Isolation and characterization of potential antibiotic producing actinomycetes from water and sediments of Lake Tana, Ethiopia

PubMed Central

Gebreyohannes, Gebreselema; Moges, Feleke; Sahile, Samuel; Raja, Nagappan

2013-01-01

Objective To isolate, evaluate and characterize potential antibiotic producing actinomycetes from water and sediments of Lake Tana, Ethiopia. Methods A total of 31 strains of actinomycetes were isolated and tested against Gram positive and Gram negative bacterial strains by primary screening. In the primary screening, 11 promising isolates were identified and subjected to solid state and submerged state fermentation methods to produce crude extracts. The fermented biomass was extracted by organic solvent extraction method and tested against bacterial strains by disc and agar well diffusion methods. The isolates were characterized by using morphological, physiological and biochemical methods. Results The result obtained from agar well diffusion method was better than disc diffusion method. The crude extract showed higher inhibition zone against Gram positive bacteria than Gram negative bacteria. One-way analysis of variance confirmed most of the crude extracts were statistically significant at 95% confidence interval. The minimum inhibitory concentration and minimum bactericidal concentration of crude extracts were 1.65 mg/mL and 3.30 mg/mL against Staphylococcus aureus, and 1.84 mg/mL and 3.80 mg/mL against Escherichia coli respectively. The growth of aerial and substrate mycelium varied in different culture media used. Most of the isolates were able to hydrolysis starch and urea; able to survive at 5% concentration of sodium chloride; optimum temperature for their growth was 30 °C. Conclusions The results of the present study revealed that freshwater actinomycetes of Lake Tana appear to have immense potential as a source of antibacterial compounds. PMID:23730554

Method and system for gas flow mitigation of molecular contamination of optics

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

Delgado, Gildardo; Johnson, Terry; Arienti, Marco

A computer-implemented method for determining an optimized purge gas flow in a semi-conductor inspection metrology or lithography apparatus, comprising receiving a permissible contaminant mole fraction, a contaminant outgassing flow rate associated with a contaminant, a contaminant mass diffusivity, an outgassing surface length, a pressure, a temperature, a channel height, and a molecular weight of a purge gas, calculating a flow factor based on the permissible contaminant mole fraction, the contaminant outgassing flow rate, the channel height, and the outgassing surface length, comparing the flow factor to a predefined maximum flow factor value, calculating a minimum purge gas velocity and amore » purge gas mass flow rate from the flow factor, the contaminant mass diffusivity, the pressure, the temperature, and the molecular weight of the purge gas, and introducing the purge gas into the semi-conductor inspection metrology or lithography apparatus with the minimum purge gas velocity and the purge gas flow rate.« less

Structure and constitution of glass and steel compound in glass-metal composite

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

Lyubimova, Olga N.; Morkovin, Andrey V.; Dryuk, Sergey A.

2014-11-14

The research using methods of optical and scanning electronic microscopy was conducted and it discovered common factors on structures and diffusing zone forming after welding glass C49-1 and steel Ct3sp in technological process of creating new glass-metal composite. Different technological modes of steel surface preliminary oxidation welded with and without glass were investigated. The time of welding was varied from minimum encountering time to the time of stabilizing width of diffusion zone.

Evaluation of the effectiveness of peracetic acid in the sterilization of dental equipment.

PubMed

Ceretta, R; Paula, M M S; Angioletto, Ev; Méier, M M; Mitellstädt, F G; Pich, C T; Junior, S A; Angioletto, E

2008-01-01

To evaluate the effectiveness of peracetic acid in the microbiological sterilisation of dental materials. Peracetic acid solution was evaluated at concentrations of 800, 1500 and 2500 ppm. At these concentrations, it was determined whether peracetic acid caused corrosion to dental instruments and induced cellular mutagenicity and cytotoxicity. In addition, the minimum inhibitory concentration (MIC), the minimum bactericidal concentration (MBC), agar diffusion and diffusion by well method, were also verified. The corrosion rate, calculated from potentiodynamic assays was 10(-6) cm/year, indicating that the product does not damage equipment. The sterilisation capacity of peracetic acid at 2500 ppm was the best. The comet assay indicated genotoxic activity at 2500 ppm. This study demonstrated the effectiveness of peracetic acid for sterilizing dental equipment, providing another alternative for the prevention of infections in clinics.

Antibacterial effect of citrus press-cakes dried by high speed and far-infrared radiation drying methods

PubMed Central

Samarakoon, Kalpa; Senevirathne, Mahinda; Lee, Won-Woo; Kim, Young-Tae; Kim, Jae-Il; Oh, Myung-Cheol

2012-01-01

In this study, the antibacterial effect was evaluated to determine the benefits of high speed drying (HSD) and far-infrared radiation drying (FIR) compared to the freeze drying (FD) method. Citrus press-cakes (CPCs) are released as a by-product in the citrus processing industry. Previous studies have shown that the HSD and FIR drying methods are much more economical for drying time and mass drying than those of FD, even though FD is the most qualified drying method. The disk diffusion assay was conducted, and the minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) were determined with methanol extracts of the dried CPCs against 11 fish and five food-related pathogenic bacteria. The disk diffusion results indicated that the CPCs dried by HSD, FIR, and FD prevented growth of all tested bacteria almost identically. The MIC and MBC results showed a range from 0.5-8.0 mg/mL and 1.0-16.0 mg/mL respectively. Scanning electron microscopy indicated that the extracts changed the morphology of the bacteria cell wall, leading to destruction. These results suggest that CPCs dried by HSD and FIR showed strong antibacterial activity against pathogenic bacteria and are more useful drying methods than that of the classic FD method in CPCs utilization. PMID:22808341

Generating a Simulated Fluid Flow over a Surface Using Anisotropic Diffusion

NASA Technical Reports Server (NTRS)

Rodriguez, David L. (Inventor); Sturdza, Peter (Inventor)

2016-01-01

A fluid-flow simulation over a computer-generated surface is generated using a diffusion technique. The surface is comprised of a surface mesh of polygons. A boundary-layer fluid property is obtained for a subset of the polygons of the surface mesh. A gradient vector is determined for a selected polygon, the selected polygon belonging to the surface mesh but not one of the subset of polygons. A maximum and minimum diffusion rate is determined along directions determined using the gradient vector corresponding to the selected polygon. A diffusion-path vector is defined between a point in the selected polygon and a neighboring point in a neighboring polygon. An updated fluid property is determined for the selected polygon using a variable diffusion rate, the variable diffusion rate based on the minimum diffusion rate, maximum diffusion rate, and the gradient vector.

Generating a Simulated Fluid Flow Over an Aircraft Surface Using Anisotropic Diffusion

NASA Technical Reports Server (NTRS)

Rodriguez, David L. (Inventor); Sturdza, Peter (Inventor)

2013-01-01

A fluid-flow simulation over a computer-generated aircraft surface is generated using a diffusion technique. The surface is comprised of a surface mesh of polygons. A boundary-layer fluid property is obtained for a subset of the polygons of the surface mesh. A pressure-gradient vector is determined for a selected polygon, the selected polygon belonging to the surface mesh but not one of the subset of polygons. A maximum and minimum diffusion rate is determined along directions determined using a pressure gradient vector corresponding to the selected polygon. A diffusion-path vector is defined between a point in the selected polygon and a neighboring point in a neighboring polygon. An updated fluid property is determined for the selected polygon using a variable diffusion rate, the variable diffusion rate based on the minimum diffusion rate, maximum diffusion rate, and angular difference between the diffusion-path vector and the pressure-gradient vector.

Electronic Nose Testing Procedure for the Definition of Minimum Performance Requirements for Environmental Odor Monitoring

PubMed Central

Eusebio, Lidia; Capelli, Laura; Sironi, Selena

2016-01-01

Despite initial enthusiasm towards electronic noses and their possible application in different fields, and quite a lot of promising results, several criticalities emerge from most published research studies, and, as a matter of fact, the diffusion of electronic noses in real-life applications is still very limited. In general, a first step towards large-scale-diffusion of an analysis method, is standardization. The aim of this paper is describing the experimental procedure adopted in order to evaluate electronic nose performances, with the final purpose of establishing minimum performance requirements, which is considered to be a first crucial step towards standardization of the specific case of electronic nose application for environmental odor monitoring at receptors. Based on the experimental results of the performance testing of a commercialized electronic nose type with respect to three criteria (i.e., response invariability to variable atmospheric conditions, instrumental detection limit, and odor classification accuracy), it was possible to hypothesize a logic that could be adopted for the definition of minimum performance requirements, according to the idea that these are technologically achievable. PMID:27657086

Electronic Nose Testing Procedure for the Definition of Minimum Performance Requirements for Environmental Odor Monitoring.

PubMed

Eusebio, Lidia; Capelli, Laura; Sironi, Selena

2016-09-21

Despite initial enthusiasm towards electronic noses and their possible application in different fields, and quite a lot of promising results, several criticalities emerge from most published research studies, and, as a matter of fact, the diffusion of electronic noses in real-life applications is still very limited. In general, a first step towards large-scale-diffusion of an analysis method, is standardization. The aim of this paper is describing the experimental procedure adopted in order to evaluate electronic nose performances, with the final purpose of establishing minimum performance requirements, which is considered to be a first crucial step towards standardization of the specific case of electronic nose application for environmental odor monitoring at receptors. Based on the experimental results of the performance testing of a commercialized electronic nose type with respect to three criteria (i.e., response invariability to variable atmospheric conditions, instrumental detection limit, and odor classification accuracy), it was possible to hypothesize a logic that could be adopted for the definition of minimum performance requirements, according to the idea that these are technologically achievable.

Shortened Mean Transit Time in CT Perfusion With Singular Value Decomposition Analysis in Acute Cerebral Infarction: Quantitative Evaluation and Comparison With Various CT Perfusion Parameters.

PubMed

Murayama, Kazuhiro; Katada, Kazuhiro; Hayakawa, Motoharu; Toyama, Hiroshi

We aimed to clarify the cause of shortened mean transit time (MTT) in acute ischemic cerebrovascular disease and examined its relationship with reperfusion. Twenty-three patients with acute ischemic cerebrovascular disease underwent whole-brain computed tomography perfusion (CTP). The maximum MTT (MTTmax), minimum MTT (MTTmin), ratio of maximum and minimum MTT (MTTmin/max), and minimum cerebral blood volume (CBV) (CBVmin) were measured by automatic region of interest analysis. Diffusion weighted image was performed to calculate infarction volume. We compared these CTP parameters between reperfusion and nonreperfusion groups and calculated correlation coefficients between the infarction core volume and CTP parameters. Significant differences were observed between reperfusion and nonreperfusion groups (MTTmin/max: P = 0.014; CBVmin ratio: P = 0.038). Regression analysis of CTP and high-intensity volume on diffusion weighted image showed negative correlation (CBVmin ratio: r = -0.41; MTTmin/max: r = -0.30; MTTmin ratio: r = -0.27). A region of shortened MTT indicated obstructed blood flow, which was attributed to the singular value decomposition method error.

Using the apparent diffusion coefficient to identifying MGMT promoter methylation status early in glioblastoma: importance of analytical method

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

Rundle-Thiele, Dayle; Day, Bryan; Stringer, Brett

Accurate knowledge of O{sup 6}-methylguanine methyltransferase (MGMT) gene promoter subtype in patients with glioblastoma (GBM) is important for treatment. However, this test is not always available. Pre-operative diffusion MRI (dMRI) can be used to probe tumour biology using the apparent diffusion coefficient (ADC); however, its ability to act as a surrogate to predict MGMT status has shown mixed results. We investigated whether this was due to variations in the method used to analyse ADC. We undertook a retrospective study of 32 patients with GBM who had MGMT status measured. Matching pre-operative MRI data were used to calculate the ADC withinmore » contrast enhancing regions of tumour. The relationship between ADC and MGMT was examined using two published ADC methods. A strong trend between a measure of ‘minimum ADC’ and methylation status was seen. An elevated minimum ADC was more likely in the methylated compared to the unmethylated MGMT group (U = 56, P = 0.0561). In contrast, utilising a two-mixture model histogram approach, a significant reduction in mean measure of the ‘low ADC’ component within the histogram was associated with an MGMT promoter methylation subtype (P < 0.0246). This study shows that within the same patient cohort, the method selected to analyse ADC measures has a significant bearing on the use of that metric as a surrogate marker of MGMT status. Thus for dMRI data to be clinically useful, consistent methods of data analysis need to be established prior to establishing any relationship with genetic or epigenetic profiling.« less

The control gain region for synchronization in non-diffusively coupled complex networks

NASA Astrophysics Data System (ADS)

Gequn, Liu; Wenhui, Li; Huijie, Yang; Knowles, Gareth

2014-07-01

The control gain region for synchronization of non-diffusively coupled networks was studied with respect to three conditions: synchronization, synchronization in finite time, and synchronization in the minimum time. Based on cancellation control methodology and master stability function formalism, we found that a complete feasible control gain region may be bounded, unbounded, empty or a union of several bounded and unbounded regions, with a similar shape to the synchronized region. An interesting possibility emerged that a network could be synchronized by both negative and positive feedback control simultaneously. By bridging synchronizability and synchronizing response speeds with a settling time index, we have developed timed synchronized region (TSR) as a substitute for the classical synchronized region to study finite time synchronization. As for the last condition, a graphical method was developed to estimate control gain with the minimum synchronization time (CGMST). Each condition has examples provided for illustration and verification.

Light polarization measurements - A method to determine the specular and diffuse light-scattering properties of both leaves and plant canopies

NASA Technical Reports Server (NTRS)

Vanderbilt, V. C.; Grant, L.

1984-01-01

The contributions of diffuse and specular reflection to the total canopy reflection of sunlight are determined experimentally for wheat at two stages of development using spectroradiometer measurements obtained at 13 wavelengths in the 480-720-nm range with a polarizing film in maximum and minimum signal-amplitude positions. The data and computation techniques are presented in tables, diagrams, and graphs, and the need to take specular reflection into account in constructing models of light/canopy interaction is stressed.

Fast secant methods for the iterative solution of large nonsymmetric linear systems

NASA Technical Reports Server (NTRS)

Deuflhard, Peter; Freund, Roland; Walter, Artur

1990-01-01

A family of secant methods based on general rank-1 updates was revisited in view of the construction of iterative solvers for large non-Hermitian linear systems. As it turns out, both Broyden's good and bad update techniques play a special role, but should be associated with two different line search principles. For Broyden's bad update technique, a minimum residual principle is natural, thus making it theoretically comparable with a series of well known algorithms like GMRES. Broyden's good update technique, however, is shown to be naturally linked with a minimum next correction principle, which asymptotically mimics a minimum error principle. The two minimization principles differ significantly for sufficiently large system dimension. Numerical experiments on discretized partial differential equations of convection diffusion type in 2-D with integral layers give a first impression of the possible power of the derived good Broyden variant.

Diffusion-weighted imaging of breast lesions: Region-of-interest placement and different ADC parameters influence apparent diffusion coefficient values.

PubMed

Bickel, Hubert; Pinker, Katja; Polanec, Stephan; Magometschnigg, Heinrich; Wengert, Georg; Spick, Claudio; Bogner, Wolfgang; Bago-Horvath, Zsuzsanna; Helbich, Thomas H; Baltzer, Pascal

2017-05-01

To investigate the influence of region-of-interest (ROI) placement and different apparent diffusion coefficient (ADC) parameters on ADC values, diagnostic performance, reproducibility and measurement time in breast tumours. In this IRB-approved, retrospective study, 149 histopathologically proven breast tumours (109 malignant, 40 benign) in 147 women (mean age 53.2) were investigated. Three radiologists independently measured minimum, mean and maximum ADC, each using three ROI placement approaches:1 - small 2D-ROI, 2 - large 2D-ROI and 3 - 3D-ROI covering the whole lesion. One reader performed all measurements twice. Median ADC values, diagnostic performance, reproducibility, and measurement time were calculated and compared between all combinations of ROI placement approaches and ADC parameters. Median ADC values differed significantly between the ROI placement approaches (p < .001). Minimum ADC showed the best diagnostic performance (AUC .928-.956), followed by mean ADC obtained from 2D ROIs (.926-.94). Minimum and mean ADC showed high intra- (ICC .85-.94) and inter-reader reproducibility (ICC .74-.94). Median measurement time was significantly shorter for the 2D ROIs (p < .001). ROI placement significantly influences ADC values measured in breast tumours. Minimum and mean ADC acquired from 2D-ROIs are useful for the differentiation of benign and malignant breast lesions, and are highly reproducible, with rapid measurement. • Region of interest placement significantly influences apparent diffusion coefficient of breast tumours. • Minimum and mean apparent diffusion coefficient perform best and are reproducible. • 2D regions of interest perform best and provide rapid measurement times.

In-vitro Antimicrobial Activities of Some Iranian Conifers

PubMed Central

Afsharzadeh, Maryam; Naderinasab, Mahboobe; Tayarani Najaran, Zahra; Barzin, Mohammad; Emami, Seyed Ahmad

2013-01-01

Male and female leaves and fruits of eleven different taxons of Iranian conifers (Cupressus sempervirens var. horizontalis, C. sempervirens var. sempervirens, C. sempervirens cv. Cereifeormis, Juniperus communis subsp. hemisphaerica, J. excelsa subsp. excelsa, J. excelsa subsp. polycarpos, J. foetidissima, J. oblonga, J. sabina, Platycladus orientalis and Taxus baccata) were collected from different localities of Iran, dried and extracted with methanol. The extracts were tested for their antimicrobial activity against Pseudomonas aeruginosa, Staphylococcus aureus, Escherichia coli and Candida albicans. The extracts were screened qualitatively using four different methods, the disc diffusion, hole plate, cylinder agar diffusion and agar dilution methods, whereas the minimum inhibitory concentrations (MIC) of each extract were determined by the agar dilution method. The best result was obtained by means of hole plate method in qualitative determination of antimicrobial activities of extracts and the greatest activity was found against S. aureus in all tested methods. PMID:24250573

Particle acceleration at shocks in the inner heliosphere

NASA Astrophysics Data System (ADS)

Parker, Linda Neergaard

This dissertation describes a study of particle acceleration at shocks via the diffusive shock acceleration mechanism. Results for particle acceleration at both quasi-parallel and quasi-perpendicular shocks are presented to address the question of whether there are sufficient particles in the solar wind thermal core, modeled as either a Maxwellian or kappa- distribution, to account for the observed accelerated spectrum. Results of accelerating the theoretical upstream distribution are compared to energetic observations at 1 AU. It is shown that the particle distribution in the solar wind thermal core is sufficient to explain the accelerated particle spectrum downstream of the shock, although the shape of the downstream distribution in some cases does not follow completely the theory of diffusive shock acceleration, indicating possible additional processes at work in the shock for these cases. Results show good to excellent agreement between the theoretical and observed spectral index for one third to one half of both quasi-parallel and quasi-perpendicular shocks studied herein. Coronal mass ejections occurring during periods of high solar activity surrounding solar maximum can produce shocks in excess of 3-8 shocks per day. During solar minimum, diffusive shock acceleration at shocks can generally be understood on the basis of single independent shocks and no other shock necessarily influences the diffusive shock acceleration mechanism. In this sense, diffusive shock acceleration during solar minimum may be regarded as Markovian. By contrast, diffusive shock acceleration of particles at periods of high solar activity (e.g. solar maximum) see frequent, closely spaced shocks that include the effects of particle acceleration at preceding and following shocks. Therefore, diffusive shock acceleration of particles at solar maximum cannot be modeled on the basis of diffusive shock acceleration as a single, independent shock and the process is essentially non-Markovian. A multiple shock model is developed based in part on the box model of (Protheroe and Stanev, 1998; Moraal and Axford, 1983; Ball and Kirk, 1992; Drury et al. 1999) that accelerates particles at multiple shocks and decompresses the particles between shocks via two methods. The first method of decompression is based on the that used by Melrose and Pope (1993), which adiabatically decompresses particles between shocks. The second method solves the cosmic ray transport equation and adiabatically decompresses between shocks and includes the loss of particles through convection and diffusion. The transport method allows for the inclusion of a temporal variability and thus allows for a more representative frequency distribution of shocks. The transport method of decompression and loss is used to accelerate particles at seventy-three shocks in a thirty day time period. Comparisons with observations taken at 1 AU during the same time period are encouraging as the model is able to reproduce the observed amplitude of the accelerated particles and in part the variability. This work provides the basis for developing more sophisticated models that can be applied to a suite of observations

Antibacterial activity study of Attacus atlas cocoon against Staphylococcus aureus and Escherichia coli with diffusion and dilution method

NASA Astrophysics Data System (ADS)

Aminah; Nugraheni, E. R.; Yugatama, A.

2018-03-01

The aim of this study was to evaluate the antibacterial activity from Attacus atlas cocoon extract against Gram-negative bacteria (Escherichia coli) and Gram-positive bacteria (Staphylococcus aureus) with 3 diffferent solvents polar, semi-polar and non polar which was ethanol, ethyl acetate and chloroform, also to determine the Minimum Inhibitory Concentration (MIC) and Minimum Bactericidal Concentration (MBC) of the extract. Cocoon was extracted with maceration method using 3 solvents with ratio of sample and solvent 1:10. Antibacterial activity of the Extracts obtained was evaluated with Agar disk diffusion method. The best result was then continued to determine the MIC and MBC of the extract using broth macro-dilution method. The results show that each of the extracts have antibacterial activity with broad spectrum against two different type of bacteria at concentration of 1 g/mL with different clear zone between these extracts. Clear zone from the biggest to the smallest against Escherichia coli was ethyl acetate (10.5 mm), chloroform (9 mm) and ethanol (8 mm). While against Staphylococcus aureus, was obtained by chloroform (12.5 mm), ethyl acetate (10.5 mm) and ethanol (7 mm). The MIC value of extracts can not be determine. The smallest MBC value against both bacteria was obtained by ethyl acetate with concentration of 3.125% b/v as a bactericidal.

The Analytical Limits of Modeling Short Diffusion Timescales

NASA Astrophysics Data System (ADS)

Bradshaw, R. W.; Kent, A. J.

2016-12-01

Chemical and isotopic zoning in minerals is widely used to constrain the timescales of magmatic processes such as magma mixing and crystal residence, etc. via diffusion modeling. Forward modeling of diffusion relies on fitting diffusion profiles to measured compositional gradients. However, an individual measurement is essentially an average composition for a segment of the gradient defined by the spatial resolution of the analysis. Thus there is the potential for the analytical spatial resolution to limit the timescales that can be determined for an element of given diffusivity, particularly where the scale of the gradient approaches that of the measurement. Here we use a probabilistic modeling approach to investigate the effect of analytical spatial resolution on estimated timescales from diffusion modeling. Our method investigates how accurately the age of a synthetic diffusion profile can be obtained by modeling an "unknown" profile derived from discrete sampling of the synthetic compositional gradient at a given spatial resolution. We also include the effects of analytical uncertainty and the position of measurements relative to the diffusion gradient. We apply this method to the spatial resolutions of common microanalytical techniques (LA-ICP-MS, SIMS, EMP, NanoSIMS). Our results confirm that for a given diffusivity, higher spatial resolution gives access to shorter timescales, and that each analytical spacing has a minimum timescale, below which it overestimates the timescale. For example, for Ba diffusion in plagioclase at 750 °C timescales are accurate (within 20%) above 10, 100, 2,600, and 71,000 years at 0.3, 1, 5, and 25 mm spatial resolution, respectively. For Sr diffusion in plagioclase at 750 °C, timescales are accurate above 0.02, 0.2, 4, and 120 years at the same spatial resolutions. Our results highlight the importance of selecting appropriate analytical techniques to estimate accurate diffusion-based timescales.

Optimization of reading conditions for flat panel displays.

PubMed

Thomas, J A; Chakrabarti, K; Kaczmarek, R V; Maslennikov, A; Mitchell, C A; Romanyukha, A

2006-06-01

Task Group 18 (TG 18) of the American Association of Physicists in Medicine has developed guidelines for Assessment of Display Performance for Medical Imaging Systems. In this document, a method for determination of the maximum room lighting for displays is suggested. It is based on luminance measurements of a black target displayed on each display device at different room illuminance levels. Linear extrapolation of the above luminance measurements vs. room illuminance allows one to determine diffuse and specular reflection coefficients. TG 18 guidelines have established recommended maximum room lighting. It is based on the characterization of the display by its minimum and maximum luminance and the description of room by diffuse and specular coefficients. We carried out these luminance measurements for three selected displays to determine their optimum viewing conditions: one cathode ray tube and two flat panels. We found some problems with the application of the TG 18 guidelines to optimize viewing conditions for IBM T221 flat panels. Introduction of the requirement for minimum room illuminance allows a more accurate determination of the optimal viewing conditions (maximum and minimum room illuminance) for IBM flat panels. It also addresses the possible loss of contrast in medical images on flat panel displays because of the effect of nonlinearity in the dependence of luminance on room illuminance at low room lighting.

Solution Methods for Certain Evolution Equations

NASA Astrophysics Data System (ADS)

Vega-Guzman, Jose Manuel

Solution methods for certain linear and nonlinear evolution equations are presented in this dissertation. Emphasis is placed mainly on the analytical treatment of nonautonomous differential equations, which are challenging to solve despite the existent numerical and symbolic computational software programs available. Ideas from the transformation theory are adopted allowing one to solve the problems under consideration from a non-traditional perspective. First, the Cauchy initial value problem is considered for a class of nonautonomous and inhomogeneous linear diffusion-type equation on the entire real line. Explicit transformations are used to reduce the equations under study to their corresponding standard forms emphasizing on natural relations with certain Riccati(and/or Ermakov)-type systems. These relations give solvability results for the Cauchy problem of the parabolic equation considered. The superposition principle allows to solve formally this problem from an unconventional point of view. An eigenfunction expansion approach is also considered for this general evolution equation. Examples considered to corroborate the efficacy of the proposed solution methods include the Fokker-Planck equation, the Black-Scholes model and the one-factor Gaussian Hull-White model. The results obtained in the first part are used to solve the Cauchy initial value problem for certain inhomogeneous Burgers-type equation. The connection between linear (the Diffusion-type) and nonlinear (Burgers-type) parabolic equations is stress in order to establish a strong commutative relation. Traveling wave solutions of a nonautonomous Burgers equation are also investigated. Finally, it is constructed explicitly the minimum-uncertainty squeezed states for quantum harmonic oscillators. They are derived by the action of corresponding maximal kinematical invariance group on the standard ground state solution. It is shown that the product of the variances attains the required minimum value only at the instances that one variance is a minimum and the other is a maximum, when the squeezing of one of the variances occurs. Such explicit construction is possible due to the relation between the diffusion-type equation studied in the first part and the time-dependent Schrodinger equation. A modication of the radiation field operators for squeezed photons in a perfect cavity is also suggested with the help of a nonstandard solution of Heisenberg's equation of motion.

Interface morphology of Mo/Si multilayer systems with varying Mo layer thickness studied by EUV diffuse scattering.

PubMed

Haase, Anton; Soltwisch, Victor; Braun, Stefan; Laubis, Christian; Scholze, Frank

2017-06-26

We investigate the influence of the Mo-layer thickness on the EUV reflectance of Mo/Si mirrors with a set of unpolished and interface-polished Mo/Si/C multilayer mirrors. The Mo-layer thickness is varied in the range from 1.7 nm to 3.05 nm. We use a novel combination of specular and diffuse intensity measurements to determine the interface roughness throughout the multilayer stack and do not rely on scanning probe measurements at the surface only. The combination of EUV and X-ray reflectivity measurements and near-normal incidence EUV diffuse scattering allows to reconstruct the Mo layer thicknesses and to determine the interface roughness power spectral density. The data analysis is conducted by applying a matrix method for the specular reflection and the distorted-wave Born approximation for diffuse scattering. We introduce the Markov-chain Monte Carlo method into the field in order to determine the respective confidence intervals for all reconstructed parameters. We unambiguously detect a threshold thickness for Mo in both sample sets where the specular reflectance goes through a local minimum correlated with a distinct increase in diffuse scatter. We attribute that to the known appearance of an amorphous-to-crystallization transition at a certain thickness threshold which is altered in our sample system by the polishing.

Diffusion coefficients of organic molecules in sucrose-water solutions and comparison with Stokes-Einstein predictions

NASA Astrophysics Data System (ADS)

Chenyakin, Yuri; Ullmann, Dagny A.; Evoy, Erin; Renbaum-Wolff, Lindsay; Kamal, Saeid; Bertram, Allan K.

2017-02-01

The diffusion coefficients of organic species in secondary organic aerosol (SOA) particles are needed to predict the growth and reactivity of these particles in the atmosphere. Previously, viscosity measurements, along with the Stokes-Einstein relation, have been used to estimate the diffusion rates of organics within SOA particles or proxies of SOA particles. To test the Stokes-Einstein relation, we have measured the diffusion coefficients of three fluorescent organic dyes (fluorescein, rhodamine 6G and calcein) within sucrose-water solutions with varying water activity. Sucrose-water solutions were used as a proxy for SOA material found in the atmosphere. Diffusion coefficients were measured using fluorescence recovery after photobleaching. For the three dyes studied, the diffusion coefficients vary by 4-5 orders of magnitude as the water activity varied from 0.38 to 0.80, illustrating the sensitivity of the diffusion coefficients to the water content in the matrix. At the lowest water activity studied (0.38), the average diffusion coefficients were 1.9 × 10-13, 1.5 × 10-14 and 7.7 × 10-14 cm2 s-1 for fluorescein, rhodamine 6G and calcein, respectively. The measured diffusion coefficients were compared with predictions made using literature viscosities and the Stokes-Einstein relation. We found that at water activity ≥ 0.6 (which corresponds to a viscosity of ≤ 360 Pa s and Tg/T ≤ 0.81), predicted diffusion rates agreed with measured diffusion rates within the experimental uncertainty (Tg represents the glass transition temperature and T is the temperature of the measurements). When the water activity was 0.38 (which corresponds to a viscosity of 3.3 × 106 Pa s and a Tg/T of 0.94), the Stokes-Einstein relation underpredicted the diffusion coefficients of fluorescein, rhodamine 6G and calcein by a factor of 118 (minimum of 10 and maximum of 977), a factor of 17 (minimum of 3 and maximum of 104) and a factor of 70 (minimum of 8 and maximum of 494), respectively. This disagreement is significantly smaller than the disagreement observed when comparing measured and predicted diffusion coefficients of water in sucrose-water mixtures.

Prediction of external corrosion for steel cylinders at the Paducah Gaseous Diffusion Plant: Application of an empirical method

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

Lyon, B.F.

1996-02-01

During the summer of 1995, ultrasonic wall thickness data were collected for 100 steel cylinders containing depleted uranium (DU) hexafluoride located at Paducah Gaseous Diffusion Plant (PGDP) in Paducah, Kentucky. The cylinders were selected for measurement to assess the condition of the more vulnerable portion of the cylinder inventory at PGDP. The purpose of this report is to apply the method used in Lyon to estimate the effects of corrosion for larger unsampled populations as a function of time. The scope of this report is limited and is not intended to represent the final analyses of available data. Future effortsmore » will include continuing analyses of available data to investigate defensible deviations from the conservative assumptions made to date. For each cylinder population considered, two basic types of analyses were conducted: (1) estimates were made of the number of cylinders as a function of time that will have a minimum wall thickness of either 0 mils (1 mil = 0.00 1 in.) or 250 mils and (2) the current minimum wall thickness distributions across cylinders were estimated for each cylinder population considered. Additional analyses were also performed investigating comparisons of the results for F and G yards with the results presented in Lyon (1995).« less

Heat capacities and thermal diffusivities of n-alkane acid ethyl esters—biodiesel fuel components

NASA Astrophysics Data System (ADS)

Bogatishcheva, N. S.; Faizullin, M. Z.; Nikitin, E. D.

2017-09-01

The heat capacities and thermal diffusivities of ethyl esters of liquid n-alkane acids C n H2 n-1O2C2H5 with the number of carbon atoms in the parent acid n = 10, 11, 12, 14, and 16 are measured. The heat capacities are measured using a DSC 204 F1 Phoenix heat flux differential scanning calorimeter (Netzsch, Germany) in the temperature range of 305-375 K. Thermal diffusivities are measured by means of laser flash method on an LFA-457 instrument (Netzsch, Germany) at temperatures of 305-400 K. An equation is derived for the dependence of the molar heat capacities of the investigated esters on temperature. It is shown that the dependence of molar heat capacity C p,m (298.15 K) on n ( n = 1-6) is close to linear. The dependence of thermal diffusivity on temperature in the investigated temperature range is described by a first-degree polynomial, but thermal diffusivity a (298.15 K) as a function of n has a minimum at n = 5.

Production of Transitional Diffused Layers by Electrospark Coating

NASA Astrophysics Data System (ADS)

Smolentsev, Vladislav P.; Boldyrev, Alexander I.; Smolentsev, Evgeniy V.; Boldyrev, Alexander A.; Mozgalin, Vladislav L.

2018-03-01

The article presents a new method for production of diffused transitional layers with nano- and microthickness by local removal of nanofilms on aluminum alloys. This allows procuring of high-quality coatings on fusible alloys (for example, on aluminum ones) by materials, the melting point of which is 2-3 times higher than that of the basis (for example, of cast iron). This permits imparting new useful properties to workpieces made from light alloys with decent values for electrochemical working. The authors show that application of coatings provides minimum heating of workpieces. This enables the regulation in temperature condition of operating environment and permits efficiency improving during the process of electrochemical working by means of higher density current supply.

The number counts and infrared backgrounds from infrared-bright galaxies

NASA Technical Reports Server (NTRS)

Hacking, P. B.; Soifer, B. T.

1991-01-01

Extragalactic number counts and diffuse backgrounds at 25, 60, and 100 microns are predicted using new luminosity functions and improved spectral-energy distribution density functions derived from IRAS observations of nearby galaxies. Galaxies at redshifts z less than 3 that are like those in the local universe should produce a minimum diffuse background of 0.0085, 0.038, and 0.13 MJy/sr at 25, 60, and 100 microns, respectively. Models with significant luminosity evolution predict backgrounds about a factor of 4 greater than this minimum.

New MYC IHC Classifier Integrating Quantitative Architecture Parameters to Predict MYC Gene Translocation in Diffuse Large B-Cell Lymphoma

PubMed Central

Dong, Wei-Feng; Canil, Sarah; Lai, Raymond; Morel, Didier; Swanson, Paul E.; Izevbaye, Iyare

2018-01-01

A new automated MYC IHC classifier based on bivariate logistic regression is presented. The predictor relies on image analysis developed with the open-source ImageJ platform. From a histologic section immunostained for MYC protein, 2 dimensionless quantitative variables are extracted: (a) relative distance between nuclei positive for MYC IHC based on euclidean minimum spanning tree graph and (b) coefficient of variation of the MYC IHC stain intensity among MYC IHC-positive nuclei. Distance between positive nuclei is suggested to inversely correlate MYC gene rearrangement status, whereas coefficient of variation is suggested to inversely correlate physiological regulation of MYC protein expression. The bivariate classifier was compared with 2 other MYC IHC classifiers (based on percentage of MYC IHC positive nuclei), all tested on 113 lymphomas including mostly diffuse large B-cell lymphomas with known MYC fluorescent in situ hybridization (FISH) status. The bivariate classifier strongly outperformed the “percentage of MYC IHC-positive nuclei” methods to predict MYC+ FISH status with 100% sensitivity (95% confidence interval, 94-100) associated with 80% specificity. The test is rapidly performed and might at a minimum provide primary IHC screening for MYC gene rearrangement status in diffuse large B-cell lymphomas. Furthermore, as this bivariate classifier actually predicts “permanent overexpressed MYC protein status,” it might identify nontranslocation-related chromosomal anomalies missed by FISH. PMID:27093450

Vitamin D3 a new drug against Candida albicans.

PubMed

Bouzid, D; Merzouki, S; Bachiri, M; Ailane, S E; Zerroug, M M

2017-03-01

In this study, we demonstrate that vitamin D 3 had fungicidal activity against Candida albicans. The susceptibility of the yeast strain to the vitamin D 3 was investigated by the antimicrobial screening using modified agar diffusion method, minimum fungistatic concentrations (MFC s ) and minimum fungicide concentrations (MFC C ) of the vitamin D 3 were determined by the broth dilution method. The antifungal activity indicted that 100μg/ml of vitamin D 3 had a power inhibition in the growth of C. albicans with zone of inhibition 12.5mm and CMF C and CMF s were 1.58±0.0764μg/ml. These values indicate that vitamin D 3 can be considered to have fungicide activity. This antifungal effect may be due to the large lipsolubility of vitamin D 3 changing the integrity of the cell membrane. Copyright © 2016 Elsevier Masson SAS. All rights reserved.

Prenylated flavonoids from Desmodium caudatum and evaluation of their anti-MRSA activity.

PubMed

Sasaki, Hisako; Kashiwada, Yoshiki; Shibata, Hirofumi; Takaishi, Yoshihisa

2012-10-01

Seven prenylated flavonoids and a prenylated chromanochroman derivative, together with eight known flavonoids, were isolated from roots of Desmodium caudatum. The 15 structures were elucidated by extensive spectroscopic analyses. The antibacterial activity of many of other compounds was evaluated against methicillin-resistant Staphylococcus aureus (MRSA: COL and 5) by a disc diffusion method, and the minimum inhibitory concentrations (MICs) to MRSA were determined. Copyright © 2012 Elsevier Ltd. All rights reserved.

Model of diffusion-assisted direct laser writing by means of nanopolymerization in the presence of radical quencher

NASA Astrophysics Data System (ADS)

Pikulin, Alexander; Bityurin, Nikita; Sokolov, Viktor I.

2015-12-01

Diffusion-assisted direct laser writing (DA-DLW) by multiphoton polymerization has been recently shown to be one of the most promising methods for the high-resolution 3D nanofabrication [I. Sakellari, et al., ACS Nano 6, 2302 (2012)]. The improvement of the writing spatial resolution has been observed under certain conditions when the mobile radical quencher (polymerization inhibitor) is added to the photosensitive composition. In this work, we present a theoretical study of this method, focusing on the resolution capabilities and optimal writing parameters. The laser beam absorption in the polymerizable composition causes the localized depletion of the quencher molecules. If the quencher depletion is balanced by its diffusion from the outside of the focal volume, the quasi-stationary non-equillibrium concentration spatial profile with zero minimum can be obtained. The polymer is then effectively formed only in the domain where the quencher is depleted. The spatially-distributed quencher, in this case, has the effect similar to that of the vortex beam in STimulated Emission Microscopy (STED).

Model of diffusion-assisted direct laser writing by means of nanopolymerization in the presence of radical quencher

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

Pikulin, Alexander, E-mail: pikulin@ufp.appl.sci-nnov.ru; Bityurin, Nikita; Institute of Applied Physics of Russian Academy of Sciences, 46, Ul’yanov Str., Nizhniy Novgorod, 603950

Diffusion-assisted direct laser writing (DA-DLW) by multiphoton polymerization has been recently shown to be one of the most promising methods for the high-resolution 3D nanofabrication [I. Sakellari, et al., ACS Nano 6, 2302 (2012)]. The improvement of the writing spatial resolution has been observed under certain conditions when the mobile radical quencher (polymerization inhibitor) is added to the photosensitive composition. In this work, we present a theoretical study of this method, focusing on the resolution capabilities and optimal writing parameters. The laser beam absorption in the polymerizable composition causes the localized depletion of the quencher molecules. If the quencher depletionmore » is balanced by its diffusion from the outside of the focal volume, the quasi-stationary non-equillibrium concentration spatial profile with zero minimum can be obtained. The polymer is then effectively formed only in the domain where the quencher is depleted. The spatially-distributed quencher, in this case, has the effect similar to that of the vortex beam in STimulated Emission Microscopy (STED)« less

Tensor distribution function

NASA Astrophysics Data System (ADS)

Leow, Alex D.; Zhu, Siwei

2008-03-01

Diffusion weighted MR imaging is a powerful tool that can be employed to study white matter microstructure by examining the 3D displacement profile of water molecules in brain tissue. By applying diffusion-sensitizing gradients along a minimum of 6 directions, second-order tensors (represetnted by 3-by-3 positive definiite matrices) can be computed to model dominant diffusion processes. However, it has been shown that conventional DTI is not sufficient to resolve more complicated white matter configurations, e.g. crossing fiber tracts. More recently, High Angular Resolution Diffusion Imaging (HARDI) seeks to address this issue by employing more than 6 gradient directions. To account for fiber crossing when analyzing HARDI data, several methodologies have been introduced. For example, q-ball imaging was proposed to approximate Orientation Diffusion Function (ODF). Similarly, the PAS method seeks to reslove the angular structure of displacement probability functions using the maximum entropy principle. Alternatively, deconvolution methods extract multiple fiber tracts by computing fiber orientations using a pre-specified single fiber response function. In this study, we introduce Tensor Distribution Function (TDF), a probability function defined on the space of symmetric and positive definite matrices. Using calculus of variations, we solve for the TDF that optimally describes the observed data. Here, fiber crossing is modeled as an ensemble of Gaussian diffusion processes with weights specified by the TDF. Once this optimal TDF is determined, ODF can easily be computed by analytical integration of the resulting displacement probability function. Moreover, principle fiber directions can also be directly derived from the TDF.

IMPORTANCE OF MERIDIONAL CIRCULATION IN FLUX TRANSPORT DYNAMO: THE POSSIBILITY OF A MAUNDER-LIKE GRAND MINIMUM

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

Karak, Bidya Binay, E-mail: bidya_karak@physics.iisc.ernet.i

2010-12-01

Meridional circulation is an important ingredient in flux transport dynamo models. We have studied its importance on the period, the amplitude of the solar cycle, and also in producing Maunder-like grand minima in these models. First, we model the periods of the last 23 sunspot cycles by varying the meridional circulation speed. If the dynamo is in a diffusion-dominated regime, then we find that most of the cycle amplitudes also get modeled up to some extent when we model the periods. Next, we propose that at the beginning of the Maunder minimum the amplitude of meridional circulation dropped to amore » low value and then after a few years it increased again. Several independent studies also favor this assumption. With this assumption, a diffusion-dominated dynamo is able to reproduce many important features of the Maunder minimum remarkably well. If the dynamo is in a diffusion-dominated regime, then a slower meridional circulation means that the poloidal field gets more time to diffuse during its transport through the convection zone, making the dynamo weaker. This consequence helps to model both the cycle amplitudes and the Maunder-like minima. We, however, fail to reproduce these results if the dynamo is in an advection-dominated regime.« less

Hydrodynamically induced fluid transfer and non-convective double-diffusion in microgravity sliding solvent diffusion cells

NASA Technical Reports Server (NTRS)

Pollmann, Konrad W.; Stodieck, Louis S.; Luttges, Marvin W.

1994-01-01

Microgravity can provide a diffusion-dominated environment for double-diffusion and diffusion-reaction experiments otherwise disrupted by buoyant convection or sedimentation. In sliding solvent diffusion cells, a diffusion interface between two liquid columns is achieved by aligning two offset sliding wells. Fluid in contact with the sliding lid of the cavities is subjected to an applied shear stress. The momentum change by the start/stop action of the well creates an additional hydrodynamical force. In microgravity, these viscous and inertial forces are sufficiently large to deform the diffusion interface and induce hydrodynamic transfer between the wells. A series of KC-135 parabolic flight experiments were conducted to characterize these effects and establish baseline data for microgravity diffusion experiments. Flow visualizations show the diffusion interface to be deformed in a sinusoidal fashion following well alignment. After the wells were separated again in a second sliding movement, the total induced liquid transfer was determined and normalized by the well aspect ratio. The normalized transfer decreased linearly with Reynolds number from 3.3 to 4.0% (w/v) for Re = 0.4 (Stokes flow) to a minimum of 1.0% for Re = 23 to 30. Reynolds numbers that provide minimum induced transfers are characterized by an interface that is highly deformed and unsuitable for diffusion measurements. Flat diffusion interfaces acceptable for diffusion measurements are obtained with Reynolds numbers on the order of 7 to 10. Microgravity experiments aboard a sounding rocket flight verified counterdiffusion of different solutes to be diffusion dominated. Ground control experiments showed enhanced mixing by double-diffusive convection. Careful selection of experimental parameters improves initial conditions and minimizes induced transfer rates.

Geographical diffusion of prazosin across Veterans Health Administration: Examination of regional variation in daily dosing and quality indicators among veterans with posttraumatic stress disorder.

PubMed

Abrams, Thad E; Lund, Brian C; Alexander, Bruce; Bernardy, Nancy C; Friedman, Matthew J

2015-01-01

Posttraumatic stress disorder (PTSD) is a high-priority treatment area for the Veterans Health Administration (VHA), and dissemination patterns of innovative, efficacious therapies can inform areas for potential improvement of diffusion efforts and quality prescribing. In this study, we replicated a prior examination of the period prevalence of prazosin use as a function of distance from Puget Sound, Washington, where prazosin was first tested as an effective treatment for PTSD and where prazosin use was previously shown to be much greater than in other parts of the United States. We tested the following three hypotheses related to prazosin geographic diffusion: (1) a positive geographical correlation exists between the distance from Puget Sound and the proportion of users treated according to a guideline recommended minimum therapeutic target dose (>/=6 mg/d), (2) an inverse geographic correlation exists between prazosin and benzodiazepine use, and (3) no geographical correlation exists between prazosin use and serotonin reuptake inhibitor/serotonin norepinephrine reuptake inhibitor (SSRI/SNRI) use. Among a national sample of veterans with PTSD, overall prazosin utilization increased from 5.5 to 14.8% from 2006 to 2012. During this time period, rates at the Puget Sound VHA location declined from 34.4 to 29.9%, whereas utilization rates at locations a minimum of 2,500 miles away increased from 3.0 to 12.8%. Rates of minimum target dosing fell from 42.6 to 34.6% at the Puget Sound location. In contrast, at distances of at least 2,500 miles from Puget Sound, minimum threshold dosing rates remained stable (range, 18.6 to 17.7%). No discernible association was demonstrated between SSRI/SNRI or benzodiazepine utilization and the geographic distance from Puget Sound. Minimal threshold dosing of prazosin correlated positively with increased diffusion of prazosin use, but there was still a distance diffusion gradient. Although prazosin adoption has improved, geographic differences persist in both prescribing rates and minimum target dosing. Importantly, these regional disparities appear to be limited to prazosin prescribing and are not meaningfully correlated with SSRI/SNRI and benzodiazepine use as indicators of PTSD prescribing quality.

Inhibitory Effects of Pterodon emarginatus Bean Oil and Extract on Staphylococcus aureus

PubMed Central

Mendes, V. S.; Sant'Anna, J. B.; Oliveira, S. C. C.; Maldonade, Iriani Rodrigues; Machado, Eleuza Rodrigues

2017-01-01

Background: Pterodon emarginatus is a tree of the Brazilian Savannah. The beans of this tree are used in folk medicine as anti-inflammatory preparations, especially for infections caused by Staphylococcus aureus. These bacteria can cause simple infections or serious illnesses such as pneumonia, meningitis, endocarditis, toxic shock syndrome, septicemia, and others. Objective: This study had the goal of verifying the effect of the essential oil (OE) from P. emarginatus on the inhibition of S. aureus in culture medium, i.e., “ in vitro” tests. Materials and Methods: The vegetable material was cut and crushed with a press. The OE was obtained by extraction using hexane, alcohol, and water. The P. emarginatus extracts obtained were used to evaluate the antimicrobial effect on S. aureus (ATCC 25923) by tests of well diffusion, disc diffusion, and microdilution. The strain used in the assays was maintained in brain heart infusion broth and nutrient agar until testing. Afterward, the bacteria were spread on agar plates with Mueller-Hinton agar medium. In the wells and on the paper discs, the OE suspensions were placed in the following volumes: 10, 15, 20, 25, 30, 40, and 80 μL and subsequently they were incubated at 35°C ± 2°C. After 24 h, the number of colony-forming unit was determined. Results: Pure OE and hydroalcoholic extract inhibited the growth of S. aureus, while aqueous extract had no effect on bacterial growth in all microbial methods used. Conclusion: Thus, the present study showed the potential of sucupira-based extracts against S. aureus growth, opening new perspectives for the evaluation of these bioactive compounds as phytopharmaceutical products. SUMMARY Plant extract act as antimicrobials to prevent and reduce bacterial contaminationBeans of Pterodon emarginatus has antibacterial propertiesExtraction with different solvents might implicate on the rate of bacterial deathThe effect of different microbiological methods (well diffusion, disc diffusion and microdilution) was evaluated on reducing CFUThe results showed by MBC that concentrations superior to 10% (v/v) using AC and 7.5% (v/v) using OE were necessary to eliminate colonies formedAccording to data of MIC, at 2.5% of AC and OE was enough to kill S. aureusThe well diffusion technique demonstrated better performance than disc diffusion test for OE and AC extractsHydroalcoholic and oil extracts of sucupira beans had highest effect against Staphylococcus aureusAqueous extract had no effect on bacterial growth in all microbial methods testedThe sucupira-based extracts is a promising source as herbal drug due to therapeutic value Abbreviations Used: OE: Essencial oil; AC: Hydroalcoholic oil extract; AQ: Aqueous extracts; MIC: Minimum inhibitory concentration; MBC: Minimum bactericidal concentration; CFU: Colony formed unit. PMID:29263627

Entropy-based artificial viscosity stabilization for non-equilibrium Grey Radiation-Hydrodynamics

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

Delchini, Marc O., E-mail: delchinm@email.tamu.edu; Ragusa, Jean C., E-mail: jean.ragusa@tamu.edu; Morel, Jim, E-mail: jim.morel@tamu.edu

2015-09-01

The entropy viscosity method is extended to the non-equilibrium Grey Radiation-Hydrodynamic equations. The method employs a viscous regularization to stabilize the numerical solution. The artificial viscosity coefficient is modulated by the entropy production and peaks at shock locations. The added dissipative terms are consistent with the entropy minimum principle. A new functional form of the entropy residual, suitable for the Radiation-Hydrodynamic equations, is derived. We demonstrate that the viscous regularization preserves the equilibrium diffusion limit. The equations are discretized with a standard Continuous Galerkin Finite Element Method and a fully implicit temporal integrator within the MOOSE multiphysics framework. The methodmore » of manufactured solutions is employed to demonstrate second-order accuracy in both the equilibrium diffusion and streaming limits. Several typical 1-D radiation-hydrodynamic test cases with shocks (from Mach 1.05 to Mach 50) are presented to establish the ability of the technique to capture and resolve shocks.« less

Modeling Cryptosporidium spp. Oocyst Inactivation in Bubble-Diffuser Ozone Contactors

DTIC Science & Technology

1998-07-01

requirements for Giardia lamblia (G. lamblia) and viruses under the Surface Water Treatment Rule (SWTR). Minimum CT requirements include relatively...parvum and C. muris ) oocysts in ozone bubble-diffuser contactors. The model is calibrated with semi-batch kinetic data, verified with pilot-scale

Characterizing molecular probes for diffusion measurements in the brain

PubMed Central

Kaur, Gurjinder; Hrabetova, Sabina; Guilfoyle, David N.; Nicholson, Charles; Hrabe, Jan

2008-01-01

Brain diffusion properties are at present most commonly evaluated by magnetic resonance (MR) diffusion imaging. MR cannot easily distinguish between the extracellular and intracellular signal components, but the older technique of Real-Time Iontophoresis (RTI) detects exclusively extracellular diffusion. Interpretation of the MR results would therefore benefit from auxiliary RTI measurements. This requires a molecular probe detectable by both techniques. Our aim was to specify a minimum set of requirements that such a diffusion probe should fulfill and apply it to two candidate probes: the cation tetramethylammonium (TMA+), used routinely in the RTI experiments, and the anion hexafluoroantimonate (SbF6−). Desirable characteristics of a molecular diffusion probe include predictable diffusion properties, stability, minimum interaction with cellular physiology, very slow penetration into the cells, and sufficiently strong and selective MR and RTI signals. These properties were evaluated using preparations of rat neocortical slices under normal and ischemic conditions, as well as solutions and agarose gel. While both molecules can be detected by MR and RTI, neither proved an ideal candidate. TMA+ was very stable but it penetrated into the cells and accumulated there within tens of minutes. SbF6− did not enter the cells as readily but it was not stable, particularly in ischemic tissue and at higher temperatures. Its presence also resulted in a decreased extracellular volume. These probe properties help to interpret previously published MR data on TMA+ diffusion and might play a role in other diffusion experiments obtained with them. PMID:18466980

Turboprop: improved PROPELLER imaging.

PubMed

Pipe, James G; Zwart, Nicholas

2006-02-01

A variant of periodically rotated overlapping parallel lines with enhanced reconstruction (PROPELLER) MRI, called turboprop, is introduced. This method employs an oscillating readout gradient during each spin echo of the echo train to collect more lines of data per echo train, which reduces the minimum scan time, motion-related artifact, and specific absorption rate (SAR) while increasing sampling efficiency. It can be applied to conventional fast spin-echo (FSE) imaging; however, this article emphasizes its application in diffusion-weighted imaging (DWI). The method is described and compared with conventional PROPELLER imaging, and clinical images collected with this PROPELLER variant are shown. Copyright 2006 Wiley-Liss, Inc.

Multiple echo multi-shot diffusion sequence.

PubMed

Chabert, Steren; Galindo, César; Tejos, Cristian; Uribe, Sergio A

2014-04-01

To measure both transversal relaxation time (T2 ) and diffusion coefficients within a single scan using a multi-shot approach. Both measurements have drawn interest in many applications, especially in skeletal muscle studies, which have short T2 values. Multiple echo single-shot schemes have been proposed to obtain those variables simultaneously within a single scan, resulting in a reduction of the scanning time. However, one problem with those approaches is the associated long echo read-out. Consequently, the minimum achievable echo time tends to be long, limiting the application of these sequences to tissues with relatively long T2 . To address this problem, we propose to extend the multi-echo sequences using a multi-shot approach, so that to allow shorter echo times. A multi-shot dual-echo EPI sequence with diffusion gradients and echo navigators was modified to include independent diffusion gradients in any of the two echoes. The multi-shot approach allows us to drastically reduce echo times. Results showed a good agreement for the T2 and mean diffusivity measurements with gold standard sequences in phantoms and in vivo data of calf muscles from healthy volunteers. A fast and accurate method is proposed to measure T2 and diffusion coefficients simultaneously, tested in vitro and in healthy volunteers. Copyright © 2013 Wiley Periodicals, Inc.

Threshold thickness for applying diffusion equation in thin tissue optical imaging

NASA Astrophysics Data System (ADS)

Zhang, Yunyao; Zhu, Jingping; Cui, Weiwen; Nie, Wei; Li, Jie; Xu, Zhenghong

2014-08-01

We investigated the suitability of the semi-infinite model of the diffusion equation when using diffuse optical imaging (DOI) to image thin tissues with double boundaries. Both diffuse approximation and Monte Carlo methods were applied to simulate light propagation in the thin tissue model with variable optical parameters and tissue thicknesses. A threshold value of the tissue thickness was defined as the minimum thickness in which the semi-infinite model exhibits the same reflected intensity as that from the double-boundary model and was generated as the final result. In contrast to our initial hypothesis that all optical properties would affect the threshold thickness, our results show that only absorption coefficient is the dominant parameter and the others are negligible. The threshold thickness decreases from 1 cm to 4 mm as the absorption coefficient grows from 0.01 mm-1 to 0.2 mm-1. A look-up curve was derived to guide the selection of the appropriate model during the optical diagnosis of thin tissue cancers. These results are useful in guiding the development of the endoscopic DOI for esophageal, cervical and colorectal cancers, among others.

Regression analysis and categorical agreement of fluconazole disk zone diameters and minimum inhibitory concentration by broth microdilution of clinical isolates of Candida.

PubMed

Aggarwal, P; Kashyap, B

2017-06-01

Rampant use of fluconazole in Candida infections has led to predominance of less susceptible non-albicans Candida over Candida albicans. The aim of the study was to determine if zone diameters around fluconazole disk can be used to estimate the minimum inhibitory concentration (MIC) for clinical isolates of Candida species and vice versa. Categorical agreement between the Clinical & Laboratory Standards Institute (CLSI) recommended disk diffusion and CLSI broth microdilution method was sought for. Antifungal susceptibility testing by disk diffusion and Broth microdilution was done as per CLSI document M44-S3 and CLSI document M27-S4 for Candida isolates respectively. Regression analysis correlating zone diameters to MIC value was done. Pearson's correlation coefficient was calculated to determine correlation between disk zone diameters and MICs. Candida albicans (33.3%) was clearly outnumbered by other non-albicans species predominantly Candida tropicalis (42.5%) and Candida glabrata (18.4%). Ten percent of the strains were resistant to fluconazole by disk diffusion and 13% by broth microdilution. MIC range for Candida albicans and Candida tropicalis ranged from≤0.25-64μg/ml while that of Candida glabrata ranged from≤0.25-128μg/ml. Categorical agreement between disk diffusion and broth microdilution was 86.8%. Pearson's coefficient of correlation was -0.5975 indicating moderate negative correlation between the two variables. Zone sizes can be used to estimate the MIC values, although with limited accuracy. There should be a constant effort to upgrade the guidelines in view of new clinical data, and laboratories should make an active effort to incorporate them. Copyright © 2017 Elsevier Masson SAS. All rights reserved.

Comparative Study of Hydroalcoholic Extracts of Momordica charantia L. against Foodborne Pathogens

PubMed Central

Rakholiya, Kalpna; Vaghela, P.; Rathod, T.; Chanda, Sumitra

2014-01-01

The antimicrobial effect of 24 different hydroalcoholic extracts (100, 75, 50 and 25% methanol and water) obtained from four parts (leaf+stem (aerial), peel, pulp and seed) of Momordica charantia L. were investigated against five Gram-positive, six Gram-negative and four fungal strains. The extraction was done by individual cold percolation method using hexane, different hydroalcoholic solvent (100, 75, 50 and 25% methanol) and water. The antimicrobial activity was done by agar well diffusion assay. The extracts, which showed >15 mm zone of inhibition, were further screened to determine minimum inhibitory concentration and minimum bactericidal concentration using a broth dilution method performed in 96-well microtitre plate. The extractive yield was highest in aqueous extracts of all the four parts closely followed by 25% methanol. Micrococcus flavus was the most susceptible Gram-positive bacteria and Pseudomonas testosteroni was the most susceptible Gram-negative bacteria. The highest antibacterial activity was shown by 100% methanol. The Gram-negative Pseudomonas spp. was more susceptible towards all the extracts than the Gram-positive bacteria or fungal strains investigated. One hundred percent and 50% methanol extracts of seed showed lowest minimum inhibitory concentration and minimum bactericidal concentration values, that is <39 and 625 μg/ml, respectively, against Pseudomonas pictorum. Therefore, these extracts would be of interest in the control of Pseudomonas spp. in food industry as well as used for therapeutic purposes. PMID:24843188

In vitro antimicrobial activity of Pistacia lentiscus L. edible oil and phenolic extract.

PubMed

Mezni, F; Aouadhi, C; Khouja, M L; Khaldi, A; Maaroufi, A

2015-01-01

Pistacia lentiscus L. is known in some Tunisian forest area by its fixed oil used in traditional medicine as an antiseptic product. This investigation is the first to study the antimicrobial activity of P.lentiscus edible oil and its phenolic extract. Oil was extracted from fruits harvested from six provenances located in Tunisia. The antimicrobial activity was tested using disc diffusion assay and the broth dilution method. Kbouch and Sidi Zid oils were most efficient (p < 0.003) against, respectively, Staphylococcus aureus and Aspergillus niger with an inhibition zone of 9.33 mm. The phenolic extract had the largest spectrum of sensitive microorganisms. The minimum inhibitory concentration and minimum bactericidal concentration results showed that all strains were inhibited by both oil and extract.

A Minimum-Residual Finite Element Method for the Convection-Diffusion Equation

DTIC Science & Technology

2013-05-01

4p . We note that these two choices of discretization for V are not mutually exclusive, and that novel choices for Vh are likely the key to yielding...the inside with the positive- definite operator A, which is precisely the discrete system that arises under the optimal test function framework of DPG...converts the fine-scale problem into a symmetric-positive definite one, allowing for a well-behaved subgrid model of fine scale behavior. We begin again

An Apparent Diffusion Coefficient Histogram Method Versus a Traditional 2-Dimensional Measurement Method for Identifying Non-Puerperal Mastitis From Breast Cancer at 3.0 T.

PubMed

Tang, Qi; Li, Qiang; Xie, Dong; Chu, Ketao; Liu, Lidong; Liao, Chengcheng; Qin, Yunying; Wang, Zheng; Su, Danke

2018-05-21

This study aimed to investigate the utility of a volumetric apparent diffusion coefficient (ADC) histogram method for distinguishing non-puerperal mastitis (NPM) from breast cancer (BC) and to compare this method with a traditional 2-dimensional measurement method. Pretreatment diffusion-weighted imaging data at 3.0 T were obtained for 80 patients (NPM, n = 27; BC, n = 53) and were retrospectively assessed. Two readers measured ADC values according to 2 distinct region-of-interest (ROI) protocols. The first protocol included the generation of ADC histograms for each lesion, and various parameters were examined. In the second protocol, 3 freehand (TF) ROIs for local lesions were generated to obtain a mean ADC value (defined as ADC-ROITF). All of the ADC values were compared by an independent-samples t test or the Mann-Whitney U test. Receiver operating characteristic curves and a leave-one-out cross-validation method were also used to determine diagnostic deficiencies of the significant parameters. The ADC values for NPM were characterized by significantly higher mean, 5th to 95th percentiles, and maximum and mode ADCs compared with the corresponding ADCs for BC (all P < 0.05). However, the minimum, skewness, and kurtosis ADC values, as well as ADC-ROITF, did not significantly differ between the NPM and BC cases. Thus, the generation of volumetric ADC histograms seems to be a superior method to the traditional 2-dimensional method that was examined, and it also seems to represent a promising image analysis method for distinguishing NPM from BC.

Characterization of diffuse orbital mass using Apparent diffusion coefficient in 3-tesla MRI.

PubMed

ElKhamary, Sahar M; Galindo-Ferreiro, Alicia; AlGhafri, Laila; Khandekar, Rajiv; Schellini, Silvana Artioli

2018-01-01

To evaluate if the apparent diffusion coefficient (ADC) value in diffusion-weighted magnetic resonance imaging (DW-MRI) improves the diagnostic accuracy of diffuse orbital masses. ADC DW-MRI was used to evaluate cases of diffuse orbital masses at our institution from 2000 to 2015. Lesions were grouped according to histopathologic diagnosis as, benign, pre-malignant and malignant. Lymphoproliferative lesions were further subgrouped as lymphoma or other lymphoproliferative lesions. The validity of the ADC value for the diffuse orbital mass was compared between groups. The area under curve (AUC) was also calculated. Thirty-nine cases of diffuse orbital masses were evaluated. The median ADC was 0.58 (25% quartile 0.48; minimum: 0.45; maximum: 1.72 × 10 (-3) ) for the malignant tumors and 1.19 (25% quartile 0.7; minimum: 0.5; maximum: 1.95 × 10 (-3)  mm (2)  s (-1) ) for benign lesions. This difference in ADC between lesions was statistically significant (Mann Whitney U test P < 0.001). The median ADC was 0.51 (25% quartile 0.48) for lymphomas and 0.9 (25% quartile 0.7) for other lymphoproliferative lesions. This difference in ADC was statistically significant (Mann Whitney U test P = 0.02). An ADC value of 0.8 × 10 (-3)  mm (2)  s (-1) was noted as the ideal threshold value for differentiating malignant from benign diffuse orbital masses. The validity of ADC in predicting a malignant or benign diffuse orbital mass had a sensitivity of 87%, specificity of 67% and accuracy of 88%. ADC is a promising imaging metric to characterize malignant and benign diffuse orbital masses and to distinguish lymphomas from other non-lymphoproliferative lesions.

49 CFR 238.123 - Emergency roof access.

Code of Federal Regulations, 2011 CFR

2011-10-01

... minimum opening of 26 inches longitudinally (i.e., parallel to the longitudinal axis of the car) by 24... be free of any rigid secondary structure (e.g., a diffuser or diffuser support, lighting back fixture... means of a structural weak point, it shall be permissible to cut through interior panels, liners, or...

Analysis of the electron-beam-induced current of a polycrystalline p-n junction when the diffusion lengths of the material on either side of a grain boundary differ

NASA Technical Reports Server (NTRS)

Von Roos, O.; Luke, K. L.

1984-01-01

The short circuit current generated by the electron beam of a scanning electron microscope in p-n junctions is reduced by enhanced recombination at grain boundaries in polycrystalline material. Frequently, grain boundaries separate the semiconductor into regions possessing different minority carrier life times. This markedly affects the short circuit current I(sc) as a function of scanning distance from the grain boundary. It will be shown theoretically that (1) the minimum of the I(sc) in crossing the grain boundary with the scanning electron beam is shifted away from the grain boundary toward the region with smaller life time (shorter diffusion length), (2) the magnitude of the minimum differs markedly from those calculated under the assumption of equal diffusion lengths on either side of the grain boundary, and (3) the minimum disappears altogether for small surface recombination velocities (s less than 10,000 cm/s). These effects become negligible, however, for large recombination velocities s at grain boundaries. For p-type silicon this happens for s not less than 100,000 cm/s.

A time-efficient acquisition protocol for multipurpose diffusion-weighted microstructural imaging at 7 Tesla.

PubMed

Sepehrband, Farshid; O'Brien, Kieran; Barth, Markus

2017-12-01

Several diffusion-weighted MRI techniques have been developed and validated during the past 2 decades. While offering various neuroanatomical inferences, these techniques differ in their proposed optimal acquisition design, preventing clinicians and researchers benefiting from all potential inference methods, particularly when limited time is available. This study reports an optimal design that enables for a time-efficient diffusion-weighted MRI acquisition scheme at 7 Tesla. The primary audience of this article is the typical end user, interested in diffusion-weighted microstructural imaging at 7 Tesla. We tested b-values in the range of 700 to 3000 s/mm 2 with different number of angular diffusion-encoding samples, against a data-driven "gold standard." The suggested design is a protocol with b-values of 1000 and 2500 s/mm 2 , with 25 and 50 samples, uniformly distributed over two shells. We also report a range of protocols in which the results of fitting microstructural models to the diffusion-weighted data had high correlation with the gold standard. We estimated minimum acquisition requirements that enable diffusion tensor imaging, higher angular resolution diffusion-weighted imaging, neurite orientation dispersion, and density imaging and white matter tract integrity across whole brain with isotropic resolution of 1.8 mm in less than 11 min. Magn Reson Med 78:2170-2184, 2017. © 2017 International Society for Magnetic Resonance in Medicine. © 2017 International Society for Magnetic Resonance in Medicine.

Antimicrobial susceptibility pattern of clinical isolates of Burkholderia pseudomallei in Bangladesh.

PubMed

Dutta, Subarna; Haq, Sabah; Hasan, Mohammad Rokibul; Haq, Jalaluddin Ashraful

2017-07-20

Melioidosis an infectious disease, caused by a Gram negative bacterium called Burkholderia pseudomallei, is endemic in Bangladesh. This organism is sensitive to limited number of antimicrobial agents and need prolonged treatment. There is no comprehensive data on the antimicrobial susceptibility profile of B. pseudomallei isolated in Bangladesh over last several years. The present study aimed to determine the antimicrobial susceptibility pattern of B. pseudomallei isolated in a tertiary care hospital of Dhaka city from 2009 to 2015. All B. pseudomallei isolated from melioidosis patients over a period of 7 years (2009-2015) in the Department of Microbiology of a 725-bed tertiary care referral hospital in Dhaka city, Bangladesh were included in the study. B. pseudomallei was identified by Gram stain, culture, specific biochemical tests, serology and PCR using specific primers constructed from 16s rRNA region of B. pseudomallei. Antimicrobial susceptibility to specific agents was determined by disk diffusion and minimum inhibitory concentration methods. A total of 20 isolates of B. pseudomallei which were isolated from patients coming from different geographic locations of Bangladesh were included in the study. All the isolates were uniformly sensitive (100%) to ceftazidime, imipenem, piperacillin-tazobactam, amoxicillin-clavulanic acid and tetracycline by both disk diffusion and MIC methods. Two strains were resistant to trimethoprim-sulfamethoxazole by disk diffusion method but were sensitive by MIC method. The MIC 50 and MIC 90 values of the above antimicrobial agents were almost similar. All the isolates were resistant to amikacin by both MIC and disk diffusion methods. The results of the study suggest that B. pseudomallei prevalent in Bangladesh were still susceptible to all recommended antimicrobial agents used for the treatment of melioidosis. However, regular monitoring is needed to detect any emergence of resistance and shifting of MIC 50 and MIC 90 values.

A secure image encryption method based on dynamic harmony search (DHS) combined with chaotic map

NASA Astrophysics Data System (ADS)

Mirzaei Talarposhti, Khadijeh; Khaki Jamei, Mehrzad

2016-06-01

In recent years, there has been increasing interest in the security of digital images. This study focuses on the gray scale image encryption using dynamic harmony search (DHS). In this research, first, a chaotic map is used to create cipher images, and then the maximum entropy and minimum correlation coefficient is obtained by applying a harmony search algorithm on them. This process is divided into two steps. In the first step, the diffusion of a plain image using DHS to maximize the entropy as a fitness function will be performed. However, in the second step, a horizontal and vertical permutation will be applied on the best cipher image, which is obtained in the previous step. Additionally, DHS has been used to minimize the correlation coefficient as a fitness function in the second step. The simulation results have shown that by using the proposed method, the maximum entropy and the minimum correlation coefficient, which are approximately 7.9998 and 0.0001, respectively, have been obtained.

Chemical composition and antibacterial activity of methanolic extract and essential oil of Iranian Teucrium polium against some of phytobacteria.

PubMed

Purnavab, S; Ketabchi, S; Rowshan, V

2015-01-01

The antibacterial activity of essential oil and methanolic extract of Teucrium polium was determined against Pseudomonas aeruginosa, Pantoea agglomerans, Brenneria nigrifluens, Rhizobium radiobacter, Rhizobium vitis, Streptomyces scabies, Ralstonia solanacearum, Xanthomonas campestris and Pectobacterium cartovorum by disc diffusion method. Minimum inhibitory concentration and minimum bactericidal concentration were determined by using the serial dilution method. Chemical composition of essential oil and methanolic extract was determined by GC-MS and HPLC. α-Pinene (25.769%) and myrcene (12.507) were of the highest percentage in T. polium essential oil, and sinapic acid (15.553 mg/g) and eugenol (6.805 mg/g) were the major compounds in the methanolic extract. Our results indicate that both methanolic extract and essential oil did not show antibacterial activity against P. aeruginosa. Also the essential oil did not show antibacterial activity against P. cartovorum. In general, both methanolic extract and essential oil showed the same antibacterial activity against R. solanacearum, P. agglomerans, B. nigrifluens and S. scabies.

Meta-analysis of diffusion metrics for the prediction of tumor grade in gliomas.

PubMed

Miloushev, V Z; Chow, D S; Filippi, C G

2015-02-01

Diffusion tensor metrics are potential in vivo quantitative neuroimaging biomarkers for the characterization of brain tumor subtype. This meta-analysis analyzes the ability of mean diffusivity and fractional anisotropy to distinguish low-grade from high-grade gliomas in the identifiable tumor core and the region of peripheral edema. A meta-analysis of articles with mean diffusivity and fractional anisotropy data for World Health Organization low-grade (I, II) and high-grade (III, IV) gliomas, between 2000 and 2013, was performed. Pooled data were analyzed by using the odds ratio and mean difference. Receiver operating characteristic analysis was performed for patient-level data. The minimum mean diffusivity of high-grade gliomas was decreased compared with low-grade gliomas. High-grade gliomas had decreased average mean diffusivity values compared with low-grade gliomas in the tumor core and increased average mean diffusivity values in the peripheral region. High-grade gliomas had increased FA values compared with low-grade gliomas in the tumor core, decreased values in the peripheral region, and a decreased fractional anisotropy difference between the tumor core and peripheral region. The minimum mean diffusivity differs significantly with respect to the World Health Organization grade of gliomas. Statistically significant effects of tumor grade on average mean diffusivity and fractional anisotropy were observed, supporting the concept that high-grade tumors are more destructive and infiltrative than low-grade tumors. Considerable heterogeneity within the literature may be due to systematic factors in addition to underlying lesion heterogeneity. © 2015 by American Journal of Neuroradiology.

Inhibitory Effects of Pterodon emarginatus Bean Oil and Extract on Staphylococcus aureus.

PubMed

Mendes, V S; Sant'Anna, J B; Oliveira, S C C; Maldonade, Iriani Rodrigues; Machado, Eleuza Rodrigues

2017-01-01

Pterodon emarginatus is a tree of the Brazilian Savannah. The beans of this tree are used in folk medicine as anti-inflammatory preparations, especially for infections caused by Staphylococcus aureus . These bacteria can cause simple infections or serious illnesses such as pneumonia, meningitis, endocarditis, toxic shock syndrome, septicemia, and others. This study had the goal of verifying the effect of the essential oil (OE) from P. emarginatus on the inhibition of S. aureus in culture medium, i.e., " in vitro " tests. The vegetable material was cut and crushed with a press. The OE was obtained by extraction using hexane, alcohol, and water. The P. emarginatus extracts obtained were used to evaluate the antimicrobial effect on S. aureus (ATCC 25923) by tests of well diffusion, disc diffusion, and microdilution. The strain used in the assays was maintained in brain heart infusion broth and nutrient agar until testing. Afterward, the bacteria were spread on agar plates with Mueller-Hinton agar medium. In the wells and on the paper discs, the OE suspensions were placed in the following volumes: 10, 15, 20, 25, 30, 40, and 80 μL and subsequently they were incubated at 35°C ± 2°C. After 24 h, the number of colony-forming unit was determined. Pure OE and hydroalcoholic extract inhibited the growth of S. aureus , while aqueous extract had no effect on bacterial growth in all microbial methods used. Thus, the present study showed the potential of sucupira-based extracts against S. aureus growth, opening new perspectives for the evaluation of these bioactive compounds as phytopharmaceutical products. Plant extract act as antimicrobials to prevent and reduce bacterial contaminationBeans of Pterodon emarginatus has antibacterial propertiesExtraction with different solvents might implicate on the rate of bacterial deathThe effect of different microbiological methods (well diffusion, disc diffusion and microdilution) was evaluated on reducing CFUThe results showed by MBC that concentrations superior to 10% (v/v) using AC and 7.5% (v/v) using OE were necessary to eliminate colonies formedAccording to data of MIC, at 2.5% of AC and OE was enough to kill S. aureus The well diffusion technique demonstrated better performance than disc diffusion test for OE and AC extractsHydroalcoholic and oil extracts of sucupira beans had highest effect against Staphylococcus aureus Aqueous extract had no effect on bacterial growth in all microbial methods testedThe sucupira-based extracts is a promising source as herbal drug due to therapeutic value Abbreviations Used: OE: Essencial oil; AC: Hydroalcoholic oil extract; AQ: Aqueous extracts; MIC: Minimum inhibitory concentration; MBC: Minimum bactericidal concentration; CFU: Colony formed unit.

MODULATION OF GALACTIC ELECTRONS IN THE HELIOSPHERE DURING THE UNUSUAL SOLAR MINIMUM OF 2006–2009: A MODELING APPROACH

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

Potgieter, M. S.; Vos, E. E.; Munini, R.

The last solar minimum activity period, and the consequent minimum modulation conditions for cosmic rays, was unusual. The highest levels of Galactic protons were recorded at Earth in late 2009 in contrast to expectations. A comprehensive model was used to study the proton modulation for the period from 2006 to 2009 in order to determine what basic processes were responsible for solar modulation during this period and why it differs from proton modulation during previous solar minimum modulation periods. This established model is now applied to studying the solar modulation of electron spectra as observed for 80 MeV–30 GeV bymore » the PAMELA space detector from mid-2006 to the end of 2009. Over this period the heliospheric magnetic field had decreased significantly until the end of 2009 while the waviness of the heliospheric current sheet decreased moderately and the observed electron spectra increased by a factor of ∼1.5 at 1.0 GeV to ∼3.5 at 100 MeV. In order to reproduce the modulation evident from seven consecutive semesters, the diffusion coefficients had to increase moderately while maintaining the basic rigidity dependence. It is confirmed that the main diffusion coefficients are independent of rigidity below ∼0.5 GV, while the drift coefficient had to be reduced below this value. The 2006–2009 solar minimum epoch indeed was different than previously observed minima, at least since the beginning of the space exploration era. This period could be called “diffusion-dominated” as was also found for the modulation of protons.« less

Atomistic modeling of dropwise condensation

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

Sikarwar, B. S., E-mail: bssikarwar@amity.edu; Singh, P. L.; Muralidhar, K.

The basic aim of the atomistic modeling of condensation of water is to determine the size of the stable cluster and connect phenomena occurring at atomic scale to the macroscale. In this paper, a population balance model is described in terms of the rate equations to obtain the number density distribution of the resulting clusters. The residence time is taken to be large enough so that sufficient time is available for all the adatoms existing in vapor-phase to loose their latent heat and get condensed. The simulation assumes clusters of a given size to be formed from clusters of smallermore » sizes, but not by the disintegration of the larger clusters. The largest stable cluster size in the number density distribution is taken to be representative of the minimum drop radius formed in a dropwise condensation process. A numerical confirmation of this result against predictions based on a thermodynamic model has been obtained. Results show that the number density distribution is sensitive to the surface diffusion coefficient and the rate of vapor flux impinging on the substrate. The minimum drop radius increases with the diffusion coefficient and the impinging vapor flux; however, the dependence is weak. The minimum drop radius predicted from thermodynamic considerations matches the prediction of the cluster model, though the former does not take into account the effect of the surface properties on the nucleation phenomena. For a chemically passive surface, the diffusion coefficient and the residence time are dependent on the surface texture via the coefficient of friction. Thus, physical texturing provides a means of changing, within limits, the minimum drop radius. The study reveals that surface texturing at the scale of the minimum drop radius does not provide controllability of the macro-scale dropwise condensation at large timescales when a dynamic steady-state is reached.« less

Linearized finite-element method solution of the ion-exchange nonlinear diffusion model

NASA Astrophysics Data System (ADS)

Badr, Mohamed M.; Swillam, Mohamed A.

2017-04-01

Ion-exchange process is one of the most common techniques used in glass waveguide fabrication. This has many advantages, such as low cost, ease of implementation, and simple equipment requirements. The technology is based on the substitution of some of the host ions in the glass (typically Na+) with other ions that possess different characteristics in terms of size and polarizability. The newly diffused ions produce a region with a relatively higher refractive index in which the light could be guided. A critical issue arises when it comes to designing such waveguides, which is carefully and precisely determining the resultant index profile. This task has been proven to be hideous as the process is generally governed by a nonlinear diffusion model with no direct general analytical solution. Furthermore, numerical solutions become unreliable-in terms of stability and mean squared error-in some cases, especially the K+-Na+ ion-exchanged waveguide, which is the best candidate to produce waveguides with refractive index differences compatible with those of the commercially available optical fibers. Linearized finite-element method formulations were used to provide a reliable tool that could solve the nonlinear diffusion model of the ion-exchange in both one- and two-dimensional spaces. Additionally, the annealed channel waveguide case has been studied. In all cases, unprecedented stability and minimum mean squared error could be achieved.

A numerical method to solve the 1D and the 2D reaction diffusion equation based on Bessel functions and Jacobian free Newton-Krylov subspace methods

NASA Astrophysics Data System (ADS)

Parand, K.; Nikarya, M.

2017-11-01

In this paper a novel method will be introduced to solve a nonlinear partial differential equation (PDE). In the proposed method, we use the spectral collocation method based on Bessel functions of the first kind and the Jacobian free Newton-generalized minimum residual (JFNGMRes) method with adaptive preconditioner. In this work a nonlinear PDE has been converted to a nonlinear system of algebraic equations using the collocation method based on Bessel functions without any linearization, discretization or getting the help of any other methods. Finally, by using JFNGMRes, the solution of the nonlinear algebraic system is achieved. To illustrate the reliability and efficiency of the proposed method, we solve some examples of the famous Fisher equation. We compare our results with other methods.

A data-drive analysis for heavy quark diffusion coefficient

NASA Astrophysics Data System (ADS)

Xu, Yingru; Nahrgang, Marlene; Cao, Shanshan; Bernhard, Jonah E.; Bass, Steffen A.

2018-02-01

We apply a Bayesian model-to-data analysis on an improved Langevin framework to estimate the temperature and momentum dependence of the heavy quark diffusion coefficient in the quark-gluon plasma (QGP). The spatial diffusion coefficient is found to have a minimum around 1-3 near Tc in the zero momentum limit, and has a non-trivial momentum dependence. With the estimated diffusion coefficient, our improved Langevin model is able to simultaneously describe the D-meson RAA and v2 in three different systems at RHIC and the LHC.

Antimicrobial effects of Citrus sinensis peel extracts against dental caries bacteria: An in vitro study

PubMed Central

Shetty, Sapna B.; Mahin-Syed-Ismail, Prabu; Varghese, Shaji; Thomas-George, Bibin; Kandathil- Thajuraj, Pathinettam; Baby, Deepak; Haleem, Shaista; Sreedhar, Sreeja

2016-01-01

Background Ethnomedicine is gaining admiration since years but still there is abundant medicinal flora which is unrevealed through research. The study was conducted to assess the in vitro antimicrobial potential and also determine the minimum inhibitory concentration (MIC) of Citrus sinensis peel extracts with a view of searching a novel extract as a remedy for dental caries pathogens. Material and Methods Aqueous and ethanol (cold and hot) extracts prepared from peel of Citrus sinensis were screened for in vitro antimicrobial activity against Streptococcus mutans and Lactobacillus acidophilus, using agar well diffusion method. The lowest concentration of every extract considered as the minimal inhibitory concentration (MIC) values were determined for both test organisms. One way ANOVA with Post Hoc Bonferroni test was applied for statistical analysis. Confidence level and level of significance were set at 95% and 5% respectively. Results Dental caries pathogens were inhibited most by hot ethanolic extract of Citrus sinensispeel followed by cold ethanolic extract. Aqueous extracts were effective at very high concentrations. Minimum inhibitory concentration of hot and cold ethanolic extracts of Citrus sinensis peel ranged between 12-15 mg/ml against both the dental caries pathogens. Conclusions Citrus sinensispeels extract was found to be effective against dental caries pathogens and contain compounds with therapeutic potential. Nevertheless, clinical trials on the effect of these plants are essential before advocating large-scale therapy. Key words:Agar well diffusion, antimicrobial activity, dental caries, Streptococcus mutans, Lactobacillus acidophilus. PMID:26855710

Demonstration and Validation of a Regenerated Cellulose Dialysis Membrane Diffusion Sampler for Monitoring Ground Water Quality and Remediation Progress at DoD Sites

DTIC Science & Technology

2007-08-30

ITRC Interstate Technology Regulatory Council LRL Laboratory reporting level LDPE Low-density polyethylene MDL Minimum detection limit MNA...diameter of the well. Another diffusion membrane sampler design consists of a tubular-shaped bag made of flexible low-density polyethylene ( LDPE ...

Phytochemical characterization, antimicrobial activity and reducing potential of seed oil, latex, machine oil and presscake of Jatropha curcas

PubMed Central

Sharma, Amit Kumar; Gangwar, Mayank; Kumar, Dharmendra; Nath, Gopal; Kumar Sinha, Akhoury Sudhir; Tripathi, Yamini Bhushan

2016-01-01

Objective: This study aims to evaluate the antimicrobial activity, phytochemical studies and thin layer chromatography analysis of machine oil, hexane extract of seed oil and methanol extract of presscake & latex of Jatropha curcas Linn (family Euphorbiaceae). Materials and Methods: J. curcas extracts were subjected to preliminary qualitative phytochemical screening to detect the major phytochemicals followed by its reducing power and content of phenol and flavonoids in different fractions. Thin layer chromatography was also performed using different solvent systems for the analysis of a number of constituents in the plant extracts. Antimicrobial activity was evaluated by the disc diffusion method, while the minimum inhibitory concentration, minimum bactericidal concentration and minimum fungicidal concentration were calculated by micro dilution method. Results: The methanolic fraction of latex and cake exhibited marked antifungal and antibacterial activities against Gram-positive and Gram-negative bacteria. Phytochemical analysis revealed the presence of alkaloids, saponins, tannins, terpenoids, steroids, glycosides, phenols and flavonoids. Reducing power showed dose dependent increase in concentration compared to standard Quercetin. Furthermore, this study recommended the isolation and separation of bioactive compounds responsible for the antibacterial activity which would be done by using different chromatographic methods such as high-performance liquid chromatography (HPLC), GC-MS etc. Conclusion: The results of the above study suggest that all parts of the plants possess potent antibacterial activity. Hence, it is important to isolate the active principles for further testing of antimicrobial and other biological efficacy. PMID:27516977

Copper ion as a new leakage tracer.

PubMed

Modaresi, J; Baharizade, M; Shareghi, A; Ahmadi, M; Daneshkazemi, A

2013-12-01

Most failures of root canal treatments are caused by bacteria. Studies showed that the most common cause of endodontic failures were the incomplete obturation of the root canal and the lack of adequate apical seal. Some in-vitro methods are used to estimate sealing quality, generally by measuring microleakage that allows the tracer agent to penetrate the filled canal. Conventional methods of evaluating the seal of endodontically treated teeth are complicated and have some drawbacks. We used copper ion diffusion method to assess the leakage and the results were compared to dye penetration method. The crowns of 21 extracted teeth were cut off at the CEJ level. After preparing the canals, the teeth were placed in tubes containing saline. They were divided randomly into 15 experimental cases; 3 positive and 3 negative controls. Positive controls were filled by single cone without sealer while the experimental and the negative control groups were filled by lateral technique. The coronal portion of gutta was removed and 9mm was left. The external surface of each tooth was coated with nail polish. Two millimeters of apical portion was immersed into 9ml of distilled water and 0.3ml of CuSO4 solution was injected into the coronal portion. After 2 days, copper sulfate was measured by an atomic absorption spectrophotometer. The teeth were then immersed in 2% methylene blue for 24 hours, sectioned and the extent of dye penetration was measured by a stereomicroscope. The maximum and minimum recorded copper ion concentrations for the experimental group were 18.37 and 2.87ppm respectively. The maximum and minimum recorded dye penetrations for the experimental group were 8.5 and 3.5mm respectively. The statistical analysis, adopting paired samples test, showed poor correlation between average recorded results of two methods. Based on our results, there was no significant correlation between the dye penetration and the copper ion diffusion methods.

Principle component analysis (PCA) for investigation of relationship between population dynamics of microbial pathogenesis, chemical and sensory characteristics in beef slices containing Tarragon essential oil.

PubMed

Alizadeh Behbahani, Behrooz; Tabatabaei Yazdi, Farideh; Shahidi, Fakhri; Mortazavi, Seyed Ali; Mohebbi, Mohebbat

2017-04-01

Principle component analysis (PCA) was employed to examine the effect of the exerted treatments on the beef shelf life as well as discovering the correlations between the studied responses. Considering the variability of the dimensions of the responses, correlation coefficients were applied to form the matrix and extract the eigenvalue. Antimicrobial effect was evaluated on 10 pathogenic microorganisms through the methods of hole-plate diffusion method, disk diffusion method, pour plate method, minimum inhibitory concentration and minimum bactericidal/fungicidal concentration. Antioxidant potential and total phenolic content were examined through the method of 2,2-diphenyl-1-picrylhydrazyl (DPPH) and Folin-Ciocalteu method, respectively. The components were identified through gas chromatography and gas chromatography/mass spectrometry. Barhang seed mucilage (BSM) based edible coating containing 0, 0.5, 1 and 1.5% (w/w) Tarragon (T) essential oil mix were applied on beef slices to control the growth of pathogenic microorganisms. Microbiological (total viable count, psychrotrophic count, Escherichia coli, Staphylococcus aureus and fungi), chemical (thiobarbituric acid, peroxide value and pH) and sensory characteristics (odor, color and overall acceptability) analysis measurements were made during the storage periodically. PCA was employed to examine the effect of the exerted treatments on the beef shelf life as well as discovering the correlations between the studied responses. Considering the variability of the dimensions of the responses, correlation coefficients were applied to form the matrix and extract the eigenvalue. The PCA showed that the properties of the uncoated meat samples on the 9th, 12th, 15th and 18th days of storage are continuously changing independent of the exerted treatments on the other samples. This reveals the effect of the exerted treatments on the samples. Copyright © 2017 Elsevier Ltd. All rights reserved.

Optimizing the Placement of Burnable Poisons in PWRs

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

Yilmaz, Serkan; Ivanov, Kostadin; Levine, Samuel

2005-07-15

The principal focus of this work is on developing a practical tool for designing the minimum amount of burnable poisons (BPs) for a pressurized water reactor using a typical Three Mile Island Unit 1 2-yr cycle as the reference design. The results of this study are to be applied to future reload designs. A new method, the Modified Power Shape Forced Diffusion (MPSFD) method, is presented that initially computes the BP cross section to force the power distribution into a desired shape. The method employs a simple formula that expresses the BP cross section as a function of the differencemore » between the calculated radial power distributions (RPDs) and the limit set for the maximum RPD. This method places BPs into all fresh fuel assemblies (FAs) having an RPD greater than the limit. The MPSFD method then reduces the BP content by reducing the BPs in fresh FAs with the lowest RPDs. Finally, the minimum BP content is attained via a heuristic fine-tuning procedure.This new BP design program has been automated by incorporating the new MPSFD method in conjunction with the heuristic fine-tuning program. The program has automatically produced excellent results for the reference core, and has the potential to reduce fuel costs and save manpower.« less

Nonelectrolyte diffusion across lipid bilayer systems

PubMed Central

1976-01-01

The permeability coefficients of a homologous series of amides from formamide through valeramide have been measured in spherical bilayers prepared by the method described by Jung. They do not depend directly on the water:ether partition coefficient which increases regularly with chain length. Instead there is a minimum at acetamide. This has been ascribed to the effect of steric hindrance on diffusion within the bilayer which increases with solute molar volume. This factor is of the same magnitude, though opposite in sign to the effect of lipid solubility, thus accounting for the minimum. The resistance to passage across the interface has been compared to the resistance to diffusion within the membrane. As the solute chain length increases the interface becomes more important, until for valeramide it comprises about 90% of the total resistance. Interface resistance is also important in urea permeation, causing urea to permeate much more slowly than an amide of comparable size, after allowance is made for the difference in the water:ether partition coefficient. Amide permeation coefficients have been compared with relative liposome permeation data measured by the rate of liposome swelling. The ratios of the two measures of permeation vary between 3 and 16 for the homologous amides. The apparent enthalpy of liposome permeation has been measured and found to be in the neighborhood of 12 kcal mol-1 essentially independent of chain length. Comparison of the bilayer permeability coefficients with those of red cells shows that red cell permeation by the lipophilic solutes resembles that of the bilayers, whereas permeation by the hydrophilic solutes differs significantly. PMID:1245835

A spectral radius scaling semi-implicit iterative time stepping method for reactive flow simulations with detailed chemistry

NASA Astrophysics Data System (ADS)

Xie, Qing; Xiao, Zhixiang; Ren, Zhuyin

2018-09-01

A spectral radius scaling semi-implicit time stepping scheme has been developed for simulating unsteady compressible reactive flows with detailed chemistry, in which the spectral radius in the LUSGS scheme has been augmented to account for viscous/diffusive and reactive terms and a scalar matrix is proposed to approximate the chemical Jacobian using the minimum species destruction timescale. The performance of the semi-implicit scheme, together with a third-order explicit Runge-Kutta scheme and a Strang splitting scheme, have been investigated in auto-ignition and laminar premixed and nonpremixed flames of three representative fuels, e.g., hydrogen, methane, and n-heptane. Results show that the minimum species destruction time scale can well represent the smallest chemical time scale in reactive flows and the proposed scheme can significantly increase the allowable time steps in simulations. The scheme is stable when the time step is as large as 10 μs, which is about three to five orders of magnitude larger than the smallest time scales in various tests considered. For the test flames considered, the semi-implicit scheme achieves second order of accuracy in time. Moreover, the errors in quantities of interest are smaller than those from the Strang splitting scheme indicating the accuracy gain when the reaction and transport terms are solved coupled. Results also show that the relative efficiency of different schemes depends on fuel mechanisms and test flames. When the minimum time scale in reactive flows is governed by transport processes instead of chemical reactions, the proposed semi-implicit scheme is more efficient than the splitting scheme. Otherwise, the relative efficiency depends on the cost in sub-iterations for convergence within each time step and in the integration for chemistry substep. Then, the capability of the compressible reacting flow solver and the proposed semi-implicit scheme is demonstrated for capturing the hydrogen detonation waves. Finally, the performance of the proposed method is demonstrated in a two-dimensional hydrogen/air diffusion flame.

Comparison of susceptibility test methods to detect penicillin susceptibility in Streptococcus pneumoniae isolates.

PubMed

Mohd Nasir, Mohd Desa; Parasakthi, Navaratnam

2004-06-01

The increasing prevalence of penicillin-resistant Streptococuus pneumoniae urges for fast and accurate susceptibility testing methods. This study evaluated the comparability of three commonly used techniques; disk diffusion, E-test and agar dilution, to detect penicillin susceptibility in clinical isolates of S. pneumoniae. Fifty pneumococcal isolates, obtained from patients at the University of Malaya Medical Centre, were selected to include both penicillin-susceptible strains and those that had decreased susceptibility (resistant and intermediate) to penicillin. The minimum inhibitory concentration (MIC) values of penicillin to serve as the reference was determined by the agar dilution method in which, based on the MIC breakpoints recommended by the National Committee for Clinical Laboratory Standards (NCCLS), 27 strains had decreased susceptibility to penicillin with 17 strains resistant and 10 intermediate. Comparing to the agar dilution method, oxacillin disk diffusion test detected all strains with decreased penicillin susceptibility as such while E-test showed a close agreement of susceptibility (92%) of the isolates to penicillin. This confirmed that oxacillin is a good screening test for S. pneumoniae isolates with decreased susceptibility to penicillin while E-test is very reliable for rapid and accurate detection of penicillin susceptibility.

Minimum area requirements for an at-risk butterfly based on movement and demography.

PubMed

Brown, Leone M; Crone, Elizabeth E

2016-02-01

Determining the minimum area required to sustain populations has a long history in theoretical and conservation biology. Correlative approaches are often used to estimate minimum area requirements (MARs) based on relationships between area and the population size required for persistence or between species' traits and distribution patterns across landscapes. Mechanistic approaches to estimating MAR facilitate prediction across space and time but are few. We used a mechanistic MAR model to determine the critical minimum patch size (CMP) for the Baltimore checkerspot butterfly (Euphydryas phaeton), a locally abundant species in decline along its southern range, and sister to several federally listed species. Our CMP is based on principles of diffusion, where individuals in smaller patches encounter edges and leave with higher probability than those in larger patches, potentially before reproducing. We estimated a CMP for the Baltimore checkerspot of 0.7-1.5 ha, in accordance with trait-based MAR estimates. The diffusion rate on which we based this CMP was broadly similar when estimated at the landscape scale (comparing flight path vs. capture-mark-recapture data), and the estimated population growth rate was consistent with observed site trends. Our mechanistic approach to estimating MAR is appropriate for species whose movement follows a correlated random walk and may be useful where landscape-scale distributions are difficult to assess, but demographic and movement data are obtainable from a single site or the literature. Just as simple estimates of lambda are often used to assess population viability, the principles of diffusion and CMP could provide a starting place for estimating MAR for conservation. © 2015 Society for Conservation Biology.

The Laplace method for probability measures in Banach spaces

NASA Astrophysics Data System (ADS)

Piterbarg, V. I.; Fatalov, V. R.

1995-12-01

Contents §1. Introduction Chapter I. Asymptotic analysis of continual integrals in Banach space, depending on a large parameter §2. The large deviation principle and logarithmic asymptotics of continual integrals §3. Exact asymptotics of Gaussian integrals in Banach spaces: the Laplace method 3.1. The Laplace method for Gaussian integrals taken over the whole Hilbert space: isolated minimum points ([167], I) 3.2. The Laplace method for Gaussian integrals in Hilbert space: the manifold of minimum points ([167], II) 3.3. The Laplace method for Gaussian integrals in Banach space ([90], [174], [176]) 3.4. Exact asymptotics of large deviations of Gaussian norms §4. The Laplace method for distributions of sums of independent random elements with values in Banach space 4.1. The case of a non-degenerate minimum point ([137], I) 4.2. A degenerate isolated minimum point and the manifold of minimum points ([137], II) §5. Further examples 5.1. The Laplace method for the local time functional of a Markov symmetric process ([217]) 5.2. The Laplace method for diffusion processes, a finite number of non-degenerate minimum points ([116]) 5.3. Asymptotics of large deviations for Brownian motion in the Hölder norm 5.4. Non-asymptotic expansion of a strong stable law in Hilbert space ([41]) Chapter II. The double sum method - a version of the Laplace method in the space of continuous functions §6. Pickands' method of double sums 6.1. General situations 6.2. Asymptotics of the distribution of the maximum of a Gaussian stationary process 6.3. Asymptotics of the probability of a large excursion of a Gaussian non-stationary process §7. Probabilities of large deviations of trajectories of Gaussian fields 7.1. Homogeneous fields and fields with constant dispersion 7.2. Finitely many maximum points of dispersion 7.3. Manifold of maximum points of dispersion 7.4. Asymptotics of distributions of maxima of Wiener fields §8. Exact asymptotics of large deviations of the norm of Gaussian vectors and processes with values in the spaces L_k^p and l^2. Gaussian fields with the set of parameters in Hilbert space 8.1 Exact asymptotics of the distribution of the l_k^p-norm of a Gaussian finite-dimensional vector with dependent coordinates, p > 1 8.2. Exact asymptotics of probabilities of high excursions of trajectories of processes of type \\chi^2 8.3. Asymptotics of the probabilities of large deviations of Gaussian processes with a set of parameters in Hilbert space [74] 8.4. Asymptotics of distributions of maxima of the norms of l^2-valued Gaussian processes 8.5. Exact asymptotics of large deviations for the l^2-valued Ornstein-Uhlenbeck process Bibliography

Innovative model-based flow rate optimization for vanadium redox flow batteries

NASA Astrophysics Data System (ADS)

König, S.; Suriyah, M. R.; Leibfried, T.

2016-11-01

In this paper, an innovative approach is presented to optimize the flow rate of a 6-kW vanadium redox flow battery with realistic stack dimensions. Efficiency is derived using a multi-physics battery model and a newly proposed instantaneous efficiency determination technique. An optimization algorithm is applied to identify optimal flow rates for operation points defined by state-of-charge (SoC) and current. The proposed method is evaluated against the conventional approach of applying Faraday's first law of electrolysis, scaled to the so-called flow factor. To make a fair comparison, the flow factor is also optimized by simulating cycles with different charging/discharging currents. It is shown through the obtained results that the efficiency is increased by up to 1.2% points; in addition, discharge capacity is also increased by up to 1.0 kWh or 5.4%. Detailed loss analysis is carried out for the cycles with maximum and minimum charging/discharging currents. It is shown that the proposed method minimizes the sum of losses caused by concentration over-potential, pumping and diffusion. Furthermore, for the deployed Nafion 115 membrane, it is observed that diffusion losses increase with stack SoC. Therefore, to decrease stack SoC and lower diffusion losses, a higher flow rate during charging than during discharging is reasonable.

Diffusion in different models of active Brownian motion

NASA Astrophysics Data System (ADS)

Lindner, B.; Nicola, E. M.

2008-04-01

Active Brownian particles (ABP) have served as phenomenological models of self-propelled motion in biology. We study the effective diffusion coefficient of two one-dimensional ABP models (simplified depot model and Rayleigh-Helmholtz model) differing in their nonlinear friction functions. Depending on the choice of the friction function the diffusion coefficient does or does not attain a minimum as a function of noise intensity. We furthermore discuss the case of an additional bias breaking the left-right symmetry of the system. We show that this bias induces a drift and that it generally reduces the diffusion coefficient. For a finite range of values of the bias, both models can exhibit a maximum in the diffusion coefficient vs. noise intensity.

The SMM Model as a Boundary Value Problem Using the Discrete Diffusion Equation

NASA Technical Reports Server (NTRS)

Campbell, Joel

2007-01-01

A generalized single step stepwise mutation model (SMM) is developed that takes into account an arbitrary initial state to a certain partial difference equation. This is solved in both the approximate continuum limit and the more exact discrete form. A time evolution model is developed for Y DNA or mtDNA that takes into account the reflective boundary modeling minimum microsatellite length and the original difference equation. A comparison is made between the more widely known continuum Gaussian model and a discrete model, which is based on modified Bessel functions of the first kind. A correction is made to the SMM model for the probability that two individuals are related that takes into account a reflecting boundary modeling minimum microsatellite length. This method is generalized to take into account the general n-step model and exact solutions are found. A new model is proposed for the step distribution.

The SMM model as a boundary value problem using the discrete diffusion equation.

PubMed

Campbell, Joel

2007-12-01

A generalized single-step stepwise mutation model (SMM) is developed that takes into account an arbitrary initial state to a certain partial difference equation. This is solved in both the approximate continuum limit and the more exact discrete form. A time evolution model is developed for Y DNA or mtDNA that takes into account the reflective boundary modeling minimum microsatellite length and the original difference equation. A comparison is made between the more widely known continuum Gaussian model and a discrete model, which is based on modified Bessel functions of the first kind. A correction is made to the SMM model for the probability that two individuals are related that takes into account a reflecting boundary modeling minimum microsatellite length. This method is generalized to take into account the general n-step model and exact solutions are found. A new model is proposed for the step distribution.

Molecular dynamics and quasidynamics simulations of the annealing of bulk and near-surface interstitials formed in molecular-beam epitaxial Si due to low-energy particle bombardment during deposition

NASA Technical Reports Server (NTRS)

Kitabatake, M.; Fons, P.; Greene, J. E.

1991-01-01

The relaxation, diffusion, and annihilation of split and hexagonal interstitials resulting from 10 eV Si irradiation of (2x1)-terminated Si(100) are investigated. Molecular dynamics and quasidynamics simulations, utilizing the Tersoff many-body potential are used in the investigation. The interstitials are created in layers two through six, and stable atomic configurations and total potential energies are derived as a function of site symmetry and layer depth. The interstitial Si atoms are allowed to diffuse, and the total potential energy changes are calculated. Lattice configurations along each path, as well as the starting configurations, are relaxed, and minimum energy diffusion paths are derived. The results show that the minimum energy paths are toward the surface and generally involved tetrahedral sites. The calculated interstitial migration activation energies are always less than 1.4 eV and are much lower in the near-surface region than in the bulk.

Phytochemical characterization, antimicrobial activity and reducing potential of seed oil, latex, machine oil and presscake of Jatropha curcas.

PubMed

Sharma, Amit Kumar; Gangwar, Mayank; Kumar, Dharmendra; Nath, Gopal; Kumar Sinha, Akhoury Sudhir; Tripathi, Yamini Bhushan

2016-01-01

This study aims to evaluate the antimicrobial activity, phytochemical studies and thin layer chromatography analysis of machine oil, hexane extract of seed oil and methanol extract of presscake & latex of Jatropha curcas Linn (family Euphorbiaceae). J. curcas extracts were subjected to preliminary qualitative phytochemical screening to detect the major phytochemicals followed by its reducing power and content of phenol and flavonoids in different fractions. Thin layer chromatography was also performed using different solvent systems for the analysis of a number of constituents in the plant extracts. Antimicrobial activity was evaluated by the disc diffusion method, while the minimum inhibitory concentration, minimum bactericidal concentration and minimum fungicidal concentration were calculated by micro dilution method. The methanolic fraction of latex and cake exhibited marked antifungal and antibacterial activities against Gram-positive and Gram-negative bacteria. Phytochemical analysis revealed the presence of alkaloids, saponins, tannins, terpenoids, steroids, glycosides, phenols and flavonoids. Reducing power showed dose dependent increase in concentration compared to standard Quercetin. Furthermore, this study recommended the isolation and separation of bioactive compounds responsible for the antibacterial activity which would be done by using different chromatographic methods such as high-performance liquid chromatography (HPLC), GC-MS etc. The results of the above study suggest that all parts of the plants possess potent antibacterial activity. Hence, it is important to isolate the active principles for further testing of antimicrobial and other biological efficacy.

Boson peak and Ioffe-Regel criterion in amorphous siliconlike materials: The effect of bond directionality.

PubMed

Beltukov, Y M; Fusco, C; Parshin, D A; Tanguy, A

2016-02-01

The vibrational properties of model amorphous materials are studied by combining complete analysis of the vibration modes, dynamical structure factor, and energy diffusivity with exact diagonalization of the dynamical matrix and the kernel polynomial method, which allows a study of very large system sizes. Different materials are studied that differ only by the bending rigidity of the interactions in a Stillinger-Weber modelization used to describe amorphous silicon. The local bending rigidity can thus be used as a control parameter, to tune the sound velocity together with local bonds directionality. It is shown that for all the systems studied, the upper limit of the Boson peak corresponds to the Ioffe-Regel criterion for transverse waves, as well as to a minimum of the diffusivity. The Boson peak is followed by a diffusivity's increase supported by longitudinal phonons. The Ioffe-Regel criterion for transverse waves corresponds to a common characteristic mean-free path of 5-7 Å (which is slightly bigger for longitudinal phonons), while the fine structure of the vibrational density of states is shown to be sensitive to the local bending rigidity.

Generalized run-and-turn motions: From bacteria to Lévy walks

NASA Astrophysics Data System (ADS)

Detcheverry, François

2017-07-01

Swimming bacteria exhibit a repertoire of motility patterns, in which persistent motion is interrupted by turning events. What are the statistical properties of such random walks? If some particular instances have long been studied, the general case where turning times do not follow a Poisson process has remained unsolved. We present a generic extension of the continuous time random walks formalism relying on operators and noncommutative calculus. The approach is first applied to a unimodal model of bacterial motion. We examine the existence of a minimum in velocity correlation function and discuss the maximum of diffusivity at an optimal value of rotational diffusion. The model is then extended to bimodal patterns and includes as particular cases all swimming strategies: run-and-tumble, run-stop, run-reverse and run-reverse-flick. We characterize their velocity correlation functions and investigate how bimodality affects diffusivity. Finally, the wider applicability of the method is illustrated by considering curved trajectories and Lévy walks. Our results are relevant for intermittent motion of living beings, be they swimming micro-organisms or crawling cells.

Cylindrical diffuser performance using a truncated plug nozzle

NASA Technical Reports Server (NTRS)

Galanga, F. L.; Mueller, T. J.

1976-01-01

Cylindrical diffuser performance for a truncated plug nozzle without external flow was tested in a blowdown wind tunnel. The nozzle was designed for an exit Mach number of 1.9 and the plug was conical in shape from the throat and converged to the axis of symmetry at an angle of 10 degrees. The diffuser section was fashioned into two 13.97 cm lengths to facilitate boring of the duct diameter and to allow for testing of two different duct lengths. A slotted hypotube was installed in the base of the diffuser to measure pressure distribution down the centerline of the diffuser. The data obtained included: the typical centerline and sidewall pressure ratio variation along the diffuser, cell pressure ratio vs overall pressure ratio for long and short diffusers and a comparison of minimum experimental cell pressure ratio vs area ratio.

Antibacterial Effect of Azadirachta indica (Neem) or Curcuma longa (Turmeric) against Enterococcus faecalis Compared with That of 5% Sodium Hypochlorite or 2% Chlorhexidine in vitro.

PubMed

Joy Sinha, Dakshita; D S Nandha, Kanwar; Jaiswal, Natasha; Vasudeva, Agrima; Prabha Tyagi, Shashi; Pratap Singh, Udai

2017-01-01

The purpose of this study was to compare the antibacterial properties of Azadirachta indica (neem) or Curcuma longa (turmeric) against Enterococcus faecalis with those of 5% sodium hypochlorite or 2% chlorhexidine as root canal irrigants in vitro. The activity of neem, chlorhexidine, sodium hypochlorite, or turmeric against E. faecalis was measured on agar plates using the agar diffusion method. The tube dilution method was used to determine the minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of the irrigants used. Chlorhexidine or neem exhibited the greatest antibacterial activity when used as endodontic irrigants against E. faecalis, followed by sodium hypochlorite. No statistically significant difference was observed between neem, sodium hypochlorite, or chlorhexidine. The MIC of neem was 1: 128, which was similar to that of chlorhexidine. The MBC for each of these irrigants was 1: 16. Neem yielded antibacterial activity equivalent to 2% chlorhexidine or sodium hypochlorite against E. faecalis, suggesting that it offers a promising alternative to the other root canal irrigants tested.

In vitro antimicrobial activity of extracts and isolated compound from Dalbergia stipulacea Roxb. leaves

NASA Astrophysics Data System (ADS)

Kumar, Arvind; Bhat, Tahir Ahmad; Singh, Rattan Deep

2017-07-01

The study was designed to examine the in vitro antimicrobial efficacy of extracts and isolated compound of Dalbergia stipulacea. Combined extracts (chloroform and methanol) of plant leaves fractionated with n-butanol loaded with column afforded a flavonoid glycoside compound identified as luteolin 4'-rutinoside. Different extracts and isolated compound exhibited pronounced antibacterial and antifungal varied activities against four bacteria (Clostridium acetobutylinium, Bacillus subtilis, Streptococcus mutans, and Pseudomonas sp.) and one fungus (Candida albicans) susceptibility were determined using disc diffusion method. The minimum inhibitory concentration (MIC) of extracts and isolated compounds was determined by broth dilution method. The maximum activity was shown by chloroform extract against C. albicans with a zone of inhibition of 17 mm and minimum activity was displayed by methanolic extract against Pseudomonas sp. with 5 mm. However, isolated compound has shown maximum activity against Pseudomonas sp. with 15 mm. The MIC values higher in methanol extract against Pseudomonas sp. and isolated compound shows good against Pseudomonas sp. and B. subtilis. Our findings indicate that plant could be used as a good antimicrobial agent in food, pharmaceutical and bio-pesticide industries.

Evaluation of the NASA Ames no. 1 7 by 10 foot wind tunnel as an acoustic test facility

NASA Technical Reports Server (NTRS)

Wilby, J. F.; Scharton, T. D.

1975-01-01

Measurements were made in the no. 1 7'x10' wind tunnel at NASA Ames Research Center, with the objectives of defining the acoustic characteristics and recommending minimum cost treatments so that the tunnel can be converted into an acoustic research facility. The results indicate that the noise levels in the test section are due to (a) noise generation in the test section, associated with the presence of solid bodies such as the pitot tube, and (b) propagation of acoustic energy from the fan. A criterion for noise levels in the test section is recommended, based on low-noise microphone support systems. Noise control methods required to meet the criterion include removal of hardware items for the test section and diffuser, improved design of microphone supports, and installation of acoustic treatment in the settling chamber and diffuser.

Chemical constituents of Helichrysum italicum (Roth) G. Don essential oil and their antimicrobial activity against Gram-positive and Gram-negative bacteria, filamentous fungi and Candida albicans.

PubMed

Djihane, Bouzid; Wafa, Nouioua; Elkhamssa, Soltani; Pedro, De Haro Juan; Maria, Angeles Esteban; Mohamed Mihoub, Zerroug

2017-07-01

The aerial parts of Helichrysum italicum (Roth) G. Don were subjected to hydrodistillation to obtain essential oils which had been analyzed by gas chromatography and gas chromatography coupled with mass spectrometry and tested for antimicrobial activity against 12 bacteria, two yeasts and four fungi by agar diffusion method. The essential oil yielded 0.44% (v/w) and 67 compounds accounting for 99.24% of the oil were identified with a high content of oxygenated sesquiterpenes (61.42%). The most oxygenated sesquiterpene compounds were α-Cedrene (13.61%), α-Curcumene (11.41%), Geranyl acetate (10.05%), Limonene (6.07%), Nerol (5.04%), Neryl acetate (4.91%) and α-Pinene (3.78%). The antimicrobial activity of the essential oil was assayed by using the disk diffusion method on Escherichia coli ATCC 25922, Staphylococcus aureus ATCC 6538, Micrococcus luteus ATCC 4698, Klebsiella pneumonia ATCC 4352, Enterococcus cereus ATCC 2035, Bacillus cereus ATCC 10876, Staphylococcus epidermidis ATCC 12228, Bacillus subtilis ATCC 9372, Pseudomonas aeruginosa ATCC 27853, Enterococcus faecalis ATCC 49452, Proteus mirabilis ATCC 35659, Listeria monocytogenes ATCC 15313 and yeasts Candida albicans ATCC 10231, Saccharomyces cerevisiae ATCC 9763 and fungi, Fusarium solani var. coeruleum , Aspergillus niger , Alternaria alternata , Ascochyta rabiei . H. italicum inhibited the growth of all the tested microorganisms except three bacteria, E. coli ATCC 25922, K. pneumonia ATCC 4352 and L. monocytogenes ATCC 15313. The most sensitive bacterium was E. cereus ATCC 2035 with minimum inhibitory and bactericidal concentrations of 0.79 μg ml -1 . A minimum fungistatic and fungicide concentration of 6.325 μg ml -1 and 12.65 μg ml -1 respectively was obtained with C. albicans ATCC 10231 and S. cerevisiae ATCC 9763. However the four fungi were more resistant with fungistatic minimum concentration ranging from 6.325 μg ml -1 to 50.6 μg ml -1 and a fungicide minimum concentration of 50.6 μg ml -1 . This antimicrobial activity could be attributed to the essential oil chemical composition. Thus this study represents a first step in the study of the chemical composition of H. italicum (Roth) G. Don collected from north Algeria and its antimicrobial properties.

Revised Ciprofloxacin Breakpoints for Salmonella: Is it Time to Write an Obituary?

PubMed

Girish, Revathy; Kumar, Anil; Khan, Sadia; Dinesh, Kavitha R; Karim, Shamsul

2013-11-01

To determine the minimum inhibitory concentration of ciprofloxacin among 50 blood stream isolates of Salmonella enterica. A total of 50 consecutive isolates of Salmonella enterica were tested for susceptibility to antimicrobials using the Kirby Bauer disk diffusion method. Minimum inhibitory concentrations were determined using Hi-Comb strips. All results were interpreted according to the CLSI guidelines. Of the 50 isolates 70%were Salmonella Typhi, 4% Salmonella paratyphi A, 2% Salmonella paratyphi B and the remaining 10% were identified only as Salmonella species. Using the CLSI 2011 breakpoints for disc diffusion, 86% (43/50) were resistant to nalidixic acid(NA), 22% (11/50) to ciprofloxacin, 12% to azithromycin, 6% to cotrimoxazole, 4% to ampicillin and 1% to chloramphenicol. The MIC50 and MIC90 of ciprofloxacin for S.Typhi were 0.181 μg/mL and 5.06 μg/mL respectively. While the same for S. paratyphi A was 0.212μg/mL and 0.228μg/mL respectively. None of the isolates were multi drug resistant and all were susceptible to ceftriaxone. Using the CLSI 2012 revised ciprofloxacin breakpoints for disc diffusion (>31mm) & MIC (<0.06 μg/mL), 90% (45/50) of these isolates were found to be resistant. MIC's of ciprofloxacin should be reported for all salmonella isolates and should be used to guide treatment. Blindly following western guidelines for a disease which is highly endemic in the subcontinent will spell the death knell of a cheap and effective drug in our armamentarium. Therefore it will be too premature to declare that "the concept of using ciprofloxacin in typhoid fever is dead!"

Diffusion behavior of Cu/Ta heterogeneous interface under high temperature and high strain: An atomistic investigation

NASA Astrophysics Data System (ADS)

Li, Ganglong; Wu, Houya; Luo, Honglong; Chen, Zhuo; Tay, Andrew A. O.; Zhu, Wenhui

2017-09-01

Three-dimensional (3D) integration technology using Cu interconnections has emerged as a promising solution to improve the performance of silicon microelectronic devices. However, Cu diffuses into SiO2 and requires a barrier layer such as Ta to ensure acceptable reliability. In this paper, the effects of temperature and strain normal to the interface on the inter-diffusion of Cu and Ta at annealing conditions are investigated using a molecular dynamics (MD) technique with embedded atomic method (EAM) potentials. Under thermal annealing conditions without strain, it is found that a Cu-rich diffusion region approximately 2 nm thick is formed at 1000 K after 10 ns of annealing. Ta is capable of diffusing into the interior of Cu but Cu hardly diffuses into the inner lattice of Ta. At the Cu side near the interface an amorphous structure is formed due to the process of diffusion. The diffusion activation energy of Cu and Ta are found to be 0.9769 and 0.586 eV, respectively. However, when a strain is applied, a large number of crystal defects are generated in the sample. As the strain is increased, extrinsic stacking faults (ESFs) and lots of Shockley partial dislocations appear. The density of the dislocations and the diffusion channels increase, promoting the diffusion of Cu atoms into the inner lattice of Ta. The thickness of the diffusion layer increases to 4 times the value when only a temperature load of 700 K is applied. The MD simulations demonstrated that Ta is very effective as a barrier layer under thermal loading only, and its effectiveness is impaired by tensile strain at the Cu/Ta interface. The simulations also clarified the mechanism that caused the impairment. The methodology and approach described in this paper can be followed further to study the effectiveness of barrier layers under various annealing and strain conditions, and to determine the minimum thickness of barrier layers required for a particular application.

Recent radial turbine research at the NASA Lewis Research Center

NASA Technical Reports Server (NTRS)

Rohlik, H. E.; Kofskey, M. G.

1971-01-01

The high efficiencies of small radial turbines led to their application in space power systems and numerous APU and shaft power engines. Experimental and analytical work associated with these systems included examination of blade-shroud clearance, blade loading, and exit diffuser design. Results indicate high efficiency over a wide range of specific speed and also insensitivity to clearance and blade loading in the radial part of the rotor. The exit diffuser investigation indicated that a conventional conical outer wall may not provide the velocity variation consistent with minimum overall diffuser loss.

A Unified Theory for the Great Plains Nocturnal Low-Level Jet

NASA Astrophysics Data System (ADS)

Shapiro, A.; Fedorovich, E.; Rahimi, S.

2014-12-01

The nocturnal low-level jet (LLJ) is a warm-season atmospheric boundary layer phenomenon common to the Great Plains of the United States and other places worldwide, typically in regions east of mountain ranges. Low-level jets develop around sunset in fair weather conditions conducive to strong radiational cooling, reach peak intensity in the pre-dawn hours, and then dissipate with the onset of daytime convective mixing. In this study we consider the LLJ as a diurnal oscillation of a stably stratified atmosphere overlying a planar slope on the rotating Earth. The oscillations arise from diurnal cycles in both the heating of the slope (mechanism proposed by Holton in 1967) and the turbulent mixing (mechanism proposed by Blackadar in 1957). The governing equations are the equations of motion, incompressibility condition, and thermal energy in the Boussinesq approximation, with turbulent heat and momentum exchange parameterized through spatially constant but diurnally varying turbulent diffusion coefficients (diffusivities). Analytical solutions are obtained for diffusivities with piecewise constant waveforms (step-changes at sunrise and sunset) and slope temperatures/buoyancies with piecewise linear waveforms (saw-tooth function with minimum at sunrise and maximum before sunset). The jet characteristics are governed by eleven parameters: slope angle, Coriolis parameter, environmental buoyancy frequency, geostrophic wind strength, daytime and nighttime diffusivities, maximum (daytime) and minimum (nighttime) slope buoyancies, duration of daylight, lag time between peak slope buoyancy and sunset, and a Newtonian cooling time scale. An exploration of the parameter space yields results that are broadly consistent with findings particular to the Holton and Blackadar theories, and agree with climatological observations, for example, that stronger jets tend to occur over slopes of 0.15-0.25 degrees characteristic of the Great Plains. The solutions also yield intriguing predictions that peak jet strength increases with attenuation of the minimum surface buoyancy, and that the single most important parameter determining jet height is the nighttime diffusivity, with weaker nightime diffusion associated with smaller jet heights. These and other highlights will be discussed in the presentation.

Scaling laws for oxygen transport across the space-filling system of respiratory membranes in the human lung

NASA Astrophysics Data System (ADS)

Hou, Chen

Space-filling fractal surfaces play a fundamental role in how organisms function at various levels and in how structure determines function at different levels. In this thesis, we develop a quantitative theory of oxygen transport to and across the surface of the highly branched, space-filling system of alveoli, the fundamental gas exchange unit (acinar airways), in the human lung. Oxygen transport in the acinar airways is by diffusion, and we treat the two steps---diffusion through the branched airways, and transfer across the alveolar membranes---as a stationary diffusion-reaction problem, taking into account that there may be steep concentration gradients between the entrance and remote alveoli (screening). We develop a renormalization treatment of this screening effect and derive an analytic formula for the oxygen current across the cumulative alveolar membrane surface, modeled as a fractal, space-filling surface. The formula predicts the current from a minimum of morphological data of the acinus and appropriate values of the transport parameters, through a number of power laws (scaling laws). We find that the lung at rest operates near the borderline between partial screening and no screening; that it switches to no screening under exercise; and that the computed currents agree with measured values within experimental uncertainties. From an analysis of the computed current as a function of membrane permeability, we find that the space-filling structure of the gas exchanger is simultaneously optimal with respect to five criteria. The exchanger (i) generates a maximum oxygen current at minimum permeability; (ii) 'wastes' a minimum of surface area; (iii) maintains a minimum residence time of oxygen in the acinar airways; (iv) has a maximum fault tolerance to loss of permeability; and (v) generates a maximum current increase when switching from rest to exercise.

Antimicrobial Activity of Endodontic Medicaments and Vehicles using Agar Well Diffusion Method on Facultative and Obligate Anaerobes

PubMed Central

Bhat, Kishore G; Sogi, Suma

2016-01-01

Aims The aim of this study was to determine the relative antimicrobial effectiveness of these endodontic medicaments and various vehicles using an agar well diffusion assay. Materials and methods Double Antibiotic Paste(DAP), modified DAP, 2% Chlorhexidine gluconate and their combination with four vehicles namely Polyethylene glycol 400 (PEG), Propylene glycol (PG), combinations of PG with PEG and lastly Glycerine were tested using agar well diffusion assay. The minimum bactericidal concentration was noted against four standard strains of organisms ie Streptococcus mutans ATCC( American Type Culture Collection) 25175, Staphylococcus aureus ATCC 12598, Enterococcus faecalis ATCC 35550 and Eschericia coli ATCC 25922. Successful endodontic therapy depends upon thorough disinfection of root canals. In some refractory cases, routine endodontic therapy is not sufficient, so intracanal medicaments are used for proper disinfection of canals. Issues of resistance, limited spectrum of activity and lack of antifungal properties, the hunt for the ideal intracanal medicament continues. In this regard, the vehicles used to form the pastes play a supportive role by forming the appropriate consistency for placement and may dramatically influence their chemical characteristics like their solubility and diffusion. Thus, inorder to use safer and equally effective intracanal medicaments, Chlorhexidine gluconate is being unveiled in this study. Results The difference between the four vehicles when combined with the same endodontic medicament studied above is nonsignificant (NS) except against Porphyromonas gingivalis. Propylene glycol is significantly effective than Glycerine when used with DAP ie C+M medicament combination. (p = 0.029) Conclusion 2% chlorhexidine gluconate and modified DAP can definitely replace DAP and triple antibiotic paste as end-odontic medicaments with chlorhexidine having an added advantage of bactericidal action, substantivity, biocompatibility, low toxicity, and lesser chances of developing resistance. How to cite this article Nalawade TM, Bhat KG, Sogi S. Antimicrobial Activity of Endodontic Medicaments and Vehicles using Agar Well Diffusion Method on Facultative and Obligate Anaerobes. Int J Clin Pediatr Dent 2016;9(4):335-341. PMID:28127166

Diffusive charge transport in graphene

NASA Astrophysics Data System (ADS)

Chen, Jianhao

The physical mechanisms limiting the mobility of graphene on SiO 2 are studied and printed graphene devices on a flexible substrate are realized. Intentional addition of charged scattering impurities is used to study the effects of charged impurities. Atomic-scale defects are created by noble-gas ions irradiation to study the effect of unitary scatterers. The results show that charged impurities and atomic-scale defects both lead to conductivity linear in density in graphene, with a scattering magnitude that agrees quantitatively with theoretical estimates. While charged impurities cause intravalley scattering and induce a small change in the minimum conductivity, defects in graphene scatter electrons between the valleys and suppress the minimum conductivity below the metallic limit. Temperature-dependent measurements show that longitudinal acoustic phonons in graphene produce a small resistivity which is linear in temperature and independent of carrier density; at higher temperatures, polar optical phonons of the SiO2 substrate give rise to an activated, carrier density-dependent resistivity. Graphene is also made into high mobility transparent and flexible field effect device via the transfer-printing method. Together the results paint a complete picture of charge carrier transport in graphene on SiO2 in the diffusive regime, and show the promise of graphene as a novel electronic material that have potential applications not only on conventional inorganic substrates, but also on flexible substrates.

A Maximum Entropy Method for Particle Filtering

NASA Astrophysics Data System (ADS)

Eyink, Gregory L.; Kim, Sangil

2006-06-01

Standard ensemble or particle filtering schemes do not properly represent states of low priori probability when the number of available samples is too small, as is often the case in practical applications. We introduce here a set of parametric resampling methods to solve this problem. Motivated by a general H-theorem for relative entropy, we construct parametric models for the filter distributions as maximum-entropy/minimum-information models consistent with moments of the particle ensemble. When the prior distributions are modeled as mixtures of Gaussians, our method naturally generalizes the ensemble Kalman filter to systems with highly non-Gaussian statistics. We apply the new particle filters presented here to two simple test cases: a one-dimensional diffusion process in a double-well potential and the three-dimensional chaotic dynamical system of Lorenz.

Impact of blood flow on diffusion coefficients of the human kidney: a time-resolved ECG-triggered diffusion-tensor imaging (DTI) study at 3T.

PubMed

Heusch, Philipp; Wittsack, Hans-Jörg; Kröpil, Patric; Blondin, Dirk; Quentin, Michael; Klasen, Janina; Pentang, Gael; Antoch, Gerald; Lanzman, Rotem S

2013-01-01

To evaluate the impact of renal blood flow on apparent diffusion coefficients (ADC) and fractional anisotropy (FA) using time-resolved electrocardiogram (ECG)-triggered diffusion-tensor imaging (DTI) of the human kidneys. DTI was performed in eight healthy volunteers (mean age 29.1 ± 3.2) using a single slice coronal echoplanar imaging (EPI) sequence (3 b-values: 0, 50, and 300 s/mm(2)) at the timepoint of minimum (20 msec after R wave) and maximum renal blood flow (200 msec after R wave) at 3T. Following 2D motion correction, region of interest (ROI)-based analysis of cortical and medullary ADC- and FA-values was performed. ADC-values of the renal cortex at maximum blood flow (2.6 ± 0.19 × 10(-3) mm(2)/s) were significantly higher than at minimum blood flow (2.2 ± 0.11 × 10(-3) mm(2)/s) (P < 0.001), while medullary ADC-values did not differ significantly (maximum blood flow: 2.2 ± 0.18 × 10(-3) mm(2)/s; minimum blood flow: 2.15 ± 0.14 × 10(-3) mm(2)/s). FA-values of the renal medulla were significantly greater at maximal blood (0.53 ± 0.05) than at minimal blood flow (0.47 ± 0.05) (P < 0.01). In contrast, cortical FA-values were comparable at different timepoints of the cardiac cycle. ADC-values in the renal cortex as well as FA-values in the renal medulla are influenced by renal blood flow. This impact has to be considered when interpreting renal ADC- and FA-values. Copyright © 2012 Wiley Periodicals, Inc.

Method and means for detecting optically transmitted signals and establishing optical interference pattern between electrodes

DOEpatents

Kostenbauder, Adnah G.

1988-01-01

A photodetector for detecting signal pulses transmitted in an optical carrier signal relies on the generation of electron-hole pairs and the diffusion of the generated electrons and holes to the electrodes on the surface of the semiconductor detector body for generating photovoltaic pulses. The detector utilizes the interference of optical waves for generating an electron-hole grating within the semiconductor body, and, by establishing an electron-hole pair maximum at one electrode and a minimum at the other electrode, a detectable voltaic pulse is generated across the electrode.

Method and means for detecting optically transmitted signals and establishing optical interference pattern between electrodes

DOEpatents

Kostenbauder, A.G.

1988-06-28

A photodetector for detecting signal pulses transmitted in an optical carrier signal relies on the generation of electron-hole pairs and the diffusion of the generated electrons and holes to the electrodes on the surface of the semiconductor detector body for generating photovoltaic pulses. The detector utilizes the interference of optical waves for generating an electron-hole grating within the semiconductor body, and, by establishing an electron-hole pair maximum at one electrode and a minimum at the other electrode, a detectable voltaic pulse is generated across the electrode. 4 figs.

Diffusive Fractionation of Lithium Isotopes in Olivine Grain Boundaries

NASA Astrophysics Data System (ADS)

Homolova, V.; Watson, E. B.

2012-12-01

Diffusive fractionation of isotopes has been documented in silicate melts, aqueous fluids, and single crystals. In polycrystalline rocks, the meeting place of two grains, or grain boundaries, may also be a site of diffusive fractionation of isotopes. We have undertaken an experimental and modeling approach to investigate diffusive fractionation of lithium (Li) isotopes by grain boundary diffusion. The experimental procedure consists of packing a Ni metal capsule with predominantly ground San Carlos olivine and subjecting the capsule to 1100C and 1GPa for two days in a piston cylinder apparatus to create a nominally dry, 'dunite rock'. After this synthesis step, the capsule is sectioned and polished. One of the polished faces of the 'dunite rock' is then juxtaposed to a source material of spodumene and this diffusion couple is subject to the same experimental conditions as the synthesis step. Li abundances and isotopic profiles (ratios of count rates) were analyzed using LA-ICP-MS. Li concentrations linearly decrease away from the source from 550ppm to the average concentration of the starting olivine (2.5ppm). As a function of distance from the source, the 7Li/6Li ratio decreases to a minimum before increasing to the background ratio of the 'dunite rock'. The 7Li/6Li ratio minimum coincides with the lowest Li concentrations above average 'dunite rock' abundances. The initial decrease in the 7Li/6Li ratio is similar to that seen in other studies of diffusive fractionation of isotopes and is thought to be caused by the higher diffusivity (D) of the lighter isotope relative to the heavier isotope. The relationship between D and mass (m) is given by (D1/D2) =(m2/m1)^β, where β is an empirical fractionation factor; 1 and 2 denote the lighter and heavier isotope, respectively. A fit to the Li isotopic data reveals an effective DLi of ~1.2x10^-12 m/s^2 and a β of 0.1. Numerical modelling was utilized to elucidate the relationship between diffusive fractionation produced in the grain boundaries versus the lattices of the individual grains of the 'dunite rock'. The model assumes a linear grain boundary juxtaposed to the long side of a rectangular crystal lattice. During a simulation, the diffusant may directly enter the lattice or the grain boundary. Once in the grain boundary, the diffusant may then continue to diffuse away from the source until the end of the simulation or, alternatively, it may be incorporated into the lattice at some point during its travels down the grain boundary. The model system is similar to that considered by Whipple-LeClaire (1963) and our model results agree well with their analytical solution. Preliminary modeling results show that the distinctive minimum in the isotopic ratio is only produced when diffusive fractionation occurs in the grain boundary and not when the fractionation occurs only in the lattice. This suggests that the isotopic profile observed in the experiments may be a product of diffusive fractionation in grain boundaries. Implications of these results extend to the longevity of Li isotopic heterogeneities in the mantle, and suggest that the isotopes of other elements, which have a large relative mass difference, may also be diffusively fractionated by grain boundary diffusion.

Antifungal Activity of Essential Oil of Eucalyptus camaldulensis Dehnh. against Selected Fusarium spp.

PubMed Central

Maina, Angeline W.; Wagacha, John M.

2017-01-01

The objective of this study was to evaluate the antifungal activity of essential oil (EO) of Eucalyptus camaldulensis Dehnh. against five Fusarium spp. commonly associated with maize. The essential oil had been extracted by steam distillation in a modified Clevenger-type apparatus from leaves of E. camaldulensis and their chemical composition characterized by gas chromatography mass spectrometry. Poisoned food technique was used to determine the percentage inhibition of mycelial growth, minimum inhibitory concentration, and minimum fungicidal concentration of the EO on the test pathogens. Antifungal activity of different concentrations of the EO was evaluated using disc diffusion method. The most abundant compounds identified in the EO were 1,8-cineole (16.2%), α-pinene (15.6%), α-phellandrene (10.0%), and p-cymene (8.1%). The EO produced complete mycelial growth inhibition in all the test pathogens at a concentration of 7-8 μL/mL after five days of incubation. The minimum inhibitory concentration and minimum fungicidal concentration of the EO on the test fungi were in the range of 7-8 μL/mL and 8–10 μL/mL, respectively. These findings confirm the fungicidal properties of E. camaldulensis essential oils and their potential use in the management of economically important Fusarium spp. and as possible alternatives to synthetic fungicides. PMID:28127308

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

Guo, X.; Florinski, V.

We present a new model that couples galactic cosmic-ray (GCR) propagation with magnetic turbulence transport and the MHD background evolution in the heliosphere. The model is applied to the problem of the formation of corotating interaction regions (CIRs) during the last solar minimum from the period between 2007 and 2009. The numerical model simultaneously calculates the large-scale supersonic solar wind properties and its small-scale turbulent content from 0.3 au to the termination shock. Cosmic rays are then transported through the background, and thus computed, with diffusion coefficients derived from the solar wind turbulent properties, using a stochastic Parker approach. Ourmore » results demonstrate that GCR variations depend on the ratio of diffusion coefficients in the fast and slow solar winds. Stream interfaces inside the CIRs always lead to depressions of the GCR intensity. On the other hand, heliospheric current sheet (HCS) crossings do not appreciably affect GCR intensities in the model, which is consistent with the two observations under quiet solar wind conditions. Therefore, variations in diffusion coefficients associated with CIR stream interfaces are more important for GCR propagation than the drift effects of the HCS during a negative solar minimum.« less

New Numerical Approaches To thermal Convection In A Compositionally Stratified Fluid

NASA Astrophysics Data System (ADS)

Puckett, E. G.; Turcotte, D. L.; Kellogg, L. H.; Lokavarapu, H. V.; He, Y.; Robey, J.

2016-12-01

Seismic imaging of the mantle has revealed large and small scale heterogeneities in the lower mantle; specifically structures known as large low shear velocity provinces (LLSVP) below Africa and the South Pacific. Most interpretations propose that the heterogeneities are compositional in nature, differing from the overlying mantle, an interpretation that would be consistent with chemical geodynamic models. The LLSVP's are thought to be very old, meaning they have persisted thoughout much of Earth's history. Numerical modeling of persistent compositional interfaces present challenges to even state-of-the-art numerical methodology. It is extremely difficult to maintain sharp composition boundaries which migrate and distort with time dependent fingering without compositional diffusion and / or artificial diffusion. The compositional boundary must persist indefinitely. In this work we present computations of an initial compositionally stratified fluid that is subject to a thermal gradient ΔT = T1 - T0 across the height D of a rectangular domain over a range of buoyancy numbers B and Rayleigh numbers Ra. In these computations we compare three numerical approaches to modeling the movement of two distinct, thermally driven, compositional fields; namely, a high-order Finte Element Method (FEM) that employs artifical viscosity to preserve the maximum and minimum values of the compositional field, a Discontinous Galerkin (DG) method with a Bound Preserving (BP) limiter, and a Volume-of-Fluid (VOF) interface tracking algorithm. Our computations demonstrate that the FEM approach has far too much numerical diffusion to yield meaningful results, the DGBP method yields much better resuts but with small amounts of each compositional field being (numerically) entrained within the other compositional field, while the VOF method maintains a sharp interface between the two compositions throughout the computation. In the figure we show a comparison of between the three methods for a computation made with B = 1.111 and Ra = 10,000 after the flow has reached 'steady state'. (R) the images computed with the standard FEM method (with artifical viscosity), (C) the images computed with the DGBP method (with no artifical viscosity or diffusion due to discretization errors) and (L) the images computed with the VOF algorithm.

Development of a miniaturized diffusive sampler for true breathing-zone sampling and thermal desorption gas chromatographic analysis.

PubMed

Lindahl, Roger; Levin, Jan-Olof; Sundgren, Margit

2009-07-01

Exposure measurements should be performed as close as possible to the nose and mouth for a more correct assessment of exposure. User-friendly sampling equipment, with a minimum of handling before, during and after measurement, should not affect ordinary work. In diffusive (passive) sampling, no extra equipment as sampling pumps is needed, making the measurements more acceptable to the user. The diffusive samplers are normally attached on a shoulder, on a breast-pocket or on the lapel. There are, however, difficulties if true breathing-zone sampling is to be performed, since available diffusive samplers normally cannot be arranged close to the nose/mouth. The purpose of this work was to study the performance of a miniaturized tube type diffusive sampler attached to a headset for true breathing-zone sampling. The basis for this miniaturization was the Perkin Elmer ATD tube. Both the size of the tube and the amount of adsorbent was decreased for the miniaturized sampler. A special tube holder to be used with a headset was designed for the mini tube. The mini tube is thermally desorbed inside a standard PE tube. The new sampler was evaluated for the determination of styrene, both in laboratory experiments and in field measurements. As reference method, diffusive sampling with standard Perkin Elmer tubes, thermal desorption and gas chromatographic (GC) analysis was used. The sampling rate was determined to 0.356 mL min(-1) (CV 9.6%) and was not significantly affected by concentration, sampling time or relative humidity.

Coupled low-energy - ring current plasma diffusion in the Jovian magnetosphere

NASA Technical Reports Server (NTRS)

Summers, D.; Siscoe, G. L.

1985-01-01

The outwardly diffusing Iogenic plasma and the simultaneously inwardly diffusing ring current plasma in the Jovian magnetosphere are described using a coupled diffusion model which incorporates the effects of the pressure gradient of the ring current into the cross-L diffusion coefficient. The coupled diffusion coefficient is derived by calculating the total energy available to drive the diffusion process. The condition is imposed that the diffusion coefficient takes on a local minimum value at some point in the region L = 7-8, at which point the gradient of the Io plasma density is specified as ramp value given by Siscoe et al. (1981). The hypothesis that the pressure gradient of the ring current causes the diminution of radial plasma transport is tested, and solution profiles for the Iogenic and ring current plasma densities are obtained which imply that the Io plasma ramp is caused by a high-density, low-energy component of the ring current hitherto unobserved directly.

Essential oil of the leaves of Ricinus communis L.: in vitro cytotoxicity and antimicrobial properties.

PubMed

Zarai, Zied; Ben Chobba, Ines; Ben Mansour, Riadh; Békir, Ahmed; Gharsallah, Néji; Kadri, Adel

2012-08-13

The aim of the present study was to appraise the antimicrobial activity of Ricinus communis L. essential oil against different pathogenic microorganisms and the cytotoxic activity against HeLa cell lines. The agar disk diffusion method was used to study the antibacterial activity of Ricinus communis L. essential oil against 12 bacterial and 4 fungi strains. The disc diameters of zone of inhibition (DD), the minimum inhibitory concentrations (MIC) and the concentration inhibiting 50% (IC50) were investigated to characterize the antimicrobial activities of this essential oil. The in vitro cytotoxicity of Ricinus communis L. essential oil was examined using a modified MTT assay; the viability and the IC50 were used to evaluate this test. The essential oil from the leaves of Ricinus communis L. was analyzed by GC-MS and bioassays were carried out. Five constituents of the oil were identified by GC-MS. The antimicrobial activity of the oil was investigated in order to evaluate its efficacy against twelve bacteria and four fungi species, using disc diffusion and minimum inhibitory concentration methods. The essential oil showed strong antimicrobial activity against all microorganisms tested with higher sensitivity for Bacillus subtilis, Staphylococcus aureus and Enterobacter cloacae. The cytotoxic and apoptotic effects of the essential oil on HeLa cell lines were examined by MTT assay. The cytotoxicity of the oil was quite strong with IC50 values less than 2.63 mg/ml for both cell lines. The present study showed the potential antimicrobial and anticarcinogenic properties of the essential oil of Ricinus communis L., indicating the possibilities of its potential use in the formula of natural remedies for the topical treatment of infections.

Idiopathic granulomatous mastitis: magnetic resonance imaging findings with diffusion MRI.

PubMed

Aslan, Hulya; Pourbagher, Aysin; Colakoglu, Tamer

2016-07-01

Idiopathic granulomatous mastitis (IGM) is a rare benign breast disease with unknown etiology which can mimic breast carcinoma, both clinically and radiologically. Magnetic resonance imaging (MRI) findings of IGM have been previously described; however there is no study evaluating diffusion-weighted MRI findings of IGM. To analyze conventional, dynamic contrast-enhanced, and diffusion-weighted MRI signal characteristics of IGM by comparing it with the contralateral normal breast parenchyma. A total of 39 patients were included in the study. On dynamic contrast-enhanced MRI, the distribution and enhancement patterns of the lesions were evaluated. We also detected the frequencies of involving quadrants, retroareolar involvement, accompanying abscess, and skin edema. T2-weighted (T2W) and STIR signal intensities and both mean and minimum apparent diffusion coefficient (ADC) values were compared with the contralateral normal parenchyma. IGM showed significantly lower mean and minimum ADC values when compared with the normal parenchyma. Signal intensities on T2W and STIR sequences of the lesion were significantly higher than the normal parenchyma. On dynamic contrast-enhanced MRI, 7.7% of the patients had mass-like contrast enhancement, 92.3% of the patients had non-mass-like contrast enhancement. Abscess was positive in 33.3% of the patients. As a result, IGM showed commonly non-mass-like lesions with restricted diffusion. Although it is a benign pathology, it may show clustered ring-like enhancement like malignant lesions. © The Foundation Acta Radiologica 2015.

Recent radial turbine research at the NASA Lewis Research Center.

NASA Technical Reports Server (NTRS)

Rohlik, H. E.; Kofskey, M. G.

1972-01-01

The major results obtained in several recent experimental programs on small radial inflow turbines for space applications are presented and discussed. Specifically, experimental and analytical work associated with these systems that has included examination of blade-shroud clearance, blade loading, and exit diffuser design, is considered. Results indicate high efficiency over a wide range of specific speed, and also insensitivity to clearance and blade loading in the radial part of the rotor. The exit diffuser investigation indicated that a conventional conical outer wall may not provide the velocity variation consistent with minimum overall diffuser loss.

Optimization of diffusion-weighted single-refocused spin-echo EPI by reducing eddy-current artifacts and shortening the echo time.

PubMed

Shrestha, Manoj; Hok, Pavel; Nöth, Ulrike; Lienerth, Bianca; Deichmann, Ralf

2018-03-30

The purpose of this work was to optimize the acquisition of diffusion-weighted (DW) single-refocused spin-echo (srSE) data without intrinsic eddy-current compensation (ECC) for an improved performance of ECC postprocessing. The rationale is that srSE sequences without ECC may yield shorter echo times (TE) and thus higher signal-to-noise ratios (SNR) than srSE or twice-refocused spin-echo (trSE) schemes with intrinsic ECC. The proposed method employs dummy scans with DW gradients to drive eddy currents into a steady state before data acquisition. Parameters of the ECC postprocessing algorithm were also optimized. Simulations were performed to obtain minimum TE values for the proposed sequence and sequences with intrinsic ECC. Experimentally, the proposed method was compared with standard DW-trSE imaging, both in vitro and in vivo. Simulations showed substantially shorter TE for the proposed method than for methods with intrinsic ECC when using shortened echo readouts. Data of the proposed method showed a marked increase in SNR. A dummy scan duration of at least 1.5 s improved performance of the ECC postprocessing algorithm. Changes proposed for the DW-srSE sequence and for the parameter setting of the postprocessing ECC algorithm considerably reduced eddy-current artifacts and provided a higher SNR.

Development of a primary diffusion source of organic vapors for gas analyzer calibration

NASA Astrophysics Data System (ADS)

Lecuna, M.; Demichelis, A.; Sassi, G.; Sassi, M. P.

2018-03-01

The generation of reference mixtures of volatile organic compounds (VOCs) at trace levels (10 ppt-10 ppb) is a challenge for both environmental and clinical measurements. The calibration of gas analyzers for trace VOC measurements requires a stable and accurate source of the compound of interest. The dynamic preparation of gas mixtures by diffusion is a suitable method for fulfilling these requirements. The estimation of the uncertainty of the molar fraction of the VOC in the mixture is a key step in the metrological characterization of a dynamic generator. The performance of a dynamic generator was monitored over a wide range of operating conditions. The generation system was simulated by a model developed with computational fluid dynamics and validated against experimental data. The vapor pressure of the VOC was found to be one of the main contributors to the uncertainty of the diffusion rate and its influence at 10-70 kPa was analyzed and discussed. The air buoyancy effect and perturbations due to the weighing duration were studied. The gas carrier flow rate and the amount of liquid in the vial were found to play a role in limiting the diffusion rate. The results of sensitivity analyses were reported through an uncertainty budget for the diffusion rate. The roles of each influence quantity were discussed. A set of criteria to minimize the uncertainty contribution to the primary diffusion source (25 µg min-1) were estimated: carrier gas flow rate higher than 37.7 sml min-1, a maximum VOC liquid mass decrease in the vial of 4.8 g, a minimum residual mass of 1 g and vial weighing times of 1-3 min. With this procedure a limit uncertainty of 0.5% in the diffusion rate can be obtained for VOC mixtures at trace levels (10 ppt-10 ppb), making the developed diffusion vials a primary diffusion source with potential to become a new reference material for trace VOC analysis.

The Gaia-ESO Survey: evidence of atomic diffusion in M67?

NASA Astrophysics Data System (ADS)

Bertelli Motta, C.; Pasquali, A.; Richer, J.; Michaud, G.; Salaris, M.; Bragaglia, A.; Magrini, L.; Randich, S.; Grebel, E. K.; Adibekyan, V.; Blanco-Cuaresma, S.; Drazdauskas, A.; Fu, X.; Martell, S.; Tautvaišienė, G.; Gilmore, G.; Alfaro, E. J.; Bensby, T.; Flaccomio, E.; Koposov, S. E.; Korn, A. J.; Lanzafame, A. C.; Smiljanic, R.; Bayo, A.; Carraro, G.; Casey, A. R.; Costado, M. T.; Damiani, F.; Franciosini, E.; Heiter, U.; Hourihane, A.; Jofré, P.; Lardo, C.; Lewis, J.; Monaco, L.; Morbidelli, L.; Sacco, G. G.; Sousa, S. G.; Worley, C. C.; Zaggia, S.

2018-07-01

Investigating the chemical homogeneity of stars born from the same molecular cloud at virtually the same time is very important for our understanding of the chemical enrichment of the interstellar medium and with it the chemical evolution of the Galaxy. One major cause of inhomogeneities in the abundances of open clusters is stellar evolution of the cluster members. In this work, we investigate variations in the surface chemical composition of member stars of the old open cluster M67 as a possible consequence of atomic diffusion effects taking place during the main-sequence phase. The abundances used are obtained from high-resolution UVES/FLAMES spectra within the framework of the Gaia-ESO Survey. We find that the surface abundances of stars on the main sequence decrease with increasing mass reaching a minimum at the turn-off. After deepening of the convective envelope in subgiant branch stars, the initial surface abundances are restored. We found the measured abundances to be consistent with the predictions of stellar evolutionary models for a cluster with the age and metallicity of M67. Our findings indicate that atomic diffusion poses a non-negligible constraint on the achievable precision of chemical tagging methods.

The Gaia-ESO Survey: Evidence of atomic diffusion in M67?

NASA Astrophysics Data System (ADS)

Motta, C. Bertelli; Pasquali, A.; Richer, J.; Michaud, G.; Salaris, M.; Bragaglia, A.; Magrini, L.; Randich, S.; Grebel, E. K.; Adibekyan, V.; Blanco-Cuaresma, S.; Drazdauskas, A.; Fu, X.; Martell, S.; TautvaišienÄ--, G.; Gilmore, G.; Alfaro, E. J.; Bensby, T.; Flaccomio, E.; Koposov, S. E.; Korn, A. J.; Lanzafame, A. C.; Smiljanic, R.; Bayo, A.; Carraro, G.; Casey, A. R.; Costado, M. T.; Damiani, F.; Franciosini, E.; Heiter, U.; Hourihane, A.; Jofré, P.; Lardo, C.; Lewis, J.; Monaco, L.; Morbidelli, L.; Sacco, G. G.; Sousa, S. G.; Worley, C. C.; Zaggia, S.

2018-04-01

Investigating the chemical homogeneity of stars born from the same molecular cloud at virtually the same time is very important for our understanding of the chemical enrichment of the interstellar medium and with it the chemical evolution of the Galaxy. One major cause of inhomogeneities in the abundances of open clusters is stellar evolution of the cluster members. In this work, we investigate variations in the surface chemical composition of member stars of the old open cluster M67 as a possible consequence of atomic diffusion effects taking place during the main-sequence phase. The abundances used are obtained from high-resolution UVES/FLAMES spectra within the framework of the Gaia-ESO Survey. We find that the surface abundances of stars on the main sequence decrease with increasing mass reaching a minimum at the turn-off. After deepening of the convective envelope in sub-giant branch stars, the initial surface abundances are restored. We found the measured abundances to be consistent with the predictions of stellar evolutionary models for a cluster with the age and metallicity of M67. Our findings indicate that atomic diffusion poses a non-negligible constraint on the achievable precision of chemical tagging methods.

The Multiple-Minima Problem in Protein Folding

NASA Astrophysics Data System (ADS)

Scheraga, Harold A.

1991-10-01

The conformational energy surface of a polypeptide or protein has many local minima, and conventional energy minimization procedures reach only a local minimum (near the starting point of the optimization algorithm) instead of the global minimum (the multiple-minima problem). Several procedures have been developed to surmount this problem, the most promising of which are: (a) build up procedure, (b) optimization of electrostatics, (c) Monte Carlo-plus-energy minimization, (d) electrostatically-driven Monte Carlo, (e) inclusion of distance restraints, (f) adaptive importance-sampling Monte Carlo, (g) relaxation of dimensionality, (h) pattern-recognition, and (i) diffusion equation method. These procedures have been applied to a variety of polypeptide structural problems, and the results of such computations are presented. These include the computation of the structures of open-chain and cyclic peptides, fibrous proteins and globular proteins. Present efforts are being devoted to scaling up these procedures from small polypeptides to proteins, to try to compute the three-dimensional structure of a protein from its amino sequence.

Antioxidant and antibacterial activity of Thai medicinal plant (Capparis micracantha)

NASA Astrophysics Data System (ADS)

Laoprom, Nonglak; Sangprom, Araya; Chaisri, Patcharaporn

2018-04-01

This work aims to study the antioxidants capacity, Total phenolic content and antibacterial activity of Thai medicinal plant for the treatment of dermatitis-related inflammations, Capparis micracantha. Crude extract from stem of Thai medicinal plant was extracted with hexane, ethyl acetate, methanol and water. The antioxidant activities (IC50) was evaluated with 1,1-diphenyl-1-princylhydrazyl (DPPH) radical scavenging assay. Total phenolic content (TPC) was determined by using Folin-Ciocalteu method. Bacterial activities was tested with four human pathogenic bacteria; Escherichia coli, Listeria monocytogenes, Staphylococcus aureus and Stapylococcus epidermidis by using agar diffusion assay. Minimum Inhibition Concentration (MIC) and Minimum Bactericidal Concentration (MBC) were also determined by broth dilution method. For antioxidant activity, the methanol fraction from stem extract showed the highest activity with an IC50 of 2.4 mg/ml. Water extraction was the high TPC with 10,136.9 mg GAE/g dry weight. Methanol and water extraction showed the remarkable inhibition of bacterial growth was shown against L. monocytogenes and S. aureus. In addition, ethyl acetate, methanol and water fraction from stem extract against S. epidermidis. The present finding suggests that the extract of C. micracantha could be used to discover bioactive natural products that may serve as pharmaceutical products.

Simultaneous multislice refocusing via time optimal control.

PubMed

Rund, Armin; Aigner, Christoph Stefan; Kunisch, Karl; Stollberger, Rudolf

2018-02-09

Joint design of minimum duration RF pulses and slice-selective gradient shapes for MRI via time optimal control with strict physical constraints, and its application to simultaneous multislice imaging. The minimization of the pulse duration is cast as a time optimal control problem with inequality constraints describing the refocusing quality and physical constraints. It is solved with a bilevel method, where the pulse length is minimized in the upper level, and the constraints are satisfied in the lower level. To address the inherent nonconvexity of the optimization problem, the upper level is enhanced with new heuristics for finding a near global optimizer based on a second optimization problem. A large set of optimized examples shows an average temporal reduction of 87.1% for double diffusion and 74% for turbo spin echo pulses compared to power independent number of slices pulses. The optimized results are validated on a 3T scanner with phantom measurements. The presented design method computes minimum duration RF pulse and slice-selective gradient shapes subject to physical constraints. The shorter pulse duration can be used to decrease the effective echo time in existing echo-planar imaging or echo spacing in turbo spin echo sequences. © 2018 International Society for Magnetic Resonance in Medicine.

Antibacterial activity, thermal stability and ab initio study of copolymer containing sulfobetaine and carboxybetaine groups

NASA Astrophysics Data System (ADS)

Tarannum, Nazia; Singh, Meenakshi; Yadav, Anil K.

2017-10-01

Here, we have explored the antibacterial activity, thermal stability and theoretical study of two copolymers that contain sulfobetaine and carboetaine moiety. Copolymers were synthesized based on Schiff base chemistry with generation of zwitterionic centres by nucleophilic addition of sultone/lactone. To predict and confirm the molecular structure of zwitterionic polyelectrolyte molecule, the theoretical study of structural features and other thermodynamic characteristics of copolymer constituents was obtained by ab initio calculations. Various parameters such as geometry optimization, energy calculations, frequency calculations and intrinsic reaction coefficient (IRC) are simulated using Hartree Fock (HF) method. The geometry optimizations are analyzed at HF/3-21 G default level of theory. The vibrational frequency is calculated via density functional theory (DFT)/B3LYP 6-31G*(d) level whose values are in accord with the experimental observed frequency. Both copolymers have been successfully assessed for antibacterial activity against Staphylococcus aureus and Pseudomonas aeuroginosa bacterial strains by disc diffusion method. The antibacterial study helped in evaluating zone of inhibition, minimum inhibitory concentration and minimum bactericidal concentration. Sulfobetaine copolymer is found to be more effective in curtailing the infection caused by bacteria as compared to carbobetaine.

Alterations in apparent diffusion coefficient values of the kidney during the cardiac cycle: Evaluation with ECG-triggered diffusion-weighted MR imaging.

PubMed

Ito, Katsuyoshi; Hayashida, Minoru; Kanki, Akihiko; Yamamoto, Akira; Tamada, Tsutomu; Yoshida, Koji; Tanabe, Masahiro

2018-05-17

To evaluate dynamic changes in apparent diffusion coefficient (ADC) values of the kidney at different time points during the cardiac cycle using electrocardiographic (ECG)-triggered diffusion-weighted MR imaging in normal subjects, and to elucidate the differences in ADC values between the right and left kidneys during a cardiac cycle. The study was approved by our institutional review board and informed consent was obtained from subjects. Twenty healthy volunteers who underwent ECG-triggered diffusion-weighted MR imaging of the kidney were included. The differences in ADC values of each kidney during different cardiac phases were compared. Additionally, the differences in maximum and minimum ADC values between the right and left kidney were also evaluated. ADC values in the right and left kidney changed significantly during the cardiac cycle (P < 0.00001). Maximum and minimum ADC values during the cardiac cycle of the left kidney were significantly higher (P = 0.026 and 0.017, respectively) than those of the right kidney. Maximum ADC value in the left kidney had a significantly strong positive correlation with the left renal vein ratio (r = 0.83, P < 0.00001). In the right kidney, maximum ADC showed a weakly positive correlation with the diameter of the right renal vein (r = 0.45, P = 0.048). ADC values of the kidney obtained using ECG-triggered diffusion-weighted MR imaging change significantly during the cardiac cycle. Maximum (systolic) ADC during the cardiac cycle of the left kidney was significantly higher than that of the right kidney, probably due to the anatomical difference in the renal vein. Copyright © 2018 Elsevier Inc. All rights reserved.

The rationale for the optimum efficiency of columns packed with new 1.9μm fully porous Titan-C18 particles-a detailed investigation of the intra-particle diffusivity.

PubMed

Gritti, Fabrice; Guiochon, Georges

2014-08-15

In a previous report, it was reported that columns packed with fully porous 1.9μm Titan-C18 particles provided a minimum reduced plate height as small as 1.7 for the most retained compound (n-octanophenone) under RPLC conditions. These particles are characterized by a relatively narrow size distribution with a relative standard deviation (RSD) of only 10%. A column packed with classical 5μm Symmetry-C18 particles, used as a reference RPLC column, generated a minimum reduced plate height of 2.1 for the same retained compound. This work demonstrates that this was due to an unusually low intra-particle diffusivity across these particles, which leads to a small longitudinal diffusion coefficient along the column. The demonstration is based on the combination of accurate measurements of the height equivalent to a theoretical plate (HETP), inverse size exclusion chromatography (ISEC), peak parking (PP), and minor disturbance method (MDM) experiments. The experimental results show that the reduced eddy dispersion HETP term (A=0.8 for a reduced velocity of 5), the internal particle porosity (ϵp=0.35), and the enrichment of acetonitrile in the pore volume (75% acetonitrile in the bulk, 85% inside the mesoporous volume) are identical on both the Titan-C18 and Symmetry-C18 columns. The difference between the internal structures of these two brands of RPLC-C18 fully porous particles lies in the values of the internal obstruction factor γp, which is 0.42 for the Symmetry-C18 but only 0.26 for the Titan-C18 particles. This is in part related to the diffusion hindrance due to the small average pore size of the Titan-C18 particles, around 59Å versus 77Å for Symmetry-C18 particles. A simple model of constriction along diffusion paths having the shape of a truncated cone suggests that the width of the pore size distribution (RSD of 30% and 20% for Titan-C18 and Symmetry-C18 particles) is mostly responsible for the difference in their obstruction factors. Copyright © 2014 Elsevier B.V. All rights reserved.

New Insights into the Fractional Order Diffusion Equation Using Entropy and Kurtosis.

PubMed

Ingo, Carson; Magin, Richard L; Parrish, Todd B

2014-11-01

Fractional order derivative operators offer a concise description to model multi-scale, heterogeneous and non-local systems. Specifically, in magnetic resonance imaging, there has been recent work to apply fractional order derivatives to model the non-Gaussian diffusion signal, which is ubiquitous in the movement of water protons within biological tissue. To provide a new perspective for establishing the utility of fractional order models, we apply entropy for the case of anomalous diffusion governed by a fractional order diffusion equation generalized in space and in time. This fractional order representation, in the form of the Mittag-Leffler function, gives an entropy minimum for the integer case of Gaussian diffusion and greater values of spectral entropy for non-integer values of the space and time derivatives. Furthermore, we consider kurtosis, defined as the normalized fourth moment, as another probabilistic description of the fractional time derivative. Finally, we demonstrate the implementation of anomalous diffusion, entropy and kurtosis measurements in diffusion weighted magnetic resonance imaging in the brain of a chronic ischemic stroke patient.

Diffusive dynamics of nanoparticles in ultra-confined media

DOE PAGES

Jacob, Jack Deodato; Conrad, Jacinta; Krishnamoorti, Ramanan; ...

2015-08-10

Differential dynamic microscopy (DDM) was used to investigate the diffusive dynamics of nanoparticles of diameter 200 400 nm that were strongly confined in a periodic square array of cylindrical nanoposts. The minimum distance between posts was 1.3 5 times the diameter of the nanoparticles. The image structure functions obtained from the DDM analysis were isotropic and could be fit by a stretched exponential function. The relaxation time scaled diffusively across the range of wave vectors studied, and the corresponding scalar diffusivities decreased monotonically with increased confinement. The decrease in diffusivity could be described by models for hindered diffusion that accountedmore » for steric restrictions and hydrodynamic interactions. The stretching exponent decreased linearly as the nanoparticles were increasingly confined by the posts. Altogether, these results are consistent with a picture in which strongly confined nanoparticles experience a heterogeneous spatial environment arising from hydrodynamics and volume exclusion on time scales comparable to cage escape, leading to multiple relaxation processes and Fickian but non-Gaussian diffusive dynamics.« less

Waste Acceptance Testing of Secondary Waste Forms: Cast Stone, Ceramicrete and DuraLith

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

Mattigod, Shas V.; Westsik, Joseph H.; Chung, Chul-Woo

2011-08-12

To support the selection of a waste form for the liquid secondary wastes from WTP, Washington River Protection Solutions has initiated secondary-waste-form testing work at Pacific Northwest National Laboratory (PNNL). In anticipation of a down-selection process for a waste form for the Solidification Treatment Unit to be added to the ETF, PNNL is conducting tests on four candidate waste forms to evaluate their ability to meet potential waste acceptance criteria for immobilized secondary wastes that would be placed in the IDF. All three waste forms demonstrated compressive strengths above the minimum 3.45 MPa (500 psi) set as a target formore » cement-based waste forms. Further, none of the waste forms showed any significant degradation in compressive strength after undergoing thermal cycling (30 cycles in a 10 day period) between -40 C and 60 C or water immersion for 90 days. The three leach test methods are intended to measure the diffusion rates of contaminants from the waste forms. Results are reported in terms of diffusion coefficients and a leachability index (LI) calculated based on the diffusion coefficients. A smaller diffusion coefficient and a larger LI are desired. The NRC, in its Waste Form Technical Position (NRC 1991), provides recommendations and guidance regarding methods to demonstrate waste stability for land disposal of radioactive waste. Included is a recommendation to conduct leach tests using the ANS 16.1 method. The resulting leachability index (LI) should be greater than 6.0. For Hanford secondary wastes, the LI > 6.0 criterion applies to sodium leached from the waste form. For technetium and iodine, higher targets of LI > 9 for Tc and LI > 11 for iodine have been set based on early waste-disposal risk and performance assessment analyses. The results of these three leach tests conducted for a total time between 11days (ASTM C1308) to 90 days (ANS 16.1) showed: (1) Technetium diffusivity: ANSI/ANS 16.1, ASTM C1308, and EPA 1315 tests indicated that all the waste forms had leachability indices better than the target LI > 9 for technetium; (2) Rhenium diffusivity: Cast Stone 2M specimens, when tested using EPA 1315 protocol, had leachability indices better than the target LI > 9 for technetium based on rhenium as a surrogate for technetium. All other waste forms tested by ANSI/ANS 16.1, ASTM C1308, and EPA 1315 test methods had leachability indices that were below the target LI > 9 for Tc based on rhenium release. These studies indicated that use of Re(VII) as a surrogate for 99Tc(VII) in low temperature secondary waste forms containing reductants will provide overestimated diffusivity values for 99Tc. Therefore, it is not appropriate to use Re as a surrogate 99Tc in future low temperature waste form studies. (3) Iodine diffusivity: ANSI/ANS 16.1, ASTM C1308, and EPA 1315 tests indicated that the three waste forms had leachability indices that were below the target LI > 11 for iodine. Therefore, it may be necessary to use a more effective sequestering material than silver zeolite used in two of the waste forms (Ceramicrete and DuraLith); (4) Sodium diffusivity: All the waste form specimens tested by the three leach methods (ANSI/ANS 16.1, ASTM C1308, and EPA 1315) exceeded the target LI value of 6; (5) All three leach methods (ANS 16.1, ASTM C1308 and EPA 1315) provided similar 99Tc diffusivity values for both short-time transient diffusivity effects as well as long-term ({approx}90 days) steady diffusivity from each of the three tested waste forms (Cast Stone 2M, Ceramicrete and DuraLith). Therefore, any one of the three methods can be used to determine the contaminant diffusivities from a selected waste form.« less

Determination of Antimicrobial Potential of Five Herbs used in Ayurveda Practices against Candida albicans, Candida parapsilosis and Methicillin Resistant Staphylococcus aureus

PubMed Central

Gunasekara, TDCP; Radhika, NDM; Ragunathan, KK; Gunathilaka, DPP; Weerasekera, MM; Hewageegana, HGSP; Arawwawala, L A D M; Fernando, SSN

2017-01-01

Background: Medicinal plants are an important source of novel antimicrobial agents. Ayurvedic treatment involves the use of a variety of medicinal plants that merit investigation. Aims: To investigate the antimicrobial activity of bark of Pongamia pinnata (L.) Pierre, stem of Rubia cordifolia Linn, leaves of Jasminum officinale Linn, stem of Berberis ceylanica C.K. Schneid. and fruit of Garcina zeylanica Roxb. Subjects and Methods: Aqueous and ethanolic extracts of dried bark of Pongamia pinnata (Magul karanda), dried stem of Rubia cordifolia Linn (Welmadata), tender leaves of Jasminum officinale Linn (Jasmine) and dried stem of Berberis ceylanica (Dāruharidrā) were prepared according to standard protocols and tested for antimicrobial activity against five clinical isolates and one standard strain each of Candida albicans (ATCC 10231), Candida parapsilosis (ATCC 22019) and six Methicillin Resistant Staphylococcus aureus (MRSA) clinical isolates using the well diffusion method. Experiments were done in triplicates using well diffusion method. The plant extracts which gave a zone of inhibition in the well diffusion assay were further tested for Minimum Inhibitory Concentrations (MIC). Results: Aqueous and ethanolic extracts of Berberis ceylanica and ethanolic extract of Rubia cordifolia had antimicrobial activity against Candida albicans and Candida parapsilosis. Aqueous and ethanolic extracts of Garcinia zeylanica, and the ethanolic extracts of Jasminum officinale, Rubia cordifolia and Pongamia pinnata had antimicrobial activity against MRSA. Conclusions: Berberis ceylanica and Rubia crodifolia had antimicrobial activity against Candida species while Garcinia zeylanica, Jasminum officinale, Rubia crodifolia and Pongamia pinnata had antimicrobial activity against MRSA. PMID:29269969

Shear wave elastography diagnosis of the diffuse sclerosing variant of papillary thyroid carcinoma: A case report.

PubMed

Xue, Nianyu; Xu, Youfeng; Huang, Pintong; Zhang, Shengmin; Wang, Hongwei; Yu, Fei

2016-08-01

The present study aimed to report the shear wave elastography (SWE) findings in a patient with the diffuse sclerosing variant of papillary thyroid carcinoma (DSVPTC). Since patients with DSVPTC may present with typical clinicopathological features and initially appear to have Hashimoto's thyroiditis, a thorough clinical evaluation and an early diagnosis are important. A 20-year-old female patient presented with a 1-month history of a neck mass and sore throat. Conventional ultrasound and SWE were performed using an AIXPLORER system with 14-5 MHz linear transducer. The patient had undergone total thyroidectomy and bilateral neck lymph node dissection, and an intraoperative pathology consultation to confirm the malignancy of lymph node metastasis. Pathological diagnosis was DSVPTC in both lobes, with lymph node metastases in the bilateral neck. The clinical presentation and serological findings were all indicative of Hashimoto's thyroiditis. Thyroid ultrasonography revealed diffuse enlargement of the both lobes, heterogenous echogenicity without mass formation, diffuse scattered microcalcifications and poor vascularization. SWE revealed stiff values of the thyroid: The mean stiffness was 99.7 kpa, the minimum stiffness was 59.1 kpa and the maximum stiffness was 180.1 kpa. The maximum stiffness of the DSVPTC (180.1 kpa) was higher compared with the diagnostic criteria of malignant thyroid nodules (65 kPa). SWE may be considered as a novel and valuable method to diagnose DSVPC.

Shear wave elastography diagnosis of the diffuse sclerosing variant of papillary thyroid carcinoma: A case report

PubMed Central

Xue, Nianyu; Xu, Youfeng; Huang, Pintong; Zhang, Shengmin; Wang, Hongwei; Yu, Fei

2016-01-01

The present study aimed to report the shear wave elastography (SWE) findings in a patient with the diffuse sclerosing variant of papillary thyroid carcinoma (DSVPTC). Since patients with DSVPTC may present with typical clinicopathological features and initially appear to have Hashimoto's thyroiditis, a thorough clinical evaluation and an early diagnosis are important. A 20-year-old female patient presented with a 1-month history of a neck mass and sore throat. Conventional ultrasound and SWE were performed using an AIXPLORER system with 14-5 MHz linear transducer. The patient had undergone total thyroidectomy and bilateral neck lymph node dissection, and an intraoperative pathology consultation to confirm the malignancy of lymph node metastasis. Pathological diagnosis was DSVPTC in both lobes, with lymph node metastases in the bilateral neck. The clinical presentation and serological findings were all indicative of Hashimoto's thyroiditis. Thyroid ultrasonography revealed diffuse enlargement of the both lobes, heterogenous echogenicity without mass formation, diffuse scattered microcalcifications and poor vascularization. SWE revealed stiff values of the thyroid: The mean stiffness was 99.7 kpa, the minimum stiffness was 59.1 kpa and the maximum stiffness was 180.1 kpa. The maximum stiffness of the DSVPTC (180.1 kpa) was higher compared with the diagnostic criteria of malignant thyroid nodules (65 kPa). SWE may be considered as a novel and valuable method to diagnose DSVPC. PMID:27446574

Combination Studies of Oreganum Vulgare Extract Fractions and Volatile Oil along with Ciprofloxacin and Fluconazole against Common Fish Pathogens

PubMed Central

Bharti, Veni; Vasudeva, Neeru; Dhuhan, Joginder Singh

2013-01-01

Purpose: The study is aimed at finding new antibiotic therapy for aquaculture due to potential of bacteria to develop resistance to the existing therapies. Use of large quantities of synthetic antibiotics in aquaculture thus has the potential to be detrimental to fish health, to the environment and wildlife and to human health. Methods: Antimicrobial potential of volatile oil and fractions of chloroform extract of Oreganum vulgare was evaluated alone and in the presence of standard antimicrobials against common fish pathogens by disc-diffusion, agar well assay and two fold microdilution method by nanodrop spectrophotometric method. Results: The best results were represented by volatile oil followed by phenolic fraction by disc-diffusion, agar well and microdilution assays (Minimum inhibitory concentration). By the interaction studies, it was observed that the volatile oil and phenolic fraction were able to inhibit the pathogens at very low concentration compared to standard drugs. The fractional inhibitory concentration index (FICI) was calculated and volatile oil and phenolic fractions were found to be synergistic against Pseudomonas fluorescens and Candida albicans. Conclusion: The experimental data suggests the use of volatile oil and phenolic fraction in combination with standard antimicrobials to maintain healthy aquaculture with lesser adverse effects as compared to synthetic antibiotic therapy. PMID:24312842

Antibacterial and phytochemical screening of Anethum graveolens, Foeniculum vulgare and Trachyspermum ammi

PubMed Central

Kaur, Gurinder J; Arora, Daljit S

2009-01-01

Background Anethum graveolens Linn., Foeniculum vulgare Mill. and Trachyspermum ammi L. are widely used traditional medicinal plants to treat various ailments. To provide a scientific basis to traditional uses of these plants, their aqueous and organic seed extracts, as well as isolated phytoconstituents were evaluated for their antibacterial potential. Methods Antibacterial activity of aqueous and organic seed extracts was assessed using agar diffusion assay, minimum inhibitory concentration and viable cell count studies; and their antibacterial effect was compared with some standard antibiotics. The presence of major phytoconstituents was detected qualitatively and quantitatively. The isolated phytoconstituents were subjected to disc diffusion assay to ascertain their antibacterial effect. Results Hot water and acetone seed extracts showed considerably good antibacterial activity against all the bacteria except Klebsiella pneumoniae and one strain of Pseudomonas aeruginosa. Minimum inhibitory concentration for aqueous and acetone seed extracts ranged from 20–80 mg/ml and 5–15 mg/ml respectively. Viable cell count studies revealed the bactericidal nature of the seed extracts. Statistical analysis proved the better/equal efficacy of some of these seed extracts as compared to standard antibiotics. Phytochemical analysis showed the presence of 2.80 – 4.23% alkaloids, 8.58 – 15.06% flavonoids, 19.71 – 27.77% tannins, 0.55–0.70% saponins and cardiac glycosides. Conclusion Antibacterial efficacy shown by these plants provides a scientific basis and thus, validates their traditional uses as homemade remedies. Isolation and purification of different phytochemicals may further yield significant antibacterial agents. PMID:19656417

Naphtho[1,2-b]furan-4,5-dione is a potent anti-MRSA agent against planktonic, biofilm and intracellular bacteria.

PubMed

Yang, Shih-Chun; Yen, Feng-Lin; Wang, Pei-Wen; Aljuffali, Ibrahim A; Weng, Yi-Han; Tseng, Chih-Hua; Fang, Jia-You

2017-09-01

Naphtho[1,2-b]furan-4,5-dione (N12D) and naphtho[2,3-b]furan-4,9-dione (N23D) are furanonaphthoquinone derivatives from natural resources. We examined the antimicrobial activity of N12D and N23D against drug-resistant Staphylococcus aureus. Minimum inhibitory concentration, minimum bactericidal concentration, bacterial viability and agar diffusion assay were conducted against methicillin-resistant S. aureus (MRSA) and clinical isolates of vancomycin-resistant S. aureus. The minimum inhibitory concentration of N12D and N23D against MRSA was 4.9-9.8 and 39 μM, respectively. With regard to the agar diffusion test, the inhibition zone of the quinone compounds was threefold larger than that of oxacillin. N12D was found to inhibit MRSA biofilm thickness from 24 to 16 μm as observed by confocal microscopy. N12D showed a significant reduction of the intracellular MRSA burden without decreasing the macrophage viability. The antibacterial mechanisms of N12D may be bacterial wall/membrane damage and disturbance of gluconeogenesis and the tricarboxylic acid cycle.

Minimum inhibitory concentration breakpoints and disk diffusion inhibitory zone interpretive criteria for tilmicosin susceptibility testing against Pasteurella multocida and Actinobacillus pleuropneumoniae associated with porcine respiratory disease.

PubMed

Shryock, Thomas R; Staples, J Mitchell; DeRosa, David C

2002-09-01

Tilmicosin is a novel macrolide antibiotic developed for exclusive use in veterinary medicine. Tilmicosin has been approved as a feed premix to control porcine respiratory disease associated with Pasteurella multocida and Actinobacillus pleuropneumoniae. The development of antimicrobial susceptibility testing guidelines for tilmicosin was predicated on the relationship of clinical efficacy studies that demonstrated a favorable therapeutic outcome, on pharmacokinetic data, and on in vitro test data, as recommended by the National Committee for Clinical Laboratory Standards (NCCLS). The approved breakpoints for the minimum inhibitory concentration dilution testing for both species are resistant, > or = 32 microg/ml, and susceptible, < or = 16 microg/ml. The zone of inhibition interpretive criteria for disk diffusion testing with a 15-microg tilmicosin disk are resistant, < or = 10 mm, and susceptible, > or = 11 mm.

Is Vancomycine Still a Choice for Chronic Osteomyelitis Empirical Therapy in Iran?

PubMed Central

Izadi, Morteza; Zamani, Mohammad Mahdi; Mousavi, Seyed Ahmad; Sadat, Seyed Mir Mostafa; Siami, Zeinab; Vais Ahmadi, Noushin; Jonaidi Jafari, Nematollah; Shirvani, Shahram; Majidi Fard, Mojgan; Imani Fooladi, Abbas Ali

2012-01-01

Background Pyogenic bacteria and especially Staphylococcus aurous (S. aurous) are the most common cause of chronic osteomyelitis. Not only treatment protocol of chronic osteomyelitis occasionally is amiss but also this malady responds to treatment difficultly. Objectives This study investigates antibiotic resistance pattern of S. aurous isolated from Iranian patients who suffer from chronic osteomyelitis by two methods: disk diffusion (Kirby bauyer) and E-test (Epsilometer test) to find Vancomycin susceptibility and MIC (Minimum inhibitory concentration). Patients and Methods One hundred and thirty one patients who suffer from chronic osteomyelitis which have been referred to both governmental and private hospitals at 2010 were tried out for culturing of osteomyelitis site (sites). Antibiotic susceptibility and MIC of isolated bacteria were investigated by Kirby bauyer and E-test respectively. Results Samples were collected from bone (73.4%), surrounding tissue (14.6%) and wound discharge (12%). S. aureus was isolated from 49.6% of the samples. According to disc diffusion, methicillin resistance S. aureus (MRSA) was 75% and Vancomycin resistance S. aurous (VRSA) was 0% and based on MIC, MRSA was 68.5% and VRSA was 0%. According to MIC experiments, maximum sensitivity was against to Vancomycin (90.2%) and ciprofloxacin (54.4%) respectively but based on disc diffusion, maximum sensitivity was against to Vancomycin (97.7%) and ciprofloxacin (43.2%), respectively (P = 0.001). E-test (9.8%) in comparison with Disc diffusion (2.3%) showed higher percent of intermediate susceptibility to Vancomycin (P = 0.017). Conclusions Comparison of antibiograms and MICs showed that Kirby bauyer technique especially for detection of VISA strains is not reliable comparison with E-test. Already VRSA strains have not detected in Iranian chronic osteomyelitis, Thus Vancomycin is the first choice for chronic osteomyelitis empirical therapy in Iran yet. PMID:23483042

Oxygen Pathways and Budget for the Eastern South Pacific Oxygen Minimum Zone

NASA Astrophysics Data System (ADS)

Llanillo, P. J.; Pelegrí, J. L.; Talley, L. D.; Peña-Izquierdo, J.; Cordero, R. R.

2018-03-01

Ventilation of the eastern South Pacific Oxygen Minimum Zone (ESP-OMZ) is quantified using climatological Argo and dissolved oxygen data, combined with reanalysis wind stress data. We (1) estimate all oxygen fluxes (advection and turbulent diffusion) ventilating this OMZ, (2) quantify for the first time the oxygen contribution from the subtropical versus the traditionally studied tropical-equatorial pathway, and (3) derive a refined annual-mean oxygen budget for the ESP-OMZ. In the upper OMZ layer, net oxygen supply is dominated by tropical-equatorial advection, with more than one-third of this supply upwelling into the Ekman layer through previously unevaluated vertical advection, within the overturning component of the regional Subtropical Cell (STC). Below the STC, at the OMZ's core, advection is weak and turbulent diffusion (isoneutral and dianeutral) accounts for 89% of the net oxygen supply, most of it coming from the oxygen-rich subtropical gyre. In the deep OMZ layer, net oxygen supply occurs only through turbulent diffusion and is dominated by the tropical-equatorial pathway. Considering the entire OMZ, net oxygen supply (3.84 ± 0.42 µmol kg-1 yr-1) is dominated by isoneutral turbulent diffusion (56.5%, split into 32.3% of tropical-equatorial origin and 24.2% of subtropical origin), followed by isoneutral advection (32.0%, split into 27.6% of tropical-equatorial origin and 4.4% of subtropical origin) and dianeutral diffusion (11.5%). One-quarter (25.8%) of the net oxygen input escapes through dianeutral advection (most of it upwelling) and, assuming steady state, biological consumption is responsible for most of the oxygen loss (74.2%).

Use of quantitative diffusion-weighted magnetic resonance imaging to predict human papilloma virus status in patients with oropharyngeal squamous cell carcinoma.

PubMed

Nakahira, Mitsuhiko; Saito, Naoko; Yamaguchi, Hiroshi; Kuba, Kiyomi; Sugasawa, Masashi

2014-05-01

Although identification of human papilloma virus (HPV) status in oropharyngeal squamous cell carcinoma (OPSCC) is essential in predicting treatment response, no imaging modality can currently determine whether a tumor is HPV-related. In this retrospective study, 26 patients with OPSCC confined to the lateral wall or the base of tongue underwent neck magnetic resonance imaging, using T1-, T2- and diffusion-weighted imaging (DWI). Apparent diffusion coefficients (ADCs) in a region of interest covering the largest available primary tumor area of OPSCC on a single slice of the ADC map were calculated using two b values (0 and 1,000 s/mm(2)). Mean and minimum ADCs were compared with HPV status, using p16 immunohistochemistry as a surrogate marker for HPV infection. Mean and minimum ADCs for HPV(+) OPSCC were significantly lower than those for HPV(-) OPSCC. A cut-off value of mean ADC for HPV(+) OPSCC of 1.027 × 10(-3) mm(2)/s yielded sensitivity and specificity of 83.33 and 78.57%, respectively. In conclusion, the present study indicates that ADC could be used to predict HPV status in patients with OPSCC.

A reaction-diffusion within-host HIV model with cell-to-cell transmission.

PubMed

Ren, Xinzhi; Tian, Yanni; Liu, Lili; Liu, Xianning

2018-06-01

In this paper, a reaction-diffusion within-host HIV model is proposed. It incorporates cell mobility, spatial heterogeneity and cell-to-cell transmission, which depends on the diffusion ability of the infected cells. In the case of a bounded domain, the basic reproduction number [Formula: see text] is established and shown as a threshold: the virus-free steady state is globally asymptotically stable if [Formula: see text] and the virus is uniformly persistent if [Formula: see text]. The explicit formula for [Formula: see text] and the global asymptotic stability of the constant positive steady state are obtained for the case of homogeneous space. In the case of an unbounded domain and [Formula: see text], the existence of the traveling wave solutions is proved and the minimum wave speed [Formula: see text] is obtained, providing the mobility of infected cells does not exceed that of the virus. These results are obtained by using Schauder fixed point theorem, limiting argument, LaSalle's invariance principle and one-side Laplace transform. It is found that the asymptotic spreading speed may be larger than the minimum wave speed via numerical simulations. However, our simulations show that it is possible either to underestimate or overestimate the spread risk [Formula: see text] if the spatial averaged system is used rather than one that is spatially explicit. The spread risk may also be overestimated if we ignore the mobility of the cells. It turns out that the minimum wave speed could be either underestimated or overestimated as long as the mobility of infected cells is ignored.

Inhibition of growth of highly resistant bacterial and fungal pathogens by a natural product.

PubMed

Hafidh, Rand R; Abdulamir, Ahmed S; Vern, Law Se; Abu Bakar, Fatimah; Abas, Faridah; Jahanshiri, Fatemeh; Sekawi, Zamberi

2011-01-01

The continuous escalation of resistant bacteria against a wide range of antibiotics necessitates discovering novel unconventional sources of antibiotics. B. oleracea L (red cabbage) is health-promoting food with proven anticancer and anti-inflammatory activities. However, it has not been researched adequately for its antimicrobial activity on potential resistant pathogens. The methanol crude extract of B. oleracea L. was investigated for a possible anti-microbial activity. The screening method was conducted using disc diffusion assay against 22 pathogenic bacteria and fungi. It was followed by evaluation of the minimum inhibitory concentration (MIC). Moreover, the antibacterial and the antifungal activities were confirmed using the minimum bactericidal concentration (MBC) and the minimum fungicidal concentration (MFC), respectively. Remarkable, antibacterial activity was evident particularly against highly infectious microorganisms such as Methicillin-resistant Staphylococcus aureus, Escherichia coli O157:H7, Pseudomonas aeruginosa, Klebsiella pneumoniae, Staphylococcus aureus, and Salmonella enterica serovar Typhimurium as well as against human fungal pathogens, Trichophyton rubrum and Aspergillus terreus. Red cabbage is a rich source of phenolic compounds, anthocyanins being the most abundant class, which might explain its potent antimicrobial action. This extract is potentially novel for future antimicrobials, inexpensive, and readily available at a large scale for pharmaceutical companies for further investigation and processing.

Inhibition of Growth of Highly Resistant Bacterial and Fungal Pathogens by a Natural Product

PubMed Central

Hafidh, Rand R; Abdulamir, Ahmed S; Vern, Law Se; Abu Bakar, Fatimah; Abas, Faridah; Jahanshiri, Fatemeh; Sekawi, Zamberi

2011-01-01

The continuous escalation of resistant bacteria against a wide range of antibiotics necessitates discovering novel unconventional sources of antibiotics. B. oleracea L (red cabbage) is health-promoting food with proven anticancer and anti-inflammatory activities. However, it has not been researched adequately for its antimicrobial activity on potential resistant pathogens. The methanol crude extract of B. oleracea L. was investigated for a possible anti-microbial activity. The screening method was conducted using disc diffusion assay against 22 pathogenic bacteria and fungi. It was followed by evaluation of the minimum inhibitory concentration (MIC). Moreover, the antibacterial and the antifungal activities were confirmed using the minimum bactericidal concentration (MBC) and the minimum fungicidal concentration (MFC), respectively. Remarkable, antibacterial activity was evident particularly against highly infectious microorganisms such as Methicillin-resistant Staphylococcus aureus, Escherichia coli O157:H7, Pseudomonas aeruginosa, Klebsiella pneumoniae, Staphylococcus aureus, and Salmonella enterica serovar Typhimurium as well as against human fungal pathogens, Trichophyton rubrum and Aspergillus terreus. Red cabbage is a rich source of phenolic compounds, anthocyanins being the most abundant class, which might explain its potent antimicrobial action. This extract is potentially novel for future antimicrobials, inexpensive, and readily available at a large scale for pharmaceutical companies for further investigation and processing. PMID:21915230

Visual pathway impairment by pituitary adenomas: quantitative diagnostics by diffusion tensor imaging.

PubMed

Lilja, Ylva; Gustafsson, Oscar; Ljungberg, Maria; Starck, Göran; Lindblom, Bertil; Skoglund, Thomas; Bergquist, Henrik; Jakobsson, Karl-Erik; Nilsson, Daniel

2017-09-01

OBJECTIVE Despite ample experience in surgical treatment of pituitary adenomas, little is known about objective indices that may reveal risk of visual impairment caused by tumor growth that leads to compression of the anterior visual pathways. This study aimed to explore diffusion tensor imaging (DTI) as a means for objective assessment of injury to the anterior visual pathways caused by pituitary adenomas. METHODS Twenty-three patients with pituitary adenomas, scheduled for transsphenoidal tumor resection, and 20 healthy control subjects were included in the study. A minimum suprasellar tumor extension of Grade 2-4, according to the SIPAP (suprasellar, infrasellar, parasellar, anterior, and posterior) scale, was required for inclusion. Neuroophthalmological examinations, conventional MRI, and DTI were completed in all subjects and were repeated 6 months after surgery. Quantitative assessment of chiasmal lift, visual field defect (VFD), and DTI parameters from the optic tracts was performed. Linear correlations, group comparisons, and prediction models were done in controls and patients. RESULTS Both the degree of VFD and chiasmal lift were significantly correlated with the radial diffusivity (r = 0.55, p < 0.05 and r = 0.48, p < 0.05, respectively) and the fractional anisotropy (r = -0.58, p < 0.05 and r = -0.47, p < 0.05, respectively) but not with the axial diffusivity. The axial diffusivity differed significantly between controls and patients with VFD, both before and after surgery (p < 0.05); however, no difference was found between patients with and without VFD. Based on the axial diffusivity and fractional anisotropy, a prediction model classified all patients with VFD correctly (sensitivity 1.0), 9 of 12 patients without VFD correctly (sensitivity 0.75), and 17 of 20 controls as controls (specificity 0.85). CONCLUSIONS DTI could detect pathology and degree of injury in the anterior visual pathways that were compressed by pituitary adenomas. The correlation between radial diffusivity and visual impairment may reflect a gradual demyelination in the visual pathways caused by an increased tumor effect. The low level of axial diffusivity found in the patient group may represent early atrophy in the visual pathways, detectable on DTI but not by conventional methods. DTI may provide objective data, detect early signs of injury, and be an additional diagnostic tool for determining indication for surgery in cases of pituitary adenomas.

Full Characterization of CO2-Oil Properties On-Chip: Solubility, Diffusivity, Extraction Pressure, Miscibility, and Contact Angle.

PubMed

Sharbatian, Atena; Abedini, Ali; Qi, ZhenBang; Sinton, David

2018-02-20

Carbon capture, storage, and utilization technologies target a reduction in net CO 2 emissions to mitigate greenhouse gas effects. The largest such projects worldwide involve storing CO 2 through enhanced oil recovery-a technologically and economically feasible approach that combines both storage and oil recovery. Successful implementation relies on detailed measurements of CO 2 -oil properties at relevant reservoir conditions (P = 2.0-13.0 MPa and T = 23 and 50 °C). In this paper, we demonstrate a microfluidic method to quantify the comprehensive suite of mutual properties of a CO 2 and crude oil mixture including solubility, diffusivity, extraction pressure, minimum miscibility pressure (MMP), and contact angle. The time-lapse oil swelling/extraction in response to CO 2 exposure under stepwise increasing pressure was quantified via fluorescence microscopy, using the inherent fluorescence property of the oil. The CO 2 solubilities and diffusion coefficients were determined from the swelling process with measurements in strong agreement with previous results. The CO 2 -oil MMP was determined from the subsequent oil extraction process with measurements within 5% of previous values. In addition, the oil-CO 2 -silicon contact angle was measured throughout the process, with contact angle increasing with pressure. In contrast with conventional methods, which require days and ∼500 mL of fluid sample, the approach here provides a comprehensive suite of measurements, 100-fold faster with less than 1 μL of sample, and an opportunity to better inform large-scale CO 2 projects.

Studies on droplet evaporation and combustion in high pressures

NASA Technical Reports Server (NTRS)

Sato, J.

1993-01-01

High pressure droplet evaporation and combustion have been studied up to 15 MPa under normal and microgravity fields. From the evaporation studies, it has been found that in the supercritical environments, the droplet evaporation rate and lifetime take a maximum and a minimum at an ambient pressure over the critical pressure. Its maximum and minimum points move toward the lower ambient pressures if the ambient temperature is increased. It has been found from the combustion studies that the burning life time takes a minimum at an ambient pressure being equal to the critical pressure. It is attributable to both the pressure dependency of the diffusion rate and the droplet evaporation characteristics described above.

DESIGN OF MINIMUM-WEIGHT DIFFUSION BATTERIES

EPA Science Inventory

Until recently, the measurement of particle sizes in aerosols was largely a laboratory exercise. Currently, however, particulates in the atmosphere and in the industrial exhaust gases are being monitored extensively in the field. While the weight and volume of laboratory apparatu...

Helium measurements of pore fluids obtained from the San Andreas Fault Observatory at Depth (SAFOD, USA) drill cores

NASA Astrophysics Data System (ADS)

Ali, S.; Stute, M.; Torgersen, T.; Winckler, G.; Kennedy, B. M.

2011-02-01

4He accumulated in fluids is a well established geochemical tracer used to study crustal fluid dynamics. Direct fluid samples are not always collectable; therefore, a method to extract rare gases from matrix fluids of whole rocks by diffusion has been adapted. Helium was measured on matrix fluids extracted from sandstones and mudstones recovered during the San Andreas Fault Observatory at Depth (SAFOD) drilling in California, USA. Samples were typically collected as subcores or from drillcore fragments. Helium concentration and isotope ratios were measured 4-6 times on each sample, and indicate a bulk 4He diffusion coefficient of 3.5 ± 1.3 × 10-8 cm2 s-1 at 21°C, compared to previously published diffusion coefficients of 1.2 × 10-18 cm2 s-1 (21°C) to 3.0 × 10-15 cm2 s-1 (150°C) in the sands and clays. Correcting the diffusion coefficient of 4Hewater for matrix porosity (˜3%) and tortuosity (˜6-13) produces effective diffusion coefficients of 1 × 10-8 cm2 s-1 (21°C) and 1 × 10-7 (120°C), effectively isolating pore fluid 4He from the 4He contained in the rock matrix. Model calculations indicate that <6% of helium initially dissolved in pore fluids was lost during the sampling process. Complete and quantitative extraction of the pore fluids provide minimum in situ porosity values for sandstones 2.8 ± 0.4% (SD, n = 4) and mudstones 3.1 ± 0.8% (SD, n = 4).

Demonstration and Validation of a Regenerated Cellulose Dialysis Membrane Diffusion Sampler for Monitoring Ground Water Quality and Remediation Progress at DoD Sites for Perchlorate and Explosives Compounds

DTIC Science & Technology

2010-09-01

Regulatory Council LRL Laboratory reporting level LDPE Low-density polyethylene MDL Minimum detection limit MNA Monitored natural attenuation...consists of a tubular-shaped bag made of flexible low-density polyethylene ( LDPE ) (Vroblesky, 2001a, 2001b). The LDPE tube is heat-sealed on one end...be constructed from small- diameter LDPE tubing that fits into small-diameter wells. These polyethylene diffusion bag (PDB) samplers have been

Demonstration and Validation of a Regenerated Cellulose Dialysis Membrane Diffusion Sampler for Monitoring Ground-Water Quality and Remediation Progress at DoD Site: Perchlorate and Ordnance Compounds

DTIC Science & Technology

2011-10-01

Regulatory Council LDPE low-density polyethylene MDL minimum detection limit NAVFAC ESC Naval Facilities Engineering Command Engineering Service...membrane sampler design consists of a tubular-shaped bag made of flexible low-density polyethylene ( LDPE ) (Vroblesky, 2001a, 2001b). The LDPE tube is...requirements, and can be constructed from small-diameter LDPE tubing that fits into small- 4 diameter wells. These polyethylene diffusion bag

The ability of selected plant essential oils to enhance the action of recommended antibiotics against pathogenic wound bacteria.

PubMed

Sienkiewicz, Monika; Łysakowska, Monika; Kowalczyk, Edward; Szymańska, Grażyna; Kochan, Ewa; Krukowska, Jolanta; Olszewski, Jurek; Zielińska-Bliźniewska, Hanna

2017-03-01

The aim of this work was to characterize the ability of essential oils to support antibiotics against pathogenic bacteria in wounds. Gram-positive and Gram-negative bacteria obtained from wound infections were identified according to standard microbiological methods. Essential oils were analysed by GC-FID-MS. The susceptibility of bacteria to antibiotics, essential oils and their combination was assessed using the disc-diffusion method. The Minimal Inhibitory Concentration and Minimum Bactericidal Concentration of the essential oils were established by the micro-dilution broth method. Although cinnamon, clove, thyme and lavender essential oils were found to have the greatest antibacterial activity when used alone, the greatest additive and synergistic effects against pathogenic wound bacteria in combination with recommended antibiotics were demonstrated by basil, clary sage and rosemary oils. Copyright © 2016 Elsevier Ltd and ISBI. All rights reserved.

Numerical method for solution of systems of non-stationary spatially one-dimensional nonlinear differential equations

NASA Technical Reports Server (NTRS)

Morozov, S. K.; Krasitskiy, O. P.

1978-01-01

A computational scheme and a standard program is proposed for solving systems of nonstationary spatially one-dimensional nonlinear differential equations using Newton's method. The proposed scheme is universal in its applicability and its reduces to a minimum the work of programming. The program is written in the FORTRAN language and can be used without change on electronic computers of type YeS and BESM-6. The standard program described permits the identification of nonstationary (or stationary) solutions to systems of spatially one-dimensional nonlinear (or linear) partial differential equations. The proposed method may be used to solve a series of geophysical problems which take chemical reactions, diffusion, and heat conductivity into account, to evaluate nonstationary thermal fields in two-dimensional structures when in one of the geometrical directions it can take a small number of discrete levels, and to solve problems in nonstationary gas dynamics.

Improvements in Technique of NMR Imaging and NMR Diffusion Measurements in the Presence of Background Gradients.

NASA Astrophysics Data System (ADS)

Lian, Jianyu

In this work, modification of the cosine current distribution rf coil, PCOS, has been introduced and tested. The coil produces a very homogeneous rf magnetic field, and it is inexpensive to build and easy to tune for multiple resonance frequency. The geometrical parameters of the coil are optimized to produce the most homogeneous rf field over a large volume. To avoid rf field distortion when the coil length is comparable to a quarter wavelength, a parallel PCOS coil is proposed and discussed. For testing rf coils and correcting B _1 in NMR experiments, a simple, rugged and accurate NMR rf field mapping technique has been developed. The method has been tested and used in 1D, 2D, 3D and in vivo rf mapping experiments. The method has been proven to be very useful in the design of rf coils. To preserve the linear relation between rf output applied on an rf coil and modulating input for an rf modulating -amplifying system of NMR imaging spectrometer, a quadrature feedback loop is employed in an rf modulator with two orthogonal rf channels to correct the amplitude and phase non-linearities caused by the rf components in the rf system. The modulator is very linear over a large range and it can generate an arbitrary rf shape. A diffusion imaging sequence has been developed for measuring and imaging diffusion in the presence of background gradients. Cross terms between the diffusion sensitizing gradients and background gradients or imaging gradients can complicate diffusion measurement and make the interpretation of NMR diffusion data ambiguous, but these have been eliminated in this method. Further, the background gradients has been measured and imaged. A dipole random distribution model has been established to study background magnetic fields Delta B and background magnetic gradients G_0 produced by small particles in a sample when it is in a B_0 field. From this model, the minimum distance that a spin can approach a particle can be determined by measuring and <{bf G}_sp{0 }{2}>. From this model, the particle concentration in a sample can be determined by measuring the lineshape of a free induction decay (fid).

Comparison of Apparent Diffusion Coefficient and Intravoxel Incoherent Motion for Differentiating among Glioblastoma, Metastasis, and Lymphoma Focusing on Diffusion-Related Parameter.

PubMed

Shim, Woo Hyun; Kim, Ho Sung; Choi, Choong-Gon; Kim, Sang Joon

2015-01-01

Brain tumor cellularity has been assessed by using apparent diffusion coefficient (ADC). However, the ADC value might be influenced by both perfusion and true molecular diffusion, and the perfusion effect on ADC can limit the reliability of ADC in the characterization of tumor cellularity, especially, in hypervascular brain tumors. In contrast, the IVIM technique estimates parameter values for diffusion and perfusion effects separately. The purpose of our study was to compare ADC and IVIM for differentiating among glioblastoma, metastatic tumor, and primary CNS lymphoma (PCNSL) focusing on diffusion-related parameter. We retrospectively reviewed the data of 128 patients with pathologically confirmed glioblastoma (n = 55), metastasis (n = 31), and PCNSL (n = 42) prior to any treatment. Two neuroradiologists independently calculated the maximum IVIM-f (fmax) and minimum IVIM-D (Dmin) by using 16 different b-values with a bi-exponential fitting of diffusion signal decay, minimum ADC (ADCmin) by using 0 and 1000 b-values with a mono-exponential fitting and maximum normalized cerebral blood volume (nCBVmax). The differences in fmax, Dmin, nCBVmax, and ADCmin among the three tumor pathologies were determined by one-way ANOVA with multiple comparisons. The fmax and Dmin were correlated to the corresponding nCBV and ADC using partial correlation analysis, respectively. Using a mono-exponential fitting of diffusion signal decay, the mean ADCmin was significantly lower in PCNSL than in glioblastoma and metastasis. However, using a bi-exponential fitting, the mean Dmin did not significantly differ in the three groups. The mean fmax significantly increased in the glioblastomas (reader 1, 0.103; reader 2, 0.109) and the metastasis (reader 1, 0.105; reader 2, 0.107), compared to the primary CNS lymphomas (reader 1, 0.025; reader 2, 0.023) (P < .001 for each). The correlation between fmax and the corresponding nCBV was highest in glioblastoma group, and the correlation between Dmin and the corresponding ADC was highest in primary CNS lymphomas group. Unlike ADC value derived from a mono-exponential fitting of diffusion signal, diffusion-related parametric value derived from a bi-exponential fitting with separation of perfusion effect doesn't differ among glioblastoma, metastasis, and PCNSL.

Molecular dynamics simulation of real-fluid mutual diffusion coefficients with the Lennard-Jones potential model

NASA Astrophysics Data System (ADS)

Stoker, J. M.; Rowley, R. L.

1989-09-01

Mutual diffusion coefficients for selected alkanes in carbon tetrachloride were calculated using molecular dynamics and Lennard-Jones (LJ) potentials. Use of effective spherical LJ parameters is desirable when possible for two reasons: (i) computer time is saved due to the simplicity of the model and (ii) the number of parameters in the model is kept to a minimum. Results of this study indicate that mutual diffusivity is particularly sensitive to the molecular size cross parameter, σ12, and that the commonly used Lorentz-Berthelot rules are inadequate for mixtures in which the component structures differ significantly. Good agreement between simulated and experimental mutual diffusivities is obtained with a combining rule for σ12 which better represents these asymmetric mixtures using pure component LJ parameters obtained from self-diffusion coefficient data. The effect of alkane chain length on the mutual diffusion coefficient is correctly predicted. While the effects of alkane branching upon the diffusion coefficient are comparable in size to the uncertainty of these calculations, the qualitative trend due to branching is also correctly predicted by the MD results.

Atomistic Simulation of High-Density Uranium Fuels

DOE PAGES

Garcés, Jorge Eduardo; Bozzolo, Guillermo

2011-01-01

We apply an atomistic modeling approach to deal with interfacial phenomena in high-density uranium fuels. The effects of Si, as additive to Al or as U-Mo-particles coating, on the behavior of the Al/U-Mo interface is modeled by using the Bozzolo-Ferrante-Smith (BFS) method for alloys. The basic experimental features characterizing the real system are identified, via simulations and atom-by-atom analysis. These include (1) the trend indicating formation of interfacial compounds, (2) much reduced diffusion of Al into U-Mo solid solution due to the high Si concentration, (3) Si depletion in the Al matrix, (4) an unexpected interaction between Mo and Simore » which inhibits Si diffusion to deeper layers in the U-Mo solid solution, and (5) the minimum amount of Si needed to perform as an effective diffusion barrier. Simulation results related to alternatives to Si dispersed in the Al matrix, such as the use of C coating of U-Mo particles or Zr instead of the Al matrix, are also shown. Recent experimental results confirmed early theoretical proposals, along the lines of the results reported in this work, showing that atomistic computational modeling could become a valuable tool to aid the experimental work in the development of nuclear fuels.« less

Antibacterial and phytochemical studies on Calotropis gigantia (L.) R. Br. latex against selected cariogenic bacteria

PubMed Central

Ishnava, Kalpesh B.; Chauhan, Jenabhai B.; Garg, Akanksha A.; Thakkar, Arpit M.

2011-01-01

In vitro antibacterial potential of the chloroform, ethyl acetate, hexane, methanol and aqueous extracts of Calotropis gigantia (L.) R. Br. was evaluated by using five cariogenic bacteria, Actinomyces viscosus, Lactobacillus acidophilus, Lactobacillus casei, Streptococcus mitis and Streptococcus mutans. Agar well diffusion method and minimum inhibitory concentration (MIC) were used for this purpose. The chloroform extracted fraction of latex showed inhibitory effect against S. mutans and L. acidophilus with MIC value of 0.032 and 0.52 mg/mL, respectively. Qualitative investigation on structure elucidation of bioactive compound using IR, NMR and GC–MS techniques revealed the presence of methyl nonanoate, a saturated fatty acid. PMID:23961166

Applications of thin-film sandwich crystallization platforms.

PubMed

Axford, Danny; Aller, Pierre; Sanchez-Weatherby, Juan; Sandy, James

2016-04-01

Examples are shown of protein crystallization in, and data collection from, solutions sandwiched between thin polymer films using vapour-diffusion and batch methods. The crystallization platform is optimal for both visualization and in situ data collection, with the need for traditional harvesting being eliminated. In wells constructed from the thinnest plastic and with a minimum of aqueous liquid, flash-cooling to 100 K is possible without significant ice formation and without any degradation in crystal quality. The approach is simple; it utilizes low-cost consumables but yields high-quality data with minimal sample intervention and, with the very low levels of background X-ray scatter that are observed, is optimal for microcrystals.

Migration of 75Se(IV) in crushed Beishan granite: Effects of the iron content.

PubMed

He, Jiangang; Ma, Bin; Kang, Mingliang; Wang, Chunli; Nie, Zhe; Liu, Chunli

2017-02-15

The diffusion of selenite (labeled with 75 Se) in compacted Beishan granite (BsG) was investigated using the in-diffusion capillary method at pH values from ∼2.0 to ∼11.0 under oxic and anoxic conditions. The results indicate that the apparent diffusion coefficient (D a ) values of selenite in BsG always reached the minimum at approximately pH 5. Unexpectedly, the D a values under oxic conditions are nearly one order of magnitude lower than those under the anoxic conditions. Further characterization reveals the existence of redox-sensitive Fe(II)-containing components, which can be responsible for the great difference in D a values. Fe(2p) X-ray photoelectron spectroscopy (XPS) results show that more Fe(III)-oxyhydroxide coating is formed on the granite's surface under aerobic conditions than is formed under anaerobic conditions. Correspondingly, Se(3d) spectra indicate that more selenium is sorbed under oxic conditions, and the sorbed amount always reached the maximum at pH values from ∼4 to ∼5. A linear combination fit of X-ray absorption near edge structure (XANES) spectroscopy data revealed that Se(0) was formed under anoxic condition and that selenite preferred to form inner-sphere complexes with Fe(III)-oxyhydroxide. Overall, this study indicates that natural Fe-bearing minerals can greatly attenuate selenite diffusion and the retardation would be enhanced under aerobic conditions. Copyright © 2016 Elsevier B.V. All rights reserved.

Correlation Between Minimum Apparent Diffusion Coefficient (ADCmin) and Tumor Cellularity: A Meta-analysis.

PubMed

Surov, Alexey; Meyer, Hans Jonas; Wienke, Andreas

2017-07-01

Diffusion-weighted imaging (DWI) is a magnetic resonance imaging (MRI) technique based on measure of water diffusion that can provide information about tissue microstructure, especially about cell count. Increase of cell density induces restriction of water diffusion and decreases apparent diffusion coefficient (ADC). ADC can be divided into three sub-parameters: ADC minimum or ADC min , mean ADC or ADC mean and ADC maximum or ADC max Some studies have suggested that ADC min shows stronger correlations with cell count in comparison to other ADC fractions and may be used as a parameter for estimation of tumor cellularity. The aim of the present meta-analysis was to summarize correlation coefficients between ADC min and cellularity in different tumors based on large patient data. For this analysis, MEDLINE database was screened for associations between ADC and cell count in different tumors up to September 2016. For this work, only data regarding ADC min were included. Overall, 12 publications with 317 patients were identified. Spearman's correlation coefficient was used to analyze associations between ADC min and cellularity. The reported Pearson correlation coefficients in some publications were converted into Spearman correlation coefficients. The pooled correlation coefficient for all included studies was ρ=-0.59 (95% confidence interval (CI)=-0.72 to -0.45), heterogeneity Tau 2 =0.04 (p<0.0001), I 2 =73%, test for overall effect Z=8.67 (p<0.00001). ADC min correlated moderately with tumor cellularity. The calculated correlation coefficient is not stronger in comparison to the reported coefficient for ADC mean and, therefore, ADC min does not represent a better means to reflect cellularity. Copyright© 2017, International Institute of Anticancer Research (Dr. George J. Delinasios), All rights reserved.

Symplastic Transport of Carboxyfluorescein in Staminal Hairs of Setcreasea purpurea Is Diffusive and Includes Loss to the Vacuole.

PubMed

Tucker, J E; Mauzerall, D; Tucker, E B

1989-07-01

The kinetics of symplastic transport in staminal hairs of Setcreasea purpurea was studied. The tip cell of a staminal hair was microinjected with carboxyfluorescein (CF) and the symplastic transport of this CF was videotaped and the digital data analyzed to produce kinetic curves. Using a finite difference equation for diffusion between cells and for loss of dye into the vacuole, kinetic curves were calculated and fitted to the observed data. These curves were matched with data from actual microinjection experiments by adjusting K (the coefficient of intercellular junction diffusion) and L (the coefficient of intracellular loss) until a minimum in the least squares difference between the curves was obtained. (a) Symplastic transport of CF was governed by diffusion through intercellular pores (plasmodesmata) and intracellular loss. Diffusion within the cell cytoplasm was never limiting. (b) Each cell and its plasmodesmata must be considered as its own diffusion system. Therefore, a diffusion coefficient cannot be calculated for an entire chain of cells. (c) The movement through plasmodesmata in either direction was the same since the data are fit by a diffusion equation. (d) Diffusion through the intercellular pores was estimated to be slower than diffusion through similar pores filled with water.

Symplastic Transport of Carboxyfluorescein in Staminal Hairs of Setcreasea purpurea Is Diffusive and Includes Loss to the Vacuole 1

PubMed Central

Tucker, Joseph E.; Mauzerall, David; Tucker, Edward B.

1989-01-01

The kinetics of symplastic transport in staminal hairs of Setcreasea purpurea was studied. The tip cell of a staminal hair was microinjected with carboxyfluorescein (CF) and the symplastic transport of this CF was videotaped and the digital data analyzed to produce kinetic curves. Using a finite difference equation for diffusion between cells and for loss of dye into the vacuole, kinetic curves were calculated and fitted to the observed data. These curves were matched with data from actual microinjection experiments by adjusting K (the coefficient of intercellular junction diffusion) and L (the coefficient of intracellular loss) until a minimum in the least squares difference between the curves was obtained. (a) Symplastic transport of CF was governed by diffusion through intercellular pores (plasmodesmata) and intracellular loss. Diffusion within the cell cytoplasm was never limiting. (b) Each cell and its plasmodesmata must be considered as its own diffusion system. Therefore, a diffusion coefficient cannot be calculated for an entire chain of cells. (c) The movement through plasmodesmata in either direction was the same since the data are fit by a diffusion equation. (d) Diffusion through the intercellular pores was estimated to be slower than diffusion through similar pores filled with water. PMID:16666864

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

Scofield, C.M.; Des Champs, N.H.

This article examines a design concept for classroom air conditioning systems that guarantees minimum ventilation rates are met. The topics of the article include new ventilation requirements, design concept, outside air induction diffuser, low-velocity ducts and plenums, the relationship of humidity to school absenteeism rates, retrofit applications, and saving energy.

Brownian ratchets: How stronger thermal noise can reduce diffusion

NASA Astrophysics Data System (ADS)

Spiechowicz, Jakub; Kostur, Marcin; Łuczka, Jerzy

2017-02-01

We study diffusion properties of an inertial Brownian motor moving on a ratchet substrate, i.e., a periodic structure with broken reflection symmetry. The motor is driven by an unbiased time-periodic symmetric force that takes the system out of thermal equilibrium. For selected parameter sets, the system is in a non-chaotic regime in which we can identify a non-monotonic dependence of the diffusion coefficient on temperature: for low temperature, it initially increases as the temperature grows, passes through its local maximum, next starts to diminish reaching its local minimum, and finally it monotonically increases in accordance with the Einstein linear relation. Particularly interesting is the temperature interval in which diffusion is suppressed by the thermal noise, and we explain this effect in terms of transition rates of a three-state stochastic model.

Brownian ratchets: How stronger thermal noise can reduce diffusion.

PubMed

Spiechowicz, Jakub; Kostur, Marcin; Łuczka, Jerzy

2017-02-01

We study diffusion properties of an inertial Brownian motor moving on a ratchet substrate, i.e., a periodic structure with broken reflection symmetry. The motor is driven by an unbiased time-periodic symmetric force that takes the system out of thermal equilibrium. For selected parameter sets, the system is in a non-chaotic regime in which we can identify a non-monotonic dependence of the diffusion coefficient on temperature: for low temperature, it initially increases as the temperature grows, passes through its local maximum, next starts to diminish reaching its local minimum, and finally it monotonically increases in accordance with the Einstein linear relation. Particularly interesting is the temperature interval in which diffusion is suppressed by the thermal noise, and we explain this effect in terms of transition rates of a three-state stochastic model.

Correlation of diffusion and perfusion MRI with Ki-67 in high-grade meningiomas.

PubMed

Ginat, Daniel T; Mangla, Rajiv; Yeaney, Gabrielle; Wang, Henry Z

2010-12-01

Atypical and anaplastic meningiomas have a greater likelihood of recurrence than benign meningiomas. The risk for recurrence is often estimated using the Ki-67 labeling index. The purpose of this study was to determine the correlation between Ki-67 and regional cerebral blood volume (rCBV) and between Ki-67 and apparent diffusion coefficient (ADC) in atypical and anaplastic meningiomas. A retrospective review of the advanced imaging and immunohistochemical characteristics of atypical and anaplastic meningiomas was performed. The relative minimum ADC, relative maximum rCBV, and specimen Ki-67 index were measured. Pearson's correlation was used to compare these parameters. There were 23 cases with available ADC maps and 20 cases with available rCBV maps. The average Ki-67 among the cases with ADC maps and rCBV maps was 17.6% (range, 5-38%) and 16.7% (range, 3-38%), respectively. The mean minimum ADC ratio was 0.91 (SD, 0.26) and the mean maximum rCBV ratio was 22.5 (SD, 7.9). There was a significant positive correlation between maximum rCBV and Ki-67 (Pearson's correlation, 0.69; p = 0.00038). However, there was no significant correlation between minimum ADC and Ki-67 (Pearson's correlation, -0.051; p = 0.70). Maximum rCBV correlated significantly with Ki-67 in high-grade meningiomas.

A Theoretical Study of Bulk and Surface Diffusion Processes for Semiconductor Materials Using First Principles Calculations

NASA Astrophysics Data System (ADS)

Roehl, Jason L.

Diffusion of point defects on crystalline surfaces and in their bulk is an important and ubiquitous phenomenon affecting film quality, electronic properties and device functionality. A complete understanding of these diffusion processes enables one to predict and then control those processes. Such understanding includes knowledge of the structural, energetic and electronic properties of these native and non-native point defect diffusion processes. Direct experimental observation of the phenomenon is difficult and microscopic theories of diffusion mechanisms and pathways abound. Thus, knowing the nature of diffusion processes, of specific point defects in given materials, has been a challenging task for analytical theory as well as experiment. The recent advances in computing technology have been a catalyst for the rise of a third mode of investigation. The advent of tremendous computing power, breakthroughs in algorithmic development in computational applications of electronic density functional theory now enables direct computation of the diffusion process. This thesis demonstrates such a method applied to several different examples of point defect diffusion on the (001) surface of gallium arsenide (GaAs) and the bulk of cadmium telluride (CdTe) and cadmium sulfide (CdS). All results presented in this work are ab initio, total-energy pseudopotential calculations within the local density approximation to density-functional theory. Single particle wavefunctions were expanded in a plane-wave basis and reciprocal space k-point sampling was achieved by Monkhorst-Pack generated k-point grids. Both surface and bulk computations employed a supercell approach using periodic boundary conditions. Ga adatom adsorption and diffusion processes were studied on two reconstructions of the GaAs(001) surface including the c(4x4) and c(4x4)-heterodimer surface reconstructions. On the GaAs(001)- c(4x4) surface reconstruction, two distinct sets of minima and transition sites were discovered for a Ga adatom relaxing from heights of 3 and 0.5 A from the surface. These two sets show significant differences in the interaction of the Ga adatom with surface As dimers and an electronic signature of the differences in this interaction was identified. The energetic barriers to diffusion were computed between various adsorption sites. Diffusion profiles for native Cd and S, adatom and vacancy, and non-native interstitial adatoms of Te, Cu and Cl were investigated in bulk wurtzite CdS. The interstitial diffusion paths considered in this work were chosen parallel to c-axis as it represents the path encountered by defects diffusing from the CdTe layer. Because of the lattice mismatch between zinc-blende CdTe and hexagonal wurtzite CdS, the c-axis in CdS is normal to the CdTe interface. The global minimum and maximum energy positions in the bulk unit cell vary for different diffusing species. This results in a significant variation, in the bonding configurations and associated strain energies of different extrema positions along the diffusion paths for various defects. The diffusion barriers range from a low of 0.42 eV for an S interstitial to a high of 2.18 eV for a S vacancy. The computed 0.66 eV barrier for a Cu interstitial is in good agreement with experimental values in the range of 0.58 - 0.96 eV reported in the literature. There exists an electronic signature in the local density of states for the s- and d-states of the Cu interstitial at the global maximum and global minimum energy position. The work presented in this thesis is an investigation into diffusion processes for semiconductor bulk and surfaces. The work provides information about these processes at a level of control unavailable experimentally giving an elaborate description into physical and electronic properties associated with diffusion at its most basic level. Not only does this work provide information about GaAs, CdTe and CdS, it is intended to contribute to a foundation of knowledge that can be extended to other systems to expand our overall understanding into the diffusion process. (Abstract shortened by UMI.)

Chemical Composition and Antibacterial Activity of Essential Oils of Tagetes minuta (Asteraceae) against Selected Plant Pathogenic Bacteria

PubMed Central

Wagacha, John M.; Dossaji, Saifuddin F.

2016-01-01

The objective of this study was to determine the chemical composition and antibacterial activity of essential oils (EOs) of Tagetes minuta against three phytopathogenic bacteria Pseudomonas savastanoi pv. phaseolicola, Xanthomonas axonopodis pv. phaseoli, and Xanthomonas axonopodis pv. manihotis. The essential oils were extracted using steam distillation method in a modified Clevenger-type apparatus while antibacterial activity of the EOs was evaluated by disc diffusion method. Gas chromatography coupled to mass spectrometry (GC/MS) was used for analysis of the chemical profile of the EOs. Twenty compounds corresponding to 96% of the total essential oils were identified with 70% and 30% of the identified components being monoterpenes and sesquiterpenes, respectively. The essential oils of T. minuta revealed promising antibacterial activities against the test pathogens with Pseudomonas savastanoi pv. phaseolicola being the most susceptible with mean inhibition zone diameters of 41.83 and 44.83 mm after 24 and 48 hours, respectively. The minimum inhibitory concentrations and minimum bactericidal concentrations of the EOs on the test bacteria were in the ranges of 24–48 mg/mL and 95–190 mg/mL, respectively. These findings provide a scientific basis for the use of T. minuta essential oils as a botanical pesticide for management of phytopathogenic bacteria. PMID:27721831

Antioxidant and antimicrobial activities of solvent fractions of Vernonia cinerea (L.) Less leaf extract.

PubMed

Sonibare, Mubo A; Aremu, Oluwafunmilola T; Okorie, Patricia N

2016-06-01

Vernonia cinerea (L.) Less is used in folk medicine as a remedy for various diseases. The present study reports antioxidant and antimicrobial activities of solvent fractions of Vernonia cinerea. The antioxidant properties of solvent fractions of V. cinerea were evaluated by determining radicals scavenging activity, total flavonoid and phenolic contents measured with the 2,2-diphenyl-1-picryl hydrazyl (DPPH) test, the aluminum chloride and the Folin-ciocalteau methods, respectively. Antimicrobial activities were tested against human pathogenic microorganisms using agar diffusion method. The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of each active extract were determined. The ethyl acetate fraction having the IC50 value of 6.50 µg/mL demonstrated comparable DPPH radical-scavenging activity with standard antioxidants, gallic acid and quercetin included in the study. All fractions displayed moderate antimicrobial potential against the tested pathogens with the zone of inhibition that ranged from 9.0 to 13.5 mm. The MIC (1.56 mg/mL) and MBC (3.13 mg/mL) indicated highest susceptibility of Candida albicans in all fractions. The results of this study showed that the solvent fractions of V. cinerea possess antioxidant and antimicrobial activities, hence justifying the folkloric use of the plant for the treatment of various ailments in traditional medicine.

Antibacterial Activity of Ethanolic Extract of Cinnamon Bark, Honey, and Their Combination Effects against Acne-Causing Bacteria

PubMed Central

Julianti, Elin; Rajah, Kasturi K.; Fidrianny, Irda

2017-01-01

Propionibacterium acnes and Staphylococcus epidermidis are the major skin bacteria that cause the formation of acne. The present study was conducted to investigate antibacterial activity of ethanolic extract of cinnamon bark, honey, and their combination against acne bacteria. The antibacterial activity of extract of cinnamon bark and honey were investigated against P. acnes and S. epidermidis using disc diffusion. Minimum inhibitory concentrations (MICs) and minimum bactericidal concentrations (MBCs) were attained using Clinical and Laboratory Standard Institute (CLSI) methods. The interaction between cinnamon bark extract and honey was determined using a checkerboards method. The results showed that the MICs of cinnamon bark extract and honey against P. acne were 256 µg/mL and 50% v/v, respectively, while those against S. epidermidis were 1024 µg/mL and 50% v/v, respectively. The MBC of cinnamon bark extract against P. acnes and S. epidermidis were more than 2048 µg/mL, whereas the MBC for honey against P. acnes and S. epidermidis were 100%. The combination of cinnamon bark extract and honey against P. acnes and S. epidermidis showed additive activity with a fractional inhibitory concentration index (FICI) value of 0.625. Therefore, the combination of cinnamon bark extract and honey has potential activity against acne-causing bacteria. PMID:28398231

[Efficacy of sodium hydroxide at 2.5 %, chlorhexidine gluconate at 0.5 % and calcium hydroxide against Candida albicans].

PubMed

Ndiaye, D; Diongue, K; Bane, K; Seck, A; Niang, S O; Lèye Benoist, F; Ndiaye, D; Touré, B

2016-12-01

Endodontic flora is dominated in the apical part of the channels by strict anaerobic and some facultative anaerobic bacteria but also by Candida yeasts, especially Candida albicans species that are involved in the maintenance and persistence of endodontic infections. Their elimination of the canal system in practice by chemo-mechanical methods of disinfection is not always guaranteed. Thus, this in vitro study was performed to determine the sensitivity of C. albicans with sodium hypochlorite (NaOCl) dosed at 2.5 %, the chlorhexidine digluconate 0.5 % and calcium hydroxide used in inter-session medication. The diffusion method was used initially to test the sensitivity of C. albicans strains with the above products. Then a dilution technique has allowed us to determine the minimum inhibitory concentration of these active products on C. albicans. Strains from infected pulp teeth of patients showed a sensitivity of C. albicans to sodium hypochlorite to a minimum inhibitory concentration less than 70μg/mL and 30μg/mL for chlorhexidine. This study demonstrated a sensitivity of C. albicans to sodium hypochlorite and chlorhexidine. Copyright © 2016. Published by Elsevier Masson SAS.

Diffusion tensor optical coherence tomography

NASA Astrophysics Data System (ADS)

Marks, Daniel L.; Blackmon, Richard L.; Oldenburg, Amy L.

2018-01-01

In situ measurements of diffusive particle transport provide insight into tissue architecture, drug delivery, and cellular function. Analogous to diffusion-tensor magnetic resonance imaging (DT-MRI), where the anisotropic diffusion of water molecules is mapped on the millimeter scale to elucidate the fibrous structure of tissue, here we propose diffusion-tensor optical coherence tomography (DT-OCT) for measuring directional diffusivity and flow of optically scattering particles within tissue. Because DT-OCT is sensitive to the sub-resolution motion of Brownian particles as they are constrained by tissue macromolecules, it has the potential to quantify nanoporous anisotropic tissue structure at micrometer resolution as relevant to extracellular matrices, neurons, and capillaries. Here we derive the principles of DT-OCT, relating the detected optical signal from a minimum of six probe beams with the six unique diffusion tensor and three flow vector components. The optimal geometry of the probe beams is determined given a finite numerical aperture, and a high-speed hardware implementation is proposed. Finally, Monte Carlo simulations are employed to assess the ability of the proposed DT-OCT system to quantify anisotropic diffusion of nanoparticles in a collagen matrix, an extracellular constituent that is known to become highly aligned during tumor development.

Fisher information and Cramér-Rao lower bound for experimental design in parallel imaging.

PubMed

Bouhrara, Mustapha; Spencer, Richard G

2018-06-01

The Cramér-Rao lower bound (CRLB) is widely used in the design of magnetic resonance (MR) experiments for parameter estimation. Previous work has considered only Gaussian or Rician noise distributions in this calculation. However, the noise distribution for multi-coil acquisitions, such as in parallel imaging, obeys the noncentral χ-distribution under many circumstances. The purpose of this paper is to present the CRLB calculation for parameter estimation from multi-coil acquisitions. We perform explicit calculations of Fisher matrix elements and the associated CRLB for noise distributions following the noncentral χ-distribution. The special case of diffusion kurtosis is examined as an important example. For comparison with analytic results, Monte Carlo (MC) simulations were conducted to evaluate experimental minimum standard deviations (SDs) in the estimation of diffusion kurtosis model parameters. Results were obtained for a range of signal-to-noise ratios (SNRs), and for both the conventional case of Gaussian noise distribution and noncentral χ-distribution with different numbers of coils, m. At low-to-moderate SNR, the noncentral χ-distribution deviates substantially from the Gaussian distribution. Our results indicate that this departure is more pronounced for larger values of m. As expected, the minimum SDs (i.e., CRLB) in derived diffusion kurtosis model parameters assuming a noncentral χ-distribution provided a closer match to the MC simulations as compared to the Gaussian results. Estimates of minimum variance for parameter estimation and experimental design provided by the CRLB must account for the noncentral χ-distribution of noise in multi-coil acquisitions, especially in the low-to-moderate SNR regime. Magn Reson Med 79:3249-3255, 2018. © 2017 International Society for Magnetic Resonance in Medicine. © 2017 International Society for Magnetic Resonance in Medicine.

Antibacterial activity of endemic Satureja Khuzistanica Jamzad essential oil against oral pathogens

PubMed Central

Seghatoleslami, Sogol; Samadi, Nasrin; Salehnia, Ali; Azimi, Shahram

2009-01-01

INTRODUCTION: To assess the antibacterial effects of an Iranian endemic essential oil, Satureja Khuzistanica Jamzad (SKJ) when used as an intracanal antiseptic and interappointment medicament. MATERIALS AND METHODS: Antimicrobial activity and minimum inhibition concentrations (MICs) of SKJ essential oil with and without calcium hydroxide (CH) against eleven aerobic, microaerophilic and anaerobic bacteria were assessed. The evaluation was carried out by agar dilution and well diffusion methods. The results were measured and recorded by an independent observer. Data were analyzed statistically using student t-test. RESULTS: The MIC for eight species was recorded in 0.31 mg/mL of essential oil. Pseudomonas aeruginosa with a MIC value of 1.25 mg/mL appeared to be the most resistant bacterium; while only 0.16 mg/mL of essential oil was sufficient to inhibit the growth of Bacillus subtilis and Staphylococcus aureus. The inhibition zone of the antiseptic oil (at 0.31 mg/mL) with E. faecalis in the well diffusion method was 13 mm; this was comparable with 12.5 mm inhibition zone value of the tetracycline disc (30 µg). No synergistic effect was found in combination of essential oil and CH powder. CONCLUSION: SKJ essential oil with the concentration of 0.31 mg/mL is effective against most of oral pathogens including E. faecalis. PMID:23864870

Antibacterial activity of different honeys against pathogenic bacteria.

PubMed

Voidarou, C; Alexopoulos, A; Plessas, S; Karapanou, A; Mantzourani, I; Stavropoulou, E; Fotou, K; Tzora, A; Skoufos, I; Bezirtzoglou, E

2011-12-01

To study the antimicrobial activity of honey, 60 samples of various botanical origin were evaluated for their antimicrobial activities against 16 clinical pathogens and their respective reference strains. The microbiological quality of honeys and the antibiotic susceptibility of the various isolates were also examined. The bioassay applied for determining the antimicrobial effect employs the well-agar diffusion method and the estimation of minimum active dilution which produces a 1mm diameter inhibition zone. All honey samples, despite their origin (coniferous, citrus, thyme or polyfloral), showed antibacterial activity against the pathogenic and their respective reference strains at variable levels. Coniferous and thyme honeys showed the highest activity with an average minimum dilution of 17.4 and 19.2% (w/v) followed by citrus and polyfloral honeys with 20.8 and 23.8% respectively. Clinical isolates of Staphylococcus aureus subsp. aureus, Escherichia coli, Salmonella enterica subsp. Enterica, Streptococcus pyogenes, Bacillus cereus and Bacillus subtilis were proven to be up to 60% more resistant than their equal reference strains thus emphasizing the variability in the antibacterial effect of honey and the need for further research. Copyright © 2011 Elsevier Ltd. All rights reserved.

Activity of Aristolochia bracteolata against Moraxella catarrhalis

PubMed Central

Khedr, Amgad I. M.; Abd AlGadir, Haidar; Takeshita, Satoshi; Shah, Mohammad Monir; Ichinose, Yoshio; Maki, Toshihide

2014-01-01

A bioassay-guided fractionation of methanol extract of Aristolochia bracteolata whole plant was carried out in order to evaluate its antimicrobial activity and to identify the active compounds in this extract. Antibacterial and antifungal activities of methanol extract against gram-positive, gram-negative, and fungal strains were investigated by the agar disk diffusion method. Among the strains tested, Moraxella catarrhalis and sea urchin-derived Bacillus sp. showed the highest sensitivity towards the methanol extract and hence they are used as test organisms for the bioassay-guided fractionation. From this extract, aristolochic acid 1 (AA-1) has been isolated and has showed the greatest antibacterial activity against both standard strain and clinical isolates of Moraxella catarrhalis with equal minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) values of 25 and 50 μg/mL. Modification of the AA-1 to AA-1 methyl ester completely abolished the antibacterial activity of the compound and the piperonylic acid moiety of AA-1 which suggested that the coexistence of phenanthrene ring and free carboxylic acid is essential for AA-1 antibacterial activity. PMID:26904734

Synthesis and characterization of the NiFe2O4@TEOS-TPS@Ag nanocomposite and investigation of its antibacterial activity

NASA Astrophysics Data System (ADS)

Allafchian, Ali R.; Jalali, S. A. H.; Amiri, R.; Shahabadi, Sh.

2016-11-01

In this study, the NiFe2O4 was embedded in (3-mercaptopropyl) trimethoxysilane (TPS) and tetraethyl orthosilicate (TEOS) using the sol-gel method. These compounds were used as the support of Ag nanoparticles (Ag NPs). The NiFe2O4@TEOS-TPS@Ag nanocomposites were obtained with the development of bonding between the silver atoms of Ag NPs and the sulfur atoms of TPS molecule. Field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FT-IR) were used for the characterization of the Ag nanocomposites. Also, the magnetic properties of these nanocomposites were studied by using a vibrating sample magnetometer (VSM) technique. The disk diffusion, minimum inhibition concentration (MIC) and minimum bactericidal concentrations (MBC) tests were used for the investigation of the antibacterial effect of this nanocomposite against bacterial strains. The synthesized nanocomposite presented high reusability and good antibacterial activity against gram-positive and gram-negative bacteria. Remarkably, this nanocomposite could be easily removed from the disinfected media by magnetic decantation.

Antibacterial activity and chemical characteristics of several Western Australian honeys compared to manuka honey and pasture honey.

PubMed

Roshan, Niloufar; Rippers, Thomas; Locher, Cornelia; Hammer, Katherine A

2017-03-01

The physicochemical parameters and antibacterial activity of 10 Western Australian (WA) and two comparator honeys were determined. Honeys showed a pH range of 4.0-4.7, colour range of 41.3-470.7 mAU, methylglyoxal levels ranging from 82.2 to 325.9 mg kg -1 and hydrogen peroxide levels after 2 h of 22.7-295.5 µM. Antibacterial activity was assessed by the disc diffusion assay, phenol equivalence assay, determination of minimum inhibitory and bactericidal concentrations and a time-kill assay. Activity was shown for all honeys by one or more method, however, activity varied according to which assay was used. Minimum inhibitory concentrations for WA honeys against 10 organisms ranged from 4.0 to >32.0% (w/v). Removal of hydrogen peroxide activity by catalase resulted in decreased activity for several honeys. Overall, the data showed that honeys in addition to those derived from Leptospermum spp. have antimicrobial activity and should not be overlooked as potential sources of clinically useful honey.

Development of a non-destructive method for determining protein nitrogen in a yellow fever vaccine by near infrared spectroscopy and multivariate calibration.

PubMed

Dabkiewicz, Vanessa Emídio; de Mello Pereira Abrantes, Shirley; Cassella, Ricardo Jorgensen

2018-08-05

Near infrared spectroscopy (NIR) with diffuse reflectance associated to multivariate calibration has as main advantage the replacement of the physical separation of interferents by the mathematical separation of their signals, rapidly with no need for reagent consumption, chemical waste production or sample manipulation. Seeking to optimize quality control analyses, this spectroscopic analytical method was shown to be a viable alternative to the classical Kjeldahl method for the determination of protein nitrogen in yellow fever vaccine. The most suitable multivariate calibration was achieved by the partial least squares method (PLS) with multiplicative signal correction (MSC) treatment and data mean centering (MC), using a minimum number of latent variables (LV) equal to 1, with the lower value of the square root of the mean squared prediction error (0.00330) associated with the highest percentage value (91%) of samples. Accuracy ranged 95 to 105% recovery in the 4000-5184 cm -1 region. Copyright © 2018 Elsevier B.V. All rights reserved.

Detection of antimicrobial activity of banana peel (Musa paradisiaca L.) on Porphyromonas gingivalis and Aggregatibacter actinomycetemcomitans: An in vitro study.

PubMed

Kapadia, Suraj Premal; Pudakalkatti, Pushpa S; Shivanaikar, Sachin

2015-01-01

Banana is used widely because of its nutritional values. In past, there are studies that show banana plant parts, and their fruits can be used to treat the human diseases. Banana peel is a part of banana fruit that also has the antibacterial activity against microorganisms but has not been studied extensively. Since, there are no studies that relate the antibacterial activity of banana peel against periodontal pathogens. Hence, the aim of this study is to determine the antimicrobial activity of banana peel extract on Porphyromonas gingivalis (P. gingivalis) and Aggregatibacter actinomycetemcomitans (A. actinomycetemcomitans). Standard strains of P. gingivalis and A. actinomycetemcomitans were used in this study which was obtained from the in-house bacterial bank of Department of Molecular Biology and Immunology at Maratha Mandal's Nathajirao G. Halgekar Institute of Dental Sciences and Research Centre. The banana peel extract was prepared, and the antibacterial activity was assessed using well agar diffusion method and minimum inhibitory concentration was assessed using serial broth dilution method. In the current study, both the tested microorganisms showed antibacterial activity. In well diffusion method, P. gingivalis and A. actinomycetemcomitans showed 15 mm and 12 mm inhibition zone against an alcoholic extract of banana peel, respectively. In serial broth dilution method P. gingivalis and A. actinomycetemcomitans were sensitive until 31.25 μg/ml dilutions. From results of the study, it is suggested that an alcoholic extract of banana peel has antimicrobial activity against P. gingivalis and A. actinomycetemcomitans.

Integrated Analysis and Visualization of Group Differences in Structural and Functional Brain Connectivity: Applications in Typical Ageing and Schizophrenia.

PubMed

Langen, Carolyn D; White, Tonya; Ikram, M Arfan; Vernooij, Meike W; Niessen, Wiro J

2015-01-01

Structural and functional brain connectivity are increasingly used to identify and analyze group differences in studies of brain disease. This study presents methods to analyze uni- and bi-modal brain connectivity and evaluate their ability to identify differences. Novel visualizations of significantly different connections comparing multiple metrics are presented. On the global level, "bi-modal comparison plots" show the distribution of uni- and bi-modal group differences and the relationship between structure and function. Differences between brain lobes are visualized using "worm plots". Group differences in connections are examined with an existing visualization, the "connectogram". These visualizations were evaluated in two proof-of-concept studies: (1) middle-aged versus elderly subjects; and (2) patients with schizophrenia versus controls. Each included two measures derived from diffusion weighted images and two from functional magnetic resonance images. The structural measures were minimum cost path between two anatomical regions according to the "Statistical Analysis of Minimum cost path based Structural Connectivity" method and the average fractional anisotropy along the fiber. The functional measures were Pearson's correlation and partial correlation of mean regional time series. The relationship between structure and function was similar in both studies. Uni-modal group differences varied greatly between connectivity types. Group differences were identified in both studies globally, within brain lobes and between regions. In the aging study, minimum cost path was highly effective in identifying group differences on all levels; fractional anisotropy and mean correlation showed smaller differences on the brain lobe and regional levels. In the schizophrenia study, minimum cost path and fractional anisotropy showed differences on the global level and within brain lobes; mean correlation showed small differences on the lobe level. Only fractional anisotropy and mean correlation showed regional differences. The presented visualizations were helpful in comparing and evaluating connectivity measures on multiple levels in both studies.

Use of linkage mapping and centrality analysis across habitat gradients to conserve connectivity of gray wolf populations in western North America.

PubMed

Carroll, Carlos; McRae, Brad H; Brookes, Allen

2012-02-01

Centrality metrics evaluate paths between all possible pairwise combinations of sites on a landscape to rank the contribution of each site to facilitating ecological flows across the network of sites. Computational advances now allow application of centrality metrics to landscapes represented as continuous gradients of habitat quality. This avoids the binary classification of landscapes into patch and matrix required by patch-based graph analyses of connectivity. It also avoids the focus on delineating paths between individual pairs of core areas characteristic of most corridor- or linkage-mapping methods of connectivity analysis. Conservation of regional habitat connectivity has the potential to facilitate recovery of the gray wolf (Canis lupus), a species currently recolonizing portions of its historic range in the western United States. We applied 3 contrasting linkage-mapping methods (shortest path, current flow, and minimum-cost-maximum-flow) to spatial data representing wolf habitat to analyze connectivity between wolf populations in central Idaho and Yellowstone National Park (Wyoming). We then applied 3 analogous betweenness centrality metrics to analyze connectivity of wolf habitat throughout the northwestern United States and southwestern Canada to determine where it might be possible to facilitate range expansion and interpopulation dispersal. We developed software to facilitate application of centrality metrics. Shortest-path betweenness centrality identified a minimal network of linkages analogous to those identified by least-cost-path corridor mapping. Current flow and minimum-cost-maximum-flow betweenness centrality identified diffuse networks that included alternative linkages, which will allow greater flexibility in planning. Minimum-cost-maximum-flow betweenness centrality, by integrating both land cost and habitat capacity, allows connectivity to be considered within planning processes that seek to maximize species protection at minimum cost. Centrality analysis is relevant to conservation and landscape genetics at a range of spatial extents, but it may be most broadly applicable within single- and multispecies planning efforts to conserve regional habitat connectivity. ©2011 Society for Conservation Biology.

Antibacterial activity of Tribulus terrestris and its synergistic effect with Capsella bursa-pastoris and Glycyrrhiza glabra against oral pathogens: an in-vitro study

PubMed Central

Soleimanpour, Saman; Sedighinia, Fereshteh Sadat; Safipour Afshar, Akbar; Zarif, Reza; Ghazvini, Kiarash

2015-01-01

Objective: In this study, antimicrobial activities of an ethanol extract of Tribulus terrestris aloneand in combination with Capsella bursa-pastoris and Glycyrrhiza glabra were examined in vitro against six pathogens namely Streptococcus mutans, Streptococcus sanguis, Actinomyces viscosus, Enterococcus faecalis Staphylococcus aureus, and Escherichia coli. Materials and methods: Antibacterial activities of the extracts were examined using disc and well diffusion methods and the minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of ethanol extracts were determined against these microorganisms using agar and broth dilution methods. Chlorhexidine was used as positive control. Results: Tribulus terrestris extract exhibited good antibacterial activity against all bacteria. Antibacterial activity of mixed extract was evaluated and exhibited that mixed extract was more effective against all bacteria than any of the cases alone which indicates the synergistic effect between these three extracts (p˂0.05). No strain showed resistance against these extracts. In agar dilution, Tribulus terrestris exhibited MIC values ranging from 35.0 to 20.0 mg/ml and mixed extract showed MIC values ranging from 12.5 to 5.0 mg/ml. The results of broth dilution method were consistent with the findings of the agar dilution method. Conclusion: This in-vitro study was a preliminary evaluation of antibacterial activity of the plants. It provided scientific evidence to support uses of T. terrestris and its mixture with C. bursa-pastoris and G. glabra for the treatment of oral infections. In-vivo studies are also required to better evaluate the effect of these extracts. PMID:26101754

The effect of the neutral sheet structure of the interplanetary magnetic field on cosmic ray distribution in space

NASA Technical Reports Server (NTRS)

Alania, M. V.; Aslamazashvili, R. G.; Bochorishvili, T.; Djapiashvili, T. V.; Tkemaladze, V. S.

1985-01-01

Results of the numerical solution of the anistoropic diffusion equation are presented. The modulation depth of galactic cosmic rays is defined by the degree of curvature of the neutral current sheet in the heliosphere. The effect of the regular interplanetary magnetic field (IMF) on cosmic ray anisotropy in the period of solar activity minimum (in 1976) is analyzed by the data of the neutron super-monitors of the world network, and the heliolatitudinal gradient and cosmic ray diffusion coefficient are defined.

Diffusion of Cd and Te adatoms on CdTe(111) surfaces: A computational study using density functional theory

NASA Astrophysics Data System (ADS)

Naderi, Ebadollah; Nanavati, Sachin; Majumder, Chiranjib; Ghaisas, S. V.

2015-01-01

CdTe is one of the most promising semiconductor for thin-film based solar cells. Here we report a computational study of Cd and Te adatom diffusion on the CdTe (111) A-type (Cd terminated) and B-type (Te terminated) surfaces and their migration paths. The atomic and electronic structure calculations are performed under the DFT formalism and climbing Nudge Elastic Band (cNEB) method has been applied to evaluate the potential barrier of the Te and Cd diffusion. In general the minimum energy site on the surface is labeled as Aa site. In case of Te and Cd on B-type surface, the sub-surface site (a site just below the top surface) is very close in energy to the A site. This is responsible for the subsurface accumulation of adatoms and therefore, expected to influence the defect formation during growth. The diffusion process of adatoms is considered from Aa (occupied) to Aa (empty) site at the nearest distance. We have explored three possible migration paths for the adatom diffusion. The adatom surface interaction is highly dependent on the type of the surface. Typically, Te interaction with both type (5.2 eV for A-type and 3.8 eV for B-type) is stronger than Cd interactions(2.4 eV for B-type and 0.39 eV for A-type). Cd interaction with the A-type surface is very weak. The distinct behavior of the A-type and B-type surfaces perceived in our study explain the need of maintaining the A-type surface during growth for smooth and stoichiometric growth.

In Vitro antibacterial efficacy of 21 Indian timber-yielding plants against multidrug-resistant bacteria causing urinary tract infection.

PubMed

Mishra, Monali P; Padhy, Rabindra N

2013-12-01

To screen methanolic leaf extracts of 21 timber-yielding plants for antibacterial activity against nine species of uropathogenic bacteria isolated from clinical samples of a hospital (Enterococcus faecalis, Staphylococcus aureus, Acinetobacter baumannii, Citrobacter freundii, Enterobacter aerogenes, Escherichia coli, Klebsiella pneumoniae, Proteus mirabilis, and Pseudomonas aeruginosa). Bacterial strains were subjected to antibiotic sensitivity tests by the Kirby-Bauer's disc diffusion method. The antibacterial potentiality of leaf extracts was monitored by the agar-well diffusion method with multidrug-resistant (MDR) strains of nine uropathogens. Two Gram-positive isolates, E. faecalis and S. aureus, were resistant to 14 of the 18 antibiotics used. Gram-negative isolates A. baumannii, C. freundii, E. aerogenes, E. coli, K. pneumoniae, P. mirabilis, and P. aeruginosa were resistant to 10, 12, 9, 11, 11, 10, and 11 antibiotics, respectively, of the 14 antibiotics used. Methanolic leaf extracts of Anogeissus acuminata had the maximum zone of inhibition size-29 mm against S. aureus and 28 mm against E. faecalis and P. aeruginosa. Cassia tora had 29 mm as the zone of inhibition size for E. faecalis, E. aerogenes, and P. aeruginosa. Based on the minimum inhibitory concentration and minimum bactericidal concentration values, the most effective 10 plants against uropathogens could be arranged in decreasing order as follows: C. tora > A. acuminata > Schleichera oleosa > Pterocarpus santalinus > Eugenia jambolana > Bridelia retusa > Mimusops elengi > Stereospermum kunthianum > Tectona grandis > Anthocephalus cadamba. The following eight plants had moderate control capacity: Artocarpus heterophyllus, Azadirachta indica, Dalbergia latifolia, Eucalyptus citriodora, Gmelina arborea, Pongamia pinnata, Pterocarpus marsupium, and Shorea robusta. E. coli, followed by A. baumannii, C. freundii, E. aerogenes, P. mirabilis, and P. aeruginosa were controlled by higher amounts/levels of leaf extracts. Phytochemicals of all plants were qualitatively estimated. A majority of timber-yielding plants studied had in vitro control capacity against MDR uropathogenic bacteria.

Antimicrobial and Anti-Inflammatory Activities of Pterygota macrocarpa and Cola gigantea (Sterculiaceae)

PubMed Central

Agyare, Christian; Koffuor, George Asumeng; Boamah, Vivian Etsiapa; Adu, Francis; Mensah, Kwesi Boadu; Adu-Amoah, Louis

2012-01-01

Pterygota macrocarpa and Cola gigantea are African medicinal plants used in traditional medicine for the treatment of sores, skin infections, and other inflammatory conditions including pains. This study therefore aims at investigating the antimicrobial properties of ethanol leaf and stem bark extracts of P. macrocarpa and C. gigantea using the agar diffusion and the micro-dilution techniques and also determining the anti-inflammatory properties of the extracts of these plants in carrageenan-induced foot edema in seven-day old chicks. The minimum inhibitory concentration of both ethanol leaf and bark extracts of P. macrocarpa against the test organisms was from 0.125 to 2.55 mg/mL and that of C. gigantea extracts was 0.125 to 2.75 mg/mL. Extracts with concentration of 50 mg/mL were most active against the test organisms according to the agar diffusion method. All the extracts of P. macrocarpa and C. gigantea at 30, 100, and 300 mg/kg body weight except ethanol leaf extract of C. gigantea exhibited significant anti-inflammatory effects (P ≤ 0.001). PMID:22690251

Critical soil conditions for oxygen stress to plant roots: Substituting the Feddes-function by a process-based model

NASA Astrophysics Data System (ADS)

Bartholomeus, Ruud P.; Witte, Jan-Philip M.; van Bodegom, Peter M.; van Dam, Jos C.; Aerts, Rien

2008-10-01

SummaryEffects of insufficient soil aeration on the functioning of plants form an important field of research. A well-known and frequently used utility to express oxygen stress experienced by plants is the Feddes-function. This function reduces root water uptake linearly between two constant pressure heads, representing threshold values for minimum and maximum oxygen deficiency. However, the correctness of this expression has never been evaluated and constant critical values for oxygen stress are likely to be inappropriate. On theoretical grounds it is expected that oxygen stress depends on various abiotic and biotic factors. In this paper, we propose a fundamentally different approach to assess oxygen stress: we built a plant physiological and soil physical process-based model to calculate the minimum gas filled porosity of the soil ( ϕgas_min) at which oxygen stress occurs. First, we calculated the minimum oxygen concentration in the gas phase of the soil needed to sustain the roots through (micro-scale) diffusion with just enough oxygen to respire. Subsequently, ϕgas_min that corresponds to this minimum oxygen concentration was calculated from diffusion from the atmosphere through the soil (macro-scale). We analyzed the validity of constant critical values to represent oxygen stress in terms of ϕgas_min, based on model simulations in which we distinguished different soil types and in which we varied temperature, organic matter content, soil depth and plant characteristics. Furthermore, in order to compare our model results with the Feddes-function, we linked root oxygen stress to root water uptake (through the sink term variable F, which is the ratio of actual and potential uptake). The simulations showed that ϕgas_min is especially sensitive to soil temperature, plant characteristics (root dry weight and maintenance respiration coefficient) and soil depth but hardly to soil organic matter content. Moreover, ϕgas_min varied considerably between soil types and was larger in sandy soils than in clayey soils. We demonstrated that F of the Feddes-function indeed decreases approximately linearly, but that actual oxygen stress already starts at drier conditions than according to the Feddes-function. How much drier is depended on the factors indicated above. Thus, the Feddes-function might cause large errors in the prediction of transpiration reduction and growth reduction through oxygen stress. We made our method easily accessible to others by implementing it in SWAP, a user-friendly soil water model that is coupled to plant growth. Since constant values for ϕgas_min in plant and hydrological modeling appeared to be inappropriate, an integrated approach, including both physiological and physical processes, should be used instead. Therefore, we advocate using our method in all situations where oxygen stress could occur.

MRI diffusion-weighted imaging (DWI) in pediatric small bowel Crohn disease: correlation with MRI findings of active bowel wall inflammation.

PubMed

Ream, Justin M; Dillman, Jonathan R; Adler, Jeremy; Khalatbari, Shokoufeh; McHugh, Jonathan B; Strouse, Peter J; Dhanani, Muhammad; Shpeen, Benjamin; Al-Hawary, Mahmoud M

2013-09-01

Restricted diffusion on diffusion-weighted imaging (DWI) sequences during magnetic resonance enterography (MRE) has been shown in segments of bowel affected by Crohn disease. However, the exact meaning of this finding, particularly within the pediatric Crohn disease population, is poorly understood. The purpose of this study was to determine the significance of bowel wall restricted diffusion in children with small bowel Crohn disease by correlating apparent diffusion coefficient (ADC) values with other MRI markers of disease activity. A retrospective review of pediatric patients (≤ 18 years of age) with Crohn disease terminal ileitis who underwent MRE with DWI at our institution between May 1, 2009 and May 31, 2011 was undertaken. All of the children had either biopsy-proven Crohn disease terminal ileitis or clinically diagnosed Crohn disease, including terminal ileal involvement by imaging. The mean minimum ADC value within the wall of the terminal ileum was determined for each examination. ADC values were tested for correlation/association with other MRI findings to determine whether a relationship exists between bowel wall restricted diffusion and disease activity. Forty-six MRE examinations with DWI in children with terminal ileitis were identified (23 girls and 23 boys; mean age, 14.3 years). There was significant negative correlation or association between bowel wall minimum ADC value and established MRI markers of disease activity, including degree of bowel wall thickening (R = (-)0.43; P = 0.003), striated pattern of arterial enhancement (P = 0.01), degree of arterial enhancement (P = 0.01), degree of delayed enhancement (P = 0.045), amount of mesenteric inflammatory changes (P < 0.0001) and presence of a stricture (P = 0.02). ADC values were not significantly associated with bowel wall T2-weighted signal intensity, length of disease involvement or mesenteric fibrofatty proliferation. Increasing bowel wall restricted diffusion (lower ADC values) is associated with multiple MRI findings that are traditionally associated with active inflammation in pediatric small bowel Crohn disease.

Coherent structure diffusivity in the edge region of Reversed Field Pinch experiments

NASA Astrophysics Data System (ADS)

Spolaore, M.; Antoni, V.; Spada, E.; Bergsåker, H.; Cavazzana, R.; Drake, J. R.; Martines, E.; Regnoli, G.; Serianni, G.; Vianello, N.

2005-01-01

Coherent structures emerging from the background turbulence have been detected by electrostatic measurements in the edge region of two Reversed Field Pinch experiments, RFX (Padua) and Extrap-T2R (Stockholm). Measurements have been performed by arrays of Langmuir probes which allowed simultaneous measurements of temperature, potential and density to be carried out. These structures have been interpreted as a dynamic balance of dipolar and monopolar vortices, whose relative population are found to depend on the local mean E × B flow shear. The contribution to the anomalous transport of these structures has been investigated and it has been found that the corresponding diffusion coeffcient accounts up to 50% of the total diffusivity. The experimental findings indicate that the diffusion coeffcient associated to the coherent structures depends on the relative population of the two types of vortices and is minimum when the two populations are equal. An interpretative model is proposed to explain this feature.

In Vitro Antibacterial Efficacy of 21 Indian Timber-Yielding Plants Against Multidrug-Resistant Bacteria Causing Urinary Tract Infection

PubMed Central

Mishra, Monali P.; Padhy, Rabindra N.

2013-01-01

Objectives To screen methanolic leaf extracts of 21 timber-yielding plants for antibacterial activity against nine species of uropathogenic bacteria isolated from clinical samples of a hospital (Enterococcus faecalis, Staphylococcus aureus, Acinetobacter baumannii, Citrobacter freundii, Enterobacter aerogenes, Escherichia coli, Klebsiella pneumoniae, Proteus mirabilis, and Pseudomonas aeruginosa). Methods Bacterial strains were subjected to antibiotic sensitivity tests by the Kirby–Bauer's disc diffusion method. The antibacterial potentiality of leaf extracts was monitored by the agar-well diffusion method with multidrug-resistant (MDR) strains of nine uropathogens. Results Two Gram-positive isolates, E. faecalis and S. aureus, were resistant to 14 of the 18 antibiotics used. Gram-negative isolates A. baumannii, C. freundii, E. aerogenes, E. coli, K. pneumoniae, P. mirabilis, and P. aeruginosa were resistant to 10, 12, 9, 11, 11, 10, and 11 antibiotics, respectively, of the 14 antibiotics used. Methanolic leaf extracts of Anogeissus acuminata had the maximum zone of inhibition size—29 mm against S. aureus and 28 mm against E. faecalis and P. aeruginosa. Cassia tora had 29 mm as the zone of inhibition size for E. faecalis, E. aerogenes, and P. aeruginosa. Based on the minimum inhibitory concentration and minimum bactericidal concentration values, the most effective 10 plants against uropathogens could be arranged in decreasing order as follows: C. tora > A. acuminata > Schleichera oleosa > Pterocarpus santalinus > Eugenia jambolana > Bridelia retusa > Mimusops elengi > Stereospermum kunthianum > Tectona grandis > Anthocephalus cadamba. The following eight plants had moderate control capacity: Artocarpus heterophyllus, Azadirachta indica, Dalbergia latifolia, Eucalyptus citriodora, Gmelina arborea, Pongamia pinnata, Pterocarpus marsupium, and Shorea robusta. E. coli, followed by A. baumannii, C. freundii, E. aerogenes, P. mirabilis, and P. aeruginosa were controlled by higher amounts/levels of leaf extracts. Phytochemicals of all plants were qualitatively estimated. Conclusions A majority of timber-yielding plants studied had in vitro control capacity against MDR uropathogenic bacteria. PMID:24524024

Enhanced diffusion with abnormal temperature dependence in underdamped space-periodic systems subject to time-periodic driving

NASA Astrophysics Data System (ADS)

Marchenko, I. G.; Marchenko, I. I.; Zhiglo, A. V.

2018-01-01

We present a study of the diffusion enhancement of underdamped Brownian particles in a one-dimensional symmetric space-periodic potential due to external symmetric time-periodic driving with zero mean. We show that the diffusivity can be enhanced by many orders of magnitude at an appropriate choice of the driving amplitude and frequency. The diffusivity demonstrates abnormal (decreasing) temperature dependence at the driving amplitudes exceeding a certain value. At any fixed driving frequency Ω normal temperature dependence of the diffusivity is restored at low enough temperatures, T

Detection of antimicrobial activity of banana peel (Musa paradisiaca L.) on Porphyromonas gingivalis and Aggregatibacter actinomycetemcomitans: An in vitro study

PubMed Central

Kapadia, Suraj Premal; Pudakalkatti, Pushpa S.; Shivanaikar, Sachin

2015-01-01

Introduction and Aim: Banana is used widely because of its nutritional values. In past, there are studies that show banana plant parts, and their fruits can be used to treat the human diseases. Banana peel is a part of banana fruit that also has the antibacterial activity against microorganisms but has not been studied extensively. Since, there are no studies that relate the antibacterial activity of banana peel against periodontal pathogens. Hence, the aim of this study is to determine the antimicrobial activity of banana peel extract on Porphyromonas gingivalis (P. gingivalis) and Aggregatibacter actinomycetemcomitans (A. actinomycetemcomitans). Material and Methods: Standard strains of P. gingivalis and A. actinomycetemcomitans were used in this study which was obtained from the in-house bacterial bank of Department of Molecular Biology and Immunology at Maratha Mandal's Nathajirao G. Halgekar Institute of Dental Sciences and Research Centre. The banana peel extract was prepared, and the antibacterial activity was assessed using well agar diffusion method and minimum inhibitory concentration was assessed using serial broth dilution method. Results: In the current study, both the tested microorganisms showed antibacterial activity. In well diffusion method, P. gingivalis and A. actinomycetemcomitans showed 15 mm and 12 mm inhibition zone against an alcoholic extract of banana peel, respectively. In serial broth dilution method P. gingivalis and A. actinomycetemcomitans were sensitive until 31.25 μg/ml dilutions. Conclusion: From results of the study, it is suggested that an alcoholic extract of banana peel has antimicrobial activity against P. gingivalis and A. actinomycetemcomitans. PMID:26681854

Determination of crystal residence timescales in magma reservoirs by diffusion modeling of dendritic phosphorus zoning patterns in olivine

NASA Astrophysics Data System (ADS)

Chakraborty, S.; Potrafke, A.

2016-12-01

Deciphering the early stages of crystallization and the chronological evolution of phenocrysts in magma reservoirs is one of the main goals in volcanology. Established approaches that model the concentration evolution of fast diffusing elements like Fe/Mg carry limited information on timescales once the concentration gradients are homogenized. Elements that diffuse more slowly, such as P and Al, become useful in these cases. We present a novel modeling tool that combines high-resolution EMP mapping of slow diffusing phosphorus in olivine with 2D kinetic modeling of the diffusive relaxation of initial chemical zoning pattern of P as well as Fe/Mg. The modeling approach offers a new possibility for determining crystal residence times in magma reservoirs. P diffusion coefficients from the experimental determination of [1] and Fe/Mg diffusion coefficients from [2] were used. The method yields a time-bracket between the minimum time required to homogenize the zoning of fast-diffusing Fe/Mg and the maximum time period for which details of chemical zoning of slow-diffusing P may be retained. To illustrate the approach we have studied the compositional zoning patterns of 7 olivine crystals from Piton de la Fournaise volcano, La Réunion. All crystals show a narrow range of forsterite contents (=Fo82-84) with fully homogenized Fe/Mg distribution, whereas P-mapping reveals oscillatory to dendritic zoning patterns [3]. P concentrations scatter in the range of 0.4 wt-% to below detection limit. Revealed phosphorus zoning patterns were considered to display the initial crystal architecture, whereas Fe and Mg zoning has been wiped out due to faster diffusion. For La Réunion magmas at 1453 K, timescales between few days to weeks were determined to be the time brackets for growth and residence of the olivine crystals in the magmas. These short residence times combined with knowledge of very fast developing dendritic crystals that have recently been revealed worldwide [e.g. 3] indicate that dendritic crystal growth in such rapidly evolving dynamic environments should be considered as a widespread feature of olivine growth and evolution of many basaltic volcanic systems. [1] Watson et al., 2015, Am Min, 100, pp. 2053-2065 [2] Dohmen et al., 2007, Phys Chem Miner, 34(6), pp. 389-407 [3] Welsch et al., 2014, Geology, 42, pp. 867-870

Antibacterial activity of essential oils extracted from Satureja hortensis against selected clinical pathogens

NASA Astrophysics Data System (ADS)

Görmez, Arzu; Yanmiş, Derya; Bozari, Sedat; Gürkök, Sumeyra

2017-04-01

The antibiotic resistance of pathogenic microorganisms has become a worldwide concern to public health. To overcome the current resistance problem, new antimicrobial agents are extremely needed. The aim of the present study was to evaluate the antibacterial activity of Satureja hortensis essential oils against seven clinical pathogens. Chemical compositions of hydro distillated essential oils from S. hortensis were analyzed by GS-MS. The antibacterial activity was investigated against Corynebacterium diphtheria, Salmonella typhimurium, Serratia plymuthica Yersinia enterocolitica, Y. frederiksenii, Y. pseudotuberculosis and Vibrio cholerae by the use of disc diffusion method and broth micro dilution method. The minimum inhibitory concentration (MIC) values of essential oils were found as low as 7.81 µg/mL. Notably, essential oils of S. hortensis exhibited remarkable antimicrobial activities against the tested clinical pathogens. The results indicate that these essential oils can be used in treatment of different infectious diseases.

Chemical composition and antimicrobial activities of essential oil from Wedelia urticifolia growing wild in Hunan Province, China.

PubMed

Hu, Junpeng; Jia, Mengmeng; Zhu, Liang

2018-04-18

The essential oil obtained from Wedelia urticifolia growing in Hunan Province, China, was analyzed for the first time by capillary GC and GC-MS. A total of 67 constituents, representing 98.68% in essential oil were identified. The major constituents of the oil were: α-pinene (8.85%), limonene (6.38%), carvacrol (6.15%), caryophyllene (6.08%), spathulenol (5.49%), sabinene (5.36%), camphor (4.34%). Antimicrobial potential of oil against bacterial strains (Pseudomonas aeruginosa, Escherichia coli and Bacillus subtilis, and Staphylococcus aureus), yeast strains (Hansenula anomala and Saccharomy cescerevisiae) and molds (Aspergillus niger, Chaetomium globosum, Mucor racemosus, and Monascus anka) was determined by disc diffusion method and broth micro dilution method, respectively. The oil exhibited promising antimicrobial effect as a diameter of zones of inhibition (16.8-24.9 mm). Minimum inhibitory concentration values of oil were ranged 62.5-1000 μg/mL.

Antimicrobial activity of chemically modified dextran derivatives.

PubMed

Tuchilus, Cristina G; Nichifor, Marieta; Mocanu, Georgeta; Stanciu, Magdalena C

2017-04-01

Cationic amphiphilic dextran derivatives with a long alkyl group attached to the reductive end of the polysaccharide chain and quaternary ammonium groups attached as pendent groups to the main dextran backbone were synthesized and tested for their antimicrobial properties against several bacteria and fungi strains. Dependence of antimicrobial activity on both polymer chemical composition (dextran molar mass, length of end alkyl group and chemical structure of ammonium groups) and type of microbes was highlighted by disc-diffusion method (diameter of inhibition zone) and broth microdilution method (minimum inhibitory concentrations). Polymers had antimicrobial activity for all strains studied, except for Pseudomonas aeruginosa ATCC 27853. The best activity against Staphylococcus aureus (Minimun Inhibitory Concentration 60μg/mL) was provided by polymers obtained from dextran with lower molecular mass (Mn=4500), C 12 H 25 or C 18 H 37 end groups, and N,N-dimethyl-N-benzylammonium pendent groups. Copyright © 2017 Elsevier Ltd. All rights reserved.

Analysis of antimicrobial, antifungal and antioxidant activities of Juniperus excelsa M. B subsp. Polycarpos (K. Koch) Takhtajan essential oil

PubMed Central

Moein, M. R.; Ghasemi, Y.; Moein, S.; Nejati, M.

2010-01-01

Juniperus excelsa M.B subsp. Polycarpos (K.Koch), collected from south of Iran, was subjected to hydrodistillation using clevenger apparatus to obtain essential oil. The essential was analyzed by gas chromatography/mass spectrometry (GC/MS) and studied for antimicrobial, antifungal and antioxidant activities. The results indicated α-pinene (67.71%) as the major compound and α-cedral (11.5%), δ3-carene (5.19%) and limonene (4.41%) in moderate amounts. Antimicrobial tests were carried out using disk diffusion method, followed by the measurement of minimum inhibitory concentration (MIC). All the Gram positive and Gram negative bacteria were susceptible to essential oil. The oil showed radical scavenging and antioxidant effects. PMID:21808554

Applications of thin-film sandwich crystallization platforms

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

Axford, Danny, E-mail: danny.axford@diamond.ac.uk; Aller, Pierre; Sanchez-Weatherby, Juan

2016-03-24

Crystallization via sandwiches of thin polymer films is presented and discussed. Examples are shown of protein crystallization in, and data collection from, solutions sandwiched between thin polymer films using vapour-diffusion and batch methods. The crystallization platform is optimal for both visualization and in situ data collection, with the need for traditional harvesting being eliminated. In wells constructed from the thinnest plastic and with a minimum of aqueous liquid, flash-cooling to 100 K is possible without significant ice formation and without any degradation in crystal quality. The approach is simple; it utilizes low-cost consumables but yields high-quality data with minimal samplemore » intervention and, with the very low levels of background X-ray scatter that are observed, is optimal for microcrystals.« less

Corrosion Performance of Nano-ZrO₂ Modified Coatings in Hot Mixed Acid Solutions.

PubMed

Xu, Wenhua; Wang, Zhenyu; Han, En-Hou; Wang, Shuai; Liu, Qian

2018-06-01

A nano-ZrO₂ modified coating system was prepared by incorporation of nano-ZrO₂ concentrates into phenolic-epoxy resin. The corrosion performance of the coatings was evaluated in hot mixed acid solution, using electrochemical methods combined with surface characterization, and the effects of nano-ZrO₂ content were specially focused on. The results showed that 1% and 3% nano-ZrO₂ addition enhanced the corrosion resistance of the coatings, while 5% nano-ZrO₂ addition declined it. The coating with 3% nano-ZrO₂ presented the minimum amount of species diffusion, the lowest average roughness (5.94 nm), and the highest C/O ratio (4.55) and coating resistance, and it demonstrated the best corrosion performance among the coating specimens.

Comparison of diffuse CO2 degassing at Miravalles and Rincón de la Vieja volcanoes (Guanacaste Province, Costa Rica)

NASA Astrophysics Data System (ADS)

Liegler, A.; Bakkar Hindeleh, H.; Deering, C. D.; Fentress, S. E.

2015-12-01

Volcanic gas emissions are a key component for monitoring volcanic activity, magmatic input of volatiles to the atmosphere and the assessment of geothermal potential in volcanic regions. Diffuse soil degassing has been shown to represent a major part of volcanic gas emissions. However, this type of gas emission has not yet been quantified in the Guanacaste province of Costa Rica; a region of the country with several large, active or dormant volcanoes. We conducted the first study of diffuse CO2 degassing at Rincón de la Vieja and Miravalles volcanoes, both located in Guanacaste. Diffuse degassing was measured using the accumulation chamber method to quantify CO2 flux in regions where hydrothermal surface features indicate anomalous activity. The total diffuse carbon dioxide flux estimated at Miravalles in two areas, together roughly 2 km2 in size, was 135 t/day and in several areas at Rincón de la Vieja a minimum of 4 t/day. Comparatively low flux values and a very local concentration (few m2) of CO2 flux were observed at the active Rincón de la Vieja volcano, compared to the dormant Miravalles volcano, where significant soil flux was found over extended areas, not only around vents. Our assessment of the origin of these differences leads to two possibilities depending on if the surface features on the two volcanoes are fed by a common hydrothermal system or two separate ones. In the former case, the different intensity of diffuse CO2 flux could indicate a different degassing behavior and stronger concentration of gas emissions at the active vent areas at Rincon de la Vieja. In the latter case, where the hydrothermal systems are not linked, the amount of CO2 degassed through the flanks of the volcanoes could indicate that different physical and chemical conditions are governing the degassing of the two systems.

The Power of Neuroimaging Biomarkers for Screening Frontotemporal Dementia

PubMed Central

McMillan, Corey T.; Avants, Brian B.; Cook, Philip; Ungar, Lyle; Trojanowski, John Q.; Grossman, Murray

2014-01-01

Frontotemporal dementia (FTD) is a clinically and pathologically heterogeneous neurodegenerative disease that can result from either frontotemporal lobar degeneration (FTLD) or Alzheimer’s disease (AD) pathology. It is critical to establish statistically powerful biomarkers that can achieve substantial cost-savings and increase feasibility of clinical trials. We assessed three broad categories of neuroimaging methods to screen underlying FTLD and AD pathology in a clinical FTD series: global measures (e.g., ventricular volume), anatomical volumes of interest (VOIs) (e.g., hippocampus) using a standard atlas, and data-driven VOIs using Eigenanatomy. We evaluated clinical FTD patients (N=93) with cerebrospinal fluid, gray matter (GM) MRI, and diffusion tensor imaging (DTI) to assess whether they had underlying FTLD or AD pathology. Linear regression was performed to identify the optimal VOIs for each method in a training dataset and then we evaluated classification sensitivity and specificity in an independent test cohort. Power was evaluated by calculating minimum sample sizes (mSS) required in the test classification analyses for each model. The data-driven VOI analysis using a multimodal combination of GM MRI and DTI achieved the greatest classification accuracy (89% SENSITIVE; 89% SPECIFIC) and required a lower minimum sample size (N=26) relative to anatomical VOI and global measures. We conclude that a data-driven VOI approach employing Eigenanatomy provides more accurate classification, benefits from increased statistical power in unseen datasets, and therefore provides a robust method for screening underlying pathology in FTD patients for entry into clinical trials. PMID:24687814

Comparison of multi-fiber reproducibility of PAS-MRI and Q-ball with empirical multiple b-value HARDI

NASA Astrophysics Data System (ADS)

Nath, Vishwesh; Schilling, Kurt G.; Blaber, Justin A.; Ding, Zhaohua; Anderson, Adam W.; Landman, Bennett A.

2017-02-01

Crossing fibers are prevalent in human brains and a subject of intense interest for neuroscience. Diffusion tensor imaging (DTI) can resolve tissue orientation but is blind to crossing fibers. Many advanced diffusion-weighted magnetic resolution imaging (MRI) approaches have been presented to extract crossing-fibers from high angular resolution diffusion imaging (HARDI), but the relative sensitivity and specificity of approaches remains unclear. Here, we examine two leading approaches (PAS and q-ball) in the context of a large-scale, single subject reproducibility study. A single healthy individual was scanned 11 times with 96 diffusion weighted directions and 10 reference volumes for each of five b-values (1000, 1500, 2000, 2500, 3000 s/mm2) for a total of 5830 volumes (over the course of three sessions). We examined the reproducibility of the number of fibers per voxel, volume fraction, and crossing-fiber angles. For each method, we determined the minimum resolvable angle for each acquisition. Reproducibility of fiber counts per voxel was generally high ( 80% consensus for PAS and 70% for q-ball), but there was substantial bias between individual repetitions and model estimated with all data ( 10% lower consensus for PAS and 15% lower for q-ball). Both PAS and q-ball predominantly discovered fibers crossing at near 90 degrees, but reproducibility was higher for PAS across most measures. Within voxels with low anisotropy, q-ball finds more intra-voxel structure; meanwhile, PAS resolves multiple fibers at greater than 75 degrees for more voxels. These results can inform researchers when deciding between HARDI approaches or interpreting findings across studies.

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

Zhao, Xin -Yu; Bhagatwala, Ankit; Chen, Jacqueline H.

In this study, the modeling of mixing by molecular diffusion is a central aspect for transported probability density function (tPDF) methods. In this paper, the newly-proposed shadow position mixing model (SPMM) is examined, using a DNS database for a temporally evolving di-methyl ether slot jet flame. Two methods that invoke different levels of approximation are proposed to extract the shadow displacement (equivalent to shadow position) from the DNS database. An approach for a priori analysis of the mixing-model performance is developed. The shadow displacement is highly correlated with both mixture fraction and velocity, and the peak correlation coefficient of themore » shadow displacement and mixture fraction is higher than that of the shadow displacement and velocity. This suggests that the composition-space localness is reasonably well enforced by the model, with appropriate choices of model constants. The conditional diffusion of mixture fraction and major species from DNS and from SPMM are then compared, using mixing rates that are derived by matching the mixture fraction scalar dissipation rates. Good qualitative agreement is found, for the prediction of the locations of zero and maximum/minimum conditional diffusion locations for mixture fraction and individual species. Similar comparisons are performed for DNS and the IECM (interaction by exchange with the conditional mean) model. The agreement between SPMM and DNS is better than that between IECM and DNS, in terms of conditional diffusion iso-contour similarities and global normalized residual levels. It is found that a suitable value for the model constant c that controls the mixing frequency can be derived using the local normalized scalar variance, and that the model constant a controls the localness of the model. A higher-Reynolds-number test case is anticipated to be more appropriate to evaluate the mixing models, and stand-alone transported PDF simulations are required to more fully enforce localness and to assess model performance.« less

An a priori DNS study of the shadow-position mixing model

DOE PAGES

Zhao, Xin -Yu; Bhagatwala, Ankit; Chen, Jacqueline H.; ...

2016-01-15

In this study, the modeling of mixing by molecular diffusion is a central aspect for transported probability density function (tPDF) methods. In this paper, the newly-proposed shadow position mixing model (SPMM) is examined, using a DNS database for a temporally evolving di-methyl ether slot jet flame. Two methods that invoke different levels of approximation are proposed to extract the shadow displacement (equivalent to shadow position) from the DNS database. An approach for a priori analysis of the mixing-model performance is developed. The shadow displacement is highly correlated with both mixture fraction and velocity, and the peak correlation coefficient of themore » shadow displacement and mixture fraction is higher than that of the shadow displacement and velocity. This suggests that the composition-space localness is reasonably well enforced by the model, with appropriate choices of model constants. The conditional diffusion of mixture fraction and major species from DNS and from SPMM are then compared, using mixing rates that are derived by matching the mixture fraction scalar dissipation rates. Good qualitative agreement is found, for the prediction of the locations of zero and maximum/minimum conditional diffusion locations for mixture fraction and individual species. Similar comparisons are performed for DNS and the IECM (interaction by exchange with the conditional mean) model. The agreement between SPMM and DNS is better than that between IECM and DNS, in terms of conditional diffusion iso-contour similarities and global normalized residual levels. It is found that a suitable value for the model constant c that controls the mixing frequency can be derived using the local normalized scalar variance, and that the model constant a controls the localness of the model. A higher-Reynolds-number test case is anticipated to be more appropriate to evaluate the mixing models, and stand-alone transported PDF simulations are required to more fully enforce localness and to assess model performance.« less

Solar Drivers of 11-yr and Long-Term Cosmic Ray Modulation

NASA Technical Reports Server (NTRS)

Cliver, E. W.; Richardson, I. G.; Ling, A. G.

2011-01-01

In the current paradigm for the modulation of galactic cosmic rays (GCRs), diffusion is taken to be the dominant process during solar maxima while drift dominates at minima. Observations during the recent solar minimum challenge the pre-eminence of drift: at such times. In 2009, the approx.2 GV GCR intensity measured by the Newark neutron monitor increased by approx.5% relative to its maximum value two cycles earlier even though the average tilt angle in 2009 was slightly larger than that in 1986 (approx.20deg vs. approx.14deg), while solar wind B was significantly lower (approx.3.9 nT vs. approx.5.4 nT). A decomposition of the solar wind into high-speed streams, slow solar wind, and coronal mass ejections (CMEs; including postshock flows) reveals that the Sun transmits its message of changing magnetic field (diffusion coefficient) to the heliosphere primarily through CMEs at solar maximum and high-speed streams at solar minimum. Long-term reconstructions of solar wind B are in general agreement for the approx. 1900-present interval and can be used to reliably estimate GCR intensity over this period. For earlier epochs, however, a recent Be-10-based reconstruction covering the past approx. 10(exp 4) years shows nine abrupt and relatively short-lived drops of B to < or approx.= 0 nT, with the first of these corresponding to the Sporer minimum. Such dips are at variance with the recent suggestion that B has a minimum or floor value of approx.2.8 nT. A floor in solar wind B implies a ceiling in the GCR intensity (a permanent modulation of the local interstellar spectrum) at a given energy/rigidity. The 30-40% increase in the intensity of 2.5 GV electrons observed by Ulysses during the recent solar minimum raises an interesting paradox that will need to be resolved.

Antibacterial activity of Tribulus terrestris and its synergistic effect with Capsella bursa-pastoris and Glycyrrhiza glabra against oral pathogens: an in-vitro study.

PubMed

Soleimanpour, Saman; Sedighinia, Fereshteh Sadat; Safipour Afshar, Akbar; Zarif, Reza; Ghazvini, Kiarash

2015-01-01

In this study, antimicrobial activities of an ethanol extract of Tribulus terrestris aloneand in combination with Capsella bursa-pastoris and Glycyrrhiza glabra were examined in vitro against six pathogens namely Streptococcus mutans, Streptococcus sanguis, Actinomyces viscosus, Enterococcus faecalis Staphylococcus aureus, and Escherichia coli. Antibacterial activities of the extracts were examined using disc and well diffusion methods and the minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of ethanol extracts were determined against these microorganisms using agar and broth dilution methods. Chlorhexidine was used as positive control. Tribulus terrestris extract exhibited good antibacterial activity against all bacteria. Antibacterial activity of mixed extract was evaluated and exhibited that mixed extract was more effective against all bacteria than any of the cases alone which indicates the synergistic effect between these three extracts (p˂0.05). No strain showed resistance against these extracts. In agar dilution, Tribulus terrestris exhibited MIC values ranging from 35.0 to 20.0 mg/ml and mixed extract showed MIC values ranging from 12.5 to 5.0 mg/ml. The results of broth dilution method were consistent with the findings of the agar dilution method. This in-vitro study was a preliminary evaluation of antibacterial activity of the plants. It provided scientific evidence to support uses of T. terrestris and its mixture with C. bursa-pastoris and G. glabra for the treatment of oral infections. In-vivo studies are also required to better evaluate the effect of these extracts.

Puzzle of magnetic moments of Ni clusters revisited using quantum Monte Carlo method.

PubMed

Lee, Hung-Wen; Chang, Chun-Ming; Hsing, Cheng-Rong

2017-02-28

The puzzle of the magnetic moments of small nickel clusters arises from the discrepancy between values predicted using density functional theory (DFT) and experimental measurements. Traditional DFT approaches underestimate the magnetic moments of nickel clusters. Two fundamental problems are associated with this puzzle, namely, calculating the exchange-correlation interaction accurately and determining the global minimum structures of the clusters. Theoretically, the two problems can be solved using quantum Monte Carlo (QMC) calculations and the ab initio random structure searching (AIRSS) method correspondingly. Therefore, we combined the fixed-moment AIRSS and QMC methods to investigate the magnetic properties of Ni n (n = 5-9) clusters. The spin moments of the diffusion Monte Carlo (DMC) ground states are higher than those of the Perdew-Burke-Ernzerhof ground states and, in the case of Ni 8-9 , two new ground-state structures have been discovered using the DMC calculations. The predicted results are closer to the experimental findings, unlike the results predicted in previous standard DFT studies.

Design optimization of piezoresistive cantilevers for force sensing in air and water

PubMed Central

Doll, Joseph C.; Park, Sung-Jin; Pruitt, Beth L.

2009-01-01

Piezoresistive cantilevers fabricated from doped silicon or metal films are commonly used for force, topography, and chemical sensing at the micro- and macroscales. Proper design is required to optimize the achievable resolution by maximizing sensitivity while simultaneously minimizing the integrated noise over the bandwidth of interest. Existing analytical design methods are insufficient for modeling complex dopant profiles, design constraints, and nonlinear phenomena such as damping in fluid. Here we present an optimization method based on an analytical piezoresistive cantilever model. We use an existing iterative optimizer to minimimize a performance goal, such as minimum detectable force. The design tool is available as open source software. Optimal cantilever design and performance are found to strongly depend on the measurement bandwidth and the constraints applied. We discuss results for silicon piezoresistors fabricated by epitaxy and diffusion, but the method can be applied to any dopant profile or material which can be modeled in a similar fashion or extended to other microelectromechanical systems. PMID:19865512

Quantitative Comparison of Minimum Inductance and Minimum Power Algorithms for the Design of Shim Coils for Small Animal Imaging

PubMed Central

HUDSON, PARISA; HUDSON, STEPHEN D.; HANDLER, WILLIAM B.; SCHOLL, TIMOTHY J.; CHRONIK, BLAINE A.

2010-01-01

High-performance shim coils are required for high-field magnetic resonance imaging and spectroscopy. Complete sets of high-power and high-performance shim coils were designed using two different methods: the minimum inductance and the minimum power target field methods. A quantitative comparison of shim performance in terms of merit of inductance (ML) and merit of resistance (MR) was made for shim coils designed using the minimum inductance and the minimum power design algorithms. In each design case, the difference in ML and the difference in MR given by the two design methods was <15%. Comparison of wire patterns obtained using the two design algorithms show that minimum inductance designs tend to feature oscillations within the current density; while minimum power designs tend to feature less rapidly varying current densities and lower power dissipation. Overall, the differences in coil performance obtained by the two methods are relatively small. For the specific case of shim systems customized for small animal imaging, the reduced power dissipation obtained when using the minimum power method is judged to be more significant than the improvements in switching speed obtained from the minimum inductance method. PMID:20411157

Nonlinear waves in reaction-diffusion systems: The effect of transport memory

NASA Astrophysics Data System (ADS)

Manne, K. K.; Hurd, A. J.; Kenkre, V. M.

2000-04-01

Motivated by the problem of determining stress distributions in granular materials, we study the effect of finite transport correlation times on the propagation of nonlinear wave fronts in reaction-diffusion systems. We obtain results such as the possibility of spatial oscillations in the wave-front shape for certain values of the system parameters and high enough wave-front speeds. We also generalize earlier known results concerning the minimum wave-front speed and shape-speed relationships stemming from the finiteness of the correlation times. Analytic investigations are made possible by a piecewise linear representation of the nonlinearity.

Antibacterial activity and effects of Colla corii asini on Salmonella typhimurium invasion in vitro and in vivo.

PubMed

Park, Kwang-Il; Lee, Mi-Ra; Oh, Tae-Woo; Kim, Kwang-Youn; Ma, Jin-Yeul

2017-12-04

Salmonella enterica serovar Typhimurium is a foodborne pathogen that triggers inflammatory responses in the intestines of humans and livestock. Colla corii asini is a traditional medicine used to treat gynecologic and chronic diseases in Korea and China. However, the antibacterial activity of Colla corii asini has been unknown. In this study, we investigated the antibacterial activity and effects of Colla corii asini extract on Salmonella typhimurium invasion. To tested for antibacterial effects of Colla corii asini extracts, we confirmed the agar diffusion using Luria solid broth medium. Also, we determined the MIC (minimum inhibitory concentration) and the MBC (minimum bactericidal concentration) value of the Colla corii asini ethanol extract (CEE) by using two-fold serial dilution methods. We evaluated the expression of salmonella invasion proteins including SipA, SipB and SipC by using Western blot and qPCR at the concentration of CEE without inhibition of bacterial growth. In vitro and vivo, we determined the inhibitory effect of invasion of S. typhimurium on CEE by using gentamicin assay and S. typhimurium-infected mice. CEE significantly inhibited the growth of Salmonella typhimurium in an agar diffuse assay and had an MIC of 0.78 mg/ml and an MBC of 1.56 mg/ml. Additionally, CEE reduced Salmonella typhimurium cell invasion via the inhibition of Salmonella typhimurium invasion proteins, such as SipA, SipB and SipC. Furthermore, CEE significantly suppressed invasion in the small intestines (ilea) of mice injected with Salmonella typhimurium. These findings show that Colla corii asini exerts antibacterial activity and suppresses Salmonella typhimurium invasion in vitro and in vivo. Together, these findings demonstrate that Colla corii asini is a potentially useful therapeutic herbal medicine for treating salmonella-mediated diseases.

Phytochemical Screening and Antimicrobial Activity of Some Medicinal Plants Against Multi-drug Resistant Bacteria from Clinical Isolates

PubMed Central

Dahiya, Praveen; Purkayastha, Sharmishtha

2012-01-01

The in vitro antibacterial activity of various solvents and water extracts of aloe vera, neem, bryophyllum, lemongrass, tulsi, oregano, rosemary and thyme was assessed on 10 multi-drug resistant clinical isolates from both Gram-positive and Gram-negative bacteria and two standard strains including Staphylococcus aureus ATCC 25923 and Escherichia coli ATCC 25922. The zone of inhibition as determined by agar well diffusion method varied with the plant extract, the solvent used for extraction, and the organism tested. Klebsiella pneumoniae 2, Escherichia coli 3 and Staphylococcus aureus 3 were resistant to the plant extracts tested. Moreover, water extracts did not restrain the growth of any tested bacteria. Ethanol and methanol extracts were found to be more potent being capable of exerting significant inhibitory activities against majority of the bacteria investigated. Staphylococcus aureus 1 was the most inhibited bacterial isolate with 24 extracts (60%) inhibiting its growth whereas Escherichia coli 2 exhibited strong resistance being inhibited by only 11 extracts (28%). The results obtained in the agar diffusion plates were in fair correlation with that obtained in the minimum inhibitory concentration tests. The minimum inhibitory concentration of tulsi, oregano, rosemary and aloe vera extracts was found in the range of 1.56-6.25 mg/ml for the multi-drug resistant Staphylococcus aureus isolates tested whereas higher values (6.25-25 mg/ml) were obtained against the multi-drug resistant isolates Klebsiella pneumoniae 1 and Escherichia coli 1 and 2. Qualitative phytochemical analysis demonstrated the presence of tannins and saponins in all plants tested. Thin layer chromatography and bioautography agar overlay assay of ethanol extracts of neem, tulsi and aloe vera indicated flavonoids and tannins as major active compounds against methicillin-resistant Staphylococcus aureus. PMID:23716873

Comparison of Experimental Methods for Estimating Matrix Diffusion Coefficients for Contaminant Transport Modeling

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

Telfeyan, Katherine Christina; Ware, Stuart Douglas; Reimus, Paul William

Diffusion cell and diffusion wafer experiments were conducted to compare methods for estimating matrix diffusion coefficients in rock core samples from Pahute Mesa at the Nevada Nuclear Security Site (NNSS). A diffusion wafer method, in which a solute diffuses out of a rock matrix that is pre-saturated with water containing the solute, is presented as a simpler alternative to the traditional through-diffusion (diffusion cell) method. Both methods yielded estimates of matrix diffusion coefficients that were within the range of values previously reported for NNSS volcanic rocks. The difference between the estimates of the two methods ranged from 14 to 30%,more » and there was no systematic high or low bias of one method relative to the other. From a transport modeling perspective, these differences are relatively minor when one considers that other variables (e.g., fracture apertures, fracture spacings) influence matrix diffusion to a greater degree and tend to have greater uncertainty than diffusion coefficients. For the same relative random errors in concentration measurements, the diffusion cell method yields diffusion coefficient estimates that have less uncertainty than the wafer method. However, the wafer method is easier and less costly to implement and yields estimates more quickly, thus allowing a greater number of samples to be analyzed for the same cost and time. Given the relatively good agreement between the methods, and the lack of any apparent bias between the methods, the diffusion wafer method appears to offer advantages over the diffusion cell method if better statistical representation of a given set of rock samples is desired.« less

Comparison of experimental methods for estimating matrix diffusion coefficients for contaminant transport modeling

NASA Astrophysics Data System (ADS)

Telfeyan, Katherine; Ware, S. Doug; Reimus, Paul W.; Birdsell, Kay H.

2018-02-01

Diffusion cell and diffusion wafer experiments were conducted to compare methods for estimating effective matrix diffusion coefficients in rock core samples from Pahute Mesa at the Nevada Nuclear Security Site (NNSS). A diffusion wafer method, in which a solute diffuses out of a rock matrix that is pre-saturated with water containing the solute, is presented as a simpler alternative to the traditional through-diffusion (diffusion cell) method. Both methods yielded estimates of effective matrix diffusion coefficients that were within the range of values previously reported for NNSS volcanic rocks. The difference between the estimates of the two methods ranged from 14 to 30%, and there was no systematic high or low bias of one method relative to the other. From a transport modeling perspective, these differences are relatively minor when one considers that other variables (e.g., fracture apertures, fracture spacings) influence matrix diffusion to a greater degree and tend to have greater uncertainty than effective matrix diffusion coefficients. For the same relative random errors in concentration measurements, the diffusion cell method yields effective matrix diffusion coefficient estimates that have less uncertainty than the wafer method. However, the wafer method is easier and less costly to implement and yields estimates more quickly, thus allowing a greater number of samples to be analyzed for the same cost and time. Given the relatively good agreement between the methods, and the lack of any apparent bias between the methods, the diffusion wafer method appears to offer advantages over the diffusion cell method if better statistical representation of a given set of rock samples is desired.

Antimicrobial Activities of Methanol, Ethanol and Supercritical CO2 Extracts of Philippine Piper betle L. on Clinical Isolates of Gram Positive and Gram Negative Bacteria with Transferable Multiple Drug Resistance

PubMed Central

Valle, Demetrio L.; Cabrera, Esperanza C.; Puzon, Juliana Janet M.; Rivera, Windell L.

2016-01-01

Piper betle L. has traditionally been used in alternative medicine in different countries for various therapeutic purposes, including as an anti-infective agent. However, studies reported in the literature are mainly on its activities on drug susceptible bacterial strains. This study determined the antimicrobial activities of its ethanol, methanol, and supercritical CO2 extracts on clinical isolates of multiple drug resistant bacteria which have been identified by the Infectious Disease Society of America as among the currently more challenging strains in clinical management. Assay methods included the standard disc diffusion method and the broth microdilution method for the determination of the minimum inhibitory concentration (MIC) and the minimum bactericidal concentrations (MBC) of the extracts for the test microorganisms. This study revealed the bactericidal activities of all the P. betle leaf crude extracts on methicillin-resistant Staphylococcus aureus (MRSA), vancomycin-resistant Enterococcus (VRE), extended spectrum β-lactamase-producing Enterobacteriaceae, carbapenem-resistant Enterobacteriaceae, and metallo-β-lactamase-producing Pseudomonas aeruginosa and Acinetobacter baumannii, with minimum bactericidal concentrations that ranged from 19μg/ml to 1250 μg/ml. The extracts proved to be more potent against the Gram positive MRSA and VRE than for the Gram negative test bacteria. VRE isolates were more susceptible to all the extracts than the MRSA isolates. Generally, the ethanol extracts proved to be more potent than the methanol extracts and supercritical CO2 extracts as shown by their lower MICs for both the Gram positive and Gram negative MDRs. MTT cytotoxicity assay showed that the highest concentration (100 μg/ml) of P. betle ethanol extract tested was not toxic to normal human dermal fibroblasts (HDFn). Data from the study firmly established P. betle as an alternative source of anti-infectives against multiple drug resistant bacteria. PMID:26741962

Antimicrobial Activities of Methanol, Ethanol and Supercritical CO2 Extracts of Philippine Piper betle L. on Clinical Isolates of Gram Positive and Gram Negative Bacteria with Transferable Multiple Drug Resistance.

PubMed

Valle, Demetrio L; Cabrera, Esperanza C; Puzon, Juliana Janet M; Rivera, Windell L

2016-01-01

Piper betle L. has traditionally been used in alternative medicine in different countries for various therapeutic purposes, including as an anti-infective agent. However, studies reported in the literature are mainly on its activities on drug susceptible bacterial strains. This study determined the antimicrobial activities of its ethanol, methanol, and supercritical CO2 extracts on clinical isolates of multiple drug resistant bacteria which have been identified by the Infectious Disease Society of America as among the currently more challenging strains in clinical management. Assay methods included the standard disc diffusion method and the broth microdilution method for the determination of the minimum inhibitory concentration (MIC) and the minimum bactericidal concentrations (MBC) of the extracts for the test microorganisms. This study revealed the bactericidal activities of all the P. betle leaf crude extracts on methicillin-resistant Staphylococcus aureus (MRSA), vancomycin-resistant Enterococcus (VRE), extended spectrum β-lactamase-producing Enterobacteriaceae, carbapenem-resistant Enterobacteriaceae, and metallo-β-lactamase-producing Pseudomonas aeruginosa and Acinetobacter baumannii, with minimum bactericidal concentrations that ranged from 19μg/ml to 1250 μg/ml. The extracts proved to be more potent against the Gram positive MRSA and VRE than for the Gram negative test bacteria. VRE isolates were more susceptible to all the extracts than the MRSA isolates. Generally, the ethanol extracts proved to be more potent than the methanol extracts and supercritical CO2 extracts as shown by their lower MICs for both the Gram positive and Gram negative MDRs. MTT cytotoxicity assay showed that the highest concentration (100 μg/ml) of P. betle ethanol extract tested was not toxic to normal human dermal fibroblasts (HDFn). Data from the study firmly established P. betle as an alternative source of anti-infectives against multiple drug resistant bacteria.

In-Vitro Activity of Saponins of Bauhinia Purpurea, Madhuca Longifolia, Celastrus Paniculatus and Semecarpus Anacardium on Selected Oral Pathogens

PubMed Central

Jyothi, K. S.; Seshagiri, M.

2012-01-01

Objective: Dental caries, periodontitis and other mucosal diseases are caused by a complex community of microorganisms. This study aimed to investigate the antimicrobial properties of saponins of four important oil yielding medicinal plant extracts on selected oral pathogens that are involved in such diseases. Materials and Methods: Saponins were extracted from Bauhinia purpurea, Madhuca longifolia, Celastrus paniculatus and Semecarpus anacardium and purified. Antimicrobial properties of these saponins against Streptococcus mutans, Streptococcus mitis, Streptococcus salivarius, Staphylococcus aureus and Lactobacillus acidophilus were determined using well diffusion method. The minimum inhibitory concentration (MIC) was determined as the lowest concentration of saponins inhibiting bacterial growth after 14 h of incubation at 37°C. The bactericidal activity was evaluated using the viable cell count method. Results: The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of Madhuca longifolia saponin on Streptococcus mutans MTCC 890, Streptococcus mitis and Staphylococcus aureus was 18.3 ± 0.15/34.4 ± 0.24 μg/ml, 19.0 ± 0.05/32.2 ± 0.0 μg/ml and 21.2 ± 0.35/39.0 ± 0.30 μg/ml, respectively and Bauhinia purpurea saponin on Streptococcus mutans MTCC 890, Staphylococcus aureus and Lactobacillus acidophilus was 26.4 ± 0.20/43.0 ± 0.40 μg/ml, 29.0 ± 0.30/39.6 ± 0.12 μg/ml and 20.2 ± 0.05/36.8 ± 0.23 μg/ml, respectively. Conclusion: The strong antimicrobial activity of Madhuca longifolia and Bauhinia purpurea may be due to the presence of complex triterpenoid saponins, oleanane type triterpenoid glycosides or atypical pentacyclic triterpenoid saponin. Hence, these extracted saponins may be used in food and oral products to prevent and control oral diseases. PMID:23323183

Impact of pentacene film thickness on the photoresponse spectra: Determination of the photocarrier generation mechanism

NASA Astrophysics Data System (ADS)

Gorgolis, S.; Giannopoulou, A.; Anastassopoulos, D.; Kounavis, P.

2012-07-01

Photocurrent response, optical absorption, and x-ray diffraction (XRD) measurements in pentacene films grown on glass substrates are performed in order to obtain an insight into the mobile photocarriers generation mechanism. For film thickness of the order of 50 nm and lower, the photocurrent response spectra are found to follow the optical absorption spectra demonstrating the so-called symbatic response. Upon increasing the film thickness, the photoresponse demonstrates a transition to the so-called antibatic response, which is characterized by a maximum and minimum photocurrent for photon energies of minimum and maximum optical absorption, respectively. The experimental results are not in accordance with the model of important surface recombination rate. By taking into account the XRD patterns, the experimental photoresponse spectra can be reproduced by model simulations assuming efficient exciton dissociation at a narrow layer of the order of 20 nm near the pentacene-substrate interface. The simulated spectra are found sensitive to the film thickness, the absolute optical absorption coefficient, and the diffusion exciton length. By comparing the experimental with the simulated spectra, it is deduced that the excitons, which are created by optical excitation in the spectral region of 1.7-2.2 eV, diffuse with a diffusion length of the order of 10-80 nm to the pentacene-substrate interface where efficiently dissociate into mobile charge carriers.

Interfaces in Si/Ge atomic layer superlattices on (001)Si: Effect of growth temperature and wafer misorientation

NASA Astrophysics Data System (ADS)

Baribeau, J.-M.; Lockwood, D. J.; Syme, R. W. G.

1996-08-01

We have used x-ray diffraction, specular reflectivity, and diffuse scattering, complemented by Raman spectroscopy, to study the interfaces in a series of (0.5 nm Ge/2 nm Si)50 atomic layer superlattices on (001)Si grown by molecular beam epitaxy in the temperature range 150-650 °C. X-ray specular reflectivity revealed that the structures have a well-defined periodicity with interface widths of about 0.2-0.3 nm in the 300-590 °C temperature range. Offset reflectivity scans showed that the diffuse scattering peaks at values of perpendicular wave vector transfer corresponding to the superlattice satellite peaks, indicating that the interfaces are vertically correlated. Transverse rocking scans of satellite peaks showed a diffuse component corresponding to an interface corrugation of typical length scale of ˜0.5 μm. The wavelength of the undulations is a minimum along the miscut direction and is typically 30-40 times larger than the surface average terrace width assuming monolayer steps, independently of the magnitude of the wafer misorientation. The amplitude of the undulation evolves with growth temperature and is minimum for growth at ˜460 °C and peaks at ˜520 °C. Raman scattering showed the chemical abruptness of the interfaces at low growth temperatures and indicated a change in the growth mode near 450 °C.

Small area silicon diffused junction X-ray detectors

NASA Technical Reports Server (NTRS)

Walton, J. T.; Pehl, R. H.; Larsh, A. E.

1982-01-01

The low-temperature performance of silicon diffused junction detectors in the measurement of low energy X-rays is reported. The detectors have an area of 0.04 sq cm and a thickness of 100 microns. The spectral resolutions of these detectors were found to be in close agreement with expected values, indicating that the defects introduced by the high-temperature processing required in the device fabrication were not deleteriously affecting the detection of low-energy X-rays. Device performance over a temperature range of 77 K to 150 K is given. These detectors were designed to detect low-energy X-rays in the presence of minimum ionizing electrons. The successful application of silicon-diffused junction technology to X-ray detector fabrication may facilitate the development of other novel silicon X-ray detector designs.

The existence of minimum speed of traveling wave solutions to a non-KPP isothermal diffusion system

NASA Astrophysics Data System (ADS)

Chen, Xinfu; Liu, Guirong; Qi, Yuanwei

2017-08-01

The reaction-diffusion system at =axx - abn ,bt = Dbxx + abn, where n ≥ 1 and D > 0, arises from many real-world chemical reactions. Whereas n = 1 is the KPP type nonlinearity, which is much studied and very important results obtained in literature not only in one dimensional spatial domains, but also multi-dimensional spaces, but n > 1 proves to be much harder. One of the interesting features of the system is the existence of traveling wave solutions. In particular, for the traveling wave solution a (x , t) = a (x - vt), b (x , t) = b (x - vt), where v > 0, if we fix lim x → - ∞ ⁡ (a , b) = (0 , 1) it was proved by many authors with different bounds v* (n , D) > 0 such that a traveling wave solution exists for any v ≥v* when n > 1. For the latest progress, see [7]. That is, the traveling wave problem exhibits the mono-stable phenomenon for traveling wave of scalar equation ut =uxx + f (u) with f (0) = f (1) = 0, f (u) > 0 in (0 , 1) and, u = 0 is unstable and u = 1 is stable. A natural and significant question is whether, like the scalar case, there exists a minimum speed. That is, whether there exists a minimum speed vmin > 0 such that traveling wave solution of speed v exists iff v ≥vmin? This is an open question, in spite of many works on traveling wave of the system in last thirty years. This is duo to the reason, unlike the KPP case, the minimum speed cannot be obtained through linear analysis at equilibrium points (a , b) = (0 , 1) and (a , b) = (1 , 0). In this work, we give an affirmative answer to this question.

Modulation of galactic cosmic rays in solar cycles 22-24: Analysis and physical interpretation

NASA Astrophysics Data System (ADS)

Kalinin, M. S.; Bazilevskaya, G. A.; Krainev, M. B.; Svirzhevskaya, A. K.; Svirzhevsky, N. S.; Starodubtsev, S. A.

2017-09-01

This work represents a physical interpretation of cosmic ray modulation in the 22nd-24th solar cycles, including an interpretation of an unusual behavior of their intensity in the last minimum of the solar activity (2008-2010). In terms of the Parker modulation model, which deals with regularly measured heliospheric characteristics, it is shown that the determining factor of the increased intensity of the galactic cosmic rays in the minimum of the 24th solar cycle is an anomalous reduction of the heliospheric magnetic field strength during this time interval under the additional influence of the solar wind velocity and the tilt angle of the heliospheric current sheet. We have used in the calculations the dependence of the diffusion tensor on the rigidity in the form K ij ∝ R 2-μ with μ = 1.2 in the sector zones of the heliospheric magnetic field and with μ = 0.8 outside the sector zones, which leads to an additional amplification of the diffusion mechanism of cosmic ray modulation. The proposed approach allows us to describe quite satisfactorily the integral intensity of protons with an energy above 0.1 GeV and the energy spectra in the minima of the 22nd-24th solar cycles at the same value of the free parameter. The determining factor of the anomalously high level of the galactic cosmic ray intensity in the minimum of the 24th solar cycle is the significant reduction of the heliospheric magnetic field strength during this time interval. The forecast of the intensity level in the minimum of the 25th solar cycle is provided.

[Experimental study of bacteriostatic activity of Chinese herbal medicines on primary cariogenic bacteria in vitro].

PubMed

Wang, S; Fan, M; Bian, Z

2001-09-01

To screen some Chinese herbal medicines for their inhibitory activity on cariogenic bacteria, and investigate their active ingredients, and measure their minimum inhibitory concentration (MIC), minimum bactericidal concentration (MBC). Active components were isolated from every tested Chinese herbal medicine by means of aqueous extraction and ethanolic extraction. Berberine was purified from Coptis chinensis Fra. Disk agar diffusion method was employed in screening herbs with inhibiting effect on cariogenic bacteria. MIC and MBC were determined by broth dilution method. Against Streptococcus mutans Ingbritt, MBCs of Magnolia officinalis ethanolic extract, Berberine, Coptis chinensis Fra aqueous extract and Coptis chinensis Fra ethanolic extract were 0.488, 0.625, 7.800 and 1.950 g/L respectively. Against Streptococcus sobrinus 6715, MBCs of Magnolia extract, Coptis chinensis Fra ethanolic extract, Rhus chinensis Mill ethanolic extract and Phellodendron chinen ethanolic extract were 0.488, 0.625, 1.950, 3.900, 3.900 and 3.900 g/L respectively. Against Actinomyces viscosus ATCC 19246, MBCs of Berberine, Coptis chinensis Fra aqueous extract, Coptis chinensis Fra ethanolic extract, Rheum palmatum L aqueous extract and Rheum palmatum L ethanolic extract were 1.250, 3.900, 3.900, 15.600 and 31.250 g/L respectively. Magnolia officinalis, Coptis chinensis Fran, Rheum palmatum L aqueous extracts exhibit strong inhibition on cariogenic bacteria. Magnolia officinalis ethanolic extract has the strongest bactericidal effects on Streptococcus mutans and Streptococcus sobrinus.

Effect of essential oils prepared from Thai culinary herbs on sessile Candida albicans cultures.

PubMed

Hovijitra, Ray S; Choonharuangdej, Suwan; Srithavaj, Theerathavaj

2016-01-01

Although medicinal herbs with fungicidal effects have been ubiquitously employed in traditional medicine, such effects of culinary herbs and spices still have to be elucidated. Therefore, it is noteworthy to determine the antifungal efficacy of some edible herbs used in Thai cuisine against sessile Candida albicans cultures, and to inquire if they can be further utilized as naturally-derived antifungals. Fourteen essential oils extracted from Thai culinary herbs and spices were tested for their antifungal activity against C. albicans using the agar disk diffusion method followed by broth micro-dilution method for the determination of minimum inhibitory concentration (MIC) and minimum fungicidal concentration. The oils with potent antifungal effects against planktonic fungi were then assessed for their effect against sessile fungus (adherent organisms and established biofilm culture). MIC of the oils against sessile C. albicans was evaluated by 2,3-bis-(2-methoxy-4-nitro-5-sulfophenyl)-2H-tetrazolium-5-carboxanilide reduction assay. All selected culinary herbs and spices, except galangal, garlic, and turmeric, exhibited inhibitory effects on planktonic yeast cells. Cinnamon bark and sweet basil leaf essential oils exhibited potent fungicidal effect on planktonic and sessile fungus. Sessile MICs were 8-16 times higher than planktonic MICs. Consequently, both cinnamon bark and sweet basil leaf herbal oils seem to be highly effective anti-Candida choices. (J Oral Sci 58, 365-371, 2016).

Designing Pulse Laser Surface Modification of H13 Steel Using Response Surface Method

NASA Astrophysics Data System (ADS)

Aqida, S. N.; Brabazon, D.; Naher, S.

2011-01-01

This paper presents a design of experiment (DOE) for laser surface modification process of AISI H13 tool steel in achieving the maximum hardness and minimum surface roughness at a range of modified layer depth. A Rofin DC-015 diffusion-cooled CO2 slab laser was used to process AISI H13 tool steel samples. Samples of 10 mm diameter were sectioned to 100 mm length in order to process a predefined circumferential area. The parameters selected for examination were laser peak power, overlap percentage and pulse repetition frequency (PRF). The response surface method with Box-Behnken design approach in Design Expert 7 software was used to design the H13 laser surface modification process. Metallographic study and image analysis were done to measure the modified layer depth. The modified surface roughness was measured using two-dimensional surface profilometer. The correlation of the three laser processing parameters and the modified surface properties was specified by plotting three-dimensional graph. The hardness properties were tested at 981 mN force. From metallographic study, the laser modified surface depth was between 37 μm and 150 μm. The average surface roughness recorded from the 2D profilometry was at a minimum value of 1.8 μm. The maximum hardness achieved was between 728 and 905 HV0.1. These findings are significant to modern development of hard coatings for wear resistant applications.

Comparison of experimental methods for estimating matrix diffusion coefficients for contaminant transport modeling

DOE PAGES

Telfeyan, Katherine Christina; Ware, Stuart Doug; Reimus, Paul William; ...

2018-01-31

Here, diffusion cell and diffusion wafer experiments were conducted to compare methods for estimating effective matrix diffusion coefficients in rock core samples from Pahute Mesa at the Nevada Nuclear Security Site (NNSS). A diffusion wafer method, in which a solute diffuses out of a rock matrix that is pre-saturated with water containing the solute, is presented as a simpler alternative to the traditional through-diffusion (diffusion cell) method. Both methods yielded estimates of effective matrix diffusion coefficients that were within the range of values previously reported for NNSS volcanic rocks. The difference between the estimates of the two methods ranged frommore » 14 to 30%, and there was no systematic high or low bias of one method relative to the other. From a transport modeling perspective, these differences are relatively minor when one considers that other variables (e.g., fracture apertures, fracture spacings) influence matrix diffusion to a greater degree and tend to have greater uncertainty than effective matrix diffusion coefficients. For the same relative random errors in concentration measurements, the diffusion cell method yields effective matrix diffusion coefficient estimates that have less uncertainty than the wafer method. However, the wafer method is easier and less costly to implement and yields estimates more quickly, thus allowing a greater number of samples to be analyzed for the same cost and time. Given the relatively good agreement between the methods, and the lack of any apparent bias between the methods, the diffusion wafer method appears to offer advantages over the diffusion cell method if better statistical representation of a given set of rock samples is desired.« less

Comparison of experimental methods for estimating matrix diffusion coefficients for contaminant transport modeling

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

Telfeyan, Katherine Christina; Ware, Stuart Doug; Reimus, Paul William

Here, diffusion cell and diffusion wafer experiments were conducted to compare methods for estimating effective matrix diffusion coefficients in rock core samples from Pahute Mesa at the Nevada Nuclear Security Site (NNSS). A diffusion wafer method, in which a solute diffuses out of a rock matrix that is pre-saturated with water containing the solute, is presented as a simpler alternative to the traditional through-diffusion (diffusion cell) method. Both methods yielded estimates of effective matrix diffusion coefficients that were within the range of values previously reported for NNSS volcanic rocks. The difference between the estimates of the two methods ranged frommore » 14 to 30%, and there was no systematic high or low bias of one method relative to the other. From a transport modeling perspective, these differences are relatively minor when one considers that other variables (e.g., fracture apertures, fracture spacings) influence matrix diffusion to a greater degree and tend to have greater uncertainty than effective matrix diffusion coefficients. For the same relative random errors in concentration measurements, the diffusion cell method yields effective matrix diffusion coefficient estimates that have less uncertainty than the wafer method. However, the wafer method is easier and less costly to implement and yields estimates more quickly, thus allowing a greater number of samples to be analyzed for the same cost and time. Given the relatively good agreement between the methods, and the lack of any apparent bias between the methods, the diffusion wafer method appears to offer advantages over the diffusion cell method if better statistical representation of a given set of rock samples is desired.« less

Molecular simulation of gas adsorption and diffusion in a breathing MOF using a rigid force field.

PubMed

García-Pérez, E; Serra-Crespo, P; Hamad, S; Kapteijn, F; Gascon, J

2014-08-14

Simulation of gas adsorption in flexible porous materials is still limited by the slow progress in the development of flexible force fields. Moreover, the high computational cost of such flexible force fields may be a drawback even when they are fully developed. In this work, molecular simulations of gas adsorption and diffusion of carbon dioxide and methane in NH2-MIL-53(Al) are carried out using a linear combination of two crystallographic structures with rigid force fields. Once the interactions of carbon dioxide molecules and the bridging hydroxyls groups of the framework are optimized, an excellent match is found for simulations and experimental data for the adsorption of methane and carbon dioxide, including the stepwise uptake due to the breathing effect. In addition, diffusivities of pure components are calculated. The pore expansion by the breathing effect influences the self-diffusion mechanism and much higher diffusivities are observed at relatively high adsorbate loadings. This work demonstrates that using a rigid force field combined with a minimum number of experiments, reproduces adsorption and simulates diffusion of carbon dioxide and methane in the flexible metal-organic framework NH2-MIL-53(Al).

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.

Stability and Behaviors of Methane/Propane and Hydrogen Micro Flames

NASA Astrophysics Data System (ADS)

Yoshimoto, Takamitsu; Kinoshita, Koichiro; Kitamura, Hideki; Tanigawa, Ryoichi

The flame stability limits essentially define the fundamental operation of the combustion system. Recently the micro diffusion flame has been remarked. The critical conditions of the flame stability limit are highly dependent on nozzle diameter, species of fuel and so on. The micro diffusion flame of Methane/Propane and Hydrogen is formed by using the micro-scale nozzle of which inner diameter is less than 1mm. The configurations and behaviors of the flame are observed directly and visualized by the high speed video camera The criteria of stability limits are proposed for the micro diffusion flame. The objectives of the present study are to get further understanding of lifting/blow-off for the micro diffusion flame. The results obtained are as follows. (1) The behaviors of the flames are classified into some regions for each diffusion flame. (2) The micro diffusion flame of Methane/Propane cannot be sustained, when the nozzle diameter is less than 0.14 mm. (3) The diffusion flame cannot be sustained below the critical fuel flow rate. (4) The minimum flow which is formed does not depends on the average jet velocity, but on the fuel flow rate. (5) the micro flame is laminar. The flame length is decided by fuel flow rate.

Antimicrobial activity of essential oils of Physalis angulata. L.

PubMed

Osho, A; Adetunji, T; Fayemi, S O; Moronkola, D O

2010-01-01

The need for a reduction in drug resistance led to the investigation of Argemone Mexicana L. as an agent against Bacillus subtilis, Klebsiella pneumoniae, Staphylococcus aureus, Pseudomonas aeruginosa, Candida albicans, Candida stellatoidea and Candida torulopsis, using well diffusion and minimum inhibitory concentrations methods. The sensitivity of Bacillus Subtilis, Klebsiella pneumoniae, Pseudomonas aeruginosa and Staphylococcus aureus to the essential oils of both the aerial and root parts were determined. Pseudomonas aeruginosa was resistant to the essential oil from both the aerial and root part of the plant. C. torulopsis, C. stellatoidea and C. albicans were susceptible to the essential oils from the aerial and root part of the plant. The minimum inhibitory concentrations ranging between 3.75 mg/ml and 4.0 mg/ml were recorded for Bacillus subtilis, Klebsiella pneumoniae by the aerial and the root extracts, but P. aeruginosa and S. aureus were not susceptible to the aerial and root extracts. The observed inhibition of selected bacteria and fungi by oils of Physalis angulata makes it a promising antimicrobial agent. This study justifies its uses for treatment of sores, cuts, intestinal and digestive problems and some skin-diseases often reported in folkloric medicine.

Chemical composition and antimicrobial activity of the essential oil of apricot seed.

PubMed

Lee, Hyun-Hee; Ahn, Jeong-Hyun; Kwon, Ae-Ran; Lee, Eun Sook; Kwak, Jin-Hwan; Min, Yu-Hong

2014-12-01

In traditional oriental medicine, apricot (Prunus armeniaca L.) seed has been used to treat skin diseases such as furuncle, acne vulgaris and dandruff, as well as coughing, asthma and constipation. This study describes the phytochemical profile and antimicrobial potential of the essential oil obtained from apricot seeds (Armeniacae Semen). The essential oil isolated by hydrodistillation was analysed by gas chromatography-mass spectroscopy. Benzaldehyde (90.6%), mandelonitrile (5.2%) and benzoic acid (4.1%) were identified. Disc diffusion, agar dilution and gaseous contact methods were performed to determine the antimicrobial activity against 16 bacteria and two yeast species. The minimum inhibitory concentrations ranged from 250 to 4000, 500 to 2000 and 250 to 1000 µg/mL for Gram-positive bacteria, Gram-negative bacteria and yeast strains, respectively. The minimum inhibitory doses by gaseous contact ranged from 12.5 to 50, 12.5 to 50 and 3.13 to 12.5 mg/L air for Gram-positive bacteria, Gram-negative bacteria and yeast strains, respectively. The essential oil exhibited a variable degree of antimicrobial activity against a range of bacteria and yeasts tested. Copyright © 2014 John Wiley & Sons, Ltd.

In-vitro screening of Malaysian honey from different floral sources for antibacterial activity on human pathogenic bacteria.

PubMed

Ng, Wen-Jie; Ken, Khai-Wei; Kumar, Roshani-Vijaya; Gunasagaran, Hemamalani; Chandramogan, Vanaysha; Lee, Ying-Yee

2014-01-01

Different researches on therapeutic effects of honey have been conducted in different regions; however the study on the potential antibacterial activity of Malaysian honey is still limited. In this study, antibacterial activities of different monofloral honey samples were tested against several common human pathogenic bacteria. The well-diffusion method, minimum inhibitory concentrations (MIC) and minimum bactericidal concentration (MBC) techniques were employed to investigate the putative antibacterial activity of Malaysian monofloral honey from Koompassia excelsa (Becc.) Taub (Tualang), Melaleuca cajuputi Powell (Gelam) and Durio zibethinus Murr. (Durian). Honey samples were tested against Staphylococcus aureus ATCC6518 and ATCC25923, Staphylococcus epidermidis ATCC12228, Enterococcus faecium LMG16192, Enterococcus faecalis LMG16216 and ATCC29212, Escherichia coli ATCC25922, Salmonella enterica serovar Typhimurium ATCC14028 and Klebsiella pneumoniae ATCC13883. Marked variations were observed in the antibacterial activity of these honey samples. Durian honey failed to produce substantial antibacterial activity, whereas Tualang and Gelam honey showed a spectrum of antibacterial activity with their growth inhibitory effects against all of the tested bacterial species including vancomycin-resistant enterococci (VRE). Present findings suggested Gelam honey possesses highest antibacterial effect among the tested Malaysian honey samples.

Antimicrobial Effect of Jasminum grandiflorum L. and Hibiscus rosa-sinensis L. Extracts Against Pathogenic Oral Microorganisms--An In Vitro Comparative Study.

PubMed

Nagarajappa, Ramesh; Batra, Mehak; Sharda, Archana J; Asawa, Kailash; Sanadhya, Sudhanshu; Daryani, Hemasha; Ramesh, Gayathri

2015-01-01

To assess and compare the antimicrobial potential and determine the minimum inhibitory concentration (MIC) of Jasminum grandiflorum and Hibiscus rosa-sinensis extracts as potential anti-pathogenic agents in dental caries. Aqueous and ethanol (cold and hot) extracts prepared from leaves of Jasminum grandiflorum and Hibiscus rosa-sinensis were screened for in vitro antimicrobial activity against Streptococcus mutans and Lactobacillus acidophilus using the agar well diffusion method. The lowest concentration of every extract considered as the minimum inhibitory concentration (MIC) was determined for both test organisms. Statistical analysis was performed with one-way analysis of variance (ANOVA). At lower concentrations, hot ethanol Jasminum grandiflorum (10 μg/ml) and Hibiscus rosa-sinensis (25 μg/ml) extracts were found to have statistically significant (P≤0.05) antimicrobial activity against S. mutans and L. acidophilus with MIC values of 6.25 μg/ml and 25 μg/ml, respectively. A proportional increase in their antimicrobial activity (zone of inhibition) was observed. Both extracts were found to be antimicrobially active and contain compounds with therapeutic potential. Nevertheless, clinical trials on the effect of these plants are essential before advocating large-scale therapy.

Antimicrobial effects of citrus sinensis peel extracts against periodontopathic bacteria: an in vitro study.

PubMed

Hussain, Khaja Amjad; Tarakji, Bassel; Kandy, Binu Purushothaman Panar; John, Jacob; Mathews, Jacob; Ramphul, Vandana; Divakar, Darshan Devang

2015-01-01

Use of plant extracts and phytochemicals with known antimicrobial properties may have great significance in therapeutic treatments. To assess the in vitro antimicrobial potential and also determine the minimum inhibitory concentration (MIC) of Citrus sinensis peel extracts with a view of searching a novel extract as a remedy for periodontal pathogens. Aqueous and ethanol (cold and hot) extracts prepared from peel of Citrus sinensis were screened for in vitro antimicrobial activity against Aggregatibacter actinomycetemcomitans, Porphyromonas gingivalis and Prevotella intermedia, using agar well diffusion method. The lowest concentration of every extract considered as the minimal inhibitory concentration (MIC) values were determined for both test organisms. Confidence level and level of significance were set at 95% and 5% respectively. Prevotella intermedia and Porphyromonas gingivalis were resistant to aqueous extracts while Aggregatibacter actinomycetemcomitans was inhibited at very high cncentrations. Hot ethanolic extracts showed significantly higher zone of inhibition than cold ethanolic extract. Minimum inhibitory concentration of hot and cold ethanolic extracts of Citrus sinensis peel ranged between 12-15 mg/ml against all three periodontal pathogens. Both extracts were found sensitive and contain compounds with therapeutic potential. Nevertheless, clinical trials on the effect of these plants are essential before advocating large-scale therapy.

A sensitivity analysis of low salinity habitats simulated by a hydrodynamic model in the Manatee River estuary in Florida, USA

NASA Astrophysics Data System (ADS)

Chen, XinJian

2012-06-01

This paper presents a sensitivity study of simulated availability of low salinity habitats by a hydrodynamic model for the Manatee River estuary located in the southwest portion of the Florida peninsula. The purpose of the modeling study was to establish a regulatory minimum freshwater flow rate required to prevent the estuarine ecosystem from significant harm. The model used in the study was a multi-block model that dynamically couples a three-dimensional (3D) hydrodynamic model with a laterally averaged (2DV) hydrodynamic model. The model was calibrated and verified against measured real-time data of surface elevation and salinity at five stations during March 2005-July 2006. The calibrated model was then used to conduct a series of scenario runs to investigate effects of the flow reduction on salinity distributions in the Manatee River estuary. Based on simulated salinity distribution in the estuary, water volumes, bottom areas and shoreline lengths for salinity less than certain predefined values were calculated and analyzed to help establish the minimum freshwater flow rate for the estuarine system. The sensitivity analysis conducted during the modeling study for the Manatee River estuary examined effects of the bottom roughness, ambient vertical eddy viscosity/diffusivity, horizontal eddy viscosity/diffusivity, and ungauged flow on the model results and identified the relative importance of these model parameters (input data) to the outcome of the availability of low salinity habitats. It is found that the ambient vertical eddy viscosity/diffusivity is the most influential factor controlling the model outcome, while the horizontal eddy viscosity/diffusivity is the least influential one.

Antimicrobial activity evaluation and comparison of methods of susceptibility for Klebsiella pneumoniae carbapenemase (KPC)-producing Enterobacter spp. isolates.

PubMed

Rechenchoski, Daniele Zendrini; Dambrozio, Angélica Marim Lopes; Vivan, Ana Carolina Polano; Schuroff, Paulo Alfonso; Burgos, Tatiane das Neves; Pelisson, Marsileni; Perugini, Marcia Regina Eches; Vespero, Eliana Carolina

The production of KPC (Klebsiella pneumoniae carbapenemase) is the major mechanism of resistance to carbapenem agents in enterobacterias. In this context, forty KPC-producing Enterobacter spp. clinical isolates were studied. It was evaluated the activity of antimicrobial agents: polymyxin B, tigecycline, ertapenem, imipenem and meropenem, and was performed a comparison of the methodologies used to determine the susceptibility: broth microdilution, Etest ® (bioMérieux), Vitek 2 ® automated system (bioMérieux) and disc diffusion. It was calculated the minimum inhibitory concentration (MIC) for each antimicrobial and polymyxin B showed the lowest concentrations for broth microdilution. Errors also were calculated among the techniques, tigecycline and ertapenem were the antibiotics with the largest and the lower number of discrepancies, respectively. Moreover, Vitek 2 ® automated system was the method most similar compared to the broth microdilution. Therefore, is important to evaluate the performance of new methods in comparison to the reference method, broth microdilution. Copyright © 2017 Sociedade Brasileira de Microbiologia. Published by Elsevier Editora Ltda. All rights reserved.

Transferred nuclear Overhauser enhancement experiments show that the monoclonal antibody strep 9 selects a local minimum conformation of a Streptococcus group A trisaccharide-hapten.

PubMed

Weimar, T; Harris, S L; Pitner, J B; Bock, K; Pinto, B M

1995-10-17

Transferred nuclear Overhauser enhancement (TRNOE) experiments have been performed to investigate the bound conformation of the trisaccharide repeating unit of the Streptococcus Group A cell-wall polysaccharide. Thus, the conformations of propyl 3-O-(2-acetamido-2-deoxy-beta-D-glucopyranosyl)-2-O-(alpha-L-rhamnopyran osyl)- alpha-L-rhamnopyranoside [C(A')B] (1) as a free ligand and when complexed to the monoclonal antibody Strep 9 were examined. Improved insights about the conformational preferences of the glycosidic linkages of the trisaccharide ligand showed that the free ligand populates various conformations in aqueous solution, thus displaying relatively flexible behavior. The NOE HNAc-H2A', which was not detected in previous work, accounts for a conformation at the beta-(1-->3) linkage with a phi angle of approximately 180 degrees. Observed TRNOEs for the complex are weak, and their analysis was further complicated by spin diffusion. With the use of transferred rotating-frame Overhauser enhancement (TRROE) experiments, the amount of spin diffusion was assessed experimentally, proving that all of the observed long-range TRNOEs arose through spin diffusion. Four interglycosidic distances, derived from the remaining TRNOEs and TRROEs, together with repulsive constraints, derived from the absence of TRROE effects, were used as input parameters in simulated annealing and molecular mechanics calculations to determine the bound conformation of the trisaccharide. Complexation by the antibody results in the selection of one defined conformation of the carbohydrate hapten. This bound conformation, which is a local energy minimum on the energy maps calculated for the trisaccharide ligand, shows only a change from a +gauche to a -gauche orientation at the psi angle of the alpha-(1-->2) linkage when compared to the global minimum conformation. The results infer that the bound conformation of the Streptococcus Group A cell-wall polysaccharide is different from its previously proposed solution structure (Kreis et al., 1995).

Common pediatric cerebellar tumors: correlation between cell densities and apparent diffusion coefficient metrics.

PubMed

Koral, Korgün; Mathis, Derek; Gimi, Barjor; Gargan, Lynn; Weprin, Bradley; Bowers, Daniel C; Margraf, Linda

2013-08-01

To test whether there is correlation between cell densities and apparent diffusion coefficient (ADC) metrics of common pediatric cerebellar tumors. This study was reviewed for issues of patient safety and confidentiality and was approved by the Institutional Review Board of the University of Texas Southwestern Medical Center and was compliant with HIPAA. The need for informed consent was waived. Ninety-five patients who had preoperative magnetic resonance imaging and surgical pathologic findings available between January 2003 and June 2011 were included. There were 37 pilocytic astrocytomas, 34 medulloblastomas (23 classic, eight desmoplastic-nodular, two large cell, one anaplastic), 17 ependymomas (13 World Health Organization [WHO] grade II, four WHO grade III), and seven atypical teratoid rhabdoid tumors. ADCs of solid tumor components and normal cerebellum were measured. Tumor-to-normal brain ADC ratios (hereafter, ADC ratio) were calculated. The medulloblastomas and ependymomas were subcategorized according to the latest WHO classification, and tumor cellularity was calculated. Correlation was sought between cell densities and mean tumor ADCs, minimum tumor ADCs, and ADC ratio. When all tumors were considered together, negative correlation was found between cellularity and mean tumor ADCs (ρ = -0.737, P < .05) and minimum tumor ADCs (ρ = -0.736, P < .05) of common pediatric cerebellar tumors. There was no correlation between cellularity and ADC ratio. Negative correlation was found between cellularity and minimum tumor ADC in atypical teratoid rhabdoid tumors (ρ = -0.786, P < .05). In atypical teratoid rhabdoid tumors, no correlation was found between cellularity and mean tumor ADC and ADC ratio. There was no correlation between the ADC metrics and cellularity of the pilocytic astrocytomas, medulloblastomas, and ependymomas. Negative correlation was found between cellularity and ADC metrics of common pediatric cerebellar tumors. Although ADC metrics are useful in the preoperative diagnosis of common pediatric cerebellar tumors and this utility is generally attributed to differences in cellularity of tumors, tumor cellularity may not be the sole determinant of the differences in diffusivity.

Improved Dot Diffusion For Image Halftoning

DTIC Science & Technology

1999-01-01

The dot diffusion method for digital halftoning has the advantage of parallelism unlike the error diffusion method. The method was recently improved...by optimization of the so-called class matrix so that the resulting halftones are comparable to the error diffused halftones . In this paper we will...first review the dot diffusion method. Previously, 82 class matrices were used for dot diffusion method. A problem with this size of class matrix is

Diffusion of hydrogen into and through γ-iron by density functional theory

NASA Astrophysics Data System (ADS)

Chohan, Urslaan K.; Koehler, Sven P. K.; Jimenez-Melero, Enrique

2018-06-01

This study is concerned with the early stages of hydrogen embrittlement on an atomistic scale. We employed density functional theory to investigate hydrogen diffusion through the (100), (110) and (111) surfaces of γ-Fe. The preferred adsorption sites and respective energies for hydrogen adsorption were established for each plane, as well as a minimum energy pathway for diffusion. The H atoms adsorb on the (100), (110) and (111) surfaces with energies of ∼4.06 eV, ∼3.92 eV and ∼4.05 eV, respectively. The barriers for bulk-like diffusion for the (100), (110) and (111) surfaces are ∼0.6 eV, ∼0.5 eV and ∼0.7 eV, respectively. We compared these calculated barriers with previously obtained experimental data in an Arrhenius plot, which indicates good agreement between experimentally measured and theoretically predicted activation energies. Texturing austenitic steels such that the (111) surfaces of grains are preferentially exposed at the cleavage planes may be a possibility to reduce hydrogen embrittlement.

Detection of Salmonella spp. with the BACTEC 9240 Automated Blood Culture System in 2008 - 2014 in Southern Iran (Shiraz): Biogrouping, MIC, and Antimicrobial Susceptibility Profiles of Isolates.

PubMed

Anvarinejad, Mojtaba; Pouladfar, Gholam Reza; Pourabbas, Bahman; Amin Shahidi, Maneli; Rafaatpour, Noroddin; Dehyadegari, Mohammad Ali; Abbasi, Pejman; Mardaneh, Jalal

2016-04-01

Human salmonellosis continues to be a major international problem, in terms of both morbidity and economic losses. The antibiotic resistance of Salmonella is an increasing public health emergency, since infections from resistant bacteria are more difficult and costly to treat. The aims of the present study were to investigate the isolation of Salmonella spp. with the BACTEC automated system from blood samples during 2008 - 2014 in southern Iran (Shiraz). Detection of subspecies, biogrouping, and antimicrobial susceptibility testing by the disc diffusion and agar dilution methods were performed. A total of 19 Salmonella spp. were consecutively isolated using BACTEC from blood samples of patients between 2008 and 2014 in Shiraz, Iran. The isolates were identified as Salmonella, based on biochemical tests embedded in the API-20E system. In order to characterize the biogroups and subspecies, biochemical testing was performed. Susceptibility testing (disc diffusion and agar dilution) and extended-spectrum β-lactamase (ESBL) detection were performed according to the clinical and laboratory standards institute (CLSI) guidelines. Of the total 19 Salmonella spp. isolates recovered by the BACTEC automated system, all belonged to the Salmonella enterica subsp. houtenae. Five isolates (26.5%) were resistant to azithromycin. Six (31.5%) isolates with the disc diffusion method and five (26.3%) with the agar dilution method displayed resistance to nalidixic acid (minimum inhibitory concentration [MIC] > 32 μg/mL). All nalidixic acid-resistant isolates were also ciprofloxacin-sensitive. All isolates were ESBL-negative. Twenty-one percent of isolates were found to be resistant to chloramphenicol (MIC ≥ 32 μg/mL), and 16% were resistant to ampicillin (MIC ≥ 32 μg/mL). The results indicate that multidrug-resistant (MDR) strains of Salmonella are increasing in number, and fewer antibiotics may be useful for treating S. enterica infections. Routine investigation and reporting of antibiotic MICs in patients presenting with Salmonella infections is suggested.

Anti-Helicobacter pylori activity of plant extracts traditionally used for the treatment of gastrointestinal disorders

PubMed Central

Cogo, Laura Lúcia; Monteiro, Cristina Leise Bastos; Miguel, Marilis Dallarmi; Miguel, Obdulio Gomes; Cunico, Miriam Machado; Ribeiro, Marcelo Lima; de Camargo, Eloá Ramalho; Kussen, Gislene Maria Botão; Nogueira, Keite da Silva; Costa, Libera Maria Dalla

2010-01-01

The antibacterial activity of plant extracts obtained from Bixa orellana L., Chamomilla recutita L., Ilex paraguariensis A. St.-Hil., Malva sylvestris L., Plantago major L. and Rheum rhaponticum L. has been evaluated against two reference strains and eleven clinical isolates of Helicobacter pylori. All the plant species chosen are used in popular Brazilian cuisine and folk medicine in the treatment of gastrointestinal disorders. Initial screening was made by the disk diffusion test and then minimum inhibitory concentration was determined by the agar dilution method. The results presented in this work demonstrated that among the plant preparations analyzed, B. orellana L., C. recutita L., I. paraguariensis A. St.-Hil. and M. sylvestris L. were capable of inhibiting the in vitro growth of H. pylori. PMID:24031496

Full Core TREAT Kinetics Demonstration Using Rattlesnake/BISON Coupling Within MAMMOTH

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

Ortensi, Javier; DeHart, Mark D.; Gleicher, Frederick N.

2015-08-01

This report summarizes key aspects of research in evaluation of modeling needs for TREAT transient simulation. Using a measured TREAT critical measurement and a transient for a small, experimentally simplified core, Rattlesnake and MAMMOTH simulations are performed building from simple infinite media to a full core model. Cross sections processing methods are evaluated, various homogenization approaches are assessed and the neutronic behavior of the core studied to determine key modeling aspects. The simulation of the minimum critical core with the diffusion solver shows very good agreement with the reference Monte Carlo simulation and the experiment. The full core transient simulationmore » with thermal feedback shows a significantly lower power peak compared to the documented experimental measurement, which is not unexpected in the early stages of model development.« less

Low-frequency polarization measurements of the diffuse radio emission of the galaxy

NASA Astrophysics Data System (ADS)

Vinyaikin, E. N.; Paseka, A. M.

2015-07-01

Polarization measurements of diffuse Galactic radio emission at 151.5, 198, 217, 237, and 290 MHz have been carried out in the direction of the North Celestial Pole, North Galactic Pole, one region of the North Polar Spur, minimum radio brightness of the Northern sky ( l = 190°, b = 50°), and in the direction l = 147°, b = 9° in the so-called FAN region with enhanced polarization. The results obtained testify to the presence of low spatial frequencies in the angular distribution of the Stokes parameters Q and U of the diffuse Galactic synchrotron emission that are not detectable in interferometric observations. The spectra of the brightness temperature of the polarized component, rotation measures, and intrinsic polarization position angles of the radio emission in the studied regions are presented.

Anticariogenic activity of the active fraction from Isertia laevis against S. mutans and S. sobrinus: comparison of two extraction methods.

PubMed

Téllez, Nohemí; Téllez, Mayra; Perdomo, Margarita; Alvarado, Andrea; Gamboa, Fredy

2010-01-01

Dental caries is considered a multi-factorial, infectious, chronic, localized, post-eruptive, transmissible disease that leads to the destruction of dental hard tissue. The recognition of Streptococcus mutans as the major bacterial species involved in dental caries has led to the implementation of prevention and control measures for eliminating or reducing it in oral cavity. The main goal of research on medicinal plants is the search for substances or compounds with antimicrobial activity. The aim of this study was to evaluate the antimicrobial activity of fractions obtained by two methods from Isertia laevis against S. mutans and S. sobrinus. The plant material was collected in Medina (Colombia), at an elevation of 550 meters above sea level. From the ethanol extract of leaves of I. laevis, fractions were obtained by two methods: extraction by column vacuum chromatography (CVC) and extraction by continuous liquid/liquid partitioning (CLLP). The evaluation of the antimicrobial activity of fractions against S. mutans and S. sobrinus was performed by well diffusion and bioautography assays. From the CVC technique, only the methanol and methanol-dichloromethane fractions showed activity against S. mutans and S. sobrinus, with a minimum inhibitory concentration of 2 mg/well. From the CLLP technique, only the dichloromethane fraction showed activity against both microorganisms, with a minimum inhibitory concentration of 1 mg/well. Compounds C1 and C2 were isolated from the three active fractions, and showed a minimum inhibitory concentration of 0.4 mg/well for S. mutans and S. sobrinus, with zones of inhibition measuring 6.5 and 6.2 mm, respectively. 1) the three active fractions of I. laevis showed activity against S. mutans and S. sobrinus, 2) compounds C1 and C2 were presen equally in the three active fractions showing activity against the two bacteria, 3) compounds C1 and C2 may be triterpenoid and/or steroidal saponin structures, and 4) the two extraction methods lead equally to obtaining the active fractions.

[Study on the antibacterial activity of four kinds of nano-hydroxyapatite composites against Enterococcus faecalis].

PubMed

Liu, Yi; Zhou, Rongjing; Wu, Hongkun

2015-06-01

This study aims to compare and determine a kind of nano-hydroxyapatite composite material with good antibacterial efficacy on Enterococcusfaecalis (E. faecalis) in vitro. We investigated the antimicrobial activity of four kinds of nano-hydroxyapatite composites, namely, silver/hydroxyapatite composite nanoparticles (Ag/nHA), yttrium/hydroxyapatite composite nanoparticles (Yi/nHA), cerium/hydroxyapatite composite nanoparticles (Ce/nHA), and hydroxyapatite nanoparticles (nHA), against E. faecalis in vitro using the agar diffusion and broth dilution method by measuring the growth inhibition zone and the minimum inhibitory concentration (MIC), respectively. The agar diffusion test results showed that Ag/nHA displayed an obvious growth inhibition zone, whereas Yi/nHA, Ce/nHA, and nHA showed no influence on E. faecalis. The MIC value of Ag/nHA was 1.0 g.L-1, and the three other materials had no effect on E.faecalis even at the high concentration of 32.0 g.L-1. Ag/nHA display a potential antimicrobial efficacy to planktonic E.faecalis. Whereas, the three other kinds of nano-hydroxyapatite composites (Yi/nHA, Ce/nHA, nHA) show no influence.

Recording and Analysis of Bowel Sounds.

PubMed

Zaborski, Daniel; Halczak, Miroslaw; Grzesiak, Wilhelm; Modrzejewski, Andrzej

2015-01-01

The aim of this study was to construct an electronic bowel sound recording system and determine its usefulness for the diagnosis of appendicitis, mechanical ileus and diffuse peritonitis. A group of 67 subjects aged 17 to 88 years including 15 controls was examined. Bowel sounds were recorded using an electret microphone placed on the right side of the hypogastrium and connected to a laptop computer. The method of adjustable grids (converted into binary matrices) was used for bowel sounds analysis. Significantly, fewer (p ≤ 0.05) sounds were found in the mechanical ileus (1004.4) and diffuse peritonitis (466.3) groups than in the controls (2179.3). After superimposing adjustable binary matrices on combined sounds (interval between sounds <0.01 s), significant relationships (p ≤ 0.05) were found between particular positions in the matrices (row-column) and the patient groups. These included the A1_T1 and A1_T2 positions and mechanical ileus as well as the A1_T2 and A1_T4 positions and appendicitis. For diffuse peritonitis, significant positions were A5_T4 and A1_T4. Differences were noted in the number of sounds and binary matrices in the groups of patients with acute abdominal diseases. Certain features of bowel sounds characteristic of individual abdominal diseases were indicated. BS: bowel sound; APP: appendicitis; IL: mechanical ileus; PE: diffuse peritonitis; CG: control group; NSI: number of sound impulses; NCI: number of combined sound impulses; MBS: mean bit-similarity; TMIN: minimum time between impulses; TMAX: maximum time between impulses; TMEAN: mean time between impulses. Zaborski D, Halczak M, Grzesiak W, Modrzejewski A. Recording and Analysis of Bowel Sounds. Euroasian J Hepato-Gastroenterol 2015;5(2):67-73.

Spectrometer system for diffuse extreme ultraviolet radiation

NASA Technical Reports Server (NTRS)

Labov, Simon E.

1989-01-01

A unique grazing incidence spectrometer system has been designed to study diffuse line emission between 80 and 650 A with 10-30 A resolution. The minimum detectable emission line strength during a 5-min observation ranges from 100-2000 ph/sq cm sec str. The instrument uses mechanically ruled reflection gratings placed in front of a linear array of mirrors. These mirrors focus the spectral image on microchannel plate detectors located behind thin filters. The field of view is 40 min of arc by 15 deg, and there is no spatial imaging. This instrument has been fabricated, calibrated, and successfully flown on a sounding rocket to observe the astronomical background radiation.

Investigation at Mach Numbers 2.98 and 2.18 of Axially Symmetric Free-jet Diffusion with a Ram-jet Engine

NASA Technical Reports Server (NTRS)

Hunczak, Henry R

1952-01-01

An investigation was conducted to determine the effectiveness of a free-jet diffuser in reducing the over-all pressure ratios required to operate a free jet with a large air-breathing engine as a test vehicle. Efficient operation of the free jet was determined with and without the considerations required for producing suitable engine-inlet flow conditions. A minimum operating pressure ration of 5.5 was attained with a ratio of nozzle-exit to engine-inlet area of 1.85. Operation of the free jet with unstable engine-inlet flow (buzz) is also included.

Isolation of Abscisic Acid from Korean Acacia Honey with Anti-Helicobacter pylori Activity

PubMed Central

Kim, SeGun; Hong, InPyo; Woo, SoonOk; Jang, HyeRi; Pak, SokCheon; Han, SangMi

2017-01-01

Background: Helicobacter pylori (H. pylori) is linked to the development of the majority of peptic ulcers and some types of gastric cancers, and its antibiotic resistance is currently found worldwide. Objective: This study is aimed at evaluating the anti-H. pylori activity of Korean acacia honey and isolating the related active components using organic solvents. Material and Methods: The crude acacia honey was extracted with n-hexane, dichloromethane, ethyl acetate (EtOAc), and n-butanol. The EtOAc extract was subjected to octadecyl-silica chromatography. The extracts and fractions were then examined for anti-H. pylori activity using the agar well diffusion method. The antimicrobial activity of abscisic acid against H. pylori was investigated by determining the minimum inhibitory concentrations (MICs), minimum bactericidal concentrations (MBCs), and by performing a time-kill assay. Results: Abscisic acid related to the botanical origins of acacia honey from Korea has been analyzed using ultra-performance liquid chromatography. The MICs and MBCs of abscisic acid were 2.7 ± 1.3 and 6.9 ± 1.9 μg/mL, respectively. The bactericidal activity of abscisic acid (at 10.8 μg/mL corresponding to 4 × MIC) killed the organism within 36–72 h. These results suggest that abscisic acid isolated from Korean acacia honey has antibacterial activity against H. pylori. Conclusion: Abscisic acid isolated from Korean acacia honey can be therapeutic and may be further exploited as a potential lead candidate for the development of treatments for H. pylori-induced infections. SUMMARY The crude acacia honey was extracted with n-hexane, dichloromethane, EtOAc, and n-butanolThe EtOAc extract yielded eight fractions and four subfractions were subsequently obtained chromatographicallyAbscisic acid was isolated from one subfractionAll the solvent extracts and fractions showed antibacterial activity against H. pyloriAbscisic acid exhibited antibacterial activity against H. pylori. Abbreviations used: MeOH: Methanol; EtOAc: Ethyl acetate; TSB: Trypticase soy broth; MIC: Minimum inhibitory concentration; MBC: Minimum bactericidal concentration; CFU: Colony-forming units; UPLC: Ultra-performance liquid chromatography; DAD: Diode array detector; UV: Ultraviolet; ODS: Octadecyl-silica; MS: Mass spectrometry; SE: Standard error. PMID:28808376

ANTIBACTERIAL ACTIVITY OF DRACONTOMELON DAO EXTRACTS ON METHICILLIN-RESISTANT S. AUREUS (MRSA) AND E. COLI MULTIPLE DRUG RESISTANCE (MDR).

PubMed

Yuniati, Yuniati; Hasanah, Nurul; Ismail, Sjarif; Anitasari, Silvia; Paramita, Swandari

2018-01-01

Staphylococcus aureus , methicillin-resistant and Escherichia coli , multidrug-resistant included in the list of antibiotic-resistant priority pathogens from WHO. As multidrug-resistant bacteria problem is increasing, it is necessary to probe new sources for identifying antimicrobial compounds. Medicinal plants represent a rich source of antimicrobial agents. One of the potential plants for further examined as antibacterial is Dracontomelon dao (Blanco) Merr. & Rolfe. The present study designed to find the antibacterial activity of D. dao stem bark extracts on Methicillin-resistant S. aureus (MRSA) and E. coli Multiple Drug Resistance (MDR), followed by determined secondary metabolites with antibacterial activity and determined the value of MIC (minimum inhibitory concentration) and MBC (minimum bactericidal concentration). D. dao stem bark extracted using 60% ethanol. Disc diffusion test methods used to find the antibacterial activity, following by microdilution methods to find the value of MIC and MBC. Secondary metabolites with antibacterial activity determined by bioautography using TLC (thin layer chromatography) methods. D. dao stem bark extracts are sensitive to MSSA, MRSA and E.coli MDR bacteria. The inhibition zone is 16.0 mm in MSSA, 11.7 mm in MRSA and 10.7 mm in E. coli MDR. The entire MBC/MIC ratios for MSSA, MRSA and E.coli MDR is lower than 4. The ratio showed bactericidal effects of D. dao stem bark extracts. In TLC results, colorless bands found to be secondary metabolites with antibacterial activity. D. dao stem bark extracts are potential to develop as antibacterial agent especially against MRSA and E. coli MDR strain.

Evaluation of wound healing, antioxidant and antimicrobial efficacy of Jasminum auriculatum Vahl. leaves

PubMed Central

Arun, Mittal; Satish, Sardana; Anima, Pandey

2016-01-01

Objective: To validate the ethno-therapeutic claim of the traditionally used plant Jasminum auriculatum (J. auriculatum) in skin diseases, by evaluating its wound healing potential along with its antioxidant and antimicrobial properties; so as to understand their role in wound healing. Materials and Methods: Excision and incision wound models were used to evaluate the wound healing activity on albino rats. The wound healing potential was assessed by measuring rate of wound contraction, epithelialization period, hydroxyproline content, skin breaking strength and histopathological parameters. Reference standard drug was Nitrofurazone ointment. The antioxidant activity was determined using 2, 2-diphenyl-1-picrylhydrazyl (DPPH) method. The antimicrobial activity was determined by agar well diffusion method and minimum inhibitory concentration by serial dilution method. Results: Higher rate of wound contraction (83.66±0.50% on 15th day), decrease in the period of epithelialization (17.83±1.6days), higher skin breaking strength (170.71±1.52g), higher collagen content and favourable histopathological changes revealed that topical application of ointment containing successive ethanolic extract (S.E.E) of J. auriculatum leaves has the most potent wound healing ability compared to control group in both the models studied. The DPPH radical scavenging activity of successive ethanolic extract was found to be 33.39µg/ml. Successive ethanolic extract was found to be most effective against Pseudomonas auregenosa having a zone of inhibition 16.65±0.6mm and the minimum inhibitory concentration was 0.78mg/ml. Conclusion: The data of this study indicate that successive ethanolic extract of the leaves exhibit potent wound healing, antioxidant and antimicrobial properties. This justifies the ethno-medicinal use of plant for the treatment of wound and microbial infections. PMID:27462552

Hybrid finite element and Brownian dynamics method for diffusion-controlled reactions.

PubMed

Bauler, Patricia; Huber, Gary A; McCammon, J Andrew

2012-04-28

Diffusion is often the rate determining step in many biological processes. Currently, the two main computational methods for studying diffusion are stochastic methods, such as Brownian dynamics, and continuum methods, such as the finite element method. This paper proposes a new hybrid diffusion method that couples the strengths of each of these two methods. The method is derived for a general multidimensional system, and is presented using a basic test case for 1D linear and radially symmetric diffusion systems.

On the meaning of the diffusion layer thickness for slow electrode reactions.

PubMed

Molina, A; González, J; Laborda, E; Compton, R G

2013-02-21

A key concept underpinning electrochemical science is that of the diffusion layer - the zone of depletion around an electrode accompanying electrolysis. The size of this zone can be found either from the simulated or measured concentration profiles (yielding the 'true' diffusion layer thickness) or, in the case of the Nernst ('linear') diffusion layer by extrapolating the concentration gradient at the electrode surface to the distance at which the concentration takes its bulk value. The latter concept is very well developed in the case of fast (so-called reversible) electrode processes, however the study of the linear diffusion layer has received scant attention in the case of slow charge transfer processes, despite its study being of great interest in the analysis of the influence of different experimental variables which determine the electrochemical response. Analytical explicit solutions for the concentration profiles, surface concentrations and real and linear diffusion layers corresponding to the application of a potential step to a slow charge transfer process are presented. From these expressions the dependence of the diffusion layer thickness on the potential, pulse time, heterogeneous rate constant and ratio of bulk concentrations of electroactive species and of diffusion coefficients is quantified. A profound influence of the reversibility degree of the charge transfer on the diffusion layer thickness is clear, showing that for non-reversible processes the real and linear diffusion layers reveal a minimum thickness which coincides with the equilibrium potential of the redox couple in the former case and with the reversible half-wave potential in the latter one.

Holographic diffuser by use of a silver halide sensitized gelatin process

NASA Astrophysics Data System (ADS)

Kim, Sun Il; Choi, Yoon Sun; Ham, Yong Nam; Park, Chong Yun; Kim, Jong Man

2003-05-01

Diffusers play an important role in liquid-crystal display (LCD) application as a beam-shaping device, a brightness homogenizer, a light-scattering device, and an imaging screen. The transmittance and diffusing angle of the diffusers are the critical aspects for the applications to the LCD. The holographic diffusers by use of various processing methods have been investigated. The diffusing characteristics of different diffusing materials and processing methods have been evaluated and compared. The micro-structures of holographic diffusers have been investigated by use of using scanning electron microscopy. The holographic diffusers by use of the silver halide sensitized gelatin (SHSG) method have the structural merits for the improvement of the quality of diffusers. The features of holographic diffuser were exceptional in terms of transmittance and diffusing angle. The replication method by use of the SHSG process can be directly used for the manufacturing of diffusers for the display application.

Ni-SDC cermet anode for medium-temperature solid oxide fuel cell with lanthanum gallate electrolyte

NASA Astrophysics Data System (ADS)

Zhang, Xinge; Ohara, Satoshi; Maric, Radenka; Mukai, Kazuo; Fukui, Takehisa; Yoshida, Hiroyuki; Nishimura, Masayoshi; Inagaki, Toru; Miura, Kazuhiro

The polarization properties and microstructure of Ni-SDC (samaria-doped ceria) cermet anodes prepared from spray pyrolysis (SP) composite powder, and element interface diffusion between the anode and a La 0.9Sr 0.1Ga 0.8Mg 0.2O 3- δ (LSGM) electrolyte are investigated as a function of anode sintering temperature. The anode sintered at 1250°C displays minimum anode polarization (with anode ohmic loss), while the anode prepared at 1300°C has the best electrochemical overpotential, viz., 27 mV at 300 mA cm -2 operating at 800°C. The anode ohmic loss gradually increases with increase in the sintering temperature at levels below 1300°C, and sharply increases at 1350°C. Electron micrographs show a clear grain growth at sintering temperatures higher than 1300°C. The anode microstructure appears to be optimized at 1300°C, in which nickel particles form a network with well-connected SDC particles finely distributed over the surfaces of the nickel particles. The anode sintered at 1350°C has severe grain growth and an apparent interface diffusion of nickel from the anode to the electrolyte. The nickel interface diffusion is assumed to be the main reason for the increment in ohmic loss, and the resulting loss in anode performance. The findings suggest that sintering Ni-SDC composite powder near 1250°C is the best method to prepare the anode on a LSGM electrolyte.

When Do Laws Matter? National Minimum-Age-of-Marriage Laws, Child Rights, and Adolescent Fertility, 1989–2007

PubMed Central

Kim, Minzee; Longhofer, Wesley; Boyle, Elizabeth Heger; Nyseth, Hollie

2014-01-01

Using the case of adolescent fertility, we ask the questions of whether and when national laws have an effect on outcomes above and beyond the effects of international law and global organizing. To answer these questions, we utilize a fixed-effect time-series regression model to analyze the impact of minimum-age-of-marriage laws in 115 poor- and middle-income countries from 1989 to 2007. We find that countries with strict laws setting the minimum age of marriage at 18 experienced the most dramatic decline in rates of adolescent fertility. Trends in countries that set this age at 18 but allowed exceptions (for example, marriage with parental consent) were indistinguishable from countries that had no such minimum-age-of-marriage law. Thus, policies that adhere strictly to global norms are more likely to elicit desired outcomes. The article concludes with a discussion of what national law means in a diffuse global system where multiple actors and institutions make the independent effect of law difficult to identify. PMID:25525281

Brief Report: Investigating Uncertainty in the Minimum Mortality Temperature: Methods and Application to 52 Spanish Cities.

PubMed

Tobías, Aurelio; Armstrong, Ben; Gasparrini, Antonio

2017-01-01

The minimum mortality temperature from J- or U-shaped curves varies across cities with different climates. This variation conveys information on adaptation, but ability to characterize is limited by the absence of a method to describe uncertainty in estimated minimum mortality temperatures. We propose an approximate parametric bootstrap estimator of confidence interval (CI) and standard error (SE) for the minimum mortality temperature from a temperature-mortality shape estimated by splines. The coverage of the estimated CIs was close to nominal value (95%) in the datasets simulated, although SEs were slightly high. Applying the method to 52 Spanish provincial capital cities showed larger minimum mortality temperatures in hotter cities, rising almost exactly at the same rate as annual mean temperature. The method proposed for computing CIs and SEs for minimums from spline curves allows comparing minimum mortality temperatures in different cities and investigating their associations with climate properly, allowing for estimation uncertainty.

Ion conduction mechanisms and thermal properties of hydrated and anhydrous phosphoric acids studied with 1H, 2H, and 31P NMR.

PubMed

Aihara, Yuichi; Sonai, Atsuo; Hattori, Mineyuki; Hayamizu, Kikuko

2006-12-14

To understand the behaviors of phosphoric acids in fuel cells, the ion conduction mechanisms of phosphoric acids in condensed states without free water and in a monomer state with water were studied by measuring the ionic conductivity (sigma) using AC impedance, thermal properties, and self-diffusion coefficients (D) and spin-lattice relaxation times (T1) with multinuclear NMR. The self-diffusion coefficient of the protons (H+ or H3O+), H2O, and H located around the phosphate were always larger than the diffusion coefficients of the phosphates and the disparity increased with increasing phosphate concentration. The diffusion coefficients of the samples containing D2O paralleled those in the protonated samples. Since the 1H NMR T1 values exhibited a minimum with temperature, it was possible to determine the correlation times and they were found to be of nanosecond order for a distance of nanometer order for a flip. The agreement of the ionic conductivities measured directly and those calculated from the diffusion coefficients indicates that the ion conduction obeys the Nernst-Einstein equation in the condensed phosphoric acids. The proton diffusion plays a dominant role in the ion conduction, especially in the condensed phosphoric acids.

Application of an improved minimum entropy deconvolution method for railway rolling element bearing fault diagnosis

NASA Astrophysics Data System (ADS)

Cheng, Yao; Zhou, Ning; Zhang, Weihua; Wang, Zhiwei

2018-07-01

Minimum entropy deconvolution is a widely-used tool in machinery fault diagnosis, because it enhances the impulse component of the signal. The filter coefficients that greatly influence the performance of the minimum entropy deconvolution are calculated by an iterative procedure. This paper proposes an improved deconvolution method for the fault detection of rolling element bearings. The proposed method solves the filter coefficients by the standard particle swarm optimization algorithm, assisted by a generalized spherical coordinate transformation. When optimizing the filters performance for enhancing the impulses in fault diagnosis (namely, faulty rolling element bearings), the proposed method outperformed the classical minimum entropy deconvolution method. The proposed method was validated in simulation and experimental signals from railway bearings. In both simulation and experimental studies, the proposed method delivered better deconvolution performance than the classical minimum entropy deconvolution method, especially in the case of low signal-to-noise ratio.

Holographic grating relaxation technique for soft matter science

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

Lesnichii, Vasilii, E-mail: vasilii.lesnichii@physchem.uni-freiburg.de; ITMO University, Kronverksky prospekt 49, Saint-Petersburg 197101; Kiessling, Andy

2016-06-17

The holographic grating relaxation technique also known as forced Rayleigh scattering consists basically in writing a holographic grating in the specimen of interest and monitoring its diffraction efficiency as a function of time, from which valuable information on mass or heat transfer and photoinduced transformations can be extracted. In a more detailed view, the shape of the relaxation curve and the relaxation rate as a function of the grating period were found to be affected by the architecture of diffusing species (molecular probes) that constitute the grating, as well as that of the environment they diffuse in, thus making itmore » possible to access and study spatial heterogeneity of materials and different modes of e.g., polymer motion. Minimum displacements and spatial domains approachable by the technique are in nanometer range, well below spatial periods of holographic gratings. In the present paper, several cases of holographic relaxation in heterogeneous media and complex motions are exemplified. Nano- to micro-structures or inhomogeneities comparable in spatial scale with holographic gratings manifest themselves in relaxation experiments via non-exponential decay (stepwise or stretched), spatial-period-dependent apparent diffusion coefficient, or unusual dependence of diffusion coefficient on molecular volume of diffusing probes.« less

Effect of nucleation time on bending response of ionic polymer–metal composite actuators

DOE PAGES

Kim, Suran; Hong, Seungbum; Choi, Yoon-Young; ...

2013-07-02

We attempted an autocatalytic electro-less plating of nickel in order to replace an electroless impregnation-reduction (IR) method in ionic polymer–metal composite (IPMC) actuators to reduce cost and processing time. Because nucleation time of Pd–Sn colloids is the determining factor of overall processing time, we used the nucleation time as our control parameter. In order to optimize nucleation time and investigate its effect on the performance of IPMC actuators, we analyzed the relationship between the nucleation time, interface morphology and electrical properties. The optimized nucleation time was 10 h. Furthermore, the trends of the performance and electrical properties as a functionmore » of nucleation time were attributed to the fact that the Ni penetration depth was determined by the minimum diffusion length of either Pd–Sn colloids or reducing agent ions. The Ni-IPMC actuators can be fabricated less than 14 h processing time without deteriorating performance of the actuators, which is comparable to Pt-IPMC prepared by IR method.« less

Fusion of Deep Learning and Compressed Domain features for Content Based Image Retrieval.

PubMed

Liu, Peizhong; Guo, Jing-Ming; Wu, Chi-Yi; Cai, Danlin

2017-08-29

This paper presents an effective image retrieval method by combining high-level features from Convolutional Neural Network (CNN) model and low-level features from Dot-Diffused Block Truncation Coding (DDBTC). The low-level features, e.g., texture and color, are constructed by VQ-indexed histogram from DDBTC bitmap, maximum, and minimum quantizers. Conversely, high-level features from CNN can effectively capture human perception. With the fusion of the DDBTC and CNN features, the extended deep learning two-layer codebook features (DL-TLCF) is generated using the proposed two-layer codebook, dimension reduction, and similarity reweighting to improve the overall retrieval rate. Two metrics, average precision rate (APR) and average recall rate (ARR), are employed to examine various datasets. As documented in the experimental results, the proposed schemes can achieve superior performance compared to the state-of-the-art methods with either low- or high-level features in terms of the retrieval rate. Thus, it can be a strong candidate for various image retrieval related applications.

Enhanced bioactivity of ZnO nanoparticles—an antimicrobial study

PubMed Central

Padmavathy, Nagarajan; Vijayaraghavan, Rajagopalan

2008-01-01

In this study, we investigate the antibacterial activity of ZnO nanoparticles with various particle sizes. ZnO was prepared by the base hydrolysis of zinc acetate in a 2-propanol medium and also by a precipitation method using Zn(NO3)2 and NaOH. The products were characterized by x-ray diffraction (XRD) analysis, transmission electron microscopy (TEM) and photoluminescence (PL) spectroscopy. Bacteriological tests such as minimum inhibitory concentration (MIC) and disk diffusion were performed in Luria-Bertani and nutrient agar media on solid agar plates and in liquid broth systems using different concentrations of ZnO by a standard microbial method for the first time. Our bacteriological study showed the enhanced biocidal activity of ZnO nanoparticles compared with bulk ZnO in repeated experiments. This demonstrated that the bactericidal efficacy of ZnO nanoparticles increases with decreasing particle size. It is proposed that both the abrasiveness and the surface oxygen species of ZnO nanoparticles promote the biocidal properties of ZnO nanoparticles. PMID:27878001

Enhanced bioactivity of ZnO nanoparticles—an antimicrobial study

NASA Astrophysics Data System (ADS)

Padmavathy, Nagarajan; Vijayaraghavan, Rajagopalan

2008-07-01

In this study, we investigate the antibacterial activity of ZnO nanoparticles with various particle sizes. ZnO was prepared by the base hydrolysis of zinc acetate in a 2-propanol medium and also by a precipitation method using Zn(NO3)2 and NaOH. The products were characterized by x-ray diffraction (XRD) analysis, transmission electron microscopy (TEM) and photoluminescence (PL) spectroscopy. Bacteriological tests such as minimum inhibitory concentration (MIC) and disk diffusion were performed in Luria-Bertani and nutrient agar media on solid agar plates and in liquid broth systems using different concentrations of ZnO by a standard microbial method for the first time. Our bacteriological study showed the enhanced biocidal activity of ZnO nanoparticles compared with bulk ZnO in repeated experiments. This demonstrated that the bactericidal efficacy of ZnO nanoparticles increases with decreasing particle size. It is proposed that both the abrasiveness and the surface oxygen species of ZnO nanoparticles promote the biocidal properties of ZnO nanoparticles.

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

Huang, Chen; Perez, Danny; Voter, Arthur F.

Hyperdynamics is a powerful method to significantly extend the time scales amenable to molecular dynamics simulation of infrequent events. One outstanding challenge, however, is the development of the so-called bias potential required by the method. In this work, we design a bias potential using information about all minimum energy pathways (MEPs) out of the current state. While this approach is not suitable for use in an actual hyperdynamics simulation, because the pathways are generally not known in advance, it allows us to show that it is possible to come very close to the theoretical boost limit of hyperdynamics while maintainingmore » high accuracy. We demonstrate this by applying this MEP-based hyperdynamics (MEP-HD) to metallic surface diffusion systems. In most cases, MEP-HD gives boost factors that are orders of magnitude larger than the best existing bias potential, indicating that further development of hyperdynamics bias potentials could have a significant payoff. Lastly, we discuss potential practical uses of MEP-HD, including the possibility of developing MEP-HD into a true hyperdynamics.« less

[Does the sampling locality influence on the antifungal activity of the flavonoids of Marrubium vulgare against Aspergillus niger and Candida albicans?].

PubMed

Bouterfas, K; Mehdadi, Z; Aouad, L; Elaoufi, M M; Khaled, M B; Latreche, A; Benchiha, W

2016-09-01

The study was undertaken to determine the effect of the sampling locality on the antifungal activity of the flavonoids extracted from the leaves of Marrubium vulgare L. against two fungal strains; Aspergillus niger ATCC 16404 and Candida albicans ATCC 10231. The leaves were collected from three different sampling localities belonging northwest Algeria: Tessala mount, M'sila forest and Ain Skhouna. The flavonoid extraction was carried out by using organic solvents with increasing polarity. A phytochemical screening was performed by staining test tubes. The inhibition diameters were measured by solid medium diffusion method. The minimum inhibitory concentrations were determined by dilution method on solid medium. The antifungal activity varied significantly (P<0.001) according to the sampling locality of the leaves, the flavonoid extract and its concentration, and the strain fungal type. The inhibition diameters varied between 8.16 and recorded 37.5mm even recording a total inhibition of fungal growth and often exceed those induced marketed antifungals (Amphotericin, Fluconazole, Terbinafine and econazole nitrate). The minimum inhibitory concentrations (MICs) obtained range between 6.25 and 100μg/mL; experiencing strong antifungal inhibition. The phytochemical screening revealed the existence of certain flavonoids classes such as flavans and flavanols which may be responsible of this remarkable antifungal power. The sampling locality of Marrubium vulgare leaves influenced on the antifungal activity of flavonoids. These have proven very good fungistatic and worth valuing in pharmacology. Copyright © 2016 Elsevier Masson SAS. All rights reserved.

Ionic-to-Electronic Conductivity Crossover in CdTe-AgI-As2Te3 Glasses: An 110mAg Tracer Diffusion Study.

PubMed

Kassem, M; Alekseev, I; Bokova, M; Le Coq, D; Bychkov, E

2018-04-12

Conductivity isotherms of (CdTe) x (AgI) 0.5- x/2 (As 2 Te 3 ) 0.5- x/2 glasses (0.0 ≤ x ≤ 0.15) reveal a nonmonotonic behavior with increasing CdTe content reminiscent of mixed cation effect in oxide and chalcogenide glasses. Nevertheless, the apparent similarity appears to be partly incorrect. Using 110m Ag tracer diffusion measurements, we show that semiconducting CdTe additions produce a dual effect: (i) decreasing the Ag + ion transport by a factor of ≈200 with a simultaneous increase of the diffusion activation energy and (ii) increasing the electronic conductivity by 1.5 orders of magnitude. Consequently, the conductivity minimum at x = 0.05 reflects an ionic-to-electronic transport crossover; the silver-ion transport number decreases by 3 orders of magnitude with increasing x.

Estimation of Leakage Potential of Selected Sites in Interstate and Tri-State Canals Using Geostatistical Analysis of Selected Capacitively Coupled Resistivity Profiles, Western Nebraska, 2004

USGS Publications Warehouse

Vrabel, Joseph; Teeple, Andrew; Kress, Wade H.

2009-01-01

With increasing demands for reliable water supplies and availability estimates, groundwater flow models often are developed to enhance understanding of surface-water and groundwater systems. Specific hydraulic variables must be known or calibrated for the groundwater-flow model to accurately simulate current or future conditions. Surface geophysical surveys, along with selected test-hole information, can provide an integrated framework for quantifying hydrogeologic conditions within a defined area. In 2004, the U.S. Geological Survey, in cooperation with the North Platte Natural Resources District, performed a surface geophysical survey using a capacitively coupled resistivity technique to map the lithology within the top 8 meters of the near-surface for 110 kilometers of the Interstate and Tri-State Canals in western Nebraska and eastern Wyoming. Assuming that leakage between the surface-water and groundwater systems is affected primarily by the sediment directly underlying the canal bed, leakage potential was estimated from the simple vertical mean of inverse-model resistivity values for depth levels with geometrically increasing layer thickness with depth which resulted in mean-resistivity values biased towards the surface. This method generally produced reliable results, but an improved analysis method was needed to account for situations where confining units, composed of less permeable material, underlie units with greater permeability. In this report, prepared by the U.S. Geological Survey in cooperation with the North Platte Natural Resources District, the authors use geostatistical analysis to develop the minimum-unadjusted method to compute a relative leakage potential based on the minimum resistivity value in a vertical column of the resistivity model. The minimum-unadjusted method considers the effects of homogeneous confining units. The minimum-adjusted method also is developed to incorporate the effect of local lithologic heterogeneity on water transmission. Seven sites with differing geologic contexts were selected following review of the capacitively coupled resistivity data collected in 2004. A reevaluation of these sites using the mean, minimum-unadjusted, and minimum-adjusted methods was performed to compare the different approaches for estimating leakage potential. Five of the seven sites contained underlying confining units, for which the minimum-unadjusted and minimum-adjusted methods accounted for the confining-unit effect. Estimates of overall leakage potential were lower for the minimum-unadjusted and minimum-adjusted methods than those estimated by the mean method. For most sites, the local heterogeneity adjustment procedure of the minimum-adjusted method resulted in slightly larger overall leakage-potential estimates. In contrast to the mean method, the two minimum-based methods allowed the least permeable areas to control the overall vertical permeability of the subsurface. The minimum-adjusted method refined leakage-potential estimation by additionally including local lithologic heterogeneity effects.

Global diffusion of cosmic rays in random magnetic fields

NASA Astrophysics Data System (ADS)

Snodin, A. P.; Shukurov, A.; Sarson, G. R.; Bushby, P. J.; Rodrigues, L. F. S.

2016-04-01

The propagation of charged particles, including cosmic rays, in a partially ordered magnetic field is characterized by a diffusion tensor whose components depend on the particle's Larmor radius RL and the degree of order in the magnetic field. Most studies of the particle diffusion presuppose a scale separation between the mean and random magnetic fields (e.g. there being a pronounced minimum in the magnetic power spectrum at intermediate scales). Scale separation is often a good approximation in laboratory plasmas, but not in most astrophysical environments such as the interstellar medium (ISM). Modern simulations of the ISM have numerical resolution of the order of 1 pc, so the Larmor radius of the cosmic rays that dominate in energy density is at least 106 times smaller than the resolved scales. Large-scale simulations of cosmic ray propagation in the ISM thus rely on oversimplified forms of the diffusion tensor. We take the first steps towards a more realistic description of cosmic ray diffusion for such simulations, obtaining direct estimates of the diffusion tensor from test particle simulations in random magnetic fields (with the Larmor radius scale being fully resolved), for a range of particle energies corresponding to 10-2 ≲ RL/lc ≲ 103, where lc is the magnetic correlation length. We obtain explicit expressions for the cosmic ray diffusion tensor for RL/lc ≪ 1, that might be used in a sub-grid model of cosmic ray diffusion. The diffusion coefficients obtained are closely connected with existing transport theories that include the random walk of magnetic lines.

What sets the minimum tokamak scrape-off layer width?

NASA Astrophysics Data System (ADS)

Joseph, Ilon

2016-10-01

The heat flux width of the tokamak scrape-off layer is on the order of the poloidal ion gyroradius, but the ``heuristic drift'' physics model is still not completely understood. In the absence of anomalous transport, neoclassical transport sets the minimum width. For plateau collisionality, the ion temperature width is set by qρi , while the electron temperature width scales as the geometric mean q(ρeρi) 1 / 2 and is close to qρi in magnitude. The width is enhanced because electrons are confined by the sheath potential and have a much longer time to radially diffuse before escaping to the wall. In the Pfirsch-Schluter regime, collisional diffusion increases the width by the factor (qR / λ) 1 / 2 where qR is the connection length and λ is the mean free path. This qualitatively agrees with the observed transition in the scaling law for detached plasmas. The radial width of the SOL electric field is determined by Spitzer parallel and ``neoclassical'' radial electric conductivity and has a similar scaling to that for thermal transport. Prepared under US DOE contract DE-AC52-07NA27344.

A Simplified Ab Initio Cosmic-ray Modulation Model with Simulated Time Dependence and Predictive Capability

NASA Astrophysics Data System (ADS)

Moloto, K. D.; Engelbrecht, N. E.; Burger, R. A.

2018-06-01

A simplified ab initio approach is followed to model cosmic-ray proton modulation, using a steady-state three-dimensional stochastic solver of the Parker transport equation that simulates some effects of time dependence. Standard diffusion coefficients based on Quasilinear Theory and Nonlinear Guiding Center Theory are employed. The spatial and temporal dependences of the various turbulence quantities required as inputs for the diffusion, as well as the turbulence-reduced drift coefficients, follow from parametric fits to results from a turbulence transport model as well as from spacecraft observations of these turbulence quantities. Effective values are used for the solar wind speed, magnetic field magnitude, and tilt angle in the modulation model to simulate temporal effects due to changes in the large-scale heliospheric plasma. The unusually high cosmic-ray intensities observed during the 2009 solar minimum follow naturally from the current model for most of the energies considered. This demonstrates that changes in turbulence contribute significantly to the high intensities during that solar minimum. We also discuss and illustrate how this model can be used to predict future cosmic-ray intensities, and comment on the reliability of such predictions.

Super-resolution reconstruction of diffusion parameters from diffusion-weighted images with different slice orientations.

PubMed

Van Steenkiste, Gwendolyn; Jeurissen, Ben; Veraart, Jelle; den Dekker, Arnold J; Parizel, Paul M; Poot, Dirk H J; Sijbers, Jan

2016-01-01

Diffusion MRI is hampered by long acquisition times, low spatial resolution, and a low signal-to-noise ratio. Recently, methods have been proposed to improve the trade-off between spatial resolution, signal-to-noise ratio, and acquisition time of diffusion-weighted images via super-resolution reconstruction (SRR) techniques. However, during the reconstruction, these SRR methods neglect the q-space relation between the different diffusion-weighted images. An SRR method that includes a diffusion model and directly reconstructs high resolution diffusion parameters from a set of low resolution diffusion-weighted images was proposed. Our method allows an arbitrary combination of diffusion gradient directions and slice orientations for the low resolution diffusion-weighted images, optimally samples the q- and k-space, and performs motion correction with b-matrix rotation. Experiments with synthetic data and in vivo human brain data show an increase of spatial resolution of the diffusion parameters, while preserving a high signal-to-noise ratio and low scan time. Moreover, the proposed SRR method outperforms the previous methods in terms of the root-mean-square error. The proposed SRR method substantially increases the spatial resolution of MRI that can be obtained in a clinically feasible scan time. © 2015 Wiley Periodicals, Inc.

Minimum Covers of Fixed Cardinality in Weighted Graphs.

ERIC Educational Resources Information Center

White, Lee J.

Reported is the result of research on combinatorial and algorithmic techniques for information processing. A method is discussed for obtaining minimum covers of specified cardinality from a given weighted graph. By the indicated method, it is shown that the family of minimum covers of varying cardinality is related to the minimum spanning tree of…

Method and Apparatus for Powered Descent Guidance

NASA Technical Reports Server (NTRS)

Acikmese, Behcet (Inventor); Blackmore, James C. L. (Inventor); Scharf, Daniel P. (Inventor)

2013-01-01

A method and apparatus for landing a spacecraft having thrusters with non-convex constraints is described. The method first computes a solution to a minimum error landing problem for a convexified constraints, then applies that solution to a minimum fuel landing problem for convexified constraints. The result is a solution that is a minimum error and minimum fuel solution that is also a feasible solution to the analogous system with non-convex thruster constraints.

SU-D-210-04: Using Radiotherapy Biomaterials to Brand and Track Deadly Cancer Cells

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

Altundal, Y; Sajo, E; Ngwa, W

Purpose: Metastasis accounts for over 90% of all cancer associated suffering and death and arguably presents the most formidable challenges in cancer management. The detection of metastatic or rare circulating tumor cells (CTCs) in blood or lymph nodes remains a formidable technological challenge. In this study, we investigated the time needed to label each cancer cell in-situ (right at the source tumor) with sufficient number of GNPs that will allow enhanced non-invasive detection via photoacoustic imaging in the lymph nodes. Such in-situ labeling can be achieved via sustained release of the GNPs from Radiotherapy (RT) biomaterials (e.g. fiducials, spacers) coated/loadedmore » with the GNP. Methods: The minimum concentration (1000 GNPs/cell for 50nm GNPs) to detect GNPs with photoacoustic imaging method was experimentally measured by Mallidi et al. and fixed at the tumor sub-volume periphery. In this work, the GNPs were assumed to diffuse from a point source, placed in the middle of a 2–3cm tumor, with an initial concentration of 7–30 mg/g. The time required to label the cells with GNPs was calculated by solving the three dimensional diffusion-reaction equation analytically. The diffusion coefficient of 10nm GNPs was experimentally determined previously. Stokes-Einstein equation was used to calculate the diffusion coefficients for other sizes (2–50nm) of GNPs. The cellular uptake rate constants for several sizes of GNPs were experimentally measured by Jin et al. Results: The time required to label the cells was found 0.635–15.91 days for 2–50nm GNPs with an initial concentration of 7 mg/g GNPs in a 2 cm tumor; 1.379–34.633 days for 2–50nm GNPs with an initial concentration of 30 mg/g GNPs in a 3cm tumor. Conclusion: Our results highlight new potential for labeling CTCs with GNPs released from smart RT biomaterials (i.e. fiducials or spacers loaded with the GNP) towards enhanced non-invasive imaging/detection via photoacoustic imaging.« less

Error reduction program: A progress report

NASA Technical Reports Server (NTRS)

Syed, S. A.

1984-01-01

Five finite differences schemes were evaluated for minimum numerical diffusion in an effort to identify and incorporate the best error reduction scheme into a 3D combustor performance code. Based on this evaluated, two finite volume method schemes were selected for further study. Both the quadratic upstream differencing scheme (QUDS) and the bounded skew upstream differencing scheme two (BSUDS2) were coded into a two dimensional computer code and their accuracy and stability determined by running several test cases. It was found that BSUDS2 was more stable than QUDS. It was also found that the accuracy of both schemes is dependent on the angle that the streamline make with the mesh with QUDS being more accurate at smaller angles and BSUDS2 more accurate at larger angles. The BSUDS2 scheme was selected for extension into three dimensions.

Modulation of the norfloxacin resistance in Staphylococcus aureus by Cordia verbenaceae DC

PubMed Central

Matias, Edinardo F.F.; Santos, Karla K. A.; Falcão-Silva, Vivyanne S.; Siqueira-Júnior, José P.; Costa, José G. M.; Coutinho, Henrique D.M.

2013-01-01

Background & objectives: Several chemical compounds isolated from natural sources have antibacterial activity and some enhance the antibacterial activity of antibiotics reversing the natural resistance of bacteria to certain antibiotics. In this study, the hexane and methanol extract of Cordia verbenaceae were assessed for antibacterial activity alone and combinated with norfloxacin against the Staphylococcus aureus strain SA1199B. Methods: The minimum inhibitory concentration (MIC) of extracts was assayed using microdilution assay and the modulatory activity was evaluated using plate diffusion assay. Results: The MIC observed varied between 256 to >1024 μg/ml. However, the antibiotic activity of norfloxacin was enhanced in the presence of subinhibitory concentrations of hexane extract of C. verbenaceae (HECV). Interpretations & conclusions: Our results indicate that Cordia verbenaceae DC. can be a source of plant derived products with antibiotic modifying activity. PMID:23481069

Diffusion-model analysis of pPb and PbPb collisions at LHC energies

NASA Astrophysics Data System (ADS)

Schulz, P.; Wolschin, G.

2018-06-01

We present an analysis of centrality-dependent pseudorapidity distributions of produced charged hadrons in pPb and PbPb collisions at the Large Hadron Collider (LHC) energy of s NN = 5.02 TeV, and of minimum-bias pPb collisions at 8.16 TeV within the non-equilibrium-statistical relativistic diffusion model (RDM). In a three-source approach, the role of the fragmentation sources is emphasized. Together with the Jacobian transformation from rapidity to pseudorapidity and the limiting fragmentation conjecture, these are essential for modeling the centrality dependence. For central PbPb collisions, a prediction at the projected FCC energy of s NN = 39 TeV is made.

Design and performance of controlled-diffusion stator compared with original double-circular-arc stator

NASA Technical Reports Server (NTRS)

Gelder, Thomas F.; Schmidt, James F.; Suder, Kenneth L.; Hathaway, Michael D.

1987-01-01

The capabilities of two stators, one with controlled-diffusion (CD) blade sections and one with double-circular-arc (DCA) blade sections, were compared. A CD stator was designed and tested that had the same chord length but half the blades of the DCA stator. The same fan rotor (tip speed, 429 m/sec; pressure ratio, 1.65) was used with each stator row. The design and analysis system is briefly described. The overall stage and rotor performances with each stator are compared, as are selected blade element data. The minimum overall efficiency decrement across the stator was approximately 1 percentage point greater with the CD balde sections than with the DCA blade sections.

Design and performance of controlled-diffusion stator compared with original double-circular-arc stator

NASA Technical Reports Server (NTRS)

Gelder, Thomas F.; Schmidt, James F.; Suder, Kenneth L.; Hathaway, Michael D.

1987-01-01

The capabilities of two stators, one with controlled-diffusion (CD) blade sections and one with double-circular-arc (DCA) blade sections, were compared. A CD stator was designed and tested that had the same chord length but half the blades of the DCA stator. The same fan rotor (tip speed, 429 m/sec; pressure ratio, 1.65) was used with each stator row. The design and analysis system is briefly described. The overall stage and rotor performances with each stator are compared, as are selected blade element data. The minimum overall efficiency decrement across the stator was approximately 1 percentage point greater with the CD blade sections than with the DCA blade sections.

An accurate computational method for the diffusion regime verification

NASA Astrophysics Data System (ADS)

Zhokh, Alexey A.; Strizhak, Peter E.

2018-04-01

The diffusion regime (sub-diffusive, standard, or super-diffusive) is defined by the order of the derivative in the corresponding transport equation. We develop an accurate computational method for the direct estimation of the diffusion regime. The method is based on the derivative order estimation using the asymptotic analytic solutions of the diffusion equation with the integer order and the time-fractional derivatives. The robustness and the computational cheapness of the proposed method are verified using the experimental methane and methyl alcohol transport kinetics through the catalyst pellet.

Reduction of skylight reflection effects in the above-water measurement of diffuse marine reflectance.

PubMed

Fougnie, B; Frouin, R; Lecomte, P; Deschamps, P Y

1999-06-20

Reflected skylight in above-water measurements of diffuse marine reflectance can be reduced substantially by viewing the surface through an analyzer transmitting the vertically polarized component of incident radiance. For maximum reduction of effects, radiometric measurements should be made at a viewing zenith angle of approximately 45 degrees (near the Brewster angle) and a relative azimuth angle between solar and viewing directions greater than 90 degrees (backscattering), preferably 135 degrees. In this case the residual reflected skylight in the polarized signal exhibits minimum sensitivity to the sea state and can be corrected to within a few 10(-4) in reflectance units. For most oceanic waters the resulting relative error on the diffuse marine reflectance in the blue and green is less than 1%. Since the water body polarizes incident skylight, the measured polarized reflectance differs from the total reflectance. The difference, however, is small for the considered geometry. Measurements made at the Scripps Institution of Oceanography pier in La Jolla, Calif., with a specifically designed scanning polarization radiometer, confirm the theoretical findings and demonstrate the usefulness of polarization radiometry for measuring diffuse marine reflectance.

Need-based activation of ammonium uptake in Escherichia coli

PubMed Central

Kim, Minsu; Zhang, Zhongge; Okano, Hiroyuki; Yan, Dalai; Groisman, Alexander; Hwa, Terence

2012-01-01

The efficient sequestration of nutrients is vital for the growth and survival of microorganisms. Some nutrients, such as CO2 and NH3, are readily diffusible across the cell membrane. The large membrane permeability of these nutrients obviates the need of transporters when the ambient level is high. When the ambient level is low, however, maintaining a high intracellular nutrient level against passive back diffusion is both challenging and costly. Here, we study the delicate management of ammonium (NH4+/NH3) sequestration by E. coli cells using microfluidic chemostats. We find that as the ambient ammonium concentration is reduced, E. coli cells first maximize their ability to assimilate the gaseous NH3 diffusing into the cytoplasm and then abruptly activate ammonium transport. The onset of transport varies under different growth conditions, but always occurring just as needed to maintain growth. Quantitative modeling of known interactions reveals an integral feedback mechanism by which this need-based uptake strategy is implemented. This novel strategy ensures that the expensive cost of upholding the internal ammonium concentration against back diffusion is kept at a minimum. PMID:23010999

Comparing diffuse optical tomography and functional magnetic resonance imaging signals during a cognitive task: pilot study

PubMed Central

Hernández-Martin, Estefania; Marcano, Francisco; Casanova, Oscar; Modroño, Cristian; Plata-Bello, Julio; González-Mora, Jose Luis

2017-01-01

Abstract. Diffuse optical tomography (DOT) measures concentration changes in both oxy- and deoxyhemoglobin providing three-dimensional images of local brain activations. A pilot study, which compares both DOT and functional magnetic resonance imaging (fMRI) volumes through t-maps given by canonical statistical parametric mapping (SPM) processing for both data modalities, is presented. The DOT series were processed using a method that is based on a Bayesian filter application on raw DOT data to remove physiological changes and minimum description length application index to select a number of singular values, which reduce the data dimensionality during image reconstruction and adaptation of DOT volume series to normalized standard space. Therefore, statistical analysis is performed with canonical SPM software in the same way as fMRI analysis is done, accepting DOT volumes as if they were fMRI volumes. The results show the reproducibility and ruggedness of the method to process DOT series on group analysis using cognitive paradigms on the prefrontal cortex. Difficulties such as the fact that scalp–brain distances vary between subjects or cerebral activations are difficult to reproduce due to strategies used by the subjects to solve arithmetic problems are considered. T-images given by fMRI and DOT volume series analyzed in SPM show that at the functional level, both DOT and fMRI measures detect the same areas, although DOT provides complementary information to fMRI signals about cerebral activity. PMID:28386575

Susceptibility of 100 filamentous fungi: comparison of two diffusion methods, Neo-Sensitabs and E-test, for amphotericin B, caspofungin, itraconazole, voriconazole and posaconazole.

PubMed

Colosi, Ioana A; Faure, Odile; Dessaigne, Bérangére; Bourdon, Cécile; Lebeau, Bernadette; Colosi, Horaţiu A; Pelloux, Hervé

2012-05-01

We compared the E-test method to that of the Neo-Sensitabs tablet diffusion assay for evaluating the in vitro susceptibility of 100 clinical isolates of filamentous fungi (Aspergillus spp., Fusarium spp., Scedosporium spp., zygomycetes and other molds) to amphotericin B, itraconazole, voriconazole, caspofungin, and posaconazole. We determined the categorical agreement level between E-test minimum inhibitory concentrations (MIC) and tablet end-points, as opposed to the following disagreement parameters: very major error - resistant parameter (R) in E-test and susceptible (S) in tablet; major error - S by E-test and R by tablet; minor error - shifts between S and susceptible dose-dependent (S-DD) or S-DD and R. We also performed linear regression analyses and computed Pearson's correlation coefficients (R values) between the log transforms of MICs and the inhibition zone diameters of the five studied antifungal agents. For itraconazole we obtained 97% categorical agreement and R = -0.727. Categorical agreement for caspofungin and voriconazole was 96% and R =-0.821 and R = -0.789, respectively. For posaconazole the categorical agreement was 94% and R =-0.743. Amphotericin B exhibited a lower degree of agreement (76%, R = -0.672), especially in studies of Aspergillus spp. Our results suggest a potential value of the Neo-Sensitabs assay for in vitro susceptibility testing of molds to itraconazole, voriconazole, caspofungin and posaconazole, while amphotericin B exhibited an overall lower degree of agreement.

Ultrafast Thermal Plasma Preparation of Solid Si Films with Potential Application in Photovoltaic Cells: A Parametric Study

NASA Astrophysics Data System (ADS)

Mostajeran Goortani, Behnam; Gitzhofer, François; Bouyer, Etienne; Mousavi, Mehdi

2009-03-01

An innovative method, namely ultrafast plasma surface melting, is developed to fabricate solid films of silicon with very high rates (150 cm2/min). The method is composed of preparing a suspension of solid particles in a volatile solvent and spreading it on a refractory substrate such as Mo. After solvent evaporation, the resulting porous layer is exposed to the flame tale of inductively coupled RF plasma to sinter and melt the surface particles and to prepare a solid film of silicon. It is shown that by controlling the flow dynamics and heat transfer around the substrate, and managing the kinetic parameters (i.e., exposure time, substrate transport speed, and reaction kinetics) in the reactor, we can produce solid crystalline Si films with the potential applications in photovoltaic cells industry. The results indicate that the optimum formation conditions with a film thickness of 250-700 μm is when the exposure time in the plasma is in the range of 5-12.5 s for a 100 × 50 mm large layer. By combining the Fourier’s law of conduction with the experimental measurements, we obtained an effective heat diffusivity and developed a model to obtain heat diffusion in the porous layer exposed to the plasma. The model further predicts the minimum and maximum exposure time for the substrate in the plasma flame as a function of material properties, the porous layer thickness and of the imposed heat flux.

Significant antibacterial activity and synergistic effects of camel lactoferrin with antibiotics against methicillin-resistant Staphylococcus aureus (MRSA).

PubMed

Redwan, Elrashdy M; El-Baky, Nawal Abd; Al-Hejin, Ahmed M; Baeshen, Mohammed N; Almehdar, Hussein A; Elsaway, Abdulrahman; Gomaa, Abu-Bakr M; Al-Masaudi, Saad Berki; Al-Fassi, Fahad A; AbuZeid, Isam Eldin; Uversky, Vladimir N

2016-01-01

Methicillin-resistant Staphylococcus aureus (MRSA) causes major healthcare problems in many countries, as it is present as several hospital- and community-associated strains. Hospital-associated MRSA is one of the most prevalent nosocomial pathogens throughout the world and infections caused by community-acquired MRSA are rising. This emphasizes the need for new and efficient anti-MRSA agents. We evaluated the antibacterial effects of camel lactoferrin (cLf) and human lactoferrin (hLf) alone and in combination with several antibiotics against MRSA. Antimicrobials were tested against MRSA and an S. aureus control strain by the agar disc diffusion method. The minimum inhibitory concentration (MIC) was determined for antimicrobials by the broth microdilution method. Synergy between cLf or hLf and antibiotics was examined by checkerboard and time-kill assays. The agar disc diffusion assay showed that MRSA growth was inhibited by cLf at 0.25-3 mg/ml and hLf at 1-3 mg/ml. cLf demonstrated 3 times higher inhibitory activity against MRSA than hLf in terms of MIC values (250 vs. 750 μg/ml, respectively). Biotinylated cLf was recognized by two membrane proteins of MRSA, 66-67 KDa. Combinations of cLf or hLf and oxacillin or vancomycin at sub-MIC levels enhanced in vitro antibacterial activity against MRSA compared with each agent alone. Copyright © 2016 Institut Pasteur. Published by Elsevier Masson SAS. All rights reserved.

Improved agar diffusion method for detecting residual antimicrobial agents.

PubMed

Tsai, C E; Kondo, F

2001-03-01

The improved agar diffusion method for determination of residual antimicrobial agents was investigated, and the sensitivities of various combinations of test organisms and assay media were determined using 7 organisms, 5 media, and 31 antimicrobial agents. Bacillus stearothermophilus and synthetic assay medium (SAM) showed the greatest sensitivity for screening penicillins (penicillin G and ampicillin). The combination of Bacillus subtilis and minimum medium (MM) was the most sensitive for tetracyclines (oxytetracycline and chlortetracycline), B. stearothermophilus and SAM or Micrococcus luteus and Mueller-Hinton agar (MHA) for detecting tylosin and erythromycin, B. subtilis and MHA for aminoglycosides (streptomycin, kanamycin, gentamicin, and dihydrostreptomycin), B. stearothermophilus and SAM for polyethers (salinomycin and lasalocid), and B. subtilis and MM or Clostridium perfringens and GAM for polypeptides (thiopeptin, enramycin, virginiamycin, and bacitracin). However, gram-negative bacterium Escherichia coli ATCC 27166 and MM were better for screening for colistin and polymixin-B. For detecting the synthetic drugs tested, the best combination was B. subtilis and MM for sulfonamides, E. coli 27166 and MM for quinolones (oxolinic acid and nalidixic acid), B. subtilis and MM for furans (furazolidone), and the bioluminescent bacterium Photobacterium phosphoreum and luminescence assay medium for chloramphenicol and oxolinic acid. The results showed that the use of four assay plates, B. stearothermophilus and SAM, B. subtilis and MM, M. luteus and MHA, and E. coli 27166 and MM, was superior to the currently available techniques for screening for residual antimicrobial agents in edible animal tissues.

Diapycnal diffusivity in the core and oxycline of the tropical North Atlantic oxygen minimum zone

NASA Astrophysics Data System (ADS)

Köllner, Manuela; Visbeck, Martin; Tanhua, Toste; Fischer, Tim

2016-08-01

Diapycnal diffusivity estimates from two Tracer Release Experiments (TREs) and microstructure measurements in the oxycline and core of the oxygen minimum zone (OMZ) in the Eastern Tropical North Atlantic (ETNA) are compared. For the first time, two TREs within the same area at different depths were realized: the Guinea Upwelling Tracer Release Experiment (GUTRE) initiated in 2008 in the oxycline at approximately 320 m depth, and the Oxygen Supply Tracer Release Experiment (OSTRE) initiated in 2012 in the core of the OMZ at approximately 410 m depth. The mean diapycnal diffusivity Dz was found to be insignificantly smaller in the OMZ core with (1.06 ± 0.24) × 10- 5 m2 s- 1 compared to (1.11 ± 0.22) × 10- 5 m2 s- 1 90 m shallower in the oxycline. Unexpectedly, GUTRE tracer was detected during two of the OSTRE surveys which showed that the estimated diapycnal diffusivity from GUTRE over a time period of seven years was within the uncertainty of the previous estimates over a time period of three years. The results are consistent with the Dz estimates from microstructure measurements and demonstrate that Dz does not vary significantly vertically in the OMZ within the depth range of 200-600 m and does not change with time. The presence of a seamount chain in the vicinity of the GUTRE injection region did not cause enhanced Dz compared to the smoother bottom topography of the OSTRE injection region, although the analysis of vertical shear spectra from ship ADCP data showed elevated internal wave energy level in the seamount vicinity. However, the two tracer patches covered increasingly overlapping areas with time and thus spatially integrated increasingly similar fields of local diffusivity, as well as the difference in local stratification counteracted the influence of roughness on Dz. For both experiments no significant vertical displacements of the tracer were observed, thus diapycnal upwelling within the ETNA OMZ is below the uncertainty level of 5 m yr- 1.

Temporally resolved electrocardiogram-triggered diffusion-weighted imaging of the human kidney: correlation between intravoxel incoherent motion parameters and renal blood flow at different time points of the cardiac cycle.

PubMed

Wittsack, Hans-Jörg; Lanzman, Rotem S; Quentin, Michael; Kuhlemann, Julia; Klasen, Janina; Pentang, Gael; Riegger, Caroline; Antoch, Gerald; Blondin, Dirk

2012-04-01

To evaluate the influence of pulsatile blood flow on apparent diffusion coefficients (ADC) and the fraction of pseudodiffusion (F(P)) in the human kidney. The kidneys of 6 healthy volunteers were examined by a 3-T magnetic resonance scanner. Electrocardiogram (ECG)-gated and respiratory-triggered diffusion-weighted imaging (DWI) and phase-contrast flow measurements were performed. Flow imaging of renal arteries was carried out to quantify the dependence of renal blood flow on the cardiac cycle. ECG-triggered DWI was acquired in the coronal plane with 16 b values in the range of 0 s/mm(2) and 750 s/mm(2) at the time of minimum (MIN) (20 milliseconds after R wave) and maximum renal blood flow (MAX) (197 ± 24 milliseconds after R wave). The diffusion coefficients were calculated using the monoexponential approach as well as the biexponential intravoxel incoherent motion model and correlated to phase-contrast flow measurements. Flow imaging showed pulsatile renal blood flow depending on the cardiac cycle. The mean flow velocity at MIN was 45 cm/s as compared with 61 cm/s at MAX. F(p) at MIN (0.29) was significantly lower than at MAX (0.40) (P = 0.001). Similarly, ADC(mono), derived from the monoexponential model, also showed a significant difference (P < 0.001) between MIN (ADC(mono) = 2.14 ± 0.08 × 10(-3) mm(2)/s) and MAX (ADC(mono) = 2.37 ± 0.04 × 10(-3) mm(2)/s). The correlation between renal blood flow and F(p) (r = 0.85) as well as ADC(mono) (r = 0.67) was statistically significant. Temporally resolved ECG-gated DWI enables for the determination of the diffusion coefficients at different time points of the cardiac cycle. ADC(mono) and FP vary significantly among acquisitions at minimum (diastole) and maximum (systole) renal blood flow. Temporally resolved ECG-gated DWI might therefore serve as a novel technique for the assessment of pulsatility in the human kidney.

Oxygen in the deep-sea: The challenge of maintaining uptake rates in a changing ocean

NASA Astrophysics Data System (ADS)

Hofmann, A. F.; Peltzer, E. T.; Brewer, P. G.

2011-12-01

Although focused on recently, ocean acidification is not the only effect of anthropogenic CO2 emissions on the ocean. Ocean warming will reduce dissolved oxygen concentrations and at the hypoxic limit for a given species this can pose challenges to marine life. The limit is traditionally reported simply as the static mass concentration property [O2]; here we treat it as a dynamic gas exchange problem for the animal analogous to gas exchange at the sea surface. The diffusive limit and its relationship to water velocity is critical for the earliest stages of marine life (eggs, embryos), but the effect is present for all animals at all stages of life. We calculate the external limiting O2 conditions for several representative metabolic rates and their relationship to flow of the bulk fluid under different environmental conditions. Ocean O2 concentrations decline by ≈ 14 μmol kg-1 for a 2 °C rise in temperature. At standard 1000 m depth conditions in the Pacific, flow over the surface would have to increase by ≈ 60% from 2.0 to 3.2 cm s-1 to compensate for this change. The functions derived allow new calculations of depth profiles of limiting O2 concentrations, as well as maximal diffusively sustainable metabolic oxygen consumption rates at various places around the world. Our treatment shows that there is a large variability in the global ocean in terms of facilitating aerobic life. This variability is greater than the variability of the oxygen concentration alone. It becomes clear that temperature and pressure dependencies of diffusion and partial pressure create a region typically around 1000 m depth where a maximal [O2] is needed to sustain a given metabolic rate. This zone of greatest physical constriction on the diffusive transport in the boundary layer is broadly consistent with the oxygen minimum zone, i.e., the zone of least oxygen concentration supply, resulting in a pronounced minimum of maximal diffusively sustainable metabolic oxygen consumption rates. This least-favorable zone for aerobic respiration is bound to expand with further ocean warming.

Antibacterial properties of parasitic mistletoe - Scurrula ferruginea (Jack) Danser of Brunei Darussalam

NASA Astrophysics Data System (ADS)

David, Sheba R.; Amni Adam, Amira; Rajabalaya, Rajan

2017-12-01

Natural products especially from plants have become subject of much interest in drug discovery. Scurrula ferruginea is parasitic mistletoe used traditionally to treat various illnesses. The aim of this study is to investigate the potential antibacterial effect of Scurrula ferruginea native to Brunei Darussalam. The plants were collected from Brunei-Muara district air-dried, pulverized into powder, extracted by water maceration and freeze dried. Later, the extract was screened by disc-diffusion assay for two bacterial strains. The positive controls were Gentamycin and Ampicillin for Staphylococcus aureus while Sulphamethoxazole was used for Escherichia coli. Dimethyl sulfoxide was the negative control for both strains. 100, 200 and 500 mg/ml of the extract were used for the assays. The extracts did not show any inhibition activity against Escherichia coli, while sulphamethoxazole, showed inhibition of 24 mm. Ampicillin, Gentamycin, 100 and 500 mg/ml extract exhibited 29, 20, 8.3 and 10.7 mm inhibition zone, respectively against Staphylococcus aureus. There was an increase in zone of inhibition on Staphylococcus aureus strain with increase in extract concentration. Further investigations including Minimum Inhibition Concentration and Minimum Bactericidal Concentration methods as well as investigation on additional bacterial strains will be conducted for confirmation of antibacterial effect of the extract.

Secondary Ion Mass Spectrometry for Mg Tracer Diffusion: Issues and Solutions

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

Tuggle, Jay; Giordani, Andrew; Kulkarni, Nagraj S

2014-01-01

A Secondary Ion Mass Spectrometry (SIMS) method has been developed to measure stable Mg isotope tracer diffusion. This SIMS method was then used to calculate Mg self- diffusivities and the data was verified against historical data measured using radio tracers. The SIMS method has been validated as a reliable alternative to the radio-tracer technique for the measurement of Mg self-diffusion coefficients and can be used as a routine method for determining diffusion coefficients.

Local Discontinuous Galerkin (LDG) Method for Advection of Active Compositional Fields with Discontinuous Boundaries: Demonstration and Comparison with Other Methods in the Mantle Convection Code ASPECT

NASA Astrophysics Data System (ADS)

He, Y.; Billen, M. I.; Puckett, E. G.

2015-12-01

Flow in the Earth's mantle is driven by thermo-chemical convection in which the properties and geochemical signatures of rocks vary depending on their origin and composition. For example, tectonic plates are composed of compositionally-distinct layers of crust, residual lithosphere and fertile mantle, while in the lower-most mantle there are large compositionally distinct "piles" with thinner lenses of different material. Therefore, tracking of active or passive fields with distinct compositional, geochemical or rheologic properties is important for incorporating physical realism into mantle convection simulations, and for investigating the long term mixing properties of the mantle. The difficulty in numerically advecting fields arises because they are non-diffusive and have sharp boundaries, and therefore require different methods than usually used for temperature. Previous methods for tracking fields include the marker-chain, tracer particle, and field-correction (e.g., the Lenardic Filter) methods: each of these has different advantages or disadvantages, trading off computational speed with accuracy in tracking feature boundaries. Here we present a method for modeling active fields in mantle dynamics simulations using a new solver implemented in the deal.II package that underlies the ASPECT software. The new solver for the advection-diffusion equation uses a Local Discontinuous Galerkin (LDG) algorithm, which combines features of both finite element and finite volume methods, and is particularly suitable for problems with a dominant first-order term and discontinuities. Furthermore, we have applied a post-processing technique to insure that the solution satisfies a global maximum/minimum. One potential drawback for the LDG method is that the total number of degrees of freedom is larger than the finite element method. To demonstrate the capabilities of this new method we present results for two benchmarks used previously: a falling cube with distinct buoyancy and viscosity, and a Rayleigh-Taylor instability of a compositionally buoyant layer. To evaluate the trade-offs in computational speed and solution accuracy we present results for these same benchmarks using the two field tracking methods available in ASPECT: active tracer particles and the entropy viscosity method.

The Effects of Allium sativum Extracts on Biofilm Formation and Activities of Six Pathogenic Bacteria

PubMed Central

Mohsenipour, Zeinab; Hassanshahian, Mehdi

2015-01-01

Background: Garlic is considered a rich source of many compounds, which shows antimicrobial effects. The ability of microorganisms to adhere to both biotic and abiotic surfaces and to form biofilm is responsible for a number of diseases of chronic nature, demonstrating extremely high resistance to antibiotics. Bacterial biofilms are complex communities of sessile microorganisms, embedded in an extracellular matrix and irreversibly attached to various surfaces. Objectives: The present study evaluated the antimicrobial activity of Allium sativum extract against the biofilms of six pathogenic bacteria and their free-living forms. The clinical isolates in this study had not been studied in any other studies, especially in regard to biofilm disruption and inhibition of biofilm cell metabolic activity. Materials and Methods: Antimicrobial activities of A. sativum L. extracts (methanol and ethanol extracts) against planktonic forms of bacteria were determined using the disc diffusion method. The minimum inhibitory concentration (MIC) and the minimum bactericidal concentration (MBC) values were evaluated by a macrobroth dilution technique. The anti-biofilm effects were assessed by microtiter plate method. Results: The results showed that the A. sativum L. extract discs did not have any zone of inhibition for the tested bacteria. However, The MIC values of A. sativum L. extracts (0.078 - 2.5 mg/mL) confirmed the high ability of these extracts for inhibition of planktonic bacteria. A. sativum L. extracts were efficient to inhibit biofilm structures and the concentration of each extract had a direct relation with the inhibitory effect. Conclusions: Finally, it can be suggested that the extracts of this plant be applied as antimicrobial agents against these pathogens, particularly in biofilm forms. PMID:26464762

Antibacterial activity of Aquilaria crassna leaf extract against Staphylococcus epidermidis by disruption of cell wall

PubMed Central

2013-01-01

Background Aquilaria crassna Pierre ex Lecomte has been traditionally used in Thailand for treatment of infectious diseases such as diarrhoea and skin diseases for a long time. The main objectives of this study were to examine antibacterial activity of the Aquilaria crassna leaf extract against Staphylococcus epidermidis and its underlying mechanism. The antioxidant activity and acute toxicity were studied as well. Methods Antioxidant activities were examined by FRAP, ABTS and DPPH scavenging methods. Antibacterial activity was conducted using disc diffusion assay and the minimum inhibitory concentration (MIC) was determined by dilution method. The minimum bactericidal concentration (MBC) was reported as the lowest concentration producing no growth of microbes in the subcultures. Morphological changes of the microbe were observed by scanning electron microscopy, while an inhibitory effect on biofilm formation was evaluated by phase contrast microscopic analysis. Bacterial cell wall integrity was assessed by transmission electron microscopy. Acute toxicity was conducted in accordance with the OECD for Testing of Chemicals (2001) guidelines. Results The extract exhibited considerable antioxidant activity. Staphylococcus epidermidis was susceptible to the extract with the MIC and MBC of 6 and 12 mg/ml, respectively. The extract caused swelling and distortion of bacterial cells and inhibited bacterial biofilm formation. Rupture of bacterial cell wall occurred after treated with the extract for 24 h. Acute toxicity test in mice showed no sign of toxicity or death at the doses of 2,000 and 15,000 mg/kg body weight. Conclusion The aqueous extract of Aquilaria crassna leaves possesses an in vitro antibacterial activity against Staphylococcus epidermidis, with no sign of acute oral toxicity in mice, probably by interfering with bacterial cell wall synthesis and inhibiting biofilm formation. PMID:23962360

Evaluation of wound healing, antioxidant and antimicrobial efficacy of Jasminum auriculatum Vahl. leaves.

PubMed

Arun, Mittal; Satish, Sardana; Anima, Pandey

2016-01-01

To validate the ethno-therapeutic claim of the traditionally used plant Jasminum auriculatum (J. auriculatum) in skin diseases, by evaluating its wound healing potential along with its antioxidant and antimicrobial properties; so as to understand their role in wound healing. Excision and incision wound models were used to evaluate the wound healing activity on albino rats. The wound healing potential was assessed by measuring rate of wound contraction, epithelialization period, hydroxyproline content, skin breaking strength and histopathological parameters. Reference standard drug was Nitrofurazone ointment. The antioxidant activity was determined using 2, 2-diphenyl-1-picrylhydrazyl (DPPH) method. The antimicrobial activity was determined by agar well diffusion method and minimum inhibitory concentration by serial dilution method. Higher rate of wound contraction (83.66±0.50% on 15th day), decrease in the period of epithelialization (17.83±1.6days), higher skin breaking strength (170.71±1.52g), higher collagen content and favourable histopathological changes revealed that topical application of ointment containing successive ethanolic extract (S.E.E) of J. auriculatum leaves has the most potent wound healing ability compared to control group in both the models studied. The DPPH radical scavenging activity of successive ethanolic extract was found to be 33.39µg/ml. Successive ethanolic extract was found to be most effective against Pseudomonas auregenosa having a zone of inhibition 16.65±0.6mm and the minimum inhibitory concentration was 0.78mg/ml. The data of this study indicate that successive ethanolic extract of the leaves exhibit potent wound healing, antioxidant and antimicrobial properties. This justifies the ethno-medicinal use of plant for the treatment of wound and microbial infections.

Phytochemical analysis and antibacterial activities extracts of mangrove leaf against the growth of some pathogenic bacteria.

PubMed

Alizadeh Behbahani, Behrooz; Tabatabaei Yazdi, Farideh; Shahidi, Fakhri; Noorbakhsh, Hamid; Vasiee, Alireza; Alghooneh, Ali

2018-01-01

In this study, the effects of water, ethanol, methanol and glycerin at five levels (0, 31.25, 83.33, 125 and 250 ml) were investigated on the efficiency of mangrove leaf extraction using mixture optimal design. The antimicrobial effect of the extracts on Streptococcus pneumoniae, Enterococcus faecium and Klebsiella pneumoniae was evaluated using disk diffusion, minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) methods. The mangrove leaf extraction components were identified through gas chromatography/mass spectrometry (GC/MS). Phytochemical analysis (alkaloids, tannins, saponins, flavone and glycosides) were evaluated based on qualitative methods. Antioxidant activity of extracts was measured using 2,2-diphenyl-1-picrylhydrazyl (DPPH), ferric reducing antioxidant potential (FRAP) methods. Maximum antimicrobial effect was observed in Enterococcus faecium and highest resistance against mangrove leaf extract in Enterococcus faecium and Klebsiella pneumoniae, respectively. Increasing concentration of mangrove extracts had a significant effect (p ≤ 0.05) on inhibition zone diameter. The MICs of the mangrove leaf extraction varied from 4 mg/ml to 16 mg/ml. The optimum formulation was found to contain glycerin (0 ml), water (28.22 ml), methanol (59.83 ml) and ethanol (161.95 ml). The results showed that the highest antioxidant activity was related to optimum extract of mangrove leaf and ethanolic extract respectively. The results of phytochemical screening of Avicennia marina leaves extract showed the existence of alkaloids, tannins, saponins, flavone and glycosides. 2-Propenoic acid, 3-phenyl- was the major compound of Avicennia marina. The results of non-significant lack of fit tests, and F value (14.62) indicated that the model was sufficiently accurate. In addition, the coefficient of variations (16.8%) showed an acceptable reproducibility. Copyright © 2017 Elsevier Ltd. All rights reserved.

Surface photovoltage method extended to silicon solar cell junction

NASA Technical Reports Server (NTRS)

Wang, E. Y.; Baraona, C. R.; Brandhorst, H. W., Jr.

1974-01-01

The conventional surface photovoltage (SPV) method is extended to the measurement of the minority carrier diffusion length in diffused semiconductor junctions of the type used in a silicon solar cell. The minority carrier diffusion values obtained by the SPV method agree well with those obtained by the X-ray method. Agreement within experimental error is also obtained between the minority carrier diffusion lengths in solar cell diffusion junctions and in the same materials with n-regions removed by etching, when the SPV method was used in the measurements.

Multi-site study of diffusion metric variability: effects of site, vendor, field strength, and echo time on regions-of-interest and histogram-bin analyses.

PubMed

Helmer, K G; Chou, M-C; Preciado, R I; Gimi, B; Rollins, N K; Song, A; Turner, J; Mori, S

2016-02-27

It is now common for magnetic-resonance-imaging (MRI) based multi-site trials to include diffusion-weighted imaging (DWI) as part of the protocol. It is also common for these sites to possess MR scanners of different manufacturers, different software and hardware, and different software licenses. These differences mean that scanners may not be able to acquire data with the same number of gradient amplitude values and number of available gradient directions. Variability can also occur in achievable b-values and minimum echo times. The challenge of a multi-site study then, is to create a common protocol by understanding and then minimizing the effects of scanner variability and identifying reliable and accurate diffusion metrics. This study describes the effect of site, scanner vendor, field strength, and TE on two diffusion metrics: the first moment of the diffusion tensor field (mean diffusivity, MD), and the fractional anisotropy (FA) using two common analyses (region-of-interest and mean-bin value of whole brain histograms). The goal of the study was to identify sources of variability in diffusion-sensitized imaging and their influence on commonly reported metrics. The results demonstrate that the site, vendor, field strength, and echo time all contribute to variability in FA and MD, though to different extent. We conclude that characterization of the variability of DTI metrics due to site, vendor, field strength, and echo time is a worthwhile step in the construction of multi-center trials.

Laboratory Experiments on Bentonite Samples: FY16 Progress

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

Ruth M. Tinnacher; Tournassat, Christophe; James A. Davis

2016-08-22

The primary goal of this study is to improve the understanding of U(VI) sorption and diffusion behavior in sodium-montmorillonite in order to support the development of realistic conceptual models describing these processes in performance assessment models while (1) accounting for potential changes in system conditions over time and space, (2) avoiding overly conservative transport predictions, and (3) using a minimum number of fitting parameters.

Evenly spaced Detrended Fluctuation Analysis: Selecting the number of points for the diffusion plot

NASA Astrophysics Data System (ADS)

Liddy, Joshua J.; Haddad, Jeffrey M.

2018-02-01

Detrended Fluctuation Analysis (DFA) has become a widely-used tool to examine the correlation structure of a time series and provided insights into neuromuscular health and disease states. As the popularity of utilizing DFA in the human behavioral sciences has grown, understanding its limitations and how to properly determine parameters is becoming increasingly important. DFA examines the correlation structure of variability in a time series by computing α, the slope of the log SD- log n diffusion plot. When using the traditional DFA algorithm, the timescales, n, are often selected as a set of integers between a minimum and maximum length based on the number of data points in the time series. This produces non-uniformly distributed values of n in logarithmic scale, which influences the estimation of α due to a disproportionate weighting of the long-timescale regions of the diffusion plot. Recently, the evenly spaced DFA and evenly spaced average DFA algorithms were introduced. Both algorithms compute α by selecting k points for the diffusion plot based on the minimum and maximum timescales of interest and improve the consistency of α estimates for simulated fractional Gaussian noise and fractional Brownian motion time series. Two issues that remain unaddressed are (1) how to select k and (2) whether the evenly-spaced DFA algorithms show similar benefits when assessing human behavioral data. We manipulated k and examined its effects on the accuracy, consistency, and confidence limits of α in simulated and experimental time series. We demonstrate that the accuracy and consistency of α are relatively unaffected by the selection of k. However, the confidence limits of α narrow as k increases, dramatically reducing measurement uncertainty for single trials. We provide guidelines for selecting k and discuss potential uses of the evenly spaced DFA algorithms when assessing human behavioral data.

Detection of high GS risk group prostate tumors by diffusion tensor imaging and logistic regression modelling.

PubMed

Ertas, Gokhan

2018-07-01

To assess the value of joint evaluation of diffusion tensor imaging (DTI) measures by using logistic regression modelling to detect high GS risk group prostate tumors. Fifty tumors imaged using DTI on a 3 T MRI device were analyzed. Regions of interests focusing on the center of tumor foci and noncancerous tissue on the maps of mean diffusivity (MD) and fractional anisotropy (FA) were used to extract the minimum, the maximum and the mean measures. Measure ratio was computed by dividing tumor measure by noncancerous tissue measure. Logistic regression models were fitted for all possible pair combinations of the measures using 5-fold cross validation. Systematic differences are present for all MD measures and also for all FA measures in distinguishing the high risk tumors [GS ≥ 7(4 + 3)] from the low risk tumors [GS ≤ 7(3 + 4)] (P < 0.05). Smaller value for MD measures and larger value for FA measures indicate the high risk. The models enrolling the measures achieve good fits and good classification performances (R 2 adj  = 0.55-0.60, AUC = 0.88-0.91), however the models using the measure ratios perform better (R 2 adj  = 0.59-0.75, AUC = 0.88-0.95). The model that employs the ratios of minimum MD and maximum FA accomplishes the highest sensitivity, specificity and accuracy (Se = 77.8%, Sp = 96.9% and Acc = 90.0%). Joint evaluation of MD and FA diffusion tensor imaging measures is valuable to detect high GS risk group peripheral zone prostate tumors. However, use of the ratios of the measures improves the accuracy of the detections substantially. Logistic regression modelling provides a favorable solution for the joint evaluations easily adoptable in clinical practice. Copyright © 2018 Elsevier Inc. All rights reserved.

Design and optimization of a single stage centrifugal compressor for a solar dish-Brayton system

NASA Astrophysics Data System (ADS)

Wang, Yongsheng; Wang, Kai; Tong, Zhiting; Lin, Feng; Nie, Chaoqun; Engeda, Abraham

2013-10-01

According to the requirements of a solar dish-Brayton system, a centrifugal compressor stage with a minimum total pressure ratio of 5, an adiabatic efficiency above 75% and a surge margin more than 12% needs to be designed. A single stage, which consists of impeller, radial vaned diffuser, 90° crossover and two rows of axial stators, was chosen to satisfy this system. To achieve the stage performance, an impeller with a 6:1 total pressure ratio and an adiabatic efficiency of 90% was designed and its preliminary geometry came from an in-house one-dimensional program. Radial vaned diffuser was applied downstream of the impeller. Two rows of axial stators after 90° crossover were added to guide the flow into axial direction. Since jet-wake flow, shockwave and boundary layer separation coexisted in the impeller-diffuser region, optimization on the radius ratio of radial diffuser vane inlet to impeller exit, diffuser vane inlet blade angle and number of diffuser vanes was carried out at design point. Finally, an optimized centrifugal compressor stage fulfilled the high expectations and presented proper performance. Numerical simulation showed that at design point the stage adiabatic efficiency was 79.93% and the total pressure ratio was 5.6. The surge margin was 15%. The performance map including 80%, 90% and 100% design speed was also presented.

Robust and Accurate Shock Capturing Method for High-Order Discontinuous Galerkin Methods

NASA Technical Reports Server (NTRS)

Atkins, Harold L.; Pampell, Alyssa

2011-01-01

A simple yet robust and accurate approach for capturing shock waves using a high-order discontinuous Galerkin (DG) method is presented. The method uses the physical viscous terms of the Navier-Stokes equations as suggested by others; however, the proposed formulation of the numerical viscosity is continuous and compact by construction, and does not require the solution of an auxiliary diffusion equation. This work also presents two analyses that guided the formulation of the numerical viscosity and certain aspects of the DG implementation. A local eigenvalue analysis of the DG discretization applied to a shock containing element is used to evaluate the robustness of several Riemann flux functions, and to evaluate algorithm choices that exist within the underlying DG discretization. A second analysis examines exact solutions to the DG discretization in a shock containing element, and identifies a "model" instability that will inevitably arise when solving the Euler equations using the DG method. This analysis identifies the minimum viscosity required for stability. The shock capturing method is demonstrated for high-speed flow over an inviscid cylinder and for an unsteady disturbance in a hypersonic boundary layer. Numerical tests are presented that evaluate several aspects of the shock detection terms. The sensitivity of the results to model parameters is examined with grid and order refinement studies.

Diffusion Monte Carlo studies of MB-pol (H2O)2-6 and (D2O)2-6 clusters: Structures and binding energies

NASA Astrophysics Data System (ADS)

Mallory, Joel D.; Mandelshtam, Vladimir A.

2016-08-01

We employ the diffusion Monte Carlo (DMC) method in conjunction with the recently developed, ab initio-based MB-pol potential energy surface to characterize the ground states of small (H2O)2-6 clusters and their deuterated isotopomers. Observables, other than the ground state energies, are computed using the descendant weighting approach. Among those are various spatial correlation functions and relative isomer fractions. Interestingly, the ground states of all clusters considered in this study, except for the dimer, are delocalized over at least two conformations that differ by the orientation of one or more water monomers with the relative isomer populations being sensitive to the isotope substitution. Most remarkably, the ground state of the (H2O)6 hexamer is represented by four distinct cage structures, while that of (D2O)6 is dominated by the prism, i.e., the global minimum geometry, with a very small contribution from a prism-book geometry. In addition, for (H2O)6 and (D2O)6, we performed DMC calculations to compute the ground states constrained to the cage and prism geometries. These calculations compared results for three different potentials, MB-pol, TTM3/F, and q-TIP4P/F.

Transient electroosmotic flow induced by DC or AC electric fields in a curved microtube.

PubMed

Luo, W-J

2004-10-15

This study investigates transient electroosmotic flow in a rectangular curved microtube in which the fluid is driven by the application of an external DC or AC electric field. The resultant flow-field evolutions within the microtube are simulated using the backwards-Euler time-stepping numerical method to clarify the relationship between the changes in the axial-flow velocity and the intensity of the applied electric field. When the electric field is initially applied or varies, the fluid within the double layer responds virtually immediately, and the axial velocity within the double layer tends to follow the varying intensity of the applied electric field. The greatest net charge density exists at the corners of the microtube as a result of the overlapping electrical double layers of the two walls. It results in local maximum or minimum axial velocities in the corners during increasing or decreasing applied electric field intensity in either the positive or negative direction. As the fluid within the double layer starts to move, the bulk fluid is gradually dragged into motion through the diffusion of momentum from the double layer. A finite time is required for the full momentum of the double layer to diffuse to the bulk fluid; hence, a certain phase shift between the applied electric field and the flow response is inevitable. The patterns of the axial velocity contours during the transient evolution are investigated in this study. It is found that these patterns are determined by the efficiency of momentum diffusion from the double layer to the central region of the microtube.

Tigecycline activity against metallo-β-lactamase-producing bacteria.

PubMed

Kumar, Simit; Bandyopadhyay, Maitreyi; Mondal, Soma; Pal, Nupur; Ghosh, Tapashi; Bandyopadhyay, Manas; Banerjee, Parthajit

2013-10-01

[corrected] Treatment of serious life-threatening multi-drug-resistant organisms poses a serious problem due to the limited therapeutic options. Tigecycline has been recently marketed as a broad-spectrum antibiotic with activity against both gram-positive and gram-negative bacteria. Even though many studies have demonstrated the activity of tigecycline against ESBL-producing Enterobacteriaceae, its activity is not well-defined against micro-organisms producing metallo-β-lactamases (MBLs), as there are only a few reports and the number of isolates tested is limited. The aim of the present study was to evaluate the activity of tigecycline against MBL-producing bacterial isolates. The isolates were tested for MBL production by (i) combined-disk test, (ii) double disc synergy test (DDST), (iii) susceptibility to aztreonam (30 μg) disk. Minimum inhibitory concentration to tigecycline was determined according to agar dilution method as per Clinical Laboratory Standards Institute (CLSI) guidelines. Disc diffusion susceptibility testing was also performed for all these isolates using tigecycline (15 μg) discs. Among the total 308 isolates included in the study, 99 were found to be MBL producers. MBL production was observed mostly in isolates from pus samples (40.47%) followed by urine (27.4%) and blood (13.09%). MBL production was observed in E. coli (41.48%), K. pneumoniae (26.67%), Proteus mirabilis (27.78%), Citrobacter spp. (41.67%), Enterobacter spp. (25.08%), and Acinetobacter spp. (27.27%). The result showed that tigecycline activity was unaffected by MBL production and it was showed almost 100% activity against all MBL-producing isolates, with most of the isolates exhibiting an MIC ranging from 0.25-8 μg/ml, except 2 MBL-producing E. coli isolates who had an MIC of 8 μg/ml. To conclude, tigecycline was found to be highly effective against MBL-producing Enterobacteriaceae and acinetobacter isolates, but the presence of resistance among organisms, even before the mass usage of the drug, warrants the need of its usage as a reserve drug. The study also found that the interpretative criteria for the disc diffusion method, recommended by the FDA, correlates well with the MIC detection methods. So, the microbiology laboratories might use the relatively easier method of disc diffusion, as compared to the comparatively tedious method of MIC determination.

26 CFR 1.412(c)(1)-3 - Applying the minimum funding requirements to restored plans.

Code of Federal Regulations, 2013 CFR

2013-04-01

... 26 Internal Revenue 5 2013-04-01 2013-04-01 false Applying the minimum funding requirements to..., Stock Bonus Plans, Etc. § 1.412(c)(1)-3 Applying the minimum funding requirements to restored plans. (a) In general—(1) Restoration method. The restoration method is a funding method that adapts the...

A comparative study of minimum norm inverse methods for MEG imaging

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

Leahy, R.M.; Mosher, J.C.; Phillips, J.W.

1996-07-01

The majority of MEG imaging techniques currently in use fall into the general class of (weighted) minimum norm methods. The minimization of a norm is used as the basis for choosing one from a generally infinite set of solutions that provide an equally good fit to the data. This ambiguity in the solution arises from the inherent non- uniqueness of the continuous inverse problem and is compounded by the imbalance between the relatively small number of measurements and the large number of source voxels. Here we present a unified view of the minimum norm methods and describe how we canmore » use Tikhonov regularization to avoid instabilities in the solutions due to noise. We then compare the performance of regularized versions of three well known linear minimum norm methods with the non-linear iteratively reweighted minimum norm method and a Bayesian approach.« less

Plastoquinol diffusion in linear photosynthetic electron transport

PubMed Central

Mitchell, Rowan; Spillmann, Andreas; Haehnel, Wolfgang

1990-01-01

The diffusion of plastoquinol and its binding to the cytochrome bf complex, which occurs during linear photosynthetic electron transport and is analogous to reaction sequences found in most energy-converting membranes, has been studied in intact thylakoid membranes. The flash-induced electron transfer between the laterally separated photosystems II and photosystems I was measured by following the sigmoidal reduction kinetics of P-700+ after previous oxidation of the intersystem electron carriers. The amount of flash-induced plastoquinol produced at photosystem II was (a) reduced by inhibition with dichlorophenyl-dimethylurea and (b) increased by giving a second saturating flash. These signals were simulated by a new model which combines a deterministic simulation of reaction kinetics with a Monte Carlo approach to the diffusion of plastoquinol, taking into account the known structural features of the thylakoid membrane. The plastoquinol molecules were assumed to be oxidized by either a diffusion-limited or a nondiffusion-limited step in a collisional mechanism or after binding to the cytochrome bf complex. The model was able to account for the experimental observations with a nondiffusion-limited collisional mechanism or with a binding mechanism, giving minimum values for the diffusion coefficient of plastoquinol of 2 × 10-8 cm2s-1 and 3 × 10-7 cm2s-1, respectively. PMID:19431770

Dynamics in Polymer Nanocomposites

NASA Astrophysics Data System (ADS)

Clarke, Nigel

2015-03-01

Since nanoparticles are increasingly being added to polymers to impart mechanical and functional properties, we are exploring how nanoparticles impact polymer dynamics with a focus on the diffusion coefficients. In high molecular weight polymer melts, chain diffusion is well described by the reptation model. Motion proceeds as a snake-like diffusion of the chain as a whole, along the contour of a tube that mimics the role of physical entanglements, or topological constraints, with other chains. In polymer nanocomposites there are additional constraints due to the dispersed nanoparticles in the polymer matrix. Chain motion can be altered by nanoparticle size, shape , aspect ratio, surface area, loading and the nature of the interactions between the nanoparticles and the polymer matrix. We have observed a minimum in the diffusion coefficient as a function of nanoparticle concentration when the nanoparticles are rod-like and a collapse of the diffusion coefficient onto a master curve when the nanoparticles are spherical. We are simulating the dynamics using molecular and dissipative particle simulations in order to provide physical insight into the local structure and dynamics, and have also carried out highly coarse grained Monte Carlo simulations of entangled polymers to explore how reptation is affected by the presence of larger scale obstacles. We acknowledge support from the NSF/EPSRC Materials World Network Program.

Black Zira essential oil: Chemical compositions and antimicrobial activity against the growth of some pathogenic strain causing infection.

PubMed

Noshad, Mohammad; Hojjati, Mohammad; Alizadeh Behbahani, Behrooz

2018-03-01

The aim of this study was to perform chemical compositions and phytochemical analysis of Black Zira essential oil and other goal of this research was to investigate the antimicrobial effects of Black Zira essential oil against Enterobacter aerogenes, Pseudomonas aeruginosa, Escherichia coli, Shigella flexneri, Staphylococcus epidermidis, Streptococcus pyogenes and Candida albicans. Black Zira essential oil was extracted by hydrodistillation method using clevenger apparatus. Black Zira essential oil chemical composition was identified through gas chromatography/mass spectrometry. γ-terpinene with a percentage of 24.8% was the major compound of Black Zira essential oil. The antimicrobial effect Black Zira essential oil was evaluated by several qualitative and quantitative methods (disk diffusion, well diffusion, microdilution broth, agar dilution and minimum bactericidal/fungicidal concentration). Phytochemical analysis Black Zira essential oil were appraised based on qualitative methods. Antioxidant activity (2,2-diphenyl-1-picrylhydrazyl and β-carotene/linoleic acid inhibition) and total phenolic content (Folin-Ciocalteu) were examined. The results of phytochemical analysis of Black Zira essential oil showed the existence of phenolic, flavonoids, saponins, alkaloids and tannins. The total phenolic content and antioxidant activity (reported as IC 50 ) of Black Zira essential oil were equal to 120.50 ± 0.50 mg GAE/g and 11.55 ± 0.25 μg/ml, respectively. The MIC of the Black Zira essential oil ranged from 1 mg/ml to 8 mg/ml, while its MBC and MFC ranged from 1 mg/ml to 16 mg/ml. The results presented that the longest and the shortest inhibition zone diameter at the concentration of 8 mg/ml pertained to C. albicans and E. aerogenes, respectively. Copyright © 2018. Published by Elsevier Ltd.

Comparison of diffusion- and pumped-sampling methods to monitor volatile organic compounds in ground water, Massachusetts Military Reservation, Cape Cod, Massachusetts, July 1999-December 2002

USGS Publications Warehouse

Archfield, Stacey A.; LeBlanc, Denis R.

2005-01-01

To evaluate diffusion sampling as an alternative method to monitor volatile organic compound (VOC) concentrations in ground water, concentrations in samples collected by traditional pumped-sampling methods were compared to concentrations in samples collected by diffusion-sampling methods for 89 monitoring wells at or near the Massachusetts Military Reservation, Cape Cod. Samples were analyzed for 36 VOCs. There was no substantial difference between the utility of diffusion and pumped samples to detect the presence or absence of a VOC. In wells where VOCs were detected, diffusion-sample concentrations of tetrachloroethene (PCE) and trichloroethene (TCE) were significantly lower than pumped-sample concentrations. Because PCE and TCE concentrations detected in the wells dominated the calculation of many of the total VOC concentrations, when VOC concentrations were summed and compared by sampling method, visual inspection also showed a downward concentration bias in the diffusion-sample concentration. The degree to which pumped- and diffusion-sample concentrations agreed was not a result of variability inherent within the sampling methods or the diffusion process itself. A comparison of the degree of agreement in the results from the two methods to 13 quantifiable characteristics external to the sampling methods offered only well-screen length as being related to the degree of agreement between the methods; however, there is also evidence to indicate that the flushing rate of water through the well screen affected the agreement between the sampling methods. Despite poor agreement between the concentrations obtained by the two methods at some wells, the degree to which the concentrations agree at a given well is repeatable. A one-time, well-bywell comparison between diffusion- and pumped-sampling methods could determine which wells are good candidates for the use of diffusion samplers. For wells with good method agreement, the diffusion-sampling method is a time-saving and cost-effective alternative to pumped-sampling methods in a long-term monitoring program, such as at the Massachusetts Military Reservation.

26 CFR 1.412(c)(1)-3T - Applying the minimum funding requirements to restored plans (temporary).

Code of Federal Regulations, 2013 CFR

2013-04-01

... 26 Internal Revenue 5 2013-04-01 2013-04-01 false Applying the minimum funding requirements to...-Sharing, Stock Bonus Plans, Etc. § 1.412(c)(1)-3T Applying the minimum funding requirements to restored plans (temporary). (a) In general—(1) Restoration method. The restoration method is a funding method...

3D absolute shape measurement of live rabbit hearts with a superfast two-frequency phase-shifting technique

PubMed Central

Wang, Yajun; Laughner, Jacob I.; Efimov, Igor R.; Zhang, Song

2013-01-01

This paper presents a two-frequency binary phase-shifting technique to measure three-dimensional (3D) absolute shape of beating rabbit hearts. Due to the low contrast of the cardiac surface, the projector and the camera must remain focused, which poses challenges for any existing binary method where the measurement accuracy is low. To conquer this challenge, this paper proposes to utilize the optimal pulse width modulation (OPWM) technique to generate high-frequency fringe patterns, and the error-diffusion dithering technique to produce low-frequency fringe patterns. Furthermore, this paper will show that fringe patterns produced with blue light provide the best quality measurements compared to fringe patterns generated with red or green light; and the minimum data acquisition speed for high quality measurements is around 800 Hz for a rabbit heart beating at 180 beats per minute. PMID:23482151

Near-near-infrared thermal lens spectroscopy to assess overtones and combination bands of sulfentrazone pesticide.

PubMed

Ventura, M; Silva, J R; Andrade, L H C; Scorza Júnior, R P; Lima, S M

2018-01-05

Thermal lens spectroscopy (TLS) in the near-near-infrared region was used to explore the absorptions of overtones and combination bands of sulfentrazone (SFZ) herbicide diluted in methanol. This spectroscopic region was chosen in order to guarantee that only thermal lens effect is noted during the experimental procedure. The results showed that it was possible to detect very low concentrations (~2ng/μL) of SFZ in methanol by determining its thermal diffusivity or the absorption coefficient due to the 3ν(NH)+1δ(CH) combination band. This minimum SFZ concentration is the limit observed by chromatography method. The findings demonstrated that the TLS can be used for precise and accurate assessment of pesticides in ecosystems. Besides, the 3ν(NH)+1δ(CH) combination band at 960nm can be used as a marker for SFZ in methanol. Copyright © 2017 Elsevier B.V. All rights reserved.

Near-near-infrared thermal lens spectroscopy to assess overtones and combination bands of sulfentrazone pesticide

NASA Astrophysics Data System (ADS)

Ventura, M.; Silva, J. R.; Andrade, L. H. C.; Scorza Júnior, R. P.; Lima, S. M.

2018-01-01

Thermal lens spectroscopy (TLS) in the near-near-infrared region was used to explore the absorptions of overtones and combination bands of sulfentrazone (SFZ) herbicide diluted in methanol. This spectroscopic region was chosen in order to guarantee that only thermal lens effect is noted during the experimental procedure. The results showed that it was possible to detect very low concentrations ( 2 ng/μL) of SFZ in methanol by determining its thermal diffusivity or the absorption coefficient due to the 3ν(NH) + 1δ(CH) combination band. This minimum SFZ concentration is the limit observed by chromatography method. The findings demonstrated that the TLS can be used for precise and accurate assessment of pesticides in ecosystems. Besides, the 3ν(NH) + 1δ(CH) combination band at 960 nm can be used as a marker for SFZ in methanol.

Synthesis, Characterization, Electrochemical Studies, and In Vitro Antibacterial Activity of Novel Thiosemicarbazone and Its Cu(II), Ni(II), and Co(II) Complexes

PubMed Central

Khan, Salman A.; Asiri, Abdullah M.; Al-Amry, Khalid; Malik, Maqsood Ahmad

2014-01-01

Metal complexes were prepared by the reaction of thiosemicarbazone with CuCl2, NiCl2, CoCl2, Cu(OAc)2, Ni(OAc)2, and Co(OAc)2. The thiosemicarbazone coordinates to metal through the thionic sulfur and the azomethine nitrogen. The thiosemicarbazone was obtained by the thiosemicarbazide with 3-acetyl-2,5-dimethylthiophene. The identities of these compounds were elucidated by IR, 1H, 13C-NMR, and GC-MS spectroscopic methods and elemental analyses. The antibacterial activity of these compounds was first tested in vitro by the disc diffusion assay against two Gram-positive and two Gram-negative bacteria, and then the minimum inhibitory concentration (MIC) was determined by using chloramphenicol as reference drug. The results showed that compound 1.1 is better inhibitor of both types of tested bacteria as compared to chloramphenicol. PMID:24523641

An efficient motion-resistant method for wearable pulse oximeter.

PubMed

Yan, Yong-Sheng; Zhang, Yuan-Ting

2008-05-01

Reduction of motion artifact and power saving are crucial in designing a wearable pulse oximeter for long-term telemedicine application. In this paper, a novel algorithm, minimum correlation discrete saturation transform (MCDST) has been developed for the estimation of arterial oxygen saturation (SaO2), based on an optical model derived from photon diffusion analysis. The simulation shows that the new algorithm MCDST is more robust under low SNRs than the clinically verified motion-resistant algorithm discrete saturation transform (DST). Further, the experiment with different severity of motions demonstrates that MCDST has a slightly better performance than DST algorithm. Moreover, MCDST is more computationally efficient than DST because the former uses linear algebra instead of the time-consuming adaptive filter used by latter, which indicates that MCDST can reduce the required power consumption and circuit complexity of the implementation. This is vital for wearable devices, where the physical size and long battery life are crucial.

The Effects of Allium sativum Extracts on Biofilm Formation and Activities of Six Pathogenic Bacteria.

PubMed

Mohsenipour, Zeinab; Hassanshahian, Mehdi

2015-08-01

Garlic is considered a rich source of many compounds, which shows antimicrobial effects. The ability of microorganisms to adhere to both biotic and abiotic surfaces and to form biofilm is responsible for a number of diseases of chronic nature, demonstrating extremely high resistance to antibiotics. Bacterial biofilms are complex communities of sessile microorganisms, embedded in an extracellular matrix and irreversibly attached to various surfaces. The present study evaluated the antimicrobial activity of Allium sativum extract against the biofilms of six pathogenic bacteria and their free-living forms. The clinical isolates in this study had not been studied in any other studies, especially in regard to biofilm disruption and inhibition of biofilm cell metabolic activity. Antimicrobial activities of A. sativum L. extracts (methanol and ethanol extracts) against planktonic forms of bacteria were determined using the disc diffusion method. The minimum inhibitory concentration (MIC) and the minimum bactericidal concentration (MBC) values were evaluated by a macrobroth dilution technique. The anti-biofilm effects were assessed by microtiter plate method. The results showed that the A. sativum L. extract discs did not have any zone of inhibition for the tested bacteria. However, The MIC values of A. sativum L. extracts (0.078 - 2.5 mg/mL) confirmed the high ability of these extracts for inhibition of planktonic bacteria. A. sativum L. extracts were efficient to inhibit biofilm structures and the concentration of each extract had a direct relation with the inhibitory effect. Finally, it can be suggested that the extracts of this plant be applied as antimicrobial agents against these pathogens, particularly in biofilm forms.

Antimicrobial activity, cytotoxicity and chemical analysis of lemongrass essential oil (Cymbopogon flexuosus) and pure citral.

PubMed

Adukwu, Emmanuel C; Bowles, Melissa; Edwards-Jones, Valerie; Bone, Heather

2016-11-01

The aim of this study was to determine the antimicrobial effects of lemongrass essential oil (C. flexuosus) and to determine cytotoxic effects of both test compounds on human dermal fibroblasts. Antimicrobial susceptibility screening was carried out using the disk diffusion method. Antimicrobial resistance was observed in four of five Acinetobacter baumannii strains with two strains confirmed as multi-drug-resistant (MDR). All the strains tested were susceptible to both lemongrass and citral with zones of inhibition varying between 17 to 80 mm. The mean minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of citral (mic-0.14 % and mbc-0.3 % v/v) was lower than that of Lemongrass (mic-0.65 % and mbc-1.1 % v/v) determined using the microtitre plate method. Cell viability using human dermal fibroblasts (HDF; 106-05a) was determined following exposure to both compounds and a control (Grapeseed oil) using the XTT assay and the IC 50 determined at 0.095 % (v/v) for citral and 0.126 % (v/v) for lemongrass. Grapeseed oil had no effect on cell viability. Live cell imaging was performed using the LumaScope 500 imaging equipment and changes in HDF cell morphology such as necrotic features and shrinkage were observed. The ability of lemongrass essential oil (EO) and citral to inhibit and kill MDR A. baumannii highlights its potential for use in the management of drug-resistant infections; however, in vitro cytotoxicity does suggest further tests are needed before in vivo or ex vivo human exposure.

Invitro Anti-mycotic Activity of Hydro Alcoholic Extracts of Some Indian Medicinal Plants against Fluconazole Resistant Candida albicans

PubMed Central

Varadarajan, Saranya; Malaisamy, Malaiyandi; Duraipandian, Chamundeeswari

2015-01-01

Background Candidiasis is one of the most common opportunistic infections caused by Candida albicans. Fluconazole is the drug of choice for prevention and management of this condition. However, the emergence of fluconazole resistant candidal strains has become a major concern. Many herbs like fenugreek, cinnamon, papaya, oregano, garlic are rich in phytochemical constituents known to express antimycotic activity. With the available information, the present research study was carried out to assess the invitro anti-mycotic activity of hydro alcoholic extracts of Trigonella foenum-graecum seeds, Cinnamomum verum bark and Carica papaya leaves and seeds against fluconazole resistant Candida albicans Materials and Methods Hydro alcoholic extracts of Trigonella foenum-graecum (seeds), Cinnamomum verum (bark), Carica papaya CO.2 strain (male and female leaves) and Carica papaya CO.2 strain (seeds) were prepared by maceration. The anti-mycotic activity of the prepared extracts against Candida albicans was assessed by agar well diffusion method. Three independent experiments were performed in triplicates and the mean and standard deviation were calculated. Minimum inhibitory concentration was determined. Results The results of the present study revealed that all the extracts exhibited anti-mycotic activity in a dose dependent manner and minimum inhibitory concentration of all the extracts was found to be 15.62 μg/ml. Conclusion The results of the present study shed light on the fact that plant extracts could be used not only as an alternate drug for management of fluconazole resistant candidiasis but also explored further for oral cancer prevention as a therapeutic adjunct. PMID:26436036

Introducing Urtica dioica, A Native Plant of Khuzestan, As an Antibacterial Medicinal Plant

PubMed Central

Motamedi, Hossein; Seyyednejad, Seyyed Mansour; Bakhtiari, Ameneh; Vafaei, Mozhan

2014-01-01

Background: Urtica dioica is a flowering plant with long history of use in folk medicine and as a food source. Objectives: This study examined in vitro antibacterial potential of alcoholic extracts of U. dioica. Materials and Methods: Hydroalcoholic extracts from aerial parts were prepared using aqueous solution of ethanol and methanol and their inhibitory effects against clinical isolates was examined by disc diffusion method at different doses. Minimum inhibitory concentrations (MIC) and minimum bactericidal concentration (MBC) indexes were also investigated. The scanning electron microscopy (SEM) analysis was also performed to find structural changes of affected bacteria consequent to exposing with extracts. Results: Both extracts were active against Bacillus cereus, Staphylococcus aureus, Staphylococcus epidermidis, and Escherichia coli with respectively 16, 10, 18, and 14 mm (methanolic) and 11, 9, 17, and 16 mm (ethanolic) inhibition zone. The MIC of ethanolic extract against S. epidermidis and E. coli was respectively 10 and 40 mg/mL. The MIC of methanolic extract against S. aureus and S. epidermidis was 40 and 10 mg/mL, respectively. The MBC was found only for S. epidermidis (20 mg/mL). In SEM analysis the round shape of S. epidermidis was changed and irregular shapes were appeared, which suggest that the main target of these extracts was cell wall. Conclusions: Extracts of U. dioica showed significant antibacterial effect against some clinically important pathogenic bacteria. Based on the obtained results it can be concluded that U. dioica is useful as antibacterial and bactericidal agent in treating infectious diseases. PMID:25625045

Growth Inhibition and Morphological Alterations of Trichophyton Rubrum Induced by Essential oil from Cymbopogon Winterianus Jowitt Ex Bor

PubMed Central

de Oliveira Pereira, Fillipe; Alves Wanderley, Paulo; Cavalcanti Viana, Fernando Antônio; Baltazar de Lima, Rita; Barbosa de Sousa, Frederico; de Oliveira Lima, Edeltrudes

2011-01-01

Trichophyton rubrum is one of the most common fungi causer of dermatophytosis, mycosis that affect humans and animals around the world. Researches aiming new products with antifungal activity become necessary to overcome difficulties on treatment of these infections. Accordingly, this study aimed to investigate the antifungal activity of essential oil from Cymbopogon winterianus against the dermatophyte T. rubrum. The antifungal screening was performed by solid medium diffusion method with 16 T. rubrum strains, minimum inhibitory concentration (MIC) and minimum fungicide concentration (MFC) were determined using the microdilution method. The effects on mycelial dry weight and morphology were also observed. Screening showed essential oil in natura inhibited all the tested strains, with inhibition zones between 24-28 mm diameter. MIC50 and MIC90 values of the essential oil were 312 μg/mL for nearly all the essayed strains (93.75 %) while the MFC50 and MFC90 values were about eight times higher than MIC for all tested strains. All tested essential oil concentrations managed to inhibit strongly the mycelium development. Main morphological changes on the fungal strains observed under light microscopy, which were provided by the essential oil include loss of conidiation, alterations concerning form and pigmentation of hyphae. In the oil presence, colonies showed folds, cream color and slightly darker than the control, pigment production was absent on the reverse and with evident folds. It is concluded that C. winterianus essential oil showed activity against T. rubrum. Therefore, it could be known as potential antifungal compound especially for protection against dermatophytosis. PMID:24031626

Extreme values and the level-crossing problem: An application to the Feller process

NASA Astrophysics Data System (ADS)

Masoliver, Jaume

2014-04-01

We review the question of the extreme values attained by a random process. We relate it to level crossings to one boundary (first-passage problems) as well as to two boundaries (escape problems). The extremes studied are the maximum, the minimum, the maximum absolute value, and the range or span. We specialize in diffusion processes and present detailed results for the Wiener and Feller processes.

Numerical Solutions for a Cylindrical Laser Diffuser Flowfield

DTIC Science & Technology

1990-06-01

exhaust conditions with minimum losses to optimize performance of the system. Thus, the handling of the system of shock waves to decelerate the flow...requirement for exhaustive experimental work will result in significant savings of both time and resources. As more advanced computers are developed, the...Mach number (ɚ.5) flows. Recent interest in hypersonic engine inlet performance has resulted in an extension of the methodology to high Mach number

Prunus mume extract exhibits antimicrobial activity against pathogenic oral bacteria.

PubMed

Seneviratne, Chamida J; Wong, Ricky W K; Hägg, Urban; Chen, Yong; Herath, Thanuja D K; Samaranayake, P Lakshman; Kao, Richard

2011-07-01

Prunus mume is a common fruit in Asia, which has been used in traditional Chinese medicine. In this study, we focused on the antimicrobial properties of Prunus mume extract against oral pathogens related to dental caries and periodontal diseases. A total of 15 oral pathogens including Streptococcus mutans, S. sobrinus, S. mitis, S. sanguinis, Lactobacillus acidophilus, P. gingivalis, Aggregatibacter actinomycetemcomitans, and Candida species were included in the study. Initially, agar diffusion assay was performed to screen the antimicrobial activities of Prunus mume extract. Minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) were then determined for sensitive species. Effect of Prunus mume extract on human oral keratinocytes (HOK) viability was also tested. In the agar diffusion assay, drug suspension of 2 g/mL was able to inhibit all the bacterial species tested, but not the fungal species. MIC and MBC range of Prunus mume extract against the oral bacteria was 0.15625-0.0003 g/mL and P. gingivalis being the most susceptible species. Prune extract did not cause any detrimental effect on HOK. Prunus mume extract may be a potential candidate for developing an oral antimicrobial agent to control or prevent dental diseases associated with oral pathogenic bacteria. © 2011 The Authors. International Journal of Paediatric Dentistry © 2011 BSPD, IAPD and Blackwell Publishing Ltd.

Improvement of band gap profile in Cu(InGa)Se{sub 2} solar cells through rapid thermal annealing

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

Chen, D.S.; College of Mathematics and Physics, Shanghai University of Electric Power, Shanghai, 200090; Yang, J.

Highlights: • Proper RTA treatment can effectively optimize band gap profile to more expected level. • Inter-diffusion of atoms account for the improvement of the graded band gap profile. • The variation of the band gap profile created an absolute gain in the efficiency by 1.22%. - Abstract: In the paper, the effect of rapid thermal annealing on non-optimal double-graded band gap profiles was investigated by using X-ray photoelectron spectroscopy and capacitance–voltage measurement techniques. Experimental results revealed that proper rapid thermal annealing treatment can effectively improve band gap profile to more optimal level. The annealing treatment could not only reducemore » the values of front band gap and minimum band gap, but also shift the position of the minimum band gap toward front electrode and enter into space charge region. In addition, the thickness of Cu(InGa)Se{sub 2} thin film decreased by 25 nm after rapid thermal annealing treatment. All of these modifications were attributed to the inter-diffusion of atoms during thermal treatment process. Simultaneously, the variation of the band gap profile created an absolute gain in the efficiency by 1.22%, short-circuit current density by 2.16 mA/cm{sup 2} and filled factor by 3.57%.« less

Some basic mathematical methods of diffusion theory. [emphasis on atmospheric applications

NASA Technical Reports Server (NTRS)

Giere, A. C.

1977-01-01

An introductory treatment of the fundamentals of diffusion theory is presented, starting with molecular diffusion and leading up to the statistical methods of turbulent diffusion. A multilayer diffusion model, designed to permit concentration and dosage calculations downwind of toxic clouds from rocket vehicles, is described. The concepts and equations of diffusion are developed on an elementary level, with emphasis on atmospheric applications.

Determination of methyl bromide in air samples by headspace gas chromatography

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

Woodrow, J.E.; McChesney, M.M.; Seiber, J.N.

1988-03-01

Methyl bromide is extensively used in agriculture (4 x 10/sup 6/ kg for 1985 in California alone as a fumigant to control nematodes, weeds, and fungi in soil and insect pests in harvested grains and nuts. Given its low boiling point (3.8/sup 0/C) and high vapor pressure (approx. 1400 Torr at 20/sup 0/C), methyl bromide will readily diffuse if not rigorously contained. Methods for determining methyl bromide and other halocarbons in air vary widely. A common practice is to trap the material from air on an adsorbent, such as polymeric resins, followed by thermal desorption either directly into the analyticalmore » instrumentation or after intermediary cryofocusing. While in some cases analytical detection limits were reasonable (parts per million range), many of the published methods were labor intensive and required special handling techniques that precluded high sample throughput. They describe here a method for the sampling and analysis of airborne methyl bromide that was designed to handle large numbers of samples through automating some critical steps of the analysis. The result was a method that allowed around-the-clock operation with a minimum of operator attention. Furthermore, the method was not specific to methyl bromide and could be used to determine other halocarbons in air.« less

Measurement of radon diffusion in polyethylene based on alpha detection

NASA Astrophysics Data System (ADS)

Rau, Wolfgang

2012-02-01

Radon diffusion in different materials has been measured in the past. Usually the diffusion measurements are based on a direct determination of the amount of radon that diffuses through a thin layer of material. Here we present a method based on the measurement of the radon daughter products which are deposited inside the material. Looking at the decay of 210Po allows us to directly measure the exponential diffusion profile characterized by the diffusion length. In addition we can determine the solubility of radon in PE. We also describe a second method to determine the diffusion constant based on the short-lived radon daughter products 218Po and 214Po, using the identical experimental setup. Measurements for regular polyethylene (PE) and High Molecular Weight Polyethylene (HMWPE) yielded diffusion lengths of (1.3±0.3) mm and (0.8±0.2) mm and solubilities of 0.5±0.1 and 0.7±0.2, respectively, for the first method; the diffusion lengths extracted from the second method are noticeably larger which may be caused by different experimental conditions during diffusion.

Committed sea-level rise for the next century from Greenland ice sheet dynamics during the past decade

PubMed Central

Price, Stephen F.; Payne, Antony J.; Howat, Ian M.; Smith, Benjamin E.

2011-01-01

We use a three-dimensional, higher-order ice flow model and a realistic initial condition to simulate dynamic perturbations to the Greenland ice sheet during the last decade and to assess their contribution to sea level by 2100. Starting from our initial condition, we apply a time series of observationally constrained dynamic perturbations at the marine termini of Greenland’s three largest outlet glaciers, Jakobshavn Isbræ, Helheim Glacier, and Kangerdlugssuaq Glacier. The initial and long-term diffusive thinning within each glacier catchment is then integrated spatially and temporally to calculate a minimum sea-level contribution of approximately 1 ± 0.4 mm from these three glaciers by 2100. Based on scaling arguments, we extend our modeling to all of Greenland and estimate a minimum dynamic sea-level contribution of approximately 6 ± 2 mm by 2100. This estimate of committed sea-level rise is a minimum because it ignores mass loss due to future changes in ice sheet dynamics or surface mass balance. Importantly, > 75% of this value is from the long-term, diffusive response of the ice sheet, suggesting that the majority of sea-level rise from Greenland dynamics during the past decade is yet to come. Assuming similar and recurring forcing in future decades and a self-similar ice dynamical response, we estimate an upper bound of 45 mm of sea-level rise from Greenland dynamics by 2100. These estimates are constrained by recent observations of dynamic mass loss in Greenland and by realistic model behavior that accounts for both the long-term cumulative mass loss and its decay following episodic boundary forcing. PMID:21576500

Committed sea-level rise for the next century from Greenland ice sheet dynamics during the past decade.

PubMed

Price, Stephen F; Payne, Antony J; Howat, Ian M; Smith, Benjamin E

2011-05-31

We use a three-dimensional, higher-order ice flow model and a realistic initial condition to simulate dynamic perturbations to the Greenland ice sheet during the last decade and to assess their contribution to sea level by 2100. Starting from our initial condition, we apply a time series of observationally constrained dynamic perturbations at the marine termini of Greenland's three largest outlet glaciers, Jakobshavn Isbræ, Helheim Glacier, and Kangerdlugssuaq Glacier. The initial and long-term diffusive thinning within each glacier catchment is then integrated spatially and temporally to calculate a minimum sea-level contribution of approximately 1 ± 0.4 mm from these three glaciers by 2100. Based on scaling arguments, we extend our modeling to all of Greenland and estimate a minimum dynamic sea-level contribution of approximately 6 ± 2 mm by 2100. This estimate of committed sea-level rise is a minimum because it ignores mass loss due to future changes in ice sheet dynamics or surface mass balance. Importantly, > 75% of this value is from the long-term, diffusive response of the ice sheet, suggesting that the majority of sea-level rise from Greenland dynamics during the past decade is yet to come. Assuming similar and recurring forcing in future decades and a self-similar ice dynamical response, we estimate an upper bound of 45 mm of sea-level rise from Greenland dynamics by 2100. These estimates are constrained by recent observations of dynamic mass loss in Greenland and by realistic model behavior that accounts for both the long-term cumulative mass loss and its decay following episodic boundary forcing.

Measurement of gas diffusion coefficient in liquid-saturated porous media using magnetic resonance imaging

NASA Astrophysics Data System (ADS)

Song, Yongchen; Hao, Min; Zhao, Yuechao; Zhang, Liang

2014-12-01

In this study, the dual-chamber pressure decay method and magnetic resonance imaging (MRI) were used to dynamically visualize the gas diffusion process in liquid-saturated porous media, and the relationship of concentration-distance for gas diffusing into liquid-saturated porous media at different times were obtained by MR images quantitative analysis. A non-iterative finite volume method was successfully applied to calculate the local gas diffusion coefficient in liquid-saturated porous media. The results agreed very well with the conventional pressure decay method, thus it demonstrates that the method was feasible of determining the local diffusion coefficient of gas in liquid-saturated porous media at different times during diffusion process.

Precombination Cloud Collapse and Baryonic Dark Matter

NASA Technical Reports Server (NTRS)

Hogan, Craig J.

1993-01-01

A simple spherical model of dense baryon clouds in the hot big bang 'strongly nonlinear primordial isocurvature baryon fluctuations' is reviewed and used to describe the dependence of cloud behavior on the model parameters, baryon mass, and initial over-density. Gravitational collapse of clouds before and during recombination is considered including radiation diffusion and trapping, remnant type and mass, and effects on linear large-scale fluctuation modes. Sufficiently dense clouds collapse early into black holes with a minimum mass of approx. 1 solar mass, which behave dynamically like collisionless cold dark matter. Clouds below a critical over-density, however, delay collapse until recombination, remaining until then dynamically coupled to the radiation like ordinary diffuse baryons, and possibly producing remnants of other kinds and lower mass. The mean density in either type of baryonic remnant is unconstrained by observed element abundances. However, mixed or unmixed spatial variations in abundance may survive in the diffuse baryon and produce observable departures from standard predictions.

An empirical assessment of implementation, adaptation, and tailoring: the evaluation of CDC's National Diffusion of VOICES/VOCES.

PubMed

Harshbarger, Camilla; Simmons, Gretchen; Coelho, Helen; Sloop, Kira; Collins, Charles

2006-08-01

The Centers for Disease Control and Prevention (CDC), through its Diffusion of Effective Behavioral Interventions (DEBI) program, trained over 260 agencies on VOICES/VOCES between August 2003 and April 2005. ORC Macro conducted interviews with agency staff 3 months after receiving VOICES/VOCES training. This article discusses the diffusion of VOICES/VOCES; agencies' adoption, adaptation, and implementation of this intervention; and needs for ongoing proactive technical assistance (TA) for agencies to successfully integrate behavioral interventions into their programs. The vastmajority of agencies implemented VOICES/VOCES with fidelity to the core elements, and agencies successfully adapted the intervention to make it more appealing to target populations. TA is needed for interventions to be successfully adapted and implemented with fidelity to the core elements, and to ensure program sustainability. More effective interventions of short duration and minimum complexity to easily match with existing resources and conditions of agency capacity among HIV prevention providers in the community are needed.

Development of a Self Aligned CMOS Process for Flash Lamp Annealed Polycrystalline Silicon TFTs

NASA Astrophysics Data System (ADS)

Bischoff, Paul

The emerging active matrix liquid crystal (AMLCD) display market requires a high performing semiconductor material to meet rising standards of operation. Currently amorphous silicon (a-Si) dominates the market but it does not have the required mobility for it to be used in AMLCD manufacturing. Other materials have been developed including crystallizing a-Si into poly-silicon. A new approach to crystallization through the use of flash lamp annealing (FLA) decreases manufacturing time and greatly improves carrier mobility. Previous work on FLA silicon for the use in CMOS transistors revealed significant lateral dopant diffusion into the channel greatly increasing the minimum channel length required for a working device. This was further confounded by the gate overlap due to misalignment during lithography patterning steps. Through the use of furnace dopant activation instead of FLA dopant activation and a self aligned gate the minimum size transistor can be greatly reduced. A new lithography mask and process flow were developed for the furnace annealing and self aligned gate. Fabrication of the self aligned devices resulted in oxidation of the Molybdenum self aligned gate. Further development is needed to successfully manufacture these devices. Non-self aligned transistors were made simultaneously with self aligned devices and used the furnace activation. These devices showed an increase in sheet resistance from 250 O to 800 O and lower mobility from 380 to 40.2 V/cm2s. The lower mobility can be contributed to an increase in implanted trap density indicating furnace annealing is an inferior activation method over FLA. The minimum transistor size however was reduced from 20 to 5 mum. With improvements in the self aligned process high performing small devices can be manufactured.

The Development of an 8-inch by 8-inch Slotted Tunnel for Mach Numbers up to 1.28

NASA Technical Reports Server (NTRS)

Little, B. H., Jr.; Cubbage, James J., Jr.

1961-01-01

An 8-inch by 8-inch transonic tunnel model with test section slotted on two opposite walls was constructed in which particular emphasis -was given to the development of slot geometry, slot-flow reentry section, and short-diffuser configurations for good test-region flow and minimum total-pressure losses. Center-line static pressures through the test section, wall static pressures through the other parts of the tunnel, and total-pressure distributions at the inlet and exit stations of the diffuser were measured- With a slot length equal to two tunnel heights and 1/14 open-area-ratio slotted walls) a test region one tunnel height in length was obtained in which the deviation from the mean Mach number was less than +/- 0.01 up to Mach number 1.15. With 1/7 open-area-ratio slotted walls, a test region 0.84 tunnel heights in length with deviation less than +/- O.01 was obtained up to Mach number 1.26. Increasing the tunnel diffuser angle from 6.4 to 10 deg. increased pressure loss through the tunnel at Mach number 1.20 from 15 percent to 20 percent of the total pressure. The use of other diffusers with equivalent angles of 10 deg. but contoured so that the initial diffusion angle was less than 10 deg. and the final angle was 200 reduced the losses to as low as 16 percent. A method for changing the test-section Mach number rapidly by controlling the flow through a bypass line from the tunnel settling chamber to the slot-flow plenum chamber of the test section was very effective. The test-section Mach number was reduced approximately 5 percent in 1/8 second by bleeding into the test section a flow of air equal to 2 percent of the mainstream flow and 30 percent in 1/4 second with bleed flow equal to 10 percent of the mainstream flow. The rate of reduction was largely determined by the opening rate of the bleed-flow-control valve.

A framework to analyze cerebral mean diffusivity using surface guided diffusion mapping in diffusion tensor imaging

PubMed Central

Kwon, Oh-Hun; Park, Hyunjin; Seo, Sang-Won; Na, Duk L.; Lee, Jong-Min

2015-01-01

The mean diffusivity (MD) value has been used to describe microstructural properties in Diffusion Tensor Imaging (DTI) in cortical gray matter (GM). Recently, researchers have applied a cortical surface generated from the T1-weighted volume. When the DTI data are analyzed using the cortical surface, it is important to assign an accurate MD value from the volume space to the vertex of the cortical surface, considering the anatomical correspondence between the DTI and the T1-weighted image. Previous studies usually sampled the MD value using the nearest-neighbor (NN) method or Linear method, even though there are geometric distortions in diffusion-weighted volumes. Here we introduce a Surface Guided Diffusion Mapping (SGDM) method to compensate for such geometric distortions. We compared our SGDM method with results using NN and Linear methods by investigating differences in the sampled MD value. We also projected the tissue classification results of non-diffusion-weighted volumes to the cortical midsurface. The CSF probability values provided by the SGDM method were lower than those produced by the NN and Linear methods. The MD values provided by the NN and Linear methods were significantly greater than those of the SGDM method in regions suffering from geometric distortion. These results indicate that the NN and Linear methods assigned the MD value in the CSF region to the cortical midsurface (GM region). Our results suggest that the SGDM method is an effective way to correct such mapping errors. PMID:26236180

Prediction of oxygen distribution in aortic valve leaflet considering diffusion and convection.

PubMed

Wang, Ling; Korossis, Sotirios; Fisher, John; Ingham, Eileen; Jin, Zhongmin

2011-07-01

Oxygen supply and transport is an important consideration in the development of tissue engineered constructs. Previous studies from our group have focused on the effect of tissue thickness on the oxygen diffusion within a three-dimensional aortic valve leaflet model, and highlighted the necessity for additional transport mechanisms such as oxygen convection. The aims of this study were to investigate the effect of interstitial fluid flow within the aortic valve leaflet, induced by the cyclic loading of the leaflet, on oxygen transport. Indentation testing and finite element modelings were employed to derive the biphasic properties of the leaflet tissue. The biphasic properties were subsequently used in the computational modeling of oxygen convection in the leaflet, which was based on the effective interstitial fluid velocity and the tissue deformation. Subsequently, the oxygen profile was predicted within the valve leaflet model by solving the diffusion and convection equation simultaneously utilizing the finite difference method. The compression modulus (E) and hydraulic permeability were determined by adapting a finite element model to the experimental indentation test on valvular tissue, E = 0.05MPa, and k =2.0 mm4/Ns. Finite element model of oxygen convection in valvular tissue incorporating the predicted biphasic properties was developed and the interstitial fluid flow rate was calculated falling in range of 0.025-0.25 mm/s depending on the tissue depth. Oxygen distribution within valvular tissue was predicted using one-dimensional oxygen diffusion model taking into consider the interstitial fluid effect. It was found that convection did enhance the oxygen transport in valvular tissue by up to 68% increase in the minimum oxygen tension within the tissue, depending on the strain level of the tissue as reaction of the magnitude and frequencies of the cardiac loading. The effective interstitial fluid velocity was found to play an important role in enhancing the oxygen transport within the valve leaflet. Such an understanding is important in the development of valvular tissue engineered constructs.

Diffusion archeology for diffusion progression history reconstruction.

PubMed

Sefer, Emre; Kingsford, Carl

2016-11-01

Diffusion through graphs can be used to model many real-world processes, such as the spread of diseases, social network memes, computer viruses, or water contaminants. Often, a real-world diffusion cannot be directly observed while it is occurring - perhaps it is not noticed until some time has passed, continuous monitoring is too costly, or privacy concerns limit data access. This leads to the need to reconstruct how the present state of the diffusion came to be from partial diffusion data. Here, we tackle the problem of reconstructing a diffusion history from one or more snapshots of the diffusion state. This ability can be invaluable to learn when certain computer nodes are infected or which people are the initial disease spreaders to control future diffusions. We formulate this problem over discrete-time SEIRS-type diffusion models in terms of maximum likelihood. We design methods that are based on submodularity and a novel prize-collecting dominating-set vertex cover (PCDSVC) relaxation that can identify likely diffusion steps with some provable performance guarantees. Our methods are the first to be able to reconstruct complete diffusion histories accurately in real and simulated situations. As a special case, they can also identify the initial spreaders better than the existing methods for that problem. Our results for both meme and contaminant diffusion show that the partial diffusion data problem can be overcome with proper modeling and methods, and that hidden temporal characteristics of diffusion can be predicted from limited data.

Diffusion archeology for diffusion progression history reconstruction

PubMed Central

Sefer, Emre; Kingsford, Carl

2015-01-01

Diffusion through graphs can be used to model many real-world processes, such as the spread of diseases, social network memes, computer viruses, or water contaminants. Often, a real-world diffusion cannot be directly observed while it is occurring — perhaps it is not noticed until some time has passed, continuous monitoring is too costly, or privacy concerns limit data access. This leads to the need to reconstruct how the present state of the diffusion came to be from partial diffusion data. Here, we tackle the problem of reconstructing a diffusion history from one or more snapshots of the diffusion state. This ability can be invaluable to learn when certain computer nodes are infected or which people are the initial disease spreaders to control future diffusions. We formulate this problem over discrete-time SEIRS-type diffusion models in terms of maximum likelihood. We design methods that are based on submodularity and a novel prize-collecting dominating-set vertex cover (PCDSVC) relaxation that can identify likely diffusion steps with some provable performance guarantees. Our methods are the first to be able to reconstruct complete diffusion histories accurately in real and simulated situations. As a special case, they can also identify the initial spreaders better than the existing methods for that problem. Our results for both meme and contaminant diffusion show that the partial diffusion data problem can be overcome with proper modeling and methods, and that hidden temporal characteristics of diffusion can be predicted from limited data. PMID:27821901

Diffusion of robotics into clinical practice in the United States: process, patient safety, learning curves, and the public health.

PubMed

Mirheydar, Hossein S; Parsons, J Kellogg

2013-06-01

Robotic technology disseminated into urological practice without robust comparative effectiveness data. To review the diffusion of robotic surgery into urological practice. We performed a comprehensive literature review focusing on diffusion patterns, patient safety, learning curves, and comparative costs for robotic radical prostatectomy, partial nephrectomy, and radical cystectomy. Robotic urologic surgery diffused in patterns typical of novel technology spreading among practicing surgeons. Robust evidence-based data comparing outcomes of robotic to open surgery were sparse. Although initial Level 3 evidence for robotic prostatectomy observed complication outcomes similar to open prostatectomy, subsequent population-based Level 2 evidence noted an increased prevalence of adverse patient safety events and genitourinary complications among robotic patients during the early years of diffusion. Level 2 evidence indicated comparable to improved patient safety outcomes for robotic compared to open partial nephrectomy and cystectomy. Learning curve recommendations for robotic urologic surgery have drawn exclusively on Level 4 evidence and subjective, non-validated metrics. The minimum number of cases required to achieve competency for robotic prostatectomy has increased to unrealistically high levels. Most comparative cost-analyses have demonstrated that robotic surgery is significantly more expensive than open or laparoscopic surgery. Evidence-based data are limited but suggest an increased prevalence of adverse patient safety events for robotic prostatectomy early in the national diffusion period. Learning curves for robotic urologic surgery are subjective and based on non-validated metrics. The urological community should develop rigorous, evidence-based processes by which future technological innovations may diffuse in an organized and safe manner.

Diffusion profiling of tumor volumes using a histogram approach can predict proliferation and further microarchitectural features in medulloblastoma.

PubMed

Schob, Stefan; Beeskow, Anne; Dieckow, Julia; Meyer, Hans-Jonas; Krause, Matthias; Frydrychowicz, Clara; Hirsch, Franz-Wolfgang; Surov, Alexey

2018-05-31

Medulloblastomas are the most common central nervous system tumors in childhood. Treatment and prognosis strongly depend on histology and transcriptomic profiling. However, the proliferative potential also has prognostical value. Our study aimed to investigate correlations between histogram profiling of diffusion-weighted images and further microarchitectural features. Seven patients (age median 14.6 years, minimum 2 years, maximum 20 years; 5 male, 2 female) were included in this retrospective study. Using a Matlab-based analysis tool, histogram analysis of whole apparent diffusion coefficient (ADC) volumes was performed. ADC entropy revealed a strong inverse correlation with the expression of the proliferation marker Ki67 (r = - 0.962, p = 0.009) and with total nuclear area (r = - 0.888, p = 0.044). Furthermore, ADC percentiles, most of all ADCp90, showed significant correlations with Ki67 expression (r = 0.902, p = 0.036). Diffusion histogram profiling of medulloblastomas provides valuable in vivo information which potentially can be used for risk stratification and prognostication. First of all, entropy revealed to be the most promising imaging biomarker. However, further studies are warranted.

Study of car-sharing diffusion criticality conditions based on human traveling network

NASA Astrophysics Data System (ADS)

Xu, Yan; Ji, Xuehong

Car-sharing program, like Car2go, is an innovative urban transportation mode where the car-sharing company provides a car fleet to offer people with the short-term access of car traveling. As a new traveling service, car-sharing platforms have been struggling hard to trigger initial users and speed up their diffusion process. Unlike new product spreading via geographical proximity people, car-sharing users usually drive sharing cars to different destinations and influence people there, and potential user decision also depends on previous user activity at all their destinations. Car-sharing user connections are mainly affected by their traveling behaviors. The influence of user traveling network on new service/product spreading process has been rarely studied before. Here, we find that the infective rate between users with the same destination is critical to the minimum user base of car-sharing diffusion. Moreover, a city with central user network is more appropriate for car-sharing. It leads to a small critical infective rate for diffusion, and a large stable market size of car-sharing service. Our study can impact car-sharing market strategies ranging from market expansion in one city to optimal market selection among different cities.

The tensor distribution function.

PubMed

Leow, A D; Zhu, S; Zhan, L; McMahon, K; de Zubicaray, G I; Meredith, M; Wright, M J; Toga, A W; Thompson, P M

2009-01-01

Diffusion weighted magnetic resonance imaging is a powerful tool that can be employed to study white matter microstructure by examining the 3D displacement profile of water molecules in brain tissue. By applying diffusion-sensitized gradients along a minimum of six directions, second-order tensors (represented by three-by-three positive definite matrices) can be computed to model dominant diffusion processes. However, conventional DTI is not sufficient to resolve more complicated white matter configurations, e.g., crossing fiber tracts. Recently, a number of high-angular resolution schemes with more than six gradient directions have been employed to address this issue. In this article, we introduce the tensor distribution function (TDF), a probability function defined on the space of symmetric positive definite matrices. Using the calculus of variations, we solve the TDF that optimally describes the observed data. Here, fiber crossing is modeled as an ensemble of Gaussian diffusion processes with weights specified by the TDF. Once this optimal TDF is determined, the orientation distribution function (ODF) can easily be computed by analytic integration of the resulting displacement probability function. Moreover, a tensor orientation distribution function (TOD) may also be derived from the TDF, allowing for the estimation of principal fiber directions and their corresponding eigenvalues.

Maximizing Information Diffusion in the Cyber-physical Integrated Network †

PubMed Central

Lu, Hongliang; Lv, Shaohe; Jiao, Xianlong; Wang, Xiaodong; Liu, Juan

2015-01-01

Nowadays, our living environment has been embedded with smart objects, such as smart sensors, smart watches and smart phones. They make cyberspace and physical space integrated by their abundant abilities of sensing, communication and computation, forming a cyber-physical integrated network. In order to maximize information diffusion in such a network, a group of objects are selected as the forwarding points. To optimize the selection, a minimum connected dominating set (CDS) strategy is adopted. However, existing approaches focus on minimizing the size of the CDS, neglecting an important factor: the weight of links. In this paper, we propose a distributed maximizing the probability of information diffusion (DMPID) algorithm in the cyber-physical integrated network. Unlike previous approaches that only consider the size of CDS selection, DMPID also considers the information spread probability that depends on the weight of links. To weaken the effects of excessively-weighted links, we also present an optimization strategy that can properly balance the two factors. The results of extensive simulation show that DMPID can nearly double the information diffusion probability, while keeping a reasonable size of selection with low overhead in different distributed networks. PMID:26569254

Polymeric hydrogen diffusion barrier, high-pressure storage tank so equipped, method of fabricating a storage tank and method of preventing hydrogen diffusion

DOEpatents

Lessing, Paul A [Idaho Falls, ID

2008-07-22

An electrochemically active hydrogen diffusion barrier which comprises an anode layer, a cathode layer, and an intermediate electrolyte layer, which is conductive to protons and substantially impermeable to hydrogen. A catalytic metal present in or adjacent to the anode layer catalyzes an electrochemical reaction that converts any hydrogen that diffuses through the electrolyte layer to protons and electrons. The protons and electrons are transported to the cathode layer and reacted to form hydrogen. The hydrogen diffusion barrier is applied to a polymeric substrate used in a storage tank to store hydrogen under high pressure. A storage tank equipped with the electrochemically active hydrogen diffusion barrier, a method of fabricating the storage tank, and a method of preventing hydrogen from diffusing out of a storage tank are also disclosed.

Polymeric hydrogen diffusion barrier, high-pressure storage tank so equipped, method of fabricating a storage tank and method of preventing hydrogen diffusion

DOEpatents

Lessing, Paul A.

2004-09-07

An electrochemically active hydrogen diffusion barrier which comprises an anode layer, a cathode layer, and an intermediate electrolyte layer, which is conductive to protons and substantially impermeable to hydrogen. A catalytic metal present in or adjacent to the anode layer catalyzes an electrochemical reaction that converts any hydrogen that diffuses through the electrolyte layer to protons and electrons. The protons and electrons are transported to the cathode layer and reacted to form hydrogen. The hydrogen diffusion barrier is applied to a polymeric substrate used in a storage tank to store hydrogen under high pressure. A storage tank equipped with the electrochemically active hydrogen diffusion barrier, a method of fabricating the storage tank, and a method of preventing hydrogen from diffusing out of a storage tank are also disclosed.

On the critical flame radius and minimum ignition energy for spherical flame initiation

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

Chen, Zheng; Burke, M. P.; Ju, Yiguang

2011-01-01

Spherical flame initiation from an ignition kernel is studied theoretically and numerically using different fuel/oxygen/helium/argon mixtures (fuel: hydrogen, methane, and propane). The emphasis is placed on investigating the critical flame radius controlling spherical flame initiation and its correlation with the minimum ignition energy. It is found that the critical flame radius is different from the flame thickness and the flame ball radius and that their relationship depends strongly on the Lewis number. Three different flame regimes in terms of the Lewis number are observed and a new criterion for the critical flame radius is introduced. For mixtures with Lewis numbermore » larger than a critical Lewis number above unity, the critical flame radius is smaller than the flame ball radius but larger than the flame thickness. As a result, the minimum ignition energy can be substantially over-predicted (under-predicted) based on the flame ball radius (the flame thickness). The results also show that the minimum ignition energy for successful spherical flame initiation is proportional to the cube of the critical flame radius. Furthermore, preferential diffusion of heat and mass (i.e. the Lewis number effect) is found to play an important role in both spherical flame initiation and flame kernel evolution after ignition. It is shown that the critical flame radius and the minimum ignition energy increase significantly with the Lewis number. Therefore, for transportation fuels with large Lewis numbers, blending of small molecule fuels or thermal and catalytic cracking will significantly reduce the minimum ignition energy.« less

Refinement of the magnetic resonance diffusion-perfusion mismatch concept for thrombolytic patient selection: insights from the desmoteplase in acute stroke trials.

PubMed

Warach, Steven; Al-Rawi, Yasir; Furlan, Anthony J; Fiebach, Jochen B; Wintermark, Max; Lindstén, Annika; Smyej, Jamal; Bharucha, David B; Pedraza, Salvador; Rowley, Howard A

2012-09-01

The DIAS-2 study was the only large, randomized, intravenous, thrombolytic trial that selected patients based on the presence of ischemic penumbra. However, DIAS-2 did not confirm the positive findings of the smaller DEDAS and DIAS trials, which also used penumbral selection. Therefore, a reevaluation of the penumbra selection strategy is warranted. In post hoc analyses we assessed the relationships of magnetic resonance imaging-measured lesion volumes with clinical measures in DIAS-2, and the relationships of the presence and size of the diffusion-perfusion mismatch with the clinical effect of desmoteplase in DIAS-2 and in pooled data from DIAS, DEDAS, and DIAS-2. In DIAS-2, lesion volumes correlated with National Institutes of Health Stroke Scale (NIHSS) at both baseline and final time points (P<0.0001), and lesion growth was inversely related to good clinical outcome (P=0.004). In the pooled analysis, desmoteplase was associated with 47% clinical response rate (n=143) vs 34% in placebo (n=73; P=0.08). For both the pooled sample and for DIAS-2, increasing the minimum baseline mismatch volume (MMV) for inclusion increased the desmoteplase effect size. The odds ratio for good clinical response between desmoteplase and placebo treatment was 2.83 (95% confidence interval, 1.16-6.94; P=0.023) for MMV >60 mL. Increasing the minimum NIHSS score for inclusion did not affect treatment effect size. Pooled across all desmoteplase trials, desmoteplase appears beneficial in patients with large MMV and ineffective in patients with small MMV. These results support a modified diffusion-perfusion mismatch hypothesis for patient selection in later time-window thrombolytic trials. Clinical Trial Registration- URL: http://www.clinicaltrials.gov. Unique Identifiers: NCT00638781, NCT00638248, NCT00111852.

Diffusion modelling of metamorphic layered coronas with stability criterion and consideration of affinity

NASA Astrophysics Data System (ADS)

Ashworth, J. R.; Sheplev, V. S.

1997-09-01

Layered coronas between two reactant minerals can, in many cases, be attributed to diffusion-controlled growth with local equilibrium. This paper clarifies and unifies the previous approaches of various authors to the simplest form of modelling, which uses no assumed values for thermochemical quantities. A realistic overall reaction must be estimated from measured overall proportions of minerals and their major element compositions. Modelling is not restricted to a particular number of components S, relative to the number of phases Φ. IfΦ > S + 1, the overall reaction is a combination of simultaneous reactions. The stepwise method, solving for the local reaction at each boundary in turn, is extended to allow for recurrence of a mineral (its presence in two parts of the layer structure separated by a gap). The equations are also given in matrix form. A thermodynamic stability criterion is derived, determining which layer sequence is truly stable if several are computable from the same inputs. A layer structure satisfying the stability criterion has greater growth rate (and greater rate of entropy production) than the other computable layer sequences. This criterion of greatest entropy production is distinct from Prigogine's theorem of minimum entropy production, which distinguishes the stationary or quasi-stationary state from other states of the same layer sequence. The criterion leads to modification of previous results for coronas comprising hornblende, spinel, and orthopyroxene between olivine (Ol) and plagioclase (Pl). The outcome supports the previous inference that Si, and particularly Al, commonly behave as immobile relative to other cation-forming major elements. The affinity (-ΔG) of a corona-forming reaction is estimated, using previous estimates of diffusion coefficient and the duration t of reaction, together with a new model quantity (-ΔG) *. For an example of the Ol + Pl reaction, a rough calculation gives (-ΔG) > 1.7RT (per mole of P1 consumed, based on a 24-oxygen formula for Pl). At 600-700°C, this represents (-ΔG) > 10kJ mol -1 and departure from equilibrium temperature by at least ˜ 100°C. The lower end of this range is petrologically reasonable and, for t < 100Ma, corresponds to a Fick's-law diffusion coefficient for Al, DAl > 10 -25m 2s -1, larger than expected for lattice diffusion but consistent with fluid-absent grain-boundary diffusion and small concentration gradients.

Antioxidant and antibacterial activities on foodborne pathogens of Artocarpus heterophyllus Lam. (Moraceae) leaves extracts.

PubMed

Loizzo, M R; Tundis, R; Chandrika, U G; Abeysekera, A M; Menichini, F; Frega, N G

2010-06-01

Total water extract, ethyl acetate, and aqueous fractions from the leaves of Artocarpus heterophyllus were evaluated for phenolic content, antioxidant, and antibacterial activities against some foodborne pathogens such as E. coli, Listeria monocytogenes, Salmonella typhimurium, Salmonella enterica, Bacillus cereus, Enterococcus faecalis, and Staphylococcus aureus. The minimum inhibitory concentration (MICs) of extract and fractions determined by the agar dilution method were ranged from 221.9 microg/mL for ethyl acetate fraction to 488.1 microg/mL for total extract. In the agar diffusion method the diameters of inhibition were 12.2 for the total extract, 10.7 and 11.5 for ethyl acetate and aqueous fractions, respectively. A. heterophyllus showed significant antioxidant activity tested in different in vitro systems (DPPH, ABTS, FRAP, and Fe(2+) chelating activity assay). In particular, in DPPH assay A. heterophyllus total extract exhibited a strong antiradical activity with an IC(50) value of 73.5 microg/mL while aqueous fraction exerted the highest activity in FRAP assay (IC(50) value of 72.0 microg/mL). The total phenols content by Folin-Ciocalteau method was determined with the purpose of testing its relationship with the antioxidant and antibacterial activities.

A flexible nonlinear diffusion acceleration method for the S N transport equations discretized with discontinuous finite elements

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

Schunert, Sebastian; Wang, Yaqi; Gleicher, Frederick

This paper presents a flexible nonlinear diffusion acceleration (NDA) method that discretizes both the S N transport equation and the diffusion equation using the discontinuous finite element method (DFEM). The method is flexible in that the diffusion equation can be discretized on a coarser mesh with the only restriction that it is nested within the transport mesh and the FEM shape function orders of the two equations can be different. The consistency of the transport and diffusion solutions at convergence is defined by using a projection operator mapping the transport into the diffusion FEM space. The diffusion weak form ismore » based on the modified incomplete interior penalty (MIP) diffusion DFEM discretization that is extended by volumetric drift, interior face, and boundary closure terms. In contrast to commonly used coarse mesh finite difference (CMFD) methods, the presented NDA method uses a full FEM discretized diffusion equation for acceleration. Suitable projection and prolongation operators arise naturally from the FEM framework. Via Fourier analysis and numerical experiments for a one-group, fixed source problem the following properties of the NDA method are established for structured quadrilateral meshes: (1) the presented method is unconditionally stable and effective in the presence of mild material heterogeneities if the same mesh and identical shape functions either of the bilinear or biquadratic type are used, (2) the NDA method remains unconditionally stable in the presence of strong heterogeneities, (3) the NDA method with bilinear elements extends the range of effectiveness and stability by a factor of two when compared to CMFD if a coarser diffusion mesh is selected. In addition, the method is tested for solving the C5G7 multigroup, eigenvalue problem using coarse and fine mesh acceleration. Finally, while NDA does not offer an advantage over CMFD for fine mesh acceleration, it reduces the iteration count required for convergence by almost a factor of two in the case of coarse mesh acceleration.« less

A flexible nonlinear diffusion acceleration method for the S N transport equations discretized with discontinuous finite elements

DOE PAGES

Schunert, Sebastian; Wang, Yaqi; Gleicher, Frederick; ...

2017-02-21

This paper presents a flexible nonlinear diffusion acceleration (NDA) method that discretizes both the S N transport equation and the diffusion equation using the discontinuous finite element method (DFEM). The method is flexible in that the diffusion equation can be discretized on a coarser mesh with the only restriction that it is nested within the transport mesh and the FEM shape function orders of the two equations can be different. The consistency of the transport and diffusion solutions at convergence is defined by using a projection operator mapping the transport into the diffusion FEM space. The diffusion weak form ismore » based on the modified incomplete interior penalty (MIP) diffusion DFEM discretization that is extended by volumetric drift, interior face, and boundary closure terms. In contrast to commonly used coarse mesh finite difference (CMFD) methods, the presented NDA method uses a full FEM discretized diffusion equation for acceleration. Suitable projection and prolongation operators arise naturally from the FEM framework. Via Fourier analysis and numerical experiments for a one-group, fixed source problem the following properties of the NDA method are established for structured quadrilateral meshes: (1) the presented method is unconditionally stable and effective in the presence of mild material heterogeneities if the same mesh and identical shape functions either of the bilinear or biquadratic type are used, (2) the NDA method remains unconditionally stable in the presence of strong heterogeneities, (3) the NDA method with bilinear elements extends the range of effectiveness and stability by a factor of two when compared to CMFD if a coarser diffusion mesh is selected. In addition, the method is tested for solving the C5G7 multigroup, eigenvalue problem using coarse and fine mesh acceleration. Finally, while NDA does not offer an advantage over CMFD for fine mesh acceleration, it reduces the iteration count required for convergence by almost a factor of two in the case of coarse mesh acceleration.« less

Computing Rates of Small Molecule Diffusion Through Protein Channels Using Markovian Milestoning

NASA Astrophysics Data System (ADS)

Abrams, Cameron

2014-03-01

Measuring diffusion rates of ligands plays a key role in understanding the kinetic processes inside proteins. For example, although many molecular simulation studies have reported free energy barriers to infer rates for CO diffusion in myoglobin (Mb), they typically do not include direct calculation of diffusion rates because of the long simulation times needed to infer these rates with statistical accuracy. We show in this talk how to apply Markovian milestoning along minimum free-energy pathways to calculate diffusion rates of CO inside Mb. In Markovian milestoning, one partitions a suitable reaction coordinate space into regions and performs restrained molecular dynamics in each region to accumulate kinetic statistics that, when assembled across regions, provides an estimate of the mean first-passage time between states. The mean escape time for CO directly from the so-called distal pocket (DP) through the histidine gate (HG) is estimated at about 24 ns, confirming the importance of this portal for CO. But Mb is known to contain several internal cavities, and cavity-to-cavity diffusion rates are also computed and used to build a complete kinetic network as a Markov state model. Within this framework, the effective mean time of escape to the solvent through HG increases to 30 ns. Our results suggest that carrier protein structure may have evolved under pressure to modulate dissolved gas release rates using a network of ligand-accessible cavities. Support: NIH R01GM100472.

Antimicrobial susceptibility of Histophilus somni isolated from clinically affected cattle in Australia.

PubMed

Goldspink, Lauren K; Mollinger, Joanne L; Barnes, Tamsin S; Groves, Mitchell; Mahony, Timothy J; Gibson, Justine S

2015-02-01

This study investigated antimicrobial resistance traits, clonal relationships and epidemiology of Histophilus somni isolated from clinically affected cattle in Queensland and New South Wales, Australia. Isolates (n = 53) were subjected to antimicrobial susceptibility testing against six antimicrobial agents (ceftiofur, enrofloxacin, florfenicol, tetracycline, tilmicosin and tulathromycin) using disc diffusion and minimum inhibitory concentration (MIC) assays. Clonal relationships were assessed using repetitive sequence PCR and descriptive epidemiological analysis was performed. The H. somni isolates appeared to be geographically clonal, with 27/53 (47%) isolates grouping in one cluster from one Australian state. On the basis of disc diffusion, 34/53 (64%) isolates were susceptible to all antimicrobial agents tested; there was intermediate susceptibility to tulathromycin in 12 isolates, tilmicosin in seven isolates and resistance to tilmicosin in one isolate. Using MIC, all but one isolate was susceptible to all antimicrobial agents tested; the non-susceptible isolate was resistant to tetracycline, but this MIC result could not be compared to disc diffusion, since there are no interpretative guidelines for disc diffusion for H. somni against tetracycline. In this study, there was little evidence of antimicrobial resistance in H. somni isolates from Australian cattle. Disc diffusion susceptibility testing results were comparable to MIC results for most antimicrobial agents tested; however, results for isolates with intermediate susceptibility or resistance to tilmicosin and tulathromycin on disc diffusion should be interpreted with caution in the absence of MIC results. Copyright © 2014 Elsevier Ltd. All rights reserved.

Atomic diffusion in metal-poor stars. II. Predictions for the Spite plateau

NASA Astrophysics Data System (ADS)

Salaris, M.; Weiss, A.

2001-09-01

We have computed a grid of up-to-date stellar evolutionary models including atomic diffusion, in order to study the evolution with time of the surface Li abundance in low-mass metal-poor stars. We discuss in detail the dependence of the surface Li evolution on the initial metallicity and stellar mass, and compare the abundances obtained from our models with the available Li measurements in Pop II stars. While it is widely accepted that the existence of the Spite Li-plateau for these stars is a strong evidence that diffusion is inhibited, we show that, when taking into account observational errors, uncertainties in the Li abundance determinations, in the T_eff scale, and in particular the size of the observed samples of stars, the Spite plateau and the Li abundances in subgiant branch stars can be reproduced also by models including fully efficient diffusion, provided that the most metal-poor field halo objects are between 13.5 and 14 Gyr old. We provide the value of the minimum number of plateau stars to observe, for discriminating between efficient or inhibited diffusion. {From} our models with diffusion we derive that the average Li abundance along the Spite plateau is about a factor of 2 lower than the primordial one. As a consequence, the derived primordial Li abundance would be consistent with a high helium and low deuterium Big Bang Nucleosynthesis; this implies a high cosmological baryon density as inferred from the analyses of the cosmic microwave background.

Monoterpene isolated from the essential oil of Trachyspermum ammi is cytotoxic to multidrug-resistant Pseudomonas aeruginosa and Staphylococcus aureus strains.

PubMed

Hosseinkhani, Faride; Jabalameli, Fereshteh; Banar, Maryam; Abdellahi, Nafiseh; Taherikalani, Morovat; Leeuwen, Willem B van; Emaneini, Mohammad

2016-04-01

The aim of this study was to determine whether an herbal extract containing monoterpene exhibited activity against multidrug-resistant Staphylococcus aureus and Pseudomonas aeruginosa isolated from clinical infection samples. The essential oil of Trachyspermum ammi (L.) Sprague ex Turrill (Apiaceae) fruit was extracted by hydrodistillation. Fruit residues were treated with hydrochloric acid and re-hydrodistilled to obtain volatile compounds. Compounds in the distilled oil were identified using gas-chromatography (GC) and GC-mass spectrometry (MS). The antibiotic susceptibility of all bacterial isolates was analyzed using both the disc diffusion method and determination of the minimum inhibitory concentration (MIC). The sensitivity of antibiotic-resistant isolates to essential oil was also determined by using the disc diffusion method and MIC determination. Of 26 clinical isolates, 92% were multidrug-resistant (MDR). Aromatic monoterpenes (thymol, paracymene, and gamma-terpinene) were the major (90%) components of the oil. Growth of S. aureus strains was successfully inhibited by the oil, with an inhibitory zone diameter (IZD) between 30-60mm and MIC <0.02μL/mL. The oil had no antimicrobial activity against clinical isolates of P. aeruginosa; rather, it prevented pigment production in these isolates. This study revealed that the essential oil of Trachyspermum ammi, which contains monoterpene, has good antibacterial potency. Monoterpenes could thus be incorporated into antimicrobial ointment formulas in order to treat highly drug-resistant S. aureus infections. Our findings also underscore the utility of research on natural products in order to combat bacterial multidrug resistance.

In vitro antifungal sensitivity of fluconazole, clotrimazole and nystatin against vaginal candidiasis in females of childbearing age.

PubMed

Khan, Fouzia; Baqai, Rakhshanda

2010-01-01

Vaginal candidiasis is the most common infection of females. A large variety of antifungal drugs are used for treatment. The objective of this study was isolation and identification of Candida from high vaginal swabs and in vitro antifungal activity of Clotrimazole, Fluconazole and Nystatin against Candida. Two hundred and fifty high vaginal swabs were collected from females reporting at different hospitals of Karachi. Wet mount was performed to observe the budding cells of Candida. Vaginal swabs were cultured on Sabouraud's dextrose agar with added antibiotics. Plates were incubated at room temperature for seven days. Chlamydospores of Candida albicans were identified on corn meal agar. Species of Candida were identified on Biggy agar. In vitro antifungal activity of Clotrimazole, Fluconazole and Nystatin was performed by MIC (Minimum inhibitory concentration), well diffusion method and disc diffusion method. Out of 250 high vaginal swabs, Candida species were isolated in 100 (40%) of cases. Out of 100, C. albican 30 (30%), C. tropicalis 21 (21%), C. parapsillosis 10 (10%), C. parakrusi 8 (8%), C. glabrata 8 (8%), C. krusei 3 (3%) were isolated. In vitro antifungal activity indicated Clotrimazole (MIC 16 and 8 microg/ml) effective against 68 (70%) of Candida SPP, Fluconazole (MIC 64 and 32 microg/ml) effective against 29 (36.2%) and Nystatin disc (100 units) was 51 (63.5%) effective. C. albicans was mainly isolated. Clotrimazole was more effective as compared to Fluconazole and Nystatin. Antifungal susceptibility testing should be determined before therapy to avoid treatment failures.

Alzheimer Classification Using a Minimum Spanning Tree of High-Order Functional Network on fMRI Dataset

PubMed Central

Guo, Hao; Liu, Lei; Chen, Junjie; Xu, Yong; Jie, Xiang

2017-01-01

Functional magnetic resonance imaging (fMRI) is one of the most useful methods to generate functional connectivity networks of the brain. However, conventional network generation methods ignore dynamic changes of functional connectivity between brain regions. Previous studies proposed constructing high-order functional connectivity networks that consider the time-varying characteristics of functional connectivity, and a clustering method was performed to decrease computational cost. However, random selection of the initial clustering centers and the number of clusters negatively affected classification accuracy, and the network lost neurological interpretability. Here we propose a novel method that introduces the minimum spanning tree method to high-order functional connectivity networks. As an unbiased method, the minimum spanning tree simplifies high-order network structure while preserving its core framework. The dynamic characteristics of time series are not lost with this approach, and the neurological interpretation of the network is guaranteed. Simultaneously, we propose a multi-parameter optimization framework that involves extracting discriminative features from the minimum spanning tree high-order functional connectivity networks. Compared with the conventional methods, our resting-state fMRI classification method based on minimum spanning tree high-order functional connectivity networks greatly improved the diagnostic accuracy for Alzheimer's disease. PMID:29249926

Evaluation of Antioxidant Activity and Growth Control Properties of Nonoscale Structure Produced from Aloe vera var. littoralis Extract on Clinical Isolates of Salmonella.

PubMed

Ranjbar, Reza; Arjomandzadegan, Mohammad; Hosseiny, Hossein

2017-07-31

The aim of the study was to examine antibacterial properties of microemulsion structure produced from Aloe vera var. littoralis extract as a new tool of nanoscale drug-like materials. Aloe vera var. littoralis ( A. littoralis ) extract was prepared by distillation method. A nonocarrier structure in the microemulsion system was prepared from the extract. Serial concentrations were prepared from 8 mg/mL extract and the nonocarrier containing 0.1 mg/mL pure extract and were evaluated by a disk diffusion method for 35 Salmonella clinical isolates. Minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) were determined by microbroth dilution assay using MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) method by an enzyme-linked immunosorbent assay(ELISA) Microplate Reader apparatus. Antioxidant activity of the extract was determined by measuring the ferric reducing ability of plasma (FRAP) assay. From 35 clinical isolates of Salmonella , 17 isolates-including resistant isolates of S.E.1103 and S.E.49-had a zone of inhibition (ZI) of 7 to 32 mm in 0.007 mg/mL of the extract. S.E.76 isolate exposed to 30 µg/mL ceftazidime disk had a ZI of 12 mm but had 10 mm in 7µg/mL of A. littoralis extract. The inhibitory effect of a nanocarrier at a concentration of 25 µg/mL by 20 mm ZI was comparable by the ceftazidime (30 µg/mL) effect. MIC 50 was 0.25 mg/mL and MBC 50 was 0.5 mg/mL by MTT method for the extract. It was shown that A.littoralis extract had antioxidant activity of 31.67 µM/mg that could be increased based on concentration. It was concluded that the nanocarrier had a significant effect on the studied isolates in comparison with ordinary antibiotics and had potential for use as a natural antioxidant and antimicrobial material in complementary medicine.

Antimicrobial activity of some essential oils against oral multidrug-resistant Enterococcus faecalis in both planktonic and biofilm state

PubMed Central

Benbelaïd, Fethi; Khadir, Abdelmounaïm; Abdoune, Mohamed Amine; Bendahou, Mourad; Muselli, Alain; Costa, Jean

2014-01-01

Objective To evaluate some essential oils in treatment of intractable oral infections, principally caused by biofilm of multidrug-resistant Enterococcus faecalis (E. faecalis), such as persistent endodontic infections in which their treatment exhibits a real challenge for dentists. Methods Ten chemically analyzed essential oils by gas chromatography-mass spectrometry were evaluated for antimicrobial activity against sensitive and resistant clinical strains of E. faecalis in both planktonic and biofilm state using two methods, disk diffusion and broth micro-dilution. Results Studied essential oils showed a good antimicrobial activity and high ability in E. faecalis biofilm eradication, whether for sensitive or multidrug-resistant strains, especially those of Origanum glandulosum and Thymbra capitata with interesting minimum inhibitory concentration, biofilm inhibitory concentration, and biofilm eradication concentration values which doesn't exceed 0.063%, 0.75%, and 1.5%, respectively. Conclusions Findings of this study indicate that essential oils extracted from aromatic plants can be used in treatment of intractable oral infections, especially caused by biofilm of multidrug-resistant E. faecalis. PMID:25182948

In vitro anti-acne activity of phytoactives from the stem bark of Artocarpus hirsutus Lam. and characterisation of pyranocycloartobiloxanthone A as a mixture of two anomers.

PubMed

Nayak, Mahadeva; Nagarajan, A; Majeed, Muhammed; Nagabhushanam, Kalyanam; Choudhury, Ambar K

2017-08-18

This study is aimed to isolate the phytoactives from the stem bark of Artocarpus hirsutus and evaluate their in vitro anti-acne activity. The ethanolic stem bark extract of A. hirsutus provided two major phytoactive constituents: (i) pyranocycloartobiloxanthone A, (1) and (ii) Artonine E, (2) whose structures were determined by NMR and MS spectroscopic analysis. The present study is the first to report compound 1 as a mixture of two anomers (α and β), approximately 70:30 ratio. Both compounds 1 and 2 were isolated for the first time from this plant. In vitro anti-acne activity of compounds 1 and 2 were evaluated by agar well diffusion method and the minimum inhibition was determined by broth micro dilution method. The result of anti-microbial activity (MIC = 2.0 μg/mL each) is comparable to antibiotic, Clindamycin (MIC = 0.03 μg/mL) and clearly demonstrate their potential as anti-acne agents.

Wetting transitions on patterned surfaces with diffuse interaction potentials embedded in a Young-Laplace formulation

NASA Astrophysics Data System (ADS)

Pashos, G.; Kokkoris, G.; Papathanasiou, A. G.; Boudouvis, A. G.

2016-01-01

The Minimum Energy Paths (MEPs) of wetting transitions on pillared surfaces are computed with the Young-Laplace equation, augmented with a pressure term that accounts for liquid-solid interactions. The interactions are smoothed over a short range from the solid phase, therefore facilitating the numerical solution of problems concerning wetting on complex surface patterns. The patterns may include abrupt geometric features, e.g., arrays of rectangular pillars, where the application of the unmodified Young-Laplace is not practical. The MEPs are obtained by coupling the augmented Young-Laplace with the modified string method from which the energy barriers of wetting transitions are eventually extracted. We demonstrate the method on a wetting transition that is associated with the breakdown of superhydrophobic behavior, i.e., the transition from the Cassie-Baxter state to the Wenzel state, taking place on a superhydrophobic pillared surface. The computed energy barriers quantify the resistance of the system to these transitions and therefore, they can be used to evaluate superhydrophobic performance or provide guidelines for optimal pattern design.

In Vitro Anti-Oxidant and Anti-Microbial Potentiality Investigation of Different Fractions of Caryota urens Leaves

PubMed Central

Azam, Shofiul; Mahmud, Md. Kayes; Naquib, Md. Hamza; Hossain, Saad Mosharraf; Alam, Mohammad Nazmul; Uddin, Md. Josim; Sajid, Irfan; Hossain, Muhammad Sazzad; Karim, Md. Salimul; Hasan, Md. Ali

2016-01-01

Background: Caryota urens is a member of the Arecaceae family and a common plant in the Southeast Asian region. This plant has been reported as an anti-microbial agent in recent years. Thus, we aimed to find out the MIC (minimum inhibitory concentration) against different pathogenic microorganism. Methods: The leaves of C. urens were extracted and fractioned using different reagents (chloroform, n-hexane and carbon tetrachloride). Disc diffusion method was implemented for the assessment of in vitro anti-microbial potency (500 and 250 µg/disc). Result: The entire fraction showed good effect (with the zone of inhibition 19–25 mm) against both gram positive (Bacillus subtilis, Bacillus megaterium, Bacillus cereus, Sarina lutea) and gram negative (Vibrio mimicus, Shigella boydii, Escherichia coli, Pseudomonas aeruginosa) bacterial pathogens and fungal strains (Aspergillus niger, Saccharomyces cerevisiae). The plants also possess effective free radical scavenging potency with an IC50 of 130.32 µg/mL. Conclusion: This finding reflects a link between the presence of anti-oxidative material and a substantial anti-microbial activity, and substantiates all previous claims against C. urens. PMID:28536384

Hyperdynamics boost factor achievable with an ideal bias potential

DOE PAGES

Huang, Chen; Perez, Danny; Voter, Arthur F.

2015-08-20

Hyperdynamics is a powerful method to significantly extend the time scales amenable to molecular dynamics simulation of infrequent events. One outstanding challenge, however, is the development of the so-called bias potential required by the method. In this work, we design a bias potential using information about all minimum energy pathways (MEPs) out of the current state. While this approach is not suitable for use in an actual hyperdynamics simulation, because the pathways are generally not known in advance, it allows us to show that it is possible to come very close to the theoretical boost limit of hyperdynamics while maintainingmore » high accuracy. We demonstrate this by applying this MEP-based hyperdynamics (MEP-HD) to metallic surface diffusion systems. In most cases, MEP-HD gives boost factors that are orders of magnitude larger than the best existing bias potential, indicating that further development of hyperdynamics bias potentials could have a significant payoff. Lastly, we discuss potential practical uses of MEP-HD, including the possibility of developing MEP-HD into a true hyperdynamics.« less

Single-molecule diffusion and conformational dynamics by spatial integration of temporal fluctuations

PubMed Central

Serag, Maged F.; Abadi, Maram; Habuchi, Satoshi

2014-01-01

Single-molecule localization and tracking has been used to translate spatiotemporal information of individual molecules to map their diffusion behaviours. However, accurate analysis of diffusion behaviours and including other parameters, such as the conformation and size of molecules, remain as limitations to the method. Here, we report a method that addresses the limitations of existing single-molecular localization methods. The method is based on temporal tracking of the cumulative area occupied by molecules. These temporal fluctuations are tied to molecular size, rates of diffusion and conformational changes. By analysing fluorescent nanospheres and double-stranded DNA molecules of different lengths and topological forms, we demonstrate that our cumulative-area method surpasses the conventional single-molecule localization method in terms of the accuracy of determined diffusion coefficients. Furthermore, the cumulative-area method provides conformational relaxation times of structurally flexible chains along with diffusion coefficients, which together are relevant to work in a wide spectrum of scientific fields. PMID:25283876

NMR diffusion simulation based on conditional random walk.

PubMed

Gudbjartsson, H; Patz, S

1995-01-01

The authors introduce here a new, very fast, simulation method for free diffusion in a linear magnetic field gradient, which is an extension of the conventional Monte Carlo (MC) method or the convolution method described by Wong et al. (in 12th SMRM, New York, 1993, p.10). In earlier NMR-diffusion simulation methods, such as the finite difference method (FD), the Monte Carlo method, and the deterministic convolution method, the outcome of the calculations depends on the simulation time step. In the authors' method, however, the results are independent of the time step, although, in the convolution method the step size has to be adequate for spins to diffuse to adjacent grid points. By always selecting the largest possible time step the computation time can therefore be reduced. Finally the authors point out that in simple geometric configurations their simulation algorithm can be used to reduce computation time in the simulation of restricted diffusion.

Eucalyptus essential oil as a natural food preservative: in vivo and in vitro antiyeast potential.

PubMed

Tyagi, Amit Kumar; Bukvicki, Danka; Gottardi, Davide; Tabanelli, Giulia; Montanari, Chiara; Malik, Anushree; Guerzoni, Maria Elisabetta

2014-01-01

In this study, the application of eucalyptus essential oil/vapour as beverages preservative is reported. The chemical composition of eucalyptus oil was determined by gas chromatography-mass spectrometry (GC-MS) and solid phase microextraction GC-MS (SPME/GC-MS) analyses. GC-MS revealed that the major constituents were 1,8-cineole (80.5%), limonene (6.5%), α-pinene (5%), and γ-terpinene (2.9%) while SPME/GC-MS showed a relative reduction of 1,8-cineole (63.9%) and an increase of limonene (13.8%), α-pinene (8.87%), and γ-terpinene (3.98%). Antimicrobial potential of essential oil was initially determined in vitro against 8 different food spoilage yeasts by disc diffusion, disc volatilization, and microdilution method. The activity of eucalyptus vapours was significantly higher than the eucalyptus oil. Minimum inhibitory concentration (MIC) and minimum fungicidal concentration (MFC) varied from 0.56 to 4.50 mg/mL and from 1.13 to 9 mg/mL, respectively. Subsequently, the combined efficacy of essential oil and thermal treatment were used to evaluate the preservation of a mixed fruit juice in a time-dependent manner. These results suggest eucalyptus oil as a potent inhibitor of food spoilage yeasts not only in vitro but also in a real food system. Currently, this is the first report that uses eucalyptus essential oil for fruit juice preservation against food spoiling yeast.

Improvement of stability of Nb 3 Sn superconductors by introducing high specific heat substances

DOE PAGES

Xu, X.; Li, P.; Zlobin, A. V.; ...

2018-01-24

High-J c Nb 3Sn conductors have low stability against perturbations, which accounts for the slow training rates of high-field Nb 3Sn magnets. While it is known that adding substances with high specific heat (C) into Nb 3Sn wires can increase their overall specific heat and thus improve their stability, there has not been a practical method that is compatible with the fabrication of long-length conductors. In this work, we put forward a scheme to introduce such substances to distributed-barrier Nb 3Sn wires, which adds minimum difficulty to the wire manufacturing process. Multifilamentary wires using a mixture of Cu and high-Cmore » Gd 2O 3 powders have been successfully fabricated along this line. Measurements showed that addition of Gd 2O 3 had no negative effects on residual resitivity ratio or non-Cu J c, and that flux jumps were remarkably reduced, and minimum quench energy values at 4.2 K, 14 T were increased by a factor of three, indicating that stability was significantly improved. We also discussed the influences of the positioning of high-C substances and their thermal diffusivity on their effectiveness in reducing the superconductor temperature rise against perturbations. Based on these results, we proposed an optimized conductor architecture to maximize the effectiveness of this approach.« less

Improvement of stability of Nb 3 Sn superconductors by introducing high specific heat substances

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

Xu, X.; Li, P.; Zlobin, A. V.

High-J c Nb 3Sn conductors have low stability against perturbations, which accounts for the slow training rates of high-field Nb 3Sn magnets. While it is known that adding substances with high specific heat (C) into Nb 3Sn wires can increase their overall specific heat and thus improve their stability, there has not been a practical method that is compatible with the fabrication of long-length conductors. In this work, we put forward a scheme to introduce such substances to distributed-barrier Nb 3Sn wires, which adds minimum difficulty to the wire manufacturing process. Multifilamentary wires using a mixture of Cu and high-Cmore » Gd 2O 3 powders have been successfully fabricated along this line. Measurements showed that addition of Gd 2O 3 had no negative effects on residual resitivity ratio or non-Cu J c, and that flux jumps were remarkably reduced, and minimum quench energy values at 4.2 K, 14 T were increased by a factor of three, indicating that stability was significantly improved. We also discussed the influences of the positioning of high-C substances and their thermal diffusivity on their effectiveness in reducing the superconductor temperature rise against perturbations. Based on these results, we proposed an optimized conductor architecture to maximize the effectiveness of this approach.« less

Bactericidal activity of herbal volatile oil extracts against multidrug-resistant Acinetobacter baumannii

PubMed Central

Intorasoot, Amornrat; Chornchoem, Piyaorn; Sookkhee, Siriwoot; Intorasoot, Sorasak

2017-01-01

Aim: The aim of the study is to investigate the antibacterial activity of 10 volatile oils extracted from medicinal plants, including galangal (Alpinia galanga Linn.), ginger (Zingiber officinale), plai (Zingiber cassumunar Roxb.), lime (Citrus aurantifolia), kaffir lime (Citrus hystrix DC.), sweet basil (Ocimum basilicum Linn.), tree basil (Ocimum gratissimum), lemongrass (Cymbopogon citratus DC.), clove (Syzygium aromaticum), and cinnamon (Cinnamomum verum) against four standard strains of Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa, Acinetobacter baumannii, and 30 clinical isolates of multidrug-resistant A. baumannii (MDR-A. baumannii). Materials and Methods: Agar diffusion, minimum inhibitory concentration, and minimum bactericidal concentration (MBC) were employed for the determination of bactericidal activity of water distilled medicinal plants. Tea tree oil (Melaleuca alternifolia) was used as positive control in this study. Results: The results indicated the volatile oil extracted from cinnamon exhibited potent antibacterial activity against the most common human pathogens, S. aureus, E. coli, P. aeruginosa, and A. baumannii. Most of volatile oil extracts were less effective against non-fermentative bacteria, P. aeruginosa. In addition, volatile oil extracted from cinnamon, clove, and tree basil possessed potent bactericidal activity against MDR-A. baumannii with MBC90 of 0.5, 1, and 2 mg/mL, respectively. Conclusions: The volatile oil extracts would be useful as alternative natural product for the treatment of the most common human pathogens and MDR-A. baumannii infections. PMID:28512603

Eucalyptus Essential Oil as a Natural Food Preservative: In Vivo and In Vitro Antiyeast Potential

PubMed Central

Bukvicki, Danka; Gottardi, Davide; Malik, Anushree; Guerzoni, Maria Elisabetta

2014-01-01

In this study, the application of eucalyptus essential oil/vapour as beverages preservative is reported. The chemical composition of eucalyptus oil was determined by gas chromatography-mass spectrometry (GC-MS) and solid phase microextraction GC-MS (SPME/GC-MS) analyses. GC-MS revealed that the major constituents were 1,8-cineole (80.5%), limonene (6.5%), α-pinene (5%), and γ-terpinene (2.9%) while SPME/GC-MS showed a relative reduction of 1,8-cineole (63.9%) and an increase of limonene (13.8%), α-pinene (8.87%), and γ-terpinene (3.98%). Antimicrobial potential of essential oil was initially determined in vitro against 8 different food spoilage yeasts by disc diffusion, disc volatilization, and microdilution method. The activity of eucalyptus vapours was significantly higher than the eucalyptus oil. Minimum inhibitory concentration (MIC) and minimum fungicidal concentration (MFC) varied from 0.56 to 4.50 mg/mL and from 1.13 to 9 mg/mL, respectively. Subsequently, the combined efficacy of essential oil and thermal treatment were used to evaluate the preservation of a mixed fruit juice in a time-dependent manner. These results suggest eucalyptus oil as a potent inhibitor of food spoilage yeasts not only in vitro but also in a real food system. Currently, this is the first report that uses eucalyptus essential oil for fruit juice preservation against food spoiling yeast. PMID:25177704

14 CFR 25.149 - Minimum control speed.

Code of Federal Regulations, 2011 CFR

2011-01-01

... 14 Aeronautics and Space 1 2011-01-01 2011-01-01 false Minimum control speed. 25.149 Section 25... Minimum control speed. (a) In establishing the minimum control speeds required by this section, the method... prevent a heading change of more than 20 degrees. (e) VMCG, the minimum control speed on the ground, is...

14 CFR 25.149 - Minimum control speed.

Code of Federal Regulations, 2010 CFR

2010-01-01

... 14 Aeronautics and Space 1 2010-01-01 2010-01-01 false Minimum control speed. 25.149 Section 25... Minimum control speed. (a) In establishing the minimum control speeds required by this section, the method... prevent a heading change of more than 20 degrees. (e) VMCG, the minimum control speed on the ground, is...

The Separation of Blood Components Using Standing Surface Acoustic Waves (SSAWs) Microfluidic Devices: Analysis and Simulation.

PubMed

Soliman, Ahmed M; Eldosoky, Mohamed A; Taha, Taha E

2017-03-29

The separation of blood components (WBCs, RBCs, and platelets) is important for medical applications. Recently, standing surface acoustic wave (SSAW) microfluidic devices are used for the separation of particles. In this paper, the design analysis of SSAW microfluidics is presented. Also, the analysis of SSAW force with Rayleigh angle effect and its attenuation in liquid-loaded substrate, viscous drag force, hydrodynamic force, and diffusion force are explained and analyzed. The analyses are provided for selecting the piezoelectric material, width of the main microchannel, working area of SAW, wavelength, minimum input power required for the separation process, and widths of outlet collecting microchannels. The design analysis of SSAW microfluidics is provided for determining the minimum input power required for the separation process with appropriated the displacement contrast of the particles.The analyses are applied for simulation the separation of blood components. The piezoelectric material, width of the main microchannel, working area of SAW, wavelength, and minimum input power required for the separation process are selected as LiNbO₃, 120 μm, 1.08 mm², 300 μm, 371 mW. The results are compared to other published results. The results of these simulations achieve minimum power consumption, less complicated setup, and high collecting efficiency. All simulation programs are built by MATLAB.

The Separation of Blood Components Using Standing Surface Acoustic Waves (SSAWs) Microfluidic Devices: Analysis and Simulation

PubMed Central

Soliman, Ahmed M.; Eldosoky, Mohamed A.; Taha, Taha E.

2017-01-01

The separation of blood components (WBCs, RBCs, and platelets) is important for medical applications. Recently, standing surface acoustic wave (SSAW) microfluidic devices are used for the separation of particles. In this paper, the design analysis of SSAW microfluidics is presented. Also, the analysis of SSAW force with Rayleigh angle effect and its attenuation in liquid-loaded substrate, viscous drag force, hydrodynamic force, and diffusion force are explained and analyzed. The analyses are provided for selecting the piezoelectric material, width of the main microchannel, working area of SAW, wavelength, minimum input power required for the separation process, and widths of outlet collecting microchannels. The design analysis of SSAW microfluidics is provided for determining the minimum input power required for the separation process with appropriated the displacement contrast of the particles.The analyses are applied for simulation the separation of blood components. The piezoelectric material, width of the main microchannel, working area of SAW, wavelength, and minimum input power required for the separation process are selected as LiNbO3, 120 μm, 1.08 mm2, 300 μm, 371 mW. The results are compared to other published results. The results of these simulations achieve minimum power consumption, less complicated setup, and high collecting efficiency. All simulation programs are built by MATLAB. PMID:28952506

Molecular diffusion of stable water isotopes in polar firn as a proxy for past temperatures

NASA Astrophysics Data System (ADS)

Holme, Christian; Gkinis, Vasileios; Vinther, Bo M.

2018-03-01

Polar precipitation archived in ice caps contains information on past temperature conditions. Such information can be retrieved by measuring the water isotopic signals of δ18O and δD in ice cores. These signals have been attenuated during densification due to molecular diffusion in the firn column, where the magnitude of the diffusion is isotopologue specific and temperature dependent. By utilizing the differential diffusion signal, dual isotope measurements of δ18O and δD enable multiple temperature reconstruction techniques. This study assesses how well six different methods can be used to reconstruct past surface temperatures from the diffusion-based temperature proxies. Two of the methods are based on the single diffusion lengths of δ18O and δD , three of the methods employ the differential diffusion signal, while the last uses the ratio between the single diffusion lengths. All techniques are tested on synthetic data in order to evaluate their accuracy and precision. We perform a benchmark test to thirteen high resolution Holocene data sets from Greenland and Antarctica, which represent a broad range of mean annual surface temperatures and accumulation rates. Based on the benchmark test, we comment on the accuracy and precision of the methods. Both the benchmark test and the synthetic data test demonstrate that the most precise reconstructions are obtained when using the single isotope diffusion lengths, with precisions of approximately 1.0 °C . In the benchmark test, the single isotope diffusion lengths are also found to reconstruct consistent temperatures with a root-mean-square-deviation of 0.7 °C . The techniques employing the differential diffusion signals are more uncertain, where the most precise method has a precision of 1.9 °C . The diffusion length ratio method is the least precise with a precision of 13.7 °C . The absolute temperature estimates from this method are also shown to be highly sensitive to the choice of fractionation factor parameterization.

Investigation of diffusion length distribution on polycrystalline silicon wafers via photoluminescence methods

PubMed Central

Lou, Shishu; Zhu, Huishi; Hu, Shaoxu; Zhao, Chunhua; Han, Peide

2015-01-01

Characterization of the diffusion length of solar cells in space has been widely studied using various methods, but few studies have focused on a fast, simple way to obtain the quantified diffusion length distribution on a silicon wafer. In this work, we present two different facile methods of doing this by fitting photoluminescence images taken in two different wavelength ranges or from different sides. These methods, which are based on measuring the ratio of two photoluminescence images, yield absolute values of the diffusion length and are less sensitive to the inhomogeneity of the incident laser beam. A theoretical simulation and experimental demonstration of this method are presented. The diffusion length distributions on a polycrystalline silicon wafer obtained by the two methods show good agreement. PMID:26364565

Sparse and Adaptive Diffusion Dictionary (SADD) for recovering intra-voxel white matter structure.

PubMed

Aranda, Ramon; Ramirez-Manzanares, Alonso; Rivera, Mariano

2015-12-01

On the analysis of the Diffusion-Weighted Magnetic Resonance Images, multi-compartment models overcome the limitations of the well-known Diffusion Tensor model for fitting in vivo brain axonal orientations at voxels with fiber crossings, branching, kissing or bifurcations. Some successful multi-compartment methods are based on diffusion dictionaries. The diffusion dictionary-based methods assume that the observed Magnetic Resonance signal at each voxel is a linear combination of the fixed dictionary elements (dictionary atoms). The atoms are fixed along different orientations and diffusivity profiles. In this work, we present a sparse and adaptive diffusion dictionary method based on the Diffusion Basis Functions Model to estimate in vivo brain axonal fiber populations. Our proposal overcomes the following limitations of the diffusion dictionary-based methods: the limited angular resolution and the fixed shapes for the atom set. We propose to iteratively re-estimate the orientations and the diffusivity profile of the atoms independently at each voxel by using a simplified and easier-to-solve mathematical approach. As a result, we improve the fitting of the Diffusion-Weighted Magnetic Resonance signal. The advantages with respect to the former Diffusion Basis Functions method are demonstrated on the synthetic data-set used on the 2012 HARDI Reconstruction Challenge and in vivo human data. We demonstrate that improvements obtained in the intra-voxel fiber structure estimations benefit brain research allowing to obtain better tractography estimations. Hence, these improvements result in an accurate computation of the brain connectivity patterns. Copyright © 2015 Elsevier B.V. All rights reserved.

An Analysis of a Finite Element Method for Convection-Diffusion Problems. Part II. A Posteriori Error Estimates and Adaptivity.

DTIC Science & Technology

1983-03-01

AN ANALYSIS OF A FINITE ELEMENT METHOD FOR CONVECTION- DIFFUSION PROBLEMS PART II: A POSTERIORI ERROR ESTIMATES AND ADAPTIVITY by W. G. Szymczak Y 6a...PERIOD COVERED AN ANALYSIS OF A FINITE ELEMENT METHOD FOR final life of the contract CONVECTION- DIFFUSION PROBLEM S. Part II: A POSTERIORI ERROR ...Element Method for Convection- Diffusion Problems. Part II: A Posteriori Error Estimates and Adaptivity W. G. Szvmczak and I. Babu~ka# Laboratory for

A simplified counter diffusion method combined with a 1D simulation program for optimizing crystallization conditions.

PubMed

Tanaka, Hiroaki; Inaka, Koji; Sugiyama, Shigeru; Takahashi, Sachiko; Sano, Satoshi; Sato, Masaru; Yoshitomi, Susumu

2004-01-01

We developed a new protein crystallization method has been developed using a simplified counter-diffusion method for optimizing crystallization condition. It is composed of only a single capillary, the gel in the silicon tube and the screw-top test tube, which are readily available in the laboratory. The one capillary can continuously scan a wide range of crystallization conditions (combination of the concentrations of the precipitant and the protein) unless crystallization occurs, which means that it corresponds to many drops in the vapor-diffusion method. The amount of the precipitant and the protein solutions can be much less than in conventional methods. In this study, lysozyme and alpha-amylase were used as model proteins for demonstrating the efficiency of this method. In addition, one-dimensional (1-D) simulations of the crystal growth were performed based on the 1-D diffusion model. The optimized conditions can be applied to the initial crystallization conditions for both other counter-diffusion methods with the Granada Crystallization Box (GCB) and for the vapor-diffusion method after some modification.

Edge-based nonlinear diffusion for finite element approximations of convection-diffusion equations and its relation to algebraic flux-correction schemes.

PubMed

Barrenechea, Gabriel R; Burman, Erik; Karakatsani, Fotini

2017-01-01

For the case of approximation of convection-diffusion equations using piecewise affine continuous finite elements a new edge-based nonlinear diffusion operator is proposed that makes the scheme satisfy a discrete maximum principle. The diffusion operator is shown to be Lipschitz continuous and linearity preserving. Using these properties we provide a full stability and error analysis, which, in the diffusion dominated regime, shows existence, uniqueness and optimal convergence. Then the algebraic flux correction method is recalled and we show that the present method can be interpreted as an algebraic flux correction method for a particular definition of the flux limiters. The performance of the method is illustrated on some numerical test cases in two space dimensions.

Reactive Power Compensation Method Considering Minimum Effective Reactive Power Reserve

NASA Astrophysics Data System (ADS)

Gong, Yiyu; Zhang, Kai; Pu, Zhang; Li, Xuenan; Zuo, Xianghong; Zhen, Jiao; Sudan, Teng

2017-05-01

According to the calculation model of minimum generator reactive power reserve of power system voltage stability under the premise of the guarantee, the reactive power management system with reactive power compensation combined generator, the formation of a multi-objective optimization problem, propose a reactive power reserve is considered the minimum generator reactive power compensation optimization method. This method through the improvement of the objective function and constraint conditions, when the system load growth, relying solely on reactive power generation system can not meet the requirement of safe operation, increase the reactive power reserve to solve the problem of minimum generator reactive power compensation in the case of load node.

Comparison of Diffusion MRI Acquisition Protocols for the In Vivo Characterization of the Mouse Spinal Cord: Variability Analysis and Application to an Amyotrophic Lateral Sclerosis Model

PubMed Central

Marcuzzo, Stefania; Bonanno, Silvia; Padelli, Francesco; Moreno-Manzano, Victoria; García-Verdugo, José Manuel; Bernasconi, Pia; Mantegazza, Renato; Bruzzone, Maria Grazia; Zucca, Ileana

2016-01-01

Diffusion-weighted Magnetic Resonance Imaging (dMRI) has relevant applications in the microstructural characterization of the spinal cord, especially in neurodegenerative diseases. Animal models have a pivotal role in the study of such diseases; however, in vivo spinal dMRI of small animals entails additional challenges that require a systematical investigation of acquisition parameters. The purpose of this study is to compare three acquisition protocols and identify the scanning parameters allowing a robust estimation of the main diffusion quantities and a good sensitivity to neurodegeneration in the mouse spinal cord. For all the protocols, the signal-to-noise and contrast-to noise ratios and the mean value and variability of Diffusion Tensor metrics were evaluated in healthy controls. For the estimation of fractional anisotropy less variability was provided by protocols with more diffusion directions, for the estimation of mean, axial and radial diffusivity by protocols with fewer diffusion directions and higher diffusion weighting. Intermediate features (12 directions, b = 1200 s/mm2) provided the overall minimum inter- and intra-subject variability in most cases. In order to test the diagnostic sensitivity of the protocols, 7 G93A-SOD1 mice (model of amyotrophic lateral sclerosis) at 10 and 17 weeks of age were scanned and the derived diffusion parameters compared with those estimated in age-matched healthy animals. The protocols with an intermediate or high number of diffusion directions provided the best differentiation between the two groups at week 17, whereas only few local significant differences were highlighted at week 10. According to our results, a dMRI protocol with an intermediate number of diffusion gradient directions and a relatively high diffusion weighting is optimal for spinal cord imaging. Further work is needed to confirm these results and for a finer tuning of acquisition parameters. Nevertheless, our findings could be important for the optimization of acquisition protocols for preclinical and clinical dMRI studies on the spinal cord. PMID:27560686

Classification of Dynamical Diffusion States in Single Molecule Tracking Microscopy

PubMed Central

Bosch, Peter J.; Kanger, Johannes S.; Subramaniam, Vinod

2014-01-01

Single molecule tracking of membrane proteins by fluorescence microscopy is a promising method to investigate dynamic processes in live cells. Translating the trajectories of proteins to biological implications, such as protein interactions, requires the classification of protein motion within the trajectories. Spatial information of protein motion may reveal where the protein interacts with cellular structures, because binding of proteins to such structures often alters their diffusion speed. For dynamic diffusion systems, we provide an analytical framework to determine in which diffusion state a molecule is residing during the course of its trajectory. We compare different methods for the quantification of motion to utilize this framework for the classification of two diffusion states (two populations with different diffusion speed). We found that a gyration quantification method and a Bayesian statistics-based method are the most accurate in diffusion-state classification for realistic experimentally obtained datasets, of which the gyration method is much less computationally demanding. After classification of the diffusion, the lifetime of the states can be determined, and images of the diffusion states can be reconstructed at high resolution. Simulations validate these applications. We apply the classification and its applications to experimental data to demonstrate the potential of this approach to obtain further insights into the dynamics of cell membrane proteins. PMID:25099798

CFD simulation of fluid dynamic and biokinetic processes within activated sludge reactors under intermittent aeration regime.

PubMed

Sánchez, F; Rey, H; Viedma, A; Nicolás-Pérez, F; Kaiser, A S; Martínez, M

2018-08-01

Due to the aeration system, biological reactors are the most energy-consuming facilities of convectional WWTPs. Many biological reactors work under intermittent aeration regime; the optimization of the aeration process (air diffuser layout, air flow rate per diffuser, aeration length …) is necessary to ensure an efficient performance; satisfying the effluent requirements with the minimum energy consumption. This work develops a CFD modelling of an activated sludge reactor (ASR) which works under intermittent aeration regime. The model considers the fluid dynamic and biological processes within the ASR. The biological simulation, which is transient, takes into account the intermittent aeration regime. The CFD modelling is employed for the selection of the aeration system of an ASR. Two different aeration configurations are simulated. The model evaluates the aeration power consumption necessary to satisfy the effluent requirements. An improvement of 2.8% in terms of energy consumption is achieved by modifying the air diffuser layout. An analysis of the influence of the air flow rate per diffuser on the ASR performance is carried out. The results show a reduction of 14.5% in the energy consumption of the aeration system when the air flow rate per diffuser is reduced. The model provides an insight into the aeration inefficiencies produced within ASRs. Copyright © 2018 Elsevier Ltd. All rights reserved.

Evaluation of the direct and diffusion methods for the determination of fluoride content in table salt

PubMed Central

Martínez-Mier, E. Angeles; Soto-Rojas, Armando E.; Buckley, Christine M.; Margineda, Jorge; Zero, Domenick T.

2010-01-01

Objective The aim of this study was to assess methods currently used for analyzing fluoridated salt in order to identify the most useful method for this type of analysis. Basic research design Seventy-five fluoridated salt samples were obtained. Samples were analyzed for fluoride content, with and without pretreatment, using direct and diffusion methods. Element analysis was also conducted in selected samples. Fluoride was added to ultra pure NaCl and non-fluoridated commercial salt samples and Ca and Mg were added to fluoride samples in order to assess fluoride recoveries using modifications to the methods. Results Larger amounts of fluoride were found and recovered using diffusion than direct methods (96%–100% for diffusion vs. 67%–90% for direct). Statistically significant differences were obtained between direct and diffusion methods using different ion strength adjusters. Pretreatment methods reduced the amount of recovered fluoride. Determination of fluoride content was influenced both by the presence of NaCl and other ions in the salt. Conclusion Direct and diffusion techniques for analysis of fluoridated salt are suitable methods for fluoride analysis. The choice of method should depend on the purpose of the analysis. PMID:20088217

Probabilistic migration modelling focused on functional barrier efficiency and low migration concepts in support of risk assessment.

PubMed

Brandsch, Rainer

2017-10-01

Migration modelling provides reliable migration estimates from food-contact materials (FCM) to food or food simulants based on mass-transfer parameters like diffusion and partition coefficients related to individual materials. In most cases, mass-transfer parameters are not readily available from the literature and for this reason are estimated with a given uncertainty. Historically, uncertainty was accounted for by introducing upper limit concepts first, turning out to be of limited applicability due to highly overestimated migration results. Probabilistic migration modelling gives the possibility to consider uncertainty of the mass-transfer parameters as well as other model inputs. With respect to a functional barrier, the most important parameters among others are the diffusion properties of the functional barrier and its thickness. A software tool that accepts distribution as inputs and is capable of applying Monte Carlo methods, i.e., random sampling from the input distributions of the relevant parameters (i.e., diffusion coefficient and layer thickness), predicts migration results with related uncertainty and confidence intervals. The capabilities of probabilistic migration modelling are presented in the view of three case studies (1) sensitivity analysis, (2) functional barrier efficiency and (3) validation by experimental testing. Based on the predicted migration by probabilistic migration modelling and related exposure estimates, safety evaluation of new materials in the context of existing or new packaging concepts is possible. Identifying associated migration risk and potential safety concerns in the early stage of packaging development is possible. Furthermore, dedicated material selection exhibiting required functional barrier efficiency under application conditions becomes feasible. Validation of the migration risk assessment by probabilistic migration modelling through a minimum of dedicated experimental testing is strongly recommended.

Enhanced diffusometric immunosensing with grafted gold nanoparticles for detection of diabetic retinopathy biomarker tumor necrosis factor-α.

PubMed

Chuang, Han-Sheng; Chen, Yu-Ju; Cheng, Hui-Pin

2018-03-15

Diffusometry is sensitive to geometric changes of particles. Target antigens can be detected through diffusivity changes resulting from their immunoreactions by functionalizing particle surface with a specific antibody. Considering that Brownian motion is a self-driven phenomenon, diffusometric immunosensing features several characteristics, such as no-washing steps, rapid detection, high flexibility, and high sensitivity. Until recently, this technique has been applied to many biomedical fields, such as monitoring of microorganism motility and diagnosis of diseases with biomarkers. Despite the abovementioned advantages, diffusivity changes in conventional diffusometry can be compromised at low-abundance antigens because proteins are much smaller than capture particles. To overcome such restriction, we present an improved diffusometric immunosensing technique by grafting additional gold nanoparticles (AuNPs) to capture particles to enhance size changes. A diabetic retinopathy (DR) biomarker, tumor necrosis factor-α was selected to evaluate the proposed immunosensing technique. Spherical AuNPs showed better enhancement than rod-like AuNPs during measurement. Limit of detection was improved by at least 100-fold down to 10pg/mL. A dichotomous method was also developed to enable rapid detection and avoid tedious calibration. The relationship of concentrations between the two solutions used can be explicitly determined by comparing diffusivity of an unknown concentration of target molecules with that of a reference solution. Minimum discernible concentration reached as low as twofold higher or lower than basal concentration. Tear samples were collected from four volunteers, including three healthy subjects and one proliferative DR patient to prove the concept in diagnosis of the disease. All data showed good agreement with preset conditions. The technique eventually provides an insight into rapid diagnoses of diseases in the early stage. Copyright © 2017 Elsevier B.V. All rights reserved.

A computational model of amoeboid cell swimming

NASA Astrophysics Data System (ADS)

Campbell, Eric J.; Bagchi, Prosenjit

2017-10-01

Amoeboid cells propel by generating pseudopods that are finger-like protrusions of the cell body that continually grow, bifurcate, and retract. Pseudopod-driven motility of amoeboid cells represents a complex and multiscale process that involves bio-molecular reactions, cell deformation, and cytoplasmic and extracellular fluid motion. Here we present a 3D model of pseudopod-driven swimming of an amoeba suspended in a fluid without any adhesion and in the absence of any chemoattractant. Our model is based on front-tracking/immersed-boundary methods, and it combines large deformation of the cell, a coarse-grain model for molecular reactions, and cytoplasmic and extracellular fluid flow. The predicted shapes of the swimming cell from our model show similarity with experimental observations. We predict that the swimming behavior changes from random-like to persistent unidirectional motion, and that the swimming speed increases, with increasing cell deformability and protein diffusivity. The unidirectionality in cell swimming is observed without any external cues and as a direct result of a change in pseudopod dynamics. We find that pseudopods become preferentially focused near the front of the cell and appear in greater numbers with increasing cell deformability and protein diffusivity, thereby increasing the swimming speed and making the cell shape more elongated. We find that the swimming speed is minimum when the cytoplasm viscosity is close to the extracellular fluid viscosity. We further find that the speed increases significantly as the cytoplasm becomes less viscous compared with the extracellular fluid, resembling the viscous fingering phenomenon observed in interfacial flows. While these results support the notion that softer cells migrate more aggressively, they also suggest a strong coupling between membrane elasticity, membrane protein diffusivity, and fluid viscosity.

Image Halftoning Using Optimized Dot Diffusion

DTIC Science & Technology

1998-01-01

ppvnath@sys.caltech.edu ABSTRACT The dot diffusion method for digital halftoning has the advantage of parallelism unlike the error diffusion ...digital halftoning : ordered dither [1], error diffusion [2], neural-net based methods [8], and more recently direct binary search (DBS) [7]. Ordered...from periodic patterns. On the other hand error diffused halftones do not suffer from periodicity and offer blue noise characteristic [3] which is

The diffusive finite state projection algorithm for efficient simulation of the stochastic reaction-diffusion master equation.

PubMed

Drawert, Brian; Lawson, Michael J; Petzold, Linda; Khammash, Mustafa

2010-02-21

We have developed a computational framework for accurate and efficient simulation of stochastic spatially inhomogeneous biochemical systems. The new computational method employs a fractional step hybrid strategy. A novel formulation of the finite state projection (FSP) method, called the diffusive FSP method, is introduced for the efficient and accurate simulation of diffusive transport. Reactions are handled by the stochastic simulation algorithm.

Application of principal component analysis to distinguish patients with schizophrenia from healthy controls based on fractional anisotropy measurements.

PubMed

Caprihan, A; Pearlson, G D; Calhoun, V D

2008-08-15

Principal component analysis (PCA) is often used to reduce the dimension of data before applying more sophisticated data analysis methods such as non-linear classification algorithms or independent component analysis. This practice is based on selecting components corresponding to the largest eigenvalues. If the ultimate goal is separation of data in two groups, then these set of components need not have the most discriminatory power. We measured the distance between two such populations using Mahalanobis distance and chose the eigenvectors to maximize it, a modified PCA method, which we call the discriminant PCA (DPCA). DPCA was applied to diffusion tensor-based fractional anisotropy images to distinguish age-matched schizophrenia subjects from healthy controls. The performance of the proposed method was evaluated by the one-leave-out method. We show that for this fractional anisotropy data set, the classification error with 60 components was close to the minimum error and that the Mahalanobis distance was twice as large with DPCA, than with PCA. Finally, by masking the discriminant function with the white matter tracts of the Johns Hopkins University atlas, we identified left superior longitudinal fasciculus as the tract which gave the least classification error. In addition, with six optimally chosen tracts the classification error was zero.

Irreversibility and entropy production in transport phenomena, III—Principle of minimum integrated entropy production including nonlinear responses

NASA Astrophysics Data System (ADS)

Suzuki, Masuo

2013-01-01

A new variational principle of steady states is found by introducing an integrated type of energy dissipation (or entropy production) instead of instantaneous energy dissipation. This new principle is valid both in linear and nonlinear transport phenomena. Prigogine’s dream has now been realized by this new general principle of minimum “integrated” entropy production (or energy dissipation). This new principle does not contradict with the Onsager-Prigogine principle of minimum instantaneous entropy production in the linear regime, but it is conceptually different from the latter which does not hold in the nonlinear regime. Applications of this theory to electric conduction, heat conduction, particle diffusion and chemical reactions are presented. The irreversibility (or positive entropy production) and long time tail problem in Kubo’s formula are also discussed in the Introduction and last section. This constitutes the complementary explanation of our theory of entropy production given in the previous papers (M. Suzuki, Physica A 390 (2011) 1904 and M. Suzuki, Physica A 391 (2012) 1074) and has given the motivation of the present investigation of variational principle.

The drift-diffusion interpretation of the electron current within the organic semiconductor characterized by the bulk single energy trap level

NASA Astrophysics Data System (ADS)

Cvikl, B.

2010-01-01

The closed solution for the internal electric field and the total charge density derived in the drift-diffusion approximation for the model of a single layer organic semiconductor structure characterized by the bulk shallow single trap-charge energy level is presented. The solutions for two examples of electric field boundary conditions are tested on room temperature current density-voltage data of the electron conducting aluminum/tris(8-hydroxyquinoline aluminum/calcium structure [W. Brütting et al., Synth. Met. 122, 99 (2001)] for which jexp∝Va3.4, within the interval of bias 0.4 V≤Va≤7. In each case investigated the apparent electron mobility determined at given bias is distributed within a given, finite interval of values. The bias dependence of the logarithm of their lower limit, i.e., their minimum values, is found to be in each case, to a good approximation, proportional to the square root of the applied electric field. On account of the bias dependence as incorporated in the minimum value of the apparent electron mobility the spatial distribution of the organic bulk electric field as well as the total charge density turn out to be bias independent. The first case investigated is based on the boundary condition of zero electric field at the electron injection interface. It is shown that for minimum valued apparent mobilities, the strong but finite accumulation of electrons close to the anode is obtained, which characterize the inverted space charge limited current (SCLC) effect. The second example refers to the internal electric field allowing for self-adjustment of its boundary values. The total electron charge density is than found typically to be of U shape, which may, depending on the parameters, peak at both or at either Alq3 boundary. It is this example in which the proper SCLC effect is consequently predicted. In each of the above two cases, the calculations predict the minimum values of the electron apparent mobility, which substantially exceed the corresponding published measurements. For this reason the effect of the drift term alone is additionally investigated. On the basis of the published empirical electron mobilities and the diffusion term revoked, it is shown that the steady state electron current density within the Al/Alq3 (97 nm)/Ca single layer organic structure may well be pictured within the drift-only interpretation of the charge carriers within the Alq3 organic characterized by the single (shallow) trap energy level. In order to arrive at this result, it is necessary that the nonzero electric field, calculated to exist at the electron injecting Alq3/Ca boundary, is to be appropriately accounted for in the computation.

A hybrid continuous-discrete method for stochastic reaction-diffusion processes.

PubMed

Lo, Wing-Cheong; Zheng, Likun; Nie, Qing

2016-09-01

Stochastic fluctuations in reaction-diffusion processes often have substantial effect on spatial and temporal dynamics of signal transductions in complex biological systems. One popular approach for simulating these processes is to divide the system into small spatial compartments assuming that molecules react only within the same compartment and jump between adjacent compartments driven by the diffusion. While the approach is convenient in terms of its implementation, its computational cost may become prohibitive when diffusive jumps occur significantly more frequently than reactions, as in the case of rapid diffusion. Here, we present a hybrid continuous-discrete method in which diffusion is simulated using continuous approximation while reactions are based on the Gillespie algorithm. Specifically, the diffusive jumps are approximated as continuous Gaussian random vectors with time-dependent means and covariances, allowing use of a large time step, even for rapid diffusion. By considering the correlation among diffusive jumps, the approximation is accurate for the second moment of the diffusion process. In addition, a criterion is obtained for identifying the region in which such diffusion approximation is required to enable adaptive calculations for better accuracy. Applications to a linear diffusion system and two nonlinear systems of morphogens demonstrate the effectiveness and benefits of the new hybrid method.

Superresolution SAR Imaging Algorithm Based on Mvm and Weighted Norm Extrapolation

NASA Astrophysics Data System (ADS)

Zhang, P.; Chen, Q.; Li, Z.; Tang, Z.; Liu, J.; Zhao, L.

2013-08-01

In this paper, we present an extrapolation approach, which uses minimum weighted norm constraint and minimum variance spectrum estimation, for improving synthetic aperture radar (SAR) resolution. Minimum variance method is a robust high resolution method to estimate spectrum. Based on the theory of SAR imaging, the signal model of SAR imagery is analyzed to be feasible for using data extrapolation methods to improve the resolution of SAR image. The method is used to extrapolate the efficient bandwidth in phase history field and better results are obtained compared with adaptive weighted norm extrapolation (AWNE) method and traditional imaging method using simulated data and actual measured data.

An improved method to estimate reflectance parameters for high dynamic range imaging

NASA Astrophysics Data System (ADS)

Li, Shiying; Deguchi, Koichiro; Li, Renfa; Manabe, Yoshitsugu; Chihara, Kunihiro

2008-01-01

Two methods are described to accurately estimate diffuse and specular reflectance parameters for colors, gloss intensity and surface roughness, over the dynamic range of the camera used to capture input images. Neither method needs to segment color areas on an image, or to reconstruct a high dynamic range (HDR) image. The second method improves on the first, bypassing the requirement for specific separation of diffuse and specular reflection components. For the latter method, diffuse and specular reflectance parameters are estimated separately, using the least squares method. Reflection values are initially assumed to be diffuse-only reflection components, and are subjected to the least squares method to estimate diffuse reflectance parameters. Specular reflection components, obtained by subtracting the computed diffuse reflection components from reflection values, are then subjected to a logarithmically transformed equation of the Torrance-Sparrow reflection model, and specular reflectance parameters for gloss intensity and surface roughness are finally estimated using the least squares method. Experiments were carried out using both methods, with simulation data at different saturation levels, generated according to the Lambert and Torrance-Sparrow reflection models, and the second method, with spectral images captured by an imaging spectrograph and a moving light source. Our results show that the second method can estimate the diffuse and specular reflectance parameters for colors, gloss intensity and surface roughness more accurately and faster than the first one, so that colors and gloss can be reproduced more efficiently for HDR imaging.

Setting Standards for Minimum Competency Tests.

ERIC Educational Resources Information Center

Mehrens, William A.

Some general questions about minimum competency tests are discussed, and various methods of setting standards are reviewed with major attention devoted to those methods used for dichotomizing a continuum. Methods reviewed under the heading of Absolute Judgments of Test Content include Nedelsky's, Angoff's, Ebel's, and Jaeger's. These methods are…

Diffusion Monte Carlo studies of MB-pol (H{sub 2}O){sub 2−6} and (D{sub 2}O){sub 2−6} clusters: Structures and binding energies

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

Mallory, Joel D.; Mandelshtam, Vladimir A.

2016-08-14

We employ the diffusion Monte Carlo (DMC) method in conjunction with the recently developed, ab initio-based MB-pol potential energy surface to characterize the ground states of small (H{sub 2}O){sub 2−6} clusters and their deuterated isotopomers. Observables, other than the ground state energies, are computed using the descendant weighting approach. Among those are various spatial correlation functions and relative isomer fractions. Interestingly, the ground states of all clusters considered in this study, except for the dimer, are delocalized over at least two conformations that differ by the orientation of one or more water monomers with the relative isomer populations being sensitivemore » to the isotope substitution. Most remarkably, the ground state of the (H{sub 2}O){sub 6} hexamer is represented by four distinct cage structures, while that of (D{sub 2}O){sub 6} is dominated by the prism, i.e., the global minimum geometry, with a very small contribution from a prism-book geometry. In addition, for (H{sub 2}O){sub 6} and (D{sub 2}O){sub 6}, we performed DMC calculations to compute the ground states constrained to the cage and prism geometries. These calculations compared results for three different potentials, MB-pol, TTM3/F, and q-TIP4P/F.« less

Measurement of effective bulk and contact resistance of gas diffusion layer under inhomogeneous compression - Part II: Thermal conductivity

NASA Astrophysics Data System (ADS)

Roy Chowdhury, Prabudhya; Vikram, Ajit; Phillips, Ryan K.; Hoorfar, Mina

2016-07-01

The gas diffusion layer (GDL) is a thin porous layer sandwiched between a bipolar plate (BPP) and a catalyst coated membrane in a fuel cell. Besides providing passage for water and gas transport from and to the catalyst layer, it is responsible for electron and heat transfer from and to the BPP. In this paper, a method has been developed to measure the GDL bulk thermal conductivity and the contact resistance at the GDL/BPP interface under inhomogeneous compression occurring in an actual fuel cell assembly. Toray carbon paper GDL TGP-H-060 was tested under a range of compression pressure of 0.34 to 1.71 MPa. The results showed that the thermal contact resistance decreases non-linearly (from 3.8 × 10-4 to 1.17 × 10-4 Km2 W-1) with increasing pressure due to increase in microscopic contact area between the GDL and BPP; while the effective bulk thermal conductivity increases (from 0.56 to 1.42 Wm-1 K-1) with increasing the compression pressure. The thermal contact resistance was found to be greater (by a factor of 1.6-2.8) than the effective bulk thermal resistance for all compression pressure ranges applied here. This measurement technique can be used to identify optimum GDL based on minimum bulk and contact resistances measured under inhomogeneous compression.

Modeling Fecal Indicator Bacteria Like Salt in Newport Bay

NASA Astrophysics Data System (ADS)

Ciglar, A. M.; Rippy, M.; Grant, S. B.

2015-12-01

Newport Bay is a harbor and estuary located in Orange County, CA that provides many water sports and recreational activities for millions of southern California residents and tourists. The aim of this study is to quickly assess exceedances of FIB in the Newport Bay which pose a health risk to recreational users. The ability to quickly assess water quality is made possible with an advection-diffusion mass transport model that uses easily measurable parameters such as volumetric flow rate from tributaries. Current FIB assessment methods for Newport Bay take a minimum of 24 hours to evaluate health risk by either culturing for FIB or running a more complex fluid dynamics model. By this time the FIB may have already reached the ocean outlet thus no longer posing a risk in the bay or recreationists may have already come in close contact with contaminated waters. The advection-diffusion model can process and disseminate health risk information within a few hours of flow rate measurements, minimizing time between an FIB exceedance and public awareness about the event. Data used to calibrate and validate the model was collected from January 2006 through February 2007. Salinity data was used for calibration and FIB data was used for validation. Both steady-state and transient conditions were assessed to determine if dry weather patterns can be simplified to the steady-state condition.

Prevalence of Methicillin-Resistant and Methicillin-Susceptible S. Aureusin the Saliva of Health Professionals

PubMed Central

de Carvalho, Milton Jorge; Pimenta, Fabiana Cristina; Hayashida, Miyeko; Gir, Elucir; da Silva, Adriana Maria; Barbosa, Caio Parente; da Silva Canini, Silvia Rita Marin; Santiago, Silvana

2009-01-01

INTRODUCTION: S. aureus is one of the main agents of nosocomial infection and is sometimes difficult to treat with currently available active antimicrobials. PURPOSE: To analyze the prevalence of methicillin-susceptible S.aureus (MSSA) and methicillin-resistant S. aureus (MRSA) as well as the MRSA antimicrobial susceptibility profile isolated in the saliva of health professionals at a large public education hospital. MATERIALS AND METHODS: The project was approved by the research and ethics committee of the institution under study. Three samples of saliva from 340 health professionals were collected. The saliva analysis used to identify S. aureus was based on mannitol fermentation tests, catalase production, coagulase, DNAse, and lecithinase. In order to detect MRSA, samples were submitted to the disk diffusion test and the oxacillin agar screening test. In order to identify the minimum inhibitory concentration, the Etest® technique was used. RESULTS: The prevalence of MSSA was 43.5% (148/340), and MRSA was 4.1% (14/340). MRSA detected by the diffusion disk test, was 100% resistant to penicillin and oxacillin, 92.9% resistant to erythromycin, 57.1% resistant to clindamycin, 42.9% resistant to ciprofloxacin and 57.1% resistant to cefoxetin. CONCLUSION: This subject is important for both the education of health professionals and for preventative measures. Standard and contact-precautions should be employed in professional practice. PMID:19488585

Instrumentation in Diffuse Optical Imaging

PubMed Central

Zhang, Xiaofeng

2014-01-01

Diffuse optical imaging is highly versatile and has a very broad range of applications in biology and medicine. It covers diffuse optical tomography, fluorescence diffuse optical tomography, bioluminescence, and a number of other new imaging methods. These methods of diffuse optical imaging have diversified instrument configurations but share the same core physical principle – light propagation in highly diffusive media, i.e., the biological tissue. In this review, the author summarizes the latest development in instrumentation and methodology available to diffuse optical imaging in terms of system architecture, light source, photo-detection, spectral separation, signal modulation, and lastly imaging contrast. PMID:24860804

Method for applying a diffusion barrier interlayer for high temperature components

DOEpatents

Wei, Ronghua; Cheruvu, Narayana S.

2016-03-08

A coated substrate and a method of forming a diffusion barrier coating system between a substrate and a MCrAl coating, including a diffusion barrier coating deposited onto at least a portion of a substrate surface, wherein the diffusion barrier coating comprises a nitride, oxide or carbide of one or more transition metals and/or metalloids and a MCrAl coating, wherein M includes a transition metal or a metalloid, deposited on at least a portion of the diffusion barrier coating, wherein the diffusion barrier coating restricts the inward diffusion of aluminum of the MCrAl coating into the substrate.

A fast semi-discrete Kansa method to solve the two-dimensional spatiotemporal fractional diffusion equation

NASA Astrophysics Data System (ADS)

Sun, HongGuang; Liu, Xiaoting; Zhang, Yong; Pang, Guofei; Garrard, Rhiannon

2017-09-01

Fractional-order diffusion equations (FDEs) extend classical diffusion equations by quantifying anomalous diffusion frequently observed in heterogeneous media. Real-world diffusion can be multi-dimensional, requiring efficient numerical solvers that can handle long-term memory embedded in mass transport. To address this challenge, a semi-discrete Kansa method is developed to approximate the two-dimensional spatiotemporal FDE, where the Kansa approach first discretizes the FDE, then the Gauss-Jacobi quadrature rule solves the corresponding matrix, and finally the Mittag-Leffler function provides an analytical solution for the resultant time-fractional ordinary differential equation. Numerical experiments are then conducted to check how the accuracy and convergence rate of the numerical solution are affected by the distribution mode and number of spatial discretization nodes. Applications further show that the numerical method can efficiently solve two-dimensional spatiotemporal FDE models with either a continuous or discrete mixing measure. Hence this study provides an efficient and fast computational method for modeling super-diffusive, sub-diffusive, and mixed diffusive processes in large, two-dimensional domains with irregular shapes.

Rotating single-shot acquisition (RoSA) with composite reconstruction for fast high-resolution diffusion imaging.

PubMed

Wen, Qiuting; Kodiweera, Chandana; Dale, Brian M; Shivraman, Giri; Wu, Yu-Chien

2018-01-01

To accelerate high-resolution diffusion imaging, rotating single-shot acquisition (RoSA) with composite reconstruction is proposed. Acceleration was achieved by acquiring only one rotating single-shot blade per diffusion direction, and high-resolution diffusion-weighted (DW) images were reconstructed by using similarities of neighboring DW images. A parallel imaging technique was implemented in RoSA to further improve the image quality and acquisition speed. RoSA performance was evaluated by simulation and human experiments. A brain tensor phantom was developed to determine an optimal blade size and rotation angle by considering similarity in DW images, off-resonance effects, and k-space coverage. With the optimal parameters, RoSA MR pulse sequence and reconstruction algorithm were developed to acquire human brain data. For comparison, multishot echo planar imaging (EPI) and conventional single-shot EPI sequences were performed with matched scan time, resolution, field of view, and diffusion directions. The simulation indicated an optimal blade size of 48 × 256 and a 30 ° rotation angle. For 1 × 1 mm 2 in-plane resolution, RoSA was 12 times faster than the multishot acquisition with comparable image quality. With the same acquisition time as SS-EPI, RoSA provided superior image quality and minimum geometric distortion. RoSA offers fast, high-quality, high-resolution diffusion images. The composite image reconstruction is model-free and compatible with various diffusion computation approaches including parametric and nonparametric analyses. Magn Reson Med 79:264-275, 2018. © 2017 International Society for Magnetic Resonance in Medicine. © 2017 International Society for Magnetic Resonance in Medicine.

A method for modeling oxygen diffusion in an agent-based model with application to host-pathogen infection

DOE PAGES

Plimpton, Steven J.; Sershen, Cheryl L.; May, Elebeoba E.

2015-01-01

This paper describes a method for incorporating a diffusion field modeling oxygen usage and dispersion in a multi-scale model of Mycobacterium tuberculosis (Mtb) infection mediated granuloma formation. We implemented this method over a floating-point field to model oxygen dynamics in host tissue during chronic phase response and Mtb persistence. The method avoids the requirement of satisfying the Courant-Friedrichs-Lewy (CFL) condition, which is necessary in implementing the explicit version of the finite-difference method, but imposes an impractical bound on the time step. Instead, diffusion is modeled by a matrix-based, steady state approximate solution to the diffusion equation. Moreover, presented in figuremore » 1 is the evolution of the diffusion profiles of a containment granuloma over time.« less

Lyman-alpha observations in the vicinity of Saturn with Copernicus

NASA Technical Reports Server (NTRS)

Barker, E.; Cazes, S.; Emerich, C.; Vidal-Madjar, A.; Owen, T.

1980-01-01

For the first time, high-resolution Ly-alpha observations of the Saturn vicinity were completed with the Princeton spectrometer on board the Copernicus satellite. They showed that near a minimum solar activity the emissions related to several sources are 250 + or - 50 rayleighs for the interplanetary medium in a near-downwind direction, less than 100 rayleighs for the rings, 200 + or - 100 rayleighs for a torus linked to the Titan orbit, and 1400 + or - 450 rayleighs for the disk of Saturn. These results induce some constraints through the corresponding theoretical evaluations: the B ring as the primary source of the atoms for the ring emissions; an efficient production mechanism for hydrogen atoms in the Titan torus; and a slightly larger eddy diffusion coefficient in the Saturn atmosphere than in the Jupiter atmosphere near solar minimum.

[Identification of filamentous fungi isolated from clinical samples by two different methods and their susceptibility results].

PubMed

Direkel, Sahin; Otağ, Feza; Aslan, Gönül; Ulger, Mahmut; Emekdaş, Gürol

2012-01-01

Molds are widely distributed in nature. Aspergillus spp. represent the most frequently observed causative agents, however less frequent pathogens Fusarium, Scedosporium and Zygomycetes have also been considered the most important causes of morbidity and mortality in profoundly immunosuppressed hosts. The aims of this study were to identify filamentous fungi isolated from clinical specimens by conventional and molecular methods, and to detect their antifungal susceptibilities. A total of 6742 clinical specimens obtained from hospitalized patients at critical units of Mersin University Medical Faculty Hospital and sent to our laboratory between April 2008-January 2010 were included in the study. The isolates were identified by classical mycological methods and polymerase chain reaction-based DNA sequencing. Susceptibilities to fluconazole and voriconazole were tested by disk diffusion method and to fluconazole, voriconazole, amfoterisin B, caspofungin and posaconazole by E-test. Filamentous fungi were isolated from 71 (1.05%) samples (13 sputum, 4 wound, 4 peritoneal fluid, 3 extrenal ear discharge, 3 abscess and one of each cerebrospinal fluid, blood, tissue biopsy, nasal swab and conjunctival swab) which belonged to 32 patients (13 female, 19 male; age range 7 months-77 years, mean age: 46.6 years). Of the patients 62.3% presented one or more risk factors such as chronic renal failure (n= 8), chronic obstructive lung disease (n= 6), malignancy (n= 6), diabetes mellitus (n= 5) and peripheral vascular disease (n= 5). Of the isolates six were identified as Aspergillus niger, six as Aspergillus flavus, five as Aspergillus fumigatus, four as Aspergillus terreus, five as Fusarium spp., two as Bipolaris spp., and one of each as Acremonium spp., Aurebasidium spp., Mucor spp., and Scedosporium spp. By conventional methods. Three isolates exhibited different identities by DNA sequencing. All Aspergillus isolates were correctly identified at species level by both methods, Other fungi were identified at genus level by conventional methods and at species level by DNA sequencing. Fluconazole minimum inhibitory concentration (MIC) values were determined as > 256 mg/L in all strains, except Scedosporium; voriconazole MIC values were < 0.38 mg/L in all Aspergillus spp. Caspofungin MIC values were > 32 mg/L for Fusarium, Scedosporium, Rhizopus and Bipolaris strains and ≤ 0.006-0.125 mg/L in all Aspergillus isolates, In three strains (Fusarium equiseti, Cylindrocarpon lichenicola and Rhizopus oryzae) posaconazole minimum inhibitory concentration (MIC) values were > 32 mg/L, however it was < 1.5 mg/L, for the other strains. Amphotericin B MIC values were > 32 mg/L for Fusarium, Scedosporium, Rhizopus and all A.terreus strains and < 2 mg/L for the others. E-test and disk diffusion test results were compatible with each other for all the antifungal agents tested. In conclusion, the identification of filamentous fungi such as Aspergillus and Fusarium spp. is easily and reliably achieved by conventional methods. Since the rate of invasive fungal infections is increasing currently, filamentous molds should be searched especially in the clinical specimens of immunocompromised patients for accurate and prompt diagnosis of such infections and to decrease the related mortality risk.

Seeking Global Minima

NASA Astrophysics Data System (ADS)

Tajuddin, Wan Ahmad

1994-02-01

Ease in finding the configuration at the global energy minimum in a symmetric neural network is important for combinatorial optimization problems. We carry out a comprehensive survey of available strategies for seeking global minima by comparing their performances in the binary representation problem. We recall our previous comparison of steepest descent with analog dynamics, genetic hill-climbing, simulated diffusion, simulated annealing, threshold accepting and simulated tunneling. To this, we add comparisons to other strategies including taboo search and one with field-ordered updating.

Diffusion on an Ising chain with kinks

NASA Astrophysics Data System (ADS)

Hamma, Alioscia; Mansour, Toufik; Severini, Simone

2009-07-01

We count the number of histories between the two degenerate minimum energy configurations of the Ising model on a chain, as a function of the length n and the number d of kinks that appear above the critical temperature. This is equivalent to count permutations of length n avoiding certain subsequences depending on d. We give explicit generating functions and compute the asymptotics. The setting considered has a role when describing dynamics induced by quantum Hamiltonians with deconfined quasi-particles.

Investigation of Shock Diffusers at Mach Number 1.85. 2 - Projecting Double-Shock Cones

DTIC Science & Technology

1947-06-17

pitot - static rake located as shown in figure 1(a). Total-pressure recoveries were measured for a series of tip projections varied in minimum steps...is shown. The position of the pitot -static rake with which these distributions were .measured is shown in figure 1(a). The data points correspond...Schroeder SUMMARY An Investigation has "been undertaken in the Cleveland 18- by 18-Inch, supersonic tunnel to determine the total-pressure

Electronics Reliability Fracture Mechanics, Volume 1. Causes of Failures of Shop Replaceable Units and Hybrid Microcircuits

DTIC Science & Technology

1992-05-01

Plate Figure H-1. Temperature Coefficient Test Circuit The forward voltage was measured at 3 different termperatures. The average TC was calculated to be...AT, rather than the average figure given by the large area Isolation diffusion. The peak temperature , rather than the average temperature , is the...components would cause the temperatures of the components to be nearer the average , particularly those near the minimum and maximum. X-I The largest

Synaptic delay in the heart: an ionophoretic study.

PubMed Central

Hill-Smith, I; Purves, R D

1978-01-01

1. Neurotransmitters were applied ionophoretically to spontaneously beating clusters of ventricular muscle cells cultured from neonatal rats. 2. Acetylcholine or its analogue carbachol produced hyperpolarization and decreased the rate of spontaneous beating. These responses had minimum latencies of about 250 msec and total durations of 6-12 sec. 3. Noradrenaline, adrenaline or isoprenaline increased the rate of spontaneous beating. The minimum latency for this effect was 3-6 sec. Following a single brief pulse the rate remained elevated for 2 min or more. 4. Chronotropic responses of intact atria from adult rats to stimulation of the autonomic nerves were of similar time course to responses of the cultured muscle cells. 5. Calculations based on the theory of diffusion showed that access of drugs to their receptors could not be rate-limiting for the observed responses, unless a diffusion barrier of rather special properties was postulated. A number of other explanations for the long latencies have been ruled out; these are most likely to be due to some physical or chemical process occurring in or under the cell membrane. 6. Attempts to mimic responses to catecholamines by intracellular application of cyclic AMP were unsuccessful, perhaps because the release of nucleotide from the pipettes was insufficient. A theoretical treatment suggests that ionophoretic efflux of anions might be greatly diminished by the opposing electro-osmotic flux. PMID:209176

A Robust and Efficient Method for Steady State Patterns in Reaction-Diffusion Systems

PubMed Central

Lo, Wing-Cheong; Chen, Long; Wang, Ming; Nie, Qing

2012-01-01

An inhomogeneous steady state pattern of nonlinear reaction-diffusion equations with no-flux boundary conditions is usually computed by solving the corresponding time-dependent reaction-diffusion equations using temporal schemes. Nonlinear solvers (e.g., Newton’s method) take less CPU time in direct computation for the steady state; however, their convergence is sensitive to the initial guess, often leading to divergence or convergence to spatially homogeneous solution. Systematically numerical exploration of spatial patterns of reaction-diffusion equations under different parameter regimes requires that the numerical method be efficient and robust to initial condition or initial guess, with better likelihood of convergence to an inhomogeneous pattern. Here, a new approach that combines the advantages of temporal schemes in robustness and Newton’s method in fast convergence in solving steady states of reaction-diffusion equations is proposed. In particular, an adaptive implicit Euler with inexact solver (AIIE) method is found to be much more efficient than temporal schemes and more robust in convergence than typical nonlinear solvers (e.g., Newton’s method) in finding the inhomogeneous pattern. Application of this new approach to two reaction-diffusion equations in one, two, and three spatial dimensions, along with direct comparisons to several other existing methods, demonstrates that AIIE is a more desirable method for searching inhomogeneous spatial patterns of reaction-diffusion equations in a large parameter space. PMID:22773849

Anti-methicillin-resistance Staphylococcus aureus (MRSA) compounds from Bauhinia kockiana Korth. And their mechanism of antibacterial activity.

PubMed

Chew, Yik Ling; Mahadi, Adlina Maisarah; Wong, Kak Ming; Goh, Joo Kheng

2018-02-20

Bauhinia kockiana originates from Peninsular Malaysia and it is grown as a garden ornamental plant. Our previous study reported that this plant exhibited fairly strong antioxidant and antimicrobial activities. This paper focused on the assessment of the antibacterial activity of B. kockiana towards methicillin-resistance Staphylococcus aureus (MRSA), to purify and to identify the antibacterial compounds, and to determine the mechanism of antibacterial activity. Antibacterial activity of B. kockiana flower was evaluated qualitatively and quantitatively using disc diffusion assay and microbroth dilution method. Minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of extracts were examined. Phytochemical analysis was performed to determine the classes of phytochemicals in the extracts. Bioactivity guided isolation was employed to purify the antibacterial agents and identified via various spectroscopy methods. Scanning electron microscopy (SEM) technique was used to evaluate the antibacterial mechanism of extract and compounds isolated. B. kockiana flower was found to exhibit fairly strong antibacterial activity towards both strains of MRSA bacteria used, MIC varies from 62.5-250 μg/mL. Tannins and flavonoids have been detected in the phytochemical analysis. Gallic acid and its ester derivatives purified from ethyl acetate extract could inhibit MRSA at 250-500 μg/mL. SEM revealed that the cells have undergone plasmolysis upon treatment with the extract and compounds. Tannins and polyphenols are the antibacterial components towards MRSA in B. kockiana. Massive leakage of the cell content observed in treated cells showed that the phytochemicals have changed the properties of the cell membranes. Amphiphilic nature of the compounds exhibited the antibacterial activity towards MRSA via three stages: (1) cell membrane attachment; (2) cell membrane fluidity modification; and (3) cell membrane structure disruption.

Evaluation of the in vitro antibacterial activity of the solvent fractions of the leaves of Rhamnus prinoides L'Herit (Rhamnaceae) against pathogenic bacteria.

PubMed

Molla, Yalew; Nedi, Teshome; Tadesse, Getachew; Alemayehu, Haile; Shibeshi, Workineh

2016-08-15

Medicinal plants play great roles in the treatment of various infectious diseases. Rhamnus prinoides is one of the medicinal plants used traditionally for treatment of bacterial diseases. The antibacterial activity of the crude extract of the plant had been shown by a previous study, but this study was undertaken to further the claimed medicinal use of the plant by screening its solvent fractions for the said activity so that it could serve as a basis for subsequent studies. The solvent fractions of the plant were obtained by successive soxhlet extraction with solvents of increasing polarity, with chloroform and methanol, followed by maceration of the marc of methanol fraction with water. The antibacterial activity of the solvent fractions was evaluated on seven bacterial species using agar well diffusion method at different concentrations (78 mg/well, 39 mg/well and 19.5 mg/well) in the presence of positive and negative controls. The minimum inhibitory concentration of the solvent fractions was determined by micro-broth dilution method using resazurin as indicator. Methanol and chloroform fractions revealed antibacterial activities against the growth of test bacterial strains with varying antibacterial spectrum and the susceptible bacterial species were Staphylococcus aureus, Streptococcus pyogen, Streptococcus pneumoniae and Salmonella typhi. The average minimum inhibitory concentration value of the methanol and chloroform fractions ranged from 8.13 mg/ml to 32.5 mg/ml and from 8.13 mg/ml to 16.25 mg/ml, respectively. The methanol and chloroform fractions demonstrated significant antibacterial activities against the growth of pathogenic bacteria but the aqueous fraction did not reveal antibacterial activity against any of the test bacteria.

Chemical composition, antimicrobial properties and toxicity evaluation of the essential oil of Cupressus lusitanica Mill. leaves from Cameroon.

PubMed

Teke, Gerald Ngo; Elisée, Kemadjou Nana; Roger, Kuiate Jules

2013-06-13

The leaves of Cupressus lusitanica Mill. are used in the western highlands of Cameroon for their medicinal property. The leaves of this species were collected in the West Region of Cameroon in August 2010 and subjected to hydrodistillation to obtain the essential oil. The oil was fractionated using adsorption column chromatography. The chemical composition of this oil and its fractions was analysed by gas chromatography-mass spectrometry (GC-MS). The essential oil and fractions were tested for antimicrobial activity against eight bacterial species and six species of Candida by the agar diffusion method. Macrodilution method was used to determine the minimum inhibition concentrations (MICs) and minimum bactericidal and/or fungicidal concentrations (MBCs and MFCs). The toxicity profile of the oil was studied using Swiss mice and Wistar albino rats. Forty-nine compounds were identified in the essential oil. The main components were germacrene D (18.5%), epi-zonarene (8.2%), cis-calamenene (8.2%), terpinen-4-ol (6.3%), linalool (6.0%) and umbellulone (6.0%). Enterococcus faecalis, Proteus mirabilis and Candida albicans were most susceptible to the oil (MICs of 1.25 and 0.16% for bacteria and fungi respectively). The estimated oral LD50 was 6.33 g/kg. There was an increase in sera ALT and AST activities while the blood cells and protein levels decreased in treated animals. The results obtained from this study support the ethnomedicinal use of C. lusitanica leaf oil in the treatment of whooping cough and skin infections though it should be used with care. This plant oil could be useful in the standardisation of phytomedicine.

Characterization, antibacterial, total antioxidant, scavenging, reducing power and ion chelating activities of green synthesized silver, copper and titanium dioxide nanoparticles using Artemisia haussknechtii leaf extract.

PubMed

Alavi, Mehran; Karimi, Naser

2017-12-12

Recently, major problem related to pathogenic bacteria is augmentation of antibiotic resistance which has been changed treatment and recovery of millions of infectious patients. The present study reports an eco-friendly, rapid and easy method for synthesis of silver (Ag), copper (Cu) and titanium dioxide (TiO 2 ) nanoparticles (NPs) using Artemisia haussknechtii leaf aqueous extract with antibacterial activities against multi-drug resistance (MDR) bacteria species. Three different concentrations (0.001, 0.01 and 0.1 M) of AgNO 3 , CuSO 4 and TiO (OH) 2 were investigated for obtaining optimum NPs green synthesis. Total phenolic content, total flavonoid content of leaf extract and total antioxidant activity (DPPH) assay were determined as radical scavenging methods. UV-Visible spectroscopy, Fourier transform infrared spectroscopy analysis, X-ray diffraction, energy dispersive X-ray spectroscopy, field emission scanning electron microscope and atomic force microscopy (AFM) were used due to NPs characterization. The size average of the Ag, Cu and TiO 2 NPs obtained were respectively 10.69 ± 5.55, 35.36 ± 44.4 and 92.58 ± 56.98 nm. In the case of antibacterial assay, disc diffusion assay, minimum inhibitory concentration, minimum bactericidal concentration, bacterial growth and morphology of four MDR species Staphylococcus aureus ATCC 43300, Staphylococcus epidermidis ATCC 12258, Serratia marcescens ATTC13880 and Escherichia coli ATCC 25922 were evaluated. Results of this study demonstrated that A. haussknechtii leaf extract with various groups of phytochemicals such as phenols and flavonoids had suitable ability in green synthesis of Ag, Cu and TiO 2 NPs. Also, Ag and Cu NPs had more antibacterial activities compared to TiO 2 NPs.

Magnetic resonance imaging for the detection, localisation, and characterisation of prostate cancer: recommendations from a European consensus meeting.

PubMed

Dickinson, Louise; Ahmed, Hashim U; Allen, Clare; Barentsz, Jelle O; Carey, Brendan; Futterer, Jurgen J; Heijmink, Stijn W; Hoskin, Peter J; Kirkham, Alex; Padhani, Anwar R; Persad, Raj; Puech, Philippe; Punwani, Shonit; Sohaib, Aslam S; Tombal, Bertrand; Villers, Arnauld; van der Meulen, Jan; Emberton, Mark

2011-04-01

Multiparametric magnetic resonance imaging (mpMRI) may have a role in detecting clinically significant prostate cancer in men with raised serum prostate-specific antigen levels. Variations in technique and the interpretation of images have contributed to inconsistency in its reported performance characteristics. Our aim was to make recommendations on a standardised method for the conduct, interpretation, and reporting of prostate mpMRI for prostate cancer detection and localisation. A consensus meeting of 16 European prostate cancer experts was held that followed the UCLA-RAND Appropriateness Method and facilitated by an independent chair. Before the meeting, 520 items were scored for "appropriateness" by panel members, discussed face to face, and rescored. Agreement was reached in 67% of 260 items related to imaging sequence parameters. T2-weighted, dynamic contrast-enhanced, and diffusion-weighted MRI were the key sequences incorporated into the minimum requirements. Consensus was also reached on 54% of 260 items related to image interpretation and reporting, including features of malignancy on individual sequences. A 5-point scale was agreed on for communicating the probability of malignancy, with a minimum of 16 prostatic regions of interest, to include a pictorial representation of suspicious foci. Limitations relate to consensus methodology. Dominant personalities are known to affect the opinions of the group and were countered by a neutral chairperson. Consensus was reached on a number of areas related to the conduct, interpretation, and reporting of mpMRI for the detection, localisation, and characterisation of prostate cancer. Before optimal dissemination of this technology, these outcomes will require formal validation in prospective trials. Copyright © 2010 European Association of Urology. Published by Elsevier B.V. All rights reserved.

Systematic screening of plant extracts from the Brazilian Pantanal with antimicrobial activity against bacteria with cariogenic relevance.

PubMed

Brighenti, F L; Salvador, M J; Delbem, Alberto Carlos Botazzo; Delbem, Ádina Cleia Bottazzo; Oliveira, M A C; Soares, C P; Freitas, L S F; Koga-Ito, C Y

2014-01-01

This study proposes a bioprospection methodology regarding the antimicrobial potential of plant extracts against bacteria with cariogenic relevance. Sixty extracts were obtained from ten plants--(1) Jatropha weddelliana, (2) Attalea phalerata, (3) Buchenavia tomentosa, (4) Croton doctoris, (5) Mouriri elliptica, (6) Mascagnia benthamiana, (7) Senna aculeata, (8) Unonopsis guatterioides, (9) Allagoptera leucocalyx and (10) Bactris glaucescens--using different extraction methods - (A) 70° ethanol 72 h/25°C, (B) water 5 min/100°C, (C) water 1 h/55°C, (D) water 72 h/25°C, (E) hexane 72 h/25°C and (F) 90° ethanol 72 h/25°C. The plants were screened for antibacterial activity at 50 mg/ml using the agar well diffusion test against Actinomyces naeslundii ATCC 19039, Lactobacillus acidophilus ATCC 4356, Streptococcus gordonii ATCC 10558, Streptococcus mutans ATCC 35688, Streptococcus sanguinis ATCC 10556, Streptococcus sobrinus ATCC 33478 and Streptococcus mitis ATCC 9811. The active extracts were tested to determine their minimum inhibitory concentration (MIC), minimum bactericidal concentration (MBC), cytotoxicity and chemical characterization. Forty-seven extracts (78%) were active against at least one microorganism. Extract 4A demonstrated the lowest MIC and MBC for all microorganisms except S. gordonii and the extract at MIC concentration was non-cytotoxic. The concentrated extracts were slightly cytotoxic. Electrospray ionization with tandem mass spectrometry analyses demonstrated that the extract constituents coincided with the mass of the terpenoids and phenolics. Overall, the best results were obtained for extraction methods A, B and C. The present work proved the antimicrobial activity of several plants. Particularly, extracts from C. doctoris were the most active against bacteria involved in dental caries disease. © 2014 S. Karger AG, Basel.

Seagrass as a potential source of natural antioxidant and anti-inflammatory agents.

PubMed

Yuvaraj, N; Kanmani, P; Satishkumar, R; Paari, A; Pattukumar, V; Arul, V

2012-04-01

Halophila spp. is a strong medicine against malaria and skin diseases and is found to be very effective in early stages of leprosy. Seagrasses are nutraceutical in nature and therefore of importance as food supplements. The antibacterial, antioxidant, and anti-inflammatory activities of Halophila ovalis R. Br. Hooke (Hydrocharitaceae) methanol extract were investigated and the chemical constituents of purified fractions were analyzed. Plant materials were collected from Pondicherry coastal line, and antimicrobial screening of crude extract, and purified fractions was carried out by the disc diffusion method and the minimum inhibitory concentration (MICs) of the purified fractions and reference antibiotics were determined by microdilution method. Antioxidant and anti-inflammatory activities were investigated in vitro. Chemical constituents of purified fractions V and VI were analyzed by gas chromatography-mass spectrometry (GC-MS), and the phytochemicals were quantitatively determined. Methanol extract inhibited the growth of Bacillus cereus at a minimum inhibitory concentration of 50 µg/mL and other Gram-negative pathogens at 75 µg/ml, except Vibrio vulnificus. Reducing power and total antioxidant level increased with increasing extract concentration. H. ovalis exhibited strong scavenging activity on 2,2-diphenyl-1-picrylhydrazyl (DPPH) and superoxide radicals at IC(50) of 0.13 and 0.65 mg/mL, respectively. Methanol extract of H. ovalis showed noticeable anti-inflammatory activity at IC(50) of 78.72 µg/mL. The GC-MS analysis of H. ovalis revealed the presence of triacylglycerols as major components in purified fractions. Quantitative analysis of phytochemicals revealed that phenols are rich in seagrass H. ovalis. These findings demonstrated that the methanol extract of H. ovalis exhibited appreciable antibacterial, noticeable antioxidant, and anti-inflammatory activities, and thus could be use as a potential source for natural health products.

Oliveria decumbens essential oil: Chemical compositions and antimicrobial activity against the growth of some clinical and standard strains causing infection.

PubMed

Alizadeh Behbahani, Behrooz; Tabatabaei Yazdi, Farideh; Vasiee, Alireza; Mortazavi, Seyed Ali

2018-01-01

Oliveria decumbens as a valuable medicinal plant is extensively used in traditional medicine. clinical and standard strains causing infection resistance to antimicrobial agents, is one of the important problems in medicine. The aim of this study was to investigate the antibacterial activities and phytochemical analysis of Oliveria decumbens essential oil on the growth of some clinical and standard strains causing infection (Pseudomonas aerogenes, Escherichia coli, Streptococcus pyogenes and Staphylococcus epidermidis). Oliveria decumbens essential oil composition was identified by gas chromatography/mass spectrometry. Phytochemical analysis (alkaloids, saponins, flavone and phenolic) essential oil of the Oliveria decumbens were appraised based on qualitative methods. Several methods (disk diffusion, minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC)) were used to appraise the antibacterial activity of the Oliveria decumbens essential oil. Thymol (28.45%) was the major compound of Oliveria decumbens essential oil. The total phenolics content (TPC) of the essential oil positively correlated with antioxidant activity (AA). The TPC and AA of Oliveria decumbens essential oil was equal to 92.45 ± 0.70 μg GAE/mg and 164.45 ± 1.20 μg/ml, respectively. The MIC of Oliveria decumbens essential oil ranged from 1 to 8 mg/ml depending on the type of bacteria (clinical and standard strains). The MBC of Oliveria decumbens essential oil varied from 1 mg/ml to 16 mg/ml. The smallest inhibition zone diameter (IZD) on different Oliveria decumbens essential oil concentrations on P. aeruginosa. Results indicate that Oliveria decumbens essential oil can prove to be an important source of AA and antibacterial and may be used for the treatment of infection diseases. Copyright © 2017 Elsevier Ltd. All rights reserved.

Blechnum Orientale Linn - a fern with potential as antioxidant, anticancer and antibacterial agent

PubMed Central

2010-01-01

Background Blechnum orientale Linn. (Blechnaceae) is used ethnomedicinally for the treatment of various skin diseases, stomach pain, urinary bladder complaints and sterilization of women. The aim of the study was to evaluate antioxidant, anticancer and antibacterial activity of five solvent fractions obtained from the methanol extract of the leaves of Blechnum orientale Linn. Methods Five solvent fractions were obtained from the methanol extract of B. orientale through successive partitioning with petroleum ether, chloroform, ethyl acetate, butanol and water. Total phenolic content was assessed using Folin-Ciocalteu's method. The antioxidant activity was determined by measuring the scavenging activity of DPPH radicals. Cytotoxic activity was tested against four cancer cell lines and a non-malignant cell using MTT assay. Antibacterial activity was assessed using the disc diffusion and broth microdilution assays. Standard phytochemical screening tests for saponins, tannins, terpenoids, flavonoids and alkaloids were also conducted. Results The ethyl acetate, butanol and water fractions possessed strong radical scavenging activity (IC50 8.6-13.0 μg/ml) and cytotoxic activity towards human colon cancer cell HT-29 (IC50 27.5-42.8 μg/ml). The three extracts were also effective against all Gram-positive bacteria tested: Bacillus cereus, Micrococcus luteus, methicillin-susceptible Staphylococcus aureus (MSSA), methicillin-resistant Staphylococcus aureus (MRSA) and Stapylococcus epidermidis(minimum inhibitory concentration MIC 15.6-250 μg/ml; minimum bactericidal concentration MBC 15.6-250 μg/ml). Phytochemical analysis revealed the presence of flavonoids, terpenoids and tannins. Ethyl acetate and butanol fractions showed highest total phenolic content (675-804 mg gallic acid equivalent/g). Conclusions The results indicate that this fern is a potential candidate to be used as an antioxidant agent, for colon cancer therapy and for treatment of MRSA infections and other MSSA/Gram-positive bacterial infectious diseases. PMID:20429956

Effect of aqueous and alcoholic Stevia (Stevia rebaudiana) extracts against Streptococcus mutans and Lactobacillus acidophilus in comparison to chlorhexidine: An in vitro study

PubMed Central

Ajagannanavar, Sunil Lingaraj; Shamarao, Supreetha; Battur, Hemant; Tikare, Shreyas; Al-Kheraif, Abdulaziz Abdullah; Al Sayed, Mohammed Sayed Al Esawy

2014-01-01

Introduction: Stevia (S. rebaudiana) a herb which has medicinal value and was used in ancient times as a remedy for a great diversity of ailments and sweetener. Leaves of Stevia contain a high concentration of Stevioside and Rebaudioside which are supposed to be sweetening agents. Aim: To compare the efficacy of aqueous and alcoholic S. rebaudiana extract against Streptococcus mutans and Lactobacillus acidophilus in comparison to chlorhexidine. Materials and Methods: In the first part of the study, various concentrations of aqueous and ethanolic Stevia extract were prepared in the laboratory of Pharmacy College. It was then subjected to microbiological assay to determine its zone of inhibition using Agar disk diffusion test and minimum inhibitory concentration (MIC) using serial broth dilution method against Streptococcus mutans and Lactobacillus acidophilus. Chlorhexidine was used as a positive control. One way Analysis of Variance (ANOVA) test was used for multiple group comparisons followed by Tukey post hoc for group wise comparisons. Results: Minimum inhibitory concentration (MIC) of aqueous and ethnolic Stevia extract against Streptococcus mutans and Lactobacillus acidophilus were 25% and 12.5% respectively. Mean zone of inhibition of the aqueous and alcoholic Stevia extracts against Streptococcus mutans at 48 hours were 22.8 mm and 26.7 mm respectively. Mean zone of inhibition of the aqueous and alcoholic Stevia extracts against Lactobacillus acidophilus at 48 hours were 14.4 mm and 15.1 mm respectively. Mean zone of inhibition of the chlorhexidine against Streptococcus mutans and Lactobacillus acidophilus at 48 hours was 20.5 and 13.2 respectively. Conclusion: The inhibitory effect shown by alcoholic Stevia extract against Streptococcus mutans and Lactobacillus acidophilus was superior when compared with that of aqueous form and was inferior when compared with Chlorhexidine. PMID:25558451

Antibacterial assay-guided isolation of active compounds from Artocarpus heterophyllus heartwoods.

PubMed

Septama, Abdi Wira; Panichayupakaranant, Pharkphoom

2015-01-01

Preparations from Artocarpus heterophyllus Lam. (Moraceae) heartwoods are used in the traditional folk medicine for the treatment of inflammation, malarial fever, and to prevent bacterial and fungal infections. The objective of this study was to isolate pure antibacterial compounds from A. heterophyllus heartwoods. The dried and powdered A. heterophyllus heartwoods were successively extracted with the following solvents: hexane, ethyl acetate, and methanol. Each of the extracts was screened for their antibacterial activities using a disc diffusion method (10 mg/disc). Their minimum inhibitory concentrations (MICs) and minimum bactericidal concentrations (MBCs) were determined using a broth microdilution method. The extract that showed the strongest antibacterial activities was fractionated to isolate the active compounds by an antibacterial assay-guided isolation process. The ethyl acetate extract exhibited the strongest antibacterial activities against Streptococcus mutans, S. pyogenes, and Bacillus subtilis with MIC values of 78, 39, and 9.8 µg/mL, respectively. Based on an antibacterial assay-guided isolation, four antibacterial compounds: cycloartocarpin (1), artocarpin (2), artocarpanone (3), and cyanomaclurin (4) were purified. Among these isolated compounds, artocarpin exhibited the strongest antibacterial activity against Gram-positive bacteria, including S. mutans, S. pyogenes, B. subtilis, Staphylococcus aureus, and S. epidermidis with MICs of 4.4, 4.4, 17.8, 8.9, and 8.9 µM, respectively, and MBCs of 8.9, 8.9, 17.8, 8.9, and 8.9 µM, respectively, while artocarpanone showed the strongest activity against Escherichia coli, a Gram-negative bacteria with MIC and MBC values of 12.9 and 25.8 µM, respectively. Only artocarpin showed inhibitory activity against Pseudomonas aeruginosa with an MIC of 286.4 µM.

Adsorption and diffusion of Ru adatoms on Ru(0001)-supported graphene: Large-scale first-principles calculations

DOE PAGES

Han, Yong; Evans, James W.

2015-10-27

Large-scale first-principles density functional theory calculations are performed to investigate the adsorption and diffusion of Ru adatoms on monolayer graphene (G) supported on Ru(0001). The G sheet exhibits a periodic moiré-cell superstructure due to lattice mismatch. Within a moiré cell, there are three distinct regions: fcc, hcp, and mound, in which the C6-ring center is above a fcc site, a hcp site, and a surface Ru atom of Ru(0001), respectively. The adsorption energy of a Ru adatom is evaluated at specific sites in these distinct regions. We find the strongest binding at an adsorption site above a C atom inmore » the fcc region, next strongest in the hcp region, then the fcc-hcp boundary (ridge) between these regions, and the weakest binding in the mound region. Behavior is similar to that observed from small-unit-cell calculations of Habenicht et al. [Top. Catal. 57, 69 (2014)], which differ from previous large-scale calculations. We determine the minimum-energy path for local diffusion near the center of the fcc region and obtain a local diffusion barrier of ~0.48 eV. We also estimate a significantly lower local diffusion barrier in the ridge region. These barriers and information on the adsorption energy variation facilitate development of a realistic model for the global potential energy surface for Ru adatoms. Furthermore, this in turn enables simulation studies elucidating diffusion-mediated directed-assembly of Ru nanoclusters during deposition of Ru on G/Ru(0001).« less

Application of multiphysics models to efficient design of experiments of solute transport across articular cartilage.

PubMed

Pouran, Behdad; Arbabi, Vahid; Weinans, Harrie; Zadpoor, Amir A

2016-11-01

Transport of solutes helps to regulate normal physiology and proper function of cartilage in diarthrodial joints. Multiple studies have shown the effects of characteristic parameters such as concentration of proteoglycans and collagens and the orientation of collagen fibrils on the diffusion process. However, not much quantitative information and accurate models are available to help understand how the characteristics of the fluid surrounding articular cartilage influence the diffusion process. In this study, we used a combination of micro-computed tomography experiments and biphasic-solute finite element models to study the effects of three parameters of the overlying bath on the diffusion of neutral solutes across cartilage zones. Those parameters include bath size, degree of stirring of the bath, and the size and concentration of the stagnant layer that forms at the interface of cartilage and bath. Parametric studies determined the minimum of the finite bath size for which the diffusion behavior reduces to that of an infinite bath. Stirring of the bath proved to remarkably influence neutral solute transport across cartilage zones. The well-stirred condition was achieved only when the ratio of the diffusivity of bath to that of cartilage was greater than ≈1000. While the thickness of the stagnant layer at the cartilage-bath interface did not significantly influence the diffusion behavior, increase in its concentration substantially elevated solute concentration in cartilage. Sufficient stirring attenuated the effects of the stagnant layer. Our findings could be used for efficient design of experimental protocols aimed at understanding the transport of molecules across articular cartilage. Copyright © 2016 Elsevier Ltd. All rights reserved.

Fractionation of lithium isotopes in magmatic systems as a natural consequence of cooling

NASA Astrophysics Data System (ADS)

Gallagher, Kerry; Elliott, Tim

2009-02-01

High-temperature, diffusive fractionation has been invoked to account for striking Li isotopic variability recently observed within individual phenocrysts and xenolith minerals. It has been argued that chemical potential gradients required to drive such diffusion arise from changes in Li partitioning between coexisting phases during cooling. If so, Li isotopic zoning should be a common occurrence but the role of temperature-dependent partition coefficients in generating Li isotopic variability remains to be tested in a quantitative manner. Here we consider a basic scenario of a phenocryst in a cooling lava, using simple parameterisations of the temperature dependence of Li partitioning and diffusivity in clinopyroxene. Our model initially produces an asymmetric isotope profile across the crystal with a δ7Li minimum that remains close to the edge of a crystal. Such a distinctive shape mimics Li isotopic profiles documented in some olivine and clinopyroxene phenocrysts, which have isotopically normal cores but anomalously light rims. The temperature dependence of both the diffusivity and the partition coefficient of Li are key factors in generating this form of diffusion profile. Continued diffusion leads to an inversion in the sense of isotopic change between core and rim and results in the whole phenocryst attaining markedly light isotopic values. Our calculations show that significant Li isotopic zoning can occur as a natural consequence of cooling magmatic systems. Crystals that have experienced more complex thermal histories (e.g. re-entrained cumulates versus true phenocrysts) will therefore exhibit contrasting isotopic profiles and, as such, these data may be useful for tracing sub-volcanic processes.

Adsorption and diffusion of Ru adatoms on Ru(0001)-supported graphene: Large-scale first-principles calculations

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

Han, Yong; Evans, James W.

2015-10-28

Large-scale first-principles density functional theory calculations are performed to investigate the adsorption and diffusion of Ru adatoms on monolayer graphene (G) supported on Ru(0001). The G sheet exhibits a periodic moiré-cell superstructure due to lattice mismatch. Within a moiré cell, there are three distinct regions: fcc, hcp, and mound, in which the C{sub 6}-ring center is above a fcc site, a hcp site, and a surface Ru atom of Ru(0001), respectively. The adsorption energy of a Ru adatom is evaluated at specific sites in these distinct regions. We find the strongest binding at an adsorption site above a C atommore » in the fcc region, next strongest in the hcp region, then the fcc-hcp boundary (ridge) between these regions, and the weakest binding in the mound region. Behavior is similar to that observed from small-unit-cell calculations of Habenicht et al. [Top. Catal. 57, 69 (2014)], which differ from previous large-scale calculations. We determine the minimum-energy path for local diffusion near the center of the fcc region and obtain a local diffusion barrier of ∼0.48 eV. We also estimate a significantly lower local diffusion barrier in the ridge region. These barriers and information on the adsorption energy variation facilitate development of a realistic model for the global potential energy surface for Ru adatoms. This in turn enables simulation studies elucidating diffusion-mediated directed-assembly of Ru nanoclusters during deposition of Ru on G/Ru(0001)« less

Diffusion coefficients of water in biobased hydrogel polymer matrices by nuclear magnetic resonance imaging

USDA-ARS?s Scientific Manuscript database

The diffusion coefficient of water in biobased hydrogels were measured utilizing a simple NMR method. This method tracks the migration of deuterium oxide through imaging data that is fit to a diffusion equation. The results show that a 5 wt% soybean oil based hydrogel gives aqueous diffusion of 1.37...

Numerical method for angle-of-incidence correction factors for diffuse radiation incident photovoltaic modules

DOE PAGES

Marion, Bill

2017-03-27

Here, a numerical method is provided for solving the integral equation for the angle-of-incidence (AOI) correction factor for diffuse radiation incident photovoltaic (PV) modules. The types of diffuse radiation considered include sky, circumsolar, horizon, and ground-reflected. The method permits PV module AOI characteristics to be addressed when calculating AOI losses associated with diffuse radiation. Pseudo code is provided to aid users in the implementation, and results are shown for PV modules with tilt angles from 0° to 90°. Diffuse AOI losses are greatest for small PV module tilt angles. Including AOI losses associated with the diffuse irradiance will improve predictionsmore » of PV system performance.« less

A Simple Accurate Alternative to the Minimum-Deviation Method for the Determination of the Refractive Index of a Prism.

ERIC Educational Resources Information Center

Waldenstrom, S.; Naqvi, K. Razi

1978-01-01

Proposes an alternative to the classical minimum-deviation method for determining the refractive index of a prism. This new "fixed angle of incidence method" may find applications in research. (Author/GA)

A hybrid continuous-discrete method for stochastic reaction–diffusion processes

PubMed Central

Zheng, Likun; Nie, Qing

2016-01-01

Stochastic fluctuations in reaction–diffusion processes often have substantial effect on spatial and temporal dynamics of signal transductions in complex biological systems. One popular approach for simulating these processes is to divide the system into small spatial compartments assuming that molecules react only within the same compartment and jump between adjacent compartments driven by the diffusion. While the approach is convenient in terms of its implementation, its computational cost may become prohibitive when diffusive jumps occur significantly more frequently than reactions, as in the case of rapid diffusion. Here, we present a hybrid continuous-discrete method in which diffusion is simulated using continuous approximation while reactions are based on the Gillespie algorithm. Specifically, the diffusive jumps are approximated as continuous Gaussian random vectors with time-dependent means and covariances, allowing use of a large time step, even for rapid diffusion. By considering the correlation among diffusive jumps, the approximation is accurate for the second moment of the diffusion process. In addition, a criterion is obtained for identifying the region in which such diffusion approximation is required to enable adaptive calculations for better accuracy. Applications to a linear diffusion system and two nonlinear systems of morphogens demonstrate the effectiveness and benefits of the new hybrid method. PMID:27703710

Isolation of Abscisic Acid from Korean Acacia Honey with Anti-Helicobacter pylori Activity.

PubMed

Kim, SeGun; Hong, InPyo; Woo, SoonOk; Jang, HyeRi; Pak, SokCheon; Han, SangMi

2017-07-01

Helicobacter pylori ( H. pylori ) is linked to the development of the majority of peptic ulcers and some types of gastric cancers, and its antibiotic resistance is currently found worldwide. This study is aimed at evaluating the anti- H. pylori activity of Korean acacia honey and isolating the related active components using organic solvents. The crude acacia honey was extracted with n -hexane, dichloromethane, ethyl acetate (EtOAc), and n -butanol. The EtOAc extract was subjected to octadecyl-silica chromatography. The extracts and fractions were then examined for anti- H. pylori activity using the agar well diffusion method. The antimicrobial activity of abscisic acid against H. pylori was investigated by determining the minimum inhibitory concentrations (MICs), minimum bactericidal concentrations (MBCs), and by performing a time-kill assay. Abscisic acid related to the botanical origins of acacia honey from Korea has been analyzed using ultra-performance liquid chromatography. The MICs and MBCs of abscisic acid were 2.7 ± 1.3 and 6.9 ± 1.9 μg/mL, respectively. The bactericidal activity of abscisic acid (at 10.8 μg/mL corresponding to 4 × MIC) killed the organism within 36-72 h. These results suggest that abscisic acid isolated from Korean acacia honey has antibacterial activity against H. pylori . Abscisic acid isolated from Korean acacia honey can be therapeutic and may be further exploited as a potential lead candidate for the development of treatments for H. pylori -induced infections. The crude acacia honey was extracted with n -hexane, dichloromethane, EtOAc, and n -butanolThe EtOAc extract yielded eight fractions and four subfractions were subsequently obtained chromatographicallyAbscisic acid was isolated from one subfractionAll the solvent extracts and fractions showed antibacterial activity against H. pylori Abscisic acid exhibited antibacterial activity against H. pylori . Abbreviations used: MeOH: Methanol; EtOAc: Ethyl acetate; TSB: Trypticase soy broth; MIC: Minimum inhibitory concentration; MBC: Minimum bactericidal concentration; CFU: Colony-forming units; UPLC: Ultra-performance liquid chromatography; DAD: Diode array detector; UV: Ultraviolet; ODS: Octadecyl-silica; MS: Mass spectrometry; SE: Standard error.

Increased diffuse radiation fraction does not significantly accelerate plant growth

NASA Astrophysics Data System (ADS)

Angert, Alon; Krakauer, Nir

2010-05-01

A recent modelling study (Mercado et al., 2009) claims that increased numbers of scattering aerosols are responsible for a substantial fraction of the terrestrial carbon sink in recent decades because higher diffuse light fraction enhances plant net primary production (NPP). Here we show that observations of atmospheric CO2 seasonal cycle and tree ring data indicate that the relation between diffuse light and NPP is actually quite weak on annual timescales. The inconsistency of these data with the modelling results may arise because the relationships used to quantify the enhancement of NPP were calibrated with eddy covariance measurements of hourly carbon uptake. The effect of diffuse-light fraction on carbon uptake could depend on timescale, since this effect varies rapidly as sun angle and cloudiness change, and since plants can respond dynamically over various timescales to change in incoming radiation. Volcanic eruptions, such as the eruption of Mount Pinatubo in 1991, provide the best available tests for the effect of an annual-scale increase in the diffuse light fraction. Following the Pinatubo Eruption, in 1992 and 1993, a sharp decrease in the atmospheric CO2 growth rate was observed. This could have resulted from enhanced plant carbon uptake. Mercado et al. (2009) argue that largely as a result of the (volcanic aerosol driven) increase in diffuse light fraction, NPP was elevated in 1992, particularly between 25° N-45° N where annual NPP was modelled to be ~0.8 PgC (~10%) above average. In a previous study (Angert et al., 2004) a biogeochemical model (CASA) linked to an atmospheric tracer model (MATCH), was used to show that a diffuse-radiation driven increase in NPP in the extratropics will enhance carbon uptake mostly in summer, leading to a lower CO2 seasonal minimum. Here we use a 'toy model' to show that this conclusion is general and model-independent. The model shows that an enhanced sink of 0.8 PgC, similar to that modelled by Mercado et al. (2009), will result in a measurable decrease (~0.6ppm) in the seasonal CO2 minimum. This holds regardless of whether the sink is the result of 1) An increase in NPP, or 2) The combined effect of a temperature-driven decrease in heterotrophic respiration (Rh) and no change in NPP. This is since both NPP and Rh peak in summer. By contrast, observations from the NOAA global CO2 monitoring network show the opposite change in the seasonal minimum in 1992 and 1993 (~0.2ppm increase) both at Mauna Loa, and in the Marine Boundary Layer mean (>20° N), which is hard to reconcile with increased NPP in northern summer. Another indicator of annual NPP is tree wood increment. Previous work (Krakauer et al., 2003) showed that the average response in tree ring series after past Pinatubo-size volcanic eruptions implied lower NPP north of 45° N, presumably as a result of shorter growing season and lower total irradiance induced by scattering aerosols, and no significant change in NPP at lower latitudes. Here we show that In 1992, after the Pinatubo eruption, ring width in the 25° N-45° N band was 99.3±2.9% of average (n=351 sites), similar to the average of 100.4±2.2% over past eruptions (n=15 eruptions) (Uncertainty is given as 2 SE.). These results are also inconsistent with substantial NPP enhancement, although a limitation of the tree-ring approach is that available measurements do not uniformly sample the latitude band. The combined evidence of tree rings and the CO2 seasonal cycle shows that the enhancement of NPP by scattering aerosols on annual timescales is weak. This result suggests that reducing aerosols through stricter pollution controls may strengthen the land carbon sink, while geo-engineering schemes which aim to mitigate global warming by spreading scattering aerosols in the stratosphere may weaken it.

Hybrid Monte Carlo-Diffusion Method For Light Propagation in Tissue With a Low-Scattering Region

NASA Astrophysics Data System (ADS)

Hayashi, Toshiyuki; Kashio, Yoshihiko; Okada, Eiji

2003-06-01

The heterogeneity of the tissues in a head, especially the low-scattering cerebrospinal fluid (CSF) layer surrounding the brain has previously been shown to strongly affect light propagation in the brain. The radiosity-diffusion method, in which the light propagation in the CSF layer is assumed to obey the radiosity theory, has been employed to predict the light propagation in head models. Although the CSF layer is assumed to be a nonscattering region in the radiosity-diffusion method, fine arachnoid trabeculae cause faint scattering in the CSF layer in real heads. A novel approach, the hybrid Monte Carlo-diffusion method, is proposed to calculate the head models, including the low-scattering region in which the light propagation does not obey neither the diffusion approximation nor the radiosity theory. The light propagation in the high-scattering region is calculated by means of the diffusion approximation solved by the finite-element method and that in the low-scattering region is predicted by the Monte Carlo method. The intensity and mean time of flight of the detected light for the head model with a low-scattering CSF layer calculated by the hybrid method agreed well with those by the Monte Carlo method, whereas the results calculated by means of the diffusion approximation included considerable error caused by the effect of the CSF layer. In the hybrid method, the time-consuming Monte Carlo calculation is employed only for the thin CSF layer, and hence, the computation time of the hybrid method is dramatically shorter than that of the Monte Carlo method.

Hybrid Monte Carlo-diffusion method for light propagation in tissue with a low-scattering region.

PubMed

Hayashi, Toshiyuki; Kashio, Yoshihiko; Okada, Eiji

2003-06-01

The heterogeneity of the tissues in a head, especially the low-scattering cerebrospinal fluid (CSF) layer surrounding the brain has previously been shown to strongly affect light propagation in the brain. The radiosity-diffusion method, in which the light propagation in the CSF layer is assumed to obey the radiosity theory, has been employed to predict the light propagation in head models. Although the CSF layer is assumed to be a nonscattering region in the radiosity-diffusion method, fine arachnoid trabeculae cause faint scattering in the CSF layer in real heads. A novel approach, the hybrid Monte Carlo-diffusion method, is proposed to calculate the head models, including the low-scattering region in which the light propagation does not obey neither the diffusion approximation nor the radiosity theory. The light propagation in the high-scattering region is calculated by means of the diffusion approximation solved by the finite-element method and that in the low-scattering region is predicted by the Monte Carlo method. The intensity and mean time of flight of the detected light for the head model with a low-scattering CSF layer calculated by the hybrid method agreed well with those by the Monte Carlo method, whereas the results calculated by means of the diffusion approximation included considerable error caused by the effect of the CSF layer. In the hybrid method, the time-consuming Monte Carlo calculation is employed only for the thin CSF layer, and hence, the computation time of the hybrid method is dramatically shorter than that of the Monte Carlo method.

Development of advanced methods for analysis of experimental data in diffusion

NASA Astrophysics Data System (ADS)

Jaques, Alonso V.

There are numerous experimental configurations and data analysis techniques for the characterization of diffusion phenomena. However, the mathematical methods for estimating diffusivities traditionally do not take into account the effects of experimental errors in the data, and often require smooth, noiseless data sets to perform the necessary analysis steps. The current methods used for data smoothing require strong assumptions which can introduce numerical "artifacts" into the data, affecting confidence in the estimated parameters. The Boltzmann-Matano method is used extensively in the determination of concentration - dependent diffusivities, D(C), in alloys. In the course of analyzing experimental data, numerical integrations and differentiations of the concentration profile are performed. These methods require smoothing of the data prior to analysis. We present here an approach to the Boltzmann-Matano method that is based on a regularization method to estimate a differentiation operation on the data, i.e., estimate the concentration gradient term, which is important in the analysis process for determining the diffusivity. This approach, therefore, has the potential to be less subjective, and in numerical simulations shows an increased accuracy in the estimated diffusion coefficients. We present a regression approach to estimate linear multicomponent diffusion coefficients that eliminates the need pre-treat or pre-condition the concentration profile. This approach fits the data to a functional form of the mathematical expression for the concentration profile, and allows us to determine the diffusivity matrix directly from the fitted parameters. Reformulation of the equation for the analytical solution is done in order to reduce the size of the problem and accelerate the convergence. The objective function for the regression can incorporate point estimations for error in the concentration, improving the statistical confidence in the estimated diffusivity matrix. Case studies are presented to demonstrate the reliability and the stability of the method. To the best of our knowledge there is no published analysis of the effects of experimental errors on the reliability of the estimates for the diffusivities. For the case of linear multicomponent diffusion, we analyze the effects of the instrument analytical spot size, positioning uncertainty, and concentration uncertainty on the resulting values of the diffusivities. These effects are studied using Monte Carlo method on simulated experimental data. Several useful scaling relationships were identified which allow more rigorous and quantitative estimates of the errors in the measured data, and are valuable for experimental design. To further analyze anomalous diffusion processes, where traditional diffusional transport equations do not hold, we explore the use of fractional calculus in analytically representing these processes is proposed. We use the fractional calculus approach for anomalous diffusion processes occurring through a finite plane sheet with one face held at a fixed concentration, the other held at zero, and the initial concentration within the sheet equal to zero. This problem is related to cases in nature where diffusion is enhanced relative to the classical process, and the order of differentiation is not necessarily a second--order differential equation. That is, differentiation is of fractional order alpha, where 1 ≤ alpha < 2. For alpha = 2, the presented solutions reduce to the classical second-order diffusion solution for the conditions studied. The solution obtained allows the analysis of permeation experiments. Frequently, hydrogen diffusion is analyzed using electrochemical permeation methods using the traditional, Fickian-based theory. Experimental evidence shows the latter analytical approach is not always appropiate, because reported data shows qualitative (and quantitative) deviation from its theoretical scaling predictions. Preliminary analysis of data shows better agreement with fractional diffusion analysis when compared to traditional square-root scaling. Although there is a large amount of work in the estimation of the diffusivity from experimental data, reported studies typically present only the analytical description for the diffusivity, without scattering. However, because these studies do not consider effects produced by instrument analysis, their direct applicability is limited. We propose alternatives to address these, and to evaluate their influence on the final resulting diffusivity values.

Comparing exposure metrics for classifying ‘dangerous heat’ in heat wave and health warning systems

PubMed Central

Zhang, Kai; Rood, Richard B.; Michailidis, George; Oswald, Evan M.; Schwartz, Joel D.; Zanobetti, Antonella; Ebi, Kristie L.; O’Neill, Marie S.

2012-01-01

Heat waves have been linked to excess mortality and morbidity, and are projected to increase in frequency and intensity with a warming climate. This study compares exposure metrics to trigger heat wave and health warning systems (HHWS), and introduces a novel multi-level hybrid clustering method to identify potential dangerously hot days. Two-level and three-level hybrid clustering analysis as well as common indices used to trigger HHWS, including spatial synoptic classification (SSC); and 90th, 95th, and 99th percentiles of minimum and relative minimum temperature (using a 10 day reference period), were calculated using a summertime weather dataset in Detroit from 1976 to 2006. The days classified as ‘hot’ with hybrid clustering analysis, SSC, minimum and relative minimum temperature methods differed by method type. SSC tended to include the days with, on average, 2.6 °C lower daily minimum temperature and 5.3 °C lower dew point than days identified by other methods. These metrics were evaluated by comparing their performance in predicting excess daily mortality. The 99th percentile of minimum temperature was generally the most predictive, followed by the three-level hybrid clustering method, the 95th percentile of minimum temperature, SSC and others. Our proposed clustering framework has more flexibility and requires less substantial meteorological prior information than the synoptic classification methods. Comparison of these metrics in predicting excess daily mortality suggests that metrics thought to better characterize physiological heat stress by considering several weather conditions simultaneously may not be the same metrics that are better at predicting heat-related mortality, which has significant implications in HHWSs. PMID:22673187

Generalized Fourier analyses of the advection-diffusion equation - Part I: one-dimensional domains

NASA Astrophysics Data System (ADS)

Christon, Mark A.; Martinez, Mario J.; Voth, Thomas E.

2004-07-01

This paper presents a detailed multi-methods comparison of the spatial errors associated with finite difference, finite element and finite volume semi-discretizations of the scalar advection-diffusion equation. The errors are reported in terms of non-dimensional phase and group speed, discrete diffusivity, artificial diffusivity, and grid-induced anisotropy. It is demonstrated that Fourier analysis provides an automatic process for separating the discrete advective operator into its symmetric and skew-symmetric components and characterizing the spectral behaviour of each operator. For each of the numerical methods considered, asymptotic truncation error and resolution estimates are presented for the limiting cases of pure advection and pure diffusion. It is demonstrated that streamline upwind Petrov-Galerkin and its control-volume finite element analogue, the streamline upwind control-volume method, produce both an artificial diffusivity and a concomitant phase speed adjustment in addition to the usual semi-discrete artifacts observed in the phase speed, group speed and diffusivity. The Galerkin finite element method and its streamline upwind derivatives are shown to exhibit super-convergent behaviour in terms of phase and group speed when a consistent mass matrix is used in the formulation. In contrast, the CVFEM method and its streamline upwind derivatives yield strictly second-order behaviour. In Part II of this paper, we consider two-dimensional semi-discretizations of the advection-diffusion equation and also assess the affects of grid-induced anisotropy observed in the non-dimensional phase speed, and the discrete and artificial diffusivities. Although this work can only be considered a first step in a comprehensive multi-methods analysis and comparison, it serves to identify some of the relative strengths and weaknesses of multiple numerical methods in a common analysis framework. Published in 2004 by John Wiley & Sons, Ltd.

Predictability of drug release from water-insoluble polymeric matrix tablets.

PubMed

Grund, Julia; Körber, Martin; Bodmeier, Roland

2013-11-01

The purpose of this study was to extend the predictability of an established solution of Fick's second law of diffusion with formulation-relevant parameters and including percolation theory. Kollidon SR (polyvinyl acetate/polyvinylpyrrolidone, 80/20 w/w) matrix tablets with various porosities (10-30% v/v) containing model drugs with different solubilities (Cs=10-170 mg/ml) and in different amounts (A=10-90% w/w) were prepared by direct compression and characterized by drug release and mass loss studies. Drug release was fitted to Fick's second law to obtain the apparent diffusion coefficient. Its changes were correlated with the total porosity of the matrix and the solubility of the drug. The apparent diffusion coefficient was best described by a cumulative normal distribution over the range of total porosities. The mean of the distribution coincided with the polymer percolation threshold, and the minimum and maximum of the distribution were represented by the diffusion coefficient in pore-free polymer and in aqueous medium, respectively. The derived model was verified, and the applicability further extended to a drug solubility range of 10-1000 mg/ml. The developed mathematical model accurately describes and predicts drug release from Kollidon SR matrix tablets. It can efficiently reduce experimental trials during formulation development. Copyright © 2013 Elsevier B.V. All rights reserved.

Preference limits of the visual dynamic range for ultra high quality and aesthetic conveyance

NASA Astrophysics Data System (ADS)

Daly, Scott; Kunkel, Timo; Sun, Xing; Farrell, Suzanne; Crum, Poppy

2013-03-01

A subjective study was conducted to investigate the preferred maximum and minimum display luminances in order to determine the dynamic ranges for future displays. Two studies address the diffuse reflective regions, and a third study tested preferences of highlight regions. Preferences, as opposed to detection thresholds, were studied to provide results more directly relevant to the viewing of entertainment or art. Test images were specifically designed to test these limits without the perceptual conflicts that usually occur in these types of studies. For the diffuse range, we found a display with a dynamic range having luminances between 0.1 and 650 cd/m2 matches the average preferences. However, to satisfy 90% of the population, a dynamic range from 0.005 and ~3,000 cd/m2 is needed. Since a display should be able to produce values brighter than the diffuse white maximum, as in specular highlights and emissive sources, the highlight study concludes that even the average preferred maximum luminance for highlight reproduction is ~4,000 cd/m2.

Diffusion of multiwall carbon nanotubes (MWCNTs) through a high density polyethylene (HDPE) geomembrane.

PubMed

Saheli, P T; Rowe, R K; Petersen, E J; O'Carroll, D M

2017-05-01

The new applications for carbon nanotubes (CNTs) in various fields and consequently their greater production volume have increased their potential release to the environment. Landfills are one of the major locations where carbon nanotubes are expected to be disposed and it is important to ensure that they can limit the release of CNTs. Diffusion of multiwall carbon nanotubes (MWCNTs) dispersed in an aqueous media through a high-density polyethylene (HDPE) geomembrane (as a part of the landfill barrier system) was examined. Based on the laboratory tests, the permeation coefficient was estimated to be less than 5.1×10 -15 m 2 /s. The potential performance of a HDPE geomembrane and geosynthetic clay liner (GCL) as parts of a composite liner in containing MWCNTs was modelled for six different scenarios. The results suggest that the low value of permeation coefficient of an HDPE geomembrane makes it an effective diffusive barrier for MWCNTs and by keeping the geomembrane defects to minimum during the construction (e.g., number of holes and length of wrinkles) a composite liner commonly used in municipal solid waste landfills will effectively contain MWCNTs.

Dissemination of physical activity promotion interventions in underserved populations.

PubMed

Yancey, Antronette K; Ory, Marcia G; Davis, Sally M

2006-10-01

Achieving minimum physical activity levels of 30 or more minutes per day will require a variety of intervention strategies to engage each segment of an aging and increasingly ethnically diverse U.S. population. This article presents a focused review of the sparse literature on the diffusion of evidence-based physical activity interventions that are culturally appropriate for underserved populations. Related literature and experiential insights inform this discussion, because so few published studies report outcome data beyond the first diffusion phase of intervention development and evaluation. Three brief case studies are presented to further illustrate and exemplify key concepts and processes at several different stages in diffusing physical activity interventions. Successful engagement of underserved populations reflects a delicate balance between embracing group customs and values and recognizing the nonmonolithic nature of any sociodemographically defined group. The costs of failing to promulgate effective physical activity interventions in these groups continue to mount, in dollars, health, and lives. Researchers, practitioners, decision makers, and policymakers must partner to bridge the evidentiary gap so that the physically active lifestyle choices become the easier choices.

Presence of time-dependent diffusion in the brachial plexus.

PubMed

Mahbub, Zaid B; Peters, Andrew M; Gowland, Penny A

2018-02-01

This work describes the development of a method to measure the variation of apparent diffusion coefficient (ADC) with diffusion time (Δ) in the brachial plexus, as a potential method of probing microstructure. Diffusion-weighted MRI with body signal suppression was used to highlight the nerves from surrounding tissues, and sequence parameters were optimized for sensitivity to change with diffusion time. A porous media-restricted diffusion model based on the Latour-Mitra equation was fitted to the diffusion time-dependent ADC data from the brachial plexus nerves and cord. The ADC was observed to reduce at long diffusion times, confirming that diffusion was restricted in the nerves and cord in healthy subjects. T2 of the nerves was measured to be 80 ± 5 ms, the diffusion coefficient was found to vary from (1.5 ± 0.1) × 10 -3 mm 2 /s at a diffusion time of 18.3 ms to (1.0 ± 0.2) × 10 -3 mm 2 /s at a diffusion time of 81.3 ms. A novel method of probing restricted diffusion in the brachial plexus was developed. Resulting parameters were comparable with values obtained previously on biological systems. Magn Reson Med 79:789-795, 2018. © 2017 International Society for Magnetic Resonance in Medicine. © 2017 International Society for Magnetic Resonance in Medicine.

SB certification handout material requirements, test methods, responsibilities, and minimum classification levels for mixture-based specification for flexible base.

DOT National Transportation Integrated Search

2012-10-01

A handout with tables representing the material requirements, test methods, responsibilities, and minimum classification levels mixture-based specification for flexible base and details on aggregate and test methods employed, along with agency and co...

Design of Multishell Sampling Schemes with Uniform Coverage in Diffusion MRI

PubMed Central

Caruyer, Emmanuel; Lenglet, Christophe; Sapiro, Guillermo; Deriche, Rachid

2017-01-01

Purpose In diffusion MRI, a technique known as diffusion spectrum imaging reconstructs the propagator with a discrete Fourier transform, from a Cartesian sampling of the diffusion signal. Alternatively, it is possible to directly reconstruct the orientation distribution function in q-ball imaging, providing so-called high angular resolution diffusion imaging. In between these two techniques, acquisitions on several spheres in q-space offer an interesting trade-off between the angular resolution and the radial information gathered in diffusion MRI. A careful design is central in the success of multishell acquisition and reconstruction techniques. Methods The design of acquisition in multishell is still an open and active field of research, however. In this work, we provide a general method to design multishell acquisition with uniform angular coverage. This method is based on a generalization of electrostatic repulsion to multishell. Results We evaluate the impact of our method using simulations, on the angular resolution in one and two bundles of fiber configurations. Compared to more commonly used radial sampling, we show that our method improves the angular resolution, as well as fiber crossing discrimination. Discussion We propose a novel method to design sampling schemes with optimal angular coverage and show the positive impact on angular resolution in diffusion MRI. PMID:23625329

The Diffuse Radiation Field at High Galactic Latitudes

NASA Astrophysics Data System (ADS)

Akshaya, M. S.; Murthy, Jayant; Ravichandran, S.; Henry, R. C.; Overduin, James

2018-05-01

We have used GALEX observations of the north and south Galactic poles to study the diffuse ultraviolet background at locations where the Galactic light is expected to be at a minimum. We find offsets of 230–290 photon units in the far-UV (1531 Å) and 480–580 photon units in the near-UV (2361 Å). Of this, approximately 120 photon units can be ascribed to dust-scattered light and another 110 photon units (190 in the near-UV) to extragalactic radiation. The remaining radiation is, as yet, unidentified and amounts to 120–180 photon units in the far-UV and 300–400 photon units in the near-UV. We find that molecular hydrogen fluorescence contributes to the far-UV when the 100 μm surface brightness is greater than 1.08 MJy sr‑1.

Testing the accuracy of correlations for multicomponent mass transport of adsorbed gases in metal-organic frameworks: diffusion of H2/CH4 mixtures in CuBTC.

PubMed

Keskin, Seda; Liu, Jinchen; Johnson, J Karl; Sholl, David S

2008-08-05

Mass transport of chemical mixtures in nanoporous materials is important in applications such as membrane separations, but measuring diffusion of mixtures experimentally is challenging. Methods that can predict multicomponent diffusion coefficients from single-component data can be extremely useful if these methods are known to be accurate. We present the first test of a method of this kind for molecules adsorbed in a metal-organic framework (MOF). Specifically, we examine the method proposed by Skoulidas, Sholl, and Krishna (SSK) ( Langmuir, 2003, 19, 7977) by comparing predictions made with this method to molecular simulations of mixture transport of H 2/CH 4 mixtures in CuBTC. These calculations provide the first direct information on mixture transport of any species in a MOF. The predictions of the SSK approach are in good agreement with our direct simulations of binary diffusion, suggesting that this approach may be a powerful one for examining multicomponent diffusion in MOFs. We also use our molecular simulation data to test the ideal adsorbed solution theory method for predicting binary adsorption isotherms and a method for predicting mixture self-diffusion coefficients.

MUTUAL DIFFUSION OF PAIRS OF RARE GASES AT DIFFERENT TEMPERATURES

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

Srivastava, B.N.; Srivastava, K.P.

1959-04-01

The eoefficient of mutual diffusion of the binary gas mixtures Ne--Ar, Ar--Krs and Ne--Kr has been determined at 0, 15, 30s and 45 C. Diffusion is allowed to take place between two diffusion bulbs through a precision capillary tube and samples of gas are withdrawn from one bulb at different times and analyzed by a differential conductivity analyzer. From the experimentally determined values of the diffusion coefficient at different temperatures the unlike interaction parameters for the above gas pairs have been calculated by two different methods on the Lennard-Jones I2:6 model. These values of the force parameters are found tomore » be in good agreement with those obtained from the usual combination rules and also from the thermal diffusion data following the method of Srivastava and Madan. These values are found to reproduce the experimental data on mutual diffusion quite satisfactorily. With Kelvin's method, these data have also been utilized to calculate the self-diffusion coefficient of neon, argons and krypton. (auth)« less

Diffusion Coefficients from Molecular Dynamics Simulations in Binary and Ternary Mixtures

NASA Astrophysics Data System (ADS)

Liu, Xin; Schnell, Sondre K.; Simon, Jean-Marc; Krüger, Peter; Bedeaux, Dick; Kjelstrup, Signe; Bardow, André; Vlugt, Thijs J. H.

2013-07-01

Multicomponent diffusion in liquids is ubiquitous in (bio)chemical processes. It has gained considerable and increasing interest as it is often the rate limiting step in a process. In this paper, we review methods for calculating diffusion coefficients from molecular simulation and predictive engineering models. The main achievements of our research during the past years can be summarized as follows: (1) we introduced a consistent method for computing Fick diffusion coefficients using equilibrium molecular dynamics simulations; (2) we developed a multicomponent Darken equation for the description of the concentration dependence of Maxwell-Stefan diffusivities. In the case of infinite dilution, the multicomponent Darken equation provides an expression for [InlineEquation not available: see fulltext.] which can be used to parametrize the generalized Vignes equation; and (3) a predictive model for self-diffusivities was proposed for the parametrization of the multicomponent Darken equation. This equation accurately describes the concentration dependence of self-diffusivities in weakly associating systems. With these methods, a sound framework for the prediction of mutual diffusion in liquids is achieved.

Using hybrid implicit Monte Carlo diffusion to simulate gray radiation hydrodynamics

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

Cleveland, Mathew A., E-mail: cleveland7@llnl.gov; Gentile, Nick

This work describes how to couple a hybrid Implicit Monte Carlo Diffusion (HIMCD) method with a Lagrangian hydrodynamics code to evaluate the coupled radiation hydrodynamics equations. This HIMCD method dynamically applies Implicit Monte Carlo Diffusion (IMD) [1] to regions of a problem that are opaque and diffusive while applying standard Implicit Monte Carlo (IMC) [2] to regions where the diffusion approximation is invalid. We show that this method significantly improves the computational efficiency as compared to a standard IMC/Hydrodynamics solver, when optically thick diffusive material is present, while maintaining accuracy. Two test cases are used to demonstrate the accuracy andmore » performance of HIMCD as compared to IMC and IMD. The first is the Lowrie semi-analytic diffusive shock [3]. The second is a simple test case where the source radiation streams through optically thin material and heats a thick diffusive region of material causing it to rapidly expand. We found that HIMCD proves to be accurate, robust, and computationally efficient for these test problems.« less

Statistical Comparison of Anomalous Cosmic Rays and Galactic Cosmic Rays during the Recently Consecutive Unusual Solar Cycles

NASA Astrophysics Data System (ADS)

Zhao, L.; Zhang, H.

2014-12-01

Anomalous cosmic rays (ACRs) carry crucial information on the coupling between solar wind and interstellar medium, as well as cosmic ray modulation within the heliosphere. Due to the distinct origins and modulation processes, the spectra and abundance of ACRs are significantly different from that of galactic cosmic rays (GCRs). Since the launch of NASA's ACE spacecraft in 1997, its CRIS and SIS instruments have continuously recorded GCR and ACR intensities of several elemental heavy-ions, spanning the whole cycle 23 and the cycle 24 maximum. Here we present a statistical comparison of ACR and GCR observed by ACE spacecraft and their possible relation to solar activity. While the differential flux of ACR also exhibits apparent anti-correlation with solar activity level, the flux of the latest prolonged solar minimum (year 2009) is approximately 5% lower than its previous solar minimum (year 1997). And the minimal level of ACR flux appears in year 2004, instead of year 2001 with the strongest solar activities. The negative indexes of the power law spectra within the energy range from 5 to 30 MeV/nuc also vary with time. The spectra get harder during the solar minimum but softer during the solar maximum. The approaching solar minimum of cycle 24 is believed to resemble the Dalton or Gleissberg Minimum with extremely low solar activity (Zolotova and Ponyavin, 2014). Therefore, the different characteristics of ACRs between the coming solar minimum and the previous minimum are also of great interest. Finally, we will also discuss the possible solar-modulation processes which is responsible for different modulation of ACR and GCR, especially the roles played by diffusion and drifts. The comparative analysis will provide valuable insights into the physical modulation process within the heliosphere under opposite solar polarity and variable solar activity levels.

The Thermal Diffusivity Measurement of the Two-layer Ceramics Using the Laser Flash Methodn

NASA Astrophysics Data System (ADS)

Akoshima, Megumi; Ogwa, Mitsue; Baba, Tetsuya; Mizuno, Mineo

Ceramics-based thermal barrier coatings are used as heat and wear shields of gas turbines. There are strong needs to evaluate thermophysical properties of coating, such as thermal conductivity, thermal diffusivity and heat capacity of them. Since the coatings are attached on substrates, it is no easy to measure these properties separately. The laser flash method is one of the most popular thermal diffusivity measurement methods above room temperature for solid materials. The surface of the plate shape specimen is heated by the pulsed laser-beam, then the time variation of the temperature of the rear surface is observed by the infrared radiometer. The laser flash method is non-contact and short time measurement. In general, the thermal diffusivity of solids that are dense, homogeneous and stable, are measured by this method. It is easy to measure thermal diffusivity of a specimen which shows heat diffusion time about 1 ms to 1 s consistent with the specimen thickness of about 1 mm to 5 mm. On the other hand, this method can be applied to measure the specific heat capacity of the solids. And it is also used to estimate the thermal diffusivity of an unknown layer in the layered materials. In order to evaluate the thermal diffusivity of the coating attached on substrate, we have developed a measurement procedure using the laser flash method. The multi-layer model based on the response function method was applied to calculate the thermal diffusivity of the coating attached on substrate from the temperature history curve observed for the two-layer sample. We have verified applicability of the laser flash measurement with the multi-layer model using the measured results and the simulation. It was found that the laser flash measurement for the layered sample using the multi-layer model was effective to estimate the thermal diffusivity of an unknown layer in the sample. We have also developed the two-layer ceramics samples as the reference materials for this procedure.

Performance evaluation of the inverse dynamics method for optimal spacecraft reorientation

NASA Astrophysics Data System (ADS)

Ventura, Jacopo; Romano, Marcello; Walter, Ulrich

2015-05-01

This paper investigates the application of the inverse dynamics in the virtual domain method to Euler angles, quaternions, and modified Rodrigues parameters for rapid optimal attitude trajectory generation for spacecraft reorientation maneuvers. The impact of the virtual domain and attitude representation is numerically investigated for both minimum time and minimum energy problems. Owing to the nature of the inverse dynamics method, it yields sub-optimal solutions for minimum time problems. Furthermore, the virtual domain improves the optimality of the solution, but at the cost of more computational time. The attitude representation also affects solution quality and computational speed. For minimum energy problems, the optimal solution can be obtained without the virtual domain with any considered attitude representation.

Frequency modulation indicator, Arnold’s web and diffusion in the Stark Quadratic-Zeeman problem

NASA Astrophysics Data System (ADS)

Cordani, Bruno

2008-11-01

We notice that the fundamental frequencies of a slightly perturbed integrable Hamiltonian system are not time-constant inside a resonance but frequency modulated, as is evident from pendulum models and wavelet analysis. Exploiting an intrinsic imprecision inherent to the numerical frequency analysis algorithm itself, hence transforming a drawback into an opportunity, we define the Frequency Modulation Indicator, a very sensitive tool in detecting where fundamental frequencies are modulated, localizing so the resonances without having to resort, as in other methods, to the integration of variational equations. For the Kepler problem, the space of the orbits with a fixed energy has the topology of the product of two 2-spheres. The perturbation Hamiltonian, averaged over the mean anomaly, has surely a maximum and a minimum, to which correspond two periodic orbits in physical space. Studying the neighbourhood of these two elliptic stable points, we are able to define adapted action-angle variables, for example, the usual but “SO(4)-rotated” Delaunay variables. The procedure, implemented in the program KEPLER, is performed transparently for the user, providing a general scheme suited for generic perturbation. The method is then applied to the Stark-Quadratic-Zeeman problem, displaying very clearly the Arnold web of the resonances. Sectioning transversely one of the resonance strips so highlighted and performing a numerical frequency analysis, one is able to locate with great precision the thin stochastic layer surrounding a separatrix. Another very long (10 8 revolutions) frequency analysis on an orbit starting here reveals, as expected, a well defined pattern, which ensures that the integration errors do not eject the point out of the layer, and moreover a very slow drift in the frequency values, clearly due to Arnold diffusion.

Antibacterial properties studies of trunk barks of Terminalia ivorensis, a commercial and medicinal species on some methicillin-resistant Staphylococci species strains.

PubMed

Coulibaly, K; Zirihi, G N; Guessennd-Kouadio, N; Oussou, K R; Dosso, M

2014-09-01

Methicillin-resistant Staphylococcus aureus, Staphylococcus epidermidis and coagulase-negative Staphylococcus infections are a worldwide concern. Terminalia ivorensis, of Combretaceae family plant, is widely used traditional medicinal in Côte d'Ivoire to treat dermal diseases (affection in which Staphylococci are implied) including local inflammation and also to treat voice-loss. This study focused to investigate the effect in vitro of the extracts of trunk barks of Terminalia ivorensis on some methicillin/oxacillin-resistant strains of Staphylococcus aureus, S. epidermidis, coagulase-negative S. and reference strain of S. aureus ATCC 25923. Antibacterial activity of aqueous, 70% ethanolic 70% and aqueous residue extracts was assessed using agar disc-diffusion method and liquid medium microdilution method in 96 multi-well micro-titer plates. This method led us to determine minimum inhibition concentration (M.I.C.) and minimum bactericidal concentration (M.B.C.). The presence of chemical groups major was detected qualitatively. Aqueous and 70% ethanolic 70% extracts showed significant activity against all the bacteria except aqueous residue when compared with the standard antibiotic oxacillin (5 µg/ml). M.I.C. for aqueous and 70% ethanolic 70% extracts ranged from 0,83-16,67 mg/ml and 0,156-13,33 mg/ml respectively. Viable cell determination revealed the bactericidal nature of the two barks extracts. The 70% ethanolic 70% extract exhibited the highest activity according to the M.B.C. values. The phytochemical analysis indicates the presence of tannins, saponins, flavonoids, terpen/sterols, coumarins, polyphenols and traces of alkaloid. The in-vitro antibacterial efficacy shown by the barks of this plant and his lushness in chimical compounds, would justify use of this one in the traditional treatment of some diseases of microbial origin. These compounds could be suggested to provide alternative solution to the development of new therapeutic agents.

Formation, optical properties, and electronic structure of thin Yb silicide films on Si(111)

NASA Astrophysics Data System (ADS)

Galkin, N. G.; Maslov, A. M.; Polyarnyi, V. O.

2005-06-01

Continuous very thin (2.5-3.0 nm) and thin (16-18 nm) ytterbium suicide films with some pinhole density (3×107- 1×108 cm-2) have been formed on Si(111) by solid phase epitaxy (SPE) and reactive deposition epitaxy (RDE) growth methods on templates. The stoichiometric ytterbium suicide (YbSi2) formation has shown in SPE grown films by AES and EELS data. Very thin Yb suicide films grown by RDE method had the silicon enrichment in YbSi2 suicide composition. The analysis of LEED data and AFM imaging has shown that ytterbium suicide films had non-oriented blocks with the polycrystalline structure. The analysis of scanning region length dependencies of the root mean square roughness deviation (σR(L)) for grown suicide films has shown that the formation of ytterbium suicide in SPE and RDE growth methods is determined by the surface diffusion of Yb atoms during the three-dimensional growth process. Optical functions (n, k, α, ɛ1, ɛ2, Im ɛ1-1, neff, ɛeff) of ytterbium silicide films grown on Si(1 1 1) have been calculated from transmittance and reflectance spectra in the energy range of 0.1-6.2 eV. Two nearly discrete absorption bands have been observed in the electronic structure of Yb silicide films with different composition, which connected with interband transitions on divalent and trivalent Yb states. It was established that the reflection coefficient minimum in R-spectra at energies higher 4.2 eV corresponds to the state density minimum in Yb suicide between divalent and trivalent Yb states. It was shown from optical data that Yb silicide films have the semi-metallic properties with low state densities at energies less 0.4 eV and high state densities at 0.5-2.5 eV.

Mixing of a passive scalar by the instability of a differentially rotating axial pinch

NASA Astrophysics Data System (ADS)

Paredes, A.; Gellert, M.; Rüdiger, G.

2016-04-01

The mean-field diffusion of passive scalars such as lithium, beryllium or temperature dispersals due to the magnetic Tayler instability of a rotating axial pinch is considered. Our study is carried out within a Taylor-Couette setup for two rotation laws: solid-body quasi-Kepler rotation. The minimum magnetic Prandtl number used is 0.05, and the molecular Schmidt number Sc of the fluid varies between 0.1 and 2. An effective diffusivity coefficient for the mixing is numerically measured by the decay of a prescribed concentration peak located between both cylinder walls. We find that only models with Sc exceeding 0.1 basically provide finite instability-induced diffusivity values. We also find that for quasi-Kepler rotation at a magnetic Mach number Mm ≃ 2, the flow transits from the slow-rotation regime to the fast-rotation regime that is dominated by the Taylor-Proudman theorem. For fixed Reynolds number, the relation between the normalized turbulent diffusivity and the Schmidt number of the fluid is always linear so that also a linear relation between the instability-induced diffusivity and the molecular viscosity results, just in the sense proposed by Schatzman (1977, A&A, 573, 80). The numerical value of the coefficient in this relation reaches a maximum at Mm ≃ 2 and decreases for larger Mm, implying that only toroidal magnetic fields on the order of 1 kG can exist in the solar tachocline.

Variational fine-grained data assimilation schemes for atmospheric chemistry transport and transformation models

NASA Astrophysics Data System (ADS)

Penenko, Alexey; Penenko, Vladimir; Tsvetova, Elena

2015-04-01

The paper concerns data assimilation problem for an atmospheric chemistry transport and transformation models. Data assimilation is carried out within variation approach on a single time step of the approximated model. A control function is introduced into the model source term (emission rate) to provide flexibility to adjust to data. This function is evaluated as the minimum of the target functional combining control function norm to a misfit between measured and model-simulated analog of data. This provides a flow-dependent and physically-plausible structure of the resulting analysis and reduces the need to calculate model error covariance matrices that are sought within conventional approach to data assimilation. Extension of the atmospheric transport model with a chemical transformations module influences data assimilation algorithms performance. This influence is investigated with numerical experiments for different meteorological conditions altering convection-diffusion processes characteristics, namely strong, medium and low wind conditions. To study the impact of transformation and data assimilation, we compare results for a convection-diffusion model (without data assimilation), convection-diffusion with assimilation, convection-diffusion-reaction (without data assimilation) and convection-diffusion-reaction-assimilation models. Both high dimensionalities of the atmospheric chemistry models and a real-time mode of operation demand for computational efficiency of the algorithms. Computational issues with complicated models can be solved by using a splitting technique. As the result a model is presented as a set of relatively independent simple models equipped with a kind of coupling procedure. With regard to data assimilation two approaches can be identified. In a fine-grained approach data assimilation is carried out on the separate splitting stages [1,2] independently on shared measurement data. The same situation arises when constructing a hybrid model out of two models each having its own assimilation scheme. In integrated schemes data assimilation is carried out with respect to the split model as a whole. First approach is more efficient from computational point of view, for in some important cases it can be implemented without iterations [2]. Its shortcoming is that control functions in different part of the model are adjusted independently thus having less evident physical sense. With the aid of numerical experiments we compare the two approaches. Work has been partially supported by COST Action ES1004 STSM Grants #16817 and #21654, RFBR 14-01-31482 mol a and 14-01-00125, Programmes # 4 Presidium RAS and # 3 MSD RAS, integration projects SB RAS #8 and #35. References: [1] V. V. Penenko Variational methods of data assimilation and inverse problems for studying the atmosphere, ocean, and environment Num. Anal. and Appl., 2009 V 2 No 4, 341-351. [2] A.V. Penenko and V.V. Penenko. Direct data assimilation method for convection-diffusion models based on splitting scheme. Computational technologies, 19(4):69-83, 2014.

A scaled-ionic-charge simulation model that reproduces enhanced and suppressed water diffusion in aqueous salt solutions.

PubMed

Kann, Z R; Skinner, J L

2014-09-14

Non-polarizable models for ions and water quantitatively and qualitatively misrepresent the salt concentration dependence of water diffusion in electrolyte solutions. In particular, experiment shows that the water diffusion coefficient increases in the presence of salts of low charge density (e.g., CsI), whereas the results of simulations with non-polarizable models show a decrease of the water diffusion coefficient in all alkali halide solutions. We present a simple charge-scaling method based on the ratio of the solvent dielectric constants from simulation and experiment. Using an ion model that was developed independently of a solvent, i.e., in the crystalline solid, this method improves the water diffusion trends across a range of water models. When used with a good-quality water model, e.g., TIP4P/2005 or E3B, this method recovers the qualitative behaviour of the water diffusion trends. The model and method used were also shown to give good results for other structural and dynamic properties including solution density, radial distribution functions, and ion diffusion coefficients.

A global ocean climatological atlas of the Turner angle: implications for double-diffusion and water-mass structure

NASA Astrophysics Data System (ADS)

You, Yuzhu

2002-11-01

The 1994 Levitus climatological atlas is used to calculate the Turner angle (named after J. Stewart Turner) to examine which oceanic water masses are favorable for double-diffusion in the form of diffusive convection or salt-fingering and which are doubly stable. This atlas complements the Levitus climatology. It reveals the major double-diffusive signals associated with large-scale water-mass structure. In total, about 44% of the oceans display double-diffusion, of which 30% is salt-fingering and 14% is diffusive double-diffusion. Results show that various central and deep waters are favorable for salt-fingering. The former is due to positive evaporation minus precipitation, and the latter is due to thermohaline circulation, i.e. the southward spreading of relatively warm, salty North Atlantic Deep Water (NADW) overlying cold, fresh Antarctic Bottom Water. In the northern Indian Ocean and eastern North Atlantic, favorable conditions for salt-fingering are found throughout the water column. The Red Sea (including the Persian Gulf) and Mediterranean Sea are the sources of warm, salty water for the ocean. As consequence, temperature and salinity in these outflow regions both decrease from the sea surface to the bottom. On the other hand, ocean currents are in general sluggish in these regions. In the polar and subpolar regions of Arctic and Antarctic, Okhotsk Sea, Gulf of Alaska, the subpolar gyre of the North Pacific, the Labrador Sea, and the Norwegian Sea, the upper layer water is favorable for diffusive convection because of high latitude surface cooling and ice melting. Weak and shallow diffusive convection is also found throughout tropical regions and the Bay of Bengal. The former is due to excessive precipitation over evaporation and rain cooling, and the latter is due to both precipitation and river runoff. Diffusive convection in the ocean's interior is unique to the South Atlantic between Antarctic Intermediate Water and upper NADW (uNADW). It is the consequence of the intrusive equatorward flow of upper Circumpolar Deep Water, which carries with it the minimum temperature and very low salinity overlying warm, salty uNADW.

Parameters estimation using the first passage times method in a jump-diffusion model

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

Khaldi, K., E-mail: kkhaldi@umbb.dz; LIMOSE Laboratory, Boumerdes University, 35000; Meddahi, S., E-mail: samia.meddahi@gmail.com

2016-06-02

The main purposes of this paper are two contributions: (1) it presents a new method, which is the first passage time (FPT method) generalized for all passage times (GPT method), in order to estimate the parameters of stochastic Jump-Diffusion process. (2) it compares in a time series model, share price of gold, the empirical results of the estimation and forecasts obtained with the GPT method and those obtained by the moments method and the FPT method applied to the Merton Jump-Diffusion (MJD) model.

The quantitative impact of the mesopore size on the mass transfer mechanism of the new 1.9μm fully porous Titan-C18 particles. I: analysis of small molecules.

PubMed

Gritti, Fabrice; Guiochon, Georges

2015-03-06

Previous data have shown that could deliver a minimum reduced plate height as small as 1.7. Additionally, the reduction of the mesopore size after C18 derivatization and the subsequent restriction for sample diffusivity across the Titan-C18 particles were found responsible for the unusually small value of the experimental optimum reduced velocity (5 versus 10 for conventional particles) and for the large values of the average reduced solid-liquid mass transfer resistance coefficients (0.032 versus 0.016) measured for a series of seven n-alkanophenones. The improvements in column efficiency made by increasing the average mesopore size of the Titan silica from 80 to 120Å are investigated from a quantitative viewpoint based on the accurate measurements of the reduced coefficients (longitudinal diffusion, trans-particle mass transfer resistance, and eddy diffusion) and of the intra-particle diffusivity, pore, and surface diffusion for the same series of n-alkanophenone compounds. The experimental results reveal an increase (from 0% to 30%) of the longitudinal diffusion coefficients for the same sample concentration distribution (from 0.25 to 4) between the particle volume and the external volume of the column, a 40% increase of the intra-particle diffusivity for the same sample distribution (from 1 to 7) between the particle skeleton volume and the bulk phase, and a 15-30% decrease of the solid-liquid mass transfer coefficient for the n-alkanophenone compounds. Pore and surface diffusion are increased by 60% and 20%, respectively. The eddy dispersion term and the maximum column efficiency (295000plates/m) remain virtually unchanged. The rate of increase of the total plate height with increasing the chromatographic speed is reduced by 20% and it is mostly controlled (75% and 70% for 80 and 120Å pore size) by the flow rate dependence of the eddy dispersion term. Copyright © 2015 Elsevier B.V. All rights reserved.

Reassembling the Information Technology Innovation Process: An Actor Network Theory Method for Managing the Initiation, Production, and Diffusion of Innovations

NASA Astrophysics Data System (ADS)

Zendejas, Gerardo; Chiasson, Mike

This paper will propose and explore a method to enhance focal actors' abilities to enroll and control the many social and technical components interacting during the initiation, production, and diffusion of innovations. The reassembling and stabilizing of such components is the challenging goal of the focal actors involved in these processes. To address this possibility, a healthcare project involving the initiation, production, and diffusion of an IT-based innovation will be influenced by the researcher, using concepts from actor network theory (ANT), within an action research methodology (ARM). The experiences using this method, and the nature of enrolment and translation during its use, will highlight if and how ANT can provide a problem-solving method to help assemble the social and technical actants involved in the diffusion of an innovation. Finally, the paper will discuss the challenges and benefits of implementing such methods to attain widespread diffusion.

Stochastic simulation of reaction-diffusion systems: A fluctuating-hydrodynamics approach

NASA Astrophysics Data System (ADS)

Kim, Changho; Nonaka, Andy; Bell, John B.; Garcia, Alejandro L.; Donev, Aleksandar

2017-03-01

We develop numerical methods for stochastic reaction-diffusion systems based on approaches used for fluctuating hydrodynamics (FHD). For hydrodynamic systems, the FHD formulation is formally described by stochastic partial differential equations (SPDEs). In the reaction-diffusion systems we consider, our model becomes similar to the reaction-diffusion master equation (RDME) description when our SPDEs are spatially discretized and reactions are modeled as a source term having Poisson fluctuations. However, unlike the RDME, which becomes prohibitively expensive for an increasing number of molecules, our FHD-based description naturally extends from the regime where fluctuations are strong, i.e., each mesoscopic cell has few (reactive) molecules, to regimes with moderate or weak fluctuations, and ultimately to the deterministic limit. By treating diffusion implicitly, we avoid the severe restriction on time step size that limits all methods based on explicit treatments of diffusion and construct numerical methods that are more efficient than RDME methods, without compromising accuracy. Guided by an analysis of the accuracy of the distribution of steady-state fluctuations for the linearized reaction-diffusion model, we construct several two-stage (predictor-corrector) schemes, where diffusion is treated using a stochastic Crank-Nicolson method, and reactions are handled by the stochastic simulation algorithm of Gillespie or a weakly second-order tau leaping method. We find that an implicit midpoint tau leaping scheme attains second-order weak accuracy in the linearized setting and gives an accurate and stable structure factor for a time step size of an order of magnitude larger than the hopping time scale of diffusing molecules. We study the numerical accuracy of our methods for the Schlögl reaction-diffusion model both in and out of thermodynamic equilibrium. We demonstrate and quantify the importance of thermodynamic fluctuations to the formation of a two-dimensional Turing-like pattern and examine the effect of fluctuations on three-dimensional chemical front propagation. By comparing stochastic simulations to deterministic reaction-diffusion simulations, we show that fluctuations accelerate pattern formation in spatially homogeneous systems and lead to a qualitatively different disordered pattern behind a traveling wave.

Stochastic simulation of reaction-diffusion systems: A fluctuating-hydrodynamics approach

DOE PAGES

Kim, Changho; Nonaka, Andy; Bell, John B.; ...

2017-03-24

Here, we develop numerical methods for stochastic reaction-diffusion systems based on approaches used for fluctuating hydrodynamics (FHD). For hydrodynamic systems, the FHD formulation is formally described by stochastic partial differential equations (SPDEs). In the reaction-diffusion systems we consider, our model becomes similar to the reaction-diffusion master equation (RDME) description when our SPDEs are spatially discretized and reactions are modeled as a source term having Poisson fluctuations. However, unlike the RDME, which becomes prohibitively expensive for an increasing number of molecules, our FHD-based description naturally extends from the regime where fluctuations are strong, i.e., each mesoscopic cell has few (reactive) molecules,more » to regimes with moderate or weak fluctuations, and ultimately to the deterministic limit. By treating diffusion implicitly, we avoid the severe restriction on time step size that limits all methods based on explicit treatments of diffusion and construct numerical methods that are more efficient than RDME methods, without compromising accuracy. Guided by an analysis of the accuracy of the distribution of steady-state fluctuations for the linearized reaction-diffusion model, we construct several two-stage (predictor-corrector) schemes, where diffusion is treated using a stochastic Crank-Nicolson method, and reactions are handled by the stochastic simulation algorithm of Gillespie or a weakly second-order tau leaping method. We find that an implicit midpoint tau leaping scheme attains second-order weak accuracy in the linearized setting and gives an accurate and stable structure factor for a time step size of an order of magnitude larger than the hopping time scale of diffusing molecules. We study the numerical accuracy of our methods for the Schlögl reaction-diffusion model both in and out of thermodynamic equilibrium. We demonstrate and quantify the importance of thermodynamic fluctuations to the formation of a two-dimensional Turing-like pattern and examine the effect of fluctuations on three-dimensional chemical front propagation. Furthermore, by comparing stochastic simulations to deterministic reaction-diffusion simulations, we show that fluctuations accelerate pattern formation in spatially homogeneous systems and lead to a qualitatively different disordered pattern behind a traveling wave.« less

Demonstration and Validation of a Regenerated Cellulose Dialysis Membrane Diffusion Sampler for Monitoring Ground-Water Quality and Remediation Progress at DoD Sites

DTIC Science & Technology

2010-04-01

LDPE low-density polyethylene LF low-flow purging LRL laboratory reporting level MDL minimum detection limit MNA monitored natural attenuation...shaped bag made of flexible low-density polyethylene ( LDPE ) (Vroblesky, 2001a, 2001b). The LDPE tube is heat-sealed on one end, filled with high...from small- diameter LDPE tubing that fits into small-diameter wells. These PDB samplers have been shown to be useful only for collection of VOCs

Study of the thermal properties of low k dielectric thin films

NASA Astrophysics Data System (ADS)

Hu, Chuan

The integration of low k material is of great importance for the performance of an electronic device as the result of shrink in the device size. The thermal conductivity of low k materials is usually much lower than that of the traditionally used SiO2 and thus a tradeoff has to be properly evaluated. The thermal conduction in amorphous thin films is not only industrially important but also scientifically interesting. Many efforts have been done to understand the "phonon" propagation in an amorphous medium. Two experimental tools to study thermal properties are developed. The photothermal technique is an optical far field method and the 3o technique is an electrical near field method. The free standing and on-wafer photothermal techniques measure the out-of-plane thermal diffusivity directly and the 3o technique measures the out-of-plane thermal conductivity under our typical experimental configurations. The thermal diffusivities of a rigid rod like polyimide PI2611 and a flexible PI2545 are measured using the photothermal technique. The thermal anisotropy is studied by comparing our measurements with the result from in-plane measurements. The porosity dependence of thermal conductivity of Xerogel is studied by 3o technique. The fast drop in thermal conductivity is explained as the result of porosity and thermal contact in solid phase. A scaling rule of thermal conductivity as a function of porosity is proposed to the show the tradeoff between the thermal and the electrical properties. The possible impact of integrating low k materials in an interconnect structure is evaluated. The effective thermal conductivity of polymeric thin films as thin as 70 A is measured by 3o technique. The interfacial thermal resistances of Al/polymer/Si sandwich structure are found to be about 2 to 10 times larger than that of Al/SiO2/Si and the bulk thermal conductivities of polymers are found to be about 5 to 10 times smaller than that of SiO 2. The thermal conductivity of amorphous material is explained using the minimum thermal length model. The interfacial thermal resistance is explained using the acoustic and diffuse mismatch models as well as roughness and inelastic scattering at the interface.

FRACTIONAL PEARSON DIFFUSIONS.

PubMed

Leonenko, Nikolai N; Meerschaert, Mark M; Sikorskii, Alla

2013-07-15

Pearson diffusions are governed by diffusion equations with polynomial coefficients. Fractional Pearson diffusions are governed by the corresponding time-fractional diffusion equation. They are useful for modeling sub-diffusive phenomena, caused by particle sticking and trapping. This paper provides explicit strong solutions for fractional Pearson diffusions, using spectral methods. It also presents stochastic solutions, using a non-Markovian inverse stable time change.

Antimicrobial activity of jasmine oil against oral microorganisms

NASA Astrophysics Data System (ADS)

Thaweboon, S.; Thaweboon, B.; Kaypetch, R.

2018-02-01

Jasmine sambac is a species of jasmine indigenous to the tropical and warm temperature regions in particular West and Southeast Asia. Essential oil extracted from the flowers of J. sambac has been shown to have anti-oxidant activity. However, very little information regarding antimicrobial activity especially oral microorganisms exists. Objective: To investigate antimicrobial effect of essential oil extracted from flowers of J. sambac against various oral microorganisms. Materials and Methods: Oral microbial strains used in the study were Streptococcus mutans KPSK2, Staphylococcus aureus ATCC 5638, Lactobacillus casei ATCC 6363, Klebsiella pneumoniae (clinical isolate), Escherichia coli ATCC 25922, Candida albicans ATCC 10231, Candida krusei ATCC 6258, Candida parapsilosis ATCC 22019, Candida tropicalis (clinical isolate), Candida glabrata ATCC 90030, Candida pseudotropicalis (clinical isolate) and Candida stellatoidia (clinical isolate). The potential of microbial growth inhibition of the oil was firstly screened by Kirby-Bauer disk diffusion method and then the minimum inhibitory concentration (MIC) was determined by agar dilution method. Results: Jasmine oil showed antimicrobial activities against S. mutans, L. casei, E. coli and all strains of Candida species with the zones of inhibition ranging from 9 to 26 mm and MIC values of 0.19-1.56 %v/v. Conclusion: Results from the present study are scientific evidence to demonstrate that jasmine oil could be employed as a natural antimicrobial agent against oral microorganisms.

Interactive Near-Field Illumination for Photorealistic Augmented Reality with Varying Materials on Mobile Devices.

PubMed

Rohmer, Kai; Buschel, Wolfgang; Dachselt, Raimund; Grosch, Thorsten

2015-12-01

At present, photorealistic augmentation is not yet possible since the computational power of mobile devices is insufficient. Even streaming solutions from stationary PCs cause a latency that affects user interactions considerably. Therefore, we introduce a differential rendering method that allows for a consistent illumination of the inserted virtual objects on mobile devices, avoiding delays. The computation effort is shared between a stationary PC and the mobile devices to make use of the capacities available on both sides. The method is designed such that only a minimum amount of data has to be transferred asynchronously between the participants. This allows for an interactive illumination of virtual objects with a consistent appearance under both temporally and spatially varying real illumination conditions. To describe the complex near-field illumination in an indoor scenario, HDR video cameras are used to capture the illumination from multiple directions. In this way, sources of illumination can be considered that are not directly visible to the mobile device because of occlusions and the limited field of view. While our method focuses on Lambertian materials, we also provide some initial approaches to approximate non-diffuse virtual objects and thereby allow for a wider field of application at nearly the same cost.

Silver nanoparticles toxicity against airborne strains of Staphylococcus spp.

PubMed

Wolny-Koładka, Katarzyna A; Malina, Dagmara K

2017-11-10

The aim of this study was to explore the toxicity of silver nanoparticles (AgNPs) synthesized by chemical reduction method assessment with regard to airborne strains of Staphylococcus spp. The first step of the experiment was the preparation of silver nanoparticle suspension. The suspension was obtained by a fast and simple chemical method involving the reduction of silver ions through a reducing factor in the presence of the suitable stabilizer required to prevent the aggregation. In the second stage, varied instrumental techniques were used for the analysis and characterization of the obtained nanostructures. Third, the bacteria of the Staphylococcus genus were isolated from the air under stable conditions with 47 sports and recreational horses, relatively. Next, isolated strains were identified using biochemical and spectrophotometric methods. The final step was the evaluation of the Staphylococcus genus sensitivity to nanosilver using the disk diffusion test. It has been proven that prepared silver nanoparticles exhibit strong antibacterial properties. The minimum inhibitory concentration for tested isolates was 30 μg/mL. It has been found that the sensitivity of Staphylococcus spp. isolated from six identified species differs considerably. The size distribution of bacterial growth inhibition zones indicates that resistance to various nanosilver concentrations is an individual strain feature, and has no connection with belonging to a specific species.

Experimental study of the nonlinear diffusion of a magnetic field and skin explosion of cylindrical conductors

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

Chaikovsky, S. A.; Datsko, I. M.; Labetskaya, N. A.

The paper presents the results of an experimental study of the skin explosion of cylindrical conductors of diameter 1–3 mm (copper, aluminum, titanium, steel 3, and stainless steel) at a peak magnetic field of 200–600 T. The experiments were carried out on the MIG pulsed power generator at a current of up to 2.5 MA and a current rise time of 100 ns. The surface explosion of a conductor was identified by the appearance of a flash of extreme ultraviolet radiation. A minimum magnetic induction has been determined below which no plasma is generated at the conductor surface. For copper, aluminum, steel 3,more » titanium, and stainless steel, the minimum magnetic induction has been estimated to be (to within 10%) 375, 270, 280, 220, and 245 T, respectively.« less

A Two Dimensional Prediction of Solar Cycle 25

NASA Astrophysics Data System (ADS)

Munoz-Jaramillo, A.; Martens, P. C.

2017-12-01

To this date solar cycle most cycle predictions have focused on the forecast of solar cycle amplitude and cycle bell-curve shape. However, recent intriguing observational results suggest that all solar cycles follow the same longitudinal path regardless of their amplitude, and have a very similar decay once they reach a sufficient level of maturity. Cast in the light of our current understanding, these results suggest that the toroidal fields inside the Sun are subject to a very high turbulent diffusivity (of the order of magnitude of mixing-length estimates), and their equatorward propagation is driven by a steady meridional flow. Assuming this is the case, we will revisit the relationship between the polar fields at minimum and the amplitude of the next cycle and deliver a new generation of polar-field based predictions that include the depth of the minimum, as well as the latitude and time of the first active regions of solar cycle 25.

Reduction of thermal conductivity in MnSi{sub 1.7} multi-layered thin films with artificially inserted Si interfaces

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

Kurosaki, Y., E-mail: yosuke.kurosaki.uy@hitachi.com; Yabuuchi, S.; Nishide, A.

We report a lowered lattice thermal conductivity in nm-scale MnSi{sub 1.7}/Si multilayers which were fabricated by controlling thermal diffusions of Mn and Si atoms. The thickness of the constituent layers is 1.5–5.0 nm, which is comparable to the phonon mean free path of both MnSi{sub 1.7} and Si. By applying the above nanostructures, we reduced the lattice thermal conductivity down to half that of bulk MnSi{sub 1.7}/Si composite materials. The obtained value of 1.0 W/K m is the experimentally observed minimum in MnSi{sub 1.7}-based materials without any heavy element doping and close to the minimum thermal conductivity. We attribute the reduced latticemore » thermal conductivity to phonon scattering at the MnSi{sub 1.7}/Si interfaces in the multilayers.« less

A method for the estimate of the wall diffusion for non-axisymmetric fields using rotating external fields

NASA Astrophysics Data System (ADS)

Frassinetti, L.; Olofsson, K. E. J.; Fridström, R.; Setiadi, A. C.; Brunsell, P. R.; Volpe, F. A.; Drake, J.

2013-08-01

A new method for the estimate of the wall diffusion time of non-axisymmetric fields is developed. The method based on rotating external fields and on the measurement of the wall frequency response is developed and tested in EXTRAP T2R. The method allows the experimental estimate of the wall diffusion time for each Fourier harmonic and the estimate of the wall diffusion toroidal asymmetries. The method intrinsically considers the effects of three-dimensional structures and of the shell gaps. Far from the gaps, experimental results are in good agreement with the diffusion time estimated with a simple cylindrical model that assumes a homogeneous wall. The method is also applied with non-standard configurations of the coil array, in order to mimic tokamak-relevant settings with a partial wall coverage and active coils of large toroidal extent. The comparison with the full coverage results shows good agreement if the effects of the relevant sidebands are considered.

Enhanced antibacterial activity of amino acids-functionalized multi walled carbon nanotubes by a simple method.

PubMed

Zardini, Hadi Zare; Amiri, Ahmad; Shanbedi, Mehdi; Maghrebi, Morteza; Baniadam, Majid

2012-04-01

Multi-walled carbon nanotubes (MWCNTs) were first functionalized by arginine and lysine under microwave radiation. Surface functionalization was confirmed by Fourier transform infrared (FTIR) spectroscopy, Raman spectroscopy, and transmission electron microscopy (TEM). After the MWCNTs were functionalized by arginine and lysine, the antibacterial activity of all treated samples was increased significantly against all bacteria that were tested. Based on the observed minimum inhibitory concentration and radial diffusion assay, the sequence of antibacterial activity was MWCNTs-arginine>MWCNTs-lysine>pristine MWCNTs. The functionalized MWCNTs were especially effective against gram-negative bacteria (e.g., Escherichia coli and Salmonella typhimurium). Interestingly, the MWCNT samples were effective against the resistant strain Staphylococcos aureus. The enhanced antibacterial activity was attributed to electrostatic adsorption of bacteria membrane due to positive charges of the functional groups on MWCNTs surface. Since MWCNTs have lower cytotoxicity than single-walled carbon nanotubes, their functionalization with cationic amino acids could be a beneficial approach in the disinfection industry. Copyright © 2011 Elsevier B.V. All rights reserved.

Flame Stabilization on Microscopic Scale of Wet Biogas with Microflame

NASA Astrophysics Data System (ADS)

Ida, Tamio; Fuchihata, Manabu; Mizuno, Satoru

Harvesting, transportation, energy conversion and the high-efficient utilization, cascade method and market formation besides become with the indispensable element in order to utilize the biomass resource. There are two type biogases; it is gasified gas from dried biomass by partially combustion and wet biogas from wet biomass by methane fermentation, especially from the livestock excrement resources. This paper discusses an experimental study for flame stabilization on microscopic scale with wet biogas (mainly 0.6CH4+0.4CO2). In this study, the microflame with the wet biogas fuels are formed by the diffusion flame on the coppered straight pipes of inner diameter 0.02mm ˜ 1.5mm. This study is obtained stability mapping on microscopic scale of formed microflame by wet biogas fuels. The flame stability limit conditions on microscopic scale of wet biogas is drawn with blow off and extinction flame double limit lines. It is suggested that minimum mixing spatial scale change by the each mixing ratio of the wet biogas.

Antibacterial activity of some bryophytes used traditionally for the treatment of burn infections.

PubMed

Singh, Meenakshi; Singh, Shweta; Nath, Virendra; Sahu, Vinay; Rawat, Ajay Kumar Singh

2011-05-01

Plagiochasma appendiculatum L. & L. (Aytoniaceae), Conocephalum conicum (L.) Necker (Conocephalaceae), Bryum argenteum Hedw. (Bryaceae), and Mnium marginatum (With.) P. Beauv. (Mniaceae) are bryophytes (liverworts and mosses) used by traditional healers for the treatment of burn, cuts, wounds, and skin disorders. This study evaluated the antibacterial activity of four bryophytes against some common bacteria responsible for burn infections. Different fractions of bryophytes were screened using the disc diffusion (qualitative) and broth microdilution (quantitative) methods, according to the guidelines of the National Committee for Clinical and Laboratory Standards. Chloroform fractions of liverworts were more active against Gram negative strains while butanol fractions of mosses had significant activity against Gram positive bacteria. Staphylococcus aureus was the most sensitive strain of those tested with the butanol fraction of M. marginatum (moss), with the strongest inhibition zone of 102.92% and minimum inhibitory concentration of 30 μg mL(-1). Our findings support the use of the bryophytes in traditional medicine for burn infections because of their significant antibacterial activity.

Assessment of antinociceptive, antipyretic and antimicrobial activity of Piper cubeba L. essential oil in animal models.

PubMed

Mothana, Ramzi; Alsaid, Mansour; Khaled, Jamal M; Alharbi, Naiyf S; Alatar, Abdulrahman; Raish, Mohammad; Al-Yahya, Mohammed; Rafatullah, Syed; Parvez, Mohammad Khalid; Ahamad, Syed Rizwan

2016-03-01

This study was designed to investigate the possible antiniciceptive, antipyretic and antimicrobial activities of the essential oil obtained from the fruits of Piper Cubeba (L.). To assess the antinociceptive and antipyretic activities, three doses (150, 300 and 600 mg/kg, i.p.) were tested in acetic acid-induced abdominal writhing, tail flick reaction and hot-plate and Brewer's yeast-induced hyperpyrexia test models in animals. Moreover, the antimicrobial activity was examined using agar diffusion method and broth micro-dilution assay for minimum inhibitory concentrations (MIC). The Piper Cubeba essential oil (PCEO) showed a marked antinociception (17, 30 and 54%) and an increase in reaction time in mice in the flick tailed and hot-plate tests. The brewer's yeast induced hyperpyrexia was decreased in a dose dependent manner. PCEO also exhibited a strong antimicrobial potential. These findings confirm the traditional analgesic indications of P. cubeba oil and provide persuasive evidence and support its use in Arab traditional medicine.

Antimicrobial effect against different bacterial strains and bacterial adaptation to essential oils used as feed additives.

PubMed

Melo, Antonio Diego Brandão; Amaral, Amanda Figueiredo; Schaefer, Gustavo; Luciano, Fernando Bittencourt; de Andrade, Carla; Costa, Leandro Batista; Rostagno, Marcos Horácio

2015-10-01

The aim of this study was to evaluate the antimicrobial activity and determine the minimum bactericidal concentration (MBC) of the essential oils derived from Origanum vulgare (oregano), Melaleuca alternifolia (tea tree), Cinnamomum cassia (cassia), and Thymus vulgaris (white thyme) against Salmonella Typhimurium, Salmonella Enteritidis, Escherichia coli, Staphylococcus aureus and Enterococcus faecalis. The study also investigated the ability of these different bacterial strains to develop adaptation after repetitive exposure to sub-lethal concentrations of these essential oils. The MBC of the essential oils studied was determined by disc diffusion and broth dilution methods. All essential oils showed antimicrobial effect against all bacterial strains. In general, the development of adaptation varied according to the bacterial strain and the essential oil (tea tree > white thyme > oregano). Therefore, it is important to use essential oils at efficient bactericidal doses in animal feed, food, and sanitizers, since bacteria can rapidly develop adaptation when exposed to sub-lethal concentrations of these oils.

Antimicrobial effect against different bacterial strains and bacterial adaptation to essential oils used as feed additives

PubMed Central

Melo, Antonio Diego Brandão; Amaral, Amanda Figueiredo; Schaefer, Gustavo; Luciano, Fernando Bittencourt; de Andrade, Carla; Costa, Leandro Batista; Rostagno, Marcos Horácio

2015-01-01

The aim of this study was to evaluate the antimicrobial activity and determine the minimum bactericidal concentration (MBC) of the essential oils derived from Origanum vulgare (oregano), Melaleuca alternifolia (tea tree), Cinnamomum cassia (cassia), and Thymus vulgaris (white thyme) against Salmonella Typhimurium, Salmonella Enteritidis, Escherichia coli, Staphylococcus aureus and Enterococcus faecalis. The study also investigated the ability of these different bacterial strains to develop adaptation after repetitive exposure to sub-lethal concentrations of these essential oils. The MBC of the essential oils studied was determined by disc diffusion and broth dilution methods. All essential oils showed antimicrobial effect against all bacterial strains. In general, the development of adaptation varied according to the bacterial strain and the essential oil (tea tree > white thyme > oregano). Therefore, it is important to use essential oils at efficient bactericidal doses in animal feed, food, and sanitizers, since bacteria can rapidly develop adaptation when exposed to sub-lethal concentrations of these oils. PMID:26424908