Distribution Of Hydrogen Ions Research Articles

Strain-Induced Uphill Hydrogen Distribution in Perovskite Oxide Films.

Incorporating hydrogen into transition-metal oxides (TMOs) provides a facile and powerful way to manipulate the performances of TMOs, and thus numerous efforts have been invested in developing hydrogenation methods and exploring the property modulation via hydrogen doping. However, the distribution of hydrogen ions, which is a key factor in determining the physicochemical properties on a microscopic scale, has not been clearly illustrated. Here, focusing on prototypical perovskite oxide (NdNiO3 and La0.67Sr0.33MnO3) epitaxial films, we find that hydrogen distribution exhibits an anomalous "uphill" feature (against the concentration gradient) under tensile strain, namely, the proton concentration enhances upon getting farther from the hydrogen source. Distinctly, under a compressive strain state, hydrogen shows a normal distribution without uphill features. The epitaxial strain significantly influences the chemical lattice coupling and the energy profile as a function of the hydrogen doping position, thus dominating the hydrogen distribution. Furthermore, the strain-(H+) distribution relationship is maintained in different hydrogenation methods (metal-alkali treatment) which is first applied to perovskite oxides. The discovery of strain-dependent hydrogen distribution in oxides provides insights into tailoring the magnetoelectric and energy-conversion functionalities of TMOs via strain engineering.

Reconfigurable perovskite nickelate electronics for artificial intelligence.

Reconfigurable devices offer the ability to program electronic circuits on demand. In this work, we demonstrated on-demand creation of artificial neurons, synapses, and memory capacitors in post-fabricated perovskite NdNiO3 devices that can be simply reconfigured for a specific purpose by single-shot electric pulses. The sensitivity of electronic properties of perovskite nickelates to the local distribution of hydrogen ions enabled these results. With experimental data from our memory capacitors, simulation results of a reservoir computing framework showed excellent performance for tasks such as digit recognition and classification of electrocardiogram heartbeat activity. Using our reconfigurable artificial neurons and synapses, simulated dynamic networks outperformed static networks for incremental learning scenarios. The ability to fashion the building blocks of brain-inspired computers on demand opens up new directions in adaptive networks.

High specific detectivity infrared detector using crystal ion slicing transferred LiTaO3 single-crystal thin films

LiTaO3 (LT) single crystalline films have been used to fabricate pyroelectric infrared detectors. Sub-micrometer thick LT films have been transferred on LT holder substrate by Crystal Ion Slicing (CIS) technology using hydrogen ions implantation and SiO2 bonding process. The surface roughness result from the Gauss distribution of hydrogen ions was decreased from 18.7 nm to 1.5 nm after Ar+ ion bombardment. The pyroelectric coefficient of CIS fabricated LT film (2 × 10−8 C/cm2·K) is comparable to that of LT bulk crystal. Detectors fabricated using the CIS fabricated LT films show larger detectivity at higher modulation frequency than the commercially available pyroelectric devices using LT bulk crystal or PZT polycrystalline thin films. The highest value of specific detectivity is 2.49 × 108 cm·Hz1/2W−1 at 300 Hz. The results demonstrate that the LT single crystal film fabricated by CIS technology is a promising material to fabricate quick response pyroelectric devices.

Acid-treatment of bio-oil in methanol: The distinct catalytic behaviours of a mineral acid catalyst and a solid acid catalyst

The different catalytic behaviour of solid acid catalyst and mineral acid catalyst towards the acid-treatment of bio-oil was investigated. The hydrogen ions in the mineral acid catalyst such as sulfuric acid homogeneously dispersed in the reaction medium made the conversion of main components of bio-oil including carboxylic acids, sugars and phenolics more efficient. In comparison, there was a steric hindrance for these components of bio-oil to access the hydrogen located in the local surface of the solid acid catalyst such as Amberlyst 70. This negatively affected their conversions during the acid-treatment. However, the inhomogeneous distribution of hydrogen ions from Amberlyst 70 in the reaction medium created high concentration of hydrogen ions in the local vicinity of the solid catalyst surface of the catalyst, which is found to be crucial for the occurrence of the etherification reactions. Understanding how the dispersion of hydrogen ions of catalyst affect the esterification of bio-oil can provide useful information for the development of the effective catalysts for upgrading of bio-oil.

IMF dependence of energetic oxygen and hydrogen ion distributions in the near‐Earth magnetosphere

AbstractEnergetic ion distributions in the near‐Earth plasma sheet can provide important information for understanding the entry of ions into the magnetosphere and their transportation, acceleration, and losses in the near‐Earth region. In this study, 11 years of energetic proton and oxygen observations (> ~274 keV) from Cluster/Research with Adaptive Particle Imaging Detectors were used to statistically study the energetic ion distributions in the near‐Earth region. The dawn‐dusk asymmetries of the distributions in three different regions (dayside magnetosphere, near‐Earth nightside plasma sheet, and tail plasma sheet) are examined in Northern and Southern Hemispheres. The results show that the energetic ion distributions are influenced by the dawn‐dusk interplanetary magnetic field (IMF) direction. The enhancement of ion intensity largely correlates with the location of the magnetic reconnection at the magnetopause. The results imply that substorm‐related acceleration processes in the magnetotail are not the only source of energetic ions in the dayside and the near‐Earth magnetosphere. Energetic ions delivered through reconnection at the magnetopause significantly affect the energetic ion population in the magnetosphere. We also believe that the influence of the dawn‐dusk IMF direction should not be neglected in models of the particle population in the magnetosphere.

The spatial distribution of hydrogen ions at topside ionosphere in local daytime

The spatial distribution of hydrogen ions at topside ionosphere in local daytime

Molecular Dynamics Simulation on Hydrogen Ion Implantation Process in Smart-Cut Technology

The hydrogen ion implantation process in Smart-Cut technology is investigated in the present paper using molecular dynamics (MD) simulations. This work focuses on the effects of the implantation energy, dose of hydrogen ions and implantation temperature on the distribution of hydrogen ions and defect rate induced by ion implantation. Numerical analysis shows that implanted hydrogen ions follow an approximate Gaussian distribution which mainly depends on the implantation energy and is independent of the hydrogen ion dose and implantation temperature. By introducing a new parameter of defect rate, the influence of the processing parameters on defect rate is also quantitatively examined.

Convective amplification of electromagnetic ion cyclotron waves from ring‐distribution protons in the inner magnetosphere

AbstractThe growth of electromagnetic ion cyclotron (EMIC) waves due to a ring distribution of hydrogen ions is examined. Though these distributions are more commonly implicated in the generation of equatorial noise, their potential for exciting EMIC waves is considered here. It is shown that since the ring distribution is nonmonotonic in perpendicular velocity, the amplification achieved by this instability is greater than bi‐Maxwellian distributions for typical observed anisotropies, because the waves can maintain resonance over a much longer part of its trajectory. For ring speeds (Vr) close to the Alfvén speed (VA), the growth rate is largest at parallel propagation but decreases less rapidly toward oblique angles compared with a bi‐Maxwellian and can have a second peak for shorter wavelengths. The ring distribution parallel thermal speed is deduced from the observation of equatorial noise because a statistical survey of this parameter is not available. A ring density to background plasma density of a few percent is sufficient to achieve moderate gain. The gain is also shown to increase with L shell since the perpendicular wave number does not rise as rapidly along the raypath as compared with smaller L. The analysis suggests that EMIC wave activity should be closely associated with equatorial noise.

Correction: Theoretical Predictions of Lactate and Hydrogen Ion Distributions in Tumours

Correction: Theoretical Predictions of Lactate and Hydrogen Ion Distributions in Tumours

Theoretical predictions of lactate and hydrogen ion distributions in tumours.

High levels of lactate and H+-ions play an important role in the invasive and metastatic cascade of some tumours. We develop a mathematical model of cellular pH regulation focusing on the activity of the Na+/H+ exchanger (NHE) and the lactate/H+ symporter (MCT) to investigate the spatial correlations of extracellular lactate and H+-ions. We highlight a crucial role for blood vessel perfusion rates in determining the spatial correlation between these two cations. We also predict critical roles for blood lactate, the activity of the MCTs and NHEs on the direction of the cellular pH gradient in the tumour. We also incorporate experimentally determined heterogeneous distributions of the NHE and MCT transporters. We show that this can give rise to a higher intracellular pH and a lower intracellular lactate but does not affect the direction of the reversed cellular pH gradient or redistribution of protons away from the glycolytic source. On the other hand, including intercellular gap junction communication in our model can give rise to a reversed cellular pH gradient and can influence the levels of pH.

Charge Accumulation Type Hydrogen Ion Image Sensor with High pH Resolution

We propose a charge transfer type ion image sensor operated using a charge accumulation technique that accumulates the output signal and integrates it temporally. This technique is expected to image hydrogen ion distributions with a high signal-to-noise (S/N) ratio. The sensor was fabricated using large-scale integration technology, so that its size was very compact, and its specialized charge transfer characteristics allowed it to amplify the signal without any external amplification. The sensor noise was independent of the sensing area size, and the noise power was determined by the noise of the source follower circuit. In 5 accumulation cycles, the S/N ratio increased by √5 times and the pH-referred noise, which indicates the pH sensor resolution, was reduced from 0.09 to 0.06 pH. The sensor effectively obtained a real-time image of the hydrogen ion distribution in a solution with a resolution of pH 0.1, which would not be possible without charge accumulation.

Fabrication of multi-sectional TiO 2 nanotube arrays by anodization

We report a facile method to grow multi-sectional TiO2 nanotube arrays consisting of alternating bamboo-shaped and smooth-walled nanotube sections by anodization. Two key factors are necessary for obtaining these morphologies. First, in order to avoid possible disruptions between the conjoint sections of the nanotube, the distribution of hydrogen ions is suggested not to be fiercely disturbed when switching from the first to the second stage. Second, to avoid the disruption of the nanotube at the joint which results from the disparity in diameters between sections, the direct current voltage is set to be the maximum of the square wave voltage. These newly developed TiO2 nanotube arrays are expected to have potential applications in solar cells, drug release and delivery systems.

Energy-angle distribution of low-energy hydrogen ions in thin aluminum and gold foils

Energy and angular distributions of hydrogen ions in thin solid foils of elements with significantly different electronic structures and atomic masses, such as Al and Au, have been measured at 9 keV using the transmission technique. The results are compared with Monte Carlo simulations using a classical scattering approach and an impact-parameter independent electronic energy loss, as well as with a simplified model containing the main physical features. In both cases, the effect of foil roughness on angular dependence of the energy loss has been included and it has been found to be responsible for the variations observed at small angles. The measured angular distributions have also been compared with standard multiple scattering functions corresponding to Thomas–Fermi and Lenz–Jensen potentials and with calculations based on 1/rn power potentials.

Dissociation constants of aromatic carboxylic acids spread at the air/water interface

The surface potential technique is employed to estimate the dissociation constant ( K) of a series of aromatic carboxylic acids in the form of Langmuir monolayers. Using electric surface potential (Δ V) measurements of monolayers spread on aqueous subphases, containing different concentrations of Na +, and applying the Gouy–Chapman theory as well as the Henderson–Hasselbalch equation, the surface pK for the investigated compounds falls in the range of 4.5–5.6 with the mean value of 5.1. The other method, based on surface potential measurements of monolayers of the parent, unsubstituted compound (5′-phenyl- m-terphenyl-4-carboxylic acid) spread on aqueous solutions with distinct pHs, leads to a pK of ca. 6.5 which corresponds to the bulk conditions. This value is shifted towards neutral pH as compared to the one calculated with the Henderson–Hasselbalch equation (5.3), owing to the inhomogeneous distribution of hydrogen ions caused by partial ionization of carboxylic groups of the monolayer molecules.

Interaction of hydrogen with tantalum surface in a high electric field

The interaction between hydrogen and a metal surface in a high electric field has been known and studied since the field ion microscope has been in use. One of the most intriguing problems of the field evaporation process in the presence of hydrogen is the change of an energy deficit distribution of hydrogen ions. These changes are different for H+, H+2 and H+3. In this paper we present some new data obtained by a high-resolution pulsed laser time-of-flight atom-probe field ion microscope.

Ion dependence of resting membrane potential of rat spermatids

The membrane potential of rat spermatids was estimated as -22 +/- 2 mV (mean +/- SEM) using three independent methods: using oxonol as a fluorescent membrane potential sensitive probe, from the passive distribution of hydrogen ions and from whole-cell patch-clamp records. The estimated permeability ratios PK+:PCl- and PNa+:PCl- of the plasma membrane of rat spermatids were 1.0 and 0.3, respectively. These data indicate that the high luminal K+ concentration found in seminiferous tubules could partially close voltage-sensitive calcium channels in these cells.

Hypophosphite ion as a 31P nuclear magnetic resonance probe of membrane potential in erythrocyte suspensions

Hypophosphorus acid has a single pKa of 1.1 and at physiological pH values it is therefore present almost entirely as the univalent hypophosphite ion. When added to a red cell suspension the ion crosses the cell membrane rapidly, via the anion exchange protein, and the intra- and extracellular populations of the ion give rise to separate 31P NMR resonances. From a single 31P NMR spectrum it was possible to determine the relative amounts of hypophosphite in the intra- and extracellular compartments and thereby estimate the corresponding concentrations. The ratio of intracellular to extracellular hypophosphite concentration was independent of the total hypophosphite concentration for cells suspended in NaCl solutions and was independent of hematocrit. The hypophosphite distribution ratio increased as extracellular NaCl was replaced iso-osmotically with citrate or sucrose, through it remained very similar to the corresponding hydrogen ion distribution ratio. Incorporation of the hypophosphite distribution ratio into the Nernst equation yielded an estimate of the membrane potential. For cells suspended in NaCl solutions the estimated potential was consistently around -10 mV.

The influence of water pH on the perivitelline fluid of perch ( Perca fluviatilis) eggs

1. 1. The diameter, trans-chorion potential difference and perivitelline-fluid pH of the eggs of perch ( Perca fluviatilis) have been measured in a range of water pH (8–4.5). The water used was relatively nutrient rich. 2. 2. Eggs transferred from pH 8 to pH 4.5 shrink; probably as a result of loss of water from perivitelline fluid. 3. 3. Trans-chorion potential differences are close to zero over the range of pH. Mean perivitelline-fluid pH is higher than external water pH at pH 6.7 and above. Below pH 6.7, mean perivitelline-fluid pH is approximately the same as external water pH. The results suggest a non-Donnan distribution of hydrogen ions. 4. 4. The results are compared with data on salmonid eggs in nutrient-poor waters.

The pH in the neighborhood of membranes generating a protonmotive force

The chemiosmotic mechanism provides a way whereby energy inherent in a chemical combustion process is extracted and transduced: first into the energy of electron X volts of the electron redox system and second into proton X volts as protons are forced to leave the interior of the cell, creating an electro-chemical protonic potential (the protonmotive force). Here we consider the distribution of potential and pH across the membrane and the phases bathing the membrane in more detail. The distribution of hydrogen ions parallel to the surface is also described. It is shown that the voltage and pH gradients due to the proton extrusion occur near to the membrane (approximately 2 nm). This implies that the pH is much lower immediately outside the membrane than in the cytoplasm or in usual neutral growth or isotonic media. It provides a link between the points of view of Mitchell and Williams. It requires that literature models for the role of the protonmotive force in the maintenance of wall thickness in Gram-positive organisms, the adhesion of microbes to surfaces, and the transport of auxin in plants be modified.

Nuclear magnetic resonance imaging: Basic principles

The physical principles underlying nuclear magnetic resonance (NMR) imaging (also known as MRI) are described. NMR is an important new non-invasive imaging modality, which does not use ionizing radiation. Its ability to map hydrogen ion distribution, and to detect two intrinsic parameters ("relaxation times") which are indicative of the immediate chemical environment of the hydrogen nuclei, results in images of superior spatial detail in the brain and spinal cord. The potential of this technique for quantitating blood flow and for the exact identification of tissues is discussed.