Stationary Crystal Research Articles

Optimisation of conditions affecting the crystallization processes of piperine from white pepper oleoresin

ABSTRACT This study focused on investigating the factors influencing both stationary and stirring-assisted crystallization processes using white pepper (Piper nigrum L.) oleoresin. Optimising the crystallization conditions was crucial for achieving high-purity and recovery of piperine. Initially, the impact of seven parameters on stationary crystallization was examined using a variable-by-variable approach. The final crystallization conditions included: (1) 96% v/v ethanol concentration, (2) ratio of oleoresin: solvent of 1:2 (g/mL), (3) crystallization temperature of 0 °C, (4) cooling rate of 20 °C/min, (5) seeding temperature of 36 °C, (6) seeding ratio of 0.5% w/w, and (7) crystallization time of 32 h. Piperine purity and recovery were determined by HPLC, resulting in 771.5 ± 4.7 mg piperine/g crystals and 36.9%, respectively. Subsequently, agitated crystallization was explored to enhance the recovery, with stirring speed being a critical factor. The optimal condition at 30 rpm led to a significant improvement in piperine recovery, increasing from 36.9% to 84%. These findings underscored the feasibility and effectiveness of the two crystallization methods employed for piperine purification in this study.

Linear stability analysis of a solidification process with convection in a bounded region of space

The morphological/dynamic instability of crystallization process in a bounded region in the presence of intense convection in liquid is studied. The paper considers a linear theory of morphological instability with a flat solid-liquid interface on the example of molten metal and magma. The mathematical model includes heat transfer equations and convective type boundary conditions at the interface. The equations for perturbations of the temperature field and interfacial boundary are found, allowing to obtain the dispersion relation. Its analysis has shown the existence of morphological instability of the flat interfacial boundary for a wide range of wavenumbers. Dynamic perturbations (perturbations of the quasi-stationary crystallization velocity) were also analyzed and two solutions for the perturbation frequency were obtained. One of them is stable and the other one is unstable. The system selects one of them depending on the action of convection. The result of morphological and dynamic instability is the appearance of a two-phase region in front of a flat solid-liquid interface. Therefore, the paper also considers the dynamic instability of stationary crystallization with a two-phase region replaced by a discontinuity surface. In this case, the dynamic instability was also found for a wide range of crystallization velocities.

Structural transformation of dusty plasma crystal in dc discharge plasma by changing confinement ring bias

We report an experimental study of the structural transition of a stable complex plasma crystal to a solid-liquid phase coexistence by the controlled adjustment of the confinement potential, while keeping all other parameters constant. The experiments are carried out on a tabletop linear dusty plasma experimental device, which consists of a circular powered electrode and an extended grounded cathode plate. A stationary crystal of melamine formaldehyde particles is formed in a background of argon plasma inside a confining ring that is isolated from the cathode by a ceramic cover. The stable crystal structure breaks in the core region and transitions to a coexistent state by carefully changing the confining potential, thereby modifying the sheath structure. The transition is confirmed by evaluating the variation in different characteristic parameters such as the pair correlation function, local bond order parameter, and dust kinetic temperature as a function of confining bias potential. It is found that melting in the core is due to the onset of dust fluctuations in the layers beneath the topmost layer, which grow in amplitude as the confining bias potential is reduced below a threshold value. The present technique of changing confinement provides a unique feature to study structural transitions of plasma crystals without affecting the overall plasma parameters. Published by the American Physical Society 2024

On Liouville-type theorems for the stationary nematic liquid crystal equations

On Liouville-type theorems for the stationary nematic liquid crystal equations

Stationary Solutions to the Three-Dimensional Compressible Nonisothermal Nematic Liquid Crystal Flows

In this paper, we study the stationary compressible nonisothermal nematic liquid crystal flows affected by the external force of general form in three-dimensional space. By using the contraction mapping principle, we prove the existence and uniqueness of strong solution around the constant state in some suitable function space.

Conditions for partial and complete crystallization suppression upon quenching from liquid state

For bulk-amorphizing alloys Мg65Сu25Y10 and Zr41,2 Тi13,8Сu12,5Ni10Ве22,5, the thickness and cooling rate of melt layers is calculated, which ensure the formation of X-ray amorphous structures typical for metallic glasses ( lC, vC ), and truly amorphous states without inclusions of «frozen-in crystallization centers» (lc*, vc* ). Correlation of the calculated values lC, vC with the known experimental estimates is C Cachieved. It is shown that both studied alloys demonstrate a predisposition to complete suppression of crystallization processes at physically correct values of the parameters lc* and vc* (10 μm; 1,3·107 K/s and 550 μm; 2,7·103 K/s for alloys based on Mg and Zr, respectively). It is concluded that the most significant factors controlling the tendency of materials to noncrystalline solidification are the decrease in the frequency of non-stationary nucleation with the increase in the rate of QLS, as well as relatively low <1018 m-3 s-1) maximum values of the rate of stationary crystallization centers formation.

Double-Electromagnetically-Induced-Transparency Ground-State Cooling of Stationary Two-Dimensional Ion Crystals.

We theoretically and experimentally investigate double-electromagnetically-induced transparency (double-EIT) cooling of two-dimensional ion crystals confined in a Paul trap. The double-EIT ground-state cooling is observed for ^{171}Yb^{+} ions with a clock state, for which EIT cooling has not been realized like many other ions with a simple Λ scheme. A cooling rate of n[over ¯][over ˙]=34(±1.8) ms^{-1} and a cooling limit of n[over ¯]=0.06(±0.059) are observed for a single ion. The measured cooling rate and limit are consistent with theoretical predictions. We apply double-EIT cooling to the transverse modes of two-dimensional (2D) crystals with up to 12 ions. In our 2D crystals, the micromotion and the transverse mode directions are perpendicular, which makes them decoupled. Therefore, the cooling on transverse modes is not disturbed by micromotion, which is confirmed in our experiment. For the center of mass mode of a 12-ion crystal, we observe a cooling rate and a cooling limit that are consistent with those of a single ion, including heating rates proportional to the number of ions. This method can be extended to other hyperfine qubits, and near ground-state cooling of stationary 2D crystals with large numbers of ions may advance the field of quantum information sciences.

Coherently Manipulated 2D Ion Crystal in a Monolithic Paul Trap

AbstractUsing a 2D ion crystal for quantum simulation and computation has been pursued for a long time. The coherent manipulation of a stationary 2D crystal in the Paul trap may be hampered by the micromotion synchronous with the oscillating electric field. Here, a simple Paul trap that stably confines over 20 ions in a stationary 2D crystal is presented. The disturbance of the micromotion in coherent operations is mitigated by making the direction of micromotion perpendicular to the transverse direction of the 2D crystal. To achieve the condition of perpendicularity, the structure of the trap electrodes is comprehensively designed, which also provides the controllability of rotating principal axes. The transverse vibrational modes by Raman laser‐beams are addressed and coherent evolution of sideband transitions on these modes observed. Moreover, this trap allows for optical access with a 0.86 numerical aperture which facilitates applying individually addressing laser‐beams. This work can be an example of realizing a 2D‐trapped‐ion based quantum simulator and computer in a Paul trap.

A Liouville theorem for three-dimensional stationary nematic liquid crystal equations

In this paper, we prove a Liouville type theorem for three-dimensional stationary liquid crystal equationsunder the condition $u,~\\nabla~d~\\in~L^{9/2,~q}(\\mathbb{R}^3)$,where $u:~\\mathbb{R}^3~\\to~\\mathbb{R}^3$ denotes the velocity field and $d:~\\mathbb{R}^3~\\to~\\mathbb{S}^2$ is the moleculardirection. The proof of this theorem is inspired by Galdis ideas of using local energy estimates in provingthe Liouville theorem for three-dimensional incompressible Navier-Stokes equations in $L^{9/2}(\\mathbb{R}^3)$ and Schoens description on the harmonic maps. We generalize Galdis results to Lorentz spaces and nematic liquid crystal systems.

Measurement of temperature of a dusty plasma from its configuration

AbstractA new concept called “configurational temperature” is introduced in the context of dusty plasma, where the temperature of the dust particles submerged in the plasma can be measured directly from the positional information of the individual dust particles and the interaction potential between the dust grains. This method does not require the velocity information of individual particles, which is a key parameter to measure the dust temperature in the conventional method. The technique is initially tested using two‐dimensional (2D) OpenMP parallel molecular dynamics and Monte Carlo simulation and then compared with the temperature evaluated from experimental data. The experiment have been carried out in the Dusty Plasma Experimental (DPEx) device, where a 2D stationary plasma crystal of melamine formaldehyde particles is formed in the cathode sheath of a DC glow discharge argon plasma. The kinetic temperature of the dust is calculated using the standard particle image velocimetry technique at different pressures. An extended simulation result for the three‐dimensional case is also presented, which can be employed for the temperature measurement of a three‐dimensional dust crystal in laboratory devices.

On Change in the Silicon Crystal Structure Implanted with Hydrogen Ions during Annealing Based on Three-Crystal X-Ray Diffractometry Data

In this paper, we present the results of a three-crystal X-ray diffractometry (XRD) study of the state of a disturbed layer formed in silicon crystals by implantation of hydrogen ions with energies of 100 + 200 + 300 keV and a total dose of 2 × 1016 cm–2 during the subsequent heat exposure in the temperature range from 200 to 1100°C. Here, X-ray studies were performed in the three-crystal XRD scheme when the sample under consideration operates as a second stationary crystal with various fixed angular detuning α from the Bragg position while the third (perfect) crystal-analyzer sweeps the angular distribution of radiation diffracted by the second crystal. Based on a comparison of the shape of diffraction and diffuse maxima for the samples under study, a qualitative conclusion about a significant transformation of radiation defects at post-implantation annealing was derived.

Melting transition of two-dimensional complex plasma crystal in the DC glow discharge

The formation of self-consistent dust crystal and its melting is a well- known phenomenon in rf generated plasmas but remains challenging in DC glow discharge plasmas. Here, we report the melting of a two- dimensional dusty plasma crystal, suspended in the cathode sheath of a DC glow discharge plasma. The experiments are carried out in a Dusty Plasma Experimental (DPEx) device which consists of a circular powered electrode and an extended grounded cathode tray. A stationary crystal of melamine formaldehyde particles is formed in a background of Argon plasma between a pair of confining strips that are placed on the cathode. The stable structure breaks and transition to a fluid state when the neutral pressure is reduced. The neutral pressure range where this melting transition is observed is an order of magnitude less than what is typically reported in rf discharge plasma. The transition is confirmed by evaluating the variation in different characteristic parameters such as the pair correlation function, Voronoi diagram, local bond order parameter, defect fraction and dust kinetic temperature as a function of background neutral pressure. For instance, the average bond order parameter (Ψ6) reduces from 0.87 to 0.4 when the neutral pressure is reduced from 15 to 11 Pa. The asymmetry of the electrode is a special feature that is believed to enable the formation of the plasma crystal.

Laue diffraction and time-resolved crystallography: a personal history.

A personal, historical view is presented of Laue X-ray diffraction and its application to time-resolved studies of dynamic processes, largely in light-sensitive biological systems. In Laue diffraction, a stationary crystal is illuminated by a polychromatic X-ray source. Laue diffraction has inherent complications largely absent in monochromatic diffraction, and consequently fell into disuse for quantitative structure determination. However, the advent of naturally polychromatic, intense, pulsed storage ring X-ray sources in the 1970s led to re-examination at Daresbury and elsewhere of its underlying principles. Laue diffraction has been successfully applied at storage ring sources to time-resolved, pump-probe crystallographic studies, whose exposure time and time resolution were progressively reduced from minutes to seconds, milliseconds, nanoseconds and 100 ps. Most recently, hard X-ray free electron laser sources have been used to generate narrow bandpass Laue diffraction patterns. The femtosecond X-ray pulses from such sources are completely destructive, generate only one diffraction pattern per tiny crystal and have unusual properties. However, they too are being applied to time-resolved crystallography to explore, for example, isomerization and rapid tertiary structural changes on the chemical, femtosecond timescale. This article is part of the theme issue 'Fifty years of synchrotron science: achievements and opportunities'.

Об изменении реальной структуры кристаллов кремния, имплантированных ионами водорода, при их отжиге по данным трехкристальной рентгеновской дифрактометрии

AbstractIn this paper, we present the results of a three-crystal X-ray diffractometry (XRD) study of the state of a disturbed layer formed in silicon crystals by implantation of hydrogen ions with energies of 100 + 200 + 300 keV and a total dose of 2 × 10^16 cm^–2 during the subsequent heat exposure in the temperature range from 200 to 1100°C. Here, X-ray studies were performed in the three-crystal XRD scheme when the sample under consideration operates as a second stationary crystal with various fixed angular detuning α from the Bragg position while the third (perfect) crystal-analyzer sweeps the angular distribution of radiation diffracted by the second crystal. Based on a comparison of the shape of diffraction and diffuse maxima for the samples under study, a qualitative conclusion about a significant transformation of radiation defects at post-implantation annealing was derived.

Mathematical modeling of the stationary nucleation and crystallization process in supersaturated systems with a crystallizer

Motivated by important industrial applications we consider the growth prosess of solid particles in a supersaturated (supercooled) system with allowance for a crystallizer. The particle-radius distribution function satisfies the second order kinetic equation supplimented by different boundary conditions. An exact steady-state analytical solution is found. We show that two different types of analytical solutions for the kinetic equation exist.

A Dynamic Ion-Atom Hybrid Trap for High-Resolution Cold-Collision Studies.

We present a dynamic ion-atom hybrid trap for studies of cold ion-neutral collisions and reactions with a significantly improved energy resolution compared with previous experiments. Our approach is based on pushing a cloud of laser-cooled Rb atoms through a stationary Coulomb crystal of cold ions by using precisely controlled, tunable radiation pressure forces. We demonstrate the tuning of the atom kinetic energies over an interval ranging from 30 mK up to 350 mK with energy spreads as low as 24 mK, inferred from the comparison of experimental time-of-flight measurements with Monte Carlo trajectory simulations. We also demonstrate the first applications of our method to the investigation of chemical reactions. Our development opens up perspectives for accurate studies of the energy dependence of the reaction rates, the dynamics, and the reaction-product ratios of the ion-neutral processes in the cold regime. It also paves the way for the realization of fully energy- and state-controlled cold-collision experiments.

A split-beam probe-pump-probe scheme for femtosecond time resolved protein X-ray crystallography.

In order to exploit the femtosecond pulse duration of X-ray Free-Electron Lasers (XFEL) operating in the hard X-ray regime for ultrafast time-resolved protein crystallography experiments, critical parameters that determine the crystallographic signal-to-noise (I/σI) must be addressed. For single-crystal studies under low absorbed dose conditions, it has been shown that the intrinsic pulse intensity stability as well as mode structure and jitter of this structure, significantly affect the crystallographic signal-to-noise. Here, geometrical parameters are theoretically explored for a three-beam scheme: X-ray probe, optical pump, X-ray probe (or “probe-pump-probe”) which will allow experimental determination of the photo-induced structure factor amplitude differences, ΔF, in a ratiometric manner, thereby internally referencing the intensity noise of the XFEL source. In addition to a non-collinear split-beam geometry which separates un-pumped and pumped diffraction patterns on an area detector, applying an additional convergence angle to both beams by focusing leads to integration over mosaic blocks in the case of well-ordered stationary protein crystals. Ray-tracing X-ray diffraction simulations are performed for an example using photoactive yellow protein crystals in order to explore the geometrical design parameters which would be needed. The specifications for an X-ray split and delay instrument that implements both an offset angle and focused beams are discussed, for implementation of a probe-pump-probe scheme at the European XFEL. We discuss possible extension of single crystal studies to serial femtosecond crystallography, particularly in view of the expected X-ray damage and ablation due to the first probe pulse.

In-house energy resolved Laue XRD measurements with a Pilatus detector

The use of 2D position and energy sensitive hybrid pixel Pilatus detectors allows performing energy-dispersive analysis of Bragg reflections [1]. This significantly improves the classical Laue experiments enabling the unique determination of the crystal lattice and resolving the higher order harmonics. It allows quantitative crystal structure determination using the Laue method without having any priory information about the crystal [2]. Such energy-dispersive Laue diffraction (EDLD) experiments can be performed with a white X-ray beam either from a synchrotron source or from conventional X-ray tubes. The second approach looks less profitable due to its lower irradiation intensity, but this can be compensated considering the better control of white beam spectra by applying different voltage/current settings during the tube operation. Thus, one can efficiently combine the primary beam and XRD measurements using the same Pilatus detector. This allows the implementation of the energy resolved (color Laue) method for any conventional XRD diffractometer equipped with a Pilatus detection system. In the present work EDLD experiments with a conventional X-ray tube were combined with corresponding primary beam measurements using a 300K Pilatus detector tuned for operation within an energy range of 4-25 keV at energy resolution <0.12 keV. Such a combination simplifies several data correction procedures (the spectral intensity distribution, the sample absorption etc.) significantly. Following our developed intensity correction protocols the structure refinement of a reference quartz sample could be achieved with R-factor <0.10. Possible applications of this method (e.g. quantitative XRD studies with stationary crystals) and the details for its further development will be discussed.

Heterolytic Cleavage of H2 Revealed by Neutron Single Crystal Diffraction

Synthetic biologically inspired complexes exhibiting reactivity similar to hydrogenase enzymes have provided evidence of hydride transfer to the metal and proton transfer to an amine, but key structural information about the intermediate is not readily discernible with X-rays. The greater sensitivity of neutron to hydrogen makes it ideal for studying the structure and dynamics of catalytic materials. The newly commissioned TOPAZ neutron single crystal diffractometer at the SNS is capable of continuous 3D diffraction space mapping from a small stationary crystal, permitting detailed structural study at atomic resolution. The structure measured on TOPAZ for an Fe-based mononuclear electrocatalyst confirms that reaction of [CpFeN-L)](BARF) (1) with H2 under mild conditions leads to heterolytic cleavage of the H-H bond into a proton and hydride[1]. The precise location of H atoms in [Fe-H···H-N]+ reveals an unconventional H-bonding interaction, where the ferrous hydridic site {Fe(II)-H-} acts as the H-bond acceptor and the nitrogen of the protic pendant amine {L-N-H+} as the H-bond donor. The neutron structure provides clear evidence of a crucial intermediate involving an Fe-H···H-N interaction in the oxidation of H2. The result clarifies the key role of the pendant amine in the iron complex and provides insights into the design of synthetic electrocatalysts sought as cost-effective alternatives to platinum in fuel cells. The reaction is also a critical step in homogeneous catalysts for hydrogenation of C=O and C=N bonds. A preliminary result from TOPAZ measurement shows that 1 undergoes further single-crystal to single-crystal chemical reaction with moisture in the air, leading to a Fe(H2O)+ complex. Abbreviations: Cp = pentafluoropyridylcyclopentadienide; N-L= 1, 5-di(tert-butyl)-3,7-di(benzyl)-1,5-diaza-3,7-diphospha-cyclooctane; BARF = [B[3,5-(CF3)2C6H3]4]–

Pulse compression and broadening by reflection from a moving front of a photonic crystal.

Previously, the effect of pulse bandwidth compression or broadening was observed in reflection from a moving front together with the Doppler shift. In this letter, an approach is presented, which alters pulse bandwidth without change in the central frequency. It occurs when light is reflected from a moving front of an otherwise stationary photonic crystal. This means that the photonic crystal lattice as such is stationary and only its boundary to the environment is moving, thus extruding (or shortening) the photonic crystal medium. The compression (broadening) factor depends on the front velocity and is the same as for the conventional Doppler shift. Complete reflection and transformation of the pulse can be achieved even with weak refractive index contrast, what makes the approach experimentally viable.