Hydrogen-Bond Symmetrization of δ-AlOOH

The δ-AIOOH can transport water into the deep mantle along cold subducting slab geothenn. We investigate the hydrogen-bond symmetrization behavior of δ-AIOOH under the relevant pressure-temperature condition of the lower mantle using ab initio molecular dynamics(AID). The static symmetrization pressure of 30.0 GPa can be reduced to 17.0 GPa at 300 K by finite-temperature(T) statistics, closer to the experimental observation of-10.0 GPa. The symmetrization pressure obtained by MD simulation is related to T by P(GPa) = 13.9(GPa) +0.01(GPa/K) × T(K). We conclude that δ-AIOOH in the lower mantle exists with symmetric hydrogen bond from its birthplace, or someplace slightly deeper, to the core-mantle boundary(CATB) along cold subducting slab geotherm. The bulk modulus decreases with T and increases anomalously upon symmetrization: K_o(GPa) =181(GPa)-0.013(GPa/K) × T(K) for δ-AIOOH with asymmetric hydrogen bond, and K_o(GPa) = 216(GPa)-0.013(GPa/K) × T(K) for δ-AIOOH with symmetric hydrogen bond. Our results provide an important insight into the existent form and properties of δ-AIOOH in the lower mantle.     

Synthesis of monolayers and bilayers of cobalt oxyhydrates (Na,K) x (H2O) y CoO2− δ

Potassium sodium cobalt oxyhydrates (Na,K)_x(H₂O)_yCoO_{2? δ} were synthesized from γ-Na_0.7CoO₂ by using aqueous KMnO₄ solution in a one-pot process. Chemical and structural analyses revealed that a partial or even almost complete replacement of K⁺ for Na⁺ in the alkaline layers occurs. Direct formation of the c ≈ 13.9 Å phase is apparently associated with the larger size of K⁺ (～1.4 Å) as compared to Na⁺ (～1.0 Å). Formation of (Na,K) _x (H₂O) _y CoO_{2? δ} not only involves de-intercalation, oxidation and hydration processes, but also an ion exchange reaction. Based on a systematic study, the phase formation of (Na,K) _x (H₂O) _y CoO_{2? δ} with c ≈ 19.6 Å is a slow process, particularly when using aqueous KMnO₄ solution with low molar ratio of KMnO₄/Na. When comparing the Co K-edge X-ray absorption spectra of (Na,K) _x (H₂O) _y CoO_{2? δ} with those of Na _x (H₂O) _y CoO₂ obtained from Br₂/CH₃CN solution, the edge energy of the main peak of the bilayered hydrate is found to be 3.5 eV higher than that of the monolayered hydrate for (Na,K) _x (H₂O) _y CoO_{2? δ}. In contrast, the edge energy of the main peak of the bilayered hydrate is 0.4 eV lower than that of the monolayered hydrate for Na _x (H₂O) _y CoO₂. In addition, the hydration behavior of monolayered of (Na,K) _x (H₂O) _y CoO_{2? δ} is different from that of Na _x (H₂O) _y CoO₂. These results seem to suggest that they are two different systems.     

Quantum size effects in δ-Pu (110) films

First-principles full-potential linearized-augmented-plane-wave (FP-LAPW) calculations have been carried out for δ-Pu (110) films up to seven layers. The layers have been studied at the non-spin-polarized-no-spin-orbit coupling (NSP-NSO), non-spin-polarized-spin-orbit coupling (NSP-SO), spin-polarized-no-spin-orbit coupling (SP-NSO), spin-polarized-spin-orbit coupling (SP-SO), antiferromagnetic-no-spin-orbit coupling (AFM-NSO), and antiferromagnetic-spin-orbit-coupling (AFM-SO) levels of theory. The ground state of δ-Pu (110) films is found to be at the AFM-SO level of theory and the surface energy is found to rapidly converge. The semi-infinite surface energy for δ-Pu (110) films is predicted to be 1.41 J/m², while the magnetic moments show an oscillating behavior, gradually approaching the bulk value of zero with increase in the number of layers. Work functions indicate a strong quantum size effect up to and including seven layers. The work function of the seven-layer δ-Pu (110) film at the ground state is found to be 2.99 eV.     

A finite size scaling analysis of the O(4)-invariant lattice δ4 theory

The critical behaviour of the three- and four-dimensional N=4 vector model is investigated by means of a Monte Carlo simulation on lattices with size between 4³ and 16³, and between 4⁴ and 12⁴, respectively. For obtaining information about some critical properties of the model, we use a method due to Binder which is based on the theory of finite size scaling. For the three-dimensional model we get estimates of the critical exponents ν and η which are compatible with estimates obtained from the ϵ-expansion. In four dimensions we study for two different values of the bare self-coupling λ (λ=1 in our normalization, and λ=∞) the scaling behaviour of some Green function ratios at the phase boundary. In both cases we find compatibility with the “predicted” scaling behaviour at the gaussian fixed point. This is another independent numerical hint that the continuum limit of the four-dimensional O(4)-invariant lattice δ⁴-model is a free field theory.     

Variations of δ(15)N-Values and Hydrolyzable Amino Acids in Settling Particles in the Ocean

Abstract The modification of nitrogen isotopic signals during particle sedimentation in the sea is of great interest for the use of sedimentary δ(15)N-values as a paleoceanographic tool. The effect of organic matter degradation on such modification was studied by analyzing nitrogen, hydrolyzable amino acids (THAA) and δ(15)N-values in a suit of marine settling particles collected from the Bay of Bengal, Indian Ocean, by using time-series sediment traps, and in underlying sediments. The flux of settling particles showed temporal variations which are related to the monsoons, the major climatic feature of this marine region. During high flux periods settling particles are enriched in nitrogenous material that is less degraded and exhibit higher δ(15)N-values than particles showing characteristics of degradation. At the sediment surface more than 95% of the settling particulate nitrogen is lost and the δ(15)N-values of the residual sedimentary nitrogen are higher than those of settling particles. The observed increase is interpreted to be due to fractionation during degradation of organic matter.     

Measuring δ(13)C values of atmospheric acetaldehyde via sodium bisulfite adsorption and cysteamine derivatisation

δ(13)C values of gaseous acetaldehyde were measured by gas chromatograph-combustion-isotope ratio mass spectrometer (GC-C-IRMS) via sodium bisulfite (NaHSO(3)) adsorption and cysteamine derivatisation. Gaseous acetaldehyde was collected via NaHSO(3)-coated Sep-Pak(?) silica gel cartridge, then derivatised with cysteamine, and then the δ(13)C value of the acetaldehyde-cysteamine derivative was measured by GC-C-IRMS. Using two acetaldehydes with different δ(13)C values, derivatisation experiments were carried out to cover concentrations between 0.009×10(-3) and 1.96×10(-3)?mg·l(-1)) of atmospheric acetaldehyde, and then δ(13)C fractionation was evaluated in the derivatisation of acetaldehyde based on stoichiometric mass balance after measuring the δ(13)C values of acetaldehyde, cysteamine and the acetaldehyde-cysteamine derivative. δ(13)C measurements in the derivertisation process showed good reproducibility (<0.5?‰) for gaseous acetaldehyde. The differences between predicted and measured δ(13)C values were 0.04-0.31?‰ for acetaldehyde-cysteamine derivative, indicating that the derivatisation introduces no isotope fractionation for gaseous acetaldehyde, and obtained δ(13)C values of acetaldehyde in ambient air at the two sites were distinct (-34.00?‰ at an urban site versus-31.00?‰ at a forest site), implying potential application of the method to study atmospheric acetaldehyde.     

Wild Rabbit Host and Some Parasites Show Trophic-Level Relationships for δ(13)C and δ(15)N: A First Report

Abstract We report the first isotopic study of an animal host-parasite system. Parasitic, intestinal nematodes, Graphidium strigosum and Passalurus ambiguus, were (15)N-enriched relative to their host, the European rabbit Oryctolagus cuniculus, while parasitic cestodes, Cittataenia denticulata and Mosgovoyia pectinata, were (15)N-depleted, suggesting different trophic relationships. Host embryos were more similar in their δ(13)C and δ(15)N values to maternal muscle than were any of the parasites. Coprophagy, the direct recycling of food by the rabbit eating its own faeces, did not lead to isotopic differences between stomach contents and faeces, suggesting that the major point for isotopic discrimination in lagomorph nitrogen metabolism is in the animal rather than in the gut. We conclude that bulk δ(13)C and δ(15)N can reveal valuable new information about host-parasite relationships, and these could be explored further at the biochemical level using compound-specific isotopic analyses.     

Parity operator and quantization of δ-functions

In the Weyl quantization scheme, the -function at the origin of phase space corresponds to the parity operator. The quantization of a functionf() on phase space is the operator f(/2)W()dM, whereM is the parity andW() the Weyl operator.     

High-precision measurements of δ2H, δ18O and δ17O in water with the aid of cavity ring-down laser spectroscopy

A thorough evaluation of measurement uncertainty together with control of short-term and long-term precision of measurements should be a basis of any successful quality assurance/quality control (QA/QC) strategy aimed at maintaining a high quality of the analytical process. Here we present the results of a comprehensive assessment of the analytical performance of a Picarro L2140-i CRDS laser spectrometer analysing δ²H, δ¹⁸O and δ¹⁷O in water. The assessment is based on results obtained during 15 months of continuous operation of this instrument (February 2017 to May 2018). The short-term precision of measured and derived quantities was 0.11, 0.036, 0.028, 0.23 ‰ and 11 per meg, for δ²H, δ¹⁸O, δ¹⁷O, d-excess and Δ¹⁷O, respectively, and is comparable to the precision reported by the manufacturer. The long-term precision of the L2140-i, defined as standard uncertainty of the time series of 153 analyses of a laboratory standard conducted throughout 15 months, was roughly two times lower (0.24, 0.053, 0.038, 0.37 ‰ and 21 per meg, for δ²H, δ¹⁸O, δ¹⁷O, d-excess and Δ¹⁷O). In-depth assessment of the measurement uncertainty of a single analysis revealed that assigned uncertainty of the calibration standards is an important component of the uncertainty budget, especially in case of δ²H analysis.     

Optical response of a δ-layer capacitor

The fabrication of two δ-layers of opposite polarity in a semiconductor constitutes a capacitor. The charge on each "plate" may be modified by photogenerating carriers to screen the dopant ions, which alters the field between them. This has the effect of changing the transition energies between confined states in the structure, which results in a substantial (60 meV) blue shift, which may be utilised in a modulator structure. These effects have been investigated using steady-state and time-resolved photoluminescence, in conjunction with band modelling.     

Products of distributions and collision of a δ-wave with a δ′-wave in a turbulent model

We study the possibility of collision of a δ-wave with a stationary δ′-wave in a model ruled by equation f (t)u _t+[u²?β(x?γ(t))u]_x = 0, where f, β and γ are given real functions and u = u(x, t) is the state variable. We adopt a solution concept which is a consistent extension of the classical solution concept. This concept is defined in the setting of a distributional product, which is not constructed by approximation processes. By a convenient choice of f, β and γ, we are able to distinguish three distinct dynamics for that collision, to which correspond phenomena of solitonic behaviour, scattering, and merging. Also, as a particular case, taking f = 2 and β = 0 we prove that the referred collision is impossible to arise in the setting of the inviscid Burgers equation. To show how this framework can be applied to other physical models, we included several results already obtained.     

Temperature dependence of elastic constants in δ-Pu

It is shown that the variation of the bulk and shear moduli in δ-Pu in a temperature range of 300–500 K is due to the phonon redistribution between different vibrational modes caused by the dispersion of the Grüneisen coefficients (phonon viscosity). The constants of interaction of the high-frequency acoustic modes with a long-wavelength deformation induced by an ultrasonic wave are estimated.     

Photoluminescence lineshape features of carbon δ-doped GaAs heterostructures

Photoluminescence lineshape properties of quasi-two-dimensional electron systems in setback δ-doped GaAs heterostructures are studied at liquid helium temperature. Contributions from the ground and the first excited two-dimensional subband are clearly observed. A simple fit to the lineshape including broadening demonstrates that there is an exponential low-energy tail associated with the ground subband. No such tail is observed for the first excited subband. The fit precisely reveals the subband bottom energies, the Fermi energy, the electron temperature and the recombination intensities. A self-consistent calculation of subband properties including the potential contribution of the setback δ-doping reproduces well the subband properties and the recombination intensities.     

The self-consistent calculation of Si δ-doped GaAs structures

In this study, we report results of a self-consistent calculation obtained for the sub-band structure of Si δ-doped GaAs material by using a new alternative method. We will discuss the influence of the δ-doping concentration and the δ-layerthickness on the sub-band structure for a non-uniform distribution, which is taken as different from the known Gaussian distribution. The confining potential, the sub-band energies, the sub-band occupations, and the Fermi energy have been calculated by solving the Schr?dinger and Poisson equations by using the Airy functions self-consistently. Received: 4 December 2000 / Accepted: 31 January 2001 / Published online: 26 April 2001