Resolution Of Phases Research Articles

Synthesis and evaluation of polymeric continuous bed (monolithic) reversed-phase gradient stationary phases for capillary liquid chromatography and capillary electrochromatography

There is a demand of novel high resolution separation media for separation of complex mixtures, particularly biological samples. One of the most flexible techniques for development of new separation media currently is synthesis of the continuous bed (monolithic) stationary phases. In this study the capillary format gradient stationary phases were formed using continuous bed (monolith) polymerization in situ. Different reversed-phase stationary phase gradients were tailored and their resolution using capillary liquid chromatography and capillary electrochromatography at isocratic mobile phase conditions was evaluated. It is demonstrated, that efficiency and resolution of the gradient stationary phases can be substantially increased comparing to the common (isotropic) stationary phases. The proposed formation approach of the gradient stationary phase is reproducible and compatible with the capillary format or microchip format separations. It can be easily automated for the separation optimizations or mass production of the capillary columns or chips.

Genome-wide definitive haplotypes determined using a collection of complete hydatidiform moles

We present genome-wide definitive haplotypes, determined using a collection of 74 Japanese complete hydatidiform moles, each carrying a genome derived from a single sperm. The haplotypes incorporate 281,439 common SNPs, genotyped with a high throughput array-based oligonucleotide hybridization technique. Comparison of haplotypes inferred from pseudoindividuals (constructed from randomized mole pairs) with those of moles showed some switch errors in resolution of phases by the computational inference method. The effects of these errors on local haplotype structure and selection of tag SNPs are discussed. We also show that definitive haplotypes of moles may be useful for elucidation of long-range haplotype structure, and should be more effective for detecting extended haplotype homozygosity indicative of positive selection.

Simulation analysis of the ability of different types of multi-electrodes to increase selectivity of detection and to reduce cross-talk

Selectivity of different one- and two-dimensional multi-electrodes and their ability to reduce cross-talk were analyzed. Signals from an individual motor unit (MU) were calculated as a single convolution of intracellular action potential (IAP) first temporal derivative and spatially filtered MU impulse response. It was shown that the uptake area (irrespective of the way it was defined) could not characterize electrode properties reliably because its estimate depended on the source parameters. Due to the different decline of individual phases of MU signals with depth, electrode should provide higher spatial and temporal resolution of the main phases for better selectivity and greater suppression of the terminal phases for cross-talk reduction. A two-dimensional normal double differentiating (NDD) electrode provided almost the same or slightly lower selectivity but weaker reduction of cross-talk than a longitudinal double differentiating (LDD) electrode. A transversal double differentiating (TDD) electrode provided a lower selectivity and weaker reduction of cross-talk than a LDD electrode. A new, BiTDD multi-electrode (performing difference between signals detected by two TDD electrodes) provided the best selectivity and reduction of cross-talk. To obtain the smallest cross-talk, a BiTDD electrode should be positioned above the end-plate region, while LDD, TDD, or NDD electrodes—above the ends of muscle that produced it. Signal differentiation improved selectivity but increased cross-talk.

Inductively coupled plasma mass spectrometry with on-line leaching: a method to assess the mobility and fractionation of elements.

A new technique has been developed to assess the mobility and site of specific elements in complex natural materials such as rocks. Concentration profiles during leaching were obtained by pumping reagents (water, 1% HNO3, 10% HNO3, 30% HNO3), either continuously or with flow injection, through a microcolumn of sample while continuously monitoring analyte signals by inductively coupled plasma mass spectrometry (ICPMS). Compared to batch extraction procedures normally used, the approach involves minimal sample preparation and reduced contamination since the leaching is performed in a closed system. Continuous on-line monitoring also allows a greater resolution of the various phases reacting with given reagent. Compared to continuous leaching, flow injection increased the resolution of the various phases using discrete injections of reagents while reducing reagent consumption and minimizing etching of the MS interface. Furthermore, sensitivity was preserved by injecting into air instead of an aqueous carrier. Whether in the continuous or flow injection modes, the proposed approach provides real-time data on what phases are breaking down and what metals are released. It can therefore be used to design effective leaching strategies and to trace isotopic compositions. However, the resulting spectra are complex and the correct determination of some elements requires high-resolution ICPMS.

Characterization of Phase Separation in Mixed Surfactant Films by Liquid Tapping Mode Atomic Force Microscopy

Two-dimensional phase separation in Langmuir films comprising mixtures of charged and neutral surfactants transferred onto graphite was observed by liquid tapping mode atomic force microscopy (LTM-AFM). Resolution of the different phases was based on the difference in surface charge density, which resulted in a difference in tip−sample electrostatic interaction and a consequent apparent difference in height despite the identical tail lengths of the two surfactants. Exploration of the effects of temperature and subphase ionic strength showed that phase separation tended to occur at low temperature and high ionic strength, while at high temperature and low ionic strength the monolayer was homogeneous. The method offers a sensitive new approach to identifying distinct phases in Langmuir films.

Hierarchical modeling and evaluation of phased-mission systems

This paper proposes a hierarchical and modular methodology for modeling and evaluation of phased-mission systems in which phases have constant predetermined duration, and where missions may evolve dynamically selecting the next phase to be performed according to the system state. A 2-level modeling is proposed: the higher one models the mission itself; the lower one models the various phases. A separate 'modeling and resolution of phases' and 'dependencies among phases' are considered. This methodology is applied using an example of a space application. This method is compared with previous models. The advantages of this approach are in the great flexibility, easy applicability and reusability of the defined models. It permits: (1) obtaining information on the overall behavior of the system; and (2) focusing on each single phase to detect system dependability bottlenecks. The explicit modeling of the phase changes: (1) is a neat and easily understandable representation of the interphase dependencies; and (2) allows a straightforward modeling of the mission-profile dynamic selection. General purpose tools available to the reliability community can easily manage the computational complexity of the analysis.

The Pseudo-Atom Approximation in Direct Phase Determination of Protein Structures.

Abstract In principle, the availability of high-resolution micrographs in electron crystallography is a direct solution of the phase problem that has been used to great advantage for the study of proteins. However, as the resolution of the determination increases, the Fourier transform of the micrograph becomes a less accurate phase source. Hence, alternative direct methods for phase determination have been evaluated, if only to extend the resolution of most reliable lower resolution phases to the limit of the electron diffraction pattern. The first demonstration of its feasibility was published in a study of bacteriorhodopsin extending 15 Å image phases to beyond 3 Å by maximum entropy and likelihood procedures i. Later studies demonstrated that convolutional methods also can be effective. In protein crystallography, there is always an interest in carrying out a true ab initio determinations, if only because of the challenge to traditional direct methods that become statistically less reliable as the number of atoms in the unit cell increases.

Slide-based laser scanning cytometry.

To show that laser scanning cytometry (LSCM) can provide data equivalent to flow cytometry (FCM) data and furnish a number of benefits, including cell relocation for visualization and several additional measurement features that may make it more suitable than FCM for pathology laboratories. A laser scanning cytometer, the LSC, was developed. Several instruments, at sites in the United States and Japan during the last two years, provided data characterizing the instrument and its usefulness. Data describing the sensitivity, precision, accuracy, utility of added measurement features and cell relocation capabilities of the LSC are presented. The data illustrate the applicability of the LSC to multiparameter DNA ploidy studies, resolution of phases of the cell cycle and cytogenetics. Because it is microscope based and measures cells on a slide, not in a flow chamber; records the position of each cell on the slide; and has higher resolution, LSCM provides a number of benefits that may make it more suitable than FCM for pathology laboratories.

Modulated Structures Induced by Phase Transformations

Abstract Modulated structures can be found in organic, inorganic and even quasicrystalline structures. They are generally detected by diffraction from the presence of satellites surrounding the Bragg reflections. Their positions may vary continuously with temperature or pressure so that the phase can be considered as incommensurately modulated. Incommensurate phases usually transform to a periodic high symmetry phase by increasing temperature and to a commensurate lock-in phase by lowering the temperature. Their domain of stability varies with temperature, pressure and with the type of compound. Examples have been identified where the interval of equilibrium vary from a few tenths to a few hundreds of degrees. Recent progress in the field of incommensurate structure analysis has been greatly favoured by the superspace group approach which is now almost exclusively applied. In many cases, the resolution of the modulated phases by diffraction methods has contributed towards the understanding of the phase ch...

Wave Analysis of the Charge Density Wave Dynamics in the Molecular Conductor (Perylene)2Pt(mnt)2 (mnt=maleonitriledithiolate)

A new method based on trie wavelet analysis of trie voltage oscillations generated above threshold electric field for depmning of trie charge density wave (CDW) in trie molecular conductor (Perylene)2Pt(mnt)2 (mnt = maleomtriledithiolate) bas been developed. This analy- sis method permits a better time resolution of trie frequencies and phases involved in trie CDW motion than that allowed by conventional Fourier analysis. Trie results are discussed in relation with current models for CDW deformations.

Kinetic resolution of different recovery phases of photoinhibited photosystem II in cold‐acclimated and non‐acclimated spinach leaves

Leaf discs from spinach were exposed to a photon flux density of 1250 μmol m−2s−1 at 5°C for 2 or 3 h in ambient air. Photoinhibition of photosystem II (PS II) was measured by means of chlorophyll fluorescence. Recovery of photosystem II was followed at 6°C and 20°C in low light or darkness for periods up to 12 h.The experimental setup allowed kinetic resolution of different phases of recovery. The experiments revealed a temperature dependent dark recovery phase and two distinct light‐ and temperature dependent phases: (1) A relatively fast, light dependent recovery phase occurred in parallel with partial recovery of basic fluorescence at 6°C and 20°C. A population of PS II centers with very slow fluorescence induction kinetics, which had accumulated during photoinhibition treatment, disappeared during this phase. This fast recovery phase is proposed to represent reactivation of photoinhibited PS II, without dissassembly or incorporation of new D1‐protein. (2) A relatively slow light‐dependent recovery phase took place at 20°C, but not at 6°C. In the presence of the chloroplast translation inhibitor streptomycin, part of the 2nd phase was inhibited. This phase is proposed to involve assembly of new Photosystem II centers, which is partly dependent on de novo synthesis of D1‐reaction center protein, but presumably is also using a preexisting pool of D1‐protein. Cold acclimation of the leaves resulted in a decreased sensitivity for photoinhibition of photosystem II. Recovery of photoinhibited photosystem II at 6°C of the cold‐acclimated leaves was faster than in non‐acclimated leaves, but this effect can be ascribed to diminished photoinhibitory damage.

Kinetic resolution of different recovery phases of photoinhibited photosystem II in cold-acclimated and non-acclimated spinach leaves

Kinetic resolution of different recovery phases of photoinhibited photosystem II in cold-acclimated and non-acclimated spinach leaves

Measurement of glycated protein by a rapid and specific method for absolute quantification of lysine-bound glucose.

We modified the liquid-chromatographic assay of Schleicher and Wieland (J Clin Chem Clin Biochem 1981; 19:81-7) for measuring lysine-bound glucose in serum proteins, increasing its performance and practicality. After precipitating serum proteins from 10- to 50-microL samples with ethanol (700 mL/L) and hydrolyzing these in 6 mol/L HCl, we inject 20 microL of the diluted hydrolysate directly into the chromatograph, which consists of an acid-resistant C18 precolumn combined with a high-resolution C18 main column. The eluent is 3.5 mmol/L H3PO4 solution containing 30 mL of acetonitrile per liter. These modifications increase sensitivity, provide excellent resolution and longevity of stationary phases, shorten assay times to 15 to 20 min, and are suited for automation. The assay is highly sensitive and highly specific, quantifying nanomoles of lysine-bound glucose per milligram of protein. A precision (CV) of 5.1% is achievable at physiological and supra-physiological glucose concentrations, and analytical recovery is 99%. This inexpensive method has been applied to serum albumin, bulk serum proteins, and preparations of low-density lipoproteins and immunoglobulins.

Amberlite XAD-4 as a Stationary Phase for Preparative Liquid Chromatography in a Radially Compressed Column

Abstract Amberlite XAD-4, a nonpolar adsorbent with a particle size of 62 to 177 μm, was packed into 58 mm i.d. x 294 mm columns and radially compressed in the Waters Prep 500 preparative liquid chromatograph. Efficiency, loading capacity (multigram samples), resolution, recovery, and types of mobile phases were major parameters studied. Since XAD-4 is chemically inert mixed solvent and pH control from 1 to 13 can be successfully used in the mobile phase. Separations illustrating these advantages and the scope of the 58 mm i.d. column are described.

Array analysis of PKP phases and their precursors

Some problems in the interpretation of core phases and their precursor have been studied by the analysis of PKP phases, recorded at the NORSAR array. A limited number of SKP phases has been used as an aid in the analysis. Processing techniques, suitable for the resolution of core phases in slowness and time are discussed, in particular the usefulness and limitations of the Vespa process for this purpose. In the various techniques the effect of the structure under the array should be taken into account. The methods used reveal the refractions and reflections at the inner core boundary and also to some extent the more complicated character of the PKP precursor. Several representative examples of interpretation of the precursors are viewed in the light of the observational results. The analysis is limited to Δ > 136°. In this range the results indicate that diffraction effects may play a more important role in the generation of the precursors than is generally assumed.

On the use of the tangent formula to extend the resolution of protein phases

On the use of the tangent formula to extend the resolution of protein phases

Kinetics of the precipitation hardening of annealed technically pure iron

1. Even when it has been cooled slowly to room temperature, annealed rimmed technically pure iron is sub ect to precipitation hardening (age hardening). After this metal has been held at room temperature for 20.000 h, or at 150°C for 300 h, the coercive force is almost doubled. 2. The coagulation of particles of the precipitated phases causes the coercive force of annealed iron to decrease to the initial value when it is heated at temperatures up to 350°C. When this is done however, particularly when the heating is for long periods, partial resolution of the phases takes place, and for this reason further heating at 150°C for 50 h again greatly increases the coercive force. Heating articles previously held at room temperature for 20,000 h, for short periods at 150–350°C causes a recovery process, and further heating for 50 h at 150°C also greatly increases the coercive force. 3. Holding annealed iron at about 250°C for 4 h stabilizes it, since in this case there is very little re-solution of phases. The coercive force proves to be about the same as after annealing. The conditions for this stabilizing treatment should, however, be found separately for each batch of iron. 4. The processes of precipitation and solution of phases in annealed iron are most rapid in the grain boundaries.