Reversed aqueductal cerebrospinal fluid net flow in idiopathic normal pressure hydrocephalus.

PubMed

Yin, L K; Zheng, J J; Zhao, L; Hao, X Z; Zhang, X X; Tian, J Q; Zheng, K; Yang, Y M

2017-11-01

The changes of CSF flow dynamics in idiopathic normal pressure hydrocephalus (iNPH) are not fully elucidated. Most previous studies took the whole cardiac cycle as a unit. In this work, it is divided into systole and diastole phase and compared between iNPH patients and normal elderly and paid special attention to the change of netflow direction. Twenty iNPH patients according to international guideline and twenty healthy volunteers were included in this study and examined by MRI. Three categories of CSF flow parameters were measured: peak velocity (V peak ), stroke volume (SV), and minute flow volume (MinV) covering the whole cycle; peak velocity (V peak-s , V peak-d ) and flow volume (Vol s , Vol d ) of the systole and diastole, respectively; net flow. Evans index (EI) was also measured and compared statistically between the two groups. EI, V peak , SV, MinV, Vol s , Vol d , and V peak-d significantly increased in iNPH group (P<0.05). V peak-s of the two groups were not significantly different (P>0.05). The net flow of 16 iNPH patients (16/20) was in the caudo-cranial direction, while 15 volunteers (15/20) were in the opposite direction, which showed statistically significant differences (P=.001). INPH patients present hyperdynamic flow with increased velocity and volume both in systole and diastole phase. Degree of rising in diastole phase exceeds that of systole phase. The resulting reversal of netflow direction may play a key role in the occurrence of ventriculomegaly in iNPH patients. © 2017 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

Analysis of iodinated haloacetic acids in drinking water by reversed-phase liquid chromatography/electrospray ionization/tandem mass spectrometry with large volume direct aqueous injection.

PubMed

Li, Yongtao; Whitaker, Joshua S; McCarty, Christina L

2012-07-06

A large volume direct aqueous injection method was developed for the analysis of iodinated haloacetic acids in drinking water by using reversed-phase liquid chromatography/electrospray ionization/tandem mass spectrometry in the negative ion mode. Both the external and internal standard calibration methods were studied for the analysis of monoiodoacetic acid, chloroiodoacetic acid, bromoiodoacetic acid, and diiodoacetic acid in drinking water. The use of a divert valve technique for the mobile phase solvent delay, along with isotopically labeled analogs used as internal standards, effectively reduced and compensated for the ionization suppression typically caused by coexisting common inorganic anions. Under the optimized method conditions, the mean absolute and relative recoveries resulting from the replicate fortified deionized water and chlorinated drinking water analyses were 83-107% with a relative standard deviation of 0.7-11.7% and 84-111% with a relative standard deviation of 0.8-12.1%, respectively. The method detection limits resulting from the external and internal standard calibrations, based on seven fortified deionized water replicates, were 0.7-2.3 ng/L and 0.5-1.9 ng/L, respectively. Copyright © 2012 Elsevier B.V. All rights reserved.

Rapid method for measuring rotenone in water at piscicidal concentrations

USGS Publications Warehouse

Dawson, V.K.; Harman, P.D.; Schultz, D.P.; Allen, J.L.

1983-01-01

A high-performance liquid chromatography (HPLC) procedure that is rapid, specific, and sensitive (limit of detection <0.005 mg/liter) was developed for monitoring application and degradation rates of rotenone. For analysis, a water sample is buffered to pH 5 and injected through a Sep Pak(R) C18 disposable cartridge. The cartridge adsorbs and retains the rotenone which then can be eluted quantitatively from the cartridge with a small volume of methanol. This step effectively concentrates the sample and provides sample cleanup. The methanol extract is analyzed directly by HPLC on an MCH 10 reverse-phase column; methanol: water (75:25, volume : volume) is the mobile phase and flow rate is 1.5 ml/minute. The rotenone is detected by ultraviolet spectrophotometry at a wavelength of 295 nm.

Photoswitchable gas permeation membranes based on azobenzene-doped liquid crystals II. Permeation-switching characterization under variable volume and variable pressure conditions

NASA Astrophysics Data System (ADS)

Glowacki, E.; Hunt, K.; Abud, D.; Marshall, K. L.

2010-08-01

Stimuli-responsive gas permeation membranes hold substantial potential for industrial processes as well as in analytical and screening applications. Such "smart" membrane systems, although prevalent in liquid mass-transfer manipulations, have yet to be realized for gas applications. We report our progress in developing gas permeation membranes in which liquid crystalline (LC) phases afford the active region of permeation. To achieve rapid and reversible switching between LC and isotropic permeation states, we harnessed the photomechanical action of mesogenic azobenzene dyes that can produce isothermal nematic-isotropic transitions. Both polymeric and low-molecular-weight LC materials were tested. Three different dye-doped LC mixtures with mesogenic azo dyes were infused into commercially available track-etched porous membranes with regular cylindrical pores (0.4 to 10.0 μm). Photoinduced isothermal phase changes in the imbibed material produced large and fully reversible changes in the permeability of the membrane to nitrogen with 5 s of irradiation at 2 mW/cm2. Using two measurement tools constructed in-house, the permeability of the photoswitched membranes was determined by both variable-pressure and variable-volume methods. Both the LC and photogenerated isotropic states demonstrate a linear permeability/pressure (ideal sorption) relationship, with up to a 16-fold difference in their permeability coefficients. Liquid crystal compositions can be chosen such that the LC phase is more permeable than the isotropic-or vice versa. This approach is the first system offering reversible tunable gas permeation membranes.

Improving the axial resolution in time-reversed ultrasonically encoded (TRUE) optical focusing with dual ultrasonic waves

NASA Astrophysics Data System (ADS)

Yang, Qiang; Xu, Xiao; Lai, Puxiang; Sang, Xinzhu; Wang, Lihong V.

2014-03-01

Focusing light inside highly scattering media beyond the ballistic regime is a challenging task in biomedical optical imaging, manipulation, and therapy. This challenge can be overcome by time reversing ultrasonically encoded (TRUE) diffuse light to the ultrasonic focus inside a turbid medium. In TRUE optical focusing, a photorefractive crystal or polymer is used as the phase conjugate mirror for optical time reversal. Accordingly, a relatively long ultrasound burst, whose duration matches the response time of the photorefractive material, is used to encode the diffuse light. With this long ultrasound burst, the resolution of the TRUE focus along the acoustic axis is poor. In this work, we used two transducers, emitting two intersecting ultrasound beams at 3.4 MHz and 3.6 MHz respectively, to modulate the diffuse light within their intersection volume at the beat frequency. We show that light encoded at the beat frequency can be time-reversed and converge to the intersection volume. Experimentally, TRUE focusing with an acoustic axial resolution of ~1.1 mm was demonstrated inside turbid media, agreeing with the theoretical estimation.

Edoxaban effects on bleeding following punch biopsy and reversal by a 4-factor prothrombin complex concentrate.

PubMed

Zahir, Hamim; Brown, Karen S; Vandell, Alexander G; Desai, Madhuri; Maa, Jen-Fue; Dishy, Victor; Lomeli, Barbara; Feussner, Annette; Feng, Wenqin; He, Ling; Grosso, Michael A; Lanz, Hans J; Antman, Elliott M

2015-01-06

The oral factor Xa inhibitor edoxaban has demonstrated safety and efficacy in stroke prevention in patients with atrial fibrillation and in the treatment and secondary prevention of venous thromboembolism. This study investigated the reversal of edoxaban's effects on bleeding measures and biomarkers by using a 4-factor prothrombin complex concentrate (4F-PCC). This was a phase 1 study conducted at a single site. This was a double-blind, randomized, placebo-controlled, 2-way crossover study to determine the reversal effect of descending doses of 4F-PCC on bleeding duration and bleeding volume following edoxaban treatment. A total of 110 subjects (17 in part 1, 93 in part 2) were treated. Intravenous administration of 4F-PCC 50, 25, or 10 IU/kg following administration of edoxaban (60 mg) dose-dependently reversed edoxaban's effects on bleeding duration and endogenous thrombin potential, with complete reversal at 50 IU/kg. Effects on prothrombin time were partially reversed at 50 IU/kg. A similar trend was seen for bleeding volume. The 4F-PCC dose-dependently reversed the effects of edoxaban (60 mg), with complete reversal of bleeding duration and endogenous thrombin potential and partial reversal of prothrombin time following 50 IU/kg. Edoxaban alone and in combination with 4F-PCC was safe and well tolerated in these healthy subjects. A dose of 50 IU/kg 4F-PCC may be suitable for reversing edoxaban anticoagulation. http://www.clinicaltrials.gov. Unique identifier: NCT02047565. © 2014 American Heart Association, Inc.

Thermodynamics of a pure substance at the triple point

NASA Astrophysics Data System (ADS)

Velasco, S.; Fernández-Pineda, C.

2007-12-01

A thermodynamic study of a pure substance at the triple point is presented. In particular, we show that the mass fractions of the phases coexisting at the triple point obey lever rules in the specific entropy-specific volume diagram, and the relative changes in the mass fractions present in each phase along reversible isochoric and adiabatic processes of a pure substance at the triple point are governed by the relative sizes of the segments of the triple-point line in the pressure-specific volume diagram and in the temperature-specific entropy diagram. Applications to the ordinary triple point of water and to the triple point of Al2SiO5 polymorphs are presented.

Reverse-Selective Diffusion in Nanocomposite Membranes

NASA Astrophysics Data System (ADS)

Hill, Reghan J.

2006-06-01

The permeability of certain polymer membranes with impenetrable nanoinclusions increases with the particle volume fraction [T. C. Merkel , Science 296, 519 (2002)SCIEAS0036-807510.1126/science.1069580]. The discovery contradicts qualitative expectations based on Maxwell’s classical theory of conduction or diffusion in composites with homogeneous phases. This Letter presents a theory based on an hypothesis that polymer chains are repelled from the inclusions during membrane casting. The accompanying increase in free volume, and hence solute diffusivity, yields bulk transport properties that are in good agreement with experiments.

Cattaraugus Creek Harbor, New York General Design Memorandum. Phase II (Detailed Design). Volume I. Main Report-GDM II.

DTIC Science & Technology

1976-03-01

of the abetract entered In Block 20, If different from Report) I$. SUPPLEMENTARY NOTES .4 19. KEY WORDS (Continue on reverse aide If neceesary and...Identify by block number) Harbors Cattaraugus Creek Flood Control 20O T’rlq 4CT Caiweut -t reverse se 0 neceeeely mid Identify by block number) The... blocked by the sand bar and lake ice at the creek mouth. During discharges developed by the com- bination of rainfall and snow melt, ice jams raise the

Amorphous Zn₂GeO₄ Nanoparticles as Anodes with High Reversible Capacity and Long Cycling Life for Li-ion Batteries

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yi, Ran; Feng, Jinkui; Lv, Dongping

2013-07-30

Amorphous and crystalline Zn₂GeO₄ nanoparticles were prepared and characterized as anode materials for Li-ion batteries. A higher reversible specific capacity of 1250 mAh/g after 500 cycles and excellent rate capability were obtained for amorphous Zn₂GeO₄ nanoparticles, compared to that of crystalline Zn₂GeO₄ nanoparticles. Small particle size, amorphous phase and incorporation of zinc and oxygen contribute synergetically to the improved performance by effectively mitigating the huge volume variations during lithiation and delithiation process.

Simultaneous achiral-chiral analysis of pharmaceutical compounds using two-dimensional reversed phase liquid chromatography-supercritical fluid chromatography.

PubMed

Venkatramani, C J; Al-Sayah, Mohammad; Li, Guannan; Goel, Meenakshi; Girotti, James; Zang, Lisa; Wigman, Larry; Yehl, Peter; Chetwyn, Nik

2016-02-01

A new interface was designed to enable the coupling of reversed phase liquid chromatography (RPLC) and supercritical fluid chromatography (SFC). This online two-dimensional chromatographic system utilizing RPLC in the first dimension and SFC in the second was developed to achieve simultaneous achiral and chiral analysis of pharmaceutical compounds. The interface consists of an eight-port, dual-position switching valve with small volume C-18 trapping columns. The peaks of interest eluting from the first RPLC dimension column were effectively focused as sharp concentration pulses on small volume C-18 trapping column/s and then injected onto the second dimension SFC column. The first dimension RPLC separation provides the achiral purity result, and the second dimension SFC separation provides the chiral purity result (enantiomeric excess). The results are quantitative enabling simultaneous achiral, chiral analysis of compounds. The interface design and proof of concept demonstration are presented. Additionally, comparative studies to conventional SFC and case studies of the applications of 2D LC-SFC in pharmaceutical analysis is presented. Copyright © 2015 Elsevier B.V. All rights reserved.

Achieving Continuous Anion Transport Domains Using Block Copolymers Containing Phosphonium Cations

DOE PAGES

Zhang, Wenxu; Liu, Ye; Jackson, Aaron C.; ...

2016-06-22

Triblock and diblock copolymers based on isoprene (Ip) and chloromethylstyrene (CMS) were synthesized in this paper by sequential polymerization using reversible addition–fragmentation chain transfer radical polymerization (RAFT). The block copolymers were quaternized with tris(2,4,6-trimethoxyphenyl)phosphine (Ar 3P) to prepare soluble ionomers. The ionomers were cast from chloroform to form anion exchange membranes (AEMs) with highly ordered morphologies. At low volume fractions of ionic blocks, the ionomers formed lamellar morphologies, while at moderate volume fractions (≥30% for triblock and ≥22% for diblock copolymers) hexagonal phases with an ionic matrix were observed. Ion conductivities were higher through the hexagonal phase matrix than inmore » the lamellar phases. Finally, promising chloride conductivities (20 mS/cm) were achieved at elevated temperatures and humidified conditions.« less

Numerical simulation of high intensity focused ultrasound temperature distribution for transcranial brain therapy

NASA Astrophysics Data System (ADS)

Zhang, Qian; Wang, Yizhe; Zhou, Wenzheng; Zhang, Ji; Jian, Xiqi

2017-03-01

To provide a reference for the HIFU clinical therapeutic planning, the temperature distribution and lesion volume are analyzed by the numerical simulation. The adopted numerical simulation is based on a transcranial ultrasound therapy model, including an 8 annular-element curved phased array transducer. The acoustic pressure and temperature elevation are calculated by using the approximation of Westervelt Formula and the Pennes Heat Transfer Equation. In addition, the Time Reversal theory and eliminating hot spot technique are combined to optimize the temperature distribution. With different input powers and exposure times, the lesion volume is evaluated based on temperature threshold theory. The lesion region could be restored at the expected location by the time reversal theory. Although the lesion volume reduces after eliminating the peak temperature in the skull and more input power and exposure time is required, the injury of normal tissue around skull could be reduced during the HIFU therapy. The prediction of thermal deposition in the skull and the lesion region could provide a reference for clinical therapeutic dose.

Electric control of magnetization reorientation in FeRh /BaTiO3 mediated by a magnetic phase transition

NASA Astrophysics Data System (ADS)

Odkhuu, Dorj

2017-10-01

Employing first-principles calculations we predict magnetization reorientation in FeRh films epitaxially grown on BaTiO3 by reversing the electric polarization or applying the strain effect, which is associated with the recently discovered voltage-induced interfacial magnetic-phase transition by R. O. Cherifi et al. [Nat. Mater. 13, 345 (2014), 10.1038/nmat3870]. We propose that this transition from antiferromagnetic to ferromagnetic phase is the results of the mutual mechanisms of the polarization-reversal-induced volume/strain expansion in the interfacial FeRh layers and the competition between direct and indirect exchange interactions. These mechanisms are mainly driven by the ferroelectrically driven hybridization between Fe and Ti 3 d orbital states at the interface. Such a strong hybridization can further involve Rh 4 d states with large spin-orbit coupling, which, rather than the Fe 3 d orbitals, is responsible for magnetization reorientation at the magnetic-phase transition. These findings point toward the feasibility of electric field control of magnetization switching associated with the magnetic-phase transition in an antiferromagnet structure.

Distribution or adsorption: the major dilemma in reversed-phase HPLC

NASA Astrophysics Data System (ADS)

Deineka, V. I.

2008-06-01

A method is suggested for analyzing the dependences obtained for different compositions of mobile eluent system phases, their slopes and intercepts, log k( i, B) = a + b log k ( i, A), where a is the intercept for the A and B stationary phases and b is the proportionality factor. An analysis requires parallel investigation of sorbate retention on at least three stationary phases with different lengths of grafted hydrocarbon radicals. The dependence of correlation parameters on the sorbate retention mechanism is discussed. It is shown that the hypothetical dependences coincide with the experimental dependences for surface sorption of resveratrol and volume distribution of triglycerides.

Two cases of malignant hypertension with reversible diffuse leukoencephalopathy exhibiting a reversible nocturnal blood pressure "riser" pattern.

PubMed

Eguchi, Kazuo; Kasahara, Kentaro; Nagashima, Akinori; Mor, Tadashi; Nii, Takanobu; Ibaraki, Kazuo; Kario, Kazuomi; Shimada, Kazuyuki

2002-05-01

We report two cases of malignant hypertension with reversible diffuse leukoencephalopathy demonstrating a nocturnal blood pressure (BP) rising pattern ("riser" pattern). Case 1 was a 54-year-old man diagnosed with malignant hypertension who presented with diffuse leukoencephalopathy and nocturnal BP rise during the acute phase. These abnormal findings diminished after treatment of hypertension. Case 2 was a 50-year-old woman diagnosed with malignant hypertension in association with leukoencephalopathy, heart failure and acute renal failure. She also presented with a "riser" pattern during the acute phase. In contrast to case 1, the leukoencephalopathy and "riser" pattern in case 2 were not improved even after 1 month of treatment. Following intensive antihypertensive treatment, renal failure was improved in case 1, but renal failure was not improved after 1 month in case 2. In conclusion, a possible explanation of this phenomenon is that a causative volume overload due to renal dysfunction produced the temporal leukoencephalopathy-like brain edema and "riser" pattern in these cases.

Investigating the evolution of the phase behavior of AOT-based w/o microemulsions in dodecane as a function of droplet volume fraction.

PubMed

Ganguly, R; Choudhury, N

2012-04-15

AOT-based water in oil (w/o) microemulsions are one of the most extensively studied reverse micellar systems because of their rich phase behavior and their ability to form in the absence of any co-surfactant. The aggregation characteristics and interaction of the microemulsion droplets in these systems are known to be governed by AOT-oil compatibility and water to AOT molar ratio (w). In this manuscript by using Dynamic Light Scattering (DLS) and viscometry techniques, we show that droplet volume fraction too plays an important role in shaping the phase behavior of these microemulsions in dodecane. The phase separation characteristics and the evolution of the viscosity and the hydrodynamic radius of the microemulsion droplets on approaching the cloud points have thus been found to undergo complete transformation as one goes from low to high droplet volume fraction even at a fixed 'w'. Modeling of the DLS data attributes this to the weakening of inter droplet attractive interaction caused by the growing dominance of the excluded volume effect with increase in droplet volume fraction. In the literature, the inter droplet attractive interaction driven phase separation in these microemulsions is explained based on gas-liquid type phase transition, conceptualized in the framework of Baxter adhesive hard sphere theory. The modeling of our viscosity data, however, does not support such proposition as the characteristic stickiness parameter (τ(-1)) of the microemulsion droplets in this system remains much lower than the critical value (τ(c)(-1)≈10.25) required to enforce such phase transition. Copyright © 2012 Elsevier Inc. All rights reserved.

Kinetic Models for Adiabatic Reversible Expansion of a Monatomic Ideal Gas.

ERIC Educational Resources Information Center

Chang, On-Kok

1983-01-01

A fixed amount of an ideal gas is confined in an adiabatic cylinder and piston device. The relation between temperature and volume in initial/final phases can be derived from the first law of thermodynamics. However, the relation can also be derived based on kinetic models. Several of these models are discussed. (JN)

Mixed-mode isolation of triazine metabolites from soil and aquifer sediments using automated solid-phase extraction

USGS Publications Warehouse

Mills, M.S.; Thurman, E.M.

1992-01-01

Reversed-phase isolation and ion-exchange purification were combined in the automated solid-phase extraction of two polar s-triazine metabolites, 2-amino-4-chloro-6-(isopropylamino)-s-triazine (deethylatrazine) and 2-amino-4-chloro-6-(ethylamino)-s-triazine (deisopropylatrazine) from clay-loam and slit-loam soils and sandy aquifer sediments. First, methanol/ water (4/1, v/v) soil extracts were transferred to an automated workstation following evaporation of the methanol phase for the rapid reversed-phase isolation of the metabolites on an octadecylresin (C18). The retention of the triazine metabolites on C18 decreased substantially when trace methanol concentrations (1%) remained. Furthermore, the retention on C18 increased with decreasing aqueous solubility and increasing alkyl-chain length of the metabolites and parent herbicides, indicating a reversed-phase interaction. The analytes were eluted with ethyl acetate, which left much of the soil organic-matter impurities on the resin. Second, the small-volume organic eluate was purified on an anion-exchange resin (0.5 mL/min) to extract the remaining soil pigments that could foul the ion source of the GC/MS system. Recoveries of the analytes were 75%, using deuterated atrazine as a surrogate, and were comparable to recoveries by soxhlet extraction. The detection limit was 0.1 ??g/kg with a coefficient of variation of 15%. The ease and efficiency of this automated method makes it viable, practical technique for studying triazine metabolites in the environment.

Alternative energy sources IV; Proceedings of the Fourth Miami International Conference, Miami Beach, FL, December 14-16, 1981. Volume 1 - Solar Collectors Storage

NASA Astrophysics Data System (ADS)

Veziroglu, T. N.

1982-10-01

Aspects of solar measurements, solar collectors, selective coatings, thermal storage, phase change storage, and heat exchangers are discussed. The analysis and testing of flat-plate solar collectors are addressed. The development and uses of plastic collectors, a solar water heating system, solar energy collecting oil barrels, a glass collector panel, and a two-phase thermosyphon system are considered. Studies of stratification in thermal storage, of packed bed and fluidized bed systems, and of thermal storage in solar towers, in wall passive systems, and in reversible chemical reactions are reported. Phase change storage by direct contact processes and in residential solar space heating and cooling is examined, as are new materials and surface characteristics for solar heat storage. The use of R-11 and Freon-113 in heat exchange is discussed. No individual items are abstracted in this volume

Investigation of Micro- and Nanosized Particle Erosion in a 90° Pipe Bend Using a Two-Phase Discrete Phase Model

PubMed Central

Safaei, M. R.; Mahian, O.; Garoosi, F.; Hooman, K.; Karimipour, A.; Kazi, S. N.; Gharehkhani, S.

2014-01-01

This paper addresses erosion prediction in 3-D, 90° elbow for two-phase (solid and liquid) turbulent flow with low volume fraction of copper. For a range of particle sizes from 10 nm to 100 microns and particle volume fractions from 0.00 to 0.04, the simulations were performed for the velocity range of 5–20 m/s. The 3-D governing differential equations were discretized using finite volume method. The influences of size and concentration of micro- and nanoparticles, shear forces, and turbulence on erosion behavior of fluid flow were studied. The model predictions are compared with the earlier studies and a good agreement is found. The results indicate that the erosion rate is directly dependent on particles' size and volume fraction as well as flow velocity. It has been observed that the maximum pressure has direct relationship with the particle volume fraction and velocity but has a reverse relationship with the particle diameter. It also has been noted that there is a threshold velocity as well as a threshold particle size, beyond which significant erosion effects kick in. The average friction factor is independent of the particle size and volume fraction at a given fluid velocity but increases with the increase of inlet velocities. PMID:25379542

A NAD(P) reductase like protein is the salicylic acid receptor in the appendix of the Sauromatum guttatum inflorescence

PubMed Central

Skubatz, Hanna; Orellana, Mónica V; Howald, William N

2013-01-01

The mode of action of the thermogenic inducers (salicylic acid, aspirin, and 2,6-dihydroxybenzoic acid) in the appendix of the Sauromatum guttatum inflorescence is poorly understood. Using ESI-MS and light scattering analysis, we have demonstrated that NAD(P) reductase like protein (RL) is the salicylic acid receptor in the Sauromatum appendix. RL was self-assembled in water into a large unit with a hydrodynamic diameter of 800 nm. In the presence of 1 pM salicylic acid, RL exhibited discontinuous and reversible volume phase transitions. The volume phase changed from 800 to 300 nm diameter and vice versa. RL stayed at each volume phase for ~4–5 min with a fast relaxation time between the 2 phases. ESI-MS analysis of RL extracted from appendices treated with salicylic acid, aspirin, and 2,6-DHBA at a micromolar range demonstrated that these compounds are capable of inducing graded conformational changes that are concentration-dependent. A strong correlation between RL conformations and heat-production induced by salicylic acid was also observed. These preliminary findings reveal structural and conformational roles for RL by which plants regulate their temperature and synchronize their time keeping mechanisms. PMID:28516022

Exchange coupling interaction in L10-FePd/α-Fe nanocomposite magnets with large maximum energy products.

PubMed

Sakuma, Noritsugu; Ohshima, Tsubasa; Shoji, Tetsuya; Suzuki, Yoshihito; Sato, Ryota; Wachi, Ayako; Kato, Akira; Kawai, Yoichiro; Manabe, Akira; Teranishi, Toshiharu

2011-04-26

Nanocomposite magnets (NCMs) consisting of hard and soft magnetic phases are expected to be instrumental in overcoming the current theoretical limit of magnet performance. In this study, structural analyses were performed on L1(0)-FePd/α-Fe NCMs with various hard/soft volume fractions, which were formed by annealing Pd/γ-Fe(2)O(3) heterostructured nanoparticles and pure Pd nanoparticles. The sample with a hard/soft volume ratio of 82/18 formed by annealing at 773 K had the largest maximum energy product (BH(max) = 10.3 MGOe). In such a sample, the interface between the hard and soft phases was coherent and the phase sizes were optimized, both of which effectively induced exchange coupling. This exchange coupling was directly observed by visualizing the magnetic interaction between the hard and soft phases using a first-order reversal curve diagram, which is a valuable tool to improve the magnetic properties of NCMs.

Black hole chemistry: thermodynamics with Lambda

NASA Astrophysics Data System (ADS)

Kubizňák, David; Mann, Robert B.; Teo, Mae

2017-03-01

We review recent developments on the thermodynamics of black holes in extended phase space, where the cosmological constant is interpreted as thermodynamic pressure and treated as a thermodynamic variable in its own right. In this approach, the mass of the black hole is no longer regarded as internal energy, rather it is identified with the chemical enthalpy. This leads to an extended dictionary for black hole thermodynamic quantities; in particular a notion of thermodynamic volume emerges for a given black hole spacetime. This volume is conjectured to satisfy the reverse isoperimetric inequality—an inequality imposing a bound on the amount of entropy black hole can carry for a fixed thermodynamic volume. New thermodynamic phase transitions naturally emerge from these identifications. Namely, we show that black holes can be understood from the viewpoint of chemistry, in terms of concepts such as Van der Waals fluids, reentrant phase transitions, and triple points. We also review the recent attempts at extending the AdS/CFT dictionary in this setting, discuss the connections with horizon thermodynamics, applications to Lifshitz spacetimes, and outline possible future directions in this field.

The Investigation of Strain-Induced Martensite Reverse Transformation in AISI 304 Austenitic Stainless Steel

NASA Astrophysics Data System (ADS)

Cios, G.; Tokarski, T.; Żywczak, A.; Dziurka, R.; Stępień, M.; Gondek, Ł.; Marciszko, M.; Pawłowski, B.; Wieczerzak, K.; Bała, P.

2017-10-01

This paper presents a comprehensive study on the strain-induced martensitic transformation and reversion transformation of the strain-induced martensite in AISI 304 stainless steel using a number of complementary techniques such as dilatometry, calorimetry, magnetometry, and in-situ X-ray diffraction, coupled with high-resolution microstructural transmission Kikuchi diffraction analysis. Tensile deformation was applied at temperatures between room temperature and 213 K (-60 °C) in order to obtain a different volume fraction of strain-induced martensite (up to 70 pct). The volume fraction of the strain-induced martensite, measured by the magnetometric method, was correlated with the total elongation, hardness, and linear thermal expansion coefficient. The thermal expansion coefficient, as well as the hardness of the strain-induced martensitic phase was evaluated. The in-situ thermal treatment experiments showed unusual changes in the kinetics of the reverse transformation (α' → γ). The X-ray diffraction analysis revealed that the reverse transformation may be stress assisted—strains inherited from the martensitic transformation may increase its kinetics at the lower annealing temperature range. More importantly, the transmission Kikuchi diffraction measurements showed that the reverse transformation of the strain-induced martensite proceeds through a displacive, diffusionless mechanism, maintaining the Kurdjumov-Sachs crystallographic relationship between the martensite and the reverted austenite. This finding is in contradiction to the results reported by other researchers for a similar alloy composition.

In situ stress relaxation mechanism of a superelastic NiTi shape memory alloy under hydrogen charging

NASA Astrophysics Data System (ADS)

Elkhal Letaief, Wissem; Hassine, Tarek; Gamaoun, Fehmi

2017-02-01

On account of its good biocompatibility, superelastic Ni-Ti arc wire alloys have been successfully used in orthodontic clinics. Nevertheless, delayed fracture in the oral cavity caused by hydrogen diffusion can be observed. The in situ stress relaxation susceptibility of a Ni-Ti shape memory alloy towards hydrogen embrittlement has been examined with respect to the current densities and imposed deformations. Orthodontic wires have been relaxed at different martensite volume fractions using current densities of 5, 10 and 20 A/m2 at 20 °C. The in situ relaxation stress shows that, for an imposed strain at the middle of the austenite-martensite transformation, the specimen fractures at the martensite-austenite reverse transformation. However, for an imposed strain at the beginning of the austenite-martensite plateau, the stress decreases in a similar way to the full austenite structure. Moreover, the stress plateau has been recorded at the reverse transformation for a short period. For the fully martensite structure, embrittlement occurs at a higher stress value. This behaviour is attributed to the interaction between the in situ austenite phase expansion and the diffusion of hydrogen in the different volume fractions of the martensite phase, produced at an imposed strain.

Origins of the anomalous stress behavior in charged colloidal suspensions under shear.

PubMed

Kumar, Amit; Higdon, Jonathan J L

2010-11-01

Numerical simulations are conducted to determine microstructure and rheology of sheared suspensions of charged colloidal particles at a volume fraction of ϕ=0.33. Over broad ranges of repulsive force strength F0 and Péclet number Pe, dynamic simulations show coexistence of ordered and disordered stable states with the state dependent on the initial condition. In contrast to the common view, at low shear rates, the disordered phase exhibits a lower viscosity (μ(r)) than the ordered phase, while this behavior is reversed at higher shear rates. Analysis shows the stress reversal is associated with different shear induced microstructural distortions in the ordered and disordered systems. Viscosity vs shear rate data over a wide range of F0 and Pe collapses well upon rescaling with the long-time self-diffusivity. Shear thinning viscosity in the ordered phase scaled as μ(r)∼Pe(-0.81) at low shear rates. The microstructural dynamics revealed in these studies explains the anomalous behavior and hysteresis loops in stress data reported in the literature.

[Determination of canthaxanthin and astaxanthin in egg yolks by reversed phase high performance liquid chromatography with diode array detection].

PubMed

He, Kang-Hao; Zou, Xiao-Li; Liu, Xiang; Zeng, Hong-Yan

2012-01-01

A method using reversed phase high performance liquid chromatography (RP-HPLC) coupled with diode array detector (DAD) was developed for the simultaneous determination of canthaxanthin and astaxanthin in egg yolks. Samples were extracted with acetonitrile in ultrasonic bath for 20 minutes and then purified by freezing-lipid filtration and solid phase extraction (SPE). After being vaporized to dryness by nitrogen blowing and made up to volume with methanol, the extract solution was chromatographically separated in C18 column with a unitary mobile phase consisting of acetonitrile. The proposed method was validated in terms of linearity, precision, accuracy, and limit of detection (LOD). Regression analysis revealed a good linearity between peak area of each analyte and its concentration (r > or = 0.998). The intra- and inter-day relative standard deviations (RSDs) were less than 3.6% and 5.2%, respectively. LODs of canthaxanthin and astaxanthin were 0.035 and 0.027 microg/mL (S/N = 3). The average recoveries of canthaxanthin and astaxanthin were 91.5% and 88.7%. The proposed method is simple, fast and easy to apply.

Effect of particle size in preparative reversed-phase high-performance liquid chromatography on the isolation of epigallocatechin gallate from Korean green tea.

PubMed

Kim, Jung Il; Hong, Seung Bum; Row, Kyung Ho

2002-03-08

To isolate epigallocatechin gallate (EGCG) of catechin compounds from Korean green tea (Bosung, Chonnam), a C18 reversed-phase preparative column (250x22 mm) packed with packings of three different sizes (15, 40-63, and 150 microm) was used. The sample extracted with water was partitioned with chloroform and ethyl acetate to remove the impurities including caffeine. The mobile phases in this experiment were composed of 0.1% acetic acid in water, acetonitrile, methanol and ethyl acetate. The injection volume was fixed at 400 microl and the flow rate was increased as the particle size becomes larger. The isolation of EGCG with particle size was compared at a preparative scale and the feasibility of separation of EGCG at larger particle sizes was confirmed. The optimum mobile phase composition for separating EGCG was experimentally obtained at the particle sizes of 15 and 40-63 microm in the isocratic mode, but EGCG was not purely separated at the particle size of 150 microm.

Optimizing separate phase light hydrocarbon recovery from contaminated unconfined aquifers

NASA Astrophysics Data System (ADS)

Cooper, Grant S.; Peralta, Richard C.; Kaluarachchi, Jagath J.

A modeling approach is presented that optimizes separate phase recovery of light non-aqueous phase liquids (LNAPL) for a single dual-extraction well in a homogeneous, isotropic unconfined aquifer. A simulation/regression/optimization (S/R/O) model is developed to predict, analyze, and optimize the oil recovery process. The approach combines detailed simulation, nonlinear regression, and optimization. The S/R/O model utilizes nonlinear regression equations describing system response to time-varying water pumping and oil skimming. Regression equations are developed for residual oil volume and free oil volume. The S/R/O model determines optimized time-varying (stepwise) pumping rates which minimize residual oil volume and maximize free oil recovery while causing free oil volume to decrease a specified amount. This S/R/O modeling approach implicitly immobilizes the free product plume by reversing the water table gradient while achieving containment. Application to a simple representative problem illustrates the S/R/O model utility for problem analysis and remediation design. When compared with the best steady pumping strategies, the optimal stepwise pumping strategy improves free oil recovery by 11.5% and reduces the amount of residual oil left in the system due to pumping by 15%. The S/R/O model approach offers promise for enhancing the design of free phase LNAPL recovery systems and to help in making cost-effective operation and management decisions for hydrogeologists, engineers, and regulators.

Liquid chromatographic determination of florfenicol in the plasma of multiple species of fish

USGS Publications Warehouse

Vue, C.; Schmidt, L.J.; Stehly, G.R.; Gingerich, W.H.

2002-01-01

A simple method was developed for determining florfenicol concentration in a small volume (250 mul) of plasma from five phylogenetically diverse species of freshwater fish. Florfenicol was isolated from the plasma matrix through C-18 solid-phase extraction and quantified by reversed-phase high-performance liquid chromatography with UV detection. The accuracy (84-104%), precision (%RSDless than or equal to8), and sensitivity (quantitation limit <30 ng/ml) of the method indicate its usefulness for conducting pharmacokinetic studies on a variety of freshwater fish. Published by Elsevier Science B.V.

Partition behavior of surfactants, butanol, and salt during application of density-modified displacement of dense non-aqueous phase liquids.

PubMed

Damrongsiri, S; Tongcumpou, C; Sabatini, D A

2013-03-15

Density-modified displacement (DMD) is a recent approach for removal of trapped dense NAPL (DNAPL). In this study, butanol and surfactant are contacted with the DNAPL to both reduce the density as well as release the trapped DNAPL (perchloroethylene: PCE). The objective of the study was to determine the distribution of each component (e.g., butanol, surfactant, water, PCE) between the original aqueous and PCE phases during the application of DMD. The results indicated that the presence of the surfactant increased the amount of n-butanol required to make the NAPL phase reach its desired density. In addition, water and anionic surfactant were found to partition along with the BuOH into the PCE phase. The water also found partitioned to reverse micelles in the modified phase. Addition of salt was seen to increase partitioning of surfactant to BuOH containing PCE phase. Subsequently, a large amount of water was solubilized into reverse micelles which lead to significantly increase in volume of the PCE phase. This work thus demonstrates the role of each component and the implications for the operation design of an aquifer treatment using the DMD technique. Copyright © 2013 Elsevier B.V. All rights reserved.

The effects of chain length, embedded polar groups, pressure, and pore shape on structure and retention in reversed-phase liquid chromatography: molecular-level insights from Monte Carlo simulations.

PubMed

Rafferty, Jake L; Siepmann, J Ilja; Schure, Mark R

2009-03-20

Particle-based simulations using the configurational-bias and Gibbs ensemble Monte Carlo techniques are carried out to probe the effects of various chromatographic parameters on bonded-phase chain conformation, solvent penetration, and retention in reversed-phase liquid chromatography (RPLC). Specifically, we investigate the effects due to the length of the bonded-phase chains (C(18), C(8), and C(1)), the inclusion of embedded polar groups (amide and ether) near the base of the bonded-phase chains, the column pressure (1, 400, and 1000 atm), and the pore shape (planar slit pore versus cylindrical pore with a 60A diameter). These simulations utilize a bonded-phase coverage of 2.9 micromol/m(2)and a mobile phase containing methanol at a molfraction of 33% (about 50% by volume). The simulations show that chain length, embedded polar groups, and pore shape significantly alter structural and retentive properties of the model RPLC system, whereas the column pressure has a relatively small effect. The simulation results are extensively compared to retention measurements. A molecular view of the RPLC retention mechanism emerges that is more complex than can be inferred from thermodynamic measurements.

[Chiral separation of five beta-blockers using di-n-hexyl L-tartrate-boric acid complex as mobile phase additive by reversed-phase liquid chromatography].

PubMed

Yang, Juan; Wang, Lijuan; Guo, Qiaoling; Yang, Gengliang

2012-03-01

A reversed-phase high performance liquid chromatographic (HPLC) method using the di-n-hexyl L-tartrate-boric acid complex as a chiral mobile phase additive was developed for the enantioseparation of five beta-blockers including propranolol, esmolol, metoprolol, bisoprolol and sotalol. In order to obtain a better enantioseparation, the influences of concentrations of di-n-butyl L-tartrate and boric acid, the type, concentration and pH of the buffer, methanol content as well as the molecular structure of analytes were extensively investigated. The separation of the analytes was performed on a Venusil MP-C18 column (250 mm x 4.6 mm, 5 microm). The mobile phase was 15 mmol/L ammonium acetate-methanol containing 60 mmol/L boric acid, 70 mmol/L di-n-hexyl L-tartrate (pH 6.00). The volume ratios of 15 mmol/L ammonium acetate to methanol were 20: 80 for propranolol, esmolol, metoprolol, bisoprolol and 30: 70 for sotalol. The flow rate was 0.5 mL/min and the detection wavelength was set at 214 nm. Under the optimized conditions, baseline enantioseparation was obtained separately for the five pairs of analytes.

Rheology of fiber suspensions using MRI

NASA Astrophysics Data System (ADS)

Jenny, M.; Ferrari, M.; Gaudel, N.; Kiesgen de Richter, S.

2018-02-01

The suspensions of non-Brownian fibers are of interest for many applications. Although many studies concerning suspensions are available in the literature, most of them concern suspensions of spherical particles. In this paper, global and local rheology of fiber suspensions are explored near the jamming transition. A critical volume fraction is extracted from the experimental data. The value of this critical volume fraction is in agreement with the expected value of the concentration of rigid rods above which the isotropic phase becomes unstable. Moreover, non-reversible effects of the shearing are observed in flow curves because of the non-Brownian behavior of the studied fibers.

Formation of hollow silica nanospheres by reverse microemulsion

NASA Astrophysics Data System (ADS)

Lin, Cheng-Han; Chang, Jen-Hsuan; Yeh, Yi-Qi; Wu, Si-Han; Liu, Yi-Hsin; Mou, Chung-Yuan

2015-05-01

Uniform hollow silica nanospheres (HSNs) synthesized with reverse microemulsion have great application potential as nanoreactors because enzymes or nanocatalysts can be easily encapsulated de novo in synthesis. Water-in-oil (w/o) reverse microemulsions comprising the polymeric surfactant polyoxyethylene (5) isooctylphenyl ether (Igepal CA-520), ammonia and water in a continuous oil phase (alkanes) coalesce into size-tunable silica nanoparticles via diffusion aggregation after the introduction of silica precursors. Here, we elucidate in detail the growth mechanism for silica nanoparticles via nucleation of ammonium-catalyzed silica oligomers from tetraethylorthosilicate (TEOS) and nanoporous aminopropyltrimethoxy silane (APTS) in the reverse microemulsion system. The formation pathway was studied in situ with small-angle X-ray scattering (SAXS). We find a four-stage process showing a sigmoidal growth behavior in time with a crossover from the induction period, early nucleation stage, coalescence growth and a final slowing down of growth. Various characterizations (TEM, N2 isotherm, dynamic light scattering, zeta potential, NMR, elemental analysis) reveal the diameters, scattering length density (SLD), mesoporosity, surface potentials and chemical compositions of the HSNs. Oil phases of alkanes with different alkyl chains are systematically employed to tune the sizes of HSNs by varying oil molar volumes, co-solvent amounts or surfactant mixture ratios. Silica condensation is incomplete in the core region, with the silica source of TEOS and APTS leading to the hollow silica nanosphere after etching with warm water.Uniform hollow silica nanospheres (HSNs) synthesized with reverse microemulsion have great application potential as nanoreactors because enzymes or nanocatalysts can be easily encapsulated de novo in synthesis. Water-in-oil (w/o) reverse microemulsions comprising the polymeric surfactant polyoxyethylene (5) isooctylphenyl ether (Igepal CA-520), ammonia and water in a continuous oil phase (alkanes) coalesce into size-tunable silica nanoparticles via diffusion aggregation after the introduction of silica precursors. Here, we elucidate in detail the growth mechanism for silica nanoparticles via nucleation of ammonium-catalyzed silica oligomers from tetraethylorthosilicate (TEOS) and nanoporous aminopropyltrimethoxy silane (APTS) in the reverse microemulsion system. The formation pathway was studied in situ with small-angle X-ray scattering (SAXS). We find a four-stage process showing a sigmoidal growth behavior in time with a crossover from the induction period, early nucleation stage, coalescence growth and a final slowing down of growth. Various characterizations (TEM, N2 isotherm, dynamic light scattering, zeta potential, NMR, elemental analysis) reveal the diameters, scattering length density (SLD), mesoporosity, surface potentials and chemical compositions of the HSNs. Oil phases of alkanes with different alkyl chains are systematically employed to tune the sizes of HSNs by varying oil molar volumes, co-solvent amounts or surfactant mixture ratios. Silica condensation is incomplete in the core region, with the silica source of TEOS and APTS leading to the hollow silica nanosphere after etching with warm water. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr01395j

Theoretical test of Jarzynski's equality for reversible volume-switching processes of an ideal gas system.

PubMed

Sung, Jaeyoung

2007-07-01

We present an exact theoretical test of Jarzynski's equality (JE) for reversible volume-switching processes of an ideal gas system. The exact analysis shows that the prediction of JE for the free energy difference is the same as the work done on the gas system during the reversible process that is dependent on the shape of path of the reversible volume-switching process.

Testing of blood products in a polytrauma model: results of a multi-institutional randomized preclinical trial.

PubMed

Alam, Hasan B; Bice, Leticia M; Butt, Muhammad U; Cho, S David; Dubick, Michael A; Duggan, Michael; Englehart, Michael S; Holcomb, John B; Morris, Melanie S; Prince, M Dale; Schreiber, Martin A; Shults, Christian; Sondeen, Jill L; Tabbara, Malek; Tieu, Brandon H; Underwood, Samantha A

2009-10-01

Trauma-induced coagulopathy, acidosis, and hypothermia form a "lethal triad" that is difficult to treat and is associated with extremely high mortality. This study was performed at three academic centers to evaluate whether resuscitation with blood components could reverse the coagulopathy in a complex polytrauma model. Yorkshire swine (40 +/- 5 kg) were subjected to a three-phase protocol: (a) "Prehospital" phase = femur fracture, hemorrhage (60% blood volume), and 30 minutes shock + infusion of saline (3x shed blood) + induction of hypothermia (33 degrees C); (b) "Early hospital" phase = grade V liver injury; and (c) "Operative" phase= liver packing. After liver packing, the animals (n = 60) were randomized to the following groups: (1) Sham-instrumentation and anesthesia without hemorrhage/injuries, (2) fresh whole blood (FWB), (3) 6% hetastarch (Hextend), (4) fresh frozen plasma/packed RBCs in 1:1 ratio (1:1 FFP/PRBC), and (5) FFP alone. Treatment volumes were equal to the volume of shed blood. Hemodynamic and physiologic parameters and coagulation profile (thrombelastography, prothrombin time, activated partial thromboplastin time, international normalized ratio, and platelets) were monitored during the experiment and for 4 hours posttreatment. At the end of prehospital phase, animals had developed significant acidosis (lactate >5 mmol/L and base deficit >9 mmol/L) and coagulopathy. Posttreatment mortality rates were 85% and 0% for the Hextend and blood component treated groups, respectively (p < 0.05). Hemodynamic parameters and survival rates were similar in groups that were treated with blood products (FWB, FFP, and FFP:PRBC). Animals treated with FFP and Hextend had significant anemia compared with the groups that received red blood cells (FWB and FFP:PRBC). Treatment with FFP and FFP:PRBC corrected the coagulopathy as effectively as FWB, whereas Hextend treatment worsened coagulopathy. In this reproducible model, we have shown that trauma-associated coagulopathy is made worse by hetastarch, but it can be rapidly reversed with the administration of blood components. Impressively, infusion of FFP, even without any red blood cells, can correct the coagulopathy and result in excellent early survival.

The Putative Liquid-Liquid Transition is a Liquid-Solid Transition in Atomistic Models of Water

NASA Astrophysics Data System (ADS)

Chandler, David; Limmer, David

2013-03-01

Our detailed and controlled studies of free energy surfaces for models of water find no evidence for reversible polyamorphism, and a general theoretical analysis of the phase behavior of cold water in nano pores shows that measured behaviors of these systems reflect surface modulation and dynamics of ice, not a liquid-liquid critical point. A few workers reach different conclusions, reporting evidence of a liquid-liquid critical point in computer simulations of supercooled water. In some cases, it appears that these contrary results are based upon simulation algorithms that are inconsistent with principles of statistical mechanics, such as using barostats that do not reproduce the correct distribution of volume fluctuations. In other cases, the results appear to be associated with difficulty equilibrating the supercooled material and mistaking metastability for coarsening of the ordered ice phase. In this case, sufficient information is available for us to reproduce the contrary results and to establish that they are artifacts of finite time sampling. This finding leads us to the conclusion that two distinct, reversible liquid phases do not exist in models of supercooled water.

A nitromethane-based HPLC system alternative to acetonitrile for carotenoid analysis of fruit and vegetables.

PubMed

Sandmann, Gerhard

2010-01-01

Acetonitrile-based HPLC systems are the most commonly used for carotenoid analysis from different plant tissues. Because of the acetonitrile shortage, an HPLC system for the separation of carotenoids on C(18) reversed-phase columns was developed in which an acetonitrile-alcohol-based mobile phase was replaced by nitromethane. This solvent comes closest to acetonitrile with respect to its elutrophic property. Our criterion was to obtain similar separation and retention times for a range of differently structured carotenoids. This was achieved by further increase in the lipophilicity with ethylacetate. For all the carotenoids which we tested, we found co-elution only of β-cryptoxanthin and lycopene. By addition of 1% of water, separation of this pair of carotenoids was also achieved. The final recommended mobile phase consisted of nitromethane : 2-propanol : ethyl acetate : water (79 : 10 : 10 : 1, by volume). On Nucleosil C(18) columns and related ones like Hypersil C(18), we obtained separation of carotenes, hydroxyl, epoxy and keto derivatives, which resembles the excellent separation properties of acetonitrile-based mobile phases on C(18) reversed phase columns. We successfully applied the newly developed HPLC system to the separation of carotenoids from different vegetables and fruit. Copyright © 2010 John Wiley & Sons, Ltd.

Minimising reversion, using seawater and magnesium chloride, caused by the dissolution of tricalcium aluminate hexahydrate.

PubMed

Palmer, Sara J; Frost, Ray L; Smith, Matthew K

2011-01-15

The increase in pH and aluminium concentration after the neutralisation of bauxite refinery residues is commonly known as reversion. This investigation reports the extent of reversion in synthetic supernatant liquor and possible methods to reduce reversion. This work is based on bauxite refinery residues produced from alumina refineries, where reversion is a real life situation in neutralised refinery residues. Tricalcium aluminate hexahydrate, a common phase in bauxite refinery residues, has been found to cause reversion. It has been established that reductions in both pH and aluminium from the seawater neutralisation process are due to the formation of 'Bayer' hydrotalcite Mg(7)Al(2)(OH)(18)(CO(3)(2-),SO(4)(2-))·xH(2)O. This is the primary mechanism involved in the removal of aluminium from solution. Increasing the volume of seawater used for the neutralisation process minimises the extent of reversion for both synthetic supernatant liquor and red mud slurry. The addition of MgCl(2)·6H(2)O also showed a reduction in reversion and confirmed that the decrease in aluminium and hydroxyl ions is due to the formation of Bayer hydrotalcite and not simply a dilution effect. Copyright © 2010 Elsevier Inc. All rights reserved.

Hydrodynamic interaction of two deformable drops in confined shear flow.

PubMed

Chen, Yongping; Wang, Chengyao

2014-09-01

We investigate hydrodynamic interaction between two neutrally buoyant circular drops in a confined shear flow based on a computational fluid dynamics simulation using the volume-of-fluid method. The rheological behaviors of interactive drops and the flow regimes are explored with a focus on elucidation of underlying physical mechanisms. We find that two types of drop behaviors during interaction occur, including passing-over motion and reversing motion, which are governed by the competition between the drag of passing flow and the entrainment of reversing flow in matrix fluid. With the increasing confinement, the drop behavior transits from the passing-over motion to reversing motion, because the entrainment of the reversing-flow matrix fluid turns to play the dominant role. The drag of the ambient passing flow is increased by enlarging the initial lateral separation due to the departure of the drop from the reversing flow in matrix fluid, resulting in the emergence of passing-over motion. In particular, a corresponding phase diagram is plotted to quantitatively illustrate the dependence of drop morphologies during interaction on confinement and initial lateral separation.

Porous Polystyrene Monoliths and Microparticles Prepared from Core Cross-linked Star (CCS) Polymers-Stabilized Emulsions.

PubMed

Chen, Qijing; Shi, Ting; Han, Fei; Li, Zihan; Lin, Chao; Zhao, Peng

2017-08-17

A hydrophobic CCS polymer of poly(benzyl methacrylate) (PBzMA) was prepared in toluene by reversible addition-fragmentation chain transfer (RAFT)-mediated dispersion polymerization. The CCS polymer, with poly(benzyl methacrylate) as the arm and crosslinked N, N'-bis(acryloyl)cystamine (BAC) as the core, was confirmed by characterization with gel permeation chromatography (GPC) and nuclear magnetic resonance (NMR) spectroscopy. Three kinds of oils (toluene, anisole and styrene) were chosen to study the emulsification properties of PBzMA CCS polymer. The oils can be emulsified by CCS polymer to form water-in-oil (w/o) emulsions. Moreover, w/o high internal phase emulsions (HIPEs) can be obtained with the increase of toluene and styrene volume fractions from 75% to 80%. Porous polystyrene monolith and microparticles were prepared from the emulsion templates and characterized by the scanning electronic microscopy (SEM). With the internal phase volume fraction increased, open-pore porous monolith was obtained.

Confocal Raman Microscopy for in Situ Measurement of Octanol-Water Partitioning within the Pores of Individual C18-Functionalized Chromatographic Particles.

PubMed

Kitt, Jay P; Harris, Joel M

2015-05-19

Octanol-water partitioning is one of the most widely used predictors of hydrophobicity and lipophilicity. Traditional methods for measuring octanol-water partition coefficients (K(ow)), including shake-flasks and generator columns, require hours for equilibration and milliliter quantities of sample solution. These challenges have led to development of smaller-scale methods for measuring K(ow). Recent advances in microfluidics have produced faster and smaller-volume approaches to measuring K(ow). As flowing volumes are reduced, however, separation of water and octanol prior to measurement and detection in small volumes of octanol phase are especially challenging. In this work, we reduce the receiver volume of octanol-water partitioning measurements from current practice by six-orders-of-magnitude, to the femtoliter scale, by using a single octanol-filled reversed-phase, octadecylsilane-modified (C18-silica) chromatographic particle as a collector. The fluid-handling challenges of working in such small volumes are circumvented by eliminating postequilibration phase separation. Partitioning is measured in situ within the pore-confined octanol phase using confocal Raman microscopy, which is capable of detecting and quantifying a wide variety of molecular structures. Equilibration times are fast (less than a minute) because molecular diffusion is efficient over distance scales of micrometers. The demonstrated amount of analyte needed to carry out a measurement is very small, less than 50 fmol, which would be a useful attribute for drug screening applications or testing of small quantities of environmentally sensitive compounds. The method is tested for measurements of pH-dependent octanol-water partitioning of naphthoic acid, and the results are compared to both traditional shake-flask measurements and sorption onto C18-modified silica without octanol present within the pores.

Theory of nematic order with aggregate dehydration for reversibly assembling proteins in concentrated solutions: Application to sickle-cell hemoglobin polymers

NASA Astrophysics Data System (ADS)

Hentschke, Reinhard; Herzfeld, Judith

1991-06-01

The reversible association of globular protein molecules in concentrated solution leads to highly polydisperse fibers, e.g., actin filaments, microtubules, and sickle-cell hemoglobin fibers. At high concentrations, excluded-volume interactions between the fibers lead to spontaneous alignment analogous to that in simple lyotropic liquid crystals. However, the phase behavior of reversibly associating proteins is complicated by the threefold coupling between the growth, alignment, and hydration of the fibers. In protein systems aggregates contain substantial solvent, which may cause them to swell or shrink, depending on osmotic stress. Extending previous work, we present a model for the equilibrium phase behavior of the above-noted protein systems in terms of simple intra- and interaggregate interactions, combined with equilibration of fiber-incorporated solvent with the bulk solvent. Specifically, we compare our model results to recent osmotic pressure data for sickle-cell hemoglobin and find excellent agreement. This comparison shows that particle interactions sufficient to cause alignment are also sufficient to squeeze significant amounts of solvent out of protein fibers. In addition, the model is in accord with findings from independent sedimentation and birefringence studies on sickle-cell hemoglobin.

Metastable superheated ice in liquid-water inclusions under high negative pressure

USGS Publications Warehouse

Roedder, E.

1967-01-01

In some microscopic inclusions (consisting of aqueous liquid and vapor) in minerals, freezing eliminates the vapor phase because of greater volume occupied by the resulting ice. When vapor fails to nucleate again on partial melting, the resulting negative pressure (hydrostatic tension) inside the inclusions permits the existence of ice I crystals under reversible, metastable equilibrium, at temperatures as high as +6.5??C and negative pressures possibly exceeding 1000 bars.

Solid-state transformations in the β-form of chlorpropamide on cooling to 100 K.

PubMed

Drebushchak, Tatiana N; Drebushchak, Valeri A; Boldyreva, Elena V

2011-04-01

A single-crystal X-ray diffraction study of the effect of cooling down to 100 K on the β-form of chlorpropamide, 4-chloro-N-(propylaminocarbonyl)benzenesulfonamide, has revealed reversible phase transitions at ∼257 K and between 150 and 125 K: β (Pbcn, Z' = 1) ⇔ β(II) (P2/c, Z' = 2) ⇔ β(III) (P2/n, a' = 2a, Z' = 4); the sequence corresponds to cooling. Despite changes in the space group and number of symmetry-independent molecules, the volume per molecule changes continuously in the temperature range 100-300 K. The phase transition at ∼257 K is accompanied by non-merohedral twinning, which is preserved on further cooling and through the second phase transition, but the original single crystal does not crack. DSC (differential scanning calorimetry) and X-ray powder diffraction investigations confirm the phase transitions. Twinning disappears on heating as the reverse transformations take place. The second phase transition is related to a change in conformation of the alkyl tail from trans to gauche in 1/4 of the molecules, regularly distributed in the space. Possible reasons for the increase in Z' upon cooling are discussed in comparison to other reported examples of processes (crystallization, phase transitions) in which organic crystals with Z' > 1 have been formed. Implications for pharmaceutical applications are discussed. © 2011 International Union of Crystallography

Installation Restoration Program. Phase 2. Confirmation/Quantification. Stage 1. Air Force Plant 6, Cobb County, Georgia. Volume 3.

DTIC Science & Technology

1986-08-09

WATER ASSESSMENT PROGRAM AIR FOsEa PLANT 6, L0CKED-GEOCIA CONPANY MARIETTA, GMO IA PROJECT NO. 611059 WELL 4W-22 WELL 4W-23 WELL MW-24 WELL 4W-25 Dace...PROGRAMo PHASE II--CONFIRMATION/QUANTIFICATION 0STAGE I Final Report for AIR FORCE PLANT 6, COBB COUNTY, GA. U.S. AIR FORCE OCCUPATIONAL AND ENVIRONMENTAL...Con uet on reverse 4 necessary arc .entir’y ay )lcx "UrCer) I;;EL_0 GROUP I SUB-GROuP Air Force Plant , Hazardous materialsI oilS’ DeB Ground water, S

Performance of an underwater acoustic volume array using time-reversal focusing.

PubMed

Root, Joseph A; Rogers, Peter H

2002-11-01

Time reversal permits acoustic focusing and beam forming in inhomogeneous and/or high-scattering environments. A volumetric array geometry can suppress back lobes and can fit a large, powerful array of elements into small spaces, like the free-water spaces on submarines. This research investigates applying the time-reversal method to an underwater acoustic volume array. The experiments evaluate the focusing performance of a 27-element volume array when different scattering structures are present within the volume of the array. The array is arranged in a 3x3x3 cubic matrix configuration with 18.75-cm vertical and horizontal element spacing. The system utilizes second-derivative Gaussian pulses to focus on a point 30 cm from the array. Results include a comparison between time-reversal focusing and standard focusing, an evaluation of the volume array's ability to suppress back lobes, and an analysis of how different scattering environments affect focal region size. Potential underwater applications for a volume array using time reversal include acoustic imaging, naval mine hunting, sonar, and underwater communications.

Performance of an underwater acoustic volume array using time-reversal focusing

NASA Astrophysics Data System (ADS)

Root, Joseph A.; Rogers, Peter H.

2002-11-01

Time reversal permits acoustic focusing and beam forming in inhomogeneous and/or high-scattering environments. A volumetric array geometry can suppress back lobes and can fit a large, powerful array of elements into small spaces, like the free-water spaces on submarines. This research investigates applying the time-reversal method to an underwater acoustic volume array. The experiments evaluate the focusing performance of a 27-element volume array when different scattering structures are present within the volume of the array. The array is arranged in a 3 x3 x3 cubic matrix configuration with 18.75-cm vertical and horizontal element spacing. The system utilizes second-derivative Gaussian pulses to focus on a point 30 cm from the array. Results include a comparison between time-reversal focusing and standard focusing, an evaluation of the volume array's ability to suppress back lobes, and an analysis of how different scattering environments affect focal region size. Potential underwater applications for a volume array using time reversal include acoustic imaging, naval mine hunting, sonar, and underwater communications. copyright 2002 Acoustical Society of America.

Reverse microemulsion synthesis of layered gadolinium hydroxide nanoparticles

NASA Astrophysics Data System (ADS)

Xu, Yadong; Suthar, Jugal; Egbu, Raphael; Weston, Andrew J.; Fogg, Andrew M.; Williams, Gareth R.

2018-02-01

A reverse microemulsion approach has been explored for the synthesis of layered gadolinium hydroxide (LGdH) nanoparticles in this work. This method uses oleylamine as a multifunctional agent, acting as surfactant, oil phase and base. 1-butanol is additionally used as a co-surfactant. A systematic study of the key reaction parameters was undertaken, including the volume ratio of surfactant (oleylamine) to water, the reaction time, synthesis temperature, and the amount of co-surfactant (1-butanol) added. It proved possible to obtain pristine LGdH materials at temperatures of 120 °C or below with an oleylamine: water ratio of 1:4. Using larger amounts of surfactant or higher temperatures caused the formation of Gd(OH)3, either as the sole product or as a major impurity phase. The LGdH particles produced have sizes of ca. 200 nm, with this size being largely independent of temperature or reaction time. Adjusting the amount of 1-butanol co-surfactant added permits the size to be varied between 200 and 300 nm.

Clustering and Network Analysis of Reverse Phase Protein Array Data.

PubMed

Byron, Adam

2017-01-01

Molecular profiling of proteins and phosphoproteins using a reverse phase protein array (RPPA) platform, with a panel of target-specific antibodies, enables the parallel, quantitative proteomic analysis of many biological samples in a microarray format. Hence, RPPA analysis can generate a high volume of multidimensional data that must be effectively interrogated and interpreted. A range of computational techniques for data mining can be applied to detect and explore data structure and to form functional predictions from large datasets. Here, two approaches for the computational analysis of RPPA data are detailed: the identification of similar patterns of protein expression by hierarchical cluster analysis and the modeling of protein interactions and signaling relationships by network analysis. The protocols use freely available, cross-platform software, are easy to implement, and do not require any programming expertise. Serving as data-driven starting points for further in-depth analysis, validation, and biological experimentation, these and related bioinformatic approaches can accelerate the functional interpretation of RPPA data.

Microstructural fingerprints of phase transitions in shock-loaded iron

NASA Astrophysics Data System (ADS)

Wang, S. J.; Sui, M. L.; Chen, Y. T.; Lu, Q. H.; Ma, E.; Pei, X. Y.; Li, Q. Z.; Hu, H. B.

2013-01-01

The complex structural transformation in crystals under static pressure or shock loading has been a subject of long-standing interest to materials scientists and physicists. The polymorphic transformation is of particular importance for iron (Fe), due to its technological and sociological significance in the development of human civilization, as well as its prominent presence in the earth's core. The martensitic transformation α-->ɛ (bcc-->hcp) in iron under shock-loading, due to its reversible and transient nature, requires non-trivial detective work to uncover its occurrence. Here we reveal refined microstructural fingerprints, needle-like colonies and three sets of {112}<111> twins with a threefold symmetry, with tell-tale features that are indicative of two sequential martensitic transformations in the reversible α-->ɛ phase transition, even though no ɛ is retained in the post-shock samples. The signature orientation relationships are consistent with previously-proposed transformation mechanisms, and the unique microstructural fingerprints enable a quantitative assessment of the volume fraction transformed.

Retention properties of novel beta-CD bonded stationary phases in reversed-phase HPLC mode.

PubMed

Zhao, Yanyan; Guo, Zhimou; Zhang, Yongping; Xue, Xingya; Xu, Qing; Li, Xiuling; Liang, Xinmiao; Zhang, Yukui

2009-05-15

With the given special structures, the CD bonded stationary phases are expected to have complementary retention properties with conventional C18 stationary phase, which will be helpful to enhance the polar selectivity in RP mode separation. In this work, two beta-cyclodextrin (beta-CD) bonded stationary phases for reversed-phase HPLC, including 1, 12-dodecyldiol linked beta-CD stationary phase (CD1) and olio (ethylene glycol) (OEG) linked beta-CD stationary phase (CD2), have been synthesized via click chemistry. The resulting materials were characterized with FT-IR and elemental analysis, which proved the successful immobilization of ligands. The similarities and differences in retention characteristics between the CD and C18 stationary phases have been elucidated by using comparative linear solvation energy relationships (LSERs). The force related to solute McGowan volume has no significant difference, while the hydrogen bonding and dipolar interactions between solutes and CD stationary phases are stronger than between solutes and C18, which is attributed to the special structures (CD and triazole groups) of CD stationary phases. Chemical origins are interpreted by comparison between CD1 and CD2. Similar dispersive interactions of CD1 and CD2 are attributed to their similar length of spacer arms. CD2 which contains OEG spacer arm has relative weaker HBD acidity but stronger HBA basicity. CD stationary phases display no serious different methylene selectivity and higher polar selectivity than in the case of C18. Higher acid selectivity and lower basic selectivity are observed on CD2 than on CD1. Distinctive retention properties and good complementary separation selectivity to C18 make the novel CD bonded stationary phases available for more application in RPLC.

Ultrafast and Highly Reversible Sodium Storage in Zinc-Antimony Intermetallic Nanomaterials

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nie, Anmin; Gan, Li-yong; Cheng, Yingchun

2015-12-17

The progress on sodium-ion battery technology faces many grand challenges, one of which is the considerably lower rate of sodium insertion/deinsertion in electrode materials due to the larger size of sodium (Na) ions and complicated redox reactions compared to the lithium-ion systems. Here, it is demonstrated that sodium ions can be reversibly stored in Zn-Sb intermetallic nanowires at speeds that can exceed 295 nm s -1. Remarkably, these values are one to three orders of magnitude higher than the sodiation rate of other nanowires electrochemically tested with in situ transmission electron micro­scopy. It is found that the nanowires display aboutmore » 161% volume expansion after the first sodiation and then cycle with an 83% reversible volume expansion. Despite their massive expansion, the nanowires can be cycled without any cracking or facture during the ultrafast sodiation/desodiation process. Additionally, most of the phases involved in the sodiation/desodiation process possess high electrical conductivity. More specifically, the NaZnSb exhibits a layered structure, which provides channels for fast Na + diffusion. This observation indicates that Zn-Sb intermetallic nanomaterials offer great promise as high rate and good cycling stability anodic materials for the next generation of sodium-ion batteries.« less

Orientation Dependence of Functional Properties in Heterophase Single Crystals of the Ti36.5Ni51.0Hf12.5 and Ti48.5Ni51.5 Alloys

NASA Astrophysics Data System (ADS)

Panchenko, E. Yu.; Chumlyakov, Yu. I.; Surikov, N. Yu.; Tagiltsev, A. I.; Vetoshkina, N. G.; Osipovich, K. S.; Maier, H.; Sehitoglu, H.

2016-03-01

The features of orientation dependence of stress-induced thermoelastic B2-( R)- B19'-martensitic transformations in single crystals of the Ti48.5Ni51.5 and Ni51.0Ti36.5Hf12.5 (at.%) alloys, which contain disperse particles of the Ti3Ni4 and H-phase, respectively, are revealed along with those of their shape-memory effects (SME) and superelasticity (SE). It is experimentally demonstrated that irrespective of the crystal structure of disperse particles measuring more than 100 nm, for their volume fraction f > 16% there is a weaker orientation dependence of the reversible strain in the cases of manifestation of SME and SE. In the orientations of Class I, wherein martensitic detwinning introduces a considerable contribution into transformation strain, the values of SME |ɛ SME | and SE |ɛ SE | decrease by over a factor of two compared to the theoretical lattice strain value |ɛ tr0 | for a B2- B19'-transformation and the experimental values of reversible strain for quenched TiNi crystals. In the orientations of Class 2, wherein detwinning of the martensite is suppressed as is the case in quenched single-phase single crystals, the reversible strain is maintained close to its theoretical value |ɛ tr0 |. Micromechanical models of interaction between the martensite and the disperse particles are proposed, which account for the weaker orientation dependence of |ɛ SME | and |ɛ SE | due to suppression of detwinning of the B19'-martensite crystals by the particles and a transition from a single-variant evolution of the stress-induced martensitic transformations to a multiple-variant evolution of transformations in the cases of increased size of the particles and their larger volume fractions.

Oxygen Tuned Local Structure and Phase-Change Performance of Germanium Telluride.

PubMed

Zhou, Xilin; Du, Yonghua; Behera, Jitendra K; Wu, Liangcai; Song, Zhitang; Simpson, Robert E

2016-08-10

The effect of oxygen on the local structure of Ge atoms in GeTe-O materials has been investigated. Oxygen leads to a significant modification to the vibrational modes of Ge octahedra, which results from a decrease in its coordination. We find that a defective octahedral Ge network is the crucial fingerprint for rapid and reversible structural transitions in GeTe-based phase change materials. The appearance of oxide Raman modes confirms phase separation into GeO and TeO at high level O doping. Counterintuitively, despite the increase in crystallization temperature of oxygen doped GeTe-O phase change materials, when GeTe-O materials are used in electrical phase change memory cells, the electrical switching energy is lower than the pure GeTe material. This switching energy reduction is ascribed to the smaller change in volume, and therefore smaller enthalpy change, for the oxygen doped GeTe materials.

Ultralow-fatigue shape memory alloy films

NASA Astrophysics Data System (ADS)

Chluba, Christoph; Ge, Wenwei; Lima de Miranda, Rodrigo; Strobel, Julian; Kienle, Lorenz; Quandt, Eckhard; Wuttig, Manfred

2015-05-01

Functional shape memory alloys need to operate reversibly and repeatedly. Quantitative measures of reversibility include the relative volume change of the participating phases and compatibility matrices for twinning. But no similar argument is known for repeatability. This is especially crucial for many future applications, such as artificial heart valves or elastocaloric cooling, in which more than 10 million transformation cycles will be required. We report on the discovery of an ultralow-fatigue shape memory alloy film system based on TiNiCu that allows at least 10 million transformation cycles. We found that these films contain Ti2Cu precipitates embedded in the base alloy that serve as sentinels to ensure complete and reproducible transformation in the course of each memory cycle.

Static magnetism and thermal switching in randomly oriented L10 FePt thin films

NASA Astrophysics Data System (ADS)

Lisfi, A.; Pokharel, S.; Alqarni, A.; Akioya, O.; Morgan, W.; Wuttig, M.

2018-05-01

Static magnetism and thermally activated magnetic relaxation were investigated in granular FePt films (20 nm-200 nm thick) with random magnetic anisotropy through hysteresis loop, torque curve and magnetization time dependence measurements. While the magnetism of thicker film (200 nm thick) is dominated by a single switching of the ordered L10 phase, thinner film (20 nm) displays a double switching, which is indicative of the presence of the disordered cubic phase. The pronounced behavior of double switching in thinner film suggests that the film grain boundary is composed of soft cubic magnetic phase. The magnetic relaxation study reveals that magnetic viscosity S of the films is strongly dependent on the external applied field and exhibits a maximum value (12 kAm) around the switching field and a vanishing behavior at low (1 kOe) and large (12 kOe) fields. The activation volume of the thermal switching was found to be much smaller than the physical volume of the granular structure due to the incoherent rotation mode of the magnetization reversal mechanism, which is established to be domain wall nucleation.

Reversed-phase single drop microextraction followed by high-performance liquid chromatography with fluorescence detection for the quantification of synthetic phenolic antioxidants in edible oil samples.

PubMed

Farajmand, Bahman; Esteki, Mahnaz; Koohpour, Elham; Salmani, Vahid

2017-04-01

The reversed-phase mode of single drop microextraction has been used as a preparation method for the extraction of some phenolic antioxidants from edible oil samples. Butylated hydroxyl anisole, tert-butylhydroquinone and butylated hydroxytoluene were employed as target compounds for this study. High-performance liquid chromatography followed by fluorescence detection was applied for final determination of target compounds. The most interesting feature of this study is the application of a disposable insulin syringe with some modification for microextraction procedure that efficiently improved the volume and stability of the solvent microdrop. Different parameters such as the type and volume of solvent, sample stirring rate, extraction temperature, and time were investigated and optimized. Analytical performances of the method were evaluated under optimized conditions. Under the optimal conditions, relative standard deviations were between 4.4 and 10.2%. Linear dynamic ranges were 20-10 000 to 2-1000 μg/g (depending on the analytes). Detection limits were 5-670 ng/g. Finally, the proposed method was successfully used for quantification of the antioxidants in some edible oil samples prepared from market. Relative recoveries were achieved from 88 to 111%. The proposed method had a simplicity of operation, low cost, and successful application for real samples. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

In situ study of LaY2Ni9 compound as Ni MH negative-electrode material

NASA Astrophysics Data System (ADS)

Latroche, M.; Isnard, O.

2008-03-01

The behavior of a Ni-MH (metal hydride) negative composite electrode made of LaY2Ni9 active material has been studied dynamically using in situ neutron diffraction during a complete charge-discharge electrochemical cycle. From the analysis of the collected diffraction patterns, the phase identity, phase amount variations and cell volume evolutions have been determined as a function of the electrochemical state of (dis)charge. The active material shows a typical two-phase behavior with equilibrium between a hydrogen-poor α phase and a hydrogen-rich β one. The lower electrochemical reversible capacity as compared to solid-gas properties has been interpreted in terms of hydrogen gas evolving during charge and kinetic limitation due to slow β to α transformation during discharge, which hinders high discharge rates.

Reverse Shape Memory Effect Related to α → γ Transformation in a Fe-Mn-Al-Ni Shape Memory Alloy

NASA Astrophysics Data System (ADS)

Peng, Huabei; Huang, Pan; Zhou, Tiannan; Wang, Shanling; Wen, Yuhua

2017-05-01

In this study, we investigated the shape memory behavior and phase transformations of solution-treated Fe43.61Mn34.74Al13.38Ni8.27 alloy between room temperature and 1173 K (900 °C). This alloy exhibits the reverse shape memory effect resulting from the phase transformation of α (bcc) → γ (fcc) between 673 K and 1073 K (400 °C and 800 °C) in addition to the shape memory effect resulting from the martensitic reverse transformation of γ' (fcc) → α (bcc) below 673 K (400 °C). There is a high density of hairpin-shaped dislocations in the α phase undergoing the martensitic reverse transformation of γ' → α. The lath γ phase, which preferentially nucleates and grows in the reversed α phase, has the same crystal orientation with the reverse-transformed γ' martensite. However, the vermiculate γ phase, which is precipitated in the α phase between lath γ phase, has different crystal orientations. The lath γ phase is beneficial to attaining better reverse shape memory effect than the vermiculate γ phase.

Fragility, network adaptation, rigidity- and stress- transitions in homogenized binary GexS100-x glasses

NASA Astrophysics Data System (ADS)

Chakraborty, Shibalik; Boolchand, Punit

2014-03-01

Binary GexS100-x glasses reveal elastic and chemical phase transitions driven by network topology. With increasing Ge content x, well defined rigidity (xc(1) =19.3%) and stress(xc(2) =24.85%) transitions and associated optical elasticity power-laws are observed in Raman scattering. Calorimetric measurements reveal a square-well like minimum with window walls that coincide with the two elastic phase transitions. Molar volumes show a trapezoidal-like minimum with edges that nearly coincide with the reversibility window. These results are signatures of the isostatically rigid nature of the elastic phase formed between the rigidity and stress transitions. Complex Cp measurements show melt fragility index, m(x) to also show a global minimum in the reversibility window, underscoring that melt dynamics encode the elastic behavior of the glass formed at Tg. The strong nature of melts formed in the IP has an important practical consequence; they lead to slow homogenization of non-stoichiometric batch compositions reacted at high temperatures. Homogenization of chalcogenides melts/glasses over a scale of a few microns is a pre-requisite to observe the intrinsic physical properties of these materials. Supported by NSF Grant DMR 0853957.

[Determination of acyclovir in mouse plasma and tissues by reversed-phase high performance liquid chromatography].

PubMed

Xu, Y; Zhou, S W; Tang, J L; Huang, L Q

2001-11-01

The aim of this study was to establish an high performance liquid chromatographic method for determining acyclovir (ACV) concentration in mouse plasma and tissues. A solution of 0.25 mL 60 g/L perchloric acid and 0.25 mL acetonitrile was added into 0.2 mL plasma or 0.2 g tissues to precipitate proteins. Following centrifugation, the supernatant obtained was injected into a reversed-phase column. Operating conditions were Hypersil ODS column(250 mm x 4.6 mm i.d., 5 microns), methanol-water-acetic acid(1:99:0.5, volume ratio) solution as mobile phase at a flow rate of 1.5 mL/min, UV detection at 252 nm. The detection limit of ACV concentration in plasma was 20 micrograms/L and that in tissues was 50 ng/g. The standard curves for ACV were linear in plasma and homogenate of tissues (r > 0.99). The precision of the method was good and the recoveries of ACV were higher than 97.5%. So this method is rapid, accurate and convenient for determination of ACV concentrations in plasma and tissues.

Stimulus-Responsive Nanoparticles and Associated (Reversible) Polymorphism via Polymerization Induced Self-assembly (PISA).

PubMed

Pei, Yiwen; Lowe, Andrew B; Roth, Peter J

2017-01-01

Polymerization-induced self-assembly (PISA) is an extremely versatile method for the in situ preparation of soft-matter nanoparticles of defined size and morphologies at high concentrations, suitable for large-scale production. Recently, certain PISA-prepared nanoparticles have been shown to exhibit reversible polymorphism ("shape-shifting"), typically between micellar, worm-like, and vesicular phases (order-order transitions), in response to external stimuli including temperature, pH, electrolytes, and chemical modification. This review summarises the literature to date and describes molecular requirements for the design of stimulus-responsive nano-objects. Reversible pH-responsive behavior is rationalised in terms of increased solvation of reversibly ionized groups. Temperature-triggered order-order transitions, conversely, do not rely on inherently thermo-responsive polymers, but are explained based on interfacial LCST or UCST behavior that affects the volume fractions of the core and stabilizer blocks. Irreversible morphology transitions, on the other hand, can result from chemical post-modification of reactive PISA-made particles. Emerging applications and future research directions of this "smart" nanoparticle behavior are reviewed. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

In situ stress measurements during electrochemical cycling of lithium-rich cathodes

NASA Astrophysics Data System (ADS)

Nation, Leah; Li, Juchuan; James, Christine; Qi, Yue; Dudney, Nancy; Sheldon, Brian W.

2017-10-01

Layered lithium transition metal oxides (Li1+xM1-xO2, M = Ni, Mn, Co) are attractive cathode materials for lithium-ion batteries due to their high reversible capacity. However, they suffer from structural changes that lead to substantial voltage fade. In this study, we use stress as a novel way to track irreversible changes in Li1.2Mn0.55Ni0.125Co0.125O2 (LR-NMC) cathodes. A unique and unpredicted stress signature is observed during the first delithiation. Initially, a tensile stress is observed, consistent with volume contraction from lithium removal, however, the stress reverses and becomes compressive with continued charging beyond 4 V vs Li/Li+, indicating volume expansion; this phenomenon is present in the first cycle only. This irreversible stress during delithiation is likely to be at least partially due to oxygen loss and the resulting cation rearrangement. Raman spectroscopy provides evidence of the layered-to-spinel phase transition after cycling in the LR-NMC films, as well as recovery of the original spectra upon re-annealing in an oxygen environment.

Santa Ana River Design Memorandum Number 1. Phase 2 GDM on the Santa Ana River Mainstem Including Santiago Creek. Volume 2. Prado Dam.

DTIC Science & Technology

1988-08-01

present and likely to be encountered during excavation. Nonetheless, the four groups do provide an adequate method for representing the different ...It different from Report) Approved for Public Release; Distribution Unlimited IS. SUPPLEMENTARY NOTES IS. KEY WORDS (Continue on reverse M e II...between the dam embankment and the spillway. The two 800-foot long conduits would be constructed by open excavation and backfill method . Downstream

In situ neutron diffraction study of deuterium gas absorption by AB5+y alloys used as negative electrode materials for Ni-MH batteries

NASA Astrophysics Data System (ADS)

Latroche, M.; Joubert, J.-M.; Guégan, A. Percheron; Isnard, O.

2004-07-01

LaNi5-type alloys store reversibly hydrogen and are used as negative electrode materials in Ni-MH batteries. Substitutions on La and Ni crystallographic sites have led to competitive materials with complex formulae Mm(Ni4.3-xMn0.4Al0.3Cox)1+y (Mm: mishmetal). Materials involving an unexpected metastable phase γ show the best cycle lives. This phase occurrence depends on the mishmetal composition, the cobalt rate and the over-stoichiometry. It is observed as a transitory phase only for charge in electrochemical process. To confirm the appearance of this phase during gas loading, in beam D2 gas absorption has been performed on two materials for which the γ phase is expected. Phase amounts and cell volumes have been measured by in situ neutron powder diffraction analysis under controlled gas pressure as a function of the state of charge.

Pressure induced phase transitions in ceramic compounds containing tetragonal zirconia

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sparks, R.G.; Pfeiffer, G.; Paesler, M.A.

Stabilized tetragonal zirconia compounds exhibit a transformation toughening process in which stress applied to the material induces a crystallographic phase transition. The phase transition is accompanied by a volume expansion in the stressed region thereby dissipating stress and increasing the fracture strength of the material. The hydrostatic component of the stress required to induce the phase transition can be investigated by the use of a high pressure technique in combination with Micro-Raman spectroscopy. The intensity of Raman lines characteristic for the crystallographic phases can be used to calculate the amount of material that has undergone the transition as a functionmore » of pressure. It was found that pressures on the order of 2-5 kBar were sufficient to produce an almost complete transition from the original tetragonal to the less dense monoclinic phase; while a further increase in pressure caused a gradual reversal of the transition back to the original tetragonal structure.« less

Phase transition and entropy inequality of noncommutative black holes in a new extended phase space

DOE Office of Scientific and Technical Information (OSTI.GOV)

Miao, Yan-Gang; Xu, Zhen-Ming, E-mail: miaoyg@nankai.edu.cn, E-mail: xuzhenm@mail.nankai.edu.cn

We analyze the thermodynamics of the noncommutative high-dimensional Schwarzschild-Tangherlini AdS black hole with the non-Gaussian smeared matter distribution by regarding a noncommutative parameter as an independent thermodynamic variable named as the noncommutative pressure . In the new extended phase space that includes this noncommutative pressure and its conjugate variable, we reveal that the noncommutative pressure and the original thermodynamic pressure related to the negative cosmological constant make the opposite effects in the phase transition of the noncommutative black hole, i.e. the former dominates the UV regime while the latter does the IR regime, respectively. In addition, by means of themore » reverse isoperimetric inequality, we indicate that only the black hole with the Gaussian smeared matter distribution holds the maximum entropy for a given thermodynamic volume among the noncommutative black holes with various matter distributions.« less

Analysis Study of Stevioside and Rebaudioside A from Stevia rebaudiana Bertoni by Normal Phase SPE and RP-HPLC

NASA Astrophysics Data System (ADS)

Martono, Y.; Rohman, A.; Riyanto, S.; Martono, S.

2018-04-01

Solid Phase Extraction (SPE) method using silica as sorbent for stevioside and rebaudiosida A analysis in Stevia rebaudiana Bertoni leaf have not been performed. The aim of this study is to develop SPE method using silica as sorbent for Reverse Phase-High Performance Liquid Chromatography (RP-HPLC) analysis of stevioside and rebaudiosida A in S. rebaudiana leaf. The results of this study indicate that the optimal conditions for normal phase SPE (silica) are conditioned with 3.0 mL of hexane. The sample loading volume is 0.1 mL. Cartridge is eluted with 1.0 mL acetonitrile: water (80: 20, v/v) to separate both analytes. The cartridge is washed with chloroform and water of 0.3 mL respectively. The developed SPE sample preparation method meets the accuracy and precision test and can be used for the analysis of stevioside and rebaudioside A by RP-HPLC.

Large-volume injection of sample diluents not miscible with the mobile phase as an alternative approach in sample preparation for bioanalysis: an application for fenspiride bioequivalence.

PubMed

Medvedovici, Andrei; Udrescu, Stefan; Albu, Florin; Tache, Florentin; David, Victor

2011-09-01

Liquid-liquid extraction of target compounds from biological matrices followed by the injection of a large volume from the organic layer into the chromatographic column operated under reversed-phase (RP) conditions would successfully combine the selectivity and the straightforward character of the procedure in order to enhance sensitivity, compared with the usual approach of involving solvent evaporation and residue re-dissolution. Large-volume injection of samples in diluents that are not miscible with the mobile phase was recently introduced in chromatographic practice. The risk of random errors produced during the manipulation of samples is also substantially reduced. A bioanalytical method designed for the bioequivalence of fenspiride containing pharmaceutical formulations was based on a sample preparation procedure involving extraction of the target analyte and the internal standard (trimetazidine) from alkalinized plasma samples in 1-octanol. A volume of 75 µl from the octanol layer was directly injected on a Zorbax SB C18 Rapid Resolution, 50 mm length × 4.6 mm internal diameter × 1.8 µm particle size column, with the RP separation being carried out under gradient elution conditions. Detection was made through positive ESI and MS/MS. Aspects related to method development and validation are discussed. The bioanalytical method was successfully applied to assess bioequivalence of a modified release pharmaceutical formulation containing 80 mg fenspiride hydrochloride during two different studies carried out as single-dose administration under fasting and fed conditions (four arms), and multiple doses administration, respectively. The quality attributes assigned to the bioanalytical method, as resulting from its application to the bioequivalence studies, are highlighted and fully demonstrate that sample preparation based on large-volume injection of immiscible diluents has an increased potential for application in bioanalysis.

High-pressure liquid chromatography with direct injection of gas sample.

PubMed

Astanin, Anton I; Baram, Grigory I

2017-06-09

The conventional method of using liquid chromatography to determine the composition of a gaseous mixture entails dissolving vapors in a suitable solvent, then obtaining a chromatograph of the resulting solution. We studied the direct introduction of a gaseous sample into a C18 reversed-phase column, followed by separation of the components by HPLC with UV detection. Since the chromatography was performed at high pressure, vapors readily dissolved in the eluent and the substances separated in the column as effectively as in liquid samples. Samples were injected into the column in two ways: a) through the valve without a flow stop; b) after stopping the flow and relieving all pressure. We showed that an injectable gas volume could reach 70% of column dead volume. When an injected gaseous sample volume was less than 10% of the column dead volume, the resulting peaks were symmetrical and the column efficiency was high. Copyright © 2017 Elsevier B.V. All rights reserved.

Osmotically Induced Reversible Transitions in Lipid-DNA Mesophases

PubMed Central

Danino, Dganit; Kesselman, Ellina; Saper, Gadiel; Petrache, Horia I.; Harries, Daniel

2009-01-01

We follow the effect of osmotic pressure on isoelectric complexes that self-assemble from mixtures of DNA and mixed neutral and cationic lipids. Using small angle x-ray diffraction and freeze-fracture cryo-electron microscopy, we find that lamellar complexes known to form in aqueous solutions can reversibly transition to hexagonal mesophases under high enough osmotic stress exerted by adding a neutral polymer. Using molecular spacings derived from x-ray diffraction, we estimate the reversible osmotic pressure-volume (Π-V) work needed to induce this transition. We find that the transition free energy is comparable to the work required to elastically bend lipid layers around DNA. Consistent with this, the required work is significantly lowered by an addition of hexanol, which is known to soften lipid bilayers. Our findings not only help to resolve the free-energy contributions associated with lipid-DNA complex formation, but they also demonstrate the importance that osmotic stress can have to the macromolecular phase geometry in realistic biological environments. PMID:19348739

Contraception with RISUG® and functional reversal through DMSO and NaHCO3 in male rabbits.

PubMed

Ansari, Abdul S; Badar, Ayesha; Balasubramanian, Krithika; Lohiya, Nirmal K

2017-01-01

The study aimed to evaluate reversal of short- and long-term vas occlusion with reversible inhibition of sperm under guidance (RISUG) using dimethyl sulfoxide (DMSO) and sodium bicarbonate (NaHCO3) in male rabbits (Oryctolagus cuniculus). Animals were divided into seven groups containing five animals each. Fortnightly, semen analysis revealed that sperm concentration and output steadily declined after vas occlusion and complete azoospermia was attained at 30-60 days postinjection. Spermatozoa reappeared at 60-75 days of reversal and normozoospermia was noticed between 135 days and 150 days in the reversal groups. All spermatozoa were found nonmotile prior to azoospermia and a gradual recovery in sperm motility was observed between 105 days and 135 days of reversal. A significant decline in viability of sperms was noticed during vas occlusion up to 30-60 days which recovered at 60-75 days postreversal and normalized by 75-105 days in the reversal groups. A significant enhancement in the sperm abnormalities was recorded in all vas occluded animals as well as those in initial periods of reversal. Other parameters, namely, semen volume, ejaculation time, pH, color, and consistency, remained unaltered during all phases of the study. Fertility test, at the intervals of 15 days, demonstrated that animals exhibited complete sterility during the entire period of vas occlusion. A gradual recovery in fertility was observed with the appearance of spermatozoa following vas occlusion reversal and 100% fertility was observed following 135-150 days of reversal. F1 progeny of reversed animals was found normal. The results suggest that reversal with DMSO or NaHCO3 is feasible, with normal progeny, following short- and long-term contraception.

Pressure-induced transformations in amorphous silicon: A computational study

NASA Astrophysics Data System (ADS)

Garcez, K. M. S.; Antonelli, A.

2014-02-01

We study the transformations between amorphous phases of Si through molecular simulations using the environment dependent interatomic potential (EDIP) for Si. Our results show that upon pressure, the material undergoes a transformation from the low density amorphous (LDA) Si to the high density amorphous (HDA) Si. This transformation can be reversed by decompressing the material. This process, however, exhibits clear hysteresis, suggesting that the transformation LDA ↔ HDA is first-order like. The HDA phase is predominantly five-fold coordinated, whereas the LDA phase is the normal tetrahedrally bonded amorphous Si. The HDA phase at 400 K and 20 GPa was submitted to an isobaric annealing up to 800 K, resulting in a denser amorphous phase, which is structurally distinct from the HDA phase. Our results also show that the atomic volume and structure of this new amorphous phase are identical to those of the glass obtained by an isobaric quenching of the liquid in equilibrium at 2000 K and 20 GPa down to 400 K. The similarities between our results and those for amorphous ices suggest that this new phase is the very high density amorphous Si.

A case of Z/E-isomers elution order inversion caused by cosolvent percentage change in supercritical fluid chromatography.

PubMed

Pokrovskiy, Oleg I; Ustinovich, Konstantin B; Usovich, Oleg I; Parenago, Olga O; Lunin, Valeriy V; Ovchinnikov, Denis V; Kosyakov, Dmitry S

2017-01-06

A case of elution order inversion caused by cosolvent percentage change in supercritical fluid chromatography was observed and investigated in some detail. Z- and E-isomers of phenylisobutylketone oxime experience an elution order reversal on most columns if the mobile phase consists of CO 2 and alcohol. At lower percentages of alcohol Z-oxime is retained less, somewhere at 2-5% coelution occurs and at larger cosolvent volume elution order reverses - Z-oxime is eluted later than E-oxime. We suppose inversion with CO 2 -ROH phases happens due to a shift in balance between two main interactions governing retention. At low ROH percentages stationary phase surface is only slightly covered by ROH molecules so oximes primarily interact with adsorption sites via hydrogen bond formation. Due to intramolecular sterical hindrance Z-oxime is less able to form hydrogen bonds and consequently is eluted first. At higher percentages alcohols occupy most of strong hydrogen bonding sites on silica surface thus leaving non-specific electrostatic interactions predominantly responsible for Z/E selectivity. Z-oxime has a much larger dipole moment than E-oxime and at these conditions it is eluted later. Additional experimental data with CO 2 -CH 3 CN, hexane-iPrOH and CHF 3 -ROH mobile phases supporting this explanation are presented. Copyright © 2016 Elsevier B.V. All rights reserved.

Microfluidic chip for peptide analysis with an integrated HPLC column, sample enrichment column, and nanoelectrospray tip.

PubMed

Yin, Hongfeng; Killeen, Kevin; Brennen, Reid; Sobek, Dan; Werlich, Mark; van de Goor, Tom

2005-01-15

Current nano-LC/MS systems require the use of an enrichment column, a separation column, a nanospray tip, and the fittings needed to connect these parts together. In this paper, we present a microfabricated approach to nano-LC, which integrates these components on a single LC chip, eliminating the need for conventional LC connections. The chip was fabricated by laminating polyimide films with laser-ablated channels, ports, and frit structures. The enrichment and separation columns were packed using conventional reversed-phase chromatography particles. A face-seal rotary valve provided a means for switching between sample loading and separation configurations with minimum dead and delay volumes while allowing high-pressure operation. The LC chip and valve assembly were mounted within a custom electrospray source on an ion-trap mass spectrometer. The overall system performance was demonstrated through reversed-phase gradient separations of tryptic protein digests at flow rates between 100 and 400 nL/min. Microfluidic integration of the nano-LC components enabled separations with subfemtomole detection sensitivity, minimal carryover, and robust and stable electrospray throughout the LC solvent gradient.

Synthetic Biology in Aqueous Compartments at the Micro- and Nanoscale

DOE Office of Scientific and Technical Information (OSTI.GOV)

Boreyko, Jonathan; Caveney, Patrick M.; Norred, Sarah L.

ABSTRACT Aqueous two-phase systems and related emulsion-based structures defined within micro- and nanoscale environments enable a bottom-up synthetic biological approach to mimicking the dynamic compartmentation of biomaterial that naturally occurs within cells. Model systems we have developed to aid in understanding these phenomena include on-demand generation and triggering of reversible phase transitions in ATPS confined in microscale droplets, morpho-logical changes in networks of femtoliter-volume aqueous droplet interface bilayers (DIBs) formulated in microfluidic channels, and temperature-driven phase transitions in interfacial lipid bilayer systems supported on micro and nanostructured substrates. For each of these cases, the dynamics were intimately linked to changesmore » in the chemical potential of water, which becomes increasingly susceptible to confinement and crowding. At these length scales, where interfacial and surface areas predominate over compartment volumes, both evaporation and osmotic forces become enhanced relative to ideal dilute solutions. Finally, consequences of confinement and crowding in cell-sized microcompartments for increasingly complex scenarios will be discussed, from single-molecule mobility measurements with fluorescence correlation spectroscopy to spatio-temporal modulation of resource sharing in cell-free gene expression bursting.« less

Synthetic Biology in Aqueous Compartments at the Micro- and Nanoscale

DOE PAGES

Boreyko, Jonathan; Caveney, Patrick M.; Norred, Sarah L.; ...

2017-07-10

ABSTRACT Aqueous two-phase systems and related emulsion-based structures defined within micro- and nanoscale environments enable a bottom-up synthetic biological approach to mimicking the dynamic compartmentation of biomaterial that naturally occurs within cells. Model systems we have developed to aid in understanding these phenomena include on-demand generation and triggering of reversible phase transitions in ATPS confined in microscale droplets, morpho-logical changes in networks of femtoliter-volume aqueous droplet interface bilayers (DIBs) formulated in microfluidic channels, and temperature-driven phase transitions in interfacial lipid bilayer systems supported on micro and nanostructured substrates. For each of these cases, the dynamics were intimately linked to changesmore » in the chemical potential of water, which becomes increasingly susceptible to confinement and crowding. At these length scales, where interfacial and surface areas predominate over compartment volumes, both evaporation and osmotic forces become enhanced relative to ideal dilute solutions. Finally, consequences of confinement and crowding in cell-sized microcompartments for increasingly complex scenarios will be discussed, from single-molecule mobility measurements with fluorescence correlation spectroscopy to spatio-temporal modulation of resource sharing in cell-free gene expression bursting.« less

Supercritical fluid reverse micelle separation

DOEpatents

Fulton, John L.; Smith, Richard D.

1993-01-01

A method of separating solute material from a polar fluid in a first polar fluid phase is provided. The method comprises combining a polar fluid, a second fluid that is a gas at standard temperature and pressure and has a critical density, and a surfactant. The solute material is dissolved in the polar fluid to define the first polar fluid phase. The combined polar and second fluids, surfactant, and solute material dissolved in the polar fluid is maintained under near critical or supercritical temperature and pressure conditions such that the density of the second fluid exceeds the critical density thereof. In this way, a reverse micelle system defining a reverse micelle solvent is formed which comprises a continuous phase in the second fluid and a plurality of reverse micelles dispersed in the continuous phase. The solute material is dissolved in the polar fluid and is in chemical equilibrium with the reverse micelles. The first polar fluid phase and the continuous phase are immiscible. The reverse micelles each comprise a dynamic aggregate of surfactant molecules surrounding a core of the polar fluid. The reverse micelle solvent has a polar fluid-to-surfactant molar ratio W, which can vary over a range having a maximum ratio W.sub.o that determines the maximum size of the reverse micelles. The maximum ratio W.sub.o of the reverse micelle solvent is then varied, and the solute material from the first polar fluid phase is transported into the reverse micelles in the continuous phase at an extraction efficiency determined by the critical or supercritical conditions.

Supercritical fluid reverse micelle separation

DOEpatents

Fulton, J.L.; Smith, R.D.

1993-11-30

A method of separating solute material from a polar fluid in a first polar fluid phase is provided. The method comprises combining a polar fluid, a second fluid that is a gas at standard temperature and pressure and has a critical density, and a surfactant. The solute material is dissolved in the polar fluid to define the first polar fluid phase. The combined polar and second fluids, surfactant, and solute material dissolved in the polar fluid is maintained under near critical or supercritical temperature and pressure conditions such that the density of the second fluid exceeds the critical density thereof. In this way, a reverse micelle system defining a reverse micelle solvent is formed which comprises a continuous phase in the second fluid and a plurality of reverse micelles dispersed in the continuous phase. The solute material is dissolved in the polar fluid and is in chemical equilibrium with the reverse micelles. The first polar fluid phase and the continuous phase are immiscible. The reverse micelles each comprise a dynamic aggregate of surfactant molecules surrounding a core of the polar fluid. The reverse micelle solvent has a polar fluid-to-surfactant molar ratio W, which can vary over a range having a maximum ratio W[sub o] that determines the maximum size of the reverse micelles. The maximum ratio W[sub o] of the reverse micelle solvent is then varied, and the solute material from the first polar fluid phase is transported into the reverse micelles in the continuous phase at an extraction efficiency determined by the critical or supercritical conditions. 27 figures.

The self-healing of defects induced by the hydriding phase transformation in palladium nanoparticles

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ulvestad, A.; Yau, A.

Nanosizing can dramatically alter material properties by enhancing surface thermodynamic contributions, shortening diffusion lengths, and increasing the number of catalytically active sites per unit volume. These mechanisms have been used to explain the improved properties of catalysts, battery materials, plasmonic materials, etc. Here we show that Pd nanoparticles also have the ability to self-heal defects in their crystal structures. Using Bragg coherent diffractive imaging, we image dislocations nucleated deep in a Pd nanoparticle during the forward hydriding phase transformation that heal during the reverse transformation, despite the region surrounding the dislocations remaining in the hydrogen-poor phase. We show that defectivemore » Pd nanoparticles exhibit sloped isotherms, indicating that defects act as additional barriers to the phase transformation. Our results resolve the formation and healing of structural defects during phase transformations at the single nanoparticle level and offer an additional perspective as to how and why nanoparticles differ from their bulk counterparts.« less

Continuous infusion of substance P into rat striatum alleviates nociceptive behavior via phosphorylation of extracellular signal-regulated kinase 1/2.

PubMed

Nakamura, Yoki; Izumi, Hiroki; Fukushige, Ryo; Shimizu, Takumi; Watanabe, Kyohei; Morioka, Norimitsu; Hama, Aldric; Takamatsu, Hiroyuki; Nakata, Yoshihiro

2014-12-01

Intraplantar injection of 0.4% formalin into the rat hind paw leads to a biphasic nociceptive response; an 'acute' phase (0-15 min) and 'tonic' phase (16-120 min), which is accompanied by significant phosphorylation of extracellular signal-regulated kinase (ERK)1/2 in the contralateral striatum at 120 min post-formalin injection. To uncover a possible relationship between the slow-onset substance P (SP) release and increased ERK1/2 phosphorylation in the striatum, continuous infusion of SP into the striatum by reverse microdialysis (0.4 μg/mL in microdialysis fiber, 1 μL/min) was performed to mimic volume neurotransmission of SP. Continuous infusion for 3 h of SP reduced the duration of 'tonic' phase nociception, and this SP effect was mediated by neurokinin 1 (NK1) receptors since pre-treatment with NK1 receptor antagonist CP96345 (10 μM) blocked the effect of SP infusion. However, formalin-induced 'tonic' phase nociception was significantly prolonged following acute injection of the MAP/ERK kinase 1/2 inhibitor PD0325901 (100 pmol) by microinjection. The coinfusion of SP and PD0325901 significantly increased the 'tonic' phase of nociception. These data demonstrate that volume transmission of striatal SP triggered by peripheral nociceptive stimulation does not lead to pain facilitation but a significant decrease of tonic nociception by the activation of the SP-NK1 receptor-ERK1/2 system. Noxious stimulation induces a slow-onset substance P (SP) release as a volume transmitter, activating extra-synaptic NK1 receptors, and evokes phosphorylation of extracellular signal-regulated kinase (ERK) 1/2. The SP-NK1-ERK1/2 system in the striatum decreases tonic nociception. © 2014 International Society for Neurochemistry.

The impact of surgeon volume on colostomy reversal outcomes after Hartmann's procedure for diverticulitis.

PubMed

Aquina, Christopher T; Probst, Christian P; Becerra, Adan Z; Hensley, Bradley J; Iannuzzi, James C; Noyes, Katia; Monson, John R T; Fleming, Fergal J

2016-11-01

Colostomy reversal after Hartmann's procedure for diverticulitis is a morbid procedure, and studies investigating factors associated with outcomes are lacking. This study identifies patient, surgeon, and hospital-level factors associated with perioperative outcomes after stoma reversal. The Statewide Planning and Research Cooperative System was queried for urgent/emergency Hartmann's procedures for diverticulitis between 2000-2012 in New York State and subsequent colostomy reversal within 1 year of the procedure. Surgeon and hospital volume were categorized into tertiles based on the annual number of colorectal resections performed each year. Bivariate and mixed-effects analyses were used to assess the association between patient, surgeon, and hospital-level factors and perioperative outcomes after colostomy reversal, including a laparoscopic approach; duration of stay; intensive care unit admission; complications; mortality; and 30-day, unscheduled readmission. Among 10,487 patients who underwent Hartmann's procedure and survived to discharge, 63% had the colostomy reversed within 1 year. After controlling for patient, surgeon, and hospital-level factors, high-volume surgeons (≥40 colorectal resections/yr) were independently associated with higher odds of a laparoscopic approach (unadjusted rates: 14% vs 7.6%; adjusted odds ratio = 1.84, 95% confidence interval = 1.12, 3.00), shorter duration of stay (median: 6 versus 7 days; adjusted incidence rate ratio = 0.87, 95% confidence interval = 0.81, 0.95), and lower odds of 90-day mortality (unadjusted rates: 0.4% vs 1.0%; adjusted odds ratio = 0.30, 95% confidence interval = 0.10, 0.88) compared with low-volume surgeons (1-15 colorectal resections/yr). High-volume surgeons are associated with better perioperative outcomes and lower health care utilization after Hartmann's reversal for diverticulitis. These findings support referral to high-volume surgeons for colostomy reversal. Copyright © 2016 Elsevier Inc. All rights reserved.

Supra-dendron Gelator Based on Azobenzene-Cyclodextrin Host-Guest Interactions: Photoswitched Optical and Chiroptical Reversibility.

PubMed

Xie, Fan; Ouyang, Guanghui; Qin, Long; Liu, Minghua

2016-12-12

A novel amphiphilic dendron (AZOC 8 GAc) with three l-glutamic acid units and an azobenzene moiety covalently linked by an alkyl spacer has been designed. The compound formed hydrogels with water at very low concentration and self-assembled into chiral-twist structures. The gel showed a reversible macroscopic volume phase transition in response to pH variations and photo-irradiation. During the photo-triggered changes, although the gel showed complete reversibility in its optical absorptions, only an incomplete chiroptical property change was achieved. On the other hand, the dendron could form a 1:1 inclusion complex through a host-guest interaction with α-cyclodextrin (α-CD), designated as supra-dendron gelator AZOC 8 GAc/α-CD. The supra-dendron showed similar gelation behavior to that of AZOC 8 GAc, but with enhanced photoisomerization-transition efficiency and chiroptical switching capacity, which was completely reversible in terms of both optical and chiroptical performances. The self-assembly of the supra-dendron is a hierarchical or multi-supramolecular self-assembling process. This work has clearly illustrated that the hierarchical and multi-supramolecular self-assembling system endows the supramolecular nanostructures or materials with superior reversible optical and chiroptical switching. © 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Phase Transition of Poly(acrylic acid-co-N-isopropylacrylamide) Core-shell Nanogels

NASA Astrophysics Data System (ADS)

Liu, Xiao-bing; Zhou, Jian-feng; Ye, Xiao-dong

2012-08-01

A series of poly(acrylic acid) macromolecular chain transfer agents with different molecular weights were synthesized by reversible addition-fragmentation chain transfer (RAFT) polymerization and characterized by 1H NMR and gel permeation chromatography. Multiresponsive core-shell nanogels were prepared by dispersion polymerization of N-isopropylacrylamide in water using these poly(potassium acrylate) macro-RAFT agents as the electrosteric stabilizer. The size of the nanogels decreases with the amount of the macro-RAFT agent, indicating that the surface area occupied by per polyelectrolyte group is a critical parameter for stabilizing the nanogels. The volume phase transition and the zeta potentials of the nanogels in aqueous solutions were studied by dynamic light scattering and zetasizer analyzer, respectively.

Transition state characterization for the reversible binding of dihydrogen to bis(2,2'-bipyridine)rhodium(I) from temperature- and pressure-dependent experimental and theoretical studies.

PubMed

Fujita, Etsuko; Brunschwig, Bruce S; Creutz, Carol; Muckerman, James T; Sutin, Norman; Szalda, David; van Eldik, Rudi

2006-02-20

Thermodynamic and kinetic parameters for the oxidative addition of H2 to [Rh(I)(bpy)2]+ (bpy = 2,2'-bipyridine) to form [Rh(III)(H)2(bpy)2]+ were determined from either the UV-vis spectrum of equilibrium mixtures of [Rh(I)(bpy)2]+ and [Rh(III)(H)2(bpy)2]+ or from the observed rates of dihydride formation following visible-light irradiation of solutions containing [Rh(III)(H)2(bpy)2]+ as a function of H2 concentration, temperature, and pressure in acetone and methanol. The activation enthalpy and entropy in methanol are 10.0 kcal mol(-1) and -18 cal mol(-1) K(-1), respectively. The reaction enthalpy and entropy are -10.3 kcal mol(-1) and -19 cal mol(-1) K(-1), respectively. Similar values were obtained in acetone. Surprisingly, the volumes of activation for dihydride formation (-15 and -16 cm(3) mol(-1) in methanol and acetone, respectively) are very close to the overall reaction volumes (-15 cm(3) mol(-1) in both solvents). Thus, the volumes of activation for the reverse reaction, elimination of dihydrogen from the dihydrido complex, are approximately zero. B3LYP hybrid DFT calculations of the transition-state complex in methanol and similar MP2 calculations in the gas phase suggest that the dihydrogen has a short H-H bond (0.823 and 0.810 Angstroms, respectively) and forms only a weak Rh-H bond (1.866 and 1.915 Angstroms, respectively). Equal partial molar volumes of the dihydrogenrhodium(I) transition state and dihydridorhodium(III) can account for the experimental volume profile found for the overall process.

Revising the lower statistical limit of x-ray grating-based phase-contrast computed tomography.

PubMed

Marschner, Mathias; Birnbacher, Lorenz; Willner, Marian; Chabior, Michael; Herzen, Julia; Noël, Peter B; Pfeiffer, Franz

2017-01-01

Phase-contrast x-ray computed tomography (PCCT) is currently investigated as an interesting extension of conventional CT, providing high soft-tissue contrast even if examining weakly absorbing specimen. Until now, the potential for dose reduction was thought to be limited compared to attenuation CT, since meaningful phase retrieval fails for scans with very low photon counts when using the conventional phase retrieval method via phase stepping. In this work, we examine the statistical behaviour of the reverse projection method, an alternative phase retrieval approach and compare the results to the conventional phase retrieval technique. We investigate the noise levels in the projections as well as the image quality and quantitative accuracy of the reconstructed tomographic volumes. The results of our study show that this method performs better in a low-dose scenario than the conventional phase retrieval approach, resulting in lower noise levels, enhanced image quality and more accurate quantitative values. Overall, we demonstrate that the lower statistical limit of the phase stepping procedure as proposed by recent literature does not apply to this alternative phase retrieval technique. However, further development is necessary to overcome experimental challenges posed by this method which would enable mainstream or even clinical application of PCCT.

SANSMIC Validation.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Weber, Paula D.; Rudeen, David Keith; Lord, David L.

2014-08-01

SANSMIC is solution mining software that was developed and utilized by SNL in its role as geotechnical advisor to the US DOE SPR for planning purposes. Three SANSMIC leach modes - withdrawal, direct, and reverse leach - have been revalidated with multiple test cases for each mode. The withdrawal mode was validated using high quality data from recent leach activity while the direct and reverse modes utilized data from historical cavern completion reports. Withdrawal results compared very well with observed data, including the location and size of shelves due to string breaks with relative leached volume differences ranging from 6more » - 10% and relative radius differences from 1.5 - 3%. Profile comparisons for the direct mode were very good with relative leached volume differences ranging from 6 - 12% and relative radius differences from 5 - 7%. First, second, and third reverse configurations were simulated in order to validate SANSMIC over a range of relative hanging string and OBI locations. The first-reverse was simulated reasonably well with relative leached volume differences ranging from 1 - 9% and relative radius differences from 5 - 12%. The second-reverse mode showed the largest discrepancies in leach profile. Leached volume differences ranged from 8 - 12% and relative radius differences from 1 - 10%. In the third-reverse, relative leached volume differences ranged from 10 - 13% and relative radius differences were %7E4 %. Comparisons to historical reports were quite good, indicating that SANSMIC is essentially the same as documented and validated in the early 1980's.« less

Effect of microthreads on coronal bone healing of narrow-diameter implants with reverse-tapered design in beagle dogs.

PubMed

Chang, Yun-Young; Kim, Su-Hwan; Park, Keun-Oh; Yun, Jeong-Ho

2017-12-01

The objective of this study was to investigate the effect of microthreads on the coronal bone healing of narrow-diameter implants with reverse-tapered design. A total of 52 implants were classified into two groups according to presence or absence of coronal microthreads, the reverse-tapered narrow-diameter implant (RTN) group, and the reverse-tapered narrow-diameter implant with microthreads (RTNM) group. The implants were installed in split-mouth design in the edentulous mandible of six dogs. Three animals were sacrificed at 4 weeks and three at 8 weeks. Resonance frequency analysis, bone measurement using microcomputed tomography (micro-CT), removal torque test, and histometric analysis were performed. No significant differences in implant stability quotient value were observed between the groups at baseline, 4 weeks, or 8 weeks. Bone measurement using micro-CT showed that bone-implant contact volume (BICV) and bone-implant contact volume ratio (BICVR) in the coronal part of RTNM were statistically higher than those in RTN at 4 and 8 weeks. Histometric analysis showed statistically higher bone-implant contact length (BICL) in the coronal part of RTNM than in RTN at 4 weeks; however, bone-implant contact ratio (BICR) was not significantly different between the groups. At 8 weeks, the BICL and BICR did not differ significantly between the groups. Removal torque test showed no significant differences between the groups at 4 and 8 weeks. The microthreads might facilitate more coronal bone-implant contact due to increased surface areas at an early healing phase; however, they did not significantly affect coronal bone healing at 8 weeks. © 2017 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

Lung microvascular transport properties measured by multiple indicator dilution methods in patients with adult respiratory distress syndrome. A comparison between patients reversing respiratory failure and those failing to reverse

DOE Office of Scientific and Technical Information (OSTI.GOV)

Harris, T.R.; Bernard, G.R.; Brigham, K.L.

1990-02-01

We conducted indicator dilution studies on the lungs of patients in the early phases of adult respiratory distress syndrome (ARDS) to test the hypothesis that capillary permeability was increased in patients with respiratory failure. Indicator dilution studies were performed using 51Cr-erythrocytes, 125I-albumin, 14C-urea, and 3H-water as tracers. The injectate was infused as a bolus into a central venous line. Peripheral arterial blood was collected and counted for radioactivity. Mathematical analysis of the indicator curves yielded cardiac output, measures of the product of capillary permeability and surface area for urea (PS and D1/2S), the intravascular lung volume (Vv), and the extravascularmore » lung water volume (Ve). Permeability was separated from surface area by normalizing PS and D1/2S to Vv. Patients could be divided into 16 in whom blood gas determinations and radiologic criteria for ARDS were reversed and 23 in whom they were not. We examined indicator dilution and other measures of lung function in the two groups to determine whether significant differences in microvascular function existed. PS and PS/Vv were significantly higher in the nonreversal patients. Ve was above normal, but not different between groups. Linear regression analysis showed significant correlations for all of the following in the nonreversal group: Ve and all measures of permeability, pulmonary vascular resistance (PVR), and the inverse of permeability-surface area measures and AaDO2 and PVR. Only measures of Ve and PS correlated in the reversal group. These results support the hypothesis that capillary permeability is increased in patients with early ARDS and continuing respiratory failure.« less

Separation of alkylphenols by normal-phase and reversed-phase high-performance liquid chromatography

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schabron, J.F.; Hurtubise, R.J.; Silver, H.F.

1978-11-01

Empirical correlation factors were developed which relate log k' values for alkylphenols, the naphthols, and two phenylphenols to structural features. Both normal-phase and reversed-phase chromatographic systems were studied. The stationary phases employed in the normal-phase work were ..mu..-Bondapak CN, ..mu..-Bondapak NH/sub 2/, and ..mu..-Porasil. The structural features which affect retention in the normal-phase chromatographic systems are the number of ortho substituents, the number of aliphatic carbons, and the number of aromatic rings. The stationary phases employed in the reversed-phase work were ..mu..-Bondapak C/sub 18/ and ..mu..-Bondapak CN. The structural features which affect retention in the reversed-phase chromatographic systems are themore » number of aliphatic carbons and the number of aromatic double bonds. On ..mu..-Bondapak C/sub 18/, the presence or absence of a nonaromatic ring is of added importance.« less

Colossal magnetic phase transition asymmetry in mesoscale FeRh stripes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Uhlir, V.; Arregi, J. A.; Fullerton, E. E.

Coupled order parameters in phase-transition materials can be controlled using various driving forces such as temperature, magnetic and electric field, strain, spin-polarized currents and optical pulses. Tuning the material properties to achieve efficient transitions would enable fast and low-power electronic devices. Here we show that the first-order metamagnetic phase transition in FeRh films becomes strongly asymmetric in mesoscale structures. In patterned FeRh stripes we observed pronounced supercooling and an avalanche-like abrupt transition from the ferromagnetic to the antiferromagnetic phase, while the reverse transition remains nearly continuous over a broad temperature range. Although modest asymmetry signatures have been found in FeRhmore » films, the effect is dramatically enhanced at the mesoscale. The activation volume of the antiferromagnetic phase is more than two orders of magnitude larger than typical magnetic heterogeneities observed in films. Finally, the collective behaviour upon cooling results from the role of long-range ferromagnetic exchange correlations that become important at the mesoscale and should be a general property of first-order metamagnetic phase transitions.« less

Colossal magnetic phase transition asymmetry in mesoscale FeRh stripes

DOE PAGES

Uhlir, V.; Arregi, J. A.; Fullerton, E. E.

2016-10-11

Coupled order parameters in phase-transition materials can be controlled using various driving forces such as temperature, magnetic and electric field, strain, spin-polarized currents and optical pulses. Tuning the material properties to achieve efficient transitions would enable fast and low-power electronic devices. Here we show that the first-order metamagnetic phase transition in FeRh films becomes strongly asymmetric in mesoscale structures. In patterned FeRh stripes we observed pronounced supercooling and an avalanche-like abrupt transition from the ferromagnetic to the antiferromagnetic phase, while the reverse transition remains nearly continuous over a broad temperature range. Although modest asymmetry signatures have been found in FeRhmore » films, the effect is dramatically enhanced at the mesoscale. The activation volume of the antiferromagnetic phase is more than two orders of magnitude larger than typical magnetic heterogeneities observed in films. Finally, the collective behaviour upon cooling results from the role of long-range ferromagnetic exchange correlations that become important at the mesoscale and should be a general property of first-order metamagnetic phase transitions.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sypek, John T.; Yu, Hang; Dusoe, Keith J.

Shape memory materials have the ability to recover their original shape after a significant amount of deformation when they are subjected to certain stimuli, for instance, heat or magnetic fields. But, their performance is often limited by the energetics and geometry of the martensitic-austenitic phase transformation. We report a unique shape memory behavior in CaFe 2As 2, which exhibits superelasticity with over 13% recoverable strain, over 3 GPa yield strength, repeatable stress–strain response even at the micrometer scale, and cryogenic linear shape memory effects near 50 K. These properties are acheived through a reversible uni-axial phase transformation mechanism, the tetragonal/orthorhombic-to-collapsed-tetragonalmore » phase transformation. These results offer the possibility of developing cryogenic linear actuation technologies with a high precision and high actuation power per unit volume for deep space exploration, and more broadly, suggest a mechanistic path to a class of shape memory materials, ThCr 2Si 2-structured intermetallic compounds.« less

A reversed-phase compatible thin-layer chromatography autography for the detection of acetylcholinesterase inhibitors.

PubMed

Ramallo, I Ayelen; García, Paula; Furlan, Ricardo L E

2015-11-01

A dual readout autographic assay to detect acetylcholinesterase inhibitors present in complex matrices adsorbed on reversed-phase or normal-phase thin-layer chromatography plates is described. Enzyme gel entrapment with an amphiphilic copolymer was used for assay development. The effects of substrate and enzyme concentrations, pH, incubation time, and incubation temperature on the sensitivity and the detection limit of the assay were evaluated. Experimental design and response surface methodology were used to optimize conditions with a minimum number of experiments. The assay allowed the detection of 0.01% w/w of physostigmine in both a spiked Sonchus oleraceus L. extract chromatographed on normal phase and a spiked Pimenta racemosa (Mill.) J.W. Moore leaf essential oil chromatographed on reversed phase. Finally, the reversed-phase thin-layer chromatography assay was applied to reveal the presence of an inhibitor in the Cymbopogon citratus (DC.) Stapf essential oil. The developed assay is able to detect acetylcholinesterase inhibitors present in complex matrixes that were chromatographed in normal phase or reversed-phase thin-layer chromatography. The detection limit for physostigmine on both normal and reversed phase was of 1×10(-4) μg. The results can be read by a change in color and/or a change in fluorescence. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Issues in measure-preserving three dimensional flow integrators: Self-adjointness, reversibility, and non-uniform time stepping

DOE PAGES

Finn, John M.

2015-03-01

Properties of integration schemes for solenoidal fields in three dimensions are studied, with a focus on integrating magnetic field lines in a plasma using adaptive time stepping. It is shown that implicit midpoint (IM) and a scheme we call three-dimensional leapfrog (LF) can do a good job (in the sense of preserving KAM tori) of integrating fields that are reversible, or (for LF) have a 'special divergence-free' property. We review the notion of a self-adjoint scheme, showing that such schemes are at least second order accurate and can always be formed by composing an arbitrary scheme with its adjoint. Wemore » also review the concept of reversibility, showing that a reversible but not exactly volume-preserving scheme can lead to a fractal invariant measure in a chaotic region, although this property may not often be observable. We also show numerical results indicating that the IM and LF schemes can fail to preserve KAM tori when the reversibility property (and the SDF property for LF) of the field is broken. We discuss extensions to measure preserving flows, the integration of magnetic field lines in a plasma and the integration of rays for several plasma waves. The main new result of this paper relates to non-uniform time stepping for volume-preserving flows. We investigate two potential schemes, both based on the general method of Ref. [11], in which the flow is integrated in split time steps, each Hamiltonian in two dimensions. The first scheme is an extension of the method of extended phase space, a well-proven method of symplectic integration with non-uniform time steps. This method is found not to work, and an explanation is given. The second method investigated is a method based on transformation to canonical variables for the two split-step Hamiltonian systems. This method, which is related to the method of non-canonical generating functions of Ref. [35], appears to work very well.« less

Four-factor prothrombin complex concentrate reverses apixaban-associated bleeding in a rabbit model of acute hemorrhage.

PubMed

Herzog, E; Kaspereit, F; Krege, W; Mueller-Cohrs, J; Doerr, B; Niebl, P; Dickneite, G

2015-12-01

Apixaban is a direct factor Xa inhibitor approved for the treatment and prevention of thromboembolic disease. There is a lack of data regarding its reversal in cases of acute bleeding or prior to emergency surgery that needs addressing. This study assessed whether a four-factor prothrombin complex concentrate (4F-PCC; Beriplex(®) /Kcentra(®) , CSL Behring) can effectively reverse apixaban-associated bleeding in an in vivo rabbit model and evaluated the correlations between in vivo hemostasis and in vitro coagulation parameters. For dose-finding purposes, anesthetized rabbits were treated with a single intravenous dose of apixaban (800-1600 μg kg(-1) ) and, following a standardized kidney incision, volume of blood loss and time to hemostasis were measured. In a subsequent study phase, anesthetized rabbits were treated with apixaban 1200 μg kg(-1) followed by 4F-PCC (6.25-100 IU kg(-1) ), and the effects on the same bleeding parameters were assessed. In parallel, coagulation parameters were monitored. Dose-dependent increases in time to hemostasis and total blood loss were observed post apixaban administration. Preincision treatment with 4F-PCC resulted in a statistically significant reversal in bleeding time (all doses) and volume (doses ≥ 12.5 IU kg(-1) ). Of the coagulation parameters measured, thrombin generation initiated using the RD reagent (phospholipids only) was the most sensitive to in vivo measures of 4F-PCC's hemostatic efficacy, although some correlations were also observed for prothrombin time and whole blood clotting time. In this rabbit model of acute hemorrhage, 4F-PCC showed potential for reversing the bleeding effects of apixaban. Clinical data in apixaban-treated patients are needed to confirm these results. © 2015 The Authors. Journal of Thrombosis and Haemostasis published by Wiley Periodicals, Inc. on behalf of International Society on Thrombosis and Haemostasis.

A simple, sensitive and rapid isocratic reversed-phase high-performance liquid chromatography method for determination and stability study of curcumin in pharmaceutical samples

PubMed Central

Amanolahi, Farjad; Mohammadi, Ali; Kazemi Oskuee, Reza; Nassirli, Hooriyeh; Malaekeh-Nikouei, Bizhan

2017-01-01

Objective: This study was designed to develop and validate a new reversed-phase high-performance liquid chromatography (RP-HPLC) method based on Q2 (R1) International Conference on Harmonization (ICH) guideline for determination of curcumin in pharmaceutical samples. Materials and Methods: The HPLC instrument method was optimized with isocratic elution with acetonitrile: ammonium acetate (45:55, v/v, pH 3.5), C18 column (150 mm×4.6 mm×5 µm particle size) and a flow rate of 1 ml/min in ambient condition and total retention time of 17 min. The volume of injection was set at 20 µl and detection was recorded at 425 nm. The robustness of the method was examined by changing the mobile phase composition, mobile phase pH, and flow rate. Results: The method was validated with respect to precision, accuracy and linearity in a concentration range of 2-100 µg/ml. The limit of detection (LOD) and limit of quantification (LOQ) were 0.25 and 0.5 µg/ml, respectively. The percentage of recovery was 98.9 to 100.5 with relative standard deviation (RSD) < 0.638%. Conclusion: The method was found to be simple, sensitive and rapid for determination of curcumin in pharmaceutical samples and had enough sensitivity to detect degradation product of curcumin produced under photolysis and hydrolysis stress condition. PMID:29062806

A Study of Intercellular Spaces in the Rabbit Jejunum during Acute Volume Expansion and after Treatment with Cholera Toxin

PubMed Central

DiBona, Donald R.; Chen, Lincoln C.; Sharp, Geoffrey W. G.

1974-01-01

The effects of acute volume expansion and of intraluminal administration of cholera toxin have been examined in rabbit jejunum. Acute volume expansion was shown to reverse the normal reabsorptive flux of water and cause significant fluid secretion. Phase and electronmicroscopic examination of the jejunal epithelium showed that marked distension of the intercellular spaces had occurred. Examination of the jejunal epithelium after treatment with cholera toxin showed that, in association with high rates of fluid secretion, the intercellular spaces were extremely small and lateral membranes of adjacent cells were in close apposition to one another. Thus the mechanisms of fluid secretion in these two situations would appear to be quite different. The secretion associated with volume expansion, and accompanied by a rise in venous pressure and bullous deformations of terminal junctions, could well be due to hydrostatic pressure applied through intercellular channels. The secretion of cholera appears to be unrelated to hydrostatic pressure and is more likely due to body-to-lumen active ion transport. Images PMID:4596506

Topological superconductivity in the extended Kitaev-Heisenberg model

NASA Astrophysics Data System (ADS)

Schmidt, Johann; Scherer, Daniel D.; Black-Schaffer, Annica M.

2018-01-01

We study superconducting pairing in the doped Kitaev-Heisenberg model by taking into account the recently proposed symmetric off-diagonal exchange Γ . By performing a mean-field analysis, we classify all possible superconducting phases in terms of symmetry, explicitly taking into account effects of spin-orbit coupling. Solving the resulting gap equations self-consistently, we map out a phase diagram that involves several topologically nontrivial states. For Γ <0 , we find a competition between a time-reversal symmetry-breaking chiral phase with Chern number ±1 and a time-reversal symmetric nematic phase that breaks the rotational symmetry of the lattice. On the other hand, for Γ ≥0 we find a time-reversal symmetric phase that preserves all the lattice symmetries, thus yielding clearly distinguishable experimental signatures for all superconducting phases. Both of the time-reversal symmetric phases display a transition to a Z2 nontrivial phase at high doping levels. Finally, we also include a symmetry-allowed spin-orbit coupling kinetic energy and show that it destroys a tentative symmetry-protected topological order at lower doping levels. However, it can be used to tune the time-reversal symmetric phases into a Z2 nontrivial phase even at lower doping.

Convection-enhanced drug delivery of interleukin-4 Pseudomonas exotoxin (PRX321): increased distribution and magnetic resonance monitoring.

PubMed

Mardor, Y; Last, D; Daniels, D; Shneor, R; Maier, S E; Nass, D; Ram, Z

2009-08-01

Convection-enhanced drug delivery (CED) enables achieving a drug concentration within brain tissue and brain tumors that is orders of magnitude higher than by systemic administration. Previous phase I/II clinical trials using intratumoral convection of interleukin-4 Pseudomonas exotoxin (PRX321) have demonstrated an acceptable safety and toxicity profile with promising signs of therapeutic activity. The present study was designed to assess the distribution efficiency and toxicity of this PRX321 using magnetic resonance imaging (MRI) and to test whether reformulation with increased viscosity could enhance drug distribution. Convection of low- [0.02% human serum albumin (HSA)] and high-viscosity (3% HSA) infusates mixed with gadolinium-diethylenetriamine pentaacetic acid and PRX321 were compared with low- and high-viscosity infusates without the drug, in normal rat brains. MRI was used for assessment of drug distribution and detection of early and late toxicity. Representative brain samples were subjected to histological examination. Distribution volumes calculated from the magnetic resonance images showed that the average distribution of 0.02% HSA was larger than that of 0.02% HSA with PRX321 by a factor of 1.98 (p < 0.02). CED of 3.0% HSA, with or without PRX321, tripled the volume of distribution compared with 0.02% HSA with PRX321 (p < 0.015). No drug-related toxicity was detected. These results suggest that the impeded convection of the PRX321 infusate used in previous clinical trials can be reversed by increasing infusate viscosity and lead to tripling of the volume of distribution. This effect was not associated with any detectable toxicity. A similar capability to reverse impeded convection was also demonstrated in a CED model using acetic acid. These results will be implemented in an upcoming phase IIb PRX321 CED trial with a high-viscosity infusate.

Intraoperative Evaluation of Reverse Bypass Using a Naturally Formed "Bonnet" Superficial Temporal Artery: Technical Note.

PubMed

Nagm, Alhusain; Horiuchi, Tetsuyoshi; Hasegawa, Takatoshi; Hongo, Kazuhiro

2016-04-01

In reverse bypass that used a naturally formed "bonnet" superficial temporal artery, intraoperative volume flow measurement quantifies flow augmentation after revascularization, confirms flow preservation, and identifies inadvertent vessel compromise. A 75-year-old man presented with transient ischemic attacks attributed to right internal carotid artery stenosis. He underwent successful reverse bypass via a naturally formed "bonnet" superficial temporal artery middle cerebral artery bypass. As the result of proper intraoperative volume flow evaluation, a successful reverse bypass was achieved. Modification of the intraoperative stroke risk and prediction of the long-term patency after reverse bypass can be achieved by meticulous intraoperative blood flow evaluation. Copyright © 2016 Elsevier Inc. All rights reserved.

Fully automated method for the liquid chromatographic determination of cyproterone acetate in plasma using restricted access material for sample pre-treatment.

PubMed

Christiaens, B; Chiap, P; Rbeida, O; Cello, D; Crommen, J; Hubert, Ph

2003-09-25

A new fully automated method for the quantitative analysis of an antiandrogenic substance, cyproterone acetate (CPA), in plasma samples has been developed using on-line solid-phase extraction (SPE) prior to the determination by reversed-phase liquid chromatography (LC). The automated method was based on the use of a precolumn packed with an internal-surface reversed-phase packing material (LiChrospher RP-4 ADS) for sample clean-up coupled to LC analysis on an octadecyl stationary phase using a column-switching system. A 200-microL volume of plasma sample was injected directly on the precolumn packed with restricted access material using a mixture of water-acetonitrile (90:10, v/v) as washing liquid. The analyte was then eluted in the back-flush mode with the LC mobile phase which consisted of a mixture of phosphate buffer, pH 7.0-acetonitrile (54:46, v/v). The elution profiles of CPA and blank plasma samples on the precolumn and the time needed for analyte transfer from the precolumn to the analytical column were determined. Different compositions of washing liquid and mobile phase were tested to reduce the interference of plasma endogenous components. UV detection was achieved at 280 nm. Finally, the developed method was validated using a new approach, namely the application of the accuracy profile based on the interval confidence at 90% of the total measurement error (bias+standard deviation). The limit of quantification of cyproterone acetate in plasma was determined at 15 ng mL(-1). The validated method should be applicable to the determination of CPA in patients treated by at least 50 mg day(-1).

Retention prediction of highly polar ionizable solutes under gradient conditions on a mixed-mode reversed-phase and weak anion-exchange stationary phase.

PubMed

Balkatzopoulou, P; Fasoula, S; Gika, H; Nikitas, P; Pappa-Louisi, A

2015-05-29

In the present work the retention of three highly polar and ionizable solutes - uric acid, nicotinic acid and ascorbic acid - was investigated on a mixed-mode reversed-phase and weak anion-exchange (RP/WAX) stationary phase in buffered aqueous acetonitrile (ACN) mobile phases. A U-shaped retention behavior was observed for all solutes with respect to the eluent organic modifier content studied in a range of 5-95% (v/v). This retention behavior clearly demonstrates the presence of a HILIC-type retention mechanism at ACN-rich hydro-organic eluents and an RP-like retention at aqueous-rich hydro-organic eluents. Hence, this column should be promising for application under both RP and HILIC gradient elution modes. For this reason, a series of programmed elution runs were carried out with increasing (RP) and decreasing (HILIC) organic solvent concentration in the mobile phase. This dual gradient process was successfully modeled by two retention models exhibiting a quadratic or a cubic dependence of the logarithm of the solute retention factor (lnk) upon the organic modifier volume fraction (φ). It was found that both models produced by gradient retention data allow the prediction of solute retention times for both types of programmed elution on the mixed-mode column. Four, in the case of the quadratic model, or five, in the case of the cubic model, initial HILIC- and RP-type gradient runs gave satisfactory retention predictions of any similar kind elution program, even with different flow rate, with an overall error of only 2.5 or 1.7%, respectively. Copyright © 2015 Elsevier B.V. All rights reserved.

[Determination of phenazine-1-carboxylic acid in anti-fungal agent M18 by high performance liquid chromatography].

PubMed

Zhu, D H; Zhu, X D; Xu, Y Q

2001-11-01

A reversed-phase HPLC method for the determination of phenazine-1-carboxylic acid (PCA) in antifungal agent M18 is established. The mobile phase was a mixture of MeOH-5 mmol/L phosphate buffer (pH 5.0) (60:40, volume ratio). The flow rate was 1.0 mL/min, and the detection wavelength was 248 nm. The linear range and detectable limit were 50 mg/L-500 mg/L and 30 mg/L respectively. The recovery was 97.53% and RSD was 1.5%. The method of PCA extraction and detection has proven to be much faster, simpler, more sensitive, accurate and reproducible than those reported already. The assay results can be used as a very important criterion for large-scale production.

Determination of solute descriptors by chromatographic methods.

PubMed

Poole, Colin F; Atapattu, Sanka N; Poole, Salwa K; Bell, Andrea K

2009-10-12

The solvation parameter model is now well established as a useful tool for obtaining quantitative structure-property relationships for chemical, biomedical and environmental processes. The model correlates a free-energy related property of a system to six free-energy derived descriptors describing molecular properties. These molecular descriptors are defined as L (gas-liquid partition coefficient on hexadecane at 298K), V (McGowan's characteristic volume), E (excess molar refraction), S (dipolarity/polarizability), A (hydrogen-bond acidity), and B (hydrogen-bond basicity). McGowan's characteristic volume is trivially calculated from structure and the excess molar refraction can be calculated for liquids from their refractive index and easily estimated for solids. The remaining four descriptors are derived by experiment using (largely) two-phase partitioning, chromatography, and solubility measurements. In this article, the use of gas chromatography, reversed-phase liquid chromatography, micellar electrokinetic chromatography, and two-phase partitioning for determining solute descriptors is described. A large database of experimental retention factors and partition coefficients is constructed after first applying selection tools to remove unreliable experimental values and an optimized collection of varied compounds with descriptor values suitable for calibrating chromatographic systems is presented. These optimized descriptors are demonstrated to be robust and more suitable than other groups of descriptors characterizing the separation properties of chromatographic systems.

Decrease in cortisol reverses human hippocampal atrophy following treatment of Cushing's disease.

PubMed

Starkman, M N; Giordani, B; Gebarski, S S; Berent, S; Schork, M A; Schteingart, D E

1999-12-15

Decreased hippocampal volume is observed in patients with Cushing's syndrome and other conditions associated with elevated cortisol levels, stress, or both. Reversibility of hippocampal neuronal atrophy resulting from stress occurs in animals. Our study investigated the potential for reversibility of human hippocampal atrophy. The study included 22 patients with Cushing's disease. Magnetic resonance brain imaging was performed prior to transsphenoidal microadenomectomy and again after treatment. Following treatment, hippocampal formation volume (HFV) increased by up to 10%. The mean percent change (3.2 +/- 2.5) was significantly greater (p < .04) than that of the comparison structure, caudate head volume (1.5 +/- 3.4). Increase in HFV was significantly associated with magnitude of decrease in urinary free cortisol (r = -.61, p < .01). This relationship strengthened after adjustments for age, duration of disease, and months elapsed since surgery (r = -.70, p < .001). There was no significant correlation between caudate head volume change and magnitude of cortisol decrease. Changes in human HFV associated with sustained hypercortisolemia are reversible, at least in part, once cortisol levels decrease. While many brain regions are likely affected by hypercortisolemia, the human hippocampus exhibits increased sensitivity to cortisol, affecting both volume loss and recovery.

Sensitive determination of nitrophenol isomers by reverse-phase high-performance liquid chromatography in conjunction with liquid-liquid extraction

USDA-ARS?s Scientific Manuscript database

A method for the highly sensitive determination of 2-, 3- and 4- nitrophenols was developed using reverse-phase high-performance liquid chromatography (RP-HPLC) with a UV photodiode array detector. Using a reverse-phase column and 40% aqueous acetonitrile as an eluent (i.e. isocratic elution), the i...

Preparation and evaluation of surface-bonded tricationic ionic liquid silica as stationary phases for high-performance liquid chromatography.

PubMed

Qiao, Lizhen; Shi, Xianzhe; Lu, Xin; Xu, Guowang

2015-05-29

Two tricationic ionic liquids were prepared and then bonded onto the surface of supporting silica materials through "thiol-ene" click chemistry as new stationary phases for high-performance liquid chromatography. The obtained columns of tricationic ionic liquids were evaluated respectively in the reversed-phase liquid chromatography (RPLC) mode and hydrophilic interaction liquid chromatography (HILIC) mode, and possess ideal column efficiency of 80,000 plates/m in the RPLC mode with naphthalene as the test solute. The tricationic ionic liquid stationary phases exhibit good hydrophobic and shape selectivity to hydrophobic compounds, and RPLC retention behavior with multiple interactions. In the HILIC mode, the retention and selectivity were evaluated through the efficient separation of nucleosides and bases as well as flavonoids, and the typical HILIC retention behavior was demonstrated by investigating retention changes of hydrophilic solutes with water volume fraction in mobile phase. The results show that the tricationic ionic liquid columns possess great prospect for applications in analysis of hydrophobic and hydrophilic samples. Copyright © 2015 Elsevier B.V. All rights reserved.

Effect of pressure on the selectivity of polymeric C18 and C30 stationary phases in reversed-phase liquid chromatography. Increased separation of isomeric fatty acid methyl esters, triacylglycerols, and tocopherols at high pressure.

PubMed

Okusa, Kensuke; Iwasaki, Yuki; Kuroda, Ikuma; Miwa, Shohei; Ohira, Masayoshi; Nagai, Toshiharu; Mizobe, Hoyo; Gotoh, Naohiro; Ikegami, Tohru; McCalley, David V; Tanaka, Nobuo

2014-04-25

A high-density, polymeric C18 stationary phase (Inertsil ODS-P) or a polymeric C30 phase (Inertsil C30) provided improved resolution of the isomeric fatty acids (FAs), FA methyl esters (FAMEs), triacylglycerols (TAGs), and tocopherols with an increase in pressure of 20-70MPa in reversed-phase HPLC. With respect to isomeric C18 FAMEs with one cis-double bond, ODS-P phase was effective for recognizing the position of a double bond among petroselinic (methyl 6Z-octadecenoate), oleic (methyl 9Z-octadecenoate), and cis-vaccenic (methyl 11Z-octadecenoate), especially at high pressure, but the differentiation between oleic and cis-vaccenic was not achieved by C30 phase regardless of the pressure. A monomeric C18 phase (InertSustain C18) was not effective for recognizing the position of the double bond in monounsaturated FAME, while the separation of cis- and trans-isomers was achieved by any of the stationary phases. The ODS-P and C30 phases provided increased separation for TAGs and β- and γ-tocopherols at high pressure. The transfer of FA, FAME, or TAG molecules from the mobile phase to the ODS-P stationary phase was accompanied by large volume reduction (-30∼-90mL/mol) resulting in a large increase in retention (up to 100% for an increase of 50MPa) and improved isomer separation at high pressure. For some isomer pairs, the ODS-P and C30 provided the opposite elution order, and in each case higher pressure improved the separation. The two stationary phases showed selectivity for the isomers having rigid structures, but only the ODS-P was effective for differentiating the position of a double bond in monounsaturated FAMEs. The results indicate that the improved isomer separation was provided by the increased dispersion interactions between the solute and the binding site of the stationary phase at high pressure. Copyright © 2014 Elsevier B.V. All rights reserved.

Study of hydrogen bonding in ethanol-water binary solutions by Raman spectroscopy

NASA Astrophysics Data System (ADS)

Li, Fabing; Men, Zhiwei; Li, Shuo; Wang, Shenghan; Li, Zhanlong; Sun, Chenglin

2018-01-01

Raman spectra of ethanol-water binary solutions have been observed at room temperature and atmospheric pressure. We find that with increasing ethanol concentration, the symmetric and asymmetric Osbnd H stretching vibrational mode (3286 and 3434 cm- 1) of water are shifted to lower frequency and the weak shoulder peak at 3615 cm- 1 (free OH) disappears. These results indicate that ethanol strengthens hydrogen bonds in water. Simultaneously, our experiment shows that Raman shifts of ethanol reverses when the volume ratio of ethanol and the overall solution is 0.2, which demonstrates that ethanol-water structure undergoes a phase transition.

Versatile digital micromirror device-based method for the recording of multilevel optical diffractive elements in photosensitive chalcogenide layers (AMTIR-1).

PubMed

Joerg, Alexandre; Vignaux, Mael; Lumeau, Julien

2016-08-01

A new alternative and versatile method for the production of diffractive optical elements (DOEs) with up to four phase levels in AMTIR-1 (Ge₃₃As₁₂Se₅₅) layers is demonstrated. The developed method proposes the use of the photosensitive properties of the layers and a specific in situ optical monitoring coupled with a reverse engineering algorithm to control the trigger points of the writing of the different diffractive patterns. Examples of various volume DOEs are presented.

Interface-induced superconductivity at ∼25 K at ambient pressure in undoped CaFe2As2 single crystals

PubMed Central

Zhao, Kui; Lv, Bing; Deng, Liangzi; Huyan, Shu-Yuan; Xue, Yu-Yi; Chu, Ching-Wu

2016-01-01

Superconductivity has been reversibly induced/suppressed in undoped CaFe2As2 (Ca122) single crystals through proper thermal treatments, with Tc at ∼25 K at ambient pressure and up to 30 K at 1.7 GPa. We found that Ca122 can be stabilized in two distinct tetragonal (T) phases at room temperature and ambient pressure: PI with a nonmagnetic collapsed tetragonal (cT) phase at low temperature and PII with an antiferromagnetic orthorhombic (O) phase at low temperature, depending on the low-temperature annealing condition. Neither phase at ambient pressure is superconducting down to 2 K. However, systematic annealing for different time periods at 350 °C on the as-synthesized crystals, which were obtained by quenching the crystal ingot from 850 °C, reveals the emergence of superconductivity over a narrow time window. Whereas the onset Tc is insensitive to the anneal time, the superconductive volume fraction evolves with the time in a dome-shaped fashion. Detailed X-ray diffraction profile analyses further reveal mesoscopically stacked layers of the PI and the PII phases. The deduced interface density correlates well with the superconducting volume measured. The transport anomalies of the T–cT transition, which is sensitive to lattice strain, and the T–O transition, which is associated with the spin-density-wave (SDW) transition, are gradually suppressed over the superconductive region, presumably due to the interface interactions between the nonmagnetic metallic cT phase and the antiferromagnetic O phase. The results provide the most direct evidence to date for interface-enhanced superconductivity in undoped Ca122, consistent with the recent theoretical prediction. PMID:27799564

Comparison of gamma-oryzanol contents in crude rice bran oils from different sources by various determination methods.

PubMed

Yoshie, Ayano; Kanda, Ayato; Nakamura, Takahiro; Igusa, Hisao; Hara, Setsuko

2009-01-01

Although there are various determination methods for gamma -oryzanol contained in rice bran oil by absorptiometry, normal-phase HPLC, and reversed-phase HPLC, their accuracies and the correlations among them have not been revealed yet. Chloroform-containing mixed solvents are widely used as mobile phases in some HPLC methods, but researchers have been apprehensive about its use in terms of safety for the human body and the environment.In the present study, a simple and accurate determination method was developed by improving the reversed-phase HPLC method. This novel HPLC method uses methanol/acetonitrile/acetic acid (52/45/3 v/v/v), a non-chlorinated solvent, as the mobile phase, and shows an excellent linearity (y = 0.9527x + 0.1241, R(2) = 0.9974) with absorptiometry. The mean relative errors among the existing 3 methods and the novel method, determined by adding fixed amounts of gamma-oryzanol into refined rice salad oil, were -4.7% for the absorptiometry, -6.8% for the existing normal-phase HPLC, +4.6% for the existing reversed-phase HPLC, and -1.6% for the novel reversed-phase HPLC method. gamma -Oryzanol content in 12 kinds of crude rice bran oils obtained from different sources were determined by the four methods. The mean content of those oils were 1.75+/-0.18% for the absorptiometry, 1.29+/-0.11% for the existing normal-phase HPLC, 1.51+/-0.10% for the existing reversed-phase HPLC, and 1.54+/-0.19% for the novel reversed-phase HPLC method.

Mechanistic information from the first volume profile analysis for a reversible intermolecular electron-transfer reaction involving pentaammine(isonicotinamide)ruthenium and cytochrome c

DOE Office of Scientific and Technical Information (OSTI.GOV)

Baensch, B.; Meier, M.; Martinez, P.

1994-10-12

The reversible intermolecular electron-transfer reaction between pentaammine(isonicotinamide)ruthenium(II/III) and horse-heart cytochrome c iron(III/II) was subjected to a detailed kinetic and thermodynamic study as a function of temperature and pressure. Theoretical calculations based on the Marcus-Hush theory were employed to predict all rate and equilibrium constants as well as activation parameters. There is an excellent agreement between the kinetically and thermodynamically determined equilibrium constants and associated pressure parameters. These data are used to construct a volume profile for the overall process, from which it follows that the transition state lies halfway between the reactant and product states on a volume basis. Themore » reorganization in the transition state has reached a similar degree in both directions of the electron-transfer process and corresponds to a {lambda}{sup {double_dagger}} value of 0.44 for this reversible reaction. This is the first complete volume profile analysis for a reversible intermolecular electron-transfer reaction.« less

Phase conjugation and time reversal in acoustics

NASA Astrophysics Data System (ADS)

Fink, Mathias

2000-07-01

This paper compares the different approaches used in acoustics to time reverse or to phase conjugate a wavefield. The basic principle of a time reversal mirror is an extension for broadband pulsed waves to the optical phase conjugated mirror designed for monochromatic waves. However, this equivalence is only valid mathematically and there are some fundamental differences between these two techniques that will be described in this paper.

Supplemental and highly-elevated tocopherol doses differentially regulate allergic inflammation: reversibility of α-tocopherol and γ-tocopherol's effects

PubMed Central

McCary, Christine A.; Abdala-Valencia, Hiam; Berdnikovs, Sergejs; Cook-Mills, Joan M.

2011-01-01

We have reported that supplemental doses of the α- and γ-tocopherol isoforms of vitamin E decrease and increase, respectively, allergic lung inflammation. We have now assessed whether these effects of tocopherols are reversible. For these studies, mice were treated with antigen and supplemental tocopherols in a first phase of treatment followed by a 4 week clearance phase and then the mice received a second phase of antigen and tocopherol treatments. The pro-inflammatory effects of supplemental levels of γ-tocopherol in phase 1 were only partially reversed by supplemental α-tocopherol in phase 2 but were completely reversed by raising α-tocopherol levels 10-fold in phase 2. When γ-tocopherol levels were increased 10-fold (highly-elevated tocopherol) so that the lung tissue γ-tocopherol levels were equal to the lung tissue levels of supplemental α-tocopherol, γ-tocopherol reduced leukocyte numbers in the lung lavage fluid. In contrast to the lung lavage fluid, highly-elevated levels of γ-tocopherol increased inflammation in the lung tissue. These regulatory effects of highly-elevated tocopherols on tissue inflammation and lung lavage fluid were reversible in a second phase of antigen challenge without tocopherols. In summary, the pro-inflammatory effects of supplemental γ-tocopherol on lung inflammation were partially reversed by supplemental levels of α-tocopherol but were completely reversed by highly-elevated-levels of α-tocopherol. Also, highly-elevated levels of γ-tocopherol were inhibitory and reversible in lung lavage but, importantly, were pro-inflammatory in lung tissue sections. These results have implications for future studies with tocopherols and provide a new context in which to review vitamin E studies in the literature. PMID:21317387

Buckling of a circular plate made of a shape memory alloy due to a reverse thermoelastic martensite transformation

NASA Astrophysics Data System (ADS)

Movchan, A. A.; Sil'chenko, L. G.

2008-02-01

We solve the axisymmetric buckling problem for a circular plate made of a shape memory alloy undergoing reverse martensite transformation under the action of a compressing load, which occurs after the direct martensite transformation under the action of a generally different (extending or compressing) load. The problem was solved without any simplifying assumptions concerning the transverse dimension of the supplementary phase transition region related to buckling. The mathematical problem was reduced to a nonlinear eigenvalue problem. An algorithm for solving this problem was proposed. It was shown that the critical buckling load under the reverse transition, which is obtained by taking into account the evolution of the phase strains, can be many times lower than the same quantity obtained under the assumption that the material behavior is elastic even for the least (martensite) values of the elastic moduli. The critical buckling force decreases with increasing modulus of the load applied at the preliminary stage of direct transition and weakly depends on whether this load was extending or compressing. In shape memory alloys (SMA), mutually related processes of strain and direct (from the austenitic into the martensite phase) or reverse thermoelastic phase transitions may occur. The direct transition occurs under cooling and (or) an increase in stresses and is accompanied by a significant decrease (nearly by a factor of three in titan nickelide) of the Young modulus. If the direct transition occurs under the action of stresses with nonzero deviator, then it is accompanied by accumulation of macroscopic phase strains, whose intensity may reach 8%. Under the reverse transition, which occurs under heating and (or) unloading, the moduli increase and the accumulated strain is removed. For plates compressed in their plane, in the case of uniform temperature distribution over the thickness, one can separate trivial processes under which the strained plate remains plane and the phase ratio has a uniform distribution over the thickness. For sufficiently high compressing loads, the trivial process of uniform compression may become unstable in the sense that, for small perturbations of the plate deflection, temperature, the phase ratio, or the load, the difference between the corresponding perturbed process and the unperturbed process may be significant. The results of several experiments concerning the buckling of SMA elements are given in [1, 2], and the statement and solution of the corresponding boundary value problems can be found in [3-11]. The experimental studies [2] and several analytic solutions obtained for the Shanley column [3, 4], rods [5-7], rectangular plates under direct [8] and reverse [9] transitions showed that the processes of thermoelastic phase transitions can significantly (by several times) decrease the critical buckling loads compared with their elastic values calculated for the less rigid martensite state of the material. Moreover, buckling does not occur in the one-phase martensite state in which the elastic moduli are minimal but in the two-phase state in which the values of the volume fractions of the austenitic and martensite phase are approximately equal to each other. This fact is most astonishing for buckling, studied in the present paper, under the reverse transition in which the Young modulus increases approximately half as much from the beginning of the phase transition to the moment of buckling. In [3-9] and in the present paper, the static buckling criterion is used. Following this criterion, the critical load is defined to be the load such that a nontrivial solution of the corresponding quasistatic problem is possible under the action of this load. If, in the problems of stability of rods and SMA plates, small perturbations of the external load are added to small perturbations of the deflection (the critical force is independent of the amplitude of the latter), then the critical forces vary depending on the value of perturbations of the external load [5, 8, 9]. Thus, in the case of small perturbations of the load, the problem of stability of SMA elements becomes indeterminate. The solution of the stability problem for SMA elements also depends on whether the small perturbations of the phase ratio and the phase strain tensor are taken into account. According to this, the problem of stability of SMA elements can be solved in the framework of several statements (concepts, hypotheses) which differ in the set of quantities whose perturbations are admissible (taken into account) in the process of solving the problem. The variety of these statements applied to the problem of buckling of SMA elements under direct martensite transformation is briefly described in [4, 5]. But, in the problem of buckling under the reverse transformation, some of these statements must be changed. The main question which we should answer when solving the problem of stability of SMA elements is whether small perturbations of the phase ratio (the volume fraction of the martensite phase q) are taken into account, because an appropriate choice significantly varies the results of solving the stability problem. If, under the transition to the adjacent form of equilibrium, the phase ratio of all points of the body is assumed to remain the same, then we deal with the "fixed phase atio" concept. The opposite approach can be classified as the "supplementary phase transition" concept (which occurs under the transition to the adjacent form of equilibrium). It should be noted that, since SMA have temperature hysteresis, the phase ratio in SMA can endure only one-sided small variations. But if we deal with buckling under the inverse transformation, then the variation in the volume fraction of the martensite phase cannot be positive. The phase ratio is not an independent variable, like loads or temperature, but, due to the constitutive relations, its variations occur together with the temperature variations and, in the framework of connected models for a majority of SMA, together with variations in the actual stresses. Therefore, the presence or absence of variations in q is determined by the presence or absence of variations in the temperature, deflection, and load, as well as by the system of constitutive relations used in this particular problem. In the framework of unconnected models which do not take the influence of actual stresses on the phase ratio into account, the "fixed phase ratio" concept corresponds to the case of absence of temperature variations. The variations in the phase ratio may also be absent in connected models in the case of specially chosen values of variations in the temperature and (or) in the external load, as well as in the case of SMA of CuMn type, for which the influence of the actual stresses on the phase compound is absent or negligible. In the framework of the "fixed phase ratio" hypothesis, the stability problem for SMA elements has a solution coinciding in form with the solution of the corresponding elastic problem, with the elastic moduli replaced by the corresponding functions of the phase ratio. In the framework of the supplementary phase transition" concept, the result of solving the stability problem essentially depends on whether the small perturbations of the external loads are taken into account in the process of solving the problem. The point is that, when solving the problem in the connected setting, the supplementary phase transition region occupies, in general, not the entire cross-section of the plate but only part of it, and the location of the boundary of this region depends on the existence and the value of these small perturbations. More precisely, the existence of arbitrarily small perturbations of the actual load can result in finite changes of the configuration of the supplementary phase transition region and hence in finite change of the critical values of the load. Here we must distinguish the "fixed load" hypothesis where no perturbations of the external loads are admitted and the "variable load" hypothesis in the opposite case. The conditions that there no variations in the external loads imply additional equations for determining the boundary of the supplementary phase transition region. If the "supplementary phase transition" concept and the "fixed load" concept are used together, then the solution of the stability problem of SMA is uniquely determined in the same sense as the solution of the elastic stability problem under the static approach. In the framework of the "variable load" concept, the result of solving the stability problem for SMA ceases to be unique. But one can find the upper and lower bounds for the critical forces which correspond to the cases of total absence of the supplementary phase transition: the upper bound corresponds to the critical load coinciding with that determined in the framework of the "fixed phase ratio" concept, and the lower bound corresponds to the case where the entire cross-section of the plate experiences the supplementary phase transition. The first version does not need any additional name, and the second version can be called as the "all-round supplementary phase transition" hypothesis. In the present paper, the above concepts are illustrated by examples of solving problems about axisymmetric buckling of a circular freely supported or rigidly fixed plate experiencing reverse martensite transformation under the action of an external force uniformly distributed over the contour. We find analytic solutions in the framework of all the above-listed statements except for the case of free support in the "fixed load" concept, for which we obtain a numerical solution.

Stratigraphy and Melt Compositions of the 3.6 and 6.7 ka Plinian Eruptions of Hudson Volcano, Chile.

NASA Astrophysics Data System (ADS)

Carey, S.; Scasso, R.; Kratzmann, D.; Naranjo, J.; Bande, A.

2005-12-01

Fallout deposits from two major Holocene eruptions of Hudson Volcano in southern Chile (3.6 ka and 6.7 ka BP, Naranjo and Stern, 1998) provide new evidence for multiple phases, including subplinian to plinian discharges and episodes of phreatomagmatic activity. Four phases have been identified for the 3.6 ka eruption. The melt was trachydacitic and did not exhibit any significant variation throughout the fall sequence. Phase one (P1) produced a commonly reverse graded, lapilli fall deposit. Phase two (P2) also produced a reverse graded, coarse lapilli fall layer. Phase three (P3) deposited a massive, poorly-sorted, silty-ash layer with pumice and minor accretionary lapilli. The final phase of the eruption (P4) laid down a commonly normal graded, coarse lapilli fall deposit. Phases P1, P2 and P4 represent fallout from high altitude plumes with minor intensity fluctuations, whereas P3 resulted from magma/water interactions and a lower eruption column. Isopach maps show a shift in the main dispersal axis for the 3.6 ka phreatomagmatic ashfall (P3), relative to the lapilli deposits. Phases 1, 2 and 4 trend generally to the east, whereas the axis for the P3 fallout trends northeast. This is likely caused by dispersal of material at different altitudes during the eruption and not a general change in the predominant wind direction. Three major phases (P1 to P3) were identified for the 6.7 ka eruption. The initial phase (P1) produced a commonly reverse graded, coarse lapilli fall deposit. The second phase (P2) produced a thick, distinctive accretionary lapilli-rich, silty-ash layer with accretionary lapilli diameters up to 2.3 cm at 35 kms from the volcano. The final phase (P3) laid down an often normal graded, coarse lapilli fall unit. The melt phase was also trachydacitic in composition and relatively uniform during the eruption, but less evolved than the magma erupted during the 3.6 ka event. The accretionary lapilli layer (P2) has been correlated with a widespread tephra in southern Patagonia, 900km to the south of Hudson volcano with an estimated bulk volume more than 18 km3 making this one of the largest Holocene eruptions in southern South America (Naranjo et al. 2001). The occurrence of extensive, fine grained accretionary lapilli-bearing beds within these two plinian eruption sequences may be related to magma/meltwater interactions triggered by eruption discharge through the summit glacier of Hudson volcano, probably related to the formation of its last superimposed or partially nested caldera (Orihashi et al., 2004).

Simultaneous Determination of Procainamide and N-acetylprocainamide in Rat Plasma by Ultra-High-Pressure Liquid Chromatography Coupled with a Diode Array Detector and Its Application to a Pharmacokinetic Study in Rats.

PubMed

Balla, Anusha; Cho, Kwan Hyung; Kim, Yu Chul; Maeng, Han-Joo

2018-03-30

A simple, sensitive, and reliable reversed-phase, Ultra-High-Pressure Liquid Chromatography (UHPLC) coupled with a Diode Array Detector (DAD) method for the simultaneous determination of Procainamide (PA) and its major metabolite, N -acetylprocainamide (NAPA), in rat plasma was developed and validated. A simple deproteinization method with methanol was applied to the rat plasma samples, which were analyzed using UHPLC equipped with DAD at 280 nm, and a Synergi™ 4 µm polar, reversed-phase column using 1% acetic acid (pH 5.5) and methanol (76:24, v / v ) as eluent in isocratic mode at a flow rate 0.2 mL/min. The method showed good linearity ( r ² > 0.998) over the concentration range of 20-100,000 and 20-10,000 ng/mL for PA and NAPA, respectively. Intra- and inter-day accuracies ranged from 97.7 to 110.9%, and precision was <10.5% for PA and 99.7 to 109.2 and <10.5%, respectively, for NAPA. The lower limit of quantification was 20 ng/mL for both compounds. This is the first report of the UHPLC-DAD bioanalytical method for simultaneous measurement of PA and NAPA. The most obvious advantage of this method over previously reported HPLC methods is that it requires small sample and injection volumes, with a straightforward, one-step sample preparation. It overcomes the limitations of previous methods, which use large sample volume and complex sample preparation. The devised method was successfully applied to the quantification of PA and NAPA after an intravenous bolus administration of 10 mg/kg procainamide hydrochloride to rats.

Interface Promoted Reversible Mg Insertion in Nanostructured Tin-Antimony Alloys

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cheng, Yingwen; Shao, Yuyan; Parent, Lucas R.

This paper demonstrates intermetallic compounds SnSb are highly active materials for reversibly hosting Mg ions. Compared with monometallic Sn and Sb, SnSb alloy exhibited exceptionally high reversible capacity (420 mAh/g), excellent rate capability and good cyclic stability. Mg insertion into pristine SnSb involves an activation process to complete, which induces particle breakdown and results in phase segregation to Sn-rich and Sb-rich phases. Both experimental analysis and DFT simulation suggest that the Sn-rich phase is particularly active and provides most of the capacity whereas the Sb-rich phase is not as active, and the interface between these two phases play a keymore » role in promoting the formation and stabilization of the cubic Sn phase that is more favorable for fast and reversible Mg insertion. We further show that activated SnSb alloy has good compatibility with simple Mg electrolytes. Overall, this work could provide new approaches for designing materials capable of reversible Mg ion insertion and new opportunities for understanding Mg electrochemistry.« less

[Influences of ion-suppressors on retention behaviors of nine food additives in reversed-phase high performance liquid chromatographic separation].

PubMed

Zhao, Yonggang; Chen, Xiaohong; Li, Xiaoping; Yao, Shanshan; Jin, Micong

2011-10-01

The influences of ion-suppressors on retention behaviors of nine food additives, i.e., acesulfame, saccharin, caffeine, aspartame, benzoic acid, sorbic acid, stevioside, dehydroacetic acid and neotame in reversed-phase high performance liquid chromatographic (RP-HPLC) separation were investigated. The organic modification effects of acids, i. e. , trifluoroacetic acid (TFA) and buffer salts, i. e. , TFA-ammonium acetate (AmAc) were studied emphatically. The relationships between retention factors of solutes and volume percentages of ion-suppressors in the mobile phase systems of acetonitrile-TFA aqueous solution and acetonitrile-TFA-AmAc aqueous solution were quantitatively established, separately. The separation of nine food additives was completed by a gradient elution with acetonitrile-TFA (0.01%, v/v)-AmAc (2. 5 mmol/L) aqueous solution as the mobile phases. An RP-HPLC method was established for the simultaneous determination of nine food additives in red wine. In the range of 10. 0 - 100. 0 mg/L, nine food additives showed good linearity with the correlation coefficients ( r2 ) larger than 0. 999 1. The limits of detection (LODs) were in the range of 0. 33 - 2. 36 mg/L and the limits of quantification (LOQs) were in the range of 1. 11 - 7. 80 mg/L. The spiked recoveries were between 87. 61% and 108. 4% with the relative standard deviations (RSDs) of 2. 2% -9. 4%. These results are of referential significance for the rapid establishment and accu- rate optimization of RP-HPLC separation for the simultaneous determination of food additives in other foods.

Analysis of nine food additives in red wine by ion-suppression reversed-phase high-performance liquid chromatography using trifluoroacetic acid and ammonium acetate as ion-suppressors.

PubMed

Zhao, Yong-Gang; Chen, Xiao-Hong; Yao, Shan-Shan; Pan, Sheng-Dong; Li, Xiao-Ping; Jin, Mi-Cong

2012-01-01

A reversed-phase high-performance liquid chromatography (RP-HPLC) method was developed for the simultaneous determination of nine food additives, i.e., acesulfame, saccharin, caffeine, aspartame, benzoic acid, sorbic acid, stevioside, dehydroacetic acid and neotame in red wine. The effects of ion-suppressors, i.e., trifluoroacetic acid (TFA) and ammonium acetate (AmAc) on retention behavior of nine food additives in RP-HPLC separation were discussed in detail. The relationships between retention factors of solutes and volume percent of ion-suppressors in the mobile-phase systems of acetonitrile-TFA aqueous solution and acetonitrile-TFA-AmAc aqueous solution were quantitatively established, respectively. The results showed that the ion suppressors had not only an ion suppression effect, but also an organic modification effect on the acidic analytes. The baseline separation of nine food additives was completed by a gradient elution with acetonitrile-TFA(0.01%, v/v)-AmAc(2.5 mmol L(-1)) aqueous solution as the mobile phase. The recoveries were between 80.2 - 99.5% for all analytes with RSDs in the range of 1.5 - 8.9%. The linearities were in the range of 0.2 - 100.0 mg L(-1) with determination coefficients (r(2)) higher than 0.9991 for all analytes. The limits of quantification (LOQs) were between 0.53 - 0.99 mg L(-1). The applicability of the proposed method to detect and quantify food additives has been demonstrated in the analysis of 30 real samples.

A sensitive microextraction by packed sorbent-based methodology combined with ultra-high pressure liquid chromatography as a powerful technique for analysis of biologically active flavonols in wines.

PubMed

Silva, Catarina L; Gonçalves, João L; Câmara, José S

2012-08-20

A new approach based on microextraction by packed sorbent (MEPS) and reversed-phase high-throughput ultra high pressure liquid chromatography (UHPLC) method that uses a gradient elution and diode array detection to quantitate three biologically active flavonols in wines, myricetin, quercetin, and kaempferol, is described. In addition to performing routine experiments to establish the validity of the assay to internationally accepted criteria (selectivity, linearity, sensitivity, precision, accuracy), experiments are included to assess the effect of the important experimental parameters such as the type of sorbent material (C2, C8, C18, SIL, and C8/SCX), number of extraction cycles (extract-discard), elution volume, sample volume, and ethanol content, on the MEPS performance. The optimal conditions of MEPS extraction were obtained using C8 sorbent and small sample volumes (250μL) in five extraction cycle and in a short time period (about 5min for the entire sample preparation step). Under optimized conditions, excellent linearity (R(values)(2)>0.9963), limits of detection of 0.006μgmL(-1) (quercetin) to 0.013μgmL(-1) (myricetin) and precision within 0.5-3.1% were observed for the target flavonols. The average recoveries of myricetin, quercetin and kaempferol for real samples were 83.0-97.7% with relative standard deviation (RSD, %) lower than 1.6%. The results obtained showed that the most abundant flavonol in the analyzed samples was myricetin (5.8±3.7μgmL(-1)). Quercetin (0.97±0.41μgmL(-1)) and kaempferol (0.66±0.24μgmL(-1)) were found in a lower concentration. The optimized MEPS(C8) method was compared with a reverse-phase solid-phase extraction (SPE) procedure using as sorbent a macroporous copolymer made from a balanced ratio of two monomers, the lipophilic divinylbenzene and the hydrophilic N-vinylpyrrolidone (Oasis HLB) were used as reference. MEPS(C8) approach offers an attractive alternative for analysis of flavonols in wines, providing a number of advantages including highest extraction efficiency (from 85.9±0.9% to 92.1±0.5%) in the shortest extraction time with low solvent consumption, fast sample throughput, more environmentally friendly and easy to perform. Copyright © 2012 Elsevier B.V. All rights reserved.

Stability Indicating HPLC Method for the Determination of Chiral Purity of R-(-)-5-[2-aminopropyl]-2-methoxybenzene Sulfonamide.

PubMed

Kasawar, G B; Farooqui, M N

2009-09-01

A chiral reverse phase liquid chromatographic method was developed for the enantiomeric resolution of racemic mixture of (-)-5-[2-aminopropyl]-2-methoxybenzene sulfonamide in bulk drug. The enantiomeric separation of sulfonamide was resolved on a Crownpak CR (+) column using perchloric acid buffer of pH 1.0 as mobile phase and with UV detection at 226 nm. The method is validated and proved to be robust. The limit of detection and quantification of S (-)-(5)-[2-aminopropyl]-2-methoxybenzene sulfonamide] was found to be 0.084 and 0.159 mug/ml, respectively for 20 mul injection volume. The percentage recovery of S (-)-(5)-[2-aminopropyl]-2-methoxybenzene sulfonamide] ranged from 99.57 to 101.88 in bulk drug samples of R (-)-(5)-[2- aminopropyl]-2-methoxybenzene sulfonamide].

Stability Indicating HPLC Method for the Determination of Chiral Purity of R-(-)-5-[2-aminopropyl]-2-methoxybenzene Sulfonamide

PubMed Central

Kasawar, G. B.; Farooqui, M. N.

2009-01-01

A chiral reverse phase liquid chromatographic method was developed for the enantiomeric resolution of racemic mixture of (-)-5-[2-aminopropyl]-2-methoxybenzene sulfonamide in bulk drug. The enantiomeric separation of sulfonamide was resolved on a Crownpak CR (+) column using perchloric acid buffer of pH 1.0 as mobile phase and with UV detection at 226 nm. The method is validated and proved to be robust. The limit of detection and quantification of S (-)-(5)-[2-aminopropyl]-2-methoxybenzene sulfonamide] was found to be 0.084 and 0.159 μg/ml, respectively for 20 μl injection volume. The percentage recovery of S (-)-(5)-[2-aminopropyl]-2-methoxybenzene sulfonamide] ranged from 99.57 to 101.88 in bulk drug samples of R (-)-(5)-[2- aminopropyl]-2-methoxybenzene sulfonamide]. PMID:20502572

Simulation of semi-explicit mechanisms of SOA formation from glyoxal in a 3-D model

NASA Astrophysics Data System (ADS)

Knote, C.; Hodzic, A.; Jimenez, J. L.; Volkamer, R.; Orlando, J. J.; Baidar, S.; Brioude, J.; Fast, J.; Gentner, D. R.; Goldstein, A. H.; Hayes, P. L.; Knighton, W. B.; Oetjen, H.; Setyan, A.; Stark, H.; Thalman, R.; Tyndall, G.; Washenfelder, R.; Waxman, E.; Zhang, Q.

2013-10-01

New pathways to form secondary organic aerosols (SOA) have been postulated recently. Glyoxal, the smallest dicarbonyl, is one of the proposed precursors. It has both anthropogenic and biogenic sources, and readily partitions into the aqueous-phase of cloud droplets and deliquesced aerosols where it undergoes both reversible and irreversible chemistry. In this work we extend the regional scale chemistry transport model WRF-Chem to include a detailed gas-phase chemistry of glyoxal formation as well as a state-of-the-science module describing its partitioning and reactions in the aqueous-phase of aerosols. A comparison of several proposed mechanisms is performed to quantify the relative importance of different formation pathways and their regional variability. The CARES/CalNex campaigns over California in summer 2010 are used as case studies to evaluate the model against observations. In all simulations the LA basin was found to be the hotspot for SOA formation from glyoxal, which contributes between 1% and 15% of the model SOA depending on the mechanism used. Our results indicate that a mechanism based only on a simple uptake coefficient, as frequently employed in global modeling studies, leads to higher SOA contributions from glyoxal compared to a more detailed description that considers aerosol phase state and chemical composition. In the more detailed simulations, surface uptake is found to be the main contributor to SOA mass compared to a volume process and reversible formation. We find that contribution of the latter is limited by the availability of glyoxal in aerosol water, which is in turn controlled by an increase in the Henry's law constant depending on salt concentrations ("salting-in"). A kinetic limitation in this increase prevents substantial partitioning of glyoxal into aerosol water at high salt concentrations. If this limitation is removed, volume pathways contribute >20% of glyoxal SOA mass, and the total mass formed (5.8% of total SOA in the LA basin) is about a third of the simple uptake coefficient formulation without consideration of aerosol phase state and composition. All these model formulations are based on very limited and recent field or laboratory data and we conclude that the current uncertainty on glyoxal SOA formation spans a factor of 10 in this domain and time period.

Superelasticity and cryogenic linear shape memory effects of CaFe 2As 2

DOE PAGES

Sypek, John T.; Yu, Hang; Dusoe, Keith J.; ...

2017-10-20

Shape memory materials have the ability to recover their original shape after a significant amount of deformation when they are subjected to certain stimuli, for instance, heat or magnetic fields. But, their performance is often limited by the energetics and geometry of the martensitic-austenitic phase transformation. We report a unique shape memory behavior in CaFe 2As 2, which exhibits superelasticity with over 13% recoverable strain, over 3 GPa yield strength, repeatable stress–strain response even at the micrometer scale, and cryogenic linear shape memory effects near 50 K. These properties are acheived through a reversible uni-axial phase transformation mechanism, the tetragonal/orthorhombic-to-collapsed-tetragonalmore » phase transformation. These results offer the possibility of developing cryogenic linear actuation technologies with a high precision and high actuation power per unit volume for deep space exploration, and more broadly, suggest a mechanistic path to a class of shape memory materials, ThCr 2Si 2-structured intermetallic compounds.« less

Synthesis of the new compound CaFe(CO 3) 2 and experimental constraints on the (Ca,Fe)CO 3 join

NASA Astrophysics Data System (ADS)

Davidson, Paula M.; Symmes, Gregory H.; Cohen, Barbara A.; Reeder, Richard J.; Lindsley, Donald H.

1993-12-01

Synthesis of the new (disordered) compound CaFe(CO 3) 2 has been achieved with the use of Fe-substituted CaCO 3(Cc ss) + Ca-substituted FeCO 3(Sid ss) as starting materials, and high CO 2 pressures. High pressure (20-30 kbar) is needed to stabilize FeCO 3 to sufficiently high temperatures for disordered CaFe(CO 3) 2 to form. Experiments provide reversed compositions of coexisting disordered phases in the CaFe join and locate the solvus temperature for CaFe(C) 3) 2 between 815 and 845°C at 30 kbars. Calculated phase relations predict that the stability of ordered CaFe(CO 3) 2 is limited to T < ˜450°C by the breakdown to Cc ss + Sid ss. A comparison of the unit-cell volume measured for disordered CaFe(CO 3) 2 vs. that estimated for ordered CaFe(CO 3) 2 suggests that increasing pressure stabilizes the disordered phase.

Low temperature synthesis of monolithic transparent Ta2O5 gels from hydrolysis of metal alkoxide

NASA Technical Reports Server (NTRS)

Bansal, Narottam P.

1993-01-01

Tantalum oxide gels in the form of transparent monoliths and powder were prepared from hydrolysis of tantalum pentaethoxide under controlled conditions using different mole ratios of Ta(OC2H5)5:C2H50H:H20:HCl. Alcohol acts as the mutual solvent and HCl as the deflocculating agent. For a fixed alkoxide:water:HCl ratio, time of gel formation increased with the alcohol to alkoxide mole ratio. Thermal evolution of the physical and structural changes in the gel was monitored by differential thermal analysis, thermogravimetric analysis, x-ray diffraction, and infrared spectroscopy. On heating to approximately 400 C, the amorphous gel crystallized into the low temperature orthorhombic phase Beta-Ta2O5, which transformed into the high temperature tetragonal phase Alpha-Ta2O5 when further heated to approximately 1450 C. The volume fraction of the crystalline phase increased with the firing temperature. The Alpha-Ta205 converted back into the low temperature phase, Beta-Ta2O5, on slow cooling through the transformation temperature of 1360 C indicating a slow but reversible transformation.

High pressure studies of A2Mo3O12 negative thermal expansion materials (A2=Al2, Fe2, FeAl, AlGa)

NASA Astrophysics Data System (ADS)

Young, Lindsay; Gadient, Jennifer; Gao, Xiaodong; Lind, Cora

2016-05-01

High pressure powder X-ray diffraction studies of several A2Mo3O12 materials (A2=Al2, Fe2, FeAl, and AlGa) were conducted up to 6-7 GPa. All materials adopted a monoclinic structure under ambient conditions, and displayed similar phase transition behavior upon compression. The initial isotropic compressibility first became anisotropic, followed by a small but distinct drop in cell volume. These patterns could be described by a distorted variant of the ambient pressure polymorph. At higher pressures, a distinct high pressure phase formed. Indexing results confirmed that all materials adopted the same high pressure phase. All changes were reversible on decompression, although some hysteresis was observed. The similarity of the high pressure cells to previously reported Ga2Mo3O12 suggested that this material undergoes the same sequence of transitions as all materials investigated in this paper. It was found that the transition pressures for all phase changes increased with decreasing radius of the A-site cations.

Effect of first dimension phase selectivity in online comprehensive two dimensional liquid chromatography (LC × LC)

PubMed Central

Gu, Haiwei; Huang, Yuan; Filgueira, Marcelo; Carr, Peter W.

2012-01-01

In this study, we examined the effect of first dimension column selectivity in reversed phase (RP) online comprehensive two dimensional liquid chromatography (LC × LC). The second dimension was always a carbon clad metal oxide reversed phase material. The hydrophobic subtraction model (HSM) and the related phase selective triangles were used to guide the selection of six different RP first dimension columns. Various kinds of samples were investigated and thus two different elution conditions were needed to cause full elution from the first dimension columns. We compared LC × LC chromatograms, contours plots, and fcoverage plots by measuring peak capacities, peak numbers, relative spatial coverage, correlation values, etc. The major finding of this study is that the carbon phase due to its rather different selectivity from other reversed phases is reasonably orthogonal to a variety of common types of bonded reversed phases. Thus quite surprisingly the six different first dimension stationary phases all showed generally similar separation patterns when paired to the second dimension carbon phase. This result greatly simplifies the task of choosing the correct pair of phases for RP × RP. PMID:21840009

Reversible Li-ion conversion reaction for a Ti xGe alloy in a Ti/Ge multilayer

DOE PAGES

Chen, Xiao; Fister, Tim T.; Esbenshade, Jennifer; ...

2017-02-13

Group IV inter-metallics electrochemically alloy with Li with stoichiometries as high as Li 4.4M (M=Si, Ge, Sn or Pb). Furthermore, this provides the second highest known specific capacity (after pure lithium metal) for lithium ion batteries, but the dramatic volume change during cycling greatly limits their use as anodes in Li-ion batteries. We describe an approach to overcome this limitation by constructing electrodes using a Ge/Ti multilayer architecture. In operando X-ray reflectivity and ex situ transmission electron microscopy are used to characterize the hetero-layer structure at various lithium stoichiometries along a lithiation/delithiation cycle. The as-deposited multilayer spontaneously forms a one-dimensionalmore » Ti xGe/Ti/Ti xGe core-shell planar structure embedded in a Ge matrix. The interfacial Ti xGe alloy is observed to be electrochemically active and exhibits reversible phase separation (i.e. a conversion reaction). Including the germanium components, the overall multilayer structure exhibits a 2.3-fold reversible vertical expansion and contraction and is shown to have improved capacity and capacity retention with respect to a Ge film with equivalent active material thickness.« less

Reversible Li-Ion Conversion Reaction for a TixGe Alloy in a Ti/Ge Multilayer.

PubMed

Chen, Xiao; Fister, Tim T; Esbenshade, Jennifer; Shi, Bing; Hu, Xianyi; Wu, Jinsong; Gewirth, Andrew A; Bedzyk, Michael J; Fenter, Paul

2017-03-08

Group IV intermetallics electrochemically alloy with Li with stoichiometries as high as Li 4.4 M (M = Si, Ge, Sn, or Pb). This provides the second highest known specific capacity (after pure lithium metal) for lithium-ion batteries, but the dramatic volume change during cycling greatly limits their use as anodes in Li-ion batteries. We describe an approach to overcome this limitation by constructing electrodes using a Ge/Ti multilayer architecture. In operando X-ray reflectivity and ex situ transmission electron microscopy are used to characterize the heterolayer structure at various lithium stoichiometries along a lithiation/delithiation cycle. The as-deposited multilayer spontaneously forms a one-dimensional Ti x Ge/Ti/Ti x Ge core-shell planar structure embedded in a Ge matrix. The interfacial Ti x Ge alloy is observed to be electrochemically active and exhibits reversible phase separation (i.e., a conversion reaction). Including the germanium components, the overall multilayer structure exhibits a 2.3-fold reversible vertical expansion and contraction and is shown to have improved capacity and capacity retention with respect to a Ge film with equivalent active material thickness.

Capillary liquid chromatography combined with pressurized liquid extraction and dispersive liquid-liquid microextraction for the determination of vitamin E in cosmetic products.

PubMed

Viñas, Pilar; Pastor-Belda, Marta; Campillo, Natalia; Bravo-Bravo, María; Hernández-Córdoba, Manuel

2014-06-01

Capillary liquid chromatography (LC) is used for the determination of tocopherols and tocotrienols in cosmetic products. Dispersive liquid-liquid microextraction (DLLME) allows the analytes to be preconcentrated into a very small volume of organic solvent which is then injected into the chromatograph running at a very low flow rate. Pressurized liquid extraction (PLE) at a high temperature and pressure was used to isolate vitamin E forms from cosmetics. The Taguchi experimental method was used to optimize the factors affecting DLLME. The parameters selected were 2mL of acetonitrile (disperser solvent), 100μL carbon tetrachloride (extraction solvent) and 10mL aqueous solution. A volume of 5μL of the organic phase was injected into the reversed-phase capillary LC system equipped with a diode array detector and using an isocratic mobile phase composed of an 95:5 (v/v) methanol:water mixture at a flow-rate of 20μLmin(-1). Quantification was carried out using aqueous standards and detection limits were in the range 0.1-0.5ngmL(-1), corresponding to 3-15ngg(-1) in the cosmetic sample. The recoveries were in the 87-105% range, with RSDs lower than 7.8%. The method was validated according to international guidelines and using a certified reference material. Copyright © 2014 Elsevier B.V. All rights reserved.

Separation and purification of hydrolyzable tannin from Geranium wilfordii Maxim by reversed-phase and normal-phase high-speed counter-current chromatography.

PubMed

Liu, Dan; Su, Zhiguo; Wang, Changhai; Gu, Ming; Xing, Siliang

2010-08-01

Three hydrolyzable tannins, geraniin, corilagin and gallic acid, main active components of Geranium wilfordii Maxim, have been separated and purified in one-step by both reversed-phase and normal-phase high-speed counter-current chromatography. Gallic acid, corilagin and geraniin were purified from 70% aqueous acetone extract of G. wilfordii Maxim with solvent system n-hexane-ethyl acetate-methanol-acetic acid-water (1:10:0.2:0.2:20) by reversed-phase high-speed counter-current chromatography at purities of 94.2, 91.0 and 91.3%, at yields of 89.3, 82.9 and 91.7%, respectively. Gallic acid, corilagin and geraniin were purified with solvent system n-hexane-ethyl acetate-methanol-acetic acid-water (0.2:10:2:1:5) by normal-phase high-speed counter-current chromatography at purities of 85.9, 92.2 and 87.6%, at yields of 87.4, 94.6 and 94.3%, respectively. It was successful for both reversed-phase and normal-phase high-speed counter-current chromatography to separate high-polarity of low-molecular-weight substances.

Effects of digital phase-conjugate light intensity on time-reversal imaging through animal tissue.

PubMed

Toda, Sogo; Kato, Yuji; Kudo, Nobuki; Shimizu, Koichi

2018-04-01

For transillumination imaging of animal tissues, we have attempted to suppress the scattering effect in a turbid medium using the time-reversal principle of phase-conjugate light. We constructed a digital phase-conjugate system to enable intensity modulation and phase modulation. Using this system, we clarified the effectiveness of the intensity information for restoration of the original light distribution through a turbid medium. By varying the scattering coefficient of the medium, we clarified the limit of time-reversal ability with intensity information of the phase-conjugate light. Experiment results demonstrated the applicability of the proposed technique to animal tissue.

Employing Extracellular Volume Cardiovascular Magnetic Resonance Measures of Myocardial Fibrosis to Foster Novel Therapeutics.

PubMed

Schelbert, Erik B; Sabbah, Hani N; Butler, Javed; Gheorghiade, Mihai

2017-06-01

Quantifying myocardial fibrosis (MF) with myocardial extracellular volume measures acquired during cardiovascular magnetic resonance promises to transform clinical care by advancing pathophysiologic understanding and fostering novel therapeutics. Extracellular volume quantifies MF by measuring the extracellular compartment depicted by the myocardial uptake of contrast relative to plasma. MF is a key domain of dysfunctional but viable myocardium among others (eg, microvascular dysfunction and cardiomyocyte/mitochondrial dysfunction). Although anatomically distinct, these domains may functionally interact. MF represents pathological remodeling in the heart associated with cardiac dysfunction and adverse outcomes likely mediated by interactions with the microvasculature and the cardiomyocyte. Reversal of MF improves key measures of cardiac dysfunction, so reversal of MF represents a likely mechanism for improved outcomes. Instead of characterizing the myocardium as homogenous tissue and using important yet still generic descriptors, such as thickness (hypertrophy) and function (diastolic or systolic), which lack mechanistic specificity, paradigms of cardiac disease have evolved to conceptualize myocardial disease and patient vulnerability based on the extent of disease involving its various compartments. Specifying myocardial compartmental involvement may then implicate cellular/molecular disease pathways for treatment and targeted pharmaceutical development and above all highlight the role of the cardiac-specific pathology in heart failure among myriad other changes in the heart and beyond. The cardiology community now requires phase 2 and 3 clinical trials to examine strategies for the regression/prevention of MF and eventually biomarkers to identify MF without reliance on cardiovascular magnetic resonance. It seems likely that efficacious antifibrotic therapy will improve outcomes, but definitive data are needed. © 2017 American Heart Association, Inc.

[Simultaneous determination of principal components and related substances of raw material drug of ammonium glycyrrhizinate by reversed-phase high performance liquid chromatography].

PubMed

Zhao, Yanyan; Liu, Liyan; Han, Yuanyuan; Li, Yueqiu; Wang, Yan; Shi, Minjian

2013-09-01

An analytical method for the simultaneous determination of 18alpha-glycyrrhizic acid, 18beta-glycyrrhizinic acid, related substances A and B and drug quality standard by reversed-phase high performance liquid chromatography (RP-HPLC) was established. The assay was carried out on a Durashell-C18 column (250 mm x 4.6 mm, 5 microm) with 10 mmol/L ammonium perchlorate (the pH value was adjusted to 8.20 with ammonia)-methanol (48:52, v/v) as mobile phase at a flow rate of 0.80 mL/min, and the detection wavelength was set at 254 nm. The column temperature was 50 degrees C and the injection volume was 10 microL. Under the separation conditions, the calibration curves of the analytes showed good linearities within the mass concentrations of 0.50 -100 mg/L (r > 0.999 9). The detection limits for 18alpha-glycyrrhizic acid, 18beta-glycyrrhizinic acid, related substances A and B were 0.15, 0.10, 0.10, 0.15 mg/L, respectively. The average recoveries were between 97.32% and 99.33% (n = 3) with the relative standard deviations (RSDs) between 0.05% and 1.06%. The method is sensitive, reproducible, and the results are accurate and reliable. The method can be used for the determination of principal components and related substances of ammonium glycyrrhizinate for the quality control of raw material drug of ammonium glycyrrhizinate.

RF model of the distribution system as a communication channel, phase 2. Volume 1: Summary Report

NASA Technical Reports Server (NTRS)

Rustay, R. C.; Gajjar, J. T.; Rankin, R. W.; Wentz, R. C.; Wooding, R.

1982-01-01

The design, implementation, and verification of a computerized model for predicting the steady-state sinusoidal response of radial (tree) configured distribution feeders was undertaken. That work demonstrated the feasibility and validity based on verification measurements made on a limited size portion of an actual live feeder. On that basis a follow-on effort concerned with (1) extending the verification based on a greater variety of situations and network size, (2) extending the model capabilities for reverse direction propagation, (3) investigating parameter sensitivities, (4) improving transformer models, and (5) investigating procedures/fixes for ameliorating propagation trouble spots was conducted. Results are summarized.

High-performance liquid chromatographic method for guanylhydrazone compounds.

PubMed

Cerami, C; Zhang, X; Ulrich, P; Bianchi, M; Tracey, K J; Berger, B J

1996-01-12

A high-performance liquid chromatographic method has been developed for a series of aromatic guanylhydrazones that have demonstrated therapeutic potential as anti-inflammatory agents. The compounds were separated using octadecyl or diisopropyloctyl reversed-phase columns, with an acetonitrile gradient in water containing heptane sulfonate, tetramethylammonium chloride, and phosphoric acid. The method was used to reliably quantify levels of analyte as low as 785 ng/ml, and the detector response was linear to at least 50 micrograms/ml using a 100 microliters injection volume. The assay system was used to determine the basic pharmacokinetics of a lead compound, CNI-1493, from serum concentrations following a single intravenous injection in rats.

Sex differences in retention after a visual or a spatial discrimination learning task in brood parasitic shiny cowbirds.

PubMed

Astié, Andrea A; Scardamaglia, Romina C; Muzio, Rubén N; Reboreda, Juan C

2015-10-01

Females of avian brood parasites, like the shiny cowbird (Molothrus bonariensis), locate host nests and on subsequent days return to parasitize them. This ecological pressure for remembering the precise location of multiple host nests may have selected for superior spatial memory abilities. We tested the hypothesis that shiny cowbirds show sex differences in spatial memory abilities associated with sex differences in host nest searching behavior and relative hippocampus volume. We evaluated sex differences during acquisition, reversal and retention after extinction in a visual and a spatial discrimination learning task. Contrary to our prediction, females did not outperform males in the spatial task in either the acquisition or the reversal phases. Similarly, there were no sex differences in either phase in the visual task. During extinction, in both tasks the retention of females was significantly higher than expected by chance up to 50 days after the last rewarded session (∼85-90% of the trials with correct responses), but the performance of males at that time did not differ than that expected by chance. This last result shows a long-term memory capacity of female shiny cowbirds, which were able to remember information learned using either spatial or visual cues after a long retention interval. Copyright © 2015 Elsevier B.V. All rights reserved.

Prediction of the retention of s-triazines in reversed-phase high-performance liquid chromatography under linear gradient-elution conditions.

PubMed

D'Archivio, Angelo Antonio; Maggi, Maria Anna; Ruggieri, Fabrizio

2014-08-01

In this paper, a multilayer artificial neural network is used to model simultaneously the effect of solute structure and eluent concentration profile on the retention of s-triazines in reversed-phase high-performance liquid chromatography under linear gradient elution. The retention data of 24 triazines, including common herbicides and their metabolites, are collected under 13 different elution modes, covering the following experimental domain: starting acetonitrile volume fraction ranging between 40 and 60% and gradient slope ranging between 0 and 1% acetonitrile/min. The gradient parameters together with five selected molecular descriptors, identified by quantitative structure-retention relationship modelling applied to individual separation conditions, are the network inputs. Predictive performance of this model is evaluated on six external triazines and four unseen separation conditions. For comparison, retention of triazines is modelled by both quantitative structure-retention relationships and response surface methodology, which describe separately the effect of molecular structure and gradient parameters on the retention. Although applied to a wider variable domain, the network provides a performance comparable to that of the above "local" models and retention times of triazines are modelled with accuracy generally better than 7%. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Predicting Retention Times of Naturally Occurring Phenolic Compounds in Reversed-Phase Liquid Chromatography: A Quantitative Structure-Retention Relationship (QSRR) Approach

PubMed Central

Akbar, Jamshed; Iqbal, Shahid; Batool, Fozia; Karim, Abdul; Chan, Kim Wei

2012-01-01

Quantitative structure-retention relationships (QSRRs) have successfully been developed for naturally occurring phenolic compounds in a reversed-phase liquid chromatographic (RPLC) system. A total of 1519 descriptors were calculated from the optimized structures of the molecules using MOPAC2009 and DRAGON softwares. The data set of 39 molecules was divided into training and external validation sets. For feature selection and mapping we used step-wise multiple linear regression (SMLR), unsupervised forward selection followed by step-wise multiple linear regression (UFS-SMLR) and artificial neural networks (ANN). Stable and robust models with significant predictive abilities in terms of validation statistics were obtained with negation of any chance correlation. ANN models were found better than remaining two approaches. HNar, IDM, Mp, GATS2v, DISP and 3D-MoRSE (signals 22, 28 and 32) descriptors based on van der Waals volume, electronegativity, mass and polarizability, at atomic level, were found to have significant effects on the retention times. The possible implications of these descriptors in RPLC have been discussed. All the models are proven to be quite able to predict the retention times of phenolic compounds and have shown remarkable validation, robustness, stability and predictive performance. PMID:23203132

Pressure, temperature, and electric field dependence of phase transformations in niobium modified 95/5 lead zirconate titanate

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dong, Wen D.; Carlos Valadez, J.; Gallagher, John A.

2015-06-28

Ceramic niobium modified 95/5 lead zirconate-lead titanate (PZT) undergoes a pressure induced ferroelectric to antiferroelectric phase transformation accompanied by an elimination of polarization and a volume reduction. Electric field and temperature drive the reverse transformation from the antiferroelectric to ferroelectric phase. The phase transformation was monitored under pressure, temperature, and electric field loading. Pressures and temperatures were varied in discrete steps from 0 MPa to 500 MPa and 25 °C to 125 °C, respectively. Cyclic bipolar electric fields were applied with peak amplitudes of up to 6 MV m{sup −1} at each pressure and temperature combination. The resulting electric displacement–electric field hysteresis loops weremore » open “D” shaped at low pressure, characteristic of soft ferroelectric PZT. Just below the phase transformation pressure, the hysteresis loops took on an “S” shape, which split into a double hysteresis loop just above the phase transformation pressure. Far above the phase transformation pressure, when the applied electric field is insufficient to drive an antiferroelectric to ferroelectric phase transformation, the hysteresis loops collapse to linear dielectric behavior. Phase stability maps were generated from the experimental data at each of the temperature steps and used to form a three dimensional pressure–temperature–electric field phase diagram.« less

Issues in measure-preserving three dimensional flow integrators: Self-adjointness, reversibility, and non-uniform time stepping

DOE Office of Scientific and Technical Information (OSTI.GOV)

Finn, John M., E-mail: finn@lanl.gov

2015-03-15

Properties of integration schemes for solenoidal fields in three dimensions are studied, with a focus on integrating magnetic field lines in a plasma using adaptive time stepping. It is shown that implicit midpoint (IM) and a scheme we call three-dimensional leapfrog (LF) can do a good job (in the sense of preserving KAM tori) of integrating fields that are reversible, or (for LF) have a “special divergence-free” (SDF) property. We review the notion of a self-adjoint scheme, showing that such schemes are at least second order accurate and can always be formed by composing an arbitrary scheme with its adjoint.more » We also review the concept of reversibility, showing that a reversible but not exactly volume-preserving scheme can lead to a fractal invariant measure in a chaotic region, although this property may not often be observable. We also show numerical results indicating that the IM and LF schemes can fail to preserve KAM tori when the reversibility property (and the SDF property for LF) of the field is broken. We discuss extensions to measure preserving flows, the integration of magnetic field lines in a plasma and the integration of rays for several plasma waves. The main new result of this paper relates to non-uniform time stepping for volume-preserving flows. We investigate two potential schemes, both based on the general method of Feng and Shang [Numer. Math. 71, 451 (1995)], in which the flow is integrated in split time steps, each Hamiltonian in two dimensions. The first scheme is an extension of the method of extended phase space, a well-proven method of symplectic integration with non-uniform time steps. This method is found not to work, and an explanation is given. The second method investigated is a method based on transformation to canonical variables for the two split-step Hamiltonian systems. This method, which is related to the method of non-canonical generating functions of Richardson and Finn [Plasma Phys. Controlled Fusion 54, 014004 (2012)], appears to work very well.« less

Analysis of microdialysate monoamines, including noradrenaline, dopamine and serotonin, using capillary ultra-high performance liquid chromatography and electrochemical detection.

PubMed

Ferry, Barbara; Gifu, Elena-Patricia; Sandu, Ioana; Denoroy, Luc; Parrot, Sandrine

2014-03-01

Electrochemical methods are very often used to detect catecholamine and indolamine neurotransmitters separated by conventional reverse-phase high performance liquid chromatography (HPLC). The present paper presents the development of a chromatographic method to detect monoamines present in low-volume brain dialysis samples using a capillary column filled with sub-2μm particles. Several parameters (repeatability, linearity, accuracy, limit of detection) for this new ultrahigh performance liquid chromatography (UHPLC) method with electrochemical detection were examined after optimization of the analytical conditions. Noradrenaline, adrenaline, serotonin, dopamine and its metabolite 3-methoxytyramine were separated in 1μL of injected sample volume; they were detected above concentrations of 0.5-1nmol/L, with 2.1-9.5% accuracy and intra-assay repeatability equal to or less than 6%. The final method was applied to very low volume dialysates from rat brain containing monoamine traces. The study demonstrates that capillary UHPLC with electrochemical detection is suitable for monitoring dialysate monoamines collected at high sampling rate. Copyright © 2014 Elsevier B.V. All rights reserved.

A Fatigue Model for Discontinuous Particulate-Reinforced Aluminum Alloy Composite: Influence of Microstructure

NASA Astrophysics Data System (ADS)

McCullough, R. R.; Jordon, J. B.; Brammer, A. T.; Manigandan, K.; Srivatsan, T. S.; Allison, P. G.; Rushing, T. W.

2014-01-01

In this paper, the use of a microstructure-sensitive fatigue model is put forth for the analysis of discontinuously reinforced aluminum alloy metal matrix composite. The fatigue model was used for a ceramic particle-reinforced aluminum alloy deformed under conditions of fully reversed strain control. Experimental results revealed the aluminum alloy to be strongly influenced by volume fraction of the particulate reinforcement phase under conditions of strain-controlled fatigue. The model safely characterizes the evolution of fatigue damage in this aluminum alloy composite into the distinct stages of crack initiation and crack growth culminating in failure. The model is able to capture the specific influence of particle volume fraction, particle size, and nearest neighbor distance in quantifying fatigue life. The model yields good results for correlation of the predicted results with the experimental test results on the fatigue behavior of the chosen aluminum alloy for two different percentages of the ceramic particle reinforcement. Further, the model illustrates that both particle size and volume fraction are key factors that govern fatigue lifetime. This conclusion is well supported by fractographic observations of the cyclically deformed and failed specimens.

Phase retrieval with the reverse projection method in the presence of object's scattering

NASA Astrophysics Data System (ADS)

Wang, Zhili; Gao, Kun; Wang, Dajiang

2017-08-01

X-ray grating interferometry can provide substantially increased contrast over traditional attenuation-based techniques in biomedical applications, and therefore novel and complementary information. Recently, special attention has been paid to quantitative phase retrieval in X-ray grating interferometry, which is mandatory to perform phase tomography, to achieve material identification, etc. An innovative approach, dubbed ;Reverse Projection; (RP), has been developed for quantitative phase retrieval. The RP method abandons grating scanning completely, and is thus advantageous in terms of higher efficiency and reduced radiation damage. Therefore, it is expected that this novel method would find its potential in preclinical and clinical implementations. Strictly speaking, the reverse projection method is applicable for objects exhibiting only absorption and refraction. In this contribution, we discuss the phase retrieval with the reverse projection method for general objects with absorption, refraction and scattering simultaneously. Especially, we investigate the influence of the object's scattering on the retrieved refraction signal. Both theoretical analysis and numerical experiments are performed. The results show that the retrieved refraction signal is the product of object's refraction and scattering signals for small values. In the case of a strong scattering, the reverse projection method cannot provide reliable phase retrieval. Those presented results will guide the use of the reverse projection method for future practical applications, and help to explain some possible artifacts in the retrieved images and/or reconstructed slices.

Molecular-level characterization of crude oil compounds combining reversed-phase high-performance liquid chromatography with off-line high-resolution mass spectrometry

USGS Publications Warehouse

Sim, Arum; Cho, Yunju; Kim, Daae; Witt, Matthias; Birdwell, Justin E.; Kim, Byung Ju; Kim, Sunghwan

2014-01-01

A reversed-phase separation technique was developed in a previous study (Loegel et al., 2012) and successfully applied to the de-asphalted fraction of crude oil. However, to the best of our knowledge, the molecular-level characterization of oil fractions obtained by reversed-phase high-performance liquid chromatography (HPLC) coupled with high-resolution mass spectrometry (MS) has not yet been reported. A detailed characterization of the oil fractions prepared by reversed-phase HPLC was performed in this study. HPLC fractionation was carried out on conventional crude oil and an oil shale pyrolysate. The analyses of the fractions showed that the carbon number of alkyl chains and the double bond equivalent (DBE) value were the major factors determining elution order. The compounds with larger DBE (presumably more condensed aromatic structures) and smaller carbon number (presumably compounds with short side chains) were eluted earlier but those compounds with lower DBE values (presumably less aromatic structures) and higher carbon number (presumably compounds with longer alkyl chains) eluted later in the chromatograms. This separation behavior is in good agreement with that expected from the principles of reversed-phase separation. The data presented in this study show that reversed-phase chromatography is effective in separating crude oil compounds and can be combined with ultrahigh-resolution MS data to better understand natural oils and oil shale pyrolysates.

Leukotriene B4 catabolism: quantitation of leukotriene B4 and its omega-oxidation products by reversed-phase high-performance liquid chromatography.

PubMed

Shak, S

1987-01-01

LTB4 and its omega-oxidation products may be rapidly, sensitively, and specifically quantitated by the methods of solid-phase extraction and reversed-phase high-performance liquid chromatography (HPLC), which are described in this chapter. Although other techniques, such as radioimmunoassay or gas chromatography-mass spectrometry, may be utilized for quantitative analysis of the lipoxygenase products of arachidonic acid, only the technique of reversed-phase HPLC can quantitate as many as 10 metabolites in a single analysis, without prior derivatization. In this chapter, we also reviewed the chromatographic theory which we utilized in order to optimize reversed-phase HPLC analysis of LTB4 and its omega-oxidation products. With this information and a gradient HPLC system, it is possible for any investigator to develop a powerful assay for the potent inflammatory mediator, LTB4, or for any other lipoxygenase product of arachidonic acid.

The effect of surgeon and hospital volume on shoulder arthroplasty perioperative quality metrics.

PubMed

Singh, Anshu; Yian, Edward H; Dillon, Mark T; Takayanagi, Miwa; Burke, Mary F; Navarro, Ronald A

2014-08-01

There has been a significant increase in both the incidence of shoulder arthroplasty and the number of surgeons performing these procedures. Literature regarding the relationship between surgeon or hospital volume and the performance of modern shoulder arthroplasty is limited. This study examines the effect of surgeon or hospital shoulder arthroplasty volume on perioperative metrics related to shoulder hemiarthroplasty, total shoulder arthroplasty, and reverse shoulder arthroplasty. Blood loss, length of stay, and operative time were the main endpoints analyzed. Prospective data were analyzed from a multicenter shoulder arthroplasty registry; 1176 primary shoulder arthroplasty cases were analyzed. Correlation and analysis of covariance were used to examine the association between surgeon and hospital volume and perioperative metrics adjusting for age, sex, and body mass index. Surgeon volume is inversely correlated with length of stay for hemiarthroplasty and total shoulder arthroplasty and with blood loss and operative time for all 3 procedures. Hospital volume is inversely correlated with length of stay for hemiarthroplasty, with blood loss for total and reverse shoulder arthroplasty, and with operative time for all 3 procedures. High-volume surgeons performed shoulder arthroplasty 30 to 50 minutes faster than low-volume surgeons did. Higher surgeon and hospital case volumes led to improved perioperative metrics with all shoulder arthroplasty procedures, including reverse total shoulder arthroplasty, which has not been previously described in the literature. Surgeon volume had a larger effect on metrics than hospital volume did. This study supports the concept that complex shoulder procedures are, on average, performed more efficiently by higher volume surgeons in higher volume centers. Copyright © 2014 Journal of Shoulder and Elbow Surgery Board of Trustees. Published by Mosby, Inc. All rights reserved.

Areal Mass Oscillations in Planar Targets Due to Feedout: Theory and Simulations.

NASA Astrophysics Data System (ADS)

Velikovich, A. L.; Schmitt, A. J.; Karasik, M.; Obenschain, S. P.; Serlin, V.; Pawley, C. J.; Gardner, J. H.; Aglitskiy, Y.; Metzler, N.

2001-10-01

When a planar shock wave breaks out at a rippled rear surface of a laser-driven target, the lateral pressure gradient in a rippled rarefaction wave propagating back to the front surface causes a lateral mass redistribution that reverses the phase of mass variation. If the driving laser pulse has no foot, then the RT growth, starting when the rarefaction wave reaches the front surface, causes the second phase reversal of mass variation, and continues at the initial phase, as consistently observed in feedout experiments on Nike. A foot of the laser pulse can cause an early phase reversal of mass variation, making the strong shock wave driven by the main pulse interact with a density variation in a rippled rarefaction wave rather than with static rear surface ripples. Theory and simulations predict that this interaction can make the phase of mass variation reverse one or three times. Then the phase of the RT growing mode would be opposite to that of the initial mass variation.

Slow equilibration of reversed-phase columns for the separation of ionized solutes.

PubMed

Marchand, D H; Williams, L A; Dolan, J W; Snyder, L R

2003-10-10

Reversed-phase columns that have been stored in buffer-free solvents can exhibit pronounced retention-time drift when buffered, low-pH mobile phases are used with ionized solutes. Whereas non-ionized compounds exhibit constant retention times within 20 min of the beginning of mobile phase flow, the retention of ionized compounds can continue to change (by 20% or more) for several hours. If mobile phase pH is changed from low to high and back again, an even longer time may be required before the column reaches equilibration at low pH. The speed of column equilibration for ionized solutes can vary significantly among different reversed-phase columns and is not affected by flow rate.

Time-reversal imaging techniques applied to tremor waveforms near Cholame, California to locate tectonic tremor

NASA Astrophysics Data System (ADS)

Horstmann, T.; Harrington, R. M.; Cochran, E. S.

2012-12-01

Frequently, the lack of distinctive phase arrivals makes locating tectonic tremor more challenging than locating earthquakes. Classic location algorithms based on travel times cannot be directly applied because impulsive phase arrivals are often difficult to recognize. Traditional location algorithms are often modified to use phase arrivals identified from stacks of recurring low-frequency events (LFEs) observed within tremor episodes, rather than single events. Stacking the LFE waveforms improves the signal-to-noise ratio for the otherwise non-distinct phase arrivals. In this study, we apply a different method to locate tectonic tremor: a modified time-reversal imaging approach that potentially exploits the information from the entire tremor waveform instead of phase arrivals from individual LFEs. Time reversal imaging uses the waveforms of a given seismic source recorded by multiple seismometers at discrete points on the surface and a 3D velocity model to rebroadcast the waveforms back into the medium to identify the seismic source location. In practice, the method works by reversing the seismograms recorded at each of the stations in time, and back-propagating them from the receiver location individually into the sub-surface as a new source time function. We use a staggered-grid, finite-difference code with 2.5 ms time steps and a grid node spacing of 50 m to compute the rebroadcast wavefield. We calculate the time-dependent curl field at each grid point of the model volume for each back-propagated seismogram. To locate the tremor, we assume that the source time function back-propagated from each individual station produces a similar curl field at the source position. We then cross-correlate the time dependent curl field functions and calculate a median cross-correlation coefficient at each grid point. The highest median cross-correlation coefficient in the model volume is expected to represent the source location. For our analysis, we use the velocity model of Thurber et al. (2006) interpolated to a grid spacing of 50 m. Such grid spacing corresponds to frequencies of up to 8 Hz, which is suitable to calculate the wave propagation of tremor. Our dataset contains continuous broadband data from 13 STS-2 seismometers deployed from May 2010 to July 2011 along the Cholame segment of the San Andreas Fault as well as data from the HRSN and PBO networks. Initial synthetic results from tests on a 2D plane using a line of 15 receivers suggest that we are able to recover accurate event locations to within 100 m horizontally and 300 m depth. We conduct additional synthetic tests to determine the influence of signal-to-noise ratio, number of stations used, and the uncertainty in the velocity model on the location result by adding noise to the seismograms and perturbations to the velocity model. Preliminary results show accurate show location results to within 400 m with a median signal-to-noise ratio of 3.5 and 5% perturbations in the velocity model. The next steps will entail performing the synthetic tests on the 3D velocity model, and applying the method to tremor waveforms. Furthermore, we will determine the spatial and temporal distribution of the source locations and compare our results to those by Sumy and others.

Maintaining Restored Bone with Bisphoshonate in the Ovariectomized Rat Skeleton: Dynamic Histomorphometry of Changes in Bone Mass

NASA Technical Reports Server (NTRS)

Jee, W. S. S.; Tang, L.; Ke, H. Z.; Setterberg, R. B.; Kimmel, D. B.

1993-01-01

This experiment contains the crucial data for the Lose, Restore and Maintain (LRM) concept, a practical approach for reversing existing osteoporosis. The LRM concept uses ovariectomy (ox) to lose bone, an anabolic agent to restore bone mass and then switches to an anti-resorptive agent to maintain bone mass. We ox'd or sham-ox'd rats for 150 days (Loss Phase), treated them with 6 mg PGE2/kg/d for 75 days to restore lost cancellous bone mass (Restore Phase) and then stopped PGE2 treatment and began treatment with 1 or 5 micro-g/kg Risedronate, a bisphosphonate twice a week for 60 days (Maintain Phase). During the Loss Phase, cancellous bone volumes of the proximal tibial metaphysis (PTM) in the ox'd rat fell to 19% of initial controls. During the Restore Phase, the PTM bone volume in ox'd rats doubled. However, when PGE2 treatment was stopped, the PGE2-induced cancellous bone disappeared. In contrast, 5 micro-g of Risedronate inhibited the bone loss and maintained it at the PGE2 treatment level. The key dynamic histomorphometry value for the restore (R) and maintenance (M) phases was the ratio of bone formation to resorption rates. The ratio was elevated to 5.8 in the R phase and depressed to 0.4 for no and 1 micro-g Risedronate treated M phase and to a ratio of near unity of 1.1 for the 5 micro-g Risedronate treatment. These findings indicate that we were successful in maintaining the new PTM bone induced by PGE2 after discontinuing PGE2 by administering enough Risedronate, a resorption inhibitor. We concluded that the LRM concept is correct and such an approach should be considered when employing anabolic agents or growth factors in the treatment of osteoporosis. Continued use of an anabolic agent may not be appropriate because of cost, potential adverse side effects and a loss of efficacy.

Maintaining Restored Bone with Bisphosphonate in the Ovariectomized Rat Skeleton: Dynamic Histomorphometry of Changes in Bone Mass

NASA Technical Reports Server (NTRS)

Jee, W. S. S.; Tang, L.; Ke, H. Z.; Setterberg, R. B.; Kimmel, D. B.

1993-01-01

This experiment contains the crucial data for the Lose, Restore and Maintain (LRM) concept, a practical approach for reversing existing osteoporosis. The LRM concept uses ovariectomy (ox) to lose bone, an anabolic agent to restore bone mass and then switches to an antiresorptive agent to maintain bone mass. We ox'd or sham-ox'd rats for 150 days (Loss Phase), treated them with 6 mg PGE(sub 2)kg/d for 75 days to restore lost cancellous bone mass (Restore Phase) and then stopped PGE(sub 2) treatment and began treatment with 1 or 5 micrograms/kg Risedronate, a bisphosphonate twice a week for 60 days (Maintain Phase). During the Loss Phase, cancellous bone volumes of the Proximal Tibial Metaphysis (PTM) in the ox'd rat fell to 19% of initial controls. During the Restore Phase, the PTM bone volume in ox'd rats doubled. However, when PGE(sub 2) treatment was stopped, the PGE(sub 2)-induced cancellous bone disappeared. In contrast, 5 miligrams of Risedronate inhibited the bone loss and maintained it at the PGE(sub 2) treatment level. The key dynamic histomorphometry value for the Restore (R) and Maintenance (M) phases was the ratio of bone formation to resorption rates. The ratio was elevated to 5.8 in the R phase and depressed to 0.4 for no and 1 miligram Risedronate treated M phase and to a ratio of near unity of 1.1 for the 5miligrams Risedronate treatment. These findings indicate that we were successful in maintaining the new PTM bone induced by PGE(sub 2) after discontinuing PGE(sub 2) by administering enough Risedronate, a resorption inhibitor. We concluded that the LRM concept is correct and such an approach should be considered when employing anabolic agents or growth factors in the treatment of osteoporosis. Continued use of an anabolic agent may not be appropriate because of cost, potential adverse side effects and a loss of efficacy.

Materials Based on Antimony and Bismuth for Sodium Storage: A Review.

PubMed

Li, Xinyan; Ni, Jiangfeng; Savilov, S V; Li, Liang

2018-06-06

Sodium-ion batteries (SIBs) that efficiently store electricity into chemical energy have been extensively pursued because of their great potential for low-cost and large-scale stationary application such as smart grid and renewable energy. Successful deployment of SIBs requires efficient anode materials that could store Na+ ions via a reversible way at reasonable rates. Materials based on antimony and bismuth are capable of storing a high-concentration of Na+ ions via a reversible alloying reaction at suitable redox potentials, and thus havedrawn substantial attention. However, these electrode materials are facing significant technical challenges, such as poor conductivity, multiple phase transformation, and severe volume swelling and shrinking, which make efficient materials design a necessity. In this review, we will give a latest overview of research progress in the design and application of electrode materials based on antimony and bismuth, and offer some value insights into their future development in sodium storage. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Left Ventricular Architecture, Long-Term Reverse Remodeling, and Clinical Outcome in Mild Heart Failure With Cardiac Resynchronization: Results From the REVERSE Trial.

PubMed

St John Sutton, Martin; Linde, Cecilia; Gold, Michael R; Abraham, William T; Ghio, Stefano; Cerkvenik, Jeffrey; Daubert, Jean-Claude

2017-03-01

This study sought to determine the effects of abnormal left ventricular (LV) architecture on cardiac remodeling and clinical outcomes in mild heart failure (HF). Cardiac resynchronization therapy (CRT) is an established treatment for HF that improves survival in part by favorably remodeling LV architecture. LV shape is a dynamic component of LV architecture on which contractile function depends. Transthoracic 2-dimensional echocardiography was used to quantify changes in LV architecture over 5 years of follow-up of patients with mild HF from the REVERSE study. REVERSE was a prospective study of patients with large hearts (LV end-diastolic dimension ≥55 mm), LV ejection fraction <40%, and QRS duration >120 ms randomly assigned to CRT-ON (n = 419) and CRT-OFF (n = 191). CRT-OFF patients were excluded from this analysis. LV dimensions, volumes, mass index, and LV ejection fraction were calculated. LV architecture was assessed using the sphericity index, as follows: (LV end-diastolic volume)/(4/3 × π × r 3 ) × 100%. LV architecture improved over time and demonstrated significant associations between LV shape, age, sex, and echocardiography metrics. Changes in LV architecture were strongly correlated with changes in LV end-systolic volume index and LV end-diastolic volume index (both p < 0.0001). Sphericity index emerged as a predictor of death and HF hospitalization in spite of the low adverse event rate. A decrease in LV end-systolic volume index >15% occurred in more than two-thirds of patients, which indicates considerable reverse remodeling. We demonstrated that change in LV architecture in patients with mild HF with CRT is associated with structural and functional remodeling. Mean LV filling pressure was elevated, and the inability to lower it was an additional predictor of HF hospitalization or death. (Resynchronization Reverses Remodeling in Systolic Left Ventricular Dysfunction [REVERSE]; NCT00271154). Copyright © 2017 American College of Cardiology Foundation. Published by Elsevier Inc. All rights reserved.

Reverse lyotropic liquid crystals from europium nitrate and P123 with enhanced luminescence efficiency.

PubMed

Yi, Sijing; Li, Qintang; Liu, Hongguo; Chen, Xiao

2014-10-02

Fabrication of lyotropic aggregates containing the lanthanide ions is becoming a preferable way to prepare novel functional materials. Here, the lyotropic liquid crystals (LLCs) of reverse hexagonal, reverse bicontinuous cubic, and lamellar phases have been constructed in sequence directly from the mixtures of Eu(NO3)3·6H2O and Pluronic P123 amphiphilc block copolymer with increasing the salt proportion. Their phase types and structural characteristics were analyzed using polarized optical microscopy (POM) and small-angle X-ray scattering (SAXS) measurements. The driving forces of reverse LLC phase formation were investigated using Fourier-transformed infrared spectroscopy (FTIR) and rheological measurements. The hydrated europium salt was found to act not only as a solvent here, but also as the bridge to form hydrogen bonding between coordinated water molecules and PEO blocks, which played a key role in the reverse LLCs formation. Compared to those in aqueous solutions and solid state, the enhanced luminescence quantum yields and prolonged excited state lifetimes were observed in two europium containing reverse mesophases. The luminescence quenching effect of lanthanide ions was efficiently suppressed, probably due to the substitution of coordinated water molecules by oxyethyl groups of P123 and ordered phase structures of LLCs, where the coordinated europium ions were confined and isolated by PEO blocks. The optimum luminescence performance was then found to exist in the reverse hexagonal phase. The obtained results on such lanthanide-induced reverse LLCs should be referable for designing new luminescent soft materials construction to expand their application fields.

Assessment of intra-particle diffusion in hydrophilic interaction liquid chromatography and reversed-phase liquid chromatography under conditions of identical packing structure.

PubMed

Song, Huiying; Desmet, Gert; Cabooter, Deirdre

2017-11-10

A recently developed stripping protocol to completely remove the stationary phase of reversed-phase liquid chromatography (RPLC) columns and turn them into hydrophilic interaction liquid chromatography (HILIC) columns with identical packing characteristics is used to study the underlying mechanisms of intra-particle diffusion in RPLC and HILIC. The protocol is applied to a column with a large geometrical volume (250×4.6mm, 5μm) to avoid extra-column effects and for compounds with a broad range in retention factors (k" from ∼0.6 to 8). Three types of behavior for the intra-particle diffusion (D part /D m ) in RPLC versus HILIC can be distinguished: for nearly unretained compounds (k"<0.6), intra-particle diffusion in HILIC is larger than in RPLC; for compounds with intermediate retention behavior (k"∼0.9-1.2), intra-particle diffusion in HILIC and RPLC are similar; and for well retained compounds (k">1.8), intra-particle diffusion in RPLC is larger than in HILIC. To explain these observations, diffusion in the stationary phase (γ s D s ) and in the stagnant mobile phase in the mesopore zone (γ mp D m ) are deduced from experimentally determined values of the intra-particle diffusion, using models derived from the Effective Medium Theory. It is demonstrated that the larger intra-particle diffusion obtained for slightly retained compounds under HILIC conditions is caused by the higher mesopore diffusion in HILIC (γ mp =0.474 for HILIC versus 0.435 for RPLC), while the larger intra-particle diffusion obtained for strongly retained compounds under RPLC conditions can be related to the much higher stationary phase diffusion in RPLC (γ s D s /D m =0.200 for RPLC versus 0.113 for HILIC). Copyright © 2017 Elsevier B.V. All rights reserved.

Comparison of different morphological parameters with duration of obstruction created experimentally in unilateral upper ureters: an animal model.

PubMed

Panda, Shasanka Shekhar; Bajpai, Minu; Mallick, Saumyaranjan; Sharma, Mehar C

2014-01-01

The objective of the following study is to determine and to compare the different morphological parameters with duration of obstruction created experimentally in unilateral upper ureters of rats. Unilateral upper ureteric obstruction was created in 60 adult Wistar rats that were reversed after predetermined intervals. Rats were sacrificed and ipsilateral kidneys were subjected for analysis of morphological parameters such as renal height, cranio-caudal diameter, antero-posterior diameter, lateral diameter, volume of the pelvis and average cortical thickness: Renal height. Renal height and cranio-caudal diameter of renal pelvis after ipsilateral upper ureteric obstruction started rising as early as 7 days of creating obstruction and were affected earlier than antero-posterior and lateral diameter and also were reversed earlier than other parameters after reversal of obstruction. Renal cortical thickness and volume of the pelvis were affected after prolonged obstruction (> 3 weeks) and were the late parameters to be reversed after reversal of obstruction. Cranio-caudal diameter and renal height were the early morphological parameters to be affected and reversed after reversal of obstruction in experimentally created ipsilateral upper ureteric obstruction.

Determination of vigabatrin in human plasma and urine by high-performance liquid chromatography with fluorescence detection.

PubMed

Erturk, S; Aktas, E S; Atmaca, S

2001-09-05

A sensitive and specific HPLC method has been developed for the assay of vigabatrin in human plasma and urine. The assay involves derivatization with 4-chloro-7-nitrobenzofurazan, solid-phase extraction on a silica column and isocratic reversed-phase chromatography with fluorescence detection. Aspartam was used as an internal standard. The assay was linear over the concentration range of 0.2-20.0 microg/ml for plasma and 1.0-15.0 microg/ml for urine with a lower limit of detection of 0.1 microg/ml using 0.1 ml of starting volume of the sample. Both the within-day and day-to-day reproducibilities and accuracies were less than 5.46% and 1.6%, respectively. After a single oral dose of 500 mg of vigabatrin, the plasma concentration and the cumulative urinary excretion of the drug were determined.

A rapid high-performance liquid-chromatographic method for simultaneously determining the concentrations of TFM and Bayer 73 in water during lampricide treatments

USGS Publications Warehouse

Dawson, V.K.

1982-01-01

The high-performance liquid-chromatography (HPLC) procedure requires only minutes per sample, is specific, and is relatively sensitive (limit of detection 18 disposable cartridge. The cartridge adsorbs and retains both the lampricides and the internal standard. The quantitative elution of the three chemicals from the cartridge with a small volume of methanol effectively concentrates the sample and provides sample cleanup. The methanol extract is then analyzed directly by HPLC on an MCH 10 reverse phase column by using a methanol:0.01 mol/L acetate buffer (87:13, v:v) as the mobile phase at 2 mL/min and detected by ultraviolet spectrophotometry at 330 (or 254) nm. A microprocessor data system further facilitates the procedure by quantifying off-scale peaks and yielding results directly in units of concentration (mg/L).

Three-dimensional localization of nanoscale battery reactions using soft X-ray tomography.

PubMed

Yu, Young-Sang; Farmand, Maryam; Kim, Chunjoong; Liu, Yijin; Grey, Clare P; Strobridge, Fiona C; Tyliszczak, Tolek; Celestre, Rich; Denes, Peter; Joseph, John; Krishnan, Harinarayan; Maia, Filipe R N C; Kilcoyne, A L David; Marchesini, Stefano; Leite, Talita Perciano Costa; Warwick, Tony; Padmore, Howard; Cabana, Jordi; Shapiro, David A

2018-03-02

Battery function is determined by the efficiency and reversibility of the electrochemical phase transformations at solid electrodes. The microscopic tools available to study the chemical states of matter with the required spatial resolution and chemical specificity are intrinsically limited when studying complex architectures by their reliance on two-dimensional projections of thick material. Here, we report the development of soft X-ray ptychographic tomography, which resolves chemical states in three dimensions at 11 nm spatial resolution. We study an ensemble of nano-plates of lithium iron phosphate extracted from a battery electrode at 50% state of charge. Using a set of nanoscale tomograms, we quantify the electrochemical state and resolve phase boundaries throughout the volume of individual nanoparticles. These observations reveal multiple reaction points, intra-particle heterogeneity, and size effects that highlight the importance of multi-dimensional analytical tools in providing novel insight to the design of the next generation of high-performance devices.

Morphology of the pancreas in type 2 diabetes: effect of weight loss with or without normalisation of insulin secretory capacity.

PubMed

Al-Mrabeh, Ahmad; Hollingsworth, Kieren G; Steven, Sarah; Taylor, Roy

2016-08-01

This study was designed to establish whether the low volume and irregular border of the pancreas in type 2 diabetes would be normalised after reversal of diabetes. A total of 29 individuals with type 2 diabetes undertook a very low energy (very low calorie) diet for 8 weeks followed by weight maintenance for 6 months. Methods were established to quantify the pancreas volume and degree of irregularity of the pancreas border. Three-dimensional volume-rendering and fractal dimension (FD) analysis of the MRI-acquired images were employed, as was three-point Dixon imaging to quantify the fat content. There was no change in pancreas volume 6 months after reversal of diabetes compared with baseline (52.0 ± 4.9 cm(3) and 51.4 ± 4.5 cm(3), respectively; p = 0.69), nor was any volumetric change observed in the non-responders. There was an inverse relationship between the volume and fat content of the pancreas in the total study population (r =-0.50, p = 0.006). Reversal of diabetes was associated with an increase in irregularity of the pancreas borders between baseline and 8 weeks (FD 1.143 ± 0.013 and 1.169 ± 0.006, respectively; p = 0.05), followed by a decrease at 6 months (1.130 ± 0.012, p = 0.006). On the other hand, no changes in FD were seen in the non-reversed group. Restoration of normal insulin secretion did not increase the subnormal pancreas volume over 6 months in the study population. A significant change in irregularity of the pancreas borders occurred after acute weight loss only after reversal of diabetes. Pancreas morphology in type 2 diabetes may be prognostically important, and its relationship to change in beta cell function requires further study.

[Liver volume, intrahepatic fat and body weight in the course of a lifestyle interventional study: Analysis with quantitative MR-based methods].

PubMed

Bongers, M N; Stefan, N; Fritsche, A; Häring, H-U; Nikolaou, K; Schick, F; Machann, J

2015-04-01

The aim of this study was to investigate potential associations between changes in liver volume, the amount of intrahepatic lipids (IHL) and body weight during lifestyle interventions. In a prospective study 150 patients with an increased risk for developing type 2 diabetes mellitus were included who followed a caloric restriction diet for 6 months. In the retrospective analysis 18 women and 9 men (age range 22-71 years) with an average body mass index (BMI) of 32 kg/m(2) were enrolled. The liver volume was determined at the beginning and after 6 months by three-dimensional magnetic resonance imaging (3D-MRI, echo gradient, opposed-phase) and IHLs were quantified by volume-selective MR spectroscopy in single voxel stimulated echo acquisition mode (STEAM). Univariable and multivariable correlation analyses between changes of liver volume (Δliver volume), intrahepatic lipids (ΔIHL) and body weight (ΔBW) were performed. Univariable correlation analysis in the whole study cohort showed associations between ΔIHL and ΔBW (r = 0.69; p < 0.0001), ΔIHL and Δliver volume (r = 0.66; p = 0.0002) as well as ΔBW and Δliver volume (r = 0.5; p = 0.0073). Multivariable correlation analysis revealed that changes of liver volume are primarily determined by changes in IHL independent of changes in body weight (β = 0.0272; 95% CI: 0.0155-0.034; p < 0.0001). Changes of liver volume during lifestyle interventions are independent of changes of body weight primarily determined by changes of IHL. These results show the reversibility of augmented liver volume in steatosis if it is possible to reduce IHLs during lifestyle interventions.

Determination of Alternaria mycotoxins in wine and juice using ionic liquid modified countercurrent chromatography as a pretreatment method followed by high-performance liquid chromatography.

PubMed

Fan, Chen; Cao, Xueli; Liu, Man; Wang, Wei

2016-03-04

Alternariol (AOH), alternariol monomethyl ether (AME), and tenuazonic acid (TeA) are some of the main Alternaria mycotoxins that can be found as contaminants in food materials. The objective of this study was to develop a pretreatment method with countercurrent chromatography (CCC) for enrichment and cleanup of trace Alternaria mycotoxins in food samples prior to high-performance liquid chromatography (HPLC) analysis. An Analytical CCC instrument with a column volume 22.5mL was used, and a two-phase solvent system composed of ethyl acetate and water modified with 6% [HOOMIM][Cl] in mass to volume ratio was selected. Under the optimized CCC operation conditions, trace amounts of AOH, AME, and TeA in large volume of liquid sample were efficiently extracted and enriched in the stationary phase, and then eluted out just by reversing the stationary phase as mobile phase in the opposite flowing direction tail-to-head. The enrichment and elution strategies are unique and can be fulfilled online with high enrichment factors (87-114) and high recoveries (81.14-110.94%). The method has been successively applied to the determination of Alternaria mycotoxins in real apple juice and wine samples with the limits of detection (LOD) in the range of 0.03-0.14μgL(-1). Totally 12 wine samples and 15 apple juice samples from the local market were analyzed. The detection rate of AOH and AME in both kinds of the samples were more than 50%, while TeA was found in relatively high level of 1.75-49.61μgL(-1) in some of the apple juice samples. The proposed method is simple, rapid, and sensitive and could also be used for the analysis and monitoring of Alternaria mycotoxin in other food samples. Copyright © 2016 Elsevier B.V. All rights reserved.

SEPARATION OF T-MAZ ETHOXYLATED SORBITAN FATTY ACID ESTERS BY REVERSE PHASE CHROMATOGRAPHY

EPA Science Inventory

The method for determination of T-MAZ ethoxylated sorbitan fatty acid esters is described. This work demonstrates that with a less retentive C8 alkyl bonded phase packing, reverse phase chromatography can be used to analyze nonionic polymer mixtures with a molecular weight range ...

Ionic liquids improved reversed-phase HPLC on-line coupled with ICP-MS for selenium speciation.

PubMed

Chen, Beibei; He, Man; Mao, Xiangju; Cui, Ran; Pang, Daiwen; Hu, Bin

2011-01-15

Room-temperature ionic liquids (RTILs) improved reversed-phase high performance liquid chromatography (RP-HPLC) on-line combined with inductively coupled plasma mass spectrometry (ICP-MS) was developed for selenium speciation. The different parameters affecting the retention behaviors of six target selenium species especially the effect of RTILs as mobile phase additives have been studied, it was found that the mobile phase consisting of 0.4% (v/v) 1-butyl-3-methylimidazolium chloride ([BMIM]Cl), 0.4% (v/v) 1-butyl-2,3-dimethylimidazolium tetrafluroborate ([BMMIM]BF(4)) and 99.2% (v/v) water has effectively improved the peak profile and six target selenium species including Na(2)SeO(3) (Se(IV)), Na(2)SeO(4) (Se(VI)), L-selenocystine (SeCys(2)), D,L-selenomethionine (SeMet), Se-methylseleno-l-cysteine (MeSeCys), seleno-D,L-ethionine (SeEt) were separated in 8 min. In order to validate the accuracy of the method, a Certified Reference Material of SELM-1 yeast sample was analyzed and the results obtained were in good agreement with the certified values. The developed method was also successfully applied to the speciation of selenium in Se-enriched yeasts and clover. For fresh Se-enriched yeast cells, it was found that the spiked SeCys(2) in living yeast cells could be transformed into SeMet. Compared with other ion-pair RP-HPLC-ICP-MS approaches for selenium speciation, the proposed method possessed the advantages including ability to regulate the retention time of the target selenium species by selecting the suitable RTILs and their concentration, simplicity, rapidness and low injection volume, thus providing wide potential applications for elemental speciation in biological systems. Copyright © 2010 Elsevier B.V. All rights reserved.

Investigation of transport process involved in FGD. Final repot, September 1, 1993--August 31, 1994

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kadambi, J.R.; Tien, J.S.; Yurteri, C.

1995-02-01

The objectives of this five year plan of study are to experimentally obtain a basic understanding of (1) turbulent flow structure of the mixing zone and it influence on particle dispersion, (2) the effect of particle loading on turbulent properties and mixing, (3) the effect of jet entrainment, (4) water spray-sorbent interaction, sorbent wetting and mixing, (5) investigate the flow field where certain ratios of jet velocity to flu gas velocity result in regions of negative flow and define onset o negative flow, and (6) sorbent reactivity in immediate mixing zone. In the first two years of the project amore » sorbent injection facility which can simulate the conditions encountered in COOLSIDE set up was designed and built. Non-intrusive laser based diagnostic tools PDA/LDA were used for flow characterization of particle laden jet in cocurrent flows. In the third year a new technique called TTLDV which combines particle transit time in measurement volume of LDV and LDV velocity measurements to simultaneously obtain non-spherical lime particle size and velocity was developed. Better sorbent injection schemes were investigated spray occurrent flow tests were conducted. During the fourth year the spray cocurrent flow interaction data was analyzed. A criterion was developed for predicting the flow reversal which results in deposition of water droplets on the duct wall (Table 3). The flow reversal occurs when the spray has entrained all the cocurrent flowing stream. The criterion is based upon the mass flow rate of the two phases. The criterion successfully predicted the flow reversals encountered in the experiments and will be a very useful practical tool. Lime laden jet occurrent flow interactions tests were completed. Tests on the swirling nozzle have been conducted. The single phase data have been analyzed while the two phase glass particle laden jet data is being analyzed.« less

Safety and Efficacy of Transcatheter Closure of Patent Ductus Arteriosus With Severe Mitral Regurgitation in Adults.

PubMed

Wang, Zhongkai; Chen, Tao; Chen, Liang; Qin, Yongwen; Zhao, Xianxian

2016-01-01

Transcatheter closure is the usual treatment for patent ductus arteriosus (PDA), but its safety and efficacy have not been reported in adult PDA patients with severe mitral regurgitation. A retrospective study on 27 consecutive patients diagnosed with PDA and severe mitral regurgitation and treated using transcatheter closure between September 2010 and September 2012 at the Department of Cardiology of Changhai Hospital in Changhai, China. Left ventricular (LV) diastolic volume and function, pulmonary artery pressure, and instantaneous reverse-flow volume were examined by echocardiography before PDA closure, immediately after closure, and 1 year after closure. After the procedure, the LV diastolic volume (P<.05) and instantaneous reverse-flow volume (P<.001) were significantly decreased. There was no effect on the ejection fraction (P>.05). Pulmonary arterial systolic pressure was unchanged 1 year after closure (from 46.41 ± 19.92 mm Hg to 45.43 ± 13.64 mm Hg; P=.58). All procedures were uneventful and only mild complications occurred (hemolysis in 2 cases, subcutaneous hematoma in 4 cases, and fever in 2 cases). Transcatheter closure can decrease the LV volume and instantaneous reverse-flow volume in adult PDA patients with severe mitral regurgitation. This procedure is effective and has a good safety profile.

Echocardiographic phase imaging to predict reverse remodeling after cardiac resynchronization therapy.

PubMed

Buss, Sebastian J; Humpert, Per M; Bekeredjian, Raffi; Hardt, Stefan E; Zugck, Christian; Schellberg, Dieter; Bauer, Alexander; Filusch, Arthur; Kuecherer, Helmut; Katus, Hugo A; Korosoglou, Grigorios

2009-05-01

The aim of our study was to investigate whether echocardiographic phase imaging (EPI) can predict response in patients who are considered for cardiac resynchronization therapy (CRT). CRT improves quality of life, exercise capacity, and outcome in patients with bundle-branch block and advanced heart failure. Previous studies used QRS duration to select patients for CRT; the accuracy of this parameter to predict functional recovery, however, is controversial. We examined 42 patients with advanced heart failure (New York Heart Association [NYHA] functional class III to IV, QRS duration >130 ms, and ejection fraction <35%) before and 6 to 8 months after CRT. Left ventricular (LV) dyssynchrony was estimated by calculating the SD of time to peak velocities (Ts-SD) by conventional tissue Doppler imaging (TDI), and the mean phase index (mean EPI-Index) was calculated by EPI in 12 mid-ventricular and basal segments. Patients who were alive and had significant relative decrease in end-systolic LV volume of Delta ESV >or=15% at 6 to 8 months of follow-up were defined as responders. All others were classified as nonresponders. The Ts-SD and the mean EPI-Index were related to Delta ESV (r = 0.43 for Ts-SD and r = 0.67 for mean EPI-Index, p < 0.01 for both), and both parameters yielded similar accuracy for the prediction of LV remodeling (area under the curve of 0.87 for TDI vs. 0.90 for EPI, difference between areas = 0.03, p = NS) and ejection fraction (EF) improvement (area under the curve of 0.87 for TDI vs. 0.93 for EPI, difference between areas = 0.06, p = NS). Furthermore, patients classified as responders by EPI (mean EPI-Index

Attractive interactions between reverse aggregates and phase separation in concentrated malonamide extractant solutions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Erlinger, C.; Belloni, L.; Zemb, T.

1999-03-30

Using small angle X-ray scattering, conductivity, and phase behavior determination, the authors show that concentrated solutions of malonamide extractants, dimethyldibutyltetradecylmalonamide (DMDBTDMA), are organized in reverse oligomeric aggregates which have many features in common with reverse micelles. The aggregation numbers of these reverse globular aggregates as well as their interaction potential are determined from absolute scattering curves. An attractive interaction is responsible for the demixing of the oil phase when in equilibrium with excess oil. Prediction of conductivity as well as the formation conditions for the third phase is possible using standard liquid theory applied to the extractant aggregates. The interactions,more » modeled with the sticky sphere model proposed by Baster, are shown to be due to steric interactions resulting from the hydrophobic tails of the extractant molecule and van der Waals forces between the highly polarizable water core of the reverse micelles. The attractive interaction in the oil phase, equilibrated with water, is determined as a function of temperature, extractant molecule concentration, and proton and neodynium(III) cation concentration. It is shown that van der Waals interactions, with an effective Hamaker constant of 3kT, quantitatively explain the behavior of DMDBTDMA in n-dodecane in terms of scattering as well as phase stability limits.« less

Separation of cannabinoids on three different mixed-mode columns containing carbon/nanodiamond/amine-polymer superficially porous particles.

PubMed

Hung, Chuan-Hsi; Zukowski, Janusz; Jensen, David S; Miles, Andrew J; Sulak, Clayton; Dadson, Andrew E; Linford, Matthew R

2015-09-01

Three mixed-mode high-performance liquid chromatography columns packed with superficially porous carbon/nanodiamond/amine-polymer particles were used to separate mixtures of cannabinoids. Columns evaluated included: (i) reversed phase (C18 ), weak anion exchange, 4.6 × 33 mm, 3.6 μm, and 4.6 × 100 mm, 3.6 μm, (ii) reversed phase, strong anion exchange (quaternary amine), 4.6×33 mm, 3.6 μm, and (iii) hydrophilic interaction liquid chromatography, 4.6 × 150 mm, 3.6 μm. Different selectivities were achieved under various mobile phase and stationary phase conditions. Efficiencies and peak capacities were as high as 54 000 N/m and 56, respectively. The reversed phase mixed-mode column (C18 ) retained tetrahydrocannabinolic acid strongly under acidic conditions and weakly under basic conditions. Tetrahydrocannabinolic acid was retained strongly on the reversed phase, strong anion exchange mixed-mode column under basic polar organic mobile phase conditions. The hydrophilic interaction liquid chromatography column retained polar cannabinoids better than the (more) neutral ones under basic conditions. A longer reversed phase (C18 ) mixed-mode column (4.6 × 100 mm) showed better resolution for analytes (and a contaminant) than a shorter column. Fast separations were achieved in less than 5 min and sometimes 2 min. A real world sample (bubble hash extract) was also analyzed by gradient elution. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Formation of reversed austenite during tempering of 14Cr-7Ni-0.3Nb-0.7Mo-0.03C super martensitic stainless steel

NASA Astrophysics Data System (ADS)

Park, Eun Seo; Yoo, Dae Kyoung; Sung, Jee Hyun; Kang, Chang Yong; Lee, Jun Hee; Sung, Jang Hyun

2004-12-01

Reversed austenite transformation and existence of retained austenite during tempering of the super martensitic stainless steel of Fe-14Cr-7Ni-0.3Nb-0.7Mo-0.03C were studied by means of experiments on microstructure and X-ray diffraction, and tensile and hardness tests. Acicular type retained austenite at the lath boundary of martensite with the interior appeared after solution annealing. This retained austenite still existed, and reversed austenite was not formed, with tempering up to 24h at 450°C. The reversed austenite began to form above 550°C, and the volume fraction of reversed austenite decreased with increasing tempering temperature after showing a maximum value of 19.2% at 650°C. This maximum volume fraction of reversed austenite was responsible for the lowest value of strength and hardness. The Ni contents of plate type reversed austenite and the surrounding matrix increased and decreased respectively, implying that the reversed austenite was formed as a result of nickel diffusion. The orientation relationships between reversed austenite and the surrounding matrix showed a K-S relationship of(bar 11bar 1)_γ //(01bar 1)_m and[011]_γ //[bar 111]_m.

Evaluation of Military Field-Water Quality. Volume 8. Performance of Mobile Water-Purification Unit (MWPU) and Pretreatment Components of the 600-GPH Reverse Osmosis Water Purification Unit (ROWPU), and Consideration of Reverse Osmosis (RO) Bypass, Potable-Water Disinfection, and Water-Quality Analysis Techniques

DTIC Science & Technology

1990-05-01

Health Risks in Potential Theaters of Operation for U.S. Military Forces. The nine volumes of this study contain a comprehensive assessment of the chemical...module. The percentage of total free chlorine ( hypochlorous acid , HOCl) plus hypochlorlte ion (OClN), measured by the Model 453 membrane sensor, varies...between the performances of the 600-Sph Reverse Osmosis Water Purification Unit (ROWPU) operated in the bypass node and ’the Mobile Water Purification

SEPARATION OF SOME RARE EARTHS BY REVERSED-PHASE PARTITION CHROMATOGRAPHY. Report No. 129/V; Rozdzielenie Niektorych Ziem Rzadkich za Pomoca Chromatografii Podzialowej z Odwroconymi Fazami

DOE Office of Scientific and Technical Information (OSTI.GOV)

Siekierski, S.; Fidelis, I.

1960-01-01

The reversed phase partition chromatography was applied to the separation of small amounts of some rare earths. As a stationary phase TBP was used. and the elution was carried out with concentrated HNO/sub 3/. (auth)

Using reversed phase high performance liquid chromatography to study the complexation of anthocyanins with β-cyclodextrin

NASA Astrophysics Data System (ADS)

Deineka, V. I.; Lapshova, M. S.; Deineka, L. A.

2014-06-01

It is shown by means of reversed phase high performance liquid chromatography (RP HPLC) with mobile phases containing additions of β-cyclodextrin that 5-glucosides of cyanidin and pelargonidin form stronger inclusion complexes than 3-glucosides; this is explained by the steric interference of the glucoside radical.

Reversible Phase Transition with Ultralarge Dielectric Relaxation Behaviors in Succinimide Lithium(I) Hybrids.

PubMed

Tang, Yun-Zhi; Wang, Bin; Zhou, Hai-Tao; Chen, Shao-Peng; Tan, Yu-Hui; Wang, Chang-Feng; Yang, Chang-Shan; Wen, He-Rui

2018-02-05

Dielectric relaxations have widely applied on high permittivity capacitors, dielectric switches, ferroelectrics, pyroelectrics, and electrical insulating materials. However, few investigations of large dielectric relaxation behaviors on organic-inorganic hybrid materials have been documented before. Here we present a novel two-dimensional succinimide lithium(I) hybrid compound, [Li(PDD) 2 ClO 4 ] n , 1, (PDD = 2,5-pyrrolidinedione = succinimide) which shows reversible phase transition behavior in the vicinity of 228 K accompanied by an unusual symmetry breaking from I4 1 /amd to C2/c. X-ray single crystal diffractions analysis indicates the twist motion of pyrrolidine heterocycles, and order-disorder motion of ClO 4 - anions triggered the reversible phase transition. By means of an intuitive crystallographic model (rattling ion model), we further illustrated the mechanism of the interesting reversible phase transition. Particularly, 1 shows ultralarge dielectric relaxation behavior in the vicinity of the phase transition by its dielectric constant dependence on temperatures and frequencies as well as its Cole-Cole relation.

Sensitivity models and design protocol for partitioning tracer tests in alluvial aquifers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jin, M.; Butler, G.W.; Jackson, R.E.

1997-11-01

Zones of dense, nonaqueous phase liquids (DNAPLs) are difficult to characterize as to their volume, composition, and spatial distribution using conventional ground-water extraction and soil-sampling methods. Such incompletely characterized sites have negative consequences for those responsible for their remedial design, e.g., the uncertainties in the optimal placement of ground-water extraction wells and in the duration of remediation. However, the recent use of the partitioning interwell tracer test (PITT) to characterize DNAPL zones at sites in New Mexico [unsaturated alluvium] and in Ohio, Texas, and Utah [saturated alluvium] demonstrates that the volume and spatial distribution of residual DNAPL can be determinedmore » with accuracy. The PITT involves injection of a suite of tracers which reversibly partition to different degrees between the DNAPL and the ground water or soil air resulting in the chromatographic separation of the tracer signals observed at the extraction well(s). The design of a PITT requires careful consideration of the hydrostratigraphic, hydraulic, and certain geochemical properties of the alluvium being tested. A three-dimensional, numerical model of a heterogeneous alluvial aquifer containing DNAPL has been developed for use with the UTCHEM simulator to demonstrate partitioning tracer testing and to address questions that are frequently raised in its application. The simulations include (1) the estimation of DNAPL volume for the simple case where only residual DNAPL is present in heterogeneous alluvium, (2) sensitivity studies to demonstrate the effect of increasingly low residual DNAPL saturation on the tracer signal, and (3) the effect of free-phase DNAPL on the estimation of the volume of DNAPL present. Furthermore, the potential interference of sedimentary organic carbon as a DNAPL surrogate on the tracer signal is considered and shown to be readily resolved by the careful choice of tracers.« less

Characterization and applications of reversed-phase column selectivity based on the hydrophobic-subtraction model.

PubMed

Marchand, D H; Snyder, L R; Dolan, J W

2008-05-16

A total of 371 reversed-phase columns have now been characterized in terms of selectivity, based on five solute-column interactions (the hydrophobic-subtraction model). The present study illustrates the use of these data for interpreting peak-tailing and column stability. New insights are also provided concerning column selectivity as a function of ligand and silica type, and the selection of columns for orthogonal separations is re-examined. Some suggestions for the quality control of reversed-phase columns during manufacture are offered.

Separation of Chloroplast Pigments Using Reverse Phase Chromatography.

ERIC Educational Resources Information Center

Reese, R. Neil

1997-01-01

Presents a protocol that uses reverse phase chromatography for the separation of chloroplast pigments. Provides a simple and relatively safe procedure for use in teaching laboratories. Discusses pigment extraction, chromatography, results, and advantages of the process. (JRH)

Reversible switching between pressure-induced amorphization and thermal-driven recrystallization in VO2(B) nanosheets

PubMed Central

Wang, Yonggang; Zhu, Jinlong; Yang, Wenge; Wen, Ting; Pravica, Michael; Liu, Zhenxian; Hou, Mingqiang; Fei, Yingwei; Kang, Lei; Lin, Zheshuai; Jin, Changqing; Zhao, Yusheng

2016-01-01

Pressure-induced amorphization (PIA) and thermal-driven recrystallization have been observed in many crystalline materials. However, controllable switching between PIA and a metastable phase has not been described yet, due to the challenge to establish feasible switching methods to control the pressure and temperature precisely. Here, we demonstrate a reversible switching between PIA and thermally-driven recrystallization of VO2(B) nanosheets. Comprehensive in situ experiments are performed to establish the precise conditions of the reversible phase transformations, which are normally hindered but occur with stimuli beyond the energy barrier. Spectral evidence and theoretical calculations reveal the pressure–structure relationship and the role of flexible VOx polyhedra in the structural switching process. Anomalous resistivity evolution and the participation of spin in the reversible phase transition are observed for the first time. Our findings have significant implications for the design of phase switching devices and the exploration of hidden amorphous materials. PMID:27426219

Four reversible and reconfigurable structures for three-phase emulsions: extended morphologies and applications

NASA Astrophysics Data System (ADS)

Ge, Xue-Hui; Geng, Yu-Hao; Zhang, Qiao-Chu; Shao, Meng; Chen, Jian; Luo, Guang-Sheng; Xu, Jian-Hong

2017-02-01

Here in this article, we classify and conclude the four morphologies of three-phase emulsions. Remarkably, we achieve the reversible transformations between every shape. Through theoretical analysis, we choose four liquid systems to form these four morphologies. Then monodispersed droplets with these four morphologies are formed through a microfluidic device and captured in a petri-dish. By replacing their ambient solution of the captured emulsions, in-situ morphology transformations between each shape are achieved. The process is well recorded through photographs and videos and they are systematical and reversible. Finally, we use the droplets structure to form an on-off switch to start and shut off the evaporation of one volatile phase to achieve the process monitoring. This could be used to initiate and quench a reaction, which offers a novel idea to achieve the switchable and reversible reaction control in multiple-phase reactions.

Reversible switching between pressure-induced amorphization and thermal-driven recrystallization in VO2(B) nanosheets.

PubMed

Wang, Yonggang; Zhu, Jinlong; Yang, Wenge; Wen, Ting; Pravica, Michael; Liu, Zhenxian; Hou, Mingqiang; Fei, Yingwei; Kang, Lei; Lin, Zheshuai; Jin, Changqing; Zhao, Yusheng

2016-07-18

Pressure-induced amorphization (PIA) and thermal-driven recrystallization have been observed in many crystalline materials. However, controllable switching between PIA and a metastable phase has not been described yet, due to the challenge to establish feasible switching methods to control the pressure and temperature precisely. Here, we demonstrate a reversible switching between PIA and thermally-driven recrystallization of VO2(B) nanosheets. Comprehensive in situ experiments are performed to establish the precise conditions of the reversible phase transformations, which are normally hindered but occur with stimuli beyond the energy barrier. Spectral evidence and theoretical calculations reveal the pressure-structure relationship and the role of flexible VOx polyhedra in the structural switching process. Anomalous resistivity evolution and the participation of spin in the reversible phase transition are observed for the first time. Our findings have significant implications for the design of phase switching devices and the exploration of hidden amorphous materials.

Spontaneous breaking of discrete symmetries in QCD on a small volume

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lucini, B.; Patella, A.; Pica, C.

2007-11-20

In a compact space with non-trivial cycles, for sufficiently small values of the compact dimensions, charge conjugation (C), spatial reflection (P) and time reversal (J) are spontaneously broken in QCD. The order parameter for the symmetry breaking is the trace of the Wilson line wrapping around the compact dimension, which acquires an imaginary part in the broken phase. We show that a physical signature for the symmetry breaking is a persistent baryonic current wrapping in the compact directions. The existence of such a current is derived analytically at first order in perturbation theory and confirmed in the non-perturbative regime bymore » lattice simulations.« less

Highly dissipative Hénon map behavior in the four-level model of the CO 2 laser with modulated losses

NASA Astrophysics Data System (ADS)

Pando L., C. L.; Acosta, G. A. Luna; Meucci, R.; Ciofini, M.

1995-02-01

We show that the four-level model for the CO 2 laser with modulated losses behaves in a qualitatively similar way as the highly dissipative Hénon map. The ubiquity of elements of the universal sequence, their related symbolic dynamics, and the presence of reverse bifurcations of chaotic bands in the model are reminiscent of the logistic map which is the limit of the Hénon map when the Jacobian equals zero. The coexistence of attractors, its dynamics related to contraction of volumes in phase space and the associated return maps can be correlated with those of the highly dissipative Hénon map.

Determination of residual nonsteroidal anti-inflammatory drugs in aqueous sample using magnetic nanoparticles modified with cetyltrimethylammonium bromide by high performance liquid chromatography.

PubMed

Khoeini Sharifabadi, Malihe; Saber-Tehrani, Mohammad; Waqif Husain, Syed; Mehdinia, Ali; Aberoomand-Azar, Parviz

2014-01-01

A simple and sensitive solid-phase extraction method for separation and preconcentration of trace amount of four nonsteroidal anti-inflammatory drugs (naproxen, indomethacin, diclofenac, and ibuprofen) using Fe3O4 magnetic nanoparticles modified with cetyltrimethylammonium bromide has been developed. For this purpose, the surface of MNPs was modified with cetyltrimethylammonium bromide (CTAB) as a cationic surfactant. Effects of different parameters influencing the extraction efficiency of drugs including the pH, amount of salt, shaking time, eluent type, the volume of solvent, amount of adsorbent, sample volume, and the time of desorption were investigated and optimized. Methanol has been used as desorption solvent and the extracts were analysed on a reversed-phase octadecyl silica column using 0.02 M phosphate-buffer (pH = 6.02) acetonitrile (65 : 35 v/v) as the mobile phase and the effluents were measured at 202 nm with ultraviolet detector. The relative standard deviation (RSD%) of the method was investigated at three concentrations (25, 50, and 200 ng/mL) and was in the range of 3.98-9.83% (n = 6) for 50 ng/mL. The calibration curves obtained for studied drugs show reasonable linearity (R (2) > 0.99) and the limit of detection (LODs) ranged between 2 and 7 ng/mL. Finally, the proposed method has been effectively employed in extraction and determination of the drugs in biological and environmental samples.

PHYSICAL EFFECTS OCCURRING DURING GENERATION AND AMPLIFICATION OF LASER RADIATION: Reversal of the contrast of optical radiation in round-trip amplifiers with a phase conjugation mirror

NASA Astrophysics Data System (ADS)

Afanas'ev, Anatolii A.; Samson, B. A.

1989-02-01

A description is given of a method for inversion of the contrast of optical radiation in a round-trip amplifier with a phase conjugation mirror and a phase nonreciprocal element. The system can be used to achieve high powers of contrast-reversed radiation because of compensation of phase distortions introduced by amplification.

A method for the direct injection and analysis of small volume human blood spots and plasma extracts containing high concentrations of organic solvents using revered-phase 2D UPLC/MS.

PubMed

Rainville, Paul D; Simeone, Jennifer L; Root, Dan S; Mallet, Claude R; Wilson, Ian D; Plumb, Robert S

2015-03-21

The emergence of micro sampling techniques holds great potential to improve pharmacokinetic data quality, reduce animal usage, and save costs in safety assessment studies. The analysis of these samples presents new challenges for bioanalytical scientists, both in terms of sample processing and analytical sensitivity. The use of two dimensional LC/MS with, at-column-dilution for the direct analysis of highly organic extracts prepared from biological fluids such as dried blood spots and plasma is demonstrated. This technique negated the need to dry down and reconstitute, or dilute samples with water/aqueous buffer solutions, prior to injection onto a reversed-phase LC system. A mixture of model drugs, including bromhexine, triprolidine, enrofloxacin, and procaine were used to test the feasibility of the method. Finally an LC/MS assay for the probe pharmaceutical rosuvastatin was developed from dried blood spots and protein-precipitated plasma. The assays showed acceptable recovery, accuracy and precision according to US FDA guidelines. The resulting analytical method showed an increase in assay sensitivity of up to forty fold as compared to conventional methods by maximizing the amount loaded onto the system and the MS response for the probe pharmaceutical rosuvastatin from small volume samples.

Reversal of Increasing Tropical Ocean Hypoxia Trends With Sustained Climate Warming

NASA Astrophysics Data System (ADS)

Fu, Weiwei; Primeau, Francois; Keith Moore, J.; Lindsay, Keith; Randerson, James T.

2018-04-01

Dissolved oxygen (O2) is essential for the survival of marine animals. Climate change impacts on future oxygen distributions could modify species biogeography, trophic interactions, biodiversity, and biogeochemistry. The Coupled Model Intercomparison Project Phase 5 models predict a decreasing trend in marine O2 over the 21st century. Here we show that this increasing hypoxia trend reverses in the tropics after 2100 in the Community Earth System Model forced by atmospheric CO2 from the Representative Concentration Pathway 8.5 and Extended Concentration Pathway 8.5. In tropical intermediate waters between 200 and 1,000 m, the model predicts a steady decline of O2 and an expansion of oxygen minimum zones (OMZs) during the 21st century. By 2150, however, the trend reverses with oxygen concentration increasing and OMZ volume shrinking through 2300. A novel five-box model approach in conjunction with output from the full Earth system model is used to separate the contributions of biological and physical processes to the trends in tropical oxygen. The tropical O2 recovery is caused mainly by reductions in tropical biological export, coupled with a modest increase in ventilation after 2200. The time-evolving oxygen distribution impacts marine nitrogen cycling, with potentially important climate feedbacks.

Mechanical and Infrared Thermography Analysis of Shape Memory Polyurethane

NASA Astrophysics Data System (ADS)

Pieczyska, Elzbieta Alicja; Maj, Michal; Kowalczyk-Gajewska, Katarzyna; Staszczak, Maria; Urbanski, Leszek; Tobushi, Hisaaki; Hayashi, Shunichi; Cristea, Mariana

2014-07-01

Multifunctional new material—polyurethane shape memory polymer (PU-SMP)—was subjected to tension carried out at room temperature at various strain rates. The influence of effects of thermomechanical couplings on the SMP mechanical properties was studied, based on the sample temperature changes, measured by a fast and sensitive infrared camera. It was found that the polymer deformation process strongly depends on the strain rate applied. The initial reversible strain is accompanied by a small drop in temperature, called thermoelastic effect. Its maximal value is related to the SMP yield point and increases upon increase of the strain rate. At higher strains, the stress and temperature significantly increase, caused by reorientation of the polymer molecular chains, followed by the stress drop and its subsequent increase accompanying the sample rupture. The higher strain rate, the higher stress, and temperature changes were obtained, since the deformation process was more dynamic and has occurred in almost adiabatic conditions. The constitutive model of SMP valid in finite strain regime was developed. In the proposed approach, SMP is described as a two-phase material composed of hyperelastic rubbery phase and elastic-viscoplastic glassy phase, while the volume content of phases is specified by the current temperature.

Cardiovascular response to prescribed detraining among recreational athletes.

PubMed

Pedlar, Charles R; Brown, Marcel G; Shave, Robert E; Otto, James M; Drane, Aimee; Michaud-Finch, Jennifer; Contursi, Miranda; Wasfy, Meagan M; Hutter, Adolph; Picard, Michael H; Lewis, Gregory D; Baggish, Aaron L

2018-04-01

Exercise-induced cardiac remodeling (EICR) and the attendant myocardial adaptations characteristic of the athlete's heart may regress during periods of exercise reduction or abstinence. The time course and mechanisms underlying this reverse remodeling, specifically the impact of concomitant plasma volume (PV) contraction on cardiac chamber size, remain incompletely understood. We therefore studied recreational runners ( n = 21, age 34 ± 7 yr; 48% male) who completed an 18-wk training program (~7 h/wk) culminating in the 2016 Boston Marathon after which total exercise exposure was confined to <2 h/wk (no single session >1 h) for 8 wk. Cardiac structure and function, exercise capacity, and PV were assessed at peak fitness (10-14 days before) and at 4 wk and 8 wk postmarathon. Mixed linear modeling adjusting for age, sex, V̇o 2peak , and marathon finish time was used to compare data across time points. Physiological detraining was evidenced by serial reductions in treadmill performance. Two distinct phases of myocardial remodeling and hematological adaptation were observed. After 4 wk of detraining, there were significant reductions in PV (Δ -6.0%, P < 0.01), left ventricular (LV) wall thickness (Δ -8.1%, <0.05), LV mass (Δ -10.3%, P < 0.001), and right atrial area (Δ -8.2%, P < 0.001). After 8 wk of detraining, there was a significant reduction in right ventricle chamber size (end-diastolic area Δ = -8.0%, P < 0.05) without further concomitant reductions in PV or LV wall thickness. Abrupt reductions in exercise training stimulus result in a structure-specific time course of reverse cardiac remodeling that occurs largely independently of PV contraction. NEW & NOTEWORTHY Significant reverse cardiac remodeling, previously documented among competitive athletes, extends to recreational runners and occurs with a distinct time course. Initial reductions in plasma volume and left ventricular (LV) mass, driven by reductions in wall thickness, are followed by contraction of the right ventricle. Consistent with data from competitive athletes, LV chamber volumes appear less responsive to detraining and may be a more permanent adaptation to sport.

Main reinforcement effects of precipitation phase Mg2Cu3Si, Mg2Si and MgCu2 on Mg-Cu-Si alloys by ab initio investigation

NASA Astrophysics Data System (ADS)

Shi, Xue-Feng; Wang, Hai-Chen; Tang, Ping-Ying; Tang, Bi-Yu

2017-09-01

To predict and compare the main reinforcement effects of the key precipitation phases Mg2Cu3Si, Mg2Si and MgCu2 in Mg-Cu-Si alloy, the structural, mechanical and electronic properties of these phases have been studied by ab initio calculations. The lowest formation enthalpy and cohesive energy indicate that Mg2Cu3Si has the strongest alloying ability and structural stability. The mechanical modulus indicates that Mg2Cu3Si has the strongest resistance to reversible shear/volume distortion and has maximum hardness. The characterization of brittle (ductile) behavior manifests that MgCu2 has favorable ductility. Meanwhile the evaluation of elastic anisotropy indicates that Mg2Si possesses elastic isotropy. Debye temperature prediction shows that Mg2Si and Mg2Cu3Si have better thermal stability. To achieve an unbiased interpretation on the phase stability and mechanical behavior of these precipitation phases, the density of states and differential charge densities are also analyzed. The current study deepens the comprehensive understanding of main reinforcement effects of these precipitation phases on Mg-Cu-Si alloys, and also benefits to optimize the overall performances of Mg-Cu-Si alloy from the hardness, ductility and thermal stability by controlling these second precipitation phases during the heat treatment process.

Study on the Electrochemical Reaction Mechanism of ZnFe2O4 by In Situ Transmission Electron Microscopy

PubMed Central

Su, Qingmei; Wang, Shixin; Yao, Libing; Li, Haojie; Du, Gaohui; Ye, Huiqun; Fang, Yunzhang

2016-01-01

A family of mixed transition–metal oxides (MTMOs) has great potential for applications as anodes for lithium ion batteries (LIBs). However, the reaction mechanism of MTMOs anodes during lithiation/delithiation is remain unclear. Here, the lithiation/delithiation processes of ZnFe2O4 nanoparticles are observed dynamically using in situ transmission electron microscopy (TEM). Our results suggest that during the first lithiation process the ZnFe2O4 nanoparticles undergo a conversion process and generate a composite structure of 1–3 nm Fe and Zn nanograins within Li2O matrix. During the delithiation process, volume contraction and the conversion of Zn and Fe take place with the disappearance of Li2O, followed by the complete conversion to Fe2O3 and ZnO not the original phase ZnFe2O4. The following cycles are dominated by the full reversible phase conversion between Zn, Fe and ZnO, Fe2O3. The Fe valence evolution during cycles evidenced by electron energy–loss spectroscopy (EELS) techniques also exhibit the reversible conversion between Fe and Fe2O3 after the first lithiation, agreeing well with the in situ TEM results. Such in situ TEM observations provide valuable phenomenological insights into electrochemical reaction of MTMOs, which may help to optimize the composition of anode materials for further improved electrochemical performance. PMID:27306189

Hydrodynamic dispersion of microswimmers in suspension

NASA Astrophysics Data System (ADS)

Martin, Matthieu; Rafaï, Salima; Peyla, Philippe

2014-11-01

In our laboratory, we study hydrodynamics of suspensions of micro-swimmers. These micro-organisms are unicellular algae Chlamydomonas Rheinhardii which are able to swim by using their flagella. The swimming dynamics of these micro-swimmers can be seen as a random walk, in absence of any kind of interaction. In addition, these algae have the property of being phototactic, i.e. they swim towards the light. Combining this property with a hydrodynamic flow, we were able to reversibly separate algae from the rest of the fluid. But for sufficiently high volume fraction, these active particles interact with each other. We are now interested in how the coupling of hydrodynamic interactions between swimmers and phototaxis can modify the swimming dynamics at the scale of the suspension. To this aim, we conduct experiments in microfluidic devices to study the dispersion of the micro-organisms in a the liquid phase as a function of the volume fraction. We show that the dispersion of an assembly of puller type microswimmers is quantitatively affected by hydrodynamics interactions. Phd student.

Synthesis and evaluation of porous polymethylsilsesquioxane microspheres as low silanol activity chromatographic stationary phase for basic compound separation.

PubMed

Huo, Zhixia; Wan, Qianhong; Chen, Lei

2018-06-08

Polymethylsilsesquioxanes (PMSQ) are potentially useful materials for liquid chromatography owing to their unique chemical, electrical and mechanical properties. Surprisingly however, no systematic studies on the use of spherical PMSQ particles as chromatographic packing have been reported. Accordingly, we present a comprehensive study aimed to characterize the chromatographic properties of this material in high performance liquid chromatography (HPLC) and to compare them with those observed on methyl (C 1 ) bonded silica phase under comparable conditions. Porous spherical particles were synthesized by a two-step hydrolysis and condensation procedure from methyltrimethoxysilane (MTMS) as a sole precursor. The as-synthesized microspheres possess spherical shape, narrow size distribution, mesoporous structure, high surface area (817 m 2  g -1 ) and reasonable carbon load (16.6%). They can be used directly as the HPLC stationary phase without the need for size classification. The PMSQ phase exhibits typical reversed-phase chromatographic properties with higher methylene selectivity and low silanol activity compared with the C 1 column. The retention mechanism for basic compounds was systematically evaluated by studying the effect of pH, ionic and solvent strength of the mobile phase. Basic compounds displayed lower retention factor and symmetric peak shape on the PMSQ column whereas longer retention and strong tailing peaks were observed on the C 1 column. The difference in retention behavior between the two columns is explained in terms of different principal retention mechanisms. Because of the low silanol activity, retention of basic compounds on the PMSQ column is governed solely by a reversed-phase mechanism. By contrast, multiple interactions including reversed-phase, cation exchange and simultaneous reversed-phase/cationic exchange interaction contribute to the retention on the C 1 column, as previously observed on other silica based reversed-phases. Furthermore, the PMSQ phase exhibited significantly enhanced stability under alkaline conditions compared with its silica-based counterpart. Taken together, the favorable morphology and pore structure combined with the benefits of low silanol activity, high pH stability and prolonged column lifetime make the newly developed PMSQ phase a promising and viable alternative to silica based reversed-phase packings for separation of basic compounds. Copyright © 2018 Elsevier B.V. All rights reserved.

Mixed-Mode Operation of Hybrid Phase-Change Nanophotonic Circuits.

PubMed

Lu, Yegang; Stegmaier, Matthias; Nukala, Pavan; Giambra, Marco A; Ferrari, Simone; Busacca, Alessandro; Pernice, Wolfram H P; Agarwal, Ritesh

2017-01-11

Phase change materials (PCMs) are highly attractive for nonvolatile electrical and all-optical memory applications because of unique features such as ultrafast and reversible phase transitions, long-term endurance, and high scalability to nanoscale dimensions. Understanding their transient characteristics upon phase transition in both the electrical and the optical domains is essential for using PCMs in future multifunctional optoelectronic circuits. Here, we use a PCM nanowire embedded into a nanophotonic circuit to study switching dynamics in mixed-mode operation. Evanescent coupling between light traveling along waveguides and a phase-change nanowire enables reversible phase transition between amorphous and crystalline states. We perform time-resolved measurements of the transient change in both the optical transmission and resistance of the nanowire and show reversible switching operations in both the optical and the electrical domains. Our results pave the way toward on-chip multifunctional optoelectronic integrated devices, waveguide integrated memories, and hybrid processing applications.

A reversed phase high performance liquid chromatography method for the determination of fumonisins B1 and B2 in food and feed using monolithic column and positive confirmation by liquid chromatography/tandem mass spectrometry.

PubMed

Khayoon, Wejdan Shakir; Saad, Bahruddin; Salleh, Baharuddin; Ismail, Nor Azliza; Abdul Manaf, Normaliza Hj; Abdul Latiff, Aishah

2010-10-29

The development of a reversed phase high performance liquid chromatography fluorescence method for the determination of the mycotoxins fumonisin B(1) and fumonisin B(2) by using silica-based monolithic column is described. The samples were first extracted using acetonitrile:water (50:50, v/v) and purified by using a C(18) solid phase extraction-based clean-up column. Then, pre-column derivatization for the analyte using ortho-phthaldialdehyde in the presence of 2-mercaptoethanol was carried out. The developed method involved optimization of mobile phase composition using methanol and phosphate buffer, injection volume, temperature and flow rate. The liquid chromatographic separation was performed using a reversed phase Chromolith(®) RP-18e column (100 mm × 4.6 mm) at 30 °C and eluted with a mobile phase of a mixture of methanol and phosphate buffer pH 3.35 (78:22, v/v) at a flow rate of 1.0 mL min(-1). The fumonisins separation was achieved in about 4 min, compared to approximately 20 min by using a C(18) particle-packed column. The fluorescence excitation and emission were at 335 nm and 440 nm, respectively. The limits of detections were 0.01-0.04 μg g(-1) fumonisin B(1) and fumonisin B(2), respectively. Good recoveries were found for spiked samples (0.1, 0.5, 1.5 μg g(-1) fumonisins B(1) and B(2)), ranging from 84.0 to 106.0% for fumonisin B(1) and from 81.0 to 103.0% for fumonisin B(2). Fifty-three samples were analyzed including 39 food and feeds and 14 inoculated corn and rice. Results show that 12.8% of the food and feed samples were contaminated with fumonisin B(1) (range, 0.01-0.51 μg g(-1)) and fumonisin B(2) (0.05 μg g(-1)). The total fumonisins in these samples however, do not exceed the legal limits established by the European Union of 0.8 μg g(-1). Of the 14 inoculated samples, 57.1% contained fumonisin B(1) (0.16-41.0 μg g(-1)) and fumonisin B(2) (range, 0.22-50.0 μg g(-1)). Positive confirmation of selected samples was carried out using liquid chromatography-tandem mass spectrometry, using triple quadrupole analyzer and operated in the multiple reaction monitoring mode. Copyright © 2010 Elsevier B.V. All rights reserved.

Reversed association between aldosterone and mortality in hemodialysis patients: Role of volume overload.

PubMed

Hung, Szu-Chun; Tarng, Der-Cherng

2016-07-01

The role of aldosterone has expanded from its genomic effects that involve renal sodium transport to nongenomic effects such as cardiac and renal fibrosis. Elevated aldosterone levels are associated with increased mortality in the general population. However, the association is reversed in patients with end-stage renal disease on maintenance hemodialysis. We have shown that the inverse association between aldosterone and mortality in hemodialysis patients is due to the confounding effect of volume overload. Volume overload, which is prevalent in patients with chronic kidney disease, is associated with both lower aldosterone concentrations and higher mortality. Our findings support salt and water restriction and treatment of hyperaldosteronemia in hemodialysis patients who have achieved strict volume control. Copyright © 2016 Elsevier Inc. All rights reserved.

First interactions between hydrogen and stress-induced reverse transformation of Ni-Ti superelastic alloy

NASA Astrophysics Data System (ADS)

Yokoyama, Ken'ichi; Hashimoto, Tatsuki; Sakai, Jun'ichi

2017-11-01

The first dynamic interactions between hydrogen and the stress-induced reverse transformation have been investigated by performing an unloading test on a Ni-Ti superelastic alloy subjected to hydrogen charging under a constant applied strain in the elastic deformation region of the martensite phase. Upon unloading the specimen, charged with a small amount of hydrogen, no change in the behaviour of the stress-induced reverse transformation is observed in the stress-strain curve, although the behaviour of the stress-induced martensite transformation changes. With increasing amount of hydrogen charging, the critical stress for the reverse transformation markedly decreases. Eventually, for a larger amount of hydrogen charging, the reverse transformation does not occur, i.e. there is no recovery of the superelastic strain. The residual martensite phase on the side surface of the unloaded specimen is confirmed by X-ray diffraction. Upon training before the unloading test, the properties of the reverse transformation slightly recover after ageing in air at room temperature. The present study indicates that to change the behaviour of the reverse transformation a larger amount of hydrogen than that for the martensite transformation is necessary. In addition, it is likely that a substantial amount of hydrogen in solid solution more strongly suppresses the reverse transformation than hydrogen trapped at defects, thereby stabilising the martensite phase.

Recovery of Picloram and 2,4-Dichlorophenoxyacetic Acid from Aqueous Samples by Reversed-Phase Solid-Phase Extraction

Treesearch

Martha J.M. Wells; Jerry L. Michael

1987-01-01

Extensive preparation of samples before chromatographic analysis is usually the most time-consuming process in the determination of many organic compounds in environmental matrices. In the past, removal of some organic from aqueous solution was commonly done by liquid/liquid extraction. However, the introduction of stable, covalently bonded reversed-phase sorbents now...

Use of nitrogen to remove solvent from through oven transfer adsorption desorption interface during analysis of polycyclic aromatic hydrocarbons by large volume injection in gas chromatography.

PubMed

Áragón, Alvaro; Toledano, Rosa M; Cortés, José M; Vázquez, Ana M; Villén, Jesús

2014-04-25

The through oven transfer adsorption desorption (TOTAD) interface allows large volume injection (LVI) in gas chromatography and the on-line coupling of liquid chromatography and gas chromatography (LC-GC), enabling the LC step to be carried out in normal as well as in reversed phase. However, large amounts of helium, which is both expensive and scarce, are necessary for solvent elimination. We describe how slight modification of the interface and the operating mode allows nitrogen to be used during the solvent elimination steps. In order to evaluate the performance of the new system, volumes ranging from 20 to 100μL of methanolic solutions of four polycyclic aromatic hydrocarbons (PAHs) were sampled. No significant differences were found in the repeatability and sensitivity of the analyses of standard PAH solutions when using nitrogen or helium. The performance using the proposed modification was similar and equally satisfactory when using nitrogen or helium for solvent elimination in the TOTAD interface. In conclusion, the use of nitrogen will make analyses less expensive. Copyright © 2014 Elsevier B.V. All rights reserved.

Highly Viscoelastic Reverse Wormlike Micellar Systems from a Mixture of Lecithin, Polyglycerol Fatty Acid Monoesters, and an Oil.

PubMed

Hashizaki, Kaname; Imai, Miko; Yako, Shuhei; Tsusaka, Hitomi; Sakanishi, Yuichi; Saito, Yoshihiro; Fujii, Makiko

2017-09-01

We report new lecithin reverse wormlike micelles with high viscoelasticity formed using lecithin/polyglycerol fatty acid monoester (PGLFA)/oil systems. In this study, the influence of the amphiphilicity (i.e., hydrophile-lipophile balance, HLB) of PGLFA on the phase behavior and rheological properties of reverse wormlike micelles was investigated in detail. PGLFAs with degrees of polymerization of polyglycerol varying between 6-40 and constituent fatty acids with chains between 6-18 carbon atoms long were used. Partial phase diagrams of the lecithin/PGLFA/n-decane systems indicated that the appropriate PGLFA could change the lecithin/oil solution into a highly viscoelastic solution comprising reverse wormlike micelles. Rheological measurements showed that all systems that formed reverse wormlike micelles exhibited an unusual phenomenon called "shear-thickening". Furthermore, reverse wormlike micelles grew as the PGLFA concentration increased and the zero-shear viscosity (η 0 ) of the solution rapidly increased. Our results indicate that the magnitude of the maximum η 0 depends on the degree of polymerization of the constituent polyglycerol in the PGLFA, while the size of the reverse micellar region and the highly viscous region in the phase diagram depends on the HLB value of the PGLFA.

Medial Prefrontal Administration of MK-801 Impairs T-maze Discrimination Reversal Learning in Weanling Rats

PubMed Central

Watson, Deborah J.; Stanton, Mark E.

2009-01-01

Several executive functions rely on the medial prefrontal cortex (mPFC) in the rat. Aspiration and neurotoxic lesions of the mPFC impair reversal learning in adult rats [1, 16, 34, 55]. Systemic administration of MK-801, an NMDA receptor antagonist, impairs T-maze reversal learning in weanling rats but the role of mPFC NMDA receptor antagonism in this effect is not known in either adult or young animals. This set of studies showed that mPFC NMDA receptors are specifically involved in T-maze discrimination reversal in weanling rats. In Experiment 1, 26-day-old rats (P26) demonstrated a dose-dependent impairment following bilateral mPFC administration of either 2.5 or 5.0 µg MK-801 or saline (vehicle) during the reversal training phase only. In Experiment 2, P26 rats were trained on the same task, but 4 groups of rats received bilateral mPFC infusions during acquisition only (MK-SAL), reversal only (SAL-MK), both phases (MK-MK) or neither phase (SAL-SAL). MK-801 impaired performance only when infused during reversal. This suggests that NMDA receptor antagonism in the mPFC is selectively involved in reversal learning during development and this may account for the previously reported effects of systemic MK-801 on T-maze discrimination reversal in weanling rats. PMID:19643149

Magnetization reversal mechanism and coercivity enhancement in three-dimensional granular Nd-Fe-B magnets studied by micromagnetic simulations

NASA Astrophysics Data System (ADS)

Lee, Jae-Hyeok; Choe, Jinhyeok; Hwang, Shinwon; Kim, Sang-Koog

2017-08-01

We studied the mechanism of magnetization reversals and coercivity enhancements in three-dimensional (3D) granular Nd-Fe-B permanent magnets using finite-element micromagnetic simulations. The magnetization reversals in the hard magnets consisting of hard-phase grains separated by relatively soft-phase grain boundaries were analyzed with reference to the simulation results for the magnetic field-dependent distributions of the local magnetizations. The saturation magnetization of the grain-boundary phase plays a crucial role in the transition between nucleation- and domain-wall-propagation-controlled reversal processes. The smaller the saturation magnetization of the grain-boundary phase is, the more preferable is the nucleation-controlled process, which results in a larger coercivity. The exchange stiffness of the grain-boundary phase determines the preferred paths of domain-wall propagations, whether inward into grains or along the grain boundaries for relatively small and large exchange stiffness, respectively. However, the exchange stiffness of the grain-boundary phase alone does not significantly contribute to coercivity enhancement in cases where the size of hard-phase grains is much greater than the exchange length. This work paves the way for the design of high-performance hard magnets of large coercivity and maximum-energy-product values.

Reversal learning and resurgence of operant behavior in zebrafish (Danio rerio).

PubMed

Kuroda, Toshikazu; Mizutani, Yuto; Cançado, Carlos R X; Podlesnik, Christopher A

2017-09-01

Zebrafish are used extensively as vertebrate animal models in biomedical research for having such features as a fully sequenced genome and transparent embryo. Yet, operant-conditioning studies with this species are scarce. The present study investigated reversal learning and resurgence of operant behavior in zebrafish. A target response (approaching a sensor) was reinforced in Phase 1. In Phase 2, the target response was extinguished while reinforcing an alternative response (approaching a different sensor). In Phase 3, extinction was in effect for the target and alternative responses. Reversal learning was demonstrated when responding tracked contingency changes between Phases 1 and 2. Moreover, resurgence occurred in 10 of 13 fish in Phase 3: Target response rates increased transiently and exceeded rates of an unreinforced control response. The present study provides the first evidence with zebrafish supporting reversal learning between discrete operant responses and a laboratory model of relapse. These findings open the possibility to assessing genetic influences of operant behavior generally and in models of relapse (e.g., resurgence, renewal, reinstatement). Copyright © 2017 Elsevier B.V. All rights reserved.

Phase behaviors of supramolecular graft copolymers with reversible bonding

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, Xu; Wang, Liquan, E-mail: jlin@ecust.edu.cn, E-mail: lq-wang@ecust.edu.cn; Jiang, Tao

2013-11-14

Phase behaviors of supramolecular graft copolymers with reversible bonding interactions were examined by the random-phase approximation and real-space implemented self-consistent field theory. The studied supramolecular graft copolymers consist of two different types of mutually incompatible yet reactive homopolymers, where one homopolymer (backbone) possesses multifunctional groups that allow second homopolymers (grafts) to be placed on. The calculations carried out show that the bonding strength exerts a pronounced effect on the phase behaviors of supramolecular graft copolymers. The length ratio of backbone to graft and the positions of functional groups along the backbone are also of importance to determine the phase behaviors.more » Phase diagrams were constructed at high bonding strength to illustrate this architectural dependence. It was found that the excess unbounded homopolymers swell the phase domains and shift the phase boundaries. The results were finally compared with the available experimental observations, and a well agreement is shown. The present work could, in principle, provide a general understanding of the phase behaviors of supramolecular graft copolymers with reversible bonding.« less

High pressure behavior of complex phosphate K2Ce[PO4]2: Grüneisen parameter and anharmonicity properties

NASA Astrophysics Data System (ADS)

Mishra, Karuna Kara; Bevara, Samatha; Ravindran, T. R.; Patwe, S. J.; Gupta, Mayanak K.; Mittal, Ranjan; Krishnan, R. Venkata; Achary, S. N.; Tyagi, A. K.

2018-02-01

Herein we reported structural stability, vibrational and thermal properties of K2Ce[PO4]2, a relatively underexplored complex phosphate of tetravalent Ce4+ from in situ high-pressure Raman spectroscopic investigations up to 28 GPa using a diamond anvil cell. The studies identified the soft phonons that lead to a reversible phase transformation above 8 GPa, and a phase coexistence of ambient (PI) and high pressure (PII) phases in a wider pressure region 6-11 GPa. From a visual representation of the computed eigen vector displacements, the Ag soft mode at 82 cm-1 is assigned as a lattice mode of K+ cation. Pressure-induced positional disorder is apparent from the substantial broadening of internal modes and the disappearance of low frequency lattice and external modes in phase PII above 18 GPa. Isothermal mode Grüneisen parameters γi of the various phonon modes are calculated and compared for several modes. Using these values, thermal properties such as average Grüneisen parameter, and thermal expansion coefficient are estimated as 0.47, and 2.5 × 10-6 K-1, respectively. The specific heat value was estimated from all optical modes obtained from DFT calculations as 314 J-mol-1 K-1. Our earlier reported temperature dependence of phonon frequencies is used to decouple the "true anharmonic" (explicit contribution at constant volume) and "quasi harmonic" (implicit contribution brought out by volume change) contributions from the total anharmonicity. In addition to the 81 cm-1 Ag lattice mode, several other lattice and external modes of PO43- ions are found to be strongly anharmonic.

A fundamental study of the impact of pressure on the adsorption mechanism in reversed-phase liquid chromatography.

PubMed

Åsberg, Dennis; Samuelsson, Jörgen; Fornstedt, Torgny

2016-07-29

A fundamental investigation of the pressure effect on individual adsorption sites was undertaken based on adsorption energy distribution and adsorption isotherm measurements. For this purpose, we measured adsorption equilibrium data at pressures ranging from 100 to 1000bar at constant flow and over a wide concentration range for three low-molecular-weight solutes, antipyrine, sodium 2-naphthalenesulfonate, and benzyltriethylammonium chloride, on an Eternity C18 stationary phase. The adsorption energy distribution was bimodal for all solutes, remaining clearly so at all pressures. The bi-Langmuir model best described the adsorption in these systems and two types of adsorption sites were identified, one with a low and another with a high energy of interaction. Evidence exists that the low-energy interactions occur at the interface between the mobile and stationary phases and that the high-energy interactions occur nearer the silica surface, deeper in the C18 layer. The contribution of each type of adsorption site to the retention factor was calculated and the change in solute molar volume from the mobile to stationary phase during the adsorption process was estimated for each type of site. The change in solute molar volume was 2-4 times larger at the high-energy site, likely because of the greater loss of solute solvation layer when penetrating deeper into the C18 layer. The association equilibrium constant increased with increasing pressure while the saturation capacity of the low-energy site remained almost unchanged. The observed increase in saturation capacity for the high-energy site did not affect the column loading capacity, which was almost identical at 50- and 950-bar pressure drops over the column. Copyright © 2016 Elsevier B.V. All rights reserved.

Phase-ambiguity resolution for QPSK modulation systems. Part 2: A method to resolve offset QPSK

NASA Technical Reports Server (NTRS)

Nguyen, Tien Manh

1989-01-01

Part 2 presents a new method to resolve the phase-ambiguity for Offset QPSK modulation systems. When an Offset Quaternary Phase-Shift-Keyed (OQPSK) communications link is utilized, the phase ambiguity of the reference carrier must be resolved. At the transmitter, two different unique words are separately modulated onto the quadrature carriers. At the receiver, the recovered carrier may have one of four possible phases, 0, 90, 180, or 270 degrees, referenced to the nominally correct phase. The IF portion of the channel may cause a phase-sense reversal, i.e., a reversal in the direction of phase rotation for a specified bit pattern. Hence, eight possible phase relationships (the so-called eight ambiguous phase conditions) between input and output of the demodulator must be resolved. Using the In-phase (I)/Quadrature (Q) channel reversal correcting property of an OQPSK Costas loop with integrated symbol synchronization, four ambiguous phase conditions are eliminated. Thus, only four possible ambiguous phase conditions remain. The errors caused by the remaining ambiguous phase conditions can be corrected by monitoring and detecting the polarity of the two unique words. The correction of the unique word polarities results in the complete phase-ambiguity resolution for the OQPSK system.

Solvation Dynamics in Different Phases of the Lyotropic Liquid Crystalline System.

PubMed

Roy, Bibhisan; Satpathi, Sagar; Gavvala, Krishna; Koninti, Raj Kumar; Hazra, Partha

2015-09-03

Reverse hexagonal (HII) liquid crystalline material based on glycerol monooleate (GMO) is considered as a potential carrier for drugs and other important biomolecules due to its thermotropic phase change and excellent morphology. In this work, the dynamics of encapsulated water, which plays important role in stabilization and formation of reverse hexagonal mesophase, has been investigated by time dependent Stokes shift method using Coumarin-343 as a solvation probe. The formation of the reverse hexagonal mesophase (HII) and transformation to the L2 phase have been monitored using small-angle X-ray scattering and polarized light microscopy experiments. REES studies suggest the existence of different polar regions in both HII and L2 systems. The solvation dynamics study inside the reverse hexagonal (HII) phase reveals the existence of two different types of water molecules exhibiting dynamics on a 120-900 ps time scale. The estimated diffusion coefficients of both types of water molecules obtained from the observed dynamics are in good agreement with the measured diffusion coefficient collected from the NMR study. The calculated activation energy is found to be 2.05 kcal/mol, which is associated with coupled rotational-translational water relaxation dynamics upon the transition from "bound" to "quasi-free" state. The observed ∼2 ns faster dynamics of the L2 phase compared to the HII phase may be associated with both the phase transformation as well as thermotropic effect on the relaxation process. Microviscosities calculated from time-resolved anisotropy studies infer that the interface is almost ∼22 times higher viscous than the central part of the cylinder. Overall, our results reveal the unique dynamical features of water inside the cylinder of reverse hexagonal and inverse micellar phases.

Sustained diffusion reversal with in-bore reperfusion in monkey stroke models: Confirmed by prospective magnetic resonance imaging

PubMed Central

Yi, Kyung Sik; Choi, Chi-Hoon; Lee, Sang-Rae; Lee, Hong Jun; Lee, Youngjeon; Jeong, Kang-Jin; Hwang, Jinwoo; Chang, Kyu-Tae

2016-01-01

Although early diffusion lesion reversal after recanalization treatment of acute ischaemic stroke has been observed in clinical settings, the reversibility of lesions observed by diffusion-weighted imaging remains controversial. Here, we present consistent observations of sustained diffusion lesion reversal after transient middle cerebral artery occlusion in a monkey stroke model. Seven rhesus macaques were subjected to endovascular transient middle cerebral artery occlusion with in-bore reperfusion confirmed by repeated prospective diffusion-weighted imaging. Early diffusion lesion reversal was defined as lesion reversal at 3 h after reperfusion. Sustained diffusion lesion reversal was defined as the difference between the ADC-derived pre-reperfusion maximal ischemic lesion volume (ADCD-P Match) and the lesion on 4-week follow-up FLAIR magnetic resonance imaging. Diffusion lesions were spatiotemporally assessed using a 3-D voxel-based quantitative technique. The ADCD-P Match was 9.7 ± 6.0% (mean ± SD) and the final infarct was 1.2–6.0% of the volume of the ipsilateral hemisphere. Early diffusion lesion reversal and sustained diffusion lesion reversal were observed in all seven animals, and the calculated percentages compared with their ADCD-P Match ranged from 8.3 to 51.9% (mean ± SD, 26.9 ± 15.3%) and 41.7–77.8% (mean ± SD, 65.4 ± 12.2%), respectively. Substantial sustained diffusion lesion reversal and early reversal were observed in all animals in this monkey model of transient focal cerebral ischaemia. PMID:27401804

Pulmonary function in microgravity

NASA Technical Reports Server (NTRS)

Guy, H. J.; Prisk, G. K.; West, J. B.

1992-01-01

We report the successful collection of a large quantity of human resting pulmonary function data on the SLS-1 mission. Preliminary analysis suggests that cardiac stroke volumes are high on orbit, and that an adaptive reduction takes at least several days, and in fact may still be in progress after 9 days on orbit. It also suggests that pulmonary capillary blood volumes are high, and remain high on orbit, but that the pulmonary interstitium is not significantly impacted. The data further suggest that the known large gravitational gradients of lung function have only a modest influence on single breath tests such as the SBN washout. They account for only approximately 25% of the phase III slope of nitrogen, on vital capacity SBN washouts. These gradients are only a moderate source of the cardiogenic oscillations seen in argon (bolus gas) and nitrogen (resident gas), on such tests. They may have a greater role in generating the normal CO2 oscillations, as here the phase relationship to argon and nitrogen reverses in microgravity, at least at mid exhalation in those subjects studied to date. Microgravity may become a useful tool in establishing the nature of the non-gravitational mechanisms that can now be seen to play such a large part in the generation of intra-breath gradients and oscillations of expired gas concentration. Analysis of microgravity multibreath nitrogen washouts, single breath washouts from more physiological pre-inspiratory volumes, both using our existing SLS-1 data, and data from the upcoming D-2 and SLS-2 missions, should be very fruitful in this regard.(ABSTRACT TRUNCATED AT 250 WORDS).

The Development of Ni-Containing Cryogenic Steels and Their Industrial Manufacturing

NASA Astrophysics Data System (ADS)

Wang, Meng; Xie, Zhang-long; Li, Cheng-gang; Liu, Zheng-yu

China has become one the largest energy consumer in the world due to the rapid growth of its economy, leading to the steady increase in the consumption of LPG, LEG and LNG in recent years. Therefore, urgent demands for the steels to be able to contain liquefied gases had emerged. Nickel containing cryogenic steels had been mainly used for liquefied gas tanks as ferritic cryogenic materials, but there are still many problems in regard of industrial production. In the present work, the optimized processing routes for 5Ni and 9Ni steels were developed at laboratory. The effect of Ni addition on the microstructure and cryogenic toughness of Ni containing steels was investigated. The results showed that the prior austenite grain size decreased from 19.8µm to 18.2µm and the ductile-brittle transition temperature decreased as Ni content increased from 5% to 9%. The quenched and tempered microstructures in 5Ni and 9Ni steels were consisted of tempered martensite and small amount of reversed austenite, with the microstructure of 5Ni steel only containing only 0.3%reversed austenite and a large amount of dispersive cementite was precipitated on ferritic matrix. With the increase of Ni addition up to 9%, the volume fraction of reversed austenite increased to about 5% and cementite precipitation was eliminated because the reversed austenite had absorbed carbon atoms from the matrix. It has been shown that cementite was harmful to the toughness of the steelas a hard second phase because it was easy for cracks' initiation and propagation when the cementite was precipitated at grain boundaries or lath boundaries. Fine grain size, more reversed austenite and less cementite precipitation are worked out to be the key factors to decrease the ductile-brittle transition temperature of 9Ni steel.

APPLICATION OF A SPRAY DEPOSITION METHOD FOR REVERSED PHASE LIQUID CHROMATOGRAPHY-MASS SPECTROMETRY

EPA Science Inventory

Four coal gasification wastewater samples were analyzed for nonvolatile and polar organics by liquid chromatography-mass spectrometry (LC/MS). Samples were separated on a reverse phase liquid chromatographic column using an aqueous solvent as the eluant. A special spray depositio...

Quality assessment of Herba Leonuri based on the analysis of multiple components using normal- and reversed-phase chromatographic methods.

PubMed

Dong, Shuya; He, Jiao; Hou, Huiping; Shuai, Yaping; Wang, Qi; Yang, Wenling; Sun, Zheng; Li, Qing; Bi, Kaishun; Liu, Ran

2017-12-01

A novel, improved, and comprehensive method for quality evaluation and discrimination of Herba Leonuri has been developed and validated based on normal- and reversed-phase chromatographic methods. To identify Herba Leonuri, normal- and reversed-phase high-performance thin-layer chromatography fingerprints were obtained by comparing the colors and R f values of the bands, and reversed-phase high-performance liquid chromatography fingerprints were obtained by using an Agilent Poroshell 120 SB-C18 within 28 min. By similarity analysis and hierarchical clustering analysis, we show that there are similar chromatographic patterns in Herba Leonuri samples, but significant differences in counterfeits and variants. To quantify the bio-active components of Herba Leonuri, reversed-phase high-performance liquid chromatography was performed to analyze syringate, leonurine, quercetin-3-O-robiniaglycoside, hyperoside, rutin, isoquercitrin, wogonin, and genkwanin simultaneously by single standard to determine multi-components method with rutin as internal standard. Meanwhile, normal-phase high-performance liquid chromatography was performed by using an Agilent ZORBAX HILIC Plus within 6 min to determine trigonelline and stachydrine using trigonelline as internal standard. Innovatively, among these compounds, bio-active components of quercetin-3-O-robiniaglycoside and trigonelline were first determined in Herba Leonuri. In general, the method integrating multi-chromatographic analyses offered an efficient way for the standardization and identification of Herba Leonuri. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Reversible switching between pressure-induced amorphization and thermal-driven recrystallization in VO2(B) nanosheets

DOE PAGES

Wang, Yonggang; Zhu, Jinlong; Yang, Wenge; ...

2016-07-18

Pressure-induced amorphization (PIA) and thermal-driven recrystallization have been observed in many crystalline materials. However, controllable switching between PIA and a metastable phase has not been described yet, due to the challenge to establish feasible switching methods to control the pressure and temperature precisely. Here, we demonstrate a reversible switching between PIA and thermally-driven recrystallization of VO 2(B) nanosheets. Comprehensive in situ experiments are performed to establish the precise conditions of the reversible phase transformations, which are normally hindered but occur with stimuli beyond the energy barrier. Spectral evidence and theoretical calculations reveal the pressure–structure relationship and the role of flexiblemore » VO x polyhedra in the structural switching process. Anomalous resistivity evolution and the participation of spin in the reversible phase transition are observed for the first time. Our findings have significant implications for the design of phase switching devices and the exploration of hidden amorphous materials.« less

In situ stress measurements during electrochemical cycling of lithium-rich cathodes

DOE PAGES

Nation, Leah; Li, Juchuan; James, Christine; ...

2017-08-29

Layered lithium transition metal oxides (Li 1+xM 1-xO 2, M= Ni, Mn, Co) are attractive cathode materials for lithium-ion batteries due to their high reversible capacity but suffer from structural changes and voltage fade. In this study, we use stress as a novel way to track irreversible changes in Li 1.2Mn 0.55Ni 0.125Co 0.125O 2 (LR-NMC) cathodes. A unique and unpredicted stress signature is observed during the first delithiation. Initially, a tensile stress is observed, consistent with volume contraction from lithium removal, however, the stress reverses and becomes compressive with continued charging beyond 4 V vs Li/Li +, indicating volumemore » expansion; this phenomenon is present in the first cycle only. The origin of this irreversible stress during delithiation is likely oxygen loss and the resulting cation rearrangement. Here, Raman spectroscopy provides evidence of the layered-to-spinel phase transition after cycling in the LR-NMC films, as well as recovery of the original spectra upon re-annealing in an oxygen environment.« less

In situ stress measurements during electrochemical cycling of lithium-rich cathodes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nation, Leah; Li, Juchuan; James, Christine

Layered lithium transition metal oxides (Li 1+xM 1-xO 2, M= Ni, Mn, Co) are attractive cathode materials for lithium-ion batteries due to their high reversible capacity but suffer from structural changes and voltage fade. In this study, we use stress as a novel way to track irreversible changes in Li 1.2Mn 0.55Ni 0.125Co 0.125O 2 (LR-NMC) cathodes. A unique and unpredicted stress signature is observed during the first delithiation. Initially, a tensile stress is observed, consistent with volume contraction from lithium removal, however, the stress reverses and becomes compressive with continued charging beyond 4 V vs Li/Li +, indicating volumemore » expansion; this phenomenon is present in the first cycle only. The origin of this irreversible stress during delithiation is likely oxygen loss and the resulting cation rearrangement. Here, Raman spectroscopy provides evidence of the layered-to-spinel phase transition after cycling in the LR-NMC films, as well as recovery of the original spectra upon re-annealing in an oxygen environment.« less

Laser-induced reversion of δ' precipitates in an Al-Li alloy: Study on temperature rise in pulsed laser atom probe.

PubMed

Khushaim, Muna; Gemma, Ryota; Al-Kassab, Talaat

2016-08-01

The influence of tuning the laser pulse energy during the analyses on the resulting microstructure in a specimen utilizing an ultra-fast laser assisted atom probe was demonstrated by a case study of a binary Al-Li alloy. The decomposition parameters, such as the size, number density, volume fraction, and composition of δ' precipitates, were carefully monitored after each analysis. A simple model was employed to estimate the corresponding specimen temperature for each value of the laser energy. The results indicated that the corresponding temperatures for the laser pulse energy in the range of 10 to 80 pJ are located inside the miscibility gap of the binary Al-Li phase diagram and fall into the metastable equilibrium field. In addition, the corresponding temperature for a laser pulse energy of 100 pJ was in fairly good agreement with reported range of  δ' solvus temperature, suggesting a result of reversion upon heating due to laser pulsing. Microsc. Res. Tech. 79:727-737, 2016. © 2016 Wiley Periodicals, Inc. © 2016 Wiley Periodicals, Inc.

Three phases hollow fiber LPME combined with HPLC-UV for extraction, preconcentration and determination of valerenic acid in Valeriana officinalis.

PubMed

Mirzaei, Mohamad; Dinpanah, Hossein

2011-07-01

In the present work, the applicability of hollow fiber-based liquid phase microextraction (HF-LPME) was evaluated for the extraction and preconcentration of valerenic acid prior to its determination by reversed-phase HPLC/UV. The target drug was extracted from 5.0 mL of aqueous solution with pH 3.5 into an organic extracting solvent (dihexyl ether) impregnated in the pores of a hollow fiber and finally back extracted into 10 μ L of aqueous solution with pH 9.5 located inside the lumen of the hollow fiber. In order to obtain high extraction efficiency, the parameters affecting the HF-LPME, including pH of the donor and acceptor phases, type of organic phase, ionic strength, the volume ratio of donor to acceptor phase, stirring rate and extraction time were studied and optimized. Under the optimized conditions, enrichment factor up to 446 was achieved and the relative standard deviation (RSD) of the method was 4.36% (n = 9). The linear range was 7.5-850 μg L⁻¹ with correlation coefficient (r²=0.999), detection limits was 2.5 μg L⁻¹ and the LOQ was 7.5 μg L⁻¹. The proposed method was evaluated by extraction and determination of valerenic acid in some Iranian wild species of Valerianaceae. Copyright © 2011 Elsevier B.V. All rights reserved.

Two-step ion-exchange chromatographic purification combined with reversed-phase chromatography to isolate C-peptide for mass spectrometric analysis.

PubMed

Kabytaev, Kuanysh; Durairaj, Anita; Shin, Dmitriy; Rohlfing, Curt L; Connolly, Shawn; Little, Randie R; Stoyanov, Alexander V

2016-02-01

A liquid chromatography with mass spectrometry on-line platform that includes the orthogonal techniques of ion exchange and reversed phase chromatography is applied for C-peptide analysis. Additional improvement is achieved by the subsequent application of cation- and anion-exchange purification steps that allow for isolating components that have their isoelectric points in a narrow pH range before final reversed-phase mass spectrometry analysis. The utility of this approach for isolating fractions in the desired "pI window" for profiling complex mixtures is discussed. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Effect of phase and orbital wave parameter choices on CS and IOS degeneracy averaged differential cross sections

DOE Office of Scientific and Technical Information (OSTI.GOV)

Khare, V.; Fitz, D.E.; Kouri, D.J.

1980-09-15

The effect of phase choice and partial wave parameter choice on CS and IOS inelastic degeneracy averaged differential cross sections is studied. An approximate simplified CS scattering amplitude for l-bar=1/2(l'+l) is derived and is shown to have a form which closely resembles the McGuire--Kouri scattering amplitude for odd ..delta..j transitions and reduces to it for even ..delta..j transitions. The choice of phase in the CS wave function is shown to result in different approximations which yield significantly different shapes for the degeneracy averaged differential cross section. Time reversal symmetry arguments are employed to select the proper phase choice. IOS calculationsmore » of the degeneracy averaged differential cross sections of He--CO, He--Cl and Ne--HD using l-bar=1/2(l+l') and the phase choice which ensures proper time reversal symmetry are found to correct the phase disagreement which was previously noted for odd ..delta..j transitions using l-bar=l or l' and either the time reversal phase or other phase choices.« less

ANALYSIS OF SELECTED PYRETHROID PESTICIDES USING REVERSE PHASE HIGH PRESSURE LIQUID CHROMATOGRAPHY/UV

EPA Science Inventory

This research was conducted in cooperation with EPA Region 4 in Athens, GA to develop a method to analyze selected pyrethroid pesticides using Reverse Phase-High Pressure Liquid Chromatography (HPLC). This HPLC method will aid researchers in separating and identifying these py...

SEPARATION AND QUANTITATION OF NITROBENZENES AND THEIR REDUCTION PRODUCTS NITROANILINES AND PHENYLENEDIAMINES BY REVERSED=PHASE HIGH-PERFORMANCE LIQUID CHROMATOGRAPHY

EPA Science Inventory

A reversed-phase high-performance liquid chromatographic method for the separation and quantitation of a mixture consisting of nitrobenzene, dinitrobenzene isomers, 1,3,5-trinitrobenzene and their reduction products: aniline, nitroanilines and phenylenediamines has been developed...

Phase reversal of vibratory signals in honeycomb may assist dancing honeybees to attract their audience.

PubMed

Tautz, J; Casas, J; Sandeman, D

2001-11-01

Forager honeybees dancing on the comb are able to attract dance-followers from distances across the comb that are too remote for tactile or visual signals to play a role. An alternative signal could be the vibrations of the comb at 200-300 Hz generated by dancing bees but which, without amplification, may not be large enough to alert remote dance-followers. We describe here, however, an unexpected property of honeycomb when it is subjected to vibration at around 200 Hz that would represent an effective amplification of the vibratory signals for remote dance-followers. We find that, at a specific distance from the origin of an imposed vibration, the walls across a single comb cell abruptly reverse the phase of their displacement and move in opposite directions to one another. Behavioural measurements show that the distance from which the majority of remote dance-followers are recruited coincides with the location of this phase-reversal phenomenon relative to the signal source. We propose that effective signal amplification by the phase-reversal phenomenon occurs when bees straddle a cell across which the phase reversal is expressed. Such a bee would be subjected to a situation in which the legs were moving towards and away from one another instead of in the same direction. In this manner, remote dance-followers could be alerted to a dancer performing in their vicinity.

Advances in organic polymer-based monolithic column technology for high-resolution liquid chromatography-mass spectrometry profiling of antibodies, intact proteins, oligonucleotides, and peptides.

PubMed

Eeltink, Sebastiaan; Wouters, Sam; Dores-Sousa, José Luís; Svec, Frantisek

2017-05-19

This review focuses on the preparation of organic polymer-based monolithic stationary phases and their application in the separation of biomolecules, including antibodies, intact proteins and protein isoforms, oligonucleotides, and protein digests. Column and material properties, and the optimization of the macropore structure towards kinetic performance are also discussed. State-of-the-art liquid chromatography-mass spectrometry biomolecule separations are reviewed and practical aspects such as ion-pairing agent selection and carryover are presented. Finally, advances in comprehensive two-dimensional LC separations using monolithic columns, in particular ion-exchange×reversed-phase and reversed-phase×reversed-phase LC separations conducted at high and low pH, are shown. Copyright © 2017 Elsevier B.V. All rights reserved.

Reversion of a Parent {130}⟨310⟩_{α^{''}} Martensitic Twinning System at the Origin of {332}⟨113⟩_{β} Twins Observed in Metastable β Titanium Alloys.

PubMed

Castany, P; Yang, Y; Bertrand, E; Gloriant, T

2016-12-09

In bcc metastable β titanium alloys, and particularly in superelastic alloys, a unique {332}⟨113⟩ twinning system occurs during plastic deformation. However, in situ synchrotron x-ray diffraction during a tensile test shows that the β phase totally transforms into α^{''} martensite under stress in a Ti-27Nb (at. %) alloy. {332}⟨113⟩_{β} twins are thus not formed directly in the β phase but are the result of the reversion of {130}⟨310⟩_{α^{''}} parent twins occurring in martensite under stress. The formation of an interfacial twin boundary ω phase is also observed to accommodate strains induced during the phase reversion.

Volumetric Analysis of Alveolar Bone Defect Using Three-Dimensional-Printed Models Versus Computer-Aided Engineering.

PubMed

Du, Fengzhou; Li, Binghang; Yin, Ningbei; Cao, Yilin; Wang, Yongqian

2017-03-01

Knowing the volume of a graft is essential in repairing alveolar bone defects. This study investigates the 2 advanced preoperative volume measurement methods: three-dimensional (3D) printing and computer-aided engineering (CAE). Ten unilateral alveolar cleft patients were enrolled in this study. Their computed tomographic data were sent to 3D printing and CAE software. A simulated graft was used on the 3D-printed model, and the graft volume was measured by water displacement. The volume calculated by CAE software used mirror-reverses technique. The authors compared the actual volumes of the simulated grafts with the CAE software-derived volumes. The average volume of the simulated bone grafts by 3D-printed models was 1.52 mL, higher than the mean volume of 1.47 calculated by CAE software. The difference between the 2 volumes was from -0.18 to 0.42 mL. The paired Student t test showed no statistically significant difference between the volumes derived from the 2 methods. This study demonstrated that the mirror-reversed technique by CAE software is as accurate as the simulated operation on 3D-printed models in unilateral alveolar cleft patients. These findings further validate the use of 3D printing and CAE technique in alveolar defect repairing.

Going nuts for nuts? The trace proteome of a Cola drink, as detected via combinatorial peptide ligand libraries.

PubMed

D'Amato, Alfonsina; Fasoli, Elisa; Kravchuk, Alexander V; Righetti, Pier Giorgio

2011-05-06

The "invisible" proteome of a Cola drink, stated to be produced with a kola nut extract, has been investigated via capture with combinatorial peptide ligand libraries (CPLL). Indeed, a few proteins in the M(r) 15-20 kDa range could be identified by treating large beverage volumes (1 L) and performing the capture with CPLLs at very acidic pH values (pH 2.2) under conditions mimicking reverse-phase adsorption. Ascertaining the presence of proteins deriving from plant extracts has confirmed the genuineness of such beverage and suggests the possibility of certifying whether soft drinks present on the market are indeed made with vegetable extracts or only with artificial chemical flavoring.

Preparation and storage of isotopically labeled reduced nicotinamide adenine dinucleotide

DOE Office of Scientific and Technical Information (OSTI.GOV)

Northrop, D.B.; Duggleby, R.G.

1987-09-01

A method for obtaining highly purified NADH in a dry, solid, and stable form is described. The method involves improvements of the ion-exchange and reversed-phase chromatographic procedures of C. J. Newton and S. M. Faynor, and D. B. Northrop. The necessary time to prepare pure NADH has been reduced to a few hours. The final product, obtained by drying the nucleotide from absolute ethanol, shows no detectable decomposition either during the drying procedure or during storage under nitrogen gas at -20 degrees C for several months. Using dry product prepared from fixed volumes of ethanolic solution, standardized solutions of knownmore » amounts of the highly purified and stored NADH can be obtained in a few seconds.« less

High-pressure Seebeck coefficients and thermoelectric behaviors of Bi and PbTe measured using a Paris-Edinburgh cell

DOE Office of Scientific and Technical Information (OSTI.GOV)

Baker, Jason; Kumar, Ravhi S.; Park, Changyong

2016-01-01

A new sample cell assembly design for the Paris-Edinburgh type large-volume press for simultaneous measurements of X-ray diffraction, electrical resistance, Seebeck coefficient and relative changes in the thermal conductance at high pressures has been developed. The feasibility of performing in situ measurements of the Seebeck coefficient and thermal measurements is demonstrated by observing well known solid–solid phase transitions of bismuth (Bi) up to 3 GPa and 450 K. A reversible polarity flip has been observed in the Seebeck coefficient across the Bi-I to Bi-II phase boundary. Also, successful Seebeck coefficient measurements have been performed for the classical high-temperature thermoelectric materialmore » PbTe under high pressure and temperature conditions. In addition, the relative change in the thermal conductivity was measured and a relative change in ZT, the dimensionless figure of merit, is described. Furthermore, this new capability enables pressure-induced structural changes to be directly correlated to electrical and thermal properties.« less

Three-dimensional localization of nanoscale battery reactions using soft X-ray tomography

DOE PAGES

Yu, Young-Sang; Farmand, Maryam; Kim, Chunjoong; ...

2018-03-02

Battery function is determined by the efficiency and reversibility of the electrochemical phase transformations at solid electrodes. The microscopic tools available to study the chemical states of matter with the required spatial resolution and chemical specificity are intrinsically limited when studying complex architectures by their reliance on two-dimensional projections of thick material. Here in this paper, we report the development of soft X-ray ptychographic tomography, which resolves chemical states in three dimensions at 11 nm spatial resolution. We study an ensemble of nano-plates of lithium iron phosphate extracted from a battery electrode at 50% state of charge. Using a setmore » of nanoscale tomograms, we quantify the electrochemical state and resolve phase boundaries throughout the volume of individual nanoparticles. These observations reveal multiple reaction points, intra-particle heterogeneity, and size effects that highlight the importance of multi-dimensional analytical tools in providing novel insight to the design of the next generation of high-performance devices.« less

High-pressure Seebeck coefficients and thermoelectric behaviors of Bi and PbTe measured using a Paris-Edinburgh cell.

PubMed

Baker, Jason; Kumar, Ravhi; Park, Changyong; Kenney-Benson, Curtis; Cornelius, Andrew; Velisavljevic, Nenad

2016-11-01

A new sample cell assembly design for the Paris-Edinburgh type large-volume press for simultaneous measurements of X-ray diffraction, electrical resistance, Seebeck coefficient and relative changes in the thermal conductance at high pressures has been developed. The feasibility of performing in situ measurements of the Seebeck coefficient and thermal measurements is demonstrated by observing well known solid-solid phase transitions of bismuth (Bi) up to 3 GPa and 450 K. A reversible polarity flip has been observed in the Seebeck coefficient across the Bi-I to Bi-II phase boundary. Also, successful Seebeck coefficient measurements have been performed for the classical high-temperature thermoelectric material PbTe under high pressure and temperature conditions. In addition, the relative change in the thermal conductivity was measured and a relative change in ZT, the dimensionless figure of merit, is described. This new capability enables pressure-induced structural changes to be directly correlated to electrical and thermal properties.

Development and validation of RP-UHPLC procedure for estimation of 5-amino salicyclic acid in 5-amino salicyclic acid rectal suppositories

NASA Astrophysics Data System (ADS)

Balaji, Jayagopal; Shivashankar, Murugesh

2017-11-01

The present study describes a simple and robust reverse phase ultra performance liquid chromatography (RP-UPLC) method for the quantification of 5-amino salicyclic acid in 5-amino salicyclic acid rectal capsules. Successful separation of Mesalamine peak from excipient peaks and diluent were achieved on a Acquity C8 (50 × 2.1 mm, 1.7 μm) and UV detector at 254 nm, 0.3 mL/min as a flow rate, and 3 μL as an injection volume. For the RP-UPLC method, phosphate buffer and methanol was used as mobile phases at ratio of 83:17 and the column temperature was 25 °C. Percentage recovery obtained in the range of 98.7 - 99.7 % and the method is linear for Mesalamine for specified concentration range with coefficient of variation (r) not less than 0.99. The proposed RP-UPLC method was found to be specific, linear, precise, accurate and robust.

Three-dimensional localization of nanoscale battery reactions using soft X-ray tomography

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yu, Young-Sang; Farmand, Maryam; Kim, Chunjoong

Battery function is determined by the efficiency and reversibility of the electrochemical phase transformations at solid electrodes. The microscopic tools available to study the chemical states of matter with the required spatial resolution and chemical specificity are intrinsically limited when studying complex architectures by their reliance on two-dimensional projections of thick material. Here in this paper, we report the development of soft X-ray ptychographic tomography, which resolves chemical states in three dimensions at 11 nm spatial resolution. We study an ensemble of nano-plates of lithium iron phosphate extracted from a battery electrode at 50% state of charge. Using a setmore » of nanoscale tomograms, we quantify the electrochemical state and resolve phase boundaries throughout the volume of individual nanoparticles. These observations reveal multiple reaction points, intra-particle heterogeneity, and size effects that highlight the importance of multi-dimensional analytical tools in providing novel insight to the design of the next generation of high-performance devices.« less

Determination of polycyclic aromatic hydrocarbons in kerosene and bio-kerosene soot.

PubMed

Andrade-Eiroa, Auréa; Leroy, Valérie; Dagaut, Philippe; Bedjanian, Yuri

2010-03-01

Here we report a new, efficient and reliable analytical methodology for sensitive and selective quantification of Polycyclic Aromatic Hydrocarbons (PAHs) in soot samples. The methodology developed is based on ultrasonic extraction of the soot-bound PAHs into small volumes of acetonitrile, purification of the extracts through C(18) Solid Phase Extraction (SPE) cartridges and analysis by Reverse Phase Liquid Chromatography (RPLC) with UV and fluorimetric detection. For the first time, we report the convenience of adapting the SPE procedure to the nature of the soot samples. As a matter of fact, extracts containing high percentage of unpolar material are recommended to be cleaned with acetone, whereas extracts poor in unpolar compounds can be efficiently cleaned with methanol. The method was satisfactorily applied to kerosene and bio-kerosene soot from atmospheric open diffusion flames (pool fires) and premixed flames achieving Quantification and Detection limits in the range ng mg(-1) soot and recoveries about 90% for most of the PAHs studied. Copyright (c) 2010 Elsevier Ltd. All rights reserved.

Jetting of a ultrasound contrast microbubble near a rigid wall

NASA Astrophysics Data System (ADS)

Sarkar, Kausik; Mobadersany, Nima

2017-11-01

Micron sized gas-bubbles coated with a stabilizing shell of lipids or proteins, are used as contrast enhancing agents for ultrasound imaging. However, they are increasingly being explored for novel applications in drug delivery through a process called sonoporation, the reversible permeabilization of the cell membrane. Under sufficiently strong acoustic excitations, bubbles form a jet and collapse near a wall. The jetting of free bubbles has been extensively studied by boundary element method (BEM). Here, for the first time, we implemented a rigorous interfacial rheological model of the shell into BEM and investigated the jet formation. The code has been carefully validated against past results. Increasing shell elasticity decreases the maximum bubble volume and the collapse time, while the jet velocity increases. The shear stress on the wall is computed and analyzed. A phase diagram as functions of excitation pressure and wall separation describes jet formation. Effects of shell elasticity and frequency on the phase diagram are investigated. Partially supported by National Science Foundation.

Simple procedures for enrichment of chlorinated aromatic pollutants from fat, water and milk for subsequent analysis by high-resolution methods

DOE Office of Scientific and Technical Information (OSTI.GOV)

Egestad, B.; Curstedt, T.; Sjoevall, J.

1982-01-01

Procedures for enrichment of non-volatile chlorinated aromatic pollutants from fat, water and milk are described. /sup 14/C-DDT was used as a model compound in recovery experiments. A several thousand-fold enrichment of DDT added to butter was achieved by two consecutive straight-phase chromatographies on Lipidex 5000. Trace amounts of DDT in liter volumes of water could be quantitatively extracted by rapid filtration through 2 ml beds of Lipidex 1000. A batch extraction procedure permitted enrichment of DDT from milk after addition of n-pentylamine, methanol and water. DDT could then be eluted from the gel with retention of more than 90% ofmore » the lipids. A reversed-phase system with Lipidex 5000 could be used for separation of TCDD from DDT and PCBs. The liquid-gel chromatographic procedures are simple and suitable for clean-up of samples prior to application of high-resolution methods. 5 tables.« less

Reversed-phase thin-layer chromatography of homologs of Antimycin-A and related derivatives

USGS Publications Warehouse

Abidi, Sharon L.

1989-01-01

Using a reversed-phase high-performance liquid chromatographic (HPLC) technique, a mixture of antimycins A was separated into eight hitherto unreported subcomponents, Ala, Alb, A2a, A2b, A3a, A3b, A4a, and A4b. Although a base-line resolution of the known four major antimycins Al, A2, A3, and A4 was readily achieved with mobile phases containing acetate buffers, the separation of the new antibiotic subcomponents was highly sensitive to variation in mobile phase conditions. The type and composition of organic modifiers, the nature of buffer salts, and the concentration of added electrolytes had profound effects on capacity factors, separation factors, and peak resolution values. Of the numerous chromatographic systems examined, a mobile phase consisting of methanol-water (70:30) and 0.005 M tetrabutylammonium phosphate at pH 3.0 yielded the most satisfactory results for the separation of the subcomponents. Reversed-phase gradient HPLC separation of the dansylated or methylated antibiotic compounds produced superior chromatographic characteristics and the presence of added electrolytes was not a critical factor for achieving separation. Differences in the chromatographic outcome between homologous and structural isomers were interpretated based on a differential solvophobic interaction rationale. Preparative reversed-phase HPLC under optimal conditions enabled isolation of pure samples of the methylated antimycin subcomponents for use in structural studies.

Microscopic reversibility and memory in soft crystals undergoing large deformations

NASA Astrophysics Data System (ADS)

Rosenfeld, Liat; Stan, Claudiu; Tang, Sindy K. Y.

2014-11-01

In this study, we explore the transition from reversible to chaotic behavior in an oscillatory shear flow of water-in-oil emulsions. The emulsion was injected through a microchannel and was forced to rearrange due to a central constriction in the channel. We study the motion of the individual droplets and their neighbors in order to determine their ability to retain their original position after several cycles of oscillations. We have found that the emulsion exhibit behaviors that vary from complete reversibility to complete irreversibility depending on the volume fraction, velocity and strain rate. The reversibility, both in the trajectory and the deformation of every drop, is reproducible even when the drops undergo many rearrangement events over distances of >150 droplet diameters. Moreover, the deformability of the drops and the high volume fraction are crucial conditions for the onset of reversibility. We provide here the first direct visualization and physical analysis of this phenomenon. This work is an important step in describing the flow of concentrated emulsions and suspensions in microchannels and is therefore crucial for understanding the behavior of droplets, bubbles and particles in droplet microfluidic applications.

Test-retest reliability of automated whole body and compartmental muscle volume measurements on a wide bore 3T MR system.

PubMed

Thomas, Marianna S; Newman, David; Leinhard, Olof Dahlqvist; Kasmai, Bahman; Greenwood, Richard; Malcolm, Paul N; Karlsson, Anette; Rosander, Johannes; Borga, Magnus; Toms, Andoni P

2014-09-01

To measure the test-retest reproducibility of an automated system for quantifying whole body and compartmental muscle volumes using wide bore 3 T MRI. Thirty volunteers stratified by body mass index underwent whole body 3 T MRI, two-point Dixon sequences, on two separate occasions. Water-fat separation was performed, with automated segmentation of whole body, torso, upper and lower leg volumes, and manually segmented lower leg muscle volumes. Mean automated total body muscle volume was 19·32 L (SD9·1) and 19·28 L (SD9·12) for first and second acquisitions (Intraclass correlation coefficient (ICC) = 1·0, 95% level of agreement -0·32-0·2 L). ICC for all automated test-retest muscle volumes were almost perfect (0·99-1·0) with 95% levels of agreement 1.8-6.6% of mean volume. Automated muscle volume measurements correlate closely with manual quantification (right lower leg: manual 1·68 L (2SD0·6) compared to automated 1·64 L (2SD 0·6), left lower leg: manual 1·69 L (2SD 0·64) compared to automated 1·63 L (SD0·61), correlation coefficients for automated and manual segmentation were 0·94-0·96). Fully automated whole body and compartmental muscle volume quantification can be achieved rapidly on a 3 T wide bore system with very low margins of error, excellent test-retest reliability and excellent correlation to manual segmentation in the lower leg. Sarcopaenia is an important reversible complication of a number of diseases. Manual quantification of muscle volume is time-consuming and expensive. Muscles can be imaged using in and out of phase MRI. Automated atlas-based segmentation can identify muscle groups. Automated muscle volume segmentation is reproducible and can replace manual measurements.

(PRESENT AT NCCU) ANALYSIS OF SELECTED PYRETHROID PESTICIDES USING REVERSE PHASE HIGH LIQUID CHROMATOGRAPHY

EPA Science Inventory

This research was conducted in cooperation with EPA Region 4 in Athens, GA to develop a method to analyze selected pyrethroid pesticides using Reverse Phase-High Pressure Liquid Chromatography (HPLC). This HPLC method will aid researchers in separating and identifying these pyre...

The impact of multiphase behaviour on coke deposition in heavy oil hydroprocessing catalysts

NASA Astrophysics Data System (ADS)

Zhang, Xiaohui

Coke deposition in heavy oil catalytic hydroprocessing remains a serious problem. The influence of multiphase behaviour on coke deposition is an important but unresolved question. A model heavy oil system (Athabasca vacuum bottoms (ABVB) + decane) and a commercial heavy oil hydrotreating catalyst (NiMo/gamma-Al 2O3) were employed to study the impact of multiphase behaviour on coke deposition. The model heavy oil mixture exhibits low-density liquid + vapour (L1V), high-density liquid + vapour (L2V), as well as low-density liquid + high-density liquid + vapour (L1L2V) phase behaviour at a typical hydroprocessing temperature (380°C). The L2 phase only arises for the ABVB composition range from 10 to 50 wt %. The phase behaviour undergoes transitions from V to L2V, to L1L2V, to L1V with increasing ABVB compositions at the pressure examined. The addition of hydrogen into the model heavy oil mixtures at a fixed mass ratio (0.0057:1) does not change the phase behaviour significantly, but shifts the phase regions and boundaries vertically from low pressure to high pressure. In the absence of hydrogen, the carbon content, surface area and pore volume losses for catalyst exposed to the L1 phase are greater than for the corresponding L2 phase despite a higher coke precursor concentration in L2 than in L1. By contrast, in the presence of hydrogen, the carbon content, surface area and pore volume losses for the catalyst exposed to the L2 phase are greater than for the corresponding L1 phase. The higher hydrogen concentration in L1 appears to reverse the observed results. In the presence of hydrogen, L2 was most closely associated with coke deposition, L1 less associated with coke deposition, and V least associated with coke deposition. Coke deposition is maximized in the phase regions where the L2 phase arises. This key result is inconsistent with expectation and coke deposition models where the extent of coke deposition, at otherwise fixed reaction conditions, is asserted to be proportional to the nominal concentration of coke precursor present in the feed. These new findings are very significant both with respect to providing guidance concerning possible operation improvement for existing processes and for the development of new upgrading processes.

A new source process for evolving repetitious earthquakes at Ngauruhoe volcano, New Zealand

NASA Astrophysics Data System (ADS)

Jolly, A. D.; Neuberg, J.; Jousset, P.; Sherburn, S.

2012-02-01

Since early 2005, Ngauruhoe volcano has produced repeating low-frequency earthquakes with evolving waveforms and spectral features which become progressively enriched in higher frequency energy during the period 2005 to 2009, with the trend reversing after that time. The earthquakes also show a seasonal cycle since January 2006, with peak numbers of events occurring in the spring and summer period and lower numbers of events at other times. We explain these patterns by the excitation of a shallow two-phase water/gas or water/steam cavity having temporal variations in volume fraction of bubbles. Such variations in two-phase systems are known to produce a large range of acoustic velocities (2-300 m/s) and corresponding changes in impedance contrast. We suggest that an increasing bubble volume fraction is caused by progressive heating of melt water in the resonant cavity system which, in turn, promotes the scattering excitation of higher frequencies, explaining both spectral shift and seasonal dependence. We have conducted a constrained waveform inversion and grid search for moment, position and source geometry for the onset of two example earthquakes occurring 17 and 19 January 2008, a time when events showed a frequency enrichment episode occurring over a period of a few days. The inversion and associated error analysis, in conjunction with an earthquake phase analysis show that the two earthquakes represent an excitation of a single source position and geometry. The observed spectral changes from a stationary earthquake source and geometry suggest that an evolution in both near source resonance and scattering is occurring over periods from days to months.

High-pressure behaviour of Cs{sub 2}V{sub 3}O{sub 8} fresnoite

DOE Office of Scientific and Technical Information (OSTI.GOV)

Grzechnik, Andrzej, E-mail: grzechnik@xtal.rwth-aachen.de; Yeon, Jeongho; Zur Loye, Hans-Conrad

2016-06-15

Crystal structure of Cs{sub 2}V{sub 3}O{sub 8} fresnoite (P4bm, Z=2) has been studied using single-crystal X-ray diffraction in a diamond anvil cell to 8.6 GPa at room temperature. Cs{sub 2}V{sub 3}O{sub 8} undergoes a reversible first-order phase transition at about 4 GPa associated with anomalies in the pressure dependencies of the lattice parameters and unit-cell volume but without any symmetry change. Both structures consist of layers of corner-sharing V{sup 5+}O{sub 4} tetrahedra and V{sup 4+}O{sub 5} tetragonal pyramids separated by the Cs{sup +} cations located between the layers. At low pressures, the compression has little effect on the polarity ofmore » the structure. Above 4 GPa, the pseudosymmetry with respect to the corresponding centrosymmetric space group P4/mbm abruptly increases. The effects of external pressure and of the A{sup +} cation substitution in the vanadate fresnoites A{sub 2}V{sub 3}O{sub 8} (A{sup +}: K{sup +}, Rb{sup +}, NH{sub 4}{sup +}, Cs{sup +}) are discussed. - Graphical abstract: Non-centrosymmetric Cs{sub 2}V{sub 3}O{sub 8} undergoes a reversible first-order phase transition at about 4 GPa associated with an abrupt change of the pseudosymmetry with respect to the centrosymmetric space group P4/mbm. Display Omitted - Highlights: • High-pressure behaviour of vanadate fresnoites depends on alkali metal cations. • The size of the alkali metal cation determines whether the high-pressure phase is centrosymmetric. • No incommensurate structures are observed upon compression.« less

Evaluation of bi-functionalized mesoporous silicas as reversed phase/cation-exchange mixed-mode sorbents for multi-residue solid phase extraction of veterinary drug residues in meat samples.

PubMed

Casado, Natalia; Pérez-Quintanilla, Damián; Morante-Zarcero, Sonia; Sierra, Isabel

2017-04-01

A SBA-15 type mesoporous silica was synthesized and bi-functionalized with octadecylsilane (C18) or octylsilane (C8), and sulfonic acid (SO 3 - ) groups in order to obtain materials with reversed-phase/strong cation-exchange mixed-mode retention mechanism. The resulting hybrid materials (SBA-15-C18-SO 3 - and SBA-15-C8-SO 3 - ) were comprehensively characterized. They showed high surface area, high pore volume and controlled porous size. Elemental analysis of the materials revealed differences in the amount of C18 and C8. SBA-15-C18-SO 3 - contained 0.19mmol/g of C18, while SBA-15-C8-SO 3 - presented 0.54mmol/g of C8. The SO 3 - groups anchored to the silica surface of the pore walls were 0.20 and 0.09mmol/g, respectively. The bi-functionalized materials were evaluated as SPE sorbents for the multi-residue extraction of 26 veterinary drug residues in meat samples using ultra-high-performance liquid chromatography coupled to mass spectrometry detector (UHPLC-MS/MS). Different sorbent amounts (100 and 200mg) and organic solvents were tested to optimize the extraction procedure. Both silicas showed big extraction potential and were successful in the extraction of the target analytes. The mixed-mode retention mechanism was confirmed by comparing both silicas with SBA-15 mesoporous silica mono-functionalized with C18 and C8. Best results were achieved with 200mg of SBA-15-C18-SO 3 - obtaining recoveries higher than 70% for the majority of analytes. Copyright © 2016 Elsevier B.V. All rights reserved.

Determination of a selection of anti-epileptic drugs and two active metabolites in whole blood by reversed phase UPLC-MS/MS and some examples of application of the method in forensic toxicology cases.

PubMed

Karinen, Ritva; Vindenes, Vigdis; Hasvold, Inger; Olsen, Kirsten Midtbøen; Christophersen, Asbjørg S; Øiestad, Elisabeth

2015-07-01

Quantitative determination of anti-epileptic drug concentrations is of great importance in forensic toxicology cases. Although the drugs are not usually abused, they are important post-mortem cases where the question of both lack of compliance and accidental or deliberate poisoning might be raised. In addition these drugs can be relevant for driving under the influence cases. A reversed phase ultra-performance liquid chromatography-tandem mass spectrometry method has been developed for the quantitative analysis of the anti-epileptic compounds carbamazepine, carbamazepine-10,11-epoxide, gabapentin, lamotrigine, levetiracetam, oxcarbazepine, 10-OH-carbazepine, phenobarbital, phenytoin, pregabalin, and topiramate in whole blood, using 0.1 mL sample volume with methaqualone as internal standard. Sample preparation was a simple protein precipitation with acetonitrile and methanol. The diluted supernatant was directly injected into the chromatographic system. Separation was performed on an Acquity UPLC® BEH Phenyl column with gradient elution and a mildly alkaline mobile phase. The mass spectrometric detection was performed in positive ion mode, except for phenobarbital, and multiple reaction monitoring was used for drug quantification. The limits of quantification for the different anti-epileptic drugs varied from 0.064 to 1.26 mg/L in blood, within-day and day-to-day relative standard deviations from 2.2 to 14.7% except for phenobarbital. Between-day variation for phenobarbital was 20.4% at the concentration level of 3.5 mg/L. The biases for all compounds were within ±17.5%. The recoveries ranged between 85 and 120%. The corrected matrix effects were 88-106% and 84-110% in ante-mortem and post-mortem whole blood samples, respectively. Copyright © 2014 John Wiley & Sons, Ltd.

Extraction of cesium, strontium and the platinium group metals from acidic high activity nuclear waste using a Purex process compatible organic extractant. Final report, December 15, 1980-August 15, 1983

DOE Office of Scientific and Technical Information (OSTI.GOV)

Davis, M.W. Jr.; Van Brunt, V.

1984-09-14

Purex process compatible organic systems which selectively and reversibly extract cesium, strontium, and palladium from synthetic mixed fission product solutions containing 3M HNO/sub 3/ have been developed. This advance makes the development of continuous solvent extraction processes for their recovery more likely. The most favorable cesium and strontium complexing solutions have been tested for radiation stability to 10/sup 7/ rad using a 0.4 x 10/sup 7/ rad/h /sup 60/Co source. The distribution coefficients dropped somewhat but remained above unity. For cesium the complexing organic solution is 5 vol % (0.1M) NNS, 27 vol % TBP and 68 vol % kerosenemore » containing 0.05m Bis 4,4',(5')(1-hydroxy 2-ethylhexyl)-benzo 18-crown-6 (Crown XVII). The NNS is a sulfonic acid cation exchanger. With an aqueous phase containing 0.006M Cs/sup +1/ in contact with an equal volume of extractant the D org/aq = 1.6 at a temperature of 25 to 35/sup 0/C. For strontium the complexing organic solution is 5 vol % (0.1M) NNS, 27 vol % TBP and 68 vol % Kerosene containing 0.02M Bis 4,4'(5') (1-hydroxyheptyl)cyclohexo 18-crown-6 (Crown XVI). With an aqueous phase containing 0.003M Sr/sup +2/ in contact with an equal volume of extractant the D org/aq = 1.98 at a temperature of 25 to 35/sup 0/C. For palladium the complexing organic solution consisted of a ratio of TBP/kerosene of 0.667 containing 0.3M Alamine 336 which is a tertiary amine anion exchanger. With an aqueous phase containing 0.0045M Pd/sup +/ in contact with an equal volume of extractant the D org/aq = 1.95 at a temperature of 25 to 35/sup 0/C.« less

Development of a novel amide-silica stationary phase for the reversed-phase HPLC separation of different classes of phytohormones.

PubMed

Aral, Hayriye; Aral, Tarık; Ziyadanoğulları, Berrin; Ziyadanoğulları, Recep

2013-11-15

A novel amide-bonded silica stationary phase was prepared starting from N-Boc-phenylalanine, cyclohexylamine and spherical silica gel (4 µm, 60 Å). The amide ligand was synthesised with high yield. The resulting amide bonded stationary phase was characterised by SEM, IR and elemental analysis. The resulting selector bearing a polar amide group is used for the reversed-phase chromatography separation of different classes of thirteen phytohormones (plant hormones). The chromatographic behaviours of these analytes on the amide-silica stationary phase were compared with those of RP-C18 column under same conditions. The effects of different separation conditions, such as mobile phase, pH value, flow rate and temperature, on the separation and retention behaviours of the 13 phytohormones in this system were studied. The optimum separation was achieved using reversed-phase HPLC gradient elution with an aqueous mobile phase containing pH=6.85 potassium phosphate buffer (20 mM) and acetonitrile with a 22 °C column temperature. Under these experimental conditions, the 12 phytohormones could be separated and detected at 230 or 270 nm within 26 min. Copyright © 2013 Elsevier B.V. All rights reserved.

The Role of Reversed Equatorial Zonal Transport in Terminating an ENSO Event

NASA Astrophysics Data System (ADS)

Chen, H. C.; Hu, Z. Z.; Huang, B.; Sui, C. H.

2016-02-01

In this study, we demonstrate that a sudden reversal of anomalous equatorial zonal current at the peaking ENSO phase triggers the rapid termination of an ENSO event. Throughout an ENSO cycle, the anomalous equatorial zonal current is strongly controlled by the concavity of the anomalous thermocline meridional structure near the equator. During the ENSO developing phase, the anomalous zonal current in the central and eastern Pacific generally enhances the ENSO growth through its zonal SST advection. In the mature phase of ENSO, however, the equatorial thermocline depth anomalies are reflected in the eastern Pacific and slowly propagate westward off the equator in both hemispheres. As a result, the concavity of the thermocline anomalies near the equator is reversed, i.e., the off-equatorial thermocline depth anomalies become higher than that on the equator for El Niño events and lower for La Niño events. This meridional change of thermocline structure reverses zonal transport rapidly in the central-to-eastern equatorial Pacific, which weakens the ENSO SST anomalies by reversed advection. More importantly, the reversed zonal mass transport weakens the existing zonal tilting of equatorial thermocline and suppresses the thermocline feedback. Both processes are concentrated in the eastern equatorial Pacific and can be effective on subseasonal time scales. These current reversal effects are built-in to the ENSO peak phase and independent of the zonal wind effect on thermocline slope. It functions as an oceanic control on ENSO evolution during both El Niño and La Niña events.

Reverse Algols

NASA Technical Reports Server (NTRS)

Leung, K. C.

1989-01-01

Reverse Algols, binary systems with a semidetached configuration in which the more massive component is in contact with the critical equipotential surface, are examined. Observational evidence for reverse Algols is presented and the parameters of seven reverse Algols are listed. The evolution of Algols and reverse Algols is discussed. It is suggested that, because reverse Algols represent the premass-reversal semidetached phase of close binary evolution, the evolutionary time scale between regular and reverse Algols is the ratio of the number of confirmed systems of these two Algol types.

Reverse Phase-ultra Flow Liquid Chromatography-diode Array Detector Quantification of Anticancerous and Antidiabetic Drug Mangiferin from 11 Species of Swertia from India.

PubMed

Kshirsagar, Parthraj R; Gaikwad, Nikhil B; Panda, Subhasis; Hegde, Harsha V; Pai, Sandeep R

2016-01-01

Genus Swertia is valued for its great medicinal potential, mainly Swertia chirayita (Roxb. ex Fleming) H. Karst. is used in traditional medicine for a wide range of diseases. Mangiferin one of xanthoids is referred with enormous pharmacological potentials. The aim of the study was to quantify and compare the anticancerous and antidiabetic drug mangiferin from 11 Swertia species from India. The study also evaluates hierarchical relationships between the species based on mangiferin content using multivariate analysis. The reverse phase-ultra flow liquid chromatography-diode array detector analyses was performed and chromatographic separation was achieved on a Lichrospher 100, C18e (5 μm) column (250-4.6 mm). Mobile phase consisting of 0.2% triethylamine (pH-4 with O-phosphoric acid) and acetonitrile (85:15) was used for separation with injection volume 20 μL and detection wave length at 257 nm. Results indicated that concentration of mangiferin has been found to vary largely between Swertia species collected from different regions. Content of mangiferin was found to be highest in Swertia minor compared to other Swertia species studied herein from the Western Ghats and Himalayan region also. The same was also evident in the multivariate analysis, wherein S. chirayita, S. minor and Swertia paniculata made a separate clade. Conclusively, the work herein provides insights of mangiferin content from 11 Swertia species of India and also presents their hierarchical relationships. To best of the knowledge this is the first report of higher content of mangiferin from any Swertia species. The present study quantifies and compares mangiferin in 11 species of Swertia from India. The study also evaluates hierarchical relationships between the species based on mangiferin content using multivariate analysis. The mangiferin content was highest in S. minor compared to the studied Swertia species. To the best of our knowledge this is the first report of higher content of mangiferin from Swertia species. Abbreviations used: LOD: Limit of detection, LOQ: Limit of quantification, RP-UFLC-DAD: Reverse phase-ultra flow liquid chromatography-diode array detector, RSD: Relative standard deviation, SAN: Swertia angustifolia, SAP: Swertia angustifolia var. pulchella, SBI: S. bimaculata, SCH: S. chirayita, SCO: S. corymbosa, SDE: S. densifolia, SDI: S. dialatata, SLA: S. lawii, SMI: S. minor; SNE: S. nervosa, and SPA: S. paniculata.

Dispersive liquid-liquid microextraction for the determination of vitamins D and K in foods by liquid chromatography with diode-array and atmospheric pressure chemical ionization-mass spectrometry detection.

PubMed

Viñas, Pilar; Bravo-Bravo, María; López-García, Ignacio; Hernández-Córdoba, Manuel

2013-10-15

A simple and rapid method was developed using reversed-phase liquid chromatography (LC) with both diode array (DAD) and atmospheric pressure chemical ionization mass spectrometric (APCI-MS) detection, for the simultaneous analysis of the vitamins ergocalciferol (D2), cholecalciferol (D3), phylloquinone (K1), menaquinone-4 (K2) and a synthetic form of vitamin K, menadione (K3). The Taguchi experimental method, an orthogonal array design (OAD), was used to optimize an efficient and clean preconcentration step based on dispersive liquid-liquid microextraction (DLLME). A factorial design was applied with six factors and three levels for each factor, namely, carbon tetrachloride volume, methanol volume, aqueous sample volume, pH of sample, sodium chloride concentration and time of the centrifugation step. The DLLME optimized procedure consisted of rapidly injecting 3 mL of acetonitrile (disperser solvent) containing 150 µL carbon tetrachloride (extraction solvent) into the aqueous sample, thereby forming a cloudy solution. Phase separation was performed by centrifugation, and the sedimented phase was evaporated with nitrogen, reconstituted with 50 µL of acetonitrile, and injected. The LC analyses were carried out using a mobile phase composed of acetonitrile, 2-propanol and water, under gradient elution. Quantification was carried out by the standard additions method. The APCI-MS spectra, in combination with UV spectra, permitted the correct identification of compounds in the food samples. The method was validated according to international guidelines and using a certified reference material. The validated method was applied for the analysis of vitamins D and K in infant foods and several green vegetables. There was little variability in the forms of vitamin K present in vegetables, with the most abundant vitamer in all the samples being phylloquinone, while menadione could not be detected. Conversely, cholecalciferol, which is present in food of animal origin, was the main form in infant foods, while ergocalciferol was not detected. Copyright © 2013 Elsevier B.V. All rights reserved.

Revisiting resolution in hydrodynamic countercurrent chromatography: tubing bore effect.

PubMed

Berthod, A; Faure, K

2015-04-17

A major challenge in countercurrent chromatography (CCC), the technique that works with a support-free biphasic liquid system, is to retain the liquid stationary phase inside the CCC column (Sf parameter). Two solutions are commercially available: the hydrostatic CCC columns, also called centrifugal partition chromatographs (CPC), with disks of interconnected channels and rotary seals, and the hydrodynamic CCC columns with bobbins of coiled open tube and no rotary seals. It was demonstrated that the amount of liquid stationary phase retained by a coiled tube was higher with larger bore tubing than with small bore tubes. At constant column volume, small bore tubing will be longer producing more efficiency than larger bore tube that will better retain the liquid stationary phase. Since the resolution equation in CCC is depending on both column efficiency and stationary phase retention ratio, the influence of the tubing bore should be studied. This theoretical work showed that there is an optimum tubing bore size depending on solute partition coefficient and mobile phase flow rate. The interesting result of the theoretical study is that larger tubing bores allow for dramatically reduced experiment durations for all solutes: in reversed phase CCC (polar mobile phase), hydrophobic solutes are usually highly retained. These apolar solutes can be separated by the same coil at high flow rates and reduced Sf with similar retention times as polar solutes separated at smaller flow rates and much higher Sf. Copyright © 2015 Elsevier B.V. All rights reserved.

Reversible Rigidity Control Using Low Melting Temperature Alloys

NASA Astrophysics Data System (ADS)

Shan, Wanliang; Lu, Tong; Majidi, Carmel

2013-03-01

Inspired by nature, materials able to achieve rapid rigidity changes have important applications for human body protection in military and many other areas. This talk presents the fabrication and design of soft-matter technologies that exhibit rapid reversible rigidity control. Fabricated with a masked deposition technique, the soft-matter composite contains liquid-phase and phase-changing metal alloys embedded in a soft and highly stretchable elastomer. The composite material can reversibly change its rigidity by three orders of magnitude and sustain large deformation.

Local Gram-Schmidt and covariant Lyapunov vectors and exponents for three harmonic oscillator problems

NASA Astrophysics Data System (ADS)

Hoover, Wm. G.; Hoover, Carol G.

2012-02-01

We compare the Gram-Schmidt and covariant phase-space-basis-vector descriptions for three time-reversible harmonic oscillator problems, in two, three, and four phase-space dimensions respectively. The two-dimensional problem can be solved analytically. The three-dimensional and four-dimensional problems studied here are simultaneously chaotic, time-reversible, and dissipative. Our treatment is intended to be pedagogical, for use in an updated version of our book on Time Reversibility, Computer Simulation, and Chaos. Comments are very welcome.

Evaluation of Military Field-Water Quality. Volume 7. Performance Evaluation of the 600-GPH Reverse Osmosis Water Purification Unit (ROWPU): reverse Osmosis (RO) Components

DTIC Science & Technology

1986-02-01

Data-for ASsessingHealthRISKS In Potential Theaters ~ of Operation forU,5. Mil-itary._orces. Jf-jr cLAss t:cAToN 9; r-.$ ’AGg UNCLASSIFIED Volume 7...Bypass, Potable-Water Disinfection,_ and Water-Quality Analysis Techniques; and Vol. 9, Data for Assessing Health Risks in Potential Theaters of Operation ...cleaning the RO elements, with objectives of improving solute rejection and reducing operating pressure. The most common method is to flush citric acid

Evaluation of a new polymeric stationary phase with reversed-phase properties for high temperature liquid chromatography.

PubMed

Vanhoenacker, Gerd; Dos Santos Pereira, Alberto; Kotsuka, Takashi; Cabooter, Deirdre; Desmet, Gert; Sandra, Pat

2010-05-07

The performance of a polymeric stationary phase with reversed-phase properties (ET-RP1) was evaluated for LC separations at elevated temperature. The most significant observation was that the reduced plate height (h) decreased from 3.4 at 25 degrees C (optimal flow 0.5 mL/min) to 2.4 at 150 degrees C (optimal flow 2.5 mL/min) which is comparable to the efficiency obtained with silica-based reversed-phase columns of 4.6mm ID operated at 0.8 mL/min. The phase showed no deterioration after long use at 150 degrees C within the pH range 1-9. Catalytic activity originating from the stationary phase material, e.g. as experienced on zirconium columns operated at elevated temperature, was absent. The performance of ET-RP1 is illustrated with the analysis of some pharmaceutical samples by LC and LC-MS. Operation at elevated temperature also allows to reduce the amount of organic modifier or to replace acetonitrile and methanol by the biodegradable ethanol. Copyright (c) 2009 Elsevier B.V. All rights reserved.

Preparation and characterization of a new microwave immobilized poly(2-phenylpropyl)methylsiloxane stationary phase for reversed phase high-performance liquid chromatography.

PubMed

Begnini, Fernanda R; Jardim, Isabel C S F

2013-07-05

A new reversed phase high-performance liquid chromatography (RP-HPLC) stationary phase was prepared and its chromatographic and physical-chemical properties were evaluated. The new stationary phase was prepared with a silica support and poly(2-phenylpropyl)methylsiloxane (PPPMS), a phenyl type polysiloxane copolymer. Since this is a new copolymer and there is little information in the literature, it was submitted to physical-chemical characterization by infrared spectroscopy and thermogravimetry. The chromatographic phase was prepared through sorption and microwave immobilization of the copolymer onto a silica support. The chromatographic performance was evaluated by employing test procedures suggested by Engelhardt and Jungheim, Tanaka and co-workers, Neue, and Szabó and Csató. These test mixtures provide information about the hydrophobic selectivity, silanophilic activity, ion-exchange capacity, shape selectivity and interaction with polar analytes of the new Si-PPPMS reversed phase. Stability tests were developed using accelerated aging tests under both basic and acidic conditions to provide information about the lifetime of the packed columns. Copyright © 2013 Elsevier B.V. All rights reserved.

Pipette-tip solid-phase extraction using polypyrrole as efficient adsorbent for extraction of avermectins and milbemycins in milk.

PubMed

Florez, Diego Hernando Ângulo; Teixeira, Roseane Andrade; da Silva, Ricky Cássio Santos; Pires, Bruna Carneiro; Dutra, Flávia Viana Avelar; Borges, Keyller Bastos

2018-05-01

In this work, we developed a HPLC method for the multidetermination of avermectins (AVM) (abamectin-ABA 1b and ABA 1a, eprinomectin-EPR, and ivermectin-IVM) and milbemycins (moxidectin-MOX) in milk samples using polypyrrole (PPy) as adsorbent material in pipette-tip solid-phase extraction (PT-PPy-SPE). PPy was characterized by scanning electron microscopy, thermogravimetric analysis, Fourier transform infrared spectroscopy, and X-ray diffraction and the data agreed with the literature. The sample preparation included the clean-up of the milk by protein precipitation (PP) with acetonitrile and extraction of the analytes by PT-PPy-SPE. The chromatographic method was developed in reverse phase and isocratic mode with flow rate at 1.2 mL min -1 and ultraviolet detection at 250 nm. The mobile phase composition was acetonitrile:methanol:water (55:25:20, v/v/v). The studied parameters and the optimized conditions for the sample preparation were washing solvent (300 μL water), volume and type of eluent (500 μL methanol), volume and pH of sample (1 mL and pH 10), amount of adsorbent material (50 mg PPy), and without addition of salt (NaCl). The method was linear over the concentration range from 20 to 3000 ng mL -1 with coefficients of correlation (r) ≥ 0.99 for all analytes and recoveries around 100%. The method developed and validated was used for the analyses of real milk samples from cow treated with Ivomec ® (IVM 3.5%), in which were found 21.51 ± 2.94 ng mL -1 of IVM. Finally, the results proved that PT-PPy-SPE coupled to HPLC-UV was economical, simple, and easy-to-perform technique. Graphical abstract Pipette-tip solid phase extraction using polypirrole as adsorbent material for determination of avermectins and milbemycins in milk.

Analytical Method Development and Validation for the Simultaneous Estimation of Abacavir and Lamivudine by Reversed-phase High-performance Liquid Chromatography in Bulk and Tablet Dosage Forms.

PubMed

Raees Ahmad, Sufiyan Ahmad; Patil, Lalit; Mohammed Usman, Mohammed Rageeb; Imran, Mohammad; Akhtar, Rashid

2018-01-01

A simple rapid, accurate, precise, and reproducible validated reverse phase high performance liquid chromatography (HPLC) method was developed for the determination of Abacavir (ABAC) and Lamivudine (LAMI) in bulk and tablet dosage forms. The quantification was carried out using Symmetry Premsil C18 (250 mm × 4.6 mm, 5 μm) column run in isocratic way using mobile phase comprising methanol: water (0.05% orthophosphoric acid with pH 3) 83:17 v/v and a detection wavelength of 245 nm and injection volume of 20 μl, with a flow rate of 1 ml/min. In the developed method, the retention times of ABAC and LAMI were found to be 3.5 min and 7.4 min, respectively. The method was validated in terms of linearity, precision, accuracy, limits of detection, limits of quantitation, and robustness in accordance with the International Conference on Harmonization guidelines. The assay of the proposed method was found to be 99% - 101%. The recovery studies were also carried out and mean % recovery was found to be 99% - 101%. The % relative standard deviation from reproducibility was found to be <2%. The proposed method was statistically evaluated and can be applied for routine quality control analysis of ABAC and LAMI in bulk and in tablet dosage form. Attempts were made to develop RP-HPLC method for simultaneous estimation of Abacavir and Lamivudine for the RP-HPLC method. The developed method was validated according to the ICH guidelines. The linearity, precision, range, robustness were within the limits as specified by the ICH guidelines. Hence the method was found to be simple, accurate, precise, economic and reproducible. So the proposed methods can be used for the routine quality control analysis of Abacavir and Lamivudine in bulk drug as well as in formulations. Abbreviations Used: HPLC: High-performance liquid chromatography, UV: Ultraviolet, ICH: International Conference on Harmonization, ABAC: Abacavir, LAMI: Lamivudine, HIV: Human immunodeficiency virus, AIDS: Acquired immunodeficiency syndrome, NRTI: Nucleoside reverse transcriptase inhibitors, ARV: Antiretroviral, RSD: Relative standard deviation, RT: Retention time, SD: Standard deviation.

Pore closure in zeolitic imidazolate frameworks under mechanical pressure.

PubMed

Henke, Sebastian; Wharmby, Michael T; Kieslich, Gregor; Hante, Inke; Schneemann, Andreas; Wu, Yue; Daisenberger, Dominik; Cheetham, Anthony K

2018-02-14

We investigate the pressure-dependent mechanical behaviour of the zeolitic imidazolate framework ZIF-4 (M(im) 2 ; M 2+ = Co 2+ or Zn 2+ , im - = imidazolate) with high pressure, synchrotron powder X-ray diffraction and mercury intrusion measurements. A displacive phase transition from a highly compressible open pore ( op ) phase with continuous porosity (space group Pbca , bulk modulus ∼1.4 GPa) to a closed pore ( cp ) phase with inaccessible porosity (space group P 2 1 / c , bulk modulus ∼3.3-4.9 GPa) is triggered by the application of mechanical pressure. Over the course of the transitions, both ZIF-4 materials contract by about 20% in volume. However, the threshold pressure, the reversibility and the immediate repeatability of the phase transition depend on the metal cation. ZIF-4(Zn) undergoes the op-cp phase transition at a hydrostatic mechanical pressure of only 28 MPa, while ZIF-4(Co) requires about 50 MPa to initiate the transition. Interestingly, ZIF-4(Co) fully returns to the op phase after decompression, whereas ZIF-4(Zn) remains in the cp phase after pressure release and requires subsequent heating to switch back to the op phase. These variations in high pressure behaviour can be rationalised on the basis of the different electron configurations of the respective M 2+ ions (3d 10 for Zn 2+ and 3d 7 for Co 2+ ). Our results present the first examples of op-cp phase transitions ( i.e. breathing transitions) of ZIFs driven by mechanical pressure and suggest potential applications of these functional materials as shock absorbers, nanodampers, or in mechanocalorics.

The Relationship between Reversed Masked Priming and the Tri-Phasic Pattern of the Lateralised Readiness Potential

PubMed Central

Seiss, Ellen; Klippel, Marie; Hope, Christopher; Boy, Frederic; Sumner, Petroc

2014-01-01

One of the potential explanations for negative compatibility effects (NCE) in subliminal motor priming tasks has been perceptual prime-target interactions. Here, we investigate whether the characteristic tri-phasic LRP pattern associated with the NCE is caused by these prime-target interactions. We found that both the prime-related phase and the critical reversal phase remain present even on trials where the target is omitted, confirming they are elicited by the prime and mask, not by prime-target interactions. We also report that shape and size of the reversal phase are associated with response speed, consistent with a causal role for the reversal for the subsequent response latency. Additionally, we analysed sequential modulation of the NCE by previous conflicting events, even though such conflict is subliminal. In accordance with previous literature, this modulation is small but significant. PMID:24728088

Simultaneous determination of the HIV nucleoside analogue reverse transcriptase inhibitors lamivudine, didanosine, stavudine, zidovudine and abacavir in human plasma by reversed phase high performance liquid chromatography.

PubMed

Verweij-van Wissen, C P W G M; Aarnoutse, R E; Burger, D M

2005-02-25

A reversed phase high performance liquid chromatography method was developed for the simultaneous quantitative determination of the nucleoside reverse transcriptase inhibitors (NRTIs) lamivudine, didanosine, stavudine, zidovudine and abacavir in plasma. The method involved solid-phase extraction with Oasis MAX cartridges from plasma, followed by high performance liquid chromatography with a SymmetryShield RP 18 column and ultraviolet detection set at a wavelength of 260 nm. The assay was validated over the concentration range of 0.015-5 mg/l for all five NRTIs. The average accuracies for the assay were 92-102%, inter- and intra-day coefficients of variation (CV) were <2.5% and extraction recoveries were higher than 97%. This method proved to be simple, accurate and precise, and is currently in use in our laboratory for the quantitative analysis of NRTIs in plasma.

Simultaneous quantification of fentanyl, sufentanil, cefazolin, doxapram and keto-doxapram in plasma using liquid chromatography - tandem mass spectrometry.

PubMed

Flint, Robert B; Bahmany, Soma; van der Nagel, Bart C H; Koch, Birgit C P

2018-05-16

A simple and specific UPLC-MS/MS method was developed and validated for simultaneous quantification of fentanyl, sufentanil, cefazolin, doxapram and its active metabolite keto-doxapram. The internal standard was fentanyl-d5 for all analytes. Chromatographic separation was achieved with a reversed phase Acquity UPLC HSS T3 column with a run-time of only 5.0 minutes per injected sample. Gradient elution was performed with a mobile phase consisting of ammonium acetate, formic acid in Milli-Q ultrapure water or in methanol with a total flow rate of 0.4 mL minute -1 . A plasma volume of only 50 μL was required to achieve both adequate accuracy and precision. Calibration curves of all 5 analytes were linear. All analytes were stable for at least 48 hours in the autosampler. The method was validated according to US Food and Drug Administration guidelines. This method allows quantification of fentanyl, sufentanil, cefazolin, doxapram and keto-doxapram, which serves purposes for research, as well as therapeutic drug monitoring, if applicable. The strength of this method is the combination of a small sample volume, a short run-time, a deuterated internal standard, an easy sample preparation method and the ability to simultaneously quantify all analytes in one run. This article is protected by copyright. All rights reserved.

Facile Fabrication of Composite Membranes with Dual Thermo- and pH-Responsive Characteristics.

PubMed

Ma, Bing; Ju, Xiao-Jie; Luo, Feng; Liu, Yu-Qiong; Wang, Yuan; Liu, Zhuang; Wang, Wei; Xie, Rui; Chu, Liang-Yin

2017-04-26

Facile fabrication of novel functional membranes with excellent dual thermo- and pH-responsive characteristics has been achieved by simply designing dual-layer composite membranes. pH-Responsive poly(styrene)-block-poly(4-vinylpyridine) (PS-b-P4VP) block copolymers and polystyrene blended with thermoresponsive poly(N-isopropylacrylamide) (PNIPAM) nanogels are respectively used to construct the top layer and bottom layer of composite membranes. The stretching/coiling conformation changes of the P4VP chains around the pK a (∼3.5-4.5) provide the composite membranes with extraordinary pH-responsive characteristics, and the volume phase transitions of PNIPAM nanogels at the pore/matrix interfaces in the bottom layer around the volume phase transition temperature (VPTT, ∼33 °C) provide the composite membranes with great thermoresponsive characteristics. The microstructures, permeability performances, and dual stimuli-responsive characteristics can be well tuned by adjusting the content of PNIPAM nanogels and the thickness of the PS-b-P4VP top layer. The water fluxes of the composite membranes can be changed in order of magnitude by changing the environment temperature and pH, and the dual thermo- and pH-responsive permeation performances of the composite membranes are satisfactorily reversible and reproducible. The membrane fabrication strategy in this work provides valuable guidance for further development of dual stimuli-responsive membranes or even multi stimuli-responsive membranes.

Simultaneous determination of azathioprine and 6-mercaptopurine in serum by reversed-phase high-performance liquid chromatography.

PubMed

Tsutsumi, K; Otsuki, Y; Kinoshita, T

1982-09-10

The simultaneous determination of azathioprine and its metabolite 6-mercaptopurine in serum by reversed-phase high-performance liquid chromatography is described. 6-Mercaptopurine was converted to a derivative, 6-mercaptopurine-N-ethylmaleimide, which is stable against autoxidation, on reaction with N-ethylmaleimide. Since the N-ethylmaleimide derivative was more hydrophobic than the parent compound, it could be extracted into ethyl acetate together with azathioprine and the derivative was retained on the reversed-phase column better than 6-mercaptopurine. In addition, 6-mercaptopurine-N-ethylmaleimide absorbed at the same wavelength (280 nm) as azathioprine. Consequently, this derivatization procedure enabled the simultaneous extraction, separation, and detection of these compounds.

GRASP/Ada (Graphical Representations of Algorithms, Structures, and Processes for Ada): The development of a program analysis environment for Ada. Reverse engineering tools for Ada, task 1, phase 2

NASA Technical Reports Server (NTRS)

Cross, James H., II

1990-01-01

The study, formulation, and generation of structures for Ada (GRASP/Ada) are discussed in this second phase report of a three phase effort. Various graphical representations that can be extracted or generated from source code are described and categorized with focus on reverse engineering. The overall goal is to provide the foundation for a CASE (computer-aided software design) environment in which reverse engineering and forward engineering (development) are tightly coupled. Emphasis is on a subset of architectural diagrams that can be generated automatically from source code with the control structure diagram (CSD) included for completeness.

Development of Ultra-Fine-Grained Structure in AISI 321 Austenitic Stainless Steel

NASA Astrophysics Data System (ADS)

Tiamiyu, A. A.; Szpunar, J. A.; Odeshi, A. G.; Oguocha, I.; Eskandari, M.

2017-12-01

Ultra-fine-grained (UFG) structure was developed in AISI 321 austenitic stainless steel (ASS) using cryogenic rolling followed by annealing treatments at 923 K, 973 K, 1023 K, and 1073 K (650 °C, 700 °C, 750 °C, and 800 °C) for different lengths of time. The α'-martensite to γ-austenite reversion behavior and the associated texture development were analyzed in the cryo-rolled specimens after annealing. The activation energy, Q, required for the reversion of α'-martensite to γ-austenite in the steel was estimated to be 80 kJ mol-1. TiC precipitates and unreversed triple junction α'-martensite played major roles in the development of UFG structure through the Zener pinning of grain boundaries. The optimum annealing temperature and time for the development of UFG structure in the cryo-rolled AISI 321 steel are (a) 923 K (650 °C) for approximately 28800 seconds and (b) 1023 K (750 °C) for 600 seconds, with average grain sizes of 0.22 and 0.31 µm, respectively. Annealing at 1023 K (750 °C) is considered a better alternative since the volume fraction of precipitated carbides in specimens annealed at 1023 K (750 °C) are less than those annealed at 923 K (650 °C). More so, the energy consumption during prolonged annealing time to achieve an UFG structure at 923 K (650 °C) is higher due to low phase reversion rate. The hardness of the UFG specimens is 195 pct greater than that of the as-received steel. The higher volume fraction of TiC precipitates in the UFG structure may be an additional source of hardening. Micro and macrotexture analysis indicated {110}〈uvw〉 as the major texture component of the austenite grains in the UFG structure. Its intensity is stronger in the specimen annealed at low temperatures.

Simulation of elution profiles in liquid chromatography - II: Investigation of injection volume overload under gradient elution conditions applied to second dimension separations in two-dimensional liquid chromatography.

PubMed

Stoll, Dwight R; Sajulga, Ray W; Voigt, Bryan N; Larson, Eli J; Jeong, Lena N; Rutan, Sarah C

2017-11-10

An important research direction in the continued development of two-dimensional liquid chromatography (2D-LC) is to improve the detection sensitivity of the method. This is especially important in applications where injection of large volumes of effluent from the first dimension ( 1 D) column into the second dimension ( 2 D) column leads to severe 2 D peak broadening and peak shape distortion. For example, this is common when coupling two reversed-phase columns and the organic solvent content of the 1 D mobile phase overwhelms the 2 D column with each injection of 1 D effluent, leading to low resolution in the second dimension. In a previous study we validated a simulation approach based on the Craig distribution model and adapted from the work of Czok and Guiochon [1] that enabled accurate simulation of simple isocratic and gradient separations with very small injection volumes, and isocratic separations with mismatched injection and mobile phase solvents [2]. In the present study we have extended this simulation approach to simulate separations relevant to 2D-LC. Specifically, we have focused on simulating 2 D separations where gradient elution conditions are used, there is mismatch between the sample solvent and the starting point in the gradient elution program, injection volumes approach or even exceed the dead volume of the 2 D column, and the extent of sample loop filling is varied. To validate this simulation we have compared results from simulations and experiments for 101 different conditions, including variation in injection volume (0.4-80μL), loop filling level (25-100%), and degree of mismatch between sample organic solvent and the starting point in the gradient elution program (-20 to +20% ACN). We find that that the simulation is accurate enough (median errors in retention time and peak width of -1.0 and -4.9%, without corrections for extra-column dispersion) to be useful in guiding optimization of 2D-LC separations. However, this requires that real injection profiles obtained from 2D-LC interface valves are used to simulate the introduction of samples into the 2 D column. These profiles are highly asymmetric - simulation using simple rectangular pulses leads to peak widths that are far too narrow under many conditions. We believe the simulation approach developed here will be useful for addressing practical questions in the development of 2D-LC methods. Copyright © 2017 Elsevier B.V. All rights reserved.

Study of structural phase transitions in quinary TiNi(MoFeAg)-based alloys

NASA Astrophysics Data System (ADS)

Gunther, Victor; Marchenko, Ekaterina; Chekalkin, Timofey; Baigonakova, Gulsharat; Kang, Ji-hoon; Kim, Ji-soon; Klopotov, Anatoliy

2017-10-01

The structural phase transitions of quinary Ti50Ni49.5-X Mo0.3Fe0.2Ag X (X  =  0, 0.1, 0.2, 0.5, 1.0, and 1.5 at%) alloys prepared by vacuum-induction melting were studied by means of the four-point-probe, x-ray diffraction (XRD), and optical microscopy methods after thermal cycling. The two-stage B2 ↔ R ↔ B19‧ reversible martensitic transformation (MT) took place in all the investigated samples. It is found that the substitution of Ag for Ni in the studied alloy when C Ag  =  0-0.5 at%, reduces the T R, M s, and M f characteristic points by 20-30 K, whereas they increase by 15-35 K when the Ag content was varied from 1.0 to 1.5 at% and the B2 ↔ R ↔ B19‧ MT was realized in the high-temperature area. XRD patterns of the studied alloys recorded at the ambient temperature detected the pure Ag phase as well as Ti2Ni precipitate with a small volume fraction (up to 5%) alongside with structural lines of B2, R, and B19‧ phases.

Revisit of pressure-induced phase transition in PbSe: Crystal structure, and thermoelastic and electrical properties

DOE PAGES

Wang, Shanmin; Zang, Chengpeng; Wang, Yongkun; ...

2015-05-04

Lead selenide, PbSe, an important lead chalcogenide semiconductor, has been investigated using in–situ high–pressure/high–temperature synchrotron x–ray diffraction and electrical resistivity measurements. For the first time, high–quality x-ray diffraction data were collected for the intermediate orthorhombic PbSe. Combined with ab initio calculations, we find a Cmcm, InI–type symmetry for the intermediate phase, which is structurally more favorable than the anti–GeS–type Pnma. At room temperature, the onset of the cubic–orthorhombic transition was observed at ~3.5 GPa with a ~3.4% volume reduction. At an elevated temperature of 1000 K, the reversed orthorhombic–to–cubic transition was observed at 6.12 GPa, indicating a positive Clapeyron slopemore » for the phase boundary. Interestingly, phase–transition induced elastic softening in PbSe was also observed, which can be mainly attributed to the loosely bonded trigonal prisms along the b–axis in the Cmcm structure. Compared with the cubic phase, orthorhombic PbSe exhibits a large negative pressure dependence of electrical resistivity. Additionally, thermoelastic properties of orthorhombic PbSe have been derived from isothermal compression data, such as temperature derivative of bulk modulus and thermally induced pressure.« less

Solid-phase extraction assisted dispersive liquid-liquid microextraction based on solidification of floating organic droplet to determine sildenafil and its analogues in dietary supplements.

PubMed

Li, Jing; Roh, Si Hun; Shaodong, Jia; Hong, Ji Yeon; Lee, Dong-Kyu; Shin, Byong-Kyu; Park, Jeong Hill; Lee, Jeongmi; Kwon, Sung Won

2017-08-01

A novel analytical method for the simultaneous determination of the concentration of sildenafil and its five analogues in dietary supplements using solid-phase extraction assisted reversed-phase dispersive liquid-liquid microextraction based on solidification of floating organic droplet combined with ion-pairing liquid chromatography with an ultraviolet detector was developed. Parameters that affect extraction efficiency were systematically investigated, including the type of solid-phase extraction cartridge, pH of the extraction environment, and the type and volume of extraction and dispersive solvent. The method linearity was in the range of 5.0-100 ng/mL for sildenafil, homosildenafil, udenafil, benzylsildenafil, and thiosildenafil and 10-100 ng/mL for acetildenafil. The coefficients of determination were ≥0.996 for all regression curves. The sensitivity values expressed as limit of detection were between 2.5 and 7.5 ng/mL. Furthermore, intraday and interday precisions expressed as relative standard deviations were less than 5.7 and 9.9%, respectively. The proposed method was successfully applied to the analysis of sildenafil and its five analogues in complex dietary supplements. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Favorable Effects of Weak Acids on Negative-Ion Electrospray Ionization Mass Spectrometry

PubMed Central

Wu, Zengru; Gao, Wenqing; Phelps, Mitch A.; Wu, Di; Miller, Duane D.; Dalton, James T.

2007-01-01

Despite widespread use in pharmacokinetic, drug metabolism, and pesticide residue studies, little is known about the factors governing response during reversed-phase liquid chromatography coupled with negative-ion electrospray ionization (ESI−) mass spectrometry. We examined the effects of various mobile-phase modifiers on the ESI− response of four selective androgen receptor modulators using a postcolumn infusion system. Acetic, propionic, and butyric acid improved the ESI− responses of analytes to varying extents at low concentrations. Formic acid suppressed ionization, as did neutral salts (ammonium formate, ammonium acetate) and bases (ammonium hydroxide, triethylamine) under most conditions. Two modifiers (2,2,2-trifluoroethanol, formaldehyde) that produce anions with high gas-phase proton affinity increased ESI− responses. However, the concentrations of these modifiers required to enhance ESI− response were higher than that of acidic modifiers, which is a phenomenon likely related to their low pKa values. 2,2,2-Trifluoroethanol increased response of more hydrophobic compounds but decreased response of a more hydrophilic compound. Formaldehyde improved response of all the compounds, especially the hydrophilic compound with lower surface activity. In summary, these results suggest that an ideal ESI− modifier should provide cations that can be easily electrochemically reduced and produce anions with small molecular volume and high gas-phase proton affinity. PMID:14750883

Microstructures, magnetic properties and coercivity mechanisms of Nd-Ce-Fe-B based alloys by Zr substitution

NASA Astrophysics Data System (ADS)

Wang, Lei; Quan, Qichen; Zhang, Lili; Hu, Xianjun; Ur Rehman, Sajjad; Jiang, Qingzheng; Du, Junfeng; Zhong, Zhenchen

2018-03-01

In this paper, the effects of Zr addition on microstructures, magnetic properties, exchange coupling, and coercivity mechanisms of Nd-Ce-Fe-B alloys fabricated by melt-spinning technique are investigated. It is found that the coercivity Hcj is enhanced significantly by Zr substitution in the (Nd0.8Ce0.2)13Fe82-xZrxB5 alloys, while the remanence Jr is reduced slightly. The Hcj increases from 12.2 to 13.7 kOe by adding Zr up to 1.5 at. %, whereas Hcj is decreased with a further increase in Zr content. The larger lattice constants and unit cell volumes of the matrix phase indicate that Zr atoms enter into the hard magnetic phase by substituting Fe sites. The reduction of Tc implies the attenuation of the exchange interaction in the 2:14:1 phase with Zr occupying the Fe sites. The weakened intergranular exchange coupling of the Zr added alloy may be attributed to the formation of a non-magnetic intergranular phase. It is worth noting that the coercivity is dominated by the pinning of domain walls at defect positions even though the nucleation of reversal domains still exists. The synergistic function between the pinning effect and the exchange coupling leads to improved magnetic properties.

The Effect of Pitching Phase on the Vortex Circulation for a Flapping Wing During Stroke Reversal

NASA Astrophysics Data System (ADS)

Burge, Matthew; Ringuette, Matthew

2017-11-01

We study the effect of pitching-phase on the circulation behavior for the 3D flow structures produced during stroke reversal for a 2-degree-of-freedom flapping wing executing hovering kinematics. Previous research has related the choice in pitching-phase with respect to the wing rotation during stroke reversal (advanced vs. symmetric pitch-timing) to a lift peak preceding stroke reversal. However, results from experiments on the time-varying circulation contributions from the 3D vortex structures across the span produced by both rotation and pitching are lacking. The objective of this research is to quantitatively examine how the spanwise circulation of these structures is affected by the pitching-phase for several reduced pitching frequencies. We employ a scaled wing model in a glycerin-water mixture and measure the time-varying velocity using multiple planes of stereo digital particle image velocimetry. Data-plane positions along the wing span are informed by the unsteady behavior of the 3D vortex structures found in our prior flow visualization movies. Individual vortices are identified to calculate their circulation. This work is aimed at understanding how the behavior of the vortex structures created during stroke reversal vary with key motion parameters. This work is supported by the National Science Foundation, Award Number 1336548, supervised by Dr. Ronald Joslin.

Learning and altering behaviours by reinforcement: neurocognitive differences between children and adults.

PubMed

Shephard, E; Jackson, G M; Groom, M J

2014-01-01

This study examined neurocognitive differences between children and adults in the ability to learn and adapt simple stimulus-response associations through feedback. Fourteen typically developing children (mean age=10.2) and 15 healthy adults (mean age=25.5) completed a simple task in which they learned to associate visually presented stimuli with manual responses based on performance feedback (acquisition phase), and then reversed and re-learned those associations following an unexpected change in reinforcement contingencies (reversal phase). Electrophysiological activity was recorded throughout task performance. We found no group differences in learning-related changes in performance (reaction time, accuracy) or in the amplitude of event-related potentials (ERPs) associated with stimulus processing (P3 ERP) or feedback processing (feedback-related negativity; FRN) during the acquisition phase. However, children's performance was significantly more disrupted by the reversal than adults and FRN amplitudes were significantly modulated by the reversal phase in children but not adults. These findings indicate that children have specific difficulties with reinforcement learning when acquired behaviours must be altered. This may be caused by the added demands on immature executive functioning, specifically response monitoring, created by the requirement to reverse the associations, or a developmental difference in the way in which children and adults approach reinforcement learning. Copyright © 2013 The Authors. Published by Elsevier Ltd.. All rights reserved.

Simultaneous estimation of lisofylline and pentoxifylline in rat plasma by high performance liquid chromatography-photodiode array detector and its application to pharmacokinetics in rat.

PubMed

Italiya, Kishan S; Sharma, Saurabh; Kothari, Ishit; Chitkara, Deepak; Mittal, Anupama

2017-09-01

Lisofylline (LSF) is an anti-inflammatory and immunomodulatory agent with proven activity in serious infections associated with cancer chemotherapy, hyperoxia-induced acute lung injury, autoimmune disorders including type-1 diabetes (T1DM) and islet rejection after islet transplantation. It is also an active metabolite of another anti-inflammatory agent, Pentoxifylline (PTX). LSF bears immense therapeutic potential in multiple pharmacological activities and hence appropriate and accurate quantification of LSF is very important. Although a number of analytical methods for quantification of LSF and PTX have been reported for pharmacokinetics and metabolic studies, each of these have certain limitations in terms of large sample volume required, complex extraction procedure and/or use of highly sophisticated instruments like LC-MS/MS. The aim of current study is to develop a simple reversed-phase HPLC method in rat plasma for simultaneous determination of LSF and PTX with the major objective of ensuring minimum sample volume, ease of extraction, economy of analysis, selectivity and avoiding use of instruments like LC-MS/MS to ensure a widespread application of the method. A simple liquid-liquid extraction method using methylene chloride as extracting solvent was used for extracting LSF and PTX from rat plasma (200μL). Samples were then evaporated, reconstituted with mobile phase and injected into HPLC coupled with photo-diode detector (PDA). LSF, PTX and 3-isobutyl 1-methyl xanthine (IBMX, internal standard) were separated on Inertsil® ODS (C18) column (250×4.6mm, 5μm) with mobile phase consisting of A-methanol B-water (50:50v/v) run in isocratic mode at flow rate of 1mL/min for 15min and detection at 273nm. The method showed linearity in the concentration range of 50-5000ng/mL with LOD of 10ng/mL and LLOQ of 50ng/mL for both LSF and PTX. Weighted linear regression analysis was also performed on the calibration data. The mean absolute recoveries were found to be 80.47±3.44 and 80.89±3.73% for LSF and PTX respectively. The method was successfully applied for studying the pharmacokinetics of LSF and PTX after IV bolus administration at dose of 25mg/kg in Wistar rat. In conclusion, a simple, sensitive, accurate and precise reversed-phase HPLC-UV method was established for simultaneous determination of LSF and PTX in rat plasma. Copyright © 2017 Elsevier B.V. All rights reserved.

Polymer depletion-driven cluster aggregation and initial phase separation in charged nanosized colloids

NASA Astrophysics Data System (ADS)

Gögelein, Christoph; Nägele, Gerhard; Buitenhuis, Johan; Tuinier, Remco; Dhont, Jan K. G.

2009-05-01

We study polymer depletion-driven cluster aggregation and initial phase separation in aqueous dispersions of charge-stabilized silica spheres, where the ionic strength and polymer (dextran) concentration are systematically varied, using dynamic light scattering and visual observation. Without polymers and for increasing salt and colloid content, the dispersions become increasingly unstable against irreversible cluster formation. By adding nonadsorbing polymers, a depletion-driven attraction is induced, which lowers the stabilizing Coulomb barrier and enhances the cluster growth rate. The initial growth rate increases with increasing polymer concentration and decreases with increasing polymer molar mass. These observations can be quantitatively understood by an irreversible dimer formation theory based on the classical Derjaguin, Landau, Verwey, and Overbeek pair potential, with the depletion attraction modeled by the Asakura-Oosawa-Vrij potential. At low colloid concentration, we observe an exponential cluster growth rate for all polymer concentrations considered, indicating a reaction-limited aggregation mechanism. At sufficiently high polymer and colloid concentrations, and lower salt content, a gas-liquidlike demixing is observed initially. Later on, the system separates into a gel and fluidlike phase. The experimental time-dependent state diagram is compared to the theoretical equilibrium phase diagram obtained from a generalized free-volume theory and is discussed in terms of an initial reversible phase separation process in combination with irreversible aggregation at later times.

Polymer depletion-driven cluster aggregation and initial phase separation in charged nanosized colloids.

PubMed

Gögelein, Christoph; Nägele, Gerhard; Buitenhuis, Johan; Tuinier, Remco; Dhont, Jan K G

2009-05-28

We study polymer depletion-driven cluster aggregation and initial phase separation in aqueous dispersions of charge-stabilized silica spheres, where the ionic strength and polymer (dextran) concentration are systematically varied, using dynamic light scattering and visual observation. Without polymers and for increasing salt and colloid content, the dispersions become increasingly unstable against irreversible cluster formation. By adding nonadsorbing polymers, a depletion-driven attraction is induced, which lowers the stabilizing Coulomb barrier and enhances the cluster growth rate. The initial growth rate increases with increasing polymer concentration and decreases with increasing polymer molar mass. These observations can be quantitatively understood by an irreversible dimer formation theory based on the classical Derjaguin, Landau, Verwey, and Overbeek pair potential, with the depletion attraction modeled by the Asakura-Oosawa-Vrij potential. At low colloid concentration, we observe an exponential cluster growth rate for all polymer concentrations considered, indicating a reaction-limited aggregation mechanism. At sufficiently high polymer and colloid concentrations, and lower salt content, a gas-liquidlike demixing is observed initially. Later on, the system separates into a gel and fluidlike phase. The experimental time-dependent state diagram is compared to the theoretical equilibrium phase diagram obtained from a generalized free-volume theory and is discussed in terms of an initial reversible phase separation process in combination with irreversible aggregation at later times.

Rational load rating of deck-girder bridges with girder end shear cracks in reverse orientation.

DOT National Transportation Integrated Search

2017-04-01

Reverse diagonal shear cracking at reinforced concrete girder supports affects many low-volume bridges built : in the early 1900s in Kansas. This phenomenon, however, is not addressed in the American Association of State : Highway and Transportation ...

Spatial and reversal learning in the Morris water maze are largely resistant to six hours of REM sleep deprivation following training

PubMed Central

Walsh, Christine M.; Booth, Victoria; Poe, Gina R.

2011-01-01

This first test of the role of REM (rapid eye movement) sleep in reversal spatial learning is also the first attempt to replicate a much cited pair of papers reporting that REM sleep deprivation impairs the consolidation of initial spatial learning in the Morris water maze. We hypothesized that REM sleep deprivation following training would impair both hippocampus-dependent spatial learning and learning a new target location within a familiar environment: reversal learning. A 6-d protocol was divided into the initial spatial learning phase (3.5 d) immediately followed by the reversal phase (2.5 d). During the 6 h following four or 12 training trials/day of initial or reversal learning phases, REM sleep was eliminated and non-REM sleep left intact using the multiple inverted flowerpot method. Contrary to our hypotheses, REM sleep deprivation during four or 12 trials/day of initial spatial or reversal learning did not affect training performance. However, some probe trial measures indicated REM sleep-deprivation–associated impairment in initial spatial learning with four trials/day and enhancement of subsequent reversal learning. In naive animals, REM sleep deprivation during normal initial spatial learning was followed by a lack of preference for the subsequent reversal platform location during the probe. Our findings contradict reports that REM sleep is essential for spatial learning in the Morris water maze and newly reveal that short periods of REM sleep deprivation do not impair concurrent reversal learning. Effects on subsequent reversal learning are consistent with the idea that REM sleep serves the consolidation of incompletely learned items. PMID:21677190

The Reversal of Direct Oral Anticoagulants in Animal Models

PubMed Central

Honickel, Markus; Akman, Necib; Grottke, Oliver

2017-01-01

ABSTRACT Several direct oral anticoagulants (DOACs), including direct thrombin and factor Xa inhibitors, have been approved as alternatives to vitamin K antagonist anticoagulants. As with any anticoagulant, DOAC use carries a risk of bleeding. In patients with major bleeding or needing urgent surgery, reversal of DOAC anticoagulation may be required, presenting a clinical challenge. The optimal strategy for DOAC reversal is being refined, and may include use of hemostatic agents such as prothrombin complex concentrates (PCCs; a source of concentrated clotting factors), or DOAC-specific antidotes (which bind their target DOAC to abrogate its activity). Though promising, most specific antidotes are still in development. Preclinical animal research is the key to establishing the efficacy and safety of potential reversal agents. Here, we summarize published preclinical animal studies on reversal of DOAC anticoagulation. These studies (n = 26) were identified via a PubMed search, and used rodent, rabbit, pig, and non-human primate models. The larger of these animals have the advantages of similar blood volume/hemodynamics to humans, and can be used to model polytrauma. We find that in addition to varied species being used, there is variability in the models and assays used between studies; we suggest that blood loss (bleeding volume) is the most clinically relevant measure of DOAC anticoagulation-related bleeding and its reversal. The studies covered indicate that both PCCs and specific reversal agents have the potential to be used as part of a clinical strategy for DOAC reversal. For the future, we advocate the development and use of standardized, clinically, and pharmacologically relevant animal models to study novel DOAC reversal strategies. PMID:28471371

Auditory sensitivity to spectral modulation phase reversal as a function of modulation depth

PubMed Central

Grose, John

2018-01-01

The present study evaluated auditory sensitivity to spectral modulation by determining the modulation depth required to detect modulation phase reversal. This approach may be preferable to spectral modulation detection with a spectrally flat standard, since listeners appear unable to perform the task based on the detection of temporal modulation. While phase reversal thresholds are often evaluated by holding modulation depth constant and adjusting modulation rate, holding rate constant and adjusting modulation depth supports rate-specific assessment of modulation processing. Stimuli were pink noise samples, filtered into seven octave-wide bands (0.125–8 kHz) and spectrally modulated in dB. Experiment 1 measured performance as a function of modulation depth to determine appropriate units for adaptive threshold estimation. Experiment 2 compared thresholds in dB for modulation detection with a flat standard and modulation phase reversal; results supported the idea that temporal cues were available at high rates for the former but not the latter. Experiment 3 evaluated spectral modulation phase reversal thresholds for modulation that was restricted to either one or two neighboring bands. Flanking bands of unmodulated noise had a larger detrimental effect on one-band than two-band targets. Thresholds for high-rate modulation improved with increasing carrier frequency up to 2 kHz, whereas low-rate modulation appeared more consistent across frequency, particularly in the two-band condition. Experiment 4 measured spectral weights for spectral modulation phase reversal detection and found higher weights for bands in the spectral center of the stimulus than for the lowest (0.125 kHz) or highest (8 kHz) band. Experiment 5 compared performance for highly practiced and relatively naïve listeners, and found weak evidence of a larger practice effect at high than low spectral modulation rates. These results provide preliminary data for a task that may provide a better estimate of sensitivity to spectral modulation than spectral modulation detection with a flat standard. PMID:29621338

Advantages of core-shell particle columns in Sequential Injection Chromatography for determination of phenolic acids.

PubMed

Chocholouš, Petr; Vacková, Jana; Srámková, Ivana; Satínský, Dalibor; Solich, Petr

2013-01-15

Currently, for Sequential Injection Chromatography (SIC), only reversed phase C18 columns have been used for chromatographic separations. This article presents the first use of three different stationary phases: three core-shell particle-packed reversed phase columns in flow systems. The aim of this work was to extend the chromatographic capabilities of the SIC system. Despite the particle-packed columns reaching system pressures of ≤ 610 PSI, their conditions matched those of a commercially produced and optimised SIC system (SIChrom™ (FIAlab(®), USA)) with a 8-port high-pressure selection valve and medium-pressure Sapphire™ syringe pump with a 4 mL reservoir and maximum system pressure of ≤ 1000 PSI. The selectivity of each of the tested columns, Ascentis(®) Express RP-Amide, Ascentis(®) Express Phenyl-Hexyl and Ascentis(®) Express C18 (30 mm × 4.6mm, core-shell particle size 2.7 μm), was compared by their ability to separate seven phenolic acids that are secondary metabolite substances widely distributed in plants. The separations of all of the components were performed by isocratic elution using binary mobile phases composed of acetonitrile and 0.065% phosphoric acid at pH 2.4 (a specific ratio was used for each column) at a flow-rate of 0.60 mL/min. The volume of the mobile phase was 3.8 mL for each separation. The injection volume of the sample was 10 μL for each separation. The UV detection wavelengths were set to 250, 280 and 325 nm. The RP-Amide column provided the highest chromatographic resolution and allowed for complete baseline separation of protocatechuic, syringic, vanillic, ferulic, sinapinic, p-coumaric and o-coumaric acids. The Phenyl-Hexyl and C18 columns were unable to completely separate the tested mixture, syringic and vanillic acid and ferulic and sinapinic acids could not be separated from one another. The analytical parameters were a LOD of 0.3 mg L(-1), a LOQ of 1.0 mg L(-1), a calibration range of 1.0-50.0 (100.0) mg L(-1) (r>0.997) and a system precision of 10 mg L(-1) with a RSD ≤ 1.65%. The high performance of the chromatography process with the RP-Amide column under optimised conditions was highlighted and well documented (HETP values ≤ 10 μm, peak symmetry ≤ 1.33, resolution ≥ 1.87 and time for one analysis <8.0 min). The results of these experiments confirmed the benefits of extending chromatographic selectivity using core-shell particle column technology in a SIC manifold. Copyright © 2012 Elsevier B.V. All rights reserved.

Simulation of semi-explicit mechanisms of SOA formation from glyoxal in aerosol in a 3-D model

NASA Astrophysics Data System (ADS)

Knote, C.; Hodzic, A.; Jimenez, J. L.; Volkamer, R.; Orlando, J. J.; Baidar, S.; Brioude, J.; Fast, J.; Gentner, D. R.; Goldstein, A. H.; Hayes, P. L.; Knighton, W. B.; Oetjen, H.; Setyan, A.; Stark, H.; Thalman, R.; Tyndall, G.; Washenfelder, R.; Waxman, E.; Zhang, Q.

2014-06-01

New pathways to form secondary organic aerosol (SOA) have been postulated recently. Glyoxal, the smallest dicarbonyl, is one of the proposed precursors. It has both anthropogenic and biogenic sources, and readily partitions into the aqueous phase of cloud droplets and deliquesced particles where it undergoes both reversible and irreversible chemistry. In this work we extend the regional scale chemistry transport model WRF-Chem to include detailed gas-phase chemistry of glyoxal formation as well as a state-of-the-science module describing its partitioning and reactions in the aerosol aqueous-phase. A comparison of several proposed mechanisms is performed to quantify the relative importance of different formation pathways and their regional variability. The CARES/CalNex campaigns over California in summer 2010 are used as case studies to evaluate the model against observations. A month-long simulation over the continental United States (US) enables us to extend our results to the continental scale. In all simulations over California, the Los Angeles (LA) basin was found to be the hot spot for SOA formation from glyoxal, which contributes between 1% and 15% of the model SOA depending on the mechanism used. Our results indicate that a mechanism based only on a reactive (surface limited) uptake coefficient leads to higher SOA yields from glyoxal compared to a more detailed description that considers aerosol phase state and chemical composition. In the more detailed simulations, surface uptake is found to give the highest SOA mass yields compared to a volume process and reversible formation. We find that the yields of the latter are limited by the availability of glyoxal in aerosol water, which is in turn controlled by an increase in the Henry's law constant depending on salt concentrations ("salting-in"). A time dependence in this increase prevents substantial partitioning of glyoxal into aerosol water at high salt concentrations. If this limitation is removed, volume pathways contribute > 20% of glyoxal-SOA mass, and the total mass formed (5.8% of total SOA in the LA basin) is about a third of the simple uptake coefficient formulation without consideration of aerosol phase state and composition. Results from the continental US simulation reveal the much larger potential to form glyoxal-SOA over the eastern continental US. Interestingly, the low concentrations of glyoxal-SOA over the western continental US are not due to the lack of a potential to form glyoxal-SOA here. Rather these small glyoxal-SOA concentrations reflect dry conditions and high salt concentrations, and the potential to form SOA mass here will strongly depend on the water associated with particles.

Ultrasonic emissions during ice nucleation and propagation in plant xylem.

PubMed

Charrier, Guillaume; Pramsohler, Manuel; Charra-Vaskou, Katline; Saudreau, Marc; Améglio, Thierry; Neuner, Gilbert; Mayr, Stefan

2015-08-01

Ultrasonic acoustic emission analysis enables nondestructive monitoring of damage in dehydrating or freezing plant xylem. We studied acoustic emissions (AE) in freezing stems during ice nucleation and propagation, by combining acoustic and infrared thermography techniques and controlling the ice nucleation point. Ultrasonic activity in freezing samples of Picea abies showed two distinct phases: the first on ice nucleation and propagation (up to 50 AE s(-1) ; reversely proportional to the distance to ice nucleation point), and the second (up to 2.5 AE s(-1) ) after dissipation of the exothermal heat. Identical patterns were observed in other conifer and angiosperm species. The complex AE patterns are explained by the low water potential of ice at the ice-liquid interface, which induced numerous and strong signals. Ice propagation velocities were estimated via AE (during the first phase) and infrared thermography. Acoustic activity ceased before the second phase probably because the exothermal heating and the volume expansion of ice caused decreasing tensions. Results indicate cavitation events at the ice front leading to AE. Ultrasonic emission analysis enabled new insights into the complex process of xylem freezing and might be used to monitor ice propagation in natura. © 2015 The Authors. New Phytologist © 2015 New Phytologist Trust.

Simple method for RF pulse measurement using gradient reversal.

PubMed

Landes, Vanessa L; Nayak, Krishna S

2018-05-01

To develop and evaluate a simple method for measuring the envelope of small-tip radiofrequency (RF) excitation waveforms in MRI, without extra hardware or synchronization. Gradient reversal approach to evaluate RF (GRATER) involves RF excitation with a constant gradient and reversal of that gradient during signal reception to acquire the time-reversed version of an RF envelope. An outer-volume suppression prepulse is used optionally to preselect a uniform volume. GRATER was evaluated in phantom and in vivo experiments. It was compared with the programmed waveform and the traditional pick-up coil method. In uniform phantom experiments, pick-up coil, GRATER, and outer-volume suppression + GRATER matched the programmed waveforms to less than 2.1%, less than 6.1%, and less than 2.4% normalized root mean square error, respectively, for real RF pulses with flip angle less than or equal to 30°, time-bandwidth product 2 to 8, and two to five excitation bands. For flip angles greater than 30°, GRATER measurement error increased as predicted by Bloch simulation. Fat-water phantom and in vivo experiments with outer-volume suppression + GRATER demonstrated less than 6.4% normalized root mean square error. The GRATER sequence measures small-tip RF envelopes without extra hardware or synchronization in just over two times the RF duration. The sequence may be useful in prescan calibration and for measurement and precompensation of RF amplifier nonlinearity. Magn Reson Med 79:2642-2651, 2018. © 2017 International Society for Magnetic Resonance in Medicine. © 2017 International Society for Magnetic Resonance in Medicine.

An assessment of the retention behaviour of polycyclic aromatic hydrocarbons on reversed phase stationary phases: selectivity and retention on C18 and phenyl-type surfaces.

PubMed

Kayillo, Sindy; Dennis, Gary R; Shalliker, R Andrew

2006-09-08

In this manuscript the retention and selectivity of a set of linear and non-linear PAHs were evaluated on five different reversed-phase columns. These phases included C18 and C18 Aqua stationary phases, as well as three phenyl phases: Propyl-phenyl, Synergi polar-RP and Cosmosil 5PBB phase. Overall, the results revealed that the phenyl-type columns offered better separation performance for the linear PAHs, while the separation of the structural isomer PAHs was enhanced on the C18 columns. The Propyl-phenyl column was found to have the highest molecular-stationary phase interactions, as evidenced by the greatest rate of change in 'S' (0.71) as a function of the molecular weight in the PAH homologous series, despite having the lowest surface coverage (3% carbon load) (where S is the slope of a plot of logk versus the solvent composition). In contrast, the C18 Aqua column, having the highest surface coverage (15% carbon load) was found to have the second lowest molecular-stationary phase interactions (rate of change in S=0.61). Interestingly, the Synergi polar-RP column, which also is a phenyl stationary phase behaved more 'C18-like' than 'phenyl-like' in many of the tests undertaken. This is probably not unexpected since all five phases were reversed phase.

Topological phases in a Kitaev chain with imbalanced pairing

NASA Astrophysics Data System (ADS)

Li, C.; Zhang, X. Z.; Zhang, G.; Song, Z.

2018-03-01

We systematically study a Kitaev chain with imbalanced pair creation and annihilation, which is introduced by non-Hermitian pairing terms. An exact phase diagram shows that the topological phase is still robust under the influence of the conditional imbalance. The gapped phases are characterized by a topological invariant, the extended Zak phase, which is defined by the biorthonormal inner product. Such phases are destroyed at the points where the coalescence of ground states occurs, associated with the time-reversal symmetry breaking. We find that the Majorana edge modes also exist in an open chain in the time-reversal symmetry-unbroken region, demonstrating the bulk-edge correspondence in such a non-Hermitian system.

Retention of nucleic acids in ion-pair reversed-phase high-performance liquid chromatography depends not only on base composition but also on base sequence.

PubMed

Qiao, Jun-Qin; Liang, Chao; Wei, Lan-Chun; Cao, Zhao-Ming; Lian, Hong-Zhen

2016-12-01

The study on nucleic acid retention in ion-pair reversed-phase high-performance liquid chromatography mainly focuses on size-dependence, however, other factors influencing retention behaviors have not been comprehensively clarified up to date. In this present work, the retention behaviors of oligonucleotides and double-stranded DNAs were investigated on silica-based C 18 stationary phase by ion-pair reversed-phase high-performance liquid chromatography. It is found that the retention of oligonucleotides was influenced by base composition and base sequence as well as size, and oligonucleotides prone to self-dimerization have weaker retention than those not prone to self-dimerization but with the same base composition. However, homo-oligonucleotides are suitable for the size-dependent separation as a special case of oligonucleotides. For double-stranded DNAs, the retention is also influenced by base composition and base sequence, as well as size. This may be attributed to the interaction of exposed bases in major or minor grooves with the hydrophobic alky chains of stationary phase. In addition, no specific influence of guanine and cytosine content was confirmed on retention of double-stranded DNAs. Notably, the space effect resulted from the stereostructure of nucleic acids also influences the retention behavior in ion-pair reversed-phase high-performance liquid chromatography. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Interaction between the Stress Phase Angle (SPA) and the Oscillatory Shear Index (OSI) Affects Endothelial Cell Gene Expression.

PubMed

Amaya, Ronny; Cancel, Limary M; Tarbell, John M

2016-01-01

Hemodynamic forces play an important role in the non-uniform distribution of atherosclerotic lesions. Endothelial cells are exposed simultaneously to fluid wall shear stress (WSS) and solid circumferential stress (CS). Due to variations in impedance (global factors) and geometric complexities (local factors) in the arterial circulation a time lag arises between these two forces that can be characterized by the temporal phase angle between CS and WSS (stress phase angle-SPA). Asynchronous flows (SPA close to -180°) that are most prominent in coronary arteries have been associated with localization of atherosclerosis. Reversing oscillatory flows characterized by an oscillatory shear index (OSI) that is great than zero are also associated with atherosclerosis localization. In this study we examined the relationship between asynchronous flows and reversing flows in altering the expression of 37 genes relevant to atherosclerosis development. In the case of reversing oscillatory flow, we observed that the asynchronous condition upregulated 8 genes compared to synchronous hemodynamics, most of them proatherogenic. Upregulation of the pro-inflammatory transcription factor NFκB p65 was confirmed by western blot, and nuclear translocation of NFκB p65 was confirmed by immunofluorescence staining. A comparative study between non-reversing flow and reversing flow found that in the case of synchronous hemodynamics, reversing flow altered the expression of 11 genes, while in the case of asynchronous hemodynamics, reversing flow altered the expression of 17 genes. Reversing flow significantly upregulated protein expression of NFκB p65 for both synchronous and asynchronous conditions. Nuclear translocation of NFκB p65 was confirmed for synchronous and asynchronous conditions in the presence of flow reversal. These data suggest that asynchronous hemodynamics and reversing flow can elicit proatherogenic responses in endothelial cells compared to synchronous hemodynamics without shear stress reversal, indicating that SPA as well as reversal flow (OSI) are important parameters characterizing arterial susceptibility to disease.

Interaction between the Stress Phase Angle (SPA) and the Oscillatory Shear Index (OSI) Affects Endothelial Cell Gene Expression

PubMed Central

Amaya, Ronny; Cancel, Limary M.; Tarbell, John M.

2016-01-01

Hemodynamic forces play an important role in the non-uniform distribution of atherosclerotic lesions. Endothelial cells are exposed simultaneously to fluid wall shear stress (WSS) and solid circumferential stress (CS). Due to variations in impedance (global factors) and geometric complexities (local factors) in the arterial circulation a time lag arises between these two forces that can be characterized by the temporal phase angle between CS and WSS (stress phase angle–SPA). Asynchronous flows (SPA close to -180°) that are most prominent in coronary arteries have been associated with localization of atherosclerosis. Reversing oscillatory flows characterized by an oscillatory shear index (OSI) that is great than zero are also associated with atherosclerosis localization. In this study we examined the relationship between asynchronous flows and reversing flows in altering the expression of 37 genes relevant to atherosclerosis development. In the case of reversing oscillatory flow, we observed that the asynchronous condition upregulated 8 genes compared to synchronous hemodynamics, most of them proatherogenic. Upregulation of the pro-inflammatory transcription factor NFκB p65 was confirmed by western blot, and nuclear translocation of NFκB p65 was confirmed by immunofluorescence staining. A comparative study between non-reversing flow and reversing flow found that in the case of synchronous hemodynamics, reversing flow altered the expression of 11 genes, while in the case of asynchronous hemodynamics, reversing flow altered the expression of 17 genes. Reversing flow significantly upregulated protein expression of NFκB p65 for both synchronous and asynchronous conditions. Nuclear translocation of NFκB p65 was confirmed for synchronous and asynchronous conditions in the presence of flow reversal. These data suggest that asynchronous hemodynamics and reversing flow can elicit proatherogenic responses in endothelial cells compared to synchronous hemodynamics without shear stress reversal, indicating that SPA as well as reversal flow (OSI) are important parameters characterizing arterial susceptibility to disease. PMID:27846267

Assessment of the chromatographic lipophilicity of eight cephalosporins on different stationary phases.

PubMed

Dąbrowska, Monika; Starek, Małgorzata; Komsta, Łukasz; Szafrański, Przemysław; Stasiewicz-Urban, Anna; Opoka, Włodzimierz

2017-04-01

The retention behaviors were investigated for a series of eight cephalosporins in thin-layer chromatography (TLC) using stationary phases of RP-2, RP-8, RP-18, NH 2 , DIOL, and CN chemically bonded silica gel. Additionally, various binary mobile phases (water/methanol and water/acetone) were used in different volume proportions. The retention behavior of the analyzed molecules was defined by R M0 constant. In addition, reversed phase high performance liquid chromatography (RP-HPLC) was performed in lipophilicity studies by using immobilized artificial membrane (IAM) stationary phase. Obtained chromatographic data (R M0 and logk' IAM ) were correlated with the lipophilicity, expressed as values of the log calculated (logP calc ) and experimental (logP exp(shake-flask) ) partition coefficient. Principal component analysis (PCA) was applied in order to obtain an overview of similarity or dissimilarity among the analyzed compounds. Hierarchical cluster analysis (HCA) was performed to compare the separation characteristics of the applied stationary phases. This study was undertaken to identify the best chromatographic system and chromatographic data processing method to enable the prediction of logP values. A comprehensive chromatographic investigation into the retention of the analyzed cephalosporins revealed a similar behavior on RP-18, RP-8 and CN stationary phases. The weak correlations obtained between experimental and certain computed lipophilicity indices revealed that R M0 and PC1/RM are relevant lipophilicity parameters and the RP-8, CN and RP-18 plates are appropriate stationary phases for lipophilicity investigation, whereas computational approaches still cannot fully replace experimentation. Copyright © 2017 Elsevier B.V. All rights reserved.

Mechanically controlling the reversible phase transformation from zinc blende to wurtzite in AlN

DOE PAGES

Li, Zhen; Yadav, Satyesh; Chen, Youxing; ...

2017-04-10

III–V and other binary octet semiconductors often take two phase forms—wurtzite (wz) and zinc blende (zb) crystal structures—with distinct functional performance at room temperature. Here, we investigate how to control the synthesized phase structure to either wz or zb phase by tuning the interfacial strain by taking AlN as a representative III–V compound. Furthermore, by applying in situ mechanical tests at atomic scale in a transmission electron microscope, we observed the reversible phase transformation from zb to wz, and characterized the transition path—the collective glide of Shockley partials on every two {111} planes of the zb AlN.

Numerical analysis of inertance pulse tube cryocooler with a modified reservoir

NASA Astrophysics Data System (ADS)

Abraham, Derick; Damu, C.; Kuzhiveli, Biju T.

2017-12-01

Pulse tube cryocoolers are used for cooling applications, where very high reliability is required as in space applications. These cryocoolers require a buffer volume depending on the temperature to be maintained and cooling load. A miniature single stage coaxial Inertance Pulse Tube Cryocooler is proposed which operates at 80 K to provide a cooling effect of at least 2 W. In this paper a pulse tube cryocooler, with modified reservoir is suggested, where the reverse fluctuation in compressor case is used instead of a steady pressure in the reservoir to bring about the desired phase shift between the pressure and the mass flow rate in the cold heat exchanger. Therefore, the large reservoir of the cryocooler is replaced by the crank volume of the hermetically sealed linear compressor, and hence the cryocooler is simplified and compact in size. The components of the cryocooler consist of a connecting tube, aftercooler, regenerator, cold heat exchanger, flow straightener, pulse tube, warm heat exchanger, inertance tube and the modified reservoir along with the losses were designed and analyzed. Each part of the cryocooler was analysed using SAGE v11 and verified with ANSYS Fluent. The simulation results clearly show that there is 50% reduction in the reservoir volume for the modified Inertance pulse tube cryocooler.

Evaluation of comprehensive multidimensional separations using reversed-phase, reversed-phase liquid chromatography/mass spectrometry for shotgun proteomics.

PubMed

Nakamura, Tatsuji; Kuromitsu, Junro; Oda, Yoshiya

2008-03-01

Two-dimensional liquid-chromatographic (LC) separation followed by mass spectrometric (MS) analysis was examined for the identification of peptides in complex mixtures as an alternative to widely used two-dimensional gel electrophoresis followed by MS analysis for use in proteomics. The present method involves the off-line coupling of a narrow-bore, polymer-based, reversed-phase column using an acetonitrile gradient in an alkaline mobile phase in the first dimension with octadecylsilanized silica (ODS)-based nano-LC/MS in the second dimension. After the first separation, successive fractions were acidified and dried off-line, then loaded on the second dimension column. Both columns separate peptides according to hydrophobicity under different pH conditions, but more peptides were identified than with the conventional technique for shotgun proteomics, that is, the combination of a strong cation exchange column with an ODS column, and the system was robust because no salts were included in the mobile phases. The suitability of the method for proteomics measurements was evaluated.

Short communication: separation and quantification of caseins and casein macropeptide using ion-exchange chromatography.

PubMed

Holland, B; Rahimi Yazdi, S; Ion Titapiccolo, G; Corredig, M

2010-03-01

The aim of this work was to improve an existing method to separate and quantify the 4 major caseins from milk samples (i.e., containing whey proteins) using ion-exchange chromatography. The separation process was carried out using a mini-preparative cation exchange column (1 or 5mL of column volume), using urea acetate as elution buffer at pH 3.5 with a NaCl gradient. All 4 major caseins were separated, and the purity of each peak was assessed using sodium dodecyl sulfate-PAGE. Purified casein fractions were also added to raw milk to confirm their elution volumes. The quantification was carried out using purified caseins in buffer as well as added directly to fresh skim milk. This method can also be employed to determine the decrease in kappa-casein and the release of the casein-macropeptide during enzymatic hydrolysis using rennet. In this case, the main advantage of using this method is the lack of organic solvents compared with the conventional method for separation of macropeptide (using reversed phase HPLC).

Two-dimensional solid-phase extraction strategy for the selective enrichment of aminoglycosides in milk.

PubMed

Shen, Aijin; Wei, Jie; Yan, Jingyu; Jin, Gaowa; Ding, Junjie; Yang, Bingcheng; Guo, Zhimou; Zhang, Feifang; Liang, Xinmiao

2017-03-01

An orthogonal two-dimensional solid-phase extraction strategy was established for the selective enrichment of three aminoglycosides including spectinomycin, streptomycin, and dihydrostreptomycin in milk. A reversed-phase liquid chromatography material (C 18 ) and a weak cation-exchange material (TGA) were integrated in a single solid-phase extraction cartridge. The feasibility of two-dimensional clean-up procedure that experienced two-step adsorption, two-step rinsing, and two-step elution was systematically investigated. Based on the orthogonality of reversed-phase and weak cation-exchange procedures, the two-dimensional solid-phase extraction strategy could minimize the interference from the hydrophobic matrix existing in traditional reversed-phase solid-phase extraction. In addition, high ionic strength in the extracts could be effectively removed before the second dimension of weak cation-exchange solid-phase extraction. Combined with liquid chromatography and tandem mass spectrometry, the optimized procedure was validated according to the European Union Commission directive 2002/657/EC. A good performance was achieved in terms of linearity, recovery, precision, decision limit, and detection capability in milk. Finally, the optimized two-dimensional clean-up procedure incorporated with liquid chromatography and tandem mass spectrometry was successfully applied to the rapid monitoring of aminoglycoside residues in milk. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Regularities of the sorption of 1,2,3,4-tetrahydroquinoline derivatives under conditions of reversed phase HPLC

NASA Astrophysics Data System (ADS)

Nekrasova, N. A.; Kurbatova, S. V.; Zemtsova, M. N.

2016-12-01

Regularities of the sorption of 1,2,3,4-tetrahydroquinoline derivatives on octadecylsilyl silica gel and porous graphitic carbon from aqueous acetonitrile solutions were investigated. The effect the molecular structure and physicochemical parameters of the sorbates have on their retention characteristics under conditions of reversed phase HPLC are analyzed.

40 CFR Appendix 6 to Subpart A of... - Reverse Phase Extraction (RPE) Method for Detection of Oil Contamination in Non-Aqueous Drilling...

Code of Federal Regulations, 2010 CFR

2010-07-01

... environment and a current awareness file of OSHA regulations regarding the safe handling of the chemicals... 40 Protection of Environment 29 2010-07-01 2010-07-01 false Reverse Phase Extraction (RPE) Method... Part 435 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) EFFLUENT GUIDELINES AND...

Preparation and application of reversed phase chromatorotor for the isolation of natural products by centrifugal preparative chromatography

USDA-ARS?s Scientific Manuscript database

A method of preparation of Chromatorotor or plates with a reversed phase (RP) solid silica gel sorbent layer has been developed for preparative centrifugal chromatography. The RP-rotor plates consist of binder free RP solid SiO2 sorbent layers of different thicknesses paked between two supported cir...

Molecular differences between deuterated and protonated polystyrenes using reversed-phase high-performance liquid chromatography.

PubMed

Kayillo, Sindy; Gray, Michael J; Shalliker, R Andrew; Dennis, Gary R

2005-05-06

Isotopic substitution is a technique used to highlight particular bonds within a molecule for kinetic, spectroscopic and structure analysis. It is presumed that although some properties such as stretching frequencies will not be the same for substituted analogues, the chemical interactions will not vary appreciably as a function of labelling. Reversed-phase liquid chromatography has been used to demonstrate that there are significant differences between the chromatographic behaviour of a sequence of deuterated and protonated oligomeric polystyrenes. Two-dimensional reversed-phase liquid chromatography was used to show that even the diasteromers of the oligomers (n = 5) have retention mechanisms that are dependent on the subtle changes to the molecular conformation and electronic structure, which are a consequence of deuteration.

Forward and reverse control system for induction motors

DOEpatents

Wright, J.T.

1987-09-15

A control system for controlling the direction of rotation of a rotor of an induction motor includes an array of five triacs with one of the triacs applying a current of fixed phase to the windings of the rotor and four of the triacs being switchable to apply either hot ac current or return ac current to the stator windings so as to reverse the phase of current in the stator relative to that of the rotor and thereby reverse the direction of rotation of the rotor. Switching current phase in the stator is accomplished by operating the gates of pairs of the triacs so as to connect either hot ac current or return ac current to the input winding of the stator. 1 fig.

Quantitative tomographic measurements of opaque multiphase flows

DOE Office of Scientific and Technical Information (OSTI.GOV)

GEORGE,DARIN L.; TORCZYNSKI,JOHN R.; SHOLLENBERGER,KIM ANN

2000-03-01

An electrical-impedance tomography (EIT) system has been developed for quantitative measurements of radial phase distribution profiles in two-phase and three-phase vertical column flows. The EIT system is described along with the computer algorithm used for reconstructing phase volume fraction profiles. EIT measurements were validated by comparison with a gamma-densitometry tomography (GDT) system. The EIT system was used to accurately measure average solid volume fractions up to 0.05 in solid-liquid flows, and radial gas volume fraction profiles in gas-liquid flows with gas volume fractions up to 0.15. In both flows, average phase volume fractions and radial volume fraction profiles from GDTmore » and EIT were in good agreement. A minor modification to the formula used to relate conductivity data to phase volume fractions was found to improve agreement between the methods. GDT and EIT were then applied together to simultaneously measure the solid, liquid, and gas radial distributions within several vertical three-phase flows. For average solid volume fractions up to 0.30, the gas distribution for each gas flow rate was approximately independent of the amount of solids in the column. Measurements made with this EIT system demonstrate that EIT may be used successfully for noninvasive, quantitative measurements of dispersed multiphase flows.« less

Determination of void volume in normal phase liquid chromatography.

PubMed

Jiang, Ping; Wu, Di; Lucy, Charles A

2014-01-10

Void volume is an important fundamental parameter in chromatography. Little prior discussion has focused on the determination of void volume in normal phase liquid chromatography (NPLC). Various methods to estimate the total void volume are compared: pycnometry; minor disturbance method based on injection of weak solvent; tracer pulse method; hold-up volume based on unretained compounds; and accessible volume based on Martin's rule and its descendants. These are applied to NPLC on silica, RingSep and DNAP columns. Pycnometry provides a theoretically maximum value for the total void volume and should be performed at least once for each new column. However, pycnometry does not reflect the volume of adsorbed strong solvent on the stationary phase, and so only yields an accurate void volume for weaker mobile phase conditions. 1,3,5-Tri-t-butyl benzene (TTBB) results in hold-up volumes that are convenient measures of the void volume for all eluent conditions on charge-transfer columns (RingSep and DNAP), but is weakly retained under weak eluent conditions on silica. Injection of the weak mobile phase component (hexane) may be used to determine void volume, but care must be exercised to select the appropriate disturbance feature. Accessible volumes, that are determined using a homologous series, are always biased low, and are not recommended as a measure of the void volume. Copyright © 2013 Elsevier B.V. All rights reserved.

Time-reversal-invariant spin-orbit-coupled bilayer Bose-Einstein condensates

NASA Astrophysics Data System (ADS)

Maisberger, Matthew; Wang, Lin-Cheng; Sun, Kuei; Xu, Yong; Zhang, Chuanwei

2018-05-01

Time-reversal invariance plays a crucial role for many exotic quantum phases, particularly for topologically nontrivial states, in spin-orbit coupled electronic systems. Recently realized spin-orbit coupled cold-atom systems, however, lack the time-reversal symmetry due to the inevitable presence of an effective transverse Zeeman field. We address this issue by analyzing a realistic scheme to preserve time-reversal symmetry in spin-orbit-coupled ultracold atoms, with the use of Hermite-Gaussian-laser-induced Raman transitions that preserve spin-layer time-reversal symmetry. We find that the system's quantum states form Kramers pairs, resulting in symmetry-protected gap closing of the lowest two bands at arbitrarily large Raman coupling. We also show that Bose gases in this setup exhibit interaction-induced layer-stripe and uniform phases as well as intriguing spin-layer symmetry and spin-layer correlation.

Influence of vitamin E acetate and other lipids on the phase behavior of mesophases based on unsaturated monoglycerides.

PubMed

Sagalowicz, L; Guillot, S; Acquistapace, S; Schmitt, B; Maurer, M; Yaghmur, A; de Campo, L; Rouvet, M; Leser, M; Glatter, O

2013-07-02

The phase behavior of the ternary unsaturated monoglycerides (UMG)-DL-α-tocopheryl acetate-water system has been studied. The effects of lipid composition in both bulk and dispersed lyotropic liquid crystalline phases and microemulsions were investigated. In excess water, progressive addition of DL-α-tocopheryl acetate to a binary UMG mixture results in the following phase sequence: reversed bicontinuous cubic phase, reversed hexagonal (H(II)) phase, and a reversed microemulsion. The action of DL-α-tocopheryl acetate is then compared to that of other lipids such as triolein, limonene, tetradecane, and DL-α-tocopherol. The impact of solubilizing these hydrophobic molecules on the UMG-water phase behavior shows some common features. However, the solubilization of certain molecules, like DL-α-tocopherol, leads to the presence of the reversed micellar cubic phase (space group number 227 and symmetry Fd3m) while the solubilization of others does not. These differences in phase behavior are discussed in terms of physical-chemical characteristics of the added lipid molecule and its interaction with UMG and water. From an applications point of view, phase behavior as a function of the solubilized content of guest molecules (lipid additive in our case) is crucial since macroscopic properties such as molecular release depend strongly on the phase present. The effect of two hydrophilic emulsifiers, used to stabilize the aqueous dispersions of UMG, was studied and compared. Those were Pluronic F127, which is the most commonly used stabilizer for these kinds of inverted type structures, and the partially hydrolyzed emulsifier lecithin (Emultop EP), which is a well accepted food-grade emulsifier. The phase behavior of particles stabilized by the partially hydrolyzed lecithin is similar to that of bulk sample at full hydration, but this emulsifier interacts significantly with the internal structure and affects it much more than F127.

High tidal volume ventilation induces NOS2 and impairs cAMP- dependent air space fluid clearance.

PubMed

Frank, James A; Pittet, Jean-Francois; Lee, Hyon; Godzich, Micaela; Matthay, Michael A

2003-05-01

Tidal volume reduction during mechanical ventilation reduces mortality in patients with acute lung injury and the acute respiratory distress syndrome. To determine the mechanisms underlying the protective effect of low tidal volume ventilation, we studied the time course and reversibility of ventilator-induced changes in permeability and distal air space edema fluid clearance in a rat model of ventilator-induced lung injury. Anesthetized rats were ventilated with a high tidal volume (30 ml/kg) or with a high tidal volume followed by ventilation with a low tidal volume of 6 ml/kg. Endothelial and epithelial protein permeability were significantly increased after high tidal volume ventilation but returned to baseline levels when tidal volume was reduced. The basal distal air space fluid clearance (AFC) rate decreased by 43% (P < 0.05) after 1 h of high tidal volume but returned to the preventilation rate 2 h after tidal volume was reduced. Not all of the effects of high tidal volume ventilation were reversible. The cAMP-dependent AFC rate after 1 h of 30 ml/kg ventilation was significantly reduced and was not restored when tidal volume was reduced. High tidal volume ventilation also increased lung inducible nitric oxide synthase (NOS2) expression and air space total nitrite at 3 h. Inhibition of NOS2 activity preserved cAMP-dependent AFC. Because air space edema fluid inactivates surfactant and reduces ventilated lung volume, the reduction of cAMP-dependent AFC by reactive nitrogen species may be an important mechanism of clinical ventilator-associated lung injury.

Comparing the selectivity and chiral separation of d- and l- fluorenylmethyloxycarbonyl chloride protected amino acids in analytical high performance liquid chromatography and supercritical fluid chromatography; evaluating throughput, economic and environmental impact.

PubMed

Vera, C M; Shock, D; Dennis, G R; Farrell, W; Shalliker, R A

2017-04-14

The chiral separation of d- and l- FMOC amino acids was undertaken using the Lux Cellulose-1 polysaccharide based chiral column in HPLC (normal phase and reverse phase) and SFC conditions. This was done to compare the relative selectivity and separation between the three separation modes and to evaluate the potential benefits of SFC separations with regards to resolution, throughput, economic and environmental impact. It was established that the separation of d- and l- FMOC amino acids in SFC displayed behaviours that were similar to both normal phase and reversed phase, rather than distinctly one or the other. Additionally, although reversed phase conditions yielded significantly higher resolution values between enantiomers across the range of amino acids studied, improvements in selectivity in SFC via the introduction of higher concentrations of formic acid in the mobile phase allowed for better resolution per unit of time. Moreover since the SFC mobile phase is composed mostly of recyclable CO 2 , there is a reduction in organic solvent consumption, which minimises the economic and environmental costs. Copyright © 2017. Published by Elsevier B.V.

Critical indices for reversible gamma-alpha phase transformation in metallic cerium

NASA Astrophysics Data System (ADS)

Soldatova, E. D.; Tkachenko, T. B.

1980-08-01

Critical indices for cerium have been determined within the framework of the pseudobinary solution theory along the phase equilibrium curve, the critical isotherm, and the critical isobar. The results obtained verify the validity of relationships proposed by Rushbrook (1963), Griffiths (1965), and Coopersmith (1968). It is concluded that reversible gamma-alpha transformation in metallic cerium is a critical-type transformation, and cerium has a critical point on the phase diagram similar to the critical point of the liquid-vapor system.

Determination of tylosin and tilmicosin residues in animal tissues by reversed-phase liquid chromatography.

PubMed

Chan, W; Gerhardt, G C; Salisbury, C D

1994-01-01

A method for the simultaneous determination of tylosin and tilmicosin residues in animal tissues is reported. Solid-phase extraction columns are used to isolate the drugs from tissue extracts. Determination is accomplished by reversed-phase liquid chromatography with UV detection at 287 nm. Mean recoveries from spiked tissues were 79.9% (coefficient of variation [CV], 8.1%) for tylosin and 92.6% (CV, 8.7%) for tilmicosin. Detection limits for tylosin and tilmicosin were 0.020 and 0.010 ppm, respectively.

Preparation of a polybutadiene stationary phase immobilized by gamma radiation for reversed-phase high-performance liquid chromatography.

PubMed

Lopes, Nilva P; Collins, Kenneth E; Jardim, Isabel C S F

2003-02-14

Polybutadiene (PBD) has been immobilized on HPLC silica by gamma radiation doses in the range from 5 to 180 kGy. Columns prepared from these reversed-phase materials, as well as from similar non-irradiated materials, were tested with standard sample mixtures and characterized by elemental analysis (% C) and infrared spectroscopy. A low dose of 5 kGy is sufficient to produce a layer of immobilized PBD which functions as an efficient and stable stationary phase. Higher doses give thicker immobilized layers having less favorable chromatographic properties.

Photoinduced local heating in silica photonic crystals for fast and reversible switching.

PubMed

Gallego-Gómez, Francisco; Blanco, Alvaro; López, Cefe

2012-12-04

Fast and reversible photonic-bandgap tunability is achieved in silica artificial opals by local heating. The effect is fully reversible as heat rapidly dissipates through the non-irradiated structure without active cooling and water is readsorbed. The performance is strongly enhanced by decreasing the photoirradiated opal volume, allowing bandgap shifts of 12 nm and response times of 20 ms. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

High pressure spectroscopic studies of phase transition in VO2

NASA Astrophysics Data System (ADS)

Basu, Raktima; Mishra, K. K.; Ravindran, T. R.; Dhara, Sandip

2018-04-01

Vanadium dioxide (VO2) exhibits a reversible first-order metal to insulator transition (MIT) at a technologically important temperature of 340K. A structural phase transition (SPT) from monoclinic M1 to rutile tetragonal R is also reported via another two intermediate phases of monoclinic M2 and triclinic T. Metastable monoclinic M2 phase of VO2 was synthesized by Mg doping in the vapour transport process. Raman spectroscopic measurements were carried out at high pressure on V1-xMgxO2 microrods. Two reversible structural phase transitions from monoclinic M2 to triclinic T at 1.6 GPa and T to monoclinic M1 at 3.2 GPa are observed and are explained by structural relaxation of the strained phases.

Reverse remodeling and the mechanism of mitral regurgitation improvement in patients with dilated cardiomyopathy.

PubMed

Kuperstein, Rafael; Blechman, Ido; Ben Zekry, Sagit; Klempfner, Robert; Freimark, Dov; Arad, Michael

2015-01-01

Functional mitral regurgitation (MR) is a common finding in dilated cardiomyopathy. Left ventricular (LV) reverse remodeling with LV size reduction and improvement in LV function is a well recognized phenomenon. We aimed to evaluate the impact of LV remodeling on the mechanism leading to functional MR. Among 188 patients with non-ischemic dilated cardiomyopathy, 10 patients significantly improved their LV function, reduced LV size and MR severity during follow-up (RRMR). A comparison was made between their baseline and follow-up echocardiographic examinations and to a matched-control group of patients who did not improve (no RRMR). LV and left atrium (LA) dimensions and volumes, LV mass (LVM), LV ejection fraction (LVEF) (Simpsons), sphericity index (SI), mitral valve tenting area (TA) coaptation distance (CD), effective regurgitant orifice (ERO), and regurgitant volume were calculated. Multivariable analysis was performed in order to evaluate which echocardiographic parameters related to MR improvement in reverse remodeling. LV and LA dimensions and volumes, LVM, SI, TA, CD, ERO and right ventricle, in the RRMR group significantly decreased at follow-up (p < 0.04 for all). When compared to no RRMR, despite a similar ERO (0.2 ± 0.05 vs. 0.2 ± 0.08, p = 0.13) and a larger regurgitant volume (38 ± 9 vs. 29 ± 8 mL, p = 0.05) and despite similar clinical characteristics and medical treatment we found significantly higher LVEF, smaller LV dimensions and volumes, smaller LVM and SI in the RRMR group (p < 0.05 for all). On multivariable analysis the SI was the sole predictor of RRMR (p = 0.04, OR = 0.76, CI 0.58-0.99). Reverse remodeling characterized by improvement in LV function, reduction in LV size and an associated reduction in MR severity is related to LV SI at baseline.

Review of Random Phase Encoding in Volume Holographic Storage

PubMed Central

Su, Wei-Chia; Sun, Ching-Cherng

2012-01-01

Random phase encoding is a unique technique for volume hologram which can be applied to various applications such as holographic multiplexing storage, image encryption, and optical sensing. In this review article, we first review and discuss diffraction selectivity of random phase encoding in volume holograms, which is the most important parameter related to multiplexing capacity of volume holographic storage. We then review an image encryption system based on random phase encoding. The alignment of phase key for decryption of the encoded image stored in holographic memory is analyzed and discussed. In the latter part of the review, an all-optical sensing system implemented by random phase encoding and holographic interconnection is presented.

Nanoscale Phase Stability Reversal During the Nucleation and Growth of Titanium Oxide Minerals

NASA Astrophysics Data System (ADS)

Hummmer, D. R.; Heaney, P. J.; Kubicki, J. D.; Kent, P. R.; Post, J. E.

2008-12-01

Fine-grained titanium oxide minerals are important in soils, where they affect a variety of geochemical processes. They are also industrially important as catalysts, pigments, food additives, and dielectrics. Recent research has indicated an apparent reversal of thermodynamic stability between TiO2 phases at the nanoscale thought to be caused by an increased contribution of surface energy to the total free energy. Time-resolved X-ray diffraction (XRD) experiments in which titanium oxides crystallize from aqueous TiCl4 solutions confirm that anatase, a metastable phase, is always the first phase to nucleate under our range of initial conditions. Rutile peaks are observed only minutes after the first appearance of anatase, after which anatase abundance slowly decreases while rutile continues to form. Whole pattern refinement of diffraction data reveals that lattice constants of both phases increase throughout the crystallization process. In addition, transmission electron microscope (TEM) observations and kinetic modeling indicate that anatase does not undergo a solid-state transformation to the rutile structure as once thought. Instead, anatase appears to re-dissolve and then feed the growth of already nucleated rutile nanocrystals. Density functional theory (DFT) calculations were employed to model 1, 2, and 3 nm particles of both mineral phases. The total surface energies calculated from these models did yield lower values for anatase than for rutile by 8-13 kJ/mol depending on particle size, indicating that surface free energy is sufficient to account for stability reversal. However, these whole-particle surface energies were much higher than the sum of energies of each particle's constituent crystallographic surfaces. We attribute the excess energy to defects associated with the edges and corners of nanoparticles, which are not present on a 2-D periodic surface. This previously unreported edge and corner energy may play a dominant role in the stability reversal of nanocrystalline titanium oxides, as well as other mineral systems susceptible to reversals in phase stability at the nanoscale.

SU-F-T-253: Volumetric Comparison Between 4D CT Amplitude and Phase Binning Mode

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yang, G; Ma, R; Reyngold, M

2016-06-15

Purpose: Motion artifact in 4DCT images can affect radiation treatment quality. To identify the most robust and accurate binning method, we compare the volume difference between targets delineated on amplitude and phase binned 4DCT scans. Methods: Varian RPM system and CT scanner were used to acquire 4DCTs of a Quasar phantom with embedded cubic and spherical objects having superior-inferior motion. Eight patients’ respiration waveforms were used to drive the phantom. The 4DCT scan was reconstructed into 10 phase and 10 amplitude bins (2 mm slices). A scan of the static phantom was also acquired. For each waveform, sphere and cubemore » volumes were generated automatically on each phase using HU thresholding. Phase (amplitude) ITVs were the union of object volumes over all phase (amplitude) binned images. The sphere and cube volumes measured in the static phantom scan were V{sub sphere}=4.19cc and V{sub cube}=27.0cc. Volume difference (VD) and dice similarity coefficient (DSC) of the ITVs, and mean volume error (MVE) defined as the average target volume percentage difference between each phase image and the static image, were used to evaluate the performance of amplitude and phase binning. Results: Averaged over the eight breathing traces, the VD and DSC of the internal target volume (ITV) between amplitude and phase binning were 3.4%±3.2% (mean ± std) and 95.9%±2.1% for sphere; 2.1%±3.3% and 98.0% ±1.5% for cube, respectively.For all waveforms, the average sphere MVE of amplitude and phase binning was 6.5% ± 5.0% and 8.2%±6.3%, respectively; and the average cube MVE of amplitude and phase binning was 5.7%±3.5%and 12.9%±8.9%, respectively. Conclusion: ITV volume and spatial overlap as assessed by VD and DSC are similar between amplitude and phase binning. Compared to phase binning, amplitude binning results in lower MVE suggesting it is less susceptible to motion artifact.« less

Reverse left ventricular remodeling after acute myocardial infarction: the prognostic impact of left ventricular global torsion.

PubMed

Spinelli, Letizia; Morisco, Carmine; Assante di Panzillo, Emiliano; Izzo, Raffaele; Trimarco, Bruno

2013-04-01

Reverse left ventricular (LV) remodeling (>10 % reduction in LV end-systolic volume) may occur in patients recovering for acute ST-elevation myocardial infarction (STEMI), undergoing percutaneous revascularization of infarct-related coronary artery (PCI). To detect whether LV global torsion obtained by two-dimensional speckle-tracking echocardiography was predictive of reverse LV remodeling, 75 patients with first anterior wall STEMI were studied before (T1) and after PCI (T2) and at 6-month follow-up. Two-year clinical follow-up was also accomplished. LV volumes and both LV sphericity index and conic index were obtained by three-dimensional echocardiography. Reverse remodeling was observed in 25 patients (33 %). By multivariate analysis, independent predictors of reverse LV remodeling were: LV conic index, T2 LV torsion and Δ torsion (difference between T2 and T1 LV torsion expressed as percentage of this latter). According to receiver operating characteristic analysis, 1.34°/cm for T2 LV torsion (sensitivity 88 % and specificity 80 %) and 54 % for Δ torsion (sensitivity 92 % and specificity 82 %) were the optimal cutoff values in predicting reverse LV remodeling. In up to 24 month follow-up, 4 non-fatal re-infarction, 7 hospitalization for heart failure and 4 cardiac deaths occurred. By multivariate Cox analysis, the best variable significantly associated with event-free survival rate was reverse LV remodeling with a hazard ratio = 9.9 (95 % confidence interval, 7.9-31.4, p < 0.01). In conclusion, reverse LV remodeling occurring after anterior wall STEMI is associated with favorable long-term outcome. The improvement of global LV torsion following coronary artery revascularization is the major predictor of reverse LV remodeling.

Spray drying of a phenolic-rich membrane filtration fraction of olive mill wastewater: Optimization and dried product quality

USDA-ARS?s Scientific Manuscript database

Olive mill wastewater (OMWW) from two California mills (3-phase and 2-phase) was subjected to a two-step membrane filtration process using a novel vibratory system. The obtained reverse osmosis retentate (RO-R) is a phenolic-rich co-product stream, and the reverse osmosis permeate is a near-pure wat...

Gradient Scouting in Reversed-Phase HPLC Revisited

ERIC Educational Resources Information Center

Alcazar, A.; Jurado, J. M.; Gonzalez, A. G.

2011-01-01

Gradient scouting is the best way to decide the most suitable elution mode in reversed-phase high-performance liquid chromatography (RP-HPLC). A simple rule for this decision involves the evaluation of the ratio [delta]t/t[subscript G] (where [delta]t is the difference in the retention time between the last and the first peak and t[subscript G] is…

Triggering the volume phase transition of core-shell Au nanorod-microgel nanocomposites with light

NASA Astrophysics Data System (ADS)

Rodríguez-Fernández, Jessica; Fedoruk, Michael; Hrelescu, Calin; Lutich, Andrey A.; Feldmann, Jochen

2011-06-01

We have coated gold nanorods (NRs) with thermoresponsive microgel shells based on poly(N-isopropylacrylamide) (pNIPAM). We demonstrate by simultaneous laser-heating and optical extinction measurements that the Au NR cores can be simultaneously used as fast optothermal manipulators (switchers) and sensitive optical reporters of the microgel state in a fully externally controlled and reversible manner. We support our results with optical modeling based on the boundary element method and 3D numerical analysis on the temperature distribution. Briefly, we show that due to the sharp increase in refractive index resulting from the optothermally triggered microgel collapse, the longitudinal plasmon band of the coated Au NRs is significantly red-shifted. The optothermal control over the pNIPAM shell, and thereby over the optical response of the nanocomposite, is fully reversible and can be simply controlled by switching on and off a NIR heating laser. In contrast to bulk solution heating, we demonstrate that light-triggering does not compromise colloidal stability, which is of primary importance for the ultimate utilization of these types of nanocomposites as remotely controlled optomechanical actuators, for applications spanning from drug delivery to photonic crystals and nanoscale motion.

Forest statistics for Southwest Georgia, 1971

Treesearch

Herbert A. Knight

1971-01-01

Acreage of commercial forest land in this 22-county area has declined by 180,000 acres. or almost 6 percent, since 1960. Over this same period, volume of growing-stock timber increased by 581 million cubic feet, or almost 27 percent, reversing a downward trend in volume between 1951 and 1960. Softwoods have accounted for 85 percent of this net gain in volume. In 1970...

Controlling the dynamics of electrons and ions in large area capacitive radio frequency plasmas via the Electrical Asymmetry Effect

NASA Astrophysics Data System (ADS)

Schuengel, Edmund

2014-10-01

The processing of large area surfaces in capacitive radio-frequency plasmas is a crucial step in the manufacturing of various high-technological products. To optimize these discharges for applications, understanding and controlling the dynamics of electrons and ions is vitally important. A recently proposed method of controlling these dynamics is based on the Electrical Asymmetry Effect (EAE): By driving the capacitive discharge with a dual-frequency voltage waveform composed of two consecutive harmonics, the symmetry of the discharge can be varied by tuning the relative phase. In this experimental study, the EAE is tested in hydrogen diluted silane discharges. The electron dynamics visualized by Phase Resolved Optical Emission Spectroscopy depends on the electrical asymmetry, the heating mode, and the presence of dust particles agglomerating in the plasma volume. In particular, a transition from the α-mode (heating by sheath expansion and field reversal) to the Ω-mode (heating by drift field in the bulk) is observed. The ion dynamics are strongly affected by the sheaths electric fields, which can be controlled via the EAE: Separate control of the flux and mean energy of ions onto the electrodes is possible via the EAE. Furthermore, investigations of the spatially resolved ion flux in the electromagnetic regime, i.e. using higher driving frequencies, reveal that the ion flux profile is controllable via the phase, as well, allowing for a significant improvement of the uniformity. Thus, it is demonstrated that the EAE is a powerful tool to control the properties of large area capacitive discharges in the volume and at the surfaces in various ways. Funded by the German Federal Ministry for the Environment, Nature conservation, and Nuclear Safety (0325210B).

Semiautomated solid-phase extraction followed by derivatisation and gas chromatography–mass spectrometry for determination of perfluoroalkyl acids in water.

PubMed

Jurado-Sánchez, Beatriz; Ballesteros, Evaristo; Gallego, Mercedes

2013-11-29

This paper describes a sensitive approach for the determination of 6 perfluoroalkyl carboxylic acids and perfluorooctane sulfonic acid in water. Samples were preconcentrated using an automatic solid-phase extraction module and then manually derivatised and determined by gas chromatography–mass spectrometry. The analytes were derivatised with a isobutyl chloroformate/isobutanol mixture, using 3% N,N-dicyclohexylcarbodiimide in pyridine as the catalyst. From a systematic comparison of several reversed-phase and anion-exchange sorbent materials for the retention of perfluoroalkyl acids, the high-est retention efficiencies (∼100%) were achieved with LiChrolut EN and Discovery DSC-SAX columns.LiChrolut EN was the sorbent selected due to several advantages (sample pH ∼1; sample flow rate,5.5 mL/min; breakthrough volume, 300 mL) over Discovery DSC-SAX (sample pH ∼6; sample flow rate,3.0 mL/min; breakthrough volume, 45 mL), for the retention of the studied compounds. Detection and quantification limits within the range of 0.1–0.5 ng/L and 0.4–1.7 ng/L, respectively, were obtained for a sorbent column of 70 mg of LiChrolut EN and 250 mL of sample, the relative standard deviation being lower than 7%. The method was applied both to the analysis of water collected at the intake (raw) and atthe exit (treated) of two drinking water treatment plants, as well as to various types of water. Few samples were positive for perfluoroalkyl acids and only one acid (perfluoroheptanoic or perfluorooctanoic) was found in each treatment plant. The highest number and concentration of analytes (perfluoroheptanoic,perfluorooctanoic and perfluorodecanoic acid) were found in one wastewater.

Reversibility and energy dissipation in adiabatic superconductor logic.

PubMed

Takeuchi, Naoki; Yamanashi, Yuki; Yoshikawa, Nobuyuki

2017-03-06

Reversible computing is considered to be a key technology to achieve an extremely high energy efficiency in future computers. In this study, we investigated the relationship between reversibility and energy dissipation in adiabatic superconductor logic. We analyzed the evolution of phase differences of Josephson junctions in the reversible quantum-flux-parametron (RQFP) gate and confirmed that the phase differences can change time reversibly, which indicates that the RQFP gate is physically, as well as logically, reversible. We calculated energy dissipation required for the RQFP gate to perform a logic operation and numerically demonstrated that the energy dissipation can fall below the thermal limit, or the Landauer bound, by lowering operation frequencies. We also investigated the 1-bit-erasure gate as a logically irreversible gate and the quasi-RQFP gate as a physically irreversible gate. We calculated the energy dissipation of these irreversible gates and showed that the energy dissipation of these gate is dominated by non-adiabatic state changes, which are induced by unwanted interactions between gates due to logical or physical irreversibility. Our results show that, in reversible computing using adiabatic superconductor logic, logical and physical reversibility are required to achieve energy dissipation smaller than the Landauer bound without non-adiabatic processes caused by gate interactions.

Predicting solubilisation features of ternary phase diagrams of fully dilutable lecithin linker microemulsions.

PubMed

Nouraei, Mehdi; Acosta, Edgar J

2017-06-01

Fully dilutable microemulsions (μEs), used to design self-microemulsifying delivery system (SMEDS), are formulated as concentrate solutions containing oil and surfactants, without water. As water is added to dilute these systems, various μEs are produced (water-swollen reverse micelles, bicontinuous systems, and oil-swollen micelles), without the onset of phase separation. Currently, the formulation dilutable μEs follows a trial and error approach that has had a limited success. The objective of this work is to introduce the use of the hydrophilic-lipophilic-difference (HLD) and net-average-curvature (NAC) frameworks to predict the solubilisation features of ternary phase diagrams of lecithin-linker μEs and the use of these predictions to guide the formulation of dilutable μEs. To this end, the characteristic curvatures (Cc) of soybean lecithin (surfactant), glycerol monooleate (lipophilic linker) and polyglycerol caprylate (hydrophilic linker) and the equivalent alkane carbon number (EACN) of ethyl caprate (oil) were obtained via phase scans with reference surfactant-oil systems. These parameters were then used to calculate the HLD of lecithin-linkers-ethyl caprate microemulsions. The calculated HLDs were able to predict the phase transitions observed in the phase scans. The NAC was then used to fit and predict phase volumes obtained from salinity phase scans, and to predict the solubilisation features of ternary phase diagrams of the lecithin-linker formulations. The HLD-NAC predictions were reasonably accurate, and indicated that the largest region for dilutable μEs was obtained with slightly negative HLD values. The NAC framework also predicted, and explained, the changes in microemulsion properties along dilution lines. Copyright © 2017 Elsevier Inc. All rights reserved.

New ordered metastable phases between the gel and subgel phases in hydrated phospholipids.

PubMed Central

Tenchov, B; Koynova, R; Rapp, G

2001-01-01

Formation of low-temperature ordered gel phases in several fully hydrated phosphatidylethanolamines (PEs) and phosphatidylcholines (PCs) with saturated chains as well as in dipalmitoylphosphatidylglycerol (DPPG) was observed by synchrotron x-ray diffraction, microcalorimetry, and densitometry. The diffraction patterns recorded during slow cooling show that the gel-phase chain reflection cooperatively splits into two reflections, signaling a transformation of the usual gel phase into a more ordered phase, with an orthorhombic chain packing (the Y-transition). This transition is associated with a small decrease (2-4 microl/g) or inflection of the partial specific volume. It is fully reversible with the temperature and displays in heating direction as a small (0.1-0.7 kcal/mol) endothermic event. We recorded a Y-transition in distearoyl PE, dipalmitoyl PE (DPPE), mono and dimethylated DPPE, distearoyl PC, dipalmitoyl PC, diC(15)PC, and DPPG. No such transition exists in dimyristoyl PE and dilauroyl PE where the gel L(beta) phase transforms directly into subgel L(c) phase, as well as in the unsaturated dielaidoyl PE. The PE and PC low-temperature phases denoted L(R1) and SGII, respectively, have different hydrocarbon chain packing. The SGII phase is with tilted chains, arranged in an orthorhombic lattice of two-nearest-neighbor type. Except for the PCs, it was also registered in ionized DPPG. In the L(R1) phase, the chains are perpendicular to the bilayer plane and arranged in an orthorhombic lattice of four-nearest-neighbor type. It was observed in PEs and in protonated DPPG. The L(R1) and SGII phases are metastable phases, which may only be formed by cooling the respective gel L(beta) and L(beta') phases, and not by heating the subgel L(c) phase. Whenever present, they appear to represent an indispensable intermediate step in the formation of the latter phase. PMID:11259300

Simultaneous determination of cations, zwitterions and neutral compounds using mixed-mode reversed-phase and cation-exchange high-performance liquid chromatography.

PubMed

Li, Jingyi; Shao, Shan; Jaworsky, Markian S; Kurtulik, Paul T

2008-03-28

A novel mixed-mode reversed-phase and cation-exchange high-performance liquid chromatography (HPLC) method is described to simultaneously determine four related impurities of cations, zwitterions and neutral compounds in developmental Drug A. The commercial column is Primesep 200 containing hydrophobic alkyl chains with embedded acidic groups in H(+) form on a silica support. The mobile phase variables of acid additives, contents of acetonitrile and concentrations of potassium chloride have been thoroughly investigated to optimize the separation. The retention factors as a function of the concentrations of potassium chloride and the percentages of acetonitrile in the mobile phases are investigated to get an insight into the retention and separation mechanisms of each related impurity and Drug A. Furthermore, the elution orders of the related impurities and Drug A in an ion-pair chromatography (IPC) are compared to those in the mixed-mode HPLC to further understand the chromatographic retention behaviors of each related impurity and Drug A. The study found that the positively charged Degradant 1, Degradant 2 and Drug A were retained by both ion-exchange and reversed-phase partitioning mechanisms. RI2, a small ionic compound, was primarily retained by ion-exchange. RI4, a neutral compound, was retained through reversed-phase partitioning without ion-exchange. Moreover, the method performance characteristics of selectivity, sensitivity and accuracy have been demonstrated to be suitable to determine the related impurities in the capsules of Drug A.

SIRT1 inhibition during the hypoinflammatory phenotype of sepsis enhances immunity and improves outcome

PubMed Central

Vachharajani, Vidula T.; Liu, Tiefu; Brown, Candice M.; Wang, Xianfeng; Buechler, Nancy L.; Wells, Jonathan David; Yoza, Barbara K.; McCall, Charles E.

2014-01-01

Mechanism-based sepsis treatments are unavailable, and their incidence is rising worldwide. Deaths occur during the early acute phase of hyperinflammation or subsequent postacute hypoinflammatory phase with sustained organ failure. The acute sepsis phase shifts rapidly, and multiple attempts to treat early excessive inflammation have uniformly failed. We reported in a sepsis cell model and human sepsis blood leukocytes that nuclear NAD+ sensor SIRT1 deacetylase remodels chromatin at specific gene sets to switch the acute-phase proinflammatory response to hypoinflammatory. Importantly, SIRT1 chromatin reprogramming is reversible, suggesting that inhibition of SIRT1 might reverse postacute-phase hypoinflammation. We tested this concept in septic mice, using the highly specific SIRT1 inhibitor EX-527, a small molecule that closes the NAD+ binding site of SIRT1. Strikingly, when administered 24 h after sepsis, all treated animals survived, whereas only 40% of untreated mice survived. EX-527 treatment reversed the inability of leukocytes to adhere at the small intestine MVI, reversed in vivo endotoxin tolerance, increased leukocyte accumulation in peritoneum, and improved peritoneal bacterial clearance. Mechanistically, the SIRT1 inhibitor restored repressed endothelial E-selectin and ICAM-1 expression and PSGL-1 expression on the neutrophils. Systemic benefits of EX-527 treatment included stabilized blood pressure, improved microvascular blood flow, and a shift toward proimmune macrophages in spleen and bone marrow. Our findings reveal that modifying the SIRT1 NAD+ axis may provide a novel way to treat sepsis in its hypoinflammatory phase. PMID:25001863

Applications of reversible covalent chemistry in analytical sample preparation.

PubMed

Siegel, David

2012-12-07

Reversible covalent chemistry (RCC) adds another dimension to commonly used sample preparation techniques like solid-phase extraction (SPE), solid-phase microextraction (SPME), molecular imprinted polymers (MIPs) or immuno-affinity cleanup (IAC): chemical selectivity. By selecting analytes according to their covalent reactivity, sample complexity can be reduced significantly, resulting in enhanced analytical performance for low-abundance target analytes. This review gives a comprehensive overview of the applications of RCC in analytical sample preparation. The major reactions covered include reversible boronic ester formation, thiol-disulfide exchange and reversible hydrazone formation, targeting analyte groups like diols (sugars, glycoproteins and glycopeptides, catechols), thiols (cysteinyl-proteins and cysteinyl-peptides) and carbonyls (carbonylated proteins, mycotoxins). Their applications range from low abundance proteomics to reversible protein/peptide labelling to antibody chromatography to quantitative and qualitative food analysis. In discussing the potential of RCC, a special focus is on the conditions and restrictions of the utilized reaction chemistry.

Reversal of clopidogrel-induced bleeding with rFVIIa in healthy subjects: a randomized, placebo-controlled, double-blind, exploratory study.

PubMed

Skolnick, Brett E; Shenouda, Magdy; Khutoryansky, Naum M; Pusateri, Anthony E; Gabriel, Don; Carr, Marcus E

2011-10-01

Clopidogrel (Plavix®) therapy, although effective for minimizing risk of thrombotic events, is also associated with potential bleeding risk. Recombinant activated FVII (rFVIIa, NovoSeven®) induces hemostasis in hemophilia patients with inhibitors (alloantibodies) and has been proposed as potential treatment for mitigating clopidogrel therapy-mediated bleeding. In this single-center, randomized, placebo-controlled, double-blind, dose-escalation, exploratory phase I trial, we assessed the safety and effects of rFVIIa in reversing clopidogrel-enhanced bleeding in an experimentally induced punch biopsy in healthy subjects. Efficacy assessments included the reversal of bleeding characteristics (bleed duration [BD], the primary end point and blood loss volume [BV] induced by punch biopsy, and thromboelastograph [TEG®] parameters) with rFVIIa or placebo after clopidogrel treatment. A significant number of subjects (56%) had limited response to clopidogrel (defined as ≤30% platelet aggregation inhibition) and were discontinued from study. The remaining subjects continued and had 4 biopsies. Of 40 subjects randomized, 37 were evaluated for efficacy. Clopidogrel treatment increased BD and BV compared with the baseline biopsy. Recombinant FVIIa (10 and 20 μg/kg) significantly mitigated the clopidogrel-induced effects on BV (P = 0.007 and P = 0.001, respectively). Early trial termination limited the evaluation of effects of higher rFVIIa doses. Subgroup analyses of subjects biopsied by the same physician demonstrated significant reduction of clopidogrel-induced BD with 20 μg/kg rFVIIa (P = 0.048). Ex vivo analysis of rFVIIa demonstrated clotting dynamics presented by parameters time to clot onset (TEG®-R) and clot angle (TEG®-A) (P < 0.005). In this clinical study, rFVIIa (10 and 20 μg/kg) reversed the effect of clopidogrel on blood loss.

Strain-assisted current-induced magnetization reversal in magnetic tunnel junctions: A micromagnetic study with phase-field microelasticity

DOE Office of Scientific and Technical Information (OSTI.GOV)

Huang, H. B., E-mail: houbinghuang@gmail.com; Department of Physics, University of Science and Technology Beijing, Beijing 100083; Hu, J. M.

2014-09-22

Effect of substrate misfit strain on current-induced in-plane magnetization reversal in CoFeB-MgO based magnetic tunnel junctions is investigated by combining micromagnetic simulations with phase-field microelasticity theory. It is found that the critical current density for in-plane magnetization reversal decreases dramatically with an increasing substrate strain, since the effective elastic field can drag the magnetization to one of the four in-plane diagonal directions. A potential strain-assisted multilevel bit spin transfer magnetization switching device using substrate misfit strain is also proposed.

DOE Office of Scientific and Technical Information (OSTI.GOV)

K., S C; M., T C

Plastic bonded explosives (PBX) generally consist of 85 - 95 % by weight energetic material, such as HMX, and 5 - 15 % polymeric binder. Understanding of the structure and morphology at elevated temperatures and pressures is important for predicting of PBX behavior in accident scenarios. The crystallographic behavior of pure HMX has been measured as functions of temperature and grain size. The investigation is extended to the high temperature behavior of PBX 9501 (95% HMX, 2.5 % Estane, 2.5 % BDNPA/F). The results show that the HMX {beta}-phase to {delta}-phase transition in PBX 9501 is similar to that inmore » neat HMX. However, in the presence of the PBX 9501 binder, {delta}-phase HMX readily converts back to {beta}-phase during cooling. Using the same temperature profile, the conversion rate decreases for each subsequent heating and cooling cycle. As observed in earlier experiments, no reverse conversion is observed without the polymer binder. It is proposed that the reversion of {delta}-phase to {beta}-phase is due to changes in the surface molecular potential caused by the influence of the polymer binder on the surface molecules of the {delta}-phase. Upon thermal cycling, the polymer binder segregates from the HMX particles and thus reduces the influence of the binder on the surface molecules. This segregation increases the resistance for the {delta}-phase to {beta}-phase transition, as demonstrated in an aged PBX 9501 material for which the reversion is not observed.« less

MRI Shows that Exhaustion Syndrome Due to Chronic Occupational Stress is Associated with Partially Reversible Cerebral Changes.

PubMed

Savic, I; Perski, A; Osika, W

2018-03-01

The present study investigates the cerebral effects of chronic occupational stress and its possible reversibility. Forty-eight patients with occupational exhaustion syndrome (29 women) and 80 controls (47 women) underwent structural magnetic resonance imaging (MRI) and neuropsychological testing. Forty-four participants (25 patients, 19 controls) also completed a second MRI scan after 1-2 years. Only patients received cognitive therapy. The stressed group at intake had reduced thickness in the right prefrontal cortex (PFC) and left superior temporal gyrus (STG), enlarged amygdala volumes, and reduced caudate volumes. Except for the caudate volume, these abnormalities were more pronounced in females. They were all related to perceived stress, which was similar for both genders. Thickness of the PFC also correlated with an impaired ability to down-modulate negative emotions. Thinning of PFC and reduction of caudate volume normalized in the follow-up. The amygdala enlargement and the left STG thinning remained. Longitudinal changes were not detected among controls. Chronic occupational stress was associated with partially reversible structural abnormalities in key regions for stress processing. These changes were dynamically correlated with the degree of perceived stress, highlighting a possible causal link. They seem more pronounced in women, and could be a substrate for an increased cerebral vulnerability to stress-related psychiatric disorders. © The Author 2017. Published by Oxford University Press. All rights reserved. For Permissions, please e-mail: journals.permissions@oup.com.

Influence of primary α-phase volume fraction on the mechanical properties of Ti-6Al-4V alloy at different strain rates and temperatures

NASA Astrophysics Data System (ADS)

Ren, Yu; Zhou, Shimeng; Luo, Wenbo; Xue, Zhiyong; Zhang, Yajing

2018-03-01

Bimodal microstructures with primary α-phase volume fractions ranging from 14.3% to 57.1% were gained in Ti-6Al-4V (Ti-64) alloy through annealed in two-phase region at various temperatures below the β-transus point. Then the influence of the primary α-phase volume fraction on the mechanical properties of Ti-64 were studied. The results show that, at room temperature and a strain rate of 10‑3 s‑1, the yield stress decreases but the fracture strain augments with added primary α-phase volume fraction. The equiaxed primary α-phase possesses stronger ability to coordinate plastic deformation, leading to the improvement of the ductile as well as degradation of the strength of Ti-64 with higher primary α-phase volume fraction. As the temperature goes up to 473 K, the quasi-static yield stress and ultimate strength decrease first and then increase with the incremental primary α-phase volume fraction, due to the interaction between the work hardening and the softening caused by the DRX and the growth of the primary α-phase. At room temperature and a strain rate of 3×103 s‑1, the varying pattern of strength with the primary α-phase volume fraction resembles that at a quasi-static strain rate. However, the flow stress significantly increases but the strain-hardening rate decreases compared to those at quasi-static strain rate due to the competition between the strain rate hardening and the thermal softening during dynamic compression process.

75 FR 50801 - Reverse Mortgage Products: Guidance for Managing Compliance and Reputation Risks

Federal Register 2010, 2011, 2012, 2013, 2014

2010-08-17

... stronger standards, particularly with respect to policies designed to avoid conflicts of interest. A... related to data collection on the volume of reverse mortgages, anti-fraud provisions, test design for the...' policies and procedures will be designed to ensure that brokers with whom they do business as agents also...

Applications of the solvation parameter model in reversed-phase liquid chromatography.

PubMed

Poole, Colin F; Lenca, Nicole

2017-02-24

The solvation parameter model is widely used to provide insight into the retention mechanism in reversed-phase liquid chromatography, for column characterization, and in the development of surrogate chromatographic models for biopartitioning processes. The properties of the separation system are described by five system constants representing all possible intermolecular interactions for neutral molecules. The general model can be extended to include ions and enantiomers by adding new descriptors to encode the specific properties of these compounds. System maps provide a comprehensive overview of the separation system as a function of mobile phase composition and/or temperature for method development. The solvation parameter model has been applied to gradient elution separations but here theory and practice suggest a cautious approach since the interpretation of system and compound properties derived from its use are approximate. A growing application of the solvation parameter model in reversed-phase liquid chromatography is the screening of surrogate chromatographic systems for estimating biopartitioning properties. Throughout the discussion of the above topics success as well as known and likely deficiencies of the solvation parameter model are described with an emphasis on the role of the heterogeneous properties of the interphase region on the interpretation and understanding of the general retention mechanism in reversed-phase liquid chromatography for porous chemically bonded sorbents. Copyright © 2016 Elsevier B.V. All rights reserved.

Pillared graphite anodes for reversible sodiation.

PubMed

Zhang, Hanyang; Li, Zhifei; Xu, Wei; Chen, Yicong; Ji, Xiulei; Lerner, Michael M

2018-08-10

There has been a major effort recently to develop new rechargeable sodium-ion electrodes. In lithium ion batteries, LiC 6 forms from graphite and desolvated Li cations during the first charge. With sodium ions, graphite only shows a significant capacity when Na + intercalates as a solvated complex, resulting in ternary graphite intercalation compounds (GICs). Although this chemistry has been shown to be highly reversible and to support high rates in small test cells, these GICs can require >250% volume expansion and contraction during cycling. Here we demonstrate the first example of GICs that reversibly sodiate/desodiate without any significant volume change. These pillared GICs are obtained by electrochemical reduction of graphite in an ether/amine co-solvent electrolyte. The initial gallery expansion, 0.36 nm, is less than half of that in diglyme-based systems, and shows a similar capacity. Thermal analyses suggest the pillaring phenomenon arises from stronger co-intercalate interactions in the GIC galleries.

Microstructural control of new intercalation layered titanoniobates with large and reversible d-spacing for easy Na+ ion uptake

PubMed Central

Park, Hyunjung; Kwon, Jiseok; Choi, Heechae; Song, Taeseup; Paik, Ungyu

2017-01-01

Key issues for Na-ion batteries are the development of promising electrode materials with favorable sites for Na+ ion intercalation/deintercalation and an understanding of the reaction mechanisms due to its high activation energy and poor electrochemical reversibility. We first report a layered H0.43Ti0.93Nb1.07O5 as a new anode material. This anode material is engineered to have dominant (200) and (020) planes with both a sufficiently large d-spacing of ~8.3 Å and two-dimensional ionic channels for easy Na+ ion uptake, which leads to a small volume expansion of ~0.6 Å along the c direction upon Na insertion (discharging) and the lowest energy barrier of 0.19 eV in the [020] plane among titanium oxide–based materials ever reported. The material intercalates and deintercalates reversibly 1.7 Na ions (~200 mAh g−1) without a capacity fading in a potential window of 0.01 to 3.0 V versus Na/Na+. Na insertion/deinsertion takes place through a solid-solution reaction without a phase separation, which prevents coherent strain or stress in the microstructure during cycling and ensures promising sodium storage properties. These findings demonstrate a great potential of H0.43Ti0.93Nb1.07O5 as the anode, and our strategy can be applied to other layered metal oxides for promising sodium storage properties. PMID:28989960

Determination of artificial sweeteners in water samples by solid-phase extraction and liquid chromatography-tandem mass spectrometry.

PubMed

Ordóñez, Edgar Y; Quintana, José Benito; Rodil, Rosario; Cela, Rafael

2012-09-21

The development and performance evaluation of an analytical method for the determination of six artificial sweeteners in environmental waters using solid-phase extraction (SPE) followed by liquid chromatography-tandem mass spectrometry are presented. To this end, different SPE alternatives have been evaluated: polymeric reversed-phase (Oasis HLB, Env+, Plexa and Strata X), and mixed-mode with either weak (Oasis WAX) or strong anionic-exchange (Oasis MAX and Plexa PAX) sorbents. Among them, reversed-phase sorbents, particularly Oasis HLB and Strata X, showed the best performance. Oasis HLB provided good trueness (recoveries: 73-112%), precision (RSD<10%) and limits of quantification (LOQ: 0.01-0.5 μg/L). Moreover, two LC separation mechanisms were evaluated: reversed-phase (RPLC) and hydrophilic interaction (HILIC), with RPLC providing better performance than HILIC. The final application of the method showed the presence of acesulfame, cyclamate, saccharin and sucralose in the wastewater and surface water samples analyzed at concentrations up to 54 μg/L. Copyright © 2012 Elsevier B.V. All rights reserved.

Comprehensive two-dimensional normal-phase liquid chromatography × reversed-phase liquid chromatography for analysis of toad skin.

PubMed

Li, Jia-Fu; Yan, Xia; Wu, Yun-Long; Fang, Mei-Juan; Wu, Zhen; Qiu, Ying-Kun

2017-04-15

An analytical two-dimensional normal-phase liquid chromatography × reversed-phase liquid chromatography (2D NPLC × RPLC) system was constructed with a newly developed thermal evaporation assisted adsorption (TEAA) interface. This novel TEAA interface with heating temperature above solvent boiling point allowed fast removal of organic NPLC solvent and successfully solved the solvent incompatibility problem between NPLC and RPLC. The system achieved rapid on-line solvent exchange between the two dimensions within a short modulation time of 190 s and was applied in the analysis of an extract from the skin of Bufo bufo gargarizans. This is the first time to realize the on-line comprehensive analysis of a moderate polar natural product by coupling NPLC with reversed phase ultra-high performance liquid chromatography (UHPLC). To be highlighted, with the TEAA interface, the 2D NPLC × RPLC system provided excellent resolution and orthogonality (75.2%), when compared with that of 2D RPLC × RPLC. Copyright © 2017 Elsevier B.V. All rights reserved.

Separation of polyethylene glycols and amino-terminated polyethylene glycols by high-performance liquid chromatography under near critical conditions.

PubMed

Wei, Y-Z; Zhuo, R-X; Jiang, X-L

2016-05-20

The separation and characterization of polyethylene glycols (PEGs) and amino-substituted derivatives on common silica-based reversed-phase packing columns using isocratic elution is described. This separation is achieved by liquid chromatography under the near critical conditions (LCCC), based on the number of amino functional end groups without obvious effect of molar mass for PEGs. The mobile phase is acetonitrile in water with an optimal ammonium acetate buffer. The separation mechanism of PEG and amino-substituted PEG under the near LCCC on silica-based packing columns is confirmed to be ion-exchange interaction. Under the LCCC of PEG backbone, with fine tune of buffer concentration, the retention factor ratios for benzylamine and phenol in buffered mobile phases, α(benzylamine/phenol)-values, were used to assess the ion-exchange capacity on silica-based reversed-phase packing columns. To the best of our knowledge, this is the first report on separation of amino-functional PEGs independent of the molar mass by isocratic elution using common C18 or phenyl reversed-phase packing columns. Copyright © 2016 Elsevier B.V. All rights reserved.

Determination of Picloram in Soil and Water by Reversed-Phase Liquid Chromatography

Treesearch

M.J.M. Wells; J.L. Michael; D.G. Neary

1984-01-01

A reversed-phase liquid chromatographic method is presneted for the determination of picloram in the parts per billion (ppb) range in soil, soil solution, and stream samples. Quanitification is effected by UV absorpation at 254 nm. Derivatization is not necessary. The method permits 92% ± 7.1 recovery from water samples and 61.8% ± 11.1 recovery from soil samples....

Naturally occurring reverse tilt domains in a high-pretilt alignment nematic liquid crystal

NASA Astrophysics Data System (ADS)

Wang, Ruiting; Atherton, Timothy J.; Zhu, Minhua; Petschek, Rolfe G.; Rosenblatt, Charles

2007-08-01

A cell whose substrates were coated with the polyamic acid SE1211 (Nissan Chemical Industries) and baked at high temperatures was filled with a nematic liquid crystal in the isotropic phase. On cooling into the nematic phase, naturally occurring and temporally and thermally robust reverse tilt domains separated by thin filamentlike walls were observed. The properties of these structures are reported.

Liver transplantation in man: morphometric analysis of the parenchymal alterations following cold ischaemia and warm ischaemia/reperfusion

PubMed Central

VIZZOTTO, LAURA; VERTEMATI, MAURIZIO; DEGNA, CARLO TOMMASINI; ASENI, PAOLO

2001-01-01

Ischaemia and reperfusion phases represent critical events during liver transplantation. The purpose of this study was to describe morphological alterations of both vascular and parenchymal compartments after ischaemia and reperfusion and to evaluate the possible relationship between morphometric parameters and biochemical/clinical data. Three needle biopsies were drawn from 20 patients who underwent orthotopic liver transplantation. The first biopsy was taken before flushing with preservation solution, and the second and the third to evaluate respectively the effects of cold ischaemia and of warm ischaemia/reperfusion. Biopsies were examined by an image analyser and morphometric parameters related to the liver parenchyma were evaluated. At the second biopsy we observed a decrease of the endothelium volume fraction while the same parameter referred to the sinusoidal lumen achieved a peak value. The hepatocytes showed a lower surface parenchymal/vascular sides ratio. This parameter was reversed at the end of the reperfusion phase; furthermore the third biopsy revealed endothelial swelling and a decreased volume fraction of the sinusoidal lumen. The results quantify the damage to the sinusoidal bed which, as already known, is one of the main targets of cold ischaemia; warm ischaemia and reperfusion accentuate endothelial damage. The end of transplantation is characterised by damage chiefly to parenchymal cells. Hepatocytes show a rearrangement of their surface sides, probably related to the alterations of the sinusoidal bed. In addition, the fluctuations of morphometric parameters during ischaemia/reperfusion correlate positively with biochemical data and clinical course of the patients. PMID:11430699

[Application of fingerprint chromatogram in quality control of Shen-Mai injection].

PubMed

Shi, Xian-zhe; Yang, Jun; Zhao, Chun-xia; Xiong, Jian-hui; Xu, Guo-wang

2002-07-01

The theory and practice of traditional Chinese medicine require some comprehensive methods to assess quality of the Chinese herbal medication. Fingerprint chromatogram is one of the feasible approaches to evaluate the quality of Chinese herbal medication. So the fingerprint chromatogram of Shen-Mai injection was established by using reversed-phase high performance liquid chromatography. The chromatographic conditions were as follows: a Hypersil C18 column was used; the mobile phase was composed of water (A) and acetontrile (B) with linear gradient elution (0-50 min, 5%-95% B, volume fraction); the flow rate was 1.0 mL/min and the UV absorbance detection was set at 202 nm. The peak-area ratios of twenty-three fingerprint peaks and internal standard (diphenyl) were taken as the criteria for quality control. The quality differences in various batches and various manufacturers of Shen-Mai injections were investigated by projection discriminance based on principal component analysis. The results show the method developed is convenient, reliable and applicable for the quality control analysis of Shen-Mai injection.

Sizes of nanobubbles from nucleation rate measurements

NASA Astrophysics Data System (ADS)

Wilemski, G.

2003-03-01

In homogeneous bubble nucleation, the critical nucleus typically has nanometer dimensions. The volume V of a critical bubble can be determined from the simple equation (partial W/partial p)_T=V, where W is the reversible work of nucleus formation and p is the ambient pressure of the liquid phase in which bubble formation is occurring. The relation, W/kT=-ln J+ln A, where J is the steady state nucleation rate and A is the weakly pressure-dependent kinetic prefactor, allows V to be determined from rate measurements. The original derivation of this equation for V from the nucleation theorem was limited to one-component, ideal gas bubbles with a gas density much smaller than that of the ambient liquid. [D. Kashchiev, Nucleation: basic theory with applications (Butterworth-Heinemann, Oxford, 2000) p. 226.] The result is actually much more general, and it will be shown that it applies to multi-component, nonideal gas bubbles, provided the same density inequality holds. When the bubble phase and liquid densities are comparable, a more complicated, but also general and rigorous result is found.

Chemometric of the retention mechanism on butyl column: effect and relation of pH and pKa.

PubMed

Kouskoura, Maria G; Mitan, Constantina V; Markopoulou, Catherine K

2015-12-01

Reversed phase chromatographic separations are optimized for analytes containing ionizable groups by adjustment of pH of mobile phases. As it seems the pK(a). values of compounds affect their retention because of the variety in their solvation. However, it is of stressful need to predict their behavior taking into account also a series of other parameters. This work focuses on the development of ten different models, using partial least squares regression, which will identify and quantify the impact of several factors in the chromatographic behavior of 104 analytes. The combined effect of their numerous characteristics is obvious since along with pH (at 2.3 and 6.2), factors such as lipophilicity, molecular volume, polar surface area and the presence of specific moieties in their structures are not diminished. On the contrary, they work increasing or counterbalancing several effects on the retention time. The models compiled can be applied to predict with reliability (R2 > 0.865 and Q2 > 0.777) the behavior of unknown drugs.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ingebretsen, O.C.; Borgen, J.; Farstad, M.

A reversed-phase liquid-chromatographic procedure is presented for quantitation or uric acid in human serum, with absorbance measured at 292 nm. The mobile phase was sodium acetate (35 mmol/L, pH 5.0)/acetonitrile (9/1 by vol). Complete precipitation of serum proteins was obtained by mixing serum (50-500 microL) with an equal volume of acetonitrile, and the precipitate was removed by centrifugation. Aliquots (20 microL) of the supernate were injected directly into the liquid chromatograph, which was adjusted so that the absorbance reading of the uric acid peak was as high as possible. Routinely, a full-scale deflection of 1.28 absorbance units was used. Themore » within-run precision (CV) was 0.6% for a serum uric acid concentration of 227 mumol/L and day-to-day precision over a 15-day period was 0.8% for uric acid of 345 mumol/L. No interferences from related compounds were observed. Researchers compared results by this method with those by kinetic and equilibrium adaptations of uricase methods. The method reported is simple, and can be used in a fully automatic liquid-chromatographic system.« less

Microwave-immobilized polybutadiene stationary phase for reversed-phase high-performance liquid chromatography.

PubMed

Lopes, Nilva P; Collins, Kenneth E; Jardim, Isabel C S F

2004-03-19

Polybutadiene (PBD) has been immobilized on high-performance liquid chromatography (HPLC) silica by microwave radiation at various power levels (52-663 W) and actuation times (3-60 min). Columns prepared from these reversed-phase HPLC materials, as well as from similar non-irradiated materials, were tested with standard sample mixtures and characterized by elemental analysis (%C) and infrared spectroscopy. A microwave irradiation of 20 min at 663 W gives a layer of immobilized PBD that presented good performance. Longer irradiation times give thicker immobilized layers having less favorable chromatographic properties.

Thermodynamics of the sorption of water-soluble vitamins in reverse-phase high performance liquid chromatography

NASA Astrophysics Data System (ADS)

Chirkin, V. A.; Karpov, S. I.; Selemenev, V. F.

2012-12-01

The thermodynamics of the sorption of certain water-soluble vitamins on a C18 reverse phase from water-acetonitrile solutions of different compositions is studied. The thermodynamic characteristics of the investigated chromatographic systems are calculated. The dependences of standard molar enthalpy and changes in entropy when the sorbate transfers from the bulk solution to the surface layer on the concentration of the organic component in the mobile phase are analyzed. The boundaries for applying the main retention models describing the sorption of the investigated compounds are discussed.

Effects of inertia on the steady shear rheology of concentrated emulsions: sign reversal of normal stress differences

NASA Astrophysics Data System (ADS)

Srivastava, Priyesh; Sarkar, Kausik

2012-11-01

The shear rheology of moderately concentrated emulsions (5-27% volume fraction) in the presence of inertia is numerically investigated. Typically, an emulsion of viscous drops experiences positive first normal stress difference (N1) and negative second normal stress difference (N2) , as has also been predicted by perturbative analysis (Choi-Schowalter model) and numerical simulation. However, recently using single drop results we have shown [Li and Sarkar, 2005, J. Rheo, 49, 1377] that introduction of inertia reverses the signs of the normal stress difference in the dilute limit. Here, we numerically investigate the effects of interactions between drops in a concentrated system. The simulation is validated against the dilute results as well as analytical relations. It also shows the reversal of signs for N1 and N2 for small Capillary numbers above a critical Reynolds number. The physics is explained by the inertia-induced orientation of the individual drops in shear. Increasing volume fraction increases the critical Reynolds number at which N1 and N2change sign. The breakdown of linearity with volume fraction with increasing concentration is also analyzed. Partially supported by NSF.

Hydrogen bond effects on compressional behavior of isotypic minerals: high-pressure polymorphism of cristobalite-like Be(OH) 2

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shelton, Hannah; Barkley, Madison C.; Downs, Robert T.

2016-05-31

Three isotypic crystals, SiO 2 (α-cristobalite), ε-Zn(OH) 2 (wülfingite), and Be(OH) 2 (β-behoite), with topologically identical frameworks of corner-connected tetrahedra, undergo displacive compression-driven phase transitions at similar pressures (1.5–2.0 GPa), but each transition is characterized by a different mechanism resulting in different structural modifications. In this study, we report the crystal structure of the high-pressure γ-phase of beryllium hydroxide and compare it with the high-pressure structures of the other two minerals. In Be(OH) 2, the transition from the ambient β-behoite phase with the orthorhombic space group P2 12 12 1 and ambient unit cell parameters a = 4.5403(4) Å, bmore » = 4.6253(5) Å, c = 7.0599(7) Å, to the high-pressure orthorhombic γ-polymorph with space group Fdd2 and unit cell parameters (at 5.3(1) GPa) a = 5.738(2) Å, b = 6.260(3) Å, c = 7.200(4) Å takes place between 1.7 and 3.6 GPa. This transition is essentially second order, is accompanied by a negligible volume discontinuity, and exhibits both displacive and reversible character. The mechanism of the phase transition results in a change to the hydrogen bond connectivities and rotation of the BeO 4 tetrahedra.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Renlund, Anita Mariana; Tappan, Alexander Smith; Miller, Jill C.

The HMX {beta}-{delta} solid-solid phase transition, which occurs as HMX is heated near 170 C, is linked to increased reactivity and sensitivity to initiation. Thermally damaged energetic materials (EMs) containing HMX therefore may present a safety concern. Information about the phase transition is vital to predictive safety models for HMX and HMX-containing EMs. We report work on monitoring the phase transition with real-time Raman spectroscopy aimed towards obtaining a better understanding of physical properties of HMX through the phase transition. HMX samples were confined in a cell of minimal free volume in a displacement-controlled or load-controlled arrangement. The cell wasmore » heated and then cooled at controlled rates while real-time Raman spectroscopic measurements were performed. Raman spectroscopy provides a clear distinction between the phases of HMX because the vibrational transitions of the molecule change with conformational changes associated with the phase transition. Temperature of phase transition versus load data are presented for both the heating and cooling cycles in the load-controlled apparatus, and general trends are discussed. A weak dependence of the temperature of phase transition on load was discovered during the heating cycle, with higher loads causing the phase transition to occur at a higher temperature. This was especially true in the temperature of completion of phase transition data as opposed to the temperature of onset of phase transition data. A stronger dependence on load was observed in the cooling cycle, with higher loads causing the reverse phase transitions to occur at a higher cooling temperature. Also, higher loads tended to cause the phase transition to occur over a longer period of time in the heating cycle and over a shorter period of time in the cooling cycle. All three of the pure HMX phases ({alpha}, {beta} and {delta}) were detected on cooling of the heated samples, either in pure form or as a mixture.« less

Modern Chemical Technology, Volume 7.

ERIC Educational Resources Information Center

Pecsok, Robert L.; Chapman, Kenneth

This volume is one of the series for the Chemical Technician Curriculum Project (ChemTeC) of the American Chemical Society funded by the National Science Foundation. It consists of discussions, exercises, and experiments on the following topics: the nature of reversible processes, equilibrium constants, variable reaction tendencies, practical…

Automated solid-phase extraction of phenolic acids using layered double hydroxide-alumina-polymer disks.

PubMed

Ghani, Milad; Palomino Cabello, Carlos; Saraji, Mohammad; Manuel Estela, Jose; Cerdà, Víctor; Turnes Palomino, Gemma; Maya, Fernando

2018-01-26

The application of layered double hydroxide-Al 2 O 3 -polymer mixed-matrix disks for solid-phase extraction is reported for the first time. Al 2 O 3 is embedded in a polymer matrix followed by an in situ metal-exchange process to obtain a layered double hydroxide-Al 2 O 3 -polymer mixed-matrix disk with excellent flow-through properties. The extraction performance of the prepared disks is evaluated as a proof of concept for the automated extraction using sequential injection analysis of organic acids (p-hydroxybenzoic acid, 3,4-dihydroxybenzoic acid, gallic acid) following an anion-exchange mechanism. After the solid-phase extraction, phenolic acids were quantified by reversed-phase high-performance liquid chromatography with diode-array detection using a core-shell silica-C18 stationary phase and isocratic elution (acetonitrile/0.5% acetic acid in pure water, 5:95, v/v). High sensitivity and reproducibility were obtained with limits of detection in the range of 0.12-0.25 μg/L (sample volume, 4 mL), and relative standard deviations between 2.9 and 3.4% (10 μg/L, n = 6). Enrichment factors of 34-39 were obtained. Layered double hydroxide-Al 2 O 3 -polymer mixed-matrix disks had an average lifetime of 50 extractions. Analyte recoveries ranged from 93 to 96% for grape juice and nonalcoholic beer samples. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

New support for high-performance liquid chromatography based on silica coated with alumina particles.

PubMed

Silveira, José Leandro R; Dib, Samia R; Faria, Anizio M

2014-01-01

A new material based on silica coated with alumina nanoparticles was proposed for use as a chromatographic support for reversed-phase high-performance liquid chromatography. Alumina nanoparticles were synthesized by a sol-gel process in reversed micelles composed of sodium bis(2-ethylhexyl)sulfosuccinate, and the support material was formed by the self-assembly of alumina layers on silica spheres. Spectroscopic and (29)Si nuclear magnetic resonance results showed evidence of chemical bonds between the alumina nanoparticles and the silica spheres, while morphological characterizations showed that the aluminized silica maintained the morphological properties of silica desired for chromatographic purposes after alumina incorporation. Stability studies indicated that bare silica showed high dissolution (~83%), while the aluminized silica remained practically unchanged (99%) after passing one liter of the alkaline mobile phase, indicating high stability under alkaline conditions. The C18 bonded aluminized silica phase showed great potential for use in high-performance liquid chromatography to separate basic molecules in the reversed-phase mode.

Purification of α-glucosidase from mouse intestine by countercurrent chromatography coupled with a reverse micelle solvent system.

PubMed

He, Kai; Zou, Zongyao; Hu, Yinran; Yang, Yong; Xiao, Yubo; Gao, Pincao; Li, Xuegang; Ye, Xiaoli

2016-02-01

Countercurrent chromatography coupled with a reverse micelle solvent was applied to separate α-glucosidase, which is stable at pH 6.0-8.8, 15-50°C. The separation conditions are as follows: stationary phase: pH 4.0 Tris-HCl buffer phase containing 50 mM Tris-HCl and 50 mM KCl; mobile phase A: isooctane containing 50 mM anionic surfactant sodium di(2-ethylhexyl)sulfosuccinate; mobile phase B: 50 mM Tris-HCl buffer containing 500 mM KCl (pH 8.0); In total, 25 mL (23.9 mg) crude enzyme was injected through the injection valve, the enzymatic reaction and sodium dodecylsulfate polyacrylamide gel electrophoresis results imply that the activity of purified α-glucosidase is 6.63-fold higher than that of the crude enzyme. Therefore, countercurrent chromatography coupled with a reverse micelle solvent is capable for protein separation and enrichment. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Unusual magnetoelectric memory and polarization reversal in the kagome staircase compound N i3V2O8

NASA Astrophysics Data System (ADS)

Liu, Y. J.; Wang, J. F.; He, Z. Z.; Lu, C. L.; Xia, Z. C.; Ouyang, Z. W.; Liu, C. B.; Chen, R.; Matsuo, A.; Kohama, Y.; Kindo, K.; Tokunaga, M.

2018-05-01

We study the electric polarization of the kagome staircase N i3V2O8 in magnetic fields up to 30 T and report a magnetoelectric memory effect controlled by bias electric fields. The explored ferroelectric phase in 19 -24 T is electrically controlled, whereas the ferroelectric phase in 2 -11 T exhibits unusual memory effects. We determine a characteristic critical magnetic field H3=11 T , below which strong memory exists and the polarization is frozen even in opposite bias fields. But when magnetic fields exceed H3, the frozen polarization is released and polarization reversal appears by tuning bias electric fields. We ascribe these phenomena to the pinning-depinning mechanism: nucleation and the accompanying pinning of chiral domain walls cooperatively induce the frozen behavior; the polarization reversal results from the depinning through the ferroelectrtic-to-paraelectric phase transition in high magnetic fields. Our experimental results reveal that the first-order phase transition plays an important role in these unusual memory effects.

'Click Chemistry' in the preparation of porous polymer-basedparticulate stationary phases for mu-HPLC separation of peptides andproteins

DOE Office of Scientific and Technical Information (OSTI.GOV)

Slater, Michael; Snauko, Marian; Svec, Frantisek

With the use of the copper(I)-catalyzed (3 + 2) azide-alkynecycloaddition, an element of "click chemistry," stationary phasescarrying long alkyl chains or soybean trypsin inhibitor have beenprepared for use in HPLC separations in the reversed-phase and affinitymodes, respectively. The ligands were attached via a triazole ring tosize monodisperse porous beads containing either alkyne or azide pendantfunctionalities. Alkyne-containing beads prepared by directcopolymerization of propargyl acrylate with ethylene dimethacrylate wereallowed to react with azidooctadecane to give a reversed-phase sorbent.Azide-functionalized beads were prepared by chemical modification ofglycidyl methacrylate particles. Subsequent reaction with a terminalaliphatic alkyne produced a reversed-phase sorbent similar to thatobtained from themore » alkyne beads. Soybean trypsin inhibitor wasfunctionalized with N-(4-pentynoyloxy) succinimide to carry alkyne groupsand then allowed to react with the azide-containing beads to produce anaffinity sorbent for trypsin. The performance of these stationary phaseswas demonstrated with the HPLC separations of a variety of peptides andproteins.« less

The separation of flavonoids from Pongamia pinnata using combination columns in high-speed counter-current chromatography with a three-phase solvent system.

PubMed

Yin, Hao; Zhang, Si; Long, Lijuan; Yin, Hang; Tian, Xinpeng; Luo, Xiongming; Nan, Haihan; He, Sha

2013-11-08

The mangrove plant Pongamia pinnata (Leguminosae) is well known as a plant pesticide. Previous studies have indicated that the flavonoids are responsible of the biological activities of the plant. A new high-speed counter-current chromatography (HSCCC) method for the separation of three flavonoids, karanjin (1), pinnatin (2), and pongaflavone (3), from P. pinnata was developed in the present study. The lower and intermediate phase (LP and IP) of a new three-phase solvent system, n-hexane-acetonitrile-dichloromethane-water, at a volume ratio of 5:5:1:5, were used as the stationary phases, while the upper phase (UP) was used as the mobile phase, and the volume ratio between the stationary phases in the CCC column could be tuned by varying the initial pumped volume ratio of the stationary phases. The CCC columns containing all three phases of the solvent system were considered combination columns. According to the theories of combination column, it is possible to optimize the retention time of the target compounds by varying the volume ratio of the stationary phases in the HSCCC combination columns, as well as the suitable volume ratios of the stationary phases for the separation of the target compounds were predicted from the partition coefficients of the compounds in the three-phase solvent system. Then, three HSCCC separations using the combination columns with initial pumped LP:IP volume ratios of 1:0, 0.9:0.1, and 0.7:0.3 were performed separately based on the prediction. Three target compounds were prepared with high purity when the initial pumped volume ratio of the stationary phases was 0.9:0.1. The baseline separation of compounds 2 and 3 was achieved on the combination column with an initial pumped volume ratio of 0.7:0.3. Furthermore, the three experiments clearly demonstrated that the retentions and resolutions of the target compounds increased with an increasing volume ratio of IP, which is consistent with the prediction for the retention times for the solutes on combination columns. The method proposed here reduces the need for solvent selection compared with the conventional method and may have broad potential applicability in the preparation of natural products. Copyright © 2013 Elsevier B.V. All rights reserved.

The physiological and pathological biophysics of phase separation and gelation of RNA binding proteins in amyotrophic lateral sclerosis and fronto-temporal lobar degeneration.

PubMed

St George-Hyslop, Peter; Lin, Julie Qiaojin; Miyashita, Akinori; Phillips, Emma C; Qamar, Seema; Randle, Suzanne J; Wang, GuoZhen

2018-04-30

Many RNA binding proteins, including FUS, contain moderately repetitive, low complexity, intrinsically disordered domains. These sequence motifs have recently been found to underpin reversible liquid: liquid phase separation and gelation of these proteins, permitting them to reversibly transition from a monodispersed state to liquid droplet- or hydrogel-like states. This function allows the proteins to serve as scaffolds for the formation of reversible membraneless intracellular organelles such as nucleoli, stress granules and neuronal transport granules. Using FUS as an example, this review examines the biophysics of this physiological process, and reports on how mutations and changes in post-translational state alter phase behaviour, and lead to neurodegenerative diseases such as amyotrophic lateral sclerosis and frontotemporal lobar degeneration. Copyright © 2018. Published by Elsevier B.V.

Tightening force and torque of nonlocking screws in a reverse shoulder prosthesis.

PubMed

Terrier, A; Kochbeck, S H; Merlini, F; Gortchacow, M; Pioletti, D P; Farron, A

2010-07-01

Reversed shoulder arthroplasty is an accepted treatment for glenohumeral arthritis associated to rotator cuff deficiency. For most reversed shoulder prostheses, the baseplate of the glenoid component is uncemented and its primary stability is provided by a central peg and peripheral screws. Because of the importance of the primary stability for a good osteo-integration of the baseplate, the optimal fixation of the screws is crucial. In particular, the amplitude of the tightening force of the nonlocking screws is clearly associated to this stability. Since this force is unknown, it is currently not accounted for in experimental or numerical analyses. Thus, the primary goal of this work is to measure this tightening force experimentally. In addition, the tightening torque was also measured, to estimate an optimal surgical value. An experimental setup with an instrumented baseplate was developed to measure simultaneously the tightening force, tightening torque and screwing angle, of the nonlocking screws of the Aquealis reversed prosthesis. In addition, the amount of bone volume around each screw was measured with a micro-CT. Measurements were performed on 6 human cadaveric scapulae. A statistically correlated relationship (p<0.05, R=0.83) was obtained between the maximal tightening force and the bone volume. The relationship between the tightening torque and the bone volume was not statistically significant. The experimental relationship presented in this paper can be used in numerical analyses to improve the baseplate fixation in the glenoid bone. Copyright (c) 2010 Elsevier Ltd. All rights reserved.

Enhanced Night Visibility Series, Volume XII : Overview of Phase II and Development of Phase III Experimental Plan

DOT National Transportation Integrated Search

2005-12-01

This volume provides an overview of the six studies that compose Phase II of the Enhanced Night Visibility project and the experimental plan for its third and final portion, Phase III. The Phase II studies evaluated up to 12 vision enhancement system...

Low-energy inelastic response in the superconducting phases of PrOs4Sb12

NASA Astrophysics Data System (ADS)

Setty, Chandan; Wang, Yuxuan; Phillips, Philip W.

2017-08-01

Recent ac susceptibility and polar Kerr effect measurements in the skutterudite superconductor PrOs4Sb12 (POS) (E. M. Levenson-Falk, E. R. Schemm, M. B. Maple, and A. Kapitulnik, arXiv:1609.07535) uncovered the nature of the superconducting double transition from a high-temperature, high-field, time-reversal symmetric phase (or the A phase) to a low-temperature, low-field, time-reversal symmetry-broken phase (or the B phase). Starting from a microscopic model, we derive a Ginzburg-Landau expansion relevant to POS that describes this entrance into the time-reversal symmetry-broken phase along the temperature axis. We also provide a study of the low-energy inelastic (Raman) response in both the A and B phases of POS, and seek additional signatures which could help reveal the exact form of the gap functions previously proposed in these phases. By appropriately manipulating the incoming and scattered light geometries, along with additional subtraction procedures and suitable assumptions, we show that one can access the various irreducible representations contained in the point group describing POS. We demonstrate how to use this technique on example order parameters proposed in POS. Depending on whether there exist nodes along the c axis, we find additional low-energy spectral weight within the superconducting gap in the Eg geometry, a feature that could pinpoint the location of nodes on the Fermi surface.

Synthetic oligonucleotide separations by mixed-mode reversed-phase/weak anion-exchange liquid chromatography.

PubMed

Zimmermann, Aleksandra; Greco, Roberto; Walker, Isabel; Horak, Jeannie; Cavazzini, Alberto; Lämmerhofer, Michael

2014-08-08

Synthetic oligonucleotides gain increasing importance in new therapeutic concepts and as probes in biological sciences. If pharmaceutical-grade purities are required, chromatographic purification using ion-pair reversed-phase chromatography is commonly carried out. However, separation selectivity for structurally closely related impurities is often insufficient, especially at high sample loads. In this study, a "mixed-mode" reversed-phase/weak anion exchanger stationary phase has been investigated as an alternative tool for chromatographic separation of synthetic oligonucleotides with minor sequence variations. The employed mixed-mode phase shows great flexibility in method development. It has been run in various gradient elution modes, viz. one, two or three parameter (mixed) gradients (altering buffer pH, buffer concentration, and organic modifier) to find optimal elution conditions and gain further insight into retention mechanisms. Compared to ion-pair reversed-phase and mere anion-exchange separation, enhanced selectivities were observed with the mixed-mode phase for 20-23 nucleotide (nt) long oligonucleotides with similar sequences. Oligonucleotides differing by 1, 2 or 3 nucleotides in length could be readily resolved and separation factors for single nucleotide replacements declined in the order Cytosine (C)/Guanine (G)>Adenine (A)/Guanine∼Guanine/Thymine (T)>Adenine/Cytosine∼Cytosine/Thymine>Adenine/Thymine. Selectivities were larger when the modification was at the 3' terminal-end, declined when it was in the middle of the sequence and was smallest when it was located at the 5' terminus. Due to the lower surface area of the 200Å pore size mixed-mode stationary phase compared to the corresponding 100Å material, lower retention times with equal selectivities under milder elution conditions were achievable. Considering high sample loading capacities of the mixed-mode anion-exchanger phase, it should have great potential for chromatographic oligonucleotide separation and purification. Copyright © 2014 Elsevier B.V. All rights reserved.

Systematic Comparison of Reverse Phase and Hydrophilic Interaction Liquid Chromatography Platforms for the Analysis of N-linked Glycans

PubMed Central

Walker, S. Hunter; Carlisle, Brandon C.; Muddiman, David C.

2013-01-01

Due to the hydrophilic nature of glycans, reverse phase chromatography has not been widely used as a glycomic separation technique coupled to mass spectrometry. Other approaches such as hydrophilic interaction chromatography and porous graphitized carbon chromatography are often employed, though these strategies frequently suffer from decreased chromatographic resolution, long equilibration times, indefinite retention, and column bleed. Herein, it is shown that through an efficient hydrazone formation derivatization of N-linked glycans (∼4 hr of additional sample preparation time which is carried out in parallel), numerous experimental and practical advantages are gained when analyzing the glycans by online reverse phase chromatography. These benefits include an increased number of glycans detected, increased peak capacity of the separation, and the ability to analyze glycans on the identical liquid chromatography-mass spectrometry platform commonly used for proteomic analyses. The data presented show that separation of derivatized N-linked glycans by reverse phase chromatography significantly out-performs traditional separation of native or derivatized glycans by hydrophilic interaction chromatography. Furthermore, the movement to a more ubiquitous separation technique will afford numerous research groups the opportunity to analyze both proteomic and glycomic samples on the same platform with minimal time and physical change between experiments, increasing the efficiency of ‘multi-omic’ biological approaches. PMID:22954204

Development of an on-line mixed-mode gel liquid chromatography×reversed phase liquid chromatography method for separation of water extract from Flos Carthami.

PubMed

Wang, Yu-Qing; Tang, Xu; Li, Jia-Fu; Wu, Yun-Long; Sun, Yu-Ying; Fang, Mei-Juan; Wu, Zhen; Wang, Xiu-Min; Qiu, Ying-Kun

2017-10-13

A novel on-line comprehensive two-dimensional liquid chromatography (2D-LC) method by coupling mixed-mode gel liquid chromatography (MMG-LC) with reversed phase liquid chromatography (RPLC) was developed. A mixture of 17 reference compounds was used to study the separation mechanism. A crude water extract of Flos Carthami was applied to evaluate the performance of the novel 2D-LC system. In the first dimension, the extract was eluted with a gradient of water/methanol over a cross-linked dextran gel Sephadex LH-20 column. Meanwhile, the advantages of size exclusion, reversed phase partition and adsorption separation mechanism were exploited before further on-line reversed phase purification on the second dimension. This novel on-line mixed-mode Sephadex LH-20×RPLC method provided higher peak resolution, sample processing ability (2.5mg) and better orthogonality (72.9%) versus RPLC×RPLC and hydrophilic interaction liquid chromatography (HILIC)×RPLC. To the best of our knowledge, this is the first report of a mixed-mode Sephadex LH-20×RPLC separation method with successful applications in on-line mode, which might be beneficial for harvesting targets from complicated medicinal plants. Copyright © 2017 Elsevier B.V. All rights reserved.

Chemical reactions in reverse micelle systems

DOEpatents

Matson, Dean W.; Fulton, John L.; Smith, Richard D.; Consani, Keith A.

1993-08-24

This invention is directed to conducting chemical reactions in reverse micelle or microemulsion systems comprising a substantially discontinuous phase including a polar fluid, typically an aqueous fluid, and a microemulsion promoter, typically a surfactant, for facilitating the formation of reverse micelles in the system. The system further includes a substantially continuous phase including a non-polar or low-polarity fluid material which is a gas under standard temperature and pressure and has a critical density, and which is generally a water-insoluble fluid in a near critical or supercritical state. Thus, the microemulsion system is maintained at a pressure and temperature such that the density of the non-polar or low-polarity fluid exceeds the critical density thereof. The method of carrying out chemical reactions generally comprises forming a first reverse micelle system including an aqueous fluid including reverse micelles in a water-insoluble fluid in the supercritical state. Then, a first reactant is introduced into the first reverse micelle system, and a chemical reaction is carried out with the first reactant to form a reaction product. In general, the first reactant can be incorporated into, and the product formed in, the reverse micelles. A second reactant can also be incorporated in the first reverse micelle system which is capable of reacting with the first reactant to form a product.

CO2 Responsive Imidazolium-Type Poly(Ionic Liquid) Gels.

PubMed

Zhang, Jing; Xu, Dan; Guo, Jiangna; Sun, Zhe; Qian, Wenjing; Zhang, Ye; Yan, Feng

2016-07-01

Poly(ionic liquid) (PIL) gels with CO2 stimulus responsiveness have been synthesized through the copolymerization of an imidazolium-type ionic liquid monomer with 2-(dimethyl amino) ethyl methacrylate. Upon bubbling with CO2 gas, the prepared PIL solution is converted to a transparent and stable gel, which can be turned back to the initial solution state after N2 bubbling. The reversible sol-gel phase transition behavior is proved by the reversible values of viscosity and ionic conductivity. The possible mechanism for such a reversible sol-gel phase transition is demonstrated by NMR, conductivity, and rheological measurements. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

[Properties of synthesized CdS nanoparticles by reverse micelle method].

PubMed

Li, Heng-Da; Wang, Qing-Wei; Zhai, Hong-Ju; Li, Wen-Lian

2008-07-01

Micelle system with reverse phase (water/CTAB/n-hexyl alcohol/n-heptane) is a weenie liquid-globelet of surface active agent molecule which can be stably and uniformly dispersed in continuous oil medium. The micelle system with reverse phase can work as a "micro-reactor" to synthesize CdS nano-particle with excellent performance. In the present article considering the effects of W value (W= [water]/[surface agent]) of the micelle system with reverse phase, we observed that the ratio of [Cd2+] and [S2-] ions to the original concentrations of the Cd2+ and S2- ions can affect the luminescent properties of CdS nano-particle. Using regurgitant treatment process the surface of CdS nano-particle can be modified, and as a result the defect emission was reduced and even disappeared, but exciton emissions markedly increased. On the other hand, a red-shift of the exciton emission peak with the increase in the particle size was observed, indicating considerable quantum confinement effect. A maximum quantum efficiency of 11% for the synthesized CdS nano-material was achieved.

Magnetic field reversal of electric polarization and magnetoelectric phase diagram of the hexaferrite Ba{sub 1.3}Sr{sub 0.7}Co{sub 0.9}Zn{sub 1.1}Fe{sub 10.8}Al{sub 1.2}O{sub 22}

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shen, Shipeng; Yan, Liqin; Chai, Yisheng

2014-01-20

Low magnetic field reversal of electric polarization has been demonstrated in the multiferroic Y-type hexaferrite Ba{sub 1.3}Sr{sub 0.7}Co{sub 0.9}Zn{sub 1.1}Fe{sub 10.8}Al{sub 1.2}O{sub 22} single crystal. The maximum magnetoelectric coefficient at 200 K reaches 1065 ps/m near zero magnetic field. By a systematic investigation of magnetic field dependence of magnetic and dielectric responses at various temperatures, we obtained the magnetoelectric phase diagram describing the detailed evolution of the spin-induced ferroelectric phases with temperature and magnetic field. Below 225 K, the transverse spin cone can be stabilized at zero magnetic field, which is responsible for the reversal behavior of electric polarization. Our study reveals howmore » to eventually achieve magnetic field reversal of electric polarization in hexaferrites at room temperature.« less

LC-MS/MS-based quantification of kynurenine metabolites, tryptophan, monoamines and neopterin in plasma, cerebrospinal fluid and brain.

PubMed

Fuertig, René; Ceci, Angelo; Camus, Sandrine M; Bezard, Erwan; Luippold, Andreas H; Hengerer, Bastian

2016-09-01

The kynurenine (KYN) pathway is implicated in diseases such as cancer, psychiatric, neurodegenerative and autoimmune disorders. Measurement of KYN metabolite levels will help elucidating the involvement of the KYN pathway in the disease pathology and inform drug development. Samples of plasma, cerebrospinal fluid or brain tissue were spiked with deuterated internal standards, processed and analyzed by LC-MS/MS; analytes were chromatographically separated by gradient elution on a C18 reversed phase analytical column without derivatization. We established an LC-MS/MS method to measure 11 molecules, namely tryptophan, KYN, 3-OH-KYN, 3-OH-anthranilic acid, quinolinic acid, picolinic acid, kynurenic acid, xanthurenic acid, serotonin, dopamine and neopterin within 5.5 min, with sufficient sensitivity to quantify these molecules in small sample volumes of plasma, cerebrospinal fluid and brain tissue.

[Atrio-ventricular pressure difference associated with mitral valve motion].

PubMed

Wang, L M; Mori, H; Minezaki, K; Shinozaki, Y; Okino, H

1990-05-01

Pressure difference (PD) across the mitral valve was analyzed by a computer-aided catheter system in dogs. Positive PD (PPD) was consistently traced in the initial phase of rapid filling. While heart rate (HR) was below 100 beat/min, a negative PD (NPD) followed the above PPD. In the period between the NPD and the 2nd PPD due to atrial contraction, PD was kept at zero, while LA and LV pressures were gradually elevated by pulmonary venous return. As HR exceeded 100, 2 positive peaks of PD merged into M-shaped or mono-peaked PD. Through higher inflow resistance produced by artificial mitral stenosis, PPD peak decayed without NPD. In mitral regurgitation with an acute volume overload, all of the PD amplitudes were exaggerated. Thus the quick reversal of PD suggested the effect in blood filling process across the mitral valve.

Electric-field-dependent phase volume fractions and enhanced piezoelectricity near the polymorphic phase boundary of (K0.5Na0.5)1-xLixNbO3 textured ceramics

NASA Astrophysics Data System (ADS)

Ge, Wenwei; Li, Jiefang; Viehland, D.; Chang, Yunfei; Messing, Gary L.

2011-06-01

The structure, ferroelectric and piezoelectric properties of <001> textured (K0.5Na0.5)0.98Li0.02NbO3 ceramics were investigated as a function of temperature and dc bias E. X-ray diffraction revealed an orthorhombic (O) → tetragonal (T) polymorphic phase boundary (PPB). Phase coexistence was found near the PPB over a 30 °C temperature range, where the relative phase volume fractions changed with temperature. Furthermore, increasing E applied along the <001> texture direction resulted in a notable increase in the volume fraction of the T phase at the expense of the O phase, effectively shifting the O → T boundary to lower temperature. An enhancement in the piezoelectric properties was found to accompany this increase in the T volume fraction.

Constant volume gas cell optical phase-shifter

DOEpatents

Phillion, Donald W.

2002-01-01

A constant volume gas cell optical phase-shifter, particularly applicable for phase-shifting interferometry, contains a sealed volume of atmospheric gas at a pressure somewhat different than atmospheric. An optical window is present at each end of the cell, and as the length of the cell is changed, the optical path length of a laser beam traversing the cell changes. The cell comprises movable coaxial tubes with seals and a volume equalizing opening. Because the cell is constant volume, the pressure, temperature, and density of the contained gas do not change as the cell changes length. This produces an exactly linear relationship between the change in the length of the gas cell and the change in optical phase of the laser beam traversing it. Because the refractive index difference between the gas inside and the atmosphere outside is very much the same, a large motion must be made to change the optical phase by the small fraction of a wavelength that is required by phase-shifting interferometry for its phase step. This motion can be made to great fractional accuracy.

Synthetic and Biopolymer Gels - Similarities and Difference.

NASA Astrophysics Data System (ADS)

Horkay, Ferenc

2006-03-01

Ion exchange plays a central role in a variety of physiological processes, such as nerve excitation, muscle contraction and cell locomotion. Hydrogels can be used as model systems for identifying fundamental chemical and physical interactions that govern structure formation, phase transition, etc. in biopolymer systems. Polyelectrolyte gels are particularly well-suited to study ion-polymer interactions because their structure and physical-chemical properties (charge density, crosslink density, etc) can be carefully controlled. They are sensitive to different external stimuli such as temperature, ionic composition and pH. Surprisingly few investigations have been made on polyelectrolyte gels in salt solutions containing both monovalent and multivalent cations. We have developed an experimental approach that combines small angle neutron scattering and osmotic swelling pressure measurements. The osmotic pressure exerted on a macroscopic scale is a consequence of changes occurring at a molecular level. The intensity of the neutron scattering signal, which provides structural information as a function of spatial resolution, is directly related to the osmotic pressure. We have found a striking similarity in the scattering and osmotic behavior of polyacrylic acid gels and DNA gels swollen in nearly physiological salt solutions. Addition of calcium ions to both systems causes a sudden volume change. This volume transition, which occurs when the majority of the sodium counterions are replaced by calcium ions, is reversible. Such reversibility implies that the calcium ions are not strongly bound by the polyanion, but are free to move along the polymer chain, which allows these ions to form temporary bridges between negative charges on adjacent chains. Mechanical measurements reveal that the elastic modulus is practically unchanged in the calcium-containing gels, i.e., ion bridging is qualitatively different from covalent crosslinks.

Isolation and recovery of selected polybrominated diphenyl ethers from human serum and sheep serum: coupling reversed-phase solid-phase disk extraction and liquid-liquid extraction techniques with a capillary gas chromatographic electron capture negative ion mass spectrometric determinative technique.

PubMed

Loconto, Paul R; Isenga, David; O'Keefe, Michael; Knottnerus, Mark

2008-01-01

Polybrominated diphenyl ethers (PBDEs) are isolated and recovered with acceptable percent recoveries from human serum via liquid-liquid extraction and column chromatographic cleanup and fractionation with quantitation using capillary gas chromatography-mass spectrometry with electron capture negative ion and selected ion monitoring. PBDEs are found in unspiked serum. An alternative sample preparation approach is developed using sheep serum that utilizes a formic acid pre-treatment followed by reversed-phase solid-phase disk extraction and normal-phase solid-phase cleanup using acidified silica gel that yields>50% recoveries. When these percent recoveries are combined with a minimized phase ratio for human serum and very low instrument detection limits, method detection limits below 500 parts-per-trillion are realized.

Physiological Role of Gap-Junctional Hemichannels

PubMed Central

Quist, Arjan Pieter; Rhee, Seung Keun; Lin, Hai; Lal, Ratneshwar

2000-01-01

Hemichannels in the overlapping regions of apposing cells plasma membranes join to form gap junctions and provide an intercellular communication pathway. Hemichannels are also present in the nonjunctional regions of individual cells and their activity is gated by several agents, including calcium. However, their physiological roles are unknown. Using techniques of atomic force microscopy (AFM), fluorescent dye uptake assay, and laser confocal immunofluorescence imaging, we have examined the extracellular calcium-dependent modulation of cell volume. In response to a change in the extracellular physiological calcium concentration (1.8 to ≤1.6 mM) in an otherwise isosmotic condition, real-time AFM imaging revealed a significant and reversible increase in the volume of cells expressing gap-junctional proteins (connexins). Volume change did not occur in cells that were not expressing connexins. However, after the transient or stable transfection of connexin43, volume change did occur. The volume increase was accompanied by cytochalasin D-sensitive higher cell stiffness, which helped maintain cell integrity. These cellular physical changes were prevented by gap-junctional blockers, oleamide and β-glycyrrhetinic acid, or were reversed by returning extracellular calcium to the normal level. We conclude that nongap-junctional hemichannels regulate cell volume in response to the change in extracellular physiological calcium in an otherwise isosmotic situation. PMID:10704454

Inlet Diameter and Flow Volume Effects on Separation and Energy Efficiency of Hydrocyclones

NASA Astrophysics Data System (ADS)

Erikli, Ş.; Olcay, A. B.

2015-08-01

This study investigates hydrocyclone performance of an oil injected screw compressor. Especially, the oil separation efficiency of a screw compressor plays a significant role for air quality and non-stop working hour of compressors has become an important issue when the efficiency in energy is considered. In this study, two separation efficiency parameters were selected to be hydrocyclone inlet diameter and flow volume height between oil reservoir surface and top of the hydrocyclone. Nine different cases were studied in which cyclone inlet diameter and flow volume height between oil reservoir surface and top were investigated in regards to separation and energy performance aspects and the effect of the parameters on the general performance appears to be causing powerful influence. Flow inside the hydrocyclone geometry was modelled by Reynolds Stress Model (RSM) and hydro particles were tracked by Discrete Phase Model (DPM). Besides, particle break up was modelled by the Taylor Analogy Breakup (TAB) model. The reversed vortex generation was observed at different planes. The upper limit of the inlet diameter of the cyclone yields the centrifugal force on particles to decrease while the flow becomes slower; and the larger diameter implies slower flow. On the contrary, the lower limit is increment in speed causes breakup problems that the particle diameters become smaller; consequently, it is harder to separate them from gas.

Asset price and trade volume relation in artificial market impacted by value investors

NASA Astrophysics Data System (ADS)

Tangmongkollert, K.; Suwanna, S.

2016-05-01

The relationship between return and trade volume has been of great interests in a financial market. The appearance of asymmetry in the price-volume relation in the bull and bear market is still unsettled. We present a model of the value investor traders (VIs) in the double auction system, in which agents make trading decision based on the pseudo fundamental price modelled by sawtooth oscillations. We investigate the system by two different time series for the asset fundamental price: one corresponds to the fundamental price in a growing phase; and the other corresponds to that in a declining phase. The simulation results show that the trade volume is proportional to the difference between the market price and the fundamental price, and that there is asymmetry between the buying and selling phases. Furthermore, the selling phase has more significant impact of price on the trade volume than the buying phase.

Optimization of the β-Elimination/Michael Addition Chemistry on Reversed-Phase Supports for Mass Spectrometry Analysis of O-Linked Protein Modifications

PubMed Central

Nika, Heinz; Nieves, Edward; Hawke, David H.; Angeletti, Ruth Hogue

2013-01-01

We previously adapted the β-elimination/Michael addition chemistry to solid-phase derivatization on reversed-phase supports, and demonstrated the utility of this reaction format to prepare phosphoseryl peptides in unfractionated protein digests for mass spectrometric identification and facile phosphorylation-site determination. Here, we have expanded the use of this technique to β-N-acetylglucosamine peptides, modified at serine/threonine, phosphothreonyl peptides, and phosphoseryl/phosphothreonyl peptides, followed in sequence by proline. The consecutive β-elimination with Michael addition was adapted to optimize the solid-phase reaction conditions for throughput and completeness of derivatization. The analyte remained intact during derivatization and was recovered efficiently from the silica-based, reversed-phase support with minimal sample loss. The general use of the solid-phase approach for enzymatic dephosphorylation was demonstrated with phosphoseryl and phosphothreonyl peptides and was used as an orthogonal method to confirm the identity of phosphopeptides in proteolytic mixtures. The solid-phase approach proved highly suitable to prepare substrates from low-level amounts of protein digests for phosphorylation-site determination by chemical-targeted proteolysis. The solid-phase protocol provides for a simple, robust, and efficient tool to prepare samples for phosphopeptide identification in MALDI mass maps of unfractionated protein digests, using standard equipment available in most biological laboratories. The use of a solid-phase analytical platform is expected to be readily expanded to prepare digest from O-glycosylated- and O-sulfonated proteins for mass spectrometry-based structural characterization. PMID:23997661

Purification of flavonoids from licorice using an off-line preparative two-dimensional normal-phase liquid chromatography/reversed-phase liquid chromatography method.

PubMed

Fan, Yunpeng; Fu, Yanhui; Fu, Qing; Cai, Jianfeng; Xin, Huaxia; Dai, Mei; Jin, Yu

2016-07-01

An orthogonal (71.9%) off-line preparative two-dimensional normal-phase liquid chromatography/reversed-phase liquid chromatography method coupled with effective sample pretreatment was developed for separation and purification of flavonoids from licorice. Most of the nonflavonoids were firstly removed using a self-made Click TE-Cys (60 μm) solid-phase extraction. In the first dimension, an industrial grade preparative chromatography was employed to purify the crude flavonoids. Click TE-Cys (10 μm) was selected as the stationary phase that provided an excellent separation with high reproducibility. Ethyl acetate/ethanol was selected as the mobile phase owing to their excellent solubility for flavonoids. Flavonoids co-eluted in the first dimension were selected for further purification using reversed-phase liquid chromatography. Multiple compounds could be isolated from one normal-phase fraction and some compounds with bad resolution in one-dimensional liquid chromatography could be prepared in this two-dimensional system owing to the orthogonal separation. Moreover, this two-dimensional liquid chromatography method was beneficial for the preparation of relatively trace flavonoid compounds, which were enriched in the first dimension and further purified in the second dimension. Totally, 24 flavonoid compounds with high purity were obtained. The results demonstrated that the off-line two-dimensional liquid chromatography method was effective for the preparative separation and purification of flavonoids from licorice. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Plug-in nanoliter pneumatic liquid dispenser with nozzle design flexibility

PubMed Central

Choi, In Ho; Kim, Hojin; Lee, Sanghyun; Baek, Seungbum; Kim, Joonwon

2015-01-01

This paper presents a novel plug-in nanoliter liquid dispensing system with a plug-and-play interface for simple and reversible, yet robust integration of the dispenser. A plug-in type dispenser was developed to facilitate assembly and disassembly with an actuating part through efficient modularization. The entire process for assembly and operation of the plug-in dispenser is performed via the plug-and-play interface in less than a minute without loss of dispensing quality. The minimum volume of droplets pneumatically dispensed using the plug-in dispenser was 124 nl with a coefficient of variation of 1.6%. The dispensed volume increased linearly with the nozzle size. Utilizing this linear relationship, two types of multinozzle dispensers consisting of six parallel channels (emerging from an inlet) and six nozzles were developed to demonstrate a novel strategy for volume gradient dispensing at a single operating condition. The droplet volume dispensed from each nozzle also increased linearly with nozzle size, demonstrating that nozzle size is a dominant factor on dispensed volume, even for multinozzle dispensing. Therefore, the proposed plug-in dispenser enables flexible design of nozzles and reversible integration to dispense droplets with different volumes, depending on the application. Furthermore, to demonstrate the practicality of the proposed dispensing system, we developed a pencil-type dispensing system as an alternative to a conventional pipette for rapid and reliable dispensing of minute volume droplets. PMID:26594263

Plug-in nanoliter pneumatic liquid dispenser with nozzle design flexibility.

PubMed

Choi, In Ho; Kim, Hojin; Lee, Sanghyun; Baek, Seungbum; Kim, Joonwon

2015-11-01

This paper presents a novel plug-in nanoliter liquid dispensing system with a plug-and-play interface for simple and reversible, yet robust integration of the dispenser. A plug-in type dispenser was developed to facilitate assembly and disassembly with an actuating part through efficient modularization. The entire process for assembly and operation of the plug-in dispenser is performed via the plug-and-play interface in less than a minute without loss of dispensing quality. The minimum volume of droplets pneumatically dispensed using the plug-in dispenser was 124 nl with a coefficient of variation of 1.6%. The dispensed volume increased linearly with the nozzle size. Utilizing this linear relationship, two types of multinozzle dispensers consisting of six parallel channels (emerging from an inlet) and six nozzles were developed to demonstrate a novel strategy for volume gradient dispensing at a single operating condition. The droplet volume dispensed from each nozzle also increased linearly with nozzle size, demonstrating that nozzle size is a dominant factor on dispensed volume, even for multinozzle dispensing. Therefore, the proposed plug-in dispenser enables flexible design of nozzles and reversible integration to dispense droplets with different volumes, depending on the application. Furthermore, to demonstrate the practicality of the proposed dispensing system, we developed a pencil-type dispensing system as an alternative to a conventional pipette for rapid and reliable dispensing of minute volume droplets.

Developing Open-Ended Questions for Surface Area and Volume of Beam

ERIC Educational Resources Information Center

Kurniawan, Henry; Putri, Ratu Ilma Indra; Hartono, Yusuf

2018-01-01

The purpose of this research was to show open-ended questions about surface area and beam volume which valid and practice, have potential effect. This research is research development which consists of two main phases: preliminary phase (preparation phase and problem design) and formative evaluation phase (evaluation and revision phases). The…

Robust tissue-air volume segmentation of MR images based on the statistics of phase and magnitude: Its applications in the display of susceptibility-weighted imaging of the brain.

PubMed

Du, Yiping P; Jin, Zhaoyang

2009-10-01

To develop a robust algorithm for tissue-air segmentation in magnetic resonance imaging (MRI) using the statistics of phase and magnitude of the images. A multivariate measure based on the statistics of phase and magnitude was constructed for tissue-air volume segmentation. The standard deviation of first-order phase difference and the standard deviation of magnitude were calculated in a 3 x 3 x 3 kernel in the image domain. To improve differentiation accuracy, the uniformity of phase distribution in the kernel was also calculated and linear background phase introduced by field inhomogeneity was corrected. The effectiveness of the proposed volume segmentation technique was compared to a conventional approach that uses the magnitude data alone. The proposed algorithm was shown to be more effective and robust in volume segmentation in both synthetic phantom and susceptibility-weighted images of human brain. Using our proposed volume segmentation method, veins in the peripheral regions of the brain were well depicted in the minimum-intensity projection of the susceptibility-weighted images. Using the additional statistics of phase, tissue-air volume segmentation can be substantially improved compared to that using the statistics of magnitude data alone. (c) 2009 Wiley-Liss, Inc.

Anchoring in a novel bimanual coordination pattern.

PubMed

Maslovat, Dana; Lam, Melanie Y; Brunke, Kirstin M; Chua, Romeo; Franks, Ian M

2009-02-01

Anchoring in cyclical movements has been defined as regions of reduced spatial or temporal variability [Beek, P. J. (1989). Juggling dynamics. PhD thesis. Amsterdam: Free University Press] that are typically found at movement reversal points. For in-phase and anti-phase movements, synchronizing reversal points with a metronome pulse has resulted in decreased anchor point variability and increased pattern stability [Byblow, W. D., Carson, R. G., & Goodman, D. (1994). Expressions of asymmetries and anchoring in bimanual coordination. Human Movement Science, 13, 3-28; Fink, P. W., Foo, P., Jirsa, V. K., & Kelso, J. A. S. (2000). Local and global stabilization of coordination by sensory information. Experimental Brain Research, 134, 9-20]. The present experiment examined anchoring during acquisition, retention, and transfer of a 90 degrees phase-offset continuous bimanual coordination pattern (whereby the right limb lags the left limb by one quarter cycle), involving horizontal flexion about the elbow. Three metronome synchronization strategies were imposed: participants either synchronized maximal flexion of the right arm (i.e., single metronome), both flexion and extension of the right arm (i.e., double metronome within-limb), or flexion of each arm (i.e., double metronome between-limb) to an auditory metronome. In contrast to simpler in-phase and anti-phase movements, synchronization of additional reversal points to the metronome did not reduce reversal point variability or increase pattern stability. Furthermore, practicing under different metronome synchronization strategies did not appear to have a significant effect on the rate of acquisition of the pattern.

Probabilistic Reversal Learning in Schizophrenia: Stability of Deficits and Potential Causal Mechanisms.

PubMed

Reddy, Lena Felice; Waltz, James A; Green, Michael F; Wynn, Jonathan K; Horan, William P

2016-07-01

Although individuals with schizophrenia show impaired feedback-driven learning on probabilistic reversal learning (PRL) tasks, the specific factors that contribute to these deficits remain unknown. Recent work has suggested several potential causes including neurocognitive impairments, clinical symptoms, and specific types of feedback-related errors. To examine this issue, we administered a PRL task to 126 stable schizophrenia outpatients and 72 matched controls, and patients were retested 4 weeks later. The task involved an initial probabilistic discrimination learning phase and subsequent reversal phases in which subjects had to adjust their responses to sudden shifts in the reinforcement contingencies. Patients showed poorer performance than controls for both the initial discrimination and reversal learning phases of the task, and performance overall showed good test-retest reliability among patients. A subgroup analysis of patients (n = 64) and controls (n = 49) with good initial discrimination learning revealed no between-group differences in reversal learning, indicating that the patients who were able to achieve all of the initial probabilistic discriminations were not impaired in reversal learning. Regarding potential contributors to impaired discrimination learning, several factors were associated with poor PRL, including higher levels of neurocognitive impairment, poor learning from both positive and negative feedback, and higher levels of indiscriminate response shifting. The results suggest that poor PRL performance in schizophrenia can be the product of multiple mechanisms. © The Author 2016. Published by Oxford University Press on behalf of the Maryland Psychiatric Research Center. All rights reserved. For permissions, please email: journals.permissions@oup.com.

Simulation studies of nucleation of ferroelectric polarization reversal.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Brennecka, Geoffrey L.; Winchester, Benjamin Michael

2014-08-01

Electric field-induced reversal of spontaneous polarization is the defining characteristic of a ferroelectric material, but the process(es) and mechanism(s) associated with the initial nucleation of reverse-polarity domains are poorly understood. This report describes studies carried out using phase field modeling of LiTaO 3, a relatively simple prototype ferroelectric material, in order to explore the effects of either mechanical deformation or optically-induced free charges on nucleation and resulting domain configuration during field-induced polarization reversal. Conditions were selected to approximate as closely as feasible those of accompanying experimental work in order to provide not only support for the experimental work but alsomore » ensure that additional experimental validation of the simulations could be carried out in the future. Phase field simulations strongly support surface mechanical damage/deformation as effective for dramatically reducing the overall coercive field (Ec) via local field enhancements. Further, optically-nucleated polarization reversal appears to occur via stabilization of latent nuclei via the charge screening effects of free charges.« less

Shear-induced structural transitions in Newtonian non-Newtonian two-phase flow

NASA Astrophysics Data System (ADS)

Cristobal, G.; Rouch, J.; Colin, A.; Panizza, P.

2000-09-01

We show the existence under shear flow of steady states in a two-phase region of a brine-surfactant system in which lyotropic dilute lamellar (non-Newtonian) and sponge (Newtonian) phases are coexisting. At high shear rates and low sponge phase-volume fractions, we report on the existence of a dynamic transition corresponding to the formation of a colloidal crystal of multilamellar vesicles (or ``onions'') immersed in the sponge matrix. As the sponge phase-volume fraction increases, this transition exhibits a hysteresis loop leading to a structural bistability of the two-phase flow. Contrary to single phase lamellar systems where it is always 100%, the onion volume fraction can be monitored continuously from 0 to 100 %.

Multipathing Via Three Parameter Common Image Gathers (CIGs) From Reverse Time Migration

NASA Astrophysics Data System (ADS)

Ostadhassan, M.; Zhang, X.

2015-12-01

A noteworthy problem for seismic exploration is effects of multipathing (both wanted or unwanted) caused by subsurface complex structures. We show that reverse time migration (RTM) combined with a unified, systematic three parameter framework that flexibly handles multipathing can be accomplished by adding one more dimension (image time) to the angle domain common image gather (ADCIG) data. RTM is widely used to generate prestack depth migration images. When using the cross-correlation image condition in 2D prestack migration in RTM, the usual practice is to sum over all the migration time steps. Thus all possible wave types and paths automatically contribute to the resulting image, including destructive wave interferences, phase shifts, and other distortions. One reason is that multipath (prismatic wave) contributions are not properly sorted and mapped in the ADCIGs. Also, multipath arrivals usually have different instantaneous attributes (amplitude, phase and frequency), and if not separated, the amplitudes and phases in the final prestack image will not stack coherently across sources. A prismatic path satisfies an image time for it's unique path; Cavalca and Lailly (2005) show that RTM images with multipaths can provide more complete target information in complex geology, as multipaths usually have different incident angles and amplitudes compared to primary reflections. If the image time slices within a cross-correlation common-source migration are saved for each image time, this three-parameter (incident angle, depth, image time) volume can be post-processed to generate separate, or composite, images of any desired subset of the migrated data. Images can by displayed for primary contributions, any combination of primary and multipath contributions (with or without artifacts), or various projections, including the conventional ADCIG (angle vs depth) plane. Examples show that signal from the true structure can be separated from artifacts caused by multiple arrivals when they have different image times. This improves the quality of images and benefits migration velocity analysis (MVA) and amplitude variation with angle (AVA) inversion.

Static and Dynamic Properties of Ferroelectric Thin Film Memories.

NASA Astrophysics Data System (ADS)

Duiker, Hendrik Matthew

Several properties of ferroelectric thin-film memories have been modeled. First, it has been observed experimentally that the bulk phase KNO_3 has a first-order phase transition, and that the transition temperature of KNO_3 thin-films increases as the thickness of the film is decreased. A Landau theory of first-order phase transitions in bulk systems has been generalized by adding surface terms to the free energy expansion to account for these transition properties. The model successfully describes the observed transition properties and predicts the existence of films in which the surfaces are ordered at temperatures higher than the bulk transition temperature. Second, the Avrami model of polarization-reversal kinetics has been modified to describe the following cases: ferroelectrics composed of a large number of small grains; ferroelectric thin-films in which nucleation occurs at the surfaces, not in the bulk; ferroelectrics in which long-range dipolar interactions significantly affect the nucleation rate; and non-square wave switching pulses. The models were verified by applying them to the results of two-dimensional Ising model simulations. It was shown that the models allow the possibility of directly obtaining microscopic parameters, such as the nucleation rate and domain wall velocity, from bulk measurements. Finally, a model describing the fatigue of ferroelectric memories has been developed. As a ferroelectric memory fatigues the spontaneous polarization per unit volume decreases, the switching time decreases, and eventually the memory "shorts out" and becomes conducting. The model assumes the following: during each polarization reversal the film undergoes, every unit cell in the film has a chance of "degrading" and thus losing an ion. Degraded cells no longer contribute to the polarization. The ions are allowed to diffuse to the surfaces of the film and form, with other ions, conducting dendrites which grow into the bulk of the film. Computer simulations performed on a two dimensional lattice with the above model successfully described the phenomena observed during the fatigue of PZT and other types of ferroelectric thin-film memories films.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yahyaoui, Samia; Rekik, Walid; Laboratoire Sciences Chimiques de Rennes

The crystal structures of 1,4-diazabicyclo[2.2.2]octane (dabco)-templated iron sulfate, (C{sub 6}H{sub 14}N{sub 2})[Fe(H{sub 2}O){sub 6}](SO{sub 4}){sub 2}, were determined at room temperature and at -173 deg. C from single-crystal X-ray diffraction. At 20 deg. C, it crystallises in the monoclinic symmetry, centrosymmetric space group P2{sub 1}/n, Z=2, a=7.964(5), b=9.100(5), c=12.065(5) A, {beta}=95.426(5) deg. and V=870.5(8) A{sup 3}. The structure consists of [Fe(H{sub 2}O){sub 6}]{sup 2+} and disordered (C{sub 6}H{sub 14}N{sub 2}){sup 2+} cations and (SO{sub 4}){sup 2-} anions connected together by an extensive three-dimensional H-bond network. The title compound undergoes a reversible phase transition of the first-order at -2.3 deg. C,more » characterized by DSC, dielectric measurement and optical observations, that suggests a relaxor-ferroelectric behavior. Below the transition temperature, the compound crystallizes in the monoclinic system, non-centrosymmetric space group Cc, with eight times the volume of the ambient phase: a=15.883(3), b=36.409(7), c=13.747(3) A, {beta}=120.2304(8){sup o}, Z=16 and V=6868.7(2) A{sup 3}. The organic moiety is then fully ordered within a supramolecular structure. Thermodiffractometry and thermogravimetric analyses indicate that its decomposition proceeds through three stages giving rise to the iron oxide. - Graphical abstract: The new dabcodiium hexaaquairon(II) bis(sulfate), (C{sub 6}H{sub 14}N{sub 2})[Fe(H{sub 2}O){sub 6}](SO{sub 4}){sub 2}, was prepared and characterized. It exhibits a supramolecular structure and undergoes a reversible order-disorder phase transition at -2.3 deg. C.« less

Rapid determination of hydrophilic phenols in olive oil by vortex-assisted reversed-phase dispersive liquid-liquid microextraction and screen-printed carbon electrodes.

PubMed

Fernández, Elena; Vidal, Lorena; Canals, Antonio

2018-05-01

A novel approach is presented to determine hydrophilic phenols in olive oil samples, employing vortex-assisted reversed-phase dispersive liquid-liquid microextraction (RP-DLLME) for sample preparation and screen-printed carbon electrodes for voltammetric analysis. The oxidation of oleuropein, hydroxytyrosol, caffeic acid, ferulic acid and tyrosol was investigated, being caffeic acid and tyrosol selected for quantification. A matrix-matching calibration using sunflower oil as analyte-free sample diluted with hexane was employed to compensate matrix effects. Samples were analyzed under optimized RP-DLLME conditions, i.e., extractant phase, 1M HCl; extractant volume, 100µL; extraction time, 2min; centrifugation time, 10min; centrifugation speed, 4000rpm. The working range showed a good linearity between 0.075 and 2.5mgL -1 (r = 0.998, N = 7) for caffeic acid, and between 0.075 and 3mgL -1 (r = 0.999, N = 8) for tyrosol. The methodological limit of detection was empirically established at 0.022mgL -1 for both analytes, which is significantly lower than average contents found in olive oil samples. The repeatability was evaluated at two different spiking levels (i.e., 0.5mgL -1 and 2mgL -1 ) and coefficients of variation ranged from 8% to 11% (n = 5). The applicability of the proposed method was tested in olive oil samples of different quality (i.e., refined olive oil, virgin olive oil and extra virgin olive oil). Relative recoveries varied between 83% and 108% showing negligible matrix effects. Finally, fifteen samples were analyzed by the proposed method and a high correlation with the traditional Folin-Ciocalteu spectrophotometric method was obtained. Thereafter, the concentrations of the fifteen oil samples were employed as input variables in linear discriminant analysis in order to distinguish between olive oils of different quality. Copyright © 2017 Elsevier B.V. All rights reserved.

Sexually dimorphic subcortical brain volumes in emerging psychosis.

PubMed

Egloff, Laura; Lenz, Claudia; Studerus, Erich; Harrisberger, Fabienne; Smieskova, Renata; Schmidt, André; Huber, Christian; Simon, Andor; Lang, Undine E; Riecher-Rössler, Anita; Borgwardt, Stefan

2018-03-28

In schizophrenic psychoses, the normal sexual dimorphism of the brain has been shown to be disrupted or even reversed. Little is known, however, at what time point in emerging psychosis this occurs. We have therefore examined, if these alterations are already present in the at-risk mental state (ARMS) for psychosis and in first episode psychosis (FEP) patients. Data from 65 ARMS (48 (73.8%) male; age=25.1±6.32) and 50 FEP (37 (74%) male; age=27±6.56) patients were compared to those of 70 healthy controls (HC; 27 (38.6%) male; age=26±4.97). Structural T1-weighted images were acquired using a 3 Tesla magnetic resonance imaging (MRI) scanner. Linear mixed effects models were used to investigate whether subcortical brain volumes are dependent on sex. We found men to have larger total brain volumes (p<0.001), and smaller bilateral caudate (p=0.008) and hippocampus volume (p<0.001) than women across all three groups. Older subjects had more GM and WM volume than younger subjects. No significant sex×group interaction was found. In emerging psychosis there still seem to exist patterns of normal sexual dimorphism in total brain and caudate volume. The only structure affected by reversed sexual dimorphism was the hippocampus, with women showing larger volumes than men even in HC. Thus, we conclude that subcortical volumes may not be primarily affected by disrupted sexual dimorphism in emerging psychosis. Copyright © 2018 The Authors. Published by Elsevier B.V. All rights reserved.

TNT Metabolites in Animal Tissues

DTIC Science & Technology

1991-06-01

bonded to the silica surface contained both a C18 (reversed-phase function) and a secondary amine (anioni exchange function) incorporated into a single ...contains both a C18, (reversed-phase function) and a secondary amine, (anion exchange function) incorporated into a single ligand in a 1:1 ratio. The...and store at 4°C. 4. Dosing of Mice with [14CITNT Young adult mice (Swiss Webster outbred strain) of both sexes weighing approximately 30 grams each

Green chiral HPLC study of the stability of Chiralcel OD under high temperature liquid chromatography and subcritical water conditions.

PubMed

Droux, S; Roy, M; Félix, G

2014-10-01

We report here the study of the stability under subcritical water conditions of one of the most popular polysaccharide chiral stationary phase (CSP): Chiralcel OD. This CSP was used under high temperature and reversed phase conditions with acetonitrile and 2-propanol as modifier, respectively. The evolution of selectivity and resolution was investigated both in normal and reversed mode conditions with five racemates after packing, heating at 150 °C and separations of some racemic compounds under different high temperatures and mobile phase conditions. The results show that after using at high temperature and subcritical water conditions the selectivity was only moderately affected while the resolution fell dramatically especially in reversed mode due to the creation of a void at the head of the columns which reflects the dissolution of the silica matrix. Copyright © 2014 Elsevier B.V. All rights reserved.

Three-Dimensionally Functionalized Reverse Phase Glycoprotein Array for Cancer Biomarker Discovery and Validation.

PubMed

Pan, Li; Aguilar, Hillary Andaluz; Wang, Linna; Iliuk, Anton; Tao, W Andy

2016-11-30

Glycoproteins have vast structural diversity that plays an important role in many biological processes and have great potential as disease biomarkers. Here, we report a novel functionalized reverse phase protein array (RPPA), termed polymer-based reverse phase glycoprotein array (polyGPA), to capture and profile glycoproteomes specifically, and validate glycoproteins. Nitrocellulose membrane functionalized with globular hydroxyaminodendrimers was used to covalently capture preoxidized glycans on glycoproteins from complex protein samples such as biofluids. The captured glycoproteins were subsequently detected using the same validated antibodies as in RPPA. We demonstrated the outstanding specificity, sensitivity, and quantitative capabilities of polyGPA by capturing and detecting purified as well as endogenous α-1-acid glycoprotein (AGP) in human plasma. We further applied quantitative N-glycoproteomics and the strategy to validate a panel of glycoproteins identified as potential biomarkers for bladder cancer by analyzing urine glycoproteins from bladder cancer patients or matched healthy individuals.

Improved image reconstruction of low-resolution multichannel phase contrast angiography

PubMed Central

P. Krishnan, Akshara; Joy, Ajin; Paul, Joseph Suresh

2016-01-01

Abstract. In low-resolution phase contrast magnetic resonance angiography, the maximum intensity projected channel images will be blurred with consequent loss of vascular details. The channel images are enhanced using a stabilized deblurring filter, applied to each channel prior to combining the individual channel images. The stabilized deblurring is obtained by the addition of a nonlocal regularization term to the reverse heat equation, referred to as nonlocally stabilized reverse diffusion filter. Unlike reverse diffusion filter, which is highly unstable and blows up noise, nonlocal stabilization enhances intensity projected parallel images uniformly. Application to multichannel vessel enhancement is illustrated using both volunteer data and simulated multichannel angiograms. Robustness of the filter applied to volunteer datasets is shown using statistically validated improvement in flow quantification. Improved performance in terms of preserving vascular structures and phased array reconstruction in both simulated and real data is demonstrated using structureness measure and contrast ratio. PMID:26835501

Left Ventricular Reverse Remodeling With Biventricular Versus Right Ventricular Pacing in Patients With Atrioventricular Block and Heart Failure in the BLOCK HF Trial.

PubMed

St John Sutton, Martin; Plappert, Ted; Adamson, Philip B; Li, Pei; Christman, Shelly A; Chung, Eugene S; Curtis, Anne B

2015-05-01

Biventricular pacing in heart failure (HF) improves survival, relieves symptoms, and attenuates left ventricular (LV) remodeling. However, little is known about biventricular pacing in HF patients with atrioventricular block because they are typically excluded from biventricular trials. The Biventricular versus Right Ventricular Pacing in Heart Failure Patients with Atrioventricular Block (BLOCK HF) trial randomized patients with atrioventricular block, New York Heart Association symptom classes I to III HF, and LV ejection fraction ≤50% to biventricular or right ventricular pacing. Doppler echocardiograms were obtained at randomization (after 30 to 60 days of right ventricular pacing postimplant) and every 6 months through 24 months. Data analysis comparing changes in 10 prespecified echo parameters over time was conducted using a Bayesian design. LV end systolic volume index was also evaluated as a predictor of mortality/morbidity. Of 691 randomized subjects, 624 had paired Doppler echocardiogram data for ≥1 analyses at 6, 12, 18, or 24 months. Biventricular pacing significantly reduced LV volume indices and intraventricular mechanical delay, and improved LV ejection fraction, consistent with LV reverse remodeling. These parameters showed little change with right ventricular pacing alone, indicating no systematic reverse remodeling with right ventricular pacing. LV end systolic volume index was predictive of mortality/morbidity; the estimated risk increased up to 1% for every 1 mL/m(2) increase in LV end systolic volume index. LV end systolic volume index is a significant predictor of mortality/morbidity in this population. Cardiac structure and function are improved with biventricular pacing for patients with atrioventricular block and LV systolic dysfunction. URL: http://www.clinicaltrials.gov. Unique identifier: NCT00267098. © 2015 American Heart Association, Inc.

A low-cost gradient system for high-performance liquid chromatography. Quantitation of complex pharmaceutical raw materials.

PubMed

Erni, F; Frei, R W

1976-09-29

A device is described that makes use of an eight-port motor valve to generate step gradients on the low-pressure side of a piston pump with a low dead volume. Such a gradient device with an automatic control unit, which also permits repetition of previous steps, can be built for about half the cost of a gradient system with two pumps. Applications of this gradient unit to the separation of complex mixtures of glycosides and alkaloids are discussed and compared with separations systems using two high-pressure pumps. The gradients that are used on reversed-phase material with solvent mixtures of water and completely miscible organic solvents are suitable for quantitative routine control of pharmaceutical products. The reproducibility of retention data is excellent over several months and, with the use of loop injectors, major components can be determined quantitatively with a reproducibility of better than 2% (relative standard deviation). The step gradient selector valve can also be used as an introduction system for very large sample volumes. Up to 11 can be injected and samples with concentrations of less than 1 ppb can be determined with good reproducibilities.

Type I clathrates as novel silicon anodes: An electrochemical and structural investigation

DOE PAGES

Li, Ying; Raghavan, Rahul; Wagner, Nicholas A.; ...

2015-05-05

In this study, silicon clathrates contain cage-like structures that can encapsulate various guest atoms or molecules. Here we present an electrochemical evaluation of type I silicon clathrates based on Ba 8Al ySi 46-y for the anode material in lithium-ion batteries. Post-cycling characterization with NMR and XRD show no discernible structural or volume changes even after electrochemical insertion of 44 Li into the clathrate structure. The observed properties are in stark contrast with lithiation of other silicon anodes, which become amorphous and suffer from larger volume changes. The lithiation/delithiation processes are proposed to occur in single phase reactions at approximately 0.2more » and 0.4 V vs. Li/Li +, respectively, distinct from other diamond cubic or amorphous silicon anodes. Reversible capacities as high as 499 mAh g -1 at a 5 mA g -1 rate were observed for silicon clathrate with composition Ba 8Al 8.54S i37.46, corresponding to Li:Si of 1.18:1. The results show that silicon clathrates could be promising durable anodes for lithium-ion batteries.« less

Type I clathrates as novel silicon anodes: An electrochemical and structural investigation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, Ying; Raghavan, Rahul; Wagner, Nicholas A.

In this study, silicon clathrates contain cage-like structures that can encapsulate various guest atoms or molecules. Here we present an electrochemical evaluation of type I silicon clathrates based on Ba 8Al ySi 46-y for the anode material in lithium-ion batteries. Post-cycling characterization with NMR and XRD show no discernible structural or volume changes even after electrochemical insertion of 44 Li into the clathrate structure. The observed properties are in stark contrast with lithiation of other silicon anodes, which become amorphous and suffer from larger volume changes. The lithiation/delithiation processes are proposed to occur in single phase reactions at approximately 0.2more » and 0.4 V vs. Li/Li +, respectively, distinct from other diamond cubic or amorphous silicon anodes. Reversible capacities as high as 499 mAh g -1 at a 5 mA g -1 rate were observed for silicon clathrate with composition Ba 8Al 8.54S i37.46, corresponding to Li:Si of 1.18:1. The results show that silicon clathrates could be promising durable anodes for lithium-ion batteries.« less

Effect of serial infusions of reconstituted high-density lipoprotein (CER-001) on coronary atherosclerosis: rationale and design of the CARAT study.

PubMed

Andrews, Jordan; Janssan, Alex; Nguyen, Tracy; Pisaniello, Anthony D; Scherer, Daniel J; Kastelein, John J P; Merkely, Bela; Nissen, Steven E; Ray, Kausik; Schwartz, Gregory G; Worthley, Stephen G; Keyserling, Connie; Dasseux, Jean-Louis; Butters, Julie; Girardi, Jacinta; Miller, Rosemary; Nicholls, Stephen J

2017-02-01

High-density lipoprotein (HDL) is believed to have atheroprotective properties, but an effective HDL-based therapy remains elusive. Early studies have suggested that infusion of reconstituted HDL promotes reverse cholesterol transport and vascular reactivity. The CER-001 Atherosclerosis Regression Acute Coronary Syndrome Trial (CARAT) is investigating the impact of infusing an engineered pre-beta HDL mimetic containing sphingomyelin (SM) and dipalmitoyl phosphatidlyglycerol (CER-001) on coronary atheroma volume in patients with a recent acute coronary syndrome (ACS). The CARAT is a phase 2, multicenter trial in which 292 patients with an ACS undergoing intracoronary ultrasonography and showing percent atheroma volume (PAV) greater than 30% are randomly assigned to treatment with ten infusions of CER-001 3 mg/kg or matching placebo, administered at weekly intervals. Intracoronary ultrasonography is repeated at the end of the treatment period. The primary endpoint is the nominal change in PAV. Safety and tolerability will also be evaluated. CARAT will establish whether serial 3 mg/kg infusions of an engineered pre-beta HDL mimetic containing SM and dipalmitoyl phosphatidlyglycerol (CER-001) will regress atherosclerotic plaque in patients with a recent ACS.

In-situ characterization of highly reversible phase transformation by synchrotron X-ray Laue microdiffraction

DOE PAGES

Chen, Xian; Tamura, Nobumichi; MacDowell, Alastair; ...

2016-05-23

The alloy Cu 25 Au 30 Zn 45 undergoes a huge first-order phase transformation (6% strain) and shows a high reversibility under thermal cycling and an unusual martensitc microstructure in sharp contrast to its nearby compositions. We discovered this alloy by systematically tuning the composition so that its lattice parameters satisfy the cofactor conditions (i.e., the kinematic conditions of compatibility between phases). It was conjectured that satisfaction of these conditions is responsible for the enhanced reversibility as well as the observed unusual fluid-like microstructure during transformation, but so far, there has been no direct evidence confirming that these observed microstructuresmore » are those predicted by the cofactor conditions. In order to verify this hypothesis, we use synchrotron X-ray Laue microdiffraction to measure the orientations and structural parameters of variants and phases near the austenite/martensite interface. The areas consisting of both austenite and multi-variants of martensite are scanned by microLaue diffraction. The cofactor conditions have been examined from the kinematic relation of lattice vectors across the interface. The continuity condition of the interface is precisely verified from the correspondent lattice vectors between two phases.« less

Aniline-modified porous graphitic carbon for hydrophilic interaction and attenuated reverse phase liquid chromatography.

PubMed

Iverson, Chad D; Lucy, Charles A

2014-12-19

Most stationary phases for hydrophilic interaction liquid chromatography (HILIC) and reversed phase liquid chromatography (RPLC) are based on silica. Porous graphitic carbon (PGC) is an attractive alternative to silica-based phases due to its chemical and thermal stability, and unique selectivity. However, native PGC is strongly hydrophobic and in some instances excessively retentive. PGC particles with covalently attached aniline groups (Dimethylaniline-PGC and Aniline-PGC) were synthesized to alter the surface polarity of PGC. First, the diazonium salt of N,N-dimethyl-p-phenylenediamine or 4-nitroaniline was adsorbed onto the PGC surface. The adsorbed salt was reduced with sodium borohydride and (Aniline-PGC only) the nitro group was further reduced with iron powder to the aniline. X-ray photoelectron spectroscopy confirmed the surface functionalities and that these moieties were introduced to the surface at concentrations of 0.9 and 2.1molecules/nm(2), respectively. These modified PGC phases (especially Aniline-PGC) were evaluated as HILIC and reversed phases. The Dimethylaniline-PGC phase displayed only weak HILIC retention of phenolic solutes. In contrast, the Aniline-PGC phase displayed up to nearly a 7-fold increase in HILIC retention vs. an aniline-silica phase and selectivity that differed from 10 other HILIC phases. Introduction of aniline groups to the PGC surface reduced the RPLC retentivity of PGC up to more than 5-fold and improved the separation efficiency up to 6-fold. The chromatographic performance of Aniline-PGC is demonstrated by separations of nucleotides, nucleosides, carboxylic acids, basic pharmaceuticals, and other compounds. Copyright © 2014 Elsevier B.V. All rights reserved.

Interactions between coherent twin boundaries and phase transition of iron under dynamic loading and unloading

NASA Astrophysics Data System (ADS)

Wang, Kun; Chen, Jun; Zhang, Xueyang; Zhu, Wenjun

2017-09-01

Phase transitions and deformation twins are constantly reported in many BCC metals under high pressure, whose interactions are of fundamental importance to understand the strengthening mechanism of these metals under extreme conditions. However, the interactions between twins and phase transition in BCC metals remain largely unexplored. In this work, interactions between coherent twin boundaries and α ↔ ɛ phase transition of iron are investigated using both non-equilibrium molecular dynamics simulations and the nudged elastic band method. Mechanisms of both twin-assisted phase transition and reverse phase transition are studied, and orientation relationships between BCC and HCP phases are found to be ⟨"separators="|11 1 ¯ ⟩ B C C||⟨"separators="|1 ¯2 1 ¯ 0 ⟩ H C P and ⟨"separators="|1 1 ¯ 0 ⟩ B C C||⟨"separators="|0001 ⟩ H C P for both cases. The twin boundary corresponds to {"separators="|10 1 ¯ 0 } H C P after the phase transition. It is amazing that the reverse transition seems to be able to "memorize" and recover the initial BCC twins. The memory would be partly lost when plastic slips take place in the HCP phase before the reverse transition. In the recovered initial BCC twins, three major twin spacings are observed, which are well explained in terms of energy barriers of transition from the HCP phase to the BCC twin. Besides, the variant selection rule of the twin assisted phase transition is also discussed. The results of present work could be expected to give some clues for producing ultra-fine grain structures in materials exhibiting martensitic phase transition.

Enantiomeric separation of type I and type II pyrethroid insecticides with different chiral stationary phases by reversed-phase high-performance liquid chromatography.

PubMed

Zhang, Ping; Yu, Qian; He, Xiulong; Qian, Kun; Xiao, Wei; Xu, Zhifeng; Li, Tian; He, Lin

2018-04-01

The enantiomeric separation of type I (bifenthrin, BF) and type II (lambda-cyhalothrin, LCT) pyrethroid insecticides on Lux Cellulose-1, Lux Cellulose-3, and Chiralpak IC chiral columns was investigated by reversed-phase high-performance liquid chromatography. Methanol/water or acetonitrile/water was used as mobile phase at a flow rate of 0.8 mL/min. The effects of chiral stationary phase, mobile phase composition, column temperature, and thermodynamic parameters on enantiomer separation were carefully studied. Bifenthrin got a partial separation on Lux Cellulose-1 column and baseline separation on Lux Cellulose-3 column, while LCT enantiomers could be completely separated on both Lux Cellulose-1 and Lux Cellulose-3 columns. Chiralpak IC provided no separation ability for both BF and LCT. Retention factor (k) and selectivity factor (α) decreased with the column temperature increasing from 10°C to 40°C for both BF and LCT enantiomers. Thermodynamic parameters including ∆H and ∆S were also calculated, and the maximum R s were not always obtained at lowest temperature. Furthermore, the quantitative analysis methods for BF and LCT enantiomers in soil and water were also established. Such results provide a new approach for pyrethroid separation under reversed-phase condition and contribute to environmental risk assessment of pyrethroids at enantiomer level. © 2017 Wiley Periodicals, Inc.

Reversible hydration and aqueous exfoliation of the acetate-intercalated layered double hydroxide of Ni and Al: Observation of an ordered interstratified phase

DOE Office of Scientific and Technical Information (OSTI.GOV)

Manohara, G.V.; Vishnu Kamath, P., E-mail: vishnukamath8@hotmail.com; Milius, Wolfgang

2012-12-15

Acetate-intercalated layered double hydroxides (LDHs) of Ni and Al undergo reversible hydration in the solid state in response to the ambient humidity. The LDH with a high layer charge (0.33/formula unit) undergoes facile hydration in a single step, whereas the LDH with a lower layer charge (0.24/formula unit) exhibits an ordered interstratified intermediate, comprising the hydrated and dehydrated layers stacked alternatively. This phase, also known as the staged S-2 phase, coexists with the end members suggesting the existence of a solution-type equilibrium between the S-2 phase and the end members of the hydration cycle. These LDHs also undergo facile aqueousmore » exfoliation into 2-5 nm-thick tactoids with a radial dimension of 0.2-0.5 {mu}m. - Graphical abstract: Schematic of the hydrated, dehydrated and interstratified phases observed during the hydration-dehydration of Ni/Al-CH{sub 3}COO LDH. Highlights: Black-Right-Pointing-Pointer Ni/Al-acetate LDHs were synthesized by HPFS method by hydrolysis of acetamide. Black-Right-Pointing-Pointer Intercalated acetate ion shows reversible hydration with variation in humidity. Black-Right-Pointing-Pointer An ordered interstratified phase was observed during hydration/dehydration cycle. Black-Right-Pointing-Pointer A solution type equilibrium is observed between hydration-dehydration phases. Black-Right-Pointing-Pointer These LDHs undergo facile aqueous exfoliation.« less

Preparation of stationary phases for reversed-phase high-performance liquid chromatography using thermal treatments at high temperature.

PubMed

Vigna, Camila R M; Bottoli, Carla B G; Collins, Kenneth E; Collins, Carol H

2007-07-13

Batches of poly(methyloctylsiloxane) (PMOS)-loaded silica were prepared by deposition from a solution of PMOS into the pores of HPLC silica. Portions of PMOS-loaded silica were subjected to a thermal treatment at 100 degrees C for 24h (condition 1) in a tube furnace under a nitrogen atmosphere. After that, the material was heated for 4h at higher temperatures (150-400 degrees C) (condition 2). Heating at higher temperatures produces polymer bilayers. Non-immobilized and thermally treated stationary phases were characterized by percent carbon, (29)Si cross-polarization magic angle spinning nuclear magnetic resonance spectroscopy and reversed-phase chromatographic performance. The results show that thermal treatment between 150 and 300 degrees C accelerates the immobilization process, possibly due to some bond breaking of the polysiloxane, with formation of strong linkages to the surface of the support, resulting in more complete coverage of the silica. The chromatographic results show an improvement of efficiency with the increase of the temperature of condition 2 up to 300 degrees C and an increase in the resolution of the components, mainly for the phase heated at 300 degrees C. Such results demonstrate that a two-step thermal treatment (100 degrees C then 150-300 degrees C) produces stationary phases with good properties for use in reversed-phase high-performance liquid chromatography.

Improved Homogeneity of the Transmit Field by Simultaneous Transmission with Phased Array and Volume Coil

PubMed Central

Avdievich, Nikolai I.; Oh, Suk-Hoon; Hetherington, Hoby P.; Collins, Christopher M.

2010-01-01

Purpose To improve the homogeneity of transmit volume coils at high magnetic fields (≥ 4 T). Due to RF field/ tissue interactions at high fields, 4–8 T, the transmit profile from head-sized volume coils shows a distinctive pattern with relatively strong RF magnetic field B1 in the center of the brain. Materials and Methods In contrast to conventional volume coils at high field strengths, surface coil phased arrays can provide increased RF field strength peripherally. In theory, simultaneous transmission from these two devices could produce a more homogeneous transmission field. To minimize interactions between the phased array and the volume coil, counter rotating current (CRC) surface coils consisting of two parallel rings carrying opposite currents were used for the phased array. Results Numerical simulations and experimental data demonstrate that substantial improvements in transmit field homogeneity can be obtained. Conclusion We have demonstrated the feasibility of using simultaneous transmission with human head-sized volume coils and CRC phased arrays to improve homogeneity of the transmit RF B1 field for high-field MRI systems. PMID:20677280

Molecular dynamics simulations of fluoropolymers in the solid state

NASA Astrophysics Data System (ADS)

Holt, David Bryan

1998-10-01

Molecular mechanics and dynamics simulations have been utilized to address the behavior of helix reversal defects in fluoropolymers. The results of the simulations confirm that helix reversals do form and migrate in PTFE crystals. The most important defect structure is a helix reversal band: two helix reversals which bracker a small chain segment (typically 6-7 backbone atoms) having the opposite helical sense from the parent molecule. Small reversal bands had velocities ranging between 100 m/s (low temperature)-250 m/s (high temperature). The size of this reversal band defect is dependent upon the helical conformation and is equal to approximately half of the helical repeat unit in the low and intermediate temperature phases. In the high temperature phase where intermolecular effects are diminished, a wider distribution of reversal band sizes was observed during the simulations. A mechanism is identified by which significant reorientation of a chain segment about the molecular axis can occur when it is bracketed by two helix reversal bands. Simulations with a model containing a perfluoromethyl (PFM) group at low temperature showed that the presence of the PFM group significantly restricts chain mobility locally. However, a significant reduction in the helix reversal defect density was observed on neighboring chains as well. During simulations in which a shear deformation was applied to the models with and without a PFM group, an increase in reversal defect density was observed. However, the helix reversal density in the sheared model containing the PFM branch was less than that in the model without a PFM branch under no shear. These data implicate helix reversal defects and associated chain segment motions in the mechanical behavior of fluoropolymer materials.

Illusion optics in chaotic light

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang Suheng; Gan Shu; Xiong Jun

2010-08-15

The time-reversal process provides the possibility to counteract the time evolution of a physical system. Recent research has shown that such a process can occur in the first-order field correlation of chaotic light and result in the spatial interference and phase-reversal diffraction in an unbalanced interferometer. Here we report experimental investigations on the invisibility cloak and illusion phenomena in chaotic light. In an unbalanced interferometer illuminated by thermal light, we have observed the cloak effect and the optical transformation of one object into another object. The experimental results can be understood by the phase-reversal diffraction, and they demonstrate the theoreticalmore » proposal of similar effects in complementary media.« less

Formation of highly structured cubic micellar lipid nanoparticles of soy phosphatidylcholine and glycerol dioleate and their degradation by triacylglycerol lipase.

PubMed

Wadsäter, Maria; Barauskas, Justas; Nylander, Tommy; Tiberg, Fredrik

2014-05-28

Lipid nanoparticles of reversed internal phase structures, such as cubic micellar (I2) structure show good drug loading ability of peptides and proteins as well as some small molecules. Due to their controllable small size and inner morphology, such nanoparticles are suitable for drug delivery using several different administration routes, including intravenous, intramuscular, and subcutaneous injection. A very interesting system in this regard, is the two component soy phosphatidylcholine (SPC)/glycerol dioleate (GDO) system, which depending on the ratio of the lipid components form a range of reversed liquid crystalline phases. For a 50/50 (w/w) ratio in excess water, these lipids have been shown to form a reversed cubic micellar (I2) phase of the Fd3m structure. Here, we demonstrate that this SPC/GDO phase, in the presence of small quantities (5-10 wt %) of Polysorbate 80 (P80), can be dispersed into nanoparticles, still with well-defined Fd3m structure. The resulting nanoparticle dispersion has a narrow size distribution and exhibit good long-term stability. In pharmaceutical applications, biodegradation pathways of the drug delivery vehicles and their components are important considerations. In the second part of the study we show how the structure of the particles evolves during exposure to a triacylglycerol lipase (TGL) under physiological-like temperature and pH. TGL catalyzes the lipolytic degradation of acylglycerides, such as GDO, to monoglycerides, glycerol, and free fatty acids. During the degradation, the interior phase of the particles is shown to undergo continuous phase transitions from the reversed I2 structure to structures of less negative curvature (2D hexagonal, bicontinuous cubic, and sponge), ultimately resulting in the formation of multilamellar vesicles.

Poly(1-allylimidazole)-grafted silica, a new specific stationary phase for reversed-phase and anion-exchange liquid chromatography.

PubMed

Sun, Min; Qiu, Hongdeng; Wang, Licheng; Liu, Xia; Jiang, Shengxiang

2009-05-01

A new specific stationary phase based on poly(1-allylimidazole)-grafted silica has been synthesized and characterized, by infrared spectra, elemental analysis, thermogravimetric analysis and X-ray photoelectron spectroscopy. The results of test showed that poly(1-allylimidazole) can effectively mask the residual silanol groups and reduce the adverse effect of residual silanol. Using this stationary phase, phenol compounds, aniline compounds, and polycyclic aromatic hydrocarbons were successfully separated with symmetric peak shapes in the reversed-phase chromatography. Inorganic anions (IO(3)(-), BrO(3)(-), Br(-), NO(3)(-), I(-), SCN(-)) were also separated completely in the anion-exchange chromatography using sodium chloride solution as the mobile phase. The effects of pH and the concentration of eluent on the separation of inorganic anions were studied. The separation mechanism appears to involve the mixed interactions of hydrogen bonding, hydrophobic, pi-pi, electrostatic, and anion-exchange interactions.

Nonspecific bactericidal activity of the lactoperoxidases-thiocyanate-hydrogen peroxide system of milk against Escherichia coli and some gram-negative pathogens.

PubMed Central

Reiter, B; Marshall, V M; BjörckL; Rosén, C G

1976-01-01

Two strains of Escherichia coli and one strain each of Salmonella typhimurium and Pseudomonas aeruginosa were killed by the bactericidal activity of the lactoperoxidase-thiocyanate-hydrogen peroxide system in milk and in a synthetic medium. H2O2 was supplied exogenously by glucose oxidase, and glucose was produced at a level which was itself noninhibitory. Two phases were distinguished: the first phase was dependent on the oxidation of SCN(-) by lactoperoxidase and H2O2, which was reversed by reducing agent, and the second phase was dependent on the presence of accumulated H2O2, which was reversed by catalase. The latter enzyme could also reverse the first phase, but only when present in excessive and unphysiological levels. The bactericidal activity was greatest at pH 5 and below, and it depended on the SCN(-)concentration and on the number of organisms. Since raw or heated milk neutralizes the acid barrier against infection in the stomach, the bactericidal system discussed may contribute to the prevention of enteric infections in neonates. PMID:5374

Higher contact force during radiofrequency ablation leads to a much larger increase in edema as compared to chronic lesion size.

PubMed

Thomas, Samuel; Silvernagel, Josh; Angel, Nathan; Kholmovski, Eugene; Ghafoori, Elyar; Hu, Nan; Ashton, John; Dosdall, Derek J; MacLeod, Rob; Ranjan, Ravi

2018-05-18

Reversible edema is a part of any radiofrequency ablation but its relationship with contact force is unknown. The goal of this study was to characterize through histology and MRI, acute and chronic ablation lesions and reversible edema with contact force. In a canine model (n = 14), chronic ventricular lesions were created with a 3.5-mm tip ThermoCool SmartTouch (Biosense Webster) catheter at 25 W or 40 W for 30 seconds. Repeat ablation was performed after 3 months to create a second set of lesions (acute). Each ablation procedure was followed by in vivo T2-weighted MRI for edema and late-gadolinium enhancement (LGE) MRI for lesion characterization. For chronic lesions, the mean scar volumes at 25 W and 40 W were 77.8 ± 34.5 mm 3 (n = 24) and 139.1 ± 69.7 mm 3 (n = 12), respectively. The volume of chronic lesions increased (25 W: P < 0.001, 40 W: P < 0.001) with greater contact force. For acute lesions, the mean volumes of the lesion were 286.0 ± 129.8 mm 3 (n = 19) and 422.1 ± 113.1 mm 3 (n = 16) for 25 W and 40 W, respectively (P < 0.001 compared to chronic scar). On T2-weighted MRI, the acute edema volume was on average 5.6-8.7 times higher than the acute lesion volume and increased with contact force (25 W: P = 0.001, 40 W: P = 0.011). With increasing contact force, there is a marginal increase in lesion size but accompanied with a significantly larger edema. The reversible edema that is much larger than the chronic lesion volume may explain some of the chronic procedure failures. © 2018 Wiley Periodicals, Inc.

Molecular-level comparison of alkylsilane and polar-embedded reversed-phase liquid chromatography systems.

PubMed

Rafferty, Jake L; Siepmann, J Ilja; Schure, Mark R

2008-08-15

Stationary phases with embedded polar groups possess several advantages over conventional alkylsilane phases, such as reduced peak tailing, enhanced selectivity for specific functional groups, and the ability to use a highly aqueous mobile phase. To gain a deeper understanding of the retentive properties of these reversed-phase packings, molecular simulations were carried out for three different stationary phases in contact with mobile phases of various water/methanol ratios. Two polar-embedded phases were modeled, namely, amide and ether containing, and compared to a conventional octadecylsilane phase. The simulations show that, due to specific hydrogen bond interactions, the polar-embedded phases take up significantly more solvent and are more ordered than their alkyl counterparts. Alkane and alcohol probe solutes indicate that the polar-embedded phases are less retentive than alkyl phases for nonpolar species, whereas polar species are more retained by them due to hydrogen bonding with the embedded groups and the increased amount of solvent within the stationary phase. This leads to a significant reduction of the free-energy barrier for the transfer of polar species from the mobile phase to residual silanols, and this reduced barrier provides a possible explanation for reduced peak tailing.

Modification of a Volume-Overload Heart Failure Model to Track Myocardial Remodeling and Device-Related Reverse Remodeling

PubMed Central

Tuzun, Egemen; Bick, Roger; Kadipasaoglu, Cihan; Conger, Jeffrey L.; Poindexter, Brian J.; Gregoric, Igor D.; Frazier, O. H.; Towbin, Jeffrey A.; Radovancevic, Branislav

2011-01-01

Purpose. To provide an ovine model of ventricular remodeling and reverse remodeling by creating congestive heart failure (CHF) and then treating it by implanting a left ventricular assist device (LVAD). Methods. We induced volume-overload heart failure in 2 sheep; 20 weeks later, we implanted an LVAD and assessed recovery 11 weeks thereafter. We examined changes in histologic and hemodynamic data and levels of cellular markers of CHF. Results. After CHF induction, we found increases in LV end-diastolic pressure, LV systolic and diastolic dimensions, wall thickness, left atrial diameter, and atrial natriuretic protein (ANP) and endothelin-1 (ET-1) levels; β-adrenergic receptor (BAR) and dystrophin expression decreased markedly. Biopsies confirmed LV remodeling. After LVAD support, LV systolic and diastolic dimensions, wall thickness, and mass, and ANP and ET-1 levels decreased. Histopathologic and hemodynamic markers improved, and BAR and dystrophin expression normalized. Conclusions. We describe a successful sheep model for ventricular and reverse remodeling. PMID:22347659

Energy Efficient Engine program advanced turbofan nacelle definition study

NASA Technical Reports Server (NTRS)

Howe, David C.; Wynosky, T. A.

1985-01-01

Advanced, low drag, nacelle configurations were defined for some of the more promising propulsion systems identified in the earlier Benefit/Cost Study, to assess the benefits associated with these advanced technology nacelles and formulate programs for developing these nacelles and low volume thrust reversers/spoilers to a state of technology readiness in the early 1990's. The study results established the design feasibility of advanced technology, slim line nacelles applicable to advanced technology, high bypass ratio turbofan engines. Design feasibility was also established for two low volume thrust reverse/spoiler concepts that meet or exceed the required effectiveness for these engines. These nacelle and thrust reverse/spoiler designs were shown to be applicable in engines with takeoff thrust sizes ranging from 24,000 to 60,000 pounds. The reduced weight, drag, and cost of the advanced technology nacelle installations relative to current technology nacelles offer a mission fuel burn savings ranging from 3.0 to 4.5 percent and direct operating cost plus interest improvements from 1.6 to 2.2 percent.

Pore-scale micro-computed-tomography imaging: Nonwetting-phase cluster-size distribution during drainage and imbibition

NASA Astrophysics Data System (ADS)

Georgiadis, A.; Berg, S.; Makurat, A.; Maitland, G.; Ott, H.

2013-09-01

We investigated the cluster-size distribution of the residual nonwetting phase in a sintered glass-bead porous medium at two-phase flow conditions, by means of micro-computed-tomography (μCT) imaging with pore-scale resolution. Cluster-size distribution functions and cluster volumes were obtained by image analysis for a range of injected pore volumes under both imbibition and drainage conditions; the field of view was larger than the porosity-based representative elementary volume (REV). We did not attempt to make a definition for a two-phase REV but used the nonwetting-phase cluster-size distribution as an indicator. Most of the nonwetting-phase total volume was found to be contained in clusters that were one to two orders of magnitude larger than the porosity-based REV. The largest observed clusters in fact ranged in volume from 65% to 99% of the entire nonwetting phase in the field of view. As a consequence, the largest clusters observed were statistically not represented and were found to be smaller than the estimated maximum cluster length. The results indicate that the two-phase REV is larger than the field of view attainable by μCT scanning, at a resolution which allows for the accurate determination of cluster connectivity.

Self-calibrating generalized phase-shifting interferometry of three phase-steps based on geometric concept of volume enclosed by a surface

NASA Astrophysics Data System (ADS)

Meneses-Fabian, Cruz

2016-12-01

This paper presents a non-iterative, fast, and simple algorithm for phase retrieval, in phase-shifting interferometry of three unknown and unequal phase-steps, based on the geometric concept of the volume enclosed by a surface. This approach can be divided in three stages; first the background is eliminated by the subtraction of two interferograms, for obtaining a secondary pattern; second, a surface is built by the product of two secondary patterns and the volume enclosed by this surface is computed; and third, the ratio between two enclosed volumes is approximated to a constant that depends on the phase-steps, with which a system of equations is established, and its solution allows the measurement of the phase-steps to be obtained. Additional advantages of this approach are its immunity to noise, and its capacity to support high spatial variations in the illumination. This approach is theoretically described and is numerically and experimentally verified.

The use of dihexyldithiocarbamate in reverse-phase HPLC of metal chelates

NASA Astrophysics Data System (ADS)

Fatimah, S. S.; Bahti, H. H.; Hastiawan, I.; Permanasari, A.

2018-05-01

Dialkyldithiocarbamates have long been used as chelating agents in reverse-phase HPLC of transition metals. In the previous study, an alkyl homolog of this type of ligand, namely dihexyldithiocarbamate (DHDTC), was synthesized and characterized. The use of this particular ligand in the revese-phase HPLC of some selected transition metal ions is now reported for the first time. The mobile phase comprising of the flow rate and of the detection, in the separation of the metal chelates of Cd (II), Fe (III), Cu (II), and Co (III), were investigated on a C-18 column. The results showed that dihexylditiocarbamate could be used for separating Cd (II), Fe(III), Cu(II), and Co(III). Therefore, it could be used in simultaneous analysis.

A servo-controlled canine model of stable severe ischemic left ventricular failure.

PubMed

Wagner, Richard L; Hood, William B; Howland, Peter A

2009-12-01

Reversible left ventricular failure was produced in conscious dogs by compromise of the coronary circulation. In animals with prior left anterior descending coronary artery occlusion, mean left atrial pressure (LAP) was incorporated into an automatic feedback control system used to inflate a balloon cuff on the circumflex (Cfx) coronary artery. The system could produce stable increases in LAP to 15-20 mm Hg. The dominating system transfer function was the ratio of LAP to balloon volume (BV), which was characterized by a fixed delay (5 s), with LAP/BV = (8e(-jomegatau ))/(0.02 + jomega). The system was stabilized by a phase lead network to reduce oscillations of LAP. A total of seven experiments were conducted in three dogs, and testing of inotropic agents was possible in three experiments under stable conditions with the pump off after an hour or more of operation. Problems encountered were 0.003-0.008 Hz oscillations in LAP in three experiments, which could usually be controlled by reducing the system gain. Late stage ventricular fibrillation occurred in all three animals, but defibrillation was easily accomplished after deflating the Cfx balloon. This system produces reversible left ventricular failure solely due to ischemia, thus closely simulating clinical heart failure due to coronary insufficiency.

Crystal structure, thermochromic and magnetic properties of organic-inorganic hybrid compound: (C7H7N2S)2CuCl4

NASA Astrophysics Data System (ADS)

Vishwakarma, Ashok K.; Kumari, Reema; Ghalsasi, Prasanna S.; Arulsamy, Navamoney

2017-08-01

The synthesis, thermal analysis, crystal structure and magnetic properties of (2-aminobenzothiazolium)2CuCl4, organic-inorganic hybrid compound, have been described. The compound crystallizes in the monoclinic space group P21/c with two formula units in a unit cell of dimensions a = 6.9522(4) Å, b = 9.6979(4) Å, c = 13.9633(6) Å, β = 97.849(3)° and volume 930.83(8) Å3 at 150(2) K. The structure consists of isolated nearly square planer [CuC14]2- units, with somewhat longer than normal Cusbnd Cl bond lengths [Cusbnd Cl (average) = 2.2711 Å]. The magnetic measurements of (2-aminobenzothiazolium)2CuCl4 using SQUID magnetometer show paramagnetic nature of the compound. Thermal measurements (TG-DTA and DSC) on this compound showed reversible phase transition at 83 °C. This transition is accompanied by the reversible change in colour of the prismatic crystal from green to dark brown, thermochromic behaviour. Temperature dependent EPR measurements on powdered sample ascertain change in coordination sphere around Cu(II) with shift in g|| = 2.150 and g⊥ = 2.071 at room temperature, typical of square planar, to g|| = 2.201 and g⊥ = 2.182 at 170 °C, typical of distorted tetrahedral geometry.

Kinetic limitations of the Mg(2)Si system for reversible hydrogen storage.

PubMed

Kelly, Stephen T; Van Atta, Sky L; Vajo, John J; Olson, Gregory L; Clemens, B M

2009-05-20

Despite the promising thermodynamics and storage capacities of many destabilized metal hydride hydrogen storage material systems, they are often kinetically limited from achieving practical and reversible behavior. Such is the case with the Mg2Si system. We investigated the kinetic mechanisms responsible for limiting the reversibility of the MgH2+Si system using thin films as a controlled research platform. We observed that the reaction MgH2 + 1/2Mg2Si + H2 is limited by the mass transport of Mg and Si into separate phases. Hydrogen readily diffuses through the Mg2Si material and nucleating MgH2 phase growth does not result in reaction completion. By depositing and characterizing multilayer films of Mg2Si and Mg with varying Mg2Si layer thicknesses, we conclude that the hydrogenation reaction consumes no more than 1 nm of Mg2Si, making this system impractical for reversible hydrogen storage.

Methods to control phase inversions and enhance mass transfer in liquid-liquid dispersions

DOEpatents

Tsouris, Constantinos; Dong, Junhang

2002-01-01

The present invention is directed to the effects of applied electric fields on liquid-liquid dispersions. In general, the present invention is directed to the control of phase inversions in liquid-liquid dispersions. Because of polarization and deformation effects, coalescence of aqueous drops is facilitated by the application of electric fields. As a result, with an increase in the applied voltage, the ambivalence region is narrowed and shifted toward higher volume fractions of the dispersed phase. This permits the invention to be used to ensure that the aqueous phase remains continuous, even at a high volume fraction of the organic phase. Additionally, the volume fraction of the organic phase may be increased without causing phase inversion, and may be used to correct a phase inversion which has already occurred. Finally, the invention may be used to enhance mass transfer rates from one phase to another through the use of phase inversions.

The Accuracy and Precision of Flow Measurements Using Phase Contrast Techniques

NASA Astrophysics Data System (ADS)

Tang, Chao

Quantitative volume flow rate measurements using the magnetic resonance imaging technique are studied in this dissertation because the volume flow rates have a special interest in the blood supply of the human body. The method of quantitative volume flow rate measurements is based on the phase contrast technique, which assumes a linear relationship between the phase and flow velocity of spins. By measuring the phase shift of nuclear spins and integrating velocity across the lumen of the vessel, we can determine the volume flow rate. The accuracy and precision of volume flow rate measurements obtained using the phase contrast technique are studied by computer simulations and experiments. The various factors studied include (1) the partial volume effect due to voxel dimensions and slice thickness relative to the vessel dimensions; (2) vessel angulation relative to the imaging plane; (3) intravoxel phase dispersion; (4) flow velocity relative to the magnitude of the flow encoding gradient. The partial volume effect is demonstrated to be the major obstacle to obtaining accurate flow measurements for both laminar and plug flow. Laminar flow can be measured more accurately than plug flow in the same condition. Both the experiment and simulation results for laminar flow show that, to obtain the accuracy of volume flow rate measurements to within 10%, at least 16 voxels are needed to cover the vessel lumen. The accuracy of flow measurements depends strongly on the relative intensity of signal from stationary tissues. A correction method is proposed to compensate for the partial volume effect. The correction method is based on a small phase shift approximation. After the correction, the errors due to the partial volume effect are compensated, allowing more accurate results to be obtained. An automatic program based on the correction method is developed and implemented on a Sun workstation. The correction method is applied to the simulation and experiment results. The results show that the correction significantly reduces the errors due to the partial volume effect. We apply the correction method to the data of in vivo studies. Because the blood flow is not known, the results of correction are tested according to the common knowledge (such as cardiac output) and conservation of flow. For example, the volume of blood flowing to the brain should be equal to the volume of blood flowing from the brain. Our measurement results are very convincing.

Probing the interior of a solid volume with time reversal and nonlinear elastic wave spectroscopy.

PubMed

Le Bas, P Y; Ulrich, T J; Anderson, B E; Guyer, R A; Johnson, P A

2011-10-01

A nonlinear scatterer is simulated in the body of a sample and demonstrates a technique to locate and define the elastic nature of the scatterer. Using the principle of time reversal, elastic wave energy is focused at the interface between blocks of optical grade glass and aluminum. Focusing of energy at the interface creates nonlinear wave scattering that can be detected on the sample perimeter with time-reversal mirror elements. The nonlinearly generated scattered signal is bandpass filtered about the nonlinearly generated components, time reversed and broadcast from the same mirror elements, and the signal is focused at the scattering location on the interface. © 2011 Acoustical Society of America

Interplay of Coulomb interactions and disorder in three-dimensional quadratic band crossings without time-reversal symmetry and with unequal masses for conduction and valence bands

NASA Astrophysics Data System (ADS)

Mandal, Ipsita; Nandkishore, Rahul M.

2018-03-01

Coulomb interactions famously drive three-dimensional quadratic band crossing semimetals into a non-Fermi liquid phase of matter. In a previous work [Nandkishore and Parameswaran, Phys. Rev. B 95, 205106 (2017), 10.1103/PhysRevB.95.205106], the effect of disorder on this non-Fermi liquid phase was investigated, assuming that the band structure was isotropic, assuming that the conduction and valence bands had the same band mass, and assuming that the disorder preserved exact time-reversal symmetry and statistical isotropy. It was shown that the non-Fermi liquid fixed point is unstable to disorder and that a runaway flow to strong disorder occurs. In this paper, we extend that analysis by relaxing the assumption of time-reversal symmetry and allowing the electron and hole masses to differ (but continuing to assume isotropy of the low energy band structure). We first incorporate time-reversal symmetry breaking disorder and demonstrate that there do not appear any new fixed points. Moreover, while the system continues to flow to strong disorder, time-reversal-symmetry-breaking disorder grows asymptotically more slowly than time-reversal-symmetry-preserving disorder, which we therefore expect should dominate the strong-coupling phase. We then allow for unequal electron and hole masses. We show that whereas asymmetry in the two masses is irrelevant in the clean system, it is relevant in the presence of disorder, such that the `effective masses' of the conduction and valence bands should become sharply distinct in the low-energy limit. We calculate the RG flow equations for the disordered interacting system with unequal band masses and demonstrate that the problem exhibits a runaway flow to strong disorder. Along the runaway flow, time-reversal-symmetry-preserving disorder grows asymptotically more rapidly than both time-reversal-symmetry-breaking disorder and the Coulomb interaction.

Phase lag control of tidally reversing mega-ripple geometry and bed stress in tidal inlets

NASA Astrophysics Data System (ADS)

Traykovski, P.

2016-02-01

Recent observations in the Columbia River Mouth, New River Inlet, and Wasque Shoals have shown that tidally reversing mega-ripples are an ubiquitous bedform morphology in energetic tidal inlets. As the name implies, these bedforms reverse asymmetry and migration direction in each half tidal cycle. With wavelengths of 2 to 5 m and heights of 0.2 to 0.5 m, these bedforms are larger than current formed ripples, but smaller than dunes. Unlike dunes which have a depth dependent geometry, observations indicate the tidally reversing mega-ripples geometry is related to the time dependent tidal flow and independent of depth. Previous empirical relations for predicting the geometry of ripples or dunes do not successfully predict the geometry of these features. A time dependent geometric model was developed that accounts for the reversal of migration and asymmetry to successfully predict bedform geometry. The model requires sufficient sediment transport in each half tidal cycle to reverse the asymmetry before the bedforms begin to grow. Both the observations and model indicate that the complete reversal of asymmetry and development of a steep lee face occurs near or after maximum flow in each half tidal cycle. This phase lag in bedform response to tidal forcing also has important implications for bed stress in tidal inlets. Observations of frictional drag in the Columbia River mouth based on a tidal momentum balance of surface slope over 10 km regressed against quadratic near bed velocity show drag coefficients that fall off as CD U-1.4. Reynolds stress measurements performed using the dual ADV differencing technique show similar relations. The Reynolds stress measurements also show a dramatic asymmetry between accelerating flows and decelerating flows with a factor of 5 increase during deceleration. Pulse coherent Doppler profiles of near bed turbulence indicate that the turbulence is dominated by energetic fluctuations in separation zones downstream of steep lee faces. The phase lag of the bedform evolution, whereby steep lee faces are only present in the decelerating phase of the tidal cycle, provides an explanation for the asymmetry and non-quadratic behavior of the drag coefficients.

Improved selectivity for high-performance liquid chromatographic determination of clonazepam in plasma of epileptic patients.

PubMed

Le Guellec, C; Gaudet, M L; Breteau, M

1998-11-20

We report a high-performance liquid chromatography method for clonazepam determination in plasma. The use of a synthetic silica-based stationary phase markedly improved clonazepam resolution compared to standard reversed-phase columns. A liquid-liquid extraction was used, associated with reversed-phase chromatography, gradient elution and ultraviolet detection. Accuracy and precision were satisfactory at therapeutic concentrations. Selectivity was studied for benzodiazepines or other antiepileptic drugs, with particular attention to newly marketed drugs i.e., gabapentine and vigabatrin. No interfering substance was evidenced. Under the conditions described, it was possible to quantify clonazepam at nanogram level even when carbamazepine was present at therapeutic concentrations.

MOD-5A wind turbine generator program design report: Volume 1: Executive Summary

NASA Technical Reports Server (NTRS)

1984-01-01

The design, development and analysis of the 7.3 MW MOD-5A wind turbine generator covering work performed between July 1980 and June 1984 is discussed. The report is divided into four volumes: Volume 1 summarizes the entire MOD-5A program, Volume 2 discusses the conceptual and preliminary design phases, Volume 3 describes the final design of the MOD-5A, and Volume 4 contains the drawings and specifications developed for the final design. Volume 1, the Executive Summary, summarizes all phases of the MOD-5A program. The performance and cost of energy generated by the MOD-5A are presented. Each subsystem - the rotor, drivetrain, nacelle, tower and foundation, power generation, and control and instrumentation subsystems - is described briefly. The early phases of the MOD-5A program, during which the design was analyzed and optimized, and new technologies and materials were developed, are discussed. Manufacturing, quality assurance, and safety plans are presented. The volume concludes with an index of volumes 2 and 3.

A validated chiral liquid chromatographic method for the enantiomeric separation of safinamide mesilate, a new anti-Parkinson drug.

PubMed

Zhang, Kai; Xue, Na; Shi, Xiaowei; Liu, Weina; Meng, Jing; Du, Yumin

2011-04-28

A enantioselective reversed-phase high performance liquid chromatographic method was developed for the enantiomeric resolution of safinamide mesilate, 2(S)-[4-(3-fluorobenzyloxy)benzylamino] propionamide methanesulfonate, a neuroprotectant with antiparkinsonian and anticonvulsant activity for the treatment of Parkinson disease. The enantiomers of safinamide mesilate were baseline resolved on a Chiralcel OD-RH (150mm×4.6mm, 5μm) column using a mobile phase system containing 300mM sodium di-hydrogen phosphate buffer (pH 3.0):methanol:acetonitrile (65:25:10, v/v/v). The resolution between the enantiomers was not less than 3.0. The pH value of buffer solution in the mobile phase has played a key role in enhancing chromatographic efficiency and resolution between the enantiomers. The developed method was validated and proved to be robust. The limit of detection and limit of quantification of (R)-enantiomer were found to be 15 and 50ng/mL, respectively, for 20μL injection volume. The percentage recovery of (R)-enantiomer was ranged from 94.2 to 103.7 in bulk drug samples of safinamide mesilate. The sample solution and mobile phase were found to be stable at least for 48h. The final optimized method was successfully applied to separate (R)-enantiomer from safinamide mesilate and was proven to be reproducible and accurate for the quantitative determination of (R)-enantiomer in bulk drugs. Copyright © 2010 Elsevier B.V. All rights reserved.

Enriched classification of parafermionic gapped phases with time-reversal symmetry

NASA Astrophysics Data System (ADS)

Xu, Wen-Tao; Zhang, Guang-Ming

2018-03-01

Based on the recently established parafermionic matrix product states, we study the classification of one-dimensional gapped phases of parafermions with time-reversal (TR) symmetry satisfying T2=1 . Without extra symmetry, it has been found that Zp parafermionic gapped phases can be classified as topological phases, spontaneous symmetry breaking (SSB) phases, and a trivial phase, which are uniquely labeled by the divisors n of p . In the presence of TR symmetry, however, the enriched classification is characterized by three indices n , κ , and μ , where κ ∈Z2 denotes the linear or projective TR actions on the edges, and μ ∈Z2 indicates the commutation relations between the TR and (fractionalized) charge operator. For the Zr-symmetric parafermionic ground states, where r =p for trivial or topological phases, and r =p /n for SSB phases, each original gapped phase with odd r is divided into two phases, while each phase with even r is further separated into four phases. The gapped parafermionic phases with the TR symmetry include the symmetry protected topological phases, symmetry enriched topological phases, and the SSB coexisting symmetry protected topological phases. From analyzing the structures and symmetries of their reduced density matrices of these resulting topological phases, we can obtain the topologically protected degeneracies of their entanglement spectra.

Newsletter for Asian and Middle Eastern Languages on Computer, Volume 1, Numbers 3 & 4.

ERIC Educational Resources Information Center

Meadow, Anthony, Ed.

1986-01-01

Volume 1, numbers 3 and 4, of the newsletter on the use of non-Western languages with computers contains the following articles: "Reversing the Screen under MS/PC-DOS" (Dan Brink); "Comments on Diacritics Using Wordstar, etc. and CP/M Software for Non-Western Languages" (Michael Broschat); "Carving Tibetan in Silicon: A…

Time-Reversal Location of the 2004 M6.0 Parkfield Earthquake Using the Vertical Component of Seismic Data.

NASA Astrophysics Data System (ADS)

Larmat, C. S.; Johnson, P.; Huang, L.; Randall, G.; Patton, H.; Montagner, J.

2007-12-01

In this work we describe Time Reversal experiments applying seismic waves recorded from the 2004 M6.0 Parkfield Earthquake. The reverse seismic wavefield is created by time-reversing recorded seismograms and then injecting them from the seismograph locations into a whole entire Earth velocity model. The concept is identical to acoustic Time-Reversal Mirror laboratory experiments except the seismic data are numerically backpropagated through a velocity model (Fink, 1996; Ulrich et al, 2007). Data are backpropagated using the finite element code SPECFEM3D (Komatitsch et al, 2002), employing the velocity model s20rts (Ritsema et al, 2000). In this paper, we backpropagate only the vertical component of seismic data from about 100 broadband surface stations located worldwide (FDSN), using the period band of 23-120s. We use those only waveforms that are highly correlated with forward-propagated synthetics. The focusing quality depends upon the type of waves back- propagated; for the vertical displacement component the possible types include body waves, Rayleigh waves, or their combination. We show that Rayleigh waves, both real and artifact, dominate the reverse movie in all cases. They are created during rebroadcast of the time reverse signals, including body wave phases, because we use point-like-force sources for injection. The artifact waves, termed "ghosts" manifest as surface waves, do not correspond to real wave phases during the forward propagation. The surface ghost waves can significantly blur the focusing at the source. We find that the ghosts cannot be easily eliminated in the manner described by Tsogka&Papanicolaou (2002). It is necessary to understand how they are created in order to remove them during TRM studies, particularly when using only the body waves. For this moderate magnitude of earthquake we demonstrate the robustness of the TRM as an alternative location method despite the restriction to vertical component phases. One advantage of TRM location is that it does not rely on a prior picking of specific phases (Larmat et al, 2006). In future work will be conducted TRM backpropagation using the horizontal displacement components of seismic data as well as study the source complexity (double couples). Our ultimate goal is to determine whether or not Time Reversal offers information about the source that cannot be obtained from other methods, or that complements other methods.

Conventional empirical law reverses in the phase transitions of 122-type iron-based superconductors

DOE PAGES

Yu, Zhenhai; Wang, Lin; Wang, Luhong; ...

2014-11-24

Phase transition of solid-state materials is a fundamental research topic in condensed matter physics, materials science and geophysics. It has been well accepted and widely proven that isostructural compounds containing different cations undergo same pressure-induced phase transitions but at progressively lower pressures as the cation radii increases. However, we discovered that this conventional law reverses in the structural transitions in 122-type iron-based superconductors. In this report, a combined low temperature and high pressure X-ray diffraction (XRD) measurement has identified the phase transition curves among the tetragonal (T), orthorhombic (O) and the collapsed-tetragonal (cT) phases in the structural phase diagram ofmore » the iron-based superconductor AFe 2As 2 (A = Ca, Sr, Eu, and Ba). As a result, the cation radii dependence of the phase transition pressure (T → cT) shows an opposite trend in which the compounds with larger ambient radii cations have a higher transition pressure.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bolton, Justin; Rzayev, Javid

Polystyrene–poly(methyl methacrylate)–polylactide (PS–PMMA–PLA) triblock bottlebrush copolymer with nearly symmetric volume fractions was synthesized by grafting from a symmetrical triblock backbone and the resulting melt was characterized by scanning electron microscopy and small-angle X-ray scattering. The copolymer backbone was prepared by sequential reversible addition–fragmentation chain transfer (RAFT) polymerization of solketal methacrylate (SM), 2-(bromoisobutyryl)ethyl methacrylate (BIEM), and 5-(trimethylsilyl)-4-pentyn-1-ol methacrylate (TPYM). PMMA branches were grafted by atom transfer radical polymerization from the poly(BIEM) segment, PS branches were grafted by RAFT polymerization from the poly(TPYM) block after installment of the RAFT agents, while PLA side chains were grafted from the deprotected poly(SM) block. Themore » resulting copolymer was found to exhibit a lamellae morphology with a domain spacing of 79 nm. Differential scanning calorimetry analysis indicated that PMMA was preferentially mixing with PS while phase separating from PLA domains.« less

Guide-star-based computational adaptive optics for broadband interferometric tomography

PubMed Central

Adie, Steven G.; Shemonski, Nathan D.; Graf, Benedikt W.; Ahmad, Adeel; Scott Carney, P.; Boppart, Stephen A.

2012-01-01

We present a method for the numerical correction of optical aberrations based on indirect sensing of the scattered wavefront from point-like scatterers (“guide stars”) within a three-dimensional broadband interferometric tomogram. This method enables the correction of high-order monochromatic and chromatic aberrations utilizing guide stars that are revealed after numerical compensation of defocus and low-order aberrations of the optical system. Guide-star-based aberration correction in a silicone phantom with sparse sub-resolution-sized scatterers demonstrates improvement of resolution and signal-to-noise ratio over a large isotome. Results in highly scattering muscle tissue showed improved resolution of fine structure over an extended volume. Guide-star-based computational adaptive optics expands upon the use of image metrics for numerically optimizing the aberration correction in broadband interferometric tomography, and is analogous to phase-conjugation and time-reversal methods for focusing in turbid media. PMID:23284179

Elaboration of austenitic stainless steel samples with bimodal grain size distributions and investigation of their mechanical behavior

NASA Astrophysics Data System (ADS)

Flipon, B.; de la Cruz, L. Garcia; Hug, E.; Keller, C.; Barbe, F.

2017-10-01

Samples of 316L austenitic stainless steel with bimodal grain size distributions are elaborated using two distinct routes. The first one is based on powder metallurgy using spark plasma sintering of two powders with different particle sizes. The second route applies the reverse-annealing method: it consists in inducing martensitic phase transformation by plastic strain and further annealing in order to obtain two austenitic grain populations with different sizes. Microstructural analy ses reveal that both methods are suitable to generate significative grain size contrast and to control this contrast according to the elaboration conditions. Mechanical properties under tension are then characterized for different grain size distributions. Crystal plasticity finite element modelling is further applied in a configuration of bimodal distribution to analyse the role played by coarse grains within a matrix of fine grains, considering not only their volume fraction but also their spatial arrangement.

Unconventional Topological Phase Transition in Two-Dimensional Systems with Space-Time Inversion Symmetry

NASA Astrophysics Data System (ADS)

Ahn, Junyeong; Yang, Bohm-Jung

2017-04-01

We study a topological phase transition between a normal insulator and a quantum spin Hall insulator in two-dimensional (2D) systems with time-reversal and twofold rotation symmetries. Contrary to the case of ordinary time-reversal invariant systems, where a direct transition between two insulators is generally predicted, we find that the topological phase transition in systems with an additional twofold rotation symmetry is mediated by an emergent stable 2D Weyl semimetal phase between two insulators. Here the central role is played by the so-called space-time inversion symmetry, the combination of time-reversal and twofold rotation symmetries, which guarantees the quantization of the Berry phase around a 2D Weyl point even in the presence of strong spin-orbit coupling. Pair creation and pair annihilation of Weyl points accompanying partner exchange between different pairs induces a jump of a 2D Z2 topological invariant leading to a topological phase transition. According to our theory, the topological phase transition in HgTe /CdTe quantum well structure is mediated by a stable 2D Weyl semimetal phase because the quantum well, lacking inversion symmetry intrinsically, has twofold rotation about the growth direction. Namely, the HgTe /CdTe quantum well can show 2D Weyl semimetallic behavior within a small but finite interval in the thickness of HgTe layers between a normal insulator and a quantum spin Hall insulator. We also propose that few-layer black phosphorus under perpendicular electric field is another candidate system to observe the unconventional topological phase transition mechanism accompanied by the emerging 2D Weyl semimetal phase protected by space-time inversion symmetry.

Chemical and magnetic properties of rapidly cooled metastable ferri-ilmenite solid solutions - IV: the fine structure of self-reversed thermoremanent magnetization

NASA Astrophysics Data System (ADS)

Robinson, Peter; McEnroe, S. A.; Fabian, K.; Harrison, R. J.; Thomas, C. I.; Mukai, H.

2014-03-01

Magnetic experiments, a Monte Carlo simulation and transmission electron microscopy observations combine to confirm variable chemical phase separation during quench and annealing of metastable ferri-ilmenite compositions, caused by inhomogeneous Fe-Ti ordering and anti-ordering. Separation begins near interfaces between growing ordered and anti-ordered domains, the latter becoming progressively enriched in ilmenite component, moving the Ti-impoverished hematite component into Fe-enriched diffusion waves near the interfaces. Even when disordered regions are eliminated, Fe-enriched waves persist and enlarge on anti-phase boundaries between growing and shrinking ordered and anti-ordered domains. Magnetic results and conceptual models show that magnetic ordering with falling T initiates in the Fe-enriched wave crests. Although representing only a tiny fraction of material, identified at highest Ts on a field-cooling curve, they control the `pre-destiny' of progressive magnetization at lower T. They can provide a positive magnetic moment in a minority of ordered ferrimagnetic material, which, by exchange coupling, then creates a self-reversed negative moment in the remaining majority. Four Ts or T ranges are recognized on typical field-cooling curves: TPD is the T range of `pre-destination'; TC is the predominant Curie T where major positive magnetization increases sharply; TMAX is where magnetization reaches a positive maximum, beyond which it is outweighed by self-reversed magnetization and TZM is the T where total magnetization passes zero. Disposition of these Ts on cooling curves indicate the fine structure of self-reversed thermoremanent magnetization. These results confirm much earlier suspicions that the `x-phase' responsible for self-reversed magnetization resides in Fe-enriched phase boundaries.

Alpha – omega and omega – alpha phase transformations in zirconium under hydrostatic pressure: A 3D mesoscale study

DOE PAGES

Yeddu, Hemantha Kumar; Zong, Hongxiang; Lookman, Turab

2015-09-28

Here, a three dimensional (3D) elastoplastic phase-field model is developed for modeling the hydrostatic pressure-induced alpha – omega phase transformation and the reverse phase transformation, i.e. omega – alpha, in zirconium (Zr). Plastic deformation and strain hardening of the material are also considered in the model. The microstructure evolution during both phase transformations is studied. The transformation start pressures at different temperatures are predicted and are plotted as a phase diagram. The effect of phase transformations on the mechanical properties of the material is also studied. The input data corresponding to pure Zr are acquired from experimental studies as wellmore » as by using the CALPHAD method. Our simulations show that three different omega variants form as laths. On release of pressure, reverse phase transformation initiates at lath boundaries. We observe that both phase transformations are martensitic in nature and also occur at the same pressure, i.e. little hysteresis. The transformation start pressures and the kinetics of the transformation predicted by our model are in good agreement with experimental results.« less

Alpha – omega and omega – alpha phase transformations in zirconium under hydrostatic pressure: A 3D mesoscale study

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yeddu, Hemantha Kumar; Zong, Hongxiang; Lookman, Turab

Here, a three dimensional (3D) elastoplastic phase-field model is developed for modeling the hydrostatic pressure-induced alpha – omega phase transformation and the reverse phase transformation, i.e. omega – alpha, in zirconium (Zr). Plastic deformation and strain hardening of the material are also considered in the model. The microstructure evolution during both phase transformations is studied. The transformation start pressures at different temperatures are predicted and are plotted as a phase diagram. The effect of phase transformations on the mechanical properties of the material is also studied. The input data corresponding to pure Zr are acquired from experimental studies as wellmore » as by using the CALPHAD method. Our simulations show that three different omega variants form as laths. On release of pressure, reverse phase transformation initiates at lath boundaries. We observe that both phase transformations are martensitic in nature and also occur at the same pressure, i.e. little hysteresis. The transformation start pressures and the kinetics of the transformation predicted by our model are in good agreement with experimental results.« less

On-line hyphenation of solid-phase extraction to chromatographic separation of sulfonamides with fused-core columns in sequential injection chromatography.

PubMed

Batista, Alex D; Chocholouš, Petr; Satínský, Dalibor; Solich, Petr; Rocha, Fábio R P

2015-02-01

On-line sample pretreatment (clean-up and analyte preconcentration) is for the first time coupled to sequential injection chromatography. The approach combines anion-exchange solid-phase extraction and the highly effective pentafluorophenylpropyl (F5) fused-core particle column for separation of eight sulfonamide antibiotics with similar structures (sulfathiazole, sulfanilamide, sulfacetamide, sulfadiazine, sulfamerazine, sulfadimidine, sulfamethoxazole and sulfadimethoxine). The stationary phase was selected after a critical comparison of the performance achieved by three fused-core reversed phase columns (Ascentis(®) Express RP-Amide, Phenyl-Hexyl, and F5) and two monolithic columns (Chromolith(®) High Resolution RP-18 and CN). Acetonitrile and acetate buffer pH 5.0 at 0.60 mL min(-1) were used as mobile phase to perform the separations before spectrophotometric detection. The first mobile phase was successfully used as eluent from SPE column ensuring transfer of a narrow zone to the chromatographic column. Enrichment factors up to 39.2 were achieved with a 500 µL sample volume. The developed procedure showed analysis time <10.5 min, resolutions >1.83 with peak symmetry ≤1.52, LODs between 4.9 and 27 µg L(-1), linear response ranges from 30.0 to 1000.0 µg L(-1) (r(2)>0.996) and RSDs of peak heights <2.9% (n=6) at a 100 µg L(-1) level and enabled the screening control of freshwater samples contaminated at the 100 µg L(-1) level. The proposed approach expanded the analytical potentiality of SIC and avoided the time-consuming batch sample pretreatment step, thus minimizing risks of sample contamination and analyte losses. Copyright © 2014 Elsevier B.V. All rights reserved.

Influence of processing parameters on microstructure and biocompatibility of surface laser sintered hydroxyapatite-SiO2 composites.

PubMed

Kivitz, E; Görke, R; Schilling, A F; Zhang, J; Heinrich, J G

2013-05-01

Silica-doped hydroxyapatite (HA) is a promising material concerning biocompatibility to natural bone, bioactivity and osteoconductive characteristics. HA exhibits phase transformations during sintering which are attendant to the change in volume and thermal strain. To avoid cracks during sintering, the exact knowledge of the phase transition temperatures is necessary. The sintering behavior of HA can be improved by adding amorphous silica with a low coefficient of thermal expansion. Therefore, the phase transformations in the system HA-SiO2 were analyzed by using differential scanning calorimetry followed by quantitative phase analysis by X-ray diffraction with the Riedveld method. The maximum sintering temperature without reversible phase transformation was defined as 1265°C. In laser surface sintered (LSS) samples, amorphous SiO2 , HA, and Si-α-TCP (or α-TCP) were detected. By comparison, only crystalline phases, such as cristobalite, HA, β-TCP, and Si-α-TCP (or α-TCP), were determined after furnace sintering. Scanning electron microscopy micrographs of furnace sintered and LSS samples show the differences in the resulting microstructures. Biocompatibility was determined by measuring cell activity of osteoblasts cultivated on four laser-sintered materials in the HA-SiO2 system in comparison to normal cell culture plastic. Cell proliferation was similar on all surfaces. The level of the cell activity on day 8 varied depending on the composition of the material and increased linearly as the amorphous SiO2 content rose. Taken together a laser-based method to develop novel biocompatible HA-SiO2 ceramics with adjustable properties and possible applications as orthopedic bioceramics are discussed. Copyright © 2012 Wiley Periodicals, Inc.

Ion-pair in-tube solid-phase microextraction and capillary liquid chromatography using a titania-based column: application to the specific lauralkonium chloride determination in water.

PubMed

Prieto-Blanco, M C; Moliner-Martínez, Y; López-Mahía, P; Campíns-Falcó, P

2012-07-27

A quick, miniaturized and on-line method has been developed for the determination in water of the predominant homologue of benzalkonium chloride, dodecyl dimethyl benzyl ammonium chloride or lauralkonium chloride (C(12)-BAK). The method is based on the formation of an ion-pair in both in-tube solid-phase microextraction (IT-SPME) and capillary liquid chromatography. The IT-SPME optimization required the study of the length and nature of the stationary phase of capillary and the processed sample volume. Because to the surfactant character of the analyte both, the extracting and replacing solvents, have played a decisive role in the IT-SPME optimized procedure. Conditioning the capillary with the mobile phase which contains the counter ion (acetate), using an organic additive (tetrabutylammonium chloride) added to the sample and a mixture water/methanol as replacing solvent (processed just before the valve is switched to the inject position), allowed to obtain good precision of the retention time and a narrow peak for C(12)-BAK. A reversed-phase capillary based TiO(2) column and a mobile phase containing ammonium acetate at pH 5.0 for controlling the interactions of cationic surfactant with titania surface were proposed. The optimized procedure provided adequate linearity, accuracy and precision at the concentrations interval of 1.5-300 μg L(-1) .The limit of detection (LOD) was 0.5 μg L(-1) using diode array detection (DAD). The applicability of proposed IT-SPME-capillary LC method has been assessed in several water samples. Copyright © 2012 Elsevier B.V. All rights reserved.

Automated segmentation and dose-volume analysis with DICOMautomaton

NASA Astrophysics Data System (ADS)

Clark, H.; Thomas, S.; Moiseenko, V.; Lee, R.; Gill, B.; Duzenli, C.; Wu, J.

2014-03-01

Purpose: Exploration of historical data for regional organ dose sensitivity is limited by the effort needed to (sub-)segment large numbers of contours. A system has been developed which can rapidly perform autonomous contour sub-segmentation and generic dose-volume computations, substantially reducing the effort required for exploratory analyses. Methods: A contour-centric approach is taken which enables lossless, reversible segmentation and dramatically reduces computation time compared with voxel-centric approaches. Segmentation can be specified on a per-contour, per-organ, or per-patient basis, and can be performed along either an embedded plane or in terms of the contour's bounds (e.g., split organ into fractional-volume/dose pieces along any 3D unit vector). More complex segmentation techniques are available. Anonymized data from 60 head-and-neck cancer patients were used to compare dose-volume computations with Varian's EclipseTM (Varian Medical Systems, Inc.). Results: Mean doses and Dose-volume-histograms computed agree strongly with Varian's EclipseTM. Contours which have been segmented can be injected back into patient data permanently and in a Digital Imaging and Communication in Medicine (DICOM)-conforming manner. Lossless segmentation persists across such injection, and remains fully reversible. Conclusions: DICOMautomaton allows researchers to rapidly, accurately, and autonomously segment large amounts of data into intricate structures suitable for analyses of regional organ dose sensitivity.

Investigation of the retention/pH profile of zwitterionic fluoroquinolones in reversed-phase and ion-interaction high performance liquid chromatography.

PubMed

Pistos, C; Tsantili-Kakoulidou, A; Koupparis, M

2005-09-15

The retention/pH profiles of three fluoroquinolones, ofloxacin, norfloxacin and ciprofloxacin, was investigated by means of reversed-phase high performance liquid chromatography (RP-HPLC) and reversed-phase ion-interaction chromatography (RP-IIC), using an octadecylsilane stationary phase and acetonitrile as organic modifier. Sodium hexanesulphonate and tetrabutylammonium hydroxide were used as sources of counter ions in ion-interaction chromatography. The retention/pH profiles under in RP-HPLC were compared to the corresponding lipophilicity/pH profiles. Despite the rather hydrophilic nature of the three fluoroquinolones positive retention factors were obtained while there was a shift of the retention maximum towards more acidic pH values. This behavior was attributed mainly to non-hydrophobic silanophilic interactions with the silanized silica gel material of the stationary phase. In ion-interaction chromatography the effect of counter ions over a broad pH range was found to be ruled rather by the ion pair formation in the mobile phase which led to a drastic decrease in retention as a consequence of the disruption of the zwitterionic structure and thereupon the deliberation of a net charge in the molecules. At pH values at which zwitterionic structure was not favored both the ion-exchange and ion pair formation mechanisms were assumed to contribute to the retention.

High-performance liquid-chromatographic separation of subcomponents of antimycin-A

USGS Publications Warehouse

Abidi, S.L.

1988-01-01

Using a reversed-phase high-performance liquid chromatographic (HPLC) technique, a mixture of antimycins A was separated into eight hitherto unreported subcomponents, Ala, Alb, A2a, A2b, A3a, A3b, A4a, and A4b. Although a base-line resolution of the known four major antimycins Al, A2, A3, and A4 was readily achieved with mobile phases containing acetate buffers, the separation of the new antibiotic subcomponents was highly sensitive to variation in mobile phase conditions. The type and composition of organic modifiers, the nature of buffer salts, and the concentration of added electrolytes had profound effects on capacity factors, separation factors, and peak resolution values. Of the numerous chromatographic systems examined, a mobile phase consisting of methanol-water (70:30) and 0.005 M tetrabutylammonium phosphate at pH 3.0 yielded the most satisfactory results for the separation of the subcomponents. Reversed-phase gradient HPLC separation of the dansylated or methylated antibiotic compounds produced superior chromatographic characteristics and the presence of added electrolytes was not a critical factor for achieving separation. Differences in the chromatographic outcome between homologous and structural isomers were interpretated based on a differential solvophobic interaction rationale. Preparative reversed-phase HPLC under optimal conditions enabled isolation of pure samples of the methylated antimycin subcomponents for use in structural studies.

Dehydrogenation kinetics and reversibility of LiAlH4-LiBH4 doped with Ti-based additives and MWCNT

NASA Astrophysics Data System (ADS)

Thaweelap, Natthaporn; Utke, Rapee

2016-11-01

Dehydrogenation kinetics and reversibility of LiAlH4-LiBH4 doped with Ti-based additives (TiCl3 and Ti-isopropoxide), multiwall carbon nanotubes (MWCNT), and MWCNT impregnated with Ti-based additives are proposed. Reduction of dehydrogenation temperature as well as improvements of kinetics and reversibility, especially decomposition of thermodynamically stable hydride (LiBH4) is obtained from the samples doped with Ti-isopropoxide and MWCNT. This can be due to the fact that the formations of LixAl(1-x)B2 and LiH-Al containing phase during dehydrogenation favor decomposition of LiH, leading to increment of hydrogen capacity, and stabilization of boron in solid state, resulting in improvement of reversibility. Besides, the curvatures and thermal conductivity of MWCNT benefit hydrogen diffusion and heat transfer during de/rehydrogenation. Nevertheless, deficient hydrogen content reversible is observed in all samples due to the irreversible of LiAlH4 and/or Li3AlH6 as well as the formation of stable phase (Li2B12H12) during de/rehydrogenation.

Topological nodal superconducting phases and topological phase transition in the hyperhoneycomb lattice

NASA Astrophysics Data System (ADS)

Bouhon, Adrien; Schmidt, Johann; Black-Schaffer, Annica M.

2018-03-01

We establish the topology of the spin-singlet superconducting states in the bare hyperhoneycomb lattice, and we derive analytically the full phase diagram using only symmetry and topology in combination with simple energy arguments. The phase diagram is dominated by two states preserving time-reversal symmetry. We find a line-nodal state dominating at low doping levels that is topologically nontrivial and exhibits surface Majorana flatbands, which we show perfectly match the bulk-boundary correspondence using the Berry phase approach. At higher doping levels, we find a fully gapped state with trivial topology. By analytically calculating the topological invariant of the nodal lines, we derive the critical point between the line-nodal and fully gapped states as a function of both pairing parameters and doping. We find that the line-nodal state is favored not only at lower doping levels but also if symmetry-allowed deformations of the lattice are present. Adding simple energy arguments, we establish that a fully gapped state with broken time-reversal symmetry likely appears covering the actual phase transition. We find this fully gapped state to be topologically trivial, while we find an additional point-nodal state at very low doing levels that also break time-reversal symmetry and has nontrivial topology with associated Fermi surface arcs. We eventually address the robustness of the phase diagram to generalized models also including adiabatic spin-orbit coupling, and we show how all but the point-nodal state are reasonably stable.

On-line comprehensive two-dimensional normal-phase liquid chromatography × reversed-phase liquid chromatography for preparative isolation of Peucedanum praeruptorum.

PubMed

Wang, Xin-Yuan; Li, Jia-Fu; Jian, Ya-Mei; Wu, Zhen; Fang, Mei-Juan; Qiu, Ying-Kun

2015-03-27

A new on-line comprehensive preparative two-dimensional normal-phase liquid chromatography × reversed-phase liquid chromatography (2D NPLC × RPLC) system was developed for the separation of complicated natural products. It was based on the use of a silica gel packed medium-pressure column as the first dimension and an ODS preparative HPLC column as the second dimension. The two dimensions were connected with normal-phase (NP) and reversed-phase (RP) enrichment units, involving a newly developed airflow assisted adsorption (AAA) technique. The instrument operation and the performance of this NPLC × RPLC separation method were illustrated by gram-scale isolation of ethanol extract from the roots of Peucedanum praeruptorum. In total, 19 compounds with high purity were obtained via automated multi-step preparative separation in a short period of time using this system, and their structures were comprehensively characterized by ESI-MS, (1)H NMR, and (13)C NMR. Including two new compounds, five isomers in two groups with identical HPLC and TLC retention values were also obtained and identified by 1D NMR and 2D NMR. This is the first report of an NPLC × RPLC system successfully applied in an on-line preparative process. This system not only solved the interfacing problem of mobile-phase immiscibility caused by NP and RP separation, it also exhibited apparent advantages in separation efficiency and sample treatment capacity compared with conventional methods. Copyright © 2015 Elsevier B.V. All rights reserved.

Plasma-gun-assisted field-reversed configuration formation in a conical θ-pinch

NASA Astrophysics Data System (ADS)

Weber, T. E.; Intrator, T. P.; Smith, R. J.

2015-04-01

Injection of plasma via an annular array of coaxial plasma guns during the pre-ionization phase of field-reversed configuration (FRC) formation is shown to catalyze the bulk ionization of a neutral gas prefill in the presence of a strong axial magnetic field and change the character of outward flux flow during field-reversal from a convective process to a much slower resistive diffusion process. This approach has been found to significantly improve FRC formation in a conical θ-pinch, resulting in a ˜350% increase in trapped flux at typical operating conditions, an expansion of accessible formation parameter space to lower densities and higher temperatures, and a reduction or elimination of several deleterious effects associated with the pre-ionization phase.

Recovery of maximally entangled quantum states by weak-measurement reversal

NASA Astrophysics Data System (ADS)

Maleki, Yusef; Zheltikov, Aleksei M.

2018-05-01

Maximal quantum entanglement provided by N00N states is a unique resource in the quest for the ultimate precision in physical measurements. Such states, however, are fragile and prone to decoherence. Even in weak-measurement schemes, as we demonstrate in this work, the phase super-resolution provided by N00N states is achieved at a cost of an N-fold enhancement of amplitude damping. Still, as the analysis presented here shows, a partial collapse of N00N states induced by weak measurements can be reversed, despite the dramatic, N-fold enhancement of amplitude damping, through appropriate reversal operations on the post-measurement state, enabling a full restoration of the Heisenberg-limit phase super-resolution of N00N states.

Changes in the planning target volume and liver volume dose based on the selected respiratory phase in respiratory-gated radiation therapy for a hepatocellular carcinoma

NASA Astrophysics Data System (ADS)

Lee, Jae-Seung; Im, In-Chul; Kang, Su-Man; Goo, Eun-Hoe; Baek, Seong-Min

2013-11-01

The aim of this study was to quantitatively analyze the changes in the planning target volume (PTV) and liver volume dose based on the respiratory phase to identify the optimal respiratory phase for respiratory-gated radiation therapy for a hepatocellular carcinoma (HCC). Based on the standardized procedure for respiratory-gated radiation therapy, we performed a 4-dimensional computed tomography simulation for 0 ˜ 90%, 30 ˜ 70%, and 40 ˜ 60% respiratory phases to assess the respiratory stability (S R ) and the defined PTV i for each respiratory phase i. A treatment plan was established, and the changes in the PTV i and dose volume of the liver were quantitatively analyzed. Most patients (91.5%) passed the respiratory stability test (S R = 0.111 ± 0.015). With standardized respiration training exercises, we were able to minimize the overall systematic error caused by irregular respiration. Furthermore, a quantitative analysis to identify the optimal respiratory phase revealed that when a short respiratory phase (40 ˜ 60%) was used, the changes in the PTV were concentrated inside the center line; thus, we were able to obtain both a PTV margin accounting for respiration and a uniform radiation dose within the PTV.

Spectroscopic characterizations of a mixed surfactant mesophase and its application in materials synthesis

NASA Astrophysics Data System (ADS)

Liu, Limin

A viscous lyotropic crystalline mesophase containing bis (2-ethylhexyl) sodium sulfosuccinate (AOT), alpha-phosphatidylcholine (lecithin), with comparable volume fractions of isooctane and water was characterized by Fourier-transform 31P and 1H nuclear magnetic resonance (NMR) spectroscopy. Shear alignment on the reverse hexagonal mesophase was reflected through both 31P NMR and 1H NMR spectra. A complicated 31P spectrum was observed as a result of superposition of chemical shifts according to the distribution of crystalline domains prior to shear. The initially disordered samples with polydomain structures became macroscopically aligned after Couette shear and the alignment retained for a long period of time. 31P NMR chemical shift anisotropy characteristics were used to elucidate orientation of the hexagonal phase. Interestingly, 1H NMR of the water, methyl and methylene groups exhibited spectral changes upon shear alignment closely corresponding with that of 31P NMR spectra. A reverse hexagonal to lamellar phase transition was manifested as an expanding of the expressed 31P NMR chemical shift anisotropy and an apparent reversal of the powder pattern with increasing water content and/or temperature. Correspondingly, 1H NMR spectra also experienced a spectral pattern transition as the water content or temperature was increased. These observations complement the findings of mesophase alignment obtained using small angle neutron scattering (SANS) and imply that 31P and 1H NMR spectroscopy can be used as probes to define microstructure and monitor orientation changes in this binary surfactant system. This is especially beneficial if these mesophases are used as templates for materials synthesis. The mesophase retains its alignment for extended periods allowing materials synthesis to be decoupled from the application of shear. Highly aligned string-like silica nanostructures were obtained through templated synthesis in the columnar hexagonal structure of the viscous lyotropic crystalline mesophase. A two-step procedure was used to first shear-align the surfactant mesophase, and then conduct synthesis under quiescent conditions in the mesophase. Polystyrene was post-grafted to the silica surface without disturbing its nanostring morphology. The coupling of materials synthesis in surfactant mesophases with processing techniques (e.g. extrusion) may result in functional materials, such as new catalyst support and membrane nanoarchitectures.

Pressure-induced reversible amorphization and an amorphous–amorphous transition in Ge2Sb2Te5 phase-change memory material

PubMed Central

Sun, Zhimei; Zhou, Jian; Pan, Yuanchun; Song, Zhitang; Mao, Ho-Kwang; Ahuja, Rajeev

2011-01-01

Ge2Sb2Te5 (GST) is a technologically very important phase-change material that is used in digital versatile disks-random access memory and is currently studied for the use in phase-change random access memory devices. This type of data storage is achieved by the fast reversible phase transition between amorphous and crystalline GST upon heat pulse. Here we report pressure-induced reversible crystalline-amorphous and polymorphic amorphous transitions in NaCl structured GST by ab initio molecular dynamics calculations. We have showed that the onset amorphization of GST starts at approximately 18 GPa and the system become completely random at approximately 22 GPa. This amorphous state has a cubic framework (c-amorphous) of sixfold coordinations. With further increasing pressure, the c-amorphous transforms to a high-density amorphous structure with trigonal framework (t-amorphous) and an average coordination number of eight. The pressure-induced amorphization is investigated to be due to large displacements of Te atoms for which weak Te–Te bonds exist or vacancies are nearby. Upon decompressing to ambient conditions, the original cubic crystalline structure is restored for c-amorphous, whereas t-amorphous transforms to another amorphous phase that is similar to the melt-quenched amorphous GST. PMID:21670255

Pressure-induced reversible amorphization and an amorphous-amorphous transition in Ge₂Sb₂Te₅ phase-change memory material.

PubMed

Sun, Zhimei; Zhou, Jian; Pan, Yuanchun; Song, Zhitang; Mao, Ho-Kwang; Ahuja, Rajeev

2011-06-28

Ge(2)Sb(2)Te(5) (GST) is a technologically very important phase-change material that is used in digital versatile disks-random access memory and is currently studied for the use in phase-change random access memory devices. This type of data storage is achieved by the fast reversible phase transition between amorphous and crystalline GST upon heat pulse. Here we report pressure-induced reversible crystalline-amorphous and polymorphic amorphous transitions in NaCl structured GST by ab initio molecular dynamics calculations. We have showed that the onset amorphization of GST starts at approximately 18 GPa and the system become completely random at approximately 22 GPa. This amorphous state has a cubic framework (c-amorphous) of sixfold coordinations. With further increasing pressure, the c-amorphous transforms to a high-density amorphous structure with trigonal framework (t-amorphous) and an average coordination number of eight. The pressure-induced amorphization is investigated to be due to large displacements of Te atoms for which weak Te-Te bonds exist or vacancies are nearby. Upon decompressing to ambient conditions, the original cubic crystalline structure is restored for c-amorphous, whereas t-amorphous transforms to another amorphous phase that is similar to the melt-quenched amorphous GST.

Simultaneous Stress and Field Control of Sustainable Switching of Ferroelectric Phases

PubMed Central

Finkel, P.; Staruch, M.; Amin, A.; Ahart, M.; Lofland, S.E.

2015-01-01

In ferroelectrics, manifestation of a strong electromechanical coupling is attributed to both engineered domain morphology and phase transformations. However, realization of large sustainable and reversible strains and polarization rotation has been limited by fatigue, nonlinearity and hysteresis losses. Here, we demonstrate that large strain and polarization rotation can be generated for over 40 × 106 cycles with little fatigue by realization of a reversible ferroelectric-ferroelectric phase transition in [011] cut Pb(In1/2Nb1/2)O3-Pb(Mg1/3Nb2/3)O3-PbTiO3 (PIN-PMN-PT) relaxor ferroelectric single crystal. Direct tuning of this effect through combination of stress and applied electric field, confirmed both macroscopically and microscopically with x-ray and Raman scattering, reveals the local symmetry while sweeping through the transition with a low applied electric field (<0.2 MV/m) under mechanical stress. The observed change in local symmetry as determined by x-ray scattering confirms a proposed polarization rotation mechanism corresponding to a transition between rhombohedral and orthorhombic phases. These results shed more light onto the nature of this reversible transformation between two ferroelectric phases and advance towards the development of a wide range of ferroic and multiferroic devices. PMID:26345729

One-pot synthesized functionalized mesoporous silica as a reversed-phase sorbent for solid-phase extraction of endocrine disrupting compounds in milks.

PubMed

Gañán, Judith; Morante-Zarcero, Sonia; Pérez-Quintanilla, Damián; Marina, María Luisa; Sierra, Isabel

2016-01-08

A new procedure for the determination of 12 naturally occurring hormones and some related synthetic chemicals in milk, commonly used as growth promoters in cattle, is reported. The method is based on liquid-liquid extraction followed by solid-phase extraction (SPE) using a new one-pot synthesized ordered mesoporous silica (of the SBA-15 type) functionalized with octadecyl groups (denoted as SBA-15-C18-CO) as reversed-phase sorbent. The analytes were eluted with methanol and then submitted to HPLC with diode array detection. Under optimal conditions, the method quantification limit for the analytes ranged from 0.023 to 1.36μg/mL. The sorbent affored the extraction of estrone, 17β-estradiol, estriol, progesterone, hexestrol, diethylstilbestrol, 4-androstene-3,17-dione, ethinylestradiol, 17α-methyltestosterone, nandrolone, prednisolone and testosterone with mean recoveries ranging from 72% to 105% (except for diethylstilbestrol) with RSD<11%. These results were comparable and, in some cases, even better than those obtained with other extraction methods, therefore SBA-15-C18-CO mesoporous silica possess a high potential as a reversed-phase sorbent for SPE of the 12 mentioned endocrine disrupting compounds in milk samples. Copyright © 2015 Elsevier B.V. All rights reserved.

The major volume /density/ of solid oxygen in equilibrium with vapor

NASA Technical Reports Server (NTRS)

Roder, H. M.

1979-01-01

Data from the literature on the molar volume of solid oxygen have been compiled and critically analyzed. A correlated and thermodynamically consistent set of molar volumes, including the volume changes at the various solid phase transitions, is presented. Evidence for the existence of a delta-solid phase is reviewed. Uncertainties in the data and in the recommended set of values are discussed.

Pore closure in zeolitic imidazolate frameworks under mechanical pressure† †Electronic supplementary information (ESI) available: Experimental details; synthetic procedures; supplementary data analyses; additional PXRD, thermal and elemental analyses as well as IR and 1H NMR spectroscopy data. See DOI: 10.1039/c7sc04952h

PubMed Central

Wharmby, Michael T.; Kieslich, Gregor; Hante, Inke; Schneemann, Andreas; Wu, Yue; Daisenberger, Dominik; Cheetham, Anthony K.

2018-01-01

We investigate the pressure-dependent mechanical behaviour of the zeolitic imidazolate framework ZIF-4 (M(im)2; M2+ = Co2+ or Zn2+, im– = imidazolate) with high pressure, synchrotron powder X-ray diffraction and mercury intrusion measurements. A displacive phase transition from a highly compressible open pore (op) phase with continuous porosity (space group Pbca, bulk modulus ∼1.4 GPa) to a closed pore (cp) phase with inaccessible porosity (space group P21/c, bulk modulus ∼3.3–4.9 GPa) is triggered by the application of mechanical pressure. Over the course of the transitions, both ZIF-4 materials contract by about 20% in volume. However, the threshold pressure, the reversibility and the immediate repeatability of the phase transition depend on the metal cation. ZIF-4(Zn) undergoes the op–cp phase transition at a hydrostatic mechanical pressure of only 28 MPa, while ZIF-4(Co) requires about 50 MPa to initiate the transition. Interestingly, ZIF-4(Co) fully returns to the op phase after decompression, whereas ZIF-4(Zn) remains in the cp phase after pressure release and requires subsequent heating to switch back to the op phase. These variations in high pressure behaviour can be rationalised on the basis of the different electron configurations of the respective M2+ ions (3d10 for Zn2+ and 3d7 for Co2+). Our results present the first examples of op–cp phase transitions (i.e. breathing transitions) of ZIFs driven by mechanical pressure and suggest potential applications of these functional materials as shock absorbers, nanodampers, or in mechanocalorics. PMID:29675212

Measurement of steep aspheric surfaces using improved two-wavelength phase-shifting interferometer

NASA Astrophysics Data System (ADS)

Zhang, Liqiong; Wang, Shaopu; Hu, Yao; Hao, Qun

2017-10-01

Optical components with aspheric surfaces can improve the imaging quality of optical systems, and also provide extra advantages such as lighter weight, smaller volume and simper structure. In order to satisfy these performance requirements, the surface error of aspheric surfaces, especially high departure aspheric surfaces must be measured accurately and conveniently. The major obstacle of traditional null-interferometry for aspheric surface under test is that specific and complex null optics need to be designed to fully compensate for the normal aberration of the aspheric surface under test. However, non-null interferometry partially compensating for the aspheric normal aberration can test aspheric surfaces without specific null optics. In this work, a novel non-null test approach of measuring the deviation between aspheric surfaces and the best reference sphere by using improved two-wavelength phase shifting interferometer is described. With the help of the calibration based on reverse iteration optimization, we can effectively remove the retrace error and thus improve the accuracy. Simulation results demonstrate that this method can measure the aspheric surface with the departure of over tens of microns from the best reference sphere, which introduces approximately 500λ of wavefront aberration at the detector.

Inverse Resistance Change Cr2Ge2Te6-Based PCRAM Enabling Ultralow-Energy Amorphization.

PubMed

Hatayama, Shogo; Sutou, Yuji; Shindo, Satoshi; Saito, Yuta; Song, Yun-Heub; Ando, Daisuke; Koike, Junichi

2018-01-24

Phase-change random access memory (PCRAM) has attracted much attention for next-generation nonvolatile memory that can replace flash memory and can be used for storage-class memory. Generally, PCRAM relies on the change in the electrical resistance of a phase-change material between high-resistance amorphous (reset) and low-resistance crystalline (set) states. Herein, we present an inverse resistance change PCRAM with Cr 2 Ge 2 Te 6 (CrGT) that shows a high-resistance crystalline reset state and a low-resistance amorphous set state. The inverse resistance change was found to be due to a drastic decrease in the carrier density upon crystallization, which causes a large increase in contact resistivity between CrGT and the electrode. The CrGT memory cell was demonstrated to show fast reversible resistance switching with a much lower operating energy for amorphization than a Ge 2 Sb 2 Te 5 memory cell. This low operating energy in CrGT should be due to a small programmed amorphous volume, which can be realized by a high-resistance crystalline matrix and a dominant contact resistance. Simultaneously, CrGT can break the trade-off relationship between the crystallization temperature and operating speed.

Bioinspired Hierarchical Nanofibrous Silver-Nanoparticle/Anatase-Rutile-Titania Composite as an Anode Material for Lithium-Ion Batteries.

PubMed

Luo, Yan; Li, Jiao; Huang, Jianguo

2016-11-29

A new bioinspired hierarchical nanofibrous silver-nanoparticle/anatase-rutile-titania (Ag-NP/A-R-titania) composite was fabricated by employing a natural cellulose substance (e.g., commercial laboratory cellulose filter paper) as the structural scaffold template, which was composed of anatase-phase titania (A-titania) nanotubes with rutile-phase titania (R-titania) nanoneedles grown on the surfaces and further silver nanoparticles (AgNPs) immobilized thereon. As it was employed as an anode material for lithium-ion batteries (LIBs), high reversible capacity, enhanced rate performance, and excellent cycling stability were achieved as compared with those of the corresponding cellulose-substance-derived nanotubular A-titania, R-titania, heterogeneous anatase/rutile titania (A-R-titania) composite, and commercial P25 powder. This benefited from its unique porous cross-linked three-dimensional structure inherited from the initial cellulose substance scaffold, which enhances the sufficient electrode/electrolyte contact, relieves the severe volume change upon cycling, and improves the amount of lithium-ion storage; moreover, the high loading content of the silver component in the composite improves the electrical conductivity of the electrode. The structural integrity of the composite was maintained upon long-term charge/discharge cycling, indicating its significant stability.

Effects of inhalational anaesthesia with low tidal volume ventilation on end-tidal sevoflurane and carbon dioxide concentrations: prospective randomized study.

PubMed

de la Matta-Martín, M; López-Herrera, D; Luis-Navarro, J C; López-Romero, J L

2014-02-01

We investigated how ventilation with low tidal volumes affects the pharmacokinetics of sevoflurane uptake during the first minutes of inhaled anaesthesia. Forty-eight patients scheduled for lung resection were randomly assigned to three groups. Patients in group 1, 2 and 3 received 3% sevoflurane for 3 min via face mask and controlled ventilation with a tidal volume of 2.2, 8 and 12 ml kg(-1), respectively (Phase 1). After tracheal intubation (Phase 2), 3% sevoflurane was supplied for 2 min using a tidal volume of 8 ml kg(-1) (Phase 3). End-tidal sevoflurane concentrations were significantly higher in group 1 at the end of phase 1 and lower at the end of phase 2 than in the other groups as follows: median of 2.5%, 2.2% and 2.3% in phase 1 for groups 1, 2 and 3, respectively (P<0.001); and 1.7%, 2.1% and 2.0% in phase 2, respectively (P<0.001). End-tidal carbon dioxide values in group 1 were significantly lower at the end of phase 1 and higher at the end of phase 2 than in the other groups as follows: median of 16.5, 31 and 29.5 mm Hg in phase 1 for groups 1, 2 and 3, respectively (P<0.001); and 46.2, 36 and 33.5 mm Hg in phase 2, respectively (P<0.001). When sevoflurane is administered with tidal volume approximating the airway dead space volume, end-tidal sevoflurane and end-tidal carbon dioxide may not correctly reflect the concentration of these gases in the alveoli, leading to misinterpretation of expired gas data. Copyright © 2013 Sociedad Española de Anestesiología, Reanimación y Terapéutica del Dolor. Published by Elsevier España. All rights reserved.

Reversible temperature regulation of electrical and thermal conductivity using liquid–solid phase transitions

PubMed Central

Zheng, Ruiting; Gao, Jinwei; Wang, Jianjian; Chen, Gang

2011-01-01

Reversible temperature tuning of electrical and thermal conductivities of materials is of interest for many applications, including seasonal regulation of building temperature, thermal storage and sensors. Here we introduce a general strategy to achieve large contrasts in electrical and thermal conductivities using first-order phase transitions in percolated composite materials. Internal stress generated during a phase transition modulates the electrical and thermal contact resistances, leading to large contrasts in the electrical and thermal conductivities at the phase transition temperature. With graphite/hexadecane suspensions, the electrical conductivity changes 2 orders of magnitude and the thermal conductivity varies up to 3.2 times near 18 °C. The generality of the approach is also demonstrated in other materials such as graphite/water and carbon nanotube/hexadecane suspensions. PMID:21505445

Reversible temperature regulation of electrical and thermal conductivity using liquid-solid phase transitions.

PubMed

Zheng, Ruiting; Gao, Jinwei; Wang, Jianjian; Chen, Gang

2011-01-01

Reversible temperature tuning of electrical and thermal conductivities of materials is of interest for many applications, including seasonal regulation of building temperature, thermal storage and sensors. Here we introduce a general strategy to achieve large contrasts in electrical and thermal conductivities using first-order phase transitions in percolated composite materials. Internal stress generated during a phase transition modulates the electrical and thermal contact resistances, leading to large contrasts in the electrical and thermal conductivities at the phase transition temperature. With graphite/hexadecane suspensions, the electrical conductivity changes 2 orders of magnitude and the thermal conductivity varies up to 3.2 times near 18 °C. The generality of the approach is also demonstrated in other materials such as graphite/water and carbon nanotube/hexadecane suspensions.

Time-reversal and rotation symmetry breaking superconductivity in Dirac materials

NASA Astrophysics Data System (ADS)

Chirolli, Luca; de Juan, Fernando; Guinea, Francisco

2017-05-01

We consider mixed symmetry superconducting phases in Dirac materials in the odd-parity channel, where pseudoscalar and vector order parameters can coexist due to their similar critical temperatures when attractive interactions are of a finite range. We show that the coupling of these order parameters to unordered magnetic dopants favors the condensation of time-reversal symmetry breaking (TRSB) phases, characterized by a condensate magnetization, rotation symmetry breaking, and simultaneous ordering of the dopant moments. We find a rich phase diagram of mixed TRSB phases characterized by peculiar bulk quasiparticles, with Weyl nodes and nodal lines, and distinctive surface states. These findings are consistent with recent experiments on NbxBi2Se3 that report evidence of point nodes, nematicity, and TRSB superconductivity induced by Nb magnetic moments.

Sign reversal of transformation entropy change in Co{sub 2}Cr(Ga,Si) shape memory alloys

DOE Office of Scientific and Technical Information (OSTI.GOV)

Xu, Xiao, E-mail: xu@material.tohoku.ac.jp; Omori, Toshihiro; Kainuma, Ryosuke

2015-11-02

In situ X-ray diffraction (XRD) measurements and compression tests were performed on Co{sub 2}Cr(Ga,Si) shape memory alloys. The reentrant martensitic transformation behavior was directly observed during the in situ XRD measurements. The high-temperature parent phase and low-temperature reentrant parent phase were found to have a continuous temperature dependence of lattice parameter, therefore suggesting that they are the same phase in nature. Moreover, compression tests were performed on a parent-phase single crystal sample; an evolution from normal to inverse temperature dependence of critical stress for martensitic transformation was directly observed. Based on the Clausius-Clapeyron analysis, a sign reversal of entropy changemore » can be expected on the same alloy.« less