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Sample records for electrospray characteristic curves

  1. Electrospray characteristic curves: in pursuit of improved performance in the nano-flow regime

    PubMed Central

    Marginean, Ioan; Kelly, Ryan T.; Page, Jason S.; Tang, Keqi

    2008-01-01

    Depending on its coordinates in the parameter space, an electrospray can manifest in one of several known regimes – stable, quasi-stable, transitional-chaotic, and non-axial – that ultimately impact measurement sensitivity and precision. An electrospray operating in cone-jet regime provides large and stable spray current, as well as smaller initial droplets that are prerequisites for higher sensitivity and quality mass spectrometric analyses. However, the dynamic conditions encountered in gradient elution-based liquid separations create difficulties for continuous operation in this regime throughout the analysis. We present a preliminary study aimed at stabilizing the electrospray in the cone-jet regime. On the basis of spray current measurements obtained using solvent conditions typically found in liquid chromatography-mass spectrometry, an improved description of the cone-jet stability island is provided by including transitions to and from the recently described astable regime. Additionally, the experimental conditions in which the astable regime marks the transition between pulsating and cone-jet regimes are further clarified. PMID:17896826

  2. Characteristic Curves.

    ERIC Educational Resources Information Center

    Walkiewicz, Thomas A.; Kirk, James R.

    1994-01-01

    Describes an experiment designed to help students gain a better understanding of the characteristics of various electronic components by incorporating a dual-trace oscilloscope in the X-Y mode in addition to direct observations of phase shifts of various signals into a laboratory exercise. (ZWH)

  3. Effect of pressure on electrospray characteristics

    SciTech Connect

    Marginean, Ioan; Page, Jason S.; Kelly, Ryan T.; Tang, Keqi; Smith, Richard D.

    2009-11-02

    An experimental study of sub-ambient pressure electrosprays is reported. The pressure domain that affords stable electrospray operation appears to be limited by the vapor pressure of the liquid. The voltage driving the electrospray is shown to have a logarithmic dependence on the pressure. This scaling amends the relationship currently in use to calculate the electric field at the tip of the meniscus of an electrified liquid

  4. The Characteristic Curves of Water

    NASA Astrophysics Data System (ADS)

    Neumaier, Arnold; Deiters, Ulrich K.

    2016-09-01

    In 1960, E. H. Brown defined a set of characteristic curves (also known as ideal curves) of pure fluids, along which some thermodynamic properties match those of an ideal gas. These curves are used for testing the extrapolation behaviour of equations of state. This work is revisited, and an elegant representation of the first-order characteristic curves as level curves of a master function is proposed. It is shown that Brown's postulate—that these curves are unique and dome-shaped in a double-logarithmic p, T representation—may fail for fluids exhibiting a density anomaly. A careful study of the Amagat curve (Joule inversion curve) generated from the IAPWS-95 reference equation of state for water reveals the existence of an additional branch.

  5. Mixtures of Receiver Operating Characteristic Curves

    PubMed Central

    Gönen, Mithat

    2014-01-01

    Rationale and Objectives ROC curves are ubiquitous in the analysis of imaging metrics as markers of both diagnosis and prognosis. While empirical estimation of ROC curves remains the most popular method, there are several reasons to consider smooth estimates based on a parametric model. Materials and Methods A mixture model is considered for modeling the distribution of the marker in the diseased population motivated by the biological observation that there is more heterogeneity in the diseased population than there is in the normal one. It is shown that this model results in an analytically tractable ROC curve which is itself a mixture of ROC curves. Results The use of CK-BB isoenzyme in diagnosis of severe head trauma is used as an example. ROC curves are fit using the direct binormal method, ROCKIT and the Box-Cox transformation as well as the proposed mixture model. The mixture model generates an ROC curve that is much closer to the empirical one than the other methods considered. Conclusions Mixtures of ROC curves can be helpful in fitting smooth ROC curves in datasets where the diseased population has higher variability than can be explained by a single distribution. PMID:23643788

  6. Electrospray ionization mass spectrometric studies on the characteristic fragmentation of Asp/cyclen conjugates.

    PubMed

    Ma, Chunying; Li, Chao; Luan, Xingrong; Zhang, Jin; Qiao, Renzhong; Zhao, Yufen

    2014-03-30

    Differentiation and structural characterization of Asp/cyclen conjugates by electrospray ionization tandem mass spectrometry (ESI-MS(n)) are significantly important for their biomedical application. Hence, the present study is conducted. The fragmentations of Asp/cyclen conjugates generated by positive ion mode electrospray ionization were examined here by low-energy collision-induced dissociation (CID). ESI-MS(n) spectra of cyclen were acquired to confirm cyclen contraction products derived from the studied compounds. The fragments derived from the Asp/cyclen conjugates were proved by deuterium-exchange experiments. Asp/cyclen conjugates displayed characteristic dissociation pathways, including cleavages of amide bonds, loss of NH3 and cyclen contraction pathways. It was observed that cleavages of C-terminal amide bonds generated b2 and b2  + H2O ions from the protonated CyclenAspAspAsp and a b1  + H2O ion from the protonated CyclenAspAsp. In addition, various cyclen contraction products were also observed. In ESI-MS(n) spectra of studied compounds, fragments of bn-1  + H2O or cyclic anhydride were generated due to facile mobilization of C-terminal or side-chain COOH protons. In addition, the cyclen contraction products were detected. These results might provide sufficient information for the identification of Asp/cyclen conjugates by mass spectrometry. Copyright © 2014 John Wiley & Sons, Ltd.

  7. The stability of Y(Q) characteristic curve

    NASA Astrophysics Data System (ADS)

    Pochylý, F.; Haluza, M.; Klas, R.

    2010-08-01

    The contribution is aimed on the analysis of Y(Q) characteristic of centrifugal pump. The main attention is concentrated on the impeller of high specific speed, especially on the diagonal pumps. It is derived, that stability of Y(Q) curve depends on the dissipative function. The analysis concludes that very important is the design of the interior of spiral case and distributor to achieve a stable Y(Q) characteristic curve.

  8. Parametric receiver operating characteristic curve analysis using mathematica.

    PubMed

    Heckerling, Paul S

    2002-07-01

    Several computer programs have been written to perform receiver operating characteristic (ROC) curve analysis, and are available in the public domain. Here, the author provides the theory and description for 'rocMath', a Mathematica program that performs parametric ROC curve analysis. The 'rocMath' program has some advantages over other ROC curve programs, including the ability to provide, through optional arguments: (a) user-specified pointwise confidence limits, as well as default 95% limits, on ROC curve area and on true-positive rates; (b) ROC curve plots with data points, a fitted curve, and user-specified pointwise confidence bands; and (c) ROC curve areas, tables, and plots based on a logistic distribution as well as on a standard normal distribution. In addition, the code of 'rocMath' can be modified to address additional ROC curve applications. The program uses Mathematica's ability to operate on purely symbolic as well as numeric data to achieve substantial coding efficiency. Limitations of the 'rocMath' program are also discussed.

  9. Receiver operating characteristic curve generalization for non-monotone relationships.

    PubMed

    Martínez-Camblor, Pablo; Corral, Norberto; Rey, Corsino; Pascual, Julio; Cernuda-Morollón, Eva

    2017-02-01

    The receiver operating characteristic curve is a popular graphical method frequently used in order to study the diagnostic capacity of continuous markers. It represents in a plot true-positive rates against the false-positive ones. Both the practical and theoretical aspects of the receiver operating characteristic curve have been extensively studied. Conventionally, it is assumed that the considered marker has a monotone relationship with the studied characteristic; i.e., the upper (lower) values of the (bio)marker are associated with a higher probability of a positive result. However, there exist real situations where both the lower and the upper values of the marker are associated with higher probability of a positive result. We propose a receiver operating characteristic curve generalization, [Formula: see text], useful in this context. All pairs of possible cut-off points, one for the lower and another one for the upper marker values, are taken into account and the best of them are selected. The natural empirical estimator for the [Formula: see text] curve is considered and its uniform consistency and asymptotic distribution are derived. Finally, two real-world applications are studied.

  10. Continuous columns for determining moisture characteristic curves of soilless substrates

    USDA-ARS?s Scientific Manuscript database

    Sound water management is essential for effectively producing nursery crops. Understanding substrate water availability is a critical component to managing irrigation properly. The objective of this paper is to report a method for generating moisture characteristic curves of soilless substrate tha...

  11. A Test Characteristic Curve Linking Method for the Testlet Model

    ERIC Educational Resources Information Center

    Li, Yanmei; Bolt, Daniel M.; Fu, Jianbin

    2005-01-01

    When tests are made up of testlets, a testlet-based item response theory (IRT) model may be used to account for local dependence among items from a common testlet. This study presents a new test characteristic curve method to link calibrations based on the Bradlow, Wainer, and Wang (1999) testlet model. Procedures for calculating the test…

  12. Electrospray device

    NASA Technical Reports Server (NTRS)

    Demmons, Nathaniel (Inventor); Martin, Roy (Inventor); Hruby, Vladimir (Inventor); Roy, Thomas (Inventor); Spence, Douglas (Inventor); Ehrbar, Eric (Inventor); Zwahlen, Jurg (Inventor)

    2011-01-01

    An electrospray device includes an electrospray emitter adapted to receive electrospray fluid; an extractor plate spaced from the electrospray emitter and having at least one aperture; and a power supply for applying a first voltage between the extractor plate and emitter for generating at least one Taylor cone emission through the aperture to create an electrospray plume from the electrospray fluid, the extractor plate as well as accelerator and shaping plates may include a porous, conductive medium for transporting and storing excess, accumulated electrospray fluid away from the aperture.

  13. 7 CFR 42.142 - Curve for obtaining Operating Characteristic (OC) curve information for skip lot sampling and...

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... the Department of Agriculture AGRICULTURAL MARKETING SERVICE (Standards, Inspections, Marketing Practices), DEPARTMENT OF AGRICULTURE COMMODITY STANDARDS AND STANDARD CONTAINER REGULATIONS STANDARDS FOR CONDITION OF FOOD CONTAINERS Miscellaneous § 42.142 Curve for obtaining Operating Characteristic (OC) curve...

  14. Experimental investigations on characteristics of stable water electrospray in air without discharge

    NASA Astrophysics Data System (ADS)

    Park, Inyong; Hong, Won Seok; Kim, Sang Bok; Kim, Sang Soo

    2017-06-01

    An experimental study was conducted to resolve previous conflicting results on water electrospray in air at atmospheric pressure. Using a small flow rate relative to that used in previous studies and a small nonmetallic nozzle, we observed stable electrospray of water in air without discharge and distinguished three distinct operating regimes for applied voltage and flow rate. The well-known cone-jet mode was observed and the general scaling law of the generated droplet size in the cone-jet mode was confirmed by direct visualization of the meniscus, jet, and generated droplets. We also observed and analyzed whipping motion in the electrified water jet.

  15. Characteristic coloring curve for white bread during baking.

    PubMed

    Onishi, Masanobu; Inoue, Michiko; Araki, Tetsuya; Iwabuchi, Hisakatsu; Sagara, Yasuyuki

    2011-01-01

    The effect of heating conditions on the crust color formation was investigated during the baking of white bread. The surface temperatures were monitored with thermocouples attached to the inside surface of the loaf pan cover. The trace of the surface color in the L(*)a(*)b(*) color coordinate system is defined as the characteristic coloring curve. The overall baking process was classified into the following four stages based on the characteristic coloring curve: i) pre-heating (surface temperature < 110 °C), ii) Maillard reaction (110-150 °C), iii) caramelization (150-200 °C), and iv) over-baking (surface temperature>200 °C). A linear relationship was observed between the L(*) decrease and the increase in weight loss of a sample at each oven air temperature. The L(*) value appeared to be suitable as an indicator to control the surface color by baking conditions.

  16. 7 CFR 42.142 - Curve for obtaining Operating Characteristic (OC) curve information for skip lot sampling and...

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... the Department of Agriculture AGRICULTURAL MARKETING SERVICE (Standards, Inspections, Marketing... CONDITION OF FOOD CONTAINERS Miscellaneous § 42.142 Curve for obtaining Operating Characteristic (OC)...

  17. Therapy operating characteristic curves: tools for precision chemotherapy.

    PubMed

    Barrett, Harrison H; Alberts, David S; Woolfenden, James M; Caucci, Luca; Hoppin, John W

    2016-04-01

    The therapy operating characteristic (TOC) curve, developed in the context of radiation therapy, is a plot of the probability of tumor control versus the probability of normal-tissue complications as the overall radiation dose level is varied, e.g., by varying the beam current in external-beam radiotherapy or the total injected activity in radionuclide therapy. This paper shows how TOC can be applied to chemotherapy with the administered drug dosage as the variable. The area under a TOC curve (AUTOC) can be used as a figure of merit for therapeutic efficacy, analogous to the area under an ROC curve (AUROC), which is a figure of merit for diagnostic efficacy. In radiation therapy, AUTOC can be computed for a single patient by using image data along with radiobiological models for tumor response and adverse side effects. The mathematical analogy between response of observers to images and the response of tumors to distributions of a chemotherapy drug is exploited to obtain linear discriminant functions from which AUTOC can be calculated. Methods for using mathematical models of drug delivery and tumor response with imaging data to estimate patient-specific parameters that are needed for calculation of AUTOC are outlined. The implications of this viewpoint for clinical trials are discussed.

  18. Effects of rail dynamics and friction characteristics on curve squeal

    NASA Astrophysics Data System (ADS)

    Ding, B.; Squicciarini, G.; Thompson, D. J.

    2016-09-01

    Curve squeal in railway vehicles is an instability mechanism that arises in tight curves under certain running and environmental conditions. In developing a model the most important elements are the characterisation of friction coupled with an accurate representation of the structural dynamics of the wheel. However, the role played by the dynamics of the rail is not fully understood and it is unclear whether this should be included in a model or whether it can be safely neglected. This paper makes use of previously developed time domain and frequency domain curve squeal models to assess whether the presence of the rail and the falling characteristics of the friction force can modify the instability mechanisms and the final response. For this purpose, the time-domain model has been updated to include the rail dynamics in terms of its state space representation in various directions. Frequency domain and time domain analyses results show that falling friction is not the only reason for squeal and rail dynamics can play an important role, especially under constant friction conditions.

  19. Exploring Alternative Characteristic Curve Approaches to Linking Parameter Estimates from the Generalized Partial Credit Model.

    ERIC Educational Resources Information Center

    Roberts, James S.; Bao, Han; Huang, Chun-Wei; Gagne, Phill

    Characteristic curve approaches for linking parameters from the generalized partial credit model were examined for cases in which common (anchor) items are calibrated separately in two groups. Three of these approaches are simple extensions of the test characteristic curve (TCC), item characteristic curve (ICC), and operating characteristic curve…

  20. Dynamic characteristics of curved nanobeams using nonlocal higher-order curved beam theory

    NASA Astrophysics Data System (ADS)

    Ganapathi, M.; Polit, O.

    2017-07-01

    Here, an analytical approach for the dynamic analysis, viz., free and forced vibrations, of curved nanobeams using nonlocal elasticity beam theory based on Eringen formulation coupled with a higher-order shear deformation accounting for through thickness stretching is investigated. The formulation is general in the sense that it can be deduced to analyse the effect of various structural theories pertaining to curved nanobeams. It also includes inplane, rotary and coupling inertia terms. The governing equations derived, using Hamiltons principle, are solved in conjunction with Naviers solutions. The free vibration results are obtained employing the standard eigenvalue analysis whereas the displacement/stress responses in time domain for the curved nanobeams subjected to rectangular pulse loading are evaluated based on Newmarks time integration scheme. The formulation is validated considering problems for which solutions are available. A comparative study is done here by different theories obtained through the formulation. The effects of various structural parameters such as thickness ratio, beam length, rise of the curved beam, loading pulse duration, and nonlocal scale parameter are brought out on the dynamic behaviours of curved nanobeams.

  1. Improved Suter-transformation for complete characteristic curves of pump-turbine

    NASA Astrophysics Data System (ADS)

    Zheng, X. B.; Guo, P. C.; Tong, H. Z.; Luo, X. Q.

    2012-11-01

    The complete characteristic curve of the pump turbine show "s" characteristic in the anti-pump and pump working-condition. The multi-numerical values of unit discharge and unit moment the curve caused by crossover and overlap phenomena of the curve may bring inconvenience for transition process analysis. In this paper, complete characteristic curves of the pump turbine were dealt with using improved Suter curve transformation method. A surface fitting were carried out for transformed WH curve. Therefore, a three-dimensioned surface was achieved. The transition process of load shedding was analyzed using the curve above-mentioned. The results show that the method used in the paper can eliminates the uneven distribution, crossover, overlapping and multi-value characteristic, thus providing convenience for the transition process analysis of pump-turbine.

  2. Fitting Item Characteristic Curves with Spline Functions. [Program Statistics Research Technical Report Series].

    ERIC Educational Resources Information Center

    Winsberg, Suzanne; And Others

    In most item response theory models a particular mathematical form is assumed for all item characteristic curves, e.g., a logistic function. It could be desirable, however, to estimate the shape of the item characteristic curves without prior restrictive assumptions about its mathematical form. We have developed a practical method of estimating…

  3. Modelling Soil Water Characteristic Curves for the Investigation of Hydrophobicity

    NASA Astrophysics Data System (ADS)

    Hallin, Ingrid; Matthews, Peter; Laudone, Maurizio; Van Keulen, Geertje; Doerr, Stefan; Francis, Lewis; Dudley, Ed; Gazze, Andrea; Quinn, Gerry; Whalley, Richard; Ashton, Rhys

    2016-04-01

    Soil hydrophobicity presents a major challenge for the future, as it reduces both plant-available water and irrigation efficiency, and can increase flooding hazards and erosion. A collaborative research project has been set up in the UK to study hydrophobicity over a wide range of length scales. At core scale, we are investigating the wetting behaviour of water repellent soils in order to model percolation through hydrophobic pore spaces. To that end, water retention measurements were carried out on both wettable and forcibly-wetted water-repellent soils collected from three locations in England and Wales. The data were then fitted with both the commonly used Van Genuchten model and an alternative model from PoreXpert, a software program that analyses and models porous materials. The Van Genuchten model fits a curve to the data using parameters related to air entry suction, irreducible water content and pore size distribution. By contrast, PoreXpert uses a Boltzmann-annealed simplex to find a best-fit curve based on parameters directly related to the void structure of the soil: the size of the voids, the shape of the void size distribution, and how the voids are connected to each other. Both Van Genuchten and PoreXpert fit the experimental data well, but where Van Genuchten forces an S-shaped curve that can mask small variations, PoreXpert gives a closer fit of no pre-defined shape that captures subtle differences between data points. This allows us to calculate differences in the effective pore and throat size distributions, and provides a mechanistic framework from which to model additional hydrologic behaviour in water repellent soil. Simulations of capillary induced wetting based on these mechanistic postulates are then compared to wicking experiments at the core scale, which can then be upscaled and applied to other soils.

  4. Flare Characteristics from X-ray Light Curves

    NASA Astrophysics Data System (ADS)

    Gryciuk, M.; Siarkowski, M.; Sylwester, J.; Gburek, S.; Podgorski, P.; Kepa, A.; Sylwester, B.; Mrozek, T.

    2017-06-01

    A new methodology is given to determine basic parameters of flares from their X-ray light curves. Algorithms are developed from the analysis of small X-ray flares occurring during the deep solar minimum of 2009, between Solar Cycles 23 and 24, observed by the Polish Solar Photometer in X-rays (SphinX) on the Complex Orbital Observations Near-Earth of Activity of the Sun-Photon (CORONAS- Photon) spacecraft. One is a semi-automatic flare detection procedure that gives start, peak, and end times for single ("elementary") flare events under the assumption that the light curve is a simple convolution of a Gaussian and exponential decay functions. More complex flares with multiple peaks can generally be described by a sum of such elementary flares. Flare time profiles in the two energy ranges of SphinX (1.16 - 1.51 keV, 1.51 - 15 keV) are used to derive temperature and emission measure as a function of time during each flare. The result is a comprehensive catalogue - the SphinX Flare Catalogue - which contains 1600 flares or flare-like events and is made available for general use. The methods described here can be applied to observations made by Geosynchronous Operational Environmental Satellites (GOES), the Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI) and other broad-band spectrometers.

  5. 7 CFR 43.105 - Operating characteristics (OC) curves.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 43.105 Agriculture Regulations of the Department of Agriculture AGRICULTURAL MARKETING SERVICE (Standards, Inspections, Marketing Practices), DEPARTMENT OF AGRICULTURE COMMODITY STANDARDS AND STANDARD CONTAINER REGULATIONS STANDARDS FOR SAMPLING PLANS Sampling Plans § 43.105 Operating characteristics...

  6. 7 CFR 43.105 - Operating characteristics (OC) curves.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 43.105 Agriculture Regulations of the Department of Agriculture AGRICULTURAL MARKETING SERVICE (Standards, Inspections, Marketing Practices), DEPARTMENT OF AGRICULTURE COMMODITY STANDARDS AND STANDARD CONTAINER REGULATIONS STANDARDS FOR SAMPLING PLANS Sampling Plans § 43.105 Operating characteristics...

  7. 7 CFR 43.105 - Operating characteristics (OC) curves.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 43.105 Agriculture Regulations of the Department of Agriculture AGRICULTURAL MARKETING SERVICE (Standards, Inspections, Marketing Practices), DEPARTMENT OF AGRICULTURE COMMODITY STANDARDS AND STANDARD CONTAINER REGULATIONS STANDARDS FOR SAMPLING PLANS Sampling Plans § 43.105 Operating characteristics...

  8. 7 CFR 43.105 - Operating characteristics (OC) curves.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 43.105 Agriculture Regulations of the Department of Agriculture AGRICULTURAL MARKETING SERVICE (Standards, Inspections, Marketing Practices), DEPARTMENT OF AGRICULTURE COMMODITY STANDARDS AND STANDARD CONTAINER REGULATIONS STANDARDS FOR SAMPLING PLANS Sampling Plans § 43.105 Operating characteristics (OC...

  9. 7 CFR 43.105 - Operating characteristics (OC) curves.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 43.105 Agriculture Regulations of the Department of Agriculture AGRICULTURAL MARKETING SERVICE (Standards, Inspections, Marketing Practices), DEPARTMENT OF AGRICULTURE COMMODITY STANDARDS AND STANDARD CONTAINER REGULATIONS STANDARDS FOR SAMPLING PLANS Sampling Plans § 43.105 Operating characteristics (OC...

  10. Influence of horizontally curved roadway section characteristics on motorcycle-to-barrier crash frequency.

    PubMed

    Gabauer, Douglas J; Li, Xiaolong

    2015-04-01

    The purpose of this study was to investigate motorcycle-to-barrier crash frequency on horizontally curved roadway sections in Washington State using police-reported crash data linked with roadway data and augmented with barrier presence information. Data included 4915 horizontal curved roadway sections with 252 of these sections experiencing 329 motorcycle-to-barrier crashes between 2002 and 2011. Negative binomial regression was used to predict motorcycle-to-barrier crash frequency using horizontal curvature and other roadway characteristics. Based on the model results, the strongest predictor of crash frequency was found to be curve radius. This supports a motorcycle-to-barrier crash countermeasure placement criterion based, at the very least, on horizontal curve radius. With respect to the existing horizontal curve criterion of 820 feet or less, curves meeting this criterion were found to increase motorcycle-to-barrier crash frequency rate by a factor of 10 compared to curves not meeting this criterion. Other statistically significant predictors were curve length, traffic volume and the location of adjacent curves. Assuming curves of identical radius, the model results suggest that longer curves, those with higher traffic volume, and those that have no adjacent curved sections within 300 feet of either curve end would likely be better candidates for a motorcycle-to-barrier crash countermeasure.

  11. Innovations in Measuring Rater Accuracy in Standard Setting: Assessing "Fit" to Item Characteristic Curves

    ERIC Educational Resources Information Center

    Hurtz, Gregory M.; Jones, J. Patrick

    2009-01-01

    Standard setting methods such as the Angoff method rely on judgments of item characteristics; item response theory empirically estimates item characteristics and displays them in item characteristic curves (ICCs). This study evaluated several indexes of rater fit to ICCs as a method for judging rater accuracy in their estimates of expected item…

  12. Multifractal Characteristics of Bimodal Mercury Pore Size Distribution Curves

    NASA Astrophysics Data System (ADS)

    dos Santos Bonini, C.; Alves, M. C.; Paz González, A.

    2012-04-01

    Characterization of Hg pore size distribution (PSDs) curves by monofractal or multifractal analysis has been demonstrated to be an useful tool, which allows a better understanding of the organization of the soil pore space. There are also evidences that multiscale analysis of different segments found in bimodal pore size distributions measured by Hg intrusion can provide further valuable information. In this study we selected bimodal PSDs from samples taken from an experimental area in São Paulo state, Brazil, where a revegetation trial was set up over saprolitic material. The saprolite was left abandoned after decapitation of an Oxisol for building purposes. The field trial consisted of various treatments with different grass species and amendments. Pore size distribution of the sampled aggregates was measured in the equivalent diameter range from 0.005 to about 50 μm and it was characterized by a bimodal pattern, so that two compartments, i.e. 0.005 to 0.2 μm and 0.2 to 50 μm, could be distinguished. The multifractal theory was used to analyse both segments. The scaling properties of these two segments could be fitted reasonably well with multifractal models. Multifractal parameters obtained for equivalent diameters for the segments > 0.2 and < 0.2 μm showed great differences. For example, entropy dimension, D1, values from the segment 0.005-0.2 μm were always lower than those for the segment 0.2-50 μm form NDI , whereas the Hólder exponent of order zero, α0, were higher for the former segment. These results indicate the probability different degrees of heterogeneity within the Hg pore size distributions studied.

  13. Receiver operating characteristic-curve limits of detection

    NASA Astrophysics Data System (ADS)

    Wysoczanski, Artur; Voigtman, Edward

    2014-10-01

    Using a simple UV LED-excited ruby fluorescence measurement system, we demonstrate that it is easily possible to obtain unbiased detection limits, despite the system deliberately having non-linear response function and non-Gaussian noise. Even when the noise precision model is heteroscedastic, but otherwise only roughly linear, the receiver operating characteristic (ROC) method readily yields results that are in accordance with a priori canonical specifications of false positives and false negatives at the detection limit. The present work demonstrates that obtaining unbiased detection limits is not abstruse and need not be mathematically complicated. Rather, detection limits continue to serve a useful purpose as part of the characterization of chemical measurement systems.

  14. The average receiver operating characteristic curve in multireader multicase imaging studies.

    PubMed

    Chen, W; Samuelson, F W

    2014-08-01

    In multireader, multicase (MRMC) receiver operating characteristic (ROC) studies for evaluating medical imaging systems, the area under the ROC curve (AUC) is often used as a summary metric. Owing to the limitations of AUC, plotting the average ROC curve to accompany the rigorous statistical inference on AUC is recommended. The objective of this article is to investigate methods for generating the average ROC curve from ROC curves of individual readers. We present both a non-parametric method and a parametric method for averaging ROC curves that produce a ROC curve, the area under which is equal to the average AUC of individual readers (a property we call area preserving). We use hypothetical examples, simulated data and a real-world imaging data set to illustrate these methods and their properties. We show that our proposed methods are area preserving. We also show that the method of averaging the ROC parameters, either the conventional bi-normal parameters (a, b) or the proper bi-normal parameters (c, da), is generally not area preserving and may produce a ROC curve that is intuitively not an average of multiple curves. Our proposed methods are useful for making plots of average ROC curves in MRMC studies as a companion to the rigorous statistical inference on the AUC end point. The software implementing these methods is freely available from the authors. METHODS for generating the average ROC curve in MRMC ROC studies are formally investigated. The area-preserving criterion we defined is useful to evaluate such methods.

  15. The association of patient characteristics and spinal curve parameters with Lenke classification types.

    PubMed

    Sponseller, Paul D; Flynn, John M; Newton, Peter O; Marks, Michelle C; Bastrom, Tracey P; Petcharaporn, Maty; McElroy, Mark J; Lonner, Baron S; Betz, Randal R

    2012-06-01

    Retrospective review. To determine the association of patient characteristics and spinal curve parameters with Lenke curve types. The Lenke curve classification may be used for surgical planning and clinical research. We retrospectively reviewed the records of 1912 patients with adolescent idiopathic scoliosis who underwent initial surgery at 21 years of age or younger; collected data on patient's age, patient's sex, primary curve magnitude (<50°, 50°-75°, and .75°), and Scoliosis Research Society (SRS) outcomes questionnaire (SRS-22) score; and compared that data by Lenke curve type. Analysis of variance and χ tests were used as appropriate (significance level, P ≤ 0.005). RESULTS.: Lenke types vary by sex: male patients had more major thoracic (types 1-4) than major thoracolumbar/lumbar (types 5 and 6) curves, fewer lumbar C-modifiers (32% vs. 44%), and less apical lumbar translation (1.1 vs. 1.7 cm). Lenke types vary by frequency: the most common type was 1 (50%); the least common, 4 (4%). Lenke types vary by magnitude: type 4 had the greatest percentage of large curves (52% of curves .75°), most smaller curves were types 1 and 5, and type 4 had the largest mean magnitude (78° ± 17°). Lenke types vary by patient age: type 5 curves occurred in the oldest patients (average age at surgery: 15.4 ± 2.2 vs. 14.3 ± 14.6 years for all others) despite having the lowest mean magnitude (P = 0.001); curve size was negatively correlated with age at surgery (r = -0.16, P = 0.001). Lenke types vary by patient self-image: patients with type 4 curves had lower preoperative SRS outcome scores for self-image than did patients with type 1 curves (P = 0.005). Lenke types vary by sex, frequency magnitude, patient age, and patient self-image, which should be considered in designing studies.

  16. Analysis of driver's characteristics on a curved road in a lattice model

    NASA Astrophysics Data System (ADS)

    Kaur, Ramanpreet; Sharma, Sapna

    2017-04-01

    The present paper investigates the effect of driver's behavior on the curved road via lattice hydrodynamic approach. The basic model for straight road is extended for the curved road and the characteristics of driver's behavior is incorporated in the lattice model. The extended model is investigated theoretically by the means of linear stability analysis and the effect of curved road and intensity of influence of driver's behavior on the traffic flow stability is examined. Through nonlinear stability analysis, the modified Korteweg-de Vries (MKdV) equation near the critical point is derived to describe the evolution properties of traffic density waves by applying the reductive perturbation method. Furthermore, the numerical simulation is carried out to validate the theoretical results which indicates that the curved road has a negative influence on the stability of the traffic flow. It is also seen that the traffic jam on a curved road can be suppressed efficiently via taking into account aggressive drivers.

  17. The average receiver operating characteristic curve in multireader multicase imaging studies

    PubMed Central

    Samuelson, F W

    2014-01-01

    Objective: In multireader, multicase (MRMC) receiver operating characteristic (ROC) studies for evaluating medical imaging systems, the area under the ROC curve (AUC) is often used as a summary metric. Owing to the limitations of AUC, plotting the average ROC curve to accompany the rigorous statistical inference on AUC is recommended. The objective of this article is to investigate methods for generating the average ROC curve from ROC curves of individual readers. Methods: We present both a non-parametric method and a parametric method for averaging ROC curves that produce a ROC curve, the area under which is equal to the average AUC of individual readers (a property we call area preserving). We use hypothetical examples, simulated data and a real-world imaging data set to illustrate these methods and their properties. Results: We show that our proposed methods are area preserving. We also show that the method of averaging the ROC parameters, either the conventional bi-normal parameters (a, b) or the proper bi-normal parameters (c, da), is generally not area preserving and may produce a ROC curve that is intuitively not an average of multiple curves. Conclusion: Our proposed methods are useful for making plots of average ROC curves in MRMC studies as a companion to the rigorous statistical inference on the AUC end point. The software implementing these methods is freely available from the authors. Advances in knowledge: Methods for generating the average ROC curve in MRMC ROC studies are formally investigated. The area-preserving criterion we defined is useful to evaluate such methods. PMID:24884728

  18. Characteristic boiling curve of carbon nanotube nanofluid as determined by the transient calorimeter technique

    NASA Astrophysics Data System (ADS)

    Xue, H. S.; Fan, J. R.; Hong, R. H.; Hu, Y. C.

    2007-04-01

    Nickel-plated copper sphere is employed as the transient calorimeter to explore the boiling heat transfer characteristics of carbon nanotube (CNT) nanofluid. As compared to water, aqueous gum arabic (GA) solution has an enhanced critical heat flux (CHF), transition boiling, and minimum heat flux in film boiling (Leidenfrost point). CNT nanofluid has higher CHF than GA solution. Better wettability and deposits on the heating surface distort the characteristic boiling curve.

  19. Effects on Scale Linking of Different Definitions of Criterion Functions for the IRT Characteristic Curve Methods

    ERIC Educational Resources Information Center

    Kim, Seonghoon; Kolen, Michael J.

    2007-01-01

    Under item response theory, the characteristic curve methods (Haebara and Stocking-Lord methods) are used to link two ability scales from separate calibrations. The linking methods use their respective criterion functions that can be defined differently according to the symmetry- and distribution-related schemes. The symmetry-related scheme…

  20. Logistic Positive Exponent Family of Models: Virtue of Asymmetric Item Characteristic Curves.

    ERIC Educational Resources Information Center

    Samejima, Fumiko

    2000-01-01

    Discusses whether the tradition of accepting point-symmetric item characteristic curves is justified by uncovering the inconsistent relationship between the difficulties of items and the order of maximum likelihood estimates of ability. In this context, proposes a family of models, called the logistic positive exponent family, that provides…

  1. Receiver Operating Characteristic Curve Analysis of Wechsler Memory Scale-Revised Scores in Epilepsy Surgery Candidates.

    ERIC Educational Resources Information Center

    Barr, William B.

    1997-01-01

    Wechsler Memory Scale-Revised (WMS-R) scores were analyzed for 82 epilepsy surgery candidates and used in combination with receiver operating characteristic curves to classify patients with left (LTL) and right (RTL) temporal lobe seizure onset. Results indicate that WMS-R scores used alone or in combination provide relatively poor discrimination…

  2. Effects on Scale Linking of Different Definitions of Criterion Functions for the IRT Characteristic Curve Methods

    ERIC Educational Resources Information Center

    Kim, Seonghoon; Kolen, Michael J.

    2007-01-01

    Under item response theory, the characteristic curve methods (Haebara and Stocking-Lord methods) are used to link two ability scales from separate calibrations. The linking methods use their respective criterion functions that can be defined differently according to the symmetry- and distribution-related schemes. The symmetry-related scheme…

  3. On the Use of Nonparametric Item Characteristic Curve Estimation Techniques for Checking Parametric Model Fit

    ERIC Educational Resources Information Center

    Lee, Young-Sun; Wollack, James A.; Douglas, Jeffrey

    2009-01-01

    The purpose of this study was to assess the model fit of a 2PL through comparison with the nonparametric item characteristic curve (ICC) estimation procedures. Results indicate that three nonparametric procedures implemented produced ICCs that are similar to that of the 2PL for items simulated to fit the 2PL. However for misfitting items,…

  4. A Comparison of Methods for Nonparametric Estimation of Item Characteristic Curves for Binary Items

    ERIC Educational Resources Information Center

    Lee, Young-Sun

    2007-01-01

    This study compares the performance of three nonparametric item characteristic curve (ICC) estimation procedures: isotonic regression, smoothed isotonic regression, and kernel smoothing. Smoothed isotonic regression, employed along with an appropriate kernel function, provides better estimates and also satisfies the assumption of strict…

  5. Evaluation of a computer program used to estimate water characteristic curve

    USDA-ARS?s Scientific Manuscript database

    The soil water characteristic curve, h(theta), can be used to estimate a variety of parameters in unsaturated soils. One practical application of h(theta) is its use by DRAINMOD, a drainage model that has been widely used in shallow water table regions, to determine the water table depth–drainage v...

  6. Use of a submersible pressure outflow cell for determination of moisture characteristic curves on rock core

    SciTech Connect

    Flint, L.E.; Flint, A.L.

    1993-06-01

    A simple device for developing moisture characteristic data curves, the submersible pressure outflow cell, was modified for application to rock core at matric potentials of 0 to -0.5 megapascals (MPa) and possibly to -1.0 Mpa. An automated system was developed to continuously and simultaneously collect data from many cells, obtain sorption and desorption characteristic curves to provide hysteretic information, and data from multi-step outflow experiments. The latter can be used to estimate unsaturated hydraulic conductivity. The system has resolved many of the problems inherent in standard measurement techniques. Model simulation of imbibition using the hysteretic data collected are in close agreement with laboratory measurements of imbibition, data collected are in close agreement with laboratory measurements of imbibition, suggesting the moisture characteristic data correctly describes the core properties.19 refs., 4 figs.

  7. Experimental study of characteristic curves of centrifugal pumps working as turbines in different specific speeds

    SciTech Connect

    Derakhshan, Shahram; Nourbakhsh, Ahmad

    2008-01-15

    Pump manufacturers do not normally provide the characteristic curves of their pumps working as turbines. Therefore, establishing a correlation between the performances of direct (pump) and reverse (turbine) modes is essential in selecting the proper machine. In this paper, several centrifugal pumps (N{sub s} < 60 (m, m{sup 3}/s)) were tested as turbines. Using experimental data, some relations were derived to predict the best efficiency point of a pump working as a turbine, based on pump hydraulic characteristics. Validity of the presented method was shown using some referenced experimental data. Two equations were presented to estimate the complete characteristic curves of centrifugal pumps as turbines based on their best efficiency point. Deviations of suggested method from experimental data were considered and discussed. Finally, a procedure was presented for selecting a suitable pump to work as a turbine in a small hydro-site. (author)

  8. Modeling geologic storage of carbon dioxide: Comparison ofnon-hysteretic and hysteretic characteristic curves

    SciTech Connect

    Doughty, Christine

    2006-07-17

    Numerical models of geologic storage of carbon dioxide (CO2)in brine-bearing formations use characteristic curves to represent theinteractions of non-wetting-phase CO2 and wetting-phase brine. When aproblem includes both injection of CO2 (a drainage process) and itssubsequent post-injection evolution (a combination of drainage andwetting), hysteretic characteristic curves are required to correctlycapture the behavior of the CO2 plume. In the hysteretic formulation,capillary pressure and relative permeability depend not only on thecurrent grid-block saturation, but also on the history of the saturationin the grid block. For a problem that involves only drainage or onlywetting, a non-hysteretic formulation, in which capillary pressure andrelative permeability depend only on the current value of the grid-blocksaturation, is adequate. For the hysteretic formulation to be robustcomputationally, care must be taken to ensure the differentiability ofthe characteristic curves both within and beyond the turning-pointsaturations where transitions between branches of the curves occur. Twoexample problems involving geologic CO2 storage are simulated withTOUGH2, a multiphase, multicomponent code for flow and transport codethrough geological media. Both non-hysteretic and hysteretic formulationsare used, to illustrate the applicability and limitations ofnon-hysteretic methods.The first application considers leakage of CO2from the storage formation to the ground surface, while the secondexamines the role of heterogeneity within the storageformation.

  9. Continuous measurement of soil-water characteristic curves at low suction levels

    NASA Astrophysics Data System (ADS)

    Ray, Richard; Bene, Katalin

    2017-04-01

    The soil-water characteristic curve (SWCC) is an important piece of information for understanding unsaturated soil behavior. With few exceptions, most of the SWCCs are developed as discrete points and are typically generated under drying path. This study presents results from automated tests that typically draw suction values to about 1 bar. Tempe cells are used with the axis translation method to generate the curves. Soils tested include fine sand, silty, and clayey sands. While a typical test starts in a saturated state and generates a drying curve, the test can be reversed any number of times to produce hysteresis behavior. Another advantage to the method is time efficiency since a curve with thousands of data points are produced in less than a week. However, careful consideration has to be made with regard to extraction rate, especially as the specimen becomes dryer. Several data sets are presented illustrating good and problematic behavior as well as hysteresis. Some suggestions are given concerning the selection of extraction rates or adjusting curves to account for extraction rate effects.

  10. Consequence analysis to determine the damage to humans from vapour cloud explosions using characteristic curves.

    PubMed

    Alonso, Fernando Díaz; Ferradás, Enrique González; Sánchez, Teresa de Jesús Jiménez; Aznar, Agustín Miñana; Gimeno, José Ruiz; Alonso, Jesús Martínez

    2008-01-15

    The aim of this paper is to provide a methodology to facilitate consequence analysis for vapour cloud explosions (VCE). Firstly, the main PROBIT equations to evaluate direct damage on humans from those accidents (eardrum rupture, death due to skull fracture, death due to whole body impact and lung damage) are discussed and the most suitable ones are selected. Secondly, a new methodology is developed to relate characteristic overpressure-impulse-distance curves for VCE, obtained in a previous paper (F. Diaz Alonso et al., Characteristic overpressure-impulse-distance curves for vapour cloud explosions using the TNO Multi-Energy model, J. Hazard. Mater. A137 (2006) 734-741) with the selected PROBIT equations. This methodology allows the determination of damage as a function of distance to the accident's origin in only one step, using explosion energy and VCE Multi-Energy charge strength as input parameters.

  11. Analysis of Characteristics of Light Curve Profiles of the Flares Erupted from Sun-like Stars

    NASA Astrophysics Data System (ADS)

    Duo, Yun; Hua-ning, Wang; Han, He

    2017-01-01

    Solar flares belong to a kind of eruptive phenomena caused by the sudden release of magnetic energy nearby sunspots. It is found that similar flares occurred as well in many Sun-like stars (called as Sun-like star flares). From the data acquired by the Kepler space telescope the SC (Short Cadence) data are mainly selected to make analysis, in order to find the characteristic parameters of light curve profiles of the flares erupted from Sun-like stars for a statistical study, and to summarize the activity features of these stellar flares. The analyzed results show that the light curve profiles and characteristic timescales of the flares of Sun-like stars are quite similar to those of solar flares, which may indicate the same physical mechanism for these two kinds of flares.

  12. 7 CFR 42.142 - Curve for obtaining Operating Characteristic (OC) curve information for skip lot sampling and...

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ...) curve information for skip lot sampling and inspection. 42.142 Section 42.142 Agriculture Regulations of the Department of Agriculture AGRICULTURAL MARKETING SERVICE (Standards, Inspections, Marketing Practices), DEPARTMENT OF AGRICULTURE COMMODITY STANDARDS AND STANDARD CONTAINER REGULATIONS STANDARDS...

  13. The Effect of Compaction on Moisture Characteristic Curves of Compactible Soils Measured in a UFAT

    NASA Astrophysics Data System (ADS)

    Baker, K. E.; Poloski, A. P.; Owen, A. T.; Lindenmeier, C. W.; Thompson, D. N.

    2001-12-01

    The objective of this study was to develop and test methods to allow the use of the Unsaturated Flow Apparatus (UFAT) for characterization of hydraulic properties of compactable soils often encountered in vadose zone environments. Use of the UFA in this application is limited by compaction of the soil under the applied centrifugal force. The UFA significantly reduces the time required to reach moisture equilibrium by applying driving forces thousands of times greater than natural driving forces for unsaturated flow through sample cores. However, the centrifugal force will also cause some soils to compress in the instrument, significantly changing the macropore volume distribution and thus the moisture characteristic curve. Moisture characteristic curves of undisturbed soil cores were measured both by traditional methods and in the UFA. Changes in pore volume distributions were estimated using X-ray micro-focus tomography (XMT) both before and after adjustment of the moisture content. Using a mathematical model, compaction of the pores at each UFA rotational speed can be accounted for and an original uncompacted macropore volume distribution can be estimated. This uncompacted macropore volume distribution can then be used to predict the moisture characteristic curve of the original soil, greatly shortening the time necessary to complete these measurements.

  14. Linking Parameters Estimated with the Generalized Graded Unfolding Model: A Comparison of the Accuracy of Characteristic Curve Methods

    ERIC Educational Resources Information Center

    Anderson Koenig, Judith; Roberts, James S.

    2007-01-01

    Methods for linking item response theory (IRT) parameters are developed for attitude questionnaire responses calibrated with the generalized graded unfolding model (GGUM). One class of IRT linking methods derives the linking coefficients by comparing characteristic curves, and three of these methods---test characteristic curve (TCC), item…

  15. Performance characteristics of a curved-channel microchannel plate with a curved input face and a plane output face

    NASA Technical Reports Server (NTRS)

    Slater, David C.; Morgan, Jeffrey S.; Timothy, J. Gethyn

    1989-01-01

    The presently performance-evaluated format, in which a high-gain curved-channel microchannel plate (M2MCP) has a spherical concave input face and a plane output face, allows the input face of the MCP (1) to match such curved focal surfaces as that of a Rowland-circle spectrometer mounting, while (2) having a high-resolution plane readout array in proximity focus with the output face. This MCP has been evaluated in a discrete-anode multicathode microchannel array detector system. The saturated modal gain was found to be inversely proportional to the length/diameter ratio of the channels and directly proportional to the applied MCP voltage.

  16. THE LICK AGN MONITORING PROJECT: PHOTOMETRIC LIGHT CURVES AND OPTICAL VARIABILITY CHARACTERISTICS

    SciTech Connect

    Walsh, Jonelle L.; Bentz, Misty C.; Barth, Aaron J.; Minezaki, Takeo; Sakata, Yu; Yoshii, Yuzuru; Baliber, Nairn; Bennert, Vardha Nicola; Street, Rachel A.; Treu, Tommaso; Li Weidong; Filippenko, Alexei V.; Stern, Daniel; Brown, Timothy M.; Canalizo, Gabriela; Gates, Elinor L.; Greene, Jenny E.; Malkan, Matthew A.; Woo, Jong-Hak

    2009-11-01

    The Lick AGN Monitoring Project targeted 13 nearby Seyfert 1 galaxies with the intent of measuring the masses of their central black holes using reverberation mapping. The sample includes 12 galaxies selected to have black holes with masses roughly in the range 10{sup 6}-10{sup 7} M {sub sun}, as well as the well-studied active galactic nucleus (AGN) NGC 5548. In conjunction with a spectroscopic monitoring campaign, we obtained broadband B and V images on most nights from 2008 February through 2008 May. The imaging observations were carried out by four telescopes: the 0.76 m Katzman Automatic Imaging Telescope, the 2 m Multicolor Active Galactic Nuclei Monitoring telescope, the Palomar 60 inch (1.5 m) telescope, and the 0.80 m Tenagra II telescope. Having well-sampled light curves over the course of a few months is useful for obtaining the broad-line reverberation lag and black hole mass, and also allows us to examine the characteristics of the continuum variability. In this paper, we discuss the observational methods and the photometric measurements, and present the AGN continuum light curves. We measure various variability characteristics of each of the light curves. We do not detect any evidence for a time lag between the B- and V-band variations, and we do not find significant color variations for the AGNs in our sample.

  17. One Curve Embedded Full-Bridge MMC Modeling Method with Detailed Representation of IGBT Characteristics

    NASA Astrophysics Data System (ADS)

    Hongyang, Yu; Zhengang, Lu; Xi, Yang

    2017-05-01

    Modular Multilevel Converter is more and more widely used in high voltage DC transmission system and high power motor drive system. It is a major topological structure for high power AC-DC converter. Due to the large module number, the complex control algorithm, and the high power user’s back ground, the MMC model used for simulation should be as accurate as possible to simulate the details of how MMC works for the dynamic testing of the MMC controller. But so far, there is no sample simulation MMC model which can simulate the switching dynamic process. In this paper, one curve embedded full-bridge MMC modeling method with detailed representation of IGBT characteristics is proposed. This method is based on the switching curve referring and sample circuit calculation, and it is sample for implementation. Based on the simulation comparison test under Matlab/Simulink, the proposed method is proved to be correct.

  18. Evaluation of curving characteristics of flexible liquid crystal displays fabricated using polycarbonate substrates

    NASA Astrophysics Data System (ADS)

    Sato, Akihito; Ishinabe, Takahiro; Fujikake, Hideo

    2016-01-01

    The improvement of the contrast ratio of flexible liquid crystal displays (LCDs) fabricated using plastic substrates in a curved state is an important problem to achieve high-quality flexible LCDs. In this study, we evaluated the distributions of in-plane phase retardation and slow axis direction of polycarbonate substrates and the effects of curvature on the electro-optical properties of flexible LCDs. As a result, we clarified that the polycarbonate substrates have high uniformity in the in-plane phase retardation and slow axis direction, and that the change in the phase retardation of the polycarbonate substrate caused by the curvature deformation has a small effect on the electro-optical characteristics of flexible LCDs. We successfully achieved a high contrast ratio of 1042:1 by fabricating the device using polycarbonate substrates. This result indicates that it is possible to realize high-quality images in flexible LCDs fabricated using polycarbonate substrates even in the curved state.

  19. High sensitive translational temperature measurement using characteristic curve of second harmonic signal in wavelength modulation spectroscopy

    NASA Astrophysics Data System (ADS)

    Matsui, Makoto; Yamada, Tohru

    2017-01-01

    A high sensitive measurement system of translational temperature of plasma was developed. In this system, which is based on wavelength modulation spectroscopy, a peak value of second harmonic signal was measured as a function of modulation depth. The translational temperature was estimated by fitting the theoretically calculated curve to the measured characteristic curve. The performance of this system was examined using microwave discharge plasma. As a result of comparison with conventional laser absorption spectroscopy, both results show good agreement in the measurable region of the laser absorption spectroscopy. Next, the measurable limit of this system was investigated by decreasing the target number density. The detectable fractional absorption was as low as 3.7 × 10-5 in which condition the signal to noise ratio was the order of single digit at the averaging number of 40. This value is more than two orders of magnitude lower than that of the laser absorption spectroscopy.

  20. Full receiver operating characteristic curve estimation using two alternative forced choice studies.

    PubMed

    Massanes, Francesc; Brankov, Jovan G

    2016-01-01

    Task-based medical image quality is typically measured by the degree to which a human observer can perform a diagnostic task in a psychophysical human observer study. During a typical study, an observer is asked to provide a numerical score quantifying his confidence as to whether an image contains a diagnostic marker or not. Such scores are then used to measure the observers' diagnostic accuracy, summarized by the receiver operating characteristic (ROC) curve and the area under ROC curve. These types of human studies are difficult to arrange, costly, and time consuming. In addition, human observers involved in this type of study should be experts on the image genre to avoid inconsistent scoring through the lengthy study. In two-alternative forced choice (2AFC) studies, known to be faster, two images are compared simultaneously and a single indicator is given. Unfortunately, the 2AFC approach cannot lead to a full ROC curve or a set of image scores. The aim of this work is to propose a methodology in which multiple rounds of the 2AFC studies are used to re-estimate an image confidence score (a.k.a. rating, ranking) and generate the full ROC curve. In the proposed approach, we treat image confidence score as an unknown rating that needs to be estimated and 2AFC as a two-player match game. To achieve this, we use the ELO rating system, which is used for calculating the relative skill levels of players in competitor-versus-competitor games such as chess. The proposed methodology is not limited to ELO, and other rating methods such as TrueSkill™, Chessmetrics, or Glicko can be also used. The presented results, using simulated data, indicate that a full ROC curve can be recovered using several rounds of 2AFC studies and that the best pairing strategy starts with the first round of pairing abnormal versus normal images (as in the classical 2AFC approach) followed by a number of rounds using random pairing. In addition, the proposed method was tested in a pilot human

  1. Full receiver operating characteristic curve estimation using two alternative forced choice studies

    PubMed Central

    Massanes, Francesc; Brankov, Jovan G.

    2016-01-01

    Abstract. Task-based medical image quality is typically measured by the degree to which a human observer can perform a diagnostic task in a psychophysical human observer study. During a typical study, an observer is asked to provide a numerical score quantifying his confidence as to whether an image contains a diagnostic marker or not. Such scores are then used to measure the observers’ diagnostic accuracy, summarized by the receiver operating characteristic (ROC) curve and the area under ROC curve. These types of human studies are difficult to arrange, costly, and time consuming. In addition, human observers involved in this type of study should be experts on the image genre to avoid inconsistent scoring through the lengthy study. In two-alternative forced choice (2AFC) studies, known to be faster, two images are compared simultaneously and a single indicator is given. Unfortunately, the 2AFC approach cannot lead to a full ROC curve or a set of image scores. The aim of this work is to propose a methodology in which multiple rounds of the 2AFC studies are used to re-estimate an image confidence score (a.k.a. rating, ranking) and generate the full ROC curve. In the proposed approach, we treat image confidence score as an unknown rating that needs to be estimated and 2AFC as a two-player match game. To achieve this, we use the ELO rating system, which is used for calculating the relative skill levels of players in competitor-versus-competitor games such as chess. The proposed methodology is not limited to ELO, and other rating methods such as TrueSkill™, Chessmetrics, or Glicko can be also used. The presented results, using simulated data, indicate that a full ROC curve can be recovered using several rounds of 2AFC studies and that the best pairing strategy starts with the first round of pairing abnormal versus normal images (as in the classical 2AFC approach) followed by a number of rounds using random pairing. In addition, the proposed method was tested in a

  2. Quantification of damage detection schemes using receiver operating characteristic (ROC) curves

    NASA Astrophysics Data System (ADS)

    Trickey, Stephen; Seaver, Mark; Nichols, Jon

    2007-04-01

    In this work we detect damage in a composite to metal bolted joint subject to ambient vibrations and strong temperature fluctuations. Damage to the joint is considered to be a degradation of the connection strength implemented by loosening the bolts. The system is excited with a signal that conforms to the Pierson-Moskowitz distribution for wave height and represents a possible loading this component would be subject to in situ. We show that as the bolts are loosened, increasing amounts of nonlinearity are introduced in the form of impact discontinuities and stick-slip behavior. The presence of the nonlinearity, hence the damage, is detected by drawing comparisons between the response data and surrogate data conforming to the null hypothesis of an undamaged, linear system. Two metrics are used for comparison purposes: nonlinear prediction error and the bicoherence. Results are displayed using Receiver Operating Characteristic (ROC) curves. The ROC curve quantifies the trade-off between false positives (type I errors) and false negatives (type II errors). Type I errors can be expressed as the probability of false alarm and 1 - type II error is the probability of detection. We demonstrate that ROC curves provide a unified quantifiable approach for directly comparing the merits of different detection schemes.

  3. Multivariate normally distributed biomarkers subject to limits of detection and receiver operating characteristic curve inference.

    PubMed

    Perkins, Neil J; Schisterman, Enrique F; Vexler, Albert

    2013-07-01

    Biomarkers are of ever-increasing importance to clinical practice and epidemiologic research. Multiple biomarkers are often measured per patient. Measurement of true biomarker levels is limited by laboratory precision, specifically measuring relatively low, or high, biomarker levels resulting in undetectable levels below, or above, a limit of detection (LOD). Ignoring these missing observations or replacing them with a constant are methods commonly used although they have been shown to lead to biased estimates of several parameters of interest, including the area under the receiver operating characteristic (ROC) curve and regression coefficients. We developed asymptotically consistent, efficient estimators, via maximum likelihood techniques, for the mean vector and covariance matrix of multivariate normally distributed biomarkers affected by LOD. We also developed an approximation for the Fisher information and covariance matrix for our maximum likelihood estimations (MLEs). We apply these results to an ROC curve setting, generating an MLE for the area under the curve for the best linear combination of multiple biomarkers and accompanying confidence interval. Point and confidence interval estimates are scrutinized by simulation study, with bias and root mean square error and coverage probability, respectively, displaying behavior consistent with MLEs. An example using three polychlorinated biphenyls to classify women with and without endometriosis illustrates how the underlying distribution of multiple biomarkers with LOD can be assessed and display increased discriminatory ability over naïve methods. Properly addressing LODs can lead to optimal biomarker combinations with increased discriminatory ability that may have been ignored because of measurement obstacles. Published by Elsevier Inc.

  4. A simple method to estimate the time-dependent receiver operating characteristic curve and the area under the curve with right censored data.

    PubMed

    Li, Liang; Greene, Tom; Hu, Bo

    2016-11-27

    The time-dependent receiver operating characteristic curve is often used to study the diagnostic accuracy of a single continuous biomarker, measured at baseline, on the onset of a disease condition when the disease onset may occur at different times during the follow-up and hence may be right censored. Due to right censoring, the true disease onset status prior to the pre-specified time horizon may be unknown for some patients, which causes difficulty in calculating the time-dependent sensitivity and specificity. We propose to estimate the time-dependent sensitivity and specificity by weighting the censored data by the conditional probability of disease onset prior to the time horizon given the biomarker, the observed time to event, and the censoring indicator, with the weights calculated nonparametrically through a kernel regression on time to event. With this nonparametric weighting adjustment, we derive a novel, closed-form formula to calculate the area under the time-dependent receiver operating characteristic curve. We demonstrate through numerical study and theoretical arguments that the proposed method is insensitive to misspecification of the kernel bandwidth, produces unbiased and efficient estimators of time-dependent sensitivity and specificity, the area under the curve, and other estimands from the receiver operating characteristic curve, and outperforms several other published methods currently implemented in R packages.

  5. Characteristics of dewatering induced drawdown curve under blocking effect of retaining wall in aquifer

    NASA Astrophysics Data System (ADS)

    Wu, Yong-Xia; Shen, Shui-Long; Yuan, Da-Jun

    2016-08-01

    For deep excavation pits that require the pumping of confined groundwater, a combination of a retaining wall and dewatering with large-diameter wells is usually adopted during excavation to improve safety. Since a retaining wall has a much lower hydraulic conductivity than the surrounding material in the aquifer, blocking of seepage to prolong the seepage path of the groundwater outside of the pit is effective. The retaining walls used during excavation dewatering cause hydraulic head drawdown inside the pit much faster than outside the pit. Thus, difference in hydraulic head between inside and outside of the pit increases. To investigate the mechanism of the blocking effect, numerical simulation using the finite difference method (FDM) was conducted to analyze the effects of pumping in the pit. The FDM results show that drawdown varies along the depth of the confined aquifer. The influence factors of drawdown inside and outside the pit include insertion depth of retaining walls, anisotropy of a confined aquifer and screen length of pumping wells. In addition, FDM results also show that the drawdown-time curve can be divided into four stages: in Stage I, drawdown inside the pit is very small and outside the pit it is almost zero; in Stage II, drawdown increases quickly with time; in Stage III, the drawdown curve is parallel to the Cooper-Jacob curve on semi-log axes; and in Stage IV, the drawdown becomes constant. These characteristics of the drawdown curve under the blocking effect of a retaining wall in an aquifer provide a way of estimating hydrogeological parameters according to pumping test results.

  6. Adjusting for covariate effects on classification accuracy using the covariate-adjusted receiver operating characteristic curve.

    PubMed

    Janes, Holly; Pepe, Margaret S

    2009-06-01

    Recent scientific and technological innovations have produced an abundance of potential markers that are being investigated for their use in disease screening and diagnosis. In evaluating these markers, it is often necessary to account for covariates associated with the marker of interest. Covariates may include subject characteristics, expertise of the test operator, test procedures or aspects of specimen handling. In this paper, we propose the covariate-adjusted receiver operating characteristic curve, a measure of covariate-adjusted classification accuracy. Nonparametric and semiparametric estimators are proposed, asymptotic distribution theory is provided and finite sample performance is investigated. For illustration we characterize the age-adjusted discriminatory accuracy of prostate-specific antigen as a biomarker for prostate cancer.

  7. Assessing the Classification Accuracy of Early Numeracy Curriculum-Based Measures Using Receiver Operating Characteristic Curve Analysis

    ERIC Educational Resources Information Center

    Laracy, Seth D.; Hojnoski, Robin L.; Dever, Bridget V.

    2016-01-01

    Receiver operating characteristic curve (ROC) analysis was used to investigate the ability of early numeracy curriculum-based measures (EN-CBM) administered in preschool to predict performance below the 25th and 40th percentiles on a quantity discrimination measure in kindergarten. Areas under the curve derived from a sample of 279 students ranged…

  8. Assessing the Classification Accuracy of Early Numeracy Curriculum-Based Measures Using Receiver Operating Characteristic Curve Analysis

    ERIC Educational Resources Information Center

    Laracy, Seth D.; Hojnoski, Robin L.; Dever, Bridget V.

    2016-01-01

    Receiver operating characteristic curve (ROC) analysis was used to investigate the ability of early numeracy curriculum-based measures (EN-CBM) administered in preschool to predict performance below the 25th and 40th percentiles on a quantity discrimination measure in kindergarten. Areas under the curve derived from a sample of 279 students ranged…

  9. A Method to Recover Useful Geothermal-Reservoir Parameters from Production Characteristic Curves (1) Steam Reservoirs

    SciTech Connect

    Iglesias, E.; Arellano, V.; Garfias, A.; Miranda, C.; Hernandez, J.; Gonzalez, J.

    1983-12-15

    In this paper we develop and demonstrate a method to estimate the reservoir pressure and a productivity index for vertical steam wells, from its production characteristic (also called output) curves. In addition, the method allows to estimate the radius of influence of the well, provided that a value of the reservoir transmisivity is available. The basic structure of the present method is: first, the measured well head mass flowrates and pressures are transformed to downhole conditions by means of a numerical simulator; then, the computed downhole variables are fitted to a simple radial model that predicts the sandface flowrate in terms of the flowing pressure. For demonstration, the method was applied to several steam wells from the Los Azufres Geothermal field. We found excellent agreement of the model with this ample set of field data. As a bonus, the processed data allowed several inferences about the steam producing zone of the reservoir: that the wells considered produce from relatively isolated pockets of steam, which are probably fed by near-by inmobile water; and that these feed zones are in poor hydraulic communication with the field surface waters. our method are that it provides a way to retrieve important reservoir information from usually available production characteristic curves, and that the method works from easily and accurately taken wellhead measurements.

  10. IGBT Switching Characteristic Curve Embedded Half-Bridge MMC Modelling and Real Time Simulation Realization

    NASA Astrophysics Data System (ADS)

    Zhengang, Lu; Hongyang, Yu; Xi, Yang

    2017-05-01

    The Modular Multilevel Converter (MMC) is one of the most attractive topologies in recent years for medium or high voltage industrial applications, such as high voltage dc transmission (HVDC) and medium voltage varying speed motor drive. The wide adoption of MMCs in industry is mainly due to its flexible expandability, transformer-less configuration, common dc bus, high reliability from redundancy, and so on. But, when the sub module number of MMC is more, the test of MMC controller will cost more time and effort. Hardware in the loop test based on real time simulator will save a lot of time and money caused by the MMC test. And due to the flexible of HIL, it becomes more and more popular in the industry area. The MMC modelling method remains an important issue for the MMC HIL test. Specifically, the VSC model should realistically reflect the nonlinear device switching characteristics, switching and conduction losses, tailing current, and diode reverse recovery behaviour of a realistic converter. In this paper, an IGBT switching characteristic curve embedded half-bridge MMC modelling method is proposed. This method is based on the switching curve referring and sample circuit calculation, and it is sample for implementation. Based on the proposed method, a FPGA real time simulation is carried out with 200ns sample time. The real time simulation results show the proposed method is correct.

  11. Therapy Operating Characteristic (TOC) Curves and their Application to the Evaluation of Segmentation Algorithms.

    PubMed

    Barrett, Harrison H; Wilson, Donald W; Kupinski, Matthew A; Aguwa, Kasarachi; Ewell, Lars; Hunter, Robert; Müller, Stefan

    2010-01-01

    This paper presents a general framework for assessing imaging systems and image-analysis methods on the basis of therapeutic rather than diagnostic efficacy. By analogy to receiver operating characteristic (ROC) curves, it utilizes the Therapy Operating Characteristic or TOC curve, which is a plot of the probability of tumor control vs. the probability of normal-tissue complications as the overall level of a radiotherapy treatment beam is varied. The proposed figure of merit is the area under the TOC, denoted AUTOC. If the treatment planning algorithm is held constant, AUTOC is a metric for the imaging and image-analysis components, and in particular for segmentation algorithms that are used to delineate tumors and normal tissues. On the other hand, for a given set of segmented images, AUTOC can also be used as a metric for the treatment plan itself. A general mathematical theory of TOC and AUTOC is presented and then specialized to segmentation problems. Practical approaches to implementation of the theory in both simulation and clinical studies are presented. The method is illustrated with a a brief study of segmentation methods for prostate cancer.

  12. Characteristic overpressure-impulse-distance curves for vapour cloud explosions using the TNO Multi-Energy model.

    PubMed

    Díaz Alonso, Fernando; González Ferradás, Enrique; Sánchez Pérez, Juan Francisco; Miñana Aznar, Agustín; Ruiz Gimeno, José; Martínez Alonso, Jesús

    2006-09-21

    A number of models have been proposed to calculate overpressure and impulse from accidental industrial explosions. When the blast is produced by ignition of a vapour cloud, the TNO Multi-Energy model is widely used. From the curves given by this model, data are fitted to obtain equations showing the relationship between overpressure, impulse and distance. These equations, referred herein as characteristic curves, can be fitted by means of power equations, which depend on explosion energy and charge strength. Characteristic curves allow the determination of overpressure and impulse at each distance.

  13. Application of Receiver Operating Characteristic (ROC) Curves for Explosives Detection Using Different Sampling and Detection Techniques

    PubMed Central

    Young, Mimy; Fan, Wen; Raeva, Anna; Almirall, Jose

    2013-01-01

    Reported for the first time are receiver operating characteristic (ROC) curves constructed to describe the performance of a sorbent-coated disk, planar solid phase microextraction (PSPME) unit for non-contact sampling of a variety of volatiles. The PSPME is coupled to ion mobility spectrometers (IMSs) for the detection of volatile chemical markers associated with the presence of smokeless powders, model systems of explosives containing diphenylamine (DPA), 2,4-dinitrotoluene (2,4-DNT) and nitroglycerin (NG) as the target analytes. The performance of the PSPME-IMS was compared with the widely accepted solid-phase microextraction (SPME), coupled to a GC-MS. A set of optimized sampling conditions for different volume containers (1–45 L) with various sample amounts of explosives, were studied in replicates (n = 30) to determine the true positive rates (TPR) and false positive detection rates (FPR) for the different scenarios. These studies were obtained in order to construct the ROC curves for two IMS instruments (a bench-top and field-portable system) and a bench top GC-MS system in low and high clutter environments. Both static and dynamic PSPME sampling were studied in which 10–500 mg quantities of smokeless powders were detected within 10 min of static sampling and 1 min of dynamic sampling.

  14. Soil water repellency characteristic curves for soil profiles with natural organic carbon gradients

    NASA Astrophysics Data System (ADS)

    Kawamoto, Ken; Müller, Karin; Moldrup, Per; de Jonge, Lis; Clothier, Brent; Hiradate, Syuntaro; Komatsu, Toshiko

    2014-05-01

    Soil water repellency (SWR) is a phenomenon that influences many soil hydrologic processes such as reduction of infiltration, increase in overland flow, and enhanced preferential flow. SWR has been observed in various soil types and textures, and the degree of SWR is greatly controlled by soil moisture content and levels of organic matter and clay. One of the key topics in SWR research is how to describe accurately the seasonal and temporal variation of SWR with the controlling factors such as soil moisture, organic matter, and clay contents for soil profiles with natural organic carbon gradients. In the present study, we summarize measured SWR data for soil profiles under different land uses and vegetation in Japan and New Zealand, and compared these with literature data. We introduce the contact angle-based evaluation of SWR and predictive models for soil water repellency characteristic curves, in which the contact angle is a function of the moisture content. We also discuss a number of novel concepts, including i) the reduction in the contact angle with soil-water contact time to describe the time dependence of SWR, ii) the relationship between the contact angles from the measured scanning curves under controlled wetting and drying cycles, and iii) the initial contact angles measured by the sessile drop method.

  15. Interrelations among the soil-water retention, hydraulic conductivity, and suction-stress characteristic curves

    USGS Publications Warehouse

    Lu, Ning; Kaya, Murat; Godt, Jonathan W.

    2014-01-01

    The three fundamental constitutive relations that describe fluid flow, strength, and deformation behavior of variably saturated soils are the soil-water retention curve (SWRC), hydraulic conductivity function (HCF), and suction-stress characteristic curve (SSCC). Until recently, the interrelations among the SWRC, HCF, and SSCC have not been well established. This work sought experimental confirmation of interrelations among these three constitutive functions. Results taken from the literature for six soils and those obtained for 11 different soils were used. Using newly established analytical relations among the SWRC, HCF, and SSCC and these test results, the authors showed that these three constitutive relations can be defined by a common set of hydromechanical parameters. The coefficient of determination for air-entry pressures determined independently using hydraulic and mechanical methods is >0.99, >0.98 for the pore size parameter, and 0.94 for the residual degree of saturation. One practical implication is that one of any of the four experiments (axis-translation, hydraulic, shear-strength, or deformation) is sufficient to quantify all three constitutive relations.

  16. Receiver operator characteristic (ROC) curves and non-normal data: an empirical study.

    PubMed

    Goddard, M J; Hinberg, I

    1990-03-01

    This paper evaluates the performance of several diagnostic kits for assessing levels of serum prostatic acid phosphatase on patients at different stages of cancer of the prostate. Each patient was studied with several kits. We compare results obtained for receiver operator characteristic (ROC) curve methodology with data assumed to follow a normal distribution, with log-transformed data assumed to follow a normal distribution, and when neither of these assumptions holds. There were important differences between the results of the different approaches. For these data, the normal distribution assumption should be used with extreme caution. The log-transformed based results compared favourably with the non-parametric, but unconsidered application of the method should be avoided.

  17. Force-time curve characteristics of dynamic and isometric muscle actions of elite women olympic weightlifters.

    PubMed

    Haff, G Gregory; Carlock, Jon M; Hartman, Michael J; Kilgore, J Lon; Kawamori, Naoki; Jackson, Janna R; Morris, Robert T; Sands, William A; Stone, Michael H

    2005-11-01

    Six elite women weightlifters were tested to evaluate force-time curve characteristics and intercorrelations of isometric and dynamic muscle actions. Subjects performed isometric and dynamic mid-thigh clean pulls at 30% of maximal isometric peak force and 100 kg from a standardized position on a 61.0 x 121.9 cm AMTI forceplate. Isometric peak force showed strong correlations to the athletes' competitive snatch, clean and jerk, and combined total (r = 0.93, 0.64, and 0.80 respectively). Isometric rate of force development showed moderate to strong relationships to the athletes' competitive snatch, clean and jerk, and combined total (r = 0.79, 0.69, and 0.80 respectively). The results of this study suggest that the ability to perform maximal snatch and clean and jerks shows some structural and functional foundation with the ability to generate high forces rapidly in elite women weightlifters.

  18. Numerical study of base pressure characteristic curve for a four-engine clustered nozzle configuration

    NASA Technical Reports Server (NTRS)

    Wang, Ten-See

    1993-01-01

    The objective of this study is to benchmark a four-engine clustered nozzle base flowfield with a computational fluid dynamics (CFD) model. The CFD model is a three-dimensional pressure-based, viscous flow formulation. An adaptive upwind scheme is employed for the spatial discretization. The upwind scheme is based on second and fourth order central differencing with adaptive artificial dissipation. Qualitative base flow features such as the reverse jet, wall jet, recompression shock, and plume-plume impingement have been captured. The computed quantitative flow properties such as the radial base pressure distribution, model centerline Mach number and static pressure variation, and base pressure characteristic curve agreed reasonably well with those of the measurement. Parametric study on the effect of grid resolution, turbulence model, inlet boundary condition and difference scheme on convective terms has been performed. The results showed that grid resolution had a strong influence on the accuracy of the base flowfield prediction.

  19. Fully non-parametric receiver operating characteristic curve estimation for random-effects meta-analysis.

    PubMed

    Martínez-Camblor, Pablo

    2017-02-01

    Meta-analyses, broadly defined as the quantitative review and synthesis of the results of related but independent comparable studies, allow to know the state of the art of one considered topic. Since the amount of available bibliography has enhanced in almost all fields and, specifically, in biomedical research, its popularity has drastically increased during the last decades. In particular, different methodologies have been developed in order to perform meta-analytic studies of diagnostic tests for both fixed- and random-effects models. From a parametric point of view, these techniques often compute a bivariate estimation for the sensitivity and the specificity by using only one threshold per included study. Frequently, an overall receiver operating characteristic curve based on a bivariate normal distribution is also provided. In this work, the author deals with the problem of estimating an overall receiver operating characteristic curve from a fully non-parametric approach when the data come from a meta-analysis study i.e. only certain information about the diagnostic capacity is available. Both fixed- and random-effects models are considered. In addition, the proposed methodology lets to use the information of all cut-off points available (not only one of them) in the selected original studies. The performance of the method is explored through Monte Carlo simulations. The observed results suggest that the proposed estimator is better than the reference one when the reported information is related to a threshold based on the Youden index and when information for two or more points are provided. Real data illustrations are included.

  20. A controlled evaluation of oral screen effects on intra-oral pressure curve characteristics.

    PubMed

    Knösel, Michael; Jung, Klaus; Kinzinger, Gero; Bauss, Oskar; Engelke, Wilfried

    2010-10-01

    The purpose of this study was to quantify the impact of oral screen (OS) application on intra-oral pressure characteristics in three malocclusion groups. Fifty-six randomly recruited participants (26 males and 30 females) who met the inclusion criteria of either an Angle Class I occlusal relationships or Angle Class II1 or II2 malocclusions, were assigned by dentition to group I (n = 31), group II1 (n = 12), or group II2 (n = 13). Two 3 minute periods of intra-oral pressure monitoring were conducted on each participant, using two different oral end fittings connected to a piezo-resistive relative pressure sensor: (1) a flexible OS and (2) a small-dimensioned air-permeable end cap (EC), which was placed laterally in the premolar region, thus recording intra-oral pressure independent of the influence of the OS. Pressure curve characteristics for both periods and between the malocclusion groups were evaluated with reference to the frequency of swallowing peaks, duration, and altitude of negative pressure plateau phases and the area under the pressure curve. Statistical analysis was undertaken using analysis of variance (ANOVA), the Wilcoxon Mann-Whitney test, and spearman correlation coefficient. A median number of two peaks (median height -20.9 mbar) and three plateau phases (median height of -2.3 mbar) may be regarded as normative for normal occlusion subjects during a 3 minute period, at rest. OS application raised the median average duration and height of intra-oral negative pressure plateau phases in the II1 subjects, exceeding those of group I, but less than the plateau duration in group II2. Median peak heights were distinctively lower in groups I and II1 during OS application. It is concluded that additional training for extension of intra-oral pressure phases may be a promising approach to pre-orthodontic Class II division 1 treatment.

  1. Validation of a Cardiovascular Disease Policy Microsimulation Model Using Both Survival and Receiver Operating Characteristic Curves.

    PubMed

    Pandya, Ankur; Sy, Stephen; Cho, Sylvia; Alam, Sartaj; Weinstein, Milton C; Gaziano, Thomas A

    2017-10-01

    Despite some advances, cardiovascular disease (CVD) remains the leading cause of death and healthcare costs in the United States. We therefore developed a comprehensive CVD policy simulation model that identifies cost-effective approaches for reducing CVD burden. This paper aims to: 1) describe our model in detail; and 2) perform model validation analyses. The model simulates 1,000,000 adults (ages 35 to 80 years) using a variety of CVD-related epidemiological data, including previously calibrated Framingham-based risk scores for coronary heart disease and stroke. We validated our microsimulation model using recent National Health and Nutrition Examination Survey (NHANES) data, with baseline values collected in 1999-2000 and cause-specific mortality follow-up through 2011. Model-based (simulated) results were compared to observed all-cause and CVD-specific mortality data (from NHANES) for the same starting population using survival curves and, in a method not typically used for disease model validation, receiver operating characteristic (ROC) curves. Observed 10-year all-cause mortality in NHANES v. the simulation model was 11.2% (95% CI, 10.3% to 12.2%) v. 10.9%; corresponding results for CVD mortality were 2.2% (1.8% to 2.7%) v. 2.6%. Areas under the ROC curves for model-predicted 10-year all-cause and CVD mortality risks were 0.83 (0.81 to 0.85) and 0.84 (0.81 to 0.88), respectively; corresponding results for 5-year risks were 0.80 (0.77 to 0.83) and 0.81 (0.75 to 0.87), respectively. The model is limited by the uncertainties in the data used to estimate its input parameters. Additionally, our validation analyses did not include non-fatal CVD outcomes due to NHANES data limitations. The simulation model performed well in matching to observed nationally representative longitudinal mortality data. ROC curve analysis, which has been traditionally used for risk prediction models, can also be used to assess discrimination for disease simulation models.

  2. Post fellowship training in "new-to-them" surgical techniques: assessment of learning curve characteristics.

    PubMed

    Miao, Jinwei; Fleury, Aimee C; Kushnir, Christina L; Silver, David F; Naik, Raj; Spirtos, Nick M

    2011-06-01

    To evaluate surgically related quality outcomes during the learning curve for board-certified or board-eligible gynecologic oncologists developing "new-to-them" surgical techniques. The study design was a retrospective review of patients with endometrial cancer clinically limited to the uterus and/or cervix undergoing TLH-BSO or TAH-BSO, aortic and pelvic lymphadenectomy(APLNDx), peritoneal washings with/without omentectomy from May 1996 to April /2006. A "senior" surgeon taught three board-certified or board-eligible gynecologic oncologists a "new-to-them" technique to perform both TLH-BSO and TAH-BSO with APLNDx using argon beam coagulation and endoscopic staplers in patients with early-stage endometrial cancer. The main outcome measures were: a) length of surgery; b) surgical measures, e.g. lymph node count; and c) peri-operative morbidity. A comparison of outcomes with the "senior" surgeon was undertaken. The learning curve characteristics were analyzed by ANOVA and curve estimate analysis. The mean operative times associated with learning a new technique to perform TLH-BSO with APLNDx and TAH-BSO with APLNDx were 155.39+/-26.32 and 102.28+/-34.22 min, respectively, with significant improvement after 20 cases (150.27+/-26.68 vs. 172.30+/-22.28, p=0.030) and 30 cases (93.30+/-24.97 vs. 124.63+/-29.73, p=0.030), respectively. Intra- and peri-operative morbidity and lymph node count were unaffected by experience. While mean operative times decreased, outcome measures of surgical quality were not adversely affected during the learning curve for post-fellowship training while acquiring "new-to-them" surgical techniques. This study emphasizes the need for "senior" surgical supervision during the initial training period. The results of this study are likely transferable to fellowship-trained gynecologic oncologists learning other "new-to-them" surgical techniques and procedures. Copyright © 2011 Elsevier Inc. All rights reserved.

  3. Improving the estimation of complete field soil water characteristic curves through field monitoring data

    NASA Astrophysics Data System (ADS)

    Bordoni, M.; Bittelli, M.; Valentino, R.; Chersich, S.; Meisina, C.

    2017-09-01

    In this work, Soil Water Characteristic Curves (SWCCs) were reconstructed through simultaneous field measurements of soil pore water pressure and water content. The objective was to evaluate whether field-based monitoring can allow for the improvement of the accuracy in SWCCs estimation with respect to the use of laboratory techniques. Moreover, field assessment of SWCCs allowed to: a) quantify the hydrological hysteresis affecting SWCCs through field data; b) analyze the effect of different temporal resolution of field measures; c) highlight the differences in SWCCs reconstructed for a particular soil during different hydrological years; d) evaluate the reliability of field reconstructed SWCCs, by the comparison between assessed and measured trends of a component of the soil water balance. These aspects were fundamental for assessing the reliability of the field reconstructed SWCCs. Field data at two Italian test-sites were measured. These test-sites were used to evaluate the goodness of field reconstructed SWCCs for soils characterized by different geomorphological, geological, physical and pedological features. Field measured or laboratory measured SWCCs data of 5 soil horizons (3 in a predominantly silty soil, 2 in a predominantly clayey one) were fitted by Van Genuchten model. Different field drying and wetting periods were identified, based on monthly meteorological conditions, in terms of rainfall and evapotranspiration amounts, of different cycles. This method allowed for a correct discrimination of the main drying and the main wetting paths from field data related and for a more reliable quantification of soil hydrological properties with respect to laboratory methodologies. Particular patterns of changes in SWCCs forms along depth could be also identified. Field SWCCs estimation is not affected by the temporal resolution of the acquisition (hours or days), as testified by similar values of Van Genuchten equation fitting parameters. Instead, hourly data

  4. Prediction of dynamic and aerodynamic characteristics of the centrifugal fan with forward curved blades

    NASA Astrophysics Data System (ADS)

    Polanský, Jiří; Kalmár, László; Gášpár, Roman

    2013-12-01

    The main aim of this paper is determine the centrifugal fan with forward curved blades aerodynamic characteristics based on numerical modeling. Three variants of geometry were investigated. The first, basic "A" variant contains 12 blades. The geometry of second "B" variant contains 12 blades and 12 semi-blades with optimal length [1]. The third, control variant "C" contains 24 blades without semi-blades. Numerical calculations were performed by CFD Ansys. Another aim of this paper is to compare results of the numerical simulation with results of approximate numerical procedure. Applied approximate numerical procedure [2] is designated to determine characteristics of the turbulent flow in the bladed space of a centrifugal-flow fan impeller. This numerical method is an extension of the hydro-dynamical cascade theory for incompressible and inviscid fluid flow. Paper also partially compares results from the numerical simulation and results from the experimental investigation. Acoustic phenomena observed during experiment, during numerical simulation manifested as deterioration of the calculation stability, residuals oscillation and thus also as a flow field oscillation. Pressure pulsations are evaluated by using frequency analysis for each variant and working condition.

  5. Hierarchical linear modeling of FIM instrument growth curve characteristics after spinal cord injury.

    PubMed

    Warschausky, S; Kay, J B; Kewman, D G

    2001-03-01

    To examine the recovery of aspects of functional independence as a continuous process using growth curve analysis. Retrospective database review of functional outcome assessment data from inception cohort. Inpatient rehabilitation unit; community. A total of 142 subjects (79.6% men; age range, 18-77yr; mean age +/- standard deviation, 36.2 +/- 15.5yr) who were admitted to a rehabilitation unit between March 1986 and November 1994 with a minimum of 4 postinjury FIM assessments. Neurologic subgroups included 63 individuals with paraplegia, 36 with low tetraplegia, 24 with high tetraplegia, and 19 with incomplete injury. FIM instrument. Growth curve analyses with hierarchical linear modeling using a decelerating recovery function yielded a reliable model in which longer rehabilitation length of stay was associated with a more rapid rate of recovery but lower plateau. Neurologic injury category had expected effects on rate and degree of recovery. Level of impairment-specific results included an age effect in which older age was associated with lower level of plateau. In specific neurologic groups there was a significant gender effect, in which men made more rapid recovery than women, and a significant effect of level of education, in which higher education was associated with more rapid rate of recovery. Rate of FIM recovery was reliably modeled in the sample with incomplete injuries, but none of the demographic predictors was significant. Functional recovery can be modeled as a decelerating rather than simple linear function. The study of predictors of recovery characteristics, including rate of recovery and plateau, offers a valuable way of understanding rehabilitative needs and outcomes. Gender and education effects on the recovery process are intriguing and warrant further investigation.

  6. Potential distribution and transmission characteristics in a curved quadrupole ion guide.

    PubMed

    Zhou, Xiaoyu; Xiong, Caiqiao; Xu, Gaoping; Liu, Hao; Tang, Yin; Zhu, Zhiqiang; Chen, Rui; Qiao, Haoxue; Tseng, Yao-Hsin; Peng, Wen-Ping; Nie, Zongxiu; Chen, Yi

    2011-02-01

    The potential distribution in the curved quadrupole is exactly characterized by the Laplace equation, and an approximate solution to the Laplace equation is calculated. We represent the Laplace equation under the coordinates named minimal rotation frame (MRF) and derive an expression on the hexapole and octopole superposition. Our conclusion is in agreement with the results by the numerical (SIMION) method. Based on the Poincare-Lighthill-Kuo (PLK) method reported in our previous work, the nonlinear effects of ion motion are investigated in detail. The frequency shift of ion motion can be well eliminated by coupling the hexapole component with a positive octopole component, and the transmission efficiency of ions is found to decrease dramatically with the increase of the ionic kinetic energy in the z-direction. Furthermore, the transmission characteristics of ions are discussed with regards to the phase-space theory. The results show that the centrifugally introduced axis shift is mainly responsible for the ion losses. A modified direct current (dc) voltage supply pattern is hence proposed to compensate for this effect.

  7. 7 CFR 42.143 - Operating Characteristic (OC) curves for on-line sampling and inspection.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... plans provided in subpart D. The OC curve and the corresponding cumulative sum sampling plans are listed... (OC) Curves for AQL=0.25 Defects per Hundred Units Identification name of OC curves Reduced ng T L S Normal ng T L S Tightened ng T L S 13 0 0 0 25 0.05 0.95 0.35 50 0.1 0.9 0.3 ng=Number of sample units in...

  8. 7 CFR 42.140 - Operating Characteristic (OC) curves for on-line sampling and inspection.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... Plan. An examination of this table reveals that there is one single and one double sampling plan that have OC curves comparable to OC curve 6. The first plan listed is a single plan requiring the... if there are 3 or more defects in the sample. In the event that the number of defects is between...

  9. 7 CFR 42.143 - Operating Characteristic (OC) curves for on-line sampling and inspection.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... distinguish between good and bad portions of production. The interpretation of these curves for portions of production is similar to the interpretation of the OC curves for stationary lots as illustrated in § 42.140(c...=Number of sample units in a subgroup. T=Subgroup tolerance.L=Acceptance limit.S=Starting value. EC02SE91...

  10. Word Frequency and Receiver Operating Characteristic Curves in Recognition Memory: Evidence for a Dual-Process Interpretation

    PubMed Central

    Arndt, Jason; Reder, Lynne M.

    2008-01-01

    Dual-process models of the word-frequency mirror effect posit that low-frequency words are recollected more often than high-frequency words, producing the hit rate differences in the word-frequency effect, whereas high-frequency words are more familiar, producing the false-alarm-rate differences. In this pair of experiments, the authors demonstrate that the analysis of receiver operating characteristic (ROC) curves provides critical information in support of this interpretation. Specifically, when participants were required to discriminate between studied nouns and their plurality reversed complements, the ROC curve was accurately described by a threshold model that is consistent with recollection-based recognition. Further, the plurality discrimination ROC curves showed characteristics consistent with the interpretation that participants recollected low-frequency items more than high-frequency items. PMID:12219793

  11. Tsunami Simulation using CIP Method with Characteristic Curve Equations and TVD-MacCormack Method

    NASA Astrophysics Data System (ADS)

    Fukazawa, Souki; Tosaka, Hiroyuki

    2015-04-01

    After entering 21st century, we already had two big tsunami disasters associated with Mw9 earthquakes in Sumatra and Japan. To mitigate the damages of tsunami, the numerical simulation technology combined with information technologies could provide reliable predictions in planning countermeasures to prevent the damage to the social system, making safety maps, and submitting early evacuation information to the residents. Shallow water equations are still solved not only for global scale simulation of the ocean tsunami propagation but also for local scale simulation of overland inundation in many tsunami simulators though three-dimensional model starts to be used due to improvement of CPU. One-dimensional shallow water equations are below: partial bm{Q}/partial t+partial bm{E}/partial x=bm{S} in which bm{Q}=( D M )), bm{E}=( M M^2/D+gD^2/2 )), bm{S}=( 0 -gDpartial z/partial x-gn2 M|M| /D7/3 )). where D[m] is total water depth; M[m^2/s] is water flux; z[m] is topography; g[m/s^2] is the gravitational acceleration; n[s/m1/3] is Manning's roughness coefficient. To solve these, the staggered leapfrog scheme is used in a lot of wide-scale tsunami simulator. But this scheme has a problem that lagging phase error occurs when courant number is small. In some practical simulation, a kind of diffusion term is added. In this study, we developed two wide-scale tsunami simulators with different schemes and compared usual scheme and other schemes in practicability and validity. One is a total variation diminishing modification of the MacCormack method (TVD-MacCormack method) which is famous for the simulation of compressible fluids. The other is the Cubic Interpolated Profile (CIP) method with characteristic curve equations transformed from shallow water equations. Characteristic curve equations derived from shallow water equations are below: partial R_x±/partial t+C_x±partial R_x±/partial x=∓ g/2partial z/partial x in which R_x±=√{gD}± u/2, C_x±=u± √{gD}. where u

  12. Prediction Accuracy of the Washington and Illinois Risk Assessment Instruments: An Application of Receiver Operating Characteristic Curve Analysis.

    ERIC Educational Resources Information Center

    Camasso, Michael J.; Jagannathan, Radha

    1995-01-01

    Compares the predictive performances of the Illinois CANTS 17B and the Washington State Risk Matrix on a sample of New Jersey child protective services cases using logistic regression and receiver operating characteristic curve analysis. Both instruments predict case recidivism, closings, and substantiation with probabilities greater than chance.…

  13. The Obsessive Compulsive Scale of the Child Behavior Checklist Predicts Obsessive-Compulsive Disorder: A Receiver Operating Characteristic Curve Analysis

    ERIC Educational Resources Information Center

    Hudziak, James J.; Althoff, Robert R.; Stanger, Catherine; van Beijsterveldt, C. E. M.; Nelson, Elliot C.; Hanna, Gregory L.; Boomsma, Dorret I.; Todd, Richard D.

    2006-01-01

    Background: The purpose of this study was to determine a score on the Obsessive Compulsive Scale (OCS) from the Child Behavior Checklist (CBCL) to screen for obsessive compulsive disorder (OCD) in children and to rigorously test the specificity and sensitivity of a single cutpoint. Methods: A receiver operating characteristic (ROC) curve analysis…

  14. Learner Characteristic Based Learning Effort Curve Mode: The Core Mechanism on Developing Personalized Adaptive E-Learning Platform

    ERIC Educational Resources Information Center

    Hsu, Pi-Shan

    2012-01-01

    This study aims to develop the core mechanism for realizing the development of personalized adaptive e-learning platform, which is based on the previous learning effort curve research and takes into account the learner characteristics of learning style and self-efficacy. 125 university students from Taiwan are classified into 16 groups according…

  15. 7 CFR 42.141 - Obtaining Operating Characteristic (OC) curve information for skip lot sampling and inspection.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... skip lot sampling and inspection. The Operating Characteristic (OC) curve information (probability of acceptance) for skip lot sampling and inspection procedures described in § 42.121 is easily obtained from the... information for skip lot sampling and inspection. 42.141 Section 42.141 Agriculture Regulations of the...

  16. A Statistical Comparison of the Blossom Blight Forecasts of MARYBLYT and Cougarblight with Receiver Operating Characteristic Curve Analysis

    USDA-ARS?s Scientific Manuscript database

    Blossom blight forecasting is an important aspect of fire blight, caused by Erwinia amylovora, management for both apple and pear. A comparison of the forecast accuracy of two common fire blight forecasters, MARYBLYT and Cougarblight, was performed with receiver operating characteristic (ROC) curve ...

  17. Laminar and turbulent surgical plume characteristics generated from curved- and straight-blade laparoscopic ultrasonic dissectors.

    PubMed

    Kim, Fernando J; Sehrt, David; Pompeo, Alexandre; Molina, Wilson R

    2014-05-01

    To characterize laparoscopic ultrasonic dissector surgical plume emission (laminar or turbulent) and investigate plume settlement time between curved and straight blades. A straight and a curved blade laparoscopic ultrasonic dissector were activated on tissue and in a liquid environment to evaluate plume emission. Plume emission was characterized as either laminar or turbulent and the plume settlement times were compared. Devices were then placed in liquid to observed consistency in the fluid disruption. Two types of plume emission were identified generating different directions of plume: laminar flow causes minimal visual obstruction by directing the aerosol downwards, while turbulent flow directs plume erratically across the cavity. Laminar plume dissipates immediately while turbulent plume reaches a second maximum obstruction approximately 0.3 s after activation and clears after 2 s. Turbulent plume was observed with the straight blade in 10 % of activations, and from the curved blade in 47 % of activations. The straight blade emitted less obstructive plume. Turbulent flow is disruptive to laparoscopic visibility with greater field obstruction and requires longer settling than laminar plume. Ultrasonic dissectors with straight blades have more consistent oscillations and generate more laminar flow compared with curved blades. Surgeons may avoid laparoscope smearing from maximum plume generation depending on blade geometry.

  18. Physical Characteristics of Faint Meteors by Light Curve and High-resolution Observations

    NASA Astrophysics Data System (ADS)

    Subasinghe, Dilini; Campbell-Brown, Margaret D.; Stokan, Edward

    2014-11-01

    The physical structure of a meteoroid may be inferred from optical observations, particularly the light curve, of a meteor. For example: a classically shaped (late peaked) light curve is seen as evidence of a solid single body, whereas a symmetric light curve may indicate a dustball structure. High-resolution optical observations show how the meteoroid fragments: continuously, leaving a long wake, or discretely, leaving several distinct pieces. Calculating the orbit of the meteoroid using two station data then allows the object to be associated with asteroidal or cometary parent bodies. Optical observations thus provide simultaneous information on meteoroid structure, fragmentation mode, and origin.CAMO (the Canadian Automated Meteor Observatory) has been continuously collecting faint (masses < 10-4 kg) two station optical meteors with image-intensified narrow field (with a resolution of up to 3 meters per pixel) and wide field (26 by 19 degrees) cameras since 2010. The narrow field, telescopic cameras allow the meteor fragmentation to be studied using a pair of mirrors to track the meteor. The wide-field cameras provide the light curve and trajectory solution.We present preliminary results from classifying light curves and high-resolution optical observations for 3000 faint meteors recorded since 2010. We find that most meteors (both asteroidal and cometary) show long trails, while meteors with short trails are the second most common morphology. It is expected that meteoroids that experience negligible fragmentation have the shortest trails, so our results imply that the majority of small meteoroids fragment during ablation. A surprising observation is that almost equal fractions of asteroidal and cometary meteors fragment (showing long trails), implying a similar structure for both types of meteoroids.

  19. Comparison of the scoliosis curve patterns and MRI syrinx cord characteristics of idiopathic syringomyelia versus Chiari I malformation.

    PubMed

    Zhu, Zezhang; Sha, Shifu; Chu, Winnie C C; Yan, Huang; Xie, Dingding; Liu, Zhen; Sun, Xu; Zhu, Weiguo; Cheng, Jack C Y; Qiu, Yong

    2016-02-01

    Although the more readily available MR imaging has brought about more incidental findings of idiopathic syringomyelia (IS), no published study has specifically addressed the clinical and imaging features of IS-associated scoliosis. Since IS and Chiari I malformation (CMI)-type syringomyelia are hypothesized to share a common underlying developmental pathomechanism, this study aimed to investigate the scoliosis curve patterns and MRI syrinx cord characteristics of patients with IS comparing with those seen in CMI. Sixty-one patients with scoliosis secondary to IS were identified and reviewed retrospectively. The curve pattern and specific curve features were recorded and compared with historic CMI controls. Location, size, and morphological appearance of the syrinx were systematically assessed on MR images. The maximal syrinx/cord ratio and rostrocaudal length of the syrinx in IS averaged 0.43 ± 0.16 (range 0.17-0.78) and 4.6 ± 2.5 (range 2-15) vertebral levels, respectively, both of which were smaller than those reported in CMI-type syringomyelia. Regarding the characteristics of IS-related scoliosis, sagittal profiles as well as the frequency of curve patterns and atypical features were all found to resemble those in patients with CMI (P > .05). Among the 47 individuals with a single thoracic curve, Fisher exact test revealed a significant correlation between curve convexity and the dominant side of deviated syrinx (83.3 % concordance rate, P = .021). In addition, apex of the thoracic curve trended toward being significantly correlated with the level of maximum expansion of the syrinx (P = .066). Radiological characteristics of scoliosis were found to be similar between idiopathic and CMI-type syrinx in both the coronal and sagittal planes, adding further evidence to the concept that these entities may be part of a spectrum of disease sharing a common pathophysiological mechanism. The thoracic spine in IS patients tended to be convex to the deviated side of

  20. The soil water characteristic as new class of closed-form parametric expressions for the flow duration curve

    NASA Astrophysics Data System (ADS)

    Sadegh, M.; Vrugt, J. A.; Gupta, H. V.; Xu, C.

    2016-04-01

    The flow duration curve is a signature catchment characteristic that depicts graphically the relationship between the exceedance probability of streamflow and its magnitude. This curve is relatively easy to create and interpret, and is used widely for hydrologic analysis, water quality management, and the design of hydroelectric power plants (among others). Several mathematical expressions have been proposed to mimic the FDC. Yet, these efforts have not been particularly successful, in large part because available functions are not flexible enough to portray accurately the functional shape of the FDC for a large range of catchments and contrasting hydrologic behaviors. Here, we extend the work of Vrugt and Sadegh (2013) and introduce several commonly used models of the soil water characteristic as new class of closed-form parametric expressions for the flow duration curve. These soil water retention functions are relatively simple to use, contain between two to three parameters, and mimic closely the empirical FDCs of 430 catchments of the MOPEX data set. We then relate the calibrated parameter values of these models to physical and climatological characteristics of the watershed using multivariate linear regression analysis, and evaluate the regionalization potential of our proposed models against those of the literature. If quality of fit is of main importance then the 3-parameter van Genuchten model is preferred, whereas the 2-parameter lognormal, 3-parameter GEV and generalized Pareto models show greater promise for regionalization.

  1. SAR raw data compression based on geometric characteristic of Gaussian curve

    NASA Astrophysics Data System (ADS)

    Liu, Juan-ni; Zhou, Quan

    2015-07-01

    Because of simple and good performance, the block adaptive quantization (BAQ) algorithm becomes a popular method for spaceborne synthetic aperture radar (SAR) raw data compression. As the distribution of SAR data can be accurately modeled as Gaussian, the algorithm adaptively quantizes the SAR data using Llyod-Max quantizer, which is optimal for standard Gaussian signal. However, due to the complexity of the imaging target features, the probability distribution function of some SAR data deviates from the Gaussian distribution, so the BAQ compression performance declined. In view of this situation, this paper proposes a method to judge whether the data satisfies Gaussian distribution by using the geometrical relationship between standard Gaussian curve and a triangle whose area is equal to that of the Gaussian curve, then getting the coordinates of the intersection of two curves, and comparing the integral value within each node to form three judgment conditions. Finally, the data satisfying these conditions is compressed by BAQ, otherwise compressed by DPCM. Experimental results indicate that the proposed scheme improves the performance compared with BAQ method.

  2. Characteristics of learning curve in minimally invasive ileal pouch-anal anastomosis in a single institution.

    PubMed

    Rencuzogullari, Ahmet; Stocchi, Luca; Costedio, Meagan; Gorgun, Emre; Kessler, Hermann; Remzi, Feza H

    2017-03-01

    Previous work from our institution has characterized the learning curve for open ileal pouch-anal anastomosis (IPAA). The purpose of the present study was to assess the learning curve of minimally invasive IPAA. Perioperative outcomes of 372 minimally invasive IPAA by 20 surgeons (10 high-volume vs. 10 low-volume surgeons) during 2002-2013, included in a prospectively maintained database, were assessed. Predicted outcome models were constructed using perioperative variables selected by stepwise logistic regression, using Akaike's information criterion. Cumulative sums (CUSUM) of differences between observed and predicted outcomes were graphed over time to identify possible improvement patterns. Institutional pelvic sepsis and other pouch morbidity rates (hemorrhage, anastomotic separation, pouch failure, fistula) significantly decreased (18.2 vs. 7.0 %, CUSUM peak after 143 cases, p = 0.001; 18.4 vs. 5.3 %, CUSUM peak after 239 cases, respectively, p < 0.001). Institutional total proctocolectomy mean operative times significantly decreased (307 min vs. 253 min, CUSUM peak after 84 cases, p < 0.001), unlike completion proctectomy (p = 0.093) or conversion rates (10 vs. 5.4 %, p = 0.235). Similar learning curves were identified among high-volume surgeons but not among low-volume surgeons. Learning curves were identified in the two busiest individual surgeons for pelvic sepsis (peaks at 47 and 9 cases, p = 0.045 and p = 0.002) and in one surgeon for operative times (CUSUM peak after 16 and 13 cases for both total proctocolectomy and completion proctectomy (p < 0.001 and p = 0.006) but not for other pouch complications (peak at 49 and 41 cases, p = 0.199 and p = 0.094). Pouch complications, particularly pelvic sepsis, are the most consistent and relevant learning curve end points in laparoscopic IPAA.

  3. Electrospray Ionization Mass Spectrometry

    SciTech Connect

    Kelly, Ryan T.; Marginean, Ioan; Tang, Keqi

    2014-06-13

    Electrospray Ionization (ESI) is a process whereby gas phase ions are created from molecules in solution. As a solution exits a narrow tube in the presence of a strong electric field, an aerosol of charged droplets are is formed that produces gas phase ions as they it desolvates. ESI-MS comprises the creation of ions by ESI and the determination of their mass to charge ratio (m/z) by MS.

  4. Research on the Integration of Bionic Geometry Modeling and Simulation of Robot Foot Based on Characteristic Curve

    NASA Astrophysics Data System (ADS)

    He, G.; Zhu, H.; Xu, J.; Gao, K.; Zhu, D.

    2017-09-01

    The bionic research of shape is an important aspect of the research on bionic robot, and its implementation cannot be separated from the shape modeling and numerical simulation of the bionic object, which is tedious and time-consuming. In order to improve the efficiency of shape bionic design, the feet of animals living in soft soil and swamp environment are taken as bionic objects, and characteristic skeleton curve, section curve, joint rotation variable, position and other parameters are used to describe the shape and position information of bionic object’s sole, toes and flipper. The geometry modeling of the bionic object is established by using the parameterization of characteristic curves and variables. Based on this, the integration framework of parametric modeling and finite element modeling, dynamic analysis and post-processing of sinking process in soil is proposed in this paper. The examples of bionic ostrich foot and bionic duck foot are also given. The parametric modeling and integration technique can achieve rapid improved design based on bionic object, and it can also greatly improve the efficiency and quality of robot foot bionic design, and has important practical significance to improve the level of bionic design of robot foot’s shape and structure.

  5. 7 CFR 42.140 - Operating Characteristic (OC) curves for on-line sampling and inspection.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... Units Comparable sampling plans Identification number of OC curve R1 nc Ac Re R2 nc Ac Re R3 nc Ac Re R4 nc Ac Re N4 nc Ac Re N5 nc Ac Re N6 nc Ac Re N7 nc Ac Re N8 nc Ac Re Single 29 1 2 84 1 2 126 0 1 315... 36 1 2 96 1 2 180 1 2 336 1 2 540 2 3 864 3 4 nc=Cumulative sample size.Ac=Acceptance...

  6. 7 CFR 42.140 - Operating Characteristic (OC) curves for on-line sampling and inspection.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... Units Comparable sampling plans Identification number of OC curve R1 nc Ac Re R2 nc Ac Re R3 nc Ac Re R4 nc Ac Re N4 nc Ac Re N5 nc Ac Re N6 nc Ac Re N7 nc Ac Re N8 nc Ac Re Single 29 1 2 84 1 2 126 0 1 315... 36 1 2 96 1 2 180 1 2 336 1 2 540 2 3 864 3 4 nc=Cumulative sample size.Ac=Acceptance...

  7. Axial plane analysis of Lenke 1A adolescent idiopathic scoliosis as an aid to identify curve characteristics.

    PubMed

    Atmaca, Halil; Inanmaz, Mustafa Erkan; Bal, Emre; Caliskan, Islam; Kose, Kamil Cagri

    2014-10-01

    Adolescent idiopathic scoliosis (AIS) is a complex three-dimensional (3D) deformity of the spine involving deviations in the frontal plane, modifications of the sagittal profile, and rotations in the transverse plane. Although Lenke classification system is based on 2D radiographs and includes sagittal thoracic and coronal lumbar modifiers, Lenke et al. suggested inclusion of axial thoracic and lumbar modifiers in the analysis. To analyze axial plane of Lenke 1A curves to identify curve characteristics. Retrospective study. Seventy patients (49 women, 21 men) with Lenke Type 1A idiopathic scoliosis were analyzed. Coronal, sagittal, and axial parameters were measured from plain radiographs that were obtained at initial medical examination of the patients. Coronal and sagittal plane and whole spine segmental vertebra rotations from thoracic 1 to lumbar 5 were evaluated in 70 AIS patients with Lenke 1A curves by using Drerup method. Three different subgroups were identified according to magnitude and direction of lower end vertebra (LEV) rotation. In Group 1 (Lenke 1A1), the direction of LEV rotation was same with other vertebrae in the main curve and the magnitude of the LEV rotation was less than -0.5°. In Group 2 (Lenke 1A2), the rotation of LEV was between -0.5° and 0.5° and so was accepted as neutral. In Group 3 (Lenke 1A3), the rotation of LEV had opposite direction with vertebrae in the main curve and the magnitude of LEV rotation was more than 0.5°. The mean thoracic Cobb angle of patients with Lenke 1A idiopathic scoliosis was 51.1° (range 37°-80°), whereas the mean lumbar Cobb angle was 16.4° (range 0°-32°). The mean angle of trunk rotation of the patients was 5.7° (range 1°-16°). In terms of maximum thoracic vertebra rotation, the mean rotation angle of Lenke 1A idiopathic curves was -18.9° (range -(9.8°-44.7°)). The mean maximum lumbar vertebra rotation was 4.5° (range -7.2° to 15.1°). Addition of axial plane analysis to conventional

  8. Electrospraying from nanofluidic capillary slot

    NASA Astrophysics Data System (ADS)

    Arscott, Steve; Troadec, David

    2005-09-01

    We present here an original electrospray emitter tip based on a nanofluidic capillary slot. The nanofabrication involves focused ion beam etching to form the slot which has a cross-section of 50×300nm and a length of 4μm. The liquid is deformed into the nanofluidic capillary slot by capillary action; the electrospray is produced by the application of a low voltage. Using a water-methanol-formic acid solution, we have observed an electrospray onset voltage of 125V. At a measured electrospray current of 1nA, the unforced flow-rate is estimated to be 110pLmin-1.

  9. An assessment of the use of characteristic drying curves for the high-temperature drying of softwood timber

    SciTech Connect

    Langrish, T.A.G.

    1999-04-01

    An explicit assessment has been carried out, using the experimental data of Pang (1994), of the applicability of the concept of a characteristic drying curve to the drying of Pinus radiata softwood timber. This concept has been used recently by Pang and Keey (1994) and Nijdam and Keey (1996) when investigating the expected drying behavior of a complete stack of timber. The concept appears to be applicable over the range of wet-bulb depressions which are common inside the stacks of timber, supporting its use in kiln-wide analysis of frying behavior.

  10. The influence of acceleration loading curve characteristics on traumatic brain injury.

    PubMed

    Post, Andrew; Blaine Hoshizaki, T; Gilchrist, Michael D; Brien, Susan; Cusimano, Michael D; Marshall, Shawn

    2014-03-21

    To prevent brain trauma, understanding the mechanism of injury is essential. Once the mechanism of brain injury has been identified, prevention technologies could then be developed to aid in their prevention. The incidence of brain injury is linked to how the kinematics of a brain injury event affects the internal structures of the brain. As a result it is essential that an attempt be made to describe how the characteristics of the linear and rotational acceleration influence specific traumatic brain injury lesions. As a result, the purpose of this study was to examine the influence of the characteristics of linear and rotational acceleration pulses and how they account for the variance in predicting the outcome of TBI lesions, namely contusion, subdural hematoma (SDH), subarachnoid hemorrhage (SAH), and epidural hematoma (EDH) using a principal components analysis (PCA). Monorail impacts were conducted which simulated falls which caused the TBI lesions. From these reconstructions, the characteristics of the linear and rotational acceleration were determined and used for a PCA analysis. The results indicated that peak resultant acceleration variables did not account for any of the variance in predicting TBI lesions. The majority of the variance was accounted for by duration of the resultant and component linear and rotational acceleration. In addition, the components of linear and rotational acceleration characteristics on the x, y, and z axes accounted for the majority of the remainder of the variance after duration.

  11. The Soil-Water Characteristic Curve of Unsaturated Tropical Residual Soil

    NASA Astrophysics Data System (ADS)

    Yusof, M. F.; Setapa, A. S.; Tajudin, S. A. A.; Madun, A.; Abidin, M. H. Z.; Marto, A.

    2016-07-01

    This study was conducted to determine the SWCC of unsaturated tropical residual soil in Kuala Lumpur, Malaysia. Undisturbed soil samples at five locations of high-risk slopes area were taken at a depth of 0.5 m using block sampler. In the determination of the SWCC, the pressure plate extractor with the capacity of 1500 kN/m2 has been used. The index properties of the soil such as natural moisture content, Atterberg limits, specific gravity, and soil classification are performed according to BS 1377: Part 2: 1990. The results of index properties show that the natural moisture content of the soil is between 36% to 46%, the plasticity index is between 10% - 26%, the specific gravity is between 2.51 - 2.61 and the soils is classified as silty organic clay of low plasticity. The SWCC data from the pressure plate extractor have been fitted with the Fredlund and Xing equation. The results show that the air entry value and residual matric suction for residual soils are in the range of 17 kN/m2 to 24 kN/m2 and 145 kN/m2 to 225 kN/m2 respectively. From the fitting curve, it is found that the average value of the Fredlund and Xing parameters such as a, n and m are in the range of 0.24-0.299, 1.7-4.8 and 0.142-0.440 respectively.

  12. Role of curvatures in determining the characteristics of a string vibrating against a doubly curved obstacle

    NASA Astrophysics Data System (ADS)

    Singh, Harkirat; Wahi, Pankaj

    2017-08-01

    The motion of a string in the presence of a doubly curved obstacle is investigated. A mathematical model has been developed for a general shape of the obstacle. However, detailed analysis has been performed for a shape relevant to the Indian stringed musical instruments like Tanpura and Sitar. In particular, we explore the effect of obstacle's curvature in the plane perpendicular to the string axis on its motion. This geometrical feature of the obstacle introduces a coupling between motions in mutually perpendicular directions over and above the coupling due to the stretching nonlinearity. We find that only one planar motion is possible for our system. Small amplitude planar motions are stable to perturbations in the perpendicular direction resulting in non-whirling motions while large amplitude oscillations lead to whirling motions. The critical amplitude of oscillations, across which there is a transition in the qualitative behavior of the non-planar trajectories, is determined using Floquet theory. Our analysis reveals that a small obstacle curvature in a direction perpendicular to the string axis leads to a considerable reduction in the critical amplitudes required for initiation of whirling motions. Hence, this obstacle curvature has a destabilizing effect on the planar motions in contrast to the curvature along the string axis which stabilizes planar motions.

  13. A global goodness-of-fit test for receiver operating characteristic curve analysis via the bootstrap method.

    PubMed

    Zou, Kelly H; Resnic, Frederic S; Talos, Ion-Florin; Goldberg-Zimring, Daniel; Bhagwat, Jui G; Haker, Steven J; Kikinis, Ron; Jolesz, Ferenc A; Ohno-Machado, Lucila

    2005-10-01

    Medical classification accuracy studies often yield continuous data based on predictive models for treatment outcomes. A popular method for evaluating the performance of diagnostic tests is the receiver operating characteristic (ROC) curve analysis. The main objective was to develop a global statistical hypothesis test for assessing the goodness-of-fit (GOF) for parametric ROC curves via the bootstrap. A simple log (or logit) and a more flexible Box-Cox normality transformations were applied to untransformed or transformed data from two clinical studies to predict complications following percutaneous coronary interventions (PCIs) and for image-guided neurosurgical resection results predicted by tumor volume, respectively. We compared a non-parametric with a parametric binormal estimate of the underlying ROC curve. To construct such a GOF test, we used the non-parametric and parametric areas under the curve (AUCs) as the metrics, with a resulting p value reported. In the interventional cardiology example, logit and Box-Cox transformations of the predictive probabilities led to satisfactory AUCs (AUC=0.888; p=0.78, and AUC=0.888; p=0.73, respectively), while in the brain tumor resection example, log and Box-Cox transformations of the tumor size also led to satisfactory AUCs (AUC=0.898; p=0.61, and AUC=0.899; p=0.42, respectively). In contrast, significant departures from GOF were observed without applying any transformation prior to assuming a binormal model (AUC=0.766; p=0.004, and AUC=0.831; p=0.03), respectively. In both studies the p values suggested that transformations were important to consider before applying any binormal model to estimate the AUC. Our analyses also demonstrated and confirmed the predictive values of different classifiers for determining the interventional complications following PCIs and resection outcomes in image-guided neurosurgery.

  14. Electrosprayed nanoparticles for drug delivery and pharmaceutical applications

    PubMed Central

    Sridhar, Radhakrishnan; Ramakrishna, Seeram

    2013-01-01

    Nanotechnology based Pharma has emerged significantly and has influenced the Pharma industry up to a considerable extent. Nanoparticles technology holds a good share of the nanotech Pharma and is significant in comparison with the other domains. Electrospraying technology answers the potential needs of nanoparticle production such as scalability, reproducibility, effective encapsulation etc. Many drugs have been electrosprayed with and without polymer carriers. Drug release characteristics are improved with the incorporation of biodegradable polymer carriers which sustain the release of encapsulated drug. Electrospraying is acknowledged as an important technique for the preparation of nanoparticles with respect to pharmaceutical applications. Herein we attempted to consolidate the reports pertaining to electrospraying and their corresponding therapeutic application area. PMID:23512013

  15. Investigation of Liner Characteristics in the NASA Langley Curved Duct Test Rig

    NASA Technical Reports Server (NTRS)

    Gerhold, Carl H.; Brown, Martha C.; Watson, Willie R.; Jones, Michael G.

    2007-01-01

    The Curved Duct Test Rig (CDTR), which is designed to investigate propagation of sound in a duct with flow, has been developed at NASA Langley Research Center. The duct incorporates an adaptive control system to generate a tone in the duct at a specific frequency with a target Sound Pressure Level and a target mode shape. The size of the duct, the ability to isolate higher order modes, and the ability to modify the duct configuration make this rig unique among experimental duct acoustics facilities. An experiment is described in which the facility performance is evaluated by measuring the sound attenuation by a sample duct liner. The liner sample comprises one wall of the liner test section. Sound in tones from 500 to 2400 Hz, with modes that are parallel to the liner surface of order 0 to 5, and that are normal to the liner surface of order 0 to 2, can be generated incident on the liner test section. Tests are performed in which sound is generated without axial flow in the duct and with flow at a Mach number of 0.275. The attenuation of the liner is determined by comparing the sound power in a hard wall section downstream of the liner test section to the sound power in a hard wall section upstream of the liner test section. These experimentally determined attenuations are compared to numerically determined attenuations calculated by means of a finite element analysis code. The code incorporates liner impedance values educed from measured data from the NASA Langley Grazing Incidence Tube, a test rig that is used for investigating liner performance with flow and with (0,0) mode incident grazing. The analytical and experimental results compare favorably, indicating the validity of the finite element method and demonstrating that finite element prediction tools can be used together with experiment to characterize the liner attenuation.

  16. Flow visualization of time-varying structural characteristics of dean vortices in a curved channel

    NASA Astrophysics Data System (ADS)

    Bella, David Wayne

    1988-12-01

    The time varying development and structure of Dean vortices were studied using flow visualization. Observations were made over a range of Dean numbers from 40 to 200 using a transparent channel with mild curvature, 40:1 aspect ratio, and an inner to outer radius ratio of 0.979. Seven flow visualization techniques were tried but only one, a wood burning smoke generator, produced usable results. Different vortex characteristics were observed and documented in sequences of photographs spaced one quarter of a second apart at locations ranging from 85 to 135 degrees from the start of curvature. Evidence is presented that supports the twisting/rocking nature of the flow.

  17. Uniqueness Results for Ill-Posed Characteristic Problems in Curved Space-Times

    NASA Astrophysics Data System (ADS)

    Ionescu, Alexandru D.; Klainerman, Sergiu

    2009-02-01

    We prove two uniqueness theorems concerning linear wave equations; the first theorem is in Minkowski space-times, while the second is in the domain of outer communication of a Kerr black hole. Both theorems concern ill-posed Cauchy problems on bifurcate, characteristic hypersurfaces. In the case of the Kerr space-time, the hypersurface is precisely the event horizon of the black hole. The uniqueness theorem in this case, based on two Carleman estimates, is intimately connected to our strategy to prove uniqueness of the Kerr black holes among smooth, stationary solutions of the Einstein-vacuum equations, as formulated in [14].

  18. Regional Curves for Bankfull Channel Characteristics in the Appalachian Plateaus, West Virginia

    USGS Publications Warehouse

    Messinger, Terence

    2009-01-01

    Streams in the Appalachian Plateaus Physiographic Province in West Virginia were classified as a single region on the basis of bankfull characteristics. Regression lines for annual peak flow and drainage area measured at streamgages in the study area at recurrence intervals between 1.2 and 1.7 years fell within the 99-percent confidence interval of the regression line for bankfull flow. Channel characteristics were intermediate among those from surrounding states and regions where comparable studies have been done. The stream reaches that were surveyed were selected for apparent stability, and to represent gradients of drainage area, elevation, and mean annual precipitation. Profiles of high-water marks left by bankfull and near-bankfull peaks were surveyed, either as part of slope-area flow measurements at ungaged reaches, or to transfer known flow information to cross sections for gaged reaches. The slope-area measurements made it possible to include ungaged sites in the study, but still relate bankfull dimensions to peak flow and frequency.

  19. The influences of the properties of impurities and defects on the dark I-V characteristic curve and output parameters of c-Si solar cells

    NASA Astrophysics Data System (ADS)

    Lu, Xiaodong; Song, Yang; Gao, Jie; Wang, Xinxin; Zhang, Yufeng

    2017-09-01

    The influences of the coating ratio of electrode, doping concentration of substrate and type of impurities and defects on the dark I-V characteristic curves and output parameters of c-Si solar cells are studied by finite difference method and the dark I-V characteristic curves under different conditions are analyzed by their ideal factors, the results show that: the dark current values under the same bias voltage will increase with the increasing of the coating ratio of electrode or doping concentration of substrate; the influences of donor-like, acceptor-like and recombination-center-like impurities and defects on the dark I-V characteristic curves have threshold effects; the parameters of the impurities and defects smaller than their corresponding threshold will have no obvious influences on dark I-V characteristic curves; the acceptor-like impurities and defects on the surface of c-Si solar cells have no influences on their dark I-V characteristic curve, but the donor-like and recombination-center-like impurities and defects have strong influences on their dark I-V characteristic curve; the variations of the output parameters of c-Si solar cells are analyzed in detail under the different properties of the impurities and defects inside and on the surfaces of c-Si solar cells.

  20. Classification of breast mass lesions using model-based analysis of the characteristic kinetic curve derived from fuzzy c-means clustering.

    PubMed

    Chang, Yeun-Chung; Huang, Yan-Hao; Huang, Chiun-Sheng; Chang, Pei-Kang; Chen, Jeon-Hor; Chang, Ruey-Feng

    2012-04-01

    The purpose of this study is to evaluate the diagnostic efficacy of the representative characteristic kinetic curve of dynamic contrast-enhanced (DCE) magnetic resonance imaging (MRI) extracted by fuzzy c-means (FCM) clustering for the discrimination of benign and malignant breast tumors using a novel computer-aided diagnosis (CAD) system. About the research data set, DCE-MRIs of 132 solid breast masses with definite histopathologic diagnosis (63 benign and 69 malignant) were used in this study. At first, the tumor region was automatically segmented using the region growing method based on the integrated color map formed by the combination of kinetic and area under curve color map. Then, the FCM clustering was used to identify the time-signal curve with the larger initial enhancement inside the segmented region as the representative kinetic curve, and then the parameters of the Tofts pharmacokinetic model for the representative kinetic curve were compared with conventional curve analysis (maximal enhancement, time to peak, uptake rate and washout rate) for each mass. The results were analyzed with a receiver operating characteristic curve and Student's t test to evaluate the classification performance. Accuracy, sensitivity, specificity, positive predictive value and negative predictive value of the combined model-based parameters of the extracted kinetic curve from FCM clustering were 86.36% (114/132), 85.51% (59/69), 87.30% (55/63), 88.06% (59/67) and 84.62% (55/65), better than those from a conventional curve analysis. The A(Z) value was 0.9154 for Tofts model-based parametric features, better than that for conventional curve analysis (0.8673), for discriminating malignant and benign lesions. In conclusion, model-based analysis of the characteristic kinetic curve of breast mass derived from FCM clustering provides effective lesion classification. This approach has potential in the development of a CAD system for DCE breast MRI.

  1. Estimating screening-mammography receiver operating characteristic (ROC) curves from stratified random samples of screening mammograms: a simulation study.

    PubMed

    Zur, Richard M; Pesce, Lorenzo L; Jiang, Yulei

    2015-05-01

    To evaluate stratified random sampling (SRS) of screening mammograms by (1) Breast Imaging Reporting and Data System (BI-RADS) assessment categories, and (2) the presence of breast cancer in mammograms, for estimation of screening-mammography receiver operating characteristic (ROC) curves in retrospective observer studies. We compared observer study case sets constructed by (1) random sampling (RS); (2) SRS with proportional allocation (SRS-P) with BI-RADS 1 and 2 noncancer cases accounting for 90.6% of all noncancer cases; (3) SRS with disproportional allocation (SRS-D) with BI-RADS 1 and 2 noncancer cases accounting for 10%-80%; and (4) SRS-D and multiple imputation (SRS-D + MI) with missing BI-RADS 1 and 2 noncancer cases imputed to recover the 90.6% proportion. Monte Carlo simulated case sets were drawn from a large case population modeled after published Digital Mammography Imaging Screening Trial data. We compared the bias, root-mean-square error, and coverage of 95% confidence intervals of area under the ROC curve (AUC) estimates from the sampling methods (200-2000 cases, of which 25% were cancer cases) versus from the large case population. AUC estimates were unbiased from RS, SRS-P, and SRS-D + MI, but biased from SRS-D. AUC estimates from SRS-P and SRS-D + MI had 10% smaller root-mean-square error than RS. Both SRS-P and SRS-D + MI can be used to obtain unbiased and 10% more efficient estimate of screening-mammography ROC curves. Copyright © 2015 AUR. Published by Elsevier Inc. All rights reserved.

  2. Receiver-operating characteristic curves for somatic cell scores and California mastitis test in Valle del Belice dairy sheep.

    PubMed

    Riggio, Valentina; Pesce, Lorenzo L; Morreale, Salvatore; Portolano, Baldassare

    2013-06-01

    Using receiver-operating characteristic (ROC) curve methodology this study was designed to assess the diagnostic effectiveness of somatic cell count (SCC) and the California mastitis test (CMT) in Valle del Belice sheep, and to propose and evaluate threshold values for those tests that would optimally discriminate between healthy and infected udders. Milk samples (n=1357) were collected from 684 sheep in four flocks. The prevalence of infection, as determined by positive bacterial culture was 0.36, 87.7% of which were minor and 12.3% major pathogens. Of the culture negative samples, 83.7% had an SCC<500,000/mL and 97.4% had <1,000,000cells/mL. When the associations between SC score (SCS) and whole sample status (culture negative vs. infected), minor pathogen status (culture negative vs. infected with minor pathogens), major pathogen status (culture negative vs. infected with major pathogens), and CMT results were evaluated, the estimated area under the ROC curve was greater for glands infected with major compared to minor pathogens (0.88 vs. 0.73), whereas the area under the curve considering all pathogens was similar to the one for minor pathogens (0.75). The estimated optimal thresholds were 3.00 (CMT), 2.81 (SCS for the whole sample), 2.81 (SCS for minor pathogens), and 3.33 (SCS for major pathogens). These correctly classified, respectively, 69.0%, 73.5%, 72.6% and 91.0% of infected udders in the samples. The CMT appeared only to discriminate udders infected with major pathogens. In this population, SCS appeared to be the best indirect test of the bacteriological status of the udder. Copyright © 2012 Elsevier Ltd. All rights reserved.

  3. Prediction of preterm and low birth weight delivery by maternal periodontal parameters: receiver operating characteristic (ROC) curve analysis.

    PubMed

    Al Habashneh, Rola; Khader, Yousef S; Jabali, Olfat Al; Alchalabi, Haifa'a

    2013-02-01

    In this study we used receiver-operating characteristic (ROC) analysis to comparatively evaluate maternal periodontal parameters to predict preterm (PB) delivery and low birth weight (LBW) delivery among Jordanian women. A total of 277 pregnant women (20 weeks of gestation or less) had periodontal examination at baseline and followed up until delivery. Gestational age and birth weight were retrieved from their medical records. ROC curve analyses were used to examine the overall discriminatory power of the studied periodontal parameters to predict PB, LBW, and PB or LBW. For the three outcome variables, the area under curve (AUC) ranged from 0.84 to 0.87 for average clinical attachment level (CAL), 0.78-0.86 for percent of sites with CAL ≥ 5 mm, 0.63-0.74 for percent of sites with CAL ≥ 6 mm, and 0.71-0.82 for number of missing teeth indicating that they had high discriminating power to predict adverse pregnancy outcomes. All other parameters had AUC less than 0.60 and thus had low discriminating power. Average CAL performed the best in predicting the studied adverse pregnancy outcomes because it has the highest AUC. The severity and extent of periodontal disease as measured by CAL can be used to predict the occurrence of adverse pregnancy outcomes.

  4. Evaluation of volume and total nucleated cell count as cord blood selection parameters: a receiver operating characteristic curve modeling approach.

    PubMed

    Jaime-Pérez, José C; Monreal-Robles, Roberto; Rodríguez-Romo, Laura N; Mancías-Guerra, Consuelo; Herrera-Garza, José Luís; Gómez-Almaguer, David

    2011-11-01

    The objective of the study was to evaluate the current standard practice of using volume and total nucleated cell (TNC) count for the selection of cord blood (CB) units for cryopreservation and further transplantation. Data on 794 CB units whose CD34+ cell content was determined by flow cytometry were analyzed by using a receiver operating characteristic (ROC) curve model to validate the performance of volume and TNC count for the selection of CB units with grafting purposes. The TNC count was the best parameter to identify CB units having 2 × 10(6) or more CD34+ cells, with an area under the ROC curve of 0.828 (95% confidence interval, 0.800-0.856; P < .01) and an efficiency of 75.4%. Combination of parameters (TNC/mononuclear cells [MNCs], efficiency 74.7%; TNC/volume, efficiency 68.9%; and volume/MNCs, efficiency 68.3%) did not lead to improvement in CB selection. All CB units having a TNC count of 8 × 10(8) or more had the required CD34+ cell dose for patients weighing 10 kg or less.

  5. Estimation of haplotype associated with several quantitative phenotypes based on maximization of area under a receiver operating characteristic (ROC) curve.

    PubMed

    Kamitsuji, Shigeo; Kamatani, Naoyuki

    2006-01-01

    An algorithm for estimating haplotypes associated with several quantitative phenotypes is proposed. The concept of a receiver operating characteristic (ROC) curve was introduced, and a linear combination of the quantitative phenotypic values was considered. This set of values was divided into two parts: values for subjects with and without a particular haplotype. The goodness of its partition was evaluated by the area under the ROC curve (AUC). The AUC value varied from 0 to 1; this value was close to 1 when the partition had high accuracy. Therefore, the strength of association between phenotypes and haplotypes was considered to be proportional to the AUC value. In our algorithm, the parameters representing a degree of association between the haplotypes and phenotypes were estimated so as to maximize the AUC value; further, the haplotype with the maximum AUC value was considered to be the best haplotype associated with the phenotypes. This algorithm was implemented by using R language. The effectiveness of our algorithm was evaluated by applying it to real genotype data of the Calpine-10 gene obtained from diabetics. The results showed that our algorithm was more reasonable and advantageous for use with several quantitative phenotypes than the generalized linear model or the neural network model.

  6. A Statistical Comparison of the Blossom Blight Forecasts of MARYBLYT and Cougarblight with Receiver Operating Characteristic Curve Analysis.

    PubMed

    Dewdney, M M; Biggs, A R; Turechek, W W

    2007-09-01

    ABSTRACT Blossom blight forecasting is an important aspect of fire blight, caused by Erwinia amylovora, management for both apple and pear. A comparison of the forecast accuracy of two common fire blight forecasters, MARYBLYT and Cougarblight, was performed with receiver operating characteristic (ROC) curve analysis and 243 data sets. The rain threshold of Cougarblight was analyzed as a separate model termed Cougarblight and rain. Data were used as a whole and then grouped into geographic regions and cultivar susceptibilities. Frequency distributions of cases and controls, orchards or regions (depending on the data set), with and without observed disease, respectively, in all data sets overlapped. MARYBLYT, Cougarblight, and Cougarblight and rain all predicted blossom blight infection better than chance (P = 0.05). It was found that the blossom blight forecasters performed equivalently in the geographic regions of the east and west coasts of North America and moderately susceptible cultivars based on the 95% confidence intervals and pairwise contrasts of the area under the ROC curve. Significant differences (P < 0.05) between the forecasts of Cougarblight and MARYBLYT were found with pairwise contrasts in the England and very susceptible cultivar data sets. Youden's index was used to determine the optimal cutpoint of both forecasters. The greatest sensitivity and specificity for MARYBLYT coincided with the use of the highest risk threshold for predictions of infection; with Cougarblight, there was no clear single risk threshold across all data sets.

  7. Effects of bottom bracings on torsional dynamic characteristics of horizontally curved twin I-girder bridges with different curvatures

    NASA Astrophysics Data System (ADS)

    Awall, Md. Robiul; Hayashikawa, Toshiro; Matsumoto, Takashi; He, Xingwen

    2012-03-01

    Curved twin I-girder bridges (CTIGBs) have low torsional stiffness that makes them vulnerable to dynamic loads. This study investigates the effects of bottom bracings on the torsional dynamic characteristics of CTIGBs. Five types of bottom bracings are designed to investigate their effects on the dynamic characteristics of CTIGBs with different curvatures under free and forced vibrations. To perform numerical investigations, three-dimensional (3-D) finite element (FE) bridge and vehicle models are established using commercial ANSYS code, and then a vehicle-bridge interaction analysis approach is proposed. Road roughness profiles generated from power spectral density and cross spectral functions are also taken into account in the analyses. The numerical results show that torsional frequencies increase significantly after providing bottom bracings, and the increasing rate depends on the type of bottom bracings and their locations of installation. Bottom bracings can act as load transmitting members from one main girder to the others. Large negative bearing forces that have occurred in bridges with small radii of curvatures can be remarkably reduced by providing bottom bracing systems. It is found that the performances of several bottom bracing systems are effective in improving the torsional dynamic characteristics of the bridges in this study.

  8. Peak flow rate and recession-curve characteristics of a karst spring in the Inner Bluegrass, central Kentucky

    USGS Publications Warehouse

    Felton, G.K.; Currens, J.C.

    1994-01-01

    The flow rate at the terminal spring of a 1929 ha karst ground-water catchment has been continuously monitored for 2 years, and 108 identifiable events were analyzed. The peak flow rates followed a beta frequency distribution with parameters ?? = 0.365 and ?? = 1.135. Events were separated into high-flow and low-flow. High-flow events had characteristics attributable to pipe flow. Correlation and stepwise regression were used to develop peak flow rate prediction equations for the combined 108 events and for the 81 low-flow events. The portion of the recession curve identified as pipe flow was a watershed constant and time invariant. The base flow was seasonal, increasing in the winter to approximately 0.071 m3s-1 and decreasing in the summer to approximately 0.014 m3s-1. ?? 1994.

  9. Characteristics of shut-in curves in hydraulic fracturing stress measurements and determination of in situ minimum compressive stress

    NASA Astrophysics Data System (ADS)

    Hayashi, Kazuo; Haimson, Bezalel C.

    1991-10-01

    Characteristics of pressure decay curves obtained after shut-in in hydraulic fracturing stress measurements are studied in detail in an effort to enhance the reliability of the minimum compressive in situ stress determination. The analysis utilizes linear theory of elasticity, fracture mechanics, and global mass balance of fracturing fluid after shut-in. A small amount of crack growth takes place almost instantaneously just after shut-in due to equilibration of injected-fluid pressure within the fracture. Thereafter, the fracture gradually closes commensurate with the amount of fluid leakage into the rock and the net compliance of the pressured system consisting of the rock, the fracture, and the tubing conveying pressurized fluid from the surface to the depth of testing. Theoretical considerations and laboratory and field data suggest the closure process after shut-in can be considered to consist of three major stages: from cessation of fracture growth until fracture tip closure (stage I), from just after fracture tip closure until complete fracture closure (stage II), and from just after complete fracture closure until the test is stopped (stage III). An analysis of these stages reveals that the inverse of the pressure decrease rate is linear with respect to the fluid pressure in stages I and III. It is also shown that the far-field minimum compressive stress can be determined on the basis of these characteristics. The method of determination of the in situ minimum compressive stress is successfully applied to a sampling of shut-in curves obtained in laboratory and field experiments.

  10. Characteristics of the pelvic axial rotation in adolescent idiopathic scoliosis: a comparison between major thoracic curve and major thoracolumbar/lumbar curve.

    PubMed

    Wang, Zhi-Wei; Wang, Wei-Jun; Sun, Ming-Hui; Liu, Zhen; Zhu, Ze-Zhang; Zhu, Feng; Qiu, Xu-Sheng; Qian, Bang-Ping; Wang, Shou-Feng; Qiu, Yong

    2014-09-01

    As the biomechanical foundation of the spine, the pelvis was found to display rotation in the transverse plane in adolescent idiopathic scoliosis (AIS). However, the possible factors influencing the pelvic axial rotation (PAR) and its mechanism in patients with AIS remain unclear. To characterize the PAR in AIS patients with right major thoracic (MT) or major left thoracolumbar/lumbar (TL/L) curve and to explore the associated influencing factors and probable mechanism of compensation by analyzing the association between PAR and other spinal radiographic parameters. Retrospective study. All patients with the primary diagnosis of AIS from January 2008 to November 2009 were retrieved from our scoliosis database. Age, Cobb angle, and apex rotation of the main curve and the compensatory curve, curve flexibility, and PAR. One-hundred thirty-two patients with right MT (14.7±1.8 years, 48±6.9°) and 83 patients with left major TL/L (14.7±1.5 years, 46±6.6°) were retrospectively reviewed. On standing full-spine posteroanterior radiographs, the PAR was quantified by the left/right hemi-pelvis width ratio (L/R ratio); then the subjects in both MT and major TL/L groups were divided into two subgroups: L/R ratio ≤1 (pelvis rotated to the right, R-PAR group); and L/R ratio >1 (pelvis rotated to the left, L-PAR group). Comparisons of all variables were performed between the L- and R-PAR subgroups; correlation and regression analysis were carried out to identify the influencing factors of PAR. The majority of the MT and major TL/L patients (75.8% vs. 60.2%) displayed right pelvic rotation, which was in the same direction as the thoracic curve. The incidence of R-PAR was greater in the MT patients than the major TL/L ones (p=.016). Lumbar flexibility in MT patients with R-PAR was greater than in MT patients with L-PAR (0.96±0.27 vs. 0.81±0.33, p=.038), which was contrary to the findings in the major TL/L patients (L-PAR>R-PAR, 0.79±0.15 vs. 0.70±0.22, p=.024). In the MT

  11. Receiver Operating Characteristic (ROC) Curve-based Prediction Model for Periodontal Disease Updated With the Calibrated Community Periodontal Index.

    PubMed

    Su, Chiu-Wen; Ming-Fang Yen, Amy; Lai, Hongmin; Chen, Hsiu-Hsi; Chen, Sam Li-Sheng

    2017-07-28

    Background The accuracy of a prediction model for periodontal disease using the community periodontal index (CPI) has been undertaken by using an area receiver operating characteristics (AUROC) curve, but how the uncalibrated CPI, as measured by general dentists trained by periodontists in a large epidemiological study, required for constructing a prediction model that affects its performance has not been researched yet. Methods We conducted a two-stage design by first proposing a validation study to calibrate the CPI between a senior periodontal specialist and trained general dentists who measured CPIs in the main study of a nationwide survey. A Bayesian hierarchical logistic regression model was applied to estimate the non-updated and updated clinical weights used for building up risk scores. How the calibrated CPI affected the performance of the updated prediction model was quantified by comparing the AUROC curves between the original and the updated model. Results The estimates regarding the calibration of CPI obtained from the validation study were 66% and 85% for sensitivity and specificity, respectively. After updating, the clinical weights of each predictor were inflated, and the risk score for the highest risk category was elevated from 434 to 630. Such an update improved the AUROC performance of the two corresponding prediction models from 62.6% (95% CI: 61.7%-63.6%) for the non-updated model to 68.9% (95% CI: 68.0%-69.6%) for the updated one, reaching a statistically significant difference (P < 0.05). Conclusions We demonstrated an improvement in the updated prediction model for periodontal disease as measured by the calibrated CPI derived from a large epidemiological survey.

  12. Fractal Characteristics of Soil Retention Curve and Particle Size Distribution with Different Vegetation Types in Mountain Areas of Northern China.

    PubMed

    Niu, Xiang; Gao, Peng; Wang, Bing; Liu, Yu

    2015-12-03

    Based on fractal theory, the fractal characteristics of soil particle size distribution (PSD) and soil water retention curve (WRC) under the five vegetation types were studied in the mountainous land of Northern China. Results showed that: (1) the fractal parameters of soil PSD and soil WRC varied greatly under each different vegetation type, with Quercus acutissima Carr. and Robina pseudoacacia Linn. mixed plantation (QRM) > Pinus thunbergii Parl. and Pistacia chinensis Bunge mixed plantation (PPM) > Pinus thunbergii Parl. (PTP) > Juglans rigia Linn. (JRL) > abandoned grassland (ABG); (2) the soil fractal dimensions of woodlands (QRM, PPM, PTP and JRL) were significantly higher than that in ABG, and mixed forests (QRM and PPM) were higher than that in pure forests (PTP and JRL); (3) the fractal dimension of soil was positively correlated with the silt and clay content but negatively correlated with the sand content; and (4) the fractal dimension of soil PSD was positively correlated with the soil WRC. These indicated that the fractal parameters of soil PSD and soil WRC could act as quantitative indices to reflect the physical properties of the soil, and could be used to describe the influences of the Return Farmland to Forests Projects on soil structure.

  13. Fractal Characteristics of Soil Retention Curve and Particle Size Distribution with Different Vegetation Types in Mountain Areas of Northern China

    PubMed Central

    Niu, Xiang; Gao, Peng; Wang, Bing; Liu, Yu

    2015-01-01

    Based on fractal theory, the fractal characteristics of soil particle size distribution (PSD) and soil water retention curve (WRC) under the five vegetation types were studied in the mountainous land of Northern China. Results showed that: (1) the fractal parameters of soil PSD and soil WRC varied greatly under each different vegetation type, with Quercus acutissima Carr. and Robina pseudoacacia Linn. mixed plantation (QRM) > Pinus thunbergii Parl. and Pistacia chinensis Bunge mixed plantation (PPM) > Pinus thunbergii Parl. (PTP) > Juglans rigia Linn. (JRL) > abandoned grassland (ABG); (2) the soil fractal dimensions of woodlands (QRM, PPM, PTP and JRL) were significantly higher than that in ABG, and mixed forests (QRM and PPM) were higher than that in pure forests (PTP and JRL); (3) the fractal dimension of soil was positively correlated with the silt and clay content but negatively correlated with the sand content; and (4) the fractal dimension of soil PSD was positively correlated with the soil WRC. These indicated that the fractal parameters of soil PSD and soil WRC could act as quantitative indices to reflect the physical properties of the soil, and could be used to describe the influences of the Return Farmland to Forests Projects on soil structure. PMID:26633458

  14. Evaluation of Models for Alternaria Brown Spot of Mandarin Under Mediterranean Conditions by Partial Receiver Operating Characteristic Curve Analysis.

    PubMed

    Bassimba, Daniel D M; Mira, Jose L; Vicent, Antonio

    2017-04-12

    Alternaria brown spot (ABS) is a serious fungal disease of mandarin in the Mediterranean Basin. Due to the rigorous fruit quality standards, models for ABS should avoid false negatives. Experiments were conducted with susceptible 'Fortune' and 'Nova' inoculated at different temperatures and leaf wetness durations, including interrupted periods. Effects of temperature and time elapsed after inoculation were also studied. Disease incidence data were fitted to generalized additive models and a generic infection model. Exposure of trap plants in affected orchards was used for model evaluation, including the Alter-Rater and a simple rule system (SRS). The predictive ability of the models was analyzed using the partial area under the receiver operating characteristic curve in the high-sensitivity range between 0.9 and 1. Postinoculation temperature had a significant effect on disease incidence, with maximum symptom expression after 30 h on Fortune and 60 h on Nova. ABS incidence did not increase after a leaf wetness interruption of 1 h on Nova and 2 h on Fortune. All the models evaluated had high false-positive rates on Fortune. Only the SRS showed a substantial strength of agreement in Nova, with a true-positive rate of 0.93 and false-positive rate of 0.16.

  15. 7 CFR 42.141 - Obtaining Operating Characteristic (OC) curve information for skip lot sampling and inspection.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... of 6.5. The OC curve for this sampling plan is curve N and R3. Also, assume that the quality of the lot is 6.5 defects per hundred units. From curve N and R3, then, the Pa is determined to be 95 percent. Then refer to the graph in § 42.142 and locate Pa of 95 percent along the horizontal axis. From...

  16. 7 CFR 42.141 - Obtaining Operating Characteristic (OC) curve information for skip lot sampling and inspection.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... of 6.5. The OC curve for this sampling plan is curve N and R3. Also, assume that the quality of the lot is 6.5 defects per hundred units. From curve N and R3, then, the Pa is determined to be 95 percent. Then refer to the graph in § 42.142 and locate Pa of 95 percent along the horizontal axis. From...

  17. 7 CFR 42.141 - Obtaining Operating Characteristic (OC) curve information for skip lot sampling and inspection.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... of 6.5. The OC curve for this sampling plan is curve N and R3. Also, assume that the quality of the lot is 6.5 defects per hundred units. From curve N and R3, then, the Pa is determined to be 95 percent. Then refer to the graph in § 42.142 and locate Pa of 95 percent along the horizontal axis. From...

  18. Electrospray formation of ring-shaped silica nanoparticles

    NASA Astrophysics Data System (ADS)

    Uchida, Kazuhiro; Higashi, Kazuhiko; Hishida, Koichi; Hotta, Atsushi; Miki, Norihisa

    2015-02-01

    Electrospray is one of the processes employed for the production of silica nanoparticles (NPs). We have experimentally determined that not only spherical but also ring-shaped NPs can be manufactured by electrospray, and that the shape of the NPs is dependent on ambient humidity and the substrate on which the NPs are deposited. Although the effect of humidity that reflects the evaporation characteristics of the suspension during flight has been reported, we have experimentally determined that the affinity of the sol suspension and the substrate play a crucial role in the formation of torus silica NPs.

  19. Applications of electrospinning/electrospraying in drug delivery.

    PubMed

    Jahangiri, Azin; Adibkia, Khosro

    2016-01-01

    During recent years, nanoscaled materials have gained much attention because of their applications in the field of pharmaceutical and biomedical sciences. Electrospinning/electrospraying, as simple, effective and single-step methods, are used in the preparation of nanostructured materials (nanofibers and nanobeads). They offer an opportunity for direct encapsulation of the different types of drug molecules. The generated nanomaterials possess high surface area with porous characteristics, and the liberation of the loaded drugs follows a controlled-release pattern. Because of their wide applications in medical/pharmaceutical researches, the aim of this editorial is to highlight the importance of electrospinning/electrospraying technologies in drug delivery.

  20. Applications of electrospinning/electrospraying in drug delivery

    PubMed Central

    Jahangiri, Azin; Adibkia, Khosro

    2016-01-01

    During recent years, nanoscaled materials have gained much attention because of their applications in the field of pharmaceutical and biomedical sciences. Electrospinning/electrospraying, as simple, effective and single-step methods, are used in the preparation of nanostructured materials (nanofibers and nanobeads). They offer an opportunity for direct encapsulation of the different types of drug molecules. The generated nanomaterials possess high surface area with porous characteristics, and the liberation of the loaded drugs follows a controlled-release pattern. Because of their wide applications in medical/pharmaceutical researches, the aim of this editorial is to highlight the importance of electrospinning/electrospraying technologies in drug delivery. PMID:27340617

  1. Effect of non-linearity of a predictor on the shape and magnitude of its receiver-operating-characteristic curve in predicting a binary outcome.

    PubMed

    Ho, Kwok M

    2017-08-31

    Area under a receiver-operating-characteristic (AUROC) curve is widely used in medicine to summarize the ability of a continuous predictive marker to predict a binary outcome. This study illustrated how a U-shaped or inverted U-shaped continuous predictor would affect the shape and magnitude of its AUROC curve in predicting a binary outcome by comparing the ROC curves of the worst first 24-hour arterial pH values of 9549 consecutive critically ill patients in predicting hospital mortality before and after centering the predictor by its mean or median. A simulation dataset with an inverted U-shaped predictor was used to assess how this would affect the shape and magnitude of the AUROC curve. An asymmetrical U-shaped relationship between pH and hospital mortality, resulting in an inverse-sigmoidal ROC curve, was observed. The AUROC substantially increased after centering the predictor by its mean (0.611 vs 0.722, difference = 0.111, 95% confidence interval [CI] 0.087-0.135), and was further improved after centering by its median (0.611 vs 0.745, difference = 0.133, 95%CI 0.110-0.157). A sigmoidal-shaped ROC curve was observed for an inverted U-shaped predictor. In summary, a non-linear predictor can result in a biphasic-shaped ROC curve; and centering the predictor can reduce its bias towards null predictive ability.

  2. Encapsulating darunavir nanocrystals within Eudragit L100 using coaxial electrospraying.

    PubMed

    Nguyen, Duong Nhat; Clasen, Christian; Van den Mooter, Guy

    2017-04-01

    Electrospraying is renowned for its simplicity and versatility, and which can effectively produce particles with well-controlled size, size distribution, particle shape, morphology and microstructure at the nano/microscale. In this study, coaxial electrospraying was used to investigate its feasibility for preparing nanoparticles made up of nanocrystals encapsulated within a polymer shell. Firstly, aqueous nanosuspensions of darunavir were prepared by wet media milling. Then the nanosuspension and solutions of an enteric polymer, Eudragit L100, were used as the inner/core liquid and outer/shell liquid in a coaxial electrospraying setup, respectively. As long as a sufficiently high voltage was applied, a stable Taylor cone-jet mode was obtained to produce very fine core-shell structure nanoparticles with high darunavir encapsulation efficiency of approximately 90%. The influence of the starting nanosuspension and the flow rates on the characteristics of the final electrosprayed particles was also evaluated. Using an optimized nanosuspension with reasonable size, size distribution and flow rates, the enteric coating layer reduced the percentage of DRV release in acidic medium in the in vitro dissolution test to ca. 20%. This study indicates that coaxial electrospraying is a potential and unique technique for encapsulating drug nanocrystals within a polymeric shell. Copyright © 2016 Elsevier B.V. All rights reserved.

  3. A Monte Carlo Study of the Effect of Item Characteristic Curve Estimation on the Accuracy of Three Person-Fit Statistics

    ERIC Educational Resources Information Center

    St-Onge, Christina; Valois, Pierre; Abdous, Belkacem; Germain, Stephane

    2009-01-01

    To date, there have been no studies comparing parametric and nonparametric Item Characteristic Curve (ICC) estimation methods on the effectiveness of Person-Fit Statistics (PFS). The primary aim of this study was to determine if the use of ICCs estimated by nonparametric methods would increase the accuracy of item response theory-based PFS for…

  4. Effects of Average Signed Area Between Two Item Characteristic Curves and Test Purification Procedures on the DIF Detection via the Mantel-Haenszel Method

    ERIC Educational Resources Information Center

    Wang, Wen-Chung; Su, Ya-Hui

    2004-01-01

    In this study we investigated the effects of the average signed area (ASA) between the item characteristic curves of the reference and focal groups and three test purification procedures on the uniform differential item functioning (DIF) detection via the Mantel-Haenszel (M-H) method through Monte Carlo simulations. The results showed that ASA,…

  5. Practical implications of some recent studies in electrospray ionization fundamentals.

    PubMed

    Cech, N B; Enke, C G

    2001-01-01

    In accomplishing successful electrospray ionization analyses, it is imperative to have an understanding of the effects of variables such as analyte structure, instrumental parameters, and solution composition. Here, we review some fundamental studies of the ESI process that are relevant to these issues. We discuss how analyte chargeability and surface activity are related to ESI response, and how accessible parameters such as nonpolar surface area and reversed phase HPLC retention time can be used to predict relative ESI response. Also presented is a description of how derivitizing agents can be used to maximize or enable ESI response by improving the chargeability or hydrophobicity of ESI analytes. Limiting factors in the ESI calibration curve are discussed. At high concentrations, these factors include droplet surface area and excess charge concentration, whereas at low concentrations ion transmission becomes an issue, and chemical interference can also be limiting. Stable and reproducible non-pneumatic ESI operation depends on the ability to balance a number of parameters, including applied voltage and solution surface tension, flow rate, and conductivity. We discuss how changing these parameters can shift the mode of ESI operation from stable to unstable, and how current-voltage curves can be used to characterize the mode of ESI operation. Finally, the characteristics of the ideal ESI solvent, including surface tension and conductivity requirements, are discussed. Analysis in the positive ion mode can be accomplished with acidified methanol/water solutions, but negative ion mode analysis necessitates special constituents that suppress corona discharge and facilitate the production of stable negative ions.

  6. Force-time curve characteristics and hormonal alterations during an eleven-week training period in elite women weightlifters.

    PubMed

    Haff, G Gregory; Jackson, Janna R; Kawamori, Naoki; Carlock, Jon M; Hartman, Michael J; Kilgore, J Lon; Morris, Robert T; Ramsey, Michael W; Sands, William A; Stone, Michael H

    2008-03-01

    The purpose of this investigation was to study the effects of an 11-week training period performed by female weightlifters. Two weeks before this investigation, baseline measures for total testosterone, cortisol, and testosterone:cortisol ratio were collected. The 11-week training program consisted of the core exercises (i.e., clean, clean and jerk, and snatch) and other supplemental exercises (i.e., clean pull, snatch pull, squat, and front squat). Hormonal, isometric, and dynamic middle thigh pull force-time curve characteristics were assessed biweekly throughout the duration of the investigation, whereas volume load and training intensity were assessed weekly throughout the investigation. The testosterone:cortisol ratio of the baseline (1.19 +/- 0.64) was significantly different from the ratio of weeks 1 (0.67 +/- 0.36) and 9 (0.94 +/- 0.66). When the week-to-week values were compared, week 1 (0.67 +/- 0.36) was significantly different (P < 0.05; eta = 0.84) from week 3 (1.06 +/- 0.54). A very strong correlation (r = -0.83; r = 0.69) was found between the percentage change of the testosterone:cortisol ratio and volume load from weeks 1 to 11. Moderate to very strong correlations were noted between the percentage change in volume load and isometric peak force, peak force during the 30% isometric peak force trial, and peak force during the 100-kg trial during the 11 weeks of training. The primary finding of this study was that alterations in training volume load can result in concomitant changes in the anabolic-to-catabolic balance, as indicated by the testosterone:cortisol ratio, and the ability to generate maximal forces.

  7. Electrospray Collection of Lunar Dust

    NASA Technical Reports Server (NTRS)

    Dziekan, Michael

    2012-01-01

    A report describes ElectroSpray Ionization based Electrostatic Precipitation (ESIEP) for collecting lunar dust particles. While some HEPA filtration processes may remove a higher fraction (>99.9 percent) of the particles, the high efficiency may not be appropriate from an overall system standpoint, especially in light of the relatively large power requirement that such systems demand. The new electrospray particle capture technology is described as a variant of electrostatic precipitation that eliminates the current drawbacks of electrostatic precipitation. The new approach replaces corona prone field with a mist of highly charged micro-droplets generated by electrospray ionization (ESI) as the mechanism by which incoming particles are attracted and captured. In electrospray, a miniscule flow rate (microliters/minute) of liquid (typically water and a small amount of salt to enhance conductivity) is fed from the tip of a needle held at a high voltage potential relative to an opposite counter electrode. At sufficient field strength, a sharp liquid meniscus forms , which emits a jet of highly charged droplets that drift through the surrounding gas and are collected on the walls of a conductive tube. Particles in the gas have a high probability of contact with the droplets either by adhering to the droplets or otherwise acquiring a high level of charge, causing them to be captured on the collecting electrode as well. The spray acts as a filtration material that is continuously introduced and removed from the gas flow, and thus can never become clogged.

  8. Physical characteristics of faint meteors by light curve and high-resolution observations, and the implications for parent bodies

    NASA Astrophysics Data System (ADS)

    Subasinghe, Dilini; Campbell-Brown, Margaret D.; Stokan, Edward

    2016-04-01

    Optical observations of faint meteors (10-7 < mass < 10-4 kg) were collected by the Canadian Automated Meteor Observatory between 2010 April and 2014 May. These high-resolution (metre scale) observations were combined with two-station light-curve observations and the meteoroid orbit to classify meteors and attempt to answer questions related to meteoroid fragmentation, strength, and light-curve shape. The F parameter was used to classify the meteor light-curve shape; the observed morphology was used to classify the fragmentation mode; and the Tisserand parameter described the origin of the meteoroid. We find that most meteor light curves are symmetric (mean F parameter 0.49), show long distinct trails (continuous fragmentation), and are cometary in origin. Meteors that show no obvious fragmentation (presumably single body objects) show mostly symmetric light curves, surprisingly, and this indicates that light-curve shape is not an indication of fragility or fragmentation behaviour. Approximately 90 per cent of meteors observed with high-resolution video cameras show some form of fragmentation. Our results also show, unexpectedly, that meteors which show negligible fragmentation are more often on high-inclination orbits (i > 60°) than low-inclination ones. We also find that dynamically asteroidal meteors fragment as often as dynamically cometary meteors, which may suggest mixing in the early Solar system, or contamination between the dynamic groups.

  9. Salt Tolerance of Desorption Electrospray Ionization (DESI)

    SciTech Connect

    Jackson, Ayanna U.; Talaty, Nari; Cooks, R G; Van Berkel, Gary J

    2007-01-01

    Suppression of ion intensity in the presence of high salt matrices is common in most mass spectrometry ionization techniques. Desorption electrospray ionization (DESI) is an ionization method that exhibits salt tolerance, and this is investigated. DESI analysis was performed on three different drug mixtures in the presence of 0, 0.2, 2, 5, 10, and 20% NaCl:KCl weight by volume from seven different surfaces. At physiological concentrations individual drugs in each mixture were observed with each surface. Collision-induced dissociation (CID) was used to provide additional confirmation for select compounds. Multiple stage experiments, to MS5, were performed for select compounds. Even in the absence of added salt, the benzodiazepine containing mixture yielded sodium and potassium adducts of carbamazepine which masked the ions of interest. These adducts were eliminated by adding 0.1% 7M ammonium acetate to the standard methanol:water (1:1) spray solvent. Comparison of the salt tolerance of DESI with that of electrospray ionization (ESI) demonstrated much better signal/noise characteristics for DESI in this study. The salt tolerance of DESI was also studied by performing limit of detection and dynamic range experiments. Even at a salt concentration significantly above physiological concentrations, select surfaces were effective in providing spectra that allowed the ready identification of the compounds of interest. The already high salt tolerance of DESI can be optimized further by appropriate choices of surface and spray solution.

  10. Radial arrays of nano-electrospray ionization emitters and methods of forming electrosprays

    DOEpatents

    Kelly, Ryan T [West Richland, WA; Tang, Keqi [Richland, WA; Smith, Richard D [Richland, WA

    2010-10-19

    Electrospray ionization emitter arrays, as well as methods for forming electrosprays, are described. The arrays are characterized by a radial configuration of three or more nano-electrospray ionization emitters without an extractor electrode. The methods are characterized by distributing fluid flow of the liquid sample among three or more nano-electrospray ionization emitters, forming an electrospray at outlets of the emitters without utilizing an extractor electrode, and directing the electrosprays into an entrance to a mass spectrometry device. Each of the nano-electrospray ionization emitters can have a discrete channel for fluid flow. The nano-electrospray ionization emitters are circularly arranged such that each is shielded substantially equally from an electrospray-inducing electric field.

  11. Estimated bankfull discharge for selected Michigan rivers and regional hydraulic geometry curves for estimating bankfull characteristics in southern Michigan rivers

    USGS Publications Warehouse

    Rachol, Cynthia M.; Boley-Morse, Kristine

    2009-01-01

    Regional hydraulic geometry curves are power-function equations that relate riffle dimensions and bankfull discharge to drainage-basin size. They are defined by data collected through surveys conducted at stable stream reaches and can be used to aid watershed managers, design engineers, and others involved in determination of the best course of action for an unstable stream. Hydraulic geometry curves provide a mechanism through which comparisons can be made between riffle dimensions collected at an unstable stream to those collected at stable streams within the same region. In 2005, a study was initiated to delineate regional hydraulic geometry curves for Michigan. After in-office review of 343 U.S. Geological Survey streamgaging stations and an extensive field reconnaissance effort, 44 stable reaches were selected for this study. Detailed surveys that included cross-sectional and longitudinal profiles and pebble counts were conducted at selected streamgages, which were distributed throughout Michigan. By use of survey data from riffle cross sections and water-surface slope, bankfull discharge was estimated and compared to flood-recurrence intervals using regional flood equations. This comparison shows that bankfull discharges in Michigan recur more frequently than every 2 years. Regional hydraulic geometry curves were developed rather than statewide curves owing to large differences in factors that control channel geometry across the State. However, after the data were subdivided according to ecoregions, it was determined that there were enough data to delineate regional hydraulic geometry curves only for the Southern Lower Michigan Ecoregion. For this ecoregion, geometry curve equations and their coefficients of determination are: Width = 8.19 x DA0.44; R2 = 0.69, Depth = 0.67 x DA0.27; R2 = 0.28, Area = 4.38 x DA0.74; R2 = 0.59, where DA is the drainage area and R2 is the coefficient of determination. By use of discharge estimates for the Southern Lower Michigan

  12. Digital electrospray for controlled deposition.

    PubMed

    Deng, Weiwei; Waits, C Mike; Gomez, Alessandro

    2010-03-01

    Many novel functional structures are now fabricated by controlled deposition as a maskless, bottom-up fabrication technique. These applications require rapid and precise deposition of minute amounts of solutions/suspensions or their ultimate particle products in predefined patterns. The electrospray is a promising alternative to the commonly used inkjet printing because it can easily handle highly viscous liquid, avoid high shear rates, and has low risk of clogging. We demonstrate a proof-of-concept digital electrospray. This system consists of a 61-nozzle array microfabricated in silicon and a 61-element digital extractor fabricated using flexible polyimide substrates. "Digital" refers to the state of each electrospray source that can be tuned either on or off independently and responsively. We showed a resolution of 675 mum and a response frequency up to 100 Hz. With similar design and industry standard fabrication procedures, it is feasible to scale up the system to O(1000) sources with spatial resolution better than 250 mum and a O(kHz) response frequency. The latter is controlled by the viscous damping time.

  13. Correlation of free-response and receiver-operating-characteristic area-under-the-curve estimates: Results from independently conducted FROC/ROC studies in mammography

    PubMed Central

    Zanca, Federica; Hillis, Stephen L.; Claus, Filip; Van Ongeval, Chantal; Celis, Valerie; Provoost, Veerle; Yoon, Hong-Jun; Bosmans, Hilde

    2012-01-01

    Purpose: From independently conducted free-response receiver operating characteristic (FROC) and receiver operating characteristic (ROC) experiments, to study fixed-reader associations between three estimators: the area under the alternative FROC (AFROC) curve computed from FROC data, the area under the ROC curve computed from FROC highest rating data, and the area under the ROC curve computed from confidence-of-disease ratings. Methods: Two hundred mammograms, 100 of which were abnormal, were processed by two image-processing algorithms and interpreted by four radiologists under the FROC paradigm. From the FROC data, inferred-ROC data were derived, using the highest rating assumption. Eighteen months afterwards, the images were interpreted by the same radiologists under the conventional ROC paradigm; conventional-ROC data (in contrast to inferred-ROC data) were obtained. FROC and ROC (inferred, conventional) data were analyzed using the nonparametric area-under-the-curve (AUC), (AFROC and ROC curve, respectively). Pearson correlation was used to quantify the degree of association between the modality-specific AUC indices and standard errors were computed using the bootstrap-after-bootstrap method. The magnitude of the correlations was assessed by comparison with computed Obuchowski-Rockette fixed reader correlations. Results: Average Pearson correlations (with 95% confidence intervals in square brackets) were: Corr(FROC, inferred ROC) = 0.76[0.64, 0.84] > Corr(inferred ROC, conventional ROC) = 0.40[0.18, 0.58] > Corr (FROC, conventional ROC) = 0.32[0.16, 0.46]. Conclusions: Correlation between FROC and inferred-ROC data AUC estimates was high. Correlation between inferred- and conventional-ROC AUC was similar to the correlation between two modalities for a single reader using one estimation method, suggesting that the highest rating assumption might be questionable. PMID:23039631

  14. Correlation of free-response and receiver-operating-characteristic area-under-the-curve estimates: Results from independently conducted FROC/ROC studies in mammography

    SciTech Connect

    Zanca, Federica; Hillis, Stephen L.; Claus, Filip; Van Ongeval, Chantal; Celis, Valerie; Provoost, Veerle; Yoon, Hong-Jun; Bosmans, Hilde

    2012-10-15

    Purpose: From independently conducted free-response receiver operating characteristic (FROC) and receiver operating characteristic (ROC) experiments, to study fixed-reader associations between three estimators: the area under the alternative FROC (AFROC) curve computed from FROC data, the area under the ROC curve computed from FROC highest rating data, and the area under the ROC curve computed from confidence-of-disease ratings. Methods: Two hundred mammograms, 100 of which were abnormal, were processed by two image-processing algorithms and interpreted by four radiologists under the FROC paradigm. From the FROC data, inferred-ROC data were derived, using the highest rating assumption. Eighteen months afterwards, the images were interpreted by the same radiologists under the conventional ROC paradigm; conventional-ROC data (in contrast to inferred-ROC data) were obtained. FROC and ROC (inferred, conventional) data were analyzed using the nonparametric area-under-the-curve (AUC), (AFROC and ROC curve, respectively). Pearson correlation was used to quantify the degree of association between the modality-specific AUC indices and standard errors were computed using the bootstrap-after-bootstrap method. The magnitude of the correlations was assessed by comparison with computed Obuchowski-Rockette fixed reader correlations. Results: Average Pearson correlations (with 95% confidence intervals in square brackets) were: Corr(FROC, inferred ROC) = 0.76[0.64, 0.84] > Corr(inferred ROC, conventional ROC) = 0.40[0.18, 0.58] > Corr (FROC, conventional ROC) = 0.32[0.16, 0.46]. Conclusions: Correlation between FROC and inferred-ROC data AUC estimates was high. Correlation between inferred- and conventional-ROC AUC was similar to the correlation between two modalities for a single reader using one estimation method, suggesting that the highest rating assumption might be questionable.

  15. Development of Web-based Load Duration Curve system for analysis of total maximum daily load and water quality characteristics in a waterbody.

    PubMed

    Kim, Jonggun; Engel, Bernard A; Park, Youn Shik; Theller, Larry; Chaubey, Indrajeet; Kong, Dong Soo; Lim, Kyoung Jae

    2012-04-30

    In many states of the US, the total maximum daily load program has been widely developed for watershed water quality restoration and management. However, the total maximum daily load is often represented as an average daily pollutant load based on average long-term flow conditions, and as such, it does not adequately describe the problems they aim to address. Without an adequate characterization of water quality problems, appropriate solutions cannot be identified and implemented. The total maximum daily load approach should consider adequate water quality characterizations based on overall flow conditions rather than on a single flow event such as average daily flow. The Load Duration Curve, which provides opportunities for enhanced pollutant source and best management practice targeting both in the total maximum daily load development and in water quality restoration efforts, has been used for the determination of appropriate total maximum daily load targets. However, at least 30 min to an hour is needed for unskilled people based on our experiences to generate the Load Duration Curve using a desktop-based spreadsheet computer program. Therefore, in this study, the Web-based Load Duration Curve system (https://engineering.purdue.edu/∼ldc/) was developed and applied to a study watershed for an analysis of the total maximum daily load and water quality characteristics in the watershed. This system provides diverse options for Flow Duration Curve and Load Duration Curve analysis of a watershed of interest in a brief time. The Web-based Load Duration Curve system is useful for characterizing the problem according to flow regimes, and for providing a visual representation that enables an easy understanding of the problem and the total maximum daily load targets. In addition, this system will be able to help researchers identify appropriate best management practices within watersheds.

  16. Heat transfer and pressure drop characteristics of the tube bank fin heat exchanger with fin punched with flow redistributors and curved triangular vortex generators

    NASA Astrophysics Data System (ADS)

    Liu, Song; Jin, Hua; Song, KeWei; Wang, LiangChen; Wu, Xiang; Wang, LiangBi

    2017-10-01

    The heat transfer performance of the tube bank fin heat exchanger is limited by the air-side thermal resistance. Thus, enhancing the air-side heat transfer is an effective method to improve the performance of the heat exchanger. A new fin pattern with flow redistributors and curved triangular vortex generators is experimentally studied in this paper. The effects of the flow redistributors located in front of the tube stagnation point and the curved vortex generators located around the tube on the characteristics of heat transfer and pressure drop are discussed in detail. A performance comparison is also carried out between the fins with and without flow redistributors. The experimental results show that the flow redistributors stamped out from the fin in front of the tube stagnation points can decrease the friction factor at the cost of decreasing the heat transfer performance. Whether the combination of the flow redistributors and the curved vortex generators will present a better heat transfer performance depends on the size of the curved vortex generators. As for the studied two sizes of vortex generators, the heat transfer performance is promoted by the flow redistributors for the fin with larger size of vortex generators and the performance is suppressed by the flow redistributors for the fin with smaller vortex generators.

  17. Heat transfer and pressure drop characteristics of the tube bank fin heat exchanger with fin punched with flow redistributors and curved triangular vortex generators

    NASA Astrophysics Data System (ADS)

    Liu, Song; Jin, Hua; Song, KeWei; Wang, LiangChen; Wu, Xiang; Wang, LiangBi

    2017-04-01

    The heat transfer performance of the tube bank fin heat exchanger is limited by the air-side thermal resistance. Thus, enhancing the air-side heat transfer is an effective method to improve the performance of the heat exchanger. A new fin pattern with flow redistributors and curved triangular vortex generators is experimentally studied in this paper. The effects of the flow redistributors located in front of the tube stagnation point and the curved vortex generators located around the tube on the characteristics of heat transfer and pressure drop are discussed in detail. A performance comparison is also carried out between the fins with and without flow redistributors. The experimental results show that the flow redistributors stamped out from the fin in front of the tube stagnation points can decrease the friction factor at the cost of decreasing the heat transfer performance. Whether the combination of the flow redistributors and the curved vortex generators will present a better heat transfer performance depends on the size of the curved vortex generators. As for the studied two sizes of vortex generators, the heat transfer performance is promoted by the flow redistributors for the fin with larger size of vortex generators and the performance is suppressed by the flow redistributors for the fin with smaller vortex generators.

  18. Analytical performance characteristics of nanoelectrospray emitters as a function of conductive coating.

    PubMed

    Smith, Douglas R; Moy, Marie A; Dolan, Anthony R; Wood, Troy D

    2006-04-01

    As miniaturization of electrospray continues to become more prevalent in the mass spectrometry arsenal, numerous types of conductive coatings have been developed with miniaturized electrospray emitters. Different conductive coatings have different properties that may lead to differences in analytical performance. This paper investigates and compares the analytical properties of a series of applied conductive coatings for low-flow electrospray ionization developed in this laboratory vs. commercially-available types. Evaporated graphite is thoroughly compared with commercially available polyaniline (PANI) coated emitters and metal coated emitters. Each set of emitters was investigated to determine various performance characteristics, including susceptibility to electrical discharge in both positive and negative ionization modes, as well as emitter reproducibility and generation of a standard curve to determine each emitter coating's limit of detection and limit of quantitation. Furthermore, evaporated graphite and polyaniline coated fused silica capillaries were investigated to determine which coating is more stable over long-term analyses and during electrical discharge.

  19. Investigation of the ionisation density dependence of the glow curve characteristics of LIF:MG,TI (TLD-100)

    PubMed Central

    Horowitz, Y. S.; Horowitz, A.; Oster, L.; Marino, S.; Datz, H.; Margaliot, M.

    2008-01-01

    The dependence of the shape of the glow curve of LiF:Mg,Ti (TLD-100) on ionisation density was investigated using irradiation with 90Sr/90Y beta rays, 60 and 250 kVp X rays, various heavy-charged particles and 0.2 and 14 MeV neutrons. Special attention is focused on the properties of high-temperature thermoluminescence; specifically, the behaviour of the high-temperature ratio (HTR) of Peaks 7 and 8 as a function of batch and annealing protocol. The correlation of Peaks 7 and 8 with average linear-energy-transfer (LET) is also investigated. The HTR of Peak 7 is found to be independent of LET for values of LET approximately >30 keV µm−1. The behaviour of the HTR of Peak 8 with LET is observed to be erratic, which suggests that applications using the HTR should separate the contributions of Peaks 7 and 8 using computerised glow curve deconvolution. The behaviour of the HTR following neutron irradiation is complex and not fully understood. The shape of composite Peak 5 is observed to be broader following high ionisation alpha particle irradiation, suggesting that the combined use of the HTR and the shape of Peak 5 could lead to improved ionisation density discrimination for particles of high LET. PMID:18667402

  20. Evaluation of hemoglobin performance in the assessment of iron stores in feto-maternal pairs in a high-risk population: receiver operating characteristic curve analysis

    PubMed Central

    Jaime-Pérez, José Carlos; García-Arellano, Gisela; Méndez-Ramírez, Nereida; González-Llano, Óscar; Gómez-Almaguer, David

    2015-01-01

    Objective By applying receiver operating characteristic curve analysis, the objective of this study was to see whether hemoglobin levels reflect body iron stores in a group of pregnant women at term who, by using serum ferritin as the reference test, had a high pre-test probability of having iron deficiency anemia. Likewise, we evaluated the ability of hemoglobin and maternal serum ferritin levels to predict iron deficiency anemia in newborns. Methods Hemoglobin and serum ferritin were measured in 187 pregnant women at term belonging to a group with a high pre-test probability of iron deficiency anemia and their newborns. Women with Hb <11.0 g/dL and newborns with cord Hb <13.0 g/dL were classified as anemic. A serum ferritin <12.0 μg/L in women and a cord blood serum ferritin <35.0 μg/L were considered to reflect empty iron stores. Receiver operating characteristic curve analysis was applied to select the cut-off points that better reflected iron stores. Results The Hb cut-off point selected by receiver operating characteristic curve analysis in women was <11.5 g/dL (sensitivity: 60.82, specificity: 53.33%, Youden Index: 0.450). Most of the newborns had normal Hb which precluded this analysis. Maternal Hb <11.0 g/dL was the cut-off point that best reflected iron deficiency anemia in newborns (sensitivity: 55.88%, specificity: 57.24%, Youden Index: 0.217). The best cut-off point of maternal serum ferritin to reflect empty iron stores in newborns was <6.0 μg/L (sensitivity: 76.47%, specificity: 31.58%, Youden Index: 0.200). Conclusion Hemoglobin concentration performed poorly to detect iron deficiency anemia in women at term with high risk for iron deficiency and their newborns. PMID:26041420

  1. Receiver operating characteristic (ROC) curve for classification of 18F-NaF uptake on PET/CT*

    PubMed Central

    Valadares, Agnes Araujo; Duarte, Paulo Schiavom; Carvalho, Giovanna; Ono, Carla Rachel; Coura-Filho, George Barberio; Sado, Heitor Naoki; Sapienza, Marcelo Tatit; Buchpiguel, Carlos Alberto

    2016-01-01

    Objective To assess the cutoff values established by ROC curves to classify 18F-NaF uptake as normal or malignant. Materials and Methods PET/CT images were acquired 1 hour after administration of 185 MBq of 18F-NaF. Volumes of interest (VOIs) were drawn on three regions of the skeleton as follows: proximal right humerus diaphysis (HD), proximal right femoral diaphysis (FD) and first vertebral body (VB1), in a total of 254 patients, totalling 762 VOIs. The uptake in the VOIs was classified as normal or malignant on the basis of the radiopharmaceutical distribution pattern and of the CT images. A total of 675 volumes were classified as normal and 52 were classified as malignant. Thirty-five VOIs classified as indeterminate or nonmalignant lesions were excluded from analysis. The standardized uptake value (SUV) measured on the VOIs were plotted on an ROC curve for each one of the three regions. The area under the ROC (AUC) as well as the best cutoff SUVs to classify the VOIs were calculated. The best cutoff values were established as the ones with higher result of the sum of sensitivity and specificity. Results The AUCs were 0.933, 0.889 and 0.975 for UD, FD and VB1, respectively. The best SUV cutoffs were 9.0 (sensitivity: 73%; specificity: 99%), 8.4 (sensitivity: 79%; specificity: 94%) and 21.0 (sensitivity: 93%; specificity: 95%) for UD, FD and VB1, respectively. Conclusion The best cutoff value varies according to bone region of analysis and it is not possible to establish one value for the whole body. PMID:26929455

  2. Confidence Intervals for the Probability of Superiority Effect Size Measure and the Area under a Receiver Operating Characteristic Curve

    ERIC Educational Resources Information Center

    Ruscio, John; Mullen, Tara

    2012-01-01

    It is good scientific practice to the report an appropriate estimate of effect size and a confidence interval (CI) to indicate the precision with which a population effect was estimated. For comparisons of 2 independent groups, a probability-based effect size estimator (A) that is equal to the area under a receiver operating characteristic curve…

  3. Confidence Intervals for the Probability of Superiority Effect Size Measure and the Area under a Receiver Operating Characteristic Curve

    ERIC Educational Resources Information Center

    Ruscio, John; Mullen, Tara

    2012-01-01

    It is good scientific practice to the report an appropriate estimate of effect size and a confidence interval (CI) to indicate the precision with which a population effect was estimated. For comparisons of 2 independent groups, a probability-based effect size estimator (A) that is equal to the area under a receiver operating characteristic curve…

  4. Hierarchical linear modeling of California Verbal Learning Test--Children's Version learning curve characteristics following childhood traumatic head injury.

    PubMed

    Warschausky, Seth; Kay, Joshua B; Chi, PaoLin; Donders, Jacobus

    2005-03-01

    California Verbal Learning Test-Children's Version (CVLT-C) indices have been shown to be sensitive to the neurocognitive effects of traumatic brain injury (TBI). The effects of TBI on the learning process were examined with a growth curve analysis of CVLT-C raw scores across the 5 learning trials. The sample with history of TBI comprised 86 children, ages 6-16 years, at a mean of 10.0 (SD=19.5) months postinjury; 37.2% had severe injury, 27.9% moderate, and 34.9% mild. The best-fit model for verbal learning was with a quadratic function. Greater TBI severity was associated with lower rate of acquisition and more gradual deceleration in the rate of acquisition. Intelligence test index scores, previously shown to be sensitive to severity of TBI, were positively correlated with rate of acquisition. Results provide evidence that the CVLT-C learning slope is not a simple linear function and further support for specific effects of TBI on verbal learning. ((c) 2005 APA, all rights reserved).

  5. The role of stenosis ratio as a predictor of surgical satisfaction in patients with lumbar spinal canal stenosis: a receiver-operator characteristic (ROC) curve analysis.

    PubMed

    Mohammadi, Hassanreza R; Azimi, Parisa; Benzel, Edward C; Shahzadi, Sohrab; Azhari, Shirzad

    2016-09-01

    The aim of this study was to elucidate independent factors that predict surgical satisfaction in lumbar spinal canal stenosis (LSCS) patients. Patients who underwent surgery were grouped based on the age, gender, duration of symptoms, walking distance, Neurogenic Claudication Outcome Score (NCOS) and the stenosis ratio (SR) described by Lurencin. We recorded on 2-year patient satisfaction using standardized measure. The optimal cut-off points in SR, NCOS and walking distance for predicting surgical satisfaction were estimated from sensitivity and specificity calculations and receiver operator characteristic (ROC) curves. One hundred fifty consecutive patients (51 male, 99 female, mean age 62.4±10.9 years) were followed up for 34±13 months (range 24-49). One, two, three and four level stenosis was observed in 10.7%, 39.3%, 36.0 % and 14.0% of patients, respectively. Post-surgical satisfaction was 78.5% at the 2 years follow up. In ROC curve analysis, the asymptotic significance is less than 0.05 in SR and the optimal cut-off value of SR to predict worsening surgical satisfaction was measured as more than 0.52, with 85.4% sensitivity and 77.4% specificity (AUC 0.798, 95% CI 0.73-0.90; P<0.01). The present study suggests that the SR, with a cut-off set a 0.52 cross-sectional area, may be superior to walking distance and NCOS in patients with degenerative lumbar stenosis considered for surgical treatment. Using a ROC curve analysis, a radiological feature, the SR, demonstrated superiority in predicting patient satisfaction, compared to functional and clinical characteristics such as walking distance and NCOS.

  6. C-reactive protein-to-albumin ratio is a predictor of hepatitis B virus related decompensated cirrhosis: time-dependent receiver operating characteristics and decision curve analysis.

    PubMed

    Huang, Si-Si; Xie, Dong-Mei; Cai, Yi-Jing; Wu, Jian-Min; Chen, Rui-Chong; Wang, Xiao-Dong; Song, Mei; Zheng, Ming-Hua; Wang, Yu-Qun; Lin, Zhuo; Shi, Ke-Qing

    2017-04-01

    Hepatitis B virus (HBV) infection remains a major health problem and HBV-related-decompensated cirrhosis (HBV-DC) usually leads to a poor prognosis. Our aim was to determine the utility of inflammatory biomarkers in predicting mortality of HBV-DC. A total of 329 HBV-DC patients were enrolled. Survival estimates for the entire study population were generated using the Kaplan-Meier method. The prognostic values for model for end-stage liver disease (MELD) score, Child-Pugh score, and inflammatory biomarkers neutrophil/lymphocyte ratio, C-reactive protein-to-albumin ratio (CAR), and lymphocyte-to-monocyte ratio (LMR) for HBV-DC were compared using time-dependent receiver operating characteristic curves and time-dependent decision curves. The survival time was 23.1±15.8 months. Multivariate analysis identified age, CAR, LMR, and platelet count as prognostic independent risk factors. Kaplan-Meier analysis indicated that CAR of at least 1.0 (hazard ratio, 7.19; 95% confidence interval, 4.69-11.03), and LMR less than 1.9 (hazard ratio, 2.40; 95% confidence interval, 1.69-3.41) were independently associated with mortality of HBV-DC. The time-dependent receiver operating characteristic indicated that CAR showed the best performance in predicting mortality of HBV-DC compared with LMR, MELD score, and Child-Pugh score. The results were also confirmed by time-dependent decision curves. CAR and LMR were associated with the prognosis of HBV-DC. CAR was superior to LMR, MELD score, and Child-Pugh score in HBV-DC mortality prediction.

  7. Analysis of DSC thermal curves for assigning a characteristic glass transition temperature, dependent on either the type or thermal history of the polymer

    SciTech Connect

    Saffell, J.R.

    1994-09-01

    DSC was used to study the thermal curve characteristics of four classical polymer glasses: polycarbonate (PC), anionic polystyrene (aPS), polysulfone, and polymethyl methacrylate (PMMA). The onset, peak, and fictive temperatures as well as endotherm characteristics were studied over two decades of heating and cooling rates. Assuming that the fictive temperature is independent of heating rate, the usefulness of T{sub onset} and ambiguity of T{sub peak} are demonstrated. The useful [heat/cool] ratio allows use of T{sub onset} to calculate the effective cooling rate of the sample (which is easier to calculate than T{sub fictive}). Comparison with results from annealed samples are shown. The fictive and onset temperatures can be used together to improve the reliability of glass temperature characterization and results are surprisingly constant between the four different types of glasses, leading to a method of providing a single temperature to characterize the thermal history/morphology using a DSC thermal curve. The peak temperature is nearly independent of thermal history, and so provides a characterization parameter that is insensitive to manufacturing and molding procedures.

  8. Detectability of planetary characteristics in disk-averaged spectra II: synthetic spectra and light-curves of earth.

    PubMed

    Tinetti, Giovanna; Meadows, Victoria S; Crisp, David; Kiang, Nancy Y; Kahn, Brian H; Bosc, Emmanuel; Fishbein, Evan; Velusamy, Thangasamy; Turnbull, Margaret

    2006-12-01

    Spatially and spectrally resolved models were used to explore the observational sensitivity to changes in atmospheric and surface properties and the detectability of surface biosignatures in the globally averaged spectra and light-curves of the Earth. Compared with previous efforts to characterize the Earth using disk-averaged models, a more comprehensive and realistic treatment of the surface and atmosphere was taken into account here. Our results are presented as a function of viewing geometry and phases at both visible/near-infrared (0.5-1.7 microm) and mid-infrared (5-25 microm) wavelength ranges, applicable to the proposed NASA-Terrestrial Planet Finder visible coronagraph and mid-infrared interferometer and to the ESADarwin mission architectures. Clouds can change the thermal emission by as much as 50% compared with the cloud-free case and increase the visible albedo by up to 500% for completely overcast cases at the dichotomy phase. Depending on the observed phase and their distribution and type, clouds can also significantly alter the spectral shape. Moreover, clouds impact the detectability of surface biosignatures in the visible wavelength range. Modeling the disk-averaged sensitivity to the "red-edge," a distinctive spectral signature of vegetation, showed that Earth's land vegetation could be seen in disk-averaged spectra, even with cloud cover, when the signal was averaged over the daily time scale. We found that vegetation is more readily discriminated from clouds at dichotomy (50% illumination) rather than at full phase. The detectability of phytoplankton was also explored, but was found to be more difficult to detect in the disk-average than land vegetation.

  9. Electrospray Droplet Impact/SIMS

    NASA Astrophysics Data System (ADS)

    Hiraoka, Kenzo

    A new type of cluster SIMS, named as electrospray droplet impact (EDI), has been developed in our laboratory. It was found that peptides deposited on the stainless steel substrate were ionized/desorbed without the accumulation of radiation products. The organic samples with film thickness thinner than 10 monolayers are desorbed/ionized with little damage underneath the surface. In general, rather strong negative ions as well as positive ions are generated. The mechanism for the ionization/desorption in EDI is much less complicated than those for MALDI and SIMS due to the fact that only very thin sample layers take part in the shock-wave excited selvedge and higher-order side reactions are largely suppressed.

  10. Electrospray Ionization on Solid Substrates

    PubMed Central

    So, Pui-Kin; Hu, Bin; Yao, Zhong-Ping

    2014-01-01

    Development of electrospray ionization on solid substrates (solid-substrate ESI) avoids the clogging problem encountered in conventional capillary-based ESI, allows more convenient sampling and permits new applications. So far, solid-substrate ESI with various materials, e.g., metals, paper, wood, fibers and biological tissue, has been developed, and applications ranging from analysis of pure compounds to complex mixtures as well as in vivo study were demonstrated. Particularly, the capability of solid-substrate ESI in direct analysis of complex samples, e.g., biological fluids and foods, has significantly facilitated mass spectrometric analysis in real-life applications and led to increasingly important roles of these techniques nowadays. In this review, various solid-substrate ESI techniques and their applications are summarized and the prospects in this field are discussed. PMID:26819900

  11. Thin-channel electrospray emitter

    DOEpatents

    Van Berkel, Gary J.

    2004-08-31

    An electrospray device includes a high voltage electrode chamber. The high voltage electrode chamber includes an inlet for receiving a fluid to be ionized and for directing the fluid into the chamber and at least one electrode having an exposed surface within the chamber. A flow channel directs fluid over a surface of the electrode and out of the chamber. The length of the flow channel over the electrode is greater than the height of the flow channel over the electrode, thereby producing enhanced mass transport to the working electrode resulting in improved electrolysis efficiency. An outlet is provided for transmitting the fluid out from the electrode chamber. A method of creating charged droplets includes flowing a fluid over an electrode where the length over the electrode is greater than the height of the fluid flowing over the electrode.

  12. Consequences of dietary energy source and energy level on energy balance, lactogenic hormones, and lactation curve characteristics of cows after a short or omitted dry period.

    PubMed

    van Hoeij, R J; Dijkstra, J; Bruckmaier, R M; Gross, J J; Lam, T J G M; Remmelink, G J; Kemp, B; van Knegsel, A T M

    2017-10-01

    Omitting the dry period (DP) generally reduces milk production in the subsequent lactation. The aim of this study was to evaluate the effect of dietary energy source-glucogenic (G) or lipogenic (L)-and energy level-standard (std) or low-on milk production; energy balance (EB); lactogenic hormones insulin, insulin-like growth factor 1 (IGF-1), and growth hormone (GH); and lactation curve characteristics between wk 1 and 44 postpartum in cows after a 0-d or 30-d DP. Cows (n = 110) were assigned randomly to 3 transition treatments: a 30-d DP with a standard energy level required for expected milk yield [30-d DP(std)], a 0-d DP with the same energy level as cows with a 30-d DP [0-d DP(std)], and a 0-d DP with a low energy level [0-d DP(low)]. In wk 1 to 7, cows were fed the same basal ration but the level of concentrate increased to 6.7 kg/d for cows fed the low energy level and to 8.5 kg/d for cows fed the standard energy level in wk 4. From wk 8 postpartum onward, cows received a G ration (mainly consisting of corn silage and grass silage) or an L ration (mainly consisting of grass silage and sugar beet pulp) with the same energy level contrast (low or std) as in early lactation. Cows fed the G ration had greater milk, lactose, and protein yields, lower milk fat percentage, greater dry matter and energy intakes, and greater plasma IGF-1 concentration compared with cows fed the L ration. Dietary energy source did not affect EB or lactation curve characteristics. In cows with a 0-d DP, the reduced energy level decreased energy intake, EB, and weekly body weight gain, but did not affect milk production or lactation curve characteristics. A 30-d DP resulted in a greater total predicted lactation yield, initial milk yield after calving, peak milk yield, energy intake, energy output in milk, days to conception [only when compared with 0-d DP(low)], plasma GH concentration [only when compared with 0-d DP(std)], and decreased weekly body weight gain compared with a 0-d DP. A

  13. Flow-duration curves

    USGS Publications Warehouse

    Searcy, James Kincheon

    1959-01-01

    The flow-duration curve is a cumulative frequency curve that shows the percent of time specified discharges were equaled or exceeded during a given period. It combines in one curve the flow characteristics of a stream throughout the range of discharge, without regard to the sequence of occurrence. If the period upon which the curve is based represents the long-term flow of a stream, the curve may be used to predict the distribution of future flows for water- power, water-supply, and pollution studies. This report shows that differences in geology affect the low-flow ends of flow-duration curves of streams in adjacent basins. Thus, duration curves are useful in appraising the geologic characteristics of drainage basins. A method for adjusting flow-duration curves of short periods to represent long-term conditions is presented. The adjustment is made by correlating the records of a short-term station with those of a long-term station.

  14. Electrospray Ionisation Mass Spectrometry: Principles and Clinical Applications

    PubMed Central

    Ho, CS; Lam, CWK; Chan, MHM; Cheung, RCK; Law, LK; Lit, LCW; Ng, KF; Suen, MWM; Tai, HL

    2003-01-01

    This mini-review provides a general understanding of electrospray ionisation mass spectrometry (ESI-MS) which has become an increasingly important technique in the clinical laboratory for structural study or quantitative measurement of metabolites in a complex biological sample. The first part of the review explains the electrospray ionisation process, design of mass spectrometers with separation capability, characteristics of the mass spectrum, and practical considerations in quantitative analysis. The second part then focuses on some clinical applications. The capability of ESI-tandem-MS in measuring bio-molecules sharing similar molecular structures makes it particularly useful in screening for inborn errors of amino acid, fatty acid, purine, pyrimidine metabolism and diagnosis of galactosaemia and peroxisomal disorders. Electrospray ionisation is also efficient in generating cluster ions for structural elucidation of macromolecules. This has fostered a new and improved approach (vs electrophoresis) for identification and quantification of haemoglobin variants. With the understanding of glycohaemoglobin structure, an IFCC reference method for glycohaemoglobin assay has been established using ESI-MS. It represents a significant advancement for the standardisation of HbA1c in diabetic monitoring. With its other applications such as in therapeutic drug monitoring, ESI-MS will continue to exert an important influence in the future development and organisation of the clinical laboratory service. PMID:18568044

  15. Remote mass spectrometric sampling of electrospray- and desorption electrospray-generated ions using an air ejector.

    PubMed

    Dixon, R Brent; Bereman, Michael S; Muddiman, David C; Hawkridge, Adam M

    2007-10-01

    A commercial air ejector was coupled to an electrospray ionization linear ion trap mass spectrometer (LTQ) to transport remotely generated ions from both electrospray (ESI) and desorption electrospray ionization (DESI) sources. We demonstrate the remote analysis of a series of analyte ions that range from small molecules and polymers to polypeptides using the AE-LTQ interface. The details of the ESI-AE-LTQ and DESI-AE-LTQ experimental configurations are described and preliminary mass spectrometric data are presented.

  16. Using Receiver Operating Characteristic Curve to Define the Cutoff Points of Voice Handicap Index Applied to Young Adult Male Smokers.

    PubMed

    Tafiadis, Dionysios; Chronopoulos, Spyridon K; Kosma, Evangelia I; Voniati, Louiza; Raptis, Vasilis; Siafaka, Vasiliki; Ziavra, Nausica

    2017-07-11

    Voice performance is an inextricable key factor of everyday life. Obviously, the deterioration of voice quality can cause various problems to human communication and can therefore reduce the performance of social skills (relevant to voice). The deterioration could be originated from changes inside the system of the vocal tract and larynx. Various prognostic methods exist, and among them is the Voice Handicap Index (VHI). This tool includes self-reported questionnaires, used for determining the cutoff points of total score and of its three domains relevant to young male Greek smokers. The interpretation of the calculated cutoff points can serve as a strong indicator of imminent or future evaluation by a clinician. Consistent with previous calculation, the VHI can also act as a feedback for smokers' voice condition and as monitoring procedure toward smoking cessation. Specifically, the sample consisted of 130 male nondysphonic smokers (aged 18-33 years) who all participated in the VHI test procedure. The test results (through receiver operating characteristic analysis) concluded to a total cutoff point score of 19.50 (sensitivity: 0.838, 1-specificity: 0). Also, in terms of constructs, the Functional domain was equal to 7.50 (sensitivity: 0.676, 1-specificity: 0.032), the Physical domain was equal to 7.50 (sensitivity: 0.706, 1-specificity: 0.032), and the Emotional domain was equal to 6.50 (sensitivity: 0.809, 1-specificity: 0.048). Copyright © 2017 The Voice Foundation. Published by Elsevier Inc. All rights reserved.

  17. Statistical evidences of seismo-ionospheric precursors applying receiver operating characteristic (ROC) curve on the GPS total electron content in China

    NASA Astrophysics Data System (ADS)

    Chen, Yuh-Ing; Huang, Chi-Shen; Liu, Jann-Yenq

    2015-12-01

    Evidence of the seismo-ionospheric precursor (SIP) is reported by statistically investigating the relationship between the total electron content (TEC) in global ionosphere map (GIM) and 56 M ⩾ 6.0 earthquakes during 1998-2013 in China. A median-based method together with the z test is employed to examine the TEC variations 30 days before and after the earthquake. It is found that the TEC significantly decreases 0600-1000 LT 1-6 days before the earthquake, and anomalously increases in 3 time periods of 1300-1700 LT 12-15 days; 0000-0500 LT 15-17 days; and 0500-0900 LT 22-28 days before the earthquake. The receiver operating characteristic (ROC) curve is then used to evaluate the efficiency of TEC for predicting M ⩾ 6.0 earthquakes in China during a specified time period. Statistical results suggest that the SIP is the significant TEC reduction in the morning period of 0600-1000 LT. The SIP is further confirmed since the area under the ROC curve is positively associated with the earthquake magnitude.

  18. Electrospray ion source with reduced analyte electrochemistry

    DOEpatents

    Kertesz, Vilmos; Van Berkel, Gary J

    2013-07-30

    An electrospray ion (ESI) source and method capable of ionizing an analyte molecule without oxidizing or reducing the analyte of interest. The ESI source can include an emitter having a liquid conduit, a working electrode having a liquid contacting surface, a spray tip, a secondary working electrode, and a charge storage coating covering partially or fully the liquid contacting surface of the working electrode. The liquid conduit, the working electrode and the secondary working electrode can be in liquid communication. The electrospray ion source can also include a counter electrode proximate to, but separated from, said spray tip. The electrospray ion source can also include a power system for applying a voltage difference between the working electrodes and a counter-electrode. The power system can deliver pulsed voltage changes to the working electrodes during operation of said electrospray ion source to minimize the surface potential of the charge storage coating.

  19. Electrospray ion source with reduced analyte electrochemistry

    DOEpatents

    Kertesz, Vilmos [Knoxville, TN; Van Berkel, Gary [Clinton, TN

    2011-08-23

    An electrospray ion (ESI) source and method capable of ionizing an analyte molecule without oxidizing or reducing the analyte of interest. The ESI source can include an emitter having a liquid conduit, a working electrode having a liquid contacting surface, a spray tip, a secondary working electrode, and a charge storage coating covering partially or fully the liquid contacting surface of the working electrode. The liquid conduit, the working electrode and the secondary working electrode can be in liquid communication. The electrospray ion source can also include a counter electrode proximate to, but separated from, said spray tip. The electrospray ion source can also include a power system for applying a voltage difference between the working electrodes and a counter-electrode. The power system can deliver pulsed voltage changes to the working electrodes during operation of said electrospray ion source to minimize the surface potential of the charge storage coating.

  20. Building damage characteristics based on surveyed data and fragility curves of the 2011 Great East Japan tsunami

    NASA Astrophysics Data System (ADS)

    Suppasri, A.; Mas, E.; Charvet, I.; Gunasekera, R.; Imai, K.; Fukutani, Y.; Abe, Y.; Imamura, F.

    2012-12-01

    A large amount of buildings was damaged or destroyed by the 2011 Great East Japan tsunami. Numerous field surveys were conducted in order to collect the tsunami inundation and building damage data in the affected areas. Therefore, this event provides us with one of the most complete datasets amongst tsunami events in history. In this study, fragility function are derived using data provided by the Ministry of Land, Infrastructure and Transportation of Japan (MLIT), with more than 250,000 surveyed structures. The dataset have details on damage level, structural material, number of stories per building and location (town). This informtaion is crucial to the understanding of the causes of building damage, as differences in structural characteristics and building location can be taken into account in the damage probability analysis. Firstly, the results show a resistant performance of RC (reinforced concrete) and steel buildings over wood or brick buildings, which is consistent with previous studies. For example, the probability that a 2 m inundation depth damages RC, steel, brick and wood buildings as level 5 (collapsed and washed away) is approximately 0.1, 0.2, 0.25 and 0.45 respectively. While all (100%) of wood buildings and most lightweight buildings were washed away when the inundation depth was greater than 10 m, only 50% or less were washed away for steel and RC structures. Secondly, three (or more) storey buildings were much stronger than one or two storey buildings. For both RC and wood structures, there are no major differences in damage probability between one and two-storey buildings; whereas the damage probability is significantly lower for multistorey structures (3 storeys or more). Finally, the effects of coastal topography on damage probability are also discussed here. At the same tsunami inundation depth, buildings along the Sanriku ria coast suffered greater damage than buildings from the plain coast in Miyagi prefecture. For example in Ishinomaki

  1. Different spectral hounsfield unit curve and high-energy virtual monochromatic image characteristics of squamous cell carcinoma compared with nonossified thyroid cartilage.

    PubMed

    Forghani, R; Levental, M; Gupta, R; Lam, S; Dadfar, N; Curtin, H D

    2015-06-01

    The attenuation of normal nonossified thyroid cartilage can be similar to that of head and neck squamous cell carcinoma on CT. We compared dual-energy CT spectral Hounsfield unit attenuation characteristics of nonossified thyroid cartilage with that of squamous cell carcinoma to determine the optimal virtual monochromatic image reconstruction energy levels for distinguishing tumor from normal nonossified thyroid cartilage. Dual-energy CT scans from 30 patients with histopathology-proved squamous cell carcinoma at different primary sites (laryngeal and nonlaryngeal) and 10 healthy patients were evaluated. Patients were scanned with a 64-section single-source scanner with fast-kilovolt (peak) switching, and scans were reconstructed at different virtual monochromatic energy levels ranging from 40 to 140 keV. Spectral attenuation curves of tumor and nonossified thyroid cartilage were quantitatively evaluated and compared. Any part of the tumor invading the cartilage, when present, was excluded from ROI analysis to avoid cross-contamination from areas where there could be a mixture of cartilage and invading tumor. Normal nonossified thyroid cartilage had a characteristic, predictable spectral attenuation curve that was different from that of tumors. The greatest difference in attenuation of nonossified cartilage compared with tumor was on virtual monochromatic images of ≥95 keV (P < .0001), with sharp contrast between the relatively high attenuation of nonossified cartilage compared with that of tumor. Head and neck squamous cell carcinoma has significantly different attenuation on virtual monochromatic images of ≥95 keV, compared with nonossified thyroid cartilage. © 2015 by American Journal of Neuroradiology.

  2. Experimental and theoretical investigation of the rocking curves measured for MoK{sub α} X-ray characteristic lines in the double-crystal nondispersive scheme

    SciTech Connect

    Marchenkov, N. V. Chukhovskii, F. N.; Blagov, A. E.

    2015-03-15

    The rocking curves (RCs) for MoK{sub α1} and MoK{sub α2} characteristic X-ray lines have been experimentally and theoretically studied in the nondispersive scheme of an X-ray double-crystal TPC-K diffractometer. The results of measurements and theoretical calculations of double-crystal RCs for characteristic X-rays from tubes with a molybdenum anode and different widths of slits show that a decrease in the slit width leads to an increase in the relative contribution of the MoK{sub α2}-line RC in comparison with the intensity of the tails of the MoK{sub α1}-line RC. It is shown that the second peak of the MoK{sub α2} line becomes increasingly pronounced in the tail of the MoK{sub α1}-line RC with a decrease in the slit width. Two plane-parallel Si plates (input faces (110), diffraction vector h 〈220〉) were used as a monochromator crystal and a sample. The results of measuring double-crystal RCs are in good agreement with theoretical calculations.

  3. Task-based detectability comparison of exponential transformation of free-response operating characteristic (EFROC) curve and channelized Hotelling observer (CHO)

    NASA Astrophysics Data System (ADS)

    Khobragade, P.; Fan, Jiahua; Rupcich, Franco; Crotty, Dominic J.; Gilat Schmidt, Taly

    2016-03-01

    This study quantitatively evaluated the performance of the exponential transformation of the free-response operating characteristic curve (EFROC) metric, with the Channelized Hotelling Observer (CHO) as a reference. The CHO has been used for image quality assessment of reconstruction algorithms and imaging systems and often it is applied to study the signal-location-known cases. The CHO also requires a large set of images to estimate the covariance matrix. In terms of clinical applications, this assumption and requirement may be unrealistic. The newly developed location-unknown EFROC detectability metric is estimated from the confidence scores reported by a model observer. Unlike the CHO, EFROC does not require a channelization step and is a non-parametric detectability metric. There are few quantitative studies available on application of the EFROC metric, most of which are based on simulation data. This study investigated the EFROC metric using experimental CT data. A phantom with four low contrast objects: 3mm (14 HU), 5mm (7HU), 7mm (5 HU) and 10 mm (3 HU) was scanned at dose levels ranging from 25 mAs to 270 mAs and reconstructed using filtered backprojection. The area under the curve values for CHO (AUC) and EFROC (AFE) were plotted with respect to different dose levels. The number of images required to estimate the non-parametric AFE metric was calculated for varying tasks and found to be less than the number of images required for parametric CHO estimation. The AFE metric was found to be more sensitive to changes in dose than the CHO metric. This increased sensitivity and the assumption of unknown signal location may be useful for investigating and optimizing CT imaging methods. Future work is required to validate the AFE metric against human observers.

  4. Growth curves and age-related changes in carcass characteristics, organs, serum parameters, and intestinal transporter gene expression in domestic pigeon (Columba livia).

    PubMed

    Gao, C Q; Yang, J X; Chen, M X; Yan, H C; Wang, X Q

    2016-04-01

    Two experiments were conducted to fit growth curves, and determine age-related changes in carcass characteristics, organs, serum biochemical parameters, and gene expression of intestinal nutrient transporters in domestic pigeon (Columba livia). In experiment 1, body weight (BW) of 30 pigeons was respectively determined at 1, 3, 7, 14, 21, 28, and 35 days old to fit growth curves and to describe the growth of pigeons. In experiment 2, eighty-four 1-day-old squabs were grouped by weight into 7 groups. On d 1, 3, 7, 14, 21, 28, and 35, twelve birds from each group were randomly selected for slaughter and post-slaughter analysis. The results showed that BW of pigeons increased rapidly from d 1 to d 28 (a 25.7-fold increase), and then had little change until d 35. The Logistic, Gompertz, and Von Bertalanffy functions can all be well fitted with the growth curve of domestic pigeons (R2>0.90) and the Gompertz model showed the highest R2value among the models (R2=0.9997). The equation of Gompertz model was Y=507.72×e-(3.76exp(-0.17t))(Y=BW of pigeon (g); t=time (day)). In addition, breast meat yield (%) increased with age throughout the experiment, whereas the leg meat yield (%) reached to the peak on d 14. Serum total protein, albumin, globulin, and glucose concentration were increased with age, whereas serum uric acid concentration was decreased (P<0.05). Furthermore, the gene expressions of nutrient transporters (y+LAT2, LAT1, B0AT1, PepT1, and NHE2) in jejunum of pigeon were increased with age. The results of correlation analysis showed the gene expressions of B0AT1, PepT1, and NHE2 had positive correlations with BW (0.73

  5. Charge emissions from electrosprays in vacuum: Mixtures of formamide with methylammonium formate

    NASA Astrophysics Data System (ADS)

    Garoz, David; Fernández de la Mora, Juan

    2013-02-01

    The charge/mass distribution f(q/m) of nanodrops and ions electrosprayed in vacuum from mixtures of formamide (FM) and methylammonium formate (MAF) is studied by time of flight mass spectrometry at MAF/FM volumetric concentrations of 5%, 10%, 25%, and 50%. Positive and negative polarities yield comparable f(q/m) curves, though the negative mode yields ˜30% larger currents. On shifting from the highest to the lowest liquid flow rates at which a cone-jet is stable, the more conductive solutions evolve from mostly drop to primarily ion emission. A purely ionic regime is not reached under any condition, but the drops achieve unusually high q/m. As a result, these sprays have excellent electrical propulsion characteristics, some being able to cover a 25-fold range of average q/m with a polydispersive efficiency typically in the range of 80%. Results of formamide electrolytes with formates and nitrates of several other amines are more briefly reported.

  6. Highly curved microchannel plates

    NASA Technical Reports Server (NTRS)

    Siegmund, O. H. W.; Cully, S.; Warren, J.; Gaines, G. A.; Priedhorsky, W.; Bloch, J.

    1990-01-01

    Several spherically curved microchannel plate (MCP) stack configurations were studied as part of an ongoing astrophysical detector development program, and as part of the development of the ALEXIS satellite payload. MCP pairs with surface radii of curvature as small as 7 cm, and diameters up to 46 mm have been evaluated. The experiments show that the gain (greater than 1.5 x 10 exp 7) and background characteristics (about 0.5 events/sq cm per sec) of highly curved MCP stacks are in general equivalent to the performance achieved with flat MCP stacks of similar configuration. However, gain variations across the curved MCP's due to variations in the channel length to diameter ratio are observed. The overall pulse height distribution of a highly curved surface MCP stack (greater than 50 percent FWHM) is thus broader than its flat counterpart (less than 30 percent). Preconditioning of curved MCP stacks gives comparable results to flat MCP stacks, but it also decreases the overall gain variations. Flat fields of curved MCP stacks have the same general characteristics as flat MCP stacks.

  7. Highly curved microchannel plates

    NASA Technical Reports Server (NTRS)

    Siegmund, O. H. W.; Cully, S.; Warren, J.; Gaines, G. A.; Priedhorsky, W.; Bloch, J.

    1990-01-01

    Several spherically curved microchannel plate (MCP) stack configurations were studied as part of an ongoing astrophysical detector development program, and as part of the development of the ALEXIS satellite payload. MCP pairs with surface radii of curvature as small as 7 cm, and diameters up to 46 mm have been evaluated. The experiments show that the gain (greater than 1.5 x 10 exp 7) and background characteristics (about 0.5 events/sq cm per sec) of highly curved MCP stacks are in general equivalent to the performance achieved with flat MCP stacks of similar configuration. However, gain variations across the curved MCP's due to variations in the channel length to diameter ratio are observed. The overall pulse height distribution of a highly curved surface MCP stack (greater than 50 percent FWHM) is thus broader than its flat counterpart (less than 30 percent). Preconditioning of curved MCP stacks gives comparable results to flat MCP stacks, but it also decreases the overall gain variations. Flat fields of curved MCP stacks have the same general characteristics as flat MCP stacks.

  8. Production and properties of electrosprayed sericin nanopowder

    NASA Astrophysics Data System (ADS)

    Hazeri, Najmeh; Tavanai, Hossein; Moradi, Ali Reza

    2012-06-01

    Sericin is a proteinous substrate that envelops fibroin (silk) fiber, and its recovery provides significant economical and social benefits. Sericin is an antibacterial agent that resists oxidation and absorbs moisture and UV light. In powder form, sericin has a wide range of applications in food, cosmetics and drug delivery. Asides from other techniques of producing powder, such as precipitation and spray drying, electrospraying can yield solid nanoparticles, particularly in the submicron range. Here, we report the production of sericin nanopowder by electrospraying. Sericin sponge was recovered from Bombyx mori cocoons through a high-temperature, high-pressure process, followed by centrifugation and freeze drying of the sericin solution. The electrospraying solution was prepared by dissolving the sericin sponge in dimethyl sulfoxide. We demonstrate that electrospraying is capable of producing sericin nanopowder with an average particle size of 25 nm, which is by far smaller than the particles produced by other techniques. The electrosprayed sericin nanopowder consists of small crystallites and exhibits a high moisture absorbance.

  9. Production and properties of electrosprayed sericin nanopowder

    PubMed Central

    Hazeri, Najmeh; Tavanai, Hossein; Moradi, Ali Reza

    2012-01-01

    Sericin is a proteinous substrate that envelops fibroin (silk) fiber, and its recovery provides significant economical and social benefits. Sericin is an antibacterial agent that resists oxidation and absorbs moisture and UV light. In powder form, sericin has a wide range of applications in food, cosmetics and drug delivery. Asides from other techniques of producing powder, such as precipitation and spray drying, electrospraying can yield solid nanoparticles, particularly in the submicron range. Here, we report the production of sericin nanopowder by electrospraying. Sericin sponge was recovered from Bombyx mori cocoons through a high-temperature, high-pressure process, followed by centrifugation and freeze drying of the sericin solution. The electrospraying solution was prepared by dissolving the sericin sponge in dimethyl sulfoxide. We demonstrate that electrospraying is capable of producing sericin nanopowder with an average particle size of 25 nm, which is by far smaller than the particles produced by other techniques. The electrosprayed sericin nanopowder consists of small crystallites and exhibits a high moisture absorbance. PMID:27877498

  10. Bradford Curves.

    ERIC Educational Resources Information Center

    Rousseau, Ronald

    1994-01-01

    Discussion of informetric distributions shows that generalized Leimkuhler functions give proper fits to a large variety of Bradford curves, including those exhibiting a Groos droop or a rising tail. The Kolmogorov-Smirnov test is used to test goodness of fit, and least-square fits are compared with Egghe's method. (Contains 53 references.) (LRW)

  11. Crystal engineering of lactose using electrospray technology: carrier for pulmonary drug delivery.

    PubMed

    Patil, Sharvil; Mahadik, Abhijeet; Nalawade, Pradeep; More, Priyesh

    2017-09-05

    Dry powder inhalers (DPIs) consisting of a powder mixture containing coarse carrier particles (generally lactose) and micronized drug particles are used for lung drug delivery. The effective drug delivery to the lungs depends on size and shape of carrier particles. Thus, various methods have been proposed for engineering lactose particles to enhance drug delivery to lungs. The objective of current work was to assess suitability of electrospray technology toward crystal engineering of lactose. Further, utility of the prepared lactose particles as a carrier in DPI was evaluated. Saturated lactose solutions were electrosprayed to obtain electrosprayed lactose (EL) particles. The polymorphic form of EL was determined using Fourier transform infrared spectroscopy, powder X-ray diffractometry, and differential scanning calorimetry. In addition, morphological, surface textural, and flow properties of EL were determined using scanning electron microscopy and Carr's index, respectively. The aerosolization properties of EL were determined using twin-stage impinger and compared with commercial lactose particles [Respitose(®) (SV003, Goch, Germany)] used in DPI formulations. EL was found to contain both isomers (α and β) of lactose having flow properties comparable to Respitose(®) (SV003). In addition, the aerosolization properties of EL were found to be significantly improved when compared to Respitose(®) (SV003) which could be attributed to morphological (high elongation ratio) and surface characteristic (smooth surface) alterations induced by electrospray technology. Electrospray technology can serve as an alternative technique for continuous manufacturing of engineered lactose particles which can be used as a carrier in DPI formulations.

  12. Electrospray droplet impact secondary ion mass spectrometry using a vacuum electrospray source.

    PubMed

    Takaishi, R; Sakai, Y; Hiraoka, K; Wada, H; Morita, S; Nakashima, T; Nonami, H

    2015-08-15

    In electrospray droplet impact (EDI) developed in our laboratory, an atmospheric pressure electrospray source has been used. To increase the ion beam intensity and reduce the evacuation load, a vacuum electrospray cluster ion source using a silica capillary was developed. A silica capillary with a tip inner diameter of 8 µm was used for vacuum electrospray using aqueous 10% methanol. To stabilize the flow rate of the liquid for nano-electrospray, a home-made constant pressure liquid pump was also developed. By using the silica tip nano-electrospray emitter and a constant pressure pump, stable electrospray with flow rate of 22 nL/min was realized without using any heating system such as laser irradiation. Comparative study of mass spectra obtained by atmospheric pressure EDI (A-EDI) and vacuum EDI (V-EDI) was made for various samples such as thermometer molecule, peptide, polystyrene, Alq(3), NPD, C(60), indium, and SiO(2). V-EDI showed slightly milder ionization than A-EDI. Because V-EDI gave higher target current (5-10 nA) than A-EDI (a few nA at most), V-EDI secondary ion mass spectrometry (SIMS) would be a useful technique for the surface and interface analysis. Copyright © 2015 John Wiley & Sons, Ltd.

  13. Capillary electrophoresis electrospray ionization mass spectrometry interface

    DOEpatents

    Smith, Richard D.; Severs, Joanne C.

    1999-01-01

    The present invention is an interface between a capillary electrophoresis separation capillary end and an electrospray ionization mass spectrometry emitter capillary end, for transporting an anolyte sample from a capillary electrophoresis separation capillary to a electrospray ionization mass spectrometry emitter capillary. The interface of the present invention has: (a) a charge transfer fitting enclosing both of the capillary electrophoresis capillary end and the electrospray ionization mass spectrometry emitter capillary end; (b) a reservoir containing an electrolyte surrounding the charge transfer fitting; and (c) an electrode immersed into the electrolyte, the electrode closing a capillary electrophoresis circuit and providing charge transfer across the charge transfer fitting while avoiding substantial bulk fluid transfer across the charge transfer fitting. Advantages of the present invention have been demonstrated as effective in providing high sensitivity and efficient analyses.

  14. Bacterial Spores Survive Electrospray Charging and Desolvation

    NASA Astrophysics Data System (ADS)

    Pratt, Sara N.; Austin, Daniel E.

    2014-05-01

    The survivability of Bacillus subtilis spores and vegetative Escherichia coli cells after electrospray from aqueous suspension was tested using mobility experiments at atmospheric pressure. E. coli did not survive electrospray charging and desolvation, but B. subtilis did. Experimental conditions ensured that any surviving bacteria were de-agglomerated, desolvated, and electrically charged. Based on mobility measurements, B. subtilis spores survived even with 2,000-20,000 positive charges. B. subtilis was also found to survive introduction into vacuum after either positive or negative electrospray. Attempts to measure the charge distribution of viable B. subtilis spores using electrostatic deflection in vacuum were inconclusive; however, viable spores with low charge states (less than 42 positive or less than 26 negative charges) were observed.

  15. Impact of molecular weight on the formation of electrosprayed chitosan microcapsules as delivery vehicles for bioactive compounds.

    PubMed

    Gómez-Mascaraque, Laura G; Sanchez, Gloria; López-Rubio, Amparo

    2016-10-05

    The molecular weight of chitosan is one of its most determinant characteristics, which affects its processability and its performance as a biomaterial. However, information about the effect of this parameter on the formation of electrosprayed chitosan microcapsules is scarce. In this work, the impact of chitosan molecular weight on its electrosprayability was studied and correlated with its effect on the viscosity, surface tension and electrical conductivity of solutions. A Discriminant Function Analysis revealed that the morphology of the electrosprayed chitosan materials could be correctly predicted using these three parameters for almost 85% of the samples. The suitability of using electrosprayed chitosan capsules as carriers for bioactive agents was also assessed by loading them with a model active compound, (-)-epigallocatechin gallate (EGCG). This encapsulation, with an estimated efficiency of around 80% in terms of preserved antioxidant activity, showed the potential to prolong the antiviral activity of EGCG against murine norovirus via gradual bioactive release combined with its protection against degradation in simulated physiological conditions.

  16. Surface tension effects on submerged electrosprays

    PubMed Central

    Marín, Álvaro G.; Loscertales, Ignacio G.; Barrero, Antonio

    2012-01-01

    Electrosprays are a powerful technique to generate charged micro/nanodroplets. In the last century, the technique has been extensively studied, developed, and recognized with a shared Nobel price in Chemistry in 2002 for its wide spread application in mass spectrometry. However, nowadays techniques based on microfluidic devices are competing to be the next generation in atomization techniques. Therefore, an interesting development would be to integrate the electrospray technique into a microfluidic liquid-liquid device. Several works in the literature have attempted to build a microfluidic electrospray with disputable results. The main problem for its integration is the lack of knowledge of the working parameters of the liquid-liquid electrospray. The “submerged electrosprays” share similar properties as their counterparts in air. However, in the microfluidic generation of micro/nanodroplets, the liquid-liquid interfaces are normally stabilized with surface active agents, which might have critical effects on the electrospray behavior. In this work, we review the main properties of the submerged electrosprays in liquid baths with no surfactant, and we methodically study the behavior of the system for increasing surfactant concentrations. The different regimes found are then analyzed and compared with both classical and more recent experimental, theoretical and numerical studies. A very rich phenomenology is found when the surface tension is allowed to vary in the system. More concretely, the lower states of electrification achieved with the reduced surface tension regimes might be of interest in biological or biomedical applications in which excessive electrification can be hazardous for the encapsulated entities. PMID:24155865

  17. Evaluation of formulae for CSF IgG synthesis using data obtained from two methods: importance of receiver operator characteristic curve analysis.

    PubMed

    McMillan, S A; Douglas, J P; Droogan, A G; Hawkins, S A

    1996-01-01

    To determine the clinical performance of three cerebrospinal fluid (CSF) IgG synthesis formulae using data obtained from two quantitation methods. Receiver operator characteristic (ROC) analysis and decision index plots were used to compare a rate nephelometric (RN) and a rocket immunoelectrophoretic (RIEP) method for quantitating albumin and IgG for use in CSF IgG synthesis formulae. Further analysis was used to determine the most clinically accurate of these formulae for a diagnosis of multiple sclerosis with regard to technical accuracy and cost effectiveness. Values for albumin and IgG determined by RN gave better sensitivities and specificities than the RIEP method when applied to all three formulae; however, when the 95% confidence limits were considered, the difference was not significant. Using the RN method with an agreed "rule in" threshold value of 90% specificity, the IgG index gave the best clinical performance. ROC curve analysis and decision index plots provide valuable tools in assessing and comparing the clinical performance of new and existing laboratory assays.

  18. Evaluation of formulae for CSF IgG synthesis using data obtained from two methods: importance of receiver operator characteristic curve analysis.

    PubMed Central

    McMillan, S A; Douglas, J P; Droogan, A G; Hawkins, S A

    1996-01-01

    AIMS: To determine the clinical performance of three cerebrospinal fluid (CSF) IgG synthesis formulae using data obtained from two quantitation methods. METHODS: Receiver operator characteristic (ROC) analysis and decision index plots were used to compare a rate nephelometric (RN) and a rocket immunoelectrophoretic (RIEP) method for quantitating albumin and IgG for use in CSF IgG synthesis formulae. Further analysis was used to determine the most clinically accurate of these formulae for a diagnosis of multiple sclerosis with regard to technical accuracy and cost effectiveness. RESULTS: Values for albumin and IgG determined by RN gave better sensitivities and specificities than the RIEP method when applied to all three formulae; however, when the 95% confidence limits were considered, the difference was not significant. Using the RN method with an agreed "rule in" threshold value of 90% specificity, the IgG index gave the best clinical performance. CONCLUSION: ROC curve analysis and decision index plots provide valuable tools in assessing and comparing the clinical performance of new and existing laboratory assays. PMID:8666680

  19. Perspective Biological Markers for Autism Spectrum Disorders: Advantages of the Use of Receiver Operating Characteristic Curves in Evaluating Marker Sensitivity and Specificity

    PubMed Central

    2015-01-01

    Autism Spectrum Disorders (ASD) are a heterogeneous group of neurodevelopmental disorders. Recognized causes of ASD include genetic factors, metabolic diseases, toxic and environmental factors, and a combination of these. Available tests fail to recognize genetic abnormalities in about 70% of ASD children, where diagnosis is solely based on behavioral signs and symptoms, which are difficult to evaluate in very young children. Although it is advisable that specific psychotherapeutic and pedagogic interventions are initiated as early as possible, early diagnosis is hampered by the lack of nongenetic specific biological markers. In the past ten years, the scientific literature has reported dozens of neurophysiological and biochemical alterations in ASD children; however no real biomarker has emerged. Such literature is here reviewed in the light of Receiver Operating Characteristic (ROC) analysis, a very valuable statistical tool, which evaluates the sensitivity and the specificity of biomarkers to be used in diagnostic decision making. We also apply ROC analysis to some of our previously published data and discuss the increased diagnostic value of combining more variables in one ROC curve analysis. We also discuss the use of biomarkers as a tool for advancing our understanding of nonsyndromic ASD. PMID:26648598

  20. Electrosprayed TiO2 nanoporous hemispheres for enhanced electron transport and device performance of formamidinium based perovskite solar cells.

    PubMed

    Ye, Tao; Ma, Shaoyang; Jiang, Xi; Petrović, Miloš; Vijila, Chellappan; Ramakrishna, Seeram; Wei, Lei

    2017-01-07

    Titanium dioxide (TiO2) nanoporous hemispheres (NHSs) with a radius of ∼200 nm are fabricated by electrospraying a hydrothermally synthesized TiO2 nanoparticle (NP) suspension solution. The resulting TiO2 NHSs are highly porous, which are beneficial to the infiltration of perovskites and provide a larger contact area, as building blocks to construct a mesoporous TiO2 layer for FA0.81MA0.15Pb(I0.836Br0.15)3 based perovskite solar cells (PSCs). By varying the TiO2 NHS collecting period (15 s, 30 s, 60 s and 90 s) during the electrospraying process, the performance of PSCs changes with different TiO2 NHS distribution densities. The optimized PSC employing TiO2 NHSs (60 s) exhibits a photovoltaic conversion efficiency (PCE) as high as 19.3% with a Jsc of 23.8 mA cm(-2), a Voc of 1.14 V and a FF of 0.71. Furthermore, the PSC possesses a reproducible PCE value with little hysteresis in its current density-voltage (J-V) curves. The small perturbation transient photovoltage (TPV) measurement reveals a longer free carrier lifetime within the TiO2 NHS based PSC than that in the TiO2 NP based PSC, and the time of flight (TOF) photoconductivity measurement shows that charge mobilities in this system are also enhanced. These characteristics make TiO2 NHSs a promising electron transport material for efficient photovoltaic devices.

  1. Combined electrophoresis-electrospray interface and method

    DOEpatents

    Smith, Richard D.; Udseth, Harold R.; Barinaga, Charles J.

    1995-01-01

    An improvement to the system and method for analyzing molecular constituents of a composition sample that comprises improvements to an electrospray ionization source for interfacing to mass spectrometers and other detection devices. The improvement consists of establishing a unique electrical circuit pattern and nozzle configuration, a metallic coated and conical shaped capillary outlet, coupled with sizing of the capillary to obtain maximum sensitivity.

  2. Dynamics of curved interfaces

    SciTech Connect

    Escudero, Carlos

    2009-08-15

    Stochastic growth phenomena on curved interfaces are studied by means of stochastic partial differential equations. These are derived as counterparts of linear planar equations on a curved geometry after a reparametrization invariance principle has been applied. We examine differences and similarities with the classical planar equations. Some characteristic features are the loss of correlation through time and a particular behavior of the average fluctuations. Dependence on the metric is also explored. The diffusive model that propagates correlations ballistically in the planar situation is particularly interesting, as this propagation becomes nonuniversal in the new regime.

  3. Flow Interface for Charge Reduced Electrospray of Nanoparticle Solutions

    PubMed Central

    Adou, Kouame; Johnston, Murray V.

    2009-01-01

    A charge reduction (CR) interface for electrospray ionization was characterized that permits simultaneous analysis of nanoparticle solutions by multiple detection methods. In the direct infusion configuration, a constant flow of analyte solution undergoes electrospray ionization (ESI). The charged aerosol is sampled directly into the atmospheric pressure inlet of a quadrupole time-of-flight mass spectrometer (QTOF) and to a CR device followed by a differential mobility analyzer (DMA) and condensation particle counter (CPC). In the plug injection configuration, analyte solution is injected into a liquid chromatograph. The effluent is split to an evaporative light scattering detector (ELSD) and the ESI interface. The charged aerosol is then sampled through the CR device directly into the CPC. Performance characteristics of the two configurations were studied with sucrose and protein solutions. When a liquid flow rate in the low µL/min range was used, the reconstructed droplet size distribution from the ESI interface had an average diameter of 184 nm with a geometric standard deviation of 1.4. For the first configuration, the linear working range was wider for ESI-MS than CR-DMA-CPC. For the second configuration, the detection efficiency, defined as the fraction of molecules flowing through the ESI interface that are ultimately detected by the CPC, was on the order of 10−6. Simultaneous measurements with ELSD and CPC were consistent with analyte molecular size and may provide a means of estimating the size of unknown particles. PMID:19924869

  4. On the electrospraying of conducting liquids in dielectric liquid baths

    NASA Astrophysics Data System (ADS)

    Gómez-Marín, Álvaro; Loscertales, Ignacio G.; Márquez, Manuel; Barrero, Antonio

    2004-11-01

    Steady cone-jets of conducting liquids inside dielectris liquid baths are easily obtained. In particular water and glycerol have been electrosprayed in either heptane or vaseline oil. Experimental results show that the current emitted from the cone-jet depends on the flow rate and the liquid properties in the same way that it does in air. On the contrary, the effects of the bath inertia plays an important role to determine the size of droplets. Also the addition of small amounts of both water-soluble and lipid-soluble surfactants changes appreciably the spray characteristics. The influence of either lipid-soluble or water soluble surfactants at different concentrations on the droplet size of a water electrospray in oil or heptane has been experimentally obtained. In the case of glycerol, the high viscosity of the fluid gives rise to very long jets presenting kink instabilitiy far from the vertex cone. Much more stable jets are obtained by adding small amounts of lipid or water-soluble surfactants. In those cases, the electric field on the very long jet of glycerol is very small and a big droplet is formed at the end of the jet.

  5. Electrospray ionization of volatiles in breath

    NASA Astrophysics Data System (ADS)

    Martínez-Lozano, P.; de La Mora, J. Fernández

    2007-08-01

    Recent work by Zenobi and colleagues [H. Chen, A. Wortmann, W. Zhang, R. Zenobi, Angew. Chem. Int. Ed. 46 (2007) 580] reports that human breath charged by contact with an electrospray (ES) cloud yields many mass peaks of species such as urea, glucose, and other ions, some with molecular weights above 1000 Da. All these species are presumed to be involatile, and to originate from breath aerosols by so-called extractive electrospray ionization EESI [H. Chen, A. Venter, R.G. Cooks, Chem. Commun. (2006) 2042]. However, prior work by Fenn and colleagues [C.M. Whitehouse, F. Levin, C.K. Meng, J.B. Fenn, Proceedings of the 34th ASMS Conference on Mass Spectrometry and Allied Topics, Denver, 1986 p. 507; S. Fuerstenau, P. Kiselev, J.B. Fenn, Proceedings of the 47th ASMS Conference on Mass Spectrometry, 1999, Dallas, TX, 1999] and by Hill and colleagues [C. Wu, W.F. Siems, H.H. Hill Jr., Anal. Chem. 72 (2000) 396] have reported the ability of electrospray drops to ionize a variety of low vapor pressure substances directly from the gas phase, without an apparent need for the vapor to be brought into the charging ES in aerosol form. The Ph.D. Thesis of Martínez-Lozano [P. Martínez-Lozano Sinués, Ph.D. Thesis, Department of Thermal and Fluid Engineering, University Carlos III of Madrid; April 5, 2006 (in Spanish); http://hdl.handle.net/10016/655] had also previously argued that the numerous human breath species observed via a similar ES ionization approach were in fact ionized directly from the vapor. Here, we observe that passage of the breath stream through a submicron filter does not eliminate the majority of the breath vapors seen in the absence of the filter. We conclude that direct vapor charging is the leading mechanism in breath ionization by electrospray drops, though aerosol ionization may also play a role.

  6. Combined electrophoresis-electrospray interface and method

    DOEpatents

    Smith, R.D.; Udseth, H.R.; Barinaga, C.J.

    1995-06-13

    An improvement to the system and method is disclosed for analyzing molecular constituents of a composition sample that comprises improvements to an electrospray ionization source for interfacing to mass spectrometers and other detection devices. The improvement consists of establishing a unique electrical circuit pattern and nozzle configuration, a metallic coated and conical shaped capillary outlet, coupled with sizing of the capillary to obtain maximum sensitivity. 10 figs.

  7. Modeling Electrospray Deposition of Nanoparticle Inks

    NASA Astrophysics Data System (ADS)

    Li, Ao; Fideles da Silva, Jefferson; Yong, Xin

    2015-11-01

    Electrospray of nanoparticle inks is of great importance to the manufacturing of functional materials. In this study, we develop a new three-dimensional multiphysics method to model the electrospray of colloidal suspension to a flat substrate. The Lagrangian Particle Tracking (LPT) transport equation is coupled to mass and heat transfer using convective droplet vaporization model, which allow us to track each particle-laden ink droplets and dry nanoparticles in the electrospray plume and probe the deposit structures. Herein, we consider dilute inks that are experimentally relevant, assuming monodisperse nanoparticles. We characterize the overall statistics of the plume and the dynamics of individual ink droplet or dry nanoparticle. It is shown that the segregation effect affects not only primary and satellite droplets but also dry nanoparticles. We observe nanoparticles deposit structure changing process, in particular time evolution of the density profile along radial direction. Our results show that the region of high nanoparticle density transitioning from only the edge to both the edge and center, which agrees with previous experimental studies.

  8. Self-assembled nanostructures via electrospraying

    NASA Astrophysics Data System (ADS)

    Jayasinghe, S. N.

    2006-07-01

    A concentrated nanoparticulate-based ethylene glycol suspension was prepared and electrosprayed at optimum and stable cone-jet mode conditions. Using laser spectroscopy, the droplets were measured and found to range within ∼0.23-3.8 μm. In parallel to spectroscopy-assisted sizing, a volume equivalence route for estimating droplet sizes was carried out by measuring contact angles and diameters of the deposits. The electrosprayed nanosuspension relics were examined using optical and transmission electron microscopy. These deposits were further characterized using energy-dispersive X-rays and selected area electron diffraction. Simultaneously deposits were formed by a controlled route through needle deposition without the presence of an electric field. The structures formed in this non-electric field driven route are compared with those formed with electric fields. Thus, elucidating electrosprays as a competing nanofabrication route for forming self-assemblies with a wide range of nanomaterials in the nanoscale for top-down based bottom-up assembly of structures.

  9. Microfabricated emitter array for an ionic liquid electrospray thruster

    NASA Astrophysics Data System (ADS)

    Nakagawa, Kaito; Tsuchiya, Toshiyuki; Takao, Yoshinori

    2017-06-01

    We have fabricated needle-shaped emitters on a Si wafer by a MEMS process, and measured the voltage-current characteristics and the frequency dependence of a bipolar pulse voltage for ionic liquid electrospray thrusters, which can be mounted on nanosatellites ( ≲ 10 kg). Although the extracted current did not increase with increasing number of emitters, probably owing to the lack of uniformity of the emitters fabricated, we have demonstrated that the emitted current depends on the gap distance between the emitter and the extractor grid electrode, and low frequencies of the bipolar pulse voltage are desirable for thruster operation. Moreover, the Bosch process is required for fabricating a reservoir of ionic liquid, which prevents undesirable electrical short circuits, and the minimum emitter pitch to prevent loss of ion beams to the extractor is estimated to be about 400 µm.

  10. Development and characterization of electrosprayed Alyssum homolocarpum seed gum nanoparticles for encapsulation of d-limonene.

    PubMed

    Khoshakhlagh, Khadije; Koocheki, Arash; Mohebbi, Mohebbat; Allafchian, Alireza

    2017-03-15

    In this study, the feasibility of developing Alyssum homolocarpum seed gum (AHSG) nanocapsules containing d-limonene by electrospraying has been investigated. d-limonene emulsions with constant AHSG (0.5% w/w) and various flavor concentrations (10-30% based on gum weight) with 0.1% Tween 20 were electrosprayed at 20kV and 0.1ml/h of flow rate. The effects of key parameters of emulsions (rheological properties, droplet size, surface tension and electrical conductivity) on the morphology of structures have been studied. The morphology of nanocapsules had strong dependency on solution properties. The aggregated irregular shaped nanoparticles were obtained from electrospraying of AHSG solution. After incorporation of 10 and 20% d-limonene, spherical nanocapsules were yielded. However, morphology of nanocapsules changed to nanofibers by increasing the flavor content to 30%. The encapsulation efficiency for 10 and 20% d-limonene loaded nanocapsules was around 87-93%. Attenuated total reflectance-fourier transform infrared spectroscopy (ATR-FTIR), X-ray diffraction (XRD), differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA) were also employed to study the physicochemical characteristics of nanocapsules. These experiments provided evidences that electrosprayed AHSG nanoparticles introduce a novel and efficient carrier for encapsulation of bioactive ingredients. Copyright © 2016 Elsevier Inc. All rights reserved.

  11. Relaxation times in single event electrospraying controlled by nozzle front surface modification.

    PubMed

    Stachewicz, Urszula; Dijksman, J Frits; Burdinski, Dirk; Yurteri, Caner U; Marijnissen, Jan C M

    2009-02-17

    Single event electrospraying (SEE) is a method for on-demand deposition of femtoliter to picoliter volumes of fluids. To determine the influence of the size of the meniscus on the characteristics of the single event electrospraying process, glass capillaries were used with and without an antiwetting coating comprising a self-assembled 1H,1H,2H,2H-perfluorodecyltrichlorosilane-based monolayer to control the meniscus size. A large difference was found in driving single event electrospraying from a small meniscus compared to what is needed to generate a single event electrospraying from a large meniscus. Furthermore, after studying the different time constants related to the electrical and the hydrodynamic phenomena, we are able to explain the timing limitations of the deposition process from both a small and a large meniscus. The hydrodynamic relaxation time is significantly reduced in the case of the modified capillary, and the timing of SEE, which determines the deposition time, is limited by the resistor-capacitor RC time of the electrical circuit needed to drive the SEE. We have built a model that describes the almost one-dimensional motion of the liquid in the capillary during pulsing. The model has been used to estimate the hydrodynamic relaxation times related to the meniscus-to-cone and cone-to-meniscus transitions during SEE. By confining the meniscus to the inner diameter of the nozzle, we are able to deposit a volume smaller than 5 pL per SEE.

  12. Fabrication of micro-patterns via near-field electrospray

    NASA Astrophysics Data System (ADS)

    Li, Wenwang; Zheng, Gaofeng; Xu, Lei; Wang, Xiang

    2016-11-01

    A near-field electrospray process is developed to deposited micro-patterns. Compared with conventional electrospray, near field electrospray uses a steel probe instead of capillary nozzle, and its nozzle-to-substrate distance is shortened to several millimeters to realize micro-scale deposition area. The liquid is supplied by discretely dipping the probe into solution in advance so that electrospray process maintains until the consumption of liquid adhered at the probe tip. The influence of solution conductivity and applied voltage on deposition are investigated, as increasing solution conductivity and high applied voltage may promote the electrospray process and enlarge the line width. In addition, micro-patterns with various materials are directly electrosprayed.

  13. A Growth Curve Analysis of the Joint Influences of Parenting Affect, Child Characteristics and Deviant Peers on Adolescent Illicit Drug Use

    ERIC Educational Resources Information Center

    Pires, Paulo; Jenkins, Jennifer M.

    2007-01-01

    This study purports that parental rejection and warmth are critical to the development of adolescent drug use, and investigates a model that also considers children's vulnerability and deviant peer affiliations. It tests mediation through the proximal risk factor of deviant peers. Poisson growth curve modeling was used to examine participants from…

  14. A Growth Curve Analysis of the Joint Influences of Parenting Affect, Child Characteristics and Deviant Peers on Adolescent Illicit Drug Use

    ERIC Educational Resources Information Center

    Pires, Paulo; Jenkins, Jennifer M.

    2007-01-01

    This study purports that parental rejection and warmth are critical to the development of adolescent drug use, and investigates a model that also considers children's vulnerability and deviant peer affiliations. It tests mediation through the proximal risk factor of deviant peers. Poisson growth curve modeling was used to examine participants from…

  15. Perspective on Electrospray Ionization and Its Relation to Electrochemistry

    NASA Astrophysics Data System (ADS)

    Pozniak, Boguslaw P.; Cole, Richard B.

    2015-03-01

    The phenomenon of electrospraying of liquids is presented from the perspective of the electrochemistry involved. Basics of current and liquid flow in the capillary and spray tip are discussed, followed by specifics of charging and discharging of the sprayed liquid surface. Fundamental theories and numerical modeling relating electrospray current to solution and spray parameters are described and then compared with our own experimentally obtained data. The method of mapping potentials and currents inside the electrospray capillary by using an inserted electrically-isolated small wire probe electrode is discussed in detail with illustrations from new and published data. Based on these experimentally obtained results, a new mathematical model is derived. The introduced "nonlinear resistor electrospray capillary model" divides the electrospray capillary into small sections, adds their contributions, and then, by transition to infinitely small section thickness, produces analytical formulas that relate current and potential maps to other properties of the electrospraying liquid: primarily conductivity and current density. The presentation of the model is undertaken from an elementary standpoint, and it offers the possibility to obtain quantitative information regarding operating parameters from typical analytical systems subjected to electrospray. The model stresses simplicity and ease of use; examples applying experimental data are shown and some predictions of the model are also presented. The developed nonlinear resistor electrospray capillary model is intended to provide a new quantitative basis for improving the understanding of electrochemical transformations occurring in the electrospray emitter. A supplemental material section gives full derivation of the model and discusses other consequences.

  16. Vacuum electrospray of volatile liquids assisted by infrared laser irradiation.

    PubMed

    Ninomiya, Satoshi; Chen, Lee Chuin; Suzuki, Hiroaki; Sakai, Yuji; Hiraoka, Kenzo

    2012-04-15

    Current large cluster sources such as C(60) or argon utilize gas-phase sources which are of low-brightness and cannot be focused efficiently to better than 1 micron diameter spot size. The development of a high-brightness large cluster ion source is of critical importance to achieve high resolution in secondary ion mass spectrometry (SIMS) imaging of organics. We propose a new high-brightness large cluster ion source, and a technique for producing a stable electrospray of volatile liquids under vacuum. It is known that vacuum electrospray of volatile liquids such as water is extremely difficult because of freezing of the liquids introduced in vacuum by evaporative cooling. To avoid freezing, the tip of the electrospray emitter was irradiated by a continuous wave infrared laser. Without continuous laser irradiation the vacuum electrospray of a water/methanol solution was unstable with respect to the shapes of the Taylor cone and current, whereas continuous laser irradiation produced a stable electrospray of water. The typical modes of electrospray were clearly observed with an optical microscope even under vacuum conditions. A stable vacuum electrospray could be achieved by improving the vacuum pressure to suppress electric discharge and by using the laser to maintain the liquid state. This is the first description of the production of a stable vacuum electrospray of volatile liquids such as water. This vacuum electrospray technique can be expected to produce a novel high-brightness large cluster ion beam source. Copyright © 2012 John Wiley & Sons, Ltd.

  17. Rapid identification of acetophenones in two Cynanchum species using liquid chromatography-electrospray ionization tandem mass spectrometry.

    PubMed

    Zhang, Xi; Shan, Lei; Huang, Hao; Yang, Xianwen; Liang, Xu; Xing, Aiting; Huang, Haiqiang; Liu, Xinru; Su, Juan; Zhang, Weidong

    2009-04-05

    Acetophenones in Cynanchum species, especially cynandione A and its derivatives, whose utilization and toxicity in herbal drugs and folk medicines has caused great interest in the chemical investigation, have extensive biological activities. In this paper, a facile method based on high-performance liquid chromatography coupled with electrospray ionization tandem mass spectrometry (HPLC-ESI-MS(n)) was developed for the analysis of cynandione A derivatives in the roots of the Cynanchum wilfordii and C. auriculatum. ESI-MS/MS and ESI-MS(n) analysis of cynandiones A and B in negative ion mode were firstly performed employing two mass spectrometers each equipped with an ion-trap and a quadrupole time-of-flight (Q-TOF) mass analyzer. The results drawn from both instruments were similar to each other. Characteristic fragmentation pathways were proposed by comparing the spectra of two standards acquired in the experiments. The fragment ions at m/z 283 and 268 were obtained, and then were used as diagnostic ions to screen and identify cynandione A derivatives from the roots of above two species, together with an HPLC-MS(n) method. Total of 28 cynandione A derivatives comprising 4 reported and 24 novel components were identified or tentatively identified. Furthermore, breakdown curves were constructed to distinguish two types of isomers among these compounds. To our knowledge, this is the first report on characterization of acetophenones by HPLC-ESI-MS(n), which allows a rapid and complete analysis of cynandione A derivatives in roots of Cynanchum species.

  18. Multi-reader multi-case studies using the area under the receiver operator characteristic curve as a measure of diagnostic accuracy: systematic review with a focus on quality of data reporting.

    PubMed

    Dendumrongsup, Thaworn; Plumb, Andrew A; Halligan, Steve; Fanshawe, Thomas R; Altman, Douglas G; Mallett, Susan

    2014-01-01

    We examined the design, analysis and reporting in multi-reader multi-case (MRMC) research studies using the area under the receiver-operating curve (ROC AUC) as a measure of diagnostic performance. We performed a systematic literature review from 2005 to 2013 inclusive to identify a minimum 50 studies. Articles of diagnostic test accuracy in humans were identified via their citation of key methodological articles dealing with MRMC ROC AUC. Two researchers in consensus then extracted information from primary articles relating to study characteristics and design, methods for reporting study outcomes, model fitting, model assumptions, presentation of results, and interpretation of findings. Results were summarized and presented with a descriptive analysis. Sixty-four full papers were retrieved from 475 identified citations and ultimately 49 articles describing 51 studies were reviewed and extracted. Radiological imaging was the index test in all. Most studies focused on lesion detection vs. characterization and used less than 10 readers. Only 6 (12%) studies trained readers in advance to use the confidence scale used to build the ROC curve. Overall, description of confidence scores, the ROC curve and its analysis was often incomplete. For example, 21 (41%) studies presented no ROC curve and only 3 (6%) described the distribution of confidence scores. Of 30 studies presenting curves, only 4 (13%) presented the data points underlying the curve, thereby allowing assessment of extrapolation. The mean change in AUC was 0.05 (-0.05 to 0.28). Non-significant change in AUC was attributed to underpowering rather than the diagnostic test failing to improve diagnostic accuracy. Data reporting in MRMC studies using ROC AUC as an outcome measure is frequently incomplete, hampering understanding of methods and the reliability of results and study conclusions. Authors using this analysis should be encouraged to provide a full description of their methods and results.

  19. Multi-Reader Multi-Case Studies Using the Area under the Receiver Operator Characteristic Curve as a Measure of Diagnostic Accuracy: Systematic Review with a Focus on Quality of Data Reporting

    PubMed Central

    Dendumrongsup, Thaworn; Plumb, Andrew A.; Halligan, Steve; Fanshawe, Thomas R.; Altman, Douglas G.; Mallett, Susan

    2014-01-01

    Introduction We examined the design, analysis and reporting in multi-reader multi-case (MRMC) research studies using the area under the receiver-operating curve (ROC AUC) as a measure of diagnostic performance. Methods We performed a systematic literature review from 2005 to 2013 inclusive to identify a minimum 50 studies. Articles of diagnostic test accuracy in humans were identified via their citation of key methodological articles dealing with MRMC ROC AUC. Two researchers in consensus then extracted information from primary articles relating to study characteristics and design, methods for reporting study outcomes, model fitting, model assumptions, presentation of results, and interpretation of findings. Results were summarized and presented with a descriptive analysis. Results Sixty-four full papers were retrieved from 475 identified citations and ultimately 49 articles describing 51 studies were reviewed and extracted. Radiological imaging was the index test in all. Most studies focused on lesion detection vs. characterization and used less than 10 readers. Only 6 (12%) studies trained readers in advance to use the confidence scale used to build the ROC curve. Overall, description of confidence scores, the ROC curve and its analysis was often incomplete. For example, 21 (41%) studies presented no ROC curve and only 3 (6%) described the distribution of confidence scores. Of 30 studies presenting curves, only 4 (13%) presented the data points underlying the curve, thereby allowing assessment of extrapolation. The mean change in AUC was 0.05 (−0.05 to 0.28). Non-significant change in AUC was attributed to underpowering rather than the diagnostic test failing to improve diagnostic accuracy. Conclusions Data reporting in MRMC studies using ROC AUC as an outcome measure is frequently incomplete, hampering understanding of methods and the reliability of results and study conclusions. Authors using this analysis should be encouraged to provide a full description of

  20. Curves and Their Properties.

    ERIC Educational Resources Information Center

    Yates, Robert C.

    This volume, a reprinting of a classic first published in 1952, presents detailed discussions of 26 curves or families of curves, and 17 analytic systems of curves. For each curve the author provides a historical note, a sketch or sketches, a description of the curve, a discussion of pertinent facts, and a bibliography. Depending upon the curve,…

  1. Electrospray of 1-Butyl-3-Methylimidazolium Dicyanamide Under Variable Flow Rate Operations

    DTIC Science & Technology

    2014-06-27

    emission product is corroborated by the change in jet diameter. Fernández de la Mora and Loscertales [29] established that the jet diameter scales as a...used in establishing potential propulsion performance at those flow rates. Electrospray scaling laws have been developed by Fernández de la Mora and...Equation (2) is consistent with Eq. (1), developed by Fernández de la Mora and Loscertales. The curve fit establishes an equivalent power of 0.5. The scale

  2. Initial slope of radiation survival curves is characteristic of the origin of primary and established cultures of human tumor cells and fibroblasts

    SciTech Connect

    Malaise, E.P.; Fertil, B.; Deschavanne, P.J.; Chavaudra, N.; Brock, W.A.

    1987-08-01

    The published survival curves of 110 human tumor cell lines and 147 nontransformed human fibroblast strains have been reanalyzed using three different statistical methods: the single hit multitarget model, the linear-quadratic model, and the mean inactivation dose. The 110 tumor cell lines were classified in two ways: (a) into three categories defined by clinical radiocurability criteria, and (b) into seven categories based on histopathology. The 147 fibroblast strains were divided into eight genetic groups. Differences in the radiosensitivities of both the tumor cell and fibroblast groups could be demonstrated only by parameters that describe the slopes of the initial part of the survival curves. The capacity of the survival level to identify significant differences between groups was dose dependent over the range 1 to 6 Gy. This relationship showed a bell-shaped curve with a maximum at 1.5 Gy for the tumor cell lines and 3 Gy for the fibroblasts. Values for intrinsic radiosensitivity for a number of groups of tumors have also been obtained by primary culture of tumor cells. These values are strictly comparable to those obtained by clonogenic methods. This confirms that intrinsic radiosensitivity is a determinant of the response of tumor cells to radiotherapy and suggests that tissue culture methods may be used as a predictive assay.

  3. Transport and Deposition of Electrosprayed Nanoparticles

    NASA Astrophysics Data System (ADS)

    Brown, Nicholas; Chiarot, Paul

    2015-11-01

    In an electrospray, high electric potentials are utilized to generate a fine aerosol of a conductive solvent. For this study, the solvent consisted of nanoparticles dispersed in alcohol. The nanoparticle suspensions act as printable nanoparticle inks. In this process, a glass capillary tube is held as a high electric potential relative to a grounded reference plate located below the tip. Droplets are ejected from the tube and are directed towards the ground plate. If the solvent is sufficiently volatile, it will rapidly evaporate while the droplets are in flight (due to the high surface area to volume ratio) leaving behind dry, highly charged nanoparticles. The droplets/nanoparticles are deposited onto a target substrate that is place onto the grounded plate. The transport of any individual droplet/nanoparticle from the emitter tip to the target substrate is a stochastic process. This transport can be modeled using a Monte Carlo simulation. The probability of an individual particle being deposited at a given location on the target substrate is directly related to the electric potential at that location. In other words, the probability function that determines the deposition is directly related to the electric potential at the substrate. The total potential is comprised of the applied electric potential required to generate the electrospray, the induced charge on the surface of the target dielectric, and the charge on the individual particles themselves. We report on the structure of droplet/nanoparticle deposits printed using electrospray. The evolution of the deposit is investigated over time using experimental studies and Monte Carlo simulations. The deposit structure passes through four distinct regimes that are characterized by repeatable bulk features.

  4. The electrospray: Fundamentals and combustion applications

    NASA Technical Reports Server (NTRS)

    Gomez, Alessandro

    1993-01-01

    Liquid fuel dispersion in practical systems is typically achieved by spraying the fuel into a polydisperse distribution of droplets evaporating and burning in a turbulent gaseous environment. In view of the nearly unsurmountable difficulties of this two-phase flow, it would be useful to use an experimental arrangement that allow a systematic study of spray evolution and burning in configurations of gradually increasing levels of complexity, starting from laminar sprays to fully turbulent ones. An Electrostatic Spray (ES) of charged droplets lends itself to this type of combustion experiments under well-defined conditions and can be used to synthesize gradually more complex spray environments. In its simplest configuration, a liquid is fed into a small metal tube maintained at several kilovolts relative to a ground electrode few centimeters away. Under the action of the electric field, the liquid meniscus at the outlet of the capillary takes a conical shape, with a thin jet emerging from the cone tip. This jet breaks up farther downstream into a fine spray of charged droplets. Several advantages distinguish the electrospray from alternative atomization techniques: the self-dispersion property of the spray due to coulombic repulsion; the absence of droplet coalescence; the potential control of the trajectories of charged droplets by suitable disposition of electrostatic fields; and the decoupling of atomization, which is strictly electrostatic, from gas flow processes. Furthermore, as recently shown in our laboratory, the electrospray can produce quasi-monodisperse droplets over a very broad size range (1-100 microns). The ultimate objective of this research project is to study the formation and burning of electrosprays of liquid fuels first in laminar regimes and then in turbulent ones. Combustion will eventually be investigated in conditions of three-dimensional droplet-droplet interaction, for which experimental studies have been limited to either qualitative

  5. Application of electrospraying as a one-step method for the fabrication of triamcinolone acetonide-PLGA nanofibers and nanobeads.

    PubMed

    Jahangiri, Azin; Davaran, Soodabeh; Fayyazi, Behnam; Tanhaei, Ali; Payab, Shahriar; Adibkia, Khosro

    2014-11-01

    The aim of the present project was to prepare triamcinolone acetonide nanofibers and nanobeads with prolonged anti-inflammatory activity. Triamcinolone acetonide-loaded PLGA nanoformulations were prepared by electrospraying method. The physicochemical and morphological properties of the fabricated nanoparticles were characterized as well. In vitro drug release of the prepared formulations was also studied. Differential scanning calorimetry and X-ray powder diffractometery showed that drug crystallinity was notably decreased during the electrospraying process. In vitro dissolution tests verified that the pure drug and physical mixtures had faster drug release pattern compared to the nanoformulations. Electrosprayed samples with the drug:polymer ratio of 1:10 revealed slower release profiles compared to those with a 1:5 ratio. Results obtained from SEM images of the prepared formulations indicated that polymer solution concentration was the critical parameter in the formation of fibers or beads; so that, fiber formation was increased proportionally with increasing polymer concentration. Moreover, the size of obtained nanostructures was also increased in order of polymer concentrations. As a final point, electrosprayed triamcinolone-loaded biodegradable micro/nanofibers and nanobeads with modified physicochemical characteristics and sustained drug release profiles were successfully prepared via simple, one-step and cost effective electrospraying technique.

  6. The thermoluminescence characteristics and the glow curves of Thulium doped silica fiber exposed to 10MV photon and 21MeV electron radiation.

    PubMed

    Alawiah, A; Alina, M S; Bauk, S; Abdul-Rashid, H A; Gieszczyk, W; Noramaliza, M N; Mahdiraji, G A; Tamchek, N; Zulkifli, M I; Bradley, D A; Marashdeh, M W

    2015-04-01

    The thermoluminescence (TL) glow curves and kinetics parameters of Thulium (Tm) doped silica cylindrical fibers (CF) are presented. A linear accelerator (LINAC) was used to deliver high-energy radiation of 21MeV electrons and 10MV photons. The CFs were irradiated in the dose range of 0.2-10Gy. The experimental glow curve data was reconstructed by using WinREMS. The WinGCF software was used for the kinetic parameters evaluation. The TL sensitivity of Tm-doped silica CF is about 2 times higher as compared to pure silica CF. Tm-doped silica CF seems to be more sensitive to 21MeV electrons than to 10MV photons. Surprisingly, no supralinearity was displayed and a sub-linear response of Tm-doped silica CF was observed within the analyzed dose range for both 21MeV electrons and 10MV photons. The Tm-doped silica CF glow curve consists of 5 individual glow peaks. The Ea of peak 4 and peak 5 was highly dependent on dose when irradiated with photons. We also noticed that the electron radiation (21MeV) caused a shift of glow peak by 7-13°C to the higher temperature region compared with photons radiation (10MV). Our Tm-doped fibers seem to give high TL response after 21MeV electrons, which gives around 2 times higher peak integral as compared with 10MV photon radiation. We concluded that peak 4 is the first-order kinetic peak and can be used as the main dosimetric peak of Tm-doped silica CF.

  7. Laser diagnostics of an evaporating electrospray

    NASA Astrophysics Data System (ADS)

    Yi, Tongxun

    2014-01-01

    An electrospray atomizer generates monodisperse, dilute sprays when working in the cone-jet mode. Evolution of an electrospray with droplet diameter below 10 μm is studied with phase Doppler particle analyzer (PDPA) and the exciplex-PLIF technique. The evaporation rate constant is determined from droplet velocity and diameter measured with a PDPA and is found to sharply increase with the velocity slip and the coflow temperature. Fluorescence around 400 nm, usually referred to as TMPD fluorescence, is calibrated with a heated, laminar, coflow vapor jet diluted with nitrogen. The TMPD fluorescence yield nonlinearly increases with temperature up to 538 K and then declines. Single-shot images show that fluorescence around 400 nm is mainly generated from TMPD vapor and that from droplets can be neglected as a first analysis; however, fluorescence around 490 nm, usually referred to as exciplex fluorescence, is generated from both droplets and fuel vapor immediately around droplets. Exciplex fluorescence is correlated with PDPA measurements and TMPD fluorescence. Effects of temperature, fuel composition, overlap of fluorescent spectra, and chemical equilibrium for exciplex formation are discussed. Technical challenges for quantitative exciplex-PLIF measurements are highlighted.

  8. Electrospray Modifications for Advancing Mass Spectrometric Analysis

    PubMed Central

    Meher, Anil Kumar; Chen, Yu-Chie

    2017-01-01

    Generation of analyte ions in gas phase is a primary requirement for mass spectrometric analysis. One of the ionization techniques that can be used to generate gas phase ions is electrospray ionization (ESI). ESI is a soft ionization method that can be used to analyze analytes ranging from small organics to large biomolecules. Numerous ionization techniques derived from ESI have been reported in the past two decades. These ion sources are aimed to achieve simplicity and ease of operation. Many of these ionization methods allow the flexibility for elimination or minimization of sample preparation steps prior to mass spectrometric analysis. Such ion sources have opened up new possibilities for taking scientific challenges, which might be limited by the conventional ESI technique. Thus, the number of ESI variants continues to increase. This review provides an overview of ionization techniques based on the use of electrospray reported in recent years. Also, a brief discussion on the instrumentation, underlying processes, and selected applications is also presented. PMID:28573082

  9. Some thoughts on electrospray ionization mechanisms.

    PubMed

    Crotti, Sara; Seraglia, Roberta; Traldi, Pietro

    2011-01-01

    Electrospray ionization (ESI) mechanisms are highly complex, due to a series of physical and chemical phenomena taking place on a complex system, as a solution is. In fact, even if the solution of an analyte in a protic medium can be considered at first sight to be a two-component system, the presence of solvent dissociation equilibria and the possible interactions solvent-solvent dissociation products, solvent dissociation products-analyte make this system highly complex, also for the presence of possible ionic compounds (for example, Na(+), K(+)) which strongly affect the above equilibria. A high number of research articles have been published, mainly devoted to charged droplet production and to gas-phase ion generation. They all show the high complexity of the processes affecting electrospray measurements related to either the chemical equilibria present in the condensed phase and to electrolysis processes at the emitter tip or to the processes occurring in the sprayed droplets. As a result, the chemical composition inside the small droplets from which the analyte ions are generated can be significantly different from those in sprayed solution. In this review, after a short survey of the proposed ESI mechanisms, some experiments are described. They were performed to examine if ion mobility in solution, before the formation of the sprayed charged droplets, can affect the ESI results. The data, obtained by studying both inorganic and organic analytes, indicate that the ESI spectra are dependent on the analyte dimension and charge state which, as a consequence, affect their ion mobility in solution.

  10. Coaxial electrospray of microparticles and nanoparticles for biomedical applications

    PubMed Central

    Zhang, Leilei; Huang, Jiwei; Si, Ting; Xu, Ronald X

    2013-01-01

    Coaxial electrospray is an electrohydrodynamic process that produces multilayer microparticles and nanoparticles by introducing coaxial electrified jets. In comparison with other microencapsulation/nanoencapsulation processes, coaxial electrospray has several potential advantages such as high encapsulation efficiency, effective protection of bioactivity and uniform size distribution. However, process control in coaxial electrospray is challenged by the multiphysical nature of the process and the complex interplay of multiple design, process and material parameters. This paper reviews the previous works and the recent advances in design, modeling and control of a coaxial electrospray process. The review intends to provide general guidance for coaxial electrospray and stimulate further research and development interests in this promising microencapsulation/nanoencapsulation process. PMID:23249155

  11. Coaxial electrospray of microparticles and nanoparticles for biomedical applications.

    PubMed

    Zhang, Leilei; Huang, Jiwei; Si, Ting; Xu, Ronald X

    2012-11-01

    Coaxial electrospray is an electrohydrodynamic process that produces multilayer microparticles and nanoparticles by introducing coaxial electrified jets. In comparison with other microencapsulation/nanoencapsulation processes, coaxial electrospray has several potential advantages such as high encapsulation efficiency, effective protection of bioactivity and uniform size distribution. However, process control in coaxial electrospray is challenged by the multiphysical nature of the process and the complex interplay of multiple design, process and material parameters. This paper reviews the previous works and the recent advances in design, modeling and control of a coaxial electrospray process. The review intends to provide general guidance for coaxial electrospray and stimulate further research and development interests in this promising microencapsulation/nanoencapsulation process.

  12. Characteristics of pulsatile blood flow through the curved bileaflet mechanical heart valve installed in two different types of blood vessels: velocity and pressure of blood flow.

    PubMed

    Bang, Jin Seok; Yoo, Song Min; Kim, Chang Nyung

    2006-01-01

    The aim of this study was to investigate the flow fields of blood flowing through the curved bileaflet mechanical heart valve. A numerical analysis was carried out with the fluid-structure interaction between the blood flow and the motion of leaflets in two different types of blood vessels (type A, with sinus blood vessel, and type B, without sinus blood vessel). When the leaflet was fully opened, a fluttering phenomenon was detected in association with the blood flow, and recirculation flows were observed in the sinus region of the blood vessel for type A. During the closing phase, regurgitation was formed between the ring and the edge of the each leaflet for both types. When the leaflet came into contact with the valve ring at the end of the closing phase, rebound of the leaflet occurred. In consideration of the entire domain, the pressure drop occurs mainly in the valve region. The present results showed tendencies similar to those obtained by previous experiments for blood flow and contribute to the development of the curved bileaflet mechanical heart valve prostheses.

  13. Structural characterization of secoiridoid glycosides by high-performance liquid chromatography/electrospray ionization mass spectrometry.

    PubMed

    Wang, Shufang; Xu, Yimin; Chen, Pinghong; Zhang, Yufeng

    2014-07-30

    The fragmentation behavior of seven secoiridoid glycosides (SIGs) isolated from Gentiana triflora Pall., a traditional Chinese medicine, was investigated by electrospray ionization ion trap mass spectrometry (ESI-IT-MS). Multistage electrospray ionization mass spectrometry (ESI-MS(n)) experiments both in positive- and negative-ion mode were used to elucidate the main fragmentation pathways of these compounds. In full scan mass spectra, different deprotonated or protonated molecules were observed for compounds with different basic structure. Ring cleavages of the aglycon moiety were observed in MS(2) spectra and the characteristic ions provided valuable information on the basic structural skeletons. Their fragmentation pathways and fragment ion structures were proposed. The established fragmentation patterns have been successfully used to identify eleven SIGs in the extract of Gentiana triflora Pall. Copyright © 2014 John Wiley & Sons, Ltd.

  14. Effect of Schroth exercises on curve characteristics and clinical outcomes in adolescent idiopathic scoliosis: protocol for a multicentre randomised controlled trial.

    PubMed

    Schreiber, Sanja; Parent, Eric C; Hedden, Douglas M; Moreau, Marc; Hill, Doug; Lou, Edmond

    2014-12-01

    The promising results of Schroth scoliosis-specific exercises for adolescent idiopathic scoliosis found in low-quality studies will be strengthened by confirmation in a randomised controlled trial. 1. Are Schroth exercises combined with standard care for 6 months more effective than standard care alone in improving radiographic and clinical outcomes for adolescents with idiopathic scoliosis? 2. Will the outcomes of the control group (who will be offered Schroth therapy delayed by 6 months) improve after 6 months of Schroth therapy? 3. Are the effects maintained 6 months after discontinuing the supervised intervention? This is an assessor-blinded and statistician-blinded randomised controlled trial with transfer of the controls to the exercise group after 6 months. Two hundred and fifty-eight consecutive adolescents with idiopathic scoliosis, aged 10 to 16 years, treated with or without a brace, with curves between 10 and 45 deg Cobb and Risser sign ≤ 3 will be recruited from three scoliosis clinics. Combined with standard care, the Schroth group will receive five individual training sessions, followed by weekly group classes and daily home exercises for 6 months. Controls will only receive standard care consisting of observation or bracing, and will be offered Schroth therapy 6 months later. Curve severity (Cobb angle) and vertebral rotation will be assessed from radiographs at baseline, 6 and 12 months. Secondary clinical outcomes (back muscle endurance, surface topography measures of posture, and self-reported perceived spinal appearance and quality of life) will be assessed at baseline, and every 3 months until 1-year follow-up. Data will be analysed using intention-to-treat linear mixed models. The results will demonstrate whether Schroth exercises combined with standard of care can improve outcomes in adolescents with idiopathic scoliosis. This study has potential to influence clinical practice worldwide, where exercises are not routinely prescribed for

  15. Nanoparticle preparation of Mefenamic acid by electrospray drying

    SciTech Connect

    Zolkepali, Nurul Karimah Bakar, Noor Fitrah Abu Anuar, Nornizar; Naim, M. Nazli; Bakar, Mohd Rushdi Abu

    2014-02-24

    Nanoparticles preparation of Mefenamic acid (MA) by using an electrospray drying method was conducted in this study. Electrospray drying is a process that uses electrostatic force to disperse a conductive liquid stream into fine charged droplets through the coulomb fission of charges in the liquid and finally dry into fine particles. Electrospray drying modes operation usually in Taylor cone jet, and it was formed by controlling applied voltage and liquid flow rate. A conductive liquid (2.77–8.55μScm{sup −1}) which is MA solution was prepared by using acetone with concentration 0.041 and 0.055 M before pumping at a flow rate of 3–6ml/h. By applying the applied voltage at 1.3–1.5 kV, Taylor cone jet mode was formed prior to the electrospray. During electrospray drying process, solvent evaporation from the droplet was occurring that leads to coulomb disruption and may generate to nanoparticles. The dried nanoparticles were collected on a grounded substrate that was placed at varying distance from the electrospray. MA particle with size range of 100–400 nm were produced by electrospray drying process. Characterization of particles by using X-ray diffractometry (XRD) and differential scanning calorimetry (DSC) show that particles formed into polymorph I.

  16. Electrospray and tandem mass spectrometry in biochemistry.

    PubMed Central

    Griffiths, W J; Jonsson, A P; Liu, S; Rai, D K; Wang, Y

    2001-01-01

    Over the last 20 years, biological MS has changed out of all recognition. This is primarily due to the development in the 1980s of 'soft ionization' methods that permit the ionization and vaporization of large, polar, and thermally labile biomolecules. These developments in ionization mode have driven the design and manufacture of smaller and cheaper mass analysers, making the mass spectrometer a routine instrument in the biochemistry laboratory today. In the present review the revolutionary 'soft ionization' methods will be discussed with particular reference to electrospray. The mass analysis of ions will be described, and the concept of tandem MS introduced. Where appropriate, examples of the application of MS in biochemistry will be provided. Although the present review will concentrate on the MS of peptides/proteins and lipids, all classes of biomolecules can be analysed, and much excellent work has been done in the fields of carbohydrate and nucleic acid biochemistry. PMID:11311115

  17. Combined electrophoresis-electrospray interface and method

    DOEpatents

    Smith, R.D.; Udseth, H.R.; Olivares, J.A.

    1994-10-18

    A system and method for analyzing molecular constituents of a composition sample include: forming a solution of the sample, separating the solution by capillary electrophoresis into an eluent of constituents longitudinally separated according to their relative electrophoretic mobilities, electrospraying the eluent to form a charged spray in which the molecular constituents have a temporal distribution; and detecting or collecting the separated constituents in accordance with the temporal distribution in the spray. A first high-voltage (e.g., 5--100 kVDC) is applied to the solution. The spray is charged by applying a second high voltage (e.g.,{+-}2--8 kVDC) between the eluent at the capillary exit and a cathode spaced in front of the exit. A complete electrical circuit is formed by a conductor which directly contacts the eluent at the capillary exit, or by conduction through a sheath electrode discharged in an annular sheath flow about the capillary exit. 21 figs.

  18. Electrospray and tandem mass spectrometry in biochemistry.

    PubMed

    Griffiths, W J; Jonsson, A P; Liu, S; Rai, D K; Wang, Y

    2001-05-01

    Over the last 20 years, biological MS has changed out of all recognition. This is primarily due to the development in the 1980s of 'soft ionization' methods that permit the ionization and vaporization of large, polar, and thermally labile biomolecules. These developments in ionization mode have driven the design and manufacture of smaller and cheaper mass analysers, making the mass spectrometer a routine instrument in the biochemistry laboratory today. In the present review the revolutionary 'soft ionization' methods will be discussed with particular reference to electrospray. The mass analysis of ions will be described, and the concept of tandem MS introduced. Where appropriate, examples of the application of MS in biochemistry will be provided. Although the present review will concentrate on the MS of peptides/proteins and lipids, all classes of biomolecules can be analysed, and much excellent work has been done in the fields of carbohydrate and nucleic acid biochemistry.

  19. Combined electrophoresis-electrospray interface and method

    DOEpatents

    Smith, R.P.; Udseth, H.R.; Olivares, J.A.

    1989-12-05

    A system and method for analyzing molecular constituents of a composition sample includes: forming a solution of the sample, separating the solution by capillary electrophoresis into an eluent of constituents longitudinally separated according to their relative electrophoretic mobilities, electrospraying the eluent to form a charged spray in which the molecular constituents have a temporal distribution; and detecting or collecting the separated constituents in accordance with the temporal distribution in the spray. A first high-voltage (e.g., 5--100 kVDC) is applied to the solution. The spray is charged by applying a second high voltage (e.g., [+-]2--8 kVDC) between the eluent at the capillary exit and a cathode spaced in front of the exit. A complete electrical circuit is formed by a conductor which directly contacts the eluent at the capillary exit, or by conduction through a sheath electrode discharged in an annular sheath flow about the capillary exit. 21 figs.

  20. Combined electrophoresis-electrospray interface and method

    DOEpatents

    Smith, Richard D.; Udseth, Harold R.; Olivares, Jose A.

    1994-10-18

    A system and method for analyzing molecular constituents of a composition sample includes: forming a solution of the sample, separating the solution by capillary electrophoresis into an eluent of constituents longitudinally separated according to their relative electrophoretic mobilities, electrospraying the eluent to form a charged spray in which the molecular constituents have a temporal distribution; and detecting or collecting the separated constituents in accordance with the temporal distribution in the spray. A first high-voltage (e.g., 5-100 KVDC) is applied to the solution. The spray is charged by applying a second high voltage (e.g., .+-.2-8 KVDC) between the eluent at the capillary exit and a cathode spaced in front of the exit. A complete electrical circuit is formed by a conductor which directly contacts the eluent at the capillary exit, or by conduction through a sheath electrode discharged in an annular sheath flow about the capillary exit.

  1. Combined electrophoresis-electrospray interface and method

    DOEpatents

    Smith, Richard P.; Udseth, Harold R.; Olivares, Jose A.

    1989-01-01

    A system and method for analyzing molecular constituents of a composition sample includes: forming a solution of the sample, separating the solution by capillary electrophoresis into an eluent of constituents longitudinally separated according to their relative electrophoretic mobilities, electrospraying the eluent to form a charged spray in which the molecular constituents have a temporal distribution; and detecting or collecting the separated constituents in accordance with the temporal distribution in the spray. A first high-voltage (e.g., 5-100 KVDC) is applied to the solution. The spray is charged by applying a second high voltage (e.g., .+-.2-8 KVDC) between the eluent at the capillary exit and a cathode spaced in front of the exit. A complete electrical circuit is formed by a conductor which directly contacts the eluent at the capillary exit, or by conduction through a sheath electrode discharged in an annular sheath flow about the capillary exit.

  2. Submerged electrosprays: a versatile approach for microencapsulation.

    PubMed

    Jayasinghe, S N

    2007-08-01

    The unearthing of fundamental science and technology associated with microencapsulation is an ongoing exciting scientific endeavour focused on by several scientists. Encapsulated structures (containing either a gas, molecules or materials) previously have been shown as having widespread applications across the physical and life sciences. In particular, such methodologies used for forming encapsulations in medical-related studies have shown great promise from diagnostics and imaging, to gene therapy and drug delivery which are only a few amongst several other applications. At present there are numerous 'jet-based' manifestations available for microencapsulation, these primarily root from either capillary or channel-based techniques. The driving mechanisms employed in these approaches exploit aerodynamic/pressure gradients to piezoelectricity. In this paper submerged electrosprays a multipurpose electric field driven jet-based technique is explored for forming near mono-dispersed encapsulations sized in the micrometer range. Our studies elucidate the ability to form microencapsulations containing either a gas or a micro/nanoparticulate-based material suspension as capsules sized in the ranges approximately 65-80 microm, approximately 8-25 microm to approximately 3-14 microm, respectively. We believe this technique can significantly contribute to the microencapsulation field of research based on both the size of the generated encapsulations to the containment of immiscible high viscosity particulate-based suspensions. Furthermore our investigations show the ability to control the production of these encapsulations in terms of both their size and rate of generation with ease; hence demonstrating this electrospray-assisted microencapsulation route as having a wide range of applications. It should be noted that in its present form this technique could be explored for generating emulsions with a variety of materials especially with living organisms for applications in the

  3. A new cluster-ion-beam source for secondary ion mass spectrometry (SIMS) using the electrospray of a pure ionic liquid under high vacuum

    NASA Astrophysics Data System (ADS)

    Fujiwara, Yukio; Saito, Naoaki; Nonaka, Hidehiko; Nakanaga, Taisuke; Ichimura, Shingo

    2010-06-01

    Electrospray characteristics were studied using a pure room-temperature molten salt (i.e., an ionic liquid) at pressures around 10 -5 Pa as well as at atmospheric pressure. The ionic liquid N,N-diethyl-N-methyl-N-(2-methoxyethyl)ammonium bis(trifluoromethanesulfonyl)imide was tested, which has negligible vapor pressure and high conductivity. During electrospray, the ionic liquid was introduced at a constant flow rate into a stainless-steel capillary (i.d. 30 μm). It was demonstrated that stable electrosprayed currents exceeding ±1 μΑ were continuously produced in both positive and negative modes. The electrosprayed currents in a high vacuum were twice those at atmospheric pressure. It was found that gas pressure rose slightly with increasing electrosprayed currents. Residual gas analysis revealed that gas component at negative mode was different from that at positive mode. Experimental results indicate that vacuum electrospray of pure ionic liquids is applicable to a massive-cluster beam source for SIMS.

  4. A research program to reduce interior noise in general aviation airplanes. Influence of depressurization and damping material on the noise reduction characteristics of flat and curved stiffened panels

    NASA Technical Reports Server (NTRS)

    Navaneethan, R.; Streeter, B.; Koontz, S.; Roskam, J.

    1981-01-01

    Some 20 x 20 aluminum panels were studied in a frequency range from 20 Hz to 5000 Hz. The noise sources used were a swept sine wave generator and a random noise generator. The effect of noise source was found to be negligible. Increasing the pressure differential across the panel gave better noise reduction below the fundamental resonance frequency due to an increase in stiffness. The largest increase occurred in the first 1 psi pressure differential. The curved, stiffened panel exhibited similar behavior, but with a lower increase of low frequency noise reduction. Depressurization on these panels resulted in decreased noise reduction at higher frequencies. The effect of damping tapes on the overall noise reduction values of the test specimens was small away from the resonance frequency. In the mass-law region, a slight and proportional improvement in noise reduction was observed by adding damping material. Adding sound absorbtion material to a panel with damping material beneficially increased noise reduction at high frequencies.

  5. An investigation of thermocapillary effects on the wetting characteristics of a heated, capillary re-supplied, curved meniscus within a capillary pore

    SciTech Connect

    Pratt, D.M.; Hallinan, K.P.

    1996-12-31

    An investigation of thermocapillary effects on a heated, evaporating meniscus formed by a wetting liquid in a vertical capillary tube has been completed. Experiments were conducted to primarily observe how the wetting characteristics of the working fluid (pentane) are affected by the dynamics associated with the heating of and evaporation from a meniscus. The results have demonstrated that interfacial thermocapillary stresses arising from liquid-vapor interfacial temperature gradients can noticeably degrade the ability of the liquid to wet the pore.

  6. Curved Finite Elements and Curve Approximation

    NASA Technical Reports Server (NTRS)

    Baart, M. L.

    1985-01-01

    The approximation of parameterized curves by segments of parabolas that pass through the endpoints of each curve segment arises naturally in all quadratic isoparametric transformations. While not as popular as cubics in curve design problems, the use of parabolas allows the introduction of a geometric measure of the discrepancy between given and approximating curves. The free parameters of the parabola may be used to optimize the fit, and constraints that prevent overspill and curve degeneracy are introduced. This leads to a constrained optimization problem in two varibles that can be solved quickly and reliably by a simple method that takes advantage of the special structure of the problem. For applications in the field of computer-aided design, the given curves are often cubic polynomials, and the coefficient may be calculated in closed form in terms of polynomial coefficients by using a symbolic machine language so that families of curves can be approximated with no further integration. For general curves, numerical quadrature may be used, as in the implementation where the Romberg quadrature is applied. The coefficient functions C sub 1 (gamma) and C sub 2 (gamma) are expanded as polynomials in gamma, so that for given A(s) and B(s) the integrations need only be done once. The method was used to find optimal constrained parabolic approximation to a wide variety of given curves.

  7. Determination of procarbazine in human plasma by liquid chromatography with electrospray ionization mass spectrometry.

    PubMed

    He, X; Batchelor, T T; Grossman, S; Supko, J G

    2004-01-25

    Procarbazine is a cytotoxic chemotherapeutic agent used in the treatment of lymphomas and brain tumors. Its pharmacokinetic behavior remains poorly understood even though more than 30 years have elapsed since the drug was approved for clinical use. To characterize the pharmacokinetics of procarbazine in brain cancer patients during a phase I trial, a method for determining the drug in human plasma by reversed-phase high-performance liquid chromatography (HPLC) with electrospray ionization mass spectrometry (ESI-MS) was developed and thoroughly validated. Plasma samples were prepared for analysis by precipitating proteins with trichloroacetic acid and washing the protein-free supernatant with methyl tert-butyl ether to remove excess acid. The solution was separated on a Luna C-18 analytical column using methanol-25 mM ammonium acetate buffer, pH 5.1 (22:78, v/v) as the mobile phase at 1.0 ml/min. A single-quadrupole mass spectrometer with an electrospray interface was operated in the selected-ion monitoring mode to detect the [M+H](+) ions at m/z 222.2 for procarbazine and at m/z 192.1 for the internal standard (3-dimethylamino-2-methylpropiophenone). Procarbazine and the internal standard eluted as sharp, symmetrical peaks with retention times (mean+/-S.D.) of 6.3+/-0.1 and 9.9+/-0.3 min, respectively. Calibration curves of procarbazine hydrochloride in human plasma at concentrations ranging from 0.5 to 50 ng/ml exhibited excellent linearity. The mean absolute recovery of the drug from plasma was 102.9+/-1.0%. Using a sample volume of 150 microl, procarbazine was determined at the 0.5 ng/ml (1.9 nM) lower limit of quantitation with a mean accuracy of 105.2% and an interday precision of 3.60% R.S.D. on 11 different days over 5 weeks. During this same time interval, the between-day accuracy for determining quality control solutions of the drug in plasma at concentrations of 2.0, 15 and 40 ng/ml ranged from 97.5 to 98.2% (mean+/-S.D., 97.9+/-0.4%) and the precision

  8. Application of co-eluting structural analog internal standards for expanded linear dynamic range in liquid chromatography/electrospray mass spectrometry.

    PubMed

    Shi, Guoen

    2003-01-01

    Non-linear standard calibration curves occur frequently in liquid chromatography/electrospray ionization mass spectrometry (LC/ESI-MS), necessitating the use of non-linear regression curve fitting or a reduction in assay dynamic range. Non-linearity can be minimized by the use of stable isotope internal standards, if the cause of curve bending is ionization saturation. Unfortunately, stable isotope internal standards can be difficult or expensive to synthesize. Structural analog internal standards, if sufficiently close to analytes both in chemical structures and HPLC retention times, may mimic the effect of stable isotope internal standards. Tentative experimental evidence supporting this concept is presented in this paper.

  9. The Analysis of the Reliability and Factorial Validity in the Basic Characteristics of Isometric F-t curve of the Leg Extensors in Well Trained Serbian Males and Females

    NASA Astrophysics Data System (ADS)

    Dopsaj, Milivoj; Ivanović, Jelena

    2011-01-01

    The aim of this research was to establish the reliability and factorial validity of different isometric basic characteristics of F-t curve related to leg extensors in well trained and healthy Serbian males and females. Sample consisted of 159 examinees. In order to assess characteristics of the F-t isometric leg extensor force, tensiometric probe and standardized "seating leg extension" test were used. The measurement range was defined by 4 variables regarding the contractile characteristics of the leg extensor isometric muscle force - 1) the level of the achieved maximal force - FmaxLegExtISO, 2) the indicator of basic (general) level of rate of force development - RFDBASICLegExtISO, 3) the time necessary to reach maximal force - tFmaxLegExtISO, 4) basic synergy index. The results showed a high statistical significance of p<0.001 in representability, generalizability and reliability for all the characteristics observed in both genders (Spearman-Brown r - 0.715 to 0.967 for males and 0.713 to 0.941 for females). As for the methodology aspect of testing, the factor analysis demonstrated the necessity of conducting at least three trials, choosing the best result from the two last trials.

  10. Electrospray-printed nanostructured graphene oxide gas sensors.

    PubMed

    Taylor, Anthony P; Velásquez-García, Luis F

    2015-12-18

    We report low-cost conductometric gas sensors that use an ultrathin film made of graphene oxide (GO) nanoflakes as transducing element. The devices were fabricated by lift-off metallization and near-room temperature, atmospheric pressure electrospray printing using a shadow mask. The sensors are sensitive to reactive gases at room temperature without requiring any post heat treatment, harsh chemical reduction, or doping with metal nanoparticles. The sensors' response to humidity at atmospheric pressure tracks that of a commercial sensor, and is linear with changes in humidity in the 10%-60% relative humidity range while consuming <6 μW. Devices with GO layers printed by different deposition recipes yielded nearly identical response characteristics, suggesting that intrinsic properties of the film control the sensing mechanism. The gas sensors successfully detected ammonia at concentrations down to 500 ppm (absolute partial pressure of ∼5 × 10(-4) T) at ∼1 T pressure, room temperature conditions. The sensor technology can be used in a great variety of applications including air conditioning and sensing of reactive gas species in vacuum lines and abatement systems.

  11. Subcellular analysis by laser ablation electrospray ionization mass spectrometry

    DOEpatents

    Vertes, Akos; Stolee, Jessica A; Shrestha, Bindesh

    2014-12-02

    In various embodiments, a method of laser ablation electrospray ionization mass spectrometry (LAESI-MS) may generally comprise micro-dissecting a cell comprising at least one of a cell wall and a cell membrane to expose at least one subcellular component therein, ablating the at least one subcellular component by an infrared laser pulse to form an ablation plume, intercepting the ablation plume by an electrospray plume to form ions, and detecting the ions by mass spectrometry.

  12. Fabrication and Testing of Tapered Electro-spray Nozzles

    DTIC Science & Technology

    2012-09-01

    oxidized nozzle with broken top cap. 15 The ultrasonic breaking of the etch mask was found to be a low-yield methodology, with some caps breaking...Fabrication and Testing of Tapered Electro-spray Nozzles by Brendan M. Hanrahan and C. Mike Waits ARL-TR-6226 September 2012...September 2012 Fabrication and Testing of Tapered Electro-spray Nozzles Brendan M. Hanrahan and C. Mike Waits Sensors and Electron Devices

  13. Laser electrospray mass spectrometry of adsorbed molecules at atmospheric pressure

    NASA Astrophysics Data System (ADS)

    Brady, John J.; Judge, Elizabeth J.; Simon, Kuriakose; Levis, Robert J.

    2010-02-01

    Atmospheric pressure mass analysis of solid phase biomolecules is performed using laser electrospray mass spectrometry (LEMS). A non-resonant femtosecond duration laser pulse vaporizes native samples at atmospheric pressure for subsequent electrospray ionization and transfer into a mass spectrometer. LEMS was used to detect a complex molecule (irinotecan HCl), a complex mixture (cold medicine formulation with active ingredients: acetaminophen, dextromethorphan HBr and doxylamine succinate), and a biological building block (deoxyguanosine) deposited on steel surfaces without a matrix molecule.

  14. Feasibility of formation of hot ions in electrospray.

    PubMed

    Takáts, Zoltán; Drahos, László; Schlosser, Gitta; Vékey, Károly

    2002-12-15

    Internal energy changes during the electrospray process have been studied. Our results suggest that, contrary to conventional wisdom, ions that are quite hot are formed in electrospray, even without acceleration in the cone-skimmer region. The main role of the curtain gas seems to be not to break up existing clusters but, rather, to cool down the nascent ions and to prevent cluster formation by shielding them from solvent vapors.

  15. Nanoparticles facilitate gene delivery to microorganisms via an electrospray process.

    PubMed

    Lee, Yi-Hsuan; Wu, Bing; Zhuang, Wei-Qin; Chen, Da-Ren; Tang, Yinjie J

    2011-02-01

    In this study, we developed a technique for delivering genes to microorganisms via electrospray of gold nanoparticles. During the electrospray process, charged monodisperse nano-droplets (a mixture of pET30a-GFP plasmid and nano-sized gold particles) were accelerated and deposited on a thin layer of non-competent Escherichia coli cells. Via antibiotic selection, transformed cells containing green fluorescent protein appeared on the agar plates. PCR amplification and restriction enzyme analysis further confirmed that pET30a-GFP plasmid had successfully been delivered into the non-competent E. coli cells. The transformation efficiencies were optimized under different electrospray conditions. Among several electrospray buffer solutions, CaCl(2) (0.01M) was found to be the best for gene delivery. Furthermore, gold nanoparticles (NPs, 50 nm diameter) significantly improved plasmid transformation efficiency by 5-7 fold (up to 2×10(6) CFU/μg plasmid) compared with that obtained using naked plasmid. Electronic microscopy images and gel electrophoresis showed that the morphology of plasmids remained unchanged during the electrospray process, but cellular membrane integrity was reduced after being electrosprayed with gold NPs and CaCl(2) buffer solutions. This gene delivery method has the potential to work for many other microorganisms. Copyright © 2010 Elsevier B.V. All rights reserved.

  16. Aerodynamic mass spectrometry interfacing of microdevices without electrospray tips.

    PubMed

    Grym, Jakub; Otevrel, Marek; Foret, Frantisek

    2006-10-01

    A new concept for electrospray coupling of microfluidic devices with mass spectrometry was developed. The sampling orifice of the time-of-flight mass spectrometer was modified with an external adapter assisting in formation and transport of the electrosprayed plume from the multichannel polycarbonate microdevice. The compact disk sized microdevice was designed with radial channels extending to the circumference of the disk. The electrospray exit ports were formed by the channel openings on the surface of the disk rim. No additional tips at the channel exits were used. Electrospray was initiated directly from the channel openings by applying high voltage between sample wells and the entrance of the external adapter. The formation of the spatially unstable droplet at the electrospray openings was eliminated by air suction provided by a pump connected to the external adapter. Compared with the air intake through the original mass spectrometer sampling orifice, more than an order of magnitude higher flow rate was achieved for efficient transport of the electrospray plume into the mass spectrometer. Additional experiments with electric potentials applied between the entrance sections of the external adapter and the mass spectrometer indicated that the air flow was the dominant transport mechanism. Basic properties of the system were tested using mathematical modeling and characterized using ESI/TOF-MS measurements of peptide and protein samples.

  17. Ambient gas influence on electrospray potential as revealed by potential mapping within the electrospray capillary.

    PubMed

    Pozniak, Boguslaw P; Cole, Richard B

    2007-05-01

    The effect of ambient gas on potentials inside the electrospray (ES) capillary was investigated. Potential measurements and differential electrospray emitter potential (DEEP) maps were obtained with the help of a small, movable, disklike platinum wire electrode inserted into the ES capillary. Typical solvents used for electrospray mass spectrometry such as methanol and mixtures of methanol-water and chloroform/methanol have been tested. It was found that oxygen is readily adsorbed from the surrounding ambient gas into the spraying liquid. Following adsorption, it resides in, or near to, the Taylor cone, thereby affecting the electrochemical potential near the ES capillary exit, as well as the character of the inherent electrochemical reactions occurring during the ES process. The potentials measured in an air environment with reactive oxygen present are contrasted against those obtained in an inert nitrogen environment. The kinetics of oxygen admission have been found to be quite fast, i.e., occurring in a matter of seconds, but it takes far longer to purge the system of oxygen by changing the ambient atmosphere to nitrogen. The oxygen effect is present in negative and positive ion modes of ES, but the total ES current is not affected by the change of ambient gas. The magnitude of the oxygen effect owing to ambient air was compared to the effect caused by initially dissolving oxygen in the solution prior to the start of ES; it was found that the presence of oxygen in the ambient gas has a far greater consequence. These results indicate that the presence of reactive gases, such as molecular oxygen, in the region of the ES emitter may have unintended secondary effects on the ES process prior to mass spectrometric analysis.

  18. Harmonic Measure of Critical Curves

    SciTech Connect

    Bettelheim, E.; Rushkin, I.; Gruzberg, I.A.; Wiegmann, P.

    2005-10-21

    Fractal geometry of critical curves appearing in 2D critical systems is characterized by their harmonic measure. For systems described by conformal field theories with central charge c{<=}1, scaling exponents of the harmonic measure have been computed by Duplantier [Phys. Rev. Lett. 84, 1363 (2000)] by relating the problem to boundary two-dimensional gravity. We present a simple argument connecting the harmonic measure of critical curves to operators obtained by fusion of primary fields and compute characteristics of the fractal geometry by means of regular methods of conformal field theory. The method is not limited to theories with c{<=}1.

  19. Investigating Effects of Climate Seasonality, Catchment Characteristics and Socio-economic Factors on the Budyko Curve Parameter w at Different Spatiotemporal Scales

    NASA Astrophysics Data System (ADS)

    Wang, W.; Xing, W.; Zou, S.

    2016-12-01

    One parameter model, Budyko-type equations have begun to be widely adopted to quantify long-term average water balance in catchment scale and, also to separate the contributions of climate change and human activities to the variation of runoff. Acknowledging that climate seasonality, landscape characteristics and socio-economic factors may multi-dimensionally affect the model parameter w. In this paper, a multivariate adaptive regression spline (MARS) model is proposed to determine statistically significant factors among the complicated factors and to identify their interactions on the model parameter w at the spatial scale. In order to investigate the impacts of climate change and human activities on the model parameter w at the temporal scale, the relationship of the parameter w in Budyko-type equation with climatic and human factors is firstly built to reveal the time-variation process of w by using an 11-year moving window, then the impacts of climate change and human activities on runoff are separated by using the sensitivity method. Quantifying the impact of climate and land use/cover change on water yield is important for catchment management planning and decision making.

  20. Voice Handicap Index and Interpretation of the Cutoff Points Using Receiver Operating Characteristic Curve as Screening for Young Adult Female Smokers.

    PubMed

    Tafiadis, Dionysios; Kosma, Evangelia I; Chronopoulos, Spyridon K; Papadopoulos, Aggelos; Drosos, Konstantinos; Siafaka, Vassiliki; Toki, Eugenia I; Ziavra, Nausica

    2017-04-06

    The relationship between smoking and alterations of the vocal tract and larynx is well known. This pathology leads to the degradation of voice performance in daily living. Multiple assessment methods of vocal tract and larynx have been developed, and in recent years they were enriched with self-reported questionnaires such as Voice Handicap Index (VHI). This study determined the cutoff points of VHI's total score and its three domains for young female smokers in Greece. These estimated cutoff points could be used by voice specialists as an indicator for further clinical evaluation (foreseeing a potential risk of developing a vocal symptom because of smoking habits). A sample of 120 female nondysphonic smokers (aged 18-31) was recruited. Participants filled out the VHI and Voice Evaluation Form. VHI's cutoff point of total score was calculated at the value of 19.50 (sensitivity: 0.780, 1-specificity: 0.133). Specifically, the construct domain of functional was 7.50 (sensitivity: 0.900, 1-specificity: 0.217), for physical it was 8.50 (sensitivity: 0.867, 1-specificity: 0.483), and for emotional it was 7.50 (sensitivity: 0.833, 1-specificity: 0.200) through the use of receiver operating characteristic. Furthermore, VHI could be used as a monitoring tool for smokers and as a feedback for smoking cessation. Copyright © 2017 The Voice Foundation. Published by Elsevier Inc. All rights reserved.

  1. Quantitative Caffeine Analysis Using a Surface Sampling Probe Electrospray Ionization Tandem Mass Spectrometry System

    SciTech Connect

    Ford, Michael J; Deibel, Michael A.; Tomkins, Bruce A; Van Berkel, Gary J

    2005-01-01

    Quantitative determination of caffeine on reversed-phase C8 thin-layer chromatography plates using a surface sampling electrospray ionization system with tandem mass spectrometry detection is reported. The thin-layer chromatography/electrospray tandem mass spectrometry method employed a deuterium-labeled caffeine internal standard and selected reaction monitoring detection. Up to nine parallel caffeine bands on a single plate were sampled in a single surface scanning experiment requiring 35 min at a surface scan rate of 44 {mu}m/s. A reversed-phase HPLC/UV caffeine assay was developed in parallel to assess the mass spectrometry method performance. Limits of detection for the HPLC/UV and thin-layer chromatography/electrospray tandem mass spectrometry methods determined from the calibration curve statistics were 0.20 ng injected (0.50 {mu}L) and 1.0 ng spotted on the plate, respectively. Spike recoveries with standards and real samples ranged between 97 and 106% for both methods. The caffeine content of three diet soft drinks (Diet Coke, Diet Cherry Coke, Diet Pepsi) and three diet sport drinks (Diet Turbo Tea, Speed Stack Grape, Speed Stack Fruit Punch) was measured. The HPLC/UV and mass spectrometry determinations were in general agreement, and these values were consistent with the quoted values for two of the three diet colas. In the case of Diet Cherry Coke and the diet sports drinks, the determined caffeine amounts using both methods were consistently higher (by 8% or more) than the literature values.

  2. Electrochemical processes in electrospray ionization mass spectrometry

    PubMed

    Mora; Van Berkel GJ; Enke; Cole; Martinez-Sanchez; Fenn

    2000-08-01

    Editorial Comment Last month we presented, as a Special Feature, a set of five articles that constituted a Commentary on the fundamentals and mechanism of electrospray ionization (ESI). These articles produced some lively discussion among the authors on the role of electrochemistry in ESI. Six authors participated in a detailed exchange of views on this topic, the final results of which constitute this month's Special Feature. We particularly hope that younger scientists will find value in this month's Special Feature, not only for the science that it teaches but also what it reveals about the processes by which scientific conclusions are drawn. To a degree, the contributions part the curtains on these processes and show science in action. We sincerely thank the contributors to this discussion. The give and take of intellectual debate is not always easy, and to a remarkable extent this set of authors has maintained good humor and friendships, even when disagreeing strongly on substance. Graham Cooks and Richard Caprioli Copyright 2000 John Wiley & Sons, Ltd.

  3. Micro-electrospray with stainless steel emitters.

    PubMed

    Shui, Wenqing; Yu, Yanling; Xu, Xuejiao; Huang, Zhenyu; Xu, Guobing; Yang, Pengyuan

    2003-01-01

    The physical processes underlying micro-electrospray (micro-ES) performance were investigated using a stainless steel (SS) emitter with a blunt tip. Sheathless micro-ES could be generated at a blunt SS tip without any tapering or sanding if ESI conditions were optimized. The Taylor cone was found to shrink around the inner diameter of the SS tubing, which permitted a low flow rate of 150 nL/min for sheathless microspray on the blunt tip (100 microm i.d. x 400 microm o.d.). It is believed that the wettability and/or hydrophobicity of SS tips are responsible for their micro-ES performance. The outlet orifice was further nipped to reduce the size of the spray cone and limit the flow rate to 50-150 nL/min, resulting in peptide detection down to attomole quantities consumed per spectrum. The SS emitter was also integrated into a polymethylmethacrylate microchip and demonstrated satisfactory performance in the analysis and identification of a myoglobin digest.

  4. Multiplexed electrospray scaling for liquid fuel injection

    NASA Astrophysics Data System (ADS)

    Waits, C. Mike; Hanrahan, Brendan; Lee, Ivan

    2010-10-01

    Evaporation and space-charge requirements are evaluated to understand the effect of device scaling and fuel preheating for a liquid fuel injector using a multiplexed electrospray (MES) configuration in compact combustion applications. This work reveals the influence of the droplet diameter, droplet velocity and droplet surface temperature as well as the surrounding gas temperature on the size and performance of microfabricated MES. Measurements from MES devices are used in the model to accurately account for the droplet diameter versus flow rate relationship, the minimum droplet diameter and the relevant droplet velocities. A maximum extractor electrode to ground electrode distance of 3.1 mm required to overcome space-charge forces is found to be independent of voltage or droplet velocity for large levels of multiplexing. This maximum distance also becomes the required evaporation length scale which imposes minimum fuel pre-heating requirements for large flow densities. Required fuel preheating is therefore evaluated for both ethanol and 1-butanol with combustor parameters relevant to fuel reformation, thermoelectric conversion, thermophotovoltaic conversion and thermionic conversion.

  5. A user-friendly, menu-driven, language-free laser characteristics curves graphing program for desk-top IBM PC compatible computers

    NASA Technical Reports Server (NTRS)

    Klutz, Glenn

    1989-01-01

    A facility was established that uses collected data and feeds it into mathematical models that generate improved data arrays by correcting for various losses, base line drift, and conversion to unity scaling. These developed data arrays have headers and other identifying information affixed and are subsequently stored in a Laser Materials and Characteristics data base which is accessible to various users. The two part data base: absorption - emission spectra and tabulated data, is developed around twelve laser models. The tabulated section of the data base is divided into several parts: crystalline, optical, mechanical, and thermal properties; aborption and emission spectra information; chemical name and formulas; and miscellaneous. A menu-driven, language-free graphing program will reduce and/or remove the requirement that users become competent FORTRAN programmers and the concomitant requirement that they also spend several days to a few weeks becoming conversant with the GEOGRAF library and sequence of calls and the continual refreshers of both. The work included becoming thoroughly conversant with or at least very familiar with GEOGRAF by GEOCOMP Corp. The development of the graphing program involved trial runs of the various callable library routines on dummy data in order to become familiar with actual implementation and sequencing. This was followed by trial runs with actual data base files and some additional data from current research that was not in the data base but currently needed graphs. After successful runs, with dummy and real data, using actual FORTRAN instructions steps were undertaken to develop the menu-driven language-free implementation of a program which would require the user only know how to use microcomputers. The user would simply be responding to items displayed on the video screen. To assist the user in arriving at the optimum values needed for a specific graph, a paper, and pencil check list was made available to use on the trial runs.

  6. From principal curves to granular principal curves.

    PubMed

    Zhang, Hongyun; Pedrycz, Witold; Miao, Duoqian; Wei, Zhihua

    2014-06-01

    Principal curves arising as an essential construct in dimensionality reduction and data analysis have recently attracted much attention from theoretical as well as practical perspective. In many real-world situations, however, the efficiency of existing principal curves algorithms is often arguable, in particular when dealing with massive data owing to the associated high computational complexity. A certain drawback of these constructs stems from the fact that in several applications principal curves cannot fully capture some essential problem-oriented facets of the data dealing with width, aspect ratio, width change, etc. Information granulation is a powerful tool supporting processing and interpreting massive data. In this paper, invoking the underlying ideas of information granulation, we propose a granular principal curves approach, regarded as an extension of principal curves algorithms, to improve efficiency and achieve a sound accuracy-efficiency tradeoff. First, large amounts of numerical data are granulated into C intervals-information granules developed with the use of fuzzy C-means clustering and the two criteria of information granulation, which significantly reduce the amount of data to be processed at the later phase of the overall design. Granular principal curves are then constructed by determining the upper and the lower bounds of the interval data. Finally, we develop an objective function using the criteria of information confidence and specificity to evaluate the granular output formed by the principal curves. We also optimize the granular principal curves by adjusting the level of information granularity (the number of clusters), which is realized with the aid of the particle swarm optimization. A number of numeric studies completed for synthetic and real-world datasets provide a useful quantifiable insight into the effectiveness of the proposed algorithm.

  7. Triiodide and mixed tri-halide anions from negative ion electrospray ionization of alkali halide solutions

    NASA Astrophysics Data System (ADS)

    Shukla, Anil

    2017-10-01

    Electrospray ionization of alkali halide solutions in the negative ion mode results in the formation of cluster ions of the general formula, (MX)nX-. However, alkali iodides form triiodide anion, I3-, in high abundance in addition to cluster ions. Br3- ions are observed in low abundance. Also, mixed tri-halide anions, I2Y-, are observed in high abundance when a small amount (<1%) of KI is added to other alkali halide solutions. These results are explained by the uniquely different physical characteristics of lithium and the iodide ions compared with others in the series.

  8. Protein Viability on Au Nanoparticles during an Electrospray and Electrostatic-Force-Directed Assembly Process

    DOE PAGES

    Mao, Shun; Lu, Ganhua; Yu, Kehan; ...

    2010-01-01

    We study the protein viability on Au nanoparticles during an electrospray and electrostatic-force-directed assembly process, through which Au nanoparticle-antibody conjugates are assembled onto the surface of carbon nanotubes (CNTs) to fabricate carbon nanotube field-effect transistor (CNTFET) biosensors. Enzyme-linked immunosorbent assay (ELISA) and field-effect transistor (FET) measurements have been used to investigate the antibody activity after the nanoparticle assembly. Upon the introduction of matching antigens, the colored reaction from the ELISA and the change in the electrical characteristic of the CNTFET device confirm that the antibody activity is preserved during the assembly process.

  9. Comparison between differently priced devices for digital capture of X-ray films using computed tomography as a gold standard: a multireader-multicase receiver operating characteristic curve study.

    PubMed

    Salazar, Antonio J; Camacho, Juan Camilo; Aguirre, Diego Andrés

    2011-05-01

    Film digitizers are a specialized technology that is available for scanning X-ray radiographs; however, their cost makes them unaffordable for developing countries. Thus, less expensive alternatives are used. The purpose of this study was to compare three devices for digital capture of X-ray films: a film digitizer (US $15,000), a flatbed scanner (US $1800), and a 10-megapixel digital camera (US $450), in terms of diagnostic accuracy, defined as the area under the receiver operating characteristic curves and computed tomography as the gold standard. The sample included 136 chest X-ray cases with computed tomography confirmation of the presence or absence of pneumothorax, interstitial opacities, or nodules. The readers were six radiologists who made observations of eight variables for each digital capture of the X-ray films: three main variables to determine the accuracy in the detection of the above-mentioned pathologies, four secondary variables to categorize other pathological classifications, and one variable regarding digital image quality. The receiver operating characteristic curves for each device and pathology were very similar. For the main variables, there was no significant statistical difference in diagnostic accuracy between the devices. For the secondary variables, >84% of cases were correctly classified, even those that were classified with the lowest image quality. High accuracy was determined for the three main variables (0.75 to 0.96), indicating good performance for all tested devices, despite their very different prices. Choosing a device for a teleradiology service should involve additional factors, such as capture time, maintenance concerns, and training requirements.

  10. Application of receiver operating characteristic curve in the assessment of the value of body mass index, waist circumference and percentage of body fat in the Diagnosis of Polycystic Ovary Syndrome in childbearing women.

    PubMed

    Dou, Pan; Ju, Huiyan; Shang, Jing; Li, Xueying; Xue, Qing; Xu, Yang; Guo, Xiaohui

    2016-08-24

    There are various parameters to analyze obesity, however, no standard reference to predict, screen or diagnose PCOS with various obesity parameters has been established, and the accuracy of these parameters still needs to be studied.This study was to use the receiver operating characteristic (ROC) curve to explore the different values of three obesity parameters, body mass index (BMI), waist circumference (WC) and percentage of body fat (PBF) in the diagnosis of polycystic ovary syndrome (PCOS) in Chinese childbearing women. Three hundred patients who were diagnosed with PCOS at Center of Reproductive Medicine and Genetics of Peking University First Hospital were enrolled in this study, and 110 healthy age-matched women were enrolled as controls. The characteristics of BMI, WC and PBF in PCOS patients were analyzed. Compared with the control group, all the three obesity parameters were significantly increased in PCOS group. In terms of ROC area under the curve, WC > PBF > BMI, and they were all significantly different from those of the control. At a cut-off point of 80.5 cm, WC has a sensitivity of 73.6 % and a specificity of 85 % in diagnosis of PCOS; At a cut-off point of 29 %, PBF has a sensitivity of 88.2 % and a specificity of 57.7 % in diagnosis of PCOS; and at a cut-off point of 26.6 kg/m(2), BMI has a sensitivity of 54.5 % and a specificity of 98 % in diagnosis of PCOS. WC, BMI and PBF are valuable in screening and diagnosis of PCOS in Chinese childbearing women. PBF can be used to screen PCOS as it has a better sensitivity, while BMI can be used in the diagnosis of PCOS as it has a better specificity.

  11. Separation and characterization of phenolic compounds from dry-blanched peanut skins by liquid chromatography-electrospray ionization mass spectrometry.

    PubMed

    Ma, Yuanyuan; Kosińska-Cagnazzo, Agnieszka; Kerr, William L; Amarowicz, Ryszard; Swanson, Ruthann B; Pegg, Ronald B

    2014-08-22

    A large variety of phenolic compounds, including phenolic acids (hydroxybenzoic acids, hydroxycinnamic acids, and their esters), stilbenes (trans-resveratrol and trans-piceatannol), flavan-3-ols (e.g., (-)-epicatechin, (+)-catechin, and their polymers {the proanthocyanidins, PACs}), other flavonoids (e.g., isoflavones, flavanols, and flavones, etc.) and biflavonoids (e.g., morelloflavone), were identified in dry-blanched peanut skins (PS) by this study. High-performance liquid chromatography (HPLC) coupled with electrospray ionization mass spectrometry (ESI-MS(n)) was applied to separate and identify the phenolic constituents. Reversed-phase HPLC was employed to separate free phenolic compounds as well as PAC monomers, dimers, and trimers. PACs with a degree of polymerization (DP) of >4 were chromatographed via hydrophilic interaction liquid chromatography (HILIC). Tentative identification of the separated phenolics was based solely on molecular ions and MS(n) fragmentation patterns acquired by ESI-MS in the negative-ion mode. The connection sequence of PAC oligomers (DP <5) could be deduced mainly through characteristic quinone methide (QM) cleavage ions. When the DP reached 6, only a proportion of the flavan-3-ols could be ascertained in the PACs because of the extremely complicated fragmentation patterns involved. The identification of free phenolic acids, stilbenes, and flavonoids was achieved by authentic commercial standards and also by published literature data. Quantification was performed based on peak areas of the UV (free phenolic compounds) or fluorescence (PACs) signals from the HPLC chromatograms and calibration curves of commercial standards. Overall, PS contain significantly more PACs compared to free phenolic compounds.

  12. Assessment of Reproducibility of Laser Electrospray Mass Spectrometry using Electrospray Deposition of Analyte

    NASA Astrophysics Data System (ADS)

    Sistani, Habiballah; Karki, Santosh; Archer, Jieutonne J.; Shi, Fengjian; Levis, Robert J.

    2017-05-01

    A nonresonant, femtosecond (fs) laser is employed to desorb samples of Victoria blue deposited on stainless steel or indium tin oxide (ITO) slides using either electrospray deposition (ESD) or dried droplet deposition. The use of ESD resulted in uniform films of Victoria blue whereas the dried droplet method resulted in the formation of a ring pattern of the dye. Laser electrospray mass spectrometry (LEMS) measurements of the ESD-prepared films on either substrate were similar and revealed lower average relative standard deviations for measurements within-film (20.9%) and between-films (8.7%) in comparison to dried droplet (75.5% and 40.2%, respectively). The mass spectral response for ESD samples on both substrates was linear (R2 > 0.99), enabling quantitative measurements over the selected range of 7.0 × 10-11 to 2.8 × 10-9 mol, as opposed to the dried droplet samples where quantitation was not possible (R2 = 0.56). The limit of detection was measured to be 210 fmol.

  13. Assessment of Reproducibility of Laser Electrospray Mass Spectrometry using Electrospray Deposition of Analyte

    NASA Astrophysics Data System (ADS)

    Sistani, Habiballah; Karki, Santosh; Archer, Jieutonne J.; Shi, Fengjian; Levis, Robert J.

    2017-03-01

    A nonresonant, femtosecond (fs) laser is employed to desorb samples of Victoria blue deposited on stainless steel or indium tin oxide (ITO) slides using either electrospray deposition (ESD) or dried droplet deposition. The use of ESD resulted in uniform films of Victoria blue whereas the dried droplet method resulted in the formation of a ring pattern of the dye. Laser electrospray mass spectrometry (LEMS) measurements of the ESD-prepared films on either substrate were similar and revealed lower average relative standard deviations for measurements within-film (20.9%) and between-films (8.7%) in comparison to dried droplet (75.5% and 40.2%, respectively). The mass spectral response for ESD samples on both substrates was linear (R2 > 0.99), enabling quantitative measurements over the selected range of 7.0 × 10-11 to 2.8 × 10-9 mol, as opposed to the dried droplet samples where quantitation was not possible (R2 = 0.56). The limit of detection was measured to be 210 fmol.

  14. Structural analysis of chromophore-labeled disaccharides and oligosaccharides by electrospray ionization mass spectrometry and high-performance liquid chromatography/electrospray ionization mass spectrometry.

    PubMed

    Li, D T; Her, G R

    1998-07-01

    Disaccharides and linear oligosaccharides were labeled with p-aminobenzoic ethyl ester (ABEE) chromophore and analyzed by negative ion electrospray ionization mass spectrometry (ESIMS). The formation of glycosylamines rather than reductive amination in the labeling reaction produced many characteristic fragment ions under in source collision-induced dissociation (CID). These ions provided unambiguous assignment of the position of the glycosidic linkages. This approach was extended to the analysis of linkages and the sequence of the linkages of several linear oligosaccharides. Additionally, the anomeric configuration of ABEE-labeled 1-3-, 1-4- and 1-6-linked glucose disaccharides could be differentiated according to the relative abundance of characteristic ions. Disaccharides with the same linkage but different monosaccharide compositions could be analyzed by on-line coupling of high-performance liquid chromatography with ESIMS.

  15. Cochlear microphonic broad tuning curves

    NASA Astrophysics Data System (ADS)

    Ayat, Mohammad; Teal, Paul D.; Searchfield, Grant D.; Razali, Najwani

    2015-12-01

    It is known that the cochlear microphonic voltage exhibits much broader tuning than does the basilar membrane motion. The most commonly used explanation for this is that when an electrode is inserted at a particular point inside the scala media, the microphonic potentials of neighbouring hair cells have different phases, leading to cancelation at the electrodes location. In situ recording of functioning outer hair cells (OHCs) for investigating this hypothesis is exceptionally difficult. Therefore, to investigate the discrepancy between the tuning curves of the basilar membrane and those of the cochlear microphonic, and the effect of phase cancellation of adjacent hair cells on the broadness of the cochlear microphonic tuning curves, we use an electromechanical model of the cochlea to devise an experiment. We explore the effect of adjacent hair cells (i.e., longitudinal phase cancellation) on the broadness of the cochlear microphonic tuning curves in different locations. The results of the experiment indicate that active longitudinal coupling (i.e., coupling with active adjacent outer hair cells) only slightly changes the broadness of the CM tuning curves. The results also demonstrate that there is a π phase difference between the potentials produced by the hair bundle and the soma near the place associated with the characteristic frequency based on place-frequency maps (i.e., the best place). We suggest that the transversal phase cancellation (caused by the phase difference between the hair bundle and the soma) plays a far more important role than longitudinal phase cancellation in the broadness of the cochlear microphonic tuning curves. Moreover, by increasing the modelled longitudinal resistance resulting the cochlear microphonic curves exhibiting sharper tuning. The results of the simulations suggest that the passive network of the organ of Corti determines the phase difference between the hair bundle and soma, and hence determines the sharpness of the

  16. Simultaneous determination of 13 aminoglycoside residues in foods of animal origin by liquid chromatography-electrospray ionization tandem mass spectrometry with two consecutive solid-phase extraction steps.

    PubMed

    Zhu, Wei-xia; Yang, Ji-zhou; Wei, Wei; Liu, Ya-feng; Zhang, Shu-sheng

    2008-10-17

    A confirmatory and quantitative method based on liquid chromatography-electrospray ionization tandem mass spectrometry (LC-ESI-MS/MS) has been developed for simultaneous determination of 13 aminoglycoside antibiotics in various samples. The aminoglycoside analytes were released and extracted from different matrices with 5% trichloroacetic acid. The influence of pH values on the solid-phase exaction (SPE) procedure has been studied. Due to different pK(a) values of the compounds, seven aminoglycosides (AGs) were quantitatively retained on Oasis HLB cartridges at pH<1 and then six aminoglycosides were retained at pH 8.5. Thus, the combination of two HLB SPE cartridges with different pH values was involved to simultaneously purify 13 aminoglycosides. The proposed two SPE steps produced high recovery yields for every aminoglycoside in five different matrices. The LC-MS/MS method was validated according to the European Union Commission directive 2002/657/EC. Good performance characteristics were obtained for recovery, precision, calibration curve, stability, specificity, decision limits (CCalpha) and detection capabilities (CCbeta) in different matrices. The optimized procedure has been successfully applied to real samples in our laboratories (n> or =200) for 1 year. It demonstrated that the new method was robust and useful for identification and quantification of 13 aminoglycosides residues in foods of animal origin.

  17. Degradation Study by Start-Up/Shut-Down Cycling of Superhydrophobic Electrosprayed Catalyst Layers Using a Localized Reference Electrode Technique.

    PubMed

    Ferreira-Aparicio, Paloma; Chaparro, Antonio M; Folgado, M Antonia; Conde, Julio J; Brightman, Edward; Hinds, Gareth

    2017-03-29

    Degradation of a polymer electrolyte membrane fuel cell (PEMFC) with electrosprayed cathode catalyst layers is investigated during cyclic start-up and shut-down events. The study is carried out within a single cell incorporating an array of reference electrodes that enables measurement of cell current as a function of local cathode potential (localized polarization curves). Accelerated degradation of the cell by start-up/shut-down cycling gives rise to inhomogeneous performance loss, which is more severe close to the gas outlet and occurs predominantly during start-up. The degradation consists primarily of loss of cathode catalyst activity and increase in cell internal resistance, which is attributed to carbon corrosion and Pt aggregation in both anode and cathode. Cells with an electrosprayed cathode catalyst layer show lower degradation rates during the first 100 cycles, compared with those of a conventional gas diffusion electrode. This difference in behavior is attributed to the high hydrophobicity of the electrosprayed catalyst layer microstructure, which retards the kinetics of corrosion of the carbon support. In the long term, however, the degradation rate is dominated by the Pt/C ratio in the cathode catalyst layer.

  18. Electrospray Ionization-Induced Protein Unfolding

    NASA Astrophysics Data System (ADS)

    Lin, Hong; Kitova, Elena N.; Johnson, Margaret A.; Eugenio, Luiz; Ng, Kenneth K. S.; Klassen, John S.

    2012-12-01

    Electrospray ionization mass spectrometry (ESI-MS) measurements were performed under a variety of solution conditions on a highly acidic sub-fragment (B3C) of the C-terminal carbohydrate-binding repeat region of Clostridium difficile toxin B, and two mutants (B4A and B4B) containing fewer acidic residues. ESI-MS measurements performed in negative ion mode on aqueous ammonium acetate solutions of B3C at low ionic strength ( I < 80 mM) revealed evidence, based on the measured charge state distribution, of protein unfolding. In contrast, no evidence of unfolding was detected from ESI-MS measurements made in positive ion mode at low I or in either mode at higher I. The results of proton nuclear magnetic resonance and circular dichroism spectroscopy measurements and gel filtration chromatography performed on solutions of B3C under low and high I conditions suggest that the protein exists predominantly in a folded state in neutral aqueous solutions with I > 10 mM. The results of ESI-MS measurements performed on B3C in a series of solutions with high I at pH 5 to 9 rule out the possibility that the structural changes are related to ESI-induced changes in pH. It is proposed that unfolding of B3C, observed in negative mode for solutions with low I, occurs during the ESI process and arises due to Coulombic repulsion between the negatively charged residues and liquid/droplet surface charge. ESI-MS measurements performed in negative ion mode on B4A and B4B also reveal a shift to higher charge states at low I but the magnitude of the changes are smaller than observed for B3C.

  19. Electrospray methodologies for characterization and deposition of nanoparticles

    NASA Astrophysics Data System (ADS)

    Modesto Lopez, Luis Balam

    Electrospray is an aerosolization method that generates highly charged droplets from solutions or suspensions and, after a series of solvent evaporation -- droplet fission cycles, it results in particles carrying multiple charges. Highly charged particles are used in a variety of applications, including particle characterization, thin film deposition, nanopatterning, and inhalation studies among several others. In this work, a soft X-ray photoionization was coupled with an electrospray to obtain monodisperse, singly charged nanoparticles for applications in online size characterization with electrical mobility analysis. Photoionization with the soft X-ray charger enhanced the diffusion neutralization rate of the highly charged bacteriophages, proteins, and solid particles. The effect of nanoparticle surface charge and nanoparticle agglomeration in liquids on the electrospray process was studied experimentally and a modified expression to calculate the effective electrical conductivity of nanosuspensions was proposed. The effective electrical conductivity of TiO2 nanoparticle suspensions is strongly dependent on the electrical double layer and the agglomeration dynamics of the particles; and such dependence is more remarkable in liquids with low ionic strength. TiO2 nanoparticle agglomerates with nearly monodisperse sizes in the nanometer and submicrometer ranges were generated, by electrospraying suspensions with tuned effective electrical conductivity, and used to deposit photocatalytic films for water-splitting. Nanostructured films of iron oxide with uniform distribution of particles over the entire deposition area were formed with an electrospray system. The micro-Raman spectra of the iron oxide films showed that transverse and longitudinal optical modes are highly sensitive to the crystallize size of the electrospray-deposited films. The fabrication of films of natural light-harvesting complexes, with the aim of designing biohybrid photovoltaic devices, was

  20. Atlas of fatigue curves

    SciTech Connect

    Boyer, H.E.

    1986-01-01

    This book contains more than 500 fatigue curves for industrial ferrous and nonferrous alloys. It also includes a thorough explanation of fatigue testing and interpretation of test results. Each curve is presented independently and includes an explanation of its particular importance. The curves are titled by standard industrial designations (AISI, CDA, AA, etc.) of the metals, and a complete reference is given to the original source to facilitate further research. The collection includes standard S-N curves, curves showing effect of surface hardening on fatigue strength, crack growth-rate curves, curves comparing the fatigue strengths of various alloys, effect of variables (i,e, temperature, humidity, frequency, aging, environment, etc.) and much, much more. This one volume consolidates the fatigue data in a single source.

  1. Fabrication of superoleophobic surfaces by mask-assisted electrospray

    NASA Astrophysics Data System (ADS)

    Al-Milaji, Karam Nashwan; Zhao, Hong

    2017-02-01

    Electrospraying technique has been demonstrated to fabricate superhydrophobic surfaces with random hierarchical roughness. Yet, it has never been employed to generate superoleophobic surfaces with patterned multiscale roughness. Here, we report a versatile approach to fabricate superoleophobic surfaces with patterned multiscale roughness using a mask-assisted electrospray technique. Superoleophobic surfaces with random hierarchical roughness by conventional electrospray without mask were also investigated for comparison purposes. Surfaces with patterned multiscale roughness were obtained by focusing the electrosprayed deposition through a mesh mask, followed by overlaying a random hierarchical roughness of electrosprayed SiO2. All the textured surfaces were treated with a low surface energy fluoropolymer to render superhydrophobicity and superoleophobicity. Superior repellency against water and hexadecane (27.5 mN/m) has been demonstrated on the surfaces with random hierarchical roughness and patterned multiscale roughness (contact angles of ∼170° and sliding angles of less than 1°). On the random hierarchical surfaces, the intrinsic re-entrant and multi-tier overhang structures in the SiO2 agglomerates enable non-wetting of low surface tension liquids. While on the surfaces with patterned roughness, the dome shape of micropillars plays a critical role in enabling superoleophobicity. The electric field focusing effect exerted by the mask is verified by COMSOL Multiphysics simulation.

  2. Incorporation of a venturi device in electrospray ionization.

    PubMed

    Zhou, Li; Yue, Bingfang; Dearden, David V; Lee, Edgar D; Rockwood, Alan L; Lee, Milton L

    2003-11-01

    Electrospray ionization has grown to be one of the most commonly used ionization techniques for mass spectrometry, and efforts continue to improve its performance. Typically, the sprayer tip must be very close to the entrance orifice of the mass spectrometer in order to maximize the conduction of ions from the sprayer into the mass spectrometer. However, because of space-charge repulsion, most ions never reach the sampling orifice. In this work, an industrial air amplifier, for which the working mechanism is based on venturi and coanda effects, was added between an electrospray ionization source and a time-of-flight mass spectrometer. When a series of reserpine solutions (0.5, 1.0, 5.0, and 10.0 microM) were monitored using mass spectrometry, an over 5-fold increase in m/z 609.3 ion intensity was measured for a separation distance of 14 mm between the electrospray tip and interface capillary inlet, as compared to when the electrospray tip was in its normal position 1 mm in front of the inlet without the amplifier. When a voltage was applied to the air amplifier to further assist in focusing the electrosprayed ions, an approximately 18-fold increase in m/z 609.3 ion intensity was obtained. In addition, a 34-fold reduction in method detection limit was observed.

  3. Internal energy and fragmentation of ions produced in electrospray sources.

    PubMed

    Gabelica, Valérie; De Pauw, Edwin

    2005-01-01

    This review addresses the determination of the internal energy of ions produced by electrospray ionization (ESI) sources, and the influence of the internal energy on analyte fragmentation. A control of the analyte internal energy is crucial for several applications of electrospray mass spectrometry, like structural studies, construction of reproducible and exportable spectral libraries, analysis of non-covalent complexes. Sections II and III summarize the Electrospray mechanisms and source design considerations which are relevant to the problem of internal energy, and Section IV gives an overview of the inter-relationships between ion internal energy, reaction time scale, and analyte fragmentation. In these three sections we tried to make the most important theoretical elements understandable by all ESI users, and their understanding requires a minimal background in physical chemistry. We then present the different approaches used to experimentally determine the ion internal energy, as well as various attempts in modeling the internal energy uptake in electrospray sources. Finally, a tentative comparison between electrospray and other ionization sources is made. As the reader will see, although many reports appeared on the subject, the knowledge in the field of internal energy of ions produced by soft ionization sources is still scarce, because of the complexity of the system, and this is what makes this area of research so interesting. The last section presents some perspectives for future research.

  4. Increasing Protein Charge State When Using Laser Electrospray Mass Spectrometry

    NASA Astrophysics Data System (ADS)

    Karki, Santosh; Flanigan, Paul M.; Perez, Johnny J.; Archer, Jieutonne J.; Levis, Robert J.

    2015-05-01

    Femtosecond (fs) laser vaporization is used to transfer cytochrome c, myoglobin, lysozyme, and ubiquitin from the condensed phase into an electrospray (ES) plume consisting of a mixture of a supercharging reagent, m-nitrobenzyl alcohol ( m-NBA), and trifluoroacetic acid (TFA), acetic acid (AA), or formic acid (FA). Interaction of acid-sensitive proteins like cytochrome c and myoglobin with the highly charged ES droplets resulted in a shift to higher charge states in comparison with acid-stable proteins like lysozyme and ubiquitin. Laser electrospray mass spectrometry (LEMS) measurements showed an increase in both the average charge states (Zavg) and the charge state with maximum intensity (Zmode) for acid-sensitive proteins compared with conventional electrospray ionization mass spectrometry (ESI-MS) under equivalent solvent conditions. A marked increase in ion abundance of higher charge states was observed for LEMS in comparison with conventional electrospray for cytochrome c (ranging from 19+ to 21+ versus 13+ to 16+) and myoglobin (ranging from 19+ to 26+ versus 18+ to 21+) using an ES solution containing m-NBA and TFA. LEMS measurements as a function of electrospray flow rate yielded increasing charge states with decreasing flow rates for cytochrome c and myoglobin.

  5. Size and distribution controllable silica microballs fabricated by electrospraying

    NASA Astrophysics Data System (ADS)

    Xu, Bojing; Wu, Pan; Jiang, Qi; Gu, Wenhua

    2015-10-01

    Silica microballs have a wide range of applications in the field of optics, electronics, biotechnology chemical industry, and so on. In this work, a new approach, electrospraying, was used to coat the silica microballs onto the glass substrate, and the coating results were compared to spin-coating and dip-coating. Good microball size control could be achieved using the electrospraying method. X-Ray Diffraction (XRD) results showed that amorphous silica microballs were obtained. From Scanning Electron Microscopy (SEM) images, we can see that uniform microball size was achieved. In general, the results are better than what can be achieved by spin-coating, and comparable to that of dip-coating. However, electrospraying has great potential in mass production, especially for large-area fabrication.

  6. Method for Continuous Monitoring of Electrospray Ion Formation

    NASA Astrophysics Data System (ADS)

    Metzler, Guille; Crathern, Susan; Bachmann, Lorin; Fernández-Metzler, Carmen; King, Richard

    2017-07-01

    A method for continuously monitoring the performance of electrospray ionization without the addition of hardware or chemistry to the system is demonstrated. In the method, which we refer to as SprayDx, cluster ions with solvent vapor natively formed by electrospray are followed throughout the collection of liquid chromatography-selected reaction monitoring data. The cluster ion extracted ion chromatograms report on the consistency of the ion formation and detection system. The data collected by the SprayDx method resemble the data collected for postcolumn infusion of analyte. The response of the cluster ions monitored reports on changes in the physical parameters of the ion source such as voltage and gas flow. SprayDx is also observed to report on ion suppression in a fashion very similar to a postcolumn infusion of analyte. We anticipate the method finding utility as a continuous readout on the performance of electrospray and other atmospheric pressure ionization processes.

  7. High pressure (>1 atm) electrospray ionization mass spectrometry.

    PubMed

    Chen, Lee Chuin; Mandal, Mridul Kanti; Hiraoka, Kenzo

    2011-03-01

    High pressure electrospray ionization mass spectrometry has been performed by pressurizing a custom made ion source chamber with compressed air to a pressure higher than the atmospheric pressure. The ion source was coupled to a commercial time-of-flight mass spectrometer using a nozzle-skimmer arrangement. The onset voltage for the electrospray of aqueous solution was found to be independent on the operating pressure. The onset voltage for the corona discharge, however, increased with the rise of pressure following the Paschen's law. Thus, besides having more working gas for the desolvation process, gaseous breakdown could also be avoided by pressurizing the ESI ion source with air to an appropriate level. Stable electrospray ionization has been achieved for the sample solution with high surface tension such as pure water in both positive and negative ion modes. Fragmentation of labile compounds during the ionization process could also be reduced by optimizing the operating pressure of the ion source.

  8. Method for Continuous Monitoring of Electrospray Ion Formation.

    PubMed

    Metzler, Guille; Crathern, Susan; Bachmann, Lorin; Fernández-Metzler, Carmen; King, Richard

    2017-07-20

    A method for continuously monitoring the performance of electrospray ionization without the addition of hardware or chemistry to the system is demonstrated. In the method, which we refer to as SprayDx, cluster ions with solvent vapor natively formed by electrospray are followed throughout the collection of liquid chromatography-selected reaction monitoring data. The cluster ion extracted ion chromatograms report on the consistency of the ion formation and detection system. The data collected by the SprayDx method resemble the data collected for postcolumn infusion of analyte. The response of the cluster ions monitored reports on changes in the physical parameters of the ion source such as voltage and gas flow. SprayDx is also observed to report on ion suppression in a fashion very similar to a postcolumn infusion of analyte. We anticipate the method finding utility as a continuous readout on the performance of electrospray and other atmospheric pressure ionization processes. Graphical Abstract ᅟ.

  9. Method for Continuous Monitoring of Electrospray Ion Formation

    NASA Astrophysics Data System (ADS)

    Metzler, Guille; Crathern, Susan; Bachmann, Lorin; Fernández-Metzler, Carmen; King, Richard

    2017-10-01

    A method for continuously monitoring the performance of electrospray ionization without the addition of hardware or chemistry to the system is demonstrated. In the method, which we refer to as SprayDx, cluster ions with solvent vapor natively formed by electrospray are followed throughout the collection of liquid chromatography-selected reaction monitoring data. The cluster ion extracted ion chromatograms report on the consistency of the ion formation and detection system. The data collected by the SprayDx method resemble the data collected for postcolumn infusion of analyte. The response of the cluster ions monitored reports on changes in the physical parameters of the ion source such as voltage and gas flow. SprayDx is also observed to report on ion suppression in a fashion very similar to a postcolumn infusion of analyte. We anticipate the method finding utility as a continuous readout on the performance of electrospray and other atmospheric pressure ionization processes. [Figure not available: see fulltext.

  10. Bio-electrosprayed living composite matrix implanted into mouse models.

    PubMed

    Jayasinghe, Suwan N; Warnes, Gary; Scotton, Chris J

    2011-10-10

    We show that composite de novo structures can be generated using bio-electrosprays. Mouse lung fibroblasts are bio-electrosprayed directly with a biopolymer to form cell-bearing matrices, which are viable even when implanted subcutaneously into murine hosts. Generated cell-bearing matrices are assessed in-vitro and found to undergo all expected cellular behaviour. Subsequent in-vivo studies demonstrate the implanted living matrices integrating as expected with the surrounding microenvironment. The in-vitro and in-vivo studies elucidate and validate the ability for either bio-electrosprays or cell electrospinning to form a desired living architecture for undergoing investigation for repairing, replacing and rejuvenating damaged and/or ageing tissues.

  11. Jean-Antoine Nollet: The father of experimental electrospray.

    PubMed

    Dumont, Quentin; Cole, Richard B

    2014-01-01

    The development of electrospray ionization mass spectrometry (ESI-MS) was a 20th century occurrence that underwent rapid acceleration especially in the 1990's. However, long prior to its coupling with mass spectrometry, the electrification of liquids had been studied in a variety of contexts. Although initial reports describing cone formation upon electrification of water drops came out of England, the first true experiments investigating the electrospray phenomenon were performed in the middle of the 18th century by Abbé Jean-Antoine Nollet. The current report, associated with the French Regional Issue of Mass Spectrometry Reviews, examines the contributions of Abbé Nollet to the earliest understanding of the electrospray phenomenon. A description of his accomplishments is placed in the context of the societal and scientific developments of the "Age of Enlightenment" out of which Jean-Antoine Nollet arose. © 2013 Wiley Periodicals, Inc.

  12. The electrospray and its application to targeted drug inhalation.

    PubMed

    Gomez, Alessandro

    2002-12-01

    This review explains the fundamentals of electrostatic spray (electrospray) atomization, with emphasis on operation in the so called cone-jet mode, which produces droplets with a very narrow size distribution. Since the control of droplet size is key to maximizing distal lung deposition, the electrospray should be well-suited to targeted drug inhalation. Electrospray droplets are a few micrometers in diameter, but they originate from a much larger nozzle, which allows nebulization of suspensions without clogging. Also discussed are: the physical principles of the break-up of the liquid ligament; droplet dispersion by Coulombic forces; and the most important scaling law linking the droplet size to liquid flow rate and liquid physical properties. The effects of the most critical of those properties may result in some restrictions on drug formulation. Droplets produced by electrospray are electrically charged, so to prevent electrostatic image forces from causing upper respiratory tract deposition. The charge is neutralized by generating a corona discharge of opposite polarity. Briefly discussed are the main differences between the laboratory systems (with which the electrospray has been quantitatively characterized during research in the past 10 years) and commercial electrospray inhalers under development at BattellePharma. Some remarkable miniaturization has incorporated liquid pump, power supply, breath activation, and dose counter into a palm-size portable device. The maximum flow rates dispersed from these devices are in the range of 8-16 microL/s, which makes them suitable for practical drug inhalation therapy. Fabrication is economically competitive with inexpensive nebulizers. Dramatic improvements in respirable dose efficiency (up to 78% by comparison with commercial metered-dose inhalers and dry powder inhalers) should ensure the commercialization of this promising technology for targeted drug inhalation.

  13. Analysis of multiple types of human cells subsequent to bioprinting with electrospraying technology

    PubMed Central

    Xin, Yu; Chai, Gang; Zhang, Ting; Wang, Xiangsheng; Qu, Miao; Tan, Andy; Bogari, Melia; Zhu, Ming; Lin, Li; Hu, Qingxi; Liu, Yuanyuan; Zhang, Yan

    2016-01-01

    The aim of the present study was to investigate bioprinting with electrospraying technology using multiple types of human cell suspensions as bio-ink, in order to lay the initial foundations for the application of the bioprinting technology in tissue engineering. In the current study, six types of human cells were selected and cultured, including human fibroblasts, human adipose-derived stem cells (hADSCs), human periodontal ligament cells (HPDLCs), adult human retinal pigment epithelial cells (ARPE-19), human umbilical vascular endothelial cells (HUVECs) and human gastric epithelial cell line (GES-1). Each cell type was divided into two groups, the experimental and control group. All the experimental group cells were electrosprayed using an electrospraying printer (voltage, 15 kV; flow rate, 150 µl/min) and collected in a petri dish placed 15 cm away from the needle (needle diameter, 0.5 mm). Subsequently, cell viability was detected by flow cytometry with a Live/Dead Viability kit. In addition, the cell morphological characteristics were observed with a phase-contrast microscope after 6 h of culturing in order to obtain adherent cells, while cell proliferation was analyzed using a Cell Counting Kit-8 assay. The control groups, without printing, were subjected to the same procedures as the experimental groups. The results of the cell viability and proliferation assays indicated a statistically significant difference after printing between the experiments and control groups only for the hADSCs (P<0.05); by contrast, no significant difference was observed in cell viability and proliferation for the other five cell types (P>0.05). In addition, there were no observable differences between all experimental and the control groups at any examined time point in the terms of cell morphological characteristics. In conclusion, bioprinting based on electrospraying technology demonstrated no distinct negative effect on cell vitality, proliferation and morphology in the

  14. Generating electrospray from microchip devices using electroosmotic pumping

    SciTech Connect

    Ramsey, R.S.; Ramsey, J.M.

    1997-03-15

    A method of generating electrospray from solutions emerging from small channels etched on planer substrates in described. The fluids are delivered using electroosmotically induced pressures and are sprayed electrostatically from the terminus of a channel by applying an electrical potential of sufficient amplitude to generate the electrospray between the microchip and a conductor spaced from the channel terminus. No major modification of the microchip is required other than to expose a channel opening. The principles that regulate the fluid delivery are described and demonstrated. A spectrum for a test compound, tetrabutylammonium iodide, that was continuously electrophoresed was obtained by coupling the microchip to an ion trap mass spectrometer. 35 refs., 6 figs.

  15. Plume collimation for laser ablation electrospray ionization mass spectrometry

    DOEpatents

    Vertes, Akos; Stolee, Jessica A.

    2016-06-07

    In various embodiments, a device may generally comprise a capillary having a first end and a second end; a laser to emit energy at a sample in the capillary to ablate the sample and generate an ablation plume in the capillary; an electrospray apparatus to generate an electrospray plume to intercept the ablation plume to produce ions; and a mass spectrometer having an ion transfer inlet to capture the ions. The ablation plume may comprise a collimated ablation plume. The device may comprise a flow cytometer. Methods of making and using the same are also described.

  16. Plume collimation for laser ablation electrospray ionization mass spectrometry

    DOEpatents

    Vertes, Akos; Stolee, Jessica A.

    2014-09-09

    In various embodiments, a device may generally comprise a capillary having a first end and a second end; a laser to emit energy at a sample in the capillary to ablate the sample and generate an ablation plume in the capillary; an electrospray apparatus to generate an electrospray plume to intercept the ablation plume to produce ions; and a mass spectrometer having an ion transfer inlet to capture the ions. The ablation plume may comprise a collimated ablation plume. The device may comprise a flow cytometer. Methods of making and using the same are also described.

  17. Low pressure electrospray ionization system and process for effective transmission of ions

    DOEpatents

    Tang, Keqi [Richland, WA; Page, Jason S [Kennewick, WA; Kelly, Ryan T [West Richland, WA; Smith, Richard D [Richland, WA

    2012-05-08

    Systems and methods that provide up to complete transmission of ions between coupled stages with low effective ion losses. An "interfaceless" electrospray ionization system is further described that operates an electrospray at a reduced pressure such that standard electrospray sample solutions can be directly sprayed into an electrodynamic ion funnel which provides ion focusing and transmission of ions into a mass analyzer. Furthermore, chambers maintained at different pressures can allow for more optimal operating conditions for an electrospray emitter and an ion guide.

  18. Electrospray ionization mass spectrometry for the hydrolysis complexes of cisplatin: implications for the hydrolysis process of platinum complexes.

    PubMed

    Feifan, Xie; Pieter, Colin; Jan, Van Bocxlaer

    2017-07-01

    Non-enzyme-dependent hydrolysis of the drug cisplatin is important for its mode of action and toxicity. However, up until today, the hydrolysis process of cisplatin is still not completely understood. In the present study, the hydrolysis of cisplatin in an aqueous solution was systematically investigated by using electrospray ionization mass spectrometry coupled to liquid chromatography. A variety of previously unreported hydrolysis complexes corresponding to monomeric, dimeric and trimeric species were detected and identified. The characteristics of the Pt-containing complexes were investigated by using collision-induced dissociation (CID). The hydrolysis complexes demonstrate distinctive and correlative CID characteristics, which provides tools for an informative identification. The most frequently observed dissociation mechanism was sequential loss of NH3 , H2 O and HCl. Loss of the Pt atom was observed as the final step during the CID process. The formation mechanisms of the observed complexes were explored and experimentally examined. The strongly bound dimeric species, which existed in solution, are assumed to be formed from the clustering of the parent compound and its monohydrated or dihydrated complexes. The role of the electrospray process in the formation of some of the observed ions was also evaluated, and the electrospray ionization-related cold clusters were identified. The previously reported hydrolysis equilibria were tested and subsequently refined via a hydrolysis study resulting in a renewed mechanistic equilibrium system of cisplatin as proposed from our results. Copyright © 2017 John Wiley & Sons, Ltd. Copyright © 2017 John Wiley & Sons, Ltd.

  19. Encapsulation of bioactive compound from extracted jasmine flower using β-Cyclodextrin via electrospray

    NASA Astrophysics Data System (ADS)

    Rahmam., S.; Naim., M. N.; Ng., E.; Mokhtar, M. Nn; Abu Bakar, N. F.

    2016-06-01

    The ability of electrospray to encapsulate the bioactive compound extracted from Jasmine flower with β-Cyclodextrion (β-CD) without any thermal-assisted processing was demonstrated in this study. The extraction of Jasmine compound were conducted using sonicator at 70 000 Hz, for 10 minutes and followed by mixing of the filtered compound with β-CD. Then, the mixture was electrosprayed under a stable Taylor cone jet mode at the voltage of 4 - 5 kV, with flow rate of 0.2 ml/hour. The aluminum substrate that used for collecting the deposit was placed at 30 cm from the needle's tip to allow the occurrence of evaporation and droplet fission until the droplet transform to solid particles. Characteristics of solidified bioactive compound from Jasmine flower (non-encapsulated compound) and solidified bioactive compound with β-CD (encapsulated compound) were studied in this work. From SEM images, it can be observed that the particles size distribution of encapsulated compound deposits have better deposition array and did not aggregate with each other compared to the non-encapsulated compound. FE-SEM images of encapsulated compound deposits indicate more solid crystal looks while non-encapsulated compound was obtained in the porous form. The electrospray process in this work has successfully encapsulated the Jasmine compound with β-CD without any thermal-assisted process. The encapsulation occurrence was determined using FTIR analysis. Identical peaks that referred to the β-CD were found on the encapsulated compound demonstrated that most deposits were encapsulated with β-CD.

  20. Novel Erythrocyte-like Graphene Microspheres with High Quality and Mass Production Capability via Electrospray Assisted Self-Assembly

    NASA Astrophysics Data System (ADS)

    Tian, Yayang; Wu, Guan; Tian, Xike; Tao, Xiaoming; Chen, Wei

    2013-11-01

    We report for the first time a novel erythrocyte-like graphene microsphere (ELGMs) which can be produced with high quality and mass production capability via electrospray assisted self-assembly. Through simple electrospray treatment of GO suspension into coagulation bath followed by chemical reduction, large quantity of ELGMs with uniform morphology and size can be obtained with production rate of around 2.4 mg/h. Compared with other 3D structures, the ELGMs have a very interesting structural characteristic of perfect exterior doughnut shape and interior porous network. Accordingly, the as-prepared porous ELGMs exhibit excellent capability for fast and recyclable removal of oil and toxic organic solvents from water, reaching up to 216 times of its weight in absorption efficiency, which is tens of times higher than that of conventional sorbent materials. It is strongly believed that the novel hierarchical graphene structures and synergy among different techniques will lead to more future advances in graphene applications.

  1. Tornado-Shaped Curves

    ERIC Educational Resources Information Center

    Martínez, Sol Sáez; de la Rosa, Félix Martínez; Rojas, Sergio

    2017-01-01

    In Advanced Calculus, our students wonder if it is possible to graphically represent a tornado by means of a three-dimensional curve. In this paper, we show it is possible by providing the parametric equations of such tornado-shaped curves.

  2. Tornado-Shaped Curves

    ERIC Educational Resources Information Center

    Martínez, Sol Sáez; de la Rosa, Félix Martínez; Rojas, Sergio

    2017-01-01

    In Advanced Calculus, our students wonder if it is possible to graphically represent a tornado by means of a three-dimensional curve. In this paper, we show it is possible by providing the parametric equations of such tornado-shaped curves.

  3. The Skipping Rope Curve

    ERIC Educational Resources Information Center

    Nordmark, Arne; Essen, Hanno

    2007-01-01

    The equilibrium of a flexible inextensible string, or chain, in the centrifugal force field of a rotating reference frame is investigated. It is assumed that the end points are fixed on the rotation axis. The shape of the curve, the skipping rope curve or "troposkien", is given by the Jacobi elliptic function sn. (Contains 3 figures.)

  4. Simulating Supernova Light Curves

    SciTech Connect

    Even, Wesley Paul; Dolence, Joshua C.

    2016-05-05

    This report discusses supernova light simulations. A brief review of supernovae, basics of supernova light curves, simulation tools used at LANL, and supernova results are included. Further, it happens that many of the same methods used to generate simulated supernova light curves can also be used to model the emission from fireballs generated by explosions in the earth’s atmosphere.

  5. The Skipping Rope Curve

    ERIC Educational Resources Information Center

    Nordmark, Arne; Essen, Hanno

    2007-01-01

    The equilibrium of a flexible inextensible string, or chain, in the centrifugal force field of a rotating reference frame is investigated. It is assumed that the end points are fixed on the rotation axis. The shape of the curve, the skipping rope curve or "troposkien", is given by the Jacobi elliptic function sn. (Contains 3 figures.)

  6. Anodic Polarization Curves Revisited

    ERIC Educational Resources Information Center

    Liu, Yue; Drew, Michael G. B.; Liu, Ying; Liu, Lin

    2013-01-01

    An experiment published in this "Journal" has been revisited and it is found that the curve pattern of the anodic polarization curve for iron repeats itself successively when the potential scan is repeated. It is surprising that this observation has not been reported previously in the literature because it immediately brings into…

  7. CURVES: curve evolution for vessel segmentation.

    PubMed

    Lorigo, L M; Faugeras, O D; Grimson, W E; Keriven, R; Kikinis, R; Nabavi, A; Westin, C F

    2001-09-01

    The vasculature is of utmost importance in neurosurgery. Direct visualization of images acquired with current imaging modalities, however, cannot provide a spatial representation of small vessels. These vessels, and their branches which show considerable variations, are most important in planning and performing neurosurgical procedures. In planning they provide information on where the lesion draws its blood supply and where it drains. During surgery the vessels serve as landmarks and guidelines to the lesion. The more minute the information is, the more precise the navigation and localization of computer guided procedures. Beyond neurosurgery and neurological study, vascular information is also crucial in cardiovascular surgery, diagnosis, and research. This paper addresses the problem of automatic segmentation of complicated curvilinear structures in three-dimensional imagery, with the primary application of segmenting vasculature in magnetic resonance angiography (MRA) images. The method presented is based on recent curve and surface evolution work in the computer vision community which models the object boundary as a manifold that evolves iteratively to minimize an energy criterion. This energy criterion is based both on intensity values in the image and on local smoothness properties of the object boundary, which is the vessel wall in this application. In particular, the method handles curves evolving in 3D, in contrast with previous work that has dealt with curves in 2D and surfaces in 3D. Results are presented on cerebral and aortic MRA data as well as lung computed tomography (CT) data.

  8. Preparation and characterization of polycaprolactone microspheres by electrospraying

    PubMed Central

    Zhou, Feng-Lei; Hubbard Cristinacce, Penny L.; Eichhorn, Stephen J.; Parker, Geoff J. M.

    2016-01-01

    ABSTRACT The ability to reproducibly produce and effectively collect electrosprayed polymeric microspheres with controlled morphology and size in bulk form is challenging. In this study, microparticles were produced by electrospraying polycaprolactone (PCL) of various molecular weights and solution concentrations in chloroform, and by collecting materials on different substrates. The resultant PCL microparticles were characterized by optical and electron microscopy to investigate the effect of molecular weight, solution concentration, applied voltage, working distance, and flow rate on their morphology and size. The work demonstrates the key role of a moderate molecular weight and/or solution concentration in the formation of spherical PCL particles via an electrospraying process. Increasing the applied voltage was found to produce smaller and more uniform PCL microparticles. There was a relatively low increase in the particle average size with an increase in the working distance and flow rate. Four types of substrates were adopted to collect electrosprayed PCL particles: a glass slide, aluminium foil, liquid bath, and copper wire. Unlike 2D bulk structures collected on the other substrates, a 3D tubular structure of microspheres was formed on the copper wire which could find application in the construction of 3D tumor mimics. PMID:27928195

  9. Desorption electrospray ionization mass spectrometry of intact bacteria

    USDA-ARS?s Scientific Manuscript database

    Desorption electrospray ionization (DESI) mass spectrometry (MS) was used to differentiate 7 bacterial species based on their measured DESI-mass spectral profile. Both Gram positive and Gram negative bacteria were tested and included Escherichia coli, Staphyloccocus aureus, Enterococcus sp., Bordete...

  10. Infrared laser-assisted desorption electrospray ionization mass spectrometry.

    PubMed

    Rezenom, Yohannes H; Dong, Jianan; Murray, Kermit K

    2008-02-01

    We have used an infrared laser for desorption of material and ionization by interaction with electrosprayed solvent. Infrared laser-assisted desorption electrospray ionization (IR LADESI) mass spectrometry was used for the direct analysis of water-containing samples under ambient conditions. An ion trap mass spectrometer was modified to include a pulsed Er:YAG laser at 2.94 microm wavelength coupled into a germanium oxide optical fiber for desorption at atmospheric pressure and a nanoelectrospray source for ionization. Analytes in aqueous solution were placed on a stainless steel target and irradiated with the pulsed IR laser. Material desorbed and ablated from the target was ionized by a continuous stream of charged droplets from the electrosprayed solvent. Peptide and protein samples analyzed using this method yield mass spectra similar to those obtained by conventional electrospray. Blood and urine were analyzed without sample pretreatment to demonstrate the capability of IR LADESI for direct analysis of biological fluids. Pharmaceutical products were also directly analyzed. Finally, the role of water as a matrix in the IR LADESI process is discussed.

  11. Metal-insulator-metal capacitor using electrosprayed nanoparticles

    NASA Astrophysics Data System (ADS)

    Véliz, Bremnen; Bermejo, Sandra; Coll, Arnau; Castañer, Luis

    2014-07-01

    An electrospray technique has been used to deposit SiO2 nanoparticles as insulator layer of a metal-insulator-metal device. Impedance spectroscopy measurements show that a 4.4 factor increase in capacitance is achieved compared to a continuous dielectric layer of the same permittivity and dimensions.

  12. Fundamentals of Biomolecule Analysis by Electrospray Ionization Mass Spectrometry

    ERIC Educational Resources Information Center

    Weinecke, Andrea; Ryzhov, Victor

    2005-01-01

    Electrospray ionization (ESI) is a soft ionization technique that allows transfer of fragile biomolecules directly from solution into the gas phase. An instrumental analysis laboratory experiment is designed that would introduce the students to the ESI technique, major parameters of the ion trap mass spectrometers and some caveats in…

  13. Fundamentals of Biomolecule Analysis by Electrospray Ionization Mass Spectrometry

    ERIC Educational Resources Information Center

    Weinecke, Andrea; Ryzhov, Victor

    2005-01-01

    Electrospray ionization (ESI) is a soft ionization technique that allows transfer of fragile biomolecules directly from solution into the gas phase. An instrumental analysis laboratory experiment is designed that would introduce the students to the ESI technique, major parameters of the ion trap mass spectrometers and some caveats in…

  14. Electrospray ionization mass spectrometry of pyrimidine base-rubidium complexes.

    PubMed

    Frańska, Magdalena

    2005-01-01

    Nucleobases and alkali metal cations, under electrospray ionisation conditions, tend to form the so-called magic number clusters (unusually stable clusters in comparison with the neighbouring ones). The effect of the ion source parameters, namely cone voltage and desolvation temperature and relative concentrations of thymine and RbCl on the [T5+Rb]+ ion abundance has been studied.

  15. Simultaneous determination of Eleutheroside B and Eleutheroside E in rat plasma by high performance liquid chromatography-electrospray ionization mass spectrometry and its application in a pharmacokinetic study.

    PubMed

    Ma, Bo; Zhang, Qi; Liu, Yinhui; Li, Jing; Xu, Qiuyu; Li, Xiaotian; Yang, Xiaojing; Yao, Di; Sun, Jingjing; Cui, Guangbo; Ying, Hanjie

    2013-02-15

    Eleutheroside B and Eleutheroside E, two kinds of the major bioactive saponins of Eleutherococcus senticosus, play a pivotal role in biologic activity. In this study, a specific and sensitive high performance liquid chromatography-electrospray ionization-tandem mass spectrometry method (HPLC-MS/MS) was developed and validated for simultaneous determination of Eleutheroside B and Eleutheroside E in rat plasma. The analytes were extracted from rat plasma via a simple protein precipitation procedure with methanol and polygonin was used as internal standard. Chromatographic separation was achieved on a C18 column using a gradient elution program with acetonitrile and water containing 0.1% ammonium hydroxide solution as the mobile phase, with a flow rate of 0.2mL/min. The detection was performed on a triple-quadrupole tandem mass spectrometer by multiple reactions monitoring (MRM) mode in a negative ion mode via electrospray ionization (ESI). The transition monitored were m/z 371 [M-H](-)→209 for Eleutheroside B, m/z 741[M-H](-)→579 for Eleutheroside E and m/z 389[M-H](-)→277 for internal standard. Linear calibration curves were obtained in the concentration range of 1-2000ng/mL for both (Eleutheroside B and Eleutheroside E), with a lower limit of quantification of 1ng/mL. Extraction recovery was over 80% in plasma. The intra- and inter-day precision (RSD) values were below 12% and accuracy (RE) was -2.80 to 5.70% at three QC levels for both. The assay was successfully applied to study pharmacokinetics behavior in rats after oral and intravenous administration of the single substances (Eleutheroside B and Eleutheroside E). And further research was performed by comparing the difference in pharmacokinetic behavior between the single substances and an aqueous extract of E. senticosus after oral administration. Significant difference in pharmacokinetic characteristics between the single substances and an aqueous extract was found in rat, which would be beneficial for

  16. Mechanics of Curved Folds

    NASA Astrophysics Data System (ADS)

    Dias, Marcelo A.; Santangelo, Christian D.

    2011-03-01

    Despite an almost two thousand year history, origami, the art of folding paper, remains a challenge both artistically and scientifically. Traditionally, origami is practiced by folding along straight creases. A whole new set of shapes can be explored, however, if, instead of straight creases, one folds along arbitrary curves. We present a mechanical model for curved fold origami in which the energy of a plastically-deformed crease is balanced by the bending energy of developable regions on either side of the crease. Though geometry requires that a sheet buckle when folded along a closed curve, its shape depends on the elasticity of the sheet. NSF DMR-0846582.

  17. Electron Transfer Reagent Anion Formation via Electrospray Ionization and Collision-induced Dissociation

    PubMed Central

    Huang, Teng-Yi; Emory, Joshua F.; O’Hair, Richard A.J.; McLuckey, Scott A.

    2011-01-01

    A strategy is described and demonstrated for the formation of reagent anions via electrospray ionization (ESI) for electron transfer dissociation (ETD). To circumvent difficulties associated with formation of high mass-to-charge ratio (m/z) reagent anions, it is desirable to form ETD reagents via means other than those that require reagent molecule vaporization. ESI is a candidate method but anions that are generally generated efficiently by ESI tend to react with multiply protonated polypeptides via proton transfer. The strategy described herein involves the use of a precursor reagent molecule that ionizes efficiently via electrospray ionization and that can subsequently be converted to an ETD reagent via gas-phase dissociation. The approach is demonstrated with arene carboxylic acids that yield strong signals associated with the deprotonated molecule and that subsequently undergo collision-induced dissociation (CID) by loss of CO2. In the present work, triply protonated KGAILKGAILR served as a test substrate for the CID product ions to give rise to ETD. Several precursor molecules were shown to be capable of generating ETD reagents via ESI followed by CID. These included 9-anthracenecarboxylic acid, 2-fluoro-5-iodobenzoic acid, and 2-(fluoranthene-8-carbonyl)-benzoic acid. The latter molecule has the most attractive set of characteristics as a precursor for a relatively high m/z ratio ETD reagent. PMID:17073403

  18. High-performance liquid chromatography with electrospray ionization ion mobility spectrometry: Characterization, data management, and applications.

    PubMed

    Zühlke, Martin; Riebe, Daniel; Beitz, Toralf; Löhmannsröben, Hans-Gerd; Andreotti, Sandro; Reinert, Knut; Zenichowski, Karl; Diener, Marc

    2016-12-01

    The combination of high-performance liquid chromatography and electrospray ionization ion mobility spectrometry facilitates the two-dimensional separation of complex mixtures in the retention and drift time plane. The ion mobility spectrometer presented here was optimized for flow rates customarily used in high-performance liquid chromatography between 100 and 1500 μL/min. The characterization of the system with respect to such parameters as the peak capacity of each time dimension and of the 2D spectrum was carried out based on a separation of a pesticide mixture containing 24 substances. While the total ion current chromatogram is coarsely resolved, exhibiting coelutions for a number of compounds, all substances can be separately detected in the 2D plane due to the orthogonality of the separations in retention and drift dimensions. Another major advantage of the ion mobility detector is the identification of substances based on their characteristic mobilities. Electrospray ionization allows the detection of substances lacking a chromophore. As an example, the separation of a mixture of 18 amino acids is presented. A software built upon the free mass spectrometry package OpenMS was developed for processing the extensive 2D data. The different processing steps are implemented as separate modules which can be arranged in a graphic workflow facilitating automated processing of data.

  19. An electrospray ionization source for thermochemical investigation with the guided ion beam mass spectrometer.

    PubMed

    Moision, R M; Armentrout, P B

    2007-06-01

    An electrospray ionization (ESI) source developed for use with the guided ion beam tandem mass spectrometer (GIBMS) is described. For accurate determination of thermochemistry using threshold collision-induced dissociation (TCID), it is essential that any source produces ions with four exacting characteristics: (1) high intensity, (2) stable signal, and well-defined energies both (3) kinetic, and (4) internal. To accomplish these objectives, the ions generated by the electrospray are collected using a radio frequency electrodynamic ion funnel and are then transferred into a hexapole ion guide where they are thermalized and subsequently passed into higher-vacuum regions for analysis. The resulting ion intensities using this source can exceed 10(6) ions/s. Stable beams (<10% variation in signal) can be generated over multiple hours. The kinetic energy distribution of ions emerging from this source has been shown to be well described by a Gaussian distribution with a full width half maximum (FWHM) of about 0.1-0.2 eV in the laboratory frame of reference. Finally, TCID results for ions generated with this source show excellent agreement with previously reported threshold values for ions generated using a variety of sources and experimental methodologies. This confirms that internal energies of the ions are well described by a Maxwell-Boltzmann distribution at room temperature.

  20. Ambient Characterization of Synthetic Fibers by Laser Ablation Electrospray Ionization Mass Spectrometry

    PubMed Central

    2017-01-01

    Direct analysis of synthetic fibers under ambient conditions is highly desired to identify the polymer, the finishes applied and irregularities that may compromise its performance and value. In this paper, laser ablation electrospray ionization ion mobility time-of-flight mass spectrometry (LAESI-IMS-TOF-MS) was used for the analysis of synthetic polymers and fibers. The key to this analysis was the absorption of laser light by aliphatic and aromatic nitrogen functionalities in the polymers. Analysis of polyamide (PA) 6, 46, 66, and 12 pellets and PA 6, 66, polyaramid and M5 fibers yielded characteristic fragment ions without any sample pretreatment, enabling their unambiguous identification. Synthetic fibers are, in addition, commonly covered with a surface layer for improved adhesion and processing. The same setup, but operated in a transient infrared matrix-assisted laser desorption electrospray ionization (IR-MALDESI) mode, allowed the detailed characterization of the fiber finish layer and the underlying polymer. Differences in finish layer distribution may cause variations in local properties of synthetic fibers. Here we also show the feasibility of mass spectrometry imaging (MSI) of the distribution of a finish layer on the synthetic fiber and the successful detection of local surface defects. PMID:28252942

  1. Molecular resolution and fragmentation of fulvic acid by electrospray ionization/multistage tandem mass spectrometry

    USGS Publications Warehouse

    Leenheer, J.A.; Rostad, C.E.; Gates, Paul M.; Furlong, E.T.; Ferrer, I.

    2001-01-01

    Molecular weight distributions of fulvic acid from the Suwannee River, Georgia, were investigated by electrospray ionization/quadrupole mass spectrometry (ESI/QMS), and fragmentation pathways of specific fulvic acid masses were investigated by electrospray ionization/ion trap multistage tandem mass spectrometry (ESI/MST/MS). ESI/QMS studies of the free acid form of low molecular weight poly(carboxylic acid) standards in 75% methanol/25% water mobile phase found that negative ion detection gave the optimum generation of parent ions that can be used for molecular weight determinations. However, experiments with poly(acrylic acid) mixtures and specific high molecular weight standards found multiply charged negative ions that gave a low bias to molecular mass distributions. The number of negative charges on a molecule is dependent on the distance between charges. ESI/MST/MS of model compounds found characteristic water loss from alcohol dehydration and anhydride formation, as well as CO2 loss from decarboxylation, and CO loss from ester structures. Application of these fragmentation pathways to specific masses of fulvic acid isolated and fragmented by ESI/MST/MS is indicative of specific structures that can serve as a basis for future structural confirmation after these hypothesized structures are synthesized.

  2. Metal Cationization Extractive Electrospray Ionization Mass Spectrometry of Compounds Containing Multiple Oxygens

    NASA Astrophysics Data System (ADS)

    Swanson, Kenneth D.; Spencer, Sandra E.; Glish, Gary L.

    2017-06-01

    Extractive electrospray ionization is an ambient ionization technique that allows real-time sampling of liquid samples, including organic aerosols. Similar to electrospray ionization, the composition of the electrospray solvent used in extractive electrospray ionization can easily be altered to form metal cationized molecules during ionization simply by adding a metal salt to the electrospray solvent. An increase in sensitivity is observed for some molecules that are lithium, sodium, or silver cationized compared with the protonated molecule formed in extractive electrospray ionization with an acid additive. Tandem mass spectrometry of metal cationized molecules can also significantly improve the ability to identify a compound. Tandem mass spectrometry of lithium and silver cationized molecules can result in an increase in the number and uniqueness of dissociation pathways relative to [M + H]+. These results highlight the potential for extractive electrospray ionization with metal cationization in analyzing complex aerosol mixtures. [Figure not available: see fulltext.

  3. Metal Cationization Extractive Electrospray Ionization Mass Spectrometry of Compounds Containing Multiple Oxygens.

    PubMed

    Swanson, Kenneth D; Spencer, Sandra E; Glish, Gary L

    2016-11-28

    Extractive electrospray ionization is an ambient ionization technique that allows real-time sampling of liquid samples, including organic aerosols. Similar to electrospray ionization, the composition of the electrospray solvent used in extractive electrospray ionization can easily be altered to form metal cationized molecules during ionization simply by adding a metal salt to the electrospray solvent. An increase in sensitivity is observed for some molecules that are lithium, sodium, or silver cationized compared with the protonated molecule formed in extractive electrospray ionization with an acid additive. Tandem mass spectrometry of metal cationized molecules can also significantly improve the ability to identify a compound. Tandem mass spectrometry of lithium and silver cationized molecules can result in an increase in the number and uniqueness of dissociation pathways relative to [M + H](+). These results highlight the potential for extractive electrospray ionization with metal cationization in analyzing complex aerosol mixtures. Graphical Abstract ᅟ.

  4. Metal Cationization Extractive Electrospray Ionization Mass Spectrometry of Compounds Containing Multiple Oxygens

    NASA Astrophysics Data System (ADS)

    Swanson, Kenneth D.; Spencer, Sandra E.; Glish, Gary L.

    2016-11-01

    Extractive electrospray ionization is an ambient ionization technique that allows real-time sampling of liquid samples, including organic aerosols. Similar to electrospray ionization, the composition of the electrospray solvent used in extractive electrospray ionization can easily be altered to form metal cationized molecules during ionization simply by adding a metal salt to the electrospray solvent. An increase in sensitivity is observed for some molecules that are lithium, sodium, or silver cationized compared with the protonated molecule formed in extractive electrospray ionization with an acid additive. Tandem mass spectrometry of metal cationized molecules can also significantly improve the ability to identify a compound. Tandem mass spectrometry of lithium and silver cationized molecules can result in an increase in the number and uniqueness of dissociation pathways relative to [M + H]+. These results highlight the potential for extractive electrospray ionization with metal cationization in analyzing complex aerosol mixtures.

  5. International transferability of accident modification functions for horizontal curves.

    PubMed

    Elvik, Rune

    2013-10-01

    Studies of the relationship between characteristics of horizontal curves and accident rate have been reported in several countries. The characteristic most often studied is the radius of a horizontal curve. Functions describing the relationship between the radius of horizontal curves and accident rate have been developed in Australia, Canada, Denmark, Germany, Great Britain, New Zealand, Norway, Portugal, Sweden, and the United States. Other characteristics of horizontal curves that have been studied include deflection angle, curve length, the presence of transition curves, super-elevation in curves and distance to adjacent curves. This paper assesses the international transferability of mathematical functions (accident modification functions) that have been developed to relate the radius of horizontal curves to their accident rate. The main research problem is whether these functions are similar, which enhances international transferability, or dissimilar, which reduces international transferability. Accident modification functions for horizontal curve radius developed in the countries listed above are synthesised. The sensitivity of the functions to other characteristics of curves than radius is examined. Accident modification functions developed in different countries have important similarities. The functions diverge with respect to accident rate in the sharpest curves.

  6. Curve Stitching in LOGO.

    ERIC Educational Resources Information Center

    Muscat, Jean-Paul

    1992-01-01

    Uses LOGO to enhance the applicability of curve stitching in the mathematics curriculum. Presents the formulas and computer programs for the construction of parabolas, concentric circles, and epicycloids. Diagrams of constructed figures are provided. (MDH)

  7. Crystallography on Curved Surfaces

    NASA Astrophysics Data System (ADS)

    Vitelli, Vincenzo; Lucks, Julius; Nelson, David

    2007-03-01

    We present a theoretical and numerical study of the static and dynamical properties that distinguish two dimensional curved crystals from their flat space counterparts. Experimental realizations include block copolymer mono-layers on lithographically patterned substrates and self-assembled colloidal particles on a curved interface. At the heart of our approach lies a simple observation: the packing of interacting spheres constrained to lie on a curved surface is necessarily frustrated even in the absence of defects. As a result, whenever lattice imperfections or topological defects are introduced in the curved crystal they couple to the pre-stress of geometric frustration giving rise to elastic potentials. These geometric potentials are non-local functions of the Gaussian curvature and depend on the position of the defects. They play an important role in stress relaxation dynamics, elastic instabilities and melting.

  8. Principal Curves and Surfaces

    DTIC Science & Technology

    1984-11-01

    the Mahalanobis distance defined in terms of t. In particular when 9 is diagonal the procedure amounts to finding the line that minimizes the weighted...the m~a~l of apj dimensional’ data set. They mhinima, the distance from the poinsa, and provide a mom-linear summary of the data. The carves awe moe...project there. The zmain theorems proms thaprincipal curves mre critical values of the expected squared distance between the points and the curve

  9. Fabrication of internally tapered capillaries for capillary electrochromatography electrospray ionization mass spectrometry.

    PubMed

    Zheng, Jack; Norton, Dean; Shamsi, Shahab A

    2006-02-15

    In this study, we report a novel procedure for fabricating internally tapered capillary columns suitable for the coupling of capillary electrochromatography (CEC) to electrospray mass spectrometry (ESI-MS). The internal tapers were prepared by slowly heating the capillary end in a methane/O2 flame. Due to continuous self-shrinking of the inner channel of the capillary, the inside diameter of the opening was reduced to 7-10 microm. The procedure is easy to handle, with no requirement for expensive equipment as well as elimination of problematic grinding of the tip. Several advantages of these new internal tapers, as compared to using externally tapered columns, are described. First, the problems of poor durability and tip breakage associated with external tapering were successfully overcome with the internal taper. A comparison of the online CEC/ESI-MS between external versus internal tapers showed that the latter provides enhanced electrospray stability, resulting in significantly lower short-term noise and very short-term noise values. In turn, the more rugged design of internal tapers allows performing CEC/MS utilizing a harsh polar organic mobile phase, which was not previously successful using an external taper due to higher operating current and electrospray arcing. Next, data on the reproducibility of the internally tapered CEC/MS column using warfarin and beta-blockers as model analytes are presented. For example, when comparing the reproducibility for separation of warfarin under reversed-phase conditions, the internal taper demonstrated superior intraday % RSD (1.6-3.4) as compared to the external taper intraday % RSD (5-6). Last, the applicability of performing quantitative CEC/MS with internally tapered capillaries is demonstrated for simultaneous enantioseparation of beta-blockers. Impressive quantitative results include good linearity of calibration curves (e.g., R2 = 0.9940-0.9988) and limit of detection as low as 30 nM. The sensitive detection of a

  10. Linear instability of curved free shear layers

    NASA Technical Reports Server (NTRS)

    Liou, William W.

    1993-01-01

    The linear inviscid hydrodynamic stability of slightly curved free mixing layers is studied in this paper. The disturbance equation is solved numerically using a shooting technique. Two mean velocity profiles that represent stably and unstably curved free mixing layers are considered. Results are shown for cases of five curvature Richardson numbers. The stability characteristics of the shear layer are found to vary significantly with the introduction of the curvature effects. The results also indicate that, in a manner similar to the Goertler vortices observed in a boundary layer along a concave wall, instability modes of spatially developing streamwise vortex pairs may appear in centrifugally unstable curved mixing layers.

  11. Search for liquids electrospraying the smallest possible nanodrops in vacuo

    NASA Astrophysics Data System (ADS)

    Alonso-Matilla, R.; Fernández-García, J.; Congdon, H.; Fernández de la Mora, J.

    2014-12-01

    Prior work with electrosprays in vacuum of mixtures of ionic liquids (ILs) and the moderately high boiling point (Tb) solvents formamide (FM) and propylene carbonate (PC) (Tb of 210 and 241 °C) has shown that the charged drops produced have reasonably narrow charge/mass distributions, controllable over a wide mass/charge range. This enables their use as propellants in electrical propulsion with specific impulse Isp varying from a few hundred to a few thousand seconds (10 kV beam energy) and with excellent propulsion efficiency. However, some limitations are imposed by the finite room temperature volatility of FM and PC. Here, we seek improved performance from propellants based on the polar but viscous solvent Sulfolane (SF; ɛ = 43.2, μ = 10.3 cP) and the low viscosity but less polar solvent tributyl phosphate (TBP; ɛ = 8.9, μ = 3.4 cP), both with Tb > 280 °C. Neither TBP nor its low viscosity mixtures with SF achieve the electrical conductivities needed to yield high Isp. Most ILs used in SF/IL mixtures tested were based on the 1-ethyl-3-methylimidazolium (EMI) or 1,3-dimethylimidazolium (DMI) cations, including EMI-BF4, EMI-N(CN)2, and DMI-N(CN)2. These combinations reach high conductivities, some approaching 3 S/m, but have limited propulsive performance because evaporation of ions directly from the electrified meniscus produces undesirable mixed beams of drops and ions. Exceptional characteristics are found in mixtures of SF with ethylammonium nitrate (EAN), where the small EA+ cation is strongly bound to the solvent, greatly delaying ion evaporation from the meniscus. Evidence on the formation of nano-jets with diameters as small as 1 nm is seen. Although unprecedented, this finding agrees with what would be expected if ion evaporation were suppressed. SF/EAN mixtures thus provide the best available sources to produce the smallest possible nanodrops, minimally polluted by ions.

  12. Search for liquids electrospraying the smallest possible nanodrops in vacuo

    SciTech Connect

    Alonso-Matilla, R.; Fernández-García, J.; Congdon, H.; Fernández de la Mora, J.

    2014-12-14

    Prior work with electrosprays in vacuum of mixtures of ionic liquids (ILs) and the moderately high boiling point (T{sub b}) solvents formamide (FM) and propylene carbonate (PC) (T{sub b} of 210 and 241 °C) has shown that the charged drops produced have reasonably narrow charge/mass distributions, controllable over a wide mass/charge range. This enables their use as propellants in electrical propulsion with specific impulse I{sub sp} varying from a few hundred to a few thousand seconds (10 kV beam energy) and with excellent propulsion efficiency. However, some limitations are imposed by the finite room temperature volatility of FM and PC. Here, we seek improved performance from propellants based on the polar but viscous solvent Sulfolane (SF; ε = 43.2, μ = 10.3 cP) and the low viscosity but less polar solvent tributyl phosphate (TBP; ε = 8.9, μ = 3.4 cP), both with T{sub b} > 280 °C. Neither TBP nor its low viscosity mixtures with SF achieve the electrical conductivities needed to yield high I{sub sp}. Most ILs used in SF/IL mixtures tested were based on the 1-ethyl-3-methylimidazolium (EMI) or 1,3-dimethylimidazolium (DMI) cations, including EMI-BF{sub 4}, EMI-N(CN){sub 2}, and DMI-N(CN){sub 2}. These combinations reach high conductivities, some approaching 3 S/m, but have limited propulsive performance because evaporation of ions directly from the electrified meniscus produces undesirable mixed beams of drops and ions. Exceptional characteristics are found in mixtures of SF with ethylammonium nitrate (EAN), where the small EA{sup +} cation is strongly bound to the solvent, greatly delaying ion evaporation from the meniscus. Evidence on the formation of nano-jets with diameters as small as 1 nm is seen. Although unprecedented, this finding agrees with what would be expected if ion evaporation were suppressed. SF/EAN mixtures thus provide the best available sources to produce the smallest possible nanodrops, minimally polluted by

  13. Thin-Layer Chromatography/Desorption Electrospray Ionization Mass Spectrometry: Investigation of Goldenseal Alkaloids

    SciTech Connect

    Van Berkel, Gary J; Tomkins, Bruce A; Kertesz, Vilmos

    2007-01-01

    Desorption electrospray ionization mass spectrometry was investigated as a means to qualitatively identify and to quantify analytes directly from developed normal-phase thin layer chromatography plates. The atmospheric sampling capillary of a commercial ion trap mass spectrometer was extended to permit sampling and ionization of analytes in bands separated on intact TLC plates (up to 10 cm x 10 cm). A surface positioning software package and the appropriate hardware enabled computer-controlled surface scanning along the length of development lanes or at fixed RF value across the plates versus the stationary desorption electrospray emitter. Goldenseal (Hydrastis canadensis) and related alkaloids and commercial dietary supplements were used as standards and samples. Alkaloid standards and samples were spotted and separated on aluminum- or glass-backed plates using established literature methods. The mass spectral signal levels as a function of desorption spray solvent were investigated with acetonitrile proving superior to methanol. The detection levels (ca. 5 ng each or 14 -28 pmol) in mass spectral full scan mode were determined statistically from the calibration curves (2.5 - 100 pmol) for the standards berberine, palmatine and hydrastinine spotted as a mixture and separated on the plates. Qualitative screening of the major alkaloids present in six different over-the-counter "goldenseal" dietary supplements was accomplished by obtaining full scan mass spectra during surface scans along the development lane in the direction of increasing RF value. In one sample, alkaloids were detected that strongly suggested the presence of at least one additional herb undeclared on the product label. These same data indicated the misidentification of one of the alkaloids in the TLC literature. Quantities of the alkaloids present in two of the samples determined using the mass spectral data were in reasonable agreement with the label values indicating the quantitative ability of

  14. Examination of Bacterial Characteristics of Anaerobic Membrane Bioreactors in Three Pilot-Scale Plants for Treating Low-Strength Wastewater by Application of the Colony-Forming-Curve Analysis Method

    PubMed Central

    Kataoka, Naoaki; Tokiwa, Yutaka; Tanaka, Yasuo; Fujiki, Kiichi; Taroda, Hiroyuki; Takeda, Kiyoshi

    1992-01-01

    Characteristic sludge ecosystems arising in anaerobic membrane bioreactors of three pilot-scale plants treating low-strength (less than 1 g of biological oxygen demand per liter) sewage or soybean-processing wastewater were examined by analysis of the colony-forming-curves (CFC) obtained by counting colonies at suitable intervals. The wastewaters, containing high amounts of suspended solids (SS) (SS/chemical oxygen demand ratio, 0.51 to 0.80), were treated by using two types of bioreactors: (i) a hydrolyzation reactor for solubilization and acidification of SS in wastewater and (ii) a methane fermentation reactor for producing methane. The colony counts for the two sewage treatment plants continued to increase even after 3 weeks of incubation, whereas those for soybean-processing wastewater reached an approximately constant level within 3 weeks of incubation. The CFCs were analyzed by correlating the rate of colony appearance on roll tubes with the physiological types of bacteria present in the bioreactors. It was found that there were large numbers of slow-colony-forming anaerobic bacteria within the bioreactors and that the viable populations consisted of a few groups with different growth rates. It is considered that the slow-growing colonies appearing after 10 days of incubation were the dominant microflora in the sewage treated by hydrolyzation reactors. In particular, highly concentrated sludge (30.0 g of mixed-liquor volatile SS per liter) retained by the membrane separation module contained a large number of such bacteria. Slow-growing colonies of these bacteria could be counted by using a sludge extract medium prepared from only the supernatant of autoclaved sludge. In addition, the highest colony counts were almost always obtained with the sludge extract medium, meaning that most of the anaerobic bacteria in these sludges have complex nutrient requirements for growth. This report also indicates the usefulness of application of the CFC analysis method to

  15. Are Driving and Overtaking on Right Curves More Dangerous than on Left Curves?

    PubMed Central

    Othman, Sarbaz; Thomson, Robert; Lannér, Gunnar

    2010-01-01

    that drivers behave differently depending on the curve direction where both speed and acceleration were higher on right than left curves. The implication of this study is that curve direction should be taken into consideration to a greater extent when designing and redesigning curves. It appears that the driver and the vehicle are influenced by different infrastructure factors depending on the curve direction. In addition, the results suggest that the vehicle dynamics response alone cannot explain the higher crash risk in right curves. Further studies of the links between driver, vehicle, and highway characteristics are needed, such as naturalistic driving studies, to identify the key safety indicators for highway safety. PMID:21050608

  16. Are driving and overtaking on right curves more dangerous than on left curves?

    PubMed

    Othman, Sarbaz; Thomson, Robert; Lannér, Gunnar

    2010-01-01

    that drivers behave differently depending on the curve direction where both speed and acceleration were higher on right than left curves. The implication of this study is that curve direction should be taken into consideration to a greater extent when designing and redesigning curves. It appears that the driver and the vehicle are influenced by different infrastructure factors depending on the curve direction. In addition, the results suggest that the vehicle dynamics response alone cannot explain the higher crash risk in right curves. Further studies of the links between driver, vehicle, and highway characteristics are needed, such as naturalistic driving studies, to identify the key safety indicators for highway safety.

  17. Curved centerline air intake for a gas turbine engine

    NASA Technical Reports Server (NTRS)

    Ruehr, W. C.; Younghans, J. L.; Smith, E. B. (Inventor)

    1980-01-01

    An inlet for a gas turbine engine was disposed about a curved centerline for the purpose of accepting intake air that is flowing at an angle to engine centerline and progressively turning that intake airflow along a curved path into alignment with the engine. This curved inlet is intended for use in under the wing locations and similar regions where airflow direction is altered by aerodynamic characteristics of the airplane. By curving the inlet, aerodynamic loss and acoustic generation and emission are decreased.

  18. Study on Bezier Curve Variable Step-length Algorithm

    NASA Astrophysics Data System (ADS)

    Xiao, Guorong; Xu, Xuemiao

    Bessel Curve also known as Bezier Curve, through which the general vector graphics software accurately draws curves, as the Bezier curve is relatively easy to calculate and its stable characteristic, in many areas it has been widely applied. However, for the deficiency of less efficiency exists in the common Bezier Curve Generation Algorithm, the selection of the parameter step-length significantly affects the accuracy and efficiency of the generated curve. This paper aims at the efficiency available in the existing Bezier Curve Generation Algorithm to propose the Variable Step-length Algorithm; by changing the parameter step-length of the curve generation algorithm, it can significantly reduce the calculations of a large number of duplicate points in the point-by-point generation algorithm; the algorithm not only maintains a higher accuracy, but also significantly improves the efficiency generated in the curve, with better application.

  19. Contact Geometry of Curves

    NASA Astrophysics Data System (ADS)

    Vassiliou, Peter J.

    2009-10-01

    Cartan's method of moving frames is briefly recalled in the context of immersed curves in the homogeneous space of a Lie group G. The contact geometry of curves in low dimensional equi-affine geometry is then made explicit. This delivers the complete set of invariant data which solves the G-equivalence problem via a straightforward procedure, and which is, in some sense a supplement to the equivariant method of Fels and Olver. Next, the contact geometry of curves in general Riemannian manifolds (M,g) is described. For the special case in which the isometries of (M,g) act transitively, it is shown that the contact geometry provides an explicit algorithmic construction of the differential invariants for curves in M. The inputs required for the construction consist only of the metric g and a parametrisation of structure group SO(n); the group action is not required and no integration is involved. To illustrate the algorithm we explicitly construct complete sets of differential invariants for curves in the Poincaré half-space H3 and in a family of constant curvature 3-metrics. It is conjectured that similar results are possible in other Cartan geometries.

  20. Sampling probe for microarray read out using electrospray mass spectrometry

    DOEpatents

    Van Berkel, Gary J.

    2004-10-12

    An automated electrospray based sampling system and method for analysis obtains samples from surface array spots having analytes. The system includes at least one probe, the probe including an inlet for flowing at least one eluting solvent to respective ones of a plurality of spots and an outlet for directing the analyte away from the spots. An automatic positioning system is provided for translating the probe relative to the spots to permit sampling of any spot. An electrospray ion source having an input fluidicly connected to the probe receives the analyte and generates ions from the analyte. The ion source provides the generated ions to a structure for analysis to identify the analyte, preferably being a mass spectrometer. The probe can be a surface contact probe, where the probe forms an enclosing seal along the periphery of the array spot surface.

  1. Electrosprayed inulin microparticles for microbiota triggered targeting of colon.

    PubMed

    Jain, Arvind K; Sood, Vishesh; Bora, Meghali; Vasita, Rajesh; Katti, Dhirendra S

    2014-11-04

    Inulin, a naturally occurring polysaccharide, was acetylated to make it processable by electrospraying, a facile and single step method for microparticle fabrication. Electrospraying process parameters were optimized for fabrication of spherical and monodisperse indomethacin (IDM) loaded inulin acetate (INA) microparticles. The apparent entrapment efficiency of IDM was determined to be 100%, whereas working encapsulation efficiency was estimated to be 35.39 ± 1.63%. Differential scanning calorimetry and X-ray diffraction analysis confirmed molecular dispersion of IDM in an amorphous state within the INA matrix. Finally, the results from in vitro release study performed in simulated gastro-intestinal fluids demonstrated that IDM was released only in simulated colonic fluid that contained inulinase. Therefore, this study demonstrates that acetylation of inulin does not alter its susceptibility to inulinase and that microparticles fabricated from INA can be developed as a colon targeting drug delivery system.

  2. Hydration of Gas-Phase Ions Formed by Electrospray Ionization

    PubMed Central

    Rodriguez-Cruz, Sandra E.; Klassen, John S.; Williams, Evan R.

    2005-01-01

    The hydration of gas-phase ions produced by electrospray ionization was investigated. Evidence that the hydrated ions are formed by two mechanisms is presented. First, solvent condensation during the expansion inside the electrospray source clearly occurs. Second, some solvent evaporation from more extensively solvated ions or droplets is apparent. To the extent that these highly solvated ions have solution-phase structures, then the final isolated gas-phase structure of the ion will be determined by the solvent evaporation process. This process was investigated for hydrated gramicidin S in a Fourier-transform mass spectrometer. Unimolecular dissociation rate constants of isolated gramicidin S ions with between 2 and 14 associated water molecules were measured. These rate constants increased from 16 to 230 s−1 with increasing hydration, with smaller values corresponding to magic numbers. PMID:10497808

  3. Electrospray on superhydrophobic nozzles treated with argon and oxygen plasma

    NASA Astrophysics Data System (ADS)

    Byun, Doyoung; Lee, Youngjong; Tran, Si Bui Quang; Nugyen, Vu Dat; Kim, Sanghoon; Park, Baeho; Lee, Sukhan; Inamdar, Niraj; Bau, Haim H.

    2008-03-01

    We report on a simple process to fabricate electrohydrodynamic spraying devices with superhydrophobic nozzles. These devices are useful, among other things, in mass spectrometry and printing technology. The superhydrophobic nozzle is created by roughening the surface of the polyfluorotetraethylene (PTFE) by argon and oxygen plasma treatment. We have developed a polymer-based electrospray device with a flat, superhydrophobic nozzle capable of maintaining a high contact angle and stable jetting.

  4. Ultrahigh vacuum deposition of organic molecules by electrospray ionization

    SciTech Connect

    Hamann, Chr.; Woltmann, R.; Hong, I-Po; Hauptmann, N.; Karan, S.; Berndt, R.

    2011-03-15

    An electrospray apparatus for deposition of organic molecules on surfaces in ultrahigh vacuum is presented. The kinetic energy at the impact and mass to charge ratio of deposited ions can be controlled by an electrostatic quadrupole deflector and an in-line quadrupole mass spectrometer. With an ion funnel in the first two vacuum stages a high ion transmission is achieved. Experiments on porphyrin cations and deoxyribonucleic acid deposited on a Au(111) surface demonstrate the capabilities of the instrument.

  5. The sales learning curve.

    PubMed

    Leslie, Mark; Holloway, Charles A

    2006-01-01

    When a company launches a new product into a new market, the temptation is to immediately ramp up sales force capacity to gain customers as quickly as possible. But hiring a full sales force too early just causes the firm to burn through cash and fail to meet revenue expectations. Before it can sell an innovative product efficiently, the entire organization needs to learn how customers will acquire and use it, a process the authors call the sales learning curve. The concept of a learning curve is well understood in manufacturing. Employees transfer knowledge and experience back and forth between the production line and purchasing, manufacturing, engineering, planning, and operations. The sales learning curve unfolds similarly through the give-and-take between the company--marketing, sales, product support, and product development--and its customers. As customers adopt the product, the firm modifies both the offering and the processes associated with making and selling it. Progress along the manufacturing curve is measured by tracking cost per unit: The more a firm learns about the manufacturing process, the more efficient it becomes, and the lower the unit cost goes. Progress along the sales learning curve is measured in an analogous way: The more a company learns about the sales process, the more efficient it becomes at selling, and the higher the sales yield. As the sales yield increases, the sales learning process unfolds in three distinct phases--initiation, transition, and execution. Each phase requires a different size--and kind--of sales force and represents a different stage in a company's production, marketing, and sales strategies. Adjusting those strategies as the firm progresses along the sales learning curve allows managers to plan resource allocation more accurately, set appropriate expectations, avoid disastrous cash shortfalls, and reduce both the time and money required to turn a profit.

  6. Liposomes self-assembled from electrosprayed composite microparticles

    NASA Astrophysics Data System (ADS)

    Yu, Deng-Guang; Yang, Jun-He; Wang, Xia; Tian, Feng

    2012-03-01

    Composite microparticles, consisting of polyvinylpyrrolidone (PVP), naproxen (NAP) and lecithin (PC), have been successfully prepared using an electrospraying process and exploited as templates to manipulate molecular self-assembly for the synthesis of liposomes in situ. Field emission scanning electron microscope (FESEM) and transmission electron microscope (TEM) observations demonstrate that the microparticles have an average diameter of 960 ± 140 nm and a homogeneous structure. X-ray diffraction (XRD) patterns, differential scanning calorimetry (DSC) and attenuated total reflectance-Fourier transform infrared (ATR-FTIR) results verify that the building blocks NAP and PC are scattered in the polymer matrix in a molecular way owing to the very fast drying of the electrospraying process and the favorable secondary interactions among the components. FESEM, scanning probe microscope (SPM) and TEM observations demonstrate that the liposomes can be achieved through molecular self-assembly in situ when the microparticles contact water thanks to ‘like prefers like’ and by means of the confinement effect of the microparticles. The liposomes have an encapsulation rate of 91.3%, and 80.7% of the drug in the liposomes can be freed into the dissolution medium in a sustained way and by a diffusion mechanism over a period of 24 h. The developed strategy not only provides a new, facile, and effective method to assemble and organize molecules of multiple components into liposomes with electrosprayed microparticles as templates, but also opens a new avenue for nanofabrication in a step-by-step and controllable way.

  7. Capillary isoelectric focusing-electrospray mass spectrometry for protein analysis

    SciTech Connect

    Tang, Q.; Harrata, A.K.; Lee, C.S.

    1995-10-01

    On-line combination of capillary isoelectric focusing (CIEF) with electrospray mass spectrometry (ESMS) as a two-dimensional separation system is demonstrated. Mixtures of model proteins including cytochrome c (horse heart), myoglobin (horse heart), and carbonic anhydrase II (bovine erythrocyte) are focused and cathodically mobilized in a polyacrylamide-coated capillary. At the end of CIEF capillary, the mobilized protein zones are analyzed by mass spectrometry coupled on-line to an electrospray interface with a coaxial sheath flow configuration. The effects of carrier ampholyte concentration on the CIEF separation and the protein electrospray ionization mass spectra are presented and discussed. In this study, the focusing effect of CIEF permits analysis of very dilute protein samples. A typical concentration factor of 50-100 times is observed. The concentration detection limit of myoglobin for a full-scan CIEF-ESMS analysis is in the range of 10{sup -7} M, 2 orders of magnitude over that possible with normal capillary zone electrophoresis ESMS. 35 refs., 5 figs., 2 tabs.

  8. Ultrasonically Aided Electrospray source for monodisperse, charged nanoparticles

    NASA Astrophysics Data System (ADS)

    Song, Weidong

    This dissertation presents a new method of producing nearly monodisperse electrospray using charged capillary standing waves. This method, based on the Ultrasonically Aided Electrospraying (UAE) technology concept invented by the author, includes the steps of dispensing a liquid on the top surface of a diaphragm so as to form a liquid film on the surface of the diaphragm, setting the diaphragm into vibration using piezoelectric transducers so as to induce capillary standing waves in the liquid film, applying electric charge to the capillary standing waves so that electrospray is extracted from the crests of the capillary standing waves. Theoretical analysis on the formation of charged particles from charged capillary standing waves at critically stable condition is performed. An experimental UAE system is designed, built, and tested and the performance of this new technology concept is assessed. Experimental results validate the capabilities of the UAE concept. The method has several applications including electric space propulsion, nano particulate technologies, nanoparticle spray coating and painting techniques, semiconductor fabrication and biomedical processes. Two example applications in electric space propulsion and nanoparticle spray coating are introduced.

  9. Hybrid Perovskite Quantum Nanostructures Synthesized by Electrospray Antisolvent-Solvent Extraction and Intercalation.

    PubMed

    Naphade, Rounak; Nagane, Satyawan; Shanker, G Shiva; Fernandes, Rohan; Kothari, Dushyant; Zhou, Yuanyuan; Padture, Nitin P; Ogale, Satishchandra

    2016-01-13

    Perovskites based on organometal lead halides have attracted great deal of scientific attention recently in the context of solar cells and optoelectronic devices due to their unique and tunable electronic and optical properties. Herein, we show that the use of electrospray technique in conjunction with the antisolvent-solvent extraction leads to novel low-dimensional quantum structures (especially 2-D nanosheets) of CH3NH3PbI3- and CH3NH3PbBr3-based layered perovskites with unusual luminescence properties. We also show that the optical bandgaps and emission characteristics of these colloidal nanomaterials can be tuned over a broad range of visible spectral region by compositional tailoring of mixed-halide (I- and Br-based) perovskites.

  10. Fast quantitative detection of cocaine in beverages using nanoextractive electrospray ionization tandem mass spectrometry.

    PubMed

    Hu, Bin; Peng, Xuejiao; Yang, Shuiping; Gu, Haiwei; Chen, Huanwen; Huan, Yanfu; Zhang, Tingting; Qiao, Xiaolin

    2010-02-01

    Without any sample pretreatment, effervescent beverage fluids were manually sprayed into the primary ion plume created by using a nanoelectrospray ionization source for direct ionization, and the analyte ions of interest were guided into an ion trap mass spectrometer for tandem mass analysis. Functional ingredients (e.g., vitamins, taurine, and caffeine, etc.) and spiked impurity (e.g., cocaine) in various beverages, such as Red Bull energy drink, Coco-cola, and Pepsi samples were rapidly identified within 1.5 s. The limit of detection was found to be 7-15 fg (S/N = 3) for cocaine in different samples using the characteristic fragment (m/z 150) observed in the MS(3) experiments. Typical relative standard deviation and recovery of this method were 6.9%-8.6% and 104%-108% for direct analysis of three actual samples, showing that nanoextractive electrospray ionization tandem mass spectrometry is a useful technique for fast screening cocaine presence in beverages.

  11. The Scanning Mass Spectrometry Probe: A Scanning Probe Electrospray Ion Source for Imaging Mass Spectrometry of Submerged Interfaces and Transient Events in Solution

    PubMed Central

    Kottke, Peter A.; Degertekin, F. Levent; Fedorov, Andrei G.

    2009-01-01

    The scanning mass spectrometry (SMS) probe is new electrospray ion source. Motivated by the need for untargeted chemical imaging of dynamic events in solution, we have exploited an approach to electrospray ionization (ESI) that allows continuous sampling from a highly localized volume (~picoliters) in a liquid environment, softly ionizes molecules in the sample to render them amenable for mass spectrometric analysis, and sends the ions to the mass spectrometer. The key underlying concepts for our approach are1)Treating the electrospray capillary inlet as a chemical scanning probe, and2)Locating the electrospray point as close as possible to the sampling point, thus providing the shortest response time possible. This approach enables chemical monitoring or imaging of submerged interfaces, providing access to details of spatial heterogeneity and temporal changes within liquid samples. It also permits direct access to liquid/ liquid interfaces for ESI-MS analysis. In this Letter we report the first demonstrations of these capabilities of the SMS probe, and describe some of the probe's basic characteristics. PMID:19904914

  12. A Novel Route to Recognizing Quaternary Ammonium Cations Using Electrospray Mass Spectrometry

    NASA Astrophysics Data System (ADS)

    Shackman, Holly M.; Ding, Wei; Bolgar, Mark S.

    2015-01-01

    Characterizing and elucidating structures is a commonplace and necessary activity in the pharmaceutical industry with mass spectrometry and NMR being the primary tools for analysis. Although many functional groups are readily identifiable, quaternary ammonium cations have proven to be difficult to unequivocally identify using these techniques. Due to the lack of an N-H bond, quaternary ammonium groups can only be detected in the 1H NMR spectra by weak signals generated from long-range 14N-H coupling, which by themselves are inconclusive evidence of a quaternary ammonium functional group. Due to their low intensity, these signals are frequently not detected. Additionally, ions cannot be differentiated in a mass spectrum as an M+ or [M + H]+ ion without prior knowledge of the compound's structure. In order to utilize mass spectrometry as a tool for determining this functionality, ion cluster formation of quaternary ammonium cations and non-quaternary amines was studied using electrospray ionization. Several mobile phase modifiers were compared; however, the addition of small amounts of trifluoroacetic acid proved superior in producing characteristic and intense [M +2TFA]- clusters for compounds containing quaternary ammonium cations when using negative electrospray. By fragmenting this characteristic ion using CID, nearly all compounds studied could be unambiguously identified as containing a quaternary ammonium cation or a non-quaternary amine attributable to the presence (non-quaternary amine) or absence (quaternary ammonium cation) of the resulting [2TFA + H]- ion in the product spectra. This method of analysis provides a rapid, novel, and reliable technique for indicating the presence of quaternary ammonium cations in order to aid in structural elucidation.

  13. Mechanism of Charging and Supercharging Molecules in Electrospray Ionization

    PubMed Central

    Iavarone, Anthony T.; Williams*, Evan R.

    2005-01-01

    The origin of the extent of charging and the mechanism by which multiply charged ions are formed in electrospray ionization have been hotly debated for over a decade. Many factors can affect the number of charges on an analyte ion. Here, we investigate the extent of charging of poly(propyleneimine) dendrimers (generations 3.0 and 5.0), cytochrome c, poly(ethylene glycol)s, and 1,n-diaminoalkanes formed from solutions of different composition. We demonstrate that in the absence of other factors, the surface tension of the electrospray droplet late in the desolvation process is a significant factor in determining the overall analyte charge. For poly(ethylene glycol)s, 1,n-diaminoalkanes, and poly(propyleneimine) dendrimers electrosprayed from single-component solutions, there is a clear relationship between the analyte charge and the solvent surface tension. Addition of m-nitrobenzyl alcohol (m-NBA) into electrospray solutions increases the charging when the original solution has a lower surface tension than m-NBA, but the degree of charging decreases when this compound is added to water, which has a higher surface tension. Similarly, the charging of cytochrome c ions formed from acidified denaturing solutions generally increases with increasing surface tension of the least volatile solvent. For the dendrimers investigated, there is a strong correlation between the average charge state of the dendrimer and the Rayleigh limiting charge calculated for a droplet of the same size as the analyte molecule and with the surface tension of the electrospray solvent. A bimodal charge distribution is observed for larger dendrimers formed from water/m-NBA solutions, suggesting the presence of more than one conformation in solution. A similar correlation is found between the extent of charging for 1,n-diaminoalkanes and the calculated Rayleigh limiting charge. These results provide strong evidence that multiply charged organic ions are formed by the charged residue mechanism. A

  14. The Disappearing Bell Curve.

    ERIC Educational Resources Information Center

    Horton, Dawn M.

    2001-01-01

    This article reviews the history of the bell curve and its application to gifted education and suggests rejection of this paradigm in favor of a focus on criteria rather than norms and a better understanding of the distribution and structure of intelligence. (Contains references.) (DB)

  15. Editorial: The Skewed Curve.

    ERIC Educational Resources Information Center

    Bausell, R. Barker

    1995-01-01

    This editorial provides an informal review of "The Bell Curve" (Herrnstein and Murray, 1994). The book, packaged as scientific writing, is an attack on affirmative action and on government attempts to foster egalitarianism. It is a political treatise that assumes that racial differences in intelligence are valid and genetic. (SLD)

  16. Graphing Polar Curves

    ERIC Educational Resources Information Center

    Lawes, Jonathan F.

    2013-01-01

    Graphing polar curves typically involves a combination of three traditional techniques, all of which can be time-consuming and tedious. However, an alternative method--graphing the polar function on a rectangular plane--simplifies graphing, increases student understanding of the polar coordinate system, and reinforces graphing techniques learned…

  17. Textbook Factor Demand Curves.

    ERIC Educational Resources Information Center

    Davis, Joe C.

    1994-01-01

    Maintains that teachers and textbook graphics follow the same basic pattern in illustrating changes in demand curves when product prices increase. Asserts that the use of computer graphics will enable teachers to be more precise in their graphic presentation of price elasticity. (CFR)

  18. Curve Fit Challenge

    ERIC Educational Resources Information Center

    Harper, Suzanne R.; Driskell, Shannon

    2005-01-01

    Graphic tips for using the Geometer's Sketchpad (GSP) are described. The methods to import an image into GSP, define a coordinate system, plot points and curve fit the function using a graphical calculator are demonstrated where the graphic features of GSP allow teachers to expand the use of the technology application beyond the classroom.

  19. Curve Fit Challenge

    ERIC Educational Resources Information Center

    Harper, Suzanne R.; Driskell, Shannon

    2005-01-01

    Graphic tips for using the Geometer's Sketchpad (GSP) are described. The methods to import an image into GSP, define a coordinate system, plot points and curve fit the function using a graphical calculator are demonstrated where the graphic features of GSP allow teachers to expand the use of the technology application beyond the classroom.

  20. Textbook Factor Demand Curves.

    ERIC Educational Resources Information Center

    Davis, Joe C.

    1994-01-01

    Maintains that teachers and textbook graphics follow the same basic pattern in illustrating changes in demand curves when product prices increase. Asserts that the use of computer graphics will enable teachers to be more precise in their graphic presentation of price elasticity. (CFR)

  1. The Axial Curve Rotator.

    ERIC Educational Resources Information Center

    Hunter, Walter M.

    This document contains detailed directions for constructing a device that mechanically produces the three-dimensional shape resulting from the rotation of any algebraic line or curve around either axis on the coordinate plant. The device was developed in response to student difficulty in visualizing, and thus grasping the mathematical principles…

  2. Straightening Out Learning Curves

    ERIC Educational Resources Information Center

    Corlett, E. N.; Morecombe, V. J.

    1970-01-01

    The basic mathematical theory behind learning curves is explained, together with implications for clerical and industrial training, evaluation of skill development, and prediction of future performance. Brief studies of textile worker and typist training are presented to illustrate such concepts as the reduction fraction (a consistent decrease in…

  3. The Bacterial Growth Curve.

    ERIC Educational Resources Information Center

    Paulton, Richard J. L.

    1991-01-01

    A procedure that allows students to view an entire bacterial growth curve during a two- to three-hour student laboratory period is described. Observations of the lag phase, logarithmic phase, maximum stationary phase, and phase of decline are possible. A nonpathogenic, marine bacterium is used in the investigation. (KR)

  4. Classification of ASKAP Vast Radio Light Curves

    NASA Technical Reports Server (NTRS)

    Rebbapragada, Umaa; Lo, Kitty; Wagstaff, Kiri L.; Reed, Colorado; Murphy, Tara; Thompson, David R.

    2012-01-01

    The VAST survey is a wide-field survey that observes with unprecedented instrument sensitivity (0.5 mJy or lower) and repeat cadence (a goal of 5 seconds) that will enable novel scientific discoveries related to known and unknown classes of radio transients and variables. Given the unprecedented observing characteristics of VAST, it is important to estimate source classification performance, and determine best practices prior to the launch of ASKAP's BETA in 2012. The goal of this study is to identify light curve characterization and classification algorithms that are best suited for archival VAST light curve classification. We perform our experiments on light curve simulations of eight source types and achieve best case performance of approximately 90% accuracy. We note that classification performance is most influenced by light curve characterization rather than classifier algorithm.

  5. Classification of ASKAP Vast Radio Light Curves

    NASA Technical Reports Server (NTRS)

    Rebbapragada, Umaa; Lo, Kitty; Wagstaff, Kiri L.; Reed, Colorado; Murphy, Tara; Thompson, David R.

    2012-01-01

    The VAST survey is a wide-field survey that observes with unprecedented instrument sensitivity (0.5 mJy or lower) and repeat cadence (a goal of 5 seconds) that will enable novel scientific discoveries related to known and unknown classes of radio transients and variables. Given the unprecedented observing characteristics of VAST, it is important to estimate source classification performance, and determine best practices prior to the launch of ASKAP's BETA in 2012. The goal of this study is to identify light curve characterization and classification algorithms that are best suited for archival VAST light curve classification. We perform our experiments on light curve simulations of eight source types and achieve best case performance of approximately 90% accuracy. We note that classification performance is most influenced by light curve characterization rather than classifier algorithm.

  6. Low pressure electrospray ionization system and process for effective transmission of ions

    DOEpatents

    Tang, Keqi [Richland, WA; Page, Jason S [Kennewick, WA; Kelly, Ryan T [Wet Richland, WA; Smith, Richard D [Richland, WA

    2010-03-02

    A system and method are disclosed that provide up to complete transmission of ions between coupled stages with low effective ion losses. A novel "interfaceless" electrospray ionization system is further described that operates the electrospray at a reduced pressure such that standard electrospray sample solutions can be directly sprayed into an electrodynamic ion funnel which provides ion focusing and transmission of ions into a mass analyzer.

  7. Determination of equilibrium association constants of ligand-DNA complexes by electrospray mass spectrometry.

    PubMed

    Gabelica, Valérie

    2010-01-01

    Electrospray mass spectrometry can be used to detect ligand-DNA noncovalent complexes formed in solution. This chapter describes how to determine equilibrium association constants of the complexes. Particular attention is devoted to describing how to tune an electrospray mass spectrometer using a 12-mer oligodeoxynucleotides duplex in order to perform these experiments. This protocol can then be applied to any nucleic acid structure that can be ionized with electrospray mass spectrometry.

  8. Liquid chromatography/electrospray ionization tandem mass spectrometry assay for determination of nicotine and metabolites, caffeine and arecoline in breast milk.

    PubMed

    Pellegrini, Manuela; Marchei, Emilia; Rossi, Silvia; Vagnarelli, Federica; Durgbanshi, Abhilasha; García-Algar, Oscar; Vall, Oriol; Pichini, Simona

    2007-01-01

    A procedure based on liquid chromatography/tandem mass spectrometry (LC/MS/MS) is described for the determination of nicotine and its principal metabolites cotinine, trans-3-hydroxycotinine and cotinine-N-oxide, caffeine and arecoline in breast milk, using N-ethylnorcotinine as internal standard. Liquid/liquid extraction with chloroform/isopropanol (95:5, v/v) was used for nicotine, cotinine, trans-3-hydroxycotinine, cotinine-N-oxide and caffeine under neutral conditions and for arecoline under basic conditions. Chromatography was performed on a C(8) reversed-phase column using a gradient of 50 mM ammonium formate, pH 5.0, and acetonitrile as a mobile phase at a flow rate of 0.5 mL/min. Separated analytes were determined by electrospray ionization tandem mass spectrometry in the positive ion mode using multiple reaction monitoring. Limits of quantification were 5 microg/L for nicotine, cotinine, trans-3-hydroxycotinine, cotinine-N-oxide and caffeine, and 50 microg/L for arecoline using 1 mL human milk per assay. Calibration curves were linear over the calibration ranges for all the substances under investigation, with a minimum r(2) > 0.998. At three concentrations spanning the linear dynamic range of the assay, mean recoveries from breast milk ranged between 71.8 and 77.4% for different analytes. This method was applied to the analysis of analytes in human milk to assess substance exposure in breast-fed infants in relation to eventual clinical outcomes. This LC/MS/MS assay provides adequate sensitivity and performance characteristics for the simultaneous quantification of biomarkers of three of the drugs most commonly used worldwide (tobacco, caffeine and areca nut).

  9. Automated in-tube solid-phase microextraction coupled with liquid chromatography-electrospray ionization mass spectrometry for the determination of selected benzodiazepines.

    PubMed

    Yuan, H; Mester, Z; Lord, H; Pawliszyn, J

    2000-01-01

    A simple, rapid, and sensitive method, which allowed us to simultaneously determine seven benzodiazepines (diazepam, nordiazepam, temazepam, oxazepam, 7-aminoflunitrazepam, N-desmethylflunitrazepam, and clonazepam) in buffer solution and in urine and serum samples, was investigated by automated in-tube solid-phase microextraction (SPME) coupled with liquid chromatography-electrospray ionization mass spectrometry (LC-ESI-MS). In-tube SPME, in which the analytes were extracted from the sample directly into an open tubular capillary column by repeated draw/eject cycles of sample solution, is an extraction technique for organic compounds in aqueous samples. The separation of benzodiazepines was carried out under ion-suppressed reversed-phase conditions by using methanol/50mM ammonium acetate in water (60:40) as a mobile phase with a Supelco LC-18 column. The optimal extraction condition was 10 draw/eject cycles of 30 mL of sample in 100mM Tris-HCl (pH 8.5) at a flow rate of 0.3 mL/min using a piece of 60-cm length Supelco-Q plot capillary column as the extraction capillary. The quantitative study was explored by operating in selected-ion monitoring (SIM) mode. The calibration curves were linear in the range from 0.5 ng/mL or 2 ng/mL to 500 ng/mL. The detection limits were from 0.02 ng/mL to 2 ng/mL. At the optimized capillary and fragmentor voltages, the characteristic ions for each compound clearly showed up in the spectra and it is possible to use the LC-MS to identify these compounds. The method was applied to the analysis of biological samples without interfering peaks. However, the recoveries for some of the compounds in serum samples need to be further improved.

  10. Comparison of Internal Energy Distributions of Ions Created by Electrospray Ionization and Laser Ablation-Liquid Vortex Capture-Electrospray Ionization

    SciTech Connect

    Cahill, John F.; Kertesz, Vilmos; Ovchinnikova, Olga S.; Van Berkel, Gary J.

    2015-06-27

    Recently a number of techniques have combined laser ablation with liquid capture for mass spectrometry spot sampling and imaging applications. The newly developed non-contact liquid-vortex capture probe has been used to efficiently collect 355 nm UV laser ablated material in a continuous flow solvent stream in which the captured material dissolves and then undergoes electrospray ionization. This sampling and ionization approach has produced what appear to be classic electrospray ionization spectra; however, the softness of this sampling/ionization process versus simple electrospray ionization has not been definitely determined. A series of benzlypyridinium salts, known as thermometer ions, were used to compare internal energy distributions between electrospray ionization and the UV laser ablation liquid-vortex capture probe electrospray combination. Measured internal energy distributions were identical between the two techniques, even with differences in laser fluence (0.7-3.1 J cm-2) and when using UV-absorbing or non-UV-absorbing sample substrates. This data indicates ions formed directly by UV laser ablation, if any, are likely an extremely small constituent of the total ion signal observed. Instead, neutral molecules, clusters or particulates ejected from the surface during laser ablation, subsequently captured and dissolved in the flowing solvent stream then electrosprayed are the predominant source of ion signal observed. The electrospray ionization process used controls the softness of the technique.

  11. Comparison of Internal Energy Distributions of Ions Created by Electrospray Ionization and Laser Ablation-Liquid Vortex Capture-Electrospray Ionization

    DOE PAGES

    Cahill, John F.; Kertesz, Vilmos; Ovchinnikova, Olga S.; ...

    2015-06-27

    Recently a number of techniques have combined laser ablation with liquid capture for mass spectrometry spot sampling and imaging applications. The newly developed non-contact liquid-vortex capture probe has been used to efficiently collect 355 nm UV laser ablated material in a continuous flow solvent stream in which the captured material dissolves and then undergoes electrospray ionization. This sampling and ionization approach has produced what appear to be classic electrospray ionization spectra; however, the softness of this sampling/ionization process versus simple electrospray ionization has not been definitely determined. A series of benzlypyridinium salts, known as thermometer ions, were used to comparemore » internal energy distributions between electrospray ionization and the UV laser ablation liquid-vortex capture probe electrospray combination. Measured internal energy distributions were identical between the two techniques, even with differences in laser fluence (0.7-3.1 J cm-2) and when using UV-absorbing or non-UV-absorbing sample substrates. This data indicates ions formed directly by UV laser ablation, if any, are likely an extremely small constituent of the total ion signal observed. Instead, neutral molecules, clusters or particulates ejected from the surface during laser ablation, subsequently captured and dissolved in the flowing solvent stream then electrosprayed are the predominant source of ion signal observed. The electrospray ionization process used controls the softness of the technique.« less

  12. Nonlinear Growth Curves in Developmental Research

    ERIC Educational Resources Information Center

    Grimm, Kevin J.; Ram, Nilam; Hamagami, Fumiaki

    2011-01-01

    Developmentalists are often interested in understanding change processes, and growth models are the most common analytic tool for examining such processes. Nonlinear growth curves are especially valuable to developmentalists because the defining characteristics of the growth process such as initial levels, rates of change during growth spurts, and…

  13. Nonlinear Growth Curves in Developmental Research

    ERIC Educational Resources Information Center

    Grimm, Kevin J.; Ram, Nilam; Hamagami, Fumiaki

    2011-01-01

    Developmentalists are often interested in understanding change processes, and growth models are the most common analytic tool for examining such processes. Nonlinear growth curves are especially valuable to developmentalists because the defining characteristics of the growth process such as initial levels, rates of change during growth spurts, and…

  14. Atlas of fatigue curves

    SciTech Connect

    Boyer, H.E.

    1986-01-01

    This Atlas was developed to serve engineers who are looking for fatigue data on a particular metal or alloy. Having these curves compiled in a single book will also facilitate the computerization of the involved data. It is pointed out that plans are under way to make the data in this book available in ASCII files for analysis by computer programs. S-N curves which typify effects of major variables are considered along with low-carbon steels, medium-carbon steels, alloy steels, HSLA steels, high-strength alloy steels, heat-resisting steels, stainless steels, maraging steels, cast irons, and heat-resisting alloys. Attention is also given to aluminum alloys, copper alloys, magnesium alloys, molybdenum, tin alloys, titanium and titanium alloys, zirconium, steel castings, closed-die forgings, powder metallurgy parts, composites, effects of surface treatments, and test results for component parts.

  15. Trishear for curved faults

    NASA Astrophysics Data System (ADS)

    Brandenburg, J. P.

    2013-08-01

    Fault-propagation folds form an important trapping element in both onshore and offshore fold-thrust belts, and as such benefit from reliable interpretation. Building an accurate geologic interpretation of such structures requires palinspastic restorations, which are made more challenging by the interplay between folding and faulting. Trishear (Erslev, 1991; Allmendinger, 1998) is a useful tool to unravel this relationship kinematically, but is limited by a restriction to planar fault geometries, or at least planar fault segments. Here, new methods are presented for trishear along continuously curved reverse faults defining a flat-ramp transition. In these methods, rotation of the hanging wall above a curved fault is coupled to translation along a horizontal detachment. Including hanging wall rotation allows for investigation of structures with progressive backlimb rotation. Application of the new algorithms are shown for two fault-propagation fold structures: the Turner Valley Anticline in Southwestern Alberta, and the Alpha Structure in the Niger Delta.

  16. LCC: Light Curves Classifier

    NASA Astrophysics Data System (ADS)

    Vo, Martin

    2017-08-01

    Light Curves Classifier uses data mining and machine learning to obtain and classify desired objects. This task can be accomplished by attributes of light curves or any time series, including shapes, histograms, or variograms, or by other available information about the inspected objects, such as color indices, temperatures, and abundances. After specifying features which describe the objects to be searched, the software trains on a given training sample, and can then be used for unsupervised clustering for visualizing the natural separation of the sample. The package can be also used for automatic tuning parameters of used methods (for example, number of hidden neurons or binning ratio). Trained classifiers can be used for filtering outputs from astronomical databases or data stored locally. The Light Curve Classifier can also be used for simple downloading of light curves and all available information of queried stars. It natively can connect to OgleII, OgleIII, ASAS, CoRoT, Kepler, Catalina and MACHO, and new connectors or descriptors can be implemented. In addition to direct usage of the package and command line UI, the program can be used through a web interface. Users can create jobs for ”training” methods on given objects, querying databases and filtering outputs by trained filters. Preimplemented descriptors, classifier and connectors can be picked by simple clicks and their parameters can be tuned by giving ranges of these values. All combinations are then calculated and the best one is used for creating the filter. Natural separation of the data can be visualized by unsupervised clustering.

  17. Mouse Curve Biometrics

    SciTech Connect

    Schulz, Douglas A.

    2007-10-08

    A biometric system suitable for validating user identity using only mouse movements and no specialized equipment is presented. Mouse curves (mouse movements with little or no pause between them) are individually classied and used to develop classication histograms, which are representative of an individual's typical mouse use. These classication histograms can then be compared to validate identity. This classication approach is suitable for providing continuous identity validation during an entire user session.

  18. Quantization on Curves

    NASA Astrophysics Data System (ADS)

    Frønsdal, Christian; Kontsevich, Maxim

    2007-02-01

    Deformation quantization on varieties with singularities offers perspectives that are not found on manifolds. The Harrison component of Hochschild cohomology, vanishing on smooth manifolds, reflects information about singularities. The Harrison 2-cochains are symmetric and are interpreted in terms of abelian *-products. This paper begins a study of abelian quantization on plane curves over mathbb{C}, being algebraic varieties of the form {mathbb{C}}^2/R, where R is a polynomial in two variables; that is, abelian deformations of the coordinate algebra mathbb{C}[x,y]/(R). To understand the connection between the singularities of a variety and cohomology we determine the algebraic Hochschild (co)homology and its Barr Gerstenhaber Schack decomposition. Homology is the same for all plane curves mathbb{C}[x,y]/R, but the cohomology depends on the local algebra of the singularity of R at the origin. The Appendix, by Maxim Kontsevich, explains in modern mathematical language a way to calculate Hochschild and Harrison cohomology groups for algebras of functions on singular planar curves etc. based on Koszul resolutions.

  19. Miniature curved artificial compound eyes.

    PubMed

    Floreano, Dario; Pericet-Camara, Ramon; Viollet, Stéphane; Ruffier, Franck; Brückner, Andreas; Leitel, Robert; Buss, Wolfgang; Menouni, Mohsine; Expert, Fabien; Juston, Raphaël; Dobrzynski, Michal Karol; L'Eplattenier, Geraud; Recktenwald, Fabian; Mallot, Hanspeter A; Franceschini, Nicolas

    2013-06-04

    In most animal species, vision is mediated by compound eyes, which offer lower resolution than vertebrate single-lens eyes, but significantly larger fields of view with negligible distortion and spherical aberration, as well as high temporal resolution in a tiny package. Compound eyes are ideally suited for fast panoramic motion perception. Engineering a miniature artificial compound eye is challenging because it requires accurate alignment of photoreceptive and optical components on a curved surface. Here, we describe a unique design method for biomimetic compound eyes featuring a panoramic, undistorted field of view in a very thin package. The design consists of three planar layers of separately produced arrays, namely, a microlens array, a neuromorphic photodetector array, and a flexible printed circuit board that are stacked, cut, and curved to produce a mechanically flexible imager. Following this method, we have prototyped and characterized an artificial compound eye bearing a hemispherical field of view with embedded and programmable low-power signal processing, high temporal resolution, and local adaptation to illumination. The prototyped artificial compound eye possesses several characteristics similar to the eye of the fruit fly Drosophila and other arthropod species. This design method opens up additional vistas for a broad range of applications in which wide field motion detection is at a premium, such as collision-free navigation of terrestrial and aerospace vehicles, and for the experimental testing of insect vision theories.

  20. Evaporation and discharge dynamics of highly charged multicomponent droplets generated by electrospray ionization.

    PubMed

    Grimm, Ronald L; Beauchamp, J L

    2010-01-28

    We investigate the Rayleigh discharge and evaporation dynamics of highly charged two-component droplets consisting principally of methanol with 2-methoxyethanol, tert-butanol, or m-nitrobenzyl alcohol. A phase Doppler anemometer (PDA) characterizes droplets generated by electrospray ionization (ESI) according to size, velocity, and charge as they move through a uniform electric field within an ion mobility spectrometer (IMS). Repeated field reversals result in droplet "ping-pong" through the PDA. This generates individual droplet histories of solvent evaporation behavior and the dynamics of charge loss to progeny droplets during Rayleigh discharge events. On average, methanol droplets discharge at 127% their Rayleigh limit of charge, q(R), and release 25% of the net charge. Charge loss from methanol/2-methoxyethanol droplets behaves similarly to pure 2-methoxyethanol droplets which release approximately 28% of their net charge. Binary methanol droplets containing up to 50% tert-butanol discharge at a lower percent q(R) than pure methanol and release a greater fraction of their net charge. Mixed 99% methanol/1% m-nitrobenzyl alcohol droplets possess discharge characteristics similar to those of methanol. However, droplets of methanol containing 2% m-nitrobenzyl evaporate down to a fixed size and charge that remains constant with no observable discharges. Quasi-steady-state evaporation models accurately describe observed evaporation phenomena in which methanol/tert-butanol droplets evaporate at a rate similar to that of pure methanol and methanol/2-methoxyethanol droplets evaporate at a rate similar to that of 2-methoxyethanol. We compare these results to previous Rayleigh discharge experiments and discuss the implications for binary solvents in electrospray mass spectrometry (ESI-MS) and field-induced droplet ionization mass spectrometry (FIDI-MS).

  1. Detection of trace levels of lead in aqueous liquids using extractive electrospray ionization tandem mass spectrometry.

    PubMed

    Liu, Chunxiao; Zhang, Xinglei; Xiao, Saijin; Jia, Bin; Cui, Shasha; Shi, Jianbo; Xu, Ning; Xie, Xi; Gu, Haiwei; Chen, Huanwen

    2012-08-30

    A sensitive approach, based on semi-quantitative measurement of the characteristic fragments in multi-stage extractive electrospray ionization mass spectrometry (EESI-MS(n)), was developed for fast detection of trace levels of lead in aqueous liquids including mineral water, lake water, tap water, energy drinks, soft drinks, beer, orange juice, and tea. A disodium ethylene-diamine-tetraacetic acid (EDTA) aqueous solution was electrosprayed to produce negatively charged primary ions which then intersected the neutral sample plume to generate anions of EDTA-Pb(II) complexes. The charged EDTA-Pb(II) complexes were characterized with multistage collision induced dissociation (CID) experiments. The limit of detection (LOD) using EESI-MS(3) was estimated to be at the level of 10(-13)g/mL for directly detecting lead in many of these samples. The linear dynamic range was higher than 2 orders of magnitude. A single sample analysis could be completed within 2 min with reasonable semi-quantitative performance, e.g., relative standard deviations (RSDs) for deionized water were 4.6-7.6% during 5 experimental runs (each of them had 10 repeated measurements). Coca-cola and Huiyuan orange juice, representative beverage samples with complex matrices, generated recovery rates of 91.5% and 129%, respectively. Our experimental data demonstrated that EESI-MS is a useful tool for the fast detection of lead in various solutions, and EESI-MS showed promises for fast screening of lead-contaminated aqueous liquid samples. Copyright © 2012 Elsevier B.V. All rights reserved.

  2. Detection and imaging of thermochromic ink compounds in erasable pens using desorption electrospray ionization mass spectrometry.

    PubMed

    Khatami, Amin; Prova, Shamina S; Bagga, Aafreen K; Yan Chi Ting, Michelle; Brar, Gurnoor; Ifa, Demian R

    2017-06-30

    Thermochromic ink pens are widely accessible worldwide and have gained popularity among the general public. These pens are very useful to undo mistakes while writing important documents or exams. They are also, however, misused in committing crimes such as counterfeiting checks or wills. Thus, the forensics community is in need of techniques that will allow these forgeries to be detected rapidly, reliably and conveniently. Thermochromic ink compounds were investigated using Desorption Electrospray Ionization (DESI) coupled with an LTQ mass spectrometer and Thin-Layer Chromatography (TLC). Tandem mass spectrometric analysis was conducted using Electrospray Ionization (ESI) coupled with an Orbitrap LTQ mass spectrometer performing Collision-Induced Dissociation (CID) for identification of ink traces. Chemical marker ions characteristic of the state of ink (visible or invisible) were identified and mapped in ink traces by the use of DESI-MS imaging. These ions can be employed by forensic experts as fingerprint markers in forged documents. The marker ions were also characterised by conducting tandem mass spectrometry using paper spray in an Orbitrap LTQ mass spectrometer. Specific chemical components yielding ions of m/z 400, 405, 615 and 786 were distinguished as only being apparent in the invisible and reappeared state of the ink. The absence of these compounds in the original state of the ink enabled their recognition as useful chemical determinants in detecting forgery. DESI-MSI was thus shown to be a very useful, convenient and reliable technique for detecting forgery in paper documents due to its fast and reproducible mode of analysis, with no sample preparation and minimal damage to the document under investigation. Copyright © 2017 John Wiley & Sons, Ltd. Copyright © 2017 John Wiley & Sons, Ltd.

  3. Cone-jet electrospray in a dielectric liquid atmosphere

    NASA Astrophysics Data System (ADS)

    Barrero, Antonio; López-Herrera, José M.; Boucard, Arnaud; Loscertales, Ignacio G.; Márquez, Manuel

    2002-11-01

    Dispersion of liquids in a gas atmosphere or vacuum by applying an intense electric field is a well-known phenomenon. In fact, when the electric field on a liquid surface reaches a threshold value, the surface becomes unstable and forms a conical meniscus from whose vertex charge and mass are emitted. The conical meniscus attached to the end of a capillary needle and the emitted jet are steady for an appropriate range of values of both the applied electric field and the flow rate injected through the needle. Semi-conducting liquids can also be steadily dispersed into a dielectric liquid atmosphere in the cone jet mode. In this work, we report some experimental results of the electrospraying of water, ethylene-glycol, and glycerol in both heptane and hexane. The technique may be of interest for the production of fine emulsions, coating of particles containing drugs or any other substance, etc. The experimental setup for the spraying does not differ substantially from those used in standard electrosprays in gas atmosphere or vacuum. Measurements of the current emitted from the cone and the size of the particles as well as their standard deviation in size have been obtained as a function of the injected flow rate and the applied voltage. A Sympatec system has been used for measurements of the droplet size and the dispersion of the hydrosol. The influence of the liquids properties, such as electrical conductivity, permittivity ratio, and surface tension of the couple of liquids, on the scaling laws has been also investigated. Results agree well with the scaling laws for electrosprays in air.

  4. Quantitation of drugs via molecularly imprinted polymer solid phase extraction and electrospray ionization mass spectrometry: benzodiazepines in human plasma.

    PubMed

    Figueiredo, Eduardo Costa; Sparrapan, Regina; Sanvido, Gustavo Braga; Santos, Mariane Gonçalves; Arruda, Marco Aurélio Zezzi; Eberlin, Marcos Nogueira

    2011-09-21

    The association of solid phase extraction with molecularly imprinted polymers (MIP) and electrospray ionization mass spectrometry (ESI-MS) is applied to the direct extraction and quantitation of benzodiazepines in human plasma. The target analytes are sequestered by MIP and directly analyzed by ESI-MS. Due to the MIP highly selective extraction, ionic suppression during ESI is minimized; hence no separation is necessary prior to ESI-MS, which greatly increases analytical speed. Benzodiazepines (medazepam, nitrazepam, diazepam, chlordiazepoxide, clonazepam and midazolam) in human plasma were chosen as a proof-of-principle case of drug analyses by MIP-ESI-MS in a complex matrix. MIP-ESI-MS displayed good figures of merits for medazepam, nitrazepam, diazepam, chlordiazepoxide and midazolam, with analytical calibration curves ranging from 10 to 250 μg L(-1) (r > 0.98) with limit of quantification <10 μg L(-1) and acceptable within-day and between-day precision and accuracy.

  5. High-performance liquid chromatography-electrospray ionization mass spectrometry determination of sodium ferulate in human plasma.

    PubMed

    Yang, Cheng; Tian, Yuan; Zhang, Zunjian; Xu, Fengguo; Chen, Yun

    2007-02-19

    A selective and sensitive high-performance liquid chromatography-electrospray ionization mass spectrometry method has been developed for the determination of sodium ferulate in human plasma. The sample preparation was a liquid-liquid extraction and chromatographic separation was achieved with an Agilent ZORBAX SB-C(18) (3.5 microm, 100 mm x 3.0 mm) column, using a mobile phase of methanol-0.05% acetic acid 40:60 (v/v). Standard curves were linear (r(2)=0.9982) over the concentration range of 0.007-4.63 nM/ml and had acceptable accuracy and precision. The within- and between-batch precisions were within 12% relative standard deviation. The lower limit of quantification (LLOQ) was 0.007 nM/ml. The validated HPLC-ESI-MS method has been used successfully to study sodium ferulate pharmacokinetics, bioavailability and bioequivalence in 20 healthy volunteers.

  6. Numerical simulation of electrospray in the cone-jet mode.

    PubMed

    Herrada, M A; López-Herrera, J M; Gañán-Calvo, A M; Vega, E J; Montanero, J M; Popinet, S

    2012-08-01

    We present a robust and computationally efficient numerical scheme for simulating steady electrohydrodynamic atomization processes (electrospray). The main simplification assumed in this scheme is that all the free electrical charges are distributed over the interface. A comparison of the results with those calculated with a volume-of-fluid method showed that the numerical scheme presented here accurately describes the flow pattern within the entire liquid domain. Experiments were performed to partially validate the numerical predictions. The simulations reproduced accurately the experimental shape of the liquid cone jet, providing correct values of the emitted electric current even for configurations very close to the cone-jet stability limit.

  7. Piecewise power laws in individual learning curves.

    PubMed

    Donner, Yoni; Hardy, Joseph L

    2015-10-01

    The notion that human learning follows a smooth power law (PL) of diminishing gains is well-established in psychology. This characteristic is observed when multiple curves are averaged, potentially masking more complex dynamics underpinning the curves of individual learners. Here, we analyzed 25,280 individual learning curves, each comprising 500 measurements of cognitive performance taken from four cognitive tasks. A piecewise PL (PPL) model explained the individual learning curves significantly better than a single PL, controlling for model complexity. The PPL model allows for multiple PLs connected at different points in the learning process. We also explored the transition dynamics between PL curve component pieces. Performance in later pieces typically surpassed that in earlier pieces, after a brief drop in performance at the transition point. The transition rate was negatively associated with age, even after controlling for overall performance. Our results suggest at least two processes at work in individual learning curves: locally, a gradual, smooth improvement, with diminishing gains within a specific strategy, which is modeled well as a PL; and globally, a discrete sequence of strategy shifts, in which each strategy is better in the long term than the ones preceding it. The piecewise extension of the classic PL of practice has implications for both individual skill acquisition and theories of learning.

  8. Brush potential curve tracer

    DOEpatents

    Finch, H.A.

    1985-06-21

    A device for analyzing commutating characteristics of a motor or generator includes a holder for supporting a plurality of probes adjacent a brush of the motor or generator. Measurements of electrical current characteristics of the probes provides information useful in analyzing operation of the machine. Methods for employing a device in accordance with the invention are also disclosed.

  9. Online coupling of digital microfluidic devices with mass spectrometry detection using an eductor with electrospray ionization.

    PubMed

    Baker, Christopher A; Roper, Michael G

    2012-03-20

    MS detection coupled with digital microfluidic (DMF) devices has most commonly been demonstrated in an offline manner using matrix assisted laser desorption ionization. In this work, an eductor is demonstrated which facilitated online coupling of DMF with electrospray ionization MS detection. The eductor consisted of a transfer capillary, a standard ESI needle, and a tapered gas nozzle. As a pulse of N(2) was applied to the nozzle, a pressure differential was induced at the outlet of the ESI needle that pulled droplets from the DMF, past the ESI needle, and into the flow of gas exiting the nozzle, allowing detection by MS. Operating position, ionization potential, and N(2) pressure were optimized, with the optimum ionization potential and N(2) pressure found to be 3206 V and 80 psi, respectively. Online MS detection was demonstrated from both open and closed DMF devices using 2.5 μL and 630 nL aqueous droplets, respectively. Relative quantitation by DMF-MS was demonstrated by mixing droplets of caffeine with droplets of theophylline on an open DMF device and comparing the peak area ratio obtained to an on-chip generated calibration curve. This eductor-based method for transferring droplets has the potential for rapid, versatile, and high-throughput microfluidic analyses.

  10. Studying the chemistry of cationized triacylglycerols using electrospray ionization mass spectrometry and density functional theory computations.

    PubMed

    Grossert, J Stuart; Cubero Herrera, Lisandra; Ramaley, Louis; Melanson, Jeremy E

    2014-08-01

    Analysis of triacylglycerols (TAGs), found as complex mixtures in living organisms, is typically accomplished using liquid chromatography, often coupled to mass spectrometry. TAGs, weak bases not protonated using electrospray ionization, are usually ionized by adduct formation with a cation, including those present in the solvent (e.g., Na(+)). There are relatively few reports on the binding of TAGs with cations or on the mechanisms by which cationized TAGs fragment. This work examines binding efficiencies, determined by mass spectrometry and computations, for the complexation of TAGs to a range of cations (Na(+), Li(+), K(+), Ag(+), NH4(+)). While most cations bind to oxygen, Ag(+) binding to unsaturation in the acid side chains is significant. The importance of dimer formation, [2TAG + M](+) was demonstrated using several different types of mass spectrometers. From breakdown curves, it became apparent that two or three acid side chains must be attached to glycerol for strong cationization. Possible mechanisms for fragmentation of lithiated TAGs were modeled by computations on tripropionylglycerol. Viable pathways were found for losses of neutral acids and lithium salts of acids from different positions on the glycerol moiety. Novel lactone structures were proposed for the loss of a neutral acid from one position of the glycerol moiety. These were studied further using triple-stage mass spectrometry (MS(3)). These lactones can account for all the major product ions in the MS(3) spectra in both this work and the literature, which should allow for new insights into the challenging analytical methods needed for naturally occurring TAGs.

  11. Microscale extraction of perchlorate in drinking water with low level detection by electrospray-mass spectrometry.

    PubMed

    Magnuson, M L; Urbansky, E T; Kelty, C A

    2000-06-21

    Improper treatment and disposal of perchlorate can be an environmental hazard in regions where solid rocket motors are used, tested, or stored. The solubility and mobility of perchlorate lends itself to ground water contamination, and some of these sources are used for drinking water. Perchlorate in drinking water has been determined at sub-mug l(-1) levels by extraction of the ion-pair formed between the perchlorate ion and a cationic surfactant with electrospray-mass spectrometry detection. Confidence in the selective quantification of the perchlorate ion is increased through both the use of the mass based detection as well as the selectivity of the ion pair. This study investigates several extraction solvents and experimental work-up procedures in order to achieve high sample throughput. The method detection limit for perchlorate based on 3.14sigma(n-1) of seven replicate injections was 300 ng l(-1) (parts-per-trillion) for methylene chloride extraction and 270 ng l(-1) for methyl isobutyl ketone extraction. Extraction with methylene chloride produces linear calibration curves, enabling standard addition to be used to quantify perchlorate in drinking water. Perchlorate determination of a contaminated water compared favorably with results determined by ion chromatography.

  12. Studying the Chemistry of Cationized Triacylglycerols Using Electrospray Ionization Mass Spectrometry and Density Functional Theory Computations

    NASA Astrophysics Data System (ADS)

    Grossert, J. Stuart; Herrera, Lisandra Cubero; Ramaley, Louis; Melanson, Jeremy E.

    2014-08-01

    Analysis of triacylglycerols (TAGs), found as complex mixtures in living organisms, is typically accomplished using liquid chromatography, often coupled to mass spectrometry. TAGs, weak bases not protonated using electrospray ionization, are usually ionized by adduct formation with a cation, including those present in the solvent (e.g., Na+). There are relatively few reports on the binding of TAGs with cations or on the mechanisms by which cationized TAGs fragment. This work examines binding efficiencies, determined by mass spectrometry and computations, for the complexation of TAGs to a range of cations (Na+, Li+, K+, Ag+, NH4 +). While most cations bind to oxygen, Ag+ binding to unsaturation in the acid side chains is significant. The importance of dimer formation, [2TAG + M]+ was demonstrated using several different types of mass spectrometers. From breakdown curves, it became apparent that two or three acid side chains must be attached to glycerol for strong cationization. Possible mechanisms for fragmentation of lithiated TAGs were modeled by computations on tripropionylglycerol. Viable pathways were found for losses of neutral acids and lithium salts of acids from different positions on the glycerol moiety. Novel lactone structures were proposed for the loss of a neutral acid from one position of the glycerol moiety. These were studied further using triple-stage mass spectrometry (MS3). These lactones can account for all the major product ions in the MS3 spectra in both this work and the literature, which should allow for new insights into the challenging analytical methods needed for naturally occurring TAGs.

  13. Determination of tetramine in marine gastropods by liquid chromatography/electrospray ionization-mass spectrometry.

    PubMed

    Kawashima, Yoko; Nagashima, Yuji; Shiomi, Kazuo

    2004-08-01

    Tetramine (tetramethylammonium ion) is found at high levels (several mg/g) in the salivary gland of buccinid gastropods and has been involved in numerous poisoning incidents after ingestion of those gastropods. A sensitive and selective determination method for tetramine, which is based on a combination of liquid chromatography (LC) and electrospray ionization-single quadrupole mass spectrometry (ESI-MS), was developed. Following separation by LC on a cation-exchange column, tetramine was easily detected by simultaneous monitoring of a molecular ion (m/z 74) at a cone voltage of 30 V and a fragment ion (m/z 58) at 70 V. A linear calibration curve was obtained in the range of 0.1-100 ng by plotting the peak areas of the molecular ion versus the amounts of tetramine. Spiking experiments demonstrated that tetramine in gastropod tissues can be determined by the LC/ESI-MS method, without being affected by sample matrices as well as the extration procedure. Applications of the new method to gastropod samples revealed that a small amount of tetramine is contained even in mid-gut gland and muscle and that tetramine in the salivary gland diffuses to other tissues during boiling and slow thawing.

  14. Dual enzyme activities assay by quantitative electrospray ionization quadrupole-time-of-flight mass spectrometry.

    PubMed

    Cai, Tingting; Zhang, Li; Wang, Haoyang; Zhang, Jing; Wang, Rong; Zhang, Yurong; Guo, Yinlong

    2012-01-01

    A practical and rapid method based on electrospray ionization quadrupole-time of flight mass spectrometry (ESI-Q-ToF MS) was developed for detecting activities of both acetylcholinesterase IAChEI and glutathione S-transferase (GST). The simultaneous study of these two enzyme activities is significant for studying human bio-functions, especially for those who take in toxic compounds and have a risk of disease. Here, the enzyme activities were represented by the conversion of enzymatic substrates and determined by quantitatively analyzing enzymatic substrates. Different internal standards were used to quantify each enzymatic substrate and the good linearity of calibration curves demonstrated the feasibility of the internal standards. The Michaelis-Menten constants (Km) of both GST and AChE were measured by this method and were consistent with values previously reported. Furthermore, we applied this approach to detect GST and AChE activities of whole bloods from four deceased and healthy people. The variation in enzyme activity was in accord with information from gas chromatography mass spectrometry [GC/MS). The screening of AChE and GST provided reliable results and strong forensic evidence. This method offers an alternative choice for detecting enzyme activities and is anticipated to have wide applications in pharmaceutical research and prevention in toxic compounds.

  15. Modeling the impact of spatial relationships on horizontal curve safety.

    PubMed

    Findley, Daniel J; Hummer, Joseph E; Rasdorf, William; Zegeer, Charles V; Fowler, Tyler J

    2012-03-01

    The curved segments of roadways are more hazardous because of the additional centripetalforces exerted on a vehicle, driver expectations, and other factors. The safety of a curve is dependent on various factors, most notably by geometric factors, but the location of a curve in relation to other curves is also thought to influence the safety of those curves because of a driver's expectation to encounter additional curves. The link between an individual curve's geometric characteristics and its safety performance has been established, but spatial considerations are typically not included in a safety analysis. The spatial considerations included in this research consisted of four components: distance to adjacent curves, direction of turn of the adjacent curves, and radius and length of the adjacent curves. The primary objective of this paper is to quantify the spatial relationship between adjacent horizontal curves and horizontal curve safety using a crash modification factor. Doing so enables a safety professional to more accurately estimate safety to allocate funding to reduce or prevent future collisions and more efficiently design new roadway sections to minimize crash risk where there will be a series of curves along a route. The most important finding from this research is the statistical significance of spatial considerations for the prediction of horizontal curve safety. The distances to adjacent curves were found to be a reliable predictor of observed collisions. This research recommends a model which utilizes spatial considerations for horizontal curve safety prediction in addition to current Highway Safety Manual prediction capabilities using individual curve geometric features. Copyright © 2011 Elsevier Ltd. All rights reserved.

  16. Curved PVDF airborne transducer.

    PubMed

    Wang, H; Toda, M

    1999-01-01

    In the application of airborne ultrasonic ranging measurement, a partially cylindrical (curved) PVDF transducer can effectively couple ultrasound into the air and generate strong sound pressure. Because of its geometrical features, the ultrasound beam angles of a curved PVDF transducer can be unsymmetrical (i.e., broad horizontally and narrow vertically). This feature is desired in some applications. In this work, a curved PVDF air transducer is investigated both theoretically and experimentally. Two resonances were observed in this transducer. They are length extensional mode and flexural bending mode. Surface vibration profiles of these two modes were measured by a laser vibrometer. It was found from the experiment that the surface vibration was not uniform along the curvature direction for both vibration modes. Theoretical calculations based on a model developed in this work confirmed the experimental results. Two displacement peaks were found in the piezoelectric active direction of PVDF film for the length extensional mode; three peaks were found for the flexural bending mode. The observed peak positions were in good agreement with the calculation results. Transient surface displacement measurements revealed that vibration peaks were in phase for the length extensional mode and out of phase for the flexural bending mode. Therefore, the length extensional mode can generate a stronger ultrasound wave than the flexural bending mode. The resonance frequencies and vibration amplitudes of the two modes strongly depend on the structure parameters as well as the material properties. For the transducer design, the theoretical model developed in this work can be used to optimize the ultrasound performance.

  17. Magnetism in curved geometries

    DOE PAGES

    Streubel, Robert; Fischer, Peter; Kronast, Florian; ...

    2016-08-17

    Extending planar two-dimensional structures into the three-dimensional space has become a general trend in multiple disciplines, including electronics, photonics, plasmonics and magnetics. This approach provides means to modify conventional or to launch novel functionalities by tailoring the geometry of an object, e.g. its local curvature. In a generic electronic system, curvature results in the appearance of scalar and vector geometric potentials inducing anisotropic and chiral effects. In the specific case of magnetism, even in the simplest case of a curved anisotropic Heisenberg magnet, the curvilinear geometry manifests two exchange-driven interactions, namely effective anisotropy and antisymmetric exchange, i.e. Dzyaloshinskii–Moriya-like interaction. Asmore » a consequence, a family of novel curvature-driven effects emerges, which includes magnetochiral effects and topologically induced magnetization patterning, resulting in theoretically predicted unlimited domain wall velocities, chirality symmetry breaking and Cherenkov-like effects for magnons. The broad range of altered physical properties makes these curved architectures appealing in view of fundamental research on e.g. skyrmionic systems, magnonic crystals or exotic spin configurations. In addition to these rich physics, the application potential of three-dimensionally shaped objects is currently being explored as magnetic field sensorics for magnetofluidic applications, spin-wave filters, advanced magneto-encephalography devices for diagnosis of epilepsy or for energy-efficient racetrack memory devices. Finally, these recent developments ranging from theoretical predictions over fabrication of three-dimensionally curved magnetic thin films, hollow cylinders or wires, to their characterization using integral means as well as the development of advanced tomography approaches are in the focus of this review.« less

  18. Magnetism in curved geometries

    SciTech Connect

    Streubel, Robert; Fischer, Peter; Kronast, Florian; Kravchuk, Volodymyr P.; Sheka, Denis D.; Gaididei, Yuri; Schmidt, Oliver G.; Makarov, Denys

    2016-08-17

    Extending planar two-dimensional structures into the three-dimensional space has become a general trend in multiple disciplines, including electronics, photonics, plasmonics and magnetics. This approach provides means to modify conventional or to launch novel functionalities by tailoring the geometry of an object, e.g. its local curvature. In a generic electronic system, curvature results in the appearance of scalar and vector geometric potentials inducing anisotropic and chiral effects. In the specific case of magnetism, even in the simplest case of a curved anisotropic Heisenberg magnet, the curvilinear geometry manifests two exchange-driven interactions, namely effective anisotropy and antisymmetric exchange, i.e. Dzyaloshinskii–Moriya-like interaction. As a consequence, a family of novel curvature-driven effects emerges, which includes magnetochiral effects and topologically induced magnetization patterning, resulting in theoretically predicted unlimited domain wall velocities, chirality symmetry breaking and Cherenkov-like effects for magnons. The broad range of altered physical properties makes these curved architectures appealing in view of fundamental research on e.g. skyrmionic systems, magnonic crystals or exotic spin configurations. In addition to these rich physics, the application potential of three-dimensionally shaped objects is currently being explored as magnetic field sensorics for magnetofluidic applications, spin-wave filters, advanced magneto-encephalography devices for diagnosis of epilepsy or for energy-efficient racetrack memory devices. Finally, these recent developments ranging from theoretical predictions over fabrication of three-dimensionally curved magnetic thin films, hollow cylinders or wires, to their characterization using integral means as well as the development of advanced tomography approaches are in the focus of this review.

  19. Magnetism in curved geometries

    NASA Astrophysics Data System (ADS)

    Streubel, Robert; Fischer, Peter; Kronast, Florian; Kravchuk, Volodymyr P.; Sheka, Denis D.; Gaididei, Yuri; Schmidt, Oliver G.; Makarov, Denys

    2016-09-01

    Extending planar two-dimensional structures into the three-dimensional space has become a general trend in multiple disciplines, including electronics, photonics, plasmonics and magnetics. This approach provides means to modify conventional or to launch novel functionalities by tailoring the geometry of an object, e.g. its local curvature. In a generic electronic system, curvature results in the appearance of scalar and vector geometric potentials inducing anisotropic and chiral effects. In the specific case of magnetism, even in the simplest case of a curved anisotropic Heisenberg magnet, the curvilinear geometry manifests two exchange-driven interactions, namely effective anisotropy and antisymmetric exchange, i.e. Dzyaloshinskii-Moriya-like interaction. As a consequence, a family of novel curvature-driven effects emerges, which includes magnetochiral effects and topologically induced magnetization patterning, resulting in theoretically predicted unlimited domain wall velocities, chirality symmetry breaking and Cherenkov-like effects for magnons. The broad range of altered physical properties makes these curved architectures appealing in view of fundamental research on e.g. skyrmionic systems, magnonic crystals or exotic spin configurations. In addition to these rich physics, the application potential of three-dimensionally shaped objects is currently being explored as magnetic field sensorics for magnetofluidic applications, spin-wave filters, advanced magneto-encephalography devices for diagnosis of epilepsy or for energy-efficient racetrack memory devices. These recent developments ranging from theoretical predictions over fabrication of three-dimensionally curved magnetic thin films, hollow cylinders or wires, to their characterization using integral means as well as the development of advanced tomography approaches are in the focus of this review.

  20. Rotation Curves of Galaxies

    NASA Astrophysics Data System (ADS)

    Kalnajs, Agris J.

    One can obtain a fairly good understanding of the relation between axially symmetric mass distributions and the rotation curves they produce without resorting to calculations. However it does require a break with tradition. The first step consists of replacing quantities such as surface density, volume density, and circular velocity with the mass in a ring, mass in a spherical shell, and the square of the circular velocity, or more precisely with 2 pi G r mu(r), 4 pi G r^2 rho(r), and Vc^2 (r). These three quantities all have the same dimensions, and are related to each other by scale-free linear operators. The second step consists of introducing ln(r) as the coordinate. On the log scale the scale-free operators becomes the more familiar convolution operations. Convolutions are easily handled by Fourier techniques and a surface density can be converted into a rotation curve or volume density in a small fraction of a second. A simple plot of 2 pi G r mu(r) as a function of ln(r) reveals the relative contributions of different radii to Vc^2(r). Such a plot also constitutes a sanity test for the fitting of various laws to photometric data. There are numerous examples in the literature of excellent fits to the tails that lack data or are poor fits around the maximum of 2 pi G r mu(r). I will discuss some exact relations between the above three quantities as well as some empirical observations such as the near equality of the maxima of 2 pi G r mu(r) and Vc^2 (r) curves for flat mass distributions.

  1. Complementary Curves of Descent

    DTIC Science & Technology

    2012-11-16

    provision of law , no person shall be subject to a penalty for failing to comply with a collection of information if it does not display a currently valid...curves of descent 5a. CONTRACT NUMBER 5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER 6. AUTHOR( S ) 5d. PROJECT NUMBER 5e. TASK NUMBER 5f. WORK UNIT...NUMBER 7. PERFORMING ORGANIZATION NAME( S ) AND ADDRESS(ES) US Naval Academy,Physics Department,Annapolis,MD,21402-1363 8. PERFORMING ORGANIZATION

  2. Meteor light curves: the relevant parameters

    NASA Astrophysics Data System (ADS)

    Brosch, N.; Helled, Ravit; Polishook, D.; Almoznino, E.; David, N.

    2004-11-01

    We investigate a uniform sample of 113 light curves of meteors collected at the Wise Observatory in 2002 November during a campaign to observe the Leonid meteor shower. We use previously defined descriptors, such as the classical skewness parameter F and a recently defined pointedness variable P, along with a number of other measurable or derived quantities, in order to explore the parameter space in search of meaningful light curve descriptors. In comparison with previous publications, we make extensive use of statistical techniques to reveal links among the various parameters and to understand their relative importance. In particular, we show that meteors with long-duration trails rise slowly to their maximal brightness and also decay slowly from the peak, while showing milder flaring than other meteors. Early skewed meteors, with their peak brightness in the first half of the light curve, show a fast rise to the peak. We show that the duration of the luminous phase of the meteor is the most important variable differentiating among the 2002 meteor trails. The skewness parameter F, which is widely used in meteor light curve analyses, appears only as the second or third in order of importance in explaining the variance among the observed light curves, with the most important parameter being related to the duration of the meteor light-producing phase. We suggest that the pointedness parameter P could possibly be useful in describing differences among meteor showers, perhaps by being related to the different compositions of meteoroids, and also in comparing observations to model light curves. We compare the derived characteristics of the 2002 meteors with model predictions and conclude that more work is required to define a consistent set of measurable and derived light-curve parameters that would characterize the light production from meteors. We suggest that meteor observers should consider publishing more characterizing parameters from the light curves they

  3. Selection of the Optimum Electrospray Voltage for Gradient Elution LC-MS Measurements

    PubMed Central

    Marginean, Ioan; Kelly, Ryan T.; Moore, Ronald J.; Prior, David C.; LaMarche, Brian L.; Tang, Keqi; Smith, Richard D.

    2009-01-01

    Changes in liquid composition during gradient elution liquid chromatography (LC) coupled to mass spectrometry (MS) analyses affect the electrospray operation. To establish methodologies for judicious selection of the electrospray voltage, we monitored in real-time the effect of the LC gradient on the spray current. The optimum range of the electrospray voltage decreased as the concentration of organic solvent in the eluent increased during reversed-phase LC analyses. These results provided the means to rationally select the voltage so as to ensure effective electrospray operation throughout gradient-elution LC separations. For analyses in which the electrospray was operated at constant voltage, a small run-to-run variation in the spray current was observed, indicating a changing electric field due to fouling or degradation of the emitter. Algorithms using feedback from spray current measurements to maintain the electrospray voltage within the optimum operating range throughout gradient elution LC-MS were evaluated. The electrospray operation with voltage regulation and at a constant, judiciously selected voltage during gradient elution LC-MS measurements produced data with similar reproducibility. SYNOPSIS Electrospray current measurements during gradient elution liquid chromatography analyses provide reliable feedback for monitoring, understanding, and improving performance. PMID:19196520

  4. Vapor Pressure of Hexamethylene Triperoxide Diamine (HMTD) Estimated Using Secondary Electrospray Ionization Mass Spectrometry.

    PubMed

    Aernecke, Matthew J; Mendum, Ted; Geurtsen, Geoff; Ostrinskaya, Alla; Kunz, Roderick R

    2015-11-25

    A rapid method for vapor pressure measurement was developed and used to derive the vapor pressure curve of the thermally labile peroxide-based explosive hexamethylene triperoxide diamine (HMTD) over the temperature range from 28 to 80 °C. This method uses a controlled flow of vapor from a solid-phase HMTD source that is presented to an ambient-pressure-ionization mass spectrometer equipped with a secondary-electrospray-ionization (SESI) source. The subpart-per-trillion sensitivity of this system enables direct detection of HMTD vapor through an intact [M + H](+) ion in real time at temperatures near 20 °C. By calibrating this method using vapor sources of cocaine and heroin, which have known pressure-temperature (P-T) curves, the temperature dependence of HMTD vapor was determined, and a Clausius-Clapeyron plot of ln[P (Pa)] vs 1/[T (K)] yielded a straight line with the expression ln[P (Pa)] = {(-11091 ± 356) × 1/[T (K)]} + 25 ± 1 (error limits are the standard error of the regression analysis). From this equation, the sublimation enthalpy of HMTD was estimated to be 92 ± 3 kJ/mol, which compares well with the theoretical estimate of 95 kJ/mol, and the vapor pressure at 20 °C was estimated to be ∼60 parts per trillion by volume, which is within a factor of 2 of previous theoretical estimates. Thus, this method provides not only the first direct experimental determination of HMTD vapor pressure but also a rapid, near-real-time capability to quantitatively measure low-vapor-pressure compounds, which will be useful for aiding in the development of training aids for bomb-sniffing canines.

  5. Desorption electrospray ionization-mass spectrometric analysis of low vapor pressure chemical particulates collected from a surface.

    PubMed

    Ewing, K J; Gibson, D; Sanghera, J; Miklos, F

    2015-01-01

    The collection of a low vapor pressure chemical simulant triethyl phosphate sorbed onto silica gel (TEP/SG) from a surface with subsequent analysis of the TEP/SG particulates using desorption electrospray ionization-mass spectrometry (DESI-MS) is described. Collection of TEP/SG particulates on a surface was accomplished using a sticky screen sampler composed of a stainless steel screen coated with partially polymerized polydimethylsiloxane (PDMS). DESI-MS analysis of TEP/SG particulates containing different percentages of TEP sorbed onto silica gel enabled the generation of response curves for the TEP ions m/z 155 and m/z 127. Using the response curves the calculation of the mass of TEP in a 25 wt% sample of TEP/SG was calculated, results show that the calculated mass of TEP was 14% different from the actual mass of TEP in the sample using the m/z 127 TEP ion response curve. Detection limits for the TEP vapor and TEP/SG particulates were calculated to be 4 μg and 6 particles, respectively.

  6. Transforming Curves into Curves with the Same Shape.

    ERIC Educational Resources Information Center

    Levine, Michael V.

    Curves are considered to have the same shape when they are related by a similarity transformation of a certain kind. This paper extends earlier work on parallel curves to curves with the same shape. Some examples are given more or less explicitly. A generalization is used to show that the theory is ordinal and to show how the theory may be applied…

  7. A Corona Discharge Initiated Electrochemical Electrospray Ionization Technique

    PubMed Central

    Lloyd, John R.; Hess, Sonja

    2009-01-01

    We report here the development of a corona discharge (CD) initiated electrochemical (EC) electrospray ionization (ESI) technique using a standard electrospray ion source. This is a new ionization technique distinct from ESI, electrochemistry inherent to ESI, APCI, and techniques using hydroxyl radicals produced under atmospheric pressure conditions. By maximizing the observable CD at the tip of a stainless steel ESI capillary, efficient electrochemical oxidation of electrochemically active compounds is observed. For electrochemical oxidation to be observed, the ionization potential of the analyte must be lower than Fe. Ferrocene labeled compounds were chosen as the electrochemically active moiety. The electrochemical cell in the ESI source was robust and generated ions with selectivity according to the ionization potential of the analytes and up to zeptomolar sensitivity. Our results indicate that CD initiated electrochemical ionization has the potential to become a powerful technique to increase the dynamic range, sensitivity and selectivity of ESI experiments. Synopsis Using a standard ESI source a corona discharge initiated electrochemical ionization technique was established resulting from the electrochemistry occurring at the CD electrode surface. PMID:19747843

  8. Transferability of the Electrospray Ionization Efficiency Scale between Different Instruments

    NASA Astrophysics Data System (ADS)

    Liigand, Jaanus; Kruve, Anneli; Liigand, Piia; Laaniste, Asko; Girod, Marion; Antoine, Rodolphe; Leito, Ivo

    2015-11-01

    For the first time, quantitative electrospray (ESI) ionization efficiencies (IE), expressed as log IE values, obtained on different mass-spectrometric setups (four mass analyzers and four ESI sources) are compared for 15 compounds of diverse properties. The general trends of change of IE with molecular structure are the same with all experimental setups. The obtained IE scales could be applied on different setups: there were no statistically significant changes in the order of ionization efficiency and the root mean of squared differences of the log IE values of compounds between the scales compiled on different instruments were found to be between 0.21 and 0.55 log units. The results show that orthogonal ESI source geometry gives better differentiating power and additional pneumatic assistance improves it even more. It is also shown that the ionization efficiency values are transferable between different mass-spectrometric setups by three anchoring points and a linear model. The root mean square error of log IE prediction ranged from 0.24 to 0.72 depending on the instrument. This work demonstrates for the first time the inter-instrument transferability of quantitative electrospray ionization efficiency data.

  9. Electrosprayed Janus Particles for Combined Photo-Chemotherapy.

    PubMed

    Sanchez-Vazquez, Brenda; Amaral, Adérito J R; Yu, Deng-Guang; Pasparakis, George; Williams, Gareth R

    2017-07-01

    This work is a proof of concept study establishing the potential of electrosprayed Janus particles for combined photodynamic therapy-chemotherapy. Sub-micron-sized particles of polyvinylpyrrolidone containing either an anti-cancer drug (carmofur) or a photosensitiser (rose bengal; RB), and Janus particles containing both in separate compartments were prepared. The functional components were present in the amorphous form in all the particles, and infrared spectroscopy indicated that intermolecular interactions formed between the different species. In vitro drug release studies showed that both carmofur and RB were released at approximately the same rate, with dissolution complete after around 250 min. Cytotoxicity studies were undertaken on model human dermal fibroblasts (HDF) and lung cancer (A549) cells, and the influence of light on cell death explored. Formulations containing carmofur as the sole active ingredient were highly toxic to both cell lines, with or without a light treatment. The RB formulations were non-toxic to HDF when no light was applied, and with photo-treatment caused large amounts of cell death for both A549 and HDF cells. The Janus formulation containing both RB and carmofur was non-toxic to HDF without light, and only slightly toxic with the photo-treatment. In contrast, it was hugely toxic to A549 cells when light was applied. The Janus particles are thus highly selective for cancer cells, and it is hence proposed that such electrosprayed particles containing both a chemotherapeutic agent and photosensitiser have great potential in combined chemotherapy/photodynamic therapy.

  10. Unexpected Analyte Oxidation during Desorption Electrospray Ionization - Mass Spectrometry

    SciTech Connect

    Pasilis, Sofie P; Kertesz, Vilmos; Van Berkel, Gary J

    2008-01-01

    During the analysis of surface spotted analytes using desorption electrospray ionization mass spectrometry (DESI-MS), abundant ions are sometimes observed that appear to be the result of oxygen addition reactions. In this investigation, the effect of sample aging, the ambient lab environment, spray voltage, analyte surface concentration, and surface type on this oxidative modification of spotted analytes, exemplified by tamoxifen and reserpine, during analysis by desorption electrospray ionization mass spectrometry was studied. Simple exposure of the samples to air and to ambient lighting increased the extent of oxidation. Increased spray voltage lead also to increased analyte oxidation, possibly as a result of oxidative species formed electrochemically at the emitter electrode or in the gas - phase by discharge processes. These oxidative species are carried by the spray and impinge on and react with the sampled analyte during desorption/ionization. The relative abundance of oxidized species was more significant for analysis of deposited analyte having a relatively low surface concentration. Increasing spray solvent flow rate and addition of hydroquinone as a redox buffer to the spray solvent were found to decrease, but not entirely eliminate, analyte oxidation during analysis. The major parameters that both minimize and maximize analyte oxidation were identified and DESI-MS operational recommendations to avoid these unwanted reactions are suggested.

  11. Targeting Sessile Droplets with Electrospray to Form Nanoparticle Deposits

    NASA Astrophysics Data System (ADS)

    Chiarot, Paul; Daeumer, Matthias; Maktabi, Sepehr; Yong, Xin

    2016-11-01

    The ability to print ordered deposits of nanoparticles has significant implications for electronics and photonics manufacturing. In this work, electrospray atomization was used to deliver dry nanoparticles to the surface of sacrificial sessile droplets. The particles were subsequently mapped to a glass substrate upon complete evaporation of the target droplet to create a deposit. The influence of the key electrospray operating parameters on the final deposit structure were explored, including: spray time, nanoparticle concentration, and initial sacrificial droplet volume. Once the nanoparticles were delivered to the interface, evaporatively-driven transport of the particles across the surface of the sessile droplet played a significant role in determining the structure of the deposit. When the contact line of the target sessile droplet was pinned during evaporation, the final deposit had greater particle density at the edge and center. The particles were distributed more uniformly across the deposit when the contact line of the target droplet moved during evaporation. The influence of thermal gradients on the final deposit structure was investigated by heating the substrate to increase the sessile droplet temperature. We also conducted computational simulations of evaporating particle-laden droplets and explored the influences of contact line behavior and nanoparticle surface chemistry on the deposit structure. This research supported by the National Science Foundation (Award 1538090).

  12. Scaling up the power of an electrospray microthruster

    NASA Astrophysics Data System (ADS)

    Lenguito, G.; Fernandez de la Mora, J.; Gomez, A.

    2014-05-01

    We report on the development of an electrospray (ES) microthruster that, by emitting fast nanodroplets, covers a wide range of specific impulse and thrust at high (>50%) propulsion efficiency. To achieve a useful thrust, many ES microthrusters must operate in parallel (multiplexing). The multiplexed electrospray microthruster (MES) is packaged in an alumina case that can operate at voltages up to ΔV = 7.56 kV and a reservoir pressure up to 5 bar. We compared nozzle arrays with 7, 37 and 91 capillaries (ID/OD = 10/30 µm). To ensure uniform flow through the various emitters, the hydraulic resistance was increased by filling the capillaries with 2.01 µm beads. The MES devices sprayed the ionic liquid ethylammonium nitrate. The 37-MES device covered a 2.6-fold range of specific impulse reaching 1870 s, and a 4.2-fold range of thrust up to 31.1 µN. The 91-MES device reached higher thrust, but it covered a narrower range. All devices operated stably for hours with modest current fluctuations. The beam cleared the electrodes, with no signs of erosion. The developed microthruster has already reached performances suitable for fine attitude control of microsatellites. Further scaling up by one order of magnitude would enable orbit change and station keeping for small satellites.

  13. On-line reaction monitoring by extractive electrospray ionisation.

    PubMed

    McCullough, Bryan J; Bristow, Tony; O'Connor, Gavin; Hopley, Chris

    2011-05-30

    The design and development of a novel extractive electrospray ionisation (EESI) device for on-line reaction monitoring is described. The EESI apparatus uses a secondary, grounded nebuliser to produce an analyte aerosol and a Venturi pump is then used to transfer a sample of the aerosol to an electrospray source where it is ionised. The EESI apparatus was then tested with a variety of small, organic molecules to assess sensitivity, linearity and dynamic range. The performance of the technique will depend on the mass spectrometer used for the experiments; in the configurations used here it has a usable dynamic range of around 3.5 orders of magnitude with a linear range of around 2.5 orders of magnitude and is capable of analysing species present down to low µg/mL with signal-to-noise ratio greater than 2.5. The use of EESI for reaction monitoring was validated using a series of mock reaction mixtures and then used to monitor the base hydrolysis of ethyl salicylate to salicylic acid. Copyright © 2011 John Wiley & Sons, Ltd.

  14. Analysis of metal-EDTA complexes by electrospray mass spectrometry

    SciTech Connect

    Baron, D.; Hering, J.G.

    1998-07-01

    Solutions of the strong complexing agent ethylenediaminetetraacetic acid (EDTA) and Cu, Pb, Cd, Al, and Fe(III) were examined by electrospray mass spectrometry (ES/MS). Uncomplexed EDTA and metal-EDTA complexes survive the electrospray process intact and can be detected simultaneously by mass spectrometry. Best sensitivity was achieved in the positive ion mode in which EDTA and EDTA-metal complexes (present in solution as anions) were detected as protonated species with a single positive charge. Except for the protonation, the aqueous metal-EDTA complexes are preserved and neither fragmentation of complexes nor formation of clusters with more than one metal or ligand were observed in the mass spectra. Detection limits are between approximately 1 to 2 {micro}M for uncomplexed EDTA and for the Cu-EDTA and Pb-EDTA complexes, with a linear range up to 10{sup {minus}4} M. Calibrations based on solutions with equimolar concentrations of EDTA and Cu or Pb can be used to quantify EDTA-metal complexes in solutions with excess EDTA or metal, and in solutions with more than one metal present. Isotopic signatures of metals in the metal-ligand complexes are preserved, allowing the identification of the metal in a metal-ligand complex. Isotopic signatures of metals can therefore aid in the identification of metal-ligand complexes in unknown samples.

  15. Development and Characterization of electrosprayed Nanoparticles for encapsulation of Curcumin.

    PubMed

    Esmaili, Zahra; Bayrami, Samaneh; Abedin Dorkoosh, Farid; Akbari Javar, Hamid; Seyedjafari, Ehsan; Zargarian, Seyed Shahrooz; Haddadi-Asl, Vahid

    2017-09-11

    Curcumin has been proven to be an effective herbal derived anti-inflammatory and antioxidant biocompatible agent. In this research PLGA (as a biocompatible and GRAS polymer) nanoparticles containing Curcumin were electrospryed from different polymeric solutions with different concentrations for the first time. Morphology of these nanoparticles in the absence/presence of Curcumin was evaluated by SEM, TEM and XPS analyses. Perfectly shaped nanoparticles with an average size of 300 and 320 nanometers were observed for neat and Curcumin loaded PLGA, respectively. Curcumin-loaded electrosprayed nanoparticles showed a normal moderate initial burst and then a prolonged release period. Weibull, Peppas and modified Korsmeyer-Peppas models were applied to study the kinetic and mechanism of curcmin release from PLGA nanoparticles. Results showed high specific surface area and spherical geometry of the nanoparticles. Effectiveness of the electrospray method as a promising technique for preparing Curcumin-loaded nanoparticles was confirmed in this study. This article is protected by copyright. All rights reserved. © 2017 Wiley Periodicals, Inc.

  16. Psychophysical evaluation of calibration curve for diagnostic LCD monitor.

    PubMed

    Uemura, Masanobu; Asai, Yoshiyuki; Yamaguchi, Michihiro; Fujita, Hideki; Shintani, Yuuko; Sanada, Shigeru

    2006-12-01

    In 1998, Digital Imaging Communications in Medicine (DICOM) proposed a calibration tool, the grayscale standard display function (GSDF), to obtain output consistency of radiographs. To our knowledge, there have been no previous reports of investigating the relation between perceptual linearity and detectability on a calibration curve. To determine a suitable calibration curve for diagnostic liquid crystal display (LCD) monitors, the GSDF and Commission Internationale de l'Eclairage (CIE) curves were compared using psychophysical gradient delta and receiver operating characteristic (ROC) analysis for clinical images. We succeeded in expressing visually recognized contrast directly using delta instead of the just noticeable difference (JND) index of the DICOM standard. As a result, we found that the visually recognized contrast at low luminance areas on the LCD monitor calibrated by the CIE curve is higher than that calibrated by the GSDF curve. On the ROC analysis, there was no significant difference in tumor detectability between GSDF and CIE curves for clinical thoracic images. However, the area parameter Az of the CIE curve is superior to that of the GSDF curve. The detectability of tumor shadows in the thoracic region on clinical images using the CIE curve was superior to that using the GSDF curve owing to the high absolute value of delta in the low luminance range. We conclude that the CIE curve is the most suitable tool for calibrating diagnostic LCD monitors, rather than the GSDF curve.

  17. Electrospray Ionization Mass Spectrometry of hexanitrohexaazaisowurtzitane (CL-20)

    SciTech Connect

    Campbell, James A.; Szecsody, Jim E.; Devary, Brooks J.; Valenzuela, Blandina R.

    2007-09-03

    Hexanitrohexaazaisowurtzitane, (C6H6N12O12, MW 438) {CL-20}, is a high-energy propellent that has been recently developed and successfully tested (Nielsen et al. 1998). CL-20 releases more energy on ignition and is more stable to accidental detonation than currently used energetic materials. It is expected to replace many of the energetic materials currently being used by the Department of Defense (DoD). The EPA method 8330 (EPA 1997) for the analysis of explosives and metabolites in soils calls for the use of UV/Vis detection. High performance liquid chromatography has been used to quantify CL-20 and precursor concentration (Bazaki et al. 1998`) at relatively high concentrations. Fourier transform infrared (FTIR) spectroscopy has been used to identify different crystal forms of CL-20 (4 isomers; Kim et al. 1998). Campbell et al. (1997) utilized particle beam mass spectrometry for the analysis of enzymatic degradation of explosives. Introduction and recent improvements of ionization techniques such as electrospray (ES) have allowed the mass spectrometer to become more widely used in liquid chromatography. Schilling(1996) also examined explosive components and metabolites using electrospray (ES) and atmospheric pressure chemical ionization (APCI) liquid chromatography/mass spectrometry (LC/MS). Schilling’s results showed that compared to thermospray LC/MS, APCI and ES were more sensitive than thermospray by at least an order of magnitude. 1,3,5-trinitro-1,3,5-triazacyclohexane (RDX), 10 nitroso-RDX metabolites, and other munitions in ground water have been analyzed using solid phase extraction and isotope dilution liquid chromatography-APCI mass spectrometry (Cassada et al. 1999). The method detection limits indicate that nitramine and nitroaromatic compounds can be routinely determined in ground water samples using electrospray LC/MS with concentration techniques utilizing solid-phase extraction. Miller et al. (1996) studied nitrated explosives with mobile phase

  18. The effect of small cations on the positive electrospray responses of proteins at low pH.

    PubMed

    Pan, Peng; McLuckey, Scott A

    2003-10-15

    Solutions consisting of protein and small molecule mixtures have been subjected to electrospray ionization to study the influence of small molecule/cation components at high concentrations on the electrospray responses of proteins. Emphasis was placed on solutions consisting of equal parts methanol and water and containing 1 vol % acetic acid. The results, therefore, are relevant to low pH solutions with significant organic content, a commonly used set of conditions in electrospray ionization mass spectrometry that tends to denature proteins. A variety of small cations/molecules were selected to sample a range of chemical characteristics. For example, sodium and cesium cations were studied to represent metal ions, tetrabutylammonium and tetramethylammonium cations were studied to represent quaternary ammonium compounds with different surface activities, and octadecylamine and glycine were studied to represent species that compete for protons but have different surface activities. A methodology for measuring relative ion suppression efficiencies was developed and applied for protein ions derived from bovine cytochrome c. The form of the small cation (i.e., metal ion, quaternary ammonium ion, or protonated molecule) did not appear to be a factor in determining the efficiency with which protein ion signals were suppressed. The extent to which ions are expected to concentrate on the surface, however, was the major factor in determining the ion suppression efficiency. Itwas found that the ion suppression efficiency of the most surface active species in this study was comparable to that of a protein on another protein after normalization by charge. These results are particularly relevant to the development of mixture analysis strategies based on ionization and tandem mass spectrometry applied to mixtures of whole proteins.

  19. Online antioxidant activity and ultra-performance LC-electrospray ionisation-quadrupole time-of-fight mass spectrometry for chemical fingerprinting of Indian polyherbal formulations.

    PubMed

    Bhandari, Pamita; Kumar, Neeraj; Khan, Shahid M; Bhutani, Kamlesh K

    2016-01-01

    A HPLC-DAD-DPPH method was developed for evaluating the 1, 1-diphenyl-2-picryl hydrazyl free radical scavenging activity of ethylacetate extracts of different polyherbal formulations (draksarista, draksava, lohasava and arvindasava) by using RP-18e column. The ethylacetate extract from polyherbal, 'draksarista' exhibited maximum free radical scavenging activity (99.9 ± 0.38%) followed by draksava (99.8 ± 0.34%), lohasava (98.5 ± 0.30%) and arvindasava (42.3 ± 0.34%) at 100 μg mL(-1). Simultaneously, ultra-performance liquid chromatography coupled with electrospray ionisation-quadrupole time-of-flight mass spectrometry (UPLC-ESI-QTOF-MS) was used to study chemical composition of the ethylacetate extracts of formulations. The characteristic electrospray mass ionisation reveals the dominance of polyphenols and their glycosides in the four polyherbal formulations.

  20. Multipulse phase resetting curves

    NASA Astrophysics Data System (ADS)

    Krishnan, Giri P.; Bazhenov, Maxim; Pikovsky, Arkady

    2013-10-01

    In this paper, we introduce and study systematically, in terms of phase response curves, the effect of dual-pulse excitation on the dynamics of an autonomous oscillator. Specifically, we test the deviations from linear summation of phase advances resulting from two small perturbations. We analytically derive a correction term, which generally appears for oscillators whose intrinsic dimensionality is >1. The nonlinear correction term is found to be proportional to the square of the perturbation. We demonstrate this effect in the Stuart-Landau model and in various higher dimensional neuronal models. This deviation from the superposition principle needs to be taken into account in studies of networks of pulse-coupled oscillators. Further, this deviation could be used in the verification of oscillator models via a dual-pulse excitation.

  1. Quantum relative Lorenz curves

    NASA Astrophysics Data System (ADS)

    Buscemi, Francesco; Gour, Gilad

    2017-01-01

    The theory of majorization and its variants, including thermomajorization, have been found to play a central role in the formulation of many physical resource theories, ranging from entanglement theory to quantum thermodynamics. Here we formulate the framework of quantum relative Lorenz curves, and show how it is able to unify majorization, thermomajorization, and their noncommutative analogs. In doing so, we define the family of Hilbert α divergences and show how it relates with other divergences used in quantum information theory. We then apply these tools to the problem of deciding the existence of a suitable transformation from an initial pair of quantum states to a final one, focusing in particular on applications to the resource theory of athermality, a precursor of quantum thermodynamics.

  2. Titration Curves: Fact and Fiction.

    ERIC Educational Resources Information Center

    Chamberlain, John

    1997-01-01

    Discusses ways in which datalogging equipment can enable titration curves to be measured accurately and how computing power can be used to predict the shape of curves. Highlights include sources of error, use of spreadsheets to generate titration curves, titration of a weak acid with a strong alkali, dibasic acids, weak acid and weak base, and…

  3. Multiple CubicBezier Curves.

    ERIC Educational Resources Information Center

    Khonsari, Michael M.; Horn, Douglas

    1990-01-01

    An algorithm is described for generating smooth curves of first-order continuity. The algorithm is composed of several cubic Bezier curves joined together at the user defined control points. Introduced is a tension control parameter which can be set thus providing additional flexibility in the design of free-form curves. (KR)

  4. Titration Curves: Fact and Fiction.

    ERIC Educational Resources Information Center

    Chamberlain, John

    1997-01-01

    Discusses ways in which datalogging equipment can enable titration curves to be measured accurately and how computing power can be used to predict the shape of curves. Highlights include sources of error, use of spreadsheets to generate titration curves, titration of a weak acid with a strong alkali, dibasic acids, weak acid and weak base, and…

  5. Chiral differentiation of the noscapine and hydrastine stereoisomers by electrospray ionization tandem mass spectrometry.

    PubMed

    Nagy, Tibor; Kuki, Ákos; Antal, Borbála; Nagy, Lajos; Purgel, Mihály; Sipos, Attila; Nagy, Miklós; Zsuga, Miklós; Kéki, Sándor

    2015-01-01

    Energy-dependent collision-induced dissociation (CID) of the dimers [2 M + Cat](+) of the noscapine and hydrastine stereoisomers was studied where Cat stands for Li(+), Na(+), K(+) and Cs(+) ions. These dimers were generated 'in situ' from the electrosprayed solution. The survival yield (SY) method was used for distinguishing the noscapine and hydrastine dimers. Significant differences were found between the characteristic collision energies (CE50, i.e. the collision energy necessary to obtain 50% fragmentation) of the homo- (R,R; S,S) and heterochiral (R,S; S,R) stereoisomers. To distinguish the enantiomer pairs L-, D-tyrosine ([M + Tyr + Cat](+)) and L-, D-lysine ([M + Lys + Cat](+)) were used as chiral selectors. Furthermore, these heterodimers [M + amino acid + Cat](+) were also applied to determine the stereoisomeric composition. It was found that the characteristic collision energy (CE50) of the noscapine and hydrastine homodimers ([2 M + Cat](+)) was inversely proportional to the ionic radius of the cations. Furthermore, the structures of the dimers [2 M + Cat](+) were studied by high level quantum chemical calculations.

  6. Automated reasoning about cubic curves.

    SciTech Connect

    Padmanabhan, R.; McCune, W.; Mathematics and Computer Science; Univ. of Manitoba

    1995-01-01

    It is well known that the n-ary morphisms defined on projective algebraic curves satisfy some strong local-to-global equational rules of derivation not satisfied in general by universal algebras. For example, every rationally defined group law on a cubic curve must be commutative. Here we extract from the geometry of curves a first order property (gL) satisfied by all morphisms defined on these curves such that the equational consequences known for projective curves can be derived automatically from a set of six rules (stated within the first-order logic with equality). First, the rule (gL) is implemented in the theorem-proving program Otter. Then we use Otter to automatically prove some incidence theorems on projective curves without any further reference to the underlying geometry or topology of the curves.

  7. Soil Water Retention Curve

    NASA Astrophysics Data System (ADS)

    Johnson, L. E.; Kim, J.; Cifelli, R.; Chandra, C. V.

    2016-12-01

    Potential water retention, S, is one of parameters commonly used in hydrologic modeling for soil moisture accounting. Physically, S indicates total amount of water which can be stored in soil and is expressed in units of depth. S can be represented as a change of soil moisture content and in this context is commonly used to estimate direct runoff, especially in the Soil Conservation Service (SCS) curve number (CN) method. Generally, the lumped and the distributed hydrologic models can easily use the SCS-CN method to estimate direct runoff. Changes in potential water retention have been used in previous SCS-CN studies; however, these studies have focused on long-term hydrologic simulations where S is allowed to vary at the daily time scale. While useful for hydrologic events that span multiple days, the resolution is too coarse for short-term applications such as flash flood events where S may not recover its full potential. In this study, a new method for estimating a time-variable potential water retention at hourly time-scales is presented. The methodology is applied for the Napa River basin, California. The streamflow gage at St Helena, located in the upper reaches of the basin, is used as the control gage site to evaluate the model performance as it is has minimal influences by reservoirs and diversions. Rainfall events from 2011 to 2012 are used for estimating the event-based SCS CN to transfer to S. As a result, we have derived the potential water retention curve and it is classified into three sections depending on the relative change in S. The first is a negative slope section arising from the difference in the rate of moving water through the soil column, the second is a zero change section representing the initial recovery the potential water retention, and the third is a positive change section representing the full recovery of the potential water retention. Also, we found that the soil water moving has traffic jam within 24 hours after finished first

  8. Ionic liquid-assisted electrospray ionization of polysaccharides.

    PubMed

    Chang, Yu-Ling; Lee, Yuan-Chun; Yang, Wen-Bin; Chen, Chung-Hsuan

    2011-04-01

    In this work, we give the report of significant detection sensitivity improvement of electrospray ionization (ESI) mass spectra of polysaccharides by adding various ionic liquid compounds into samples. Mass spectra obtained were greatly simplified and appeared to be similar to spectra from matrix-assisted laser desorption/ionization due to the narrow charge number distribution. Mass spectra of polysaccharides with the attachment of either anion or cation of ionic liquid compounds were observed. No protonated or deprotonated polysaccharide ions were detected when ionic liquid compounds were added into samples. Little alkali-attached polysaccharide ions were observed. Ionic liquid-assisted ESI (ILA-ESI) mass spectrometry has significantly improved the detection sensitivity of large neutral polysaccharide compounds. Copyright © 2011 John Wiley & Sons, Ltd.

  9. Improved Imaging Resolution in Desorption Electrospray Ionization Mass Spectrometry

    SciTech Connect

    Kertesz, Vilmos; Van Berkel, Gary J

    2008-01-01

    Imaging resolution of desorption electrospray ionization mass spectrometry (DESI-MS) was investigated using printed patterns on paper and thin-layer chromatography (TLC) plate surfaces. Resolution approaching 40 m was achieved with a typical DESI-MS setup, which is approximately 5 times better than the best resolution reported previously. This improvement was accomplished with careful control of operational parameters (particularly spray tip-to-surface distance, solvent flow rate, and spacing of lane scans). Also, an appropriately strong analyte/surface interaction and uniform surface texture on the size scale no larger that the desired imaging resolution were required to achieve this resolution. Overall, conditions providing the smallest possible effective desorption/ionization area in the DESI impact plume region and minimizing the analyte redistribution on the surface during analysis led to the improved DESI-MS imaging resolution.

  10. Collisional cooling of large ions in electrospray mass spectrometry.

    PubMed

    Chernushevich, Igor V; Thomson, Bruce A

    2004-03-15

    Collisional cooling of ions in the rf-only multipole guides has become a method of choice for coupling electrospray sources to various mass analyzers. Normally parameters of such ion guides (length, pressure) provide enough thermalization and focusing for ions in a wide mass range. Noncovalent complexes, however, have more compact conformations than denatured biomolecules of similar mass and, therefore may not be transmitted efficiently through standard ion guides, as demonstrated by theoretical analysis, simulations, and experiments. Several methods of improving collisional cooling for large compact ions have been developed on a quadrupole time-of-flight instrument, which include operating the ion guides at higher pressure and trapping ions to increase the cooling time. Improved transmission of heavy ions obtained with those methods is studied in experiments with proteasome 20S, an oligomeric protein noncovalent complex with molecular weight around 692,000, and a few other compounds.

  11. Combined electrophoretic-separation and electrospray method and system

    DOEpatents

    Smith, Richard D.; Olivares, Jose A.

    1989-01-01

    A system and method for analyzing molecular constituents of a composition sample includes: forming a solution of the sample, separating the solution by capillary zone electrophoresis into an eluent of constituents longitudinally separated according to their relative electrophoretic mobilities, electrospraying the eluent to form a charged spray in which the molecular constituents have a temporal distribution; and detecting or collecting the separated constituents in accordance with the temporal distribution in the spray. A first high-voltage (e.g., 5-100 KVDC) is applied to the solution. The spray is charged by applying a second high voltage (e.g., .+-.2-8 KVDC) between the eluent at the capillary exit and a cathode spaced in front of the exit. A complete electrical circuit is formed by a conductor which directly contacts the eluent at the capillary exit.

  12. Electrohydrodynamic simulation of an electrospray in a colloid thruster

    NASA Astrophysics Data System (ADS)

    Jugroot, Manish; Forget, Martin; Malardier-Jugroot, Cecile

    2012-02-01

    A precise understanding of electrosprays is highly interesting as the complexity of micro-technology (such as nano-material processing, spacecraft propulsion and mass-spectrometers) systems increases. A multi-component CFD-based model coupling fluid dynamics, charged species dynamics and electric field is developed. The simulations describe the charged fluid interface with emphasis on the Taylor cone formation and cone-jet transition under the effect of a electric field. The goal is to recapture this transition from a rounded liquid interface into a Taylor cone from an initial uniform distribution, without making assumptions on the behaviour, geometry or charge distribution of the system. The time evolution of the interface highlights the close interaction among space charge, coulombic forces and the surface tension, which appear as governing and competing processes in the transition. The results from the coupled formalism provide valuable insights on the physical phenomena and will be applied to a colloid thruster for small spacecrafts.

  13. pH Effects on Electrospray Ionization Efficiency

    NASA Astrophysics Data System (ADS)

    Liigand, Jaanus; Laaniste, Asko; Kruve, Anneli

    2017-03-01

    Electrospray ionization efficiency is known to be affected by mobile phase composition. In this paper, a detailed study of analyte ionization efficiency dependence on mobile phase pH is presented. The pH effect was studied on 28 compounds with different chemical properties. Neither p K a nor solution phase ionization degree by itself was observed to be sufficient at describing how aqueous phase pH affects the ionization efficiency of the analyte. Therefore, the analyte behavior was related to various physicochemical properties via linear discriminant analyses. Distinction between pH-dependent and pH-independent compounds was achieved using two parameters: number of potential charge centers and hydrogen bonding acceptor capacity (in the case of 80% acetonitrile) or polarity of neutral form of analyte and p K a (in the case of 20% acetonitrile). It was also observed that decreasing pH may increase ionization efficiency of a compound by more than two orders of magnitude.

  14. Planar flow-by electrode capacitive electrospray ion source

    DOEpatents

    Van Berkel, Gary J.

    2004-01-13

    An electrospray ion source includes a chamber including a channel region therein, the channel including at least one inlet for directing a solution into the channel and at least a first and a second outlet for transmitting the solution or derivatives therefrom out from channel. Structure for separating ions in the solution is provided from separating the solution into at least a first and a second flow stream portion. The first flow stream portion is enriched in negative ions and the second flow stream portion is enriched in positive ions. The first flow stream portion is adapted to exit the chamber through the first outlet while the second flow stream portion is adapted to exit the chamber through the second outlet. A method of charge separation can include the step of simultaneously providing at least two gas phase ion stream portions having opposite polarity.

  15. Influence of boric acid on electrospray ionization efficiency.

    PubMed

    Rebane, Riin; Herodes, Koit

    2012-01-01

    Liquid chromatography electrospray ionization mass-spectrometry (LC-ESI-MS) was used to analyze 9-fluorenylmethylmethoxycarbonyl chloride (Fmoc-Cl) and diethyl ethoxymethylenemalonate (Deemm) derivatives of three amino acids and five other compounds. Influence of boric acid on their ionization was investigated and dramatic impact on the signal was observed. The strongest signal suppression (6% of signal remains) was observed for the Deemm derivative of beta-Alanine (with ammonium acetate in eluent). With only formic acid as the eluent pH modifier, signal enhancement was observed, being largest for Fmoc-Cl derivative of Phenylalanine, 267%. Investigation of the influence of boric acid shows that it is a possible signal enhancer for LC-ESI-MS analysis.

  16. Combined electrophoretic-separation and electrospray method and system

    DOEpatents

    Smith, R.D.; Olivares, J.A.

    1989-06-27

    A system and method for analyzing molecular constituents of a composition sample includes: forming a solution of the sample, separating the solution by capillary zone electrophoresis into an eluent of constituents longitudinally separated according to their relative electrophoretic mobilities, electrospraying the eluent to form a charged spray in which the molecular constituents have a temporal distribution; and detecting or collecting the separated constituents in accordance with the temporal distribution in the spray. A first high-voltage (e.g., 5--100 kVDC) is applied to the solution. The spray is charged by applying a second high voltage (e.g., [+-]2--8 kVDC) between the eluent at the capillary exit and a cathode spaced in front of the exit. A complete electrical circuit is formed by a conductor which directly contacts the eluent at the capillary exit. 10 figs.

  17. Coupling Electrochemistry with Probe Electrospray Ionization Mass Spectrometry.

    PubMed

    Cai, Yi; Liu, Pengyuan; Held, Michael A; Dewald, Howard D; Chen, Hao

    2016-04-18

    A new coupling of electrochemistry with mass spectrometry (MS) using probe electrospray ionization (PESI) is presented. Due to the high salt tolerance of PESI, the detection of electrochemical reaction products in room-temperature ionic liquids (RTILs) is realized for the first time. Furthermore, PESI-MS allows the analysis of electrochemical reaction products on different or multiple electrode surfaces. In addition, peptides and proteins fractionated through isoelectric focusing (IEF) in the presence of an external electric field can also be directly analyzed by using PESI-MS, suggesting a new and rapid characterization means for the IEF technique. This study reveals the versatility of EC/PESI-MS, which could have an impact in electrochemistry and bioanalysis fields.

  18. Perfect bell nozzle parametric and optimization curves

    NASA Technical Reports Server (NTRS)

    Tuttle, J. L.; Blount, D. H.

    1983-01-01

    Nozzle contour data for untruncated Bell nozzles with expansion area ratios to 6100 and a specific heat ratio of 1.2 are provided. Curves for optimization of nozzles for maximum thrust coefficient within a given length, surface area, or area ratio are included. The nozzles are two dimensional axisymmetric and calculations were performed using the method of characteristics. Drag due to wall friction was included in the final thrust coefficient.

  19. Birational maps that send biquadratic curves to biquadratic curves

    NASA Astrophysics Data System (ADS)

    Roberts, John A. G.; Jogia, Danesh

    2015-02-01

    Recently, many papers have begun to consider so-called non-Quispel-Roberts-Thompson (QRT) birational maps of the plane. Compared to the QRT family of maps which preserve each biquadratic curve in a fibration of the plane, non-QRT maps send a biquadratic curve to another biquadratic curve belonging to the same fibration or to a biquadratic curve from a different fibration of the plane. In this communication, we give the general form of a birational map derived from a difference equation that sends a biquadratic curve to another. The necessary and sufficient condition for such a map to exist is that the discriminants of the two biquadratic curves are the same (and hence so are the j-invariants). The result allows existing examples in the literature to be better understood and allows some statements to be made concerning their generality.

  20. Desorption electrospray ionization mass spectrometry for high-throughput analysis of pharmaceutical samples in the ambient environment.

    PubMed

    Chen, Huanwen; Talaty, Nari N; Takáts, Zoltán; Cooks, R Graham

    2005-11-01

    Desorption electrospray ionization (DESI) allows mass spectrometry to be used for on-line high-throughput monitoring of pharmaceutical samples in the ambient environment, without prior sample preparation. Positive and negative ion DESI are used to characterize the active ingredients in pharmaceutical samples formulated as tablets, ointments, and liquids. Compounds of a wide variety of chemical types are detected in these complex matrices. The effects on analytical performance of operating parameters, including the electrospray high voltage, heated capillary temperature, solvent infusion rate, and solvent composition, are evaluated and optimized. In addition to experiments in which a simple solvent is sprayed onto the solid analyte samples, reactive desorption is performed by adding reagents to the solvent spray to generate particularly stable or characteristic ions with the analytes of interest. A variable-speed moving belt was built for high-throughput sampling and used to provide rapid qualitative and semiquantitative information on drug constituents in tablets. Sampling rates as high as 3 samples/s are achieved in the ambient environment. Relative standard deviations of the relative ion abundances for major components in the mass spectra are in the range of 2-8%. Impurities and components present at levels as low as approximately 0.1% are identified and carryover effects are minimized in high-throughput on-line analysis of pharmaceutical samples.

  1. Novel Erythrocyte-like Graphene Microspheres with High Quality and Mass Production Capability via Electrospray Assisted Self-Assembly

    PubMed Central

    Tian, Yayang; Wu, Guan; Tian, Xike; Tao, Xiaoming; Chen, Wei

    2013-01-01

    We report for the first time a novel erythrocyte-like graphene microsphere (ELGMs) which can be produced with high quality and mass production capability via electrospray assisted self-assembly. Through simple electrospray treatment of GO suspension into coagulation bath followed by chemical reduction, large quantity of ELGMs with uniform morphology and size can be obtained with production rate of around 2.4 mg/h. Compared with other 3D structures, the ELGMs have a very interesting structural characteristic of perfect exterior doughnut shape and interior porous network. Accordingly, the as-prepared porous ELGMs exhibit excellent capability for fast and recyclable removal of oil and toxic organic solvents from water, reaching up to 216 times of its weight in absorption efficiency, which is tens of times higher than that of conventional sorbent materials. It is strongly believed that the novel hierarchical graphene structures and synergy among different techniques will lead to more future advances in graphene applications. PMID:24270315

  2. Application of spray-drying and electrospraying/electospinning for poorly water-soluble drugs: a particle engineering approach.

    PubMed

    Bohr, Adam; Boetker, Johan P; Rades, Thomas; Rantanen, Jukka; Yang, Mingshi

    2014-01-01

    Solid dispersions have been widely studied as an attractive formulation strategy for the increasingly prevalent poorly water-soluble drug compounds, including herbal medicines, often leading to improvements in drug dissolution rate and bioavailability. However, several challenges are encountered with solid dispersions, for instance regarding their physical stability, and the full potential of these formulations has yet to be reached. Solid dispersions have mainly been used to produce immediate release systems using water-soluble polymers but an extended release system may provide equal or better performance due to enhancement in the pharmacokinetics and low variability in plasma concentration. Progress in processing technologies and particle engineering provides new opportunities to prepare particle-based solid dispersions with control of physical characteristics and tailored drug release kinetics. Spray-drying and electrospraying are both technologies that allow production and continuous manufacturing of particle-based amorphous solid dispersions in a single step process and electrospinning further allows the production of fiber based systems. This review presents the use of spray drying and electrospraying/electrospinning as techniques for preparing particle-based solid dispersions, describes the particle formation processes via numerical and experimental models and discusses particle engineering using these techniques. Examples are given on the applications of these techniques for preparing solid dispersions and the challenges associated with the techniques such as stability, preparation of final dosage form and scale-up are also discussed.

  3. Detection of over 100 selenium metabolites in selenized yeast by liquid chromatography electrospray time-of-flight mass spectrometry.

    PubMed

    Gilbert-López, Bienvenida; Dernovics, Mihaly; Moreno-González, David; Molina-Díaz, Antonio; García-Reyes, Juan F

    2017-08-15

    The characterization of the selenometabolome of Selenized(Se)-yeast, that is the fraction of water soluble low-molecular weight Se-metabolites produced in Se-yeast is of paramount interest to expand the knowledge on the composition of this food supplement. In this work, we have applied liquid chromatography electrospray time-of-flight mass spectrometry (LC-TOFMS) to search for Se-species from the low molecular weight range fraction of the selenized yeast used for food supplements. Prior to LC-TOFMS, sample treatment consisted of ultrasound assisted water extraction followed by size exclusion fractionation assisted with off-line inductively coupled plasma mass spectrometry detection of isotope (82)Se. The fraction corresponding to low-molecular weight species was subjected to LC-TOFMS using electrospray ionization in the positive ion mode. The detection of the suspected selenized species has been based on the information obtained from accurate mass measurements of both the protonated molecules and fragments from in-source CID fragmentation; along with the characteristic isotope pattern exhibited by the presence of Se. The approach enables the detection of 103 selenized species, most of them not previously reported, in the range from ca. 300-650Da. Besides the detection of selenium species, related sulphur derivate metabolites were detected based on the accurate mass shift due to the substitution of sulphur and selenium. Copyright © 2017. Published by Elsevier B.V.

  4. A novel method for bacterial inactivation using electrosprayed water nanostructures

    NASA Astrophysics Data System (ADS)

    Pyrgiotakis, Georgios; McDevitt, James; Yamauchi, Toshiyuki; Demokritou, Philip

    2012-08-01

    This is a study focusing on the potential to deactivate biological agents (bacteria and endospores) using engineered water nanostructures (EWNS). The EWNS were generated using an electrospray device that collects water by condensing atmospheric water vapor on a Peltier-cooled electrode. A high voltage is applied between the collection electrode and a grounded electrode resulting in aerosolization of the condensed water and a constant generation of EWNS. Gram-negative Serratia marcescens, gram-positive Staphylococcus aureus, and Bacillus atrophaeus endospores were placed on stainless steel coupons and exposed to generated EWNS at multiple time intervals. Upon exposures, the bacteria were recovered and placed on nutrient agar to grow, and the colony forming units were counted. Ozone levels as well as air temperature and relative humidity were monitored during the experiments. Qualitative confirmation of bacterial destruction was also obtained by transmission electron microscopy. In addition, important EWNS aerosol properties such as particle number concentration as a function of size as well as the average surface charge of the generated EWNS were measured using real-time instrumentation. It was shown that the novel electrospray method can generate over time a constant flux of EWNS. EWNS have a peak number concentration of 8,000 particles per cubic centimeter with a modal peak size around 20 nm. The average surface charge of the generated EWNS was found to be 10 ± 2 electrons per particle. In addition, it was shown that the EWNS have the potential to deactivate both bacteria types from surfaces. At the same administrate dose, however, the endospores were not inactivated. This novel method and the unique properties of the generated EWNS could potentially be used to develop an effective, environmentally friendly, and inexpensive method for bacteria inactivation.

  5. Water-assisted femtosecond laser machining of electrospray nozzles on glass microfluidic devices.

    PubMed

    An, Ran; Hoffman, Michelle D; Donoghue, Margaret A; Hunt, Alan J; Jacobson, Stephen C

    2008-09-15

    Using water-assisted femtosecond laser machining, we fabricated electrospray nozzles on glass coverslips and on assembled microfluidic devices. Machining the nozzles after device assembly facilitated alignment of the nozzles over the microchannels. The basic nozzle design is a through-hole in the coverslip to pass liquids and a trough machined around the through-hole to confine the electrospray and prevent liquid from wicking across the glass surface. Electrospray from the nozzles was stable with and without pressure-driven flow applied and was evaluated using mass spectra of the peptide bradykinin.

  6. On-line capillary isoelectric focusing-electrospray mass spectrometry for protein characterization

    SciTech Connect

    Tang, Qing; Harrata, K.A.; Lee, C.S.

    1996-12-31

    The integration of capillary isoelectric focusing (CIEF) with electrospray mass spectrometry (ESMS) as a two-dimensional separation system for protein characterization will be presented. Mixtures of protein variants are focused and cathodically mobilized in a polyacrylamide coated capillary. At the end of CIEF capillary, the mobilized protein zones are analyzed by mass spectrometry coupled on-line to an electrospray interface with a coaxial sheath flow configuration. The effects of carrier ampholyte concentration on the CIEF separation and the protein electrospray mass spectra will be discussed. On-line CIEF-ESMS with superior resolving power, speed, and sensitivity will be demonstrated for the analysis of hemoglobin and glycoprotein variants.

  7. Electrospray neutralization process and apparatus for generation of nano-aerosol and nano-structured materials

    SciTech Connect

    Bailey, Charles L.; Morozov, Victor; Vsevolodov, Nikolai N.

    2010-08-17

    The claimed invention describes methods and apparatuses for manufacturing nano-aerosols and nano-structured materials based on the neutralization of charged electrosprayed products with oppositely charged electrosprayed products. Electrosprayed products include molecular ions, nano-clusters and nano-fibers. Nano-aerosols can be generated when neutralization occurs in the gas phase. Neutralization of electrospan nano-fibers with molecular ions and charged nano-clusters may result in the formation of fibrous aerosols or free nano-mats. Nano-mats can also be produced on a suitable substrate, forming efficient nano-filters.

  8. Effect of Fuselage and Tail Surfaces on Low-speed Yawing Characteristics of a Swept-wing Model as Determined in Curved-flow Test Section of Langley Stability Tunnel

    NASA Technical Reports Server (NTRS)

    Bird, John D; Jaquet, Byron M; Cowan, John W

    1951-01-01

    Results are presented of a wind-tunnel investigation made to determine the influence of the fuselage and tail surfaces on the rotary derivatives in yawing flight of a transonic-airplane configuration having 45 degrees sweptback wing and tail surfaces. The tests were run in the curved-flow test section of the Langley stability tunnel at a Reynolds number of 1.07 X 10 to the sixth power and consisted of balance measurements throughout the angle-of-attack range for several flight-path radii of curvature. The results are compared with data from forced-oscillation and free-oscillation tests, and a description of testing techniques used is included.

  9. A proposal of the diagnosis-dynamic characteristic (DDC) model describing the relation between search time and confidence levels for a dichotomous judgment, and its application to ROC curve generation

    NASA Astrophysics Data System (ADS)

    Matsumoto, Toru; Fukuda, Nobuo; Furukawa, Akira; Suwa, Koji; Wada, Shinichi; Matsumoto, Mitsuomi; Sone, Shusuke

    2006-03-01

    When physicians inspect an image, they make up a certain degree of confidence that the image are abnormal; p(t), or normal; n(t)[n(t)=1-p(t)]. After infinite time of the inspection, they reach the equilibrium levels of the confidence of p*=p(∞) and n*=n(∞). There are psychological conflicts between the decisions of normal and abnormal. We assume that the decision of "normal" is distracted by the decision of "abnormal" by a factor of k(1 + ap), and in an inverse direction by a factor of k(1 + bn), where k ( > 0) is a parameter that relates with image quality and skill of the physicians, and a and b are unknown constants. After the infinite time of inspection, the conflict reaches the equilibrium, which satisfies the equation, k(1 + ap*)n* = k(1 + bn*)p*. Here we define a parameter C, which is 2p*/[p*(1 - p*)]. After the infinite time of inspection, the conflict reaches the equilibrium, which satisfies t that changes in the confidence level with the time (dp/dt) is proportional to [k(1+ap)n - k(1+bn)p], i.e. k[-cp2 + (c - 2)p + 1]. Solving the differential equation, we derived the equation; t(p) and p(t) depending with the parameters; k, c, S. S (0-1) is the value arbitrary selected and related with probability of "abnormal" before the image inspection (S = p(0)). Image reading studies were executed for CT images. ROC curves were generated both by the traditional 4-step score-based method and by the confidence level; p estimated from the equation t(p) of the DDC model using observed judgment time. It was concluded that ROC curves could be generated by measuring time for dichotomous judgment without the subjective scores of diagnostic confidence and applying the DDC model.

  10. Langevin Equation on Fractal Curves

    NASA Astrophysics Data System (ADS)

    Satin, Seema; Gangal, A. D.

    2016-07-01

    We analyze random motion of a particle on a fractal curve, using Langevin approach. This involves defining a new velocity in terms of mass of the fractal curve, as defined in recent work. The geometry of the fractal curve, plays an important role in this analysis. A Langevin equation with a particular model of noise is proposed and solved using techniques of the Fα-Calculus.

  11. Reflection of curved shock waves

    NASA Astrophysics Data System (ADS)

    Mölder, S.

    2017-09-01

    Shock curvatures are related to pressure gradients, streamline curvatures and vorticity in flows with planar and axial symmetry. Explicit expressions, in an influence coefficient format, are used to relate post-shock pressure gradient, streamline curvature and vorticity to pre-shock gradients and shock curvature in steady flow. Using higher order, von Neumann-type, compatibility conditions, curved shock theory is applied to calculate the flow near singly and doubly curved shocks on curved surfaces, in regular shock reflection and in Mach reflection. Theoretical curved shock shapes are in good agreement with computational fluid dynamics calculations and experiment.

  12. Reflection of curved shock waves

    NASA Astrophysics Data System (ADS)

    Mölder, S.

    2017-03-01

    Shock curvatures are related to pressure gradients, streamline curvatures and vorticity in flows with planar and axial symmetry. Explicit expressions, in an influence coefficient format, are used to relate post-shock pressure gradient, streamline curvature and vorticity to pre-shock gradients and shock curvature in steady flow. Using higher order, von Neumann-type, compatibility conditions, curved shock theory is applied to calculate the flow near singly and doubly curved shocks on curved surfaces, in regular shock reflection and in Mach reflection. Theoretical curved shock shapes are in good agreement with computational fluid dynamics calculations and experiment.

  13. Shape Preserving Interpolation by Curves

    DTIC Science & Technology

    2001-07-01

    curves Given data 1i E R2 , i = 0,..., N, we consider a curve r : [a, b] -- R2 satisfying r(ti) = Ii , i = 0,..., N, (3.1) for values a = to < tj...tN = b. For a closed curve the situation is extended periodically so that Ii +N =10, ti+N =ti, i E Z, r(t+b-a) =r(t), tc R. 3.1 Desirable properties...para- meterisation). When all vi = 0, r will reduce to the usual C2 cubic spline interpolant. As vi --+ oc, the curve is ’pulled tight’ at Ii and as

  14. Manipulating internal energy of protonated biomolecules in electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry.

    PubMed

    Guo, Xinghua; Duursma, Marc C; Kistemaker, Piet G; Nibbering, Nico M M; Vekey, Karoly; Drahos, Laszlo; Heeren, Ron M A

    2003-06-01

    The internal energy of protonated leucine enkephalin has been manipulated in electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry with two newly designed pump-probe experiments. Blackbody infrared radiation was applied to pump an ion population into a well-defined internal energy distribution below the dissociation threshold. Following this pumping stage, the internal energy distribution was probed using on-resonance collisional activation to dissociate the ions. These pump-probe experiments were carried out in two different ways: (a) using on-resonance collisional activation with variable kinetic energies to dissociate the ions at a constant initial ion temperature (determining the precursor ion survival percentage as a function of kinetic energy) and (b) using on-resonance collisional activation with a constant kinetic energy to dissociate the ions at variable initial ion temperatures (to investigate the ion survival yield-initial ion temperature dependence). Using this approach, a detailed study of the effects of the initial ion temperature, the probing kinetic energy and the internal energy loss rate on the effective conversion efficiency of (laboratory-frame) kinetic energy to internal energy was conducted. This conversion efficiency was found to be dependent on the initial ion temperature. Depending on the experimental conditions the conversion efficiency (for collisions with argon) was estimated to be about 4.0 +/- 1.7%, which agrees with that obtained from a theoretical modeling. Finally, the reconstructed curves of the ion survival yield versus the mode of the (final) total internal energy distribution of the activated ion population (after pump and probe events) at different pump-probe conditions reveal the internal energy content of the activated ions. Copyright 2003 John Wiley & Sons, Ltd.

  15. Differentiating Microbial Forensic qPCR Target and Control Products by Electrospray Ionization Mass Spectrometry

    PubMed Central

    Motley, S. Timothy; Redden, Cassie L.; Sannes-Lowery, Kristin A.; Eshoo, Mark W.; Hofstadler, Steven A.; Burans, James P.

    2013-01-01

    Molecular bioforensic research is dependent on rapid and sensitive methods such as real-time PCR (qPCR) for the identification of microorganisms. The use of synthetic positive control templates containing small modifications outside the primer and probe regions is essential to ensure all aspects of the assay are functioning properly, including the primers and probes. However, a typical qPCR or reverse transcriptase qPCR (qRT-PCR) assay is limited in differentiating products generated from positive controls and biological samples because the fluorescent probe signals generated from each type of amplicon are indistinguishable. Additional methods used to differentiate amplicons, including melt curves, secondary probes, and amplicon sequencing, require significant time to implement and validate and present technical challenges that limit their use for microbial forensic applications. To solve this problem, we have developed a novel application of electrospray ionization mass spectrometry (ESI-MS) to rapidly differentiate qPCR amplicons generated with positive biological samples from those generated with synthetic positive controls. The method has sensitivity equivalent to qPCR and supports the confident and timely determination of the presence of a biothreat agent that is crucial for policymakers and law enforcement. Additionally, it eliminates the need for time-consuming methods to confirm qPCR results, including development and validation of secondary probes or sequencing of small amplicons. In this study, we demonstrate the effectiveness of this approach with microbial forensic qPCR assays targeting multiple biodefense agents (bacterial, viral, and toxin) for the ability to rapidly discriminate between a positive control and a positive sample. PMID:23675878

  16. Rapid screening of residual pesticides on fruits and vegetables using thermal desorption electrospray ionization mass spectrometry.

    PubMed

    Shiea, Christopher; Huang, Yeou-Lih; Liu, De-Lin; Chou, Chih-Chang; Chou, Jo-Han; Chen, Peng-Yu; Shiea, Jentaie; Huang, Min-Zong

    2015-01-30

    Conventional mass spectrometry is encumbered by laborious and inconvenient sample pretreatment. Ambient thermal desorption electrospray ionization mass spectrometry (TD-ESI-MS) is most noted for its rapid, simple, and sensitive detection capabilities. In this study, TD-ESI-MS was used to rapidly characterize residual pesticides on the surfaces of fruits and vegetables. A direct sampling probe was used to obtain analytes from sample surfaces. MS and MS/MS analyses were performed on fruits and vegetables via TD-ESI-MS. External calibration curves and reproducibility tests were performed using liquid pesticide standards. Pesticide decay and distribution on samples was studied, as well as the removal of residual pesticides via soaking in water or detergent baths. Since sample pretreatment was unnecessary, an analysis was completed in approximately 15 s or less, with no visible sample damage. Mass spectra were obtained for 22 pesticides. Linear calibrations (R(2) from 0.9414-0.999) had limits of detection as low as 0.5 µg·L(-1), with satisfactory reproducibilities for liquids and solids. Pesticides on sample surfaces decayed over 2 weeks under ambient conditions. Residual pesticides localized at the fruit peel. Detergent baths removed more pesticide than water baths. TD-ESI-MS was used to rapidly screen residual pesticides in liquids and solids. Pesticides were found on fruits and vegetables, where the decay, distribution, and removal of pesticides on samples were also explored. Due to short analysis times, the technique allows for high-throughput analyses for applications in food and environmental safety. Copyright © 2014 John Wiley & Sons, Ltd.

  17. Quantitative Detection of Trace Malachite Green in Aquiculture Water Samples by Extractive Electrospray Ionization Mass Spectrometry

    PubMed Central

    Fang, Xiaowei; Yang, Shuiping; Chingin, Konstantin; Zhu, Liang; Zhang, Xinglei; Zhou, Zhiquan; Zhao, Zhanfeng

    2016-01-01

    Exposure to malachite green (MG) may pose great health risks to humans; thus, it is of prime importance to develop fast and robust methods to quantitatively screen the presence of malachite green in water. Herein the application of extractive electrospray ionization mass spectrometry (EESI-MS) has been extended to the trace detection of MG within lake water and aquiculture water, due to the intensive use of MG as a biocide in fisheries. This method has the advantage of obviating offline liquid-liquid extraction or tedious matrix separation prior to the measurement of malachite green in native aqueous medium. The experimental results indicate that the extrapolated detection limit for MG was ~3.8 μg·L−1 (S/N = 3) in lake water samples and ~0.5 μg·L−1 in ultrapure water under optimized experimental conditions. The signal intensity of MG showed good linearity over the concentration range of 10–1000 μg·L−1. Measurement of practical water samples fortified with MG at 0.01, 0.1 and 1.0 mg·L−1 gave a good validation of the established calibration curve. The average recoveries and relative standard deviation (RSD) of malachite green in lake water and Carassius carassius fish farm effluent water were 115% (6.64% RSD), 85.4% (9.17% RSD) and 96.0% (7.44% RSD), respectively. Overall, the established EESI-MS/MS method has been demonstrated suitable for sensitive and rapid (<2 min per sample) quantitative detection of malachite green in various aqueous media, indicating its potential for online real-time monitoring of real life samples. PMID:27529262

  18. Differentiating microbial forensic qPCR target and control products by electrospray ionization mass spectrometry.

    PubMed

    Motley, S Timothy; Redden, Cassie L; Sannes-Lowery, Kristin A; Eshoo, Mark W; Hofstadler, Steven A; Burans, James P; Rosovitz, M J

    2013-06-01

    Molecular bioforensic research is dependent on rapid and sensitive methods such as real-time PCR (qPCR) for the identification of microorganisms. The use of synthetic positive control templates containing small modifications outside the primer and probe regions is essential to ensure all aspects of the assay are functioning properly, including the primers and probes. However, a typical qPCR or reverse transcriptase qPCR (qRT-PCR) assay is limited in differentiating products generated from positive controls and biological samples because the fluorescent probe signals generated from each type of amplicon are indistinguishable. Additional methods used to differentiate amplicons, including melt curves, secondary probes, and amplicon sequencing, require significant time to implement and validate and present technical challenges that limit their use for microbial forensic applications. To solve this problem, we have developed a novel application of electrospray ionization mass spectrometry (ESI-MS) to rapidly differentiate qPCR amplicons generated with positive biological samples from those generated with synthetic positive controls. The method has sensitivity equivalent to qPCR and supports the confident and timely determination of the presence of a biothreat agent that is crucial for policymakers and law enforcement. Additionally, it eliminates the need for time-consuming methods to confirm qPCR results, including development and validation of secondary probes or sequencing of small amplicons. In this study, we demonstrate the effectiveness of this approach with microbial forensic qPCR assays targeting multiple biodefense agents (bacterial, viral, and toxin) for the ability to rapidly discriminate between a positive control and a positive sample.

  19. Quantitative analysis of diclazuril in animal plasma by liquid chromatography/electrospray ionization mass spectrometry.

    PubMed

    Croubels, Siska; Cherlet, Marc; De Backer, Patrick

    2002-01-01

    A novel, sensitive and specific method for the quantitative determination of diclazuril in animal plasma using liquid chromatography combined with electrospray ionization tandem mass spectrometry (LC/ESI-MS/MS) with negative ion detection is presented. Extraction of the samples was performed with a rapid deproteinization step using acetonitrile. Chromatography of diclazuril and the internal standard was achieved on a Nucleosil ODS 5-microm column, using a gradient elution with 0.01 M ammonium acetate and acetonitrile. To obtain the highest sensitivity and specificity possible, the mass spectrometer was operated in the multiple reaction monitoring (MRM) mode. The method was validated according to the requirements defined by the European Community. Calibration curves using plasma fortified between 1-100 ng/mL and 100-2000 ng/mL showed good linear correlation (r >or= 0.9991, goodness-of-fit coefficient

  20. Quantitative Detection of Trace Malachite Green in Aquiculture Water Samples by Extractive Electrospray Ionization Mass Spectrometry.

    PubMed

    Fang, Xiaowei; Yang, Shuiping; Chingin, Konstantin; Zhu, Liang; Zhang, Xinglei; Zhou, Zhiquan; Zhao, Zhanfeng

    2016-08-11

    Exposure to malachite green (MG) may pose great health risks to humans; thus, it is of prime importance to develop fast and robust methods to quantitatively screen the presence of malachite green in water. Herein the application of extractive electrospray ionization mass spectrometry (EESI-MS) has been extended to the trace detection of MG within lake water and aquiculture water, due to the intensive use of MG as a biocide in fisheries. This method has the advantage of obviating offline liquid-liquid extraction or tedious matrix separation prior to the measurement of malachite green in native aqueous medium. The experimental results indicate that the extrapolated detection limit for MG was ~3.8 μg·L(-1) (S/N = 3) in lake water samples and ~0.5 μg·L(-1) in ultrapure water under optimized experimental conditions. The signal intensity of MG showed good linearity over the concentration range of 10-1000 μg·L(-1). Measurement of practical water samples fortified with MG at 0.01, 0.1 and 1.0 mg·L(-1) gave a good validation of the established calibration curve. The average recoveries and relative standard deviation (RSD) of malachite green in lake water and Carassius carassius fish farm effluent water were 115% (6.64% RSD), 85.4% (9.17% RSD) and 96.0% (7.44% RSD), respectively. Overall, the established EESI-MS/MS method has been demonstrated suitable for sensitive and rapid (<2 min per sample) quantitative detection of malachite green in various aqueous media, indicating its potential for online real-time monitoring of real life samples.

  1. Technical note: Air compared to nitrogen as nebulizing and drying gases for electrospray ionization mass spectrometry.

    PubMed

    Mielczarek, P; Silberring, J; Smoluch, M

    2016-01-01

    In the present study we tested the application of compressed air instead of pure nitrogen as the nebulizing and drying gas, and its influence on the quality of electrospray ionization (ESI) mass spectra. The intensities of the signals corresponding to protonated molecules were significantly (twice) higher when air was used. Inspection of signal-to-noise (S/N) ratios revealed that, in both cases, sensitivity was comparable. A higher ion abundance after the application of compressed air was followed by a higher background. Another potential risk of using air in the ESI source is the possibility for sample oxidation due to the presence of oxygen. To test this, we selected five easily oxidizing compounds to verify their susceptibility to oxidation. In particular, the presence of methionine was of interest. For all the compounds studied, no oxidation was observed. Amodiaquine oxidizes spontaneously in water solutions and its oxidized form can be detected a few hours after preparation. Direct comparison of the spectra where nitrogen was used with the corresponding spectra obtained when air was applied did not show significant differences. The only distinction was slightly different patterns of adducts when air was used. The difference concerns acetonitrile, which forms higher signals when air is the nebulizing gas. It is also important that the replacement of nitrogen with air does not affect quantitative data. The prepared calibration curves also visualize an intensity twice as high (independent of concentration within tested range) of the signal where air was applied. We have used our system continuously for three months with air as the nebulizing and drying gas and have not noticed any unexpected signal deterioration caused by additional source contamination from the air. Moreover, compressed air is much cheaper and easily available using oil-free compressors or pumps.

  2. Poly(amidoamine)-Cholesterol Conjugate Nanoparticles Obtained by Electrospraying as Novel Tamoxifen Delivery System

    PubMed Central

    Cavalli, R.; Bisazza, A.; Bussano, R.; Trotta, M.; Civra, A.; Lembo, D.; Ranucci, E.; Ferruti, P.

    2011-01-01

    A new poly(amidoamine)-cholesterol (PAA-cholesterol) conjugate was synthesized, characterized and used to produce nanoparticles by the electrospraying technique. The electrospraying is a method of liquid atomization that consists in the dispersion of a solution into small charged droplets by an electric field. Tuning the electrospraying process parameters spherical PAA-chol nanoparticles formed. The PAA-cholesterol nanoparticles showed sizes lower than 500 nm and spherical shape. The drug incorporation capacity was investigated using tamoxifen, a lipophilic anticancer drug, as model drug. The incorporation of the tamoxifen did not affect the shape and sizes of nanoparticles showing a drug loading of 40%. Tamoxifen-loaded nanoparticles exhibited a higher dose-dependent cytotoxicity than free tamoxifen, while blank nanoparticles did not show any cytotoxic effect at the same concentrations. The electrospray technique might be proposed to produce tamoxifen-loaded PAA-chol nanoparticle in powder form without any excipient in a single step. PMID:21785731

  3. Poly(amidoamine)-Cholesterol Conjugate Nanoparticles Obtained by Electrospraying as Novel Tamoxifen Delivery System.

    PubMed

    Cavalli, R; Bisazza, A; Bussano, R; Trotta, M; Civra, A; Lembo, D; Ranucci, E; Ferruti, P

    2011-01-01

    A new poly(amidoamine)-cholesterol (PAA-cholesterol) conjugate was synthesized, characterized and used to produce nanoparticles by the electrospraying technique. The electrospraying is a method of liquid atomization that consists in the dispersion of a solution into small charged droplets by an electric field. Tuning the electrospraying process parameters spherical PAA-chol nanoparticles formed. The PAA-cholesterol nanoparticles showed sizes lower than 500 nm and spherical shape. The drug incorporation capacity was investigated using tamoxifen, a lipophilic anticancer drug, as model drug. The incorporation of the tamoxifen did not affect the shape and sizes of nanoparticles showing a drug loading of 40%. Tamoxifen-loaded nanoparticles exhibited a higher dose-dependent cytotoxicity than free tamoxifen, while blank nanoparticles did not show any cytotoxic effect at the same concentrations. The electrospray technique might be proposed to produce tamoxifen-loaded PAA-chol nanoparticle in powder form without any excipient in a single step.

  4. Preparation of inorganic/organic polymer hybrid microcapsules with high encapsulation efficiency by an electrospray technique.

    PubMed

    Yunoki, Ayumi; Tsuchiya, Eiko; Fukui, Yu; Fujii, Akihiro; Maruyama, Tatsuo

    2014-08-13

    Microcapsules composed of calcium phosphate and chitosan were prepared in a single step by electrospraying. An aqueous solution containing calcium chloride and chitosan was electrosprayed into a phosphate solution to form a calcium phosphate shell on the sprayed droplets. The resulting microcapsules were 350 μm in average diameter. Investigation using fluorescently labeled chitosan and XRD measurements revealed that the shells of the microcapsules were composed of calcium phosphate (mainly hydroxyapatite) and chitosan. Instead of chitosan, poly(diallyldimethylammonium chloride) and polyethylene glycol were also available for microcapsule production by electrospraying. Variations in the electrospraying conditions resulted in a variety of microcapsule shapes. Various types of substrates were successfully encapsulated in microcapsules with a high encapsulation efficiency (more than 80%). Finally, we succeeded in the encapsulation of living yeast cells in microcapsules, and observed their growth within these microcapsules.

  5. DEVELOPMENT OF AN ELECTROSPRAY MASS SPECTROMETRIC METHOD FOR DETERMINING PERCHLORATE IN FERTILIZERS

    EPA Science Inventory

    An electrospray mass spectrometric method has been developed for application to agricultural and horticultural fertilizers to determine perchlorate. After fertilizers are leached or dissolved in water, the method relies on the formation of stable ion pair complex of the perchlor...

  6. The updated bottom up solution applied to atmospheric pressure photoionization and electrospray ionization mass spectrometry

    USDA-ARS?s Scientific Manuscript database

    The Updated Bottom Up Solution (UBUS) was recently applied to atmospheric pressure chemical ionization (APCI) mass spectrometry (MS) of triacylglycerols (TAGs). This report demonstrates that the UBUS applies equally well to atmospheric pressure photoionization (APPI) MS and to electrospray ionizatio...

  7. DEVELOPMENT OF AN ELECTROSPRAY MASS SPECTROMETRIC METHOD FOR DETERMINING PERCHLORATE IN FERTILIZERS

    EPA Science Inventory

    An electrospray mass spectrometric method has been developed for application to agricultural and horticultural fertilizers to determine perchlorate. After fertilizers are leached or dissolved in water, the method relies on the formation of stable ion pair complex of the perchlor...

  8. Residual Agar Determination in Bacterial Spores by Electrospray Ionization Mass Spectrometry

    SciTech Connect

    Wahl, Karen L.; Colburn, Heather A.; Wunschel, David S.; Petersen, Catherine E.; Jarman, Kristin H.; Valentine, Nancy B.

    2010-02-15

    Presented here is an analytical method to detect residual agar from a bacterial spore sample as an indication of culturing on an agar plate. This method is based on the resolubilization of agar polysaccharide from a bacterial spore sample, enzymatic digestion, followed by electrospray ionization tandem mass spectrometry (ESI-MSn) analysis for detection of a specific agar fragment ion. A range of Bacillus species and strains were selected to demonstrate the effectiveness of this approach. The characteristic agar fragment ion was detected in the spores grown on agar that were washed from 1 to 5 times, irradiated or non-irradiated and not in the spores grown in broth. A sample containing approximately 108 spores is currently needed for confident detection of residual agar from culture on agar plates in the presence of bacterial spores with a limit of detection of approximately 1 ppm agar spiked into a broth-grown spore sample. The results of a proficiency test with 42 blinded samples are presented demonstrating the utility of this method with no false positives and only 3 false negatives for samples that were below the detection level of the method as documented.

  9. Characterization of N,N-dimethyl amino acids by electrospray ionization-tandem mass spectrometry.

    PubMed

    Naresh Chary, V; Sudarshana Reddy, B; Kumar, Ch Dinesh; Srinivas, R; Prabhakar, S

    2015-05-01

    Methylation is an essential metabolic process for a number of critical reactions in the body. Methyl groups are involved in the healthy function of the body life processes, by conducting methylation process involving specific enzymes. In these processes, various amino acids are methylated, and the occurrence of methylated amino acids in nature is diverse. Nowadays, mass-spectrometric-based identification of small molecules as biomarkers for diseases is a growing research. Although all dimethyl amino acids are metabolically important molecules, mass spectral data are available only for a few of them in the literature. In this study, we report synthesis and characterization of all dimethyl amino acids, by electrospray ionization-tandem mass spectrometry (MS/MS) experiments on protonated molecules. The MS/MS spectra of all the studied dimethyl amino acids showed preliminary loss of H2O + CO to form corresponding immonium ions. The other product ions in the spectra are highly characteristic of the methyl groups on the nitrogen and side chain of the amino acids. The amino acids, which are isomeric and isobaric with the studied dimethyl amino acids, gave distinctive MS/MS spectra. The study also included MS/MS analysis of immonium ions of dimethyl amino acids that provide information on side chain structure, and it is further tested to determine the N-terminal amino acid of the peptides.

  10. Complexation of malic acid with cadmium(II) probed by electrospray ionization mass spectrometry.

    PubMed

    Jaklová Dytrtová, Jana; Jakl, Michal; Schröder, Detlef

    2012-02-15

    Electrospray ionization was used as a technique for the characterization of the interactions between cadmium(II) ions and malic acid (1) in aqueous solution. Particular attention was paid to the nature of the species formed, which generally correspond to complexes of CdX(+) cations with neutral malic acid, where X either is the counterion of the metal salt used as a precursor (i.e. X=Cl, I) or corresponds to singly deprotonated malic acid. In pure water solutions, also highly coordinated complexes [Cd(1-H)(1)(2)](+) and [CdCl(1)(2)](+) were detected, whereas the most abundant complexes detected in a sample of soil solution were: [Cd(1-H)(1)](+) and [CdCl(1)](+). With respect to possible application in environmental analysis, the effects of (i) metal salts present in solution, (ii) modest mineralization, and (iii) the matrices of real soil solutions were probed. While the presence of other metals leads to additional complexes, the characteristic species containing both cadmium(II) and malic acid can still be detected with good sensitivity. Copyright © 2012 Elsevier B.V. All rights reserved.

  11. Rapid differentiation of nucleotide phosphoramidate diastereomers by electrospray ionization tandem mass spectrometry.

    PubMed

    Bao, Donghui; Reddy, P Ganapati; Ross, Bruce S; Sofia, Michael J

    2012-08-30

    Nucleotide phosphoramidates are prodrugs which effectively deliver the active nucleotide to target tissues. It was shown that the individual phosphoramidate diastereomers have different antiviral activity, although the active nucleotide is the same. Therefore, a fast and simple analytical method is needed to characterize the individual diastereomeric phosphoramidate prodrugs. Stock solutions of diastereomeric nucleotide phosphoramidate prodrugs, i.e., 5'-phosphate derivatives of the β-D-2'-deoxy-2'-α-fluoro-2'-β-C-methyluridine nucleotide, were made in 25% acetonitrile to achieve a final concentration of 10 µg/mL. The samples were studied using high-performance liquid chromatography (HPLC) coupled with electrospray ionization tandem mass spectrometry (ESI-MS/MS). The MS/MS spectra of diastereomeric pairs showed substantial differences in the relative abundances of a characteristic ion in negative mode, which is proposed to be a cyclic phosphoramidate ion. Results were confirmed by the MS/MS spectrum of an analog without the NH proton and deuterium exchange experiment. Furthermore, the diastereomer-specific fragmentation behavior in negative ESI-MS was used to characterize a series of nucleotide phosphoramidates with different amino acid and aromatic substituents. An HPLC/MS/MS method was developed for the differentiation of the diastereomers of phosphoramidate prodrugs. In negative mode MS/MS spectra, the cyclic phosphoramidate ions yielded unambiguous distinction. This method presented a rapid and simple way for the characterization of nucleotide phosphoramidates. Copyright © 2012 John Wiley & Sons, Ltd.

  12. Simultaneous determination of trace oxyhalides and haloacetic acids using suppressed ion chromatography-electrospray mass spectrometry.

    PubMed

    Barron, Leon; Paull, Brett

    2006-05-15

    A new analytical procedure for the simultaneous determination of trace oxyhalides and haloacetic acids (HAs) in drinking water and aqueous soil extracts is described. The method uses micro-bore ion chromatography (IC) coupled with suppressed conductivity (SC) and electrospray ionization mass spectrometric detection (ESI-MS). The IC-SC-ESI-MS system included a secondary flow of 100% MeOH, which was added to the column eluate (post-suppressor) and resulted in a significant increase in sensitivity for all analytes. All ESI-MS parameters were optimized for HA analysis and sensitivity quantitatively compared to suppressed conductivity. Full analytical performance characteristics for the developed method are presented for monochloro-, monobromo-, dichloro-, dibromo-, trichloro-, bromochloro, chlorodifluoro-, trifluoro-, dichlorobromo- and dibromochloroacetic acid, as well as the oxyhalides iodate, bromate, chlorate and perchlorate. In the case of the HAs, an optimised 25-fold SPE preconcentration method meant all analytes could be readily detected well below the USEPA 60mug/L regulatory limit using conductivity and/or ESI-MS. The IC-ESI-MS method was applied to the determination of oxyhalides and HAs in both soil extracts and drinking water samples. Soil samples were extracted using ultra pure water with subsequent determination of perchlorate at 1.68mug/g of soil. A drinking water sample containing HAs was preconcentrated using LiChrolut EN solid phase extraction cartridges with subsequent sulphate and chloride removal. Total HAs were determined at 13mug/L.

  13. Online coupling of electrochemical reactions with liquid sample desorption electrospray ionization-mass spectrometry.

    PubMed

    Li, Jiwen; Dewald, Howard D; Chen, Hao

    2009-12-01

    The combination of electrochemistry (EC) and mass spectrometry (MS) is a powerful analytical tool to study redox reactions. This work reports the online coupling of a thin-layer electrochemical flow cell with liquid sample desorption electrospray ionization mass spectrometry (DESI-MS) and its applications in investigating various electrochemical reactions of biological molecules such as oxidative formation and reductive cleavage of disulfide bonds and online derivatization of peptides/proteins. As a result of the direct sampling nature of DESI, several useful features of such a coupling have been found, including simple instrumentation, fast response time (e.g., 3.6 s in the case of dopamine oxidation), freedom to choose a favorable ionization mode of DESI or traditional electrolysis solvent systems, and the absence of background signal possibly resulting from ionization when the cell is off (e.g., in the case of dopamine oxidation). More importantly, with the use of this new coupling apparatus, three disulfide bonds of insulin were fully cleaved by electrolytic reduction and both the A and B chains of the protein were successfully detected online by DESI-MS. In addition, online tagging of free cysteine residues of peptides/proteins employing electrogenerated dopamine o-quinone can be performed. These revealed characteristics of the coupling along with examined electrochemical reactions suggest that EC/DESI-MS has good potential in bioanalysis.

  14. Alginate-based microcapsules generated with the coaxial electrospray method for clinical application.

    PubMed

    Barron, Catherine; He, Jia-Qiang

    2017-09-01

    Alginate-based microencapsulation of cells has made a significant impact on the fields of regenerative medicine and tissue engineering mainly because of its ability to provide immunoisolation for the encapsulated material. This characteristic has allowed for the successful transplantation of non-autologous cells in several clinical trials for life threatening conditions, such as diabetes, myocardial infarction, and neurodegenerative disorders. Methods for alginate hydrogel microencapsulation have been well developed for various types of cells and can generate microcapsules of different diameters, degradation time, and composition. It appears the most prominent and successful method in clinical applications is the coaxial electrospray method, which can be used to generate both homogenous and non-homogeneous microcapsules with uniform size on the order of 100 μm. The present review aims to discuss why alginate hydrogel is an ideal biomaterial for the encapsulation of cells, how alginate-based microcapsules are generated, and methods of modifying the microcapsules for specific clinical treatments. This review will also discuss clinical applications that have utilized alginate-based microencapsulation in the treatment of diabetes, ischemic heart disease, and neurodegenerative diseases.

  15. Light extraction block with curved surface

    DOEpatents

    Levermore, Peter; Krall, Emory; Silvernail, Jeffrey; Rajan, Kamala; Brown, Julia J.

    2016-03-22

    Light extraction blocks, and OLED lighting panels using light extraction blocks, are described, in which the light extraction blocks include various curved shapes that provide improved light extraction properties compared to parallel emissive surface, and a thinner form factor and better light extraction than a hemisphere. Lighting systems described herein may include a light source with an OLED panel. A light extraction block with a three-dimensional light emitting surface may be optically coupled to the light source. The three-dimensional light emitting surface of the block may includes a substantially curved surface, with further characteristics related to the curvature of the surface at given points. A first radius of curvature corresponding to a maximum principal curvature k.sub.1 at a point p on the substantially curved surface may be greater than a maximum height of the light extraction block. A maximum height of the light extraction block may be less than 50% of a maximum width of the light extraction block. Surfaces with cross sections made up of line segments and inflection points may also be fit to approximated curves for calculating the radius of curvature.

  16. The wavelength dependence of Triton's light curve

    NASA Technical Reports Server (NTRS)

    Hillier, J.; Veverka, J.; Helfenstein, P.; Mcewen, A.

    1991-01-01

    Using Voyager observations, it is demonstrated that Triton's orbital light curve is strongly wavelength-dependent, a characteristic which readily explains some of the apparent discrepancies among pre-Voyager telescopic measurements. Specifically, a light curve amplitude (peak to peak) is found that decreases systematically with increasing wavelength from about 0.08 magnitude (peak to peak) near 200 nm to less than 0.02 magnitude near 1000 nm. Peak brightness occurs near 90 deg orbital longitude (leading hemisphere). The brightness variation across this hemisphere is close to sinusoidal; the variation across the darker hemisphere is more complex. The decrease in light curve amplitude with increasing wavelength appears to be due to a decrease in contrast among surface markings, rather than to atmospheric obscuration. The model also explains the observed decrease in the amplitude of Triton's light curve at visible wavelengths over the past decade, a decrease related to the current migration of the subsolar latitude toward the south pole; it is predicted that this trend will continue into the 1990s.

  17. Electrospray-assisted ultraviolet aerodynamic particle sizer spectrometer for real-time characterization of bacterial particles.

    PubMed

    Jung, Jae Hee; Lee, Jung Eun; Hwang, Gi Byoung; Lee, Byung Uk; Lee, Seung Bok; Jurng, Jong Soo; Bae, Gwi Nam

    2010-01-15

    The ultraviolet aerodynamic particle sizer (UVAPS) spectrometer is a novel, commercially available aerosol counter for real-time, continuous monitoring of viable bioaerosols based on the fluorescence induced from living microorganisms. For aerosolization of liquid-based microorganisms, general aerosolization methods such as atomization or nebulization may not be adequate for an accurate and quantitative characterization of the microorganisms because of the formation of agglomerated particles. In such cases, biological electrospray techniques have an advantage because they generate nonagglomerated particles, attributable to the repulsive electrical forces among particles with unipolar charges. Biological electrosprays are quickly gaining potential for the detection and control of living organisms in applications ranging from mass spectrometry to developmental microbiology. In this study, we investigated the size distribution, total concentration, and fluorescence percentage of bacterial particles in a real-time manner by electrospray-assisted UVAPS. A suspension containing Escherichia coli as a test microorganism was sprayed in a steady cone-jet mode using a specially designed electrospray system with a point-to-orifice-plate configuration based on charge-reduced electrospray size spectrometry. With the electrospray process, 98% of the total E. coli particle number concentration had a size of <1 mum and the geometric mean diameter was 0.779 mum, as compared with the respective values of 78% and 0.907 mum after nebulization. The fractions of fluorescence responsive particles and of particles that contained viable organisms in culture were 12% and 7%, respectively, from the electrospray process and 34% and 24% from nebulization. These results demonstrate that (1) the presence of agglomerated particles can lead to markedly overestimated fluorescence and culturability percentages compared with the values obtained from nonagglomerated particles, and (2) electrospray

  18. Learning curves in health care.

    PubMed

    Waldman, J Deane; Yourstone, Steven A; Smith, Howard L

    2003-01-01

    This article explores the uses of learning curve theory in medicine. Though effective application of learning curve theory in health care can result in higher quality and lower cost, it is seldom methodically applied in clinical practice. Fundamental changes are necessary in the corporate culture of medicine in order to capitalize maximally on the benefits of learning.

  19. Psychophysical tuning curves at very high frequencies

    NASA Astrophysics Data System (ADS)

    Yasin, Ifat; Plack, Christopher J.

    2005-10-01

    For most normal-hearing listeners, absolute thresholds increase rapidly above about 16 kHz. One hypothesis is that the high-frequency limit of the hearing-threshold curve is imposed by the transmission characteristics of the middle ear, which attenuates the sound input [Masterton et al., J. Acoust. Soc. Am. 45, 966-985 (1969)]. An alternative hypothesis is that the high-frequency limit of hearing is imposed by the tonotopicity of the cochlea [Ruggero and Temchin, Proc. Nat. Acad. Sci. U.S.A. 99, 13206-13210 (2002)]. The aim of this study was to test these hypotheses. Forward-masked psychophysical tuning curves (PTCs) were derived for signal frequencies of 12-17.5 kHz. For the highest signal frequencies, the high-frequency slopes of some PTCs were steeper than the slope of the hearing-threshold curve. The results also show that the human auditory system displays frequency selectivity for characteristic frequencies (CFs) as high as 17 kHz, above the frequency at which absolute thresholds begin to increase rapidly. The findings suggest that, for CFs up to 17 kHz, the high-frequency limitation in humans is imposed in part by the middle-ear attenuation, and not by the tonotopicity of the cochlea.

  20. Breakthrough curve moments scaling in hyporheic exchange

    NASA Astrophysics Data System (ADS)

    Bellin, A.; Tonina, D.; Marzadri, A.

    2015-02-01

    The interaction between stream flow and bed forms creates an uneven distribution of near-bed energy heads, which is the driving force of hyporheic exchange. Owing to the large disparity of advection characteristic times in the stream and within the hyporheic zone, solute mass exchange is often modeled by considering the latter as an immobile region. In a recent contribution Gónzalez-Pinzón et al. (2013) showed that existing models employing this hypothesis are structurally inconsistent with the scaling revealed by the analysis of 384 breakthrough curves collected in 44 streams across five continents. Motivated by this result, we analyze the scaling characteristics of a model that we recently developed by combining the analytical solution of the advective flow within the hyporheic zone with a Lagrangian solute transport model. Results show that similarly to the experimental data our model predicts breakthrough curves with a constant skewness, irrespective of the stream size, and that the scaling of the first three moments observed by Gónzalez-Pinzón et al. (2013) is also respected. Moreover, we propose regression curves that relate the first three moments of the residence time distribution with the alternate bar dimensionless depth (YBM*), a quantity that is easily measurable in the field. The connection between BTC moments and YBM* opens new possibilities for modeling transport processes at the catchment scale.

  1. Study of superhydrophobic electrosprayed catalyst layers using a localized reference electrode technique

    NASA Astrophysics Data System (ADS)

    Chaparro, A. M.; Ferreira-Aparicio, P.; Folgado, M. A.; Brightman, E.; Hinds, G.

    2016-09-01

    The performance of electrosprayed cathode catalyst layers in a polymer electrolyte membrane fuel cell (PEMFC) is studied using a localized reference electrode technique. Single cells with an electrosprayed cathode catalyst layer show an increase of >20% in maximum power density under standard testing conditions, compared with identical cells assembled with a conventional, state-of-the-art, gas diffusion cathode. When operated at high current density (1.2 A cm-2) the electrosprayed catalyst layers show more homogeneous distribution of the localized cathode potential, with a standard deviation from inlet to outlet of <50 mV, compared with 79 mV for the conventional gas diffusion cathode. Higher performance and homogeneity of cell response is attributed to the superhydrophobic nature of the macroporous electrosprayed catalyst layer structure, which enhances the rate of expulsion of liquid water from the cathode. On the other hand, at low current densities (<0.5 A cm-2), the electrosprayed layers exhibit more heterogeneous distribution of cathode potential than the conventional cathodes; this behavior is attributed to less favorable kinetics for oxygen reduction in very hydrophobic catalyst layers. The optimum performance may be obtained with electrosprayed catalyst layers employing a high Pt/C catalyst ratio.

  2. Secondary electrospray ionization of complex vapor mixtures. Theoretical and experimental approach.

    PubMed

    Vidal-de-Miguel, Guillermo; Herrero, Ana

    2012-06-01

    In secondary electrospray ionization (SESI) systems, gaseous analytes exposed to an electrospray plume become ionized after charge is transferred from the charging electrosprayed particles (the charging agent) to the vapor species. Currently available SESI models are valid for simplified systems having only one type of electrosprayed species, which ionizes only one single vapor species, and for the limit of low vapor concentration. More realistic models require considering other effects. Here we develop a theoretical model that accounts for the effects of high vapor concentration, saturation effects, interferences between different vapor species, and electrosprays producing different types of species from the liquid phase. In spite of the relatively high complexity of the problem, we find simple relations between the different ionic species concentrations that hold independently of the particular ion source configuration. Our model suggests that an ideal SESI system should use highly concentrated charging agents composed preferably of only one dominating species with low mobility. Experimental measurements with a MeOH-H(2)O-NH(3) electrospray and a mixture of fatty acids and lactic acid served to test the theory, which gives good qualitative results. These results also suggest that the SESI ionization mechanism is primarily based on ions rather than on charged droplets.

  3. Analytical Characterization of the Electrospray Ion Source in the Nanoflow Regime

    SciTech Connect

    Marginean, Ioan; Kelly, Ryan T.; Prior, David C.; Lamarche, Brian L.; Tang, Keqi; Smith, Richard D.

    2008-09-01

    We provide a thorough characterization of the low-flow electrospray as an ionization source for mass spectrometry (MS) using solutions typical for reversed-phase liquid chromatography. As expected, the electrospray operating regime strongly affects the MS signal; however, contrary to conventional wisdom, the pulsating regime consistently offers better performance than the cone-jet regime in these experimental conditions. We explain this observation by a highly efficient ionization achieved by the pulsating electrospray at low flow rates, rendering the increased charge generated by a cone-jet electrospray detrimental for transmission from atmospheric pressure to vacuum through a heated capillary interface. Over a wide range of voltages, the pulsating electrospray provides a relatively constant MS signal intensity, which depends significantly on the distance between the emitter and the MS inlet. For cone-jet electrosprays the MS signal decreases slightly with increasing voltage, but the signal is less affected by the emitter-inlet distance. At flow rates up to 100 nL/min the MS signal increases with increasing flow rate due to the larger number of ions supplied into the gas phase. At flow rates greater than 100 nL/min, the signal reaches a plateau due to increasingly unsatisfactory ionization efficiency at larger flow rates.

  4. Analytical Characterization of the Electrospray Ion Source in the Nanoflow Regime

    PubMed Central

    Marginean, Ioan; Kelly, Ryan T.; Prior, David C.; LaMarche, Brian L.; Tang, Keqi; Smith, Richard D.

    2009-01-01

    A detailed characterization of a conventional low-flow electrospray ionization (ESI) source for mass spectrometry (MS) using solution compositions typical of reversed-phase liquid chromatography is reported. Contrary to conventional wisdom, the pulsating regime consistently provided better ESI-MS performance than the cone-jet regime for the interface and experimental conditions studied. This observation is supported by additional measurements showing that a conventional heated capillary interface affords more efficient sampling and transmission for the charged aerosol generated by a pulsating electrospray. The pulsating electrospray provided relatively constant MS signal intensities over a wide range of voltages, while the signal decreased slightly with increasing voltage for the cone-jet electrospray. The MS signal also decreased with increasing emitter-interface distance for both pulsating and cone-jet electrosprays due to the expansion of the charged aerosol plume. At flow rates below 100 nL/min the MS signal increased with increasing flow rate due to increased number of gas-phase ions produced. At flow rates greater than 100 nL/min, the signal reached a plateau due to decreasing ionization efficiency at larger flow rates. These results suggest approaches for improving MS interface performance for low-flow (nano- to micro-) electrosprays. PMID:18661954

  5. Controlled release behaviour of protein-loaded microparticles prepared via coaxial or emulsion electrospray

    PubMed Central

    Wang, Ying; Yang, Xiaoping; Liu, Wentao; Zhang, Feng; Cai, Qing; Deng, Xuliang

    2013-01-01

    Biodegradable poly (lactic-co-glycolic acid) (PLGA) microparticles are an effective way to achieve sustained drug release. In this study, we investigated a sustained release model of PLGA microparticles with incorporated protein via either emulsion or coaxial electrospray techniques. PLGA (75:25) was used as the carrier, and bovine serum albumin as a model protein. Coaxial electrospray resulted in a type of core–shell structure with mean diameters of 2.41 ± 0.60 µm and a centralised protein distribution within the core. Emulsion electrospray formed bigger microparticles with mean diameters of 22.75 ± 8.05 µm and a heterogeneous protein distribution throughout the microparticles. The coaxial electrospray microparticles presented a much slighter burst release than the emulsion electrospray microparticles. Loading efficiency was significantly higher (p < 0.05) in the coaxial group than emulsion group. This indicated that both emulsion and coaxial electrospray could produce protein-loaded microparticles with sustained release behaviour, but the former revealed a superior approach for drug delivery. PMID:23346923

  6. Controlled release behaviour of protein-loaded microparticles prepared via coaxial or emulsion electrospray.

    PubMed

    Wang, Ying; Yang, Xiaoping; Liu, Wentao; Zhang, Feng; Cai, Qing; Deng, Xuliang

    2013-01-01

    Biodegradable poly (lactic-co-glycolic acid) (PLGA) microparticles are an effective way to achieve sustained drug release. In this study, we investigated a sustained release model of PLGA microparticles with incorporated protein via either emulsion or coaxial electrospray techniques. PLGA (75:25) was used as the carrier, and bovine serum albumin as a model protein. Coaxial electrospray resulted in a type of core-shell structure with mean diameters of 2.41 ± 0.60 µm and a centralised protein distribution within the core. Emulsion electrospray formed bigger microparticles with mean diameters of 22.75 ± 8.05 µm and a heterogeneous protein distribution throughout the microparticles. The coaxial electrospray microparticles presented a much slighter burst release than the emulsion electrospray microparticles. Loading efficiency was significantly higher (p < 0.05) in the coaxial group than emulsion group. This indicated that both emulsion and coaxial electrospray could produce protein-loaded microparticles with sustained release behaviour, but the former revealed a superior approach for drug delivery.

  7. Using the Electrochemistry of the Electrospray Ion Source

    SciTech Connect

    Van Berkel, Gary J; Kertesz, Vilmos

    2007-01-01

    Electrospray mass spectrometry (ES-MS) is one of the more widely used analysis methods in science today, impacting fields as diverse as conventional chemistry to biotechnology and materials science. , Even 20 years after bursting onto the mass spectrometry scene, the underlying processes in ES ionization continue to be better understood exposing new opportunities for the technique. , , , , Such is the case for the improved understanding related to the electrochemical processes inherent to the operation of this ion source, , , which is the topic of this report. Electrospray ionization involves three main steps prior to mass analysis: the generation and charging of the ES droplets; droplet evaporation and the production of gas-phase ions; and secondary processes that modify the gas-phase ions in the atmosphere and the sub-atmospheric pressure sampling regions of the mass spectrometer. Integral to the generation and charging of the ES droplets are electrochemical reactions that occur at the conductive contact/solution interface within or near the ES emitter to maintain the quasi-continuous production of charged droplets and ultimately gas-phase ions. The basic electrochemical phenomena concerning the ES ion source were first brought to wide attention in the mass spectrometry community by Kebarle and co-workers in the early 1990's,8 but the electrochemistry of electrostatic spray devices and possible analytical consequences resulting from this phenomenon were realized and discussed in the literature at least as far back as the mid-1970's. When asked to intercede in a debate on the significance of electrochemistry in the ES ionization (ESI) process, 2002 Nobel Laureate in Chemistry John Fenn noted that to him " the idea that electrochemical reactions might be taking place in an ES ion source was too obvious to mention. That products of such reactions are of vital significance in the overall ESI process was much less obvious. Indeed, it seems fair to say that with few

  8. The detection of piroxicam, tenoxicam and their metabolites in equine urine by electrospray ionisation ion trap mass spectrometry.

    PubMed

    McKinney, Andrew R; Suann, Craig J; Stenhouse, Allen M

    2004-01-01

    An investigation has been conducted into the metabolism and urinary excretion of orally administered piroxicam and tenoxicam in the horse. The major component detected in urine after the administration of piroxicam was 5'-hydroxypiroxicam, which was detectable up to 24 h post-administration. Unchanged piroxicam was present only as a minor component. In contrast, unchanged tenoxicam was the major component observed after the administration of tenoxicam, being detectable for 72 h post-administration, while 5'-hydroxytenoxicam was a minor component. Phase II beta-glucuronide conjugation in each case was found to be negligible. The ion trap mass spectral characteristics of piroxicam, tenoxicam, 5'-hydroxypiroxicam and 5'-hydroxytenoxicam under electrospray ionisation conditions were examined in some detail.

  9. The analysis of high explosives by liquid chromatography/electrospray ionization mass spectrometry: multiplexed detection of negative ion adducts.

    PubMed

    Mathis, John A; McCord, Bruce R

    2005-01-01

    The negative ion electrospray ionization mass spectrometric (ESI-MS) detection of adducts of high explosives with chloride, formate, acetate, and nitrate was used to demonstrate the gas-phase interaction of neutral explosives with these anions. The relative intensities of the adduct species were determined to compare the competitive formation of the selected high explosives and anions. The relative stability of the adduct species varies, yielding preferential formation of certain anionic adducts with different high explosives. To exploit this effect, an isocratic high-performance liquid chromatography (HPLC)/ESI-MS method was developed and used for the simultaneous analysis of high explosives using two different techniques for the addition of the anionic additives; pre- and post-column. The results show that the pre-column approach provides similar results with improved selectivity for specific explosives. By detecting characteristic adduct species for each explosive, this method provides a qualitative and quantitative approach for the analysis and identification of high explosives.

  10. Quantitative Thin-Layer Chromatography/Mass Spectrometry Analysis of Caffeine Using a Surface Sampling Probe Electrospray Ionization Tandem Mass Spectrometry System

    SciTech Connect

    Ford, Michael J; Deibel, Michael A.; Tomkins, Bruce A; Van Berkel, Gary J

    2005-01-01

    Quantitative determination of caffeine on reversed-phase C8 thin-layer chromatography plates using a surface sampling electrospray ionization system with tandem mass spectrometry detection is reported. The thin-layer chromatography/electrospray tandem mass spectrometry method employed a deuterium-labeled caffeine internal standard and selected reaction monitoring detection. Up to nine parallel caffeine bands on a single plate were sampled in a single surface scanning experiment requiring 35 min at a surface scan rate of 44 {mu}m/s. A reversed-phase HPLC/UV caffeine assay was developed in parallel to assess the mass spectrometry method performance. Limits of detection for the HPLC/UV and thin-layer chromatography/electrospray tandem mass spectrometry methods determined from the calibration curve statistics were 0.20 ng injected (0.50 {mu}L) and 1.0 ng spotted on the plate, respectively. Spike recoveries with standards and real samples ranged between 97 and 106% for both methods. The caffeine content of three diet soft drinks (Diet Coke, Diet Cherry Coke, Diet Pepsi) and three diet sport drinks (Diet Turbo Tea, Speed Stack Grape, Speed Stack Fruit Punch) was measured. The HPLC/UV and mass spectrometry determinations were in general agreement, and these values were consistent with the quoted values for two of the three diet colas. In the case of Diet Cherry Coke and the diet sports drinks, the determined caffeine amounts using both methods were consistently higher (by 8% or more) than the literature values.

  11. Quantitative thin-layer chromatography/mass spectrometry analysis of caffeine using a surface sampling probe electrospray ionization tandem mass spectrometry system.

    PubMed

    Ford, Michael J; Deibel, Michael A; Tomkins, Bruce A; Van Berkel, Gary J

    2005-07-15

    Quantitative determination of caffeine on reversed-phase C8 thin-layer chromatography plates using a surface sampling electrospray ionization system with tandem mass spectrometry detection is reported. The thin-layer chromatography/electrospray tandem mass spectrometry method employed a deuterium-labeled caffeine internal standard and selected reaction monitoring detection. Up to nine parallel caffeine bands on a single plate were sampled in a single surface scanning experiment requiring 35 min at a surface scan rate of 44 mum/s. A reversed-phase HPLC/UV caffeine assay was developed in parallel to assess the mass spectrometry method performance. Limits of detection for the HPLC/UV and thin-layer chromatography/electrospray tandem mass spectrometry methods determined from the calibration curve statistics were 0.20 ng injected (0.50 muL) and 1.0 ng spotted on the plate, respectively. Spike recoveries with standards and real samples ranged between 97 and 106% for both methods. The caffeine content of three diet soft drinks (Diet Coke, Diet Cherry Coke, Diet Pepsi) and three diet sport drinks (Diet Turbo Tea, Speed Stack Grape, Speed Stack Fruit Punch) was measured. The HPLC/UV and mass spectrometry determinations were in general agreement, and these values were consistent with the quoted values for two of the three diet colas. In the case of Diet Cherry Coke and the diet sports drinks, the determined caffeine amounts using both methods were consistently higher (by approximately 8% or more) than the literature values.

  12. Deployment of a Curved Truss

    NASA Technical Reports Server (NTRS)

    Giersch, Louis R.; Knarr, Kevin

    2010-01-01

    Structures capable of deployment into complex, three-dimensional trusses have well known space technology applications such as the support of spacecraft payloads, communications antennas, radar reflectors, and solar concentrators. Such deployable trusses could also be useful in terrestrial applications such as the rapid establishment of structures in military and emergency service situations, in particular with regard to the deployment of enclosures for habitat or storage. To minimize the time required to deploy such an enclosure, a single arch-shaped truss is preferable to multiple straight trusses arranged vertically and horizontally. To further minimize the time required to deploy such an enclosure, a synchronous deployment with a single degree of freedom is also preferable. One method of synchronizing deployment of a truss is the use of a series of gears; this makes the deployment sequence predictable and testable, allows the truss to have a minimal stowage volume, and the deployed structure exhibits the excellent stiffness-to-mass and strength-to-mass ratios characteristic of a truss. A concept for using gears with varying ratios to deploy a truss into a curved shape has been developed and appears to be compatible with both space technology applications as well as potential use in terrestrial applications such as enclosure deployment. As is the case with other deployable trusses, this truss is formed using rigid elements (e.g., composite tubes) along the edges, one set of diagonal elements composed of either cables or folding/hinged rigid members, and the other set of diagonal elements formed by a continuous cable that is tightened by a motor or hand crank in order to deploy the truss. Gears of varying ratios are used to constrain the deployment to a single degree of freedom, making the deployment synchronous, predictable, and repeatable. The relative sizes of the gears and the relative dimensions of the diagonal elements determine the deployed geometry (e

  13. Consistency results for the ROC curves of fused classifiers

    NASA Astrophysics Data System (ADS)

    Bjerkaas, Kristopher S.; Oxley, Mark E.; Bauer, Kenneth W., Jr.

    2004-08-01

    The U.S. Air Force is researching the fusion of multiple sensors and classifiers. Given a finite collection of classifiers to be fused one seeks a new classifier with improved performance. An established performance quantifier is the Receiver Operating Characteristic (ROC) curve. This curve allows one to view the probability of detection versus probability of false alarm in one graph. In reality only finite data is available so only an approximate ROC curve can be constructed. Previous research shows that one does not have to perform an experiment for this new fused classifier to determine its ROC curve. If the ROC curve for each individual classifier has been determined, then formulas for the ROC curve of the fused classifier exist for certain fusion rules. This will be an enormous saving in time and money since the performance of many fused classifiers will be determined without having to perform tests on each one. But, again, these will be approximate ROC curves, since they are based on finite data. We show that if the individual approximate ROC curves are consistent then the approximate ROC curve for the fused classifier is also consistent under certain circumstances. We give the details for these circumstances, as well as some examples related to sensor fusion.

  14. A high-frequency electrospray driven by gas volume charges

    SciTech Connect

    Lastochkin, Dmitri; Chang, H.-C.

    2005-06-15

    High-frequency (>10 kHz) ac electrospray is shown to eject volatile dielectric liquid drops by an entirely different mechanism from dc sprays. The steady dc Taylor conic tip is absent and continuous spraying of submicron drops is replaced by individual dynamic pinchoff events involving the entire drop. We attribute this spraying mechanism to a normal Maxwell force produced by an undispersed plasma cloud in front of the meniscus that produces a visible glow at the spherical tip. The volume charge within the cloud is formed by electron-induced gas ionization of the evaporated liquid and produces a large normal field that is much higher than the nominal applied field such that drop ejection occurs at a voltage (at high frequencies) that is as much as ten times lower than that for dc sprays. The ejection force is sensitive to the liquid properties (but not its electrolyte composition), the ac frequency and trace amounts of inert gases, which are believed to catalyze the ionization reactions. As electroneutral drops are ejected, due to the large (>100) ratio between individual drop ejection time and the ac frequency, this mechanism can produce large (microns) electroneutral drops at relatively low voltages.

  15. Next Generation of Electrosprayed Fibers for Tissue Regeneration

    PubMed Central

    Hong, Jong Kyu

    2011-01-01

    Electrospinning is a widely established polymer-processing technology that allows generation of fibers (in nanometer to micrometer size) that can be collected to form nonwoven structures. By choosing suitable process parameters and appropriate solvent systems, fiber size can be controlled. Since the technology allows the possibility of tailoring the mechanical properties and biological properties, there has been a significant effort to adapt the technology in tissue regeneration and drug delivery. This review focuses on recent developments in adapting this technology for tissue regeneration applications. In particular, different configurations of nozzles and collector plates are summarized from the view of cell seeding and distribution. Further developments in obtaining thick layers of tissues and thin layered membranes are discussed. Recent advances in porous structure spatial architecture parameters such as pore size, fiber size, fiber stiffness, and matrix turnover are summarized. In addition, possibility of developing simple three-dimensional models using electrosprayed fibers that can be utilized in routine cell culture studies is described. PMID:21210761

  16. Is electrospray emission really due to columbic forces?

    SciTech Connect

    Aliotta, Francesco Ponterio, Rosina C.; Salvato, Gabriele; Vasi, Cirino; Calandra, Pietro; Pochylski, Mikolaj

    2014-09-15

    Electrospray ionization (ESI) is a widely adopted soft ionization method for mass spectroscopy (MS). In spite of the undeniable success of the technique, its mechanisms are difficult to be analytically modelled because the process is characterized by non-equilibrium conditions. The common belief is that the formation of gas-phase ions takes place at the apex of the Taylor cone via electrophoretic charging. The charge balance implies that a conversion of electrons to ions should occur at the metal-liquid interface of the injector needle. We have detected that the above description is based on unproved assumptions which are not consistent with the correct evaluation of the problem. The comparison between experiments performed under the usual geometry and observations obtained under symmetric field configurations suggests that the emitted droplets cannot be significantly charged or, at least, that any possible ionization mechanism is so poorly efficient to ensure that columbic forces cannot play a major role in jet formation, even in cases where the liquid consists of a solution of ionic species. Further work is required to clearly understand how ionization occurs in ESI-MS.

  17. Multidrug encapsulation by coaxial tri-capillary electrospray.

    PubMed

    Lee, Yi-Hsuan; Bai, Meng-Yi; Chen, Da-Ren

    2011-01-01

    This study describes how a coaxial tri-capillary electrospray (ES) system can synthesize monodisperse PLGA-coated particles containing multiple drugs in one step. The coaxial arrangement of three separate capillaries in an ES nozzle enables production of composite particles with tri-layered structures without the complicated steps involved in emulsion processes. Various materials can be encapsulated in separate layers of individual composite particles without regard for the hydroscopic property of drugs. At the proper spray setting, nearly 100% drug encapsulation efficiency can be achieved. By varying the feed flowrate of spray solutions, the overall particle sizes, ranging from submicrometer to micrometer, and the thickness of the layers in produced particles can also be controlled. Size and tri-layered structure of the composite particles were characterized by SEM and laser scanning confocal microscopy (LSCM). We further explored the spray technique in the production of tri-layered composite particles having a controlled multidrug-release profile, and compared the release profiles of both core-shell structured particles (produced by coaxial dual-capillary ES) and tri-layered ones (produced by coaxial tri-capillary ES). The comparison showed that composite particles with the tri-layered structure can release multiple drugs in distinct kinetic phases. We further demonstrated that the release profile of tri-layered composite particles can be effectively controlled by varying the thickness and chemical composition of their individual layers. Copyright © 2010 Elsevier B.V. All rights reserved.

  18. Electrochemistry combined on-line with electrospray mass spectrometry

    SciTech Connect

    Zhou, F.; Berkel, G.J.V.

    1995-10-15

    In this paper a variety of methods to couple electrochemistry on-line with electrospray mass spectrometry (EC/ES-MS) are presented, and the fundamental and analytical utility of this hybrid technique is illustrated. The major problems encountered in coupling EC and ES-MS are discussed, and means to overcome them are presented. Three types of electrochemical flow cells, viz., a thin-layer electrode flow-by cell, a tubular electrode flow-through cell, and a porous electrode flow-through cell, are discussed in regard to their suitability for this coupling. Methods for coupling each of these electrochemical cells on-line with ES-MS, either floated at or decoupled from the ES high voltage and controlled by a constant current supply, a constant potential supply, or a potentiostat are presented. Three applications are used to illustrate the utility and versatility of the EC/ES-MS combination: (1) the ionization of neutral analytes (i.e., perylene) for detection by ES-MS, (2) the study of the products of electrode reactions (i.e., nickel(II) octaethylporphyrin oxidation products), including relatively short-lived products (i.e., {Beta}-carotene oxidation products), and (3) the enhanced determination of metals (i.e., elemental silver) achieved by coupling anodic stripping voltammetry on-line with ES-MS. 52 refs., 6 figs.

  19. Micro-nano hierarchical superhydrophobic electrospray-synthesized silica layers.

    PubMed

    Kim, Ji-Yeong; Kim, Eun-Kyeong; Kim, Sang Sub

    2013-02-15

    This paper reports the preparation of superhydrophobic SiO(2) layers with a micro-nano hierarchical surface structure. SiO(2) layers, which were rough on the microscale, were prepared using an electrospraying method combined with a sol-gel chemical route. To create a nanoscale structure, the surface of the SiO(2) layers was coated with Au nanoparticles using an ultraviolet-enhanced chemical reduction process, resulting in a micro-nano hierarchical surface structure. A subsequent fluorination treatment with a solution containing trichloro(1H,1H,2H,2H-perfluorooctyl)silane resulted in fluorination of the micro-nano hierarchical SiO(2) layers. The resulting SiO(2) layers showed outstanding repellency toward a range of liquid droplets, for example, a water-repellency of 170°. The surface fraction and work of adhesion of the fluorinated, micro-nano hierarchical SiO(2) layers were estimated using the Cassie-Baxter and Young-Dupre equations, respectively. The long-term durability and ultraviolet resistance of the superhydrophobic SiO(2) layers prepared in this study highlight their potential in a range of practical applications. Copyright © 2012 Elsevier Inc. All rights reserved.

  20. Advances in drug delivery via electrospun and electrosprayed nanomaterials

    PubMed Central

    Zamani, Maedeh; Prabhakaran, Molamma P; Ramakrishna, Seeram

    2013-01-01

    Electrohydrodynamic (EHD) techniques refer to procedures that utilize electrostatic forces to fabricate fibers or particles of different shapes with sizes in the nano-range to a few microns through electrically charged fluid jet. Employing different techniques, such as blending, surface modification, and coaxial process, there is a great possibility of incorporating bioactive such molecules as drugs, DNA, and growth factors into the nanostructures fabricated via EHD techniques. By careful selection of materials and processing conditions, desired encapsulation efficiency as well as preserved bioactivity of the therapeutic agents can be achieved. The drug-loaded nanostructures produced can be applied via different routes, such as implantation, injection, and topical or oral administration for a wide range of disease treatment. Taking advantage of the recent developments in EHD techniques like the coaxial process or multilayered structures, individually controlled delivery of multiple drugs is achievable, which is of great demand in cancer therapy and growth-factor delivery. This review summarizes the most recent techniques and postmodification methods to fabricate electrospun nanofibers and electrosprayed particles for drug-delivery applications. PMID:23976851