine whether the transfer of mtDNA involves whole mitochondria, we injected B16ρ 0 mouse melanoma cells into syngeneic C57BL/6N su9-DsRed2 mice that express red fluorescent protein in their mitochondria. We document that mtDNA is acquired by transfer of whole mitochondria from the host animal, leading to normalisation of mitochondrial respiration. Additionally, knockdown of key mitochondrial complex I (NDUFV1) and complex II (SDHC) subunits by shRNA in B16ρ 0 cells abolished or significantly retarded their ability to form tumours. Collectively, these results show that intact mitochondria with their mtDNA payload are transferred in the developing tumour, and provide functional evidence for an essential role of oxidative phosphorylation in cancer.

A comparison of 15 Hz sine on-line and off-line magnetic stimulation affecting the voltage-gated sodium channel currents of prefrontal cortex pyramidal neurons

NASA Astrophysics Data System (ADS)

Zheng, Yu; Dong, Lei; Gao, Yang; Dou, Jun-Rong; Li, Ze-yan

2016-10-01

Combined with the use of patch-clamp techniques, repetitive transcranial magnetic stimulation (rTMS) has proven to be a noninvasive neuromodulation tool that can inhibit or facilitate excitability of neurons after extensive research. The studies generally focused on the method: the neurons are first stimulated in an external standard magnetic exposure device, and then moved to the patch-clamp to record electrophysiological characteristics (off-line magnetic exposure). Despite its universality, real-time observation of the effects of magnetic stimulation on the neurons is more effective (on-line magnetic stimulation). In this study, we selected a standard exposure device for magnetic fields acting on mouse prefrontal cortex pyramidal neurons, and described a new method that a patch-clamp setup was modified to allow on-line magnetic stimulation. By comparing the off-line exposure and on-line stimulation of the same magnetic field intensity and frequency affecting the voltage-gated sodium channel currents, we succeeded in proving the feasibility of the new on-line stimulation device. We also demonstrated that the sodium channel currents of prefrontal cortex pyramidal neurons increased significantly under the 15 Hz sine 1 mT, and 2 mT off-line magnetic field exposure and under the 1 mT and 2 mT on-line magnetic stimulation, and the rate of acceleration was most significant on 2 mT on-line magnetic stimulation. This study described the development of a new on-line magnetic stimulator and successfully demonstrated its practicability for scientific stimulation of neurons.

Joint Inversion of 3d Mt/gravity/magnetic at Pisagua Fault.

NASA Astrophysics Data System (ADS)

Bascur, J.; Saez, P.; Tapia, R.; Humpire, M.

2017-12-01

This work shows the results of a joint inversion at Pisagua Fault using 3D Magnetotellurics (MT), gravity and regional magnetic data. The MT survey has a poor coverage of study area with only 21 stations; however, it allows to detect a low resistivity zone aligned with the Pisagua Fault trace that it is interpreted as a damage zone. The integration of gravity and magnetic data, which have more dense sampling and coverage, adds more detail and resolution to the detected low resistivity structure and helps to improve the structure interpretation using the resulted models (density, magnetic-susceptibility and electrical resistivity). The joint inversion process minimizes a multiple target function which includes the data misfit, model roughness and coupling norms (crossgradient and direct relations) for all geophysical methods considered (MT, gravity and magnetic). This process is solved iteratively using the Gauss-Newton method which updates the model of each geophysical method improving its individual data misfit, model roughness and the coupling with the other geophysical models. For solving the model updates of magnetic and gravity methods were developed dedicated 3D inversion software codes which include the coupling norms with additionals geophysical parameters. The model update of the 3D MT is calculated using an iterative method which sequentially filters the priority model and the output model of a single 3D MT inversion process for obtaining the resistivity model coupled solution with the gravity and magnetic methods.

Determining the structure-mechanics relationships of dense microtubule networks with confocal microscopy and magnetic tweezers-based microrheology.

PubMed

Yang, Yali; Valentine, Megan T

2013-01-01

The microtubule (MT) cytoskeleton is essential in maintaining the shape, strength, and organization of cells. Its spatiotemporal organization is fundamental for numerous dynamic biological processes, and mechanical stress within the MT cytoskeleton provides an important signaling mechanism in mitosis and neural development. This raises important questions about the relationships between structure and mechanics in complex MT structures. In vitro, reconstituted cytoskeletal networks provide a minimal model of cell mechanics while also providing a testing ground for the fundamental polymer physics of stiff polymer gels. Here, we describe our development and implementation of a broad tool kit to study structure-mechanics relationships in reconstituted MT networks, including protocols for the assembly of entangled and cross-linked MT networks, fluorescence imaging, microstructure characterization, construction and calibration of magnetic tweezers devices, and mechanical data collection and analysis. In particular, we present the design and assembly of three neodymium iron boron (NdFeB)-based magnetic tweezers devices optimized for use with MT networks: (1) high-force magnetic tweezers devices that enable the application of nano-Newton forces and possible meso- to macroscale materials characterization; (2) ring-shaped NdFeB-based magnetic tweezers devices that enable oscillatory microrheology measurements; and (3) portable magnetic tweezers devices that enable direct visualization of microscale deformation in soft materials under applied force. Copyright © 2013 Elsevier Inc. All rights reserved.

Horizontal transfer of whole mitochondria restores tumorigenic potential in mitochondrial DNA-deficient cancer cells

PubMed Central

Dong, Lan-Feng; Kovarova, Jaromira; Bajzikova, Martina; Bezawork-Geleta, Ayenachew; Svec, David; Endaya, Berwini; Sachaphibulkij, Karishma; Coelho, Ana R; Sebkova, Natasa; Ruzickova, Anna; Tan, An S; Kluckova, Katarina; Judasova, Kristyna; Zamecnikova, Katerina; Rychtarcikova, Zuzana; Gopalan, Vinod; Andera, Ladislav; Sobol, Margarita; Yan, Bing; Pattnaik, Bijay; Bhatraju, Naveen; Truksa, Jaroslav; Stopka, Pavel; Hozak, Pavel; Lam, Alfred K; Sedlacek, Radislav; Oliveira, Paulo J; Kubista, Mikael; Agrawal, Anurag; Dvorakova-Hortova, Katerina; Rohlena, Jakub; Berridge, Michael V; Neuzil, Jiri

2017-01-01

Recently, we showed that generation of tumours in syngeneic mice by cells devoid of mitochondrial (mt) DNA (ρ0 cells) is linked to the acquisition of the host mtDNA. However, the mechanism of mtDNA movement between cells remains unresolved. To determine whether the transfer of mtDNA involves whole mitochondria, we injected B16ρ0 mouse melanoma cells into syngeneic C57BL/6Nsu9-DsRed2 mice that express red fluorescent protein in their mitochondria. We document that mtDNA is acquired by transfer of whole mitochondria from the host animal, leading to normalisation of mitochondrial respiration. Additionally, knockdown of key mitochondrial complex I (NDUFV1) and complex II (SDHC) subunits by shRNA in B16ρ0 cells abolished or significantly retarded their ability to form tumours. Collectively, these results show that intact mitochondria with their mtDNA payload are transferred in the developing tumour, and provide functional evidence for an essential role of oxidative phosphorylation in cancer. DOI: http://dx.doi.org/10.7554/eLife.22187.001 PMID:28195532

The effect of magnetic field on copper in various corrosive medium

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ang, L. Y.; Othman, N. K.; Jalar, A.

2014-09-03

The effect of applied magnetic field on the corrosion behaviour of copper within various corrosive medium is investigated. The copper coupon is immersed in 0.5 M HCl, 0.5 M NaCl and 0.5 M NaOH with or without applying up to 40 mT magnetic fields for 24 hours. The weight loss of copper coupon in HCl increased up to 96.56% with applied magnetic fields. However, in NaOH medium, only 33.33% more weight loss was observed and no difference were observed for coupons in NaCl when magnetic field is applied. This observation indicates that corrosion behaviour in HCl and NaOH is controlledmore » by mass transport that can be influenced by the induced magneto hydrodynamics effect when magnetic field is applied. There was no change in weight loss of copper in NaCl when magnetic field is applied because the corrosion mechanism of copper in NaCl is governed by electron charge transfer.« less

Exploration of the validity of weak magnets as a suitable placebo in trials of magnetic therapy.

PubMed

Greaves, C J; Harlow, T N

2008-06-01

To investigate whether 50 mT magnetic bracelets would be suitable as a placebo control condition for studying the pain relieving effects of higher strength magnetic bracelets in arthritis. Randomised controlled comparison between groups given either a weak 50 mT or a higher strength 180 mT magnetic bracelets to test. Four arthritis support groups in Devon, UK. One hundred sixteen people with osteoarthritis and rheumatoid arthritis. Beliefs about group allocation and expectation of benefit. There was no significant difference between groups in beliefs about allocation to the 'active magnet' group. Participants were however more likely to have an expectation of benefit (pain relief) with the higher strength magnetic bracelets. Asking about perceived group allocation is not sufficient to rule out placebo effects in trials of magnetic bracelets which use weak magnets as a control condition. There are differences in expectation of benefit between different magnet strengths.

Retroviral gene transfer of an antisense construct against membrane type 1 matrix metalloproteinase reduces the invasiveness of rheumatoid arthritis synovial fibroblasts.

PubMed

Rutkauskaite, Edita; Volkmer, Dagmar; Shigeyama, Yukio; Schedel, Jörg; Pap, Geza; Müller-Ladner, Ulf; Meinecke, Ingmar; Alexander, Dorothea; Gay, Renate E; Drynda, Susanne; Neumann, Wolfram; Michel, Beat A; Aicher, Wilhelm K; Gay, Steffen; Pap, Thomas

2005-07-01

Membrane type 1 matrix metalloproteinase (MT1-MMP) is expressed prominently in rheumatoid arthritis synovial fibroblasts (RASFs), but the specific contribution of MT1-MMP to fibroblast-mediated destruction of articular cartilage is incompletely understood. This study used gene transfer of an antisense expression construct to assess the effects of MT1-MMP inhibition on the invasiveness of RASFs. Retroviral gene transfer of a pLXIN vector-based antisense RNA expression construct (MT1-MMPalphaS) to MT1-MMP was used to stably transduce RASFs. Levels of MT1-MMP RNA and protein were determined by quantitative polymerase chain reaction, Western blotting, and immunocytochemistry in MT1-MMPalphaS-transduced RASFs as well as in control cells, with monitoring for 60 days. The effects of MT1-MMPalphaS on the invasiveness of RASFs were analyzed in the SCID mouse co-implantation model of RA. MT1-MMPalphaS-transduced RASFs produced high levels of antisense RNA that exceeded endogenous levels of MT1-MMP messenger RNA by 15-fold and resulted in a down-regulation of MT1-MMP at the protein level. Inhibition of MT1-MMP production was maintained for 60 days and significantly reduced the invasiveness of RASFs in the SCID mouse model. Whereas prominent invasion into cartilage by non-transduced and mock-transduced RASFs was observed (mean invasion scores 3.0 and 3.1, respectively), MT1-MMPalphaS-transduced cells showed only moderate invasiveness (mean invasion score 1.8; P < 0.05). The data demonstrate that an antisense RNA expression construct against MT1-MMP can be generated and expressed in RASFs for at least 60 days. Inhibition of MT1-MMP significantly reduces the cartilage degradation by RASFs.

Anticipating and addressing workplace static magnetic field effects at levels <0.5 mT.

PubMed

Emery, R J; Hopkins, J R; Charlton, M A

2000-11-01

Magnetic resonance, once a research tool limited to the basic sciences, has experienced an increase in popularity due to its unique ability to analyze certain living systems in vivo. Expanding applications in the biomedical sciences have resulted in magnetic sources being located in research institutions nationally. Space and resource limitations sometimes necessitate siting magnetic resonance units in proximity to other institutional operations. For magnetic field shielding and personnel protection considerations, the generally accepted 0.5 mT (milliTesla) limit for implanted cardiac devices is commonly used as the conservative basis for decisions. But the effects of magnetic fields on equipment can be easily observed at levels far below 0.5 mT, often resulting in concern and apprehension on the part of personnel in the surrounding areas. Responding to recurrent worker concerns spawned by noticeable effects on equipment at exposure levels <0.5 mT can strain finite radiation safety program resources. To enhance the ability to anticipate possible facility incompatibility issues associated with the installation of magnetic sources, a literature review was conducted to summarize documented equipment effects. Various types of equipment were found to be impacted at levels ranging down to perhaps 0.001 mT. Armed with this information, practicing radiation safety professionals can better anticipate facility incompatibility issues and improve their responses to worker concerns initiated by observed effects on equipment.

Widespread unidirectional transfer of mitochondrial DNA: a case in western Palaearctic water frogs.

PubMed

Plötner, J; Uzzell, T; Beerli, P; Spolsky, C; Ohst, T; Litvinchuk, S N; Guex, G-D; Reyer, H-U; Hotz, H

2008-05-01

Interspecies transfer of mitochondrial (mt) DNA is a common phenomenon in plants, invertebrates and vertebrates, normally linked with hybridization of closely related species in zones of sympatry or parapatry. In central Europe, in an area north of 48 degrees N latitude and between 8 degrees and 22 degrees E longitude, western Palaearctic water frogs show massive unidirectional introgression of mtDNA: 33.7% of 407 Rana ridibunda possessed mtDNA specific for Rana lessonae. By contrast, no R. lessonae with R. ridibunda mtDNA was observed. That R. ridibunda with introgressed mitochondrial genomes were found exclusively within the range of the hybrid Rana esculenta and that most hybrids had lessonae mtDNA (90.4% of 335 individuals investigated) is evidence that R. esculenta serves as a vehicle for transfer of lessonae mtDNA into R. ridibunda. Such introgression has occurred several times independently. The abundance and wide distribution of individuals with introgressed mitochondrial genomes show that R. lessonae mt genomes work successfully in a R. ridibunda chromosomal background despite their high sequence divergence from R. ridibunda mtDNAs (14.2-15.2% in the ND2/ND3 genes). Greater effectiveness of enzymes encoded by R. lessonae mtDNA may be advantageous to individuals of R. ridibunda and probably R. esculenta in the northern parts of their ranges.

Realization of metamagnetic martensitic transformation with multifunctional properties in Co50V34Ga16 Heusler alloy

NASA Astrophysics Data System (ADS)

Liu, Changqin; Li, Zhe; Zhang, Yuanlei; Huang, Yinsheng; Ye, Miaofu; Sun, Xiaodong; Zhang, Guojie; Cao, Yiming; Xu, Kun; Jing, Chao

2018-05-01

In this work, we have developed a ferromagnetic shape memory alloy Co50V34Ga16 with a metamagnetic martensitic transformation (MT) from the high-magnetization austenitic phase to the low-magnetization martensitic phase. As a consequence of a strong coupling between structure and magnetic degrees of freedom, the metamagnetic MT of this alloy is relatively sensitive to the external magnetic field, thus giving rise to a field-induced reverse MT. Associated with such a unique behavior, both considerable inverse magnetocaloric effect (9.6 J/kg K) and magnetostrain (0.07%) have also been obtained under the magnetic field change of 3 T. Our experimental results indicate that this kind of Co-V based alloy probably becomes an alternatively promising candidate for applications in magnetic sensors and magnetic refrigeration.

Integration of microwave tomography with magnetic resonance for improved breast imaging

PubMed Central

Meaney, Paul M.; Golnabi, Amir H.; Epstein, Neil R.; Geimer, Shireen D.; Fanning, Margaret W.; Weaver, John B.; Paulsen, Keith D.

2013-01-01

Purpose: Breast magnetic resonance imaging is highly sensitive but not very specific for the detection of breast cancer. Opportunities exist to supplement the image acquisition with a more specific modality provided the technical challenges of meeting space limitations inside the bore, restricted breast access, and electromagnetic compatibility requirements can be overcome. Magnetic resonance (MR) and microwave tomography (MT) are complementary and synergistic because the high resolution of MR is used to encode spatial priors on breast geometry and internal parenchymal features that have distinct electrical properties (i.e., fat vs fibroglandular tissue) for microwave tomography. Methods: The authors have overcome integration challenges associated with combining MT with MR to produce a new coregistered, multimodality breast imaging platform—magnetic resonance microwave tomography, including: substantial illumination tank size reduction specific to the confined MR bore diameter, minimization of metal content and composition, reduction of metal artifacts in the MR images, and suppression of unwanted MT multipath signals. Results: MR SNR exceeding 40 dB can be obtained. Proper filtering of MR signals reduces MT data degradation allowing MT SNR of 20 dB to be obtained, which is sufficient for image reconstruction. When MR spatial priors are incorporated into the recovery of MT property estimates, the errors between the recovered versus actual dielectric properties approach 5%. Conclusions: The phantom and human subject exams presented here are the first demonstration of combining MT with MR to improve the accuracy of the reconstructed MT images. PMID:24089930

Preventing the transmission of pathogenic mitochondrial DNA mutations: Can we achieve long-term benefits from germ-line gene transfer?

PubMed

Samuels, David C; Wonnapinij, Passorn; Chinnery, Patrick F

2013-03-01

Mitochondrial medicine is one of the few areas of genetic disease where germ-line transfer is being actively pursued as a treatment option. All of the germ-line transfer methods currently under development involve some carry-over of the maternal mitochondrial DNA (mtDNA) heteroplasmy, potentially delivering the pathogenic mutation to the offspring. Rapid changes in mtDNA heteroplasmy have been observed within a single generation, and so any 'leakage' of mutant mtDNA could lead to mtDNA disease in future generations, compromising the reproductive health of the first generation, and leading to repeated interventions in subsequent generations. To determine whether this is a real concern, we developed a model of mtDNA heteroplasmy inheritance by studying 87 mother-child pairs, and predicted the likely outcome of different levels of 'mutant mtDNA leakage' on subsequent maternal generations. This showed that, for a clinical threshold of 60%, reducing the proportion of mutant mtDNA to <5% dramatically reduces the chance of disease recurrence in subsequent generations, but transmitting >5% mutant mtDNA was associated with a significant chance of disease recurrence. Mutations with a lower clinical threshold were associated with a higher risk of recurrence. Our findings provide reassurance that, at least from an mtDNA perspective, methods currently under development have the potential to effectively eradicate pathogenic mtDNA mutations from subsequent generations.

XML Storage for Magnetotelluric Transfer Functions: Towards a Comprehensive Online Reference Database

NASA Astrophysics Data System (ADS)

Kelbert, A.; Blum, C.

2015-12-01

Magnetotelluric Transfer Functions (MT TFs) represent most of the information about Earth electrical conductivity found in the raw electromagnetic data, providing inputs for further inversion and interpretation. To be useful for scientific interpretation, they must also contain carefully recorded metadata. Making these data available in a discoverable and citable fashion would provide the most benefit to the scientific community, but such a development requires that the metadata is not only present in the file but is also searchable. The most commonly used MT TF format to date, the historical Society of Exploration Geophysicists Electromagnetic Data Interchange Standard 1987 (EDI), no longer supports some of the needs of modern magnetotellurics, most notably accurate error bars recording. Moreover, the inherent heterogeneity of EDI's and other historic MT TF formats has mostly kept the community away from healthy data sharing practices. Recently, the MT team at Oregon State University in collaboration with IRIS Data Management Center developed a new, XML-based format for MT transfer functions, and an online system for long-term storage, discovery and sharing of MT TF data worldwide (IRIS SPUD; www.iris.edu/spud/emtf). The system provides a query page where all of the MT transfer functions collected within the USArray MT experiment and other field campaigns can be searched for and downloaded; an automatic on-the-fly conversion to the historic EDI format is also included. To facilitate conversion to the new, more comprehensive and sustainable, XML format for MT TFs, and to streamline inclusion of historic data into the online database, we developed a set of open source format conversion tools, which can be used for rotation of MT TFs as well as a general XML <-> EDI converter (https://seiscode.iris.washington.edu/projects/emtf-fcu). Here, we report on the newly established collaboration between the USGS Geomagnetism Program and the Oregon State University to gather and convert both historic and modern-day MT or related transfer functions into the searchable database at the IRIS DMC. The more complete and free access to these previously collected MT TFs will be of great value to MT scientists both in planning future surveys, and then to leverage the value of the new data at the inversion and interpretation stage.

Nuclear transfer to prevent mitochondrial DNA disorders: revisiting the debate on reproductive cloning.

PubMed

Bredenoord, A L; Dondorp, W; Pennings, G; De Wert, G

2011-02-01

Preclinical experiments are currently performed to examine the feasibility of several types of nuclear transfer to prevent mitochondrial DNA (mtDNA) disorders. Whereas the two most promising types of nuclear transfer to prevent mtDNA disorders, spindle transfer and pronuclear transfer, do not amount to reproductive cloning, one theoretical variant, blastomere transfer does. This seems the most challenging both technically and ethically. It is prohibited by many jurisdictions and also the scientific community seems to avoid it. Nevertheless, this paper examines the moral acceptability of blastomere transfer as a method to prevent mtDNA disorders. The reason for doing so is that most objections against reproductive cloning refer to reproductive adult cloning, while blastomere transfer would amount to reproductive embryo cloning. After clarifying this conceptual difference, this paper examines whether the main non-safety objections brought forward against reproductive cloning also apply in the context of blastomere transfer. The conclusion is that if this variant were to become safe and effective, dismissing it because it would involve reproductive cloning is unjustified. Nevertheless, as it may lead to more complex ethical appraisals than the other variants, researchers should initially focus on the development of the other types of nuclear transfer to prevent mtDNA disorders. Copyright © 2010 Reproductive Healthcare Ltd. Published by Elsevier Ltd. All rights reserved.

Chemical exchange rotation transfer (CERT) on human brain at 3 Tesla.

PubMed

Lin, Eugene C; Li, Hua; Zu, Zhongliang; Louie, Elizabeth A; Lankford, Christopher L; Dortch, Richard D; Does, Mark D; Gore, John C; Gochberg, Daniel F

2018-05-25

To test the ability of a novel pulse sequence applied in vivo at 3 Tesla to separate the contributions to the water signal from amide proton transfer (APT) and relayed nuclear Overhauser enhancement (rNOE) from background direct water saturation and semisolid magnetization transfer (MT). The lack of such signal source isolation has confounded conventional chemical exchange saturation transfer (CEST) imaging. We quantified APT and rNOE signals using a chemical exchange rotation transfer (CERT) metric, MTR double . A range of duty cycles and average irradiation powers were applied, and results were compared with conventional CEST analyses using asymmetry (MTR asym ) and extrapolated magnetization transfer (EMR). Our results indicate that MTR double is more specific than MTR asym and, because it requires as few as 3 data points, is more rapid than methods requiring a complete Z-spectrum, such as EMR. In white matter, APT (1.5 ± 0.5%) and rNOE (2.1 ± 0.7%) were quantified by using MTR double with a 30% duty cycle and a 0.5-µT average power. In addition, our results suggest that MTR double is insensitive to B 0 inhomogeneity, further magnifying its speed advantage over CEST metrics that require a separate B 0 measurement. However, MTR double still has nontrivial sensitivity to B 1 inhomogeneities. We demonstrated that MTR double is an alternative metric to evaluate APT and rNOE, which is fast, robust to B 0 inhomogeneity, and easy to process. © 2018 International Society for Magnetic Resonance in Medicine.

Self-assembled molecular magnets on patterned silicon substrates: bridging bio-molecules with nanoelectronics.

PubMed

Chang, Chia-Ching; Sun, Kien Wen; Lee, Shang-Fan; Kan, Lou-Sing

2007-04-01

The paper reports the methods of preparing molecular magnets and patterning of the molecules on a semiconductor surface. A highly magnetically aligned metallothionein containing Mn and Cd (Mn,Cd-MT-2) is first synthesized, and the molecules are then placed into nanopores prepared on silicon (001) surfaces using electron beam lithography and reactive ion-etching techniques. We have observed the self-assemble growth of the MT molecules on the patterned Si surface such that the MT molecules have grown into rod or ring type three-dimensional nanostructures, depending on the patterned nanostructures on the surface. We also provide scanning electron microscopy, atomic force microscopy, and magnetic force microscope studies of the molecular nanostructures. This engineered molecule shows molecular magnetization and is biocompatible with conventional semiconductors. These features make Mn,Cd-MT-2 a good candidate for biological applications and sensing sources of new nanodevices. Using molecular self-assembly and topographical patterning of the semiconductor substrate, we can close the gap between bio-molecules and nanoelectronics built into the semiconductor chip.

Longitudinal assessment of mouse renal injury using high-resolution anatomic and magnetization transfer MR imaging.

PubMed

Wang, Feng; Jiang, Rosie; Takahashi, Keiko; Gore, John; Harris, Raymond C; Takahashi, Takamune; Quarles, C Chad

2014-11-01

The purpose of this study is to evaluate the utility of high-resolution non-invasive endogenous high-field MRI methods for the longitudinal structural and quantitative assessments of mouse kidney disease using the model of unilateral ureter obstruction (UUO). T1-weighted, T2-weighted and magnetization transfer (MT) imaging protocols were optimized to improve the regional contrast in mouse kidney. Conventional T1 and T2 weighted images were collected in UUO mice on day 0 (~3h), day 1, day 3 and day 6 after injury, on a 7 T small animal MRI system. Cortical and medullary thickness, corticomedullary contrast and Magnetization Transfer Ratio (MTR) were assessed longitudinally. Masson trichrome staining was used to histologically assess changes in tissue microstructure. Over the course of UUO progression there were significant (p<0.05) changes in thickness of cortex and outer medulla, and regional changes in T2 signal intensity and MTR values. Histological changes included tubular cell death, tubular dilation, urine retention, and interstitial fibrosis, assessed by histology. The MRI measures of renal cortical and medullary atrophy, cortical-medullary differentiation and MTR changes provide an endogenous, non-invasive and quantitative evaluation of renal morphology and tissue composition during UUO progression. Copyright © 2014 Elsevier Inc. All rights reserved.

31 P magnetic resonance fingerprinting for rapid quantification of creatine kinase reaction rate in vivo.

PubMed

Wang, Charlie Y; Liu, Yuchi; Huang, Shuying; Griswold, Mark A; Seiberlich, Nicole; Yu, Xin

2017-12-01

The purpose of this work was to develop a 31 P spectroscopic magnetic resonance fingerprinting (MRF) method for fast quantification of the chemical exchange rate between phosphocreatine (PCr) and adenosine triphosphate (ATP) via creatine kinase (CK). A 31 P MRF sequence (CK-MRF) was developed to quantify the forward rate constant of ATP synthesis via CK ( kfCK), the T 1 relaxation time of PCr ( T1PCr), and the PCr-to-ATP concentration ratio ( MRPCr). The CK-MRF sequence used a balanced steady-state free precession (bSSFP)-type excitation with ramped flip angles and a unique saturation scheme sensitive to the exchange between PCr and γATP. Parameter estimation was accomplished by matching the acquired signals to a dictionary generated using the Bloch-McConnell equation. Simulation studies were performed to examine the susceptibility of the CK-MRF method to several potential error sources. The accuracy of nonlocalized CK-MRF measurements before and after an ischemia-reperfusion (IR) protocol was compared with the magnetization transfer (MT-MRS) method in rat hindlimb at 9.4 T (n = 14). The reproducibility of CK-MRF was also assessed by comparing CK-MRF measurements with both MT-MRS (n = 17) and four angle saturation transfer (FAST) (n = 7). Simulation results showed that CK-MRF quantification of kfCK was robust, with less than 5% error in the presence of model inaccuracies including dictionary resolution, metabolite T 2 values, inorganic phosphate metabolism, and B 1 miscalibration. Estimation of kfCK by CK-MRF (0.38 ± 0.02 s -1 at baseline and 0.42 ± 0.03 s -1 post-IR) showed strong agreement with MT-MRS (0.39 ± 0.03 s -1 at baseline and 0.44 ± 0.04 s -1 post-IR). kfCK estimation was also similar between CK-MRF and FAST (0.38 ± 0.02 s -1 for CK-MRF and 0.38 ± 0.11 s -1 for FAST). The coefficient of variation from 20 s CK-MRF quantification of kfCK was 42% of that by 150 s MT-MRS acquisition and was 12% of that by 20 s FAST acquisition. This study demonstrates the potential of a 31 P spectroscopic MRF framework for rapid, accurate and reproducible quantification of chemical exchange rate of CK in vivo. Copyright © 2017 John Wiley & Sons, Ltd.

Influence of electromagnetic interference on implanted cardiac arrhythmia devices in and around a magnetically levitated linear motor car.

PubMed

Fukuta, Motoyuki; Mizutani, Noboru; Waseda, Katsuhisa

2005-01-01

This study was designed to determine the susceptibility of implanted cardiac arrhythmia devices to electromagnetic interference in and around a magnetically levitated linear motor car [High-Speed Surface Transport (HSST)]. During the study, cardiac devices were connected to a phantom model that had similar characteristics to the human body. Three pacemakers from three manufacturers and one implantable cardioverter-defibrillator (ICD) were evaluated in and around the magnetically levitated vehicle. The system is based on a normal conductive system levitated by the attractive force of magnets and propelled by a linear induction motor without wheels. The magnetic field strength at 40 cm from the vehicle in the nonlevitating state was 0.12 mT and that during levitation was 0.20 mT. The magnetic and electric field strengths on a seat close to the variable voltage/variable frequency inverter while the vehicle was moving and at rest were 0.13 mT, 2.95 V/m and 0.04 mT, 0.36 V/m, respectively. Data recorded on a seat close to the reactor while the vehicle was moving and at rest were 0.09 mT, 2.45 V/m and 0.05 mT, 1.46 V/m, respectively. Measured magnetic and electric field strengths both inside and outside the linear motor car were too low to result in device inactivation. No sensing, pacing, or arrhythmic interactions were noted with any pacemaker or ICD programmed in either bipolar and unipolar configurations. In conclusion, our data suggest that a permanent programming change or a device failure is unlikely to occur and that the linear motor car system is probably safe for patients with one of the four implanted cardiac arrhythmia devices used in this study under the conditions tested.

Enhancement of invertase production by Aspergillus niger OZ-3 using low-intensity static magnetic fields.

PubMed

Taskin, Mesut; Esim, Nevzat; Genisel, Mucip; Ortucu, Serkan; Hasenekoglu, Ismet; Canli, Ozden; Erdal, Serkan

2013-01-01

The aim of this study is to investigate the effect of low-intensity static magnetic fields (SMFs) on invertase activity and growth on different newly identified molds. The most positive effect of SMFs on invertase activity and growth was observed for Aspergillus niger OZ-3. The submerged production of invertase was performed with the spores obtained at the different exposure times (120, 144, 168, and 196 hr) and magnetic field intensities (0.45, 3, 5, 7, and 9 mT). The normal magnetic field of the laboratory was assayed as 0.45 mT (control). Optimization of magnetic field intensity and exposure time significantly increased biomass production and invertase activity compared to 0.45 mT. The maximum invertase activity (51.14 U/mL) and biomass concentration (4.36 g/L) were achieved with the spores obtained at the 144 hr exposure time and 5 mT magnetic field intensity. The effect of low-intensity static magnetic fields (SMFs) on invertase activities of molds was investigated for the first time in the present study. As an additional contribution, a new hyper-invertase-producing mold strain was isolated.

Sensitivity of MRI parameters within intervertebral discs to the severity of adolescent idiopathic scoliosis.

PubMed

Huber, Maxime; Gilbert, Guillaume; Roy, Julien; Parent, Stefan; Labelle, Hubert; Périé, Delphine

2016-11-01

To measure magnetic resonance imaging (MRI) parameters including relaxation times (T 1 ρ, T 2 ), magnetization transfer (MT) and diffusion parameters (mean diffusivity [MD], fractional anisotropy [FA]) of intervertebral discs in adolescents with idiopathic scoliosis, and to investigate the sensitivity of these MR parameters to the severity of the spine deformities. Thirteen patients with adolescent idiopathic scoliosis and three control volunteers with no history of spine disease underwent an MRI acquisition at 3T including the mapping of T 1 ρ, T 2 , MT, MD, and FA. The apical zone included all discs within the scoliotic curve while the control zone was composed of other discs. The severity was analyzed through low (<32°) versus high (>40°) Cobb angles. One-way analysis of variance (ANOVA) and agglomerative hierarchical clustering (AHC) were performed. Significant differences were found between the apical zone and the control zone for T 2 (P = 0.047), and between low and high Cobb angles for T 2 (P = 0.014) and MT (P = 0.002). AHC showed two distinct clusters, one with mainly low Cobb angles and one with mainly high Cobb angles, for the MRI parameters measured within the apical zone, with an accuracy of 0.9 and a Matthews correlation coefficient (MCC) of 0.8. Within the control zone, the AHC showed no clear classification (accuracy of 0.6 and MCC of 0.2). We successfully performed an in vivo multiparametric MRI investigation of young patients with adolescent idiopathic scoliosis. The MRI parameters measured within the intervertebral discs were found to be sensitive to intervertebral disc degeneration occurring with scoliosis and to the severity of scoliosis. J. Magn. Reson. Imaging 2016;44:1123-1131. © 2016 International Society for Magnetic Resonance in Medicine.

Sub-millitesla magnetic field effects on the recombination reaction of flavin and ascorbic acid radicals

NASA Astrophysics Data System (ADS)

Evans, Emrys W.; Kattnig, Daniel R.; Henbest, Kevin B.; Hore, P. J.; Mackenzie, Stuart R.; Timmel, Christiane R.

2016-08-01

Even though the interaction of a <1 mT magnetic field with an electron spin is less than a millionth of the thermal energy at room temperature (kBT), it still can have a profound effect on the quantum yields of radical pair reactions. We present a study of the effects of sub-millitesla magnetic fields on the photoreaction of flavin mononucleotide with ascorbic acid. Direct control of the reaction pathway is achieved by varying the rate of electron transfer from ascorbic acid to the photo-excited flavin. At pH 7.0, we verify the theoretical prediction that, apart from a sign change, the form of the magnetic field effect is independent of the initial spin configuration of the radical pair. The data agree well with model calculations based on a Green's function approach that allows multinuclear spin systems to be treated including the diffusive motion of the radicals, their spin-selective recombination reactions, and the effects of the inter-radical exchange interaction. The protonation states of the radicals are uniquely determined from the form of the magnetic field-dependence. At pH 3.0, the effects of two chemically distinct radical pair complexes combine to produce a pronounced response to ˜500 μT magnetic fields. These findings are relevant to the magnetic responses of cryptochromes (flavin-containing proteins proposed as magnetoreceptors in birds) and may aid the evaluation of effects of weak magnetic fields on other biologically relevant electron transfer processes.

MnZn-ferrites: Targeted Material Design for New Emerging Application Products

NASA Astrophysics Data System (ADS)

Zaspalis, V. T.; Tsakaloudi, V.; Kogias, G.

2014-07-01

In this article the main characteristics for emerging MnZn-ferrite applications are described on the basis of the new demands they possess on the ferrite material development. A number of recently developed MnZn-ferrite materials is presented together with the main scientific principles lying behind their development. These include: (i) high saturation flux density MnZn-ferrites (i.e. Bsat=550 mT at 10 kHz, 1200 A/m, 100°C), (ii) low power losses MnZn-ferrites (i.e. Pv~210 mW cm-3 at 100 kHz, 200mT, 100°C), (iii) MnZn-ferrites with broad temperature stability (i.e. PV<375 mW cm-3 for 25°C

In Vivo Evaluation of Magnetic Targeting in Mice Colon Tumors with Ultra-Magnetic Liposomes Monitored by MRI.

PubMed

Thébault, Caroline J; Ramniceanu, Grégory; Michel, Aude; Beauvineau, Claire; Girard, Christian; Seguin, Johanne; Mignet, Nathalie; Ménager, Christine; Doan, Bich-Thuy

2018-06-25

The development of theranostic nanocarriers as an innovative therapy against cancer has been improved by targeting properties in order to optimize the drug delivery to safely achieve its desired therapeutic effect. The aim of this paper is to evaluate the magnetic targeting (MT) efficiency of ultra-magnetic liposomes (UML) into CT26 murine colon tumor by magnetic resonance imaging (MRI). Dynamic susceptibility contrast MRI was applied to assess the bloodstream circulation time. A novel semi-quantitative method called %I 0.25 , based on the intensity distribution in T 2 * -weighted MRI images was developed to compare the accumulation of T 2 contrast agent in tumors with or without MT. To evaluate the efficiency of magnetic targeting, the percentage of pixels under the intensity value I 0.25 (I 0.25  = 0.25(I max  - I min )) was calculated on the intensity distribution histogram. This innovative method of processing MRI images showed the MT efficiency by a %I 0.25 that was significantly higher in tumors using MT compared to passive accumulation, from 15.3 to 28.6 %. This methodology was validated by ex vivo methods with an iron concentration that is 3-fold higher in tumors using MT. We have developed a method that allows a semi-quantitative evaluation of targeting efficiency in tumors, which could be applied to different T 2 contrast agents.

Preventing the transmission of pathogenic mitochondrial DNA mutations: can we achieve long-term benefits from germ-line gene transfer?

PubMed Central

Samuels, David C.; Wonnapinij, Passorn; Chinnery, Patrick F.

2013-01-01

Mitochondrial medicine is one of the few areas of genetic disease where germ-line transfer is being actively pursued as a treatment option. All of the germ-line transfer methods currently under development involve some carry-over of the maternal mitochondrial DNA (mtDNA) heteroplasmy, potentially delivering the pathogenic mutation to the offspring. Rapid changes in mtDNA heteroplasmy have been observed within a single generation, and so any ‘leakage’ of mutant mtDNA could lead to mtDNA disease in future generations, compromising the reproductive health of the first generation, and leading to repeated interventions in subsequent generations. To determine whether this is a real concern, we developed a model of mtDNA heteroplasmy inheritance by studying 87 mother–child pairs, and predicted the likely outcome of different levels of ‘mutant mtDNA leakage’ on subsequent maternal generations. This showed that, for a clinical threshold of 60%, reducing the proportion of mutant mtDNA to <5% dramatically reduces the chance of disease recurrence in subsequent generations, but transmitting >5% mutant mtDNA was associated with a significant chance of disease recurrence. Mutations with a lower clinical threshold were associated with a higher risk of recurrence. Our findings provide reassurance that, at least from an mtDNA perspective, methods currently under development have the potential to effectively eradicate pathogenic mtDNA mutations from subsequent generations. PMID:23297368

Improvement of spin-exchange optical pumping of xenon-129 using in situ NMR measurement in ultra-low magnetic field

NASA Astrophysics Data System (ADS)

Takeda, Shun; Kumagai, Hiroshi

2018-02-01

Hyperpolarized (HP) noble gas has attracted attention in NMR / MRI. In an ultra-low magnetic field, the effectiveness of signal enhancement by HP noble gas should be required because reduction of the signal intensity is serious. One method of generating HP noble gas is spin exchange optical pumping which uses selective excitation of electrons of alkali metal vapor and spin transfer to nuclear spin by collision to noble gas. Although SEOP does not require extreme cooling or strong magnetic field, generally it required large-scale equipment including high power light source to generate HP noble gas with high efficiency. In this study, we construct a simply generation system of HP xenon-129 by SEOP with an ultralow magnetic field (up to 1 mT) and small-scale light source (about 1W). In addition, we measure in situ NMR signal at the same time, and then examine efficient conditions for SEOP in ultra-low magnetic fields.

[Transcranial magnetic therapy in the treatment of psychoautonomous disturbances in children with diabetes mellitus type 1].

PubMed

Filina, N Iu; Bolotova, N V; Manukian, V Iu; Nikolaeva, N V; Kompaniets, O V

2009-01-01

Results of a clinical-physiological study of 80 children with diabetes mellitus type 1 with psychoautonomous disturbances are presented. Forty patients of the main group received transcranial magnetic therapy (TcMT), 40 patients of the control group had placebo sessions of TcMT with magnetic power supply switched off. TcMT was applied using bitemporal method, running regime with modulation frequency 1-10 Hz. Patients received 10 sessions. Positive changes were found in the main group compared to the controls. In the main group, TcMT sessions allowed to normalize the autonomous status in 75% of children and to improve psychoemotional state in 55%. The correction of psychoemotional status of children changed their behavior towards diabetes, improved control and compensation of the disease.

Molecular MRI differentiation between primary central nervous system lymphomas and high-grade gliomas using endogenous protein-based amide proton transfer MR imaging at 3 Tesla

PubMed Central

Jiang, Shanshan; Yu, Hao; Wang, Xianlong; Lu, Shilong; Li, Yufa; Feng, Lyujin; Zhang, Yi; Heo, Hye-Young; Lee, Dong-Hoon; Zhou, Jinyuan; Wen, Zhibo

2015-01-01

Objectives To show the ability of using the amide-proton-transfer-weighted (APTW) MRI signals as imaging biomarkers to differentiate primary central-nervous-system lymphomas (PCNSLs) from high-grade gliomas (HGGs). Methods Eleven patients with lymphomas and 21 patients with HGGs were examined. Magnetization-transfer (MT) spectra over an offset range of ±6 ppm and the conventional MT ratio (MTR) at 15.6 ppm were acquired. The APTW signals, total chemical-exchange-saturation-transfer signal (integral between 0 and 5 ppm, CESTtotal), and MTR signal were obtained and compared between PCNSLs and HGGs. The diagnostic performance was assessed with the receiver-operating-characteristic-curve analysis. Results The PCNSLs usually showed more homogeneous APTW hyperintensity (spatially compared to the normal brain tissue) than the HGGs. The APTWmax, APTWmax-min, and CESTtotal signal intensities were significantly lower (P < 0.05, 0.001, and 0.05, respectively), while the APTWmin and MTR were significantly higher (both P < 0.01) in PCNSL lesions than in HGG lesions. The APTW values in peritumoral oedema were significantly lower for PCNSLs than for HGGs (P < 0.01). APTWmax-min had the highest area under the receiver-operating-characteristic curve (0.963) and accuracy (94.1%) in differentiating PCNSLs from HGGs. Conclusions The protein-based APTW signal would be a valuable MRI biomarker by which to identify PCNSLs and HGGs presurgically. PMID:25925361

Magnetic field gradient driven self-assembly of superparamagnetic nanoparticles using programmable magnetically-recorded templates

NASA Astrophysics Data System (ADS)

Ye, L.; Qi, B.; Lawton, T. G.; Mefford, O. T.; Rinaldi, C.; Garzon, S.; Crawford, T. M.

2013-03-01

Using the enormous magnetic field gradients (100 MT/m @ z =20 nm) present near the surface of magnetic recording media, we demonstrate the fabrication of diffraction gratings with lines consisting entirely of magnetic nanoparticles assembled from a colloidal fluid onto a disk drive medium, followed by transfer to a flexible and transparent polymer thin film. These nanomanufactured gratings have line spacings programmed with commercial magnetic recording and are inherently concave with radii of curvature controlled by varying the polymer film thickness. The diffracted intensity increases non-monotonically with the length of time the colloidal fluid remains on the disk surface. In addition to comparing longitudinal and perpendicular magnetic recording, a combination of spectral diffraction efficiency measurements, magnetometry, scanning electron microscopy and inductively coupled plasma atomic emmission spectroscopy of these gratings are employed to understand colloidal nanoparticle dynamics in this extreme gradient limit. Such experiments are necessary to optimize nanoparticle assembly and obtain uniform patterned features. This low-cost and sustainable approach to nanomanufacturing could enable low-cost, high-quality diffraction gratings as well as more complex polymer nanocomposite materials assembled with single-nanometer precision.

Magnetic stimulation of marigold seed

NASA Astrophysics Data System (ADS)

Afzal, I.; Mukhtar, K.; Qasim, M.; Basra, S. M. A.; Shahid, M.; Haq, Z.

2012-10-01

The effects of magnetic field treatments of French marigold seeds on germination, early seedling growth and biochemical changes of seedlings were studied under controlled conditions. For this purpose, seeds were exposed to five different magnetic seed treatments for 3 min each. Most of seed treatments resulted in improved germination speed and spread, root and shoot length, seed soluble sugars and a-amylase activity. Magnetic seed treatment with 100 mT maximally improved germination, seedling vigour and starch metabolism as compared to control and other seed treatments. In emergence experiment, higher emergence percentage (4-fold), emergence index (5-fold) and vigorous seedling growth were obtained in seeds treated with 100 mT. Overall, the enhancement of marigold seeds by magnetic seed treatment with 100 mT could be related to enhanced starch metabolism. The results suggest that magnetic field treatments of French marigold seeds have the potential to enhance germination, early growth and biochemical parameters of seedlings.

Realizing "2001: A Space Odyssey": Piloted Spherical Torus Nuclear Fusion Propulsion

NASA Technical Reports Server (NTRS)

Williams, Craig H.; Dudzinski, Leonard A.; Borowski, Stanley K.; Juhasz, Albert J.

2005-01-01

A conceptual vehicle design enabling fast, piloted outer solar system travel was created predicated on a small aspect ratio spherical torus nuclear fusion reactor. The initial requirements were satisfied by the vehicle concept, which could deliver a 172 mt crew payload from Earth to Jupiter rendezvous in 118 days, with an initial mass in low Earth orbit of 1,690 mt. Engineering conceptual design, analysis, and assessment was performed on all major systems including artificial gravity payload, central truss, nuclear fusion reactor, power conversion, magnetic nozzle, fast wave plasma heating, tankage, fuel pellet injector, startup/re-start fission reactor and battery bank, refrigeration, reaction control, communications, mission design, and space operations. Detailed fusion reactor design included analysis of plasma characteristics, power balance/utilization, first wall, toroidal field coils, heat transfer, and neutron/x-ray radiation. Technical comparisons are made between the vehicle concept and the interplanetary spacecraft depicted in the motion picture 2001: A Space Odyssey.

Dissociating basal forebrain and medial temporal amnesic syndromes: insights from classical conditioning.

PubMed

Myer, Catherine E; Bryant, Deborah; DeLuca, John; Gluck, Mark A

2002-01-01

In humans, anterograde amnesia can result from damage to the medial temporal (MT) lobes (including hippocampus), as well as to other brain areas such as basal forebrain. Results from animal classical conditioning studies suggest that there may be qualitative differences in the memory impairment following MT vs. basal forebrain damage. Specifically, delay eyeblink conditioning is spared after MT damage in animals and humans, but impaired in animals with basal forebrain damage. Recently, we have likewise shown delay eyeblink conditioning impairment in humans with amnesia following anterior communicating artery (ACoA) aneurysm rupture, which damages the basal forebrain. Another associative learning task, a computer-based concurrent visual discrimination, also appears to be spared in MT amnesia while ACoA amnesics are slower to learn the discriminations. Conversely, animal and computational models suggest that, even though MT amnesics may learn quickly, they may learn qualitatively differently from controls, and these differences may result in impaired transfer when familiar information is presented in novel combinations. Our initial data suggests such a two-phase learning and transfer task may provide a double dissociation between MT amnesics (spared initial learning but impaired transfer) and ACoA amnesics (slow initial learning but spared transfer). Together, these emerging data suggest that there are subtle but dissociable differences in the amnesic syndrome following damage to the MT lobes vs. basal forebrain, and that these differences may be most visible in non-declarative tasks such as eyeblink classical conditioning and simple associative learning.

The role of edema and demyelination in chronic T1 black holes: a quantitative magnetization transfer study.

PubMed

Levesque, Ives; Sled, John G; Narayanan, Sridar; Santos, A Carlos; Brass, Steven D; Francis, Simon J; Arnold, Douglas L; Pike, G Bruce

2005-02-01

To use quantitative magnetization transfer imaging (qMTI) in an investigation of T1-weighted hypointensity observed in clinical magnetic resonance imaging (MRI) scans of multiple sclerosis (MS) patients, which has previously been proposed as a more specific indicator of tissue damage than the more commonly detected T2 hyperintensity. A cross-sectional study of 10 MS patients was performed using qMTI. A total of 60 MTI measurements were collected in each patient at a resolution of 2 x 2 x 7 mm, over a range of saturation pulses. The observed T1 and T2 were also measured. qMT model parameters were estimated using a voxel-by-voxel fit. A total of 65 T2-hyperintense lesions were identified; 53 were also T1 hypointense. In these black holes, the qMTI-derived semisolid pool fraction F correlated negatively with T(1,obs) (r2 = 0.76; P < 0.0001). The water pool absolute size (PDf) showed a weaker correlation with T(1,obs) (positive, r2 = 0.53; P < 0.0001). The magnetization transfer ratio (MTR) showed a similarly strong correlation with F and a weaker correlation with PDf (r2 = 0.18; P < 0.04). T1 increases in chronic black holes strongly correlated with the decline in semisolid pool size, and somewhat less to the confounding effect of edema. MTR was less sensitive than T(1,obs) to liquid pool changes associated with edema. (c) 2005 Wiley-Liss, Inc.

Experimental evaluation of ballistic hazards in imaging diagnostic center.

PubMed

Karpowicz, Jolanta; Gryz, Krzysztof

2013-04-01

Serious hazards for human health and life and devices in close proximity to the magnetic resonance scanners (MRI scanners) include the effects of being hit by ferromagnetic objects attracted by static magnetic field (SMF) produced by scanner magnet - the so-called ballistic hazards classified among indirect electromagnetic hazards. International safety guidelines and technical literature specify different SMF threshold values regarding ballistic hazards - e.g. 3 mT (directive 2004/40/EC, EN 60601-2-33), and 30 mT (BMAS 2009, directive proposal 2011). Investigations presented in this article were performed in order to experimentally verify SMF threshold for ballistic hazards near MRI scanners used in Poland. Investigations were performed with the use of a laboratory source of SMF (0-30 mT) and MRI scanners of various types. The levels of SMF in which metal objects of various shapes and 0.4-500 g mass are moved by the field influence were investigated. The distance from the MRI scanners (0.2-3T) where hazards may occur were also investigated. Objects investigated under laboratory conditions were moved by SMF of 2.2-15 mT magnetic flux density when they were freely suspended, but were moved by the SMF of 5.6-22 mT when they were placed on a smooth surface. Investigated objects were moved in fields of 3.5-40 mT by MRI scanners. Distances from scanner magnet cover, where ballistic hazards might occur are: up to 0.5 m for 0.2-0.3T scanners; up to 1.3 m for 0.5T scanners; up to 2.0 m for 1.5T scanners and up to 2.5 m for 3T scanners (at the front and back of the magnet). It was shown that SMF of 3 mT magnetic flux density should be taken as the threshold for ballistic hazards. Such level is compatible with SMF limit value regarding occupational safety and health-protected areas/zones, where according to the Polish labor law the procedures of work environment inspection and prevention measures regarding indirect electromagnetic hazards should be applied. Presented results do not support the increase up to 30 mT of the SMF limit for protected area.

Intracellular gene transfer in action: Dual transcription and multiple silencings of nuclear and mitochondrial cox2 genes in legumes

PubMed Central

Adams, Keith L.; Song, Keming; Roessler, Philip G.; Nugent, Jacqueline M.; Doyle, Jane L.; Doyle, Jeff J.; Palmer, Jeffrey D.

1999-01-01

The respiratory gene cox2, normally present in the mitochondrion, was previously shown to have been functionally transferred to the nucleus during flowering plant evolution, possibly during the diversification of legumes. To search for novel intermediate stages in the process of intracellular gene transfer and to assess the evolutionary timing and frequency of cox2 transfer, activation, and inactivation, we examined nuclear and mitochondrial (mt) cox2 presence and expression in over 25 legume genera and mt cox2 presence in 392 genera. Transfer and activation of cox2 appear to have occurred during recent legume evolution, more recently than previously inferred. Many intermediate stages of the gene transfer process are represented by cox2 genes in the studied legumes. Nine legumes contain intact copies of both nuclear and mt cox2, although transcripts could not be detected for some of these genes. Both cox2 genes are transcribed in seven legumes that are phylogenetically interspersed with species displaying only nuclear or mt cox2 expression. Inactivation of cox2 in each genome has taken place multiple times and in a variety of ways, including loss of detectable transcripts or transcript editing and partial to complete gene loss. Phylogenetic evidence shows about the same number (3–5) of separate inactivations of nuclear and mt cox2, suggesting that there is no selective advantage for a mt vs. nuclear location of cox2 in plants. The current distribution of cox2 presence and expression between the nucleus and mitochondrion in the studied legumes is probably the result of chance mutations silencing either cox2 gene. PMID:10570164

Study on the effect of magnetic field treatment of newly isolated Paenibacillus sp.

PubMed

Li, Jie; Yi, Yanli; Cheng, Xilei; Zhang, Dageng; Irfan, Muhammad

2015-12-01

Symbiotic nitrogen fixation in plants occurs in roots with the help of some bacteria which help in soil nitrogen fertility management. Isolation of significant environment friendly bacteria for nitrogen fixation is very important to enhance yield in plants. In this study effect of different magnetic field intensity and treatment time was studied on the morphology, physiology and nitrogen fixing capacity of newly isolated Paenibaccilus sp. from brown soil. The bacterium was identified by 16S rDNA sequence having highest similarity (99%) with Paenibacillus sp as revealed by BLAST. Different magnetic intensities such as 100mT, 300mT and 500mT were applied with processing time of 0, 5, 10, 20 and 30 minutes. Of all these treatment 300mT with processing time of 10 minutes was found to be most suitable treatment. Results revealed that magnetic treatment improve the growth rate with shorter generation time leading to increased enzyme activities (catalase, peroxidase and superoxide dismutase) and nitrogen fixing efficiencies. High magnetic field intensity (500mT) caused ruptured cell morphology and decreased enzyme activities which lead to less nitrogen fixation. It is concluded that appropriate magnetic field intensity and treatment time play a vital role in the growth of soil bacteria which increases the nitrogen fixing ability which affects the yield of plant. These results were very helpful in future breading programs to enhance the yield of soybean.

Performing the Millikan experiment at the molecular scale: Determination of atomic Millikan-Thomson charges by computationally measuring atomic forces.

PubMed

Rogers, T Ryan; Wang, Feng

2017-10-28

An atomic version of the Millikan oil drop experiment is performed computationally. It is shown that for planar molecules, the atomic version of the Millikan experiment can be used to define an atomic partial charge that is free from charge flow contributions. We refer to this charge as the Millikan-Thomson (MT) charge. Since the MT charge is directly proportional to the atomic forces under a uniform electric field, it is the most relevant charge for force field developments. The MT charge shows good stability with respect to different choices of the basis set. In addition, the MT charge can be easily calculated even at post-Hartree-Fock levels of theory. With the MT charge, it is shown that for a planar water dimer, the charge transfer from the proton acceptor to the proton donor is about -0.052 e. While both planar hydrated cations and anions show signs of charge transfer, anions show a much more significant charge transfer to the hydration water than the corresponding cations. It might be important to explicitly model the ion charge transfer to water in a force field at least for the anions.

Iron Oxide Nanocrystals for Magnetic Hyperthermia Applications

PubMed Central

Armijo, Leisha M.; Brandt, Yekaterina I.; Mathew, Dimple; Yadav, Surabhi; Maestas, Salomon; Rivera, Antonio C.; Cook, Nathaniel C.; Withers, Nathan J.; Smolyakov, Gennady A.; Adolphi, Natalie; Monson, Todd C.; Huber, Dale L.; Smyth, Hugh D. C.; Osiński, Marek

2012-01-01

Magnetic nanocrystals have been investigated extensively in the past several years for several potential applications, such as information technology, MRI contrast agents, and for drug conjugation and delivery. A specific property of interest in biomedicine is magnetic hyperthermia—an increase in temperature resulting from the thermal energy released by magnetic nanocrystals in an external alternating magnetic field. Iron oxide nanocrystals of various sizes and morphologies were synthesized and tested for specific losses (heating power) using frequencies of 111.1 kHz and 629.2 kHz, and corresponding magnetic field strengths of 9 and 25 mT. Polymorphous nanocrystals as well as spherical nanocrystals and nanowires in paramagnetic to ferromagnetic size range exhibited good heating power. A remarkable 30 °C temperature increase was observed in a nanowire sample at 111 kHz and magnetic field of 25 mT (19.6 kA/m), which is very close to the typical values of 100 kHz and 20 mT used in medical treatments. PMID:28348300

TetraMag: A compact magnetizing device based on eight rotating permanent magnets

NASA Astrophysics Data System (ADS)

Gilbert, M.; Mertins, H.-Ch.; Tesch, M.; Berges, O.; Feilbach, Herbert; Schneider, C. M.

2012-02-01

In this paper we describe a novel magnetizing device based on eight rotatable permanent magnets arranged in a quadrupolar configuration, which is termed the TetraMag. TetraMag creates stable and homogeneous magnetic fields at the sample position with a resolution of 0.02 mT tunable between -570 mT and +570 mT. The field direction is continuously rotatable between 0° and 360° within the sample plane, while the field strength is maintained. A simplified mathematical description of TetraMag is developed leading to magnetic field calculations which are in good agreement with the experimental results. This versatile device avoids electrical energy dissipation, cooling mechanisms, and hysteresis effects known from classical electromagnets. It is ultrahigh vacuum compatible and it offers a completely free optical path over 180° for magneto-optical experiments. It is suitable for scattering experiments with synchrotron radiation and neutrons and may be employed in a large class of magnetization experiments.

Magnetic, in situ, mineral characterization of Chelyabinsk meteorite thin section

NASA Astrophysics Data System (ADS)

Nabelek, Ladislav; Mazanec, Martin; Kdyr, Simon; Kletetschka, Gunther

2015-06-01

Magnetic images of Chelyabinsk meteorite's (fragment F1 removed from Chebarkul lake) thin section have been unraveled by a magnetic scanning system from Youngwood Science and Engineering (YSE) capable of resolving magnetic anomalies down to 10-3 mT range from about 0.3 mm distance between the probe and meteorite surface (resolution about 0.15 mm). Anomalies were produced repeatedly, each time after application of magnetic field pulse of varying amplitude and constant, normal or reversed, direction. This process resulted in both magnetizing and demagnetizing of the meteorite thin section, while keeping the magnetization vector in the plane of the thin section. Analysis of the magnetic data allows determination of coercivity of remanence (Bcr) for the magnetic sources in situ. Value of Bcr is critical for calculating magnetic forces applicable during missions to asteroids where gravity is compromised. Bcr was estimated by two methods. First method measured varying dipole magnetic field strength produced by each anomaly in the direction of magnetic pulses. Second method measured deflections of the dipole direction from the direction of magnetic pulses. Bcr of magnetic sources in Chelyabinsk meteorite ranges between 4 and 7 mT. These magnetic sources enter their saturation states when applying 40 mT external magnetic field pulse.

Development of a Magnetic-Core, Transverse-Field AF Demagnetizer

NASA Astrophysics Data System (ADS)

Schillinger, W. E.; Morris, E. R.; Coe, R. S.; Finn, D. R.

2016-12-01

A standard cleaning technique in the study of a rock's natural remanent magnetization (NRM) is progressive Alternating Field Demagnetization (AFD). However, for a significant fraction of samples, demagnetization is not completed by the maximum field of 200 mT or less available in commercial instruments; a field at least two or three times higher is needed. The data from 0 to 160 mT for a resistant red bed sample from Tibet is shown below. It just starts to reveal the sample's characteristic component, but this interpretation would have been tenuous, since 85% of the NRM remained untouched. Continued demagnetization to 500 mT helps a great deal, reducing the NRM to just 30% of its initial value and proving that the segment from 160 to 500 mT indeed trends toward the origin. We have constructed an alternating field (AF) demagnetizer that can routinely operate at fields of up to 0.6 Tesla. It uses a magnetic core in an air-cooled coil and is compatible with our existing sample handler for automated demagnetization and measurement experiments. Nonlinearities of the magnetic core are not a significant problem; even harmonics of the magnetic field are ≤1 ppm of the fundamental and so generate negligible anhysteretic remanence. A surprising result during the testing was that the coil's inductance changed with magnetic field. This made it necessary to add an auto-tuning feature, to keep the drive's frequency on the coil's resonance. We have recently added the ability to include a DC field of up to 0.5 mT, parallel to the alternating field, to perform Anhysteretic Remanent Magnetization (ARM), partial ARM experiments and anisotropy of ARM. We will report on these ARM results at the AGU meeting. Currently the maximum field we can obtain is 600 mT, but by reshaping the core to minimize flux leakage, significantly higher fields should be attainable, since the saturation flux density of the core material is 1.5T.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Constable, S.A.; Orange, Arnold S.; Hoversten, G. Michael

Induction in electrically conductive seawater attenuates themagnetotelluric (MT) fields and, coupled with a minimum around 1 Hz inthe natural magnetic field spectrum, leads to a dramatic loss of electricand magnetic field power on the sea floor at periods shorter than 1000 s,For this reason the marine MT method traditionally has been used only atperiods of 10(3) to 10(5) s to probe deep mantle structure; rarely does asea-floor MT response extend to a 100-s period. To be useful for mappingcontinental shelf structure at depths relevant to petroleum exploration,however, MT measurements need to be made at periods between 1 and 1000 s.Thismore » can be accomplished using ac-coupled sensors, induction coils forthe magnetic field, and an electric field amplifier developed for marinecontrolled-source applications. The electrically quiet sea floor allowsthe attenuated electric field to be amplified greatly before recording;in deep (l-km) water, motional noise in magnetic field sensors appearsnot to be a problem. In shallower water, motional noise does degrade themagnetic measurement, but sea-floor magnetic records can be replaced byland recordings, producing an effective sea-surface MT response. Fieldtrials of such equipment in l-km-deep water produced good-quality MTresponses at periods of 3 to 1000 s: in shallower water, responses to afew hertz can be obtained. Using an autonomous sea-floor data loggerdeveloped at Scripps Institution of Oceanography, marine surveys of 50 to100 sites are feasible.« less

Nure aerial gamma-ray and magnetic reconnaissance survey: Chugach/Yakutat area, Alaska, Mt. Saint Elias Quadrangle

DOE Office of Scientific and Technical Information (OSTI.GOV)

Not Available

1978-10-01

Volume II contains the following data on Mt. Saint Elias, Alaska: geologic base map, flight path map, anomaly maps (U, Th, K, UlTh, UlK, ThlK), radiometric multiple-parameter stacked profiles, magnetic and ancillary profile data, and statistical data. (LK)

Sub-millitesla magnetic field effects on the recombination reaction of flavin and ascorbic acid radicals

DOE Office of Scientific and Technical Information (OSTI.GOV)

Evans, Emrys W.; Henbest, Kevin B.; Timmel, Christiane R., E-mail: christiane.timmel@chem.ox.ac.uk, E-mail: stuart.mackenzie@chem.ox.ac.uk

Even though the interaction of a <1 mT magnetic field with an electron spin is less than a millionth of the thermal energy at room temperature (k{sub B}T), it still can have a profound effect on the quantum yields of radical pair reactions. We present a study of the effects of sub-millitesla magnetic fields on the photoreaction of flavin mononucleotide with ascorbic acid. Direct control of the reaction pathway is achieved by varying the rate of electron transfer from ascorbic acid to the photo-excited flavin. At pH 7.0, we verify the theoretical prediction that, apart from a sign change, themore » form of the magnetic field effect is independent of the initial spin configuration of the radical pair. The data agree well with model calculations based on a Green’s function approach that allows multinuclear spin systems to be treated including the diffusive motion of the radicals, their spin-selective recombination reactions, and the effects of the inter-radical exchange interaction. The protonation states of the radicals are uniquely determined from the form of the magnetic field-dependence. At pH 3.0, the effects of two chemically distinct radical pair complexes combine to produce a pronounced response to ∼500 μT magnetic fields. These findings are relevant to the magnetic responses of cryptochromes (flavin-containing proteins proposed as magnetoreceptors in birds) and may aid the evaluation of effects of weak magnetic fields on other biologically relevant electron transfer processes.« less

Limiting depth of magnetization in cratonic lithosphere

NASA Technical Reports Server (NTRS)

Toft, Paul B.; Haggerty, Stephen E.

1988-01-01

Values of magnetic susceptibility and natural remanent magnetization (NRM) of clino-pyroxene-garnet-plagioclase granulite facies lower crustal xenoliths from a kimberlite in west Africa are correlated to bulk geochemistry and specific gravity. Thermomagnetic and alternating-field demagnetization analyses identify magnetite (Mt) and native iron as the dominant magnetic phases (totaling not more than 0.1 vol pct of the rocks) along with subsidiary sulfides. Oxidation states of the granulites are not greater than MW, observed Mt occurs as rims on coarse (about 1 micron) Fe particles, and inferred single domain-pseudosingle domain Mt may be a result of oxidation of fine-grained Fe. The deepest limit of lithospheric ferromagnetism is 95 km, but a limit of 70 km is most reasonable for the West African Craton and for modeling Magsat anomalies over exposed Precambrian shields.

Scanning SQUID microscope with an in-situ magnetization/demagnetization field for geological samples

NASA Astrophysics Data System (ADS)

Du, Junwei; Liu, Xiaohong; Qin, Huafeng; Wei, Zhao; Kong, Xiangyang; Liu, Qingsong; Song, Tao

2018-04-01

Magnetic properties of rocks are crucial for paleo-, rock-, environmental-magnetism, and magnetic material sciences. Conventional rock magnetometers deal with bulk properties of samples, whereas scanning microscope can map the distribution of remanent magnetization. In this study, a new scanning microscope based on a low-temperature DC superconducting quantum interference device (SQUID) equipped with an in-situ magnetization/demagnetization device was developed. To realize the combination of sensitive instrument as SQUID with high magnetizing/demagnetizing fields, the pick-up coil, the magnetization/demagnetization coils and the measurement mode of the system were optimized. The new microscope has a field sensitivity of 250 pT/√Hz at a coil-to-sample spacing of ∼350 μm, and high magnetization (0-1 T)/ demagnetization (0-300 mT, 400 Hz) functions. With this microscope, isothermal remanent magnetization (IRM) acquisition and the according alternating field (AF) demagnetization curves can be obtained for each point without transferring samples between different procedures, which could result in position deviation, waste of time, and other interferences. The newly-designed SQUID microscope, thus, can be used to investigate the rock magnetic properties of samples at a micro-area scale, and has a great potential to be an efficient tool in paleomagnetism, rock magnetism, and magnetic material studies.

Magnetic field affects enzymatic ATP synthesis.

PubMed

Buchachenko, Anatoly L; Kuznetsov, Dmitry A

2008-10-01

The rate of ATP synthesis by creatine kinase extracted from V. xanthia venom was shown to depend on the magnetic field. The yield of ATP produced by enzymes with 24Mg2+ and 26Mg2+ ions in catalytic sites increases by 7-8% at 55 mT and then decreases at 80 mT. For enzyme with 25Mg2+ ion in a catalytic site, the ATP yield increases by 50% and 70% in the fields 55 and 80 mT, respectively. In the Earth field the rate of ATP synthesis by enzyme, in which Mg2+ ion has magnetic nucleus 25Mg, is 2.5 times higher than that by enzymes, in which Mg2+ ion has nonmagnetic, spinless nuclei 24Mg or 26Mg. Both magnetic field effect and magnetic isotope effect demonstrate that the ATP synthesis is an ion-radical process, affected by Zeeman interaction and hyperfine coupling in the intermediate ion-radical pair.

Variations of the Geomagnetic Field During the Holocene-Pleistocene: Relative Paleointensity Records From South-Western Argentina

NASA Astrophysics Data System (ADS)

Gogorza, C. S.

2008-05-01

I present a review of the research carried out by the Group of Geomagnetism at Universidad Nacional del Centro (Argentina) on paleointensity records from bottom sediments from three lakes: Escondido (Gogorza et al., 2004), Moreno (Gogorza et al., 2006) and El Trébol (Gogorza et al., 2007; Irurzun et al., 2008) (South-Western Argentina, 41° S, 71° 30'W). Based on these studies, we construct a first relative (RPI) stack for South-Western Argentina covering the last 21,000 14C years BP. The degree of down-core homogeneity of magnetic mineral content as well as magnetic mineral concentration and grain sizes vary between all lakes and are quantified by high-resolution rock magnetic measurements. Rock magnetic studies suggest that the main carriers of magnetization are ferrimagnetic minerals, predominantly pseudo-single domain magnetite The remanent magnetization at 20 mT (NRM20mT) was normalized using the anhysteric remanent magnetization at 20mT (ARM20mT), the saturation of the isothermal remanent at 20 mT (SIRM20mT) and the low field magnetic susceptibility {k}. Coherence function analysis indicates that the normalised records are free of environmental influences. Our paleointensity (NRM20mT/ ARM20mT) versus age curve shows a good agreement with published records from other parts of the world suggesting that, in suitable sediments, paleointensity of the geomagnetic field can give a globally coherent, dominantly dipolar signal. References Gogorza, C.S.G., Irurzun, M.A., Chaparro, M.A.E., Lirio, J.M., Nuñez, H., Bercoff, P.G., Sinito, A.M. Relative Paleointensity of the Geomagnetic Field over the last 21,000 years bp from Sediment Cores, Lake El Trébol, (Patagonia, Argentina). Earth, Planets and Space. V58(10), 1323-1332. 2006. Gogorza, C.S.G., Sinito, A.M., Lirio, J.M., Nuñez, H., Chaparro, M.A.E., Bertorello, H.R. Paleointensity Studies on Holocene-Pleistocene Sediments from Lake Escondido, Argentina. Physical of the Earth and Planetary Interiors, Elsevier, ISSN 0031-9201. V145, 219-238. 2004. Gogorza, C.S.G., Torcida, S., Irurzun, A., Chaparro, M.A.E., Sinito, A.M. A Pseudo-Thellier Relative Paleointensity Record in Sediments From Lake El Trébol, South Argentina. Geofísica Internacional. In Revision. 2007. Irurzun, M.A., Gogorza, C.S.G., Torcida, S., Lirio, J.M., Núnez, H., Bercoff, P., Chaparro, M.A.E., Sinito, A.M. Rock Magnetic Properties and Relative Paleointensity Stack Between 11 and 21 14C kyr B.P. from Sediment Cores, Lake Moreno (Patagonia, Argentina). In Preparation. 2008.

Multilayer film shields for the protection of PMT from constant magnetic field.

PubMed

Dmitrenko, V V; Besson, David; Nyunt, PhyoWai; Grabchikov, S S; Grachev, V M; Muraviev-Smirnov, C C; Ulin, S E; Uteshev, Z M; Vlasik, K F

2015-01-01

Photomultiplier tubes (PMTs) are widely used in physical experiments as well as in applied devices. PMTs are sensitive to magnetic field, so creation of effective magnetic shields for their protection is very important. In this paper, the results of measurements of shielding effectiveness of multilayer film magnetic shields on PMT-85 are presented. Shields were formed by alternating layers of a material with high magnetic permeability (Ni-Fe) and high electric conductivity-Cu. The maximum number of bilayers reached 45. It is shown that in weak magnetic fields up to 0.5 mT, the output signal amplitude from PMT-85 does not change for all used multilayer shields. In strong magnetic field of 2-4 mT, the output signal amplitude decrease with 10%-40% depending from the number of layers in the shield. The Pulse distribution of PMT-85 in magnetic field 0.2-4 mT slightly changed in the range 1.1%-1.3% for the case when the number of layers do not exceed 10 and practically did not change for a shield with 45 double layers.

Acute and chronic effects of exposure to a 1-mT magnetic field on the cytoskeleton, stress proteins, and proliferation of astroglial cells in culture

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bodega, G.; Forcada, I.; Suarez, I.

This paper reports the effects of exposure to static, sinusoidal (50 Hz), and combined static/sinusoidal magnetic fields on cultured astroglial cells. Confluent primary cultures of astroglial cells were exposed to a 1-mT sinusoidal, static, or combined magnetic field for 1 h. In another experiment, cells were exposed to the combined magnetic field for 1, 2, and 4 h. The hsp25, hsp60, hsp70, actin, and glial fibrillary acidic protein contents of the astroglial cells were determined by immunoblotting 24 h after exposure. No significant differences were seen between control and exposed cells with respect to their contents of these proteins, neithermore » were any changes in cell morphology observed. In a third experiment to determine the effect of a chronic (11-day) exposure to a combined 1-mT static/sinusoidal magnetic field on the proliferation of cultured astroglial cells, no significant differences were seen between control, sham-exposed, or exposed cells. These results suggest that exposure to 1-mT sinusoidal, static, or combined magnetic fields has no significant effects on the stress, cytoskeletal protein levels in, or proliferation of cultured astroglial cells.« less

Contrast Enhancement in TOF cerebral angiography at 7 T using Saturation and MT pulses under SAR constraints: impact of VERSE and sparse pulses

PubMed Central

Schmitter, Sebastian; Bock, Michael; Johst, Sören; Auerbach, Edward J.; Uğurbil, Kâmil; Van de Moortele, Pierre-François

2011-01-01

Cerebral 3D time of flight (TOF) angiography significantly benefits from ultra high fields, mainly due to higher SNR and to longer T1 relaxation time of static brain tissues, however, SAR significantly increases with B0. Thus, additional RF pulses commonly used at lower field strengths to improve TOF contrast such as saturation of venous signal and improved background suppression by magnetization transfer typically cannot be used at higher fields. In this work we aimed at reducing SAR for each RF pulse category in a TOF sequence. We use the VERSE principle for the slab selective TOF excitation as well as the venous saturation RF pulses. Additionally, MT pulses are implemented by sparsely applying the pulses only during acquisition of the central k-space lines to limit their SAR contribution. Image quality, angiographic contrast and SAR reduction were investigated as a function of VERSE parameters and of the total number of MT pulses applied. Based on these results, a TOF protocol was generated that increases the angiographic contrast by more than 50% and reduces subcutaneous fat signal while keeping the resulting SAR within regulatory limits. PMID:22139829

Negative magnetic anomaly over Mt. Resnik, a subaerially erupted volcanic peak beneath the West Antarctic Ice Sheet

USGS Publications Warehouse

Behrendt, John C.; Finn, C.; Morse, D.L.; Blankenship, D.D.

2006-01-01

Mt. Resnik is one of the previously reported 18 subaerially erupted volcanoes (in the West Antarctic rift system), which have high elevation and high bed relief beneath the WAIS in the Central West Antarctica (CWA) aerogeophysical survey. Mt. Resnik lies 300 m below the surface of the West Antarctic Ice Sheet (WAIS); it has 1.6 km topographic relief, and a conical form defined by radar ice-sounding of bed topography. It has an associated complex negative magnetic anomaly revealed by the CWA survey. We calculated and interpreted magnetic models fit to the Mt. Resnik anomaly as a volcanic source comprising both reversely and normally magnetized (in the present field direction) volcanic flows, 0.5-2.5-km thick, erupted subaerially during a time of magnetic field reversal. The Mt. Resnik 305-nT anomaly is part of an approximately 50- by 40-km positive anomaly complex extending about 30 km to the west of the Mt. Resnik peak, associated with an underlying source complex of about the same area, whose top is at the bed of the WAIS. The bed relief of this shallow source complex has a maximum of only about 400 m, whereas the modeled source is >3 km thick. From the spatial relationship we interpret that this source and Mt Resnik are approximately contemporaneous. Any subglacially (older?) erupted edifices comprising hyaloclastite or other volcanic debris, which formerly overlaid the source to the west, were removed by the moving WAIS into which they were injected as is the general case for the ???1000 volcanic centers at the base of the WAIS. The presence of the magnetic field reversal modeled for Mt. Resnik may represent the Bruhnes-Matayama reversal at 780 ka (or an earlier reversal). There are ???100 short-wavelength, steep-gradient, negative magnetic anomalies observed over the West Antarctic Ice Sheet (WAIS), or about 10% of the approximately 1000 short-wavelength, shallow-source, high-amplitude (50- >1000 nT) "volcanic" magnetic anomalies in the CWA survey. These negative anomalies indicate volcanic activity during a period of magnetic reversal and therefore must also be at least 780 ka. The spatial extent and volume of volcanism can now be reassessed for the 1.2 ?? 106 km2 region of the WAIS characterized by magnetic anomalies defining interpreted volcanic centers associated with the West Antarctic rift system. The CWA covers an area of 3.54 ?? 105 km2; forty-four percent of that area exhibits short-wavelength, high-amplitude anomalies indicative of volcanic centers and subvolcanic intrusions. This equates to an area of 0.51 ?? 105 km2 and a volume of 106 km3 beneath the ice-covered West Antarctic rift system, of sufficient extent to be classified as a large igneous province interpreted to be of Oligocene to recent age.

The influence of static magnetic field (50 mT) on development and motor behaviour of Tenebrio (Insecta, Coleoptera).

PubMed

Todorović, Dajana; Marković, Tamara; Prolić, Zlatko; Mihajlović, Spomenko; Rauš, Snežana; Nikolić, Ljiljana; Janać, Branka

2013-01-01

There is considerable concern about potential effects associated with exposure to magnetic fields on organisms. Therefore, duration of pupa-adult development and motor behaviour of adults were analyzed in Tenebrio obscursus and T. molitor after exposure to static magnetic field (50 mT). The experimental groups were: Control (kept 5 m from the magnets), groups which pupae and adults were placed closer to the North pole, or closer to the South pole of magnetic dipole. The pupae were exposed to the magnetic field until the moment of adult eclosion. The pupa-adult development dynamics were recorded daily. Subsequently, behaviour (distance travelled, average speed and immobility) of adults exposed to the magnetic field was monitored in a circular open field arena. Static magnetic field did not affect pupa-adult developmental dynamic of examined Tenebrio species. Exposure to magnetic field did not significantly change motor behaviour of T. obscurus adults. The changes in the motor behaviour of T. molitor induced by static magnetic field were opposite in two experimental groups developed closer to the North pole or closer to the South pole of magnetic dipole. Static magnetic field (50 mT) did not affect on pupa-adult development dynamic of two examined Tenebrio species, but modulated their motor behaviour.

Formation of Extremely Low-mass White Dwarf Binaries

NASA Astrophysics Data System (ADS)

Sun, M.; Arras, P.

2018-05-01

Motivated by the discovery of several pulsating, extremely low-mass white dwarfs (ELM WDs, mass M ≲ 0.18 M ⊙) that likely have WD companions, this paper discusses binary formation models for these systems. ELM WDs are formed using angular momentum losses by magnetic braking. Evolutionary models are constructed using the Modules for Experiments in Stellar Astrophysics (MESA), with ELM WD progenitors in the range 1.0 ≲ M d/M ⊙ ≲ 1.5 and WD companions in the range 0.4 ≲ M a/M ⊙ ≲ 0.9. A prescription to reduce magnetic braking for thin surface convection zones is included. Upon the thinning of the evolved donor envelope, the donor star shrinks out of contact and mass transfer (MT) ceases, revealing the ELM WD. Systems with low masses have previously been suggested as possible AM CVNs. Systems with high masses, up to the limit M ≃ 0.18 M ⊙ at which shell flashes occur on the WD cooling track, tend to expand out to orbital periods P orb ≳ 15 hr. In between this range, ELM WDs may become pulsators both as pre-WDs and on the WD cooling track. Brickhill’s criterion for convective mode driving is used to estimate the location of the blue edge of the g-mode instability strip. In the appendix, we show that the formation of an ELM WD by unstable MT or a common-envelope event is unlikely. Stable Roche-lobe overflow with conservative MT produces only M ≳ 0.2 M ⊙.

Two-stage magnetic orientation of uric acid crystals as gout initiators

NASA Astrophysics Data System (ADS)

Takeuchi, Y.; Miyashita, Y.; Mizukawa, Y.; Iwasaka, M.

2014-01-01

The present study focuses on the magnetic behavior of uric acid crystals, which are responsible for gout. Under a sub-Tesla (T)-level magnetic field, rotational motion of the crystals, which were caused by diamagnetic torque, was observed. We used horizontal magnetic fields with a maximum magnitude of 500 mT generated by an electromagnet to observe the magnetic orientation of the uric acid microcrystals by a microscope. The uric acid crystals showed a perpendicular magnetic field orientation with a minimum threshold of 130 mT. We speculate that the distinct diamagnetic anisotropy in the uric acid crystals resulted in their rotational responses.

Additional mitochondrial DNA influences the interactions between the nuclear and mitochondrial genomes in a bovine embryo model of nuclear transfer.

PubMed

Srirattana, Kanokwan; St John, Justin C

2018-05-08

We generated cattle embryos using mitochondrial supplementation and somatic cell nuclear transfer (SCNT), named miNT, to determine how additional mitochondrial DNA (mtDNA) modulates the nuclear genome. To eliminate any confounding effects from somatic cell mtDNA in intraspecies SCNT, donor cell mtDNA was depleted prior to embryo production. Additional oocyte mtDNA did not affect embryo development rates but increased mtDNA copy number in blastocyst stage embryos. Moreover, miNT-derived blastocysts had different gene expression profiles when compared with SCNT-derived blastocysts. Additional mtDNA increased expression levels of genes involved in oxidative phosphorylation, cell cycle and DNA repair. Supplementing the embryo culture media with a histone deacetylase inhibitor, Trichostatin A (TSA), had no beneficial effects on the development of miNT-derived embryos, unlike SCNT-derived embryos. When compared with SCNT-derived blastocysts cultured in the presence of TSA, additional mtDNA alone had beneficial effects as the activity of glycolysis may increase and embryonic cell death may decrease. However, these beneficial effects were not found with additional mtDNA and TSA together, suggesting that additional mtDNA alone enhances reprogramming. In conclusion, additional mtDNA increased mtDNA copy number and expression levels of genes involved in energy production and embryo development in blastocyst stage embryos emphasising the importance of nuclear-mitochondrial interactions.

Magnetically-tunable rebound property for variable elastic devices made of magnetic elastomer and polyurethane foam

NASA Astrophysics Data System (ADS)

Oguro, Tsubasa; Endo, Hiroyuki; Kawai, Mika; Mitsumata, Tetsu

2017-12-01

A device consisting of a phase of magnetic elastomer, a phase of polyurethane foam (PUF), and permanent magnet was fabricated and the stress-strain curves for the two-phase magnetic elastomer were measured by a uniaxial compression measurement. A disk of magnetic elastomer was adhered on a disk of PUF by an adhesive agent. The PUF thickness was varied from 1 mm to 5 mm while the thickness of magnetic elastomers was constant at 5 mm. The stress at a strain of 0.15 for the two-phase magnetic elastomers was evaluated in the absence and in the presence of a magnetic field of 410 mT. The stress at 0 mT decreased remarkably with the PUF thickness due to the deformation of the PUF phase. On the other hand, the stress at 410 mT slightly decreased with the thickness; however, it kept high values even at high thickness. When the PUF thickness was 5 mm, the maximum stress increment with 45 times to the off-field stress was observed. An experiment using ping-pong balls demonstrated that the coefficient of restitution for the two-phase magnetic elastomers can be dramatically altered by the magnetic field.

Manipulation of permanent magnetic polymer micro-robots: a new approach towards guided wireless capsule endoscopy

NASA Astrophysics Data System (ADS)

Hilbich, D.; Rahbar, A.; Khosla, A.; Gray, B. L.

2012-10-01

We present the initial experimental results for manipulating micro-robots featuring permanent magnetic polymer magnets for guided wireless endoscopy applications. The magnetic polymers are fabricated by doping polydimethylsiloxane (PDMS) with permanent isotropic rare earth magnetic powder (MQFP 12-5) with an average particle size of 6 μm. The prepared magnetic nanocomposite polymer (M-NCP) is patterned in the desired shape against a plexiglass mold via soft lithography techniques. It is observed that the fabricated micro-robot magnets have a magnetic field strength of 50 mT and can easily be actuated by applying a field of 8.3 mT (field measured at the capsule's position) and moved at a rate of 5 inches/second.

[MRI monitoring of autologous hyaline cartilage grafts in the knee joint: a follow-up study over 12 months].

PubMed

Müller-Horvat, C; Schick, F; Claussen, C D; Grönewäller, E

2004-12-01

To evaluate the suitability of different MR sequences for monitoring the stage of maturation of hyaline cartilage grafts in the knee joint and the early detection of complications like hypertrophy. In addition, it was analyzed whether indirect MR arthrography can indicate debonding of the graft. MRI examinations were performed in 19 patients, aged 17 - 48 years, with autologous transplantation of a hyaline cartilage tissue graft after knee trauma. Examination dates were prior to transplantation to localize the defect, and 6 weeks, 3, 6 and 12 months after transplantation to control morphology and maturation of the autologous graft. Standard T2- and proton-density-weighted turbo spin echo (TSE) sequences and T1-weighted spin echo (SE) sequences were used, as well as gradient echo (GRE) sequences with and without magnetization transfer (MT) prepulses. In some cases, indirect MR arthrography was performed. Cartilage defect and the hyaline cartilage graft could be detected in all 19 patients. Hypertrophy of the graft could be found early in 3 patients and debonding in 1 patient. For depicting the graft a short time after surgery, T2-weighted TSE-sequences showed the best results. Six and 12 months after transplantation, spoiled 3D-GRE-sequences like FLASH3D (fast low angle shot) showed reduced artifacts due to magnetic residues from the surgery. Difference images from GRE-sequences with and without MT pulse provided high contrast between cartilage and surrounding tissue. The quantification of the MT effect showed an assimilation of the graft to the original cartilage within 12 months. Indirect MR arthrography showed subchondral contrast medium even 12 months after transplantation in 3 patients. MRI allows a reliable depiction of the hyaline graft and provides very early detection of complications like hypertrophy. The MT effect seems to be correlated with maturation of the graft and allows selective depiction of normal cartilage and engrafted cartilage.

Joint 3D Inversion of ZTEM Airborne and Ground MT Data with Application to Geothermal Exploration

NASA Astrophysics Data System (ADS)

Wannamaker, P. E.; Maris, V.; Kordy, M. A.

2017-12-01

ZTEM is an airborne electromagnetic (EM) geophysical technique developed by Geotech Inc® where naturally propagated EM fields originating with regional and global lightning discharges (sferics) are measured as a means of inferring subsurface electrical resistivity structure. A helicopter-borne coil platform (bird) measuring the vertical component of magnetic (H) field variations along a flown profile is referenced to a pair of horizontal coils at a fixed location on the ground in order to estimate a tensor H-field transfer function. The ZTEM method is distinct from the traditional magnetotelluric (MT) method in that the electric (E) fields are not considered because of the technological challenge of measuring E-fields in the dielectric air medium. This can lend some non-uniqueness to ZTEM interpretation because a range of conductivity structures in the earth depending upon an assumed background earth resistivity model can fit ZTEM data to within tolerance. MT data do not suffer this particular problem, but they are cumbersome to acquire in their common need for land-based transport often in near-roadless areas and for laying out and digging the electrodes and H coils. The complementary nature of ZTEM and MT logistics and resolution has motivated development of schemes to acquire appropriate amounts of each data type in a single survey and to produce an earth image through joint inversion. In particular, consideration is given to surveys where only sparse MT soundings are needed to drastically reduce the non-uniqueness associated with background uncertainty while straining logistics minimally. Synthetic and field data are analysed using 2D and 3D finite element platforms developed for this purpose. Results to date suggest that indeed dense ZTEM surveys can provide detailed heterogeneous model images with large-scale averages constrained by a modest number of MT soundings. Further research is needed in determining the allowable degree of MT sparseness and the relative weighting of the two data sets in joint inversion.

In vitro T lymphocyte adherence capabilities under the influence of lower induction values (0.1 - 0.01 mT) of 50 Hz external magnetic fields

NASA Astrophysics Data System (ADS)

Čoček, A.; Jandová, A.; Hahn, A.; Mártonová, J.; Ambruš, M.; Dohnalová, A.; Nedbalová, M.; Pokorný, J.

2011-12-01

Our research thus far has concerned the impact of external magnetic fields (50 Hz) and low (0.01-10 mT) induction on adherence capabilities of T lymphocytes obtained from the blood of patients with head and neck tumors. We know that the in vitro adherence capability of T lymphocytes towards surfaces in cancer patients is less than that of control. Previously, we have found that exposure to magnetic fields (50 Hz / 0.01-10 mT) increases the capability of T lymphocytes, in larynx/pharynx cancer patients, to adhere in vitro to surfaces, achieving almost physiological values, in not only pre-treatment patients but also those receiving treatment in the course of follow-up. The capability of T lymphocytes in controls (voluntary blood donors) to adhere to surfaces was also increased (50 Hz / 0.01-0.5 mT). The present study concentrates on the significance of the level of magnetic field induction in order to determine whether low induction values can restore T lymphocytes adherence capabilities. Testing a set of 20 patients showed a statistically significant difference (p < 0.05) in the in vitro adherence capacity of T lymphocytes between both 0.01 and 0.05, and 0.1 mT induction levels. In the control group (patients diagnosed with chronic sensorineural hearing loss) there was even a statistically significant difference between induction values of 0.05 and 0.01 mT. Therefore, we concluded that lower induction values resulted in a more biologically significant response.

Ammonia synthesis using magnetic induction method (MIM)

NASA Astrophysics Data System (ADS)

Puspitasari, P.; Razak, J. Abd; Yahya, N.

2012-09-01

The most challenging issues for ammonia synthesis is to get the high yield. New approach of ammonia synthesis by using Magnetic Induction Method (MIM) and the Helmholtz Coils has been proposed. The ammonia detection was done by using Kjeldahl Method and FTIR. The system was designed by using Autocad software. The magnetic field of MIM was vary from 100mT-200mT and the magnetic field for the Helmholtz coils was 14mT. The FTIR result shows that ammonia has been successfully formed at stretching peaks 1097,1119,1162,1236, 1377, and 1464 cm-1. UV-VIS result shows the ammonia bond at 195nm of wavelength. The ammonia yield was increase to 244.72μmole/g.h by using the MIM and six pairs of Helmholtz coils. Therefore this new method will be a new promising method to achieve the high yield ammonia at ambient condition (at 25δC and 1atm), under the Magnetic Induction Method (MIM).

Helicopter magnetic and electromagnetic surveys at Mounts Adams, Baker and Rainier, Washington: implications for debris flow hazards and volcano hydrology

USGS Publications Warehouse

Finn, Carol A.; Deszcz-Pan, Maria

2011-01-01

High‐resolution helicopter magnetic and electromagnetic (HEM) data flown over the rugged, ice‐covered Mt. Adams, Mt. Baker and Mt. Rainier volcanoes (Washington), reveal the distribution of alteration, water and ice thickness essential to evaluating volcanic landslide hazards. These data, combined with geological mapping and rock property measurements, indicate the presence of appreciable thicknesses (>500 m) of water‐saturated hydrothermally altered rock west of the modern summit of Mount Rainier in the Sunset Amphitheater region and in the central core of Mount Adams north of the summit. Alteration at Mount Baker is restricted to thinner (<300 m) zones beneath Sherman Crater and the Dorr Fumarole Fields. The EM data identified water‐saturated rocks from the surface to the detection limit (100–200 m) in discreet zones at Mt. Rainier and Mt Adams and over the entire summit region at Mt. Baker. The best estimates for ice thickness are obtained over relatively low resistivity (<800 ohm‐m) ground for the main ice cap on Mt. Adams and over most of the summit of Mt. Baker. The modeled distribution of alteration, pore fluids and partial ice volumes on the volcanoes helps identify likely sources for future alteration‐related debris flows, including the Sunset Amphitheater region at Mt. Rainier, steep cliffs at the western edge of the central altered zone at Mount Adams and eastern flanks of Mt. Baker.

Neurofunctional changes after a single mirror therapy intervention in chronic ischemic stroke.

PubMed

Novaes, Morgana M; Palhano-Fontes, Fernanda; Peres, Andre; Mazzetto-Betti, Kelley; Pelicioni, Maristela; Andrade, Kátia C; Dos Santos, Antonio Carlos; Pontes-Neto, Octavio; Araujo, Draulio

2018-03-20

Mirror therapy (MT) is becoming an alternative rehabilitation strategy for various conditions, including stroke. Although recent studies suggest the positive benefit of MT in chronic stroke motor recovery, little is known about its neural mechanisms. To identify functional brain changes induced by a single MT intervention in ischemic stroke survivors, assessed by both transcranial magnetic stimulation (TMS) and functional magnetic resonance imaging (fMRI). TMS and fMRI were used to investigate 15 stroke survivors immediately before and after a single 30-min MT session. We found statistically significant increase in post-MT motor evoked potential (MEP) amplitude (increased excitability) from the affected primary motor cortex (M1), when compared to pre-MT MEP. Post-MT fMRI maps were associated with a more organized and constrained pattern, with a more focal M1 activity within the affected hemisphere after MT, limited to the cortical area of hand representation. Furthermore, we find a change in the balance of M1 activity toward the affected hemisphere. In addition, significant correlation was found between decreased fMRI β-values and increased MEP amplitude post-MT, in the affected hemisphere. Our study suggests that a single MT intervention in stroke survivors is related to increased MEP of the affected limb, and a more constrained activity of the affected M1, as if activity had become more constrained and limited to the affected hemisphere.

Whole-Brain In-vivo Measurements of the Axonal G-Ratio in a Group of 37 Healthy Volunteers

PubMed Central

Mohammadi, Siawoosh; Carey, Daniel; Dick, Fred; Diedrichsen, Joern; Sereno, Martin I.; Reisert, Marco; Callaghan, Martina F.; Weiskopf, Nikolaus

2015-01-01

The g-ratio, quantifying the ratio between the inner and outer diameters of a fiber, is an important microstructural characteristic of fiber pathways and is functionally related to conduction velocity. We introduce a novel method for estimating the MR g-ratio non-invasively across the whole brain using high-fidelity magnetization transfer (MT) imaging and single-shell diffusion MRI. These methods enabled us to map the MR g-ratio in vivo across the brain's prominent fiber pathways in a group of 37 healthy volunteers and to estimate the inter-subject variability. Effective correction of susceptibility-related distortion artifacts was essential before combining the MT and diffusion data, in order to reduce partial volume and edge artifacts. The MR g-ratio is in good qualitative agreement with histological findings despite the different resolution and spatial coverage of MRI and histology. The MR g-ratio holds promise as an important non-invasive biomarker due to its microstructural and functional relevance in neurodegeneration. PMID:26640427

Efficiency of cellular growth when creating small pockets of electric current along the walls of cells.

PubMed

Kletetschka, Gunther; Zila, Vojtech; Klimova, Lucie

2014-04-01

Pulses up to 11 Tesla magnetic fields may generate pockets of currents along the walls of cellular material and may interfere with the overall ability of cell division. We used prokaryotic cells (Escherichia coli) and eukaryotic cells (murine fibroblasts) and exposed them to magnetic pulses of intensities ranging from 1 millitesla (mT) to 11,000 mT. We found prokaryotic cells to be more sensitive to magnetic field pulses than eukaryotic cells.

Cytoplasmic transfer of heritable elements other than mtDNA from SAMP1 mice into mouse tumor cells suppresses their ability to form tumors in C57BL6 mice.

PubMed

Shimizu, Akinori; Tani, Haruna; Takibuchi, Gaku; Ishikawa, Kaori; Sakurazawa, Ryota; Inoue, Takafumi; Hashimoto, Tetsuo; Nakada, Kazuto; Takenaga, Keizo; Hayashi, Jun-Ichi

2017-11-04

In a previous study, we generated transmitochondrial P29mtSAMP1 cybrids, which had nuclear DNA from the C57BL6 (referred to as B6) mouse strain-derived P29 tumor cells and mitochondrial DNA (mtDNA) exogenously-transferred from the allogeneic strain SAMP1. Because P29mtSAMP1 cybrids did not form tumors in syngeneic B6 mice, we proposed that allogeneic SAMP1 mtDNA suppressed tumor formation of P29mtSAMP1 cybrids. To test this hypothesis, current study generated P29mt(sp)B6 cybrids carrying all genomes (nuclear DNA and mtDNA) from syngeneic B6 mice by eliminating SAMP1 mtDNA from P29mtSAMP1 cybrids and reintroducing B6 mtDNA. However, the P29mt(sp)B6 cybrids did not form tumors in B6 mice, even though they had no SAMP1 mtDNA, suggesting that SAMP1 mtDNA is not involved in tumor suppression. Then, we examined another possibility of whether SAMP1 mtDNA fragments potentially integrated into the nuclear DNA of P29mtSAMP1 cybrids are responsible for tumor suppression. We generated P29 H (sp)B6 cybrids by eliminating nuclear DNA from P29mt(sp)B6 cybrids and reintroducing nuclear DNA with no integrated SAMP1 mtDNA fragment from mtDNA-less P29 cells resistant to hygromycin in selection medium containing hygromycin. However, the P29 H (sp)B6 cybrids did not form tumors in B6 mice, even though they carried neither SAMP1 mtDNA nor nuclear DNA with integrated SAMP1 mtDNA fragments. Moreover, overproduction of reactive oxygen species (ROS) and bacterial infection were not involved in tumor suppression. These observations suggest that tumor suppression was caused not by mtDNA with polymorphic mutations or infection of cytozoic bacteria but by hypothetical heritable cytoplasmic elements other than mtDNA from SAMP1 mice. Copyright © 2017 The Authors. Published by Elsevier Inc. All rights reserved.

Phospholipid bilayer relaxation dynamics as revealed by the pulsed electron-electron double resonance of spin labels

NASA Astrophysics Data System (ADS)

Syryamina, V. N.; Dzuba, S. A.

2012-10-01

Electron paramagnetic resonance (EPR) spectroscopy in the form of pulsed electron-electron double resonance (ELDOR) was applied to 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) phospholipid bilayers containing lipids that were spin-labeled at different carbon positions along the lipid acyl chain. Pulsed ELDOR detects motionally induced spin flips of nitrogen nuclei in the nitroxide spin labels, which manifests itself as magnetization transfer (MT) in the nitroxide EPR spectrum. The MT effect was observed over a wide temperature range (100-225 K) on a microsecond time scale. In line with a previous study on molecular glasses [N. P. Isaev and S. A. Dzuba, J. Chem. Phys. 135, 094508 (2011), 10.1063/1.3633241], the motions that induce MT effect were suggested to have the same nature as those in dielectric secondary (β) Johari-Goldstein fast relaxation. The results were compared with literature dielectric relaxation data for POPC bilayers, revealing some common features. Molecular motions resulting in MT are faster for deeper spin labels in the membrane interior. The addition of cholesterol to the bilayer suppresses the lipid motions near the steroid nucleus and accelerates the lipid motions beyond the steroid nucleus, in the bilayer interior. This finding was attributed to the lipid acyl chains being more ordered near the steroid nucleus and less ordered in the bilayer interior. The motions are absent in dry lipids, indicating that the motions are determined by intermolecular interactions in the bilayer.

Clinical Outcome After Mechanical Thrombectomy in Non-elderly Patients with Acute Ischemic Stroke in the Anterior Circulation: Primary Admission Versus Patients Referred from Remote Hospitals.

PubMed

Pfaff, J; Pham, M; Herweh, C; Wolf, M; Ringleb, P A; Schönenberger, S; Bendszus, M; Möhlenbruch, M

2017-06-01

Stroke networks have been installed to increase access to advanced stroke specific treatments like mechanical thrombectomy (MT). This concept often requires patients to be transferred to a comprehensive stroke center (CSC) offering MT. Do patient referral, transportation, and logistic effort translate into clinical outcomes comparable to patients admitted primarily to the CSC? We categorized 112 patients with acute ischemic stroke in the anterior circulation, who received MT at our institution, into primary admissions (A) and referrals from either local (B) or regional (C) hospitals, assessed the clinical outcome, and tested the impact of distance and delay of transportation from the referring remote hospital. The median time from symptom onset to initial CT was similar in all groups (p = 0,939). Patients who were transferred to the CSC had significantly increasing median time between initial CT and MT (in minutes (interquartile range [IQR]); A: 83 [68-120]; B: 174 [159-208]; C: 220 [181-235]; p < 0.001) and median time between onset to MT (in minutes [IQR]; A: 178 [150-210]; B: 274 [238-349]; C: 293 [256-329]; p < 0.001). After 90 days of MT there was no significant difference in clinical outcome (modified Rankin Scale ≤ 2) between primary admitted and referred patients (p = 0.502). Clinical outcome in patients who received MT after transfer from either local or regional remote hospitals was not significantly worse than in patients primarily admitted to the CSC. In the event of an acute ischemic stroke patients living in urban or rural areas should, despite a possible delay, have access to MT.

[Measurements of the flux densities of static magnetic fields generated by two types of dental magnetic attachments and their retentive forces].

PubMed

Xu, Chun; Chao, Yong-lie; Du, Li; Yang, Ling

2004-05-01

To measure and analyze the flux densities of static magnetic fields generated by two types of commonly used dental magnetic attachments and their retentive forces, and to provide guidance for the clinical application of magnetic attachments. A digital Gaussmeter was used to measure the flux densities of static magnetic fields generated by two types of magnetic attachments, under four circumstances: open-field circuit; closed-field circuit; keeper and magnet slid laterally for a certain distance; and existence of air gap between keeper and magnet. The retentive forces of the magnetic attachments in standard closed-field circuit, with the keeper and magnet sliding laterally for a certain distance or with a certain air gap between keeper and magnet were measured by a tensile testing machine. There were flux leakages under both the open-field circuit and closed-field circuit of the two types of magnetic attachments. The flux densities on the surfaces of MAGNEDISC 800 (MD800) and MAGFIT EX600W (EX600) magnetic attachments under open-field circuit were 275.0 mT and 147.0 mT respectively. The flux leakages under closed-field circuit were smaller than those under open-field circuit. The respective flux densities on the surfaces of MD800 and EX600 magnetic attachments decreased to 11.4 mT and 4.5 mT under closed-field circuit. The flux density around the magnetic attachment decreased as the distance from the surface of the attachment increased. When keeper and magnet slid laterally for a certain distance or when air gap existed between keeper and magnet, the flux leakage increased in comparison with that under closed-field circuit. Under the standard closed-field circuit, the two types of magnetic attachments achieved the largest retentive forces. The retentive forces of MD800 and EX600 magnetic attachments under the standard closed-field circuit were 6.20 N and 4.80 N respectively. The retentive forces decreased with the sliding distance or with the increase of air gap between keeper and magnet. The magnetic attachments have flux leakages. When they are used in patients' oral cavities, if keeper and magnet are not attached accurately, the flux leakage will increase, and at the same time the retentive force will decrease. Therefore the keeper and magnet should be attached accurately in clinical application.

No evidence of persisting unrepaired nuclear DNA single strand breaks in distinct types of cells in the brain, kidney, and liver of adult mice after continuous eight-week 50 Hz magnetic field exposure with flux density of 0.1 mT or 1.0 mT.

PubMed

Korr, Hubert; Angstman, Nicholas B; Born, Tatjana B; Bosse, Kerstin; Brauns, Birka; Demmler, Martin; Fueller, Katja; Kántor, Orsolya; Kever, Barbara M; Rahimyar, Navida; Salimi, Sepideh; Silny, Jiri; Schmitz, Christoph

2014-01-01

It has been hypothesized in the literature that exposure to extremely low frequency electromagnetic fields (50 or 60 Hz) may lead to human health effects such as childhood leukemia or brain tumors. In a previous study investigating multiple types of cells from brain and kidney of the mouse (Acta Neuropathologica 2004; 107: 257-264), we found increased unrepaired nuclear DNA single strand breaks (nDNA SSB) only in epithelial cells of the choroid plexus in the brain using autoradiographic methods after a continuous eight-week 50 Hz magnetic field (MF) exposure of adult mice with flux density of 1.5 mT. In the present study we tested the hypothesis that MF exposure with lower flux densities (0.1 mT, i.e., the actual exposure limit for the population in most European countries, and 1.0 mT) shows similar results to those in the previous study. Experiments and data analysis were carried out in a similar way as in our previous study. Continuous eight-week 50 Hz MF exposure with 0.1 mT or 1.0 mT did not result in increased persisting unrepaired nDNA SSB in distinct types of cells in the brain, kidney, and liver of adult mice. MF exposure with 1.0 mT led to reduced unscheduled DNA synthesis (UDS) in epithelial cells in the choroid plexus of the fourth ventricle in the brain (EC-CP) and epithelial cells of the cortical collecting duct in the kidney, as well as to reduced mtDNA synthesis in neurons of the caudate nucleus in the brain and in EC-CP. No evidence was found for increased persisting unrepaired nDNA SSB in distinct types of cells in the brain, kidney, and liver of adult mice after continuous eight-week 50 Hz magnetic field exposure with flux density of 0.1 mT or 1.0 mT.

Magnetic Field Measurements Based on Terfenol Coated Photonic Crystal Fibers

PubMed Central

Quintero, Sully M. M.; Martelli, Cicero; Braga, Arthur M. B.; Valente, Luiz C. G.; Kato, Carla C.

2011-01-01

A magnetic field sensor based on the integration of a high birefringence photonic crystal fiber and a composite material made of Terfenol particles and an epoxy resin is proposed. An in-fiber modal interferometer is assembled by evenly exciting both eigenemodes of the HiBi fiber. Changes in the cavity length as well as the effective refractive index are induced by exposing the sensor head to magnetic fields. The magnetic field sensor has a sensitivity of 0.006 (nm/mT) over a range from 0 to 300 mT with a resolution about ±1 mT. A fiber Bragg grating magnetic field sensor is also fabricated and employed to characterize the response of Terfenol composite to the magnetic field. PMID:22247655

Effect of mirror therapy combined with somatosensory stimulation on motor recovery and daily function in stroke patients: A pilot study.

PubMed

Lin, Keh-Chung; Chen, Yu-Ting; Huang, Pai-Chuan; Wu, Ching-Yi; Huang, Wen-Ling; Yang, Hsiu-Wen; Lai, Hui-Tsz; Lu, Hung-Ju

2014-07-01

Mirror therapy (MT) has been recommended as a simple, inexpensive approach to treat motor dysfunction. The use of a mesh glove (MG) was suggested to normalize muscle tone that ameliorates motor impairment. Combining two efficient treatment protocols might maximize the benefits from training. This study investigated the effects of MT combined with MG (MG + MT) versus MT alone on motor performance and daily function after stroke. Sixteen patients with chronic unilateral stroke were recruited. A randomized two-group pretest and posttest design was used to randomly assign participants to MG + MT or MT groups. MT involves repetitive bimanual, symmetrical movement practice in which the individual moves the affected limb as much as she/he could while watching the reflective illusion of the unaffected limb's movements from a mirror. The MG + MT group wore a MG on the affected hand during the MT. The Modified Ashworth scale of muscle spasticity (MAS), Action Research Arm Test (ARAT), Box and Block Test (BBT), and Functional Independence Measure (FIM) were administered to evaluate spasticity, and motor and daily function. The results for the BBT (p = 0.013), total scores (p = 0.031), grasping subscales (p = 0.036) of ARAT, and FIM transfer scores (p = 0.013) presented significantly large effects in favor of the MG + MT group. Combining MG with MT significantly improves manual dexterity, grasping, and transfer performance. Adding the MG component into the MT likely increased the richness of sensory input and improved the movement performance more than MT alone. Copyright © 2012. Published by Elsevier B.V.

Quantitative description of proton exchange processes between water and endogenous and exogenous agents for WEX, CEST, and APT experiments.

PubMed

Zhou, Jinyuan; Wilson, David A; Sun, Phillip Zhe; Klaus, Judith A; Van Zijl, Peter C M

2004-05-01

The proton exchange processes between water and solutes containing exchangeable protons have recently become of interest for monitoring pH effects, detecting cellular mobile proteins and peptides, and enhancing the detection sensitivity of various low-concentration endogenous and exogenous species. In this work, the analytic expressions for water exchange (WEX) filter spectroscopy, chemical exchange-dependent saturation transfer (CEST), and amide proton transfer (APT) experiments are derived by the use of Bloch equations with exchange terms. The effects of the initial states for the system, the difference between a steady state and a saturation state, and the relative contributions of the forward and backward exchange processes are discussed. The theory, in combination with numerical calculations, provides a useful tool for designing experimental schemes and assessing magnetization transfer (MT) processes between water protons and solvent-exchangeable protons. As an example, the case of endogenous amide proton exchange in the rat brain at 4.7 T is analyzed in detail. Copyright 2004 Wiley-Liss, Inc.

Rock Magnetic Properties, Paleosecular Variation Record and Relative Paleointensity Stack between 11 and 21 14C kyr B.P. From Sediment Cores, Lake Moreno (Argentina)

NASA Astrophysics Data System (ADS)

Gogorza, C. S.; Irurzun, M. A.; Lirio, J. M.; Nunez, H.; Chaparro, M. A.; Sinito, A. M.

2008-05-01

We conducted a detailed study of natural remanence and rock magnetic properties on sediments cores from lake Moreno (South-Western Argentina). Based on these measurements, we constructed a paleosecular variation (PSV) record (Irurzun et al., 2008) and a relative paleointensity stack for the period 11-21 14C. The Declination and Inclination logs of the characteristic remanent magnetization for the cores as function of shortened depth are obtained. The data from all cores were combined to obtain a composite record using the Fisher method. Comparison between stacked inclination and declination records of lake Moreno and results obtained in previous works, lake Escondido (Gogorza et al., 1999; Gogorza et al., 2002) and lake El Trébol (Irurzun et al., 2008), shows good agreement. This agreement made possible to transform the stacked curves into time series that spans the interval 11 and 21 14C kyr B.P. Rock magnetic properties of the sediments cores showed uniform magnetic mineralogy and grain size, suggesting that they were suitable for relative paleointensity studies. The remanent magnetization at 20mT (NRM20mT) was normalized using the anhysteric remanent magnetization at 20mT (ARM20mT), the saturation of the isothermal remanent magnetization at 20mT (SIRM20mT) and the low field magnetic susceptibility {k}. Coherence analysis showed that the normalized records were not affected by local environmental conditions. The recorded pseudo-Thellier paleointensity was compared with records obtained from conventional normalizing methods. Comparing the paleointensity curves with others obtained previously in other lakes in the area has allowed us to reach reliable conclusions about centennial-scale features. References: Gogorza, C.S.G., Sinito, A.M., Di Tommaso, I., Vilas, J.F., Creer, K., Núnez, H. Holocene Geomagnetic Secular Variations Recorded by Sediments from Escondido lake (South Argentina). Earth, Planets and Space, V51(2), 93- 106. 1999. Gogorza, C.S.G., Sinito, A.M., Lirio, J.M., Núnez, H., Chaparro, M.A.E., Vilas, J.F. Paleosecular Variations 0- 19,000 Years Recorded by Sediments from Escondido lake (Argentina). Physical of the Earth and Planetary Interiors, Elsevier, V133(1-4), 35-55. 2002. Irurzun, M.A., Gogorza, C.S.G., Sinito, A.M., Chaparro, M.A.E., Nuñez, H., Lirio, J.M. Paleosecular Variations 12-20 kyr. as Recorded by Sediments From lake Moreno (Southern Argentina). Studia Geophysica et Geodaetica. In Press. 2008.

Gigantic transverse x-ray magnetic circular dichroism in ultrathin Co in Au/Co/Au(001)

NASA Astrophysics Data System (ADS)

Koide, T.; Mamiya, K.; Asakura, D.; Osatune, Y.; Fujimori, A.; Suzuki, Y.; Katayama, T.; Yuasa, S.

2014-04-01

Transverse-geometry x-ray magnetic circular dichroism (TXMCD) measurements on Au/Co-staircase/Au(001) reveal the orbital origin of intrinsic in-plane magnetic anisotropy A gigantic TXMCD was successfully observed at the Co L3,2 edges for Co thickness (tC0) in the 2-monolayer regime. A TXMCD-sum-rule analysis shows a remarkable enhancement of an orbital-moment anisotropy (Δmorb) and of an in-plane magnetic dipole moment (m||T). Both Δmorb and m||T exhibit close similarity in tCo dependence, reflecting the in-plane magnetic anisotropy These observations evidence that extremely strong, intrinsic, in-plane magnetic anisotropy originates from the anisotropic orbital part of the wave function, dominating the dipole-dipole-interaction-derived, extrinsic, in-plane magnetic anisotropy.

Phylogeny and temporal diversification of darters (Percidae: Etheostomatinae).

PubMed

Near, Thomas J; Bossu, Christen M; Bradburd, Gideon S; Carlson, Rose L; Harrington, Richard C; Hollingsworth, Phillip R; Keck, Benjamin P; Etnier, David A

2011-10-01

Discussions aimed at resolution of the Tree of Life are most often focused on the interrelationships of major organismal lineages. In this study, we focus on the resolution of some of the most apical branches in the Tree of Life through exploration of the phylogenetic relationships of darters, a species-rich clade of North American freshwater fishes. With a near-complete taxon sampling of close to 250 species, we aim to investigate strategies for efficient multilocus data sampling and the estimation of divergence times using relaxed-clock methods when a clade lacks a fossil record. Our phylogenetic data set comprises a single mitochondrial DNA (mtDNA) gene and two nuclear genes sampled from 245 of the 248 darter species. This dense sampling allows us to determine if a modest amount of nuclear DNA sequence data can resolve relationships among closely related animal species. Darters lack a fossil record to provide age calibration priors in relaxed-clock analyses. Therefore, we use a near-complete species-sampled phylogeny of the perciform clade Centrarchidae, which has a rich fossil record, to assess two distinct strategies of external calibration in relaxed-clock divergence time estimates of darters: using ages inferred from the fossil record and molecular evolutionary rate estimates. Comparison of Bayesian phylogenies inferred from mtDNA and nuclear genes reveals that heterospecific mtDNA is present in approximately 12.5% of all darter species. We identify three patterns of mtDNA introgression in darters: proximal mtDNA transfer, which involves the transfer of mtDNA among extant and sympatric darter species, indeterminate introgression, which involves the transfer of mtDNA from a lineage that cannot be confidently identified because the introgressed haplotypes are not clearly referable to mtDNA haplotypes in any recognized species, and deep introgression, which is characterized by species diversification within a recipient clade subsequent to the transfer of heterospecific mtDNA. The results of our analyses indicate that DNA sequences sampled from single-copy nuclear genes can provide appreciable phylogenetic resolution for closely related animal species. A well-resolved near-complete species-sampled phylogeny of darters was estimated with Bayesian methods using a concatenated mtDNA and nuclear gene data set with all identified heterospecific mtDNA haplotypes treated as missing data. The relaxed-clock analyses resulted in very similar posterior age estimates across the three sampled genes and methods of calibration and therefore offer a viable strategy for estimating divergence times for clades that lack a fossil record. In addition, an informative rank-free clade-based classification of darters that preserves the rich history of nomenclature in the group and provides formal taxonomic communication of darter clades was constructed using the mtDNA and nuclear gene phylogeny. On the whole, the appeal of mtDNA for phylogeny inference among closely related animal species is diminished by the observations of extensive mtDNA introgression and by finding appreciable phylogenetic signal in a modest sampling of nuclear genes in our phylogenetic analyses of darters.

In Situ and Ex Situ Low-Field NMR Spectroscopy and MRI Endowed by SABRE Hyperpolarization**

PubMed Central

Barskiy, Danila A.; Kovtunov, Kirill V.; Koptyug, Igor V.; He, Ping; Groome, Kirsten A.; Best, Quinn A.; Shi, Fan; Goodson, Boyd M.; Shchepin, Roman V.; Truong, Milton L.; Coffey, Aaron M.; Waddell, Kevin W.; Chekmenev, Eduard Y.

2015-01-01

By using 5.75 and 47.5 mT nuclear magnetic resonance (NMR) spectroscopy, up to 105-fold sensitivity enhancement through signal amplification by reversible exchange (SABRE) was enabled, and subsecond temporal resolution was used to monitor an exchange reaction that resulted in the buildup and decay of hyperpolarized species after parahydrogen bubbling. We demonstrated the high-resolution low-field proton magnetic resonance imaging (MRI) of pyridine in a 47.5 mT magnetic field endowed by SABRE. Molecular imaging (i.e. imaging of dilute hyperpolarized substances rather than the bulk medium) was conducted in two regimes: in situ real-time MRI of the reaction mixture (in which pyridine was hyperpolarized), and ex situ MRI (in which hyperpolarization decays) of the liquid hyperpolarized product. Low-field (milli-Tesla range, e.g. 5.75 and 47.5 mT used in this study) parahydrogen-enhanced NMR and MRI, which are free from the limitations of high-field magnetic resonance (including susceptibility-induced gradients of the static magnetic field at phase interfaces), potentially enables new imaging applications as well as differentiation of hyperpolarized chemical species on demand by exploiting spin manipulations with static and alternating magnetic fields. PMID:25367202

Influence of volume magnetostriction on the thermodynamic properties of Ni-Mn-Ga shape memory alloys

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kosogor, Anna; Institute of Magnetism, 36-b, Vernadsky Str., Kyiv 03142; Donetsk Institute for Physics and Engineering, Kyiv 03028

2015-10-07

In the present article, the thermodynamic properties of Ni-Mn-Ga ferromagnetic shape memory alloys exhibiting the martensitic transformations (MTs) above and below Curie temperature are compared. It is shown that when MT goes below Curie temperature, the elastic and thermal properties of alloy noticeably depend on magnetization value due to spontaneous volume magnetostriction. However, the separation of magnetic parts from the basic characteristics of MT is a difficult task, because the volume magnetostriction does not qualitatively change the transformational behaviour of alloy. This problem is solved for several Ni-Mn-Ga alloys by means of the quantitative theoretical analysis of experimental data obtainedmore » in the course of stress-strain tests. For each alloy, the entropy change and the transformation heat evolved in the course of MT are evaluated, first, from the results of stress-strain tests and, second, from differential scanning calorimetry data. For all alloys, a quantitative agreement between the values obtained in two different ways is observed. It is shown that the magnetic part of transformation heat exceeds the non-magnetic one for the Ni-Mn-Ga alloys undergoing MTs in ferromagnetic state, while the elevated values of transformation heat measured for the alloys undergoing MTs in paramagnetic state are caused by large MT strains.« less

Influence of volume magnetostriction on the thermodynamic properties of Ni-Mn-Ga shape memory alloys

NASA Astrophysics Data System (ADS)

Kosogor, Anna; L'vov, Victor A.; Cesari, Eduard

2015-10-01

In the present article, the thermodynamic properties of Ni-Mn-Ga ferromagnetic shape memory alloys exhibiting the martensitic transformations (MTs) above and below Curie temperature are compared. It is shown that when MT goes below Curie temperature, the elastic and thermal properties of alloy noticeably depend on magnetization value due to spontaneous volume magnetostriction. However, the separation of magnetic parts from the basic characteristics of MT is a difficult task, because the volume magnetostriction does not qualitatively change the transformational behaviour of alloy. This problem is solved for several Ni-Mn-Ga alloys by means of the quantitative theoretical analysis of experimental data obtained in the course of stress-strain tests. For each alloy, the entropy change and the transformation heat evolved in the course of MT are evaluated, first, from the results of stress-strain tests and, second, from differential scanning calorimetry data. For all alloys, a quantitative agreement between the values obtained in two different ways is observed. It is shown that the magnetic part of transformation heat exceeds the non-magnetic one for the Ni-Mn-Ga alloys undergoing MTs in ferromagnetic state, while the elevated values of transformation heat measured for the alloys undergoing MTs in paramagnetic state are caused by large MT strains.

Negative hydrogen ion production in a helicon plasma source

NASA Astrophysics Data System (ADS)

Santoso, J.; Manoharan, R.; O'Byrne, S.; Corr, C. S.

2015-09-01

In order to develop very high energy (>1 MeV) neutral beam injection systems for applications, such as plasma heating in fusion devices, it is necessary first to develop high throughput negative ion sources. For the ITER reference source, this will be realised using caesiated inductively coupled plasma devices, containing either hydrogen or deuterium discharges, operated with high rf input powers (up to 90 kW per driver). It has been suggested that due to their high power coupling efficiency, helicon devices may be able to reduce power requirements and potentially obviate the need for caesiation due to the high plasma densities achievable. Here, we present measurements of negative ion densities in a hydrogen discharge produced by a helicon device, with externally applied DC magnetic fields ranging from 0 to 8.5 mT at 5 and 10 mTorr fill pressures. These measurements were taken in the magnetised plasma interaction experiment at the Australian National University and were performed using the probe-based laser photodetachment technique, modified for the use in the afterglow of the plasma discharge. A peak in the electron density is observed at ˜3 mT and is correlated with changes in the rf power transfer efficiency. With increasing magnetic field, an increase in the negative ion fraction from 0.04 to 0.10 and negative ion densities from 8 × 1014 m-3 to 7 × 1015 m-3 is observed. It is also shown that the negative ion densities can be increased by a factor of 8 with the application of an external DC magnetic field.

Removal of hexavalent chromium from wastewater using PPy/Fe3O4 magnetic nanocomposite influenced by rotating magnetic field from two pole three-phase induction motor

NASA Astrophysics Data System (ADS)

Aigbe, U. O.; Ho, W. H.; Maity, A.; Khenfouch, M.; Srinivasu, V.

2018-03-01

The influence of varying rotating magnetic field using a 2-pole three-phase induction motor on the removal of hexavalent chromium ions from wastewater using polypyrrole magnetic nanocomposite was explored in this study. Hexavalent chromium removal in this study was observed to be pH dependent under the influence of rotating magnetic field, as the percentage removal of hexavalent chromium decreased with increase in pH. The percentage amount of hexavalent chromium ions removed from the aqueous solution increased as the rotating magnetic field intensity was increased from 8.96-12.15 mT in the anticlockwise direction and 10.10-13.38 mT in the clockwise direction with maximum removals of 73% and 81% observed.

Interhospital Transfer Before Thrombectomy Is Associated With Delayed Treatment and Worse Outcome in the STRATIS Registry (Systematic Evaluation of Patients Treated With Neurothrombectomy Devices for Acute Ischemic Stroke)

PubMed Central

Saver, Jeffrey L.; Zaidat, Osama O.; Jahan, Reza; Aziz-Sultan, Mohammad Ali; Klucznik, Richard P.; Haussen, Diogo C.; Hellinger, Frank R.; Yavagal, Dileep R.; Yao, Tom L.; Liebeskind, David S.; Jadhav, Ashutosh P.; Gupta, Rishi; Hassan, Ameer E.; Martin, Coleman O.; Bozorgchami, Hormozd; Kaushal, Ritesh; Nogueira, Raul G.; Gandhi, Ravi H.; Peterson, Eric C.; Dashti, Shervin R.; Given, Curtis A.; Mehta, Brijesh P.; Deshmukh, Vivek; Starkman, Sidney; Linfante, Italo; McPherson, Scott H.; Kvamme, Peter; Grobelny, Thomas J.; Hussain, Muhammad S.; Thacker, Ike; Vora, Nirav; Chen, Peng Roc; Monteith, Stephen J.; Ecker, Robert D.; Schirmer, Clemens M.; Sauvageau, Eric; Abou-Chebl, Alex; Derdeyn, Colin P.; Maidan, Lucian; Badruddin, Aamir; Siddiqui, Adnan H.; Dumont, Travis M.; Alhajeri, Abdulnasser; Taqi, M. Asif; Asi, Khaled; Carpenter, Jeffrey; Boulos, Alan; Jindal, Gaurav; Puri, Ajit S.; Chitale, Rohan; Deshaies, Eric M.; Robinson, David H.; Kallmes, David F.; Baxter, Blaise W.; Jumaa, Mouhammad A.; Sunenshine, Peter; Majjhoo, Aniel; English, Joey D.; Suzuki, Shuichi; Fessler, Richard D.; Delgado Almandoz, Josser E.; Martin, Jerry C.; Mueller-Kronast, Nils H.

2017-01-01

Background: Endovascular treatment with mechanical thrombectomy (MT) is beneficial for patients with acute stroke suffering a large-vessel occlusion, although treatment efficacy is highly time-dependent. We hypothesized that interhospital transfer to endovascular-capable centers would result in treatment delays and worse clinical outcomes compared with direct presentation. Methods: STRATIS (Systematic Evaluation of Patients Treated With Neurothrombectomy Devices for Acute Ischemic Stroke) was a prospective, multicenter, observational, single-arm study of real-world MT for acute stroke because of anterior-circulation large-vessel occlusion performed at 55 sites over 2 years, including 1000 patients with severe stroke and treated within 8 hours. Patients underwent MT with or without intravenous tissue plasminogen activator and were admitted to endovascular-capable centers via either interhospital transfer or direct presentation. The primary clinical outcome was functional independence (modified Rankin Score 0–2) at 90 days. We assessed (1) real-world time metrics of stroke care delivery, (2) outcome differences between direct and transfer patients undergoing MT, and (3) the potential impact of local hospital bypass. Results: A total of 984 patients were analyzed. Median onset-to-revascularization time was 202.0 minutes for direct versus 311.5 minutes for transfer patients (P<0.001). Clinical outcomes were better in the direct group, with 60.0% (299/498) achieving functional independence compared with 52.2% (213/408) in the transfer group (odds ratio, 1.38; 95% confidence interval, 1.06–1.79; P=0.02). Likewise, excellent outcome (modified Rankin Score 0–1) was achieved in 47.4% (236/498) of direct patients versus 38.0% (155/408) of transfer patients (odds ratio, 1.47; 95% confidence interval, 1.13–1.92; P=0.005). Mortality did not differ between the 2 groups (15.1% for direct, 13.7% for transfer; P=0.55). Intravenous tissue plasminogen activator did not impact outcomes. Hypothetical bypass modeling for all transferred patients suggested that intravenous tissue plasminogen activator would be delayed by 12 minutes, but MT would be performed 91 minutes sooner if patients were routed directly to endovascular-capable centers. If bypass is limited to a 20-mile radius from onset, then intravenous tissue plasminogen activator would be delayed by 7 minutes and MT performed 94 minutes earlier. Conclusions: In this large, real-world study, interhospital transfer was associated with significant treatment delays and lower chance of good outcome. Strategies to facilitate more rapid identification of large-vessel occlusion and direct routing to endovascular-capable centers for patients with severe stroke may improve outcomes. Clinical Trial Registration: URL: https://www.clinicaltrials.gov. Unique identifier: NCT02239640. PMID:28943516

Interhospital Transfer Before Thrombectomy Is Associated With Delayed Treatment and Worse Outcome in the STRATIS Registry (Systematic Evaluation of Patients Treated With Neurothrombectomy Devices for Acute Ischemic Stroke).

PubMed

Froehler, Michael T; Saver, Jeffrey L; Zaidat, Osama O; Jahan, Reza; Aziz-Sultan, Mohammad Ali; Klucznik, Richard P; Haussen, Diogo C; Hellinger, Frank R; Yavagal, Dileep R; Yao, Tom L; Liebeskind, David S; Jadhav, Ashutosh P; Gupta, Rishi; Hassan, Ameer E; Martin, Coleman O; Bozorgchami, Hormozd; Kaushal, Ritesh; Nogueira, Raul G; Gandhi, Ravi H; Peterson, Eric C; Dashti, Shervin R; Given, Curtis A; Mehta, Brijesh P; Deshmukh, Vivek; Starkman, Sidney; Linfante, Italo; McPherson, Scott H; Kvamme, Peter; Grobelny, Thomas J; Hussain, Muhammad S; Thacker, Ike; Vora, Nirav; Chen, Peng Roc; Monteith, Stephen J; Ecker, Robert D; Schirmer, Clemens M; Sauvageau, Eric; Abou-Chebl, Alex; Derdeyn, Colin P; Maidan, Lucian; Badruddin, Aamir; Siddiqui, Adnan H; Dumont, Travis M; Alhajeri, Abdulnasser; Taqi, M Asif; Asi, Khaled; Carpenter, Jeffrey; Boulos, Alan; Jindal, Gaurav; Puri, Ajit S; Chitale, Rohan; Deshaies, Eric M; Robinson, David H; Kallmes, David F; Baxter, Blaise W; Jumaa, Mouhammad A; Sunenshine, Peter; Majjhoo, Aniel; English, Joey D; Suzuki, Shuichi; Fessler, Richard D; Delgado Almandoz, Josser E; Martin, Jerry C; Mueller-Kronast, Nils H

2017-12-12

Endovascular treatment with mechanical thrombectomy (MT) is beneficial for patients with acute stroke suffering a large-vessel occlusion, although treatment efficacy is highly time-dependent. We hypothesized that interhospital transfer to endovascular-capable centers would result in treatment delays and worse clinical outcomes compared with direct presentation. STRATIS (Systematic Evaluation of Patients Treated With Neurothrombectomy Devices for Acute Ischemic Stroke) was a prospective, multicenter, observational, single-arm study of real-world MT for acute stroke because of anterior-circulation large-vessel occlusion performed at 55 sites over 2 years, including 1000 patients with severe stroke and treated within 8 hours. Patients underwent MT with or without intravenous tissue plasminogen activator and were admitted to endovascular-capable centers via either interhospital transfer or direct presentation. The primary clinical outcome was functional independence (modified Rankin Score 0-2) at 90 days. We assessed (1) real-world time metrics of stroke care delivery, (2) outcome differences between direct and transfer patients undergoing MT, and (3) the potential impact of local hospital bypass. A total of 984 patients were analyzed. Median onset-to-revascularization time was 202.0 minutes for direct versus 311.5 minutes for transfer patients ( P <0.001). Clinical outcomes were better in the direct group, with 60.0% (299/498) achieving functional independence compared with 52.2% (213/408) in the transfer group (odds ratio, 1.38; 95% confidence interval, 1.06-1.79; P =0.02). Likewise, excellent outcome (modified Rankin Score 0-1) was achieved in 47.4% (236/498) of direct patients versus 38.0% (155/408) of transfer patients (odds ratio, 1.47; 95% confidence interval, 1.13-1.92; P =0.005). Mortality did not differ between the 2 groups (15.1% for direct, 13.7% for transfer; P =0.55). Intravenous tissue plasminogen activator did not impact outcomes. Hypothetical bypass modeling for all transferred patients suggested that intravenous tissue plasminogen activator would be delayed by 12 minutes, but MT would be performed 91 minutes sooner if patients were routed directly to endovascular-capable centers. If bypass is limited to a 20-mile radius from onset, then intravenous tissue plasminogen activator would be delayed by 7 minutes and MT performed 94 minutes earlier. In this large, real-world study, interhospital transfer was associated with significant treatment delays and lower chance of good outcome. Strategies to facilitate more rapid identification of large-vessel occlusion and direct routing to endovascular-capable centers for patients with severe stroke may improve outcomes. URL: https://www.clinicaltrials.gov. Unique identifier: NCT02239640. © 2017 The Authors.

The mitochondrial genome in embryo technologies.

PubMed

Hiendleder, S; Wolf, E

2003-08-01

The mammalian mitochondrial genome encodes for 37 genes which are involved in a broad range of cellular functions. The mitochondrial DNA (mtDNA) molecule is commonly assumed to be inherited through oocyte cytoplasm in a clonal manner, and apparently species-specific mechanisms have evolved to eliminate the contribution of sperm mitochondria after natural fertilization. However, recent evidence for paternal mtDNA inheritance in embryos and offspring questions the general validity of this model, particularly in the context of assisted reproduction and embryo biotechnology. In addition to normal mt DNA haplotype variation, oocytes and spermatozoa show remarkable differences in mtDNA content and may be affected by inherited or acquired mtDNA aberrations. All these parameters have been correlated with gamete quality and reproductive success rates. Nuclear transfer (NT) technology provides experimental models for studying interactions between nuclear and mitochondrial genomes. Recent studies demonstrated (i) a significant effect of mtDNA haplotype or other maternal cytoplasmic factors on the efficiency of NT; (ii) phenotypic differences between transmitochondrial clones pointing to functionally relevant nuclear-cytoplasmic interactions; and (iii) neutral or non-neutral selection of mtDNA haplotypes in heteroplasmic conditions. Mitochondria form a dynamic reticulum, enabling complementation of mitochondrial components and possibly mixing of different mtDNA populations in heteroplasmic individuals. Future directions of research on mtDNA in the context of reproductive biotechnology range from the elimination of adverse effects of artificial heteroplasmy, e.g. created by ooplasm transfer, to engineering of optimized constellations of nuclear and cytoplasmic genes for the production of superior livestock.

Distribution of the coenzyme M pathway of epoxide metabolism among ethene- and vinyl chloride-degrading Mycobacterium strains.

PubMed

Coleman, Nicholas V; Spain, Jim C

2003-10-01

An epoxyalkane:coenzyme M (CoM) transferase (EaCoMT) enzyme was recently found to be active in the aerobic vinyl chloride (VC) and ethene assimilation pathways of Mycobacterium strain JS60. In the present study, EaCoMT activity and genes were investigated in 10 different mycobacteria isolated on VC or ethene from diverse environmental samples. In all cases, epoxyethane metabolism in cell extracts was dependent on CoM, with average specific activities of EaCoMT between 380 and 2,910 nmol/min/mg of protein. PCR with primers based on conserved regions of EaCoMT genes from Mycobacterium strain JS60 and the propene oxidizers Xanthobacter strain Py2 and Rhodococcus strain B-276 yielded fragments (834 bp) of EaCoMT genes from all of the VC- and ethene-assimilating isolates. The Mycobacterium EaCoMT genes form a distinct cluster and are more closely related to the EaCoMT of Rhodococcus strain B-276 than that of Xanthobacter strain Py2. The incongruence of the EaCoMT and 16S rRNA gene trees and the fact that isolates from geographically distant locations possessed almost identical EaCoMT genes suggest that lateral transfer of EaCoMT among the Mycobacterium strains has occurred. Pulsed-field gel electrophoresis revealed large linear plasmids (110 to 330 kb) in all of the VC-degrading strains. In Southern blotting experiments, the strain JS60 EaCoMT gene hybridized to many of the plasmids. The CoM-mediated pathway of epoxide metabolism appears to be universal in alkene-assimilating mycobacteria, possibly because of plasmid-mediated lateral gene transfer.

Spin Wave Theory in Two-Dimensional Coupled Antiferromagnets

NASA Astrophysics Data System (ADS)

Shimahara, Hiroshi

2018-04-01

We apply spin wave theory to two-dimensional coupled antiferromagnets. In particular, we primarily examine a system that consists of small spins coupled by a strong exchange interaction J1, large spins coupled by a weak exchange interaction J2, and an anisotropic exchange interaction J12 between the small and large spins. This system is an effective model of the organic antiferromagnet λ-(BETS)2FeCl4 in its insulating phase, in which intriguing magnetic phenomena have been observed, where the small and large spins correspond to π electrons and 3d spins, respectively. BETS stands for bis(ethylenedithio)tetraselenafulvalene. We obtain the antiferromagnetic transition temperature TN and the sublattice magnetizations m(T) and M(T) of the small and large spins, respectively, as functions of the temperature T. When T increases, m(T) is constant with a slight decrease below TN, even where M(T) decreases significantly. When J1 ≫ J12 and J2 = 0, an analytical expression for TN is derived. The estimated value of TN and the behaviors of m(T) and M(T) agree with the observations of λ-(BETS)2FeCl4.

Practical Guide for Flame Bending of Pipe

DTIC Science & Technology

1991-08-01

cleaned. This surface inspection should be in the form of either a dye penetrant or magnetic particle inspection depending on the base material type...fairly accurate and marked on the pipe with a permanent marks-a-lot black ink pen, chalk, soapstone , or other marker which endures flame temperatures...orifice tip. The area to be heated was Magnetic Particle (MT) Inspected any heating and after the final heat. The MT inspectionssatisfactory. prior to Were

A Monolithic CMOS Magnetic Hall Sensor with High Sensitivity and Linearity Characteristics

PubMed Central

Huang, Haiyun; Wang, Dejun; Xu, Yue

2015-01-01

This paper presents a fully integrated linear Hall sensor by means of 0.8 μm high voltage complementary metal-oxide semiconductor (CMOS) technology. This monolithic Hall sensor chip features a highly sensitive horizontal switched Hall plate and an efficient signal conditioner using dynamic offset cancellation technique. An improved cross-like Hall plate achieves high magnetic sensitivity and low offset. A new spinning current modulator stabilizes the quiescent output voltage and improves the reliability of the signal conditioner. The tested results show that at the 5 V supply voltage, the maximum Hall output voltage of the monolithic Hall sensor microsystem, is up to ±2.1 V and the linearity of Hall output voltage is higher than 99% in the magnetic flux density range from ±5 mT to ±175 mT. The output equivalent residual offset is 0.48 mT and the static power consumption is 20 mW. PMID:26516864

A Monolithic CMOS Magnetic Hall Sensor with High Sensitivity and Linearity Characteristics.

PubMed

Huang, Haiyun; Wang, Dejun; Xu, Yue

2015-10-27

This paper presents a fully integrated linear Hall sensor by means of 0.8 μm high voltage complementary metal-oxide semiconductor (CMOS) technology. This monolithic Hall sensor chip features a highly sensitive horizontal switched Hall plate and an efficient signal conditioner using dynamic offset cancellation technique. An improved cross-like Hall plate achieves high magnetic sensitivity and low offset. A new spinning current modulator stabilizes the quiescent output voltage and improves the reliability of the signal conditioner. The tested results show that at the 5 V supply voltage, the maximum Hall output voltage of the monolithic Hall sensor microsystem, is up to ±2.1 V and the linearity of Hall output voltage is higher than 99% in the magnetic flux density range from ±5 mT to ±175 mT. The output equivalent residual offset is 0.48 mT and the static power consumption is 20 mW.

A magnetostrictive composite-fiber Bragg Grating sensor.

PubMed

Quintero, Sully M M; Braga, Arthur M B; Weber, Hans I; Bruno, Antonio C; Araújo, Jefferson F D F

2010-01-01

This paper presents a light and compact optical fiber Bragg Grating sensor for DC and AC magnetic field measurements. The fiber is coated by a thick layer of a magnetostrictive composite consisting of particles of Terfenol-D dispersed in a polymeric matrix. Among the different compositions for the coating that were tested, the best magnetostrictive response was obtained using an epoxy resin as binder and a 30% volume fraction of Terfenol-D particles with sizes ranging from 212 to 300 μm. The effect of a compressive preload in the sensor was also investigated. The achieved resolution was 0.4 mT without a preload or 0.3 mT with a compressive pre-stress of 8.6 MPa. The sensor was tested at magnetic fields of up to 750 mT under static conditions. Dynamic measurements were conducted with a magnetic unbalanced four-pole rotor.

Identifying Water on Mt. Baker and Mt. St. Helens, WA with Geophysics: Implications for Volcanic Landslide Hazards

NASA Astrophysics Data System (ADS)

Finn, C.; Bedrosian, P.; Wisniewski, M.; Deszcz-Pan, M.

2015-12-01

Groundwater position, abundance, and flow rates within a volcano affect the transmission of fluid pressure, transport of mass and heat and formation of mechanically weak hydrothermal alteration influencing the stability of volcanoes. In addition, eruptions can shatter volcanic rocks, weakening the edifice. Helicopter magnetic and electromagnetic (HEM) data collected over Mt. Baker and Mt. St. Helens volcanoes reveal the distribution of water, shattered volcanic rocks and hydrothermal alteration essential to evaluating volcanic landslide hazards. These data, combined with geological mapping and rock property measurements, indicate the presence of localized <100 m thick zones of water-saturated hydrothermally altered rock beneath Sherman Crater and the Dorr Fumarole Fields at Mt. Baker. Nuclear magnetic resonance data indicate that the hydrothermal clays contain ~50% bound water with no evidence for free water ponded beneath the ice. The HEM data suggest water-saturated fresh volcanic rocks from the surface to the detection limit (~100 m) over the entire summit of Mt. Baker (below the ice). A 50-100 m thick high resistivity layer (>1500 ohm-m) corresponding to domes, debris avalanche, volcanic rocks and glaciers mantles the crater at Mt. St. Helens. Shallow low resistivity layers corresponding to fresh, cold water and hot brines are observed below the high resistivity surface in EM data. Shallow ground water mainly concentrates in shattered dome material in the crater of Mt. St. Helens. Aeromagnetic data indicate the location of basalts sandwiched between debris avalanche deposits and shattered dome material. The combination of the EM and magnetic data help map the location of the shattered dome material that is considered to be the failure surface for the 1980 debris avalanche. The EM data image the regional groundwater table near the base of the volcano. The geophysical identification of groundwater and weak layers constrain landslide hazards assessments.

Magnetic properties and heavy metal contents of automobile emission particulates*

PubMed Central

Lu, Sheng-gao; Bai, Shi-qiang; Cai, Jing-bo; Xu, Chang

2005-01-01

Measurements of the magnetic properties and total contents of Cu, Cd, Pb and Fe in 30 automobile emission particulate samples indicated the presence of magnetic particles in them. The values of frequency dependent susceptibility (χ fd) showed the absence of superparamagnetic (SP) grains in the samples. The IRM20 mT (isothermal remanent magnetization at 20 mT) being linearly proportional to SIRM (saturation isothermal remanent magnetization) (R 2=0.901), suggested that ferrimagnetic minerals were responsible for the magnetic properties of automobile emission particulates. The average contents of Cu, Cd, Pb and Fe in automobile emission particulates were 95.83, 22.14, 30.58 and 34727.31 mg/kg, respectively. Significant positive correlations exist between the magnetic parameters and the contents of Pb, Cu and Fe. The magnetic parameters of automobile emission particulates reflecting concentration of magnetic particles increased linearly with increase of Pb and Cu content, showed that the magnetic measurement could be used as a preliminary index for detection of Pb and Cu pollution. PMID:16052705

Miniature mechanical transfer optical coupler

DOEpatents

Abel, Philip [Overland Park, KS; Watterson, Carl [Kansas City, MO

2011-02-15

A miniature mechanical transfer (MT) optical coupler ("MMTOC") for optically connecting a first plurality of optical fibers with at least one other plurality of optical fibers. The MMTOC may comprise a beam splitting element, a plurality of collimating lenses, and a plurality of alignment elements. The MMTOC may optically couple a first plurality of fibers disposed in a plurality of ferrules of a first MT connector with a second plurality of fibers disposed in a plurality of ferrules of a second MT connector and a third plurality of fibers disposed in a plurality of ferrules of a third MT connector. The beam splitting element may allow a portion of each beam of light from the first plurality of fibers to pass through to the second plurality of fibers and simultaneously reflect another portion of each beam of light from the first plurality of fibers to the third plurality of fibers.

In situ and ex situ low-field NMR spectroscopy and MRI endowed by SABRE hyperpolarization.

PubMed

Barskiy, Danila A; Kovtunov, Kirill V; Koptyug, Igor V; He, Ping; Groome, Kirsten A; Best, Quinn A; Shi, Fan; Goodson, Boyd M; Shchepin, Roman V; Truong, Milton L; Coffey, Aaron M; Waddell, Kevin W; Chekmenev, Eduard Y

2014-12-15

By using 5.75 and 47.5 mT nuclear magnetic resonance (NMR) spectroscopy, up to 10(5)-fold sensitivity enhancement through signal amplification by reversible exchange (SABRE) was enabled, and subsecond temporal resolution was used to monitor an exchange reaction that resulted in the buildup and decay of hyperpolarized species after parahydrogen bubbling. We demonstrated the high-resolution low-field proton magnetic resonance imaging (MRI) of pyridine in a 47.5 mT magnetic field endowed by SABRE. Molecular imaging (i.e. imaging of dilute hyperpolarized substances rather than the bulk medium) was conducted in two regimes: in situ real-time MRI of the reaction mixture (in which pyridine was hyperpolarized), and ex situ MRI (in which hyperpolarization decays) of the liquid hyperpolarized product. Low-field (milli-Tesla range, e.g. 5.75 and 47.5 mT used in this study) parahydrogen-enhanced NMR and MRI, which are free from the limitations of high-field magnetic resonance (including susceptibility-induced gradients of the static magnetic field at phase interfaces), potentially enables new imaging applications as well as differentiation of hyperpolarized chemical species on demand by exploiting spin manipulations with static and alternating magnetic fields. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Magnetic field effect in organic films and devices

NASA Astrophysics Data System (ADS)

Gautam, Bhoj Raj

In this work, we focused on the magnetic field effect in organic films and devices, including organic light emitting diodes (OLEDs) and organic photovoltaic (OPV) cells. We measured magnetic field effect (MFE) such as magnetoconductance (MC) and magneto-electroluminescence (MEL) in OLEDs based on several pi- conjugated polymers and small molecules for fields |B|<100 mT. We found that both MC(B) and MEL(B) responses in bipolar devices and MC(B) response in unipolar devices are composed of two B-regions: (i) an 'ultra-small' region at |B| < 1-2 mT, and (ii) a monotonic response region at |B| >˜2mT. Magnetic field effect (MFE) measured on three isotopes of Poly (dioctyloxy) phenylenevinylene (DOO-PPV) showed that both regular and ultra-small effects are isotope dependent. This indicates that MFE response in OLED is mainly due to the hyperfine interaction (HFI). We also performed spectroscopy of the MFE including magneto-photoinduced absorption (MPA) and magneto-photoluminescence (MPL) at steady state conditions in several systems. This includes pristine Poly[2-methoxy-5-(2-ethylhexyl-oxy)-1,4-phenylene-vinylene] (MEH-PPV) films, MEH-PPV films subjected to prolonged illumination, and MEH-PPV/[6,6]-Phenyl C61 butyric acid methyl ester (PCBM) blend, as well as annealed and pristine C60 thin films. For comparison, we also measured MC and MEL in organic diodes based on the same materials. By directly comparing the MPA and MPL responses in films to MC and MEL in organic diodes based on the same active layers, we are able to relate the MFE in organic diodes to the spin densities of the excitations formed in the device, regardless of whether they are formed by photon absorption or carrier injection from the electrodes. We also studied magneto-photocurrent (MPC) and power conversion efficiency (PCE) of a 'standard' Poly (3-hexylthiophene)/PCBM device at various Galvinoxyl radical wt%. We found that the MPC reduction with Galvinoxyl wt% follows the same trend as that of the PCE enhancement. In addition, we also measured the MPC response of a series of OPV cells. We attribute the observed broad MPC to short-lived charge transfer complex species, where spin mixing is caused by the difference, Deltag of the donor/acceptor g factors; whereas narrow MPC is due to HFI within long-lived polaron-pairs.

[Effect of general magnetotherapy on specific activity of blood phagocytes in patients with ischemic heart disease].

PubMed

Ishutin, I S; Klemenkov, S V; Lesovskaia, M I; Spiridonova, M S; Krotova, T K; Ishutin, E I; Tsyganova, O B

2007-01-01

In general magnetotherapy for patients with hyporeactive phagocytes (less than 67% from the level of normal chelicoluminescent response) the adequate level of magnetic induction is 1 mT, for patients with normoreactive phagocytes--0.5 mT and for patients with hyperreactive phagocytes (more than 133% from the level of normal chelicoluminescent response)--0.75 mT daily.

UNDERSTANDING SOLAR TORSIONAL OSCILLATIONS FROM GLOBAL DYNAMO MODELS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Guerrero, G.; Smolarkiewicz, P. K.; Pino, E. M. de Gouveia Dal

2016-09-01

The phenomenon of solar “torsional oscillations” (TO) represents migratory zonal flows associated with the solar cycle. These flows are observed on the solar surface and, according to helioseismology, extend through the convection zone. We study the origin of the TO using results from a global MHD simulation of the solar interior that reproduces several of the observed characteristics of the mean-flows and magnetic fields. Our results indicate that the magnetic tension (MT) in the tachocline region is a key factor for the periodic changes in the angular momentum transport that causes the TO. The torque induced by the MT atmore » the base of the convection zone is positive at the poles and negative at the equator. A rising MT torque at higher latitudes causes the poles to speed up, whereas a declining negative MT torque at the lower latitudes causes the equator to slow-down. These changes in the zonal flows propagate through the convection zone up to the surface. Additionally, our results suggest that it is the magnetic field at the tachocline that modulates the amplitude of the surface meridional flow rather than the opposite as assumed by flux-transport dynamo models of the solar cycle.« less

Electrical characterization of gold-DNA-gold structures in presence of an external magnetic field by means of I-V curve analysis.

PubMed

Khatir, Nadia Mahmoudi; Banihashemian, Seyedeh Maryam; Periasamy, Vengadesh; Ritikos, Richard; Abd Majid, Wan Haliza; Abdul Rahman, Saadah

2012-01-01

This work presents an experimental study of gold-DNA-gold structures in the presence and absence of external magnetic fields with strengths less than 1,200.00 mT. The DNA strands, extracted by standard method were used to fabricate a Metal-DNA-Metal (MDM) structure. Its electric behavior when subjected to a magnetic field was studied through its current-voltage (I-V) curve. Acquisition of the I-V curve demonstrated that DNA as a semiconductor exhibits diode behavior in the MDM structure. The current versus magnetic field strength followed a decreasing trend because of a diminished mobility in the presence of a low magnetic field. This made clear that an externally imposed magnetic field would boost resistance of the MDM structure up to 1,000.00 mT and for higher magnetic field strengths we can observe an increase in potential barrier in MDM junction. The magnetic sensitivity indicates the promise of using MDM structures as potential magnetic sensors.

Electrical Characterization of Gold-DNA-Gold Structures in Presence of an External Magnetic Field by Means of I–V Curve Analysis

PubMed Central

Khatir, Nadia Mahmoudi; Banihashemian, Seyedeh Maryam; Periasamy, Vengadesh; Ritikos, Richard; Majid, Wan Haliza Abd; Rahman, Saadah Abdul

2012-01-01

This work presents an experimental study of gold-DNA-gold structures in the presence and absence of external magnetic fields with strengths less than 1,200.00 mT. The DNA strands, extracted by standard method were used to fabricate a Metal-DNA-Metal (MDM) structure. Its electric behavior when subjected to a magnetic field was studied through its current-voltage (I–V) curve. Acquisition of the I–V curve demonstrated that DNA as a semiconductor exhibits diode behavior in the MDM structure. The current versus magnetic field strength followed a decreasing trend because of a diminished mobility in the presence of a low magnetic field. This made clear that an externally imposed magnetic field would boost resistance of the MDM structure up to 1,000.00 mT and for higher magnetic field strengths we can observe an increase in potential barrier in MDM junction. The magnetic sensitivity indicates the promise of using MDM structures as potential magnetic sensors. PMID:22737025

The influence of low-frequency magnetic field on plasma antioxidant capacity and heart rate.

PubMed

Ciejka, Elzbieta B; Goraca, Anna

2009-01-01

Low-frequency magnetic field is widely applied as magnetotherapy in physiotherapeutic treatment. Recognition of positive and negative effects of the magnetic field has been the subject of numerous studies. Experimental studies concern, among others, the effect of this field on the heart rate and plasma antioxidant capacity. The aim of the study was to check whether a time-variable magnetic field of constant frequency and induction affects the heart rate and plasma antioxidant capacity. The tests were performed on Spraque-Dawley rats exposed to the magnetic field of the following parameters: frequency - 40 Hz, induction - 7 mT, time of exposure - 30 and 60 minutes. The measurements of ECG and plasma antioxidant capacity expressed in the number of reduced iron ions were performed on experimental animals: before, after a single exposure and after 14 days of exposure. A significant decrease of the heart rate was observed after 14 days of exposure. A variable magnetic field of the parameters: frequency - 40 Hz, induction - 7 mT and exposure time of 14 days caused an increase of the organism antioxidant defence, whereas a variable magnetic field of the frequency of 40 Hz, induction - 7 mT and exposure time 60 minutes for 14 days caused a significant decrease of the organism antioxidant defence. The exposure time affects heart rate, plasma antioxidant capacity and the organism defense ability against free radicals.

Enhancement of germination, growth, and photosynthesis in soybean by pre-treatment of seeds with magnetic field.

PubMed

Shine, M B; Guruprasad, K N; Anand, Anjali

2011-09-01

Experiments were conducted to study the effect of static magnetic fields on the seeds of soybean (Glycine max (L.) Merr. var: JS-335) by exposing the seeds to different magnetic field strengths from 0 to 300 mT in steps of 50 mT for 30, 60, and 90 min. Treatment with magnetic fields improved germination-related parameters like water uptake, speed of germination, seedling length, fresh weight, dry weight and vigor indices of soybean seeds under laboratory conditions. Improvement over untreated control was 5-42% for speed of germination, 4-73% for seedling length, 9-53% for fresh weight, 5-16% for dry weight, and 3-88% and 4-27% for vigor indices I and II, respectively. Treatment of 200 mT (60 min) and 150 mT (60 min), which were more effective than others in increasing most of the seedling parameters, were further explored for their effect on plant growth, leaf photosynthetic efficiency, and leaf protein content under field conditions. Among different growth parameters, leaf area, and leaf fresh weight showed maximum enhancement (more than twofold) in 1-month-old plants. Polyphasic chlorophyll a fluorescence (OJIP) transients from magnetically treated plants gave a higher fluorescence yield at the J-I-P phase. The total soluble protein map (SDS-polyacrylamide gel) of leaves showed increased intensities of the bands corresponding to a larger subunit (53 KDa) and smaller subunit (14 KDa) of Rubisco in the treated plants. We report here the beneficial effect of pre-sowing magnetic treatment for improving germination parameters and biomass accumulation in soybean. Copyright © 2011 Wiley-Liss, Inc.

In-Vivo Proton Magnetic Resonance Spectroscopy of 2-Hydroxyglutarate in Isocitrate Dehydrogenase-Mutated Gliomas: A Technical Review for Neuroradiologists.

PubMed

Kim, Hyeonjin; Kim, Sungjin; Lee, Hyeong Hun; Heo, Hwon

2016-01-01

The diagnostic and prognostic potential of an onco-metabolite, 2-hydroxyglutarate (2HG) as a proton magnetic resonance spectroscopy (1H-MRS) detectable biomarker of the isocitrate dehydrogenase (IDH)-mutated (IDH-MT) gliomas has drawn attention of neuroradiologists recently. However, due to severe spectral overlap with background signals, quantification of 2HG can be very challenging. In this technical review for neuroradiologists, first, the biochemistry of 2HG and its significance in the diagnosis of IDH-MT gliomas are summarized. Secondly, various 1H-MRS methods used in the previous studies are outlined. Finally, wereview previous in vivo studies, and discuss the current status of 1H-MRS in the diagnosis of IDH-MT gliomas.

On-Chip Magnetic Bead Manipulation and Detection Using a Magnetoresistive Sensor-Based Micro-Chip: Design Considerations and Experimental Characterization

PubMed Central

Gooneratne, Chinthaka P.; Kodzius, Rimantas; Li, Fuquan; Foulds, Ian G.; Kosel, Jürgen

2016-01-01

The remarkable advantages micro-chip platforms offer over cumbersome, time-consuming equipment currently in use for bio-analysis are well documented. In this research, a micro-chip that includes a unique magnetic actuator (MA) for the manipulation of superparamagnetic beads (SPBs), and a magnetoresistive sensor for the detection of SPBs is presented. A design methodology, which takes into account the magnetic volume of SPBs, diffusion and heat transfer phenomena, is presented with the aid of numerical analysis to optimize the parameters of the MA. The MA was employed as a magnetic flux generator and experimental analysis with commercially available COMPEL™ and Dynabeads® demonstrated the ability of the MA to precisely transport a small number of SPBs over long distances and concentrate SPBs to a sensing site for detection. Moreover, the velocities of COMPEL™ and Dynabead® SPBs were correlated to their magnetic volumes and were in good agreement with numerical model predictions. We found that 2.8 μm Dynabeads® travel faster, and can be attracted to a magnetic source from a longer distance, than 6.2 μm COMPEL™ beads at magnetic flux magnitudes of less than 10 mT. The micro-chip system could easily be integrated with electronic circuitry and microfluidic functions, paving the way for an on-chip biomolecule quantification device. PMID:27571084

On-Chip Magnetic Bead Manipulation and Detection Using a Magnetoresistive Sensor-Based Micro-Chip: Design Considerations and Experimental Characterization.

PubMed

Gooneratne, Chinthaka P; Kodzius, Rimantas; Li, Fuquan; Foulds, Ian G; Kosel, Jürgen

2016-08-26

The remarkable advantages micro-chip platforms offer over cumbersome, time-consuming equipment currently in use for bio-analysis are well documented. In this research, a micro-chip that includes a unique magnetic actuator (MA) for the manipulation of superparamagnetic beads (SPBs), and a magnetoresistive sensor for the detection of SPBs is presented. A design methodology, which takes into account the magnetic volume of SPBs, diffusion and heat transfer phenomena, is presented with the aid of numerical analysis to optimize the parameters of the MA. The MA was employed as a magnetic flux generator and experimental analysis with commercially available COMPEL™ and Dynabeads(®) demonstrated the ability of the MA to precisely transport a small number of SPBs over long distances and concentrate SPBs to a sensing site for detection. Moreover, the velocities of COMPEL™ and Dynabead(®) SPBs were correlated to their magnetic volumes and were in good agreement with numerical model predictions. We found that 2.8 μm Dynabeads(®) travel faster, and can be attracted to a magnetic source from a longer distance, than 6.2 μm COMPEL™ beads at magnetic flux magnitudes of less than 10 mT. The micro-chip system could easily be integrated with electronic circuitry and microfluidic functions, paving the way for an on-chip biomolecule quantification device.

All fiber magnetic field sensor with Ferrofluid-filled tapered microstructured optical fiber interferometer.

PubMed

Deng, Ming; Huang, Can; Liu, Danhui; Jin, Wei; Zhu, Tao

2015-08-10

An ultra-compact optical fiber magnetic field sensor based on a microstructured optical fiber (MOF) modal interference and ferrofluid (FF) has been proposed and experimentally demonstrated. The magnetic field sensor was fabricated by splicing a tapered germanium-doped index guided MOF with six big holes injected with FF to two conventional single-mode fibers. The transmission spectra of the proposed sensor under different magnetic field intensities have been measured and theoretically analyzed. Due to an efficient interaction between the magnetic nanoparticles in FF and the excited cladding mode, the magnetic field sensitivity reaches up to117.9pm/mT with a linear range from 0mT to 30mT. Moreover, the fabrication process of the proposed sensor is simple, easy and cost-effective. Therefore, it will be a promising candidate for military, aviation industry, and biomedical applications, especially, for the applications where the space is limited.

Visible light-induced magnetization change of the cyano-bridged 3 d-4 f heterobimetallic

NASA Astrophysics Data System (ADS)

Li, Guangming; Sato, Osamu; Akitsu, Takashiro; Einaga, Yasuaki

2004-10-01

A visible light-induced magnetization change of the 3d-4f heterometallic, [Nd(DMF)4(H2O)3(μ-NC)Co(CN)5]·H2O (DMF=N,N-dimethylformamide), is observed and described. The plots of χMT versus T of the complex showed that the χMT values, after visible light illumination, were enhanced by about 25% as compared to before irradiation in the temperature range of 5-40 K.

Source Biases in Magnetotelluric Transfer Functions due to Pc3/Pc4 ( 10-100s) Geomagnetic Activity at Mid-Latitudes

NASA Astrophysics Data System (ADS)

Murphy, B. S.; Egbert, G. D.

2017-12-01

Discussion of possible bias in magnetotelluric (MT) transfer functions due to the finite spatial scale of external source fields has largely focused on long periods (>1000 s), where skin depths are large, and high latitudes (>60° N), where sources are dominated by narrow electrojets. However, a significant fraction ( 15%) of the 1000 EarthScope USArray apparent resistivity and phase curves exhibit nonphysical "humps" over a narrow period range (typically between 25-60 s) that are suggestive of narrow-band source effects. Maps of locations in the US where these biases are seen support this conclusion: they mostly occur in places where the Earth is highly resistive, such as cratonic regions, where skin depths are largest and hence where susceptibility to bias from short-wavelength sources would be greatest. We have analyzed EarthScope MT time series using cross-phase techniques developed in the space physics community to measure the period of local field line resonances associated with geomagnetic pulsations (Pc's). In most cases the biases occur near the periods of field line resonance determined from this analysis, suggesting that at mid-latitude ( 30°-50° N) Pc's can bias the time-averaged MT transfer functions. Because Pc's have short meridional wavelengths (hundreds of km), even at these relatively short periods the plane-wave assumption of the MT technique may be violated, at least in resistive domains with large skin depths. It is unclear if these biases (generally small) are problematic for MT data inversion, but their presence in the transfer functions is already a useful zeroth-order indicator of resistive regions of the Earth.

[Effect of extremely low frequency magnetic field on glutathione in rat muscles].

PubMed

Ciejka, Elzbieta; Jakubowska, Ewa; Zelechowska, Paulina; Huk-Kolega, Halina; Kowalczyk, Agata; Goraca, Anna

2014-01-01

Free radicals (FR) are atoms, molecules or their fragments. Their excess leads to the development of oxidizing stress, the cause of many neoplastic, neurodegenerative and inflammatory diseases, and aging of the organism. Industrial pollution, tobacco smoke, ionizing radiation, ultrasound and magnetic field are the major FR exogenous sources. The low frequency magnetic field is still more commonly applied in the physical therapy. The aim of the presented study was to evaluate the effect of extremely low frequency magnetic field used in the magnetotherapy on the level of total glutathione, oxidized and reduced, and the redox state of the skeletal muscle cells, depending on the duration of exposure to magnetic field. The male rats, weight of 280-300 g, were randomly devided into 3 experimental groups: controls (group I) and treatment groups exposed to extremely low frequency magnetic field (ELF-MF) (group II exposed to 40 Hz, 7 mT for 0.5 h/day for 14 days and group III exposed to 40 Hz, 7 mT for 1 h/day for 14 days). Control rats were kept in a separate room not exposed to extremely low frequency magnetic field. Immediately after the last exposure, part of muscles was taken under pentobarbital anesthesia. Total glutathione, oxidized and reduced, and the redox state in the muscle tissue of animals were determined after exposure to magnetic fields. Exposure to low magnetic field: 40 Hz, 7 mT for 30 min/day and 60 min/day for 2 weeks significantly increased the total glutathione levels in the skeletal muscle compared to the control group (p < 0.001). Exposure to magnetic fields used in the magnetic therapy plays an important role in the development of adaptive mechanisms responsible for maintaining the oxidation-reduction balance in the body and depends on exposure duration.

Missing genes, multiple ORFs, and C-to-U type RNA editing in Acrasis kona (Heterolobosea, Excavata) mitochondrial DNA.

PubMed

Fu, Cheng-Jie; Sheikh, Sanea; Miao, Wei; Andersson, Siv G E; Baldauf, Sandra L

2014-08-21

Discoba (Excavata) is an ancient group of eukaryotes with great morphological and ecological diversity. Unlike the other major divisions of Discoba (Jakobida and Euglenozoa), little is known about the mitochondrial DNAs (mtDNAs) of Heterolobosea. We have assembled a complete mtDNA genome from the aggregating heterolobosean amoeba, Acrasis kona, which consists of a single circular highly AT-rich (83.3%) molecule of 51.5 kb. Unexpectedly, A. kona mtDNA is missing roughly 40% of the protein-coding genes and nearly half of the transfer RNAs found in the only other sequenced heterolobosean mtDNAs, those of Naegleria spp. Instead, over a quarter of A. kona mtDNA consists of novel open reading frames. Eleven of the 16 protein-coding genes missing from A. kona mtDNA were identified in its nuclear DNA and polyA RNA, and phylogenetic analyses indicate that at least 10 of these 11 putative nuclear-encoded mitochondrial (NcMt) proteins arose by direct transfer from the mitochondrion. Acrasis kona mtDNA also employs C-to-U type RNA editing, and 12 homologs of DYW-type pentatricopeptide repeat (PPR) proteins implicated in plant organellar RNA editing are found in A. kona nuclear DNA. A mapping of mitochondrial gene content onto a consensus phylogeny reveals a sporadic pattern of relative stasis and rampant gene loss in Discoba. Rampant loss occurred independently in the unique common lineage leading to Heterolobosea + Tsukubamonadida and later in the unique lineage leading to Acrasis. Meanwhile, mtDNA gene content appears to be remarkably stable in the Acrasis sister lineage leading to Naegleria and in their distant relatives Jakobida. © The Author(s) 2014. Published by Oxford University Press on behalf of the Society for Molecular Biology and Evolution.

In vivo field-cycling relaxometry using an insert coil for magnetic field offset.

PubMed

Pine, Kerrin J; Goldie, Fred; Lurie, David J

2014-11-01

The T(1) of tissue has a strong dependence on the measurement magnetic field strength. T(1) -dispersion could be a useful contrast parameter, but is unavailable to clinical MR systems which operate at fixed magnetic field strength. The purpose of this work was to implement a removable insert magnet coil for field-cycling T(1) -dispersion measurements on a vertical-field MRI scanner, by offsetting the static field over a volume of interest. An insert magnet coil was constructed for use with a whole-body sized 59 milli-Tesla (mT) vertical-field, permanent-magnet based imager. The coil has diameter 38 cm and thickness 6.1 cm and a homogeneous region (± 5%) of 5 cm DSV, offset by 5 cm from the coil surface. Surface radiofrequency (RF) coils were also constructed. The insert coil was used in conjunction with a surface RF coil and a volume-localized inversion-recovery pulse sequence to plot T(1) -dispersion in a human volunteer's forearm over a range of field strengths from 1 mT to 70 mT. T(1) -dispersion measurements were demonstrated on a fixed-field MRI scanner, using an insert coil. This demonstrates the feasibility of relaxation dispersion measurements on an otherwise conventional MR imager, facilitating the exploitation of T(1) -dispersion contrast for enhanced diagnosis. Copyright © 2013 Wiley Periodicals, Inc.

Pretraining Cortical Thickness Predicts Subsequent Perceptual Learning Rate in a Visual Search Task.

PubMed

Frank, Sebastian M; Reavis, Eric A; Greenlee, Mark W; Tse, Peter U

2016-03-01

We report that preexisting individual differences in the cortical thickness of brain areas involved in a perceptual learning task predict the subsequent perceptual learning rate. Participants trained in a motion-discrimination task involving visual search for a "V"-shaped target motion trajectory among inverted "V"-shaped distractor trajectories. Motion-sensitive area MT+ (V5) was functionally identified as critical to the task: after 3 weeks of training, activity increased in MT+ during task performance, as measured by functional magnetic resonance imaging. We computed the cortical thickness of MT+ from anatomical magnetic resonance imaging volumes collected before training started, and found that it significantly predicted subsequent perceptual learning rates in the visual search task. Participants with thicker neocortex in MT+ before training learned faster than those with thinner neocortex in that area. A similar association between cortical thickness and training success was also found in posterior parietal cortex (PPC). © The Author 2015. Published by Oxford University Press. All rights reserved. For Permissions, please e-mail: journals.permissions@oup.com.

Effects of pulsed and sinusoid electromagnetic fields on human chondrocytes cultivated in a collagen matrix.

PubMed

Schmidt-Rohlfing, Bernhard; Silny, Jiri; Woodruff, Seth; Gavenis, Karsten

2008-08-01

Although several effects of electromagnetic fields (EMFs) on articular cartilage have been reported in recent studies, the use of EMFs to treat osteoarthritis remains a matter of debate. In an in vitro study, human chondrocytes harvested from osteoarthritic knee joints were released from their surrounding matrix and transferred in defined concentration into a 3D matrix (type-I collagen gel). The cultivation, performed under standard conditions, lasted up to 14 days. During this time, treatment groups were continuously exposed to either sinusoid or pulsed electromagnetic fields (PEMFs). The PEMFs revealed the following characteristics: maximum magnetic flux density of 2 mT, frequency of the bursts of 16.7 Hz with each burst consisting of 20 pulses. Similarly, the sinusoid EMFs also induced a maximum flux density of 2 mT with a frequency of 50 Hz. Control groups consisting of equal number of samples were not exposed to EMF. Immunohistological examinations of formalin-fixed, paraffin-embedded samples revealed positive staining for type-II collagen and proteoglycans in the immediate pericellular region with no differences between the two different treatment groups and the control groups. With increasing cultivation time, both type-II collagen and aggrecan gene expression declined, but no significant differences in gene expression were found between the treatment and control groups. In conclusion, using our in vitro setting, we were unable to detect any effects of pulsed and sinusoidal magnetic fields on human adult osteoarthritic chondrocytes.

Improving Keyhole Stability by External Magnetic Field in Full Penetration Laser Welding

NASA Astrophysics Data System (ADS)

Li, Min; Xu, Jiajun; Huang, Yu; Rong, Youmin

2018-05-01

An external magnetic field was used to improve the keyhole stability in full penetration laser welding 316L steel. The increase of magnetic field strength gave rise to a shorter flying time of the spatter, a weaker size and brightness of the spatter, and a larger spreading area of vapor plume. This suggested that the dynamic behavior of the keyhole was stabilized by the external magnetic field. In addition, a stronger magnetic field could result in a more homogeneous distribution of laser energy, which increased the width of the weld zone, and the height of the bottom weld zone from 381 μm (0 mT) to 605 μm (50 mT). Dendrite and cellular crystal near the weld center disappeared, and grain size was refined. The external magnetic field was beneficial to the keyhole stability and improved the joint quality, because the weld pool was stirred by a Lorentz force resulting from the coupling effect of the magnetic field and inner thermocurrent.

The magnetic properties of BaCo0.5Ni0.5F4

NASA Astrophysics Data System (ADS)

Xu, Qingyu; Dai, Chuanjun; Han, Zhida; Li, Qi

2018-05-01

The family of BaMF4 with M of magnetic 3d transition metal ions is the typical multiferroic material. Pure phase solid solution of BaCoF4 and BaNiF4 with molar ratio of 1:1 (BaCo0.5Ni0.5F4) is prepared by solid state reaction, which has been confirmed by X ray diffraction patterns. Field dependent magnetization measurements only show the linear curve with temperature down to 5 K, indicating the antiferromagnetic nature. Compared with BaCoF4 and BaNiF4, no significant enhancement of magnetization is observed, indicating the absence of ferrimagnetism and the random distribution of Co and Ni ions. The low temperature magnetic anomalies are studied by zero field cooled (ZFC) and field cooled (FC) temperature dependent magnetization (M-T) measurements. A bifurcation between FC and ZFC M-T curves happens at 118 K, indicating the onset of 2-dimensional antiferromagnetism. The magnetization maximum at 87 K is attributed to the 2-dimensional antiferromagnetic clusters, followed by the drastic decrease of magnetization, which is due to the onset of 3-dimensional antiferromagnetism. A dip is observed in FC M-T curve at 40 K, which is attributed to the 3-dimensional antiferromagnetic clusters. A drastic increase of magnetization is observed at 9 K, which is due to the uncompensated isolated spins. Exchange bias is clearly observed, with blocking temperature of 90 K. The contribution from surface spin glass has been excluded by the AC magnetization measurements, and the mechanism has been explained by the exchange coupling between the two antiferromagnetic phases.

76 FR 27914 - Television Broadcasting Services; Kalispell, MT

Federal Register 2010, 2011, 2012, 2013, 2014

2011-05-13

... FEDERAL COMMUNICATIONS COMMISSION 47 CFR Part 73 [MB Docket No. 11-20; RM-11619, DA 11-750] Television Broadcasting Services; Kalispell, MT AGENCY: Federal Communications Commission. ACTION: Final rule... rulemaking filed by Montana State University (``MSU'') requesting that channel *46 be transferred from the...

Mitochondrial Transfer by Photothermal Nanoblade Restores Metabolite Profile in Mammalian Cells.

PubMed

Wu, Ting-Hsiang; Sagullo, Enrico; Case, Dana; Zheng, Xin; Li, Yanjing; Hong, Jason S; TeSlaa, Tara; Patananan, Alexander N; McCaffery, J Michael; Niazi, Kayvan; Braas, Daniel; Koehler, Carla M; Graeber, Thomas G; Chiou, Pei-Yu; Teitell, Michael A

2016-05-10

mtDNA sequence alterations are challenging to generate but desirable for basic studies and potential correction of mtDNA diseases. Here, we report a new method for transferring isolated mitochondria into somatic mammalian cells using a photothermal nanoblade, which bypasses endocytosis and cell fusion. The nanoblade rescued the pyrimidine auxotroph phenotype and respiration of ρ0 cells that lack mtDNA. Three stable isogenic nanoblade-rescued clones grown in uridine-free medium showed distinct bioenergetics profiles. Rescue lines 1 and 3 reestablished nucleus-encoded anapleurotic and catapleurotic enzyme gene expression patterns and had metabolite profiles similar to the parent cells from which the ρ0 recipient cells were derived. By contrast, rescue line 2 retained a ρ0 cell metabolic phenotype despite growth in uridine-free selection. The known influence of metabolite levels on cellular processes, including epigenome modifications and gene expression, suggests metabolite profiling can help assess the quality and function of mtDNA-modified cells. Copyright © 2016 Elsevier Inc. All rights reserved.

Relative suppression of magical thinking: a transcranial magnetic stimulation study.

PubMed

Bell, Vaughan; Reddy, Venu; Halligan, Peter; Kirov, George; Ellis, Hadyn

2007-05-01

The tendency to perceive meaning in noise (apophenia) has been linked to "magical thinking" (MT), a distinctive form of thinking associated with a range of normal cognitive styles, anomalous perceptual experiences and frank psychosis. Important aspects of MT include the propensity to imbue meaning or causality to events that might otherwise be considered coincidental. Structures in the lateral temporal lobes have been hypothesised to be involved in both the clinical and nonclinical aspects of MT. Accordingly, in this study we used single-pulse transcranial magnetic stimulation (TMS) to stimulate either the left or right lateral temporal areas, or the vertex, of 12 healthy participants (balanced for similar levels of MT, delusional ideation and temporal lobe disturbance) while they were required to indicate if they had "detected" pictures, claimed to be present by the experimenters, in visual noise. Relative to the vertex, TMS inhibition of the left lateral temporal area produced significant reduced tendency to report meaningful information, suggesting that left lateral temporal activation may be more important in MT and therefore producing and supporting anomalous beliefs and experiences. The effect cannot simply be explained by TMS induced cognitive slowing as reaction times were not affected.

NMR/MRI with hyperpolarized gas and high Tc SQUID

DOEpatents

Schlenga, Klaus; de Souza, Ricardo E.; Wong-Foy, Annjoe; Clarke, John; Pines, Alexander

2000-01-01

A method and apparatus for the detection of nuclear magnetic resonance (NMR) signals and production of magnetic resonance imaging (MRI) from samples combines the use of hyperpolarized inert gases to enhance the NMR signals from target nuclei in a sample and a high critical temperature (Tc) superconducting quantum interference device (SQUID) to detect the NMR signals. The system operates in static magnetic fields of 3 mT or less (down to 0.1 mT), and at temperatures from liquid nitrogen (77K) to room temperature. Sample size is limited only by the size of the magnetic field coils and not by the detector. The detector is a high Tc SQUID magnetometer designed so that the SQUID detector can be very close to the sample, which can be at room temperature.

Fundamental study on the magnetic field control method using multiple HTS coils for Magnetic Drug Delivery System

NASA Astrophysics Data System (ADS)

Hirano, R.; Kim, S. B.; Nakagawa, T.; Tomisaka, Y.; Ueda, H.

2017-07-01

The magnetic drug delivery system (MDDS) is a key technology to reduce the side effects in the medical applications, and the magnetic force control is very important issue in MDDS. In this application, the strength of magnetic field and gradient required to MDDS devices are 54 mT and 5.5 T/m, respectively. We proposed the new magnetic force control system that consists of the multiple racetrack HTS magnets. We can control the magnetic field gradient along the longitudinal direction by the arrangement of the multiple racetrack HTS magnets and operating current of each magnet. When the racetrack HTS magnets were used, the critical current was reduced by the self-magnetic field. Therefore, the shape design of HTS magnet to reduce the magnet field into the surface of HTS tapes was required. Therefore, the electromagnetic analysis based on finite element method (FEM) was carried out to design and optimize the shape of multiple racetrack HTS magnet. We were able to suppress the reduction of critical current by placing the magnetic substance at upper and lower side of the HTS magnets. It was confirmed that obtained maximum values of magnetic field strength and field gradient were 33 mT and 0.18 T/m, respectively.

Mitochondrial Transfer from Wharton's Jelly Mesenchymal Stem Cell to MERRF Cybrid Reduces Oxidative Stress and Improves Mitochondrial Bioenergetics

PubMed Central

Liou, Chia-Wei; Chen, Shang-Der; Wang, Pei-Wen; Chuang, Jiin-Haur; Tiao, Mao-Meng; Hsu, Te-Yao

2017-01-01

Myoclonus epilepsy associated with ragged-red fibers (MERRF) is a maternally inherited mitochondrial disease affecting neuromuscular functions. Mt.8344A>G mutation in mitochondrial DNA (mtDNA) is the most common cause of MERRF syndrome and has been linked to an increase in reactive oxygen species (ROS) level and oxidative stress, as well as impaired mitochondrial bioenergetics. Here, we tested whether WJMSC has therapeutic potential for the treatment of MERRF syndrome through the transfer of mitochondria. The MERRF cybrid cells exhibited a high mt.8344A>G mutation ratio, enhanced ROS level and oxidative damage, impaired mitochondrial bioenergetics, defected mitochondria-dependent viability, exhibited an imbalance of mitochondrial dynamics, and are susceptible to apoptotic stress. Coculture experiments revealed that mitochondria were intercellularly conducted from the WJMSC to the MERRF cybrid. Furthermore, WJMSC transferred mitochondria exclusively to cells with defective mitochondria but not to cells with normal mitochondria. MERRF cybrid following WJMSC coculture (MF+WJ) demonstrated improvement of mt.8344A>G mutation ratio, ROS level, oxidative damage, mitochondrial bioenergetics, mitochondria-dependent viability, balance of mitochondrial dynamics, and resistance against apoptotic stress. WJMSC-derived mitochondrial transfer and its therapeutic effect were noted to be blocked by F-actin depolymerizing agent cytochalasin B. Collectively, the WJMSC ability to rescue cells with defective mitochondrial function through donating healthy mitochondria may lead to new insights into the development of more efficient strategies to treat diseases related to mitochondrial dysfunction. PMID:28607632

The Application of COMSOL Multiphysics Package on the Modelling of Complex 3-D Lithospheric Electrical Resistivity Structures - A Case Study from the Proterozoic Orogenic belt within the North China Craton

NASA Astrophysics Data System (ADS)

Guo, L.; Yin, Y.; Deng, M.; Guo, L.; Yan, J.

2017-12-01

At present, most magnetotelluric (MT) forward modelling and inversion codes are based on finite difference method. But its structured mesh gridding cannot be well adapted for the conditions with arbitrary topography or complex tectonic structures. By contrast, the finite element method is more accurate in calculating complex and irregular 3-D region and has lower requirement of function smoothness. However, the complexity of mesh gridding and limitation of computer capacity has been affecting its application. COMSOL Multiphysics is a cross-platform finite element analysis, solver and multiphysics full-coupling simulation software. It achieves highly accurate numerical simulations with high computational performance and outstanding multi-field bi-directional coupling analysis capability. In addition, its AC/DC and RF module can be used to easily calculate the electromagnetic responses of complex geological structures. Using the adaptive unstructured grid, the calculation is much faster. In order to improve the discretization technique of computing area, we use the combination of Matlab and COMSOL Multiphysics to establish a general procedure for calculating the MT responses for arbitrary resistivity models. The calculated responses include the surface electric and magnetic field components, impedance components, magnetic transfer functions and phase tensors. Then, the reliability of this procedure is certificated by 1-D, 2-D and 3-D and anisotropic forward modeling tests. Finally, we establish the 3-D lithospheric resistivity model for the Proterozoic Wutai-Hengshan Mts. within the North China Craton by fitting the real MT data collected there. The reliability of the model is also verified by induced vectors and phase tensors. Our model shows more details and better resolution, compared with the previously published 3-D model based on the finite difference method. In conclusion, COMSOL Multiphysics package is suitable for modeling the 3-D lithospheric resistivity structures under complex tectonic deformation backgrounds, which could be a good complement to the existing finite-difference inversion algorithms.

Complete mitochondrial genome of Ostrea denselamellosa (Bivalvia, Ostreidae).

PubMed

Yu, Hong; Kong, Lingfeng; Li, Qi

2016-01-01

The complete mitochondrial (mt) genome of the flat oyster, Ostrea denselamellosa, was determined using Long-PCR and genome walking techniques in this study. The total length of the mt genome sequence of O. denselamellosa was 16,227 bp, which is the smallest reported Ostreidae mt genome to date. It contained 12 protein-coding genes (lacking of ATP8), 23 transfer RNA genes, and two ribosomal RNA genes. A bias towards a higher representation of nucleotides A and T (60.7%) was detected in the mt genome of O. denselamellosa. The rrnL was split into two fragments (3' half, 711 bp; 5' half, 509 bp), which seems to be the unique characteristics of Ostreidae mt genomes.

Development of device for quantifying magnetic nanoparticle tracers accumulating in sentinel lymph nodes

NASA Astrophysics Data System (ADS)

Kuwahata, Akihiro; Kaneko, Miki; Chikaki, Shinichi; Kusakabe, Moriaki; Sekino, Masaki

2018-05-01

The developed device with electromagnetic coils and small permanent magnets quantifies the iron contents of superparamagnetic iron oxide nanoparticles for sentinel lymph node (SLN) biopsy. To remove diamagnetic and paramagnetic components and detect only superparamagnetic components, a 2nd harmonics signal is detected by a gradiometer under a moderate AC magnetic field (1-2 mT) with the fundamental frequency (2.944 kHz) of the coils and DC magnetic field (1-2 mT) of the magnets. The detection limit with a signal-to-noise ratio of 5 is approximately 0.28 μg of iron, and the device has a wide dynamic range of 104, 0.28 μg-2.8 mg. Additional coils and permanent magnets play an important role producing the optimum distribution of AC/DC magnetic fields for an iron distribution-independent and SLN size-independent quantification. We demonstrated the quantification of the iron in phantoms, which have a size of 3-20 mm with varied iron distributions and contain magnetic nanoparticles numerically. These results indicate that the developed device is useful for quantifying the magnetic nanoparticles accumulating in SLNs.

EMSCOPE - Electromagnetic Component of EarthScope Backbone and Transportable Array Experiments 2006-2008

NASA Astrophysics Data System (ADS)

Egbert, G.; Evans, R.; Ingate, S.; Livelybrooks, D.; Mickus, K.; Park, S.; Schultz, A.; Unsworth, M.; Wannamaker, P.

2007-12-01

USArray (http://www.iris.edu/USArray) in conjunction with EMSOC (Electromagnetic Studies of the Continents) (http://emsoc.ucr.edu/emsoc) is installing magnetotelluric (MT) stations as part of Earthscope. The MT component of Earthscope consists of permanent (Backbone) and transportable long period stations to record naturally occurring, time varying electric and magnetic fields to produce a regional lithospheric/asthensospheric electrical conductivity map of the United States. The recent arrival of 28 long period MT instruments allows for the final installation of the Backbone stations throughout the US and yearly transportable array studies. The Backbone MT survey consists of 7 stations spaced throughout the continental US with preliminary installation at Soap Creek, Oregon; Parkfield, California; Braden, Missouri and Socorro, New Mexico.Siting and permitting are underway or completed at stations in eastern Montana, northern Wisconsin and Virginia. These stations will be recording for at least five years to determine electrical conductivities at depths that extend into the mantle transition zone. The first transportable array experiment was performed in the summer and fall of 2006 in central and eastern Oregon (Oregon Pilot Project) using equipment loaned from EMSOC. Thirty-one long period MT stations were recorded with 14 to 21 day occupations. Preliminary 3D inverse models indicate several lithospheric electrical conductivity anomalies including a linear zone marked by low-high conductivity transition along the Klamath-Blue Mountain Lineament associated with a linear trend of gravity minima. High electrical conductivity values occur in the upper crust under the accreted terrains in the Blue Mountains region. The second transportable array experiment was performed in the summer and fall of 2007 and completes coverage of the Oregon, Washington, and western Idaho, targeting the Cascadia subduction zone, Precambrian boundaries, and sub-basalt lithologies. The 2008 transportable MT experiment will focus on the Snake River Plain and the Yellowstone Hot Spot. The disposition of future USArray magnetotelluric geotransects will be the subject of an upcoming NSF-supported planning workshop. Time series are available now from the IRIS data center (www.iris.edu/data), and magnetotelluric transfer functions will soon be available.

Rock Magnetic Fabrics, Paleomagnetic Vectors, and Rock Magnetic Cyclostratigraphy of the Marcellus FM, Sunbury PA

NASA Astrophysics Data System (ADS)

Minguez, D. A.; Kodama, K. P.

2013-12-01

We present the preliminary results of a multi-faceted rock magnetic study conducted on 195 samples from the Oatka Creek member of the Marcellus formation, where it has been extracted from the subsurface as a drill core near Sunbury, PA. Samples were oriented based on bedding attitude observed within the core and were removed from the core at a spacing of ≈0.25 meters starting from the base (depth ≈ 500 meters) and spanning 51 meters of stratigraphic section. The results of measurements of the anisotropy of magnetic susceptibility (AMS) consistently demonstrate a nearly triaxial fabric with maximum principal axes clustering east-west and horizontal in geographic coordinates, nearly parallel to the direction of bedding strike. AMS minimum principal axes cluster near the pole to the bedding plane. Anisotropy of anhysteretic remanence (AAR) applied with a 100 mT peak field and a 97 μT bias field in 9 orientations demonstrates a markedly different fabric, with maximum principal axis clustering north-south and horizontal in geographic coordinates. Minimum principal axes of AAR cluster steeply (~60-70 degrees) to the west. The discrepancy between AAR and AMS fabrics likely indicates the AMS is dominated by paramagnetic clays, and thus may be interpreted as an east-west intersection lineation of clay particles dipping gently north or south. Paleomagnetic directions obtained using Alternating Field (AF) demagnetization in 5 mT steps up to 110 mT demonstrates a high coercivity remanence (>35 mT) with a south and shallow direction (D= 183.4 I=-14.7). This result is consistent with previous studies of the Marcellus formation and the Devonian Catskill red beds. Thermal demagnetization experiments demonstrate a similar magnetization removed by temperatures between 250 and 350 degrees Celsius, however, continued heating results in the acquisition of strong, inconsistent magnetizations likely the result of oxidizing iron sulfides. Thermal demagnetization of orthogonal partial ARMs applied in 100 mT and 50 mT peak fields was conducted on a subset of samples sealed in aluminum foil with alumina-silica cement to prevent oxidization. The results demonstrate that the low coercivity pARM is removed by 400 degrees Celsius and the high coercivity pARM, which is only 10% of the total remanence, is removed by 600 degrees Celsius. The results suggest the presence of low coercivity Fe sulfides and high coercivity magnetite. Lastly, time series analysis of bulk magnetic susceptibility using the Multi-Taper Method (MTM) demonstrates oscillations with a wavelength of 18 meters above the 99% confidence level with respect to the robust red noise. This wavelength may have a duration of 405 kyr given ancillary chronostratigraphic evidence.

Preimplantation death of xenomitochondrial mouse embryo harbouring bovine mitochondria

PubMed Central

Kawahara, Manabu; Koyama, Shiori; Iimura, Satomi; Yamazaki, Wataru; Tanaka, Aiko; Kohri, Nanami; Sasaki, Keisuke; Takahashi, Masashi

2015-01-01

Mitochondria, cellular organelles playing essential roles in eukaryotic cell metabolism, are thought to have evolved from bacteria. The organization of mtDNA is remarkably uniform across species, reflecting its vital and conserved role in oxidative phosphorylation (OXPHOS). Our objectives were to evaluate the compatibility of xenogeneic mitochondria in the development of preimplantation embryos in mammals. Mouse embryos harbouring bovine mitochondria (mtB-M embryos) were prepared by the cell-fusion technique employing the haemagglutinating virus of Japan (HVJ). The mtB-M embryos showed developmental delay at embryonic days (E) 3.5 after insemination. Furthermore, none of the mtB-M embryos could implant into the maternal uterus after embryo transfer, whereas control mouse embryos into which mitochondria from another mouse had been transferred developed as well as did non-manipulated embryos. When we performed quantitative PCR (qPCR) of mouse and bovine ND5, we found that the mtB-M embryos contained 8.3% of bovine mitochondria at the blastocyst stage. Thus, contamination with mitochondria from another species induces embryonic lethality prior to implantation into the maternal uterus. The heteroplasmic state of these xenogeneic mitochondria could have detrimental effects on preimplantation development, leading to preservation of species-specific mitochondrial integrity in mammals. PMID:26416548

Gene conversion as a mechanism for divergence of a chloroplast tRNA gene inserted in the mitochondrial genome of Brassica oleracea.

PubMed Central

Dron, M; Hartmann, C; Rode, A; Sevignac, M

1985-01-01

We have characterized a 1.7 kb sequence, containing a tRNA Leu2 gene shared by the ct and mt genomes of Brassica oleracea. The two sequences are completely homologous except in two short regions where two distinct gene conversion events have occurred between two sets of direct repeats leading to the insertion of 5 bp in the T loop of the mt copy of the ct gene. This is the first evidence that gene conversion represents the initial evolutionary step in inactivation of transferred ct genes in the mt genome. We also indicate that organelle DNA transfer by organelle fusion is an ongoing process which could be useful in genetic engineering. PMID:4080548

Magnetically tunable elasticity for magnetic hydrogels consisting of carrageenan and carbonyl iron particles.

PubMed

Mitsumata, Tetsu; Honda, Atomu; Kanazawa, Hiroki; Kawai, Mika

2012-10-11

A new class of magnetoelastic gel that demonstrates drastic and reversible changes in storage modulus without using strong magnetic fields was obtained. The magnetic gel consists of carrageenan and carbonyl iron particles. The magnetic gel with a volume fraction of magnetic particles of 0.30 exhibited a reversible increase by a factor of 1400 of the storage modulus upon a magnetic field of 500 mT, which is the highest value in the past for magnetorheological soft materials. It is considered that the giant magnetoelastic behavior is caused by both high dispersibility and high mobility of magnetic particles in the carrageenan gel. The off-field storage modulus of the magnetic gel at volume fractions below 0.30 obeyed the Krieger-Dougherty equation, indicating random dispersion of magnetic particles. At 500 mT, the storage modulus was higher than 4.0 MPa, which is equal to that of magnetic fluids, indicating that the magnetic particles move and form a chain structure by magnetic fields. Morphological study revealed the evidence that the magnetic particles embedded in the gel were aligned in the direction of magnetic fields, accompanied by stretching of the gel network. We conclude that the giant magnetoelastic phenomenon originates from the chain structure consisting of magnetic particles similar to magnetic fluids.

Low-temperature magnetic properties of Heusler compounds Ru2-xFexCrSi (x=0.1,0.3,and0.5)

NASA Astrophysics Data System (ADS)

Ito, Masakazu; Hisamatsu, Toru; Rokkaku, Tsugumi; Shigeta, Iduru; Manaka, Hirotaka; Terada, Norio; Hiroi, Masahiko

2010-07-01

We carried out magnetization M(T) and specific-heat CP(T) measurements of the new Heusler compounds Ru2-xFexCrSi (x=0.1,0.3,and0.5) , which exhibit spin-glass freezing. M(T) has peak- and irreversibility-type anomalies. The temperatures at which these anomalies appear have magnetic field dependence described by the Gabay-Toulouse and de Almeida-Thouless lines in the low-field range. For the magnetic specific heat Cm(T) , we did not observe a discontinuity indicating long-range magnetic phase transition but a broad hump characteristic of spin-glass freezing. Cm(T) in the low-temperature range is described as a combination of linear- and quadratic- T terms. The quadratic- T dependence of Cm(T) is probably associated with excitation of the Ising component of the freezing spins.

Improvement of persistent magnetic field trapping in bulk Y-Ba-Cu-O superconductors

NASA Technical Reports Server (NTRS)

Chen, In-Gann; Weinstein, Roy

1993-01-01

For type-II superconductors, magnetic field can be trapped due to persistent internal supercurrent. Quasi-persistent magnetic fields near 2 T at 60 K (and 1.4 T at 77 K) have been measured in minimagnets made of proton-irradiated melt-textured Y-Ba-Cu-O (MT-Y123) samples. Using the trapping effect, high-field permanent magnets with dipole, quadrupole, or more complicated configurations can be made of existing MT-Y123 material, thus bypassing the need for high-temperature superconductor (HTS) wires. A phenomenological current model has been developed to account for the trapped field intensity and profile in HTS samples. This model is also a guide to select directions of materials development to further improve field trapping properties. General properties such as magnetic field intensities, spatial distributions, stabilities, and temperature dependence of trapped field are discussed.

Dynamics of magnetic-field-induced clustering in ionic ferrofluids from Raman scattering

NASA Astrophysics Data System (ADS)

Heinrich, D.; Goñi, A. R.; Thomsen, C.

2007-03-01

Using Raman spectroscopy, the authors have investigated the aggregation/disgregation of magnetic nanoparticles in dense ionic ferrofluids (IFF) into clusters due to the action of an inhomogeneous external magnetic field. Evidence for changes in particle density and/or effective cluster size were obtained from the variation of the Raman intensity in a time window from 10sto10min for magnetic fields up to 350mT and at a temperature of 28°C. Clustering sets in already at very low fields (>15mT) and the IFF samples exhibit a clear hysteresis in the Raman spectra after releasing the magnetic field, which lasts for many hours at room temperature. The authors determined the characteristic times of the two competing processes, that of field-induced cluster formation and, at room temperature, that of thermal-activated dissociation, to range from 100to150s.

Parallel loss of nuclear-encoded mitochondrial aminoacyl-tRNA synthetases and mtDNA-encoded tRNAs in Cnidaria.

PubMed

Haen, Karri M; Pett, Walker; Lavrov, Dennis V

2010-10-01

Unlike most animal mitochondrial (mt) genomes, which encode a set of 22 transfer RNAs (tRNAs) sufficient for mt protein synthesis, those of cnidarians have only retained one or two tRNA genes. Whether the missing cnidarian mt-tRNA genes relocated outside the main mt chromosome or were lost remains unclear. It is also unknown what impact the loss of tRNA genes had on other components of the mt translational machinery. Here, we explored the nuclear genome of the cnidarian Nematostella vectensis for the presence of mt-tRNA genes and their corresponding mt aminoacyl-tRNA synthetases (mt-aaRS). We detected no candidates for mt-tRNA genes and only two mt-aaRS orthologs. At the same time, we found that all but one cytosolic aaRS appear to be targeted to mitochondria. These results indicate that the loss of mt-tRNAs in Cnidaria is genuine and occurred in parallel with the loss of nuclear-encoded mt-aaRS. Our phylogenetic analyses of individual aaRS revealed that although the nearly total loss of mt-aaRS is rare, aaRS gene deletion and replacement have occurred throughout the evolution of Metazoa.

Mitochondrial genetic diversity, selection and recombination in a canine transmissible cancer

PubMed Central

Strakova, Andrea; Ní Leathlobhair, Máire; Wang, Guo-Dong; Yin, Ting-Ting; Airikkala-Otter, Ilona; Allen, Janice L; Allum, Karen M; Bansse-Issa, Leontine; Bisson, Jocelyn L; Castillo Domracheva, Artemio; de Castro, Karina F; Corrigan, Anne M; Cran, Hugh R; Crawford, Jane T; Cutter, Stephen M; Delgadillo Keenan, Laura; Donelan, Edward M; Faramade, Ibikunle A; Flores Reynoso, Erika; Fotopoulou, Eleni; Fruean, Skye N; Gallardo-Arrieta, Fanny; Glebova, Olga; Häfelin Manrique, Rodrigo F; Henriques, Joaquim JGP; Ignatenko, Natalia; Koenig, Debbie; Lanza-Perea, Marta; Lobetti, Remo; Lopez Quintana, Adriana M; Losfelt, Thibault; Marino, Gabriele; Martincorena, Inigo; Martínez Castañeda, Simón; Martínez-López, Mayra F; Meyer, Michael; Nakanwagi, Berna; De Nardi, Andrigo B; Neunzig, Winifred; Nixon, Sally J; Onsare, Marsden M; Ortega-Pacheco, Antonio; Peleteiro, Maria C; Pye, Ruth J; Reece, John F; Rojas Gutierrez, Jose; Sadia, Haleema; Schmeling, Sheila K; Shamanova, Olga; Ssuna, Richard K; Steenland-Smit, Audrey E; Svitich, Alla; Thoya Ngoka, Ismail; Vițălaru, Bogdan A; de Vos, Anna P; de Vos, Johan P; Walkinton, Oliver; Wedge, David C; Wehrle-Martinez, Alvaro S; van der Wel, Mirjam G; Widdowson, Sophie AE; Murchison, Elizabeth P

2016-01-01

Canine transmissible venereal tumour (CTVT) is a clonally transmissible cancer that originated approximately 11,000 years ago and affects dogs worldwide. Despite the clonal origin of the CTVT nuclear genome, CTVT mitochondrial genomes (mtDNAs) have been acquired by periodic capture from transient hosts. We sequenced 449 complete mtDNAs from a global population of CTVTs, and show that mtDNA horizontal transfer has occurred at least five times, delineating five tumour clades whose distributions track two millennia of dog global migration. Negative selection has operated to prevent accumulation of deleterious mutations in captured mtDNA, and recombination has caused occasional mtDNA re-assortment. These findings implicate functional mtDNA as a driver of CTVT global metastatic spread, further highlighting the important role of mtDNA in cancer evolution. DOI: http://dx.doi.org/10.7554/eLife.14552.001 PMID:27185408

Two-dimensional inverse and three-dimensional forward modeling of MT (magnetotelluric) data to evaluate the mineral potential of the Amphitheater Mountains, Alaska, USA

USGS Publications Warehouse

Pellerin, Louise; Schmidt, Jeanine M.; Hoversten, G. Michael

2003-01-01

As part of an integrated geological and geophysical study to assess the mineral potential in the Amphitheater Mountains of south-central Alaska, USA, two magnetotelluric (MT) profiles were acquired during the summer of 2002. The two parallel MT lines, along with helicopter electromagnetic (HEM) and magnetic data acquired by the State of Alaska Division of Geological and Geophysical Surveys and new detailed U.S. Geological Survey gravity data, are being used to investigate a feeder system to a Late Triassic flood basalt, the Nikolai Greenstone. The platinum-group-element-bearing, layered, and mafic-ultramafic sills of the Fish Lake and Tangle complexes and the geophysical responses suggest the presence of a substantial root of ultramafic material below the Amphitheater synform and several conductive, dense, magnetic, and possibly sulfide-bearing lenses within the surrounding Tangle Formation. The Amphitheater synform was defined by a prominent magnetic anomaly and the repetition of geologic units. Data from the HEM survey were used to assess and correct static shifts in the MT data. A striking conductivity anomaly was observable in the MT apparent resistivity data at sites on each line. Two-dimensional (2-D) inversion was used to model the geometry of the synform structure, electrical properties related to possible mineralization in the top few kilometers, and a feeder root to the magmatic system substantiated with potential field and geological models. The synform plunges to the west with the highly conductive zone ranging from depths of roughly 1.5 to 3.5 km where sampled. Two sensitivity analyses were performed to aid in assessment decisions. First, 2-D models were evaluated from several algorithms, including the rapid-relaxation inversion, the conjugate-gradient method, and Occam?s inversion with the use of different combinations of the apparent resistivity and phase for the transverse electric and magnetic modes. Second, a three-dimensional forward model, developed from the 2-D MT models and other geophysical and geological information, was constructed to further understand the response that could not be fit with the 2-D models.

Bound Pool Fractions Complement Diffusion Measures to Describe White Matter Micro and Macrostructure

PubMed Central

Stikov, Nikola; Perry, Lee M.; Mezer, Aviv; Rykhlevskaia, Elena; Wandell, Brian A.; Pauly, John M.; Dougherty, Robert F.

2010-01-01

Diffusion imaging and bound pool fraction (BPF) mapping are two quantitative magnetic resonance imaging techniques that measure microstructural features of the white matter of the brain. Diffusion imaging provides a quantitative measure of the diffusivity of water in tissue. BPF mapping is a quantitative magnetization transfer (qMT) technique that estimates the proportion of exchanging protons bound to macromolecules, such as those found in myelin, and is thus a more direct measure of myelin content than diffusion. In this work, we combine BPF estimates of macromolecular content with measurements of diffusivity within human white matter tracts. Within the white matter, the correlation between BPFs and diffusivity measures such as fractional anisotropy and radial diffusivity was modest, suggesting that diffusion tensor imaging and bound pool fractions are complementary techniques. We found that several major tracts have high BPF, suggesting a higher density of myelin in these tracts. We interpret these results in the context of a quantitative tissue model. PMID:20828622

Optimization of magnetic field-assisted ultrasonication for the disintegration of waste activated sludge using Box-Behnken design with response surface methodology.

PubMed

Guan, Su; Deng, Feng; Huang, Si-Qi; Liu, Shu-Yang; Ai, Le-Xian; She, Pu-Ying

2017-09-01

This study investigated for the first time the feasibility of using a magnetic field for sludge disintegration. Approximately 41.01% disintegration degree (DD) was reached after 30min at 180mT magnetic field intensity upon separate magnetic field treatment. Protein and polysaccharide contents significantly increased. This test was optimized using a Box-Behnken design (BBD) with response surface methodology (RSM) to fit the multiple equation of the DD. The maximum DD was 43.75% and the protein and polysaccharide contents increased to 56.71 and 119.44mg/L, respectively, when the magnetic field strength was 119.69mT, reaction time was 30.49min, and pH was 9.82 in the optimization experiment. We then analyzed the effects of ultrasound alone. We are the first to combine magnetic field with ultrasound to disintegrate waste-activated sludge (WAS). The optimum effect was obtained with the application of ultrasound alone at 45kHz frequency, with a DD of about 58.09%. By contrast, 62.62% DD was reached in combined magnetic field and ultrasound treatment. This combined test was also optimized using BBD with RSM to fit the multiple equation of DD. The maximum DD of 64.59% was achieved when the magnetic field intensity was 197.87mT, ultrasonic frequency was 42.28kHz, reaction time was 33.96min, and pH was 8.90. These results were consistent with those of particle size and electron microscopy analyses. This research proved that a magnetic field can effectively disintegrate WAS and can be combined with other physical techniques such as ultrasound for optimal results. Copyright © 2017 Elsevier B.V. All rights reserved.

Synthesis of FeCo magnetic nanoalloys and investigation of heating properties for magnetic fluid hyperthermia

NASA Astrophysics Data System (ADS)

Çelik, Özer; Fırat, Tezer

2018-06-01

In this study, size controlled FeCo colloidal magnetic nanoalloys in the range of 11.5-37.2 nm were synthesized by surfactant assistant ball milling method. Magnetic separation technique was performed subsequent to synthesis process so as to obtain magnetic nanoalloy fluid with narrow size distribution. Particle distribution was determined by transmission electron microscope (TEM) while X-ray diffraction (XRD) measurements verified FeCo alloy formation as BCC structure. Vibrating sample magnetometer (VSM) method was used to investigate magnetic properties of nanoalloys. Maximum saturation magnetization and maximum coercivity were obtained as 172 Am2/kg for nanoparticles with the mean size of 37.2 nm and 19.4 mT for nanoparticles with the mean size of 13.3 nm, respectively. The heating ability of FeCo magnetic nanoalloys was determined through calorimetrical measurements for magnetic fluid hyperthermia (MFH) applications. Heat generation mechanisms were investigated by using linear response theory and Stoner-Wohlfarth (S-W) model. Specific absorption rate (SAR) values were obtained in the range of 2-15 W/g for magnetic field frequency of 171 kHz and magnetic field strength in between 6 and 14 mT.

Effect of low-frequency electromagnetic fields on the Escherichia coli growth for application in riverbank filtration

NASA Astrophysics Data System (ADS)

Selamat, Rossitah; Abustan, Ismail; Arshad, Mohd Rizal; Kamal, Nurul Hana Mokhtar

2017-10-01

A 50 Hz low-frequency electromagnetic field (LF-EMF) could give removal effect on the growth of Escherichia coli (E. coli) in the riverbank filtration (RBF) was studied. The LF-EMF strengths were varied from 2 to 10 mT using coil column induce magnetic fields. For this study, two different columns with a diameter of 50 mm and 80 mm were applied; 1.5mm copper wires with the number of turns between 300 to 600 turns. Water samples were flowed into the column at flowrate of 50mL/min with temperature in range of 28-30°C. This study, it was found that the LF-EMF has significant removal effects on E. coli growth, where the removal of 100% of E. coli at 6 mT and 8 mT after 6 hrs exposed. Moreover, for shorter exposure period of 3 hrs exposed, 82% of E. coli removal were detected in 80 mm column for 8 mT and 10 mT magnetic field. These findings indicate that the application of LF-EMF is able to decrease the E. coli, can be and efficient in E. coli growth from river water intake. Thus, the results from this study proved that the utilization of LF-EMF is able to decrease the concentrations of E. coli, and contributes in slowing down their growth. Also, it can be indicated that the LF-EMF kill a part of E. coli exposed in the river water with the large magnetic field and long-time exposure.

Multiparametric MRI Assessment of Human Articular Cartilage Degeneration: Correlation with Quantitative Histology and Mechanical Properties

PubMed Central

Rautiainen, Jari; Nissi, Mikko J.; Salo, Elli-Noora; Tiitu, Virpi; Finnilä, Mikko A.J.; Aho, Olli-Matti; Saarakkala, Simo; Lehenkari, Petri; Ellermann, Jutta; Nieminen, Miika T.

2014-01-01

Purpose To evaluate the sensitivity of quantitative MRI techniques (T1, T1,Gd, T2, continous wave (CW) T1ρ dispersion, adiabatic T1ρ, adiabatic T2ρ, RAFF and inversion-prepared magnetization transfer (MT)) for assessment of human articular cartilage with varying degrees of natural degeneration. Methods Osteochondral samples (n = 14) were obtained from the tibial plateaus of patients undergoing total knee replacement. MRI of the specimens was performed at 9.4 T and the relaxation time maps were evaluated in the cartilage zones. For reference, quantitative histology, OARSI grading and biomechanical measurements were performed and correlated with MRI findings. Results All MRI parameters, except T1,Gd, showed statistically significant differences in tangential and full-thickness ROIs between early and advanced osteoarthritis (OA) groups, as classified by OARSI grading. CW-T1ρ showed significant dispersion in all ROIs and featured classical laminar structure of cartilage with spin-lock powers below 1000 Hz. Adiabatic T1ρ, T2ρ, CW-T1ρ, MT and RAFF correlated strongly with OARSI grade and biomechanical parameters. Conclusion MRI parameters were able to differentiate between early and advanced OA. Furthermore, rotating frame methods, namely adiabatic T1ρ, adiabatic T2ρ, CW-T1ρ and RAFF, as well as MT experiment correlated strongly with biomechanical parameters and OARSI grade, suggesting high sensitivity of the parameters for cartilage degeneration. PMID:25104181

[Exposure to static magnetic field and health hazards during the operation of magnetic resonance scanners].

PubMed

Karpowicz, Jolanta; Gryz, Krzysztof; Politański, Piotr; Zmyślony, Marek

2011-01-01

Magnetic resonance imaging (MRI) scanners belong to the most modern imaging diagnostic devices, which involve workers' exposure to static magnetic fields (SMF) during the preparation and performance of MRI examinations. This paper presents the data on workers' exposure to SMF in the vicinity of MRI scanners and the analysis of SMF-related biological effects and health hazards to find out whether softening the legislative requirements concerning protection against SMF exposure of workers involved in MRI diagnostics is justified. Measurements in the vicinity of 1.5 T MRI magnets showed that exposure to SMF by various scanners depends on both SMF of magnets and scanners design, as well as on work organization. In a routine examination of one patient the radiographer is exposed to SMF exceeding 0.5 mT for app. 1.5-7 min, and up to 1.3 min to SMF exceeding 70 mT. In examinations of patients who need more attention, the duration of exposure may be significantly longer. The mean values (B mean) of exposure to SMF are 5.6-85 mT (mean 30 +/- 19 mT, N = 16). These data demonstrate that only well designed procedures, proper organization of workplace and awareness of workers how to attend the patients without being exposed to strong SMF allow for meeting the requirements of labor law concerning workers' exposure to SMF. The analysis of the available literature on biological effects of SMF has disclosed the lack of data on health effects of many years exposure of workers and the abundance of data demonstrating the biological activity of SMF. Therefore, a radical softening of legislative requirements concerning the exposure of workers' head or trunk is premature, and what is more, it is not indispensable for the development of MRI diagnostic. Such an action should be preceded by extensive international investigations on the health status of workers exposed to electromagnetic fields by MRI scanners.

A multifunctional energy-saving magnetic field generator.

PubMed

Xiong, Hui; Sun, Wanpeng; Liu, Jinzhen; Shi, Jinhua

2018-03-01

To improve the energy utilization of magnetic field generators for biological applications, a multifunctional energy-saving magnetic field generator (ESMFG) is presented. It is capable of producing both an alternating magnetic field (AMF) and a bipolar pulse magnetic field (BPMF) with high energy-saving and energy-reuse rates. Based on a theoretical analysis of an RLC second-order circuit, the energy-saving and energy-reuse rates of both types of magnetic fields can be calculated and are found to have acceptable values. The results of an experimental study using the proposed generator show that for the BPMF, the peak current reaches 130 A and the intensity reaches 70.3 mT. For the AMF, the intensity is 11.0 mT and the RMS current is 20 A. The energy-saving and energy-reuse rates for the AMF generator are 61.3% and 63.5%, respectively, while for the BPMF generator, the energy-saving rate is 33.6%. Thus, the proposed ESMFG has excellent potential for use in biomedical applications.

A multifunctional energy-saving magnetic field generator

NASA Astrophysics Data System (ADS)

Xiong, Hui; Sun, Wanpeng; Liu, Jinzhen; Shi, Jinhua

2018-03-01

To improve the energy utilization of magnetic field generators for biological applications, a multifunctional energy-saving magnetic field generator (ESMFG) is presented. It is capable of producing both an alternating magnetic field (AMF) and a bipolar pulse magnetic field (BPMF) with high energy-saving and energy-reuse rates. Based on a theoretical analysis of an RLC second-order circuit, the energy-saving and energy-reuse rates of both types of magnetic fields can be calculated and are found to have acceptable values. The results of an experimental study using the proposed generator show that for the BPMF, the peak current reaches 130 A and the intensity reaches 70.3 mT. For the AMF, the intensity is 11.0 mT and the RMS current is 20 A. The energy-saving and energy-reuse rates for the AMF generator are 61.3% and 63.5%, respectively, while for the BPMF generator, the energy-saving rate is 33.6%. Thus, the proposed ESMFG has excellent potential for use in biomedical applications.

The experimental study of the DC dielectric breakdown strength in magnetic fluids

NASA Astrophysics Data System (ADS)

Kopčanský, P.; Tomčo, L.; Marton, K.; Koneracká, M.; Potočová, I.; Timko, M.

2004-05-01

Magnetic fluids have been studied for use as a high-voltage insulation. High-voltage measurements on magnetic fluids based on transformer oil, as a function of volume concentrations of magnetite particles and applied magnetic field, showed the increase of the DC dielectric breakdown strength opposite transformer oil, if the saturation magnetization of magnetic fluid is up to 4 mT approximately.

High-Temperature Magnetism as a Probe for Structural and Compositional Uniformity in Ligand-Capped Magnetite Nanoparticles

PubMed Central

2015-01-01

To investigate magnetostructural relationships in colloidal magnetite (Fe3O4) nanoparticles (NPs) at high temperature (300–900 K), we measured the temperature dependence of magnetization (M) of oleate-capped magnetite NPs ca. 20 nm in size. Magnetometry revealed an unusual irreversible high-temperature dependence of M for these NPs, with dip and loop features observed during heating–cooling cycles. Detailed characterizations of as-synthesized and annealed Fe3O4 NPs as well as reference ligand-free Fe3O4 NPs indicate that both types of features in M(T) are related to thermal decomposition of the capping ligands. The ligand decomposition upon the initial heating induces a reduction of Fe3+ to Fe2+ and the associated dip in M, leading to more structurally and compositionally uniform magnetite NPs. Having lost the protective ligands, the NPs continually sinter during subsequent heating cycles, resulting in divergent M curves featuring loops. The increase in M with sintering proceeds not only through elimination of a magnetically dead layer on the particle surface, as a result of a decrease in specific surface area with increasing size, but also through an uncommonly invoked effect resulting from a significant change in Fe3+/Fe2+ ratio with heat treatment. The interpretation of irreversible features in M(T) indicates that reversible M(T) behavior, conversely, can be expected only for ligand-free, structurally and compositionally uniform magnetite NPs, suggesting a general applicability of high-temperature M(T) measurements as an analytical method for probing the structure and composition of magnetic nanomaterials. PMID:25506407

Mitochondrial transfer from Wharton's jelly-derived mesenchymal stem cells to mitochondria-defective cells recaptures impaired mitochondrial function.

PubMed

Lin, Hung-Yu; Liou, Chia-Wei; Chen, Shang-Der; Hsu, Te-Yao; Chuang, Jiin-Haur; Wang, Pei-Wen; Huang, Sheng-Teng; Tiao, Mao-Meng; Chen, Jin-Bor; Lin, Tsu-Kung; Chuang, Yao-Chung

2015-05-01

Adult mesenchymal stem cell (MSC)-conducted mitochondrial transfer has been recently shown to rescue cellular bioenergetics and prevent cell death caused by mitochondrial dysfunction. Wharton's jelly-derived MSCs (WJMSCs) harvested from postpartum umbilical cords are an accessible and abundant source of stem cells. This study aimed to determine the capability of WJMSCs to transfer their own mitochondria and rescue impaired oxidative phosphorylation (OXPHOS) and bioenergetics caused by mitochondrial DNA defects. To do this, WJMSCs were co-cultured with mitochondrial DNA (mtDNA)-depleted ρ(0) cells and the recapture of mitochondrial function was evaluated. WJMSCs were shown to be capable of transferring their own mitochondria into ρ(0) cells and underwent interorganellar mixture within these cells. Permissive culture media (BrdU-containing and pyruvate- and uridine-free) sieved out a survival cell population from the co-cultured WJMSCs (BrdU-sensitive) and ρ(0) cells (pyruvate/uridine-free). The survival cells had mtDNA identical to that of WJMSCs, whereas they expressed cellular markers identical to that of ρ(0) cells. Importantly, these ρ(0)-plus -WJMSC-mtDNA (ρ(+W)) cells recovered the expression of mtDNA-encoded proteins and exhibited functional oxygen consumption and respiratory control, as well as the activity of electron transport chain (ETC) complexes I, II, III and IV. In addition, ETC complex V-inhibitor-sensitive ATP production and metabolic shifting were also recovered. Furthermore, cellular behaviors including attachment-free proliferation, aerobic viability and OXPHOS-reliant cellular motility were also regained after mitochondrial transfer by WJMSCs. The therapeutic effect of WJMSCs-derived mitochondrial transfer was able to stably sustain for at least 45 passages. In conclusion, this study suggests that WJMSCs may serve as a potential therapeutic strategy for diseases linked to mitochondrial dysfunction through the donation of healthy mitochondria to cells with genetic mitochondrial defects. Copyright © 2015 Elsevier B.V. All rights reserved.

Investigation of Electron Transfer-Based Photonic and Electro-Optic Materials and Devices

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bromenshenk, Jerry J; Abbott, Edwin H; Dickensheets, David

2008-03-28

Montana's state program began its sixth year in 2006. The project's research cluster focused on physical, chemical, and biological materials that exhibit unique electron-transfer properties. Our investigators have filed several patents and have also have established five spin-off businesses (3 MSU, 2 UM) and a research center (MT Tech). In addition, this project involved faculty and students at three campuses (MSU, UM, MT Tech) and has a number of under-represented students, including 10 women and 5 Native Americans. In 2006, there was an added emphasis on exporting seminars and speakers via the Internet from UM to Chief Dull Knife Communitymore » College, as well as work with the MT Department of Commerce to better educate our faculty regarding establishing small businesses, licensing and patent issues, and SBIR program opportunities.« less

Thermodynamic properties of Heusler Fe2VSi

NASA Astrophysics Data System (ADS)

Ito, Masakazu; Kai, Keita; Furuta, Tatsuya; Manaka, Hirotaka; Terada, Norio; Hiroi, Masahiko; Kondo, Akihiro; Kindo, Koichi

2018-05-01

We investigated temperature, T, dependence of magnetization, M(T), electrical resistivity, ρ(T), and specific heat, Cp(T), for the Heusler compound Fe2VSi. M(T) shows anomalies at TN1 ˜ 115 K and at TN2 ˜ 35 K. The anomaly at TN1 is caused by the magnetic transition with a crystal structural change. On the other hand, ρ(T) and Cp(T) show only anomaly at TN1, and no trace of anomaly at TN2 is observed. Because of the irreversibility of M(T), which is the characteristic of spin-glass freezing, appears below TN2, a spin-glass freezing may occur at TN2. From the analogy of the Heusler compound (Fe1-xVx ) 3Si with the cubic D03 crystal structure, (0 ≤ x ≤ 0.2), we suggested that the atomic disorder of V site by the Fe atoms gives rise to the magnetic frustration. This could be cause for the spin-glass freezing. By the Clausius-Clapeyron relation, pressure, P, derivative of TN1, (d/TN 1 d P ), is estimated to be ˜-10 K/Gpa.

Impact of selected magnetic fields on the therapeutic effect in patients with lumbar discopathy: A prospective, randomized, single-blinded, and placebo-controlled clinical trial.

PubMed

Taradaj, Jakub; Ozon, Marcin; Dymarek, Robert; Bolach, Bartosz; Walewicz, Karolina; Rosińczuk, Joanna

2018-03-23

Interdisciplinary physical therapy together with pharmacological treatment constitute conservative treatment strategies related to low back pain (LBP). There is still a lack of high quality studies aimed at an objective evaluation of physiotherapeutic procedures according to their effectiveness in LBP. The aim of this study is to carry out a prospective, randomized, single-blinded, and placebocontrolled clinical trial to evaluate the effectiveness of magnetic fields in discopathy-related LBP. A group of 177 patients was assessed for eligibility based on inclusion and exclusion criteria. In the end, 106 patients were randomly assigned into 5 comparative groups: A (n = 23; magnetic therapy: 10 mT, 50 Hz); B (n = 23; magnetic therapy: 5 mT, 50 Hz); C (n = 20; placebo magnetic therapy); D (n = 20; magnetic stimulation: 49.2 μT, 195 Hz); and E (n = 20; placebo magnetic stimulation). All patients were assessed using tests for pain intensity, degree of disability and range of motion. Also, postural stability was assessed using a stabilographic platform. In this study, positive changes in all clinical outcomes were demonstrated in group A (p < 0.05). The most effective clinical effect was observed for pain reduction (p < 0.05), improvement of the range of motion (p < 0.05) and functional ability of the spine (p <0.05). It is also worth noting that the effects in the majority of the measured indicators were mostly short-term (p > 0.05). It was determined that the application of magnetic therapy (10 mT, 50 Hz, 20 min) significantly reduces pain symptoms and leads to an improvement of functional ability in patients with LBP.

Phase transitions, magnetotransport and magnetocaloric effects in a new family of quaternary Ni-Mn-In-Z Heusler alloys.

PubMed

Kazakov, Alexander; Prudnikov, Valerii; Granovsky, Alexander; Perov, Nikolai; Dubenko, Igor; Pathak, Arjun Kumar; Samanta, Tapas; Stadler, Shane; Ali, Naushad; Zhukov, Arcady; Ilyin, Maxim; Gonzalez, Julian

2012-09-01

The magnetic, magnetotransport, and magnetocaloric properties near compound phase transitions in Ni50Mn35In14Z (Z = In, Ge, Al), and Ni48Co2Mn35In15 Heusler alloys have been studied using VSM and SQUID magnetometers (at magnetic fields (H) up to 5 T), four-probe method (at H = 0.005-1.5 T), and an adiabatic magnetocalorimeter (for H changes up to deltaH = 1.8 T), respectively. The martensitic transformation (MT) is accompanied by large magnetoresistance (up to 70%), a significant change in resistivity (up to 200%), and a sign reversal of the ordinary Hall effect coefficient, all related to a strong change in the electronic spectrum at the MT. The field dependences of the Hall resistance are complex in the vicinity of the MT, indicating a change in the relative concentrations of the austenite and martensite phases at strong fields. Negative and positive changes in adiabatic temperatures of about -2 K and +2 K have been observed in the vicinity of MT and Curie temperatures, respectively, for deltaH = 1.8 T.

Magnetic properties and structural characterization of layered (Cr0.5Mn0.5)2AuC synthesized by thermally induced substitutional reaction in (Cr0.5Mn0.5)2GaC

NASA Astrophysics Data System (ADS)

Lai, Chung-Chuan; Tao, Quanzheng; Fashandi, Hossein; Wiedwald, Ulf; Salikhov, Ruslan; Farle, Michael; Petruhins, Andrejs; Lu, Jun; Hultman, Lars; Eklund, Per; Rosen, Johanna

2018-02-01

The magnetic properties of the new phase (Cr0.5Mn0.5)2AuC are compared to the known MAX-phase (Cr0.5Mn0.5)2GaC, where the former was synthesized by thermally induced substitution reaction of Au for Ga in (Cr0.5Mn0.5)2GaC. The reaction introduced a lattice expansion of ˜3% along the c-axis, an enhancement of the coercive field from 30 mT to 140 mT, and a reduction of the Curie temperature and the saturation magnetization. Still, (Cr0.5Mn0.5)2AuC displays similar features in the magnetic field- and temperature-dependent magnetization curves as previously reported magnetic MAX phases, e.g., (Cr0.5Mn0.5)2GaC and (Mo0.5Mn0.5)2GaC. The work suggests a pathway for tuning the magnetic properties of MAX phases.

Field Line Mapping of the Polar Cap Neutral Density Anomaly

NASA Astrophysics Data System (ADS)

Sutton, E. K.; Lin, C. S.; Huang, C. Y.; Cooke, D. L.

2016-12-01

Polar cap neutral density anomaly (PCNDA) events of localized density enhancement with a half size around 700-1000 km had been frequently detected by CHAMP satellite at around 400 km during major magnetic storms with Dst < -100 nT. Density enhancement is probably produced via Joule heating of the thermosphere when a significant amount of energy is deposited in the polar cap. We have identified 12 PCNDA events measured by CHAMP during two major magnetic storms including one initiated by a large solar wind pressure pulse. Their density anomaly locations are found to scatter randomly within the polar circle of 80o magnetic latitude in the geomagnetic coordinate. However after transformed to the Geocentric Solar Wind (GSW) coordinates, their locations become aligned in the direction of solar wind velocity. To better understand the polar cap energy deposition we trace magnetic field lines to the magnetosphere up to 30 earth radii from the ionosphere at 400 km using the data-based Tsyganenko T95 and TS05 magnetic field models. Field line tracing is performed in the GSW coordinate along the CHAMP orbit as well as for the whole polar cap. Each traced magnetic field line is classified into one of the three categories, (1) magnetosphere closed field line (MC) crossing the equatorial plane within 30 earth radii, (2) open field line connected to the magnetopause (MP), or (3) open field line connected to the magnetotail lobe (MT). For nine PCNDA events among the 10 events that we are able to conduct tracing, field lines originated from the density anomaly regions are classified as MT. Only one outlier event in association with a very large IMF BZ is classified as MP. Furthermore the separation angle between the density anomaly peak and the MP-MT field line separation point at 400 km on the X- and Z-axes meridian plane varies from -4o to 16o. Based on these results we speculate that convective electric fields and field aligned currents in the ionosphere might be enhanced near the MP-MT separation point during magnetic storms, resulting in intense localized Joule heating of the thermosphere.

Transfer Kernel Common Spatial Patterns for Motor Imagery Brain-Computer Interface Classification.

PubMed

Dai, Mengxi; Zheng, Dezhi; Liu, Shucong; Zhang, Pengju

2018-01-01

Motor-imagery-based brain-computer interfaces (BCIs) commonly use the common spatial pattern (CSP) as preprocessing step before classification. The CSP method is a supervised algorithm. Therefore a lot of time-consuming training data is needed to build the model. To address this issue, one promising approach is transfer learning, which generalizes a learning model can extract discriminative information from other subjects for target classification task. To this end, we propose a transfer kernel CSP (TKCSP) approach to learn a domain-invariant kernel by directly matching distributions of source subjects and target subjects. The dataset IVa of BCI Competition III is used to demonstrate the validity by our proposed methods. In the experiment, we compare the classification performance of the TKCSP against CSP, CSP for subject-to-subject transfer (CSP SJ-to-SJ), regularizing CSP (RCSP), stationary subspace CSP (ssCSP), multitask CSP (mtCSP), and the combined mtCSP and ssCSP (ss + mtCSP) method. The results indicate that the superior mean classification performance of TKCSP can achieve 81.14%, especially in case of source subjects with fewer number of training samples. Comprehensive experimental evidence on the dataset verifies the effectiveness and efficiency of the proposed TKCSP approach over several state-of-the-art methods.

Transfer Kernel Common Spatial Patterns for Motor Imagery Brain-Computer Interface Classification

PubMed Central

Dai, Mengxi; Liu, Shucong; Zhang, Pengju

2018-01-01

Motor-imagery-based brain-computer interfaces (BCIs) commonly use the common spatial pattern (CSP) as preprocessing step before classification. The CSP method is a supervised algorithm. Therefore a lot of time-consuming training data is needed to build the model. To address this issue, one promising approach is transfer learning, which generalizes a learning model can extract discriminative information from other subjects for target classification task. To this end, we propose a transfer kernel CSP (TKCSP) approach to learn a domain-invariant kernel by directly matching distributions of source subjects and target subjects. The dataset IVa of BCI Competition III is used to demonstrate the validity by our proposed methods. In the experiment, we compare the classification performance of the TKCSP against CSP, CSP for subject-to-subject transfer (CSP SJ-to-SJ), regularizing CSP (RCSP), stationary subspace CSP (ssCSP), multitask CSP (mtCSP), and the combined mtCSP and ssCSP (ss + mtCSP) method. The results indicate that the superior mean classification performance of TKCSP can achieve 81.14%, especially in case of source subjects with fewer number of training samples. Comprehensive experimental evidence on the dataset verifies the effectiveness and efficiency of the proposed TKCSP approach over several state-of-the-art methods. PMID:29743934

Sulfonated Styrene-(ethylene-co-butylene)-styrene/Montmorillonite Clay Nanocomposites: Synthesis, Morphology, and Properties

PubMed Central

2008-01-01

Sulfonated styrene-(ethylene-butylene)-styrene triblock copolymer (SSEBS) was synthesized by reaction of acetyl sulfate with SEBS. SSESB-clay nanocomposites were then prepared from hydrophilic Na-montmorillonite (MT) and organically (quaternary amine) modified hydrophobic nanoclay (OMT) at very low loading. SEBS did not show improvement in properties with MT-based nanocomposites. On sulfonation (3 and 6 weight%) of SEBS, hydrophilic MT clay-based nanocomposites exhibited better mechanical, dynamic mechanical, and thermal properties, and also controlled water–methanol mixture uptake and permeation and AC resistance. Microstructure determined by X-ray diffraction, atomic force microscopy, and transmission electron microscopy due to better dispersion of MT nanoclay particles and interaction of MT with SSEBS matrix was responsible for this effect. The resulting nanocomposites have potential as proton transfer membranes for Fuel Cell applications.

Genome-Wide Transcriptional Changes and Lipid Profile Modifications Induced by Medicago truncatula N5 Overexpression at an Early Stage of the Symbiotic Interaction with Sinorhizobium meliloti

PubMed Central

Santi, Chiara; Molesini, Barbara; Guzzo, Flavia; Vitulo, Nicola

2017-01-01

Plant lipid-transfer proteins (LTPs) are small basic secreted proteins, which are characterized by lipid-binding capacity and are putatively involved in lipid trafficking. LTPs play a role in several biological processes, including the root nodule symbiosis. In this regard, the Medicago truncatula nodulin 5 (MtN5) LTP has been proved to positively regulate the nodulation capacity, controlling rhizobial infection and nodule primordia invasion. To better define the lipid transfer protein MtN5 function during the symbiosis, we produced MtN5-downregulated and -overexpressing plants, and we analysed the transcriptomic changes occurring in the roots at an early stage of Sinorhizobium meliloti infection. We also carried out the lipid profile analysis of wild type (WT) and MtN5-overexpressing roots after rhizobia infection. The downregulation of MtN5 increased the root hair curling, an early event of rhizobia infection, and concomitantly induced changes in the expression of defence-related genes. On the other hand, MtN5 overexpression favoured the invasion of the nodules by rhizobia and determined in the roots the modulation of genes that are involved in lipid transport and metabolism as well as an increased content of lipids, especially galactolipids that characterize the symbiosome membranes. Our findings suggest the potential participation of LTPs in the synthesis and rearrangement of membranes occurring during the formation of the infection threads and the symbiosome membrane. PMID:29257077

Genome-Wide Transcriptional Changes and Lipid Profile Modifications Induced by Medicago truncatula N5 Overexpression at an Early Stage of the Symbiotic Interaction with Sinorhizobium meliloti.

PubMed

Santi, Chiara; Molesini, Barbara; Guzzo, Flavia; Pii, Youry; Vitulo, Nicola; Pandolfini, Tiziana

2017-12-19

Plant lipid-transfer proteins (LTPs) are small basic secreted proteins, which are characterized by lipid-binding capacity and are putatively involved in lipid trafficking. LTPs play a role in several biological processes, including the root nodule symbiosis. In this regard, the Medicago truncatula nodulin 5 (MtN5) LTP has been proved to positively regulate the nodulation capacity, controlling rhizobial infection and nodule primordia invasion. To better define the lipid transfer protein MtN5 function during the symbiosis, we produced MtN5-downregulated and -overexpressing plants, and we analysed the transcriptomic changes occurring in the roots at an early stage of Sinorhizobium meliloti infection. We also carried out the lipid profile analysis of wild type (WT) and MtN5-overexpressing roots after rhizobia infection. The downregulation of MtN5 increased the root hair curling, an early event of rhizobia infection, and concomitantly induced changes in the expression of defence-related genes. On the other hand, MtN5 overexpression favoured the invasion of the nodules by rhizobia and determined in the roots the modulation of genes that are involved in lipid transport and metabolism as well as an increased content of lipids, especially galactolipids that characterize the symbiosome membranes. Our findings suggest the potential participation of LTPs in the synthesis and rearrangement of membranes occurring during the formation of the infection threads and the symbiosome membrane.

Seed orientation and magnetic field strength have more influence on tomato seed performance than relative humidity and duration of exposure to non-uniform static magnetic fields.

PubMed

Poinapen, Danny; Brown, Daniel C W; Beeharry, Girish K

2013-09-15

Different factors (e.g., light, humidity, and temperature) including exposure to static magnetic fields (SMFs), referred here as critical factors, can significantly affect horticultural seed performance. However, the link between magnetic field parameters and other interdependent factors affecting seed viability is unclear. The importance of these critical factors affecting tomato (Solanum lycopersicum L.) var. MST/32 seed performance was assessed after performing several treatments based on a L9 (3(4)) (four factors at three levels) orthogonal array (OA) design. The variable factors in the design were magnetic flux density (R1=332.1±37.8mT; R2=108.7±26.9mT; and R3=50.6±10.5mT), exposure time (1, 2, and 24h), seed orientation (North polarity, South polarity, and control - no magnetic field), and relative humidity (RH) (7.0, 25.5, and 75.5%). After seed moisture content stabilisation at the different chosen RH, seeds were exposed in dark under laboratory conditions to several treatments based on the OA design before performance evaluation. Treatments not employing magnetic field exposure were used as controls. Results indicate that electrolyte leakage rate was reduced by a factor of 1.62 times during seed imbibition when non-uniform SMFs were employed. Higher germination (∼11.0%) was observed in magnetically-exposed seeds than in non-exposed ones, although seedlings emerging from SMF treatments did not show a consistent increase in biomass accumulation. The respective influence of the four critical factors tested on seed performance was ranked (in decreasing order) as seed orientation to external magnetic fields, magnetic field strength, RH, and exposure time. This study suggests a significant effect of non-uniform SMFs on seed performance with respect to RH, and more pronounced effects are observed during seed imbibition rather than during later developmental stages. Copyright © 2013 Elsevier GmbH. All rights reserved.

Mitochondrial DNA of Vitis vinifera and the issue of rampant horizontal gene transfer.

PubMed

Goremykin, Vadim V; Salamini, Francesco; Velasco, Riccardo; Viola, Roberto

2009-01-01

The mitochondrial genome of grape (Vitis vinifera), the largest organelle genome sequenced so far, is presented. The genome is 773,279 nt long and has the highest coding capacity among known angiosperm mitochondrial DNAs (mtDNAs). The proportion of promiscuous DNA of plastid origin in the genome is also the largest ever reported for an angiosperm mtDNA, both in absolute and relative terms. In all, 42.4% of chloroplast genome of Vitis has been incorporated into its mitochondrial genome. In order to test if horizontal gene transfer (HGT) has also contributed to the gene content of the grape mtDNA, we built phylogenetic trees with the coding sequences of mitochondrial genes of grape and their homologs from plant mitochondrial genomes. Many incongruent gene tree topologies were obtained. However, the extent of incongruence between these gene trees is not significantly greater than that observed among optimal trees for chloroplast genes, the common ancestry of which has never been in doubt. In both cases, we attribute this incongruence to artifacts of tree reconstruction, insufficient numbers of characters, and gene paralogy. This finding leads us to question the recent phylogenetic interpretation of Bergthorsson et al. (2003, 2004) and Richardson and Palmer (2007) that rampant HGT into the mtDNA of Amborella best explains phylogenetic incongruence between mitochondrial gene trees for angiosperms. The only evidence for HGT into the Vitis mtDNA found involves fragments of two coding sequences stemming from two closteroviruses that cause the leaf roll disease of this plant. We also report that analysis of sequences shared by both chloroplast and mitochondrial genomes provides evidence for a previously unknown gene transfer route from the mitochondrion to the chloroplast.

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.

Direct measurement of hematite individual particle anisotropy: implications for inclination shallowing in red bed DRMs.

NASA Astrophysics Data System (ADS)

Bilardello, D.; Kodama, K. P.

2007-12-01

Methods to correct for the observed inclination shallowing in sedimentary rocks have been proposed that are based on either models of the geomagnetic field and the resulting directional distribution of paleomagnetic vectors or the magnetic anisotropy of the magnetic minerals carrying the remanence. One limitation of the anisotropy method for hematite-bearing red beds has been the isolation and determination of a rock's detrital hematite individual particle anisotropy. Up to now, our red bed inclination shallowing corrections have been dependent on estimates of hematite individual particle anisotropy using data fit to theoretical correction curves. We have developed a technique for preferentially extracting the detrital hematite particles in a sample in order to directly measure their individual particle anisotropy. The method involves crushing of the sample followed by ball milling and sieving to ensure that the rock particles are smaller than 4Φ. The resulting slurry was then placed in an ultrasonic cleaner for at least 24 hours and finally centrifuged at 1000 rpm for 20 minutes in order to separate the dense, gray iron oxide particles from the red pigmentary grains. The gray, iron oxide-rich slurry was collected by hand and circulated in a magnetic extraction apparatus. The magnetic separate was then collected over a period of two to three weeks. Small amounts of the magnetic separates where mixed in a slow-drying epoxy resin for 24 hours and placed in a DC magnetic field (100 mT to 180 mT) in order to align the grains. The bulk IRM anisotropy of the epoxy samples provides an average individual particle anisotropy for the magnetic grains. Separates were collected from samples of the Mauch Chunk Fm. of Pennsylvania, the Maringouin and the Shepody Fms of New Brunswick/ Nova Scotia and the Kapusaliang Fm. of northwestern China. IRM acquisitions experiments were performed in fields of up to 1.2 T in order to identify the magnetic mineralogies present. Remanence appears to be carried by a low coercivity phase (~50 mT) interpreted to be secondary magnetite and a higher coercivity phase (~350 mT) interpreted to be primary hematite for the Shepody and Maringouin Fms or just one high coercivity component (200- 250 mT) interpreted as primary hematite for the Mauch Chunk and Kapusaliang Fms. Hematite individual particle anisotropy was measured by imparting a 1.2 T IRM to the specimens in 9 different orientations followed by AF demagnetization at 100 mT. Calculated individual particle anisotropy values ranged between 1.28 and 1.45 with bulk anisotropies of ~$40%. Inclination corrections using the directly measured individual particle anisotropies indicate significant inclination shallowing for the Mauch Chunk and Kapusaliang Fms, while more moderate shallowing for the Maringouin and Shepody Fms. Curve fitting techniques with added constraints give a good first order approximation of the individual particle anisotropy, however direct measurement is preferable. The measured particle anisotropies for hematite are low and suggest that there is the potential for significant amounts of shallowing for a hematite DRM. This observation is consistent with redeposition experiments performed by Tauxe and Kent [1984] and the notion that depositional inclination of hematite may suffer from more shallowing than magnetite because of its lower spontaneous magnetization making it more affected by gravitational forces.

Strategic Positioning and Biased Activity of the Mitochondrial Calcium Uniporter in Cardiac Muscle*

PubMed Central

De La Fuente, Sergio; Fernandez-Sanz, Celia; Vail, Caitlin; Agra, Elorm J.; Holmstrom, Kira; Sun, Junhui; Mishra, Jyotsna; Williams, Dewight; Finkel, Toren; Murphy, Elizabeth; Joseph, Suresh K.; Sheu, Shey-Shing; Csordás, György

2016-01-01

Control of myocardial energetics by Ca2+ signal propagation to the mitochondrial matrix includes local Ca2+ delivery from sarcoplasmic reticulum (SR) ryanodine receptors (RyR2) to the inner mitochondrial membrane (IMM) Ca2+ uniporter (mtCU). mtCU activity in cardiac mitochondria is relatively low, whereas the IMM surface is large, due to extensive cristae folding. Hence, stochastically distributed mtCU may not suffice to support local Ca2+ transfer. We hypothesized that mtCU concentrated at mitochondria-SR associations would promote the effective Ca2+ transfer. mtCU distribution was determined by tracking MCU and EMRE, the proteins essential for channel formation. Both proteins were enriched in the IMM-outer mitochondrial membrane (OMM) contact point submitochondrial fraction and, as super-resolution microscopy revealed, located more to the mitochondrial periphery (inner boundary membrane) than inside the cristae, indicating high accessibility to cytosol-derived Ca2+ inputs. Furthermore, MCU immunofluorescence distribution was biased toward the mitochondria-SR interface (RyR2), and this bias was promoted by Ca2+ signaling activity in intact cardiomyocytes. The SR fraction of heart homogenate contains mitochondria with extensive SR associations, and these mitochondria are highly enriched in EMRE. Size exclusion chromatography suggested for EMRE- and MCU-containing complexes a wide size range and also revealed MCU-containing complexes devoid of EMRE (thus disabled) in the mitochondrial but not the SR fraction. Functional measurements suggested more effective mtCU-mediated Ca2+ uptake activity by the mitochondria of the SR than of the mitochondrial fraction. Thus, mtCU “hot spots” can be formed at the cardiac muscle mitochondria-SR associations via localization and assembly bias, serving local Ca2+ signaling and the excitation-energetics coupling. PMID:27637331

Force determination in lateral magnetic tweezers combined with TIRF microscopy.

PubMed

Madariaga-Marcos, J; Hormeño, S; Pastrana, C L; Fisher, G L M; Dillingham, M S; Moreno-Herrero, F

2018-03-01

Combining single-molecule techniques with fluorescence microscopy has attracted much interest because it allows the correlation of mechanical measurements with directly visualized DNA : protein interactions. In particular, its combination with total internal reflection fluorescence microscopy (TIRF) is advantageous because of the high signal-to-noise ratio this technique achieves. This, however, requires stretching long DNA molecules across the surface of a flow cell to maximize polymer exposure to the excitation light. In this work, we develop a module to laterally stretch DNA molecules at a constant force, which can be easily implemented in regular or combined magnetic tweezers (MT)-TIRF setups. The pulling module is further characterized in standard flow cells of different thicknesses and glass capillaries, using two types of micrometer size superparamagnetic beads, long DNA molecules, and a home-built device to rotate capillaries with mrad precision. The force range achieved by the magnetic pulling module was between 0.1 and 30 pN. A formalism for estimating forces in flow-stretched tethered beads is also proposed, and the results compared with those of lateral MT, demonstrating that lateral MT achieve higher forces with lower dispersion. Finally, we show the compatibility with TIRF microscopy and the parallelization of measurements by characterizing DNA binding by the centromere-binding protein ParB from Bacillus subtilis. Simultaneous MT pulling and fluorescence imaging demonstrate the non-specific binding of BsParB on DNA under conditions restrictive to condensation.

The full mitochondrial genome sequence of Raillietina tetragona from chicken (Cestoda: Davaineidae).

PubMed

Liang, Jian-Ying; Lin, Rui-Qing

2016-11-01

In the present study, the complete mitochondrial DNA (mtDNA) sequence of Raillietina tetragona was sequenced and its gene contents and genome organizations was compared with that of other tapeworm. The complete mt genome sequence of R. tetragona is 14,444 bp in length. It contains 12 protein-coding genes, two ribosomal RNA genes, 22 transfer RNA genes, and two non-coding region. All genes are transcribed in the same direction and have a nucleotide composition high in A and T. The contents of A + T of the complete mt genome are 71.4% for R. tetragona. The R. tetragona mt genome sequence provides novel mtDNA marker for studying the molecular epidemiology and population genetics of Raillietina and has implications for the molecular diagnosis of chicken cestodosis caused by Raillietina.

Computer task performance by subjects with Duchenne muscular dystrophy.

PubMed

Malheiros, Silvia Regina Pinheiro; da Silva, Talita Dias; Favero, Francis Meire; de Abreu, Luiz Carlos; Fregni, Felipe; Ribeiro, Denise Cardoso; de Mello Monteiro, Carlos Bandeira

2016-01-01

Two specific objectives were established to quantify computer task performance among people with Duchenne muscular dystrophy (DMD). First, we compared simple computational task performance between subjects with DMD and age-matched typically developing (TD) subjects. Second, we examined correlations between the ability of subjects with DMD to learn the computational task and their motor functionality, age, and initial task performance. The study included 84 individuals (42 with DMD, mean age of 18±5.5 years, and 42 age-matched controls). They executed a computer maze task; all participants performed the acquisition (20 attempts) and retention (five attempts) phases, repeating the same maze. A different maze was used to verify transfer performance (five attempts). The Motor Function Measure Scale was applied, and the results were compared with maze task performance. In the acquisition phase, a significant decrease was found in movement time (MT) between the first and last acquisition block, but only for the DMD group. For the DMD group, MT during transfer was shorter than during the first acquisition block, indicating improvement from the first acquisition block to transfer. In addition, the TD group showed shorter MT than the DMD group across the study. DMD participants improved their performance after practicing a computational task; however, the difference in MT was present in all attempts among DMD and control subjects. Computational task improvement was positively influenced by the initial performance of individuals with DMD. In turn, the initial performance was influenced by their distal functionality but not their age or overall functionality.

Training of Attentional Filtering, but Not of Memory Storage, Enhances Working Memory Efficiency by Strengthening the Neuronal Gatekeeper Network.

PubMed

Schmicker, Marlen; Schwefel, Melanie; Vellage, Anne-Katrin; Müller, Notger G

2016-04-01

Memory training (MT) in older adults with memory deficits often leads to frustration and, therefore, is usually not recommended. Here, we pursued an alternative approach and looked for transfer effects of 1-week attentional filter training (FT) on working memory performance and its neuronal correlates in young healthy humans. The FT effects were compared with pure MT, which lacked the necessity to filter out irrelevant information. Before and after training, all participants performed an fMRI experiment that included a combined task in which stimuli had to be both filtered based on color and stored in memory. We found that training induced processing changes by biasing either filtering or storage. FT induced larger transfer effects on the untrained cognitive function than MT. FT increased neuronal activity in frontal parts of the neuronal gatekeeper network, which is proposed to hinder irrelevant information from being unnecessarily stored in memory. MT decreased neuronal activity in the BG part of the gatekeeper network but enhanced activity in the parietal storage node. We take these findings as evidence that FT renders working memory more efficient by strengthening the BG-prefrontal gatekeeper network. MT, on the other hand, simply stimulates storage of any kind of information. These findings illustrate a tight connection between working memory and attention, and they may open up new avenues for ameliorating memory deficits in patients with cognitive impairments.

Effects of magnetic fields on dissolution of arthritis causing crystals

NASA Astrophysics Data System (ADS)

Takeuchi, Y.; Iwasaka, M.

2015-05-01

The number of gout patients has rapidly increased because of excess alcohol and salt intake. The agent responsible for gout is the monosodium urate (MSU) crystal. MSU crystals are found in blood and consist of uric acid and sodium. As a substitute for drug dosing or excessive water intake, physical stimulation by magnetic fields represents a new medical treatment for gout. In this study, we investigated the effects of a magnetic field on the dissolution of a MSU crystal suspension. The white MSU crystal suspension was dissolved in an alkaline solution. We measured the light transmission of the MSU crystal suspension by a transmitted light measuring system. The magnetic field was generated by a horizontal electromagnet (maximum field strength was 500 mT). The MSU crystal suspension that dissolved during the application of a magnetic field of 500 mT clearly had a higher dissolution rate when compared with the control sample. We postulate that the alkali solution promoted penetration upon diamagnetic rotation and this magnetic field orienting is because of the pronounced diamagnetic susceptibility anisotropy of the MSU crystal. The results indicate that magnetic fields represent an effective gout treatment approach.

78 FR 21071 - Fisheries of the Northeastern United States; Atlantic Herring Fishery; Sub-ACL (Annual Catch...

Federal Register 2010, 2011, 2012, 2013, 2014

2013-04-09

...-ACL (Annual Catch Limit) Harvested for Management Area 2 AGENCY: National Marine Fisheries Service... limit (ACL), optimum yield, domestic harvest and processing, U.S. at-sea processing, border transfer...); the 2013 sub-ACL allocated to Area 2 is 22,146 mt, and 0 mt of the sub-ACL is set aside for research...

Does Feedback-Related Brain Response during Reinforcement Learning Predict Socio-motivational (In-)dependence in Adolescence?

PubMed Central

Raufelder, Diana; Boehme, Rebecca; Romund, Lydia; Golde, Sabrina; Lorenz, Robert C.; Gleich, Tobias; Beck, Anne

2016-01-01

This multi-methodological study applied functional magnetic resonance imaging to investigate neural activation in a group of adolescent students (N = 88) during a probabilistic reinforcement learning task. We related patterns of emerging brain activity and individual learning rates to socio-motivational (in-)dependence manifested in four different motivation types (MTs): (1) peer-dependent MT, (2) teacher-dependent MT, (3) peer-and-teacher-dependent MT, (4) peer-and-teacher-independent MT. A multinomial regression analysis revealed that the individual learning rate predicts students’ membership to the independent MT, or the peer-and-teacher-dependent MT. Additionally, the striatum, a brain region associated with behavioral adaptation and flexibility, showed increased learning-related activation in students with motivational independence. Moreover, the prefrontal cortex, which is involved in behavioral control, was more active in students of the peer-and-teacher-dependent MT. Overall, this study offers new insights into the interplay of motivation and learning with (1) a focus on inter-individual differences in the role of peers and teachers as source of students’ individual motivation and (2) its potential neurobiological basis. PMID:27199873

Near-surface structure of the Central Scandinavian Caledonides in northern Trøndelag, Norway, from correlation of seismic and MT profiles using gravity and magnetic data

NASA Astrophysics Data System (ADS)

Ebbing, J.; Goerigk, L.; Nasuti, A.; Roberts, D.; Korja, T. J.; Smirnov, M.

2014-12-01

The deep geology of northern Trøndelag is somewhat speculative as the Central Scandinavian Caledonides are intersected by the Møre-Trøndelag Fault Complex (MTFC) and only a few depth-penetrating geophysical profiles exist. Here, we correlate the mapped geological units and faults between a seismic-reflection profile and a MT profile. The seismic-reflection data were acquired in 5 segments over the period 1986-1990. The westernmost section of the seismic profile is dominated by a complex pattern of reflections and diffractions. This type of pattern is typical of polydeformed terranes with a mixture of contrasting felsic and mafic lithologies. The two steeply-dipping strands of the MTFC (Hitra-Snåsa and Verran faults) that transect the profile do not show any distinctive signature in the seismic data. The MT data were acquired in 2007 from the Swedish border to the Norwegian coast. The conductivity profile shows some distinct vertical changes as well as changes from the near-surface to shallow depths. The strands of the MTFC show especially a distinctive change in conductivity. The two profiles are almost parallel but separated by 100 km. To correlate the structures seen on both profiles, we have applied lineament analysis and 3D modelling of the gravity and magnetic field. The tilt derivative of the magnetic and isostatic gravity anomaly clearly allows us to identify and link the main geological boundaries between the profiles and to trace the strands of the MTFC from one profile to the other. This trend analysis indicates that at least the Verran Fault visibly modifies the pattern of seismic reflections. However, the main change in crustal lithology occurs farther to the west, almost at the coast where the Tarva Fault intersects the MT profile. This integrated analysis shows the benefit of combining gravity and magnetic interpretations with MT and seismic data to enable us to understand the near-surface geology and structure in more detail.

Twin-enhanced magnetic torque

NASA Astrophysics Data System (ADS)

Hobza, Anthony; García-Cervera, Carlos J.; Müllner, Peter

2018-07-01

Magnetic shape memory alloys experience magnetic-field-induced torque due to magnetocrystalline anisotropy and shape anisotropy. In a homogeneous magnetic field, torque results in bending of long samples. This study investigates the torque on a single crystal of Ni-Mn-Ga magnetic shape memory alloy constrained with respect to bending in an external magnetic field. The dependence of the torque on external magnetic field magnitude, strain, and twin boundary structure was studied experimentally and with computer simulations. With increasing magnetic field, the torque increased until it reached a maximum near 700 mT. Above 200 mT, the torque was not symmetric about the equilibrium orientation for a sample with one twin boundary. The torque on two specimen with equal strain but different twin boundary structures varied systematically with the spatial arrangement of crystallographic twins. Numerical simulations show that twin boundaries suppress the formation of 180° domains if the direction of easy magnetization between two twin boundaries is parallel to a free surface and the magnetic field is perpendicular to that surface. For a particular twin microstructure, the torque decreases with increasing strain by a factor of six due to the mutual compensation of magnetocrystalline and shape anisotropy. When free rotation is suppressed such as in transducers of magneto-mechanical actuators, magnetic-field-induced torque creates strong bending forces, which may cause friction and failure under cyclic loading.

Controlling the orientation of spin-correlated radical pairs by covalent linkage to nanoporous anodic aluminum oxide membranes.

PubMed

Chen, Hsiao-Fan; Gardner, Daniel M; Carmieli, Raanan; Wasielewski, Michael R

2013-10-07

Ordered multi-spin assemblies are required for developing solid-state molecule-based spintronics. A linear donor-chromophore-acceptor (D-C-A) molecule was covalently attached inside the 150 nm diam. nanopores of an anodic aluminum oxide (AAO) membrane. Photoexcitation of D-C-A in a 343 mT magnetic field results in sub-nanosecond, two-step electron transfer to yield the spin-correlated radical ion pair (SCRP) (1)(D(+)˙-C-A(-)˙), which then undergoes radical pair intersystem crossing (RP-ISC) to yield (3)(D(+)˙-C-A(-)˙). RP-ISC results in S-T0 mixing to selectively populate the coherent superposition states |S'> and |T'>. Microwave-induced transitions between these states and the unpopulated |T(+1)> and |T(-1)> states result in spin-polarized time-resolved EPR (TREPR) spectra. The dependence of the electron spin polarization (ESP) phase of the TREPR spectra on the orientation of the AAO membrane pores relative to the externally applied magnetic field is used to determine the overall orientation of the SCRPs within the pores at room temperature.

A versatile UHV transport and measurement chamber for neutron reflectometry under UHV conditions

NASA Astrophysics Data System (ADS)

Syed Mohd, A.; Pütter, S.; Mattauch, S.; Koutsioubas, A.; Schneider, H.; Weber, A.; Brückel, T.

2016-12-01

We report on a versatile mini ultra-high vacuum (UHV) chamber which is designed to be used on the MAgnetic Reflectometer with high Incident Angle of the Jülich Centre for Neutron Science at Heinz Maier-Leibnitz Zentrum in Garching, Germany. Samples are prepared in the adjacent thin film laboratory by molecular beam epitaxy and moved into the compact chamber for transfer without exposure to ambient air. The chamber is based on DN 40 CF flanges and equipped with sapphire view ports, a small getter pump, and a wobble stick, which serves also as sample holder. Here, we present polarized neutron reflectivity measurements which have been performed on Co thin films at room temperature in UHV and in ambient air in a magnetic field of 200 mT and in the Q-range of 0.18 Å-1. The results confirm that the Co film is not contaminated during the polarized neutron reflectivity measurement. Herewith it is demonstrated that the mini UHV transport chamber also works as a measurement chamber which opens new possibilities for polarized neutron measurements under UHV conditions.

A versatile UHV transport and measurement chamber for neutron reflectometry under UHV conditions.

PubMed

Syed Mohd, A; Pütter, S; Mattauch, S; Koutsioubas, A; Schneider, H; Weber, A; Brückel, T

2016-12-01

We report on a versatile mini ultra-high vacuum (UHV) chamber which is designed to be used on the MAgnetic Reflectometer with high Incident Angle of the Jülich Centre for Neutron Science at Heinz Maier-Leibnitz Zentrum in Garching, Germany. Samples are prepared in the adjacent thin film laboratory by molecular beam epitaxy and moved into the compact chamber for transfer without exposure to ambient air. The chamber is based on DN 40 CF flanges and equipped with sapphire view ports, a small getter pump, and a wobble stick, which serves also as sample holder. Here, we present polarized neutron reflectivity measurements which have been performed on Co thin films at room temperature in UHV and in ambient air in a magnetic field of 200 mT and in the Q-range of 0.18 Å -1 . The results confirm that the Co film is not contaminated during the polarized neutron reflectivity measurement. Herewith it is demonstrated that the mini UHV transport chamber also works as a measurement chamber which opens new possibilities for polarized neutron measurements under UHV conditions.

[Influence of extremely low frequency magnetic field on total protein and -sh groups concentrations in liver homogenates].

PubMed

Ciejka, Elżbieta; Kowalczyk, Agata; Gorąca, Anna

2014-01-01

Free radicals are atoms, molecules or their fragments, whose excess leads to the development of oxidative stress, the cause of many neoplastic, neurodegenerative and inflammatory diseases, as well as aging of organisms. Industrial pollution, tobacco smoke, ionizing radiation, ultrasound and magnetic fields are the major exogenous sources of free radicals. The low frequency mag- netic field is commonly applied in physiotherapy. The aim of the present study was to evaluate the effect of extremely low frequency magnetic field (1L.F-MF) on the concentration ofsullhydryl groups (-SH) and proteins in liver tissues of experimental animals de- pending on the time of exposure to the field. Twenty one Sprague-D)awley male rats, aged 3-4 months were randomly divided into 3 experimental groups (each containing 7 animals): controls (group I), the rats exposed to IEI.F-MF of 40 Hz, 7 mT (this kind of the ELF-MF is mostly used in magnetotherapy), 30 min/day for 2 weeks (group II) and the rats exposed to 40 Hz, 7 mT for 60 min/day for 2 weeks (group III). The concentrations of proteins and sulfhydryl groups in the liver tissues were determined after exposure to magnetic fields. Exposure to low magnetic field: 40 Hz, 7 mT for 30 min/day and 60 min/day for 2 weeks caused a significant increase in the concentration of-SH groups and total protein levels in the liver tissues. The study results suggest that exposure to magnetic fields leads to the development of adaptive mechanisms to maintain the balance in the body oxidation-reduction and in the case of the studied parameters does not depend on the time of exposure.

Mitochondrial Replacement Therapy in Reproductive Medicine

PubMed Central

Wolf, Don P.; Mitalipov, Nargiz; Mitalipov, Shoukhrat

2015-01-01

Mitochondrial dysfunction is implicated in disease and in age-related infertility. Mitochondrial replacement therapies (MRT) in oocytes or zygotes such as pronuclear (PNT), spindle (ST) or polar body (PBT) transfer could prevent second generation transmission of mitochondrial DNA (mtDNA) defects. PNT, associated with high levels of mtDNA carryover in mice but low levels in human embryos, carries ethical issues secondary to donor embryo destruction. ST, developed in primates, supports normal development to adults and low mtDNA carryover. PBT in mice, coupled with PN or ST, may increase the yield of reconstructed embryos with low mtDNA carryover. MRT also offers replacement of the deficient cytoplasm in oocytes from older patients, with the expectation of high pregnancy rates following in vitro fertilization. PMID:25573721

Complete magnetic field dependence of SABRE-derived polarization.

PubMed

Kiryutin, Alexey S; Yurkovskaya, Alexandra V; Zimmermann, Herbert; Vieth, Hans-Martin; Ivanov, Konstantin L

2018-07-01

Signal amplification by reversible exchange (SABRE) is a promising hyperpolarization technique, which makes use of spin-order transfer from parahydrogen (the H 2 molecule in its singlet spin state) to a to-be-polarized substrate in a transient organometallic complex, termed the SABRE complex. In this work, we present an experimental method for measuring the magnetic field dependence of the SABRE effect over an ultrawide field range, namely, from 10 nT to 10 T. This approach gives a way to determine the complete magnetic field dependence of SABRE-derived polarization. Here, we focus on SABRE polarization of spin-1/2 hetero-nuclei, such as 13 C and 15 N and measure their polarization in the entire accessible field range; experimental studies are supported by calculations of polarization. Features of the field dependence of polarization can be attributed to level anticrossings in the spin system of the SABRE complex. Features at magnetic fields of the order of 100 nT-1 μT correspond to "strong coupling" of protons and hetero-nuclei, whereas features found in the mT field range stem from "strong coupling" of the proton system. Our approach gives a way to measuring and analyzing the complete SABRE field dependence, to probing NMR parameters of SABRE complexes and to optimizing the polarization value. Copyright © 2017 John Wiley & Sons, Ltd.

Paleomagnetic and rock magnetic investigation of an exceptionally pristine sample from Mars

NASA Astrophysics Data System (ADS)

Rochette, P.; Gattacceca, J.; Cournède, C.; Sautter, V.

2012-04-01

Unaltered samples from Mars are available as meteorites recovered right after their fall. Only 4 of them were available (the last one fell 50 yrs ago) until the recovery of a Martian meteorite fallen in Morocco in July 2010. We obtained a 1.8 g sample away from the fusion crust of this fall (named Tissint), to study its magnetic properties. Petrographic examination indicates the meteorite is an olivine-phyric shergottite, with pyrrhotite and chromite as the only identified potentially magnetic minerals. Rock magnetism is fully consistent with pyrrhotite-bearing shergottites [1], with a high coercivity of remanence (Mrs/Ms ≈0.4, Bcr of 80 mT, S ratio of -0.75, etc). Ms is about 0.15 Am2/kg, equivalent to 1 wt.% pyrrhotite. Micromagnetometric investigation should allow to identify the mineral phase responsible for remanence and solve the debate on chromite [2] versus pyrrhotite [1]. Magnetic anisotropy and NRM are directionally consistent in oriented subsamples. The meteorite shows no sign of remagnetization by magnet application (a customary practice among meteorite hunters). NRM is very hard with respect to alternating field demagnetization with a median destructive field of about 70 mT. Very low NRM/IRM derivative ratio (REM' integrated between 10 and 80 mT is about 2 10-4, the lowest ever measured in a meteorite) suggest NRM acquisition in very low ambient field (<1 µT). Moreover, the high coercivity of the NRM and the increasing REM' value with alternating field suggest that the NRM may be a shock-hardened magnetization (for instance a primary thermoremanent magnetization acquired in a crustal remanent field of a few µT, and later shocked in a similar field). Indeed this meteorite has suffered high shock pressure, as evidenced by amorphization of plagioclase and formation of numerous large melt pockets. [1] Rochette P et al. Meteorit. Planet. Sci, 40, 529-540 (2005) [2] Yu Y.J., Earth Planet. Sci. Lett. 250, 27-37 (2006)

Magnetic enhancement of Baltic Sea sapropels by greigite magnetofossils

NASA Astrophysics Data System (ADS)

Reinholdsson, M.; Snowball, I.; Zillén, L.; Lenz, C.; Conley, D. J.

2013-03-01

Magnetotactic bacteria (MTB) are known to biosynthesise single-domain magnetite (Fe3O4) for geomagnetic navigation and their relict magnetosomes (called magnetofossils) can control the magnetic properties of lake and marine sediments. Magnetotactic bacteria also produce greigite (Fe3S4) magnetosomes but, compared to those made of magnetite, relatively little is known about the sedimentary environments where they are produced and the magnetic properties of the preserved particles. We studied the magnetic properties of sediment cores from two basins (the North Central Baltic Proper and eastern Gotland Basin) that currently experience hypoxia and we discovered the magnetic enhancement of older laminated sapropels, which are a signal of past occurrences of anoxia and hypoxia in the Baltic Sea. Magnetic concentrates extracted from the laminated sapropels were characterised by transmission electron microscopy and energy dispersive X-ray spectrometry and we identified only single-domain greigite (Fe3S4) particles with a mean size of 55×75 nm, which we interpret as magnetofossils due to diagnostic chains of individual particles separated by an intact dividing membrane. The degree of magnetic enhancement in the laminated sapropels has a positive relationship with loss-on-ignition data, which indicates a link between the production of greigite magnetosomes, organic matter supply and preservation and redox conditions. The coercive force of collections of non-interacting greigite magnetofossils is ∼13 mT, which is considerably lower than the magnetite counterparts (∼30 mT) and strictly non-bacterial and larger greigite single-domain grains (∼60 mT). The values of the interparametric ratios of SIRM/χ, χARM/SIRM and χARM/χ that we obtain for our greigite magnetofossils overlap with those previously considered to be diagnostic of magnetosomal magnetite. The presence of bacterial greigite, which is easily detected by magnetic measurements, forms a proxy for hypoxia and anoxia, thus aiding the palaeoenvironmental interpretation of how oxygen conditions in the Baltic Sea have changed over time.

[Influence of low frequency magnetic field used in magnetotherapy on interleukin 6 (IL-6) contents in rat heart and brain].

PubMed

Ciejka, Elżbieta; Skibska, Beata; Gorąca, Anna

2017-06-27

The human population is exposed ever more frequently to magnetic fields (MF). This is due to both technological progress and development of the economy as well as to advances made in medical science. That is why the thorough understanding and systematized knowledge about mechanisms by which MF exerts its effects on living organisms play such an important role. In this context the health of MF-exposed people is the subject of particular concern. The aim of the study was to evaluate the effect of extremely low frequency magnetic field (ELFMF) used in magnetotherapy on the concentration of interleukin 6 (IL-6) in rat heart and brain. The male rats were randomly divided into 3 experimental groups: group I - control, without contact with magnetic field; group II - exposed to bipolar, rectangular magnetic field 40 Hz, induction "peak-to-peak" 7 mT 30 min/day for 2 weeks; and group III - exposed to bipolar, rectangular magnetic field 40 Hz, 7 mT 60 min/day for 2 weeks. Concentration of IL-6 in the heart and brain of animals was measured after MF exposure. Exposure to ELFMF: 40 Hz, induction "peak-to-peak" 7 mT 30 min/day for 2 weeks caused a significant IL-6 increase in rat hearts compared to the control group (p < 0.05) and a non-significant IL-6 decrease in rat brain. The magnetic field applied for 60 min resulted in non-significant IL-6 increase in rat hearts compared to the control group and significant IL-6 decrease in rat brain (p < 0.05). The influence of magnetic field on inflammation in the body varies depending on the MF parameters and the affected tissues or cells. Med Pr 2017;68(4):517-523. This work is available in Open Access model and licensed under a CC BY-NC 3.0 PL license.

Time-efficient high-resolution whole-brain three-dimensional macromolecular proton fraction mapping

PubMed Central

Yarnykh, Vasily L.

2015-01-01

Purpose Macromolecular proton fraction (MPF) mapping is a quantitative MRI method that reconstructs parametric maps of a relative amount of macromolecular protons causing the magnetization transfer (MT) effect and provides a biomarker of myelination in neural tissues. This study aimed to develop a high-resolution whole-brain MPF mapping technique utilizing a minimal possible number of source images for scan time reduction. Methods The described technique is based on replacement of an actually acquired reference image without MT saturation by a synthetic one reconstructed from R1 and proton density maps, thus requiring only three source images. This approach enabled whole-brain three-dimensional MPF mapping with isotropic 1.25×1.25×1.25 mm3 voxel size and scan time of 20 minutes. The synthetic reference method was validated against standard MPF mapping with acquired reference images based on data from 8 healthy subjects. Results Mean MPF values in segmented white and gray matter appeared in close agreement with no significant bias and small within-subject coefficients of variation (<2%). High-resolution MPF maps demonstrated sharp white-gray matter contrast and clear visualization of anatomical details including gray matter structures with high iron content. Conclusions Synthetic reference method improves resolution of MPF mapping and combines accurate MPF measurements with unique neuroanatomical contrast features. PMID:26102097

DOE Office of Scientific and Technical Information (OSTI.GOV)

Do, Minhwa; Jang, Won-Gu; Hwang, Jeong Hee

Highlights: Black-Right-Pointing-Pointer We success serial SCNT through the third generation using pig fibroblasts. Black-Right-Pointing-Pointer Donor-specific mtDNA in the recloned pigs was detected. Black-Right-Pointing-Pointer SCNT affect mtDNA mounts. -- Abstract: Somatic cell nuclear transfer (SCNT) has been established for the transmission of specific nuclear DNA. However, the fate of donor mitochondrial DNA (mtDNA) remains unclear. Here, we examined the fate of donor mtDNA in recloned pigs through third generations. Fibroblasts of recloned pigs were obtained from offspring of each generation produced by fusion of cultured fibroblasts from a Minnesota miniature pig (MMP) into enucleated oocytes of a Landrace pig. The D-loopmore » regions from the mtDNA of donor and recipient differ at nucleotide sequence positions 16050 (A{yields}T), 16062 (T{yields}C), and 16135 (G{yields}A). In order to determine the fate of donor mtDNA in recloned pigs, we analyzed the D-loop region of the donor's mtDNA by allele-specific PCR (AS-PCR) and real-time PCR. Donor mtDNA was successfully detected in all recloned offspring (F1, F2, and F3). These results indicate that heteroplasmy that originate from donor and recipient mtDNA is maintained in recloned pigs, resulting from SCNT, unlike natural reproduction.« less

Element-specific observation of the ferromagnetic ordering process in UCoAl via soft x-ray magnetic circular dichroism

NASA Astrophysics Data System (ADS)

Takeda, Yukiharu; Saitoh, Yuji; Okane, Tetsuo; Yamagami, Hiroshi; Matsuda, Tatsuma D.; Yamamoto, Etsuji; Haga, Yoshinori; Ōnuki, Yoshichika

2018-05-01

We have performed soft x-ray magnetic circular dichroism (XMCD) experiments on the itinerant-electron metamagnet UCoAl at the U 4 d -5 f (N4 ,5) and Co 2 p -3 d (L2 ,3) absorption edges in order to investigate the magnetic properties of the U 5 f and Co 3 d electrons separately. From the line shape of the XMCD spectrum, it is deduced that the orbital magnetic moment of the Co 3 d electrons is unusually large. Through the systematic temperature (T )- and magnetic field (H )-dependent XMCD measurements, we have obtained two types of the magnetization curve as a function of H and T (M-H curve and M-T curve, respectively). The metamagnetic transition from a paramagnetic state to a field-induced ferromagnetic state was clearly observed under 15 K at HM. The value of the HM and its T dependence agree well between the U and Co sites, and the bulk magnetization. Whereas, we have discovered the remarkable differences in the M-H and M-T curves between the U and Co sites. The present findings clearly show that the role of the Co 3 d electrons should be considered more carefully in order to understand the origin of the magnetic ordering in UCoAl.

Time-resolved luminescence measurements of the magnetic field effect on paramagnetic photosensitizers in photodynamic reactions

NASA Astrophysics Data System (ADS)

Mermut, O.; Bouchard, J.-P.; Cormier, J.-F.; Desroches, P.; Diamond, K. R.; Fortin, M.; Gallant, P.; Leclair, S.; Marois, J.-S.; Noiseux, I.; Morin, J.-F.; Patterson, M. S.; Vernon, M.

2008-02-01

The development of multimodal molecular probes and photosensitizing agents for use in photodynamic therapy (PDT) is vital for optimizing and monitoring cytotoxic responses. We propose a combinatorial approach utilizing photosensitizing molecules that are both paramagnetic and luminescent with multimodal functionality to perturb, control, and monitor molecular-scale reaction pathways in PDT. To this end, a time-domain single photon counting lifetime apparatus with a 400 nm excitation source has been developed and integrated with a variable low field magnet (0- 350mT). The luminescence lifetime decay function was measured in the presence of a sweeping magnetic field for a custom designed photosensitizing molecule in which photoinduced electron transfer was studied The photosensitizer studied was a donor-acceptor complex synthesized using a porphyrin linked to a fullerene molecule. The magneto-optic properties were investigated for the free-base photosensitizer complex as well as those containing either diamagnetic (paired electron) or paramagnetic (unpaired electron) metal centers, Zn(II) and Cu(II). The magnetic field was employed to affect and modify the spin states of radical pairs of the photosensitizing agents via magnetically induced hyperfine and Zeeman effects. Since the Type 1 reaction pathway of an excited triplet state photosensitizer involves the production of radical species, lifetime measurements were conducted at low dissolved oxygen concentration (0.01ppm) to elucidate the dependence of the magnetic perturbation on the photosensitization mechanistic pathway. To optimize the magnetic response, a solvent study was performed examining the dependence of the emission properties on the magnetic field in solutions of varying dielectric constants. Lastly, the cytotoxicity in murine tumor cell suspensions was investigated for the novel porphyrin-fullerene complex by inducing photodynamic treatments and determining the associated cell survival.

μSR investigation of magnetism and magnetoelectric coupling in Cu2OSeO3

NASA Astrophysics Data System (ADS)

Maisuradze, A.; Guguchia, Z.; Graneli, B.; Rønnow, H. M.; Berger, H.; Keller, H.

2011-08-01

A detailed zero- and transverse-field muon spin rotation investigation of magnetism and the magnetoelectric coupling in Cu2OSeO3 is reported. An internal magnetic field Bint(T=0)=85.37(25) mT was found, in agreement with a ferrimagnetic state below Tc=57.0(1) K. The temperature dependence of the magnetic order parameter is well described by the relation Bint=B(0)(1-(T/Tc)2)β˜ with an effective exponent β˜≃0.39(1), which is close to the critical exponent β≃1/3 for a three-dimensional (3D) magnetic system. Just above Tc the muon relaxation rate follows the power law λ(T)∝(T/Tc-1)-ω˜ with ω˜=1.06(9), which is characteristic for 3D ferromagnets. Measurements of Bint(T) with and without an applied electrostatic field E=1.66×105 V/m suggest a possible electric-field effect of magnitude ΔBV=BV(0V)-BV(500V)=-0.4(4) mT.

Stress remagnetization in pyrrhotite-calcite synthetic aggregates

NASA Astrophysics Data System (ADS)

Robion, Philippe; Borradaile, Graham J.

2001-01-01

Stress-induced remagnetization has been applied to multidomain pyrrhotite-calcite synthetic aggregates in a triaxial rig. Experimental deformation used 150MPa confining pressure, a constant strain rate of 10-5 s-1 and applied differential stresses of up to 70MPa. New components of magnetization, parallel to the direction of the pressure vessel field, were added to the pre-deformational magnetization. The intensity of remagnetization (M'-M0) increases with the intensity of the applied differential stress and affects the coercivity fraction below 15mT. Bulk shortening is less than 8 per cent, thus grain rotation cannot explain selective remagnetization of the low-coercivity fraction. Remagnetization is thus attributed to deformational viscous remanent magnetization (DVRM). It is observed that high-coercivity (>15mT) grains do not remagnetize. There is, however, slight progressive rotation of pre-deformational magnetization with increasing strain up to 8 per cent of bulk shortening. The lack of piezoremanent magnetization in the high-coercivity range may be due to defects introduced in pyrrhotite during sample preparation. Experiments using synthetic pyrrhotite, expected to show low dislocation densities, would be necessary to test this effect.

50 Hz sinusoidal magnetic fields do not affect human lymphocyte activation and proliferation in vitro

NASA Astrophysics Data System (ADS)

Capri, Miriam; Mesirca, Pietro; Remondini, Daniel; Carosella, Simona; Pasi, Sara; Castellani, Gastone; Franceschi, Claudio; Bersani, Ferdinando

2004-12-01

In the last 30 years, an increasing public concern about the possible harmful effects of electromagnetic fields generated by power lines and domestic appliances has pushed the scientific community to search for a correct and comprehensive answer to this problem. In this work the effects of exposure to 50 Hz sinusoidal magnetic fields, with a magnetic flux density of 0.05 mT and 2.5 mT (peak values), were studied on human peripheral blood mononuclear cells (PBMCs) collected from healthy young and elderly donors. Cell activation and proliferation were investigated by using flow cytometry techniques and 3H-TdR incorporation assays, respectively. The results obtained indicated that exposure to the fields altered neither DNA synthesis nor the capacity of lymphocytes to enter the activation phase and progress into the cell cycle. Thus, the conclusions are that two important functional phases of human lymphocytes, such as activation and proliferation, are not affected by exposures to 50 Hz magnetic fields similar to those found under power lines.

Robust fully-compensated ferrimagnetism and semiconductivity in inverse Heusler compounds: Ti2VZ (Z = P, As, Sb, Bi)

NASA Astrophysics Data System (ADS)

Zhang, Y. J.; Liu, Z. H.; Liu, G. D.; Ma, X. Q.; Cheng, Z. X.

2018-03-01

Compensated ferrimagnets, due to their zero net magnetization and potential for large spin-polarization, have been attracting more and more attention in the field of spintronics. We demonstrate potential candidate materials among the inverse Heusler compounds Ti2VZ (Z = P, As, Sb, Bi) by first principles calculations. It is found that these compounds with 18 valence electrons per unit cell have zero net magnetic moment with compensated sublattice magnetization, as anticipated by a variant of Slater-Pauling rule of Mt = NV - 18, where Mt is the total spin magnetic moment per formula unit and NV is the number of valence electrons per formula unit, and show semiconducting behavior in both spin channels with a moderate exchange splitting, as with ordinary ferromagnetic semiconductors. Furthermore, the fully compensated ferrimagnetism and semiconductivity are rather robust over a wide range of lattice contraction and expansion. Due to the above distinct advantages, these compounds will be promising candidates for spintronic applications.

Expanding the functional human mitochondrial DNA database by the establishment of primate xenomitochondrial cybrids

PubMed Central

Kenyon, Lesley; Moraes, Carlos T.

1997-01-01

The nuclear and mitochondrial genomes coevolve to optimize approximately 100 different interactions necessary for an efficient ATP-generating system. This coevolution led to a species-specific compatibility between these genomes. We introduced mitochondrial DNA (mtDNA) from different primates into mtDNA-less human cells and selected for growth of cells with a functional oxidative phosphorylation system. mtDNA from common chimpanzee, pigmy chimpanzee, and gorilla were able to restore oxidative phosphorylation in the context of a human nuclear background, whereas mtDNA from orangutan, and species representative of Old-World monkeys, New-World monkeys, and lemurs were not. Oxygen consumption, a sensitive index of respiratory function, showed that mtDNA from chimpanzee, pigmy chimpanzee, and gorilla replaced the human mtDNA and restored respiration to essentially normal levels. Mitochondrial protein synthesis was also unaltered in successful “xenomitochondrial cybrids.” The abrupt failure of mtDNA from primate species that diverged from humans as recently as 8–18 million years ago to functionally replace human mtDNA suggests the presence of one or a few mutations affecting critical nuclear–mitochondrial genome interactions between these species. These cellular systems provide a demonstration of intergenus mtDNA transfer, expand more than 20-fold the number of mtDNA polymorphisms that can be analyzed in a human nuclear background, and provide a novel model for the study of nuclear–mitochondrial interactions. PMID:9256447

Preliminary magnetostratigraphy and environmental magnetism of the Lower Cretaceous from the Italian Dolomites

NASA Astrophysics Data System (ADS)

Savian, J. F.; Jovane, L.; Florindo, F.; Lukeneder, A.

2011-12-01

The Lower Cretaceous (~146 to 100 Ma) represents an enigmatic time interval for paleoclimatic, paleogeography and paleomagnetic evolution of the Earth's history. The climatic changes include global oceanic anoxic events (OAEs), biotic changes, global excursions of carbon and strontium isotopes, rises in eustatic sea level and paleotemperature. Paleoceanography was marked by a rapid rate of ocean spreading in the Atlantic. The opening of the Atlantic Ocean was wide enough to allow significant circulation of masses of waters across the equator. This period is furthermore important for the oceanographic events occurring at the base of the Aptian (Selli Level). This period also present one of the most intriguing geomagnetic events: the long normal Cretaceous superchron, lasted for almost 40 million years. We study here the lower Cretaceous deposits of the Puez section in the Dolomites (northern Italy) which represents a continuous section during this period. The samples collected represent marine sedimentary materials of the Biancone and Puez formations. The Puez section consists essentially of green-grey to red limestones and calcareous marls. We present preliminary results of integrated magnetostratigraphic analysis, including a detailed lithostratigraphy and environmental magnetism. We recognize magnetic behavior that are relative to normal polarity (the normal Cretaceous superchron), with a short reverse interval that might represent the M-1r event. We also recognize a series of normal and reverse polarities (below the normal Cretaceous superchron) which can be referred to the magnetozones M1/M5. The environmental magnetic data consists of magnetic susceptibility (χ), natural remanent magnetization (NRM), anhysteretic remanent magnetization (ARM), isothermal remanent magnetization (IRM) at 900 mT and backfield isothermal remanent magnetization (BIRM) at 100 mT and 300 mT. Derived parameters, such as S-ratio (S300=BIRM300/IRM900) and hard isothermal remanent magnetization (HIRM=[IRM900+BIRM300]/2), both were used to investigate the magnetic coercivity of the magnetic carriers. The integrated records indicate that the magnetic mineral assemblage is dominated by low-coercivity minerals, probably magnetite and/or low-titanium titanomagnetite for the upper part of the section. There is a mixture of low and high-coercivity materials in the lower part of the section sections, probably magnetite and hematite. The new magnetostratigraphy allows to constrain the age of the sediments and the environmental magnetism provide information that will be helpful to understand the sedimentation processes.

Grey matter damage and overall cognitive impairment in primary progressive multiple sclerosis.

PubMed

Tur, C; Penny, S; Khaleeli, Z; Altmann, D R; Cipolotti, L; Ron, M; Thompson, A J; Ciccarelli, O

2011-11-01

To identify associations between cognitive impairment and imaging measures in a cross-sectional study of patients with primary progressive multiple sclerosis (PPMS). Neuropsychological tests were administered to 27 patients with PPMS and 31 controls. Patients underwent brain conventional magnetic resonance imaging (MRI) sequences, volumetric scans and magnetization transfer (MT) imaging; MT ratio (MTR) parameters, grey matter (GM) and normal-appearing white matter (NAWM) volumes, and WM T2 lesion load (T2LL) were obtained. In patients, multiple linear regression models identified the imaging measure associated with the abnormal cognitive tests independently from the other imaging variables. Partial correlation coefficients (PCC) were reported. Patients performed worse on tests of attention/speed of visual information processing, delayed verbal memory, and executive function, and had a worse overall cognitive performance index, when compared with controls. In patients, a lower GM peak location MTR was associated with worse overall cognitive performance (p < 0.001, PCC = 0.77). GM mean and peak height MTR showed the strongest association with the estimated verbal intelligence quotient (IQ) decline (p < 0.001, PCC = -0.62), and executive function (p < 0.001, PCC = 0.79). NAWM volume was associated with attention/speed of visual information processing (p < 0.001, PCC = 0.74), while T2LL was associated with delayed verbal memory (p = 0.007, PCC = -0.55). The finding of strong associations between GM MTR, NAWM volume and T2LL and specific cognitive impairments suggests that models that predict cognitive impairment in PPMS should include comprehensive MRI assessments of both GM and WM. However, GM MTR appears to be the main correlate of overall cognitive dysfunction, underlining the role of abnormal GM integrity in determining cognitive impairment in PPMS.

Effect of stationary magnetic field strengths of 150 and 200 mT on reactive oxygen species production in soybean.

PubMed

Shine, M B; Guruprasad, K N; Anand, Anjali

2012-07-01

Our previous investigation reported the beneficial effect of pre-sowing magnetic treatment for improving germination parameters and biomass accumulation in soybean. In this study, soybean seeds treated with static magnetic fields of 150 and 200 mT for 1 h were evaluated for reactive oxygen species (ROS) and activity of antioxidant enzymes. Superoxide and hydroxyl radicals were measured in embryos and hypocotyls of germinating seeds by electron paramagnetic resonance spectroscopy and kinetics of superoxide production; hydrogen peroxide and antioxidant activities were estimated spectrophotometrically. Magnetic field treatment resulted in enhanced production of ROS mediated by cell wall peroxidase while ascorbic acid content, superoxide dismutase and ascorbate peroxidase activity decreased in the hypocotyl of germinating seeds. An increase in the cytosolic peroxidase activity indicated that this antioxidant enzyme had a vital role in scavenging the increased H(2)O(2) produced in seedlings from the magnetically treated seeds. Hence, these studies contribute to our first report on the biochemical basis of enhanced germination and seedling growth in magnetically treated seeds of soybean in relation to increased production of ROS. Copyright © 2012 Wiley Periodicals, Inc.

Testing new methodologies and assessing their potential for reservoir characterisation: Geoelectrical studies in the Northwest Carboniferous Basin (Ireland).

NASA Astrophysics Data System (ADS)

Ogaya, Xènia; Campanyà, Joan; Rath, Volker; Jones, Alan G.; Reay, Derek; Raine, Rob; McConnell, Brian; Ledo, Juanjo

2016-04-01

The overarching objective of this study is to improve our methods of characterising saline aquifers by integrating newly acquired electromagnetic data with existing geophysical and geological data. The work presented here is part of an ongoing project to evaluate Ireland's potential for onshore carbon sequestration (IRECCSEM; funded by Science Foundation Ireland). The methodology presented in this characterisation work is not only relevant for studying the potential for onshore carbon sequestration, but is generally applicable for aquifer characterisation, particularly for the evaluation of geothermal resources in appropriate geological settings. We present first results of the three-dimensional (3D) modelling and inversion of the magnetotelluric (MT) data acquired in the Northwest Carboniferous Basin (Ireland) in summer 2015. The electrical resistivity distribution beneath the survey area is constrained using a joint inversion of three different types of electromagnetic data: MT impedance tensor responses (Z), geomagnetic transfer functions (GTF) and inter-station horizontal magnetic transfer-functions (HMT). The preliminary 3D resistivity model obtained reveals the geoelectrical structure of the subsurface, which is translated into parameters relevant to fluid flow. The electromagnetic data were acquired along profiles linking four wells drilled in the area and the available well log data from those wells are used to evaluate some of the existing petrophysical relationships and calibrate them for the study area. This allows us to interpolate the rock physical properties from one well to another well, using the computed geoelectrical model as a reference. The obtained results are compared to available independent geological and geophysical data in order to analyse the validity of this technique, to characterise the uncertainties inherent to our approach, and to assess the potential of this methodology for reservoir characterisation.

JTEC panel report on machine translation in Japan

NASA Technical Reports Server (NTRS)

Carbonell, Jaime; Rich, Elaine; Johnson, David; Tomita, Masaru; Vasconcellos, Muriel; Wilks, Yorick

1992-01-01

The goal of this report is to provide an overview of the state of the art of machine translation (MT) in Japan and to provide a comparison between Japanese and Western technology in this area. The term 'machine translation' as used here, includes both the science and technology required for automating the translation of text from one human language to another. Machine translation is viewed in Japan as an important strategic technology that is expected to play a key role in Japan's increasing participation in the world economy. MT is seen in Japan as important both for assimilating information into Japanese as well as for disseminating Japanese information throughout the world. Most of the MT systems now available in Japan are transfer-based systems. The majority of them exploit a case-frame representation of the source text as the basis of the transfer process. There is a gradual movement toward the use of deeper semantic representations, and some groups are beginning to look at interlingua-based systems.

Magnetic study of meteorites recovered in the Atacama desert (Chile): implications for meteorite paleomagnetism and the stability of hot desert surfaces (Invited)

NASA Astrophysics Data System (ADS)

Uehara, M.; Gattacceca, J.; Valenzuela, M.; Demory, F.; Rochette, P.

2010-12-01

Hot deserts are one of the large reservoirs of meteorites on Earth (about 25% of total meteorites), and some groups of rare meteorites (Rumuruti chondrites or lunar meteorites for instance). Therefore, the paleomagnetic record of hot desert meteorites is potentially a good source of information about the ancient extraterrestrial magnetic fields. However, meteorites recovered in hot deserts have typical terrestrial residence times (their so-called terrestrial ages) in the order of a few to several tens of kyr. During that time, a desert meteorite is exposed to the geomagnetic field, and is likely to acquire a Viscous Remanent Magnetization (VRM) whose intensity is controlled, among other things, by the stability of the desert surface. Moreover, with increasing terrestrial age, metallic and sulphide phases that are the dominant magnetic minerals in meteorites are oxidized and form potentially magnetic weathering minerals, resulting in the possible destruction of the primary remanence and acquisition of secondary terrestrial chemical remanence (CRM). Therefore, the paleomagnetic study of desert meteorites must take into account these terrestrial processes, in order to isolate the extraterrestrial magnetic record. We report here the paleomagnetic data obtained from 8 ordinary chondrites (3 H- and 5 L-chondrites) collected by our group in the Atacama desert (Chile) and oriented in situ with respect to the geographic north. Optical microscopy found that their weathering grades are W3 (60 - 95 % of metal is replaced by oxi-/hydroxides, 4 samples), W2 (moderate oxidation of metal, 20 - 60 % replaced; 2 samples), and W1 (only minor oxidation, 2 samples). Alternating field demagnetization experiments up to 100 mT found that W1 and W2 samples have a very low coercivity component (< 5 mT) and show unstable demagnetization paths above 10 mT, a behavior similar to that of freshly fallen ordinary chondrites. On the other hand, the more weathered samples (weathering stage W3) have medium to high coercivity components (20 ~ 100 mT) in addition to low coercivity components (<10mT). Thermal demagnetization experiments up to 300 °C found that W1 ~ W3 samples have low temperature components unblocked below 110 ~ 200 °C, which are plausibly VRM or CRM. Only W3 samples have directionally stable medium temperature component (150 ~ 300 °C or higher). In a given meteorite, the directions of mutually oriented samples are identical in W3 meteorites, but are scattered in W1 and W2 meteorites (like in most meteorite falls). These results indicate that the weathered samples (W3) have much more homogeneous and stable Natural Remanent Magnetizations than weakly weathered (W2 ~ W1) samples. Therefore, the W3 meteorites appear almost completely re-magnetized during terrestrial weathering. The directions of magnetization do no point toward the north, but the inclinations of the high temperature components of W3 samples are clustered around -40°, corresponding to the inclination of the average dipole field inclination at the find location. This suggests that the meteorites have moved on the desert surface by creeping movements.

3-D Magnetotelluric Forward Modeling And Inversion Incorporating Topography By Using Vector Finite-Element Method Combined With Divergence Corrections Based On The Magnetic Field (VFEH++)

NASA Astrophysics Data System (ADS)

Shi, X.; Utada, H.; Jiaying, W.

2009-12-01

The vector finite-element method combined with divergence corrections based on the magnetic field H, referred to as VFEH++ method, is developed to simulate the magnetotelluric (MT) responses of 3-D conductivity models. The advantages of the new VFEH++ method are the use of edge-elements to eliminate the vector parasites and the divergence corrections to explicitly guarantee the divergence-free conditions in the whole modeling domain. 3-D MT topographic responses are modeling using the new VFEH++ method, and are compared with those calculated by other numerical methods. The results show that MT responses can be modeled highly accurate using the VFEH+ +method. The VFEH++ algorithm is also employed for the 3-D MT data inversion incorporating topography. The 3-D MT inverse problem is formulated as a minimization problem of the regularized misfit function. In order to avoid the huge memory requirement and very long time for computing the Jacobian sensitivity matrix for Gauss-Newton method, we employ the conjugate gradient (CG) approach to solve the inversion equation. In each iteration of CG algorithm, the cost computation is the product of the Jacobian sensitivity matrix with a model vector x or its transpose with a data vector y, which can be transformed into two pseudo-forwarding modeling. This avoids the full explicitly Jacobian matrix calculation and storage which leads to considerable savings in the memory required by the inversion program in PC computer. The performance of CG algorithm will be illustrated by several typical 3-D models with horizontal earth surface and topographic surfaces. The results show that the VFEH++ and CG algorithms can be effectively employed to 3-D MT field data inversion.

Detection and characterization of cultural noise sources in magnetotelluric data: individual and joint analysis of the polarization attributes of the electric and magnetic field time-series in the time-frequency domain

NASA Astrophysics Data System (ADS)

Escalas, M.; Queralt, P.; Ledo, J.; Marcuello, A.

2012-04-01

Magnetotelluric (MT) method is a passive electromagnetic technique, which is currently used to characterize sites for the geological storage of CO2. These later ones are usually located nearby industrialized, urban or farming areas, where man-made electromagnetic (EM) signals contaminate the MT data. The identification and characterization of the artificial EM sources which generate the so-called "cultural noise" is an important challenge to obtain the most reliable results with the MT method. The polarization attributes of an EM signal (tilt angle, ellipticity and phase difference between its orthogonal components) are related to the character of its source. In a previous work (Escalas et al. 2011), we proposed a method to distinguish natural signal from cultural noise in the raw MT data. It is based on the polarization analysis of the MT time-series in the time-frequency domain, using a wavelet scheme. We developed an algorithm to implement the method, and was tested with both synthetic and field data. In 2010, we carried out a controlled-source electromagnetic (CSEM) experiment in the Hontomín site (the Research Laboratory on Geological Storage of CO2 in Spain). MT time-series were contaminated at different frequencies with the signal emitted by a controlled artificial EM source: two electric dipoles (1 km long, arranged in North-South and East-West directions). The analysis with our algorithm of the electric field time-series acquired in this experiment was successful: the polarization attributes of both the natural and artificial signal were obtained in the time-frequency domain, highlighting their differences. The processing of the magnetic field time-series acquired in the Hontomín experiment has been done in the present work. This new analysis of the polarization attributes of the magnetic field data has provided additional information to detect the contribution of the artificial source in the measured data. Moreover, the joint analysis of the polarization attributes of the electric and magnetic field has been crucial to fully characterize the properties and the location of the noise source. Escalas, M., Queralt, P., Ledo, J., Marcuello, A., 2011. Identification of cultural noise sources in magnetotelluric data: estimating polarization attributes in the time-frequency domain using wavelet analysis. Geophysical Research Abstracts Vol. 13, EGU2011-6085. EGU General Assembly 2011.

Timely access to specialist medical oncology services closer to home for rural patients: experience from the Townsville Teleoncology Model.

PubMed

Sabesan, Sabe; Roberts, Lynden J; Aiken, Peter; Joshi, Abhishek; Larkins, Sarah

2014-08-01

Prior to 2009, the teleoncology model of the Townsville Cancer Centre (TCC) did not achieve its aims of equal waiting times for rural and urban patients and the provision of reliable, local acute cancer care. From 2007-2009, 60 new patients from Mt Isa travelled to TCC for their first consultation and their first dose of chemotherapy. Six of these patients required inter-hospital transfers and eight required urgent flights to attend outpatient clinics. Only 50% these rural patients (n = 30) were reviewed within one week of their referral, compared with 90% of Townsville patients. A descriptive study. TCC provides teleoncology services to 21 rural towns; the largest is Mt Isa, Qld. Specialist review of 90% of urgent cases within 24 hours, and 90% of non-urgent cases within one week of referral via videoconferencing. A 50% reduction in inpatient inter-hospital transfers from Mt Isa to Townsville. Employment of a half-time medical officer and a half-time cancer care coordinator, and implementation of new policies. Between 2009 and 2011, TCC provided cancer care to 70 new patients from Mt Isa. Of these new patients, 93% (65/70) were seen within one week of referral. All 17 patients requiring urgent reviews were seen within 24 hours of referral and managed locally thus eliminating the need for inpatient inter-hospital transfers. Provision of timely acute cancer care closer to home requires an increase in the rural case complexity and human resources. © 2014 National Rural Health Alliance Inc.

On the Serpentinization Degree (S) of IODP Expedition 357 Atlantis Massif Rocks: Insights from Rock Magnetic Properties and Microscopic Magnetic Mineralogy Study of six Sites

NASA Astrophysics Data System (ADS)

Herrero-Bervera, E.; Whattam, S. A.; Frederichs, T.

2016-12-01

We have studied the magnetic properties of 37 serpentinized samples recovered via drilling during IODP Expedition 357, Atlantis Massif. We have recovered various lithologies including ultamafic rocks (primarily extensively serpentinized), subordidate gabbros, dolerites (small-scale melt injections) and schists. We have conducted remanence and induced magnetic experiments on the samples to determine for instance the degree of serpentinization (S). Stepwise alternating field and thermal demagnetization experiments from 2.5 to 70 mT and from 28 to 700°C, respectively, yielded univectorial diagrams showing the removal of secondary components (e.g., VRM, IRM, CRM) by isolating a characteristic component (ChRM) at various fields and temperatures. The normalized intensity of demagnetization (J/Jo) shows that the decrease of the magnetization of the specimens where about 50% of the original magnetization and is lost at about 5 mT and 100°C (i.e., Median Destructive Field). The stereograms show magnetic stability of the specimens by determining the directional behavior after 4 demagnetization steps (from 7.5-10 mT fields and low temperatures). Induced magnetization such as SIRM's, hysteresis saturation loops, back-fields and FORC experiments were performed. Diagnostic values of Mrs/Ms and Brc/Bc determine the domain structure of a magnetic sample. The magnetic grain sizes were determined using the protocol of Dunlop [2000]. Most of the samples were distributed over the Single (SD), Pseudo-Single Domain (PSD) and a few over the Multi Domain (MD) ranges with a certain degree of clustering on the PSD range. Curie points were obtained by measuring their low-field susceptibility vs. temperature from 28°C up to 700°C in an Argon atmosphere showing a minimum of 1-4 magnetic mineral phases with temperatures ranging from 100°C up to 640°C. These phases are predominantly Ti-poor, Ti-rich magnetite, maghemite and magnetite as corroborated by microscopic analysis as well as the Verwey transition (Tv≈110-120K). Samples studied show appreciable variation in bulk susceptibility (77.8 x 10-3 to 0.31 x 10-3 SI units). The samples are characterized by low, intermediate and high degree of serpentinization based on the results of their magnetic properties (e,g, Kappa, density, magnetic stability and Mrs/Ms vs Bcr/Bc).

A Magnetostrictive Composite-Fiber Bragg Grating Sensor

PubMed Central

Quintero, Sully M. M.; Braga, Arthur M. B.; Weber, Hans I.; Bruno, Antonio C.; Araújo, Jefferson F. D. F.

2010-01-01

This paper presents a light and compact optical fiber Bragg Grating sensor for DC and AC magnetic field measurements. The fiber is coated by a thick layer of a magnetostrictive composite consisting of particles of Terfenol-D dispersed in a polymeric matrix. Among the different compositions for the coating that were tested, the best magnetostrictive response was obtained using an epoxy resin as binder and a 30% volume fraction of Terfenol-D particles with sizes ranging from 212 to 300 μm. The effect of a compressive preload in the sensor was also investigated. The achieved resolution was 0.4 mT without a preload or 0.3 mT with a compressive pre-stress of 8.6 MPa. The sensor was tested at magnetic fields of up to 750 mT under static conditions. Dynamic measurements were conducted with a magnetic unbalanced four-pole rotor. PMID:22163644

First Results from SERPENT Marine MT Study

NASA Astrophysics Data System (ADS)

Naif, S.; Key, K. W.; Constable, S.; Evans, R. L.

2010-12-01

In April 2010 we conducted a controlled source electromagnetic (CSEM) and magnetotelluric (MT) survey over the Middle Americas subduction zone offshore Nicaragua. Seismic and heat flow studies have been conducted in the region to explore the role water plays at convergent margins, yet the quantity of water entering the downgoing slab remains poorly constrained. Electrical conductivity, however, is highly sensitive to the amount and distribution of water in the crust, and possibly mantle. Our broadband marine MT receivers recorded electric and magnetic field variations at the seafloor in water depths ranging from 60-5100 m. A total of 54 receiver deployments along a 300 km profile resulted in the largest MT dataset ever collected over an active subduction zone, all recorded in a single 28 day cruise aboard the R/V Melville. Spectrograms of the raw data show strong signal, including a significant magnetic storm from 5/2 to 5/3. Robust multiple station processing of the MT data produced high quality apparent resistivity and phase estimates for periods of roughly 10-20,000 s. Impedance polar diagrams and skew estimates display an evolution of 1D structure on the abyssal plain, 2D structure at the outer rise, 3D structure on/near the trench, and 1D-2D structure along the continental shelf. The MT responses generally lack the severe anisotropy usually associated with the ocean-side coast effect in near-shore MT studies. However, large distortions are evident at a few sites on the prism side of the trench, where extremely high skews are strongly localized in both space and frequency; these are spatially correlated with cusps in apparent resistivity and negative phase wrapping of the TE mode. We suspect this is caused by a combination of severe bathymetric effects and local variations in conductivity structure. Initial modeling results will be presented.

Smart RISUG: a potential new contraceptive and its magnetic field-mediated sperm interaction.

PubMed

Jha, Rakhi K; Jha, Pradeep K; Guha, Sujoy K

2009-01-01

The rationale and technique underlying a novel concept of noninvasive fertility control by a new Cuproferrogel contraceptive drug, iron oxide-copper-styrene maleic anhydride-dimethyl sulphoxide (Fe3O4-Cu-SMA-DMSO) composite named 'Smart RISUG' (smart reversible inhibition of sperm under guidance) in presence of pulsed magnetic field (PMF; 1 mT to 800 mT) is explained. It was synthesized by dispersing iron oxide particles and copper particles into SMA-DMSO (male contraceptive RISUG) and characterized for particle distribution, particle size measurement and transmittance peaks, etc. Interaction of the RISUG particles as well as Smart RISUG particles with Albino rat sperm cell was studied in presence as well as absence of PMF. To find an explanation to increased reaching of the Smart RISUG drug into sperm under influence of magnetic field, the transport properties were characterized by high resolution transmission electron microscopy and atomic force microscopy. Smart RISUG could be mobilized into sperm cell membrane at the PMF, 760 mT in about 50 seconds. Adoption of novel drug Smart RISUG involving new technique may open the pathway for non surgical control of drug distribution, detection and restoration of the normal fertility after removal of the contraceptive from the male/female reproductive tube in presence of electromagnetic field.

Measuring Magnetic Oscillations in the Solar Photosphere: Coordinated Observations with MDI, ASP and MWO

NASA Astrophysics Data System (ADS)

Norton, A. A.; Ulrich, R. K.

2000-03-01

A comprehensive observing effort was undertaken to simultaneously obtain full Stokes profiles as well as longitudinal magnetogram maps of a positive plage region on 8 December, 1998 with the Michelson Doppler Imager, the Advanced Stokes Polarimeter and Mt. Wilson Observatory magnetograph. We compare 1.2'' spatially-averaged signals of velocities as well as filter magnetograph longitudinal flux signals with Stokes determined fluctuations in filling factor, field inclination, magnetic flux and field strength. The velocity signals are in excellent agreement. Michelson Doppler Imager magnetic flux correlates best with fluctuations in the Advanced Stokes Polarimeter filling factor, not inclination angle or field strength. A correlated flux and filling factor change in the absence of a field strength fluctuation can be understood in terms of internally unperturbed flux tubes being buffeted by external pressure fluctuations. The 12.5'' square aperture spatially averaged Mt. Wilson magnetograph signals are compared with Michelson Doppler Imager signals from the corresponding observing area. Velocity signals are in superb agreement. Magnetic signals exhibit similar oscillatory behavior. Lack of Advanced Stokes Polarimeter data for this time excludes interpretation of magnetic fluctuations as due to filling factor or field inclination angle. Mt. Wilson Observatory simultaneous sampling of the nickel and sodium spectral line profiles with several wing pairs allowed inter-comparison of signals from different heights of formation. Slight phase shifts and large propagation speeds for the velocity signals are indicative of modified standing waves. Phase speeds associated with magnetic signals are characteristic of photospheric Alfvén speeds for plage fields. The phase speed increase with height agrees with the altitude dependence of the Alfvén speed. The observed fluctuations and phases are interpreted as a superposition of signatures from the horizontal component of the driving mechanism sweeping the field lines in/out of the resolution area and the magnetic response of the flux tube to this buffeting.

Evolution of phase transformation and magnetic properties with Fe content in Ni55-x Fe x Mn20Ga25 Heusler alloys

NASA Astrophysics Data System (ADS)

Zhang, Yuanlei; Li, Zhe; He, Xijia; Huang, Yinsheng; Xu, Kun; Jing, Chao

2018-02-01

A series of Ni55-x Fe x Mn20Ga25 (0  ⩽  x  ⩽  5) Heusler alloys was prepared to investigate their phase transitions and magnetic properties. At room temperature, these alloys present various crystal structures, and the unit cell volume enlarges with increase of Fe content in both austenite and martensite. Multiple magneto-structural transformations were observed in the parent alloy (x  =  0). In the process of cooling, it undergoes martensitic transformation (MT) from L21-type paramagnetic austenite to L10-type ferromagnetic martensite, accompanying an intermartensitic transformation (IMT, 7M  →  L10). By establishing a detailed phase diagram, we found that both MT and IMT shift to lower temperature simultaneously, while the ferromagnetic (FM) transition of austenite moves to higher temperature as Fe increases. With the further increase of Fe content beyond a critical value, both the IMT and the FM transitions split off from MT, and the former follows with the transforming sequence of 7M  →  5M. Based on the experimental data, some key magnetic parameters have been obtained in this system. The calculated magnetocrystalline anisotropy constant ({{K}1} ) of martensite quickly increases as Fe increases, and then it almost reaches a saturated value (~5.5  ×  105 J m-3) for the alloys with x  >  3. However, the spontaneous magnetic moment ({μs} ) attains a peak value of about 4.2 μ B/f.u. in the alloy with x  =  4, which is not consistent with the linear increasing of effective magnetic moment ({μef f} ). Further magnetic measurements with hydrostatic pressure indicate that such a discrepancy could be ascribed to the competition between the magnetic exchange interaction and the volume change of unit cell governed by the dopant Fe content.

High variability of mitochondrial gene order among fungi.

PubMed

Aguileta, Gabriela; de Vienne, Damien M; Ross, Oliver N; Hood, Michael E; Giraud, Tatiana; Petit, Elsa; Gabaldón, Toni

2014-02-01

From their origin as an early alpha proteobacterial endosymbiont to their current state as cellular organelles, large-scale genomic reorganization has taken place in the mitochondria of all main eukaryotic lineages. So far, most studies have focused on plant and animal mitochondrial (mt) genomes (mtDNA), but fungi provide new opportunities to study highly differentiated mtDNAs. Here, we analyzed 38 complete fungal mt genomes to investigate the evolution of mtDNA gene order among fungi. In particular, we looked for evidence of nonhomologous intrachromosomal recombination and investigated the dynamics of gene rearrangements. We investigated the effect that introns, intronic open reading frames (ORFs), and repeats may have on gene order. Additionally, we asked whether the distribution of transfer RNAs (tRNAs) evolves independently to that of mt protein-coding genes. We found that fungal mt genomes display remarkable variation between and within the major fungal phyla in terms of gene order, genome size, composition of intergenic regions, and presence of repeats, introns, and associated ORFs. Our results support previous evidence for the presence of mt recombination in all fungal phyla, a process conspicuously lacking in most Metazoa. Overall, the patterns of rearrangements may be explained by the combined influences of recombination (i.e., most likely nonhomologous and intrachromosomal), accumulated repeats, especially at intergenic regions, and to a lesser extent, mobile element dynamics.

The Complete Chloroplast and Mitochondrial Genome Sequences of Boea hygrometrica: Insights into the Evolution of Plant Organellar Genomes

PubMed Central

Wang, Xumin; Deng, Xin; Zhang, Xiaowei; Hu, Songnian; Yu, Jun

2012-01-01

The complete nucleotide sequences of the chloroplast (cp) and mitochondrial (mt) genomes of resurrection plant Boea hygrometrica (Bh, Gesneriaceae) have been determined with the lengths of 153,493 bp and 510,519 bp, respectively. The smaller chloroplast genome contains more genes (147) with a 72% coding sequence, and the larger mitochondrial genome have less genes (65) with a coding faction of 12%. Similar to other seed plants, the Bh cp genome has a typical quadripartite organization with a conserved gene in each region. The Bh mt genome has three recombinant sequence repeats of 222 bp, 843 bp, and 1474 bp in length, which divide the genome into a single master circle (MC) and four isomeric molecules. Compared to other angiosperms, one remarkable feature of the Bh mt genome is the frequent transfer of genetic material from the cp genome during recent Bh evolution. We also analyzed organellar genome evolution in general regarding genome features as well as compositional dynamics of sequence and gene structure/organization, providing clues for the understanding of the evolution of organellar genomes in plants. The cp-derived sequences including tRNAs found in angiosperm mt genomes support the conclusion that frequent gene transfer events may have begun early in the land plant lineage. PMID:22291979

Analysis of the Complete Mitochondrial Genome Sequence of the Diploid Cotton Gossypium raimondii by Comparative Genomics Approaches

PubMed Central

Paterson, Andrew H.; Wang, Xuelin; Xu, Yiqing; Wu, Dongyang; Qu, Yanshu; Jiang, Anna; Ye, Qiaolin

2016-01-01

Cotton is one of the most important economic crops and the primary source of natural fiber and is an important protein source for animal feed. The complete nuclear and chloroplast (cp) genome sequences of G. raimondii are already available but not mitochondria. Here, we assembled the complete mitochondrial (mt) DNA sequence of G. raimondii into a circular genome of length of 676,078 bp and performed comparative analyses with other higher plants. The genome contains 39 protein-coding genes, 6 rRNA genes, and 25 tRNA genes. We also identified four larger repeats (63.9 kb, 10.6 kb, 9.1 kb, and 2.5 kb) in this mt genome, which may be active in intramolecular recombination in the evolution of cotton. Strikingly, nearly all of the G. raimondii mt genome has been transferred to nucleus on Chr1, and the transfer event must be very recent. Phylogenetic analysis reveals that G. raimondii, as a member of Malvaceae, is much closer to another cotton (G. barbadense) than other rosids, and the clade formed by two Gossypium species is sister to Brassicales. The G. raimondii mt genome may provide a crucial foundation for evolutionary analysis, molecular biology, and cytoplasmic male sterility in cotton and other higher plants. PMID:27847816

Metabolic rescue in pluripotent cells from patients with mtDNA disease.

PubMed

Ma, Hong; Folmes, Clifford D L; Wu, Jun; Morey, Robert; Mora-Castilla, Sergio; Ocampo, Alejandro; Ma, Li; Poulton, Joanna; Wang, Xinjian; Ahmed, Riffat; Kang, Eunju; Lee, Yeonmi; Hayama, Tomonari; Li, Ying; Van Dyken, Crystal; Gutierrez, Nuria Marti; Tippner-Hedges, Rebecca; Koski, Amy; Mitalipov, Nargiz; Amato, Paula; Wolf, Don P; Huang, Taosheng; Terzic, Andre; Laurent, Louise C; Izpisua Belmonte, Juan Carlos; Mitalipov, Shoukhrat

2015-08-13

Mitochondria have a major role in energy production via oxidative phosphorylation, which is dependent on the expression of critical genes encoded by mitochondrial (mt)DNA. Mutations in mtDNA can cause fatal or severely debilitating disorders with limited treatment options. Clinical manifestations vary based on mutation type and heteroplasmy (that is, the relative levels of mutant and wild-type mtDNA within each cell). Here we generated genetically corrected pluripotent stem cells (PSCs) from patients with mtDNA disease. Multiple induced pluripotent stem (iPS) cell lines were derived from patients with common heteroplasmic mutations including 3243A>G, causing mitochondrial encephalomyopathy and stroke-like episodes (MELAS), and 8993T>G and 13513G>A, implicated in Leigh syndrome. Isogenic MELAS and Leigh syndrome iPS cell lines were generated containing exclusively wild-type or mutant mtDNA through spontaneous segregation of heteroplasmic mtDNA in proliferating fibroblasts. Furthermore, somatic cell nuclear transfer (SCNT) enabled replacement of mutant mtDNA from homoplasmic 8993T>G fibroblasts to generate corrected Leigh-NT1 PSCs. Although Leigh-NT1 PSCs contained donor oocyte wild-type mtDNA (human haplotype D4a) that differed from Leigh syndrome patient haplotype (F1a) at a total of 47 nucleotide sites, Leigh-NT1 cells displayed transcriptomic profiles similar to those in embryo-derived PSCs carrying wild-type mtDNA, indicative of normal nuclear-to-mitochondrial interactions. Moreover, genetically rescued patient PSCs displayed normal metabolic function compared to impaired oxygen consumption and ATP production observed in mutant cells. We conclude that both reprogramming approaches offer complementary strategies for derivation of PSCs containing exclusively wild-type mtDNA, through spontaneous segregation of heteroplasmic mtDNA in individual iPS cell lines or mitochondrial replacement by SCNT in homoplasmic mtDNA-based disease.

Effect of Earth and Mars departure delays on human missions to Mars

NASA Technical Reports Server (NTRS)

Desai, Prasun N.; Tartabini, Paul V.

1993-01-01

This study determines the impact on the initial mass in low-Earth orbit (IMLEO) for delaying departure from Mars and Earth by 5, 15, and 30 days, once a nominal mission to Mars has been selected. Additionally, the use of a deep space maneuver (DSM) is attempted to alleviate the IMLEO penalties. Three different classes of missions are analyzed using chemical and nuclear thermal propulsion systems in the 2000-2025 time-frame: opposition, conjunction, and fast-transfer conjunction. The results indicate that Mars and Earth delays can lead to large IMLEO penalties. Opposition and fast-transfer conjunction class missions have the highest IMLEO penalties, upwards of 432.4 mt and 1977.3 mt, respectively. Conjunction class missions, on the other hand, tend to be insensitive to Mars and Earth delays having IMLEO penalties under 103.5 mt. As expected, nuclear thermal propulsion had significantly lower IMLEO penalties as compared to chemical propulsion. The use of a DSM is found not to have a significant impact on reducing the IMLEO penalties. Through this investigation, the effect of off-nominal departure conditions on the overall mission (i.e., IMLEO) can be gained, enabling mission designers to incorporate the influence of off-nominal departure conditions of the interplanetary trajectory in the overall conceptual design process of a Mars transfer vehicle.

Medicago truncatula Mtha1-2 mutants loose metabolic responses to mycorrhizal colonization.

PubMed

Hubberten, Hans-Michael; Sieh, Daniela; Zöller, Daniela; Hoefgen, Rainer; Krajinski, Franziska

2015-01-01

Bidirectional nutrient transfer is one of the key features of the arbuscular mycorrhizal symbiosis. Recently we were able to identify a Medicago truncatula mutant (mtha1-2) that is defective in the uptake of phosphate from the periarbuscular space due to a lack of the energy providing proton gradient provided by the symbiosis specific proton ATPase MtHA1 In order to further characterize the impact of fungal colonization on the plant metabolic status, without the beneficial aspect of improved mineral nutrition, we performed leaf ion analyses in mutant and wildtype plants with and without fungal colonization. Although frequency of fungal colonization was unaltered, the mutant did not show a positive growth response to mycorrhizal colonization. This indicates that nutrient transfer into the plant cell fails in the truncated arbuscules due to lacking expression of a functional MtHA1 protein. The leaves of wildtype plants showed clear metabolic responses to root mycorrhizal colonization, whereas no changes of leaf metabolite levels of mycorrhizal mtha1-2 plants were detected, even though they were colonized. These results show that MtHa1 is indispensable for a functional mycorrhizal symbiosis and, moreover, suggest that fungal root colonization per se does not depend on nutrient transfer to the plant host.

The Pioneer XI high field fluxgate magnetometer

NASA Technical Reports Server (NTRS)

Acuna, M. A.; Ness, N. F.

1975-01-01

The high field fluxgate magnetometer experiment flown aboard the Pioneer XI spacecraft is described. This extremely simple instrument was used to extend the spacecraft's upper-limit measurement capability by approximately an order of magnitude (from 0.14 mT to 1.00 mT) with minimum power and volume requirements. This magnetometer was designed to complement the low-field measurements provided by a helium vector magnetometer and utilizes magnetic ring core sensors with biaxial orthogonal sense coils. The instrument is a single-range, triaxial-fluxgate magnetometer capable of measuring fields of up to 1 mT along each orthogonal axis, with a maximum resolution of 1 microT.

Complete Mitochondrial Genome of Echinostoma hortense (Digenea: Echinostomatidae).

PubMed

Liu, Ze-Xuan; Zhang, Yan; Liu, Yu-Ting; Chang, Qiao-Cheng; Su, Xin; Fu, Xue; Yue, Dong-Mei; Gao, Yuan; Wang, Chun-Ren

2016-04-01

Echinostoma hortense (Digenea: Echinostomatidae) is one of the intestinal flukes with medical importance in humans. However, the mitochondrial (mt) genome of this fluke has not been known yet. The present study has determined the complete mt genome sequences of E. hortense and assessed the phylogenetic relationships with other digenean species for which the complete mt genome sequences are available in GenBank using concatenated amino acid sequences inferred from 12 protein-coding genes. The mt genome of E. hortense contained 12 protein-coding genes, 22 transfer RNA genes, 2 ribosomal RNA genes, and 1 non-coding region. The length of the mt genome of E. hortense was 14,994 bp, which was somewhat smaller than those of other trematode species. Phylogenetic analyses based on concatenated nucleotide sequence datasets for all 12 protein-coding genes using maximum parsimony (MP) method showed that E. hortense and Hypoderaeum conoideum gathered together, and they were closer to each other than to Fasciolidae and other echinostomatid trematodes. The availability of the complete mt genome sequences of E. hortense provides important genetic markers for diagnostics, population genetics, and evolutionary studies of digeneans.

Complete Mitochondrial Genome of Echinostoma hortense (Digenea: Echinostomatidae)

PubMed Central

Liu, Ze-Xuan; Zhang, Yan; Liu, Yu-Ting; Chang, Qiao-Cheng; Su, Xin; Fu, Xue; Yue, Dong-Mei; Gao, Yuan; Wang, Chun-Ren

2016-01-01

Echinostoma hortense (Digenea: Echinostomatidae) is one of the intestinal flukes with medical importance in humans. However, the mitochondrial (mt) genome of this fluke has not been known yet. The present study has determined the complete mt genome sequences of E. hortense and assessed the phylogenetic relationships with other digenean species for which the complete mt genome sequences are available in GenBank using concatenated amino acid sequences inferred from 12 protein-coding genes. The mt genome of E. hortense contained 12 protein-coding genes, 22 transfer RNA genes, 2 ribosomal RNA genes, and 1 non-coding region. The length of the mt genome of E. hortense was 14,994 bp, which was somewhat smaller than those of other trematode species. Phylogenetic analyses based on concatenated nucleotide sequence datasets for all 12 protein-coding genes using maximum parsimony (MP) method showed that E. hortense and Hypoderaeum conoideum gathered together, and they were closer to each other than to Fasciolidae and other echinostomatid trematodes. The availability of the complete mt genome sequences of E. hortense provides important genetic markers for diagnostics, population genetics, and evolutionary studies of digeneans. PMID:27180575

The complete mitochondrial genome of Rapana venosa (Gastropoda, Muricidae).

PubMed

Sun, Xiujun; Yang, Aiguo

2016-01-01

The complete mitochondrial (mt) genome of the veined rapa whelk, Rapana venosa, was determined using genome walking techniques in this study. The total length of the mt genome sequence of R. venosa was 15,271 bp, which is comparable to the reported Muricidae mitogenomes to date. It contained 13 protein-coding genes, 21 transfer RNA genes, and two ribosomal RNA genes. A bias towards a higher representation of nucleotides A and T (69%) was detected in the mt genome of R. venosa. A small number of non-coding nucleotides (302 bp) was detected, and the largest non-coding region was 74 bp in length.

Interaction of Motor Training and Intermittent Theta Burst Stimulation in Modulating Motor Cortical Plasticity: Influence of BDNF Val66Met Polymorphism

PubMed Central

Lee, Mina; Kim, Song E.; Kim, Won Sup; Lee, Jungyeun; Yoo, Hye Kyung; Park, Kee-Duk; Choi, Kyoung-Gyu; Jeong, Seon-Yong; Kim, Byung Gon; Lee, Hyang Woon

2013-01-01

Cortical physiology in human motor cortex is influenced by behavioral motor training (MT) as well as repetitive transcranial magnetic stimulation protocol such as intermittent theta burst stimulation (iTBS). This study aimed to test whether MT and iTBS can interact with each other to produce additive changes in motor cortical physiology. We hypothesized that potential interaction between MT and iTBS would be dependent on BDNF Val66Met polymorphism, which is known to affect neuroplasticity in the human motor cortex. Eighty two healthy volunteers were genotyped for BDNF polymorphism. Thirty subjects were assigned for MT alone, 23 for iTBS alone, and 29 for MT + iTBS paradigms. TMS indices for cortical excitability and motor map areas were measured prior to and after each paradigm. MT alone significantly increased the motor cortical excitability and expanded the motor map areas. The iTBS alone paradigm also enhanced excitability and increased the motor map areas to a slightly greater extent than MT alone. A combination of MT and iTBS resulted in the largest increases in the cortical excitability, and the representational motor map expansion of MT + iTBS was significantly greater than MT or iTBS alone only in Val/Val genotype. As a result, the additive interaction between MT and iTBS was highly dependent on BDNF Val66Met polymorphism. Our results may have clinical relevance in designing rehabilitative strategies that combine therapeutic cortical stimulation and physical exercise for patients with motor disabilities. PMID:23451258

Interaction of motor training and intermittent theta burst stimulation in modulating motor cortical plasticity: influence of BDNF Val66Met polymorphism.

PubMed

Lee, Mina; Kim, Song E; Kim, Won Sup; Lee, Jungyeun; Yoo, Hye Kyung; Park, Kee-Duk; Choi, Kyoung-Gyu; Jeong, Seon-Yong; Kim, Byung Gon; Lee, Hyang Woon

2013-01-01

Cortical physiology in human motor cortex is influenced by behavioral motor training (MT) as well as repetitive transcranial magnetic stimulation protocol such as intermittent theta burst stimulation (iTBS). This study aimed to test whether MT and iTBS can interact with each other to produce additive changes in motor cortical physiology. We hypothesized that potential interaction between MT and iTBS would be dependent on BDNF Val66Met polymorphism, which is known to affect neuroplasticity in the human motor cortex. Eighty two healthy volunteers were genotyped for BDNF polymorphism. Thirty subjects were assigned for MT alone, 23 for iTBS alone, and 29 for MT + iTBS paradigms. TMS indices for cortical excitability and motor map areas were measured prior to and after each paradigm. MT alone significantly increased the motor cortical excitability and expanded the motor map areas. The iTBS alone paradigm also enhanced excitability and increased the motor map areas to a slightly greater extent than MT alone. A combination of MT and iTBS resulted in the largest increases in the cortical excitability, and the representational motor map expansion of MT + iTBS was significantly greater than MT or iTBS alone only in Val/Val genotype. As a result, the additive interaction between MT and iTBS was highly dependent on BDNF Val66Met polymorphism. Our results may have clinical relevance in designing rehabilitative strategies that combine therapeutic cortical stimulation and physical exercise for patients with motor disabilities.

Use of Second Generation Coated Conductors for Efficient Shielding of dc Magnetic Fields (Postprint)

DTIC Science & Technology

2010-07-15

layer of superconducting film, can attenuate an external magnetic field of up to 5 mT by more than an order of magnitude. For comparison purposes...appears to be especially promising for the realization of large scale high-Tc superconducting screens. 15. SUBJECT TERMS magnetic screens, current...realization of large scale high-Tc superconducting screens. © 2010 American Institute of Physics. doi:10.1063/1.3459895 I. INTRODUCTION Magnetic screening

The effect of surface grain reversal on the AC losses of sintered Nd-Fe-B permanent magnets

NASA Astrophysics Data System (ADS)

Moore, Martina; Roth, Stefan; Gebert, Annett; Schultz, Ludwig; Gutfleisch, Oliver

2015-02-01

Sintered Nd-Fe-B magnets are exposed to AC magnetic fields in many applications, e.g. in permanent magnet electric motors. We have measured the AC losses of sintered Nd-Fe-B magnets in a closed circuit arrangement using AC fields with root mean square-values up to 80 mT (peak amplitude 113 mT) over the frequency range 50 to 1000 Hz. Two magnet grades with different dysprosium content were investigated. Around the remanence point the low grade material (1.7 wt% Dy) showed significant hysteresis losses; whereas the losses in the high grade material (8.9 wt% Dy) were dominated by classical eddy currents. Kerr microscopy images revealed that the hysteresis losses measured for the low grade magnet can be mainly ascribed to grains at the sample surface with multiple domains. This was further confirmed when the high grade material was subsequently exposed to DC and AC magnetic fields. Here a larger number of surface grains with multiple domains are also present once the step in the demagnetization curve attributed to the surface grain reversal is reached and a rise in the measured hysteresis losses is evident. If in the low grade material the operating point is slightly offset from the remanence point, such that zero field is not bypassed, its AC losses can also be fairly well described with classical eddy current theory.

Effects of extremely low frequency magnetic field on oxidative balance in brain of rats.

PubMed

Ciejka, Elzbieta; Kleniewska, P; Skibska, B; Goraca, A

2011-12-01

Extremely low frequency magnetic field (ELF-MF) may result in oxidative DNA damage and lipid peroxidation with an ultimate effect on a number of systemic disturbances and cell death. The aim of the study is to assess the effect of ELF-MF parameters most frequently used in magnetotherapy on reactive oxygen species generation (ROS) in brain tissue of experimental animals depending on the time of exposure to this field. The research material included adult male Sprague-Dawley rats, aged 3-4 months. The animals were divided into 3 groups: I - control (shame) group; II - exposed to the following parameters of the magnetic field: 7 mT, 40 Hz, 30 min/day, 10 days; III - exposed to the ELF-MF parameters of 7 mT, 40 Hz, 60 min/day, 10 days. The selected parameters of oxidative stress: thiobarbituric acid reactive substances (TBARS), hydrogen peroxide (H(2)O(2)), total free sulphydryl groups (-SH groups) and protein in brain homogenates were measured after the exposure of rats to the magnetic field. ELF-MF parameters of 7 mT, 40 Hz, 30 min/day for 10 days caused a significant increase in lipid peroxidation and insignificant increase in H(2)O(2) and free -SH groups. The same ELF-MF parameters but applied for 60 min/day caused a significant increase in free -SH groups and protein concentration in the brain homogenates indicating the adaptive mechanism. The study has shown that ELF-MF applied for 30 min/day for 10 days can affect free radical generation in the brain. Prolongation of the exposure to ELF-MF (60/min/day) caused adaptation to this field. The effect of ELF-MF irradiation on oxidative stress parameters depends on the time of animal exposure to magnetic field.

Magnetic properties of the ammonolysis product of α-Fe powder containing a small amount of aluminum

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tsugawa, Yuta; Maubuchi, Yuji; Motohashi, Teruki

2015-02-15

Magnetite was prepared containing a small amount of aluminum and its nitride was generated through low temperature ammonolysis following reduction under hydrogen. The nitrided product was determined by XRD to be a mixture of “α″-Fe{sub 16}N{sub 2}” having a slightly deformed crystal structure from α″-Fe{sub 16}N{sub 2} and the residual α-Fe. Magnetic coercivity of the mixture was decreased from the value of 150 mT obtained for the nitride product made without aluminum, due to the precipitation of nonmagnetic amorphous alumina in the low temperature nitrided bcc (Fe{sub 1−x}Al{sub x}) with x≤0.03. The aluminum-doped nitride product in which the “α″-Fe{sub 16}N{submore » 2}” fraction was 30 at% exhibited magnetization at 1.5 T of approximately 200 Am{sup 2}kg{sup −1} at room temperature and its magnetic coercivity was 20 mT. - Graphical abstract: Magnetic iron nitride particles were separated by nonmagnetic amorphous γ-alumina. Magnetic coercivity was decreased by reducing the magnetic interaction between the particles. - Highlights: • Magnetic coercivity decreased in α”-Fe{sub 16}N{sub 2} like compound as a soft magnet. • Small amount of Al addition was effective in its preparation. • Magnetic interaction decreased between the “α”-Fe{sub 16}N{sub 2}” particles.« less

Generalized analytic solutions and response characteristics of magnetotelluric fields on anisotropic infinite faults

NASA Astrophysics Data System (ADS)

Bing, Xue; Yicai, Ji

2018-06-01

In order to understand directly and analyze accurately the detected magnetotelluric (MT) data on anisotropic infinite faults, two-dimensional partial differential equations of MT fields are used to establish a model of anisotropic infinite faults using the Fourier transform method. A multi-fault model is developed to expand the one-fault model. The transverse electric mode and transverse magnetic mode analytic solutions are derived using two-infinite-fault models. The infinite integral terms of the quasi-analytic solutions are discussed. The dual-fault model is computed using the finite element method to verify the correctness of the solutions. The MT responses of isotropic and anisotropic media are calculated to analyze the response functions by different anisotropic conductivity structures. The thickness and conductivity of the media, influencing MT responses, are discussed. The analytic principles are also given. The analysis results are significant to how MT responses are perceived and to the data interpretation of the complex anisotropic infinite faults.

The human mitochondrial single-stranded DNA-binding protein displays distinct kinetics and thermodynamics of DNA binding and exchange

PubMed Central

Qian, Yufeng; Johnson, Kenneth A.

2017-01-01

The human mitochondrial ssDNA-binding protein (mtSSB) is a homotetrameric protein, involved in mtDNA replication and maintenance. Although mtSSB is structurally similar to SSB from Escherichia coli (EcoSSB), it lacks the C-terminal disordered domain, and little is known about the biophysics of mtSSB–ssDNA interactions. Here, we characterized the kinetics and thermodynamics of mtSSB binding to ssDNA by equilibrium titrations and stopped-flow kinetic measurements. We show that the mtSSB tetramer can bind to ssDNA in two distinct binding modes: (SSB)30 and (SSB)60, defined by DNA binding site sizes of 30 and 60 nucleotides, respectively. We found that the binding mode is modulated by magnesium ion and NaCl concentration, but unlike EcoSSB, the mtSSB does not show negative intersubunit cooperativity. Global fitting of both the equilibrium and kinetic data afforded estimates for the rate and equilibrium constants governing the formation of (SSB)60 and (SSB)30 complexes and for the transitions between the two binding modes. We found that the mtSSB tetramer binds to ssDNA with a rate constant near the diffusion limit (2 × 109 m−1 s−1) and that longer DNA (≥60 nucleotides) rapidly wraps around all four monomers, as revealed by FRET assays. We also show that the mtSSB tetramer can directly transfer from one ssDNA molecule to another via an intermediate with two DNA molecules bound to the mtSSB. In conclusion, our results indicate that human mtSSB shares many physicochemical properties with EcoSSB and that the differences may be explained by the lack of an acidic, disordered C-terminal tail in human mtSSB protein. PMID:28615444

Geomagnetic Survey to Explore High-Temperature Geothermal System in Blawan-Ijen, East Java, Indonesia

NASA Astrophysics Data System (ADS)

Daud, Yunus; Rosid, Syamsu; Fahmi, Fikri; Yunus, Faris Maulana; Muflihendri, Reza

2018-02-01

Ijen geothermal area is high-temperature geothermal system located in Bondowoso regency, East Java. It is categorized as caldera-hosted geothermal system which is covered by quaternary andesitic volcanic rocks with steep topography at the surrounding. Several surface thermal manifestations are found, such as altered rocks near Mt. Kukusan and a group of Blawan hotsprings in the northern part of the caldera. Geomagnetic survey was conducted at 72 stations which is distributed inside the caldera to delineate the existence of hydrothermal activity. Magnetic anomaly was obtained by reducing total magnetic measured on the field by IGRF and diurnal variation. Reduction to pole (RTP) method was applied with geomagnetic inclination of about -32°. In general, the result shows that high magnetic anomaly is distributed at the boundary of study area, while low magnetic anomaly is observed in the centre. The low anomaly indicates demagnetized rock that probably caused by hydrothermal activity. It has a good correlation with surface alteration observed close to Mt. Kukusan as well as high temperature reservoir drilled in the centre of caldera. Accordingly, the low magnetic anomaly also presents the possibility of geothermal reservoir in Ijen geothermal area.

Magnetic Field Effects on Photoelectrochemical Reactions of Porphyrin-Viologen Linked Compounds in an Ionic Liquid

NASA Astrophysics Data System (ADS)

Tahara, Hironobu; Yonemura, Hiroaki; Harada, Satoko; Yamada, Sunao

2011-08-01

Magnetic field effects (MFEs) on photoelectrochemical reactions of three porphyrin-viologen linked compounds with various methylene groups [ZnP(n)V (n=4,6,8)] were examined in 1-butyl-3-methylimidazolium tetrafluoroborate ([BMIM][BF4]) as an ionic liquid using a two-electrode cell. Stable anodic photocurrents are produced by irradiating ZnP(n)V (n=4,6,8) in [BMIM][BF4] with visible light, and the MFEs on photocurrents were clearly observed in ZnP(n)V (n=4,6,8). The MFEs on photocurrents increase with magnetic field for lower magnetic fields (B ≤200 mT) and are constant for higher magnetic fields (B > 200 mT). The magnitude of the MFEs in ZnP(n)V (n=6,8) are larger than that in ZnP(4)V. The MFEs can be explained by radical pair mechanism. The magnitude of the MFEs is larger than those in electrodes modified with ZnP(n)V (n=4,6,8) as Langmuir-Blodgett films. The results are most likely attributable to the properties of [BMIM][BF4] and the mechanism of photoelectrochemical reaction.

PubMed Central

Di Mauro, S.

2010-01-01

In this brief review, I have highlighted recent advances in several areas of mitochondrial medicine, including mtDNA-related diseases, mendelian mitochondrial encephalomyopathies, and therapy. The pathogenic mechanisms of mtDNA mutations, especially those affecting mitochondrial protein synthesis, are still largely unknown. The pathogenicity of homoplasmic mtDNA mutations has become evident but has also called attention to modifying nuclear genes, yet another example of impaired intergenomic signaling. The functional significance of the homoplasmic changes associated with mitochondrial haplogroups has been confirmed. Among the mendelian disorders, a new form of “indirect hit” has been described, in which the ultimate pathogenesis is toxic damage to the respiratory chain. Three therapeutic strategies look promising: (i) allogeneic hematopoietic stem cell transplantation in MNGIE (mitochondrial neurogastrointestinal encephalomyopathy); (ii) bezafibrate, an activator of PGC-1α, has proven effective in animal models of mitochondrial myopathy; and (iii) pronucleus transfer into a normal oocyte is effective in eliminating maternal transmission of mtDNA, thus preventing the appearance of mtDNA-related disorders. PMID:21314015

Structure of Mycobacterium tuberculosis phosphopantetheine adenylyltransferase in complex with the feedback inhibitor CoA reveals only one active-site conformation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wubben, T.; Mesecar, A.D.; UIC)

Phosphopantetheine adenylyltransferase (PPAT) catalyzes the penultimate step in the coenzyme A (CoA) biosynthetic pathway, reversibly transferring an adenylyl group from ATP to 4'-phosphopantetheine to form dephosphocoenzyme A (dPCoA). To complement recent biochemical and structural studies on Mycobacterium tuberculosis PPAT (MtPPAT) and to provide further insight into the feedback regulation of MtPPAT by CoA, the X-ray crystal structure of the MtPPAT enzyme in complex with CoA was determined to 2.11 {angstrom} resolution. Unlike previous X-ray crystal structures of PPAT-CoA complexes from other bacteria, which showed two distinct CoA conformations bound to the active site, only one conformation of CoA is observedmore » in the MtPPAT-CoA complex.« less

A proposed definition of microbiota transplantation for regulatory purposes

PubMed Central

Hoffmann, Diane E.; Palumbo, Francis B.; Rowthorn, Virginia; von Rosenvinge, Erik

2017-01-01

ABSTRACT The advent of fecal microbiota transplantation (FMT) and the prospect of other types of microbiota transplants (MT), e.g. vaginal, skin, oral and nasal, are challenging regulatory agencies. Although FDA is regulating FMT (as a biologic), there is currently no widely accepted or agreed upon scientific or legal definition of FMT or MT. The authors report on discussions regarding a definition of MT that took place among a working group of stakeholders convened under a National Institutes for Allergies and Infectious Diseases grant to address the regulation of MT. In arriving at a definition, the group considered the 1) nature of the material being transplanted; 2) degree of manipulation of the transferred materials prior to implantation; 3) ability to characterize the transplanted product using external techniques; and 4) origin of the stool product (single vs multiple donors). PMID:28318396

The complete mitochondrial genome of a stonefly species, Kamimuria chungnanshana Wu, 1948 (Plecoptera: Perlidae).

PubMed

Wang, Kai; Ding, Shuangmei; Yang, Ding

2016-09-01

This study determined the complete mitochondrial (mt) genome of the stonefly, Kamimuria chungnanshana Wu, 1948. The mt genome is 15, 943 bp in size and contains 37 canonical genes which include 22 transfer RNA genes, 13 protein-coding genes, and two ribosomal RNA genes, the control region is 1062 bp in length. The phylogenetic tree shows that Kamimuria chungnanshana is sister group of Kamimuria wangi.

Chondrule magnetic properties

NASA Technical Reports Server (NTRS)

Wasilewski, P. J.; Obryan, M. V.

1994-01-01

The topics discussed include the following: chondrule magnetic properties; chondrules from the same meteorite; and REM values (the ratio for remanence initially measured to saturation remanence in 1 Tesla field). The preliminary field estimates for chondrules magnetizing environments range from minimal to a least several mT. These estimates are based on REM values and the characteristics of the remanence initially measured (natural remanence) thermal demagnetization compared to the saturation remanence in 1 Tesla field demagnetization.

Characterization of protease from bacillus sp. on medium containing FeCl3 exposed to magnetic field 0.2 mt

NASA Astrophysics Data System (ADS)

Sumardi; Agustrina, Rochmah; Nugroho Ekowati, Christina; Selvie Pasaribu, Yovita

2018-03-01

This purpose of this research is to determine the character of the protease enzymes from Bacillus sp. on media content of FeCl3 exposed to 0.2 mT magnetic field. The data obtained were analyzed descriptively. The result showed that protease enzyme without Fe resulted in the highest activity at pH 8, temperature. 30°C with the addition of activator Mn2+, and Vmax of 0.28 U/ml, and Km of 4.60 U/ml. The protease enzyme on media without magnetic field exposure and containing Fe yielded the highest activity at pH 8, temperature 30°C with the addition of activator Mn2+, and Vmax of 0.33 U/ml, and Km of 5.64 U/ml. The protease enzyme on medium with magnetic field exposure and use Fe as inductors have the highest activity at pH 9, the temperature of 55° C with the addition of activator Mn2+, and Vmax of 0.35 U/ml, and Km 10.04 U/ml.

Magnetic and dielectric study of Fe-doped CdSe nanoparticles

NASA Astrophysics Data System (ADS)

Das, Sayantani; Banerjee, Sourish; Bandyopadhyay, Sudipta; Sinha, Tripurari Prasad

2018-01-01

Nanoparticles of cadmium selenide (CdSe) and Fe (5% and 10%) doped CdSe have been synthesized by soft chemical route and found to have cubic structure. The magnetic field dependent magnetization measurement of the doped samples indicates the presence of anti-ferromagnetic order. The temperature dependent magnetization (M-T) measurement under zero field cooled and field cooled conditions has also ruled out the presence of ferromagnetic component in the samples at room temperature as well as low temperature. In order to estimate the anti-ferromagnetic coupling among the doped Fe atoms, an M-T measurement at 500 Oe has been carried out, and the Curie-Weiss temperature θ of the samples has been estimated from the inverse of susceptibility versus temperature plots. The dielectric relaxation peaks are observed in the spectra of imaginary part of dielectric constant. The temperature dependent relaxation time is found to obey the Arrhenius law having activation energy 0.4 eV for Fe doped samples. The frequency dependent conductivity spectra are found to obey the power law. [Figure not available: see fulltext.

Metal organic framework Cu9Cl2(cpa)6 as tunable molecular magnet

NASA Astrophysics Data System (ADS)

Hamilton, Heather S. C.; Farmer, William M.; Skinner, Samuel F.; ter Haar, Leonard W.

2018-05-01

Chemical modifications of the magnetic metal organic framework (MOF) Cu9X2(cpa)6.42H2O (X = F, Cl, Br; cpa = anion of 2-carboxypentonicacid) have been investigated as a means of modifying, in a tunable manner, the magnetism of this 2-D material best described as a triangles-in-triangles (TIT) or triangulated-Kagomé-latttice (TKL). Since numerous theoretical studies have already attempted to describe the enigmatic ground state of this Heisenberg lattice, tunable chemical modifications should provide an excellent opportunity to expand this class of materials for studies concerning fundamental physics of frustrated spins, and applications such as adiabatic demagnetization refrigeration (ADR) that depend on the magnetocaloric effect (MCE). The chemical modification investigated is the intercalation of d- and f-orbital ions into the voids of the framework (channels of nearly 20 Å diameter). Magnetic measurements in the temperature range 1.8 - 300 K confirm signature features of TKL magnetism in intercalated samples persist, specifically: i) large negative Weiss constant (θCW); ii) absence of a phase transition down to 1.8 K; iii) minimum in χMT; iv) low temperature χMT values increasingly divergent at low fields indicating net ferromagnetic correlations; and, v) increasing field dependence of magnetization at low temperatures suggestive of intermediate plateaus, or ferrimagnetism, not saturation.

Transformation behavior of Ni-Mn-Ga in the low-temperature limit.

PubMed

Pérez-Landazábal, J I; Recarte, V; Sánchez-Alarcos, V; Chernenko, V A; Barandiarán, J M; Lázpita, P; Rodriguez Fernández, J; Righi, L

2012-07-11

The magnetic, magnetocaloric and thermal characteristics have been studied in a Ni(50.3)Mn(20.8)Ga(27.6)V(1.3) ferromagnetic shape memory alloy (FSMA) transforming martensitically at around 40 K. The alloy shows first a transformation from austenite to an intermediate phase and then a partial transformation to an orthorhombic martensite, all the phases being ferromagnetically ordered. The thermomagnetization dependences enabled observation of the magnetocaloric effect in the vicinity of the martensitic transformation (MT). The Debye temperature and the density of states at the Fermi level are equal to θ(D) = (276 ± 4) K and 1.3 states/atom eV , respectively, and scarcely dependent on the magnetic field. The MT exhibited by Ni-Mn-Ga FSMAs at very low temperatures is distinctive in the sense that it is accompanied by a hardly detectable entropy change as a sign of a small driving force. The enhanced stability of the cubic phase and the low driving force of the MT stem from the reduced density of states near the Fermi level.

A new petrological and geophysical investigation of the present-day plumbing system of Mount Vesuvius

NASA Astrophysics Data System (ADS)

Pommier, A.; Tarits, P.; Hautot, S.; Pichavant, M.; Scaillet, B.; Gaillard, F.

2010-07-01

A model of the electrical resistivity of Mt. Vesuvius has been elaborated to investigate the present structure of the volcanic edifice. The model is based on electrical conductivity measurements in the laboratory, on geophysical information, in particular, magnetotelluric (MT) data, and on petrological and geochemical constraints. Both 1-D and 3-D simulations explored the effect of depth, volume and resistivity of either one or two reservoirs in the structure. For each configuration tested, modeled MT transfer functions were compared to field transfer functions from field magnetotelluric studies. The field electrical data are reproduced with a shallow and very conductive layer (˜0.5 km depth, 1.2 km thick, 5 ohm.m resistive) that most likely corresponds to a saline brine present beneath the volcano. Our results are also compatible with the presence of cooling magma batches at shallow depths (<3-4 km depth). The presence of a deeper body at ˜8 km depth, as suggested by seismic studies, is consistent with the observed field transfer functions if such a body has an electrical resistivity > ˜100 ohm.m. According to a petro-physical conductivity model, such a resistivity value is in agreement either with a low-temperature, crystal-rich magma chamber or with a small quantity of hotter magma interconnected in the resistive surrounding carbonates. However, the low quality of MT field data at long periods prevent from placing strong constraints on a potential deep magma reservoir. A comparison with seismic velocity values tends to support the second hypothesis. Our findings would be consistent with a deep structure (8-10 km depth) made of a tephriphonolitic magma at 1000°C, containing 3.5 wt%H2O, 30 vol.% crystals, and interconnected in carbonates in proportions ˜45% melt -55% carbonates.

Limited Near and Far Transfer Effects of Jungle Memory Working Memory Training on Learning Mathematics in Children with Attentional and Mathematical Difficulties.

PubMed

Nelwan, Michel; Kroesbergen, Evelyn H

2016-01-01

The goal of this randomized controlled trial was to investigate whether Jungle Memory working memory training (JM) affects performance on working memory tasks, performance in mathematics and gains made on a mathematics training (MT) in school aged children between 9-12 years old ( N = 64) with both difficulties in mathematics, as well as attention and working memory. Children were randomly assigned to three groups and were trained in two periods: (1) JM first, followed by MT, (2) MT first, followed by JM, and (3) a control group that received MT only. Bayesian analyses showed possible short term effects of JM on near transfer measures of verbal working memory, but none on visual working memory. Furthermore, support was found for the hypothesis that children that received JM first, performed better after MT than children who did not follow JM first or did not train with JM at all. However, these effects could be explained at least partly by frequency of training effects, possibly due to motivational issues, and training-specific factors. Furthermore, it remains unclear whether the effects found on improving mathematics were actually mediated by gains in working memory. It is argued that JM might not train the components of working memory involved in mathematics sufficiently. Another possible explanation can be found in the training's lack of adaptivity, therefore failing to provide the children with tailored instruction and feedback. Finally, it was hypothesized that, since effect sizes are generally small, training effects are bound to a critical period in development.

Limited Near and Far Transfer Effects of Jungle Memory Working Memory Training on Learning Mathematics in Children with Attentional and Mathematical Difficulties

PubMed Central

Nelwan, Michel; Kroesbergen, Evelyn H.

2016-01-01

The goal of this randomized controlled trial was to investigate whether Jungle Memory working memory training (JM) affects performance on working memory tasks, performance in mathematics and gains made on a mathematics training (MT) in school aged children between 9–12 years old (N = 64) with both difficulties in mathematics, as well as attention and working memory. Children were randomly assigned to three groups and were trained in two periods: (1) JM first, followed by MT, (2) MT first, followed by JM, and (3) a control group that received MT only. Bayesian analyses showed possible short term effects of JM on near transfer measures of verbal working memory, but none on visual working memory. Furthermore, support was found for the hypothesis that children that received JM first, performed better after MT than children who did not follow JM first or did not train with JM at all. However, these effects could be explained at least partly by frequency of training effects, possibly due to motivational issues, and training-specific factors. Furthermore, it remains unclear whether the effects found on improving mathematics were actually mediated by gains in working memory. It is argued that JM might not train the components of working memory involved in mathematics sufficiently. Another possible explanation can be found in the training’s lack of adaptivity, therefore failing to provide the children with tailored instruction and feedback. Finally, it was hypothesized that, since effect sizes are generally small, training effects are bound to a critical period in development. PMID:27708595

Persistent-current magnetizations of Nb3Sn Rutherford cables and extracted strands

NASA Astrophysics Data System (ADS)

Collings, E. W.; Sumption, M. D.; Myers, C. S.; Wang, X.; Dietderich, D. R.; Yagotyntsev, K.; Nijhuis, A.

2017-12-01

The magnetizations of eight high-gradient quadrupole cables designated HQ and QXF and a pair of strands, identical in architecture but with different effective strand diameters extracted from an HQ and a related QXF cable, were measured. In the service of field quality assessment, the cable magnetizations and losses were measured by pickup coil magnetometry at 4.2 K in face-on fields, B m , of ± 400 mT at frequencies, f, of up to 60 mHz. Based on the coupling component of loss, Q coup , the coupling magnetization M coup = Q coup /4B m was derived for a ramp rate of 7.5 mT/s. Persistent current (shielding) magnetization and loss (M sh and Q h,strand ) were measured on short pieces of extracted strand by vibrating sample magnetometry at 4.2 K. Unpenetrated M-B loops to ± 400 mT and fully penetrated loops to ± 14 T were obtained. M coup can be easily controlled and reduced to relatively small values by introducing cores and adjusting the preparation conditions. But in low fields near injection Nb3Sn’s high J c and correspondingly high M sh,cable may call for magnetic compensation to preserve field quality. The suitably adjusted cable and strand fully penetrated M-B loops were in reasonable accord leading to the conclusion that strand magnetization is a useful measure of cable magnetization, and that when suitably manipulated can provide input to magnet field error calculations.

Optical fiber magnetic field sensors with TbDyFe magnetostrictive thin films as sensing materials.

PubMed

Yang, Minghong; Dai, Jixiang; Zhou, Ciming; Jiang, Desheng

2009-11-09

Different from usually-used bulk magnetostrictive materials, magnetostrictive TbDyFe thin films were firstly proposed as sensing materials for fiber-optic magnetic field sensing characterization. By magnetron sputtering process, TbDyFe thin films were deposited on etched side circle of a fiber Bragg Grating (FBG) as sensing element. There exists more than 45pm change of FBG wavelength when magnet field increase up to 50 mT. The response to magnetic field is reversible, and could be applicable for magnetic and current sensing.

A simple and low-cost permanent magnet system for NMR

NASA Astrophysics Data System (ADS)

Chonlathep, K.; Sakamoto, T.; Sugahara, K.; Kondo, Y.

2017-02-01

We have developed a simple, easy to build, and low-cost magnet system for NMR, of which homogeneity is about 4 ×10-4 at 57 mT, with a pair of two commercially available ferrite magnets. This homogeneity corresponds to about 90 Hz spectral resolution at 2.45 MHz of the hydrogen Larmor frequency. The material cost of this NMR magnet system is little more than 100. The components can be printed by a 3D printer.

Individual Differences in the Alignment of Structural and Functional Markers of the V5/MT Complex in Primates

PubMed Central

Large, I.; Bridge, H.; Ahmed, B.; Clare, S.; Kolasinski, J.; Lam, W. W.; Miller, K. L.; Dyrby, T. B.; Parker, A. J.; Smith, J. E. T.; Daubney, G.; Sallet, J.; Bell, A. H.; Krug, K.

2016-01-01

Extrastriate visual area V5/MT in primates is defined both structurally by myeloarchitecture and functionally by distinct responses to visual motion. Myelination is directly identifiable from postmortem histology but also indirectly by image contrast with structural magnetic resonance imaging (sMRI). First, we compared the identification of V5/MT using both sMRI and histology in Rhesus macaques. A section-by-section comparison of histological slices with in vivo and postmortem sMRI for the same block of cortical tissue showed precise correspondence in localizing heavy myelination for V5/MT and neighboring MST. Thus, sMRI in macaques accurately locates histologically defined myelin within areas known to be motion selective. Second, we investigated the functionally homologous human motion complex (hMT+) using high-resolution in vivo imaging. Humans showed considerable intersubject variability in hMT+ location, when defined with myelin-weighted sMRI signals to reveal structure. When comparing sMRI markers to functional MRI in response to moving stimuli, a region of high myelin signal was generally located within the hMT+ complex. However, there were considerable differences in the alignment of structural and functional markers between individuals. Our results suggest that variation in area identification for hMT+ based on structural and functional markers reflects individual differences in human regional brain architecture. PMID:27371764

DC magnetic field sensing based on the nonlinear magnetoelectric effect in magnetic heterostructures

NASA Astrophysics Data System (ADS)

Burdin, Dmitrii; Chashin, Dmitrii; Ekonomov, Nikolai; Fetisov, Leonid; Fetisov, Yuri; Shamonin, Mikhail

2016-09-01

Recently, highly sensitive magnetic field sensors using the magnetoelectric effect in composite ferromagnetic-piezoelectric layered structures have been demonstrated. However, most of the proposed concepts are not useful for measuring dc magnetic fields, because the conductivity of piezoelectric layers results in a strong decline of the sensor’s sensitivity at low frequencies. In this paper, a novel functional principle of magnetoelectric sensors for dc magnetic field measurements is described. The sensor employs the nonlinear effect of voltage harmonic generation in a composite magnetoelectric structure under the simultaneous influence of a strong imposed ac magnetic field and a weak dc magnetic field to be measured. This physical effect arises due to the nonlinear dependence of the magnetostriction in the ferromagnetic layer on the magnetic field. A sensor prototype comprising of a piezoelectric fibre transducer sandwiched between two layers of the amorphous ferromagnetic Metglas® alloy was fabricated. The specifications regarding the magnetic field range, frequency characteristics, and noise level were studied experimentally. The prototype showed the responsivity of 2.5 V mT-1 and permitted the measurement of dc magnetic fields in the range of ~10 nT to about 0.4 mT. Although sensor operation is based on the nonlinear effect, the sensor response can be made linear with respect to the measured magnetic field in a broad dynamic range extending over 5 orders of magnitude. The underlying physics is explained through a simplified theory for the proposed sensor. The functionality, differences and advantages of the magnetoelectric sensor compare well with fluxgate magnetometers. The ways to enhance the sensor performance are considered.

Development on electromagnetic impedance function modeling and its estimation

NASA Astrophysics Data System (ADS)

Sutarno, D.

2015-09-01

Today the Electromagnetic methods such as magnetotellurics (MT) and controlled sources audio MT (CSAMT) is used in a broad variety of applications. Its usefulness in poor seismic areas and its negligible environmental impact are integral parts of effective exploration at minimum cost. As exploration was forced into more difficult areas, the importance of MT and CSAMT, in conjunction with other techniques, has tended to grow continuously. However, there are obviously important and difficult problems remaining to be solved concerning our ability to collect process and interpret MT as well as CSAMT in complex 3D structural environments. This talk aim at reviewing and discussing the recent development on MT as well as CSAMT impedance functions modeling, and also some improvements on estimation procedures for the corresponding impedance functions. In MT impedance modeling, research efforts focus on developing numerical method for computing the impedance functions of three dimensionally (3-D) earth resistivity models. On that reason, 3-D finite elements numerical modeling for the impedances is developed based on edge element method. Whereas, in the CSAMT case, the efforts were focused to accomplish the non-plane wave problem in the corresponding impedance functions. Concerning estimation of MT and CSAMT impedance functions, researches were focused on improving quality of the estimates. On that objective, non-linear regression approach based on the robust M-estimators and the Hilbert transform operating on the causal transfer functions, were used to dealing with outliers (abnormal data) which are frequently superimposed on a normal ambient MT as well as CSAMT noise fields. As validated, the proposed MT impedance modeling method gives acceptable results for standard three dimensional resistivity models. Whilst, the full solution based modeling that accommodate the non-plane wave effect for CSAMT impedances is applied for all measurement zones, including near-, transition-as well as the far-field zones, and consequently the plane wave correction is no longer needed for the impedances. In the resulting robust impedance estimates, outlier contamination is removed and the self consistency between the real and imaginary parts of the impedance estimates is guaranteed. Using synthetic and real MT data, it is shown that the proposed robust estimation methods always yield impedance estimates which are better than the conventional least square (LS) estimation, even under condition of severe noise contamination. A recent development on the constrained robust CSAMT impedance estimation is also discussed. By using synthetic CSAMT data it is demonstrated that the proposed methods can produce usable CSAMT transfer functions for all measurement zones.

Development on electromagnetic impedance function modeling and its estimation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sutarno, D., E-mail: Sutarno@fi.itb.ac.id

2015-09-30

Today the Electromagnetic methods such as magnetotellurics (MT) and controlled sources audio MT (CSAMT) is used in a broad variety of applications. Its usefulness in poor seismic areas and its negligible environmental impact are integral parts of effective exploration at minimum cost. As exploration was forced into more difficult areas, the importance of MT and CSAMT, in conjunction with other techniques, has tended to grow continuously. However, there are obviously important and difficult problems remaining to be solved concerning our ability to collect process and interpret MT as well as CSAMT in complex 3D structural environments. This talk aim atmore » reviewing and discussing the recent development on MT as well as CSAMT impedance functions modeling, and also some improvements on estimation procedures for the corresponding impedance functions. In MT impedance modeling, research efforts focus on developing numerical method for computing the impedance functions of three dimensionally (3-D) earth resistivity models. On that reason, 3-D finite elements numerical modeling for the impedances is developed based on edge element method. Whereas, in the CSAMT case, the efforts were focused to accomplish the non-plane wave problem in the corresponding impedance functions. Concerning estimation of MT and CSAMT impedance functions, researches were focused on improving quality of the estimates. On that objective, non-linear regression approach based on the robust M-estimators and the Hilbert transform operating on the causal transfer functions, were used to dealing with outliers (abnormal data) which are frequently superimposed on a normal ambient MT as well as CSAMT noise fields. As validated, the proposed MT impedance modeling method gives acceptable results for standard three dimensional resistivity models. Whilst, the full solution based modeling that accommodate the non-plane wave effect for CSAMT impedances is applied for all measurement zones, including near-, transition-as well as the far-field zones, and consequently the plane wave correction is no longer needed for the impedances. In the resulting robust impedance estimates, outlier contamination is removed and the self consistency between the real and imaginary parts of the impedance estimates is guaranteed. Using synthetic and real MT data, it is shown that the proposed robust estimation methods always yield impedance estimates which are better than the conventional least square (LS) estimation, even under condition of severe noise contamination. A recent development on the constrained robust CSAMT impedance estimation is also discussed. By using synthetic CSAMT data it is demonstrated that the proposed methods can produce usable CSAMT transfer functions for all measurement zones.« less

Manipulating the Mitochondrial Genome To Enhance Cattle Embryo Development

PubMed Central

Srirattana, Kanokwan; St. John, Justin C.

2017-01-01

The mixing of mitochondrial DNA (mtDNA) from the donor cell and the recipient oocyte in embryos and offspring derived from somatic cell nuclear transfer (SCNT) compromises genetic integrity and affects embryo development. We set out to generate SCNT embryos that inherited their mtDNA from the recipient oocyte only, as is the case following natural conception. While SCNT blastocysts produced from Holstein (Bos taurus) fibroblasts were depleted of their mtDNA, and oocytes derived from Angus (Bos taurus) cattle possessed oocyte mtDNA only, the coexistence of donor cell and oocyte mtDNA resulted in blastocysts derived from nondepleted cells. Moreover, the use of the reprogramming agent, Trichostatin A (TSA), further improved the development of embryos derived from depleted cells. RNA-seq analysis highlighted 35 differentially expressed genes from the comparison between blastocysts generated from nondepleted cells and blastocysts from depleted cells, both in the presence of TSA. The only differences between these two sets of embryos were the presence of donor cell mtDNA, and a significantly higher mtDNA copy number for embryos derived from nondepleted cells. Furthermore, the use of TSA on embryos derived from depleted cells positively modulated the expression of CLDN8, TMEM38A, and FREM1, which affect embryonic development. In conclusion, SCNT embryos produced by mtDNA depleted donor cells have the same potential to develop to the blastocyst stage without the presumed damaging effect resulting from the mixture of donor and recipient mtDNA. PMID:28500053

Magnetism variations and susceptibility hysteresis at the metal-insulator phase transition temperature of VO2 in a composite film containing vanadium and tungsten oxides

NASA Astrophysics Data System (ADS)

Akande, Amos A.; Rammutla, Koena E.; Moyo, Thomas; Osman, Nadir S. E.; Nkosi, Steven S.; Jafta, Charl J.; Mwakikunga, Bonex W.

2015-02-01

We report on the magnetic property of 0.67-WO3+0.33-VOx mixture film deposit on the corning glass substrate using the chemical sol-gel and atmospheric pressure chemical vapor deposition (APCVD) methods. The XRD and Raman spectroscopy confirm species of both materials, and the morphological studies with FIB-SEM and TEM reveal segregation of W and V atoms. XPS reveals that V4+ from VO2 forms only 11% of the film; V3+ in the form of V2O3 form 1% of the film, 21% is V5+ from V2O5 and 67% is given to W6+ from WO3. The analysis of the ESR data shows some sharp changes in the magnetism near the metal-to-insulator (MIT), which could be theoretically interpreted as the ordering or alignment of electron spins from net moment nature to parallel alignment of magnetic moment. The derivatives of magnetic susceptibility established the thermally induced magnetic property: two distinct transitions of 339 K for heating data and 338 K for cooling data for 151.2 mT field were obtained. Similar results were also obtained for 308.7 mT field, 336 K for heating data and 335 K for cooling data. VSM results confirm a paramagnetic phase with a small amount of magnetically ordered phase.

Removal of Escherichia coli via low frequency electromagnetic field in riverbank filtration system.

NASA Astrophysics Data System (ADS)

Selamat, Rossitah; Abustan, Ismail; Rizal Arshad, Mohd; Mokhtar Kamal, Nurul Hana

2018-04-01

The removal of Escherichia coli (E. coli) via low frequency of electromagnetic field (LF-EMF) with different magnetic field was studied. LF-EMF is known as a high magnetic susceptibility method, which could affect E. coli growth without the usage of chemicals. The aim of this study was to investigate the removal of E. coli by using LF-EMF in water abstraction for the riverbank filtration (RBF) application. The effect of LF-EMF with the intensity of 2 to 10mT and 50Hz on coiled column of 1mm copper wire at 1 to 6 hours was assessed. The removal of E. coli after exposing to LF-EMF on the column model was measured using most probable number (MPN/100mL) and colonies forming unit (CFU/100mL) methods. Water flows into the column were varied up to 6 hours and with flowrate of 100 mL/min. Experimental results demonstrate that 100% of E. coli was removed at 8mT after 6 hours exposure. The magnetic field at 10mT removed 100% of E. coli after 4 hours exposure. The results obtained in this study proved that the LF-EMF was efficient in E. coli removal from RBF system. These finding indicated that the LF-EMF intensities and time of exposure can affect the removal of E. coli.

Magnetic to magnetic and kinetic to magnetic energy transfers at the top of the Earth's core

NASA Astrophysics Data System (ADS)

Huguet, Ludovic; Amit, Hagay; Alboussière, Thierry

2016-11-01

We develop the theory for the magnetic to magnetic and kinetic to magnetic energy transfer between different spherical harmonic degrees due to the interaction of fluid flow and radial magnetic field at the top of the Earth's core. We show that non-zero secular variation of the total magnetic energy could be significant and may provide evidence for the existence of stretching secular variation, which suggests the existence of radial motions at the top of the Earth's core-whole core convection or MAC waves. However, the uncertainties of the small scales of the geomagnetic field prevent a definite conclusion. Combining core field and flow models we calculate the detailed magnetic to magnetic and kinetic to magnetic energy transfer matrices. The magnetic to magnetic energy transfer shows a complex behaviour with local and non-local transfers. The spectra of magnetic to magnetic energy transfers show clear maxima and minima, suggesting an energy cascade. The kinetic to magnetic energy transfers, which are much weaker due to the weak poloidal flow, are either local or non-local between degree one and higher degrees. The patterns observed in the matrices resemble energy transfer patterns that are typically found in 3-D MHD numerical simulations.

Novel Compound Heterozygous Mutations Expand the Recognized Phenotypes of FARS2-Linked Disease.

PubMed

Walker, Melissa A; Mohler, Kyle P; Hopkins, Kyle W; Oakley, Derek H; Sweetser, David A; Ibba, Michael; Frosch, Matthew P; Thibert, Ronald L

2016-08-01

Mutations in mitochondrial aminoacyl-tRNA synthetases are an increasingly recognized cause of human diseases, often arising in individuals with compound heterozygous mutations and presenting with system-specific phenotypes, frequently neurologic. FARS2 encodes mitochondrial phenylalanyl transfer ribonucleic acid (RNA) synthetase (mtPheRS), perturbations of which have been reported in 6 cases of an infantile, lethal disease with refractory epilepsy and progressive myoclonus. Here the authors report the case of juvenile onset refractory epilepsy and progressive myoclonus with compound heterozygous FARS2 mutations. The authors describe the clinical course over 6 years of care at their institution and diagnostic studies including electroencephalogram (EEG), brain magnetic resonance imaging (MRI), serum and cerebrospinal fluid analyses, skeletal muscle biopsy histology, and autopsy gross and histologic findings, which include features shared with Alpers-Huttenlocher syndrome, Leigh syndrome, and a previously published case of FARS2 mutation associated infantile onset disease. The authors also present structure-guided analysis of the relevant mutations based on published mitochondrial phenylalanyl transfer RNA synthetase and related protein crystal structures as well as biochemical analysis of the corresponding recombinant mutant proteins. © The Author(s) 2016.

Tunneling magnetoresistance sensors with different coupled free layers

NASA Astrophysics Data System (ADS)

Liu, Yen-Fu; Yin, Xiaolu; Yang, Yi; Ewing, Dan; De Rego, Paul J.; Liou, Sy-Hwang

2017-05-01

Large differences of magnetic coercivity (HC), exchange coupling field (HE), and tunneling magnetoresistance ratio (TMR) in magnetic tunnel junctions with different coupled free layers are discussed. We demonstrate that the magnetization behavior of the free layer is not only dominated by the interfacial barrier layer but also affected largely by the magnetic or non-magnetic coupled free layers. All these parameters are sensitively controlled by the magnetic nanostructure, which can be tuned also by the magnetic annealing process. The optimized sensors exhibit a large field sensitivity of up to 261%/mT in the region of the reversal synthetic ferrimagnet at the pinned layers.

Magnetic irreversibility: An important amendment in the zero-field-cooling and field-cooling method

NASA Astrophysics Data System (ADS)

Teixeira Dias, Fábio; das Neves Vieira, Valdemar; Esperança Nunes, Sabrina; Pureur, Paulo; Schaf, Jacob; Fernanda Farinela da Silva, Graziele; de Paiva Gouvêa, Cristol; Wolff-Fabris, Frederik; Kampert, Erik; Obradors, Xavier; Puig, Teresa; Roa Rovira, Joan Josep

2016-02-01

The present work reports about experimental procedures to correct significant deviations of magnetization data, caused by magnetic relaxation, due to small field cycling by sample transport in the inhomogeneous applied magnetic field of commercial magnetometers. The extensively used method for measuring the magnetic irreversibility by first cooling the sample in zero field, switching on a constant applied magnetic field and measuring the magnetization M(T) while slowly warming the sample, and subsequently measuring M(T) while slowly cooling it back in the same field, is very sensitive even to small displacement of the magnetization curve. In our melt-processed YBaCuO superconducting sample we observed displacements of the irreversibility limit up to 7 K in high fields. Such displacements are detected only on confronting the magnetic irreversibility limit with other measurements, like for instance zero resistance, in which the sample remains fixed and so is not affected by such relaxation. We measured the magnetic irreversibility, Tirr(H), using a vibrating sample magnetometer (VSM) from Quantum Design. The zero resistance data, Tc0(H), were obtained using a PPMS from Quantum Design. On confronting our irreversibility lines with those of zero resistance, we observed that the Tc0(H) data fell several degrees K above the Tirr(H) data, which obviously contradicts the well known properties of superconductivity. In order to get consistent Tirr(H) data in the H-T plane, it was necessary to do a lot of additional measurements as a function of the amplitude of the sample transport and extrapolate the Tirr(H) data for each applied field to zero amplitude.

Noncollinear antiferromagnetic Mn3Sn films

NASA Astrophysics Data System (ADS)

Markou, A.; Taylor, J. M.; Kalache, A.; Werner, P.; Parkin, S. S. P.; Felser, C.

2018-05-01

Noncollinear hexagonal antiferromagnets with almost zero net magnetization were recently shown to demonstrate giant anomalous Hall effect. Here, we present the structural and magnetic properties of noncollinear antiferromagnetic Mn3Sn thin films heteroepitaxially grown on Y:ZrO2 (111) substrates with a Ru underlayer. The Mn3Sn films were crystallized in the hexagonal D 019 structure with c -axis preferred (0001) crystal orientation. The Mn3Sn films are discontinuous, forming large islands of approximately 400 nm in width, but are chemical homogeneous and characterized by near perfect heteroepitaxy. Furthermore, the thin films show weak ferromagnetism with an in-plane uncompensated magnetization of M =34 kA/m and coercivity of μ0Hc=4.0 mT at room temperature. Additionally, the exchange bias effect was studied in Mn3Sn /Py bilayers. Exchange bias fields up to μ0HEB=12.6 mT can be achieved at 5 K. These results show Mn3Sn films to be an attractive material for applications in antiferromagnetic spintronics.

Magnetic study of Co-doped CdSe nanoparticles

NASA Astrophysics Data System (ADS)

Das, Sayantani; Banerjee, Sourish; Sinha, T. P.

2018-04-01

Cobalt (2 %, 5 % and 10 %) doped cadmium selenide (CdSe) nanoparticles have been synthesized by soft chemical route. The XRD pattern shows the cubic structure of the sample. Crystallization temperature of the samples is calculated using differential scanning calorimeter. The average particle size of all the samples is found to be ˜ 25 nm. Field dependent (M-H) and temperature dependent (M-T) magnetization explains the presence of ferromagnetic components in the samples at room temperature and low temperature. In order to estimate the antiferromagnetic coupling among the doped TM atoms, an M-T measurement at 500 Oe has been carried out under zero field cooled (ZFC) and field cooled (FC) conditions and Curie-Weiss temperature θ of the samples has been estimated from 1/χ vs T plots.

Laser induced local modification of magnetic domain in Co/Pt multilayer

NASA Astrophysics Data System (ADS)

Talapatra, A.; Mohanty, J.

2016-11-01

Manipulation of magnetic system by the use of laser has drawn the attention of contemporary research. We demonstrate here the modification of magnetic domain in perpendicularly magnetized Co/Pt multilayer by using ultrashort laser pulse. The as-prepared sample shows an out-of-plane saturation magnetic field of 803.4 mT and almost zero remanence with a labyrinth-like domain pattern at room temperature. Atomistic simulation showed that interaction with femto-second laser results in demagnetization of the material in 200 fs followed by a slower recovery. As it indicates a net loss in magnetization, so magnetic force microscopy is carried out to investigate the equilibrium state after the system is relaxed. Demagnetized random domains appeared at the centre of the laser spot with having a rim at the boundary which signifies a deterministic switching with respect to the neighbouring area. Rotation of domains at the central area with the application of small transverse field (100 mT) proves the region to be magnetically weaker. Systematic 3D micromagnetic simulation has been performed to model the laser induced change by selective reduction of anisotropy which is discussed in detail. This shows shrinking of domains to a near circular pattern to minimize the magnetostatic energy. 50% reduction in anisotropy energy is observed with increasing the total energy of the system and a sharp increase in demagnetization energy also takes place simultaneously. This also satisfies the anisotropy in domain rotation with the application of transverse field.

Matched dipole probe for precise electron density measurements in magnetized and non-magnetized plasmas

NASA Astrophysics Data System (ADS)

Rafalskyi, Dmytro; Aanesland, Ane

2015-09-01

We present a plasma diagnostics method based on impedance measurements of a short matched dipole placed in the plasma. This allows measuring the local electron density in the range from 1012-1015 m-3 with a magnetic field of at least 0-50 mT. The magnetic field strength is not directly influencing the data analysis and requires only that the dipole probe is oriented perpendicularly to the magnetic field. As a result, the magnetic field can be non-homogeneous or even non-defined within the probe length without any effect on the final tolerance of the measurements. The method can be applied to plasmas of relatively small dimensions (< 10 cm) and doesn't require any special boundary conditions. The high sensitivity of the impedance measurements is achieved by using a miniature matching system installed close to the probe tip, which also allows to suppress sheath resonance effects. We experimentally show here that the tolerance of the electron density measurements reaches values lower than 1%, both with and without the magnetic field. The method is successfully validated by both analytical modeling and experimental comparison with Langmuir probes. The validation experiments are conducted in a low pressure (1 mTorr) Ar discharge sustained in a 10 cm size plasma chamber with and without a transversal magnetic field of about 20 mT. This work was supported by a Marie Curie International Incoming Fellowships within FP7 (NEPTUNE PIIF-GA-2012-326054).

Segmentation of the Cascadia Forearc in Southwestern Washington—Evidence from New Potential-Field Data

NASA Astrophysics Data System (ADS)

Blakely, R. J.; Wells, R. E.; Sherrod, B. L.; Brocher, T. M.

2016-12-01

Newly acquired potential-field data, geologic mapping, and recorded seismicity indicate that the Cascadia subduction zone is segmented in southwestern Washington by a left-stepping, possibly active crustal structure spanning nearly the entire onshore portion of the forearc. The east-striking, southward verging Doty thrust fault is an important part of this trans-forearc structure. As mapped, the eastern end of the 50-km-long Doty fault connects with the northwestern termination of ongoing seismicity on the north-northwest-striking Mt. St. Helens seismic zone (MSHSZ), suggesting that the Doty fault and MSHSZ may be kinematically linked. Westward, the mapped Doty fault terminates at and may link to mapped faults striking northwestward to 35 km north of Grays Harbor, a total northwest distance of 85 km. A newly acquired aeromagnetic survey over the Doty fault and MSHSZ, and existing gravity data, emphasize Crescent Formation and other Eocene volcanic rocks in the hanging wall of the Doty fault with up to 4 km of vertical throw. Most MSHSZ epicenters fall within a broad (5- to 10-km wide) magnetic low extending 50 km north-northwestward from Mt. St Helens. The magnetic low skirts around the western margin of the Miocene-age Spirit Lake pluton, but otherwise is not obviously associated with topography or mapped geology. We suggest that dextral slip on the MSHSZ is distributed across a broad, northwest-striking area that includes the magnetic low and is transferred to compressional slip on the Doty fault. The Doty fault demarcates a clear north-to-south decrease in the density of episodic tremor, suggesting that the thrust fault may intersect or modulate over-pressured fluids generated above the slab (Wells et al., in review). The Doty fault, MSHSZ, and neighboring structures are consistent with a dextral shear couple (Wells and Coe, 1985) and consequent clockwise crustal rotation extending across the entire landward portion of the Cascadia forearc, from the Pacific Coast to the Cascadia arc and from Grays Harbor to the Portland basin in northwestern Oregon.

Electrostatic focal spot correction for x-ray tubes operating in strong magnetic fields.

PubMed

Lillaney, Prasheel; Shin, Mihye; Hinshaw, Waldo; Fahrig, Rebecca

2014-11-01

A close proximity hybrid x-ray/magnetic resonance (XMR) imaging system offers several critical advantages over current XMR system installations that have large separation distances (∼5 m) between the imaging fields of view. The two imaging systems can be placed in close proximity to each other if an x-ray tube can be designed to be immune to the magnetic fringe fields outside of the MR bore. One of the major obstacles to robust x-ray tube design is correcting for the effects of the MR fringe field on the x-ray tube focal spot. Any fringe field component orthogonal to the x-ray tube electric field leads to electron drift altering the path of the electron trajectories. The method proposed in this study to correct for the electron drift utilizes an external electric field in the direction of the drift. The electric field is created using two electrodes that are positioned adjacent to the cathode. These electrodes are biased with positive and negative potential differences relative to the cathode. The design of the focusing cup assembly is constrained primarily by the strength of the MR fringe field and high voltage standoff distances between the anode, cathode, and the bias electrodes. From these constraints, a focusing cup design suitable for the close proximity XMR system geometry is derived, and a finite element model of this focusing cup geometry is simulated to demonstrate efficacy. A Monte Carlo simulation is performed to determine any effects of the modified focusing cup design on the output x-ray energy spectrum. An orthogonal fringe field magnitude of 65 mT can be compensated for using bias voltages of +15 and -20 kV. These bias voltages are not sufficient to completely correct for larger orthogonal field magnitudes. Using active shielding coils in combination with the bias electrodes provides complete correction at an orthogonal field magnitude of 88.1 mT. Introducing small fields (<10 mT) parallel to the x-ray tube electric field in addition to the orthogonal field does not affect the electrostatic correction technique. However, rotation of the x-ray tube by 30° toward the MR bore increases the parallel magnetic field magnitude (∼72 mT). The presence of this larger parallel field along with the orthogonal field leads to incomplete correction. Monte Carlo simulations demonstrate that the mean energy of the x-ray spectrum is not noticeably affected by the electrostatic correction, but the output flux is reduced by 7.5%. The maximum orthogonal magnetic field magnitude that can be compensated for using the proposed design is 65 mT. Larger orthogonal field magnitudes cannot be completely compensated for because a pure electrostatic approach is limited by the dielectric strength of the vacuum inside the x-ray tube insert. The electrostatic approach also suffers from limitations when there are strong magnetic fields in both the orthogonal and parallel directions because the electrons prefer to stay aligned with the parallel magnetic field. These challenging field conditions can be addressed by using a hybrid correction approach that utilizes both active shielding coils and biasing electrodes.

Electrostatic focal spot correction for x-ray tubes operating in strong magnetic fields

PubMed Central

Lillaney, Prasheel; Shin, Mihye; Hinshaw, Waldo; Fahrig, Rebecca

2014-01-01

Purpose: A close proximity hybrid x-ray/magnetic resonance (XMR) imaging system offers several critical advantages over current XMR system installations that have large separation distances (∼5 m) between the imaging fields of view. The two imaging systems can be placed in close proximity to each other if an x-ray tube can be designed to be immune to the magnetic fringe fields outside of the MR bore. One of the major obstacles to robust x-ray tube design is correcting for the effects of the MR fringe field on the x-ray tube focal spot. Any fringe field component orthogonal to the x-ray tube electric field leads to electron drift altering the path of the electron trajectories. Methods: The method proposed in this study to correct for the electron drift utilizes an external electric field in the direction of the drift. The electric field is created using two electrodes that are positioned adjacent to the cathode. These electrodes are biased with positive and negative potential differences relative to the cathode. The design of the focusing cup assembly is constrained primarily by the strength of the MR fringe field and high voltage standoff distances between the anode, cathode, and the bias electrodes. From these constraints, a focusing cup design suitable for the close proximity XMR system geometry is derived, and a finite element model of this focusing cup geometry is simulated to demonstrate efficacy. A Monte Carlo simulation is performed to determine any effects of the modified focusing cup design on the output x-ray energy spectrum. Results: An orthogonal fringe field magnitude of 65 mT can be compensated for using bias voltages of +15 and −20 kV. These bias voltages are not sufficient to completely correct for larger orthogonal field magnitudes. Using active shielding coils in combination with the bias electrodes provides complete correction at an orthogonal field magnitude of 88.1 mT. Introducing small fields (<10 mT) parallel to the x-ray tube electric field in addition to the orthogonal field does not affect the electrostatic correction technique. However, rotation of the x-ray tube by 30° toward the MR bore increases the parallel magnetic field magnitude (∼72 mT). The presence of this larger parallel field along with the orthogonal field leads to incomplete correction. Monte Carlo simulations demonstrate that the mean energy of the x-ray spectrum is not noticeably affected by the electrostatic correction, but the output flux is reduced by 7.5%. Conclusions: The maximum orthogonal magnetic field magnitude that can be compensated for using the proposed design is 65 mT. Larger orthogonal field magnitudes cannot be completely compensated for because a pure electrostatic approach is limited by the dielectric strength of the vacuum inside the x-ray tube insert. The electrostatic approach also suffers from limitations when there are strong magnetic fields in both the orthogonal and parallel directions because the electrons prefer to stay aligned with the parallel magnetic field. These challenging field conditions can be addressed by using a hybrid correction approach that utilizes both active shielding coils and biasing electrodes. PMID:25370658

Magnetotelluric studies of the Caldas Novas geothermal reservoir, Brazil

NASA Astrophysics Data System (ADS)

de Lugão, Patricia Pastana; LaTerra, Emanuele Francesco; Kriegshäuser, Berthold; Fontes, Sergio L.

2002-01-01

A magnetotelluric (MT) survey was conducted on the Caldas Novas geothermal reservoir located in the state of Goiás, Central Brazil. The region of Caldas Novas is a popular tourist spot because of the occurrence of hot water springs. The purpose of the first MT survey in this area is to provide more information on the geoelectrical structure of this important geothermal reservoir. The MT method is a frequency domain technique that utilizes naturally occurring magnetic and electric signals as source to obtain a resistivity map of the subsurface. Since temperature and permeability are some of the factors controlling electrical resistivity, MT is widely utilized for surveying geothermal areas such as Caldas Novas. Data were acquired along two profiles crossing the Serra de Caldas (Caldas Mountains) with a total of 25 MT stations. Frequencies of acquisition were in the range from 0.008 to 176 Hz. Spacing between stations were usually around 5 km. Apparent resistivity and phase data from the transverse electric (TE) and transverse magnetic (TM) modes were computed for both profiles. Very high (100,000 Ω m) apparent resistivity values in the TM mode indicate distortion, possibly caused by 3-D resistive structures. In this work, we focus on Profile 2, which was acquired aligned at N40°E, approximately following the direction of weakness N50°E. Two-dimensional (2-D) inversion suggests a basin-like model with very high-resistivity block structures associated with concentric faulting below the Caldas Mountains inside a resistive basin that extends to depths of approximately 25-30 km. This model is in good agreement with gravity data and the available geological information in the area and can help delineate areas of new geothermal reservoirs. The high resistivity associated with the depression in the MT model can be interpreted as caused by the low-permeability quartzites that form the Caldas Mountains. Although the survey configuration does not allow for a full three-dimensional (3-D) interpretation, a 3-D resistivity model was constructed and the MT responses computed. The 3-D synthetic data explains the behavior of both the TE and TM modes in this faulted resistive environment.

Design, fabrication and characterization of an arrayable all-polymer microfluidic valve employing highly magnetic rare-earth composite polymer

NASA Astrophysics Data System (ADS)

Rahbar, Mona; Shannon, Lesley; Gray, Bonnie L.

2016-05-01

We present a new magnetically actuated microfluidic valve that employs a highly magnetic composite polymer (M-CP) containing rare-earth hard-magnetic powder for its actuating element and for its valve seat. The M-CP offers much higher magnetization compared to the soft-magnetic, ferrite-based composite polymers typically used in microfluidic applications. Each valve consists of a permanently magnetized M-CP flap and valve seat mounted on a microfluidic channel system fabricated in poly(dimethylsiloxane) (PDMS). Each valve is actuated under a relatively small external magnetic field of 80 mT provided by a small permanent magnet mounted on a miniature linear actuator. The performance of the valve with different flap thicknesses is characterized. In addition, the effect of the magnetic valve seat on the valve’s performance is also characterized. It is experimentally shown that a valve with a 2.3 mm flap thickness, actuated under an 80 mT magnetic field, is capable of completely blocking liquid flow at a flow rate of 1 ml min-1 for pressures up to 9.65 kPa in microfluidic channels 200 μm wide and 200 μm deep. The valve can also be fabricated into an array for flow switching between multiple microfluidic channels under continuous flow conditions. The performance of arrays of valves for flow routing is demonstrated for flow rates up to 5 ml min-1 with larger microfluidic channels of up to 1 mm wide and 500 μm deep. The design of the valves is compatible with other commonly used polymeric microfluidic components, as well as other components that use the same novel permanently magnetic composite polymer, such as our previously reported cilia-based mixing devices.

Rock Magnetic Properties of Laguna Carmen (Tierra del Fuego, Argentina): Implications for Paleomagnetic Reconstruction

NASA Astrophysics Data System (ADS)

Gogorza, C. G.; Orgeira, M. J.; Ponce, F.; Fernández, M.; Laprida, C.; Coronato, A.

2013-05-01

We report preliminary results obtained from a multi-proxy analysis including paleomagnetic and rock-magnetic studies of two sediment cores of Laguna Carmen (53°40'60" S 68°19'0" W, ~83m asl) in the semiarid steppe in northern Tierra del Fuego island, Southernmost Patagonia, Argentina. Two short cores (115 cm) were sampled using a Livingstone piston corer during the 2011 southern fall. Sediments are massive green clays (115 to 70 cm depth) with irregularly spaced thin sandy strata and lens. Massive yellow clay with thin sandy strata continues up to 30 cm depth; from here up to 10 cm yellow massive clays domain. The topmost 10 cm are mixed yellow and green clays with fine sand. Measurements of intensity and directions of Natural Remanent Magnetization (NRM), magnetic susceptibility, isothermal remanent magnetization, saturation isothermal remanent magnetization (SIRM), back field and anhysteretic remanent magnetization at 100 mT (ARM100mT) were performed and several associated parameters calculated (ARM100mT/k and SIRM/ ARM100mT). Also, as a first estimate of relative magnetic grain-size variations, the median destructive field of the NRM (MDFNRM), was determined. Additionally, we present results of magnetic parameters measured with vibrating sample magnetometer (VSM). The stability of the NRM was analyzed by alternating field demagnetization. The magnetic properties have shown variable values, showing changes in both grain size and concentration of magnetic minerals. It was found that the main carrier of remanence is magnetite with the presence of hematite in very low percentages. This is the first paleomagnetic study performed in lakes located in the northern, semiarid fuegian steppe, where humid-dry cycles have been interpreted all along the Holocene from an aeolian paleosoil sequence (Orgeira et el, 2012). Comparison between paleomagnetic records of Laguna Carmen and results obtained in earlier studies carried out at Laguna Potrok Aike (Gogorza et al., 2012) were performed. References Gogorza, C.S.G., Irurzun, M.A., Sinito, A.M., Lisé-Pronovost, A., St-Onge, G., Haberzettl, T., Ohlendorf, C., Kastner, S., Zolitschka, B., 2012. High-resolution paleomagnetic records from Laguna Potrok Aike (Patagonia, Argentina) for the last 16,000 years. Geochemistry Geophysics Geosystems. 13, Q12Z37. Orgeira, M.J., Vásquez, C.A., Coronato, A., Ponce, F., Moreto, A., Osterrieth, M, Egli, R., Onorato, R., 2012. Magnetic properties of Holocene edaphized silty eolian sediments from Tierra del Fuego (Argentina). Revista de la Sociedad Geológica de España. 25 (1-2), 45-56.

Effect of freeze-dryer design on drying rate of an amorphous protein-formulation determined with a gravimetric technique.

PubMed

Gieseler, Henning; Lee, Geoffrey

2008-01-01

A freeze-drying balance was used to determine momentary drying-rate, m(t), of a sucrose/BSA formulation contained in a vial with varying shelf packing density, Ø2. A comparison between two different laboratory-scale freeze-dryers was made. The effects of Ø2 on m(t) differed between the two units, attributed to drying chamber design and its effects on heat transfer. At high Ø2 the differences are annulled because of the shielding effects of surrounding vials. Parallel effects of Ø2 were also found on product temperature, Tb, measured in the balance vial. Tb was used to calculate vial heat transfer coefficient, Kv. Kv was strongly reduced with increasing Ø2, but reached a plateau value at high Ø2.

Northeastern Pacific mantle conductivity profile from long-period magnetotelluric sounding using Hawaii-to-California submarine cable data

NASA Astrophysics Data System (ADS)

Lizarralde, Daniel; Chave, Alan; Hirth, Greg; Schultz, Adam

1995-09-01

We present results of a long-period magnetotelluric (MT) investigation of the electrical structure beneath the eastern North Pacific. The electric field data consist of ˜2 years of continuously recorded voltages across an unpowered, ˜4000-km-long submarine telephone cable (HAW-1) extending from Point Arena, California, to Oahu, Hawaii. The electric field measurements are coherent to some degree with magnetic field measurements from Honolulu Observatory at periods of 0.1 to 45 days. This coherence is enhanced at long periods over that observed with point electric field sensors due to horizontal averaging of the motional electric fields of spatial scale smaller than the cable length, significantly diminishing their effect. Robust, controlled leverage MT response estimates and their jacknife confidence limits are computed for the HAW-1 to Honolulu data. An equivalent scalar MT response obtained from Honolulu magnetic variations data is used to correct the HAW-1 MT response for static shift and to extend the MT response estimate to periods of 100 days. The composite response function satisfies necessary and sufficient conditions for consistency with a one-dimensional conductivity structure and is most sensitive to structure between 150 and 1000 km. Inversion of the MT response reveals a conductive zone (0.05-0.1 S/m) between 150 and 400 km depth and a positive gradient below 500 km; these observations are consistent with previous MT studies in the North Pacific. This upper mantle conductivity is too high to be explained by solid-state conduction in dry olivine using reasonable mantle geotherms. Calculations based on measurements of hydrogen solubility and diffusivity in olivine indicate that H+ dissolved in olivine, possibly combined with a lattice preferred orientation consistent with measured seismic anisotropy, provide sufficient conductivity enhancement to explain the inversion results. The high conductivity may also be explained by the presence of gravitationally stable partial melt. Comparison of the HAW-1 results with long-period MT studies conducted on land reveals differences in upper mantle conductivity between different tectonic regimes. In particular, the upper mantle beneath the Pacific Ocean is considerably more conductive than that beneath the Canadian shield and similar in conductivity to that beneath the Basin and Range.

Magnetic Properties of the Chelyabinsk meteorite

NASA Astrophysics Data System (ADS)

Bezaeva, N. S.; Badyukov, D. D.; Nazarov, M. A.; Rochette, P.; Feinberg, J. M.

2013-12-01

The Chelyabinsk meteorite (the fall of February 15, 2013; Russia) is a LL5 ordinary chondrite. Numerous (thousands) stones fell as a shower to the south and the south-west of the city of Chelyabinsk. The stones consist of two intermixed lithologies, with the majority (2/3) being a light lithology with a typical chondritic texture and shock stage S4 (~30 GPa). The second lithology (1/3) is an impact melt breccia (IMB) consisting of blackened chondrite fragments embedded in a fine-grained matrix. We investigated the magnetic properties of the meteorite stones collected immediately after the fall by the expedition of the Vernadsky Institute, Moscow. The low-field magnetic susceptibility (χ0) of 174 fragments (135 chondritic and 39 IMB) weighing >3 g was measured. Each sample was measured three times in mutually perpendicular directions to average anisotropy. Also hysteresis loops (saturation magnetization Ms, coercivity Bc) and back-field remanence demagnetization curves (coercivity of remanence Bcr) in the temperature range from 10K to 700°C and other characteristics of some pieces (NRM, SIRM with their thermal and alternating field demagnetization spectra) were acquired. The mean logχ0 is 4.57×0.09 (s.d.) for the light lithology and 4.65×0.09 (s.d.) (×10-9 m3/kg) for the IMB, indicating that IMB is slightly richer in metal than the light chondritic lithology. According to [1], Chelyabinsk is three times more magnetic than the average LL5 fall, but similar to other metal-rich LL5 (e.g., Paragould, Aldsworth, Bawku, Richmond), as well as L/LL chondrites (e.g., Glanerbrug, Knyahinya, Qidong). The estimation of metal content from the Ms value gives 3.7 wt.% for the light fragments and 4.1 wt.% for IMB whereas the estimation from χ0 yields overestimated contents, e.g., 6.9 wt.% for the light lithology. Thermomagnetic curves Ms(T) up to 800°C identify the main magnetic carriers at room temperature (T0) and above as taenite and kamacite (no tetrataenite found), in accordance with mineralogical data. Additional magnetic analyses [2] confirm the absence of tetrataenite and show that metal grains are primarily multidomain and magnetically soft (Bc<2 mT and Bcr<23 mT) at T0. However, at temperatures <75 K, the magnetic remanence of the Chelyabinsk chondrite is dominated by high coercivity chromite with much higher Bcr (606 mT for the light lithology and 157 mT for IMB). These results are consistent with previously published data on ordinary chondrites [3]. Acknowledgments: This research was funded by a U.S. National Science Foundation IRM Visiting Fellowship. References: [1] Rochette P. et al. 2003. MAPS 38: 251-268. [2] Bezaeva N.S. et al. 2013. Geochem. Int. 51(7): 568-574. [3] Gattacceca J. et al. 2011. Geoph. Res. Lett. 38: L10203.

Platelet-mediated transformation of mtDNA-less human cells: Analysis of phenotypic variability among clones from normal individuals-and complementation behavior of the tRNA[sup Lys] mutation causing myoclonic epilepsy and ragged red fibers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chomyn, A.; Lai, S.T.; Shakeley, R.

1994-06-01

In the present work, the authors demonstrate the possibility of using human blood platelets as mitochondrial donors for the repopulation of mtDNA-less ([rho][sup o]) cells. The noninvasive nature of platelet isolation, combined with the prolonged viability of platelet mitochondria and the simplicity and efficiency of the mitochondria-transfer procedure, has substantially increased the applicability of the [rho][sup o] cell transformation approach for mitochondrial genetic analysis and for the study of mtDNA-linked diseases. This approach has been applied to platelets from several normal human individuals and one individual affected by the myoclonic-epilepsy-and-ragged-red-fibers (MERRF) encephalomyopathy. A certain variability in respiratory capacity was observedmore » among the platelet-derived [rho][sup o] cell transformants from a given normal subject, and it was shown to be unrelated to their mtDNA content. The results of sequential transfer of mitochondria from selected transformants into a [rho][sup o] cell line different from the first [rho][sup o] acceptor strongly suggest that this variability reflected, at least in part, differences in nuclear gene content and/or activity among the original recipient cells. A much greater variability in respiratory capacity was observed among the transformants derived from the MERRF patient and was found to be related to the presence and amount of the mitochondrial tRNA[sup Lys] mutation associated with the MERRF syndrome. An analysis of the relationship between proportion of mtDNA carrying the MERRF mutation and degree of respiratory activity in various transformations derived from the MERRF patient revealed an unusual complementation behavior of the tRNA[sup Lys] mutation, possibly reflecting the distribution of mutant mtDNA among the platelet mitochondria. 29 refs., 4 figs., 1 tab.« less

Magnetostatic interactions in a natural magnetite-ulvospinel intergrowth system

NASA Astrophysics Data System (ADS)

Evans, M. E.; Krasa, D.; Williams, W.; Winklhofer, M.

2005-12-01

The difficult problem of magnetostatic interactions in naturally-occurring minerals has a long history but a renewed attack on it is currently being driven by recent advances in instrumentation and computing power. We report a new investigation of a finely exsolved magnetite/ulvöspinel intergrowth first studied magnetically by Evans & Wayman (1974) and more recently by Harrison et al. (2002). Transmission electron micrographs reveal a rectilinear pattern of tiny magnetite blocks separated by ulvöspinel sheets. The magnetite blocks have a gaussian size distribution with mean and standard deviation of 193 and 46 nm, respectively (n ~ 500), with the separation between nearest neighbours being typically 40 nm, but often much less. Thermomagnetic analysis yields a well-defined Curie point of 548°C indicating that the ``magnetite" actually has a compostion of Fe2.9Ti0.1O4. Routine hysteresis measurements immediately reflect the interaction between neighbouring ``magnetite" regions, with Mrs/Ms = 0.22, well below the expected value for non-interacting single-domain particles. The corresponding FORC diagram clearly reveals the interaction fields with Hi = 30 mT (full-width at half-maximum, FWHM) centred on a well-defined Hc peak at 20 mT. Furthermore, the maximum interaction field observed (~50 mT) agrees well with that expected from simple theory and micromagnetic calculations. Elimination of the intergrowth structure by heating in an evacuated quartz vial for 2 hours at 1000 °C leads to marked changes in the magnetic properties: Mrs/Ms drops to 0.11, Hcr/Hc increases from 1.98 to 2.73, the main peak on the FORC diagram shifts to 6 mT and the interaction field profile drastically narrows (FWHM Hi = 14 mT).

[Possibilities of magnetotherapy in stabilization of visual function in patients with glaucoma].

PubMed

Bisvas Shutanto Kumar; Listopadova, N A

1996-01-01

Courses of magnetotherapy (MT) using ATOS device with 33 mT magnetic field induction were administered to 31 patients (43 eyes) with primary open-angle glaucoma with compensated intraocular pressure. The operation mode was intermittent, with 1.0 to 1.5 Hz field rotation frequency by 6 radii. The procedure is administered to a patient in a sitting posture with magnetic inductor held before the eye. The duration of a session is 10 min, a course consists of 10 sessions. Untreated eyes (n = 15) of the same patients were examined for control. The patients were examined before and 4 to 5 months after MT course. Vision acuity improved by 0.16 diopters, on an average, in 29 eyes (96.7%) out of 30 with vision acuity below 1.0 before treatment. Visocontrastometry was carried out using Visokontrastometer-DT device with spatial frequency range from 0.4 to 19 cycle/degree (12 frequencies) and 125 x 125 monitor. The orientation of lattices was horizontal and vertical. The contrasts ranged from 0.03 to 0.9 (12 levels). MT brought about an improvement of spatial contrast sensitivity by at least 7 values of 12 levels in 22 (84.6%) out of 26 eyes and was unchanged in 4 eyes. Visual field was examined using Humphry automated analyzer. A 120-point threshold test was used. After a course of MT, visual field deficit decreased by at least 10% in 31 (72%) out of 43 eyes, increased in 3, and was unchanged in 9 eyes; on an average, visual field deficit decreased by 22.4% vs. the initial value. After 4 to 5 months the changes in the vision acuity and visual field deficit were negligible. In controls these parameters did not appreciably change over the entire follow-up period.

Effect of magnetic field on the physical properties of water

NASA Astrophysics Data System (ADS)

Wang, Youkai; Wei, Huinan; Li, Zhuangwen

2018-03-01

In this study, the effect of magnetic field (MF) on the partial physical properties of water are reported, tap water (TW) and 4 types of magnetized water (MW) were measured in the same condition. It was found that the properties of TW were changed following the MF treatment, shown as the increase of evaporation amount, the decrease of specific heat and boiling point after magnetization, the changes depend on the magnetization effect. In addition, magnetic field strength (MFS) has a marked influence on the magnetization effect, the optimal magnetizing condition was determined as the MFS of 300 mT. The findings of this study offered a facile approach to improve cooling and power generation efficiency in industrial.

The Effects of rTMS Combined with Motor Training on Functional Connectivity in Alpha Frequency Band.

PubMed

Jin, Jing-Na; Wang, Xin; Li, Ying; Jin, Fang; Liu, Zhi-Peng; Yin, Tao

2017-01-01

It has recently been reported that repetitive transcranial magnetic stimulation combined with motor training (rTMS-MT) could improve motor function in post-stroke patients. However, the effects of rTMS-MT on cortical function using functional connectivity and graph theoretical analysis remain unclear. Ten healthy subjects were recruited to receive rTMS immediately before application of MT. Low frequency rTMS was delivered to the dominant hemisphere and non-dominant hand performed MT over 14 days. The reaction time of Nine-Hole Peg Test and electroencephalography (EEG) in resting condition with eyes closed were recorded before and after rTMS-MT. Functional connectivity was assessed by phase synchronization index (PSI), and subsequently thresholded to construct undirected graphs in alpha frequency band (8-13 Hz). We found a significant decrease in reaction time after rTMS-MT. The functional connectivity between the parietal and frontal cortex, and the graph theory statistics of node degree and efficiency in the parietal cortex increased. Besides the functional connectivity between premotor and frontal cortex, the degree and efficiency of premotor cortex showed opposite results. In addition, the number of connections significantly increased within inter-hemispheres and inter-regions. In conclusion, this study could be helpful in our understanding of how rTMS-MT modulates brain activity. The methods and results in this study could be taken as reference in future studies of the effects of rTMS-MT in stroke patients.

[Relationship between mitochondrial DNA copy number, membrane potential of human embryo and embryo morphology].

PubMed

Zhao, H; Teng, X M; Li, Y F

2017-11-25

Objective: To explore the relationship between the embryo with the different morphological types in the third day and its mitochondrial copy number, the membrane potential. Methods: Totally 117 embryos with poor development after normal fertilization and were not suitable transferred in the fresh cycle and 106 frozen embryos that were discarded voluntarily by infertility patients with in vitro fertilization-embryo transfer after successful pregnancy were selected. According to evaluation of international standard in embryos, all cleavage stage embryos were divided into class Ⅰ frozen embryo group ( n= 64), class Ⅱ frozen embryo group ( n= 42) and class Ⅲ fresh embryonic group (not transplanted embryos; n= 117). Real-time PCR and confocal microscopy methods were used to detect mitochondrial DNA (mtDNA) copy number and the mitochondrial membrane potential of a single embryo. The differences between embryo quality and mtDNA copy number and membrane potential of each group were compared. Results: The copy number of mtDNA and the mitochondrial membrane potential in class Ⅲ fresh embryonic group [(1.7±1.0)×10(5) copy/μl, 1.56±0.32] were significantly lower than those in class Ⅰ frozen embryo group [(3.4±1.7)×10(5) copy/μl, 2.66±0.21] and class Ⅱ frozen embryo group [(2.6±1.2)×10(5) copy/μl, 1.80±0.32; all P< 0.05]. The copy number of mtDNA and the mitochondrial membrane potential in classⅠ frozen embryo group were significantly higher than those in classⅡ frozen embryo group (both P< 0.05). Conclusion: The mtDNA copy number and the mitochondrial membrane potential of embryos of the better quality embryo are higher.

Structural and magnetic properties of the nanocomposite materials based on a mesoporous silicon dioxide matrix

NASA Astrophysics Data System (ADS)

Grigor'eva, N. A.; Eckerlebe, H.; Eliseev, A. A.; Lukashin, A. V.; Napol'skii, K. S.; Kraje, M.; Grigor'ev, S. V.

2017-03-01

The structural and magnetic properties of the mesoporous systems based on silicon dioxide with a regular hexagonal arrangement of pores several microns in length and several nanometers in diameter, which are filled with iron compound nanofilaments in various chemical states, are studied in detail. The studies are performed using the following mutually complementary methods: transmission electron microscopy, SQUID magnetometry, electron spin resonance, Mössbauer spectroscopy, polarized neutron small-angle diffraction, and synchrotron radiation diffraction. It is shown that the iron nanoparticles in pores are mainly in the γ phase of Fe2O3 with a small addition of the α phase and atomic iron clusters. The effective magnetic field acting on a nanofilament from other nanofilaments is 11 mT and has a dipole nature, the ferromagnetic-paramagnetic transition temperature is in the range 76-94 K depending on the annealing temperature of the samples, and the temperature that corresponds to the change in the magnetic state of the iron oxide nanofilaments is T ≈ 50-60 K at H = 0 and T ≈ 80 K at H = 300 mT. It is also shown that the magnetization reversal of an array of nanofilaments is caused by the magnetostatic interaction between nanofilaments at the fields that are lower than the saturation field.

Mitochondrial genomes of Meloidogyne chitwoodi and M. incognita (Nematoda: Tylenchina): comparative analysis, gene order and phylogenetic relationships with other nematodes.

PubMed

Humphreys-Pereira, Danny A; Elling, Axel A

2014-01-01

Root-knot nematodes (Meloidogyne spp.) are among the most important plant pathogens. In this study, the mitochondrial (mt) genomes of the root-knot nematodes, M. chitwoodi and M. incognita were sequenced. PCR analyses suggest that both mt genomes are circular, with an estimated size of 19.7 and 18.6-19.1kb, respectively. The mt genomes each contain a large non-coding region with tandem repeats and the control region. The mt gene arrangement of M. chitwoodi and M. incognita is unlike that of other nematodes. Sequence alignments of the two Meloidogyne mt genomes showed three translocations; two in transfer RNAs and one in cox2. Compared with other nematode mt genomes, the gene arrangement of M. chitwoodi and M. incognita was most similar to Pratylenchus vulnus. Phylogenetic analyses (Maximum Likelihood and Bayesian inference) were conducted using 78 complete mt genomes of diverse nematode species. Analyses based on nucleotides and amino acids of the 12 protein-coding mt genes showed strong support for the monophyly of class Chromadorea, but only amino acid-based analyses supported the monophyly of class Enoplea. The suborder Spirurina was not monophyletic in any of the phylogenetic analyses, contradicting the Clade III model, which groups Ascaridomorpha, Spiruromorpha and Oxyuridomorpha based on the small subunit ribosomal RNA gene. Importantly, comparisons of mt gene arrangement and tree-based methods placed Meloidogyne as sister taxa of Pratylenchus, a migratory plant endoparasitic nematode, and not with the sedentary endoparasitic Heterodera. Thus, comparative analyses of mt genomes suggest that sedentary endoparasitism in Meloidogyne and Heterodera is based on convergent evolution. Copyright © 2014 Elsevier B.V. All rights reserved.

Effects of 17 α-methyltestosterone on transcriptome, gonadal histology and sex steroid hormones in rare minnow Gobiocypris rarus.

PubMed

Gao, Jiancao; Liu, Shaozhen; Zhang, Yingying; Yang, Yanping; Yuan, Cong; Chen, Shu; Wang, Zaizhao

2015-09-01

The 17α-methyltestosterone (MT), a synthetic androgen, is known for its interference effects on the endocrine system. Aiming to investigate the transcriptome profiling of gonads induced by MT and to understand the molecular mechanism by which MT causes adverse effects in fish, transcriptome profiling of gonads, gonadal histology and the sex steroid hormones in response to MT were analyzed in Gobiocypris rarus. Eight libraries, 4 from the ovary and 4 from the testis, were constructed and sequenced and then a total number of clean reads per sample ranging from 7.03 to 9.99 million were obtained. In females, a total of 191 transcripts were differentially regulated by MT, consisting of 102 up-regulated transcripts and 89 down-regulated transcripts. In males, 268 differentially expressed genes with 108 up-regulated and 160 down-regulated were detected upon MT exposure. Testosterone serves as the major sex steroid hormone content in G. rarus of both sexes. The concentrations of 17β-estradiol, testosterone and 11-ketotestosterone were significantly increased in females and decreased in males after MT exposure. Interestingly, MT caused a decreased number of vitellogenic oocytes in the ovary and spermatozoa in the testis. After MT exposure, four differentially expressed genes (ndufa4, slc1a3a, caskin-2 and rpt3) were found in G. rarus of both sexes. Overall, we suggest that MT seemed to affect genes involved in pathways related to physiological processes in the gonads of G. rarus. These processes include the electron transfer of Complex IV, endothelial cell activation, axon growth and guidance, and proteasome assembly and glutamate transport metabolic. Copyright © 2015 Elsevier Inc. All rights reserved.

The Direct Referral to Endovascular Center criteria: a proposal for pre-hospital evaluation of acute stroke in the Madrid Stroke Network.

PubMed

Rodríguez-Pardo, J; Fuentes, B; Alonso de Leciñana, M; Ximénez-Carrillo, Á; Zapata-Wainberg, G; Álvarez-Fraga, J; Barriga, F J; Castillo, L; Carneado-Ruiz, J; Díaz-Guzman, J; Egido-Herrero, J; de Felipe, A; Fernández-Ferro, J; Frade-Pardo, L; García-Gallardo, Á; García-Pastor, A; Gil-Núñez, A; Gómez-Escalonilla, C; Guillán, M; Herrero-Infante, Y; Masjuan-Vallejo, J; Ortega-Casarrubios, M Á; Vivancos-Mora, J; Díez-Tejedor, E

2017-03-01

For patients with acute ischaemic stroke due to large-vessel occlusion, it has recently been shown that mechanical thrombectomy (MT) with stent retrievers is better than medical treatment alone. However, few hospitals can provide MT 24 h/day 365 days/year, and it remains unclear whether selected patients with acute stroke should be directly transferred to the nearest MT-providing hospital to prevent treatment delays. Clinical scales such as Rapid Arterial Occlusion Evaluation (RACE) have been developed to predict large-vessel occlusion at a pre-hospital level, but their predictive value for MT is low. We propose new criteria to identify patients eligible for MT, with higher accuracy. The Direct Referral to Endovascular Center criteria were defined based on a retrospective cohort of 317 patients admitted to a stroke center. The association of age, sex, RACE scale score and blood pressure with the likelihood of receiving MT were analyzed. Cut-off points with the highest association were thereafter evaluated in a prospective cohort of 153 patients from nine stroke units comprising the Madrid Stroke Network. Patients with a RACE scale score ≥ 5, systolic blood pressure <190 mmHg and age <81 years showed a significantly higher probability of undergoing MT (odds ratio, 33.38; 95% confidence interval, 12-92.9). This outcome was confirmed in the prospective cohort, with 68% sensitivity, 84% specificity, 42% positive and 94% negative predictive values for MT, ruling out 83% of hemorrhagic strokes. The Direct Referral to Endovascular Center criteria could be useful for identifying patients suitable for MT. © 2017 EAN.

Leber Hereditary Optic Neuropathy: Exemplar of an mtDNA Disease.

PubMed

Wallace, Douglas C; Lott, Marie T

2017-01-01

The report in 1988 that Leber Hereditary Optic Neuropathy (LHON) was the product of mitochondrial DNA (mtDNA) mutations provided the first demonstration of the clinical relevance of inherited mtDNA variation. From LHON studies, the medical importance was demonstrated for the mtDNA showing its coding for the most important energy genes, its maternal inheritance, its high mutation rate, its presence in hundreds to thousands of copies per cell, its quantitatively segregation of biallelic genotypes during both mitosis and meiosis, its preferential effect on the most energetic tissues including the eye and brain, its wide range of functional polymorphisms that predispose to common diseases, and its accumulation of mutations within somatic tissues providing the aging clock. These features of mtDNA genetics, in combination with the genetics of the 1-2000 nuclear DNA (nDNA) coded mitochondrial genes, is not only explaining the genetics of LHON but also providing a model for understanding the complexity of many common diseases. With the maturation of LHON biology and genetics, novel animal models for complex disease have been developed and new therapeutic targets and strategies envisioned, both pharmacological and genetic. Multiple somatic gene therapy approaches are being developed for LHON which are applicable to other mtDNA diseases. Moreover, the unique cytoplasmic genetics of the mtDNA has permitted the first successful human germline gene therapy via spindle nDNA transfer from mtDNA mutant oocytes to enucleated normal mtDNA oocytes. Such LHON lessons are actively being applied to common ophthalmological diseases like glaucoma and neurological diseases like Parkinsonism.

The complete mitochondrial genome sequence of Eimeria magna (Apicomplexa: Coccidia).

PubMed

Tian, Si-Qin; Cui, Ping; Fang, Su-Fang; Liu, Guo-Hua; Wang, Chun-Ren; Zhu, Xing-Quan

2015-01-01

In the present study, we determined the complete mitochondrial DNA (mtDNA) sequence of Eimeria magna from rabbits for the first time, and compared its gene contents and genome organizations with that of seven Eimeria spp. from domestic chickens. The size of the complete mt genome sequence of E. magna is 6249 bp, which consists of 3 protein-coding genes (cytb, cox1 and cox3), 12 gene fragments for the large subunit (LSU) rRNA, and 7 gene fragments for the small subunit (SSU) rRNA, without transfer RNA genes, in accordance with that of Eimeria spp. from chickens. The putative direction of translation for three genes (cytb, cox1 and cox3) was the same as those of Eimeria species from domestic chickens. The content of A + T is 65.16% for E. magna mt genome (29.73% A, 35.43% T, 17.09 G and 17.75% C). The E. magna mt genome sequence provides novel mtDNA markers for studying the molecular epidemiology and population genetics of Eimeria spp. and has implications for the molecular diagnosis and control of rabbit coccidiosis.

Structure of the Hat Creek graben region: Implications for the structure of the Hat Creek graben and transfer of right-lateral shear from the Walker Lane north of Lassen Peak, northern California, from gravity and magnetic anomalies

USGS Publications Warehouse

Langenheim, Victoria; Jachens, Robert C.; Clynne, Michael A.; Muffler, L. J. Patrick

2016-01-01

Interpretation of magnetic and new gravity data provides constraints on the geometry of the Hat Creek Fault, the amount of right-lateral offset in the area between Mt. Shasta and Lassen Peak, and confirmation of the influence of pre-existing structure on Quaternary faulting. Neogene volcanic rocks coincide with short-wavelength magnetic anomalies of both normal and reversed polarity, whereas a markedly smoother magnetic field occurs over the Klamath Mountains and its Paleogene cover. Although the magnetic field over the Neogene volcanic rocks is complex, the Hat Creek Fault, which is one of the most prominent normal faults in the region and forms the eastern margin of the Hat Creek Valley, is marked by the eastern edge of a north-trending magnetic and gravity high 20-30 km long. Modeling of these anomalies indicates that the fault is a steeply dipping (~75-85°) structure. The spatial relationship of the fault as modeled by the potential-field data, the youngest strand of the fault, and relocated seismicity suggests that deformation continues to step westward across the valley, consistent with a component of right-lateral slip in an extensional environment. Filtered aeromagnetic data highlight a concealed magnetic body of Mesozoic or older age north of Hat Creek Valley. The body’s northwest margin strikes northeast and is linear over a distance of ~40 km. Within the resolution of the aeromagnetic data (1-2 km), we discern no right-lateral offset of this body. Furthermore, Quaternary faults change strike or appear to end, as if to avoid this concealed magnetic body and to pass along its southeast edge, suggesting that pre-existing crustal structure influenced younger faulting, as previously proposed based on gravity data.

Na-doped La0.7Ca0.3MnO3 compounds exhibiting a large magnetocaloric effect near room temperature

NASA Astrophysics Data System (ADS)

Chi Linh, Dinh; Thi Ha, Nguyen; Huu Duc, Nguyen; Giang Nam, Le Huu; Bau, Le Viet; Manh An, Nguyen; Yu, Seong-Cho; Dang Thanh, Tran

2018-03-01

In this work, we have investigated the magnetic properties and the magnetocaloric effect of La0.7-xNaxCa0.3MnO3 compounds, which were prepared by a conventional solid-state reaction technique. The Rietveld refinement results suggested that the samples are single phase belonging to an orthorhombic structure (space group Pnma). Analyzing temperature dependence of magnetization M(T) revealed that the Curie temperature (TC) increases with increasing Na content (x). Their TC value is found to be 260-298 K for x=0.0-0.1, respectively. Base on M(T) data measured at different applied magnetic fields (H), temperature dependence of magnetic entropy change ΔSm(T) data for all the samples was calculated by using a phenomenological model. In the vicinity of TC, -ΔSm(T) curve reaches a maximum value (denoted as |ΔSmax|), which gradually increases with increasing H. Under 12 kOe, the value of |ΔSmax| is in a range of 1.47-5.19 J/kg K corresponding to the relative cooling power RCP=57.12-75.88 J/kg. Applied the universal master curve method for the magnetic entropy change, we concluded that Na-doped in La0.7-xNaxCa0.3MnO3 compounds leads to modification the nature of the magnetic phase transition from the first- to the second-order.

Quenching of light flickering in synthetic guanine crystals in aqueous solutions under strong static magnetic fields

NASA Astrophysics Data System (ADS)

Mootha, A.; Takanezawa, Y.; Iwasaka, M.

2018-05-01

The present study focused on the vibration of micro crystal particles of guanine due to Brownian motion. The organic particle has a refractive index of 1.83 and caused a flickering of light. To test the possibility of using magnetic properties under wet conditions, changes in the frequency of particle vibration by applying magnetic fields were investigated. At first, we found that the exposure at 5 T inhibited the flickering light intensities and the particle vibration slightly decreased. Next, we carried out a high speed camera measurement of the Brownian motion of the particle with a time resolution of 100 flame per second (fps) with and without magnetic field exposures. It was revealed that the vibrational speed of synthetic particles was enhanced at 500 mT. Detailed analyses of the particle vibration by changing the direction of magnetic fields versus the light source revealed that the Brownian motion's vibrational frequency was entrained under magnetic fields at 500 mT, and an increase in vibration speed to 20Hz was observed. Additional measurements of light scattering fluctuation using photo-detector and analyses on auto-correlation also confirmed this speculation. The studied Brownian vibration may be influenced by the change in mechanical interactions between the vibration particles and surrounding medium. The discovered phenomena can be applied for molecular and biological interactions in future studies.

A simple and low-cost permanent magnet system for NMR.

PubMed

Chonlathep, K; Sakamoto, T; Sugahara, K; Kondo, Y

2017-02-01

We have developed a simple, easy to build, and low-cost magnet system for NMR, of which homogeneity is about 4×10 -4 at 57mT, with a pair of two commercially available ferrite magnets. This homogeneity corresponds to about 90Hz spectral resolution at 2.45MHz of the hydrogen Larmor frequency. The material cost of this NMR magnet system is little more than $100. The components can be printed by a 3D printer. Copyright © 2016 Elsevier Inc. All rights reserved.

The effect of hydrostatic pressure up to 1.61 GPa on the Morin transition of hematite-bearing rocks: Implications for planetary crustal magnetization

NASA Astrophysics Data System (ADS)

Bezaeva, Natalia S.; Demory, François; Rochette, Pierre; Sadykov, Ravil A.; Gattacceca, Jérôme; Gabriel, Thomas; Quesnel, Yoann

2015-12-01

We present new experimental data on the dependence of the Morin transition temperature (TM) on hydrostatic pressure up to 1.61 GPa, obtained on a well-characterized multidomain hematite-bearing sample from a banded iron formation. We used a nonmagnetic high-pressure cell for pressure application and a Superconducting Quantum Interference Device magnetometer to measure the isothermal remanent magnetization (IRM) under pressure on warming from 243 K to room temperature (T0). IRM imparted at T0 under pressure in 270 mT magnetic field (IRM270mT) is not recovered after a cooling-warming cycle. Memory effect under pressure was quantified as IRM recovery decrease of 10%/GPa. TM, determined on warming, reaches T0 under hydrostatic pressure 1.38-1.61 GPa. The pressure dependence of TM up to 1.61 GPa is positive and essentially linear with a slope dTM/dP = (25 ± 2) K/GPa. This estimate is more precise than previous ones and allows quantifying the effect of a pressure wave on the upper crust magnetization, with special emphasis on Mars.

Proof of principle experiments for helicon discharges in hydrogen

NASA Astrophysics Data System (ADS)

Briefi, Stefan; Fantz, Ursel

2013-09-01

In order to reduce the amount of power required for generating CW hydrogen discharges with high electron densities and a high degree of dissociation via RF coupling, the helicon concept is investigated. For this purpose a small laboratory experiment (length of the discharge vessel 40 cm, diameter 10 cm) has been built up. The RF generator has a maximum power of 600 W (frequency 13.56 MHz) and a Nagoya type III antenna is applied. As water cooling was avoided in constructing the experiment for simplicity, the induction coils can only generate a rather low magnetic field up to 14 mT. The performed investigations cover a variation of the RF power and the magnetic field in a pressure range between 0.3 and 10 Pa. Around a magnetic field of 3 mT the low field peak which is typical for helicon discharges could be observed. As the high density mode of helicon discharges has not yet been reached, a different RF generator (2 MHz, 2 KW) and water cooled induction coils will be applied in a next step in order to increase the available power and the magnetic field.

Ultrasoft magnetic films investigated with Lorentz tranmission electron microscopy and electron holography.

PubMed

De Hosson, Jeff Th M; Chechenin, Nicolai G; Alsem, Daan-Hein; Vystavel, Tomas; Kooi, Bart J; Chezan, Antoni R; Boerma, Dik O

2002-08-01

As a tribute to the scientific work of Professor Gareth Thomas in the field of structure-property relationships this paper delineates a new possibility of Lorentz transmission electron microscopy (LTEM) to study the magnetic properties of soft magnetic films. We show that in contrast to the traditional point of view, not only does the direction of the magnetization vector in nano-crystalline films make a correlated small-angle wiggling, but also the magnitude of the magnetization modulus fluctuates. This fluctuation produces a rapid modulation in the LTEM image. A novel analysis of the ripple structure in nano-crystalline Fe-Zr-N film corresponds to an amplitude of the transversal component of the magnetization deltaMy of 23 mT and a longitudinal fluctuation of the magnetization of the order of deltaMx = 30 mT. The nano-crystalline (Fe99Zr1)1-xNx films have been prepared by DC magnetron reactive sputtering with a thickness between 50 and 1000 nm. The grain size decreased monotonically with N content from typically 100 nm in the case of N-free films to less than 10 nm for films containing 8 at%. The specimens were examined with a JEOL 2010F 200 kV transmission electron microscope equipped with a post column energy filter (GIF 2000 Gatan Imaging Filter). For holography, the microscope is mounted with a biprism (JEOL biprism with a 0.6 microm diameter platinum wire).

Magnetic field sensing based on tilted fiber Bragg grating coated with nanoparticle magnetic fluid

NASA Astrophysics Data System (ADS)

Yang, Dexing; Du, Lei; Xu, Zengqi; Jiang, Yajun; Xu, Jian; Wang, Meirong; Bai, Yang; Wang, Haiyan

2014-02-01

A magnetic field sensor based on a tilted fiber Bragg grating (TFBG) coated with magnetic fluid is proposed and demonstrated experimentally. The sensing element is made by injecting the magnetic fluid into a capillary tube which contains a TFBG. The resonant wavelengths of the cladding modes of TFBG shift by varying the magnetic field which is perpendicular to the axis of TFBG. The results indicate that the resonant wavelength shifts of the cladding modes show a nonlinear dependence on the magnetic field. As the magnetic field increases to 32 mT, the largest resonant wavelength shift reaches to 106 pm. Moreover, this sensor shows good repeatability when it is used for magnetic field sensing.

Mutations in Mitochondrial DNA From Pancreatic Ductal Adenocarcinomas Associate With Survival Times of Patients and Accumulate as Tumors Progress.

PubMed

Hopkins, Julia F; Denroche, Robert E; Aguiar, Jennifer A; Notta, Faiyaz; Connor, Ashton A; Wilson, Julie M; Stein, Lincoln D; Gallinger, Steven; Boutros, Paul C

2018-05-01

Somatic mutations have been found in the mitochondria in different types of cancer cells, but it is not clear whether these affect tumorigenesis or tumor progression. We analyzed mitochondrial genomes of 268 early-stage, resected pancreatic ductal adenocarcinoma tissues and paired non-tumor tissues. We defined a mitochondrial somatic mutation (mtSNV) as a position where the difference in heteroplasmy fraction between tumor and normal sample was ≥0.2. Our analysis identified 304 mtSNVs, with at least 1 mtSNV in 61% (164 of 268) of tumor samples. The noncoding control region had the greatest proportion of mtSNVs (60 of 304 mutations); this region contains sites that regulate mitochondrial DNA transcription and replication. Frequently mutated genes included ND5, RNR2, and CO1, plus 29 mutations in transfer RNA genes. mtSNVs in 2 separate mitochondrial genes (ND4 and ND6) were associated with shorter overall survival time. This association appeared to depend on the level of mtSNV heteroplasmy. Non-random co-occurrence between mtSNVs and mutations in nuclear genes indicates interactions between nuclear and mitochondrial DNA. In an analysis of primary tumors and metastases from 6 patients, we found tumors to accumulate mitochondrial mutational mutations as they progress. Copyright © 2018 AGA Institute. Published by Elsevier Inc. All rights reserved.

Recombination of mitochondrial DNA without selection pressure among compatible strains of the Aspergillus niger species aggregate.

PubMed

Tóth, B; Hamari, Z; Ferenczy, L; Varga, J; Kevei, F

1998-03-01

Previous mitochondrial transmission experiments between oligomycin-resistant and oligomycin-sensitive incompatible strains of the A. niger aggregate bearing various mtDNA RFLP profiles resulted in a great variety of mitochondrial recombinants under selection pressure. Apart from the recombinant mtDNAs, resistant clones harbouring unchanged RFLP profiles of resistant donor mtDNAs with the recipient nuclear backgrounds were rarely isolated. These strains were anastomosed with nuclearly isogenic oligomycin-sensitive recipient partners and the mitochondria of the resulting progeny were examined under non-selective conditions. These experiments provide insights into events which are possibly similar to those occurring in nature. The heterokaryons obtained formed both oligomycin-resistant and -sensitive sectors, most of which were found to be homoplasmons. Progenies harbouring oligomycin-resistant and -sensitive mtDNAs may originate either from individual recombination events or be due to parental segregation. MtDNA recombination might take place in the heterokaryons without selection by oligomycin. The most frequent recombinant types of mtDNA RFLP profiles were indistinguishable from those recombinant mtDNAs which were frequently obtained under selection pressure from directed transfer experiments between incompatible strains. We present evidence that mixed mitochondrial populations may influence the compatibility reactions in the presence of an isogenic nuclear background, that recombination may take place without selection pressure, and that the process does not require specific nuclear sequences of both parental strains.

Integrated magnetic tweezers and single-molecule FRET for investigating the mechanical properties of nucleic acid.

PubMed

Long, Xi; Parks, Joseph W; Stone, Michael D

2016-08-01

Many enzymes promote structural changes in their nucleic acid substrates via application of piconewton forces over nanometer length scales. Magnetic tweezers (MT) is a single molecule force spectroscopy method widely used for studying the energetics of such mechanical processes. MT permits stable application of a wide range of forces and torques over long time scales with nanometer spatial resolution. However, in any force spectroscopy experiment, the ability to monitor structural changes in nucleic acids with nanometer sensitivity requires the system of interest to be held under high degrees of tension to improve signal to noise. This limitation prohibits measurement of structural changes within nucleic acids under physiologically relevant conditions of low stretching forces. To overcome this challenge, researchers have integrated a spatially sensitive fluorescence spectroscopy method, single molecule-FRET, with MT to allow simultaneous observation and manipulation of nanoscale structural transitions over a wide range of forces. Here, we describe a method for using this hybrid instrument to analyze the mechanical properties of nucleic acids. We expect that this method for analysis of nucleic acid structure will be easily adapted for experiments aiming to interrogate the mechanical responses of other biological macromolecules. Copyright © 2016 Elsevier Inc. All rights reserved.

Transcranial Magnetic Stimulation (TMS) as a Tool for Early Diagnosis and Prognostication in Cortico-Basal Ganglia Degeneration (CBD) Syndromes: Review of Literature and Case Report.

PubMed

Issac, Thomas Gregor; Chandra, Sadanandavalli Retnaswami; Nagaraju, B C

2016-01-01

Cortico basal degeneration (CBD) of the brain is a rare progressive neurodegenerative disease which encompasses unique neuropsychiatric manifestations. Early diagnosis is essential for initiating proper treatment and favorable outcome. Transcranial Magnetic Stimulation (TMS), a well-known technique for assessment of cortical excitatory and inhibitory properties. It was suggested that in a degenerative disease like CBD which involves the cortex as well as the subcortical structures, comparing both hemispheres, a differential pattern in TMS can be obtained which would help in early identification, prognostication and early therapeutic intervention. We describe a case of CBD with corroborative clinical and imaging picture wherein single pulse TMS was used over both the hemispheres measuring the following parameters of interest which included: Motor Threshold (MT), Central Motor Conduction Time (CMCT) and Silent Period (SP). Differential patterns of MT, CMCT and SP was obtained by stimulating over both the hemispheres with the affected hemisphere showing significantly reduced MT and prolonged CMCT implying early impairment of cortical and subcortical structures thereby revealing the potential application of TMS being utilized in a novel way for early detection and prognostication in CBD syndromes.

Annealing free magnetic tunnel junction sensors

NASA Astrophysics Data System (ADS)

Knudde, S.; Leitao, D. C.; Cardoso, S.; Freitas, P. P.

2017-04-01

Annealing is a major step in the fabrication of magnetic tunnel junctions (MTJs). It sets the exchange bias between the pinned and antiferromagnetic layers, and helps to increase the tunnel magnetoresistance (TMR) in both amorphous and crystalline junctions. Recent research on MTJs has focused on MgO-based structures due to their high TMR. However, the strict process control and mandatory annealing step can limit the scope of the application of these structures as sensors. In this paper, we present AlOx-based MTJs that are produced by ion beam sputtering and remote plasma oxidation and show optimum transport properties with no annealing. The microfabricated devices show TMR values of up to 35% and using NiFe/CoFeB free layers provides tunable linear ranges, leading to coercivity-free linear responses with sensitivities of up to 5.5%/mT. The top-pinned synthetic antiferromagnetic reference shows a stability of about 30 mT in the microfabricated devices. Sensors with linear ranges of up to 60 mT are demonstrated. This paves the way for the integration of MTJ sensors in heat-sensitive applications such as flexible substrates, or for the design of low-footprint on-chip multiaxial sensing devices.

Integrated magnetic tweezers and single-molecule FRET for investigating the mechanical properties of nucleic acid

PubMed Central

Long, Xi; Parks, Joseph W.; Stone, Michael D.

2017-01-01

Many enzymes promote structural changes in their nucleic acid substrates via application of piconewton forces over nanometer length scales. Magnetic tweezers (MT) is a single molecule force spectroscopy method widely used for studying the energetics of such mechanical processes. MT permits stable application of a wide range of forces and torques over long time scales with nanometer spatial resolution. However, in any force spectroscopy experiment, the ability to monitor structural changes in nucleic acids with nanometer sensitivity requires the system of interest to be held under high degrees of tension to improve signal to noise. This limitation prohibits measurement of structural changes within nucleic acids under physiologically relevant conditions of low stretching forces. To overcome this challenge, researchers have integrated a spatially sensitive fluorescence spectroscopy method, single molecule-FRET, with MT to allow simultaneous observation and manipulation of nanoscale structural transitions over a wide range of forces. Here, we describe a method for using this hybrid instrument to analyze the mechanical properties of nucleic acids. We expect that this method for analysis of nucleic acid structure will be easily adapted for experiments aiming to interrogate the mechanical responses of other biological macromolecules. PMID:27320203

Dissection of a single rat muscle-tendon complex changes joint moments exerted by neighboring muscles: implications for invasive surgical interventions.

PubMed

Maas, Huub; Baan, Guus C; Huijing, Peter A

2013-01-01

The aim of this paper is to investigate mechanical functioning of a single skeletal muscle, active within a group of (previously) synergistic muscles. For this purpose, we assessed wrist angle-active moment characteristics exerted by a group of wrist flexion muscles in the rat for three conditions: (i) after resection of the upper arm skin; (ii) after subsequent distal tenotomy of flexor carpi ulnaris muscle (FCU); and (iii) after subsequent freeing of FCU distal tendon and muscle belly from surrounding tissues (MT dissection). Measurements were performed for a control group and for an experimental group after recovery (5 weeks) from tendon transfer of FCU to extensor carpi radialis (ECR) insertion. To assess if FCU tenotomy and MT dissection affects FCU contributions to wrist moments exclusively or also those of neighboring wrist flexion muscles, these data were compared to wrist angle-moment characteristics of selectively activated FCU. FCU tenotomy and MT dissection decreased wrist moments of the control group at all wrist angles tested, including also angles for which no or minimal wrist moments were measured when activating FCU exclusively. For the tendon transfer group, wrist flexion moment increased after FCU tenotomy, but to a greater extent than can be expected based on wrist extension moments exerted by selectively excited transferred FCU. We conclude that dissection of a single muscle in any surgical treatment does not only affect mechanical characteristics of the target muscle, but also those of other muscles within the same compartment. Our results demonstrate also that even after agonistic-to-antagonistic tendon transfer, mechanical interactions with previously synergistic muscles do remain present.

Magnetic-time model at off-season germination

NASA Astrophysics Data System (ADS)

Mahajan, Tarlochan Singh; Pandey, Om Prakash

2014-03-01

Effect of static magnetic field on germination of mung beans is described. Seeds of mung beans, were exposed in batches to static magnetic fields of 87 to 226 mT intensity for 100 min. Magnetic time constant - 60.743 Th (Tesla hour) was determined experimentally. High value of magnetic time constant signifies lower effect of magnetic field on germination rate as this germination was carried out at off-season (13°C). Using decay function, germination magnetic constant was calculated. There was a linear increase in germination magnetic constant with increasing intensity of magnetic field. Calculated values of mean germination time, mean germination rate, germination rate coefficient, germination magnetic constant, transition time, water uptake, indicate that the impact of applied static magnetic field improves the germination of mung beans seeds even in off-season

Magnetic-field-induced DNA strand breaks in brain cells of the rat.

PubMed Central

Lai, Henry; Singh, Narendra P

2004-01-01

In previous research, we found that rats acutely (2 hr) exposed to a 60-Hz sinusoidal magnetic field at intensities of 0.1-0.5 millitesla (mT) showed increases in DNA single- and double-strand breaks in their brain cells. Further research showed that these effects could be blocked by pretreating the rats with the free radical scavengers melatonin and N-tert-butyl-alpha-phenylnitrone, suggesting the involvement of free radicals. In the present study, effects of magnetic field exposure on brain cell DNA in the rat were further investigated. Exposure to a 60-Hz magnetic field at 0.01 mT for 24 hr caused a significant increase in DNA single- and double-strand breaks. Prolonging the exposure to 48 hr caused a larger increase. This indicates that the effect is cumulative. In addition, treatment with Trolox (a vitamin E analog) or 7-nitroindazole (a nitric oxide synthase inhibitor) blocked magnetic-field-induced DNA strand breaks. These data further support a role of free radicals on the effects of magnetic fields. Treatment with the iron chelator deferiprone also blocked the effects of magnetic fields on brain cell DNA, suggesting the involvement of iron. Acute magnetic field exposure increased apoptosis and necrosis of brain cells in the rat. We hypothesize that exposure to a 60-Hz magnetic field initiates an iron-mediated process (e.g., the Fenton reaction) that increases free radical formation in brain cells, leading to DNA strand breaks and cell death. This hypothesis could have an important implication for the possible health effects associated with exposure to extremely low-frequency magnetic fields in the public and occupational environments. PMID:15121512

Sulfur Modifications of the Wobble U34 in tRNAs and their Intracellular Localization in Eukaryotic Cells

PubMed Central

Nakai, Yumi; Nakai, Masato; Yano, Takato

2017-01-01

The wobble uridine (U34) of transfer RNAs (tRNAs) for two-box codon recognition, i.e., tRNALysUUU, tRNAGluUUC, and tRNAGlnUUG, harbor a sulfur- (thio-) and a methyl-derivative structure at the second and fifth positions of U34, respectively. Both modifications are necessary to construct the proper anticodon loop structure and to enable them to exert their functions in translation. Thio-modification of U34 (s2U34) is found in both cytosolic tRNAs (cy-tRNAs) and mitochondrial tRNAs (mt-tRNAs). Although l-cysteine desulfurase is required in both cases, subsequent sulfur transfer pathways to cy-tRNAs and mt-tRNAs are different due to their distinct intracellular locations. The s2U34 formation in cy-tRNAs involves a sulfur delivery system required for the biosynthesis of iron-sulfur (Fe/S) clusters and certain resultant Fe/S proteins. This review addresses presumed sulfur delivery pathways for the s2U34 formation in distinct intracellular locations, especially that for cy-tRNAs in comparison with that for mt-tRNAs. PMID:28218716

Sulfur Modifications of the Wobble U34 in tRNAs and their Intracellular Localization in Eukaryotic Cells.

PubMed

Nakai, Yumi; Nakai, Masato; Yano, Takato

2017-02-18

The wobble uridine (U 34 ) of transfer RNAs (tRNAs) for two-box codon recognition, i.e., tRNA Lys UUU , tRNA Glu UUC , and tRNA Gln UUG , harbor a sulfur- (thio-) and a methyl-derivative structure at the second and fifth positions of U 34 , respectively. Both modifications are necessary to construct the proper anticodon loop structure and to enable them to exert their functions in translation. Thio-modification of U 34 (s²U 34 ) is found in both cytosolic tRNAs (cy-tRNAs) and mitochondrial tRNAs (mt-tRNAs). Although l-cysteine desulfurase is required in both cases, subsequent sulfur transfer pathways to cy-tRNAs and mt-tRNAs are different due to their distinct intracellular locations. The s²U 34 formation in cy-tRNAs involves a sulfur delivery system required for the biosynthesis of iron-sulfur (Fe/S) clusters and certain resultant Fe/S proteins. This review addresses presumed sulfur delivery pathways for the s²U 34 formation in distinct intracellular locations, especially that for cy-tRNAs in comparison with that for mt-tRNAs.

Equilibrium reconstruction in an iron core tokamak using a deterministic magnetisation model

NASA Astrophysics Data System (ADS)

Appel, L. C.; Lupelli, I.; JET Contributors

2018-02-01

In many tokamaks ferromagnetic material, usually referred to as an iron-core, is present in order to improve the magnetic coupling between the solenoid and the plasma. The presence of the iron core in proximity to the plasma changes the magnetic topology with consequent effects on the magnetic field structure and the plasma boundary. This paper considers the problem of obtaining the free-boundary plasma equilibrium solution in the presence of ferromagnetic material based on measured constraints. The current approach employs a model described by O'Brien et al. (1992) in which the magnetisation currents at the iron-air boundary are represented by a set of free parameters and appropriate boundary conditions are enforced via a set of quasi-measurements on the material boundary. This can lead to the possibility of overfitting the data and hiding underlying issues with the measured signals. Although the model typically achieves good fits to measured magnetic signals there are significant discrepancies in the inferred magnetic topology compared with other plasma diagnostic measurements that are independent of the magnetic field. An alternative approach for equilibrium reconstruction in iron-core tokamaks, termed the deterministic magnetisation model is developed and implemented in EFIT++. The iron is represented by a boundary current with the gradients in the magnetisation dipole state generating macroscopic internal magnetisation currents. A model for the boundary magnetisation currents at the iron-air interface is developed using B-Splines enabling continuity to arbitrary order; internal magnetisation currents are allocated to triangulated regions within the iron, and a method to enable adaptive refinement is implemented. The deterministic model has been validated by comparing it with a synthetic 2-D electromagnetic model of JET. It is established that the maximum field discrepancy is less than 1.5 mT throughout the vacuum region enclosing the plasma. The discrepancies of simulated magnetic probe signals are accurate to within 1% for signals with absolute magnitude greater than 100mT; in all other cases agreement is to within 1mT. The effect of neglecting the internal magnetisation currents increases the maximum discrepancy in the vacuum region to >20mT, resulting in errors of 5%-10% in the simulated probe signals. The fact that the previous model neglects the internal magnetisation currents (and also has additional free parameters when fitting the measured data) makes it unsuitable for analysing data in the absence of plasma current. The discrepancy of the poloidal magnetic flux within the vacuum vessel is to within 0.1Wb. Finally the deterministic model is applied to an equilibrium force-balance solution of a JET discharge using experimental data. It is shown that the discrepancies of the outboard separatrix position, and the outer strike-point position inferred from Thomson Scattering and Infrared camera data are much improved beyond the routine equilibrium reconstruction, whereas the discrepancy of the inner strike-point position is similar.

Effect of ELF magnetic fields on lipid peroxidation, sperm count, p53, and trace elements.

PubMed

Akdag, M Zulkuf; Dasdag, Suleyman; Aksen, Feyzan; Isik, Birgul; Yilmaz, Fahri

2006-11-01

Some epidemiological and laboratory studies suggest a possible connection between extremely low-frequency (ELF) magnetic fields and certain illnesses, such as cancer, immune suppression, as well as reproductive toxic effects and abnormalities. Therefore, the aim of this study was to investigate the effects of ELF magnetic fields (1.35 mT) on sperm count, malondialdehyde concentration, the histology of such organs as the testes, brain, liver, and kidney tissues, p53 immunoreactivity of bone marrow, and the serum concentrations of Cu2+, Zn2+, Mn2+, and Fe3+ in rats. Sixteen Sprague-Dawley male rats were divided into two groups. The rats in the experimental group were exposed to an ELF magnetic field 2 hr/day for 2 months (7 days a week). The rats in the control group were not exposed to the ELF magnetic field. The exposure was performed in a Faraday cage (130 x 65 x 80 cm) with grounded shielding against the electric component. The Mann-Whitney U-test was used for the statistical analysis of the data. Magnetic field measurements showed that, under the experimental conditions, the magnetic field-exposure system produced a stable flux density of 1.35+/-0.018 mT and a stable frequency of 50 Hz, with negligible harmonics and no transients. However, no statistically significant alteration was observed in the parameters measured in this study except in Mn2+ concentrations (p<0.001). The present study found no evidence of an adverse effect of ELF magnetic fields on the measured parameters except for significantly increased Mn2+ concentrations (p<0.001).

The mitochondrial genome of Protostrongylus rufescens – implications for population and systematic studies

PubMed Central

2013-01-01

Background Protostrongylus rufescens is a metastrongyloid nematode of small ruminants, such as sheep and goats, causing protostrongylosis. In spite of its importance, the ecology and epidemiology of this parasite are not entirely understood. In addition, genetic data are scant for P. rufescens and related metastrongyloids. Methods The mt genome was amplified from a single adult worm of P. rufescens (from sheep) by long-PCR, sequenced using 454-technology and annotated using bioinformatic tools. Amino acid sequences inferred from individual genes of the mt genomes were concatenated and subjected to phylogenetic analysis using Bayesian inference. Results The circular mitochondrial genome was 13,619 bp in length and contained two ribosomal RNA, 12 protein-coding and 22 transfer RNA genes, consistent with nematodes of the order Strongylida for which mt genomes have been determined. Phylogenetic analysis of the concatenated amino acid sequence data for the 12 mt proteins showed that P. rufescens was closely related to Aelurostrongylus abstrusus, Angiostrongylus vasorum, Angiostrongylus cantonensis and Angiostrongylus costaricensis. Conclusions The mt genome determined herein provides a source of markers for future investigations of P. rufescens. Molecular tools, employing such mt markers, are likely to find applicability in studies of the population biology of this parasite and the systematics of lungworms. PMID:24025317

Association between mitochondrial DNA haplotype compatibility and increased efficiency of bovine intersubspecies cloning.

PubMed

Yan, Hao; Yan, Zhonghai; Ma, Qingwen; Jiao, Fei; Huang, Shuzhen; Zeng, Fanyi; Zeng, Yitao

2011-01-01

Reconstructed embryos derived from intersubspecies somatic cell nuclear transfer (SCNT) have poorer developmental potential than those from intrasubspecies SCNT. Based on our previous study that Holstein dairy bovine (HD) mitochondrial DNA (mtDNA) haplotype compatibility between donor karyoplast and recipient cytoplast is crucial for SCNT embryo development, we performed intersubspecies SCNT using HD as donor karyoplast and Luxi yellow heifer (LY) as recipient cytoplast according to mtDNA haplotypes determined by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) analysis. The results demonstrated that intersubspecies mtDNA homotype SCNT embryos had higher pre- and post-implantation developmental competence than intrasubspecies mtDNA heterotype embryos as well as improved blastocyst reprogramming status, including normal H3K9 dimethylation pattern and promoter hypomethylation of pluripotent genes such as Oct4 and Sox2, suggesting that intersubspecies SCNT using LY oocytes maintains HD cloning efficiency and may reprogram HD nuclei to develop into a normal cloned animal ultimately. Our results indicated that karyoplast-cytoplast interactions and mtDNA haplotype compatibility may affect bovine intersubspecies SCNT efficiency. This study on bovine intersubspecies SCNT is valuable for understanding the mechanisms of mtDNA haplotype compatibility between karyoplast and cytoplast impacting the bovine SCNT efficiency, and provides an alternative and economic resource for HD cloning. Copyright © 2011. Published by Elsevier Ltd.

Dynamics of paramagnetic agents by off-resonance rotating frame technique in the presence of magnetization transfer effect

NASA Astrophysics Data System (ADS)

Zhang, Huiming; Xie, Yang

2007-02-01

The simple method for measuring the rotational correlation time of paramagnetic ion chelates via off-resonance rotating frame technique is challenged in vivo by the magnetization transfer effect. A theoretical model for the spin relaxation of water protons in the presence of paramagnetic ion chelates and magnetization transfer effect is described. This model considers the competitive relaxations of water protons by the paramagnetic relaxation pathway and the magnetization transfer pathway. The influence of magnetization transfer on the total residual z-magnetization has been quantitatively evaluated in the context of the magnetization map and various difference magnetization profiles for the macromolecule conjugated Gd-DTPA in cross-linked protein gels. The numerical simulations and experimental validations confirm that the rotational correlation time for the paramagnetic ion chelates can be measured even in the presence of strong magnetization transfer. This spin relaxation model also provides novel approaches to enhance the detection sensitivity for paramagnetic labeling by suppressing the spin relaxations caused by the magnetization transfer. The inclusion of the magnetization transfer effect allows us to use the magnetization map as a simulation tool to design efficient paramagnetic labeling targeting at specific tissues, to design experiments running at low RF power depositions, and to optimize the sensitivity for detecting paramagnetic labeling. Thus, the presented method will be a very useful tool for the in vivo applications such as molecular imaging via paramagnetic labeling.

Fast torsional waves and strong magnetic field within the Earth's core.

PubMed

Gillet, Nicolas; Jault, Dominique; Canet, Elisabeth; Fournier, Alexandre

2010-05-06

The magnetic field inside the Earth's fluid and electrically conducting outer core cannot be directly probed. The root-mean-squared (r.m.s.) intensity for the resolved part of the radial magnetic field at the core-mantle boundary is 0.3 mT, but further assumptions are needed to infer the strength of the field inside the core. Recent diagnostics obtained from numerical geodynamo models indicate that the magnitude of the dipole field at the surface of a fluid dynamo is about ten times weaker than the r.m.s. field strength in its interior, which would yield an intensity of the order of several millitesla within the Earth's core. However, a 60-year signal found in the variation in the length of day has long been associated with magneto-hydrodynamic torsional waves carried by a much weaker internal field. According to these studies, the r.m.s. strength of the field in the cylindrical radial direction (calculated for all length scales) is only 0.2 mT, a figure even smaller than the r.m.s. strength of the large-scale (spherical harmonic degree n

Energy transfers in large-scale and small-scale dynamos

NASA Astrophysics Data System (ADS)

Samtaney, Ravi; Kumar, Rohit; Verma, Mahendra

2015-11-01

We present the energy transfers, mainly energy fluxes and shell-to-shell energy transfers in small-scale dynamo (SSD) and large-scale dynamo (LSD) using numerical simulations of MHD turbulence for Pm = 20 (SSD) and for Pm = 0.2 on 10243 grid. For SSD, we demonstrate that the magnetic energy growth is caused by nonlocal energy transfers from the large-scale or forcing-scale velocity field to small-scale magnetic field. The peak of these energy transfers move towards lower wavenumbers as dynamo evolves, which is the reason for the growth of the magnetic fields at the large scales. The energy transfers U2U (velocity to velocity) and B2B (magnetic to magnetic) are forward and local. For LSD, we show that the magnetic energy growth takes place via energy transfers from large-scale velocity field to large-scale magnetic field. We observe forward U2U and B2B energy flux, similar to SSD.

The direct, not V1-mediated, functional influence between the thalamus and middle temporal complex in the human brain is modulated by the speed of visual motion.

PubMed

Gaglianese, A; Costagli, M; Ueno, K; Ricciardi, E; Bernardi, G; Pietrini, P; Cheng, K

2015-01-22

The main visual pathway that conveys motion information to the middle temporal complex (hMT+) originates from the primary visual cortex (V1), which, in turn, receives spatial and temporal features of the perceived stimuli from the lateral geniculate nucleus (LGN). In addition, visual motion information reaches hMT+ directly from the thalamus, bypassing the V1, through a direct pathway. We aimed at elucidating whether this direct route between LGN and hMT+ represents a 'fast lane' reserved to high-speed motion, as proposed previously, or it is merely involved in processing motion information irrespective of speeds. We evaluated functional magnetic resonance imaging (fMRI) responses elicited by moving visual stimuli and applied connectivity analyses to investigate the effect of motion speed on the causal influence between LGN and hMT+, independent of V1, using the Conditional Granger Causality (CGC) in the presence of slow and fast visual stimuli. Our results showed that at least part of the visual motion information from LGN reaches hMT+, bypassing V1, in response to both slow and fast motion speeds of the perceived stimuli. We also investigated whether motion speeds have different effects on the connections between LGN and functional subdivisions within hMT+: direct connections between LGN and MT-proper carry mainly slow motion information, while connections between LGN and MST carry mainly fast motion information. The existence of a parallel pathway that connects the LGN directly to hMT+ in response to both slow and fast speeds may explain why MT and MST can still respond in the presence of V1 lesions. Copyright © 2014 IBRO. Published by Elsevier Ltd. All rights reserved.

Geophysical Exploration Technologies for the Deep Lithosphere Research: An Education Materials for High School Students

NASA Astrophysics Data System (ADS)

Xu, H.; Xu, C.; Luo, S.; Chen, H.; Qin, R.

2012-12-01

The science of Geophysics applies the principles of physics to study of the earth. Geophysical exploration technologies include the earthquake seismology, the seismic reflection and refraction methods, the gravity method, the magnetic method and the magnetotelluric method, which are used to measure the interior material distribution, their structure and the tectonics in the lithosphere of the earth. Part of the research project in SinoProbe-02-06 is to develop suitable education materials for carton movies targeting the high school students and public. The carton movies include five parts. The first part includes the structures of the earth's interior and variation in their physical properties that include density, p-wave, s-wave and so on, which are the fundamentals of the geophysical exploration technologies. The second part includes the seismology that uses the propagation of elastic waves through the earth to study the structure and the material distribution of the earth interior. It can be divided into earthquake seismology and artifice seismics commonly using reflection and refraction. The third part includes the magnetic method. Earth's magnetic field (also known as the geomagnetic field)extends from the Earth's inner core to where it meets the solar wind, a stream of energetic particles emanating from the Sun. The aim of magnetic survey is to investigate subsurface geology on the basis of anomalies in the Earth's magnetic field resulting from the magnetic properties of the underlying rocks. The magnetic method in the lithosphere attempts to use magnetic disturbance to analyse the regional geological structure and the magnetic boundaries of the crust. The fourth part includes the gravity method. A gravity anomaly results from the inhomogeneous distribution of density of the Earth. Usually gravity anomalies contain superposed anomalies from several sources. The long wave length anomalies due to deep density contrasts are called regional anomalies. They are important for understanding the large-scale structure of the earth's crust under major geographic features, such as mountain ranges, oceanic ridges and subduction zones. Short wave length residual anomalies are due to shallow anomalous masses that may be of interest for commercial exploitation. The last part is the magnetotellurics (MT), which is an electromagnetic geophysical method of imaging the earth's subsurface by measuring natural variations of electrical and magnetic fields at the Earth's surface. The long-period MT technique is used to exploration deep crustal. MT has been used to investigate the distribution of silicate melts in the Earth's mantle and crust and to better understand the plate-tectonic processes.

Basin Characterisation by Means of Joint Inversion of Electromagnetic Geophysical Data, Borehole Data and Multivariate Statistical Methods: The Loop Head Peninsula, Western Ireland, Case Study

NASA Astrophysics Data System (ADS)

Campanya, J. L.; Ogaya, X.; Jones, A. G.; Rath, V.; McConnell, B.; Haughton, P.; Prada, M.

2016-12-01

The Science Foundation Ireland funded project IRECCSEM project (www.ireccsem.ie) aims to evaluate Ireland's potential for onshore carbon sequestration in saline aquifers by integrating new electromagnetic geophysical data with existing geophysical and geological data. One of the objectives of this component of IRECCSEM is to characterise the subsurface beneath the Loop Head Peninsula (part of Clare Basin, Co. Clare, Ireland), and identify major electrical resistivity structures that can guide an interpretation of the carbon sequestration potential of this area. During the summer of 2014, a magnetotelluric (MT) survey was carried out on the Loop Head Peninsula, and data from a total of 140 sites were acquired, including audio-magnetotelluric (AMT), and broadband magnetotelluric (BBMT). The dataset was used to generate shallow three-dimensional (3-D) electrical resistivity models constraining the subsurface to depths of up to 3.5 km. The three-dimensional (3-D) joint inversions were performed using three different types of electromagnetic data: MT impedance tensor (Z), geomagnetic transfer functions (T), and inter-station horizontal magnetic transfer-functions (H). The interpretation of the results was complemented with second-derivative models of the resulting electrical resistivity models, and a quantitative comparison with borehole data using multivariate statistical methods. Second-derivative models were used to define the main interfaces between the geoelectrical structures, facilitating superior comparison with geological and seismic results, and also reducing the influence of the colour scale when interpreting the results. Specific analysis was performed to compare the extant borehole data with the electrical resistivity model, identifying those structures that are better characterised by the resistivity model. Finally, the electrical resistivity model was also used to propagate some of the physical properties measured in the borehole, when a good relation was possible between the different types of data. The final results were compared with independent geological and geophysical data for a high-quality interpretation.

Mitochondrial electron transport is inhibited by disappearance of metallothionein in human bronchial epithelial cells following exposure to silver nitrate.

PubMed

Miyayama, Takamitsu; Arai, Yuta; Suzuki, Noriyuki; Hirano, Seishiro

2013-03-08

Silver (Ag) possesses antibacterial activity and has been used in wound dressings and deodorant powders worldwide. However, the metabolic behavior and biological roles of Ag in mammals have not been well characterized. In the present study, we exposed human bronchial epithelial cells (BEAS-2B) to AgNO3 and investigated uptake and intracellular distribution of Ag, expression of metallothionein (MT), generation of reactive oxygen species (ROS), and changes in mitochondrial respiration. The culture medium concentration of Ag decreased with time and stabilized at 12h. The concentration of both Ag and MT in the soluble cellular fraction increased up to 3h and then decreased, indicating that cytosolic Ag relocated to the insoluble fraction of the cells. The levels of mRNAs for the major human MT isoforms MT-I and MT-II paralleled with the protein levels of Ag-MT. The intensity of fluorescence derived from ROS was elevated in the mitochondrial region at 24h. Ag decreased mitochondrial oxygen consumption in a dose-dependent manner and the activity of mitochondrial complex I-IV enzymes was significantly inhibited following exposure to Ag. In a separate experiment, we found that hydrogen peroxide (H2O2) at concentrations as low as 0.001% (equivalent to the concentration of H2O2 in Ag-exposed cells) removed Ag from MT. These results suggest MT was decomposed by cytosolic H2O2, and then Ag released from MT relocated to insoluble cellular fractions and inhibited electron chain transfer of mitochondrial complexes, which eventually led to cell damage. Crown Copyright © 2013. Published by Elsevier Ireland Ltd. All rights reserved.

Guidance of Magnetic Nanocontainers for Treating Alzheimer's Disease Using an Electromagnetic, Targeted Drug-Delivery Actuator.

PubMed

Do, Ton Duc; Ul Amin, Faiz; Noh, Yeongil; Kim, Myeong Ok; Yoon, Jungwon

2016-03-01

The "impermeability" of the blood-brain barrier (BBB) has hindered effective treatment of central nervous system (CNS) disorders such as Alzheimer's disease (AD), which is one of the most common neurodegenerative disorders. A drug can be delivered to a targeted disease site effectively by applying a strong electromagnetic force to the conjugate of a drug and magnetic nanocontainers. This study developed a novel nanotechnology-based strategy to deliver therapeutic agents to the brain via the BBB as a possible therapeutic approach for AD. First, a novel approach for an electromagnetic actuator for guiding nanocontainers is introduced. Then, we analyzed the in vivo uptake in mice experimentally to evaluate the capacity of the nanocontainers. In the mouse model, we demonstrated that magnetic particles can cross the normal BBB when subjected to external electromagnetic fields of 28 mT (0.43 T/m) and 79.8 mT (1.39 T/m). Our study also assessed the differential effects of pulsed (0.25, 0.5, and 1 Hz) and constant magnetic fields on the transport of particles across the BBB in mice injected with magnetic nanoparticles (MNPs) via a tail vein. The applied magnetic field was either kept constant or pulsed on and off. Relative to a constant magnetic field, the rate of MNP uptake and transport across the BBB was enhanced significantly by a pulsed magnetic field. Localization inside the brain was established using fluorescent MNPs. These results using 770-nm fluorescent carboxyl magnetic nanocontainers demonstrated the feasibility of the proposed electromagnetic targeted drug delivery actuator. These results establish an effective strategy for regulating the biodistribution of MNPs in the brain through the application of an external electromagnetic field. This might be a valuable targeting system for AD diagnosis and therapy.

Effects of vial packing density on drying rate during freeze-drying of carbohydrates or a model protein measured using a vial-weighing technique.

PubMed

Gieseler, Henning; Lee, Geoffrey

2008-02-01

To determine the effects of vial packing density in a laboratory freeze dryer on drying rate profiles of crystalline and amorphous formulations. The Christ freeze-drying balance measured cumulative water loss, m(t), and instantaneous drying rate, m(t), of water, mannitol, sucrose and sucrose/BSA formulations in commercial vials. Crystalline mannitol shows drying rate behaviour indicative of a largely homogeneous dried-product layer. The drying rate behaviour of amorphous sucrose indicates structural heterogeneity, postulated to come from shrinkage or microcollapse. Trehalose dries more slowly than sucrose. Addition of BSA to either disaccharide decreases primary drying time. Higher vial packing density greatly reduces drying rate because of effects of radiation heat transfer from chamber walls to test vial. Plots of m(t) versus radical t and m(t) versus layer thickness (either ice or dried-product) allow interpretation of changes in internal cake morphology during drying. Vial packing density greatly influences these profiles.

The complete mitochondrial genome of rabbit pinworm Passalurus ambiguus: genome characterization and phylogenetic analysis.

PubMed

Liu, Guo-Hua; Li, Sheng; Zou, Feng-Cai; Wang, Chun-Ren; Zhu, Xing-Quan

2016-01-01

Passalurus ambiguus (Nematda: Oxyuridae) is a common pinworm which parasitizes in the caecum and colon of rabbits. Despite its significance as a pathogen, the epidemiology, genetics, systematics, and biology of this pinworm remain poorly understood. In the present study, we sequenced the complete mitochondrial (mt) genome of P. ambiguus. The circular mt genome is 14,023 bp in size and encodes of 36 genes, including 12 protein-coding, two ribosomal RNA, and 22 transfer RNA genes. The mt gene order of P. ambiguus is the same as that of Wellcomia siamensis, but distinct from that of Enterobius vermicularis. Phylogenetic analyses based on concatenated amino acid sequences of 12 protein-coding genes by Bayesian inference (BI) showed that P. ambiguus was more closely related to W. siamensis than to E. vermicularis. This mt genome provides novel genetic markers for studying the molecular epidemiology, population genetics, systematics of pinworm of animals and humans, and should have implications for the diagnosis, prevention, and control of passaluriasis in rabbits and other animals.

In vivo sensing of proteolytic activity with an NSET-based NIR fluorogenic nanosensor.

PubMed

Ku, Minhee; Hong, Yoochan; Heo, Dan; Lee, Eugene; Hwang, Seungyeon; Suh, Jin-Suck; Yang, Jaemoon

2016-03-15

Biomedical in vivo sensing methods in the near-infrared (NIR) range, which that provide relatively high photon transparency, separation from auto-fluorescence background, and extended sensitivity, are being used increasingly for non-invasive mapping and monitoring of molecular events in cancer cells. In this study, we fabricated an NIR fluorogenic nanosensor based on the nanoparticle surface energy transfer effect, by conjugation of fluorescent proteolytic enzyme-specific cleavable peptides with gold nanorods (GNRs). Membrane-anchored membrane type 1-matrix metalloproteinases (MT1-MMPs), a family of zinc-dependent proteolytic enzymes, can induce the metastatic potential of cancer cells by promoting degradation of the extracellular matrix. Therefore, sensitive detection of MT1-MMP activity can provide essential information in the clinical setting. We have applied in vivo NIR sensing to evaluate MT1-MMP activity, as an NIR imaging target, in an MT1-MMP-expressing metastatic tumor mouse model. Copyright © 2015 Elsevier B.V. All rights reserved.

Mitoepigenetics and drug addiction.

PubMed

Sadakierska-Chudy, Anna; Frankowska, Małgorzata; Filip, Małgorzata

2014-11-01

Being the center of energy production in eukaryotic cells, mitochondria are also crucial for various cellular processes including intracellular Ca(2+) signaling and generation of reactive oxygen species (ROS). Mitochondria contain their own circular DNA which encodes not only proteins, transfer RNA and ribosomal RNAs but also non-coding RNAs. The most recent line of evidence indicates the presence of 5-methylcytosine and 5-hydroxymethylcytosine in mitochondrial DNA (mtDNA); thus, the level of gene expression - in a way similar to nuclear DNA - can be regulated by direct epigenetic modifications. Up to now, very little data shows the possibility of epigenetic regulation of mtDNA. Mitochondria and mtDNA are particularly important in the nervous system and may participate in the initiation of drug addiction. In fact, some addictive drugs enhance ROS production and generate oxidative stress that in turn alters mitochondrial and nuclear gene expression. This review summarizes recent findings on mitochondrial function, mtDNA copy number and epigenetics in drug addiction. Copyright © 2014 Elsevier Inc. All rights reserved.

Exceptionally large magneto-optical response in dispersions of plate-like nanocrystallites and magnetic nanoparticles

NASA Astrophysics Data System (ADS)

May, Kathrin; Eremin, Alexey; Stannarius, Ralf; Szabó, Balázs; Börzsönyi, Tamás; Appel, Ingo; Behrens, Silke; Klein, Susanne

2017-06-01

We introduce a binary colloidal system with an exceptionally strong magneto-optical response. Its induced optical birefringence at even low magnetic fields (in the mT range) reaches a value with the same order of magnitude as that of nematic liquid crystals. This system is based on a binary mixture of plate-like, non-magnetic pigment nanoparticles and a small volume fraction (< 1 v %) of spherical magnetic nanoparticles. In the field-free state, the suspension is isotropic. Birefringence is caused by an alignment of the pigment platelets, commanded by shape-anisotropic agglomerates of the magnetic nanoparticles in an external magnetic field. We give a semiquantitative discussion about this.

Adoptive Cell Therapy of Induced Regulatory T Cells Expanded by Tolerogenic Dendritic Cells on Murine Autoimmune Arthritis.

PubMed

Yang, Jie; Liu, Lidong; Yang, Yiming; Kong, Ning; Jiang, Xueyu; Sun, Juan; Xie, Rufeng

2017-01-01

Tolerogenic dendritic cells (tDCs) can expand TGF- β -induced regulatory T cells (iTregs); however, the therapeutic utility of these expanded iTregs in autoimmune diseases remains unknown. We sought to determine the properties of iTregs expanded by mature tolerogenic dendritic cells (iTreg mtDC ) in vitro and explore their potential to ameliorate collagen-induced arthritis (CIA) in a mouse model. After induction by TGF- β and expansion by mature tDCs (mtDCs), the phenotype and proliferation of iTreg mtDC were assessed by flow cytometry. The ability of iTregs and iTreg mtDC to inhibit CD4 + T cell proliferation and suppress Th17 cell differentiation was compared. Following adoptive transfer of iTregs and iTreg mtDC to mice with CIA, the clinical and histopathologic scores, serum levels of IFN- γ , TNF- α , IL-17, IL-6, IL-10, TGF- β and anti-CII antibodies, and the distribution of the CD4 + Th subset were assessed. Compared with iTregs, iTreg mtDC expressed higher levels of Foxp3 and suppressed CD4 + T cell proliferation and Th17 cell differentiation to a greater extent. In vivo, iTreg mtDC reduced the severity and progression of CIA more significantly than iTregs, which was associated with a modulated inflammatory cytokine profile, reduced anti-CII IgG levels, and polarized Treg/Th17 balance. This study highlights the potential therapeutic utility of iTreg mtDC in autoimmune arthritis and should facilitate the future design of iTreg immunotherapeutic strategies.

The mitochondrial genomes of Amphiascoides atopus and Schizopera knabeni (Harpacticoida: Miraciidae) reveal similarities between the copepod orders Harpacticoida and Poecilostomatoida.

PubMed

Easton, Erin E; Darrow, Emily M; Spears, Trisha; Thistle, David

2014-03-15

Members of subclass Copepoda are abundant, diverse, and-as a result of their variety of ecological roles in marine and freshwater environments-important, but their phylogenetic interrelationships are unclear. Recent studies of arthropods have used gene arrangements in the mitochondrial (mt) genome to infer phylogenies, but for copepods, only seven complete mt genomes have been published. These data revealed several within-order and few among-order similarities. To increase the data available for comparisons, we sequenced the complete mt genome (13,831base pairs) of Amphiascoides atopus and 10,649base pairs of the mt genome of Schizopera knabeni (both in the family Miraciidae of the order Harpacticoida). Comparison of our data to those for Tigriopus japonicus (family Harpacticidae, order Harpacticoida) revealed similarities in gene arrangement among these three species that were consistent with those found within and among families of other copepod orders. Comparison of the mt genomes of our species with those known from other copepod orders revealed the arrangement of mt genes of our Harpacticoida species to be more similar to that of Sinergasilus polycolpus (order Poecilostomatoida) than to that of T. japonicus. The similarities between S. polycolpus and our species are the first to be noted across the boundaries of copepod orders and support the possibility that mt-gene arrangement might be used to infer copepod phylogenies. We also found that our two species had extremely truncated transfer RNAs and that gene overlaps occurred much more frequently than has been reported for other copepod mt genomes. Published by Elsevier B.V.

Adiabatic magnetocaloric effect in Ni50Mn35In15 ribbons

NASA Astrophysics Data System (ADS)

Álvarez-Alonso, P.; Aguilar-Ortiz, C. O.; Camarillo, J. P.; Salazar, D.; Flores-Zúñiga, H.; Chernenko, V. A.

2016-11-01

Heusler-type Ni-Mn-based metamagnetic shape memory alloys (MetaMSMAs) are promising candidates for magnetic refrigeration. To increase heat exchange rate and efficiency of cooling, the material should have a high surface/volume ratio. In this work, the typical Ni50Mn35In15 MetaMSMA was selected to fabricate thin ribbons by melt-spinning. The characteristic transformations of the ribbons were determined by calorimetry, X-ray diffraction, scanning electron microscopy and thermomagnetization measurements. The inverse and conventional magnetocaloric effects (MCEs) associated with the martensitic transformation (MT) and the ferromagnetic transition of the austenite (TCA), respectively, were measured directly by the adiabatic method (ΔTad) and indirectly by estimating the magnetic entropy change from magnetization measurements. It is found that the ribbons exhibit large values of ΔTad = -1.1 K at μ0ΔH = 1.9 T, in the vicinity of the MT temperature of 300 K for inverse MCE, and ΔTad = 2.3 K for conventional MCE at TCA = 309 K. This result strongly motivates further development of different MetaMSMA refrigerants shaped as ribbons.

Magnetic susceptibility characterisation of superparamagnetic microspheres

NASA Astrophysics Data System (ADS)

Grob, David Tim; Wise, Naomi; Oduwole, Olayinka; Sheard, Steve

2018-04-01

The separation of magnetic materials in microsystems using magnetophoresis has increased in popularity. The wide variety and availability of magnetic beads has fuelled this drive. It is important to know the magnetic characteristics of the microspheres in order to accurately use them in separation processes integrated on a lab-on-a-chip device. To investigate the magnetic susceptibility of magnetic microspheres, the magnetic responsiveness of three types of Dynabeads microspheres were tested using two different approaches. The magnetophoretic mobility of individual microspheres is studied using a particle tracking system and the magnetization of each type of Dynabeads microsphere is measured using SQUID relaxometry. The magnetic beads' susceptibility is obtained at four different applied magnetic fields in the range of 38-70 mT for both the mobility and SQUID measurements. The susceptibility values in both approaches show a consistent magnetic field dependence.

Three-dimensional magnetotelluric inversion in practice—the electrical conductivity structure of the San Andreas Fault in Central California

NASA Astrophysics Data System (ADS)

Tietze, Kristina; Ritter, Oliver

2013-10-01

3-D inversion techniques have become a widely used tool in magnetotelluric (MT) data interpretation. However, with real data sets, many of the controlling factors for the outcome of 3-D inversion are little explored, such as alignment of the coordinate system, handling and influence of data errors and model regularization. Here we present 3-D inversion results of 169 MT sites from the central San Andreas Fault in California. Previous extensive 2-D inversion and 3-D forward modelling of the data set revealed significant along-strike variation of the electrical conductivity structure. 3-D inversion can recover these features but only if the inversion parameters are tuned in accordance with the particularities of the data set. Based on synthetic 3-D data we explore the model space and test the impacts of a wide range of inversion settings. The tests showed that the recovery of a pronounced regional 2-D structure in inversion of the complete impedance tensor depends on the coordinate system. As interdependencies between data components are not considered in standard 3-D MT inversion codes, 2-D subsurface structures can vanish if data are not aligned with the regional strike direction. A priori models and data weighting, that is, how strongly individual components of the impedance tensor and/or vertical magnetic field transfer functions dominate the solution, are crucial controls for the outcome of 3-D inversion. If deviations from a prior model are heavily penalized, regularization is prone to result in erroneous and misleading 3-D inversion models, particularly in the presence of strong conductivity contrasts. A `good' overall rms misfit is often meaningless or misleading as a huge range of 3-D inversion results exist, all with similarly `acceptable' misfits but producing significantly differing images of the conductivity structures. Reliable and meaningful 3-D inversion models can only be recovered if data misfit is assessed systematically in the frequency-space domain.

NASA missions studies magnetic space explosions

NASA Image and Video Library

2017-12-08

Every day, invisible magnetic explosions are happening around Earth, on the surface of the sun and across the universe. These explosions, known as magnetic reconnection, occur when magnetic field lines cross, releasing stored magnetic energy. Such explosions are a key way that clouds of charged particles — plasmas — are accelerated throughout the universe. In Earth’s magnetosphere — the giant magnetic bubble surrounding our planet — these magnetic reconnections can fling charged particles toward Earth, triggering auroras. Read more: go.nasa.gov/2mnMtDm Video caption - In this simulation, a reconnection even pushes a blob of plasma toward Earth. The jet blown in the opposite direction wobbles due to the unstable conditions. Credit: NASA’s Goddard Space Flight Center/Yi-Hsin Liu/Joy Ng, producer

Improvements of the magnetic field design for SPIDER and MITICA negative ion beam sources

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chitarin, G., E-mail: chitarin@igi.cnr.it; University of Padova, Dept. of Management and Engineering, Strad. S. Nicola 3, 36100 Vicenza; Agostinetti, P.

2015-04-08

The design of the magnetic field configuration in the SPIDER and MITICA negative ion beam sources has evolved considerably during the past four years. This evolution was driven by three factors: 1) the experimental results of the large RF-driven ion sources at IPP, which have provided valuable indications on the optimal magnetic configurations for reliable RF plasma source operation and for large negative ion current extraction, 2) the comprehensive beam optics and heat load simulations, which showed that the magnetic field configuration in the accelerator is crucial for keeping the heat load due to electrons on the accelerator grids withinmore » tolerable limits, without compromising the optics of the negative ion beam in the foreseen operating scenarios, 3) the progress of the detailed mechanical design of the accelerator, which stimulated the evaluation of different solutions for the correction of beamlet deflections of various origin and for beamlet aiming. On this basis, new requirements and solution concepts for the magnetic field configuration in the SPIDER and MITICA beam sources have been progressively introduced and updated until the design converged. The paper presents how these concepts have been integrated into a final design solution based on a horizontal “long-range” field (few mT) in combination with a “local” vertical field of some tens of mT on the acceleration grids.« less

Structural and magnetic properties of the nanocomposite materials based on a mesoporous silicon dioxide matrix

DOE Office of Scientific and Technical Information (OSTI.GOV)

Grigor’eva, N. A., E-mail: natali@lns.pnpi.spb.ru; Eckerlebe, H.; Eliseev, A. A.

2017-03-15

The structural and magnetic properties of the mesoporous systems based on silicon dioxide with a regular hexagonal arrangement of pores several microns in length and several nanometers in diameter, which are filled with iron compound nanofilaments in various chemical states, are studied in detail. The studies are performed using the following mutually complementary methods: transmission electron microscopy, SQUID magnetometry, electron spin resonance, Mössbauer spectroscopy, polarized neutron small-angle diffraction, and synchrotron radiation diffraction. It is shown that the iron nanoparticles in pores are mainly in the γ phase of Fe{sub 2}O{sub 3} with a small addition of the α phase andmore » atomic iron clusters. The effective magnetic field acting on a nanofilament from other nanofilaments is 11 mT and has a dipole nature, the ferromagnetic–paramagnetic transition temperature is in the range 76–94 K depending on the annealing temperature of the samples, and the temperature that corresponds to the change in the magnetic state of the iron oxide nanofilaments is T ≈ 50–60 K at H = 0 and T ≈ 80 K at H = 300 mT. It is also shown that the magnetization reversal of an array of nanofilaments is caused by the magnetostatic interaction between nanofilaments at the fields that are lower than the saturation field.« less

2D data-space cross-gradient joint inversion of MT, gravity and magnetic data

NASA Astrophysics Data System (ADS)

Pak, Yong-Chol; Li, Tonglin; Kim, Gang-Sop

2017-08-01

We have developed a data-space multiple cross-gradient joint inversion algorithm, and validated it through synthetic tests and applied it to magnetotelluric (MT), gravity and magnetic datasets acquired along a 95 km profile in Benxi-Ji'an area of northeastern China. To begin, we discuss a generalized cross-gradient joint inversion for multiple datasets and model parameters sets, and formulate it in data space. The Lagrange multiplier required for the structural coupling in the data-space method is determined using an iterative solver to avoid calculation of the inverse matrix in solving the large system of equations. Next, using model-space and data-space methods, we inverted the synthetic data and field data. Based on our result, the joint inversion in data-space not only delineates geological bodies more clearly than the separate inversion, but also yields nearly equal results with the one in model-space while consuming much less memory.

Photochemical primary process of photo-Fries rearrangement reaction of 1-naphthyl acetate as studied by MFE probe.

PubMed

Gohdo, Masao; Takamasu, Tadashi; Wakasa, Masanobu

2011-01-14

Photo-Fries rearrangement reactions of 1-naphthyl acetate (NA) in n-hexane and in cyclohexane were studied by the magnetic field effect probe (MFE probe) under magnetic fields (B) of 0 to 7 T. Transient absorptions of the 1-naphthoxyl radical, T-T absorption of NA, and a short-lifetime intermediate (τ = 24 ns) were observed by a nanosecond laser flash photolysis technique. In n-hexane, the yield of escaped 1-naphthoxyl radicals dropped dramatically upon application of a 3 mT field, but then the yield increased with increasing B for 3 mT < B≤ 7 T. These observed MFEs can be explained by the hyperfine coupling and the Δg mechanisms through the singlet radical pair. The fact that MFEs were observed for the present photo-Fries rearrangement reaction indicates the presence of a singlet radical pair intermediate with a lifetime as long as several tens of nanoseconds.

Response of Cultured Neuronal Network Activity After High-Intensity Power Frequency Magnetic Field Exposure

PubMed Central

Saito, Atsushi; Takahashi, Masayuki; Makino, Kei; Suzuki, Yukihisa; Jimbo, Yasuhiko; Nakasono, Satoshi

2018-01-01

High-intensity and low frequency (1–100 kHz) time-varying electromagnetic fields stimulate the human body through excitation of the nervous system. In power frequency range (50/60 Hz), a frequency-dependent threshold of the external electric field-induced neuronal modulation in cultured neuronal networks was used as one of the biological indicator in international guidelines; however, the threshold of the magnetic field-induced neuronal modulation has not been elucidated. In this study, we exposed rat brain-derived neuronal networks to a high-intensity power frequency magnetic field (hPF-MF), and evaluated the modulation of synchronized bursting activity using a multi-electrode array (MEA)-based extracellular recording technique. As a result of short-term hPF-MF exposure (50–400 mT root-mean-square (rms), 50 Hz, sinusoidal wave, 6 s), the synchronized bursting activity was increased in the 400 mT-exposed group. On the other hand, no change was observed in the 50–200 mT-exposed groups. In order to clarify the mechanisms of the 400 mT hPF-MF exposure-induced neuronal response, we evaluated it after blocking inhibitory synapses using bicuculline methiodide (BMI); subsequently, increase in bursting activity was observed with BMI application, and the response of 400 mT hPF-MF exposure disappeared. Therefore, it was suggested that the response of hPF-MF exposure was involved in the inhibitory input. Next, we screened the inhibitory pacemaker-like neuronal activity which showed autonomous 4–10 Hz firing with CNQX and D-AP5 application, and it was confirmed that the activity was reduced after 400 mT hPF-MF exposure. Comparison of these experimental results with estimated values of the induced electric field (E-field) in the culture medium revealed that the change in synchronized bursting activity occurred over 0.3 V/m, which was equivalent to the findings of a previous study that used the external electric fields. In addition, the results suggested that the potentiation of neuronal activity after 400 mT hPF-MF exposure was related to the depression of autonomous activity of pacemaker-like neurons. Our results indicated that the synchronized bursting activity was increased by hPF-MF exposure (E-field: >0.3 V/m), and the response was due to reduced inhibitory pacemaker-like neuronal activity. PMID:29662453

Magnetic study of the low temperature anomalies in the underdoped PrBCO compound

NASA Astrophysics Data System (ADS)

Lahoubi, Mahieddine

2018-05-01

The low temperature anomalous magnetic properties of a non-superconducting PrBCO6+x compound in an underdoped oxygen state of concentration (x = 0.44) are characterized by paraprocess magnetic susceptibility χH(T) measurements carried out as a function of temperature T under different values of a DC magnetic field H up to 110 kOe. The derivatives dχH(T)/dT curves reveal a significant reduction with increasing H in the Néel temperature TN = 9 K of the Pr antiferromagnetic (AFM) ordering for which the transition subsists at 100 kOe. The small anomaly at T2 = 6-7 K is confirmed at 20 kOe and the previous spin reorientation attributed to this transition temperature seems to be suppressed above 60 kOe. The well defined anomaly in the vicinity of the low-critical point Tcr = 4-5 K which occurs simultaneously, is still present when the strength of H is increased up to 100 kOe. Weak field induced phase transitions are observed between T2 and TN at a low transition-field (Ht<11 kOe) in the differential magnetic susceptibility dMT(H)/dH as a function of H deduced from the isothermal magnetizations MT(H) with H up to 21 kOe, whereas a weak ferromagnetic behavior of the Pr sublattice appears below Tcr. The magnetic field effects give rise to more evidence for the Pr-Cu(2) coupling with 'exchange-frustrated AFM' interactions and ascertain the main role of the Pr sublattice whereas the Cu(2) sublattice seems to be less efficient.

Magnetic micro/nanoparticle flocculation-based signal amplification for biosensing

PubMed Central

Mzava, Omary; Taş, Zehra; İçöz, Kutay

2016-01-01

We report a time and cost efficient signal amplification method for biosensors employing magnetic particles. In this method, magnetic particles in an applied external magnetic field form magnetic dipoles, interact with each other, and accumulate along the magnetic field lines. This magnetic interaction does not need any biomolecular coating for binding and can be controlled with the strength of the applied magnetic field. The accumulation can be used to amplify the corresponding pixel area that is obtained from an image of a single magnetic particle. An application of the method to the Escherichia coli 0157:H7 bacteria samples is demonstrated in order to show the potential of the approach. A minimum of threefold to a maximum of 60-fold amplification is reached from a single bacteria cell under a magnetic field of 20 mT. PMID:27354793

Transcranial magnetic stimulation reveals the content of visual short-term memory in the visual cortex.

PubMed

Silvanto, Juha; Cattaneo, Zaira

2010-05-01

Cortical areas involved in sensory analysis are also believed to be involved in short-term storage of that sensory information. Here we investigated whether transcranial magnetic stimulation (TMS) can reveal the content of visual short-term memory (VSTM) by bringing this information to visual awareness. Subjects were presented with two random-dot displays (moving either to the left or to the right) and they were required to maintain one of these in VSTM. In Experiment 1, TMS was applied over the motion-selective area V5/MT+ above phosphene threshold during the maintenance phase. The reported phosphene contained motion features of the memory item, when the phosphene spatially overlapped with memory item. Specifically, phosphene motion was enhanced when the memory item moved in the same direction as the subjects' V5/MT+ baseline phosphene, whereas it was reduced when the motion direction of the memory item was incongruent with that of the baseline V5/MT+ phosphene. There was no effect on phosphene reports when there was no spatial overlap between the phosphene and the memory item. In Experiment 2, VSTM maintenance did not influence the appearance of phosphenes induced from the lateral occipital region. These interactions between VSTM maintenance and phosphene appearance demonstrate that activity in V5/MT+ reflects the motion qualities of items maintained in VSTM. Furthermore, these results also demonstrate that information in VSTM can modulate the pattern of visual activation reaching awareness, providing evidence for the view that overlapping neuronal populations are involved in conscious visual perception and VSTM. 2010. Published by Elsevier Inc.

Migration of mitochondrial DNA in the nuclear genome of colorectal adenocarcinoma.

PubMed

Srinivasainagendra, Vinodh; Sandel, Michael W; Singh, Bhupendra; Sundaresan, Aishwarya; Mooga, Ved P; Bajpai, Prachi; Tiwari, Hemant K; Singh, Keshav K

2017-03-29

Colorectal adenocarcinomas are characterized by abnormal mitochondrial DNA (mtDNA) copy number and genomic instability, but a molecular interaction between mitochondrial and nuclear genome remains unknown. Here we report the discovery of increased copies of nuclear mtDNA (NUMT) in colorectal adenocarcinomas, which supports link between mtDNA and genomic instability in the nucleus. We name this phenomenon of nuclear occurrence of mitochondrial component as numtogenesis. We provide a description of NUMT abundance and distribution in tumor versus matched blood-derived normal genomes. Whole-genome sequence data were obtained for colon adenocarcinoma and rectum adenocarcinoma patients participating in The Cancer Genome Atlas, via the Cancer Genomics Hub, using the GeneTorrent file acquisition tool. Data were analyzed to determine NUMT proportion and distribution on a genome-wide scale. A NUMT suppressor gene was identified by comparing numtogenesis in other organisms. Our study reveals that colorectal adenocarcinoma genomes, on average, contains up to 4.2-fold more somatic NUMTs than matched normal genomes. Women colorectal tumors contained more NUMT than men. NUMT abundance in tumor predicted parallel abundance in blood. NUMT abundance positively correlated with GC content and gene density. Increased numtogenesis was observed with higher mortality. We identified YME1L1, a human homolog of yeast YME1 (yeast mitochondrial DNA escape 1) to be frequently mutated in colorectal tumors. YME1L1 was also mutated in tumors derived from other tissues. We show that inactivation of YME1L1 results in increased transfer of mtDNA in the nuclear genome. Our study demonstrates increased somatic transfer of mtDNA in colorectal tumors. Our study also reveals sex-based differences in frequency of NUMT occurrence and that NUMT in blood reflects NUMT in tumors, suggesting NUMT may be used as a biomarker for tumorigenesis. We identify YME1L1 as the first NUMT suppressor gene in human and demonstrate that inactivation of YME1L1 induces migration of mtDNA to the nuclear genome. Our study reveals that numtogenesis plays an important role in the development of cancer.

Extremely Low Frequency Magnetic Field (50 Hz, 0.5 mT) Reduces Oxidative Stress in the Brain of Gerbils Submitted to Global Cerebral Ischemia

PubMed Central

Rauš Balind, Snežana; Selaković, Vesna; Radenović, Lidija; Prolić, Zlatko; Janać, Branka

2014-01-01

Magnetic field as ecological factor has influence on all living beings. The aim of this study was to determine if extremely low frequency magnetic field (ELF-MF, 50 Hz, 0.5 mT) affects oxidative stress in the brain of gerbils submitted to 10-min global cerebral ischemia. After occlusion of both carotid arteries, 3-month-old gerbils were continuously exposed to ELF-MF for 7 days. Nitric oxide and superoxide anion production, superoxide dismutase activity and index of lipid peroxidation were examined in the forebrain cortex, striatum and hippocampus on the 7th (immediate effect of ELF-MF) and 14th day after reperfusion (delayed effect of ELF-MF). Ischemia per se increased oxidative stress in the brain on the 7th and 14th day after reperfusion. ELF-MF also increased oxidative stress, but to a greater extent than ischemia, only immediately after cessation of exposure. Ischemic gerbils exposed to ELF-MF had increased oxidative stress parameters on the 7th day after reperfusion, but to a lesser extent than ischemic or ELF-MF-exposed animals. On the 14th day after reperfusion, oxidative stress parameters in the brain of these gerbils were mostly at the control levels. Applied ELF-MF decreases oxidative stress induced by global cerebral ischemia and thereby reduces possible negative consequences which free radical species could have in the brain. The results presented here indicate a beneficial effect of ELF-MF (50 Hz, 0.5 mT) in the model of global cerebral ischemia. PMID:24586442

Magnetic nanoparticle thermometry independent of Brownian relaxation

NASA Astrophysics Data System (ADS)

Zhong, Jing; Schilling, Meinhard; Ludwig, Frank

2018-01-01

An improved method of magnetic nanoparticle (MNP) thermometry is proposed. The phase lag ϕ of the fundamental f 0 harmonic is measured to eliminate the influence of Brownian relaxation on the ratio of 3f 0 to f 0 harmonic amplitudes applying a phenomenological model, thus allowing measurements in high-frequency ac magnetic fields. The model is verified by simulations of the Fokker-Planck equation. An MNP spectrometer is calibrated for the measurements of the phase lag ϕ and the amplitudes of 3f 0 and f 0 harmonics. Calibration curves of the harmonic ratio and tanϕ are measured by varying the frequency (from 10 Hz to 1840 Hz) of ac magnetic fields with different amplitudes (from 3.60 mT to 4.00 mT) at a known temperature. A phenomenological model is employed to fit the calibration curves. Afterwards, the improved method is proposed to iteratively compensate the measured harmonic ratio with tanϕ, and consequently calculate temperature applying the static Langevin function. Experimental results on SHP-25 MNPs show that the proposed method significantly improves the systematic error to 2 K at maximum with a relative accuracy of about 0.63%. This demonstrates the feasibility of the proposed method for MNP thermometry with SHP-25 MNPs even if the MNP signal is affected by Brownian relaxation.

Absence of 60-Hz, 0.1-mT magnetic field-induced changes in oncogene transcription rates or levels in CEM-CM3 cells.

PubMed

Jahreis, G P; Johnson, P G; Zhao, Y L; Hui, S W

1998-12-22

Our objective was to assess the reproducibility of the 60-Hz magnetic field-induced, time-dependent transcription changes of c-fos, c-jun and c-myc oncogenes in CEM-CM3 cells reported by Phillips et al. (Biochim. Biophys. Acta, 1132 (1992) 140-144). Cells were exposed to a 60-Hz magnetic field (MF) at 0.1 mT (rms), generated by a pair of Helmholtz coils energized in a reinforcing (MF) mode, or to a null magnetic field when the coils were energized in a bucking (sham) mode. After MF or sham exposure for 15, 30, 60 or 120 min, nuclei and cytoplasmic RNA were extracted. Transcription rates were measured by a nuclear run-on assay, and values were normalized against either their zero-time exposure values, or against those of the c-G3PDH (housekeeping) gene at the same time points. There was no significant difference, at P=0.05, detected between MF and either sham-exposed or control cells at any time point. Transcript levels of the oncogenes were measured by Northern analysis and normalized as above. No significant difference (P=0.05) in transcript levels between MF and either sham-exposed or control cells was detected.

Volcanic rocks and subglacial volcanism beneath the West Antarctic Ice Sheet in the West Antarctic Rift System, (WAIS) from aeromagnetic and radar ice sounding - Thiel Subglacial Volcano as possible source of the ash layer in the WAISCORE

NASA Astrophysics Data System (ADS)

Behrendt, J. C.

2012-12-01

Radar ice sounding and aeromagnetic surveys reported over the West Antarctic Ice Sheet (WAIS) have been interpreted as evidence of subglacial volcanic eruptions over a very extensive area (>500,000 km2 ) of the volcanically active West Antarctic rift system interpreted as caused by subglacial volcanic rocks. Several active volcanoes have shown evidence of eruption through the WAIS and several other active volcanoes are present beneath the WAIS reported from radar and aeromagnetic data. Five-kilometer spaced coincident aeromagnetic and radar ice sounding surveys since 1990 provide three dimensional characterization of the magnetic field and bed topography beneath the ice sheet. These 5-50-km-width, semicircular magnetic anomalies range from 100->1000 nT as observed ~1 km over the 2-3 km thick ice have been interpreted as evidence of subglacial eruptions. Comparison of a carefully selected subset of ~400 of the >1000 high-amplitude anomalies in the CWA survey having topographic expression at the glacier bed, showed >80% had less than 200-m relief. About 18 high-amplitude subglacial magnetic sources also have high topography and bed relief (>600 m) interpreted as subaerially erupted volcanic peaks when the WAIS was absent, whose competent lava flows protected their edifices from erosion. All of these would have high elevation above sea-level, were the ice removed and glacial rebound to have occurred. Nine of these subaerially erupted volcanoes are concentrated in the WAIS divide area. Behrendt et al., 1998 interpreted a circular ring of positive magnetic anomalies overlying the WAIS divide as caused by a volcanic caldera. The area is characterized by high elevation bed topography. The negative regional magnetic anomaly surrounding the caldera anomalies was interpreted as the result of a shallow Curie isotherm. High heat flow inferred from temperature logging in the WAISCORE (G. Clow 2012, personal communication; Conway, 2011) and a prominent volcanic ash layer in the core (Dunbar, 2011) are consistent with the magnetic data. A prominent subaerially-erupted subglacial volcano, here named Mt Thiel, about 100 km distant to the NE, at approximately 78o 25' S, 111o 20' W, may be the source of the ash layer. This peak is characterized by a ~400-nT positive magnetic anomaly which Behrendt el, 2004, modeled as having apparent susceptibility contrasts of .034 and .15 SI. From its appearance (and the moat surrounding it), Mt. Thiel has subsided somewhat since initial eruption as is the case for Mt. Erebus and the Hawaiian Island chain. I suggest that Mt Thiel, about 100 km distance from the WAISCORE, may be the source of the ash layer. The present rapid changes in the WAIS resulting from global warming, could be accelerated by subglacial volcanism

Effects of high-intensity static magnetic fields on a root-based bioreactor system for space applications

NASA Astrophysics Data System (ADS)

Villani, Maria Elena; Massa, Silvia; Lopresto, Vanni; Pinto, Rosanna; Salzano, Anna Maria; Scaloni, Andrea; Benvenuto, Eugenio; Desiderio, Angiola

2017-11-01

Static magnetic fields created by superconducting magnets have been proposed as an effective solution to protect spacecrafts and planetary stations from cosmic radiations. This shield can deflect high-energy particles exerting injurious effects on living organisms, including plants. In fact, plant systems are becoming increasingly interesting for space adaptation studies, being useful not only as food source but also as sink of bioactive molecules in future bioregenerative life-support systems (BLSS). However, the application of protective magnetic shields would generate inside space habitats residual magnetic fields, of the order of few hundreds milli Tesla, whose effect on plant systems is poorly known. To simulate the exposure conditions of these residual magnetic fields in shielded environment, devices generating high-intensity static magnetic field (SMF) were comparatively evaluated in blind exposure experiments (250 mT, 500 mT and sham -no SMF-). The effects of these SMFs were assayed on tomato cultures (hairy roots) previously engineered to produce anthocyanins, known for their anti-oxidant properties and possibly useful in the setting of BLSS. Hairy roots exposed for periods ranging from 24 h to 11 days were morphometrically analyzed to measure their growth and corresponding molecular changes were assessed by a differential proteomic approach. After disclosing blind exposure protocol, a stringent statistical elaboration revealed the absence of significant differences in the soluble proteome, perfectly matching phenotypic results. These experimental evidences demonstrate that the identified plant system well tolerates the exposure to these magnetic fields. Results hereby described reinforce the notion of using this plant organ culture as a tool in ground-based experiments simulating space and planetary environments, in a perspective of using tomato 'hairy root' cultures as bioreactor of ready-to-use bioactive molecules during future long-term space missions.

Critical current and flux dynamics in Ag-doped FeSe superconductor

NASA Astrophysics Data System (ADS)

Galluzzi, A.; Polichetti, M.; Buchkov, K.; Nazarova, E.; Mancusi, D.; Pace, S.

2017-02-01

The measurements of DC magnetization as a function of the temperature M(T), magnetic field M(H), and time M(t) have been performed in order to compare the superconducting and pinning properties of an undoped FeSe0.94 sample and a silver doped FeSe0.94 + 6 wt% Ag sample. The M(T) curves indicate an improvement of the superconducting critical temperature and a reduction of the non-superconducting phase Fe7Se8 due to the silver doping. This is confirmed by the field and temperature dependent critical current density Jc(H,T) extracted from the superconducting hysteresis loops at different temperatures within the Bean critical state model. Moreover, the combined analysis of the Jc(T) and of the pinning force Fp(H/Hirr) indicate that the pinning mechanisms in both samples can be described in the framework of the collective pinning theory. The U*(T, J) curves show a pinning crossover from an elastic creep regime of intermediate size flux bundles, for low temperatures, to a plastic creep regime at higher temperatures for both the samples. Finally, the vortex hopping attempt time has been evaluated for both samples and the results are comparable with the values reported in the literature for high Tc materials.

Regional analysis of the magnetization transfer ratio of the brain in mild Alzheimer disease and amnestic mild cognitive impairment.

PubMed

Mascalchi, M; Ginestroni, A; Bessi, V; Toschi, N; Padiglioni, S; Ciulli, S; Tessa, C; Giannelli, M; Bracco, L; Diciotti, S

2013-01-01

Manually drawn VOI-based analysis shows a decrease in magnetization transfer ratio in the hippocampus of patients with Alzheimer disease. We investigated with whole-brain voxelwise analysis the regional changes of the magnetization transfer ratio in patients with mild Alzheimer disease and patients with amnestic mild cognitive impairment. Twenty patients with mild Alzheimer disease, 27 patients with amnestic mild cognitive impairment, and 30 healthy elderly control subjects were examined with high-resolution T1WI and 3-mm-thick magnetization transfer images. Whole-brain voxelwise analysis of magnetization transfer ratio maps was performed by use of Statistical Parametric Mapping 8 software and was supplemented by the analysis of the magnetization transfer ratio in FreeSurfer parcellation-derived VOIs. Voxelwise analysis showed 2 clusters of significantly decreased magnetization transfer ratio in the left hippocampus and amygdala and in the left posterior mesial temporal cortex (fusiform gyrus) of patients with Alzheimer disease as compared with control subjects but no difference between patients with amnestic mild cognitive impairment and either patients with Alzheimer disease or control subjects. VOI analysis showed that the magnetization transfer ratio in the hippocampus and amygdala was significantly lower (bilaterally) in patients with Alzheimer disease when compared with control subjects (ANOVA with Bonferroni correction, at P < .05). Mean magnetization transfer ratio values in the hippocampus and amygdala in patients with amnestic mild cognitive impairment were between those of healthy control subjects and those of patients with mild Alzheimer disease. Support vector machine-based classification demonstrated improved classification performance after inclusion of magnetization transfer ratio-related features, especially between patients with Alzheimer disease versus healthy subjects. Bilateral but asymmetric decrease of magnetization transfer ratio reflecting microstructural changes of the residual GM is present not only in the hippocampus but also in the amygdala in patients with mild Alzheimer disease.

Nonhelical inverse transfer of a decaying turbulent magnetic field.

PubMed

Brandenburg, Axel; Kahniashvili, Tina; Tevzadze, Alexander G

2015-02-20

In the presence of magnetic helicity, inverse transfer from small to large scales is well known in magnetohydrodynamic (MHD) turbulence and has applications in astrophysics, cosmology, and fusion plasmas. Using high resolution direct numerical simulations of magnetically dominated self-similarly decaying MHD turbulence, we report a similar inverse transfer even in the absence of magnetic helicity. We compute for the first time spectral energy transfer rates to show that this inverse transfer is about half as strong as with helicity, but in both cases the magnetic gain at large scales results from velocity at similar scales interacting with smaller-scale magnetic fields. This suggests that both inverse transfers are a consequence of universal mechanisms for magnetically dominated turbulence. Possible explanations include inverse cascading of the mean squared vector potential associated with local near two dimensionality and the shallower k^{2} subinertial range spectrum of kinetic energy forcing the magnetic field with a k^{4} subinertial range to attain larger-scale coherence. The inertial range shows a clear k^{-2} spectrum and is the first example of fully isotropic magnetically dominated MHD turbulence exhibiting weak turbulence scaling.

A 33 kyr Paleomagnetic Secular Variation Record from Fish Lake, Utah

NASA Astrophysics Data System (ADS)

Reilly, B. T.; Stoner, J. S.; Hatfield, R. G.; Ziegler, L. B.; Abbott, M. B.; Larsen, D. J.; Hillman, A. L.

2014-12-01

We present a new North American lacustrine PSV record spanning the last ~ 33 ka from Fish Lake, Utah. Eleven meters of sediment were recovered from three holes with overlapping drives using a UWITECH coring system. Magnetic susceptibility was measured in the field to ensure stratigraphic completeness and to provide real time information on the material recovered. The recovered lake stratigraphy includes three distinct facies, interpreted to represent the post-glacial (0.75-6.75 m), last glacial maximum (LGM)/deglaciation (6.75-9.5 m), and pre-LGM period (9.5-11.75 m), with an initial chronology constrained by ten radiocarbon dates. CT scans were made on each section and used to monitor for coring deformation and establish precise stratigraphic correlation. Magnetic remanence was studied using AF demagnetization of u-channel samples measured on the OSU 2-G Enterprises u-channel magnetometer. The NRM is characterized by a viscous remanent magnetization (VRM), present throughout the core but successfully removed by 20 mT AF demagnetization. Weak NRM intensities in the post-glacial interval (3-6 x 10-4 A/m before AF demagnetization and 1-3 x 10-4 A/m following 20 mT AF demagnetization) approach the sensitivity of the u-channel magnetometer with increasing demagnetization and result in high MAD values during PCA analysis. Accordingly, we choose to use the NRM measured after 20 mT AF demagnetization for the post-glacial sediments to avoid both the VRM overprint and noise introduced due to week intensities at higher demagnetization steps. Major inclination features are consistent with other western North American PSV records providing confidence in this approach. NRM intensities are significantly higher below 6.75 m, reflecting increased terrigenous input during the LGM/deglaciation and pre LGM periods. A stable magnetization is isolated using a PCA over the 20-60 mT AF demagnetization steps, yielding MAD values of <1 and ~2, respectively. Declination is rotated to a mean of zero and inclinations vary around geocentric axial dipole predictions for the site's location further suggesting that a reliable PSV record is preserved. The continuous PSV record reveals higher amplitude swings during the late Pleistocene. Here we assess the reliability and implications of these observations.

Mitigating Space Weather Impacts on the Power Grid in Real-Time: Applying 3-D EarthScope Magnetotelluric Data to Forecasting Reactive Power Loss in Power Transformers

NASA Astrophysics Data System (ADS)

Schultz, A.; Bonner, L. R., IV

2017-12-01

Current efforts to assess risk to the power grid from geomagnetic disturbances (GMDs) that result in geomagnetically induced currents (GICs) seek to identify potential "hotspots," based on statistical models of GMD storm scenarios and power distribution grounding models that assume that the electrical conductivity of the Earth's crust and mantle varies only with depth. The NSF-supported EarthScope Magnetotelluric (MT) Program operated by Oregon State University has mapped 3-D ground electrical conductivity structure across more than half of the continental US. MT data, the naturally occurring time variations in the Earth's vector electric and magnetic fields at ground level, are used to determine the MT impedance tensor for each site (the ratio of horizontal vector electric and magnetic fields at ground level expressed as a complex-valued frequency domain quantity). The impedance provides information on the 3-D electrical conductivity structure of the Earth's crust and mantle. We demonstrate that use of 3-D ground conductivity information significantly improves the fidelity of GIC predictions over existing 1-D approaches. We project real-time magnetic field data streams from US Geological Survey magnetic observatories into a set of linear filters that employ the impedance data and that generate estimates of ground level electric fields at the locations of MT stations. The resulting ground electric fields are projected to and integrated along the path of power transmission lines. This serves as inputs to power flow models that represent the power transmission grid, yielding a time-varying set of quasi-real-time estimates of reactive power loss at the power transformers that are critical infrastructure for power distribution. We demonstrate that peak reactive power loss and hence peak risk for transformer damage from GICs does not necessarily occur during peak GMD storm times, but rather depends on the time-evolution of the polarization of the GMD's inducing fields and the complex ground (3-D) electric field response, and the resulting alignment of the ground electric fields with the power transmission line paths. This is informing our efforts to provide a set of real-time tools for power grid operators to use in mitigating damage from space weather events.

Development of multi-metal interaction model for Daphnia magna: Significance of metallothionein in cellular redistribution.

PubMed

Wang, Xiangrui; Liu, Jianyu; Tan, Qiaoguo; Ren, Jinqian; Liang, Dingyuan; Fan, Wenhong

2018-04-30

Despite the great progress made in metal-induced toxicity mechanisms, a critical knowledge gap still exists in predicting adverse effects of heavy metals on living organisms in the natural environment, particularly during exposure to multi-metals. In this study, a multi-metal interaction model of Daphnia manga was developed in an effort to provide reasonable explanations regarding the joint effects resulting from exposure to multi-metals. Metallothionein (MT), a widely used biomarker, was selected. In this model, MT was supposed to play the role of a crucial transfer protein rather than detoxifying protein. Therefore, competitive complexation of metals to MT could highly affect the cellular metal redistribution. Thus, competitive complexation of MT in D. magna with metals like Pb 2+ , Cd 2+ and Cu 2+ was qualitatively studied. The results suggested that Cd 2+ had the highest affinity towards MT, followed by Pb 2+ and Cu 2+ . On the other hand, the combination of MT with Cu 2+ appeared to alter its structure which resulted in higher affinity towards Pb 2+ . Overall, the predicted bioaccumulation of metals under multi-metal exposure was consisted with earlier reported studies. This model provided an alternative angle for joint effect through a combination of kinetic process and internal interactions, which could help to develop future models predicting toxicity to multi-metal exposure. Copyright © 2017 Elsevier Inc. All rights reserved.

The Application of Curve Fitting on the Voltammograms of Various Isoforms of Metallothioneins–Metal Complexes

PubMed Central

Merlos Rodrigo, Miguel Angel; Molina-López, Jorge; Jimenez Jimenez, Ana Maria; Planells Del Pozo, Elena; Adam, Pavlina; Eckschlager, Tomas; Zitka, Ondrej; Richtera, Lukas; Adam, Vojtech

2017-01-01

The translation of metallothioneins (MTs) is one of the defense strategies by which organisms protect themselves from metal-induced toxicity. MTs belong to a family of proteins comprising MT-1, MT-2, MT-3, and MT-4 classes, with multiple isoforms within each class. The main aim of this study was to determine the behavior of MT in dependence on various externally modelled environments, using electrochemistry. In our study, the mass distribution of MTs was characterized using MALDI-TOF. After that, adsorptive transfer stripping technique with differential pulse voltammetry was selected for optimization of electrochemical detection of MTs with regard to accumulation time and pH effects. Our results show that utilization of 0.5 M NaCl, pH 6.4, as the supporting electrolyte provides a highly complicated fingerprint, showing a number of non-resolved voltammograms. Hence, we further resolved the voltammograms exhibiting the broad and overlapping signals using curve fitting. The separated signals were assigned to the electrochemical responses of several MT complexes with zinc(II), cadmium(II), and copper(II), respectively. Our results show that electrochemistry could serve as a great tool for metalloproteomic applications to determine the ratio of metal ion bonds within the target protein structure, however, it provides highly complicated signals, which require further resolution using a proper statistical method, such as curve fitting. PMID:28287470

Electrochemical studies of mesoporous and copper-modified mesoporous TiO2 -anode material

NASA Astrophysics Data System (ADS)

Ajay Kumar, R.; Venkateswara Rao, A.; Rajesh, Ch.

2018-05-01

Herein, we developed a method to synthesize highly ordered mesoporous TiO2 (MT) and copper-modified M- TiO2 (CMT) with a high surface area by the hydrothermal method using Pluronic P-123 as a surfactant at 150 ° C. CMT with different copper concentrations (0.1, 0.2 and 0.3%) was synthesized. The structural characterization studies revealed that MT and CMT particles are in anatase phase. The average particle size was found to be 24± 0.8 nm for MT and that of CMT was 25± 0.6 , 27± 0.4 and 28± 0.3 nm, respectively. The presence of ordered spherical MT and CMT particles with uniform size distribution was confirmed by performing morphological studies using FE-SEM. Optical absorption studies indicate the presence of copper because of the red shift in the band gap and also a broad peak around 800nm when compared with MT. EIS studies point out an increase in conductivity from MT through 0.3% CMT by a decrease in the charge transfer resistance. Further, charge-discharge studies were carried on this material at room temperature for lithium-ion battery applications. CMT with 0.3% copper showed high initial discharge capacity and better cyclability. The results indicate that this material can act as a promising negative electrode.

Mitochondrial DNA transfer to the nucleus generates extensive insertion site variation in maize.

PubMed

Lough, Ashley N; Roark, Leah M; Kato, Akio; Ream, Thomas S; Lamb, Jonathan C; Birchler, James A; Newton, Kathleen J

2008-01-01

Mitochondrial DNA (mtDNA) insertions into nuclear chromosomes have been documented in a number of eukaryotes. We used fluorescence in situ hybridization (FISH) to examine the variation of mtDNA insertions in maize. Twenty overlapping cosmids, representing the 570-kb maize mitochondrial genome, were individually labeled and hybridized to root tip metaphase chromosomes from the B73 inbred line. A minimum of 15 mtDNA insertion sites on nine chromosomes were detectable using this method. One site near the centromere on chromosome arm 9L was identified by a majority of the cosmids. To examine variation in nuclear mitochondrial DNA sequences (NUMTs), a mixture of labeled cosmids was applied to chromosome spreads of ten diverse inbred lines: A188, A632, B37, B73, BMS, KYS, Mo17, Oh43, W22, and W23. The number of detectable NUMTs varied dramatically among the lines. None of the tested inbred lines other than B73 showed the strong hybridization signal on 9L, suggesting that there is a recent mtDNA insertion at this site in B73. Different sources of B73 and W23 were examined for NUMT variation within inbred lines. Differences were detectable, suggesting either that mtDNA is being incorporated or lost from the maize nuclear genome continuously. The results indicate that mtDNA insertions represent a major source of nuclear chromosomal variation.

Electron-spin dynamics in Mn-doped GaAs using time-resolved magneto-optical techniques

NASA Astrophysics Data System (ADS)

Akimov, I. A.; Dzhioev, R. I.; Korenev, V. L.; Kusrayev, Yu. G.; Zhukov, E. A.; Yakovlev, D. R.; Bayer, M.

2009-08-01

We study the electron-spin dynamics in p -type GaAs doped with magnetic Mn acceptors by means of time-resolved pump-probe and photoluminescence techniques. Measurements in transverse magnetic fields show a long spin-relaxation time of 20 ns that can be uniquely related to electrons. Application of weak longitudinal magnetic fields above 100 mT extends the spin-relaxation times up to microseconds which is explained by suppression of the Bir-Aronov-Pikus spin relaxation for the electron on the Mn acceptor.

Dynamic model of a micro-tubular solid oxide fuel cell stack including an integrated cooling system

NASA Astrophysics Data System (ADS)

Hering, Martin; Brouwer, Jacob; Winkler, Wolfgang

2017-02-01

A novel dynamic micro-tubular solid oxide fuel cell (MT-SOFC) and stack model including an integrated cooling system is developed using a quasi three-dimensional, spatially resolved, transient thermodynamic, physical and electrochemical model that accounts for the complex geometrical relations between the cells and cooling-tubes. The modeling approach includes a simplified tubular geometry and stack design including an integrated cooling structure, detailed pressure drop and gas property calculations, the electrical and physical constraints of the stack design that determine the current, as well as control strategies for the temperature. Moreover, an advanced heat transfer balance with detailed radiative heat transfer between the cells and the integrated cooling-tubes, convective heat transfer between the gas flows and the surrounding structures and conductive heat transfer between the solid structures inside of the stack, is included. The detailed model can be used as a design basis for the novel MT-SOFC stack assembly including an integrated cooling system, as well as for the development of a dynamic system control strategy. The evaluated best-case design achieves very high electrical efficiency between around 75 and 55% in the entire power density range between 50 and 550 mW /cm2 due to the novel stack design comprising an integrated cooling structure.

Mitochondrial DNA transmission and confounding mitochondrial influences in cloned cattle and pigs.

PubMed

Takeda, Kumiko

2013-04-01

Although somatic cell nuclear transfer (SCNT) is a powerful tool for production of cloned animals, SCNT embryos generally have low developmental competency and many abnormalities. The interaction between the donor nucleus and the enucleated ooplasm plays an important role in early embryonic development, but the underlying mechanisms that negatively impact developmental competency remain unclear. Mitochondria have a broad range of critical functions in cellular energy supply, cell signaling, and programmed cell death; thus, affect embryonic and fetal development. This review focuses on mitochondrial considerations influencing SCNT techniques in farm animals. Donor somatic cell mitochondrial DNA (mtDNA) can be transmitted through what has been considered a "bottleneck" in mitochondrial genetics via the SCNT maternal lineage. This indicates that donor somatic cell mitochondria have a role in the reconstructed cytoplasm. However, foreign somatic cell mitochondria may affect the early development of SCNT embryos. Nuclear-mitochondrial interactions in interspecies/intergeneric SCNT (iSCNT) result in severe problems. A major biological selective pressure exists against survival of exogenous mtDNA in iSCNT. Yet, mtDNA differences in SCNT animals did not reflect transfer of proteomic components following proteomic analysis. Further study of nuclear-cytoplasmic interactions is needed to illuminate key developmental characteristics of SCNT animals associated with mitochondrial biology.

Electron-cyclotron damping of helicon waves in low diverging magnetic fields

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lafleur, T.; Charles, C.; Boswell, R. W.

2011-04-15

Particle-in-cell simulations are performed to investigate wave propagation and absorption behavior of low-field (B{sub 0}<5 mT) helicon waves in the presence of a diverging magnetic field. The 1D electromagnetic simulations, which include experimental external magnetic field profiles, provide strong evidence for electron-cyclotron damping of helicon waves in the spatially decaying nonuniform magnetic field. For a dipole-type magnetic field configuration, the helicon waves are absence in the downstream (lower field) region of the plasma and are observed to be completely absorbed. As the magnetic field is changed slightly however, wave damping decreases, and waves are able to propagate freely downstream, confirmingmore » previous experimental measurements of this phenomenon.« less

An induction heater device for studies of magnetic hyperthermia and specific absorption ratio measurements

NASA Astrophysics Data System (ADS)

Cano, M. E.; Barrera, A.; Estrada, J. C.; Hernandez, A.; Cordova, T.

2011-11-01

The development of a device for generating ac magnetic fields based on a resonant inverter is presented, which has been specially designed to carry out experiments of magnetic hyperthermia. By determining the electric current in the LC resonant circuit, a maximum intensity of magnetic field around of 15 mT is calculated, with a frequency around of 206 kHz. This ac magnetic field is able to heat powdered magnetic materials embedded in biological systems to be used in biomedical applications. Indeed, in order to evaluate the sensitivity of the device we also present the measurements of the specific absorption rate in phantoms performed with commercially prepared Fe3O4 and distilled water at different concentrations.

The complete mitochondrial genome of Setaria digitata (Nematoda: Filarioidea): Mitochondrial gene content, arrangement and composition compared with other nematodes.

PubMed

Yatawara, Lalani; Wickramasinghe, Susiji; Rajapakse, R P V J; Agatsuma, Takeshi

2010-09-01

In the present study, we determined the complete mitochondrial (mt) genome sequence (13,839bp) of parasitic nematode Setaria digitata and its structure and organization compared with Onchocerca volvulus, Dirofilaria immitis and Brugia malayi. The mt genome of S. digitata is slightly larger than the mt genomes of other filarial nematodes. S. digitata mt genome contains 36 genes (12 protein-coding genes, 22 transfer RNAs and 2 ribosomal RNAs) that are typically found in metazoans. This genome contains a high A+T (75.1%) content and low G+C content (24.9%). The mt gene order for S. digitata is the same as those for O. volvulus, D. immitis and B. malayi but it is distinctly different from other nematodes compared. The start codons inferred in the mt genome of S. digitata are TTT, ATT, TTG, ATG, GTT and ATA. Interestingly, the initiation codon TTT is unique to S. digitata mt genome and four protein-coding genes use this codon as a translation initiation codon. Five protein-coding genes use TAG as a stop codon whereas three genes use TAA and four genes use T as a termination codon. Out of 64 possible codons, only 57 are used for mitochondrial protein-coding genes of S. digitata. T-rich codons such as TTT (18.9%), GTT (7.9%), TTG (7.8%), TAT (7%), ATT (5.7%), TCT (4.8%) and TTA (4.1%) are used more frequently. This pattern of codon usage reflects the strong bias for T in the mt genome of S. digitata. In conclusion, the present investigation provides new molecular data for future studies of the comparative mitochondrial genomics and systematic of parasitic nematodes of socio-economic importance. 2010 Elsevier B.V. All rights reserved.

Development and Technology Transfer of the Syncro Blue Tube (Gabriel) Magnetically Guided Feeding Tube

DTIC Science & Technology

2017-06-01

other documentation. TITLE: Development and Technology Transfer of the Syncro Blue Tube (Gabriel) Magnetically Guided Feeding Tube REPORT DOCUMENTATION...TITLE AND SUBTITLE Development and Technology Transfer of the Syncro Blue Tube (Gabriel) Magnetically Guided Feeding Tube 5a. CONTRACT NUMBER W81XWH-09-2...Technical Abstract: Further Development and Technology Transfer of the Syncro BLUETUBE™ (Gabriel) Magnetically Guided Feeding Tube. New Primary

Magnetic biomonitoring of roadside pollution in the restricted Midagahara area of Mt. Tateyama, Toyama, Japan.

PubMed

Kawasaki, Kazuo; Horikawa, Keiji; Sakai, Hideo

2017-04-01

Magnetic biomonitoring techniques and in situ topsoil magnetic susceptibility measurements have been shown to be rapid, cost-effective, and useful methods for investigating roadside pollution. However, combustible vegetation in samples makes it very difficult to use them in high-temperature magnetic experiments although the thermal alteration of spontaneous magnetization is a fundamental magnetic property and can be used to identify reliably the magnetic minerals. Here, we report the first magnetic biomonitoring results of dust deposited on plant leaves along the Tateyama-Kurobe Alpine route at the highly protected Midagahara wetland areas of Mt. Tateyama in Toyama, Japan. In-field magnetic susceptibility from 15 sites (161 points) shows higher susceptibilities near the roadside. Dust deposited on the leaves of Sasa kurilensis, or dwarf bamboo, has been wiped off at 12 sites (64 samples) with a commercial ethanol wipe sheet or silica wool damped in ethanol and subjected to rock magnetic analyses. Thermomagnetic remanence curves and low-temperature behaviors for samples collected near the roadside using silica wool show clearly that the main magnetic mineral in the dust is partially oxidized magnetite. Further, detailed rock magnetic analyses and elemental analyses of leaves in the study area indicate that (a) the magnetic mineralogy on leaves' surface is consistent throughout the study area and (b) higher saturation isothermal remanent magnetization intensities as well as higher concentrations of Pb, Fe, Cr, and Y are observed near the roadside, i.e., the closer to the roadside, the more anthropogenic materials, including partially oxidized magnetite, are present. Also, microscopic observations show the lack of spherical grains, indicating that dust on the roadside leaves is derived from passing vehicle rather than industrial process. Both rock magnetic and geochemical results show that S. kurilensis would be an excellent candidate for investigating air pollution. Also, the proposed wiping-off method of collecting dust from plant surfaces is an effective non-destructive method that can be applied even in highly restricted collection areas, because detailed magnetic mineralogy, including superparamagnetic minerals, could be determined with the use of silica wool for use in both high- and low-temperature experiments.

Pollen-based temperature and precipitation inferences for the montane forest of Mt. Kilimanjaro during the last Glacial and the Holocene

NASA Astrophysics Data System (ADS)

Schüler, L.; Hemp, A.; Behling, H.

2014-01-01

The relationship between modern pollen-rain taxa and measured climate variables was explored along the elevational gradient of the southern slope of Mt. Kilimanjaro, Tanzania. Pollen assemblages in 28 pollen traps positioned on 14 montane forest vegetation plots were identified and their relationship with climate variables was examined using multivariate statistical methods. Canonical correspondence analysis revealed that the mean annual temperature, mean annual precipitation and minimum temperature each account for significant fractions of the variation in pollen taxa. A training set of 107 modern pollen taxa was used to derive temperature and precipitation transfer functions based on pollen subsets using weighted-averaging-partial-least-squares (WA-PLS) techniques. The transfer functions were then applied to a fossil pollen record from the montane forest of Mt. Kilimanjaro and the climate parameter estimates for the Late Glacial and the Holocene on Mt. Kilimanjaro were inferred. Our results present the first quantitatively reconstructed temperature and precipitation estimates for Mt Kilimanjaro and give highly interesting insights into the past 45 000 yr of climate dynamics in tropical East Africa. The climate reconstructions are consistent with the interpretation of pollen data in terms of vegetation and climate history of afro-montane forest in East Africa. Minimum temperatures above the frostline as well as increased precipitation turn out to be crucial for the development and expansion of montane forest during the Holocene. In contrast, consistently low minimum temperatures as well as about 25% drier climate conditions prevailed during the pre LGM, which kept the montane vegetation composition in a stable state. In prospective studies, the quantitative climate reconstruction will be improved by additional modern pollen rain data, especially from lower elevations with submontane dry forests and colline savanna vegetation in order to extend the reference climate gradient.

Structure of Mycobacterium tuberculosis mtFabD, a malonyl-CoA:acyl carrier protein transacylase (MCAT).

PubMed

Ghadbane, Hemza; Brown, Alistair K; Kremer, Laurent; Besra, Gurdyal S; Fütterer, Klaus

2007-10-01

Mycobacteria display a unique and unusual cell-wall architecture, central to which is the membrane-proximal mycolyl-arabinogalactan-peptidoglycan core (mAGP). The biosynthesis of mycolic acids, which form the outermost layer of the mAGP core, involves malonyl-CoA:acyl carrier protein transacylase (MCAT). This essential enzyme catalyses the transfer of malonyl from coenzyme A to acyl carrier protein AcpM, thus feeding these two-carbon units into the chain-elongation cycle of the type II fatty-acid synthase. The crystal structure of M. tuberculosis mtFabD, the mycobacterial MCAT, has been determined to 3.0 A resolution by multi-wavelength anomalous dispersion. Phasing was facilitated by Ni2+ ions bound to the 20-residue N-terminal affinity tag, which packed between the two independent copies of mtFabD.

Development and expansion of high-quality control region databases to improve forensic mtDNA evidence interpretation.

PubMed

Irwin, Jodi A; Saunier, Jessica L; Strouss, Katharine M; Sturk, Kimberly A; Diegoli, Toni M; Just, Rebecca S; Coble, Michael D; Parson, Walther; Parsons, Thomas J

2007-06-01

In an effort to increase the quantity, breadth and availability of mtDNA databases suitable for forensic comparisons, we have developed a high-throughput process to generate approximately 5000 control region sequences per year from regional US populations, global populations from which the current US population is derived and global populations currently under-represented in available forensic databases. The system utilizes robotic instrumentation for all laboratory steps from pre-extraction through sequence detection, and a rigorous eight-step, multi-laboratory data review process with entirely electronic data transfer. Over the past 3 years, nearly 10,000 control region sequences have been generated using this approach. These data are being made publicly available and should further address the need for consistent, high-quality mtDNA databases for forensic testing.

Magnetic field effects and waves in complex plasmas

NASA Astrophysics Data System (ADS)

Kählert, Hanno; Melzer, André; Puttscher, Marian; Ott, Torben; Bonitz, Michael

2018-05-01

Magnetic fields can modify the physical properties of a complex plasma in various different ways. Weak magnetic fields in the mT range affect only the electrons while strong fields in the Tesla regime also magnetize the ions. In a rotating dusty plasma, the Coriolis force substitutes the Lorentz force and can be used to create an effective magnetization for the strongly coupled dust particles while leaving electrons and ions unaffected. Here, we present a summary of our recent experimental and theoretical work on magnetized complex plasmas. We discuss the dynamics of dust particles in magnetized discharges, the wave spectra of strongly coupled plasmas, and the excitations in confined plasmas. Contribution to the Topical Issue "Fundamentals of Complex Plasmas", edited by Jürgen Meichsner, Michael Bonitz, Holger Fehske, Alexander Piel.

Magnetic Resonance Arterial Spin Tagging for Non-Invasive Pharmacokinetic Analysis of Breast Cancer

DTIC Science & Technology

2000-10-01

sequence software that we had developed for this project. In addition, we revised the pulse sequences to utilize the high performance gradients (40 mT/ m ...peak, 150 mT/ m /ms rise) of the system. We believe these revised sequences will provide better arterial spin tagged data for perfusion measurement. All...U.... ...... ... -- v p I _1 i-:F~ ----- ! - .Ag Jig. H aI .. M e fI6lo 3 ~ ~ 2 0’,~- A.11. I 1 1 9 - HP ~ ~ IM I 15 L 1 1 8 = NIAt I C J1 5

FeTi oxide mineralogy and the origin of normal and reverse remanent magnetization in dacitic pumice blocks from Mt. Shasta, California

USGS Publications Warehouse

Lawson, C.A.; Nord, G.L.; Champion, D.E.

1987-01-01

Detailed mineralogical analyses and rock magnetic experiments have made it possible to directly identify the FeTi oxide phases responsible for the normal and reverse magnetic components of two dacitic pumice blocks from Mt. Shasta, California. Both samples contain a normal component carried by 100 ??m size multi-domain (MD) titanomagnetite (Usp11-24). One sample also contains a second normal component carried by < 10 ??m size pseudo-single domain (PSD) or single domain (SD) Ti-free magnetite (Usp1) found in the dacitic glass. The MD titanomagnetite and PSD or SD magnetite dominate the strong field magnetic signal, but only the PSD or SD magnetite has any influence on the remanence signal. Unlike the strong field signal, the remanence signal of both samples is dominated by a reverse NRM component. This reverse component is carried by 100 ??m size ferrian ilmenite (Ilm53-65). The compositions of the ilmenites in both samples are within the range of compositions (Ilm50-75) known to have the ability to acquire self-reversing thermoremanent magnetizations (TRM). The results of the Lowric-Fuller test indicate that the remanence signal is dominated by PSD or SD carriers. Because one sample contains only large MD titanomagnetite and no SD Ti-free magnetite (in addition to ferrian ilmenite), the ferrian ilmenite must be a PSD or SD carrier. Oxide and pyroxene geothermometry indicate the FeTi oxides in the pumice crystallized at temperatures between 880 and 945??C. This temperature range is within the disordered region of the ilmenite-hematite phase diagram for Ilm53-65. Previous work on synthetic Ilm70 and Ilm80 has shown that cooling through the order-disorder transition into the ordered region develops a transformation-induced microstructure consisting of cation-ordered domains with disordered domain boundaries. An Ilm58-59 grain from one of the Mt. Shasta samples was examined in the transmission electron microscope and was found to contain 100-200 A?? diameter cation-ordered domains. These domains arose during cooling through the transition temperature, which is estimated at 800??C for Ilm58-59. The presence of the disordered domain boundaries provides an explanation for the magnetic behavior of the ferrian ilmenite. (1) The disordered boundaries are the higher Curie point phase necessary for the operation of the self-reversal mechanism. (2) The disordered domain boundaries either inhibit the formation of magnetic domain walls or restrict magnetic domain wall movement accounting for the PSD or SD behavior of the ferrian ilmenite. ?? 1987.

The Influence of a Rotating Magnetic Field on Solidification from a Traveling Solvent Zone

NASA Technical Reports Server (NTRS)

Gillies, Donald C.

1997-01-01

Application of a high frequency rotating magnetic field (50-400Hz) (RMF) with a strength of the order of 1 mT can be used to influence the fluid flow in an electrically conductive melt. The advantage of the RMF during the traveling solvent zone method for growth of semiconductor materials will be discussed. Preliminary modeling results for cadmium telluride growth from a tellurium solvent zone will be discussed.

Electrical Conductivity Model of the Mantle Lithosphere of the Slave Craton (NW Canada) and its tectonic interpretation in the context of Geochemical Results

NASA Astrophysics Data System (ADS)

Lezaeta, P.; Chave, A.; Evans, R.; Jones, A. G.; Ferguson, I.

2002-12-01

The Slave Craton, northwestern Canada, contains the oldest known rocks on Earth, with exposed outcrop over an area of about 600x400 km2. The discovery of economic diamondiferous kimberlite pipes during the early 1990s motivated extensive research in the region. Over the last six years, four types of deep-probing magnetotelluric (MT) surveys were conducted within the framework of diverse geoscientific programs, aimed at determining the regional-scale electrical structures of the craton. Two of the surveys involved novel acquisition; one through frozen lake ice along ice roads during winter, and the second deploying ocean-bottom instrumentation from float planes during summer. The latter surveys required one year of recording between summers, thus allowing long period transfer functions that lead to mantle penetration depths of over 300 km. Two-dimensional modeling of the MT data from along the winter road showed the existence of a high conductivity zone at depths of 80-120 km beneath the central Slave craton. This anomalous region is spatially coincident with an ultradepleted harzburgitic layer in the upper mantle that was interpreted by others to be related to a subducted slab emplaced during the mid-Archean. A 3-D electrical conductivity model of the Slave lithosphere has been obtained, by trial and error, to fit the magnetic transfer and MT response functions from the lake experiments. This 3-D model traces the central Slave conductor as a NE-SW oriented mantle structure. Its NE-SW orientation coincides with that of a late fold belt system, with the first phase of craton-wide plutonism at ca 2630-2590 Ma, three-part subdivision of the craton based on SKS results, and with a G10 (garnet) geochemical mantle boundaries. All of these highlight a NE-SW structural grain to the lithospheric mantle of the craton, in sharp contrast to the N-S grain of the crust. Constraints on the depth range and lateral extension of the electrical conductive structure are obtained through a sensitivity analysis to verify a recent hypothesis about tectonic imbrication of lithosphere emplaced at ca 2.6 Ga in which SE-NW subduction is proposed. If such subduction has taken place, and arc-related or oceanic lithosphere has been trapped in the system, then an enhanced conductivity in the mantle deepening to NW supports the tectonic model.

Disorders of motion and depth.

PubMed

Nawrot, Mark

2003-08-01

Damage to the human homologue of area MT produces a motion perception deficit similar to that found in the monkey with MT lesions. Even temporary disruption of MT processing with transcranial magnetic stimulation can produce a temporary akinetopsia [127]. Motion perception deficits, however, also are found with a variety of subcortical lesions and other neurologic disorders that can best be described as causing a disconnection within the motion processing stream. The precise role of these subcortical structures, such as the cerebellum, remains to be determined. Simple motion perception, moreover, is only a part of MT function. It undoubtedly has an important role in the perception of depth from motion and stereopsis [112]. Psychophysical studies using aftereffects in normal observers suggest a link between stereo mechanisms and the perception of depth from motion [9-11]. There is even a simple correlation between stereo acuity and the perception of depth from motion [128]. Future studies of patients with cortical lesions will take a closer look at depth perception in association with motion perception and should provide a better understanding of how motion and depth are processed together.

Human blindsight is mediated by an intact geniculo-extrastriate pathway

PubMed Central

Ajina, Sara; Pestilli, Franco; Rokem, Ariel; Kennard, Christopher; Bridge, Holly

2015-01-01

Although damage to the primary visual cortex (V1) causes hemianopia, many patients retain some residual vision; known as blindsight. We show that blindsight may be facilitated by an intact white-matter pathway between the lateral geniculate nucleus and motion area hMT+. Visual psychophysics, diffusion-weighted magnetic resonance imaging and fibre tractography were applied in 17 patients with V1 damage acquired during adulthood and 9 age-matched controls. Individuals with V1 damage were subdivided into blindsight positive (preserved residual vision) and negative (no residual vision) according to psychophysical performance. All blindsight positive individuals showed intact geniculo-hMT+ pathways, while this pathway was significantly impaired or not measurable in blindsight negative individuals. Two white matter pathways previously implicated in blindsight: (i) superior colliculus to hMT+ and (ii) between hMT+ in each hemisphere were not consistently present in blindsight positive cases. Understanding the visual pathways crucial for residual vision may direct future rehabilitation strategies for hemianopia patients. DOI: http://dx.doi.org/10.7554/eLife.08935.001 PMID:26485034

Ultrasound assessment of hamstring muscle size using posterior thigh muscle thickness.

PubMed

Abe, Takashi; Loenneke, Jeremy P; Thiebaud, Robert S

2016-05-01

Several studies have investigated the relationship between ultrasound-measured muscle thickness (MT) and individual muscle cross-sectional area (CSA) and muscle volume (MV) in extremity and trunk muscles; however, the hamstring muscle has not been studied. The purpose of this study was to examine the relationship between posterior thigh MT by ultrasound and the muscle CSA and MV of the hamstring obtained by magnetic resonance imaging (MRI). Ten young women aged 20-31 had MT measured by ultrasound at three sites on the medial anterior (50% of thigh length; TL) and posterior (50% and 70% of TL) aspects of the thigh. On the same day, a series of continuous muscle CSA along the thigh was measured by MRI. In each slice, the anatomical CSA of the hamstring (biceps femoris, semitendinosus and semimembranosus) and quadriceps muscle was analysed, and the CSAs at 50% and 70% of TL and maximal CSA of the hamstring (CSAmax ) were determined. MV was calculated by multiplying CSA by slice thickness. A significant correlation was observed between posterior 50% MT and 50% hamstring CSA (r = 0·848, P = 0·002) and between posterior 70% MT and 70% hamstring CSA (r = 0·679, P = 0·031). Posterior 50% MT (r = 0·732, P = 0·016) and 50% MTxTL (r = 0·873, P = 0·001) were also correlated to hamstring MV. Anterior:posterior 50% thigh MT ratio was correlated to MV ratio of quadriceps and hamstring muscles (r = 0·803, P = 0·005). Our results suggest that posterior thigh MT reflects hamstring muscle CSA and MV. The anterior:posterior MT ratio may serve as a surrogate for MV ratio of quadriceps and hamstring. © 2014 Scandinavian Society of Clinical Physiology and Nuclear Medicine. Published by John Wiley & Sons Ltd.

End-member modelling of isothermal remanent magnetization (IRM) acquisition curves: a novel approach to diagnose remagnetization

NASA Astrophysics Data System (ADS)

Gong, Z.; Dekkers, M. J.; Heslop, D.; Mullender, T. A. T.

2009-08-01

To identify remagnetization is essential for palaeomagnetic studies and their geodynamic implications. The traditional approach is often based on directional analysis of palaeomagnetic data and field tests, which may be inconclusive if the apparent polar wander path (APWP) is poorly constrained or if the remagnetization predates folding. In several cases, rock magnetic work, particularly, the measurement of hysteresis loops allows identification of the so-called `remagnetized' and `non-remagnetized' trends. However, for weakly magnetic samples, this approach can be equivocal. Here, to improve the diagnosis of remagnetization, we investigated 192 isothermal remanent magnetization (IRM) acquisition curves (up to 700 mT) of remagnetized and non-remagnetized limestones from the Organyà Basin, northern Spain. Also, 96 IRM acquisition curves from non-remagnetized marls were studied as a cross-check for the non-remagnetized limestones. A non-parametric end-member modelling approach is used to analyse the IRM acquisition curve data sets. First, remagnetized and non-remagnetized groups were treated separately. Two or three end-members were found to adequately describe the data variability: one end-member represents the high-coercivity contribution, whereas the low-coercivity part can be described by either one end-member or two reasonably similar end-members. In the remagnetized limestones, the low-coercivity end-members tend to saturate at higher field values than in the non-remagnetized limestones. When the entire data set was processed together, a three-end-member model was judged optimal. This model consists of a high-coercivity end-member, a low-coercivity end-member that saturates at ~300-400 mT and a low-coercivity end-member that approximately saturates at 700 mT. Higher contributions of the latter end-member appear to occur dominantly in the remagnetized limestones, whereas the reverse is true for the non-remagnetized limestones, so they plot in clearly distinguishable areas. Meanwhile, the IRM curves from non-remagnetized marls show a behaviour similar to that of the non-remagnetized end-member in the limestones. Therefore, this new approach can be a very useful tool to diagnose remagnetization in weakly magnetic limestones and marls. We recommend applying it to other areas of potentially remagnetized low-intensity sediments.

Paleomagnetic and Rock Magnetic Study of Oligocene-Holocene Sedimentary Rocks from Northern Dominican Republic: Evidence of Vertical Axis Rotations

NASA Astrophysics Data System (ADS)

Anson Sanchez, M.; Kodama, K. P.; Pueyo, E. L.; Soto, R.; Garcia-Senz, J.; Escuder-Viruete, J.; Pastor-Galan, D.

2017-12-01

A paleomagnetic and rock magnetic study was conducted in the northern Dominican Republic to detect vertical axis rotations in an active left-lateral, strike slip fault zone. 191 samples from 21 sites were collected from a variety of lithologies including limestones, conglomerates, calcarenites and marls that ranged in age from the Oligocene to the Holocene. The rock magnetic portion of the study focused on the identification of magnetic minerals using coercivity, and Curie temperature (c vs temperature) measurement, modeling of IRM acquisition curves, and thermal demagnetization of IRMs (Lowrie, 19901). In the paleomagnetic portion of the study characteristic remanences (ChRMs) were isolated using thermal demagnetization (19 steps up to 680ºC) and alternating field (AF) demagnetization (17 steps up to 100 mT). In most cases the characteristic remanence is carried by magnetite, with peak unblocking temperatures of 575ºC. This interpretation was supported by c vs. T results that yielded Curie temperatures of 580˚C. In only a few cases (7 samples) higher unblocking temperatures suggested hematite as the magnetic carrier. The modeling of IRM acquisition curves, that shows two coercivity components, further supports the presence of magnetite. 75% of the IRM is carried by the low-coercivity component (100-300 mT, magnetite). 25% of the IRM is carried by the high-coercivity component (1.2-1.6T) characteristic of hematite. The IRM acquisition data was collected from 24 samples (3-4 from each of the lithologies sampled). IRMs were acquired in fields from 4mT to 1T in 23 steps. The paleomagnetic results show a grouping by tectonic blocks with one group having westerly ChRM declinations (268˚-295˚) and a second group having northerly ChRM declinations (357˚-035˚). In most cases, inclinations are intermediate ( 35˚), in agreement with the 24˚-31˚ expected inclinations for Dominican Republic in the period Oligocene to Holocene. The rotation of the tectonic blocks, as detected by the declinations, is consistent with a left-lateral strike-slip motion across the main fault in the area. 1Lowrie, 1990, GRL, 17, 159-162

Contextual Interference Effects in Learning Three Badminton Serves.

ERIC Educational Resources Information Center

Goode, Sinah; Magill, Richard A.

1986-01-01

This study was made to validate results obtained in laboratory research. Thirty female students learned three badminton serves in either a low, mixed, or high interference practice schedule and were given a retention and transfer test. Results are discussed. (Author/MT)

Mechanical force antagonizes the inhibitory effects of RecX on RecA filament formation in Mycobacterium tuberculosis

PubMed Central

Le, Shimin; Chen, Hu; Zhang, Xinghua; Chen, Jin; Patil, K. Neelakanteshwar; Muniyappa, Kalappa; Yan, Jie

2014-01-01

Efficient bacterial recombinational DNA repair involves rapid cycles of RecA filament assembly and disassembly. The RecX protein plays a crucial inhibitory role in RecA filament formation and stability. As the broken ends of DNA are tethered during homologous search, RecA filaments assembled at the ends are likely subject to force. In this work, we investigated the interplay between RecX and force on RecA filament formation and stability. Using magnetic tweezers, at single molecular level, we found that Mycobacterium tuberculosis (Mt) RecX could catalyze stepwise de-polymerization of preformed MtRecA filament in the presence of ATP hydrolysis at low forces (<7 pN). However, applying larger forces antagonized the inhibitory effects of MtRecX, and a partially de-polymerized MtRecA filament could re-polymerize in the presence of MtRecX, which cannot be explained by previous models. Theoretical analysis of force-dependent conformational free energies of naked ssDNA and RecA nucleoprotein filament suggests that mechanical force stabilizes RecA filament, which provides a possible mechanism for the observation. As the antagonizing effect of force on the inhibitory function of RecX takes place in a physiological range; these findings broadly suggest a potential mechanosensitive regulation during homologous recombination. PMID:25294832

Abnormal Magnetic Field Effects on Electrogenerated Chemiluminescence

NASA Astrophysics Data System (ADS)

Pan, Haiping; Shen, Yan; Wang, Hongfeng; He, Lei; Hu, Bin

2015-03-01

We report abnormal magnetic field effects on electrogenerated chemiluminescence (MFEECL) based on triplet emission from the Ru(bpy)3Cl2-TPrA electrochemical system: the appearance of MFEECL after magnetic field ceases. In early studies the normal MFEECL have been observed from electrochemical systems during the application of magnetic field. Here, the abnormal MFEECL suggest that the activated charge-transfer [Ru(bpy)33+ … TPrA•] complexes may become magnetized in magnetic field and experience a long magnetic relaxation after removing magnetic field. Our analysis indicates that the magnetic relaxation can gradually increase the density of charge-transfer complexes within reaction region due to decayed magnetic interactions, leading to a positive component in the abnormal MFEECL. On the other hand, the magnetic relaxation facilitates an inverse conversion from triplets to singlets within charge-transfer complexes. The inverse triplet --> singlet conversion reduces the density of triplet light-emitting states through charge-transfer complexes and gives rise to a negative component in the abnormal MFEECL. The combination of positive and negative components can essentially lead to a non-monotonic profile in the abnormal MFEECL after ceasing magnetic field. Nevertheless, our experimental studies may reveal un-usual magnetic behaviors with long magnetic relaxation from the activated charge-transfer [Ru(bpy)33+ … TPrA•] complexes in solution at room temperature.

Maternal Betaine Supplementation during Gestation Enhances Expression of mtDNA-Encoded Genes through D-Loop DNA Hypomethylation in the Skeletal Muscle of Newborn Piglets.

PubMed

Jia, Yimin; Song, Haogang; Gao, Guichao; Cai, Demin; Yang, Xiaojing; Zhao, Ruqian

2015-11-25

Betaine has been widely used in animal and human nutrition to promote muscle growth and performance, yet it remains unknown whether maternal betaine supplementation during gestation affects the metabolic characteristics of neonatal skeletal muscles. In the present study, feeding sows with betaine-supplemented diets throughout gestation significantly upregulated the expression of mtDNA-encoded OXPHOS genes (p < 0.05), including COX1, COX2, and ND5, in the muscle of newborn piglets, which was associated with enhanced mitochondrial COX enzyme activity (p < 0.05). Concurrently, maternal betaine supplementation increased the plasma betaine concentration and muscle expression of methyl transfer enzymes (p < 0.05), BHMT and GNMT, in offspring piglets. Nevertheless, Dnmt3a was downregulated at the level of both mRNA and protein, which was associated with a hypomethylated mtDNA D-loop region (p < 0.05). These results suggest that maternal betaine supplementation during gestation enhances expression of mtDNA-encoded genes through D-loop DNA hypomethylation in the skeletal muscle of newborn piglets.

Structure of Mycobacterium tuberculosis mtFabD, a malonyl-CoA:acyl carrier protein transacylase (MCAT)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ghadbane, Hemza; Brown, Alistair K.; Kremer, Laurent

2007-10-01

Binding of Ni{sup 2+} ions to the uncleaved affinity tag facilitated de novo phasing of the crystal structure of M. tuberculosis mtFabD to 3.0 Å resolution. Mycobacteria display a unique and unusual cell-wall architecture, central to which is the membrane-proximal mycolyl-arabinogalactan-peptidoglycan core (mAGP). The biosynthesis of mycolic acids, which form the outermost layer of the mAGP core, involves malonyl-CoA:acyl carrier protein transacylase (MCAT). This essential enzyme catalyses the transfer of malonyl from coenzyme A to acyl carrier protein AcpM, thus feeding these two-carbon units into the chain-elongation cycle of the type II fatty-acid synthase. The crystal structure of M. tuberculosismore » mtFabD, the mycobacterial MCAT, has been determined to 3.0 Å resolution by multi-wavelength anomalous dispersion. Phasing was facilitated by Ni{sup 2+} ions bound to the 20-residue N-terminal affinity tag, which packed between the two independent copies of mtFabD.« less

A combinatorial filtering method for magnetotelluric time-series based on Hilbert-Huang transform

NASA Astrophysics Data System (ADS)

Cai, Jianhua

2014-11-01

Magnetotelluric (MT) time-series are often contaminated with noise from natural or man-made processes. A substantial improvement is possible when the time-series are presented as clean as possible for further processing. A combinatorial method is described for filtering of MT time-series based on the Hilbert-Huang transform that requires a minimum of human intervention and leaves good data sections unchanged. Good data sections are preserved because after empirical mode decomposition the data are analysed through hierarchies, morphological filtering, adaptive threshold and multi-point smoothing, allowing separation of noise from signals. The combinatorial method can be carried out without any assumption about the data distribution. Simulated data and the real measured MT time-series from three different regions, with noise caused by baseline drift, high frequency noise and power-line contribution, are processed to demonstrate the application of the proposed method. Results highlight the ability of the combinatorial method to pick out useful signals, and the noise is suppressed greatly so that their deleterious influence is eliminated for the MT transfer function estimation.

Characterization of the complete mitochondrial genome of Marshallagia marshalli and phylogenetic implications for the superfamily Trichostrongyloidea.

PubMed

Sun, Miao-Miao; Han, Liang; Zhang, Fu-Kai; Zhou, Dong-Hui; Wang, Shu-Qing; Ma, Jun; Zhu, Xing-Quan; Liu, Guo-Hua

2018-01-01

Marshallagia marshalli (Nematoda: Trichostrongylidae) infection can lead to serious parasitic gastroenteritis in sheep, goat, and wild ruminant, causing significant socioeconomic losses worldwide. Up to now, the study concerning the molecular biology of M. marshalli is limited. Herein, we sequenced the complete mitochondrial (mt) genome of M. marshalli and examined its phylogenetic relationship with selected members of the superfamily Trichostrongyloidea using Bayesian inference (BI) based on concatenated mt amino acid sequence datasets. The complete mt genome sequence of M. marshalli is 13,891 bp, including 12 protein-coding genes, 22 transfer RNA genes, and 2 ribosomal RNA genes. All protein-coding genes are transcribed in the same direction. Phylogenetic analyses based on concatenated amino acid sequences of the 12 protein-coding genes supported the monophylies of the families Haemonchidae, Molineidae, and Dictyocaulidae with strong statistical support, but rejected the monophyly of the family Trichostrongylidae. The determination of the complete mt genome sequence of M. marshalli provides novel genetic markers for studying the systematics, population genetics, and molecular epidemiology of M. marshalli and its congeners.

Biosynthesis of t-Butyl in Apratoxin A: Functional Analysis and Architecture of a PKS Loading Module.

PubMed

Skiba, Meredith A; Sikkema, Andrew P; Moss, Nathan A; Lowell, Andrew N; Su, Min; Sturgis, Rebecca M; Gerwick, Lena; Gerwick, William H; Sherman, David H; Smith, Janet L

2018-05-08

The unusual feature of a t-butyl group is found in several marine-derived natural products including apratoxin A, a Sec61 inhibitor produced by the cyanobacterium Moorea bouillonii PNG 5-198. Here, we determine that the apratoxin A t-butyl group is formed as a pivaloyl acyl carrier protein (ACP) by AprA, the polyketide synthase (PKS) loading module of the apratoxin A biosynthetic pathway. AprA contains an inactive "pseudo" GCN5-related N-acetyltransferase domain (ΨGNAT) flanked by two methyltransferase domains (MT1 and MT2) that differ distinctly in sequence. Structural, biochemical, and precursor incorporation studies reveal that MT2 catalyzes unusually coupled decarboxylation and methylation reactions to transform dimethylmalonyl-ACP, the product of MT1, to pivaloyl-ACP. Further, pivaloyl-ACP synthesis is primed by the fatty acid synthase malonyl acyltransferase (FabD), which compensates for the ΨGNAT and provides the initial acyl-transfer step to form AprA malonyl-ACP. Additionally, images of AprA from negative stain electron microscopy reveal multiple conformations that may facilitate the individual catalytic steps of the multienzyme module.

Mitochondrial genomes of the green macroalga Ulva pertusa (Ulvophyceae, Chlorophyta): novel insights into the evolution of mitogenomes in the Ulvophyceae.

PubMed

Liu, Feng; Melton, James T; Bi, Yuping

2017-10-01

To further understand the trends in the evolution of mitochondrial genomes (mitogenomes or mtDNAs) in the Ulvophyceae, the mitogenomes of two separate thalli of Ulva pertusa were sequenced. Two U. pertusa mitogenomes (Up1 and Up2) were 69,333 bp and 64,602 bp in length. These mitogenomes shared two ribosomal RNAs (rRNAs), 28 transfer RNAs (tRNAs), 29 protein-coding genes, and 12 open reading frames. The 4.7 kb difference in size was attributed to variation in intron content and tandem repeat regions. A total of six introns were present in the smaller U. pertusa mtDNA (Up2), while the larger mtDNA (Up1) had eight. The larger mtDNA had two additional group II introns in two genes (cox1 and cox2) and tandem duplication mutations in noncoding regions. Our results showed the first case of intraspecific variation in chlorophytan mitogenomes and provided further genomic data for the undersampled Ulvophyceae. © 2017 Phycological Society of America.

Animal Mitochondrial DNA as We Do Not Know It: mt-Genome Organization and Evolution in Nonbilaterian Lineages

PubMed Central

Pett, Walker

2016-01-01

Abstract Animal mitochondrial DNA (mtDNA) is commonly described as a small, circular molecule that is conserved in size, gene content, and organization. Data collected in the last decade have challenged this view by revealing considerable diversity in animal mitochondrial genome organization. Much of this diversity has been found in nonbilaterian animals (phyla Cnidaria, Ctenophora, Placozoa, and Porifera), which, from a phylogenetic perspective, form the main branches of the animal tree along with Bilateria. Within these groups, mt-genomes are characterized by varying numbers of both linear and circular chromosomes, extra genes (e.g. atp9, polB, tatC), large variation in the number of encoded mitochondrial transfer RNAs (tRNAs) (0–25), at least seven different genetic codes, presence/absence of introns, tRNA and mRNA editing, fragmented ribosomal RNA genes, translational frameshifting, highly variable substitution rates, and a large range of genome sizes. This newly discovered diversity allows a better understanding of the evolutionary plasticity and conservation of animal mtDNA and provides insights into the molecular and evolutionary mechanisms shaping mitochondrial genomes. PMID:27557826

A method to track rotational motion for use in single-molecule biophysics.

PubMed

Lipfert, Jan; Kerssemakers, Jacob J W; Rojer, Maylon; Dekker, Nynke H

2011-10-01

The double helical nature of DNA links many cellular processes such as DNA replication, transcription, and repair to rotational motion and the accumulation of torsional strain. Magnetic tweezers (MTs) are a single-molecule technique that enables the application of precisely calibrated stretching forces to nucleic acid tethers and to control their rotational motion. However, conventional magnetic tweezers do not directly monitor rotation or measure torque. Here, we describe a method to directly measure rotational motion of particles in MT. The method relies on attaching small, non-magnetic beads to the magnetic beads to act as fiducial markers for rotational tracking. CCD images of the beads are analyzed with a tracking algorithm specifically designed to minimize crosstalk between translational and rotational motion: first, the in-plane center position of the magnetic bead is determined with a kernel-based tracker, while subsequently the height and rotation angle of the bead are determined via correlation-based algorithms. Evaluation of the tracking algorithm using both simulated images and recorded images of surface-immobilized beads demonstrates a rotational resolution of 0.1°, while maintaining a translational resolution of 1-2 nm. Example traces of the rotational fluctuations exhibited by DNA-tethered beads confined in magnetic potentials of varying stiffness demonstrate the robustness of the method and the potential for simultaneous tracking of multiple beads. Our rotation tracking algorithm enables the extension of MTs to magnetic torque tweezers (MTT) to directly measure the torque in single molecules. In addition, we envision uses of the algorithm in a range of biophysical measurements, including further extensions of MT, tethered particle motion, and optical trapping measurements.

Microstructural Investigation, Raman and Magnetic Studies on Chemically Synthesized Nanocrystalline Ni-Doped Gadolinium Oxide (Gd1.90Ni0.10O3- δ )

NASA Astrophysics Data System (ADS)

Sarkar, B. J.; Mandal, J.; Dalal, M.; Bandyopadhyay, A.; Satpati, B.; Chakrabarti, P. K.

2018-03-01

Nanocrystalline Ni-doped gadolinium oxide (Gd1.90Ni0.10O3- δ , GNO) is synthesized by co-precipitation method. The as-prepared sample is annealed in vacuum at 700°C for 6 h. Analyses of the x-ray diffractogram by Rietveld refinement method, transmission electron microscopy and Raman spectroscopy of GNO recorded at room temperature confirmed the pure crystallographic phase and complete substitution of Ni-ions in Gd2O3 lattice. Magnetization ( M) as a function of temperature ( T) and magnetic field ( H) is measured by a superconducting quantum interference device magnetometer, which suggests the presence of ferromagnetic/antiferromagnetic phases together with a paramagnetic phase. From the M-T curve it can be shown that the ferromagnetic phase dominates over para-/antiferromagnetic phases in the temperature range of 300-100 K, but from 100 K to 50 K, the antiferromagnetic phase dominates over ferro-/paramagnetic phases. Hysteresis loops recorded at different temperatures indicate the presence of weak ferro-/antiferromagnetism, which dominates in the low field region (˜ 4000 Oe), above which magnetization increases linearly. The sharp increase of magnetization in M-T curve observed in the temperature range of 50-5 K confirms the presence of dominating ferromagnetic plus paramagnetic phase over antiferromagnetic part. For the first time a combined formula generated from three-dimensional (3D) spin wave model and Johnston formula is proposed to analyze the coexistence of different magnetic phases in different temperature ranges. Interestingly, the combined formula successfully explains the co-existence of different magnetic phases along with their contribution at different temperatures. The onset of ferromagnetism in Gd1.90Ni0.10O3- δ is explained by oxygen vacancy mediated F-centre exchange (FCE) coupling mechanism.

Modulation of spin transfer torque amplitude in double barrier magnetic tunnel junctions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Clément, P.-Y.; Baraduc, C., E-mail: claire.baraduc@cea.fr; Chshiev, M.

2015-09-07

Magnetization switching induced by spin transfer torque is used to write magnetic memories (Magnetic Random Access Memory, MRAM) but can be detrimental to the reading process. It would be quite convenient therefore to modulate the efficiency of spin transfer torque. A solution is adding an extra degree of freedom by using double barrier magnetic tunnel junctions with two spin-polarizers, with controllable relative magnetic alignment. We demonstrate, for these structures, that the amplitude of in-plane spin transfer torque on the middle free layer can be efficiently tuned via the magnetic configuration of the electrodes. Using the proposed design could thus pavemore » the way towards more reliable read/write schemes for MRAM. Moreover, our results suggest an intriguing effect associated with the out-of-plane (field-like) spin transfer torque, which has to be further investigated.« less

Effect of low frequency magnetic fields on the growth of MNP-treated HT29 colon cancer cells

NASA Astrophysics Data System (ADS)

Spyridopoulou, K.; Makridis, A.; Maniotis, N.; Karypidou, N.; Myrovali, E.; Samaras, T.; Angelakeris, M.; Chlichlia, K.; Kalogirou, O.

2018-04-01

Recent investigations have attempted to understand and exploit the impact of magnetic field-actuated internalized magnetic nanoparticles (MNPs) on the proliferation rate of cancer cells. Due to the complexity of the parameters governing magnetic field-exposure though, individual studies to date have raised contradictory results. In our approach we performed a comparative analysis of key parameters related to the cell exposure of cancer cells to magnetic field-actuated MNPs, and to the magnetic field, in order to better understand the factors affecting cellular responses to magnetic field-stimulated MNPs. We used magnetite MNPs with a hydrodynamic diameter of 100 nm and studied the proliferation rate of MNPs-treated versus untreated HT29 human colon cancer cells, exposed to either static or alternating low frequency magnetic fields with varying intensity (40-200 mT), frequency (0-8 Hz) and field gradient. All three parameters, field intensity, frequency, and field gradient affected the growth rate of cells, with or without internalized MNPs, as compared to control MNPs-untreated and magnetic field-untreated cells. We observed that the growth inhibitory effects induced by static and rotating magnetic fields were enhanced by pre-treating the cells with MNPs, while the growth promoting effects observed in alternating field-treated cells were weakened by MNPs. Compared to static, rotating magnetic fields of the same intensity induced a similar extend of cell growth inhibition, while alternating fields of varying intensity (70 or 100 mT) and frequency (0, 4 or 8 Hz) induced cell proliferation in a frequency-dependent manner. These results, highlighting the diverse effects of mode, intensity, and frequency of the magnetic field on cell growth, indicate that consistent and reproducible results can be achieved by controlling the complexity of the exposure of biological samples to MNPs and external magnetic fields, through monitoring crucial experimental parameters. We demonstrate that further research focusing on the accurate manipulation of the aforementioned magnetic field exposure parameters could lead to the development of successful non-invasive therapeutic anticancer approaches.

Exchanges of sediment between the flood plain and channel of the Amazon River in Brazil

USGS Publications Warehouse

Dunne, T.; Mertes, L.A.K.; Meade, R.H.; Richey, J.E.; Forsberg, B.R.

1998-01-01

Sediment transport through the Brazilian sector of the Amazon River valley, a distance of 2010 km, involves exchanges between the channel and the flood plain that in each direction exceed the annual flux of sediment out of the river at O??bidos (???1200 Mt yr-1). The exchanges occur through bank erosion, bar deposition, settling from diffuse overbank flow, and sedimentation in flood-plain channels. We estimated the magnitude of these exchanges for each of 10 reaches of the valley, and combined them with calculations of sediment transport into and out of the reaches based on sediment sampling and flow records to define a sediment budget for each reach. Residuals in the sediment budget of a reach include errors of estimation and erosion or deposition within the channel. The annual supply of sediment entering the channel from bank erosion was estimated to average 1570 Mt yr-1 (1.3 ?? the O??bidos flux) and the amount transferred from channel transport to the bars (380 Mt yr-1) and the flood plain (460 Mt yr-1 in channelized flow; 1230 Mt yr-1 in diffuse overbank flow) totaled 2070 Mt yr-1 (1.7 ?? the O??bidos flux). Thus, deposition on the bars and flood plain exceeded bank erosion by 500 Mt yr-1 over a 10-16 yr period. Sampling and calculation of sediment loads in the channel indicate a net accumulation in the valley floor of approximately 200 Mt yr-1 over 16 yr, crudely validating the process-based calculations of the sediment budget, which in turn illuminate the physical controls on each exchange process. Another 300-400 Mt yr-1 are deposited in a delta plain downstream of O??bidos. The components of the sediment budget reflect hydrologie characteristics of the valley floor and geomorphic characteristics of the channel and flood plain, which in turn are influenced by tectonic features of the Amazon structural trough.

Survival of Skin Graft between Transgenic Cloned Dogs and Non-Transgenic Cloned Dogs

PubMed Central

Kim, Geon A; Oh, Hyun Ju; Kim, Min Jung; Jo, Young Kwang; Choi, Jin; Park, Jung Eun; Park, Eun Jung; Lim, Sang Hyun; Yoon, Byung Il; Kang, Sung Keun; Jang, Goo; Lee, Byeong Chun

2014-01-01

Whereas it has been assumed that genetically modified tissues or cells derived from somatic cell nuclear transfer (SCNT) should be accepted by a host of the same species, their immune compatibility has not been extensively explored. To identify acceptance of SCNT-derived cells or tissues, skin grafts were performed between cloned dogs that were identical except for their mitochondrial DNA (mtDNA) haplotypes and foreign gene. We showed here that differences in mtDNA haplotypes and genetic modification did not elicit immune responses in these dogs: 1) skin tissues from genetically-modified cloned dogs were successfully transplanted into genetically-modified cloned dogs with different mtDNA haplotype under three successive grafts over 63 days; and 2) non-transgenic cloned tissues were accepted into transgenic cloned syngeneic recipients with different mtDNA haplotypes and vice versa under two successive grafts over 63 days. In addition, expression of the inserted gene was maintained, being functional without eliciting graft rejection. In conclusion, these results show that transplanting genetically-modified tissues into normal, syngeneic or genetically-modified recipient dogs with different mtDNA haplotypes do not elicit skin graft rejection or affect expression of the inserted gene. Therefore, therapeutically valuable tissue derived from SCNT with genetic modification might be used safely in clinical applications for patients with diseased tissues. PMID:25372489

Analyses of Mitogenome Sequences Revealed that Asian Citrus Psyllids (Diaphorina citri) from California Were Related to Those from Florida.

PubMed

Wu, Fengnian; Kumagai, Luci; Cen, Yijing; Chen, Jianchi; Wallis, Christopher M; Polek, MaryLou; Jiang, Hongyan; Zheng, Zheng; Liang, Guangwen; Deng, Xiaoling

2017-08-31

Asian citrus psyllid (ACP, Diaphorina citri Kuwayama) transmits "Candidatus Liberibacter asiaticus" (CLas), an unculturable alpha-proteobacterium associated with citrus Huanglongbing (HLB). CLas has recently been found in California. Understanding ACP population diversity is necessary for HLB regulatory practices aimed at reducing CLas spread. In this study, two circular ACP mitogenome sequences from California (mt-CApsy, ~15,027 bp) and Florida (mt-FLpsy, ~15,012 bp), USA, were acquired. Each mitogenome contained 13 protein coding genes, 2 ribosomal RNA and 22 transfer RNA genes, and a control region varying in sizes. The Californian mt-CApsy was identical to the Floridian mt-FLpsy, but different from the mitogenome (mt-GDpsy) of Guangdong, China, in 50 single nucleotide polymorphisms (SNPs). Further analyses were performed on sequences in cox1 and trnAsn regions with 100 ACPs, SNPs in nad1-nad4-nad5 locus through PCR with 252 ACP samples. All results showed the presence of a Chinese ACP cluster (CAC) and an American ACP cluster (AAC). We proposed that ACP in California was likely not introduced from China based on our current ACP collection but somewhere in America. However, more studies with ACP samples from around the world are needed. ACP mitogenome sequence analyses will facilitate ACP population research.

The complete mitochondrial genomes of five Eimeria species infecting domestic rabbits.

PubMed

Liu, Guo-Hua; Tian, Si-Qin; Cui, Ping; Fang, Su-Fang; Wang, Chun-Ren; Zhu, Xing-Quan

2015-12-01

Rabbit coccidiosis caused by members of the genus Eimeria can cause enormous economic impact worldwide, but the genetics, epidemiology and biology of these parasites remain poorly understood. In the present study, we sequenced and annotated the complete mitochondrial (mt) genomes of five Eimeria species that commonly infect the domestic rabbits. The complete mt genomes of Eimeria intestinalis, Eimeria flavescens, Eimeria media, Eimeria vejdovskyi and Eimeria irresidua were 6261bp, 6258bp, 6168bp, 6254bp, 6259bp in length, respectively. All of the mt genomes consist of 3 genes for proteins (cytb, cox1, and cox3), 14 gene fragments for the large subunit (LSU) rRNA and 11 gene fragments for the small subunit (SSU) rRNA, but no transfer RNA (tRNA) genes. The gene order of the mt genomes is similar to that of Plasmodium, but distinct from Haemosporida and Theileria. Phylogenetic analyses based on full nucleotide sequences using Bayesian analysis revealed that the monophyly of the Eimeria of rabbits was strongly statistically supported with a Bayesian posterior probabilities. These data provide novel mtDNA markers for studying the population genetics and molecular epidemiology of the Eimeria species, and should have implications for the molecular diagnosis, prevention and control of coccidiosis in rabbits. Copyright © 2015 Elsevier Inc. All rights reserved.

High intensity proton injector for facility of antiproton and ion research

DOE Office of Scientific and Technical Information (OSTI.GOV)

Berezov, R., E-mail: r.berezov@gsi.de; Brodhage, R.; Fils, J.

The high current ion source with the low energy beam transport (LEBT) will serve as injector into the proton LINAC to provide primary proton beam for the production of antiprotons. The pulsed ion source developed and built in CEA/Saclay operates with a frequency of 2.45 GHz based on ECR plasma production with two coils with 87.5 mT magnetic field necessary for the electron cyclotron resonance. The compact LEBT consists of two solenoids with a maximum magnetic field of 500 mT including two integrated magnetic steerers to adjust the horizontal and vertical beam positions. The total length of the compact LEBTmore » is 2.3 m and was made as short as possible to reduced emittance growth along the beam line. To measure ion beam intensity behind the pentode extraction system, between solenoids and at the end of the beam line, two current transformers and a Faraday cup are installed. To get information about the beam quality and position, the diagnostic chamber with different equipment will be installed between the two solenoids. This article reports the current status of the proton injector for the facility of antiproton and ion research.« less

Magnetic field activated lipid-polymer hybrid nanoparticles for stimuli-responsive drug release.

PubMed

Kong, Seong Deok; Sartor, Marta; Hu, Che-Ming Jack; Zhang, Weizhou; Zhang, Liangfang; Jin, Sungho

2013-03-01

Stimuli-responsive nanoparticles (SRNPs) offer the potential of enhancing the therapeutic efficacy and minimizing the side-effects of chemotherapeutics by controllably releasing the encapsulated drug at the target site. Currently controlled drug release through external activation remains a major challenge during the delivery of therapeutic agents. Here we report a lipid-polymer hybrid nanoparticle system containing magnetic beads for stimuli-responsive drug release using a remote radio frequency (RF) magnetic field. These hybrid nanoparticles show long-term stability in terms of particle size and polydispersity index in phosphate-buffered saline (PBS). Controllable loading of camptothecin (CPT) and Fe(3)O(4) in the hybrid nanoparticles was demonstrated. RF-controlled drug release from these nanoparticles was observed. In addition, cellular uptake of the SRNPs into MT2 mouse breast cancer cells was examined. Using CPT as a model anticancer drug the nanoparticles showed a significant reduction in MT2 mouse breast cancer cell growth in vitro in the presence of a remote RF field. The ease of preparation, stability, and controllable drug release are the strengths of the platform and provide the opportunity to improve cancer chemotherapy. Copyright © 2012 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Relaxation-based viscosity mapping for magnetic particle imaging.

PubMed

Utkur, M; Muslu, Y; Saritas, E U

2017-05-07

Magnetic particle imaging (MPI) has been shown to provide remarkable contrast for imaging applications such as angiography, stem cell tracking, and cancer imaging. Recently, there is growing interest in the functional imaging capabilities of MPI, where 'color MPI' techniques have explored separating different nanoparticles, which could potentially be used to distinguish nanoparticles in different states or environments. Viscosity mapping is a promising functional imaging application for MPI, as increased viscosity levels in vivo have been associated with numerous diseases such as hypertension, atherosclerosis, and cancer. In this work, we propose a viscosity mapping technique for MPI through the estimation of the relaxation time constant of the nanoparticles. Importantly, the proposed time constant estimation scheme does not require any prior information regarding the nanoparticles. We validate this method with extensive experiments in an in-house magnetic particle spectroscopy (MPS) setup at four different frequencies (between 250 Hz and 10.8 kHz) and at three different field strengths (between 5 mT and 15 mT) for viscosities ranging between 0.89 mPa · s-15.33 mPa · s. Our results demonstrate the viscosity mapping ability of MPI in the biologically relevant viscosity range.

Relaxation-based viscosity mapping for magnetic particle imaging

NASA Astrophysics Data System (ADS)

Utkur, M.; Muslu, Y.; Saritas, E. U.

2017-05-01

Magnetic particle imaging (MPI) has been shown to provide remarkable contrast for imaging applications such as angiography, stem cell tracking, and cancer imaging. Recently, there is growing interest in the functional imaging capabilities of MPI, where ‘color MPI’ techniques have explored separating different nanoparticles, which could potentially be used to distinguish nanoparticles in different states or environments. Viscosity mapping is a promising functional imaging application for MPI, as increased viscosity levels in vivo have been associated with numerous diseases such as hypertension, atherosclerosis, and cancer. In this work, we propose a viscosity mapping technique for MPI through the estimation of the relaxation time constant of the nanoparticles. Importantly, the proposed time constant estimation scheme does not require any prior information regarding the nanoparticles. We validate this method with extensive experiments in an in-house magnetic particle spectroscopy (MPS) setup at four different frequencies (between 250 Hz and 10.8 kHz) and at three different field strengths (between 5 mT and 15 mT) for viscosities ranging between 0.89 mPa · s-15.33 mPa · s. Our results demonstrate the viscosity mapping ability of MPI in the biologically relevant viscosity range.

Longitudinal evaluation of T1ρ and T2 spatial distribution in osteoarthritic and healthy medial knee cartilage.

PubMed

Schooler, J; Kumar, D; Nardo, L; McCulloch, C; Li, X; Link, T M; Majumdar, S

2014-01-01

To investigate longitudinal changes in laminar and spatial distribution of knee articular cartilage magnetic resonance imaging (MRI) T1ρ and T2 relaxation times, in individuals with and without medial compartment cartilage defects. All subjects (at baseline n = 88, >18 years old) underwent 3-Tesla knee MRI at baseline and annually thereafter for 3 years. The MR studies were evaluated for presence of cartilage defects (modified Whole-Organ Magnetic Resonance Imaging Scoring - mWORMS), and quantitative T1ρ and T2 relaxation time maps. Subjects were segregated into those with (mWORMS ≥2) and without (mWORMS ≤1) cartilage lesions at the medial tibia (MT) or medial femur (MF) at each time point. Laminar (bone and articular layer) and spatial (gray level co-occurrence matrix - GLCM) distribution of the T1ρ and T2 relaxation time maps were calculated. Linear regression models (cross-sectional) and Generalized Estimating Equations (GEEs) (longitudinal) were used. Global T1ρ, global T2 and articular layer T2 relaxation times at the MF, and global and articular layer T2 relaxation times at the MT, were higher in subjects with cartilage lesions compared to those without lesions. At the MT global T1ρ relaxation times were higher at each time point in subjects with lesions. MT T1ρ and T2 became progressively more heterogeneous than control compartments over the course of the study. Spatial distribution of T1ρ and T2 relaxation time maps in medial knee OA using GLCM technique may be a sensitive indicator of cartilage deterioration, in addition to whole-compartment relaxation time data. Copyright © 2013 Osteoarthritis Research Society International. Published by Elsevier Ltd. All rights reserved.

Structure and Dynamics of Nonionic Surfactant Aggregates in Layered Materials.

PubMed

Guégan, Régis; Veron, Emmanuel; Le Forestier, Lydie; Ogawa, Makoto; Cadars, Sylvian

2017-09-26

The aggregation of surfactants on solid surfaces as they are adsorbed from solution is the basis of numerous technological applications such as colloidal stabilization, ore flotation, and floor cleaning. The understanding of both the structure and the dynamics of surfactant aggregates applies to the development of alternative ways of preparing hybrid layered materials. For this purpose, we study the adsorption of the triethylene glycol mono n-decyl ether (C 10 E 3 ) nonionic surfactant onto a synthetic montmorillonite (Mt), an aluminosilicate clay mineral for organoclay preparation with important applications in materials sciences, catalysis, wastewater treatment, or as drug delivery. The aggregation mechanisms follow those observed in an analogous natural Mt, with the condensation of C 10 E 3 in a bilayer arrangement once the surfactant self-assembles in a lamellar phase beyond the critical micelle concentration, underlining the importance of the surfactant state in solution. Solid-state 1 H nuclear magnetic resonance (NMR) at fast magic-angle spinning (MAS) and high magnetic field combined with 1 H- 13 C correlation experiments and different types of 13 C NMR experiments selectively probes mobile or rigid moieties of C 10 E 3 in three different aggregate organizations: (i) a lateral monolayer, (ii) a lateral bilayer, and (iii) a normal bilayer. High-resolution 1 H{ 27 Al} CP- 1 H- 1 H spin diffusion experiments shed light on the proximities and dynamics of the different fragments and fractions of the intercalated surfactant molecules with respect to the Mt surface. 23 Na and 1 H NMR measurements combined with complementary NMR data, at both molecular and nanometer scales, precisely pointed out the location of the C 10 E 3 ethylene oxide hydrophilic group in close contact with the Mt surface interacting through ion-dipole or van der Waals interactions.

Overexpression of miR-26b-5p regulates the cell cycle by targeting CCND2 in GC-2 cells under exposure to extremely low frequency electromagnetic fields.

PubMed

Liu, Yong; Liu, Wen-Bin; Liu, Kai-Jun; Ao, Lin; Cao, Jia; Zhong, Julia Li; Liu, Jin-Yi

2016-01-01

The increasing prevalence of extremely low frequency electromagnetic fields (ELF-EMFs) exposure has raised considerable public concern regarding the potential hazardous effects of ELF-EMFs on male reproductive function. Increasing evidence indicates that miRNAs are necessary for spermatogenesis and male fertility. However, the regulation of miRNA expression and the roles of miRNAs in response to ELF-EMFs remain unclear. In our study, mouse spermatocyte-derived GC-2 cells were intermittently exposed to a 50 Hz ELF-EMF for 72 h (5 min on/10 min off) at magnetic field intensities of 1 mT, 2 mT and 3 mT. MiR-26b-5p was differentially expressed in response to different magnetic field intensities of ELF-EMFs. The host gene CTDSP1 showed an unmethylation status in GC-2 cells at different magnetic field intensities of ELF-EMF exposure. MiR-26b-5p had no significant, obvious influence on the cell viability, apoptosis or cell cycle of GC-2 cells. However, the overexpression of miR-26b-5p significantly decreased the percentage of G0/G1 phase cells and slightly increased the percentage of S phase cells compared to the sham group that was exposed to a 50 Hz ELF-EMF. Computational algorithms identified Cyclin D2 (CCND2) as a direct target of miR-26b-5p. MiR-26b-5p and a 50 Hz ELF-EMF altered the expression of CCND2 at both the mRNA and protein levels. Overexpressed miR-26b-5p in GC-2 cells can change the mRNA expression of CCND2 following 50 Hz ELF-EMF at 3 mT. These findings demonstrate that miR-26b-5p could serve as a potential biomarker following 50 Hz ELF-EMF exposure, and miR-26b-5p-CCND2-mediated cell cycle regulation might play a pivotal role in the biological effects of ELF-EMFs.

Functional Assessment of Corticospinal System Excitability in Karate Athletes.

PubMed

Moscatelli, Fiorenzo; Messina, Giovanni; Valenzano, Anna; Monda, Vincenzo; Viggiano, Andrea; Messina, Antonietta; Petito, Annamaria; Triggiani, Antonio Ivano; Ciliberti, Michela Anna Pia; Monda, Marcellino; Capranica, Laura; Cibelli, Giuseppe

2016-01-01

To investigate the involvement of the primary motor cortex (M1) in the coordination performance of karate athletes through transcranial magnetic stimulation (TMS). Thirteen right-handed male karate athletes (25.0±5.0 years) and 13 matched non-athlete controls (26.7±6.2 years) were enrolled. A single-pulse TMS was applied using a figure-eight coil stimulator. Resting motor threshold (rMT) was determined. Surface electromyography was recorded from the first dorsal interosseous muscle. Motor evoked potential (MEP) latencies and amplitudes at rMT, 110%, and 120% of rMT were considered. Functional assessment of the coordination performance was assessed by in-phase (IP) and anti-phase (AP) homolateral hand and foot coordination tasks performed at 80, 120, and 180 bpm. Compared to controls, athletes showed lower rMT (p<0.01), shorter MEP latency (p<0.01) and higher MEP amplitude (p<0.01), with a significant correlation (r = 0.50, p<0.01) between rMT and MEP latency. Coordination decreased with increasing velocity, and better IP performances emerged compared to AP ones (p<0.001). In general, a high correlation between rMT and coordination tasks was found for both IP and AP conditions. With respect to controls, karate athletes present a higher corticospinal excitability indicating the presence of an activity-dependent alteration in the balance and interactions between inhibitory and facilitatory circuits determining the final output from the M1. Furthermore, the high correlation between corticospinal excitability and coordination performance could support sport-specific neurophysiological arrangements.

New geophysical views of Mt.Melbourne Volcano (East Antarctica)

NASA Astrophysics Data System (ADS)

Armadillo, E.; Gambetta, M.; Ferraccioli, F.; Corr, H.; Bozzo, E.

2009-05-01

Mt. Melbourne volcano is located along the transition between the Transantarctic Mountains and the West Antarctic Rift System. Recent volcanic activity is suggested by the occurrence of blankets of pyroclastic pumice and scoria fall around the eastern and southern flanks of Mt Melbourne and by pyroclastic layers interbedded with the summit snows. Geothermal activity in the crater area of Mount Melbourne may be linked to the intrusion of dykes within the last 200 years. Geophysical networks suggest that Mount Melbourne is a quiescent volcano, possibly characterised by slow internal dynamics. During the 2002-2003 Italian Antarctic campaign a high-resolution aeromagnetic survey was performed within the TIMM (Tectonics and Interior of Mt. Melbourne area) project. This helicopter-borne survey was flown at low-altitude and in drape-mode configuration (305 m above terrain) with a line separation less than 500 m. Our new high-resolution magnetic maps reveal the largely ice-covered magmatic and tectonic patters in the Mt. Melbourne volcano area. Additionally, in the frame of the UK-Italian ISODYN-WISE project (2005-06), an airborne ice-sounding radar survey was flown. We combine the sub-ice topography with images and models of the interior of Mt. Melbourne volcano, as derived from the high resolution aeromagnetic data and land gravity data. Our new geophysical maps and models also provide a new tool to study the regional setting of the volcano. In particular we re-assess whether there is geophysical evidence for coupling between strike-slip faulting, the Terror Rift, and Mount Melbourne volcano.

Paleomagnetic Study of Marine Sediment Core OR715-21 from Eastern Offshore of Taiwan

NASA Astrophysics Data System (ADS)

Lee, T.; Wei, K.; Huh, C.

2009-12-01

This study presents paleomagnetic secular variation results of a marine sediment core, named as OR715-21, taken from eastern offshore of Taiwan (121.5°E, 22.7°N, water depth 760 m). The total recovered length is 1.87 meters. Sediments in the core mainly consist of gray clay and silt. Planktonic foraminiferal shells (>250 μm, >6 mg, Globigerinoides spp. and Orbulina universa) were picked from six levels of the core and subjected to AMS 14C dating for constructing the age model. The results indicated that this core could support the information for the last 7000 years. The averaged sedimentation rate is estimated to be of about 26.5 cm/kyr. Psuedo-single domain (PSD) magnetite is identified as the most important magnetic carrier. Alternating field (AF) demagnetization was applied to treat the u-channel samples of the core. The median destructive field of the samples distributed between 15~25 mT. The characteristic remanent magnetization could be resolved after 20 mT cleaning. The paleo-declinations of the samples varied about ±200 around their mean and their paleo-inclinations varied between 300 and 500 . The variation pattern of the paleo-declination is somehow similar to the pattern compiled by Hyoto et al. (1993) based on the lake and marine sediment records from Japan except the varied amplitude is less between 4000 and 5000 yrB.P. Using NRM/ARM after 20 mT cleaning to simulate the paleo-intensity secular variation, our record shows that an increased trend began from 6500 yrB.P. to 3000 yrB.P., but decreased after. Magnetic proxies of this core indicate that 4 stages of environmental changes has happened in the area studied: (1) high magnetite abundance with relative low oxidized magnetic mineral contents occurred during ~6900 to 6200 yrB.P.; (2) a relative low abundance of magnetite with relative high oxidized magnetic minerals during ~6200 to ~5400 yrB.P.; (3) an abnormal low HIRM with relative higher ARM/SIRM could be found during the time period of ~5400 to 4200 yrB.P. and (4) relative stable magnetic mineral assembly was found after ~4000 yrB.P. Such variation might be related to the path change of the Kuritio current in the surrounding area. Undoubted it needs to be further studied.

Magnetotelluric evidence for massive sulphide mineralization in intruded sediments of the outer Vøring Basin, mid-Norway

NASA Astrophysics Data System (ADS)

Corseri, Romain; Senger, Kim; Selway, Kate; Abdelmalak, Mohamed Mansour; Planke, Sverre; Jerram, Dougal A.

2017-06-01

A highly conductive body (0.1-0.8 Ω·m) is identified at mid-crustal depth (8-13 km) in the north Gjallar Ridge from magnetotelluric (MT) data and further investigated in light of other remote-sensing geophysical data (seismic reflection, gravity, aeromagnetic). A commercial 3D controlled-source electromagnetic survey was conducted in the Vøring Basin in 2014 and, although primarily designed for hydrocarbon exploration, good quality MT data were extracted at periods ranging from 100 to 103 s. Dimensionality analysis indicates clear 1D to 2D characteristics in the MT data. 2D inversion was carried out on four profiles (totalling 94 km) oriented perpendicular to the electromagnetic strike and one profile along strike ( 45 km), using a 1D subset of the data. All inversions converged quickly to RMS values close to unity and display a very good agreement with borehole resistivity data from well 6705/10-1 located in the survey area. A striking feature on all profiles is a highly conductive (0.1-0.8 Ω·m) body at 8-13 km depth. To explain the prominent conductive anomaly, integration of geophysical data favours the hypothesis of electrical conduction across well-connected mineral network in pre-Cretaceous sediments. Seismic interpretation suggests a link between the conductor and intruded sedimentary successions below a detachment level and associated low-angle faults. In the Vøring Basin, low magnetic signal and temperature at the conductor's depth indicate that such thick mineral deposits could display non-magnetic behaviour while occurring well below the magnetite Curie isotherm ( 585 °C). Natural occurrences and magnetic properties of common iron-sulphide minerals favour a geological interpretation of mid-crustal conductivity as thick pyrrhotite deposits formed in intrusion's contact metamorphic aureoles.

Nested Helmholtz coil design for producing homogeneous transient rotating magnetic fields

NASA Astrophysics Data System (ADS)

Podaru, George; Moore, John; Dani, Raj Kumar; Prakash, Punit; Chikan, Viktor

2015-03-01

Electromagnets that can produce strong rotating magnetic fields at kHz frequencies are potentially very useful to exert rotating force on magnetic nanoparticles as small as few nanometers in size. In this article, the construction of a pulsed high-voltage rotating electromagnet is demonstrated based on a nested Helmholtz coil design. The energy for the coils is provided by two high-voltage discharge capacitors. The triggered spark gaps used in the experiments show sufficient accuracy to achieve the high frequency rotating magnetic field. The measured strength of the rotating magnetic field is 200 mT. This magnetic field is scalable by increasing the number of turns on the coils, by reducing the dimensions of the coils and by increasing the discharge current/voltage of the capacitors.

Magnetic properties of chemical remanent magnetization in synthetic and natural goethite - Prospects for a natural remanent magnetization/thermoremanent magnetization ratio paleomagnetic stability test?

NASA Astrophysics Data System (ADS)

Dekkers, Mark J.; Rochette, Pierre

1992-11-01

Results are presented of measurements of chemical remanent magnetization properties in natural goethite and in goethite samples synthesized under controlled field conditions (horizontally directed field of 0.30 mT) at 30 C and 55 C, with and without the presence of microfiber glass filters. Results indicate that both the temperature and the presence of a substrate (microfiber glass filters) affect the goethite aging process and the magnetic properties of the resulting goethite. The goethite aging from ferrihydrite was much faster at 55 C than at 30 C, likely because of increased ion diffusion velocity in solution. Results of goethite aging in the presence of other mineral substrate (gibbsite) indicate that the type of mineral substrate is important.

Effect of Departure Delays on Manned Mars Mission Selection

NASA Technical Reports Server (NTRS)

Desai, Prasun N.; Tartabini, Paul V.

1995-01-01

This study determines the effect on the initial mass in low Earth orbit (IMLEO) of delaying departure from Mars and Earth by 5, 15, and 30 days, once a nominal mission to Mars has been selected. Additionally, the use of a deep-space maneuver (DSM) is considered in order to alleviate the IMLEO penalties. Three different classes of missions are analyzed, using chemical and nuclear thermal propulsion systems in the 2000-2025 time frame: opposition, conjunction, and fast-transfer conjunction. The results indicate that Mars and Earth delays can lead to large IMLEO penalties. Opposition and fast-transfer conjunction-class missions have the highest IMLEO penalties, upwards of 432.4 and 1977.3 metric tons (mt), respectively. Conjunction-class missions, on the other hand, tend to be insensitive to Mars and Earth delays, having IMLEO penalties under 103.5 mt. As expected, nuclear thermal propulsion had significantly lower IMLEO penalties than chemical propulsion. The use of a DSM does not significantly reduce the penalties. The results of this study can enable mission designers to incorporate the influence of off-nominal departure conditions of the interplanetary trajectory in the overall conceptual design of a Mars transfer vehicle.

Earthquakes drive large-scale submarine canyon development and sediment supply to deep-ocean basins.

PubMed

Mountjoy, Joshu J; Howarth, Jamie D; Orpin, Alan R; Barnes, Philip M; Bowden, David A; Rowden, Ashley A; Schimel, Alexandre C G; Holden, Caroline; Horgan, Huw J; Nodder, Scott D; Patton, Jason R; Lamarche, Geoffroy; Gerstenberger, Matthew; Micallef, Aaron; Pallentin, Arne; Kane, Tim

2018-03-01

Although the global flux of sediment and carbon from land to the coastal ocean is well known, the volume of material that reaches the deep ocean-the ultimate sink-and the mechanisms by which it is transferred are poorly documented. Using a globally unique data set of repeat seafloor measurements and samples, we show that the moment magnitude ( M w ) 7.8 November 2016 Kaikōura earthquake (New Zealand) triggered widespread landslides in a submarine canyon, causing a powerful "canyon flushing" event and turbidity current that traveled >680 km along one of the world's longest deep-sea channels. These observations provide the first quantification of seafloor landscape change and large-scale sediment transport associated with an earthquake-triggered full canyon flushing event. The calculated interevent time of ~140 years indicates a canyon incision rate of 40 mm year -1 , substantially higher than that of most terrestrial rivers, while synchronously transferring large volumes of sediment [850 metric megatons (Mt)] and organic carbon (7 Mt) to the deep ocean. These observations demonstrate that earthquake-triggered canyon flushing is a primary driver of submarine canyon development and material transfer from active continental margins to the deep ocean.

Earthquakes drive large-scale submarine canyon development and sediment supply to deep-ocean basins

PubMed Central

Mountjoy, Joshu J.; Howarth, Jamie D.; Orpin, Alan R.; Barnes, Philip M.; Bowden, David A.; Rowden, Ashley A.; Schimel, Alexandre C. G.; Holden, Caroline; Horgan, Huw J.; Nodder, Scott D.; Patton, Jason R.; Lamarche, Geoffroy; Gerstenberger, Matthew; Micallef, Aaron; Pallentin, Arne; Kane, Tim

2018-01-01

Although the global flux of sediment and carbon from land to the coastal ocean is well known, the volume of material that reaches the deep ocean—the ultimate sink—and the mechanisms by which it is transferred are poorly documented. Using a globally unique data set of repeat seafloor measurements and samples, we show that the moment magnitude (Mw) 7.8 November 2016 Kaikōura earthquake (New Zealand) triggered widespread landslides in a submarine canyon, causing a powerful “canyon flushing” event and turbidity current that traveled >680 km along one of the world’s longest deep-sea channels. These observations provide the first quantification of seafloor landscape change and large-scale sediment transport associated with an earthquake-triggered full canyon flushing event. The calculated interevent time of ~140 years indicates a canyon incision rate of 40 mm year−1, substantially higher than that of most terrestrial rivers, while synchronously transferring large volumes of sediment [850 metric megatons (Mt)] and organic carbon (7 Mt) to the deep ocean. These observations demonstrate that earthquake-triggered canyon flushing is a primary driver of submarine canyon development and material transfer from active continental margins to the deep ocean. PMID:29546245

Electropermanent magnet actuation for droplet ferromicrofluidics

PubMed Central

Padovani, José I.; Jeffrey, Stefanie S.; Howe, Roger T.

2016-01-01

Droplet actuation is an essential mechanism for droplet-based microfluidic systems. On-demand electromagnetic actuation is used in a ferrofluid-based microfluidic system for water droplet displacement. Electropermanent magnets (EPMs) are used to induce 50 mT magnetic fields in a ferrofluid filled microchannel with gradients up to 6.4 × 104 kA/m2. Short 50 µs current pulses activate the electropermanent magnets and generate negative magnetophoretic forces that range from 10 to 70 nN on 40 to 80 µm water-in-ferrofluid droplets. Maximum droplet displacement velocities of up to 300 µm/s are obtained under flow and no-flow conditions. Electropermanent magnet-activated droplet sorting under continuous flow is demonstrated using a split-junction microfluidic design. PMID:27583301

An Undergraduate Summer Research Program Through A University-Community College Partnership: Design and Results

NASA Astrophysics Data System (ADS)

Hood, Carol E.; Hood, Michael; Woodney, Laura

2016-06-01

We present a model for an undergraduate summer research program in astronomy targeted at 2-year and 4-year students and the short-term success of student participants. California State University San Bernardino (CSUSB) is Hispanic Serving Institution (HSI) serving 16,000 students, with no dominant ethnic or racial majority. Most (80%) CSUSB students are first-generation college students, and many of the students - both minority and “majority” - are economically disadvantaged and cannot afford to take on research projects without compensation. Approximately 60 percent of our students transfer from two year colleges, and all of the local community colleges are also officially designated as minority serving institutions. Mt. San Antonio College (Mt. SAC) is the largest single-campus community college in the state of California. It serves a student population of approximately 60,000 students (~35,000 full-time equivalent), also with no dominant ethnic or racial majority. Mt. SAC is currently 5th in the state in transfer ranking into the CSU system.In an effort to involve students in research as early as possible, we selected 2 students from each campus to participate in a summer research program. This program taught students observational techniques, data reduction and analysis skills, and then allowed them to work on more complex faculty astronomical research projects. These students were not selected based on their grades, or specific courses completed, simply based on their essays expressing their interests in astronomy. Students were only required to have already completed at least 1 physics or astronomy class and typically would be classified as freshman or sophomores. This program ran for 2 summers, before funding ran out. By the end of each summer, students were able to run the state-of-the-art campus observatory, and many chose to continue working on their research projects into the school year. To date, 3 students were selected for further summer research programs at SETI, CIERA, UC-Irvine, and NASA centers JPL and Armstrong. An additional 3 students have obtained employment directly or indirectly related to the skills they developed in the program and 2 of the Mt. SAC students have transferred to 4-year institutions.

Magnetic skyrmions in confined geometries: Effect of the magnetic field and the disorder

NASA Astrophysics Data System (ADS)

Juge, Roméo; Je, Soong-Geun; de Souza Chaves, Dayane; Pizzini, Stefania; Buda-Prejbeanu, Liliana D.; Aballe, Lucia; Foerster, Michael; Locatelli, Andrea; Menteş, Tevfik Onur; Sala, Alessandro; Maccherozzi, Francesco; Dhesi, Sarnjeet S.; Auffret, Stéphane; Gautier, Eric; Gaudin, Gilles; Vogel, Jan; Boulle, Olivier

2018-06-01

We report on the effect of the lateral confinement and a perpendicular magnetic field on isolated room-temperature magnetic skyrmions in sputtered Pt/Co/MgO nanotracks and nanodots. We show that the skyrmions size can be easily tuned by playing on the lateral dimensions of the nanostructures and by using external magnetic field amplitudes of a few mT, which allow to reach sub-100 nm diameters. Our XMCD-PEEM observations also highlight the important role of the pinning on the skyrmions size and stability under an out-of-plane magnetic field. Micromagnetic simulations reveal that the effect of local pinning can be well accounted for by considering the thin film grain structure with local anisotropy variations and reproduce well the dependence of the skyrmion diameter on the magnetic field and the geometry.

Effect of electromagnetic fields on some biomechanical and biochemical properties of rat’s blood

NASA Astrophysics Data System (ADS)

Mohaseb, M. A.; Shahin, F. A.; Ali, F. M.; Baieth, H. A.

2017-06-01

In order to study the effect of electromagnetic fields (0.3 mT, 50 Hz) on some biomechanical and biochemical properties of rats’ blood, healthy thirty male albino rats of 150 ± 10 g were divided into three equal groups namely A, B1, B2. Group A used as a control group, group B1 was continuously exposed to a magnetic field of (0.3 mT, 50 Hz) for a period of 21 days for direct effect studies. Group B2 was continuously exposed to the same magnetic field for the same period of time, then was housed away from the magnetic field for a period of 45 days for delayed effects studies. After examination, the results indicated that the apparent viscosity and the consistency index increased significantly and very high significantly for groub B1 and B2 compared to control at P<0.05. Red blood cell counts (RBCs) membrane elasticity had significantly and very high significantly decreased for groups B1 and B2. Moreover, delayed effects studies indicated that there is deterioration in the bone marrow functions. These results are supported by the blood film image, where irregularities and deformations in the RBCs membranes had been occurred. We conclude that the cell membrane properties are highly affected by the extremely low frequency (ELF) magnetic fields, which proved to be biologically toxic.

Construction and Evaluation of Rodent-Specific rTMS Coils.

PubMed

Tang, Alexander D; Lowe, Andrea S; Garrett, Andrew R; Woodward, Robert; Bennett, William; Canty, Alison J; Garry, Michael I; Hinder, Mark R; Summers, Jeffery J; Gersner, Roman; Rotenberg, Alexander; Thickbroom, Gary; Walton, Joseph; Rodger, Jennifer

2016-01-01

Rodent models of transcranial magnetic stimulation (TMS) play a crucial role in aiding the understanding of the cellular and molecular mechanisms underlying TMS induced plasticity. Rodent-specific TMS have previously been used to deliver focal stimulation at the cost of stimulus intensity (12 mT). Here we describe two novel TMS coils designed to deliver repetitive TMS (rTMS) at greater stimulation intensities whilst maintaining spatial resolution. Two circular coils (8 mm outer diameter) were constructed with either an air or pure iron-core. Peak magnetic field strength for the air and iron-cores were 90 and 120 mT, respectively, with the iron-core coil exhibiting less focality. Coil temperature and magnetic field stability for the two coils undergoing rTMS, were similar at 1 Hz but varied at 10 Hz. Finite element modeling of 10 Hz rTMS with the iron-core in a simplified rat brain model suggests a peak electric field of 85 and 12.7 V/m, within the skull and the brain, respectively. Delivering 10 Hz rTMS to the motor cortex of anaesthetized rats with the iron-core coil significantly increased motor evoked potential amplitudes immediately after stimulation (n = 4). Our results suggest these novel coils generate modest magnetic and electric fields, capable of altering cortical excitability and provide an alternative method to investigate the mechanisms underlying rTMS-induced plasticity in an experimental setting.

Molecular MRI in the Earth's Magnetic Field Using Continuous Hyperpolarization of a Biomolecule in Water.

PubMed

Rovedo, Philipp; Knecht, Stephan; Bäumlisberger, Tim; Cremer, Anna Lena; Duckett, Simon B; Mewis, Ryan E; Green, Gary G R; Burns, Michael; Rayner, Peter J; Leibfritz, Dieter; Korvink, Jan G; Hennig, Jürgen; Pütz, Gerhard; von Elverfeldt, Dominik; Hövener, Jan-Bernd

2016-06-30

In this work, we illustrate a method to continuously hyperpolarize a biomolecule, nicotinamide, in water using parahydrogen and signal amplification by reversible exchange (SABRE). Building on the preparation procedure described recently by Truong et al. [ J. Phys. Chem. B , 2014 , 118 , 13882 - 13889 ], aqueous solutions of nicotinamide and an Ir-IMes catalyst were prepared for low-field NMR and MRI. The (1)H-polarization was continuously renewed and monitored by NMR experiments at 5.9 mT for more than 1000 s. The polarization achieved corresponds to that induced by a 46 T magnet (P = 1.6 × 10(-4)) or an enhancement of 10(4). The polarization persisted, although reduced, if cell culture medium (DPBS with Ca(2+) and Mg(2+)) or human cells (HL-60) were added, but was no longer observable after the addition of human blood. Using a portable MRI unit, fast (1)H-MRI was enabled by cycling the magnetic field between 5 mT and the Earth's field for hyperpolarization and imaging, respectively. A model describing the underlying spin physics was developed that revealed a polarization pattern depending on both contact time and magnetic field. Furthermore, the model predicts an opposite phase of the dihydrogen and substrate signal after one exchange, which is likely to result in the cancelation of some signal at low field.

Electronic structure and magnetic properties of Pr-Co intermetallics: ab initio FP-LAPW calculations and correlation with experiments

NASA Astrophysics Data System (ADS)

Bakkari, Karim; Fersi, Riadh; Kebir Hlil, El; Bessais, Lotfi; Thabet Mliki, Najeh

2018-03-01

First-principle calculations combining density functional theory and the full-potential linearized augmented plane wave (FP-LAPW) method are performed to investigate the electronic and magnetic structure of Pr2Co7 in its two polymorphic forms, (2:7 H) and (2:7 R), for the first time. This type of calculation was also performed for PrCo5 and PrCo2 intermetallics. We have computed the valence density of states separately for spin-up and spin-down states in order to investigate the electronic band structure. This is governed by the strong contribution of the partial DOS of 3d-Co bands compared to the partial DOS of the 4f-Pr bands. Such a high ferromagnetic state is discussed in terms of the strong spin polarization observed in the total DOS. The magnetic moments carried by the Co and Pr atoms located in several sites for all compounds are computed. These results mainly indicate that cobalt atoms make a dominant contribution to the magnetic moments. The notable difference in the atomic moments of Pr and Co atoms between different structural slabs is explained in terms of the magnetic characteristics of the PrCo2 and PrCo5 compounds and the local chemical environments of the Pr and Co atoms in different structural slabs of Pr2Co7. From spin-polarized calculations we have simulated the 3d and 4f band population to estimate the local magnetic moments. These results are in accordance with the magnetic moments calculated using the FP-LAPW method. In addition, the exchange interactions J ij are calculated and used as input for M(T) simulations. Involving the data obtained from the electronic structure calculations, the appropriate Padé Table is applied to simulate the magnetization M(T) and to estimate the mean-field Curie temperature. We report a fairly good agreement between the ab initio calculation of magnetization and Curie temperature with the experimental data.

Analysis, results and conclusion of magnetotelluric data acquired in northern Switzerland

NASA Astrophysics Data System (ADS)

Shah, Neeraj; Samrock, Friedemann; Grayver, Alexander; Saar, Martin O.

2017-04-01

In early 2016, a magnetotelluric (MT) survey of the Aargau region of northern Switzerland was performed in order to understand the potential of the magnetotelluric method to characterise the electrical resistivity properties of the subsurface in Switzerland, and more widely, in areas with high amounts of cultural electromagnetic (EM) noise. Subsurface electrical resisitivity properties are interesting as they can help identify underground aquifers or geothermal resources and possibly provide insight into the large-scale movement of fluid. The north of Switzerland is a challenging and representative environment, with significant EM infrastructure, including powerlines and numerous other sources of noise related to human activity and use of industrial equipment. Here, we present the results of the survey together with detailed analysis of the issues encountered and challenges faced when doing this survey. In particular, we concentrate on data quality issues in the raw time series, the impact of using a remote reference over single site processing and the distribution of transfer functions. The final set of transfer functions for the survey, which includes twelve successful sites, is shown to suffer from noise issues in certain frequency ranges. A 1-D inversion of SSQ averaged transfer functions and comparison to existing borehole data demonstrates that geologic data is captured in the MT data recorded in northern Switzerland. Further, 2-D forward modelling supports the idea that good geologic information exists in the data despite the noise issues, which for now, impede a robust multi-dimensional inversion. Finally, suggestions for future work and methods to improve the quality of data when surveying in high EM noise environments are offered with a view to being able to reliably perform MT surveys closer to urban environments.

Structural investigation of cellobiose dehydrogenase IIA: Insights from small angle scattering into intra- and intermolecular electron transfer mechanisms

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bodenheimer, Annette M.; O'Dell, William B.; Oliver, Ryan C.

Background: Cellobiose dehydrogenases have gained interest due to their potential applications in sectors from biofuel production to biomedical devices. The CDHIIA variant is comprised of a cytochrome domain (CYT), a dehydrogenase domain (DH), and a carbohydrate-binding module (CBM) that are connected by two flexible linkers. Upon cellobiose oxidation at the DH, intramolecular electron transfer (IaET) occurs from the DH to the CYT. In vivo, CDHIIA CYT subsequently performs intermolecular electron transfer (IeET) to a lytic polysaccharide monooxygenase (LPMO). The relevant solution-state CDH domain conformations for IaET and IeET have not been fully characterized.Methods: Small-angle X-ray and neutron scattering measurements ofmore » oxidized CDHIIA from Myriococcum thermophilum and Neurospora crassa were performed to investigate the structural landscape explored in solution by MtCDHIIA and NcCDHIIA in response to cations, pH, and the presence of an electron acceptor, LPMO9D from N. crassa.Results: The scattering data complemented by modeling show that, under oxidizing conditions, MtCDHIIA undergoes global conformational rearrangement in the presence of Ca2+. Oxidized NcCDHIIA exhibits conformational changes upon pH variation and, in the presence of NcLPMO9D, primarily adopts a compact conformation.Conclusions: These results demonstrate different conformational responses of oxidized MtCDHIIA and NcCDHIIA to changes in environment. The results also reveal a shift in the oxidized NcCDHIIA conformational landscape toward interdomain compaction upon co-incubation with NcLPMO9D.General significance: The present study is the first report on the structural landscapes explored in solution by oxidized cellobiose dehydrogenases under various cation concentrations, pH conditions and in the presence of an electron-accepting LPMO.« less

Structural investigation of cellobiose dehydrogenase IIA: Insights from small angle scattering into intra- and intermolecular electron transfer mechanisms

DOE PAGES

Bodenheimer, Annette M.; O'Dell, William B.; Oliver, Ryan C.; ...

2018-01-31

Background: Cellobiose dehydrogenases have gained interest due to their potential applications in sectors from biofuel production to biomedical devices. The CDHIIA variant is comprised of a cytochrome domain (CYT), a dehydrogenase domain (DH), and a carbohydrate-binding module (CBM) that are connected by two flexible linkers. Upon cellobiose oxidation at the DH, intramolecular electron transfer (IaET) occurs from the DH to the CYT. In vivo, CDHIIA CYT subsequently performs intermolecular electron transfer (IeET) to a lytic polysaccharide monooxygenase (LPMO). The relevant solution-state CDH domain conformations for IaET and IeET have not been fully characterized.Methods: Small-angle X-ray and neutron scattering measurements ofmore » oxidized CDHIIA from Myriococcum thermophilum and Neurospora crassa were performed to investigate the structural landscape explored in solution by MtCDHIIA and NcCDHIIA in response to cations, pH, and the presence of an electron acceptor, LPMO9D from N. crassa.Results: The scattering data complemented by modeling show that, under oxidizing conditions, MtCDHIIA undergoes global conformational rearrangement in the presence of Ca2+. Oxidized NcCDHIIA exhibits conformational changes upon pH variation and, in the presence of NcLPMO9D, primarily adopts a compact conformation.Conclusions: These results demonstrate different conformational responses of oxidized MtCDHIIA and NcCDHIIA to changes in environment. The results also reveal a shift in the oxidized NcCDHIIA conformational landscape toward interdomain compaction upon co-incubation with NcLPMO9D.General significance: The present study is the first report on the structural landscapes explored in solution by oxidized cellobiose dehydrogenases under various cation concentrations, pH conditions and in the presence of an electron-accepting LPMO.« less

Composition-dependent properties and phase stability of Fe-Pd ferromagnetic shape memory alloys: A first-principles study

NASA Astrophysics Data System (ADS)

Li, Chun-Mei; Hu, Yan-Fei

2017-12-01

The composition-dependent properties and their correlation with the phase stability of Fe75+xPd25-x (- 10.0 ≤x ≤10.0 ) alloys are systematically investigated by using first-principles exact muffin-tin orbitals (EMTO)-coherent potential approximation (CPA) calculations. It is shown that the martensitic transformation (MT) from L 12 to body-centered-tetragonal (bct) occurs in the ordered alloys with about -5.0 ≤x ≤10.0 . In both the L 12 and bct phases, the evaluated a and c/a agree well with the available experimental data; the average magnetic moment per atom increases whereas the local magnetic moments of Fe atoms, dependent on both their positions and the structure of the alloy, decrease with increasing x. The tetragonal shear elastic constant of the L 12 phase ( C ' ) decreases whereas that of the bct phase (Cs) increases with x. The tetragonality of the martensite ( |1 -c /a | ) increases whereas its energy relative to the austenite with a negative value decreases with Fe addition. All these effects account for the increase of MT temperature (TM) with x. The MT from L 12 to bct is finally confirmed originating from the splitting of Fe 3d Eg and T2 g bands upon tetragonal distortion due to the Jahn-Teller effect.

OCCUPATIONAL EXPOSURE OF NMR SPECTROMETRISTS TO STATIC AND RADIOFREQUENCY FIELDS.

PubMed

Berlana, Tania; Úbeda, Alejandro

2017-12-01

Occupational exposure to static and radiofrequency fields emitted by nuclear magnetic resonance spectrometers was assessed through systematic field metering during operation of 19 devices in nine research centers. Whereas no measurable levels of radiofrequency radiation were registered outside the spectrometers, significant exposure to static field was detected, with maximum values recorded at the user's hand (B = 683.00 mT) and head-thorax (B = 135.70 mT) during spectrometer manipulation. All values were well below the exposure limits set by the European standard for workers protection against the effects of acute field exposure only. As for potential effects of chronic exposure, waiting for more complete knowledge, adoption of technical and operational strategies for exposure minimizing is advisable. In this respect, the data revealed that compared with standard magnetic shielding, ultrashield technology allows a 20-65-fold reduction of the field strength received by the operator. © The Author 2017. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

[Magnetotherapy of initial manifestations of cerebrovascular disorders in hypertension].

PubMed

Miasnikov, I G

1992-01-01

The paper is concerned with the data on 147 subjects who underwent magnetotherapy with the unit "Magniter-AMT-01" applied to the cervical area. The main group included 102 subjects, 45 person served as control. The purpose of the work was to base the application of MT under inpatient and home conditions with the use of the above-indicated unit. In view of this fact, a study was made of cerebral hemo- and thermodynamics with the aid of rheoencephalography and encephaloradiothermography under the action of different modes of the functioning of the unit "Magniter-AMT-01" (pulse and variable magnet induction fields 12-15 mTl and 30-35 mTl). A method of measuring magnetosensitivity of patients depending on the temperature reaction of the brain to a single MT session was elaborated. The greatest clinical effect was attained with the use of pulse magnetic field 15 mTl. Magnetotherapy with the use of the unit "Magniter-AMT-01" provided good results under inpatient and home conditions. The magnetosensitive patients demonstrated the highest effect.

Juvenile Leigh syndrome, optic atrophy, ataxia, dystonia, and epilepsy due to T14487C mutation in the mtDNA-ND6 gene: a mitochondrial syndrome presenting from birth to adolescence.

PubMed

Leshinsky-Silver, Esther; Shuvalov, Ruslan; Inbar, Shani; Cohen, Sarit; Lev, Dorit; Lerman-Sagie, Tally

2011-04-01

An increasing number of reports describe mutations in mitochondrial DNA coding regions, especially in mitochondrial DNA- encoded nicotinamide adenine dinucleotide dehydrogenase subunit genes of the respiratory chain complex I, as causing early-onset Leigh syndrome. The authors report the molecular findings in a 24-year-old patient with juvenile-onset Leigh syndrome presenting with optic atrophy, ataxia dystonia, and epilepsy. A brain magnetic resonance imaging revealed bilateral basal ganglia and thalamic hypointensities, and a magnetic resonance spectroscopy revealed an increased lactate peak. The authors identified a T14487C change causing M63V substitution in the mitochondrial ND6 gene. The mutation was heteroplasmic in muscle and blood samples, with different mutation loads, and was absent in the patient's mother's urine and blood samples. They suggest that the T14487C mtDNA mutation should be analyzed in Leigh syndrome, presenting with optic atrophy, ataxia, dystonia, and epilepsy, regardless of age.

Remanent magnetic properties of unbrecciated eucrites

NASA Technical Reports Server (NTRS)

Cisowski, Stanley M.

1991-01-01

This study examines the remanent magnetic properties of five unbrecciated eucrites, ranging from the coarse-grained cumulate Moore County to the quenched melt rock ALH 81001 in order to assess the strength of the magnetic field associated with their parent body during their formation. Two of the meteorites are judged as unlikely to have preserved their primary thermal remanence because of large variations in subsample remanence intensity and direction (Ibitira), and lack of NRM resistance to AF and thermal demagnetization (PCA 82502). The lack of a strong (greater than 0.01 mT) magnetizing field during their cooling on the eucrite parent body is inferred from the low normalized NRM intensities for subsamples of ALH 81001 and Yamato 791195.

An abnormal periventricular magnetization transfer ratio gradient occurs early in multiple sclerosis.

PubMed

Brown, J William L; Pardini, Matteo; Brownlee, Wallace J; Fernando, Kryshani; Samson, Rebecca S; Prados Carrasco, Ferran; Ourselin, Sebastien; Gandini Wheeler-Kingshott, Claudia A M; Miller, David H; Chard, Declan T

2017-02-01

In established multiple sclerosis, tissue abnormality-as assessed using magnetization transfer ratio-increases close to the lateral ventricles. We aimed to determine whether or not (i) these changes are present from the earliest clinical stages of multiple sclerosis; (ii) they occur independent of white matter lesions; and (iii) they are associated with subsequent conversion to clinically definite multiple sclerosis and disability. Seventy-one subjects had MRI scanning a median of 4.6 months after a clinically isolated optic neuritis (49 females, mean age 33.5 years) and were followed up clinically 2 and 5 years later. Thirty-seven healthy controls (25 females, mean age 34.4 years) were also scanned. In normal-appearing white matter, magnetization transfer ratio gradients were measured 1-5 mm and 6-10 mm from the lateral ventricles. In control subjects, magnetization transfer ratio was highest adjacent to the ventricles and decreased with distance from them; in optic neuritis, normal-appearing white matter magnetization transfer ratio was lowest adjacent to the ventricles, increased over the first 5 mm, and then paralleled control values. The magnetization transfer ratio gradient over 1-5 mm differed significantly between the optic neuritis and control groups [+0.059 percentage units/mm (pu/mm) versus -0.033 pu/mm, P = 0.010], and was significantly steeper in those developing clinically definite multiple sclerosis within 2 years compared to those who did not (0.132 pu/mm versus 0.016 pu/mm, P = 0.020). In multivariate binary logistic regression the magnetization transfer ratio gradient was independently associated with the development of clinically definite multiple sclerosis within 2 years (magnetization transfer ratio gradient odds ratio 61.708, P = 0.023; presence of T 2 lesions odds ratio 8.500, P = 0.071). At 5 years, lesional measures overtook magnetization transfer ratio gradients as significant predictors of conversion to multiple sclerosis. The magnetization transfer ratio gradient was not significantly affected by the presence of brain lesions [T 2 lesions (P = 0.918), periventricular T 2 lesions (P = 0.580) or gadolinium-enhancing T 1 lesions (P = 0.724)]. The magnetization transfer ratio gradient also correlated with Expanded Disability Status Scale score 5 years later (Spearman r = 0.313, P = 0.027). An abnormal periventricular magnetization transfer ratio gradient occurs early in multiple sclerosis, is clinically relevant, and may arise from one or more mechanisms that are at least partly independent of lesion formation. © The Author (2016). Published by Oxford University Press on behalf of the Guarantors of Brain. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

An abnormal periventricular magnetization transfer ratio gradient occurs early in multiple sclerosis

PubMed Central

Brown, J William L; Pardini, Matteo; Brownlee, Wallace J; Fernando, Kryshani; Samson, Rebecca S; Prados Carrasco, Ferran; Ourselin, Sebastien; Gandini Wheeler-Kingshott, Claudia A M; Miller, David H; Chard, Declan T

2017-01-01

Abstract In established multiple sclerosis, tissue abnormality—as assessed using magnetization transfer ratio—increases close to the lateral ventricles. We aimed to determine whether or not (i) these changes are present from the earliest clinical stages of multiple sclerosis; (ii) they occur independent of white matter lesions; and (iii) they are associated with subsequent conversion to clinically definite multiple sclerosis and disability. Seventy-one subjects had MRI scanning a median of 4.6 months after a clinically isolated optic neuritis (49 females, mean age 33.5 years) and were followed up clinically 2 and 5 years later. Thirty-seven healthy controls (25 females, mean age 34.4 years) were also scanned. In normal-appearing white matter, magnetization transfer ratio gradients were measured 1–5 mm and 6–10 mm from the lateral ventricles. In control subjects, magnetization transfer ratio was highest adjacent to the ventricles and decreased with distance from them; in optic neuritis, normal-appearing white matter magnetization transfer ratio was lowest adjacent to the ventricles, increased over the first 5 mm, and then paralleled control values. The magnetization transfer ratio gradient over 1–5 mm differed significantly between the optic neuritis and control groups [+0.059 percentage units/mm (pu/mm) versus −0.033 pu/mm, P = 0.010], and was significantly steeper in those developing clinically definite multiple sclerosis within 2 years compared to those who did not (0.132 pu/mm versus 0.016 pu/mm, P = 0.020). In multivariate binary logistic regression the magnetization transfer ratio gradient was independently associated with the development of clinically definite multiple sclerosis within 2 years (magnetization transfer ratio gradient odds ratio 61.708, P = 0.023; presence of T2 lesions odds ratio 8.500, P = 0.071). At 5 years, lesional measures overtook magnetization transfer ratio gradients as significant predictors of conversion to multiple sclerosis. The magnetization transfer ratio gradient was not significantly affected by the presence of brain lesions [T2 lesions (P = 0.918), periventricular T2 lesions (P = 0.580) or gadolinium-enhancing T1 lesions (P = 0.724)]. The magnetization transfer ratio gradient also correlated with Expanded Disability Status Scale score 5 years later (Spearman r = 0.313, P = 0.027). An abnormal periventricular magnetization transfer ratio gradient occurs early in multiple sclerosis, is clinically relevant, and may arise from one or more mechanisms that are at least partly independent of lesion formation. PMID:28043954

Magnetization reversal in ferromagnetic thin films induced by spin-orbit interaction with Slonczewski-like spin transfer torque

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, Jia, E-mail: lijia@wipm.ac.cn

2014-10-07

We theoretically investigate the dynamics of magnetization in ferromagnetic thin films induced by spin-orbit interaction with Slonczewski-like spin transfer torque. We reproduce the experimental results of perpendicular magnetic anisotropy films by micromagnetic simulation. Due to the spin-orbit interaction, the magnetization can be switched by changing the direction of the current with the assistant of magnetic field. By increasing the current amplitude, wider range of switching events can be achieved. Time evolution of magnetization has provided us a clear view of the process, and explained the role of minimum external field. Slonczewski-like spin transfer torque modifies the magnetization when current ismore » present. The magnitude of the minimum external field is determined by the strength of the Slonczewski-like spin transfer torque. The investigations may provide potential applications in magnetic memories.« less

The role of metallothioneins, selenium and transfer to offspring in mercury detoxification in Franciscana dolphins (Pontoporia blainvillei).

PubMed

Romero, M B; Polizzi, P; Chiodi, L; Das, K; Gerpe, M

2016-08-15

The concentrations of mercury (Hg), selenium (Se) and metallothioneins (MT) were evaluated in fetuses, calves, juveniles and adults of the endangered coastal Franciscana dolphin (Pontoporia blainvillei) from Argentina. Mercury concentrations varied among analyzed tissues (liver, kidney, muscle and brain), with liver showing the higher concentrations in all specimens. An age-dependent accumulation was found in liver, kidney and brain. No significant relationship between Hg and MT concentrations was found for all tissues analyzed. Hepatic Hg molar concentrations were positively correlated with those of Se, indicating a great affinity between these two elements. Furthermore, dark granules of HgSe were observed in Kupffer cells in the liver by electron microscopy, suggesting the role of this macrophage in the detoxification of Hg. A transfer of Hg through placenta was proved. The presence of Hg in brain in all age classes did not show concentrations associated with neurotoxicity. Copyright © 2016 Elsevier Ltd. All rights reserved.

Three-dimensional magnetotelluric imaging of the 1997 Kagoshima earthquake doublet, Southwest Japan

NASA Astrophysics Data System (ADS)

Asamori, K.; Makuuchi, A.; Umeda, K.

2013-12-01

The 1997 Kagoshima earthquake doublet struck on unrecognized active faults lacking clear surface expression where very few large earthquakes have occurred. Two shallow moderate earthquakes occurred in the northwestern part of Kagoshima province, on March 26 (Mw 6.1) and May 13 (Mw 6.0) in 1997, both followed by intensive aftershock sequences. Aftershock distribution of the 1997 earthquake doublet reflects complicated rupture process attributed to the geological (rheological) conditions and coupling of hydraulic pressure as well as tectonic shear stress. For advanced understanding of dynamic interactions between fluids and faulting, it is imperative to obtain three-dimensional (3-D) images of the electrical resistivity structure around the seismogenic faults. In this study, we conduct magnetotelluric (MT) soundings in and around the source region of the 1997 Kagoshima earthquake sequence and perform a 3-D inversion of wideband MT data above a depth of 30 km. MT stations were deployed around the aftershock area of the 1997 Kagoshima earthquake. All of 42 MT sites were set up in the land area. The data were collected using five component (three magnetic and two telluric components) wide-band MT instruments (Phoenix MTU-5 system) in February, 2013. The data were acquired in the frequency range from 0.000343 to 320 Hz. The recording duration ranged from 2 to 8 days. As the cultural noises severely affect the measurements, the time series analysis focused on the nocturnal data when there were fewer noise. A simultaneous remote reference measurement was carried out at the Sawauchi site (1300 km northeast of the study area). Using the remote reference technique (Gamble et al., 1979), we were able to reduce the unfavorable cultural noises. The observed apparent resistivity and phase data were inverted simultaneously using the 3-D inversion code of Sasaki (2004). In this inversion, the 3-D blocks were set up in the crust and upper mantle. These block size in the horizontal and vertical directions were 2-6 km and 0.9-20 km, respectively. The obtained 3-D resistivity model acquired through the inversion shows as follows. (1) Two anomalous conductive bodies (< 30 ohm-m) are clearly visible in the upper and lower crust beneath the seismic source region, and seem to be combined and extend down to the uppermost mantle. (2) These conductive bodies are located just beside the two mainshocks in the upper crust. (3) These results suggest that the generation of two large earthquakes is not a pure mechanical process, but is closely related to heterogeneities in the material property and stress field due to the relatively effective transfer of fluids from the upper mantle.

Magnetic field enhanced electroluminescence in organic light emitting diodes based on electron donor-acceptor exciplex blends

NASA Astrophysics Data System (ADS)

Baniya, Sangita; Basel, Tek; Sun, Dali; McLaughlin, Ryan; Vardeny, Zeev Valy

2016-03-01

A useful process for light harvesting from injected electron-hole pairs in organic light emitting diodes (OLED) is the transfer from triplet excitons (T) to singlet excitons (S) via reverse intersystem crossing (RISC). This process adds a delayed electro-luminescence (EL) emission component that is known as thermally activated delayed fluorescence (TADF). We have studied electron donor (D)/acceptor(A) blends that form an exciplex manifold in which the energy difference, ΔEST between the lowest singlet (S1) and triplet (T1) levels is relatively small (<100 meV), and thus allows RISC at ambient temperature. We found that the EL emission in OLED based on the exciplex blend is enhanced up to 40% by applying a relatively weak magnetic field of 50 mT at ambient. Moreover the MEL response is activated with activation energy similar that of the EL emission. This suggests that the large magneto-EL originates from an additional spin-mixing channel between singlet and triplet states of the generated exciplexes, which is due to TADF. We will report on the MEL dependencies on the temperature, bias voltage, and D-A materials for optimum OLED performance. Supported by SAMSUNG Global Research Outreach (GRO) program, and also by the NSF-Material Science & Engineering Center (MRSEC) program at the University of Utah (DMR-1121252).

Chromatin immunoprecipitation in microfluidic droplets: towards fast and cheap analyses.

PubMed

Teste, Bruno; Champ, Jerome; Londono-Vallejo, Arturo; Descroix, Stéphanie; Malaquin, Laurent; Viovy, Jean-Louis; Draskovic, Irena; Mottet, Guillaume

2017-01-31

Genetic organization is governed by the interaction of DNA with histone proteins, and differential modifications of these proteins is a fundamental mechanism of gene regulation. Histone modifications are primarily studied through chromatin immunoprecipitation (ChIP) assays, however conventional ChIP procedures are time consuming, laborious and require a large number of cells. Here we report for the first time the development of ChIP in droplets based on a microfluidic platform combining nanoliter droplets, magnetic beads (MB) and magnetic tweezers (MT). The droplet approach enabled compartmentalization and improved mixing, while reducing the consumption of samples and reagents in an integrated workflow. Anti-histone antibodies grafted to MB were used as a solid support to capture and transfer the target chromatin from droplets to droplets in order to perform chromatin immunoprecipitation, washing, elution and purification of DNA. We designed a new ChIP protocol to investigate four different types of modified histones with known roles in gene activation or repression. We evaluated the performances of this new ChIP in droplet assay in comparison with conventional methods. The proposed technology dramatically reduces analytical time from a few days to 7 hours, simplifies the ChIP protocol and decreases the number of cells required by 100 fold while maintaining a high degree of sensitivity and specificity. Therefore this droplet-based ChIP assay represents a new, highly advantageous and convenient approach to epigenetic analyses.

Activation of the Human MT Complex by Motion in Depth Induced by a Moving Cast Shadow

PubMed Central

Katsuyama, Narumi; Usui, Nobuo; Taira, Masato

2016-01-01

A moving cast shadow is a powerful monocular depth cue for motion perception in depth. For example, when a cast shadow moves away from or toward an object in a two-dimensional plane, the object appears to move toward or away from the observer in depth, respectively, whereas the size and position of the object are constant. Although the cortical mechanisms underlying motion perception in depth by cast shadow are unknown, the human MT complex (hMT+) is likely involved in the process, as it is sensitive to motion in depth represented by binocular depth cues. In the present study, we examined this possibility by using a functional magnetic resonance imaging (fMRI) technique. First, we identified the cortical regions sensitive to the motion of a square in depth represented via binocular disparity. Consistent with previous studies, we observed significant activation in the bilateral hMT+, and defined functional regions of interest (ROIs) there. We then investigated the activity of the ROIs during observation of the following stimuli: 1) a central square that appeared to move back and forth via a moving cast shadow (mCS); 2) a segmented and scrambled cast shadow presented beside the square (sCS); and 3) no cast shadow (nCS). Participants perceived motion of the square in depth in the mCS condition only. The activity of the hMT+ was significantly higher in the mCS compared with the sCS and nCS conditions. Moreover, the hMT+ was activated equally in both hemispheres in the mCS condition, despite presentation of the cast shadow in the bottom-right quadrant of the stimulus. Perception of the square moving in depth across visual hemifields may be reflected in the bilateral activation of the hMT+. We concluded that the hMT+ is involved in motion perception in depth induced by moving cast shadow and by binocular disparity. PMID:27597999

Noninvasive amide proton transfer magnetic resonance imaging in evaluating the grading and cellularity of gliomas.

PubMed

Bai, Yan; Lin, Yusong; Zhang, Wei; Kong, Lingfei; Wang, Lifu; Zuo, Panli; Vallines, Ignacio; Schmitt, Benjamin; Tian, Jie; Song, Xiaolei; Zhou, Jinyuan; Wang, Meiyun

2017-01-24

Using noninvasive magnetic resonance imaging techniques to accurately evaluate the grading and cellularity of gliomas is beneficial for improving the patient outcomes. Amide proton transfer imaging is a noninvasive molecular magnetic resonance imaging technique based on chemical exchange saturation transfer mechanism that detects endogenous mobile proteins and peptides in biological tissues. Between August 2012 and November 2015, a total number of 44 patients with pathologically proven gliomas were included in this study. We compared the capability of amide proton transfer magnetic resonance imaging with that of noninvasive diffusion-weighted imaging and noninvasive 3-dimensional pseudo-continuous arterial spin imaging in evaluating the grading and cellularity of gliomas. Our results reveal that amide proton transfer magnetic resonance imaging is a superior imaging technique to diffusion-weighted imaging and 3-dimensional pseudo-continuous arterial spin imaging in the grading of gliomas. In addition, our results showed that the Ki-67 index correlated better with the amide proton transfer-weighted signal intensity than with the apparent diffusion coefficient value or the cerebral blood flow value in the gliomas. Amide proton transfer magnetic resonance imaging is a promising method for predicting the grading and cellularity of gliomas.

Optical Orientation of Mn2+ Ions in GaAs in Weak Longitudinal Magnetic Fields

NASA Astrophysics Data System (ADS)

Akimov, I. A.; Dzhioev, R. I.; Korenev, V. L.; Kusrayev, Yu. G.; Sapega, V. F.; Yakovlev, D. R.; Bayer, M.

2011-04-01

We report on optical orientation of Mn2+ ions in bulk GaAs subject to weak longitudinal magnetic fields (B≤100mT). A manganese spin polarization of 25% is directly evaluated by using spin-flip Raman scattering. The dynamical Mn2+ polarization occurs due to the s-d exchange interaction with optically oriented conduction band electrons. Time-resolved photoluminescence reveals a nontrivial electron spin dynamics, where the oriented Mn2+ ions tend to stabilize the electron spins.

New Methods of Low-Field Magnetic Resonance Imaging for Application to Traumatic Brain Injury

DTIC Science & Technology

2013-02-01

magnet based ), the development of novel high-speed parallel imaging detection systems, and work on advanced adaptive reconstruction methods ...signal many times within the acquisition time . We present here a new method for 3D OMRI based on b-SSFP at a constant field of 6.5 mT that provides up...developing injury-sensitive MRI based on the detection of free radicals associat- ed with injury using the Overhauser effect and subsequently imaging that

MTpy: A Python toolbox for magnetotellurics

NASA Astrophysics Data System (ADS)

Krieger, Lars; Peacock, Jared R.

2014-11-01

We present the software package MTpy that allows handling, processing, and imaging of magnetotelluric (MT) data sets. Written in Python, the code is open source, containing sub-packages and modules for various tasks within the standard MT data processing and handling scheme. Besides the independent definition of classes and functions, MTpy provides wrappers and convenience scripts to call standard external data processing and modelling software. In its current state, modules and functions of MTpy work on raw and pre-processed MT data. However, opposite to providing a static compilation of software, we prefer to introduce MTpy as a flexible software toolbox, whose contents can be combined and utilised according to the respective needs of the user. Just as the overall functionality of a mechanical toolbox can be extended by adding new tools, MTpy is a flexible framework, which will be dynamically extended in the future. Furthermore, it can help to unify and extend existing codes and algorithms within the (academic) MT community. In this paper, we introduce the structure and concept of MTpy. Additionally, we show some examples from an everyday work-flow of MT data processing: the generation of standard EDI data files from raw electric (E-) and magnetic flux density (B-) field time series as input, the conversion into MiniSEED data format, as well as the generation of a graphical data representation in the form of a Phase Tensor pseudosection.

Targeted transgenic overexpression of mitochondrial thymidine kinase (TK2) alters mitochondrial DNA (mtDNA) and mitochondrial polypeptide abundance: transgenic TK2, mtDNA, and antiretrovirals.

PubMed

Hosseini, Seyed H; Kohler, James J; Haase, Chad P; Tioleco, Nina; Stuart, Tami; Keebaugh, Erin; Ludaway, Tomika; Russ, Rodney; Green, Elgin; Long, Robert; Wang, Liya; Eriksson, Staffan; Lewis, William

2007-03-01

Mitochondrial toxicity limits nucleoside reverse transcriptase inhibitors (NRTIs) for acquired immune deficiency syndrome. NRTI triphosphates, the active moieties, inhibit human immunodeficiency virus reverse transcriptase and eukaryotic mitochondrial DNA polymerase pol-gamma. NRTI phosphorylation seems to correlate with mitochondrial toxicity, but experimental evidence is lacking. Transgenic mice (TGs) with cardiac overexpression of thymidine kinase isoforms (mitochondrial TK2 and cytoplasmic TK1) were used to study NRTI mitochondrial toxicity. Echocardiography and nuclear magnetic resonance imaging defined cardiac performance and structure. TK gene copy and enzyme activity, mitochondrial (mt) DNA and polypeptide abundance, succinate dehydrogenase and cytochrome oxidase histochemistry, and electron microscopy correlated with transgenesis, mitochondrial structure, and biogenesis. Antiretroviral combinations simulated therapy. Untreated hTK1 or TK2 TGs exhibited normal left ventricle mass. In TK2 TGs, cardiac TK2 gene copy doubled, activity increased 300-fold, and mtDNA abundance doubled. Abundance of the 17-kd subunit of complex I, succinate dehydrogenase histochemical activity, and cristae density increased. NRTIs increased left ventricle mass 20% in TK2 TGs. TK activity increased 3 logs in hTK1 TGs, but no cardiac phenotype resulted. NRTIs abrogated functional effects of transgenically increased TK2 activity but had no effect on TK2 mtDNA abundance. Thus, NRTI mitochondrial phosphorylation by TK2 is integral to clinical NRTI mitochondrial toxicity.

Vestibular Activation Differentially Modulates Human Early Visual Cortex and V5/MT Excitability and Response Entropy

PubMed Central

Guzman-Lopez, Jessica; Arshad, Qadeer; Schultz, Simon R; Walsh, Vincent; Yousif, Nada

2013-01-01

Head movement imposes the additional burdens on the visual system of maintaining visual acuity and determining the origin of retinal image motion (i.e., self-motion vs. object-motion). Although maintaining visual acuity during self-motion is effected by minimizing retinal slip via the brainstem vestibular-ocular reflex, higher order visuovestibular mechanisms also contribute. Disambiguating self-motion versus object-motion also invokes higher order mechanisms, and a cortical visuovestibular reciprocal antagonism is propounded. Hence, one prediction is of a vestibular modulation of visual cortical excitability and indirect measures have variously suggested none, focal or global effects of activation or suppression in human visual cortex. Using transcranial magnetic stimulation-induced phosphenes to probe cortical excitability, we observed decreased V5/MT excitability versus increased early visual cortex (EVC) excitability, during vestibular activation. In order to exclude nonspecific effects (e.g., arousal) on cortical excitability, response specificity was assessed using information theory, specifically response entropy. Vestibular activation significantly modulated phosphene response entropy for V5/MT but not EVC, implying a specific vestibular effect on V5/MT responses. This is the first demonstration that vestibular activation modulates human visual cortex excitability. Furthermore, using information theory, not previously used in phosphene response analysis, we could distinguish between a specific vestibular modulation of V5/MT excitability from a nonspecific effect at EVC. PMID:22291031

Interpreting the Effects of Pulse Remagnetization on Animal Behavior

NASA Astrophysics Data System (ADS)

Kirschvink, J. L.; Wang, C. X.; Golash, H. N.; Hilburn, I. A.; Wu, D. A.; Crucilla, S. J.; Badal, Y. D.; Shimojo, S.

2017-12-01

Observations of geomagnetic sensitivity by migratory and homing animals have puzzled biophysicists for over 70 years. Widely dismissed as biophysically implausible due to the lack of physiological ferromagnetic materials [e.g., D.R. Griffin, 1944, 1952], clear and reproducible responses to earth-strength magnetic fields is now firmly established in organisms ranging from Bacteria, Protists, and Animals from numerous phyla, including mollusks, arthropods, and the chordates. Behavior demands sensory transduction, as external stimuli only `get into the nervous system' through sensory cells specialized to transduce the physical stimulus into a modulated stream of action potentials in neurons. Three basic biophysical mechanisms could plausibly explain the biophysical transduction of geomagnetic cues, including electrical induction, hyperfine magnetic field effects on photo-activated free radicals (the `Quantum Compass'), or receptor cells containing biologically-precipitated crystals of a ferromagnetic mineral like magnetite (Fe3O4). The definitive test of a ferromagnetic receptor is the pulse-remagnetization experiment, in which you apply a brief, unidirectional magnetic pulse of about 1 mS in duration, configured to exceed the coercive force of the SD particles and reverse the orientation of the magnetic moment wrt to the crystal axis (typically, a pulse few tens of mT is adequate). A pulse configured in this fashion can be well below the dB/dt level needed to fire a sensory nerve through the induced electric fields. The pulse produces a permanent flip in magnetization direction, the same way information is coded on magnetic tape. Magnetotactic bacteria, exposed to such a pulse, reverse their magnetic swimming directions passively. There are now over 16 peer-reviewed papers in which this experiment has been applied to animals, including birds, all of which show clear and long-lasting effects of the pulse. Such a pulse would have no lasting effect on a quantum compass. Initial experiments with a magnetic pulse of 70 mT on a large primate show a clear effect, although the results are … complex!

Microfluidic active mixers employing ultra-high aspect-ratio rare-earth magnetic nano-composite polymer artificial cilia

NASA Astrophysics Data System (ADS)

Rahbar, Mona; Shannon, Lesley; Gray, Bonnie L.

2014-02-01

We present a new micromixer based on highly magnetic, flexible, high aspect-ratio, artificial cilia that are fabricated as individual micromixer elements or in arrays for improved mixing performance. These new cilia enable high efficiency, fast mixing in a microchamber, and are controlled by small electromagnetic fields. The artificial cilia are fabricated using a new micromolding process for nano-composite polymers. Cilia fibers with aspect-ratios as high as 8:0.13 demonstrate the fabrication technique's capability in creating ultra-high aspect-ratio microstructures. Cilia, which are realized in polydimethylsiloxane doped with rare-earth magnetic powder, are magnetized to produce permanent magnetic structures with bidirectional deflection capabilities, making them highly suitable as mixers controlled by electromagnetic fields. Due to the high magnetization level of the polarized nano-composite polymer, we are able to use miniature electromagnets providing relatively small magnetic fields of 1.1 to 7 mT to actuate the cilia microstructures over a very wide motion range. Mixing performances of a single cilium, as well as different arrays of multiple cilia ranging from 2 to 8 per reaction chamber, are characterized and compared with passive diffusion mixing performance. The mixer cilia are actuated at different amplitudes and frequencies to optimize mixing performance. We demonstrate that more than 85% of the total volume of the reaction chamber is fully mixed after 3.5 min using a single cilium mixer at 7 mT compared with only 20% of the total volume mixed with passive diffusion. The time to achieve over 85% mixing is further reduced to 70 s using an array of eight cilia microstructures. The novel microfabrication technique and use of rare-earth permanently-magnetizable nano-composite polymers in mixer applications has not been reported elsewhere by other researchers. We further demonstrate improved mixing over other cilia micromixers as enabled by the high aspect-ratio, high flexibility, and magnetic properties of our cilia micromixer elements.

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/m shows periodic variation with the greatest variability in the Bridge Creek Member. Preliminary spectral analysis of each data set indicates a dominant cyclicity that is of considerably lower frequency than the limestone/shale couplets characteristic of Greenhorn Limestone.

Comparison of cardiac and 60 Hz magnetically induced electric fields measured in anesthetized rats

DOE Office of Scientific and Technical Information (OSTI.GOV)

Miller, D.L.; Creim, J.A.

1997-06-01

Extremely low frequency magnetic fields interact with an animal by inducing internal electric fields, which are in addition to the normal endogenous fields present in living animals. Male rats weighing about 560 g each were anesthetized with ketamine and xylazine. Small incisions were made in the ventral body wall at the chest and upper abdomen to position a miniature probe for measuring internal electric fields. The calibration constant for the probe size was 5.7 mm, with a flat response from at least 12 Hz to 20 kHz. A cardiac signal, similar to the normal electrocardiogram with a heart rate ofmore » about 250 bpm, was readily obtained at the chest. Upon analysis of its spectrum, the cardiac field detected by the probe had a broad maximum at 32--95 Hz. When the rates were exposed to a 1 mT, 60 Hz magnetic field, a spike appeared in the spectrum at 60 Hz. The peak-to-peak magnitudes of electric fields associated with normal heart function were comparable to fields induced by a 1 mT magnetic field at 60 Hz for those positions measured on the body surface. Within the body, or in different directions relative to the applied field, the induced fields were reduced. The cardiac field increased near the heart, becoming much larger than the induced field. Thus, the cardiac electric field, together with the other endogenous fields, combine with induced electric fields and help to provide reference levels for the induced-field dosimetry of ELF magnetic field exposures of living animals.« less

A high-resolution combined scanning laser and widefield polarizing microscope for imaging at temperatures from 4 K to 300 K.

PubMed

Lange, M; Guénon, S; Lever, F; Kleiner, R; Koelle, D

2017-12-01

Polarized light microscopy, as a contrast-enhancing technique for optically anisotropic materials, is a method well suited for the investigation of a wide variety of effects in solid-state physics, as, for example, birefringence in crystals or the magneto-optical Kerr effect (MOKE). We present a microscopy setup that combines a widefield microscope and a confocal scanning laser microscope with polarization-sensitive detectors. By using a high numerical aperture objective, a spatial resolution of about 240 nm at a wavelength of 405 nm is achieved. The sample is mounted on a 4 He continuous flow cryostat providing a temperature range between 4 K and 300 K, and electromagnets are used to apply magnetic fields of up to 800 mT with variable in-plane orientation and 20 mT with out-of-plane orientation. Typical applications of the polarizing microscope are the imaging of the in-plane and out-of-plane magnetization via the longitudinal and polar MOKE, imaging of magnetic flux structures in superconductors covered with a magneto-optical indicator film via the Faraday effect, or imaging of structural features, such as twin-walls in tetragonal SrTiO 3 . The scanning laser microscope furthermore offers the possibility to gain local information on electric transport properties of a sample by detecting the beam-induced voltage change across a current-biased sample. This combination of magnetic, structural, and electric imaging capabilities makes the microscope a viable tool for research in the fields of oxide electronics, spintronics, magnetism, and superconductivity.

A high-resolution combined scanning laser and widefield polarizing microscope for imaging at temperatures from 4 K to 300 K

NASA Astrophysics Data System (ADS)

Lange, M.; Guénon, S.; Lever, F.; Kleiner, R.; Koelle, D.

2017-12-01

Polarized light microscopy, as a contrast-enhancing technique for optically anisotropic materials, is a method well suited for the investigation of a wide variety of effects in solid-state physics, as, for example, birefringence in crystals or the magneto-optical Kerr effect (MOKE). We present a microscopy setup that combines a widefield microscope and a confocal scanning laser microscope with polarization-sensitive detectors. By using a high numerical aperture objective, a spatial resolution of about 240 nm at a wavelength of 405 nm is achieved. The sample is mounted on a 4He continuous flow cryostat providing a temperature range between 4 K and 300 K, and electromagnets are used to apply magnetic fields of up to 800 mT with variable in-plane orientation and 20 mT with out-of-plane orientation. Typical applications of the polarizing microscope are the imaging of the in-plane and out-of-plane magnetization via the longitudinal and polar MOKE, imaging of magnetic flux structures in superconductors covered with a magneto-optical indicator film via the Faraday effect, or imaging of structural features, such as twin-walls in tetragonal SrTiO3. The scanning laser microscope furthermore offers the possibility to gain local information on electric transport properties of a sample by detecting the beam-induced voltage change across a current-biased sample. This combination of magnetic, structural, and electric imaging capabilities makes the microscope a viable tool for research in the fields of oxide electronics, spintronics, magnetism, and superconductivity.

Fully automated two-step assay for detection of metallothionein through magnetic isolation using functionalized γ-Fe2O3 particles.

PubMed

Merlos Rodrigo, Miguel Angel; Krejcova, Ludmila; Kudr, Jiri; Cernei, Natalia; Kopel, Pavel; Richtera, Lukas; Moulick, Amitava; Hynek, David; Adam, Vojtech; Stiborova, Marie; Eckschlager, Tomas; Heger, Zbynek; Zitka, Ondrej

2016-12-15

Metallothioneins (MTs) are involved in heavy metal detoxification in a wide range of living organisms. Currently, it is well known that MTs play substantial role in many pathophysiological processes, including carcinogenesis, and they can serve as diagnostic biomarkers. In order to increase the applicability of MT in cancer diagnostics, an easy-to-use and rapid method for its detection is required. Hence, the aim of this study was to develop a fully automated and high-throughput assay for the estimation of MT levels. Here, we report the optimal conditions for the isolation of MTs from rabbit liver and their characterization using MALDI-TOF MS. In addition, we described a two-step assay, which started with an isolation of the protein using functionalized paramagnetic particles and finished with their electrochemical analysis. The designed easy-to-use, cost-effective, error-free and fully automated procedure for the isolation of MT coupled with a simple analytical detection method can provide a prototype for the construction of a diagnostic instrument, which would be appropriate for the monitoring of carcinogenesis or MT-related chemoresistance of tumors. Copyright © 2016 Elsevier B.V. All rights reserved.

Fast macromolecular proton fraction mapping of the human liver in vivo for quantitative assessment of hepatic fibrosis

PubMed Central

Yarnykh, Vasily L.; Tartaglione, Erica V.; Ioannou, George N.

2015-01-01

Macromolecular proton fraction (MPF) is a quantitative MRI parameter determining the magnetization transfer (MT) effect in tissues and defined as a relative amount of immobile macromolecular protons involved into magnetization exchange with mobile water protons. MPF has a potential for quantitative assessment of fibrous tissue due to intrinsically high MPF specific for collagen. The goal of this study was to investigate a relationship between histologically determined fibrosis stage and MPF in the liver parenchyma measured using a recently developed fast single-point clinically-targeted MPF mapping method. Optimal saturation parameters for single-point liver MPF measurements were determined from the analysis of liver Z-spectra in vivo based on the error propagation model. Sixteen patients with chronic hepatitis C viral infection underwent 3T MRI using an optimized liver MPF mapping protocol. Fourteen patients had prior liver biopsy with histologically staged fibrosis (METAVIR scores F0-F3), and two patients had clinically diagnosed cirrhosis (score F4 was assigned). The protocol included four breath-hold three-dimensional scans with 2×3×6 mm3 resolution and 10 transverse sections: 1) dynamic acquisition of MT-weighted and reference images; 2) dynamic acquisition of three images for variable flip angle T1 mapping; 3) dual-echo B0 map; and 4) actual flip-angle imaging B1 map. Average liver MPF was determined as the mode of MPF histograms. MPF was significantly increased in patients with clinically significant fibrosis (scores F2-F4, n=6) compared to patients with no or mild fibrosis (scores F0-F1, n=10): 6.49±0.36% vs. 5.94±0.26%, P<0.01 (Mann-Whitney test). MPF and fibrosis score were strongly positively correlated with the Spearman's rank correlation coefficient 0.80 (P<0.001). This study demonstrates the feasibility of fast MPF mapping of the human liver in vivo and confirms the hypothesis that MPF is increased in hepatic fibrosis and associated with fibrosis stage. MPF may be useful as a non-invasive imaging biomarker of hepatic fibrosis. PMID:26503401

Enhancing Mechanical and Thermal Properties of Epoxy Nanocomposites via Alignment of Magnetized SiC Whiskers.

PubMed

Townsend, James; Burtovyy, Ruslan; Aprelev, Pavel; Kornev, Konstantin G; Luzinov, Igor

2017-07-12

This research is focused on the fabrication and properties of epoxy nanocomposites containing magnetized SiC whiskers (MSiCWs). To this end, we report an original strategy for fabrication of magnetically active SiCWs by decorating the whiskers with magnetic (iron oxide) nanoparticles via polymer-polymer (poly(acrylic acid)/poly(2-vinyl pyridine)) complexation. The obtained whiskers demonstrated a substantial magnetic response in the polymerizing epoxy resin, with application of only a 20 mT (200 G) magnetic field. We also found that the whiskers chemically reacted with the epoxy resin, causing formation of an extended interphase near the boundary of the whiskers. The SiC whiskers oriented with the magnetic field demonstrated positive effects on the behavior of epoxy-based nanocomposites. Namely, the aligned MSiCWs enhanced the thermomechanical properties of the materials significantly above that of the neat epoxy and epoxy nanocomposite, with randomly oriented whiskers.

Protection of mice deficient in mature B cells from West Nile virus infection by passive and active immunization

PubMed Central

Draves, Kevin E.; Young, Lucy B.; Bryan, Marianne A.; Dresch, Christiane; Diamond, Michael S.; Gale, Michael

2017-01-01

B cell activating factor receptor (BAFFR)-/- mice have a profound reduction in mature B cells, but unlike μMT mice, they have normal numbers of newly formed, immature B cells. Using a West Nile virus (WNV) challenge model that requires antibodies (Abs) for protection, we found that unlike wild-type (WT) mice, BAFFR-/- mice were highly susceptible to WNV and succumbed to infection within 8 to 12 days after subcutaneous virus challenge. Although mature B cells were required to protect against lethal infection, infected BAFFR-/- mice had reduced WNV E-specific IgG responses and neutralizing Abs. Passive transfer of immune sera from previously infected WT mice rescued BAFFR-/- and fully B cell-deficient μMT mice, but unlike μMT mice that died around 30 days post-infection, BAFFR-/- mice survived, developed WNV-specific IgG Abs and overcame a second WNV challenge. Remarkably, protective immunity could be induced in mature B cell-deficient mice. Administration of a WNV E-anti-CD180 conjugate vaccine 30 days prior to WNV infection induced Ab responses that protected against lethal infection in BAFFR-/- mice but not in μMT mice. Thus, the immature B cells present in BAFFR-/- and not μMT mice contribute to protective antiviral immunity. A CD180-based vaccine may promote immunity in immunocompromised individuals. PMID:29176765

Complete mitochondrial genome and evolutionary analysis of Turritopsis dohrnii, the "immortal" jellyfish with a reversible life-cycle.

PubMed

Lisenkova, A A; Grigorenko, A P; Tyazhelova, T V; Andreeva, T V; Gusev, F E; Manakhov, A D; Goltsov, A Yu; Piraino, S; Miglietta, M P; Rogaev, E I

2017-02-01

Turritopsis dohrnii (Cnidaria, Hydrozoa, Hydroidolina, Anthoathecata) is the only known metazoan that is capable of reversing its life cycle via morph rejuvenation from the adult medusa stage to the juvenile polyp stage. Here, we present a complete mitochondrial (mt) genome sequence of T. dohrnii, which harbors genes for 13 proteins, two transfer RNAs, and two ribosomal RNAs. The T. dohrnii mt genome is characterized by typical features of species in the Hydroidolina subclass, such as a high A+T content (71.5%), reversed transcriptional orientation for the large rRNA subunit gene, and paucity of CGN codons. An incomplete complementary duplicate of the cox1 gene was found at the 5' end of the T. dohrnii mt chromosome, as were variable repeat regions flanking the chromosome. We identified species-specific variations (nad5, nad6, cob, and cox1 genes) and putative selective constraints (atp8, nad1, nad2, and nad5 genes) in the mt genes of T. dohrnii, and predicted alterations in tertiary structures of respiratory chain proteins (NADH4, NADH5, and COX1 proteins) of T. dohrnii. Based on comparative analyses of available hydrozoan mt genomes, we also determined the taxonomic relationships of T. dohrnii, recovering Filifera IV as a paraphyletic taxon, and assessed intraspecific diversity of various Hydrozoa species. Copyright © 2016 Elsevier Inc. All rights reserved.