An NMR-Based Analysis of Soil–Water Characteristics

Both direct and indirect methods for determining soil–water characteristic curves rely on determination of some empirical coefficients, which may not necessarily represent real microscopic mechanisms. Proton nuclear magnetic resonance (NMR) is a powerful tool for investigating water content and their interaction with solid particles in porous media. The NMR technique is widely used in food science and petroleum. In the present study, proton NMR spin–spin relaxation time (T ₂) distribution measurement is integrated with a Tempe apparatus to characterize the hydraulic processes of unsaturated soils, shedding insights into the microscopic mechanisms of pore water distribution and migration in the soil during hydraulic cycles. It is revealed that during a drying process the drainage of pore water occurs sequentially from larger pores to smaller pores, whereas in a wetting process the water invades into the soil sequentially from smaller pores to larger pores. A new procedure is developed which can be used to determine the pore size distribution of the soil based on the NMR T ₂ distribution measurements; compared to the traditional methods, the new method is rapid and non-destructive. The new procedure is validated by comparing the new result with the measurement of the mercury intrusion porosimetry.     

Phase Equilibrium and Critical Phenomena in the n-Pentan–Water and n-Hexane–Water Systems at High Temperatures and Pressures

Russian Physics Journal - PVTx-properties of the H2O – n-C5H12 and H2O – n-C6H14 mixtures are measured in the temperature range 303-680 K at pressures up to 60 MPa. The measurements...     

Water–fat separation with parallel imaging based on BLADE

Uniform suppression of fat signal is desired in clinical applications. Based on phase differences introduced by different chemical shift frequencies, Dixon method and its variations are used as alternatives of fat saturation methods, which are sensitive to B0 inhomogeneities. Iterative Decomposition of water and fat with Echo Asymmetry and Least squares estimation (IDEAL) separates water and fat images with flexible echo shifting. Periodically Rotated Overlapping ParallEL Lines with Enhanced Reconstruction (PROPELLER, alternatively termed as BLADE), in conjunction with IDEAL, yields Turboprop IDEAL (TP-IDEAL) and allows for decomposition of water and fat signal with motion correction. However, the flexibility of its parameter setting is limited, and the related phase correction is complicated. To address these problems, a novel method, BLADE-Dixon, is proposed in this study. This method used the same polarity readout gradients (fly-back gradients) to acquire in-phase and opposed-phases images, which led to less complicated phase correction and more flexible parameter setting compared to TP-IDEAL. Parallel imaging and undersampling were integrated to reduce scan time. Phantom, orbit, neck and knee images were acquired with BLADE-Dixon. Water–fat separation results were compared to those measured with conventional turbo spin echo (TSE) Dixon and TSE with fat saturation, respectively, to demonstrate the performance of BLADE-Dixon.     

Laser–Induced Fluorescence Detection of Carbamates Traces in Water

The absorption and fluorescence spectra of carbaryl (CB), carbofuran (CF) and carbendazim (MBC) have been studied. Fluorescence lifetime and fluorescence quantum yields are also reported as well as the influence of pH, solvent and presence of humic acids on fluorescence. The limit of detection (LD) of the three compounds has been measured by direct analysis by laser-induced fluorescence (LIF) using a pulsed YAG laser with an Optical Parametric Oscillator (OPO) as excitation source and an Intensified Charged Coupled Device (ICCD) camera for the fluorescence detection. Instrumental LD found for CB, for MBC and for CF are respectively 4, 50 and 1000 ng L⁻¹. In tap water, the LD obtained is 800 ng L⁻¹ for MBC and 20,000 ng L⁻¹ for CF. For CB, the use of a time shift between excitation and emission allows to reach a LD of 20 ng L⁻¹ in tap water.     

Translational Mobility of Components and Structure of Water–Ethanol Solutions

The concentration dependences of self-diffusion coefficients of water and ethanol molecules in water–ethanol solutions are obtained by the method of nuclear magnetic resonance spectroscopy with the pulse magnetic field gradient. On the basis of the ideas of hydration of ethanol molecules, the obtained dependences are interpreted and assumptions are made about the structural organization of water–ethanol solutions in the region of diluted and concentrated solutions.     

Capillary–Gravity Water Waves with Discontinuous Vorticity: Existence and Regularity Results

In this paper we construct periodic capillarity–gravity water waves with an arbitrary bounded vorticity distribution. This is achieved by re-expressing, in the height function formulation of the water wave problem, the boundary condition obtained from Bernoulli’s principle as a nonlocal differential equation. This enables us to establish the existence of weak solutions of the problem by using elliptic estimates and bifurcation theory. Secondly, we investigate the a priori regularity of these weak solutions and prove that they are in fact strong solutions of the problem, describing waves with a real-analytic free surface. Moreover, assuming merely integrability of the vorticity function, we show that any weak solution corresponds to flows having real-analytic streamlines.     

Determination of Cd in Water Samples by Hollow-Fiber–Supported Liquid-Membrane Extraction Coupled with Thermospray-Flame–Furnace Atomic-Absorption Spectrometry

ABSTRACT

A new method of hollow-fiber–supported liquid-membrane extraction (HF-SLME) coupled with thermospray-flame–furnace atomic-absorption spectrometry (TS-FF-AAS) for the determination of cadmium in water samples was developed. 1-Octanol was immobilized in the pores of the polypropylene hollow fiber as liquid membrane and used as the acceptor solution. Cd was selectively extracted from water samples into 1-octanol that filled the inner part of hollow fiber as the acceptor solution. The authors evaluated in detail some parameters that influence extraction and determination, such as the concentration of sodium diethyldithiocarbamate (DDTC), pH of samples, stirring rate, extraction time, flow rate of the pump, and interferences. Under optimized conditions, an enrichment factor of 146 could be obtained. In combination with thermospray-flame–furnace atomic-absorption spectrometry, a very low limit of detection (LOD) (5 ng L^?1) was achieved. The relative standard deviation (RSD) was 4.3% for five determinations of 0.1 ng mL^?1 cadmium. The accuracy of this method was validated by determination of certified reference water samples (GBW(E) 08607 and GSBZ(E) 50009-88). The proposed method was also applied to the determination of cadmium in tap water and river water, with the recoveries in the range of 90–96% for spiked samples.     

Comparative Study on Heat Transfer Enhancement of Low Volume Concentration of Al2o3–Water and Carbon Nano-Tube–Water Nano-Fluids in Transition Regime Using Helical Screw Tape Inserts

This study reports the comparison of heat transfer and friction factor characteristics of helical screw inserts in Al₂O₃–water and carbon nano-tube–water nano-fluids through a straight pipe in transition regime with constant heat flux boundary condition. Experiments were carried out by using 0.15% volume concentration of Al₂O₃–water and carbon nano-tube–water nano-fluid with helical tape inserts of twist ratio, TR = 1.5, 2.5, and 3. The thermal performance of helical screw tape inserts with the carbon nano-tube–water nano-fluid is found -to be higher when compared to the Al₂O₃–water nano-fluid. In addition, the maximum enhancement in heat transfer was obtained for the carbon nano-tube–water nano-fluid with helical tape inserts of twist ratio 1.5. The increase in pressure drop of the Al₂O₃–water nano-fluid with helical screw tape inserts is found to be higher compared to the carbon nano-tube–water nano-fluid helical screw tape inserts at lower value of twist ratio.     

Unusual EPR Spectra with Inverse Axial g values of Chlorosalicylate–Cu(II)–2,6-Pyridinedimethanol Complex in Frozen Water–Methanol Solution

Copper(II) complex systems containing 3,5-di, 4-, or 5-chlorosalicylic acids (X-ClsalH) and different copper(II) salts (copper acetate (Cu(ac)₂) or copper sulphate (CuSO₄)), with varying 2,6-pyridinedimethanol (pydime) concentration, [Cu(ac)₂(aq) or CuSO₄(aq) + 2 (X-ClsalH(solv)) + x pydime(solv)], where X = 3,5-di, 4-, or 5- and x = 0, 1, 2, 4, or 8, were prepared. The effects of two copper(II) salts (containing anions of different basicity) and N-donor ligand (pydime) with varying ligand-to-metal ratio (x) on the formation of resulting complexes were studied by electron paramagnetic resonance (EPR) spectroscopy in frozen water/methanol (1:3 v/v) solutions. For x ≥ 2, unusual Cu(II) EPR spectra with "inverse" axial g values of (g _⊥ > g _∥ > 2.0023) were observed, which can indicate the compressed octahedral geometry of the central copper atom with the unpaired electron/hole localized on the $ d_{{z^{2} }} $ orbital. However, for x = 1, composite Cu(II) EPR spectra with both "usual" and "inverse" axial g values were detected. Finally, for x = 0 (ligand not present) Cu(II) EPR spectra only with the ‘usual’ axial g values of g _∥ > g _⊥ > 2.0023 were collected, which can indicate the elongated octahedral geometry of the central copper atom with the unpaired electron/hole localized on $ d_{{x^{2} - y^{2} }} $ orbital. The above described observations are independent of the usage of different copper(II) salts and X-chlorosalicylic acids.     

Specific Solvation of a 4-DASPI Dye in a Water–Ethylene Glycol Binary Solvent

Optics and Spectroscopy - The solvatochromic shifts of the maxima of the absorption spectra of a 4-DASPI dye (4-[4-(dimethylamino)styryl]-1-methylpyridinium iodide) in a water–ethylene glycol...     

Influence of the Structure of Water–Alcohol Solutions of Dyes on Their Molecular Association

The spectral and luminescence characteristics of water and water–ethanol solutions of dyes have been investigated. The efficiency of the process of association of dye molecules and the structure of the complexes formed depending on their concentration and the solvent composition have been established. The presence of inhomogeneities in the distribution of dissolved complex molecules in the water matrix which determine the high efficiency of the association processes in water solutions as compared with other solvents is shown. The characteristic sizes of these inhomogeneities have been estimated.     

Role of Aging in the Formation of Non-spherical Nanostructures during Laser–Matter Interaction in Water

Optics and Spectroscopy - Pulsed laser ablation of different surfaces in liquid environment has broad prospects to selectively synthesize nanoparticles (NPs) with specific optical properties, as...     

Water–heat migration and frost-heave behavior of a saturated silty clay with a water supply

In this study, a large-scale one-directional freezing experiment with water supply was performed to investigate the water–heat migration and frost-heave behavior of the saturated silty clay. The results indicate that the temperature gradient is larger in the frozen zone than that in the unfrozen zone because of the heat release of the supplied water and its water–ice phase change during the freezing process. Furthermore, the different parts of the total frost heave are evaluated, respectively, and it is also found that the frost heave can be reduced if the advance rate of the freezing front is effectively controlled even if external water is sufficient.     

To the Problem of the Water Transparency Bandwidth (1.8–11.2 eV) and Hydrogen Bonds

It is experimentally detected the gravity center of theOHband of Raman scattering (RS) of picosecond pulses in water shifts by ~40 cm^?1 (~0.005 eV) to the high-frequency wing due to shortening the time of observation of the hydrogen bond restructuring in comparison with RS of nanosecond pulses. It was shown that declarative negation of hydrogen bonds and the introduction of the water transparency window half-width (5 eV) or (11.2 eV as seen in Fig. 1 of the paper by V. G. Artemov [Bulletin of the Lebedev Physics Institute 42, 187-191 (2015)] should be regarded as incorrect. These values multiply exceed the well known half-width in the range of 650–360 nm (~1.8 eV [1] which is defined by the fundamental absorption region and OH stretching vibration band overtones from the side of UV and IR regions, respectively.     

Infrared Spectra Interpretations of Clay-Adsorbed Water in Relation to the “Anomalous” Water Controversy

Abstract

The nature of surface adsorbed water has been the subject of countless investigations. Much of the discussion has centered around the degree and strength of H-bonding to surface groups and between adjacent water molecules.^1,2 Water condensed into glass or quartz capillaries sometimes has unusual properties. This unusual water has been referred to as “orthowater,”³ “anomalous water,”^4,5,6 and “polywater”^7,8 and was thought by some to be polymers of water formed by specific surface catalysis.^1–3 Several possible structures of “polywater” have been suggested which require formation of symmetrical or very strong H-bonds between water molecules.^4,6,7 Infrared spectra of polywater have been presented^7,8 and the strongest absorption band which appeared at 1595 cm^?1 was assigned to the symmetric O-H-O bond. However, more recent investigations suggest that the observed polywater bands may actually be SO₄ ^2-, -COOH^?, or HCO₃ ^? bands, impurities collected by surface diffusion,⁹ or bands of a HNO₃ solution formed by corona discharge.¹⁰ Other observers^11,12 suggest that polywater may be a hydrosol formed by surface contaminates.     

Investigation on Heat Transfer and Pressure Drop of Copper–Water Nanofluid Flow in Plain and Perforated Channels

This article reports an experimental study on copper–water nanofluid flow inside plain and perforated channels. The effects of flow rate and nanoparticle concentration on the heat transfer and pressure drop are studied. It is found that the perforated channel has a remarkable heat transfer enhancement of 24.6%. Furthermore, by using the copper–water nanofluid instead of the base fluid, the heat transfer coefficient as well as pressure drop are increased for both plain and perforated channels. A noticeable thermal performance factor of 1.34 is obtained for the simultaneous utilization of both the heat transfer enhancement techniques considered in this article.     

Application of Gas Chromatography–Atomic Fluorescence Spectrometry Hyphenated System for Speciation of Butyltin Compounds in Water Samples

ABSTRACT

A laboratory-established capillary gas chromatography (GC)–atomic fluorescence spectrometry (AFS) hyphenated system was applied to butyltin speciation in water samples. Monobutyltin (MBT), dibutyltin (DBT), and tributyltin (TBT) were extracted and preconcentrated with headspace solid-phase microextraction (SPME) technique after derivatization using KBH₄, and then determined by GC-AFS directly. The experimental conditions—including the flow rates of carrier gas, argon and hydrogen–and the lamp current—were optimized in detail. Under the optimum conditions, the detection limits for MBT, DBT, and TBT, calculated as three times the baseline noise, were 10, 0.2, and 0.1 ng mL^?1 Sn, respectively. Good linear relationships were obtained when the concentrations of MBT, DBT, and TBT increased to 3000, 100, and 200 ng mL^?1 Sn. The relative standard deviations (RSDs) of five replicates were 5.2%, 7.4%, and 7.1% for MBT, DBT, and TBT, respectively. The recoveries of MBT, DBT, and TBT in three different types of water samples (seawater, tap water, and wastewater) were between 72.1% and 97.9%, indicating that the proposed method was accurate and feasible for speciation analysis of butyltin compounds in water samples.     

EPR Study of 5-Chlorosalicylate-Cu(II)-3-Pyridylmethanol Ternary Complex Systems in Frozen Water–Methanol Solutions

Two copper(II) ternary complex systems containing 5-chlorosalicylic acid (5-ClsalH) and different copper(II) salts with varying 3-pyridylmethanol (ron = ronicol) concentration, system I [CuSO₄ (aq) +2(5-ClsalH(solv)) + xron(l)] and system II [Cu(ac)₂(aq) + 2(5-ClsalH(solv)) + xron(l)], where x = 0, 2, 4, 6 and 8, were prepared and studied by electron paramagnetic resonance (EPR) spectroscopy in frozen water–methanol solutions to observe the effects of different copper(II) salts and varying neutral ligand concentration on the formation of resulting complexes in solution. The trend in g-values (g _|| > g _⊥ > 2.0023) indicates that the unpaired electron on the copper ion is localized in the d_{x² - y²} d_{{x}^{\rm{2}} - {y}^{\rm{2}}} orbital. The detailed analysis of the second-derivative Cu(II) EPR spectra has shown well-resolved ¹⁴N superhyperfine splitting in the perpendicular part of the axially symmetric spectra. The resolution of nitrogen superhyperfine multiplet patterns increased with increase in the ronicol concentration (ligand-to-metal ratio x). The number of superhyperfine lines was found to be constant (nonet) when x > 4 for system I and x ≥ 4 for system II. This fact indicates that for these x-values four equivalent nitrogen atoms could be coordinated to the central copper atom in the equatorial plane of both systems.     

Flow Characteristics of Deionized Water in Microtubes

We investigate the deionized water flows in microtubes made of quartz at high pressure under steady flow condition in situations that （i） pure nitrogen is used as the pressure source, and the experimental pressure is 0.1-1 MPa; （ii） the inner diameters of the experimental microtubes are from 6μm to 50μm. The results indicate that （i） the flow characteristics of the microtubes with inner diameters of 50μm, 20μm, 15μm,10μm agree well with the traditional macro flow mechanics, （ii） there are obvious warps as compared with theoretical values in 6μm microtubes.