High Pressure Field Research Articles

Influence of High Pressure and Magnetic Fields on the Magnetic and Transport Anomalies in Nd7Rh3

The compound, Nd 7 Rh 3 , has been recently shown by us to exhibit exceptional magnetic and transport behavior. There are at least two antiferromagnetic transitions as a function of temperature (10 and 32 K) with the 10 K-transition being first-order-like at low fields; in addition, there is a field-induced first-order (metamagnetic) transition at temperatures well below 10 K. We have investigated the influence of external pressure (<15 kbar) on the magnetic and transport anomalies for this compound. We find that the two transition temperatures interestingly vary in opposite directions with increasing pressure and that the external pressure suppresses the critical field required to induce the metamagnetic magnetism. External pressure, while retaining (magnetic) phase co-existence phenomenon and percolative electrical conduction after field cycling (similar to the behavior known for by-now well-known manganites), suppresses the magnitude of magnetoresistance at high fields. We also report heat-capacity data in the presence of magnetic fields and it appears that the linear term decreases in the presence of a magnetic field as though there is a band splitting effect.

Competition of Magnetic Order and Superconductivity in CeRhIn5

We report on ac calorimetry of CeRhIn 5 at low temperature under high pressure and high magnetic field. In zero field the antiferromagnetic order vanishes near p c \star = 2 GPa presumably due to a first order transition. The application of a magnetic field H ∥( a , b ) plane above p c \star induces a second transition, which suggests the coexistence of long range antiferromagnetic order and gapped superconducting state. The field-induced state vanishes close to the expected quantum critical point in absence of superconductivity. Resistivity measurements above the critical pressure p c indicate the unusual metallic state in the normal phase. A schematic field-pressure phase diagram at low temperature is presented.

Donor–acceptor origin of fullerene C60 dimerization

AbstractThe fullerene dimerization is considered as a consequence of donor–acceptor interaction between monomer molecules which is significant for C60+C60 binary system. The dimerization is provided by a two‐well structure of the ground state energy term. Analyzing characteristics of the term, proven by quantum–chemical calculations at different starting intermolecular distances, mechanisms of both physically (photoexcitation, thermal, high pressure, plasma, electron beam, and electric field) and chemically (alkali‐metal adducts AC60) stimulated dimerization processes are suggested. © 2007 Wiley Periodicals, Inc. Int J Quantum Chem, 2007

El proceso tradicional de elaboración del pimentón de Murcia y sus posibles innovaciones

The traditional method of Spanish paprika processing in the Murcia Region is under the official category Denomination of Origin “Paprika of Murcia”. The process consists basically in manual harvesting the fruit in full ripe stage, drying, removing the peduncle and seeds, hammer and stone milling for crushing and grinding, transmission, mixing and granulating, sterilization, packaging and refrigerated storage. The details about the paprika processing operations are reported. In a second part the main control points of paprika processing, paprika quality traits and risks are also mentioned. The innovations proposed for paprika processing and unit operations in the literature include application of hygienic food processing design, paprika processing in a nitrogen flow, heat pretreatments before grinding or applied to shredded pepper, high hydrostatic pressure or high intensity electrical field pulse, irradiation, osmotic dehydration, lyophilization, mixing and coating, and modified atmosphere packaging. The traditional method of Spanish paprika processing in the Murcia Region is under the official category Denomination of Origin “Paprika of Murcia”. The process consists basically in manual harvesting the fruit in full ripe stage, drying, removing the peduncle and seeds, hammer and stone milling for crushing and grinding, transmission, mixing and granulating, sterilization, packaging and refrigerated storage. The details about the paprika processing operations are reported. In a second part the main control points of paprika processing, paprika quality traits and risks are also mentioned. The innovations proposed for paprika processing and unit operations in the literature include application of hygienic food processing design, paprika processing in a nitrogen flow, heat pretreatments before grinding or applied to shredded pepper, high hydrostatic pressure or high intensity electrical field pulse, irradiation, osmotic dehydration, lyophilization, mixing and coating, and modified atmosphere packaging.

Review: Potential of High Hydrostatic Pressure and Pulsed Electric Fields for Energy Efficient and Environmentally Friendly Food Processing

The application of emerging, novel processing techniques such as high hydrostatic pressure or pulsed electric fields can be utilized to replace, enhance or modify conventional techniques of food production. In addition to quality improvements and consumer benefits by gentle microbial inactivation and improvement of mass transfer processes, their potential to improve energy efficiency and sustainability of food production will be discussed within this review.

Localization of 4 f State in YbRh2Si2 under Magnetic Field and High Pressure: Comparison with CeRh2Si2

We present detailed measurements of the electrical resistivity and microcalorimetry under magnetic field and high pressure which confirm the proximity of YbRh 2 Si 2 to a quantum critical point at ambient pressure. Our data seems to rule out the divergence of the heavy quasiparticle mass at the magnetic field tuned quantum critical point. Further Mössbauer spectroscopy gives evidence that the observed ESR resonance cannot be assigned directly to the trivalent Yb local spin dynamics. We report for the first time on quantum oscillations in YbRh 2 Si 2 . The obtained angular dependence is compared with band-structure calculation. A significant change of the resistivity and specific heat under high pressure and magnetic field is observed. Above 5 GPa ferromagnetic coupling plays the dominant role. The unusual high pressure phase diagram of YbRh 2 Si 2 cannot be explained in term of the Doniach phase diagram. In Yb heavy fermion case, slow valence fluctuations may occur due to an occupation number of the trivalent state which differs notably from unity. The differences between the Ce and Yb heavy fermion systems are discussed. In particular a comparison is made between CeRh 2 Si 2 and YbRh 2 Si 2 . The observed field and pressure variations of the Hall voltage in CeRh 2 Si 2 are not straightforwardly linked to the change in the Fermi surface topology. A tiny change in the 4 f electron occupation number will have a huge effect on the effective mass of different orbits of the complex band structure and thus on the Hall effect in this multiband electronic structure. A similar scenario must be certainly considered for YbRh 2 Si 2 .

Development of an extraction type magnetometer under high pressure and high magnetic fields over 200 kOe in the hybrid magnet

An extraction-type magnetometer has been developed, which is performed under pressures up to 12 kbar using a miniature high-pressure clamp-cell, in magnetic fields up to 270 kOe using our hybrid magnet and at the temperature range from 1.5 to 300 K. Magnetization curves can be measured for absolute value over 0.04 emu. We confirmed that resolution is about ±0.01 emu under high pressures and high magnetic fields if a sample has the magnetic moment of about 3 emu. For demonstrating the ability of the instrument, high field magnetization curves for SmMn2Ge2under high pressures are presented.

CFD를 이용한 범포 주위의 유동장 특성

This research aims at establishing the fundamental characteristics of the kite through the analysis of the flow field around various types of kites. The approach of this study were adopted for the analysis; visualization by CFD(computational fluid dynamics). Also, the lift/drag and PIV(particle image velocimetry) tests of kites had been performed in our previous finding. For this situation, models of canvas kite were designed by solidworks(design program) for the CFD test using the same conditions as in the lift/drag tests. And we utilized FloWorks as a CFD analysis program. The results obtained from the above approach are summarized as follows: According to comparison of the measured and analyzed results from mechanical tests, PIV and CFD test, the results of all test were similar. The numerical results of lift-coefficient and drag-coefficient were 5-20% less than those of the tests when attack angle is <TEX>$10^{\circ},\;20^{\circ}\;and\;30^{\circ}$</TEX>. In particular, it showed the 20% discrepancy at <TEX>$40^{\circ}$</TEX>. The numerical results of the ratio of drag and lift were 8-13% less than those of the tests at <TEX>$10^{\circ}$</TEX> and 10% less than those of the tests at <TEX>$20^{\circ},\;30^{\circ}\;and\;40^{\circ}$</TEX>. Pressure distribution gradually became stable at <TEX>$10^{\circ}$</TEX>. In particular, the rectangular and triangular types had the centre of the high pressure field towards the leading edge and the inverted triangular type had it towards the trailing edge. The increase of the attack angle resulted in the eddy in order of the rectangular, triangular and inverted triangular type. The magnitude of the eddy followed the same order. The effect of edge-eddy was biggest in the triangular type followed by the rectangular and then the inverted triangular type. The action point of dynamic pressure as a function of the attack angle was close to the rear area of the model with the small attack angle, and with large attack angle, the action point was close to the front part of the model.

Coexistence of antiferromagnetism and superconductivity inCeRhIn5under high pressure and magnetic field

We report on detailed ac calorimetry measurements under high pressure and magnetic field of CeRhIn5. Under hydrostatic pressure the antiferromagnetic order vanishes near p_c*=2 GPa due to a first order transition. Superconductivity is found for pressures above 1.5 GPa inside the magnetic ordered phase. However, the superconductivity differ from the pure homogeneous superconducting ground state above 2 GPa. The application of an external magnetic field H || ab induces a transition inside the superconducting state above pc* which is strongly related to the re-entrance of the antiferromagnetism with field. This field-induced supplementary state vanishes above the quantum critical point in this system. The analogy to CeCoIn5 is discussed.

Determination of the nonlinear parameter by propagating and modeling finite amplitude plane waves

The acoustic nonlinear parameter, B∕A, is an important piece of data whenever high intensity pressure fields are under consideration. In this work, an alternative method is proposed to measure this parameter. First, the method involves measuring the sound velocity and nonlinear waveform distortion of a finite amplitude plane wave propagating through a medium, Butanediol, whose density and attenuation law have been preliminarily determined. Measurements were performed in the nearfield of a piston where plane wave propagation regime exists. Impulse response of the hydrophone was determined and pressure waveforms were obtained by a convolution process. Then, the method involves modeling, in time domain and under experimental conditions, the theoretical nonlinear waveform distortion and fitting it to the experimental results by adjusting the B∕A parameter. Comparative measurements were performed using the technique of parametric interaction. The respective results for the two methods (B∕A=11.0±10% and 10.9±5%) are in a good agreement despite a smaller degree of accuracy for the proposed method.

Recommendations and guidelines for the performance of accurate heat transfer measurements in rapid forming processes

The published requirements for accurate measurement of heat transfer at the interface between two bodies have been reviewed. A strategy for reliable measurement has been established, based on the depth of the temperature sensors in the medium, on the inverse method parameters and on the time response of the sensors. Sources of both deterministic and stochastic errors have been investigated and a method to evaluate them has been proposed, with the help of a normalisation technique. The key normalisation variables are the duration of the heat input and the maximum heat flux density. An example of application of this technique in the field of high pressure die casting is demonstrated. The normalisation study, coupled with previous determination of the heat input duration, makes it possible to determine the optimum location for the sensors, along with an acceptable sampling rate and the thermocouples critical response-time (as well as eventual filter characteristics). Results from the gauge are used to assess the suitability of the initial design choices. In particular the unavoidable response time of the thermocouples is estimated by comparison with the normalised simulation.

New generation of multifunctional mobile high-pressure oil and gas field pumping units

Technical data and description of basic versions of UNB type of mobile pumping units designed for operation with almost any abrasive-containing, fast-hardening, corrosive, and other fluid media having densities of up to 2.4 g/cm3 are given. The equipment of the units is mounted on truck chassis fit for long-distance traveling.

An analysis on structure of impinging and free diesel spray with exciplex fluorescence method in high temperature and pressure field

Because an injected spray development process consists of impinging and free spray in the diesel engine, it is needed to analyze the impinging spray and free spray, simultaneously, in order to study the diesel spray behavior. To dominate combustion characteristics in diesel engine is interaction between injected fuel and ambient gas, that is, process of mixture formation. Also it is very important to analyze liquid and vapor phases of injected fuel on the investigation of mixing process, respectively and simultaneously. Therefore, in this study, the behavior characteristics of the liquid phase and the vapor phase of diesel spray was studied by using exciplex fluorescence method in high temperature and injection pressure field. Finally, it can be confirmed that the distribution of vapor concentration is more uniform in the case of the high injection than in that of the low injection pressure.

Magnetic properties of Ce(Fe 1− xCo x) 2 under high pressure

We have studied the magnetic properties of Ce(Fe 1− x Co x ) 2 with x = 0 and 0.05 by magnetization measurements under high pressure. In both compound, the remarkable suppression of the magnetization is observed below T * in the ferromagnetic (FM) state under 1.2 GPa. T * shifts to lower temperature with increasing the magnetic field, and the extrapolated value to the zero magnetic field is estimated to be 95 and 123 K. These high pressure and magnetic field effects are probably due to the enhancement and the suppression of the AFM spin fluctuation, respectively.

Microbial inactivation by new technologies of food preservation

The increasing consumer demand for 'fresh-like' foods has led to much research effort in the last 20 years to develop new mild methods for food preservation. Nonthermal methods allow micro-organisms to be inactivated at sublethal temperatures thus better preserving the sensory, nutritional and functional properties of foods. The aim of this review is to provide an overview of the microbiological aspects of the most relevant nonthermal technologies for microbial inactivation currently under study, including irradiation, high hydrostatic pressure, pulsed electric field and ultrasound under pressure. Topics covered are the mechanisms of inactivation, sensitivity of different microbial groups and factors affecting it and kinetics of inactivation.

こんなことができる放射光（５）物理学分野における放射光結晶学 電子自由度秩序の観測―共鳴Ｘ線散乱で探る静的・動的構造―

In strongly correlated electron systems, it has been known that three degrees of freedom of electrons, that is, charge, spin and orbital play very important roles in their electronic and magnetic properties. In this report we show the resonant X-ray scattering is a very powerful tool to observe charge, spin, and orbital orderings. Synchrotron X-ray diffraction experiments in high pressure and magnetic field are introduced to reveal the mechanism of the orderings. It is also reported that the orbital excitation is studied by resonant inelastic X-ray scattering.

A study on the behavior of evaporating diesel spray using LIEF measurement and kiva code

The effects of change in injection pressure on spray structure in high temperature and pressure field have been investigated. The analysis of liquid and vapor phases of injected fuel is important for emissions control of diesel engines. Therefore, this work examines the evaporating spray structure using a constant volume vessel. The injection pressure is selected as the experimental parameter, is changed from 400 bar to 800 bar by using a common rail injection system. Also, we conducted simulation study by modified KIVA-II code. The results of simulation study are compared with experimental results. The images of liquid and vapor phase for free spray were simultaneously taken by exciplex fluorescence method. As experimental results, the vapor concentration of injected fuel is leaner due to the increase of atomization in the case of the high injection pressure than in that of the low injection pressure. The calculated results obtained by modified KIVA-II code show good agreements with experimental results.

Ion Mobility Spectrometer with Radial Collisional Focusing

An ion mobility spectrometer that has its mobility cell as a 20-segment quadrupole and functionally the q2 of a triple-quadrupole mass spectrometer has been assembled and tested. The combination of high cell pressure (maximum of 4 Torr of helium) and low axial field (20-160 V per 20.2 cm) results in negligible internal excitation of the ions despite applications of rf and axial fields. The presence of collisional focusing ensures efficient ion transmission and good sensitivity. Collision cross sections of atomic, cluster, peptide, and protein ions were measured and found comparable to literature and calculated cross sections.

Marine gas hydrate: Fabric, quantification and free gas content. Examples from Hydrate Ridge–Cascadia margin

A recent advance in the investigation of internal gas hydrate structure and in small scale quantification is based on a combination of a new coring device and computerized x-ray tomography (CT). This approach has been chosen because gas hydrate is only stable within a special (low) temperature and (high) pressure field. A MultiAutoclaveCorer, developed by the Technical University of Berlin, is in principle similar to a piston corer and has the size of a multiple corer. During the deployments on Hydrate Ridge, two pressure vessels filled with seafloor samples could be recovered. They were CT-investigated after the cruise in a medical clinic close to San Francisco. As a result, a 3-D-dataset of the cores is available which allows to quantify the components’ gas hydrate, sediment and free gas and also shows the distribution and orientation of the gas bubbles. One of the pressure vessels showed a distinct gas hydrate horizon where the gas hydrate content reached close to 50 vol%. Within this horizon there was a free gas content of 2.4 vol%. The preferential bubble orientation, compared to free gas in soft marine sediments, is horizontal, not vertical, which is an indicator for the mechanism of gas hydrate formation.

New preservation technologies: Possibilities and limitations

A lot of research in the field of food science has focused on new preservation technologies but very few of these methods have been implemented by the food industry until now. This article describes the most intensively investigated new preservation methods with their possibilities and especially their limitations, often hampering their implementation by the food industry. Many alternative ‘non-thermal’ treatments have been proposed with high hydrostatic pressure and pulsed electrical fields being the most investigated ones. Both techniques allow killing of vegetative microorganisms but fail until now, when applied alone, to destroy spores. New packaging systems are introduced such as modified atmosphere packaging and active packaging systems. The latter systems have until now a limited application in practice due to incompatibility with legislation, limited effectivity and thermolability of active compounds. Natural compounds, such as essential oils, chitosan, nisin or lysozyme, are investigated to replace chemical preservatives and to obtain ‘green label’ products. Their application is mainly hampered due to interaction of the natural compounds with food ingredients and due to changes in the organoleptical properties when introduced in a food. The application of protective cultures, able or unable to produce antimicrobial compounds such as bacteriocins are proposed to inhibit growth of unwanted microorganisms. The activity of bacteriocins is however often limited due to its narrow activity spectrum, its inactivation due to interaction with food ingredients or proteolytic action of the food, its limited diffusion in solid matrixes and the occurrence of loss of bacteriocinogenicity of the culture and of resistance of the target organisms. This overview nuances the application of the above mentioned preservation techniques and focuses on draw backs on their application by the food industry.