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Sample records for reverse schreinemakers method

  1. Rediscovering Schreinemakers' Theorem.

    ERIC Educational Resources Information Center

    Bathurst, Bruce

    1983-01-01

    Schreinemakers' theorem (arrangement of curves around an invariant point), derived from La Chatelier's principle, can be rediscovered by students asked to use the principle when solving a natural problem such as "How does diluting a mineral/fluid alter shape of a pressure/temperature diagram?" Background information and instructional…

  2. A composite phase diagram of structure H hydrates using Schreinemakers' geometric approach

    USGS Publications Warehouse

    Mehta, A.P.; Makogon, T.Y.; Burruss, R.C.; Wendlandt, R.F.; Sloan, E.D.

    1996-01-01

    A composite phase diagram is presented for Structure H (sH) clathrate hydrates. In this work, we derived the reactions occurring among the various phases along each four-phase (Ice/Liquid water, liquid hydrocarbon, vapor, and hydrate) equilibrium line. A powerful method (though seldom used in chemical engineering) for multicomponent equilibria developed by Schreinemakers is applied to determine the relative location of all quadruple (four-phase) lines emanating from three quintuple (five-phase) points. Experimental evidence validating the approximate phase diagram is also provided. The use of Schreinemakers' rules for the development of the phase diagram is novel for hydrates, but these rules may be extended to resolve the phase space of other more complex systems commonly encountered in chemical engineering.

  3. Subroutine bundls, a fortran IV program to determine schreinemakers bundles

    NASA Astrophysics Data System (ADS)

    Linde, J.; Andrew, A. S.

    Given an entire set of relevant balanced equations, BUNDLS and associated subroutines select all invariant points and order univariant lines around these points. Invariant points are formed by taking every set of m absent phases from each reaction. All revelant univariant lines are ordered around each invariant point by a direct application of the rules of Schreinemakers. The program also calculates true angular values for PT, P-μ x1 or μ y-μ x diagrams.

  4. A time-reversal lattice Boltzmann method

    NASA Astrophysics Data System (ADS)

    Vergnault, E.; Malaspinas, O.; Sagaut, P.

    2011-09-01

    In this paper we address the time-reversed simulation of viscous flows by the lattice Boltzmann method (LB). The theoretical derivation of the reversed LB from the Boltzmann equation is detailed, and the method implemented for weakly compressible flows using the D2Q9 scheme. The implementation of boundary conditions is also discussed. The accuracy and stability are illustrated by four test cases, namely the propagation of an acoustic wave in a medium at rest and in an uniform mean flow, the Taylor-Green vortex decay and the vortex pair-wall collision.

  5. Application of the Conditioned Reverse Path Method

    NASA Astrophysics Data System (ADS)

    Garibaldi, L.

    2003-01-01

    The conditioned reverse path (CRP) method has been applied to identify the non-linear behaviour of a beam-like structure, both ends clamped, one with a non-linear stiffness characteristic. The same method was already successfully applied to the identification of another COST benchmark, known as the VTT non-linear suspension. This benchmark shows the enhancements of the technique, now applied to a real multi-degree-of-freedom (mdof) system, with single-point excitation subject to bending modes; the non-linearity is acting on one end of the beam in terms of displacements. The CRP technique is based on the construction of a hierarchy of uncorrelated response components in the frequency domain, allowing the estimation of the coefficients of the non-linearities away from the location of the applied excitation and also the identification of the linear dynamic compliance matrix when the number of excitations is smaller than the number of response locations.

  6. [Historical survey of modern reversible contraceptive methods].

    PubMed

    Mbabajende, V

    1986-04-01

    were flexible and capable of returning to their original shape after insertion. The Lippes loop was the 1st highly successful IUD. Bioactive IUDs containing copper were developed in the 1970s. Research is underway to develop IUDs which will resist expulsion, reduce bleeding, be more appropriate for multiparas, and last longer. IUDs are used to treat intrauterine adhesions as well as for contraception. A gummy substance used to block the cervix was described in Egypt in 1850 BC. Japanese and Chinese prostitutes of antiquity placed oiled bamboo paper at the cervical opening for contraception. Diaphragms and cervical caps were developed in the 19th century in Germany. Large scale production became possible after 1880 with the development of better, more durable, and cheaper rubber. An Egyptian writing in 3500 BC began the study of spermicides. Numerous substances such as lemon juice and honey have been placed in the vagina to avoid pregnancy. Such substances are available to all women and some were reasonably effective. Current research is directed toward development of spermicides which will also prevent sexually transmitted diseases. The 1st condoms were made of animal skins by an English physician to prevent transmission of venereal diseases. Rubber condoms appeared in the early 20th century and are widely utilized in some family planning programs. Pregnancy vaccines and a reversible hormonal method for men are among methods under development.

  7. Linear Multistep Methods for Integrating Reversible Differential Equations

    NASA Astrophysics Data System (ADS)

    Evans, N. Wyn; Tremaine, Scott

    1999-10-01

    This paper studies multistep methods for the integration of reversible dynamical systems, with particular emphasis on the planar Kepler problem. It has previously been shown by Cano & Sanz-Serna that reversible linear multisteps for first-order differential equations are generally unstable. Here we report on a subset of these methods-the zero-growth methods-that evade these instabilities. We provide an algorithm for identifying these rare methods. We find and study all zero-growth, reversible multisteps with six or fewer steps. This select group includes two well-known second-order multisteps (the trapezoidal and explicit midpoint methods), as well as three new fourth-order multisteps-one of which is explicit. Variable time steps can be readily implemented without spoiling the reversibility. Tests on Keplerian orbits show that these new reversible multisteps work well on orbits with low or moderate eccentricity, although at least 100 steps per radian are required for stability.

  8. Method for distinguishing multiple targets using time-reversal acoustics

    DOEpatents

    Berryman, James G.

    2004-06-29

    A method for distinguishing multiple targets using time-reversal acoustics. Time-reversal acoustics uses an iterative process to determine the optimum signal for locating a strongly reflecting target in a cluttered environment. An acoustic array sends a signal into a medium, and then receives the returned/reflected signal. This returned/reflected signal is then time-reversed and sent back into the medium again, and again, until the signal being sent and received is no longer changing. At that point, the array has isolated the largest eigenvalue/eigenvector combination and has effectively determined the location of a single target in the medium (the one that is most strongly reflecting). After the largest eigenvalue/eigenvector combination has been determined, to determine the location of other targets, instead of sending back the same signals, the method sends back these time reversed signals, but half of them will also be reversed in sign. There are various possibilities for choosing which half to do sign reversal. The most obvious choice is to reverse every other one in a linear array, or as in a checkerboard pattern in 2D. Then, a new send/receive, send-time reversed/receive iteration can proceed. Often, the first iteration in this sequence will be close to the desired signal from a second target. In some cases, orthogonalization procedures must be implemented to assure the returned signals are in fact orthogonal to the first eigenvector found.

  9. Reverse radiance: a fast accurate method for determining luminance

    NASA Astrophysics Data System (ADS)

    Moore, Kenneth E.; Rykowski, Ronald F.; Gangadhara, Sanjay

    2012-10-01

    Reverse ray tracing from a region of interest backward to the source has long been proposed as an efficient method of determining luminous flux. The idea is to trace rays only from where the final flux needs to be known back to the source, rather than tracing in the forward direction from the source outward to see where the light goes. Once the reverse ray reaches the source, the radiance the equivalent forward ray would have represented is determined and the resulting flux computed. Although reverse ray tracing is conceptually simple, the method critically depends upon an accurate source model in both the near and far field. An overly simplified source model, such as an ideal Lambertian surface substantially detracts from the accuracy and thus benefit of the method. This paper will introduce an improved method of reverse ray tracing that we call Reverse Radiance that avoids assumptions about the source properties. The new method uses measured data from a Source Imaging Goniometer (SIG) that simultaneously measures near and far field luminous data. Incorporating this data into a fast reverse ray tracing integration method yields fast, accurate data for a wide variety of illumination problems.

  10. An improved acquisition scheme for the reverse projection method

    NASA Astrophysics Data System (ADS)

    Wei, C.; Wu, Z.; Wali, F.; Luo, R.; Tian, Y.

    2017-06-01

    In recent years, efforts have been made on the information extraction method in x-ray grating-based phase contrast imaging. Among them, the reverse projection method proposed by P.P. Zhu in 2010 features as a fast, low-dose method to extract information without stepping the gratings. It enables to extend the phase contrast imaging system to the vivo studies. However, it has strict requirement on the system stability and the source stability. In this manuscript, an improved acquisition scheme has been proposed using a staggered grating making the reverse projection method more efficient with a lower requirement of the system and source stability.

  11. Machinery alignment tables: Face-OD and reverse indicator methods

    SciTech Connect

    Buck, G.S.

    1984-01-01

    Many alignment techniques are too complex for practical use, and guessing never provides the needed precision. The face-OD (face-rim) and reverse indicator methods are the two most popular techniques experienced millwrights use, but both methods require time-consuming calculations. These tables replace the graphs, formulas, and calculations used to determine shim requirements. Contents: Face-OD method and reverse indicator method: Setting up Data forms. Equations and calculations. Examples. Alignment Tolerances. Errors in taking data. Typical alignment tolerances. Indicator sag. Cause of indicator sag. Correction of indicator sag. Typical values of indicator sag. Hot alignment. References.

  12. A comparison of reverse osmosis membrane cleaning methods

    SciTech Connect

    Siler, J.L.

    1992-01-09

    Testing was conducted at TNX to evaluate the reverse osmosis (RO) cleaning methods in use at the F/H Effluent Treatment Facility (ETF). The present ETF membrane cleaning protocol involves a low-pressure-no-permeation method using NAOH. This work has examined the effectiveness of the present ETF method, due to the lack of improvement following the cleanings sometimes observed. This study has evaluated both low pressure (15--20 psi with no permeation) and high pressure (200 psi with permeation) cleaning methods with sequential cleanings using NAOH and Filmtec Alkaline Cleaner. The importance of the cleaning sequence with these two chemicals was also examined.

  13. A comparison of reverse osmosis membrane cleaning methods

    SciTech Connect

    Siler, J.L.

    1992-01-09

    Testing was conducted at TNX to evaluate the reverse osmosis (RO) cleaning methods in use at the F/H Effluent Treatment Facility (ETF). The present ETF membrane cleaning protocol involves a low-pressure-no-permeation method using NAOH. This work has examined the effectiveness of the present ETF method, due to the lack of improvement following the cleanings sometimes observed. This study has evaluated both low pressure (15--20 psi with no permeation) and high pressure (200 psi with permeation) cleaning methods with sequential cleanings using NAOH and Filmtec Alkaline Cleaner. The importance of the cleaning sequence with these two chemicals was also examined.

  14. Acoustic imaging with time reversal methods: From medicine to NDT

    NASA Astrophysics Data System (ADS)

    Fink, Mathias

    2015-03-01

    This talk will present an overview of the research conducted on ultrasonic time-reversal methods applied to biomedical imaging and to non-destructive testing. We will first describe iterative time-reversal techniques that allow both focusing ultrasonic waves on reflectors in tissues (kidney stones, micro-calcifications, contrast agents) or on flaws in solid materials. We will also show that time-reversal focusing does not need the presence of bright reflectors but it can be achieved only from the speckle noise generated by random distributions of non-resolved scatterers. We will describe the applications of this concept to correct distortions and aberrations in ultrasonic imaging and in NDT. In the second part of the talk we will describe the concept of time-reversal processors to get ultrafast ultrasonic images with typical frame rates of order of 10.000 F/s. It is the field of ultrafast ultrasonic imaging that has plenty medical applications and can be of great interest in NDT. We will describe some applications in the biomedical domain: Quantitative Elasticity imaging of tissues by following shear wave propagation to improve cancer detection and Ultrafast Doppler imaging that allows ultrasonic functional imaging.

  15. Reversals.

    ERIC Educational Resources Information Center

    National Center on Educational Media and Materials for the Handicapped, Columbus, OH.

    Selected from the National Instructional Materials Information System (NIMIS)--a computer based on-line interactive retrieval system on special education materials--the bibliography covers nine materials for remediating reversals in handicapped students at the early childhood and elementary levels. Entries are presented in order of NIMIS accession…

  16. Methods of torque ripple reduction for flux reversal motor

    NASA Astrophysics Data System (ADS)

    Vakil, Gaurang; Sheth, N. K.; Miller, David

    2009-04-01

    This paper presents two-dimensional finite element based results for various methods of torque ripple reduction in flux-reversal motors. The effects of variation in magnet and rotor pole heights, rotor pole skewing, and multiple teeth per rotor pole on the cogging torque, developed torque, torque ripple, and phase inductance and also an optimum value of the magnet and rotor pole heights, skew angle, and choice of teeth per rotor pole with the teeth depth resulting in torque ripple reduction are presented.

  17. Integration of Boltzmann machine and reverse analysis method

    NASA Astrophysics Data System (ADS)

    Mamuda, Mamman; Sathasivam, Saratha

    2015-10-01

    Reverse analysis method is actually a data mining technique to unearth relationships between data. By knowing the connection strengths by using Hopfield network, we can extract the relationships in data sets. Hopfield networks have recognized that some relaxation schemes have a joined cost function and the states of the network converge to local minima of this function. It had performed optimization of a well-defined function. However, there is no guarantee to find the best minimum in the network. Thus, Boltzmann machine has been introduced to overcome this problem. In this paper, we integrate both approaches to enhance data mining. We limit our work to Horn clauses.

  18. On the orthogonalised reverse path method for nonlinear system identification

    NASA Astrophysics Data System (ADS)

    Muhamad, P.; Sims, N. D.; Worden, K.

    2012-09-01

    The problem of obtaining the underlying linear dynamic compliance matrix in the presence of nonlinearities in a general multi-degree-of-freedom (MDOF) system can be solved using the conditioned reverse path (CRP) method introduced by Richards and Singh (1998 Journal of Sound and Vibration, 213(4): pp. 673-708). The CRP method also provides a means of identifying the coefficients of any nonlinear terms which can be specified a priori in the candidate equations of motion. Although the CRP has proved extremely useful in the context of nonlinear system identification, it has a number of small issues associated with it. One of these issues is the fact that the nonlinear coefficients are actually returned in the form of spectra which need to be averaged over frequency in order to generate parameter estimates. The parameter spectra are typically polluted by artefacts from the identification of the underlying linear system which manifest themselves at the resonance and anti-resonance frequencies. A further problem is associated with the fact that the parameter estimates are extracted in a recursive fashion which leads to an accumulation of errors. The first minor objective of this paper is to suggest ways to alleviate these problems without major modification to the algorithm. The results are demonstrated on numerically-simulated responses from MDOF systems. In the second part of the paper, a more radical suggestion is made, to replace the conditioned spectral analysis (which is the basis of the CRP method) with an alternative time domain decorrelation method. The suggested approach - the orthogonalised reverse path (ORP) method - is illustrated here using data from simulated single-degree-of-freedom (SDOF) and MDOF systems.

  19. Reverse Engineering Cellular Networks with Information Theoretic Methods

    PubMed Central

    Villaverde, Alejandro F.; Ross, John; Banga, Julio R.

    2013-01-01

    Building mathematical models of cellular networks lies at the core of systems biology. It involves, among other tasks, the reconstruction of the structure of interactions between molecular components, which is known as network inference or reverse engineering. Information theory can help in the goal of extracting as much information as possible from the available data. A large number of methods founded on these concepts have been proposed in the literature, not only in biology journals, but in a wide range of areas. Their critical comparison is difficult due to the different focuses and the adoption of different terminologies. Here we attempt to review some of the existing information theoretic methodologies for network inference, and clarify their differences. While some of these methods have achieved notable success, many challenges remain, among which we can mention dealing with incomplete measurements, noisy data, counterintuitive behaviour emerging from nonlinear relations or feedback loops, and computational burden of dealing with large data sets. PMID:24709703

  20. Reversible integer wavelet transform for blind image hiding method

    PubMed Central

    Bibi, Nargis; Mahmood, Zahid; Akram, Tallha; Naqvi, Syed Rameez

    2017-01-01

    In this article, a blind data hiding reversible methodology to embed the secret data for hiding purpose into cover image is proposed. The key advantage of this research work is to resolve the privacy and secrecy issues raised during the data transmission over the internet. Firstly, data is decomposed into sub-bands using the integer wavelets. For decomposition, the Fresnelet transform is utilized which encrypts the secret data by choosing a unique key parameter to construct a dummy pattern. The dummy pattern is then embedded into an approximated sub-band of the cover image. Our proposed method reveals high-capacity and great imperceptibility of the secret embedded data. With the utilization of family of integer wavelets, the proposed novel approach becomes more efficient for hiding and retrieving process. It retrieved the secret hidden data from the embedded data blindly, without the requirement of original cover image. PMID:28498855

  1. Methods of Forming Visual Hydrogen Detector with Variable Reversibility

    NASA Technical Reports Server (NTRS)

    Muradov, Nazim Z. (Inventor)

    2014-01-01

    Methods, processes and compositions are provided for a visual or chemochromic hydrogen-detector with variable or tunable reversible color change. The working temperature range for the hydrogen detector is from minus 100 C to plus 500 C. A hydrogen-sensitive pigment, including, but not limited to, oxides, hydroxides and polyoxo-compounds of tungsten, molybdenum, vanadium, chromium and combinations thereof, is combined with nano-sized metal activator particles and preferably, coated on a porous or woven substrate. In the presence of hydrogen, the composition rapidly changes its color from white or light-gray or light-tan to dark gray, navy-blue or black depending on the exposure time and hydrogen concentration in the medium. After hydrogen exposure ceases, the original color of the hydrogen-sensitive pigment is restored, and the visual hydrogen detector can be used repeatedly. By changing the composition of the hydrogen-sensitive pigment, the time required for its complete regeneration is varied from a few seconds to several days.

  2. Reversible rigid coupling apparatus and method for borehole seismic transducers

    DOEpatents

    Owen, Thomas E.; Parra, Jorge O.

    1992-01-01

    An apparatus and method of high resolution reverse vertical seismic profile (VSP) measurements is shown. By encapsulating the seismic detector and heaters in a meltable substance (such as wax), the seismic detector can be removably secured in a borehole in a manner capable of measuring high resolution signals in the 100 to 1000 hertz range and higher. The meltable substance is selected to match the overall density of the detector package with the underground formation, yet still have relatively low melting point and rigid enough to transmit vibrations to accelerometers in the seismic detector. To minimize voids in the meltable substance upon solidification, the meltable substance is selected for minimum shrinkage, yet still having the other desirable characteristics. Heaters are arranged in the meltable substance in such a manner to allow the lowermost portion of the meltable substance to cool and solidify first. Solidification continues upwards from bottom-to-top until the top of the meltable substance is solidified and the seismic detector is ready for use. To remove, the heaters melt the meltable substance and the detector package is pulled from the borehole.

  3. Some alternate methods of energy recovery from reverse osmosis plants

    SciTech Connect

    Guy, D.B.; Singh, R.

    1982-07-01

    Only random information is available on the subject of energy recovery from reverse osmosis plants. This study includes an attempt to collect this information and bring it up to date. The equipment discussed includes classic turbines, reversed pump turbines, integrated hydroturbines and work exchangers, including integrated pump and power recovery units. A short description of each type of equipment is given, followed by advantages and disadvantages, including their state of development. Plants that are or will be using them are enumerated, as are some development possibilities.

  4. Reversible geling co-polymer and method of making

    DOEpatents

    Gutowska, Anna

    2005-12-27

    The present invention is a thereapeutic agent carrier having a thermally reversible gel or geling copolymer that is a linear random copolymer of an [meth-]acrylamide derivative and a hydrophilic comonomer, wherein the linear random copolymer is in the form of a plurality of linear chains having a plurality of molecular weights greater than or equal to a minimum geling molecular weight cutoff and a therapeutic agent.

  5. Reversible BWR fuel assembly and method of using same

    SciTech Connect

    Freeman, T.R.; Wilson, J.F.; Knott, R.P.

    1987-04-07

    A nuclear fuel assembly is described comprising: (a) a flow channel; (b) a lower nozzle assembly structurally attached to the flow channel to form therewith an external envelope; (c) an invertible fuel bundle adapted to be inserted into the envelope, the fuel bundle comprising elongated fuel rods held in a spaced lateral array between top and bottom tie plates. Each of the top and bottom tie plates is substantially identical and has means for supporting the fuel bundle within the envelope in either of two mutually inverted vertical orientations whereby the orientation of the fuel bundle in a flow channel may be reversed during burn-up operation.

  6. Modified reverse tapering method to prevent frequency shift of the radiation in the planar undulator

    NASA Astrophysics Data System (ADS)

    Shim, Chi Hyun; Ko, In Soo; Parc, Yong Woon

    2017-03-01

    This paper presents a modified reverse tapering method to generate a polarized soft x ray in x-ray free-electron lasers (XFELs) with a higher photon power and a shorter undulator length than the simple linear reverse tapering method. In the proposed method, a few untapered planar undulators are added before the simple linear reverse tapering section of the undulator line. This simple modification prevents the frequency shift of the radiation that occurs when the simple linear reverse tapering method is applied to planar undulators. In the proposed method, the total length of planar undulators decreased in spite of the additional untapered undulators. When the modified reverse tapering method is used with four untapered planar undulators, the total length of the planar undulators is 64.6 m. On the other hand, the required length of the planar undulators is 94.6 m when the simple linear reverse tapering method is used. The proposed method gives us a way to generate a soft x-ray pulse (1.24 keV) with a high degree of polarization (>0.99 ) and radiation power (>30 GW ) at the new undulator line with a 10-GeV electron beam in the Pohang Accelerator Laboratory X-ray Free-Electron Laser. This method can be applied in the existing XFELs in the world without any change in the undulator lines.

  7. Factors inhibiting the use of reversible contraceptive methods in rural south India.

    PubMed

    Rajaretnam, T; Deshpande, R V

    1994-01-01

    In two rural districts in South India, the contraceptive prevalence rate for all modern family planning methods was 41 percent, and that for all reversible methods was only about 2 percent in 1990. Interviews with 35 health program professionals, 815 currently married women of reproductive age, 136 of their husbands, and 60 community leaders revealed that neither the demand for reversible methods nor the supply of services was strong in the study areas. Program managers and field-workers were not popularizing reversible methods, and therefore couples were unable to learn about their benefits. According to the authors, a strong commitment from program managers at all levels is needed to increase reversible-method use, and adequate services should be made available at clinics and in villages.

  8. Predicting the past: a simple reverse stand table projection method

    Treesearch

    Quang V. Cao; Shanna M. McCarty

    2006-01-01

    A stand table gives number of trees in each diameter class. Future stand tables can be predicted from current stand tables using a stand table projection method. In the simplest form of this method, a future stand table can be expressed as the product of a matrix of transitional proportions (based on diameter growth rates) and a vector of the current stand table. There...

  9. Health monitoring of bolted joints using the time reversal method and piezoelectric transducers

    NASA Astrophysics Data System (ADS)

    Tao, Wang; Shaopeng, Liu; Junhua, Shao; Yourong, Li

    2016-02-01

    In this paper, the time reversal method based on piezoelectric active sensing is investigated for health monitoring of bolted joints. Experiments are conducted on bolted joints to study the relationship between the time reversal focused signal peak amplitudes and the bolt preload. Two piezoelectric patches are bonded on two different sides of a bolted joint. Any one of the piezoelectric patches can be used as an actuator to generate an ultrasonic wave, and the other one can be used as a sensor to detect the propagated wave. With the time reversal method, the received response signal is reversed in the time domain and then is re-emitted as an excitation signal to acquire the time reversal focused signals. The experimental results show that the time reversal focused signal peak amplitudes increase with the increasing bolt preload until reaching saturation, and when the bolt preload increases to a certain value, the focused signal peak amplitudes will remain unchanged. Experiments show that the surface roughness of the bolted joint impacts the saturation value. A higher surface roughness value corresponds to a higher saturation value. In addition, the proposed method has a high signal to noise ratio benefiting from the time reversal method time and space focusing ability.

  10. Reverse and direct methods for solving the characteristic equation

    NASA Astrophysics Data System (ADS)

    Lozhkin, Alexander; Bozek, Pavol; Lyalin, Vadim; Tarasov, Vladimir; Tothova, Maria; Sultanov, Ravil

    2016-06-01

    Fundamentals of information-linguistic interpretation of the geometry presented shortly. The method of solving the characteristic equation based on Euler's formula is described. The separation of the characteristic equation for several disassembled for Jordan curves. Applications of the theory for problems of mechatronics outlined briefly.

  11. 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.

  12. Combustion-engine Temperatures by the Sodium Line-reversal Method

    NASA Technical Reports Server (NTRS)

    Brevoort, Maurice J

    1936-01-01

    The sodium line-reversal method has been used in some preliminary measurements of flame temperature. Improvements in the method involving a photographic recorder and a means of correcting for the dirtiness of the windows are described. The temperatures so obtained are compared with those calculated from pressure diagrams.

  13. Time Reversed Electromagnetics as a Novel Method for Wireless Power Transfer

    NASA Astrophysics Data System (ADS)

    Challa, Anu; Anlage, Steven M.; Tesla Team

    Taking advantage of ray-chaotic enclosures, time reversal has been shown to securely transmit information via short-wavelength waves between two points, yielding noise at all other sites. In this presentation, we propose a method to adapt the signal-focusing technique to electromagnetic signals in order to transmit energy to portable devices. Relying only on the time-reversal invariance properties of waves, the technique is unencumbered by the inversely-proportional-to-distance path loss or precise orientation requirements of its predecessors, making it attractive for power transfer applications. We inject a short microwave pulse into a complex, wave-chaotic chamber and collect the resulting long time-domain signal at a designated transceiver. The signal is then time reversed and emitted from the collection site, collapsing as a time-reversed replica of the initial pulse at the injection site. When amplified, this reconstruction is robust, as measured through metrics of peak-to-peak voltage and energy transfer ratio. We experimentally demonstrate that time reversed collapse can be made on a moving target, and propose a way to selectively target devices through nonlinear time-reversal. University of Maryland Gemstone Team TESLA: Frank Cangialosi, Anu Challa, Tim Furman, Tyler Grover, Patrick Healey, Ben Philip, Brett Potter, Scott Roman, Andrew Simon, Liangcheng Tao, Alex Tabatabai.

  14. Nonlinear identification of base-isolated buildings by reverse path method

    NASA Astrophysics Data System (ADS)

    Xie, Liyu; Mita, Akira

    2009-03-01

    The performance of reverse path methods applied to identify the underlying linear model of base-isolated structures is investigated. The nonlinear rubber bearings are considered as nonlinear components attached to an underlying linear model. The advantage of reverse path formulation is that it can separate the linearity and nonlinearity of the structure, extract the nonlinearity and identify the underlying linear structure. The difficulty lies in selecting the nonlinearity function of the hysteretic force due to its multi-valued property and path-dependence. In the thesis, the hysteretic force is approximated by the polynomial series of displacement and velocity. The reverse path formulation is solved by Nonlinear Identification through Feedback of Output (NIFO) methods using least-square solution. Numerical simulation is carried out to investigate the identification performance.

  15. Comparison of reverse-engineering methods using an in silico network.

    PubMed

    Camacho, Diogo; Vera Licona, Paola; Mendes, Pedro; Laubenbacher, Reinhard

    2007-12-01

    The reverse engineering of biochemical networks is a central problem in systems biology. In recent years several methods have been developed for this purpose, using techniques from a variety of fields. A systematic comparison of the different methods is complicated by their widely varying data requirements, making benchmarking difficult. Also, because of the lack of detailed knowledge about most real networks, it is not easy to use experimental data for this purpose. This paper contains a comparison of four reverse-engineering methods using data from a simulated network. The network is sufficiently realistic and complex to include many of the challenges that data from real networks pose. Our results indicate that the two methods based on genetic perturbations of the network outperform the other methods, including dynamic Bayesian networks and a partial correlation method.

  16. Limitations of a metabolic network-based reverse ecology method for inferring host-pathogen interactions.

    PubMed

    Takemoto, Kazuhiro; Aie, Kazuki

    2017-05-25

    Host-pathogen interactions are important in a wide range of research fields. Given the importance of metabolic crosstalk between hosts and pathogens, a metabolic network-based reverse ecology method was proposed to infer these interactions. However, the validity of this method remains unclear because of the various explanations presented and the influence of potentially confounding factors that have thus far been neglected. We re-evaluated the importance of the reverse ecology method for evaluating host-pathogen interactions while statistically controlling for confounding effects using oxygen requirement, genome, metabolic network, and phylogeny data. Our data analyses showed that host-pathogen interactions were more strongly influenced by genome size, primary network parameters (e.g., number of edges), oxygen requirement, and phylogeny than the reserve ecology-based measures. These results indicate the limitations of the reverse ecology method; however, they do not discount the importance of adopting reverse ecology approaches altogether. Rather, we highlight the need for developing more suitable methods for inferring host-pathogen interactions and conducting more careful examinations of the relationships between metabolic networks and host-pathogen interactions.

  17. A centrifugal method for the evaluation of polymer membranes for reverse osmosis

    NASA Technical Reports Server (NTRS)

    Hollahan, J. R.; Wydeven, T.; Mccullough, R. P.

    1973-01-01

    A rapid and simple method employing the laboratory centrifuge shows promise for evaluation of membrane performance during reverse osmosis. Results are presented for cellulose acetate membranes for rejection of salt and urea dissolved solids. Implications of the study are to rapid screening of membrane performance, use in laboratories with limited facilities, and possible space waste water purification.

  18. A centrifugal method for the evaluation of polymer membranes for reverse osmosis

    NASA Technical Reports Server (NTRS)

    Hollahan, J. R.; Wydeven, T.; Mccullough, R. P.

    1973-01-01

    A rapid and simple method employing the laboratory centrifuge shows promise for evaluation of membrane performance during reverse osmosis. Results are presented for cellulose acetate membranes for rejection of salt and urea dissolved solids. Implications of the study are to rapid screening of membrane performance, use in laboratories with limited facilities, and possible space waste water purification.

  19. Multiple line arrays for the characterization of aeroacoustic sources using a time-reversal method.

    PubMed

    Mimani, A; Doolan, C J; Medwell, P R

    2013-10-01

    This letter investigates the use of multiple line arrays (LAs) in a Time-Reversal Mirror for localizing and characterizing multipole aeroacoustic sources in a uniform subsonic mean flow using a numerical Time-Reversal (TR) method. Regardless of the original source characteristics, accuracy of predicting the source location can be significantly improved using at least two LAs. Furthermore, it is impossible to determine the source characteristics using a single LA, rather a minimum of two are required to establish either the monopole or dipole source nature, while four LAs (fully surrounding the source) are required for characterizing a lateral quadrupole source.

  20. Optical efficiency of solar concentrators by a reverse optical path method.

    PubMed

    Parretta, A; Antonini, A; Milan, E; Stefancich, M; Martinelli, G; Armani, M

    2008-09-15

    A method for the optical characterization of a solar concentrator, based on the reverse illumination by a Lambertian source and measurement of intensity of light projected on a far screen, has been developed. It is shown that the projected light intensity is simply correlated to the angle-resolved efficiency of a concentrator, conventionally obtained by a direct illumination procedure. The method has been applied by simulating simple reflective nonimaging and Fresnel lens concentrators.

  1. Method of electric field flow fractionation wherein the polarity of the electric field is periodically reversed

    DOEpatents

    Stevens, Fred J.

    1992-01-01

    A novel method of electric field flow fractionation for separating solute molecules from a carrier solution is disclosed. The method of the invention utilizes an electric field that is periodically reversed in polarity, in a time-dependent, wave-like manner. The parameters of the waveform, including amplitude, frequency and wave shape may be varied to optimize separation of solute species. The waveform may further include discontinuities to enhance separation.

  2. Achieving cost-neutrality with long-acting reversible contraceptive methods.

    PubMed

    Trussell, James; Hassan, Fareen; Lowin, Julia; Law, Amy; Filonenko, Anna

    2015-01-01

    This analysis aimed to estimate the average annual cost of available reversible contraceptive methods in the United States. In line with literature suggesting long-acting reversible contraceptive (LARC) methods become increasingly cost-saving with extended duration of use, it aimed to also quantify minimum duration of use required for LARC methods to achieve cost-neutrality relative to other reversible contraceptive methods while taking into consideration discontinuation. A three-state economic model was developed to estimate relative costs of no method (chance), four short-acting reversible (SARC) methods (oral contraceptive, ring, patch and injection) and three LARC methods [implant, copper intrauterine device (IUD) and levonorgestrel intrauterine system (LNG-IUS) 20 mcg/24 h (total content 52 mg)]. The analysis was conducted over a 5-year time horizon in 1000 women aged 20-29 years. Method-specific failure and discontinuation rates were based on published literature. Costs associated with drug acquisition, administration and failure (defined as an unintended pregnancy) were considered. Key model outputs were annual average cost per method and minimum duration of LARC method usage to achieve cost-savings compared to SARC methods. The two least expensive methods were copper IUD ($304 per women, per year) and LNG-IUS 20 mcg/24 h ($308). Cost of SARC methods ranged between $432 (injection) and $730 (patch), per women, per year. A minimum of 2.1 years of LARC usage would result in cost-savings compared to SARC usage. This analysis finds that even if LARC methods are not used for their full durations of efficacy, they become cost-saving relative to SARC methods within 3 years of use. Previous economic arguments in support of using LARC methods have been criticized for not considering that LARC methods are not always used for their full duration of efficacy. This study calculated that cost-savings from LARC methods relative to SARC methods, with discontinuation rates

  3. A Modified Lamb Wave Time-Reversal Method for Health Monitoring of Composite Structures

    PubMed Central

    Zeng, Liang; Lin, Jing; Huang, Liping

    2017-01-01

    Because the time reversal operator of Lamb waves varies with frequency in composite structures, the reconstructed signal deviates from the input signal even in undamaged cases. The damage index captures the discrepancy between the two signals without differentiating the effects of time reversal operator from those of damage. This results in the risk of false alarm. To solve this issue, a modified time reversal method (MTRM) is proposed. In this method, the frequency dependence of the time reversal operator is compensated by two steps. First, an amplitude modulation is placed on the input signal, which is related to the excitability, detectability, and attenuation of the Lamb wave mode. Second, the damage index is redefined to measure the deviation between the reconstructed signal and the modulated input signal. This could indicate the presence of damage with better performance. An experimental investigation is then conducted on a carbon fiber-reinforced polymer (CFRP) laminate to illustrate the effectiveness of the MTRM for identifying damage. The results show that the MTRM may provide a promising tool for health monitoring of composite structures. PMID:28445395

  4. Synthesis of alpha-chymotrypsin/polymer composites by a reverse micelle/gas antisolvent method.

    PubMed

    Li, Wei; Zhang, Jianling; Zhang, Chaoxing; Feng, Xiaoying; Han, Buxing; Yang, Guanying

    2007-09-01

    Alpha-chymotrypsin (CT)/polyvinylpyrrolidone (PVP) composites was synthesized by combination of reverse micelles and CO(2). In this method, the two reverse micellar solutions containing CT and PVP, respectively, were first mixed, then compressed CO(2) was used as an antisolvent to precipitate the CT and PVP simultaneously and CT/PVP composites were successfully prepared. The morphology of the obtained CT/PVP composites was characterized by transmission electron microscopy (TEM). The FTIR spectra of the composites showed that there was interaction between CT and PVP. The storage activity of the enzyme immobilized on the polymer by this method was higher than that of the pure enzyme. This method has some advantages and can be easily applied to the synthesis of some other enzyme/polymer composites.

  5. Acoustic reverse time migration and perfectly matched layer in boundary-conforming grids by elliptic method

    NASA Astrophysics Data System (ADS)

    Wang, Ying; Zhou, Hui; Chen, Hanming; Sheng, Shanbo; Yuan, Sanyi

    2015-11-01

    Traditionally, finite difference method is chosen as a fast and accurate solution method for numerical simulation of wave equation. However, finite difference method faces obstacles when surface topography and irregular interfaces exist. Boundary-conforming grids by the elliptic method provide an optimal choice for finite difference wavefield simulation in complicated domains containing not only surface topography but also irregular interfaces. By such grids, the calculations of spatial derivatives are transformed by a chain rule into those in the regular computational space, where traditional finite difference schemes are still applicable. Boundary-conforming grids are superior to other irregular grid methods, such as interpolation method, mapping method and unstructured grids, on the aspects of generality, in accuracy and stability. This paper comprehensively applies the elliptic method and acoustic wave equation simulation, reverse time migration, perfectly matched layers in such boundary-conforming grids. The two-dimensional acoustic wave equation is compactly reformulated in boundary-conforming grids by the elliptic method for forward modeling and reverse time migration, and the symmetric and compact form of perfectly matched layers expressed in curvilinear coordinate system are applied to suppress artificial reflections. A stable and explicit second order accuracy finite difference method is used for discretization. Two models are presented to evaluate the ability of boundary-conforming grids to deal with surface topography and complex interfaces, and to demonstrate the feasibility of wavefield propagation and reverse time migration. Comparisons between the numerical simulations with and without the perfectly matched layers are performed to show the effect of the reformulated perfectly matched layer.

  6. Time-reversible always stable predictor-corrector method for molecular dynamics of polarizable molecules.

    PubMed

    Kolafa, Jirí

    2004-02-01

    An improved method for classic molecular dynamics of polarizable molecules is proposed. The method uses a predictor, one evaluation of the electrostatic field per integration step, and relaxation (damping). The self-consistent solution is approximated with error of the second order (with respect to the timestep). The time reversibility (long-time energy conservation) error is of the (2n - 1)th order, where n is the predictor length. The method is easy to implement, efficient, accurate, and suitable for any model of polarizability.

  7. The research of springback compensation design method based on reverse modeling

    NASA Astrophysics Data System (ADS)

    Wang, Ru; Zhai, Fenlou; Wu, Bing; Ji, Yutong

    2017-08-01

    To solve the springback problem of automotive covering parts, a springback compensation design method of Stamping die based on reverse modeling is researched. By the Alignment module in Poly Works software, springback analysis is quickly implemented. Then, According to the results of springback analysis, the springback compensation design method which used the smooth displacement adjustment theory is established. At last, Set an inner plate of wheel housing as example, the methods has been applied in springback analysis of the part and springback compensation design of the die-face, which effectively reduces the times of compensation in try pressing stage and improves productivity.

  8. Optimizing selectivity during reversed-phase high performance liquid chromatography method development: prioritizing experimental conditions.

    PubMed

    Snyder, Lloyd R; Dolan, John W

    2013-08-09

    Several different conditions can be varied to improve selectivity for reversed-phase chromatography (RPC). A reexamination of literature data suggests that changes in selectivity due to a change of column or mobile phase pH are largely replicated by changes in temperature or mobile phase composition (concentrations of acetonitrile and/or methanol). This suggests a reconsideration of the role of mobile phase pH and the column during method development.

  9. Application of Carbonate Reservoir using waveform inversion and reverse-time migration methods

    NASA Astrophysics Data System (ADS)

    Kim, W.; Kim, H.; Min, D.; Keehm, Y.

    2011-12-01

    Recent exploration targets of oil and gas resources are deeper and more complicated subsurface structures, and carbonate reservoirs have become one of the attractive and challenging targets in seismic exploration. To increase the rate of success in oil and gas exploration, it is required to delineate detailed subsurface structures. Accordingly, migration method is more important factor in seismic data processing for the delineation. Seismic migration method has a long history, and there have been developed lots of migration techniques. Among them, reverse-time migration is promising, because it can provide reliable images for the complicated model even in the case of significant velocity contrasts in the model. The reliability of seismic migration images is dependent on the subsurface velocity models, which can be extracted in several ways. These days, geophysicists try to obtain velocity models through seismic full waveform inversion. Since Lailly (1983) and Tarantola (1984) proposed that the adjoint state of wave equations can be used in waveform inversion, the back-propagation techniques used in reverse-time migration have been used in waveform inversion, which accelerated the development of waveform inversion. In this study, we applied acoustic waveform inversion and reverse-time migration methods to carbonate reservoir models with various reservoir thicknesses to examine the feasibility of the methods in delineating carbonate reservoir models. We first extracted subsurface material properties from acoustic waveform inversion, and then applied reverse-time migration using the inverted velocities as a background model. The waveform inversion in this study used back-propagation technique, and conjugate gradient method was used in optimization. The inversion was performed using the frequency-selection strategy. Finally waveform inversion results showed that carbonate reservoir models are clearly inverted by waveform inversion and migration images based on the

  10. Reversed-phase HPLC method for the estimation of acetaminophen, ibuprofen and chlorzoxazone in formulations.

    PubMed

    Ravisankar, S; Vasudevan, M; Gandhimathi, M; Suresh, B

    1998-08-01

    A simple, precise and rapid reversed-phase HPLC method was developed for the simultaneous estimation of acetaminophen, ibuprofen and chlorzoxazone in formulations. The method was carried out on a Kromasil(R) C(8) column using a mixture of 0.2% triethylamine:acetonitrile (adjusted to pH 3.2 using dilute orthophosphoric acid), and detection was carried out at 215 nm using ketoprofen as internal standard. All these drugs showed linearity in the range of 2-10 mug ml(-1), and limits of quantification was found to be 10, 50 and 20 ng ml(-1) for acetaminophen, ibuprofen and chlorzoxazone, respectively.

  11. The reversibility error method (REM): a new, dynamical fast indicator for planetary dynamics

    NASA Astrophysics Data System (ADS)

    Panichi, Federico; Goździewski, Krzyszof; Turchetti, Giorgio

    2017-06-01

    We describe the reversibility error method (REM) and its applications to planetary dynamics. REM is based on the time-reversibility analysis of the phase-space trajectories of conservative Hamiltonian systems. The round-off errors break the time reversibility and the displacement from the initial condition, occurring when we integrate it forward and backward for the same time interval, is related to the dynamical character of the trajectory. If the motion is chaotic, in the sense of non-zero maximal Lyapunov characteristic exponent (mLCE), then REM increases exponentially with time, as exp λt, while when the motion is regular (quasi-periodic), then REM increases as a power law in time, as tα, where α and λ are real coefficients. We compare the REM with a variant of mLCE, the mean exponential growth factor of nearby orbits. The test set includes the restricted three-body problem and five resonant planetary systems: HD 37124, Kepler-60, Kepler-36, Kepler-29 and Kepler-26. We found a very good agreement between the outcomes of these algorithms. Moreover, the numerical implementation of REM is astonishing simple, and is based on solid theoretical background. The REM requires only a symplectic and time-reversible (symmetric) integrator of the equations of motion. This method is also CPU efficient. It may be particularly useful for the dynamical analysis of multiple planetary systems in the Kepler sample, characterized by low-eccentricity orbits and relatively weak mutual interactions. As an interesting side result, we found a possible stable chaos occurrence in the Kepler-29 planetary system.

  12. High-performance liquid chromatographic method for determination of reversible isomers of SU5416.

    PubMed

    Sistla, Anand; Yang, Wei-Lien; Shenoy, Narmada

    2006-03-31

    SU5416 shows light-induced reversible geometric isomerism. A simple, reliable, isocratic HPLC method using an UV-vis detector at lambda(425nm) was developed. The method provides efficient (R(S)=3.5) analysis of the two isomers with retention of the isomeric integrity. Additionally, the method has linearity over a wide range (50-1000microg/mL, r(2)=0.99), is accurate (99-102%, RSD <4%), and reproducible (RSD <0.8%). The method was used for analyzing pharmaceutical samples and understanding the kinetics of SU5416 isomers in methanol. In addition, this method can be used for quantifying the non-isolatable E-isomer.

  13. Dialogue on reverse-engineering assessment and methods: the DREAM of high-throughput pathway inference.

    PubMed

    Stolovitzky, Gustavo; Monroe, Don; Califano, Andrea

    2007-12-01

    The biotechnological advances of the last decade have confronted us with an explosion of genetics, genomics, transcriptomics, proteomics, and metabolomics data. These data need to be organized and structured before they may provide a coherent biological picture. To accomplish this formidable task, the availability of an accurate map of the physical interactions in the cell that are responsible for cellular behavior and function would be exceedingly helpful, as these data are ultimately the result of such molecular interactions. However, all we have at this time is, at best, a fragmentary and only partially correct representation of the interactions between genes, their byproducts, and other cellular entities. If we want to succeed in our quest for understanding the biological whole as more than the sum of the individual parts, we need to build more comprehensive and cell-context-specific maps of the biological interaction networks. DREAM, the Dialogue on Reverse Engineering Assessment and Methods, is fostering a concerted effort by computational and experimental biologists to understand the limitations and to enhance the strengths of the efforts to reverse engineer cellular networks from high-throughput data. In this chapter we will discuss the salient arguments of the first DREAM conference. We will highlight both the state of the art in the field of reverse engineering as well as some of its challenges and opportunities.

  14. Distortion correction in EPI using an extended PSF method with a reversed phase gradient approach.

    PubMed

    In, Myung-Ho; Posnansky, Oleg; Beall, Erik B; Lowe, Mark J; Speck, Oliver

    2015-01-01

    In echo-planar imaging (EPI), such as commonly used for functional MRI (fMRI) and diffusion-tensor imaging (DTI), compressed distortion is a more difficult challenge than local stretching as spatial information can be lost in strongly compressed areas. In addition, the effects are more severe at ultra-high field (UHF) such as 7T due to increased field inhomogeneity. To resolve this problem, two EPIs with opposite phase-encoding (PE) polarity were acquired and combined after distortion correction. For distortion correction, a point spread function (PSF) mapping method was chosen due to its high correction accuracy and extended to perform distortion correction of both EPIs with opposite PE polarity thus reducing the PSF reference scan time. Because the amount of spatial information differs between the opposite PE datasets, the method was further extended to incorporate a weighted combination of the two distortion-corrected images to maximize the spatial information content of a final corrected image. The correction accuracy of the proposed method was evaluated in distortion-corrected data using both forward and reverse phase-encoded PSF reference data and compared with the reversed gradient approaches suggested previously. Further we demonstrate that the extended PSF method with an improved weighted combination can recover local distortions and spatial information loss and be applied successfully not only to spin-echo EPI, but also to gradient-echo EPIs acquired with both PE directions to perform geometrically accurate image reconstruction.

  15. A shape-based inter-layer contours correspondence method for ICT-based reverse engineering

    PubMed Central

    Duan, Liming; Yang, Shangpeng; Zhang, Gui; Feng, Fei; Gu, Minghui

    2017-01-01

    The correspondence of a stack of planar contours in ICT (industrial computed tomography)-based reverse engineering, a key step in surface reconstruction, is difficult when the contours or topology of the object are complex. Given the regularity of industrial parts and similarity of the inter-layer contours, a specialized shape-based inter-layer contours correspondence method for ICT-based reverse engineering was presented to solve the above problem based on the vectorized contours. In this paper, the vectorized contours extracted from the slices consist of three graphical primitives: circles, arcs and segments. First, the correspondence of the inter-layer primitives is conducted based on the characteristics of the primitives. Second, based on the corresponded primitives, the inter-layer contours correspond with each other using the proximity rules and exhaustive search. The proposed method can make full use of the shape information to handle industrial parts with complex structures. The feasibility and superiority of this method have been demonstrated via the related experiments. This method can play an instructive role in practice and provide a reference for the related research. PMID:28489867

  16. A shape-based inter-layer contours correspondence method for ICT-based reverse engineering.

    PubMed

    Duan, Liming; Yang, Shangpeng; Zhang, Gui; Feng, Fei; Gu, Minghui

    2017-01-01

    The correspondence of a stack of planar contours in ICT (industrial computed tomography)-based reverse engineering, a key step in surface reconstruction, is difficult when the contours or topology of the object are complex. Given the regularity of industrial parts and similarity of the inter-layer contours, a specialized shape-based inter-layer contours correspondence method for ICT-based reverse engineering was presented to solve the above problem based on the vectorized contours. In this paper, the vectorized contours extracted from the slices consist of three graphical primitives: circles, arcs and segments. First, the correspondence of the inter-layer primitives is conducted based on the characteristics of the primitives. Second, based on the corresponded primitives, the inter-layer contours correspond with each other using the proximity rules and exhaustive search. The proposed method can make full use of the shape information to handle industrial parts with complex structures. The feasibility and superiority of this method have been demonstrated via the related experiments. This method can play an instructive role in practice and provide a reference for the related research.

  17. Newmark-Beta-FDTD method for super-resolution analysis of time reversal waves

    NASA Astrophysics Data System (ADS)

    Shi, Sheng-Bing; Shao, Wei; Ma, Jing; Jin, Congjun; Wang, Xiao-Hua

    2017-09-01

    In this work, a new unconditionally stable finite-difference time-domain (FDTD) method with the split-field perfectly matched layer (PML) is proposed for the analysis of time reversal (TR) waves. The proposed method is very suitable for multiscale problems involving microstructures. The spatial and temporal derivatives in this method are discretized by the central difference technique and Newmark-Beta algorithm, respectively, and the derivation results in the calculation of a banded-sparse matrix equation. Since the coefficient matrix keeps unchanged during the whole simulation process, the lower-upper (LU) decomposition of the matrix needs to be performed only once at the beginning of the calculation. Moreover, the reverse Cuthill-Mckee (RCM) technique, an effective preprocessing technique in bandwidth compression of sparse matrices, is used to improve computational efficiency. The super-resolution focusing of TR wave propagation in two- and three-dimensional spaces is included to validate the accuracy and efficiency of the proposed method.

  18. Method for the preparation of thin-skinned asymmetric reverse osmosis membranes and products thereof

    NASA Technical Reports Server (NTRS)

    Wydeven, T. J. (Inventor); Katz, M. G.

    1984-01-01

    A method for preparing water insoluble asymmetric membranes from water soluble polymers is discussed. The process involves casting a film of the polymer, partially drying it, and then contacting it with a concentrated solution of a transition metal salt. The transition metal ions render the polymer insoluable and are believed to form a complex with it. Optionally, the polymer is crosslinked with heat or radiation. The most preferred polymer is poly(vinyl alcohol). The most preferred complexing salt is copper sulfate. The process and the metal ion linked membranes are discussed. The membranes are reverse osmosis membranes.

  19. Non-contraceptive benefits of hormonal and intrauterine reversible contraceptive methods.

    PubMed

    Bahamondes, Luis; Valeria Bahamondes, M; Shulman, Lee P

    2015-01-01

    Most contraceptive methods present benefits beyond contraception; however, despite a large body of evidence, many healthcare professionals (HCPs), users and potential users are unaware of those benefits. This review evaluates the evidence for non-contraceptive benefits of hormonal and non-hormonal contraceptive methods. We searched the medical publications in PubMed, POPLINE, CENTRAL, EMBASE and LILACS for relevant articles, on non-contraceptive benefits of the use of hormonal and intrauterine reversible contraceptive methods, which were published in English between 1980 and July 2014. Articles were identified using the following search terms: 'contraceptive methods', 'benefits', 'cancer', 'anaemia', 'heavy menstrual bleeding (HMB)', 'endometrial hyperplasia', 'endometriosis' and 'leiomyoma'. We identified, through the literature search, evidence that some combined oral contraceptives have benefits in controlling HMB and anaemia, reducing the rate of endometrial, ovarian and colorectal cancer and ectopic pregnancy as well as alleviating symptoms of premenstrual dysphoric disorder. Furthermore, the use of the levonorgestrel-releasing intrauterine system also controls HMB and anaemia and endometrial hyperplasia and cancer, reduces rates of endometrial polyps in users of tamoxifen and alleviates pain associated with endometriosis and adenomyosis. Depot medroxyprogesterone acetate controls crises of pain associated with sickle cell disease and endometriosis. Users of the etonogestrel-releasing contraceptive implant have the benefits of a reduction of pain associated with endometriosis, and users of the copper intrauterine device have reduced rates of endometrial and cervical cancer. Despite the high contraceptive effectiveness of many hormonal and intrauterine reversible contraceptive methods, many HCPs, users and potential users are concerned mainly about side effects and safety of both hormonal and non-hormonal contraceptive methods, and there is scarce information

  20. Novel in vitro transport method for screening the reversibility of P-glycoprotein inhibitors.

    PubMed

    Netsomboon, Kesinee; Laffleur, Flavia; Suchaoin, Wongsakorn; Bernkop-Schnürch, Andreas

    2016-03-01

    The purpose of this study was to establish a novel in vitro method for screening reversibility of P-glycoprotein (P-gp) inhibitors. Caco-2 cells with 21days of cultivation were used as an in vitro model. Transport of rhodamine 123 in the presence of various inhibitors and after removing of inhibitors was determined. Transport of rhodamine 123 at 4°C and in the secretory direction assured that Caco-2 cells exhibited P-gp function at all time of experiment. The apparent permeability coefficient (Papp) of rhodamine 123 in the presence of verapamil, cyclosporin A, ritonavir, quinidine, N-ethylmaleimide, Cremophor® EL, Tween 80 and poly(acrylic acid)-cysteine-2-mercaptonicotinic acid (PAA-cys-2MNA) was 2.3-, 3.8-, 2.3-, 3.1, 7.5-, 2.1-, 2.9- and 2.5-fold higher than Papp of rhodamine 123 alone. After removing of the inhibitors, Papp decreased to the same range of control except in the case of N-ethylmaleimide which was 2.4-fold higher than the control. These results revealed a reversible inhibition of verapamil, cyclosporin A, ritonavir, quinidine, Cremophor® EL, Tween 80 and PAA-cys-2MNA and an irreversible inhibition of N-ethylmaleimide for P-gp. Thus, this novel established that in vitro method might be an effective tool for screening the reversibility of inhibition of P-gp inhibitors. Copyright © 2015 Elsevier B.V. All rights reserved.

  1. The reverse-direction method links mass experimental data to human diseases.

    PubMed

    Ogura, Hideki; Atsumi, Toru; Bando, Hidenori; Sabharwal, Lavannya; Yamada, Moe; Jiang, Jing-Jing; Nakamura, Akihiro; Arima, Yasunobu; Kamimura, Daisuke; Murakami, Masaaki

    2014-02-01

    Genome-wide analyses such as DNA microarray, RNA sequencing and RNA interference-based high-throughput screening are prevalent to decipher a biological process of interest, and provide a large quantity of data to be processed. An ultimate goal for researchers must be extrapolation of their data to human diseases. We have conducted functional genome-wide screenings to elucidate molecular mechanisms of the inflammation amplifier, a NFκB/STAT3-dependent machinery that potently drives recruitment of immune cells to promote inflammation. Using a public database of genome-wide association studies (GWAS), we recently reported the reverse-direction method by which our mass screening data were successfully linked to many human diseases. As an example, the epiregulin-epidermal growth factor receptor pathway was identified as a regulator of the inflammation amplifier, and associated with human diseases by GWAS. In fact, serum epiregulin levels were higher in patients with chronic inflammatory disorders. The reverse-direction method can be a useful tool to narrow mass data down to focus on human disease-related genes.

  2. Simple reversed-phase liquid chromatography method for determination of tocopherols in edible plant oils.

    PubMed

    Gliszczyńska-Swigło, Anna; Sikorska, Ewa

    2004-09-10

    A simple and rapid reversed-phase high-performance liquid chromatography method for determination of alpha-, (beta + gamma), and delta-tocopherols in edible plant oils has been developed. Oils are diluted in 2-propanol and injected directly onto Symmetry C18 column. Methanol and acetonitrile (1:1) are used as a mobile phase. Tocopherols are detected using fluorescence detector set at excitation and emission wavelength 295 nm and 325 nm, respectively. The method is precise (R.S.D. not higher than 2.24%) and sensitive-detection limits (DL) are 8 ng/ml for gamma- and delta-tocopherols and 28 ng/ml for alpha-tocopherol; quantification limits (QL) were calculated as three times higher than DL.

  3. Digital Sequences and a Time Reversal-Based Impact Region Imaging and Localization Method

    PubMed Central

    Qiu, Lei; Yuan, Shenfang; Mei, Hanfei; Qian, Weifeng

    2013-01-01

    To reduce time and cost of damage inspection, on-line impact monitoring of aircraft composite structures is needed. A digital monitor based on an array of piezoelectric transducers (PZTs) is developed to record the impact region of impacts on-line. It is small in size, lightweight and has low power consumption, but there are two problems with the impact alarm region localization method of the digital monitor at the current stage. The first one is that the accuracy rate of the impact alarm region localization is low, especially on complex composite structures. The second problem is that the area of impact alarm region is large when a large scale structure is monitored and the number of PZTs is limited which increases the time and cost of damage inspections. To solve the two problems, an impact alarm region imaging and localization method based on digital sequences and time reversal is proposed. In this method, the frequency band of impact response signals is estimated based on the digital sequences first. Then, characteristic signals of impact response signals are constructed by sinusoidal modulation signals. Finally, the phase synthesis time reversal impact imaging method is adopted to obtain the impact region image. Depending on the image, an error ellipse is generated to give out the final impact alarm region. A validation experiment is implemented on a complex composite wing box of a real aircraft. The validation results show that the accuracy rate of impact alarm region localization is approximately 100%. The area of impact alarm region can be reduced and the number of PZTs needed to cover the same impact monitoring region is reduced by more than a half. PMID:24084123

  4. Digital sequences and a time reversal-based impact region imaging and localization method.

    PubMed

    Qiu, Lei; Yuan, Shenfang; Mei, Hanfei; Qian, Weifeng

    2013-10-01

    To reduce time and cost of damage inspection, on-line impact monitoring of aircraft composite structures is needed. A digital monitor based on an array of piezoelectric transducers (PZTs) is developed to record the impact region of impacts on-line. It is small in size, lightweight and has low power consumption, but there are two problems with the impact alarm region localization method of the digital monitor at the current stage. The first one is that the accuracy rate of the impact alarm region localization is low, especially on complex composite structures. The second problem is that the area of impact alarm region is large when a large scale structure is monitored and the number of PZTs is limited which increases the time and cost of damage inspections. To solve the two problems, an impact alarm region imaging and localization method based on digital sequences and time reversal is proposed. In this method, the frequency band of impact response signals is estimated based on the digital sequences first. Then, characteristic signals of impact response signals are constructed by sinusoidal modulation signals. Finally, the phase synthesis time reversal impact imaging method is adopted to obtain the impact region image. Depending on the image, an error ellipse is generated to give out the final impact alarm region. A validation experiment is implemented on a complex composite wing box of a real aircraft. The validation results show that the accuracy rate of impact alarm region localization is approximately 100%. The area of impact alarm region can be reduced and the number of PZTs needed to cover the same impact monitoring region is reduced by more than a half.

  5. 3D Modeling of Earthquakes using Time-Reversal or Adjoint Methods

    NASA Astrophysics Data System (ADS)

    Hjorleifsdottir, V.; Liu, Q.; Tromp, J.

    2006-12-01

    The availability of global broad-band seismic data has allowed for detailed modeling of slip on a fault plane for many recent large earthquakes. This is a difficult process involving many trade-offs between model parameters. Although the whole waveform contains information about the earthquake, most studies focus on limited parts of the time series to extract source information. This is in part to avoid errors from not accurately accounting for 3D structure along the propagation path. By modeling earthquakes using 3D structure one could use more of the time series to constrain the source process, thereby reducing the trade-offs. Further, the effect of assuming a 1D structure in the source region on source models has not been carefully studied, especially for subduction zones where the structure is often very heterogeneous. Traditional inversion techniques require computation of a large Green's function library, which can become very computationally expensive in the case of 3D modeling. A 3D time-stepping method would require two simulations for each sub fault, once a location and orientation of the fault plane has been chosen. An alternative would be to use an `adjoint' method, which computes the gradient of the misfit function for a given model in only two simulations (Tarantola Geoph.~1984, Tromp et al.~GJI 2005). Combining this with a conjugate gradient method, we can obtain a final model from much fewer 3D simulations than by computing the whole Green's function library, reducing the computational cost. In it's simplest form an adjoint method for inverting for source parameters can be viewed as a time-reversal experiment performed with a wave-propagation code (McMechan GJRAS 1982). The recorded seismograms are inserted as simultaneous sources at the location of the receiver and the computed wave field (which we call the adjoint wavefield) is recorded on an array around the earthquake location. A special case is the source-scanning or stacking algorithm as used

  6. High sensitive method detection of plant RNA viruses by electrochemiluminescence reverse transcription PCR

    NASA Astrophysics Data System (ADS)

    Tang, Ya-bing; Xing, Da; Zhu, De-bin; Zhou, Xiao-ming

    2007-05-01

    It is well known that plant and animal viruses had widely spread the whole of world, and made a big loss in farming and husbandry. It is necessary that a highly efficient and accurate virus's detection method was developed. This research combines reverse transcription polymerase chain reaction (RT-PCR) technique with electrochemiluminescence method, to detect plant RNA viruses for the first time. Biotin-probe hybridizes with PCR product to specific select the target for detection, thus can avoid pseudo-positive result. TBR-probe hybridizes with PCR product to emit light for ECL detection. Specific nucleic acid sequences (20bp) were added to 5' terminal all of the primers, which can improve the chance of hybridization between TBR-probe and PCR product. At the same time, one of the PCR product chain can hybridize two Ru-probes, the ECL signal is intensified. The method was used to detect Odntoglossum ringspot virus ORSV, Sugarcane mosaic virus ScMV, Sorghum mosaic virus SrMV, and Maize dwarf mosaic virus MDMV, the experiment results show that this method could reliably identity virus infected plant samples. In a word, this method has higher sensitivity and lower cost than others. It can effectively detect the plant viruses with simplicity, stability, and high sensitivity.

  7. Ultrasonic guided wave based damage imaging by time-reversal method in frequency-wavenumber domain

    NASA Astrophysics Data System (ADS)

    Xu, C. G.; Xu, B. Q.; Luo, Y.; Xu, G. D.; Lu, L. Z.

    2017-05-01

    More attention has been drawn to ultrasonic guided waves (UGW) based damage detection method for its advantages of wide range inspection of large scale structures. However, complex propagation characteristics of guided waves as well as traditional contact ultrasonic transducers limit its application for the practical damage detection. By combining Scanning Laser Doppler vibrometer (SLDV) technology, Time-Reversal method in frequency-wavenumber domain (f-k RTM) can compensate for the dispersive nature of Lamb waves, localize multiple damage sites and identify their sizes without time consuming numerical calculation. In this work, we adopt f-k RTM for damage detection in plate-like structure. Instead of SLDV in experiment, 3D finite element numerical method is adopted to obtain scattered ultrasonic guided wavefield data with high spatial resolution. The direct path waves were extracted to obtain the incident wavefield while the scattered signals were used to calculate the scattering wave field. Damage imaging can also be achieved by introducing crosscorrelation imaging condition. Imaging results show that the method is very effective for crack localization and boundary shape-recognition. Numerical simulation results and imaging algorithm laid the foundation for the method applied in experiment and practice.

  8. An improved human visual system based reversible data hiding method using adaptive histogram modification

    NASA Astrophysics Data System (ADS)

    Hong, Wien; Chen, Tung-Shou; Wu, Mei-Chen

    2013-03-01

    Jung et al., IEEE Signal Processing Letters, 18, 2, 95, 2011 proposed a reversible data hiding method considering the human visual system (HVS). They employed the mean of visited neighboring pixels to predict the current pixel value, and estimated the just noticeable difference (JND) of the current pixel. Message bits are then embedded by adjusting the embedding level according to the calculated JND. Jung et al.'s method achieved excellent image quality. However, the embedding algorithm they used may result in over modification of pixel values and a large location map, which may deteriorate the image quality and decrease the pure payload. The proposed method exploits the nearest neighboring pixels to predict the visited pixel value and to estimate the corresponding JND. The cover pixels are preprocessed adaptively to reduce the size of the location map. We also employ an embedding level selection mechanism to prevent near-saturated pixels from being over modified. Experimental results show that the image quality of the proposed method is higher than that of Jung et al.'s method, and the payload can also be increased due to the reduction of the location map.

  9. Using nonlinear optimization methods to reverse engineer liner material properties from EFP tests

    SciTech Connect

    Murphy, M.J.; Baker, E.L.

    1995-02-27

    The utility of variable metric nonlinear optimization methods for reverse engineering liner material constitutive modeling parameters is described. We use an effective new code created by coupling the nonlinear optimization code NLQPEB with the DYNA2D finite element hydrocode. The optimization code determines the ``best`` set of liner material properties by running DYNA2D in a loop, varying the liner model constitutive parameters, and minimizing the difference between the EFP profiles of the calculation and experiment. The results of four different EFP warhead tests with the same copper liner material are used to determine material parameters for the Steinberg-Guinan, Johnson-Cook, & Armstrong-Zerilli models. In a companion paper we describe the successful application of this methodology to the forward engineering of liner contours to achieve desired EFP shapes. The methodology of utilizing a coupled optimization/finite element code provides a significant improvement in warhead designs and the warhead design process.

  10. System and method for manipulating domain pinning and reversal in ferromagnetic materials

    DOEpatents

    Silevitch, Daniel M.; Rosenbaum, Thomas F.; Aeppli, Gabriel

    2013-10-15

    A method for manipulating domain pinning and reversal in a ferromagnetic material comprises applying an external magnetic field to a uniaxial ferromagnetic material comprising a plurality of magnetic domains, where each domain has an easy axis oriented along a predetermined direction. The external magnetic field is applied transverse to the predetermined direction and at a predetermined temperature. The strength of the magnetic field is varied at the predetermined temperature, thereby isothermally regulating pinning of the domains. A magnetic storage device for controlling domain dynamics includes a magnetic hard disk comprising a uniaxial ferromagnetic material, a magnetic recording head including a first magnet, and a second magnet. The ferromagnetic material includes a plurality of magnetic domains each having an easy axis oriented along a predetermined direction. The second magnet is positioned adjacent to the magnetic hard disk and is configured to apply a magnetic field transverse to the predetermined direction.

  11. A recombinant DNA method for understanding the mechanism of Salmonella reverse mutations: Role of repair

    SciTech Connect

    Felton, J.S.; Wu, R.; Shen, N.H.; Healy, S.K.; Fuscoe, J.C.

    1988-10-01

    This is a report of an investigation of the specific changes in the DNA of Salmonella revertants induced by environmental mutagens and their metabolites. These compounds were chosen because they specifically induce frameshift lesions in strains TA1538 and TA98. DNA lesions in these strains are analyzed in the hisD gene and can lead to reversion of histidine dependence by either deletions, insertions, or suppressor mutations. The understanding of the types of DNA-base changes induced by both a mutagen and its metabolites can lead to a better understanding of not only the mutational process and repair mechanisms, but also the potency and mode of action of specific metabolites and their corresponding DNA adduct(s). The detailed developed of the methods used for this research and the original findings with benzo(a)pyrene have been recently published. 4 refs., 2 figs.

  12. Synthesis of nanosilver particles by reverse micelle method and study of their bactericidal properties

    NASA Astrophysics Data System (ADS)

    Dung, Tran Thi Ngoc; Buu, Ngo Quoc; Viet Quang, Dang; Thi Ha, Huynh; Bang, Le Anh; Hoai Chau, Nguyen; Thi Ly, Nguyen; Trung, Nguyen Vu

    2009-09-01

    Nanosilver particles have been synthesized by the reverse micelle method, where AgNO3 was used as a silver ions source, NaBH4 and quercetin - as reducing agents, CTAB, SDOSS and AOT- as surfactants, while the stabilizer was Vietnamese chitosan. Studying the factors influencing the process of nanosilver particle formation, it was shown that the particle size of the nanosilver products depends on the concentration of the reaction components and their stoichiometric ratio. It was also shown that the reaction system using AOT surfactant is capable of producing nanosilver particles with smallest nanoparticles (phiav ~ 5 nm) and good particle-size distribution. The study on bactericidal activity of the nanosilver products indicated that the disinfecting solution with a nanosilver concentration of 3 ppm was able to inhibit all E.coli and Coliforms, TPC and fungi at 15 ppm, while Vibrio cholerae cells were inactivated completely with 0.5 ppm of nanosilver after 30 minutes exposition.

  13. Reversible electro-optic device employing aprotic molten salts and method

    DOEpatents

    Warner, Benjamin P.; McCleskey, T. Mark; Burrell, Anthony K.; Hall, Simon B.

    2008-01-08

    A single-compartment reversible mirror device having a solution of aprotic molten salt, at least one soluble metal-containing species comprising metal capable of being electrodeposited, and at least one anodic compound capable of being oxidized was prepared. The aprotic molten salt is liquid at room temperature and includes lithium and/or quaternary ammonium cations, and anions selected from trifluoromethylsulfonate (CF.sub.3SO.sub.3.sup.-), bis(trifluoromethylsulfonyl)imide ((CF.sub.3SO.sub.2).sub.2N.sup.-), bis(perfluoroethylsulfonyl)imide ((CF.sub.3CF.sub.2SO.sub.2).sub.2N.sup.-) and tris(trifluoromethylsulfonyl)methide ((CF.sub.3SO.sub.2).sub.3C.sup.-). A method for preparing substantially pure molten salts is also described.

  14. Reversible Electro-Optic Device Employing Aprotic Molten Salts And Method

    DOEpatents

    Warner, Benjamin P.; McCleskey, T. Mark; Burrell, Anthony K.; Hall, Simon B.

    2005-03-01

    A single-compartment reversible mirror device having a solution of aprotic molten salt, at least one soluble metal-containing species comprising metal capable of being electrodeposited, and at least one anodic compound capable of being oxidized was prepared. The aprotic molten salt is liquid at room temperature and includes lithium and/or quaternary ammonium cations, and anions selected from trifluoromethylsulfonate (CF.sub.3 SO.sub.3.sup.-), bis(trifluoromethylsulfonyl)imide ((CF.sub.3 SO.sub.2).sub.2 N.sup.-), bis(perfluoroethylsulfonyl)imide ((CF.sub.3 CF.sub.2 SO.sub.2).sub.2 N.sup.-) and tris(trifluoromethylsulfonyl)methide ((CF.sub.3 SO.sub.2).sub.3 C.sup.-). A method for preparing substantially pure molten salts is also described.

  15. Theoretical investigation on nevirapine and HIV-1 reverse transcriptase binding site interaction, based on ONIOM method

    NASA Astrophysics Data System (ADS)

    Kuno, Mayuso; Hannongbua, Supa; Morokuma, Keiji

    2003-10-01

    The ONIOM method was applied to the interaction of nevirapine with the HIV-1 reverse transcriptase binding site. The isolated complex of pyridine (part of nevirapine) and methyl phenol (part of Tyr181) was found at the MP2/6-31+G(d) level to have stacking interaction with 8.8 kcal/mol binding energy. Optimization of nevirapine and Tyr181 geometry in the pocket of 16 amino acid residues at the ONIOM3(MP2/6-31G(d):HF/3-21G:PM3) level gave the complex structure with weak hydrogen bonding but without stacking interaction. The binding energy of 8.9 kcal/mol comes almost entirely from the interaction of nevirapine with amino acid residues other than Tyr181.

  16. Interferometric measurement method for Z2 invariants of time-reversal invariant topological insulators

    NASA Astrophysics Data System (ADS)

    Grusdt, Fabian; Abanin, Dmitry; Demler, Eugene

    2013-05-01

    Recently experiments with ultracold atoms started to explore topological phases in 1D optical lattices. While transport measurements are challenging in these systems, ways to directly measure topological quantum numbers using a combination of Bloch oscillations and Ramsey interferometry have been explored (Atala et al., arXiv:1212.0572). In this talk I will present ways to measure the Z2 topological quantum numbers of two and three dimensional time-reversal invariant (TR) topological insulators. In this case non-Abelian Bloch oscillations can be combined with Ramsey interferometry to map out the topological properties of a given band-structure. Our method is very general and works even in the presence of accidental degeneracies. The applicability of the scheme is discussed for different theoretically proposed implementations of TR topological insulators using ultracold atoms. F. G. is grateful to Harvard University for hospitality and acknowledges financial support from Graduate School Materials Science in Mainz (MAINZ).

  17. Reasons for discontinuation of reversible contraceptive methods by women with epilepsy.

    PubMed

    Mandle, Hannah B; Cahill, Kaitlyn E; Fowler, Kristen M; Hauser, W Allen; Davis, Anne R; Herzog, Andrew G

    2017-05-01

    To report the reasons for discontinuation of contraceptive methods by women with epilepsy (WWE). These retrospective data come from a web-based survey regarding the contraceptive practices of 1,144 WWE in the community, ages 18-47 years. We determined the frequencies of contraceptive discontinuations and the reasons for discontinuation. We compared risk ratios for rates of discontinuation among contraceptive methods and categories. We used chi-square analysis to test the independence of discontinuation reasons among the various contraceptive methods and categories and when stratified by antiepileptic drug (AED) categories. Nine hundred fifty-nine of 2,393 (40.6%) individual, reversible contraceptive methods were discontinued. One-half (51.8%) of the WWE who discontinued a method discontinued at least two methods. Hormonal contraception was discontinued most often (553/1,091, 50.7%) with a risk ratio of 1.94 (1.54-2.45, p < 0.0001) compared to intrauterine devices (IUDs), the category that was discontinued the least (57/227, 25.1%). Among all individual methods, the contraceptive patch was stopped most often (79.7%) and the progestin-IUD was stopped the least (20.1%). The top three reasons for discontinuation among all methods were reliability concerns (13.9%), menstrual problems (13.5%), and increased seizures (8.6%). There were significant differences among discontinuation rates and reasons when stratified by AED category for hormonal contraception but not for any other contraceptive category. Contraception counseling for WWE should consider the special experience profiles that are unique to this special population on systemic hormonal contraception. Wiley Periodicals, Inc. © 2017 International League Against Epilepsy.

  18. Sequence-specific detection method for reverse transcription, loop-mediated isothermal amplification of HIV-1.

    PubMed

    Curtis, Kelly A; Rudolph, Donna L; Owen, S Michele

    2009-06-01

    HIV diagnosis at the point-of-care or in resource-limited settings poses considerable challenges due to time and cost limitations. Currently, nucleic acid-based tests are the only reliable method for diagnosing recent infections during the window period post-infection and pre-seroconversion, but these tests are only suitable for well-equipped laboratory settings. The reverse transcription loop-mediated isothermal amplification (RT-LAMP) technology exhibits characteristics that are ideal for the development of a rapid, cost-effective nucleic acid-based test for detection of HIV DNA and RNA. In this study, a sequence-specific detection method was developed for immediate, naked-eye visualization of RT-LAMP products with high sensitivity and specificity. The rapid detection method was incorporated into the HIV-1-specific RT-LAMP assay and validated using minute volumes of whole blood from HIV-1-infected individuals. Together with the minimal sample preparation time and one-step, isothermal amplification reaction, the sequence-specific detection method adds to the overall versatility of the RT-LAMP assay and enhances the applicability for use at point-of-care or resource-limited sites.

  19. Time-reversal transcranial ultrasound beam focusing using a k-space method.

    PubMed

    Jing, Yun; Meral, F Can; Clement, Greg T

    2012-02-21

    This paper proposes the use of a k-space method to obtain the correction for transcranial ultrasound beam focusing. Mirroring past approaches, a synthetic point source at the focal point is numerically excited, and propagated through the skull, using acoustic properties acquired from registered computed tomography of the skull being studied. The received data outside the skull contain the correction information and can be phase conjugated (time reversed) and then physically generated to achieve a tight focusing inside the skull, by assuming quasi-plane transmission where shear waves are not present or their contribution can be neglected. Compared with the conventional finite-difference time-domain method for wave propagation simulation, it will be shown that the k-space method is significantly more accurate even for a relatively coarse spatial resolution, leading to a dramatically reduced computation time. Both numerical simulations and experiments conducted on an ex vivo human skull demonstrate that precise focusing can be realized using the k-space method with a spatial resolution as low as only 2.56 grid points per wavelength, thus allowing treatment planning computation on the order of minutes.

  20. Development of the simple and sensitive method for lipoxygenase assay in AOT/isooctane reversed micelles.

    PubMed

    Park, Kyung Min; Kim, Yu Na; Choi, Seung Jun; Chang, Pahn-Shick

    2013-06-01

    In this study, we investigated the possibility of reversed micelles, widely used as an enzyme reactor for lipases, for the determination of lipoxygenase activity. Although it is rapid and simple, reversed micelles have some limitations, such as interference by UV-absorbing materials and surfactant. Lipoxygenase activity in the reversed micelles was determined by reading the absorbance of the lipid hydroperoxidation product (conjugated diene) at 234 nm. Among surfactants and organic media, AOT and isooctane were most effective for the dioxygenation of linoleic acid in reversed micelles. The strong absorbance of AOT in the UV region is a major obstacle for the direct application of the AOT/isooctane reversed micelles to lipoxygenase activity determination. To prevent interference by AOT, we added an AOT removal step in the procedure for lipoxygenase activity determination in reversed micelles. The lipoxygenase activity was dependent on water content, and maximum activity was obtained at an R-value of 10.

  1. A nodal discontinuous Galerkin method for reverse-time migration on GPU clusters

    NASA Astrophysics Data System (ADS)

    Modave, A.; St-Cyr, A.; Mulder, W. A.; Warburton, T.

    2015-11-01

    Improving both accuracy and computational performance of numerical tools is a major challenge for seismic imaging and generally requires specialized implementations to make full use of modern parallel architectures. We present a computational strategy for reverse-time migration (RTM) with accelerator-aided clusters. A new imaging condition computed from the pressure and velocity fields is introduced. The model solver is based on a high-order discontinuous Galerkin time-domain (DGTD) method for the pressure-velocity system with unstructured meshes and multirate local time stepping. We adopted the MPI+X approach for distributed programming where X is a threaded programming model. In this work we chose OCCA, a unified framework that makes use of major multithreading languages (e.g. CUDA and OpenCL) and offers the flexibility to run on several hardware architectures. DGTD schemes are suitable for efficient computations with accelerators thanks to localized element-to-element coupling and the dense algebraic operations required for each element. Moreover, compared to high-order finite-difference schemes, the thin halo inherent to DGTD method reduces the amount of data to be exchanged between MPI processes and storage requirements for RTM procedures. The amount of data to be recorded during simulation is reduced by storing only boundary values in memory rather than on disk and recreating the forward wavefields. Computational results are presented that indicate that these methods are strong scalable up to at least 32 GPUs for a three-dimensional RTM case.

  2. A reversed phase high performance liquid chromatographic method for determination of rapamycin.

    PubMed

    Sobhani, Hamideh; Shafaati, Alireza; Nafissi-Varcheh, Nastaran; Aboofazeli, Reza

    2013-01-01

    Easily degradating and various isomeric forms of rapamycin (Sirolimus) face the determination of this compound to many challenges. In this study, we developed and validated the isocratic reversed phase high performance liquid chromatographic (RP-HPLC) method for rapamycin. Separation was performed on a C8 column (MZ, 15 × 4.6 mm, 5 μm particle size) using methanol:water (80:20 v/v) as the mobile phase with the flow rate of 1 mL/min. The column temperature was set at 57°C and the detection was carried out at the wavelength of 277 nm. The method was linear over a concentration range of 0.025-2 μg/mL. The coefficient of variation of intra- and inter-day, assessed at three concentration levels of 0.075, 0.3 and 0.900 μg/mL, was less than 2%. Limit of quantification (LOQ) was found 25 ng/mL. The method with high percent recovery and short retention time of rapamycin, was found to be simple, rapid and reproducible.

  3. Development and Validation of Reversed-Phase High Performance Liquid Chromatographic Method for Hydroxychloroquine Sulphate.

    PubMed

    Singh, A; Roopkishora; Singh, C L; Gupta, R; Kumar, S; Kumar, M

    2015-01-01

    In the present work new, simple reversed-phase high performance liquid chromatographic method was developed and validated for the determination of hydroxychloroquine sulphate in blood plasma. Chloroquine sulphate was used as an internal standard. The chromatographic separation was achieved with octadecyl silane Hypersil C18 column (250×6 mm, 5 μm) using water and organic (acetonitrile:methanol: 50:50, v/v) mobile phase in 75:25 v/v ratio, with sodium 1-pentanesulfonate and phosphoric acid. This organic phase was maintained at pH 3.0 by orthophosphoric acid. The flow rate of 2.0 ml/min(.) with detection at 343 nm was used in the analysis. The calibration curve of standard hydroxychloroquine sulphate was linear in range 0.1-20.0 μg/ml. The method was validated with respected to linearity, range, precision, accuracy, specificity and robustness studies according to ICH guidelines. The method was found to be accurate and robust to analyze the hydroxychloroquine sulphate in plasma samples.

  4. Quasi-reversibility method for data assimilation in models of mantle dynamics

    NASA Astrophysics Data System (ADS)

    Ismail-Zadeh, A.; Korotkii, A.; Schubert, G.; Tsepelev, I.

    2007-09-01

    Rapid progress in imaging deep Earth structures using seismic tomography and in studies of physical and chemical properties of mantle rocks facilitates research in assimilation of data related to mantle dynamics. In this paper, we present a new numerical approach for data assimilation, which allows for incorporating observations (at present) and unknown initial conditions (in the past) for mantle temperature and flow into a 3-D dynamic model in order to determine the initial conditions. The dynamic model is described by the backward heat, motion and continuity equations. The use of the quasi-reversibility (QRV) method implies the introduction into the backward heat equation of the additional term involving the product of a small regularization parameter and a higher order temperature derivative. The data assimilation in this case is based on a search of the best fit between the forecast model state and the observations by minimizing the regularization parameter. We apply the QRV data assimilation method to restore the evolution of (i) mantle plumes (a synthetic case study) and (ii) the lithospheric slab imaged by teleseismic body-wave tomography in the southeastern Carpathians. For both models the present temperature and mantle flow are assimilated to the geological past, and the prominent features of mantle structures are recovered. We then model the evolution of the mantle structures forward in time starting from the restored state to the present state and estimate the accuracy of the model predictions. The results of the QRV data assimilation are compared to that obtained by the variational (VAR) and backward advection data assimilation. Although the accuracy of the QRV data assimilation is lower than that of the VAR data assimilation, the QRV method does not require any additional smoothing of the input data or filtering of temperature noise as the VAR method does. Based on the results and the comparison of the methods, we consider the QRV method to be a highly

  5. Drift-oscillatory steering with the forward-reverse method for calculating the potential of mean force

    NASA Astrophysics Data System (ADS)

    Nategholeslam, Mostafa; Holland, Bryan W.; Gray, C. G.; Tomberli, Bruno

    2011-02-01

    We present a method that enables the use of the forward-reverse (FR) method of Kosztin on a broader range of problems in soft matter physics. Our method, which we call the oscillating forward-reverse (OFR) method, adds an oscillatory steering potential to the constant velocity steering potential of the FR method. This enables the calculation of the potential of mean force (PMF) in a single unidirectional oscillatory drift, rather than multiple drifts in both directions as required by the FR method. By following small forward perturbations with small reverse perturbations, the OFR method is able to generate a piecewise reverse path that follows the piecewise forward path much more closely than any practical set of paths used in the FR method. We calculate the PMF for four different systems: a dragged Brownian oscillator, a pair of atoms in a Lennard-Jones liquid, a Na+-Cl- ion pair in an aqueous solution, and a deca-alanine molecule being stretched in an implicit solvent. In all cases, the PMF results are in good agreement with those published previously using various other methods, and, to our knowledge, we give for the first time PMFs calculated by nonequilibrium methods for the Lennard-Jones and Na+-Cl- systems.

  6. Detecting a subsurface cylinder by a Time Reversal MUSIC like method

    NASA Astrophysics Data System (ADS)

    Solimene, Raffaele; Dell'Aversano, Angela; Leone, Giovanni

    2014-05-01

    In this contribution the problem of imaging a buried homogeneous circular cylinder is dealt with for a two-dimensional scalar geometry. Though the addressed geometry is extremely simple as compared to real world scenarios, it can be considered of interest for a classical GPR civil engineering applicative context: that is the subsurface prospecting of urban area in order to detect and locate buried utilities. A large body of methods for subsurface imaging have been presented in literature [1], ranging from migration algorithms to non-linear inverse scattering approaches. More recently, also spectral estimation methods, which benefit from sub-array data arrangement, have been proposed and compared in [2].Here a Time Reversal MUSIC (TRM) like method is employed. TRM has been initially conceived to detect point-like scatterers and then generalized to the case of extended scatterers [3]. In the latter case, no a priori information about the scatterers is exploited. However, utilities often can be schematized as circular cylinders. Here, we develop a TRM variant which use this information to properly tailor the steering vector while implementing TRM. Accordingly, instead of a spatial map [3], the imaging procedure returns the scatterer's parameters such as its center position, radius and dielectric permittivity. The study is developed by numerical simulations. First the free-space case is considered in order to more easily introduce the idea and the problem mathematical structure. Then the analysis is extended to the half-space case. In both situations a FDTD forward solver is used to generate the synthetic data. As usual in TRM, a multi-view/multi-static single-frequency configuration is considered and emphasis is put on the role played by the number of available sensors. Acknowledgement This work benefited from networking activities carried out within the EU funded COST Action TU1208 "Civil Engineering Applications of Ground Penetrating Radar." [1] A. Randazzo and R

  7. Reverse engineering and verification of gene networks: principles, assumptions, and limitations of present methods and future perspectives.

    PubMed

    He, Feng; Balling, Rudi; Zeng, An-Ping

    2009-11-01

    Reverse engineering of gene networks aims at revealing the structure of the gene regulation network in a biological system by reasoning backward directly from experimental data. Many methods have recently been proposed for reverse engineering of gene networks by using gene transcript expression data measured by microarray. Whereas the potentials of the methods have been well demonstrated, the assumptions and limitations behind them are often not clearly stated or not well understood. In this review, we first briefly explain the principles of the major methods, identify the assumptions behind them and pinpoint the limitations and possible pitfalls in applying them to real biological questions. With regard to applications, we then discuss challenges in the experimental verification of gene networks generated from reverse engineering methods. We further propose an optimal experimental design for allocating sampling schedule and possible strategies for reducing the limitations of some of the current reverse engineering methods. Finally, we examine the perspectives for the development of reverse engineering and urge the need to move from revealing network structure to the dynamics of biological systems.

  8. Symmetry analysis for nonlinear time reversal methods applied to nonlinear acoustic imaging

    NASA Astrophysics Data System (ADS)

    Dos Santos, Serge; Chaline, Jennifer

    2015-10-01

    Using symmetry invariance, nonlinear Time Reversal (TR) and reciprocity properties, the classical NEWS methods are supplemented and improved by new excitations having the intrinsic property of enlarging frequency analysis bandwidth and time domain scales, with now both medical acoustics and electromagnetic applications. The analysis of invariant quantities is a well-known tool which is often used in nonlinear acoustics in order to simplify complex equations. Based on a fundamental physical principle known as symmetry analysis, this approach consists in finding judicious variables, intrinsically scale dependant, and able to describe all stages of behaviour on the same theoretical foundation. Based on previously published results within the nonlinear acoustic areas, some practical implementation will be proposed as a new way to define TR-NEWS based methods applied to NDT and medical bubble based non-destructive imaging. This paper tends to show how symmetry analysis can help us to define new methodologies and new experimental set-up involving modern signal processing tools. Some example of practical realizations will be proposed in the context of biomedical non-destructive imaging using Ultrasound Contrast Agents (ACUs) where symmetry and invariance properties allow us to define a microscopic scale-invariant experimental set-up describing intrinsic symmetries of the microscopic complex system.

  9. An efficient higher-order PML in WLP-FDTD method for time reversed wave simulation

    NASA Astrophysics Data System (ADS)

    Wei, Xiao-Kun; Shao, Wei; Ou, Haiyan; Wang, Bing-Zhong

    2016-09-01

    Derived from a stretched coordinate formulation, a higher-order complex frequency shifted (CFS) perfectly matched layer (PML) is proposed for the unconditionally stable finite-difference time-domain (FDTD) method based on weighted Laguerre polynomials (WLPs). The higher-order PML is implemented with an auxiliary differential equation (ADE) approach. In order to further improve absorbing performance, the parameter values of stretching functions in the higher-order PML are optimized by the multi-objective genetic algorithm (MOGA). The optimal solutions can be chosen from the Pareto front for trading-off between two independent objectives. It is shown in a numerical test that the higher-order PML is efficient in terms of attenuating propagating waves and reducing late time reflections. Moreover, the higher-order PML can be placed very close to the wall when analyzing the channel characteristics of time reversal (TR) waves in a multipath indoor environment. Numerical examples of TR wave propagation demonstrate the availability of the proposed method.

  10. A rapid and reversible skull optical clearing method for monitoring cortical blood flow

    NASA Astrophysics Data System (ADS)

    Zhang, Chao; Zhao, Yanjie; Shi, Rui; Zhu, Dan

    2016-03-01

    In vivo cortex optical imaging is of great important for revealing both structural and functional architecture of brain with high temporal-spatial resolution. To reduce the limitation of turbid skull, researchers had to establish various skull windows or directly expose cortex through craniotomy. Here we developed a skull optical clearing method to make skull transparent. Laser speckle contrast imaging technique was used to monitor the cortical blood flow after topical treatment with the optical clearing agents. The results indicated that the image contrast increased gradually, and then maintained at a high level after 15 min for adult mice, which made the image quality and resolution of micro-vessels nearly approximate to those of exposed cortex. Both the cortical blood flow velocity almost kept constant after skull became transparent. Besides, the treatment of physiological saline on the skull could make skull return to the initial state again and the skull could become transparent again when SOCS retreated it. Thus, we could conclude that the skull optical clearing method was rapid, valid, reversible and safe, which provided us available approach for performing the cortical structural and functional imaging at high temporal-spatial resolution.

  11. Bubbler: A Novel Ultra-High Power Density Energy Harvesting Method Based on Reverse Electrowetting.

    PubMed

    Hsu, Tsung-Hsing; Manakasettharn, Supone; Taylor, J Ashley; Krupenkin, Tom

    2015-11-16

    We have proposed and successfully demonstrated a novel approach to direct conversion of mechanical energy into electrical energy using microfluidics. The method combines previously demonstrated reverse electrowetting on dielectric (REWOD) phenomenon with the fast self-oscillating process of bubble growth and collapse. Fast bubble dynamics, used in conjunction with REWOD, provides a possibility to increase the generated power density by over an order of magnitude, as compared to the REWOD alone. This energy conversion approach is particularly well suited for energy harvesting applications and can enable effective coupling to a broad array of mechanical systems including such ubiquitous but difficult to utilize low-frequency energy sources as human and machine motion. The method can be scaled from a single micro cell with 10(-6) W output to power cell arrays with a total power output in excess of 10 W. This makes the fabrication of small light-weight energy harvesting devices capable of producing a wide range of power outputs feasible.

  12. Bubbler: A Novel Ultra-High Power Density Energy Harvesting Method Based on Reverse Electrowetting

    PubMed Central

    Hsu, Tsung-Hsing; Manakasettharn, Supone; Taylor, J. Ashley; Krupenkin, Tom

    2015-01-01

    We have proposed and successfully demonstrated a novel approach to direct conversion of mechanical energy into electrical energy using microfluidics. The method combines previously demonstrated reverse electrowetting on dielectric (REWOD) phenomenon with the fast self-oscillating process of bubble growth and collapse. Fast bubble dynamics, used in conjunction with REWOD, provides a possibility to increase the generated power density by over an order of magnitude, as compared to the REWOD alone. This energy conversion approach is particularly well suited for energy harvesting applications and can enable effective coupling to a broad array of mechanical systems including such ubiquitous but difficult to utilize low-frequency energy sources as human and machine motion. The method can be scaled from a single micro cell with 10−6 W output to power cell arrays with a total power output in excess of 10 W. This makes the fabrication of small light-weight energy harvesting devices capable of producing a wide range of power outputs feasible. PMID:26567850

  13. Novel method of doxorubicin-SPION reversible association for magnetic drug targeting.

    PubMed

    Munnier, E; Cohen-Jonathan, S; Linassier, C; Douziech-Eyrolles, L; Marchais, H; Soucé, M; Hervé, K; Dubois, P; Chourpa, I

    2008-11-03

    A new method of reversible association of doxorubicin (DOX) to superparamagnetic iron oxide nanoparticles (SPION) is developed for magnetically targeted chemotherapy. The efficacy of this approach is evaluated in terms of drug loading, delivery kinetics and cytotoxicity in vitro. Aqueous suspensions of SPION (ferrofluids) were prepared by coprecipitation of ferric and ferrous chlorides in alkaline medium followed by surface oxidation by ferric nitrate and surface treatment with citrate ions. The ferrofluids were loaded with DOX using a pre-formed DOX-Fe(2+) complex. The resulting drug loading was as high as 14% (w/w). This value exceeds the maximal loading known from literature up today. The release of DOX from the nanoparticles is strongly pH-dependent: at pH 7.4 the amount of drug released attains a plateau of approximately 85% after 1h, whereas at pH 4.0 the release is almost immediate. At both pH, the released drug is iron-free. The in vitro cytotoxicity of the DOX-loaded SPION on the MCF-7 breast cancer cell line is similar to that of DOX in solution or even higher, at low-drug concentrations. The present study demonstrates the potential of the novel method of pH-sensitive DOX-SPION association to design novel magnetic nanovectors for chemotherapy.

  14. Bubbler---A Novel Ultra High Power Density Energy Harvesting Method Based on Reverse Electrowetting

    NASA Astrophysics Data System (ADS)

    Hsu, Tsung-Hsing

    A novel approach to direct conversion of mechanical energy into electrical energy has been proposed and experimentally and theoretically investigated. The method combines previously demonstrated reverse electrowetting on dielectric (REWOD) phenomenon with the fast self-oscillating process of bubble growth and collapse inside a conductive liquid placed in contact with a dielectric-covered electrode. Fast bubble dynamics, used in conjunction with REWOD, can enable extremely high power densities, in excess of 10 kW/m2. The method can be scaled in power from microwatts to tens of watts, and can enable direct coupling to a wide range of mechanical energy sources, which make it particularly attractive for energy harvesting applications. We believe that this approach can enable extraction of useful energy from various non-traditional sources including thermal expansion of buildings, human motion, and vehicle and machinery movement. Also, this makes the fabrication of small light-weight energy harvesting devices capable of producing a wide range of power outputs feasible.

  15. The Reverse Time Migration technique coupled with Interior Penalty Discontinuous Galerkin method.

    NASA Astrophysics Data System (ADS)

    Baldassari, C.; Barucq, H.; Calandra, H.; Denel, B.; Diaz, J.

    2009-04-01

    Seismic imaging is based on the seismic reflection method which produces an image of the subsurface from reflected waves recordings by using a tomography process and seismic migration is the industrial standard to improve the quality of the images. The migration process consists in replacing the recorded wavefields at their actual place by using various mathematical and numerical methods but each of them follows the same schedule, according to the pioneering idea of Claerbout: numerical propagation of the source function (propagation) and of the recorded wavefields (retropropagation) and next, construction of the image by applying an imaging condition. The retropropagation step can be realized accouting for the time reversibility of the wave equation and the resulting algorithm is currently called Reverse Time Migration (RTM). To be efficient, especially in three dimensional domain, the RTM requires the solution of the full wave equation by fast numerical methods. Finite element methods are considered as the best discretization method for solving the wave equation, even if they lead to the solution of huge systems with several millions of degrees of freedom, since they use meshes adapted to the domain topography and the boundary conditions are naturally taken into account in the variational formulation. Among the different finite element families, the spectral element one (SEM) is very interesting because it leads to a diagonal mass matrix which dramatically reduces the cost of the numerical computation. Moreover this method is very accurate since it allows the use of high order finite elements. However, SEM uses meshes of the domain made of quadrangles in 2D or hexaedra in 3D which are difficult to compute and not always suitable for complex topographies. Recently, Grote et al. applied the IPDG (Interior Penalty Discontinuous Galerkin) method to the wave equation. This approach is very interesting since it relies on meshes with triangles in 2D or tetrahedra in 3D

  16. Kinetic Analysis of Parallel-Consecutive First-Order Reactions with a Reversible Step: Concentration-Time Integrals Method

    ERIC Educational Resources Information Center

    Mucientes, A. E.; de la Pena, M. A.

    2009-01-01

    The concentration-time integrals method has been used to solve kinetic equations of parallel-consecutive first-order reactions with a reversible step. This method involves the determination of the area under the curve for the concentration of a given species against time. Computer techniques are used to integrate experimental curves and the method…

  17. Kinetic Analysis of Parallel-Consecutive First-Order Reactions with a Reversible Step: Concentration-Time Integrals Method

    ERIC Educational Resources Information Center

    Mucientes, A. E.; de la Pena, M. A.

    2009-01-01

    The concentration-time integrals method has been used to solve kinetic equations of parallel-consecutive first-order reactions with a reversible step. This method involves the determination of the area under the curve for the concentration of a given species against time. Computer techniques are used to integrate experimental curves and the method…

  18. Reverse phase-HPLC and HPTLC methods for determination of gemifloxacin mesylate in human plasma.

    PubMed

    Rote, A R; Pingle, S P

    2009-11-01

    Two simple, rapid, sensitive and economic chromatographic methods have been developed for determination of gemifloxacin mesylate in human plasma by using internal standard. First method depends on reverse phase high performance liquid chromatography. The plasma sample was extracted using chloroform:acetic acid (5.4:0.1, v/v). A concentration range from 30 to 600 ng/ml was used for calibration curve. The percent recovery of gemifloxacin mesylate was found to be 80.06-84.88. The mobile phase used consist of methanol:sodium acetate (1%):ortho phosphoric acid (65:35:0.5, v/v/v) with pH 2.1 and flow rate 0.8 ml/min in isocratic mode. The separation was carried out by UV-detector at wavelength 263 nm. Second method depends on high performance thin layer chromatography. The plasma sample was extracted using chloroform:acetic acid (5.9:0.1, v/v). A concentration range from 50 to 600 ng/spot was used for calibration curve. The percent recovery of gemifloxacin mesylate was found to be 80.01-86.17. The mobile phase used consists of ethyl acetate:methanol:ammonia (8.0:4.0:3.0, v/v/v). Densitometric analysis was carried out at wavelength 254 nm. The R(f) values for gemifloxacin mesylate and linezolide were 0.33+/-0.03 and 0.69+/-0.03 respectively. The stability of gemifloxacin mesylate in plasma was confirmed during three freeze-thaw cycles (-20 degrees C), on bench during 12 h. The proposed method was validated statistically and by performing recovery study for determination of gemifloxacin mesylate in human plasma.

  19. Health monitoring of cuplok scaffold joint connection using piezoceramic transducers and time reversal method

    NASA Astrophysics Data System (ADS)

    Zhang, Liuyu; Wang, Chenyu; Huo, Linsheng; Song, Gangbing

    2016-03-01

    Cuplok scaffolds are widely used to form temporary supporting structures when constructing bridges and other structures all over the world. The safety and stability of cuplok scaffolds are important issues during construction. Cuplok scaffolds are subjected to various types of vibrations, which may loosen the cuplok connection, negatively impacting the stability of the structure and even leading to severe accidents. In this paper, the authors propose a time reversal (TR) method to monitor the looseness status of the cuplok connection by using stress wave-based active sensing. Lead zirconate titanate (PZT), a commonly used piezoceramic material with a strong piezoelectric effect, is employed. In the proposed approach, PZT patches are used as sensors and actuators to monitor the cuplok joint looseness. One PZT patch is bonded to the vertical bar and two PZT patches are bonded to the cross bars of the cuplok scaffold. The PZT patch on the vertical bar is used as an actuator to generate a stress wave and the other two PZT patches are used as sensors to detect the propagated waves through the cuplok connection, the looseness of which will directly impact the stress wave propagation. The TR method is used to analyse the transmitted signal between the PZT patches through the cuplok connection. By comparing the peak values of the TR focused signal, it can be found that the peak value increases as the tightness of the cuplok connection increases. Therefore, the peak value of the TR focused signal can be used to monitor the tightness of the cuplok connection. In addition, the experimental results demonstrated that the TR method is superior to the energy method in consistency, sensitivity and anti-noise properties.

  20. Global trends in use of long-acting reversible and permanent methods of contraception: Seeking a balance.

    PubMed

    Joshi, Ritu; Khadilkar, Suvarna; Patel, Madhuri

    2015-10-01

    The global trend shows that the use of permanent contraception to prevent unintended pregnancy is high. Although the trend also shows a rise in the use of long-acting reversible methods, these are still underutilized despite having contraceptive as well as non-contraceptive benefits. Lack of knowledge among women, dependence on the provider for information, and provider bias for permanent contraception are cited as reasons for this reduced uptake. Training of healthcare providers and increased patient awareness about the effectiveness of long-acting reversible contraceptive methods will increase their uptake and help prevent unintended pregnancies.

  1. PSRna: Prediction of small RNA secondary structures based on reverse complementary folding method.

    PubMed

    Li, Jin; Xu, Chengzhen; Wang, Lei; Liang, Hong; Feng, Weixing; Cai, Zhongxi; Wang, Ying; Cong, Wang; Liu, Yunlong

    2016-08-01

    Prediction of RNA secondary structures is an important problem in computational biology and bioinformatics, since RNA secondary structures are fundamental for functional analysis of RNA molecules. However, small RNA secondary structures are scarce and few algorithms have been specifically designed for predicting the secondary structures of small RNAs. Here we propose an algorithm named "PSRna" for predicting small-RNA secondary structures using reverse complementary folding and characteristic hairpin loops of small RNAs. Unlike traditional algorithms that usually generate multi-branch loops and 5[Formula: see text] end self-folding, PSRna first estimated the maximum number of base pairs of RNA secondary structures based on the dynamic programming algorithm and a path matrix is constructed at the same time. Second, the backtracking paths are extracted from the path matrix based on backtracking algorithm, and each backtracking path represents a secondary structure. To improve accuracy, the predicted RNA secondary structures are filtered based on their free energy, where only the secondary structure with the minimum free energy was identified as the candidate secondary structure. Our experiments on real data show that the proposed algorithm is superior to two popular methods, RNAfold and RNAstructure, in terms of sensitivity, specificity and Matthews correlation coefficient (MCC).

  2. IR imaging simulation and analysis for aeroengine exhaust system based on reverse Monte Carlo method

    NASA Astrophysics Data System (ADS)

    Chen, Shiguo; Chen, Lihai; Mo, Dongla; Shi, Jingcheng

    2014-11-01

    The IR radiation characteristics of aeroengine are the important basis for IR stealth design and anti-stealth detection of aircraft. With the development of IR imaging sensor technology, the importance of aircraft IR stealth increases. An effort is presented to explore target IR radiation imaging simulation based on Reverse Monte Carlo Method (RMCM), which combined with the commercial CFD software. Flow and IR radiation characteristics of an aeroengine exhaust system are investigated, which developing a full size geometry model based on the actual parameters, using a flow-IR integration structured mesh, obtaining the engine performance parameters as the inlet boundary conditions of mixer section, and constructing a numerical simulation model of engine exhaust system of IR radiation characteristics based on RMCM. With the above models, IR radiation characteristics of aeroengine exhaust system is given, and focuses on the typical detecting band of IR spectral radiance imaging at azimuth 20°. The result shows that: (1) in small azimuth angle, the IR radiation is mainly from the center cone of all hot parts; near the azimuth 15°, mixer has the biggest radiation contribution, while center cone, turbine and flame stabilizer equivalent; (2) the main radiation components and space distribution in different spectrum is different, CO2 at 4.18, 4.33 and 4.45 micron absorption and emission obviously, H2O at 3.0 and 5.0 micron absorption and emission obviously.

  3. A reversible jump method for Bayesian phylogenetic inference with a nonhomogeneous substitution model.

    PubMed

    Gowri-Shankar, Vivek; Rattray, Magnus

    2007-06-01

    Nonhomogeneous substitution models have been introduced for phylogenetic inference when the substitution process is nonstationary, for example, when sequence composition differs between lineages. Existing models can have many parameters, and it is then difficult and computationally expensive to learn the parameters and to select the optimal model complexity. We extend an existing nonhomogeneous substitution model by introducing a reversible jump Markov chain Monte Carlo method for efficient Bayesian inference of the model order along with other phylogenetic parameters of interest. We also introduce a new hierarchical prior which leads to more reasonable results when only a small number of lineages share a particular substitution process. The method is implemented in the PHASE software, which includes specialized substitution models for RNA genes with conserved secondary structure. We apply an RNA-specific nonhomogeneous model to a structure-based alignment of rRNA sequences spanning the entire tree of life. A previous study of the same genes from a similar set of species found robust evidence for a mesophilic last universal common ancestor (LUCA) by inference of the G+C composition at the root of the tree. In the present study, we find that the helical GC composition at the root is strongly dependent on the root position. With a bacterial rooting, we find that there is no longer strong support for either a mesophile or a thermophile LUCA, although a hyperthermophile LUCA remains unlikely. We discuss reasons why results using only RNA helices may differ from results using all aligned sites when applying nonhomogeneous models to RNA genes.

  4. HRMC: Hybrid Reverse Monte Carlo method with silicon and carbon potentials

    NASA Astrophysics Data System (ADS)

    Opletal, G.; Petersen, T. C.; O'Malley, B.; Snook, I. K.; McCulloch, D. G.; Yarovsky, I.

    2008-05-01

    Fortran 77 code is presented for a hybrid method of the Metropolis Monte Carlo (MMC) and Reverse Monte Carlo (RMC) for the simulation of amorphous silicon and carbon structures. In additional to the usual constraints of the pair correlation functions and average coordination, the code also incorporates an optional energy constraint. This energy constraint is in the form of either the Environment Dependent Interatomic Potential (applicable to silicon and carbon) and the original and modified Stillinger-Weber potentials (applicable to silicon). The code also allows porous systems to be modeled via a constraint on porosity and internal surface area using a novel restriction on the available simulation volume. Program summaryProgram title: HRMC version 1.0 Catalogue identifier: AEAO_v1_0 Program summary URL:http://cpc.cs.qub.ac.uk/summaries/AEAO_v1_0.html Program obtainable from: CPC Program Library, Queen's University, Belfast, N. Ireland Licensing provisions: Standard CPC licence, http://cpc.cs.qub.ac.uk/licence/licence.html No. of lines in distributed program, including test data, etc.: 200 894 No. of bytes in distributed program, including test data, etc.: 907 557 Distribution format: tar.gz Programming language: FORTRAN 77 Computer: Any computer capable of running executables produced by the g77 Fortran compiler Operating system: Unix, Windows RAM: Depends on the type of empirical potential use, number of atoms and which constraints are employed Classification: 7.7 Nature of problem: Atomic modeling using empirical potentials and experimental data Solution method: Monte Carlo Additional comments: The code is not standard FORTRAN 77 but includes some additional features and therefore generates errors when compiled using the Nag95 compiler. It does compile successfully with the GNU g77 compiler ( http://www.gnu.org/software/fortran/fortran.html). Running time: Depends on the type of empirical potential use, number of atoms and which constraints are employed. The

  5. A facile photopolymerization method for fabrication of pH and light dual reversible stimuli-responsive surfaces.

    PubMed

    Wu, Shaopeng; Zhu, Xiaoqun; Yang, Jinliang; Nie, Jun

    2015-04-04

    Dual reversible surfaces with pH and light responsive properties were prepared via two-stage photopolymerization by grafting dimethylaminoethyl methacrylate (DMAEMA) and 2-methyl-4-phenylazo acrylate (MPA-Azo) on a substrate. The wettability of the modified surface could be reversibly controlled because of the protonation and deprotonation of DMAEMA at different pH values and the photoisomerization of MPA-Azo under UV irradiation at different wavelengths. This facile two-stage photopolymerization method has potential applications in fabrication of various external stimuli-responsive surfaces in the future.

  6. An imaging method for the covered damage region of strand wire based on dual time reversal using piezoceramic transducers

    NASA Astrophysics Data System (ADS)

    Xiaobin, Hong; Jianxi, Zhou; Peisong, Lin; Guojian, Huang

    2017-10-01

    According to damage detection of strand wire structures covered by anchor clip, an ultrasonic guided wave damage imaging detection method based on dual time reversal was suggested. It utilizes the characteristic of the guided waves traversing the whole tested region and the characteristic of time reversal making the signals gathered in the source at the same time. First, a modulation signal is excited by piezoceramic transducers at one end of the detected region of the strand and the reflection signals and the transmission signals are acquired. Then, a non-defective finite element simulation model corresponding to the detected strand is established. The extracted reflection and transmission damage signals can be imported respectively into the non-defective simulation model after time reversal processing to re-spread. The propagation of the reversal signal in the simulation model causes the model nodes to produce a displacement. These displacements can be extracted separately and calculated by dual time reversal operation, which means multiplying the nodes of the same coordinates at each of the two results. Finally, the result of the focusing operation is accumulated at all times and the damage region can be calculated. The focus results are presented by the point cloud. Experimental results show that the difficulties of traditional time focusing in strand wire structures can be overcome, and the damage region can be imaged preliminarily with a small relative error.

  7. A simple method for measuring excess adsorption isotherms of organic eluent components on reversed-phase packing materials.

    PubMed

    Ohashi, Junji; Harada, Makoto; Okada, Tetsuo

    2017-02-01

    A simple frontal analysis method has been developed for the reliable measurement of excess adsorption isotherms of an organic component on reversed-phase adsorbents in a series of programmed concentration steps. In the present method, a peak, which is produced by refractive index change in column eluate, is detected at 589 nm; it represents the elution volume of the boundary. The method is applied to the measurement of the excess adsorption isotherms of organic eluent components from water on commercially available reversed-phase stationary phases. The results are in good agreement with the previously reported isotherms. We also measure the excess adsorption isotherms of organic eluent components from solutions containing electrolytes. There are not any interference peaks on the elution traces. The method is thus reliably applicable to the evaluation of the excess adsorption of organic eluent components in practical systems.

  8. A comprehensive assessment of methods for de-novo reverse-engineering of genome-scale regulatory networks.

    PubMed

    Narendra, Varun; Lytkin, Nikita I; Aliferis, Constantin F; Statnikov, Alexander

    2011-01-01

    De-novo reverse-engineering of genome-scale regulatory networks is an increasingly important objective for biological and translational research. While many methods have been recently developed for this task, their absolute and relative performance remains poorly understood. The present study conducts a rigorous performance assessment of 32 computational methods/variants for de-novo reverse-engineering of genome-scale regulatory networks by benchmarking these methods in 15 high-quality datasets and gold-standards of experimentally verified mechanistic knowledge. The results of this study show that some methods need to be substantially improved upon, while others should be used routinely. Our results also demonstrate that several univariate methods provide a "gatekeeper" performance threshold that should be applied when method developers assess the performance of their novel multivariate algorithms. Finally, the results of this study can be used to show practical utility and to establish guidelines for everyday use of reverse-engineering algorithms, aiming towards creation of automated data-analysis protocols and software systems.

  9. The savory method can not green deserts or reverse climate change

    USDA-ARS?s Scientific Manuscript database

    Mr. Allan Savory addressed one of the major environmental challenges of our time – rapidly increasing atmospheric CO2 concentrations and climate warming - in a video presentation entitled, "How to green the world's deserts and reverse climate change" that was presented at the 2013 TED (Technology, E...

  10. General method allowing the use of 100% aqueous loading conditions in reversed-phase liquid chromatography.

    PubMed

    Pettersson, Sylvia Winkel; Persson, Börje S; Nyström, Mats

    2004-04-15

    Reversed-phase HPLC purification of peptides, using n-alkyl modified spherical silica, has become a widely used technique within the pharmaceutical industry. One drawback of these materials is the necessity of having at least 5% organic modifier in the mobile phase, in order to avoid de-wetting of the porous stationary phase. For some preparative reversed-phase separations, it is an advantage if the feed solution can be loaded onto the column under 100% aqueous conditions. This study describes the use of post-column pressure control to avoid de-wetting of regular reversed-phase stationary phases when operated under 100% aqueous conditions. The applicability of post-column pressure control as a means of maintaining the column fully wetted is demonstrated with various buffers and with packing materials having different alkyl-chain lengths. Two peptides, insulin and oxytocin, in overloaded quantities, were loaded under 100% aqueous conditions onto a regular C8 column, and then eluted by a acetonitrile gradient following standard procedures. The retention volume and the peak shape showed that the separation was satisfactory, and proved that post-column pressure control can be used to overcome wettability problems, which are otherwise often observed for reversed-phase packing materials with high ligand density.

  11. HRMC_1.1: Hybrid Reverse Monte Carlo method with silicon and carbon potentials

    NASA Astrophysics Data System (ADS)

    Opletal, G.; Petersen, T. C.; O'Malley, B.; Snook, I. K.; McCulloch, D. G.; Yarovsky, I.

    2011-02-01

    The Hybrid Reverse Monte Carlo (HRMC) code models the atomic structure of materials via the use of a combination of constraints including experimental diffraction data and an empirical energy potential. This energy constraint is in the form of either the Environment Dependent Interatomic Potential (EDIP) for carbon and silicon and the original and modified Stillinger-Weber potentials applicable to silicon. In this version, an update is made to correct an error in the EDIP carbon energy calculation routine. New version program summaryProgram title: HRMC version 1.1 Catalogue identifier: AEAO_v1_1 Program summary URL:http://cpc.cs.qub.ac.uk/summaries/AEAO_v1_1.html Program obtainable from: CPC Program Library, Queen's University, Belfast, N. Ireland Licensing provisions: Standard CPC licence, http://cpc.cs.qub.ac.uk/licence/licence.html No. of lines in distributed program, including test data, etc.: 36 991 No. of bytes in distributed program, including test data, etc.: 907 800 Distribution format: tar.gz Programming language: FORTRAN 77 Computer: Any computer capable of running executables produced by the g77 Fortran compiler. Operating system: Unix, Windows RAM: Depends on the type of empirical potential use, number of atoms and which constraints are employed. Classification: 7.7 Catalogue identifier of previous version: AEAO_v1_0 Journal reference of previous version: Comput. Phys. Comm. 178 (2008) 777 Does the new version supersede the previous version?: Yes Nature of problem: Atomic modelling using empirical potentials and experimental data. Solution method: Monte Carlo Reasons for new version: An error in a term associated with the calculation of energies using the EDIP carbon potential which results in incorrect energies. Summary of revisions: Fix to correct brackets in the two body part of the EDIP carbon potential routine. Additional comments: The code is not standard FORTRAN 77 but includes some additional features and therefore generates errors when

  12. Reverse transcription strand invasion based amplification (RT-SIBA): a method for rapid detection of influenza A and B.

    PubMed

    Eboigbodin, Kevin; Filén, Sanna; Ojalehto, Tuomas; Brummer, Mirko; Elf, Sonja; Pousi, Kirsi; Hoser, Mark

    2016-06-01

    Rapid and accurate diagnosis of influenza viruses plays an important role in infection control, as well as in preventing the misuse of antibiotics. Isothermal nucleic acid amplification methods offer significant advantages over the polymerase chain reaction (PCR), since they are more rapid and do not require the sophisticated instruments needed for thermal cycling. We previously described a novel isothermal nucleic acid amplification method, 'Strand Invasion Based Amplification' (SIBA®), with high analytical sensitivity and specificity, for the detection of DNA. In this study, we describe the development of a variant of the SIBA method, namely, reverse transcription SIBA (RT-SIBA), for the rapid detection of viral RNA targets. The RT-SIBA method includes a reverse transcriptase enzyme that allows one-step reverse transcription of RNA to complementary DNA (cDNA) and simultaneous amplification and detection of the cDNA by SIBA under isothermal reaction conditions. The RT-SIBA method was found to be more sensitive than PCR for the detection of influenza A and B and could detect 100 copies of influenza RNA within 15 min. The development of RT-SIBA will enable rapid and accurate diagnosis of viral RNA targets within point-of-care or central laboratory settings.

  13. Tomography, Adjoint Methods, Time-Reversal, and Banana-Doughnut Kernels

    NASA Astrophysics Data System (ADS)

    Tape, C.; Tromp, J.; Liu, Q.

    2004-12-01

    We demonstrate that Fréchet derivatives for tomographic inversions may be obtained based upon just two calculations for each earthquake: one calculation for the current model and a second, `adjoint', calculation that uses time-reversed signals at the receivers as simultaneous, fictitious sources. For a given model~m, we consider objective functions χ(m) that minimize differences between waveforms, traveltimes, or amplitudes. We show that the Fréchet derivatives of such objective functions may be written in the generic form δ χ=∫ VK_m( {x}) δ ln m( {x}) d3 {x}, where δ ln m=δ m/m denotes the relative model perturbation. The volumetric kernel Km is defined throughout the model volume V and is determined by time-integrated products between spatial and temporal derivatives of the regular displacement field {s} and the adjoint displacement field {s} obtained by using time-reversed signals at the receivers as simultaneous sources. In waveform tomography the time-reversed signal consists of differences between the data and the synthetics, in traveltime tomography it is determined by synthetic velocities, and in amplitude tomography it is controlled by synthetic displacements. For each event, the construction of the kernel Km requires one forward calculation for the regular field {s} and one adjoint calculation involving the fields {s} and {s}. For multiple events the kernels are simply summed. The final summed kernel is controlled by the distribution of events and stations and thus determines image resolution. In the case of traveltime tomography, the kernels Km are weighted combinations of banana-doughnut kernels. We demonstrate also how amplitude anomalies may be inverted for lateral variations in elastic and anelastic structure. The theory is illustrated based upon 2D spectral-element simulations.

  14. Alternative methods for assessing bronchodilator reversibility in chronic obstructive pulmonary disease

    PubMed Central

    Hadcroft, J; Calverley, P

    2001-01-01

    BACKGROUND—Bronchodilator reversibility testing is recommended in all patients with chronic obstructive pulmonary disease (COPD) but does not predict improvements in breathlessness or exercise performance. Two alternative ways of assessing lung mechanics—measurement of end expiratory lung volume (EELV) using the inspiratory capacity manoeuvre and application of negative expiratory pressure (NEP) during tidal breathing to detect tidal airflow limitation—do relate to the degree of breathlessness in COPD. Their usefulness as end points in bronchodilator reversibility testing has not been examined.
METHODS—We studied 20 patients with clinically stable COPD (mean age 69.9 (1.5) years, 15 men, forced expiratory volume in one second (FEV1) 29.5 (1.6)% predicted) with tidal flow limitation as assessed by their maximum flow-volume loop. Spirometric parameters, slow vital capacity (SVC), inspiratory capacity (IC), and NEP were measured seated, before and after nebulised saline, and at intervals after 5 mg nebulised salbutamol and 500 µg nebulised ipratropium bromide. The patients attended twice and the treatment order was randomised.
RESULTS—Mean FEV1, FVC, SVC, and IC were unchanged after saline but the degree of tidal flow limitation varied. FEV1 improved significantly after salbutamol and ipratropium (0.11 (0.02) l and 0.09 (0.02) l, respectively) as did the other lung volumes with further significant increases after the combination. Tidal volume and mean expiratory flow increased significantly after all bronchodilators but breathlessness fell significantly only after the combination treatment. The initial NEP score was unrelated to subsequent changes in lung volume.
CONCLUSIONS—NEP is not an appropriate measurement of acute bronchodilator responsiveness. Changes in IC were significantly larger than those in FEV1 and may be more easily detected. However, our data showed no evidence for separation of "reversible" and "irreversible" groups whatever

  15. Alternative methods for assessing bronchodilator reversibility in chronic obstructive pulmonary disease.

    PubMed

    Hadcroft, J; Calverley, P M

    2001-09-01

    Bronchodilator reversibility testing is recommended in all patients with chronic obstructive pulmonary disease (COPD) but does not predict improvements in breathlessness or exercise performance. Two alternative ways of assessing lung mechanics-measurement of end expiratory lung volume (EELV) using the inspiratory capacity manoeuvre and application of negative expiratory pressure (NEP) during tidal breathing to detect tidal airflow limitation-do relate to the degree of breathlessness in COPD. Their usefulness as end points in bronchodilator reversibility testing has not been examined. We studied 20 patients with clinically stable COPD (mean age 69.9 (1.5) years, 15 men, forced expiratory volume in one second (FEV(1)) 29.5 (1.6)% predicted) with tidal flow limitation as assessed by their maximum flow-volume loop. Spirometric parameters, slow vital capacity (SVC), inspiratory capacity (IC), and NEP were measured seated, before and after nebulised saline, and at intervals after 5 mg nebulised salbutamol and 500 microg nebulised ipratropium bromide. The patients attended twice and the treatment order was randomised. Mean FEV(1), FVC, SVC, and IC were unchanged after saline but the degree of tidal flow limitation varied. FEV(1) improved significantly after salbutamol and ipratropium (0.11 (0.02) l and 0.09 (0.02) l, respectively) as did the other lung volumes with further significant increases after the combination. Tidal volume and mean expiratory flow increased significantly after all bronchodilators but breathlessness fell significantly only after the combination treatment. The initial NEP score was unrelated to subsequent changes in lung volume. NEP is not an appropriate measurement of acute bronchodilator responsiveness. Changes in IC were significantly larger than those in FEV(1) and may be more easily detected. However, our data showed no evidence for separation of "reversible" and "irreversible" groups whatever outcome measure was adopted.

  16. A reliable and reproducible method for the lipase assay in an AOT/isooctane reversed micellar system: modification of the copper-soap colorimetric method.

    PubMed

    Kwon, Chang Woo; Park, Kyung-Min; Choi, Seung Jun; Chang, Pahn-Shick

    2015-09-01

    The copper-soap method, which is based on the absorbance of a fatty acid-copper complex at 715 nm, is a widely used colorimetric assay to determine the lipase activity in reversed micellar system. However, the absorbance of the bis(2-ethylhexyl) sodium sulfosuccinate (AOT)-copper complex prevents the use of an AOT/isooctane reversed micellar system. An extraction step was added to the original procedure to remove AOT and eliminate interference from the AOT-copper complex. Among the solvents tested, acetonitrile was determined to be the most suitable because it allows for the generation of a reproducible calibration curve with oleic acid that is independent of the AOT concentrations. Based on the validation data, the modified method, which does not experience interference from the AOT-copper complex, could be a useful method with enhanced accuracy and reproducibility for the lipase assay.

  17. Synthesis and characterization of α-NaYF4: Yb, Er nanoparticles by reverse microemulsion method

    NASA Astrophysics Data System (ADS)

    Gunaseelan, M.; Senthilselvan, J.

    2016-05-01

    A simple and cost effective reverse microemulsion system was newly designed to synthesis NaYF4:20%Yb,2%Er upconverting luminescent nanoparticles. XRD results confirms the cubic structure of NaYF4 nanophosphor in the as prepared condition without any other impurity phases. The as-prepared sample itself having highly crystalline nanoparticle with well dispersed uniform morphology is the advantage of this reverse microemulsion process. HRTEM images of as prepared and calcined samples revealed spherical nanoclusters morphology with size of ~210 nm and ~245 nm respectively. The characteristic absorption wavelength that occurs at 980 nm due to transition of energy levels 2F5/2 to 2F7/2 for Yb3+ rare earth ion in as prepared and calcined upconversion nanoparticle confirms the presence of Yb3+ by UV-Visible spectroscopy which can act as a sensitizer for photonic upconversion. Therefore the absorption at NIR region and emission spectrum at visible region suggests that NaYF4:20%Yb,2%Er is suitable for upcoversion process, due to its optical property and chemical stability this material also be useful for bio imaging applications.

  18. Improved reverse projection method for large refraction angle in grating-based x-ray phase contrast imaging

    NASA Astrophysics Data System (ADS)

    Wei, Wenbin; Wu, Zhao; Wei, Chenxi; Hu, Yue; Liu, Gang; Tian, Yangchao

    2016-03-01

    Grating-based x-ray phase contrast imaging has attracted significant attentions in the past years due to its capability in achieving x-ray phase contrast imaging with low brilliance source. The reverse projection (RP) method is a novel fast and low dose information extraction approach, which bases on the linear approximation of the shifting curve around its half-slope. However, when the refraction angle is beyond the linear range of the shifting curve, the extracted information is no longer credible. In this paper, we present an improved retrieval method by calculating an inverse function. Compared with the original retrieval method, our method does not rely on the first order approximation, and thus is suitable for large refraction angle. Theoretical derivations and numerical simulations are performed to confirm the accuracy of the method.

  19. Broken time reversal symmetry states in superconductors using the ultrafast pump-probe method

    NASA Astrophysics Data System (ADS)

    Setty, Chandan; Hu, Jiangping

    2015-03-01

    The excitation of vibrational modes by ultrafast optical pulses can be a useful probe of the electronic ground state in a solid through the electron-phonon interactions. In this work, we show that the phase of the oscillations of reflectivity/transmissivity as a function of the delay time can contain signatures of broken time reversal symmetry (BTRS) in the superconducting ground state. To illustrate this, we consider a simple Hamiltonian consisting of a two band electronic part and a phononic part; additionally, we include terms which couple electrons to phonons and light. In the absence of dissipation, we show that on entry into the BTRS superconducting state, the phase of the reflectivity oscillations deviates from the normal state values of +/- π/2 in a continuous fashion. We will also comment on the effects of dissipation and the dependence of our result on the opacity of the superconductor.

  20. A clinical method for detecting bronchial reversibility using a breath sound spectrum analysis in infants.

    PubMed

    Enseki, Mayumi; Nukaga, Mariko; Tabata, Hideyuki; Hirai, Kota; Matsuda, Shinichi; Mochizuki, Hiroyuki

    2017-05-01

    Using a breath sound analyzer, we investigated clinical parameters for detecting bronchial reversibility in infants. A total of 59 infants (4-39 months, mean age 7.8 months) were included. In Study 1, the intra- and inter-observer variability was measured in 23 of 59 infants. Breath sound parameters, the frequency at 99% of the maximum frequency (F99), frequency at 25%, 50%, and 75% of the power spectrum (Q25, Q50, and Q75), and highest frequency of inspiratory breath sounds (HFI), and parameters obtained using the ratio of parameters, i.e. spectrum curve indices, the ratio of the third and fourth area to total area (A3/AT and B4/AT, respectively) and ratio of power and frequency at F75 and F50 (RPF75 and RPF50), were calculated. In Study 2, the relationship between parameters of breath sounds and age and stature were studied. In Study 3, breath sounds were studied before and after β2 agonist inhalation. In Study 1, the data showed statistical intra- and inter-observer reliability in A3/AT (p=0.042 and 0.034, respectively) and RPF50 (p=0.001 and 0.001, respectively). In Study 2, there were no significant relationships between age, height, weight, and BMI. In Study 3, A3/AT and RPF50 significantly changed after β2 agonist inhalation (p=0.001 and p<0.001, respectively). Breath sound analysis can be performed in infants, as in older children, and the spectrum curve indices are not significantly affected by age-related factors. These sound parameters may play a role in the assessment of bronchial reversibility in infants. Copyright © 2016 The Japanese Respiratory Society. Published by Elsevier B.V. All rights reserved.

  1. Advanced feedback control methods in EXTRAP T2R reversed field pinch

    NASA Astrophysics Data System (ADS)

    Yadikin, D.; Brunsell, P. R.; Paccagnella, R.

    2006-07-01

    Previous experiments in the EXTRAP T2R reversed field pinch device have shown the possibility of suppression of multiple resistive wall modes (RWM). A feedback system has been installed in EXTRAP T2R having 100% coverage of the toroidal surface by the active coil array. Predictions based on theory and the previous experimental results show that the number of active coils should be sufficient for independent stabilization of all unstable RWMs in the EXTRAP T2R. Experiments using different feedback schemes are performed, comparing the intelligent shell, the fake rotating shell, and the mode control with complex feedback gains. Stabilization of all unstable RWMs throughout the discharge duration of td≈10τw is seen using the intelligent shell feedback scheme. Mode rotation and the control of selected Fourier harmonics is obtained simultaneously using the mode control scheme with complex gains. Different sensor signals are studied. A feedback system with toroidal magnetic field sensors could have an advantage of lower feedback gain needed for the RWM suppression compared to the system with radial magnetic field sensors. In this study, RWM suppression is demonstrated, using also the toroidal field component as a sensor signal in the feedback system.

  2. Reversible Cryopreservation of Living Cells Using an Electron Microscopy Cryo-Fixation Method.

    PubMed

    Huebinger, Jan; Han, Hong-Mei; Grabenbauer, Markus

    2016-01-01

    Rapid cooling of aqueous solutions is a useful approach for two important biological applications: (I) cryopreservation of cells and tissues for long-term storage, and (II) cryofixation for ultrastructural investigations by electron and cryo-electron microscopy. Usually, both approaches are very different in methodology. Here we show that a novel, fast and easy to use cryofixation technique called self-pressurized rapid freezing (SPRF) is-after some adaptations-also a useful and versatile technique for cryopreservation. Sealed metal tubes with high thermal diffusivity containing the samples are plunged into liquid cryogen. Internal pressure builds up reducing ice crystal formation and therefore supporting reversible cryopreservation through vitrification of cells. After rapid rewarming of pressurized samples, viability rates of > 90% can be reached, comparable to best-performing of the established rapid cooling devices tested. In addition, the small SPRF tubes allow for space-saving sample storage and the sealed containers prevent contamination from or into the cryogen during freezing, storage, or thawing.

  3. Advanced feedback control methods in EXTRAP T2R reversed field pinch

    SciTech Connect

    Yadikin, D.; Brunsell, P. R.; Paccagnella, R.

    2006-07-15

    Previous experiments in the EXTRAP T2R reversed field pinch device have shown the possibility of suppression of multiple resistive wall modes (RWM). A feedback system has been installed in EXTRAP T2R having 100% coverage of the toroidal surface by the active coil array. Predictions based on theory and the previous experimental results show that the number of active coils should be sufficient for independent stabilization of all unstable RWMs in the EXTRAP T2R. Experiments using different feedback schemes are performed, comparing the intelligent shell, the fake rotating shell, and the mode control with complex feedback gains. Stabilization of all unstable RWMs throughout the discharge duration of t{sub d}{approx_equal}10{tau}{sub w} is seen using the intelligent shell feedback scheme. Mode rotation and the control of selected Fourier harmonics is obtained simultaneously using the mode control scheme with complex gains. Different sensor signals are studied. A feedback system with toroidal magnetic field sensors could have an advantage of lower feedback gain needed for the RWM suppression compared to the system with radial magnetic field sensors. In this study, RWM suppression is demonstrated, using also the toroidal field component as a sensor signal in the feedback system.

  4. A simple, inexpensive method for preparing cell lysates suitable for downstream reverse transcription quantitative PCR.

    PubMed

    Shatzkes, Kenneth; Teferedegne, Belete; Murata, Haruhiko

    2014-04-11

    Sample nucleic acid purification can often be rate-limiting for conventional quantitative PCR (qPCR) workflows. We recently developed high-throughput virus microneutralization assays using an endpoint assessment approach based on reverse transcription qPCR (RT-qPCR). The need for cumbersome RNA purification is circumvented in our assays by making use of a commercial reagent that can easily generate crude cell lysates amenable to direct analysis by one-step RT-qPCR. In the present study, we demonstrate that a simple buffer containing a non-ionic detergent can serve as an inexpensive alternative to commercially available reagents for the purpose of generating RT-qPCR-ready cell lysates from MDCK cells infected with influenza virus. We have found that addition of exogenous RNase inhibitor as a buffer component is not essential in order to maintain RNA integrity, even following stress at 37 °C incubation for 1-2 hours, in cell-lysate samples either freshly prepared or previously stored frozen at -80 °C.

  5. A simple, inexpensive method for preparing cell lysates suitable for downstream reverse transcription quantitative PCR

    PubMed Central

    Shatzkes, Kenneth; Teferedegne, Belete; Murata, Haruhiko

    2014-01-01

    Sample nucleic acid purification can often be rate-limiting for conventional quantitative PCR (qPCR) workflows. We recently developed high-throughput virus microneutralization assays using an endpoint assessment approach based on reverse transcription qPCR (RT-qPCR). The need for cumbersome RNA purification is circumvented in our assays by making use of a commercial reagent that can easily generate crude cell lysates amenable to direct analysis by one-step RT-qPCR. In the present study, we demonstrate that a simple buffer containing a non-ionic detergent can serve as an inexpensive alternative to commercially available reagents for the purpose of generating RT-qPCR-ready cell lysates from MDCK cells infected with influenza virus. We have found that addition of exogenous RNase inhibitor as a buffer component is not essential in order to maintain RNA integrity, even following stress at 37°C incubation for 1–2 hours, in cell-lysate samples either freshly prepared or previously stored frozen at −80°C. PMID:24722424

  6. Development of a reverse transcription polymerase chain reaction method for yellow fever virus detection.

    PubMed

    Méndez, María C; Domingo, Cristina; Tenorio, Antonio; Pardo, Lissethe C; Rey, Gloria J; Méndez, Jairo A

    2013-09-01

    Yellow fever is considered a re-emerging disease and is endemic in tropical regions of Africa and South America. At present, there are no standardized or commercialized kits available for yellow fever virus detection. Therefore, diagnosis must be made by time-consuming routine techniques, and sometimes, the virus or its proteins are not detected. Furthermore, co-circulation with other flaviviruses, including dengue virus, increases the difficulty of diagnosis. To develop a specific reverse transcriptase-polymerase chain reaction (RT-PCR) and nested PCR-based assay to improve the detection and diagnosis of yellow fever virus using both serum and fresh tissue samples. RT-PCR primers were designed to amplify a short fragment of all yellow fever virus genotypes reported. A second set of primers was used in a nested PCR to increase sensitivity. Thirty-three clinical samples were tested with the standardized reaction. The expected amplicon was obtained in 25 out of 33 samples analyzed using this approach, and 2 more samples tested positive after a subsequent nested PCR approach. This improved technique not only ensures the specific detection of a wide range of yellow fever virus genotypes but also may increase the sensitivity of detection by introducing a second round of amplification, allowing a rapid differential diagnosis between dengue and yellow fever infection, which is required for effective surveillance and opportune epidemiologic measures.

  7. Reversible Cryopreservation of Living Cells Using an Electron Microscopy Cryo-Fixation Method

    PubMed Central

    Huebinger, Jan; Han, Hong-Mei

    2016-01-01

    Rapid cooling of aqueous solutions is a useful approach for two important biological applications: (I) cryopreservation of cells and tissues for long-term storage, and (II) cryofixation for ultrastructural investigations by electron and cryo-electron microscopy. Usually, both approaches are very different in methodology. Here we show that a novel, fast and easy to use cryofixation technique called self-pressurized rapid freezing (SPRF) is–after some adaptations–also a useful and versatile technique for cryopreservation. Sealed metal tubes with high thermal diffusivity containing the samples are plunged into liquid cryogen. Internal pressure builds up reducing ice crystal formation and therefore supporting reversible cryopreservation through vitrification of cells. After rapid rewarming of pressurized samples, viability rates of > 90% can be reached, comparable to best-performing of the established rapid cooling devices tested. In addition, the small SPRF tubes allow for space-saving sample storage and the sealed containers prevent contamination from or into the cryogen during freezing, storage, or thawing. PMID:27711254

  8. Development and validation of stability indicating method for the determination of exemestane by reverse phase high performance liquid chromatography.

    PubMed

    Konda, Bharath; Tiwari, Ravi N; Fegade, Harshal

    2011-09-01

    Exemestane is an aromatase inhibitor used in the treatment of breast cancer. A selective stability-indicating reversed-phase high performance liquid chromatography (RP-HPLC) method has been developed which can separate and accurately quantitate low levels of exemestane. The stability-indicating capability of the method was demonstrated by adequate separation of exemestane and all the degradation product peaks from exemestane peak and also from each other in stability samples of exemestane. Chromatographic separation of exemestane and its degraded products were achieved by using isocratic elution at a flow rate of 1.0 mL/min on a C18 reverse phase column (Phenomenex, size: 250 × 4.60 mm, particle size 5 μm) at ambient temperature. The mobile phase used for the analysis was acetonitrile-water (60:40, %v/v) with UV visible detection at 242 nm. The proposed method was used to study the degradation behavior of drug under various stress conditions as per ICH recommended guidelines.

  9. A reversed-phase HPLC-UV method developed and validated for simultaneous quantification of six alkaloids from Nicotiana spp.

    PubMed

    Moghbel, Nahid; Ryu, BoMi; Steadman, Kathryn J

    2015-08-01

    A reversed-phase HPLC-UV method was developed, optimized, and validated for the separation and quantitation of six target alkaloids from leaves of Nicotiana species (nicotine, nornicotine, anatabine, anabasine, myosmine, and cotinine). A bidentate reversed-phase C18 column was used as stationary phase and an alkaline ammonium formate buffer and acetonitrile as mobile phase. The alkaloids were well separated in a short run time of 13min with mobile phase pH 10.5 and a small gradient of 9-13% acetonitrile, and detected using UV at 260nm. Peak parameters were acceptable for all six closely related alkaloids. The proposed method has enough linearity with correlation coefficient >0.999 within the investigated range for all tested alkaloids. Satisfactory precision was achieved for both intra- and inter-day assay, with RSD less than 2% for all alkaloid standards. Reproducibility was also within the acceptable range of RSD <2%. Limit of detection was 1.6μg/mL for nicotine and below 1μg/mL for all other alkaloids. The limit of quantification was 2.8 and 4.8μg/mL for nornicotine and nicotine respectively, and below 2μg/mL for all other alkaloids. The method was successfully applied for simultaneous analysis of alkaloids in leaves of Nicotiana benthamiana.

  10. A method for determination of phosphatidylethanol from high density lipoproteins by reversed-phase HPLC with TOF-MS detection.

    PubMed

    Tolonen, Ari; Lehto, Tiina M; Hannuksela, Minna L; Savolainen, Markku J

    2005-06-01

    Phosphatidylethanol (PEth) is a unique phospholipid that is formed in the body only in the presence of ethanol. According to a new hypothesis, blood high-density lipoprotein (HDL) particles may act as carriers of PEth and mediate part of the antiatherogenic effects of moderate alcohol drinking. Liquid chromatographic method using reversed-phase C8 column and negative ion mode electrospray ionization-mass spectrometry detection with time-of-flight (TOF) instrument was developed for the determination of very small amounts of PEth that might be present on blood HDL particles. The samples used in the current study were human HDL spiked with PEth and internal standard phosphatidylpropanol (PProp). The use of reversed-phase column enabled a short analysis time of 19 min/injection, which is only one-third of the earlier normal-phase methods reported. Because of the narrow bore column (2.1 mm i.d.) and short analysis time, the solvent consumption was decreased. The sensitivity of detection obtained with TOF-MS was better than that of previous methods, with the detection limit being as low as 1 ng/ml in injected sample (20 pg on-column approximately 28 fmol PEth), corresponding to approximately 6.7 ng of PEth in milliliter of unprepared HDL. Good linearity of detection was obtained for a range of 1-100 ng/ml of PEth, whereas all of the deviations in precision and accuracy were less than 15%.

  11. Development and validation of a reversed-phase HPLC method for the determination of ezetimibe in pharmaceutical dosage forms.

    PubMed

    Sistla, R; Tata, V S S K; Kashyap, Y V; Chandrasekar, D; Diwan, P V

    2005-09-15

    Ezetimibe belongs to a group of selective and very effective 2-azetidione cholesterol absorption inhibitors that act on the level of cholesterol entry into enterocytes. A rapid, specific reversed-phase HPLC method has been developed for assaying ezetimibe in pharmaceutical dosage forms. The assay involved an isocratic elution of ezetimibe in a Kromasil 100 C18 column using a mobile phase composition of water (pH 6.8, 0.05%, w/v 1-heptane sulfonic acid) and acetonitrile (30:70, v/v). The flow rate was 0.5 ml/min and the analyte monitored at 232 nm. The assay method was found to be linear from 0.5 to 50 microg/ml. All the validation parameters were within the acceptance range. The developed method was successfully applied to estimate the amount of ezetimibe in tablets.

  12. Detection methods for rice viruses by a reverse-transcription loop-mediated isothermal amplification (RT-LAMP).

    PubMed

    Sasaya, Takahide

    2015-01-01

    Developing a quick and accurate method to diagnose rice viruses in host plants and in vector insects is very important to control virus diseases of rice. A reverse-transcription loop-mediated isothermal amplification (RT-LAMP) assay, one of the most promising molecular diagnostic methods, was established to detect nine viruses, including eight RNA viruses and one DNA virus, in infected rice plants and the viruliferous vector insects. The sensitivities of the assays were either higher than or similar to those of one-step RT-PCR. With a combination of rapid RNA extraction and a RT-LAMP assay, these nine viruses were detected within 2 h from infected rice plants and the viruliferous insects without expensive or unusual equipment. This RT-LAMP method for rice viruses can therefore be adopted not only for diagnosis but also to study the epidemiology and molecular pathology of rice viruses.

  13. One-step preparation of chitosan-coated cationic liposomes by an improved supercritical reverse-phase evaporation method.

    PubMed

    Otake, Katsuto; Shimomura, Takeshi; Goto, Toshihiro; Imura, Tomohiro; Furuya, Takeshi; Yoda, Satoshi; Takebayashi, Yoshihiro; Sakai, Hideki; Abe, Masahiko

    2006-04-25

    High-pressure carbon dioxide in contact with water dissolves to form carbonic acid, causing a decrease in pH. By use of these characteristics of a CO2/H2O biphasic system, chitosan-coated cationic liposomes of l-alpha-dipalmitoylphosphatidylcholine were successfully prepared by an improved supercritical reverse-phase evaporation (ISCRPE) method. Liposome-chitosan complexes carrying a positive charge were prepared in a single-step procedure without the use of acid or organic solvent, including ethanol. The maximum trapping efficiency of liposomes prepared by the ISCRPE method was 17%, with or without the addition of chitosan, compared to only 2% for liposomes prepared by the Bangham method. Furthermore, the liposomal dispersion was stable at room temperature in a sealed tube for over 30 days.

  14. A reverse Monte Carlo method for deriving optical constants of solids from reflection electron energy-loss spectroscopy spectra

    SciTech Connect

    Da, B.; Sun, Y.; Ding, Z. J.; Mao, S. F.; Zhang, Z. M.; Jin, H.; Yoshikawa, H.; Tanuma, S.

    2013-06-07

    A reverse Monte Carlo (RMC) method is developed to obtain the energy loss function (ELF) and optical constants from a measured reflection electron energy-loss spectroscopy (REELS) spectrum by an iterative Monte Carlo (MC) simulation procedure. The method combines the simulated annealing method, i.e., a Markov chain Monte Carlo (MCMC) sampling of oscillator parameters, surface and bulk excitation weighting factors, and band gap energy, with a conventional MC simulation of electron interaction with solids, which acts as a single step of MCMC sampling in this RMC method. To examine the reliability of this method, we have verified that the output data of the dielectric function are essentially independent of the initial values of the trial parameters, which is a basic property of a MCMC method. The optical constants derived for SiO{sub 2} in the energy loss range of 8-90 eV are in good agreement with other available data, and relevant bulk ELFs are checked by oscillator strength-sum and perfect-screening-sum rules. Our results show that the dielectric function can be obtained by the RMC method even with a wide range of initial trial parameters. The RMC method is thus a general and effective method for determining the optical properties of solids from REELS measurements.

  15. A reverse Monte Carlo method for deriving optical constants of solids from reflection electron energy-loss spectroscopy spectra

    NASA Astrophysics Data System (ADS)

    Da, B.; Sun, Y.; Mao, S. F.; Zhang, Z. M.; Jin, H.; Yoshikawa, H.; Tanuma, S.; Ding, Z. J.

    2013-06-01

    A reverse Monte Carlo (RMC) method is developed to obtain the energy loss function (ELF) and optical constants from a measured reflection electron energy-loss spectroscopy (REELS) spectrum by an iterative Monte Carlo (MC) simulation procedure. The method combines the simulated annealing method, i.e., a Markov chain Monte Carlo (MCMC) sampling of oscillator parameters, surface and bulk excitation weighting factors, and band gap energy, with a conventional MC simulation of electron interaction with solids, which acts as a single step of MCMC sampling in this RMC method. To examine the reliability of this method, we have verified that the output data of the dielectric function are essentially independent of the initial values of the trial parameters, which is a basic property of a MCMC method. The optical constants derived for SiO2 in the energy loss range of 8-90 eV are in good agreement with other available data, and relevant bulk ELFs are checked by oscillator strength-sum and perfect-screening-sum rules. Our results show that the dielectric function can be obtained by the RMC method even with a wide range of initial trial parameters. The RMC method is thus a general and effective method for determining the optical properties of solids from REELS measurements.

  16. Early Impact of the Affordable Care Act on Uptake of Long-acting Reversible Contraceptive Methods.

    PubMed

    Pace, Lydia E; Dusetzina, Stacie B; Keating, Nancy L

    2016-09-01

    The Affordable Care Act (ACA) required most private insurance plans to cover contraceptive services without patient cost-sharing as of January 2013 for most plans. Whether the ACA's mandate has impacted long-acting reversible contraceptives (LARC) use is unknown. The aim of this article is to assess trends in LARC cost-sharing and uptake before and one year after implementation of the ACA's contraceptive mandate. A retrospective cohort study using Truven Health MarketScan claims data from January 2010 to December 2013. Women aged 18-45 years with continuous insurance coverage with claims for oral contraceptive pills, patches, rings, injections, or LARC during 2010-2013 (N=3,794,793). Descriptive statistics were used to assess trends in LARC cost-sharing and uptake from 2010 through 2013. Interrupted time series models were used to assess the association of time, ACA, and time after the ACA on LARC cost-sharing and initiation rates, adjusting for patient and plan characteristics. The proportion of claims with $0 cost-sharing for intrauterine devices and implants, respectively, rose from 36.6% and 9.3% in 2010 to 87.6% and 80.5% in 2013. The ACA was associated with a significant increase in these proportions and in their rate of increase (level and slope change both P<0.001). LARC uptake increased over time with no significant change in level of LARC use after ACA implementation in January 2013 (P=0.44) and a slightly slower rate of growth post-ACA than previously reported (β coefficient for trend, -0.004; P<0.001). The ACA has significantly decreased LARC cost-sharing, but during its first year had not yet increased LARC initiation rates.

  17. Reverse transcription polymerase chain reaction-based method for selectively detecting vegetative cells of toxigenic Clostridium difficile.

    PubMed

    Senoh, Mitsutoshi; Kato, Haru; Murase, Tomoko; Hagiya, Hideharu; Tagashira, Yasuaki; Fukuda, Tadashi; Iwaki, Masaaki; Yamamoto, Akihiko; Shibayama, Keigo

    2014-11-01

    The laboratory diagnostic methods for Clostridium difficile infection (CDI) include toxigenic culture, enzyme immunoassays (EIAs) to detect the toxins of C. difficile, and nucleic acid amplification tests (NAATs) to detect C. difficile toxin genes, but each of these methods has disadvantages; toxigenic cultures require a long time to produce results, EIAs have low sensitivity, and NAATs that target DNA cannot distinguish vegetative cells from spores and dead cells. Here we report a new detection method that uses reverse transcription polymerase chain reaction to target the toxin-gene transcripts. This method was able to specifically detect the vegetative cells of toxigenic C. difficile in fecal samples in spike tests, with a minimum detection limit of 5 × 10(2) colony-forming units per 100 mg of stool specimen. The performance of this method was also demonstrated in a pilot scale evaluation using clinical fecal specimens, which showed that this method may be more sensitive than EIA and requires a shorter time than toxigenic culture. This method could potentially be applied in the clinical laboratory to detect C. difficile in fecal specimens. The ability of this method to discriminate the presence of vegetative cells from spores and dead cells could help to further the understanding of CDI.

  18. Validated stability-indicating reversed-phase-HPLC method for simultaneous determination of orphenadrine citrate, caffeine and aspirin.

    PubMed

    Darwish, Khaled; Salama, Ismail; Mostafa, Samia; El-Sadek, Mohamed

    2012-01-01

    New, simple, rapid and precise reversed-phase high-performance liquid chromatographic method was developed for the simultaneous determination of orphenadrine citrate, caffeine and aspirin in presence of aspirin degradation products, orphenadrine citrate and caffeine process related impurities, and excipients. Good resolution and quantization were achieved on reversed-phase column [Phenomenex™ Luna ODS C(18) (25 cm×4.6 mm, 5 µm particles)]. Gradient elution based on; eluant [A]: 0.1% triethylamine in aqueous potassium dihydrogen phosphate buffer (50 mM; pH 3.0), while as, eluant [B]: acetonitrile, at a flow rate of 1.5 mL min(-1). UV quantitation was set at 215 nm. Linearity was exhibited for orphenadrine citrate, caffeine and aspirin within 0.5-150, 0.5-360 or 0.7-301 µg mL(-1) ranges, respectively. Satisfactory validation results were ascertained in terms of low limits of quantiation (6.33×10(-2)-7.94×10(-2)), mean percentage recovery (98.9-101.4%), precision (<2%) and robustness. The proposed method was proved to be specific, robust and accurate for the determination of cited drugs in pharmaceutical preparations in presence of their degradation products.

  19. A METHOD TO REMOVE ENVIRONMENTAL INHIBITORS PRIOR TO THE DETECTION OF WATERBORNE ENTERIC VIRUSES BY REVERSE TRANSCRIPTION-POLYMERASE CHAIN REACTION

    EPA Science Inventory

    A method was developed to remove environmental inhibitors from sample concentrates prior to detection of human enteric viruses using the reverse transcription-polymerase chain reaction (RT-PCR).Environmental inhibitors, concentrated along with viruses during water sample processi...

  20. A METHOD TO REMOVE ENVIRONMENTAL INHIBITORS PRIOR TO THE DETECTION OF WATERBORNE ENTERIC VIRUSES BY REVERSE TRANSCRIPTION-POLYMERASE CHAIN REACTION

    EPA Science Inventory

    A method was developed to remove environmental inhibitors from sample concentrates prior to detection of human enteric viruses using the reverse transcription-polymerase chain reaction (RT-PCR).Environmental inhibitors, concentrated along with viruses during water sample processi...

  1. Lipophilicity data for some preservatives estimated by reversed-phase liquid chromatography and different computation methods.

    PubMed

    Casoni, Dorina; Kot-Wasik, Agata; Namieśnik, Jacek; Sârbu, Costel

    2009-03-20

    The chromatographic behavior of some preservatives was performed by reversed-phase high-performance liquid chromatography on C18 (LiChroCART, Purosphere RP-18e), C8 (Zorbax, Eclipse XDB-C8), CN100 (Säulentechnik, Lichrosphere) and NH(2) (Supelcosil LC-NH(2)) columns. The lipophilicity estimated for the first time on the first three columns are comparable and very well correlated. The mobile phase was a mixture of methanol-water (0.1% formic acid) in different volume proportions from 40% to 60% (v/v) for RP-C18, RP-C8 and RP-CN100 column (exception for parabens on RP-C8 column-the methanol concentrations being from 55% to 65%) and from 30% to 50% (v/v) for RP-NH(2). Highly significant correlations were obtained between different experimental indices of lipophilicity (logk(w), S, phi(0), mean of k and logk, and scores of k and logk corresponding to the first principal component) and computed logP values, and C8 column seems to be more suited for estimating the lipophilicity of the investigated compounds. These direct correlations offer a very good opportunity to derive powerful predictive models via Collander-type equations. The reliability of scores values as lipophilic indices is shown by their high correlation with the logK(ow) obtained using classical "shake-flask" technique, logk(w) and also some of the computed logP values. In addition, the results obtained applying PCA to the retention data may be used in interpreting the molecular mechanism of interactions between eluents and stationary phases with different polarity and to explain the chromatographic behavior of compounds. Finally, the "congeneric lipophilicity chart" described by the scores corresponding to the first principal component has the effect of separating compounds from each other more effectively from congeneric ((dis)similarity) point of view. The parabens and tert-butylhydroquinone appeared to be the most lipophilic preservatives.

  2. Reversible Thermoset Adhesives

    NASA Technical Reports Server (NTRS)

    Mac Murray, Benjamin C. (Inventor); Tong, Tat H. (Inventor); Hreha, Richard D. (Inventor)

    2016-01-01

    Embodiments of a reversible thermoset adhesive formed by incorporating thermally-reversible cross-linking units and a method for making the reversible thermoset adhesive are provided. One approach to formulating reversible thermoset adhesives includes incorporating dienes, such as furans, and dienophiles, such as maleimides, into a polymer network as reversible covalent cross-links using Diels Alder cross-link formation between the diene and dienophile. The chemical components may be selected based on their compatibility with adhesive chemistry as well as their ability to undergo controlled, reversible cross-linking chemistry.

  3. Determination of proteins by a reverse biuret method combined with the copper-bathocuproine chelate reaction.

    PubMed

    Matsushita, M; Irino, T; Komoda, T; Sakagishi, Y

    1993-07-16

    A method of protein determination has been developed which combines the biuret reaction and the copper(I)-bathocuproine chelate reaction. Protein in the specimen forms a Cu(2+)-protein chelate complex (biuret reaction) during the first step. Excess Cu2+ is reduced to Cu+ by ascrobic acid, allowing the Cu+ to form a Cu(+)-bathocuproine chelate complex during the second step. The amount of Cu(+)-bathocuproine chelate complex formed is inversely proportional to the protein concentration. The sensitivity (epsilon = 1.4 x 10(6) 1.mol-1.cm-1 against human albumin) of this method was higher than that of the original Lowry (9.8 x 10(5)), pyrogallol red (1.0 x 10(6)) and commercially available Coomassie Brilliant Blue G.250 methods (6.7 x 10(5)). The color intensities of human gamma-globulin, human globulin (fractions IV-1 and IV-4), bovine albumin, egg albumin and horse gamma-globulin against human albumin (100%) ranged from 92 to 101%. The results obtained with the present method (y) correlated well with those determined by the biuret method (r = 0.998, y = 0.98 chi - 0.002, x = 1.31, y = 1.29 g/l) in 30 diluted sera. These results confirm that this assay is similar in sensitivity to the original Lowry method, is rapid and has similar reactivity to each of the various proteins in biological fluids.

  4. Improved quality-by-design compliant methodology for method development in reversed-phase liquid chromatography.

    PubMed

    Debrus, Benjamin; Guillarme, Davy; Rudaz, Serge

    2013-10-01

    A complete strategy dedicated to quality-by-design (QbD) compliant method development using design of experiments (DOE), multiple linear regressions responses modelling and Monte Carlo simulations for error propagation was evaluated for liquid chromatography (LC). The proposed approach includes four main steps: (i) the initial screening of column chemistry, mobile phase pH and organic modifier, (ii) the selectivity optimization through changes in gradient time and mobile phase temperature, (iii) the adaptation of column geometry to reach sufficient resolution, and (iv) the robust resolution optimization and identification of the method design space. This procedure was employed to obtain a complex chromatographic separation of 15 antipsychotic basic drugs, widely prescribed. To fully automate and expedite the QbD method development procedure, short columns packed with sub-2 μm particles were employed, together with a UHPLC system possessing columns and solvents selection valves. Through this example, the possibilities of the proposed QbD method development workflow were exposed and the different steps of the automated strategy were critically discussed. A baseline separation of the mixture of antipsychotic drugs was achieved with an analysis time of less than 15 min and the robustness of the method was demonstrated simultaneously with the method development phase. Copyright © 2013 Elsevier B.V. All rights reserved.

  5. A Comprehensive Comparison of Normalization Methods for Loading Control and Variance Stabilization of Reverse-Phase Protein Array Data

    PubMed Central

    Liu, Wenbin; Ju, Zhenlin; Lu, Yiling; Mills, Gordon B; Akbani, Rehan

    2014-01-01

    Loading control (LC) and variance stabilization of reverse-phase protein array (RPPA) data have been challenging mainly due to the small number of proteins in an experiment and the lack of reliable inherent control markers. In this study, we compare eight different normalization methods for LC and variance stabilization. The invariant marker set concept was first applied to the normalization of high-throughput gene expression data. A set of “invariant” markers are selected to create a virtual reference sample. Then all the samples are normalized to the virtual reference. We propose a variant of this method in the context of RPPA data normalization and compare it with seven other normalization methods previously reported in the literature. The invariant marker set method performs well with respect to LC, variance stabilization and association with the immunohistochemistry/florescence in situ hybridization data for three key markers in breast tumor samples, while the other methods have inferior performance. The proposed method is a promising approach for improving the quality of RPPA data. PMID:25374453

  6. A comprehensive comparison of normalization methods for loading control and variance stabilization of reverse-phase protein array data.

    PubMed

    Liu, Wenbin; Ju, Zhenlin; Lu, Yiling; Mills, Gordon B; Akbani, Rehan

    2014-01-01

    Loading control (LC) and variance stabilization of reverse-phase protein array (RPPA) data have been challenging mainly due to the small number of proteins in an experiment and the lack of reliable inherent control markers. In this study, we compare eight different normalization methods for LC and variance stabilization. The invariant marker set concept was first applied to the normalization of high-throughput gene expression data. A set of "invariant" markers are selected to create a virtual reference sample. Then all the samples are normalized to the virtual reference. We propose a variant of this method in the context of RPPA data normalization and compare it with seven other normalization methods previously reported in the literature. The invariant marker set method performs well with respect to LC, variance stabilization and association with the immunohistochemistry/florescence in situ hybridization data for three key markers in breast tumor samples, while the other methods have inferior performance. The proposed method is a promising approach for improving the quality of RPPA data.

  7. A single reversed-phase UPLC method for quantification of levofloxacin in aqueous humour and pharmaceutical dosage forms.

    PubMed

    Gupta, Himanshu; Aqil, M; Khar, R K; Ali, Asgar; Chander, Prakash

    2010-07-01

    An attempt was made to develop a single, rapid, specific, and sensitive gradient reversed-phase ultra-performance liquid chromatographic method for quantitative analysis of levofloxacin. The single method thus developed is applied for the quantification of levofloxacin both in aqueous humour as well as pharmaceutical dosage forms (i.e., tablets and eye drops). The newly developed method is applicable for pharmacokinetic studies of eye formulations. The chromatographic separation of levofloxacin was achieved on a Waters Acquity HSS T-3 column (100 x 2.1 mm, 1.8 microm) within a short run-time of 5 min. The method was validated according to the ICH guidelines with respect to system suitability, linearity, limit of quantitation and detection, precision, accuracy, robustness, and specificity. Forced degradation studies were also performed in levofloxacin bulk drug samples to demonstrate the stability-indicating power of the developed ultra-performance liquid chromatography method. The developed method was then successfully applied for the ocular pharmacokinetic study of levofloxacin eye formulations and assay of levofloxacin pharmaceutical dosage form.

  8. A simple method for simultaneous determination of basic dyes encountered in food preparations by reversed-phase HPLC.

    PubMed

    Dixit, Sumita; Khanna, Subhash K; Das, Mukul

    2011-01-01

    The present method utilizes a simple pretreatment step, cleanup on polyamide SPE cartridges, and HPLC resolution on reversed-phase C18 for the detection of the three basic nonpermitted dyes encountered in food matrixes. Polyamide cartridges were chosen because both acidic and basic dyes can be cleaned up due to their amphoteric nature. Analysis was performed on a reversed-phase C18 micro-Bondapak column using the isocratic mixture of acetonitrile-sodium acetate with a flow rate of 1.5 mL/min and a programmable lambda(max) specific visible detection to monitor colors, achieving higher sensitivity and expanded scope to test multicolor blends. All the colors showed linearity with the regression coefficient, from 0.9983 to 0.9995. The LOD and LOQ ranged between 0.107 and 0.754 mg/L and 0.371 and 2.27 mg/L or mg/kg, respectively. The intraday and interday precision gave good RSDs, and percentage recoveries in different food matrixes ranged from 75 to 96.5%. The study demonstrates that the use of a combination of a simple SPE cleanup and HPLC resolution with UV-Vis end point detection was successful in screening the presence of these three basic nonpermitted dyes individually or in blend, in a variety of food matrixes.

  9. An Analysis of Contraceptive Discontinuation among Female, Reversible Method Users in Urban Honduras

    PubMed Central

    Barden-O’Fallon, Janine; Speizer, Ilene S.; Cálix, Javier; Rodriguez, Francisco

    2013-01-01

    A panel study examining the effects of individual characteristics, side effects experienced, and service quality on contraceptive discontinuation was undertaken in four urban areas of Honduras. Data were collected from October 2006 to December 2007. The baseline population included 800 women aged 15–44 who were new or continuing users of the injectable, IUD, or oral contraceptive pill. A total of 671 women (84%) were re-interviewed after one year. Life tables and Cox proportional hazards models are used to present discontinuation rates and factors associated with contraceptive discontinuation. Among new users, discontinuation of the baseline method at 12 months was high (45%); especially for users of the injectable (50%). In the hazards model, service quality had little effect on discontinuation, while individual characteristics and the experience of specific side effects showed significant effects. The results suggest that programs should emphasize continuous contraceptive coverage rather than continuous use of a particular method. PMID:21500697

  10. A rapid method for establishment of a reverse genetics system for canine parvovirus.

    PubMed

    Yu, Yongle; Su, Jun; Wang, Jigui; Xi, Ji; Mao, Yaping; Hou, Qiang; Zhang, Xiaomei; Liu, Weiquan

    2017-08-14

    Canine parvovirus (CPV) is an important and highly prevalent pathogen of dogs that causes acute hemorrhagic enteritis disease. Here, we describe a rapid method for the construction and characterization of a full-length infectious clone (rCPV) of CPV. Feline kidney (F81) cells were transfected with rCPV incorporating an engineered EcoR I site that served as a genetic marker. The rescued virus was indistinguishable from that of wild-type virus in its biological properties.

  11. Method and apparatus for remote sensing of molecular species at nanoscale utilizing a reverse photoacoustic effect

    DOEpatents

    Su, Ming [Oviedo, FL; Thundat, Thomas G [Knoxville, TN; Hedden, David [Lenoir City, TN

    2010-02-23

    A method and apparatus for identifying a sample, involves illuminating the sample with light of varying wavelengths, transmitting an acoustic signal against the sample from one portion and receiving a resulting acoustic signal on another portion, detecting a change of phase in the acoustic signal corresponding to the light of varying wavelengths, and analyzing the change of phase in the acoustic signal for the varying wavelengths of illumination to identify the sample. The apparatus has a controlled source for illuminating the sample with light of varying wavelengths, a transmitter for transmitting an acoustic wave, a receiver for receiving the acoustic wave and converting the acoustic wave to an electronic signal, and an electronic circuit for detecting a change of phase in the acoustic wave corresponding to respective ones of the varying wavelengths and outputting the change of phase for the varying wavelengths to allow identification of the sample. The method and apparatus can be used to detect chemical composition or visual features. A transmission mode and a reflection mode of operation are disclosed. The method and apparatus can be applied at nanoscale to detect molecules in a biological sample.

  12. Estimating the Lipophilicity of Natural Products using a Polymeric Reversed Phase HPLC Method

    PubMed Central

    Zheng, Bo; West, Lyndon M.

    2012-01-01

    The integration of physicochemical profiling screens such as Log P into natural products drug discovery programs is emerging as an approach to front-load drug-like properties of natural product libraries for high-throughput screening. In this study a fast-gradient HPLC method using a polystyrene-divinylbenzene PRP-1 column was developed to estimate the lipophilicity of marine natural products. An excellent correlation was found between the results of the experimental determined and the literature log P values for a diverse set of commercially available drugs using the PRP-1 column. The log P of a series of 24 marine natural products were evaluated using the new method and a good correlation was observed between the experimentally determined and software calculated log P values. Some discrepancies were observed between the measured value of log P and the software calculations of the natural products containing halogens atoms. The method is rapid, insensitive to impurities, and requires very little compound and is amenable for integration into a natural products drug discovery research program. PMID:22851883

  13. A reversed-phase high performance liquid chromatography method for quantification of methotrexate in cancer patients serum.

    PubMed

    Li, Yuan-dong; Li, Yan; Liang, Ning-sheng; Yang, Fan; Kuang, Zhi-peng

    2015-10-01

    A simple, rapid and sensitive reversed-phase high performance liquid chromatography (HPLC) method has been developed for the determination of methotrexate in human serum. After deproteinization of the serum with 40% silver nitrate solution, methotrexate and internal standard (IS) were separated on a reversed-phase column with a mobile phase consisting of 10mM sodium phosphate buffer (pH6.40)-methanol (78:22%, v/v) and ultraviolet detection at 310nm. The linearity is evaluated by a calibration curve in the concentration range of 0.05-10.0μg/mL and presented a correlation coefficient of 0.9995. The absolute recoveries were 97.52±3.9% and 96.87±3.7% for methotrexate and ferulic acid (internal standard), respectively. The intra- and inter-day precision were less 6.19 and 5.89%, respectively (n=6). The limit of quantitation was 0.02μg/mL and the limit of detection was 0.006μg/mL. The complete analysis was achieved less than 10min with no interference from endogenous components or 22 examined drugs. This method was validated by using serum samples from high-dose methotrexate treated patients with osteosarcoma, breast cancer, acute leukemia and lymphoma. The method was demonstrated to be a simple, rapid and reliable approach in quantification of methotrexate in serum samples from patients with high-dose methotrexate therapy. Copyright © 2015 Elsevier B.V. All rights reserved.

  14. A stability-indicating reversed-phase high-performance liquid chromatography method for Ambrisentan: an endothelin receptor antagonist.

    PubMed

    Satheeshkumar, Nanjappan; Naveenkumar, Gandham

    2014-09-01

    A stability-indicating reversed-phase high-performance liquid chromatography (HPLC) method was developed for the determination of ambrisentan, a drug used in the treatment of pulmonary hypertension. The desired chromatographic separation was achieved on a Kromasil C18 column (250 × 4.6 mm, 5 µm) using the mobile phase acetonitrile-ammonium formate (pH 3.0; 0.02 M) in gradient mode. The flow rate was set at 1.0 mL/min, and chromatograms were extracted at 262 nm using a photodiode array detector. The method was successfully validated in accordance to International Conference on Harmonization (ICH) guidelines acceptance criteria for linearity, accuracy, precision, robustness and forced degradation studies, which further proved the stability-indicating power. Linearity of ambrisentan peak area responses was demonstrated within the concentration range of 25-200 µg/mL. The limits of detection and quantitation were 0.2 and 0.6 µg/mL, respectively. Forced degradation studies were performed on ambrisentan bulk drug samples as per ICH guidelines to demonstrate the stability-indicating power of the HPLC method. Significant degradation was observed during acidic hydrolysis, neutral hydrolysis and oxidative stress. The degradation products were well resolved from primary peak of ambrisentan, indicating that the method is specific and stability indicating. The newly developed method is applicable for assay determination of active pharmaceutical ingredient.

  15. Spectrophotometric and reversed-phase high-performance liquid chromatographic method for the determination of doxophylline in pharmaceutical formulations.

    PubMed

    Joshi, Hr; Patel, Ah; Captain, Ad

    2010-07-01

    Two methods are described for determination of Doxophylline in a solid dosage form. The first method was based on ultraviolet (UV)-spectrophotometric determination of the drug. It involves absorbance measurement at 274 nm (λ(max) of Doxophylline) in 0.1 N hydrochloric acid. The calibration curve was linear, with the correlation coefficient between 0.99 and 1.0 over a concentration range of 0.20-30 mg/ml for the drug. The second method was based on high-performance liquid chromatography (HPLC) separation of the drug in reverse-phase mode using the Hypersil ODS C(18) column (250 × 4.6 mm, 5 mm). The mobile phase constituted of buffer acetonitrile (80:20) and pH adjusted to 3.0, with dilute orthophosphoric acid delivered at a flow rate 1.0 ml/min. Detection was performed at 210 nm. Separation was completed within 7 min. The calibration curve was linear, with the correlation coefficient between 0.99 and 1.0 over a concentration range of 0.165-30 mg/ml for the drug. The relative standard deviation was found to be <2.0% for the UV-spectrophotometry and HPLC methods. Both these methods have been successively applied to the solid dosage pharmaceutical formulation, and were fully validated according to ICH guidelines.

  16. A validated reverse-phase HPLC analytical method for the quantification of phenolic compounds in Baccharis dracunculifolia.

    PubMed

    de Sousa, João Paulo B; da Silva Filho, Ademar A; Bueno, Paula C P; Gregório, Luiz E; Furtado, Niege A J C; Jorge, Renata F; Bastos, Jairo K

    2009-01-01

    Baccharis dracunculifolia, which has great potential for the development of new phytotherapeutic medicines, is the most important botanical source of the southeastern Brazilian propolis, known as green propolis on account of its color. To develop a reliable reverse-phase HPLC chromatographic method for the analysis of phenolic compounds in both B. dracunculifolia raw material and its hydroalcoholic extracts. The method utilised a C(18) CLC-ODS (M) (4.6 x 250 mm) column with nonlinear gradient elution and UV detection at 280 nm. A procedure for the extraction of phenolic compounds using aqueous ethanol 90%, with the addition of veratraldehyde as the internal standard, was developed allowing the quantification of 10 compounds: caffeic acid, coumaric acid, ferulic acid, cinnamic acid, aromadendrin-4'-methyl ether, isosakuranetin, drupanin, artepillin C, baccharin and 2,2-dimethyl-6-carboxyethenyl-2H-1-benzopyran acid. The developed method gave a good detection response with linearity in the range 20.83-800 microg/mL and recovery in the range 81.25-93.20%, allowing the quantification of the analysed standards. The method presented good results for the following parameters: selectivity, linearity, accuracy, precision, robustness, as well as limit of detection and limit of quantitation. Therefore, this method could be considered as an analytical tool for the quality control of B. dracunculifolia raw material and its products in both cosmetic and pharmaceutical companies.

  17. An Evaluation of Active Learning Causal Discovery Methods for Reverse-Engineering Local Causal Pathways of Gene Regulation.

    PubMed

    Ma, Sisi; Kemmeren, Patrick; Aliferis, Constantin F; Statnikov, Alexander

    2016-03-04

    Reverse-engineering of causal pathways that implicate diseases and vital cellular functions is a fundamental problem in biomedicine. Discovery of the local causal pathway of a target variable (that consists of its direct causes and direct effects) is essential for effective intervention and can facilitate accurate diagnosis and prognosis. Recent research has provided several active learning methods that can leverage passively observed high-throughput data to draft causal pathways and then refine the inferred relations with a limited number of experiments. The current study provides a comprehensive evaluation of the performance of active learning methods for local causal pathway discovery in real biological data. Specifically, 54 active learning methods/variants from 3 families of algorithms were applied for local causal pathways reconstruction of gene regulation for 5 transcription factors in S. cerevisiae. Four aspects of the methods' performance were assessed, including adjacency discovery quality, edge orientation accuracy, complete pathway discovery quality, and experimental cost. The results of this study show that some methods provide significant performance benefits over others and therefore should be routinely used for local causal pathway discovery tasks. This study also demonstrates the feasibility of local causal pathway reconstruction in real biological systems with significant quality and low experimental cost.

  18. Synthesis and characterization of nanophase zirconia : reverse micelle method and neutron scattering study.

    SciTech Connect

    Li, X.

    1998-11-23

    Zirconia is an important transition-metal oxide for catalytic applications. It has been widely used in automotive exhaust treatment, methanol synthesis, isomerization, alkylation, etc. [1]. Nanophase materials have unique physiochemical properties such as quantum size effects, high surface area, uniform morphology, narrow size distribution, and improvement of sintering rates[2]. Microemulsion method provides the means for controlling the microenvironment under which specific chemical reactions may occur in favoring the formation of homogeneous, nanometer-size particles. In this paper, we report the synthesis of nanophase zirconia and the characterization of the microemulsions as well as the powders by small- and wide-angle neutron scattering techniques.

  19. A facile method for reversibly linking a recombinant protein to DNA.

    PubMed

    Goodman, Russell P; Erben, Christoph M; Malo, Jonathan; Ho, Wei M; McKee, Mireya L; Kapanidis, Achillefs N; Turberfield, Andrew J

    2009-06-15

    We present a facile method for linking recombinant proteins to DNA. It is based on the nickel-mediated interaction between a hexahistidine tag (His(6)-tag) and DNA functionalized with three nitrilotriacetic acid (NTA) groups. The resulting DNA-protein linkage is site-specific. It can be broken quickly and controllably by the addition of a chelating agent that binds nickel. We have used this new linker to bind proteins to a variety of DNA motifs commonly used in the fabrication of nanostructures by DNA self-assembly.

  20. Long-acting reversible contraceptive acceptability and unintended pregnancy among women presenting for short-acting methods: a randomized patient preference trial.

    PubMed

    Hubacher, David; Spector, Hannah; Monteith, Charles; Chen, Pai-Lien; Hart, Catherine

    2017-02-01

    Measures of contraceptive effectiveness combine technology and user-related factors. Observational studies show higher effectiveness of long-acting reversible contraception compared with short-acting reversible contraception. Women who choose long-acting reversible contraception may differ in key ways from women who choose short-acting reversible contraception, and it may be these differences that are responsible for the high effectiveness of long-acting reversible contraception. Wider use of long-acting reversible contraception is recommended, but scientific evidence of acceptability and successful use is lacking in a population that typically opts for short-acting methods. The objective of the study was to reduce bias in measuring contraceptive effectiveness and better isolate the independent role that long-acting reversible contraception has in preventing unintended pregnancy relative to short-acting reversible contraception. We conducted a partially randomized patient preference trial and recruited women aged 18-29 years who were seeking a short-acting method (pills or injectable). Participants who agreed to randomization were assigned to 1 of 2 categories: long-acting reversible contraception or short-acting reversible contraception. Women who declined randomization but agreed to follow-up in the observational cohort chose their preferred method. Under randomization, participants chose a specific method in the category and received it for free, whereas participants in the preference cohort paid for the contraception in their usual fashion. Participants were followed up prospectively to measure primary outcomes of method continuation and unintended pregnancy at 12 months. Kaplan-Meier techniques were used to estimate method continuation probabilities. Intent-to-treat principles were applied after method initiation for comparing incidence of unintended pregnancy. We also measured acceptability in terms of level of happiness with the products. Of the 916

  1. Vasectomy reversal.

    PubMed

    Belker, A M

    1987-02-01

    A vasovasostomy may be performed on an outpatient basis with local anesthesia, but also may be performed on an outpatient basis with epidural or general anesthesia. Local anesthesia is preferred by most of my patients, the majority of whom choose this technique. With proper preoperative and intraoperative sedation, patients sleep lightly through most of the procedure. Because of the length of time often required for bilateral microsurgical vasoepididymostomy, epidural or general anesthesia and overnight hospitalization are usually necessary. Factors influencing the preoperative choice for vasovasostomy or vasoepididymostomy in patients undergoing vasectomy reversal are considered. The preoperative planned choice of vasovasostomy or vasoepididymostomy for patients having vasectomy reversal described herein does not have the support of all urologists who regularly perform these procedures. My present approach has evolved as the data reported in Tables 1 and 2 have become available, but it may change as new information is evaluated. However, it offers a logical method for planning choices of anesthesia and inpatient or outpatient status for patients undergoing vasectomy reversal procedures.

  2. Blue-Emitting Small Silica Particles Incorporating ZnSe-Based Nanocrystals Prepared by Reverse Micelle Method

    PubMed Central

    Ando, Masanori; Li, Chunliang; Yang, Ping; Murase, Norio

    2007-01-01

    ZnSe-based nanocrystals (ca. 4-5 nm in diameter) emitting in blue region (ca. 445 nm) were incorporated in spherical small silica particles (20–40 nm in diameter) by a reverse micelle method. During the preparation, alkaline solution was used to deposit the hydrolyzed alkoxide on the surface of nanocrystals. It was crucially important for this solution to include Zn2+ ions and surfactant molecules (thioglycolic acid) to preserve the spectral properties of the final silica particles. This is because these substances in the solution prevent the surface of nanocrystals from deterioration by dissolution during processing. The resultant silica particles have an emission efficiency of 16% with maintaining the photoluminescent spectral width and peak wavelength of the initial colloidal solution. PMID:18350119

  3. Particular interaction between efavirenz and the HIV-1 reverse transcriptase binding site as explained by the ONIOM2 method

    NASA Astrophysics Data System (ADS)

    Nunrium, Peerapol; Kuno, Mayuso; Saen-oon, Suwipa; Hannongbua, Supa

    2005-03-01

    Particular interaction between efavirenz and the HIV-1 reverse transcriptase binding site was investigated, based on the B3LYP/6-31G(d,p) and ONIOM2 methods. The interaction between efavirenz and Lys101 was found to be the strongest interaction, typically, -11.29 kcal/mol. The stability of this complex system leads to the foundation of the estimated binding energy of approximately -22.66 kcal/mol. Moreover, two hydrogen bonds between benzoxazin-2-one, and the backbone carbonyl oxygen and the backbone amino hydrogen of Lys101 were observed. These hydrogen bond interactions play an important role in the bound efavirenz/HIV-1 RT complex.

  4. A New Long-Term Reversible Contraception Method: Sexual and Metabolic Impact

    PubMed Central

    Visconti, F; Zullo, F; Marra, M.L; De Masellis, G; Caiazza, M; Cibarelli, F; Buonomo, B; Guida, M.

    2012-01-01

    Background Data relating to the influence of hormonal contraception on sexual life are conflicting and mostly they refer to oral contraceptives. In this study we evaluated the effect of a long-acting contraceptive on sexual function, metabolism and bleeding pattern variations. Methods: 23 women with a permanent partner and an active sexual life completed a specific questionnaire at the start of the study and after cycles 3 and 6 of contraceptive use; a blood sample was performed or metabolic evaluation and a “bleeding calendar” was compiled by the patients. Conclusion: There is an increase of quality and frequency of sexual function after 6 month of contraception; there aren’t significant change in metabolic parameters and is detectable a modification of bleeding patterns. PMID:23905067

  5. Inferring Regulatory Networks from Experimental Morphological Phenotypes: A Computational Method Reverse-Engineers Planarian Regeneration

    PubMed Central

    Lobo, Daniel; Levin, Michael

    2015-01-01

    Transformative applications in biomedicine require the discovery of complex regulatory networks that explain the development and regeneration of anatomical structures, and reveal what external signals will trigger desired changes of large-scale pattern. Despite recent advances in bioinformatics, extracting mechanistic pathway models from experimental morphological data is a key open challenge that has resisted automation. The fundamental difficulty of manually predicting emergent behavior of even simple networks has limited the models invented by human scientists to pathway diagrams that show necessary subunit interactions but do not reveal the dynamics that are sufficient for complex, self-regulating pattern to emerge. To finally bridge the gap between high-resolution genetic data and the ability to understand and control patterning, it is critical to develop computational tools to efficiently extract regulatory pathways from the resultant experimental shape phenotypes. For example, planarian regeneration has been studied for over a century, but despite increasing insight into the pathways that control its stem cells, no constructive, mechanistic model has yet been found by human scientists that explains more than one or two key features of its remarkable ability to regenerate its correct anatomical pattern after drastic perturbations. We present a method to infer the molecular products, topology, and spatial and temporal non-linear dynamics of regulatory networks recapitulating in silico the rich dataset of morphological phenotypes resulting from genetic, surgical, and pharmacological experiments. We demonstrated our approach by inferring complete regulatory networks explaining the outcomes of the main functional regeneration experiments in the planarian literature; By analyzing all the datasets together, our system inferred the first systems-biology comprehensive dynamical model explaining patterning in planarian regeneration. This method provides an automated

  6. Inferring regulatory networks from experimental morphological phenotypes: a computational method reverse-engineers planarian regeneration.

    PubMed

    Lobo, Daniel; Levin, Michael

    2015-06-01

    Transformative applications in biomedicine require the discovery of complex regulatory networks that explain the development and regeneration of anatomical structures, and reveal what external signals will trigger desired changes of large-scale pattern. Despite recent advances in bioinformatics, extracting mechanistic pathway models from experimental morphological data is a key open challenge that has resisted automation. The fundamental difficulty of manually predicting emergent behavior of even simple networks has limited the models invented by human scientists to pathway diagrams that show necessary subunit interactions but do not reveal the dynamics that are sufficient for complex, self-regulating pattern to emerge. To finally bridge the gap between high-resolution genetic data and the ability to understand and control patterning, it is critical to develop computational tools to efficiently extract regulatory pathways from the resultant experimental shape phenotypes. For example, planarian regeneration has been studied for over a century, but despite increasing insight into the pathways that control its stem cells, no constructive, mechanistic model has yet been found by human scientists that explains more than one or two key features of its remarkable ability to regenerate its correct anatomical pattern after drastic perturbations. We present a method to infer the molecular products, topology, and spatial and temporal non-linear dynamics of regulatory networks recapitulating in silico the rich dataset of morphological phenotypes resulting from genetic, surgical, and pharmacological experiments. We demonstrated our approach by inferring complete regulatory networks explaining the outcomes of the main functional regeneration experiments in the planarian literature; By analyzing all the datasets together, our system inferred the first systems-biology comprehensive dynamical model explaining patterning in planarian regeneration. This method provides an automated

  7. An Evaluation of Active Learning Causal Discovery Methods for Reverse-Engineering Local Causal Pathways of Gene Regulation

    PubMed Central

    Ma, Sisi; Kemmeren, Patrick; Aliferis, Constantin F.; Statnikov, Alexander

    2016-01-01

    Reverse-engineering of causal pathways that implicate diseases and vital cellular functions is a fundamental problem in biomedicine. Discovery of the local causal pathway of a target variable (that consists of its direct causes and direct effects) is essential for effective intervention and can facilitate accurate diagnosis and prognosis. Recent research has provided several active learning methods that can leverage passively observed high-throughput data to draft causal pathways and then refine the inferred relations with a limited number of experiments. The current study provides a comprehensive evaluation of the performance of active learning methods for local causal pathway discovery in real biological data. Specifically, 54 active learning methods/variants from 3 families of algorithms were applied for local causal pathways reconstruction of gene regulation for 5 transcription factors in S. cerevisiae. Four aspects of the methods’ performance were assessed, including adjacency discovery quality, edge orientation accuracy, complete pathway discovery quality, and experimental cost. The results of this study show that some methods provide significant performance benefits over others and therefore should be routinely used for local causal pathway discovery tasks. This study also demonstrates the feasibility of local causal pathway reconstruction in real biological systems with significant quality and low experimental cost. PMID:26939894

  8. A reverse-transcription PCR method for detecting all known ephemeroviruses in clinical samples.

    PubMed

    Blasdell, Kim R; Adams, Mathew M; Davis, Steven S; Walsh, Susan J; Aziz-Boaron, Orly; Klement, Eyal; Tesh, Robert B; Walker, Peter J

    2013-08-01

    Bovine ephemeral fever virus (BEFV) is an economically important vector-borne pathogen of cattle in tropical and sub-tropical regions of Australia, Asia, Africa and the Middle East. Although clinical cases of bovine ephemeral fever are usually attributed to BEFV, definitive diagnosis is rarely performed and at least two other related viruses, kotonkon virus (KOTV; an ephemerovirus) and Fukuoka virus (FUKAV; an unassigned rhabdovirus), can cause similar clinical signs. As vaccines have been developed against BEFV but not against KOTV or FUKAV, a test capable of detecting and differentiating these pathogens would be useful. In the present study, an RT-PCR method using degenerate primers designed to a region of block III of the polymerase (L) gene was developed and optimised for primer annealing temperature and MgCl₂ concentration. The RT-PCR detected all known ephemeroviruses and several other closely related insect-transmitted rhabdoviruses, including FUKAV. Viruses could be identified by subsequent sequencing and phylogenetic analysis of the amplicons. BEFV could be detected using tissue culture isolates or cattle blood to a sensitivity of 500 RNA copies per reaction. This test will be useful for establishing the identity of the causative agent of bovine ephemeral fever from field samples and cultured isolates.

  9. Sea-going hardware for the cloud albedo method of reversing global warming.

    PubMed

    Salter, Stephen; Sortino, Graham; Latham, John

    2008-11-13

    Following the review by Latham et al. (Latham et al. 2008 Phil. Trans. R. Soc. A 366) of a strategy to reduce insolation by exploiting the Twomey effect, the present paper describes in outline the rationale and underlying engineering hardware that may bring the strategy from concept to operation. Wind-driven spray vessels will sail back and forth perpendicular to the local prevailing wind and release micron-sized drops of seawater into the turbulent boundary layer beneath marine stratocumulus clouds. The combination of wind and vessel movements will treat a large area of sky. When residues left after drop evaporation reach cloud level they will provide many new cloud condensation nuclei giving more but smaller drops and so will increase the cloud albedo to reflect solar energy back out to space. If the possible power increase of 3.7W m-2 from double pre-industrial CO2 is divided by the 24-hour solar input of 340W m-2, a global albedo increase of only 1.1 per cent will produce a sufficient offset. The method is not intended to make new clouds. It will just make existing clouds whiter. This paper describes the design of 300 tonne ships powered by Flettner rotors rather than conventional sails. The vessels will drag turbines resembling oversized propellers through the water to provide the means for generating electrical energy. Some will be used for rotor spin, but most will be used to create spray by pumping 30 kgs-1 of carefully filtered water through banks of filters and then to micro-nozzles with piezoelectric excitation to vary drop diameter. The rotors offer a convenient housing for spray nozzles with fan assistance to help initial dispersion. The ratio of solar energy reflected by a drop at the top of a cloud to the energy needed to make the surface area of the nucleus on which it has grown is many orders of magnitude and so the spray quantities needed to achieve sufficient global cooling are technically feasible.

  10. Do International Health Partnerships contribute to reverse innovation? a mixed methods study of THET-supported partnerships in the UK.

    PubMed

    Kulasabanathan, Kavian; Issa, Hamdi; Bhatti, Yasser; Prime, Matthew; Del Castillo, Jacqueline; Darzi, Ara; Harris, Matthew

    2017-04-18

    International health partnerships (IHPs) are changing, with an increased emphasis on mutual accountability and joint agenda setting for both the high- and the low- or middle-income country (LMIC) partners. There is now an important focus on the bi-directionality of learning however for the UK partners, this typically focuses on learning at the individual level, through personal and professional development. We sought to evaluate whether this learning also takes the shape of 'Reverse Innovation' -when an idea conceived in a low-income country is subsequently adopted in a higher-income country. This mixed methods study used an initial scoping survey of all the UK-leads of the Tropical Health Education Trust (THET)-supported International Health Partnerships (n = 114) to ascertain the extent to which the IHPs are or have been vehicles for Reverse Innovation. The survey formed the sampling frame for further deep-dive interviews to focus on volunteers' experiences and attitudes to learning from LMICs. Interviews of IHP leads (n = 12) were audio-recorded and transcribed verbatim. Survey data was analysed descriptively. Interview transcripts were coded thematically, using an inductive approach. Survey response rate was 27% (n = 34). The majority (70%) strongly agreed that supporting LMIC partners best described the mission of the partnership but only 13% of respondents strongly agreed that learning about new innovations and models was a primary mission of their partnership. Although more than half of respondents reported having observed innovative practice in the LMIC, only one IHP respondent indicated that this has led to Reverse Innovation. Interviews with a sample of survey respondents revealed themes primarily around how learning is conceptualised, but also a central power imbalance between the UK and LMIC partners. Paternalistic notions of knowledge could be traced to partnership power dynamics and latent attitudes to LMICs. Given the global flow of

  11. Rapid Estimation of Tadalafil by Reverse-phase High-performance Liquid Chromatography Method in Bulk and Tablet Formulation

    PubMed Central

    Sonawane, P. H.; Panzade, P. S.; Kale, M. A.

    2013-01-01

    The simple, selective, precise and accurate reverse-phase high-performance liquid chromatography method was developed and validated for analysis of tadalafil in bulk and tablet dosage form. The column was Inertsil C18 (150×4.6 mm; 5 μm) in isocratic mode. The mobile phase used was phosphate buffer (10 mM, pH 3.2) and acetonitrile (50:50% v/v) at the flow rate of 1.0 ml/min with ultraviolet detection at 295 nm at ambient temperature. The retention time for tadalafil was found to be 4.01 min. Linearity was observed in the concentration range from 60 to 140 μg/ml for tadalafil with a correlation coefficient of (r2) 0.9998. The method was validated according to International Conference on Harmonisation guidelines in terms of linearity, accuracy, precision and specificity. Hence, the proposed method can be utilized for routine quality control of tadalafil in bulk and tablet dosage form. PMID:24019575

  12. Comparison of reversible-jump Markov-chain-Monte-Carlo learning approach with other methods for missing enzyme identification.

    PubMed

    Geng, Bo; Zhou, Xiaobo; Zhu, Jinmin; Hung, Y S; Wong, Stephen T C

    2008-04-01

    Computational identification of missing enzymes plays a significant role in accurate and complete reconstruction of metabolic network for both newly sequenced and well-studied organisms. For a metabolic reaction, given a set of candidate enzymes identified according to certain biological evidences, a powerful mathematical model is required to predict the actual enzyme(s) catalyzing the reactions. In this study, several plausible predictive methods are considered for the classification problem in missing enzyme identification, and comparisons are performed with an aim to identify a method with better performance than the Bayesian model used in previous work. In particular, a regression model consisting of a linear term and a nonlinear term is proposed to apply to the problem, in which the reversible jump Markov-chain-Monte-Carlo (MCMC) learning technique (developed in [Andrieu C, Freitas Nando de, Doucet A. Robust full Bayesian learning for radial basis networks 2001;13:2359-407.]) is adopted to estimate the model order and the parameters. We evaluated the models using known reactions in Escherichia coli, Mycobacterium tuberculosis, Vibrio cholerae and Caulobacter cresentus bacteria, as well as one eukaryotic organism, Saccharomyces Cerevisiae. Although support vector regression also exhibits comparable performance in this application, it was demonstrated that the proposed model achieves favorable prediction performance, particularly sensitivity, compared with the Bayesian method.

  13. Reversed-phase ion-pair liquid chromatography method for purification of duplex DNA with single base pair resolution

    PubMed Central

    Wysoczynski, Christina L.; Roemer, Sarah C.; Dostal, Vishantie; Barkley, Robert M.; Churchill, Mair E. A.; Malarkey, Christopher S.

    2013-01-01

    Obtaining quantities of highly pure duplex DNA is a bottleneck in the biophysical analysis of protein–DNA complexes. In traditional DNA purification methods, the individual cognate DNA strands are purified separately before annealing to form DNA duplexes. This approach works well for palindromic sequences, in which top and bottom strands are identical and duplex formation is typically complete. However, in cases where the DNA is non-palindromic, excess of single-stranded DNA must be removed through additional purification steps to prevent it from interfering in further experiments. Here we describe and apply a novel reversed-phase ion-pair liquid chromatography purification method for double-stranded DNA ranging in lengths from 17 to 51 bp. Both palindromic and non-palindromic DNA can be readily purified. This method has the unique ability to separate blunt double-stranded DNA from pre-attenuated (n-1, n-2, etc) synthesis products, and from DNA duplexes with single base pair overhangs. Additionally, palindromic DNA sequences with only minor differences in the central spacer sequence of the DNA can be separated, and the purified DNA is suitable for co-crystallization of protein–DNA complexes. Thus, double-stranded ion-pair liquid chromatography is a useful approach for duplex DNA purification for many applications. PMID:24013567

  14. Development and validation of a reversed-phase HPLC method for the quantification of paclitaxel in different PLGA nanocarriers.

    PubMed

    Furman, Christophe; Carpentier, Rodolphe; Barczyk, Amélie; Chavatte, Philippe; Betbeder, Didier; Lipka, Emmanuelle

    2017-03-31

    A reversed-phase high-performance liquid chromatography (RP-HPLC) method has been developed and validated for the quantification of paclitaxel encapsulated in biodegradable poly(lactic-co-glycolic) (PLGA) copolymer nanoparticles. This simple (isocratic mode, without additive) and rapid (retention time of the paclitaxel under 4 minutes) methodology permits the detection of low quantities of paclitaxel in nanoparticulate formulations and the determination of the encapsulation efficiency (EE). Analysis was achieved on an octadecyl stationary phase. The isocratic mobile phase consisted of acetonitrile:water 80:20 (v/v) (flow rate = 0.8 mL/min). Stability of free paclitaxel was preliminary studied in those chromatographic conditions. The calibration curve was linear in the concentration range of 2 to 10 μg/mL (R(2) = 0.9994). The method was specific with valuable trueness, repeatability (intra-day precision) and intermediate precision (inter-day precision) based on relative standard deviation (RSD) values (less than 2%). The limits of detection (LOD) and quantification (LOQ) were 0.56 and 1.85 ng/mL respectively. This developed method was successfully employed for quantifying paclitaxel in PLGA 50:50 co-polymer nanoparticles. The accurate knowledge of the encapsulated paclitaxel concentration is essential to define the quantities of PLGA nanoparticles necessary to achieve the in vitro cell viability study. This article is protected by copyright. All rights reserved.

  15. Determination of nitrate and nitrite in Hanford defense waste(HDW) by reverse polarity capillary zone electrophoresis (RPCE)method

    SciTech Connect

    Metcalf, S.G.

    1998-06-10

    This paper describes the first application of reverse polarity capillary zone electrophoresis (RPCE) for rapid and accurate determination of nitrate and nitrite in Hanford Defense Waste (HDW). The method development was carried out by using Synthetic Hanford Waste (SHW), followed by the analysis of 4 real HDW samples. Hexamethonium bromide (HMB) was used as electroosmotic flow modifier in borate buffer at pH 9.2 to decrease the electroosmotic flow (EOF) in order to enhance the speed of analysis and the resolution of nitrate and nitrite in high ionic strength HDW samples. The application of this capillary zone electrophoresis method, when compared with ion chromatography for two major components of HDW, nitrate and nitrite slightly reduced analysis time, eliminated most pre-analysis handling of the highly radioactive sample, and cut analysis wastes by more than 2 orders of magnitude. The analysis of real HDW samples that were validated by using sample spikes showed a concentration range of 1.03 to 1.42 M for both nitrate. The migration times of the real HDW and the spiked HDW samples were within a precision of less than 3% relative standard deviation. The selectivity ratio test used for peak confirmation of the spiked samples was within 96% of the real sample. Method reliability was tested by spiking the matrix with 72.4 mM nitrate and nitrite. Recoveries for these spiked samples were 93-103%.

  16. Development and evaluation of a digital dental modeling method based on grating projection and reverse engineering software.

    PubMed

    Zhou, Qin; Wang, Zhenzhen; Chen, Jun; Song, Jun; Chen, Lu; Lu, Yi

    2016-01-01

    For reasons of convenience and economy, attempts have been made to transform traditional dental gypsum casts into 3-dimensional (3D) digital casts. Different scanning devices have been developed to generate digital casts; however, each has its own limitations and disadvantages. The purpose of this study was to develop an advanced method for the 3D reproduction of dental casts by using a high-speed grating projection system and noncontact reverse engineering (RE) software and to evaluate the accuracy of the method. The methods consisted of 3 main steps: the scanning and acquisition of 3D dental cast data with a high-resolution grating projection system, the reconstruction and measurement of digital casts with RE software, and the evaluation of the accuracy of this method using 20 dental gypsum casts. The common anatomic landmarks were measured directly on the gypsum casts with a Vernier caliper and on the 3D digital casts with the Geomagic software measurement tool. Data were statistically assessed with the t test. The grating projection system had a rapid scanning speed, and smooth 3D dental casts were obtained. The mean differences between the gypsum and 3D measurements were approximately 0.05 mm, and no statistically significant differences were found between the 2 methods (P>.05), except for the measurements of the incisor tooth width and maxillary arch length. A method for the 3D reconstruction of dental casts was developed by using a grating projection system and RE software. The accuracy of the casts generated using the grating projection system was comparable with that of the gypsum casts. Copyright © 2016 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.

  17. Comparison of different methods of RNA isolation for plum pox virus detection by reverse transcription-polymerase chain reaction.

    PubMed

    Faggioli, F; Pasquini, G; Barba, M

    1998-09-01

    The diagnosis of plum pox virus (PPV) is still considered one of the most important aspects of the "sharka" problem. In fact, different studies demonstrated an uneven distribution of the virus in infected trees due to a high variability in virus concentration. These aspects complicate the PPV diagnosis. To date, biological, serological and molecular assays have been successively developed in order to obtain sensitive and efficient PPV detection techniques. In particular, the polymerase chain reaction (PCR) technique seems to be promising and can be considered the most sensitive and reliable one. Preparation of viral RNA is still a fundamental step in reverse transcription-PCR (RT-PCR) technique, especially when applied to large scale testing, i.e., for certification purposes. In order to find the most rapid and efficient procedure, we have compared three different procedures of extraction of viral RNA to be processed RT-PCR. Their common characteristics is their capacity to extract the RNA from a small amount of plant tissue without organic solvents in the extraction fluid. The procedures were as follows: an immuno-capture (IC) method using a specific antiserum, a silica-capture (SC) method using a non-specific matrix, and a simple and rapid RNA extraction (RE) method. They all were followed by one-tube RT-PCR. The obtained results show that all the three techniques allowed a successful amplification and detection of PPV in tested samples except the SC-PCR method which proved less effective. In fact, the IC-PCR and RE-PCR methods amplified and detected PPV in all isolates tested, while the SC-PCR method was able to reveal the presence of the virus in apricot and infected control samples only.

  18. Implementation of reverse flotation method to reduce reactive and non-reactive silica in bauxite ore from West Kalimantan

    NASA Astrophysics Data System (ADS)

    Wulandari, Winny; Purwasasmita, Mubiar; Sanwani, Edy; Pixelina, Adinda Asri; Maulidan, Agus

    2017-01-01

    This paper reports a study that implements reverse flotation method to separate silica from West Kalimantan bauxite ores. The study is aimed to find the good process condition to obtain low-silica bauxite as the feed for the Bayer process. The experiments were carried out in a 1 L of flotation cell tank. Dodecylamine was used as the collector, starch as the depressant, and MIBC as the frother. The varied parameters were solid content to solution (15-30% w/w), and pH (6 - 10). The results of XRF of products show that in all reverse flotation experiments, the ratio of alumina to silica (Al/Si) are increased from 7 up to 14. The increase of solid percentage in the flotation gives a good result for Al/Si ratio as well as alumina and silica recovery in concentrate, with 30% w/w solid percentage to solution increases Al/Si ratio to 14.38, with silica recovery of 20%. The good separation with variation of depressants is obtained with depressant concentration of 400 g/ton bauxite, with Al/Si ratio in concentrate 15 and ratio in tailing 7. For the pH variation, the good condition is obtained at pH 8, while for collector concentration, the good condition is obtained at 200 g/ton bauxite. XRD analysis of the feed indicates that bauxite ore consists of gibbsite, diaspore, kaolinite, halloysite, quartz, boehmite, hematite and rutile. It is found that the concentrate has similar minerals, but halloysite became very minor or classified as a trace.

  19. Association of Short-term Bleeding and Cramping Patterns with Long-Acting Reversible Contraceptive Method Satisfaction

    PubMed Central

    Diedrich, Justin T.; Desai, Sanyukta; Zhao, Qiuhong; Secura, Gina; Madden, Tessa; Peipert, Jeffrey F.

    2014-01-01

    Objectives To examine the short-term (3 and 6-month), self-reported bleeding and cramping patterns with intrauterine devices (IUDs) and the contraceptive implant, and the association of these symptoms with method satisfaction. Study Design We analyzed 3 and 6-month survey data from IUD and implant users in the Contraceptive CHOICE Project, a prospective cohort study. Participants who received a long-acting reversible contraceptive (LARC) method (levonorgestrel intrauterine system (LNG-IUS), copper IUD, or the etonogestrel implant) and completed their 3- and 6-month surveys were included. Univariable and multivariable analyses were performed to examine the association of bleeding and cramping patterns with short-term satisfaction. Results Our analytic sample included 5,011 CHOICE participants: 3001 LNG-IUS users, 826 copper IUD users, and 1184 implant users. At 3 months, over 65% of LNG-IUS and implant users reported no change or decreased cramping, while 63% of copper IUD users reported increased menstrual cramping. Lighter bleeding was reported by 67% of LNG-IUS users, 58% of implant users, and 8% of copper IUD users. Satisfaction of all LARC methods was high (≥90%) and significantly higher than non-LARC methods (p<0.001). LARC users with increased menstrual cramping (HR 0.96, 95% CI 0.92 – 0.99), heavier bleeding (HR 0.91, 95% CI 0.87 – 0.96), and increased bleeding frequency (HR 0.92, 95% CI 0.89 – 0.96) were less likely to report being very satisfied at 6 months. Conclusion Regardless of the LARC method, satisfaction at 3 and 6 months is very high. Changes in self-reported bleeding and cramping are associated with short-term LARC satisfaction. PMID:25046805

  20. Year-long validation study and reference values for urinary amino acids using a reversed-phase HPLC method.

    PubMed

    Venta, R

    2001-03-01

    Reversed-phase HPLC (RP-HPLC) has become an alternative to ion-exchange chromatography for amino acid analysis in biological fluids. However, validation studies for its urine application are limited, and the corresponding reference values have not been reported extensively. We studied the long-term performance of a commercial HPLC method for urine amino acid analysis and established specific age-related reference values for urine amino acid excretion. Method performance was continuously assessed by recovery and precision studies with urine samples and controls, respectively. Healthy individuals were prospectively analyzed throughout a 5-year period. Excretion of individual amino acids, expressed as mmol/mol of creatinine, was included in six age-related groups for random urine samples (0-1 month, 1-12 months, 1-3 years, 3-8 years, 8-16 years, and >16 years) and in two groups for 24-h urine collections (8-16 years and >16 years). Over a 1-year period, CVs for retention times were <0.5% and 3.3% for within- and between-run imprecision, respectively. For amino acid concentrations, within-run CVs were 2.9-17% and between-run CVs were 7.1-46% for the same period. Amino acid recoveries were 78-122%. Reference intervals for 35 amino acids were calculated and compared with the concentrations observed in patients diagnosed with specific pathologies. A few statistically significant differences were found between the reference intervals derived using random and 24-h urine collections. Long-term reliability of the RP-HPLC method for urine amino acid analysis has been demonstrated. Representative age-related reference intervals for the RP-HPLC method in both random urine and 24-h urine collections have been established, and their feasibility for diagnosis of aminoaciduria has been shown. These intervals could serve as a guide for laboratories changing to HPLC methods.

  1. Room Temperature Synthesis of Magnetite (Fe3-δO4) Nanoparticles by a Simple Reverse Co-Precipitation Method

    NASA Astrophysics Data System (ADS)

    Mahmed, N.; Heczko, O.; Söderberg, O.; Hannula, S.-P.

    2011-10-01

    Magnetite (Fe3-δO4) nanoparticles with the size less than 30 nm have been synthesized by using a simple reverse co-precipitation method at room temperature. During the process, ferrous sulfate (FeSO4·7H2O) powder was used as an iron precursor, and ammonium hydroxide (NH4OH) as a precipitating agent. The experiment was carried out in ambient atmosphere without any surfactant added. In this method, the base solution for the precipitation process was adjusted to have a pH value suitable for the formation of the magnetite phase. The iron salt precursor was added into the solution during the synthesis by two different synthesis protocols. The phase, morphology and magnetic characteristic of differently synthesized magnetite particles were characterized by using an X-ray diffraction (XRD), transmission electron microscope (TEM) and vibrating sample magnetometer (VSM). The morphologies of the particles were spherical or irregular in shape depending on the synthesis protocol used. Magnetic measurement shows that the particles are ferromagnetic at room temperature with relatively high saturation magnetization and low hysteresis. The saturation magnetization and magnetic hysteresis of the particles varied with preparation reaction conditions and the resulting oxidation state of the particles.

  2. Methods matter: A primer on permanent and reversible interference techniques in animals for investigators of human neuropsychology.

    PubMed

    Bell, Andrew H; Bultitude, Janet H

    2017-09-21

    The study of patients with brain lesions has contributed greatly to our understanding of the biological bases of human cognition, but this approach also has several unavoidable limitations. Research that uses animal models complements and extends human neuropsychology by addressing many of these limitations. In this review, we provide an overview of permanent and reversible animal lesion techniques for researchers of human neuropsychology, with the aim of highlighting how these methods provide a valuable adjunct to behavioural, neuroimaging, physiological, and clinical investigations in humans. Research in animals has provided important lessons about how the limitations of one or more techniques, or differences in their mechanism of action, has impacted upon the understanding of brain organisation and function. These cautionary tales highlight the importance of striving for a thorough understanding of how any intereference technique works (whether in animal or human), and for how to best use animal research to clarify the precise mechanisms underlying temporary lesion methods in humans. Copyright © 2017 The Authors. Published by Elsevier Ltd.. All rights reserved.

  3. Investigation of noise properties in grating-based x-ray phase tomography with reverse projection method

    NASA Astrophysics Data System (ADS)

    Bao, Yuan; Wang, Yan; Gao, Kun; Wang, Zhi-Li; Zhu, Pei-Ping; Wu, Zi-Yu

    2015-10-01

    The relationship between noise variance and spatial resolution in grating-based x-ray phase computed tomography (PCT) imaging is investigated with reverse projection extraction method, and the noise variances of the reconstructed absorption coefficient and refractive index decrement are compared. For the differential phase contrast method, the noise variance in the differential projection images follows the same inverse-square law with spatial resolution as in conventional absorption-based x-ray imaging projections. However, both theoretical analysis and simulations demonstrate that in PCT the noise variance of the reconstructed refractive index decrement scales with spatial resolution follows an inverse linear relationship at fixed slice thickness, while the noise variance of the reconstructed absorption coefficient conforms with the inverse cubic law. The results indicate that, for the same noise variance level, PCT imaging may enable higher spatial resolution than conventional absorption computed tomography (ACT), while ACT benefits more from degraded spatial resolution. This could be a useful guidance in imaging the inner structure of the sample in higher spatial resolution. Project supported by the National Basic Research Program of China (Grant No. 2012CB825800), the Science Fund for Creative Research Groups, the Knowledge Innovation Program of the Chinese Academy of Sciences (Grant Nos. KJCX2-YW-N42 and Y4545320Y2), the National Natural Science Foundation of China (Grant Nos. 11475170, 11205157, 11305173, 11205189, 11375225, 11321503, 11179004, and U1332109).

  4. Rapid and specific detection of H3 swine influenza virus using reverse transcription loop-mediated isothermal amplification method.

    PubMed

    Gu, H; Qi, X; Li, X; Jiang, H; Wang, Y; Liu, F; Lu, S; Yang, Y; Liu, F

    2010-04-01

    The main objective of our study is to develop a reverse transcriptase loop-mediated isothermal amplification (RT-LAMP)-based system for rapid and specific detection of H3 swine influenza virus (SIV). The system, H3 RT-LAMP, contained a set of six novel primers that targeted eight distinct regions of the viral haemagglutinin (HA) gene that are highly conserved among H3 influenza A viruses but not between H3 and other subtypes. H3 RT-LAMP accurately and specifically detected H3 SIV of different isolates from culture and from swine lung samples. The system is at least 10-fold more sensitive than the conventional RT-PCR assay and even comparable to the real-time RT-PCR method, with the detection limit of about one plaque-forming unit per reaction. Of 27 swine lung samples tested, 11 samples were positive in reactions with the RT-LAMP and real-time RT-PCR methods, while only 7 were positive with the conventional RT-PCR assay. Importantly, the assay can be completed within 45 min and is faster than the conventional RT-PCR and real-time RT-PCR approaches. Our results provide the first direct evidence that RT-LAMP is highly specific and sensitive for detecting H3 SIV. These results suggest that LAMP offers a promising alternative tool for rapid, inexpensive and specific diagnosis of influenza virus infection of swine and other animals in frontline settings.

  5. New method for the visual detection of human respiratory syncytial virus using reverse transcription loop-mediated amplification.

    PubMed

    Mu, Yonglin; Zeng, Jiawei; Chen, Qianqian; Liu, Jia; Wang, Lili; Yao, Fujia; Cui, Meng; He, Zhixiang; Zhang, Chiyu; Xiao, Ming; Lan, Ke

    2014-09-01

    Human respiratory syncytial virus (HRSV) is a seasonal respiratory pathogen that causes respiratory infection in children and the elderly. A new, reverse transcriptase loop-mediated isothermal amplification (RT-LAMP) assay was developed for the rapid (within 1h), simultaneous detection of A and B group HRSV. Primers specific for groups A and B were designed to amplify the N and L genes of HRSV, respectively. A fluorescent dye, calcein, was used as an indicator for the endpoint visual detection and/or real-time amplification of HRSV RNA. The detection limit of the new method was 281.17 50% tissue culture infective doses (TCID50)/ml for HRSV A and 1.58 TCID50/ml for HRSV B. To evaluate the validity of this method, a comparison with RT-PCR was performed using 77 nasopharyngeal swabs as samples. Both RT-LAMP and RT-PCR detected HRSV in 38 HRSV samples, yielding a positive rate of 49%. Of the RT-LAMP positive samples, 36 (95%) were also positive by RT-PCR, while two were negative by RT-PCR. Among the 36 RT-LAMP and RT-PCR positive samples, 11 belonged to HRSV group A, while 25 belonged to group B. The results show that the new RT-LAMP is simple, rapid and well suited for HRSV diagnosis, especially in a limited-resource setting.

  6. Extracting Lane Geometry and Topology Information from Vehicle Fleet Trajectories in Complex Urban Scenarios Using a Reversible Jump Mcmc Method

    NASA Astrophysics Data System (ADS)

    Roeth, O.; Zaum, D.; Brenner, C.

    2017-05-01

    Highly automated driving (HAD) requires maps not only of high spatial precision but also of yet unprecedented actuality. Traditionally small highly specialized fleets of measurement vehicles are used to generate such maps. Nevertheless, for achieving city-wide or even nation-wide coverage, automated map update mechanisms based on very large vehicle fleet data gain importance since highly frequent measurements are only to be obtained using such an approach. Furthermore, the processing of imprecise mass data in contrast to few dedicated highly accurate measurements calls for a high degree of automation. We present a method for the generation of lane-accurate road network maps from vehicle trajectory data (GPS or better). Our approach therefore allows for exploiting today's connected vehicle fleets for the generation of HAD maps. The presented algorithm is based on elementary building blocks which guarantees useful lane models and uses a Reversible Jump Markov chain Monte Carlo method to explore the models parameters in order to reconstruct the one most likely emitting the input data. The approach is applied to a challenging urban real-world scenario of different trajectory accuracy levels and is evaluated against a LIDAR-based ground truth map.

  7. In situ growth of manganese oxide on 3D graphene by a reverse microemulsion method for supercapacitors

    NASA Astrophysics Data System (ADS)

    Wei, Bing; Wang, Lidong; Wang, Yang; Yuan, Yinan; Miao, Qinghua; Yang, Ziyue; Fei, Weidong

    2016-03-01

    In this study, a new, effective strategy is reported for the fabrication of composites using manganese oxide (MnO2) grown in situ on three-dimensional (3D) graphene by the reverse microemulsion (water-in-oil) method. A uniform coating of nanoscale MnO2 layers can be observed on the internal surface of 3D graphene, which could benefit rapid ionic and electronic transport. The electrochemical performance of the MnO2/3D graphene composites is optimized by the control of the composite structure and mass loading of MnO2. The MnO2/3D graphene composite thus prepared exhibits a significantly high specific capacitance of 659.7 F g-1 at 0.3 A g-1 and an excellent retention life of 106% after 1000 cycles. The facile synthesis and excellent electrochemical performance of the MnO2/3D graphene composites indicate that the developed method demonstrates potential applications for the fabrication of novel electrode materials for use in energy storage devices.

  8. A Novel Multi-Sensor Environmental Perception Method Using Low-Rank Representation and a Particle Filter for Vehicle Reversing Safety.

    PubMed

    Zhang, Zutao; Li, Yanjun; Wang, Fubing; Meng, Guanjun; Salman, Waleed; Saleem, Layth; Zhang, Xiaoliang; Wang, Chunbai; Hu, Guangdi; Liu, Yugang

    2016-06-09

    Environmental perception and information processing are two key steps of active safety for vehicle reversing. Single-sensor environmental perception cannot meet the need for vehicle reversing safety due to its low reliability. In this paper, we present a novel multi-sensor environmental perception method using low-rank representation and a particle filter for vehicle reversing safety. The proposed system consists of four main steps, namely multi-sensor environmental perception, information fusion, target recognition and tracking using low-rank representation and a particle filter, and vehicle reversing speed control modules. First of all, the multi-sensor environmental perception module, based on a binocular-camera system and ultrasonic range finders, obtains the distance data for obstacles behind the vehicle when the vehicle is reversing. Secondly, the information fusion algorithm using an adaptive Kalman filter is used to process the data obtained with the multi-sensor environmental perception module, which greatly improves the robustness of the sensors. Then the framework of a particle filter and low-rank representation is used to track the main obstacles. The low-rank representation is used to optimize an objective particle template that has the smallest L-1 norm. Finally, the electronic throttle opening and automatic braking is under control of the proposed vehicle reversing control strategy prior to any potential collisions, making the reversing control safer and more reliable. The final system simulation and practical testing results demonstrate the validity of the proposed multi-sensor environmental perception method using low-rank representation and a particle filter for vehicle reversing safety.

  9. A Novel Multi-Sensor Environmental Perception Method Using Low-Rank Representation and a Particle Filter for Vehicle Reversing Safety

    PubMed Central

    Zhang, Zutao; Li, Yanjun; Wang, Fubing; Meng, Guanjun; Salman, Waleed; Saleem, Layth; Zhang, Xiaoliang; Wang, Chunbai; Hu, Guangdi; Liu, Yugang

    2016-01-01

    Environmental perception and information processing are two key steps of active safety for vehicle reversing. Single-sensor environmental perception cannot meet the need for vehicle reversing safety due to its low reliability. In this paper, we present a novel multi-sensor environmental perception method using low-rank representation and a particle filter for vehicle reversing safety. The proposed system consists of four main steps, namely multi-sensor environmental perception, information fusion, target recognition and tracking using low-rank representation and a particle filter, and vehicle reversing speed control modules. First of all, the multi-sensor environmental perception module, based on a binocular-camera system and ultrasonic range finders, obtains the distance data for obstacles behind the vehicle when the vehicle is reversing. Secondly, the information fusion algorithm using an adaptive Kalman filter is used to process the data obtained with the multi-sensor environmental perception module, which greatly improves the robustness of the sensors. Then the framework of a particle filter and low-rank representation is used to track the main obstacles. The low-rank representation is used to optimize an objective particle template that has the smallest L-1 norm. Finally, the electronic throttle opening and automatic braking is under control of the proposed vehicle reversing control strategy prior to any potential collisions, making the reversing control safer and more reliable. The final system simulation and practical testing results demonstrate the validity of the proposed multi-sensor environmental perception method using low-rank representation and a particle filter for vehicle reversing safety. PMID:27294931

  10. Association of short-term bleeding and cramping patterns with long-acting reversible contraceptive method satisfaction.

    PubMed

    Diedrich, Justin T; Desai, Sanyukta; Zhao, Qiuhong; Secura, Gina; Madden, Tessa; Peipert, Jeffrey F

    2015-01-01

    We sought to examine the short-term (3- and 6-month), self-reported bleeding and cramping patterns with intrauterine devices (IUDs) and the contraceptive implant, and the association of these symptoms with method satisfaction. We analyzed 3- and 6-month survey data from IUD and implant users in the Contraceptive CHOICE Project, a prospective cohort study. Participants who received a long-acting reversible contraceptive (LARC) method (levonorgestrel-releasing intrauterine system [LNG-IUS], copper IUD, or the etonogestrel implant) and completed their 3- and 6-month surveys were included. Univariable and multivariable analyses were performed to examine the association of bleeding and cramping patterns with short-term satisfaction. Our analytic sample included 5011 Contraceptive CHOICE Project participants: 3001 LNG-IUS users, 826 copper IUD users, and 1184 implant users. At 3 months, >65% of LNG-IUS and implant users reported no change or decreased cramping, while 63% of copper IUD users reported increased menstrual cramping. Lighter bleeding was reported by 67% of LNG-IUS users, 58% of implant users, and 8% of copper IUD users. Satisfaction of all LARC methods was high (≥90%). LARC users with increased menstrual cramping (relative risk adjusted [RRadj], 0.78; 95% confidence interval [CI], 0.72-0.85), heavier bleeding (RRadj, 0.83; 95% CI, 0.76-0.92), and increased bleeding frequency (RRadj, 0.73; 95% CI, 0.67-0.80) were less likely to report being very satisfied at 6 months. Regardless of the LARC method, satisfaction at 3 and 6 months is very high. Changes in self-reported bleeding and cramping are associated with short-term LARC satisfaction. Copyright © 2015 Elsevier Inc. All rights reserved.

  11. Time reversal optical tomography and decomposition methods for detection and localization of targets in highly scattering turbid media

    NASA Astrophysics Data System (ADS)

    Wu, Binlin

    New near-infrared (NIR) diffuse optical tomography (DOT) approaches were developed to detect, locate, and image small targets embedded in highly scattering turbid media. The first approach, referred to as time reversal optical tomography (TROT), is based on time reversal (TR) imaging and multiple signal classification (MUSIC). The second approach uses decomposition methods of non-negative matrix factorization (NMF) and principal component analysis (PCA) commonly used in blind source separation (BSS) problems, and compare the outcomes with that of optical imaging using independent component analysis (OPTICA). The goal is to develop a safe, affordable, noninvasive imaging modality for detection and characterization of breast tumors in early growth stages when those are more amenable to treatment. The efficacy of the approaches was tested using simulated data, and experiments involving model media and absorptive, scattering, and fluorescent targets, as well as, "realistic human breast model" composed of ex vivo breast tissues with embedded tumors. The experimental arrangements realized continuous wave (CW) multi-source probing of samples and multi-detector acquisition of diffusely transmitted signal in rectangular slab geometry. A data matrix was generated using the perturbation in the transmitted light intensity distribution due to the presence of absorptive or scattering targets. For fluorescent targets the data matrix was generated using the diffusely transmitted fluorescence signal distribution from the targets. The data matrix was analyzed using different approaches to detect and characterize the targets. The salient features of the approaches include ability to: (a) detect small targets; (b) provide three-dimensional location of the targets with high accuracy (~within a millimeter or 2); and (c) assess optical strength of the targets. The approaches are less computation intensive and consequently are faster than other inverse image reconstruction methods that

  12. Pre-stack Reverse-Time Migration Method for Imaging Subsurface Structures of the Himalaya-Tibet Collision Zone

    NASA Astrophysics Data System (ADS)

    Zhu, W.; Ge, Z.; Huang, Q.

    2015-12-01

    We use pre-stack reverse-time migration (RTM) of converted waves to image crust and mantle structures of the Himalaya-Tibet collision zone. Multi-component seismic data are back propagated using FDTD method of elastic wave. P and SV components are separated through the divergence and curl of the reconstructed wave-field. Cross-correlation imaging condition is applied between the back propagated P and SV wave-fields to reconstruct the location of the points where conversion (e.g., P-to-S or S-to-P) occurred. Unlike traditional CCP receiver function stacking, this method does not rely on 1-D assumptions about the geometry of structures, so that it is able to cope with dipping interface, steep faults. Then we applied this method on data of the southern segment of Hi-CLIMB. The chosen seismic array consists of 76 stations and it is 260-kilometer-long extending northward from the Ganges Basin and across the Himalayas. By pre-stack RTM, we have constructed an image of the crust and upper mantle beneath the Himalayas. The image reveals that the Moho dip from a normal depth of 45 km at distance of 120 km ~ 190 km to a much deeper depth of 65 km at 200 km ~ 270 km under southern Tibet. There are also some weak signal in the crust with the same trend of Moho at this region. This may also be related to the underthrusting of Indian plate beneath Tibet. This result of pre-stack RTM consists with previous results obtained by receiver function, but has a steeper change of the depth of Moho.

  13. Identification of Staphylococcus species and subspecies by the chaperonin 60 gene identification method and reverse checkerboard hybridization.

    PubMed Central

    Goh, S H; Santucci, Z; Kloos, W E; Faltyn, M; George, C G; Driedger, D; Hemmingsen, S M

    1997-01-01

    A previous study (S. H. Goh et al., J. Clin. Microbiol. 34:818-823, 1996) demonstrated that a 600-bp region of the chaperonin 60 (Cpn60) genes from various bacterial isolates could be amplified by PCR with a pair of degenerate primers and that the products could be used as species-specific probes for Staphylococcus aureus, S. epidermidis, S. haemolyticus, S. lugdunensis, S. saprophyticus, and S. schleiferi. To further validate the utility of bacterial Cpn60 genes as universal targets for bacterial identification (ID), reverse checkerboard chemiluminescent hybridization experiments were performed with DNA probes from 34 different Staphylococcus species and subspecies. With the exception of probes from the Cpn60 genes of S. intermedius and S. delphini, which cross hybridized, all were species specific. Two subspecies of both S. capitis and S. cohnii were differentiated from one another, while DNAs from the two S. schleiferi subspecies cross hybridized. When 40 known Staphylococcus isolates were tested in a blind experiment by the Cpn60 gene method, 36 strains, representing six species and one subspecies (S. sciuri, S. caseolyticus, S. hominis, S. warneri, S. hyicus, S. haemolyticus, and S. capitis subsp. ureolyticus), were correctly identified. DNA from the four remaining isolates, known to be S. hyicus bovine strains, failed to hybridize to DNA from the S. hyicus target strain or any other Staphylococcus species. However, DNAs from these S. hyicus isolates did cross hybridize with each other. New DNA sequence data and evidence from previous studies suggest some genetic divergence between the two groups of S. hyicus isolates. Our results demonstrate that this Cpn60 gene-based ID method has the potential to be a basic method for bacterial ID. Studies are in progress to further validate the utility of this Cpn60 gene system for ID of Staphylococcus and other genera, including those of slow-growing microorganisms. PMID:9399505

  14. High stability of the immunomodulatory GK-1 synthetic peptide measured by a reversed phase high-performance liquid chromatography method.

    PubMed

    Cervantes-Torres, Jacquelynne; Segura-Velázquez, René; Padilla, Patricia; Sciutto, Edda; Fragoso, Gladis

    2017-08-15

    The 18-mer anionic peptide GK-1 has been successfully employed to improve the immunogenicity and protective response induced by the influenza vaccine and exhibited some degree of protection against experimental murine melanoma. In this study, a sensitive and quantitative reversed-phase HPLC method was developed to study GK-1 stability under different pH, temperature and storage time. The analysis was carried out on a Sunfire C18 column with mobile phase of acetonitrile-water containing 0.02% TFA. The detection was performed on an UV/Vis Detector at 220nm. The method was validated with respect to linearity, limits of detection and quantification, precision and selectivity. The linear calibration curves were obtained in the concentration range of 0.015-0.24mg/mL (r(2)=0.99) with lower limits of detection (LOD) and quantification (LOQ) of 0.001 and 0.018mg/mL, respectively. The intra- and inter-day precision (relative standard deviation, R.S.D.) values were below 3% at all quality control levels. Forced degradation studies were conducted by introducing a sample of GK-1 peptide standard solution to different conditions of pH (from 2 to 8), temperature (4, 25 and 40°C) and storage time (10days to 6 months). The peptide GK-1 showed to be stable under different ranges of pH and temperature; however it was susceptible to prolonged storage at room temperature. Results shown in this study sustain the high stability of the GK-1 peptide using a reliable new selective and precise method suitable for its analysis. Copyright © 2017 Elsevier B.V. All rights reserved.

  15. The Impact of Balanced Counseling on Contraceptive Method Choice and Determinants of Long Acting and Reversible Contraceptive Continuation in Nepal.

    PubMed

    Sapkota, Sabitri; Rajbhandary, Ruchita; Lohani, Shilpa

    2016-03-08

    Introduction Long-acting reversible contraceptives (LARCs) reduce rates of unintended pregnancies and repeat abortion. Uptake and continuation rates of LARCs are very low in Nepal, despite free provision from most health facilities. We sought to establish the effectiveness of a new approach to LARC promotion in Nepal. Methods We examined change in contraceptive method mix in Nepal using service data resulting from introduction of a balanced counseling (BC) approach to family planning (FP). All staff located at nine randomly selected FP sites were trained and began applying BC in April and May 2014. Women who accepted LARCs from a participating facility were re-contacted at 1, 3, 6 and 12 months. We estimated the LARC continuation rate and assessed determinants of continuation using descriptive analysis, Kaplan-Meier survival curves and univariate and multivariate Cox proportional hazard analysis. Results A total of 5744 women received BC between April and July 2014. 1580 women (27.5 %) took up LARCs, raising its contribution to contraceptive method mix at [organization] to 40 %, significantly higher than the 15 % recorded in 2013. 913 women were followed-up, and the LARC continuation rate at 12 months was 82 %. Women's reported satisfaction with LARC [AHR 0.23; 95 % CI 0.14-0.39, p = 0.000] was the single strongest determinant of LARC continuation after adjusting for all background characteristics. Discussion The findings suggest BC is an effective approach for increasing LARC uptake in Nepal. The rate of LARC continuation and its determinants are important inputs to strategies for improved delivery of FP services.

  16. Method and apparatus for cold gas reinjection in through-flow and reverse-flow wave rotors

    NASA Technical Reports Server (NTRS)

    Nalim, M. Razi (Inventor); Paxson, Daniel E. (Inventor)

    1999-01-01

    A method and apparatus for cold gas reinjection in through-flow and reverse-flow wave rotors having a plurality of channels formed around a periphery thereof. A first port injects a supply of cool air into the channels. A second port allows the supply of cool air to exit the channels and flow to a combustor. A third port injects a supply of hot gas from the combustor into the channels. A fourth port allows the supply of hot gas to exit the channels and flow to a turbine. A diverting port and a reinjection port are connected to the second and third ports, respectively. The diverting port diverts a portion of the cool air exiting through the second port as reinjection air. The diverting port is fluidly connected to the reinjection port which reinjects the reinjection air back into the channels. The reinjection air evacuates the channels of the hot gas resident therein and cools the channel walls, a pair of end walls of the rotor, ducts communicating with the rotor and subsequent downstream components. In a second embodiment, the second port receives all of the cool air exiting the channels and the diverting port diverts a portion of the cool air just prior to the cool air flowing to the combustor.

  17. Development of a reverse-transcription loop-mediated isothermal amplification method for detection of rabbit hemorrhagic disease virus.

    PubMed

    Yuan, Dongwei; Guo, Dongchun; Liu, Jiasen; Si, Changde; Jiang, Qian; Lin, Huan; Yang, Tiankuo; Qu, Liandong

    2013-02-01

    Rabbit hemorrhagic disease virus (RHDV) causes haemagglutination and severe liver damage, with a high mortality rate. To develop a rapid and sensitive method for the surveillance of RHDV, a one-step reverse transcription-loop-mediated isothermal amplification (RT-LAMP) assay was established using a set of four primers specific for the VP60 gene segment of RHDV. The established assay was performed at 64°C for 40 min under isothermal conditions, and the results were visualized directly by electrophoresis or as fluorescent signals under ultraviolet light. The detection limit of the RT-LAMP assay was 10 copies of viral RNA per reaction, which was comparable to quantitative real-time RT-PCR, and 100-fold more sensitive than standard RT-PCR. Furthermore, seven viral RNAs of field isolates in China could be detected successfully using this assay. Overall, the newly established RT-LAMP assay indicates the potential usefulness of the technique as a simple, rapid and sensitive procedure, and can visually detect RHDV infection without the need for any specialized equipment.

  18. Assembly and electroanalytical performance of Prussian blue/polypyrrole composite nanoparticles synthesized by the reverse micelle method

    PubMed Central

    Miao, Yuqing; Liu, Jiwei

    2009-01-01

    We report on the characterization, assembly and electroanalytical performance of Prussian blue/polypyrrole (PBPPy) composite nanoparticles synthesized by the reverse micelle method. Scanning electron microscopy suggests the formation of nanosized PBPPy particles with diameters between 40 and 50 nm. Optical absorption confirms that the particles are composed of Prussian blue (PB) and polypyrrole. PB and PBPPy nanoparticles were anchored onto the surface of cysteine-modified Au electrodes. Cyclic voltammetry experiments show that PB- or PBPPy-modified electrodes exhibit intrinsic electrochemical properties and a high electrocatalytic activity towards H2O2. PBPPy-modified electrodes exhibit a higher sensitivity to H2O2 than PB-modified electrodes. A linear calibration curve in the concentration range 0.99 μM–8.26 mM H2O2 is constructed with a detection limit of 0.23 μM at a signal-to-noise ratio of 3. Excellent stability is observed for PBPPy-composite-nanoparticle-modified electrodes even in a pH 6 phosphate buffer solution with a high H2O2 concentration (0.99 mM). Glutaraldehyde and were also employed to immobilize glucose oxidase for the development of PBPPy-based biosensors. The results show that PBPPy composite nanoparticles can be used to develop oxidase-based biosensors. PMID:27877288

  19. Assembly and electroanalytical performance of Prussian blue/polypyrrole composite nanoparticles synthesized by the reverse micelle method.

    PubMed

    Miao, Yuqing; Liu, Jiwei

    2009-04-01

    We report on the characterization, assembly and electroanalytical performance of Prussian blue/polypyrrole (PBPPy) composite nanoparticles synthesized by the reverse micelle method. Scanning electron microscopy suggests the formation of nanosized PBPPy particles with diameters between 40 and 50 nm. Optical absorption confirms that the particles are composed of Prussian blue (PB) and polypyrrole. PB and PBPPy nanoparticles were anchored onto the surface of cysteine-modified Au electrodes. Cyclic voltammetry experiments show that PB- or PBPPy-modified electrodes exhibit intrinsic electrochemical properties and a high electrocatalytic activity towards H2O2. PBPPy-modified electrodes exhibit a higher sensitivity to H2O2 than PB-modified electrodes. A linear calibration curve in the concentration range 0.99 μM-8.26 mM H2O2 is constructed with a detection limit of 0.23 μM at a signal-to-noise ratio of 3. Excellent stability is observed for PBPPy-composite-nanoparticle-modified electrodes even in a pH 6 phosphate buffer solution with a high H2O2 concentration (0.99 mM). Glutaraldehyde and [Formula: see text] were also employed to immobilize glucose oxidase for the development of PBPPy-based biosensors. The results show that PBPPy composite nanoparticles can be used to develop oxidase-based biosensors.

  20. Long-acting reversible contraception method use among Title X providers and non-Title X providers in California.

    PubMed

    Park, Hye-Youn; Rodriguez, Maria I; Hulett, Denis; Darney, Philip D; Thiel de Bocanegra, Heike

    2012-11-01

    Publicly funded family planning services play an important role in reducing unintended pregnancy by providing access to effective contraception. We assessed whether California family planning providers receiving federal Title X funds are more likely to offer on-site long-acting reversible contraception (LARC) methods than those who do not receive these funds. Using 2009 administrative data, we examined on-site utilization of LARC by clinic type (Title X public, non-Title X public, or private) and constructed beta-binomial logistic regression models. The odds of on-site LARC services in non-Title X public and private providers were decreased by 35% [Odds Ratio (OR)=0.65, 95% confidence interval (CI) 0.54-0.79] and 61% [OR=0.39, 95% CI 0.32-0.47], respectively, compared to those of Title X providers after controlling for clinic size, urban/rural location, and proportion of teen, African-American, and Latina clients. On-site utilization of LARC is a potential quality indicator for family planning programs. Title X resources are associated with increased use of LARC. Published by Elsevier Inc.

  1. A codon-shuffling method to prevent reversion during production of replication-defective herpesvirus stocks: Implications for herpesvirus vaccines.

    PubMed

    Li, Gang; Ward, Charles; Yeasmin, Rukhsana; Skiena, Steven; Krug, Laurie T; Forrest, J Craig

    2017-03-13

    Herpesviruses establish life-long chronic infections that place infected hosts at risk for severe disease. Herpesvirus genomes readily undergo homologous recombination (HR) during productive replication, often leading to wild-type (WT) reversion during complementation of replication-defective and attenuated viruses via HR with the helper gene provided in trans. To overcome this barrier, we developed a synthetic-biology approach based on a technique known as codon shuffling. Computer-assisted algorithms redistribute codons in a helper gene, thereby eliminating regions of homology, while enabling manipulation of factors such as codon-pair bias and CpG content to effectively titrate helper-gene protein levels. We apply this technique to rescue the replication of a murine gammaherpesvirus engineered with a mutation in the major immediate-early transactivator protein RTA. Complementation with codon-shuffled RTA constructs did not yield any WT revertant virus, a sharp contrast to WT virus contamination frequently observed during complementation with an unmodified helper gene. We further demonstrate the importance of eliminating WT virus contamination in an animal model of gammaherpesvirus lethality. We propose complementation by codon shuffling as a means to produce replication-defective or attenuated viruses. This method has immediate utility for investigating roles of essential genes in viral replication and will better enable future development of herpesvirus vaccines.

  2. A codon-shuffling method to prevent reversion during production of replication-defective herpesvirus stocks: Implications for herpesvirus vaccines

    PubMed Central

    Li, Gang; Ward, Charles; Yeasmin, Rukhsana; Skiena, Steven; Krug, Laurie T.; Forrest, J. Craig

    2017-01-01

    Herpesviruses establish life-long chronic infections that place infected hosts at risk for severe disease. Herpesvirus genomes readily undergo homologous recombination (HR) during productive replication, often leading to wild-type (WT) reversion during complementation of replication-defective and attenuated viruses via HR with the helper gene provided in trans. To overcome this barrier, we developed a synthetic-biology approach based on a technique known as codon shuffling. Computer-assisted algorithms redistribute codons in a helper gene, thereby eliminating regions of homology, while enabling manipulation of factors such as codon-pair bias and CpG content to effectively titrate helper-gene protein levels. We apply this technique to rescue the replication of a murine gammaherpesvirus engineered with a mutation in the major immediate-early transactivator protein RTA. Complementation with codon-shuffled RTA constructs did not yield any WT revertant virus, a sharp contrast to WT virus contamination frequently observed during complementation with an unmodified helper gene. We further demonstrate the importance of eliminating WT virus contamination in an animal model of gammaherpesvirus lethality. We propose complementation by codon shuffling as a means to produce replication-defective or attenuated viruses. This method has immediate utility for investigating roles of essential genes in viral replication and will better enable future development of herpesvirus vaccines. PMID:28287622

  3. Best Viral Elution Method Available for Quantification of Enteroviruses in Sludge by Both Cell Culture and Reverse Transcription-PCR

    PubMed Central

    Monpoeho, S.; Maul, A.; Mignotte-Cadiergues, B.; Schwartzbrod, L.; Billaudel, S.; Ferré, V.

    2001-01-01

    The aim of this study was to select one or several virus extraction techniques that enable simultaneous detection of enterovirus genomes and infectious particles in different types of urban sludge. Eight techniques were compared by using 16 different liquid and solid sludge samples. The numbers of infectious enteroviruses in cell cultures were determined by using the most-probable-number method. The enterovirus genome was quantified by a single-tube reverse transcription-PCR using TaqMan technology. The results were statistically analyzed by Friedman's test, a nonparametric test for analysis of randomized block data using only ranks in terms of extraction technique efficiency. Two techniques seemed to yield higher viral titers as determined by simultaneous detection by cell culture and PCR. The first involved a 10% beef extract solution at pH 9 and sonication; the second involved a 0.3 M NaCl–7% beef extract solution at pH 7.5 followed by Freon treatment. In solid sludge, no significant differences were observed among the eight techniques tested. Both of the best techniques can be used for simultaneous detection of infectious enterovirus particles and genomes in any type of urban sludge. PMID:11375154

  4. Baseline-free delamination inspection in composite plates by synthesizing non-contact air-coupled Lamb wave scan method and virtual time reversal algorithm

    NASA Astrophysics Data System (ADS)

    Liu, Zenghua; Yu, Hongtao; Fan, Junwei; Hu, Yanan; He, Cunfu; Wu, Bin

    2015-04-01

    In the paper, we combined air-coupled Lamb wave scan method and virtual time reversal (VTR) algorithm and proposed a composite baseline-free delamination inspection technique of composite plates. According to VTR algorithm, time reversal process is virtually performed through signal operations and the hardware manipulation for time reversal is not required. Baseline-free damage inspection can be achieved by comparing the first input actuation signal with the reconstructed final signal obtained by VTR algorithm. An air-coupled Lamb wave scan method combined with VTR-based probabilistic imaging algorithm is developed for delamination inspection of composite plates. Carbon fiber-reinforced composite plates with the delaminations of different shapes and sizes were experimentally tested. The testing results are well in accordance with the actual delamination locations and sizes as well as the results obtained with the commercial point-to-point immersion C-scan system.

  5. Quality assessment of Herba Leonuri based on the analysis of multi-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

    2017-09-27

    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 Rf values of the bands, and reversed-phase HPLC 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 HPLC 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 HPLC 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. This article is protected by copyright. All rights reserved. This article is protected by copyright. All rights reserved.

  6. A weighted reverse Cuthill-McKee procedure for finite element method algorithms to solve strongly anisotropic electrodynamic problems

    SciTech Connect

    Cristofolini, Andrea; Latini, Chiara; Borghi, Carlo A.

    2011-02-01

    This paper presents a technique for improving the convergence rate of a generalized minimum residual (GMRES) algorithm applied for the solution of a algebraic system produced by the discretization of an electrodynamic problem with a tensorial electrical conductivity. The electrodynamic solver considered in this work is a part of a magnetohydrodynamic (MHD) code in the low magnetic Reynolds number approximation. The code has been developed for the analysis of MHD interaction during the re-entry phase of a space vehicle. This application is a promising technique intensively investigated for the shock mitigation and the vehicle control in the higher layers of a planetary atmosphere. The medium in the considered application is a low density plasma, characterized by a tensorial conductivity. This is a result of the behavior of the free electric charges, which tend to drift in a direction perpendicular both to the electric field and to the magnetic field. In the given approximation, the electrodynamics is described by an elliptical partial differential equation, which is solved by means of a finite element approach. The linear system obtained by discretizing the problem is solved by means of a GMRES iterative method with an incomplete LU factorization threshold preconditioning. The convergence of the solver appears to be strongly affected by the tensorial characteristic of the conductivity. In order to deal with this feature, the bandwidth reduction in the coefficient matrix is considered and a novel technique is proposed and discussed. First, the standard reverse Cuthill-McKee (RCM) procedure has been applied to the problem. Then a modification of the RCM procedure (the weighted RCM procedure, WRCM) has been developed. In the last approach, the reordering is performed taking into account the relation between the mesh geometry and the magnetic field direction. In order to investigate the effectiveness of the methods, two cases are considered. The RCM and WRCM procedures

  7. A new multichannel time reversal focusing method for circumferential Lamb waves and its applications for defect detection in thick-walled pipe with large-diameter.

    PubMed

    Liu, Zenghua; Xu, Qinglong; Gong, Yu; He, Cunfu; Wu, Bin

    2014-09-01

    This paper proposes a new multichannel time reversal focusing (MTRF) method for circumferential Lamb waves which is based on modified time reversal algorithm and applies this method for detecting different kinds of defects in thick-walled pipe with large-diameter. The principle of time reversal of circumferential Lamb waves in pipe is presented along with the influence from multiple guided wave modes and propagation paths. Experimental study is carried out in a thick-walled and large-diameter pipe with three artificial defects, namely two axial notches on its inner and outer surface respectively, and a corrosion-like defect on its outer surface. By using the proposed MTRF method, the multichannel signals focus at the defects, leading to the amplitude improvement of the defect scattered signal. Besides, another energy focus arises in the direct signal due to the partial compensation of dispersion and multimode of circumferential Lamb waves, alongside the multichannel focusing, during MTRF process. By taking the direct focus as a time base, accurate defect localization is implemented. Secondly, a new phenomenon is exhibited in this paper that defect scattered wave packet appears just before the right boundary of truncation window after time reversal, and to which two feasible explanations are given. Moreover, this phenomenon can be used as the theoretical basis in the determination of defect scattered waves in time reversal response signal. At last, in order to detect defects without prior knowing their exact position, a large-range truncation window is used in the proposed method. As a result, the experimental operation of MTRF method is simplified and defect detection and localization are well accomplished. Copyright © 2014 Elsevier B.V. All rights reserved.

  8. Removal of Gangue Minerals Containing Major Elements from Karlıova-Derinçay (Bingöl) Lignite Using a Reverse Flotation Method

    NASA Astrophysics Data System (ADS)

    Temel, Halime Abakay

    2015-12-01

    The removal of gangue minerals containing major elements was investigated using a reverse flotation method. Experiments were conducted on lignite samples, with high-ash and low-sulphur contents taken from a lignite field in Karlıova-Derinçay (Bingöl), Turkey. Predominant gangue minerals in the samples were found to be quartz, gypsum, feldspar minerals, mica minerals, and clays (smectite group). Preliminary flotation studies showed that gangue materials are more buoyant than the lignite sample. Some parameters that markedly influence the effectiveness of reverse flotation, such as grinding time, pH, collector type and volume, frother type and volume, and salt, were investigated. Quartz was found to cause a major problem in terms of reverse flotation. Flotation measurements showed that anionic collectors in an acidic medium result in the following element reduction order: sulphur trioxide > ferric oxide > magnesium oxide > calcium oxide > silicon dioxide > aluminium oxide.

  9. A short-scan method for k(3) estimation with moderately reversible PET ligands: application of irreversible model to early-phase PET data.

    PubMed

    Sato, Koichi; Fukushi, Kiyoshi; Shinotoh, Hitoshi; Shimada, Hitoshi; Tanaka, Noriko; Hirano, Shigeki; Irie, Toshiaki

    2012-02-15

    Long dynamic scans (60-120 min) are often required for estimating the k(3) value, an index of receptor density, by positron emission tomography (PET). However, the precision of k(3) is usually low in kinetic analyses for reversible PET ligands compared with irreversible ligands. That is largely due to unstable estimation of the dissociation rate constant, k(4). We propose a novel '3P+' method for estimating k(3) of moderately reversible ligands, where a 3-parameter model without k(4) is applied to early-phase PET data to obtain a good model-fit of k(3) estimation. By using [(11)C] Pittsburgh compound B (PIB) (k(4) = 0.018/min) as an example of a moderately reversible ligand, the 3P+ method simulation with a 28 min PET scan yielded less than 3% k(3) relative bias with a +100% k(3) change. In [(11)C]PIB PET scans of 15 normal controls (NC) and nine patients with Alzheimer's disease (AD), the 3P+ method provided a precise k(3) estimate (mean SE of 13.6% in parietal cortex; covariance matrix method). The results revealed linear correlations (r = 0.964) of parietal k(3) values in 24 subjects between 28minute 3P+ method and conventional 90 minute 4-parameter method. A good separation of k(3) between NC and AD groups (P < 0.001; t-test) was replicated in 28 minute 3P+ method. The short-scan 3P+ method may be a practical alternative method for analyzing reversible ligands.

  10. Bioluminescence-Based Method for Measuring Assimilable Organic Carbon in Pretreatment Water for Reverse Osmosis Membrane Desalination ▿

    PubMed Central

    Weinrich, Lauren A.; Schneider, Orren D.; LeChevallier, Mark W.

    2011-01-01

    A bioluminescence-based assimilable organic carbon (AOC) test was developed for determining the biological growth potential of seawater within the reverse osmosis desalination pretreatment process. The test uses Vibrio harveyi, a marine organism that exhibits constitutive luminescence and is nutritionally robust. AOC was measured in both a pilot plant and a full-scale desalination plant pretreatment. PMID:21148685

  11. Bioluminescence-based method for measuring assimilable organic carbon in pretreatment water for reverse osmosis membrane desalination.

    PubMed

    Weinrich, Lauren A; Schneider, Orren D; LeChevallier, Mark W

    2011-02-01

    A bioluminescence-based assimilable organic carbon (AOC) test was developed for determining the biological growth potential of seawater within the reverse osmosis desalination pretreatment process. The test uses Vibrio harveyi, a marine organism that exhibits constitutive luminescence and is nutritionally robust. AOC was measured in both a pilot plant and a full-scale desalination plant pretreatment.

  12. Magnetic and structural studies on CoFe2O4 nanoparticles synthesized by co-precipitation, normal micelles and reverse micelles methods

    NASA Astrophysics Data System (ADS)

    Sharifi, Ibrahim; Shokrollahi, H.; Doroodmand, Mohammad Mahdi; Safi, R.

    2012-05-01

    Cobalt ferrite nanoparticles were synthesized by the chemical co-precipitation, normal micelles and reverse micelles methods of iron and cobalt chlorides. X-ray diffraction analysis, Fourier Transform Infrared (FTIR) and Vibrating Sample Magnetometer were carried out at room temperature to study the structural and magnetic properties. X-ray patterns revealed the production of a broad single cubic phase with the average particle sizes of ∼12 nm, 5 nm and 8 nm for co-precipitation, normal micelles and reverse micelles methods, respectively. The FTIR measurements between 400 and 4000 cm-1 confirmed the intrinsic cation vibrations of spinel structure for each one of the three methods. Moreover, the average particle sizes were lower than the single domain size (128 nm) and higher than the super-paramagnetic size (2-3 nm) at room temperature. The results revealed that the magnetic properties depend on the particle size and cation distribution, whereas the role of particle size is more significant.

  13. Reversible dementias

    PubMed Central

    Tripathi, Manjari; Vibha, Deepti

    2009-01-01

    In recent years, more attention has been given to the early diagnostic evaluation of patients with dementia which is essential to identify patients with cognitive symptoms who may have treatable conditions. Guidelines suggest that all patients presenting with dementia or cognitive symptoms should be evaluated with a range of laboratory tests, and with structural brain imaging with computed tomography (CT) or magnetic resonance imaging (MRI). While many of the disorders reported as ‘reversible dementias’ are conditions that may well be associated with cognitive or behavioral symptoms, these symptoms are not always sufficiently severe to fulfill the clinical criteria for dementia. Thus, while the etiology of a condition may be treatable it should not be assumed that the associated dementia is fully reversible. Potentially reversible dementias should be identified and treatment considered, even if the symptoms are not sufficiently severe to meet the clinical criteria for dementia, and even if partial or full reversal of the cognitive symptoms cannot be guaranteed. In the literature, the most frequently observed potentially reversible conditions identified in patients with cognitive impairment or dementia are depression, adverse effects of drugs, drug or alcohol abuse, space-occupying lesions, normal pressure hydrocephalus, and metabolic conditions land endocrinal conditions like hypothyroidism and nutritional conditions like vitamin B-12 deficiency. Depression is by far the most common of the potentially reversible conditions. The review, hence addresses the common causes of reversible dementia and the studies published so far. PMID:21416018

  14. Reverse shoulder arthroplasty: The Singapore General Hospital experience and a simple method of measuring change in the center-of-rotation

    PubMed Central

    Ang, Chay-You; Lai, Kah-Weng; Tjiauw Tjoen, Denny Lie; Chang Chee Cheng, Paul

    2015-01-01

    Introduction This study reviews the outcomes of reverse shoulder arthroplasty (RSA) and introduces a novel method of measuring changes in the center-of-rotation (COR) of the shoulder joint post-operatively. Methods We performed 10 reverse shoulders in 2011. Patients were evaluated pre-operatively and post-operatively using the Constant Score. The COR of the shoulder was determined pre- and post-operatively on radiographs and the differences were analysed. Results There was significant improvement in Constant Scores post-operatively with reduction in pain and increase in strength. Medialisation but not distalisation of the COR was achieved. Discussion Longer follow-up studies and studies on survivalship are required. PMID:25972701

  15. Size-controlled synthesis of ZrO{sub 2}-TiO{sub 2} nanoparticles prepared via reverse micelle method

    SciTech Connect

    Ghiaci, Mehran Aghaei, Hamidreza; Abbaspur, Alireza

    2008-05-06

    Zirconium-titanium mixed oxide nanoparticles have been synthesized using microreactors made of bis-(2-ethylhexyl) sulfosuccinate (AOT)/water/n-hexane microemulsions. The control of particle size was achieved by varying the process variables, such as water-to-surfactant molar ratio and reagent concentration. Their sizes, appearances, crystal structures, pore diameter and surface area were characterized by TEM, XRD, N{sub 2} adsorption/desorption methods. The results revealed that samples prepared in reverse micelles had no crystalline phase. The Beckmann rearrangement of cyclohexanone oxime on ZrO{sub 2}-TiO{sub 2} nanoparticles was carried out in a fixed-bed down flow reactor to investigate the effect of particle size on catalytic activity and selectivity. Samples synthesized in reverse micelles had better reaction performance than samples prepared via sol-gel method. A parallel relationship could be drawn between the catalytic activity and the particle size as well as the selectivity of the catalyst.

  16. Reversible Sterilization

    ERIC Educational Resources Information Center

    Largey, Gale

    1977-01-01

    Notes that difficult questions arise concerning the use of sterilization for alleged eugenic and euthenic purposes. Thus, how reversible sterilization will be used with relation to the poor, mentally ill, mentally retarded, criminals, and minors, is questioned. (Author/AM)

  17. Reversible Sterilization

    ERIC Educational Resources Information Center

    Largey, Gale

    1977-01-01

    Notes that difficult questions arise concerning the use of sterilization for alleged eugenic and euthenic purposes. Thus, how reversible sterilization will be used with relation to the poor, mentally ill, mentally retarded, criminals, and minors, is questioned. (Author/AM)

  18. Reversible Cardiomyopathies

    PubMed Central

    Patel, Harsh; Madanieh, Raef; Kosmas, Constantine E; Vatti, Satya K; Vittorio, Timothy J

    2015-01-01

    Cardiomyopathies (CMs) have many etiological factors that can result in severe structural and functional dysregulation. Fortunately, there are several potentially reversible CMs that are known to improve when the root etiological factor is addressed. In this article, we discuss several of these reversible CMs, including tachycardia-induced, peripartum, inflammatory, hyperthyroidism, Takotsubo, and chronic illness–induced CMs. Our discussion also includes a review on their respective pathophysiology, as well as possible management solutions. PMID:26052233

  19. 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.

  20. Structure-enhanced methods in the development of non-nucleoside inhibitors targeting HIV reverse transcriptase variants.

    PubMed

    Frey, Kathleen M

    2015-01-01

    Resistance continues to emerge as a leading cause for antiretroviral treatment failure. Several mutations in HIV reverse transcriptase (RT) confer resistance to non-nucleoside inhibitors (NNRTIs), vital components of antiretroviral combination therapies. Since the majority of mutations are located in the NNRTI binding pocket, crystal structures of RT variants in complex with NNRTIs have provided ideas for new drug design strategies. This article reviews the impact of RT crystal structures on the multidisciplinary design and development of new inhibitors with improved resistance profiles.

  1. Synthesis and characterization of α-NaYF{sub 4}: Yb, Er nanoparticles by reverse microemulsion method

    SciTech Connect

    Gunaseelan, M.; Senthilselvan, J.

    2016-05-06

    A simple and cost effective reverse microemulsion system was newly designed to synthesis NaYF{sub 4}:20%Yb,2%Er upconverting luminescent nanoparticles. XRD results confirms the cubic structure of NaYF{sub 4} nanophosphor in the as prepared condition without any other impurity phases. The as-prepared sample itself having highly crystalline nanoparticle with well dispersed uniform morphology is the advantage of this reverse microemulsion process. HRTEM images of as prepared and calcined samples revealed spherical nanoclusters morphology with size of ~210 nm and ~245 nm respectively. The characteristic absorption wavelength that occurs at 980 nm due to transition of energy levels {sup 2}F{sub 5/2} to {sup 2}F{sub 7/2} for Yb{sup 3+} rare earth ion in as prepared and calcined upconversion nanoparticle confirms the presence of Yb{sup 3+} by UV-Visible spectroscopy which can act as a sensitizer for photonic upconversion. Therefore the absorption at NIR region and emission spectrum at visible region suggests that NaYF{sub 4}:20%Yb,2%Er is suitable for upcoversion process, due to its optical property and chemical stability this material also be useful for bio imaging applications.

  2. Development of reverse transcription loop-mediated isothermal amplification assay as a simple detection method of Chrysanthemum stem necrosis virus in chrysanthemum and tomato.

    PubMed

    Suzuki, Ryoji; Fukuta, Shiro; Matsumoto, Yuho; Hasegawa, Toru; Kojima, Hiroko; Hotta, Makiko; Miyake, Noriyuki

    2016-10-01

    For a simple and rapid detection of Chrysanthemum stem necrosis virus (CSNV) from chrysanthemum and tomato, a reverse transcription loop-mediated isothermal amplification (RT-LAMP) assay was developed. A primer set designed to the genome sequences of CSNV worked most efficiently at 63°C and could detect CSNV RNA within 12min by fluorescence monitoring using an isothermal DNA amplification and fluorescence detection device. The result of a specificity test using seven other viruses and one viroid-infectable chrysanthemum or tomato showed that the assay could amplify CSNV specifically, and a sensitivity comparison showed that the RT-LAMP assay was as sensitive as the reverse transcriptase polymerase chain reaction. The RT-LAMP assay using crude RNA, extracted simply, could detect CSNV. Overall, the RT-LAMP assay was found to be a simple, specific, convenient, and time-saving method for CSNV detection.

  3. High-frequency Total Focusing Method (TFM) imaging in strongly attenuating materials with the decomposition of the time reversal operator associated with orthogonal coded excitations

    NASA Astrophysics Data System (ADS)

    Villaverde, Eduardo Lopez; Robert, Sébastien; Prada, Claire

    2017-02-01

    In the present work, the Total Focusing Method (TFM) is used to image defects in a High Density Polyethylene (HDPE) pipe. The viscoelastic attenuation of this material corrupts the images with a high electronic noise. In order to improve the image quality, the Decomposition of the Time Reversal Operator (DORT) filtering is combined with spatial Walsh-Hadamard coded transmissions before calculating the images. Experiments on a complex HDPE joint demonstrate that this method improves the signal-to-noise ratio by more than 40 dB in comparison with the conventional TFM.

  4. Optimization of the elution buffer and concentration method for detecting hepatitis E virus in swine liver using a nested reverse transcription-polymerase chain reaction and real-time reverse transcription-polymerase chain reaction.

    PubMed

    Son, Na Ry; Seo, Dong Joo; Lee, Min Hwa; Seo, Sheungwoo; Wang, Xiaoyu; Lee, Bog-Hieu; Lee, Jeong-Su; Joo, In-Sun; Hwang, In-Gyun; Choi, Changsun

    2014-09-01

    The aim of this study was to develop an optimal technique for detecting hepatitis E virus (HEV) in swine livers. Here, three elution buffers and two concentration methods were compared with respect to enhancing recovery of HEV from swine liver samples. Real-time reverse transcription-polymerase chain reaction (RT-PCR) and nested RT-PCR were performed to detect HEV RNA. When phosphate-buffered saline (PBS, pH 7.4) was used to concentrate HEV in swine liver samples using ultrafiltration, real-time RT-PCR detected HEV in 6 of the 26 samples. When threonine buffer was used to concentrate HEV using polyethylene glycol (PEG) precipitation and ultrafiltration, real-time RT-PCR detected HEV in 1 and 3 of the 26 samples, respectively. When glycine buffer was used to concentrate HEV using ultrafiltration and PEG precipitation, real-time RT-PCR detected HEV in 1 and 3 samples of the 26 samples, respectively. When nested RT-PCR was used to detect HEV, all samples tested negative regardless of the type of elution buffer or concentration method used. Therefore, the combination of real-time RT-PCR and ultrafiltration with PBS buffer was the most sensitive and reliable method for detecting HEV in swine livers. Copyright © 2014 Elsevier B.V. All rights reserved.

  5. Reversible Computing

    DTIC Science & Technology

    1980-02-01

    will have been introduced. 9. Reversible celular autemata We shall assume the reader to have some familiarity with the concept of cel- lular...10003 Mr. Kin B. Thcmpson 1 copy Technical Director Information Systems Divisia.i Naval Research Laboratory (OP-91T) Technical Information Division

  6. Reverse mortgages.

    PubMed

    Farnesi, D

    1995-09-01

    Elders and their families are often caught in a financial bind when it comes to paying for much-needed home care services. Reverse mortgages may offer a solution to elderly home care clients who own their homes but have a limited income with which to maintain their independence.

  7. REVERSE OSMOSIS,

    DTIC Science & Technology

    acetate membranes. Mechanisms of the process and porous cellulose acetate membrane technology are briefly reviewed. Based on a general capillary...The reverse osmosis process is discussed with particular reference to systems involving aqueous solutions and Loeb-Sourirajan-type porous cellulose

  8. Development and Validation of a Reversed-phase HPLC Method for Assay of the Decapeptide Cetrorelix Acetate in Bulk and Pharmaceutical Dosage Forms.

    PubMed

    Hooshfar, Shirin; Mortazavi, Seyed Alireza; Piryaei, Mohammad; Ramandi Darzi, Hossein; Shahsavari, Nahid; Kobarfard, Farzad

    2014-01-01

    A gradient reversed-phase high performance liquid chromatography (HPLC) method was developed for the assay of cetrorelix acetate, a synthetic decapeptide with gonadotropin-releasing hormone (GnRH) antagonistic activity used in infertility treatment. The HPLC method, which is used to determine cetrorelix in bulk and pharmaceutical dosage forms, was validated per ICH guidelines. The chromatographic separation was achieved on a C18 reversed-phase column using acetonitrile, water and trifluoroacetic acid (TFA) as mobile phase and wavelength was set at 275 nm. The calibration curve was linear (r2 = 0.999) over cetrorelix concentrations ranging from 62.50 to 12.50 μg/mL (n = 6). The limits of detection (LOD) and quantification (LOQ) were calculated from the peak-to-noise ratio as 15.6 and 62.5 μg/mL, respectively. The method had an accuracy of > 97% and intra- and inter-day RSD of < 0.3% and < 1.6%, respectively and was validated with excellent specificity, sensitivity, and stability. The validated method was successfully applied for determination of cetrorelix in bulk and pharmaceutical dosage forms.

  9. Development and Validation of a Reversed-phase HPLC Method for Assay of the Decapeptide Cetrorelix Acetate in Bulk and Pharmaceutical Dosage Forms

    PubMed Central

    Hooshfar, Shirin; Mortazavi, Seyed Alireza; Piryaei, Mohammad; Ramandi Darzi, Hossein; Shahsavari, Nahid; Kobarfard, Farzad

    2014-01-01

    A gradient reversed-phase high performance liquid chromatography (HPLC) method was developed for the assay of cetrorelix acetate, a synthetic decapeptide with gonadotropin-releasing hormone (GnRH) antagonistic activity used in infertility treatment. The HPLC method, which is used to determine cetrorelix in bulk and pharmaceutical dosage forms, was validated per ICH guidelines. The chromatographic separation was achieved on a C18 reversed-phase column using acetonitrile, water and trifluoroacetic acid (TFA) as mobile phase and wavelength was set at 275 nm. The calibration curve was linear (r2 = 0.999) over cetrorelix concentrations ranging from 62.50 to 12.50 μg/mL (n = 6). The limits of detection (LOD) and quantification (LOQ) were calculated from the peak-to-noise ratio as 15.6 and 62.5 μg/mL, respectively. The method had an accuracy of > 97% and intra- and inter-day RSD of < 0.3% and < 1.6%, respectively and was validated with excellent specificity, sensitivity, and stability. The validated method was successfully applied for determination of cetrorelix in bulk and pharmaceutical dosage forms. PMID:24711828

  10. Development and Validation of a Reversed-Phase HPLC Method for the Quantitative Determination of Ten Polyphenols Extracted from Apple Peel.

    PubMed

    Ran, Junjian; Sun, Huadi; Zhu, Mingming; Chen, Juan; Zhao, Ruixiang

    2016-01-01

    A method based on a reversed-phase HPLC method was established, optimized, and validated for the separation and quantitation of 10 polyphenols extracted from the peel of apple species. A bidentate reversed-phase C18 column was used as stationary phase, and an acidified water buffer and methanol were used as mobile phase. The polyphenols were well separated and detected using UV at 280 and 320 nm. Validation parameters, such as linearity, LOD, LOQ, accuracy, and precision, were acceptable for all 10 polyphenols. The proposed method has enough linearity with correlation coefficient >0.99 within the investigated range for all tested polyphenols. The LOD was 0.24 μg/mL for ellagic acid and <0.2 μg/mL for all other polyphenols. The LOQ was 9.39 × 10(-2) μg/mL for chlorogenic acid, and ellagic acid, 2.82 × 10(-2) μg/mL for caffeic acid and >0.1 μg/mL for all other polyphenols. Recovery was within the acceptable range from 98.38 to 100.39% for all polyphenols standards. Satisfactory precision was achieved for both intra- and interday assay, with RSD <2%. The method was successfully applied for simultaneous analysis of polyphenols from apple peel.

  11. A Reverse Engineering method for 3d parametric modeling of geometries based on processing of laser scanning data and a sweep technique

    NASA Astrophysics Data System (ADS)

    Varitis, E.

    2016-11-01

    A Reverse Engineering (RE) method for parametric modelling is presented in this paper. According to this method laser scanning data are processed by means of an algorithm and a parametric geometry is produced. The algorithm generates a spline used as a driving curve for a 2D profile, both approximated from the point cloud data, with the final geometry being produced through with a sweep based technique. The method was applied to digitize a commercial product, a bottle, and the geometry was reconstructed at high accuracy and surface quality. Finally the results of the proposed method were compared with auto surfacing from *.stl files and with surfaces generated by means of sweep commands without converting curves to splines.

  12. Densitometric HPTLC method for qualitative, quantitative analysis and stability study of Coenzyme Q10 in pharmaceutical formulations utilizing normal and reversed-phase silica gel plates.

    PubMed

    Abdel-Kader, Maged Saad; Alam, Prawez; Alqasoumi, Saleh Ibrahim

    2016-03-01

    Two simple, precise and stability-indicating densitometric HPTLC method were developed and validated for qualitative and quantitative analysis of Coenzyme Q10 in pharmaceutical formulations using normal-phase (Method I) and reversed phase (Method II) silica gel TLC plates. Both methods were developed and validated with 10×20 cm glass-backed plates coated with 0.2 mm layers of either silica gel 60 F254 (E-Merck, Germany) using hexane-ethyl acetate (8.5:1.5 v/v) as developing system (Method I) or RP-18 silica gel 60 F254 (E-Merck, Germany) using methanol-acetone (4:6 v/v) as mobile phase (Method II). Both analyses were scanned with a densitometer at 282 nm. Linearity was found in the ranges 50-800 ng/spot (r(2)=0.9989) and 50-800 ng/spot (r(2)=0.9987) for Method I and Method II respectively. Stability of Coenzyme Q10 was explored by the two methods using acid, base, hydrogen peroxide, temperature and different solvents. Due to the efficiency of the method in separating Coenzyme Q10 from other ingredients including its degradation products, it can be applied for quality control, standardization of different pharmaceutical formulations and stability study.

  13. Evaluation of the TRCRtest NV-W for norovirus detection in stools by the Transcription-Reverse Transcription Concerted method.

    PubMed

    Medici, Maria Cristina; Tummolo, Fabio; Albonetti, Valeria; Pinardi, Federica; Ferraglia, Francesca; Chezzi, Carlo; Arcangeletti, Maria Cristina; De Conto, Flora; Calderaro, Adriana

    2013-11-01

    A novel molecular assay, TRCRtest NV-W, based on a transcription-reverse transcription concerted reaction (TRC) for isothermal amplification and real-time detection of norovirus in stools was assessed and compared with an RT-nPCR. Archived stools positive for either different types or variants of norovirus genogroups I and II or other enteric viruses were used to assess the sensitivity and specificity of the novel assay. The TRC assay was 100% specific since it detected all the noroviruses tested and it did not display cross reactivity with other enteric viruses. When screening a collection of 387 stools with the TRC and RT-nPCR assays, the TRC displayed concordance, sensitivity, specificity, positive and negative predictive values of 96.6%, 81%, 99.7%, 98.1%, and 96.3%, respectively, after retesting the negative specimens. Additional PCRs and/or sequencing, used to understand inconsistent results between TRC and RT-nPCR, confirmed all positive results and did not reveal nucleotide variations in the TRC probe and primers binding sites. The TRC assay may be a rapid and ease of use tool for the detection of noroviruses in clinical virology laboratories even in the face of rapidly evolving noroviruses. Copyright © 2013 Elsevier B.V. All rights reserved.

  14. Detection of Single-Domain Co2FeAl Nanoparticles Using First-Order Reversal Curve Method

    NASA Astrophysics Data System (ADS)

    Alikhanzadeh-Arani, Sima; Almasi-Kashi, Mohammad; Pezeshki-Nejad, Zahra; Ramazani, Abdolali; Salavati-Niasari, Masoud

    2016-10-01

    Half-Heusler nanostructures of Co2FeAl alloys, synthesized via coprecipitation route, were found to contain both hard- and soft-phases magnetic grains, mapped using first-order reversal curves (FORCs) diagrams. The obtained results confirmed that these powders are highly interacting as a single-domain magnetizing system. A significant dependence of the morphology and particle size on the annealing rate was represented by scanning electron microscopy (SEM), transmission electron microscopy (TEM), and high-resolution TEM images. The presence of the strong magnetizing interaction between the nanoparticles led to the formation of chain-like structure stabilized by PVP polymer. By increasing the annealing rate from 278.15 K/min to 288.15 K/min (5 °C/min to 15 °C/min), the grain shape changed from long nanochain to nonuniform agglomerated grains. Additionally, the magnetic characteristics of the prepared alloys were found to be affected by tuning the annealing rate.

  15. 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.

  16. Column reversed-phase high-performance liquid chromatographic method for simultaneous determination of rabeprazole sodium and domperidone in combined tablet dosage form.

    PubMed

    Sabnis, Shweta Sadanand; Dnvandev, Dhavale Nilesh; Jadhav, Vijay Yeshawantrao; Gandhi, Santosh Vilashchand

    2008-01-01

    A new, simple column reversed-phase high-performance liquid chromatographic (HPLC) method for simultaneous determination of rabeprazole sodium (RAB) and domperidone (DOM) in a combined tablet dosage form has been developed and validated. Determination was performed using a Jasco HPLC system with a HiQ SiL octadecylsilane (C18) column (250 x 4.6 mm id), acetonitrile-0.1 M ammonium acetate (50 + 50, v/v) mobile phase, and paracetamol as an internal standard. The detection was performed using a UV detector set at 280 nm. The method was validated with respect to linearity, accuracy, precision, and robustness. Beer's law was obeyed in the concentration range of 1.0-10.0 and 0.5-5.0 microg/mL for RAB and DOM, respectively. The method has been successfully applied for the analysis of drugs in a pharmaceutical formulation.

  17. Sensitive and rapid reversed-phase liquid chromatography-fluorescence method for determining bisphenol A diglycidyl ether in aqueous-based food simulants.

    PubMed

    Paseiro Losada, P; López Mahía, P; Vázquez Odériz, L; Simal Lozano, J; Simal Gándara, J

    1991-01-01

    A method has been developed for determination of bisphenol A diglycidyl ether (BADGE) in 3 aqueous-based food simulants: water, 15% (v/v) ethanol, and 3% (w/v) acetic acid. BADGE is extracted with C18 cartridges and the extract is concentrated under a stream of nitrogen. BADGE is quantitated by reversed-phase liquid chromatography with fluorescence detection. Relative precision at 200 micrograms/L was 3.4%, the detection limit of the method was 0.1 micrograms/L, and recoveries of spiking concentrations from 1 to 8 micrograms/L were nearly 100%. Relative standard deviations for the method ranged from 3.5 to 5.9%, depending on the identity of the spiked aqueous-based food simulant.

  18. Development and validation of a reversed-phase liquid chromatographic method for analysis of estradiol valerate and medroxyprogesterone acetate in a tablet formulation.

    PubMed

    Segall, A; Hormaechea, F; Vitale, M; Perez, V; Pizzorno, M T

    1999-04-01

    A simple and accurate liquid chromatographic method was developed for estimation of estradiol valerate and medroxyprogesterone acetate in pharmaceuticals. Drugs were chromatographed on a reverse phase C18 column, using a mixture (30:70) of ammonium nitrate buffer and acetonitrile and eluants monitored at a wavelength of 280 nm. Solution concentrations were measured on a weight basis to avoid the use of an internal standard. The method was statistically validated for its linearity, accuracy, precision and selectivity. Due to its simplicity and accuracy, the authors believe that the method may be used for routine quality control analysis. It does not require any specific sample preparation except the use of a column guard before the analytical column and suitable prefilter attached to the syringe prior to injection.

  19. [A case of atypical type of Sturge-Weber syndrome demonstrated reversible change by MRI FLAIR method in ictus and in postictal state].

    PubMed

    Sasaki, M; Igarashi, K; Suzuki, S; Saito, K

    1999-07-01

    We report a patient of atypical type of Sturge-Weber syndrome who demonstrated a reversible change by MRI FLAIR method in ictus and postictal state. A 5-year-old boy was admitted to our hospital because of severe headache, vomiting and loss of consciousness with his eyes conjugated to left for a few minutes. He had no facial nevus and other abnormal findings in physical examination. CT scan showed two small calcifications in the right occipital lobe. Postcontrast T 1-weighted image of MRI demonstrated a right parieto-occipital leptomeningeal enhancement. We diagnosed this case as an atypical type of Sturge-Weber syndrome. Although, on admission, FLAIR method showed the area of high signal intensity, after anticonvulsant therapy, those abnormal area disappeared. It is presumably detected by FLAIR method slight extravasation of plasma element in the surface of the brain due to regional hyperperfusion in ictus.

  20. Stability-indicating reversed-phase HPLC method development and characterization of impurities in vortioxetine utilizing LC-MS, IR and NMR.

    PubMed

    Liu, Lei; Cao, Na; Ma, Xingling; Xiong, Kaihe; Sun, Lili; Zou, Qiaogen; Yao, Lili

    2016-01-05

    The current study reports the development and validation of a stability-indicating reversed phase HPLC method for the separation and identification of potential impurities in vortioxetine, a recently developed antidepressant. The structures of a new compound and four process-related impurities formed during the synthesis were characterized and confirmed by NMR, MS, and IR spectroscopy analyses. The most probable formation mechanisms of the impurities identified were proposed. Based on the characterization data, the new compound was proposed to be 1-[4-[(2,4-dimethylphenyl)thio]phenyl]-piperazine. In addition, an efficient chromatographic method was optimized to separate and quantify the impurities, which were obtained in the 0.05-0.75 μg/mL range. The developed HPLC method was validated with respect to accuracy, precision, linearity, robustness, and limits of detection and quantitation.

  1. Test Method for the Fatigue Life of Layered TiB/Ti Functionally Graded Beams Subjected to Fully Reversed Bending

    NASA Astrophysics Data System (ADS)

    Byrd, Larry; Rickerd, Greg; Wyen, Travis; Cooley, Glenn; Quast, Jeff

    2008-02-01

    Sonic fatigue of aircraft is characterized by fully reversed bending of components subjected to acoustic excitation. This problem is compounded in high temperature environments because solutions for acoustics which tend to result in stiff structures make thermal problems worse. Conversely solutions to the thermal problem which allow expansion often fail in the presence of high acoustic levels. Errors in fatigue life prediction in the combined environment often range from a factor of 4 to 10. This results in either heavy, overly stiff structure or premature failure. This work will test the hypothesis that the fatigue life of a layered functionally graded material (FGM) will be dominated by the failure of the stiffest outer layer. This is based on the observation that for isotropic materials the life is approximately 90% crack initiation and only 10% crack growth before failure. Four sets of cantilever specimens will be tested using an electro-mechanical shaker for base excitation. The excitation will be narrow band random around the fundamental frequency. Two sets of specimens are of uniform composition consisting of 85%TiB/Ti and two are graded specimens consisting of layers that vary from commercially pure titanium to 85%TiB/Ti. Strain vs number of cycles to failure curves will be generated with both constant amplitude sine and narrow band random around the fundamental frequency excitation. The results will be examined to compare life of the uniform material to the functionally graded material. Also to be studied will be the use of Miner's rule to predict the fatigue life of the randomly excited specimens.

  2. Measurement of hold-up volumes in reverse-phase liquid chromatography Definition and comparison between static and dynamic methods.

    PubMed

    Gritti, Fabrice; Kazakevich, Yuri; Guiochon, Georges

    2007-08-17

    The hold-up volumes, V(M) of two series of RPLC adsorbents were measured using three different approaches. The first method is based on the difference between the volumes of the empty column tube (150x4.6mm) and of the material packed inside the column. It is considered as giving the correct value of V(M). This method combines the results of the BET characterization of the adsorbent before packing (giving the specific pore volume), of carbon element analysis (giving the mass fraction of silica and alkyl bonded chains), of Helium pycnometry (providing silica density), and of inverse size exclusion chromatography (ISEC) performed on the packed column (yielding the interparticle volume). The second method is static pycnometry, which consists in weighing the masses of the chromatographic column filled with two distinct solvents of different densities. The last method is based on the thermodynamic definition of the hold-up volume and uses the dynamic minor disturbance method (MDM) with binary eluents. The experimental results of these three non-destructive methods are compared. They exhibit significant, systematic differences. Pycnometry underestimates V(M) by a few percent for adsorbents having a high carbon content. The results of the MDM method depend strongly on the choice of the binary solution used and may underestimate or overestimate V(M). The hold-up volume V(M) of the RPLC adsorbents tested is best measured by the MDM method using a mixture of ethanol and water.

  3. Development and validation of reversed phase high performance liquid chromatography method for determination of dexpanthenol in pharmaceutical formulations.

    PubMed

    Kulikov, A U; Zinchenko, A A

    2007-02-19

    This paper describes the validation of an isocratic HPLC method for the assay of dexpanthenol in aerosol and gel. The method employs the Vydac Proteins C4 column with a mobile phase of aqueous solution of trifluoroacetic acid and UV detection at 206 nm. A linear response (r>0.9999) was observed in the range of 13.0-130 microg mL(-1). The method shows good recoveries and intra and inter-day relative standard deviations were less than 1.0%. Validation parameters as specificity, accuracy and robustness were also determined. The method can be used for dexpanthenol assay of panthenol aerosol and gel with dexpanthenol as the method separates dexpanthenol from aerosol or gel excipients.

  4. Reversed-phase HPLC/FD method for the quantitative analysis of the neurotoxin BMAA (β-N-methylamino-L-alanine) in cyanobacteria.

    PubMed

    Cianca, R C Cervantes; Baptista, M S; Silva, Luís Pinto da; Lopes, V R; Vasconcelos, V M

    2012-03-01

    A method has been developed and optimized in order to detect and quantify the non-protein amino acid β-N-methylamino-L-alanine(BMAA) in cyanobacteria. The novelty of the method is that we have used methanol instead of acetonitrile as the eluent. The method includes extraction with 0.1 M trichloroacetic acid (free BMAA) or protein hydrolysis with 6 M hydrochloric acid (total BMAA), derivatization with AQC (6-aminoquinolyl-N-hydroxysuccinimidyl carbamate) and reversed-phase high-performance liquid chromatography analysis with fluorescence detection (HPLC/FD). Detection limits ranged from 0.35 to 0.75 pg injected, while quantification limits ranged from 1.10 to 2.55 pg injected for total and free BMAA hydrolysis, respectively. The linear response range was up to 850 pmol in both methods, embracing three orders of magnitude. The method was successfully applied to a lyophilized estuarine species of Nostoc (LEGE 06077). All previous published methods for BMAA quantification, using HPLC/FD, have reported the usage of acetonitrile. This is the first report using methanol as the mobile phase. Although the elution strength differs with both solvents, the final method proved efficient for the quantification of BMAA in this complex sample. The method resulted effective, low-priced, and simple, being suitable for routine monitoring of BMAA in cyanobacteria.

  5. A rapid hydrolysis method and DABS-Cl derivatization for complete amino acid analysis of octreotide acetate by reversed phase HPLC.

    PubMed

    Akhlaghi, Yousef; Ghaffari, Solmaz; Attar, Hossein; Alamir Hoor, Amir

    2015-11-01

    Octreotide as a synthetic cyclic octapeptide is a somatostatin analog with longer half-life and more selectivity for inhibition of the growth hormone. The acetate salt of octreotide is currently used for medical treatment of somatostatin-related disorders such as endocrine and carcinoid tumors, acromegaly, and gigantism. Octreotide contains both cysteine and tryptophan residues which make the hydrolysis part of its amino acid analysis procedure very challenging. The current paper introduces a fast and additive-free method which preserves tryptophan and cysteine residues during the hydrolysis. Using only 6 M HCl, this hydrolysis process is completed in 30 min at 150 °C. This fast hydrolysis method followed by pre-column derivatization of the released amino acids with 4-N,N-dimethylaminoazobenzene-4'-sulfonyl chloride (DABS-Cl) which takes only 20 min, makes it possible to do the complete amino acid analysis of an octreotide sample in a few hours. The highly stable-colored DABS-Cl derivatives can be detected in 436 nm in a reversed phase chromatographic system, which eliminates spectral interferences to a great extent. The amino acid analysis of octreotide acetate including hydrolysis, derivatization, and reversed phase HPLC determination was validated according to International Conference of Harmonization (ICH) guidelines.

  6. Development of a reversed-phase high-performance liquid chromatographic method for analyzing furanocoumarin components in citrus fruit juices and Chinese herbal medicines.

    PubMed

    Lin, Ying-Ku; Sheu, Ming-Thau; Huang, Chia-Hui; Ho, Hsiu-O

    2009-03-01

    A rapid and sensitive reversed-phase high performance liquid chromatographic method for the quantitation of five furanocoumarins (bergaptol, psoralen, bergapten, 6',7'-dihydroxybergamottin, and bergamottin) is developed and validated. HPLC analysis of these five furanocoumarins is performed on a reversed-phase Inertsil ODS-2 column with a particle size of 5 microm. Using only water and acetonitrile as solvents, good separation, good precision, and high accuracy are obtained for the analysis of furanocoumarin components. This method is validated and applied to analyze the composition of five furanocoumarins in four citrus fruit juices (grapefruit, pomelo I, pomelo II, and shaddock) and ten Chinese herbal medicines (Bai-Zhi, Qiang-Huo, Du-Huo, Fang-Feng, Dang-Gui, Huang-Qin, Gan-Cao, Chen-Pi, Ge-Gen, and Yin-Chen-Hao) prepared by water decoction or an alcohol infusion. Results show that four of the five furanocoumarins (but not bergapten) are detected in grapefruit, pomelo I, and pomelo II, and the highest amount of these components is found in grapefruit juice. In the ten Chinese herbal medicines, the five furanocoumarins are not detected in Ge-Gen or Yin-Chen-Hao. The remaining herbs contain various compositions and amounts of furanocoumarins. In general, Chinese herbal medicines prepared by the 40% ethanol infusion contain larger amounts of furanocoumarins than those prepared by hot water decoction.

  7. Application of a reverse dot blot DNA-DNA hydridization method to quantify host-feeding tendencies of two sibling species in the Anopheles gambiae complex.

    PubMed

    Fritz, M L; Miller, J R; Bayoh, M N; Vulule, J M; Landgraf, J R; Walker, E D

    2013-12-01

    A DNA-DNA hybridization method, reverse dot blot analysis (RDBA), was used to identify Anopheles gambiae s.s. and Anopheles arabiensis (Diptera: Culicidae) hosts. Of 299 blood-fed and semi-gravid An. gambiae s.l. collected from Kisian, Kenya, 244 individuals were identifiable to species; of these, 69.5% were An. arabiensis and 29.5% were An. gambiae s.s. Host identifications with RDBA were comparable with those of conventional polymerase chain reaction (PCR) followed by direct sequencing of amplicons of the vertebrate mitochondrial cytochrome b gene. Of the 174 amplicon-producing samples used to compare these two methods, 147 were identifiable by direct sequencing and 139 of these were identifiable by RDBA. Anopheles arabiensis bloodmeals were mostly (94.6%) bovine in origin, whereas An. gambiae s.s. fed upon humans more than 91.8% of the time. Tests by RDBA detected that two of 112 An. arabiensis contained blood from more than one host species, whereas PCR and direct sequencing did not. Recent use of insecticide-treated bednets in Kisian is likely to have caused the shift in the dominant vector species from An. gambiae s.s. to An. arabiensis. Reverse dot blot analysis provides an opportunity to study changes in host-feeding by members of the An. gambiae complex in response to the broadening distribution of vector control measures targeting host-selection behaviours. © 2013 The Royal Entomological Society.

  8. Reversed-phase vortex-assisted liquid-liquid microextraction: a new sample preparation method for the determination of amygdalin in oil and kernel samples.

    PubMed

    Hosseini, Mohammad; Heydari, Rouhollah; Alimoradi, Mohammad

    2015-02-01

    A novel, simple, and rapid reversed-phase vortex-assisted liquid-liquid microextraction coupled with high-performance liquid chromatography has been introduced for the extraction, clean-up, and preconcentration of amygdalin in oil and kernel samples. In this technique, deionized water was used as the extracting solvent. Unlike the reversed-phase dispersive liquid-liquid microextraction, dispersive solvent was eliminated in the proposed method. Various parameters that affected the extraction efficiency, such as extracting solvent volume and its pH, vortex, and centrifuging times were evaluated and optimized. The calibration curve shows good linearity (r(2) = 0.9955) and precision (RSD < 5.2%) in the range of 0.07-20 μg/mL. The limit of detection and limit of quantitation were 0.02 and 0.07 μg/mL, respectively. The recoveries were in the range of 96.0-102.0% with relative standard deviation values ranging from 4.0 to 5.1%. Unlike the conventional extraction methods for plant extracts, no evaporative and re-solubilizing operations were needed in the proposed technique.

  9. Fast and sensitive method to determine parabens by capillary electrophoresis using automatic reverse electrode polarity stacking mode: application to hair samples.

    PubMed

    Sako, Alysson V F; Dolzan, Maressa D; Micke, Gustavo Amadeu

    2015-09-01

    This paper describes a fast and sensitive method for the determination of methyl, ethyl, propyl, and butylparaben in hair samples by capillary electrophoresis using automatic reverse electrode polarity stacking mode. In the proposed method, solutions are injected using the flush command of the analysis software (940 mbar) and the polarity switching is carried out automatically immediately after the sample injection. The advantages compared with conventional stacking methods are the increased analytical frequency, repeatability, and inter-day precision. All analyses were performed in a fused silica capillary (50 cm, 41.5 cm in effective length, 50 μm i.d.), and the background electrolyte was composed of 20 mmol L(-1) sodium tetraborate in 10 % of methanol, pH 9.3. For the reverse polarity, -25 kV/35 s was applied followed by application of +30 kV for the electrophoretic run. Temperature was set at 20 °C, and all analytes were monitored at 297 nm. The method showed acceptable linearity (r (2) > 0.997) in the studied range of 0.1-5.0 mg L(-1), limits of detection below 0.017 mg L(-1), and inter-day, intra-day, and instrumental precision better than 6.2, 3.6, and 4.6 %, respectively. Considering parabens is widely used as a preservative in many products and the reported possibility of damage to the hair and also to human health caused by these compounds, the proposed method was applied to evaluate the adsorption of parabens in hair samples. The results indicate that there is a greater adsorption of methylparaben compared to the other parabens tested and also dyed hairs had a greater adsorption capacity for parabens than natural hairs.

  10. Method and tool to reverse the charges in anti-reflection films used for solar cell applications

    DOEpatents

    Sharma, Vivek; Tracy, Clarence

    2017-01-31

    A method is provided for making a solar cell. The method includes providing a stack including a substrate, a barrier layer disposed on the substrate, and an anti-reflective layer disposed on the barrier layer, where the anti-reflective layer has charge centers. The method also includes generating a corona with a charging tool and contacting the anti-reflective layer with the corona thereby injecting charge into at least some of the charge centers in the anti-reflective layer. Ultra-violet illumination and temperature-based annealing may be used to modify the charge of the anti-reflective layer.

  11. Development and evaluation of a culture-independent method for source determination of fecal wastes in surface and storm waters using reverse transcriptase-PCR detection of FRNA coliphage genogroup gene sequences.

    EPA Science Inventory

    A complete method, incorporating recently improved reverse transcriptase-PCR primer/probe assays and including controls for determining interferences to phage recoveries from water sample concentrates and for detecting interferences to their analysis, was developed for the direct...

  12. Development and evaluation of a culture-independent method for source determination of fecal wastes in surface and storm waters using reverse transcriptase-PCR detection of FRNA coliphage genogroup gene sequences

    EPA Science Inventory

    A complete method, incorporating recently improved reverse transcriptase-PCR primer/probe assays and including controls for determining interferences to phage recoveries from water sample concentrates and for detecting interferences to their analysis, was developed for the direct...

  13. Development and evaluation of a culture-independent method for source determination of fecal wastes in surface and storm waters using reverse transcriptase-PCR detection of FRNA coliphage genogroup gene sequences.

    EPA Science Inventory

    A complete method, incorporating recently improved reverse transcriptase-PCR primer/probe assays and including controls for determining interferences to phage recoveries from water sample concentrates and for detecting interferences to their analysis, was developed for the direct...

  14. Development and evaluation of a culture-independent method for source determination of fecal wastes in surface and storm waters using reverse transcriptase-PCR detection of FRNA coliphage genogroup gene sequences

    EPA Science Inventory

    A complete method, incorporating recently improved reverse transcriptase-PCR primer/probe assays and including controls for determining interferences to phage recoveries from water sample concentrates and for detecting interferences to their analysis, was developed for the direct...

  15. Revolving Loan Fund: A Novel Approach to Increasing Access to Long-Acting Reversible Contraception Methods in Community Health Centers.

    PubMed

    Evans, Megan L; Breeze, Janis L; Paulus, Jessica K; Meadows, Audra

    2017-06-16

    The aim of this study was to assess the impact of a revolving loan fund (RLF) on timing of device insertion and long-acting reversible contraception (LARC) access among a high-risk urban population at 3 Boston community health centers. Three health centers were identified to implement a RLF. Each clinic received $5000 from the RLF to purchase LARC devices. Data collected through medical record review retrospectively 1 year prior to start of the RLF and prospectively for 1 year thereafter included patient demographics, type of LARC selected, patient's date of documented interest in a LARC device, and date of insertion. The effect of a RLF on delay to LARC insertion was tested using negative binomial regression, controlling for site and potential confounding variables between the pre- and post-RLF periods. Three urban community health centers. Reproductive-aged women who received family planning services at the 3 participating health centers. Increasing access to LARC and decreasing wait times to LARC insertion after implementation of the RLF. Data on 133 patients in the pre-RLF group and 205 in the post-RLF group were collected. There were no statistically significant differences in demographic or clinical characteristics between the 2 time periods. LARC uptake increased significantly from the pre- to post-RLF period, specifically among implant users. There was a statistically significant decrease in the mean number of days in delay from interest to insertion from the pre- to post-RLF period (pre-RLF: 31.3 ± 50.6 days; post-RLF: 13.6 ± 16.7 days, adjusted P < .001). The reasons for the delay did not differ significantly between the 2 time periods. The RLF decreased wait time for the devices and increased overall insertion rates. This may serve as a promising solution to improve LARC access in community health centers. This project could be expanded to include more health centers, creating a city wide RLF. This expansion could allow for further data analysis

  16. A method for the rapid discovery of naturally occurring products by proteins immobilized on magnetic beads and reverse affinity chromatography.

    PubMed

    Arai, Midori A; Kobatake, Eiji; Koyano, Takashi; Kowithayakorn, Thaworn; Kato, Shigeaki; Ishibashi, Masami

    2009-12-01

    A highly efficient screening method for naturally occurring products that bind to a specific target protein was demonstrated by using hVDR magnetic beads. The native ligand 1alpha,25(OH)2 VD3 (1) was selectively bound by hVDR magnetic beads when present in a mixture of natural compounds. Furthermore, this method was shown to be applicable to the identification of natural products that interact with a specific protein immobilized on the beads from an extract of a natural resource. Two new natural compounds were isolated by this method. This approach will be helpful for the discovery of novel, naturally occurring products that bind to specific target proteins. This method has the further advantages that it can identify the HPLC peak corresponding to the target compound for isolation, as well as provide important UV, CD, or MS profile information.

  17. Content determination of the flavonoids in the different parts and different species of Abelmoschus esculentus L. by reversed phase-high performance liquid chromatograph and colorimetric method

    PubMed Central

    Lin, Yin; Lu, Min-feng; Liao, Hai-bing; Li, Yu-xian; Han, Wei; Yuan, Ke

    2014-01-01

    Background: This research will establish the ultraviolet colorimetric method to determine the total flavonoid content in different species and different parts of Abelmoschus esculentus L. Materials and Methods: We establish the reversed-phase high-performance liquid chromatograph (RP-HPLC) method to determine the content of the three flavonoid glycosides in different species and different parts of the A. esculentus. Adopt the NaNO2-Al (NO3)3-NaOH colorimetric method to determine the total flavonoid content; at the same time, adopt the RP-HPLC method to determine the contents of the three flavonoid glycosides. Using the methods of ultraviolet colorimetry and RP-HPLC, we determined and analyzed the total flavonoid content and the content of the three flavonoid glycosides in different species and different parts of A. esculentus. Results: There are great distribution differences of the total flavonoids and the three flavonoid glycosides in different species and parts of A. esculentus. Among them, the content of the effective constituents in the flower is relatively high, next is in the fruit. In the different species of A. esculentus, the content of the flavonoids of finger relatively high. The HPLC method established in this research is simple and convenient and its results are accurate and reliable. In addition, it has a very good repeatability. Conclusion: The results provided the reference data for the medicinal use of A. esculentus and it can be used in quality analyzing of its effective constituents. PMID:25210315

  18. Validation and application of a new reversed phase HPLC method for in vitro dissolution studies of rabeprazole sodium in delayed-release tablets.

    PubMed

    Nawaz, Md Saddam

    2013-01-01

    The purpose of this study was to develop and validate a new reversed phase high performance liquid chromatographic (RP-HPLC) method to quantify in vitro dissolution assay of rabeprazole sodium in pharmaceutical tablet dosage form. Method development was performed on C 18, 100 × 4.6 mm ID, and 10  μ m particle size column, and injection volume was 20  μ L using a diode array detector (DAD) to monitor the detection at 280 nm. The mobile phase consisted of buffer: acetonitrile at a ratio of 60 : 40 (v/v), and the flow rate was maintained at 1.0 mL/min. The method was validated in terms of suitability, linearity, specificity, accuracy, precision, stability, and sensitivity. Linearity was observed over the range of concentration 0.05-12.0  μ g/mL, and the correlation coefficient was found excellent >0.999. The method was specific with respect to rabeprazole sodium, and the peak purity was found 99.99%. The method was precise and had relative standard deviations (RSD) less than 2%. Accuracy was found in the range of 99.9 to 101.9%. The method was robust in different variable conditions and reproducible. This proposed fast, reliable, cost-effective method can be used as quality control tool for the estimation of rabeprazole sodium in routine dissolution test analysis.

  19. Validation and Application of a New Reversed Phase HPLC Method for In Vitro Dissolution Studies of Rabeprazole Sodium in Delayed-Release Tablets

    PubMed Central

    Nawaz, Md. Saddam

    2013-01-01

    The purpose of this study was to develop and validate a new reversed phase high performance liquid chromatographic (RP-HPLC) method to quantify in vitro dissolution assay of rabeprazole sodium in pharmaceutical tablet dosage form. Method development was performed on C 18, 100 × 4.6 mm ID, and 10 μm particle size column, and injection volume was 20 μL using a diode array detector (DAD) to monitor the detection at 280 nm. The mobile phase consisted of buffer: acetonitrile at a ratio of 60 : 40 (v/v), and the flow rate was maintained at 1.0 mL/min. The method was validated in terms of suitability, linearity, specificity, accuracy, precision, stability, and sensitivity. Linearity was observed over the range of concentration 0.05–12.0 μg/mL, and the correlation coefficient was found excellent >0.999. The method was specific with respect to rabeprazole sodium, and the peak purity was found 99.99%. The method was precise and had relative standard deviations (RSD) less than 2%. Accuracy was found in the range of 99.9 to 101.9%. The method was robust in different variable conditions and reproducible. This proposed fast, reliable, cost-effective method can be used as quality control tool for the estimation of rabeprazole sodium in routine dissolution test analysis. PMID:24062966

  20. Rapid method for the preparation of 125I-labelled human growth hormone for receptor studies, using reverse-phase high performance liquid chromatography

    SciTech Connect

    Ilondo, M.M.; Dehart, I.; De Meyts, P.

    1986-01-29

    Human growth hormone was labelled with 125 Iodine by the stoichiometric modification of the chloramine-T method to a specific activity of 50-80 microCi/microgram, and the iodinated mixture was purified by reverse-phase high performance liquid chromatography using a C18 column (SynChropak RP-P) and a linear gradient. Compared with the usual Sephadex G-100 chromatography, HPLC gave a much better separation, with a higher yield and a considerably reduced analysis time (30 min vs 5 h). The (125I)-labelled preparation had normal binding to IM-9 lymphocyte receptors. The maximum bindability of the HPLC-purified preparation approximated 90%, which is the best value so far reported for human growth hormone. It is concluded that HPLC is a fast, convenient and reproducible method for obtaining an improved (125I)-labelled human growth hormone for receptor studies.

  1. A rapid monitoring method for inorganic arsenic in rice flour using reversed phase-high performance liquid chromatography-inductively coupled plasma mass spectrometry.

    PubMed

    Narukawa, Tomohiro; Chiba, Koichi; Sinaviwat, Savarin; Feldmann, Jörg

    2017-01-06

    A new rapid monitoring method by means of high performance liquid chromatography-inductively coupled plasma mass spectrometry (HPLC-ICP-MS) following the heat-assisted extraction was developed for measurement of total inorganic arsenic species in rice flour. As(III) and As(V) eluted at the same retention time and completely separated from organoarsenic species by an isocratic elution program on a reversed phase column. Therefore, neither ambiguous oxidation of arsenite to arsenate nor the integration of two peaks were necessary to determine directly the target analyte inorganic arsenic. Rapid injection allowed measuring 3 replicates within 6min and this combined with a quantitative extraction of all arsenic species from rice flour by a 15min HNO3-H2O2 extraction makes this the fastest laboratory based method for inorganic arsenic in rice flour. Copyright © 2016 Elsevier B.V. All rights reserved.

  2. Development of LC chiral methods for neutral pharmaceutical related compounds using reversed phase and normal phase liquid chromatography with different types of polysaccharide stationary phases.

    PubMed

    Zhou, Lili; Welch, Chris; Lee, Clair; Gong, Xiaoyi; Antonucci, Vincent; Ge, Zhihong

    2009-05-01

    The enantioselectivity of a collection of neutral pharmaceutical compounds on six different types of polysaccharide chiral stationary phases (CSPs), Chiralpak AD (and AD-RH), Chiralcel OD (and OD-RH), Chiralpak OJ (and OJ-R), Chiralcel AS (and AS-RH), Sepapak-2 and Sepapak-4 are compared using reversed phase (RPLC) and normal phase liquid chromatography (NPLC). Screening strategies for maximizing the probability of achieving an initial chiral separation hit for neutral compounds using both RPLC and NPLC are described. Further method optimizations are demonstrated by modifying parameters such as organic modifier composition, eluent pH or CSP particle size. Several practical examples of the application of chiral methods for the study of synthetic reaction mixtures are presented. The most critical validation aspects, including limit of detection, specificity, and ruggedness, are also briefly presented.

  3. A New General Method for Simultaneous Fitting of Temperature- and Concentration-Dependence of Reaction Rates Yields Kinetic and Thermodynamic Parameters for HIV Reverse Transcriptase Specificity.

    PubMed

    Li, An; Ziehr, Jessica L; Johnson, Kenneth A

    2017-03-02

    Recent studies have demonstrated the dominant role of induced-fit in enzyme specificity of HIV reverse transcriptase and many other enzymes. However, relevant thermodynamic parameters are lacking and equilibrium thermodynamic methods are of no avail because the key parameters can only determined by kinetic measurement. By modifying KinTek Explorer software, we present a new general method for globally fitting data collected over a range of substrate concentrations and temperatures and apply it to HIV reverse transcriptase. Fluorescence stopped-flow methods were used to record the kinetics of enzyme conformational changes that monitor nucleotide binding and incorporation. The nucleotide concentration dependence was measured at temperatures ranging from 5 to 37C and the raw data were fit globally to derive a single set of rate constants at 37C and a set of activation enthalpy terms to account for the kinetics at all other temperatures. This comprehensive analysis afforded thermodynamic parameters for nucleotide binding (Kd, ΔG, ΔH, ΔS at 37C), and kinetic parameters for enzyme conformational changes and chemistry (rate constants and activation enthalpy). Comparisons between wild-type enzyme and a mutant resistant to nucleoside analogs used to treat HIV infections reveal that the ground state binding is weaker and the activation enthalpy for the conformational change step is significantly larger for the mutant. Further studies to explore the structural underpinnings of the observed thermodynamics and kinetics of the conformational change step may help to design better analogs to treat HIV infections and other diseases. Our new method is generally applicable to enzyme and chemical kinetics.

  4. A reverse-phase liquid chromatography/mass spectrometry method for the analysis of high-molecular-weight fructooligosaccharides.

    PubMed

    Harrison, Scott J; Fraser, Karl; Lane, Geoffrey A; Villas-Boas, Silas; Rasmussen, Susanne

    2009-12-01

    Many important crop and forage plants accumulate polymeric water-soluble carbohydrates as fructooligosaccharides (or fructans). We have developed an improved method for the analysis of the full fructan complement in plant extracts based on porous graphitized carbon chromatography coupled to negative electrospray ionization mass spectrometry. By the use of profile data collection and multiple charge state ions, the effective mass range of the ion trap was extended to allow for the analysis of very high-molecular-weight oligosaccharides. This method allows the separation and quantification of isomeric fructan oligomers ranging from degree of polymerization (DP) 3 to DP 49.

  5. Rapid Development and Validation of Improved Reversed-Phase High-performance Liquid Chromatography Method for the Quantification of Mangiferin, a Polyphenol Xanthone Glycoside in Mangifera indica.

    PubMed

    Naveen, P; Lingaraju, H B; Prasad, K Shyam

    2017-01-01

    Mangiferin, a polyphenolic xanthone glycoside from Mangifera indica, is used as traditional medicine for the treatment of numerous diseases. The present study was aimed to develop and validate a reversed-phase high-performance liquid chromatography (RP-HPLC) method for the quantification of mangiferin from the bark extract of M. indica. RP-HPLC analysis was performed by isocratic elution with a low-pressure gradient using 0.1% formic acid: acetonitrile (87:13) as a mobile phase with a flow rate of 1.5 ml/min. The separation was done at 26°C using a Kinetex XB-C18 column as stationary phase and the detection wavelength at 256 nm. The proposed method was validated for linearity, precision, accuracy, limit of detection, limit of quantification, and robustness by the International Conference on Harmonisation guidelines. In linearity, the excellent correlation coefficient more than 0.999 indicated good fitting of the curve and also good linearity. The intra- and inter-day precision showed < 1% of relative standard deviation of peak area indicated high reliability and reproducibility of the method. The recovery values at three different levels (50%, 100%, and 150%) of spiked samples were found to be 100.47, 100.89, and 100.99, respectively, and low standard deviation value < 1% shows high accuracy of the method. In robustness, the results remain unaffected by small variation in the analytical parameters, which shows the robustness of the method. Liquid chromatography-mass spectrometry analysis confirmed the presence of mangiferin with M/Z value of 421. The assay developed by HPLC method is a simple, rapid, and reliable for the determination of mangiferin from M. indica. The present study was intended to develop and validate an RP-HPLC method for the quantification of mangiferin from the bark extract of M. indica. The developed method was validated for linearity, precision, accuracy, limit of detection, limit of quantification and robustness by International Conference

  6. Rapid Development and Validation of Improved Reversed-Phase High-performance Liquid Chromatography Method for the Quantification of Mangiferin, a Polyphenol Xanthone Glycoside in Mangifera indica

    PubMed Central

    Naveen, P.; Lingaraju, H. B.; Prasad, K. Shyam

    2017-01-01

    Mangiferin, a polyphenolic xanthone glycoside from Mangifera indica, is used as traditional medicine for the treatment of numerous diseases. The present study was aimed to develop and validate a reversed-phase high-performance liquid chromatography (RP-HPLC) method for the quantification of mangiferin from the bark extract of M. indica. RP-HPLC analysis was performed by isocratic elution with a low-pressure gradient using 0.1% formic acid: acetonitrile (87:13) as a mobile phase with a flow rate of 1.5 ml/min. The separation was done at 26°C using a Kinetex XB-C18 column as stationary phase and the detection wavelength at 256 nm. The proposed method was validated for linearity, precision, accuracy, limit of detection, limit of quantification, and robustness by the International Conference on Harmonisation guidelines. In linearity, the excellent correlation coefficient more than 0.999 indicated good fitting of the curve and also good linearity. The intra- and inter-day precision showed < 1% of relative standard deviation of peak area indicated high reliability and reproducibility of the method. The recovery values at three different levels (50%, 100%, and 150%) of spiked samples were found to be 100.47, 100.89, and 100.99, respectively, and low standard deviation value < 1% shows high accuracy of the method. In robustness, the results remain unaffected by small variation in the analytical parameters, which shows the robustness of the method. Liquid chromatography–mass spectrometry analysis confirmed the presence of mangiferin with M/Z value of 421. The assay developed by HPLC method is a simple, rapid, and reliable for the determination of mangiferin from M. indica. SUMMARY The present study was intended to develop and validate an RP-HPLC method for the quantification of mangiferin from the bark extract of M. indica. The developed method was validated for linearity, precision, accuracy, limit of detection, limit of quantification and robustness by International

  7. Development and validation of a reversed-phase high-performance liquid chromatography method for routine identification and purity assessment of high-purity steviol glycoside sweeteners.

    PubMed

    Bililign, Tsion; Moore, Jeffrey C; Tan, Shane; Leeks, Allan T

    2014-02-12

    The widespread application of stevia-based sweeteners in food products has resulted in the need for reliable analytical methods for measuring the purity and identity of high-purity steviol glycoside ingredients. The objective of this research was to develop and validate a new reversed-phase separation method capable of separating and quantifying nine steviol glycosides present in typical high-purity stevia extract ingredients. Results of the study established the linearity of the method at a correlation factor of 1.000 for the two major components and other minor components of this food ingredient. Method accuracy values were in the range of 99.1-100.9%. The percent relative standard deviation for six independent assay determinations was 1.0%. The method was determined to be robust for minor changes in column temperature, initial acetonitrile content, flow rate, and wavelength. The validated high-performance liquid chromatography method was found to be suitable to be included by USP as a Food Chemicals Codex compendial standard for steviol glycosides.

  8. Spectrophotometric and reversed-phase high-performance liquid chromatographic methods for simultaneous determination of escitalopram oxalate and clonazepam in combined tablet dosage form.

    PubMed

    Gandhi, Santosh Vilashchand; Dhavale, Nilesh Dnyandev; Jadhav, Vijay Yeshawantrao; Sabnis, Shweta Sadanand

    2008-01-01

    Simple, accurate, precise, and sensitive ultraviolet spectrophotometric and reversed-phase high-performance liquid chromatographic (RP-HPLC) methods for simultaneous estimation of escitalopram oxalate (ESC) and clonazepam (CLO) in combined tablet dosage form have been developed and validated. The spectroscopic method employs an absorbance correction method using 238.6 and 308 nm as 2 wavelengths for estimation with methanol and water as solvents. Beer's law is obeyed in the concentration range of 10.0-50.0 and 0.5-3.0 micro/mL for ESC and CLO, respectively. The RP-HPLC method uses a Jasco HPLC system with HiQ SiL C18 column (250 x 4.6 mm id) acetonitrile-0.005 M tetrabutylammonium hydrogen sulfate (55 + 45, v/v) as the mobile phase, and satranidazole as an internal standard. The detection was carried out using an ultraviolet detector set at 287 nm. For the HPLC method, Beer's law is obeyed in the concentration range of 10.0-60.0 and 0.5-3.0 microg/mL for ESC and CLO, respectively. Both methods have been successfully applied for the analysis of the drugs in a pharmaceutical formulation. Results of analysis were validated statistically and by recovery studies.

  9. Development of methods for detection and quantification of avian influenza and Newcastle disease viruses in compost by real-time reverse transcription polymerase chain reaction and virus isolation.

    PubMed

    Guan, J; Chan, M; Ma, B; Grenier, C; Wilkie, D C; Pasick, J; Brooks, B W; Spencer, J L

    2008-05-01

    Composting has been used for disposal of poultry carcasses and manure following outbreaks caused by avian influenza virus (AIV) and Newcastle disease virus (NDV), but methods are needed to test for survival of the viruses in compost to ensure biosecurity. Methods developed in the present study include extracting viruses from compost and purifying viral RNA. The extracted viruses were detected by virus isolation using embryonated chicken eggs, and the purified RNA was detected by real-time reverse transcription PCR (RRT-PCR). The virus isolation and the RRT-PCR methods were evaluated with 3 compost preparations that were produced from chicken manure mixed with corn silage, wood shavings, or wheat straw. The detection limits of both methods were 1,700 and 1,000 embryo lethal doses of AIV and NDV per gram of compost, respectively. The copy number of viral RNA quantified by RRT-PCR was highly correlated with the amount of virus in compost. The results suggested that the RRT-PCR method may be used as an alternative to the virus isolation method for rapid detection and accurate quantification of AIV and NDV in compost.

  10. Development and validation of reversed phase high-performance liquid chromatography method for estimation of lercanidipine HCl in pure form and from nanosuspension formulation

    PubMed Central

    Chonkar, Ankita D.; Managuli, Renuka S.; Rao, Josyula Venkata; Udupa, Nayanabhirama

    2015-01-01

    Aim: Quantitative estimation of lercanidipine HCl in bulk material as well as from nanosuspension formulations via a developed reverse phase HPLC method. Materials and Methods: Optimized chromatographic condition was used to achieve separation on a Kromasil (100-5c18 250 × 4.6 mm) column using Shimadzu HPLC system. The mobile phase consisted of a mixture of acetate buffer (20 mM pH 4.5) and acetonitrile in the ratio of 10:90, v/v. It is pumped through the chromatographic system at a flow rate of 1 ml/min. The detection was carried out at 240 nm using ultraviolet-visible spectrophotometry detector. The method was validated as per Q2 (R1) guidelines, and suitability of the developed method was established by optimized nanosuspension formulation. Results: The method is specific to lercanidipine (RT: 7.7 min), and has ability to resolve the analyte peak from excipient interferences. It is linear (regression coefficient: 0.9993), accurate (average recovery: 100%), and passed all the system suitability requirements. Conclusion: Developed method was found applicable for evaluation of drug content, content uniformity, and analyzing samples of dissolution studies of nanosuspension. PMID:26792958

  11. A simple method for the synthesis of a polar-embedded and polar-endcapped reversed-phase chromatographic packing with low activity of residue silanols.

    PubMed

    Liu, Hai-yan; Li, Zhi-yong; Liu, Dan; Xue, Ying-wen; Shi, Zhi-guo

    2016-04-22

    Octadecyl bonded silica (ODS) is the most popular packing for reversed-phase chromatography. However, it generally demonstrates bad resolution for polar analytes because of the residue silanols and its poor stability in aqueous mobile phase. To address the problem, a new reversed-phase packing containing both polar-embedded and polar-endcapped moieties was proposed. It was prepared by a very simple method, in which the epoxide addition reaction of 3-glycidoxypropyltrimethoxysilane with 1-octadecanethiol proceeded simultaneously with the reaction of silane coupling onto silica particles. By controlling the molecular ratio of 3-glycidoxypropyltrimethoxysilane to 1-octadecanethiol higher than 1.0 (1.56 for the present study), both polar-embedded and polar-endcapped moieties were achieved onto the packing. The performance of the packing was evaluated in detail. The results demonstrated that neutral, acidic and basic analytes were well separated on the packing. The column efficiency for phenanthrene was 34,200 theoretical plates per meter. In addition, four nucleotides can be separated in 100% phosphate buffered saline solution with good reproducibility, which indicates the packing has good stability in aqueous mobile phase. Amitriptyline, a typical basic analytes, was eluted out with relatively symmetric peak shape (asymmetry factor of 1.36), which implies that the packing has not suffered from the negative effect of residue silanols significantly. Good stability in buffer solution of pH ranging from 2.0 to 10.0 was also documented for the packing.

  12. Method development for pharmaceutics: some solutions for tuning selectivity in reversed phase and hydrophilic interaction liquid chromatography.

    PubMed

    Ruta, Josephine; Boccard, Julien; Cabooter, Deirdre; Rudaz, Serge; Desmet, Gert; Veuthey, Jean-Luc; Guillarme, Davy

    2012-04-07

    In LC method development, the choice of suitable experimental conditions is often challenging for the analyst because of the huge diversity of stationary phases, mobile phase pH and organic modifiers, that could significantly alter the selectivity. The influence of these parameters on selectivity was experimentally tested in both RPLC and HILIC conditions for the analysis of 45 pharmaceutical compounds covering a wide range of physico-chemical properties. Principal component analysis (PCA) models were built to assess the resulting multivariate dataset. The complementarity between RPLC and HILIC was clearly demonstrated. The importance of mobile phase pH as one of the main experimental factors to be considered was confirmed. The RPLC and HILIC methods were thus employed for the analysis of a drug cocktail containing two substrates and their numerous desmethylated metabolites. All the compounds were finally resolved in both modes, with a very distinct elution order. In addition, the possibility to combine columns of different selectivity was highlighted using a column coupler set-up and found to be extremely promising. The same type of experiments was also carried out for the impurity profiling of an antihistaminic drug. In this example, compounds of very distinct polarity were satisfactorily eluted in both RPLC and HILIC modes, using suitable conditions of pH and stationary phase. In conclusion, this study demonstrates the complementary and interest of RPLC and HILIC in the case of pharmaceutical method development.

  13. Method to predict the bandwidth of elution profile under the linear gradient elution in reversed-phase HPLC.

    PubMed

    Lee, Ju Weon; Row, Kyung Ho

    2009-01-01

    Solute migration in a chromatographic column is an important consideration when designing batch or continuous chromatographic separation processes. Most design methods for the chromatographic processes are based on the equilibrium theory which concerns only the migration velocity of the solute. However, in real cases, it is important to predict the zone spreading which occurs by axial dispersion and mass transfer resistance. To predict the actual solute profiles in the column or effluent stream, numerical methods to solve nonlinear partial differential equations have been used. However, these methods involve much time and expense. In this work, two different rate factors are considered to predict the characteristics of the solute profiles. The first is solute migration velocity and the second is the zone spreading rate. The zone spreading rate can be estimated by the apparent axial dispersion coefficient which is obtained from the height of the equivalent theoretical plate in particular. Four benzene derivatives (benzene, toluene, p-xylene, and acetophenone) were used as model solutes, and two mobile phase systems, water/methanol and water/ACN, were used in RP-HPLC. The bandwidths and retention times of the solutes were predicted under several linear gradient conditions. The predicted and experimental bandwidths and retention times showed good agreement.

  14. Method to Calculate the Protamine Dose Necessary for Reversal of Heparin as a Function of Activated Clotting Time in Patients Undergoing Cardiac Surgery

    PubMed Central

    Cuenca, Javier Suárez; Diz, Pilar Gayoso; Sampedro, Francisco Gude; Zincke, J. Marcos Gómez; Acuña, Helena Rey; Fontanillo, M. Manuela Fontanillo

    2013-01-01

    Abstract: Activated clotting time (ACT) has been used to monitor coagulation and guide management of anticoagulation control in patients undergoing cardiac surgery for decades. However, reversal of heparin with protamine is typically empirically based on total heparin administered. Dose-related adverse effects of protamine are well described. The aim of this study was to evaluate a heparin reversal strategy based on calculation of the protamine dose based on ACT measurements. We present a method using a mathematical formula based on the dose–response line (1). To check the formula, we performed a retrospective observational cohort study of 177 patients undergoing cardiac surgery with cardiopulmonary bypass (CPB). The study group of 80 patients was administered the dose of protamine obtained using our formula, and the control group of 97 patients was administered the empirically calculated dose. The ACT returned to normal values in patients who were given doses of protamine that were calculated using our formula; all but two had a final ACT of 141. The application of the formula resulted in a significant reduction in the dose of protamine (p < .023). The formula we present is a valid method for calculating the dose of protamine necessary to neutralize heparin. This same method can be used working with a target ACT to adjust the dose of heparin. As a result of its functionality, it allows application on a daily basis standardizing the process. We believe that the formula we developed can be applied in all those procedures in which it is necessary to anticoagulate patients with heparin and later neutralization (cardiac surgery with or without CPB, vascular surgery, procedures of interventional cardiology, and extracorporeal depuration procedures). PMID:24649571

  15. Reversed-phase ion-pair liquid chromatographic method for determination of reaction equilibria involving ionic species: exemplification of the method using ligand substitution reactions of ethylenediaminetetraacetatochromium(III) ion with acetate and phosphate ions.

    PubMed

    Sato, Emiko; Miya, Seiko; Saitoh, Kazunori; Saito, Shingo; Shibukawa, Masami

    2011-02-18

    A reversed-phase ion-pair liquid chromatographic method is presented for the determination of reaction equilibria involving ionic species of the same charge sign as reactant and product compounds. It has been demonstrated that ion-exchange chromatography or reversed-phase ion-pair chromatography is a useful tool for the determination of equilibrium constants of chemical reactions involving ionic species such as metal complexation reactions. Previous work with these methods has been based on the assumption that the limiting retention factors of the reactant and product species are constant independent of concentration of the chemical species (X) in the mobile phase, which reacts with the analyte compound. However, when all the reactant and product species are ions of the same charge sign as that of the species X, it is virtually impossible to apply these methods to the equilibrium constant determination because the retention factors of both the reactant and product species may depend on the concentration of X. In this study, an alternative approach was developed that estimates the limiting retention factors of ionic species from the dependence of the retention factor on the ionic strength of the mobile phase. Ligand substitution reactions of ethylenediaminetetraacetatochromium(III) ion with acetate and phosphate ions were used as model reactions to test this method. The equilibrium constants determined by this method are in good agreement with those obtained by a UV-visible spectrophotometric method.

  16. Plasma amino-acid determinations by reversed-phase HPLC: Improvement of the orthophthalaldehyde method and comparison with ion exchange chromatography.

    PubMed

    Ziegler, F; Le Boucher, J; Coudray-Lucas, C; Cynober, L

    1992-01-01

    Reversed-phase high performance liquid chromatographic (RPHPLC) determination of amino-acids with on-line pre-column ortho-phthalaldehyde (OPA) derivatization and fluorescence detection is rapid and sensitive. However, high-performance ionexchange chromatography (HP-IEC) with post-column ninhydrine reaction is the most widely used amino-acid (AA) assay for biological samples. These two methods have been compared for the determination of individual plasma AA concentrations.An excellent correlation (p methods, but a paired t-test showed slight differences for 13 AA. The within-batch reproducibility of the RPHPLC method was comparable to that of the HP-IEC method. The analysis was about three times faster with RP-HPLC, and sensitivity was l00-fold better. However, aspartic acid, proline and cysteine were not identified by the RP-HPLC method, while the tryptophan quantification is possible.RP-HPLC with automated pre-column OPA derivatization is clearly a suitable alternative for assaying physiological AA and may be particularly useful for AA present at low concentrations (free tryptophan, plasma 3-methylhistidine).

  17. Development and validation of a new stability indicating reversed phase liquid chromatographic method for the determination of prednisolone acetate and impurities in an ophthalmic suspension.

    PubMed

    Marley, Adrian; Stalcup, Apryll M; Connolly, Damian

    2015-01-01

    A new stability indicating reversed phase high performance liquid chromatography (RP-HPLC) method was developed and validated under current International Conference of Harmonisation (ICH) guidance for the determination of prednisolone acetate (PAC) and impurities in an ophthalmic suspension. The developed method is presented as an alternative to a modified version of the current RP-HPLC method described in the USP monograph for the assay of PAC in an ophthalmic suspension. Along with the assay of PAC, the new method is also capable of identifying and quantifying eight selected PAC impurities and degradation products in an ophthalmic suspension. Using an Agilent Poroshell 120 EC-C18 100 mm × 4.6mm (dp: 2.7 μm) column set to 60°C with step gradient elution generated using mobile phase A: acetonitrile/water (10:90) (v/v) and mobile phase B: acetonitrile delivered at 1.2 mL min(-1), all peaks of interest are eluted in 33 min with resolution of 1.5 between the critical pairs. The developed method was validated for PAC and impurities to ICH recommendations for accuracy, linearity, precision (repeatability), limit of detection, limit of quantitation, robustness and specificity.

  18. Development and Validation of a Reversed-phase HPLC Method for Simultaneous Determination of Aspirin, Atorvastatin Calcium and Clopidogrel Bisulphate in Capsules.

    PubMed

    Londhe, S V; Deshmukh, R S; Mulgund, S V; Jain, K S

    2011-01-01

    A simple, accurate, rapid and precise isocratic reversed-phase high-performance liquid chromatographic method has been developed and validated for simultaneous determination of aspirin, atorvastatin calcium and clopidogrel bisulphate in capsules. The chromatographic separation was carried out on an Inertsil ODS analytical column (150×4.6 mm; 5 μm) with a mixture of acetonitrile:phosphate buffer pH 3.0 adjusted with o-phosphoric acid (50:50, v/v) as mobile phase; at a flow rate of 1.2 ml/min. UV detection was performed at 235 nm. The retention times were 1.89, 6.6 and 19.8 min. for aspirin, atorvastatin calcium and clopidogrel bisulphate, respectively. Calibration plots were linear (r(2)>0.998) over the concentration range 5-30 μg/ml for atorvastatin calcium and 30-105 μg/ml for aspirin and clopidogrel bisulphate. The method was validated for accuracy, precision, specificity, linearity, and sensitivity. The proposed method was successfully used for quantitative analysis of capsules. No interference from any component of pharmaceutical dosage form was observed. Validation studies revealed that method is specific, rapid, reliable, and reproducible. The high recovery and low relative standard deviation confirm the suitability of the method for routine determination of aspirin, atorvastatin calcium and clopidogrel bisulphate in bulk drug and capsule dosage form.

  19. A novel reverse phase stability indicating RP-UPLC method for the quantitative determination of fifteen related substances in Ranolazine drug substance and drug product.

    PubMed

    Malati, Vakamulla; Reddy, Anumala Raghupati; Mukkanti, K; Suryanarayana, M V

    2012-08-15

    A gradient reverse-phase ultra performance liquid chromatographic (RP-UPLC) method was developed for the quantitative determination of Ranolazine and potential process-related impurities (starting materials, positional isomers, degradants and byproducts) at the level of 0.1 μg mL(-1) to 0.3 μg mL(-1). Fifteen potential impurities were identified in the crude samples during the process development. Tentative structures for all the impurities were assigned based on m/z values from LC-MS/MS analysis. This method can be used for the quality control of both drug substance and drug product. All these impurities were separated with a gradient UPLC method by using a polar embedded Waters Acquity BEH RP18 100 mm × 2.1 mm,1.7 μm column, monobasic sodium buffer, a basic organic modifier and acetonitrile in the mobile phase. Further, this method is also capable of separating a major oxidative degradant Di-N-oxide. Impurities having electron donating groups(+I effect) on the phenyl ring increased the retention by improved п-п interactions. The drug was subjected to the International Conference on Harmonization (ICH)-prescribed hydrolytic, oxidative, photolytic and thermal stress conditions. The performance of the method was validated according to the present ICH guidelines for specificity, limit of detection, limit of quantification, linearity, accuracy, precision, ruggedness and robustness.

  20. Plasma amino-acid determinations by reversed-phase HPLC: Improvement of the orthophthalaldehyde method and comparison with ion exchange chromatography

    PubMed Central

    Ziegler, Frédéric; Le Boucher, Jacques; Coudray-Lucas, Colette

    1992-01-01

    Reversed-phase high performance liquid chromatographic (RPHPLC) determination of amino-acids with on-line pre-column ortho-phthalaldehyde (OPA) derivatization and fluorescence detection is rapid and sensitive. However, high-performance ionexchange chromatography (HP-IEC) with post-column ninhydrine reaction is the most widely used amino-acid (AA) assay for biological samples. These two methods have been compared for the determination of individual plasma AA concentrations. An excellent correlation (p ≤ 0.003) was found between the results given by an RP-HPLC system (Varian) and a classical AA autoanalyser (Biotronik LC 5001). Most AA concentrations were similar with the two methods, but a paired t-test showed slight differences for 13 AA. The within-batch reproducibility of the RPHPLC method was comparable to that of the HP-IEC method. The analysis was about three times faster with RP-HPLC, and sensitivity was l00-fold better. However, aspartic acid, proline and cysteine were not identified by the RP-HPLC method, while the tryptophan quantification is possible. RP-HPLC with automated pre-column OPA derivatization is clearly a suitable alternative for assaying physiological AA and may be particularly useful for AA present at low concentrations (free tryptophan, plasma 3-methylhistidine). PMID:18924933

  1. Comparative Evaluation of Three Homogenization Methods for Isolating Middle East Respiratory Syndrome Coronavirus Nucleic Acids From Sputum Samples for Real-Time Reverse Transcription PCR

    PubMed Central

    Yong, Dongeun; Ki, Chang-Seok; Kim, Jae-Seok; Seong, Moon-Woo; Lee, Hyukmin

    2016-01-01

    Background Real-time reverse transcription PCR (rRT-PCR) of sputum samples is commonly used to diagnose Middle East respiratory syndrome coronavirus (MERS-CoV) infection. Owing to the difficulty of extracting RNA from sputum containing mucus, sputum homogenization is desirable prior to nucleic acid isolation. We determined optimal homogenization methods for isolating viral nucleic acids from sputum. Methods We evaluated the following three sputum-homogenization methods: proteinase K and DNase I (PK-DNase) treatment, phosphate-buffered saline (PBS) treatment, and N-acetyl-L-cysteine and sodium citrate (NALC) treatment. Sputum samples were spiked with inactivated MERS-CoV culture isolates. RNA was extracted from pretreated, spiked samples using the easyMAG system (bioMérieux, France). Extracted RNAs were then subjected to rRT-PCR for MERS-CoV diagnosis (DiaPlex Q MERS-coronavirus, SolGent, Korea). Results While analyzing 15 spiked sputum samples prepared in technical duplicate, false-negative results were obtained with five (16.7%) and four samples (13.3%), respectively, by using the PBS and NALC methods. The range of threshold cycle (Ct) values observed when detecting upE in sputum samples was 31.1–35.4 with the PK-DNase method, 34.7–39.0 with the PBS method, and 33.9–38.6 with the NALC method. Compared with the control, which were prepared by adding a one-tenth volume of 1:1,000 diluted viral culture to PBS solution, the ranges of Ct values obtained by the PBS and NALC methods differed significantly from the mean control Ct of 33.2 (both P<0.0001). Conclusions The PK-DNase method is suitable for homogenizing sputum samples prior to RNA extraction. PMID:27374711

  2. Pre-stack reverse-time migration based on the time-space domain adaptive high-order finite-difference method in acoustic VTI medium

    NASA Astrophysics Data System (ADS)

    Yan, Hongyong; Liu, Yang

    2013-02-01

    With the increment of seismic exploration precision requirement, it is significant to develop the anisotropic migration methods. Pre-stack reverse-time migration (RTM) is performed based on acoustic vertical transversely isotropic (VTI) wave equations, and the accuracy and efficiency of RTM strongly depend on the algorithms used for wave equation numerical solution. Finite-difference (FD) methods have been widely used in numerical solution of wave equations. The conventional FD method derives spatial FD coefficients from the space domain dispersion relation, and it is difficult to satisfy the time-space domain dispersion relation of the wave equation exactly. In this paper, we adopt a time-space domain FD method to solve acoustic VTI wave equations. Dispersion analysis and numerical modelling results demonstrate that the time-space domain FD method has greater accuracy than the conventional FD method under the same discretizations. The time-space domain high-order FD method is also applied in the wavefield extrapolation of acoustic VTI pre-stack RTM. The model tests demonstrate that the acoustic VTI pre-stack RTM based on the time-space domain FD method can obtain better images than that based on the conventional FD method, and the processing results show that the imaging quality of the acoustic VTI RTM is clearer and more correct than that of acoustic isotropic RTM. Meanwhile, in the process of wavefield forward and backward extrapolation, we employ adaptive variable-length spatial operators to compute spatial derivatives to improve the computational efficiency effectively almost without reducing the imaging accuracy.

  3. In vitro comparison of RNA preparation methods for detection of feline calicivirus in urine of cats by use of a reverse transcriptase-polymerase chain reaction assay.

    PubMed

    Scansen, Brian A; Kruger, John M; Wise, Annabel G; Venta, Patrick J; Bartlett, Paul C; Maes, Roger K

    2005-05-01

    To compare 5 methods of preparation of RNA from feline urine samples for use in a feline calicivirus (FCV), p30 gene-based, real-time reverse-transcriptase polymerase chain reaction (RT-PCR) assay. Urine and blood samples from 6 specific-pathogen-free cats. Aliquots of each urine sample (unmodified, centrifuged, or mixed with whole or hemolyzed blood) were spiked with FCV and serially diluted in urine. Serial dilutions of FCV in tissue culture medium were used as positive controls. Viral RNA was prepared via dilution and thermal inactivation (DT method), polyethylene glycol precipitation (PEG method), isolation with oligo(dT)25-coated magnetic beads (dTMB method), or extraction by use of 2 silica gel-based columns (RN or QA method). Lower detection limits and mean RT-PCR threshold cycle (Ct) values associated with each RNA preparation method and sample type were compared. Because DT-prepared samples yielded negative results via RT-PCR assay, this method was not evaluated. Lower detection limits (TCID50/sample) for the assay in urine were 1950, 104, 11, and 7 for PEG-, dTMB-, RN-, and QA-prepared samples, respectively. For RN and QA preparations, Ct values were similar and significantly lower than those for dTMB and PEG preparations. Overall, urine modifications did not affect FCV RNA detection in dTMB-, QA-, and RN-prepared samples. Of the methods evaluated, the RN and QA methods of RNA preparation were most appropriate for the FCV RT-PCR assay. An RT-PCR assay optimized for detection of FCV in feline urine may aid investigations of FCV-induced urinary tract diseases in cats.

  4. A Validated Reverse Phase HPLC Analytical Method for Quantitation of Glycoalkaloids in Solanum lycocarpum and Its Extracts

    PubMed Central

    Tiossi, Renata Fabiane Jorge; Miranda, Mariza Abreu; de Sousa, João Paulo Barreto; Praça, Fabíola Silva Garcia; Bentley, Maria Vitória Lopes Badra; McChesney, James Dewey; Bastos, Jairo Kenupp

    2012-01-01

    Solanum lycocarpum (Solanaceae) is native to the Brazilian Cerrado. Fruits of this species contain the glycoalkaloids solasonine (SN) and solamargine (SM), which display antiparasitic and anticancer properties. A method has been developed for the extraction and HPLC-UV analysis of the SN and SM in different parts of S. lycocarpum, mainly comprising ripe and unripe fruits, leaf, and stem. This analytical method was validated and gave good detection response with linearity over a dynamic range of 0.77–1000.00 μg mL−1 and recovery in the range of 80.92–91.71%, allowing a reliable quantitation of the target compounds. Unripe fruits displayed higher concentrations of glycoalkaloids (1.04% ± 0.01 of SN and 0.69% ± 0.00 of SM) than the ripe fruits (0.83% ± 0.02 of SN and 0.60% ± 0.01 of SM). Quantitation of glycoalkaloids in the alkaloidic extract gave 45.09% ± 1.14 of SN and 44.37% ± 0.60 of SM, respectively. PMID:22567576

  5. Development of validated high-temperature reverse-phase UHPLC-PDA analytical method for simultaneous analysis of five natural isothiocyanates in cruciferous vegetables.

    PubMed

    Robin; Arora, Rohit; Arora, Saroj; Vig, Adarsh Pal

    2018-01-15

    In the present study reverse-phase UHPLC-PDA technique was developed at 60°C for simultaneous quantification of allyl, 3-butenyl, 4-(methylthio)butyl, benzyl and phenethyl isothiocyanates. The validation parameter showed a very good linearity, with a correlation coefficient of 1.00 for all detected standard analytes. Also, high precision and accuracy were observed with lowest obtained values of 1.39% and 99.1%, respectively. Different varieties of three plants, viz. Brassica rapa var. rapa L., Raphanus sativus L. var. oleiformis Pers. and Eruca sativa Mill., were analyzed with this method. After analysis, 4-(methylthio)butyl isothiocyanate was observed to be the major component in the varieties of arugula. Allyl, benzyl and phenethyl isothiocyanates were detected in turnip varieties and, in addition, 3-butenyl isothiocyanate was detected in radish varieties. Copyright © 2017 Elsevier Ltd. All rights reserved.

  6. A Binary-Like Approach for the Computer Assisted Method Development of Isocratic and Programmed Ternary Solvent Elutions in Reversed-Phase Liquid Chromatography

    PubMed Central

    García-Lavandeira, J.; Martinez-Pontevedra, J.A.; Cela, R.

    2012-01-01

    A specific tool to enable exploration of multisolvent isocratic and programmed elutions for the computer assisted method development of reversed-phase liquid chromatography separations is described. The tool is purposely identical to those used in the optimization of binary solvent systems, which are by far the most commonly used by chromatographers. Existing data from failed binary solvent optimization processes are reused to explore ternary solvent systems with a few additional isocratic and programmed runs. This allows the development of efficient retention models for ternary systems, although the work of the chromatographer remains identical to that for optimization of binary systems. The retention models are used to develop an unattended optimization process and finally, the chromatographer selects the most satisfactory solution for testing and implementing in routine analysis. The process is exemplified with a mixture of 12 compounds that cannot be separated satisfactorily in aqueous binary solvent systems with methanol and acetonitrile as modifiers. PMID:22291054

  7. Development of a reversed-phase high-performance liquid chromatography method for the analysis of components from a closed-loop insulin delivery system.

    PubMed

    Sawicka, Kirsty; Sahota, Tarsem; Taylor, M Joan; Tanna, Sangeeta

    2006-11-03

    A reversed-phase HPLC method has been developed which enables separation of the three components of a closed-loop insulin delivery system, namely concanavalin A methacrylamide (Con A-MA), dextran methacrylate (Dex-MA) and bovine insulin. The analysis of Con A-MA represents a significant challenge due to the formation of multiple conformations on contact with the chromatographic surface and the mobile phase. The extent of conformational change is shown to be dependent on a number of parameters: column temperature, mobile phase pH, contact time with the chromatographic surface, salt type and concentration and the organic modifier. By manipulation of these variables, protein denaturation can be minimised and recovery improved.

  8. Promotion by humus-reducing bacteria for the degradation of UV254 absorbance in reverse-osmosis concentrates pretreated with O3-assisted UV-Fenton method.

    PubMed

    Xia, Jiaohui; Zhang, Hui; Ding, Shaoxuan; Li, Changyu; Ding, Jincheng; Lu, Jie

    2017-07-12

    The primary pollutants in reverse-osmosis concentrates (ROC) are the substances with the UV absorbance at 254 nm (UV254), which is closely related to humic substances that can be degraded by humus-reducing bacteria. This work studied the degradation characteristics of humus-reducing bacteria in ROC treatment. The physiological and biochemical characteristics of humus-reducing bacteria were investigated, and the effects of pH values and electron donors on the reduction of humic analog, antraquinone-2, 6-disulfonate were explored to optimize the degradation. Furthermore, the O3-assisted UV-Fenton method was applied for the pretreatment of ROC, and the degradation of UV254 absorbance was apparently promoted with their removal rate, reaching 84.2% after 10 days of degradation by humus-reducing bacteria.

  9. Prestack reverse-time migration with a time-space domain adaptive high-order staggered-grid finite-difference method

    NASA Astrophysics Data System (ADS)

    Yan, Hongyong; Liu, Yang; Zhang, Hao

    2013-03-01

    With advanced computational power, prestack reverse-time migration (RTM) is being used increasingly in seismic imaging. The accuracy and efficiency of RTM strongly depends on the algorithms used for numerical solutions of wave equations. Hence, how to solve the wave equation accurately and rapidly is very important in the process of RTM. In this paper, in order to improve the accuracy of the numerical solution, we use a time-space domain staggered-grid finite-difference (SFD) method to solve the acoustic wave equation, and develop a new acoustic prestack RTM scheme based on this time-space domain high-order SFD. Synthetic and real data tests demonstrate that the RTM scheme improves the imaging quality significantly compared with the conventional SFD RTM. Meanwhile, in the process of wavefield extrapolation, we apply adaptive variable-length spatial operators to compute spatial derivatives to decrease computational costs effectively with little reduction of the accuracy of the numerical solutions.

  10. Probing the A1 to L1{sub 0} transformation in FeCuPt using the first order reversal curve method

    SciTech Connect

    Gilbert, Dustin A.; Liu, Kai; Liao, Jung-Wei; Wang, Liang-Wei; Lai, Chih-Huang; Lau, June W.; Klemmer, Timothy J.; Thiele, Jan-Ulrich

    2014-08-01

    The A1-L1{sub 0} phase transformation has been investigated in (001) FeCuPt thin films prepared by atomic-scale multilayer sputtering and rapid thermal annealing (RTA). Traditional x-ray diffraction is not always applicable in generating a true order parameter, due to non-ideal crystallinity of the A1 phase. Using the first-order reversal curve (FORC) method, the A1 and L1{sub 0} phases are deconvoluted into two distinct features in the FORC distribution, whose relative intensities change with the RTA temperature. The L1{sub 0} ordering takes place via a nucleation-and-growth mode. A magnetization-based phase fraction is extracted, providing a quantitative measure of the L1{sub 0} phase homogeneity.

  11. Comparative Evaluation of Three Homogenization Methods for Isolating Middle East Respiratory Syndrome Coronavirus Nucleic Acids From Sputum Samples for Real-Time Reverse Transcription PCR.

    PubMed

    Sung, Heungsup; Yong, Dongeun; Ki, Chang Seok; Kim, Jae Seok; Seong, Moon Woo; Lee, Hyukmin; Kim, Mi Na

    2016-09-01

    Real-time reverse transcription PCR (rRT-PCR) of sputum samples is commonly used to diagnose Middle East respiratory syndrome coronavirus (MERS-CoV) infection. Owing to the difficulty of extracting RNA from sputum containing mucus, sputum homogenization is desirable prior to nucleic acid isolation. We determined optimal homogenization methods for isolating viral nucleic acids from sputum. We evaluated the following three sputum-homogenization methods: proteinase K and DNase I (PK-DNase) treatment, phosphate-buffered saline (PBS) treatment, and N-acetyl-L-cysteine and sodium citrate (NALC) treatment. Sputum samples were spiked with inactivated MERS-CoV culture isolates. RNA was extracted from pretreated, spiked samples using the easyMAG system (bioMérieux, France). Extracted RNAs were then subjected to rRT-PCR for MERS-CoV diagnosis (DiaPlex Q MERS-coronavirus, SolGent, Korea). While analyzing 15 spiked sputum samples prepared in technical duplicate, false-negative results were obtained with five (16.7%) and four samples (13.3%), respectively, by using the PBS and NALC methods. The range of threshold cycle (Ct) values observed when detecting upE in sputum samples was 31.1-35.4 with the PK-DNase method, 34.7-39.0 with the PBS method, and 33.9-38.6 with the NALC method. Compared with the control, which were prepared by adding a one-tenth volume of 1:1,000 diluted viral culture to PBS solution, the ranges of Ct values obtained by the PBS and NALC methods differed significantly from the mean control Ct of 33.2 (both P<0.0001). The PK-DNase method is suitable for homogenizing sputum samples prior to RNA extraction.

  12. Reversed phase-high performance liquid chromatographic method for simultaneous estimation of tolperisone hydrochloride and etodolac in a combined fixed dose oral formulations

    PubMed Central

    Patel, Mit J.; Badmanaban, R.; Patel, C. N.

    2011-01-01

    A reversed-phase liquid chromatographic (RP-HPLC) method was developed for the simultaneous determination of tolperisone hydrochloride (TOLP) and etodolac (ETD) in a combined fixed dose oral formulation. The analysis was carried out using a phenomenax C-18, pre-packed column. A mobile phase containing a phosphate buffer (pH 5.5) : Methanol : Acetonitrile : Tri-ethylamine (40 : 40 : 20 : 1.5), with the pH adjusted to orthophosphoric acid, was pumped at a flow rate of 1.0 ml min1 with a UV-detector and PDA detection at 257 nm. Retention time was 3.91 minutes and 6.89 minutes for TOLP and ETD, respectively. The method was validated for linearity, accuracy, precision, sensitivity, and specificity. The method showed good linearity in the range of 3 – 21 μg ml for TOLP μg / ml and 8 – 56 μg / ml for ETD. The detection limit of the proposed method was 0.16 μg / ml and 0.58 μg / ml for TOLP and ETD, respectively. The quantification limit of the proposed method was 0.51 μg / ml and 1.7 μg / ml for TOLP and ETD, respectively. The % recovery was within the range of 99.42 – 101.15 for TOLP and 98.63 – 100.94 for ETD. The percentage RSD for precision of the method was found to be less than 2%. The method was validated as per the International Conference on Harmonization (ICH) guidelines. The developed method could be applied for routine analysis of TOLP and ETD in tablet dosage form. PMID:23781442

  13. Reversed phase-high performance liquid chromatographic method for simultaneous estimation of tolperisone hydrochloride and etodolac in a combined fixed dose oral formulations.

    PubMed

    Patel, Mit J; Badmanaban, R; Patel, C N

    2011-04-01

    A reversed-phase liquid chromatographic (RP-HPLC) method was developed for the simultaneous determination of tolperisone hydrochloride (TOLP) and etodolac (ETD) in a combined fixed dose oral formulation. The analysis was carried out using a phenomenax C-18, pre-packed column. A mobile phase containing a phosphate buffer (pH 5.5) : Methanol : Acetonitrile : Tri-ethylamine (40 : 40 : 20 : 1.5), with the pH adjusted to orthophosphoric acid, was pumped at a flow rate of 1.0 ml min(1) with a UV-detector and PDA detection at 257 nm. Retention time was 3.91 minutes and 6.89 minutes for TOLP and ETD, respectively. The method was validated for linearity, accuracy, precision, sensitivity, and specificity. The method showed good linearity in the range of 3 - 21 μg ml for TOLP μg / ml and 8 - 56 μg / ml for ETD. The detection limit of the proposed method was 0.16 μg / ml and 0.58 μg / ml for TOLP and ETD, respectively. The quantification limit of the proposed method was 0.51 μg / ml and 1.7 μg / ml for TOLP and ETD, respectively. The % recovery was within the range of 99.42 - 101.15 for TOLP and 98.63 - 100.94 for ETD. The percentage RSD for precision of the method was found to be less than 2%. The method was validated as per the International Conference on Harmonization (ICH) guidelines. The developed method could be applied for routine analysis of TOLP and ETD in tablet dosage form.

  14. Method for the Determination of β-Carotene in Supplements and Raw Materials by Reversed-Phase Liquid Chromatography: Single Laboratory Validation

    PubMed Central

    Schierle, Joseph; Pietsch, Bernd; Ceresa, Alan; Fizet, Christian; Waysek, Edward H.

    2008-01-01

    A single laboratory validation (SLV) study was conducted for a liquid Chromatography (LC) method for the determination of total and all-trans-β-carotene in a variety of dietary supplements, including multivitamin tablets, softgels, capsules, and beadlet raw materials. Extraction variants were developed for the different types of supplements tested based upon the supplement type and level of β-carotene. Water dispersible formulations such as powders, emulsions, tablets, and capsules were enzymatically digested with protease and extracted with dichloromethane–ethanol. Oily suspensions were directly dissolved in dichloromethane–ethanol. After appropriate dilution or concentration, the extracts were chromatographed by using either a reversed-phase C18 column or, in products containing high amounts of α-carotene, a reversed-phase C30 column. The LC systems provided linear responses in the range of 0.1–50 μg β-carotene/mL. The main geometrical isomers of β-carotene (all-trans, 9-cis, 13-cis, and 15-cis) were well separated from each other and from other carotenoids such as α-carotene, cryptoxanthin, lutein, lycopene, and zeaxanthin. Duplicate determinations of total β-carotene performed by 2 technicians in 8 different test materials on 5 different days resulted in relative standard deviations of 1.2–4.4%. Recoveries determined for supplements and beadlet raw material spiked with β-carotene levels of 10 μg to 100 mg/test portion and 0.2–40%, respectively, ranged from 97.5 to 102.1%. On the basis of the accuracy, precision, and recovery results from the SLV study, the method is suggested for a collaborative study on the determination of total and all-trans-β-carotene in dietary supplements. PMID:15493663

  15. A Study into the Effects of Method of Teaching Reading--Synthetic (Reading-Typing Program) and Analytic (Basic Reading Series)--Upon Reversal Errors Made by Children in Grades One Through Four.

    ERIC Educational Resources Information Center

    Wojtcuk, Albert John

    The purpose of this study was to examine the effects of two methods of teaching reading upon reversal errors. A sample of 210 pupils in grades one through four were selected for this study. One half of the group had learned to read through an analytic method while the other half had learned through a synthetic method. Since the synthetic group had…

  16. Development and Application of a Reversed-Phase High-Performance Liquid Chromatographic Method for Quantitation and Characterization of a Chikungunya Virus-Like Particle Vaccine

    PubMed Central

    Shytuhina, Anastasija; Pristatsky, Pavlo; He, Jian; Casimiro, Danilo R.; Schwartz, Richard M.; Hoang, Van M.; Ha, Sha

    2014-01-01

    To effectively support the development of a Chikungunya (CHIKV) virus-like particle (VLP) vaccine, a sensitive and robust high-performance liquid chromatography (HPLC) method that can quantitate CHIKV VLPs and monitor product purity throughout the manufacturing process is needed. We developed a sensitive reversed-phase HPLC (RP-HPLC) method that separates capsid, E1, and E2 proteins in CHIKV VLP vaccine with good resolution. Each protein component was verified by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) and matrix-assisted laser desorption/ionization time-of-flight (MALDI-ToF) mass spectrometry (MS). The post-translational modifications on the viral glycoproteins E1 and E2 were further identified by intact protein mass measurements with liquid chromatography-mass spectrometry (LC-MS). The RP-HPLC method has a linear range of 0.51–12 μg protein, an accuracy of 96–106% and a precision of 12% RSD, suitable for vaccine product release testing. In addition, we demonstrated that the RP-HPLC method is useful for characterizing viral glycoprotein post-translational modifications, monitoring product purity during process development and assessing product stability during formulation development. PMID:25234500

  17. A stability-indicating, ion-pairing, reversed-phase liquid chromatography method for studies of daunorubicin degradation in i.v. infusion fluids.

    PubMed

    Respaud, R; Quenum, L; Plichon, C; Tournamille, J F; Gyan, E; Antier, D; Viaud-Massuard, M C

    2013-09-01

    A new stability-indicating method based on high-performance liquid chromatography coupled to ultraviolet and evaporative light scattering detection (HPLC-UV-ELSD) was developed for the quantification of daunorubicin. This is an ion-pairing, reversed-phase method. The column was a Synergi MAX-RP C12 4 μm (150 mm × 4.6 mm). The mobile phase was 6.2mM nonafluoropentanoic acid in aqueous solution and acetonitrile under isocratic elution mode. The drug was subjected to oxidation, basic and acid hydrolysis to apply stress conditions. Good resolution was achieved between daunorubicin, related products and all degradation products in an overall analytical run time of approximately 16 min with the parent compound daunorubicin eluting at approximately 8 min. The method was fully validated according to ICH guidelines and SFSTP protocols in terms of accuracy, precision, specificity and linearity. For daunorubicin, the decision criteria selected consisted of the acceptability limits (±3%) and the proportion of results within the calculated tolerance intervals (95%). In conclusion, the proposed analytical procedures were validated over the selected validation domains daunorubicin (0.25-0.45 mg/mL) and shown to provide a very effective method. Physical and chemical stability study was carried out on daunorubicin preparation in our hospital centralized pharmacy unit.

  18. ICH guidance in practice: validated reversed-phase HPLC method for the determination of active mangiferin from extracts of Mangifera indica Linn.

    PubMed

    Gowda, Nagaraj; Kumar, Pradeep; Panghal, Surender; Rajshree, Mashru

    2010-02-01

    This study presents the development and validation of a reversed-phase liquid chromatographic method for the determination of mangiferin (MGN) in alcoholic extracts of mangifera indica. A Lichrospher 100 C(18)-ODS (250 x 4.6 mm, 5 microm size) (Merck, Whitehouse Station, NJ) prepacked column and a mobile phase of potassium dihydrogen orthophosphate (0.01M) pH 2.7 +/- 0.2-acetonitrile (15:85, v/v) with the flow rate of 1 mL/min was used. MGN detection was achieved at a wavelength monitored at 254 nm with SPD-M 10A vp PDA detector or SPD 10AD vp UV detector in combination with class LC 10A software. The proposed method was validated as prescribed by International Conference on Harmonization (ICH) with respect to linearity, specificity, accuracy, precision, stability, and quantification. The method validation was realized using alcoholic extracts and raw materials of leaves and barks. All the validation parameters were within the acceptable limits, and the developed analytical method can successfully be applied for MGN determination.

  19. A method for simultaneous analysis of phytosterols and phytosterol esters in tobacco leaves using non aqueous reversed phase chromatography and atmospheric pressure chemical ionization mass spectrometry detector.

    PubMed

    Ishida, Naoyuki

    2014-05-02

    While numerous analytical methods for phytosterols have been reported, the similar polarity and large molecules of phytosterol esters have made the methods lengthy and complicated. For this reason, an analytical method that could completely separate phytosterol esters including the higher fatty acids such as palmitic acid, stearic acid, oleic acid, linoleic acid and linolenic acid in addition to phytosterols without preliminary separation was developed. The separation was accomplished by non-aqueous reversed phase chromatography technique using only acetone and acetonitrile. An atmospheric pressure chemical ionization/mass spectrometry detector configured at selected ion monitoring mode was hyphenated with the separation system to detect phytosterols and phytosterol esters. Twenty-four types of these were consequently separated and then identified with their authentic components. The calibration curve was drawn in the range of about 5 to 25,000 ng/mL with a regression coefficient over 0.999. The limit of detection and limit of quantification, respectively, ranged from 0.9 to 3.0 ng/mL and from 3.0 to 11.0 ng/mL. Recovery rates ranged from 80 to 120%. The quantification results were subjected to statistical analysis and hierarchical clustering analysis, and were used to determine the differences in the amounts of phytosterols and phytosterol esters across tobacco leaves. The newly developed method succeeded in clarifying the whole composition of phytosterols and phytosterol esters in tobacco leaves and in explaining compositional differences across the variety of tobacco leaves.

  20. Development of a real-time reverse transcription loop-mediated isothermal amplification method for the rapid detection of porcine epidemic diarrhea virus.

    PubMed

    Yu, Xuewu; Shi, Lin; Lv, Xiaoping; Yao, Wei; Cao, Minghui; Yu, Hanxun; Wang, Xiurong; Zheng, Shimin

    2015-05-14

    Porcine epidemic diarrhea (PED) is an acute and highly contagious enteric disease characterized by severe enteritis, vomiting and watery diarrhea in swine. Recently, the outbreak of the epidemic disease has been a serious problem in swine industry. The objective of this study is to develop a rapid, sensitive, and real-time reverse transcription loop-mediated isothermal amplification (RT-LAMP) method for the detection of porcine epidemic diarrhea virus (PEDV) in less equipped laboratories. The optimal reaction condition of the current real-time RT-LAMP for PEDV was 62 °C for 45 min. It was capable of detecting PEDV from clinical samples and differentiating PEDV from several related porcine viruses, while it did not require additional expensive equipment. The minimum detection limit of the real-time RT-LAMP assay was 0.07PFU per reaction for PEDV RNA, making this assay approximately 100-fold more sensitive than that of one-step RT-PCR. By screening a panel of clinical specimens, the results showed that this method presented a similar sensitivity with real-time RT-PCR and was somewhat sensitive than one-step RT-PCR in detection of clinical samples. In this study, we have developed a new real-time RT-LAMP method, which is rapid, sensitive and efficient to detect PEDV.This method holds great promises not only in laboratory detection and discrimination of PEDV but also in large scale field and clinical studies.

  1. A novel three-step method for preparation of a TiB2-promoted LiBH4-MgH2 composite for reversible hydrogen storage.

    PubMed

    Kang, Xiangdong; Wang, Kuikui; Zhong, Yujie; Yang, Bing; Wang, Ping

    2013-02-14

    The reversible dehydrogenation properties of the 2LiBH(4)-MgH(2) composite can be effectively improved by incorporating heterogeneous nucleation agents, typically transition metal borides. A careful study of the 2LiBH(4)-MgH(2) composite with a titanium trifluoride (TiF(3)) additive finds that using the conventional one-step milling method renders only a partial conversion from TiF(3) to titanium boride (TiB(2)) through an intermediate of titanium hydride (TiH(2)). Based on a fundamental understanding of the reaction processes of the system, we developed a three-step preparation method, which involves pre-milling the LiBH(4)-TiF(3) mixture, isothermal treatment and milling together with MgH(2). A combination of phase/chemical state/microstructural analyses using X-ray diffraction, X-ray photoelectron spectroscopy and transmission electron microscopy techniques shows that the newly developed method can effectively promote the formation of TiB(2) and meanwhile, ensure a homogeneous dispersion of TiB(2) nanoparticles in the composite matrix. As a consequence, the composite sample prepared by the new method exhibits a favorable combination of high hydrogen capacity, fast reaction kinetics and satisfactory cyclic stability.

  2. A Single Gradient Stability-Indicating Reversed-Phase LC Method for the Estimation of Impurities in Omeprazole and Domperidone Capsules.

    PubMed

    Seshadri, Raja Kumar; Raghavaraju, Thummala Veera; Chakravarthy, Ivon Elisha

    2013-01-01

    A gradient reversed-phase liquid chromatographic (RP-LC) method was developed for the quantitative estimation of impurities in the pharmaceutical dosage form of Omeprazole and Domperidone capsules. The developed method is a stability-indicating test method for the estimation of impurities generated during the formulation and storage of Omeprazole and Domperidone capsules. The chromatographic separation was achieved on a column packed with octadecyl silane, having a column length of 250 mm and diameter of 4.6 mm with a particle size of 5 μm, and by following a gradient program using a combination of a monobasic potassium phosphate buffer (0.05M) and acetonitrile. Since the spectral properties were similar, both compounds' individual impurities were estimated at 285 nm. Forced degradation studies were performed on Omeprazole pellets (enteric coated) and Domperidone pellets (SR coated) encapsulated in size '1' hard gelatin capsules. Omeprazole and Domperidone were degraded using acid hydrolysis (0.1 N hydrochloric acid), base (0.1 N sodium hydroxide), oxidation (50% hydrogen peroxide), heat (105 °C), and UV light (254 nm). The established method was validated and found to be linear, accurate, precise, specific, robust, and rugged.

  3. Performance comparison of partial least squares-related variable selection methods for quantitative structure retention relationships modelling of retention times in reversed-phase liquid chromatography.

    PubMed

    Talebi, Mohammad; Schuster, Georg; Shellie, Robert A; Szucs, Roman; Haddad, Paul R

    2015-12-11

    The relative performance of six multivariate data analysis methods derived from or combined with partial least squares (PLS) has been compared in the context of quantitative structure-retention relationships (QSRR). These methods include, GA (genetic algorithm)-PLS, Monte Carlo uninformative variable elimination (MC-UVE), competitive adaptive reweighted sampling (CARS), iteratively retaining informative variables (IRIV), variable iterative space shrinkage approach (VISSA) and PLS with automated backward selection of predictors (autoPLS). A set of 825 molecular descriptors was computed for 86 suspected sports doping compounds and used for predicting their gradient retention times in reversed-phase liquid chromatography (RPLC). The correlation between molecular descriptors selected by each technique and the retention time was established using the PLS method. All models derived from a selected subset of descriptors outperformed the reference PLS model derived from all descriptors, with very small demands of computational time and effort. A performance comparison indicated great diversity of these methods in selecting the most relevant molecular descriptors, ranging from 28 for CARS to 263 for MC-UVE. While VISSA provided the lowest degree of over-fitting for the training set, CARS demonstrated the best compromise between the prediction accuracy and the number of selected descriptors, with the prediction error of as low as 46s for the external test set. Only ten descriptors were found to be common for all models, with the characteristics of these descriptors being representative of the retention mechanism in RPLC.

  4. Salivary aldehyde dehydrogenase--reversible oxidation of the enzyme and its inhibition by caffeine, investigated using fluorimetric method.

    PubMed

    Wierzchowski, Jacek; Pietrzak, Monika; Szelag, Malgorzata; Wroczyński, Piotr

    2008-05-01

    We have applied fluorimetric method to monitor aldehyde dehydrogenase (ALDH*) activity in human saliva samples to study inactivation, reactivation and inhibition of the enzyme. Saliva samples were collected to buffer stock solution, containing various thiols, and assayed in the presence of the fluorogenic substrate 6-dimethylamino-2-naphthaldehyde and NAD(+). Fluorescence of the produced 6-dimethylamino-2-naphthalene carboxylate was used to measure the reaction rate. Kinetic parameters for the highly fluorogenic substrate, 6-dimethylamino-2-naphthaldehyde were measured, with apparent K(m) of 7.9 microM at pH 7.3. The apparent K(m) for NAD(+) was 1.2 microM. The observed ALDH activity is unstable in the absence of thiols, but can be stabilized by 1mM glutathione, and inactivated enzyme can be re-activated within 10 min by treatment of 0.5 mM DTT. Two-assay procedure was applied to measure degree of inactivation of ALDH in saliva samples. It was found that degree of ALDH inactivation in fresh samples, stabilized by glutathione, is between 0% and 90%, with average value ca. 40%. Caffeine and theophylline were shown to be moderate inhibitors of salivary ALDH. Oxidation of the salivary ALDH in fresh saliva may be reliably measured using fluorimetric two-assay procedure. Preliminary statistics indicate that in most individuals this enzyme is partially inactive. Inhibition of the salivary ALDH by caffeine may have consequences for nutrition safety.

  5. Development and validation of a reverse phase-liquid chromatographic method for the estimation of butylated hydroxytoluene as antioxidant in paricalcitol hard gelatin capsule formulation dosage form

    PubMed Central

    Vaghela, Bhupendrasinh; Rao, Surendra Singh; Sharma, Nitish; Balakrishna, P.; Reddy, A. Malleshwar

    2011-01-01

    Introduction: A novel and simple isocratic reverse phase liquid chromatographic (RP-LC) method was developed for the quantitative determination of antioxidant-butylated hydroxy toluene (BHT) in paricalcitol hard gelatin capsule. In the paricalcitol capsule BHT concentration is very low. This method is precisely able to estimate BHT at low concentration at about 0.0039 μg/mL and to separate BHT from paricalcitol main compound and other oil-based excipients. Materials and Methods: The method was developed by using ACE-C18 (250 × 4.6 mm) 5-μm column with mobile phase containing a mixture of solvent A (water) and solvent B (methanol) in the ratio of 5:95 v/v, respectively. The flow rate was 0.8 mL/min with column temperature of 45°C and detection wavelength at 277 nm. The developed method was validated as per ICH guidelines with respect to specificity, linearity, limit of detection, limit of quantification, accuracy, precision and robustness. Results: In the precision study the % RSD for the result of BHT was below 1.5% at target concentration level. The limit of detection, limit of quantification are 0.0013 μg/ mL and 0.0039 μg/mL, respectively and precision at LOQ level (0.0039 μg/mL) was with 6.2% RSD. The method was linear with concentration rage of 0.0039-0.64 μg/ mL with the correlation coefficient greater than 0.999 and % bias at 100% level are within + 2%. The percentage recoveries for BHT were calculated observed from 98.8 to 104.8%. Conclusion: The developed method was found to be precise, accurate, linear, selective and robust. PMID:23781463

  6. An off-line high pH reversed-phase fractionation and nano-liquid chromatography-mass spectrometry method for global proteomic profiling of cell lines.

    PubMed

    Wang, Hang; Sun, Shengnan; Zhang, Yi; Chen, Si; Liu, Ping; Liu, Bin

    2015-01-01

    Liquid chromatography coupled to tandem mass spectrometry (LC/MS/MS) and first-dimensional fractionation is widely used for reducing sample complexity in large-scale proteomic profiling experiments. However, the limited number of proteins identified and the relatively long running time are a barrier to the successful application of this approach. In this study, off-line high pH reversed-phase fractionation (RPF) was combined with nano-LC-MS/MS in order to develop an improved method for global proteomic profiling of different cell lines. In the first dimensional reverse phase HPLC separation, 300 μg of digested cell protein was separated into 78 fractions under high pH conditions and condensed into 26 fractions for the second nano-LC-MS/MS analysis at low pH. The chromatographic conditions for the first and second steps were optimized, and the accuracy and reproducibility of protein quantification were investigated with an average Pearson correlation coefficient of 0.94. The method was then applied in the identification of proteins in six common cell lines (DMS, MFM, HepG2, U2OS, 293T and yeast), which resulted in identification of 7300-8500 and 8956 proteins in heavy/light labeled and label-free cell samples, respectively, in 1.5 days. The performance of the developed method was compared with isoelectric focusing (IEF)-nano-LC-MS/MS and the previously reported method; and off-line high pH RPF-nano-LC-MS/MS proved advantageous in terms of the number of proteins identified and the analytical time needed to achieve a successful global proteomic profiling outcome. The RPF-nano-LC-MS/MS method identified more proteins from low abundance (150 μg) samples with an average sequence coverage for each cell line of 23.4-35.1%. RPF-nano-LC-MS/MS may therefore be an efficient alternative tool for achieving improved proteomic coverage of multiple cell lines. Copyright © 2014 Elsevier B.V. All rights reserved.

  7. Reversed phase liquid chromatography method with fluorescence detection of gemifloxacin in rat plasma and its application to the pharmacokinetic study.

    PubMed

    Kaiser, Moacir; Grünspan, Lauren D; Costa, Teresa Dalla; Tasso, Leandro

    2011-11-15

    A simple, accurate and precise high-performance liquid chromatographic method with fluorescence detection was developed and validated for the determination of gemifloxacin (GEM) in rat plasma using furosemide as internal standard (I.S.). Plasma samples were pretreated by direct deproteinization and all samples and standard solutions were chromatographed at 45°C using triethylamine solution (0.5%, v/v, pH 3.0±0.1), methanol and acetonitrile (63:30:7, v/v/v) as the mobile phase. Chromatographic resolution was achieved using a RP-C(18) column (Atlantis, Waters, 150 mm × 4.6 mm, 5 μm) at a flow rate of 1.0 mL min(-1) and an injection volume of 30 μL. The analytes were measured by fluorescence detection with excitation and emission wavelengths of 344 nm and 399 nm, respectively. The retention times for GEM and I.S. were approximately 7.5 and 12.6 min, respectively. The lower limit of quantitation (LLOQ) was 20 ng mL(-1) and the calibration curves were linear over a concentration range of 20-5000 ng mL(-1). The intra- and inter-day precisions, expressed by relative standard deviation (R.S.D.) were lower than 6.24% and 4.49%, respectively. The accuracy ranged from 91.3% to 112% and from 98.8% to 106% for the lower and upper limit of quantitation of the calibration curve, respectively. Ratio of peak area of analyte to I.S. was used for quantification of plasma samples. No interferences from endogenous substances were found. The recovery of GEM and I.S. from plasma was greater than 90%. Drug stability in plasma was shown at room temperature for 4h, after three freeze-thaw cycles for 24h, in freezer at -80°C for 60 days, and in the autosampler after processing for 12h. The utility of the assay was confirmed by the successful analysis of plasma samples from GEM pharmacokinetics studies in the rats after intravenous administration. Copyright © 2011 Elsevier B.V. All rights reserved.

  8. A high pH based reversed-phase high performance liquid chromatographic method for the analysis of aminoglycoside plazomicin and its impurities.

    PubMed

    Tan, Li; Wlasichuk, Kenneth B; Schmidt, Donald E; Campbell, Robert L; Hirtzer, Pam; Cheng, Lisa; Karr, Dane E

    2012-07-01

    A reversed-phase high performance liquid chromatographic (RP-HPLC) method has been developed for the aminoglycoside (AG) plazomicin (ACHN-490). This method employed a high pH mobile phase (pH>11) with a gradient of 0.25 M ammonium hydroxide in water and acetonitrile, an XBridge C(18) column and UV detection at 210 nm. Although the molar UV absorption of plazomicin is weak, the high pH conditions of this method allow for higher loadings, which compensates for the inherent low UV sensitivity. Under these high pH conditions, impurities and degradants were base line separated from plazomicin. The mobile phases used for this method allowed for on-line mass detection for the impurities and degradants. The RP-HPLC method has been validated in terms of specificity, linearity and range, accuracy, and precision. The analytical method met specificity requirements of a homogenous peak with no interferences from the blank or from the known impurities in plazomicin. The linearity of the method for the plazomicin impurity determination was excellent, with a coefficient of determination (r(2)) of 0.9993, over the freebase (FB) concentration range of 0.0025-3.0 mg/mL. The method is capable of detecting impurities down to 0.1% of the peak area of plazomicin. A single point standard at a concentration of 1.0 mg/mL FB was validated over the range of 50-150% for quantitation of the freebase content (the assay) in bulk drug substance. The mean recoveries of FB are in the range 98.6-102.0% with a mean RSD (relative standard deviation) <1.0%. The study also examined the method precision for purity, impurities and the assay with two instruments on two different days. The method showed adequate accuracy and precision for the intended use. This high pH method was successfully used to determine the impurity and measure the drug content in the final plazomicin drug substance. In addition, the method with an on-line mass spectrometry detector has been used to characterize the structures of the

  9. Apparatus and method for controlling the rotary airlocks in a coal processing system by reversing the motor current rotating the air lock

    DOEpatents

    Groombridge, Clifton E.

    1996-01-01

    An improvement to a coal processing system where hard materials found in the coal may cause jamming of either inflow or outflow rotary airlocks, each driven by a reversible motor. The instantaneous current used by the motor is continually monitored and compared to a predetermined value. If an overcurrent condition occurs, indicating a jamming of the airlock, a controller means starts a "soft" reverse rotation of the motor thereby clearing the jamming. Three patterns of the motor reversal are provided.

  10. Development and validation of a reversed-phase HPLC method for determination of nitrendipine in rat plasma: application to pharmacokinetic studies.

    PubMed

    Venishetty, Vinay Kumar; Durairaj, Chandrasekar; Sistla, Ramakrishna; Yamsani, Madhusudhan Rao; Diwan, Prakash V

    2007-04-01

    A simple and sensitive method for the determination of nitrendipine in rat plasma was developed using high-performance liquid chromatography (HPLC). The procedure involves extraction of nitrendipine in dichloromethane/sodium hydroxide, followed by reversed phase HPLC using a Waters, Spherisorb ODS2 (250 x 4.6 mm, 5 microm) column and UV detection at 238 nm. The retention times of nitrendipine and internal standard (felodipine) were 5.0 min and 7.5 min, respectively. The calibration curves were linear over the range of 5 ng/mL (lower limit of quantification, LOQ) to 200 ng/mL for nitrendipine. The intra- and inter-day coefficients of variation for all criteria of validation were less than 15% over the linearity range. The sensitivity and precision of the method were within the accepted limits (< 15%) throughout the validation period. The present method was also successfully applied for the study of plasma pharmacokinetics of nitrendipine loaded solid lipid nanoparticles (SLN) in rats.

  11. Development of a Reverse Transcription Loop-Mediated Isothermal Amplification Method for the Rapid Detection of Subtype H7N9 Avian Influenza Virus

    PubMed Central

    Bao, Hongmei; Zhao, Yuhui; Wang, Yunhe; Xu, Xiaolong; Shi, Jianzhong; Zeng, Xianying; Wang, Xiurong; Chen, Hualan

    2014-01-01

    A novel influenza A (H7N9) virus has emerged in China. To rapidly detect this virus from clinical samples, we developed a reverse transcription loop-mediated isothermal amplification (RT-LAMP) method for the detection of the H7N9 virus. The minimum detection limit of the RT-LAMP assay was 0.01 PFU H7N9 virus, making this method 100-fold more sensitive to the detection of the H7N9 virus than conventional RT-PCR. The H7N9 virus RT-LAMP assays can efficiently detect different sources of H7N9 influenza virus RNA (from chickens, pigeons, the environment, and humans). No cross-reactive amplification with the RNA of other subtype influenza viruses or of other avian respiratory viruses was observed. The assays can effectively detect H7N9 influenza virus RNA in drinking water, soil, cloacal swab, and tracheal swab samples that were collected from live poultry markets, as well as human H7N9 virus, in less than 30 min. These results suggest that the H7N9 virus RT-LAMP assays were efficient, practical, and rapid diagnostic methods for the epidemiological surveillance and diagnosis of influenza A (H7N9) virus from different resource samples. PMID:24689044

  12. Development and validation of a reversed-phase HPLC method for simultaneous estimation of ambroxol hydrochloride and azithromycin in tablet dosage form.

    PubMed

    Shaikh, K A; Patil, S D; Devkhile, A B

    2008-12-15

    A simple, precise and accurate reversed-phase liquid chromatographic method has been developed for the simultaneous estimation of ambroxol hydrochloride and azithromycin in tablet formulations. The chromatographic separation was achieved on a Xterra RP18 (250 mm x 4.6 mm, 5 microm) analytical column. A Mixture of acetonitrile-dipotassium phosphate (30 mM) (50:50, v/v) (pH 9.0) was used as the mobile phase, at a flow rate of 1.7 ml/min and detector wavelength at 215 nm. The retention time of ambroxol and azithromycin was found to be 5.0 and 11.5 min, respectively. The validation of the proposed method was carried out for specificity, linearity, accuracy, precision, limit of detection, limit of quantitation and robustness. The linear dynamic ranges were from 30-180 to 250-1500 microg/ml for ambroxol hydrochloride and azithromycin, respectively. The percentage recovery obtained for ambroxol hydrochloride and azithromycin were 99.40 and 99.90%, respectively. Limit of detection and quantification for azithromycin were 0.8 and 2.3 microg/ml, for ambroxol hydrochloride 0.004 and 0.01 microg/ml, respectively. The developed method can be used for routine quality control analysis of titled drugs in combination in tablet formulation.

  13. Development and Validation of Reverse-phase High-performance Liquid Chromatography Method for Estimation of Citicoline Sodium in Bulk and Dosage Form.

    PubMed

    Maradiya, H K; Pansara, Vasundhara H

    2013-03-01

    A simple, accurate, precise and sensitive reverse-phase high-performance liquid chromatography method for the determination of citicoline sodium has been developed and validated. Drug was resolved on a C18 column (Phenomenex Luna, 250×4.6 mm, 10μ), utilizing mobile phase of potassium dihydrogen phosphate buffer and acetonitrile in a ratio of 30:70. Mobile phase was delivered at the flow rate of 1.0 ml/min and detection was carried out at 272 nm. Separation was completed within 2.22 min. Calibration curve was linear with good correlation coefficient (R(2)=0.999) over a concentration range 10-60 μg/ml. Recovery was between 98.84 and 101.76%. Method was found to be reproducible with relative standard deviation for intra and interday precision of <2.0% over the said concentration range. The method was successfully applied to the determination of the citicoline sodium, it can be very useful and an alternate to performing the stability studies.

  14. Development of the reverse passive latex agglutination method for the detection and quantification of the genus Nitrospira in the wastewater treatment process.

    PubMed

    Okumura, Takekazu; Nagai, Fumiko; Yamamoto, Shuta; Hashimoto, Toshikazu; Ito, Masahiko; Sawada, Haruji

    2008-02-01

    This report describes a new immunological method for the detection and quantification of Nitrospira populations using the reverse passive latex agglutination (RPLA). The numbers of the genus Nitrospira have been quantified only by molecular biological techniques such as FISH and quantitative PCR to date. Using high-density latex particles and a specific polyclonal antibody, Nitrospira populations in the wastewater treatment process were quantified in the shortest 4 h of incubation. The minimum detectable number of Nitrospira cells was 7.0x10(5) (log(10) 5.85) cells/ml. It is thought that the RPLA method can quantify Nitrospira populations more simply, economically, and speedily than molecular biological techniques or the culture method, because this procedure has a simple protocol and does not require the use of specialized equipment, expensive reagents, or technical skill. Therefore it is applicable for use in the everyday control and maintenance of water quality in wastewater treatment facilities where equipment is not sufficient or in the field.

  15. Development of a reverse transcription loop-mediated isothermal amplification method for the rapid detection of subtype H7N9 avian influenza virus.

    PubMed

    Bao, Hongmei; Zhao, Yuhui; Wang, Yunhe; Xu, Xiaolong; Shi, Jianzhong; Zeng, Xianying; Wang, Xiurong; Chen, Hualan

    2014-01-01

    A novel influenza A (H7N9) virus has emerged in China. To rapidly detect this virus from clinical samples, we developed a reverse transcription loop-mediated isothermal amplification (RT-LAMP) method for the detection of the H7N9 virus. The minimum detection limit of the RT-LAMP assay was 0.01 PFU H7N9 virus, making this method 100-fold more sensitive to the detection of the H7N9 virus than conventional RT-PCR. The H7N9 virus RT-LAMP assays can efficiently detect different sources of H7N9 influenza virus RNA (from chickens, pigeons, the environment, and humans). No cross-reactive amplification with the RNA of other subtype influenza viruses or of other avian respiratory viruses was observed. The assays can effectively detect H7N9 influenza virus RNA in drinking water, soil, cloacal swab, and tracheal swab samples that were collected from live poultry markets, as well as human H7N9 virus, in less than 30 min. These results suggest that the H7N9 virus RT-LAMP assays were efficient, practical, and rapid diagnostic methods for the epidemiological surveillance and diagnosis of influenza A (H7N9) virus from different resource samples.

  16. Development of a reverse transcription loop-mediated isothermal amplification method for the rapid detection of avian influenza virus subtype H7.

    PubMed

    Bao, Hongmei; Wang, Xiurong; Zhao, Yuhui; Sun, Xiaodong; Li, Yanbing; Xiong, Yongzhong; Chen, Hualan

    2012-01-01

    A rapid and sensitive reverse transcription loop-mediated isothermal amplification (RT-LAMP) method for the detection of the H7 avian influenza virus (H7 AIV) isotype was developed. The minimum detection limit of the RT-LAMP assay was 0.1-0.01 PFU per reaction for H7 AIV RNA, making this assay 100-fold more sensitive than the conventional RT-PCR method. This RT-LAMP assay also has the capacity to detect both high- and low-pathogenic H7 AIV strains. Using a pool of RNAs extracted from influenza viruses corresponding to all 15 HA subtypes (in addition to other avian pathogenic viruses), the RT-LAMP system was confirmed to amplify only H7 AIV RNA. Furthermore, specific pathogen free (SPF) chickens were infected artificially with H7 AIV, throat and cloacal swabs were collected, and viral shedding was examined using viral isolation, RT-PCR and RT-LAMP. Shedding was detected following viral isolation and RT-LAMP one day after infection, whereas viral detection using RT-PCR was effective only on day 3 post-infection. These results indicate that the RT-LAMP method could facilitate epidemiological surveillance and the rapid diagnosis of the avian influenza subtype H7. Copyright © 2011 Elsevier B.V. All rights reserved.

  17. Simple differentiation method of mumps Hoshino vaccine strain from wild strains by reverse transcription loop-mediated isothermal amplification (RT-LAMP).

    PubMed

    Yoshida, Naoko; Fujino, Motoko; Ota, Yoshinori; Notomi, Tsugunori; Nakayama, Tetsuo

    2007-01-26

    Mumps virus is still circulating and annual mumps outbreaks occur with fluctuating magnitudes in Japan. Aseptic meningitis has been reported after vaccination and it would be of importance to determine whether this was related to the vaccination. The objective of this study was to develop a sensitive, specific and rapid diagnostic method for the differentiation of the Hoshino vaccine strain from circulating wild types. We developed a reverse transcription loop-mediated isothermal amplification (RT-LAMP) method of the hemagglutinin neuraminidase (HN) region for the detection of mumps virus genome from clinical samples. The typical ladder pattern disappeared after the LAMP products of the Hoshino vaccine strain were digested with ScaI, but those of wild types were not cut by ScaI. We obtained 19 cerebro spinal fluids (CSF) from the patients with aseptic meningitis and 17 salivary swab samples from the patients with acute parotitis after mumps vaccination, in which one case was complicated with orchitis. Mumps virus genome was detected in 18 CSF samples and in all NPS by RT-LAMP. The Hoshino vaccine strain was identified in 16 out of 18 CSF RT-LAMP positives and in 11 out of 17 NPS samples and the remaining samples were identified as wild types. RT-LAMP followed by ScaI digestion is a sensitive, simple and rapid differential method and useful for laboratory surveillance for vaccine-adverse events.

  18. [A reverse phase high performance liquid chromatography-UV spectrometry method for the analysis of several intrinsic adrenal delta 4-steroid concentrations].

    PubMed

    Saisho, S; Shimozawa, K; Yata, J

    1986-12-20

    Taking an advantage of the property of delta 4-steroid that have a maximum absorbance around 250 nm wave-length of ultraviolet, we devised an assay method for the determination of serum delta 4-steroids concentration using a reverse phase high performance liquid chromatography (HPLC)-UV spectrometry. The assay procedure was as follows: A mixed solvent containing methanol, acetonitrile and water in 55/3/42 by volume was used as a mobile phase, and which was pumped at a constant flow rate of 1.5 ml/min. The main column and precolumn used were ERC-ODS-1161 (phi 6 mm X 10 cm) and ERC-ODS-1652 (phi 6mm X 3 cm), respectively. Two liquid-liquid extraction methods were used. One was a conventional method using dichloromethane for an extraction solvent, and the other was a simplified method using Extrelut column and ethyl acetate. Before a practical assay we examined the retention time of each steroid determined and its ratio of peak height to that of the internal standard (dexamethasone). We found good correlations between the concentrations of cortisol (F), 17 alpha-hydroxyprogesterone (17-OHP) and 21-deoxycortisol (21-DOF) estimated by this HPLC method and those by highly specific radioimmunoassay method. The concentrations of cortisone (E) and F of eight umbilical venous blood specimens were 159.7 +/- 26.3 (Mean +/- SD) ng/ml and 93.3 +/- 58.9 ng/ml, respectively, and 17-OHP was detected 7 of them and its concentration was 17.4 +/- 12.4 ng/ml. On the other hand, 17-OHP and 21-DOF peaks could not be detected in 1 month old normal infants.(ABSTRACT TRUNCATED AT 250 WORDS)

  19. Stability-indicating capillary zone electrophoresis method for the assessment of recombinant human interleukin-11 and its correlation with reversed-phase liquid chromatography and biossay.

    PubMed

    Souto, Ricardo Bizogne; Stamm, Fernanda Pavani; Schumacher, Jéssica Barbieri; Cardoso, Clovis Dervil Appratto; de Freitas, Guilherme Weber; Perobelli, Rafaela Ferreira; Dalmora, Sérgio Luiz

    2014-06-01

    A stability-indicating capillary zone electrophoresis (CZE) method was validated for the analysis of recombinant human interleukin-11(rhIL-11) using rupatadine fumarate, as internal standard (IS). A fused-silica capillary, (50 µm i.d.; effective length, 40 cm) was used at 25°C; the applied voltage was 20 kV. The background electrolyte solution consisted of 50 mmol L(-1) sodium dihydrogen phosphate solution at pH 3.0. Injections were performed using a pressure mode at 50 mbar for 45 s, with detection by photodiode array detector set at 196 nm. Specificity and stability-indicating capability were established in degradation studies, which also showed that there was no interference of the excipients. The method was linear over the concentration range of 1.0-300 µg mL(-1) (r(2)=0.9992) and the limit of detection (LOD) and limit of quantitation (LOQ) were 0.2 µg mL(-1) and 1.0 µg mL(-1), respectively. The accuracy was 100.4% with bias lower than 1.1%. Moreover, the in vitro cytotoxicity test of the degraded products showed significant differences (p<0.05). The method was applied for the content/potency assessment of rhIL-11 in biopharmaceutical formulations, and the results were correlated to those of a validated reversed-phase LC method (RP-LC) and an TF-1 cell culture assay, showing non-significant differences (p>0.05). In addition the CZE and RP-LC methods were applied for the analysis of rhIL-11 in human plasma. Therefore, the proposed alternative method can be applied to monitor stability, to assure the batch-to-batch consistency and quality of the bulk and finished biotechnology-derived medicine.

  20. Detection of avian retroviruses in vaccines by amplification on DF-1 cells with immunostaining and fluorescent product-enhanced reverse transcriptase endpoint methods.

    PubMed

    Birmingham, Cheryl L; Dupont, Dominique; Riou, Patrice; Armanet, Corinne; Edamura, Kerrie Nichol; Martinho, Briolange; Serres, Aurelie; Jacouton, Severine; Detrez, Valerie; McNeil, Bryan; Schreiber, Martha; Gaillac, David; Bonnevay, Thierry; Gisonni-Lex, Lucy; Mallet, Laurent

    2013-05-01

    In order to ensure the safety of vaccines produced on avian cells, rigorous testing for the absence of avian retroviruses must be performed. Current methods used to detect avian retroviruses often exhibit a high invalid-test/false-positive rate, rely on hard-to-secure reagents, and/or have readouts that are difficult to standardize. Herein, we describe the development and validation of two consistent and sensitive methods for the detection of avian retroviruses in vaccines: viral amplification on DF-1 cells followed by immunostaining for the detection of avian leukosis virus (ALV) and viral amplification on DF-1 cells followed by fluorescent product-enhanced reverse transcriptase (F-PERT) for the detection of all avian retroviruses. Both assays share an infectivity stage on DF-1 cells followed by a different endpoint readout depending on the retrovirus to be detected. Validation studies demonstrated a limit of detection of one 50% cell culture infectious dose (CCID(50))/ml for retrovirus in a 30-ml test inoculum volume for both methods, which was as sensitive as a classical method used in the vaccine industry, namely, viral amplification on primary chicken embryo fibroblasts followed by the complement fixation test for avian leukosis virus (COFAL). Furthermore, viral amplification on DF-1 cells followed by either immunostaining or F-PERT demonstrated a sensitivity that exceeds the regulatory requirements for detection of ALV strains. A head-to-head comparison of the two endpoint methods showed that viral amplification on DF-1 cells followed by F-PERT is a suitable method to be used as a stand-alone test to ensure that vaccine preparations are free from infectious avian retroviruses.

  1. Time reversal method for damage detection of cracked plates in the medium frequency range: the case of wavelength-size cracks

    NASA Astrophysics Data System (ADS)

    Pasco, Yann; Pinsonnault, Jérôme; Berry, Alain; Masson, Patrice; Micheau, Philippe

    2006-03-01

    The use of time reversal methods for localization and characterization of damages in plates is usually combined with high frequency guided waves in a local elastic wave propagation formulation. In such a situation, pulses and echos may be clearly separated in time. As a consequence, the diffracted field on a damage with large geometrical dimensions compared to the wavelength used for wave propagation allows to consider the structure itself as "near infinite" because the modal behavior is not apparent. However, those high requencies may not be required and in the presented approach, medium frequencies are used and boundary conditions need to be considered. The interest of this frequency range is in using lightweight signal processing devices limited to low data transfer rates as expected for in flight fuselage skin inspections. It also allows to filter artifacts like very small damages in the structure. This study focuses on the case of wavelengths which are in the order of the largest geometrical dimension of the cracks. In the paper, a modelling tool is first extended to describe the vibration behavior of pristine and damaged finite thin plates in the low and medium frequency range below 50 kHz. The proposed analytical model employs a Hierarchical Trigonometric Functions Set (HTFS) to characterize homogeneous plates with through cracks. To approximate the effect of a small crack in a plate for all combinations of classical boundary conditions, high order approximation functions are required. The proposed approach takes the advantage of the stability of the HTFS for these high orders. A notable advantage of this model is that it does not require a dense uniform meshing of the plate, with a minimum of 10 nodes per wavelength, as most finite element models require. The time reversal concept introduced before is thus validated with this model for a finite plate with known boundary conditions. Experimental validation of the model is conducted in the time domain for

  2. Rapid evaluation of reverse-osmosis membranes

    NASA Technical Reports Server (NTRS)

    Hollahan, J. R.; Wydeven, T.

    1972-01-01

    Simultaneous reverse-osmosis tests conducted with centrifuges having multiple compartment heads are discussed. Equipment for retaining reverse-osmosis membrane is illustrated. Method of conducting tests is described.

  3. Simultaneous determination of linagliptin and metformin by reverse phase-high performance liquid chromatography method: An application in quantitative analysis of pharmaceutical dosage forms.

    PubMed

    Vemula, Prathyusha; Dodda, Dilip; Balekari, Umamahesh; Panga, Shyam; Veeresham, Ciddi

    2015-01-01

    To enhance patient compliance toward treatment in diseases like diabetes, usually a combination of drugs is prescribed. Therefore, an anti-diabetic fixed-dose combination of 2.5 mg of linagliptin 500 mg of metformin was taken for simultaneous estimation of both the drugs by reverse phase-high performance liquid chromatography (RP-HPLC) method. The present study aimed to develop a simple and sensitive RP-HPLC method for the simultaneous determination of linagliptin and metformin in pharmaceutical dosage forms. The chromatographic separation was designed and evaluated by using linagliptin and metformin working standard and sample solutions in the linearity range. Chromatographic separation was performed on a C18 column using a mobile phase of 70:30 (v/v) mixture of methanol and 0.05 M potassium dihydrogen orthophosphate (pH adjusted to 4.6 with orthophosphoric acid) delivered at a flow rate of 0.6 mL/min and UV detection at 267 nm. Linagliptin and metformin shown linearity in the range of 2-12 μg/mL and 400-2400 μg/mL respectively with correlation co-efficient of 0.9996 and 0.9989. The resultant findings analyzed for standard deviation (SD) and relative standard deviation to validate the developed method. The retention time of linagliptin and metformin was found to be 6.3 and 4.6 min and separation was complete in <10 min. The method was validated for linearity, accuracy and precision were found to be acceptable over the linearity range of the linagliptin and metformin. The method was found suitable for the routine quantitative analysis of linagliptin and metformin in pharmaceutical dosage forms.

  4. Development and validation of reversed-phase high-performance liquid chromatography method for estimation of rizatriptan benzoate in oral strip formulations

    PubMed Central

    Bhagawati, S. T.; Reddy, M. Sreenivasa; Avadani, Kiran; Muddukrishna, B.S.; Dengale, Swapnil J.; Bhat, Krishnamurthy

    2014-01-01

    Aim: A simple, accurate, precise, and reproducible reversed-phase high-performance liquid chromatography (RP-HPLC) method was developed and validated for the determination of rizatriptan benzoate in oral strip formulations. Methodology: Separation was achieved under optimized chromatographic condition on a Hiper C18 column (250 mm × 4.6 mm, 5 m) using Shimadzu HPLC. The mobile phase consisted of phosphate buffer (20 mM pH adjusted to 3.2 ± 0.005 with ortho phosphoric acid): Methanol in the ratio of 70:30 v/v with isocratic elution at a flow rate of 1 ml/min at ambient temperature was performed. The detection was carried out at 225 nm using photodiode array detector. The method was validated as per Q1A (R2) guidelines and suitability of developed method was ascertained by using optimized oral strip formulation. Results: The retention time of rizatriptan benzoate was found to be 5.17 min, and the calibration curve was linear in the concentration range of 0.20-20 mg/mL (r2= 0.9998). The limit of detection and the limit of quantitation were found to be 0.016 mg/mL and 0.0528 mg/mL, respectively. Method validation parameters were found to be within the specified limits. The percentage drug content of oral strips formulation was found to be 98.96 ± 1.37. Conclusion: The proposed HPLC method may be used efficiently for routine and quality control analysis of rizatriptan benzoate in pharmaceutical formulations. PMID:25538465

  5. Multi-walled carbon nanotubes as alternative reversed-dispersive solid phase extraction materials in pesticide multi-residue analysis with QuEChERS method.

    PubMed

    Zhao, Pengyue; Wang, Lei; Zhou, Li; Zhang, Fengzu; Kang, Shu; Pan, Canping

    2012-02-17

    A multi-residue method based on modified QuEChERS sample preparation with multi-walled carbon nanotubes (MWCNTs) as reversed-dispersive solid phase extraction (r-DSPE) material and gas chromatography-mass spectrometry determination by selected ion monitoring (GC/MS-SIM) mode was validated on 30 representative pesticides residues in vegetables and fruits. The acetonitrile-based QuEChERS (quick, easy, cheap, effective, rugged and safe) sample preparation technique was used to obtain the extracts, and the further cleanup was carried out by applying r-DSPE. It was found that the amount of MWCNTs influenced the cleanup performance and the recoveries. The optimal amount of 10mg MWCNTs was suitable for cleaning up all selected matrices, as a suitable alternative r-DSPE material to primary secondary amine (PSA). This method was validated on cabbage, spinach, grape and orange spiked at concentration levels of 0.02 and 0.2 mg/kg. The recoveries of 30 pesticides were in the range of 71-110%, with relative standard deviations (RSDs, n=5) lower than 15%. Matrix effects were observed by comparing the slope of matrix-matched standard calibration with that of solvent. Good linearity was achieved at the concentration levels of 0.02-0.5 mg/L. The limits of quantification (LOQs) and the limits of detection (LODs) for 30 pesticides ranged from 0.003 to 0.05 mg/kg and 0.001 to 0.02 mg/kg at the signal-to-noise ratio (S/N) of 10 and 3, respectively. The method was successfully applied to analysis real samples in Beijing. In conclusion, the modified QuEChERS method with MWCNTs cleanup step showed reliable method validation performances and good cleanup effects in this study.

  6. New in situ capture quantitative (real-time) reverse transcription-PCR method as an alternative approach for determining inactivation of Tulane virus.

    PubMed

    Wang, Dapeng; Xu, Shuxia; Yang, David; Young, Glenn M; Tian, Peng

    2014-04-01

    Human noroviruses (HuNoVs) are the major cause of epidemic nonbacterial gastroenteritis. Although quantitative (real-time) reverse transcription-PCR (qRT-PCR) is widely used for detecting HuNoVs, it only detects the presence of viral RNA and does not indicate viral infectivity. Human blood group antigens (HBGAs) have been identified as receptors/co-receptors for both HuNoVs and Tulane virus (TV) and are crucial for viral infection. We propose that viral infectivity can be evaluated with a molecular assay based on receptor-captured viruses. In this study, we employed TV as an HuNoV surrogate to validate the HBGA-based capture qRT-PCR method against the 50% tissue culture infectious dose (TCID50) method. We employed type B HBGA on an immuno-well module to concentrate TV, followed by amplification of the captured viral genome by in situ qRT-PCR. We first demonstrated that this in situ capture qRT-PCR (ISC-qRT-PCR) method could effectively concentrate and detect TV. We then treated TV under either partial or full inactivation conditions and measured the remaining infectivity by ISC-qRT-PCR and a tissue culture-based amplification method (TCID50). We found that the ISC-qRT-PCR method could be used to evaluate virus inactivation deriving from damage to the capsid and study interactions between the capsid and viral receptor. Heat, chlorine, and ethanol treatment primarily affect the capsid structure, which in turns affects the ability of the capsid to bind to viral receptors. Inactivation of the virus by these methods could be reflected by the ISC-qRT-PCR method and confirmed by TCID50 assay. However, the loss of the infectivity caused by damage to the viral genome (such as that from UV irradiation) could not be effectively reflected by this method. Despite this limitation, the ISC-qRT-PCR provides an alternative approach to determine inactivation of Tulane virus. A particular advantage of the ISC-qRT-PCR method is that it is also a faster and easier method to effectively

  7. A reversed-phase high-performance liquid chromatographic method for the determination of zafirlukast in pharmaceutical formulations and human plasma.

    PubMed

    Süslü, Incilay; Altinöz, Sacide

    2006-01-01

    Zafirlukast (ZAF) is a leukotriene receptor antagonist used in the treatment of chronic asthma. In this study, a simple and sensitive reversed-phase, high-performance liquid chromatographic method was developed for the determination of ZAF in pharmaceutical formulations and human plasma. Piribedil was used as an internal standard. Analysis was carried out on a Nucleosil C18 100 A (150 mm x 4.6 mm id, 5 Vm) column with acetonitrile-pH 3.0 acetate buffer (70 + 30, v/v) as the mobile phase at a flow rate of 0.8 mL/min. The peak was detected by an ultraviolet detector set at a wavelength of 240 nm. The retention times were about 3.9 min for piribedil and 5.8 min for ZAF. The developed method was applied to the determination of ZAF in its pharmaceutical formulation and spiked human plasma. For quantification of ZAF in spiked plasma, proteins were precipitated with ethanol before chromatographic analysis. The calibration range was linear from 49.69-437.50 ng/mL in spiked plasma. The absolute recovery from spiked plasma was 98.73 +/- 0.42% at a concentration of 254.78 ng/mL of ZAF. No endogenous substances from plasma were found to interfere.

  8. Development and validation of a reversed-phase ion-pair high-performance liquid chromatographic method for the determination of risedronate in pharmaceutical preparations.

    PubMed

    Kyriakides, Demetra; Panderi, Irene

    2007-02-12

    A stability indicating, reversed-phase ion-pair high-performance liquid chromatographic method was developed and validated for the determination of risedronate in pharmaceutical dosage forms. The determination was performed on a BDS C(18) analytical column (250 mm x 4.6 mm i.d., 5 microm particle size); the mobile phase consisted of 0.005 M tetrabutylammonium hydroxide and 0.005 M pyrophosphate sodium (pH 7.0) mixed with acetonitrile in a ratio (78:22, v/v) and pumped at a flow rate 1.00 mL min(-1). The ultraviolet (UV) detector was operated at 262 nm. The retention times of magnesium ascorbyl phosphate, which was used as internal standard and risedronate were 4.94 and 5.95 min, respectively. The calibration graph was ranged from 2.50 to 20.00 microg mL(-1), while detection and quantitation limits were found to be 0.48 and 1.61 microg mL(-1), respectively. The intra- and inter-day percentage relative standard deviations, %R.S.D., were less than 5.9%, while the relative percentage error, %E(r), was less than 0.4%. The method was applied to the quality control of commercial tablets and content uniformity test and proved to be suitable for rapid and reliable quality control.

  9. Synthesis of MSnO{sub 3} (M = Ba, Sr) nanoparticles by reverse micelle method and particle size distribution analysis by whole powder pattern modeling

    SciTech Connect

    Ahmed, Jahangeer; Blakely, Colin K.; Bruno, Shaun R.; Poltavets, Viktor V.

    2012-09-15

    Highlights: ► BaSnO{sub 3} and SrSnO{sub 3} nanoparticles synthesized using the reverse micelle method. ► Particle size and size distribution studied by whole powder pattern modeling. ► Nanoparticles are of optimal size for investigation in dye-sensitized solar cells. -- Abstract: Light-to-electricity conversion efficiency in dye-sensitized solar cells critically depends not only on the dye molecule, semiconducting material and redox shuttle selection but also on the particle size and particle size distribution of the semiconducting photoanode. In this study, nanocrystalline BaSnO{sub 3} and SrSnO{sub 3} particles have been synthesized using the microemulsion method. Particle size distribution was studied by whole powder pattern modeling which confirmed narrow particle size distribution with an average size of 18.4 ± 8.3 nm for SrSnO{sub 3} and 15.8 ± 4.2 nm for BaSnO{sub 3}. These values are in close agreement with results of transmission electron microscopy. The prepared materials have optimal microstructure for successive investigation in dye-sensitized solar cells.

  10. Application of a reverse dot blot, DNA-DNA hydridization method to quantify host-feeding tendencies of two sibling species in the Anopheles gambiae complex

    PubMed Central

    Fritz, Megan L; Miller, James R; Bayoh, M Nabie; Vulule, John M; Landgraf, Jeffrey R; Walker, Edward D

    2012-01-01

    A DNA-DNA hybridization method, reverse dot blot analysis (RDBA), was used for identification of Anopheles gambiae s.s. and An. arabiensis hosts. Of 299 blood fed and half gravid An. gambiae s.l. collected from Kisian, Kenya, 244 individuals were identifiable to species; 69.5% were An. arabiensis, and 29.5% were An. gambiae s.s. Host identifications with RDBA were comparable to conventional PCR followed by direct sequencing of amplicons of the vertebrate mitochondrial cytochrome B gene. Of the 174 amplicon-producing samples used for comparison of these two methods, 147 were identifiable by direct sequencing, and 139 of these same by RDBA. An. arabiensis blood meals were mostly (>90%) bovine in origin, whereas An. gambiae s.s. fed upon humans > 90% of the time. RDBA detected that 2 of 112 An. arabiensis had blood from more than one host species, whereas PCR and direct sequencing did not. Recent insecticide-treated bednet (ITN) use in Kisian has likely caused the shift in the dominant vector species from An. gambiae s.s. to An. arabiensis. RDBA provides an opportunity to study changes in host-feeding by members of the An. gambiae complex as a response to the broadening distribution of vector control measures targeting host-selection behaviors. PMID:24188164

  11. Development of a new SPME-HPLC-UV method for the analysis of nitro explosives on reverse phase amide column and application to analysis of aqueous samples.

    PubMed

    Gaurav; Malik, Ashok Kumar; Rai, P K

    2009-12-30

    A rapid, simple, sensitive and accurate quantitative method has been developed for the determination of eleven nitroaromatic components by solid phase microextraction (SPME) coupled to high performance liquid chromatography (HPLC) with UV detection from aqueous samples. PDMS/DVB resin fiber (60 microm) was used for concurrent extraction of all the analytes from aqueous matrix. Static desorption was carried out in the desorption chamber of SPME-HPLC interface containing mobile phase; methanol:water 43:57 (v/v) with subsequent liquid chromatographic analysis at isocratic flow rate of 1.3 mL/min and detection at 254 nm. A reverse phase amide column (5 microm) was used as a separation medium. The limit of detection (S/N=3) for TNT and Tetryl was found to be 0.35 and 0.54 ng/mL, respectively. Developed method has been applied successfully to the analysis of aqueous samples obtained from environmental and industrial sources like river water, ground water, drinking water and industrial waste water.

  12. Original reverse transcription polymerase chain reaction method to obtain the full-length cDNA of rice tungro spherical virus.

    PubMed

    Perrin, Y; Hull, R

    1999-05-01

    A two-step reverse transcription reaction combined with long PCR was developed in order to obtain the full-length cDNA from the 12.2 kbp genomic RNA of rice tungro spherical virus. A first step reverse transcription, performed at 45 degrees C using a reverse transcriptase deprived of RNase H activity, allowed the synthesis of a nearly full-length cDNA of 11.7 kbp. A second step reaction, carried out at 65 degrees C using a thermostable polymerase, was necessary to destabilise secondary structures present at the 5' extremity of the RNA template which hampered the reverse transcription reaction in this region. The full-length cDNA obtained by the two-step reverse transcription was amplified successfully by long PCR and subsequently cloned into a plasmid vector. The cloned cDNA showed toxicity and proved to be unstable when amplified in E. coli.

  13. Determination of tocopherol and tocotrienol content of Greek barley varieties under conventional and organic cultivation techniques using validated reverse phase high-performance liquid chromatography method.

    PubMed

    Tsochatzis, Emmanouil D; Bladenopoulos, Konstantinos; Papageorgiou, Maria

    2012-06-01

    Tocotrienols and tocopherols (tocols) are important phytochemical compounds with antioxidant activity and potential benefits for human health. Among cereals, barley is a good source of tocols. In the present study the effect of two cultivation methods, organic and conventional, on the tocol content in 12 Greek barley varieties was investigated. A validated reverse phase high-performance liquid chromatography method (RP-HPLC) with fluorescence detection (excitation at 292 nm, emission at 335 nm) was applied along with direct solvent extraction with acetonitrile at a 1:30 (w/v) sample/solvent ratio for tocol quantification. The results showed statistically significant differences (P < 0.05) between the two cultivation methods (except for δ-tocopherol) as well as among varieties. In the case of organic cultivation the four homologues of tocotrienol (α-, β + γ- and δ-) increased, by 3.05-37.14% for α-tocotrienol, 15.51-41.09% for (β + γ)-tocotrienol and 30.45-196.61% for δ-tocotrienol, while those of tocopherol (α- and β + γ- but not δ-) decreased, by 5.90-36.34% for α-tocopherol and 2.84-46.49% for (β + γ)-tocopherol. A simple correlation analysis between tocols revealed a good correlation between (β + γ)-tocotrienol and δ-tocotrienol. Although there was a significant decrease in the important α-tocopherol in the varieties studied under organic cultivation, there was an overall increase in tocotrienol content. The cultivation method (organic or conventional) had an important effect on tocotrienol and tocopherol concentrations in barley. An overall increase in total tocol content and a clear increment in the tocotrienol/tocopherol ratio were observed. Copyright © 2012 Society of Chemical Industry.

  14. Reverse phase high performance liquid chromatographic method development based on ultravioletvisible detector for the analysis of 1-hydroxypyrene (PAH biomarker) in human urine.

    PubMed

    Kamal, Atif; Gulfraz, Mohammad; Anwar, Mohammad Asad; Malik, Riffat Naseem

    2015-01-01

    1-hydroxypyrene is an important biomarker of exposure to polycyclic aromatic hydrocarbons (PAHs), which appears in the urine of exposed human subjects. In developing countries, where advanced instruments are not available, the importance of this biomarker demands convenient and sensitive methods for determination purposes. This study aimed at developing a methodology to quantify 1-hydroxypyrene (a biomarker of PAHs exposure) based on the UV-visible detector in the reverse phase high pressure liquid chromatography (HPLC). A 20 μl injection of sample was used for manual injection into the HPLC Shimadzu, equipped with the SPD-20 A UV-visible detector, the LC-20AT pump and the DGU-20A5 degasser. The C-18 column was used for the purpose of the analysis. The method showed a good linearity (the range: R2 = 0.979-0.989), and high detectability up to the nmol level. The average retention was 6.37, with the accuracy of 2%, and the percentage of recovery remained 108%. The overall performance of this method was comparable (in terms of detection sensitivity) and relatively better than previously reported studies using the HPLC system equipped with the UV-detector. This method is suitable and reliable for the detection/quantification of the 1-OHP in human urine samples, using the UV-detector, however, it is less sensitive as compared to the results of a florescence detector. This work is available in Open Access model and licensed under a CC BY-NC 3.0 PL license.

  15. A novel method of real-time reverse-transcription loop-mediated isothermal amplification developed for rapid and quantitative detection of human astrovirus.

    PubMed

    Wei, Haiyan; Zeng, Jing; Deng, Congliang; Zheng, Chengzhong; Zhang, Ximeng; Ma, Dan; Yi, Yong

    2013-03-01

    A one-step, real-time reverse-transcription loop-mediated isothermal amplification (rRT-LAMP) method targeting the 5' end of the capsid gene for rapid and quantitative detection of human astrovirus serotype 1 (HAstV 1) was developed. The assay is highly sensitive and comparable to real-time RT-PCR (rRT-PCR), with a detection limit of ∼100 RNA copies per assay. The specificity of the method was validated by the absence of any cross-reaction with RNA samples of HAstV 2-8 and other gastroenteritis viruses, followed by nucleotide sequencing of the amplified product. Fecal specimens (n=120) obtained from children under five years of age with gastroenteritis were tested by rRT-LAMP, rRT-PCR and transmission electron microscopy (TEM). Six (5%) of these samples were determined to be positive by both rRT-LAMP and rRT-PCR assay, and these two nucleic acid amplification methods resulted in a 200% increase in detection rates for HAstV infection compared with TEM alone. Furthermore, the rRT-LAMP assay is much more rapid than rRT-PCR and generates results in less than 20min for positive samples. The quantitation of viral load in stool specimens was determined from the standard curve plot of time-of-positivity versus initial RNA concentration. Most viral loads were determined to be within the range of 10(5)-10(8) copies. The results highlight the significance of the rapid rRT-LAMP method as a diagnostic and routine screening tool for the analysis of stool samples in hospital laboratories.

  16. Development and validation of a simple and isocratic reversed-phase HPLC method for the determination of rilpivirine from tablets, nanoparticles and HeLa cell lysates

    PubMed Central

    Date, Abhijit A.; Shibata, Annemarie; Bruck, Patrick; Destache, Christopher J.

    2015-01-01

    In the present investigation, a simple and isocratic HPLC-UV method was developed and validated for determination of rilpivirine (RPV) from dosage forms (tablets and nanoparticles) and biological matrices like HeLa cell lysates. The separation and analysis of RPV was carried out under isocratic conditions using (a) a Gemini reversed-phase C18 column (5 μm; 4.6 × 150 mm) maintained at 35°C, (b) a mobile phase consisting of a mixture of acetonitrile and 25 mM potassium dihydrogen phosphate (in the ratio 50:50 v/v) at a flow rate of 0.6 mL/min and (c) atazanavir as an internal standard. The total run time was 17 min and the analysis of RPV and internal standard was carried out at 290 nm. The method was found to be linear (r2 value > 0.998), specific, accurate and precise over the concentration range of 0.025–2 μg/mL. The lower limit of quantification was 0.025 μg/mL, the limit of detection was 0.008 μg/mL and the recovery of RPV was >90%. The stability of the RPV analytical method was confirmed at various conditions such as room temperature (24 h), −20°C (7 days), three freeze–thaw cycles and storage in an autosampler (4°C for 48 h). The method was successfully applied for the determination of RPV from conventional dosage forms like tablets, from polymeric nanoparticles and from biological matrices like HeLa cell lysates. PMID:25298145

  17. Development and validation of a reversed-phase HPLC method for CYP1A2 phenotyping by use of a caffeine metabolite ratio in saliva.

    PubMed

    Begas, Elias; Kouvaras, Evangelos; Tsakalof, Andreas K; Bounitsi, Maria; Asprodini, Eftihia Konstadinos

    2015-11-01

    CYP1A2 is important for metabolizing various clinically used drugs. Phenotyping of CYP1A2 may prove helpful for drug individualization therapy. Several HPLC methods have been developed for quantification of caffeine metabolites in plasma and urine. Aim of the present study was to develop a valid and simple HPLC method for evaluating CYP1A2 activity during exposure in xenobiotics by the use of human saliva. Caffeine and paraxanthine were isolated from saliva by liquid-liquid extraction (chlorophorm/isopropanol 85/15v/v). Extracts were analyzed by reversed-phase HPLC on a C18 column with mobile phase 0.1% acetic acid/methanol/acetonitrile (80/20/2 v/v) and detected at 273nm. Caffeine and paraxanthine elution times were <13min with no interferences from impurities or caffeine metabolites. Detector response was linear (0.10-8.00µg/ml, R(2) >0.99), recovery was >93% and bias <4.47%. Intra- and inter-day precision was <5.14% (n=6). The limit of quantitation was 0.10µg/ml and the limit of detection was 0.018±0.002µg/mL for paraxanthine and 0.032±0.002µg/ml for caffeine. Paraxanthine/caffeine ratio of 34 healthy volunteers was significantly higher in smokers (p<0.001). Saliva paraxanthine/caffeine ratios and urine metabolite ratios were highly correlated (r=0.85, p<0.001). The method can be used for the monitoring of CYP1A2 activity in clinical practice and in studies relevant to exposure to environmental and pharmacological xenobiotics.

  18. A rapid impregnation method for loading desired amounts of extractant on prepacked reversed-phase columns for high performance liquid chromatographic separation of metal ions.

    PubMed

    Ramzan, Muhammad; Kifle, Dejene; Wibetoe, Grethe

    2017-06-02

    A time-efficient impregnation method for loading extractant onto reversed-phase columns was developed, using di-(2-ethylhexyl) phosphoric acid (HDEHP) as a model extractant. The optimal loading conditions for the impregnation process of a standard analytical scale column was achieved by dissolving an appropriate amount of HDEHP (per void volume) in n-pentane, flushing the column with two void volumes (5mL) of impregnation solution and heating the column for a short time to remove the solvent. The process takes about one hour, a significant time reduction compared to commonly used impregnation methods (17-23h). The chromatographic traits for separation of the lighter lanthanides (La-Gd) using columns impregnated under different conditions were evaluated; heating for short period of time gave improved column performance most likely due to the presence of n-pentane in the pores of the support material. A linear relation was found (R(2)=0.9934) for the amount of HDEHP loaded as a function of HDEHP concentration in the impregnation solution. The coated amounts of HDEHP were in the range of 0.29-2.25mmol per column by flushing with 5mL of impregnation solution containing 0.3-5.0mmol of HDEHP per void volume. This 'flush-evaporate' impregnation method allowed for loading a pre-determined amount of extractant and produces very small amounts of organic waste. An overview of the various impregnation approaches previously used for extractant coating on prepacked columns and bulk support materials is also presented. Copyright © 2017 Elsevier B.V. All rights reserved.

  19. Development and validation of a stability-indicating reverse phase ultra performance liquid chromatographic method for the estimation of nebivolol impurities in active pharmaceutical ingredients and pharmaceutical formulation.

    PubMed

    Thummala, Veera Raghava Raju; Lanka, Mohana Krishna

    2015-10-01

    A sensitive, stability-indicating gradient reverse phase ultra performance liquid chromatographic method has been developed for the quantitative estimation of nebivolol impurities in active pharmaceutical ingredient (API) and pharmaceutical formulation. Efficient chromatographic separation was achieved on an Acquity BEH C18 column (100 mm x 2.1 mm, 1.7 μm) with mobile phase of a gradient mixture. The flow rate of the mobile phase was 0.18 mL/min with column temperature of 30 degrees C and detection wavelength of 281 nm. The relative response factor values of (R*)-2-( benzylamino)-1-((S*)-6-fluorochroman-2-yl) ethanol ((R x S*) NBV-), (R)-1-((R)-6-fluorochroman-2-yl)-2-((S)-2-((S)-6-fluoro-chroman-2-yl)-2-hydroxyethyl-amino) ethanol ((RRSS) NBV-3), 1-(chroman-2-yl)-2-(2-(6-fluorochroman-2-yl)-2-hydroxyethyl amino) ethanol (monodesfluoro impurity), (S)-1-((R)-6-fluorochroman-2-yl)-2-((R)-2 (S*)-6-fluoro-chroman-2-yl)-2-hydroxyethylamino) ethanol hydrochloride ((RSRS) NBV-3) and (R*)-1-((S*)-6-fluorochroman-2-yl)-2-((S*)-2-((S*)-6-fluoro-chroman-2-yl)-2-hydroxyethylamino) ethanol ((R* S* S* S*) NBV-2) were 0.65, 0.91, 0.68, 0.92 and 0.91 respectively. Nebivolol formulation sample was subjected to the stress conditions of acid, base, oxidative, hydrolytic, thermal, humidity and photolytic degradation. Nebivolol was found to degrade significantly under peroxide stress condition. The degradation products were well resolved from nebivolol and its impurities. The peak purity test results confirmed that the nebivolol peak was homogenous and pure in all stress samples and the mass balance was found to be more than 98%, thus proving the stability-indicating power of the method. The developed method was validated according to International Conference on Hormonization (ICH) guidelines with respect to specificity, linearity, limits of detection and quantification, accuracy, precision and robustness.

  20. A diagnostic one-step real-time reverse transcription polymerase chain reaction method for accurate detection of influenza virus type A

    PubMed Central

    Behzadi, Mohammad Amin; Alborzi, Abdolvahab

    2016-01-01

    Introduction Influenza A is known as a public health concern worldwide. In this study, a novel one-step real-time reverse transcription polymerase chain reaction (rtRT-PCR) assay was designed and optimized for the detection of influenza A viruses. Material and methods The primers and probe were designed based on the analysis of 90 matrix nucleotide sequence data of influenza type A subtypes from the GenBank database of the National Center for Biotechnology Information (NCBI). The influenza virus A/Tehran/5652/2010 (H1N1 pdm09) was used as a reference. The rtRT-PCR assay was optimized, compared with that of the World Health Organization (WHO), and its analytical sensitivity, specificity and reproducibility were evaluated. In total, 64 nasopharyngeal swabs from patients with influenza-like illness (ILI) and 41 samples without ILI symptoms were tested for the virus, using conventional cell culture, direct immunofluorescence antibody (DFA) methods, and one-step rtRT-PCR with the designed primer set and probe and the WHO’s. Results The optimized assay results were similar to the WHO’s. The optimized assay results were similar to WHO’s, with non-significant differences for 10–103 copies of viral RNA/reaction (p > 0.05). It detected 10 copies of viral RNA/reaction with high reproducibility and no cross reactivity with other respiratory viruses. A specific cytopathic effect was observed in 6/64 (9.37%) of the ILI group using conventional culture and DFA staining methods; however, it was not seen in non-ILI. Also, the results of our assay and the WHO’s were similar to those of viral isolation and DFA staining. Conclusions Given the high specificity, sensitivity and reproducibility of this novel assay, it can serve as a reliable diagnostic tool for the detection of influenza A viruses in clinical specimens and lab experiments. PMID:27904520

  1. A method for assessment of the genotoxicity of mainstream cigarette-smoke by use of the bacterial reverse-mutation assay and an aerosol-based exposure system.

    PubMed

    Kilford, Joanne; Thorne, David; Payne, Rebecca; Dalrymple, Annette; Clements, Julie; Meredith, Clive; Dillon, Debbie

    2014-07-15

    To date there are no widely accepted methods for the toxicological testing of complex gaseous mixtures and aerosols, such as cigarette smoke, although some modifications to the standard regulatory methods have been developed and used. Historically, routine testing of cigarettes has primarily focused on the particulate fraction of cigarette smoke. However, this fraction may not accurately reflect the full toxicity and mutagenicity of the smoke aerosol as a whole, which contains semi-volatiles and short-lived products of combustion. In this study we have used a modified version of the bacterial reverse-mutation (Ames) assay for the testing of mainstream smoke generated from 3R4F reference cigarettes with a Vitrocell(®) VC 10 exposure system. This method has been evaluated in four strains of Salmonella typhimurium (TA98, TA100, YG1024 and YG1042) and one strain of Escherichia coli (WP2 uvrA pKM101) in the absence and presence of a metabolic activation system. Following exposure at four concentrations of diluted mainstream cigarette-smoke, concentration-related and reproducible increases in the number of revertants were observed in all four Salmonella strains. E. coli strain WP2 uvrA pKM101 was unresponsive at the four concentrations tested. To quantify the exposure dose and to enable biological response to be plotted as a function of deposited mass, quartz-crystal microbalances were included in situ in the smoke-exposure set-up. This methodology was further assessed by comparing the responses of strain YG1042 to mainstream cigarette-smoke on a second VC 10 Smoking Robot. In summary, the Ames assay can be successfully modified to assess the toxicological impact of mainstream cigarette-smoke.

  2. Apparatus and method for controlling the rotary airlocks in a coal processing system by reversing the motor current rotating the air lock

    SciTech Connect

    Groombridge, C.E.

    1996-11-19

    An improvement is described to a coal processing system where hard materials found in the coal may cause jamming of either inflow or outflow rotary airlocks, each driven by a reversible motor. The instantaneous current used by the motor is continually monitored and compared to a predetermined value. If an overcurrent condition occurs, indicating a jamming of the airlock, a controller means starts a ``soft`` reverse rotation of the motor thereby clearing the jamming. Three patterns of the motor reversal are provided. 10 figs.

  3. Rapid genome detection of Schmallenberg virus and bovine viral diarrhea virus by use of isothermal amplification methods and high-speed real-time reverse transcriptase PCR.

    PubMed

    Aebischer, Andrea; Wernike, Kerstin; Hoffmann, Bernd; Beer, Martin

    2014-06-01

    Over the past few years, there has been an increasing demand for rapid and simple diagnostic tools that can be applied outside centralized laboratories by using transportable devices. In veterinary medicine, such mobile test systems would circumvent barriers associated with the transportation of samples and significantly reduce the time to diagnose important infectious animal diseases. Among a wide range of available technologies, high-speed real-time reverse transcriptase quantitative PCR (RT-qPCR) and the two isothermal amplification techniques loop-mediated isothermal amplification (LAMP) and recombinase polymerase amplification (RPA) represent three promising candidates for integration into mobile pen-side tests. The aim of this study was to investigate the performance of these amplification strategies and to evaluate their suitability for field application. In order to enable a valid comparison, novel pathogen-specific assays have been developed for the detection of Schmallenberg virus and bovine viral diarrhea virus. The newly developed assays were evaluated in comparison with established standard RT-qPCR using samples from experimentally or field-infected animals. Even though all assays allowed detection of the target virus in less than 30 min, major differences were revealed concerning sensitivity, specificity, robustness, testing time, and complexity of assay design. These findings indicated that the success of an assay will depend on the integrated amplification technology. Therefore, the application-specific pros and cons of each method that were identified during this study provide very valuable insights for future development and optimization of pen-side tests.

  4. Rapid Genome Detection of Schmallenberg Virus and Bovine Viral Diarrhea Virus by Use of Isothermal Amplification Methods and High-Speed Real-Time Reverse Transcriptase PCR

    PubMed Central

    Aebischer, Andrea; Wernike, Kerstin; Beer, Martin

    2014-01-01

    Over the past few years, there has been an increasing demand for rapid and simple diagnostic tools that can be applied outside centralized laboratories by using transportable devices. In veterinary medicine, such mobile test systems would circumvent barriers associated with the transportation of samples and significantly reduce the time to diagnose important infectious animal diseases. Among a wide range of available technologies, high-speed real-time reverse transcriptase quantitative PCR (RT-qPCR) and the two isothermal amplification techniques loop-mediated isothermal amplification (LAMP) and recombinase polymerase amplification (RPA) represent three promising candidates for integration into mobile pen-side tests. The aim of this study was to investigate the performance of these amplification strategies and to evaluate their suitability for field application. In order to enable a valid comparison, novel pathogen-specific assays have been developed for the detection of Schmallenberg virus and bovine viral diarrhea virus. The newly developed assays were evaluated in comparison with established standard RT-qPCR using samples from experimentally or field-infected animals. Even though all assays allowed detection of the target virus in less than 30 min, major differences were revealed concerning sensitivity, specificity, robustness, testing time, and complexity of assay design. These findings indicated that the success of an assay will depend on the integrated amplification technology. Therefore, the application-specific pros and cons of each method that were identified during this study provide very valuable insights for future development and optimization of pen-side tests. PMID:24648561

  5. Solid-liquid work of adhesion of coarse-grained models of n-hexane on graphene layers derived from the conditional reversible work method

    SciTech Connect

    Ardham, Vikram Reddy; Leroy, Frédéric E-mail: f.leroy@theo.chemie.tu-darmstadt.de; Deichmann, Gregor; Vegt, Nico F. A. van der E-mail: f.leroy@theo.chemie.tu-darmstadt.de

    2015-12-28

    We address the question of how reducing the number of degrees of freedom modifies the interfacial thermodynamic properties of heterogeneous solid-liquid systems. We consider the example of n-hexane interacting with multi-layer graphene which we model both with fully atomistic and coarse-grained (CG) models. The CG models are obtained by means of the conditional reversible work (CRW) method. The interfacial thermodynamics of these models is characterized by the solid-liquid work of adhesion W{sub SL} calculated by means of the dry-surface methodology through molecular dynamics simulations. We find that the CRW potentials lead to values of W{sub SL} that are larger than the atomistic ones. Clear understanding of the relationship between the structure of n-hexane in the vicinity of the surface and W{sub SL} is elucidated through a detailed study of the energy and entropy components of W{sub SL}. We highlight the crucial role played by the solid-liquid energy fluctuations. Our approach suggests that CG potentials should be designed in such a way that they preserve the range of solid-liquid interaction energies, but also their fluctuations in order to preserve the reference atomistic value of W{sub SL}. Our study thus opens perspectives into deriving CG interaction potentials that preserve the thermodynamics of solid-liquid contacts and will find application in studies that intend to address materials driven by interfaces.

  6. Design of a fully-fiber multi-chord interferometer and a new phase-shift demodulation method for field-reversed configuration

    SciTech Connect

    Fang, Dongfan Sun, Qizhi; Zhao, Xiaoming; Jia, Yuesong

    2014-05-15

    A 633 nm laser interferometer has been designed based on a novel concept, which, without the acousto-optic modulator or the demodulator circuit, adopts the fibers to connect all elements except photodetectors and oscilloscope in this system to make it more compact, portable, and efficient. The noteworthy feature is to mathematically compare the two divided interference signals, which have the same phase-shift caused by the electron density but possess the different initial phase and low angular frequencies. It is possible to read the plasma density directly on the oscilloscope by our original mathematic demodulation method without a camera. Based on the Abel inversion algorithm, the radial electron density profiles versus time can be obtained by using the multi-chord system. The designed measurable phase shift ranges from 0 to 2π rad corresponding to the maximum line integral of electron density less than 3.5 × 10{sup 17} cm{sup −2}, and the phase accuracy is about 0.017 rad corresponding to the line integral of electron density accuracy of 1 × 10{sup 15} cm{sup −2}. After the construction of eight-chord interferometer, it will provide the detailed time resolved information of the spatial distribution of the electron density in the field-reversed configuration (FRC) plasma target produced by the “Yingguang-1” programmed-discharge device, which is being constructed in the Key Laboratory of Pulsed Power, China Academy of Engineering Physics.

  7. Development and application of a reverse transcription loop-mediated isothermal amplification method for rapid detection of Duck hepatitis A virus type 1.

    PubMed

    Yang, Limin; Li, Jing; Bi, Yuhai; Xu, Lei; Liu, Wenjun

    2012-12-01

    We developed and evaluated a reverse transcription loop-mediated isothermal amplification (RT-LAMP) assay for detecting Duck hepatitis A virus type 1 (DHAV-1). The amplification could be finished in 1 h under isothermal conditions at 63 °C by employing a set of four primers targeting the 2C gene of DHAV-1. The RT-LAMP assay showed higher sensitivity than the RT-PCR with a detection limit of 0.1 ELD(50) 0.1 ml(-1) of DHAV-1. The RT-LAMP assay was highly specific; no cross-reactivity was observed from the samples of other related viruses, bacteria, allantoic fluid of normal chicken embryos, or the livers of uninfected ducks. Thirty clinical samples were subjected to detection by RT-LAMP, RT-PCR, and virus isolation, which obtained completely consistent, positive results. As a simple, rapid, and accurate detection method, this RT-LAMP assay has important potential applications in the clinical diagnosis of DHAV-1.

  8. Quantitative Structure activity Relationship Analysis of Pyridinone HIV-1 Reverse Transcriptase Inhibitors using the k Nearest Neighbor Method and QSAR-based Database Mining

    NASA Astrophysics Data System (ADS)

    Medina-Franco, Jose Luis; Golbraikh, Alexander; Oloff, Scott; Castillo, Rafael; Tropsha, Alexander

    2005-04-01

    We have developed quantitative structure-activity relationship (QSAR) models for 44 non-nucleoside HIV-1 reverse transcriptase inhibitors (NNRTIs) of the pyridinone derivative type. The k nearest neighbor ( kNN) variable selection approach was used. This method utilizes multiple descriptors such as molecular connectivity indices, which are derived from two-dimensional molecular topology. The modeling process entailed extensive validation including the randomization of the target property (Y-randomization) test and the division of the dataset into multiple training and test sets to establish the external predictive power of the training set models. QSAR models with high internal and external accuracy were generated, with leave-one-out cross-validated R 2 ( q 2) values ranging between 0.5 and 0.8 for the training sets and R 2 values exceeding 0.6 for the test sets. The best models with the highest internal and external predictive power were used to search the National Cancer Institute database. Derivatives of the pyrazolo[3,4- d]pyrimidine and phenothiazine type were identified as promising novel NNRTIs leads. Several candidates were docked into the binding pocket of nevirapine with the AutoDock (version 3.0) software. Docking results suggested that these types of compounds could be binding in the NNRTI binding site in a similar mode to a known non-nucleoside inhibitor nevirapine.

  9. Determination of beef tallow in lard through a multidimensional off-line non-aqueous reversed phase-argentation LC method coupled to mass spectrometry.

    PubMed

    Dugo, Paola; Kumm, Tiina; Fazio, Alessia; Dugo, Giovanni; Mondello, Luigi

    2006-03-01

    The presence of tallow in lard is not easy to determine, due to the similarity of the composition of these two animal fats, which differ mainly in the distribution of fatty acids (FA) in the three positions of the glycerol molecule. The determination of the composition of the triacylglycerol (TAG) fraction of lard, tallow, and their mixtures was investigated by HPLC in combination with atmospheric pressure chemical ionization mass spectrometry (APCI-MS). The presence of tallow in lard was determined through the study of the sn-POP/sn-PPO ratio by multidimensional HPLC. The off-line bidimensional system was attained through the coupling of non-aqueous reversed phase (NARP)-HPLC and silver ion (Ag)-HPLC. The primary column eluate was fractionated and the fraction containing POP/PPO isomers was injected onto the secondary column, allowing the separation of positional isomers, unresolved in the first dimension. Peak assignment was carried out by combining retention data with APCI-MS spectral information. The fatty acid distribution along the glycerol backbone, determined by Ag-HPLC, was confirmed through diglyceride ion ratios derived from APCI-MS analysis. Method validation was carried out in preliminary applications on standard TAGs. The analytical results obtained show that even a 5% addition of tallow to lard modifies the distribution of positional isomers.

  10. A method for simultaneous detection and identification of Brazilian dog- and vampire bat-related rabies virus by reverse transcription loop-mediated isothermal amplification assay.

    PubMed

    Saitou, Yasumasa; Kobayashi, Yuki; Hirano, Shinji; Mochizuki, Nobuyuki; Itou, Takuya; Ito, Fumio H; Sakai, Takeo

    2010-09-01

    At present, the sporadic occurrence of human rabies in Brazil can be attributed primarily to dog- and vampire bat-related rabies viruses. Reverse transcription loop-mediated isothermal amplification (RT-LAMP) was employed as a simultaneous detection method for both rabies field variants within 60 min. Vampire bat-related rabies viruses could be distinguished from dog variants by digesting amplicons of the RT-LAMP reaction using the restriction enzyme AlwI. Amplification and digestion could both be completed within 120 min after RNA extraction. In addition, the RT-LAMP assay also detected rabies virus in isolates from Brazilian frugivorous bats and Ugandan dog, bovine and goat samples. In contrast, there were false negative results from several Brazilian insectivorous bats and all of Chinese dog, pig, and bovine samples using the RT-LAMP assay. This study showed that the RT-LAMP assay is effective for the rapid detection of rabies virus isolates from the primary reservoir in Brazil. Further improvements are necessary so that the RT-LAMP assay can be employed for the universal detection of genetic variants of rabies virus in the field.

  11. Optimization and validation of a reversed-phase high performance liquid chromatography method for the measurement of bovine liver methylmalonyl-coenzyme a mutase activity

    PubMed Central

    2013-01-01

    Background Methylmalonyl-CoA mutase (MCM) is an adenosylcobalamin-dependent enzyme that catalyses the interconversion of (2R)-methylmalonyl-CoA to succinyl-CoA. In humans, a deficit in activity of MCM, due to an impairment of intracellular formation of adenosylcobalamin and methylcobalamin results in a wide spectrum of clinical manifestations ranging from moderate to fatal. Consequently, MCM is the subject of abundant literature. However, there is a lack of consensus on the reliable method to monitor its activity. This metabolic pathway is highly solicited in ruminants because it is essential for the utilization of propionate formed during ruminal fermentation. In lactating dairy cows, propionate is the major substrate for glucose formation. In present study, a reversed-phase high performance liquid chromatography (RP-HPLC) was optimized and validated to evaluate MCM activity in bovine liver. The major aim of the study was to describe the conditions to optimize reproducibility of the method and to determine stability of the enzyme and its product during storage and processing of samples. Results Specificity of the method was good, as there was no interfering peak from liver extract at the retention times corresponding to methylmalonyl-CoA or succinyl-CoA. Repeatability of the method was improved as compared to previous RP-HPLC published data. Using 66 μg of protein, intra-assay coefficient of variation (CV) of specific activities, ranged from 0.90 to 8.05% and the CV inter-day was 7.40%. Storage and processing conditions (frozen homogenate of fresh tissue vs. fresh homogenate of tissue snapped in liquid nitrogen) did not alter the enzyme activity. The analyte was also stable in liver crude extract for three frozen/thawed cycles when stored at -20°C and thawed to room temperature. Conclusions The improved method provides a way for studying the effects of stages of lactation, diet composition, and physiology in cattle on MCM activity over long periods of time

  12. Development of reversed-phase high performance liquid chromatography methods for quantification of two isomeric flavones and the application of the methods to pharmacokinetic studies in rats.

    PubMed

    Whitted, Crystal L; Palau, Victoria E; Torrenegra, Ruben D; Harirforoosh, Sam

    2015-09-15

    Isomers 5,7-dihydroxy-3,6,8-trimethoxy-2-phenyl-4H-chromen-4-one (5,7-dihydroxy-3,6,8 trimethoxy flavone) (flavone A) and 3,5-dihydroxy-6,7,8-trimethoxy-2-phenyl-4H-chromen-4-one (3,5-dihydroxy-6,7,8-trimethoxy flavone) (flavone B) have recently demonstrated differential antineoplastic activities against pancreatic cancer in vitro. These studies also indicated that these compounds target highly tumorigenic cells while sparing normal cells. The in vivo antitumor activities of these flavones have not been determined, and detection protocols for these compounds are needed to conduct pre-clinical assays following intravenous dosing. Here, we report methods developed using acetonitrile to extract two flavone isomers and corresponding internal standards, celecoxib and diclofenac, from rat plasma. Separation was achieved using a Shimadzu liquid chromatography system with a C18 column and mobile phase acetonitrile/water (60:40 and 70:30 for flavones A and B, respectively) containing 0.2% acetic acid and 0.05% triethylamine at a flow rate of 0.4mL/min and detection at 245nm. Calibration curves ranging from 250 to 2500ng/mL and 2500 to 100,000ng/mL for both flavones were linear (r(2)≥0.99) with the lower limits of quantification being 250ng/mL. Recovery of concentrations 250, 1000, 2500, 5000, and 100,000ng/mL ranged from 87 to 116% and 84 to 103% (n=3) for flavone A and B, respectively. Stability of both flavones after a freezing/thawing cycle yielded a mean peak ratio ≥0.92 when compared to freshly extracted samples. Intravenous administration of a 20mg/kg dose in rats yielded half-lives of 83.68±56.61 and 107.45±53.31min with clearance values of 12.99±13.78 and 80.79±35.06mL/min/kg for flavones A and B, respectively.

  13. Development of an analytical method using reversed-phase HPLC-PDA for a semipurified extract of Paullinia cupana var. sorbilis (guaraná).

    PubMed

    Klein, Traudi; Longhini, Renata; de Mello, João Carlos Palazzo

    2012-01-15

    The Neotropical plant 'guaraná' has been widely used in medicine, cosmetics, and industry because of its versatile biological activities. These effects are mainly attributed to the presence of polyphenols. An efficient, precise, and reliable method was developed for quantification of the polyphenols catechin and epicatechin in guaraná extract solution, using HPLC-PDA detection. The ideal conditions for the analysis of a semipurified extract of guaraná (EPA), using solutions of 0.05% TFA-water (phase A) and 0.05% TFA in acetonitrile:methanol (75:25, vv(-1)) (phase B) as mobile phases were established. Gradient reversed-phase chromatography was performed using a guard cartridge (C18, 4.6mm×20mm, 4μm) and column (C18, 250mm×4.6mm, 4μm), flow of 0.5mLmin(-1) and detection at 280nm. The main validation parameters of the method were also determined. The method was linear over a range of 18.75-300μgmL(-1) for catechin and epicatechin, with detection limits of 0.70 and 0.88μgmL(-1) and quantification limits of 2.13 and 2.67μgmL(-1), respectively. The method also showed consistent mean recoveries of 91.3±3.8%, 2.14 RSD and 93.4±3.1, 2.74 RSD of catechin and epicatechin respectively. The relative standard deviations were relatively low: intra-day (0.72% and 0.66% for catechin and epicatechin, respectively) and inter-day (0.93% and 0.75% for catechin and epicatechin, respectively). The semipurified extract showed catechin, epicatechin, and caffeine contents of 180.75, 278.87, and 300.87μgmg(-1), respectively. The results demonstrated the efficiency, precision, accuracy, and robustness of the proposed method. The solutions remained stable for a sufficient time (one week) to complete the analytical process. Copyright © 2011 Elsevier B.V. All rights reserved.

  14. Rapid detection method for hepatitis A virus from lettuce by a combination of filtration and integrated cell culture-real-time reverse transcription PCR.

    PubMed

    Hyeon, Ji-Yeon; Chon, Jung-Whan; Park, Chankyu; Lee, Joong-Bok; Choi, In-Soo; Kim, Moo-Sang; Seo, Kun-Ho

    2011-10-01

    We have developed a rapid and simple method for filtration using a positively charged membrane to concentrate hepatitis A virus (HAV) from lettuce and an integrated cell culture-real-time reverse transcription PCR (ICC-real-time RT-PCR) to detect infectious HAV. The most suitable buffer for HAV concentration by filtration was 100 mM Tris-HCl, 50 mM glycine (pH 9.5). Filtration using the NanoCeram matrix was compared with polyethylene glycol precipitation for viral concentration from lettuce inoculated with 6 log RNA copies of HAV. The recovery rate of filtration was statistically higher than that of polyethylene glycol precipitation (47.3 versus 24.9%, respectively). The sensitivity of ICC-real-time RT-PCR for detection of infectious HAV was determined by inoculation of FRhK-4 cells with HAV (4 log to 0 log RNA copies). ICC-real-time RT-PCR detected infectious HAV on average 5 days earlier than cytopathic effects at all inoculation levels. HAV recovered from lettuce (approximately 3 log RNA copies) was also analyzed with ICC-real-time RT-PCR. Infectious HAV was detected within 2 days postinfection by ICC-real-time RT-PCR, whereas cytopathic effects were not observed until 7 days postinfection. Coupled with a virus concentration and purification system using a positively charged membrane, ICC-real-time RT-PCR has the potential to become a novel and rapid method for the detection of infectious HAV in vegetables.

  15. A new back-and-forth iterative method for time-reversed convection modeling: Implications for the Cenozoic evolution of 3-D structure and dynamics of the mantle

    NASA Astrophysics Data System (ADS)

    Glišović, Petar; Forte, Alessandro M.

    2016-06-01

    The 3-D distribution of buoyancy in the convecting mantle drives a suite of convection-related manifestations. Although seismic tomography is providing increasingly resolved images of the present-day mantle heterogeneity, the distribution of mantle density variations in the geological past is unknown, and, by implication, this is true for the convection-related observables. The one major exception is tectonic plate motions, since geologic data are available to estimate their history and they currently provide the only available constraints on the evolution of 3-D mantle buoyancy in the past. We developed a new back-and-forth iterative method for time-reversed convection modeling with a procedure for matching plate velocity data at different instants in the past. The crucial aspect of this reconstruction methodology is to ensure that at all times plates are driven by buoyancy forces in the mantle and not vice versa. Employing tomography-based retrodictions over the Cenozoic, we estimate the global amplitude of the following observables: dynamic surface topography, the core-mantle boundary ellipticity, the free-air gravity anomalies, and the global divergence rates of tectonic plates. One of the major benefits of the new data assimilation method is the stable recovery of much shorter wavelength changes in heterogeneity than was possible in our previous work. We now resolve what appears to be two-stage subduction of the Farallon plate under the western U.S. and a deeply rooted East African Plume that is active under the Ethiopian volcanic fields during the Early Eocene.

  16. Reverse transcription-PCR methods significantly impact richness and composition measures of expressed fungal cellobiohydrolase I genes in soil and litter.

    PubMed

    Weber, Carolyn F; Kuske, Cheryl R

    2011-09-01

    The importance of soil fungi in complex carbon degradation and the recent identification of genes involved in this process have sparked considerable interest in examining fungal gene expression in situ. Expression of target eukaryotic genes is commonly examined using reverse transcription (RT)-PCR, during which single-stranded (ss) complementary DNA (cDNA) is synthesized from an oligo (dT) primer and the gene of interest is subsequently amplified by PCR using gene specific primers. Another method that is being increasingly employed in environmental gene expression studies is SMART PCR, which generates and amplifies double-stranded (ds) complementary DNA (cDNA) from sscDNA using PCR, prior to gene-specific PCR. We performed a replicated comparison of these two methods using RNA extracted from forest soil and litter to determine if the two approaches yielded comparable results. Richness, composition and reproducibility of gene expression profiles of the fungal glycosyl hydrolase family 7 (GH7) cellobiohydrolase I gene (cbhI) were examined when amplified from sscDNA or dscDNA synthesized using SMART PCR. In the dscDNA libraries from soil or litter samples, richness was significantly reduced and the composition was altered relative to sscDNA libraries. Library composition was significantly more reproducible among replicate sscDNA libraries than among parallel dscDNA libraries from litter. In sum, the reduced richness and altered composition produced in the dscDNA libraries could substantially influence ecological interpretations of the data. Defining the factors underpinning the methodological biases will potentially aid in optimizing the design of gene expression studies in soils and other complex environmental samples. Published by Elsevier B.V.

  17. Evaluation of the BioPlex 2200 syphilis system as a first-line method of reverse-sequence screening for syphilis diagnosis.

    PubMed

    Marangoni, Antonella; Nardini, Paola; Foschi, Claudio; Moroni, Alessandra; D'Antuono, Antonietta; Bacchi Reggiani, Letizia; Cevenini, Roberto

    2013-07-01

    Despite recent technological advances, the diagnosis of syphilis remains a challenging enterprise. Actually, most high-volume laboratories have adopted the "reverse algorithm" due several factors, including the potential to automate testing. Recently, immunoassays processed on random-access systems have been proposed as screening tests. The purpose of this study was to evaluate diagnostic performances of BioPlex 2200 Syphilis IgG and BioPlex 2200 Syphilis IgM, tests based on Multiplex Flow technology, in comparison with the performance of Architect Syphilis TP, a chemiluminescent immunoassay for the detection of IgG and/or IgM anti-Treponema pallidum antibodies. A retrospective study was performed with a panel of 100 blood donor sera, a panel of 350 clinical and laboratory-characterized syphilitic sera, and 170 samples obtained from subjects with potentially interfering conditions. Moreover, 200 unselected samples submitted to the Microbiology Laboratory of St. Orsola Hospital in Bologna for routine screening for syphilis were evaluated. As confirmatory tests, T. pallidum hemagglutination and Western blot assays were used. Considering the IgG Western blot (WB) assay to be the gold standard method, BioPlex 2200 Syphilis IgG specificity was far higher than Architect Syphilis TP specificity (89.7% versus 78.4%, respectively), whereas the sensitivity was 100% for both automated methods. Compared to the IgM WB assay, BioPlex 2200 Syphilis IgM performed with a specificity of 94.9%, whereas the sensitivity was 84.8%. Considering the excellent ease of use and automation, the high sample throughput and its valuable analytical performances, BioPlex Syphilis 2200 IgG could represent a suitable choice for high-volume laboratories. BioPlex Syphilis 2200 IgM could be considered a good addition to IgG testing for uncovering active infections.

  18. Bone distribution study of anti leprotic drug clofazimine in rat bone marrow cells by a sensitive reverse phase liquid chromatography method.

    PubMed

    Srikanth, Cheruvu Hanumanth; Joshi, Pankaj; Bikkasani, Anil Kumar; Porwal, Konica; Gayen, Jiaur R

    2014-06-01

    The aim of the present study was to investigate the distribution of clofazimine (CLF) in rat bone marrow cells by a validated reverse phase high performance liquid chromatography. CLF and chlorzoxazone (I.S) were extracted by liquid-liquid extraction from plasma and rat bone marrow cells. The chromatographic separation was performed in isocratic mode by the mobile phase consisting of 10mM ammonium formate (pH 3.0 with formic acid) and acetonitrile in a ratio of 50:50 (v/v). The method was accurate and precise in the linear range of 15.6-2000.0 ng/mL with a correlation coefficient (r(2)) of 0.996 and 0.995 in rat plasma and bone marrow cells, respectively. After single oral dose of 20mg/kg, the maximum concentration of CLF in plasma and bone marrow cells were obtained at 12h with the concentrations of 593.2 and 915.4 ng/mL, respectively. The AUC0-t and mean elimination half life (t1/2) of CLF in bone marrow cells were 54339.02 ng h/mL and 52.46 h, respectively, which signified the low body clearance and high distribution of CLF in bone marrow cells. The single oral dose pharmacokinetic investigation was confirmed the CLF endure for a long period in rat due to high distribution in various tissues. The developed method was successfully applied to the estimation of the pharmacokinetic parameters of CLF in plasma and bone marrow cells after administration of single oral dose of 20mg/kg to rats.

  19. Rapid detection of tdh and trh mRNAs of Vibrio parahaemolyticus by the transcription-reverse transcription concerted (TRC) method.

    PubMed

    Masuda, Noriyoshi; Yasukawa, Kiyoshi; Isawa, Yuichi; Horie, Ryuichi; Saitoh, Juichi; Ishiguro, Takahiko; Nakaguchi, Yoshitsugu; Nishibuchi, Mitsuaki; Hayashi, Toshinori

    2004-01-01

    We developed a novel method named the transcription-reverse transcription concerted (TRC) method and an instrument that allowed rapid and completely homogeneous real-time monitoring of RNA isothermal sequence amplification without any post-amplification analysis in our previous study [Ishiguro et al., Anal. Biochem., 314, 77-86 (2003)]. In this study, we newly established rapid and sensitive TRC systems for the detection of the mRNAs transcribed from two major virulence genes of Vibrio parahaemolyticus: the tdh gene encoding the thermostable direct hemolysin (tdh) and the trh gene encoding the thermostable direct hemolysin-related hemolysin. Examination of the standard RNAs prepared in vitro showed that a positive result, increase in the fluorescence intensity to the cut-off value within 25 min, was obtained for as few as 100 copies of RNA. The TRC method specific to the trh mRNA detected the mRNAs transcribed from the trh1 and trh2 genes, two representative trh variants sharing 84% sequence identity. The detection time gave a linear relationship to the logarithm of starting RNA copies ranging from 10(3) to 10(7) copies, showing that quantitative analysis is possible. The detection time for 10(3) copies of the standard RNAs ranged from 11 to 15 min. Examination of the total RNAs extracted from the standard strains of V. parahaemolyticus demonstrated that the new TRC systems are sufficiently sensitive to detect as few as 100 CFUs of the strains carrying the target genes. Total RNA preparations extracted from 24 strains of V. parahaemolyticus, 52 strains belonging to 31 other species of the genus Vibrio and 11 strains belonging to 8 species of non-Vibrio genera were examined. The results of the detection of tdh- and trh-specific mRNAs by the two TRC systems and those of the respective genes by the DNA colony hybridization method agreed. We conclude that the new TRC systems are rapid, highly sensitive, easy to manipulate, and are suitable for routine examination of

  20. Optimization and qualification of a quantitative reversed-phase HPLC method for hemagglutinin in influenza preparations and its comparative evaluation with biochemical assays.

    PubMed

    Lorbetskie, Barry; Wang, Jun; Gravel, Caroline; Allen, Cynthia; Walsh, Mike; Rinfret, Aline; Li, Xuguang; Girard, Michel

    2011-04-18

    A previously described reversed-phase HPLC (RP-HPLC) method based on fast separations on a non-porous silica stationary phase [1] was optimized and qualified for the quantitative determination of hemagglutinin (HA) in influenza vaccine preparations. Optimization of the gradient elution conditions led to improved separation of the HA1 subunit from other vaccine constituents. The sensitivity of the method was significantly increased by using native fluorescence detection, resulting in an approximately 10-fold increase as compared to UV-vis detection. This enabled the elimination of the concentration step described in the original method and allowed direct analysis of vaccine preparations. The method was qualified for linearity, range, limit of detection, limit of quantitation and precision. Overall, it was found to be linear over the range of 2.5-100 μg HA/mL for all subtypes examined. This range covered 50-150% of the concentration found for individual strains in seasonal influenza vaccines and in the pandemic H1N1 vaccine. The limit of detection and limit of quantitation for each subtype were found to be suitable for the method's intended purpose and compared well to values found by the single radial immunodiffusion (SRID). The repeatability of the method gave RSD values below 5% for both retention time and peak areas. As expected for intermediate precision, larger RSD values for peak area were obtained but were below 10% and deemed acceptable. The RP-HPLC results were compared to Western blot analysis using a HA universal antibody for a set of 15 monovalent A/California H1N1 preparations and showed good correlation. Similarly, the quantitative nature of the RP-HPLC method was assessed in relation to the SRID assay currently used for the determination of the HA content in bulk antigen and final vaccine preparations. Thus, for a series of 23 monovalent A/Brisbane/59/2007 H1N1 bulks, ranging between 12.7 and 15.9 μg HA/mL by SRID, the RP-HPLC values were found to

  1. 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.

    PubMed

    Harris, T R; Bernard, G R; Brigham, K L; Higgins, S B; Rinaldo, J E; Borovetz, H S; Sibbald, W J; Kariman, K; Sprung, C 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 extravascular 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.(ABSTRACT TRUNCATED AT 250 WORDS)

  2. 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.

  3. 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.

  4. Sensitive method for plasma and tumor Ko143 quantification using reversed-phase high-performance liquid chromatography and fluorescence detection.

    PubMed

    Zander, Serge A L; Beijnen, Jos H; van Tellingen, Olaf

    2013-01-15

    The fumitremorgin C analogue Ko143 is a potent and selective inhibitor of the ATP-binding cassette transporter ABCG2. To support in vivo ABCG2 resistance studies, we developed a sensitive and selective method for Ko143 quantification in plasma and tumor samples, using the parent compound fumitremorgin C as internal standard. Sample pretreatment by liquid-liquid extraction in diethyl ether yielded a recovery of 50% from human and mouse plasma. Pretreated samples were separated by reversed-phase high-performance liquid chromatography with fluorescence detection at 295nm excitation and 350nm emission wavelengths. Sharp chromatographic peaks were obtained with a 5μm GraceSmart C18 column. The mobile phase consisted of methanol:10mM ammonium acetate pH 5.0 (62:38, v/v), delivered at a flow rate of 0.2mL/min. Acceptable accuracy and precision of ±15% were achieved within the linear dynamic range of the calibration curve (2-500ng/mL) for human and mouse plasma samples. Mouse tumor tissue samples required the use of a calibration curve prepared in the same matrix due to the lower recovery of 40% from this matrix. Then, accuracy and precision were within the generally accepted range of ±15% for bioanalytical assays. Ko143 was stable in human plasma for up to 3 repeated freeze-thaw cycles and when stored at room temperature for up to 72h. However, when kept at room temperature in mouse plasma, Ko143 was rapidly degraded by esterase activity, which could be prevented by collection of blood into sodium fluoride-containing tubes and maintaining samples on ice during pretreatment. A preliminary pharmacokinetics study in mice demonstrated the applicability of this assay for ABCG2 resistance studies in vivo.

  5. A new method to assess the accuracy of a Cone Beam Computed Tomography scanner by using a non-contact reverse engineering technique.

    PubMed

    Martorelli, Massimo; Ausiello, Pietro; Morrone, Renato

    2014-04-01

    Today Cone Beam Computed Tomography (CBCT) has become an important image technique for dento-maxilla facial applications. In the paper a new method to assess the geometric accuracy of these systems was proposed. It uses a free form benchmark model and a non-contact Reverse Engineering (RE) system. The test geometry chosen for this study was designed in such a way that it simulated human spongy bone, cortical bone, gingiva and teeth and it composed of removable free form parts. It was acquired with a high-resolution laser scanner (D700 Scanner - 3Shape, Denmark). The reference 3D surface models obtained with the laser scanner was compared with the 3D models that were created from a CBCT system (Scanora 3D - Soderex, Finland) and from a traditional Multi-Slice Computed Tomography (MSCT) scanner (LightSpeed VCT 64 Slice - General Electric, USA) at different reconstruction settings, using an iterative closest point algorithm (ICP) in Geomagic(®) software. The comparison between the different pairs of CAD models clearly shows that there is a good overlap between the models. Although the results obtained in this study could lead to increase the use of CBCT for an increasing number of dental procedures, the publication of the European Commission guidelines represents a baseline on which the clinicians should rely heavily when considering the use of CBCT in their practice. The results of this research show that the accuracy of CBCT 3D models is comparable to MSCT 3D models. Copyright © 2014 Elsevier Ltd. All rights reserved.

  6. An expedient reverse-phase high-performance chromatography (RP-HPLC) based method for high-throughput analysis of deferoxamine and ferrioxamine in urine.

    PubMed

    Arshad, Bushra; Iqbal, Tahira; Akram, Sumia; Mushtaq, Muhammad

    2017-02-01

    The present study was planned to optimize and validate an expedient reverse-phase high chromatography (RP-HPLC) based protocol for the analysis of deferoxamine (DFO) and ferrioxamine (FO) in urinary execration of patients suffering β-thalassemia major. The optimized RP-HPLC method was found to be linear over the wide range of DFO and FO concentration (1-90 μg/mL) with appreciable recovery rates (79.64-97.30%) of quality controls at improved detection and quantitation limits and acceptable inter and intraday variability. Real-time analysis of DFO and FO in the urine of thalassemic patients (male and female) at different intervals of Desferal®(Novartis Pharmaceuticals Corporation) injection revealed DFO and FO excretion at significantly (p < 0) different rates. The maximum concentrations of DFO (76.7 ± 3.06 μg/mL) and FO (74.2 ± 3.25 μg/mL) were found in urine samples, collected after 6 h of drug infusion while the minimum levels of DFO (1.10 ± 0.12 μg/mL) and FO (2.97 ± 0.13 μg/mL) were excreted by patients after 24 h. The present paper offers balanced conditions for an expedient, reliable and quick determination of DFO and FO in urine samples. Copyright © 2016 John Wiley & Sons, Ltd.

  7. Stability-indicating capillary zone electrophoresis method for the assessment of recombinant human granulocyte-macrophage colony-stimulating factor and its correlation with reversed-phase liquid chromatography method and bioassay.

    PubMed

    Dalmora, Sergio Luiz; Butzge, Cairo dos Santos; Machado, Francine Trevisan; Walter, Maurício Elesbão; Dalmora, Maria Elisabeth de Ávila; Souto, Ricardo Bizogne

    2012-05-30

    A stability-indicating capillary zone electrophoresis (CZE) method was validated for the analysis of granulocyte-macrophage colony-stimulating factor (rhGM-CSF) using leuprorelin acetate (LA), as internal standard (IS). A fused-silica capillary (75 μm i.d.; effective length, 72 cm) was used at 25 °C; the applied voltage was 12 kV. The background electrolyte solution consisted of 50mM di-sodium hydrogen phosphate solution at pH 8.8. Injections were performed using a pressure mode at 50 mbar for 9s, with detection by photodiode array detector set at 200 nm. Specificity and stability-indicating capability were established in degradation studies, which also showed that there was no interference of the excipients. The method was linear over the concentration range of 2.5-200 μg mL(-1) (r(2)=0.9995) and the limit of detection (LOD) and limit of quantitation (LOQ) were 0.79 μg mL(-1) and 2.5 μg mL(-1), respectively. The accuracy was 99.14% with bias lower than 1.40%. The method was applied to the quantitative analysis of biopharmaceutical formulations, and the results were correlated to those of a validated reversed-phase LC method (RP-LC), and an in vitro bioassay, showing non-significant differences (p>0.05).

  8. Reversible simulation of irreversible computation

    NASA Astrophysics Data System (ADS)

    Li, Ming; Tromp, John; Vitányi, Paul

    1998-09-01

    Computer computations are generally irreversible while the laws of physics are reversible. This mismatch is penalized by among other things generating excess thermic entropy in the computation. Computing performance has improved to the extent that efficiency degrades unless all algorithms are executed reversibly, for example by a universal reversible simulation of irreversible computations. All known reversible simulations are either space hungry or time hungry. The leanest method was proposed by Bennett and can be analyzed using a simple ‘reversible’ pebble game. The reachable reversible simulation instantaneous descriptions (pebble configurations) of such pebble games are characterized completely. As a corollary we obtain the reversible simulation by Bennett and, moreover, show that it is a space-optimal pebble game. We also introduce irreversible steps and give a theorem on the tradeoff between the number of allowed irreversible steps and the memory gain in the pebble game. In this resource-bounded setting the limited erasing needs to be performed at precise instants during the simulation. The reversible simulation can be modified so that it is applicable also when the simulated computation time is unknown.

  9. A method for determining regioisomer abundances of polyunsaturated triacylglycerols in omega-3 enriched fish oils using reversed-phase liquid chromatography and triple-stage mass spectrometry.

    PubMed

    Cubero Herrera, Lisandra; Ramaley, Louis; Potvin, Michael A; Melanson, Jeremy E

    2013-08-15

    Reversed-phase high performance liquid chromatography (RP-HPLC), followed by post-column addition of lithium salts and electrospray ionisation triple-stage mass spectrometry (ESI-MS(3)) of lithiated TAG adducts, is shown to provide a useful method for the positional analysis of triacylglycerols (TAGs) in fish oils containing eicosapentaenoic (EPA, 20:5) and docosahexaenoic acids (DHA, 22:6). One prominent fragmentation pathway in the ESI-MS(3) of these adduct ions involves the loss of a fatty acid from the sn-1/3 position in the first step followed by the loss of an α,β-unsaturated fatty acid from the sn-2 position in the second. Regioisomeric TAGs of the type ABA and AAB produced abundant product ions - [ABA+Li-RACOOH-R'BCHCHCOOH](+) and [AAB+Li-RACOOH-R'ACHCHCOOH](+) - the relative intensities of which were dependent on the position of acyl substituents. Standard solutions of TAGs containing different ratios of the regioisomeric pairs MME/MEM, PPE/PEP, PPD/PDP, EEP/EPE and DDP/DPD (M=14:0, P=16:0, E=20:5, D=22:6) were analysed by ESI-MS(3) with a quadrupole linear ion trap instrument. Methodology developed on the standards was applied to quantifying the relative isomeric abundances of EPA and DHA in several fish oil samples. DHA was preferentially located at the sn-2 position in both DHA-containing TAGs studied, while EPA was either observed at near equal levels in all positions, or predominantly at the sn-1 and -3 positions in some cases. The analysis protocol allows for quantification of the designated regioisomers in one simple, rapid chromatographic procedure using a single column and has the advantage of specificity over other methods for the positional analysis of TAGs, since it eliminates interferences associated with co-eluting TAGs of the same molecular weight that yield isobaric diacylglycerol-like product ions. Crown Copyright © 2013. Published by Elsevier Ltd. All rights reserved.

  10. Reversible brazing process

    SciTech Connect

    Pierce, J.D.; Stephens, J.J.; Walker, C.A.

    1999-09-14

    A method of reversibly brazing surfaces together is disclosed. An interface is affixed to each surface. The interfaces can be affixed by processes such as mechanical joining, welding, or brazing. The two interfaces are then brazed together using a brazing process that does not defeat the surface to interface joint. Interfaces of materials such as Ni-200 can be affixed to metallic surfaces by welding or by brazing with a first braze alloy. The Ni-200 interfaces can then be brazed together using a second braze alloy. The second braze alloy can be chosen so that it minimally alters the properties of the interfaces to allow multiple braze, heat and disassemble, rebraze cycles.

  11. Reversible brazing process

    DOEpatents

    Pierce, Jim D.; Stephens, John J.; Walker, Charles A.

    1999-01-01

    A method of reversibly brazing surfaces together. An interface is affixed to each surface. The interfaces can be affixed by processes such as mechanical joining, welding, or brazing. The two interfaces are then brazed together using a brazing process that does not defeat the surface to interface joint. Interfaces of materials such as Ni-200 can be affixed to metallic surfaces by welding or by brazing with a first braze alloy. The Ni-200 interfaces can then be brazed together using a second braze alloy. The second braze alloy can be chosen so that it minimally alters the properties of the interfaces to allow multiple braze, heat and disassemble, rebraze cycles.

  12. Long-acting reversible contraception.

    PubMed

    Peck, Susan A

    2013-10-01

    Although short-acting reversible hormonal contraceptives, such as oral contraceptives and the contraceptive patch and vaginal ring, remain the most commonly used contraceptive methods in the United States, they are also associated with the highest failure rates. Long-acting reversible contraception (LARC) methods, such as intrauterine devices and contraceptive implants, offer high continuation rates and very low failure rates, and are safe for use in most women. The provision of LARC methods to adolescent, young adult and nulliparous women is a relatively new concept that offers an innovative option for these populations.

  13. Design and Assessment of a Real Time Reverse Transcription-PCR Method to Genotype Single-Stranded RNA Male-Specific Coliphages (Family Leviviridae).

    EPA Science Inventory

    A real-time, reverse transcription-PCR (RT-qPCR) assay was developed to differentiate the four genogroups of male-specific ssRNA coliphages (FRNA) (family Leviviridae). As FRNA display a trend of source-specificity (human sewage or animal waste) at the genogroup level, this assa...

  14. Design and Assessment of a Real Time Reverse Transcription-PCR Method to Genotype Single-Stranded RNA Male-Specific Coliphages (Family Leviviridae).

    EPA Science Inventory

    A real-time, reverse transcription-PCR (RT-qPCR) assay was developed to differentiate the four genogroups of male-specific ssRNA coliphages (FRNA) (family Leviviridae). As FRNA display a trend of source-specificity (human sewage or animal waste) at the genogroup level, this assa...

  15. Direct method for determination of Sudan I in FD&C Yellow No. 6 and D&C Orange No. 4 by reversed-phase liquid chromatography.

    PubMed

    Petigara, Bhakti R; Scher, Alan L

    2007-01-01

    A reversed-phase liquid chromatographic method was developed to determine parts-per-million and higher levels of Sudan 1, 1-(phenylazo)-2-naphthalenol, in the disulfo monoazo color additive FD&C Yellow No. 6 and in a related monosulfo monoazo color additive, D&C Orange No. 4. Sudan I, the corresponding unsulfonated monoazo dye, is a known impurity in these color additives. The color additives are dissolved in water and methanol, and the filtered solutions are directly chromatographed, without extraction or concentration, by using gradient elution at 0.25 mL/min. Calibrations from peak areas at 485 nm were linear. At a 99% confidence level, the limits of determination were 0.008 microg Sudan I/mL (0.4 ppm) in FD&C Yellow No. 6 and 0.011 microg Sudan I/mL (0.00011%) in D&C Orange No. 4. The confidence intervals were 0.202 +/- 0.002 microg Sudan I/mL (10.1 +/- 0.1 ppm) near the specification level for Sudan I in FD&C Yellow No. 6 and 20.0 +/- 0.2 microg Sudan I/mL (0.200 +/- 0.002%) near the highest concentration of Sudan I found in D&C Orange No. 4. A survey was conducted to determine Sudan I in 28 samples of FD&C Yellow No. 6 from 17 international manufacturers over 3 years, and in a pharmacology-tested sample. These samples were found to contain undetected levels (16 samples), 0.5-9.7 ppm Sudan I (0.01-0.194 microg Sudan I/mL in analyzed solutions; 11 samples including the pharmacology sample), and > or =10 ppm Sudan I (> or = 0.2 microg Sudan I/mL; 2 samples). Analyses of 21 samples of D&C Orange No. 4 from 8 international manufacturers over 4 years found Sudan I at undetected levels (8 samples), 0.0005 to < 0.005% Sudan I (0.05 to < 0.5 microg Sudan I/mL in analyzed solutions; 3 samples, including a pharmacology batch), 0.005 to <0.05% Sudan I (0.5 to <5 microg Sudan I/mL; 9 samples), and 0.18% Sudan I (18 microg Sudan I/mL; 1 sample).

  16. A field based detection method for Rose rosette virus using isothermal probe-based Reverse transcription-recombinase polymerase amplification assay.

    PubMed

    Babu, Binoy; Washburn, Brian K; Ertek, Tülin Sarigül; Miller, Steven H; Riddle, Charles B; Knox, Gary W; Ochoa-Corona, Francisco M; Olson, Jennifer; Katırcıoğlu, Yakup Zekai; Paret, Mathews L

    2017-09-01

    Rose rosette disease, caused by Rose rosette virus (RRV; genus Emaravirus) is a major threat to the rose industry in the U.S. The only strategy currently available for disease management is early detection and eradication of the infected plants, thereby limiting its potential spread. Current RT-PCR based diagnostic methods for RRV are time consuming and are inconsistent in detecting the virus from symptomatic plants. Real-time RT-qPCR assay is highly sensitive for detection of RRV, but it is expensive and requires well-equipped laboratories. Both the RT-PCR and RT-qPCR cannot be used in a field-based testing for RRV. Hence a novel probe based, isothermal reverse transcription-recombinase polymerase amplification (RT-exoRPA) assay, using primer/probe designed based on the nucleocapsid gene of the RRV has been developed. The assay is highly specific and did not give a positive reaction to other viruses infecting roses belonging to both inclusive and exclusive genus. Dilution assays using the in vitro transcript showed that the primer/probe set is highly sensitive, with a detection limit of 1 fg/μl. In addition, a rapid technique for the extraction of viral RNA (<5min) has been standardized from RRV infected tissue sources, using PBS-T buffer (pH 7.4), which facilitates the virus adsorption onto the PCR tubes at 4°C for 2min, followed by denaturation to release the RNA. RT-exoRPA analysis of the infected plants using the primer/probe indicated that the virus could be detected from leaves, stems, petals, pollen, primary roots and secondary roots. In addition, the assay was efficiently used in the diagnosis of RRV from different rose varieties, collected from different states in the U.S. The entire process, including the extraction can be completed in 25min, with less sophisticated equipments. The developed assay can be used with high efficiency in large scale field testing for rapid detection of RRV in commercial nurseries and landscapes. Copyright © 2017 Elsevier B

  17. Effects of the Drop-set and Reverse Drop-set Methods on the Muscle Activity and Intramuscular Oxygenation of the Triceps Brachii among Trained and Untrained Individuals

    PubMed Central

    Goto, Masahiro; Nirengi, Shinsuke; Kurosawa, Yuko; Nagano, Akinori; Hamaoka, Takafumi

    2016-01-01

    Influence of different load exercise to muscle activity during subsequent exercise with 75% of one repetition maximum (RM) load among trained and untrained individuals was verified. Resistance-trained men who were involved in resistance training (n = 16) and healthy young men who did not exercise regularly (n = 16) were recruited for this study. Each subject performed bench pressing with a narrow grip exercise using two different training set methods, the drop-set (DS) (3 sets × 2-10 repetitions with 95-75% of 1RM) and the reverse drop-set (RDS) (3 sets × 3-10 repetitions with 55-75% of 1RM). The mean concentric contraction power, root mean square (RMS) of electromyography (EMG), area under the oxygenated hemoglobin (Oxy-Hb) curve, and time constant for muscle oxygen consumption (TcVO2mus) values of the triceps brachii were measured during and after the DS and RDS. The trained group demonstrated significantly higher mean muscle power (242.9 ± 39.6 W vs. 215.8 ± 31.7 W), RMS of EMG (86.4 ± 10.4 % vs. 68.3 ± 9.6 %), and area under the Oxy-Hb curve (38.6 ± 7.4 %• sec vs. 29.3 ± 5.8 %• sec) values during the DS than during the RDS (p < 0.05). However, in the untrained group none of the parameters differed significantly for both the DS and RDS. Furthermore, a negative correlation was detected between the area under the Oxy-Hb curve and muscle thickness (r = -0.51, p < 0.01). Long-term effects of DS on muscle strengthening and hypertrophy will be explored in further research. Key points The DS induced greater motor unit activation and intramuscular hypoxia in people who have been regularly performing resistance exercises for more than one year than the RDS. No mechanical or metabolic differences were detected between the DS and RDS among the subjects who had not participated in regular resistance training. The thicker a person’s muscles are, the more resistant they are to the induction of acute intramuscular hypoxia during muscle contraction. PMID:27928200

  18. DNA Aptamers to Human Immunodeficiency Virus Reverse Transcriptase Selected by a Primer-Free SELEX Method: Characterization and Comparison with Other Aptamers

    PubMed Central

    Lai, Yi-Tak

    2012-01-01

    A 30-nucleotide DNA aptamer (5′-AGGAAGGCTTTAGGTCTGAGATCTCGGAAT-3′, denoted PF1) selected for high affinity to human immunodeficiency virus reverse transcriptase (HIV RT) using a primer-free SELEX (systematic evolution of ligands by exponential enrichment) method was characterized to determine features promoting tight binding. PF1's equilibrium dissociation constant for RT was ∼80 nM, over 10-fold lower than a random 30-mer. Changing the 2 terminal diguanosine repeats (underlined above) to diadenosine or dithymidine modestly decreased binding. Any changes to the 2 central diguanosines dramatically decreased binding. Binding was highly sensitive to length, with any truncations that deleted part of the 4 diguanosine motifs resulting in a 6-fold or more decrease in affinity. Even a construct with all the diguanosine motifs but lacking the 5′ terminal A and 3 nucleotides at the 3′ end showed ∼3-fold binding decrease. Changes to the nucleotides between the diguanosines, even those that did not alter PF1's low secondary structure (free energy of folding ΔG=−0.61 kcal/mol), dramatically decreased binding, suggesting sequence specificity. Despite the diguanosine motifs, circular dichroism (CD) spectra indicated that PF1 did not form a G-quartet. PF1 inhibited HIV RT synthesis with a half-maximal inhibitory value (IC50) of ∼60 nM. Larger, more structured RT DNA aptamers based on the HIV polypurine tract and those that formed G-quartets (denoted S4 and R1T) were more potent inhibitors, with IC50 values of ∼4 and ∼1 nM, respectively. An RNA pseudoknot aptamer (denoted 1.1) showed an IC50 near 4 nM. Competition binding assays with PF1 and several previously characterized RT aptamers indicated that they all bound at or near the primer–template pocket. These other more structured and typically larger aptamers bound more tightly than PF1 to RT based on filter binding assays. Results indicate that PF1 represents a new class of RT aptamers that are

  19. Extension of the invariant environment refinement technique + reverse Monte Carlo method of structural modelling for interpreting experimental structure factors: The cases of amorphous silicon, phosphorus, and liquid argon

    NASA Astrophysics Data System (ADS)

    Gereben, Orsolya; Pusztai, László

    2011-08-01

    The invariant environment refinement technique, as applied to reverse Monte Carlo modelling [invariant environment refinement technique + reverse Monte Carlo (INVERT + RMC); M. J. Cliffe, M. T. Dove, D. A. Drabold, and A. L. Goodwin, Phys. Rev. Lett. 104, 125501 (2010), 10.1103/PhysRevLett.104.125501], is extended so that it is now applicable for interpreting the structure factor (instead of the pair distribution function). The new algorithm, called the local invariance calculation, is presented by the examples of amorphous silicon, phosphorus, and liquid argon. As a measure of the effectiveness of the new algorithm, the ratio of exactly fourfold coordinated Si atoms was larger than obtained previously by the INVERT-RMC scheme.

  20. Tubal Ligation Reversal

    MedlinePlus

    ... seal off the fallopian tubes, such as the Essure or Adiana systems, generally aren't reversible. In ... electrocautery). Some types of sterilization, such as the Essure system, are not considered reversible. Even if tubal ...

  1. Spin transfer torque and dc bias magnetic field effects on the magnetization reversal time of nanoscale ferromagnets at very low damping: Mean first-passage time versus numerical methods

    NASA Astrophysics Data System (ADS)

    Byrne, D. J.; Coffey, W. T.; Dowling, W. J.; Kalmykov, Y. P.; Titov, S. V.

    2016-02-01

    Spin transfer torque and bias field effects on the magnetization reversal time of a nanoscale ferromagnet are investigated in the very-low-damping regime via the energy-controlled diffusion equation. That equation is rooted in a generalization of the Kramers escape rate theory for point Brownian particles in a potential to the magnetic relaxation of a macrospin. Using the mean first-passage method, the reversal time is then evaluated in closed integral form for a nanomagnet with the free-energy density given in the standard form of superimposed easy-plane and in-plane easy-axis anisotropies with the dc bias field along the easy axis. The results completely agree with those yielded by independent numerical methods.

  2. Vasectomy and its reversal.

    PubMed

    Belker, A M

    1985-12-01

    Techniques, results, complications, and medicolegal aspects of vasectomy are discussed in this article. Emphasis is placed on techniques that prevent spontaneous recanalization of the ends of the vas deferens after vasectomy. Factors that affect the reversibility of vasectomy are discussed. New microsurgical techniques of vasectomy reversal are described, and results of these new techniques are compared with results of nonmicrosurgical techniques of vasectomy reversal. Indications for bypass vasoepididymostomy during vasectomy reversal procedures, as well as techniques for performing vasoepididymostomy, are discussed.

  3. Reverse Correlation in Neurophysiology

    ERIC Educational Resources Information Center

    Ringach, Dario; Shapley, Robert

    2004-01-01

    This article presents a review of reverse correlation in neurophysiology. We discuss the basis of reverse correlation in linear transducers and in spiking neurons. The application of reverse correlation to measure the receptive fields of visual neurons using white noise and m-sequences, and classical findings about spatial and color processing in…

  4. Long-Acting Reversible Contraception (LARC): IUD and Implant

    MedlinePlus

    f AQ FREQUENTLY ASKED QUESTIONS FAQ184 CONTRACEPTION Long-Acting Reversible Contraception (LARC): IUD and Implant • What are long-acting reversible contraception (LARC) methods? • How effective are LARC methods? • How ...

  5. Quantum Operation Time Reversal

    SciTech Connect

    Crooks, Gavin E.

    2008-03-25

    The dynamics of an open quantum system can be described by a quantum operation: A linear, complete positive map of operators. Here, I exhibit a compact expression for the time reversal of a quantum operation, which is closely analogous to the time reversal of a classical Markov transition matrix. Since open quantum dynamics are stochastic, and not, in general, deterministic, the time reversal is not, in general, an inversion of the dynamics. Rather, the system relaxes toward equilibrium in both the forward and reverse time directions. The probability of a quantum trajectory and the conjugate, time reversed trajectory are related by the heat exchanged with the environment.

  6. Object discrimination reversal as a method to assess cognitive impairment in nonhuman primate enhanced pre- and postnatal developmental (ePPND) studies: statistical power analysis.

    PubMed

    Cappon, Gregg D; Bowman, Christopher J; Hurtt, Mark E; Grantham, Lonnie E

    2012-10-01

    An important aspect of the enhanced pre- and postnatal developmental (ePPND) toxicity study in nonhuman primates (NHP) is that it combines in utero and postnatal assessments in a single study. However, it is unclear if NHP ePPND studies are suitable to perform all of the evaluations incorporated into rodent PPND studies. To understand the value of including cognitive assessment in a NHP ePPND toxicity study, we performed a power analysis of object discrimination reversal task data using a modified Wisconsin General Testing Apparatus (ODR-WGTA) from two NHP ePPND studies. ODR-WGTA endpoints evaluated were days to learning and to first reversal, and number of reversals. With α = 0.05 and a one-sided t-test, a sample of seven provided 80% power to predict a 100% increase in all three of the ODR-WGTA endpoints; a sample of 25 provided 80% power to predict a 50% increase. Similar power analyses were performed with data from the Cincinnati Water Maze (CWM) and passive avoidance tests from three rat PPND toxicity studies. Groups of 5 and 15 in the CWM and passive avoidance test, respectively, provided 80% power to detect a 100% change. While the power of the CWM is not far superior to the NHP ODR-WGTA, a clear advantage is the routine use of larger sample size, with a group of 20 rats the CWM provides ~90% power to detect a 50% change. Due to the limitations on the number of animals, the ODR-WGTA may not be suitable for assessing cognitive impairment in NHP ePPND studies.

  7. Rapid Detection of Subtype H10N8 Influenza Virus by One-Step Reverse Transcription–Loop-Mediated Isothermal Amplification Methods

    PubMed Central

    Bao, Hongmei; Feng, Xiaoxiao; Ma, Yong; Shi, Jianzhong; Zhao, Yuhui; Gu, Linlin

    2015-01-01

    We developed hemagglutinin- and neuraminidase-specific one-step reverse transcription–loop-mediated isothermal amplification assays for detecting the H10N8 virus. The detection limit of the assays was 10 copies of H10N8 virus, and the assays did not amplify nonspecific RNA. The assays can detect H10N8 virus from chicken samples with high sensitivity and specificity, and they can serve as an effective tool for detecting and monitoring H10N8 virus in live poultry markets. PMID:26378283

  8. Rapid Detection of Subtype H10N8 Influenza Virus by One-Step Reverse Transcription-Loop-Mediated Isothermal Amplification Methods.

    PubMed

    Bao, Hongmei; Feng, Xiaoxiao; Ma, Yong; Shi, Jianzhong; Zhao, Yuhui; Gu, Linlin; Wang, Xiurong; Chen, Hualan

    2015-12-01

    We developed hemagglutinin- and neuraminidase-specific one-step reverse transcription-loop-mediated isothermal amplification assays for detecting the H10N8 virus. The detection limit of the assays was 10 copies of H10N8 virus, and the assays did not amplify nonspecific RNA. The assays can detect H10N8 virus from chicken samples with high sensitivity and specificity, and they can serve as an effective tool for detecting and monitoring H10N8 virus in live poultry markets. Copyright © 2015, American Society for Microbiology. All Rights Reserved.

  9. A reversible molecular valve

    PubMed Central

    Nguyen, Thoi D.; Tseng, Hsian-Rong; Celestre, Paul C.; Flood, Amar H.; Liu, Yi; Stoddart, J. Fraser; Zink, Jeffrey I.

    2005-01-01

    In everyday life, a macroscopic valve is a device with a movable control element that regulates the flow of gases or liquids by blocking and opening passageways. Construction of such a device on the nanoscale level requires (i) suitably proportioned movable control elements, (ii) a method for operating them on demand, and (iii) appropriately sized passageways. These three conditions can be fulfilled by attaching organic, mechanically interlocked, linear motor molecules that can be operated under chemical, electrical, or optical stimuli to stable inorganic porous frameworks (i.e., by self-assembling organic machinery on top of an inorganic chassis). In this article, we demonstrate a reversibly operating nanovalve that can be turned on and off by redox chemistry. It traps and releases molecules from a maze of nanoscopic passageways in silica by controlling the operation of redox-activated bistable [2]rotaxane molecules tethered to the openings of nanopores leading out of a nanoscale reservoir. PMID:16006520

  10. Reverse photoacoustic standoff spectroscopy

    DOEpatents

    Van Neste, Charles W [Kingston, TN; Senesac, Lawrence R [Knoxville, TN; Thundat, Thomas G [Knoxville, TN

    2011-04-12

    A system and method are disclosed for generating a reversed photoacoustic spectrum at a greater distance. A source may emit a beam to a target and a detector measures signals generated as a result of the beam being emitted on the target. By emitting a chopped/pulsed light beam to the target, it may be possible to determine the target's optical absorbance by monitoring the intensity of light collected at the detector at different wavelengths. As the wavelength of light is changed, the target may absorb or reject each optical frequency. Rejection may increase the intensity at the sensing element and absorption may decrease the intensity. Accordingly, an identifying spectrum of the target may be made with the intensity variation of the detector as a function of illuminating wavelength.

  11. Stagnation point reverse flow combustor

    NASA Technical Reports Server (NTRS)

    Zinn, Ben T. (Inventor); Neumeier, Yedidia (Inventor); Seitzman, Jerry M. (Inventor); Jagoda, Jechiel (Inventor); Weksler, Yoav (Inventor)

    2008-01-01

    A method for combusting a combustible fuel includes providing a vessel having an opening near a proximate end and a closed distal end defining a combustion chamber. A combustible reactants mixture is presented into the combustion chamber. The combustible reactants mixture is ignited creating a flame and combustion products. The closed end of the combustion chamber is utilized for directing combustion products toward the opening of the combustion chamber creating a reverse flow of combustion products within the combustion chamber. The reverse flow of combustion products is intermixed with combustible reactants mixture to maintain the flame.

  12. Evaluation of rapid and sensitive reverse transcription loop-mediated isothermal amplification method for detecting infectious pancreatic necrosis virus in chum salmon (Oncorhynchus keta).

    PubMed

    Suebsing, Rungkarn; Oh, Myung-Joo; Kim, Jeong-Ho

    2011-07-01

    Reverse transcription loop-mediated isothermal amplification (RT-LAMP) was developed for detecting Infectious pancreatic necrosis virus (IPNV) in chum salmon (Oncorhynchus keta) in Korea. The RT-LAMP is a novel approach of nucleic acid gene amplification with high specificity, sensitivity, and rapidity under isothermal conditions. Based on the VP2/NS gene sequence of VR-299 and Jasper strains, a set of 6 IPNV-specific primers was designed to recognize 8 diverse sequences of the IPNV RNA. The assay was successfully optimized to detect IPNV at 65°C in 30 min. The detection limit was 0.075 tissue culture infectious dose infecting 50% of inoculated cultures per milliliter (TCID(50)/ml) from IPNV-infected rainbow trout gonad (RTG)-2 cells, whereas nested reverse transcription polymerase chain reaction (nRT-PCR) had a sensitivity of 7.5 TCID(50)/ml. Using RT-LAMP assay, field samples were analyzed and the results compared with those of nRT-PCR assay. Two hundred and sixty-six out of 659 (40.4%) samples were IPNV-positive by RT-LAMP, whereas 182 of 659 samples (27.6%) were IPNV-positive by nRT-PCR. The results indicate that RT-LAMP can be a useful tool for early field diagnosis of IPNV.

  13. A method for rapid detection and genotype identification of hepatitis C virus 1-6 by one-step reverse transcription loop-mediated isothermal amplification.

    PubMed

    Nyan, Dougbeh-Chris; Swinson, Kevin L

    2016-02-01

    Hepatitis C virus (HCV) is probably the leading cause of liver cirrhosis and hepatocellular carcinoma globally. Diagnostic tools conventionally used for the detection and identification of HCV infection are technically demanding, time-consuming, and costly for resource-limited environments. This study reports the development of the first rapid loop-mediated reverse transcription isothermal amplification assay that rapidly detects and identifies HCV genotypes in blood components. RNA extracted from donor plasma and serum specimens was applied to a one-step reverse transcription loop-mediated isothermal amplification reaction performed with HCV-specific oligonucleotides. Reactions were conducted at 63.5 °C for 30-60 min. The diagnostic characteristics of the assay were investigated and validated with clinical specimens. Electrophoretic analysis of amplification revealed detection and identification of HCV genotypes 1-6. Positive amplification revealed unique ladder-like banding patterns that identified each HCV genotype. The assay demonstrated a sensitivity of 91.5% and specificity of 100%. Rapid naked-eye detection of HCV infection was facilitated by observation of an intense fluorescent glow of amplified targets under UV illumination. These diagnostic characteristics highlight the potential utility of this assay for the rapid detection and genotype identification of HCV infection in field and point-of-care settings in endemic regions and resource-limited environments. Copyright © 2015 The Authors. Published by Elsevier Ltd.. All rights reserved.

  14. Bottom-up derivation of conservative and dissipative interactions for coarse-grained molecular liquids with the conditional reversible work method

    SciTech Connect

    Deichmann, Gregor; Marcon, Valentina; Vegt, Nico F. A. van der

    2014-12-14

    Molecular simulations of soft matter systems have been performed in recent years using a variety of systematically coarse-grained models. With these models, structural or thermodynamic properties can be quite accurately represented while the prediction of dynamic properties remains difficult, especially for multi-component systems. In this work, we use constraint molecular dynamics simulations for calculating dissipative pair forces which are used together with conditional reversible work (CRW) conservative forces in dissipative particle dynamics (DPD) simulations. The combined CRW-DPD approach aims to extend the representability of CRW models to dynamic properties and uses a bottom-up approach. Dissipative pair forces are derived from fluctuations of the direct atomistic forces between mapped groups. The conservative CRW potential is obtained from a similar series of constraint dynamics simulations and represents the reversible work performed to couple the direct atomistic interactions between the mapped atom groups. Neopentane, tetrachloromethane, cyclohexane, and n-hexane have been considered as model systems. These molecular liquids are simulated with atomistic molecular dynamics, coarse-grained molecular dynamics, and DPD. We find that the CRW-DPD models reproduce the liquid structure and diffusive dynamics of the liquid systems in reasonable agreement with the atomistic models when using single-site mapping schemes with beads containing five or six heavy atoms. For a two-site representation of n-hexane (3 carbons per bead), time scale separation can no longer be assumed and the DPD approach consequently fails to reproduce the atomistic dynamics.

  15. Bottom-up derivation of conservative and dissipative interactions for coarse-grained molecular liquids with the conditional reversible work method.

    PubMed

    Deichmann, Gregor; Marcon, Valentina; van der Vegt, Nico F A

    2014-12-14

    Molecular simulations of soft matter systems have been performed in recent years using a variety of systematically coarse-grained models. With these models, structural or thermodynamic properties can be quite accurately represented while the prediction of dynamic properties remains difficult, especially for multi-component systems. In this work, we use constraint molecular dynamics simulations for calculating dissipative pair forces which are used together with conditional reversible work (CRW) conservative forces in dissipative particle dynamics (DPD) simulations. The combined CRW-DPD approach aims to extend the representability of CRW models to dynamic properties and uses a bottom-up approach. Dissipative pair forces are derived from fluctuations of the direct atomistic forces between mapped groups. The conservative CRW potential is obtained from a similar series of constraint dynamics simulations and represents the reversible work performed to couple the direct atomistic interactions between the mapped atom groups. Neopentane, tetrachloromethane, cyclohexane, and n-hexane have been considered as model systems. These molecular liquids are simulated with atomistic molecular dynamics, coarse-grained molecular dynamics, and DPD. We find that the CRW-DPD models reproduce the liquid structure and diffusive dynamics of the liquid systems in reasonable agreement with the atomistic models when using single-site mapping schemes with beads containing five or six heavy atoms. For a two-site representation of n-hexane (3 carbons per bead), time scale separation can no longer be assumed and the DPD approach consequently fails to reproduce the atomistic dynamics.

  16. Development and evaluation of a simple assay for Marburg virus detection using a reverse transcription-loop-mediated isothermal amplification method.

    PubMed

    Kurosaki, Yohei; Grolla, Allen; Fukuma, Aiko; Feldmann, Heinz; Yasuda, Jiro

    2010-07-01

    Marburg virus (MARV) causes a severe hemorrhagic fever in humans with a high mortality rate. The rapid and accurate identification of the virus is required to appropriately provide infection control and outbreak management. Here, we developed and evaluated a one-step reverse transcription-loop-mediated isothermal amplification (RT-LAMP) assay for the rapid and simple detection of MARV. By combining two sets of primers specific for the Musoke and Ravn genetic lineages, a multiple RT-LAMP assay detected MARV strains of both lineages, and no cross-reactivity with other hemorrhagic fever viruses (Ebola virus and Lassa virus) was observed. The assay could detect 10(2) copies of the viral RNA per tube within 40 min by real-time monitoring of the turbidities of the reaction mixtures. The assay was further evaluated using viral RNA extracted from clinical specimens collected in the 2005 Marburg hemorrhagic fever outbreak in Angola and yielded positive results for samples containing MARV at greater than 10(4) 50% tissue culture infective doses/ml, exhibiting 78% (14 of 18 samples positive) consistency with the results of a reverse transcription-PCR assay carried out in the field laboratory. The results obtained by both agarose gel electrophoresis and naked-eye judgment indicated that the RT-LAMP assay developed in this study is an effective tool for the molecular detection of MARV. Furthermore, it seems suitable for use for field diagnostics or in laboratories in areas where MARV is endemic.

  17. The eyeglass reversal.

    PubMed

    Oh, Songjoo

    2011-07-01

    Some figures, such as the Necker cube, are spontaneously reversible between alternative percepts. Before learning those skilled reversals, how do people achieve reversals for the very first time? It has been known that, in the case of a first reversal, people can be expected to see the reversal when given specific information about how the figures are ambiguous. This point was confirmed by using drawing versions of reversible figures. To demonstrate how intention plays a role in the initial reversal of a real object, a pair of regular eyeglasses, reversible in perspective, were presented to naïve observers in monocular vision. When the eyeglasses were viewed inwardly and the observers were given information that the eyeglasses could be ambiguous, they were able to easily see the reversal. When the eyeglasses were viewed outwardly, observers saw it only after they had been informed of exactly what the two alternative percepts were.Interestingly, many observers often mistakenly saw the inwardly viewed eyeglasses as placed outwardly from the beginning of the observation, while they saw the outwardly viewed eyeglasses correctly. Taking these results together, for the first reversal of a real object, the specificity of intention varies with the ambiguity of the object.

  18. Ice ages and geomagnetic reversals

    NASA Technical Reports Server (NTRS)

    Wu, Patrick

    1992-01-01

    There have been speculations on the relationship between climatic cooling and polarity reversals of the earth's magnetic field during the Pleistocene. Two of the common criticisms on this relationship have been the reality of these short duration geomagnetic events and the accuracy of their dates. Champion et al. (1988) have reviewed recent progress in this area. They identified a total of 10 short-duration polarity events in the last 1 Ma and 6 of these events have been found in volcanic rocks, which also have K-Ar dates. Supposing that the speculated relationship between climatic cooling and geomagnetic reversals actually exist, two mechanisms that assume climatic cooling causes short period magnetic reversals will be investigated. These two methods are core-mantle boundary topography and transfer of the rotational energy to the core.

  19. Reversible logic for supercomputing.

    SciTech Connect

    DeBenedictis, Erik P.

    2005-05-01

    This paper is about making reversible logic a reality for supercomputing. Reversible logic offers a way to exceed certain basic limits on the performance of computers, yet a powerful case will have to be made to justify its substantial development expense. This paper explores the limits of current, irreversible logic for supercomputers, thus forming a threshold above which reversible logic is the only solution. Problems above this threshold are discussed, with the science and mitigation of global warming being discussed in detail. To further develop the idea of using reversible logic in supercomputing, a design for a 1 Zettaflops supercomputer as required for addressing global climate warming is presented. However, to create such a design requires deviations from the mainstream of both the software for climate simulation and research directions of reversible logic. These deviations provide direction on how to make reversible logic practical.

  20. Perspective: reverse evolution.

    PubMed

    Teotónio, H; Rose, M R

    2001-04-01

    For some time, the reversibility of evolution was primarily discussed in terms of comparative patterns. Only recently has this problem been studied using experimental evolution over shorter evolutionary time frames. This has raised questions of definition, experimental procedure, and the hypotheses being tested. Experimental evolution has provided evidence for multiple population genetic mechanisms in reverse evolution, including pleiotropy and mutation accumulation. It has also pointed to genetic factors that might prevent reverse evolution, such as a lack of genetic variability, epistasis, and differential genotype-by-environment interactions. The main focus of this perspective is on laboratory studies and their relevance to the genetics of reverse evolution. We discuss reverse evolution experiments with Drosophila, bacterial, and viral populations. Field studies of the reverse evolution of melanism in the peppered moth are also reviewed.

  1. HIV-1 Reverse Transcription

    PubMed Central

    Hu, Wei-Shau; Hughes, Stephen H.

    2012-01-01

    Reverse transcription and integration are the defining features of the Retroviridae; the common name “retrovirus” derives from the fact that these viruses use a virally encoded enzyme, reverse transcriptase (RT), to convert their RNA genomes into DNA. Reverse transcription is an essential step in retroviral replication. This article presents an overview of reverse transcription, briefly describes the structure and function of RT, provides an introduction to some of the cellular and viral factors that can affect reverse transcription, and discusses fidelity and recombination, two processes in which reverse transcription plays an important role. In keeping with the theme of the collection, the emphasis is on HIV-1 and HIV-1 RT. PMID:23028129

  2. Characterisation of reversed-phase liquid chromatography stationary phases for the analysis of basic pharmaceuticals: eluent properties and comparison of empirical test methods.

    PubMed

    Vervoort, R J; Ruyter, E; Debets, A J; Claessens, H A; Cramers, C A; de Jong, G J

    2001-10-05

    The reversed-phase liquid chromatographic analysis of basic pharmaceuticals can be problematic. Both the properties of the eluent and the stationary phase can influence the chromatographic performance. Therefore selection of suitable experimental conditions for the analysis of basic compounds can be difficult. This paper shows that the organic modifier and the nature of the buffer influence the eluent properties. Moreover, the nature and amount of modifier also influence the basicity of the analytes. Investigations showed that the nature of the buffer can have a significant influence on retention and peak shape of basic compounds. Test procedures using basic analytes as test probes provided relevant information with respect to selecting columns to analyse basic pharmaceutical compounds. Test procedures using compounds like aniline, phenol and benzene were found to be less suitable.

  3. Detection and identification of dengue virus isolates from Brazil by a simplified reverse transcription-polymerase chain reaction (RT-PCR) method.

    PubMed

    Figueiredo, L T; Batista, W C; Igarashi, A

    1997-01-01

    We show here a simplified RT-PCR for identification of dengue virus types 1 and 2. Five dengue virus strains, isolated from Brazilian patients, and yellow fever vaccine 17DD as a negative control, were used in this study. C6/36 cells were infected and supernatants were collected after 7 days. The RT-PCR, done in a single reaction vessel, was carried out following a 1/10 dilution of virus in distilled water or in a detergent mixture containing Nonidet P40. The 50 microliters assay reaction mixture included 50 pmol of specific primers amplifying a 482 base pair sequence for dengue type 1 and 210 base pair sequence for dengue type 2. In other assays, we used dengue virus consensus primers having maximum sequence similarity to the four serotypes, amplifying a 511 base pair sequence. The reaction mixture also contained 0.1 mM of the four deoxynucleoside triphosphates, 7.5 U of reverse transcriptase, 1U of thermostable Taq DNA polymerase. The mixture was incubated for 5 minutes at 37 degrees C for reverse transcription followed by 30 cycles of two-step PCR amplification (92 degrees C for 60 seconds, 53 degrees C for 60 seconds) with slow temperature increment. The PCR products were subjected to 1.7% agarose gel electrophoresis and visualized by UV light after staining with ethidium bromide solution. Low virus titer around 10(3, 6) TCID50/ml was detected by RT-PCR for dengue type 1. Specific DNA amplification was observed with all the Brazilian dengue strains by using dengue virus consensus primers. As compared to other RT-PCRs, this assay is less laborious, done in a shorter time, and has reduced risk of contamination.

  4. Directed, strong, and reversible immobilization of proteins tagged with a β-trefoil lectin domain: a simple method to immobilize biomolecules on plain agarose matrixes.

    PubMed

    López-Gallego, Fernando; Acebrón, Ivan; Mancheño, Jose Miguel; Raja, Sebastian; Lillo, M Pilar; Guisán Seijas, Jose Manuel

    2012-03-21

    A highly stable lipase from Geobacillus thermocatenolatus (BTL2) and the enhanced green fluorescent protein from Aquorea victoria (EGFP) were recombinantly produced N-terminally tagged to the lectin domain of the hemolytic pore-forming toxin LSLa from the mushroom Laetiporus sulphureus . Such a domain (LSL(150)), recently described as a novel fusion tag, is based on a β-trefoil scaffold with two operative binding sites for galactose or galactose-containing derivatives. The fusion proteins herein analyzed have enabled us to characterize the binding mode of LSL(150) to polymeric and solid substrates such as agarose beads. The lectin-fusion proteins are able to be quantitatively bound to both cross-linked and non-cross-linked agarose matrixes in a very rapid manner, resulting in a surprisingly dynamic protein distribution inside the porous beads that evolves from heterogeneous to homogeneous along the postimmobilization time. Such dynamic distribution can be related to the reversible nature of the LSL(150)-agarose interaction. Furthermore, this latter interaction is temperature dependent since it is 4-fold stronger when the immobilization takes place at 25 °C than when it does at 4 °C. The strongest lectin-agarose interaction is also quite stable under a survey of different conditions such as high temperatures (up to 60 °C) or high organic solvent concentrations (up to 60% of acetonitrile). Notably, the use of cross-linked agarose would endow the system with more robustness due to its better mechanical properties compared to the noncross-linked one. The stability of the LSL(150)-agarose interaction would prevent protein leaching during the operation process unless high pH media are used. In summary, we believe that the LSL(150) lectin domain exhibits interesting structural features as an immobilization domain that makes it suitable to reversibly immobilize industrially relevant enzymes in very simple carriers as agarose.

  5. Reverse design of the automatic transmission case

    NASA Astrophysics Data System (ADS)

    Li, Yuan; Li, Yuan; Wu, Jiao; Jiang, Wangping; Zhang, Zhou

    2017-04-01

    The 3D point cloud data of the AT case are achieved by 3D scanning, and the 3D model are set up by multi-curve-surface reverse design method. The free modal FEM model of the case is built, the modal frequencies and the modes of first 6 orders show that the reverse design model meets the design requirements.

  6. Reverse Core Engine with Thrust Reverser

    NASA Technical Reports Server (NTRS)

    Suciu, Gabriel L. (Inventor); Chandler, Jesse M. (Inventor)

    2017-01-01

    An engine system has a gas generator, a bi-fi wall surrounding at least a portion of the gas generator, a casing surrounding a fan, and the casing having first and second thrust reverser doors which in a deployed position abut each other and the bi-fi wall.

  7. A simple semi-preparative reversed-phase HPLC/PDA method for separation and quantification of glycyrrhizin in nine samples of Glycyrrhiza glabra root collected from different geographical origins.

    PubMed

    Basar, Norazah; Talukdar, Anupam D; Nahar, Lutfun; Stafford, Angela; Kushiev, Habibjon; Kan, Asuman; Sarker, Satyajit D

    2014-01-01

    Glycyrrhiza glabra L. (Fabaceae), commonly known as 'liquorice', is one of the most popular ingredients in several traditional herbal medicinal preparations, and glycyrrhizin is the major glycoside present in this plant. The content of glycyrrhizin may vary among G. glabra samples collected from various geographical origins, which may affect the therapeutic efficacy. Thus, quantification of glycyrrhizin in G. glabra samples is important. To develop and validate a simple semi-preparative reversed-phase HPLC with photodiode array (PDA) method for separation and quantification of glycyrrhizin in nine samples of G. glabra root collected from various geographical origins. Dried and ground root of G. glabra was Soxhlet-extracted sequentially with n-hexane and methanol (MeOH). The separation and quantification of glycyrrhizin was achieved on a C18 reversed-phase semi-preparative column using a gradient mobile phase, 30-100% solvent B in solvent A in 30 min (solvent A: 0.1% v/v trifluoroacetic acid (TFA) in water and solvent B: 0.1% v/v of TFA in MeOH), at a flow rate of 3.00 mL/min and UV detection at 254 nm. A simple semi-preparative reversed-phase HPLC/PDA method allowing clear separation and quantification of glycyrrhizin content in nine samples has been validated in terms of linearity, selectivity, limits of detection, precision, accuracy and detection. Concentration levels of glycyrrhizin were between 0.177 and 0.688% w/w of dry materials. This method is precise, less time consuming and more cost effective, and can be used for the quality control of any G. glabra sample with regard to its glycyrrhizin contents. Copyright © 2014 John Wiley & Sons, Ltd.

  8. Development of anion-exchange/reversed-phase high performance liquid chromatography-inductively coupled plasma-mass spectrometry methods for the speciation of bio-available iodine and bromine from edible seaweed.

    PubMed

    Romarís-Hortas, Vanessa; Bermejo-Barrera, Pilar; Moreda-Piñeiro, Antonio

    2012-05-04

    Anion exchange high performance liquid chromatography hyphenated with inductively coupled plasma-mass spectrometry has been novelly applied to assess inorganic (iodide and iodate) and organic (3-iodotyrosine - MIT, and 3,5-diiodotyrosine - DIT) iodine species in a single chromatographic run. The optimized operating conditions (Dionex IonPac AS7, gradient elution with 175 mM ammonium nitrate plus 15% (v/v) methanol, pH 3.8, as a mobile phase and flow rates within the 0.5-1.5 mL min(-1) range) have also been used to perform inorganic bromine speciation analysis (bromide and bromate). The developed method has been applied for determining the bio-available contents of iodine and bromine species in dialyzates from edible seaweed. Reverse phase high performance liquid chromatography (Zorbax Eclipse XDB-C8, gradient elution with 0.2% (m/m) acetic acid, and 0.2% (m/m) acetic acid in methanol, as mobile phases, and a constant flow rate of 0.75 mL min(-1)) also hyphenated with inductively coupled plasma-mass spectrometry was used to confirm the presence of organic iodine species (MIT and DIT) in the dialyzates. The verification of the presence of iodinated amino acids (MIT and DIT) in the extracts was also performed by reverse phase high performance liquid chromatography-electrospray ionization-mass spectrometry (LTQ Orbitrap). The developed methods have provided good repeatability (RSD values lower than 10% for both anion exchange and reverse phase separations) and analytical recoveries within the 90-105% range for all cases. The in vitro bio-availability method consisted of a simulated gastric and an intestinal digestion/dialysis (10 kDa molecular weight cut-off - MWCO) two-stage procedure. Iodide and MIT were the main bio-available species quantified, whereas bromide was the major bromine species found in the extracts.

  9. A Flow Method for Chemiluminescence Determination of Antimony(III) and Antimony(V) Using a Rhodamine B-Cetyltrimethylammonium Chloride Reversed Micelle System Following On-Line Extraction.

    PubMed

    Hasanin, Tamer H A; Yamamoto, Tomoyuki; Okamoto, Yasuaki; Ishizaka, Shoji; Fujiwara, Terufumi

    2016-01-01

    A rapid and sensitive flow method, based on the combination of on-line solvent extraction with reversed micellar mediated chemiluminescence (CL) detection using rhodamine B (RB), was developed for the determination of antimony(III) and antimony(V) in aqueous samples. The on-line extraction procedure involved ion-pair formation of the antimony(V) chloro-complex anion with the protonated RBH(+) ion and its extraction from an aqueous hydrochloric acid solution into toluene, followed by phase separation using a microporous membrane. When in a flow cell of a detector, the ion-pair in the extract driven was mixed with the reversed micellar solution of cetyltrimethylammonium chloride in 1-hexanol-cyclohexane/water (0.60 mol dm(-3) H2SO4) containing cerium(IV), its uptake by the reversed micelles and the subsequent CL oxidation of RB with Ce(IV) occurred easily, then the produced CL signal was measured. Using the proposed flow method under the optimized experimental conditions, a detection limit (DL) of 0.35 μmol dm(-3) and a linear calibration graph with a dynamic range from DL to 16 μmol dm(-3) were obtained for Sb(V) with a precision of 1.4% relative standard deviation (n = 5) at the Sb(V) concentration of 8.2 μmol dm(-3). The present method was successfully applied to the determination of Sb(V) in water samples and to the differential determination of Sb(III) and Sb(V) in copper electrolyte industrial samples, where total antimony Sb(III) + Sb(V) was determined after oxidation of Sb(III) to Sb(V) with Ce(IV) and Sb(III) was calculated by difference, for which the DL was almost the same as that for Sb(V).

  10. Quantum reverse hypercontractivity

    SciTech Connect

    Cubitt, Toby; Kastoryano, Michael; Montanaro, Ashley; Temme, Kristan

    2015-10-15

    We develop reverse versions of hypercontractive inequalities for quantum channels. By generalizing classical techniques, we prove a reverse hypercontractive inequality for tensor products of qubit depolarizing channels. We apply this to obtain a rapid mixing result for depolarizing noise applied to large subspaces and to prove bounds on a quantum generalization of non-interactive correlation distillation.

  11. Clocked Thrust Reversers

    NASA Technical Reports Server (NTRS)

    Suciu, Gabriel L. (Inventor); Chandler, Jesse M. (Inventor)

    2017-01-01

    An aircraft includes a fuselage including a propulsion system supported within an aft portion. A thrust reverser is mounted proximate to the propulsion system for directing thrust in a direction to slow the aircraft. The thrust reverser directs thrust at an angle relative to a vertical plane to reduce interference on control surfaces and reduce generation of underbody lift.

  12. Reverse Transfer Student Study.

    ERIC Educational Resources Information Center

    Slark, Julie

    After a preliminary study revealed that 21% of all credit students at Santa Ana College (SAC) had previously attended a four-year institution, a further study was conducted to determine the educational interests and matriculation patterns of these reverse transfer students. A sample of 360 reverse transfer students was selected for interviews,…

  13. Ultrasonic Time Reversal Mirrors

    NASA Astrophysics Data System (ADS)

    Fink, Mathias; Montaldo, Gabriel; Tanter, Mickael

    2004-11-01

    For more than ten years, time reversal techniques have been developed in many different fields of applications including detection of defects in solids, underwater acoustics, room acoustics and also ultrasound medical imaging and therapy. The essential property that makes time reversed acoustics possible is that the underlying physical process of wave propagation would be unchanged if time were reversed. In a non dissipative medium, the equations governing the waves guarantee that for every burst of sound that diverges from a source there exists in theory a set of waves that would precisely retrace the path of the sound back to the source. If the source is pointlike, this allows focusing back on the source whatever the medium complexity. For this reason, time reversal represents a very powerful adaptive focusing technique for complex media. The generation of this reconverging wave can be achieved by using Time Reversal Mirrors (TRM). It is made of arrays of ultrasonic reversible piezoelectric transducers that can record the wavefield coming from the sources and send back its time-reversed version in the medium. It relies on the use of fully programmable multi-channel electronics. In this paper we present some applications of iterative time reversal mirrors to target detection in medical applications.

  14. Time reversal acoustics for small targets using decomposition of the time reversal operator

    NASA Astrophysics Data System (ADS)

    Simko, Peter C.

    The method of time reversal acoustics has been the focus of considerable interest over the last twenty years. Time reversal imaging methods have made consistent progress as effective methods for signal processing since the initial demonstration that physical time reversal methods can be used to form convergent wave fields on a localized target, even under conditions of severe multipathing. Computational time reversal methods rely on the properties of the so-called 'time reversal operator' in order to extract information about the target medium. Applications for which time reversal imaging have previously been explored include medical imaging, non-destructive evaluation, and mine detection. Emphasis in this paper will fall on two topics within the general field of computational time reversal imaging. First, we will examine previous work on developing a time reversal imaging algorithm based on the MUltiple SIgnal Classification (MUSIC) algorithm. MUSIC, though computationally very intensive, has demonstrated early promise in simulations using array-based methods applicable to true volumetric (three-dimensional) imaging. We will provide a simple algorithm through which the rank of the time reversal operator subspaces can be properly quantified so that the rank of the associated null subspace can be accurately estimated near the central pulse wavelength in broadband imaging. Second, we will focus on the scattering from small acoustically rigid two dimensional cylindrical targets of elliptical cross section. Analysis of the time reversal operator eigenmodes has been well-studied for symmetric response matrices associated with symmetric systems of scattering targets. We will expand these previous results to include more general scattering systems leading to asymmetric response matrices, for which the analytical complexity increases but the physical interpretation of the time reversal operator remains unchanged. For asymmetric responses, the qualitative properties of the

  15. Estimation and uncertainty of reversible Markov models

    NASA Astrophysics Data System (ADS)

    Trendelkamp-Schroer, Benjamin; Wu, Hao; Paul, Fabian; Noé, Frank

    2015-11-01

    Reversibility is a key concept in Markov models and master-equation models of molecular kinetics. The analysis and interpretation of the transition matrix encoding the kinetic properties of the model rely heavily on the reversibility property. The estimation of a reversible transition matrix from simulation data is, therefore, crucial to the successful application of the previously developed theory. In this work, we discuss methods for the maximum likelihood estimation of transition matrices from finite simulation data and present a new algorithm for the estimation if reversibility with respect to a given stationary vector is desired. We also develop new methods for the Bayesian posterior inference of reversible transition matrices with and without given stationary vector taking into account the need for a suitable prior distribution preserving the meta-stable features of the observed process during posterior inference. All algorithms here are implemented in the PyEMMA software — http://pyemma.org — as of version 2.0.

  16. A novel ultrasound-assisted back extraction reverse micelles method coupled with gas chromatography-flame ionization detection for determination of aldehydes in heated edibles oils.

    PubMed

    Ramezani, Zahra; Mirzajani, Roya; Kardani, Fatemeh

    2015-12-01

    A novel ultrasound-assisted back extraction reverse micelles coupled with gas chromatography-flame ionization detection has been developed for the extraction and determination of some short chain aldehydes in different heated edible oil samples. After the homogenization of the oil samples with Triton X-100, 200 μL of methanol was added to facilitate the phase separation. The aqueous micelle phase has been separated by centrifugation, then it was treated with a mixture of H2O: CHCl3 and ultrasonic vibration, were used to effectively back-extraction of the analytes into the chloroform phase. The sedimented organic phase was obtained after centrifugation, withdrawn into the microsyringe and directly injected into the GC-FID system. The calibration graphs were linear in the range 0.05-20 mg L(-1). The limits of detection were in the range of 0.02-0.15 mg L(-1). This procedure was successfully applied for determination of propanal, butanal, hexanal and heptanal in real heated oil samples.

  17. Porcine reproductive and respiratory syndrome virus: interlaboratory ring trial to evaluate real-time reverse transcription polymerase chain reaction detection methods.

    PubMed

    Wernike, Kerstin; Bonilauri, Paolo; Dauber, Malte; Errington, Jane; LeBlanc, Neil; Revilla-Fernández, Sandra; Hjulsager, Charlotte; Isaksson, Mats; Stadejek, Tomasz; Beer, Martin; Hoffmann, Bernd

    2012-09-01

    To compare the real-time reverse transcription quantitative polymerase chain reaction (RT-qPCR) assays used for the diagnosis of Porcine reproductive and respiratory syndrome virus (PRRSV), a Europe-wide interlaboratory ring trial was conducted. A variety of PRRSV strains including North American (NA) and European (EU) genotype isolates were analyzed by the participants. Great differences regarding qualitative diagnostics as well as analytical sensitivity were observed between the individual RT-qPCR systems, especially when investigating strains from the EU genotype. None of the assays or commercial kits used in the ring trial could identify all different PRRSV strains with an optimal analytical and diagnostic sensitivity. The genetic variability of the PRRSV strains, which is supposed to hinder the diagnostic of the RT-PCR because of mutations at the primer binding sites, was also confirmed by sequencing and subsequent phylogenetic analysis. In summary, a major problem in PRRSV diagnostics by RT-qPCR is false-negative results. To achieve maximum safety in the molecular diagnosis of PRRSV, the combined usage of different assays or kits is highly recommended.

  18. Fabrication of thin copper mesh for electromagnetic interference of display panel by pulse reverse current method and study on the microstructure by small angle neutron scattering

    NASA Astrophysics Data System (ADS)

    Kim, Man; Lee, Joo-Yul; Choi, Yong

    2012-10-01

    A copper sheet with mesh was mass-produced by continuously combining three techniques, electroforming with pulse-reverse current, transfer technique onto a transparent polyimide (PI) film and oxidation processes. Thiourea as an organic additive in a modified copper sulfate bath changes the reduction potentials of copper complexes, which results in effectively controlling the crystal orientation, surface roughness and microstructure of the copper layer. An electroformed copper layer without thiourea has a relatively rough surface with an average surface roughness of about 144.7 nm, whereas, the copper layers with thiourea have a smooth surface with an average surface roughness in the range of 6.3 to 12.1 nm. The copper layers with thiourea have a preferred orientation of crystal structure such that Cu (111) peak intensity increases, whereas, Cu(220) peak intensity decreases with thiourea addition. Electroforming with a rectangular pulse current density including etching at +640 mAcm-2 for 1.8 msec and plating at -160 mAcm-2 for 4 msec in a modified copper sulfate bath with 200 ppm-thiourea at 25 °C is one of optimum conditions to massproduce a copper mesh sheet roll with 300 μm pitch, 10 μm mesh width and thickness, and 200 m long.

  19. Evaluation of a New Assay in Comparison with Reverse Hybridization and Sequencing Methods for Hepatitis C Virus Genotyping Targeting Both 5′ Noncoding and Nonstructural 5b Genomic Regions▿

    PubMed Central

    Martró, Elisa; González, Victoria; Buckton, Andrew J.; Saludes, Verónica; Fernández, Gema; Matas, Lurdes; Planas, Ramón; Ausina, Vicenç

    2008-01-01

    We report the evaluation of a new real-time PCR assay for hepatitis C virus (HCV) genotyping. The assay design is such that genotype 1 isolates are typed by amplification targeting the nonstructural 5b (NS5b) subgenomic region. Non-genotype 1 isolates are typed by type-specific amplicon detection in the 5′ noncoding region (5′NC) (method 1; HCV genotyping analyte-specific reagent assay). This method was compared with 5′NC reverse hybridization (method 2; InnoLiPA HCV II) and 5′NC sequencing (method 3; Trugene HCV 5′NC). Two hundred ninety-five sera were tested by method 1; 223 of them were also typed by method 2 and 89 by method 3. Sequencing and phylogenetic analysis of an NS5b fragment were used to resolve discrepant results. Suspected multiple-genotype infections were confirmed by PCR cloning and pyrosequencing. Even though a 2% rate of indeterminates was obtained with method 1, concordance at the genotype level with results with methods 2 and 3 was high. Among eight discordant results, five mixed infections were confirmed. Genotype 1 subtyping efficiencies were 100%, 77%, and 74% for methods 1, 2, and 3, respectively; there were 11/101 discordants between methods 1 and 2 (method 1 was predominantly correct) and 2/34 between methods 2 and 3. Regarding genotype 2, subtyping efficiencies were 100%, 45%, and 92% by methods 1, 2, and 3, respectively; NS5b sequencing of discordants (16/17) revealed a putative new subtype within genotype 2 and that most subtype calls were not correct. Although only sequencing-based methods provide the possibility of identifying new variants, the real-time PCR method is rapid, straightforward, and simple to interpret, thus providing a good single-step alternative to more-time-consuming assays. PMID:17989191

  20. Removal of organic micro-pollutants (phenol, aniline and nitrobenzene) via forward osmosis (FO) process: Evaluation of FO as an alternative method to reverse osmosis (RO).

    PubMed

    Cui, Yue; Liu, Xiang-Yang; Chung, Tai-Shung; Weber, Martin; Staudt, Claudia; Maletzko, Christian

    2016-03-15

    In this study, we have explored and compared the effectiveness of using (1) lab-fabricated forward osmosis (FO) membranes under both FO and reverse osmosis (RO) modes and (2) commercially available RO membranes under the RO mode for the removal of organic micro-pollutants. The lab-fabricated FO membranes are thin film composite (TFC) membranes consisting of a polyamide layer and a porous substrate cast from three different materials; namely, Matrimid, polyethersulfone (PESU) and sulfonated polyphenylene sulfone (sPPSU). The results show that the FO mode is superior to the RO mode in the removal of phenol, aniline and nitrobenzene from wastewater. The rejections of all three TFC membranes to all the three organic micro-pollutants under the FO processes are higher than 72% and can be even higher than 90% for aniline when a 1000 ppm aromatic aqueous solution and 1 M NaCl are employed as feeds. These performances outperform the results obtained from themselves and commercially available RO membranes under the RO mode. In addition, the rejection can be maintained even when treating a more concentrated feed solution (2000 ppm). The removal performance can be further enhanced by using a more concentrated draw solution (2 M). The water flux is almost doubled, and the rejection increment can reach up to 17%. Moreover, it was observed that annealing as a post-treatment would help compact the membrane selective layer and further enhance the separating efficiency. The obtained organic micro-pollutant rejections and water fluxes under various feasible operating conditions indicate that the FO process has potential to be a viable treatment for wastewater containing organic micro-pollutants. Copyright © 2016 Elsevier Ltd. All rights reserved.

  1. Real-time reverse transcription polymerase chain reaction method for detection of Canine distemper virus modified live vaccine shedding for differentiation from infection with wild-type strains.

    PubMed

    Wilkes, Rebecca P; Sanchez, Elena; Riley, Matthew C; Kennedy, Melissa A

    2014-01-01

    Canine distemper virus (CDV) remains a common cause of infectious disease in dogs, particularly in high-density housing situations such as shelters. Vaccination of all dogs against CDV is recommended at the time of admission to animal shelters and many use a modified live virus (MLV) vaccine. From a diagnostic standpoint for dogs with suspected CDV infection, this is problematic because highly sensitive diagnostic real-time reverse transcription polymerase chain reaction (RT-PCR) tests are able to detect MLV virus in clinical samples. Real-time PCR can be used to quantitate amount of virus shedding and can differentiate vaccine strains from wild-type strains when shedding is high. However, differentiation by quantitation is not possible in vaccinated animals during acute infection, when shedding is low and could be mistaken for low level vaccine virus shedding. While there are gel-based RT-PCR assays for differentiation of vaccine strains from field strains based on sequence differences, the sensitivity of these assays is unable to match that of the real-time RT-PCR assay currently used in the authors' laboratory. Therefore, a real-time RT-PCR assay was developed that detects CDV MLV vaccine strains and distinguishes them from wild-type strains based on nucleotide sequence differences, rather than the amount of viral RNA in the sample. The test is highly sensitive, with detection of as few as 5 virus genomic copies (corresponding to 10(-1) TCID(50)). Sequencing of the DNA real-time products also allows phylogenetic differentiation of the wild-type strains. This test will aid diagnosis during outbreaks of CDV in recently vaccinated animals.

  2. Use of real-time reverse transcriptase polymerase chain reaction assay and cell culture methods for detection of swine influenza A viruses.

    PubMed

    Landolt, Gabriele A; Karasin, Alexander I; Hofer, Christian; Mahaney, Julie; Svaren, John; Olsen, Christopher W

    2005-01-01

    To evaluate sensitivity and specificity of a real-time reverse transcriptase polymerase chain reaction (RT-PCR) assay performed on pooled nasal swab specimens, compared with virus isolation performed on individual nasal swab specimens by use of 2 cell culture lines for detection of swine influenza A viruses. 900 nasal swab specimens obtained from pigs at an abattoir and 62 nasal swab specimens submitted for diagnostic testing. Primers were chosen to amplify a conserved portion of the influenza virus matrix gene. Assay sensitivity was initially determined by testing serial dilutions of various subtypes of swine influenza viruses. Sensitivity and specificity were confirmed by use of nasal swab specimens with or without addition of known concentrations of influenza virus and further validated by testing nasal swab specimens obtained through an abattoir surveillance program or submitted for diagnostic testing. Aliquots of specimens were pooled in sets of 10, and results of real-time RT-PCR assays were compared with results of virus isolation of individual specimens in Madin Darby canine kidney (MDCK) and mink lung (Mv1Lu) cells. Real-time RT-PCR assay was highly specific (100%) and sensitive (88% to 100%). Among the 16 viruses isolated, 3 grew only in Mv1Lu cells and 3 grew only in MDCK cells. Results indicate that real-time RT-PCR assay is a fast and accurate test for screening numerous nasal swab specimens for swine influenza virus. Some viruses were isolated in only MDCK or Mv1Lu cells, indicating that use of >1 cell line may be required to isolate a broad range of influenza A viruses.

  3. Locating S-wave sources for the SPE-5 explosion using time reversal methods and a close-in, 1000 sensor network

    NASA Astrophysics Data System (ADS)

    Myers, S. C.; Pitarka, A.; Mellors, R. J.

    2016-12-01

    The Source Physics Experiment (SPE) is producing new data to study the generation of seismic waves from explosive sources. Preliminary results show that far-field S-waves are generated both within the non-elastic volume surrounding explosive sources and by P- to S-wave scattering. The relative contribution of non-elastic phenomenology and elastic-wave scattering to far-field S-waves has been debated for decades, and numerical simulations based on the SPE experiments are addressing this question. The match between observed and simulated data degrades with event-station distance and with increasing time in each seismogram. This suggests that a more accurate model of subsurface elastic properties could result in better agreement between observed and simulated seismograms. A detailed model of subsurface structure has been developed using geologic maps and the extensive database of borehole logs, but uncertainty in structural details remains high. The large N instrument deployment during the SPE-5 experiment offers an opportunity to use time-reversal techniques to back project the wave field into the subsurface to locate significant sources of scattered energy. The large N deployment was nominally 1000, 5 Hz sensors (500 Z and 500 3C geophones) deployed in a roughly rectangular array to the south and east of the SPE-5 shot. Sensor spacing was nominally 50 meters in the interior portion of the array and 100 meters in the outer region, with two dense lines at 25 m spacing. The array covers the major geologic boundary between the Yucca Flat basin and the granitic Climax Stock in which the SPE experiments have been conducted. Improved mapping of subsurface scatterers is expected to result in better agreement between simulated and observed seismograms and aid in our understanding of S-wave generation from explosions. This work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under contract DE-AC52-07NA27344.

  4. Quantitation of cytosine deaminase mRNA by real-time reverse transcription polymerase chain reaction: a sensitive method for assessing 5-fluorocytosine toxicity in vitro.

    PubMed

    Miller, C Ryan; Gustin, Allen N; Buchsbaum, Donald J; Vickers, Selwyn M; Manne, Upender; Grizzle, William E; Cloud, Gretchen A; Diasio, Robert B; Johnson, Martin R

    2002-02-15

    Cytosine deaminase/5-fluorocytosine (CD/5-FC) is a promising strategy for local cancer gene therapy. We hypothesized that CD expression within tumor cells would be directly related to efficacy and that quantitation of markers of CD expression such as mRNA, protein, and enzyme activity would therefore facilitate prediction of 5-FC toxicity. These three markers were thus quantitated by real-time quantitative reverse transcription polymerase chain reaction (Q-RT-PCR), semiquantitative immunocytochemistry (ICC), and 5-[(3)H]FC enzyme assay, respectively. Results with human colon (LS174T) cancer cells infected with a replication-incompetent adenovirus encoding CD (AdCMVCD) demonstrated a significant correlation between CD mRNA and enzyme activity up to 24 h postinfection. A direct correlation was found between CD dose (AdCMVCD PFU/cell) and CD mRNA and protein expression (P < 0.002) in both LS174T and BxPC-3 pancreatic cancer cells, but the relationship with enzyme activity was less strong in LS174T cells (P = 0.09). A remarkable concordance existed among Q-RT-PCR, ICC and enzyme assays with both cell lines. Importantly, CD dose and mRNA and protein expression inversely correlated with 5-FC IC(50) (P < 0.02). Quantitation of CD markers also facilitated identification of factors governing differential susceptibility to CD/5-FC. These results suggest that Q-RT-PCR will be useful for monitoring transgene expression in future studies using improved CD-based expression vectors and may also be useful in predicting the response to CD/5-FC therapy, which is likely to be heterogeneous in the patient population.

  5. Detection of Viral Pathogens by Reverse Transcriptase PCR and of Microbial Indicators by Standard Methods in the Canals of the Florida Keys

    PubMed Central

    Griffin, Dale W.; Gibson, Charles J.; Lipp, Erin K.; Riley, Kelley; Paul, John H.; Rose, Joan B.

    1999-01-01

    In order to assess the microbial water quality in canal waters throughout the Florida Keys, a survey was conducted to determine the concentration of microbial fecal indicators and the presence of human pathogenic microorganisms. A total of 19 sites, including 17 canal sites and 2 nearshore water sites, were assayed for total coliforms, fecal coliforms, Escherichia coli, Clostridium perfringens, enterococci, coliphages, F-specific (F+) RNA coliphages, Giardia lamblia, Cryptosporidium parvum, and human enteric viruses (polioviruses, coxsackie A and B viruses, echoviruses, hepatitis A viruses, Norwalk viruses, and small round-structured viruses). Numbers of coliforms ranged from <1 to 1,410, E. coli organisms from <1 to 130, Clostridium spp. from <1 to 520, and enterococci from <1 to 800 CFU/100 ml of sample. Two sites were positive for coliphages, but no F+ phages were identified. The sites were ranked according to microbial water quality and compared to various water quality standards and guidelines. Seventy-nine percent of the sites were positive for the presence of enteroviruses by reverse transcriptase PCR (polioviruses, coxsackie A and B viruses, and echoviruses). Sixty-three percent of the sites were positive for the presence of hepatitis A viruses. Ten percent of the sites were positive for the presence of Norwalk viruses. Ninety-five percent of the sites were positive for at least one of the virus groups. These results indicate that the canals and nearshore waters throughout the Florida Keys are being impacted by human fecal material carrying human enteric viruses through current wastewater treatment strategies such as septic tanks. Exposure to canal waters through recreation and work may be contributing to human health risks. PMID:10473424

  6. Reverse engineering of integrated circuits

    DOEpatents

    Chisholm, Gregory H.; Eckmann, Steven T.; Lain, Christopher M.; Veroff, Robert L.

    2003-01-01

    Software and a method therein to analyze circuits. The software comprises several tools, each of which perform particular functions in the Reverse Engineering process. The analyst, through a standard interface, directs each tool to the portion of the task to which it is most well suited, rendering previously intractable problems solvable. The tools are generally used iteratively to produce a successively more abstract picture of a circuit, about which incomplete a priori knowledge exists.

  7. Gene expression assay in blood and various tissues using a single-tube real-time reverse transcription-polymerase chain reaction method using an oligodeoxythymidine-immobilized polymerase chain reaction tube.

    PubMed

    Harikai, N; Saito, S; Tanaka, A; Kinoshita, K

    2009-06-01

    A single-tube real-time reverse transcription-polymerase chain reaction (RT-PCR) method has been developed which makes it possible to conduct the entire procedure, from nucleic acid extraction to product detection, in a single PCR tube. In this study, we developed the method using an oligodeoxythymidine-immobilized PCR tube, which enables simple and rapid mRNA extraction and quantification of target genes in blood and other tissues. The beta-actin gene was analyzed from lysates of blood and various tissues using this method. The data showed a good correlation between the plotted threshold cycle values and log(10) of blood and tissue amounts without a reduction in PCR efficiency. Gene expression of interleukin-1beta in blood from lipopolysaccharide (LPS)-stimulated rats and of beta(3)-adrenoceptors in adipose tissue from SHRSP.Z-Lepr (fa)/IzmDmcr (obese SHRSP) rats was also analyzed using the single-tube method, as well as a general real-time RT-PCR method, using RNA purified with a silica membrane column. In both methods, the copy number ratio of interleukin-1beta to beta-actin in LPS-stimulated rats was higher than in control rats, and the ratio of beta(3)-adrenoceptors to beta-actin in obese SHRSP rats was lower than in lean littermates. These results indicate that the single-tube method can provide results equivalent to those from general real-time RTPCR methods in gene expression analysis.

  8. Offline solid-phase extraction for preconcentration of pharmaceuticals and personal care products in environmental water and their simultaneous determination using the reversed phase high-performance liquid chromatography method.

    PubMed

    G Archana; Dhodapkar, Rita; Kumar, Anupama

    2016-09-01

    The present study reports a precise and simple offline solid-phase extraction (SPE) coupled with reversed-phase high-performance liquid chromatography (RP-HPLC) method for the simultaneous determination of five representative and commonly present pharmaceuticals and personal care products (PPCPs), a new class of emerging pollutants in the aquatic environment. The target list of analytes including ciprofloxacin, acetaminophen, caffeine benzophenone and irgasan were separated by a simple HPLC method. The column used was a reversed-phase C18 column, and the mobile phase was 1 % acetic acid and methanol (20:80 v/v) under isocratic conditions, at a flow rate of 1 mL min(-1). The analytes were separated and detected within 15 min using the photodiode array detector (PDA). The linearity of the calibration curves were obtained with correlation coefficients 0.98-0.99.The limit of detection (LOD), limit of quantification (LOQ), precision, accuracy and ruggedness demonstrated the reproducibility, specificity and sensitivity of the developed method. Prior to the analysis, the SPE was performed using a C18 cartridge to preconcentrate the targeted analytes from the environmental water samples. The developed method was applied to evaluate and fingerprint PPCPs in sewage collected from a residential engineering college campus, polluted water bodies such as Nag river and Pili river and the influent and effluent samples from a sewage treatment plant (STP) situated at Nagpur city, in the peak summer season. This method is useful for estimation of pollutants present in microquantities in the surface water bodies and treated sewage as compared to nanolevel pollutants detected by mass spectrometry (MS) detectors.

  9. Quantitation of the main constituents of vanilla by reverse phase HPLC and ultra-high-pressure-liquid-chromatography with UV detection: method validation and performance comparison.

    PubMed

    Cicchetti, Esmeralda; Chaintreau, Alain

    2009-09-01

    Vanilla's main constituents, i. e., vanillin, para-hydroxybenzaldehyde, and their corresponding acids, can be easily quantified by RP LC with UV detection and external calibration. This paper describes two methods that were developed using HPLC and ultra-high-pressure LC (UHPLC), respectively, and validated according to the International Conference on Harmonisation of Technical Requirements for Registration of Pharmaceuticals for Human Use (ICH). Both methods were highly specific, exhibited good linearities with high precision, and achieved good accuracies of quantitative results. The UHPLC method was more sensitive, five times shorter, and gave better peak resolutions than the HPLC alternative.

  10. An algebra of reversible computation.

    PubMed

    Wang, Yong

    2016-01-01

    We design an axiomatization for reversible computation called reversible ACP (RACP). It has four extendible modules: basic reversible processes algebra, algebra of reversible communicating processes, recursion and abstraction. Just like process algebra ACP in classical computing, RACP can be treated as an axiomatization foundation for reversible computation.

  11. [Posterior reversible encephalopathy syndrome].

    PubMed

    Petrović, Branko; Kostić, Vladimir; Sternić, Nadezda; Kolar, Jovo; Tasić, Nebojsa

    2003-01-01

    with lowering of blood pressure, better mental state and better vision. There was no sign of left hemiparesis on the 7th day. On the 9th day there were no symptoms or sign of disease. Control brain CT (15th day) was normal. ETHIOPATHOGENESIS: Most common causes of PRES are hypertensive encephalopathy [6-8], pre-eclampsia/eclampsia [9-12] cyclosporin A administration [13-22] and uremic encephalopathy [23]. There are several theories about the mechanism for PRES in hypertensive encephalopathy (reversible vasospasm and hyperperfusion) and administration of cyclosporin A (neurotoxic effect). Most common symptoms are headache, nausea, vomiting, confusion, behavioural changes, changes of conciousness (from somnolencia to stupor), vision disturbances (blurred vision, haemianopsia, cortical blindness) and epileptic manifestations (mostly focal attacks with secondary generalisation). Mental functions are characterised with decreased activity and reactivity, confusion, loss of concentration and mild type of amnesia. Lethargy is often initial sign, sometimes accompanied with phases of agitation. Stupor and coma rarely occurred. In patients with hypertensive encephalopathy and eclampsia high blod pressure is registered. Neurological examination revealed vision changes and damages of mental function as well as increased reflex activity. Today, brain MRI and CT are considered the most important diagnostic method for the diagnosis and follow-up of patients with PRES [6]. Brain MRI better detects smaller focal parenhim abnormalities than brain CT. The most often neuroradiological finding is relatively symmetrical oedema of white cerebral tissue in parieto-occipital regions of both cerebral hemispheres. Gray cerebral tissue is sometimes involved, usually in mild form of disease. Diagnosis of this "cortical" form of PRES is possible by MR FLAIR (Fluid-Attenuated Inversion Recovery) technique [5]. Therapeutic strategy depends on the cause of PRES and clinical picture. Most important are

  12. Rapid Contraceptive Uptake and Changing Method Mix With High Use of Long-Acting Reversible Contraceptives in Crisis-Affected Populations in Chad and the Democratic Republic of the Congo

    PubMed Central

    Rattan, Jesse; Noznesky, Elizabeth; Curry, Dora Ward; Galavotti, Christine; Hwang, Shuyuan; Rodriguez, Mariela

    2016-01-01

    ABSTRACT The global health community has recognized that expanding the contraceptive method mix is a programmatic imperative since (1) one-third of unintended pregnancies are due to method failure or discontinuation, and (2) the addition of a new method to the existing mix tends to increase total contraceptive use. Since July 2011, CARE has been implementing the Supporting Access to Family Planning and Post-Abortion Care (SAFPAC) initiative to increase the availability, quality, and use of contraception, with a particular focus on highly effective and long-acting reversible methods—intrauterine devices (IUDs) and implants—in crisis-affected settings in Chad and the Democratic Republic of the Congo (DRC). This initiative supports government health systems at primary and referral levels to provide a wide range of contraceptive services to people affected by conflict and/or displacement. Before the initiative, long-acting reversible methods were either unknown or unavailable in the intervention areas. However, as soon as trained providers were in place, we noted a dramatic and sustained increase in new users of all contraceptive methods, especially implants, with total new clients reaching 82,855, or 32% of the estimated number of women of reproductive age in the respective catchment areas in both countries, at the end of the fourth year. Demand for implants was very strong in the first 6 months after provider training. During this time, implants consistently accounted for more than 50% of the method mix, reaching as high as 89% in Chad and 74% in DRC. To ensure that all clients were getting the contraceptive method of their choice, we conducted a series of discussions and sought feedback from different stakeholders in order to modify program strategies. Key program modifications included more focused communication in mass media, community, and interpersonal channels about the benefits of IUDs while reinforcing the wide range of methods available and refresher

  13. Development and validation of a novel stability-indicating reversed-phase high-performance liquid chromatography method for assay of loratadine and determination of its related compounds.

    PubMed

    Lu, Jun; Wei, Yu-Chien; Markovich, Robert J; Rustum, Abu M

    2010-01-01

    Loratadine is an important active pharmaceutical ingredient used in a wide variety of prescription and over-the-counter products for the treatment and relief of allergy symptoms. A novel stability-indicating gradient ion-pair RP-HPLC method for assay of loratadine and determination of both of its degradation compounds and process impurities has been developed. This method can separate loratadine from its eight structurally related compounds; it can also separate all of the related compounds from each other in less than 20 min. The stability-indicating capability of this method has been demonstrated by analyzing aged stability samples of loratadine. A 15 cm x 4.6 mm id YMC-Pack Pro C18 HPLC column was the primary column and a 15 cm x 4.6 mm id SunFire C18 column has been identified as an alternate (truly equivalent) column for this method. This gradient method uses mobile phases consisting of acetonitrile and an aqueous solution of 10 mM sodium acetate and 5 mM sodium dodecyl sulfate at pH 5.5. The new HPLC method was validated according to International Conference on Harmonization guidelines and proved to be suitable for routine QC use.

  14. Reversible shape memory

    NASA Astrophysics Data System (ADS)

    Sheiko, Sergei; Zhou, Jing; White, Sarah; Ashby, Valerie

    2012-02-01

    An ``Achilles' heel'' of shape memory materials is that shape transformations triggered by an external stimulus are usually irreversible. Here we present a new concept of reversible transitions between two well-defined shapes by controlling hierarchic crystallization of a dual-network elastomer. The reversibility was demonstrated for different types of shape transformations including rod bending, winding of a helical coil, and widening an aperture. The distinct feature of the reversible shape alterations is that both counter-shapes are infinitely stable at a temperature of exploitation. Shape reversibility is highly desirable property in many practical applications such as non-surgical removal of a previously inserted catheter and handfree wrapping up of an earlier unraveled solar sail on a space shuttle.

  15. Reversing the arms race

    SciTech Connect

    von Hippel, F. ); Sagdeev, R.Z. )

    1992-01-01

    This paper contains proceedings of Reversing The Arms Race. Topics covered include: Verifying Reductions of Nuclear Warheads; Verifying Limits on Nuclear-Armed Cruise Missiles; and The Technical Basis for Warhead Detection.

  16. Uncommon Indications for Reverse Total Shoulder Arthroplasty

    PubMed Central

    Hyun, Yoon Suk; Huri, Gazi; Garbis, Nickolas G.

    2013-01-01

    Total shoulder arthroplasty and shoulder hemiarthroplasty have been the traditional method for treating a variety of shoulder conditions, including arthritis, cuff tear arthropathy, and some fracture types. However, these procedures did not provide consistently good results for patients with torn rotator cuffs. The development of the reverse prosthesis by Grammont in the late 20th century revolutionized the treatment of the rotator-cuff-deficient shoulder with arthritis. The main indication for the reverse prosthesis remains the patient with cuff tear arthropathy who has pain and loss of motion. Because the reverse total shoulder arthroplasty produced such good results in these patients, the indications for the reverse prosthesis have expanded to include other shoulder conditions that have previously been difficult to treat successfully and predictably. This review discusses and critically reviews these newer indications for the reverse total shoulder arthroplasty. PMID:24340143

  17. Uncommon indications for reverse total shoulder arthroplasty.

    PubMed

    Hyun, Yoon Suk; Huri, Gazi; Garbis, Nickolas G; McFarland, Edward G

    2013-12-01

    Total shoulder arthroplasty and shoulder hemiarthroplasty have been the traditional method for treating a variety of shoulder conditions, including arthritis, cuff tear arthropathy, and some fracture types. However, these procedures did not provide consistently good results for patients with torn rotator cuffs. The development of the reverse prosthesis by Grammont in the late 20th century revolutionized the treatment of the rotator-cuff-deficient shoulder with arthritis. The main indication for the reverse prosthesis remains the patient with cuff tear arthropathy who has pain and loss of motion. Because the reverse total shoulder arthroplasty produced such good results in these patients, the indications for the reverse prosthesis have expanded to include other shoulder conditions that have previously been difficult to treat successfully and predictably. This review discusses and critically reviews these newer indications for the reverse total shoulder arthroplasty.

  18. Is Household Wealth Associated With Use of Long-Acting Reversible and Permanent Methods of Contraception? A Multi-Country Analysis.

    PubMed

    Ugaz, Jorge I; Chatterji, Minki; Gribble, James N; Banke, Kathryn

    2016-03-01

    As programs continue to expand access to family planning information, services, and products, it is critical that these efforts be undertaken with an equity lens, ensuring that regardless of socioeconomic status, all women and couples can use the method that meets their needs. This study explores the relationship between household wealth and the use of long-acting and permanent methods (LAPMs) versus short-acting methods of contraception among modern method users, using multivariate analyses based on Demographic Health Survey data from 30 developing countries conducted between 2006 and 2013. Overall, and controlling for relevant individual and household characteristics including age, number of living children, education, and urban/rural residence, we found that wealthier women were more likely than poorer women to use LAPMs instead of short-acting methods: 20 of the 30 countries showed a positive and statistically significant association between wealth and LAPM use. For 10 of those countries, however, LAPM use was significantly higher only for the top (1 or 2) wealthiest quintiles. Eight countries showed no broad pattern of association, while in 2 countries-Bangladesh and India-poorer women were more likely to use LAPMs than wealthier women. The positive association between wealth and LAPM use was found most consistently in the Latin American and the Caribbean countries in our sample. These findings can help program implementers respond better to women's needs for modern contraception, especially in reaching women from lower- and middle-income households.

  19. Is Household Wealth Associated With Use of Long-Acting Reversible and Permanent Methods of Contraception? A Multi-Country Analysis

    PubMed Central

    Ugaz, Jorge I; Chatterji, Minki; Gribble, James N; Banke, Kathryn

    2016-01-01

    Abstract As programs continue to expand access to family planning information, services, and products, it is critical that these efforts be undertaken with an equity lens, ensuring that regardless of socioeconomic status, all women and couples can use the method that meets their needs. This study explores the relationship between household wealth and the use of long-acting and permanent methods (LAPMs) versus short-acting methods of contraception among modern method users, using multivariate analyses based on Demographic Health Survey data from 30 developing countries conducted between 2006 and 2013. Overall, and controlling for relevant individual and household characteristics including age, number of living children, education, and urban/rural residence, we found that wealthier women were more likely than poorer women to use LAPMs instead of short-acting methods: 20 of the 30 countries showed a positive and statistically significant association between wealth and LAPM use. For 10 of those countries, however, LAPM use was significantly higher only for the top (1 or 2) wealthiest quintiles. Eight countries showed no broad pattern of association, while in 2 countries—Bangladesh and India—poorer women were more likely to use LAPMs than wealthier women. The positive association between wealth and LAPM use was found most consistently in the Latin American and the Caribbean countries in our sample. These findings can help program implementers respond better to women’s needs for modern contraception, especially in reaching women from lower- and middle-income households. PMID:27016543

  20. Fast gradient elution reversed-phase liquid chromatography with diode-array detection as a high-throughput screening method for drugs of abuse. II. Data analysis.

    PubMed

    Porter, Sarah E G; Stoll, Dwight R; Paek, Changyub; Rutan, Sarah C; Carr, Peter W

    2006-12-29

    In Part I of this work, we developed a method for the detection of drugs of abuse in biological samples based on fast gradient elution liquid-chromatography coupled with diode array spectroscopic detection (LC-DAD). In this part of the work, we apply the chemometric method of target factor analysis (TFA) to the chromatograms. This algorithm identifies the target compounds present in chromatograms based on a spectral library, resolves nearly co-eluting components, and differentiates between drugs with similar spectra. The ability to resolve highly overlapped peaks using the spectral data afforded by the DAD is what distinguishes the present method from conventional library searching methods. Our library has a mean list length (MLL) of 1.255 and a discriminating power of 0.997 when both retention index and spectral factors are considered. The algorithm compares a library of 47 different compounds of toxicological relevance to unknown samples and identifies which compounds are present based on spectral and retention index matching. The application of a corrected retention index for identification rather than raw retention times compensates for long-term and column-to-column retention time shifts and allows for the use of a single library of spectral and retention data. Training data sets were used to establish the search and identification parameters of the method. A validation data set of 70 chromatograms was used to calculate the sensitivity (correct identification of positives) and specificity (correct identification of negatives) of the method, which were found to be 92% and 94%, respectively.

  1. Bioanalytical method development and validation for the determination of glycine in human cerebrospinal fluid by ion-pair reversed-phase liquid chromatography-tandem mass spectrometry.

    PubMed

    Jiang, Jian; James, Christopher A; Wong, Philip

    2016-09-05

    A LC-MS/MS method has been developed and validated for the determination of glycine in human cerebrospinal fluid (CSF). The validated method used artificial cerebrospinal fluid as a surrogate matrix for calibration standards. The calibration curve range for the assay was 100-10,000ng/mL and (13)C2, (15)N-glycine was used as an internal standard (IS). Pre-validation experiments were performed to demonstrate parallelism with surrogate matrix and standard addition methods. The mean endogenous glycine concentration in a pooled human CSF determined on three days by using artificial CSF as a surrogate matrix and the method of standard addition was found to be 748±30.6 and 768±18.1ng/mL, respectively. A percentage difference of -2.6% indicated that artificial CSF could be used as a surrogate calibration matrix for the determination of glycine in human CSF. Quality control (QC) samples, except the lower limit of quantitation (LLOQ) QC and low QC samples, were prepared by spiking glycine into aliquots of pooled human CSF sample. The low QC sample was prepared from a separate pooled human CSF sample containing low endogenous glycine concentrations, while the LLOQ QC sample was prepared in artificial CSF. Standard addition was used extensively to evaluate matrix effects during validation. The validated method was used to determine the endogenous glycine concentrations in human CSF samples. Incurred sample reanalysis demonstrated reproducibility of the method. Copyright © 2016 Elsevier B.V. All rights reserved.

  2. Reversible Seeding in Storage Rings

    SciTech Connect

    Ratner, Daniel; Chao, Alex; /SLAC

    2011-12-14

    We propose to generate steady-state microbunching in a storage ring with a reversible seeding scheme. High gain harmonic generation (HGHG) and echo-enabled harmonic generation (EEHG) are two promising methods for microbunching linac electron beams. Because both schemes increase the energy spread of the seeded beam, they cannot drive a coherent radiator turn-by-turn in a storage ring. However, reversing the seeding process following the radiator minimizes the impact on the electron beam and may allow coherent radiation at or near the storage ring repetition rate. In this paper we describe the general idea and outline a proof-of-principle experiment. Electron storage rings can drive high average power light sources, and free-electron lasers (FELs) are now producing coherent light sources of unprecedented peak brightness While there is active research towards high repetition rate FELs (for example, using energy recovery linacs), at present there are still no convenient accelerator-based sources of high repetition rate, coherent radiation. As an alternative avenue, we recently proposed to establish steady-state microbunching (SSMB) in a storage ring. By maintaining steady-state coherent microbunching at one point in the storage ring, the beam generates coherent radiation at or close to the repetition rate of the storage ring. In this paper, we propose a method of generating a microbunched beam in a storage ring by using reversible versions of linac seeding schemes.

  3. 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, 2011 CFR

    2011-07-01

    ... Contamination in Non-Aqueous Drilling Fluids (NAF) 1.0Scope and Application 1.1This method is used for determination of crude or formation oil, or other petroleum oil contamination, in non-aqueous drilling fluids... for Detection of Oil Contamination in Non-Aqueous Drilling Fluids (NAF) 6 Appendix 6 to Subpart A...

  4. 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

    ... Contamination in Non-Aqueous Drilling Fluids (NAF) 1.0Scope and Application 1.1This method is used for determination of crude or formation oil, or other petroleum oil contamination, in non-aqueous drilling fluids... for Detection of Oil Contamination in Non-Aqueous Drilling Fluids (NAF) 6 Appendix 6 to Subpart A...

  5. 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, 2012 CFR

    2012-07-01

    ...) 1.0Scope and Application 1.1This method is used for determination of crude or formation oil, or... a positive/negative test to determine a presence of crude oil in NAF prior to discharging drill... oils at a concentration of 0.1% in drilling fluid (vol/vol), 50% of representative crude oils at...

  6. Transfer of a Mycobacterium tuberculosis genotyping method, Spoligotyping, from a reverse line-blot hybridization, membrane-based assay to the Luminex multianalyte profiling system.

    PubMed

    Cowan, Lauren S; Diem, Lois; Brake, Mary Catherine; Crawford, Jack T

    2004-01-01

    Spoligotyping using Luminex technology was shown to be a highly reproducible method suitable for high-throughput analysis. Spoligotyping of 48 isolates using the traditional membrane-based assay and the Luminex assay yielded concordant results for all isolates. The Luminex platform provides greater flexibility and cost effectiveness than the membrane-based assay.

  7. Transfer of a Mycobacterium tuberculosis Genotyping Method, Spoligotyping, from a Reverse Line-Blot Hybridization, Membrane-Based Assay to the Luminex Multianalyte Profiling System

    PubMed Central

    Cowan, Lauren S.; Diem, Lois; Brake, Mary Catherine; Crawford, Jack T.

    2004-01-01

    Spoligotyping using Luminex technology was shown to be a highly reproducible method suitable for high-throughput analysis. Spoligotyping of 48 isolates using the traditional membrane-based assay and the Luminex assay yielded concordant results for all isolates. The Luminex platform provides greater flexibility and cost effectiveness than the membrane-based assay. PMID:14715809

  8. Synthesis, separation, and characterization of amphiphilic sulfated oligosaccharides enabled by reversed-phase ion pairing LC and LC-MS methods.

    PubMed

    Fenner, Amanda M; Kerns, Robert J

    2011-12-13

    Synthesis of amphiphilic oligosaccharides is problematic because traditional methods for separating and purifying oligosaccharides, including sulfated oligosaccharides, are generally not applicable to working with amphiphilic sugars. We report here RPIP-LC and LC-MS methods that enable the synthesis, separation, and characterization of amphiphilic N-arylacyl O-sulfonated aminoglycosides, which are being pursued as small-molecule glycosaminoglycan mimics. The methods described in this work for separating and characterizing these amphiphilic saccharides are further applied to a number of uses: monitoring the progression of sulfonation reactions with analytical RP-HPLC, characterizing sulfate content for individual molecules with ESI-MS, determining the degree of sulfation for products having mixed degrees of sulfation with HPLC and LC-MS, and purifying products with benchtop C18 column chromatography. We believe that the methods described here will be broadly applicable to enabling the synthesis, separation, and characterization of amphiphilic, sulfated, and phosphorylated oligosaccharides and other types of molecules substituted to varying degrees with both anionic and hydrophobic groups.

  9. On thermodynamic and microscopic reversibility

    SciTech Connect

    Crooks, Gavin E.

    2011-07-12

    The word 'reversible' has two (apparently) distinct applications in statistical thermodynamics. A thermodynamically reversible process indicates an experimental protocol for which the entropy change is zero, whereas the principle of microscopic reversibility asserts that the probability of any trajectory of a system through phase space equals that of the time reversed trajectory. However, these two terms are actually synonymous: a thermodynamically reversible process is microscopically reversible, and vice versa.

  10. Development of a reverse transcription-loop-mediated isothermal amplification assay for detection of pandemic (H1N1) 2009 virus as a novel molecular method for diagnosis of pandemic influenza in resource-limited settings.

    PubMed

    Kubo, Toru; Agoh, Masanobu; Mai, Le Q; Fukushima, Kiyoyasu; Nishimura, Hidekazu; Yamaguchi, Akinori; Hirano, Manabu; Yoshikawa, Akira; Hasebe, Futoshi; Kohno, Shigeru; Morita, Kouichi

    2010-03-01

    This paper reports on the development of a one-step, real-time reverse transcription-loop-mediated isothermal amplification (RT-LAMP) assay targeting the hemagglutinin (HA) gene for the rapid molecular-based detection of pandemic (H1N1) 2009 virus. The detection limit of the pandemic (H1N1) 2009 virus HA-specific RT-LAMP assay was same as that of the currently used real-time reverse transcription-PCR method. The assay detected the pandemic (H1N1) 2009 virus HA gene in 136 RNA samples extracted from nasopharyngeal swab specimens from Japanese and Vietnamese patients. No cross-reactive amplification with the RNA of other seasonal influenza viruses was observed, and the detection of specific viral genome targets in clinical specimens was achieved in less than 40 min. The sensitivity and specificity of the pandemic (H1N1) 2009 virus HA-specific RT-LAMP assay obtained in this study were 97.8% and 100%, respectively. Use of the (H1N1) 2009 virus HA-specific RT-LAMP assay will enable the faster and easier diagnosis of pandemic (H1N1) 2009 virus infection, especially in resource-limited situations in developing countries.

  11. Development of a Reverse Transcription-Loop-Mediated Isothermal Amplification Assay for Detection of Pandemic (H1N1) 2009 Virus as a Novel Molecular Method for Diagnosis of Pandemic Influenza in Resource-Limited Settings▿

    PubMed Central

    Kubo, Toru; Agoh, Masanobu; Mai, Le Q.; Fukushima, Kiyoyasu; Nishimura, Hidekazu; Yamaguchi, Akinori; Hirano, Manabu; Yoshikawa, Akira; Hasebe, Futoshi; Kohno, Shigeru; Morita, Kouichi

    2010-01-01

    This paper reports on the development of a one-step, real-time reverse transcription-loop-mediated isothermal amplification (RT-LAMP) assay targeting the hemagglutinin (HA) gene for the rapid molecular-based detection of pandemic (H1N1) 2009 virus. The detection limit of the pandemic (H1N1) 2009 virus HA-specific RT-LAMP assay was same as that of the currently used real-time reverse transcription-PCR method. The assay detected the pandemic (H1N1) 2009 virus HA gene in 136 RNA samples extracted from nasopharyngeal swab specimens from Japanese and Vietnamese patients. No cross-reactive amplification with the RNA of other seasonal influenza viruses was observed, and the detection of specific viral genome targets in clinical specimens was achieved in less than 40 min. The sensitivity and specificity of the pandemic (H1N1) 2009 virus HA-specific RT-LAMP assay obtained in this study were 97.8% and 100%, respectively. Use of the (H1N1) 2009 virus HA-specific RT-LAMP assay will enable the faster and easier diagnosis of pandemic (H1N1) 2009 virus infection, especially in resource-limited situations in developing countries. PMID:20071551

  12. Development and validation of a reversed-phase column liquid chromatographic method for the determination of five cephalosporins in pharmaceutical preparations.

    PubMed

    Elkady, Ehab F; Abbas, Samah S

    2011-01-01

    A new, simple, rapid, and precise RP-HPLC method has been developed and validated for the determination of five cephalosporins, namely, cefalexin, cefoperazone, ceftriaxone, ceftazidime, and cefepime. The method has been applied successfully for simultaneous determination of cefalexin in a binary mixture with sodium benzoate in a suspension, and cefoperazone in a binary mixture with sulbactam in vials. Chromatographic separation was achieved on a Waters microBondapak C18 column (250 x 4.6 mm id, 10 pm particle size) using the mobile phase monobasic potassium phosphate (50 mM, pH 4.6)-acetonitrile (80 + 20, v/v) with UV detection. A flow rate of 1 mL/min was applied. Linearity, accuracy, and precision were found to be acceptable over the concentration range of 30-300, 3-30, and 15-120 microg/mL for the studied cephalosporins, sodium benzoate, and sulbactam, respectively. The optimized method proved to be specific, robust, and accurate for QC of the cited drugs in their pharmaceutical preparations.

  13. Development and validation of a reversed-phase high-performance thin-layer chromatography-densitometric method for determination of atorvastatin calcium in bulk drug and tablets.

    PubMed

    Shirkhedkar, Atul A; Surana, Sanjay J

    2010-01-01

    Atorvastatin calcium is a synthetic HMG-CoA reductase inhibitor that is used as a cholesterol-lowering agent. A simple, sensitive, selective, and precise RP-HPTLC-densitometric determination of atorvastatin calcium both as bulk drug and from pharmaceutical formulation was developed and validated according to International Conference on Harmonization guidelines. The method used aluminum sheets precoated with silica gel 60 RP18F254S as the stationary phase, and the mobile phase consisted of methanol-water (3.5 + 1.5, v/v). The system gave a compact band for atorvastatin calcium with an Rf value of 0.62 +/- 0.02. Densitometric quantification was carried out at 246 nm. The linear regression analysis data for the calibration plots showed a good linear relationship with r = 0.9992 in the working concentration range of 100-800 ng/band. The method was validated for precision, accuracy, ruggedness, robustness, specificity, recovery, LOD, and LOQ. The LOD and LOQ were 6 and 18 ng, respectively. The drug underwent hydrolysis when subjected to acidic conditions and was found to be stable under alkali, oxidation, dry heat, and photodegradation conditions. Statistical analysis proved that the developed RP-HPTLC-densitometry method is reproducible and selective and that it can be applied for identification and quantitative determination of atorvastatin calcium in bulk drug and tablet formulation.

  14. Development of an ion-pair reversed-phase HPLC method with indirect UV detection for determination of phosphates and phosphites as impurities in sodium risedronate.

    PubMed

    Breuzovska, Katerina; Dimitrovska, Aneta; Kitanovski, Zoran; Petrusevska, Jelena; Ribarska, Jasmina Tonic; Jolevska, Suzana Trajkovic

    2010-01-01

    A method based on RP-HPLC with indirect UV detection was developed for the determination of phosphates and phosphites as impurities in sodium risedronate. RP separation of the phosphates and phosphites was achieved by adding tetrabutylammonium hydroxide as an ion-pairing agent in the mobile phase. Potassium hydrogen phthalate was added to the mobile phase as an ionic chromophore in order to obtain high background absorption of the mobile phase. Separation was performed on a C18 column using a mixture of pH 8.2 buffer (containing 0.5 mM tetrabutylammonium hydroxide and 1 mM phthalate) and acetonitrile (95 + 5, v/v) as the mobile phase, with indirect UV detection at 248 nm. The validation of the method included determination of specificity/selectivity, linearity, LOD, LOQ, accuracy, precision, and robustness. The LOD was 0.86 microg/mL for phosphates and 0.76 microg/mL for phosphites. The LOQ was 2.60 microg/mL for phosphates and 2.29 microg/mL for phosphites. The developed method is suitable for quantitative determination of phosphates and phosphites as impurities in QC of sodium risedronate.

  15. Development and validation of a reversed-phase HPLC method for simultaneous analysis of butylhydroxyanisol, simvastatin and its impurities in tablet dosage forms.

    PubMed

    El Karbane, M; Azougagh, M; Amood A L-Kamarany, M; Bouchafra, H; Cherrah, Y; Bouklouze, A

    2014-07-01

    A simple, rapid, and sensitive RP-HPLC method using photodiode array detection was developed and validated for the simultaneous determination of butylhydroxyanisol and simvastatin with its impurities in tablet forms. Chromatographic separation was achieved on a Phenomenex Hypersil (250×4.6 mm, 5 μm) column using the mobile phase acetonitrile-sodium acetate (12 mM) buffered to 4.2 with glacial acetic acid. The flow rate was 1.7 mL/min, and the UV detection were made at 238 nm for simvastatin and its impurities and at 290 nm for butylhydroxyanisol. The system suitability solution used for peak impurity identification was generated in-situ without use of any impurity reference standard. The method was validated according to ICH Q2(R1) guidelines, and the acceptance criteria for accuracy, precision, linearity, specificity, robustness, LOD, and LOQ, were met in all cases. Moreover, the reproducibility results obtained by 22 Official Medicines Control Laboratories (OMCL) of European Directorate were satisfactory. The compounds selected for impurity validation were based on those found during long term and accelerate stability studies carried out on several formulation tablets from Moroccan and other markets. The described method was robust and successfully applied in quality control laboratories for routine analysis to determine the butylhydroxyanisol and simvastatin with its impurities content in tablet dosage forms.

  16. Validation of a Reversed-Phase High Performance Liquid Chromatography Method for the Simultaneous Analysis of Cysteine and Reduced Glutathione in Mouse Organs

    PubMed Central

    Brundu, Serena; Nencioni, Lucia; Celestino, Ignacio; Coluccio, Paolo; Palamara, Anna Teresa; Fraternale, Alessandra

    2016-01-01

    A depletion of reduced glutathione (GSH) has been observed in pathological conditions and in aging. Measuring GSH in tissues using mouse models is an excellent way to assess GSH depletion and the potential therapeutic efficacy of drugs used to maintain and/or restore cellular redox potential. A high performance liquid chromatography (HPLC) method for the simultaneous determination of GSH and cysteine (Cys) in mouse organs was validated according to USA and European standards. The method was based on separation coupled with ultraviolet detection and precolumn derivatization with 5,5′-dithiobis-(2-nitrobenzoic acid) (DTNB). The required validation parameters, that are, selectivity, linearity, lower limit of quantification, precision, accuracy, recovery, and stability, were studied for spleen, lymph nodes, pancreas, and brain. The results showed that the lower limits of quantification were 0.313 μM and 1.25 μM for Cys and GSH, respectively. Intraday and interday precisions were less than 11% and 14%, respectively, for both compounds. The mean extraction recoveries of Cys and GSH from all organs were more than 93% and 86%, respectively. Moreover, the stability of both analytes during sample preparation and storage was demonstrated. The method was accurate, reliable, consistent, and reproducible and it was useful to determine Cys and GSH in the organs of different mouse strains. PMID:26885246

  17. A reverse phased high-pressure liquid chromatographic method for the estimation of a poisonous matter in Strychnos nux-vomica

    PubMed Central

    Hashim, Achu; Mohammed, Rafique; Umar, Dilshad; Veena, Vaswani R.; Bahija, Basheer; Kusai, Baroudi

    2015-01-01

    Seeds of Strychnos nux-vomica were subjected to preliminary phytochemical tests and its presence was confirmed by thin layer chromatography (TLC) method. The TLC profile of the methanolic extract of seeds of S. nux-vomica was developed using the solvent system toluene:chloroform:methanol in the ratio 8:2:1. The plate was observed in visible light after spraying with Dragendorff's reagent (specific method). High-performance liquid chromatography (HPLC) profile of the methanolic extracts of S. nux-vomica was developed, and the amount of strychnine seems to be 0.36% (w/w) in the seeds. The TLC and HPLC profiles developed are very valuable for the identification of the original drug from their adulterants. The TLC profile identifies the presence of strychnine in the plant material. The quantification method for the strychnine in the seeds can be used for the quality standardization of the raw drug because the strychnine is reported to have some toxicity. PMID:26317074

  18. Higher detectability method for the analysis of nucleosides, putative tumor biomarkers, in blood serum samples by CE-UV with reversed EOF.

    PubMed

    Buzatto, Adriana Zardini; Guedes, Sumaya Ferreira; de Oliveira Silva, Mariana; Gallafrio, Jéssica Mirela; Simionato, Ana Valéria Colnaghi

    2015-12-01

    The development and validation of methodologies for the analysis of biological samples is of outcome importance in order to obtain trustworthy results. This work reports a novel CE-UV method for the assessment of nucleosides, putative tumor biomarkers, in blood serum. The separation of seven nucleosides within c.a. 20 min has been achieved with: BGE 30 mmol/L borate at pH 9.90, 50 mmol/L CTAB, and 10% methanol; V = -10 kV; T = 20°C; and capillary dimensions of 56 cm × 50 μm. The sample plug was concentrated by a modified large volume sample stacking strategy that provided better detectability. Validation showed that the method is suitable for bioanalytical purposes and initial applications in serum samples from healthy subjects are also presented. Finally, statistical methods were applied to verify the effect of characteristics such as age, smoking habits, and alcohol consumption on nucleoside concentrations in blood serum. Univariate statistical analysis tests emphasized the need for age matching, which was confirmed by PCA-DA and PLS-DA. Cancer history in the nearby family may also interfere in nucleoside levels in blood serum, since adenosine concentrations were statistically higher for volunteers who declared having diseased relatives. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  19. An ion-pairing, reversed-phase liquid chromatography method to assess the cross-contamination of cancer chemotherapy infusions prepared in a dual-operator aseptic isolator.

    PubMed

    Brachet, G; Bruno, C; Boulay, D; Tournamille, J F; Gyan, E; Viaud-Massuard, M C; Respaud, R

    2016-09-01

    Cytotoxics are usually prepared in a centralized pharmacy unit in a controlled hospital environment. Despite the rigorous operating procedures used for such preparations, contamination is theoretically possible - for example due to vial switches. Therefore products ought to be checked in order to determine whether quality control measures are adequate. Numerous strategies have been applied locally to ensure the safety of both patients and operators but the efficacy of these methodologies has not previously been examined. The aim of this study was to develop an analytical method sensitive enough to detect traces of anti-cancer drugs, in order to evaluate cross-contamination between infusions prepared in a dual-operator isolator in the dedicated pharmacy unit. We developed a high performance liquid chromatography (HPLC) method with ultraviolet (UV) detection to identify and quantify the following seven drugs: 5-Fluorouracil, Cytarabine, Gemcitabine, Irinotecan, Doxorubicin, Epirubicin, and Daunorubicin. We assessed the levels of cross-contamination in 20 random preparations. We achieved separation of the seven drugs in less than 28 min, with a lower limit of quantification capable of detecting cross-contamination. An assessment of 20 preparations revealed no cross-contamination. We developed a reproducible and sensitive HPLC method which could be a potentially useful tool for use in practice. We checked the level of cross-contamination in anti-cancer drug infusions and confirmed that the process in current use was safe. This study is the first to assess cross-contamination in anti-cancer preparations. This work is the first step in an extensive programme of quality control, whose aim is to ensure the safety of both patients and operators. Copyright © 2015 John Wiley & Sons, Ltd. Development of a reproducible and sensitive HPLC method capable of detecting seven anticancer drugs. This method could be used alongside MS detection, to check for biological contamination

  20. Gradient liquid chromatographic retention time prediction for suspect screening applications: A critical assessment of a generalised artificial neural network-based approach across 10 multi-residue reversed-phase analytical methods.

    PubMed

    Barron, Leon P; McEneff, Gillian L

    2016-01-15

    For the first time, the performance of a generalised artificial neural network (ANN) approach for the prediction of 2492 chromatographic retention times (tR) is presented for a total of 1117 chemically diverse compounds present in a range of complex matrices and across 10 gradient reversed-phase liquid chromatography-(high resolution) mass spectrometry methods. Probabilistic, generalised regression, radial basis function as well as 2- and 3-layer multilayer perceptron-type neural networks were investigated to determine the most robust and accurate model for this purpose. Multi-layer perceptrons most frequently yielded the best correlations in 8 out of 10 methods. Averaged correlations of predicted versus measured tR across all methods were R(2)=0.918, 0.924 and 0.898 for the training, verification and test sets respectively. Predictions of blind test compounds (n=8-84 cases) resulted in an average absolute accuracy of 1.02±0.54min for all methods. Within this variation, absolute accuracy was observed to marginally improve for shorter runtimes, but was found to be relatively consistent with respect to analyte retention ranges (~5%). Finally, optimised and replicated network dependency on molecular descriptor data is presented and critically discussed across all methods. Overall, ANNs were considered especially suitable for suspects screening applications and could potentially be utilised in bracketed-type analyses in combination with high resolution mass spectrometry.

  1. Reversible collisionless magnetic reconnection

    SciTech Connect

    Ishizawa, A.; Watanabe, T.-H.

    2013-10-15

    Reversible magnetic reconnection is demonstrated for the first time by means of gyrokinetic numerical simulations of a collisionless magnetized plasma. Growth of a current-driven instability in a sheared magnetic field is accompanied by magnetic reconnection due to electron inertia effects. Following the instability growth, the collisionless reconnection is accelerated with development of a cross-shaped structure of current density, and then all field lines are reconnected. The fully reconnected state is followed by the secondary reconnection resulting in a weakly turbulent state. A time-reversed simulation starting from the turbulent state manifests that the collisionless reconnection process proceeds inversely leading to the initial state. During the reversed reconnection, the kinetic energy is reconverted into the original magnetic field energy. In order to understand the stability of reversed process, an external perturbation is added to the fully reconnected state, and it is found that the accelerated reconnection is reversible when the deviation of the E × B streamlines due to the perturbation is comparable with or smaller than a current layer width.

  2. Development and validation of a reversed-phase ultra-performance liquid chromatographic method for the simultaneous determination of six drugs used for combined hypertension therapy.

    PubMed

    Kaila, Harshad O; Ambasana, Mrunal A; Shah, Anamik K

    2013-01-01

    A simple, rapid, and reliable ultra-performance LC assay method has been developed for the simultaneous estimation of orally administered hypertension drugs (atenolol, hydrochlorothiazide, amlodipine besylate, indapamide, nifedipine, and lercanidipine hydrochloride), any of which may be administered with atenolol in combined hypertension therapy. Chromatography was carried out at 25 degrees C on a 2.1 x 50 mm id, 1.7 microm particle size Acquity BEH C18 column with the isocratic mobile phase 0.01 M, 4.0 pH aqueous phosphate buffer-acetonitrile (50 + 50, v/v) at a flow rate of 0.35 mL/min. All drugs were separated in less than 4 min with good resolution and minimal tailing, without interference by excipients. The method was validated according to International Conference on Harmonization guidelines, and the acceptance criteria for accuracy, precision, linearity, specificity, and system suitability were met in all cases. The column effluent was monitored at 230 nm. The detector response was linear in the range of 1-20 microg/mL of these drugs. LOD obtained was 0.04 microg/mL for atenolol, 0.02 microg/mL for hydrochlorothiazide, 0.03 microg/mL for amlodipine besylate, 0.03 microg/mL for indapamide, 0.02 microg.mL for nifedipine, and 0.01 microg/mL for lercanidipine hydrochloride. The suggested method has the advantage that all the drugs can be quantified alone or in combination with atenolol using a single mobile phase.

  3. Quantitative LC-MS/MS method in urine for the detection of drugs used to reverse the effects of chemical castration.

    PubMed

    Lee, Sooyeun; Kang, So-young; Ji, Dajeong; Baeck, Seungkyung; Lee, Sangki; Oh, Seung Min; Chung, Kyu Hyuck

    2013-04-01

    The chemical castration law, which targets child molesters with recidivism, was introduced in Korea in 2011. For this, leuprolide, a gonadotropin-releasing hormone agonist, is used to decrease testosterone production and suppress libido. In order to achieve efficient law enforcement, it is necessary to monitor intentional ingestion of drugs that antagonize the effect of leuprolide. Therefore, an analytical method for the simultaneous detection of mirodenafil, sildenafil, tadalafil, udenafil, vardenafil, icariin, alprostadil, and yohimbine, which are the major impotence treatment drugs, legitimately or otherwise, in Korea, as well as their selected metabolites, in human urine was established and validated using liquid chromatography-tandem mass spectrometry (LC-MS/MS). First, different sample preparation methods, two solid-phase extractions with different cartridges and protein precipitation, were compared and protein precipitation was chosen for the entire study because it showed better matrix effects and recoveries. Thus, the drugs and metabolites in urine were extracted by protein precipitation and then filtered and analyzed by LC-MS/MS with polarity switching electrospray ionization. The validation results of selectivity, matrix effect, recovery, linearity, intra- and inter-assay precision and accuracy were satisfactory. The limits of detection ranged from 0.25 to 10 ng/mL, and the limits of quantification were 2.5 to 50 ng/mL. The drugs and metabolites in urine did not show any degradation under storage for 7 and 15 days at 4 and -20 °C as well as after three freeze-thaw cycles. The developed method will be very useful for monitoring the illegal use of impotence treatment drugs.

  4. An Improved RP-HPLC (Reversed-Phase, High-Performance Liquid Chromatography) Method for Determining Nitroaromatics and Nitramines in Water

    DTIC Science & Technology

    1988-11-01

    high - performance liquid chromatography on an LC-18 column. The method employs dilution of an aqueous sample 1:1 with methanol, filtration through a 0.5 micro meter Millex-Sr filter, separation on the LC-18 column using a 1:1 water-methanol eluent, and determination by UV-254 nm. A careful comparison was made with an earlier standard protocol, which uses separation on an LC-8 column with a 50:38:12 water-methanol-acetonitrile eluent. overall, the new procedure provides better separation for a wider range of analytes and equivalent recovery for all

  5. A Validated Reverse Phase HPLC Method for the Determination of Disodium EDTA in Meropenem Drug Substance with UV-Detection using Precolumn Derivatization Technique

    PubMed Central

    Narola, Bhavil; Singh, A.S.; Mitra, M.; Santhakumar, P.R.; Chandrashekhar, T.G.

    2011-01-01

    This paper deals with development and validation of a high performance liquid chromatographic method for the quantitative determination of disodium EDTA (Ethylenediaminetetraacetic acid) in Meropenem active pharmaceutical ingredient (API). EDTA was derivatized with Ferric chloride solution by heating at 70 °C in water bath for about 20 minutes and the chromatographic separation achieved by injecting 100 μL of the derivatized mixture into a Waters HPLC system with photodiode array detector using a Phenomenex Luna C18(2) column (250 × 4.6 mm), 5 μ. The mobile phase consisting of 5% methanol and 95% of 0.7 g/L solution of Tetra butyl ammonium bromide and 4.6 g/L solution of sodium acetate trihydrate in water (pH adjusted to 4.0 with the help of acetic acid glacial) and a flow rate of 1 milliliter/minute. EDTA eluted at approximately 6 minutes. The method was suitably validated with respect to specificity, linearity of response, precision, accuracy, ruggedness, stability in analytical solution, limit of quantitation and detection and robustness for its intended use. PMID:21760705

  6. Characterization of process-related impurities including forced degradation products of alogliptin benzoate and the development of the corresponding reversed-phase high-performance liquid chromatography method.

    PubMed

    Zhou, YuXia; Zhou, WenTao; Sun, LiLi; Zou, QiaoGen; Wei, Ping; OuYang, PingKai

    2014-06-01

    The characterization of process-related impurities and forced degradants of alogliptin benzoate (Alb) in bulk drugs and a stability-indicating HPLC method for the separation and quantification of all the impurities were investigated. Alb was found to be unstable under acid and alkali stress conditions and two major degradation products (Imp-F and Imp-G) were observed. The optimum separation was achieved on Kromasil C18 (250 × 4.6 mm, 5 μm) using 0.1% perchloric acid (pH adjusted to 3.0 with triethylamine) and acetonitrile as a mobile phase in gradient mode. The proposed method was found to be stability indicating, precise, linear (0.10-75.0 μg/mL), accurate, sensitive, and robust for the quantitation of Alb and its process-related substances and degradation products. The structures of 11 impurities were characterized and confirmed by NMR spectroscopy, MS, and IR spectroscopy, and the most probable formation mechanisms of all impurities were proposed according to the synthesis route. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  7. Reversibility of liver fibrosis.

    PubMed

    Sun, Mengxi; Kisseleva, Tatiana

    2015-09-01

    Liver fibrosis is a serious health problem worldwide, which can be induced by a wide spectrum of chronic liver injuries. However, until today, there is no effective therapy available for liver fibrosis except the removal of underlying etiology or liver transplantation. Recent studies indicate that liver fibrosis is reversible when the causative agent(s) is removed. Understanding of mechanisms of liver fibrosis regression will lead to the identification of new therapeutic targets for liver fibrosis. This review summarizes recent research progress on mechanisms of reversibility of liver fibrosis. While most of the research has been focused on HSCs/myofibroblasts and inflammatory pathways, the crosstalk between different organs, various cell types and multiple signaling pathways should not be overlooked. Future studies that lead to fully understanding of the crosstalk between different cell types and the molecular mechanism underlying the reversibility of liver fibrosis will definitely give rise to new therapeutic strategies to treat liver fibrosis.

  8. A simple method for the assay of colistin in human plasma, using pre-column derivatization with 9-fluorenylmethyl chloroformate in solid-phase extraction cartridges and reversed-phase high-performance liquid chromatography.

    PubMed

    Li, J; Milne, R W; Nation, R L; Turnidge, J D; Coulthard, K; Johnson, D W

    2001-09-25

    A simple, selective and sensitive high-performance liquid chromatographic (HPLC) method is described for the determination of colistin in human plasma. Derivatization with 9-fluorenylmethyl chloroformate was performed in the same solid-phase extraction C18 cartridge used for sample pre-treatment, followed by reversed-phase HPLC with fluorimetric detection. Quantification was achieved using the ratio of the summed peak areas of colistin A and B derivatives to that of the derivative of netilmicin (internal standard). Linear calibration curves were obtained within the concentrations of colistin sulfate from 0.10 to 4.0 mg/l in plasma. Accuracy was within 10% and reproducibility (RSD) was less than 10%.

  9. A novel rapid method for simultaneous determination of eight active compounds in silymarin using a reversed-phase UPLC-UV detector.

    PubMed

    Liu, Hong; Du, Zhenxia; Yuan, Qipeng

    2009-12-15

    A novel rapid chromatographic method based on utilization of UPLC column was developed for the analysis of eight active compounds in silymarin. The analysis was performed on a Waters Acquity UPLC system with an Acquity UPLC(BEH) C18 column (5mmx2.1mm I.D., 1.7mum) and a gradient elution of methanol and water containing 0.01% formic acid with a run time of 9min, in which the retention time of the last analyte was 5.8min. And all eight active compounds achieved complete separation. Comparison of system performance with conventional HPLC was made with respect to analysis time, efficiency and sensitivity. The results indicated that the type of column, the type of mobile phase and the modified addition were significant to the separation of isomeric compounds in herb extracts.

  10. Dynamics of magnetization reversal

    NASA Astrophysics Data System (ADS)

    Safonov, Vladimir L.

    2000-03-01

    Advanced magnetic recording systems are designed for extremely high areal densities and data rate. These two aspects require both magnetization reversal at very short times (< 1 ns) and long term ( ~ 5-10 years) stability against thermal fluctuations. There are two basic physics problems associated with these requirements. The first is a characterization of thermal-dynamic reversal over very wide time range. The second is an understanding of the physics of the relaxation mechanisms. Both these subjects will be reviewed in this talk. Thermal dynamic reversal requires solution of the Landau-Lifshitz equation with fluctuations. We have solved this problem in terms of the ``random walk" dynamics of a nonlinear oscillator [1,2]. The expressions for the switching field versus pulse time are analytic and show good agreement with measurements on CrO_2. Our studies of fundamental relaxation mechanisms have involved a two step approach. First the results of computer simulations of magnetization reversal without phenomenological damping will be discussed. In this case coherent rotation of the magnetization excites spin waves during which an excess of Zeeman energy is transformed to anisotropy and exchange energies. However, for fine grains whose size is sufficiently small so that the grain magnetization is virtually uniform, non-linear spin waves cannot assist reversal [3]. A new analytic model of reversal that couples coherent rotation to impurity ions by an anisotropic exchange mechanism will be discussed. These impurity ions are assumed to relax at a very high rate to the lattice. [1] V.L.Safonov, JMMM 195, 523 (1999); J.Appl.Phys. 85, 4370 (1999). [2] V.L.Safonov, H.N.Bertram, MMM'99, CU-09. [3] V.L.Safonov, H.N.Bertram, J.Appl.Phys. 85, 5072 (1999); MMM'99, CD-11.

  11. Comparison of real-time PCR, reverse transcriptase real-time PCR, loop-mediated isothermal amplification, and the FDA conventional microbiological method for the detection of Salmonella spp. in produce.

    PubMed

    Zhang, Guodong; Brown, Eric W; González-Escalona, Narjol

    2011-09-01

    Contamination of foods, especially produce, with Salmonella spp. is a major concern for public health. Several methods are available for the detection of Salmonella in produce, but their relative efficiency for detecting Salmonella in commonly consumed vegetables, often associated with outbreaks of food poisoning, needs to be confirmed. In this study, the effectiveness of three molecular methods for detection of Salmonella in six produce matrices was evaluated and compared to the FDA microbiological detection method. Samples of cilantro (coriander leaves), lettuce, parsley, spinach, tomato, and jalapeno pepper were inoculated with Salmonella serovars at two different levels (10(5) and <10(1) CFU/25 g of produce). The inoculated produce was assayed by the FDA Salmonella culture method (Bacteriological Analytical Manual) and by three molecular methods: quantitative real-time PCR (qPCR), quantitative reverse transcriptase real-time PCR (RT-qPCR), and loop-mediated isothermal amplification (LAMP). Comparable results were obtained by these four methods, which all detected as little as 2 CFU of Salmonella cells/25 g of produce. All control samples (not inoculated) were negative by the four methods. RT-qPCR detects only live Salmonella cells, obviating the danger of false-positive results from nonviable cells. False negatives (inhibition of either qPCR or RT-qPCR) were avoided by the use of either a DNA or an RNA amplification internal control (IAC). Compared to the conventional culture method, the qPCR, RT-qPCR, and LAMP assays allowed faster and equally accurate detection of Salmonella spp. in six high-risk produce commodities.

  12. Comparison of Real-Time PCR, Reverse Transcriptase Real-Time PCR, Loop-Mediated Isothermal Amplification, and the FDA Conventional Microbiological Method for the Detection of Salmonella spp. in Produce ▿ †

    PubMed Central

    Zhang, Guodong; Brown, Eric W.; González-Escalona, Narjol

    2011-01-01

    Contamination of foods, especially produce, with Salmonella spp. is a major concern for public health. Several methods are available for the detection of Salmonella in produce, but their relative efficiency for detecting Salmonella in commonly consumed vegetables, often associated with outbreaks of food poisoning, needs to be confirmed. In this study, the effectiveness of three molecular methods for detection of Salmonella in six produce matrices was evaluated and compared to the FDA microbiological detection method. Samples of cilantro (coriander leaves), lettuce, parsley, spinach, tomato, and jalapeno pepper were inoculated with Salmonella serovars at two different levels (105 and <101 CFU/25 g of produce). The inoculated produce was assayed by the FDA Salmonella culture method (Bacteriological Analytical Manual) and by three molecular methods: quantitative real-time PCR (qPCR), quantitative reverse transcriptase real-time PCR (RT-qPCR), and loop-mediated isothermal amplification (LAMP). Comparable results were obtained by these four methods, which all detected as little as 2 CFU of Salmonella cells/25 g of produce. All control samples (not inoculated) were negative by the four methods. RT-qPCR detects only live Salmonella cells, obviating the danger of false-positive results from nonviable cells. False negatives (inhibition of either qPCR or RT-qPCR) were avoided by the use of either a DNA or an RNA amplification internal control (IAC). Compared to the conventional culture method, the qPCR, RT-qPCR, and LAMP assays allowed faster and equally accurate detection of Salmonella spp. in six high-risk produce commodities. PMID:21803916

  13. Reverse shoulder arthroplasty.

    PubMed

    Jarrett, Claudius D; Brown, Brandon T; Schmidt, Christopher C

    2013-07-01

    The reverse shoulder arthroplasty is considered to be one of the most significant technological advancements in shoulder reconstructive surgery over the past 30 years. It is able to successfully decrease pain and improve function for patients with rotator cuff-deficient shoulders. The glenoid is transformed into a sphere that articulates with a humeral socket. The current reverse prosthesis shifts the center of rotation more medial and distal, improving the deltoid's mechanical advantage. This design has resulted in successful improvement in both active shoulder elevation and in quality of life. Copyright © 2013 Elsevier Inc. All rights reserved.

  14. Development of a method based on on-line reversed phase liquid chromatography and gas chromatography coupled by means of an adsorption-desorption interface for the analysis of selected chiral volatile compounds in methyl jasmonate treated strawberries.

    PubMed

    de la Peña Moreno, Fernando; Blanch, Gracia Patricia; Flores, Gema; Ruiz Del Castillo, Maria Luisa

    2010-02-12

    A method based on the use of the through oven transfer adsorption-desorption (TOTAD) interface in on-line coupling between reversed phase liquid chromatography and gas chromatography (RPLC-GC) for the determination of chiral volatile compounds was developed. In particular, the method was applied to the study of the influence of methyl jasmonate (MJ) treatment on the production and enantiomeric composition of selected aroma compounds in strawberry. The compounds studied were ethyl 2-methylbutanoate, linalool and 4-hydroxy-2,5-dimethyl-3(2H)-furanone (i.e. furaneol), which were examined on days 3, 6 and 9 after treatment. The method developed resulted in relative standard deviations (RSDs) of 21.6%, 8.1% and 9.8% and limits of detection (LD) of 0.04, 0.07 and 0.02mg/l for ethyl 2-methylbutanoate, linalool and furaneol, respectively. The application of the RPLC-TOTAD-GC method allowed higher levels of ethyl 2-methylbutanoate, linalool and furaneol to be detected, particularly after 9 days of treatment. Besides, MJ demonstrated to affect the enantiomeric distribution of ethyl 2-methylbutanoate. On the contrary, the enantiomeric composition of linalool and furaneol kept constant in both control and MJ-treated strawberries throughout the study. These results are discussed.

  15. Fast Gradient Elution Reversed-Phase HPLC with Diode-Array Detection as a High Throughput Screening Method for Drugs of Abuse

    SciTech Connect

    Peter W. Carr; K.M. Fuller; D.R. Stoll; L.D. Steinkraus; M.S. Pasha; Glenn G. Hardin

    2005-12-30

    A new approach has been developed by modifying a conventional gradient elution liquid chromatograph for the high throughput screening of biological samples to detect the presence of regulated intoxicants. The goal of this work was to improve the speed of a gradient elution screening method over current approaches by optimizing the operational parameters of both the column and the instrument without compromising the reproducibility of the retention times, which are the basis for the identification. Most importantly, the novel instrument configuration substantially reduces the time needed to re-equilibrate the column between gradient runs, thereby reducing the total time for each analysis. The total analysis time for each gradient elution run is only 2.8 minutes, including 0.3 minutes for column reequilibration between analyses. Retention times standard calibration solutes are reproducible to better than 0.002 minutes in consecutive runs. A corrected retention index was adopted to account for day-to-day and column-to-column variations in retention time. The discriminating power and mean list length were calculated for a library of 47 intoxicants and compared with previous work from other laboratories to evaluate fast gradient elution HPLC as a screening tool.

  16. Conformation depends on 4D-QSAR analysis using EC-GA method: pharmacophore identification and bioactivity prediction of TIBOs as non-nucleoside reverse transcriptase inhibitors.

    PubMed

    Akyüz, Lalehan; Sarıpınar, Emin

    2013-08-01

    The electron conformational and genetic algorithm methods (EC-GA) were integrated for the identification of the pharmacophore group and predicting the anti HIV-1 activity of tetrahydroimidazo[4,5,1-jk][1,4]benzodiazepinone (TIBO) derivatives. To reveal the pharmacophore group, each conformation of all compounds was arranged by electron conformational matrices of congruity. Multiple comparisons of these matrices, within given tolerances for high active and low active TIBO derivatives, allow the identification of the pharmacophore group that refers to the electron conformational submatrix of activity. The effects of conformations, internal and external validation were investigated by four different models based on an ensemble of conformers and a single conformer, both with and without a test set. Model 1 using an ensemble of conformers for the training (39 compounds) and test sets (13 compounds), obtained by the optimum seven parameters, gave satisfactory results (R²(training) = 0.878, R²(test)= 0.910, q² = 0.840, q²(ext1) = 0.926 and q²(ext2) = 0.900).

  17. Efficient purification of active bufadienolides by a class separation method based on hydrophilic solid-phase extraction and reversed-phase high performance liquid chromatography.

    PubMed

    Li, Xiaolong; Liu, Yanfang; Shen, Aijin; Wang, Chaoran; Yan, Jingyu; Zhao, Weijie; Liang, Xinmiao

    2014-08-01

    Traditional Chinese medicines (TCMs) have played a significant role in the process of discovering natural bioactive compounds, especially in anticancer therapeutics. However, the components of TCMs are complex mixtures with wide variation in polarity and content, which leads to inefficiency in the process of active compound discovery from TCMs. In this paper, the popular strategy of utilizing "pre-fractionated natural product libraries" has been improved by a new class separation approach to accelerate the process. As an example, the skin of Bufo bufo gargarizans Cantor, a well-known TCM, mainly contains two distinct bufadienolide classes: amino acid-conjugated bufadienolides (AACBs) and free form bufadienolides (AAUBs). We utilized hydrophilic interaction liquid chromatography solid-phase extraction (HILIC-SPE) to resolve the two types of bufadienolides, which co-eluted on C18 columns. By this strategy, twelve bufadienolides of the two types were purified via prep-HPLC from one active fraction, and eight of them were identified by (1)H NMR and (13)C NMR. These results indicated that the class separation method not only overcame the limited orthogonality in a 2D-RPLC×RPLC system but also accelerated the process of active compound discovery.

  18. Sequential Polarity-Reversing Circuit

    NASA Technical Reports Server (NTRS)

    Labaw, Clayton C.

    1994-01-01

    Proposed circuit reverses polarity of electric power supplied to bidirectional dc motor, reversible electro-mechanical actuator, or other device operating in direction depending on polarity. Circuit reverses polarity each time power turned on, without need for additional polarity-reversing or direction signals and circuitry to process them.

  19. Sequential Polarity-Reversing Circuit

    NASA Technical Reports Server (NTRS)

    Labaw, Clayton C.

    1994-01-01

    Proposed circuit reverses polarity of electric power supplied to bidirectional dc motor, reversible electro-mechanical actuator, or other device operating in direction depending on polarity. Circuit reverses polarity each time power turned on, without need for additional polarity-reversing or direction signals and circuitry to process them.

  20. Method for the determination of lycopene in supplements and raw material by reversed-phase liquid chromatography: single-laboratory validation.

    PubMed

    Miller, André; Pietsch, Bernd; Faccin, Nicole; Schierle, Joseph; Waysek, Edward H

    2008-01-01

    A single-laboratory validation study was conducted for a liquid chromatographic (LC) method for the determination of total and all-trans-lycopene in a variety of dietary supplements and raw materials. Gelatin-based and other water-dispersible beadlets, or tablets, capsules, and softgels containing such product forms, were digested with protease. Alginate formulations and the respective applications were treated with an alkaline sodium EDTA acetate buffer to release lycopene from the matrix. Lycopene and other carotenoids were extracted from the resulting aqueous suspensions with dichloromethane and ethanol. Oily product forms were directly dissolved in dichloromethane and ethanol. The extracts were chromatographed on an isocratic high-performance LC system using a C16 alkylamide modified silica column that provided satisfactory resolution of all-trans-lycopene from its predominant cis-isomers and separated the lycopene isomers from other carotenoids such as alpha- and beta-carotene, cryptoxanthin, lutein, and zeaxanthin. The within-day precision relative standard deviation (RSD) for the determination of total lycopene ranged from 0.9 to 5.7% over concentration ranges of 50-200 g/kg for raw materials and 0.3-24 g/kg for dietary supplements. The intermediate precision RSD (total RSD) ranged from 0.8 to 8.9%. Recoveries obtained for beadlet and tablet material for the different extraction variants ranged from 95.0 to 102.1% at levels of 0.02-20 g/kg for tablets and from 95.0 to 101.1% at levels of 1-200 g/kg for beadlet material.

  1. New reversed phase-high performance liquid chromatographic method for selective separation of yttrium from all rare earth elements employing nitrilotriacetate complexes in anion exchange mode.

    PubMed

    Dybczyński, Rajmund S; Kulisa, Krzysztof; Pyszynska, Marta; Bojanowska-Czajka, Anna

    2015-03-20

    Separation of Y from other rare earth elements (REE) is difficult because of similarity of its ionic radius to ionic radii of Tb, Dy and Ho. In the new RP-HPLC system with C18 column, tetra-n-butyl ammonium hydroxide (TBAOH) as an ion interaction reagent (IIR), nitrilotriacetic acid (NTA) as a complexing agent at pH=2.8-3.5, and post column derivatization with Arsenazo III, yttrium is eluted in the region of light REE, between Nd and Sm and is base line separated from Nd and Sm and even from promethium. Simple model employing literature data on complex formation of REE with NTA and based on anion exchange mechanism was developed to foresee the order of elution of individual REE. The model correctly predicted that lanthanides up to Tb will be eluted in the order of increasing Atomic Number (At.No.) but all heavier REE will show smaller retention factors than Tb. Concurrent UV/VIS detection at 658nm and the use of radioactive tracers together with γ-ray spectrometric measurements made possible to establish an unique elution order of elution of REE: La, Ce, Pr, Nd, Pm, Y, Sm, Er, Ho, Tm, Yb, Eu, Lu, Dy+Gd, Tb, Sc. The real place of Y however, in this elution series differs from that predicted by the model (Y between Sm and Eu). The method described in this work enables selective separation of Y from La, Ce, Pr, Nd, Pm, Sm and all heavier REE treated as a group.

  2. Detection of Echinoderm Microtubule Associated Protein Like 4-Anaplastic Lymphoma Kinase Fusion Genes in Non-small Cell Lung Cancer Clinical Samples by a Real-time Quantitative Reverse Transcription Polymerase Chain Reaction Method.

    PubMed

    Zhao, Jing; Zhao, Jin-Yin; Chen, Zhi-Xia; Zhong, Wei; Li, Long-Yun; Liu, Li-Cheng; Hu, Xiao-Xu; Chen, Wei-Jun; Wang, Meng-Zhao

    2016-12-20

    Objective To establish a real-time quantitative reverse transcription polymerase chain reaction assay (qRT-PCR) for the rapid, sensitive, and specific detection of echinoderm microtubule associated protein like 4-anaplastic lymphoma kinase (EML4-ALK) fusion genes in non-small cell lung cancer. Methods The specific primers for the four variants of EML4-ALK fusion genes (V1, V2, V3a, and V3b) and Taqman fluorescence probes for the detection of the target sequences were carefully designed by the Primer Premier 5.0 software. Then, using pseudovirus containing EML4-ALK fusion genes variants (V1, V2, V3a, and V3b) as the study objects, we further analyzed the lower limit, sensitivity, and specificity of this method. Finally, 50 clinical samples, including 3 ALK-fluorescence in situ hybridization (FISH) positive specimens, were collected and used to detect EML4-ALK fusion genes using this method. Results The lower limit of this method for the detection of EML4-ALK fusion genes was 10 copies/μl if no interference of background RNA existed. Regarding the method's sensitivity, the detection resolution was as high as 1% and 0.5% in the background of 500 and 5000 copies/μl wild-type ALK gene, respectively. Regarding the method's specificity, no non-specific amplification was found when it was used to detect EML4-ALK fusion genes in leukocyte and plasma RNA samples from healthy volunteers. Among the 50 clinical samples, 47 ALK-FISH negative samples were also negative. Among 3 ALK-FISH positive samples, 2 cases were detected positive using this method, but another was not detected because of the failure of RNA extraction. Conclusion The proposed qRT-PCR assay for the detection of EML4-ALK fusion genes is rapid, simple, sensitive, and specific, which is deserved to be validated and widely used in clinical settings.

  3. 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.

  4. Time reversal communication system

    DOEpatents

    Candy, James V.; Meyer, Alan W.

    2008-12-02

    A system of transmitting a signal through a channel medium comprises digitizing the signal, time-reversing the digitized signal, and transmitting the signal through the channel medium. The channel medium may be air, earth, water, tissue, metal, and/or non-metal.

  5. Reversible Chemochromic Hydrogen Detectors

    NASA Technical Reports Server (NTRS)

    2008-01-01

    The Florida Solar Energy Center (FSEC), affiliated with the University of Central Florida, has invented a reversible pigment that changes from light beige to blue when exposed to hydrogen and back to light beige when exposed to atmospheric oxygen. In laboratory and environmental studies, the FSEC pigment in its tape form failed to change color adequately when exposed to hydrogen after one day of exposure at Kennedy Space Center's Beach Corrosion Test Facility. The reversible hydrogen-detecting tape also lost its ability to change color after being placed in an environmental chamber at 45 C for one day. The first attempts at extruding the reversible pigment into various polymers were unsuccessful because of the pigment's poor thermal stability. The goal of this project was to formulate a pigment with improved thermal and environmental stability for extrusion into a variety of appropriate polymer matrices. The formulation of the reversible hydrogen-detecting pigment was modified by removing one reagent and chemically modifying the hydrogen sensitive ingredient. This was intended to improve the hydrophobicity of the pigment and alter the thermal degradation mechanism.

  6. Engineering Encounters: Reverse Engineering

    ERIC Educational Resources Information Center

    McGowan, Veronica Cassone; Ventura, Marcia; Bell, Philip

    2017-01-01

    This column presents ideas and techniques to enhance your science teaching. This month's issue shares information on how students' everyday experiences can support science learning through engineering design. In this article, the authors outline a reverse-engineering model of instruction and describe one example of how it looked in our fifth-grade…

  7. Reversing Discrimination: A Perspective

    ERIC Educational Resources Information Center

    Pati, Gopal; Reilly, Charles W.

    1977-01-01

    Examines the debate over affirmative action and reverse discrimination, and discusses how and why the present dilemma has developed. Suggests that organizations can best address the problem through an honest, in-depth analysis of their organizational structure and management practices. (JG)

  8. Reversing Flow Test Facility

    NASA Astrophysics Data System (ADS)

    Roach, P. D.

    1986-04-01

    The Reversing Flow Test Facility (RFTF) is intended for the study of fluid flow and heat transfer under the reversing-flow conditions that occur in Stirling engines. The facility consists of four major parts: (1) Mechanical Drive - two cylinders with cam-driven pistons which generate the reversing gas flow, (2) Test Section - a U-shaped section containing instrumented test pieces, (3) Instruments -l high-speed transducers for measuring gas pressure and temperature, piston positions, and other system parameters, and (4) Data Acquisition System - a computer-based system able to acquire, store, display and analyze the data from the instruments. The RFTF can operate at pressures up to 8.0 MPa, hot-side temperatures to 800 deg. C, and flow-reversal frequencies to 50 Hz. Operation to data has used helium as the working gas at pressures of 3.0 and 6.0 MPa, at ambient temperature, and at frequencies from 1 to 50 Hz. The results show that both frictional and inertial parts of the pressure drop are significant in the heater, coolers and connecting tubes; the inertial part is negligible in the regenerators. In all cases, the frictional part of the pressure drop is nearly in phase with the mass flow.

  9. Reversible cerebral vasoconstriction syndrome.

    PubMed

    Lee, R; Ramadan, H; Bamford, J

    2013-01-01

    Reversible cerebral vasoconstriction syndrome (RCVS) is an underdiagnosed condition which usually presents as severe headache with or without neurological deficit. We report the case of a 55-year-old woman who presented with headache and multifocal intracerebral haemorrhage. We review the literature regarding the presentation, pathophysiology and management of RCVS and discuss how to differentiate it from cerebral vasculitis.

  10. Language Reversion Revisited.

    ERIC Educational Resources Information Center

    De Bot, Kees; Clyne, Michael

    1989-01-01

    A longitudinal study on language maintenance and loss among Dutch-English bilinguals in Australia revealed little loss in both languages over the years. This leads to the hypothesis of a "critical threshold" that must be reached to retain the second language. First language reversion appears commonly among immigrants who did not reach this…

  11. Reversible Photoswitching of Carbon Dots

    PubMed Central

    Khan, Syamantak; Verma, Navneet Chandra; Gupta, Abhishek; Nandi, Chayan Kanti

    2015-01-01

    We present a method of reversible photoswitching in carbon nanodots with red emission. A mechanism of electron transfer is proposed. The cationic dark state, formed by the exposure of red light, is revived back to the bright state with the very short exposure of blue light. Additionally, the natural on-off state of carbon dot fluorescence was tuned using an electron acceptor molecule. Our observation can make the carbon dots as an excellent candidate for the super-resolution imaging of nanoscale biomolecules within the cell. PMID:26078266

  12. A flow method based on solvent extraction coupled on-line to a reversed micellar mediated chemiluminescence detection for selective determination of gold(III) and gallium(III) in water and industrial samples.

    PubMed

    Hasanin, Tamer H A; Okamoto, Yasuaki; Fujiwara, Terufumi

    2016-02-01

    A rapid and sensitive flow method, based on the combination of on-line solvent extraction with reversed micellar mediated chemiluminescence (CL) detection using rhodamine B (RB), was investigated for the selective determination of Au(III) and Ga(III) in aqueous solutions. 2.0 M HCl was the optimum for extracting Au(III) while a 5.0M HCl solution containing 2.5M LiCl was selected as an optimum acidic medium for extraction of Ga(III). The Au(III) and Ga(III) chloro-complex anions were extracted from the above aqueous acidic solutions into toluene as their ion-pair complexes with the protonated RBH(+) ion followed by membrane phase separation in a flow system. In a flow cell of a detector, the extract was mixed with the reversed micellar solution of cetyltrimethylammonium chloride (CTAC) in 1-hexanol-cyclohexane/water (1.0M HCl) containing 0.10 M cerium(IV) and 0.05 M lithium sulfate. Then uptake of the ion-pair by the CTAC reversed micelles and the subsequent CL oxidation of RB with Ce(IV) occurred easily and the CL signals produced were recorded. Using a flow injection system, a detection limit (DL) of 0.4 μM Au(III) and 0.6 μM Ga(III), and linear calibration graphs with dynamic ranges from the respective DLs to 10 μM for Au(III) and Ga(III) were obtained under the optimized experimental conditions. The relative standard deviations (n=6) obtained at 2.0 µM Au(III) and 4.0 µM Ga(III) were 3.0% and 2.4%, respectively. The presented CL methodology has been applied for the determination of Au(III) and Ga(III) in water and industrial samples with satisfactory results. Copyright © 2015 Elsevier B.V. All rights reserved.

  13. Development and validation of a reversed-phase high-performance liquid chromatographic method with solid-phase extraction for the quantification of hydrochlorothiazide in ex vivo permeation studies.

    PubMed

    Onnainty, R; Schenfeld, E M; Longhi, M R; Quevedo, M A; Granero, G E

    2017-08-01

    Hydrochlorothiazide (HCT) is a diuretic used to treat hypertension. In order to study its intestinal permeation behavior applying an ex vivo methodology, a rapid, sensitive and selective reversed-phase liquid chromatography (RP-HPLC) method coupled with UV detection (RP-HPLC UV) was developed for the analysis of HCT in TC199 culture medium used as mucosal and serosal solutions in the everted rat intestinal sac model. Also, analytical procedures for the quantification of HCT by RP-HPLC with UV detection required a sample preparation step by solid-phase extraction. The method was validated in the concentration range of 8.05 × 10(-7) to 3.22 × 10(-5)  m for HCT. Chromatographic parameters, namely carry-over, lower limit of quantification (1.4491 × 10(-7)  m), limit of detection (3.8325 × 10(-8)  m), selectivity, inter- and intraday precision and extraction recovery, were determined and found to be adequate for the intended purposes. The validated method was successfully used for permeability assays across rat intestinal epithelium applying the ex vivo everted rat gut sac methodology to study the permeation behavior of HCT. Copyright © 2017 John Wiley & Sons, Ltd.

  14. Quantitation of mRNA levels of steroid 5alpha-reductase isozymes: A method that combines one-step reverse transcription-polymerase chain reaction and separation by capillary electrophoresis.

    PubMed

    Torres, Jesús M; Ortega, Esperanza

    2004-02-01

    We developed an accurate, rapid, and modestly labor-intensive method to precisely quantitate mRNA species by one-step reverse transcription-polymerase chain reaction (RT-PCR). This approach combines the high specificity of quantitative competitive PCR