Efficiency and resistance of the artificial oxalate protection treatment on marble against chemical weathering

The artificial oxalate protection method was analyzed in laboratory experiments in order to achieve an optimum treatment application and concentration giving rise to its most effective protective nature. Spectroscopic (Fourier transform infrared, Micro-Raman and UV-vis colorimetry), microscopic (scanning electron microscope) and contact-angle analyses were carried out to characterize Carrara marble samples before and after application of the treatment to validate its efficiency. The resistance effects against chemical weathering were subsequently observed in a lab-controlled weak acid rain experiment. An acid spray at pH 5.5, representative of normal rain was used to provoke degrade of natural marble, marble treated with the artificial oxalate protective at concentrations of 0.4 and 5% and marble treated with a commercial organic silicon product. Run-off solutions sampled at timely intervals were tested for any change in pH followed by ion chromatography measurements for the presence of calcium ions in solution. The chromatography results of the oxalate treatment applied at a 5% concentration are analogous to an organic commercial product indicating its validity as a method for the conservation of carbonate substrates conferring protection to stone materials against acid environments.     

EPR and optical study of Mn doped ammonium oxalate monohydrate

Studies on fine and hyperfine structures of paramagnetic resonance spectra in single crystals of Mn²⁺: ammonium oxalate monohydrate are reported. As sufficient numbers of lines were not obtained at room temperature, measurements have been done at liquid nitrogen temperature and at the frequency of X-band. The Mn²⁺ spin Hamiltonian parameters have been evaluated employing a large number of resonant line positions observed for various orientations of the external magnetic field and the surrounding crystalline field has been discussed. The values of the zero field parameters that give good fit to the observed EPR spectra have been evaluated. The values obtained for g, A, B, D, E and a are 2.0002±0.0002, (100±2)×10⁻⁴, (79.5±2)×10⁻⁴, (257±2)×10⁻⁴, (85±2)×10⁻⁴ and (−18±1)×10⁻⁴ cm⁻¹, respectively. The percentage of covalency of the metal-ligand bond is also determined. The optical absorption study has been done at room temperature. The observed bands are assigned as transitions from the ⁶A_1g(S) ground state to various excited quartet levels of Mn²⁺ ion in a cubic crystalline field. The electron repulsion parameters (B and C), the crystal field splitting parameter(Dq) and the Trees correction (α) providing good fit to the observed optical spectra have been estimated and the values obtained for the parameters are B=897, C=2144, Dq=910 and α=76 cm⁻¹.     

EPR and optical absorption study of Cr-doped ammonium oxalate monohydrate single crystals

The electron paramagnetic resonance (EPR) study of the Cr³⁺-doped ammonium oxalate monohydrate (AOM) single crystal is done at room temperature. Two magnetically inequivalent sites for chromium are observed. The hyperfine structure for Cr⁵³ isotope is also obtained. The spin Hamiltonian parameters are evaluated as: D=(309±2)×10⁻⁴ cm⁻¹, E=(103±2)×10⁻⁴ cm⁻¹, g=1.9820±0.0002, A=(161±2)×10⁻⁴ cm⁻¹ for site I and D=(309±2)×10⁻⁴ cm⁻¹, E=(103±2)×10⁻⁴ cm⁻¹, g=1.9791±0.0002, A=(160±2)×10⁻⁴ cm⁻¹ for site II, respectively. On the basis of EPR data the site symmetry of Cr³⁺ doped single crystal is discussed. The optical absorption spectra are recorded in 195-925 nm wavelength range at room temperature. The energy values of different orbital levels are determined. On the basis of EPR and optical data, the nature of bonding in the crystal is discussed. The values of different parameters are B=803, C=3531, D_q=2208 cm⁻¹, h=0.59 and k=0.21, where B and C are Racah parameters, D_q is crystal field parameter and h and k are nephelauxetic parameters, respectively.     

草酸铵作稳定剂石墨原子吸收法直接测量土壤悬浮液中微量镉

本研究了石墨炉原子吸收法直接测量土壤浮液中微量镉。比较子不同基体改进剂及背景吸收对测量的影响。并以草酸铵为稳定剂对悬液的稳定性进行了研究，结果表明在碱性条件下，使用０．００７ｍｏｌ·Ｌ＾－１的草酸铵作稳定剂时，土壤悬浮液比较稳定。应用固体悬浮液进样方法，直接测定了土壤样品中的微量镉。     

Mössbauer studies of 151Eu in europium oxalate, europium bissalen ammonium and europium benzoate

Although a number of europium water insoluble chelates have been prepared for several decades, the covalent nature of these compounds has never been established in any quantitative fashion. Shifts in the I.R. bands and conductivity measurements of these salts were hitherto used to qualitatively compare their molecular nature. In this communique we have used temperature coefficients of ¹⁵¹Eu Mössbauer spectra to determine the Debye temperatures (θ _D) of three europium chelates: namely europium oxalate, europium bissalen ammonium (recently reported) and europium benzoate and compared their θ _D with the measured θ _D of the known ionic EuF₃. Additionally, the mean square amplitude (<x ²) of these four compounds was computed and plotted as a function of temperature giving in each case a reasonable linear plot. It was interesting to note that the θ _D of the most ionic EuF₃ was greatest (283 ± 10 K) followed by the oxalate (166 ± 15 K), then the europium bissalen ammonium (133 ± 5 K) and lastly the europium benzoate with a θ _D of (105 ± 5 K).     

Mechanism of LiFePO4 solid-phase synthesis using iron (II) oxalate and ammonium dihydrophosphate as precursors

An experimental study of the thermolysis mechanism of FeC₂O₄, NH₄H₂PO₄, Li₂CO₃, and citric acid from the viewpoint of the usage of a mixture of these compounds in lithium power engineering for the solid-state synthesis of LiFePO₄ and its composite with carbon LiFePO₄/C as well as comparison of experimental data with thermodynamic calculations were made in the temperature range from 25 up to 1,000 °C. The oxides Fe₃O₄, Fe₂O₃, and FeO were detected as the intermediate products of thermolysis of ferrous oxalate in these conditions. Various paths of oxalate decomposition may well proceed concurrently with the predomination of this or that path under slight changes in the experimental conditions. The formation of orthorhombic lithium phosphate Li₃PO₄ is detected just in a blend grinded at room temperature, and Li₃PO₄ and NH₄PO₃ are the basis of triphylite synthesis at increased temperatures (up to 800 °C). A new phase of single-substituted anhydrous lithium citrate C₆H₇O₇Li is formed at room temperature if citric acid C₆H₈O₇?H₂O is used as an organic precursor. The thermal treatment, at which citric acid can form a carbon coating with a maximum conductivity, was estimated experimentally. To identify the products of chemical reactions, structural characterization, and comparative analysis of samples synthesized at several temperatures, a set of techniques was used, namely TG with gas release analysis, Mossbauer spectroscopy, X-ray diffraction, transmission electron microscopy, scanning electron microscopy, surface microanalysis, laser diffraction analyses. Galvanostatic cycling was used to study the electrochemical properties of the LiFePO₄/C electrode material.     

Complete Lamb-shift calculation to order α5 by applying the methods of non-relativistic quantum electrodynamics

Summary It is shown, for the first time to our knowledge, that the Lamb shift for the states of hydrogenic atoms can be almost completely calculated by applying the methods of non-relativistic quantum electrodynamics and without using the Dirac equation and the second quantization for the electron. By taking into account the spin-orbit interaction, the complete Lamb shift to order α⁵ is calculated for different hydrogenic states. The author of this paper has agreed to not receive the proofs for correction.     

Characterization of iron nitrides prepared by spark erosion,plasma nitriding,and plasma immersion ion implantation

The effect of the nitrogen uptake in α-iron upon spark erosion in gaseous and liquid ammonia, plasma nitriding, and plasma immersion ion implantation is studied. The resulting phases and hyperfine parameters, measured by the Mössbauer spectroscopy, are discussed from the point of view of initial conditions of their preparation and subsequent heat and/or mechanical treatment. Spark erosion in the ammonia gas produces fine particles with the dominating ferromagnetic α-Fe phase (50%). The 20% of specimen volume form α′-Fe and α′′-Fe₁₆N₂ phases. The last 30% occupy the γ′-Fe₄N, ferro- and paramagnetic ε phases, and γ-Fe(N). Nitriding in the liquid ammonia allows to incorporate the higher content of nitrogen into α-iron particles which results in the formation of paramagnetic ε(ζ)-Fe₂N phase. This phase also dominates the surface of α-iron specimen implanted by nitrogen using plasma immersion ion implantation at 300°C/3 h, where high uptake of nitrogen (approx. 30 at%) is reached. Plasma nitriding at 510°C results in the formation of γ′-Fe₄N phase.     

Synthesis and characterization of lithium ferrite by oxalate precursor route

Nanocrystalline lithium ferrite (LiFe₅O₈) powders have been synthesized by oxalate precursor route. The effects of Fe³⁺/Li⁺ mole ratio, and annealing temperature on the formation, crystalline size, morphology and magnetic properties were systematically studied. The Fe³⁺/Li⁺ mole ratio was controlled from 5 to 3.33 while the annealing temperature was controlled from 600 to 1100 °C. The resultant powders were investigated by differential thermal analyzer (DTA), X-ray diffractometer (XRD), scanning electron microscopy (SEM) and vibrating sample magnetometer (VSM). DTA results showed that LiFe₅O₈ phase started to form at around 520 °C. XRD indicated that LiFe₅O₈ phase always contained α-Fe₂O₃ impurity and the hematite phase formation increased by increasing the annealing temperature ?850 °C for different Fe³⁺/Li⁺ mole ratios 5, 4.55 and 3.85. Moreover, lithium ferrite phase was formed with high conversion percentage at critical annealing temperature 750–800 °C. Single well crystalline LiFe₅O₈ phase was obtained at Fe³⁺/Li⁺ mole ratio 3.33 and annealing temperatures from 800 to 1000 °C. Maximum saturation magnetization (68.7 emu/g) was achieved for the formed lithium ferrite phase at Fe³⁺/Li⁺ mole ratio 3.33 and annealing temperature 1000 °C.     

Influence of porosity on artificial deterioration of marble and limestone by heating

Testing of stone consolidants to be used on-site, as well as research on new consolidating products, requires suitable stone samples, with deteriorated but still uniform and controllable characteristics. Therefore, a new methodology to artificially deteriorate stone samples by heating, exploiting the anisotropic thermal deformation of calcite crystals, has recently been proposed. In this study, the heating effects on a variety of lithotypes was evaluated and the influence of porosity in determining the actual heating effectiveness was specifically investigated. One marble and four limestones, having comparable calcite amounts but very different porosity, were heated at 400 °C for 1 hour. A systematic comparison between porosity, pore size distribution, water absorption, sorptivity and ultrasonic pulse velocity of unheated and heated samples was performed. The results of the study show that the initial stone porosity plays a very important role, as the modifications in microstructural, physical and mechanical properties are way less pronounced for increasing porosity. Heating was thus confirmed as a very promising artificial deterioration method, whose effectiveness in producing alterations that suitably resemble those actually experienced in the field depends on the initial porosity of the stone to be treated.     

Cochlear toughening,protection, and potentiation of noise-induced trauma by non-Gaussian noise

An interrupted noise exposure of sufficient intensity, presented on a daily repeating cycle, produces a threshold shift (TS) following the first day of exposure. TSs measured on subsequent days of the exposure sequence have been shown to decrease relative to the initial TS. This reduction of TS, despite the continuing daily exposure regime, has been called a cochlear toughening effect and the exposures referred to as toughening exposures. Four groups of chinchillas were exposed to one of four different noises presented on an interrupted (6 h/day for 20 days) or noninterrupted (24 h/day for 5 days) schedule. The exposures had equivalent total energy, an overall level of 100 dB(A) SPL, and approximately the same flat, broadband long-term spectrum. The noises differed primarily in their temporal structures; two were Gaussian and two were non-Gausssian, nonstationary. Brainstem auditory evoked potentials were used to estimate hearing thresholds and surface preparation histology was used to determine sensory cell loss. The experimental results presented here show that: (1) Exposures to interrupted high-level, non-Gaussian signals produce a toughening effect comparable to that produced by an equivalent interrupted Gaussian noise. (2) Toughening, whether produced by Gaussian or non-Gaussian noise, results in reduced trauma compared to the equivalent uninterrupted noise, and (3) that both continuous and interrupted non-Gaussian exposures produce more trauma than do energy and spectrally equivalent Gaussian noises. Over the course of the 20-day exposure, the pattern of TS following each day's exposure could exhibit a variety of configurations. These results do not support the equal energy hypothesis as a unifying principal for estimating the potential of a noise exposure to produce hearing loss.     

Efficiency of FIR Sew Excitation by Aperture, Prism, and Mesh Methods

The high efficiencies (25-41%) of Surface Electromagnetic Waves excitation were obtained in the FIR region on metals, doped A³B5 semiconductors and ferroelectric crystals. These efficiencies are considerably higher than obtained in the 10m region on the metal surfaces. The experimentally measured optimum gapheight correlates with the calculated SEW field decay constant into the air. The surface roughness plays very a important part in SEW excitation and propagation characteristics.     

Removal of chloridazon by natural and ammonium kerolite samples

The adsorption of chloridazon (5-amino-4-chloro-2-phenylpyridazin-3(2H)-one) on natural and ammonium kerolite samples from aqueous solution at 10, 25 and 40 °C has been studied by using batch experiments. The experimental data points were fitted to the Langmuir equation in order to calculate the adsorption capacities (X_m) of the samples; two straight lines were obtained, which indicates that the adsorption process takes place in two different stages. Values for X_m1 (first stage) ranged from 1.1 × 10⁻² mol kg⁻¹ for natural kerolite at 40 °C up to 5.1 × 10⁻² mol kg⁻¹ for ammonium kerolite at 10 °C and the values for X_m2 (second stage) ranged from 9.1 × 10⁻² mol kg⁻¹ for natural kerolite at 40 °C up to 14 × 10⁻² mol kg⁻¹ for natural kerolite at 10 °C. The adsorption experiments showed on the one hand, that the ammonium kerolite is more effective than natural kerolite to adsorb chloridazon in the range of temperature studied and on the other hand, that the lower temperature, the more effective the adsorption of chloridazon on the adsorbents studied.     

Instrumental and process considerations for the fabrication ofsilicon-on-insulators (SOI) structures by plasma immersion ionimplantation

Plasma immersion ion implantation (PIII) has recently been shown to be a viable method to fabricate silicon-on-insulator (SOI) materials using either the SPIMOX (separation by plasma implantation of oxygen) or the ion cut/wafer bonding method. We have recently modified and characterized a new generation plasma immersion ion implanter for SOI fabrication, and this paper will discuss some of the instrumental and processing issues, including the plasma source, mean free path consideration, and dc sheath characteristics     

A hard-tube pulser of 60 kV, 10 A for experiment and modeling inplasma immersion ion implantation

This paper describes an experiment and modeling in plasma immersion ion implantation using a high-voltage pulsed power system. This consists of a high-voltage pulse generator that uses a hard tube switch. The reason for using this type of circuit category in the Plasma Immersion Ion Implantation (PIII) facility rather than a previously used pulse-forming network (PFN) circuit configuration is stated. The experimental results of the application of this device to a glow discharge PIII are also discussed. In order to assess these results, a simple electrical model describes the plasma as a resistive load in parallel with a capacitance taking into account the pulse rise-time distortion caused by a long connecting coaxial cable. Plasma parameters for PIII processing, such as ion average implantation current and plasma sheath thickness, are calculated from the experimental settings     

Synthesis,growth, vibrational,optical and thermal studies of potassium diboro oxalate single crystals

Single crystals of novel semiorganic material, potassium diboro-oxalate (PDO) have been grown from aqueous solution by slow evaporation technique. The lattice parameters for the grown crystals were determined by the single crystal X-ray diffraction analysis and the crystallinity of the grown crystal was confirmed by powder X-ray diffraction analysis. The presence of functional groups was estimated qualitatively by using Fourier transform infrared (FTIR) analysis. The optical absorption spectrum shows that the UV cut-off wavelength for the grown crystal is at 240 nm and the band gap was calculated. The thermal stability of the grown crystal was studied by using TG/DTA analysis. The second harmonic generation and the phase-matchable tests were performed by Kurtz powder technique. The crystal perfection was analyzed by SEM photographs.     

Coherence masking protection for mid-frequency formants by adults and children

Coherence masking protection (CMP) refers to the phenomenon in which a target formant is labeled at lower signal-to-noise levels when presented with a stable cosignal consisting of two other formants than when presented alone. This effect has been reported primarily for adults with first-formant (F1) targets and F2/F3 cosignals, but has also been found for children, in fact in greater magnitude. In this experiment, F2 was the target and F1/F3 was the cosignal. Results showed similar effects for each age group as had been found for F1 targets. Implications for auditory prostheses for listeners with hearing loss are discussed.     

Proceeding on the riddles of ketene pyrolysis by applying ab initio quantum chemical computational methods in a detailed kinetic modeling study

As ketene is a crucial intermediate for the high-temperature combustion of oxygenated hydrocarbons in general, an in-depth understanding of its chemistry is a fundamental requirement for the kinetic modeling of bio-based fuels. To gain a profound insight into the decomposition of ketene and subsequent reaction pathways high level ab initio methods were used. DSD-PBEP86/cc-pVTZ level of theory was applied for the geometries and frequencies, while single-point energies were determined at the CCSDT-1a level of theory extrapolated to the basis set limit. The reaction rate parameters for 38 reactions involved in the ketene chemistry including C1 to C4 species like acetylene, ethylene, propyne and allene were computed. For a total of 16 species, the thermochemistry were updated. The calculated rate parameters and the two new species cyclopropenone and 1,4-dioxo-1,3-butadiene were used to update the AramcoMech 3.0 base mechanism, which was then validated against speciation measurements during ketene pyrolysis. A reaction pathway analysis was performed to find the most prominent reactions at the investigated conditions and to discuss the simulation results. A significant improvement in the model’s prediction capability was found when applying the newly calculated reaction rate parameter and thermochemical data.