Solubility of hydrogen in aqueous solutions of sodium and potassium bicarbonate from 293 to 333 K

An experimental study is presented of the hydrogen solubility in aqueous salt solutions containing sodium and potassium bicarbonate from 293 to 333 K. For this purpose, gas consumption measurements have been performed by determining the ultimate pressure decrease in an intensively stirred, high pressure autoclave. Experiments were carried out at salt concentrations up to 1.0 mol kg-1. At higher salt molalities, the hydrogen solubility was too low to be measured reliably. It was demonstrated that the hydrogen solubility followed the well-known Sechenov salt concentration dependence. At 298 K, the Sechenov or salting-out parameters were equal to 0.41 and 0.32 kg mol-1 for sodium and potassium bicarbonate, respectively. Fairly good agreement was obtained with the salting-out parameters predicted by a recently developed empirical estimation method. The concentration ratio of the bicarbonate and carbonate ions showed only a minor influence on the hydrogen solubility. Furthermore, the Sechenov parameter was found to be a weak function of temperature. Virtually the same, linear temperature dependence was observed for both bicarbonate salts studied, i.e. −0.0023 and −0.0024 kg mol-1 K-1 for sodium and potassium bicarbonate, respectively

Chemical equilibrium of hydrogen and aqueous solutions of 1:1 bicarbonate and formate salts with a common cation

This was accomplished for the sodium (M = Na), potassium (M = K) and ammonium (M = NH4) systems by measuring the equilibrium composition. This reaction was allowed to proceed from both sides of the equilibrium in a suspension of Pd/C and Pd/γ-Al2O3 catalyst particles, and was carried out at 20, 40 and 60°C for hydrogen pressures ranging from 0.5 to 10 bar. The total salt concentration in the reaction mixture was varied up to the solubility limit. The experimental equilibrium data were interpreted by taking the nonideality of the aqueous electrolyte solution into account according to the multicomponent, extended Pitzer model. Calculation of the activity coefficients was based on parameters of the single electrolyte subsystems. From the experimental results, the values of the standard Gibbs energy and enthalpy change of the reaction could be derived, namely −0.72 and −20.5 kJ mol−1, respectively. Determination of the standard Gibbs energy and enthalpy of formation of the aqueous formate ion yielded values of, successively, −350.5 and −426.7 kJ mol−1. The thermodynamic chemical equilibrium constant of the hydrogenation reaction was correlated by the equation K1 = exp (2.22×103((T/K)−1). In the range of process conditions studied, both the equilibrium conversion and the solubility of the electrolyte mixture were predicted within 5% error on the basis of the thermodynamic model used

Solubility of hydrogen in aqueous solutions of sodium and potassium bicarbonate from 293 to 333 K

An experimental study is presented of the hydrogen solubility in aqueous salt solutions containing sodium and potassium bicarbonate from 293 to 333 K. For this purpose, gas consumption measurements have been performed by determining the ultimate pressure decrease in an intensively stirred, high pressure autoclave. Experiments were carried out at salt concentrations up to 1.0 mol kg-1. At higher salt molalities, the hydrogen solubility was too low to be measured reliably. It was demonstrated that the hydrogen solubility followed the well-known Sechenov salt concentration dependence. At 298 K, the Sechenov or salting-out parameters were equal to 0.41 and 0.32 kg mol-1 for sodium and potassium bicarbonate, respectively. Fairly good agreement was obtained with the salting-out parameters predicted by a recently developed empirical estimation method. The concentration ratio of the bicarbonate and carbonate ions showed only a minor influence on the hydrogen solubility. Furthermore, the Sechenov parameter was found to be a weak function of temperature. Virtually the same, linear temperature dependence was observed for both bicarbonate salts studied, i.e. −0.0023 and −0.0024 kg mol-1 K-1 for sodium and potassium bicarbonate, respectively

Secondary Damage after Traumatic Brain Injury: Epidemiology, Pathophysiology and Therapy

Traumatic brain injury (TBI) is defined as a microscopic or macroscopic injury to the brain caused by external physical forces. Road traffic accidents, falls, sports injuries (i.e. boxing), recreational accidents (i.e. parachute jumping), the use of firearms, assault, child abuse, and several rare causes e.g. the use of nail guns or lawn mowers have all been described as causes of TBI. The pathology of TBI can be classified by mechanism (closed versus penetrating); clinical severity (Glasgow Coma Scale) and structural damage (imaging e.g. CT-examination). In most cases TBI is graded according to injury severity assessing the level of consciousness of the patient by, most frequently, the Glasgow Coma Scale (GCS). The GCS scores patients based on their ability to open their eyes, perform limb movements and respond adequately to simple questions (Teasdale and Jennett 1974) (see table 1). Mild TBI, e.g. a light concussion, is defined as a patient with a GCS of 13-15 possibly suffering from short-term memory and concentration deficits (Rimel et al., 1981; Mosenthal et al., 2004). Moderate TBI is scored by a GCS of 9-12, e.g. a lethargic and stuporous patient. A comatose patient, unable to open eyes or follow commands has been severely injured and has a GCS of 3-8

Wigner crystalization about ν\nu=3

We measure a resonance in the frequency dependence of the real diagonal conductivity, Re[$\sigma_{xx}$], near integer filling factor, $\nu=3$. This resonance depends strongly on $\nu$, with peak frequency $f_{pk} \approx 1.7$ GHz at $\nu=3.04$ or 2.92 close to integer $\nu$, but $f_{pk} \approx$ 600 MHz at $\nu=3.19$ or 2.82, the extremes of where the resonance is visible. The dependence of $f_{pk}$ upon $n^*$, the density of electrons in the partially filled level, is discussed and compared with similar measurments by Chen {\it et al.}\cite{yong} about $\nu=1$ and 2. We interpret the resonance as due to a pinned Wigner crystal phase with density $n^*$ about the $\nu=3$ state.Comment: for proceedings of EP2DS-15 (Nara) to appear in Physica

The Nature of the Hall Insulator

We have conducted an experimental study of the linear transport properties of the magnetic-field induced insulating phase which terminates the quantum Hall (QH) series in two dimensional electron systems. We found that a direct and simple relation exists between measurements of the longitudinal resistivity, $\rho_{xx}$, in this insulating phase and in the neighboring QH phase. In addition, we find that the Hall resistivity, $\rho_{xy}$, can be quantized in the insulating phase. Our results indicate that a close relation exists between the conduction mechanism in the insulator and in the QH liquid.Comment: RevTeX, 4 pages, 4 figure

High Magnetic Field Microwave Conductivity of 2D Electrons in an Array of Antidots

We measure the high magnetic field ($B$) microwave conductivity, Re$\sigma_{xx}$, of a high mobility 2D electron system containing an antidot array. Re$\sigma_{xx}$ vs frequency ($f$) increases strongly in the regime of the fractional quantum Hall effect series, with Landau filling $1/3<\nu<2/3$. At microwave $f$, Re$\sigma_{xx}$ vs $B$ exhibits a broad peak centered around $\nu=1/2$. On the peak, the 10 GHz Re$\sigma_{xx}$ can exceed its dc-limit value by a factor of 5. This enhanced microwave conductivity is unobservable for temperature $T \gtrsim 0.5$ K, and grows more pronounced as $T$ is decreased. The effect may be due to excitations supported by the antidot edges, but different from the well-known edge magnetoplasmons.Comment: 4 pages, 3 figures, revtex

Experimental Evidence for a Spin-Polarized Ground State in the \nu=5/2 Fractional Quantum Hall Effect

We study the \nu=5/2 even-denominator fractional quantum Hall effect (FQHE) over a wide range of magnetic (B) field in a heterojunction insulated gate field-effect transistor (HIGFET). The electron density can be tuned from n=0 to 7.6 \times 10^{11} cm^{-2} with a peak mobility \mu = 5.5 \times 10^6 cm^2/Vs. The \nu=5/2 state shows a strong minimum in diagonal resistance and a developing Hall plateau at magnetic fields as high as 12.6T. The strength of the energy gap varies smoothly with B-field. We interpret these observations as strong evidence for a spin-polarized ground state at \nu=5/2.Comment: new references adde

Anomalous Behavior of 2+ Excitations around 132Sn

In certain neutron-rich Te isotopes, a decrease in the energy of the first excited 2+ state is accompanied by a decrease in the E2 strength to that state from the ground state, contradicting simple systematics and general intuition about quadrupole collectivity. We use a separable quadrupole-plus-pairing Hamiltonian and the quasiparticle random phase approximation to calculate energies, B(E2,0+ -> 2+) strengths, and g factors for the lowest 2+ states near 132Sn (Z >= 50). We trace the anomalous behavior in the Te isotopes to a reduced neutron pairing above the N = 82 magic gap.Comment: 1 figure added. to be published in Phys. Rev.

The P2X7 receptor contributes to seizures and inflammation-driven long-lasting brain hyperexcitability following hypoxia in neonatal mice.

Neonatal seizures represent a clinical emergency. However, current anti-seizure medications fail to resolve seizures in ~50% of infants. The P2X7 receptor (P2X7R) is an important driver of inflammation, and evidence suggests that P2X7R contributes to seizures and epilepsy in adults. However, no genetic proof has yet been provided to determine what contribution P2X7R makes to neonatal seizures, its effects on inflammatory signalling during neonatal seizures, and the therapeutic potential of P2X7R-based treatments on long-lasting brain excitability. Neonatal seizures were induced by global hypoxia in 7-day-old mouse pups (P7). The role of P2X7Rs during seizures was analysed in P2X7R-overexpressing and knockout mice. Treatment of wild-type mice after hypoxia with the P2X7R antagonist JNJ-47965567 was used to determine the effects of the P2X7R on long-lasting brain hyperexcitability. Cell type-specific P2X7R expression was analysed in P2X7R-EGFP reporter mice. RNA sequencing was used to monitor P2X7R-dependent hippocampal downstream signalling. P2X7R deletion reduced seizure severity, whereas P2X7R overexpression exacerbated seizure severity and reduced responsiveness to anti-seizure medication. P2X7R deficiency led to an anti-inflammatory phenotype in microglia, and treatment of mice with a P2X7R antagonist reduced long-lasting brain hyperexcitability. RNA sequencing identified several pathways altered in P2X7R knockout mice after neonatal hypoxia, including a down-regulation of genes implicated in inflammation and glutamatergic signalling. Treatments based on targeting the P2X7R may represent a novel therapeutic strategy for neonatal seizures with P2X7Rs contributing to the generation of neonatal seizures, driving inflammatory processes and long-term hyperexcitability states