Tens Of Μm Research Articles

Effect of pH and monovalent cations on the Raman spectrum of water: Basics revisited and application to measure concentration gradients at water/solid interface in Si3N4 biomaterial

The effect of hydrogen carbonate (HCO3−) and cations (Na+, K+) solvated in water were revisited according to high spectrally resolved Raman measurements. Water solutions with different bicarbonate concentrations or added with increasing amounts of monovalent cations were examined with respect to their Raman spectra both in the bulk state and at the solid/liquid interface with a silicon nitride (Si3N4) bioceramic. Spectroscopic calibrations confirmed that the Raman emission from OH-stretching in water is sensitive to molarity variations (in the order of tens of mM). The concentration gradient developed at the solid/liquid interface in cation-added solutions interacting with a Si3N4 surface was measured and found to be peculiar to individual cations. Local variation in pH was detected in ionic solutions interacting with Si3N4 samples, which might represent a useful property for Si3N4 in a number of biomedical applications.

Detection of uranium mill tailings settlement using satellite-based radar interferometry

The feasibility of monitoring erosion and settlement of earthen covers on uranium mill tailings impoundment was evaluated using synthetic aperture radar (SAR) coherence analysis, differential radar interferometry (DInSAR) and multi-temporal interferometry. A total of 13 ERS-1/-2 SAR images were acquired between August 22, 1996 and December 14, 2000 over two uranium mill tailings sites located in north-western New Mexico, USA. These SAR datasets were screened based on meteorological conditions at the time of acquisition, eliminating those acquired during (a) rain and thunderstorms, (b) mist or fog or, (c) during overcast conditions. Preliminary coherence analysis allowed us to better understand the dynamics of land disposal sites, to identify useful and relevant time domains and define the appropriate parameters for subsequent InSAR analyses. DInSAR allowed us to measure differential settlement of tens of mm over two 3 to 4month periods. The Small BAseline Subset (SBAS) technique identified spatial variations in the rate of settlement ranging from approximately1mm/yr to 10mm/yr. Although the extent of the analysis was limited by the availability of archived SAR data, the results demonstrated that monitoring using on-demand SAR data should yield reliable measurements of surface displacements earthen covers.

Soft X-ray angle-resolved photoemission with micro-positioning techniques for metallic V₂O₃.

Soft X-ray angle-resolved photoemission has been performed for metallic V2O3. By combining a microfocus beam (40 µm × 65 µm) and micro-positioning techniques with a long-working-distance microscope, it has been possible to observe band dispersions from tiny cleavage surfaces with a typical size of several tens of µm. The photoemission spectra show a clear position dependence, reflecting the morphology of the cleaved sample surface. By selecting high-quality flat regions on the sample surface, it has been possible to perform band mapping using both photon-energy and polar-angle dependences, opening the door to three-dimensional angle-resolved photoemission spectroscopy for typical three-dimensional correlated materials where large cleavage planes are rarely obtained.

High-Yield Synthesis of Helical Carbon Nanofibers Using Iron Oxide Fine Powder as a Catalyst

Carbon nanocoil (CNC), which is synthesized by a catalytic chemical vapor deposition (CCVD) method, has a coil diameter of 300–900 nm and a length of several tens of μm. Although it is very small, CNC is predicted to have a high mechanical strength and hence is expected to have a use in nanodevices such as electromagnetic wave absorbers and field emitters. For nanodevice applications, it is necessary to synthesize CNC in high yield and purity. In this study, we improved the conditions of catalytic layer formation and CCVD. Using optimized CVD conditions, a CNC layer with a thickness of >40 μm was grown from a SnO2/Fe2O3/SnO2 catalyst on a substrate, and its purity increased to 81% ± 2%.

Potassium Regulation of the NaK-ATPase Pump Currents in Mammalian Skeletal Muscle Fibers

Adult skeletal muscles express two Na,K-ATPase isoforms, α1 and α2. α2, the sole isoform expressed in the transverse tubules, comprises up to 90% of total Na,K-ATPase. α2 in resting muscle operates well below its maximum turnover rate; but is rapidly stimulated, by yet unknown mechanisms, during muscle contraction, helping maintaining excitation and resist fatigue. We tested the hypothesis that α2 activity may be regulated by extracellular K over the physiological range of K concentrations that occur in the t-tubules. Na,K-ATPase driven current (Ipump) was measured in enzymatically isolated FDB fibers voltage clamped at −90 mV using a two microlectrode amplifier. Ipump was identified as a ouabain- and temperature-sensitive outward current activated by Ko in fibers rendered electrically passive. Intracellular solutions (filling both electrodes) contained (mM): 1EGTA, 0.5CaCl2, 5MgCl2, 20MOPS, 5gluthathion-H2, 90K-asparte, and 5ATP-Na2, 5-phosphocreatine-Na2, and 30Na-aspartate to promote forward pump cycling. External solutions contained (mM): 2CaCl2, 1MgCl2, 10glucose, 10MOPS; and inversely varying amounts of KCl (0-40) and NaCL (154-114) to maintain osmolarity. TTX (400nM), nifedipine (20 μM), Ba (1mM) and 9-anthracene-carboxilic-acid (200μM) were added to block main ionic currents. All solutions had pH=7.4 and 300mOmal/kgH2O. Ipump was activated in a concentration-dependent manner by raising [K]o from 0 to 40mM, and eliminated by washing out K. Ipump was prevented by pretreatment with 10μM ouabain or inhibited by addition of ouabain, and was steeply temperature-dependent. Maximal Ipump vs. [K]o was fitted to obtain the Km for pump activation by K. Results demonstrate that α2 in skeletal muscle is regulated by changes in extracellular K over tens of mM, suggesting that this isoform is adapted to respond to expected demands of Na/K transport in the t-tubules during sustained activity. (Supported by the National institutes of Health, USA)

Simultaneous preparation of cellulose nanocrystals and micron-sized porous colloidal particles of cellulose by TEMPO-mediated oxidation

TEMPO-mediated oxidation of microgranular cellulose results in particles of three different length scales: cellulose nanocrystals as well as small (μm) and larger (tens of μm) porous particles with high charge density.

Application of the Ion Beam Graft Polymerization Method to the Thin Film Diagnosis

The ion beam graft polymerization (IBGP) method was applied to diagnosis of thin film of several tens μm or less thickness. After a sample stacked on polyethylene film was irradiated with proton beam, polyethylene was graft-polymerized with acrylic acid monomer. From observation of the graft-polymerized polyethylene, information inside the sample are obtained. Demonstrations of the diagnosis method were conducted for a leaf sample and a polyvinyl acetate film contained some voids. Using imitation samples made of metal and polymer sheets, some characteristics of this method was obtained. This method is useful for diagnosis for voids in thin film.

Borings and etchings in the Upper Bathonian-Lower Callovian oolite of the Paris Basin (France)

The oolite of the Dalle Nacree Formation in the Paris Basin is made of marine calcareous ooids with, from base to top, radial (and therefore likely to have been calcite), concentric and micritic fabrics, each corresponding to a discrete stratigraphic unit. Several hardgrounds and oolitic pebble-cobble layers in the succession are encrusted and bored. Three main types of boring have been identified ranging in sizes from some tens of µm (sponge borings) to centimeters (bivalve borings), with an intermediate category (worm borings). Some worm borings have rough walls, where early marine fibrous cement is less corroded than the cortices of cemented ooids. The key to understanding this differential dissolution could be related to organic matter, present within the ooid cortices but lacking in the fibrous cement. Polychaete worms that use chemical means (enzymes or acids) to bore are probably responsible for these peculiar borings. A secondary conclusion is that partly or fully leached ooid cortices do not necessarily indicate an original aragonitic mineralogy of the dissolved parts.

Bidimensional Particle-In-Cell simulations for laser-driven proton acceleration using ultra-short, ultra-high contrast laser

In this paper, we report on bi-dimensional Particle-In-Cell simulations performed in order to reproduce the laser-driven proton acceleration obtained when a commercial 200 TW Ti:Sa Laser hits a solid target. The laser-to prepulse contrast was enhanced using plasma mirrors yielding to a main-to-prepulse contrast of ∼1012. We varied the pulse duration from 30 fs to 500 fs and the target thickness from 30 nm to several tens of μm. The on-target laser energy was up to 1.8 J leading to an intensity in excess of 1020 W cm−2. A comparison between numerical and existing experimental data [S. Fourmaux et al., Phys. Plasmas 20, 013110 (2013)] is performed, showing a good agreement between experimental results and simulations which confirms that for ultra-thin targets there is an optimum expansion regime. This regime depends on the target thickness and on the laser intensity: if the target is too expanded, the laser travels through the target without being able to deposit its energy within the target. If the target is not sufficiently expanded, the laser energy is reflected by the target. It is important to note that maximum proton energies are reached at longer pulse durations (in the 100 fs regime) than what is currently the best compression pulse length for this type of lasers (typically 20–30 fs). This duration, around 50–100 fs, can be considered a minimum energy transfer time between hot electrons to ions during the considered acceleration process.

Projection imaging with directional electron and proton beams emitted from an ultrashort intense laser-driven thin foil target

Projection images of a metal mesh produced by directional MeV electron beam together with directional proton beam, emitted simultaneously from a thin foil target irradiated by an ultrashort intense laser, are recorded on an imaging plate for the electron imaging and on a CR-39 nuclear track detector for the proton imaging. The directional electron beam means the portion of the electron beam which is emitted along the same direction (i.e., target normal direction) as the proton beam. The mesh patterns are projected to each detector by the electron beam and the proton beam originated from tiny virtual sources of ~20 µm and ~10 µm diameters, respectively. Based on the observed quality and magnification of the projection images, we estimate sizes and locations of the virtual sources for both beams and characterize their directionalities. To carry out physical interpretation of the directional electron beam qualitatively, we perform 2D particle-in-cell simulation which reproduces a directional escaping electron component, together with a non-directional dragged-back electron component, the latter mainly contributes to building a sheath electric field for proton acceleration. The experimental and simulation results reveal various possible applications of the simultaneous, synchronized electron and proton sources to radiography and pump-probe measurements with temporal resolution of ~ps and spatial resolution of a few tens of µm.

Composite diamond films for short-mm wave and THz traveling wave tube windows

With an increase in frequency, the diamond thickness of the microwave windows for short-mm wave and THz traveling wave tubes (TWTs) approaches 100μm or even tens of μm. This poses problems of mechanical strength and air tightness to the polycrystalline diamond (PCD) window. To overcome these problems, we have studied a composite diamond film that consists of PCD and ultra-nanocrystalline diamond (UNCD). First, SEM was used to examine the early growing process of UNCD on PCD. The 5μm thick UNCD grown on 40μm PCD exhibited a hillock structure with densely packed ≤20nm granules, in contrast to the PCD layer showing randomly packed, micrometer sized grains. Then, the effect of UNCD thickness on fracture strength and thermal conductivity was studied using the test samples with thin layers of UNCD having thicknesses of 1, 2.5, 5, and 10μm on 100μm thick PCD films, respectively. The fracture strengths of all the films are 2–3 times higher than that of the PCD films, which is 350±150MPa. As expected, the thermal conductivity of the samples measured at ~20°C decreases with an increase in UNCD thickness, particularly in the range of 0 to 2.5μm. At a thickness of 10μm, the thermal conductivity was found to be ~10W/cm∗K. Finally, a 100μm sandwich-like structure with a total UNCD thickness of 10μm was fabricated and two 180GHz TWT windows were assembled. RF tests show that for the operating frequency range of 175 to 185GHz, the transmission loss (S21) was found to be ≤1.22 and ≤1.71dB, respectively, indicating an excellent RF performance. Mechanical strength and air tightness of the windows were also found improved and able to meet the requirement of the device. This work provides a novel approach for fabricating relatively thin diamond films for RF applications, such as TWT windows.

Phase-slope and phase measurements of tunable CW-THz radiation with terahertz comb for wide-dynamic-range, high-resolution, distance measurement of optically rough object.

Phase measurement of continuous-wave terahertz (CW-THz) radiation is a potential tool for direct distance and imaging measurement of optically rough objects due to its high robustness to optical rough surfaces. However, the 2π phase ambiguity in the phase measurement of single-frequency CW-THz radiation limits the dynamic range of the measured distance to the order of the wavelength used. In this article, phase-slope measurement of tunable CW-THz radiation with a THz frequency comb was effectively used to extend the dynamic range up to 1.834 m while maintaining an error of a few tens µm in the distance measurement of an optically rough object. Furthermore, a combination of phase-slope measurement of tunable CW-THz radiation and phase measurement of single-frequency CW-THz radiation enhanced the distance error to a few µm within the dynamic range of 1.834 m without any influence from the 2π phase ambiguity. The proposed method will be a powerful tool for the construction and maintenance of large-scale structures covered with optically rough surfaces.

Mineralogical and microfabric characteristics of magnetite in the Wuyang Precambrian BIFs, southern North China Craton: Implications for genesis and depositional processes of the associated BIFs

Precambrian Banded Iron Formations (BIFs) are widely distributed in the North China Craton (NCC). Among them, the Wuyang BIFs located in the southern margin of NCC occur in the Late Archaean Tieshanmiao Formation and can be subdivided in two different sub-types: (i) quartz–magnetite BIFs (QMB), consisting of magnetite, fine-microcrystalline quartz and minor calcite and (ii) pyroxene–magnetite BIFs (PMB), composed of pyroxene, fine-microcrystalline quartz and subordinate feldspars. Both sub-types display apparent discrepancies in terms of petrography and mineral composition.As shown in Electron BackScattered Diffraction (EBSD) images and micrographs, magnetite grains from the QMB range in size from tens up to hundreds of μm, whereas magnetite crystals from the PMB can be up to a few tens of μm across. The X-ray diffraction (XRD) structural data indicate that magnetite from both BIF sub-types is equiaxed (cubic) and was generated by sedimentary metamorphic processes. The cell parameters of magnetite in the QMB are a=b=c=8.396Å and Z=8, which deviate slightly from these of magnetite in the PMB: a=b=c=8.394Å and Z=8. The analytical results of Raman spectroscopy analysis revealed micro-structural signatures of both magnetite (Raman shifts near 552cm−1 and 673cm−1) and hematite (Raman shifts near 227cm−1, 295cm−1 and 413cm−1). In magnetite from both QMB and PMB, the crystallinity degree is similar for magnetite micro-structures but varies significantly for hematite micro-structures. Oxygen fugacity (fO2) conditions fluctuated during the recrystallization of magnetite in the QMB, whereas no evident variation of fO2 occurred during the formation of magnetite in the PMB. Analytical results of laser ablation inductively-coupled plasma mass spectrometry (LA-ICP-MS) show that the Si, Al and Mg abundances are higher in magnetite from the QMB, whereas the Ti and Mn contents are more elevated in magnetite from the PMB. Magnetite composition also denotes that both BIF sub-types are sedimentary-metamorphic origin, whereas the deposition of PMB was also affected by volcanic activities. Overall data indicate that the differences in the depositional environment of each BIF sub-type are due to the involvement of volcanic eruption processes in the genesis of the PMB. Thus, this paper indicated that the QMB was deposited by chemical deposition at the long-term interval of volcanic eruptions, and the PMB were the product of chemical deposition affected by the volcanic eruption.

Concept for a time-of-flight Small Angle Neutron Scattering instrument at the European Spallation Source

A new Small Angle Neutron Scattering instrument is proposed for the European Spallation Source. The pulsed source requires a time-of-flight analysis of the gathered neutrons at the detector. The optimal instrument length is found to be rather large, which allows for a polarizer and a versatile collimation. The polarizer allows for studying magnetic samples and incoherent background subtraction. The wide collimation will host VSANS and SESANS options that increase the resolution of the instrument towards µm and tens of µm, respectively. Two 1m2 area detectors will cover a large solid angle simultaneously. The expected gains for this new instrument will lie in the range between 20 and 36, depending on the assessment criteria, when compared to up-to-date reactor based instruments. This will open new perspectives for fast kinetics, weakly scattering samples, and multi-dimensional contrast variation studies.

Highly conductive freestanding graphene films as anode current collectors for flexible lithium-ion batteries.

The electrodes in lithium-ion batteries (LIBs) are typically films that are arranged on metal foil current collectors with a thickness of several tens of μm. Here, we report on the preparation of a thick free-standing graphene film synthesized by CVD as an alternative to Cu foil as an anode current collector. As a model system, MoS2 anodes with a flower-like morphology were anchored onto the surface of the thick graphene film. A hybrid and binder free anode without a conventional metal current collector exhibited an excellent capacity value of around 580 mAh/g (@50 mA/g) and reasonable charge/discharge cyclability. The work presented here may stimulate the use of graphene films as replacements for conventional current collectors and additive free electrode in LIBs.

Performance of a Medipix3RX spectroscopic pixel detector with a high resistivity gallium arsenide sensor.

High resistivity gallium arsenide is considered a suitable sensor material for spectroscopic X-ray imaging detectors. These sensors typically have thicknesses between a few hundred μm and 1 mm to ensure a high photon detection efficiency. However, for small pixel sizes down to several tens of μm, an effect called charge sharing reduces a detector's spectroscopic performance. The recently developed Medipix3RX readout chip overcomes this limitation by implementing a charge summing circuit, which allows the reconstruction of the full energy information of a photon interaction in a single pixel. In this work, we present the characterization of the first Medipix3RX detector assembly with a 500 μm thick high resistivity, chromium compensated gallium arsenide sensor. We analyze its properties and demonstrate the functionality of the charge summing mode by means of energy response functions recorded at a synchrotron. Furthermore, the imaging properties of the detector, in terms of its modulation transfer functions and signal-to-noise ratios, are investigated. After more than one decade of attempts to establish gallium arsenide as a sensor material for photon counting detectors, our results represent a breakthrough in obtaining detector-grade material. The sensor we introduce is therefore suitable for high resolution X-ray imaging applications.

Synthesis of Single-Phase Gd-Doped Ceria Nanopowders by Radio Frequency Thermal Plasma Treatment

Gd-doped ceria nanopowders were synthesized using Radio Frequency (RF) thermal plasma. The powders were prepared by ball-milling Gd2O3 and CeO2 powders of several tens of μm in size at the cation ratio of 8:2 and 9:1. The prepared precursors were treated by RF thermal plasma at a plate power level of ~140 kVA, and then, small-sized powders (~50 nm) were retrieved by filtration. Transmission Electron Microscopy, Electron Energy Loss Spectroscopy, and Selected-Area Electron-Diffraction images of the as-synthesized powders showed that Gd atoms were incorporated into the CeO2 particles. In addition, no crystalline peak for Gd2O3 appeared in the X-ray diffraction patterns of the as-synthesized powders, which is attributed to the solid solution of Gd3+ into the CeO2 lattices. Finally, Inductively Coupled Plasma-Optical Emission Spectrometry analysis data revealed relatively small changes within 3 at.% in the cation composition between the ball milled powder mixtures and the nanoscale powders prepared from these mixtures.

Measurement of OH (X2Σ) in immediate vicinity of dielectric surface under pulsed dielectric barrier discharge at atmospheric pressure using two geometries of laser-induced fluorescence

The behavior of the ground state OH radical was studied in humid air using pulsed surface dielectric barrier discharge. The validity of OH measurement in immediate vicinity of the dielectric surface was discussed using two geometries of laser-induced fluorescence (LIF) measurement, and surface distribution and temporal profiles of OH were examined. A comparison of parallel- and perpendicular-LIF techniques for OH measurement revealed that OH was mostly produced in a region several tens of μm above the dielectric surface. The surface distribution profile of OH agreed well with that of N2(C), and in both cases, the total production generated by a discharge pulse was proportional to the discharge energy. The OH local density in surface streamer channels was estimated to be 1.3 × 1015 cm−3 according to the decay rate of OH, which was similar to that in corona discharge. Additionally, the local density of OH remained constant regardless of discharge energies. These results indicate that the yield of OH increased with the discharge energy owing to expansion of the surface streamer region, increase in streamer radius or thickness or the number of branches, whereas the local density of OH in the streamer channel remained constant regardless of discharge energy.

Tungsten damage and melt losses under plasma accelerator exposure with ITER ELM relevant conditions

Experimental simulations of ITER edge-localized mode have been performed with a Kh-50 quasi-stationary plasma accelerator. Heat loads exceeded the tungsten melting threshold. Droplet splashing and the solid dust ejection were observed. Droplets were emitted during the plasma exposure and dust generation dominated after the end of a plasma pulse, at the time of the material cooling. A decrease in the droplet velocity at an increase in the surface heat load was observed. It could be attributed to growing sizes of the droplets at higher energy loads. After one hundred pulses were performed at loads below the tungsten melting and above the cracking threshold, some porosity appeared. Such defects achieved dimensions of several tens of μm. A heat load amounting to half the cracking threshold (0.3 MJ m−2) could lead to the appearance of fatigue cracks after 100 plasma pulses. In this case the appearance of cracks could be caused by the accumulation and redistribution of linear defects (dislocations) in the affected tungsten layer.

Wireless Communication By an Autonomous Self-Powered Cyborg Insect

Wireless Communication By an Autonomous Self-Powered Cyborg Insect