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https://www.readbyqxmd.com/read/29144442/propagation-of-fibrillar-structural-forms-in-proteins-stopped-by-naturally-occurring-short-polypeptide-chain-fragments
#1
Irena Roterman, Mateusz Banach, Leszek Konieczny
Amyloids characterized by unbounded growth of fibrillar structures cause many pathological processes. Such unbounded propagation is due to the presence of a propagating hydrophobicity field around the fibril's main axis, preventing its closure (unlike in globular proteins). Interestingly, similar fragments, commonly referred to as solenoids, are present in many naturally occurring proteins, where their propagation is arrested by suitably located "stopper" fragments. In this work, we analyze the distribution of hydrophobicity in solenoids and in their corresponding "stoppers" from the point of view of the fuzzy oil drop model (called FOD in this paper)...
November 16, 2017: Pharmaceuticals
https://www.readbyqxmd.com/read/29136791/a-flow-injection-procedure-using-layered-double-hydroxide-for-on-line-pre-concentration-of-fluoride
#2
Diego P Rocha, Gabriel C Terra, Thaís S Nery, Jairo Tronto, Frederico G Pinto, Sidnei G Silva, Nívia M M Coelho
This work showed a flow system designed with solenoid valves for preconcentration of fluoride using SPADNS method in water samples. The analyte was preconcentrated in a mini-column coated with Layered Double Hydroxides (LDH) used as adsorbent. Then, the fluoride ions were eluted with 0.5molL(-1) sodium hydroxide and determined by spectrophotometry. The variables that affect the system such adsorbent mass, type of eluent, solutions flow rate, reagent concentration and pH effect were critically evaluated. Under optimized conditions, the detection limit, coefficient of variation, linear range and preconcentration factor were estimated at 15µgL(-1) (99...
February 1, 2018: Talanta
https://www.readbyqxmd.com/read/29118664/kinematic-dynamos-in-spheroidal-geometries
#3
D J Ivers
The kinematic dynamo problem is solved numerically for a spheroidal conducting fluid of possibly large aspect ratio with an insulating exterior. The solution method uses solenoidal representations of the magnetic field and the velocity by spheroidal toroidal and poloidal fields in a non-orthogonal coordinate system. Scaling of coordinates and fields to a spherical geometry leads to a modified form of the kinematic dynamo problem with a geometric anisotropic diffusion and an anisotropic current-free condition in the exterior, which is solved explicitly...
October 2017: Proceedings. Mathematical, Physical, and Engineering Sciences
https://www.readbyqxmd.com/read/29117519/high-tensile-strength-of-engineered-%C3%AE-solenoid-fibrils-via-sonication-and-pulling
#4
Zeyu Peng, Amanda S Parker, Maria D R Peralta, Krishnakumar M Ravikumar, Daniel L Cox, Michael D Toney
We present estimates of ultimate tensile strength (UTS) for two engineered β-solenoid protein mutant fibril structures (spruce budworm and Rhagium inquisitor antifreeze proteins) derived from sonication-based measurements and from force pulling molecular dynamics simulations, both in water. Sonication experiments generate limiting scissioned fibrils with a well-defined length-to-width correlation for the mutant spruce budworm protein and the resultant UTS estimate is 0.66 ± 0.08 GPa. For fibrils formed from engineered R...
November 7, 2017: Biophysical Journal
https://www.readbyqxmd.com/read/29116057/numerical-assessment-of-low-frequency-dosimetry-from-sampled-magnetic-fields
#5
Fabio Freschi, Luca Giaccone, Vincenzo Cirimele, Aldo Canova
Low-frequency dosimetry is commonly assessed by evaluating the electric field in the human body using the scalar potential finite dif- ference method. This method is effective only when the sources of the magnetic field are completely known and the magnetic vector po- tential can be analytically computed. The aim of the paper is to present a rigorous method to characterize the source term when only the magnetic flux density is available at discrete points, e.g. in case of field measurements. The method is based on the solution of the discrete magnetic curl equation...
November 8, 2017: Physics in Medicine and Biology
https://www.readbyqxmd.com/read/29108586/exploiting-an-automated-microfluidic-hydrodynamic-sequential-injection-system-for-determination-of-phosphate
#6
Wanpen Khongpet, Somkid Pencharee, Chanida Puangpila, Supaporn Kradtap Hartwell, Somchai Lapanantnoppakhun, Jaroon Jakmunee
A microfluidic hydrodynamic sequential injection (μHSI) spectrophotometric system was designed and fabricated. The system was built by laser engraving a manifold pattern on an acrylic block and sealing with another flat acrylic plate to form a microfluidic channel platform. The platform was incorporated with small solenoid valves to obtain a portable setup for programmable control of the liquid flow into the channel according to the HSI principle. The system was demonstrated for the determination of phosphate using a molybdenum blue method...
January 15, 2018: Talanta
https://www.readbyqxmd.com/read/29064686/extraordinarily-stable-amyloid-fibrils-engineered-from-structurally-defined-%C3%AE-solenoid-proteins
#7
Zeyu Peng, Maria D R Peralta, Michael D Toney
The self-assembly of biological molecules into ordered nanostructures is an attractive method for fabricating novel nanomaterials. Nucleic acid-based nanostructures suffer from limitations to functionalization and stability. Alternatively, protein-based nanostructures have advantageous chemical properties, but design facility lags behind that of nucleic acids. Structurally defined fibrils engineered from β-solenoid proteins (BSPs) form under mild conditions [Peralta, M. D. R., et al. (2015) ACS Nano 9, 449-463] and are good candidates for novel nanomaterials because of the defined sequence-to-structure relationship and tunable properties...
November 3, 2017: Biochemistry
https://www.readbyqxmd.com/read/29060671/em-fields-comparison-between-planar-vs-solenoidal-%C3%AE-ms-coil-designs-for-nerve-stimulation
#8
Giorgio Bonmassar, Laleh Golestanirad
Micro-magnetic stimulation (μMS) is an emerging neurostimulation technology that promises to revolutionize the therapeutic stimulation of the human nervous system. μMS uses sub-millimeter sized coils that can be implemented in the central nervous system to elicit neuronal activation using magnetically induced electric currents. By their microscopic size, μMS coils can be acutely implanted in deep brain structures to deliver therapeutic stimulation with effects analogous to those achieved by state-of-the-art deep brain stimulation (DBS)...
July 2017: Conference Proceedings: Annual International Conference of the IEEE Engineering in Medicine and Biology Society
https://www.readbyqxmd.com/read/29059553/design-and-construction-of-a-quadruple-resonance-mas-nmr-probe-for-investigation-of-extensively-deuterated-biomolecules
#9
Kelsey A Collier, Suvrajit Sengupta, Catalina A Espinosa, John E Kelly, Jessica I Kelz, Rachel W Martin
Extensive deuteration is frequently used in solid-state NMR studies of biomolecules because it dramatically reduces both homonuclear ((1)H-(1)H) and heteronuclear ((1)H-(13)C and (1)H-(15)N) dipolar interactions. This approach greatly improves resolution, enables low-power rf decoupling, and facilitates (1)H-detected experiments even in rigid solids at moderate MAS rates. However, the resolution enhancement is obtained at some cost due the reduced abundance of protons available for polarization transfer. Although deuterium is a useful spin-1 NMR nucleus, in typical experiments the deuterons are not directly utilized because the available probes are usually triple-tuned to (1)H,(13)C and (15)N...
October 12, 2017: Journal of Magnetic Resonance
https://www.readbyqxmd.com/read/29054801/why-do-antifreeze-proteins-require-a-solenoid
#10
M Banach, L Konieczny, I Roterman
Proteins whose presence prevents water from freezing in living organisms at temperatures below 0 °C are referred to as antifreeze proteins. This group includes molecules of varying size (from 30 to over 300 aa) and variable secondary/supersecondary conformation. Some of these proteins also contain peculiar structural motifs called solenoids. We have applied the fuzzy oil drop model in the analysis of four categories of antifreeze proteins: 1 - very small proteins, i.e. helical peptides (below 40 aa); 2 - small globular proteins (40-100 aa); 3 - large globular proteins (>100 aa) and 4 - proteins containing solenoids...
October 17, 2017: Biochimie
https://www.readbyqxmd.com/read/29049871/a-table-top-pxi-based-low-field-spectrometer-for-solution-dynamic-nuclear-polarization
#11
Joshua R Biller, Karl F Stupic, J Moreland
We present the development of a portable dynamic nuclear polarization (DNP) instrument based on the PCI eXtensions for Instrumentation (PXI) platform. The main purpose of the instrument is for study of (1) H polarization enhancements in solution through the Overhauser mechanism at low magnetic fields. A DNP probe set was constructed for use at 6.7 mT, using a modified Alderman-Grant (MAG) resonator at 241 MHz for saturation of the electron transition. The solenoid for detection of the enhanced (1) H signal at 288 kHz was constructed with Litz wire...
October 19, 2017: Magnetic Resonance in Chemistry: MRC
https://www.readbyqxmd.com/read/29049030/evidence-for-the-confinement-of-magnetic-monopoles-in-quantum-spin-ice
#12
P M Sarte, A A Aczel, G Ehlers, C Stock, B D Gaulin, C Mauws, M B Stone, S Calder, S E Nagler, J W Hollett, H D Zhou, J S Gardner, J P Attfield, C R Wiebe
Magnetic monopoles are hypothesised elementary particles connected by Dirac strings that behave like infinitely thin solenoids (Dirac 1931 Proc. R. Soc. A 133 60). Despite decades of searching, free magnetic monopoles and their Dirac strings have eluded experimental detection, although there is substantial evidence for deconfined magnetic monopole quasiparticles in spin ice materials (Castelnovo et al 2008 Nature 326 411). Here we report the detection of a hierarchy of unequally-spaced magnetic excitations via high resolution inelastic neutron spectroscopic measurements on the quantum spin ice candidate [Formula: see text] [Formula: see text] [Formula: see text]...
October 19, 2017: Journal of Physics. Condensed Matter: An Institute of Physics Journal
https://www.readbyqxmd.com/read/29041071/characterization-of-micron-size-hydrogen-clusters-using-mie-scattering
#13
S Jinno, H Tanaka, R Matsui, M Kanasaki, H Sakaki, M Kando, K Kondo, A Sugiyama, M Uesaka, Y Kishimoto, Y Fukuda
Hydrogen clusters with diameters of a few micrometer range, composed of 10(8-10) hydrogen molecules, have been produced for the first time in an expansion of supercooled, high-pressure hydrogen gas into a vacuum through a conical nozzle connected to a cryogenic pulsed solenoid valve. The size distribution of the clusters has been evaluated by measuring the angular distribution of laser light scattered from the clusters. The data were analyzed based on the Mie scattering theory combined with the Tikhonov regularization method including the instrumental functions, the validity of which was assessed by performing a calibration study using a reference target consisting of standard micro-particles with two different sizes...
August 7, 2017: Optics Express
https://www.readbyqxmd.com/read/29028543/a-pulse-programmable-parahydrogen-polarizer-using-a-tunable-electromagnet-and-dual-channel-nmr-spectrometer
#14
Aaron M Coffey, Roman V Shchepin, Bibo Feng, Raul D Colon, Ken Wilkens, Kevin W Waddell, Eduard Y Chekmenev
Applications of parahydrogen induced polarization (PHIP) often warrant conversion of the chemically-synthesized singlet-state spin order into net heteronuclear magnetization. In order to obtain optimal yields from the overall hyperpolarization process, catalytic hydrogenation must be tightly synchronized to subsequent radiofrequency (RF) transformations of spin order. Commercial NMR consoles are designed to synchronize applied waves on multiple channels and consequently are well-suited as controllers for these types of hyperpolarization experiments that require tight coordination of RF and non-RF events...
September 30, 2017: Journal of Magnetic Resonance
https://www.readbyqxmd.com/read/28991173/a-gas-chromatographic-system-for-the-detection-of-ethylene-gas-using-ambient-air-as-a-carrier-gas
#15
Nayyer Abbas Zaidi, Muhammad Waseem Tahir, Michael J Vellekoop, Walter Lang
Ethylene gas is a naturally occurring gas that has an influence on the shelf life of fruit during their transportation in cargo ships. An unintentional exposure of ethylene gas during transportation results in a loss of fruit. A gas chromatographic system is presented here for the detection of ethylene gas. The gas chromatographic system was assembled using a preconcentrator, a printed 3D printed gas chromatographic column, a humidity sensor, solenoid valves, and an electrochemical ethylene gas sensor. Ambient air was used as a carrier gas in the gas chromatographic system...
October 7, 2017: Sensors
https://www.readbyqxmd.com/read/28966476/a-persistent-mode-0-5-t-solid-nitrogen-cooled-mgb2-magnet-for-mri
#16
Jiayin Ling, John P Voccio, Seungyong Hahn, Timing Qu, Juan Bascuñán, Yukikazu Iwasa
This paper presents construction details and test results of a persistent-mode 0.5-T MgB2 magnet developed at the Francis Bitter Magnet Lab, MIT. The magnet, of 276-mm inner diameter and 290-mm outer diameter, consisted of a stack of 8 solenoidal coils with a total height of 460 mm. Each coil was wound with monofilament MgB2 wire, equipped with a persistent-current switch and terminated with a superconducting joint, forming an individual superconducting loop. Resistive solder joints connected the 8 coils in series...
February 2017: Superconductor Science & Technology
https://www.readbyqxmd.com/read/28964184/magnetic-field-homogeneity-of-a-conical-coaxial-coil-pair
#17
F J Salazar, F J Nieves, A Bayón, F Gascón
An analytical study of the magnetic field created by a double-conical conducting sheet is presented. The analysis is based on the expansion of the magnetic field in terms of Legendre polynomials. It is demonstrated analytically that the angle of the conical surface that produces a nearly homogeneous magnetic field coincides with that of a pair of loops that fulfills the Helmholtz condition. From the results obtained, we propose an electric circuit formed by pairs of isolated conducting loops tightly wound around a pair of conical surfaces, calculating numerically the magnetic field produced by this system and its heterogeneity...
September 2017: Review of Scientific Instruments
https://www.readbyqxmd.com/read/28946058/radiofrequency-fields-in-mas-solid-state-nmr-probes
#18
Zdeněk Tošner, Armin Purea, Jochem O Struppe, Sebastian Wegner, Frank Engelke, Steffen J Glaser, Bernd Reif
We present a detailed analysis of the radiofrequency (RF) field over full volume of a rotor that is generated in a solenoid coil. On top of the usually considered static distribution of amplitudes along the coil axis we describe dynamic radial RF inhomogeneities induced by sample rotation. During magic angle spinning (MAS), the mechanical rotation of the sample about the magic angle, a spin packet travels through areas of different RF fields and experiences periodical modulations of both the RF amplitude and the phase...
September 6, 2017: Journal of Magnetic Resonance
https://www.readbyqxmd.com/read/28945197/evidence-for-the-confinement-of-magnetic-monopoles-in-quantum-spin-ice
#19
Paul Maximo Sarte, Adam Aczel, Georg Ehlers, Christopher Stock, Bruce D Gaulin, Cole Mauws, Matthew B Stone, Stuart Calder, Stephen Nagler, Joshua Hollett, Haidong Zhou, Jason S Gardner, J Paul Attfield, Christopher R Wiebe
Magnetic monopoles are hypothesised elementary particles connected by Dirac strings that behave like infinitely thin solenoids [Dirac 1931 Proc. Roy. Soc. A 133 60]. Despite decades of searches, free magnetic monopoles and their Dirac strings have eluded experimental detection, although there is substantial evidence for deconfined magnetic monopole quasiparticles in spin ice materials [Castelnovo, Moessner & Sondhi 2008 Nature 326 411]. Here we report the detection of a hierarchy of unequally-spaced magnetic excitations via high resolution inelastic neutron spectroscopic measurements on the quantum spin ice candidate Pr<sub>2</sub>Sn<sub>2</sub>O<sub>7</sub>...
September 25, 2017: Journal of Physics. Condensed Matter: An Institute of Physics Journal
https://www.readbyqxmd.com/read/28934238/a-tool-to-automatically-analyze-electromagnetic-tracking-data-from-high-dose-rate-brachytherapy-of-breast-cancer-patients
#20
Th I Götz, G Lahmer, V Strnad, Ch Bert, B Hensel, A M Tomé, E W Lang
During High Dose Rate Brachytherapy (HDR-BT) the spatial position of the radiation source inside catheters implanted into a female breast is determined via electromagnetic tracking (EMT). Dwell positions and dwell times of the radiation source are established, relative to the patient's anatomy, from an initial X-ray-CT-image. During the irradiation treatment, catheter displacements can occur due to patient movements. The current study develops an automatic analysis tool of EMT data sets recorded with a solenoid sensor to assure concordance of the source movement with the treatment plan...
2017: PloS One
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