High Pressure Research Papers - Academia.edu (original) (raw)

The Timor-Tanimbar region constitutes part of the non-volcanic outer Banda Arc of Eastern Indonesia. Here, the world's youngest 'A'-type high-pressure metamorphic belt crops out with different stages of evolution. Whereas an advanced domal uplift stage is seen in Timor island, the high-pressure (HP) metamorphic belt is still in the first stage of tectonic extrusion on the eastern small islands of Kisar, Leti, Moa, Sermata and Laibobar. The metamorphic rocks on Leti are among the best exposed in the islands. They are tectonically juxtaposed against overlying ultramafic rocks and underlying unmetamorphosed continental shelf sediments, bound by normal and reverse faults, respectively. The Leti metapelites display four progressive metamorphic zones: chlorite-biotite, garnet, chloritoid-staurolite and kyanite zones, with increasing grade. Zonation in Leti metabasite unit is comparable, and progressively changes from blueschist-greenschist transition (BS/GS), through epidote-amphibolite (EA), to amphibolite (AM) facies, with increasing grade. The highest-grade metapelites and metabasites occupy structurally intermediate levels.

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- Geology, Geochemistry, Geophysics, High Pressure
- by Thomas Pettke
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- Pharmacology, Biochemistry, Bioinformatics, Evolutionary Biology

This paper provides a review of the tectonic evolution of central-southern Africa from Mesoproterozoic to earliest Palaeozoic times, using available geological information and a robust U-Pb zircon database. During the late Mesoproterozoic, the southern margin of the Congo-Tanzania-Bangweulu Craton was characterized by suprasubduction-zone magmatism and the accretion of arc and microcontinental fragments. Magmatism within the adjacent Irumide Belt formed by recycling of older continental crust. Ophiolite blocks, possibly part of an olistostromal mélange, are present in a Neoproterozoic sequence overlying the Irumide Belt, and the occurrence of high-pressure/low-temperature subduction-zone metamorphism and protracted Neoproterozoic suprasubduction-zone magmatism demonstrates that there was an ocean to the south (present-day coordinates) of the Congo-Tanzania-Bangweulu Craton until the amalgamation of Gondwana at 550-520 Ma, indicating that the Congo-Tanzania-Bangweulu Craton was not part of Rodinia. On the basis of their different ages and styles of magmatism, the Mesoproterozoic Kibaran Belt, Choma-Kalomo Block and Irumide Belt are not components of the same orogen, therefore precluding a sub-Saharanwide, linked 'Kibaran' (sensu lato) orogenic event. Evidence is presented to illustrate that the Congo-Tanzania-Bangweulu and Kalahari Cratons developed independently until their final collision during the Pan-African Orogeny along the Damara-Lufilian-Zambezi Orogen at c. 550-520 Ma.

- by Bert De Waele
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- Geology, High Pressure, Southern Africa, Time Use

AbstractÐThe electrochemical compression of hydrogen is well known since years. But new developments of the polymer electrolyte membrane (PEM) fuel cells make it possible to realize the electrochemical compression in a PEM-cell with high eciency. A new cell design of PEM-cells for operation with a high pressure dierence between anode side and cathode side was developed. The puri®cation of hydrogen from carbon monoxide of the reformer gas can be integrated in the hydrogen compressor cell. Operation parameters are presented. #

- by Juergen Garche
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- Engineering, High Pressure, Hydrogen Storage, Fuel Cell

Amino acids are the essential building blocks of proteins and peptides. They can also take part in intermediary metabolism and act as precur- sors to common biogenic amine neurotransmitters. Certain amino acids act as neurotransmitters and are the major excitatory (aspartate and glutamate) and inhibitory (GABA and taurine) commands in the central nervous system. The measurement of the profile of these neuroactive amino acids can assist with the characterization and our understanding of the factors and potential causes of various neurological conditions. Amino acids are difficult to detect directly as they lack a suitable chro - mophore, so derivatives are often prepared. A specific challenge of the analytical method is realized when analyses in low volume samples are at low concentrations, as is the case with brain microdialysis samples. Isoindole derivatives of amino acids, formed through a well-established reaction with o-phthalaldehyde (OPA) and 2-mercaptoethanol (β-ME), can now ...

- by Ian Acworth and +2
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- High Pressure, Glutamate, Central Nervous System, High Resolution

The huge advance of high-pressure techniques came with the design of the diamond anvil cell (DAC) achieving multidisciplinary character. DAC makes possible to investigate the changes in the electronic properties induced by local or crystal modifications of the material under high pressures without changing the chemical composition (Fig. 1). Traditional spectroscopic techniques used in material characterization labs like optical absorption, luminescence, excitation, lifetimes or Raman can be systematically applied previous adaptation to work with microsamples. So, it is possible to establish different pressure effects on materials: energy level shifts, local structure modifications or structural phase transitions and their consequences on the electronic and vibrational properties; changes in color due to pressure (piezochromism), high spin to low spin transitions, excited-state crossovers, etc. The different sensitivity of excited states to crystal-field strength enables the energy tuning of the states responsible of the optical properties (usually d orbitals in transition metal ions and f orbitals in lanthanides) for inducing resonance between levels producing exotic effects like upconversion, i. e., convert low energy radiation into higher energy from the emitting ions. The aim of this contribution is to illustrate, with selected examples, the effect of pressure on insulators [1-4] and semiconductor materials [5], which have been explored in our group recently.

- by Rafael Valiente
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- High Pressure, Phase Transitions, Luminescence, Optical physics

The correlated metal UCoGe is a weak itinerant ferromagnet with a Curie temperature T C = 3 K and a superconductor with a transition temperature T s = 0.6 K. We review its basic thermal, magnetic  on the macro and microscopic scale  and transport properties, as well as the response to high pressure. The data unambiguously show that superconductivity and ferromagnetism coexist below T s = 0.6 K and are carried by the same 5f electrons. We present evidence that UCoGe is a p-wave superconductor and argue that superconductivity is mediated by critical ferromagnetic spin fluctuations.

The expansion of a laser-ablation plume into different ambient gases is investigated theoretically using a two-fluid gas-dynamic model and experimentally with time-of-flight mass spectrometry. Both calculations and measurements, performed for laser ablation of YBa 2 Cu 3 O 7−x in oxygen or noble gases, reveal an oscillatory behaviour of plume expansion dynamics which is strongly dependent on the molecular weight of the ambient gas. Simple gas-dynamic considerations based on the analogy between an ablation plume and a supersonic underexpanded gaseous jet are found to explain a number of the effects of the interaction between the plume and the background gas. The effect of plume focusing observed previously at fairly high pressures of various ambient gases is reasonably described using the phenomenology of the underexpanded jet. The analogy also predicts vortex formation at the plume periphery.

- by Alexander Bulgakov
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- Engineering, High Pressure, Time-of-flight mass spectrometry, Gas Dynamics

The C 7 H 7 potential energy surface was studied from first principles to determine the benzyl radical decomposition mechanism. The investigated high temperature reaction pathway involves 15 accessible energy wells connected by 25 transition states. The analysis of the potential energy surface, performed determining kinetic constants of each elementary reaction using conventional transition state theory, evidenced that the reaction mechanism has as rate determining step the isomerization of the 1,3-cyclopentadiene, 5-vinyl radical to the 2-cyclopentene,5-ethenylidene radical and that the fastest reaction channel is dissociation to fulvenallene and hydrogen. This is in agreement with the literature evidences reporting that benzyl decomposes to hydrogen and a C 7 H 6 species. The benzyl high-pressure decomposition rate constant estimated assuming equilibrium between the rate determining step transition state and benzyl is k 1 (T) = 1.44 Â 10 13 T 0.453 exp(À38400/T) s À1 , in good agreement with the literature data. As fulvenallene reactivity is mostly unknown, we investigated its reaction with hydrogen, which has been proposed in the literature as a possible decomposition route. The reaction proceeds fast both backward to form again benzyl and, if hydrogen adds to allene, forward toward the decomposition into the cyclopentadienyl radical and acetylene with high-pressure kinetic constants k 2 (T) = 8.82 Â 10 8 T 1.20 exp(1016/T) and k 3 (T) = 1.06 Â 10 8 T 1.35 exp(1716/T) cm 3 /mol/s, respectively. The computed rate constants were then inserted in a detailed kinetic mechanism and used to simulate shock tube literature experiments.

- by Carlo Cavallotti and +1
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- Mechanical Engineering, Chemical Engineering, High Pressure, Kinetics

We performed comparative study of phase relations in Fe 1-x Ni x (0.10 B x B 0.22 atomic fraction) and Fe 0.90 Ni 0.10-x C x (0.1 B x B 0.5 atomic fraction) systems at pressures to 45 GPa and temperatures to 2,600 K using laser-heated diamond anvil cell and large-volume press (LVP) techniques. We show that laser heating of Fe,Ni alloys in DAC even to relatively low temperatures can lead to the contamination of the sample with the carbon coming from diamond anvils, which results in the decomposition of the alloy into iron-and nickel-rich phases. Based on the results of LVP experiments with Fe-Ni-C system (at pressures up to 20 GPa and temperatures to 2,300 K) we demonstrate decrease of carbon solubility in Fe,Ni alloy with pressure.

- by Natalia Dubrovinskaia
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- Materials Engineering, Geochemistry, High Pressure, Iron

The behavior of binary mixtures of carbon dioxide+alkanol (1-butanol, 2-butanol, 1-pentanol, or 2-pentanol) at high pressures was modeled using the Stryjek-Vera version of the Peng-Robinson equation of state. Two mixing rules were compared for this purpose: the classical one-fluid van der Waals and the Wong-Sandler mixing rules. In the case of the latter mixing rule, the NRTL model for the excess Gibbs free energy was used. We observed that both mixing rules can reproduce the qualitative aspects of the critical diagrams of these binary mixtures. A comparison of the results shows that there is no clear superiority of one mixing rule over the other in terms of the ability to predict the critical behavior of these mixtures.

- by Stanley Sandler
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- Chemical Engineering, High Pressure, Carbon Dioxide, Gibbs Free Energy

The photocatalytic disinfection of Escherichia coli, a pathogenic micro-organism was investigated. An aqueous suspension of the micro-organism (1 × 10 8 cfu/ml) and neat TiO 2 or silver-loaded TiO 2 were irradiated with a high pressure mercury lamp for various time periods at neutral pH (7.0). Silver loading (1%, w/w) dramatically reduced the illumination time for complete degradation (less than 1-2 min) and minimum catalyst concentration was determined as 0.1 mg/ml. Possible killing mechanism and intermediate products were also determined. Occurrence of lipidperoxidation which produces malondialdehyde (MDA) was proposed but the method employed was so effective that all micro-organisms and intermediate products were further degraded to harmless products.

- by Ferda Candan
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- Engineering, High Pressure, Photochemistry, Biological Sciences

In this study, fracture experiments on multiphase material samples have been carried out using high speed water jets. Based on fracture geometry measurements and on grain analyses it was found that the fracture of this type of materials by water jet impingement is a highly localized process at low pressure ranges. Beyond a critical pressure range of about 30 times the material's tensile strength a change in the material behaviour was observed. This result is in agreement with a theory suggested by Powell and Simpson. To explain the local character of the failure process, a simplified fracture model is introduced which resulted in a relation between a fracture probability parameter and the fracture width in the damaged materials.

- by Andreas Momber
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- Materials Engineering, Mechanical Engineering, Civil Engineering, High Pressure

Yarrowia lipolytica converts methyl ricinoleate to c-decalactone, a high-value fruity aroma compound. The highest amount of 3-hydroxy-c-decalactone produced by the yeast (263 mg l -1 ) occurred by increasing the k L a up to 120 h )1 at atmospheric pressure; above it, its concentration decreased, suggesting a predominance of the activity of 3-hydroxyacyl-CoA dehydrogenase. Cultures were grown under high-pressure, i.e., under increased O 2 solubility, but, although growth was accelerated, c-decalactone production decreased. However, by applying 0.5 MPa during growth and biotransformation gave increased concentrations of dec)2-en-4-olide and dec-3-en-4-olide (70 mg l )1 ).

- by Nelma Gomes
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- Engineering, Technology, High Pressure, Biotechnology

Apple juice and apple cider were inoculated with Escherichia coli K-12 and processed using a highpressure homogenizer to study bacterial inactivation. Seven levels of pressure ranging from 50 to 350 MPa were used in the high-pressure homogenizer. Two types of chitosan (regular and water soluble) with 2 levels of concentration 0.01% and 0.1% were investigated for synergistic effect with high-pressure homogenization for the bacterial inactivation. E. coli K-12 inactivation was evaluated as a function of homogenizing pressure at different concentration of 2 types of chitosan in apple juice and cider. High-pressure homogenization (HPH) induced significant inactivation in the range of 100 to 200 MPa, while thermal inactivation was the primary factor for the bacterial inactivation above 250 MPa. Significant (P < 0.05) 2-way interactions involving pressure and type of substrate or pressure and chitosan concentration were observed during the study. The homogenization pressure and the incremental quantity of chitosan (both types) acted synergistically with the pressure to give higher inactivation. Significantly (P < 0.05) higher inactivation was observed in apple juice than apple cider at same homogenizing pressure. No effect of type of chitosan was observed on the bacterial inactivation.

- by Saurabh Kumar
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- Chemical Engineering, Food Science, High Pressure, Food

Gas flow in a transmission line is described by a set of three coupled partial differential equations (PDE) expressing conservation of mass, momentum and energy; the gas properties are described by a non-ideal equation of state. A technique is introduced which reduces the energy equation into a single parameter in the mass equation without the assumption of isothermal or isentropic flow.

- by J. Van Deen
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- Applied Mathematics, High Pressure, Applied Mathematical Modelling, Transmission Line

This article focuses on the application of high pressure laser flash photolysis for studies on selected hemoprotein reactions with the objective to establish details of the underlying reaction mechanisms. In this context, particular attention is given to the reactions of small molecules such as dioxygen, carbon monoxide, and nitric oxide with selected hemoproteins (hemoglobin, myoglobin, neuroglobin and cytochrome P450 cam ), as well as to photo-induced electron transfer reactions occurring in hemoproteins (particularly in various types of cytochromes). Mechanistic conclusions based on the interpretation of the obtained activation volumes are discussed in this account.

- by Rudi Van Eldik and +1
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- High Pressure, Biological Sciences, Carbon Monoxide, Lasers

A novel approach to improve the bioavailability and stability of atorvastatin (AT) was developed by constructing a nano-sized polymer-atorvastatin conjugate. Firstly, a novel chitosan-atorvastatin (CH-AT) conjugate was efficiently synthesized through amide coupling reaction. The formation of conjugate was confirmed by 1 H NMR and FT-IR spectrometry. Nano-sized conjugate with a mean size of 215.3 ± 14.2 nm was prepared by the process of high pressure homogenization (HPH). Scanning electron microscopy (SEM) revealed that CH-AT nano-conjugate possess smooth surface whereas X-ray diffraction (XRD) spectra demonstrated amorphous nature of nano-conjugate. Further, CH-AT nano-conjugate showed solubility enhancement of nearly 4-fold and 100-fold compared to CH-AT conjugate and pure AT, respectively. In vitro drug release studies in simulated gastric fluid and simulated intestinal fluid suggested sustained release of AT from the conjugate. Additionally, the nano-conjugate significantly reduced the acidic degradation of AT. The plasma-concentration time profile of AT after oral administration of CH-AT nano-conjugate (2574 ± 95.4 ng/mL) to rat exhibited nearly 5-fold increase in bioavailability compared with AT suspension (583 ± 55.5 ng/mL). Finally, variable bioavailability, as observed for AT suspension was also reduced when AT was administered in form of CH-AT nano-conjugate. Taken together these data demonstrate that chitosan conjugate nano-prodrugs may be used as sustained polymeric prodrugs for enhancing bioavailability.

- by Gaurav Jain and +4
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- High Pressure, Chitosan, Scanning Electron Microscopy, Intestinal Mucosa

The Levitated Dipole Experiment (LDX) is a novel concept that examines plasma compressibility as a method for stable magnetic confinement of fusion grade plasmas. The experiment uses a 0.8 m diameter ring-type dipole coil that is levitated at the center of a 5 m diameter 3 m tall vacuum chamber to confine the plasma. This persistent mode, floating coil is wound from a prereacted Nb 3 Sn conductor and encased in a toroidally shaped, constant volume helium cryostat to eliminate external connections to the coil during levitated operation. Although the peak field on the inductively charged floating coil is only 5.3 T, Nb 3 Sn conductor was selected because of its higher temperature capability. The cryostat, with on-board helium supply, is designed for 6-8 hours of levitated operation as the heat leak gradually warms the coil from 5 to 10 K. The cryostat consists of three concentric shells: a sealed, high pressure Inconel helium vessel that contains the floating coil and heat exchangers that are used to recool the coil before operation, a high heat capacity fiberglass-lead radiation shield, and an outer vacuum shell. The shells are kept separated by a support system designed to withstand impact forces up to 10 g in the case of a levitation failure. The paper summarizes the manufacture and initial driven-mode test of the floating coil, and describes the design, manufacture and test of the cryostat.

- by Darren T Garnier
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- Materials Engineering, Condensed Matter Physics, High Pressure, Heat Exchanger
- by Artor Niccoli Asabella
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- High Pressure, Quality of life, Treatment Outcome, Constipation

The formation, stability and physico-chemical properties of TiO 2 powders are strongly influenced by the actual synthesis and processing routes employed. Pure and metal-doped nanostructured TiO 2 samples were obtained using the sol-gel... more

- by Christoph Schick
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- Analytical Chemistry, High Pressure, Synchrotron Radiation, Titanium dioxide

The behaviour of spoilage and pathogenic microorganisms was evaluated after high-pressure treatment (600 MPa 6 min, 31 8C) and during chilled storage at 4 8C for up to 120 days of commercial meat products. The objective was to determine if this pressure treatment is a valid process to reduce the safety risks associated with Salmonella and Listeria monocytogenes, and if it effectively avoids or delays the growth of spoilage microorganisms during the chilled storage time evaluated. The meat products covered by this study were cooked meat products (sliced cooked ham, pH 6.25, a w 0.978), dry cured meat products (sliced dry cured ham, pH 5.81, a w 0.890), and raw marinated meats (sliced marinated beef loin, pH 5.88, a w 0.985). HPP at 600 MPa for 6 min was an efficient method for avoiding the growth of yeasts and Enterobacteriaceae with a potential to produce off-flavours and for delaying the growth of lactic acid bacteria as spoilage microorganisms. HPP reduced the safety risks associated with Salmonella and L. monocytogenes in sliced marinated beef loin. D Industrial relevance: High pressure is a preservation technique which seems a natural choice for meat and meat products. However, it has taken quite a while until products treated at an industrial level are appearing. The study aimed at cooked and dry cured ham and at marinated beef loin and the evaluation of microbial growth during subsequent extended chilled storage. Clearly high pressure treatment reduced microbial risks over non treated products and the authors rightly point to the composition of the products as one key factor influencing the effectiveness of high pressure processing.

- by Marta Hugas
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- Engineering, High Pressure, Biological Sciences, SHELF LIFE

We present the results of an experiment performed at PSI to investigate muon catalyzed fusion in pure deuterium gas of 5% density (LHD) at temperatures ranging from 28 K to 350 K. Using a new high pressure ionization chamber the reactions... more

- by Evgeny Maev
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- High Pressure, Hyperfine Interactions, Temperature Dependence

The Gibbs free energy and volume changes attendant upon hydration of cordierites in the system magnesian cordierite-water have been extracted from the published high pressure experimental data at PH~o =Ptot~l, assuming an ideal one site model for H20 in cordierite. Incorporating the dependence of A G and A V on temperature, which was found to be linear within the experimental conditions of 500~176 and 1-10,000bars, the relation between the water content of cordierite and P, T and fH~O has been formulated as ~crd __ H20-[exp-~{64,775-32.26T+G~l' 2ro-P(9xlO-4T-O.5142)}] § The equation can be used to compute H20 in cordierites at PH~o < 1. Our results at different P, T and partial pressure of water, assuming ideal mixing of H20 and CO 2 in the vapour phase, are in very good agreement with the experimental data of Johannes and Schreyer (1977, 1981). Applying the formulation to determine X ~ in the H20 garnet-cordierite-sillimanite-plagioclase-quartz granulites of Finnish Lapland as a test case, good agreement with the gravimetrically determined water contents of cordierite was obtained. Pressure estimates, from a thermodynamic modelling of the Fe-cordierite-almandine-sillimanite-quartz equilibrium at Pn~o=0 and Pn~o=Ptotal, for assemblages from South India, Scottish Caledonides, Daly Bay and Hara Lake areas are compatible with those derived from the garnetplagioclase-sillimanite-quartz geobarometer.

- by Abhijit Bhattacharya
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- Geology, Geochemistry, Thermodynamics, High Pressure

A microbial survival curve is constructed by plotting the number of recoverable cells or their logarithm vs. the exposure time to the hostile agent, be it high or low temperature, a chemical preservative or disinfectant, etc. Since the recovery is usually done in a medium and under conditions that favor growth, the result is insensitive to whether the counted survivors are intact or injured. If or when both the total number of survivors and those remaining intact follow a Weibullian decay pattern (with different parameters), then the momentary number of injured cells will be the momentary difference between the two. Such a scenario can be easily modeled mathematically and the resulting model enables to simulate a variety of survived-injury patterns in thermal and non-thermal food preservation processes. Under certain conditions according to this model, almost all the survivors would be injured to at least some extent and hence may perish during the food's storage and transportation. Isothermal survival-injury curves generated with the Weibullian model based on the above considerations were in general agreement with published experimental data. In principle, the methodology can be extended to simulate mortality-injury patterns under dynamic conditions, i.e., when the temperature or chemical agent's concentration vary with time. Whether a cell is considered injured depends on the recovery method, e.g., on whether it can or cannot grow in a saline medium. Thus recovery in different media may yield somewhat different quantitative results but very unlikely a qualitatively different pattern. Although the model used was based on that microbial mortality and injury both follow the Weibullian model, very similar results would have been obtained had other survival modes been assumed.

- by Maria Corradini
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- Microbiology, Mathematics, High Pressure, Kinetics

Densities were measured for the liquid benzene and 1,3,5-trimethylbenzene, and for nine of their mixtures at four temperatures between 298.15 and 328.15 K and at pressures up to 40 MPa. An apparatus for density measurements of liquids and liquid mixtures whose main part is a high-pressure vibrating-tube densimeter working in a static mode was used for the measurement. The density data were fitted to the Tait equation and the isothermal compressibilities were calculated with the aid of this equation. Excess molar volumes were also calculated from the densities and fitted to the Redlich-Kister equation.

- by Zdenek Wagner
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- Chemical Engineering, High Pressure, Classical Physics, Fluid phase equilibria

La Serena cheeses, made from Merino ewes' raw milk, were high-pressure (HP)-treated at 300 or 400 MPa for 10 min at 10 1C, on days 2 or 50 of ripening. Cheeses treated by HP on day 2 showed higher pH values than control cheese on day 3, but cheeses treated by HP on days 2 or 50 and control cheese had similar pH values on day 60. Breakdown of caseins was delayed by HP treatment of cheeses on day 2. Cheeses treated by HP on day 2 showed higher levels of hydrophilic peptides, lower levels of hydrophobic peptides, lower hydrophobic peptides: hydrophilic peptides ratios, and higher total contents of free amino acids than those of control cheese. HP treatment of cheese on day 50 scarcely affected proteolysis of 60-day-old cheeses. Fracturability, hardness and elasticity values of cheeses treated by HP on day 2 were higher than those of control cheese and of cheeses treated on day 50. Cheeses treated at 400 MPa on day 2 received the lowest scores for quality of taste from panellists, whereas the rest of HP-treated cheeses did not differ from control cheese. r

- by Manuel Nuñez
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- High Pressure, Taste, Dairy, Texture

A novel combination of high performance low pressure chromatography with multisyringe flow injection analysis is presented. This system comprises a multisyringe module, three low pressure solenoid valves, a monolithic Chromolith Flash RP-18e column and a diode array spectrophotometer. UV detection is carried out at 250nm. AutoAnalysis software is used for instrumental control and automated data collection. The results obtained with multisyringe liquid chromatography (MSC) were compared with those obtained with a HPLC system using similar conditions. The chromatographic parameters were calculated from a mixture of anthracene and thiourea using a mobile phase containing acetonitrile-water (60:40) at a flow rate of 2mlmin(-1). The proposed MSC system has been successfully applied to the determination of amoxicillin, ampicillin and cephalexin using a mobile phase of sodium acetate buffer (pH 6.2, 0.1moll(-1))-methanol (90:10) at a flow rate of 2mlmin(-1). The low-cost, flexibility and s...

- by Victor Cerda
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- Analytical Chemistry, Water, High Pressure, Flow Injection Analysis

Piezoelectric composites comprising dispersions of free-flowing calcium-modified lead titanate powders in a poly( vinylidene fluoride) matrix have been developed and characterized as materials for hydrophone applications. We find that these composites provide highly desirable properties: (1) high figures of merit, g,d,=50( k.S) X 10-l" mz N-', and a relatively low dielectric loss tangent, less than 0.018; (2) convenient melt processibility; (3) no significant sensitivity changes in going to high pressures ( 14 MPa or 2 kpsi) ; (4) thermal stability of the poled state for months at 100°C; and (5) easy fabrication. This performance results from material choices and from special ceramic powder processing and composite preparation methods that optimize the achievable degree of ceramic poling, the remanent polarization, and the transfer of mechanical energy to the dispersed ceramic. Materials design concepts, composite processing, and device construction and evaluation are described. 0 1998 Elsevier Science S.A.

- by zafar Iqbal
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- Materials Engineering, Mechanical Engineering, High Pressure, Materials Design
- by Eklabya Sharma
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- Environmental Engineering, Civil Engineering, High Pressure, Water quality

This paper presents an experimental study on the homogeneous dispersion of nanoparticles in nanofluids. In this study, various physical treatment techniques based on two-step method, including stirrer, ultrasonic bath, ultrasonic disruptor, and high-pressure homogenizer were systematically tested to verify their versatility for preparing stable nanofluids. Initially carbon black and silver nanoparticles dispersed in base fluids with the presence of surfactant were found to be highly agglomerated with the hydrodynamic diameter of 330 nm to 585 nm, respectively. After both CB and Ag nanofluids were treated by various two-step methods, stirrer, ultrasonic bath, and ultrasonic disrupter was found to do a poor performance in deagglomeration process for the initial particle clusters. However, the high-pressure homogenizer produced the average diameter of the CB and Ag particles of 45 nm and 35 nm, respectively, indicating that among various physical treatment techniques employed in this study, the high-pressure homogenizer was the most effective method to break down the agglomerated nanoparticles suspended in base fluids. In order to prepare another nanofluid with much smaller primary nanoparticles, we also employed a modified magnetron sputtering system, in which the sputtered nanoparticles were designed to directly mix with the running surfactant-added silicon oil thin film formed on a rolling drum (i.e. one-step method). We observed that Ag nanoparticles produced by the modified magnetron sputtering system were homogeneously dispersed and long-term stable in the silicon oil-based fluid, and the average diameter of Ag nanoparticles was found to be~3 nm, indicating that the modified magnetron sputtering system is also an effective one-step method to prepare stable nanofluids.

- by Soo Kim
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- Mechanical Engineering, Chemical Engineering, Design, Production

A v a i l a b l e a t w w w . s c i e n c e d i r e c t . c o m j o u r n a l h o m e p a g e : w w w . e l s e v i e r . c o m / l o c a t e / h e i n t e r n a t i o n a l j o u r n a l o f h y d r o g e n e n e r g y 3 6 ( 2 0 1 1 ) 8... more

A v a i l a b l e a t w w w . s c i e n c e d i r e c t . c o m j o u r n a l h o m e p a g e : w w w . e l s e v i e r . c o m / l o c a t e / h e i n t e r n a t i o n a l j o u r n a l o f h y d r o g e n e n e r g y 3 6 ( 2 0 1 1 ) 8 6 4 1 e8 6 4 4

- by Gilbert Henaff
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- Engineering, High Pressure, Fatigue crack growth, Hydrogen Energy

A BSTRACT : A high-pressure optical cell was designed and fabricated for the measurement of hydrate phase equilibria. These measurements were carried out using Raman spectroscopy, which provided molecular microscopic evidence of hydrate dissociation, along with macroscopic temperature and pressure evidence. Initial measurements were made of hydrates formed from methane (CH 4 ) dissolved in deionized water. Distinct signatures of CH 4 in different phases (aqueous and sI hydrate) were the basis for this study. Time resolved Raman spectra monitored the dissociation of hydrate as cell temperature was increased. The spectra depicted the transition of CH 4 in the two cavities of sI hydrate to CH 4 dissolved in water. A pressure trace of the experiment indicated a slight jump in pressure of about 30 psi (0.2 MPa) at the hydrate dissociation point, which agreed with the Raman spectroscopic data. Experimental data obtained using this method agreed well with literature data for the simple methane system. The technique demonstrated that the optical cell is suitable for Raman measurements of hydrate phase equilibria at high pressures. Ultimately, this procedure will be used to measure thermodynamic conditions for more complex systems.

- by vu thieu
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- High Pressure, Raman Spectroscopy, Multidisciplinary

The low-temperature isobaric heat capacities (C p ) of b-and c-Mg 2 SiO 4 were measured at the range of 1.8-304.7 K with a thermal relaxation method using the Physical Property Measurement System. The obtained standard entropies (S°2 98 ) of b-and c-Mg 2 SiO 4 are 86.4 ± 0.4 and 82.7 ± 0.5 J/mol K, respectively. Enthalpies of transitions among a-, b-and c-Mg 2 SiO 4 were measured by high-temperature dropsolution calorimetry with gas-bubbling technique. The enthalpies of the a-b and b-c transitions at 298 K (DH°2 98 ) in Mg 2 SiO 4 are 27.2 ± 3.6 and 12.9 ± 3.3 kJ/ mol, respectively. Calculated a-b and b-c transition boundaries were generally consistent with those determined by high-pressure experiments within the errors. Combining the measured DH°2 98 and DS°2 98 with selected data of in situ X-ray diffraction experiments at high pressure, the DH°2 98 and DS°2 98 of the a-b and b-c transitions were optimized. Calculation using the optimized data tightly constrained the a-b and b-c transition boundaries in the P, T space. The slope of a-b transition boundary is 3.1 MPa/K at 13.4 GPa and 1,400 K, and that of b-c boundary 5.2 MPa/K at 18.7 GPa and 1,600 K. The post-spinel transition boundary of c-Mg 2 SiO 4 to MgSiO 3 perovskite plus MgO was also calculated, using the optimized data on c-Mg 2 SiO 4 and available enthalpy and entropy data on MgSiO 3 perovskite and MgO. The calculated post-spinel boundary with a Clapeyron slope of -2.6 ± 0.2 MPa/K is located at pressure consistent with the 660 km discontinuity, considering the error of the thermodynamic data.

- by Masaki Akaogi
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- Materials Engineering, Geochemistry, Thermodynamics, Polymorphism

A method for quantifying laser-induced fluorescence (LIF) signals and planar laser-induced fluorescence (PLIF) images of the OH and NO radicals in high pressure flames is presented. The fluorescence signal per unit radical mole fraction is modeled as a function of temperature, pressure, overall flame stoichiometry and laser spectral bandwidth. A recently developed model (JQSRT, 51, 51 I; Appl. Phys. B, 57, 249)'.* for electronic quenching cross-sections of OH and NO is utilized to express the fluorescence yield as a function of these parameters. The models are confirmed using single-point measurements in the burnt gas region of a flat flame burner at up to 10 atm. The measurements are performed at points in the flame where the temperature, pressure, OH and NO mole fraction are all known. For fuel-lean flames at elevated pressure, interference from the O2 Schumann-Runge system was found with NO A + X(0,0) fluorescence measurements. This interference must be considered when selecting an appropriate NO transition in this type of environment.

- by Brett Battles
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- High Pressure, Atmospheric sciences, Methane, Laser Induced Fluorescence

We calculate by molecular dynamics the optical functions of MgO in the far infrared region 100-1000 cm −1 , for pressures up to 40 GPa and temperatures up to 4000 K. An ab initio parametrized many-body force field is used to generate the trajectories. Infrared spectra are obtained from the time correlation of the polarization, and from Kramers-Kronig relations. The calculated spectra agree well with experimental data at ambient pressure. We find that the infrared absorption of MgO at CO 2 laser frequencies increases substantially with both pressure and temperature and we argue that this may explain the underestimation, with respect to theoretical calculations, of the high-pressure melting temperature of MgO determined in CO 2 laser-heated diamond-anvil cell experiments.

- by Yunfeng Liang
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- Engineering, High Pressure, Chemical Physics, Physical sciences

The GKSS Forschungszentrum Geesthacht, Germany, will setup a new high-energy beamline specialized for texture, strain and imaging measurements for materials science at the Hamburger Synchrotronstrahlungslabor HASYLAB of the Deutsches Elektronen-Synchrotron DESY. Four different experiments will be installed at the new wiggler HARWI-II. The high pressure cell will be run by the GFZ Potsdam, Germany, the high-energy diffractometer together with a microtomography camera will be run by the GKSS. A further station will allow space for the diffraction enhanced imaging setup. The optics will provide for a small white beam (0.5 mm × 0.5 mm) and a large monochromatic X-ray beam (50 mm × 10 mm) with an energy range of 20 to 250 keV.

- by Klaus-Dieter Liss
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- Materials Science, High Pressure, Synchrotron Radiation, X Rays

Two high performance flow atomic absorption (HPF-AAS) related techniques were chosen to assess their suitability for the determination of several trace elements in complex environmental and biological samples. The technique selected were the Hydraulic High Pressure Nebulization Atomic Absorption Spectrometry (HHPN-AAS), and the Hydraulic High Pressure Nebulization Flame Furnace Atomic Absorption Spectrometry (HHPN-FF-AAS), which were applied directly, or after using off line liquid-liquid separation-preconcentration-back extraction procedures. Analytical methodologies were developed for Be, Sr, Ba, V, Cr, Mn, Fe, Co, Ni, Cu, Mo, Cd, Ag, Al, Tl, Pb, and Bi, for a variety of samples such as river and seawater, river and marine sediments, soft tissue of mussels, tunicate siphons, aquatic plants, and human samples of clinical interest such as placentas, umbilical cords, and cardiovascular tissues from surgical procedures. The analytical efficiency of the techniques was also proved in a proposed trace metal fractionation approach for river and seawater samples. All samples collected in this work were obtained from the North of Chile, where the most important economic activity is the mining industry.

- by Domingo A Roman
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- Analytical Chemistry, High Pressure, Trace Metals, Aquatic Plants

Large amounts of fly ash (FA) and limestone powder (LP) wastes are accumulating in countries all over the world. Most of these wastes are abandoned and cause certain serious environmental problems and health hazards. In this study, LP waste and class-C FA were used to produce a composite material without the addition of portland cement. LP was mixed with the FA at levels of 10, 20 and 30% by volume in the samples. LP and FA were mixed, wetted and compressed under high pressure in a steel mould. The compressive and flexural strengths were measured, and ultrasonic pulse velocity tests were performed on samples at ages of 7, 28 and 90 days. Density, water absorption and thermal conductivity values were also determined for the samples aged for 28 days. Preliminary results obtained from the tests indicate that masonry composites can be produced using LP, FA and water.

- by Paki Turgut
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- Mechanical Engineering, Chemical Engineering, Materials Science, Manufacturing

A new gasdynamic launcher is described, in which intact projectiles weighing at least 1 gram can be accelerated to mass velocities of 15-20 km/s. The system employs a conventional 2-stage light gas gun, with the barrel modified and filled with helium to act as a pump tube for a third stage. The key feature of the launcher is that the peak pressure in the third stage can be maintained below 2.5 GPa, thus assuring high efficiency and the integrity of the projectile.

- by Lewis Glenn
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- High Pressure, Optimization, Projectiles, Mathematical Models

The present paper deals with an experimental convective heat transfer investigation around a film-cooled, high-pressure gas turbine rotor blade mounted in a stationary, linear cascade arrangement. The measurements were performed in the von Karman Institute Isentropic Light Piston Compression Tube facility. The test blade was made of Macor glass ceramic and was instrumented with thin film gages. The coolant flow was ejected simultaneously through the leading edge (three rows of holes), the suction side (two rows of holes), and the pressure side (one row of holes). The effects of overall mass weight ratio, coolant to free-stream temperature ratio, and free-stream turbulence were successively investigated.

- by Cengiz Camci
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- Mechanical Engineering, Aerospace Engineering, Convection, Turbulence

The notion of dominant designs deals with dominance in the market and the dominant design is thought to be dominant because of market selection forces. The notion thus ignores the possible selection that takes place in pre-market R&D stages of technological trajectories. In this paper we ask the question whether pre-market selection takes place and if this can lead to

- by Harro van Lente
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- High Pressure, Hydrogen Storage, Fuel Cell, Selection Criteria

We have analyzed the model organism Caenorhabditis elegans with the help of phase-contrast x-ray tomography. This work combines techniques from x-ray imaging studies of single biological cells by in-line holography with three-dimensional reconstruction and furthermore extends these studies to the multicellular level. To preserve the sub-cellular ultrastructure of the nematodes, we used the near-native sample preparation of high-pressure freezing as commonly used in the field of electron microscopy. For the presented samples, a standard, non-magnifying parallel-beam setting, as well as a magnifying, divergent-beam setting using nanofocusing optics is evaluated based on their tomographic reconstruction potential. In this paper, we address difficulties in sample preparation and issues of image processing. By experimental refinement and through optimized reconstruction procedures, we were able to perform x-ray imaging studies on a living specimen.

A typical process of pressure swing adsorption (PSA) for H2 purification consists of a sequence of stages involving high pressure adsorption and low pressure desorption at a determined temperature. If it is desired to optimize a process already installed, the pressure cannot be easily modified.In this work the viability of modifying other operative variables was studied. For it, in the

- by Marcelo tagliabue
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- Engineering, Cryogenics, High Pressure, Adsorption

Molecular dynamics simulations of fused silica at shock pressures reproduce the experimental equation of state of this material and explain its characteristic shape. We demonstrate that shock waves modify the medium-range order of this amorphous system, producing changes that are only clearly revealed by its ring size distribution. The ring size distribution remains practically unchanged during elastic compression but varies continuously after the transition to the plastic regime.

- by Lilian P Davila and +2
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- High Pressure, Physical sciences, Fused Silica Etching, Size Distribution

Determination of the lattice dynamics of Sn at high pressure has represented a major experimental challenge and eluded previous attempts. Here we report the first successful measurement of the phonon density of states of Sn at high pressure to 64 GPa using nuclear resonant inelastic x-ray scattering. We also present density functional theory calculations that are in excellent agreement with the measured data. The results of this combined experimental and theoretical study establish reliable phonon density of states of Sn at high pressure. It makes possible an accurate description of its thermodynamic properties that are of great importance and interest in high pressure research.

- by Sven Rudin
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- High Pressure, Physical sciences, Normal Modes, Lattice Dynamics

Evolution of sea fog has been investigated using three-dimensional Mesoscale Model 5 (MM5) simulations. The study focused on widespread fog-cloud layers advected along the California coastal waters during 14-16 April 1999. According to analysis of the simulated trajectories, the intensity of air mass modification during this advection significantly depended on whether there were clouds along the trajectories and whether the modification took place over the land or ocean. The air mass, with its trajectory endpoint in the area where the fog was observed and simulated, gradually cooled despite the gradual increase in sea-surface temperature along the trajectory. Modelling results identified cloud-top cooling as a major determinant of marine-layer cooling and turbulence generation along the trajectories. Scale analysis showed that the radiative cooling term in the thermodynamic equation overpowered surface sensible and latent heat fluxes, and entrainment terms in cases of the transformation of marine clouds along the trajectories. Transformation of air masses along the trajectories without clouds and associated cloud-top cooling led to fog-free conditions at the endpoints of the trajectories over the ocean. The final impact on cloud-fog transition was determined by the interaction of synoptic and boundary-layer processes. Dissipation of sea fog was a consequence of a complex interplay between advection, synoptic evolution, and development of local circulations. Movement of the high-pressure system over land induced weakening of the along-shore advection and synoptic-pressure gradients, and allowed development of offshore flows that facilitated fog dissipation.

- by Clive Dorman
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- Thermodynamics, Boundary Layer Meteorology, High Pressure, Sea surface temperature