An analytically based numerical method for computing view factors in real urban environments

NASA Astrophysics Data System (ADS)

Lee, Doo-Il; Woo, Ju-Wan; Lee, Sang-Hyun

2018-01-01

A view factor is an important morphological parameter used in parameterizing in-canyon radiative energy exchange process as well as in characterizing local climate over urban environments. For realistic representation of the in-canyon radiative processes, a complete set of view factors at the horizontal and vertical surfaces of urban facets is required. Various analytical and numerical methods have been suggested to determine the view factors for urban environments, but most of the methods provide only sky-view factor at the ground level of a specific location or assume simplified morphology of complex urban environments. In this study, a numerical method that can determine the sky-view factors ( ψ ga and ψ wa ) and wall-view factors ( ψ gw and ψ ww ) at the horizontal and vertical surfaces is presented for application to real urban morphology, which are derived from an analytical formulation of the view factor between two blackbody surfaces of arbitrary geometry. The established numerical method is validated against the analytical sky-view factor estimation for ideal street canyon geometries, showing a consolidate confidence in accuracy with errors of less than 0.2 %. Using a three-dimensional building database, the numerical method is also demonstrated to be applicable in determining the sky-view factors at the horizontal (roofs and roads) and vertical (walls) surfaces in real urban environments. The results suggest that the analytically based numerical method can be used for the radiative process parameterization of urban numerical models as well as for the characterization of local urban climate.

Sampling and analysis for radon-222 dissolved in ground water and surface water

USGS Publications Warehouse

DeWayne, Cecil L.; Gesell, T.F.

1992-01-01

Radon-222 is a naturally occurring radioactive gas in the uranium-238 decay series that has traditionally been called, simply, radon. The lung cancer risks associated with the inhalation of radon decay products have been well documented by epidemiological studies on populations of uranium miners. The realization that radon is a public health hazard has raised the need for sampling and analytical guidelines for field personnel. Several sampling and analytical methods are being used to document radon concentrations in ground water and surface water worldwide but no convenient, single set of guidelines is available. Three different sampling and analytical methods - bubbler, liquid scintillation, and field screening - are discussed in this paper. The bubbler and liquid scintillation methods have high accuracy and precision, and small analytical method detection limits of 0.2 and 10 pCi/l (picocuries per liter), respectively. The field screening method generally is used as a qualitative reconnaissance tool.

Study of Surface Wave Propagation in Fluid-Saturated Porous Solids.

NASA Astrophysics Data System (ADS)

Azcuaga, Valery Francisco Godinez

1995-01-01

This study addresses the surface wave propagation phenomena on fluid-saturated porous solids. The analytical method for calculation of surface wave velocities (Feng and Johnson, JASA, 74, 906, 1983) is extended to the case of a porous solid saturated with a wetting fluid in contact with a non-wetting fluid, in order to study a material combination suitable for experimental investigation. The analytical method is further extended to the case of a non-wetting fluid/wetting fluid-saturated porous solid interface with an arbitrary finite surface stiffness. These extensions of the analytical method allows to theoretically study surface wave propagation phenomena during the saturation process. A modification to the 2-D space-time reflection Green's function (Feng and Johnson, JASA, 74, 915, 1983) is introduced in order to simulate the behavior of surface wave signals detected during the experimental investigation of surface wave propagation on fluid-saturated porous solids (Nagy, Appl. Phys. Lett., 60, 2735, 1992). This modification, together with the introduction of an excess attenuation for the Rayleigh surface mode, makes it possible to explain the apparent velocity changes observed on the surface wave signals during saturation. Experimental results concerning the propagation of surface waves on an alcohol-saturated porous glass are presented. These experiments were performed at frequencies of 500 and 800 kHz and show the simultaneous propagation of the two surface modes predicted by the extended analytical method. Finally an analysis of the displacements associated with the different surface modes is presented. This analysis reveals that it is possible to favor the generation of the Rayleigh surface mode or of the slow surface mode, simply by changing the type of transducer used in the generation of surface waves. Calculations show that a shear transducer couples more energy into the Rayleigh mode, whereas a longitudinal transducer couples more energy into the slow surface mode. Experimental results obtained with the modified experimental system show a qualitative agreement with the theoretical predictions.

Note: Model identification and analysis of bivalent analyte surface plasmon resonance data.

PubMed

Tiwari, Purushottam Babu; Üren, Aykut; He, Jin; Darici, Yesim; Wang, Xuewen

2015-10-01

Surface plasmon resonance (SPR) is a widely used, affinity based, label-free biophysical technique to investigate biomolecular interactions. The extraction of rate constants requires accurate identification of the particular binding model. The bivalent analyte model involves coupled non-linear differential equations. No clear procedure to identify the bivalent analyte mechanism has been established. In this report, we propose a unique signature for the bivalent analyte model. This signature can be used to distinguish the bivalent analyte model from other biphasic models. The proposed method is demonstrated using experimentally measured SPR sensorgrams.

Method and apparatus for detecting an analyte

DOEpatents

Allendorf, Mark D [Pleasanton, CA; Hesketh, Peter J [Atlanta, GA

2011-11-29

We describe the use of coordination polymers (CP) as coatings on microcantilevers for the detection of chemical analytes. CP exhibit changes in unit cell parameters upon adsorption of analytes, which will induce a stress in a static microcantilever upon which a CP layer is deposited. We also describe fabrication methods for depositing CP layers on surfaces.

Exact analytical modeling of magnetic vector potential in surface inset permanent magnet DC machines considering magnet segmentation

NASA Astrophysics Data System (ADS)

Jabbari, Ali

2018-01-01

Surface inset permanent magnet DC machine can be used as an alternative in automation systems due to their high efficiency and robustness. Magnet segmentation is a common technique in order to mitigate pulsating torque components in permanent magnet machines. An accurate computation of air-gap magnetic field distribution is necessary in order to calculate machine performance. An exact analytical method for magnetic vector potential calculation in surface inset permanent magnet machines considering magnet segmentation has been proposed in this paper. The analytical method is based on the resolution of Laplace and Poisson equations as well as Maxwell equation in polar coordinate by using sub-domain method. One of the main contributions of the paper is to derive an expression for the magnetic vector potential in the segmented PM region by using hyperbolic functions. The developed method is applied on the performance computation of two prototype surface inset magnet segmented motors with open circuit and on load conditions. The results of these models are validated through FEM method.

A comparative review of optical surface contamination assessment techniques

NASA Technical Reports Server (NTRS)

Heaney, James B.

1987-01-01

This paper will review the relative sensitivities and practicalities of the common surface analytical methods that are used to detect and identify unwelcome adsorbants on optical surfaces. The compared methods include visual inspection, simple reflectometry and transmissiometry, ellipsometry, infrared absorption and attenuated total reflectance spectroscopy (ATR), Auger electron spectroscopy (AES), scanning electron microscopy (SEM), secondary ion mass spectrometry (SIMS), and mass accretion determined by quartz crystal microbalance (QCM). The discussion is biased toward those methods that apply optical thin film analytical techniques to spacecraft optical contamination problems. Examples are cited from both ground based and in-orbit experiments.

A new multi-domain method based on an analytical control surface for linear and second-order mean drift wave loads on floating bodies

NASA Astrophysics Data System (ADS)

Liang, Hui; Chen, Xiaobo

2017-10-01

A novel multi-domain method based on an analytical control surface is proposed by combining the use of free-surface Green function and Rankine source function. A cylindrical control surface is introduced to subdivide the fluid domain into external and internal domains. Unlike the traditional domain decomposition strategy or multi-block method, the control surface here is not panelized, on which the velocity potential and normal velocity components are analytically expressed as a series of base functions composed of Laguerre function in vertical coordinate and Fourier series in the circumference. Free-surface Green function is applied in the external domain, and the boundary integral equation is constructed on the control surface in the sense of Galerkin collocation via integrating test functions orthogonal to base functions over the control surface. The external solution gives rise to the so-called Dirichlet-to-Neumann [DN2] and Neumann-to-Dirichlet [ND2] relations on the control surface. Irregular frequencies, which are only dependent on the radius of the control surface, are present in the external solution, and they are removed by extending the boundary integral equation to the interior free surface (circular disc) on which the null normal derivative of potential is imposed, and the dipole distribution is expressed as Fourier-Bessel expansion on the disc. In the internal domain, where the Rankine source function is adopted, new boundary integral equations are formulated. The point collocation is imposed over the body surface and free surface, while the collocation of the Galerkin type is applied on the control surface. The present method is valid in the computation of both linear and second-order mean drift wave loads. Furthermore, the second-order mean drift force based on the middle-field formulation can be calculated analytically by using the coefficients of the Fourier-Laguerre expansion.

Method For Chemical Sensing Using A Microfabricated Teeter-Totter Resonator

DOEpatents

Adkins, Douglas Ray; Heller, Edwin J.; Shul, Randy J.

2004-11-30

A method for sensing a chemical analyte in a fluid stream comprises providing a microfabricated teeter-totter resonator that relies upon a Lorentz force to cause oscillation in a paddle, applying a static magnetic field substantially aligned in-plane with the paddle, energizing a current conductor line on a surface of the paddle with an alternating electrical current to generate the Lorentz force, exposing the resonator to the analyte, and detecting the response of the oscillatory motion of the paddle to the chemical analyte. Preferably, a chemically sensitive coating is disposed on at least one surface of the paddle to enhance the sorption of the analyte by the paddle. The concentration of the analyte in a fluid stream can be determined by measuring the change in the resonant frequency or phase of the teeter-totter resonator as the chemical analyte is added to or removed from the paddle.

Device and method for enhanced collection and assay of chemicals with high surface area ceramic

DOEpatents

Addleman, Raymond S.; Li, Xiaohong Shari; Chouyyok, Wilaiwan; Cinson, Anthony D.; Bays, John T.; Wallace, Krys

2016-02-16

A method and device for enhanced capture of target analytes is disclosed. This invention relates to collection of chemicals for separations and analysis. More specifically, this invention relates to a solid phase microextraction (SPME) device having better capability for chemical collection and analysis. This includes better physical stability, capacity for chemical collection, flexible surface chemistry and high affinity for target analyte.

Adequacy of surface analytical tools for studying the tribology of ceramics

NASA Technical Reports Server (NTRS)

Sliney, H. E.

1986-01-01

Surface analytical tools are very beneficial in tribological studies of ceramics. Traditional methods of optical microscopy, XRD, XRF, and SEM should be combined with newer surface sensitive techniques especially AES and XPS. ISS and SIMS can also be useful in providing additional compositon details. Tunneling microscopy and electron energy loss spectroscopy are less known techniques that may also prove useful.

Selectivity in analytical chemistry: two interpretations for univariate methods.

PubMed

Dorkó, Zsanett; Verbić, Tatjana; Horvai, George

2015-01-01

Selectivity is extremely important in analytical chemistry but its definition is elusive despite continued efforts by professional organizations and individual scientists. This paper shows that the existing selectivity concepts for univariate analytical methods broadly fall in two classes: selectivity concepts based on measurement error and concepts based on response surfaces (the response surface being the 3D plot of the univariate signal as a function of analyte and interferent concentration, respectively). The strengths and weaknesses of the different definitions are analyzed and contradictions between them unveiled. The error based selectivity is very general and very safe but its application to a range of samples (as opposed to a single sample) requires the knowledge of some constraint about the possible sample compositions. The selectivity concepts based on the response surface are easily applied to linear response surfaces but may lead to difficulties and counterintuitive results when applied to nonlinear response surfaces. A particular advantage of this class of selectivity is that with linear response surfaces it can provide a concentration independent measure of selectivity. In contrast, the error based selectivity concept allows only yes/no type decision about selectivity. Copyright © 2014 Elsevier B.V. All rights reserved.

Generation of gas-phase ions from charged clusters: an important ionization step causing suppression of matrix and analyte ions in matrix-assisted laser desorption/ionization mass spectrometry.

PubMed

Lou, Xianwen; van Dongen, Joost L J; Milroy, Lech-Gustav; Meijer, E W

2016-12-30

Ionization in matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) is a very complicated process. It has been reported that quaternary ammonium salts show extremely strong matrix and analyte suppression effects which cannot satisfactorily be explained by charge transfer reactions. Further investigation of the reasons causing these effects can be useful to improve our understanding of the MALDI process. The dried-droplet and modified thin-layer methods were used as sample preparation methods. In the dried-droplet method, analytes were co-crystallized with matrix, whereas in the modified thin-layer method analytes were deposited on the surface of matrix crystals. Model compounds, tetrabutylammonium iodide ([N(Bu) 4 ]I), cesium iodide (CsI), trihexylamine (THA) and polyethylene glycol 600 (PEG 600), were selected as the test analytes given their ability to generate exclusively pre-formed ions, protonated ions and metal ion adducts respectively in MALDI. The strong matrix suppression effect (MSE) observed using the dried-droplet method might disappear using the modified thin-layer method, which suggests that the incorporation of analytes in matrix crystals contributes to the MSE. By depositing analytes on the matrix surface instead of incorporating in the matrix crystals, the competition for evaporation/ionization from charged matrix/analyte clusters could be weakened resulting in reduced MSE. Further supporting evidence for this inference was found by studying the analyte suppression effect using the same two sample deposition methods. By comparing differences between the mass spectra obtained via the two sample preparation methods, we present evidence suggesting that the generation of gas-phase ions from charged matrix/analyte clusters may induce significant suppression of matrix and analyte ions. The results suggest that the generation of gas-phase ions from charged matrix/analyte clusters is an important ionization step in MALDI-MS. Copyright © 2016 John Wiley & Sons, Ltd. Copyright © 2016 John Wiley & Sons, Ltd.

High heating rate thermal desorption for molecular surface sampling

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

Ovchinnikova, Olga S.; Van Berkel, Gary J.

2016-03-29

A method for analyzing a sample having at least one analyte includes the step of heating the sample at a rate of at least 10.sup.6 K/s to thermally desorb at least one analyte from the sample. The desorbed analyte is collected. The analyte can then be analyzed.

Method of sections in analytical calculations of pneumatic tires

NASA Astrophysics Data System (ADS)

Tarasov, V. N.; Boyarkina, I. V.

2018-01-01

Analytical calculations in the pneumatic tire theory are more preferable in comparison with experimental methods. The method of section of a pneumatic tire shell allows to obtain equations of intensities of internal forces in carcass elements and bead rings. Analytical dependencies of intensity of distributed forces have been obtained in tire equator points, on side walls (poles) and pneumatic tire bead rings. Along with planes in the capacity of secant surfaces cylindrical surfaces are used for the first time together with secant planes. The tire capacity equation has been obtained using the method of section, by means of which a contact body is cut off from the tire carcass along the contact perimeter by the surface which is normal to the bearing surface. It has been established that the Laplace equation for the solution of tasks of this class of pneumatic tires contains two unknown values that requires the generation of additional equations. The developed computational schemes of pneumatic tire sections and new equations allow to accelerate the pneumatic tire structure improvement process during engineering.

Analytical caustic surfaces

NASA Technical Reports Server (NTRS)

Schmidt, R. F.

1987-01-01

This document discusses the determination of caustic surfaces in terms of rays, reflectors, and wavefronts. Analytical caustics are obtained as a family of lines, a set of points, and several types of equations for geometries encountered in optics and microwave applications. Standard methods of differential geometry are applied under different approaches: directly to reflector surfaces, and alternatively, to wavefronts, to obtain analytical caustics of two sheets or branches. Gauss/Seidel aberrations are introduced into the wavefront approach, forcing the retention of all three coefficients of both the first- and the second-fundamental forms of differential geometry. An existing method for obtaining caustic surfaces through exploitation of the singularities in flux density is examined, and several constant-intensity contour maps are developed using only the intrinsic Gaussian, mean, and normal curvatures of the reflector. Numerous references are provided for extending the material of the present document to the morphologies of caustics and their associated diffraction patterns.

System and method for laser assisted sample transfer to solution for chemical analysis

DOEpatents

Van Berkel, Gary J; Kertesz, Vilmos

2014-01-28

A system and method for laser desorption of an analyte from a specimen and capturing of the analyte in a suspended solvent to form a testing solution are described. The method can include providing a specimen supported by a desorption region of a specimen stage and desorbing an analyte from a target site of the specimen with a laser beam centered at a radiation wavelength (.lamda.). The desorption region is transparent to the radiation wavelength (.lamda.) and the sampling probe and a laser source emitting the laser beam are on opposite sides of a primary surface of the specimen stage. The system can also be arranged where the laser source and the sampling probe are on the same side of a primary surface of the specimen stage. The testing solution can then be analyzed using an analytical instrument or undergo further processing.

Photonic Crystal Fiber-Based Surface Plasmon Resonance Sensor with Selective Analyte Channels and Graphene-Silver Deposited Core

PubMed Central

Rifat, Ahmmed A.; Mahdiraji, G. Amouzad; Chow, Desmond M.; Shee, Yu Gang; Ahmed, Rajib; Adikan, Faisal Rafiq Mahamd

2015-01-01

We propose a surface plasmon resonance (SPR) sensor based on photonic crystal fiber (PCF) with selectively filled analyte channels. Silver is used as the plasmonic material to accurately detect the analytes and is coated with a thin graphene layer to prevent oxidation. The liquid-filled cores are placed near to the metallic channel for easy excitation of free electrons to produce surface plasmon waves (SPWs). Surface plasmons along the metal surface are excited with a leaky Gaussian-like core guided mode. Numerical investigations of the fiber’s properties and sensing performance are performed using the finite element method (FEM). The proposed sensor shows maximum amplitude sensitivity of 418 Refractive Index Units (RIU−1) with resolution as high as 2.4 × 10−5 RIU. Using the wavelength interrogation method, a maximum refractive index (RI) sensitivity of 3000 nm/RIU in the sensing range of 1.46–1.49 is achieved. The proposed sensor is suitable for detecting various high RI chemicals, biochemical and organic chemical analytes. Additionally, the effects of fiber structural parameters on the properties of plasmonic excitation are investigated and optimized for sensing performance as well as reducing the sensor’s footprint. PMID:25996510

IMPROVED METHOD FOR THE STORAGE OF GROUND WATER SAMPLES CONTAINING VOLATILE ORGANIC ANALYTES

EPA Science Inventory

The sorption of volatile organic analytes from water samples by the Teflon septum surface used with standard glass 40-ml sample collection vials was investigated. Analytes tested included alkanes, isoalkanes, olefins, cycloalkanes, a cycloalkene, monoaromatics, a polynuclear arom...

An improved 3D MoF method based on analytical partial derivatives

NASA Astrophysics Data System (ADS)

Chen, Xiang; Zhang, Xiong

2016-12-01

MoF (Moment of Fluid) method is one of the most accurate approaches among various surface reconstruction algorithms. As other second order methods, MoF method needs to solve an implicit optimization problem to obtain the optimal approximate surface. Therefore, the partial derivatives of the objective function have to be involved during the iteration for efficiency and accuracy. However, to the best of our knowledge, the derivatives are currently estimated numerically by finite difference approximation because it is very difficult to obtain the analytical derivatives of the object function for an implicit optimization problem. Employing numerical derivatives in an iteration not only increase the computational cost, but also deteriorate the convergence rate and robustness of the iteration due to their numerical error. In this paper, the analytical first order partial derivatives of the objective function are deduced for 3D problems. The analytical derivatives can be calculated accurately, so they are incorporated into the MoF method to improve its accuracy, efficiency and robustness. Numerical studies show that by using the analytical derivatives the iterations are converged in all mixed cells with the efficiency improvement of 3 to 4 times.

Laser modification of graphene oxide layers

NASA Astrophysics Data System (ADS)

Malinský, Petr; Macková, Anna; Cutroneo, Mariapompea; Siegel, Jakub; Bohačová, Marie; Klímova, Kateřina; Švorčík, Václav; Sofer, Zdenĕk

2018-01-01

The effect of linearly polarized laser irradiation with various energy densities was successfully used for reduction of graphene oxide (GO). The ion beam analytical methods (RBS, ERDA) were used to follow the elemental composition which is expected as the consequence of GO reduction. The chemical composition analysis was accompanied by structural study showing changed functionalities in the irradiated GO foils using spectroscopy techniques including XPS, FTIR and Raman spectroscopy. The AFM was employed to identify the surface morphology and electric properties evolution were subsequently studied using standard two point method measurement. The used analytical methods report on reduction of irradiated graphene oxide on the surface and the decrease of surface resistivity as a growing function of the laser beam energy density.

[Progress in the application of laser ablation ICP-MS to surface microanalysis in material science].

PubMed

Zhang, Yong; Jia, Yun-hai; Chen, Ji-wen; Shen, Xue-jing; Liu, Ying; Zhao, Leiz; Li, Dong-ling; Hang, Peng-cheng; Zhao, Zhen; Fan, Wan-lun; Wang, Hai-zhou

2014-08-01

In the present paper, apparatus and theory of surface analysis is introduced, and the progress in the application of laser ablation ICP-MS to microanalysis in ferrous, nonferrous and semiconductor field is reviewed in detail. Compared with traditional surface analytical tools, such as SEM/EDS (scanning electron microscopy/energy dispersive spectrum), EPMA (electron probe microanalysis analysis), AES (auger energy spectrum), etc. the advantage is little or no sample preparation, adjustable spatial resolution according to analytical demand, multi-element analysis and high sensitivity. It is now a powerful complementary method to traditional surface analytical tool. With the development of LA-ICP-MS technology maturing, more and more analytical workers will use this powerful tool in the future, and LA-ICP-MS will be a super star in elemental analysis field just like LIBS (Laser-induced breakdown spectroscopy).

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.

A sample preparation method for recovering suppressed analyte ions in MALDI TOF MS.

PubMed

Lou, Xianwen; de Waal, Bas F M; Milroy, Lech-Gustav; van Dongen, Joost L J

2015-05-01

In matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI TOF MS), analyte signals can be substantially suppressed by other compounds in the sample. In this technical note, we describe a modified thin-layer sample preparation method that significantly reduces the analyte suppression effect (ASE). In our method, analytes are deposited on top of the surface of matrix preloaded on the MALDI plate. To prevent embedding of analyte into the matrix crystals, the sample solution were prepared without matrix and efforts were taken not to re-dissolve the preloaded matrix. The results with model mixtures of peptides, synthetic polymers and lipids show that detection of analyte ions, which were completely suppressed using the conventional dried-droplet method, could be effectively recovered by using our method. Our findings suggest that the incorporation of analytes in the matrix crystals has an important contributory effect on ASE. By reducing ASE, our method should be useful for the direct MALDI MS analysis of multicomponent mixtures. Copyright © 2015 John Wiley & Sons, Ltd.

Approximate analytic solutions to 3D unconfined groundwater flow within regional 2D models

NASA Astrophysics Data System (ADS)

Luther, K.; Haitjema, H. M.

2000-04-01

We present methods for finding approximate analytic solutions to three-dimensional (3D) unconfined steady state groundwater flow near partially penetrating and horizontal wells, and for combining those solutions with regional two-dimensional (2D) models. The 3D solutions use distributed singularities (analytic elements) to enforce boundary conditions on the phreatic surface and seepage faces at vertical wells, and to maintain fixed-head boundary conditions, obtained from the 2D model, at the perimeter of the 3D model. The approximate 3D solutions are analytic (continuous and differentiable) everywhere, including on the phreatic surface itself. While continuity of flow is satisfied exactly in the infinite 3D flow domain, water balance errors can occur across the phreatic surface.

Surface Plasmon Resonance: New Biointerface Designs and High-Throughput Affinity Screening

NASA Astrophysics Data System (ADS)

Linman, Matthew J.; Cheng, Quan Jason

Surface plasmon resonance (SPR) is a surface optical technique that measures minute changes in refractive index at a metal-coated surface. It has become increasingly popular in the study of biological and chemical analytes because of its label-free measurement feature. In addition, SPR allows for both quantitative and qualitative assessment of binding interactions in real time, making it ideally suited for probing weak interactions that are often difficult to study with other methods. This chapter presents the biosensor development in the last 3 years or so utilizing SPR as the principal analytical technique, along with a concise background of the technique itself. While SPR has demonstrated many advantages, it is a nonselective method and so, building reproducible and functional interfaces is vital to sensing applications. This chapter, therefore, focuses mainly on unique surface chemistries and assay approaches to examine biological interactions with SPR. In addition, SPR imaging for high-throughput screening based on microarrays and novel hyphenated techniques involving the coupling of SPR to other analytical methods is discussed. The chapter concludes with a commentary on the current state of SPR biosensing technology and the general direction of future biosensor research.

Reactive ion etched substrates and methods of making and using

DOEpatents

Rucker, Victor C [San Francisco, CA; Shediac, Rene [Oakland, CA; Simmons, Blake A [San Francisco, CA; Havenstrite, Karen L [New York, NY

2007-08-07

Disclosed herein are substrates comprising reactive ion etched surfaces and specific binding agents immobilized thereon. The substrates may be used in methods and devices for assaying or isolating analytes in a sample. Also disclosed are methods of making the reactive ion etched surfaces.

Enhanced spot preparation for liquid extractive sampling and analysis

DOEpatents

Van Berkel, Gary J.; King, Richard C.

2015-09-22

A method for performing surface sampling of an analyte, includes the step of placing the analyte on a stage with a material in molar excess to the analyte, such that analyte-analyte interactions are prevented and the analyte can be solubilized for further analysis. The material can be a matrix material that is mixed with the analyte. The material can be provided on a sample support. The analyte can then be contacted with a solvent to extract the analyte for further processing, such as by electrospray mass spectrometry.

A free energy-based surface tension force model for simulation of multiphase flows by level-set method

NASA Astrophysics Data System (ADS)

Yuan, H. Z.; Chen, Z.; Shu, C.; Wang, Y.; Niu, X. D.; Shu, S.

2017-09-01

In this paper, a free energy-based surface tension force (FESF) model is presented for accurately resolving the surface tension force in numerical simulation of multiphase flows by the level set method. By using the analytical form of order parameter along the normal direction to the interface in the phase-field method and the free energy principle, FESF model offers an explicit and analytical formulation for the surface tension force. The only variable in this formulation is the normal distance to the interface, which can be substituted by the distance function solved by the level set method. On one hand, as compared to conventional continuum surface force (CSF) model in the level set method, FESF model introduces no regularized delta function, due to which it suffers less from numerical diffusions and performs better in mass conservation. On the other hand, as compared to the phase field surface tension force (PFSF) model, the evaluation of surface tension force in FESF model is based on an analytical approach rather than numerical approximations of spatial derivatives. Therefore, better numerical stability and higher accuracy can be expected. Various numerical examples are tested to validate the robustness of the proposed FESF model. It turns out that FESF model performs better than CSF model and PFSF model in terms of accuracy, stability, convergence speed and mass conservation. It is also shown in numerical tests that FESF model can effectively simulate problems with high density/viscosity ratio, high Reynolds number and severe topological interfacial changes.

Development of Aeroservoelastic Analytical Models and Gust Load Alleviation Control Laws of a SensorCraft Wind-Tunnel Model Using Measured Data

NASA Technical Reports Server (NTRS)

Silva, Walter A.; Vartio, Eric; Shimko, Anthony; Kvaternik, Raymond G.; Eure, Kenneth W.; Scott,Robert C.

2007-01-01

Aeroservoelastic (ASE) analytical models of a SensorCraft wind-tunnel model are generated using measured data. The data was acquired during the ASE wind-tunnel test of the HiLDA (High Lift-to-Drag Active) Wing model, tested in the NASA Langley Transonic Dynamics Tunnel (TDT) in late 2004. Two time-domain system identification techniques are applied to the development of the ASE analytical models: impulse response (IR) method and the Generalized Predictive Control (GPC) method. Using measured control surface inputs (frequency sweeps) and associated sensor responses, the IR method is used to extract corresponding input/output impulse response pairs. These impulse responses are then transformed into state-space models for use in ASE analyses. Similarly, the GPC method transforms measured random control surface inputs and associated sensor responses into an AutoRegressive with eXogenous input (ARX) model. The ARX model is then used to develop the gust load alleviation (GLA) control law. For the IR method, comparison of measured with simulated responses are presented to investigate the accuracy of the ASE analytical models developed. For the GPC method, comparison of simulated open-loop and closed-loop (GLA) time histories are presented.

Development of Aeroservoelastic Analytical Models and Gust Load Alleviation Control Laws of a SensorCraft Wind-Tunnel Model Using Measured Data

NASA Technical Reports Server (NTRS)

Silva, Walter A.; Shimko, Anthony; Kvaternik, Raymond G.; Eure, Kenneth W.; Scott, Robert C.

2006-01-01

Aeroservoelastic (ASE) analytical models of a SensorCraft wind-tunnel model are generated using measured data. The data was acquired during the ASE wind-tunnel test of the HiLDA (High Lift-to-Drag Active) Wing model, tested in the NASA Langley Transonic Dynamics Tunnel (TDT) in late 2004. Two time-domain system identification techniques are applied to the development of the ASE analytical models: impulse response (IR) method and the Generalized Predictive Control (GPC) method. Using measured control surface inputs (frequency sweeps) and associated sensor responses, the IR method is used to extract corresponding input/output impulse response pairs. These impulse responses are then transformed into state-space models for use in ASE analyses. Similarly, the GPC method transforms measured random control surface inputs and associated sensor responses into an AutoRegressive with eXogenous input (ARX) model. The ARX model is then used to develop the gust load alleviation (GLA) control law. For the IR method, comparison of measured with simulated responses are presented to investigate the accuracy of the ASE analytical models developed. For the GPC method, comparison of simulated open-loop and closed-loop (GLA) time histories are presented.

Immobilization of Fab' fragments onto substrate surfaces: A survey of methods and applications.

PubMed

Crivianu-Gaita, Victor; Thompson, Michael

2015-08-15

Antibody immobilization onto surfaces has widespread applications in many different fields. It is desirable to bind antibodies such that their fragment-antigen-binding (Fab) units are oriented away from the surface in order to maximize analyte binding. The immobilization of only Fab' fragments yields benefits over the more traditional whole antibody immobilization technique. Bound Fab' fragments display higher surface densities, yielding a higher binding capacity for the analyte. The nucleophilic sulfide of the Fab' fragments allows for specific orientations to be achieved. For biosensors, this indicates a higher sensitivity and lower detection limit for a target analyte. The last thirty years have shown tremendous progress in the immobilization of Fab' fragments onto gold, Si-based, polysaccharide-based, plastic-based, magnetic, and inorganic surfaces. This review will show the current scope of Fab' immobilization techniques available and illustrate methods employed to minimize non-specific adsorption of undesirables. Furthermore, a variety of examples will be given to show the versatility of immobilized Fab' fragments in different applications and future directions of the field will be addressed, especially regarding biosensors. Copyright © 2015 Elsevier B.V. All rights reserved.

Nucleic acid-coupled colorimetric analyte detectors

DOEpatents

Charych, Deborah H.; Jonas, Ulrich

2001-01-01

The present invention relates to methods and compositions for the direct detection of analytes and membrane conformational changes through the detection of color changes in biopolymeric materials. In particular, the present invention provide for the direct colorimetric detection of analytes using nucleic acid ligands at surfaces of polydiacetylene liposomes and related molecular layer systems.

Formulation of dynamical theory of X-ray diffraction for perfect crystals in the Laue case using the Riemann surface.

PubMed

Saka, Takashi

2016-05-01

The dynamical theory for perfect crystals in the Laue case was reformulated using the Riemann surface, as used in complex analysis. In the two-beam approximation, each branch of the dispersion surface is specified by one sheet of the Riemann surface. The characteristic features of the dispersion surface are analytically revealed using four parameters, which are the real and imaginary parts of two quantities specifying the degree of departure from the exact Bragg condition and the reflection strength. By representing these parameters on complex planes, these characteristics can be graphically depicted on the Riemann surface. In the conventional case, the absorption is small and the real part of the reflection strength is large, so the formulation is the same as the traditional analysis. However, when the real part of the reflection strength is small or zero, the two branches of the dispersion surface cross, and the dispersion relationship becomes similar to that of the Bragg case. This is because the geometrical relationships among the parameters are similar in both cases. The present analytical method is generally applicable, irrespective of the magnitudes of the parameters. Furthermore, the present method analytically revealed many characteristic features of the dispersion surface and will be quite instructive for further numerical calculations of rocking curves.

Regarding on the prototype solutions for the nonlinear fractional-order biological population model

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

Baskonus, Haci Mehmet, E-mail: hmbaskonus@gmail.com; Bulut, Hasan

2016-06-08

In this study, we have submitted to literature a method newly extended which is called as Improved Bernoulli sub-equation function method based on the Bernoulli Sub-ODE method. The proposed analytical scheme has been expressed with steps. We have obtained some new analytical solutions to the nonlinear fractional-order biological population model by using this technique. Two and three dimensional surfaces of analytical solutions have been drawn by wolfram Mathematica 9. Finally, a conclusion has been submitted by mentioning important acquisitions founded in this study.

Generations of orthogonal surface coordinates

NASA Technical Reports Server (NTRS)

Blottner, F. G.; Moreno, J. B.

1980-01-01

Two generation methods were developed for three dimensional flows where the computational domain normal to the surface is small. With this restriction the coordinate system requires orthogonality only at the body surface. The first method uses the orthogonal condition in finite-difference form to determine the surface coordinates with the metric coefficients and curvature of the coordinate lines calculated numerically. The second method obtains analytical expressions for the metric coefficients and for the curvature of the coordinate lines.

Adapting Surface Ground Motion Relations to Underground conditions: A case study for the Sudbury Neutrino Observatory in Sudbury, Ontario, Canada

NASA Astrophysics Data System (ADS)

Babaie Mahani, A.; Eaton, D. W.

2013-12-01

Ground Motion Prediction Equations (GMPEs) are widely used in Probabilistic Seismic Hazard Assessment (PSHA) to estimate ground-motion amplitudes at Earth's surface as a function of magnitude and distance. Certain applications, such as hazard assessment for caprock integrity in the case of underground storage of CO2, waste disposal sites, and underground pipelines, require subsurface estimates of ground motion; at present, such estimates depend upon theoretical modeling and simulations. The objective of this study is to derive correction factors for GMPEs to enable estimation of amplitudes in the subsurface. We use a semi-analytic approach along with finite-difference simulations of ground-motion amplitudes for surface and underground motions. Spectral ratios of underground to surface motions are used to calculate the correction factors. Two predictive methods are used. The first is a semi-analytic approach based on a quarter-wavelength method that is widely used for earthquake site-response investigations; the second is a numerical approach based on elastic finite-difference simulations of wave propagation. Both methods are evaluated using recordings of regional earthquakes by broadband seismometers installed at the surface and at depths of 1400 m and 2100 m in the Sudbury Neutrino Observatory, Canada. Overall, both methods provide a reasonable fit to the peaks and troughs observed in the ratios of real data. The finite-difference method, however, has the capability to simulate ground motion ratios more accurately than the semi-analytic approach.

Analytical and Numerical Studies of Active and Passive Microwave Ocean Remote Sensing

DTIC Science & Technology

2001-09-30

of both analytical and efficient numerical methods for electromagnetics and hydrodynamics. New insights regarding these phenomena can then be applied to improve microwave active and passive remote sensing of the ocean surface.

Gold Nanorods as Plasmonic Sensors for Particle Diffusion.

PubMed

Wulf, Verena; Knoch, Fabian; Speck, Thomas; Sönnichsen, Carsten

2016-12-01

Plasmonic gold nanoparticles are normally used as sensor to detect analytes permanently bound to their surface. If the interaction between the analyte and the nanosensor surface is negligible, it only diffuses through the sensor's sensing volume, causing a small temporal shift of the plasmon resonance position. By using a very sensitive and fast detection scheme, we are able to detect these small fluctuations in the plasmon resonance. With the help of a theoretical model consistent with our detection geometry, we determine the analyte's diffusion coefficient. The method is verified by observing the trends upon changing diffusor size and medium viscosity, and the diffusion coefficients obtained were found to reflect reduced diffusion close to a solid interface. Our method, which we refer to as NanoPCS (for nanoscale plasmon correlation spectroscopy), is of practical importance for any application involving the diffusion of analytes close to nanoparticles.

Spectral properties of thermal fluctuations on simple liquid surfaces below shot-noise levels.

PubMed

Aoki, Kenichiro; Mitsui, Takahisa

2012-07-01

We study the spectral properties of thermal fluctuations on simple liquid surfaces, sometimes called ripplons. Analytical properties of the spectral function are investigated and are shown to be composed of regions with simple analytic behavior with respect to the frequency or the wave number. The derived expressions are compared to spectral measurements performed orders of magnitude below shot-noise levels, which is achieved using a novel noise reduction method. The agreement between the theory of thermal surface fluctuations and the experiment is found to be excellent, elucidating the spectral properties of the surface fluctuations. The measurement method requires relatively only a small sample both spatially (few μm) and temporally (~20 s). The method also requires relatively weak light power (~0.5 mW) so that it has a broad range of applicability, including local measurements, investigations of time-dependent phenomena, and noninvasive measurements.

High-Contrast Gratings based Spoof Surface Plasmons

NASA Astrophysics Data System (ADS)

Li, Zhuo; Liu, Liangliang; Xu, Bingzheng; Ning, Pingping; Chen, Chen; Xu, Jia; Chen, Xinlei; Gu, Changqing; Qing, Quan

2016-02-01

In this work, we explore the existence of spoof surface plasmons (SSPs) supported by deep-subwavelength high-contrast gratings (HCGs) on a perfect electric conductor plane. The dispersion relation of the HCGs-based SSPs is derived analyt- ically by combining multimode network theory with rigorous mode matching method, which has nearly the same form with and can be degenerated into that of the SSPs arising from deep-subwavelength metallic gratings (MGs). Numerical simula- tions validate the analytical dispersion relation and an effective medium approximation is also presented to obtain the same analytical dispersion formula. This work sets up a unified theoretical framework for SSPs and opens up new vistas in surface plasmon optics.

Evaluating the performance of free-formed surface parts using an analytic network process

NASA Astrophysics Data System (ADS)

Qian, Xueming; Ma, Yanqiao; Liang, Dezhi

2018-03-01

To successfully design parts with a free-formed surface, the critical issue of how to evaluate and select a favourable evaluation strategy before design is raised. The evaluation of free-formed surface parts is a multiple criteria decision-making (MCDM) problem that requires the consideration of a large number of interdependent factors. The analytic network process (ANP) is a relatively new MCDM method that can systematically deal with all kinds of dependences. In this paper, the factors, which come from the life-cycle and influence the design of free-formed surface parts, are proposed. After analysing the interdependence among these factors, a Hybrid ANP (HANP) structure for evaluating the part’s curved surface is constructed. Then, a HANP evaluation of an impeller is presented to illustrate the application of the proposed method.

A potential energy surface for the process H2 + H2O yielding H + H + H2O - Ab initio calculations and analytical representation

NASA Technical Reports Server (NTRS)

Schwenke, David W.; Walch, Stephen P.; Taylor, Peter R.

1991-01-01

Extensive ab initio calculations on the ground state potential energy surface of H2 + H2O were performed using a large contracted Gaussian basis set and a high level of correlation treatment. An analytical representation of the potential energy surface was then obtained which reproduces the calculated energies with an overall root-mean-square error of only 0.64 mEh. The analytic representation explicitly includes all nine internal degrees of freedom and is also well behaved as the H2 dissociates; it thus can be used to study collision-induced dissociation or recombination of H2. The strategy used to minimize the number of energy calculations is discussed, as well as other advantages of the present method for determining the analytical representation.

Radiophysical methods of diagnostics the Earth's ionosphere and the underlying earth's surface by remote sensing in the short-wave range of radio waves

NASA Astrophysics Data System (ADS)

Belov, S. Yu.; Belova, I. N.

2017-11-01

Monitoring of the earth's surface by remote sensing in the short-wave band can provide quick identification of some characteristics of natural systems. This band range allows one to diagnose subsurface aspects of the earth, as the scattering parameter is affected by irregularities in the dielectric permittivity of subsurface structures. This method based on the organization of the monitoring probe may detect changes in these environments, for example, to assess seismic hazard, hazardous natural phenomena such as earthquakes, as well as some man-made hazards and etc. The problem of measuring and accounting for the scattering power of the earth's surface in the short-range of radio waves is important for a number of purposes, such as diagnosing properties of the medium, which is of interest for geological, environmental studies. In this paper, we propose a new method for estimating the parameters of incoherent signal/noise ratio. The paper presents the results of comparison of the measurement method from the point of view of their admissible relative analytical errors. The new method is suggested. Analysis of analytical error of estimation of this parameter allowed to recommend new method instead of standard method. A comparative analysis and shows that the analytical (relative) accuracy of the determination of this parameter new method on the order exceeds the widely-used standard method.

Detection and mapping of trace explosives on surfaces under ambient conditions using multiphoton electron extraction spectroscopy (MEES).

PubMed

Tang, Shisong; Vinerot, Nataly; Fisher, Danny; Bulatov, Valery; Yavetz-Chen, Yehuda; Schechter, Israel

2016-08-01

Multiphoton electron extraction spectroscopy (MEES) is an analytical method in which UV laser pulses are utilized for extracting electrons from solid surfaces in multiphoton processes under ambient conditions. Counting the emitted electrons as a function of laser wavelength results in detailed spectral features, which can be used for material identification. The method has been applied to detection of trace explosives on a variety of surfaces. Detection was possible on dusty swabs spiked with explosives and also in the standard dry-transfer contamination procedure. Plastic explosives could also be detected. The analytical limits of detection (LODs) are in the sub pmole range, which indicates that MEES is one of the most sensitive detection methods for solid surface under ambient conditions. Scanning the surface with the laser allows for its imaging, such that explosives (as well as other materials) can be located. The imaging mode is also useful in forensic applications, such as detection of explosives in human fingerprints. Copyright © 2016 Elsevier B.V. All rights reserved.

Concentration Gradient Immunoassay I. A Rapid Immunoassay Based on Interdiffusion and Surface Binding in a Microchannel

PubMed Central

Nelson, Kjell E.; Foley, Jennifer O.; Yager, Paul

2008-01-01

We describe a novel microfluidic immunoassay method based on the diffusion of a small molecule analyte into a parallel-flowing stream containing cognate antibody. This interdiffusion results in a steady-state gradient of antibody binding site occupancy transverse to convective flow. In contrast to the diffusion immunoassay (Hatch et al. Nature Biotechnology,19:461−465 (2001)), this antibody occupancy gradient is interrogated by a sensor surface coated with a functional analog of the analyte. Antibodies with at least one unoccupied binding site may specifically bind to this functionalized surface, leading to a quantifiable change in surface coverage by the antibody. SPR imaging is used to probe the spatial distribution of antibody binding to the surface and, therefore, the outcome of the assay. We show that the pattern of antibody binding to the SPR sensing surface correlates with the concentration of a model analyte (phenytoin) in the sample stream. Using an inexpensive disposable microfluidic device, we demonstrate assays for phenytoin ranging in concentration from 75 to 1000 nM in phosphate buffer. At a total volumetric flow rate of 90 nL/sec, the assays are complete within 10 minutes. Inclusion of an additional flow stream on the side of the antibody stream opposite to that of the sample enables simultaneous calibration of the assay. This assay method is suitable for rapid quantitative detection of low-molecular weight analytes for point-of-care diagnostic instrumentation. PMID:17437332

A Colloidal Route to Detection of Organic Molecules Based on Surface-Enhanced Raman Spectroscopy Using Nanostructured Substrate Derived from Aerosols

NASA Astrophysics Data System (ADS)

Gen, Masao; Kakuta, Hideo; Kamimoto, Yoshihito; Wuled Lenggoro, I.

2011-06-01

A detection method based on the surface-enhanced Raman spectroscopy (SERS)-active substrate derived from aerosol nanoparticles and a colloidal suspension for detecting organic molecules of a model analyte (a pesticide) is proposed. This approach can detect the molecules of the derived from its solution with the concentration levels of ppb. For substrate fabrication, a gas-phase method is used to directly deposit Ag nanoparticles on to a silicon substrate having pyramidal structures. By mixing the target analyte with a suspension of Ag colloids purchased in advance, clotianidin analyte on Ag colloid can exist in junctions of co-aggregated Ag colloids. Using (i) a nanostructured substrate made from aerosol nanoparticles and (ii) colloidal suspension can increase the number of activity spots.

Analytical Methods to Distinguish the Positive and Negative Spectra of Mineral and Environmental Elements Using Deep Ablation Laser-Induced Breakdown Spectroscopy (LIBS).

PubMed

Kim, Dongyoung; Yang, Jun-Ho; Choi, Soojin; Yoh, Jack J

2018-01-01

Environments affect mineral surfaces, and the surface contamination or alteration can provide potential information to understanding their regional environments. However, when investigating mineral surfaces, mineral and environmental elements appear mixed in data. This makes it difficult to determine their atomic compositions independently. In this research, we developed four analytical methods to distinguish mineral and environmental elements into positive and negative spectra based on depth profiling data using laser-induced breakdown spectroscopy (LIBS). The principle of the methods is to utilize how intensity varied with depth for creating a new spectrum. The methods were applied to five mineral samples exposed to four environmental conditions including seawater, crude oil, sulfuric acid, and air as control. The proposed methods are then validated by applying the resultant spectra to principal component analysis and data were classified by the environmental conditions and atomic compositions of mineral. By applying the methods, the atomic information of minerals and environmental conditions were successfully inferred in the resultant spectrum.

Rapid detection and identification of energetic materials with surface enhanced raman spectrometry (SERS)

DOEpatents

Han, Thomas Yong-Jin; Valdez, Carlos A; Olson, Tammy Y; Kim, Sung Ho; Satcher, Jr., Joe H

2015-04-21

In one embodiment, a system includes a plurality of metal nanoparticles functionalized with a plurality of organic molecules tethered thereto, wherein the plurality of organic molecules preferentially interact with one or more analytes when placed in proximity therewith. According to another embodiment, a method for detecting analytes includes contacting a fluid having one or more analytes of interest therein with a plurality of metal nanoparticles, each metal nanoparticle having a plurality of organic molecules tethered thereto, and detecting Raman scattering from an analyte of interest from the fluid, the analyte interacting with one or more of the plurality of organic molecules. In another embodiment, a method includes chemically modifying a plurality of cyclodextrin molecules at a primary hydroxyl moiety to create a chemical handle, and tethering the plurality of cyclodextrin molecules to a metal nanoparticle using the chemical handle. Other systems and methods for detecting analytes are also described.

Comparative study of solar optics for paraboloidal concentrators

NASA Technical Reports Server (NTRS)

Wen, L.; Poon, P.; Carley, W.; Huang, L.

1979-01-01

Different analytical methods for computing the flux distribution on the focal plane of a paraboloidal solar concentrator are reviewed. An analytical solution in algebraic form is also derived for an idealized model. The effects resulting from using different assumptions in the definition of optical parameters used in these methodologies are compared and discussed in detail. These parameters include solar irradiance distribution (limb darkening and circumsolar), reflector surface specular spreading, surface slope error, and concentrator pointing inaccuracy. The type of computational method selected for use depends on the maturity of the design and the data available at the time the analysis is made.

A Critical Comparison of Some Methods for Interpolation of Scattered Data

DTIC Science & Technology

1979-12-01

because faster evaluation of the local interpolants is possible. KAll things considered, the method of choice here seems to be the Modified Quadratic...topography and other irregular surfaces," J. of Geophysical Research 76 ( 1971 ) 1905-1915I’ [23) HARDY, Rolland L. - "Analytical topographic surfaces by

Analytical and Experimental Evaluation of the Heat Transfer Distribution over the Surfaces of Turbine Vanes

NASA Technical Reports Server (NTRS)

Hylton, L. D.; Mihelc, M. S.; Turner, E. R.; Nealy, D. A.; York, R. E.

1983-01-01

Three airfoil data sets were selected for use in evaluating currently available analytical models for predicting airfoil surface heat transfer distributions in a 2-D flow field. Two additional airfoils, representative of highly loaded, low solidity airfoils currently being designed, were selected for cascade testing at simulated engine conditions. Some 2-D analytical methods were examined and a version of the STAN5 boundary layer code was chosen for modification. The final form of the method utilized a time dependent, transonic inviscid cascade code coupled to a modified version of the STAN5 boundary layer code featuring zero order turbulence modeling. The boundary layer code is structured to accommodate a full spectrum of empirical correlations addressing the coupled influences of pressure gradient, airfoil curvature, and free-stream turbulence on airfoil surface heat transfer distribution and boundary layer transitional behavior. Comparison of pedictions made with the model to the data base indicates a significant improvement in predictive capability.

Analytical and experimental evaluation of the heat transfer distribution over the surfaces of turbine vanes

NASA Astrophysics Data System (ADS)

Hylton, L. D.; Mihelc, M. S.; Turner, E. R.; Nealy, D. A.; York, R. E.

1983-05-01

Three airfoil data sets were selected for use in evaluating currently available analytical models for predicting airfoil surface heat transfer distributions in a 2-D flow field. Two additional airfoils, representative of highly loaded, low solidity airfoils currently being designed, were selected for cascade testing at simulated engine conditions. Some 2-D analytical methods were examined and a version of the STAN5 boundary layer code was chosen for modification. The final form of the method utilized a time dependent, transonic inviscid cascade code coupled to a modified version of the STAN5 boundary layer code featuring zero order turbulence modeling. The boundary layer code is structured to accommodate a full spectrum of empirical correlations addressing the coupled influences of pressure gradient, airfoil curvature, and free-stream turbulence on airfoil surface heat transfer distribution and boundary layer transitional behavior. Comparison of pedictions made with the model to the data base indicates a significant improvement in predictive capability.

Surface enhanced Raman spectroscopy based nanoparticle assays for rapid, point-of-care diagnostics

NASA Astrophysics Data System (ADS)

Driscoll, Ashley J.

Nucleotide and immunoassays are important tools for disease diagnostics. Many of the current laboratory-based analytical diagnostic techniques require multiple assay steps and long incubation times before results are acquired. In the development of bioassays designed for detecting the emergence and spread of diseases in point-of-care (POC) and remote settings, more rapid and portable analytical methods are necessary. Nanoparticles provide simple and reproducible synthetic methods for the preparation of substrates that can be applied in colloidal assays, providing gains in kinetics due to miniaturization and plasmonic substrates for surface enhanced spectroscopies. Specifically, surface enhanced Raman spectroscopy (SERS) is finding broad application as a signal transduction method in immunological and nucleotide assays due to the production of narrow spectral peaks from the scattering molecules and the potential for simultaneous multiple analyte detection. The application of SERS to a no-wash, magnetic capture assay for the detection of West Nile Virus Envelope and Rift Valley Fever Virus N antigens is described. The platform utilizes colloid based capture of the target antigen in solution, magnetic collection of the immunocomplexes and acquisition of SERS spectra by a handheld Raman spectrometer. The reagents for a core-shell nanoparticle, SERS based assay designed for the capture of target microRNA implicated in acute myocardial infarction are also characterized. Several new, small molecule Raman scatterers are introduced and used to analyze the enhancing properties of the synthesized gold coated-magnetic nanoparticles. Nucleotide and immunoassay platforms have shown improvements in speed and analyte capture through the miniaturization of the capture surface and particle-based capture systems can provide a route to further surface miniaturization. A reaction-diffusion model of the colloidal assay platform is presented to understand the interplay of system parameters such as particle diameter, initial analyte concentration and dissociation constants. The projected sensitivities over a broad range of assay conditions are examined and the governing regime of particle systems reported. The results provide metrics in the design of more robust analytics that are of particular interest for POC diagnostics.

Simultaneous analysis of multiple classes of antimicrobials in environmental water samples using SPE coupled with UHPLC-ESI-MS/MS and isotope dilution.

PubMed

Tran, Ngoc Han; Chen, Hongjie; Do, Thanh Van; Reinhard, Martin; Ngo, Huu Hao; He, Yiliang; Gin, Karina Yew-Hoong

2016-10-01

A robust and sensitive analytical method was developed for the simultaneous analysis of 21 target antimicrobials in different environmental water samples. Both single SPE and tandem SPE cartridge systems were investigated to simultaneously extract multiple classes of antimicrobials. Experimental results showed that good extraction efficiencies (84.5-105.6%) were observed for the vast majority of the target analytes when extraction was performed using the tandem SPE cartridge (SB+HR-X) system under an extraction pH of 3.0. HPLC-MS/MS parameters were optimized for simultaneous analysis of all the target analytes in a single injection. Quantification of target antimicrobials in water samples was accomplished using 15 isotopically labeled internal standards (ILISs), which allowed the efficient compensation of the losses of target analytes during sample preparation and correction of matrix effects during UHPLC-MS/MS as well as instrument fluctuations in MS/MS signal intensity. Method quantification limit (MQL) for most target analytes based on SPE was below 5ng/L for surface waters, 10ng/L for treated wastewater effluents, and 15ng/L for raw wastewater. The method was successfully applied to detect and quantify the occurrence of the target analytes in raw influent, treated effluent and surface water samples. Copyright © 2016 Elsevier B.V. All rights reserved.

New Material for Surface-Enhanced Raman Spectroscopy

NASA Technical Reports Server (NTRS)

Farquharson, Stuart; Nelson, Chad; Lee, Yuan

2004-01-01

A chemical method of synthesis and application of coating materials that are especially suitable for surface-enhanced Raman spectroscopy (SERS) has been developed. The purpose of this development is to facilitate the utilization of the inherently high sensitivity of SERS to detect chemicals of interest (analytes) in trace amounts, without need for lengthy sample preparation. Up to now, the use of SERS has not become routine because the methods available have not been able to reproduce sampling conditions and provide quantitative measurements. In contrast, the coating materials of the present method enable analysis with minimum preparation of samples, and SERS measurements made using these materials are reproducible and reversible. Moreover, unlike in methods investigated in prior efforts to implement SERS, sampling is not restricted to such specific environments as electrolytes or specific solvents. The coating materials of this method are porous glasses, formed in sol-gel processes, that contain small particles of gold or silver metal. Materials of this type can be applied to the sample-contact surfaces of a variety of sampling and sensing devices, including glass slides, glass vials, fiber-optic probes, and glass tubes. Glass vials with their insides coated according to this method are particularly convenient for SERS to detect trace chemicals in solutions: One simply puts a sample solution containing the analyte(s) into a vial, then puts the vial into a Raman spectrometer for analysis. The chemical ingredients and the physical conditions of the sol-gel process have been selected so that the porous glass formed incorporates particles of the desired metal with size(s) to match the wavelength(s) of the SERS excitation laser in order to optimize the generation of surface plasmons. The ingredients and processing conditions have further been chosen to tailor the porosity and polarity of the glass to optimize the sample flow and the interaction between the analyte(s) and the plasmon field that generates Raman photons. The porous silica network of a sol-gel glass creates a unique environment for stabilizing SERS-active metal particles. Relative to other material structures that could be considered for SERS, the porous silica network offers higher specific surface area and thus greater interaction between analyte molecules and metal particles. Efforts to perform SERS measurements with the help of sampling devices coated by this method have been successful. In tests, numerous organic and inorganic chemicals were analyzed in several solvents, including water. The results of the tests indicate that the SERS measurements were reproducible within 10 percent and linear over five orders of magnitude. One measure of the limits of detectability of chemicals in these tests was found to be a concentration of 300 parts per billion. Further development may eventually make it possible to realize the full potential sensitivity of SERS for detecting some analytes in quantities as small as a single molecule.

Chemical and biological sensing using tuning forks

DOEpatents

Tao, Nongjian; Boussaad, Salah

2012-07-10

A device for sensing a chemical analyte is disclosed. The device is comprised of a vibrating structure having first and second surfaces and having an associated resonant frequency and a wire coupled between the first and second surfaces of the vibrating structure, wherein the analyte interacts with the wire and causes a change in the resonant frequency of the vibrating structure. The vibrating structure can include a tuning fork. The vibrating structure can be comprised of quartz. The wire can be comprised of polymer. A plurality of vibrating structures are arranged in an array to increase confidence by promoting a redundancy of measurement or to detect a plurality of chemical analytes. A method of making a device for sensing a chemical analyte is also disclosed.

Desorption atmospheric pressure photoionization.

PubMed

Haapala, Markus; Pól, Jaroslav; Saarela, Ville; Arvola, Ville; Kotiaho, Tapio; Ketola, Raimo A; Franssila, Sami; Kauppila, Tiina J; Kostiainen, Risto

2007-10-15

An ambient ionization technique for mass spectrometry, desorption atmospheric pressure photoionization (DAPPI), is presented, and its application to the rapid analysis of compounds of various polarities on surfaces is demonstrated. The DAPPI technique relies on a heated nebulizer microchip delivering a heated jet of vaporized solvent, e.g., toluene, and a photoionization lamp emitting 10-eV photons. The solvent jet is directed toward sample spots on a surface, causing the desorption of analytes from the surface. The photons emitted by the lamp ionize the analytes, which are then directed into the mass spectrometer. The limits of detection obtained with DAPPI were in the range of 56-670 fmol. Also, the direct analysis of pharmaceuticals from a tablet surface was successfully demonstrated. A comparison of the performance of DAPPI with that of the popular desorption electrospray ionization method was done with four standard compounds. DAPPI was shown to be equally or more sensitive especially in the case of less polar analytes.

Modeling convection-diffusion-reaction systems for microfluidic molecular communications with surface-based receivers in Internet of Bio-Nano Things

PubMed Central

Akan, Ozgur B.

2018-01-01

We consider a microfluidic molecular communication (MC) system, where the concentration-encoded molecular messages are transported via fluid flow-induced convection and diffusion, and detected by a surface-based MC receiver with ligand receptors placed at the bottom of the microfluidic channel. The overall system is a convection-diffusion-reaction system that can only be solved by numerical methods, e.g., finite element analysis (FEA). However, analytical models are key for the information and communication technology (ICT), as they enable an optimisation framework to develop advanced communication techniques, such as optimum detection methods and reliable transmission schemes. In this direction, we develop an analytical model to approximate the expected time course of bound receptor concentration, i.e., the received signal used to decode the transmitted messages. The model obviates the need for computationally expensive numerical methods by capturing the nonlinearities caused by laminar flow resulting in parabolic velocity profile, and finite number of ligand receptors leading to receiver saturation. The model also captures the effects of reactive surface depletion layer resulting from the mass transport limitations and moving reaction boundary originated from the passage of finite-duration molecular concentration pulse over the receiver surface. Based on the proposed model, we derive closed form analytical expressions that approximate the received pulse width, pulse delay and pulse amplitude, which can be used to optimize the system from an ICT perspective. We evaluate the accuracy of the proposed model by comparing model-based analytical results to the numerical results obtained by solving the exact system model with COMSOL Multiphysics. PMID:29415019

Modeling convection-diffusion-reaction systems for microfluidic molecular communications with surface-based receivers in Internet of Bio-Nano Things.

PubMed

Kuscu, Murat; Akan, Ozgur B

2018-01-01

We consider a microfluidic molecular communication (MC) system, where the concentration-encoded molecular messages are transported via fluid flow-induced convection and diffusion, and detected by a surface-based MC receiver with ligand receptors placed at the bottom of the microfluidic channel. The overall system is a convection-diffusion-reaction system that can only be solved by numerical methods, e.g., finite element analysis (FEA). However, analytical models are key for the information and communication technology (ICT), as they enable an optimisation framework to develop advanced communication techniques, such as optimum detection methods and reliable transmission schemes. In this direction, we develop an analytical model to approximate the expected time course of bound receptor concentration, i.e., the received signal used to decode the transmitted messages. The model obviates the need for computationally expensive numerical methods by capturing the nonlinearities caused by laminar flow resulting in parabolic velocity profile, and finite number of ligand receptors leading to receiver saturation. The model also captures the effects of reactive surface depletion layer resulting from the mass transport limitations and moving reaction boundary originated from the passage of finite-duration molecular concentration pulse over the receiver surface. Based on the proposed model, we derive closed form analytical expressions that approximate the received pulse width, pulse delay and pulse amplitude, which can be used to optimize the system from an ICT perspective. We evaluate the accuracy of the proposed model by comparing model-based analytical results to the numerical results obtained by solving the exact system model with COMSOL Multiphysics.

DETERMINATION OF ECOLOGICALLY RELEVANT PHARMACEUTICALS AND THEIR SELECTED METABOLITES IN EFFLUENT AND SURFACE WATER USING UPLC/MS/MS

EPA Science Inventory

Objective is to develop analytical methods including SPE and UPLC/MS/MS needed to analyze over 60 human prescription pharamceuticals and metabolites belonging to a multitude of different classes in surface waters and wastewater effluent. The methods will be used in future studies...

An Evaluation of Fractal Surface Measurement Methods for Characterizing Landscape Complexity from Remote-Sensing Imagery

NASA Technical Reports Server (NTRS)

Lam, Nina Siu-Ngan; Qiu, Hong-Lie; Quattrochi, Dale A.; Emerson, Charles W.; Arnold, James E. (Technical Monitor)

2001-01-01

The rapid increase in digital data volumes from new and existing sensors necessitates the need for efficient analytical tools for extracting information. We developed an integrated software package called ICAMS (Image Characterization and Modeling System) to provide specialized spatial analytical functions for interpreting remote sensing data. This paper evaluates the three fractal dimension measurement methods: isarithm, variogram, and triangular prism, along with the spatial autocorrelation measurement methods Moran's I and Geary's C, that have been implemented in ICAMS. A modified triangular prism method was proposed and implemented. Results from analyzing 25 simulated surfaces having known fractal dimensions show that both the isarithm and triangular prism methods can accurately measure a range of fractal surfaces. The triangular prism method is most accurate at estimating the fractal dimension of higher spatial complexity, but it is sensitive to contrast stretching. The variogram method is a comparatively poor estimator for all of the surfaces, particularly those with higher fractal dimensions. Similar to the fractal techniques, the spatial autocorrelation techniques are found to be useful to measure complex images but not images with low dimensionality. These fractal measurement methods can be applied directly to unclassified images and could serve as a tool for change detection and data mining.

Ultra-trace levels analysis of microcystins and nodularin in surface water by on-line solid-phase extraction with high-performance liquid chromatography tandem mass spectrometry.

PubMed

Balest, Lydia; Murgolo, Sapia; Sciancalepore, Lucia; Montemurro, Patrizia; Abis, Pier Paolo; Pastore, Carlo; Mascolo, Giuseppe

2016-06-01

An on-line solid phase extraction coupled with high-performance liquid chromatography in tandem with mass spectrometry (on-line SPE/HPLC/MS-MS) method for the determination of five microcystins and nodularin in surface waters at submicrogram per liter concentrations has been optimized. Maximum recoveries were achieved by carefully optimizing the extraction sample volume, loading solvent, wash solvent, and pH of the sample. The developed method was also validated according to both UNI EN ISO IEC 17025 and UNICHIM guidelines. Specifically, ten analytical runs were performed at three different concentration levels using a reference mix solution containing the six analytes. The method was applied for monitoring the concentrations of microcystins and nodularin in real surface water during a sampling campaign of 9 months in which the ELISA method was used as standard official method. The results of the two methods were compared showing good agreement when the highest concentration values of MCs were found. Graphical abstract An on-line SPE/HPLC/MS-MS method for the determination of five microcystins and nodularin in surface waters at sub μg L(-1) was optimized and compared with ELISA assay method for real samples.

Measurement of surface contamination by certain antineoplastic drugs using high-performance liquid chromatography: applications in occupational hygiene investigations in hospital environments.

PubMed

Rubino, F M; Floridia, L; Pietropaolo, A M; Tavazzani, M; Colombi, A

1999-01-01

Within the context of continuing interest in occupational hygiene of hospitals as workplaces, the authors report the results of a preliminary study on surface contamination by certain antineoplastic drugs (ANDs), recently performed in eight cancer departments of two large general hospitals in Milan, Italy. Since reliable quantitative information on the exposure levels to individual drugs is mandatory to establish a strong interpretative framework for correctly assessing the health risks associated with manipulation of ANDs and rationally advise intervention priorities for exposure abatement, two automated analytical methods were set up using reverse-phase high-performance liquid chromatography for the measurement of contamination by 1) methotrexate (MTX) and 2) the three most important nucleoside analogue antineoplastic drugs (5-fluorouracil 5FU, Cytarabin CYA, Gemcytabin GCA) on surfaces such as those of preparation hoods and work-benches in the pharmacies of cancer wards. The methods are characterized by short analysis time (7 min) under isocratic conditions, by the use of a mobile phase with a minimal content of organic solvent and by high sensitivity, adequate to detect surface contamination in the 5-10 micrograms/m2 range. To exemplify the performance of the analytical methods in the assessment of contamination levels from the target analyte ANDs, data are reported on the contamination levels measured on various surfaces (such as on handles, floor surfaces and window panes, even far from the preparation hood). Analyte concentrations corresponding to 0.8-1.5 micrograms of 5FU were measured on telephones, 0.85-28 micrograms/m2 of CYA were measured on tables, 1.2-1150 micrograms/m2 of GCA on furniture and floors. Spillage fractions between 1-5% of the used ANDs (daily use 5FU 7-13 g; CYA 0.1-7.1 g; GCA 0.2-5 g) were measured on the disposable polythene-backed paper cover sheet of the preparation hood.

Model uncertainty of various settlement estimation methods in shallow tunnels excavation; case study: Qom subway tunnel

NASA Astrophysics Data System (ADS)

Khademian, Amir; Abdollahipour, Hamed; Bagherpour, Raheb; Faramarzi, Lohrasb

2017-10-01

In addition to the numerous planning and executive challenges, underground excavation in urban areas is always followed by certain destructive effects especially on the ground surface; ground settlement is the most important of these effects for which estimation there exist different empirical, analytical and numerical methods. Since geotechnical models are associated with considerable model uncertainty, this study characterized the model uncertainty of settlement estimation models through a systematic comparison between model predictions and past performance data derived from instrumentation. To do so, the amount of surface settlement induced by excavation of the Qom subway tunnel was estimated via empirical (Peck), analytical (Loganathan and Poulos) and numerical (FDM) methods; the resulting maximum settlement value of each model were 1.86, 2.02 and 1.52 cm, respectively. The comparison of these predicted amounts with the actual data from instrumentation was employed to specify the uncertainty of each model. The numerical model outcomes, with a relative error of 3.8%, best matched the reality and the analytical method, with a relative error of 27.8%, yielded the highest level of model uncertainty.

Accurate anharmonic zero-point energies for some combustion-related species from diffusion Monte Carlo

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

Harding, Lawrence B.; Georgievskii, Yuri; Klippenstein, Stephen J.

Full dimensional analytic potential energy surfaces based on CCSD(T)/cc-pVTZ calculations have been determined for 48 small combustion related molecules. The analytic surfaces have been used in Diffusion Monte Carlo calculations of the anharmonic, zero point energies. Here, the resulting anharmonicity corrections are compared to vibrational perturbation theory results based both on the same level of electronic structure theory and on lower level electronic structure methods (B3LYP and MP2).

Accurate Anharmonic Zero-Point Energies for Some Combustion-Related Species from Diffusion Monte Carlo.

PubMed

Harding, Lawrence B; Georgievskii, Yuri; Klippenstein, Stephen J

2017-06-08

Full-dimensional analytic potential energy surfaces based on CCSD(T)/cc-pVTZ calculations have been determined for 48 small combustion-related molecules. The analytic surfaces have been used in Diffusion Monte Carlo calculations of the anharmonic zero-point energies. The resulting anharmonicity corrections are compared to vibrational perturbation theory results based both on the same level of electronic structure theory and on lower-level electronic structure methods (B3LYP and MP2).

Accurate anharmonic zero-point energies for some combustion-related species from diffusion Monte Carlo

DOE PAGES

Harding, Lawrence B.; Georgievskii, Yuri; Klippenstein, Stephen J.

2017-05-17

Full dimensional analytic potential energy surfaces based on CCSD(T)/cc-pVTZ calculations have been determined for 48 small combustion related molecules. The analytic surfaces have been used in Diffusion Monte Carlo calculations of the anharmonic, zero point energies. Here, the resulting anharmonicity corrections are compared to vibrational perturbation theory results based both on the same level of electronic structure theory and on lower level electronic structure methods (B3LYP and MP2).

Mixing of two co-directional Rayleigh surface waves in a nonlinear elastic material.

PubMed

Morlock, Merlin B; Kim, Jin-Yeon; Jacobs, Laurence J; Qu, Jianmin

2015-01-01

The mixing of two co-directional, initially monochromatic Rayleigh surface waves in an isotropic, homogeneous, and nonlinear elastic solid is investigated using analytical, finite element method, and experimental approaches. The analytical investigations show that while the horizontal velocity component can form a shock wave, the vertical velocity component can form a pulse independent of the specific ratios of the fundamental frequencies and amplitudes that are mixed. This analytical model is then used to simulate the development of the fundamentals, second harmonics, and the sum and difference frequency components over the propagation distance. The analytical model is further extended to include diffraction effects in the parabolic approximation. Finally, the frequency and amplitude ratios of the fundamentals are identified which provide maximum amplitudes of the second harmonics as well as of the sum and difference frequency components, to help guide effective material characterization; this approach should make it possible to measure the acoustic nonlinearity of a solid not only with the second harmonics, but also with the sum and difference frequency components. Results of the analytical investigations are then confirmed using the finite element method and the experimental feasibility of the proposed technique is validated for an aluminum specimen.

A numerical test of the topographic bias

NASA Astrophysics Data System (ADS)

Sjöberg, L. E.; Joud, M. S. S.

2018-02-01

In 1962 A. Bjerhammar introduced the method of analytical continuation in physical geodesy, implying that surface gravity anomalies are downward continued into the topographic masses down to an internal sphere (the Bjerhammar sphere). The method also includes analytical upward continuation of the potential to the surface of the Earth to obtain the quasigeoid. One can show that also the common remove-compute-restore technique for geoid determination includes an analytical continuation as long as the complete density distribution of the topography is not known. The analytical continuation implies that the downward continued gravity anomaly and/or potential are/is in error by the so-called topographic bias, which was postulated by a simple formula of L E Sjöberg in 2007. Here we will numerically test the postulated formula by comparing it with the bias obtained by analytical downward continuation of the external potential of a homogeneous ellipsoid to an inner sphere. The result shows that the postulated formula holds: At the equator of the ellipsoid, where the external potential is downward continued 21 km, the computed and postulated topographic biases agree to less than a millimetre (when the potential is scaled to the unit of metre).

An analytical method for computing atomic contact areas in biomolecules.

PubMed

Mach, Paul; Koehl, Patrice

2013-01-15

We propose a new analytical method for detecting and computing contacts between atoms in biomolecules. It is based on the alpha shape theory and proceeds in three steps. First, we compute the weighted Delaunay triangulation of the union of spheres representing the molecule. In the second step, the Delaunay complex is filtered to derive the dual complex. Finally, contacts between spheres are collected. In this approach, two atoms i and j are defined to be in contact if their centers are connected by an edge in the dual complex. The contact areas between atom i and its neighbors are computed based on the caps formed by these neighbors on the surface of i; the total area of all these caps is partitioned according to their spherical Laguerre Voronoi diagram on the surface of i. This method is analytical and its implementation in a new program BallContact is fast and robust. We have used BallContact to study contacts in a database of 1551 high resolution protein structures. We show that with this new definition of atomic contacts, we generate realistic representations of the environments of atoms and residues within a protein. In particular, we establish the importance of nonpolar contact areas that complement the information represented by the accessible surface areas. This new method bears similarity to the tessellation methods used to quantify atomic volumes and contacts, with the advantage that it does not require the presence of explicit solvent molecules if the surface of the protein is to be considered. © 2012 Wiley Periodicals, Inc. Copyright © 2012 Wiley Periodicals, Inc.

A novel sampling method for identification of endogenous skin surface compounds by use of DART-MS and MALDI-MS.

PubMed

Mess, Aylin; Enthaler, Bernd; Fischer, Markus; Rapp, Claudius; Pruns, Julia K; Vietzke, Jens-Peter

2013-01-15

Identification of endogenous skin surface compounds is an intriguing challenge in comparative skin investigations. Notably, this short communication is focused on the analysis of small molecules, e.g. natural moisturizing factor (NMF) components and lipids, using a novel sampling method with DIP-it samplers for non-invasive examination of the human skin surface. As a result, extraction of analytes directly from the skin surface by use of various solvents can be replaced with the mentioned procedure. Screening of measureable compounds is achieved by direct analysis in real time mass spectrometry (DART-MS) without further sample preparation. Results are supplemented by dissolving analytes from the DIP-it samplers by use of different solvents, and subsequent matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) measurements. An interesting comparison of the mentioned MS techniques for determination of skin surface compounds in the mass range of 50-1000 Da is presented. Copyright © 2012 Elsevier B.V. All rights reserved.

Surface enhanced Raman scattering spectroscopic waveguide

DOEpatents

Lascola, Robert J; McWhorter, Christopher S; Murph, Simona H

2015-04-14

A waveguide for use with surface-enhanced Raman spectroscopy is provided that includes a base structure with an inner surface that defines a cavity and that has an axis. Multiple molecules of an analyte are capable of being located within the cavity at the same time. A base layer is located on the inner surface of the base structure. The base layer extends in an axial direction along an axial length of an excitation section. Nanoparticles are carried by the base layer and may be uniformly distributed along the entire axial length of the excitation section. A flow cell for introducing analyte and excitation light into the waveguide and a method of applying nanoparticles may also be provided.

Effective Wettability of Heterogenous Fracture Surfaces Using the Lattice-Boltzmann Method

NASA Astrophysics Data System (ADS)

E Santos, J.; Prodanovic, M.; Landry, C. J.

2017-12-01

Fracture walls in the subsurface are often structured by minerals of different composition (potentially further altered in contact with fluids during hydrocarbon extraction or CO2 sequestration), this yields in a heterogeneous wettability of the surface in contact with the fluids. The focus of our work is to study how surfaces presenting different mineralogy and roughness affect multiphase flow in fractures. Using the Shan-Chen model of the lattice-Boltzmann method (LBM) we define fluid interaction and surface attraction parameters to simulate a system of a wetting and a non-wetting fluid. In this work, we use synthetically created fractures presenting different arrangements of wetting and non-wetting patches, and with or without roughness; representative of different mineralogy, similar workflow can be applied to fractures extracted from X-ray microtomography images of fractures porous media. The results from the LBM simulations provide an insight on how the distribution of mineralogy and surface roughness are related with the observed macroscopic contact angle. We present a comparison between the published analytical models, and our results based on surface areas, spatial distribution and local fracture aperture. The understanding of the variables that affect the contact angle is useful for the comprehension of multiphase processes in naturally fractured reservoirs like primary oil production, enhanced oil recovery and CO2 sequestration. The macroscopic contact angle analytical equations for heterogeneous surfaces with variable roughness are no longer valid in highly heterogeneous systems; we quantify the difference thus offering an alternative to analytical models.

Solitary wave solutions and their interactions for fully nonlinear water waves with surface tension in the generalized Serre equations

NASA Astrophysics Data System (ADS)

Dutykh, Denys; Hoefer, Mark; Mitsotakis, Dimitrios

2018-04-01

Some effects of surface tension on fully nonlinear, long, surface water waves are studied by numerical means. The differences between various solitary waves and their interactions in subcritical and supercritical surface tension regimes are presented. Analytical expressions for new peaked traveling wave solutions are presented in the dispersionless case of critical surface tension. Numerical experiments are performed using a high-accurate finite element method based on smooth cubic splines and the four-stage, classical, explicit Runge-Kutta method of order 4.

Methods of analysis by the U.S. Geological Survey National Water Quality Laboratory; determination of selected carbamate pesticides in water by high-performance liquid chromatography

USGS Publications Warehouse

Werner, S.L.; Johnson, S.M.

1994-01-01

As part of its primary responsibility concerning water as a national resource, the U.S. Geological Survey collects and analyzes samples of ground water and surface water to determine water quality. This report describes the method used since June 1987 to determine selected total-recoverable carbamate pesticides present in water samples. High- performance liquid chromatography is used to separate N-methyl carbamates, N-methyl carbamoyloximes, and an N-phenyl carbamate which have been extracted from water and concentrated in dichloromethane. Analytes, surrogate compounds, and reference compounds are eluted from the analytical column within 25 minutes. Two modes of analyte detection are used: (1) a photodiode-array detector measures and records ultraviolet-absorbance profiles, and (2) a fluorescence detector measures and records fluorescence from an analyte derivative produced when analyte hydrolysis is combined with chemical derivatization. Analytes are identified and confirmed in a three-stage process by use of chromatographic retention time, ultraviolet (UV) spectral comparison, and derivatization/fluorescence detection. Quantitative results are based on the integration of single-wavelength UV-absorbance chromatograms and on comparison with calibration curves derived from external analyte standards that are run with samples as part of an instrumental analytical sequence. Estimated method detection limits vary for each analyte, depending on the sample matrix conditions, and range from 0.5 microgram per liter to as low as 0.01 microgram per liter. Reporting levels for all analytes have been set at 0.5 microgram per liter for this method. Corrections on the basis of percentage recoveries of analytes spiked into distilled water are not applied to values calculated for analyte concentration in samples. These values for analyte concentrations instead indicate the quantities recovered by the method from a particular sample matrix.

A method for determining spiral-bevel gear tooth geometry for finite element analysis

NASA Technical Reports Server (NTRS)

Handschuh, Robert F.; Litvin, Faydor L.

1991-01-01

An analytical method was developed to determine gear tooth surface coordinates of face-milled spiral bevel gears. The method uses the basic gear design parameters in conjunction with the kinematical aspects of spiral bevel gear manufacturing machinery. A computer program, SURFACE, was developed. The computer program calculates the surface coordinates and outputs 3-D model data that can be used for finite element analysis. Development of the modeling method and an example case are presented. This analysis method could also find application for gear inspection and near-net-shape gear forging die design.

The Thin Oil Film Equation

NASA Technical Reports Server (NTRS)

Brown, James L.; Naughton, Jonathan W.

1999-01-01

A thin film of oil on a surface responds primarily to the wall shear stress generated on that surface by a three-dimensional flow. The oil film is also subject to wall pressure gradients, surface tension effects and gravity. The partial differential equation governing the oil film flow is shown to be related to Burgers' equation. Analytical and numerical methods for solving the thin oil film equation are presented. A direct numerical solver is developed where the wall shear stress variation on the surface is known and which solves for the oil film thickness spatial and time variation on the surface. An inverse numerical solver is also developed where the oil film thickness spatial variation over the surface at two discrete times is known and which solves for the wall shear stress variation over the test surface. A One-Time-Level inverse solver is also demonstrated. The inverse numerical solver provides a mathematically rigorous basis for an improved form of a wall shear stress instrument suitable for application to complex three-dimensional flows. To demonstrate the complexity of flows for which these oil film methods are now suitable, extensive examination is accomplished for these analytical and numerical methods as applied to a thin oil film in the vicinity of a three-dimensional saddle of separation.

Analytical prediction of the heat transfer from a blood vessel near the skin surface when cooled by a symmetrical cooling strip

NASA Technical Reports Server (NTRS)

Chato, J. C.; Shitzer, A.

1971-01-01

An analytical method was developed to estimate the amount of heat extracted from an artery running close to the skin surface which is cooled in a symmetrical fashion by a cooling strip. The results indicate that the optimum width of a cooling strip is approximately three times the depth to the centerline of the artery. The heat extracted from an artery with such a strip is about 0.9 w/m-C which is too small to affect significantly the temperature of the blood flow through a main blood vessel, such as the carotid artery. The method is applicable to veins as well.

Apparatus for rapid measurement of aerosol bulk chemical composition

DOEpatents

Lee, Yin-Nan E.; Weber, Rodney J.

2003-01-01

An apparatus and method for continuous on-line measurement of chemical composition of aerosol particles with a fast time resolution are provided. The apparatus includes a modified particle size magnifier for producing activated aerosol particles and a collection device which collects the activated aerosol particles into a liquid stream for quantitative analysis by analytical methods. The method provided for on-line measurement of chemical composition of aerosol particles includes exposing aerosol carrying sample air to hot saturated steam thereby forming activated aerosol particles; collecting the activated aerosol particles by a collection device for delivery as a jet stream onto an impaction surface; flushing off the activated aerosol particles from the impaction surface into a liquid stream for delivery of the collected liquid stream to an analytical instrument for quantitative measurement.

An analytic treatment of gravitational microlensing for sources of finite size at large optical depths

NASA Technical Reports Server (NTRS)

Deguchi, Shuji; Watson, William D.

1988-01-01

Statistical methods are developed for gravitational lensing in order to obtain analytic expressions for the average surface brightness that include the effects of microlensing by stellar (or other compact) masses within the lensing galaxy. The primary advance here is in utilizing a Markoff technique to obtain expressions that are valid for sources of finite size when the surface density of mass in the lensing galaxy is large. The finite size of the source is probably the key consideration for the occurrence of microlensing by individual stars. For the intensity from a particular location, the parameter which governs the importance of microlensing is determined. Statistical methods are also formulated to assess the time variation of the surface brightness due to the random motion of the masses that cause the microlensing.

PFAS methods and guidance for sampling and analyzing water and other environmental media (Technical Brief)

EPA Pesticide Factsheets

EPA's methods for analyzing PFAS in environmental media are in various stages of development. This fact sheet summarizes EPA's analytical methods development for groundwater, surface water, wastewater, and solids, including soils, sediments, and biosolids

Pesticides in near-surface aquifers: An assessment using highly sensitive analytical methods and tritium

USGS Publications Warehouse

Kolpin, D.W.; Goolsby, D.A.; Thurman, E.M.

1995-01-01

In 1992, the U.S. Geological Survey (USGS) determined the distribution of pesticides in near-surface aquifers of the midwestern USA to be much more widespread than originally determined during a 1991 USGS study. The frequency of pesticide detection increased from 28.4% during the 1991 study to 59.0% during the 1992 study. This increase in pesticide detection was primarily the result of a more sensitive analytical method that used reporting limits as much as 20 times lower than previously available and a threefold increase in the number of pesticide metabolites analyzed. No pesticide concentrations exceeded the U.S. Environmental Protection Agency's (USEPAs) maximum contaminant levels or health advisory levels for drinking water. However, five of the six most frequently detected compounds during 1992 were pesticide metabolites that currently do not have drinking water standards determined. The frequent presence of pesticide metabolites for this study documents the importance of obtaining information on these compounds to understand the fate and transport of pesticides in the hydrologic system. It appears that the 56 parent compounds analyzed follow similar pathways through the hydrologic system as atrazine. When atrazine was detected by routine or sensitive analytical methods, there was an increased likelihood of detecting additional parent compounds. As expected, the frequency of pesticide detection was highly dependent on the analytical reporting limit. The number of atrazine detections more than doubled as the reporting limit decreased from 0.10 to 0.01 µg/L. The 1992 data provided no indication that the frequency of pesticide detection would level off as improved analytical methods provide concentrations below 0.003 µg/L. A relation was determined between groundwater age and the frequency of pesticide detection, with 15.8% of the samples composed of pre-1953 water and 70.3% of the samples of post-1953 water having a detection of at least one pesticide or metabolite. Pre-1953 water is less likely to contain pesticides because it tends to predate the use of pesticides to increase crop production in the Midwest. Pre-1953 water was more likely to occur in the near-surface bedrock aquifers (50.0%) than in the near-surface unconsolidated aquifers (9.1%) sampled.

Stripping Voltammetry

NASA Astrophysics Data System (ADS)

Lovrić, Milivoj

Electrochemical stripping means the oxidative or reductive removal of atoms, ions, or compounds from an electrode surface (or from the electrode body, as in the case of liquid mercury electrodes with dissolved metals) [1-5]. In general, these atoms, ions, or compounds have been preliminarily immobilized on the surface of an inert electrode (or within it) as the result of a preconcentration step, while the products of the electrochemical stripping will dissolve in the electrolytic solution. Often the product of the electrochemical stripping is identical to the analyte before the preconcentration. However, there are exemptions to these rules. Electroanalytical stripping methods comprise two steps: first, the accumulation of a dissolved analyte onto, or in, the working electrode, and, second, the subsequent stripping of the accumulated substance by a voltammetric [3, 5], potentiometric [6, 7], or coulometric [8] technique. In stripping voltammetry, the condition is that there are two independent linear relationships: the first one between the activity of accumulated substance and the concentration of analyte in the sample, and the second between the maximum stripping current and the accumulated substance activity. Hence, a cumulative linear relationship between the maximum response and the analyte concentration exists. However, the electrode capacity for the analyte accumulation is limited and the condition of linearity is satisfied only well below the electrode saturation. For this reason, stripping voltammetry is used mainly in trace analysis. The limit of detection depends on the factor of proportionality between the activity of the accumulated substance and the bulk concentration of the analyte. This factor is a constant in the case of a chemical accumulation, but for electrochemical accumulation it depends on the electrode potential. The factor of proportionality between the maximum stripping current and the analyte concentration is rarely known exactly. In fact, it is frequently ignored. For the analysis it suffices to establish the linear relationship empirically. The slope of this relationship may vary from one sample to another because of different influences of the matrix. In this case the concentration of the analyte is determined by the method of standard additions [1]. After measuring the response of the sample, the concentration of the analyte is deliberately increased by adding a certain volume of its standard solution. The response is measured again, and this procedure is repeated three or four times. The unknown concentration is determined by extrapolation of the regression line to the concentration axis [9]. However, in many analytical methods, the final measurement is performed in a standard matrix that allows the construction of a calibration plot. Still, the slope of this plot depends on the active area of the working electrode surface. Each solid electrode needs a separate calibration plot, and that plot must be checked from time to time because of possible deterioration of the electrode surface [2].

Method 1200: Analytical Protocol for Non-Typhoidal Salmonella in Drinking Water and Surface Water

EPA Pesticide Factsheets

Method 1200 is used for identification, confirmation and quantitation of non-typhoidal Salmonella in water samples, using selective and non-selective media followed by biochemical and serological confirmation.

Noninvasive noble metal nanoparticle arrays for surface-enhanced Raman spectroscopy of proteins

NASA Astrophysics Data System (ADS)

Inya-Agha, Obianuju; Forster, Robert J.; Keyes, Tia E.

2007-02-01

Noble metal nanoparticles arrays are well established substrates for surface enhanced Raman spectroscopy (SERS). Their ability to enhance optical fields is based on the interaction of their surface valence electrons with incident electromagnetic radiation. In the array configuration, noble metal nanoparticles have been used to produce SER spectral enhancements of up to 10 8 orders of magnitude, making them useful for the trace analysis of physiologically relevant analytes such as proteins and peptides. Electrostatic interactions between proteins and metal surfaces result in the preferential adsorption of positively charged protein domains onto metal surfaces. This preferential interaction has the effect of disrupting the native conformation of the protein fold, with a concomitant loss of protein function. A major historic advantage of Raman microspectroscopy has been is its non-invasive nature; protein denaturation on the metal surfaces required for SER spectroscopy renders it a much more invasive technique. Further, part of the analytical power of Raman spectroscopy lies in its use as a secondary conformation probe. The protein structural loss which occurs on the metal surface results in secondary conformation readings which are not true to the actual native state of the analyte. This work presents a method for chemical fabrication of noble metal SERS arrays with surface immobilized layers which can protect protein native conformation without excessively mitigating the electromagnetic enhancements of spectra. Peptide analytes are used as model systems for proteins. Raman spectra of alpha lactalbumin on surfaces and when immobilized on these novel arrays are compared. We discuss the ability of the surface layer to protect protein structure whilst improving signal intensity.

Application of surface analytical methods for hazardous situation in the Adriatic Sea: monitoring of organic matter dynamics and oil pollution

NASA Astrophysics Data System (ADS)

Pletikapić, Galja; Ivošević DeNardis, Nadica

2017-01-01

Surface analytical methods are applied to examine the environmental status of seawaters. The present overview emphasizes advantages of combining surface analytical methods, applied to a hazardous situation in the Adriatic Sea, such as monitoring of the first aggregation phases of dissolved organic matter in order to potentially predict the massive mucilage formation and testing of oil spill cleanup. Such an approach, based on fast and direct characterization of organic matter and its high-resolution visualization, sets a continuous-scale description of organic matter from micro- to nanometre scales. Electrochemical method of chronoamperometry at the dropping mercury electrode meets the requirements for monitoring purposes due to the simple and fast analysis of a large number of natural seawater samples enabling simultaneous differentiation of organic constituents. In contrast, atomic force microscopy allows direct visualization of biotic and abiotic particles and provides an insight into structural organization of marine organic matter at micro- and nanometre scales. In the future, merging data at different spatial scales, taking into account experimental input on micrometre scale, observations on metre scale and modelling on kilometre scale, will be important for developing sophisticated technological platforms for knowledge transfer, reports and maps applicable for the marine environmental protection and management of the coastal area, especially for tourism, fishery and cruiser trafficking.

Determination of Matric Suction and Saturation Degree for Unsaturated Soils, Comparative Study - Numerical Method versus Analytical Method

NASA Astrophysics Data System (ADS)

Chiorean, Vasile-Florin

2017-10-01

Matric suction is a soil parameter which influences the behaviour of unsaturated soils in both terms of shear strength and permeability. It is a necessary aspect to know the variation of matric suction in unsaturated soil zone for solving geotechnical issues like unsaturated soil slopes stability or bearing capacity for unsaturated foundation ground. Mathematical expression of the dependency between soil moisture content and it’s matric suction (soil water characteristic curve) has a powerful character of nonlinearity. This paper presents two methods to determine the variation of matric suction along the depth included between groundwater level and soil level. First method is an analytical approach to emphasize one direction steady state unsaturated infiltration phenomenon that occurs between the groundwater level and the soil level. There were simulated three different situations in terms of border conditions: precipitations (inflow conditions on ground surface), evaporation (outflow conditions on ground surface), and perfect equilibrium (no flow on ground surface). Numerical method is finite element method used for steady state, two-dimensional, unsaturated infiltration calculus. Regarding boundary conditions there were simulated identical situations as in analytical approach. For both methods, was adopted the equation proposed by van Genuchten-Mualen (1980) for mathematical expression of soil water characteristic curve. Also for the unsaturated soil permeability prediction model was adopted the equation proposed by van Genuchten-Mualen. The fitting parameters of these models were adopted according to RETC 6.02 software in function of soil type. The analyses were performed in both methods for three major soil types: clay, silt and sand. For each soil type were concluded analyses for three situations in terms of border conditions applied on soil surface: inflow, outflow, and no flow. The obtained results are presented in order to highlight the differences/similarities between the methods and the advantages / disadvantages of each one.

Method and apparatus for optimized sampling of volatilizable target substances

DOEpatents

Lindgren, Eric R.; Phelan, James M.

2004-10-12

An apparatus for capturing, from gases such as soil gas, target analytes. Target analytes may include emanations from explosive materials or from residues of explosive materials. The apparatus employs principles of sorption common to solid phase microextraction, and is best used in conjunction with analysis means such as a gas chromatograph. To sorb target analytes, the apparatus functions using various sorptive structures to capture target analyte. Depending upon the embodiment, those structures may include a capillary tube including an interior surface on which sorptive material (similar to that on the surface of a SPME fiber) is supported (along with means for moving gases through the capillary tube so that the gases come into close proximity to the sorptive material). In one disclosed embodiment, at least one such sorptive structure is associated with an enclosure including an opening in communication with the surface of a soil region potentially contaminated with buried explosive material such as unexploded ordnance. Emanations from explosive materials can pass into and accumulate in the enclosure where they are sorbed by the sorptive structures. Also disclosed is the use of heating means such as microwave horns to drive target analytes into the soil gas from solid and liquid phase components of the soil.

Surface Characterization.

ERIC Educational Resources Information Center

Fulghum, J. E.; And Others

1989-01-01

This review is divided into the following analytical methods: ion spectroscopy, electron spectroscopy, scanning tunneling microscopy, atomic force microscopy, optical spectroscopy, desorption techniques, and X-ray techniques. (MVL)

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.

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.

Gold Nanoparticle-Aptamer-Based LSPR Sensing of Ochratoxin A at a Widened Detection Range by Double Calibration Curve Method

NASA Astrophysics Data System (ADS)

Liu, Boshi; Huang, Renliang; Yu, Yanjun; Su, Rongxin; Qi, Wei; He, Zhimin

2018-04-01

Ochratoxin A (OTA) is a type of mycotoxin generated from the metabolism of Aspergillus and Penicillium, and is extremely toxic to humans, livestock, and poultry. However, traditional assays for the detection of OTA are expensive and complicated. Other than OTA aptamer, OTA itself at high concentration can also adsorb on the surface of gold nanoparticles (AuNPs), and further inhibit AuNPs salt aggregation. We herein report a new OTA assay by applying the localized surface plasmon resonance effect of AuNPs and their aggregates. The result obtained from only one single linear calibration curve is not reliable, and so we developed a “double calibration curve” method to address this issue and widen the OTA detection range. A number of other analytes were also examined, and the structural properties of analytes that bind with the AuNPs were further discussed. We found that various considerations must be taken into account in the detection of these analytes when applying AuNP aggregation-based methods due to their different binding strengths.

An analytical solution of Richards' equation providing the physical basis of SCS curve number method and its proportionality relationship

NASA Astrophysics Data System (ADS)

Hooshyar, Milad; Wang, Dingbao

2016-08-01

The empirical proportionality relationship, which indicates that the ratio of cumulative surface runoff and infiltration to their corresponding potentials are equal, is the basis of the extensively used Soil Conservation Service Curve Number (SCS-CN) method. The objective of this paper is to provide the physical basis of the SCS-CN method and its proportionality hypothesis from the infiltration excess runoff generation perspective. To achieve this purpose, an analytical solution of Richards' equation is derived for ponded infiltration in shallow water table environment under the following boundary conditions: (1) the soil is saturated at the land surface; and (2) there is a no-flux boundary which moves downward. The solution is established based on the assumptions of negligible gravitational effect, constant soil water diffusivity, and hydrostatic soil moisture profile between the no-flux boundary and water table. Based on the derived analytical solution, the proportionality hypothesis is a reasonable approximation for rainfall partitioning at the early stage of ponded infiltration in areas with a shallow water table for coarse textured soils.

How to determine spiral bevel gear tooth geometry for finite element analysis

NASA Technical Reports Server (NTRS)

Handschuh, Robert F.; Litvin, Faydor L.

1991-01-01

An analytical method was developed to determine gear tooth surface coordinates of face milled spiral bevel gears. The method combines the basic gear design parameters with the kinematical aspects for spiral bevel gear manufacturing. A computer program was developed to calculate the surface coordinates. From this data a 3-D model for finite element analysis can be determined. Development of the modeling method and an example case are presented.

Devices and methods to detect and quantify trace gases

DOEpatents

Allendorf, Mark D.; Robinson, Alex

2016-05-03

Sensing devices based on a surface acoustic wave ("SAW") device coated with an absorbent crystalline or amorphous layer for detecting at least one chemical analyte in a gaseous carrier. Methods for detecting the presence of a chemical analyte in a gaseous carrier using such devices are also disclosed. The sensing devices and methods for their use may be configured for sensing chemical analytes selected from the group consisting of water vapor, carbon dioxide, methanol, ethanol, carbon monoxide, nitric oxide, nitrous oxide, organic amines, organic compounds containing NO.sub.2 groups, halogenated hydrocarbons, acetone, hexane, toluene, isopropanol, alcohols, alkanes, alkenes, benzene, functionalized aromatics, ammonia (NH.sub.3), phosgene (COCl.sub.2), sulfur mustard, nerve agents, sulfur dioxide, tetrahydrofuran (THF) and methyltertbutyl ether (MTBE) and combinations thereof.

Experimental design and multiple response optimization. Using the desirability function in analytical methods development.

PubMed

Candioti, Luciana Vera; De Zan, María M; Cámara, María S; Goicoechea, Héctor C

2014-06-01

A review about the application of response surface methodology (RSM) when several responses have to be simultaneously optimized in the field of analytical methods development is presented. Several critical issues like response transformation, multiple response optimization and modeling with least squares and artificial neural networks are discussed. Most recent analytical applications are presented in the context of analytLaboratorio de Control de Calidad de Medicamentos (LCCM), Facultad de Bioquímica y Ciencias Biológicas, Universidad Nacional del Litoral, C.C. 242, S3000ZAA Santa Fe, ArgentinaLaboratorio de Control de Calidad de Medicamentos (LCCM), Facultad de Bioquímica y Ciencias Biológicas, Universidad Nacional del Litoral, C.C. 242, S3000ZAA Santa Fe, Argentinaical methods development, especially in multiple response optimization procedures using the desirability function. Copyright © 2014 Elsevier B.V. All rights reserved.

Oxygen accumulation on metal surfaces investigated by XPS, AES and LEIS, an issue for sputter depth profiling under UHV conditions

NASA Astrophysics Data System (ADS)

Steinberger, R.; Celedón, C. E.; Bruckner, B.; Roth, D.; Duchoslav, J.; Arndt, M.; Kürnsteiner, P.; Steck, T.; Faderl, J.; Riener, C. K.; Angeli, G.; Bauer, P.; Stifter, D.

2017-07-01

Depth profiling using surface sensitive analysis methods in combination with sputter ion etching is a common procedure for thorough material investigations, where clean surfaces free of any contamination are essential. Hence, surface analytic studies are mostly performed under ultra-high vacuum (UHV) conditions, but the cleanness of such UHV environments is usually overrated. Consequently, the current study highlights the in principle known impact of the residual gas on metal surfaces (Fe, Mg, Al, Cr and Zn) for various surface analytics methods, like X-ray photoelectron spectroscopy (XPS), Auger electron spectroscopy (AES) and low-energy ion scattering (LEIS). The investigations with modern, state-of-the-art equipment showed different behaviors for the metal surfaces in UHV during acquisition: (i) no impact for Zn, even after long time, (ii) solely adsorption of oxygen for Fe, slight and slow changes for Cr and (iii) adsorption accompanied by oxide formation for Al and Mg. The efficiency of different counter measures was tested and the acquired knowledge was finally used for ZnMgAl coated steel to obtain accurate depth profiles, which exhibited before serious artifacts when data acquisition was performed in an inconsiderate way.

Effect of vibration on retention characteristics of screen acquisition systems. [for surface tension propellant acquisition

NASA Technical Reports Server (NTRS)

Tegart, J. R.; Aydelott, J. C.

1978-01-01

The design of surface tension propellant acquisition systems using fine-mesh screen must take into account all factors that influence the liquid pressure differentials within the system. One of those factors is spacecraft vibration. Analytical models to predict the effects of vibration have been developed. A test program to verify the analytical models and to allow a comparative evaluation of the parameters influencing the response to vibration was performed. Screen specimens were tested under conditions simulating the operation of an acquisition system, considering the effects of such parameters as screen orientation and configuration, screen support method, screen mesh, liquid flow and liquid properties. An analytical model, based on empirical coefficients, was most successful in predicting the effects of vibration.

System for the design, manufacture, and testing of custom lenses with known amounts of high-order aberrations.

PubMed

Chernyak, Dimitri A; Campbell, Charles E

2003-11-01

Now that excimer laser systems can be programmed to correct complex aberrations of the eye on the basis of wave-front measurements, a method is needed to test the accuracy of the system from measurement through treatment. A closed-loop test method was developed to ensure that treatment plans generated by a wavefront measuring system were accurately transferred to and executed by the excimer laser. A surface was analytically defined, and a Shack-Hartmann-based wave-front system was used to formulate a treatment plan, which was downloaded to an excimer laser system. A plastic lens was ablated by the laser and then returned to the wave-front device, where it was measured and compared with the analytically defined wave-front surface. The two surfaces agreed up to 6th-order Zernike terms, validating the accuracy of the system.

A laser interferometer for measuring skin friction in three-dimensional flows

NASA Technical Reports Server (NTRS)

Monson, D. J.

1983-01-01

A new, nonintrusive method is described for measuring skin friction in three-dimensional flows with unknown direction. The method uses a laser interferometer to measure the changing slope of a thin oil film applied to a surface experiencing shear stress. The details of the method are described, and skin friction measurements taken in a swirling three-dimensional boundary-layer flow are presented. Comparisons between analytical results and experimental values from the laser interferometer method and from a bidirectional surface-fence gauge are made.

Surface engineered nanoparticles for improved surface enhanced Raman scattering applications and method for preparing same

DOEpatents

Simmons, Blake A [San Francisco, CA; Talin, Albert Alec [Livermore, CA

2009-11-27

A method for producing metal nanoparticles that when associated with an analyte material will generate an amplified SERS spectrum when the analyte material is illuminated by a light source and a spectrum is recorded. The method for preparing the metal nanoparticles comprises the steps of (i) forming a water-in-oil microemulsion comprising a bulk oil phase, a dilute water phase, and one or more surfactants, wherein the water phase comprises a transition metal ion; (ii) adding an aqueous solution comprising a mild reducing agent to the water-in-oil microemulsion; (iii) stirring the water-in-oil microemulsion and aqueous solution to initiate a reduction reaction resulting in the formation of a fine precipitate dispersed in the water-in-oil microemulsion; and (iv) separating the precipitate from the water-in-oil microemulsion.

pH-Triggered Molecular Alignment for Reproducible SERS Detection via an AuNP/Nanocellulose Platform

PubMed Central

Wei, Haoran; Vikesland, Peter J.

2015-01-01

The low affinity of neutral and hydrophobic molecules towards noble metal surfaces hinders their detection by surface-enhanced Raman spectroscopy (SERS). Herein, we present a method to enhance gold nanoparticle (AuNP) surface affinity by lowering the suspension pH below the analyte pKa. We developed an AuNP/bacterial cellulose (BC) nanocomposite platform and applied it to two common pollutants, carbamazepine (CBZ) and atrazine (ATZ) with pKa values of 2.3 and 1.7, respectively. Simple mixing of the analytes with AuNP/BC at pH < pKa resulted in consistent electrostatic alignment of the CBZ and ATZ molecules across the nanocomposite and highly reproducible SERS spectra. Limits of detection of 3 nM and 11 nM for CBZ and ATZ, respectively, were attained. Tests with additional analytes (melamine, 2,4-dichloroaniline, 4-chloroaniline, 3-bromoaniline, and 3-nitroaniline) further illustrate that the AuNP/BC platform provides reproducible analyte detection and quantification while avoiding the uncontrolled aggregation and flocculation of AuNPs that often hinder low pH detection. PMID:26658696

pH-Triggered Molecular Alignment for Reproducible SERS Detection via an AuNP/Nanocellulose Platform

NASA Astrophysics Data System (ADS)

Wei, Haoran; Vikesland, Peter J.

2015-12-01

The low affinity of neutral and hydrophobic molecules towards noble metal surfaces hinders their detection by surface-enhanced Raman spectroscopy (SERS). Herein, we present a method to enhance gold nanoparticle (AuNP) surface affinity by lowering the suspension pH below the analyte pKa. We developed an AuNP/bacterial cellulose (BC) nanocomposite platform and applied it to two common pollutants, carbamazepine (CBZ) and atrazine (ATZ) with pKa values of 2.3 and 1.7, respectively. Simple mixing of the analytes with AuNP/BC at pH < pKa resulted in consistent electrostatic alignment of the CBZ and ATZ molecules across the nanocomposite and highly reproducible SERS spectra. Limits of detection of 3 nM and 11 nM for CBZ and ATZ, respectively, were attained. Tests with additional analytes (melamine, 2,4-dichloroaniline, 4-chloroaniline, 3-bromoaniline, and 3-nitroaniline) further illustrate that the AuNP/BC platform provides reproducible analyte detection and quantification while avoiding the uncontrolled aggregation and flocculation of AuNPs that often hinder low pH detection.

Determination of Perfluorinated Compounds in the Upper Mississippi River Basin

EPA Science Inventory

Despite ongoing efforts to develop robust analytical methods for the determination of perfluorinated compounds (PFCs) such as perfluorooctanesulfonate (PFOS) and perfluorooctanoic acid (PFOA) in surface water, comparatively little has been published on method performance, and the...

Material for surface-enhanced Raman spectroscopy, and SER sensors and method for preparing same

NASA Technical Reports Server (NTRS)

Farquharson, Stuart (Inventor); Nelson, Chad (Inventor); Lee, Yuan-Hsiang (Inventor)

2003-01-01

Metal-doped sol-gel materials, suitable for use as sensors for surface-enhanced Raman spectroscopic analysis for trace chemical detection, are produced by effecting gelation and solvent removal of a doped sol-gel under mild temperature conditions. At least in certain instances reaction and drying will desirably be effected in an oxygen-starved environment. The metal of the sol-gel material functions, when irradiated, to produce a plasmon field for interaction with molecules of an analyte in contact therewith, increasing by orders of magnitude Raman photons that are generate by excitation radiation, and the method allows matching of the metal and metal particle size to a wavelength of light (or incident radiation, e.g., laser radiation) to generate surface plasmons. The porosity of the sol-gel material dramatically increases the surface area, and thereby the amount of metal exposed for analyte interaction. The sensors provided may be in the form of glass vials, fiber optics, multi-well micro-sample plates, etc., having surface coatings of the doped sol-gel material, to provide sampling systems for use in a Raman instrument.

Nonlinear Analyte Concentration Gradients for One-Step Kinetic Analysis Employing Optical Microring Resonators

PubMed Central

Marty, Michael T.; Kuhnline Sloan, Courtney D.; Bailey, Ryan C.; Sligar, Stephen G.

2012-01-01

Conventional methods to probe the binding kinetics of macromolecules at biosensor surfaces employ a stepwise titration of analyte concentrations and measure the association and dissociation to the immobilized ligand at each concentration level. It has previously been shown that kinetic rates can be measured in a single step by monitoring binding as the analyte concentration increases over time in a linear gradient. We report here the application of nonlinear analyte concentration gradients for determining kinetic rates and equilibrium binding affinities in a single experiment. A versatile nonlinear gradient maker is presented, which is easily applied to microfluidic systems. Simulations validate that accurate kinetic rates can be extracted for a wide range of association and dissociation rates, gradient slopes and curvatures, and with models for mass transport. The nonlinear analyte gradient method is demonstrated with a silicon photonic microring resonator platform to measure prostate specific antigen-antibody binding kinetics. PMID:22686186

Nonlinear analyte concentration gradients for one-step kinetic analysis employing optical microring resonators.

PubMed

Marty, Michael T; Sloan, Courtney D Kuhnline; Bailey, Ryan C; Sligar, Stephen G

2012-07-03

Conventional methods to probe the binding kinetics of macromolecules at biosensor surfaces employ a stepwise titration of analyte concentrations and measure the association and dissociation to the immobilized ligand at each concentration level. It has previously been shown that kinetic rates can be measured in a single step by monitoring binding as the analyte concentration increases over time in a linear gradient. We report here the application of nonlinear analyte concentration gradients for determining kinetic rates and equilibrium binding affinities in a single experiment. A versatile nonlinear gradient maker is presented, which is easily applied to microfluidic systems. Simulations validate that accurate kinetic rates can be extracted for a wide range of association and dissociation rates, gradient slopes, and curvatures, and with models for mass transport. The nonlinear analyte gradient method is demonstrated with a silicon photonic microring resonator platform to measure prostate specific antigen-antibody binding kinetics.

Analytical Methods for Biomass Characterization during Pretreatment and Bioconversion

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

Pu, Yunqiao; Meng, Xianzhi; Yoo, Chang Geun

2016-01-01

Lignocellulosic biomass has been introduced as a promising resource for alternative fuels and chemicals because of its abundance and complement for petroleum resources. Biomass is a complex biopolymer and its compositional and structural characteristics largely vary depending on its species as well as growth environments. Because of complexity and variety of biomass, understanding its physicochemical characteristics is a key for effective biomass utilization. Characterization of biomass does not only provide critical information of biomass during pretreatment and bioconversion, but also give valuable insights on how to utilize the biomass. For better understanding biomass characteristics, good grasp and proper selection ofmore » analytical methods are necessary. This chapter introduces existing analytical approaches that are widely employed for biomass characterization during biomass pretreatment and conversion process. Diverse analytical methods using Fourier transform infrared (FTIR) spectroscopy, gel permeation chromatography (GPC), and nuclear magnetic resonance (NMR) spectroscopy for biomass characterization are reviewed. In addition, biomass accessibility methods by analyzing surface properties of biomass are also summarized in this chapter.« less

Bessel function expansion to reduce the calculation time and memory usage for cylindrical computer-generated holograms.

PubMed

Sando, Yusuke; Barada, Daisuke; Jackin, Boaz Jessie; Yatagai, Toyohiko

2017-07-10

This study proposes a method to reduce the calculation time and memory usage required for calculating cylindrical computer-generated holograms. The wavefront on the cylindrical observation surface is represented as a convolution integral in the 3D Fourier domain. The Fourier transformation of the kernel function involving this convolution integral is analytically performed using a Bessel function expansion. The analytical solution can drastically reduce the calculation time and the memory usage without any cost, compared with the numerical method using fast Fourier transform to Fourier transform the kernel function. In this study, we present the analytical derivation, the efficient calculation of Bessel function series, and a numerical simulation. Furthermore, we demonstrate the effectiveness of the analytical solution through comparisons of calculation time and memory usage.

An Analytical Model of Nanometer Scale Viscoelastic Properties of Polymer Surfaces Measured Using an Atomic Force Microscope

DTIC Science & Technology

2011-03-01

efficient partially buoyant cargo airlifters, fuel-efficient hybrid wing- body aircraft, and hyperprecision low-collateral damage munitions [17]. In order to...between the tip and the surface, or between the tip and the small layer of condensed water on the surface [78]. The third method is a continuum model...crystal near the ringing conditions. The second is by applying an alternating voltage to the piezo crystal in the z-direction. The third method is to

Sensitive ionization of non-volatile analytes using protein solutions as spray liquid in desorption electrospray ionization mass spectrometry.

PubMed

Zhu, Zhiqiang; Han, Jing; Zhang, Yan; Zhou, Yafei; Xu, Ning; Zhang, Bo; Gu, Haiwei; Chen, Huanwen

2012-12-15

Desorption electrospray ionization (DESI) is the most popular ambient ionization technique for direct analysis of complex samples without sample pretreatment. However, for many applications, especially for trace analysis, it is of interest to improve the sensitivity of DESI-mass spectrometry (MS). In traditional DESI-MS, a mixture of methanol/water/acetic acid is usually used to generate the primary ions. In this article, dilute protein solutions were electrosprayed in the DESI method to create multiply charged primary ions for the desorption ionization of trace analytes on various surfaces (e.g., filter paper, glass, Al-foil) without any sample pretreatment. The analyte ions were then detected and structurally characterized using a LTQ XL mass spectrometer. Compared with the methanol/water/acetic acid (49:49:2, v/v/v) solution, protein solutions significantly increased the signal levels of non-volatile compounds such as benzoic acid, TNT, o-toluidine, peptide and insulin in either positive or negative ion detection mode. For all the analytes tested, the limits of detection (LODs) were reduced to about half of the original values which were obtained using traditional DESI. The results showed that the signal enhancement is highly correlated with the molecular weight of the proteins and the selected solid surfaces. The proposed DESI method is a universal strategy for rapid and sensitive detection of trace amounts of strongly bound and/or non-volatile analytes, including explosives, peptides, and proteins. The results indicate that the sensitivity of DESI can be further improved by selecting larger proteins and appropriate solid surfaces. Copyright © 2012 John Wiley & Sons, Ltd.

A SIMPLE, EFFICIENT SOLUTION OF FLUX-PROFILE RELATIONSHIPS IN THE ATMOSPHERIC SURFACE LAYER

EPA Science Inventory

This note describes a simple scheme for analytical estimation of the surface layer similarity functions from state variables. What distinguishes this note from the many previous papers on this topic is that this method is specifically targeted for numerical models where simplici...

Trace analysis of 28 steroids in surface water, wastewater and sludge samples by rapid resolution liquid chromatography-electrospray ionization tandem mass spectrometry.

PubMed

Liu, Shan; Ying, Guang-Guo; Zhao, Jian-Liang; Chen, Feng; Yang, Bin; Zhou, Li-Jun; Lai, Hua-Jie

2011-03-11

A sensitive rapid resolution liquid chromatography-tandem mass spectrometry (RRLC-MS/MS) method, combined with solid-phase extraction, ultrasonic extraction and silica gel cartridge cleanup, was developed for 28 steroids including 4 estrogens (estrone (E1), 17β-estradiol (E2), 17α-ethynyl estradiol (EE2), diethylstilbestrol (DES)), 14 androgens (androsta-1,4-diene-3,17-dione (ADD), 17α-trenbolone, 17β-trenbolone, 4-androstene-3,17-dione, 19-nortestoserone, 17β-boldenone, 17α-boldenone, testosterone (T), epi-androsterone (EADR), methyltestosterone (MT), 4-hydroxy-androst-4-ene-17-dione (4-OHA), 5α-dihydrotestosterone (5α-DHT), androsterone (ADR), stanozolol (S)), 5 progestagens (progesterone (P), ethynyl testosterone (ET), 19-norethindrone, norgestrel, medroxyprogesterone (MP)), and 5 glucocorticoids (cortisol, cortisone, prednisone, prednisolone, dexamethasone) in surface water, wastewater and sludge samples. The recoveries of surface water, influents, effluents and sludge samples were 90.6-119.0% (except 5α-DHT was 143%), 44.0-200%, 60.7-123% and 62.6-138%, respectively. The method detection limits for the 28 analytes in surface water, influents, effluents and freeze-dried sludge samples were 0.01-0.24 ng/L, 0.02-1.44 ng/L, 0.01-0.49 ng/L and 0.08-2.06 ng/g, respectively. This method was applied in the determination of the residual steroidal hormones in two surface water of Danshui River, 12 wastewater and 8 sludge samples from two wastewater treatment plants (Meihu and Huiyang WWTPs) in Guangdong (China). Ten analytes were detected in surface water samples with concentrations ranging between 0.4 ng/L (17β-boldenone) and 55.3 ng/L (5α-DHT); twenty analytes in the wastewater samples with concentrations ranging between 0.3 ng/L (P) and 621 ng/L (5α-DHT); and 12 analytes in the sludge samples with concentrations ranging between 1.6 ng/g (E1) and 372 ng/g (EADR). Copyright © 2011 Elsevier B.V. All rights reserved.

Direct analyte-probed nanoextraction coupled to nanospray ionization-mass spectrometry of drug residues from latent fingerprints.

PubMed

Clemons, Kristina; Wiley, Rachel; Waverka, Kristin; Fox, James; Dziekonski, Eric; Verbeck, Guido F

2013-07-01

Here, we present a method of extracting drug residues from fingerprints via Direct Analyte-Probed Nanoextraction coupled to nanospray ionization-mass spectrometry (DAPNe-NSI-MS). This instrumental technique provides higher selectivity and lower detection limits over current methods, greatly reducing sample preparation, and does not compromise the integrity of latent fingerprints. This coupled to Raman microscopy is an advantageous supplement for location and identification of trace particles. DAPNe uses a nanomanipulator for extraction and differing microscopies for localization of chemicals of interest. A capillary tip with solvent of choice is placed in a nanopositioner. The surface to be analyzed is placed under a microscope, and a particle of interest is located. Using a pressure injector, the solvent is injected onto the surface where it dissolves the analyte, and then extracted back into the capillary tip. The solution is then directly analyzed via NSI-MS. Analyses of caffeine, cocaine, crystal methamphetamine, and ecstasy have been performed successfully. © 2013 American Academy of Forensic Sciences.

Modal ring method for the scattering of sound

NASA Technical Reports Server (NTRS)

Baumeister, Kenneth J.; Kreider, Kevin L.

1993-01-01

The modal element method for acoustic scattering can be simplified when the scattering body is rigid. In this simplified method, called the modal ring method, the scattering body is represented by a ring of triangular finite elements forming the outer surface. The acoustic pressure is calculated at the element nodes. The pressure in the infinite computational region surrounding the body is represented analytically by an eigenfunction expansion. The two solution forms are coupled by the continuity of pressure and velocity on the body surface. The modal ring method effectively reduces the two-dimensional scattering problem to a one-dimensional problem capable of handling very high frequency scattering. In contrast to the boundary element method or the method of moments, which perform a similar reduction in problem dimension, the model line method has the added advantage of having a highly banded solution matrix requiring considerably less computer storage. The method shows excellent agreement with analytic results for scattering from rigid circular cylinders over a wide frequency range (1 is equal to or less than ka is less than or equal to 100) in the near and far fields.

Development of an integrated laboratory system for the monitoring of cyanotoxins in surface and drinking waters.

PubMed

Triantis, Theodoros; Tsimeli, Katerina; Kaloudis, Triantafyllos; Thanassoulias, Nicholas; Lytras, Efthymios; Hiskia, Anastasia

2010-05-01

A system of analytical processes has been developed in order to serve as a cost-effective scheme for the monitoring of cyanobacterial toxins on a quantitative basis, in surface and drinking waters. Five cyclic peptide hepatotoxins, microcystin-LR, -RR, -YR, -LA and nodularin were chosen as the target compounds. Two different enzyme-linked immunosorbent assays (ELISA) were validated in order to serve as primary quantitative screening tools. Validation results showed that the ELISA methods are sufficiently specific and sensitive with limits of detection (LODs) around 0.1 microg/L, however, matrix effects should be considered, especially with surface water samples or bacterial mass methanolic extracts. A colorimetric protein phosphatase inhibition assay (PPIA) utilizing protein phosphatase 2A and p-nitrophenyl phosphate as substrate, was applied in microplate format in order to serve as a quantitative screening method for the detection of the toxic activity associated with cyclic peptide hepatotoxins, at concentration levels >0.2 microg/L of MC-LR equivalents. A fast HPLC/PDA method has been developed for the determination of microcystins, by using a short, 50mm C18 column, with 1.8 microm particle size. Using this method a 10-fold reduction of sample run time was achieved and sufficient separation of microcystins was accomplished in less than 3 min. Finally, the analytical system includes an LC/MS/MS method that was developed for the determination of the 5 target compounds after SPE extraction. The method achieves extremely low limits of detection (<0.02 microg/L), in both surface and drinking waters and it is used for identification and verification purposes as well as for determinations at the ppt level. An analytical protocol that includes the above methods has been designed and validated through the analysis of a number of real samples. Copyright 2009 Elsevier Ltd. All rights reserved.

Mutual influence of molecular diffusion in gas and surface phases

NASA Astrophysics Data System (ADS)

Hori, Takuma; Kamino, Takafumi; Yoshimoto, Yuta; Takagi, Shu; Kinefuchi, Ikuya

2018-01-01

We develop molecular transport simulation methods that simultaneously deal with gas- and surface-phase diffusions to determine the effect of surface diffusion on the overall diffusion coefficients. The phenomenon of surface diffusion is incorporated into the test particle method and the mean square displacement method, which are typically employed only for gas-phase transport. It is found that for a simple cylindrical pore, the diffusion coefficients in the presence of surface diffusion calculated by these two methods show good agreement. We also confirm that both methods reproduce the analytical solution. Then, the diffusion coefficients for ink-bottle-shaped pores are calculated using the developed method. Our results show that surface diffusion assists molecular transport in the gas phase. Moreover, the surface tortuosity factor, which is known to be uniquely determined by physical structure, is influenced by the presence of gas-phase diffusion. This mutual influence of gas-phase diffusion and surface diffusion indicates that their simultaneous calculation is necessary for an accurate evaluation of the diffusion coefficients.

An algebraic homotopy method for generating quasi-three-dimensional grids for high-speed configurations

NASA Technical Reports Server (NTRS)

Moitra, Anutosh

1989-01-01

A fast and versatile procedure for algebraically generating boundary conforming computational grids for use with finite-volume Euler flow solvers is presented. A semi-analytic homotopic procedure is used to generate the grids. Grids generated in two-dimensional planes are stacked to produce quasi-three-dimensional grid systems. The body surface and outer boundary are described in terms of surface parameters. An interpolation scheme is used to blend between the body surface and the outer boundary in order to determine the field points. The method, albeit developed for analytically generated body geometries is equally applicable to other classes of geometries. The method can be used for both internal and external flow configurations, the only constraint being that the body geometries be specified in two-dimensional cross-sections stationed along the longitudinal axis of the configuration. Techniques for controlling various grid parameters, e.g., clustering and orthogonality are described. Techniques for treating problems arising in algebraic grid generation for geometries with sharp corners are addressed. A set of representative grid systems generated by this method is included. Results of flow computations using these grids are presented for validation of the effectiveness of the method.

(Bio)Sensing Using Nanoparticle Arrays: On the Effect of Analyte Transport on Sensitivity.

PubMed

Lynn, N Scott; Homola, Jiří

2016-12-20

There has recently been an extensive amount of work regarding the development of optical, electrical, and mechanical (bio)sensors employing planar arrays of surface-bound nanoparticles. The sensor output for these systems is dependent on the rate at which analyte is transported to, and interacts with, each nanoparticle in the array. There has so far been little discussion on the relationship between the design parameters of an array and the interplay of convection, diffusion, and reaction. Moreover, current methods providing such information require extensive computational simulation. Here we demonstrate that the rate of analyte transport to a nanoparticle array can be quantified analytically. We show that such rates are bound by both the rate to a single NP and that to a planar surface (having equivalent size as the array), with the specific rate determined by the fill fraction: the ratio between the total surface area used for biomolecular capture with respect to the entire sensing area. We characterize analyte transport to arrays with respect to changes in numerous parameters relevant to experiment, including variation of the nanoparticle shape and size, packing density, flow conditions, and analyte diffusivity. We also explore how analyte capture is dependent on the kinetic parameters related to an affinity-based biosensor, and furthermore, we classify the conditions under which the array might be diffusion- or reaction-limited. The results obtained herein are applicable toward the design and optimization of all (bio)sensors based on nanoparticle arrays.

The relationship between purely stochastic sampling error and the number of technical replicates used to estimate concentration at an extreme dilution

USDA-ARS?s Scientific Manuscript database

For any analytical system the population mean (mu) number of entities (e.g., cells or molecules) per tested volume, surface area, or mass also defines the population standard deviation (sigma = square root of mu ). For a preponderance of analytical methods, sigma is very small relative to mu due to...

Topography measurements and applications in ballistics and tool mark identifications*

PubMed Central

Vorburger, T V; Song, J; Petraco, N

2016-01-01

The application of surface topography measurement methods to the field of firearm and toolmark analysis is fairly new. The field has been boosted by the development of a number of competing optical methods, which has improved the speed and accuracy of surface topography acquisitions. We describe here some of these measurement methods as well as several analytical methods for assessing similarities and differences among pairs of surfaces. We also provide a few examples of research results to identify cartridge cases originating from the same firearm or tool marks produced by the same tool. Physical standards and issues of traceability are also discussed. PMID:27182440

Nanoscale Surface Plasmonics Sensor With Nanofluidic Control

NASA Technical Reports Server (NTRS)

Wei, Jianjun; Singhal, Sameer; Waldeck, David H.; Kofke, Matthew

2013-01-01

Conventional quantitative protein assays of bodily fluids typically involve multiple steps to obtain desired measurements. Such methods are not well suited for fast and accurate assay measurements in austere environments such as spaceflight and in the aftermath of disasters. Consequently, there is a need for a protein assay technology capable of routinely monitoring proteins in austere environments. For example, there is an immediate need for a urine protein assay to assess astronaut renal health during spaceflight. The disclosed nanoscale surface plasmonics sensor provides a core detection method that can be integrated to a lab-on-chip device that satisfies the unmet need for such a protein assay technology. Assays based upon combinations of nanoholes, nanorings, and nanoslits with transmission surface plasmon resonance (SPR) are used for assays requiring extreme sensitivity, and are capable of detecting specific analytes at concentrations as low as picomole to femtomole level in well-controlled environments. The device operates in a transmission mode configuration in which light is directed at one planar surface of the array, which functions as an optical aperture. The incident light induces surface plasmon light transmission from the opposite surface of the array. The presence of a target analyte is detected by changes in the spectrum of light transmitted by the array when a target analyte induces a change in the refractive index of the fluid within the nanochannels. This occurs, for example, when a target analyte binds to a receptor fixed to the walls of the nanochannels in the array. Independent fluid handling capability for individual nanoarrays on a nanofluidic chip containing a plurality of nanochannel arrays allows each array to be used to sense a different target analyte and/or for paired arrays to analyze control and test samples simultaneously in parallel. The present invention incorporates transmission mode nanoplasmonics and nanofluidics into a single, microfluidically controlled device. The device comprises one or more arrays of aligned nanochannels that are in fluid communication with inflowing and outflowing fluid handling manifolds that control the flow of fluid through the arrays. The array acts as an aperture in a plasmonic sensor. Fluid, in the form of a liquid or a gas and comprising a sample for analysis, is moved from an inlet manifold through the nanochannel array, and out through an exit manifold. The fluid may also contain a reagent used to modify the interior surfaces of the nanochannels, and/or a reagent required for the detection of an analyte.

Measurement of "total" microcystins using the MMPB/LC/MS/MS method, and application to HAB impacted surface waters-presentation

EPA Science Inventory

The detection and quantification of microcystins, a family of toxins associated with harmful algal blooms, is complicated by their structural diversity and a lack of commercially available analytical standards for method development. As a result, most detection methods have focus...

Pharmaceuticals and personal care products (PPCPs) in surface and treated waters of Louisiana, USA and Ontario, Canada.

PubMed

Boyd, Glen R; Reemtsma, Helge; Grimm, Deborah A; Mitra, Siddhartha

2003-07-20

A newly developed analytical method was used to measure concentrations of nine pharmaceuticals and personal care products (PPCPs) in samples from two surface water bodies, a sewage treatment plant effluent and various stages of a drinking water treatment plant in Louisiana, USA, and from one surface water body, a drinking water treatment plant and a pilot plant in Ontario, Canada. The analytical method provides for simultaneous extraction and quantification of the following broad range of PPCPs and endocrine-disrupting chemicals: naproxen; ibuprofen; estrone; 17beta-estradiol; bisphenol A; clorophene; triclosan; fluoxetine; and clofibric acid. Naproxen was detected in Louisiana sewage treatment plant effluent at 81-106 ng/l and Louisiana and Ontario surface waters at 22-107 ng/l. Triclosan was detected in Louisiana sewage treatment plant effluent at 10-21 ng/l. Of the three surface waters sampled, clofibric acid was detected in Detroit River water at 103 ng/l, but not in Mississippi River or Lake Pontchartrain waters. None of the other target analytes were detected above their method detection limits. Based on results at various stages of treatment, conventional drinking-water treatment processes (coagulation, flocculation and sedimentation) plus continuous addition of powdered activated carbon at a dosage of 2 mg/l did not remove naproxen from Mississippi River waters. However, chlorination, ozonation and dual media filtration processes reduced the concentration of naproxen below detection in Mississippi River and Detroit River waters and reduced clofibric acid in Detroit River waters. Results of this study demonstrate that existing water treatment technologies can effectively remove certain PPCPs. In addition, our study demonstrates the importance of obtaining data on removal mechanisms and byproducts associated with PPCPs and other endocrine-disrupting chemicals in drinking water and sewage treatment processes.

Electromagnetic fields due to a horizontal electric dipole antenna laid on the surface of a two-layer medium

NASA Technical Reports Server (NTRS)

Tsang, L.; Kong, J. A.

1974-01-01

With applications to geophysical subsurface probings, electromagnetic fields due to a horizontal electric dipole laid on the surface of a two-layer medium are solved by a combination of analytic and numerical methods. Interference patterns are calculated for various layer thickness. The results are interpreted in terms of normal modes, and the accuracies of the methods are discussed.

From observational to analytical morphology of the stratum corneum: progress avoiding hazardous animal and human testings

PubMed Central

Piérard, Gérald E; Courtois, Justine; Ritacco, Caroline; Humbert, Philippe; Fanian, Ferial; Piérard-Franchimont, Claudine

2015-01-01

Background In cosmetic science, noninvasive sampling of the upper part of the stratum corneum is conveniently performed using strippings with adhesive-coated discs (SACD) and cyanoacrylate skin surface strippings (CSSSs). Methods Under controlled conditions, it is possible to scrutinize SACD and CSSS with objectivity using appropriate methods of analytical morphology. These procedures apply to a series of clinical conditions including xerosis grading, comedometry, corneodynamics, corneomelametry, corneosurfametry, corneoxenometry, and dandruff assessment. Results With any of the analytical evaluations, SACD and CSSS provide specific salient information that is useful in the field of cosmetology. In particular, both methods appear valuable and complementary in assessing the human skin compatibility of personal skincare products. Conclusion A set of quantitative analytical methods applicable to the minimally invasive and low-cost SACD and CSSS procedures allow for a sound assessment of cosmetic effects on the stratum corneum. Under regular conditions, both methods are painless and do not induce adverse events. Globally, CSSS appears more precise and informative than the regular SACD stripping. PMID:25767402

Improved full analytical polygon-based method using Fourier analysis of the three-dimensional affine transformation.

PubMed

Pan, Yijie; Wang, Yongtian; Liu, Juan; Li, Xin; Jia, Jia

2014-03-01

Previous research [Appl. Opt.52, A290 (2013)] has revealed that Fourier analysis of three-dimensional affine transformation theory can be used to improve the computation speed of the traditional polygon-based method. In this paper, we continue our research and propose an improved full analytical polygon-based method developed upon this theory. Vertex vectors of primitive and arbitrary triangles and the pseudo-inverse matrix were used to obtain an affine transformation matrix representing the spatial relationship between the two triangles. With this relationship and the primitive spectrum, we analytically obtained the spectrum of the arbitrary triangle. This algorithm discards low-level angular dependent computations. In order to add diffusive reflection to each arbitrary surface, we also propose a whole matrix computation approach that takes advantage of the affine transformation matrix and uses matrix multiplication to calculate shifting parameters of similar sub-polygons. The proposed method improves hologram computation speed for the conventional full analytical approach. Optical experimental results are demonstrated which prove that the proposed method can effectively reconstruct three-dimensional scenes.

Solid Lubrication Fundamentals and Applications. Chapter 2

NASA Technical Reports Server (NTRS)

Miyoshi, Kazuhisa

1998-01-01

This chapter describes powerful analytical techniques capable of sampling tribological surfaces and solid-film lubricants. Some of these techniques may also be used to determine the locus of failure in a bonded structure or coated substrate; such information is important when seeking improved adhesion between a solid-film lubricant and a substrate and when seeking improved performance and long life expectancy of solid lubricants. Many examples are given here and through-out the book on the nature and character of solid surfaces and their significance in lubrication, friction, and wear. The analytical techniques used include the late spectroscopic methods.

Validation of the enthalpy method by means of analytical solution

NASA Astrophysics Data System (ADS)

Kleiner, Thomas; Rückamp, Martin; Bondzio, Johannes; Humbert, Angelika

2014-05-01

Numerical simulations moved in the recent year(s) from describing the cold-temperate transition surface (CTS) towards an enthalpy description, which allows avoiding incorporating a singular surface inside the model (Aschwanden et al., 2012). In Enthalpy methods the CTS is represented as a level set of the enthalpy state variable. This method has several numerical and practical advantages (e.g. representation of the full energy by one scalar field, no restriction to topology and shape of the CTS). The proposed method is rather new in glaciology and to our knowledge not verified and validated against analytical solutions. Unfortunately we are still lacking analytical solutions for sufficiently complex thermo-mechanically coupled polythermal ice flow. However, we present two experiments to test the implementation of the enthalpy equation and corresponding boundary conditions. The first experiment tests particularly the functionality of the boundary condition scheme and the corresponding basal melt rate calculation. Dependent on the different thermal situations that occur at the base, the numerical code may have to switch to another boundary type (from Neuman to Dirichlet or vice versa). The main idea of this set-up is to test the reversibility during transients. A former cold ice body that run through a warmer period with an associated built up of a liquid water layer at the base must be able to return to its initial steady state. Since we impose several assumptions on the experiment design analytical solutions can be formulated for different quantities during distinct stages of the simulation. The second experiment tests the positioning of the internal CTS in a parallel-sided polythermal slab. We compare our simulation results to the analytical solution proposed by Greve and Blatter (2009). Results from three different ice flow-models (COMIce, ISSM, TIMFD3) are presented.

Trace and surface analysis of ceramic layers of solid oxide fuel cells by mass spectrometry.

PubMed

Becker, J S; Breuer, U; Westheide, J; Saprykin, A I; Holzbrecher, H; Nickel, H; Dietze, H J

1996-06-01

For the trace analysis of impurities in thick ceramic layers of a solid oxide fuel cell (SOFC) sensitive solid-state mass spectrometric methods, such as laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) and radiofrequency glow discharge mass spectrometry (rf-GDMS) have been developed and used. In order to quantify the analytical results of LA-ICP-MS, the relative sensitivity coefficients of elements in a La(0.6)Sr(0.35)MnO(3) matrix have been determined using synthetic standards. Secondary ion mass spectrometry (SIMS) - as a surface analytical method - has been used to characterize the element distribution and diffusion profiles of matrix elements on the interface of a perovskite/Y-stabilized ZrO(2) layer. The application of different mass spectrometric methods for process control in the preparation of ceramic layers for the SOFC is described.

Comparison of NMR simulations of porous media derived from analytical and voxelized representations.

PubMed

Jin, Guodong; Torres-Verdín, Carlos; Toumelin, Emmanuel

2009-10-01

We develop and compare two formulations of the random-walk method, grain-based and voxel-based, to simulate the nuclear-magnetic-resonance (NMR) response of fluids contained in various models of porous media. The grain-based approach uses a spherical grain pack as input, where the solid surface is analytically defined without an approximation. In the voxel-based approach, the input is a computer-tomography or computer-generated image of reconstructed porous media. Implementation of the two approaches is largely the same, except for the representation of porous media. For comparison, both approaches are applied to various analytical and digitized models of porous media: isolated spherical pore, simple cubic packing of spheres, and random packings of monodisperse and polydisperse spheres. We find that spin magnetization decays much faster in the digitized models than in their analytical counterparts. The difference in decay rate relates to the overestimation of surface area due to the discretization of the sample; it cannot be eliminated even if the voxel size decreases. However, once considering the effect of surface-area increase in the simulation of surface relaxation, good quantitative agreement is found between the two approaches. Different grain or pore shapes entail different rates of increase of surface area, whereupon we emphasize that the value of the "surface-area-corrected" coefficient may not be universal. Using an example of X-ray-CT image of Fontainebleau rock sample, we show that voxel size has a significant effect on the calculated surface area and, therefore, on the numerically simulated magnetization response.

Nanomechanical membrane-type surface stress sensor.

PubMed

Yoshikawa, Genki; Akiyama, Terunobu; Gautsch, Sebastian; Vettiger, Peter; Rohrer, Heinrich

2011-03-09

Nanomechanical cantilever sensors have been emerging as a key device for real-time and label-free detection of various analytes ranging from gaseous to biological molecules. The major sensing principle is based on the analyte-induced surface stress, which makes a cantilever bend. In this letter, we present a membrane-type surface stress sensor (MSS), which is based on the piezoresistive read-out integrated in the sensor chip. The MSS is not a simple "cantilever," rather it consists of an "adsorbate membrane" suspended by four piezoresistive "sensing beams," composing a full Wheatstone bridge. The whole analyte-induced isotropic surface stress on the membrane is efficiently transduced to the piezoresistive beams as an amplified uniaxial stress. Evaluation of a prototype MSS used in the present experiments demonstrates a high sensitivity which is comparable with that of optical methods and a factor of more than 20 higher than that obtained with a standard piezoresistive cantilever. The finite element analyses indicate that changing dimensions of the membrane and beams can substantially increase the sensitivity further. Given the various conveniences and advantages of the integrated piezoresistive read-out, this platform is expected to open a new era of surface stress-based sensing.

Apparatus for rapid measurement of aerosol bulk chemical composition

DOEpatents

Lee, Yin-Nan E.; Weber, Rodney J.; Orsini, Douglas

2006-04-18

An apparatus for continuous on-line measurement of chemical composition of aerosol particles with a fast time resolution is provided. The apparatus includes an enhanced particle size magnifier for producing activated aerosol particles and an enhanced collection device which collects the activated aerosol particles into a liquid stream for quantitative analysis by analytical means. Methods for on-line measurement of chemical composition of aerosol particles are also provided, the method including exposing aerosol carrying sample air to hot saturated steam thereby forming activated aerosol particles; collecting the activated aerosol particles by a collection device for delivery as a jet stream onto an impaction surface; and flushing off the activated aerosol particles from the impaction surface into a liquid stream for delivery of the collected liquid stream to an analytical instrument for quantitative measurement.

Improved resolution of fluoroquinolones using cetyltrimethyl ammonium bromide-micellar electrokinetic chromatography and its application to residue analysis in surface water.

PubMed

Prutthiwanasan, Brompoj; Suntornsuk, Leena

2018-06-18

A simple micellar electrokinetic chromatography (MEKC), using cetyltrimethyl ammonium bromide (CTAB) as micelles, for the determination of ciprofloxacin (CIP), enrofloxacin (ENR), norfloxacin (NOR) and ofloxacin (OFL) residues in surface water was developed. Peak Master was used for predicting amounts of analyte ionic forms to reduce numbers of tedious experiments in optimizing the analyte capacity factors. A baseline separation (R s  > 2.8) of the analytes was achieved in 7 min using 15 mM sodium dihydrogen phosphate (pH 6.0) containing 3 mM CTAB and a capillary with an effective length of 56.0 cm. A negative polarity voltage of 20 kV was used to enable the migration of the cationic micelles toward the detection site. The method shows good linearity in a range of 5 and 20 μg mL -1 and precision (%RSD < 6.45). Percent recoveries of the method were in a range of 65.1-88.7%. The limits of detection and quantitation were in the ranges of 1-2 and 3-5 μg mL -1 , respectively. Two steps sample clean-up and preconcentration of surface water samples by hydrophilic-lipophilic balance and fluoroquinolone-molecularly imprinted polymer were advantageous for removal of humic acids and enabling the detection of fluoroquinolone residues in the samples. Finally, the method was applied for fluoroquinolone residues analysis of surface water in Thailand. Copyright © 2018 Elsevier B.V. All rights reserved.

Three-Dimensional Solution of the Free Vibration Problem for Metal-Ceramic Shells Using the Method of Sampling Surfaces

NASA Astrophysics Data System (ADS)

Kulikov, G. M.; Plotnikova, S. V.

2017-03-01

The possibility of using the method of sampling surfaces (SaS) for solving the free vibration problem of threedimensional elasticity for metal-ceramic shells is studied. According to this method, in the shell body, an arbitrary number of SaS parallel to its middle surface are selected in order to take displacements of these surfaces as unknowns. The SaS pass through the nodes of a Chebyshev polynomial, which improves the convergence of the SaS method significantly. As a result, the SaS method can be used to obtain analytical solutions of the vibration problem for metal-ceramic plates and cylindrical shells that asymptotically approach the exact solutions of elasticity as the number of SaS tends to infinity.

Surface enhanced Raman scattering substrates prepared by thermal evaporation on liquid surfaces.

PubMed

Ye, Ziran; Sun, Guofang; Sui, Chenghua; Yan, Bo; Gao, Fan; Cai, Pinggen; Lv, Bin; Li, Yun; Chen, Naibo; Xu, Fengyun; Wang, Ke; Ye, Gaoxiang; Yang, Shikuan

2018-06-25

We present an effective surface-enhancement Raman scattering(SERS) substrate enabled by depositing metallic film on a liquid surface at room temperature. Thermal evaporation is used to deposit Au atoms on silicone oil surface and then form quasi-continuous films. Due to the isotropic characteristics of the liquid surface, this film consists of substantial nanoparticles with uniform diameter, which is different from films fabricated on solid substrates and can be served as an applicable substrate for SERS detection. With the assistance of this substrate, SERS signals of Rhodamine 6G(R6G) were significantly enhanced, the dependence between SERS spectra and film thickness was investigated. Analytical simulation results confirm the experimental observations and the superiorities of our proposed method for preparation of SERS substrate. This work provides a potential application of metallic film deposition on free-sustained surface and holds promise as an efficient sensor in rapid trace detection of small molecule analytes. © 2018 IOP Publishing Ltd.

The Influence of Roughness on Gear Surface Fatigue

NASA Technical Reports Server (NTRS)

Krantz, Timothy

2005-01-01

Gear working surfaces are subjected to repeated rolling and sliding contacts, and often designs require loads sufficient to cause eventual fatigue of the surface. This research provides experimental data and analytical tools to further the understanding of the causal relationship of gear surface roughness to surface fatigue. The research included evaluations and developments of statistical tools for gear fatigue data, experimental evaluation of the surface fatigue lives of superfinished gears with a near-mirror quality, and evaluations of the experiments by analytical methods and surface inspections. Alternative statistical methods were evaluated using Monte Carlo studies leading to a final recommendation to describe gear fatigue data using a Weibull distribution, maximum likelihood estimates of shape and scale parameters, and a presumed zero-valued location parameter. A new method was developed for comparing two datasets by extending the current methods of likelihood-ratio based statistics. The surface fatigue lives of superfinished gears were evaluated by carefully controlled experiments, and it is shown conclusively that superfinishing of gears can provide for significantly greater lives relative to ground gears. The measured life improvement was approximately a factor of five. To assist with application of this finding to products, the experimental condition was evaluated. The fatigue life results were expressed in terms of specific film thickness and shown to be consistent with bearing data. Elastohydrodynamic and stress analyses were completed to relate the stress condition to fatigue. Smooth-surface models do not adequately explain the improved fatigue lives. Based on analyses using a rough surface model, it is concluded that the improved fatigue lives of superfinished gears is due to a reduced rate of near-surface micropitting fatigue processes, not due to any reduced rate of spalling (sub-surface) fatigue processes. To complete the evaluations, surface inspection were completed. The surface topographies of the ground gears changed substantially due to running, but the topographies of the superfinished gears were essentially unchanged with running.

An analytical method for predicting the geometrical and optical properties of the human lens under accommodation

PubMed Central

Sheil, Conor J.; Bahrami, Mehdi; Goncharov, Alexander V.

2014-01-01

We present an analytical method to describe the accommodative changes in the human crystalline lens. The method is based on the geometry-invariant lens model, in which the gradient-index (GRIN) iso-indicial contours are coupled to the external shape. This feature ensures that any given number of iso-indicial contours does not change with accommodation, which preserves the optical integrity of the GRIN structure. The coupling also enables us to define the GRIN structure if the radii and asphericities of the external lens surfaces are known. As an example, the accommodative changes in lenticular radii and central thickness were taken from the literature, while the asphericities of the external surfaces were derived analytically by adhering to the basic physical conditions of constant lens volume and its axial position. The resulting changes in lens geometry are consistent with experimental data, and the optical properties are in line with expected values for optical power and spherical aberration. The aim of the paper is to provide an anatomically and optically accurate lens model that is valid for 3 mm pupils and can be used as a new tool for better understanding of accommodation. PMID:24877022

An analytical method for predicting the geometrical and optical properties of the human lens under accommodation.

PubMed

Sheil, Conor J; Bahrami, Mehdi; Goncharov, Alexander V

2014-05-01

We present an analytical method to describe the accommodative changes in the human crystalline lens. The method is based on the geometry-invariant lens model, in which the gradient-index (GRIN) iso-indicial contours are coupled to the external shape. This feature ensures that any given number of iso-indicial contours does not change with accommodation, which preserves the optical integrity of the GRIN structure. The coupling also enables us to define the GRIN structure if the radii and asphericities of the external lens surfaces are known. As an example, the accommodative changes in lenticular radii and central thickness were taken from the literature, while the asphericities of the external surfaces were derived analytically by adhering to the basic physical conditions of constant lens volume and its axial position. The resulting changes in lens geometry are consistent with experimental data, and the optical properties are in line with expected values for optical power and spherical aberration. The aim of the paper is to provide an anatomically and optically accurate lens model that is valid for 3 mm pupils and can be used as a new tool for better understanding of accommodation.

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

Addleman, Raymond S; Atkinson, David A; Bays, John T

An enhanced swipe sampler and method of making are described. The swipe sampler is made of a fabric containing selected glass, metal oxide, and/or oxide-coated glass or metal fibers. Fibers are modified with silane ligands that are directly attached to the surface of the fibers to functionalize the sampling surface of the fabric. The swipe sampler collects various target analytes including explosives and other threat agents on the surface of the sampler.

Quantitative SIMS Imaging of Agar-Based Microbial Communities.

PubMed

Dunham, Sage J B; Ellis, Joseph F; Baig, Nameera F; Morales-Soto, Nydia; Cao, Tianyuan; Shrout, Joshua D; Bohn, Paul W; Sweedler, Jonathan V

2018-05-01

After several decades of widespread use for mapping elemental ions and small molecular fragments in surface science, secondary ion mass spectrometry (SIMS) has emerged as a powerful analytical tool for molecular imaging in biology. Biomolecular SIMS imaging has primarily been used as a qualitative technique; although the distribution of a single analyte can be accurately determined, it is difficult to map the absolute quantity of a compound or even to compare the relative abundance of one molecular species to that of another. We describe a method for quantitative SIMS imaging of small molecules in agar-based microbial communities. The microbes are cultivated on a thin film of agar, dried under nitrogen, and imaged directly with SIMS. By use of optical microscopy, we show that the area of the agar is reduced by 26 ± 2% (standard deviation) during dehydration, but the overall biofilm morphology and analyte distribution are largely retained. We detail a quantitative imaging methodology, in which the ion intensity of each analyte is (1) normalized to an external quadratic regression curve, (2) corrected for isomeric interference, and (3) filtered for sample-specific noise and lower and upper limits of quantitation. The end result is a two-dimensional surface density image for each analyte. The sample preparation and quantitation methods are validated by quantitatively imaging four alkyl-quinolone and alkyl-quinoline N-oxide signaling molecules (including Pseudomonas quinolone signal) in Pseudomonas aeruginosa colony biofilms. We show that the relative surface densities of the target biomolecules are substantially different from values inferred through direct intensity comparison and that the developed methodologies can be used to quantitatively compare as many ions as there are available standards.

Prediction of Experimental Surface Heat Flux of Thin Film Gauges using ANFIS

NASA Astrophysics Data System (ADS)

Sarma, Shrutidhara; Sahoo, Niranjan; Unal, Aynur

2018-05-01

Precise quantification of surface heat fluxes in highly transient environment is of paramount importance from the design point of view of several engineering equipment like thermal protection or cooling systems. Such environments are simulated in experimental facilities by exposing the surface with transient heat loads typically step/impulsive in nature. The surface heating rates are then determined from highly transient temperature history captured by efficient surface temperature sensors. The classical approach is to use thin film gauges (TFGs) in which temperature variations are acquired within milliseconds, thereby allowing calculation of surface heat flux, based on the theory of one-dimensional heat conduction on a semi-infinite body. With recent developments in the soft computing methods, the present study is an attempt for the application of intelligent system technique, called adaptive neuro fuzzy inference system (ANFIS) to recover surface heat fluxes from a given temperature history recorded by TFGs without having the need to solve lengthy analytical equations. Experiments have been carried out by applying known quantity of `impulse heat load' through laser beam on TFGs. The corresponding voltage signals have been acquired and surface heat fluxes are estimated through classical analytical approach. These signals are then used to `train' the ANFIS model, which later predicts output for `test' values. Results from both methods have been compared and these surface heat fluxes are used to predict the non-linear relationship between thermal and electrical properties of the gauges that are exceedingly pertinent to the design of efficient TFGs. Further, surface plots have been created to give an insight about dimensionality effect of the non-linear dependence of thermal/electrical parameters on each other. Later, it is observed that a properly optimized ANFIS model can predict the impulsive heat profiles with significant accuracy. This paper thus shows the appropriateness of soft computing technique as a practically constructive replacement for tedious analytical formulation and henceforth, effectively quantifies the modeling of TFGs.

Climate reconstruction from borehole temperatures influenced by groundwater flow

NASA Astrophysics Data System (ADS)

Kurylyk, B.; Irvine, D. J.; Tang, W.; Carey, S. K.; Ferguson, G. A. G.; Beltrami, H.; Bense, V.; McKenzie, J. M.; Taniguchi, M.

2017-12-01

Borehole climatology offers advantages over other climate reconstruction methods because further calibration steps are not required and heat is a ubiquitous subsurface property that can be measured from terrestrial boreholes. The basic theory underlying borehole climatology is that past surface air temperature signals are reflected in the ground surface temperature history and archived in subsurface temperature-depth profiles. High frequency surface temperature signals are attenuated in the shallow subsurface, whereas low frequency signals can be propagated to great depths. A limitation of analytical techniques to reconstruct climate signals from temperature profiles is that they generally require that heat flow be limited to conduction. Advection due to groundwater flow can thermally `contaminate' boreholes and result in temperature profiles being rejected for regional climate reconstructions. Although groundwater flow and climate change can result in contrasting or superimposed thermal disturbances, groundwater flow will not typically remove climate change signals in a subsurface thermal profile. Thus, climate reconstruction is still possible in the presence of groundwater flow if heat advection is accommodated in the conceptual and mathematical models. In this study, we derive a new analytical solution for reconstructing surface temperature history from borehole thermal profiles influenced by vertical groundwater flow. The boundary condition for the solution is composed of any number of sequential `ramps', i.e. periods with linear warming or cooling rates, during the instrumented and pre-observational periods. The boundary condition generation and analytical temperature modeling is conducted in a simple computer program. The method is applied to reconstruct climate in Winnipeg, Canada and Tokyo, Japan using temperature profiles recorded in hydrogeologically active environments. The results demonstrate that thermal disturbances due to groundwater flow and climate change must be considered in a holistic manner as opposed to isolating either perturbation as was done in prior analytical studies.

Development of a validated liquid chromatographic method for quantification of sorafenib tosylate in the presence of stress-induced degradation products and in biological matrix employing analytical quality by design approach.

PubMed

Sharma, Teenu; Khurana, Rajneet Kaur; Jain, Atul; Katare, O P; Singh, Bhupinder

2018-05-01

The current research work envisages an analytical quality by design-enabled development of a simple, rapid, sensitive, specific, robust and cost-effective stability-indicating reversed-phase high-performance liquid chromatographic method for determining stress-induced forced-degradation products of sorafenib tosylate (SFN). An Ishikawa fishbone diagram was constructed to embark upon analytical target profile and critical analytical attributes, i.e. peak area, theoretical plates, retention time and peak tailing. Factor screening using Taguchi orthogonal arrays and quality risk assessment studies carried out using failure mode effect analysis aided the selection of critical method parameters, i.e. mobile phase ratio and flow rate potentially affecting the chosen critical analytical attributes. Systematic optimization using response surface methodology of the chosen critical method parameters was carried out employing a two-factor-three-level-13-run, face-centered cubic design. A method operable design region was earmarked providing optimum method performance using numerical and graphical optimization. The optimum method employed a mobile phase composition consisting of acetonitrile and water (containing orthophosphoric acid, pH 4.1) at 65:35 v/v at a flow rate of 0.8 mL/min with UV detection at 265 nm using a C 18 column. Response surface methodology validation studies confirmed good efficiency and sensitivity of the developed method for analysis of SFN in mobile phase as well as in human plasma matrix. The forced degradation studies were conducted under different recommended stress conditions as per ICH Q1A (R2). Mass spectroscopy studies showed that SFN degrades in strongly acidic, alkaline and oxidative hydrolytic conditions at elevated temperature, while the drug was per se found to be photostable. Oxidative hydrolysis using 30% H 2 O 2 showed maximum degradation with products at retention times of 3.35, 3.65, 4.20 and 5.67 min. The absence of any significant change in the retention time of SFN and degradation products, formed under different stress conditions, ratified selectivity and specificity of the systematically developed method. Copyright © 2017 John Wiley & Sons, Ltd.

Investigation of the capillary flow through open surface microfluidic structures

NASA Astrophysics Data System (ADS)

Taher, Ahmed; Jones, Benjamin; Fiorini, Paolo; Lagae, Liesbet

2017-02-01

The passive nature of capillary microfluidics for pumping and actuation of fluids is attractive for many applications including point of care medical diagnostics. For such applications, there is often the need to spot dried chemical reagents in the bottom of microfluidic channels after device fabrication; it is often more practical to have open surface devices (i.e., without a cover or lid). However, the dynamics of capillary driven flow in open surface devices have not been well studied for many geometries of interest. In this paper, we investigate capillary flow in an open surface microchannel with a backward facing step. An analytical model is developed to calculate the capillary pressure as the liquid-vapor interface traverses a backward facing step in an open microchannel. The developed model is validated against results from Surface Evolver liquid-vapor surface simulations and ANSYS Fluent two-phase flow simulations using the volume of fluid approach. Three different aspect ratios (inlet channel height by channel width) were studied. The analytical model shows good agreement with the simulation results from both modeling methods for all geometries. The analytical model is used to derive an expression for the critical aspect ratio (the minimum channel aspect ratio for flow to proceed across the backward facing step) as a function of contact angle.

Biopharmaceutical production: Applications of surface plasmon resonance biosensors.

PubMed

Thillaivinayagalingam, Pranavan; Gommeaux, Julien; McLoughlin, Michael; Collins, David; Newcombe, Anthony R

2010-01-15

Surface plasmon resonance (SPR) permits the quantitative analysis of therapeutic antibody concentrations and impurities including bacteria, Protein A, Protein G and small molecule ligands leached from chromatography media. The use of surface plasmon resonance has gained popularity within the biopharmaceutical industry due to the automated, label free, real time interaction that may be exploited when using this method. The application areas to assess protein interactions and develop analytical methods for biopharmaceutical downstream process development, quality control, and in-process monitoring are reviewed. 2009 Elsevier B.V. All rights reserved.

Predictive Analytical Model for Isolator Shock-Train Location in a Mach 2.2 Direct-Connect Supersonic Combustion Tunnel

NASA Astrophysics Data System (ADS)

Lingren, Joe; Vanstone, Leon; Hashemi, Kelley; Gogineni, Sivaram; Donbar, Jeffrey; Akella, Maruthi; Clemens, Noel

2016-11-01

This study develops an analytical model for predicting the leading shock of a shock-train in the constant area isolator section in a Mach 2.2 direct-connect scramjet simulation tunnel. The effective geometry of the isolator is assumed to be a weakly converging duct owing to boundary-layer growth. For some given pressure rise across the isolator, quasi-1D equations relating to isentropic or normal shock flows can be used to predict the normal shock location in the isolator. The surface pressure distribution through the isolator was measured during experiments and both the actual and predicted locations can be calculated. Three methods of finding the shock-train location are examined, one based on the measured pressure rise, one using a non-physics-based control model, and one using the physics-based analytical model. It is shown that the analytical model performs better than the non-physics-based model in all cases. The analytic model is less accurate than the pressure threshold method but requires significantly less information to compute. In contrast to other methods for predicting shock-train location, this method is relatively accurate and requires as little as a single pressure measurement. This makes this method potentially useful for unstart control applications.

Per- and Polyfluoroalkyl Substances (PFAS): Sampling ...

EPA Pesticide Factsheets

Per- and polyfluoroalkyl substances (PFAS) are a large group of manufactured compounds used in a variety of industries, such as aerospace, automotive, textiles, and electronics, and are used in some food packaging and firefighting materials. For example, they may be used to make products more resistant to stains, grease and water. In the environment, some PFAS break down very slowly, if at all, allowing bioaccumulation (concentration) to occur in humans and wildlife. Some have been found to be toxic to laboratory animals, producing reproductive, developmental, and systemic effects in laboratory tests. EPA's methods for analyzing PFAS in environmental media are in various stages of development. This technical brief summarizes the work being done to develop robust analytical methods for groundwater, surface water, wastewater, and solids, including soils, sediments, and biosolids. The U.S. Environmental Protection Agency’s (EPA) methods for analyzing PFAS in environmental media are in various stages of development. EPA is working to develop robust analytical methods for groundwater, surface water, wastewater, and solids, including soils, sediments, and biosolids.

Broadband impedance boundary conditions for the simulation of sound propagation in the time domain.

PubMed

Bin, Jonghoon; Yousuff Hussaini, M; Lee, Soogab

2009-02-01

An accurate and practical surface impedance boundary condition in the time domain has been developed for application to broadband-frequency simulation in aeroacoustic problems. To show the capability of this method, two kinds of numerical simulations are performed and compared with the analytical/experimental results: one is acoustic wave reflection by a monopole source over an impedance surface and the other is acoustic wave propagation in a duct with a finite impedance wall. Both single-frequency and broadband-frequency simulations are performed within the framework of linearized Euler equations. A high-order dispersion-relation-preserving finite-difference method and a low-dissipation, low-dispersion Runge-Kutta method are used for spatial discretization and time integration, respectively. The results show excellent agreement with the analytical/experimental results at various frequencies. The method accurately predicts both the amplitude and the phase of acoustic pressure and ensures the well-posedness of the broadband time-domain impedance boundary condition.

Determination of stoichiometry and concentration of trace elements in thin BaxSr1-xTiO3 perovskite layers.

PubMed

Becker, J S; Boulyga, S F

2001-07-01

This paper describes an analytical procedure for determining the stoichiometry of BaxSr1-xTiO3 perovskite layers using inductively coupled plasma mass spectrometry (ICP-MS). The analytical results of mass spectrometry measurements are compared to those of X-ray fluorescence analysis (XRF). The performance and the limits of solid-state mass spectrometry analytical methods for the surface analysis of thin BaxSr1-xTiO3 perovskite layers sputtered neutral mass spectrometry (SNMS)--are investigated and discussed.

Parent and conjugated estrogens and progestagens in surface water of the Santa Ana River: Determination, occurrence, and risk assessment

USDA-ARS?s Scientific Manuscript database

This study presents a sensitive analytical method using high performance liquid chromatography tandem mass spectrometry for the simultaneous monitoring of five estrogen conjugates, six estrogens and two progestagens in surface water of the Santa Ana River. Samples at ten representative sites along t...

Mathematical and computational studies of equilibrium capillary free surfaces

NASA Technical Reports Server (NTRS)

Albright, N.; Chen, N. F.; Concus, P.; Finn, R.

1977-01-01

The results of several independent studies are presented. The general question is considered of whether a wetting liquid always rises higher in a small capillary tube than in a larger one, when both are dipped vertically into an infinite reservoir. An analytical investigation is initiated to determine the qualitative behavior of the family of solutions of the equilibrium capillary free-surface equation that correspond to rotationally symmetric pendent liquid drops and the relationship of these solutions to the singular solution, which corresponds to an infinite spike of liquid extending downward to infinity. The block successive overrelaxation-Newton method and the generalized conjugate gradient method are investigated for solving the capillary equation on a uniform square mesh in a square domain, including the case for which the solution is unbounded at the corners. Capillary surfaces are calculated on the ellipse, on a circle with reentrant notches, and on other irregularly shaped domains using JASON, a general purpose program for solving nonlinear elliptic equations on a nonuniform quadrilaterial mesh. Analytical estimates for the nonexistence of solutions of the equilibrium capillary free-surface equation on the ellipse in zero gravity are evaluated.

The dynamics and control of large flexible space structures, 3. Part A: Shape and orientation control of a platform in orbit using point actuators

NASA Technical Reports Server (NTRS)

Bainum, P. M.; Reddy, A. S. S. R.; Krishna, R.; James, P. K.

1980-01-01

The dynamics, attitude, and shape control of a large thin flexible square platform in orbit are studied. Attitude and shape control are assumed to result from actuators placed perpendicular to the main surface and one edge and their effect on the rigid body and elastic modes is modelled to first order. The equations of motion are linearized about three different nominal orientations: (1) the platform following the local vertical with its major surface perpendicular to the orbital plane; (2) the platform following the local horizontal with its major surface normal to the local vertical; and (3) the platform following the local vertical with its major surface perpendicular to the orbit normal. The stability of the uncontrolled system is investigated analytically. Once controllability is established for a set of actuator locations, control law development is based on decoupling, pole placement, and linear optimal control theory. Frequencies and elastic modal shape functions are obtained using a finite element computer algorithm, two different approximate analytical methods, and the results of the three methods compared.

Analytical derivatives of the individual state energies in ensemble density functional theory method. I. General formalism

DOE PAGES

Filatov, Michael; Liu, Fang; Martínez, Todd J.

2017-07-21

The state-averaged (SA) spin restricted ensemble referenced Kohn-Sham (REKS) method and its state interaction (SI) extension, SI-SA-REKS, enable one to describe correctly the shape of the ground and excited potential energy surfaces of molecules undergoing bond breaking/bond formation reactions including features such as conical intersections crucial for theoretical modeling of non-adiabatic reactions. Until recently, application of the SA-REKS and SI-SA-REKS methods to modeling the dynamics of such reactions was obstructed due to the lack of the analytical energy derivatives. Here, the analytical derivatives of the individual SA-REKS and SI-SA-REKS energies are derived. The final analytic gradient expressions are formulated entirelymore » in terms of traces of matrix products and are presented in the form convenient for implementation in the traditional quantum chemical codes employing basis set expansions of the molecular orbitals. Finally, we will describe the implementation and benchmarking of the derived formalism in a subsequent article of this series.« less

Enhancing reproducibility of SALDI MS detection by concentrating analytes within laser spot.

PubMed

Teng, Fei; Zhu, Qunyan; Wang, Yalei; Du, Juan; Lu, Nan

2018-03-01

Surface-assisted laser desorption/ionization time-of-flight mass spectrometry (SALDI TOF MS) has become one of the most important analytical methods due to its less interference at low molecular weight range. However, it is still a challenge to obtain a good reproducibility of SALDI TOF MS because of the inhomogeneous distribution of analyte molecules induced by coffee ring effect. We propose a universal and reliable method to eliminate the coffee ring effect by concentrating all the analyte molecules within the laser spot. This method exhibits an excellent reproducibility of spot-to-spot and substrate-to-substrate, and the relative standard deviations (RSDs) for different concentrations are lower than 12.6%. It also performs good linear dependency (R 2 > 0.98) in the log-log plot with the concentration range of 1nM to 1μM, and the limit of detection for R6G is down to 1fmol. Copyright © 2017 Elsevier B.V. All rights reserved.

Ball assisted device for analytical surface sampling

DOEpatents

ElNaggar, Mariam S; Van Berkel, Gary J; Covey, Thomas R

2015-11-03

A system for sampling a surface includes a sampling probe having a housing and a socket, and a rolling sampling sphere within the socket. The housing has a sampling fluid supply conduit and a sampling fluid exhaust conduit. The sampling fluid supply conduit supplies sampling fluid to the sampling sphere. The sampling fluid exhaust conduit has an inlet opening for receiving sampling fluid carried from the surface by the sampling sphere. A surface sampling probe and a method for sampling a surface are also disclosed.

Reconnaissance survey of sulfonamide, sulfonylurea, and imidazolinone herbicides in surface streams and groundwater of the Midwestern United States

USGS Publications Warehouse

Steinheimer, T.R.; Pfeiffer, R.L.; Scoggin, K.D.; Battaglin, W.A.

2000-01-01

The study objective was to conduct a small scale synoptic survey of representative water resources draining agricultural land for occurrence of several herbicide residues. These new classes of herbicides are commonly applied pre-emergence or post-emergence in conservation tillage systems to control grasses and broadleaf weeds in cropped and noncropped areas. Both surface water and groundwater samples were collected from 44 midwestern locations during the summer of 1997, and analyzed for herbicide residues of 15 sulfonylurea and imidazolinone chemicals, and one sulfonamide. Each site was sampled between mid-June and late-October with several stream sites sampled twice. The method, developed jointly by the chemical manufacturer's and the U.S. Environmental Protection Agency, provides a 100 ng/L limit of quantitation in surface water for all analytes. Analytes were detected and identity confirmed in surface water at six sites and in ground water at two sites. The most frequently detected herbicides were imazaquin, imazethapyr, and nicosulfuron. For field studies in which the source of surface and ground water associated with the farming system on the agricultural landscape is known, the sensitivity of the method can be improved with only minor modifications in detection criteria.

Validation of Direct Analysis Real Time source/Time-of-Flight Mass Spectrometry for organophosphate quantitation on wafer surface.

PubMed

Hayeck, Nathalie; Ravier, Sylvain; Gemayel, Rachel; Gligorovski, Sasho; Poulet, Irène; Maalouly, Jacqueline; Wortham, Henri

2015-11-01

Microelectronic wafers are exposed to airborne molecular contamination (AMC) during the fabrication process of microelectronic components. The organophosphate compounds belonging to the dopant group are one of the most harmful groups. Once adsorbed on the wafer surface these compounds hardly desorb and could diffuse in the bulk of the wafer and invert the wafer from p-type to n-type. The presence of these compounds on wafer surface could have electrical effect on the microelectronic components. For these reasons, it is of importance to control the amount of these compounds on the surface of the wafer. As a result, a fast quantitative and qualitative analytical method, nondestructive for the wafers, is needed to be able to adjust the process and avoid the loss of an important quantity of processed wafers due to the contamination by organophosphate compounds. Here we developed and validated an analytical method for the determination of organic compounds adsorbed on the surface of microelectronic wafers using the Direct Analysis in Real Time-Time of Flight-Mass Spectrometry (DART-ToF-MS) system. Specifically, the developed methodology concerns the organophosphate group. Copyright © 2015 Elsevier B.V. All rights reserved.

Analytical solutions of the planar cyclic voltammetry process for two soluble species with equal diffusivities and fast electron transfer using the method of eigenfunction expansions

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

Samin, Adib; Lahti, Erik; Zhang, Jinsuo, E-mail: zhang.3558@osu.edu

Cyclic voltammetry is a powerful tool that is used for characterizing electrochemical processes. Models of cyclic voltammetry take into account the mass transport of species and the kinetics at the electrode surface. Analytical solutions of these models are not well-known due to the complexity of the boundary conditions. In this study we present closed form analytical solutions of the planar voltammetry model for two soluble species with fast electron transfer and equal diffusivities using the eigenfunction expansion method. Our solution methodology does not incorporate Laplace transforms and yields good agreement with the numerical solution. This solution method can be extendedmore » to cases that are more general and may be useful for benchmarking purposes.« less

Heat transfer to and from vegetated surfaces - An analytical method for the bulk exchange coefficients

NASA Technical Reports Server (NTRS)

Massman, William J.

1987-01-01

The semianalytical model outlined in a previous study (Massman, 1987) to describe momentum exchange between the atmosphere and vegetated surfaces is extended to include the exchange of heat. The methods employed are based on one-dimensional turbulent diffusivities, and use analytical solutions to the steady-state diffusion equation. The model is used to assess the influence that the canopy foliage structure and density, the wind profile structure within the canopy, and the shelter factor can have upon the inverse surface Stanton number (kB exp -1), as well as to explore the consequences of introducing a scalar displacement height which can be different from the momentum displacement height. In general, the triangular foliage area density function gives results which agree more closely with observations than that for constant foliage area density. The intended application of this work is for parameterizing the bulk aerodynamic resistances for heat and momentum exchange for use within large-scale models of plant-atmosphere exchanges.

Application of surface analytical methods in thin film analysis

NASA Astrophysics Data System (ADS)

Wen, Xingu

Self-assembly and the sol-gel process are two promising methods for the preparation of novel materials and thin films. In this research, these two methods were utilized to prepare two types of thin films: self-assembled monolayers of peptides on gold and SiO2 sol-gel thin films modified with Ru(II) complexes. The properties of the resulting thin films were investigated by several analytical techniques in order to explore their potential applications in biomaterials, chemical sensors, nonlinear optics and catalysis. Among the analytical techniques employed in the study, surface analytical techniques, such as X-ray photoelectron spectroscopy (XPS) and grazing angle reflection absorption Fourier transform infrared spectroscopy (RA-FTIR), are particularly useful in providing information regarding the compositions and structures of the thin films. In the preparation of peptide thin films, monodisperse peptides were self-assembled on gold substrate via the N-terminus-coupled lipoic acid. The film compositions were investigated by XPS and agreed well with the theoretical values. XPS results also revealed that the surface coverage of the self-assembled films was significantly larger than that of the physisorbed films and that the chemisorption between the peptides and gold surface was stable in solvent. Studies by angle dependent XPS (ADXPS) and grazing angle RA-FTIR indicated that the peptides were on average oriented at a small angle from the surface normal. By using a model of orientation distribution function, both the peptide tilt angle and film thickness can be well calculated. Ru(II) complex doped SiO2 sol-gel thin films were prepared by low temperature sol-gel process. The ability of XPS coupled with Ar + ion sputtering to provide both chemical and compositional depth profile information of these sol-gel films was evaluated. This technique, together with UV-VIS and electrochemical measurements, was used to investigate the stability of Ru complexes in the composite films. The stability of Ru complexes with respect to dopant leaching was dependent on the film microstructures. Three methods aiming to improve the dopant stability were also explored. In addition, the ion exchange properties of the composite films, upon exposure to various ions in aqueous solutions, were investigated by XPS, and the ion exchange mechanism was elucidated.

Functional Interfaces Constructed by Controlled/Living Radical Polymerization for Analytical Chemistry.

PubMed

Wang, Huai-Song; Song, Min; Hang, Tai-Jun

2016-02-10

The high-value applications of functional polymers in analytical science generally require well-defined interfaces, including precisely synthesized molecular architectures and compositions. Controlled/living radical polymerization (CRP) has been developed as a versatile and powerful tool for the preparation of polymers with narrow molecular weight distributions and predetermined molecular weights. Among the CRP system, atom transfer radical polymerization (ATRP) and reversible addition-fragmentation chain transfer (RAFT) are well-used to develop new materials for analytical science, such as surface-modified core-shell particles, monoliths, MIP micro- or nanospheres, fluorescent nanoparticles, and multifunctional materials. In this review, we summarize the emerging functional interfaces constructed by RAFT and ATRP for applications in analytical science. Various polymers with precisely controlled architectures including homopolymers, block copolymers, molecular imprinted copolymers, and grafted copolymers were synthesized by CRP methods for molecular separation, retention, or sensing. We expect that the CRP methods will become the most popular technique for preparing functional polymers that can be broadly applied in analytical chemistry.

Participant Interaction in Asynchronous Learning Environments: Evaluating Interaction Analysis Methods

ERIC Educational Resources Information Center

Blanchette, Judith

2012-01-01

The purpose of this empirical study was to determine the extent to which three different objective analytical methods--sequence analysis, surface cohesion analysis, and lexical cohesion analysis--can most accurately identify specific characteristics of online interaction. Statistically significant differences were found in all points of…

Spiral wound extraction cartridge

DOEpatents

Wisted, Eric E.; Lundquist, Susan H.

1999-01-01

A cartridge device for removing an analyte from a fluid comprises a hollow core, a sheet composite comprising a particulate-loaded porous membrane and optionally at least one reinforcing spacer sheet, the particulate being capable of binding the analyte, the sheet composite being formed into a spiral configuration about the core, wherein the sheet composite is wound around itself and wherein the windings of sheet composite are of sufficient tightness so that adjacent layers are essentially free of spaces therebetween, two end caps which are disposed over the core and the lateral ends of the spirally wound sheet composite, and means for securing the end caps to the core, the end caps also being secured to the lateral ends of the spirally wound sheet composite. A method for removing an analyte from a fluid comprises the steps of providing a spirally wound element of the invention and passing the fluid containing the analyte through the element essentially normal to a surface of the sheet composite so as to bind the analyte to the particulate of the particulate-loaded porous membrane, the method optionally including the step of eluting the bound analyte from the sheet composite.

Sound Emission of Rotor Induced Deformations of Generator Casings

NASA Technical Reports Server (NTRS)

Polifke, W.; Mueller, B.; Yee, H. C.; Mansour, Nagi (Technical Monitor)

2001-01-01

The casing of large electrical generators can be deformed slightly by the rotor's magnetic field. The sound emission produced by these periodic deformations, which could possibly exceed guaranteed noise emission limits, is analysed analytically and numerically. From the deformation of the casing, the normal velocity of the generator's surface is computed. Taking into account the corresponding symmetry, an analytical solution for the acoustic pressure outside the generator is round in terms of the Hankel function of second order. The normal velocity or the generator surface provides the required boundary condition for the acoustic pressure and determines the magnitude of pressure oscillations. For the numerical simulation, the nonlinear 2D Euler equations are formulated In a perturbation form for low Mach number Computational Aeroacoustics (CAA). The spatial derivatives are discretized by the classical sixth-order central interior scheme and a third-order boundary scheme. Spurious high frequency oscillations are damped by a characteristic-based artificial compression method (ACM) filter. The time derivatives are approximated by the classical 4th-order Runge-Kutta method. The numerical results are In excellent agreement with the analytical solution.

Method and apparatus for selective capture of gas phase analytes using metal .beta.-diketonate polymers

DOEpatents

Harvey, Scott D [Kennewick, WA

2011-06-21

A process and sensor device are disclosed that employ metal .beta.-diketonate polymers to selectively capture gas-phase explosives and weaponized chemical agents in a sampling area or volume. The metal .beta.-diketonate polymers can be applied to surfaces in various analytical formats for detection of: improvised explosive devices, unexploded ordinance, munitions hidden in cargo holds, explosives, and chemical weapons in public areas.

Comparison of analytical and experimental steadyand unsteady-pressure distributions at Mach number 0.78 for a high-aspect-ratio supercritical wing model with oscillating control surfaces

NASA Technical Reports Server (NTRS)

Mccain, W. E.

1984-01-01

The unsteady aerodynamic lifting surface theory, the Doublet Lattice method, with experimental steady and unsteady pressure measurements of a high aspect ratio supercritical wing model at a Mach number of 0.78 were compared. The steady pressure data comparisons were made for incremental changes in angle of attack and control surface deflection. The unsteady pressure data comparisons were made at set angle of attack positions with oscillating control surface deflections. Significant viscous and transonic effects in the experimental aerodynamics which cannot be predicted by the Doublet Lattice method are shown. This study should assist development of empirical correction methods that may be applied to improve Doublet Lattice calculations of lifting surface aerodynamics.

Monitoring the Presence of 13 Active Compounds in Surface Water Collected from Rural Areas in Northwestern Spain

PubMed Central

Iglesias, Alejandra; Nebot, Carolina; Vázquez, Beatriz I.; Coronel-Olivares, Claudia; Franco Abuín, Carlos M.; Cepeda, Alberto

2014-01-01

Drug residues are considered environmental contaminants, and their occurrence has recently become a matter of concern. Analytical methods and monitoring systems are therefore required to control the continuous input of these drug residues into the environment. This article presents a suitable HPLC-ESI-MS/MS method for the simultaneous extraction, detection and quantification of residues of 13 drugs (antimicrobials, glucocorticosteroids, anti-inflammatories, anti-hypertensives, anti-cancer drugs and triphenylmethane dyes) in surface water. A monitoring study with 549 water samples was carried out in northwestern Spain to detect the presence of drug residues over two sampling periods during 2010, 2011 and 2012. Samples were collected from rural areas with and without farming activity and from urban areas. The 13 analytes were detected, and 18% of the samples collected showed positive results for the presence of at least one analyte. More collection sites were located in rural areas than in urban areas. However, more positive samples with higher concentrations and a larger number of analytes were detected in samples collected from sites located after the discharge of a WWTP. Results indicated that the WWTPs seems to act as a concentration point. Positive samples were also detected at a site located near a drinking water treatment plant. PMID:24837665

Monitoring the presence of 13 active compounds in surface water collected from rural areas in northwestern Spain.

PubMed

Iglesias, Alejandra; Nebot, Carolina; Vázquez, Beatriz I; Coronel-Olivares, Claudia; Abuín, Carlos M Franco; Cepeda, Alberto

2014-05-15

Drug residues are considered environmental contaminants, and their occurrence has recently become a matter of concern. Analytical methods and monitoring systems are therefore required to control the continuous input of these drug residues into the environment. This article presents a suitable HPLC-ESI-MS/MS method for the simultaneous extraction, detection and quantification of residues of 13 drugs (antimicrobials, glucocorticosteroids, anti-inflammatories, anti-hypertensives, anti-cancer drugs and triphenylmethane dyes) in surface water. A monitoring study with 549 water samples was carried out in northwestern Spain to detect the presence of drug residues over two sampling periods during 2010, 2011 and 2012. Samples were collected from rural areas with and without farming activity and from urban areas. The 13 analytes were detected, and 18% of the samples collected showed positive results for the presence of at least one analyte. More collection sites were located in rural areas than in urban areas. However, more positive samples with higher concentrations and a larger number of analytes were detected in samples collected from sites located after the discharge of a WWTP. Results indicated that the WWTPs seems to act as a concentration point. Positive samples were also detected at a site located near a drinking water treatment plant.

Semi-permeable surface analytical reversed-phase column for the improved trace analysis of acidic pesticides in water with coupled-column reversed-phase liquid chromatography with UV detection. Determination of bromoxynil and bentazone in surface water.

PubMed

Hogendoorn, E A; Westhuis, K; Dijkman, E; Heusinkveld, H A; den Boer, A C; Evers, E A; Baumann, R A

1999-10-08

The coupled-column (LC-LC) configuration consisting of a 3 microm C18 column (50 x 4.6 mm I.D.) as the first column and a 5 microm C18 semi-permeable-surface (SPS) column (150 x 4.6 mm I.D.) as the second column appeared to be successful for the screening of acidic pesticides in surface water samples. In comparison to LC-LC employing two C18 columns, the combination of C18/SPS-C18 significantly decreased the baseline deviation caused by the hump of the co-extracted humic substances when using UV detection (217 nm). The developed LC-LC procedure allowed the simultaneous determination of the target analytes bentazone and bromoxynil in uncleaned extracts of surface water samples to a level of 0.05 microg/l in less than 15 min. In combination with a simple solid-phase extraction step (200 ml of water on a 500 mg C18-bonded silica) the analytical procedure provides a high sample throughput. During a period of about five months more than 200 ditch-water samples originating from agricultural locations were analyzed with the developed procedure. Validation of the method was performed by randomly analyzing recoveries of water samples spiked at levels of 0.1 microg/l (n=10), 0.5 microg/l (n=7) and 2.5 microg/l (n=4). Weighted regression of the recovery data showed that the method provides overall recoveries of 95 and 100% for bentazone and bromoxynil, respectively, with corresponding intra-laboratory reproducibilities of 10 and 11%, respectively. Confirmation of the analytes in part of the samples extracts was carried out with GC-negative ion chemical ionization MS involving a derivatization step with bis(trifluoromethyl)benzyl bromide. No false negatives or positives were observed.

Phononic band gaps and phase singularities in the ultrasonic response from toughened composites

NASA Astrophysics Data System (ADS)

Smith, Robert A.; Nelson, Luke J.; Mienczakowski, Martin J.

2018-04-01

Ultrasonic 3D characterization of ply-level features in layered composites, such as out-of-plane wrinkles and ply drops, is now possible with carefully applied analytic-signal analysis. Study of instantaneous amplitude, phase and frequency in the ultrasonic response has revealed some interesting effects, which become more problematic for 3D characterization as the inter-ply resin-layer thicknesses increase. In modern particle-toughened laminates, the thicker resin layers cause phase singularities to be observed; these are locations where the instantaneous amplitude is zero, so the instantaneous phase is undefined. The depth at which these occur has been observed experimentally to vary with resin- layer thickness, such that a phase-singularity surface is formed; beyond this surface, the ultrasonic response is reduced and significantly more difficult to interpret, so a method for removing the effect would be advantageous. The underlying physics has been studied using an analytical one-dimensional multi-layer model. This has been sufficient to determine that the cause is linked to a phononic band gap in the ultrasound transmitted through multiple equally-spaced partial reflectors. As a result, the phase singularity also depends on input-pulse center frequency and bandwidth. Various methods for overcoming the confusing effects in the data have been proposed and subsequently investigated using the analytical model. This paper will show experimental and modelled evidence of phase-singularities and phase-singularity surfaces, as well as the success of methods for reducing their effects.

Quantitative estimation of minimum offset for multichannel surface-wave survey with actively exciting source

USGS Publications Warehouse

Xu, Y.; Xia, J.; Miller, R.D.

2006-01-01

Multichannel analysis of surface waves is a developing method widely used in shallow subsurface investigations. The field procedures and related parameters are very important for successful applications. Among these parameters, the source-receiver offset range is seldom discussed in theory and normally determined by empirical or semi-quantitative methods in current practice. This paper discusses the problem from a theoretical perspective. A formula for quantitatively evaluating a layered homogenous elastic model was developed. The analytical results based on simple models and experimental data demonstrate that the formula is correct for surface wave surveys for near-surface applications. ?? 2005 Elsevier B.V. All rights reserved.

A calibration method for fringe reflection technique based on the analytical phase-slope description

NASA Astrophysics Data System (ADS)

Wu, Yuxiang; Yue, Huimin; Pan, Zhipeng; Liu, Yong

2018-05-01

The fringe reflection technique (FRT) has been one of the most popular methods to measure the shape of specular surface these years. The existing system calibration methods of FRT usually contain two parts, which are camera calibration and geometric calibration. In geometric calibration, the liquid crystal display (LCD) screen position calibration is one of the most difficult steps among all the calibration procedures, and its accuracy is affected by the factors such as the imaging aberration, the plane mirror flatness, and LCD screen pixel size accuracy. In this paper, based on the deduction of FRT analytical phase-slope description, we present a novel calibration method with no requirement to calibrate the position of LCD screen. On the other hand, the system can be arbitrarily arranged, and the imaging system can either be telecentric or non-telecentric. In our experiment of measuring the 5000mm radius sphere mirror, the proposed calibration method achieves 2.5 times smaller measurement error than the geometric calibration method. In the wafer surface measuring experiment, the measurement result with the proposed calibration method is closer to the interferometer result than the geometric calibration method.

A novel and sensitive fluorescence sensor for glutathione detection by controlling the surface passivation degree of carbon quantum dots.

PubMed

Pan, Jiahong; Zheng, Zengyao; Yang, Jianying; Wu, Yaoyu; Lu, Fushen; Chen, Yaowen; Gao, Wenhua

2017-05-01

A novel fluorescence sensor based on controlling the surface passivation degree of carbon quantum dots (CQDs) was developed for glutathione (GSH) detection. First, we found that the fluorescence intensity of the CQDs which was obtained by directly pyrolyzing citric acid would increased largely after the surface passivation treatment by 1-ethyl-3-(3-dimethylaminopropyl)-carbodiimide (EDC). In the light of this phenomenon, we designed a simple, rapid and selective fluorescence sensor based on the surface passivated CQDs. A certain and excess amount of EDC were mixed with GSH, part of EDC would form a stable complex with GSH owing to the exposed sulfhydryl group of GSH. As the synthesized CQDs were added into the above mixture solution, the fluorescence intensity of the (EDC/GSH)/CQDs mixture solution could be directly related to the amount of GSH. Compared to other fluorescence analytical methods, the fluorescence sensor we design is neither the traditional fluorescent "turn on" probes nor "turn off" probes. It is a new fluorescence analytical method that target object indirectly control the surface passivation degree of CQDs so that it can realize the detection of the target object. Moreover, the proposed method manifested great advantages including short analysis time, low cost and ease of operation. Copyright © 2017 Elsevier B.V. All rights reserved.

Multi-phase-field method for surface tension induced elasticity

NASA Astrophysics Data System (ADS)

Schiedung, Raphael; Steinbach, Ingo; Varnik, Fathollah

2018-01-01

A method, based on the multi-phase-field framework, is proposed that adequately accounts for the effects of a coupling between surface free energy and elastic deformation in solids. The method is validated via a number of analytically solvable problems. In addition to stress states at mechanical equilibrium in complex geometries, the underlying multi-phase-field framework naturally allows us to account for the influence of surface energy induced stresses on phase transformation kinetics. This issue, which is of fundamental importance on the nanoscale, is demonstrated in the limit of fast diffusion for a solid sphere, which melts due to the well-known Gibbs-Thompson effect. This melting process is slowed down when coupled to surface energy induced elastic deformation.

Development and validation of a highly sensitive gas chromatographic-mass spectrometric screening method for the simultaneous determination of nanogram levels of fentanyl, sufentanil and alfentanil in air and surface contamination wipes.

PubMed

Van Nimmen, Nadine F J; Veulemans, Hendrik A F

2004-05-07

A highly sensitive gas chromatographic-mass spectrometric (GC-MS) analytical method for the determination of the opioid narcotics fentanyl, alfentanil, and sufentanil in industrial hygiene personal air samples and surface contamination wipes was developed and comprehensively validated. Sample preparation involved a single step extraction of the samples with methanol, fortified with a fixed amount of the penta-deuterated analogues of the opioid narcotics as internal standard. The GC-MS analytical procedure using selected ion monitoring (SIM) was shown to be highly selective. Linearity was shown for levels of extracted wipe and air samples corresponding to at least 0.1-2 times their surface contamination limit (SCL) and accordingly to 0.1-2 times their time weighted average occupational exposure limit (OEL-TWA) based on a full shift 9601 air sample. Extraction recoveries were determined for spiked air samples and surface wipes and were found to be quantitative for both sampling media in the entire range studied. The air sampling method's limit of detection (LOD) was determined to be 0.4 ng per sample for fentanyl and sufentanil and 1.6 ng per sample for alfentanil, corresponding to less than 1% of their individual OEL for a full shift air sample (9601). The limit of quantification (LOQ) was found to be 1.4, 1.2, and 5.0 ng per filter for fentanyl, sufentanil, and alfentanil, respectively. The wipe sampling method had LODs of 4 ng per wipe for fentanyl and sufentanil and 16 ng per wipe for alfentanil and LOQs of respectively, 14, 12, and 50 ng per wipe. The analytical intra-assay precision of the air sampling and wipe sampling method, defined as the coefficient of variation on the analytical result of six replicate spiked media was below 10 and 5%, respectively, for all opioids at all spike levels. Accuracy expressed as relative error was determined to be below 10%, except for alfentanil at the lowest spike level (-13.1%). The stability of the opioids during simulated air sampling was investigated. For fentanyl and sufentanil a quantitative recovery was observed at all spike levels, while for alfentanil recoveries ranged from 60.3 to 85.4%. When spiked air samples were stored at ambient temperature and at -15 degrees C quantitative recovery was found for fentanyl and sufentanil after 7 and 14 days. For alfentanil a slight loss seemed to occur upon storage during 7 days, being more explicit after 14 days. Ambient storage of spiked wipes seemed to lead to significant losses of all opioids studied, yielding recoveries of 37.7-88.3%. Upon storage of similar wipes at -15 degrees C a significantly higher recovery was found ranging from 77.3 to 88.3%. The developed analytical and sampling procedures have been recently applied in an explorative field study of which the results of surface contamination wipe sampling are presented in this paper. To our knowledge, this is the first study addressing the development and validation of analytical procedures for the assessment of external occupational exposure to potent opioid narcotics.

Analysis of discontinuities across thin inhomogeneities, groundwater/surface water interactions in river networks, and circulation about slender bodies using slit elements in the Analytic Element Method

USDA-ARS?s Scientific Manuscript database

Groundwater and surface water contain interfaces across which hydrologic functions are discontinuous. Thin elements with high hydraulic conductivity in a porous media focus groundwater, which flows through such inhomogeneities and causes an abrupt change in stream function across their interfaces, a...

Toxin Detection by Surface Plasmon Resonance

PubMed Central

Hodnik, Vesna; Anderluh, Gregor

2009-01-01

Significant efforts have been invested in the past years for the development of analytical methods for fast toxin detection in food and water. Immunochemical methods like ELISA, spectroscopy and chromatography are the most used in toxin detection. Different methods have been linked, e.g. liquid chromatography and mass spectrometry (LC-MS), in order to detect as low concentrations as possible. Surface plasmon resonance (SPR) is one of the new biophysical methods which enables rapid toxin detection. Moreover, this method was already included in portable sensors for on-site determinations. In this paper we describe some of the most common methods for toxin detection, with an emphasis on SPR. PMID:22573957

Develop cost effective field monitoring and laboratory methods to measure groups of contaminants of emerging concern and/or legacy chemicals and pathogens

EPA Science Inventory

Analytical chemistry methods were developed to quantify numerous emerging contaminants (ECs), such as pharmaceuticals (i.e., tamoxifen, tamoxifen metabolites, aromatase inhibitors, antibiotics, illicit drugs, over-the-counter drugs) in aqueous samples (wastewater, surface waters)...

Improving the Analysis of Anthocyanidins from Blueberries Using Response Surface Methodology

USDA-ARS?s Scientific Manuscript database

Background: Recent interest in the health promoting potential of anthocyanins points to the need for robust and reliable analytical methods. It is essential to know that the health promoting chemicals are present in juices and other products processed from whole fruit. Many different methods have be...

Local Modelling of Groundwater Flow Using Analytic Element Method Three-dimensional Transient Unconfined Groundwater Flow With Partially Penetrating Wells and Ellipsoidal Inhomogeneites

NASA Astrophysics Data System (ADS)

Jankovic, I.; Barnes, R. J.; Soule, R.

2001-12-01

The analytic element method is used to model local three-dimensional flow in the vicinity of partially penetrating wells. The flow domain is bounded by an impermeable horizontal base, a phreatic surface with recharge and a cylindrical lateral boundary. The analytic element solution for this problem contains (1) a fictitious source technique to satisfy the head and the discharge conditions along the phreatic surface, (2) a fictitious source technique to satisfy specified head conditions along the cylindrical boundary, (3) a method of imaging to satisfy the no-flow condition across the impermeable base, (4) the classical analytic solution for a well and (5) spheroidal harmonics to account for the influence of the inhomogeneities in hydraulic conductivity. Temporal variations of the flow system due to time-dependent recharge and pumping are represented by combining the analytic element method with a finite difference method: analytic element method is used to represent spatial changes in head and discharge, while the finite difference method represents temporal variations. The solution provides a very detailed description of local groundwater flow with an arbitrary number of wells of any orientation and an arbitrary number of ellipsoidal inhomogeneities of any size and conductivity. These inhomogeneities may be used to model local hydrogeologic features (such as gravel packs and clay lenses) that significantly influence the flow in the vicinity of partially penetrating wells. Several options for specifying head values along the lateral domain boundary are available. These options allow for inclusion of the model into steady and transient regional groundwater models. The head values along the lateral domain boundary may be specified directly (as time series). The head values along the lateral boundary may also be assigned by specifying the water-table gradient and a head value at a single point (as time series). A case study is included to demonstrate the application of the model in local modeling of the groundwater flow. Transient three-dimensional capture zones are delineated for a site on Prairie Island, MN. Prairie Island is located on the Mississippi River 40 miles south of the Twin Cities metropolitan area. The case study focuses on a well that has been known to contain viral DNA. The objective of the study was to assess the potential for pathogen migration toward the well.

Quantitative determination of BAF312, a S1P-R modulator, in human urine by LC-MS/MS: prevention and recovery of lost analyte due to container surface adsorption.

PubMed

Li, Wenkui; Luo, Suyi; Smith, Harold T; Tse, Francis L S

2010-02-15

Analyte loss due to non-specific binding, especially container surface adsorption, is not uncommon in the quantitative analysis of urine samples. In developing a sensitive LC-MS/MS method for the determination of a drug candidate, BAF312, in human urine, a simple procedure was outlined for identification, confirmation and prevention of analyte non-specific binding to a container surface and to recover the 'non-specific loss' of an analyte, if no transfer has occurred to the original urine samples. Non-specific binding or container surface adsorption can be quickly identified by using freshly spiked urine calibration standards and pre-pooled QC samples during a LC-MS/MS feasibility run. The resulting low recovery of an analyte in urine samples can be prevented through the use of additives, such as the non-ionic surfactant Tween-80, CHAPS and others, to the container prior to urine sample collection. If the urine samples have not been transferred from the bulk container, the 'non-specific binding' of an analyte to the container surface can be reversed by the addition of a specified amount of CHAPS, Tween-80 or bovine serum albumin, followed by appropriate mixing. Among the above agents, Tween-80 is the most cost-effective. beta-cyclodextrin may be suitable in stabilizing the analyte of interest in urine via pre-treating the matrix with the agent. However, post-addition of beta-cyclodextrin to untreated urine samples does not recover the 'lost' analyte due to non-specific binding or container surface adsorption. In the case of BAF312, a dynamic range of 0.0200-20.0 ng/ml in human urine was validated with an overall accuracy and precision for QC sample results ranging from -3.2 to 5.1% (bias) and 3.9 to 10.2% (CV), respectively. Pre- and post-addition of 0.5% (v/v) Tween-80 to the container provided excellent overall analyte recovery and minimal MS signal suppression when a liquid-liquid extraction in combination with an isocratic LC separation was employed. The compound was stable in 0.5% Tween-80 treated human urine QC samples for at least 24 h at room temperature, after three freeze/thaw cycles with storage at < or =-60 degrees C and for at least 3 months when stored at < or =-60 degrees C. The current work could serve as a simple example in trouble shooting non-specific binding or container surface adsorption in quantitative analysis of urine samples. Copyright 2010. Published by Elsevier B.V.

Free-form surface design method for a collimator TIR lens.

PubMed

Tsai, Chung-Yu

2016-04-01

A free-form (FF) surface design method is proposed for a general axial-symmetrical collimator system consisting of a light source and a total internal reflection lens with two coupled FF boundary surfaces. The profiles of the boundary surfaces are designed using a FF surface construction method such that each incident ray is directed (refracted and reflected) in such a way as to form a specified image pattern on the target plane. The light ray paths within the system are analyzed using an exact analytical model and a skew-ray tracing approach. In addition, the validity of the proposed FF design method is demonstrated by means of ZEMAX simulations. It is shown that the illumination distribution formed on the target plane is in good agreement with that specified by the user. The proposed surface construction method is mathematically straightforward and easily implemented in computer code. As such, it provides a useful tool for the design and analysis of general axial-symmetrical optical systems.

An analytical drain current model for symmetric double-gate MOSFETs

NASA Astrophysics Data System (ADS)

Yu, Fei; Huang, Gongyi; Lin, Wei; Xu, Chuanzhong

2018-04-01

An analytical surface-potential-based drain current model of symmetric double-gate (sDG) MOSFETs is described as a SPICE compatible model in this paper. The continuous surface and central potentials from the accumulation to the strong inversion regions are solved from the 1-D Poisson's equation in sDG MOSFETs. Furthermore, the drain current is derived from the charge sheet model as a function of the surface potential. Over a wide range of terminal voltages, doping concentrations, and device geometries, the surface potential calculation scheme and drain current model are verified by solving the 1-D Poisson's equation based on the least square method and using the Silvaco Atlas simulation results and experimental data, respectively. Such a model can be adopted as a useful platform to develop the circuit simulator and provide the clear understanding of sDG MOSFET device physics.

Modeling the propagation of electromagnetic waves over the surface of the human body

NASA Astrophysics Data System (ADS)

Vendik, I. B.; Vendik, O. G.; Kirillov, V. V.; Pleskachev, V. V.; Tural'chuk, P. A.

2016-12-01

The results of modeling and an experimental study of electromagnetic (EM) waves in microwave range propagating along the surface of the human body have been presented. The parameters of wave propagation, such as the attenuation and phase velocity, have also been investigated. The calculation of the propagation of EM waves by the numerical method FDTD (finite difference time domain), as well as the use of the analytical model of the propagation of the EM wave along flat and curved surfaces has been fulfilled. An experimental study on a human body has been conducted. It has been shown that creeping waves are slow and exhibit a noticeable dispersion, while the surface waves are dispersionless and propagate at the speed of light in free space. A comparison of the results of numerical simulation, analytical calculation, and experimental investigations at a frequency of 2.55 GHz has been carried out.

A screening tool for delineating subregions of steady recharge within groundwater models

USGS Publications Warehouse

Dickinson, Jesse; Ferré, T.P.A.; Bakker, Mark; Crompton, Becky

2014-01-01

We have developed a screening method for simplifying groundwater models by delineating areas within the domain that can be represented using steady-state groundwater recharge. The screening method is based on an analytical solution for the damping of sinusoidal infiltration variations in homogeneous soils in the vadose zone. The damping depth is defined as the depth at which the flux variation damps to 5% of the variation at the land surface. Groundwater recharge may be considered steady where the damping depth is above the depth of the water table. The analytical solution approximates the vadose zone diffusivity as constant, and we evaluated when this approximation is reasonable. We evaluated the analytical solution through comparison of the damping depth computed by the analytic solution with the damping depth simulated by a numerical model that allows variable diffusivity. This comparison showed that the screening method conservatively identifies areas of steady recharge and is more accurate when water content and diffusivity are nearly constant. Nomograms of the damping factor (the ratio of the flux amplitude at any depth to the amplitude at the land surface) and the damping depth were constructed for clay and sand for periodic variations between 1 and 365 d and flux means and amplitudes from nearly 0 to 1 × 10−3 m d−1. We applied the screening tool to Central Valley, California, to identify areas of steady recharge. A MATLAB script was developed to compute the damping factor for any soil and any sinusoidal flux variation.

Spatiotemporal and geometric optimization of sensor arrays for detecting analytes fluids

DOEpatents

Lewis, Nathan S.; Freund, Michael S.; Briglin, Shawn M.; Tokumaru, Phil; Martin, Charles R.; Mitchell, David T.

2006-10-17

Sensor arrays and sensor array systems for detecting analytes in fluids. Sensors configured to generate a response upon introduction of a fluid containing one or more analytes can be located on one or more surfaces relative to one or more fluid channels in an array. Fluid channels can take the form of pores or holes in a substrate material. Fluid channels can be formed between one or more substrate plates. Sensor can be fabricated with substantially optimized sensor volumes to generate a response having a substantially maximized signal to noise ratio upon introduction of a fluid containing one or more target analytes. Methods of fabricating and using such sensor arrays and systems are also disclosed.

Spatiotemporal and geometric optimization of sensor arrays for detecting analytes in fluids

DOEpatents

Lewis, Nathan S [La Canada, CA; Freund, Michael S [Winnipeg, CA; Briglin, Shawn S [Chittenango, NY; Tokumaru, Phillip [Moorpark, CA; Martin, Charles R [Gainesville, FL; Mitchell, David [Newtown, PA

2009-09-29

Sensor arrays and sensor array systems for detecting analytes in fluids. Sensors configured to generate a response upon introduction of a fluid containing one or more analytes can be located on one or more surfaces relative to one or more fluid channels in an array. Fluid channels can take the form of pores or holes in a substrate material. Fluid channels can be formed between one or more substrate plates. Sensor can be fabricated with substantially optimized sensor volumes to generate a response having a substantially maximized signal to noise ratio upon introduction of a fluid containing one or more target analytes. Methods of fabricating and using such sensor arrays and systems are also disclosed.

Analysis of haloacetic acids, bromate, and dalapon in natural waters by ion chromatography-tandem mass spectrometry.

PubMed

Wu, Shimin; Anumol, Tarun; Gandhi, Jay; Snyder, Shane A

2017-03-03

The addition of oxidants for disinfecting water can lead to the formation of potentially carcinogenic compounds referred to as disinfection byproducts (DBPs). Haloacetic acids (HAAs) are one of the most widely detected DBPs in US water utilities and some of them are regulated by the US Environmental Protection Agency (USEPA). The present study developed a method to analyze all the compounds in the USEPA method 557 (nine HAAs, bromate and dalapon) plus four potentially more toxic iodinated HAAs in water by coupling ion chromatography with tandem mass spectrometry (IC-MS/MS). This aqueous direct injection method has significant advantages over traditional GC methods, which require a derivatization and sample extraction that are laborious, time-consuming, and can negatively impact reproducibility. The method developed in this study requires half the time of the current USEPA method 557 on IC-MS/MS while including more compounds and achieving sub-μg/L level method detection limits (MDLs) for all 15 target analytes. The single laboratory lowest concentration minimum reporting level (LCMRL) has also been determined in reagent water, which ranged from 0.011 to 0.62μg/L for the analytes. The mean recoveries of the analytes during matrix spike recovery tests were 77-125% in finished drinking water and 81-112% in surface water. This method was then applied to untreated, chlorinated, and chloraminated groundwater and surface water samples. Bromate and 9 HAAs were detected at different levels in some of these samples. Copyright © 2017 Elsevier B.V. All rights reserved.

Advances in spectroscopic methods for quantifying soil carbon

USGS Publications Warehouse

Reeves, James B.; McCarty, Gregory W.; Calderon, Francisco; Hively, W. Dean

2012-01-01

The current gold standard for soil carbon (C) determination is elemental C analysis using dry combustion. However, this method requires expensive consumables, is limited by the number of samples that can be processed (~100/d), and is restricted to the determination of total carbon. With increased interest in soil C sequestration, faster methods of analysis are needed, and there is growing interest in methods based on diffuse reflectance spectroscopy in the visible, near-infrared or mid-infrared spectral ranges. These spectral methods can decrease analytical requirements and speed sample processing, be applied to large landscape areas using remote sensing imagery, and be used to predict multiple analytes simultaneously. However, the methods require localized calibrations to establish the relationship between spectral data and reference analytical data, and also have additional, specific problems. For example, remote sensing is capable of scanning entire watersheds for soil carbon content but is limited to the surface layer of tilled soils and may require difficult and extensive field sampling to obtain proper localized calibration reference values. The objective of this chapter is to discuss the present state of spectroscopic methods for determination of soil carbon.

Potential energy surface fitting by a statistically localized, permutationally invariant, local interpolating moving least squares method for the many-body potential: Method and application to N{sub 4}

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

Bender, Jason D.; Doraiswamy, Sriram; Candler, Graham V., E-mail: truhlar@umn.edu, E-mail: candler@aem.umn.edu

2014-02-07

Fitting potential energy surfaces to analytic forms is an important first step for efficient molecular dynamics simulations. Here, we present an improved version of the local interpolating moving least squares method (L-IMLS) for such fitting. Our method has three key improvements. First, pairwise interactions are modeled separately from many-body interactions. Second, permutational invariance is incorporated in the basis functions, using permutationally invariant polynomials in Morse variables, and in the weight functions. Third, computational cost is reduced by statistical localization, in which we statistically correlate the cutoff radius with data point density. We motivate our discussion in this paper with amore » review of global and local least-squares-based fitting methods in one dimension. Then, we develop our method in six dimensions, and we note that it allows the analytic evaluation of gradients, a feature that is important for molecular dynamics. The approach, which we call statistically localized, permutationally invariant, local interpolating moving least squares fitting of the many-body potential (SL-PI-L-IMLS-MP, or, more simply, L-IMLS-G2), is used to fit a potential energy surface to an electronic structure dataset for N{sub 4}. We discuss its performance on the dataset and give directions for further research, including applications to trajectory calculations.« less

New approaches to wipe sampling methods for antineoplastic and other hazardous drugs in healthcare settings.

PubMed

Connor, Thomas H; Smith, Jerome P

2016-09-01

At the present time, the method of choice to determine surface contamination of the workplace with antineoplastic and other hazardous drugs is surface wipe sampling and subsequent sample analysis with a variety of analytical techniques. The purpose of this article is to review current methodology for determining the level of surface contamination with hazardous drugs in healthcare settings and to discuss recent advances in this area. In addition it will provide some guidance for conducting surface wipe sampling and sample analysis for these drugs in healthcare settings. Published studies on the use of wipe sampling to measure hazardous drugs on surfaces in healthcare settings drugs were reviewed. These studies include the use of well-documented chromatographic techniques for sample analysis in addition to newly evolving technology that provides rapid analysis of specific antineoplastic. Methodology for the analysis of surface wipe samples for hazardous drugs are reviewed, including the purposes, technical factors, sampling strategy, materials required, and limitations. The use of lateral flow immunoassay (LFIA) and fluorescence covalent microbead immunosorbent assay (FCMIA) for surface wipe sample evaluation is also discussed. Current recommendations are that all healthc a re settings where antineoplastic and other hazardous drugs are handled include surface wipe sampling as part of a comprehensive hazardous drug-safe handling program. Surface wipe sampling may be used as a method to characterize potential occupational dermal exposure risk and to evaluate the effectiveness of implemented controls and the overall safety program. New technology, although currently limited in scope, may make wipe sampling for hazardous drugs more routine, less costly, and provide a shorter response time than classical analytical techniques now in use.

Electroanalytical method for determination of lead(II) in orange and apple using kaolin modified platinum electrode.

PubMed

El Mhammedi, M A; Achak, M; Bakasse, M; Chtaini, A

2009-08-01

This paper reports on the use of platinum electrode modified with kaolin (K/Pt) and square wave voltammetry for analytical detection of trace lead(II) in pure water, orange and apple samples. The electroanalytical procedure for determination of the Pb(II) comprises two steps: the chemical accumulation of the analyte under open-circuit conditions followed by the electrochemical detection of the preconcentrated species using square wave voltammetry. The analytical performances of the extraction method has been explored by studying the incubating time, and effect of interferences due to other ions. During the preconcentration step, Pb(II) was accumulated on the surface of the kaolin. The observed detection and quantification limits in pure water were 3.6x10(-9)molL(-1) and 1.2x10(-8)molL(-1), respectively. The precision of the method was also determined; the results was 2.35% (n=5).

Neutron radiative capture methods for surface elemental analysis

USGS Publications Warehouse

Trombka, J.I.; Senftle, F.; Schmadebeck, R.

1970-01-01

Both an accelerator and a 252Cf neutron source have been used to induce characteristic gamma radiation from extended soil samples. To demonstrate the method, measurements of the neutron-induced radiative capture and activation gamma rays have been made with both Ge(Li) and NaI(Tl) detectors, Because of the possible application to space flight geochemical analysis, it is believed that NaI(Tl) detectors must be used. Analytical procedures have been developed to obtain both qualitative and semiquantitative results from an interpretation of the measured NaI(Tl) pulse-height spectrum. Experiment results and the analytic procedure are presented. ?? 1970.

Extracting surface diffusion coefficients from batch adsorption measurement data: application of the classic Langmuir kinetics model.

PubMed

Chu, Khim Hoong

2017-11-09

Surface diffusion coefficients may be estimated by fitting solutions of a diffusion model to batch kinetic data. For non-linear systems, a numerical solution of the diffusion model's governing equations is generally required. We report here the application of the classic Langmuir kinetics model to extract surface diffusion coefficients from batch kinetic data. The use of the Langmuir kinetics model in lieu of the conventional surface diffusion model allows derivation of an analytical expression. The parameter estimation procedure requires determining the Langmuir rate coefficient from which the pertinent surface diffusion coefficient is calculated. Surface diffusion coefficients within the 10 -9 to 10 -6  cm 2 /s range obtained by fitting the Langmuir kinetics model to experimental kinetic data taken from the literature are found to be consistent with the corresponding values obtained from the traditional surface diffusion model. The virtue of this simplified parameter estimation method is that it reduces the computational complexity as the analytical expression involves only an algebraic equation in closed form which is easily evaluated by spreadsheet computation.

Comparison of real-time PCR methods for the detection of Naegleria fowleri in surface water and sediment.

PubMed

Streby, Ashleigh; Mull, Bonnie J; Levy, Karen; Hill, Vincent R

2015-05-01

Naegleria fowleri is a thermophilic free-living ameba found in freshwater environments worldwide. It is the cause of a rare but potentially fatal disease in humans known as primary amebic meningoencephalitis. Established N. fowleri detection methods rely on conventional culture techniques and morphological examination followed by molecular testing. Multiple alternative real-time PCR assays have been published for rapid detection of Naegleria spp. and N. fowleri. Foursuch assays were evaluated for the detection of N. fowleri from surface water and sediment. The assays were compared for thermodynamic stability, analytical sensitivity and specificity, detection limits, humic acid inhibition effects, and performance with seeded environmental matrices. Twenty-one ameba isolates were included in the DNA panel used for analytical sensitivity and specificity analyses. N. fowleri genotypes I and III were used for method performance testing. Two of the real-time PCR assays were determined to yield similar performance data for specificity and sensitivity for detecting N. fowleri in environmental matrices.

Comparison of real-time PCR methods for the detection of Naegleria fowleri in surface water and sediment

PubMed Central

Streby, Ashleigh; Mull, Bonnie J.; Levy, Karen

2015-01-01

Naegleria fowleri is a thermophilic free-living ameba found in freshwater environments worldwide. It is the cause of a rare but potentially fatal disease in humans known as primary amebic meningoencephalitis. Established N. fowleri detection methods rely on conventional culture techniques and morphological examination followed by molecular testing. Multiple alternative real-time PCR assays have been published for rapid detection of Naegleria spp. and N. fowleri. Four such assays were evaluated for the detection of N. fowleri from surface water and sediment. The assays were compared for thermodynamic stability, analytical sensitivity and specificity, detection limits, humic acid inhibition effects, and performance with seeded environmental matrices. Twenty-one ameba isolates were included in the DNA panel used for analytical sensitivity and specificity analyses. N. fowleri genotypes I and III were used for method performance testing. Two of the real-time PCR assays were determined to yield similar performance data for specificity and sensitivity for detecting N. fowleri in environmental matrices. PMID:25855343

Evaluation of analytical procedures for prediction of turbulent boundary layers on a porous wall

NASA Technical Reports Server (NTRS)

Towne, C. E.

1974-01-01

An analytical study has been made to determine how well current boundary layer prediction techniques work when there is mass transfer normal to the wall. The data that were considered in this investigation were for two-dimensional, incompressible, turbulent boundary layers with suction and blowing. Some of the bleed data were taken in an adverse pressure gradient. An integral prediction method was used three different porous wall skin friction relations, in addition to a solid-surface relation for the suction cases. A numerical prediction method was also used. Comparisons were made between theoretical and experimental skin friction coefficients, displacement and momentum thicknesses, and velocity profiles. The integral method with one of the porous wall skin friction laws gave very good agreement with data for most of the cases considered. The use of the solid-surface skin friction law caused the integral to overpredict the effectiveness of the bleed. The numerical techniques also worked well for most of the cases.

Achieving optimal SERS through enhanced experimental design.

PubMed

Fisk, Heidi; Westley, Chloe; Turner, Nicholas J; Goodacre, Royston

2016-01-01

One of the current limitations surrounding surface-enhanced Raman scattering (SERS) is the perceived lack of reproducibility. SERS is indeed challenging, and for analyte detection, it is vital that the analyte interacts with the metal surface. However, as this is analyte dependent, there is not a single set of SERS conditions that are universal. This means that experimental optimisation for optimum SERS response is vital. Most researchers optimise one factor at a time, where a single parameter is altered first before going onto optimise the next. This is a very inefficient way of searching the experimental landscape. In this review, we explore the use of more powerful multivariate approaches to SERS experimental optimisation based on design of experiments and evolutionary computational methods. We particularly focus on colloidal-based SERS rather than thin film preparations as a result of their popularity. © 2015 The Authors. Journal of Raman Spectroscopy published by John Wiley & Sons, Ltd.

Realistic Analytical Polyhedral MRI Phantoms

PubMed Central

Ngo, Tri M.; Fung, George S. K.; Han, Shuo; Chen, Min; Prince, Jerry L.; Tsui, Benjamin M. W.; McVeigh, Elliot R.; Herzka, Daniel A.

2015-01-01

Purpose Analytical phantoms have closed form Fourier transform expressions and are used to simulate MRI acquisitions. Existing 3D analytical phantoms are unable to accurately model shapes of biomedical interest. It is demonstrated that polyhedral analytical phantoms have closed form Fourier transform expressions and can accurately represent 3D biomedical shapes. Theory The derivations of the Fourier transform of a polygon and polyhedron are presented. Methods The Fourier transform of a polyhedron was implemented and its accuracy in representing faceted and smooth surfaces was characterized. Realistic anthropomorphic polyhedral brain and torso phantoms were constructed and their use in simulated 3D/2D MRI acquisitions was described. Results Using polyhedra, the Fourier transform of faceted shapes can be computed to within machine precision. Smooth surfaces can be approximated with increasing accuracy by increasing the number of facets in the polyhedron; the additional accumulated numerical imprecision of the Fourier transform of polyhedra with many faces remained small. Simulations of 3D/2D brain and 2D torso cine acquisitions produced realistic reconstructions free of high frequency edge aliasing as compared to equivalent voxelized/rasterized phantoms. Conclusion Analytical polyhedral phantoms are easy to construct and can accurately simulate shapes of biomedical interest. PMID:26479724

A silver nanoislands on silica spheres platform: enriching trace amounts of analytes for ultrasensitive and reproducible SERS detection.

PubMed

Wang, Zhongshun; Feng, Lei; Xiao, Dongyang; Li, Ning; Li, Yao; Cao, Danfeng; Shi, Zuosen; Cui, Zhanchen; Lu, Nan

2017-11-09

The performance of surface-enhanced Raman scattering (SERS) for detecting trace amounts of analytes depends highly on the enrichment of the diluted analytes into a small region that can be detected. A super-hydrophobic delivery (SHD) process is an excellent process to enrich even femtomolar analytes for SERS detection. However, it is still challenging to easily fabricate a low detection limit, high sensitivity and reproducible SHD-SERS substrate. In this article, we present a cost-effective and fewer-step method to fabricate a SHD-SERS substrate, named the "silver nanoislands on silica spheres" (SNOSS) platform. It is easily prepared via the thermal evaporation of silver onto a layer of super-hydrophobic paint, which contains single-scale surface-fluorinated silica spheres. The SNOSS platform performs reproducible detection, which brings the relative standard deviation down to 8.85% and 5.63% for detecting 10 -8 M R6G in one spot and spot-to-spot set-ups, respectively. The coefficient of determination (R 2 ) is 0.9773 for R6G. The SNOSS platform can be applied to the quantitative detection of analytes whose concentrations range from sub-micromolar to femtomolar levels.

High-performance liquid chromatography determination of red wine tannin stickiness.

PubMed

Revelette, Matthew R; Barak, Jennifer A; Kennedy, James A

2014-07-16

Red wine astringency is generally considered to be the sensory result of salivary protein precipitation following tannin-salivary protein interaction and/or tannin adhering to the oral mucosa. Astringency in red wine is often described using qualitative terms, such as hard and soft. Differences in qualitative description are thought to be due in part to the tannin structure. Tannin chemistry contributions to qualitative description have been shown to correlate with the enthalpy of interaction between tannin and a hydrophobic surface. On the basis of these findings, a method was developed that enabled the routine determination of the thermodynamics of the tannin interaction with a hydrophobic surface (polystyrene divinylbenzene) for tannins in red wine following direct injection. The optimized analytical method monitored elution at four different column temperatures (25-40 °C, in 5 °C increments), had a 20 min run time, and was monitored at 280 nm. The results of this study confirm that the calculated thermodynamics of the interaction are intensive and, therefore, provide specific thermodynamic information. Variation in the enthalpy of interaction between tannin and a hydrophobic surface (tannin stickiness) is a unique, concentration-independent analytical parameter. The method, in addition to providing information on tannin stickiness, provides the tannin concentration.

A computational method for the coupled solution of reaction-diffusion equations on evolving domains and manifolds: Application to a model of cell migration and chemotaxis.

PubMed

MacDonald, G; Mackenzie, J A; Nolan, M; Insall, R H

2016-03-15

In this paper, we devise a moving mesh finite element method for the approximate solution of coupled bulk-surface reaction-diffusion equations on an evolving two dimensional domain. Fundamental to the success of the method is the robust generation of bulk and surface meshes. For this purpose, we use a novel moving mesh partial differential equation (MMPDE) approach. The developed method is applied to model problems with known analytical solutions; these experiments indicate second-order spatial and temporal accuracy. Coupled bulk-surface problems occur frequently in many areas; in particular, in the modelling of eukaryotic cell migration and chemotaxis. We apply the method to a model of the two-way interaction of a migrating cell in a chemotactic field, where the bulk region corresponds to the extracellular region and the surface to the cell membrane.

Desorption in Mass Spectrometry.

PubMed

Usmanov, Dilshadbek Tursunbayevich; Ninomiya, Satoshi; Chen, Lee Chuin; Saha, Subhrakanti; Mandal, Mridul Kanti; Sakai, Yuji; Takaishi, Rio; Habib, Ahsan; Hiraoka, Kenzo; Yoshimura, Kentaro; Takeda, Sen; Wada, Hiroshi; Nonami, Hiroshi

2017-01-01

In mass spectrometry, analytes must be released in the gas phase. There are two representative methods for the gasification of the condensed samples, i.e. , ablation and desorption. While ablation is based on the explosion induced by the energy accumulated in the condensed matrix, desorption is a single molecular process taking place on the surface. In this paper, desorption methods for mass spectrometry developed in our laboratory: flash heating/rapid cooling, Leidenfrost phenomenon-assisted thermal desorption (LPTD), solid/solid friction, liquid/solid friction, electrospray droplet impact (EDI) ionization/desorption, and probe electrospray ionization (PESI), will be described. All the methods are concerned with the surface and interface phenomena. The concept of how to desorb less-volatility compounds from the surface will be discussed.

An isotope-dilution standard GC/MS/MS method for steroid hormones in water

USGS Publications Warehouse

Foreman, William T.; Gray, James L.; ReVello, Rhiannon C.; Lindley, Chris E.; Losche, Scott A.

2013-01-01

An isotope-dilution quantification method was developed for 20 natural and synthetic steroid hormones and additional compounds in filtered and unfiltered water. Deuterium- or carbon-13-labeled isotope-dilution standards (IDSs) are added to the water sample, which is passed through an octadecylsilyl solid-phase extraction (SPE) disk. Following extract cleanup using Florisil SPE, method compounds are converted to trimethylsilyl derivatives and analyzed by gas chromatography with tandem mass spectrometry. Validation matrices included reagent water, wastewater-affected surface water, and primary (no biological treatment) and secondary wastewater effluent. Overall method recovery for all analytes in these matrices averaged 100%; with overall relative standard deviation of 28%. Mean recoveries of the 20 individual analytes for spiked reagent-water samples prepared along with field samples analyzed in 2009–2010 ranged from 84–104%, with relative standard deviations of 6–36%. Detection levels estimated using ASTM International’s D6091–07 procedure range from 0.4 to 4 ng/L for 17 analytes. Higher censoring levels of 100 ng/L for bisphenol A and 200 ng/L for cholesterol and 3-beta-coprostanol are used to prevent bias and false positives associated with the presence of these analytes in blanks. Absolute method recoveries of the IDSs provide sample-specific performance information and guide data reporting. Careful selection of labeled compounds for use as IDSs is important because both inexact IDS-analyte matches and deuterium label loss affect an IDS’s ability to emulate analyte performance. Six IDS compounds initially tested and applied in this method exhibited deuterium loss and are not used in the final method.

Development of analytical methods for multiplex bio-assay with inductively coupled plasma mass spectrometry.

PubMed

Ornatsky, Olga I; Kinach, Robert; Bandura, Dmitry R; Lou, Xudong; Tanner, Scott D; Baranov, Vladimir I; Nitz, Mark; Winnik, Mitchell A

2008-01-01

Advances in the development of highly multiplexed bio-analytical assays with inductively coupled plasma mass spectrometry (ICP-MS) detection are discussed. Use of novel reagents specifically designed for immunological methods utilizing elemental analysis is presented. The major steps of method development, including selection of elements for tags, validation of tagged reagents, and examples of multiplexed assays, are considered in detail. The paper further describes experimental protocols for elemental tagging of antibodies, immunostaining of live and fixed human leukemia cells, and preparation of samples for ICP-MS analysis. Quantitative analysis of surface antigens on model cell lines using a cocktail of seven lanthanide labeled antibodies demonstrated high specificity and concordance with conventional immunophenotyping.

Rapid and sensitive detection of synthetic cannabinoids AMB-FUBINACA and α-PVP using surface enhanced Raman scattering (SERS)

NASA Astrophysics Data System (ADS)

Islam, Syed K.; Cheng, Yin Pak; Birke, Ronald L.; Green, Omar; Kubic, Thomas; Lombardi, John R.

2018-04-01

The application of surface enhanced Raman scattering (SERS) has been reported as a fast and sensitive analytical method in the trace detection of the two most commonly known synthetic cannabinoids AMB-FUBINACA and alpha-pyrrolidinovalerophenone (α-PVP). FUBINACA and α-PVP are two of the most dangerous synthetic cannabinoids which have been reported to cause numerous deaths in the United States. While instruments such as GC-MS, LC-MS have been traditionally recognized as analytical tools for the detection of these synthetic drugs, SERS has been recently gaining ground in the analysis of these synthetic drugs due to its sensitivity in trace analysis and its effectiveness as a rapid method of detection. This present study shows the limit of detection of a concentration as low as picomolar for AMB-FUBINACA while for α-PVP, the limit of detection is in nanomolar concentration using SERS.

An algorithm for analytical solution of basic problems featuring elastostatic bodies with cavities and surface flaws

NASA Astrophysics Data System (ADS)

Penkov, V. B.; Levina, L. V.; Novikova, O. S.; Shulmin, A. S.

2018-03-01

Herein we propose a methodology for structuring a full parametric analytical solution to problems featuring elastostatic media based on state-of-the-art computing facilities that support computerized algebra. The methodology includes: direct and reverse application of P-Theorem; methods of accounting for physical properties of media; accounting for variable geometrical parameters of bodies, parameters of boundary states, independent parameters of volume forces, and remote stress factors. An efficient tool to address the task is the sustainable method of boundary states originally designed for the purposes of computerized algebra and based on the isomorphism of Hilbertian spaces of internal states and boundary states of bodies. We performed full parametric solutions of basic problems featuring a ball with a nonconcentric spherical cavity, a ball with a near-surface flaw, and an unlimited medium with two spherical cavities.

A simple analytical aerodynamic model of Langley Winged-Cone Aerospace Plane concept

NASA Technical Reports Server (NTRS)

Pamadi, Bandu N.

1994-01-01

A simple three DOF analytical aerodynamic model of the Langley Winged-Coned Aerospace Plane concept is presented in a form suitable for simulation, trajectory optimization, and guidance and control studies. The analytical model is especially suitable for methods based on variational calculus. Analytical expressions are presented for lift, drag, and pitching moment coefficients from subsonic to hypersonic Mach numbers and angles of attack up to +/- 20 deg. This analytical model has break points at Mach numbers of 1.0, 1.4, 4.0, and 6.0. Across these Mach number break points, the lift, drag, and pitching moment coefficients are made continuous but their derivatives are not. There are no break points in angle of attack. The effect of control surface deflection is not considered. The present analytical model compares well with the APAS calculations and wind tunnel test data for most angles of attack and Mach numbers.

Impact desolvation of electrosprayed microdroplets--a new ionization method for mass spectrometry of large biomolecules.

PubMed

Aksyonov, S A; Williams, P

2001-01-01

Impact desolvation of electrosprayed microdroplets (IDEM) is a new method for producing gas-phase ions of large biomolecules. Analytes are dissolved in an electrolyte solution which is electrosprayed in vacuum, producing highly charged micron and sub-micron sized droplets (microdroplets). These microdroplets are accelerated through potential differences approximately 5 - 10 kV to velocities of several km/s and allowed to impact a target surface. The energetic impacts vaporize the droplets and release desolvated gas-phase ions of the analyte molecules. Oligonucleotides (2- to 12-mer) and peptides (bradykinin, neurotensin) yield singly and doubly charged molecular ions with no detectable fragmentation. Because the extent of multiple charging is significantly less than in atmospheric pressure electrospray ionization, and the method produces ions largely free of adducts from solutions of high ionic strength, IDEM has some promise as a method for coupling to liquid chromatographic techniques and for mixture analysis. Ions are produced in vacuum at a flat equipotential surface, potentially allowing efficient ion extraction. Copyright 2001 John Wiley & Sons, Ltd.

Ultrasonic assessment of additive manufactured Ti-6Al-4V

NASA Astrophysics Data System (ADS)

Schehl, Norman; Kramb, Vicki; Dierken, Josiah; Aldrin, John; Schwalbach, Edwin; John, Reji

2018-04-01

Additive Manufacturing (AM) processes offer the potential for manufacturing cost savings and rapid insertion into service through production of near net shape components for complicated structures. Use of these parts in high reliability applications such as those in the aerospace industry will require nondestructive characterization methods to ensure post-process material quality in as-built condition. Ultrasonic methods can be used for this quality verification. Depending on the application, the service life of AM components can be sensitive to the part surface condition. The surface roughness and layered structure inherent to the electron-beam powder-bed fusion process necessitates new approaches to evaluate subsurface material integrity in its presence. Experimental methods and data analytics may improve the evaluation of as-built additively manufactured materials. This paper discusses the assessment of additively manufactured EBM Ti-6Al-4V panels using ultrasonic methods and the data analytics applied to evaluate material integrity. The assessment was done as an exploratory study as the discontinuities of interest in these test samples were not known when the measurements were performed. Water immersion ultrasonic techniques, including pulse-echo and through transmission with 10 MHz focused transducers, were used to explore the material integrity of as-built plates. Subsequent destructive mechanical tests of specimens extracted from the plates provided fracture locations indicating critical flaws. To further understand the effect of surface-roughness, an evaluation of ultrasonic response in the presence of as-built surfaces and with the surface removed was performed. The assessment of additive manufactured EBM Ti-6Al-4V panels with ultrasonic techniques indicated that ultrasonic energy was attenuated by the as-built surface roughness. In addition, feature detection was shown to be sensitive to experimental ultrasonic parameters and flaw morphology.

In vivo monitoring of distributional transport kinetics and extravasation of quantum dots in living rat liver

NASA Astrophysics Data System (ADS)

Su, Cheng-Kuan; Sun, Yuh-Chang

2013-04-01

Although the unique optical properties of surface-modified quantum dots (QDs) have attracted wide interest in molecular biology and bioengineering, there are very few reports of their in vivo biodistribution, due to a lack of analytical techniques for characterizing the dynamic variation of QDs in living animals. In this study, we used an in vivo online monitoring system and a batch-wise elemental analytical method to investigate the biodistribution/extravasation of various surface-modified CdTeSe/ZnS (QDs) in rat liver. It is found that the surface modification dictated not only the blood retention profile but also the degree of extravasation and the clearance of extracellular QDs, making it an important variable for regulating the transfer and exchange process of QDs among three physiological compartments—bloodstream, extracellular space and Kupffer cells/hepatocytes.

Separation of oligopeptides, nucleobases, nucleosides and nucleotides using capillary electrophoresis/electrochromatography with sol-gel modified inner capillary wall.

PubMed

Svobodová, Jana; Kofroňová, Olga; Benada, Oldřich; Král, Vladimír; Mikšík, Ivan

2017-09-29

The aim of this article is to study the modification of an inner capillary wall with sol-gel coating (pure silica sol-gel or silica sol-gel containing porphyrin-brucine conjugate) and determine its influence on the separation process using capillary electrophoresis/electrochromatography method. After modification of the inner capillary surface the separation of analytes was performed using two different phosphate buffers (pH 2.5 and 9.0) and finally the changes in electrophoretic mobilities of various samples were calculated. To confirm that the modification of the inner capillary surface was successful, the parts of the inner surfaces of capillaries were observed using scanning electron microscopy. The analytes used as testing samples were oligopeptides, nucleosides, nucleobases and finally nucleotides. Copyright © 2017 Elsevier B.V. All rights reserved.

Method for Pre-Conditioning a Measured Surface Height Map for Model Validation

NASA Technical Reports Server (NTRS)

Sidick, Erkin

2012-01-01

This software allows one to up-sample or down-sample a measured surface map for model validation, not only without introducing any re-sampling errors, but also eliminating the existing measurement noise and measurement errors. Because the re-sampling of a surface map is accomplished based on the analytical expressions of Zernike-polynomials and a power spectral density model, such re-sampling does not introduce any aliasing and interpolation errors as is done by the conventional interpolation and FFT-based (fast-Fourier-transform-based) spatial-filtering method. Also, this new method automatically eliminates the measurement noise and other measurement errors such as artificial discontinuity. The developmental cycle of an optical system, such as a space telescope, includes, but is not limited to, the following two steps: (1) deriving requirements or specs on the optical quality of individual optics before they are fabricated through optical modeling and simulations, and (2) validating the optical model using the measured surface height maps after all optics are fabricated. There are a number of computational issues related to model validation, one of which is the "pre-conditioning" or pre-processing of the measured surface maps before using them in a model validation software tool. This software addresses the following issues: (1) up- or down-sampling a measured surface map to match it with the gridded data format of a model validation tool, and (2) eliminating the surface measurement noise or measurement errors such that the resulted surface height map is continuous or smoothly-varying. So far, the preferred method used for re-sampling a surface map is two-dimensional interpolation. The main problem of this method is that the same pixel can take different values when the method of interpolation is changed among the different methods such as the "nearest," "linear," "cubic," and "spline" fitting in Matlab. The conventional, FFT-based spatial filtering method used to eliminate the surface measurement noise or measurement errors can also suffer from aliasing effects. During re-sampling of a surface map, this software preserves the low spatial-frequency characteristic of a given surface map through the use of Zernike-polynomial fit coefficients, and maintains mid- and high-spatial-frequency characteristics of the given surface map by the use of a PSD model derived from the two-dimensional PSD data of the mid- and high-spatial-frequency components of the original surface map. Because this new method creates the new surface map in the desired sampling format from analytical expressions only, it does not encounter any aliasing effects and does not cause any discontinuity in the resultant surface map.

Comprehensive characterizations of nanoparticle biodistribution following systemic injection in mice

NASA Astrophysics Data System (ADS)

Liao, Wei-Yin; Li, Hui-Jing; Chang, Ming-Yao; Tang, Alan C. L.; Hoffman, Allan S.; Hsieh, Patrick C. H.

2013-10-01

Various nanoparticle (NP) properties such as shape and surface charge have been studied in an attempt to enhance the efficacy of NPs in biomedical applications. When trying to undermine the precise biodistribution of NPs within the target organs, the analytical method becomes the determining factor in measuring the precise quantity of distributed NPs. High performance liquid chromatography (HPLC) represents a more powerful tool in quantifying NP biodistribution compared to conventional analytical methods such as an in vivo imaging system (IVIS). This, in part, is due to better curve linearity offered by HPLC than IVIS. Furthermore, HPLC enables us to fully analyze each gram of NPs present in the organs without compromising the signals and the depth-related sensitivity as is the case in IVIS measurements. In addition, we found that changing physiological conditions improved large NP (200-500 nm) distribution in brain tissue. These results reveal the importance of selecting analytic tools and physiological environment when characterizing NP biodistribution for future nanoscale toxicology, therapeutics and diagnostics.Various nanoparticle (NP) properties such as shape and surface charge have been studied in an attempt to enhance the efficacy of NPs in biomedical applications. When trying to undermine the precise biodistribution of NPs within the target organs, the analytical method becomes the determining factor in measuring the precise quantity of distributed NPs. High performance liquid chromatography (HPLC) represents a more powerful tool in quantifying NP biodistribution compared to conventional analytical methods such as an in vivo imaging system (IVIS). This, in part, is due to better curve linearity offered by HPLC than IVIS. Furthermore, HPLC enables us to fully analyze each gram of NPs present in the organs without compromising the signals and the depth-related sensitivity as is the case in IVIS measurements. In addition, we found that changing physiological conditions improved large NP (200-500 nm) distribution in brain tissue. These results reveal the importance of selecting analytic tools and physiological environment when characterizing NP biodistribution for future nanoscale toxicology, therapeutics and diagnostics. Electronic supplementary information (ESI) available. See DOI: 10.1039/c3nr03954d

Methods for investigating biosurfactants and bioemulsifiers: a review.

PubMed

Satpute, Surekha K; Banpurkar, Arun G; Dhakephalkar, Prashant K; Banat, Ibrahim M; Chopade, Balu A

2010-06-01

Microorganisms produce biosurfactant (BS)/bioemulsifier (BE) with wide structural and functional diversity which consequently results in the adoption of different techniques to investigate these diverse amphiphilic molecules. This review aims to compile information on different microbial screening methods, surface active products extraction procedures, and analytical terminologies used in this field. Different methods for screening microbial culture broth or cell biomass for surface active compounds production are also presented and their possible advantages and disadvantages highlighted. In addition, the most common methods for purification, detection, and structure determination for a wide range of BS and BE are introduced. Simple techniques such as precipitation using acetone, ammonium sulphate, solvent extraction, ultrafiltration, ion exchange, dialysis, ultrafiltration, lyophilization, isoelectric focusing (IEF), and thin layer chromatography (TLC) are described. Other more elaborate techniques including high pressure liquid chromatography (HPLC), infra red (IR), gas chromatography-mass spectroscopy (GC-MS), nuclear magnetic resonance (NMR), and fast atom bombardment mass spectroscopy (FAB-MS), protein digestion and amino acid sequencing are also elucidated. Various experimental strategies including static light scattering and hydrodynamic characterization for micelles have been discussed. A combination of various analytical methods are often essential in this area of research and a numbers of trials and errors to isolate, purify and characterize various surface active agents are required. This review introduces the various methodologies that are indispensable for studying biosurfactants and bioemulsifiers.

Speckle-field propagation in 'frozen' turbulence: brightness function approach

NASA Astrophysics Data System (ADS)

Dudorov, Vadim V.; Vorontsov, Mikhail A.; Kolosov, Valeriy V.

2006-08-01

Speckle-field long- and short-exposure spatial correlation characteristics for target-in-the-loop (TIL) laser beam propagation and scattering in atmospheric turbulence are analyzed through the use of two different approaches: the conventional Monte Carlo (MC) technique and the recently developed brightness function (BF) method. Both the MC and the BF methods are applied to analysis of speckle-field characteristics averaged over target surface roughness realizations under conditions of 'frozen' turbulence. This corresponds to TIL applications where speckle-field fluctuations associated with target surface roughness realization updates occur within a time scale that can be significantly shorter than the characteristic atmospheric turbulence time. Computational efficiency and accuracy of both methods are compared on the basis of a known analytical solution for the long-exposure mutual correlation function. It is shown that in the TIL propagation scenarios considered the BF method provides improved accuracy and requires significantly less computational time than the conventional MC technique. For TIL geometry with a Gaussian outgoing beam and Lambertian target surface, both analytical and numerical estimations for the speckle-field long-exposure correlation length are obtained. Short-exposure speckle-field correlation characteristics corresponding to propagation in 'frozen' turbulence are estimated using the BF method. It is shown that atmospheric turbulence-induced static refractive index inhomogeneities do not significantly affect the characteristic correlation length of the speckle field, whereas long-exposure spatial correlation characteristics are strongly dependent on turbulence strength.

Speckle-field propagation in 'frozen' turbulence: brightness function approach.

PubMed

Dudorov, Vadim V; Vorontsov, Mikhail A; Kolosov, Valeriy V

2006-08-01

Speckle-field long- and short-exposure spatial correlation characteristics for target-in-the-loop (TIL) laser beam propagation and scattering in atmospheric turbulence are analyzed through the use of two different approaches: the conventional Monte Carlo (MC) technique and the recently developed brightness function (BF) method. Both the MC and the BF methods are applied to analysis of speckle-field characteristics averaged over target surface roughness realizations under conditions of 'frozen' turbulence. This corresponds to TIL applications where speckle-field fluctuations associated with target surface roughness realization updates occur within a time scale that can be significantly shorter than the characteristic atmospheric turbulence time. Computational efficiency and accuracy of both methods are compared on the basis of a known analytical solution for the long-exposure mutual correlation function. It is shown that in the TIL propagation scenarios considered the BF method provides improved accuracy and requires significantly less computational time than the conventional MC technique. For TIL geometry with a Gaussian outgoing beam and Lambertian target surface, both analytical and numerical estimations for the speckle-field long-exposure correlation length are obtained. Short-exposure speckle-field correlation characteristics corresponding to propagation in 'frozen' turbulence are estimated using the BF method. It is shown that atmospheric turbulence-induced static refractive index inhomogeneities do not significantly affect the characteristic correlation length of the speckle field, whereas long-exposure spatial correlation characteristics are strongly dependent on turbulence strength.

Spiral wound extraction cartridge

DOEpatents

Wisted, E.E.; Lundquist, S.H.

1999-04-27

A cartridge device for removing an analyte from a fluid comprises a hollow core, a sheet composite comprising a particulate-loaded porous membrane and optionally at least one reinforcing spacer sheet, the particulate being capable of binding the analyte, the sheet composite being formed into a spiral configuration about the core, wherein the sheet composite is wound around itself and wherein the windings of sheet composite are of sufficient tightness so that adjacent layers are essentially free of spaces therebetween, two end caps which are disposed over the core and the lateral ends of the spirally wound sheet composite, and means for securing the end caps to the core, the end caps also being secured to the lateral ends of the spirally wound sheet composite. A method for removing an analyte from a fluid comprises the steps of providing a spirally wound element of the invention and passing the fluid containing the analyte through the element essentially normal to a surface of the sheet composite so as to bind the analyte to the particulate of the particulate-loaded porous membrane, the method optionally including the step of eluting the bound analyte from the sheet composite. 4 figs.

Method and apparatus for optimized sampling of volatilizable target substances

DOEpatents

Lindgren, Eric R.; Phelan, James M.

2002-01-01

An apparatus for capturing, from gases such as soil gas, target analytes. Target analytes may include emanations from explosive materials or from residues of explosive materials. The apparatus employs principles of sorption common to solid phase microextraction, and is best used in conjunction with analysis means such as a gas chromatograph. To sorb target analytes, the apparatus functions using various sorptive structures to capture target analyte. Depending upon the embodiment, those structures may include 1) a conventional solid-phase microextraction (SPME) fiber, 2) a SPME fiber suspended in a capillary tube (with means provided for moving gases through the capillary tube so that the gases come into close proximity to the suspended fiber), and 3) a capillary tube including an interior surface on which sorptive material (similar to that on the surface of a SPME fiber) is supported (along with means for moving gases through the capillary tube so that the gases come into close proximity to the sorptive material). In one disclosed embodiment, at least one such sorptive structure is associated with an enclosure including an opening in communication with the surface of a soil region potentially contaminated with buried explosive material such as unexploded ordnance. Emanations from explosive materials can pass into and accumulate in the enclosure where they are sorbed by the sorptive structures. Also disclosed is the use of heating means such as microwave horns to drive target analytes into the soil gas from solid and liquid phase components of the soil.

3D Tensorial Elastodynamics for Isotropic Media on Vertically Deformed Meshes

NASA Astrophysics Data System (ADS)

Shragge, J. C.

2017-12-01

Solutions of the 3D elastodynamic wave equation are sometimes required in industrial and academic applications of elastic reverse-time migration (E-RTM) and full waveform inversion (E-FWI) that involve vertically deformed meshes. Examples include incorporating irregular free-surface topography and handling internal boundaries (e.g., water bottom) directly into the computational meshes. In 3D E-RTM and E-FWI applications, the number of forward modeling simulations can number in the tens of thousands (per iteration), which necessitates the development of stable, accurate and efficient 3D elastodynamics solvers. For topographic scenarios, most finite-difference solution approaches use a change-of-variable strategy that has a number of associated computational challenges, including difficulties in handling of the free-surface boundary condition. In this study, I follow a tensorial approach and use a generalized family of analytic transforms to develop a set of analytic equations for 3D elastodynamics that directly incorporates vertical grid deformations. Importantly, this analytic approach allows for the specification of an analytic free-surface boundary condition appropriate for vertically deformed meshes. These equations are both straightforward and efficient to solve using a velocity-stress formulation with finite-difference (MFD) operators implemented on a fully staggered grid. Moreover, I demonstrate that the use of mimetic finite difference (MFD) methods allows stable, accurate, and efficient numerical solutions to be simulated for typical topographic scenarios. Examples demonstrate that high-quality elastic wavefields can be generated for topographic surfaces exhibiting significant topographic relief.

Installation Restoration Program. Phase II. Confirmation/Quantification. Stage 1. Volume 2. Appendix J-M.

DTIC Science & Technology

1985-06-28

1984 to April 1985 includedr installation of 27 raw mnitor wells and 11 amh l’,(1 zjit~s, collecticn cf seive~t, sarples ftw surfac , soil, shallowv...modifying a sampling and analytical program that addresses the requirements of the project. If project requirements necessitate different quality...reagent blank and at least five (5) different concentrations of thl analyte. A modification of the method of Hubaux and Vos will be used to deter

Investigation and Development of Advanced Surface Microanalysis Techniques and Methods

DTIC Science & Technology

1983-04-01

California 94402 and Stephen L. Grube Watkins-Johnson 440 Kings Village Road Scotts Valley, California 95066 as published in Analytical Chemistry , 1985, 57...34 E. Silberg , T. Y. Chang, E. A. Caridi, C. A. Evans Jr. and C. J. Hitzman in Gallium Arsenide and Related Compounds 1982, 10th International Symposium...Spectrometry," P. K. Chu and S. L. Grube, Analytical Chemistry . 13. "Direct Lateral and In-Depth Distributional Analysis for Ionic - Contaminants in

Surface-enhanced Raman spectroscopy for the detection of pathogenic DNA and protein in foods

NASA Astrophysics Data System (ADS)

Chowdhury, Mustafa H.; Atkinson, Brad; Good, Theresa; Cote, Gerard L.

2003-07-01

Traditional Raman spectroscopy while extremely sensitive to structure and conformation, is an ineffective tool for the detection of bioanalytes at the sub milimolar level. Surface Enhanced Raman Spectroscopy (SERS) is a technique developed more recently that has been used with applaudable success to enhance the Raman cross-section of a molecule by factors of 106 to 1014. This technique can be exploited in a nanoscale biosensor for the detection of pathogenic proteins and DNA in foods by using a biorecognition molecule to bring a target analyte in close proximity to the mental surface. This is expected to produce a SERS signal of the target analyte, thus making it possible to easily discriminate between the target analyte and possible confounders. In order for the sensor to be effective, the Raman spectra of the target analyte would have to be distinct from that of the biorecognition molecule, as both would be in close proximity to the metal surface and thus be subjected to the SERS effect. In our preliminary studies we have successfully used citrate reduced silver colloidal particles to obtain unique SERS spectra of α-helical and β-sheet bovine serum albumin (BSA) that served as models of an α helical antiobiody (biorecognition element) and a β-sheet target protein (pathogenic prion). In addition, the unique SERS spectra of double stranded and single stranded DNA were also obtained where the single stranded DNA served as the model for the biorecognition element and the double stranded DNA served as themodel for the DNA probe/target hybrid. This provides a confirmation of the feasibility of the method which opens opportunities for potentially wide spread applications in the detection of food pathogens, biowarefare agents, andother bio-analytes.

An Analytical Comparison of the Acoustic Analogy and Kirchhoff Formulation for Moving Surfaces

NASA Technical Reports Server (NTRS)

Brentner, Kenneth S.; Farassat, F.

1997-01-01

The Lighthill acoustic analogy, as embodied in the Ffowcs Williams-Hawkings (FW-H) equation, is compared with the Kirchhoff formulation for moving surfaces. A comparison of the two governing equations reveals that the main Kirchhoff advantage (namely nonlinear flow effects are included in the surface integration) is also available to the FW-H method if the integration surface used in the FW-H equation is not assumed impenetrable. The FW-H equation is analytically superior for aeroacoustics because it is based upon the conservation laws of fluid mechanics rather than the wave equation. This means that the FW-H equation is valid even if the integration surface is in the nonlinear region. This is demonstrated numerically in the paper. The Kirchhoff approach can lead to substantial errors if the integration surface is not positioned in the linear region. These errors may be hard to identify. Finally, new metrics based on the Sobolev norm are introduced which may be used to compare input data for both quadrupole noise calculations and Kirchhoff noise predictions.

Advanced wide-field surface plasmon microscopy of single adsorbing nanoparticles

NASA Astrophysics Data System (ADS)

Nizamov, Shavkat; Scherbahn, Vitali; Mirsky, Vladimir M.

2017-05-01

In-situ detection and characterization of nanoparticles in biological media as well as in food or other complex samples is still a big challenge for existing analytical methods. Here we describe a label-free and cost-effective analytical method for detection of nanoparticles in the concentration range 106 -1010 NPs/ml. The proposed method is based on the surface plasmon resonance microscopy (SPRM) with a large field of view ( 1.3mm2 ). It is able to detect and count adsorbing nanoparticles individually, totally up to the hundreds of thousands of NPs on the sensor surface. At constant diffusion conditions the detection rate is proportional to the number concentration of NPs, this provides an approach to determine the NPs concentration. The adsorption of nanoparticle can be manipulated by the surface functionalization, pH and electrolyte concentration of suspensions. Images of detected nanoparticles can be quantified in order to characterize them individually. The image intensity grows quasi-linearly with nanoparticle size for the given material. However, the size and material of nanoparticle cannot be resolved directly from the image. For determination of chemical composition, SPRM can be assisted by electrochemical analysis. In this case, the gold sensor surface is used both as a resonant media for plasmon microscopy and as a working electrode. Under potential sweep, the adsorbed NPs can be subjected to electrochemical dissolution, which is detected optically. The potential of this conversion characterizes the material of NPs.

Optimization of magnet end-winding geometry

NASA Astrophysics Data System (ADS)

Reusch, Michael F.; Weissenburger, Donald W.; Nearing, James C.

1994-03-01

A simple, almost entirely analytic, method for the optimization of stress-reduced magnet-end winding paths for ribbon-like superconducting cable is presented. This technique is based on characterization of these paths as developable surfaces, i.e., surfaces whose intrinsic geometry is flat. The method is applicable to winding mandrels of arbitrary geometry. Computational searches for optimal winding paths are easily implemented via the technique. Its application to the end configuration of cylindrical Superconducting Super Collider (SSC)-type magnets is discussed. The method may be useful for other engineering problems involving the placement of thin sheets of material.

Quantitative on-line preconcentration-liquid chromatography coupled with tandem mass spectrometry method for the determination of pharmaceutical compounds in water.

PubMed

Idder, Salima; Ley, Laurent; Mazellier, Patrick; Budzinski, Hélène

2013-12-17

One of the current environmental issues concerns the presence and fate of pharmaceuticals in water bodies as these compounds may represent a potential environmental problem. The characterization of pharmaceutical contamination requires powerful analytical method able to quantify these pollutants at very low concentration (few ng L(-1)). In this work, a multi-residue analytical methodology (on-line solid phase extraction-liquid chromatography-triple quadrupole mass spectrometry using positive and negative electrospray ionization) has been developed and validated for 40 multi-class pharmaceuticals and metabolites for tap and surface waters. This on-line SPE method was very convenient and efficient compared to classical off-line SPE method because of its shorter total run time including sample preparation and smaller sample volume (1 mL vs up to 1 L). The optimized method included several therapeutic classes as lipid regulators, antibiotics, beta-blockers, non-steroidal anti-inflammatories, antineoplastic, etc., with various physicochemical properties. Quantification has been achieved with the internal standards. The limits of detection are between 0.7 and 15 ng L(-1) for drinking waters and 2-15 ng L(-1) for surface waters. The inter-day precision values are below 20% for each studied level. The improvement and strength of the analytical method has been verified along a monitoring of these 40 pharmaceuticals in Isle River, a French stream located in the South West of France. During this survey, 16 pharmaceutical compounds have been detected. Copyright © 2013 Elsevier B.V. All rights reserved.

Analytic solution of field distribution and demagnetization function of ideal hollow cylindrical field source

NASA Astrophysics Data System (ADS)

Xu, Xiaonong; Lu, Dingwei; Xu, Xibin; Yu, Yang; Gu, Min

2017-09-01

The Halbach type hollow cylindrical permanent magnet array (HCPMA) is a volume compact and energy conserved field source, which have attracted intense interests in many practical applications. Here, using the complex variable integration method based on the Biot-Savart Law (including current distributions inside the body and on the surfaces of magnet), we derive analytical field solutions to an ideal multipole HCPMA in entire space including the interior of magnet. The analytic field expression inside the array material is used to construct an analytic demagnetization function, with which we can explain the origin of demagnetization phenomena in HCPMA by taking into account an ideal magnetic hysteresis loop with finite coercivity. These analytical field expressions and demagnetization functions provide deeper insight into the nature of such permanent magnet array systems and offer guidance in designing optimized array system.

A method to design blended rolled edges for compact range reflectors

NASA Technical Reports Server (NTRS)

Gupta, Inder J.; Burnside, Walter D.

1989-01-01

A method to design blended rolled edges for arbitrary rim shape compact range reflectors is presented. The reflectors may be center-fed or offset-fed. The method leads to rolled edges with minimal surface discontinuities. It is shown that the reflectors designed using the prescribed method can be defined analytically using simple expressions. A procedure to obtain optimum rolled edges parameter is also presented. The procedure leads to blended rolled edges that minimize the diffracted fields emanating from the junction between the paraboloid and the rolled edge surface while satisfying certain constraints regarding the reflector size and the minimum operating frequency of the system.

A method to design blended rolled edges for compact range reflectors

NASA Technical Reports Server (NTRS)

Gupta, Inder J.; Ericksen, Kurt P.; Burnside, Walter D.

1990-01-01

A method to design blended rolled edges for arbitrary rim shape compact range reflectors is presented. The reflectors may be center-fed or offset-fed. The method leads to rolled edges with minimal surface discontinuities. It is shown that the reflectors designed using the prescribed method can be defined analytically using simple expressions. A procedure to obtain optimum rolled edges parameters is also presented. The procedure leads to blended rolled edges that minimize the diffracted fields emanating from the junction between the paraboloid and the rolled edge surface while satisfying certain constraints regarding the reflector size and the minimum operating frequency of the system.

Surface-Enhanced Raman Scattering (SERS) for Detection in Immunoassays. Applications, fundamentals, and optimization

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

Driskell, Jeremy Daniel

2006-08-09

Immunoassays have been utilized for the detection of biological analytes for several decades. Many formats and detection strategies have been explored, each having unique advantages and disadvantages. More recently, surface-enhanced Raman scattering (SERS) has been introduced as a readout method for immunoassays, and has shown great potential to meet many key analytical figures of merit. This technology is in its infancy and this dissertation explores the diversity of this method as well as the mechanism responsible for surface enhancement. Approaches to reduce assay times are also investigated. Implementing the knowledge gained from these studies will lead to a more sensitivemore » immunoassay requiring less time than its predecessors. This dissertation is organized into six sections. The first section includes a literature review of the previous work that led to this dissertation. A general overview of the different approaches to immunoassays is given, outlining the strengths and weaknesses of each. Included is a detailed review of binding kinetics, which is central for decreasing assay times. Next, the theoretical underpinnings of SERS is reviewed at its current level of understanding. Past work has argued that surface plasmon resonance (SPR) of the enhancing substrate influences the SERS signal; therefore, the SPR of the extrinsic Raman labels (ERLs) utilized in our SERS-based immunoassay is discussed. Four original research chapters follow the Introduction, each presented as separate manuscripts. Chapter 2 modifies a SERS-based immunoassay previously developed in our group, extending it to the low-level detection of viral pathogens and demonstrating its versatility in terms of analyte type, Chapter 3 investigates the influence of ERL size, material composition, and separation distance between the ERLs and capture substrate on the SERS signal. This chapter links SPR with SERS enhancement factors and is consistent with many of the results from theoretical treatments of SPR and SERS. Chapter 4 introduces a novel method of reducing sample incubation time via capture substrate rotation. Moreover, this work led to a method of virus quantification without the use of standards. Chapter 5 extends the methodology developed in Chapter 4 to both the antigen and ERL labeling step to perform assays with improved analytical performance in less time than can be accomplished in diffusion controlled assays. This dissertation concludes with a general summary and speculates on the future of this exciting approach to carrying out immunoassays.« less

The detection and mapping of the spatial distribution of insect defense compounds by desorption atmospheric pressure photoionization Orbitrap mass spectrometry.

PubMed

Rejšek, Jan; Vrkoslav, Vladimír; Hanus, Robert; Vaikkinen, Anu; Haapala, Markus; Kauppila, Tiina J; Kostiainen, Risto; Cvačka, Josef

2015-07-30

Many insects use chemicals synthesized in exocrine glands and stored in reservoirs to protect themselves. Two chemically defended insects were used as models for the development of a new rapid analytical method based on desorption atmospheric pressure photoionization-mass spectrometry (DAPPI-MS). The distribution of defensive chemicals on the insect body surface was studied. Since these chemicals are predominantly nonpolar, DAPPI was a suitable analytical method. Repeatability of DAPPI-MS signals and effects related to non-planarity and roughness of samples were investigated using acrylic sheets uniformly covered with an analyte. After that, analytical figures of merit of the technique were determined. The spatial distribution of (E)-1-nitropentadec-1-ene, a toxic nitro compound synthesized by soldiers of the termite Prorhinotermes simplex, was investigated. Then, the spatial distribution of the unsaturated aldehydes (E)-hex-2-enal, (E)-4-oxohex-2-enal, (E)-oct-2-enal, (E,E)-deca-2,4-dienal and (E)-dec-2-enal was monitored in the stink bug Graphosoma lineatum. Chemicals present on the body surface were scanned along the median line of the insect from the head to the abdomen and vice versa, employing either the MS or MS(2) mode. In this fast and simple way, the opening of the frontal gland on the frons of termite soldiers and the position of the frontal gland reservoir, extending deep into the abdominal cavity, were localized. In the stink bug, the opening of the metathoracic scent glands (ostiole) on the ventral side of the thorax as well as the gland reservoir in the median position under the ventral surface of the anterior abdomen were detected and localized. The developed method has future prospects in routine laboratory use in life sciences. Copyright © 2015 Elsevier B.V. All rights reserved.

Low-to-moderate Reynolds number swirling flow in an annular channel with a rotating end wall.

PubMed

Davoust, Laurent; Achard, Jean-Luc; Drazek, Laurent

2015-02-01

This paper presents a new method for solving analytically the axisymmetric swirling flow generated in a finite annular channel from a rotating end wall, with no-slip boundary conditions along stationary side walls and a slip condition along the free surface opposite the rotating floor. In this case, the end-driven swirling flow can be described from the coupling between an azimuthal shear flow and a two-dimensional meridional flow driven by the centrifugal force along the rotating floor. A regular asymptotic expansion based on a small but finite Reynolds number is used to calculate centrifugation-induced first-order correction to the azimuthal Stokes flow obtained as the solution at leading order. For solving the first-order problem, the use of an integral boundary condition for the vorticity is found to be a convenient way to attribute boundary conditions in excess for the stream function to the vorticity. The annular geometry is characterized by both vertical and horizontal aspect ratios, whose respective influences on flow patterns are investigated. The vertical aspect ratio is found to involve nontrivial changes in flow patterns essentially due to the role of corner eddies located on the left and right sides of the rotating floor. The present analytical method can be ultimately extended to cylindrical geometries, irrespective of the surface opposite the rotating floor: a wall or a free surface. It can also serve as an analytical tool for monitoring confined rotating flows in applications related to surface viscosimetry or crystal growth from the melt.

An analytic model for acoustic scattering from an impedance cylinder placed normal to an impedance plane

NASA Astrophysics Data System (ADS)

Swearingen, Michelle E.

2004-04-01

An analytic model, developed in cylindrical coordinates, is described for the scattering of a spherical wave off a semi-infinite reight cylinder placed normal to a ground surface. The motivation for the research is to have a model with which one can simulate scattering from a single tree and which can be used as a fundamental element in a model for estimating the attenuation in a forest comprised of multiple tree trunks. Comparisons are made to the plane wave case, the transparent cylinder case, and the rigid and soft ground cases as a method of theoretically verifying the model for the contemplated range of model parameters. Agreement is regarded as excellent for these benchmark cases. Model sensitivity to five parameters is also explored. An experiment was performed to study the scattering from a cylinder normal to a ground surface. The data from the experiment is analyzed with a transfer function method to yield frequency and impulse responses, and calculations based on the analytic model are compared to the experimental data. Thesis advisor: David C. Swanson Copies of this thesis written in English can be obtained from

Peptide interfaces with graphene: an emerging intersection of analytical chemistry, theory, and materials.

PubMed

Russell, Shane R; Claridge, Shelley A

2016-04-01

Because noncovalent interface functionalization is frequently required in graphene-based devices, biomolecular self-assembly has begun to emerge as a route for controlling substrate electronic structure or binding specificity for soluble analytes. The remarkable diversity of structures that arise in biological self-assembly hints at the possibility of equally diverse and well-controlled surface chemistry at graphene interfaces. However, predicting and analyzing adsorbed monolayer structures at such interfaces raises substantial experimental and theoretical challenges. In contrast with the relatively well-developed monolayer chemistry and characterization methods applied at coinage metal surfaces, monolayers on graphene are both less robust and more structurally complex, levying more stringent requirements on characterization techniques. Theory presents opportunities to understand early binding events that lay the groundwork for full monolayer structure. However, predicting interactions between complex biomolecules, solvent, and substrate is necessitating a suite of new force fields and algorithms to assess likely binding configurations, solvent effects, and modulations to substrate electronic properties. This article briefly discusses emerging analytical and theoretical methods used to develop a rigorous chemical understanding of the self-assembly of peptide-graphene interfaces and prospects for future advances in the field.

Analytical solutions for tomato peeling with combined heat flux and convective boundary conditions

NASA Astrophysics Data System (ADS)

Cuccurullo, G.; Giordano, L.; Metallo, A.

2017-11-01

Peeling of tomatoes by radiative heating is a valid alternative to steam or lye, which are expensive and pollutant methods. Suitable energy densities are required in order to realize short time operations, thus involving only a thin layer under the tomato surface. This paper aims to predict the temperature field in rotating tomatoes exposed to the source irradiation. Therefore, a 1D unsteady analytical model is presented, which involves a semi-infinite slab subjected to time dependent heating while convective heat transfer takes place on the exposed surface. In order to account for the tomato rotation, the heat source is described as the positive half-wave of a sinusoidal function. The problem being linear, the solution is derived following the Laplace Transform Method. In addition, an easy-to-handle solution for the problem at hand is presented, which assumes a differentiable function for approximating the source while neglecting convective cooling, the latter contribution turning out to be negligible for the context at hand. A satisfying agreement between the two analytical solutions is found, therefore, an easy procedure for a proper design of the dry heating system can be set up avoiding the use of numerical simulations.

The Robin Hood method - A novel numerical method for electrostatic problems based on a non-local charge transfer

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

Lazic, Predrag; Stefancic, Hrvoje; Abraham, Hrvoje

2006-03-20

We introduce a novel numerical method, named the Robin Hood method, of solving electrostatic problems. The approach of the method is closest to the boundary element methods, although significant conceptual differences exist with respect to this class of methods. The method achieves equipotentiality of conducting surfaces by iterative non-local charge transfer. For each of the conducting surfaces, non-local charge transfers are performed between surface elements, which differ the most from the targeted equipotentiality of the surface. The method is tested against analytical solutions and its wide range of application is demonstrated. The method has appealing technical characteristics. For the problemmore » with N surface elements, the computational complexity of the method essentially scales with N {sup {alpha}}, where {alpha} < 2, the required computer memory scales with N, while the error of the potential decreases exponentially with the number of iterations for many orders of magnitude of the error, without the presence of the Critical Slowing Down. The Robin Hood method could prove useful in other classical or even quantum problems. Some future development ideas for possible applications outside electrostatics are addressed.« less

HPLC-DAD method development and validation for the quantification of hydroxymethylfurfural in corn chips by means of response surface optimisation.

PubMed

Salvatierra Virgen, Sara; Ceballos-Magaña, Silvia Guillermina; Salvatierra-Stamp, Vilma Del Carmen; Sumaya-Martínez, Maria Teresa; Martínez-Martínez, Francisco Javier; Muñiz-Valencia, Roberto

2017-12-01

In recent years, there has been an increased concern about the presence of toxic compounds derived from the Maillard reaction produced during food cooking at high temperatures. The main toxic compounds derived from this reaction are acrylamide and hydroxymethylfurfural (HMF). The majority of analytical methods require sample treatments using solvents which are highly polluting for the environment. The difficulty of quantifying HMF in complex fried food matrices encourages the development of new analytical methods. This paper provides a rapid, sensitive and environmentally-friendly analytical method for the quantification of HMF in corn chips using HPLC-DAD. Chromatographic separation resulted in a baseline separation for HMF in 3.7 min. Sample treatment for corn chip samples first involved a leaching process using water and afterwards a solid-phase extraction (SPE) using HLB-Oasis polymeric cartridges. Sample treatment optimisation was carried out by means of Box-Behnken fractional factorial design and Response Surface Methodolog y to examine the effects of four variables (sample weight, pH, sonication time and elution volume) on HMF extraction from corn chips. The SPE-HPLC-DAD method was validated. The limits of detection and quantification were 0.82 and 2.20 mg kg -1 , respectively. Method precision was evaluated in terms of repeatability and reproducibility as relative standard deviations (RSDs) using three concentration levels. For repeatability, RSD values were 6.9, 3.6 and 2.0%; and for reproducibility 18.8, 7.9 and 2.9%. For a ruggedness study the Yuden test was applied and the result demonstrated the method as robust. The method was successfully applied to different corn chip samples.

Quantitative evaluation of analyte transport on microfluidic paper-based analytical devices (μPADs).

PubMed

Ota, Riki; Yamada, Kentaro; Suzuki, Koji; Citterio, Daniel

2018-02-07

The transport efficiency during capillary flow-driven sample transport on microfluidic paper-based analytical devices (μPADs) made from filter paper has been investigated for a selection of model analytes (Ni 2+ , Zn 2+ , Cu 2+ , PO 4 3- , bovine serum albumin, sulforhodamine B, amaranth) representing metal cations, complex anions, proteins and anionic molecules. For the first time, the transport of the analytical target compounds rather than the sample liquid, has been quantitatively evaluated by means of colorimetry and absorption spectrometry-based methods. The experiments have revealed that small paperfluidic channel dimensions, additional user operation steps (e.g. control of sample volume, sample dilution, washing step) as well as the introduction of sample liquid wicking areas allow to increase analyte transport efficiency. It is also shown that the interaction of analytes with the negatively charged cellulosic paper substrate surface is strongly influenced by the physico-chemical properties of the model analyte and can in some cases (Cu 2+ ) result in nearly complete analyte depletion during sample transport. The quantitative information gained through these experiments is expected to contribute to the development of more sensitive μPADs.

Towards an Airframe Noise Prediction Methodology: Survey of Current Approaches

NASA Technical Reports Server (NTRS)

Farassat, Fereidoun; Casper, Jay H.

2006-01-01

In this paper, we present a critical survey of the current airframe noise (AFN) prediction methodologies. Four methodologies are recognized. These are the fully analytic method, CFD combined with the acoustic analogy, the semi-empirical method and fully numerical method. It is argued that for the immediate need of the aircraft industry, the semi-empirical method based on recent high quality acoustic database is the best available method. The method based on CFD and the Ffowcs William- Hawkings (FW-H) equation with penetrable data surface (FW-Hpds ) has advanced considerably and much experience has been gained in its use. However, more research is needed in the near future particularly in the area of turbulence simulation. The fully numerical method will take longer to reach maturity. Based on the current trends, it is predicted that this method will eventually develop into the method of choice. Both the turbulence simulation and propagation methods need to develop more for this method to become useful. Nonetheless, the authors propose that the method based on a combination of numerical and analytical techniques, e.g., CFD combined with FW-H equation, should also be worked on. In this effort, the current symbolic algebra software will allow more analytical approaches to be incorporated into AFN prediction methods.

Quantitative Analysis of Fullerene Nanomaterials in Environmental Systems: A Critical Review

PubMed Central

Isaacson, Carl W.; Kleber, Markus; Field, Jennifer A.

2009-01-01

The increasing production and use of fullerene nanomaterials has led to calls for more information regarding the potential impacts that releases of these materials may have on human and environmental health. Fullerene nanomaterials, which are comprised of both fullerenes and surface-functionalized fullerenes, are used in electronic, optic, medical and cosmetic applications. Measuring fullerene nanomaterial concentrations in natural environments is difficult because they exhibit a duality of physical and chemical characteristics as they transition from hydrophobic to polar forms upon exposure to water. In aqueous environments, this is expressed as their tendency to initially (i) self assemble into aggregates of appreciable size and hydrophobicity, and subsequently (ii) interact with the surrounding water molecules and other chemical constituents in natural environments thereby acquiring negative surface charge. Fullerene nanomaterials may therefore deceive the application of any single analytical method that is applied with the assumption that fullerenes have but one defining characteristic (e.g., hydrophobicity). [1] We find that analytical procedures are needed to account for the potentially transitory nature of fullerenes in natural environments through the use of approaches that provide chemically-explicit information including molecular weight and the number and identity of surface functional groups. [2] We suggest that sensitive and mass-selective detection, such as that offered by mass spectrometry when combined with optimized extraction procedures, offers the greatest potential to achieve this goal. [3] With this review, we show that significant improvements in analytical rigor would result from an increased availability of well characterized authentic standards, reference materials, and isotopically-labeled internal standards. Finally, the benefits of quantitative and validated analytical methods for advancing the knowledge on fullerene occurrence, fate, and behavior are indicated. PMID:19764203

The integration of a mesh reflector to a 15-foot box truss structure. Task 3: Box truss analysis and technology development

NASA Technical Reports Server (NTRS)

Bachtell, E. E.; Thiemet, W. F.; Morosow, G.

1987-01-01

To demonstrate the design and integration of a reflective mesh surface to a deployable truss structure, a mesh reflector was installed on a 15 foot box truss cube. The specific features demonstrated include: (1) sewing seams in reflective mesh; (2) mesh stretching to desired preload; (3) installation of surface tie cords; (4) installation of reflective surface on truss; (5) setting of reflective surface; (6) verification of surface shape/accuracy; (7) storage and deployment; (8) repeatability of reflector surface; and (9) comparison of surface with predicted shape using analytical methods developed under a previous task.

Communication — Modeling polymer-electrolyte fuel-cell agglomerates with double-trap kinetics

DOE PAGES

Pant, Lalit M.; Weber, Adam Z.

2017-04-14

A new semi-analytical agglomerate model is presented for polymer-electrolyte fuel-cell cathodes. The model uses double-trap kinetics for the oxygen-reduction reaction, which can capture the observed potential-dependent coverage and Tafel-slope changes. An iterative semi-analytical approach is used to obtain reaction rate constants from the double-trap kinetics, oxygen concentration at the agglomerate surface, and overall agglomerate reaction rate. The analytical method can predict reaction rates within 2% of the numerically simulated values for a wide range of oxygen concentrations, overpotentials, and agglomerate sizes, while saving simulation time compared to a fully numerical approach.

Progress in Preparation of Monodisperse Polymer Microspheres

NASA Astrophysics Data System (ADS)

Zhang, Hongyan

2017-12-01

The monodisperse crosslinked polymer microspheres have attracted much attention because of their superior thermal and solvent resistance, mechanical strength, surface activity and adsorption properties. They are of wide prospects for using in many fields such as biomedicine, electronic science, information technology, analytical chemistry, standard measurement and environment protection etc. Functional polymer microspheres prepared by different methods have the outstanding surface property, quantum size effect and good potential future in applications with its designable structure, controlled size and large ratio of surface to volume. Scholars of all over the world have focused on this hot topic. The preparation method and research progress in functional polymer microspheres are addressed in the paper.

Surface Fractal Analysis for Estimating the Fracture Energy Absorption of Nanoparticle Reinforced Composites

PubMed Central

Pramanik, Brahmananda; Tadepalli, Tezeswi; Mantena, P. Raju

2012-01-01

In this study, the fractal dimensions of failure surfaces of vinyl ester based nanocomposites are estimated using two classical methods, Vertical Section Method (VSM) and Slit Island Method (SIM), based on the processing of 3D digital microscopic images. Self-affine fractal geometry has been observed in the experimentally obtained failure surfaces of graphite platelet reinforced nanocomposites subjected to quasi-static uniaxial tensile and low velocity punch-shear loading. Fracture energy and fracture toughness are estimated analytically from the surface fractal dimensionality. Sensitivity studies show an exponential dependency of fracture energy and fracture toughness on the fractal dimensionality. Contribution of fracture energy to the total energy absorption of these nanoparticle reinforced composites is demonstrated. For the graphite platelet reinforced nanocomposites investigated, surface fractal analysis has depicted the probable ductile or brittle fracture propagation mechanism, depending upon the rate of loading. PMID:28817017

Proceedings ICASS 2017

NASA Astrophysics Data System (ADS)

Fu, Qiang; Schaaf, Peter

2018-07-01

This special issue of the high impact international peer reviewed journal Applied Surface Science represents the proceedings of the 2nd International Conference on Applied Surface Science ICASS held 12-16 June 2017 in Dalian China. The conference provided a forum for researchers in all areas of applied surface science to present their work. The main topics of the conference are in line with the most popular areas of research reported in Applied Surface Science. Thus, this issue includes current research on the role and use of surfaces in chemical and physical processes, related to catalysis, electrochemistry, surface engineering and functionalization, biointerfaces, semiconductors, 2D-layered materials, surface nanotechnology, energy, new/functional materials and nanotechnology. Also the various techniques and characterization methods will be discussed. Hence, scientific research on the atomic and molecular level of material properties investigated with specific surface analytical techniques and/or computational methods is essential for any further progress in these fields.

Application of Surface Analysis Methods to Nanomaterials: Summaryof ISO/TC 201 Technical Report: ISO 14187:2011 -Surface Chemical Analysis- Characterization of Nanomaterials

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

Baer, Donald R.

ISO Technical Report (TR) 14187 provides an introduction to (and examples of) the information that can be obtained about nanostructured materials using surface-analysis tools. In addition, both general issues and challenges associated with characterising nanostructured materials and the specific opportunities and challenges associated with individual analytical methods are identified. As the size of objects or components of materials approaches a few nanometres, the distinctions among 'bulk', 'surface' and 'particle' analysis blur. This Technical Report focuses on issues specifically relevant to surface chemical analysis of nanostructured materials. The report considers a variety of analysis methods but focuses on techniques that aremore » in the domain of ISO/TC 201 including Auger electron spectroscopy, X-ray photoelectron spectroscopy, secondary ion mass spectrometry, and scanning probe microscopy. Measurements of nanoparticle surface properties such as surface potential that are often made in a solution are not discussed.« less

Methods for analysis of cracks in three-dimensional solids

NASA Technical Reports Server (NTRS)

Raju, I. S.; Newman, J. C., Jr.

1984-01-01

Various analytical and numerical methods used to evaluate the stress intensity factors for cracks in three-dimensional (3-D) solids are reviewed. Classical exact solutions and many of the approximate methods used in 3-D analyses of cracks are reviewed. The exact solutions for embedded elliptic cracks in infinite solids are discussed. The approximate methods reviewed are the finite element methods, the boundary integral equation (BIE) method, the mixed methods (superposition of analytical and finite element method, stress difference method, discretization-error method, alternating method, finite element-alternating method), and the line-spring model. The finite element method with singularity elements is the most widely used method. The BIE method only needs modeling of the surfaces of the solid and so is gaining popularity. The line-spring model appears to be the quickest way to obtain good estimates of the stress intensity factors. The finite element-alternating method appears to yield the most accurate solution at the minimum cost.

Investigating Arsenic Contents in Surface and Drinking Water by Voltammetry and the Method of Standard Additions

ERIC Educational Resources Information Center

Cheng, Anran; Tyne, Rebecca; Kwok, Yu Ting; Rees, Louis; Craig, Lorraine; Lapinee, Chaipat; D'Arcy, Mitch; Weiss, Dominik J.; Salau¨n, Pascal

2016-01-01

Testing water samples for arsenic contamination has become an important water quality issue worldwide. Arsenic usually occurs in very small concentrations, and a sensitive analytical method is needed. We present here a 1-day laboratory module developed to introduce Earth Sciences and/or Chemistry student undergraduates to key aspects of this…

Desorption in Mass Spectrometry

PubMed Central

Usmanov, Dilshadbek Tursunbayevich; Ninomiya, Satoshi; Chen, Lee Chuin; Saha, Subhrakanti; Mandal, Mridul Kanti; Sakai, Yuji; Takaishi, Rio; Habib, Ahsan; Hiraoka, Kenzo; Yoshimura, Kentaro; Takeda, Sen; Wada, Hiroshi; Nonami, Hiroshi

2017-01-01

In mass spectrometry, analytes must be released in the gas phase. There are two representative methods for the gasification of the condensed samples, i.e., ablation and desorption. While ablation is based on the explosion induced by the energy accumulated in the condensed matrix, desorption is a single molecular process taking place on the surface. In this paper, desorption methods for mass spectrometry developed in our laboratory: flash heating/rapid cooling, Leidenfrost phenomenon-assisted thermal desorption (LPTD), solid/solid friction, liquid/solid friction, electrospray droplet impact (EDI) ionization/desorption, and probe electrospray ionization (PESI), will be described. All the methods are concerned with the surface and interface phenomena. The concept of how to desorb less-volatility compounds from the surface will be discussed. PMID:28337398

Mechanism of total electron emission yield reduction using a micro-porous surface

NASA Astrophysics Data System (ADS)

Ye, Ming; Wang, Dan; He, Yongning

2017-03-01

Suppression of the total secondary electron yield (TEY) of metal surfaces is important in many areas such as accelerator, satellite, and Hall thruster. Among TEY suppression techniques, micro-porous surfaces have been demonstrated as an effective method. In this work, we developed an analytical model that is able to obtain the contributions of TEY from both the 1st and 2nd generation secondary electrons (SEs). Calculation results show that the TEY contributed by the bottom of the hole dominates the TEY of the micro-porous surface with the aspect ratio we have chosen. Thus, we developed the following design guidance for the improvement of the TEY suppression efficiency of the micro-porous surface: either lower the TEY of the bottom or guide its SEs to the lateral side of the hole. To verify this idea, we performed the following numerical simulations: a micro-hole with its inner surfaces coated with a low TEY material and a micro-hole with nano-triangular grooves or nano-truncated cone pillars embedded at its bottom. Compared with a usual micro-hole, the proposed hybrid micro/nano structures show improved TEY suppression efficiency as expected from the analytical model. The percentage ratios of the 1st and 2nd generation SEs obtained from the simulation agree well with the predictions of the analytical model. What is more, we also present the results of the emitting angle distribution of SEs which represent remarkable deviation from the usual cosine distribution.

Surface Analysis of Nerve Agent Degradation Products by ...

EPA Pesticide Factsheets

Report This sampling and analytical procedure was developed and applied by a single laboratory to investigate nerve agent degradation products, which may persist at a contaminated site, via surface wiping followed by analytical characterization. The performance data presented demonstrate the fitness-for-purpose regarding surface analysis in that single laboratory. Surfaces (laminate, glass, galvanized steel, vinyl tile, painted drywall and treated wood) were wiped with cotton gauze wipes, sonicated, extracted with distilled water, and filtered. Samples were analyzed with direct injection electrospray ionization liquid chromatography tandem mass spectrometry (ESI-LC/MS/MS) without derivatization. Detection limit data were generated for all analytes of interest on a laminate surface. Accuracy and precision data were generated from each surface fortified with these analytes.

Surface charge method for molecular surfaces with curved areal elements I. Spherical triangles

NASA Astrophysics Data System (ADS)

Yu, Yi-Kuo

2018-03-01

Parametrizing a curved surface with flat triangles in electrostatics problems creates a diverging electric field. One way to avoid this is to have curved areal elements. However, charge density integration over curved patches appears difficult. This paper, dealing with spherical triangles, is the first in a series aiming to solve this problem. Here, we lay the ground work for employing curved patches for applying the surface charge method to electrostatics. We show analytically how one may control the accuracy by expanding in powers of the the arc length (multiplied by the curvature). To accommodate not extremely small curved areal elements, we have provided enough details to include higher order corrections that are needed for better accuracy when slightly larger surface elements are used.

Development of analytical methods for multiplex bio-assay with inductively coupled plasma mass spectrometry

PubMed Central

Ornatsky, Olga I.; Kinach, Robert; Bandura, Dmitry R.; Lou, Xudong; Tanner, Scott D.; Baranov, Vladimir I.; Nitz, Mark; Winnik, Mitchell A.

2008-01-01

Advances in the development of highly multiplexed bio-analytical assays with inductively coupled plasma mass spectrometry (ICP-MS) detection are discussed. Use of novel reagents specifically designed for immunological methods utilizing elemental analysis is presented. The major steps of method development, including selection of elements for tags, validation of tagged reagents, and examples of multiplexed assays, are considered in detail. The paper further describes experimental protocols for elemental tagging of antibodies, immunostaining of live and fixed human leukemia cells, and preparation of samples for ICP-MS analysis. Quantitative analysis of surface antigens on model cell lines using a cocktail of seven lanthanide labeled antibodies demonstrated high specificity and concordance with conventional immunophenotyping. PMID:19122859

Fluorescence lifetime imaging and Fourier transform infrared spectroscopy of Michelangelo's David.

PubMed

Comelli, Daniela; Valentini, Gianluca; Cubeddu, Rinaldo; Toniolo, Lucia

2005-09-01

We developed a combined procedure for the analysis of works of art based on a portable system for fluorescence imaging integrated with analytical measurements on microsamples. The method allows us to localize and identify organic and inorganic compounds present on the surface of artworks. The fluorescence apparatus measures the temporal and spectral features of the fluorescence emission, excited by ultraviolet (UV) laser pulses. The kinetic of the emission is studied through a fluorescence lifetime imaging system, while an optical multichannel analyzer measures the fluorescence spectra of selected points. The chemical characterization of the compounds present on the artistic surfaces is then performed by means of analytical measurements on microsamples collected with the assistance of the fluorescence maps. The previous concepts have been successfully applied to study the contaminants on the surface of Michelangelo's David. The fluorescence analysis combined with Fourier transform infrared (FT-IR) measurements revealed the presence of beeswax, which permeates most of the statue surface, and calcium oxalate deposits mainly arranged in vertical patterns and related to rain washing.

Solvothermal synthesis of selenium nano and microspheres deposited on silicon surface by microwave-assisted method

NASA Astrophysics Data System (ADS)

Ahmad, Muthanna

2016-10-01

This work describes a new application of the solvothermal method, based on the microwave heating, for the synthesis of nano and microparticles of selenium. The reaction of selenium with hydrofluoric acid on the silicon surface is induced by microwave irradiation under high pressure and temperature of 60 bar and 160 °C, respectively. This method allows the deposition of spherical-like particles on the in situ etched silicon surface. The size of deposited selenium spheres scales from tens of nanometers up to tens of micrometers. The morphology and composition of the deposited selenium were analyzed by various analytical techniques. The formation dynamic of spherical structure is explained on the base of reduction of selenium species by hydrogen inside gas bubbles which are generated on the silicon surface by the etching process.

Thermal desorption of metals from tungsten single crystal surfaces

NASA Technical Reports Server (NTRS)

Bauer, E.; Bonczek, F.; Poppa, H.; Todd, G.

1975-01-01

After a short review of experimental methods used to determine desorption energies and frequencies the assumptions underlying the theoretical analysis of experimental data are discussed. Recent experimental results on the flash desorption of Cu, Ag, and Au from clean, well characterized W (110) and (100) surfaces are presented and analyzed in detail with respect to the coverage dependence. The results obtained clearly reveal the limitations of previous analytical methods and of the experimental technique per se (such as structure and phase changes below and in the temperature region in which desorption occurs).

Implementing and testing a panel-based method for modeling acoustic scattering from CFD input

NASA Astrophysics Data System (ADS)

Swift, S. Hales

Exposure of sailors to high levels of noise in the aircraft carrier deck environment is a problem that has serious human and economic consequences. A variety of approaches to quieting exhausting jets from high-performance aircraft are undergoing development. However, testing of noise abatement solutions at full-scale may be prohibitively costly when many possible nozzle treatments are under consideration. A relatively efficient and accurate means of predicting the noise levels resulting from engine-quieting technologies at personnel locations is needed. This is complicated by the need to model both the direct and the scattered sound field in order to determine the resultant spectrum and levels. While the direct sound field may be obtained using CFD plus surface integral methods such as the Ffowcs-Williams Hawkings method, the scattered sound field is complicated by its dependence on the geometry of the scattering surface--the aircraft carrier deck, aircraft control surfaces and other nearby structures. In this work, a time-domain boundary element method, or TD-BEM, (sometimes referred to in terms of source panels) is proposed and developed that takes advantage of and offers beneficial effects for the substantial planar components of the aircraft carrier deck environment and uses pressure gradients as its input. This method is applied to and compared with analytical results for planar surfaces, corners and spherical surfaces using an analytic point source as input. The method can also accept input from CFD data on an acoustic data surface by using the G1A pressure gradient formulation to obtain pressure gradients on the surface from the flow variables contained on the acoustic data surface. The method is also applied to a planar scattering surface characteristic of an aircraft carrier flight deck with an acoustic data surface from a supersonic jet large eddy simulation, or LES, as input to the scattering model. In this way, the process for modeling the complete sound field (assuming the availability of an acoustic data surface from a time-realized numerical simulation of the jet flow field) is outlined for a realistic group of source location, scattering surface location and observer locations. The method was able to successfully model planar cases, corners and spheres with a level of error that is low enough for some engineering purposes. Significant benefits were realized for fully planar surfaces including high parallelizability and avoidance of interaction between portions of the paneled boundary. When the jet large eddy simulation case was considered the method was able to capture a substantial portion of the spectrum including the peak frequency region and a majority of the spectral energy with good fidelity.

Analytical study on the thermal performance of a partially wet constructal T-shaped fin

NASA Astrophysics Data System (ADS)

Hazarika, Saheera Azmi; Zeeshan, Mohd; Bhanja, Dipankar; Nath, Sujit

2017-07-01

The present paper addresses the thermal analysis of a T-shaped fin under partially wet condition by adopting a cubic variation of the humidity ratio of saturated air with the corresponding fin surface temperature. The point separating the dry and wet parts may lie either in the flange or stem part of the fin and so, two different cases having different governing equations and boundary conditions are analyzed in this paper. Since the governing equations are highly non-linear, they are solved by using an analytical technique called the Differential Transform Method and subsequently, the dry fin length, temperature distribution and fin performances are evaluated and analyzed for a wide range of the various psychometric, geometric and thermo-physical parameters. Finally, it can be highlighted that relative humidity has a pronounced effect on the performance parameters when the fin surface is partially wet whereas this effect is marginally small for fully wet surface.

Methods for computing comet core temperatures

NASA Astrophysics Data System (ADS)

McKay, C. P.; Squyres, S. W.; Reynolds, R. T.

1986-06-01

The temperature profile within the comet nucleus provides the key to an understanding of the history of the volatiles within a comet. Certain difficulties arise in connection with current cometary temperature models. It is shown that the constraint of zero net heat flow can be used to derive general analytical expressions which will allow for the determination of comet core temperature for a spherically symmetric comet, taking into account information about the surface temperature and the thermal conductivity. The obtained results are compared with the expression for comet core temperatures considered by Klinger (1981). Attention is given to analytical results, an example case, and numerical models. The formalization developed makes it possible to determine the core temperature on the basis of the numerical models of the surface temperature.

Shell Corrections Stabilizing Superheavy Nuclei and Semi-spheroidal Atomic Clusters

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

Poenaru, Dorin N.

2008-01-24

The macroscopic-microscopic method is used to illustrate the shell effect stabilizing superheavy nuclei and to study the stability of semi-spheroidal clusters deposited on planar surfaces. The alpha decay of superheavy nuclei is calculated using three models: the analytical superasymmetric fission model; the universal curve, and the semiempirical formula taking into account the shell effects. Analytical relationships are obtained for the energy levels of the new semi-spheroidal harmonic oscillator (SSHO) single-particle model and for the surface and curvature energies of the semi-spheroidal clusters. The maximum degeneracy of the SSHO is reached at a super-deformed prolate shape for which the minimum ofmore » the liquid drop model energy is also attained.« less

Development of a multi-residue analytical methodology based on liquid chromatography-tandem mass spectrometry (LC-MS/MS) for screening and trace level determination of pharmaceuticals in surface and wastewaters.

PubMed

Gros, Meritxell; Petrović, Mira; Barceló, Damiá

2006-11-15

This paper describes development, optimization and validation of a method for the simultaneous determination of 29 multi-class pharmaceuticals using off line solid phase extraction (SPE) followed by liquid chromatography-triple quadrupole mass spectrometry (LC-MS-MS). Target compounds include analgesics and non-steroidal anti-inflammatories (NSAIDs), lipid regulators, psychiatric drugs, anti-histaminics, anti-ulcer agent, antibiotics and beta-blockers. Recoveries obtained were generally higher than 60% for both surface and wastewaters, with exception of several compounds that yielded lower, but still acceptable recoveries: ranitidine (50%), sotalol (50%), famotidine (50%) and mevastatin (34%). The overall variability of the method was below 15%, for all compounds and all tested matrices. Method detection limits (MDL) varied between 1 and 30ng/L and from 3 to 160ng/L for surface and wastewaters, respectively. The precision of the method, calculated as relative standard deviation (R.S.D.), ranged from 0.2 to 6% and from 1 to 11% for inter and intra-day analysis, respectively. A detailed study of matrix effects was performed in order to evaluate the suitability of different calibration approaches (matrix-matched external calibration, internal calibration, extract dilution) to reduce analyte suppression or enhancement during instrumental analysis. The main advantages and drawbacks of each approach are demonstrated, justifying the selection of internal standard calibration as the most suitable approach for our study. The developed analytical method was successfully applied to the analysis of pharmaceutical residues in WWTP influents and effluents, as well as in river water. For both, river and wastewaters, the most ubiquitous compounds belonged to the group of anti-inflammatories and analgesics, antibiotics, the lipid regulators being acetaminophen, trimethoprim, ibuprofen, ketoprofen, atenolol, propranolol, mevastatin, carbamazepine and ranitidine the most frequently detected compounds.

Development of a defect stream function, law of the wall/wake method for compressible turbulent boundary layers. Ph.D. Thesis

NASA Technical Reports Server (NTRS)

Wahls, Richard A.

1990-01-01

The method presented is designed to improve the accuracy and computational efficiency of existing numerical methods for the solution of flows with compressible turbulent boundary layers. A compressible defect stream function formulation of the governing equations assuming an arbitrary turbulence model is derived. This formulation is advantageous because it has a constrained zero-order approximation with respect to the wall shear stress and the tangential momentum equation has a first integral. Previous problems with this type of formulation near the wall are eliminated by using empirically based analytic expressions to define the flow near the wall. The van Driest law of the wall for velocity and the modified Crocco temperature-velocity relationship are used. The associated compressible law of the wake is determined and it extends the valid range of the analytical expressions beyond the logarithmic region of the boundary layer. The need for an inner-region eddy viscosity model is completely avoided. The near-wall analytic expressions are patched to numerically computed outer region solutions at a point determined during the computation. A new boundary condition on the normal derivative of the tangential velocity at the surface is presented; this condition replaces the no-slip condition and enables numerical integration to the surface with a relatively coarse grid using only an outer region turbulence model. The method was evaluated for incompressible and compressible equilibrium flows and was implemented into an existing Navier-Stokes code using the assumption of local equilibrium flow with respect to the patching. The method has proven to be accurate and efficient.

Electride Mediated Surface Enhanced Raman Scattering (SERS)

NASA Technical Reports Server (NTRS)

Anderson, Mark S. (Inventor)

2016-01-01

An electride may provide surface enhanced Raman scattering (SERS). The electride, a compound where the electrons serve as anions, may be a ceramic electride, such as a conductive ceramic derived from mayenite, or an organic electride, for example. The textured electride surface or electride particles may strongly enhance the Raman scattering of organic or other Raman active analytes. This may also provide a sensitive method for monitoring the chemistry and electronic environment at the electride surface. The results are evidence of a new class of polariton (i.e., a surface electride-polariton resonance mechanism) that is analogous to the surface plasmon-polariton resonance that mediates conventional SERS.

An experimental and analytical method for approximate determination of the tilt rotor research aircraft rotor/wing download

NASA Technical Reports Server (NTRS)

Jordon, D. E.; Patterson, W.; Sandlin, D. R.

1985-01-01

The XV-15 Tilt Rotor Research Aircraft download phenomenon was analyzed. This phenomenon is a direct result of the two rotor wakes impinging on the wing upper surface when the aircraft is in the hover configuration. For this study the analysis proceeded along tow lines. First was a method whereby results from actual hover tests of the XV-15 aircraft were combined with drag coefficient results from wind tunnel tests of a wing that was representative of the aircraft wing. Second, an analytical method was used that modeled that airflow caused gy the two rotors. Formulas were developed in such a way that acomputer program could be used to calculate the axial velocities were then used in conjunction with the aforementioned wind tunnel drag coefficinet results to produce download values. An attempt was made to validate the analytical results by modeling a model rotor system for which direct download values were determinrd..

Wettability of graphitic-carbon and silicon surfaces: MD modeling and theoretical analysis

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

Ramos-Alvarado, Bladimir; Kumar, Satish; Peterson, G. P.

2015-07-28

The wettability of graphitic carbon and silicon surfaces was numerically and theoretically investigated. A multi-response method has been developed for the analysis of conventional molecular dynamics (MD) simulations of droplets wettability. The contact angle and indicators of the quality of the computations are tracked as a function of the data sets analyzed over time. This method of analysis allows accurate calculations of the contact angle obtained from the MD simulations. Analytical models were also developed for the calculation of the work of adhesion using the mean-field theory, accounting for the interfacial entropy changes. A calibration method is proposed to providemore » better predictions of the respective contact angles under different solid-liquid interaction potentials. Estimations of the binding energy between a water monomer and graphite match those previously reported. In addition, a breakdown in the relationship between the binding energy and the contact angle was observed. The macroscopic contact angles obtained from the MD simulations were found to match those predicted by the mean-field model for graphite under different wettability conditions, as well as the contact angles of Si(100) and Si(111) surfaces. Finally, an assessment of the effect of the Lennard-Jones cutoff radius was conducted to provide guidelines for future comparisons between numerical simulations and analytical models of wettability.« less

Three-Dimensional Piecewise-Continuous Class-Shape Transformation of Wings

NASA Technical Reports Server (NTRS)

Olson, Erik D.

2015-01-01

Class-Shape Transformation (CST) is a popular method for creating analytical representations of the surface coordinates of various components of aerospace vehicles. A wide variety of two- and three-dimensional shapes can be represented analytically using only a modest number of parameters, and the surface representation is smooth and continuous to as fine a degree as desired. This paper expands upon the original two-dimensional representation of airfoils to develop a generalized three-dimensional CST parametrization scheme that is suitable for a wider range of aircraft wings than previous formulations, including wings with significant non-planar shapes such as blended winglets and box wings. The method uses individual functions for the spanwise variation of airfoil shape, chord, thickness, twist, and reference axis coordinates to build up the complete wing shape. An alternative formulation parameterizes the slopes of the reference axis coordinates in order to relate the spanwise variation to the tangents of the sweep and dihedral angles. Also discussed are methods for fitting existing wing surface coordinates, including the use of piecewise equations to handle discontinuities, and mathematical formulations of geometric continuity constraints. A subsonic transport wing model is used as an example problem to illustrate the application of the methodology and to quantify the effects of piecewise representation and curvature constraints.

A surface plasmon resonance based biochip for the detection of patulin toxin

NASA Astrophysics Data System (ADS)

Pennacchio, Anna; Ruggiero, Giuseppe; Staiano, Maria; Piccialli, Gennaro; Oliviero, Giorgia; Lewkowicz, Aneta; Synak, Anna; Bojarski, Piotr; D'Auria, Sabato

2014-08-01

Patulin is a toxic secondary metabolite of a number of fungal species belonging to the genera Penicillium and Aspergillus. One important aspect of the patulin toxicity in vivo is an injury of the gastrointestinal tract including ulceration and inflammation of the stomach and intestine. Recently, patulin has been shown to be genotoxic by causing oxidative damage to the DNA, and oxidative DNA base modifications have been considered to play a role in mutagenesis and cancer initiation. Conventional analytical methods for patulin detection involve chromatographic analyses, such as HPLC, GC, and, more recently, techniques such as LC/MS and GC/MS. All of these methods require the use of extensive protocols and the use of expensive analytical instrumentation. In this work, the conjugation of a new derivative of patulin to the bovine serum albumin for the production of polyclonal antibodies is described, and an innovative competitive immune-assay for detection of patulin is presented. Experimentally, an important part of the detection method is based on the optical technique called surface plasmon resonance (SPR). Laser beam induced interactions between probe and target molecules in the vicinity of gold surface of the biochip lead to the shift in resonance conditions and consequently to slight but easily detectable change of reflectivity.

Nano-objects as biomaterials: immense opportunities, significant challenges and the important use of surface analytical methods

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

Baer, Donald R.; Shutthanandan, Vaithiyalingam

Nano-sized objects are increasingly important as biomaterials and their surfaces play critical roles in determining their beneficial or deleterious behaviors in biological systems. Important characteristics of nanomaterials that impact their application in many areas are described with a strong focus on the importance of particle surfaces and surface characterization. Understanding aspects of the inherent nature of nano-objects and the important role that surfaces play in these applications is a universal need for any research or product development using such materials in biological applications. The role of surface analysis methods in collecting critical information about the nature of particle surfaces andmore » physicochemical properties of nano-objects is described along with the importance of including sample history and analysis results in a record of provenance information regarding specific batches of nano-objects.« less

Micelle assisted thin-film solid phase microextraction: a new approach for determination of quaternary ammonium compounds in environmental samples.

PubMed

Boyacı, Ezel; Pawliszyn, Janusz

2014-09-16

Determination of quaternary ammonium compounds (QACs) often is considered to be a challenging undertaking owing to secondary interactions of the analytes' permanently charged quaternary ammonium head or hydrophobic tail with the utilized labware. Here, for the first time, a micelle assisted thin-film solid phase microextraction (TF-SPME) using a zwitterionic detergent 3-[(3-cholamidopropyl)dimethylammonio]-1-propanesulfonate (CHAPS) as a matrix modifier is introduced as a novel approach for in-laboratory sample preparation of the challenging compounds. The proposed micelle assisted TF-SPME method offers suppression/enhancement free electrospray ionization of analytes in mass spectrometric detection, minimal interaction of the micelles with the TF-SPME coating, and chromatographic stationary phase and analysis free of secondary interactions. Moreover, it was found that the matrix modifier has multiple functions; when its concentration is found below the critical micelle concentration (CMC), the matrix modifier primarily acts as a surface deactivator; above its CMC, it acts as a stabilizer for QACs. Additionally, shorter equilibrium extraction times in the presence of the modifier demonstrated that micelles also assist in the transfer of analytes from the bulk of the sample to the surface of the coating. The developed micelle assisted TF-SPME protocol using the 96-blade system requires only 30 min of extraction and 15 min of desorption. Together with a conditioning step (15 min), the entire method is 60 min; considering the advantage of using the 96-blade system, if all the blades in the brush are used, the sample preparation time per sample is 0.63 min. Moreover, the recoveries for all analytes with the developed method were found to range within 80.2-97.3%; as such, this method can be considered an open bed solid phase extraction. The proposed method was successfully validated using real samples.

Analytical solution describing pesticide volatilization from soil affected by a change in surface condition.

PubMed

Yates, S R

2009-01-01

An analytical solution describing the fate and transport of pesticides applied to soils has been developed. Two pesticide application methods can be simulated: point-source applications, such as idealized shank or a hot-gas injection method, and a more realistic shank-source application method that includes a vertical pesticide distribution in the soil domain due to a soil fracture caused by a shank. The solutions allow determination of the volatilization rate and other information that could be important for understanding fumigant movement and in the development of regulatory permitting conditions. The solutions can be used to characterize differences in emissions relative to changes in the soil degradation rate, surface barrier conditions, application depth, and soil packing. In some cases, simple algebraic expressions are provided that can be used to obtain the total emissions and total soil degradation. The solutions provide a consistent methodology for determining the total emissions and can be used with other information, such as field and laboratory experimental data, to support the development of fumigant regulations. The uses of the models are illustrated by several examples.

Enhanced biosensor performance using an avidin-biotin bridge for antibody immobilization

NASA Astrophysics Data System (ADS)

Narang, Upvan; Anderson, George P.; King, Keeley D.; Liss, Heidi S.; Ligler, Frances S.

1997-05-01

Maintaining antibody function after immobilization is critical to the performance of a biosensor. The conventional methods to immobilize antibodies onto surfaces are via covalent attachment using a crosslinker or by adsorption. Often, these methods of immobilization result in partial denaturation of the antibody and conformational changes leading to a reduced activity of the antibody. In this paper, we report on the immobilization of antibodies onto the surface of an optical fiber through an avidin-biotin bridge for the detection of ricin, ovalbumin, and Bacillus globigii (Bg). The assays are performed in a sandwich format. First, a capture antibody is immobilized, followed by the addition of the analyte. Finally, a fluorophore- labeled antibody is added for the specific detection of the analyte. The evanescent wave-induced fluorescence is coupled back through the same fiber to be detected using a photodiode. In all cases, we observe an improved performance of the biosensor, i.e., lower limit of detection and wide linear dynamic range, for the assays in which the antibody is immobilized via avidin-biotin bridges compared to covalent attachment method.

Providing the physical basis of SCS curve number method and its proportionality relationship from Richards' equation

NASA Astrophysics Data System (ADS)

Hooshyar, M.; Wang, D.

2016-12-01

The empirical proportionality relationship, which indicates that the ratio of cumulative surface runoff and infiltration to their corresponding potentials are equal, is the basis of the extensively used Soil Conservation Service Curve Number (SCS-CN) method. The objective of this paper is to provide the physical basis of the SCS-CN method and its proportionality hypothesis from the infiltration excess runoff generation perspective. To achieve this purpose, an analytical solution of Richards' equation is derived for ponded infiltration in shallow water table environment under the following boundary conditions: 1) the soil is saturated at the land surface; and 2) there is a no-flux boundary which moves downward. The solution is established based on the assumptions of negligible gravitational effect, constant soil water diffusivity, and hydrostatic soil moisture profile between the no-flux boundary and water table. Based on the derived analytical solution, the proportionality hypothesis is a reasonable approximation for rainfall partitioning at the early stage of ponded infiltration in areas with a shallow water table for coarse textured soils.

A radiosity-based model to compute the radiation transfer of soil surface

NASA Astrophysics Data System (ADS)

Zhao, Feng; Li, Yuguang

2011-11-01

A good understanding of interactions of electromagnetic radiation with soil surface is important for a further improvement of remote sensing methods. In this paper, a radiosity-based analytical model for soil Directional Reflectance Factor's (DRF) distributions was developed and evaluated. The model was specifically dedicated to the study of radiation transfer for the soil surface under tillage practices. The soil was abstracted as two dimensional U-shaped or V-shaped geometric structures with periodic macroscopic variations. The roughness of the simulated surfaces was expressed as a ratio of the height to the width for the U and V-shaped structures. The assumption was made that the shadowing of soil surface, simulated by U or V-shaped grooves, has a greater influence on the soil reflectance distribution than the scattering properties of basic soil particles of silt and clay. Another assumption was that the soil is a perfectly diffuse reflector at a microscopic level, which is a prerequisite for the application of the radiosity method. This radiosity-based analytical model was evaluated by a forward Monte Carlo ray-tracing model under the same structural scenes and identical spectral parameters. The statistics of these two models' BRF fitting results for several soil structures under the same conditions showed the good agreements. By using the model, the physical mechanism of the soil bidirectional reflectance pattern was revealed.

Analysis of Environmental Contamination resulting from ...

EPA Pesticide Factsheets

Catastrophic incidents can generate a large number of samples with analytically diverse types including forensic, clinical, environmental, food, and others. Environmental samples include water, wastewater, soil, air, urban building and infrastructure materials, and surface residue. Such samples may arise not only from contamination from the incident but also from the multitude of activities surrounding the response to the incident, including decontamination. This document summarizes a range of activities to help build laboratory capability in preparation for analysis following a catastrophic incident, including selection and development of fit-for-purpose analytical methods for chemical, biological, and radiological contaminants. Fit-for-purpose methods are those which have been selected to meet project specific data quality objectives. For example, methods could be fit for screening contamination in the early phases of investigation of contamination incidents because they are rapid and easily implemented, but those same methods may not be fit for the purpose of remediating the environment to safe levels when a more sensitive method is required. While the exact data quality objectives defining fitness-for-purpose can vary with each incident, a governing principle of the method selection and development process for environmental remediation and recovery is based on achieving high throughput while maintaining high quality analytical results. This paper illu

Algorithm for Surface of Translation Attached Radiators (A-STAR). Volume 1: Formulation of the analysis

NASA Astrophysics Data System (ADS)

Medgyesimitschang, L. N.; Putnam, J. M.

1982-05-01

A general analytical formulation, based on the method of moments (MM) is described for solving electromagnetic problems associated with off-surface (wire) and aperture radiators on finite-length cylinders of arbitrary cross section, denoted in this report as bodies of translation (BOT). This class of bodies can be used to model structures with noncircular cross sections such as wings, fins and aircraft fuselages.

Air and Surface Sampling Method for Assessing Exposures to Quaternary Ammonium Compounds Using Liquid Chromatography Tandem Mass Spectrometry.

PubMed

LeBouf, Ryan F; Virji, Mohammed Abbas; Ranpara, Anand; Stefaniak, Aleksandr B

2017-07-01

This method was designed for sampling select quaternary ammonium (quat) compounds in air or on surfaces followed by analysis using ultraperformance liquid chromatography tandem mass spectrometry. Target quats were benzethonium chloride, didecyldimethylammonium bromide, benzyldimethyldodecylammonium chloride, benzyldimethyltetradecylammonium chloride, and benzyldimethylhexadecylammonium chloride. For air sampling, polytetrafluoroethylene (PTFE) filters are recommended for 15-min to 24-hour sampling. For surface sampling, Pro-wipe® 880 (PW) media was chosen. Samples were extracted in 60:40 acetonitrile:0.1% formic acid for 1 hour on an orbital shaker. Method detection limits range from 0.3 to 2 ng/ml depending on media and analyte. Matrix effects of media are minimized through the use of multiple reaction monitoring versus selected ion recording. Upper confidence limits on accuracy meet the National Institute for Occupational Safety and Health 25% criterion for PTFE and PW media for all analytes. Using PTFE and PW analyzed with multiple reaction monitoring, the method quantifies levels among the different quats compounds with high precision (<10% relative standard deviation) and low bias (<11%). The method is sensitive enough with very low method detection limits to capture quats on air sampling filters with only a 15-min sample duration with a maximum assessed storage time of 103 days before sample extraction. This method will support future exposure assessment and quantitative epidemiologic studies to explore exposure-response relationships and establish levels of quats exposures associated with adverse health effects. © The Author 2017. Published by Oxford University Press on behalf of the British Occupational Hygiene Society.

Amplified biosensing using the horseradish peroxidase-mimicking DNAzyme as an electrocatalyst.

PubMed

Pelossof, Gilad; Tel-Vered, Ran; Elbaz, Johann; Willner, Itamar

2010-06-01

The hemin/G-quadruplex horseradish peroxidase-mimicking DNAzyme is assembled on Au electrodes. It reveals bioelectrocatalytic properties and electrocatalyzes the reduction of H(2)O(2). The bioelectrocatalytic functions of the hemin/G-quadruplex DNAzyme are used to develop electrochemical sensors that follow the activity of glucose oxidase and biosensors for the detection of DNA or low-molecular-weight substrates (adenosine monophosphate, AMP). Hairpin nucleic structures that include the G-quadruplex sequence in a caged configuration and the nucleic acid sequence complementary to the analyte DNA, or the aptamer sequence for AMP, are immobilized on Au-electrode surfaces. In the presence of the DNA analyte, or AMP, the hairpin structures are opened, and the hemin/G-quadruplex horseradish peroxidase-mimicking DNAzyme structures are generated on the electrode surfaces. The bioelectrocatalytic cathodic currents generated by the functionalized electrodes, upon the electrochemical reduction of H(2)O(2), provide a quantitative measure for the detection of the target analytes. The DNA target was analyzed with a detection limit of 1 x 10(-12) M, while the detection limit for analyzing AMP was 1 x 10(-6) M. Methods to regenerate the sensing surfaces are presented.

Exact Analytic Solution for a Ballistic Orbiting Wind

NASA Astrophysics Data System (ADS)

Wilkin, Francis P.; Hausner, Harry

2017-07-01

Much theoretical and observational work has been done on stellar winds within binary systems. We present a new solution for a ballistic wind launched from a source in a circular orbit. The solution is that of a single wind—no second wind is included in the system and the shocks that arise are those due to the orbiting wind interacting with itself. Our method emphasizes the curved streamlines in the corotating frame, where the flow is steady-state, allowing us to obtain an exact solution for the mass density at all pre-shock locations. Assuming an initially isotropic wind, fluid elements launched from the interior hemisphere of the wind will be the first to cross other streamlines, resulting in a spiral structure bounded by two shock surfaces. Streamlines from the outer wind hemisphere later intersect these shocks as well. An analytic solution is obtained for the geometry of the two shock surfaces. Although the inner and outer shock surfaces asymptotically trace Archimedean spirals, our tail solution suggests many crossings where the shocks overlap, beyond which the analytic solution cannot be continued. Our solution can be readily extended to an initially anisotropic wind.

Material property analytical relations for the case of an AFM probe tapping a viscoelastic surface containing multiple characteristic times

PubMed Central

López-Guerra, Enrique A

2017-01-01

We explore the contact problem of a flat-end indenter penetrating intermittently a generalized viscoelastic surface, containing multiple characteristic times. This problem is especially relevant for nanoprobing of viscoelastic surfaces with the highly popular tapping-mode AFM imaging technique. By focusing on the material perspective and employing a rigorous rheological approach, we deliver analytical closed-form solutions that provide physical insight into the viscoelastic sources of repulsive forces, tip–sample dissipation and virial of the interaction. We also offer a systematic comparison to the well-established standard harmonic excitation, which is the case relevant for dynamic mechanical analysis (DMA) and for AFM techniques where tip–sample sinusoidal interaction is permanent. This comparison highlights the substantial complexity added by the intermittent-contact nature of the interaction, which precludes the derivation of straightforward equations as is the case for the well-known harmonic excitations. The derivations offered have been thoroughly validated through numerical simulations. Despite the complexities inherent to the intermittent-contact nature of the technique, the analytical findings highlight the potential feasibility of extracting meaningful viscoelastic properties with this imaging method. PMID:29114450

Analytical drain current model for symmetric dual-gate amorphous indium gallium zinc oxide thin-film transistors

NASA Astrophysics Data System (ADS)

Qin, Ting; Liao, Congwei; Huang, Shengxiang; Yu, Tianbao; Deng, Lianwen

2018-01-01

An analytical drain current model based on the surface potential is proposed for amorphous indium gallium zinc oxide (a-InGaZnO) thin-film transistors (TFTs) with a synchronized symmetric dual-gate (DG) structure. Solving the electric field, surface potential (φS), and central potential (φ0) of the InGaZnO film using the Poisson equation with the Gaussian method and Lambert function is demonstrated in detail. The compact analytical model of current-voltage behavior, which consists of drift and diffusion components, is investigated by regional integration, and voltage-dependent effective mobility is taken into account. Comparison results demonstrate that the calculation results obtained using the derived models match well with the simulation results obtained using a technology computer-aided design (TCAD) tool. Furthermore, the proposed model is incorporated into SPICE simulations using Verilog-A to verify the feasibility of using DG InGaZnO TFTs for high-performance circuit designs.

Surface enhanced Raman scattering imaging of developed thin-layer chromatography plates.

PubMed

Freye, Chris E; Crane, Nichole A; Kirchner, Teresa B; Sepaniak, Michael J

2013-04-16

A method for hyphenating surface enhanced Raman scattering (SERS) and thin-layer chromatography (TLC) is presented that employs silver-polymer nanocomposites as an interface. Through the process of conformal blotting, analytes are transferred from TLC plates to nanocomposite films before being imaged via SERS. A procedure leading to maximum blotting efficiency was established by investigating various parameters such as time, pressure, and type and amount of blotting solvent. Additionally, limits of detection were established for test analytes malachite green isothiocyanate, 4-aminothiophenol, and Rhodamine 6G (Rh6G) ranging from 10(-7) to 10(-6) M. Band broadening due to blotting was minimal (∼10%) as examined by comparing the spatial extent of TLC-spotted Rh6G via fluorescence and then the SERS-based spot size on the nanocomposite after the blotting process. Finally, a separation of the test analytes was carried out on a TLC plate followed by blotting and the acquisition of distance × wavenumber × intensity three-dimensional TLC-SERS plots.

Aggregated silver nanoparticles based surface-enhanced Raman scattering enzyme-linked immunosorbent assay for ultrasensitive detection of protein biomarkers and small molecules.

PubMed

Liang, Jiajie; Liu, Hongwu; Huang, Caihong; Yao, Cuize; Fu, Qiangqiang; Li, Xiuqing; Cao, Donglin; Luo, Zhi; Tang, Yong

2015-06-02

Lowering the detection limit is critical to the design of bioassays required for medical diagnostics, environmental monitoring, and food safety regulations. The current sensitivity of standard color-based analyte detection limits the further use of enzyme-linked immunosorbent assays (ELISAs) in research and clinical diagnoses. Here, we demonstrate a novel method that uses the Raman signal as the signal-generating system of an ELISA and combines surface-enhanced Raman scattering (SERS) with silver nanoparticles aggregation for ultrasensitive analyte detection. The enzyme label of the ELISA controls the dissolution of Raman reporter-labeled silver nanoparticles through hydrogen peroxide and generates a strong Raman signal when the analyte is present. Using this assay, prostate-specific antigen (PSA) and the adrenal stimulant ractopamine (Rac) were detected in whole serum and urine at the ultralow concentrations of 10(-9) and 10(-6) ng/mL, respectively. The methodology proposed here could potentially be applied to other molecules detection as well as PSA and Rac.

Determination of phenol compounds in surface water matrices by bar adsorptive microextraction-high performance liquid chromatography-diode array detection.

PubMed

Neng, Nuno R; Nogueira, José M F

2014-07-03

Bar adsorptive microextraction combined with liquid desorption followed by high performance liquid chromatography with diode array detection (BAµE-LD/HPLC-DAD) is proposed for the determination of trace levels of five phenol compounds (3-nitrophenol, 4-nitrophenol, bisphenol-A, 4-n-octylphenol and 4-n-nonylphenol) in surface water matrices. By using a polystyrene-divinylbenzene copolymer (PS-DVB) sorbent phase, high selectivity and efficiency is achieved even against polydimethylsiloxane through stir bar sorptive extraction. Assays performed by BAµE(PS-DVB)-LD/HPLC-DAD on 25 mL water samples spiked at the 10.0 µg/L levels yielded recoveries over 88.0%±5.7% for all five analytes, under optimized experimental conditions. The analytical performance showed good precision (RSD<15%), detection limits of 0.25 µg/L and linear dynamic ranges (1.0-25.0 μg/L) with determination coefficient higher than 0.9904. By using the standard addition method, the application of the present method to surface water matrices allowed very good performances at the trace level. The proposed methodology proved to be a suitable alternative to monitor phenol compounds in surface water matrices, showing to be easy to implement, reliable, sensitive and requiring a low sample volume.

Combining Laser Ablation/Liquid Phase Collection Surface Sampling and High-Performance Liquid Chromatography Electrospray Ionization Mass Spectrometry

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

Ovchinnikova, Olga S; Kertesz, Vilmos; Van Berkel, Gary J

This paper describes the coupling of ambient pressure transmission geometry laser ablation with a liquid phase sample collection method for surface sampling and ionization with subsequent mass spectral analysis. A commercially available autosampler was adapted to produce a liquid droplet at the end of the syringe injection needle while in close proximity to the surface to collect the sample plume produced by laser ablation. The sample collection was followed by either flow injection or a high performance liquid chromatography (HPLC) separation of the extracted components and detection with electrospray ionization mass spectrometry (ESI-MS). To illustrate the analytical utility of thismore » coupling, thin films of a commercial ink sample containing rhodamine 6G and of mixed isobaric rhodamine B and 6G dyes on glass microscope slides were analyzed. The flow injection and HPLC/ESI-MS analysis revealed successful laser ablation, capture and, with HPLC, the separation of the two compounds. The ablated circular area was about 70 m in diameter for these experiments. The spatial sampling resolution afforded by the laser ablation, as well as the ability to use sample processing methods like HPLC between the sample collection and ionization steps, makes this combined surface sampling/ionization technique a highly versatile analytical tool.« less

Polyethylenimine-assisted seed-mediated synthesis of gold nanoparticles for surface-enhanced Raman scattering studies

NASA Astrophysics Data System (ADS)

Philip, Anish; Ankudze, Bright; Pakkanen, Tuula T.

2018-06-01

Large-sized gold nanoparticles (AuNPs) were synthesized with a new polyethylenimine - assisted seed - mediated method for surface-enhanced Raman scattering (SERS) studies. The size and polydispersity of gold nanoparticles are controlled in the growth step with the amounts of polyethylenimine (PEI) and seeds. Influence of three silicon oxide supports having different surface morphologies, namely halloysite (Hal) nanotubes, glass plates and inverse opal films of SiO2, on the performance of gold nanoparticles in Raman scattering of a 4-aminothiophenol (4-ATP) analyte was investigated. Electrostatic interaction between positively charged polyethylenimine-capped AuNPs and negatively charged surfaces of silicon oxide supports was utilized in fabrication of the SERS substrates using deposition and infiltration methods. The Au-photonic crystal of the three SERS substrate groups is the most active one as it showed the highest analytical enhancement factor (AEF) and the lowest detection limit of 1x10-8 M for 4-ATP. Coupling of the optical properties of photonic crystals with the plasmonic properties of AuNPs provided Au-photonic crystals with the high SERS activity. The AuNPs clusters formed both in the photonic crystal and on the glass plate are capable of forming more hot spots as compared to sparsely distributed AuNPs on Hal nanotubes and thereby increasing the SERS enhancement.

Role of the heat accumulation effect in the multipulse modes of the femtosecond laser microstructuring of silicon

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

Guk, I. V., E-mail: corchand@gmail.com; Shandybina, G. D.; Yakovlev, E. B.

2016-05-15

The results of quantitative evaluation of the heat accumulation effect during the femtosecond laser microstructuring of the surface of silicon are presented for discussion. In the calculations, the numerical–analytical method is used, in which the dynamics of electronic processes and lattice heating are simulated by the numerical method, and the cooling stage is described on the basis of an analytical solution. The effect of multipulse irradiation on the surface temperature is studied: in the electronic subsystem, as the dependence of the absorbance on the excited carrier density and the dependence of the absorbance on the electron-gas temperature; in the latticemore » subsystem, as the variation in the absorbance from pulse to pulse. It was shown that, in the low-frequency pulse-repetition mode characteristic of the femtosecond microstructuring of silicon, the heat accumulation effect is controlled not by the residual surface temperature by the time of the next pulse arrival, which corresponds to conventional concepts, but by an increase in the maximum temperature from pulse to pulse, from which cooling begins. The accumulation of the residual temperature of the surface can affect the microstructuring process during irradiation near the evaporation threshold or with increasing pulse-repetition rate.« less

Application of techniques to identify coal-mine and power-generation effects on surface-water quality, San Juan River basin, New Mexico and Colorado

USGS Publications Warehouse

Goetz, C.L.; Abeyta, Cynthia G.; Thomas, E.V.

1987-01-01

Numerous analytical techniques were applied to determine water quality changes in the San Juan River basin upstream of Shiprock , New Mexico. Eight techniques were used to analyze hydrologic data such as: precipitation, water quality, and streamflow. The eight methods used are: (1) Piper diagram, (2) time-series plot, (3) frequency distribution, (4) box-and-whisker plot, (5) seasonal Kendall test, (6) Wilcoxon rank-sum test, (7) SEASRS procedure, and (8) analysis of flow adjusted, specific conductance data and smoothing. Post-1963 changes in dissolved solids concentration, dissolved potassium concentration, specific conductance, suspended sediment concentration, or suspended sediment load in the San Juan River downstream from the surface coal mines were examined to determine if coal mining was having an effect on the quality of surface water. None of the analytical methods used to analyzed the data showed any increase in dissolved solids concentration, dissolved potassium concentration, or specific conductance in the river downstream from the mines; some of the analytical methods used showed a decrease in dissolved solids concentration and specific conductance. Chaco River, an ephemeral stream tributary to the San Juan River, undergoes changes in water quality due to effluent from a power generation facility. The discharge in the Chaco River contributes about 1.9% of the average annual discharge at the downstream station, San Juan River at Shiprock, NM. The changes in water quality detected at the Chaco River station were not detected at the downstream Shiprock station. It was not possible, with the available data, to identify any effects of the surface coal mines on water quality that were separable from those of urbanization, agriculture, and other cultural and natural changes. In order to determine the specific causes of changes in water quality, it would be necessary to collect additional data at strategically located stations. (Author 's abstract)

HUMAN EYE OPTICS: Determination of positions of optical elements of the human eye

NASA Astrophysics Data System (ADS)

Galetskii, S. O.; Cherezova, T. Yu

2009-02-01

An original method for noninvasive determining the positions of elements of intraocular optics is proposed. The analytic dependence of the measurement error on the optical-scheme parameters and the restriction in distance from the element being measured are determined within the framework of the method proposed. It is shown that the method can be efficiently used for determining the position of elements in the classical Gullstrand eye model and personalised eye models. The positions of six optical surfaces of the Gullstrand eye model and four optical surfaces of the personalised eye model can be determined with an error of less than 0.25 mm.

Analyzing chromatographic data using multilevel modeling.

PubMed

Wiczling, Paweł

2018-06-01

It is relatively easy to collect chromatographic measurements for a large number of analytes, especially with gradient chromatographic methods coupled with mass spectrometry detection. Such data often have a hierarchical or clustered structure. For example, analytes with similar hydrophobicity and dissociation constant tend to be more alike in their retention than a randomly chosen set of analytes. Multilevel models recognize the existence of such data structures by assigning a model for each parameter, with its parameters also estimated from data. In this work, a multilevel model is proposed to describe retention time data obtained from a series of wide linear organic modifier gradients of different gradient duration and different mobile phase pH for a large set of acids and bases. The multilevel model consists of (1) the same deterministic equation describing the relationship between retention time and analyte-specific and instrument-specific parameters, (2) covariance relationships relating various physicochemical properties of the analyte to chromatographically specific parameters through quantitative structure-retention relationship based equations, and (3) stochastic components of intra-analyte and interanalyte variability. The model was implemented in Stan, which provides full Bayesian inference for continuous-variable models through Markov chain Monte Carlo methods. Graphical abstract Relationships between log k and MeOH content for acidic, basic, and neutral compounds with different log P. CI credible interval, PSA polar surface area.

Acoustic propagation operators for pressure waves on an arbitrarily curved surface in a homogeneous medium

NASA Astrophysics Data System (ADS)

Sun, Yimin; Verschuur, Eric; van Borselen, Roald

2018-03-01

The Rayleigh integral solution of the acoustic Helmholtz equation in a homogeneous medium can only be applied when the integral surface is a planar surface, while in reality almost all surfaces where pressure waves are measured exhibit some curvature. In this paper we derive a theoretically rigorous way of building propagation operators for pressure waves on an arbitrarily curved surface. Our theory is still based upon the Rayleigh integral, but it resorts to matrix inversion to overcome the limitations faced by the Rayleigh integral. Three examples are used to demonstrate the correctness of our theory - propagation of pressure waves acquired on an arbitrarily curved surface to a planar surface, on an arbitrarily curved surface to another arbitrarily curved surface, and on a spherical cap to a planar surface, and results agree well with the analytical solutions. The generalization of our method for particle velocities and the calculation cost of our method are also discussed.

A globally convergent and closed analytical solution of the Blasius equation with beneficial applications

NASA Astrophysics Data System (ADS)

Zheng, Jun; Han, Xinyue; Wang, ZhenTao; Li, Changfeng; Zhang, Jiazhong

2017-06-01

For about a century, people have been trying to seek for a globally convergent and closed analytical solution (CAS) of the Blasius Equation (BE). In this paper, we proposed a formally satisfied solution which could be parametrically expressed by two power series. Some analytical results of the laminar boundary layer of a flat plate, that were not analytically given in former studies, e.g. the thickness of the boundary layer and higher order derivatives, could be obtained based on the solution. Besides, the heat transfer in the laminar boundary layer of a flat plate with constant temperature could also be analytically formulated. Especially, the solution of the singular situation with Prandtl number Pr=0, which seems impossible to be analyzed in prior studies, could be given analytically. The method for finding the CAS of Blasius equation was also utilized in the problem of the boundary layer regulation through wall injection and slip velocity on the wall surface.

Three-Dimensional Dynamic Deformation Measurements Using Stereoscopic Imaging and Digital Speckle Photography

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

Prentice, H. J.; Proud, W. G.

2006-07-28

A technique has been developed to determine experimentally the three-dimensional displacement field on the rear surface of a dynamically deforming plate. The technique combines speckle analysis with stereoscopy, using a modified angular-lens method: this incorporates split-frame photography and a simple method by which the effective lens separation can be adjusted and calibrated in situ. Whilst several analytical models exist to predict deformation in extended or semi-infinite targets, the non-trivial nature of the wave interactions complicates the generation and development of analytical models for targets of finite depth. By interrogating specimens experimentally to acquire three-dimensional strain data points, both analytical andmore » numerical model predictions can be verified more rigorously. The technique is applied to the quasi-static deformation of a rubber sheet and dynamically to Mild Steel sheets of various thicknesses.« less

A sensitive multi-residue method for the determination of 35 micropollutants including pharmaceuticals, iodinated contrast media and pesticides in water.

PubMed

Valls-Cantenys, Carme; Scheurer, Marco; Iglesias, Mònica; Sacher, Frank; Brauch, Heinz-Jürgen; Salvadó, Victoria

2016-09-01

A sensitive, multi-residue method using solid-phase extraction followed by liquid chromatography-tandem mass spectrometry (LC-MS/MS) was developed to determine a representative group of 35 analytes, including corrosion inhibitors, pesticides and pharmaceuticals such as analgesic and anti-inflammatory drugs, five iodinated contrast media, β-blockers and some of their metabolites and transformation products in water samples. Few other methods are capable of determining such a broad range of contrast media together with other analytes. We studied the parameters affecting the extraction of the target analytes, including sorbent selection and extraction conditions, their chromatographic separation (mobile phase composition and column) and detection conditions using two ionisation sources: electrospray ionisation (ESI) and atmospheric pressure chemical ionisation (APCI). In order to correct matrix effects, a total of 20 surrogate/internal standards were used. ESI was found to have better sensitivity than APCI. Recoveries ranging from 79 to 134 % for tap water and 66 to 144 % for surface water were obtained. Intra-day precision, calculated as relative standard deviation, was below 34 % for tap water and below 21 % for surface water, groundwater and effluent wastewater. Method quantification limits (MQL) were in the low ng L(-1) range, except for the contrast agents iomeprol, amidotrizoic acid and iohexol (22, 25.5 and 17.9 ng L(-1), respectively). Finally, the method was applied to the analysis of 56 real water samples as part of the validation procedure. All of the compounds were detected in at least some of the water samples analysed. Graphical Abstract Multi-residue method for the determination of micropollutants including pharmaceuticals, iodinated contrast media and pesticides in waters by LC-MS/MS.

A general method for computing the total solar radiation force on complex spacecraft structures

NASA Technical Reports Server (NTRS)

Chan, F. K.

1981-01-01

The method circumvents many of the existing difficulties in computational logic presently encountered in the direct analytical or numerical evaluation of the appropriate surface integral. It may be applied to complex spacecraft structures for computing the total force arising from either specular or diffuse reflection or even from non-Lambertian reflection and re-radiation.

Experimental and analytical transonic flutter characteristics of a geared-elevator configuration

NASA Technical Reports Server (NTRS)

Ruhlin, C. L.; Doggett, R. V., Jr.; Gregory, R. A.

1980-01-01

The flutter model represented the aft fuselage and empennage of a proposed supersonic transport airplane and had an all movable horizontal tail with a geared elevator. It was tested mounted from a sting in the transonic dynamics tunnel. Symmetric flutter boundaries were determined experimentally at Mach numbers from 0.7 to 1.14 for a geared elevator configuration (gear ratio of 2.8 to 1.0) and an ungeared elevator configuration (gear ratio of 1.0 to 1.0). Gearing the elevator increased the experimental flutter dynamic pressures about 20 percent. Flutter calculations were made for the geared elevator configuration by using two analytical methods based on subsonic lifting surface theory. Both methods analyzed the stabilizer and elevator as a single, deforming surface, but one method also allowed the elevator to be analyzed as hinged from the stabilizer. All analyses predicted lower flutter dynamic pressures than experiment with best agreement (within 12 percent) for the hinged elevator method. Considering the model as mounted from a flexible rather than rigid sting in the analyses, had only a slight effect on the flutter results but was significant in that a sting related vibration mode was identified as a potentially flutter critical mode.

A hybrid analytical model for open-circuit field calculation of multilayer interior permanent magnet machines

NASA Astrophysics Data System (ADS)

Zhang, Zhen; Xia, Changliang; Yan, Yan; Geng, Qiang; Shi, Tingna

2017-08-01

Due to the complicated rotor structure and nonlinear saturation of rotor bridges, it is difficult to build a fast and accurate analytical field calculation model for multilayer interior permanent magnet (IPM) machines. In this paper, a hybrid analytical model suitable for the open-circuit field calculation of multilayer IPM machines is proposed by coupling the magnetic equivalent circuit (MEC) method and the subdomain technique. In the proposed analytical model, the rotor magnetic field is calculated by the MEC method based on the Kirchhoff's law, while the field in the stator slot, slot opening and air-gap is calculated by subdomain technique based on the Maxwell's equation. To solve the whole field distribution of the multilayer IPM machines, the coupled boundary conditions on the rotor surface are deduced for the coupling of the rotor MEC and the analytical field distribution of the stator slot, slot opening and air-gap. The hybrid analytical model can be used to calculate the open-circuit air-gap field distribution, back electromotive force (EMF) and cogging torque of multilayer IPM machines. Compared with finite element analysis (FEA), it has the advantages of faster modeling, less computation source occupying and shorter time consuming, and meanwhile achieves the approximate accuracy. The analytical model is helpful and applicable for the open-circuit field calculation of multilayer IPM machines with any size and pole/slot number combination.

Descriptive and Computer Aided Drawing Perspective on an Unfolded Polyhedral Projection Surface

NASA Astrophysics Data System (ADS)

Dzwierzynska, Jolanta

2017-10-01

The aim of the herby study is to develop a method of direct and practical mapping of perspective on an unfolded prism polyhedral projection surface. The considered perspective representation is a rectilinear central projection onto a surface composed of several flat elements. In the paper two descriptive methods of drawing perspective are presented: direct and indirect. The graphical mapping of the effects of the representation is realized directly on the unfolded flat projection surface. That is due to the projective and graphical connection between points displayed on the polyhedral background and their counterparts received on the unfolded flat surface. For a significant improvement of the construction of line, analytical algorithms are formulated. They draw a perspective image of a segment of line passing through two different points determined by their coordinates in a spatial coordinate system of axis x, y, z. Compared to other perspective construction methods that use information about points, for computer vision and the computer aided design, our algorithms utilize data about lines, which are applied very often in architectural forms. Possibility of drawing lines in the considered perspective enables drawing an edge perspective image of an architectural object. The application of the changeable base elements of perspective as a horizon height and a station point location enable drawing perspective image from different viewing positions. The analytical algorithms for drawing perspective images are formulated in Mathcad software, however, they can be implemented in the majority of computer graphical packages, which can make drawing perspective more efficient and easier. The representation presented in the paper and the way of its direct mapping on the flat unfolded projection surface can find application in presentation of architectural space in advertisement and art.

An adjoint method for gradient-based optimization of stellarator coil shapes

NASA Astrophysics Data System (ADS)

Paul, E. J.; Landreman, M.; Bader, A.; Dorland, W.

2018-07-01

We present a method for stellarator coil design via gradient-based optimization of the coil-winding surface. The REGCOIL (Landreman 2017 Nucl. Fusion 57 046003) approach is used to obtain the coil shapes on the winding surface using a continuous current potential. We apply the adjoint method to calculate derivatives of the objective function, allowing for efficient computation of analytic gradients while eliminating the numerical noise of approximate derivatives. We are able to improve engineering properties of the coils by targeting the root-mean-squared current density in the objective function. We obtain winding surfaces for W7-X and HSX which simultaneously decrease the normal magnetic field on the plasma surface and increase the surface-averaged distance between the coils and the plasma in comparison with the actual winding surfaces. The coils computed on the optimized surfaces feature a smaller toroidal extent and curvature and increased inter-coil spacing. A technique for computation of the local sensitivity of figures of merit to normal displacements of the winding surface is presented, with potential applications for understanding engineering tolerances.

Reagentless, Structure-Switching, Electrochemical Aptamer-Based Sensors

NASA Astrophysics Data System (ADS)

Schoukroun-Barnes, Lauren R.; Macazo, Florika C.; Gutierrez, Brenda; Lottermoser, Justine; Liu, Juan; White, Ryan J.

2016-06-01

The development of structure-switching, electrochemical, aptamer-based sensors over the past ˜10 years has led to a variety of reagentless sensors capable of analytical detection in a range of sample matrices. The crux of this methodology is the coupling of target-induced conformation changes of a redox-labeled aptamer with electrochemical detection of the resulting altered charge transfer rate between the redox molecule and electrode surface. Using aptamer recognition expands the highly sensitive detection ability of electrochemistry to a range of previously inaccessible analytes. In this review, we focus on the methods of sensor fabrication and how sensor signaling is affected by fabrication parameters. We then discuss recent studies addressing the fundamentals of sensor signaling as well as quantitative characterization of the analytical performance of electrochemical aptamer-based sensors. Although the limits of detection of reported electrochemical aptamer-based sensors do not often reach that of gold-standard methods such as enzyme-linked immunosorbent assays, the operational convenience of the sensor platform enables exciting analytical applications that we address. Using illustrative examples, we highlight recent advances in the field that impact important areas of analytical chemistry. Finally, we discuss the challenges and prospects for this class of sensors.

Analysis of surface tris (2,3-dibromopropyl) phosphate on chlorobutyl rubber SCAPE suits. [flame retardant coatings

NASA Technical Reports Server (NTRS)

Schehl, T. A.; Bennett, H. D.; Bryan, C. J.; Bright, C. W.

1978-01-01

Tris (2,30-dibromopropyl) phosphate was used to confer flame retardant properties on butyl rubber formulations used in protective clothing such as the self-contained atmospheric protective ensembles (SCAPE suits) worn at Kennedy Space Center in support of Apollo, Skylab, and Apollo-Soyuz missions since 1966. Because tris (2,3-dibromopropyl) phosphate is mutagenic, surface concentrations of the compound in SCAPE suits were investigated as were as potential methods of removing or isolating it. Analytical procedures for determining surface concentrations of the tris compound on non-porous materials are described. Soap-and-water washing is the most efficient method of removing the compound from fabricated SCAPE suits and unused material.

Method for predicting dry mechanical properties from wet wood and standing trees

DOEpatents

Meglen, Robert R.; Kelley, Stephen S.

2003-08-12

A method for determining the dry mechanical strength for a green wood comprising: illuminating a surface of the wood to be determined with light between 350-2,500 nm, the wood having a green moisture content; analyzing the surface using a spectrometric method, the method generating a first spectral data, and using a multivariate analysis to predict the dry mechanical strength of green wood when dry by comparing the first spectral data with a calibration model, the calibration model comprising a second spectrometric method of spectral data obtained from a reference wood having a green moisture content, the second spectral data correlated with a known mechanical strength analytical result obtained from a reference wood when dried and having a dry moisture content.

A SIMPLE COLORIMETRIC METHOD TO DETECT BIOLOGICAL EVIDENCE OF HUMAN EXPOSURE TO MICROCYSTINS

EPA Science Inventory

Toxic cyanobacteria are contaminants of surface waters worldwide. Microcystins are some of the most commonly detected toxins. Biological evidence of human exposure may be difficult to obtain due to limitations associated with cost, laboratory capacity, analytic support, and exp...

Exact density-potential pairs from complex-shifted axisymmetric systems

NASA Astrophysics Data System (ADS)

Ciotti, Luca; Marinacci, Federico

2008-07-01

In a previous paper, the complex-shift method has been applied to self-gravitating spherical systems, producing new analytical axisymmetric density-potential pairs. We now extend the treatment to the Miyamoto-Nagai disc and the Binney logarithmic halo, and we study the resulting axisymmetric and triaxial analytical density-potential pairs; we also show how to obtain the surface density of shifted systems from the complex shift of the surface density of the parent model. In particular, the systems obtained from Miyamoto-Nagai discs can be used to describe disc galaxies with a peanut-shaped bulge or with a central triaxial bar, depending on the direction of the shift vector. By using a constructive method that can be applied to generic axisymmetric systems, we finally show that the Miyamoto-Nagai and the Satoh discs, and the Binney logarithmic halo cannot be obtained from the complex shift of any spherical parent distribution. As a by-product of this study, we also found two new generating functions in closed form for even and odd Legendre polynomials, respectively.

Rapid determination of floral aroma compounds of lilac blossom by fast gas chromatography combined with surface acoustic wave sensor.

PubMed

Oh, Se Yeon; Shin, Hyun Du; Kim, Sung Jean; Hong, Jongki

2008-03-07

A novel analytical method using fast gas chromatography combined with surface acoustic wave sensor (GC/SAW) has been developed for the detection of volatile aroma compounds emanated from lilac blossom (Syringa species: Syringa vulgaris variginata and Syringa dilatata). GC/SAW could detect and quantify various fragrance emitted from lilac blossom, enabling to provide fragrance pattern analysis results. The fragrance pattern analysis could easily characterize the delicate differences in aromas caused by the substantial difference of chemical composition according to different color and shape of petals. Moreover, the method validation of GC/SAW was performed for the purpose of volatile floral actual aroma analysis, achieving a high reproducibility and excellent sensitivity. From the validation results, GC/SAW could serve as an alternative analytical technique for the analysis of volatile floral actual aroma of lilac. In addition, headspace solid-phase microextraction (HS-SPME) GC-MS was employed to further confirm the identification of fragrances emitted from lilac blossom and compared to GC/SAW.

Surface-enhanced Raman sensor for trace chemical detection in water

NASA Astrophysics Data System (ADS)

Lee, Vincent Y.; Farquharson, Stuart; Rainey, Petrie M.

1999-11-01

Surface-enhanced Raman spectroscopy (SERS) promises to be one of the most sensitive methods for chemical detection and in recent years SERS has been used for chemical, biochemical, environmental, and physiological applications. A variety of methods using various media (electrodes, colloids, and substrates) have been successfully developed to enhance Raman signals by six orders of magnitude and more. However, SERS has not become a routine analytical technique because these methods are unable to provide quantitative measurements. This is largely due to the inability to fabricate a sampling medium that provides reversible chemical adsorption, analysis-to-analysis reproducibility, unrestricted solution requirements (reagent concentration and pH) or sample phase (liquid or solid). In an effort to overcome these restrictions, we have developed metal-doped sol-gels to provide surface-enhancement of Raman scattering.

The Rack-Gear Tool Generation Modelling. Non-Analytical Method Developed in CATIA, Using the Relative Generating Trajectories Method

NASA Astrophysics Data System (ADS)

Teodor, V. G.; Baroiu, N.; Susac, F.; Oancea, N.

2016-11-01

The modelling of a curl of surfaces associated with a pair of rolling centrodes, when it is known the profile of the rack-gear's teeth profile, by direct measuring, as a coordinate matrix, has as goal the determining of the generating quality for an imposed kinematics of the relative motion of tool regarding the blank. In this way, it is possible to determine the generating geometrical error, as a base of the total error. The generation modelling allows highlighting the potential errors of the generating tool, in order to correct its profile, previously to use the tool in machining process. A method developed in CATIA is proposed, based on a new method, namely the method of “relative generating trajectories”. They are presented the analytical foundation, as so as some application for knows models of rack-gear type tools used on Maag teething machines.

On analyticity of linear waves scattered by a layered medium

NASA Astrophysics Data System (ADS)

Nicholls, David P.

2017-10-01

The scattering of linear waves by periodic structures is a crucial phenomena in many branches of applied physics and engineering. In this paper we establish rigorous analytic results necessary for the proper numerical analysis of a class of High-Order Perturbation of Surfaces methods for simulating such waves. More specifically, we prove a theorem on existence and uniqueness of solutions to a system of partial differential equations which model the interaction of linear waves with a multiply layered periodic structure in three dimensions. This result provides hypotheses under which a rigorous numerical analysis could be conducted for recent generalizations to the methods of Operator Expansions, Field Expansions, and Transformed Field Expansions.

The Measurement of Unsteady Surface Pressure Using a Remote Microphone Probe.

PubMed

Guan, Yaoyi; Berntsen, Carl R; Bilka, Michael J; Morris, Scott C

2016-12-03

Microphones are widely applied to measure pressure fluctuations at the walls of solid bodies immersed in turbulent flows. Turbulent motions with various characteristic length scales can result in pressure fluctuations over a wide frequency range. This property of turbulence requires sensing devices to have sufficient sensitivity over a wide range of frequencies. Furthermore, the small characteristic length scales of turbulent structures require small sensing areas and the ability to place the sensors in very close proximity to each other. The complex geometries of the solid bodies, often including large surface curvatures or discontinuities, require the probe to have the ability to be set up in very limited spaces. The development of a remote microphone probe, which is inexpensive, consistent, and repeatable, is described in the present communication. It allows for the measurement of pressure fluctuations with high spatial resolution and dynamic response over a wide range of frequencies. The probe is small enough to be placed within the interior of typical wind tunnel models. The remote microphone probe includes a small, rigid, and hollow tube that penetrates the model surface to form the sensing area. This tube is connected to a standard microphone, at some distance away from the surface, using a "T" junction. An experimental method is introduced to determine the dynamic response of the remote microphone probe. In addition, an analytical method for determining the dynamic response is described. The analytical method can be applied in the design stage to determine the dimensions and properties of the RMP components.

Probing mass-transport and binding inhomogeneity in macromolecular interactions by molecular interferometric imaging

NASA Astrophysics Data System (ADS)

Zhao, Ming; Wang, Xuefeng; Nolte, David

2009-02-01

In solid-support immunoassays, the transport of target analyte in sample solution to capture molecules on the sensor surface controls the detected binding signal. Depletion of the target analyte in the sample solution adjacent to the sensor surface leads to deviations from ideal association, and causes inhomogeneity of surface binding as analyte concentration varies spatially across the sensor surface. In the field of label-free optical biosensing, studies of mass-transport-limited reaction kinetics have focused on the average response on the sensor surface, but have not addressed binding inhomogeneities caused by mass-transport limitations. In this paper, we employ Molecular Interferometric Imaging (MI2) to study mass-transport-induced inhomogeneity of analyte binding within a single protein spot. Rabbit IgG binding to immobilized protein A/G was imaged at various concentrations and under different flow rates. In the mass-transport-limited regime, enhanced binding at the edges of the protein spots was caused by depletion of analyte towards the center of the protein spots. The magnitude of the inhomogeneous response was a function of analyte reaction rate and sample flow rate.

Thiolated poly(ɛ-caprolactone) macroligand with vacant coordination sites on gold substrate: Synthesis and surface characterization

NASA Astrophysics Data System (ADS)

Farah, Abdiaziz A.; Zheng, Susan H.; Morin, Sylvie; Bensebaa, Farid; Pietro, William J.

2007-04-01

Surface-confined telechelic poly(ɛ-caprolactone) macroligand with two distinct functional groups per polymeric chain has been synthesized and characterized. The molecular microstructure of the macroligand with regard to the properties of the end-capped functionalities and with those on surface substrate has been studied by solution and surface analytical methods (i.e., X-ray photoelectron spectroscopy (XPS), grazing angle reflectance-Fourier transform IR spectroscopy (GA-FTIR), water contact angle measurements, and atomic force microscopy (AFM)) to elucidate the structure and properties of such multifunctional polymer on gold (1 1 1) substrate.

Rough SERS substrate based on gold coated porous silicon layer prepared on the silicon backside surface

NASA Astrophysics Data System (ADS)

Dridi, H.; Haji, L.; Moadhen, A.

2017-04-01

We report in this paper a novel method to elaborate rough Surface Enhanced Raman Scattering (SERS) substrate. A single layer of porous silicon was formed on the silicon backside surface. Morphological characteristics of the porous silicon layer before and after gold deposition were influenced by the rough character (gold size). The reflectance measurements showed a dependence of the gold nano-grains size on the surface nature, through the Localized Surface Plasmon (LSP) band properties. SERS signal of Rhodamine 6G used as a model analyte, adsorbed on the rough porous silicon layer revealed a marked enhancement of its vibrational modes intensities.

Comparison of analytical and experimental subsonic steady and unsteady pressure distributions for a high-aspect-ratio-supercritical wing model with oscillating control surfaces

NASA Technical Reports Server (NTRS)

Mccain, W. E.

1982-01-01

The results of a comparative study using the unsteady aerodynamic lifting surface theory, known as the Doublet Lattice method, and experimental subsonic steady- and unsteady-pressure measurements, are presented for a high-aspect-ratio supercritical wing model. Comparisons of pressure distributions due to wing angle of attack and control-surface deflections were made. In general, good correlation existed between experimental and theoretical data over most of the wing planform. The more significant deviations found between experimental and theoretical data were in the vicinity of control surfaces for both static and oscillatory control-surface deflections.

A simple fabrication of plasmonic surface-enhanced Raman scattering (SERS) substrate for pesticide analysis via the immobilization of gold nanoparticles on UF membrane

NASA Astrophysics Data System (ADS)

Hong, Jangho; Kawashima, Ayato; Hamada, Noriaki

2017-06-01

In this study, we developed a facile fabrication method to access a highly reproducible plasmonic surface enhanced Raman scattering substrate via the immobilization of gold nanoparticles on an Ultrafiltration (UF) membrane using a suction technique. This was combined with a simple and rapid analyte concentration and detection method utilizing portable Raman spectroscopy. The minimum detectable concentrations for aqueous thiabendazole standard solution and thiabendazole in orange extract are 0.01 μg/mL and 0.125 μg/g, respectively. The partial least squares (PLS) regression plot shows a good linear relationship between 0.001 and 100 μg/mL of analyte, with a root mean square error of prediction (RMSEP) of 0.294 and a correlation coefficient (R2) of 0.976 for the thiabendazole standard solution. Meanwhile, the PLS plot also shows a good linear relationship between 0.0 and 2.5 μg/g of analyte, with an RMSEP value of 0.298 and an R2 value of 0.993 for the orange peel extract. In addition to the detection of other types of pesticides in agricultural products, this highly uniform plasmonic substrate has great potential for application in various environmentally-related areas.

Surface Plasmon Resonance-Based Fiber Optic Sensors Utilizing Molecular Imprinting

PubMed Central

Gupta, Banshi D.; Shrivastav, Anand M.; Usha, Sruthi P.

2016-01-01

Molecular imprinting is earning worldwide attention from researchers in the field of sensing and diagnostic applications, due to its properties of inevitable specific affinity for the template molecule. The fabrication of complementary template imprints allows this technique to achieve high selectivity for the analyte to be sensed. Sensors incorporating this technique along with surface plasmon or localized surface plasmon resonance (SPR/LSPR) provide highly sensitive real time detection with quick response times. Unfolding these techniques with optical fiber provide the additional advantages of miniaturized probes with ease of handling, online monitoring and remote sensing. In this review a summary of optical fiber sensors using the combined approaches of molecularly imprinted polymer (MIP) and the SPR/LSPR technique is discussed. An overview of the fundamentals of SPR/LSPR implementation on optical fiber is provided. The review also covers the molecular imprinting technology (MIT) with its elementary study, synthesis procedures and its applications for chemical and biological anlayte detection with different sensing methods. In conclusion, we explore the advantages, challenges and the future perspectives of developing highly sensitive and selective methods for the detection of analytes utilizing MIT with the SPR/LSPR phenomenon on optical fiber platforms. PMID:27589746

Second derivatives for approximate spin projection methods

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

Thompson, Lee M.; Hratchian, Hrant P., E-mail: hhratchian@ucmerced.edu

2015-02-07

The use of broken-symmetry electronic structure methods is required in order to obtain correct behavior of electronically strained open-shell systems, such as transition states, biradicals, and transition metals. This approach often has issues with spin contamination, which can lead to significant errors in predicted energies, geometries, and properties. Approximate projection schemes are able to correct for spin contamination and can often yield improved results. To fully make use of these methods and to carry out exploration of the potential energy surface, it is desirable to develop an efficient second energy derivative theory. In this paper, we formulate the analytical secondmore » derivatives for the Yamaguchi approximate projection scheme, building on recent work that has yielded an efficient implementation of the analytical first derivatives.« less

Ultrasensitive biochemical sensing device and method of sensing analytes

DOEpatents

Pinchuk, Anatoliy

2017-06-06

Systems and methods biochemically sense a concentration of a ligand using a sensor having a substrate having a metallic nanoparticle array formed onto a surface of the substrate. A light source is incident on the surface. A matrix is deposited over the nanoparticle array and contains a protein adapted to binding the ligand. A detector detects s-polarized and p-polarized light from the reflective surface. Spacing of nanoparticles in the array and wavelength of light are selected such that plasmon resonance occurs with an isotropic point such that -s and -p polarizations of the incident light result in substantially identical surface Plasmon resonance, wherein binding of the ligand to the protein shifts the resonance such that differences between the -S and -P polarizations give in a signal indicative of presence of the ligand.

Two types of modes in finite size one-dimensional coaxial photonic crystals: General rules and experimental evidence

NASA Astrophysics Data System (ADS)

El Boudouti, E. H.; El Hassouani, Y.; Djafari-Rouhani, B.; Aynaou, H.

2007-08-01

We demonstrate analytically and experimentally the existence and behavior of two types of modes in finite size one-dimensional coaxial photonic crystals made of N cells with vanishing magnetic field on both sides. We highlight the existence of N-1 confined modes in each band and one mode by gap associated to either one or the other of the two surfaces surrounding the structure. The latter modes are independent of N . These results generalize our previous findings on the existence of surface modes in two semi-infinite superlattices obtained from the cleavage of an infinite superlattice between two cells. The analytical results are obtained by means of the Green’s function method, whereas the experiments are carried out using coaxial cables in the radio-frequency regime.

Unexpected Analyte Oxidation during Desorption Electrospray Ionization - Mass Spectrometry

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

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 resultmore » 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.« less

Optical biosensors using surface plasmon resonance

NASA Astrophysics Data System (ADS)

Homola, Jiri; Brynda, Eduard; Tobiska, Petr; Tichy, Ivo; Skvor, Jiri

1999-12-01

We present a surface plasmon resonance sensor base on prism excitation of surface plasmons and spectral interrogation. For specific detection of biomolecular analytes, multilayers of monoclonal antibodies are immobilized on the surface of the sensor. Detection of biomolecular analytes such as human (beta) -2)-microglobulin, choriogonadotropin, hepatitis B surface antigen, salmonella enteritidis is demonstrated.

Comparative Measurement of Microcystins in Diverse Surface ...

EPA Pesticide Factsheets

The measurement of microcystins, cyanotoxins associated with cyanobacterial blooms which are increasingly prevalent in inland waters, is complicated by the diversity of congeners which have been observed in the environment. At present, more than 150 microcystin congeners have been identified, and this poses a significant challenge to analytical methods intended to assess human health risks in surface and drinking water systems. The most widely employed analytical method at present is the ADDA-ELISA technique which is potentially sensitive to all microcystins, but it is primarily intended as a semi-quantitative method, and questions have been raised regarding the potential for cross-reactivity and false positives. LC-MS/MS methods targeting specific congeners, such as US EPA Method 544, are intended for use as a secondary confirmation following a positive ELISA response, but these techniques can target only those congeners for which commercial standards are available. Accordingly, they are not suitable for ascertaining the safety of a given water sample, given the potential for omitting unknown microcystin congeners which might be present.An alternative approach involves oxidative transformation of microcystins to a common product, 2-methyl-3-methoxy-4-phenylbutyric acid, or MMPB. Measuring MMPB by LC-MS/MS can potentially provide a metric for the sum of all microcystin congeners present in a sample, subject to the efficiency and overall yield of conversion. The

Comparative measurement of microcystins in diverse surface ...

EPA Pesticide Factsheets

The measurement of microcystins, cyanotoxins associated with cyanobacterial blooms which are increasingly prevalent in inland waters, is complicated by the diversity of congeners which have been observed in the environment. At present, more than 150 microcystin congeners have been identified, and this poses a significant challenge to analytical methods intended to assess human health risks in surface and drinking water systems. The most widely employed analytical method at present is the ADDA-ELISA technique which is potentially sensitive to all microcystins, but it is primarily intended as a semi-quantitative method, and questions have been raised regarding the potential for cross-reactivity and false positives. LC-MS/MS methods targeting specific congeners, such as US EPA Method 544, are intended for use as a secondary confirmation following a positive ELISA response, but these techniques can target only those congeners for which commercial standards are available. Accordingly, they not suitable for ascertaining the safety of a given water sample, given the potential for omitting unknown microcystin congeners which might be present.An alternative approach involves oxidative transformation of microcystins to a common product, 2-methyl-3-methoxy-4-phenylbutyric acid, or MMPB. Measuring MMPB by LC-MS/MS can potentially provide a metric for the sum of all microcystin congeners present in a sample, subject to the efficiency and overall yield of conversion. The pres

Nanomaterials-based biosensors for detection of microorganisms and microbial toxins.

PubMed

Sutarlie, Laura; Ow, Sian Yang; Su, Xiaodi

2017-04-01

Detection of microorganisms and microbial toxins is important for health and safety. Due to their unique physical and chemical properties, nanomaterials have been extensively used to develop biosensors for rapid detection of microorganisms with microbial cells and toxins as target analytes. In this paper, the design principles of nanomaterials-based biosensors for four selected analyte categories (bacteria cells, toxins, mycotoxins, and protozoa cells), closely associated with the target analytes' properties is reviewed. Five signal transducing methods that are less equipment intensive (colorimetric, fluorimetric, surface enhanced Raman scattering, electrochemical, and magnetic relaxometry methods) is described and compared for their sensory performance (in term oflimit of detection, dynamic range, and response time) for all analyte categories. In the end, the suitability of these five sensing principles for on-site or field applications is discussed. With a comprehensive coverage of nanomaterials, design principles, sensing principles, and assessment on the sensory performance and suitability for on-site application, this review offers valuable insight and perspective for designing suitable nanomaterials-based microorganism biosensors for a given application. Copyright © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Analytical method for the evaluation of the outdoor air contamination by emerging pollutants using tree leaves as bioindicators.

PubMed

Barroso, Pedro José; Martín, Julia; Santos, Juan Luis; Aparicio, Irene; Alonso, Esteban

2018-01-01

In this work, an analytical method, based on sonication-assisted extraction, clean-up by dispersive solid-phase extraction and determination by liquid chromatography-tandem mass spectrometry, has been developed and validated for the simultaneous determination of 15 emerging pollutants in leaves from four ornamental tree species. Target compounds include perfluorinated organic compounds, plasticizers, surfactants, brominated flame retardant, and preservatives. The method was optimized using Box-Behnken statistical experimental design with response surface methodology and validated in terms of recovery, accuracy, precision, and method detection and quantification limits. Quantification of target compounds was carried out using matrix-matched calibration curves. The highest recoveries were achieved for the perfluorinated organic compounds (mean values up to 87%) and preservatives (up to 88%). The lowest recoveries were achieved for plasticizers (51%) and brominated flame retardant (63%). Method detection and quantification limits were in the ranges 0.01-0.09 ng/g dry matter (dm) and 0.02-0.30 ng/g dm, respectively, for most of the target compounds. The method was successfully applied to the determination of the target compounds on leaves from four tree species used as urban ornamental trees (Citrus aurantium, Celtis australis, Platanus hispanica, and Jacaranda mimosifolia). Graphical abstract Analytical method for the biomonitorization of emerging pollutants in outdoor air.

Chemical analysis of acoustically levitated drops by Raman spectroscopy.

PubMed

Tuckermann, Rudolf; Puskar, Ljiljana; Zavabeti, Mahta; Sekine, Ryo; McNaughton, Don

2009-07-01

An experimental apparatus combining Raman spectroscopy with acoustic levitation, Raman acoustic levitation spectroscopy (RALS), is investigated in the field of physical and chemical analytics. Whereas acoustic levitation enables the contactless handling of microsized samples, Raman spectroscopy offers the advantage of a noninvasive method without complex sample preparation. After carrying out some systematic tests to probe the sensitivity of the technique to drop size, shape, and position, RALS has been successfully applied in monitoring sample dilution and preconcentration, evaporation, crystallization, an acid-base reaction, and analytes in a surface-enhanced Raman spectroscopy colloidal suspension.

A comparison of finite element and analytic models of acoustic scattering from rough poroelastic interfaces.

PubMed

Bonomo, Anthony L; Isakson, Marcia J; Chotiros, Nicholas P

2015-04-01

The finite element method is used to model acoustic scattering from rough poroelastic surfaces. Both monostatic and bistatic scattering strengths are calculated and compared with three analytic models: Perturbation theory, the Kirchhoff approximation, and the small-slope approximation. It is found that the small-slope approximation is in very close agreement with the finite element results for all cases studied and that perturbation theory and the Kirchhoff approximation can be considered valid in those instances where their predictions match those given by the small-slope approximation.

High Rayleigh number convection in rectangular enclosures with differentially heated vertical walls and aspect ratios between zero and unity

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

Kassemi, S.A.

1988-04-01

High Rayleigh number convection in a rectangular cavity with insulated horizontal surfaces and differentially heated vertical walls was analyzed for an arbitrary aspect ratio smaller than or equal to unity. Unlike previous analytical studies, a systematic method of solution based on linearization technique and analytical iteration procedure was developed to obtain approximate closed-form solutions for a wide range of aspect ratios. The predicted velocity and temperature fields are shown to be in excellent agreement with available experimental and numerical data.

High Rayleigh number convection in rectangular enclosures with differentially heated vertical walls and aspect ratios between zero and unity

NASA Technical Reports Server (NTRS)

Kassemi, Siavash A.

1988-01-01

High Rayleigh number convection in a rectangular cavity with insulated horizontal surfaces and differentially heated vertical walls was analyzed for an arbitrary aspect ratio smaller than or equal to unity. Unlike previous analytical studies, a systematic method of solution based on linearization technique and analytical iteration procedure was developed to obtain approximate closed-form solutions for a wide range of aspect ratios. The predicted velocity and temperature fields are shown to be in excellent agreement with available experimental and numerical data.

Biosensors for hepatitis B virus detection.

PubMed

Yao, Chun-Yan; Fu, Wei-Ling

2014-09-21

A biosensor is an analytical device used for the detection of analytes, which combines a biological component with a physicochemical detector. Recently, an increasing number of biosensors have been used in clinical research, for example, the blood glucose biosensor. This review focuses on the current state of biosensor research with respect to efficient, specific and rapid detection of hepatitis B virus (HBV). The biosensors developed based on different techniques, including optical methods (e.g., surface plasmon resonance), acoustic wave technologies (e.g., quartz crystal microbalance), electrochemistry (amperometry, voltammetry and impedance) and novel nanotechnology, are also discussed.

Hierarchical zwitterionic modification of a SERS substrate enables real-time drug monitoring in blood plasma

NASA Astrophysics Data System (ADS)

Sun, Fang; Hung, Hsiang-Chieh; Sinclair, Andrew; Zhang, Peng; Bai, Tao; Galvan, Daniel David; Jain, Priyesh; Li, Bowen; Jiang, Shaoyi; Yu, Qiuming

2016-11-01

Surface-enhanced Raman spectroscopy (SERS) is an ultrasensitive analytical technique with molecular specificity, making it an ideal candidate for therapeutic drug monitoring (TDM). However, in critical diagnostic media including blood, nonspecific protein adsorption coupled with weak surface affinities and small Raman activities of many analytes hinder the TDM application of SERS. Here we report a hierarchical surface modification strategy, first by coating a gold surface with a self-assembled monolayer (SAM) designed to attract or probe for analytes and then by grafting a non-fouling zwitterionic polymer brush layer to effectively repel protein fouling. We demonstrate how this modification can enable TDM applications by quantitatively and dynamically measuring the concentrations of several analytes--including an anticancer drug (doxorubicin), several TDM-requiring antidepressant and anti-seizure drugs, fructose and blood pH--in undiluted plasma. This hierarchical surface chemistry is widely applicable to many analytes and provides a generalized platform for SERS-based biosensing in complex real-world media.

Reflectance Infrared Spectroscopy on Operating Surface Acoustic Wave Chemical Sensors During Exposure to Gas-Phase Analytes

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

Hierlemann, A.; Hill, M.; Ricco, A.J.

We have developed instrumentation to enable the combination of surface acoustic wave (SAW) sensor measurements with direct, in-situ molecular spectroscopic measurements to understand the response of the SAW sensors with respect to the interfacial chemistry of surface-confined sensing films interacting with gas-phase analytes. Specifically, the instrumentation and software was developed to perform in-situ Fourier-transform infrared external-reflectance spectroscopy (FTIR-ERS) on operating SAW devices during dosing of their chemically modified surfaces with analytes. By probing the surface with IR spectroscopy during gas exposure, it is possible to understand in unprecedented detail the interaction processes between the sorptive SAW coatings and the gaseousmore » analyte molecules. In this report, we provide details of this measurement system, and also demonstrate the utility of these combined measurements by characterizing the SAW and FTIR-ERS responses of organic thin-film sensor coatings interacting with gas-phase analytes.« less

Biosensing in a microelectrofluidic system using optical whispering-gallery mode spectroscopy

PubMed Central

Huang, Lei; Guo, Zhixiong

2011-01-01

Label-free detection of biomolecules using an optical whispering-gallery mode sensor in a microelectrofluidic channel is simulated. Negatively charged bovine serum albumin is considered as the model protein analyte. The analyte transport in aqueous solution is controlled by an externally applied electrical field. The finite element method is employed for solving the equations of the charged species transport, the Poisson equation of electric potential, the equations of conservation of momentum and energy, and the Helmholtz equations of electromagnetic waves. The adsorption process of the protein molecules on the microsensor head surface is monitored by the resonance frequency shifts. Frequency shift caused by temperature variation due to Joule heating is analyzed and found to be negligible. The induced shifts behave in a manner similar to Langmuir-like adsorption kinetics; but the time constant increases due to the presence of the external electrical field. A correlation of the frequency shift, the analyte feed concentration in the solution, and the applied voltage gradient is obtained, in which an excellent linear relationship between the frequency shift and the analyte concentration is revealed. The applied voltage gradient enhances significantly the analyte concentration in the vicinity of the sensor surface; thus, the sensor sensitivity which has a power function of the voltage gradient with exponent 2.85 in the controlled voltage range. Simulated detection of extremely low protein concentration to the pico-molar level is carried out. PMID:22662041

Steady and Oscillatory, Subsonic and Supersonic, Aerodynamic Pressure and Generalized Forces for Complex Aircraft Configurations and Applications to Flutter. M.S. Thesis

NASA Technical Reports Server (NTRS)

Chen, L. T.

1975-01-01

A general method for analyzing aerodynamic flows around complex configurations is presented. By applying the Green function method, a linear integral equation relating the unknown, small perturbation potential on the surface of the body, to the known downwash is obtained. The surfaces of the aircraft, wake and diaphragm (if necessary) are divided into small quadrilateral elements which are approximated with hyperboloidal surfaces. The potential and its normal derivative are assumed to be constant within each element. This yields a set of linear algebraic equations and the coefficients are evaluated analytically. By using Gaussian elimination method, equations are solved for the potentials at the centroids of elements. The pressure coefficient is evaluated by the finite different method; the lift and moment coefficients are evaluated by numerical integration. Numerical results are presented, and applications to flutter are also included.

A method for the analysis of nonlinearities in aircraft dynamic response to atmospheric turbulence

NASA Technical Reports Server (NTRS)

Sidwell, K.

1976-01-01

An analytical method is developed which combines the equivalent linearization technique for the analysis of the response of nonlinear dynamic systems with the amplitude modulated random process (Press model) for atmospheric turbulence. The method is initially applied to a bilinear spring system. The analysis of the response shows good agreement with exact results obtained by the Fokker-Planck equation. The method is then applied to an example of control-surface displacement limiting in an aircraft with a pitch-hold autopilot.

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

Jenkins, T.F.; Thorne, P.G.; Myers, K.F.

Salting-out solvent extraction (SOE) was compared with cartridge and membrane solid-phase extraction (SPE) for preconcentration of nitroaromatics, nitramines, and aminonitroaromatics prior to determination by reversed-phase high-performance liquid chromatography. The solid phases used were manufacturer-cleaned materials, Porapak RDX for the cartridge method and Empore SDB-RPS for the membrane method. Thirty-three groundwater samples from the Naval Surface Warfare Center, Crane, Indiana, were analyzed using the direct analysis protocol specified in SW846 Method 8330, and the results were compared with analyses conducted after preconcentration using SOE with acetonitrile, cartridge-based SPE, and membrane-based SPE. For high-concentration samples, analytical results from the three preconcentration techniquesmore » were compared with results from the direct analysis protocol; good recovery of all target analytes was achieved by all three pre-concentration methods. For low-concentration samples, results from the two SPE methods were correlated with results from the SOE method; very similar data was obtained by the SOE and SPE methods, even at concentrations well below 1 microgram/L.« less

Sample handling in surface sensitive chemical and biological sensing: a practical review of basic fluidics and analyte transport.

PubMed

Orgovan, Norbert; Patko, Daniel; Hos, Csaba; Kurunczi, Sándor; Szabó, Bálint; Ramsden, Jeremy J; Horvath, Robert

2014-09-01

This paper gives an overview of the advantages and associated caveats of the most common sample handling methods in surface-sensitive chemical and biological sensing. We summarize the basic theoretical and practical considerations one faces when designing and assembling the fluidic part of the sensor devices. The influence of analyte size, the use of closed and flow-through cuvettes, the importance of flow rate, tubing length and diameter, bubble traps, pressure-driven pumping, cuvette dead volumes, and sample injection systems are all discussed. Typical application areas of particular arrangements are also highlighted, such as the monitoring of cellular adhesion, biomolecule adsorption-desorption and ligand-receptor affinity binding. Our work is a practical review in the sense that for every sample handling arrangement considered we present our own experimental data and critically review our experience with the given arrangement. In the experimental part we focus on sample handling in optical waveguide lightmode spectroscopy (OWLS) measurements, but the present study is equally applicable for other biosensing technologies in which an analyte in solution is captured at a surface and its presence is monitored. Explicit attention is given to features that are expected to play an increasingly decisive role in determining the reliability of (bio)chemical sensing measurements, such as analyte transport to the sensor surface; the distorting influence of dead volumes in the fluidic system; and the appropriate sample handling of cell suspensions (e.g. their quasi-simultaneous deposition). At the appropriate places, biological aspects closely related to fluidics (e.g. cellular mechanotransduction, competitive adsorption, blood flow in veins) are also discussed, particularly with regard to their models used in biosensing. Copyright © 2014 Elsevier B.V. All rights reserved.

Buckling analysis of stiff thin films suspended on a substrate with tripod surface relief structure

NASA Astrophysics Data System (ADS)

Yu, Qingmin; Chen, Furong; Li, Ming; Cheng, Huanyu

2017-09-01

A wavy configuration is a simple yet powerful structural design strategy, which has been widely used in flexible and stretchable electronics. A buckled structure created from a prestretch-contact-release process represents an early effort. Substrates with engineered surface relief structures (e.g., rectangular islands or tripod structure) have enabled stretchability to the devices without sacrificing their electric performance (e.g., high areal coverage for LEDs/photovoltaics/batteries/supercapacitors). In particular, the substrate with a tripod surface relief structure allows wrinkled devices to be suspended on a soft tripod substrate. This minimizes the contact area between devices and the deformed substrate, which contributes to a significantly reduced interfacial stress/strain. To uncover the underlying mechanism of such a design, we exploit the energy method to analytically investigate the buckling and postbuckling behaviors of stiff films suspended on a stretchable polymeric substrate with a tripod surface relief structure. Validated by finite element analysis, the predications from such an analytical study elucidate the deformed profile and maximum strain in the buckled and postbuckled stiff thin device films, providing a useful toolkit for future experimental designs.

Surface patterning of soft polymer film-coated cylinders via an electric field.

PubMed

Li, Bo; Li, Yue; Xu, Guang-Kui; Feng, Xi-Qiao

2009-11-04

Using the linear stability analysis method, we investigate the surface wrinkling of a thin polymer coating on a cylinder in an externally applied electric field. It is demonstrated that energy competition between surface energy, van der Waals interactive potential energy and electrostatic interaction energy may lead to ordered patterns on the film surface. The analytical solutions are derived for the critical conditions of both longitudinal and circumferential instabilities. The wavelengths of the generated surface patterns can be mediated by changing the magnitude of the electric field. Our analysis shows that the surface morphology is sensitive to the curvature radius of the fiber, especially in the micrometer and nanometer length scales. Furthermore, we suggest a potential approach for fabricating hierarchical patterns on curved surfaces.

Visualizing the Solute Vaporization Interference in Flame Atomic Absorption Spectroscopy

ERIC Educational Resources Information Center

Dockery, Christopher R.; Blew, Michael J.; Goode, Scott R.

2008-01-01

Every day, tens of thousands of chemists use analytical atomic spectroscopy in their work, often without knowledge of possible interferences. We present a unique approach to study these interferences by using modern response surface methods to visualize an interference in which aluminum depresses the calcium atomic absorption signal. Calcium…

Multimedia Sampling During The Application Of Biosolids On A Land Test Site (Presentation)

EPA Science Inventory

The goal of this research study was to evaluate air and soil sampling methods and analytical techniques for commercial land application of biosolids. Biosolids, were surface applied at agronomic rates to an agricultural field. During the period of August 2004 to January 2005, 3...

DEVELOPMENT OF TECHNIQUES FOR EDDY-CORRELATION MEASUREMENTS OF NON-METHANE VOLATILE ORGANIC COMPOUND FLUXED IN THE ATMOSPHERE

EPA Science Inventory

An analytical technique for the measurement of the exchange (flux) of trace gases between the earth's surface and the atmosphere will be developed. Measurements will rely on the eddy correlation method (ECM). Target compounds are biogenically and anthropogenically emitted v...

Method of predicting mechanical properties of decayed wood

DOEpatents

Kelley, Stephen S.

2003-07-15

A method for determining the mechanical properties of decayed wood that has been exposed to wood decay microorganisms, comprising: a) illuminating a surface of decayed wood that has been exposed to wood decay microorganisms with wavelengths from visible and near infrared (VIS-NIR) spectra; b) analyzing the surface of the decayed wood using a spectrometric method, the method generating a first spectral data of wavelengths in VIS-NIR spectra region; and c) using a multivariate analysis to predict mechanical properties of decayed wood by comparing the first spectral data with a calibration model, the calibration model comprising a second spectrometric method of spectral data of wavelengths in VIS-NIR spectra obtained from a reference decay wood, the second spectral data being correlated with a known mechanical property analytical result obtained from the reference decayed wood.

Analytical and numerical solution for wave reflection from a porous wave absorber

NASA Astrophysics Data System (ADS)

Magdalena, Ikha; Roque, Marian P.

2018-03-01

In this paper, wave reflection from a porous wave absorber is investigated theoretically and numerically. The equations that we used are based on shallow water type model. Modification of motion inside the absorber is by including linearized friction term in momentum equation and introducing a filtered velocity. Here, an analytical solution for wave reflection coefficient from a porous wave absorber over a flat bottom is derived. Numerically, we solve the equations using the finite volume method on a staggered grid. To validate our numerical model, comparison of the numerical reflection coefficient is made against the analytical solution. Further, we implement our numerical scheme to study the evolution of surface waves pass through a porous absorber over varied bottom topography.

The non-Gaussian joint probability density function of slope and elevation for a nonlinear gravity wave field. [in ocean surface

NASA Technical Reports Server (NTRS)

Huang, N. E.; Long, S. R.; Bliven, L. F.; Tung, C.-C.

1984-01-01

On the basis of the mapping method developed by Huang et al. (1983), an analytic expression for the non-Gaussian joint probability density function of slope and elevation for nonlinear gravity waves is derived. Various conditional and marginal density functions are also obtained through the joint density function. The analytic results are compared with a series of carefully controlled laboratory observations, and good agreement is noted. Furthermore, the laboratory wind wave field observations indicate that the capillary or capillary-gravity waves may not be the dominant components in determining the total roughness of the wave field. Thus, the analytic results, though derived specifically for the gravity waves, may have more general applications.

Analytical solution for the transient wave propagation of a buried cylindrical P-wave line source in a semi-infinite elastic medium with a fluid surface layer

NASA Astrophysics Data System (ADS)

Shan, Zhendong; Ling, Daosheng

2018-02-01

This article develops an analytical solution for the transient wave propagation of a cylindrical P-wave line source in a semi-infinite elastic solid with a fluid layer. The analytical solution is presented in a simple closed form in which each term represents a transient physical wave. The Scholte equation is derived, through which the Scholte wave velocity can be determined. The Scholte wave is the wave that propagates along the interface between the fluid and solid. To develop the analytical solution, the wave fields in the fluid and solid are defined, their analytical solutions in the Laplace domain are derived using the boundary and interface conditions, and the solutions are then decomposed into series form according to the power series expansion method. Each item of the series solution has a clear physical meaning and represents a transient wave path. Finally, by applying Cagniard's method and the convolution theorem, the analytical solutions are transformed into the time domain. Numerical examples are provided to illustrate some interesting features in the fluid layer, the interface and the semi-infinite solid. When the P-wave velocity in the fluid is higher than that in the solid, two head waves in the solid, one head wave in the fluid and a Scholte wave at the interface are observed for the cylindrical P-wave line source.

Modeling of normal contact of elastic bodies with surface relief taken into account

NASA Astrophysics Data System (ADS)

Goryacheva, I. G.; Tsukanov, I. Yu

2018-04-01

An approach to account the surface relief in normal contact problems for rough bodies on the basis of an additional displacement function for asperities is considered. The method and analytic expressions for calculating the additional displacement function for one-scale and two-scale wavy relief are presented. The influence of the microrelief geometric parameters, including the number of scales and asperities density, on additional displacements of the rough layer is analyzed.

Micromechanics of Interfaces in High Temperature Composites

DTIC Science & Technology

1992-05-30

the development of analytical solutions to solve the eigenstrain problem of both a single fiber (treated as a cylindrical inclusion) in an elastic... eigenstrain in a half space by using Green’s functions. Green’s functions were obtained for problems of an elastic half space with a free surface or rigidly...normal to the crack surface, the eigenstrain £3, for the equivalent inclusion method is introduced to simulate the bridged crack. Specially £33 in DO

Methods of analysis by the U.S. Geological Survey National Water Quality Laboratory; extraction of nitroaromatic compounds from water by polystyrene divinylbenzene cartridge and determination by high-performance liquid chromatography

USGS Publications Warehouse

Lindley, C.E.; Burkhardt, M.R.; DeRusseau, S.N.

1994-01-01

Organic explosives are determined in samples of ground water and surface water with emphasis on identifying and quantifying trinitrotoluene (TNT) metabolites. Water samples are filtered to remove suspended particulate material and passed through a polystyrene divinylbenzene-packed cartridge by a vacuum-extraction system. The target analytes subsequently are eluted with acetonitrile. A high-performance liquid chromatograph (HPLC) equipped with a photodiode-array detector is used for sample analysis. Analytes are separated on an octadecylsilane column using a methanol, water, and acetonitrile gradient elution. The compounds 2,4- and 2,6-dinitrotoluene are separated through an independent, isocratic elution. Method detection limits, on the basis of a 1-liter sample size, range from 0.11 to 0.32 microgram per liter. Recoveries averaged from 71 to 101 percent for 13 analytes in one set of HPLC-grade water fortified at about 1 microgram per liter. The method is limited to use by analysts experienced in handling explosive materials. (USGS)

Analytical method for measuring cosmogenic 35S in natural waters

DOE PAGES

Uriostegui, Stephanie H.; Bibby, Richard K.; Esser, Bradley K.; ...

2015-05-18

Here, cosmogenic sulfur-35 in water as dissolved sulfate ( 35SO 4) has successfully been used as an intrinsic hydrologic tracer in low-SO 4, high-elevation basins. Its application in environmental waters containing high SO 4 concentrations has been limited because only small amounts of SO 4 can be analyzed using current liquid scintillation counting (LSC) techniques. We present a new analytical method for analyzing large amounts of BaSO 4 for 35S. We quantify efficiency gains when suspending BaSO 4 precipitate in Inta-Gel Plus cocktail, purify BaSO 4 precipitate to remove dissolved organic matter, mitigate interference of radium-226 and its daughter productsmore » by selection of high purity barium chloride, and optimize LSC counting parameters for 35S determination in larger masses of BaSO 4. Using this improved procedure, we achieved counting efficiencies that are comparable to published LSC techniques despite a 10-fold increase in the SO 4 sample load. 35SO 4 was successfully measured in high SO 4 surface waters and groundwaters containing low ratios of 35S activity to SO 4 mass demonstrating that this new analytical method expands the analytical range of 35SO 4 and broadens the utility of 35SO 4 as an intrinsic tracer in hydrologic settings.« less

Potential role of gold nanoparticles for improved analytical methods: an introduction to characterizations and applications.

PubMed

Wu, Chung-Shu; Liu, Fu-Ken; Ko, Fu-Hsiang

2011-01-01

Nanoparticle-based material is a revolutionary scientific and engineering venture that will invariably impact the existing analytical separation and preconcentration for a variety of analytes. Nanoparticles can be regarded as a hybrid between small molecule and bulk material. A material on the nanoscale produces considerable changes on various properties, making them size- and shape-dependent. Gold nanoparticles (Au NPs), one of the wide variety of core materials available, coupled with tunable surface properties in the form of inorganic or inorganic-organic hybrid have been reported as an excellent platform for a broad range of analytical methods. This review aims to introduce the basic principles, examples, and descriptions of methods for the characterization of Au NPs by using chromatography, electrophoresis, and self-assembly strategies for separation science. Some of the latest important applications of using Au NPs as stationary phases toward open-tubular capillary electrochromatography, gas chromatography, and liquid chromatography as well as roles of run buffer additive to enhance separation and preconcentration in the field of chromatographic, electrophoretic and in chip-based systems are reviewed. Additionally, we review Au NPs-assisted state-of-the-art techniques involving the use of micellar electrokinetic chromatography, an online diode array detector, solid-phase extraction, and mass spectrometry for the preconcentration of some chemical compounds and biomolecules.

Controlled positioning of analytes and cells on a plasmonic platform for glycan sensing using surface enhanced Raman spectroscopy.

PubMed

Tabatabaei, Mohammadali; Wallace, Gregory Q; Caetano, Fabiana A; Gillies, Elizabeth R; Ferguson, Stephen S G; Lagugné-Labarthet, François

2016-01-01

The rise of molecular plasmonics and its application to ultrasensitive spectroscopic measurements has been enabled by the rational design and fabrication of a variety of metallic nanostructures. Advanced nano and microfabrication methods are key to the development of such structures, allowing one to tailor optical fields at the sub-wavelength scale, thereby optimizing excitation conditions for ultrasensitive detection. In this work, the control of both analyte and cell positioning on a plasmonic platform is enabled using nanofabrication methods involving patterning of fluorocarbon (FC) polymer (C 4 F 8 ) thin films on a plasmonic platform fabricated by nanosphere lithography (NSL). This provides the possibility to probe biomolecules of interest in the vicinity of cells using plasmon-mediated surface enhanced spectroscopies. In this context, we demonstrate the surface enhanced biosensing of glycan expression in different cell lines by surface enhanced Raman spectroscopy (SERS) on these plasmonic platforms functionalized with 4-mercaptophenylboronic acid (4-MPBA) as the Raman reporter. These cell lines include human embryonic kidney (HEK 293), C2C12 mouse myoblasts, and HeLa (Henrietta Lacks) cervical cancer cells. A distinct glycan expression is observed for cancer cells compared to other cell lines by confocal SERS mapping. This suggests the potential application of these versatile SERS platforms for differentiating cancerous from non-cancerous cells.

Analytical Chemistry of Surfaces: Part II. Electron Spectroscopy.

ERIC Educational Resources Information Center

Hercules, David M.; Hercules, Shirley H.

1984-01-01

Discusses two surface techniques: X-ray photoelectron spectroscopy (ESCA) and Auger electron spectroscopy (AES). Focuses on fundamental aspects of each technique, important features of instrumentation, and some examples of how ESCA and AES have been applied to analytical surface problems. (JN)

Determination of nicotine by surface-enhanced Raman scattering (SERS)

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

Barber, T.E.; List, M.S.; Haas, J.W. III

1994-11-01

The analytical application of surface-enhanced Raman spectroscopy (SERS) to the determination of nicotine is demonstrated. A simple spectroelectrochemical method using a copper or silver electrode as the SERS substrate has been developed, consisting of three steps: polishing a working electrode to a mirror finish; roughening the electrode in an electrolyte solution; and, finally, depositing the nicotine analyte onto the roughened electrode after immersion in a sample solution. During the reduction cycle, a large enhancement in nicotine Raman scattering is observed at the electrode surface. The intensity of the SERS signal on a silver electrode is linear with concentration from 10more » to 900 ppb, with an estimated detection limit of 7 ppb. The total analysis time per sample is approximately five minutes. This procedure has been used to analyze the extract from a cigarette side-stream smoke sample (environmental tobacco smoke); the SERS results agree well with those of conventional gas chromatographic analysis.« less

Back-support large laser mirror unit: mounting modeling and analysis

NASA Astrophysics Data System (ADS)

Wang, Hui; Zhang, Zheng; Long, Kai; Liu, Tianye; Li, Jun; Liu, Changchun; Xiong, Zhao; Yuan, Xiaodong

2018-01-01

In high-power laser system, the surface wavefront of large optics has a close link with its structure design and mounting method. The back-support transport mirror design is presently being investigated as a means in China's high-power laser system to hold the optical component firmly while minimizing the distortion of its reflecting surface. We have proposed a comprehensive analytical framework integrated numerical modeling and precise metrology for the mirror's mounting performance evaluation while treating the surface distortion as a key decision variable. The combination of numerical simulation and field tests demonstrates that the comprehensive analytical framework provides a detailed and accurate approach to evaluate the performance of the transport mirror. It is also verified that the back-support transport mirror is effectively compatible with state-of-the-art optical quality specifications. This study will pave the way for future research to solidify the design of back-support large laser optics in China's next generation inertial confinement fusion facility.

A solid phase extraction-ion chromatography with conductivity detection procedure for determining cationic surfactants in surface water samples.

PubMed

Olkowska, Ewa; Polkowska, Żaneta; Namieśnik, Jacek

2013-11-15

A new analytical procedure for the simultaneous determination of individual cationic surfactants (alkyl benzyl dimethyl ammonium chlorides) in surface water samples has been developed. We describe this methodology for the first time: it involves the application of solid phase extraction (SPE-for sample preparation) coupled with ion chromatography-conductivity detection (IC-CD-for the final determination). Mean recoveries of analytes between 79% and 93%, and overall method quantification limits in the range from 0.0018 to 0.038 μg/mL for surface water and CRM samples were achieved. The methodology was applied to the determination of individual alkyl benzyl quaternary ammonium compounds in environmental samples (reservoir water) and enables their presence in such types of waters to be confirmed. In addition, it is a simpler, less time-consuming, labour-intensive, avoiding use of toxic chloroform and significantly less expensive methodology than previously described approaches (liquid-liquid extraction coupled with liquid chromatography-mass spectrometry). Copyright © 2013 Elsevier B.V. All rights reserved.

Analytical Solution for Interface Flow to a Sink With an Upconed Saline Water Lens: Strack's Regimes Revisited

NASA Astrophysics Data System (ADS)

Kacimov, A. R.; Obnosov, Y. V.

2018-01-01

A study is made of a steady, two-dimensional groundwater flow with a horizontal well (drain), which pumps out freshwater from an aquifer sandwiched between a horizontal bedrock and ponded soil surface, and containing a lens-shaped static volume of a heavier saline water (DNAPL-dense nonaqueous phase liquid) as a free surface. For flow toward a line sink, an explicit analytical solution is obtained by a conformal mapping of the hexagon in the complex potential plane onto a reference plane and the Keldysh-Sedov integral representation of a mixed boundary-value problem for a complex physical coordinate. The interface is found as a function of the pumping rate, the well locus, the ratio of liquid densities, and the hydraulic heads at the soil surface and in the well. The shape with two inflexion points and fronts varies from a small-thickness bedrock-spread pancake to a critical curvilinear triangle, which cusps toward the sink. The problem is mathematically solvable in a relatively narrow band of geometric and hydraulic parameters. A similar analytic solution for a static heavy bubble confined by a closed-curve interface (no contact with the bedrock) is outlined as an illustration of the method to solve a mixed boundary-value problem.

Analytical Round Robin for Elastic-Plastic Analysis of Surface Cracked Plates: Phase I Results

NASA Technical Reports Server (NTRS)

Wells, D. N.; Allen, P. A.

2012-01-01

An analytical round robin for the elastic-plastic analysis of surface cracks in flat plates was conducted with 15 participants. Experimental results from a surface crack tension test in 2219-T8 aluminum plate provided the basis for the inter-laboratory study (ILS). The study proceeded in a blind fashion given that the analysis methodology was not specified to the participants, and key experimental results were withheld. This approach allowed the ILS to serve as a current measure of the state of the art for elastic-plastic fracture mechanics analysis. The analytical results and the associated methodologies were collected for comparison, and sources of variability were studied and isolated. The results of the study revealed that the J-integral analysis methodology using the domain integral method is robust, providing reliable J-integral values without being overly sensitive to modeling details. General modeling choices such as analysis code, model size (mesh density), crack tip meshing, or boundary conditions, were not found to be sources of significant variability. For analyses controlled only by far-field boundary conditions, the greatest source of variability in the J-integral assessment is introduced through the constitutive model. This variability can be substantially reduced by using crack mouth opening displacements to anchor the assessment. Conclusions provide recommendations for analysis standardization.

Chemical Detection and Identification Techniques for Exobiology Flight Experiments

NASA Technical Reports Server (NTRS)

Kojiro, Daniel R.; Sheverev, Valery A.; Khromov, Nikolai A.

2002-01-01

Exobiology flight experiments require highly sensitive instrumentation for in situ analysis of the volatile chemical species that occur in the atmospheres and surfaces of various bodies within the solar system. The complex mixtures encountered place a heavy burden on the analytical Instrumentation to detect and identify all species present. The minimal resources available onboard for such missions mandate that the instruments provide maximum analytical capabilities with minimal requirements of volume, weight and consumables. Advances in technology may be achieved by increasing the amount of information acquired by a given technique with greater analytical capabilities and miniaturization of proven terrestrial technology. We describe here methods to develop analytical instruments for the detection and identification of a wide range of chemical species using Gas Chromatography. These efforts to expand the analytical capabilities of GC technology are focused on the development of detectors for the GC which provide sample identification independent of the GC retention time data. A novel new approach employs Penning Ionization Electron Spectroscopy (PIES).

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

Hoenig, M.; Elsen, Y.V.; Cauter, R.V.

The progressive degradation of the pyrolytic graphite surface of atomizers provides variable and misleading results of molybdenum peak-height measurements. The changes in the peak shapes produce no analytical problems during the lifetime of the atomizer (approx.300 firings) when integrated absorbance (A.s signals) is considered and the possible base-line drifts are controlled. This was demonstrated on plant samples mineralized by simple digestion with a mixture of HNO/sub 3/ and H/sub 2/O/sub 2/. The value of this method was assessed by comparison with a standard dry oxidation method and by molybdenum determination in National Bureau of Standards reference plant samples. The relativemore » standard deviations (n = 5) of the full analytical procedure do not exceed 7%. 13 references, 3 figures, 3 tables.« less

Hazardous Drug Residue on Exterior Vial Surfaces: Evaluation of a Commercial Manufacturing Process

PubMed Central

Power, Luci A.; Sessink, Paul J. M.; Charbonneau, Flay

2014-01-01

Abstract Purpose: Hazardous drug residue on the exterior surface of drug vials poses a potential risk for exposure of health care workers involved in handling these products. The purpose of this article is to heighten the awareness of this serious issue and to evaluate a commercial manufacturing process for removing and containing hazardous drug (HD) residue on exterior vial surfaces. Additionally, findings from this study are interpreted, incorporated into the current body of evidence, and discussed by experts in this field. Methods: This study includes separate evaluations for the presence or absence of surface drug contamination on the vials of 3 HD products: 5-fluorouracil, cisplatin, and methotrexate. The drug products were packaged in vials using a patented prewashing/decontamination method, application of a polyvinylchloride (PVC) base, and use of clear glass vials. An additional step of encasing the vial in a shrink-wrapped sheath was used for 5-fluorouracil and cisplatin. Results: Of all 5-fluorouracil (110 vials), methotrexate (60 vials), and cisplatin (60 vials) tested, only 2 had detectable amounts of surface residue. One 5-fluorouracil vial was found to have approximately 4 mg of 5-fluorouracil on the surface of the vial. The second contaminated vial was cisplatin, which was discovered to have 131 ng of platinum, equal to 200 ng of cisplatin or 0.2 μL of cisplatin solution, on the vial sheath. Conclusion: Using validated extraction and analytic methods, all but 2 of the 230 tested vials were found to be free of surface drug contamination. Pharmacy leaders need to take an active role in promoting the need for clean HD vials. Manufacturers should be required to provide their clients with data derived from externally validated analytic studies, reporting the level of HD contamination on the exterior of their vial products. PMID:24958942

Reversible Immobilization of Proteins in Sensors and Solid-State Nanopores.

PubMed

Ananth, Adithya; Genua, María; Aissaoui, Nesrine; Díaz, Leire; Eisele, Nico B; Frey, Steffen; Dekker, Cees; Richter, Ralf P; Görlich, Dirk

2018-05-01

The controlled functionalization of surfaces with proteins is crucial for many analytical methods in life science research and biomedical applications. Here, a coating for silica-based surfaces is established which enables stable and selective immobilization of proteins with controlled orientation and tunable surface density. The coating is reusable, retains functionality upon long-term storage in air, and is applicable to surfaces of complex geometry. The protein anchoring method is validated on planar surfaces, and then a method is developed to measure the anchoring process in real time using silicon nitride solid-state nanopores. For surface attachment, polyhistidine tags that are site specifically introduced into recombinant proteins are exploited, and the yeast nucleoporin Nsp1 is used as model protein. Contrary to the commonly used covalent thiol chemistry, the anchoring of proteins via polyhistidine tag is reversible, permitting to take proteins off and replace them by other ones. Such switching in real time in experiments on individual nanopores is monitored using ion conductivity. Finally, it is demonstrated that silica and gold surfaces can be orthogonally functionalized to accommodate polyhistidine-tagged proteins on silica but prevent protein binding to gold, which extends the applicability of this surface functionalization method to even more complex sensor devices. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Nonplanar Method for Predicting Incompressible Aerodynamic Coefficients of Rectangular Wings with Circular-Arc Camber. Ph.D. Thesis - Virginia Polytechnic Institute

NASA Technical Reports Server (NTRS)

Lamar, J. E.

1971-01-01

The development of a nonplanar lifting surface method having a continuous distribution of singularities and satisfying the tangent flow boundary condition on the mean camber surface is given. The method predicts some incompressible longitudinal aerodynamic coefficients of rectangular wings which have circular-arc camber. The solution method is of the integral-equation type and the resulting surface integrals are evaluated by either using numerical or analytical techniques, as are appropriate. Applications are made and the results compared with those from an exact two-dimensional circular-arc camber solution, a three-dimensional flat-wing solution which represents the camber by a projected slope onto the flat surface, and a flat-wing experiment. From these comparisons, the present method is found to predict well the flat-wing experiment and limiting values, in addition to the center of pressure variation at an angle of attack of zero for any camber. For wings having camber ratios larger than about 1.25% and moderate to high aspect ratios, the results deterioriate due to the inadequacy of lifting pressure modes employed.

Numerical simulation of KdV equation by finite difference method

NASA Astrophysics Data System (ADS)

Yokus, A.; Bulut, H.

2018-05-01

In this study, the numerical solutions to the KdV equation with dual power nonlinearity by using the finite difference method are obtained. Discretize equation is presented in the form of finite difference operators. The numerical solutions are secured via the analytical solution to the KdV equation with dual power nonlinearity which is present in the literature. Through the Fourier-Von Neumann technique and linear stable, we have seen that the FDM is stable. Accuracy of the method is analyzed via the L2 and L_{∞} norm errors. The numerical, exact approximations and absolute error are presented in tables. We compare the numerical solutions with the exact solutions and this comparison is supported with the graphic plots. Under the choice of suitable values of parameters, the 2D and 3D surfaces for the used analytical solution are plotted.

Spectrophotometric determination of sulphate in automotive fuel ethanol by sequential injection analysis using dimethylsulphonazo(III) reaction.

PubMed

de Oliveira, Fabio Santos; Korn, Mauro

2006-01-15

A sensitive SIA method was developed for sulphate determination in automotive fuel ethanol. This method was based on the reaction of sulphate with barium-dimethylsulphonazo(III) leading to a decrease on the magnitude of analytical signal monitored at 665 nm. Alcohol fuel samples were previously burned up to avoid matrix effects for sulphate determinations. Binary sampling and stop-flow strategies were used to increase the sensitivity of the method. The optimization of analytical parameter was performed by response surface method using Box-Behnker and central composite designs. The proposed sequential flow procedure permits to determine up to 10.0mg SO(4)(2-)l(-1) with R.S.D. <2.5% and limit of detection of 0.27 mg l(-1). The method has been successfully applied for sulphate determination in automotive fuel alcohol and the results agreed with the reference volumetric method. In the optimized condition the SIA system carried out 27 samples per hour.

Lagrangian based methods for coherent structure detection

NASA Astrophysics Data System (ADS)

Allshouse, Michael R.; Peacock, Thomas

2015-09-01

There has been a proliferation in the development of Lagrangian analytical methods for detecting coherent structures in fluid flow transport, yielding a variety of qualitatively different approaches. We present a review of four approaches and demonstrate the utility of these methods via their application to the same sample analytic model, the canonical double-gyre flow, highlighting the pros and cons of each approach. Two of the methods, the geometric and probabilistic approaches, are well established and require velocity field data over the time interval of interest to identify particularly important material lines and surfaces, and influential regions, respectively. The other two approaches, implementing tools from cluster and braid theory, seek coherent structures based on limited trajectory data, attempting to partition the flow transport into distinct regions. All four of these approaches share the common trait that they are objective methods, meaning that their results do not depend on the frame of reference used. For each method, we also present a number of example applications ranging from blood flow and chemical reactions to ocean and atmospheric flows.

Analysis of space charge fields using the Lienard-Wiechert potential and the method of images during the photoemission of the electron beam from the cathode

NASA Astrophysics Data System (ADS)

Salah, Wa'el

2017-01-01

We present a numerical analysis of the space charge effect and the effect of image charge force on the cathode surface for a laser-driven RF-photocathode gun. In this numerical analysis, in the vicinity of the cathode surface, we used an analytical method based on Lienard-Weichert retarded potentials. The analytical method allows us to calculate longitudinal and radial electric fields, and the azimuth magnetic field due to both space charge effect and the effect of the image charge force. We calculate the electro-magnetic fields in the following two conditions for the "ELSA" photoinjector. The first condition is in the progress of photoemission, which corresponds to the inside of the emitted beam, and the second condition is at the end of the photoemission. The electromagnetic fields due to the space charge effect and the effect of the image charge force, and the sum of them, which corresponds to the global electro-magnetic fields, are shown. Based on these numerical results, we discussed the effects of the space charge and the image charge in the immediate vicinity of the cathode.

Acoustic emission source location in composite structure by Voronoi construction using geodesic curve evolution.

PubMed

Gangadharan, R; Prasanna, G; Bhat, M R; Murthy, C R L; Gopalakrishnan, S

2009-11-01

Conventional analytical/numerical methods employing triangulation technique are suitable for locating acoustic emission (AE) source in a planar structure without structural discontinuities. But these methods cannot be extended to structures with complicated geometry, and, also, the problem gets compounded if the material of the structure is anisotropic warranting complex analytical velocity models. A geodesic approach using Voronoi construction is proposed in this work to locate the AE source in a composite structure. The approach is based on the fact that the wave takes minimum energy path to travel from the source to any other point in the connected domain. The geodesics are computed on the meshed surface of the structure using graph theory based on Dijkstra's algorithm. By propagating the waves in reverse virtually from these sensors along the geodesic path and by locating the first intersection point of these waves, one can get the AE source location. In this work, the geodesic approach is shown more suitable for a practicable source location solution in a composite structure with arbitrary surface containing finite discontinuities. Experiments have been conducted on composite plate specimens of simple and complex geometry to validate this method.

Micro transflection on a metallic stick: an innovative approach of reflection infrared spectroscopy for minimally invasive investigation of painting varnishes.

PubMed

Rosi, Francesca; Legan, Lea; Miliani, Costanza; Ropret, Polonca

2017-05-01

A new analytical approach, based on micro-transflection measurements from a diamond-coated metal sampling stick, is presented for the analysis of painting varnishes. Minimally invasive sampling is performed from the varnished surface using the stick, which is directly used as a transflection substrate for micro Fourier transform infrared (FTIR) measurements. With use of a series of varnished model paints, the micro-transflection method has been proved to be a valuable tool for the identification of surface components thanks to the selectivity of the sampling, the enhancement of the absorbance signal, and the easier spectral interpretation because the profiles are similar to transmission mode ones. Driven by these positive outcomes, the method was then tested as tool supporting noninvasive reflection FTIR spectroscopy during the assessment of varnish removal by solvent cleaning on paint models. Finally, the integrated analytical approach based on the two reflection methods was successfully applied for the monitoring of the cleaning of the sixteenth century painting Presentation in the Temple by Vittore Carpaccio. Graphical Abstract Micro-transflection FTIR on a metallic stick for the identification of varnishes during painting cleanings.

Effect of different analyte diffusion/adsorption protocols on SERS signals

NASA Astrophysics Data System (ADS)

Li, Ruoping; Petschek, Rolfe G.; Han, Junhe; Huang, Mingju

2018-07-01

The effect of different analyte diffusion/adsorption protocols was studied which is often overlooked in surface-enhanced Raman scattering (SERS) technique. Three protocols: highly concentrated dilution (HCD) protocol, half-half dilution (HHD) protocol and layered adsorption (LA) protocol were studied and the SERS substrates were monolayer films of 80 nm Ag nanoparticles (NPs) which were modified by polyvinylpyrrolidone. The diffusion/adsorption mechanisms were modelled using the diffusion equation and the electromagnetic field distribution of two adjacent Ag NPs was simulated by the finite-different time-domain method. All experimental data and theoretical analysis suggest that different diffusion/adsorption behaviour of analytes will cause different SERS signal enhancements. HHD protocol could produce the most uniform and reproducible samples, and the corresponding signal intensity of the analyte is the strongest. This study will help to understand and promote the use of SERS technique in quantitative analysis.

Theory and practical understanding of the migration behavior of proteins and peptides in CE and related techniques.

PubMed

Freitag, Ruth; Hilbrig, Frank

2007-07-01

CEC is defined as an analytical method, where the analytes are separated on a chromatographic column in the presence of an applied voltage. The separation of charged analytes in CEC is complex, since chromatographic interaction, electroosmosis and electrophoresis contribute to the experimentally observed behavior. The putative contribution of effects such as surface electrodiffusion has been suggested. A sound theoretical treatment incorporating all effects is currently not available. The question of whether the different effects contribute in an independent or an interdependent manner is still under discussion. In this contribution, the state-of-the-art in the theoretical description of the individual contributions as well as models for the retention behavior and in particular possible dimensionless 'retention factors' is discussed, together with the experimental database for the separation of charged analytes, in particular proteins and peptides, by CEC and related techniques.

User's manual for the one-dimensional hypersonic experimental aero-thermodynamic (1DHEAT) data reduction code

NASA Technical Reports Server (NTRS)

Hollis, Brian R.

1995-01-01

A FORTRAN computer code for the reduction and analysis of experimental heat transfer data has been developed. This code can be utilized to determine heat transfer rates from surface temperature measurements made using either thin-film resistance gages or coaxial surface thermocouples. Both an analytical and a numerical finite-volume heat transfer model are implemented in this code. The analytical solution is based on a one-dimensional, semi-infinite wall thickness model with the approximation of constant substrate thermal properties, which is empirically corrected for the effects of variable thermal properties. The finite-volume solution is based on a one-dimensional, implicit discretization. The finite-volume model directly incorporates the effects of variable substrate thermal properties and does not require the semi-finite wall thickness approximation used in the analytical model. This model also includes the option of a multiple-layer substrate. Fast, accurate results can be obtained using either method. This code has been used to reduce several sets of aerodynamic heating data, of which samples are included in this report.

Modal Ring Method for the Scattering of Electromagnetic Waves

NASA Technical Reports Server (NTRS)

Baumeister, Kenneth J.; Kreider, Kevin L.

1993-01-01

The modal ring method for electromagnetic scattering from perfectly electric conducting (PEC) symmetrical bodies is presented. The scattering body is represented by a line of finite elements (triangular) on its outer surface. The infinite computational region surrounding the body is represented analytically by an eigenfunction expansion. The modal ring method effectively reduces the two dimensional scattering problem to a one-dimensional problem similar to the method of moments. The modal element method is capable of handling very high frequency scattering because it has a highly banded solution matrix.

Sol-gel chemical sensors for surface-enhanced Raman spectroscopy

NASA Astrophysics Data System (ADS)

Lee, Vincent Y.; Farquharson, Stuart; Kwon, Hueong-Chan; Shahriari, Mahmoud R.; Rainey, Petrie M.

1999-02-01

Surface-enhanced Raman spectroscopy (SERS) promises to be one of the most sensitive methods for chemical detection. Unfortunately, the inability of SERS to perform quantitative chemical analysis has slowed its general use in laboratories. This is largely due to the difficulty of manufacturing either active surfaces that yield reproducible enhancements, or surfaces that are capable of reversible chemical adsorption, or both. In an effort to meet this need, we have developed metal-doped sol-gels that provide surface-enhancement of Raman scattering. The porous silica network offers a unique environment for stabilizing SER active metal particles and the high surface area increases the interaction between the analyte and metal particles. This eliminates the need to concentrate the analyte on the surface by evaporating the solvent. The sol-gel is easily coated on a variety of surfaces, such as fiber optics, glass slides, or glass tubing, and can be designed into sample flow systems. Here we present the development of both gold- and silver-doped sol-gels, which have been used to coat the inside walls of glass sample vials for SERS applications. The performance of the metal-doped sol-gels was evaluated using p-aminobenzoic acid, to establish enhancement factors, detection limits, dynamic response range, reversibility, reproducibility, and suitability to commercial spectrometers. Measurements of trace chemicals, such as adenine and cocaine, are also presented.

Bayesian-based estimation of acoustic surface impedance: Finite difference frequency domain approach.

PubMed

Bockman, Alexander; Fackler, Cameron; Xiang, Ning

2015-04-01

Acoustic performance for an interior requires an accurate description of the boundary materials' surface acoustic impedance. Analytical methods may be applied to a small class of test geometries, but inverse numerical methods provide greater flexibility. The parameter estimation problem requires minimizing prediction vice observed acoustic field pressure. The Bayesian-network sampling approach presented here mitigates other methods' susceptibility to noise inherent to the experiment, model, and numerics. A geometry agnostic method is developed here and its parameter estimation performance is demonstrated for an air-backed micro-perforated panel in an impedance tube. Good agreement is found with predictions from the ISO standard two-microphone, impedance-tube method, and a theoretical model for the material. Data by-products exclusive to a Bayesian approach are analyzed to assess sensitivity of the method to nuisance parameters.

A simple hydrodynamic model of a laminar free-surface jet in horizontal or vertical flight

NASA Astrophysics Data System (ADS)

Haustein, Herman D.; Harnik, Ron S.; Rohlfs, Wilko

2017-08-01

A useable model for laminar free-surface jet evolution during flight, for both horizontal and vertical jets, is developed through joint analytical, experimental, and simulation methods. The jet's impingement centerline velocity, recently shown to dictate stagnation zone heat transfer, encompasses the entire flow history: from pipe-flow velocity profile development to profile relaxation and jet contraction during flight. While pipe-flow is well-known, an alternative analytic solution is presented for the centerline velocity's viscous-driven decay. Jet-contraction is subject to influences of surface tension (We), pipe-flow profile development, in-flight viscous dissipation (Re), and gravity (Nj = Re/Fr). The effects of surface tension and emergence momentum flux (jet thrust) are incorporated analytically through a global momentum balance. Though emergence momentum is related to pipe flow development, and empirically linked to nominal pipe flow-length, it can be modified to incorporate low-Re downstream dissipation as well. Jet contraction's gravity dependence is extended beyond existing uniform-velocity theory to cases of partially and fully developed profiles. The final jet-evolution model relies on three empirical parameters and compares well to present and previous experiments and simulations. Hence, micro-jet flight experiments were conducted to fill-in gaps in the literature: jet contraction under mild gravity-effects, and intermediate Reynolds and Weber numbers (Nj = 5-8, Re = 350-520, We = 2.8-6.2). Furthermore, two-phase direct numerical simulations provided insight beyond the experimental range: Re = 200-1800, short pipes (Z = L/d . Re ≥ 0.01), variable nozzle wettability, and cases of no surface tension and/or gravity.

Hazardous drug residue on exterior vial surfaces: evaluation of a commercial manufacturing process.

PubMed

Power, Luci A; Sessink, Paul J M; Gesy, Kathy; Charbonneau, Flay

2014-04-01

Hazardous drug residue on the exterior surface of drug vials poses a potential risk for exposure of health care workers involved in handling these products. The purpose of this article is to heighten the awareness of this serious issue and to evaluate a commercial manufacturing process for removing and containing hazardous drug (HD) residue on exterior vial surfaces. Additionally, findings from this study are interpreted, incorporated into the current body of evidence, and discussed by experts in this field. This study includes separate evaluations for the presence or absence of surface drug contamination on the vials of 3 HD products: 5-fluorouracil, cisplatin, and methotrexate. The drug products were packaged in vials using a patented prewashing/decontamination method, application of a polyvinylchloride (PVC) base, and use of clear glass vials. An additional step of encasing the vial in a shrink-wrapped sheath was used for 5-fluorouracil and cisplatin. Of all 5-fluorouracil (110 vials), methotrexate (60 vials), and cisplatin (60 vials) tested, only 2 had detectable amounts of surface residue. One 5-fluorouracil vial was found to have approximately 4 mg of 5-fluorouracil on the surface of the vial. The second contaminated vial was cisplatin, which was discovered to have 131 ng of platinum, equal to 200 ng of cisplatin or 0.2 μL of cisplatin solution, on the vial sheath. Using validated extraction and analytic methods, all but 2 of the 230 tested vials were found to be free of surface drug contamination. Pharmacy leaders need to take an active role in promoting the need for clean HD vials. Manufacturers should be required to provide their clients with data derived from externally validated analytic studies, reporting the level of HD contamination on the exterior of their vial products.

Unpolarized emissivity with shadow and multiple reflections from random rough surfaces with the geometric optics approximation: application to Gaussian sea surfaces in the infrared band.

PubMed

Bourlier, Christophe

2006-08-20

The emissivity from a stationary random rough surface is derived by taking into account the multiple reflections and the shadowing effect. The model is applied to the ocean surface. The geometric optics approximation is assumed to be valid, which means that the rough surface is modeled as a collection of facets reflecting locally the light in the specular direction. In particular, the emissivity with zero, single, and double reflections are analytically calculated, and each contribution is studied numerically by considering a 1D sea surface observed in the near infrared band. The model is also compared with results computed from a Monte Carlo ray-tracing method.

A Generalized Wall Function

NASA Technical Reports Server (NTRS)

Shih, Tsan-Hsing; Povinelli, Louis A.; Liu, Nan-Suey; Potapczuk, Mark G.; Lumley, J. L.

1999-01-01

The asymptotic solutions, described by Tennekes and Lumley (1972), for surface flows in a channel, pipe or boundary layer at large Reynolds numbers are revisited. These solutions can be extended to more complex flows such as the flows with various pressure gradients, zero wall stress and rough surfaces, etc. In computational fluid dynamics (CFD), these solutions can be used as the boundary conditions to bridge the near-wall region of turbulent flows so that there is no need to have the fine grids near the wall unless the near-wall flow structures are required to resolve. These solutions are referred to as the wall functions. Furthermore, a generalized and unified law of the wall which is valid for whole surface layer (including viscous sublayer, buffer layer and inertial sublayer) is analytically constructed. The generalized law of the wall shows that the effect of both adverse and favorable pressure gradients on the surface flow is very significant. Such as unified wall function will be useful not only in deriving analytic expressions for surface flow properties but also bringing a great convenience for CFD methods to place accurate boundary conditions at any location away from the wall. The extended wall functions introduced in this paper can be used for complex flows with acceleration, deceleration, separation, recirculation and rough surfaces.

Development of an ultra-high-pressure liquid chromatography-tandem mass spectrometry multi-residue sulfonamide method and its application to water, manure slurry, and soils from swine rearing facilities.

PubMed

Shelver, Weilin L; Hakk, Heldur; Larsen, Gerald L; DeSutter, Thomas M; Casey, Francis X M

2010-02-19

An analytical method was developed using ultra-high-pressure liquid chromatography-triple quadrupole-tandem mass spectrometry (UHPLC-TQ-MS/MS) to simultaneously analyze 14 sulfonamides (SA) in 6 min. Despite the rapidity of the assay the system was properly re-equilibrated in this time. No carryover was observed even after high analyte concentrations. The instrumental detection limit based on signal-to-noise ratio (S/N)>3, was below 1 pg/microL (5 pg on column) for all SAs except sulfachloropyridazine. Surface water, ground water, soil, and slurry manure contained in storage ponds in and around swine [Sus scrofa domesticus] rearing facilities were analyzed. Sample cleanup for ground water and surface water included using solid phase extraction (SPE) using Oasis hydrophilic-lipophilic balance (HLB) cartridges. The soil and slurry manure required tandem strong anion exchange (SAX) and HLB solid phase extraction cartridges for sample cleanup. With few exceptions, the recoveries ranged from 60 to 100% for all matrices. The minimum detectable levels were below 2.0 ng/L for water, 30 ng/L for slurry manure, and 45 ng/kg for soil except for sulfachloropyridazine. The coefficient of variation (CV) was within 20% for most of the compounds analyzed. Using this method, sulfamethazine concentrations of 2250-5060 ng/L, sulfamethoxazole concentrations of 108-1.47 x 10(6)ng/L, and sulfathiazole concentrations of 785-1700 ng/L were found in the slurry manure. Sulfadimethoxine (2.0-32 ng/L), sulfamethazine (2.0-5.1 ng/L), and sulfamethoxazole (20.5-43.0 ng/L) were found in surface water and ground water. In top soil (0-15 cm), sulfamethazine ranged 34.5-663 ng/kg dry weight in those locations that received slurry manure as a nutrient; no SAs were found in the soil depths between 46 and 61 cm. The speed makes the method practical for medium to high throughput applications. The sensitivity and positive analyte identification make the method suitable for the demanding requirements for real world applications. Published by Elsevier B.V.

Fabrication of a novel biosensor for macromolecules detection through molecular imprinting technique

NASA Astrophysics Data System (ADS)

Yu, Yingjie

There is an increasing need for precise molecular detection as a diagnostic tool for early identification of diseases, pathogens, and abnormal protein levels in the body. Typical chemical analytical methods are generally costly, unstable, and time-consuming. Molecular imprinting (MI) technique, based on the "lock and key model", could be a simple method to overcome those shortcomings. In this study, a self-assembled monolayer (SAM) was employed as a platform to fabricate MI biosensor for detection of macromolecules. I demonstrated that, when the monolayer was formed on a rough surface, this method was in fact templating molecules in three dimensions, and hence was not limited by the height of the monolayer, but rather by the height of the roughness. This hypothesis was tested on biomolecules of multiple length scales. The SAM is assembled on the walls of the niche, forming a 3D pattern of the analyte uniquely molded to its contour. The surfaces with multi-scale roughness were prepared by evaporation of gold onto electropolished (smooth) and unpolished (rough) Si wafers, where the native roughness was found to have a normal distribution centered around 5 and 90 nm respectively. Our studies, using molecules, such as proteins, i.e., hemoglobin, ranging from a few nanometers, to viruses (i.e. polio, adenovirus), ranging from several tens of nanometers, and protein complexes ranging from several hundred nanometers, showed that when the size of the analyte matched the roughness of the gold surface, this method was very effective and could detect even small changes in the configuration, such as those induced by changes in the pH of the system. The detection method was further quantified by applying it to the detection of CEA in pancreatic cyst fluid obtained from 18 patients under IRB 95867-6. The results of the MI biosensor were directly compared with those obtained using ELISA in the hospital pathology laboratory with excellent agreement, except that the MI biosensor used only 1% of the volume of the ELISA test and produced results in less than 5 minutes, as compared to at least 10 hours.

The investigation of photo-induced chemiluminescence on Co2+-doped TiO2 nanoparticles and its analytical application.

PubMed

Li, Guixin; Nan, Hongyan; Zheng, Xingwang

2009-07-01

A novel space- and time-resolved photo-induced chemiluminescence (PICL) analytical method was developed based on the photocatalysis of the Co2+-doped TiO2 nanoparticles. The PICL reaction procedure under the photocatalysis of Co2+-doped TiO2 nanoparticles was investigated using cyclic voltammetry and potentiometry. Meanwhile, the effect of the electrical double layer outside the Co2+-doped TiO2 nanoparticles on the PICL was investigated by contrasting with the Co2+-doped TiO2-SiO2 core-shell nanoparticles. Significantly, the CL intensity increased apparently and the time of the CL was prolonged in the presence of procaterol hydrochloride because the mechanism of the enhanced PICL reaction may be modified. The route of the PICL was changed due to the participation of the procaterol hydrochloride enriched at the surface of the Co2+-doped TiO2-SiO2 in the PICL reaction, which prolonged the time of the CL reaction and resulted in the long-term PICL. The analytical characteristics of the proposed in-situ PICL method were investigated using the procaterol hydrochloride as the model analyte. The investigation results showed that this new PICL analytical method offered higher sensitivity to the analysis of the procaterol hydrochloride and the PICL intensity was linear with the concentration of the procaterol hydrochloride in the range from ca. 2.0 x 10(-10) to 1.0 x 10(-8) g mL(-1).

Prediction of Time Response of Electrowetting

NASA Astrophysics Data System (ADS)

Lee, Seung Jun; Hong, Jiwoo; Kang, Kwan Hyoung

2009-11-01

It is very important to predict the time response of electrowetting-based devices, such as liquid lenses, reflective displays, and optical switches. We investigated the time response of electrowetting, based on an analytical and a numerical method, to find out characteristic scales and a scaling law for the switching time. For this, spreading process of a sessile droplet was analyzed based on the domain perturbation method. First, we considered the case of weakly viscous fluids. The analytical result for the spreading process was compared with experimental results, which showed very good agreement in overall time response. It was shown that the overall dynamics is governed by P2 shape mode. We derived characteristic scales combining the droplet volume, density, and surface tension. The overall dynamic process was scaled quite well by the scales. A scaling law was derived from the analytical solution and was verified experimentally. We also suggest a scaling law for highly viscous liquids, based on results of numerical analysis for the electrowetting-actuated spreading process.

Sample displacement chromatography as a method for purification of proteins and peptides from complex mixtures

PubMed Central

Gajdosik, Martina Srajer; Clifton, James; Josic, Djuro

2012-01-01

Sample displacement chromatography (SDC) in reversed-phase and ion-exchange modes was introduced approximately twenty years ago. This method takes advantage of relative binding affinities of components in a sample mixture. During loading, there is a competition among different sample components for the sorption on the surface of the stationary phase. SDC was first used for the preparative purification of proteins. Later, it was demonstrated that this kind of chromatography can also be performed in ion-exchange, affinity and hydrophobic-interaction mode. It has also been shown that SDC can be performed on monoliths and membrane-based supports in both analytical and preparative scale. Recently, SDC in ion-exchange and hydrophobic interaction mode was also employed successfully for the removal of trace proteins from monoclonal antibody preparations and for the enrichment of low abundance proteins from human plasma. In this review, the principals of SDC are introduced, and the potential for separation of proteins and peptides in micro-analytical, analytical and preparative scale is discussed. PMID:22520159

Surface scanning through a cylindrical tank of coupling fluid for clinical microwave breast imaging exams

PubMed Central

Pallone, Matthew J.; Meaney, Paul M.; Paulsen, Keith D.

2012-01-01

Purpose: Microwave tomographic image quality can be improved significantly with prior knowledge of the breast surface geometry. The authors have developed a novel laser scanning system capable of accurately recovering surface renderings of breast-shaped phantoms immersed within a cylindrical tank of coupling fluid which resides completely external to the tank (and the aqueous environment) and overcomes the challenges associated with the optical distortions caused by refraction from the air, tank wall, and liquid bath interfaces. Methods: The scanner utilizes two laser line generators and a small CCD camera mounted concentrically on a rotating gantry about the microwave imaging tank. Various calibration methods were considered for optimizing the accuracy of the scanner in the presence of the optical distortions including traditional ray tracing and image registration approaches. In this paper, the authors describe the construction and operation of the laser scanner, compare the efficacy of several calibration methods—including analytical ray tracing and piecewise linear, polynomial, locally weighted mean, and thin-plate-spline (TPS) image registrations—and report outcomes from preliminary phantom experiments. Results: The results show that errors in calibrating camera angles and position prevented analytical ray tracing from achieving submillimeter accuracy in the surface renderings obtained from our scanner configuration. Conversely, calibration by image registration reliably attained mean surface errors of less than 0.5 mm depending on the geometric complexity of the object scanned. While each of the image registration approaches outperformed the ray tracing strategy, the authors found global polynomial methods produced the best compromise between average surface error and scanner robustness. Conclusions: The laser scanning system provides a fast and accurate method of three dimensional surface capture in the aqueous environment commonly found in microwave breast imaging. Optical distortions imposed by the imaging tank and coupling bath diminished the effectiveness of the ray tracing approach; however, calibration through image registration techniques reliably produced scans of submillimeter accuracy. Tests of the system with breast-shaped phantoms demonstrated the successful implementation of the scanner for the intended application. PMID:22755695

Development of an analytical method for the simultaneous analysis of MCPD esters and glycidyl esters in oil-based foodstuffs.

PubMed

Ermacora, Alessia; Hrnčiřík, Karel

2014-01-01

Substantial progress has been recently made in the development and optimisation of analytical methods for the quantification of 2-MCPD, 3-MCPD and glycidyl esters in oils and fats, and there are a few methods currently available that allow a reliable quantification of these contaminants in bulk oils and fats. On the other hand, no standard method for the analysis of foodstuffs has yet been established. The aim of this study was the development and validation of a new method for the simultaneous quantification of 2-MCPD, 3-MCPD and glycidyl esters in oil-based food products. The developed protocol includes a first step of liquid-liquid extraction and purification of the lipophilic substances of the sample, followed by the application of a previously developed procedure based on acid transesterification, for the indirect quantification of these contaminants in oils and fats. The method validation was carried out on food products (fat-based spreads, creams, margarine, mayonnaise) manufactured in-house, in order to control the manufacturing process and account for any food matrix-analyte interactions (the sample spiking was carried out on the single components used for the formulations rather than the final products). The method showed good accuracy (the recoveries ranged from 97% to 106% for bound 3-MCPD and 2-MCPD and from 88% to 115% for bound glycidol) and sensitivity (the LOD was 0.04 and 0.05 mg kg(-1) for bound MCPD and glycidol, respectively). Repeatability and reproducibility were satisfactory (RSD below 2% and 5%, respectively) for all analytes. The levels of salts and surface-active compounds in the formulation were found to have no impact on the accuracy and the other parameters of the method.

Electrostatic Interactions between OmpG Nanopore and Analyte Protein Surface Can Distinguish between Glycosylated Isoforms.

PubMed

Fahie, Monifa A; Chen, Min

2015-08-13

The flexible loops decorating the entrance of OmpG nanopore move dynamically during ionic current recording. The gating caused by these flexible loops changes when a target protein is bound. The gating is characterized by parameters including frequency, duration, and open-pore current, and these features combine to reveal the identity of a specific analyte protein. Here, we show that OmpG nanopore equipped with a biotin ligand can distinguish glycosylated and deglycosylated isoforms of avidin by their differences in surface charge. Our studies demonstrate that the direct interaction between the nanopore and analyte surface, induced by the electrostatic attraction between the two molecules, is essential for protein isoform detection. Our technique is remarkably sensitive to the analyte surface, which may provide a useful tool for glycoprotein profiling.

Monitoring of platinum surface contamination in seven Dutch hospital pharmacies using inductively coupled plasma mass spectrometry

PubMed Central

Huitema, A. D. R.; Bakker, E. N.; Douma, J. W.; Schimmel, K. J. M.; van Weringh, G.; de Wolf, P. J.; Schellens, J. H. M.; Beijnen, J. H.

2007-01-01

Objective: To develop, validate, and apply a method for the determination of platinum contamination, originating from cisplatinum, oxaliplatinum, and carboplatinum. Methods: Inductively coupled plasma mass spectrometry (ICP-MS) was used to determine platinum in wipe samples. The sampling procedure and the analytical conditions were optimised and the assay was validated. The method was applied to measure surface contamination in seven Dutch hospital pharmacies. Results: The developed method allowed reproducible quantification of 0.50 ng l−1 platinum (5 pg/wipe sample). Recoveries for stainless steel and linoleum surfaces ranged between 50.4 and 81.4% for the different platinum compounds tested. Platinum contamination was reported in 88% of the wipe samples. Although a substantial variation in surface contamination of the pharmacies was noticed, in most pharmacies, the laminar-airflow (LAF) hoods, the floor in front of the LAF hoods, door handles, and handles of service hatches showed positive results. This demonstrates that contamination is spread throughout the preparation rooms. Conclusion: We developed and validated an ultra sensitive and reliable ICP-MS method for the determination of platinum in surface samples. Surface contamination with platinum was observed in all hospital pharmacies sampled. The interpretation of these results is, however, complicated. PMID:17377802

Application of sunflower stalk-carbon nitride nanosheets as a green sorbent in the solid-phase extraction of polycyclic aromatic hydrocarbons followed by high-performance liquid chromatography.

PubMed

Marzi Khosrowshahi, Elnaz; Razmi, Habib

2018-02-08

A green biocomposite of sunflower stalks and graphitic carbon nitride nanosheets has been applied as a solid-phase extraction adsorbent for sample preparation of five polycyclic aromatic hydrocarbons in different solutions using high-performance liquid chromatography with ultraviolet detection. Before the modification, sunflower stalks exhibited relatively low adsorption to the polycyclic aromatic hydrocarbons extraction. The modified sunflower stalks showed increased adsorption to the analytes extraction due to the increase in surface and existence of a π-π interaction between the analytes and graphitic carbon nitride nanosheets on the surface. Under the optimal conditions, the limits of detection and quantification for five polycyclic aromatic hydrocarbons compounds could reach 0.4-32 and 1.2-95 ng/L, respectively. The method accuracy was evaluated using recovery measurements in spiked real samples and good recoveries from 71 to 115% with relative standard deviations of <10% have been achieved. The developed method was successfully applied for polycyclic aromatic hydrocarbons determination in various samples-well water, tap water, soil, vegetable, and barbequed meat (kebab)-with analytes contents ranging from 0.065 to 13.3 μg/L. The prepared green composite as a new sorbent has some advantages including ease of preparation, low cost, and good reusability. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Q-controlled amplitude modulation atomic force microscopy in liquids: An analysis

NASA Astrophysics Data System (ADS)

Hölscher, H.; Schwarz, U. D.

2006-08-01

An analysis of amplitude modulation atomic force microscopy in liquids is presented with respect to the application of the Q-Control technique. The equation of motion is solved by numerical and analytic methods with and without Q-Control in the presence of a simple model interaction force adequate for many liquid environments. In addition, the authors give an explicit analytical formula for the tip-sample indentation showing that higher Q factors reduce the tip-sample force. It is found that Q-Control suppresses unwanted deformations of the sample surface, leading to the enhanced image quality reported in several experimental studies.

A simplified analytical solution for thermal response of a one-dimensional, steady state transpiration cooling system in radiative and convective environment

NASA Technical Reports Server (NTRS)

Kubota, H.

1976-01-01

A simplified analytical method for calculation of thermal response within a transpiration-cooled porous heat shield material in an intense radiative-convective heating environment is presented. The essential assumptions of the radiative and convective transfer processes in the heat shield matrix are the two-temperature approximation and the specified radiative-convective heatings of the front surface. Sample calculations for porous silica with CO2 injection are presented for some typical parameters of mass injection rate, porosity, and material thickness. The effect of these parameters on the cooling system is discussed.

Solvent jet desorption capillary photoionization-mass spectrometry.

PubMed

Haapala, Markus; Teppo, Jaakko; Ollikainen, Elisa; Kiiski, Iiro; Vaikkinen, Anu; Kauppila, Tiina J; Kostiainen, Risto

2015-03-17

A new ambient mass spectrometry method, solvent jet desorption capillary photoionization (DCPI), is described. The method uses a solvent jet generated by a coaxial nebulizer operated at ambient conditions with nitrogen as nebulizer gas. The solvent jet is directed onto a sample surface, from which analytes are extracted into the solvent and ejected from the surface in secondary droplets formed in collisions between the jet and the sample surface. The secondary droplets are directed into the heated capillary photoionization (CPI) device, where the droplets are vaporized and the gaseous analytes are ionized by 10 eV photons generated by a vacuum ultraviolet (VUV) krypton discharge lamp. As the CPI device is directly connected to the extended capillary inlet of the MS, high ion transfer efficiency to the vacuum of MS is achieved. The solvent jet DCPI provides several advantages: high sensitivity for nonpolar and polar compounds with limit of detection down to low fmol levels, capability of analyzing small and large molecules, and good spatial resolution (250 μm). Two ionization mechanisms are involved in DCPI: atmospheric pressure photoionization, capable of ionizing polar and nonpolar compounds, and solvent assisted inlet ionization capable of ionizing larger molecules like peptides. The feasibility of DCPI was successfully tested in the analysis of polar and nonpolar compounds in sage leaves and chili pepper.

Interfacing Capillary-Based Separations to Mass Spectrometry Using Desorption Electrospray Ionization

PubMed Central

Barbula, Griffin K.; Safi, Samir; Chingin, Konstantin; Perry, Richard H.; Zare, Richard N.

2014-01-01

The powerful hybrid analysis method of capillary-based separations followed by mass spectrometric analysis gives substantial chemical identity and structural information. It is usually carried out using electrospray ionization. However, the salts and detergents used in the mobile phase for electrokinetic separations suppress ionization efficiencies and contaminate the inlet of the mass spectrometer. This report describes a new method that uses desorption electrospray ionization (DESI) to overcome these limitations. Effluent from capillary columns is deposited on a rotating Teflon disk that is covered with paper. As the surface rotates, the temporal separation of the eluting analytes (i.e., the electropherogram) is spatially encoded on the surface. Then, using DESI, surface-deposited analytes are preferentially ionized, reducing the effects of ion suppression and inlet contamination on signal. With the use of this novel approach, two capillary-based separations were performed: a mixture of the rhodamine dyes at milligram/milliliter levels in a 10 mM sodium borate solution was separated by capillary electrophoresis, and a mixture of three cardiac drugs at milligram/milliliter levels in a 12.5 mM sodium borate and 12.5 mM sodium dodecyl sulfate solution was separated by micellar electrokinetic chromatography. In both experiments, the negative effects of detergents and salts on the MS analyses were minimized. PMID:21319740

A method for computing ion energy distributions for multifrequency capacitive discharges

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

Wu, Alan C. F.; Lieberman, M. A.; Verboncoeur, J. P.

2007-03-01

The ion energy distribution (IED) at a surface is an important parameter for processing in multiple radio frequency driven capacitive discharges. An analytical model is developed for the IED in a low pressure discharge based on a linear transfer function that relates the time-varying sheath voltage to the time-varying ion energy response at the surface. This model is in good agreement with particle-in-cell simulations over a wide range of single, dual, and triple frequency driven capacitive discharge excitations.

FREE-SURFACE SEPARATION OF STEAM AND WATER FOR APPLICATION IN A MARINE REACTOR AT 1000 PSIG

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

Steamer, A.G.; Ongman, H.D.

1960-07-13

A series of free-surface steam separation tests were carried out at 1000 psig to obtain data to aid in checking out analytical methods for the effect of ship-s motion on steam separation. Data are presented on the shape and height of the steam-water interface with respect to the indicated water level for two vessel sizes. Further data are presented on the effects of water level and downcomer water velocity on steam carryunder. (auth)

APC: A New Code for Atmospheric Polarization Computations

NASA Technical Reports Server (NTRS)

Korkin, Sergey V.; Lyapustin, Alexei I.; Rozanov, Vladimir V.

2014-01-01

A new polarized radiative transfer code Atmospheric Polarization Computations (APC) is described. The code is based on separation of the diffuse light field into anisotropic and smooth (regular) parts. The anisotropic part is computed analytically. The smooth regular part is computed numerically using the discrete ordinates method. Vertical stratification of the atmosphere, common types of bidirectional surface reflection and scattering by spherical particles or spheroids are included. A particular consideration is given to computation of the bidirectional polarization distribution function (BPDF) of the waved ocean surface.

Comparison Between Sea Surface Wind Speed Estimates From Reflected GPS Signals and Buoy Measurements

NASA Technical Reports Server (NTRS)

Garrison, James L.; Katzberg, Steven J.; Zavorotny, Valery U.

2000-01-01

Reflected signals from the Global Positioning System (GPS) have been collected from an aircraft at approximately 3.7 km altitude on 5 different days. Estimation of surface wind speed by matching the shape of the reflected signal correlation function against analytical models was demonstrated. Wind speed obtained from this method agreed with that recorded from buoys to with a bias of less than 0.1 m/s, and with a standard derivation of 1.3 meters per second.

Experts workshop on the ecotoxicological risk assessment of ionizable organic chemicals: Towards a science-based framework for chemical assessment

EPA Science Inventory

There is a growing need to develop analytical methods and tools that can be applied to assess the environmental risks associated with charged, polar, and ionisable organic chemicals, such as those used as active pharmaceutical ingredients, biocides, and surface active chemicals. ...

Quantum mechanical/molecular mechanical/continuum style solvation model: second order Møller-Plesset perturbation theory.

PubMed

Thellamurege, Nandun M; Si, Dejun; Cui, Fengchao; Li, Hui

2014-05-07

A combined quantum mechanical/molecular mechanical/continuum (QM/MM/C) style second order Møller-Plesset perturbation theory (MP2) method that incorporates induced dipole polarizable force field and induced surface charge continuum solvation model is established. The Z-vector method is modified to include induced dipoles and induced surface charges to determine the MP2 response density matrix, which can be used to evaluate MP2 properties. In particular, analytic nuclear gradient is derived and implemented for this method. Using the Assisted Model Building with Energy Refinement induced dipole polarizable protein force field, the QM/MM/C style MP2 method is used to study the hydrogen bonding distances and strengths of the photoactive yellow protein chromopore in the wild type and the Glu46Gln mutant.

A three-dimensional semi-analytical solution for predicting drug release through the orifice of a spherical device.

PubMed

Simon, Laurent; Ospina, Juan

2016-07-25

Three-dimensional solute transport was investigated for a spherical device with a release hole. The governing equation was derived using the Fick's second law. A mixed Neumann-Dirichlet condition was imposed at the boundary to represent diffusion through a small region on the surface of the device. The cumulative percentage of drug released was calculated in the Laplace domain and represented by the first term of an infinite series of Legendre and modified Bessel functions of the first kind. Application of the Zakian algorithm yielded the time-domain closed-form expression. The first-order solution closely matched a numerical solution generated by Mathematica(®). The proposed method allowed computation of the characteristic time. A larger surface pore resulted in a smaller effective time constant. The agreement between the numerical solution and the semi-analytical method improved noticeably as the size of the orifice increased. It took four time constants for the device to release approximately ninety-eight of its drug content. Copyright © 2016 Elsevier B.V. All rights reserved.

Quasi-analytical treatment of spatially averaged radiation transfer in complex terrain

NASA Astrophysics Data System (ADS)

Löwe, H.; Helbig, N.

2012-04-01

We provide a new quasi-analytical method to compute the topographic influence on the effective albedo of complex topography as required for meteorological, land-surface or climate models. We investigate radiative transfer in complex terrain via the radiosity equation on isotropic Gaussian random fields. Under controlled approximations we derive expressions for domain averages of direct, diffuse and terrain radiation and the sky view factor. Domain averaged quantities are related to a type of level-crossing probability of the random field which is approximated by longstanding results developed for acoustic scattering at ocean boundaries. This allows us to express all non-local horizon effects in terms of a local terrain parameter, namely the mean squared slope. Emerging integrals are computed numerically and fit formulas are given for practical purposes. As an implication of our approach we provide an expression for the effective albedo of complex terrain in terms of the sun elevation angle, mean squared slope, the area averaged surface albedo, and the direct-to-diffuse ratio of solar radiation. As an application, we compute the effective albedo for the Swiss Alps and discuss possible generalizations of the method.

Surface acoustic wave nebulization facilitating lipid mass spectrometric analysis.

PubMed

Yoon, Sung Hwan; Huang, Yue; Edgar, J Scott; Ting, Ying S; Heron, Scott R; Kao, Yuchieh; Li, Yanyan; Masselon, Christophe D; Ernst, Robert K; Goodlett, David R

2012-08-07

Surface acoustic wave nebulization (SAWN) is a novel method to transfer nonvolatile analytes directly from the aqueous phase to the gas phase for mass spectrometric analysis. The lower ion energetics of SAWN and its planar nature make it appealing for analytically challenging lipid samples. This challenge is a result of their amphipathic nature, labile nature, and tendency to form aggregates, which readily precipitate clogging capillaries used for electrospray ionization (ESI). Here, we report the use of SAWN to characterize the complex glycolipid, lipid A, which serves as the membrane anchor component of lipopolysaccharide (LPS) and has a pronounced tendency to clog nano-ESI capillaries. We also show that unlike ESI SAWN is capable of ionizing labile phospholipids without fragmentation. Lastly, we compare the ease of use of SAWN to the more conventional infusion-based ESI methods and demonstrate the ability to generate higher order tandem mass spectral data of lipid A for automated structure assignment using our previously reported hierarchical tandem mass spectrometry (HiTMS) algorithm. The ease of generating SAWN-MS(n) data combined with HiTMS interpretation offers the potential for high throughput lipid A structure analysis.

Temperature field for radiative tomato peeling

NASA Astrophysics Data System (ADS)

Cuccurullo, G.; Giordano, L.

2017-01-01

Nowadays peeling of tomatoes is performed by using steam or lye, which are expensive and polluting techniques, thus sustainable alternatives are searched for dry peeling and, among that, radiative heating seems to be a fairly promising method. This paper aims to speed up the prediction of surface temperatures useful for realizing dry-peeling, thus a 1D-analytical model for the unsteady temperature field in a rotating tomato exposed to a radiative heating source is presented. Since only short times are of interest for the problem at hand, the model involves a semi-infinite slab cooled by convective heat transfer while heated by a pulsating heat source. The model being linear, the solution is derived following the Laplace Transform method. A 3D finite element model of the rotating tomato is introduced as well in order to validate the analytical solution. A satisfactory agreement is attained. Therefore, two different ways to predict the onset of the peeling conditions are available which can be of help for proper design of peeling plants. Particular attention is paid to study surface temperature uniformity, that being a critical parameter for realizing an easy tomato peeling.

Use of a novel cation-exchange restricted-access material for automated sample clean-up prior to the determination of basic drugs in plasma by liquid chromatography.

PubMed

Chiap, P; Rbeida, O; Christiaens, B; Hubert, Ph; Lubda, D; Boos, K S; Crommen, J

2002-10-25

A new kind of silica-based restricted-access material (RAM) has been tested in pre-columns for the on-line solid-phase extraction (SPE) of basic drugs from directly injected plasma samples before their quantitative analysis by reversed-phase liquid chromatography (LC), using the column switching technique. The outer surface of the porous RAM particlescontains hydrophilic diol groups while sulphonic acid groups are bound to the internal surface, which gives the sorbent the properties of a strong cation exchanger towards low molecular mass compounds. Macromolecules such as proteins have no access to the internal surface of the pre-column due to their exclusion from the pores and are then flushed directly out. The retention capability of this novel packing material has been tested for some hydrophilic basic drugs, such as atropine, fenoterol, ipratropium, procaine, sotalol and terbutaline, used as model compounds. The influence of the composition of the washing liquid on the retention of the analytes in the pre-column has been investigated. The elution profiles of the different compounds and the plasma matrix as well as the time needed for the transfer of the analytes from the pre-column to the analytical column were determined in order to deduce the most suitable conditions for the clean-up step and develop on-line methods for the LC determination of these compounds in plasma. The cationic exchange sorbent was also compared to another RAM, namely RP-18 ADS (alkyl diol silica) sorbent with respect to retention capability towards basic analytes.

Adaptable Detection Strategies in Membrane-Based Immunoassays: Calibration-Free Quantitation with Surface-Enhanced Raman Scattering Readout.

PubMed

Skuratovsky, Aleksander; Soto, Robert J; Porter, Marc D

2018-06-19

This paper presents a method for immunometric biomarker quantitation that uses standard flow-through assay reagents and obviates the need for constructing a calibration curve. The approach relies on a nitrocellulose immunoassay substrate with multiple physical addresses for analyte capture, each modified with different amounts of an analyte-specific capture antibody. As such, each address generates a distinctly different readout signal that is proportional to the analyte concentration in the sample. To establish the feasibility of this concept, equations derived from antibody-antigen binding equilibrium were first applied in modeling experiments. Next, nitrocellulose membranes with multiple capture antibody addresses were fabricated for detection of a model analyte, human Immunoglobulin G (hIgG), by a heterogeneous sandwich immunoassay using antibody-modified gold nanoparticles (AuNPs) as the immunolabel. Counting the number of colored capture addresses visible to the unassisted eye enabled semiquantitative hIgG determination. We then demonstrated that, by leveraging the localized surface plasmon resonance of the AuNPs, surface-enhanced Raman spectroscopy (SERS) can be used for quantitative readout. By comparing the SERS signal intensities from each capture address with values predicted using immunoassay equilibrium theory, the concentration of hIgG can be determined (∼30% average absolute deviation) without reference to a calibration curve. This work also demonstrates the ability to manipulate the dynamic range of the assay over ∼4 orders of magnitude (from 2 ng mL -1 to 10 μg mL -1 ). The potential prospects in applying this concept to point-of-need diagnostics are also discussed.

Analyte preconcentration in nanofluidic channels with nonuniform zeta potential

NASA Astrophysics Data System (ADS)

Eden, A.; McCallum, C.; Storey, B. D.; Pennathur, S.; Meinhart, C. D.

2017-12-01

It is well known that charged analytes in the presence of nonuniform electric fields concentrate at locations where the relevant driving forces balance, and a wide range of ionic stacking and focusing methods are commonly employed to leverage these physical mechanisms in order to improve signal levels in biosensing applications. In particular, nanofluidic channels with spatially varying conductivity distributions have been shown to provide increased preconcentration of charged analytes due to the existence of a finite electric double layer (EDL), in which electrostatic attraction and repulsion from charged surfaces produce nonuniform transverse ion distributions. In this work, we use numerical simulations to show that one can achieve greater levels of sample accumulation by using field-effect control via wall-embedded electrodes to tailor the surface potential heterogeneity in a nanochannel with overlapped EDLs. In addition to previously demonstrated stacking and focusing mechanisms, we find that the coupling between two-dimensional ion distributions and the axial electric field under overlapped EDL conditions can generate an ion concentration polarization interface in the middle of the channel. Under an applied electric field, this interface can be used to concentrate sample ions between two stationary regions of different surface potential and charge density. Our numerical model uses the Poisson-Nernst-Planck system of equations coupled with the Stokes equation to demonstrate the phenomenon, and we discuss in detail the driving forces behind the predicted sample enhancement. The numerical velocity and salt concentration profiles exhibit good agreement with analytical results from a simplified one-dimensional area-averaged model for several limiting cases, and we show predicted amplification ratios of up to 105.

Graphene oxide assisted electromembrane extraction with gas chromatography for the determination of methamphetamine as a model analyte in hair and urine samples.

PubMed

Bagheri, Hasan; Zavareh, Alireza Fakhari; Koruni, Mohammad Hossein

2016-03-01

In the present study, graphene oxide reinforced two-phase electromembrane extraction (EME) coupled with gas chromatography was applied for the determination of methamphetamine as a model analyte in biological samples. The presence of graphene oxide in the hollow fiber wall can increase the effective surface area, interactions with analyte and polarity of support liquid membrane that leads to an enhancement in the analyte migration. To investigate the influence of the presence of graphene oxide in the support liquid membrane on the extraction efficiency, a comparative study was performed between graphene oxide and graphene oxide/EME methods. The extraction parameters such as type of organic solvent, pH of the donor phase, stirring speed, time, voltage, salt addition and the concentration of graphene oxide were optimized. Under the optimum conditions, the proposed microextraction technique provided low limit of detection (2.4 ng/mL), high preconcentration factor (195-198) and high relative recovery (95-98.5%). Finally, the method was successfully employed for the determination of methamphetamine in urine and hair samples. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

New method of extrapolation of the resistance of a model planing boat to full size

NASA Technical Reports Server (NTRS)

Sottorf, W

1942-01-01

The previously employed method of extrapolating the total resistance to full size with lambda(exp 3) (model scale) and thereby foregoing a separate appraisal of the frictional resistance, was permissible for large models and floats of normal size. But faced with the ever increasing size of aircraft a reexamination of the problem of extrapolation to full size is called for. A method is described by means of which, on the basis of an analysis of tests on planing surfaces, the variation of the wetted surface over the take-off range is analytically obtained. The friction coefficients are read from Prandtl's curve for turbulent boundary layer with laminar approach. With these two values a correction for friction is obtainable.

Boundary Electron and Beta Dosimetry-Quantification of the Effects of Dissimilar Media on Absorbed Dose

NASA Astrophysics Data System (ADS)

Nunes, Josane C.

1991-02-01

This work quantifies the changes effected in electron absorbed dose to a soft-tissue equivalent medium when part of this medium is replaced by a material that is not soft -tissue equivalent. That is, heterogeneous dosimetry is addressed. Radionuclides which emit beta particles are the electron sources of primary interest. They are used in brachytherapy and in nuclear medicine: for example, beta -ray applicators made with strontium-90 are employed in certain ophthalmic treatments and iodine-131 is used to test thyroid function. More recent medical procedures under development and which involve beta radionuclides include radioimmunotherapy and radiation synovectomy; the first is a cancer modality and the second deals with the treatment of rheumatoid arthritis. In addition, the possibility of skin surface contamination exists whenever there is handling of radioactive material. Determination of absorbed doses in the examples of the preceding paragraph requires considering boundaries of interfaces. Whilst the Monte Carlo method can be applied to boundary calculations, for routine work such as in clinical situations, or in other circumstances where doses need to be determined quickly, analytical dosimetry would be invaluable. Unfortunately, few analytical methods for boundary beta dosimetry exist. Furthermore, the accuracy of results from both Monte Carlo and analytical methods has to be assessed. Although restricted to one radionuclide, phosphorus -32, the experimental data obtained in this work serve several purposes, one of which is to provide standards against which calculated results can be tested. The experimental data also contribute to the relatively sparse set of published boundary dosimetry data. At the same time, they may be useful in developing analytical boundary dosimetry methodology. The first application of the experimental data is demonstrated. Results from two Monte Carlo codes and two analytical methods, which were developed elsewhere, are compared with experimental data. Monte Carlo results compare satisfactory with experimental results for the boundaries considered. The agreement with experimental results for air interfaces is of particular interest because of discrepancies reported previously by another investigator who used data obtained from a different experimental technique. Results from one of the analytical methods differ significantly from the experimental data obtained here. The second analytical method provided data which approximate experimental results to within 30%. This is encouraging but it remains to be determined whether this method performs equally well for other source energies.

Adhesive-Bonded Composite Joint Analysis with Delaminated Surface Ply Using Strain-Energy Release Rate

NASA Technical Reports Server (NTRS)

Chadegani, Alireza; Yang, Chihdar; Smeltzer, Stanley S. III

2012-01-01

This paper presents an analytical model to determine the strain energy release rate due to an interlaminar crack of the surface ply in adhesively bonded composite joints subjected to axial tension. Single-lap shear-joint standard test specimen geometry with thick bondline is followed for model development. The field equations are formulated by using the first-order shear-deformation theory in laminated plates together with kinematics relations and force equilibrium conditions. The stress distributions for the adherends and adhesive are determined after the appropriate boundary and loading conditions are applied and the equations for the field displacements are solved. The system of second-order differential equations is solved to using the symbolic computation tool Maple 9.52 to provide displacements fields. The equivalent forces at the tip of the prescribed interlaminar crack are obtained based on interlaminar stress distributions. The strain energy release rate of the crack is then determined by using the crack closure method. Finite element analyses using the J integral as well as the crack closure method are performed to verify the developed analytical model. It has been shown that the results using the analytical method correlate well with the results from the finite element analyses. An attempt is made to predict the failure loads of the joints based on limited test data from the literature. The effectiveness of the inclusion of bondline thickness is justified when compared with the results obtained from the previous model in which a thin bondline and uniform adhesive stresses through the bondline thickness are assumed.

New method to design stellarator coils without the winding surface

NASA Astrophysics Data System (ADS)

Zhu, Caoxiang; Hudson, Stuart R.; Song, Yuntao; Wan, Yuanxi

2018-01-01

Finding an easy-to-build coils set has been a critical issue for stellarator design for decades. Conventional approaches assume a toroidal ‘winding’ surface, but a poorly chosen winding surface can unnecessarily constrain the coil optimization algorithm, This article presents a new method to design coils for stellarators. Each discrete coil is represented as an arbitrary, closed, one-dimensional curve embedded in three-dimensional space. A target function to be minimized that includes both physical requirements and engineering constraints is constructed. The derivatives of the target function with respect to the parameters describing the coil geometries and currents are calculated analytically. A numerical code, named flexible optimized coils using space curves (FOCUS), has been developed. Applications to a simple stellarator configuration, W7-X and LHD vacuum fields are presented.

The Sulphur Poisoning Behaviour of Gadolinia Doped Ceria Model Systems in Reducing Atmospheres

PubMed Central

Gerstl, Matthias; Nenning, Andreas; Iskandar, Riza; Rojek-Wöckner, Veronika; Bram, Martin; Hutter, Herbert; Opitz, Alexander Karl

2016-01-01

An array of analytical methods including surface area determination by gas adsorption using the Brunauer, Emmett, Teller (BET) method, combustion analysis, XRD, ToF-SIMS, TEM and impedance spectroscopy has been used to investigate the interaction of gadolinia doped ceria (GDC) with hydrogen sulphide containing reducing atmospheres. It is shown that sulphur is incorporated into the GDC bulk and might lead to phase changes. Additionally, high concentrations of silicon are found on the surface of model composite microelectrodes. Based on these data, a model is proposed to explain the multi-facetted electrochemical degradation behaviour encountered during long term electrochemical measurements. While electrochemical bulk properties of GDC stay largely unaffected, the surface polarisation resistance is dramatically changed, due to silicon segregation and reaction with adsorbed sulphur. PMID:28773771

Method for measuring thermal accommodation coefficients of gases on thin film surfaces using a MEMS sensor structure

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

Grau, Mario, E-mail: mario.grau@hs-rm.de; Völklein, Friedemann; Meier, Andreas

A method for measuring the thermal accommodation coefficient α for surface-/gas interfaces is presented. It allows the determination of α for thin films produced by a variety of deposition technologies, such as chemical vapor deposition, physical vapor deposition, and atomic layer deposition (ALD). The setup is based on two microelectromechanical systems (MEMS) Pirani sensors facing each other in a defined positioning. Because these MEMS sensors show a very high sensitivity in their individual molecular flow regimes, it is possible to measure the accommodation coefficients of gases without the disturbing influence of the transition regime. This paper presents the analytical backgroundmore » and the actual measurement principle. The results for air and nitrogen molecules on sputtered Au and Pt surfaces are presented.« less

Cyanoacrylate Skin Surface Stripping and the 3S-Biokit Advent in Tropical Dermatology: A Look from Liège

PubMed Central

Piérard, Gérald E.; Piérard-Franchimont, Claudine; Paquet, Philippe; Hermanns-Lê, Trinh; Delvenne, Philippe

2014-01-01

In the dermatopathology field, some simple available laboratory tests require minimum equipment for establishing a diagnosis. Among them, the cyanoacrylate skin surface stripping (CSSS), formerly named skin surface biopsy or follicular biopsy, represents a convenient low cost procedure. It is a minimally invasive method collecting a continuous sheet of stratum corneum and horny follicular casts. In the vast majority of cases, it is painless and is unassociated with adverse events. CSSS can be performed in subjects of any age. The method has a number of applications in diagnostic dermatopathology and cosmetology, as well as in experimental dermatology settings. A series of derived analytic procedures include xerosis grading, comedometry, corneofungimetry, corneodynamics of stratum corneum renewal, corneomelametry, corneosurfametry, and corneoxenometry. PMID:25177726

Determination of 3,6-dinitrobenzo[e]pyrene in surface soil and airborne particles by high-performance liquid chromatography with fluorescence detection.

PubMed

Hasei, Tomohiro; Watanabe, Tetsushi; Hirayama, Teruhisa

2006-11-24

We developed a sensitive analytical method and an efficient clean-up method to quantify 3,6-dinitrobenzo[e]pyrene (3,6-DNBeP) in surface soil and airborne particles. After purification using a silica gel column and two reversed-phase columns, 3,6-DNBeP was reduced to 3,6-diaminobenzo[e]pyrene by a catalyst column and analyzed by high-performance liquid chromatography (HPLC) with a fluorescence detector. 3,6-DNBeP was detected in all of the soil samples and airborne particles examined. The concentration of 3,6-DNBeP in surface soil and airborne particles was determined in the ranges of 347-5007 pg/g of soil and 137-1238 fg/m3, respectively.

Whispering Gallery Optical Resonator Spectroscopic Probe and Method

NASA Technical Reports Server (NTRS)

Anderson, Mark S. (Inventor)

2014-01-01

Disclosed herein is a spectroscopic probe comprising at least one whispering gallery mode optical resonator disposed on a support, the whispering gallery mode optical resonator comprising a continuous outer surface having a cross section comprising a first diameter and a second diameter, wherein the first diameter is greater than the second diameter. A method of measuring a Raman spectrum and an Infra-red spectrum of an analyte using the spectroscopic probe is also disclosed.

Analytical approximation of a distorted reflector surface defined by a discrete set of points

NASA Technical Reports Server (NTRS)

Acosta, Roberto J.; Zaman, Afroz A.

1988-01-01

Reflector antennas on Earth orbiting spacecrafts generally cannot be described analytically. The reflector surface is subjected to a large temperature fluctuation and gradients, and is thus warped from its true geometrical shape. Aside from distortion by thermal stresses, reflector surfaces are often purposely shaped to minimize phase aberrations and scanning losses. To analyze distorted reflector antennas defined by discrete surface points, a numerical technique must be applied to compute an interpolatory surface passing through a grid of discrete points. In this paper, the distorted reflector surface points are approximated by two analytical components: an undistorted surface component and a surface error component. The undistorted surface component is a best fit paraboloid polynomial for the given set of points and the surface error component is a Fourier series expansion of the deviation of the actual surface points, from the best fit paraboloid. By applying the numerical technique to approximate the surface normals of the distorted reflector surface, the induced surface current can be obtained using physical optics technique. These surface currents are integrated to find the far field radiation pattern.

Roka Listeria detection method using transcription mediated amplification to detect Listeria species in select foods and surfaces. Performance Tested Method(SM) 011201.

PubMed

Hua, Yang; Kaplan, Shannon; Reshatoff, Michael; Hu, Ernie; Zukowski, Alexis; Schweis, Franz; Gin, Cristal; Maroni, Brett; Becker, Michael; Wisniewski, Michele

2012-01-01

The Roka Listeria Detection Assay was compared to the reference culture methods for nine select foods and three select surfaces. The Roka method used Half-Fraser Broth for enrichment at 35 +/- 2 degrees C for 24-28 h. Comparison of Roka's method to reference methods requires an unpaired approach. Each method had a total of 545 samples inoculated with a Listeria strain. Each food and surface was inoculated with a different strain of Listeria at two different levels per method. For the dairy products (Brie cheese, whole milk, and ice cream), our method was compared to AOAC Official Method(SM) 993.12. For the ready-to-eat meats (deli chicken, cured ham, chicken salad, and hot dogs) and environmental surfaces (sealed concrete, stainless steel, and plastic), these samples were compared to the U.S. Department of Agriculture/Food Safety and Inspection Service-Microbiology Laboratory Guidebook (USDA/FSIS-MLG) method MLG 8.07. Cold-smoked salmon and romaine lettuce were compared to the U.S. Food and Drug Administration/Bacteriological Analytical Manual, Chapter 10 (FDA/BAM) method. Roka's method had 358 positives out of 545 total inoculated samples compared to 332 positive for the reference methods. Overall the probability of detection analysis of the results showed better or equivalent performance compared to the reference methods.

Computed Potential Energy Surfaces and Minimum Energy Pathways for Chemical Reactions

NASA Technical Reports Server (NTRS)

Walch, Stephen P.; Langhoff, S. R. (Technical Monitor)

1994-01-01

Computed potential energy surfaces are often required for computation of such parameters as rate constants as a function of temperature, product branching ratios, and other detailed properties. For some dynamics methods, global potential energy surfaces are required. In this case, it is necessary to obtain the energy at a complete sampling of all the possible arrangements of the nuclei, which are energetically accessible, and then a fitting function must be obtained to interpolate between the computed points. In other cases, characterization of the stationary points and the reaction pathway connecting them is sufficient. These properties may be readily obtained using analytical derivative methods. We have found that computation of the stationary points/reaction pathways using CASSCF/derivative methods, followed by use of the internally contracted CI method to obtain accurate energetics, gives usefull results for a number of chemically important systems. The talk will focus on a number of applications including global potential energy surfaces, H + O2, H + N2, O(3p) + H2, and reaction pathways for complex reactions, including reactions leading to NO and soot formation in hydrocarbon combustion.

A boundary integral equation method using auxiliary interior surface approach for acoustic radiation and scattering in two dimensions.

PubMed

Yang, S A

2002-10-01

This paper presents an effective solution method for predicting acoustic radiation and scattering fields in two dimensions. The difficulty of the fictitious characteristic frequency is overcome by incorporating an auxiliary interior surface that satisfies certain boundary condition into the body surface. This process gives rise to a set of uniquely solvable boundary integral equations. Distributing monopoles with unknown strengths over the body and interior surfaces yields the simple source formulation. The modified boundary integral equations are further transformed to ordinary ones that contain nonsingular kernels only. This implementation allows direct application of standard quadrature formulas over the entire integration domain; that is, the collocation points are exactly the positions at which the integration points are located. Selecting the interior surface is an easy task. Moreover, only a few corresponding interior nodal points are sufficient for the computation. Numerical calculations consist of the acoustic radiation and scattering by acoustically hard elliptic and rectangular cylinders. Comparisons with analytical solutions are made. Numerical results demonstrate the efficiency and accuracy of the current solution method.

Monitoring of emerging pollutants in Guadiamar River basin (South of Spain): analytical method, spatial distribution and environmental risk assessment.

PubMed

Garrido, Eva; Camacho-Muñoz, Dolores; Martín, Julia; Santos, Antonio; Santos, Juan Luis; Aparicio, Irene; Alonso, Esteban

2016-12-01

Guadiamar River is located in the southwest of the Iberian Peninsula and connects two protected areas in the South of Spain: Sierra Morena and Doñana National Park. It is sited in an area affected by urban, industrial and agriculture sewage pollution and with tradition on intensive mining activities. Most of the studies performed in this area have been mainly focused on the presence of heavy metals and, until now, little is known about the occurrence of other contaminants such as emerging organic pollutants (EOPs). In this work, an analytical method has been optimized and validated for monitoring of forty-seven EOPs in surface water. The analytical method has been applied to study the distribution and environmental risk of these pollutants in Guadiamar River basin. The analytical method was based on solid-phase extraction and determination by liquid chromatography-triple quadrupole-tandem mass spectrometry. The 60 % of the target compounds were found in the analyzed samples. The highest concentrations were found for two plasticizers (bisphenol A and di(2-ethyhexyl)phthalate, mean concentration up to 930 ng/L) and two pharmaceutical compounds (caffeine (up to 623 ng/L) and salicylic acid (up to 318 ng/L)). This study allowed to evaluate the potential sources (industrial or urban) of the studied compounds and the spatial distribution of their concentrations along the river. Environmental risk assessment showed a major risk on the south of the river, mainly due to discharges of wastewater effluents.

Analytical methods of the U.S. Geological Survey's New York District Water-Analysis Laboratory

USGS Publications Warehouse

Lawrence, Gregory B.; Lincoln, Tricia A.; Horan-Ross, Debra A.; Olson, Mark L.; Waldron, Laura A.

1995-01-01

The New York District of the U.S. Geological Survey (USGS) in Troy, N.Y., operates a water-analysis laboratory for USGS watershed-research projects in the Northeast that require analyses of precipitation and of dilute surface water and soil water for major ions; it also provides analyses of certain chemical constituents in soils and soil gas samples.This report presents the methods for chemical analyses of water samples, soil-water samples, and soil-gas samples collected in wateshed-research projects. The introduction describes the general materials and technicques for each method and explains the USGS quality-assurance program and data-management procedures; it also explains the use of cross reference to the three most commonly used methods manuals for analysis of dilute waters. The body of the report describes the analytical procedures for (1) solution analysis, (2) soil analysis, and (3) soil-gas analysis. The methods are presented in alphabetical order by constituent. The method for each constituent is preceded by (1) reference codes for pertinent sections of the three manuals mentioned above, (2) a list of the method's applications, and (3) a summary of the procedure. The methods section for each constitutent contains the following categories: instrumentation and equipment, sample preservation and storage, reagents and standards, analytical procedures, quality control, maintenance, interferences, safety considerations, and references. Sufficient information is presented for each method to allow the resulting data to be appropriately used in environmental investigations.

Experimental validation of a sub-surface model of solar power for distributed marine sensor systems

NASA Astrophysics Data System (ADS)

Hahn, Gregory G.; Cantin, Heather P.; Shafer, Michael W.

2016-04-01

The capabilities of distributed sensor systems such as marine wildlife telemetry tags could be significantly enhanced through the integration of photovoltaic modules. Photovoltaic cells could be used to supplement the primary batteries for wildlife telemetry tags to allow for extended tag deployments, wherein larger amounts of data could be collected and transmitted in near real time. In this article, we present experimental results used to validate and improve key aspects of our original model for sub-surface solar power. We discuss the test methods and results, comparing analytic predictions to experimental results. In a previous work, we introduced a model for sub-surface solar power that used analytic models and empirical data to predict the solar irradiance available for harvest at any depth under the ocean's surface over the course of a year. This model presented underwater photovoltaic transduction as a viable means of supplementing energy for marine wildlife telemetry tags. The additional data provided by improvements in daily energy budgets would enhance the temporal and spatial comprehension of the host's activities and/or environments. Photovoltaic transduction is one method that has not been widely deployed in the sub-surface marine environments despite widespread use on terrestrial and avian species wildlife tag systems. Until now, the use of photovoltaic cells for underwater energy harvesting has generally been disregarded as a viable energy source in this arena. In addition to marine telemetry systems, photovoltaic energy harvesting systems could also serve as a means of energy supply for autonomous underwater vehicles (AUVs), as well as submersible buoys for oceanographic data collection.

Miniaturized Temperature-Controlled Planar Chromatography (Micro-TLC) as a Versatile Technique for Fast Screening of Micropollutants and Biomarkers Derived from Surface Water Ecosystems and During Technological Processes of Wastewater Treatment.

PubMed

Ślączka-Wilk, Magdalena M; Włodarczyk, Elżbieta; Kaleniecka, Aleksandra; Zarzycki, Paweł K

2017-07-01

There is increasing interest in the development of simple analytical systems enabling the fast screening of target components in complex samples. A number of newly invented protocols are based on quasi separation techniques involving microfluidic paper-based analytical devices and/or micro total analysis systems. Under such conditions, the quantification of target components can be performed mainly due to selective detection. The main goal of this paper is to demonstrate that miniaturized planar chromatography has the capability to work as an efficient separation and quantification tool for the analysis of multiple targets within complex environmental samples isolated and concentrated using an optimized SPE method. In particular, we analyzed various samples collected from surface water ecosystems (lakes, rivers, and the Baltic Sea of Middle Pomerania in the northern part of Poland) in different seasons, as well as samples collected during key wastewater technological processes (originating from the "Jamno" wastewater treatment plant in Koszalin, Poland). We documented that the multiple detection of chromatographic spots on RP-18W microplates-under visible light, fluorescence, and fluorescence quenching conditions, and using the visualization reagent phosphomolybdic acid-enables fast and robust sample classification. The presented data reveal that the proposed micro-TLC system is useful, inexpensive, and can be considered as a complementary method for the fast control of treated sewage water discharged by a municipal wastewater treatment plant, particularly for the detection of low-molecular mass micropollutants with polarity ranging from estetrol to progesterone, as well as chlorophyll-related dyes. Due to the low consumption of mobile phases composed of water-alcohol binary mixtures (less than 1 mL/run for the simultaneous separation of up to nine samples), this method can be considered an environmentally friendly and green chemistry analytical tool. The described analytical protocol can be complementary to those involving classical column chromatography (HPLC) or various planar microfluidic devices.

Polydopamine-coated magnetic nanoparticles for isolation and enrichment of estrogenic compounds from surface water samples followed by liquid chromatography-tandem mass spectrometry determination.

PubMed

Capriotti, Anna Laura; Cavaliere, Chiara; La Barbera, Giorgia; Piovesana, Susy; Samperi, Roberto; Zenezini Chiozzi, Riccardo; Laganà, Aldo

2016-06-01

Estrogens, phytoestrogens, and mycoestrogens may enter into the surface waters from different sources, such as effluents of municipal wastewater treatment plants, industrial plants, and animal farms and runoff from agricultural areas. In this work, a multiresidue analytical method for the determination of 17 natural estrogenic compounds, including four steroid estrogens, six mycoestrogens, and seven phytoestrogens, in river water samples has been developed. (Fe3O4)-based magnetic nanoparticles coated by polydopamine (Fe3O4@pDA) were used for dispersive solid-phase extraction, and the final extract was analyzed by ultra-high performance liquid chromatography coupled with tandem mass spectrometry. The Fe3O4 magnetic nanoparticles were prepared by a co-precipitation procedure, coated by pDA, and characterized by scanning electron microscopy, infrared spectroscopy, and elemental analysis. The sample preparation method was optimized in terms of extraction recovery, matrix effect, selectivity, trueness, precision, method limits of detection, and method limits of quantification (MLOQs). For all the 17 analytes, recoveries were >70 % and matrix effects were below 30 % when 25 mL of river water sample was treated with 90 mg of Fe3O4@pDA nanoparticles. Selectivity was tested by spiking river water samples with 50 other compounds (mycotoxins, antibacterials, conjugated hormones, UV filters, alkylphenols, etc.), and only aflatoxins and some benzophenones showed recoveries >60 %. This method proved to be simple and robust and allowed the determination of natural estrogenic compounds belonging to different classes in surface waters with MLOQs ranging between 0.003 and 0.1 μg L(-1). Graphical Abstract Determination of natural estrogenic compounds in water by magnetic solid phase extraction followed by liquid chromatography-tandem mass spectrometry analysis.

Computing the Free Energy Barriers for Less by Sampling with a Coarse Reference Potential while Retaining Accuracy of the Target Fine Model.

PubMed

Plotnikov, Nikolay V

2014-08-12

Proposed in this contribution is a protocol for calculating fine-physics (e.g., ab initio QM/MM) free-energy surfaces at a high level of accuracy locally (e.g., only at reactants and at the transition state for computing the activation barrier) from targeted fine-physics sampling and extensive exploratory coarse-physics sampling. The full free-energy surface is still computed but at a lower level of accuracy from coarse-physics sampling. The method is analytically derived in terms of the umbrella sampling and the free-energy perturbation methods which are combined with the thermodynamic cycle and the targeted sampling strategy of the paradynamics approach. The algorithm starts by computing low-accuracy fine-physics free-energy surfaces from the coarse-physics sampling in order to identify the reaction path and to select regions for targeted sampling. Thus, the algorithm does not rely on the coarse-physics minimum free-energy reaction path. Next, segments of high-accuracy free-energy surface are computed locally at selected regions from the targeted fine-physics sampling and are positioned relative to the coarse-physics free-energy shifts. The positioning is done by averaging the free-energy perturbations computed with multistep linear response approximation method. This method is analytically shown to provide results of the thermodynamic integration and the free-energy interpolation methods, while being extremely simple in implementation. Incorporating the metadynamics sampling to the algorithm is also briefly outlined. The application is demonstrated by calculating the B3LYP//6-31G*/MM free-energy barrier for an enzymatic reaction using a semiempirical PM6/MM reference potential. These modifications allow computing the activation free energies at a significantly reduced computational cost but at the same level of accuracy compared to computing full potential of mean force.

A new carbon-based magnetic material for the dispersive solid-phase extraction of UV filters from water samples before liquid chromatography-tandem mass spectrometry analysis.

PubMed

Piovesana, Susy; Capriotti, Anna Laura; Cavaliere, Chiara; La Barbera, Giorgia; Samperi, Roberto; Zenezini Chiozzi, Riccardo; Laganà, Aldo

2017-07-01

Magnetic solid-phase extraction is one of the most promising new extraction methods for liquid samples before ultra-high-performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) analysis. Several types of materials, including carbonaceous ones, have been prepared for this purpose. In this paper, for the first time, the preparation, characterization, and sorption capability of Fe 3 O 4 -graphitized carbon black (mGCB) composite toward some compounds of environmental interest were investigated. The synthesized mGCB consisted of micrometric GCB particles with 55 m 2  g -1 surface area bearing some carbonyl and hydroxyl functionalities and the surface partially decorated by Fe 3 O 4 microparticles. The prepared mGCB was firstly tested as an adsorbent for the extraction from surface water of 50 pollutants, including estrogens, perfluoroalkyl compounds, UV filters, and quinolones. The material showed good affinity to many of the tested compounds, except carboxylates and glucoronates; however, some compounds were difficult to desorb. Ten UV filters belonging to the chemical classes of benzophenones and p-aminobenzoates were selected, and parameters were optimized for the extraction of these compounds from surface water before UHPLC-MS/MS determination. Then, the method was validated in terms of linearity, trueness, intra-laboratory precision, and detection and quantification limits. In summary, the method performance (trueness, expressed as analytical recovery, 85-114%; RSD 5-15%) appears suitable for the determination of the selected compounds at the level of 10-100 ng L -1 , with detection limits in the range of 1-5 ng L -1 . Finally, the new method was compared with a published one, based on conventional solid-phase extraction with GCB, showing similar performance in real sample analysis. Graphical Abstract Workflow of the analytical method based on magnetic solid-phase extraction followed by LC-MS/MS determination.

Computing the Free Energy Barriers for Less by Sampling with a Coarse Reference Potential while Retaining Accuracy of the Target Fine Model

PubMed Central

2015-01-01

Proposed in this contribution is a protocol for calculating fine-physics (e.g., ab initio QM/MM) free-energy surfaces at a high level of accuracy locally (e.g., only at reactants and at the transition state for computing the activation barrier) from targeted fine-physics sampling and extensive exploratory coarse-physics sampling. The full free-energy surface is still computed but at a lower level of accuracy from coarse-physics sampling. The method is analytically derived in terms of the umbrella sampling and the free-energy perturbation methods which are combined with the thermodynamic cycle and the targeted sampling strategy of the paradynamics approach. The algorithm starts by computing low-accuracy fine-physics free-energy surfaces from the coarse-physics sampling in order to identify the reaction path and to select regions for targeted sampling. Thus, the algorithm does not rely on the coarse-physics minimum free-energy reaction path. Next, segments of high-accuracy free-energy surface are computed locally at selected regions from the targeted fine-physics sampling and are positioned relative to the coarse-physics free-energy shifts. The positioning is done by averaging the free-energy perturbations computed with multistep linear response approximation method. This method is analytically shown to provide results of the thermodynamic integration and the free-energy interpolation methods, while being extremely simple in implementation. Incorporating the metadynamics sampling to the algorithm is also briefly outlined. The application is demonstrated by calculating the B3LYP//6-31G*/MM free-energy barrier for an enzymatic reaction using a semiempirical PM6/MM reference potential. These modifications allow computing the activation free energies at a significantly reduced computational cost but at the same level of accuracy compared to computing full potential of mean force. PMID:25136268

Poly-Gaussian model of randomly rough surface in rarefied gas flow

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

Aksenova, Olga A.; Khalidov, Iskander A.

2014-12-09

Surface roughness is simulated by the model of non-Gaussian random process. Our results for the scattering of rarefied gas atoms from a rough surface using modified approach to the DSMC calculation of rarefied gas flow near a rough surface are developed and generalized applying the poly-Gaussian model representing probability density as the mixture of Gaussian densities. The transformation of the scattering function due to the roughness is characterized by the roughness operator. Simulating rough surface of the walls by the poly-Gaussian random field expressed as integrated Wiener process, we derive a representation of the roughness operator that can be appliedmore » in numerical DSMC methods as well as in analytical investigations.« less

Simultaneous quantification of the boar-taint compounds skatole and androstenone by surface-enhanced Raman scattering (SERS) and multivariate data analysis.

PubMed

Sørensen, Klavs M; Westley, Chloe; Goodacre, Royston; Engelsen, Søren Balling

2015-10-01

This study investigates the feasibility of using surface-enhanced Raman scattering (SERS) for the quantification of absolute levels of the boar-taint compounds skatole and androstenone in porcine fat. By investigation of different types of nanoparticles, pH and aggregating agents, an optimized environment that promotes SERS of the analytes was developed and tested with different multivariate spectral pre-processing techniques, and this was combined with variable selection on a series of analytical standards. The resulting method exhibited prediction errors (root mean square error of cross validation, RMSECV) of 2.4 × 10(-6) M skatole and 1.2 × 10(-7) M androstenone, with a limit of detection corresponding to approximately 2.1 × 10(-11) M for skatole and approximately 1.8 × 10(-10) for androstenone. The method was subsequently tested on porcine fat extract, leading to prediction errors (RMSECV) of 0.17 μg/g for skatole and 1.5 μg/g for androstenone. It is clear that this optimized SERS method, when combined with multivariate analysis, shows great potential for optimization into an on-line application, which will be the first of its kind, and opens up possibilities for simultaneous detection of other meat-quality metabolites or pathogen markers. Graphical abstract Artistic rendering of a laser-illuminated gold colloid sphere with skatole and androstenone adsorbed on the surface.

Analytical Quality by Design in pharmaceutical quality assurance: Development of a capillary electrophoresis method for the analysis of zolmitriptan and its impurities.

PubMed

Orlandini, Serena; Pasquini, Benedetta; Caprini, Claudia; Del Bubba, Massimo; Pinzauti, Sergio; Furlanetto, Sandra

2015-11-01

A fast and selective CE method for the determination of zolmitriptan (ZOL) and its five potential impurities has been developed applying the analytical Quality by Design principles. Voltage, temperature, buffer concentration, and pH were investigated as critical process parameters that can influence the critical quality attributes, represented by critical resolution values between peak pairs, analysis time, and peak efficiency of ZOL-dimer. A symmetric screening matrix was employed for investigating the knowledge space, and a Box-Behnken design was used to evaluate the main, interaction, and quadratic effects of the critical process parameters on the critical quality attributes. Contour plots were drawn highlighting important interactions between buffer concentration and pH, and the gained information was merged into the sweet spot plots. Design space (DS) was established by the combined use of response surface methodology and Monte Carlo simulations, introducing a probability concept and thus allowing the quality of the analytical performances to be assured in a defined domain. The working conditions (with the interval defining the DS) were as follows: BGE, 138 mM (115-150 mM) phosphate buffer pH 2.74 (2.54-2.94); temperature, 25°C (24-25°C); voltage, 30 kV. A control strategy was planned based on method robustness and system suitability criteria. The main advantages of applying the Quality by Design concept consisted of a great increase of knowledge of the analytical system, obtained throughout multivariate techniques, and of the achievement of analytical assurance of quality, derived by probability-based definition of DS. The developed method was finally validated and applied to the analysis of ZOL tablets. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Mathematical Modeling of Torsional Surface Wave Propagation in a Non-Homogeneous Transverse Isotropic Elastic Solid Semi-Infinite Medium Under a Layer

NASA Astrophysics Data System (ADS)

Sethi, M.; Sharma, A.; Vasishth, A.

2017-05-01

The present paper deals with the mathematical modeling of the propagation of torsional surface waves in a non-homogeneous transverse isotropic elastic half-space under a rigid layer. Both rigidities and density of the half-space are assumed to vary inversely linearly with depth. Separation of variable method has been used to get the analytical solutions for the dispersion equation of the torsional surface waves. Also, the effects of nonhomogeneities on the phase velocity of torsional surface waves have been shown graphically. Also, dispersion equations have been derived for some particular cases, which are in complete agreement with some classical results.

A LITERATURE REVIEW OF WIPE SAMPLING METHODS ...

EPA Pesticide Factsheets

Wipe sampling is an important technique for the estimation of contaminant deposition in buildings, homes, or outdoor surfaces as a source of possible human exposure. Numerousmethods of wipe sampling exist, and each method has its own specification for the type of wipe, wetting solvent, and determinative step to be used, depending upon the contaminant of concern. The objective of this report is to concisely summarize the findings of a literature review that was conducted to identify the state-of-the-art wipe sampling techniques for a target list of compounds. This report describes the methods used to perform the literature review; a brief review of wipe sampling techniques in general; an analysis of physical and chemical properties of each target analyte; an analysis of wipe sampling techniques for the target analyte list; and asummary of the wipe sampling techniques for the target analyte list, including existing data gaps. In general, no overwhelming consensus can be drawn from the current literature on how to collect a wipe sample for the chemical warfare agents, organophosphate pesticides, and other toxic industrial chemicals of interest to this study. Different methods, media, and wetting solvents have been recommended and used by various groups and different studies. For many of the compounds of interest, no specific wipe sampling methodology has been established for their collection. Before a wipe sampling method (or methods) can be established for the co

Study of zeolite influence on analytical characteristics of urea biosensor based on ion-selective field-effect transistors

PubMed Central

2014-01-01

A possibility of the creation of potentiometric biosensor by adsorption of enzyme urease on zeolite was investigated. Several variants of zeolites (nano beta, calcinated nano beta, silicalite, and nano L) were chosen for experiments. The surface of pH-sensitive field-effect transistors was modified with particles of zeolites, and then the enzyme was adsorbed. As a control, we used the method of enzyme immobilization in glutaraldehyde vapour (without zeolites). It was shown that all used zeolites can serve as adsorbents (with different effectiveness). The biosensors obtained by urease adsorption on zeolites were characterized by good analytical parameters (signal reproducibility, linear range, detection limit and the minimal drift factor of a baseline). In this work, it was shown that modification of the surface of pH-sensitive field-effect transistors with zeolites can improve some characteristics of biosensors. PMID:24636423

Paper-based microfluidic approach for surface-enhanced raman spectroscopy and highly reproducible detection of proteins beyond picomolar concentration.

PubMed

Saha, Arindam; Jana, Nikhil R

2015-01-14

Although microfluidic approach is widely used in various point of care diagnostics, its implementation in surface enhanced Raman spectroscopy (SERS)-based detection is challenging. This is because SERS signal depends on plasmonic nanoparticle aggregation induced generation of stable electromagnetic hot spots and in currently available microfluidic platform this condition is difficult to adapt. Here we show that SERS can be adapted using simple paper based microfluidic system where both the plasmonic nanomaterials and analyte are used in mobile phase. This approach allows analyte induced controlled particle aggregation and electromagnetic hot spot generation inside the microfluidic channel with the resultant SERS signal, which is highly reproducible and sensitive. This approach has been used for reproducible detection of protein in the pico to femtomolar concentration. Presented approach is simple, rapid, and cost-effective, and requires low sample volume. Method can be extended for SERS-based detection of other biomolecules.

XPS Protocol for the Characterization of Pristine and Functionalized Single Wall Carbon Nanotubes

NASA Technical Reports Server (NTRS)

Sosa, E. D.; Allada, R.; Huffman, C. B.; Arepalli, S.

2009-01-01

Recent interest in developing new applications for carbon nanotubes (CNT) has fueled the need to use accurate macroscopic and nanoscopic techniques to characterize and understand their chemistry. X-ray photoelectron spectroscopy (XPS) has proved to be a useful analytical tool for nanoscale surface characterization of materials including carbon nanotubes. Recent nanotechnology research at NASA Johnson Space Center (NASA-JSC) helped to establish a characterization protocol for quality assessment for single wall carbon nanotubes (SWCNTs). Here, a review of some of the major factors of the XPS technique that can influence the quality of analytical data, suggestions for methods to maximize the quality of data obtained by XPS, and the development of a protocol for XPS characterization as a complementary technique for analyzing the purity and surface characteristics of SWCNTs is presented. The XPS protocol is then applied to a number of experiments including impurity analysis and the study of chemical modifications for SWCNTs.

Simultaneous determination of PPCPs, EDCs, and artificial sweeteners in environmental water samples using a single-step SPE coupled with HPLC-MS/MS and isotope dilution.

PubMed

Tran, Ngoc Han; Hu, Jiangyong; Ong, Say Leong

2013-09-15

A high-throughput method for the simultaneous determination of 24 pharmaceuticals and personal care products (PPCPs), endocrine disrupting chemicals (EDCs) and artificial sweeteners (ASs) was developed. The method was based on a single-step solid phase extraction (SPE) coupled with high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) and isotope dilution. In this study, a single-step SPE procedure was optimized for simultaneous extraction of all target analytes. Good recoveries (≥ 70%) were observed for all target analytes when extraction was performed using Chromabond(®) HR-X (500 mg, 6 mL) cartridges under acidic condition (pH 2). HPLC-MS/MS parameters were optimized for the simultaneous analysis of 24 PPCPs, EDCs and ASs in a single injection. Quantification was performed by using 13 isotopically labeled internal standards (ILIS), which allows correcting efficiently the loss of the analytes during SPE procedure, matrix effects during HPLC-MS/MS and fluctuation in MS/MS signal intensity due to instrument. Method quantification limit (MQL) for most of the target analytes was below 10 ng/L in all water samples. The method was successfully applied for the simultaneous determination of PPCPs, EDCs and ASs in raw wastewater, surface water and groundwater samples collected in a local catchment area in Singapore. In conclusion, the developed method provided a valuable tool for investigating the occurrence, behavior, transport, and the fate of PPCPs, EDCs and ASs in the aquatic environment. Copyright © 2013 Elsevier B.V. All rights reserved.

Primary particle diameter differentiation and bimodality identification by five analytical methods using gold nanoparticle size distributions synthesized by pulsed laser ablation in liquids

NASA Astrophysics Data System (ADS)

Letzel, Alexander; Gökce, Bilal; Menzel, Andreas; Plech, Anton; Barcikowski, Stephan

2018-03-01

For a known material, the size distribution of a nanoparticle colloid is a crucial parameter that defines its properties. However, measured size distributions are not easy to interpret as one has to consider weighting (e.g. by light absorption, scattering intensity, volume, surface, number) and the way size information was gained. The radius of a suspended nanoparticle can be given as e.g. sphere equivalent, hydrodynamic, Feret or radius of gyration. In this study, gold nanoparticles in water are synthesized by pulsed-laser ablation (LAL) and fragmentation (LFL) in liquids and characterized by various techniques (scanning transmission electron microscopy (STEM), small-angle X-ray scattering (SAXS), analytical disc centrifugation (ADC), dynamic light scattering (DLS) and UV-vis spectroscopy with Mie-Gans Theory) to study the comparability of different analytical techniques and determine the method that is preferable for a given task related to laser-generated nanoparticles. In particular, laser-generated colloids are known to be bimodal and/or polydisperse, but bimodality is sometimes not analytically resolved in literature. In addition, frequently reported small size shifts of the primary particle mode around 10 nm needs evaluation of its statistical significance related to the analytical method. Closely related to earlier studies on SAXS, different colloids in defined proportions are mixed and their size as a function of the nominal mixing ratio is analyzed. It is found that the derived particle size is independent of the nominal mixing ratio if the colloid size fractions do not overlap considerably. Conversely, the obtained size for colloids with overlapping size fractions strongly depends on the nominal mixing ratio since most methods cannot distinguish between such fractions. Overall, SAXS and ADC are very accurate methods for particle size analysis. Further, the ability of different methods to determine the nominal mixing ratio of sizes fractions is studied experimentally.

Study on formation of step bunching on 6H-SiC (0001) surface by kinetic Monte Carlo method

NASA Astrophysics Data System (ADS)

Li, Yuan; Chen, Xuejiang; Su, Juan

2016-05-01

The formation and evolution of step bunching during step-flow growth of 6H-SiC (0001) surfaces were studied by three-dimensional kinetic Monte Carlo (KMC) method and compared with the analytic model based on the theory of Burton-Cabera-Frank (BCF). In the KMC model the crystal lattice was represented by a structured mesh which fixed the position of atoms and interatomic bonding. The events considered in the model were adatoms adsorption and diffusion on the terrace, and adatoms attachment, detachment and interlayer transport at the step edges. In addition, effects of Ehrlich-Schwoebel (ES) barriers at downward step edges and incorporation barriers at upwards step edges were also considered. In order to obtain more elaborate information for the behavior of atoms in the crystal surface, silicon and carbon atoms were treated as the minimal diffusing species. KMC simulation results showed that multiple-height steps were formed on the vicinal surface oriented toward [ 1 1 bar 00 ] or [ 11 2 bar 0 ] directions. And then the formation mechanism of the step bunching was analyzed. Finally, to further analyze the formation processes of step bunching, a one-dimensional BCF analytic model with ES and incorporation barriers was used, and then it was solved numerically. In the BCF model, the periodic boundary conditions (PBC) were applied, and the parameters were corresponded to those used in the KMC model. The evolution character of step bunching was consistent with the results obtained by KMC simulation.

Hierarchical zwitterionic modification of a SERS substrate enables real-time drug monitoring in blood plasma

PubMed Central

Sun, Fang; Hung, Hsiang-Chieh; Sinclair, Andrew; Zhang, Peng; Bai, Tao; Galvan, Daniel David; Jain, Priyesh; Li, Bowen; Jiang, Shaoyi; Yu, Qiuming

2016-01-01

Surface-enhanced Raman spectroscopy (SERS) is an ultrasensitive analytical technique with molecular specificity, making it an ideal candidate for therapeutic drug monitoring (TDM). However, in critical diagnostic media including blood, nonspecific protein adsorption coupled with weak surface affinities and small Raman activities of many analytes hinder the TDM application of SERS. Here we report a hierarchical surface modification strategy, first by coating a gold surface with a self-assembled monolayer (SAM) designed to attract or probe for analytes and then by grafting a non-fouling zwitterionic polymer brush layer to effectively repel protein fouling. We demonstrate how this modification can enable TDM applications by quantitatively and dynamically measuring the concentrations of several analytes—including an anticancer drug (doxorubicin), several TDM-requiring antidepressant and anti-seizure drugs, fructose and blood pH—in undiluted plasma. This hierarchical surface chemistry is widely applicable to many analytes and provides a generalized platform for SERS-based biosensing in complex real-world media. PMID:27834380

Residue determination and levels of glyphosate in surface waters, sediments and soils associated with oil palm plantation in Tasik Chini, Pahang, Malaysia

NASA Astrophysics Data System (ADS)

Mardiana-Jansar, K.; Ismail, B. S.

2014-09-01

Levels of glyphosate and its main metabolite were determined in surface water, soil and sediment samples from an oil palm plantation area located at Tasik Chini, Pahang, Malaysia. The optimization analytical method has been developed for the determination of glyphosate herbicide and its metabolite amino-methyl-phosphonic acid (AMPA) in surface waters to a level of 0.1μg/L, while in sediments and soils to a level of 0.5μg/g with a good linearity in the calibration range of 1-100μg/L. The procedure involves a pre-columnderivatization step with 9-fluorenyl-methyl-chloroformate (FMOC-Cl) yielding highly fluorescent derivatives of the analytes which can be determined by HPLC with fluorescence detection. In the field, levels of glyphosate in surface waters ranges from not detected to 1.0mg/L, while in soils and sediments were from not detected to 6.0mg/kg. For AMPA, the residues in surface waters were between not detected to 2.0mg/L, while in soil and sediment samples were from not detected to 5mg/kg. This variation of glyphosate and AMPA levels depended directly on time of pesticide application and the season.

Sensitive molecular diagnostics using surface-enhanced resonance Raman scattering (SERRS)

NASA Astrophysics Data System (ADS)

Faulds, Karen; Graham, Duncan; McKenzie, Fiona; MacRae, Douglas; Ricketts, Alastair; Dougan, Jennifer

2009-02-01

Surface enhanced resonance Raman scattering (SERRS) is an analytical technique with several advantages over competitive techniques in terms of improved sensitivity and multiplexing. We have made great progress in the development of SERRS as a quantitative analytical method, in particular for the detection of DNA. SERRS is an extremely sensitive and selective technique which when applied to the detection of labelled DNA sequences allows detection limits to be obtained which rival, and in most cases, are better than fluorescence. Here the conditions are explored which will enable the successful detection of DNA using SERRS. The enhancing surface which is used is crucial and in this case suspensions of nanoparticles were used as they allow quantitative behaviour to be achieved and allow analogous systems to current fluorescence based systems to be made. The aggregation conditions required to obtain SERRS of DNA are crucial and herein we describe the use of spermine as an aggregating agent. The nature of the label which is used, be it fluorescent, positively or negatively charged also effects the SERRS response and these conditions are again explored here. We have clearly demonstrated the ability to identify the components of a mixture of 5 analytes in solution by using two different excitation wavelengths and also of a 6-plex using data analysis techniques. These conditions will allow the use of SERRS for the detection of target DNA in a meaningful diagnostic assay.

Equivalent complex conductivities representing the effects of T-tubules and folded surface membranes on the electrical admittance and impedance of skeletal muscles measured by external-electrode method

NASA Astrophysics Data System (ADS)

Sekine, Katsuhisa

2017-12-01

In order to represent the effects of T-tubules and folded surface membranes on the electrical admittance and impedance of skeletal muscles measured by the external-electrode method, analytical relations for the equivalent complex conductivities of hypothetical smooth surface membranes were derived. In the relations, the effects of each tubule were represented by the admittance of a straight cable. The effects of the folding of a surface membrane were represented by the increased area of surface membranes. The equivalent complex conductivities were represented as summation of these effects, and the effects of the T-tubules were different between the transversal and longitudinal directions. The validity of the equivalent complex conductivities was supported by the results of finite-difference method (FDM) calculations made using three-dimensional models in which T-tubules and folded surface membranes were represented explicitly. FDM calculations using the equivalent complex conductivities suggested that the electrically inhomogeneous structure due to the existence of muscle cells with T-tubules was sufficient for explaining the experimental results previously obtained using the external-electrode method. Results of FDM calculations in which the structural changes caused by muscle contractions were taken into account were consistent with the reported experimental results.

Metrological approach to quantitative analysis of clinical samples by LA-ICP-MS: A critical review of recent studies.

PubMed

Sajnóg, Adam; Hanć, Anetta; Barałkiewicz, Danuta

2018-05-15

Analysis of clinical specimens by imaging techniques allows to determine the content and distribution of trace elements on the surface of the examined sample. In order to obtain reliable results, the developed procedure should be based not only on the properly prepared sample and performed calibration. It is also necessary to carry out all phases of the procedure in accordance with the principles of chemical metrology whose main pillars are the use of validated analytical methods, establishing the traceability of the measurement results and the estimation of the uncertainty. This review paper discusses aspects related to sampling, preparation and analysis of clinical samples by laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) with emphasis on metrological aspects, i.e. selected validation parameters of the analytical method, the traceability of the measurement result and the uncertainty of the result. This work promotes the introduction of metrology principles for chemical measurement with emphasis to the LA-ICP-MS which is the comparative method that requires studious approach to the development of the analytical procedure in order to acquire reliable quantitative results. Copyright © 2018 Elsevier B.V. All rights reserved.

Reusable biocompatible interface for immobilization of materials on a solid support

DOEpatents

Salamon, Zdzislaw; Schmidt, Richard A.; Tollin, Gordon; Macleod, H. Angus

1996-01-01

A method for the formation of a biocompatible film composed of a self-assembled bilayer membrane deposited on a planar surface. This bilayer membrane is capable of immobilizing materials to be analyzed in an environment very similar to their native state. Materials so immobilized may be subject to any of a number of analytical techniques.

Possibilities of application of the swirling flows in cooling systems of laser mirrors

NASA Astrophysics Data System (ADS)

Shanin, Yu; Chernykh, A.

2018-03-01

The paper presents analytical investigations into advanced cooling systems of the laser mirrors with heat exchange intensification by methods of ordered vortex impact on a coolant flow structure. Advantages and effectiveness of the proposed cooling systems have been estimated to reduction displacement of an optical mirror surface due to a flexure.

Investigation of the persistence of nerve agent degradation analytes on surfaces through wipe sampling and detection with ultrahigh performance liquid chromatography-tandem mass spectrometry.

PubMed

Willison, Stuart A

2015-01-20

The persistence of chemical warfare nerve agent degradation analytes on surfaces is important, from indicating the presence of nerve agent on a surface to guiding environmental restoration of a site after a release. Persistence was investigated for several chemical warfare nerve agent degradation analytes on indoor surfaces and presents an approach for wipe sampling of surfaces, followed by wipe extraction and liquid chromatography-tandem mass spectrometry detection. Commercially available wipe materials were investigated to determine optimal wipe recoveries. Tested surfaces included porous/permeable (vinyl tile, painted drywall, and wood) and largely nonporous/impermeable (laminate, galvanized steel, and glass) surfaces. Wipe extracts were analyzed by ultrahigh performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). UPLC provides a separation of targeted degradation analytes in addition to being nearly four times faster than high-performance liquid chromatography, allowing for greater throughput after a large-scale contamination incident and subsequent remediation events. Percent recoveries from nonporous/impermeable surfaces were 60-103% for isopropyl methylphosphonate (IMPA), GB degradate; 61-91% for ethyl methylphosphonate (EMPA), VX degradate; and 60-98% for pinacolyl methylphosphonate (PMPA), GD degradate. Recovery efficiencies for methyl phosphonate (MPA), nerve agent degradate, and ethylhydrogen dimethylphosphonate (EHDMAP), GA degradate, were lower, perhaps due to matrix effects. Diisopropyl methylphosphonate, GB impurity, was not recovered from surfaces. The resulting detection limits for wipe extracts were 0.065 ng/cm(2) for IMPA, 0.079 ng/cm(2) for MPA, 0.040 ng/cm(2) for EMPA, 0.078 ng/cm(2) for EHDMAP, and 0.013 ng/cm(2) for PMPA. The data indicate that laboratories may hold wipe samples for up to 30 days prior to analysis. Target analytes were observed to persist on surfaces for at least 6 weeks.

Control of the Intrinsic Sensor Response to Volatile Organic Compounds with Fringing Electric Fields.

PubMed

Henning, Alex; Swaminathan, Nandhini; Vaknin, Yonathan; Jurca, Titel; Shimanovich, Klimentiy; Shalev, Gil; Rosenwaks, Yossi

2018-01-26

The ability to control surface-analyte interaction allows tailoring chemical sensor sensitivity to specific target molecules. By adjusting the bias of the shallow p-n junctions in the electrostatically formed nanowire (EFN) chemical sensor, a multiple gate transistor with an exposed top dielectric layer allows tuning of the fringing electric field strength (from 0.5 × 10 7 to 2.5 × 10 7 V/m) above the EFN surface. Herein, we report that the magnitude and distribution of this fringing electric field correlate with the intrinsic sensor response to volatile organic compounds. The local variations of the surface electric field influence the analyte-surface interaction affecting the work function of the sensor surface, assessed by Kelvin probe force microscopy on the nanometer scale. We show that the sensitivity to fixed vapor analyte concentrations can be nullified and even reversed by varying the fringing field strength, and demonstrate selectivity between ethanol and n-butylamine at room temperature using a single transistor without any extrinsic chemical modification of the exposed SiO 2 surface. The results imply an electric-field-controlled analyte reaction with a dielectric surface extremely compelling for sensitivity and selectivity enhancement in chemical sensors.

A topological study of gravity free-surface waves generated by bluff bodies using the method of steepest descents

PubMed Central

2016-01-01

The standard analytical approach for studying steady gravity free-surface waves generated by a moving body often relies upon a linearization of the physical geometry, where the body is considered asymptotically small in one or several of its dimensions. In this paper, a methodology that avoids any such geometrical simplification is presented for the case of steady-state flows at low speeds. The approach is made possible through a reduction of the water-wave equations to a complex-valued integral equation that can be studied using the method of steepest descents. The main result is a theory that establishes a correspondence between different bluff-bodied free-surface flow configurations, with the topology of the Riemann surface formed by the steepest descent paths. Then, when a geometrical feature of the body is modified, a corresponding change to the Riemann surface is observed, and the resultant effects to the water waves can be derived. This visual procedure is demonstrated for the case of two-dimensional free-surface flow past a surface-piercing ship and over an angled step in a channel. PMID:27493559

Characterization of cap-shaped silver particles for surface-enhanced fluorescence effects.

PubMed

Yamaguchi, Tetsuji; Kaya, Takatoshi; Takei, Hiroyuki

2007-05-15

Surface-enhanced fluorescence has potentially many desirable properties as an analytical method for medical diagnostics, but the effect observed so far is rather modest and only in conjunction with fluorophores with low quantum yields. Coupled with the fact that preparation of suitable surfaces at low costs has been difficult, this has limited its utilities. Here we report a novel method for forming uniform and reproducible surfaces with respectable enhancement ratios even for high-quantum-yield fluorophores. Formation of dense surface-adsorbed latex spheres on a flat surface via partial aggregation, followed by evaporation of silver, results in a film consisting of cap-shaped silver particles at high densities. Binding of fluorescence biomolecules, either through physisorption or antigen-antibody reaction, was performed, and enhancements close to 50 have been observed with fluorophores such as R-phycoerythrin and Alexa 546-labeled, bovine serum albumin, both of which have quantum yields around 0.8. We attribute this to the unique shape of the silver particle and the presence of abundant gaps among adjacent particles at high densities. The effectiveness of the new surface is also demonstrated with IL-6 sandwich assays.

DNA conformation on surfaces measured by fluorescence self-interference.

PubMed

Moiseev, Lev; Unlü, M Selim; Swan, Anna K; Goldberg, Bennett B; Cantor, Charles R

2006-02-21

The conformation of DNA molecules tethered to the surface of a microarray may significantly affect the efficiency of hybridization. Although a number of methods have been applied to determine the structure of the DNA layer, they are not very sensitive to variations in the shape of DNA molecules. Here we describe the application of an interferometric technique called spectral self-interference fluorescence microscopy to the precise measurement of the average location of a fluorescent label in a DNA layer relative to the surface and thus determine specific information on the conformation of the surface-bound DNA molecules. Using spectral self-interference fluorescence microscopy, we have estimated the shape of coiled single-stranded DNA, the average tilt of double-stranded DNA of different lengths, and the amount of hybridization. The data provide important proofs of concept for the capabilities of novel optical surface analytical methods of the molecular disposition of DNA on surfaces. The determination of DNA conformations on surfaces and hybridization behavior provide information required to move DNA interfacial applications forward and thus impact emerging clinical and biotechnological fields.

Analysis of environmental contamination resulting from catastrophic incidents: part 2. Building laboratory capability by selecting and developing analytical methodologies.

PubMed

Magnuson, Matthew; Campisano, Romy; Griggs, John; Fitz-James, Schatzi; Hall, Kathy; Mapp, Latisha; Mullins, Marissa; Nichols, Tonya; Shah, Sanjiv; Silvestri, Erin; Smith, Terry; Willison, Stuart; Ernst, Hiba

2014-11-01

Catastrophic incidents can generate a large number of samples of analytically diverse types, including forensic, clinical, environmental, food, and others. Environmental samples include water, wastewater, soil, air, urban building and infrastructure materials, and surface residue. Such samples may arise not only from contamination from the incident but also from the multitude of activities surrounding the response to the incident, including decontamination. This document summarizes a range of activities to help build laboratory capability in preparation for sample analysis following a catastrophic incident, including selection and development of fit-for-purpose analytical methods for chemical, biological, and radiological contaminants. Fit-for-purpose methods are those which have been selected to meet project specific data quality objectives. For example, methods could be fit for screening contamination in the early phases of investigation of contamination incidents because they are rapid and easily implemented, but those same methods may not be fit for the purpose of remediating the environment to acceptable levels when a more sensitive method is required. While the exact data quality objectives defining fitness-for-purpose can vary with each incident, a governing principle of the method selection and development process for environmental remediation and recovery is based on achieving high throughput while maintaining high quality analytical results. This paper illustrates the result of applying this principle, in the form of a compendium of analytical methods for contaminants of interest. The compendium is based on experience with actual incidents, where appropriate and available. This paper also discusses efforts aimed at adaptation of existing methods to increase fitness-for-purpose and development of innovative methods when necessary. The contaminants of interest are primarily those potentially released through catastrophes resulting from malicious activity. However, the same techniques discussed could also have application to catastrophes resulting from other incidents, such as natural disasters or industrial accidents. Further, the high sample throughput enabled by the techniques discussed could be employed for conventional environmental studies and compliance monitoring, potentially decreasing costs and/or increasing the quantity of data available to decision-makers. Published by Elsevier Ltd.

An intercomparison of three methods for the large-scale isolation of oceanic dissolved organic matter

USGS Publications Warehouse

Green, Nelson W.; Perdue, E. Michael; Aiken, George R.; Butler, Kenna D.; Chen, Hongmei; Dittmar, Thorsten; Niggemann, Jutta; Stubbins, Aron

2014-01-01

Dissolved organic matter (DOM) was isolated from large volumes of deep (674 m) and surface (21 m) ocean water via reverse osmosis/electrodialysis (RO/ED) and two solid-phase extraction (SPE) methods (XAD-8/4 and PPL) at the Natural Energy Laboratory of Hawaii Authority (NELHA). By applying the three methods to common water samples, the efficiencies of XAD, PPL and RO/ED DOM isolation were compared. XAD recovered 42% of dissolved organic carbon (DOC) from deep water (25% with XAD-8; 17% with XAD-4) and 30% from surface water (16% with XAD-8; 14% with XAD-4). PPL recovered 61 ± 3% of DOC from deep water and 61% from surface water. RO/ED recovered 82 ± 3% of DOC from deep water, 14 ± 3% of which was recovered in a sodium hydroxide rinse, and 75 ± 5% of DOC from surface water, with 12 ± 2% in the sodium hydroxide rinse. The highest recoveries of all were achieved by the sequential isolation of DOC, first with PPL and then via RO/ED. This combined technique recovered 98% of DOC from a deep water sample and 101% of DOC from a surface water sample. In total, 1.9, 10.3 and 1.6 g-C of DOC were collected via XAD, PPL and RO/ED, respectively. Rates of DOC recovery using the XAD, PPL and RO/ED methods were 10, 33 and 10 mg-C h− 1, respectively. Based upon C/N ratios, XAD isolates were heavily C-enriched compared with water column DOM, whereas RO/ED and PPL ➔ RO/ED isolate C/N values were most representative of the original DOM. All techniques are suitable for the isolation of large amounts of DOM with purities suitable for most advanced analytical techniques. Coupling PPL and RO/ED techniques may provide substantial progress in the search for a method to quantitatively isolate oceanic DOC, bringing the entirety of the DOM pool within the marine chemist's analytical window.

Carbon nanotubes as adsorbent of solid-phase extraction and matrix for laser desorption/ionization mass spectrometry.

PubMed

Pan, Chensong; Xu, Songyun; Zou, Hanfa; Guo, Zhong; Zhang, Yu; Guo, Baochuan

2005-02-01

A method with carbon nanotubes functioning both as the adsorbent of solid-phase extraction (SPE) and the matrix for matrix assisted laser desorption/ionization mass spectrometry (MALDI-MS) to analyze small molecules in solution has been developed. In this method, 10 microL suspensions of carbon nanotubes in 50% (vol/vol) methanol were added to the sample solution to extract analytes onto surface of carbon nanotubes because of their dramatic hydrophobicity. Carbon nanotubes in solution are deposited onto the bottom of tube with centrifugation. After removing the supernatant fluid, carbon nanotubes are suspended again with dispersant and pipetted directly onto the sample target of the MALDI-MS to perform a mass spectrometric analysis. It was demonstrated by analysis of a variety of small molecules that the resolution of peaks and the efficiency of desorption/ionization on the carbon nanotubes are better than those on the activated carbon. It is found that with the addition of glycerol and sucrose to the dispersant, the intensity, the ratio of signal to noise (S/N), and the resolution of peaks for analytes by mass spectrometry increased greatly. Compared with the previously reported method by depositing sample solution onto thin layer of carbon nanotubes, it is observed that the detection limit for analytes can be enhanced about 10 to 100 times due to solid-phase extraction of analytes in solution by carbon nanotubes. An acceptable result of simultaneously quantitative analysis of three analytes in solution has been achieved. The application in determining drugs spiked into urine has also been realized.

Methods of analysis by the U.S. Geological Survey National Water Quality Laboratory; determination of pesticides in water by Carbopak-B solid-phase extraction and high-preformance liquid chromatography

USGS Publications Warehouse

Werner, Stephen L.; Burkhardt, Mark R.; DeRusseau, Sabrina N.

1996-01-01

In accordance with the needs of the National Water-Quality Assessment Program (NAWQA), the U.S. Geological Survey has developed and implemented a graphitized carbon-based solid-phase extraction and high-performance liquid chromatographic analytical method. The method is used to determine 41 pesticides and pesticide metabolites that are not readily amenable to gas chromatography or other high-temperature analytical techniques. Pesticides are extracted from filtered environmental water samples using a 0.5-gram graphitized carbon-based solid-phase cartridge, eluted from the cartridge into two analytical fractions, and analyzed using high-performance liquid chromatography with photodiode-array detection. The upper concentration limit is 1.6 micrograms per liter (=B5g/L) for most compounds. Single-operator method detection limits in organic-free water samples ranged from 0.006 to 0.032 =B5g/L= Recoveries in organic-free water samples ranged from 37 to 88 percent. Recoveries in ground- and surface-water samples ranged from 29 to 94 percent. An optional on-site extraction procedure allows for samples to be collected and processed at remote sites where it is difficult to ship samples to the laboratory within the recommended pre-extraction holding time of 7 days.

Label-Free QCM Immunosensor for the Detection of Ochratoxin A

PubMed Central

Ertekin, Özlem; Laguna, Duygu Ercan; Özen, Fehime Şeyma; Öztürk, Zafer Ziya; Öztürk, Selma

2018-01-01

Ochratoxin A (OTA) is a potent mycotoxin that poses a risk in food and feed moieties and subject to worldwide regulation. Laboratory-based analytical methods are traditionally employed for reliable OTA quantification, but these methods cannot provide rapid and on-site analysis, where biosensors fill this gap. In this study a label-free quartz crystal microbalance (QCM)-based immunosensor for the detection of OTA, which is one of the most important small molecule contaminants, was developed by direct immobilization of OTA to amine-bearing sensor surfaces using 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide (EDC)/N-Hydroxysuccinimide (NHS) chemistry. The protein-free sensor surface enabled regeneration of sensor surface with 50 mM NaOH and 1% SDS up to 13 times without loss of performance, which would disrupt a protein-containing sensor surface. We developed a QCM immunosensor using the developed sensor surface with a 17.2–200 ng/mL detection range which can be used for on-site detection of feedstuffs. PMID:29641432

Label-Free QCM Immunosensor for the Detection of Ochratoxin A.

PubMed

Pirinçci, Şerife Şeyda; Ertekin, Özlem; Laguna, Duygu Ercan; Özen, Fehime Şeyma; Öztürk, Zafer Ziya; Öztürk, Selma

2018-04-11

Ochratoxin A (OTA) is a potent mycotoxin that poses a risk in food and feed moieties and subject to worldwide regulation. Laboratory-based analytical methods are traditionally employed for reliable OTA quantification, but these methods cannot provide rapid and on-site analysis, where biosensors fill this gap. In this study a label-free quartz crystal microbalance (QCM)-based immunosensor for the detection of OTA, which is one of the most important small molecule contaminants, was developed by direct immobilization of OTA to amine-bearing sensor surfaces using 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide (EDC)/N-Hydroxysuccinimide (NHS) chemistry. The protein-free sensor surface enabled regeneration of sensor surface with 50 mM NaOH and 1% SDS up to 13 times without loss of performance, which would disrupt a protein-containing sensor surface. We developed a QCM immunosensor using the developed sensor surface with a 17.2-200 ng/mL detection range which can be used for on-site detection of feedstuffs.

Current distribution in a three-dimensional IC analyzed by a perturbation method. Part 1: A simple steady state theory

NASA Technical Reports Server (NTRS)

Edmonds, Larry D.

1987-01-01

The steady state current distribution in a three dimensional integrated circuit is presented. A device physics approach, based on a perturbation method rather than an equivalent lumped circuit approach, is used. The perturbation method allows the various currents to be expressed in terms of elementary solutions which are solutions to very simple boundary value problems. A Simple Steady State Theory is the subtitle because the most obvious limitation of the present version of the analysis is that all depletion region boundary surfaces are treated as equipotential surfaces. This may be an adequate approximation in some applications but it is an obvious weakness in the theory when applied to latched states. Examples that illustrate the use of these analytical methods are not given because they will be presented in detail in the future.

Quantum mechanical/molecular mechanical/continuum style solvation model: Second order Møller-Plesset perturbation theory

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

Thellamurege, Nandun M.; Si, Dejun; Cui, Fengchao

A combined quantum mechanical/molecular mechanical/continuum (QM/MM/C) style second order Møller-Plesset perturbation theory (MP2) method that incorporates induced dipole polarizable force field and induced surface charge continuum solvation model is established. The Z-vector method is modified to include induced dipoles and induced surface charges to determine the MP2 response density matrix, which can be used to evaluate MP2 properties. In particular, analytic nuclear gradient is derived and implemented for this method. Using the Assisted Model Building with Energy Refinement induced dipole polarizable protein force field, the QM/MM/C style MP2 method is used to study the hydrogen bonding distances and strengths ofmore » the photoactive yellow protein chromopore in the wild type and the Glu46Gln mutant.« less

Sample processing approach for detection of ricin in surface samples.

PubMed

Kane, Staci; Shah, Sanjiv; Erler, Anne Marie; Alfaro, Teneile

2017-12-01

With several ricin contamination incidents reported over the past decade, rapid and accurate methods are needed for environmental sample analysis, especially after decontamination. A sample processing method was developed for common surface sampling devices to improve the limit of detection and avoid false negative/positive results for ricin analysis. Potential assay interferents from the sample matrix (bleach residue, sample material, wetting buffer), including reference dust, were tested using a Time-Resolved Fluorescence (TRF) immunoassay. Test results suggested that the sample matrix did not cause the elevated background fluorescence sometimes observed when analyzing post-bleach decontamination samples from ricin incidents. Furthermore, sample particulates (80mg/mL Arizona Test Dust) did not enhance background fluorescence or interfere with ricin detection by TRF. These results suggested that high background fluorescence in this immunoassay could be due to labeled antibody quality and/or quantity issues. Centrifugal ultrafiltration devices were evaluated for ricin concentration as a part of sample processing. Up to 30-fold concentration of ricin was observed by the devices, which serve to remove soluble interferents and could function as the front-end sample processing step to other ricin analytical methods. The procedure has the potential to be used with a broader range of environmental sample types and with other potential interferences and to be followed by other ricin analytical methods, although additional verification studies would be required. Published by Elsevier B.V.

Fourier decomposition of segmented magnets with radial magnetization in surface-mounted PM machines

NASA Astrophysics Data System (ADS)

Tiang, Tow Leong; Ishak, Dahaman; Lim, Chee Peng

2017-11-01

This paper presents a generic field model of radial magnetization (RM) pattern produced by multiple segmented magnets per rotor pole in surface-mounted permanent magnet (PM) machines. The magnetization vectors from either odd- or even-number of magnet blocks per pole are described. Fourier decomposition is first employed to derive the field model, and later integrated with the exact 2D analytical subdomain method to predict the magnetic field distributions and other motor global quantities. For the assessment purpose, a 12-slot/8-pole surface-mounted PM motor with two segmented magnets per pole is investigated by using the proposed field model. The electromagnetic performances of the PM machines are intensively predicted by the proposed magnet field model which include the magnetic field distributions, airgap flux density, phase back-EMF, cogging torque, and output torque during either open-circuit or on-load operating conditions. The analytical results are evaluated and compared with those obtained from both 2D and 3D finite element analyses (FEA) where an excellent agreement has been achieved.

An analytical design procedure for the determination of effective leading edge extensions on thick delta wings

NASA Technical Reports Server (NTRS)

Ghaffari, F.; Chaturvedi, S. K.

1984-01-01

An analytical design procedure for leading edge extensions (LEE) was developed for thick delta wings. This LEE device is designed to be mounted to a wing along the pseudo-stagnation stream surface associated with the attached flow design lift coefficient of greater than zero. The intended purpose of this device is to improve the aerodynamic performance of high subsonic and low supersonic aircraft at incidences above that of attached flow design lift coefficient, by using a vortex system emanating along the leading edges of the device. The low pressure associated with these vortices would act on the LEE upper surface and the forward facing area at the wing leading edges, providing an additional lift and effective leading edge thrust recovery. The first application of this technique was to a thick, round edged, twisted and cambered wing of approximately triangular planform having a sweep of 58 deg and aspect ratio of 2.30. The panel aerodynamics and vortex lattice method with suction analogy computer codes were employed to determine the pseudo-stagnation stream surface and an optimized LEE planform shape.

Determination of phenoxyacid herbicides and their phenolic metabolites in surface and drinking water.

PubMed

Marchese, Stefano; Perret, Daniela; Gentili, Alessandra; D'Ascenzo, Guiseppe; Faberi, Angelo

2002-01-01

An evaluation was made of the feasibility of using reversed-phase liquid chromatography/tandem mass spectrometry with an electrospray interface (LC/ESI-MS/MS) to measure traces of phenoxyacid herbicides and their metabolites in surface and drinking water samples. The procedure involved passing 0.5 L of river and drinking water samples through a 0.5 g graphitized carbon black (GCB) extraction cartridge. Recovery was higher than 85% irrespective of the aqueous matrix in which the analytes were dissolved. A conventional 4.6-mm i.d. reversed-phase LC C-18 column operating with a mobile phase flow rate of 1 mL/min was used to chromatograph the analytes. A flow of 200 microL/min of the column effluent was diverted to the ESI source. The limits of detection (signal-to-noise ratio = 3) of the method for the pesticides considered in drinking and surface water samples are less than 0.1 ng/L for phenoxyacid herbicides, and about 5-10 ng/L for their metabolites (2,4-dichlorophenol and 4-chloro-2-methylphenol). Copyright 2001 John Wiley & Sons, Ltd.

SUPRAMOLECULAR COMPOSITE MATERIALS FROM CELLULOSE, CHITOSAN AND CYCLODEXTRIN: FACILE PREPARATION AND THEIR SELECTIVE INCLUSION COMPLEX FORMATION WITH ENDOCRINE DISRUPTORS

PubMed Central

Duri, Simon; Tran, Chieu D.

2013-01-01

We have successfully developed a simple and one step method to prepare high performance supramolecular polysaccharide composites from cellulose (CEL), chitosan (CS) and (2,3,6-tri-O-acetyl)-α-, β- and γ-cyclodextrin (α-, β- and γ-TCD). In this method, [BMIm+Cl−], an ionic liquid (IL), was used as a solvent to dissolve and prepare the composites. Since majority (>88%) of the IL used was recovered for reuse, the method is recyclable. XRD, FT-IR, NIR and SEM were used to monitor the dissolution process and to confirm that the polysaccharides were regenerated without any chemical modifications. It was found that unique properties of each component including superior mechanical properties (from CEL), excellent adsorbent for pollutants and toxins (from CS) and size/structure selectivity through inclusion complex formation (from TCDs) remain intact in the composites. Specifically, results from kinetics and adsorption isotherms show that while CS-based composites can effectively adsorb the endocrine disruptors (polychlrophenols, bisphenol-A), its adsorption is independent on the size and structure of the analytes. Conversely, the adsorption by γ-TCD-based composites exhibits strong dependency on size and structure of the analytes. For example, while all three TCD-based composites (i.e., α-, β- and γ-TCD) can effectively adsorb 2-, 3- and 4-chlorophenol, only γ-TCD-based composite can adsorb analytes with bulky groups including 3,4-dichloro- and 2,4,5-trichlorophenol. Furthermore, equilibrium sorption capacities for the analytes with bulky groups by γ-TCD-based composite are much higher than those by CS-based composites. Together, these results indicate that γ-TCD-based composite with its relatively larger cavity size can readily form inclusion complexes with analytes with bulky groups, and through inclusion complex formation, it can strongly adsorb much more analytes and with size/structure selectivity compared to CS-based composites which can adsorb the analyte only by surface adsorption. PMID:23517477

Radiation Heat Transfer Between Diffuse-Gray Surfaces Using Higher Order Finite Elements

NASA Technical Reports Server (NTRS)

Gould, Dana C.

2000-01-01

This paper presents recent work on developing methods for analyzing radiation heat transfer between diffuse-gray surfaces using p-version finite elements. The work was motivated by a thermal analysis of a High Speed Civil Transport (HSCT) wing structure which showed the importance of radiation heat transfer throughout the structure. The analysis also showed that refining the finite element mesh to accurately capture the temperature distribution on the internal structure led to very large meshes with unacceptably long execution times. Traditional methods for calculating surface-to-surface radiation are based on assumptions that are not appropriate for p-version finite elements. Two methods for determining internal radiation heat transfer are developed for one and two-dimensional p-version finite elements. In the first method, higher-order elements are divided into a number of sub-elements. Traditional methods are used to determine radiation heat flux along each sub-element and then mapped back to the parent element. In the second method, the radiation heat transfer equations are numerically integrated over the higher-order element. Comparisons with analytical solutions show that the integration scheme is generally more accurate than the sub-element method. Comparison to results from traditional finite elements shows that significant reduction in the number of elements in the mesh is possible using higher-order (p-version) finite elements.

Design and Optimization of Nanomaterials for Sensing Applications

NASA Astrophysics Data System (ADS)

Sanderson, Robert Noboru

Nanomaterials, materials with one or more of their dimensions on the nanoscale, have emerged as an important field in the development of next-generation sensing systems. Their high surface-to-volume ratio makes them useful for sensing, but also makes them sensitive to processing defects and inherent material defects. To develop and optimize these systems, it is thus necessary to characterize these defects to understand their origin and how to work around them. Scanning probe microscopy (SPM) techniques like atomic force microscopy (AFM) and scanning tunneling microscopy (STM) are important characterization methods which can measure nanoscale topography and electronic structure. These methods are appealing in nanomaterial systems because they are non-damaging and provide local, high-resolution data, and so are capable of detecting nanoscale features such as single defect sites. There are difficulties, however, in the interpretation of SPM data. For instance, AFM-based methods are prone to experimental artifacts due to long-range interactions, such as capacitive crosstalk in Kelvin probe force microscopy (KPFM), and artifacts due to the finite size of the probe tip, such as incorrect surface tracking at steep topographical features. Mechanical characterization (via force spectroscopy) of nanomaterials with significant nanoscale variations, such as tethered lipid bilayer membranes (tLBMs), is also difficult since variations in the bulk system's mechanical behavior must be distinguished from local fluctuations. Additionally, interpretation of STM data is non-trivial due to local variations in electron density in addition to topographical variations. In this thesis we overcome some limitations of SPM methods by supplementing them with additional surface analytical methods as well as computational methods, and we characterize several nanomaterial systems. Current-carrying vapor-liquid-solid Si nanowires (useful for interdigitated-electrode-based sensors) are characterized using finite-element-method (FEM)-supplemented KPFM to retrieve useful information about processing defects, contact resistance, and the primary charge carriers. Next, a tLBM system's stiffness and the stiffness' dependence on tethering molecule concentration is measured using statistical analysis of thousands of AFM force spectra, demonstrating a biosensor-compatible system with a controllable bulk rigidity. Finally, we utilize surface analytical techniques to inform the development of a novel three-dimensional graphene system for sensing applications.

Lagrangian based methods for coherent structure detection

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

Allshouse, Michael R., E-mail: mallshouse@chaos.utexas.edu; Peacock, Thomas, E-mail: tomp@mit.edu

There has been a proliferation in the development of Lagrangian analytical methods for detecting coherent structures in fluid flow transport, yielding a variety of qualitatively different approaches. We present a review of four approaches and demonstrate the utility of these methods via their application to the same sample analytic model, the canonical double-gyre flow, highlighting the pros and cons of each approach. Two of the methods, the geometric and probabilistic approaches, are well established and require velocity field data over the time interval of interest to identify particularly important material lines and surfaces, and influential regions, respectively. The other twomore » approaches, implementing tools from cluster and braid theory, seek coherent structures based on limited trajectory data, attempting to partition the flow transport into distinct regions. All four of these approaches share the common trait that they are objective methods, meaning that their results do not depend on the frame of reference used. For each method, we also present a number of example applications ranging from blood flow and chemical reactions to ocean and atmospheric flows.« less

The Surface Density Distribution in the Solar Nebula

NASA Technical Reports Server (NTRS)

Davis, Sanford S.

2004-01-01

The commonly used minimum mass power law representation of the pre-solar nebula is reanalyzed using a new cumulative-mass-model. This model predicts a smoother surface density approximation compared with methods based on direct computation of surface density. The density is quantified using two independent analytical formulations. First, a best-fit transcendental function is applied directly to the basic planetary data. Next a solution to the time-dependent disk evolution equation is parametrically adapted to the solar nebula data. The latter model is shown to be a good approximation to the finite-size early Solar Nebula, and by extension to other extra solar protoplanetary disks.

X-Ray Fluorescence Determination of the Surface Density of Chromium Nanolayers

NASA Astrophysics Data System (ADS)

Mashin, N. I.; Chernjaeva, E. A.; Tumanova, A. N.; Ershov, A. A.

2014-01-01

An auxiliary system consisting of thin-film layers of chromium deposited on a polymer film substrate is used to construct calibration curves for the relative intensities of the K α lines of chromium on bulk substrates of different elements as functions of the chromium surface density in the reference samples. Correction coefficients are calculated to take into account the absorption of primary radiation from an x-ray tube and analytical lines of the constituent elements of the substrate. A method is developed for determining the surface density of thin films of chromium when test and calibration samples are deposited on substrates of different materials.

Native State Mass Spectrometry, Surface Plasmon Resonance, and X-ray Crystallography Correlate Strongly as a Fragment Screening Combination.

PubMed

Woods, Lucy A; Dolezal, Olan; Ren, Bin; Ryan, John H; Peat, Thomas S; Poulsen, Sally-Ann

2016-03-10

Fragment-based drug discovery (FBDD) is contingent on the development of analytical methods to identify weak protein-fragment noncovalent interactions. Herein we have combined an underutilized fragment screening method, native state mass spectrometry, together with two proven and popular fragment screening methods, surface plasmon resonance and X-ray crystallography, in a fragment screening campaign against human carbonic anhydrase II (CA II). In an initial fragment screen against a 720-member fragment library (the "CSIRO Fragment Library") seven CA II binding fragments, including a selection of nonclassical CA II binding chemotypes, were identified. A further 70 compounds that comprised the initial hit chemotypes were subsequently sourced from the full CSIRO compound collection and screened. The fragment results were extremely well correlated across the three methods. Our findings demonstrate that there is a tremendous opportunity to apply native state mass spectrometry as a complementary fragment screening method to accelerate drug discovery.

Numerical Modeling of Ablation Heat Transfer

NASA Technical Reports Server (NTRS)

Ewing, Mark E.; Laker, Travis S.; Walker, David T.

2013-01-01

A unique numerical method has been developed for solving one-dimensional ablation heat transfer problems. This paper provides a comprehensive description of the method, along with detailed derivations of the governing equations. This methodology supports solutions for traditional ablation modeling including such effects as heat transfer, material decomposition, pyrolysis gas permeation and heat exchange, and thermochemical surface erosion. The numerical scheme utilizes a control-volume approach with a variable grid to account for surface movement. This method directly supports implementation of nontraditional models such as material swelling and mechanical erosion, extending capabilities for modeling complex ablation phenomena. Verifications of the numerical implementation are provided using analytical solutions, code comparisons, and the method of manufactured solutions. These verifications are used to demonstrate solution accuracy and proper error convergence rates. A simple demonstration of a mechanical erosion (spallation) model is also provided to illustrate the unique capabilities of the method.

Analytical Characterisation of Nanoscale Zero-Valent Iron: A ...

EPA Pesticide Factsheets

Zero-valent iron nanoparticles (nZVI) have been widely tested as they are showing significant promise for environmental remediation. However, many recent studies have demonstrated that their mobility and reactivity in subsurface environments are significantly affected by their tendency to aggregate. Both the mobility and reactivity of nZVI mainly depends on properties such as particle size, surface chemistry and bulk composition. In order to ensure efficient remediation, it is crucial to accurately assess and understand the implications of these properties before deploying these materials into contaminated environments. Many analytical techniques are now available to determine these parameters and this paper provides a critical review of their usefulness and limitations for nZVI characterisation. These analytical techniques include microscopy and light scattering techniques for the determination of particle size, size distribution and aggregation state, and X-ray techniques for the characterisation of surface chemistry and bulk composition. Example characterisation data derived from commercial nZVI materials is used to further illustrate method strengths and limitations. Finally, some important challenges with respect to the characterisation of nZVI in groundwater samples are discussed. In recent years, manufactured nanoparticles (MNPs) have attracted increasing interest for their potential applications in the treatment of contaminated soil and water. In compar

Combined imaging and chemical sensing using a single optical imaging fiber.

PubMed

Bronk, K S; Michael, K L; Pantano, P; Walt, D R

1995-09-01

Despite many innovations and developments in the field of fiber-optic chemical sensors, optical fibers have not been employed to both view a sample and concurrently detect an analyte of interest. While chemical sensors employing a single optical fiber or a noncoherent fiberoptic bundle have been applied to a wide variety of analytical determinations, they cannot be used for imaging. Similarly, coherent imaging fibers have been employed only for their originally intended purpose, image transmission. We herein report a new technique for viewing a sample and measuring surface chemical concentrations that employs a coherent imaging fiber. The method is based on the deposition of a thin, analyte-sensitive polymer layer on the distal surface of a 350-microns-diameter imaging fiber. We present results from a pH sensor array and an acetylcholine biosensor array, each of which contains approximately 6000 optical sensors. The acetylcholine biosensor has a detection limit of 35 microM and a fast (< 1 s) response time. In association with an epifluorescence microscope and a charge-coupled device, these modified imaging fibers can display visual information of a remote sample with 4-microns spatial resolution, allowing for alternating acquisition of both chemical analysis and visual histology.

Online analysis of chlorine stable isotopes in chlorinated ethylenes: an inter-laboratory study

NASA Astrophysics Data System (ADS)

Bernstein, Anat; Shouakar-Stash, Orfan; Hunkeler, Daniel; Sakaguchi-Söder, Kaori; Laskov, Christine; Aravena, Ramon; Elsner, Martin

2010-05-01

In the last decade, compound-specific stable isotopes analysis of groundwater pollutants became an important tool to identify different sources of the same pollutant and for tracking natural attenuating processes in the sub-surface. It has been shown that trends in the isotopic composition of the target compounds can shed light on in-situ processes that are otherwise difficult to track. Analytical methods of carbon, nitrogen and hydrogen were established and are by now frequently used for a variety of organic pollutants. Yet, the motivation of introducing analytical methods for new isotopes is emerging. This motivation is further enhanced, as advantages of using two or more stable isotopes for gaining better insight on degradation pathways are well accepted. One important element which demands the development of appropriate analytical methods is chlorine, which is found in various groups of organic pollutants, among them the chlorinated ethylenes. Chlorinated ethylenes are considered as high priority environmental pollutants, and the development of suitable chlorine isotope methods for this group of pollutants is highly desired. Ideally, stable isotope techniques should have the capability to determine the isotopic composition of and individual target compound in a non-pure mixture, without the requirement of a laborious off-line treatment. Indeed, in the last years two different concepts for on-line chlorine isotope analysis methods were introduced, by using either a standard quadrapole GC/MS (Sakaguchi-Söder et al., 2007) or by using a GC/IRMS (Shouakar-Stash et al., 2006). We present a comparison of the performances of two concepts, carried out in five different laboratories: Waterloo (GC/IRMS), Neuchâtel (GC/MS), Darmstadt (GC/MS), Tübingen (GC/MS) and Munich (GC/IRMS). This comparison was performed on pure trichloroethylene and dichloroethylene products of different manufactures, as well as trichloroethylene and dichloroethylene samples that were exposed to biodegradation. This study sets standards for further application of these techniques to distinguish sources and track degradation processes in the sub-surface.

Experimental investigation of elastic mode control on a model of a transport aircraft

NASA Technical Reports Server (NTRS)

Abramovitz, M.; Heimbaugh, R. M.; Nomura, J. K.; Pearson, R. M.; Shirley, W. A.; Stringham, R. H.; Tescher, E. L.; Zoock, I. E.

1981-01-01

A 4.5 percent DC-10 derivative flexible model with active controls is fabricated, developed, and tested to investigate the ability to suppress flutter and reduce gust loads with active controlled surfaces. The model is analyzed and tested in both semispan and complete model configuration. Analytical methods are refined and control laws are developed and successfully tested on both versions of the model. A 15 to 25 percent increase in flutter speed due to the active system is demonstrated. The capability of an active control system to significantly reduce wing bending moments due to turbulence is demonstrated. Good correlation is obtained between test and analytical prediction.

Molecular recognition in gas sensing: Results from acoustic wave and in-situ FTIR measurements

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

Hierlemann, A.; Ricco, A.J.; Bodenhoefer, K.

Surface acoustic wave (SAW) measurements were combined with direct, in-situ molecular spectroscopy to understand the interactions of surface-confined sensing films with gas-phase analytes. This was accomplished by collecting Fourier-transform infrared external-reflectance spectra (FTIR-ERS) on operating SAW devices during dosing of their specifically coated surfaces with key analytes.

Evaluation of on-line concentration coupled to liquid chromatography tandem mass spectrometry for the quantification of neonicotinoids and fipronil in surface water and tap water.

PubMed

Montiel-León, Juan Manuel; Duy, Sung Vo; Munoz, Gabriel; Amyot, Marc; Sauvé, Sébastien

2018-04-01

A study was initiated to investigate a fast and reliable method for the determination of selected systemic insecticides in water matrixes and to evaluate potential sources of bias in their analysis. Acetamiprid, clothianidin, desnitro-imidacloprid, dinotefuran, fipronil, imidacloprid, nitenpyram, thiacloprid, and thiamethoxam were amenable to analysis via on-line sample enrichment hyphenated to ultra-high-performance liquid chromatography tandem mass spectrometry. The selection of on-line solid-phase extraction parameters was dictated by a multicriterion desirability approach. A 2-mL on-line injection volume with a 1500 μL min -1 loading flow rate met the objectives sought in terms of chromatographic requirements, extraction efficiency, sensitivity, and precision. A total analysis time of 8 min per sample was obtained with method limits of detection in the range of 0.1-5 ng L -1 for the scope of targeted analytes. Automation at the sample concentration step yielded intraday and interday precisions in the range of 1-23 and 2-26%, respectively. Factors that could affect the whole method accuracy were further evaluated in matrix-specific experiments. The impact of the initial filtration step on analyte recovery was evaluated in ultra-pure water, tap water, and surface water. Out of the nine membranes tested, glass fiber filters and polyester filters appeared as the most appropriate materials. Sample storage stability was also investigated across the three matrix types; the targeted analytes displayed suitable stability during 28 days at either 4 °C or - 20 °C, with little deviations (± 10%) with respect to the initial T 0 concentration. Method applicability was demonstrated in a range of tap water and surface water samples from the province of Québec, Canada. Results from the present survey indicated a predominance of thiamethoxam (< 0.5-10 and 3-61 ng L -1 in tap water and river water, respectively), clothianidin (< 0.5-6 and 2-88 ng L -1 in tap water and river water, respectively), and imidacloprid (< 0.1-1 and 0.8-38 ng L -1 in tap water and river water, respectively) among the targeted analytes. Graphical abstract ᅟ Development of solid-phase extraction coupled on-line to UHPLC-MS/MS for the rapid screening of systemic insecticides in water.

Determination of linear short chain aliphatic aldehyde and ketone vapors in air using a polystyrene-coated quartz crystal nanobalance sensor.

PubMed

Mirmohseni, Abdolreza; Olad, Ali

2010-01-01

A polystyrene coated quartz crystal nanobalance (QCN) sensor was developed for use in the determination of a number of linear short-chain aliphatic aldehyde and ketone vapors contained in air. The quartz crystal was modified by a thin-layer coating of a commercial grade general purpose polystyrene (GPPS) from Tabriz petrochemical company using a solution casting method. Determination was based on frequency shifts of the modified quartz crystal due to the adsorption of analytes at the surface of modified electrode in exposure to various concentrations of analytes. The frequency shift was found to have a linear relation to the concentration of analytes. Linear calibration curves were obtained for 7-70 mg l(-1) of analytes with correlation coefficients in the range of 0.9935-0.9989 and sensitivity factors in the range of 2.07-6.74 Hz/mg l(-1). A storage period of over three months showed no loss in the sensitivity and performance of the sensor.

Calculation of Thermally-Induced Displacements in Spherically Domed Ion Engine Grids

NASA Technical Reports Server (NTRS)

Soulas, George C.

2006-01-01

An analytical method for predicting the thermally-induced normal and tangential displacements of spherically domed ion optics grids under an axisymmetric thermal loading is presented. A fixed edge support that could be thermally expanded is used for this analysis. Equations for the displacements both normal and tangential to the surface of the spherical shell are derived. A simplified equation for the displacement at the center of the spherical dome is also derived. The effects of plate perforation on displacements and stresses are determined by modeling the perforated plate as an equivalent solid plate with modified, or effective, material properties. Analytical model results are compared to the results from a finite element model. For the solid shell, comparisons showed that the analytical model produces results that closely match the finite element model results. The simplified equation for the normal displacement of the spherical dome center is also found to accurately predict this displacement. For the perforated shells, the analytical solution and simplified equation produce accurate results for materials with low thermal expansion coefficients.