A molecular level study of liquid water with a flexible water model

The structural properties of water at different temperatures and pressures have been investigated by using a flexible water model and the inherent structure mechanism. The presence of 60$^\circ$ peak in the O--O--O angle distribution function and the behaviours of the hydrogen bonds in the first shell indicate that some water molecules in the second shell move toward the central molecules through the bending (not breaking) of hydrogen bonds and even become first-shell molecules of the central molecule on the basis of the O--O cutoff distance but not first-shell molecules by means of the hydrogen-bond criterion. The inherent-structure analysis of the O--O radial distribution functions at different pressures shows that the first peak is almost independent of the pressure; the position of second peak moves from 0.45 to 0.32nm as the pressure increases from $1\times 10^5$Pa to $1\times 10^9$Pa. This particularly evident pressure effect, i.e. the constant nearest-neighbours and the transformation of outer-neighbours on the basis of O--O distance, together with the results at different temperatures, gives a positive evidence for the two-state outer-neighbour mixture model: liquid water is a mixture of Ice-Ih-type-bonding and Ice-II-type bonding structures.     

Electronic absorption spectra of ascorbic acid in water and water–dialkylsulfoxide mixtures

Gaussian analysis (LinkFit program) was used to deconvolute overlapping absorption bands due to neutral and anionic forms of ascorbic acid (AA). It has been shown that the neutral form of AA predominates in aqueous solutions of AA containing dialkylsulfoxides (DASO) because a hydrogen-bonded complex forms between DASO and AA molecules.     

Blind estimation of shallow water acoustic channel

This paper proposed a method for blind estimation of underwater channels in shallow water environment by using received data at a single hydrophone or from single beam. First,the received signal is used for source signal reconstruction by means of signal-dependent TF(Time-Frequency)distribution,in association with instantaneous frequency estimation and TF inversion.Then the shallow-water channel estimation is achieved via WRELAX technique by use of the received signal and the estimated source signal.Finally,the results of numerical simulation and experimental test from real data taken in South China Sea trial have proved satisfactory.It is shown that the proposed method is useful for underwater channel estimation.     

Theoretical study of adsorption of water vapor on surface of metallic uranium

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Estimation of lake water—groundwater interactions in meromictic mining lakes by modelling isotope signatures of lake water

Abstract

A method is presented to assess lake water–groundwater interactions by modelling isotope signatures of lake water using meteorological parameters and field data. The modelling of δ¹⁸O and δD variations offers information about the groundwater influx into a meromictic Lusatian mining lake. Therefore, a water balance model is combined with an isotope water balance model to estimate analogies between simulated and measured isotope signatures within the lake water body. The model is operated with different evaporation rates to predict δ¹⁸O and δD values in a lake that is only controlled by weather conditions with neither groundwater inflow nor outflow. Comparisons between modelled and measured isotope values show whether the lake is fed by the groundwater or not. Furthermore, our investigations show that an adaptation of the Craig and Gordon model [H. Craig, L.I. Gordon. Deuterium and oxygen-18 variations in the ocean and the marine atmosphere. In Stable Isotopes in Oceanographic Studies and Paleotemperature, Spoleto, E. Tongiorgi (Ed.), pp. 9–130, Consiglio Nazionale delle Ricerche, Laboratorio di Geologia Nucleare, Pisa (1965).] to specific conditions in temperate regions seems necessary.     

Infrared spectroscopy of solid mixed ammonia–water and acetylene–water aerosol particles

Mixed water aerosols are important components of planetary and lunar atmospheres. In this work, we use rapid-scan Fourier transform infrared (IR) spectroscopy to study solid ammonia–water and acetylene–water aerosol particles formed in a bath gas cooling cell at 78 K. With this set-up, we record time-dependent extinction spectra of particle ensembles in the mid-IR to monitor changes to the internal structure of the aerosol particles. Both ammonia–water and acetylene–water were found to form molecularly mixed structures. The mixing is observed by monitoring the profile for the ammonia ν₂ band and the acetylene ν₅ band, both of which are sensitive to particle properties. Depending on the injection conditions, the mixed particles form either immediately after sample injection or after a short mixing period of several tens of minutes. We confirm the formation of mixed particles by comparing the experimental spectra with spectra calculated with the vibrational exciton model.     

Variations of water’s local-structure induced by solvation of NaCl

The researches on the structure of water and its changes induced by solutes are of enduring interests. The changes of the local structure of liquid water induced by NaCl solute under ambient conditions are studied and presented quantitatively with some order parameters and visualized with 2-body and 3-body correlation functions. The results show that, after the NaCl are solvated, the translational order t of water is decreased for the suppression of the second hydration shells around H₂O molecules; the tetrahedral order ｜q｜ of water is also decreased and its favorite distribution peak moves from 0.76 to 0.5. In addition, the orientational freedom k and the diffusion coefficient D of water molecules are reduced because of new formed hydrogen-bonding structures between water and solvated ions.     

Ignition of a floating droplet of organic coal–water fuel

The results of experimental investigations are presented for the ignition of droplets (particles) of organic coal–water fuels (OCWFs) floating in a flow of an oxidizer using a special combustion chamber from high-temperature quartz glass. The temperature and the velocity of motion of the oxidizer vary in the ranges of 500–900 K and 0.5–3 m/s. The initial sizes (radii) of fuel droplets amounted to 0.3–1.5 mm. As the basic OCWF components, particles (of 80–100 µm in size) of brown coal “B2,” water, mazut, and waste castor and compressor oils are used. With use of the system of high-velocity video registration, the conditions providing for floating of OCWF particles without initiation of burning and with the subsequent steady ignition are established. Four modes of OCWF-droplet ignition with different trajectories of their motion in the combustion chamber are singled out. The times of the OCWF-ignition delay in dependence on the size of fuel particles and oxidizer temperatures are determined. The deviations of the OCWF-ignition-delay times obtained under conditions of suspension of a droplet on the thermocouple junction and while floating in the oxidizer flow are established.     

Anomalies of the natural convection of water near 3.98°C

Natural convection of water in a cylindrical cavity with an open surface at a temperature of about 3.98°C (temperature of the maximum water density) is accompanied by typical anomalies on time dependences of temperatures of water layers. In particular, stabilization of temperature T_st is observed in the bottom region of the cavity and duration of such stabilization t_st may reach several hours depending on the experimental conditions. The results for solutions of sodium chloride and ethanol at a relatively low rate of water cooling show that temperature T_st coincides with temperature T_max corresponding to the maximum density of solutions.     

The equivalent potential of water molecules for electronic structure of lysine

In order to get more reliable electronic structures of proteins in aqueous solution, it is necessary to construct a potential of water molecules for protein’s electronic structure calculation. The lysine is a hydrophilic amino acid. It is positively charged (Lys+) in neutral water solution. The first-principles, all-electron, ab initio calcula-tions, based on the density functional theory, have been performed to construct such an equivalent potential of water molecules for lysine (Lys+). The process consists of three parts. First, the electronic structure of the cluster containing Lys+ and water molecules is calculated. By adjusting the positions of water molecules, the geometric structure of the cluster having minimum total energy is determined. Then, based on the structure, the electronic structure of Lys+ with the potential of water molecules is calculated using the self-consistent cluster-embedding (SCCE) method. Finally, the electronic structure of Lys+ with the potential of dipoles is calculated. The dipoles are adjusted so that the electronic structure of Lys+ with the potential of dipoles is close to that of water molecules. Thus the equivalent potential of water molecules for the electronic structure of lysine is obtained. The major effect of water molecules on lysine’s electronic structure is raising the occupied eigenvalues about 0.5032 eV, and broadening energy gap 89%. The effect of water molecules on the electronic structure of lysine can be simulated by dipoles potential.     

Low-temperature ignition of droplets of suspension organic water–carbon fuels

The conditions and integral characteristics of stable low-temperature ignition of droplets of suspension organic water–coal fuels are established by using the means of high-speed video-detection. The oxidizer temperature for these conditions varies in the range of 600–900 K (much below the temperatures in furnace chambers of modern power installations exceeding 1200 K). The velocity of the oxidizer-flow motion varies from 0.5 to 5 m/s, and the sizes (conditional radii) of droplets vary from 0.5 to 1.5 mm. The times of initiation of burning under conditions of low-temperature heating and the duration of the complete combustion of droplets of the corresponding compositions of organic water-coal fuels are determined. The necessary and sufficient conditions of stable ignition are singled out for promising organic water–coal fuels.     

Study of solid–liquid interface in water dispersions of microcrystalline celluloses

Interaction on the solid–liquid surface in dispersions of microcrystalline cellulose (MCC) with various particle sizes has been studied by means of rheological methods. It was shown that the MCC dispersions possess shear-thinning rheological properties. An inversely proportional relationship between the average particle size of the MCC particles and the viscosity of the dispersions was discovered. This phenomenon is explained by the decrease of water mobility with increase in the specific surface of the MCC particles. Irreversible closing of the MCC pores reduces the viscosity of water dispersions. Addition of some water-soluble polymers leads to a considerable increase in viscosity due to formation of macromolecular net composed of solid particles.     

Dielectric anomalous response of water at 60 °C

Recently, the paraelectric response of water was investigated in the range 0–100 °C. It showed an almost perfect Curie–Weiss behaviour up to 60 °C, but a slight change in slope of 1/ε_d versus T at 60 °C was overlooked. In this work, we report optical extinction measurements on metallic (gold and silver) nanoparticles dispersed in water, annealed at various temperatures in the range from 20 to 90 °C. An anomalous response at 60 °C is clearly detectable, which we associate to a subtle structural transformation in the water molecules at that temperature. This water anomaly is also manifested by means of a blue shift in the longitudinal surface plasmon resonance of the metallic nanoparticles for the solutions annealed at temperatures higher than about 60 °C. A reanalysis of 1/ε_d (T) for water in the whole temperature range leads us to conclude that the water molecule undergoes a subtle transformation from a low temperature (0–60 °C) configuration with a dipole moment μ₁ = 2.18 D (close to the molecular dipole moment of ice) to a high temperature (60–100 °C) configuration with μ₂ = 1.87 D (identical to the molecular dipole moment in water vapour).     

Behavior of an oppositely charged oil–water interface

Abstract  

This paper virtually presents induced behavior of an oppositely charged oil–water interface with the use of a high-speed camera. The elevation behavior of an oil–water interface is demonstrated experimentally, using a transparent acrylic cylindrical container (176 mm in inner diameter, 450 mm in height) with the bottom half (100 mm) filled with deionized water and the top half (between 50 and 150 mm) with an immiscible oil (viscosity 1 or 5 cSt). Copper fragments are inserted into each liquid (at top and bottom) to serve as electrodes, i.e., the oil layer is negatively charged, and the water layer is positively charged. A high-DC-voltage power supply provides potential difference of the order between about 1 and 30 kV. As a result, three kinds of behavior are observed, i.e.: (1) rotary motion on the interface in lower electric field supplied about E = 0.013 kV/mm; (2) fluctuation on the interface in medium electric field supplied about E = 0.021 kV/mm; (3) elevation of the interface in higher electric field supplied between E = 0.04 and 0.65 kV/mm (which depends on the depth of the oil layer).     

Raman lidar measurements of tropospheric water vapor over Hefei

L625 Raman lidar has been developed for water vapor measurements over Hefei, China since September 2000. By transmitting laser beam of frequency-tripled Nd:YAG laser, Raman scattering signals of water vapor and nitrogen molecules are simultaneously detected by the cooled photomultipliers with photon counting mode. Water vapor mixing ratios measured by Raman lidar show the good agreements with radiosonde observations, which indicates this Raman lidar is reliable. Many observation cases show that aerosol optical parameters have the good correlation with water vapor distribution in the lower troposphere.     

High-resolution inverse Raman spectroscopy of the ν1 band of water vapor

The Raman spectrum of the ν₁ band of water vapor at 7 Torr and 296 K, and at 84 Torr and 404 K, has been measured using high-resolution inverse Raman spectroscopy. The frequencies and relative intensities of the observed transitions are compared to a spectral model based on infrared data. Self-broadening coefficients have been determined for 22 lines from J = 0 to J = 8.     

Effect of sound waveguide on near-field in shallow water

1IntroductionThaditionallyallalysesofradiatingsoundcharacteristicofunderwatersourcesareper-formedwiththeradiatingsourcepassingafordhydrophoneand/orareceiverarraywithinveryshortrange.Andthen,themeasuredfieldisconvertedtothenormalsourcelevelac-cordingtothesphericalattenuationlaw.However,itiswellknownthatthewaveguideeffectcontributestosoundfield,whichisnottakenintoaccounitocorrectthesourcelevel.Ontheotherhand,thesoundwavguldewillbringaboutdifferenteffectatdifferentfrequencies.Ifthesaznespherical…     

Effective orientation of water in 1,4-dioxane···water: the rotational spectrum of the H2 17O isotopologue

The measurements of the rotational spectrum of 1,4-dioxane-water complex, performed by pulsed jet Fourier transform microwave spectroscopy, have been extended to the 7–18.5 GHz frequency region and to two additional isotopologues, 1,4-dioxane···H₂ ¹⁷O and 1,4-dioxane···HOD. The effective orientation of water in the complex has been obtained from the ¹⁷O quadrupole coupling constants.