scholarly journals Evaluation of four sampling devices for Burkholderia pseudomallei laboratory aerosol studies

2021 ◽  
Vol 15 (2) ◽  
pp. e0009001
Author(s):  
Michael Schuit ◽  
Sierra Gardner ◽  
Jill Taylor ◽  
Paul Dabisch
Keyword(s):  
Animal Models ◽  
Burkholderia Pseudomallei ◽  
Culture Media ◽  
Accurate Determination ◽  
Field Studies ◽  
Cascade Impactor ◽  
Laboratory Studies ◽  
Air Samples ◽  
Sampling Process

Previous field and laboratory studies investigating airborne Burkholderia pseudomallei have used a variety of different aerosol samplers to detect and quantify concentrations of the bacteria in aerosols. However, the performance of aerosol samplers can vary in their ability to preserve the viability of collected microorganisms, depending on the resistance of the organisms to impaction, desiccation, or other stresses associated with the sampling process. Consequently, sampler selection is critical to maximizing the probability of detecting viable microorganisms in collected air samples in field studies and for accurate determination of aerosol concentrations in laboratory studies. To inform such decisions, the present study assessed the performance of four laboratory aerosol samplers, specifically the all-glass impinger (AGI), gelatin filter, midget impinger, and Mercer cascade impactor, for collecting aerosols containing B. pseudomallei generated from suspensions in two types of culture media. The results suggest that the relative performance of the sampling devices is dependent on the suspension medium utilized for aerosolization. Performance across the four samplers was similar for aerosols generated from suspensions supplemented with 4% glycerol. However, for aerosols generated from suspensions without glycerol, use of the filter sampler or an impactor resulted in significantly lower estimates of the viable aerosol concentration than those obtained with either the AGI or midget impinger. These results demonstrate that sampler selection has the potential to affect estimation of doses in inhalational animal models of melioidosis, as well as the likelihood of detection of viable B. pseudomallei in the environment, and will be useful to inform design of future laboratory and field studies.

Characterization of Triazine-Resistant Giant Foxtail (Setaria faberi) and its Control in No-tillage Corn (Zea mays)

Weed Science ◽  
1989 ◽  
Vol 37 (4) ◽  
pp. 591-595 ◽  
Author(s):  
Ronald L. Ritter ◽  
Lisa M. Kaufman ◽  
Thomas J. Monaco ◽  
William P. Novitzky ◽  
Donald E. Moreland
Keyword(s):  
Zea Mays ◽  
Field Studies ◽  
Differential Sensitivity ◽  
No Tillage ◽  
Laboratory Studies ◽  
Annual Grass ◽  
Setaria Faberi ◽  
Giant Foxtail

Triazine-resistant giant foxtail was identified in 1984 near Delta, PA. In field studies conducted from 1985 to 1987, preemergence applications of atrazine with cyanazine or simazine provided poor (≤60%) season-long control of this annual grass in no-tillage corn. Best season-long preemergence control was obtained with metolachlor or microencapsulated formulations of alachlor or EPTC. Postemergence applications of cyanazine or tridiphane + atrazine + crop oil provided poor giant foxtail control. Postdirected applications of paraquat resulted in fair (≥70%) control of giant foxtail through midseason. In greenhouse studies, triazineresistant (R) giant foxtail tolerated preemergence applications of atrazine or simazine at dosages to 9.0 kg ai/ha. Triazine-sensitive (S) giant foxtail was injured by 2.2 kg/ha and higher rates of atrazine and simazine. In laboratory studies, the I50for inhibition by atrazine of photoinduced electron transport in thylakoids isolated from S and R biotypes was determined to be 0.24 and 205 μM, respectively. The differential sensitivity was paralleled by simazine. However, the limited solubility of simazine prevented determination of an I50value with thylakoids from the R biotype.

scholarly journals Comparison of Capillary Electrophoresis and Liquid Chromatography for Determination of Sulfonylurea Herbicides in Soil

1999 ◽  
Vol 82 (6) ◽  
pp. 1534-1541 ◽  
Author(s):  
Hubert J Menne ◽  
Karin Janowitz ◽  
Bernhard M Berger
Keyword(s):  
Capillary Electrophoresis ◽  
Liquid Chromatography ◽  
Solid Phase ◽  
Field Studies ◽  
Operating Costs ◽  
Sulfonylurea Herbicides ◽  
Laboratory Studies ◽  
Coefficients Of Variation ◽  
Chlorimuron Ethyl

Abstract Two analytical methods developed for degradation studies in soil were compared for the simultaneous determination of sulfonylurea herbicides. The compounds were extracted with phosphate buffer from soil samples after purification and enrichment steps by solid-phase extraction. Samples were analyzed by liquid chromatography (LC) or capillary electrophoresis (CE) with UV detection. Amidosulfuron, bensulfuron-methyl, chlorimuron-ethyl, chlorsulfuron, ethametsulfuron-methyl, metsulfuron-methyl, nicosulfuron, primisulfuron-methyl, sulfometuron-methyl, thifensulfuron-methyl, triasulfuron, and tribenuron-methyl were separated within 90 and 35 min by LC and CE, respectively. Average recoveries, determined with LC for 5 sulfonylureas in 1–100 μg/kg soil ranged from 74 to 103%, and those determined with CE for 10 sulfonylureas in 2-20 μg/kg soil ranged from 87 to 105%. Bensulfuron-methyl was recovered at lower levels of 52%. The limits of quantitation were 1.0 and 2.0 μg/kg soil for LC and CE, respectively. Coefficients of variation were higher for CE than for LC. Although both methods are suitable, the LC method, which is more sensitive and accurate than the CE method, is preferred for field studies. However, CE, which was shown to be faster with lower operating costs and unlimited repeatability of the analysis due to little injection volumes, is preferred for laboratory studies.

scholarly journals Quantitative Analysis of Thyroid Hormone Metabolites in Cell Culture Samples Using LC-MS/MS

2015 ◽  
Vol 4 (Suppl. 1) ◽  
pp. 51-58 ◽  
Author(s):  
Daniel Rathmann ◽  
Eddy Rijntjes ◽  
Julika Lietzow ◽  
Josef Köhrle
Keyword(s):  
Cell Culture ◽  
Matrix Effects ◽  
Culture Media ◽  
Accurate Determination ◽  
Liquid Extraction ◽  
Process Efficiency ◽  
Phenol Red ◽  
Cell Culture Media ◽  
Liquid Liquid Extraction

A liquid-liquid extraction and liquid chromatography-electrospray ionization tandem mass spectrometry (LC-MS/MS) method to determine iodothyronines and thyronamines (TAM) from cell culture media was developed. Thyroid hormones (TH) are metabolized by sequential deiodination to eventually yield thyronine (T₀), but can also be decarboxylated, resulting in TAM. The method presented here for extraction of DMEM/F12 cell culture media is a fundamental procedure for a precise determination of 9 TH and 6 TAM from a single LC run. Analytes and internal standards (IS) were extracted from DMEM/F12 (w/o phenol red) by liquid-liquid extraction using isopropanol-TBME (30:70 v/v). Measurement of TH and TAM was performed during a 10-min run time using 13C6-T4, 13C6-T3, 13C6-rT3, 13C6-3,3′T2 and 2H4-T1AM as IS. Calibration curves covered 11 calibrators measured as triplicates each for the analysis of the 9 TH and 6 TAM metabolites, and the 5 IS were linear and reproducible in the range of 0.12-120 nM (R2 0.991-0.999) for all calibrators. The lower limit of quantification was 0.078-0.234 nM. Method validation and robustness were demonstrated by the analysis of precision, accuracy, process efficiency, matrix effects and recoveries, as well as intra- and interassay stability. These parameters were investigated for high, middle and low concentrations of quality controls of all 9 TH and 6 TAM metabolites. This validated, sensitive and interaction-free LC-MS/MS method allows rapid analysis and accurate determination of TH and TAM from DMEM/F12 (w/o phenol red) conditioned media and seems to be easily transferable and applied to commonly used buffers and cell culture media.

scholarly journals Multifunctional MOF-based Electrochemiluminescent Nanocubes for an Ultrasensitive Biosensing Strategy of B. Pseudomallei Determination Coupled With 3D Magnetic Walking Nanomachine

2021 ◽  
Author(s):  
Yuexin Wang ◽  
Bo Shen ◽  
Cai Li ◽  
Haiping Wu ◽  
Yanshuang Wang ◽  
...  
Keyword(s):  
Disease Surveillance ◽  
Burkholderia Pseudomallei ◽  
Detection Method ◽  
Accurate Determination ◽  
Serum Samples ◽  
Exonuclease Iii ◽  
Specific Performance ◽  
Versatile Tool ◽  
Exo Iii

Abstract Burkholderia pseudomallei (B. pseudomallei) can cause melioidosis that is usually fatal. A reliable and rapid detection method is greatly needed for disease surveillance and diagnosis. Herein, an ultrasensitive electrochemiluminescence (ECL) biosensor was constructed for accurate determination of B. pseudomallei coupled with multifunctional Au@Co-MOF@ABEI nanocubes and 3D magnetic walking nanomachine. The synthesized nanocubes could not only immobilize enormous ABEI but exhibit superior peroxidase-like activity to decompose H2O2 to produce plentiful reactive oxygen species (ROSs) that could further react with ABEI, so that the enhanced ECL signals were achieved. Meanwhile, the target-activated walking nanomachine was efficiently driven by Exonuclease III (Exo III) for further improving the sensitivity of the biosensor. As a result, the fabricated ECL biosensor could detect pathogenic gene down to 60.3 aM with a linear range from 100.0 aM to 100.0 pM. Moreover, the biosensing platform successfully achieved the determination of B. pseudomallei down to 9.0 CFU mL−1 in serum samples. This work exhibited an ultrasensitive and specific performance for B. pseudomallei detection, which would become a versatile tool in the early diagnosis and treatment of melioidosis.

A quantitative approach to inner shell losses

1978 ◽  
Vol 36 (1) ◽  
pp. 526-527 ◽  
Author(s):  
R.D. Leapman ◽  
P. Rez ◽  
D.F. Mayers
Keyword(s):  
Energy Transfer ◽  
Cross Section ◽  
Cross Sections ◽  
Accurate Determination ◽  
Background Intensity ◽  
Core Excitation ◽  
Quantitative Basis ◽  
Cross Section Differential ◽  
Bound Electrons

Microanalysis by EELS has been developing rapidly and though the general form of the spectrum is now understood there is a need to put the technique on a more quantitative basis (1,2). Certain aspects important for microanalysis include: (i) accurate determination of the partial cross sections, σx(α,ΔE) for core excitation when scattering lies inside collection angle a and energy range ΔE above the edge, (ii) behavior of the background intensity due to excitation of less strongly bound electrons, necessary for extrapolation beneath the signal of interest, (iii) departures from the simple hydrogenic K-edge seen in L and M losses, effecting σx and complicating microanalysis. Such problems might be approached empirically but here we describe how computation can elucidate the spectrum shape.The inelastic cross section differential with respect to energy transfer E and momentum transfer q for electrons of energy E0 and velocity v can be written as

Fast calibration of CBED patterns for quantitative analysis

1993 ◽  
Vol 51 ◽  
pp. 674-675
Author(s):  
M.A. Gribelyuk ◽  
M. Rühle
Keyword(s):  
Reciprocal Lattice ◽  
Accurate Determination ◽  
Incident Beam ◽  
Crystal Thickness ◽  
Structure Model ◽  
Beam Direction ◽  
Transmitted Beam ◽  
Reciprocal Vector ◽  
On Line

A new method is suggested for the accurate determination of the incident beam direction K, crystal thickness t and the coordinates of the basic reciprocal lattice vectors V1 and V2 (Fig. 1) of the ZOLZ plans in pixels of the digitized 2-D CBED pattern. For a given structure model and some estimated values Vest and Kest of some point O in the CBED pattern a set of line scans AkBk is chosen so that all the scans are located within CBED disks.The points on line scans AkBk are conjugate to those on A0B0 since they are shifted by the reciprocal vector gk with respect to each other. As many conjugate scans are considered as CBED disks fall into the energy filtered region of the experimental pattern. Electron intensities of the transmitted beam I0 and diffracted beams Igk for all points on conjugate scans are found as a function of crystal thickness t on the basis of the full dynamical calculation.

Computer-Assisted High-Re Solution TEM

1990 ◽  
Vol 48 (1) ◽  
pp. 162-163
Author(s):  
F.A. Ponce ◽  
H. Hikashi
Keyword(s):  
Signal To Noise Ratio ◽  
Accurate Determination ◽  
Computer Software ◽  
Video Camera ◽  
Image Contrast ◽  
Objective Lens ◽  
Computer Assisted ◽  
Optical Parameters ◽  
Astigmatism Correction

The determination of the atomic positions from HRTEM micrographs is only possible if the optical parameters are known to a certain accuracy, and reliable through-focus series are available to match the experimental images with calculated images of possible atomic models. The main limitation in interpreting images at the atomic level is the knowledge of the optical parameters such as beam alignment, astigmatism correction and defocus value. Under ordinary conditions, the uncertainty in these values is sufficiently large to prevent the accurate determination of the atomic positions. Therefore, in order to achieve the resolution power of the microscope (under 0.2nm) it is necessary to take extraordinary measures. The use of on line computers has been proposed [e.g.: 2-5] and used with certain amount of success.We have built a system that can perform operations in the range of one frame stored and analyzed per second. A schematic diagram of the system is shown in figure 1. A JEOL 4000EX microscope equipped with an external computer interface is directly linked to a SUN-3 computer. All electrical parameters in the microscope can be changed via this interface by the use of a set of commands. The image is received from a video camera. A commercial image processor improves the signal-to-noise ratio by recursively averaging with a time constant, usually set at 0.25 sec. The computer software is based on a multi-window system and is entirely mouse-driven. All operations can be performed by clicking the mouse on the appropiate windows and buttons. This capability leads to extreme friendliness, ease of operation, and high operator speeds. Image analysis can be done in various ways. Here, we have measured the image contrast and used it to optimize certain parameters. The system is designed to have instant access to: (a) x- and y- alignment coils, (b) x- and y- astigmatism correction coils, and (c) objective lens current. The algorithm is shown in figure 2. Figure 3 shows an example taken from a thin CdTe crystal. The image contrast is displayed for changing objective lens current (defocus value). The display is calibrated in angstroms. Images are stored on the disk and are accessible by clicking the data points in the graph. Some of the frame-store images are displayed in Fig. 4.

Orientation of processes of biological nitrogen transformation in winter rye agroecosystems under different levels of fertilization background

2016 ◽  
Vol 3 (3) ◽  
pp. 28-34
Author(s):  
V. Volkogon ◽  
I. Korotka
Keyword(s):  
Root Zone ◽  
Field Studies ◽  
Nitrogen Transformation ◽  
Mineral Nitrogen ◽  
Nitrogen Fertilizers ◽  
Winter Rye ◽  
Podzolic Soils ◽  
Microbial Preparation ◽  
Biological Nitrogen

Aim. To determine physiologically expedient rates of mineral nitrogen in winter rye production on sod-podzol- ic soils based on the orientation of the processes of biological nitrogen transformation in the plants rhizosphere. Methods. Field studies, gas chromatography determination of potential nitrogen fi xation activity and potential emissions of N 2 O. Results. The results obtained have demonstrated that the rates of mineral nitrogen, not ex- ceeding 60 kg/ha, can be considered physiologically expedient for winter rye production on sod-podzolic soils. Under the application of microbial preparation Diazobakteryn, there is a higher physiological need of plants for nitrogen, which allows increasing the rates of nitrogen fertilizers up to 90 kg/ha. Conclusions. The orienta- tion of the processes of biological nitrogen transformation in the root zone of plants is a reliable indicator of determining the appropriateness of nitrogen fertilization of crops.

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