Image-guided Placement of Magnetic Neuroparticles as a Potential High-Resolution Brain-Machine Interface

We are developing methods of noninvasively delivering magnetic neuroparticles™ via intranasal administration followed by image-guided magnetic propulsion to selected locations in the brain. Once placed, the particles can activate neurons via vibrational motion or magnetoelectric stimulation. Similar particles might be used to read out neuronal electrical pulses via spintronic or liquid-crystal magnetic interactions, for fast bidirectional brain-machine interface. We have shown that particles containing liquid crystals can be read out with magnetic resonance imaging (MRI) using embedded magnetic nanoparticles and that the signal is visible even for voltages comparable to physiological characteristics. Such particles can be moved within the brain (e.g., across midline) without causing changes to neurological firing

The Prokaryotic Complex of Modern and Buried Soils on the Kamchatka Peninsula

A prokaryotic heterotrophic mesophilic community was studied in volcanic soil samples from Kamchatka. A phylogenetic and physiological characterization of the prokaryotic complex of modern and buried soils of the Kamchatka Peninsula is given. Volcanic Paleolithic soils (2500 and 11,300 years old) and their modern equivalents were investigated. It was found that the biomass of metabolically active prokaryotes in modern volcanic and Paleolithic soils reached 50 and 40 µg/g, respectively. The proportion of archaea in the metabolically active prokaryotic complex varied from 20% to 30% and increased in variants with the application of the nitrogen-containing biopolymer chitin. The application of the additional resource to paleovolcanic soils led to an incremental increase in the proportion of metabolically active prokaryotes, which reached 50% of the total prokaryotic biomass detected, indicating the high metabolic potential of the considered soils. Phylogenetic structure characteristics of the prokaryotic metabolically active component of modern and buried volcanic soil were established by molecular biology methods (metagenomic analysis, FISH method). The phylum Proteobacteria (74%), Acidobacteria, and Actinobacteria (14% combined) were dominant in modern soils; phylum Acidobacteria (51.8%) was dominant in paleosoils, whereas Chloroflexi (21%) and Proteobacteria (9%) were subdominant. It was determined that the potential activity of the microbial hydrolytic community, as measured by the relative response to the added resource (chitin), was found to increase in a series from modern to paleovolcanic soil. It was demonstrated that several key genes of the nitrogen cycle responsible for the processes of molecular nitrogen fixation, nitrification, and denitrification (nifH, amoA, nirK) were present in both modern and buried horizons

The Prokaryotic Complex of Modern and Buried Soils on the Kamchatka Peninsula

A prokaryotic heterotrophic mesophilic community was studied in volcanic soil samples from Kamchatka. A phylogenetic and physiological characterization of the prokaryotic complex of modern and buried soils of the Kamchatka Peninsula is given. Volcanic Paleolithic soils (2500 and 11,300 years old) and their modern equivalents were investigated. It was found that the biomass of metabolically active prokaryotes in modern volcanic and Paleolithic soils reached 50 and 40 µg/g, respectively. The proportion of archaea in the metabolically active prokaryotic complex varied from 20% to 30% and increased in variants with the application of the nitrogen-containing biopolymer chitin. The application of the additional resource to paleovolcanic soils led to an incremental increase in the proportion of metabolically active prokaryotes, which reached 50% of the total prokaryotic biomass detected, indicating the high metabolic potential of the considered soils. Phylogenetic structure characteristics of the prokaryotic metabolically active component of modern and buried volcanic soil were established by molecular biology methods (metagenomic analysis, FISH method). The phylum Proteobacteria (74%), Acidobacteria, and Actinobacteria (14% combined) were dominant in modern soils; phylum Acidobacteria (51.8%) was dominant in paleosoils, whereas Chloroflexi (21%) and Proteobacteria (9%) were subdominant. It was determined that the potential activity of the microbial hydrolytic community, as measured by the relative response to the added resource (chitin), was found to increase in a series from modern to paleovolcanic soil. It was demonstrated that several key genes of the nitrogen cycle responsible for the processes of molecular nitrogen fixation, nitrification, and denitrification (nifH, amoA, nirK) were present in both modern and buried horizons

Metabolically Active Prokaryotic Complex in Grassland and Forests’ Sod-Podzol under Polycyclic Aromatic Hydrocarbon Influence

Molecular genetic techniques (FISH, RT-PCR, and metagenomic analysis) were used to investigate the comparative functional biodiversity in the prokaryotic complex in grassland and forests’ sod-podzol under polycyclic aromatic hydrocarbon influence. The polluted samples showed a decrease in the biomass of the prokaryotic community representatives and a change in the metabolically active dominants–representatives of the Bacteria and Archaea domains compared to the control samples. The suppression of the metabolic activity of prokaryote cells under the influence of PAHs in sod-podzolic soil under meadow vegetation was more pronounced compared to soils under forest vegetation. The representatives of prokaryotes that are sensitive and resistant to the studied PAHs were identified. The representatives of the phylogenetic groups from the bacterial complex resistant to PAH pollution were Proteobacteria (Alphaproteobacteria), Bacteroidetes, Firmicutes, Chloroflexi, and Thaumarhaeota in the archaeal complex. Representatives of the phylum Acidobacteria and Actinobacteria (Streptosporangiales) are noted among those sensitive to PAH contamination. The presence and expression of the functional alkane monooxygenase (alkB) gene were established in all the experimental variants studied. In the plant variants, the number of copies of alkB genes increased by an order of magnitude and the biomass of metabolically active prokaryotic representatives with the functional alkB gene doubled compared to the unpolluted territories. The copy number index of the alkB gene can be used as one of the parameters when characterizing an ecosystem for the presence of PAH pollutants

Middle-infrared echelle cross-dispersion spectrometer ACS-MIR for the ExoMars Trace Gas Orbiter

International audienceThe middle-infrared (MIR) echelle spectrometer is one channel of the Atmospheric Chemistry Suite (ACS) package dedicated for the studies of the Martian atmosphere on board ExoMars Trace Gas Orbiter (TGO) planned for launch in 2016. The MIR channel of ACS is a cross-dispersion echelle instrument dedicated to solar occultation measurements in the range of 2.3–4.2 μm with the resolving power of ~50,000. MIR is dedicated to sensitive measurements of trace gases. The MIR channel consists of entry optics, an echelle spectrometer with a 140x250 mm grating and two-mirror collimator, two secondary steerable gratings, and a cryogenically cooled MCT detector array with proximity optics. The spectrometer operates in high orders of diffraction, allowing to acquire up to 17 orders at one detector frame, and to cover simultaneously ~300-nm spectral interval within the spectral range. The mechanism allows moving the secondary grating with a characteristic time of ~0.1 s. This concept is novel for space application. The instrument is a complete block with power and data interfaces, and the overall mass of 12 kg. The protoflight model of MIR is completed, integrated within the ACS suite, and is undergoing tests at the spacecraft. © (2015) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only

Electric-field responsive contrast agent based on liquid crystals and magnetic nanoparticles

The properties of liquid crystal-magnetic nanoparticle composites have potential for sensing in the body. We study the response of a liquid crystal-magnetic nanoparticle (LC-MNP) composite to applied potentials of hundreds of volts per meter. Measuring samples using X-ray diffraction (XRD) and imaging composites using magnetic resonance imaging (MRI), we demonstrate that electric potentials applied across centimeter scale LC-MNP composite samples can be detected using XRD and MRI techniques

Increasing the oscillation frequency of strong magnetic fields above 101 kHz significantly raises peripheral nerve excitation thresholds

Purpose: A time-varying magnetic field can cause unpleasant peripheral nerve stimulation (PNS) when the maximum excursion of the magnetic field (ΔB) is above a frequency-dependent threshold level [P. Mansfield and P. R. Harvey, Magn. Reson. Med. 29, 746–758 (1993)]. Clinical and research magnetic resonance imaging (MRI) gradient systems have been designed to avoid such bioeffects by adhering to regulations and guidelines established on the basis of clinical trials. Those trials, generally employing sinusoidal waveforms, tested human responses to magnetic fields at frequencies between 0.5 and 10 kHz [W. Irnich and F. Schmitt, Magn. Reson. Med. 33, 619–623 (1995), T. F. Budinger et al., J. Comput. Assist. Tomogr. 15, 909–914 (1991), and D. J. Schaefer et al., J. Magn. Reson. Imaging 12, 20–29 (2000)]. PNS thresholds for frequencies higher than 10 kHz had been extrapolated, using physiological models [J. P. Reilly et al., IEEE Trans. Biomed. Eng. BME-32(12), 1001–1011 (1985)]. The present study provides experimental data on human PNS thresholds to oscillating magnetic field stimulation from 2 to 183 kHz. Sinusoidal waveforms were employed for several reasons: (1) to facilitate comparison with earlier reports that used sine waves, (2) because prior designers of fast gradient hardware for generalized waveforms (e.g., including trapezoidal pulses) have employed quarter-sine-wave resonant circuits to reduce the rise- and fall-times of pulse waveforms, and (3) because sinusoids are often used in fast pulse sequences (e.g., spiral scans) [S. Nowak, U.S. patent 5,245,287 (14 September 1993) and K. F. King and D. J. Schaefer, J. Magn. Reson. Imaging 12, 164–170 (2000)]. Methods: An IRB-approved prospective clinical trial was performed, involving 26 adults, in which one wrist was exposed to decaying sinusoidal magnetic field pulses at frequencies from 2 to 183 kHz and amplitudes up to 0.4 T. Sham exposures (i.e., with no magnetic fields) were applied to all subjects. Results: For 0.4 T pulses at 2, 25, 59, 101, and 183 kHz, stimulation was reported by 22 (84.6%), 24 (92.3%), 15 (57.7%), 2 (7.7%), and 1 (3.8%) subjects, respectively. Conclusions: The probability of PNS due to brief biphasic time-varying sinusoidal magnetic fields with magnetic excursions up to 0.4 T is shown to decrease significantly at and above 101 kHz. This phenomenon may have particular uses in dynamic scenarios (e.g., cardiac imaging) and in studying processes with short decay times (e.g., electron paramagnetic resonance imaging, bone and solids imaging). The study suggests the possibility of new designs for human and preclinical MRI systems that may be useful in clinical practice and scientific research