Measurement scheme to detect α relaxation time of glass-forming liquid

A measurement scheme for detecting the α relaxation time(τ) of glass-forming liquid is proposed, which is based on the measured ionic conductivity of the liquid doped with probing ions by low-and middle-frequency dielectric spectroscopy and according to the Nernst–Einstein, Stokes–Einstein, and Maxwell equations. The obtained τ values of glycerol and propylene carbonate by the scheme are consistent with those obtained by traditional dielectric spectroscopy, which confirms its reliability and accuracy. Moreover, the τ of 1,2-propanediol in a larger temperature range is compared with existing data.     

Computation of effective electron–phonon relaxation times in a high-Tc superconductor using the measured track radii

Energy relaxation processes after fast heavy ions passage through YBa₂Cu₃O_7−δ single crystal have been calculated. Effective times τ of electron–atom energy relaxation have been determined as fitting parameters for each pair of the measured track radius and the value of dE/dx. The latter quantity has been chosen over the interval of 20–40 keV/nm. The calculated results are compared with short pulse laser experiments and with Allen's theory, which predicts almost a linear dependence of τ on electron temperature.     

Melting curve of copper measured to 16 GPa using a multi-anvil press

The melting temperature, T _m, of copper has been determined from ambient pressure to 16 GPa using multi-anvil techniques. The melting curve obtained (T _m=1355(5)+44.5(31)P?0.61(21)P ², with T _m in Kelvin and P in GPa) is in good agreement with both the previous experimental studies and with recent ab initio calculations.     

Simultaneous measurement of liquid water film thickness and vapor temperature using near-infrared tunable diode laser spectroscopy

A fiber-based multiplexed tunable diode-laser absorption sensor with three near-infrared distributed-feedback diode lasers at ∼1.4 μm is used for simultaneous nonintrusive measurements of liquid water film thickness and vapor-phase temperature. Water film thicknesses are derived from broad-band absorption determined at two fixed wavelengths while gas-phase temperature above the film is obtained via two-line thermometry using the fast wavelength tuning with line-integrating absorption. Probing the liquid film at two wavelengths with significantly different liquid-phase absorption cross sections allows discriminating against additional signal losses due to surface fowling, reflection, and beam steering. The technique is demonstrated for liquid layers of defined thicknesses and in time-resolved measurements of evaporating films.     

Determination of the vapor–liquid transition of square-well particles using a novel generalized-canonical-ensemble-based method

The square-well(SW) potential is one of the simplest pair potential models and its phase behavior has been clearly revealed, therefore it has become a benchmark for checking new theories or numerical methods. We introduce the generalized canonical ensemble(GCE) into the isobaric replica exchange Monte Carlo(REMC) algorithm to form a novel isobaric GCE-REMC method, and apply it to the study of vapor–liquid transition of SW particles. It is validated that this method can reproduce the vapor–liquid diagram of SW particles by comparing the estimated vapor–liquid binodals and the critical point with those from the literature. The notable advantage of this method is that the unstable vapor–liquid coexisting states,which cannot be detected using conventional sampling techniques, are accessed with a high sampling efficiency. Besides,the isobaric GCE-REMC method can visit all the possible states, including stable, metastable or unstable states during the phase transition over a wide pressure range, providing an effective pathway to understand complex phase transitions during the nucleation or crystallization process in physical or biological systems.     

Ultrafast solid–liquid–vapor phase change of a gold film induced by pico- to femtosecond lasers

Melting, vaporization and resolidification processes of thin gold film irradiated by a femtosecond pulse laser are studied numerically. The nonequilibrium heat transfer in electrons and lattice is described using a two-temperature model. The solid–liquid interfacial velocity, as well as elevated melting temperature and depressed solidification temperature, is obtained by considering the interfacial energy balance and nucleation dynamics. An iterative procedure based on energy balance and gas kinetics law to track the location of liquid–vapor interface is utilized to obtain the material removal by vaporization. The effect of surface heat loss by thermal radiation was discussed. The influences of laser fluence and duration on the evaporation process are studied. Results show that higher laser fluence and shorter laser pulse width lead to higher interfacial temperature, deeper melting and ablation depths.     

Energy calibration of a BC501A liquid scintillator using a γ-γ coincidence technique

An accurate energy calibration of a BC501A liquid scintillator by means of Compton scattering of γ-rays is described.The energy resolution and the position of the Compton edge have been precisely determined using a γ-γ coincidence technique and fitting the coincidence spectrum with a Gaussian function superimposed on a quadratic polynomial for the background.The position of the Compton edge relative to the position of the maximum and the half height of the distribution in dependence on the relevant energy resolution is discussed in detail.The results indicate that the maximum energy of the recoil Compton electron does not occur at the half height distribution but at 0.90±0.05 of the maximum height in the energy range considered.The energy resolution varies from 15.6% to 8.02% for electrons in the energy region from 0.5 MeV to 3 MeV.     

Evaluation of the brain pH using a phosphorus magnetic resonance spectroscopy technique – a comparison of women and men

The aim of this study was to determine the reference value of pH in healthy women and men using the phosphorus magnetic resonance spectroscopy technique. The brains of 65 young volunteers were examined. The intracellular pH was calculated in the group of women and the group of men. In both groups, the average pH was slightly alkaline (respectively 7.10?±?0.08 and 7.08?±?0.12). No statistically significant sex difference in brain pH was found. Thus, in case if this method is used to estimate possible brain pathology in the young population, it is not needed to take the gender factor into consideration.     

Detection of a P-induced liquid ⇌ solid-phase transformation using multiple acoustic transducers in a multi-anvil apparatus

A technique for detecting and measuring phase transitions in a multi-anvil apparatus by measuring the change in travel time for a longitudinal sound wave as a function of pressure is reported. The system measures the time for pulsed ultrasonic signals to travel through a high pressure assembly with a sample in the center. Upon phase change from liquid to solid, the travel time shows an abrupt decrease due to the intrinsic increase in velocity in the sample and a reduced delay between the triggering of an amplitude threshold and the arrival of the waveform. As a proof of concept, results are shown for mercury as it undergoes pressure-induced liquid ? solid transitions at room temperature. We propose that this non-destructive technique may be valuable in situations where other in situ probing techniques cannot be readily used to provide information about changes of state and potentially to study transition kinetics at high pressures as well.     

Fine structure of the emission spectrum of a two-dimensional electron–hole liquid in SiGe/Si quantum wells

The fine structure of the emission spectrum of a quasi-two-dimensional electron–hole liquid in shallow SiGe/Si quantum wells is observed experimentally. This fine structure is explained by the occurrence of steps in the density of states resulting from the coexistence of light and heavy holes in the liquid phase and by the interaction of charge carriers with charge-density oscillations in the liquid.     

High-resolution infrared Fourier transform spectroscopy of SO in the X3Σ− and a1Δ electronic states

The v = 1 ← 0 vibration-rotation absorption bands of ³²S¹⁶O, ³⁴S¹⁶O, and ³²S¹⁸O in the ground electronic state, X³Σ⁻, and the v = 1 ← 0 vibration-rotation band of ³²S¹⁶O in the first excited electronic state, a¹Δ, were measured at 0.004 cm⁻¹ unapodized resolution with a high-resolution Fourier transform spectrometer coupled to a long path absorption cell. The v = 2 ← 0 vibration-rotation band of ³²S¹⁶O in the X³Σ⁻ state was also observed. Line positions for P- and R-branch transitions up to N = 44 for ³²S¹⁶O have been measured and analyzed yielding improved molecular parameters. The present measurements are compared with previous infrared and microwave measurements.     

In-situ characterization of metal clusters supported on a birefringent substrate using reflectance difference spectroscopy

Reflectance difference spectroscopy has been applied for the in-situ characterization of the growth of Ag cluster films on insulating birefringent Al₂O₃ (10[`1]0)(10\overline{1}0) substrates in the spectral range of 1.5–5 eV. Information on the individual cluster, cluster film morphology and growth are derived from the anisotropy of the in-plane plasmon resonances in comparison with scanning electron microscopy images. In particular, the evolution of the dipolar resonance has been attributed to two distinct stages of coarsening involving particle aggregation and ripening, and to the development of anisotropic particle shapes for higher Ag coverages. The effect of the formation of anisotropic electrostatic images in the birefringent substrate is used to explain the spectra even in the absence of structural anisotropies.     

Adsorption of the cysteine–tryptophan dipeptide at the Au(110)/liquid interface studied using reflection anisotropy spectroscopy

The adsorption of a cysteine–tryptophan dipeptide has been monitored at a Au(110)/electrolyte interface using reflection anisotropy spectroscopy. At ?0.6 V the dipeptide adsorbed through the formation of Au–S bonds and a link between the NH₂ group at the Au surface. As the applied potential was changed to + 0.6 V the NH₂ group left the surface and the spectra suggest that two dipeptides form a disulphide bridge that binds to the Au surface. This event is accompanied by changes in the orientation of, and possibly interactions between, tryptophan moieties. Returning the applied potential to ?0.6 V failed to re-establish the initial population of Au–S bonds and the changes induced in the region of the spectrum associated with the tryptophan's by the positive potentials were permanent on the time scale of an hour. Subtle changes associated with the tryptophan moieties indicate that the orientation of the tryptophans is very sensitive to the applied potential. Cycling of the potential showed a stable inter-conversion between Au–S bonds and Au–disulphide bonds at low scan rates, but at higher scan rates not all the broken disulphide bonds were able to reform. Irreversible changes were also observed in the tryptophan region of the spectrum during potential cycling.     

Laser cutting of silicon with the liquid jet guided laser using a chlorine-containing jet media

In this paper results for liquid media are presented, which are used the first time as liquid jet for cutting of silicon with laser chemical processing (LCP). The liquids contain a perfluoro-carbon compound as solvent and elemental chlorine as etching agent for silicon. Experiments were performed to investigate its influence on groove form and maximum achieved groove depth. It is shown that with the addition of low-concentration chlorine, the groove depth can already be significantly increased. The groove shape could be changed from a V-profile to a U-profile. Furthermore, an about four times greater groove depth was achieved by applying a saturated chlorine solution compared to groove depths without using chlorine. Finally, a theory is given and discussed to describe the phenomena observed.     

Characterization of T-55 sorbent using 57Fe Mössbauer spectroscopy with a high velocity resolution

A new sorbent T-55 with mixed ferrocyanide surface modification developed for Cs⁺ sorption was characterized using Mössbauer spectroscopy with a high velocity resolution in comparison with K₂Ni[Fe(CN)₆] and K₄[Fe(CN)₆ samples. The main sorption active component of T-55 sorbent was determined as K₂Ni[Fe(CN)₆].     

Study of NiFe2O4 nanoparticles using Mössbauer spectroscopy with a high velocity resolution

The nanocrystalline NiFe₂O₄ particles prepared by solution combustion synthesis technique using different fuels such as ethylene-diamine-tetra-acetic acid (NA sample) and urea (NB sample) were studied using magnetic measurement and ⁵⁷Fe Mössbauer spectroscopy with a high velocity resolution. The temperature dependence of magnetization is different for the two samples. Mössbauer spectra demonstrate the necessity to use more than two magnetic sextets, usually used to fit the NiFe₂O₄ nanoparticles spectra. Evaluation of the different local microenvironments for Fe in both tetrahedral (A) and octahedral (B) sites, caused by different Ni^2?+? occupation of octahedral sites, demonstrates at least five different local microenvironments for both A and B sites. Therefore, the Mössbauer spectra were fitted by using ten magnetic sextets which are related to the spread ⁵⁷Fe location in octahedral and tetrahedral sites.     

Stoichiometric transfer by infrared pulsed laser deposition of y-doped Bi–Sr–Ca–Cu–O investigated using time-resolved optical emission spectroscopy

Pulsed laser deposition of Bi₂Sr2Ca_1–x YxCu₂O_8+δ (Bi-22Y2) with x = 0, 0.30, and 0.49 on an MgO (100) substrate was conducted using a Q-switched 1064 nm Nd:YAG laser The laser-produced plasma (LPP) emission was collected during the deposition. Time-resolved optical emission spectroscopy reveals that the plasma plume consists of neutral atoms and ions. SEM images indicate that clusters of correct stoichiometry arrive on the substrate surface. Our result confirms that IR PLD transfers material stoichiometrically.     

Comparison of the thermal stability of the α, β and γ phases in poly(vinylidene fluoride) based on in situ thermal Fourier transform infrared spectroscopy

The electroactive β phase of poly(vinylidene fluoride) (PVDF) is induced due to the aging time of PVDF solutions. The feasibility of the combination of the three crystalline polymorphs (α, β and γ) is demonstrated where their relative proportion within the PVDF film can be tailored by the simple monitoring of the preparation conditions. To identify all these phases, Fourier transform infrared (FT-IR) spectroscopy is carried out and it is spotlighted that the vibrational bands at 510 and 841 cm^?1 are not sufficient to state the formation of the β phase. The main aim of this work is devoted to develop a better understanding on the thermal stability of these several phases of PVDF, which has a longstanding ambiguity persisting in this area. It has been found that the in situ thermal FT-IR spectroscopy is one of the best alternatives to understand this important issue. It is ascertained that the β phase is the least thermally stable phase among α, β and γ phases, whereas the γ phase is the most thermally stable phase.     

Re-examination of Dronino iron meteorite and its weathering products using Mössbauer spectroscopy with a high velocity resolution

Re-examination of Dronino iron meteorite and products of its weathering in the internal and external surface layers was carried out using Mössbauer spectroscopy with a high velocity resolution. New results showed the presence of α-Fe(Ni, Co), α ₂-Fe(Ni, Co) and γ-Fe(Ni, Co) phases with variations in Ni concentration in Dronino metallic iron alloy. The surface weathering products were supposed as magnetite and/or maghemite, goethite with different particles size and probably ferrihydrite in the internal layer and goethite with different particles size and probably ferrihydrite in the external layer.