Evaluation of Ph and granite/hot water interaction under geothermal conditions

Abstract

The in-situ laboratory measurement of pH in a granite-hot water reaction system has been undertaken under flowing conditions. The calculation of fluid pH and multi-component chemical equilibria in the granite-hot water reaction system was made, using the calculation program SOLVEQ92. In this study, the chemical equilibrium relationship of granite and hot water interaction was also deduced using the some program. The measurement of in-situ pH in the granite-hot water reaction system was undertaken in the temperature and pressure range of 100–250°C and 20MPa respectively. The in-situ pH value shows good agreement with the pH calculation value with regard to multi-component chemical equilibria. As a result of this work, it is reasonable to suggest that the pH of reservoir fluids in geothermal system can be readily estimated by use of the SOLVEQ92 calculation program, which provides a ‘calculated’ pH value.     

Onset of Rayleigh-Bénard convection in a ternary liquid system and the Onsager law with generalized thermal diffusion

For the ternary system isopropanol-ethanol-water, a model was proposed to estimate the cross diffusion coefficients from measurements of the critical parameters for the onset of Rayleigh-Bénard convection, together with the consideration of the reciprocity laws of Onsager. Among the three forms of the chemical potentials used, not a single chemical potential was found to provide a correlation between the Onsager laws and the experimental data. The present study shows that consideration of a generalized thermal diffusion term taking account of all components is adequate to estimate quantitative values of the cross diffusion coefficients.     

INDIRECT METAL ION (K+, NA+, MG2+, AND CA2+) QUANTIFICATION FROM INFRARED SPECTROSCOPY

ABSTRACT

In this paper, we report the use of Mid-FTIR spectroscopy coupled with Partial Least Squares method for the quantitative determination of various alkaline and alkaline earth metals in aqueous solution owing to their interactions with sucrose. First of all, prediction equations that linked cation concentration to the spectral data were established independently for each ion (K⁺, Na⁺, Mg²⁺ or Ca²⁺): very high correlation coefficient values between the two first axes and the chemical values were obtained. Moreover, a good prediction could be made whatever the nature of ion involved in interaction with sucrose. Then, all spectral data have been gathered for generating a common prediction equation. In this case, the predictions of metal ion concentration are almost as much accurate. For both regression models, Mg²⁺ appears to provide the best precision in quantification. Nevertheless, the different types of aqueous solution, regarding to ions, can be discriminated on the basis of their spectral data set up with the three mostly correlated axes of the PCA.     

A Note on the Mechanism of Vacancy Production in Ultra-High-Speed deformation

Various possible and conceivable mechanisms of vacancy production in crystal during rapid deformation are considered, in attempt to explain how a large number of vacancy clusters can be produced with or without existence of dislocations during ultra-high-speed deformation of crystalline materials and to determine whether or not vacancy formation alone can effect deformation. Theoretical discussions mainly address the geometrical aspect of vacancy production, and are, therefore, neither quantitative in nature nor conclusive. Nevertheless, in connection with the present note, the author wishes to emphasize the importance of vacancy production in ultra-high-speed deformation of materials.     

Relevance of the displacement damage concept for the evaluation of radiation effects in metals

Abstract

Changes in dimensions, mechanical properties and chemical composition due to irradiation by different particles at elevated temperatures are compared on the basis of atomic displacements derived from low temperature resistivity damage rates. The available data on void swelling, irradiation creep and room temperature hardening correlate reasonably well on this basis. The correlation seems poor for hardening at high temperatures and even worse for fracture properties and chemical effects (solute segregation, precipitate growth). The results are discussed in terms of the basic damage processes.     

On the influence of two coexisting species of susceptibility-producing structures on the R21 relaxation rate

PurposeTissue microstructure can influence quantitative magnetic resonance imaging such as relaxation rate measurements. Consequently, relaxation rate mapping can provide useful information on tissue microstructure. In this work, the theory on relaxation mechanisms of the change of the relaxation rate ∆R₂^⁎ in the presence of spherical susceptibility sources in a spin bearing medium is validated in simulations and phantom experiments for the coexistence of two species of susceptibility sources.MethodsThe influence of coexisting spherical perturbers with magnetic susceptibilitys of different signs was evaluated in Monte Carlo simulations including diffusion effects in the surrounding medium. Simulations were compared with relaxometry measurements at 1.5 Tesla and at 3 Tesla. The phantoms used to validate the simulations were built from agarose gel containing calcium carbonate and tungsten carbide particles of different size and concentration.ResultsThe Monte Carlo simulations showed, that the change in relaxation rate only depends on the overall amount of susceptibility producing structures in the simulation volume and no difference was found, if mixtures of positive and negative particles were simulated. Phantom measurements within the static dephasing regime showed linear additivity of the effects from positive and negative susceptibility sources that were present within the same voxel.ConclusionsIn summary, both the simulations and the phantom measurements showed that changes in the relaxation rate ΔR₂^⁎ add up linearly for spherical particles with different susceptibilities within the same voxel if the conditions for the static dephasing regime are fulfilled. If particles with different susceptibilities have both different sizes and violate the conditions of the static dephasing regime, effects on relaxation rates might no longer be linear.     

Gas Chromatography-Fourier Transform Infrared Spectrometry

Abstract

Difficult mixture analysis problems can usually be simplified when chromatographic separating techniques are employed to isolate individual mixture components. Many different discrimination methods based on observation of physical or chemical properties have been developed to detect substances Separated by gas chromatography. These detectors facilitate quantitative analysis when mixture component identities are known but provide little structural information for identification of unknown mixture components. On the other hand, mass spectrometry and infrared spectroscopy can provide a wealth of structural information. Mass spectra and infrared spectra are representative of eluent structure in a complementary manner. Mass spectrometry is often used to obtain molecular weight information and can be used to distinguish homologues. Infrared spectra reveal molecular functionalities and are particularly useful for isomer discrimination.     

Thermal Analysis for Velocity,Kinetics, and Enthalpy Reaction Measurements in Microfluidic Devices

Abstract

The aim of this work is to present new devices for the measurement of velocity, kinetics, and enthalpy of chemical reactions occurring in a microfluidic chip, co-flow, or droplets flow. The thermal analysis goes from the macroscopic approach by microcalorimetry to microscopic analysis inside the microchannel by IR thermography. Concerning microcalorimetry, the enthalpy is deduced from the measurement of the global heat flux dissipated by the chemical reaction as a function of the molar flow rate. A validation is presented on a well-known acid-base reaction. This device can be combined with an IR camera for local characterization. The processing of the measured temperature fields allows the estimation of properties of great importance for chemical engineers, such as heating source distribution (i.e., the kinetics) of the chemical reaction along the channel. A validation experiment of a temperature field processing method is proposed with the Joule effect. From such a previous experiment, a Peclet field is estimated and used in a further step in order to study an acid-base co-flow configuration. Finally, a first tentative of thermal characterization inside droplets flow during an acid-base chemical reaction is also presented.     

QCD versus recent experimental data on lepton pair production at accelerator energies

New and precise experimental results on Drell-Yan pair production at accelerator energies are now available, both in π^? andp-nucleus interactions. These data are analyzed within the QCD framework including soft gluon resummation. It is shown that a quantitative agreement of the theory with experimental data can be reasonably managed. In particular, the soft gluon resummation is shown to build up nicely the so-calledK-factor. The pion formfactor is deduced from experimental data, but is rather sensitive to the nuclear structure functions we use. Definite nuclear structure functions are needed.     

The construction and performance of a high pressure continuous flow preparative apparatus

Abstract

A continuous flow chemical reactor operating at up to 4 kbar has been constructed and used in a variety of preparative applications with acid-catalysed reactions. The rates of reactions under flowing conditions were found to be considerably greater than those carried out under comparable static conditions.     

Simulation of the interaction between an edge dislocation and ⟨111⟩ interstitial dislocation loops in α-iron

ABSTRACT

The dependence of the interactions of intermediate-size ½<111> self-interstitial atom (SIA) loops with an edge dislocation on strain rate and temperature was investigated by molecular dynamics (MD) simulations for the interatomic potential derived by Ackland et al. (A97). For low temperatures (T?=?1?K), the mechanisms of the interactions were in agreement with recent literature. It was shown that a second passing of the dislocation through the loop led to a different mechanism than the one that occurred upon first passing. Since these mechanisms are associated with different SIA loop sizes, and since the loop lost a number of SIAs upon first interaction, it was deduced that the dividing threshold between large and small loops (rendering them strong or weak obstacles, respectively) is at the vicinity of the loop size studied (169 SIAs). For higher temperatures (T?=?300?K), the strain rate dependence proved strong: for low strain rates, the dislocation absorbed the loop as a double super-jog almost immediately and continued its glide unimpeded. For a high strain rate, the dislocation was initially pinned due to the formation of an almost sessile segment leading to high critical stress.     

Empirical field mapping for gradient nonlinearity correction of multi-site diffusion weighted MRI

BackgroundAchieving inter-site / inter-scanner reproducibility of diffusion weighted magnetic resonance imaging (DW-MRI) metrics has been challenging given differences in acquisition protocols, analysis models, and hardware factors.PurposeMagnetic field gradients impart scanner-dependent spatial variations in the applied diffusion weighting that can be corrected if the gradient nonlinearities are known. However, retrieving manufacturer nonlinearity specifications is not well supported and may introduce errors in interpretation of units or coordinate systems. We propose an empirical approach to mapping the gradient nonlinearities with sequences that are supported across the major scanner vendors.Study typeProspective observational study.SubjectsA spherical isotropic diffusion phantom, and a single human control volunteer.Field strength/sequence3 T (two scanners). Stejskal-Tanner spin echo sequence with b-values of 1000, 2000 s/mm² with 12, 32, and 384 diffusion gradient directions per shell.AssessmentWe compare the proposed correction with the prior approach using manufacturer specifications against typical diffusion pre-processing pipelines (i.e., ignoring spatial gradient nonlinearities). In phantom data, we evaluate metrics against the ground truth. In human and phantom data, we evaluate reproducibility across scans, sessions, and hardware.Statistical testsWilcoxon rank-sum test between uncorrected and corrected data.ResultsIn phantom data, our correction method reduces variation in mean diffusivity across sessions over uncorrected data (p < 0.05). In human data, we show that this method can also reduce variation in mean diffusivity across scanners (p < 0.05).ConclusionOur method is relatively simple, fast, and can be applied retroactively. We advocate incorporating voxel-specific b-value and b-vector maps should be incorporated in DW-MRI harmonization preprocessing pipelines to improve quantitative accuracy of measured diffusion parameters.     

Influence of water based embedding media composition on the relaxation properties of fixed tissue

BackgroundIn MRI of formalin-fixed tissue one of the problems is the dependence of tissue relaxation properties on formalin composition and composition of embedding medium (EM) used for scanning. In this study, we investigated molecular mechanisms by which the EM composition affects T2 relaxation directly and T1 relaxation indirectly.ObjectiveTo identify principal components of formaldehyde based EM and the mechanism by which they affect relaxation properties of fixed tissue.MethodsWe recorded high resolution ¹H NMR spectra of common formalin fixatives at temperatures in the range of 5 °C to 45 °C. We also measured T1 and T2 relaxation times of various organs of formalin fixed (FF) zebrafish at 7 T at 21 °C and 31 °C in several EM with and without fixative or gadolinium contrast agents.ResultsWe showed that the major source of T2 variability is chemical exchange between protons from EM hydroxyls and water, mediated by the presence of phosphate ions. The exchange rate increases with temperature, formaldehyde concentration in EM and phosphate concentration in EM. Depending on which side of the coalescence the system resides, the temperature increase can lead to either shortening or prolongation of T2, or to no noticeable change at all when very close to the coalescence. Chemical exchange can be minimized by washing out from EM the fixative, the phosphate or both.ConclusionThe dependence of T2 in fixed tissue on the fixative origin and composition described in prior literature could be attributed to the phosphate buffer accelerated chemical exchange among the fixative hydroxyls and the tissue water. More consistent results in the relaxation measurements could be obtained by stricter control of the fixative composition or by scanning fixed tissue in PBS without fixative.     

Raman Spectroscopy Can Detect and Monitor Cancer at Cellular Level: Analysis of Resistant and Sensitive Subtypes of Testicular Cancer Cell Lines

Abstract: Raman spectroscopy has been applied to analyze testicular cancer cell lines. Spectral differences between resistant and sensitive subtypes of testicular cancer cell line 833k samples were successfully analysed. The technique allowed reproducible and quantitative analysis of the specimen and illustrated the chemical specifications of the samples precisely. Six pairs of testicular cancer cell line 833k were studied and the findings were backed by statistical methods; that is, partial least squares discriminant analysis (PLS-DA).

It was concluded that Raman spectroscopy can objectively differentiate between resistant and sensitive cell lines. These results suggest that in the future it may be possible to use cell lines and diagnostic Raman spectroscopy for preoperative classification of biological molecules. Further research is underway to determine whether results obtained from spectroscopic analysis of cell lines can be applied to actual human tissue samples.     

The impact of reduced chemistry on auto-ignition of H2 in turbulent flows

The auto-ignition behaviour of hydrogen in a turbulent flow field has been studied through a combination of detailed and systematically reduced chemistry with a transported PDF approach closed at the joint-scalar level. Radiation is accounted for through the RADCAL method and the inclusion of enthalpy into the joint-scalar PDF. Molecular mixing is closed using the modified Curl's model with the mixing frequency accounted for via two algebraic closures. The main aim of the work is to compare the impact of alternative chemical mechanisms on auto-ignition and to explore the accuracy that can be expected when reactive scalars are sequentially removed through the application of quasi-steady-state approximations (QSSAs). Two different detailed mechanisms were tested to establish the effects of intrinsic uncertainties in the detailed chemistry and to provide reference points to past work. The mechanisms feature nine solved species and 19 or 20 reversible chemical reactions. The chemical mechanisms were subsequently systematically reduced to five, four and three independent scalars through the successive introduction of QSSAs for H₂O₂, HO₂ and O. Resulting inaccuracies were quantified following each simplification step with reference to experimental data obtained in shock tubes and under turbulent flow conditions in the Cabra burner configuration. A sensitivity analysis was also performed to identify the relative impact of uncertainties in key reactions as compared to systematic simplification process. It was found that alternative recommended rates for the O + H₂ = OH + H reaction have an impact on the point of flame stabilization that is similar to that observed as a consequence of the simplification process. The work also shows that realistic results can be obtained with simplified chemistry. However, it is also concluded that the temporal evolution of the radical pool and the point of stabilization is affected by the introduction of a QSSA for the O radical. Furthermore, it is shown by comparisons with time resolved OH radical data obtained in shock tubes that the progressive elimination of species via QSSA leads to a shortening of ignition delay times and that the same effects are present, but less severe, in turbulent flow fields.     

A neutron diffraction study of the high pressure structural phase transition in (CD3ND3)2MnCl4

Abstract

High-pressure neutron diffraction experiments have been performed at room temperature on a powdered sample of the perovskite type-layer compound (CD₃ND₃)₂MnCl₄. A phase transition from the orthorhombic room-temperature phase (ORT) to a new high-pressure phase (HP) is demonstrated at 20.5 ± 0.2 kbars. A monoclinic unit cell with lattice parameters a = 6.824 (5) Å; b = 7.409 (8) Å c = 17.126 (12) Å and β = 82.94(9)° has been inferred for the HP phase, consistent with a two-dimensional perovskite-type structure. The HP phase appears to be much more compact than ORT; it is characterized, in particular, by an important compression (?10%) of the inter-layer distance. Space groups P2/c or P2₁/c consistent with the experimental data have been deduced for the HP phase, after group theoretical considerations based on shear transformation and order-disorder mechanisms.     

RIE-induced damage and contamination in silicon

Abstract

Reactive ion etching always causes a dynamic radiation effect to crystalline silicon, beacause of an energetic particle bombardment. RIE induced radiation effects are mostly confined to the near surface within a projected range of impinging ions, but point defects, which are highly mobile at room temperatures, can migrate further into the bulk before a damaged surface layer is etched away. Competition between etch rates and damage rates ultimately determines a degree of the RIE damage residue: the slower the etch rate, the heavier the damage may be accumulated at the near surface, eventually leading to amorphization of the surface region. Also, a removal of the surface layer due to etching or sputtering enhances a chemical reaction between a bare surface and incoming radicals. This easily forms a foreign material on the surface which gives rise to a serious contamination problem. A post-cleaning at a low temperature is highly desirable whenever the surface of active devices must be exposed to reactive plasmas.     

Isotopengeochemische Untersuchungen an organischen Substanzen aus Sedimenten der Hilsmulde (Nordwestdeutschland)

Abstract

Model coalification experiments have been carried out using organic matter in sediments from the Hils syncline. In the experiments we wanted to elucidate, to what extent different facies situations can be observed in the investigated region and which conclusions can be drawn regarding the type of originating substances for hydrocarbons adsorbed in drilling cores. As a result of chemical and isotope analyses the organic substances should be characterized not only as pure sapropelites but show in different degree the participation of humic organic matter.

The obtained data of the several evaluation methods used for the characterization of organic matter are in good agreement for the particular samples.     

Numerical simulation of laminar co-flow methane–oxygen diffusion flames: effect of chemical kinetic mechanisms

Laminar co-flow methane–oxygen flames issuing into the unconfined atmosphere have been studied. A numerical model, which employs different chemical kinetics sub-models, including a skeletal mechanism with 43 reaction steps and 18 species and four global reaction mechanisms (two 2-steps and two 4-steps mechanisms), and an optically thin radiation sub-model, has been employed in the simulations. Numerical model has been validated against the experimental results available in literature. The numerical predictions from the global kinetic mechanisms have been compared with the 43-steps mechanism predictions. At all oxygen flow rates, the predictions of the distributions of temperature, mass fractions of CH₄, O₂ and CO₂ by the 2-steps mechanisms are closer to 43-steps mechanism. The overall distribution of H₂O predicted by 2-steps mechanisms is close to that of 43-steps except for the maximum value. Especially at higher oxygen flow rates, the modified 2-steps mechanism predicts these quantities much closer to those predicted by the 43-steps mechanism. Further, the 2-steps mechanisms predict location of the reaction zone accurately. However, they can just give an idea of overall CO distribution in terms of the axial and radial locations within which CO will almost be consumed, but not its maximum value in the domain. The 4-steps mechanisms predict the trend of variation of these quantities quite reasonably. However, they under-predict the location of the reaction zone. At higher oxygen flow rates, the predictions by 4-steps mechanisms becomes better, especially in the prediction of maximum CO and H₂O. Over all, the modified 2-steps mechanism can be recommended for reasonable and economical predictions of oxy-rich methane flames.